Title of Invention	A FUEL INJECTION CONTROL APPARATUS FOR AN INTERNAL COMBUSTION ENGINE
Abstract	1042The present invention relates to a fuel injection control apparatus for an internal combustion engine. An intake bottom pressure PMB is compared with a predetermined value b, so that a fIrst map and a second map are switched for processing a standard fuel injection amount TP. The predetermined value b is used for evaluation of the load of the engine. An engine rotation speed NE and the intake bottom pressure PMB are used as the parameters in the fIrst map. The engine rotation speed NE and an intake average pressure PMA V are used as the parameters in the second map. Thus, a final fuel injection amount can be precisely processed using the engine rotation speed and the intake pressure in order to be valid over the range where a load condition of the engine varies. Thus, emissions are decreased and drivability is improved.

Title of Invention

A FUEL INJECTION CONTROL APPARATUS FOR AN INTERNAL COMBUSTION ENGINE

Abstract

1042The present invention relates to a fuel injection control apparatus for an internal combustion engine. An intake bottom pressure PMB is compared with a predetermined value b, so that a fIrst map and a second map are switched for processing a standard fuel injection amount TP. The predetermined value b is used for evaluation of the load of the engine. An engine rotation speed NE and the intake bottom pressure PMB are used as the parameters in the fIrst map. The engine rotation speed NE and an intake average pressure PMA V are used as the parameters in the second map. Thus, a final fuel injection amount can be precisely processed using the engine rotation speed and the intake pressure in order to be valid over the range where a load condition of the engine varies. Thus, emissions are decreased and drivability is improved.

Full Text	FUEL INJECTION CONTROL APPARATUS FOR INTERNAL COMBUSTION ENGINE HAVING FUEL INJECTION AMOUNT SWITCHING FUNCTION Description The present invention relates to a fuel injection control apparatus of an internal combustion engine that controls the fuel injection amount of the injection operation, which is in accordance with the load condition of the internal combustion engine. Generally, in some known injection systems, in order to control the engine, the fuel injection amount is controlled according to the rotational speed of the internal combustion engine (engine) and variation of the intake pressure. According to JP-A-10-280995 (page 2 to page 3), emissions can be decreased and overall engine and driving performance, hereafter, "drivability, " canbeimprovedby accurately processing a fuel injection amount for each cylinder of a two-cylinder engine using an output signal from one intake pressure sensor. In this document, the fuel injection amount is processed using the engine rotation speed and the difference in pressure between atmospheric pressure and the intake bottom pressure, as parameters. However, emissions are increased and drivability is decreased in a specific range, that is, when the throttle opening degree of the throttle valve is substantially small, hereinafter known as "the range." Here, the intake bottom pressure is measured in the vicinity of the end of the intake stroke of the engine, that is, near bottom dead center. The intake bottom pressure varies very little, even though the intake airflow rate changes throughout the intake stroke. Accordingly, variation of the intake airflow rate is not reflected in the fuel injection amount. As a result, a lean air-fuel ratio exists, thereby increasing emissions and reducing drivability. Additionally, variation of the intake pressure is more pronounced in the compression stroke, which is immediately after the intake stroke, or during an expansion (combustion) stroke, than the variation of the intake bottom pressure when the throttle opening degree of the throttle valve is substantially small. To solve the above problems, embodiments of the present invention pertain to a fuel injection control apparatus of an internal combustion engine so that engine emissions can be decreased and drivability can be improved. The fuel injection amount can be precisely processed based on the engine rotation speed and the intake pressure, over a range where the load condition varies. The range includes a condition where the throttle of the throttle valve of the engine is substantially closed. An engine rotation speed detection means detects the engine rotation speed. An intake pressure detection means detects the pressure of an intake passage, which is located downstream of a throttle valve. An engine controlling means controls an operation condition of the engine using the fuel injection amount, which is processed based on one of the first map and the second map that are switched in accordance with a load condition of the internal combustion engine. A first map storing means stores a first map, which is defined using the engine rotation speed and the intake bottom pressure as parameters. A second map storing means stores a second map, which is defined using the engine rotation speed and the intake average pressure as parameters. An intake bottom pressure processing means processes the intake bottom pressure, which is the minimum intake pressure in every combustion cycle of the internal combustion engine. An intake average pressure processing means processes the intake average pressure, which is averaged intake pressure over a predetermined period in every combustion cycle of the internal combustion engine. The predetermined period includes at least a compression stroke or an expansion (combustion) stroke. That is, the first map and the second map are switched when the fuel injection amount is processed, so that the fuel injection amount is precisely processed. The fuel injection amount is validover the range where the load condition of the engine varies. The first map corresponds to a range where the load of the engine is medium to high, and the second map corresponds to a range where the load of the engine is low. Thus, emissions can be reduced and drivability can be improved. The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings, wherein: FIG. 1 is apartialcross-sectionalviewof partof an internal combustion engine and a diagram of peripheral devices showing a fuel feed control apparatus of the internal combustion engine according to an embodiment of the present invention; FIG. 2 is a flowchart of an intake bottom pressure processing procedure performed in a CPU of an ECU that is used in the fuel injection control apparatus of the internal combustion engine according to an embodiment of the present invention; FIG. 3 is a flowchart showing an intake average pressure processing procedure performed in a CPU of an ECU that is used in the fuel injection control apparatus of the internal combustion engine according to an embodiment; FIG. 4 is a graph showing transitions of various sensor signals and various control amounts corresponding to the flowcharts of FIG. 2 and FIG. 3; FIG. 5 is a flowchart of a standard fuel injection amount processing procedure performed in a CPU of an ECU that is used in the fuel injection control apparatus of the internal combustion engine according to an embodiment; FIG. 6 is a flowchart of a first variation of a standard fuel injection amount processing procedure performed in a CPU of an ECU that is used in the fuel injection control apparatus of the internal combustion engine according to an embodiment; FIG. 7 is a flowchart showing a second variation of a standard fuel injection amount processing procedure performed in a CPU of an ECU that is used in the fuel injection control apparatus of the internal combustion engine according to an embodiment; and FIG. 8 is a flowchart showing a third variation of a standard fuel injection amount processing procedure performed in a CPU of an ECU that is used in the fuel injection control apparatus of the internal combustion engine according to an embodiment. As shown in FIG. 1/ an engine 1 is an internal combustion engine that has one cylinder (single-cylinder engine). Air is supplied from an air cleaner 3 toward an air intake passage 2 of the engine 1. A throttle valve 11 is provided midstream of the air intake passage 2. The throttle valve 11 is opened and closed by operation of an accelerator pedal (not shown) or the like, in accordance with the demand of the driver, so that the intake air flow rate toward the air intake passage 2 is controlled. Fuel is injected with the intake air from an injector (fuel injection valve) 5. The fuel injection valve 5 is provided in the air intake passage 2 of the engine 1, near an intake port 4. The fuel is press-transferred from a fuel tank (not shown) by a fuel pump. The pressure of the fuel is controlled by a pressure regulator. A predetermined amount of the fuel injection and a predetermined amount of the intake air becomes an air-fuel mixture. Subsequently, the air-fuel mixture is supplied toward a combustion chamber through the intake valve 6. The throttle valve 11 is disposed midstream of the air intake passage 2 - A throttle opening sensor 21 is provided on the throttle valve 11 for detecting the throttle opening degree TA, which corresponds to a stepping degree of an accelerator pedal or the like. The throttle-opening sensor 21 includes an idle SW (not shown) for detecting a condition, where the throttle valve 11 is substantially fully closed. An intake pressure sensor 22 is provided downstream of the throttle valve 11 for detecting the intake pressure PM in the air intake passage 2. A water temperature sensor 23 is provided in the engine 1 for detecting the cooling water temperature THW. A crank angle sensor 24 is provided proximate the crankshaft 13 of the engine 1 for detecting the crank angle [^CA] in accordance with the rotation of the crankshaft 13. The engine rotation speed NE of the engine 1 is processed based on the crank angle, which is detected by the crank angle sensor 24. A spark plug or ignition plug 14 is provided so as to be oriented toward the inside of a combustion chamber 7 of the engine 1. The ignition plug 14 is supplied with high voltage from an ignition coil / igniter 15, so that the mixture gas in the combustion chamber 7 is ignited and burned. The ignition plug 14 is energized based on an ignition signal, which is synchronized with a crank angle detected by the crank angle sensor 24. The ignition signal is produced by an ECU (Electronic Control Unit) 30- Thus, the mixture gas in the combustion chamber 7 is burned (expanded), so that driving power is obtained. The exhaust gas after combustion is led from an exhaust valve 8 toward an exhaust passage 9 through an exhaust manifold- Subsequently, the exhaust gas is discharged into the outside air- The ECU 30 comprises a CPU 31, a ROM 32, a RAM 33, a B/U RAM 34 (back-up RAM), an I/O circuit 35 and a bus line 36. The CPU 31 is a central processing unit for performing a wide variety of arithmetic processing. The ROM 32 stores control programs and control data- The RAM 33 stores various data or the like. The bus line 36 internally wires the components in the ECU 30 described above. The ECU 30 retrieves the throttle opening degree TA from the throttle opening sensor 21, the intake pressure PM from the intake pressure sensor 22, the cooling water temperature THW from the water temperature sensor 23, the engine rotation speed NE from the crank angle sensor 24 and the like. The ECU 30 delivers control signals that are based on the above various kinds of the sensor signal toward the injector 5, the ignition plug 14, the ignition coil/igniter 15 and the like. The injector 5 is controlled based on the fuel injection time and the fuel injection amount. The ignition plug 14 and the ignition coil/igniter 15 are controlled based on ignition time. Next, a processing routine of the intake bottom pressure PMB is described based on the flow chart shown in FIG. 2 with reference to FIG. 4. The intake bottom pressure is the minimum intake pressure in every combustion cycle of the internal combustion engine. The routine is performed by the CPU 31 of the ECU 30, and used for the fuel injection control apparatus of the internal combustion engine according to one embodiment of the present invention. Here, FIG. 4 is a graph or time chart showing transitions of various kinds of the sensor signal and various kinds of the control amount, corresponding to a processing routine shown in FIG. 2 and FIG. 3 (described later). As shown in FIG. 4, each engine stroke, that is, intake compression - expansion (combustion) • exhaust is measured based on a cam angle signal from the cam angle sensor (not shown) and the crank angle signal from the crank angle sensor 24. The position of the triangular pointer indicates maximum compression or TDC (Top Dead Center) of the cylinder of the engine 1. This intake bottom pressure processing routine is repeatedly performed by the CPU 31 at a certain interval. As shown in FIG. 2, the present intake pressure PM is stored in step SlOl. Next, the routine proceeds to step S102, where a relation is evaluated whether a crank angle signal counter NNUM is equal to a predetermined value a. As shown in FIG. 4, for example, '!" is the predetermined value a (Fig. 2), which represents the completion point of the expansion (combustion) stroke. The crank angle signal counter NNUM indicates a crank angle position. For example, the crank angle signal counter NNUM is set to "0" at a standard crank angle position, corresponding to a cam angle signal that is generated by the cam angle sensor (not shown) . The standard crank angle position is detected by the crank angle sensor 24, which is provided at the crank shaft 13 of the engine 1. One combustion cycle consists of four strokes or cycles (intake -> compression -^ expansion (combustion) - exhaust), and is equivalent to 720 [** CA] (crank angle). The crank angle signal is generated every 30 [° CA] so as to increase the crank angle position in increments of +1, so that the crank angle position varies from 0 to 23 with respect to one combustion cycle. The incremental counting is repeatedly performed such that the crank angle position is reset to 0 when the crank angle exceeds 23. In the case that the relation makes a positive determination in step S102 (i.e., the crank angle counter NNUM equals the predetermined value a, which is at time tO and at time t2 in FIG. 4 ), the routine proceeds to step S103. The intake bottom pressure PMB is initialized at a predetermined maximum value in step S103. On the other hand, in the case that the relation makes a negative determination in step S102, (i.e., the crank angle signal counter NNUM is other than the predetermined value a), step SI03 is skipped. Next, the routine proceeds to step SI04, where a relation is evaluated to determine whether the intake bottom air pressure PMB is greater than the present intake pressure PM. In the case that the relation makes a positive determination in step SI 04 (i.e., the intake bottom air pressure PMB is greater than the present intake pressure PM), the routine proceeds to step S105. Step S105 replaces the intake bottom pressure PMB with the present intake pressure PM, and returns the routine. On the other hand, in the case that the relation makes a negative determination in step SI04, (i.e., the intake bottom air pressure PMB is equal to or less than the present intake pressure PM), step S105 is skipped, so that the intake bottom air pressure PMB is not replaced by the present intake pressure PM. Subsequently, the routine is terminated. As shown in FIG. 4, a detection system of the intake pressure is used in the engine 1, such as a single-cylinder engine ( including, a multi-cylinder engine) in this embodiment. The intake pressure PM becomes negative in the intake stroke, subsequently; it gradually increases, and approaches atmospheric pressure by flowing air into the intake passage 2 from an opening of the throttle valve 11 after finishing the intake stroke. The intake bottom pressure processing routine replaces the intake bottom pressure PMB one after another. The intake bottom pressure PMB at the time tl (shown in FIG. 4) is measured as the intake bottom pressure PMB [kPa: kilopascal] of the present combustion cycle (720 [° CA]). Next, a processing routine of the intake average pressure PMAV is described based on the flow chart shown in FIG. 3 with reference to FIG. 4. The intake average pressure is averaged pressure over a predetermined period in every combustion cycle of the internal combustion engine, the predetermined period including at least a compression stroke or an expansion stroke. The routine is performed by the CPU 31 of the ECU 30, and used for the fuel injection control apparatus of the internal combustion engine according to one embodiment of the present invention. The intake average pressure processing routine is repeatedly performed by the CPU 31 for a predetermined period at a certain interval in every combustion cycle of the engine 1. The predetermined period includes at least a compression stroke and an expansion (combustion) stroke. As shown in FIG. 3, a relationship is evaluated in step S201, such as whether the crank angle signal counter NNUM is equal to or greater than a predetermined value p (for example,"19" which represents the starting point of the compression stroke in FIG. 4). In the case that the relation makes a negative determination in step S201 (i.e., the crank angle signal counter NNUM is less than the predetermined value p), the routine proceeds to step S204 . A relation is evaluated in step S204 to determine whether the crank angle signal counter NNUM is less than a predetermined value Y (for example,"?" which represents the ending point of the expansion (combustion) stroke in FIG. 4). In the case that the relation makes a negative determination in step S204 (i.e., the crank angle signal counter NNUM is equal to or greater than the predetermined value y), the routine proceeds to step S208, A relation is evaluated in step S208 to determine whether the crank angle signal counter NNUM is equal to the predetermined value y. In the case that the relation makes a negative determination in step S208 (i.e., the crank angle signal counter NNUM is greater than the predetermined value y) / the routine proceeds to step S202. An intake pressure summation counter C is reset to "0" in step S202. Next, the routine proceeds to step S203, where an intake pressure summation value PMSM is reset to "0," subsequently the routine is terminated. On the other hand, in the case that the relation makes a positive determination in step S204 (i.e., the crank angle signal counter NNUM is less than the predetermined value y), the routine proceeds to step S205. The intake pressure PM, which is currently detected, is added to the intake pressure summation value PMSMO, which is integrated up to the previous processing, so that the intake pressure summation value PMSM is processed in step 5205. On the other hand, in the case that the relation makes a positive determination in step S201 (i.e., the crank angle signal counter NNUM is equal to or greater than the predetermined value (5), the routine proceeds to step S205 as well. The intake pressure PM, which is currently detected, is added to the intake pressure summation value PMSMO, which is integrated up to the previous processing, so that the intake pressure summation value PMSM is processed in step S205. The range, where the crank angle signal counter NNUM is equal to or greater than the predetermined value p and equal to or less than the predetermined value y, is defined within a crank angle range in the intake stroke, the compression stroke and the expansion (combustion) stroke, in this embodiment. The range corresponds to the predetermined period in every combustion cycle of the engine 1. The predetermined period at least includes the combustion stroke and the expansion (combustion) stroke. Next, the routine proceeds to step S206, where the intake pressure summation counter C is increased in increments of +1. Then, the routine is terminated. On the other hand, in the case that the relation makes a positive determination in step S208 (i.e., the crank angle signal counter NNUM becomes equal to the predetermined value y), the routine proceeds to step S207. The intake pressure summation value PMSM, which is processed in step S205, is divided by the summation counter C, which is processed in step S206, so that the intake average pressure PMAV is processed. Subsequently, the routine is terminated. Next, a processing routine of a standard fuel injection amount TP is described based according to the flow chart shown in FIG. 5. The routine is performed by the CPU 31 of the ECU 30, and used for the fuel injection control apparatus of the internal combustion engine according to one embodiment of the present invention. The standard fuel injection amount processing routine is repeatedly performed by the CPU 31 at a certain interval, in every combustion cycle of the engine 1. As shown in FIG. 5, the engine rotation speed NE is stored in step S301. Next, the routine proceeds to step S302, where the intake bottom pressure PMB is stored. The intake bottom pressure PMB is processed in FIG. 2 as described above. Next, the routine proceeds to step S303, where the intake average pressure PMAV is stored. The intake average pressure PMAV is processed in FIG. 3 as described above. Next, the routine proceeds to step S304 where a relation is evaluated, such as whether the intake bottom pressure PMB is equal to or less than a predetermined value 6. In the case that the relation makes a positive determination in step S304 (i.e., the intake bottom pressure PMB is equal to or less than the predetermined value 6), the operation condition of the engine 1 is estimated to be near or at the idling rotation speed/ so that the routine proceeds to step S305. The standard fuel injection amount TP is processed based on the engine rotation speed NE and the intake average pressure PMAV, using a map that is stored in the ROM 32 in step S305. Subsequently, the routine is terminated. The engine rotation speed NE is stored in step S301, and the intake average pressure PMAV is stored in step S303. On the other hand, in the case that the relation makes a negative determination in step S304 (i.e., the intake bottom pressure PMB is greater than the predetermined value 6), the operating condition of the engine 1 is estimated to be away from the vicinity of the idling rotation speed. Subsequently, the routine proceeds to step S306. The standard fuel injection amount TP is processed in step S306 based on the engine rotation speed NE and the intake bottom pressure PMB using another map, which is stored in the ROM 32. Subsequently, the routine is terminated. The engine rotation speed NE is stored at step S301, and the intake bottom pressure PMB is stored at step S302. Various kinds of known compensation are performed to the standard fuel injection amount TP, which is processed by this routine, so that a final fuel injection amount TAU is processed. The fuel is supplied from the injector 5 to the engine 1 using the final fuel injection amount TAU. The fuel injection control apparatus of the internal combustion engine includes the crank angle sensor 24, the intake pressure sensor 22, the intake bottom pressure processing means, the intake average pressure processing means, the ROM 32 of the ECU 3 0,and the engine controlling means. The crank angle sensor 24 is an engine rotation speed detection means for detecting the rotation speed of the engine 1. The intake pressure sensor 22 is an intake pressure detection means for detecting the intake pressure PM in the intake passage 2, which is provided downstream of the throttle valve 11 of the engine 1. The intake bottom pressure processing means is performed by the CPU 31 of the ECU 30 for processing the intake bottom pressure PMB, which is the minimum intake pressure in every combustion cycle of the engine 1. The intake average pressure processing means is performed by the CPU 31 of the ECU 30 for processing the intake average pressure PMAV, which is the averaged intake pressure over the predetermined period in every combustion cycle of the engine 1. The predetermined period includes at least a compression stroke or the expansion (combustion) stroke. The ROM 32 of the ECU 30 is the first map storing means and the second map storing means. The first map storing means stores the first map which is used for processing the standard fuel injection amount TP for supplying fuel to the engine 1, xising the engine rotation speed NE and the intake bottom pressure PMB as parameters. The second map storing means stores the second map, which is used for processing the standard fuel injection amount TP for supplying fuel to the engine 1, using the engine rotation speed NE and the intake average pressure PMAV as parameters. The engine controlling means is performed by the CPU 31 of the ECU 3 0 for controlling the operating condition o*f the engine 1 using the final fuel injection amount TAU. The final fuel injection amount TAU is obtained by performing various kinds of compensation to the standard fuel injection amount TP. The standard fuel injection amount TP is obtained from one of the first map and the second map that are switched in accordance with the load condition of the engine 1. Additionally, the engine 1 is a single-cylinder engine. The final fuel injection amount TAU can be precisely processed for supplying fuel to the engine 1, using the engine rotation speed NE and the intake pressure PM, by switching the first map and the second map when the standard fuel injection amount TP is processed. The amount TP is processed such that the final fuel injection amount TAU for supplying fuel to the engine 1 is valid over the range where the load condition of the engine 1 varies. Thus, emissions can be decreased, and the drivability can be improved. The engine rotation speed NE and the intake average pressure PMAV are used as the parameters in the second map. The engine rotation speed NE and the intake bottom pressure PMB are used as the parameters in the first map. In the case that the engine 1 is a single-cylinder engine, variation of the intake pressure is apt to explicitly appear, so that the intake bottom pressure PMB and the intake average pressure PMAV can be precisely processed. The engine controlling means is performed by the CPU 31 of the ECU 30 of the fuel injection control apparatus of the internal combustion engine in this embodiment. The engine controlling means processes the standard fuel injection amount TP using the second map stored in the ROM 32 and the first map stored in the ROM 32 as the load condition of the engine 1. The second map is used when the intake bottom pressure PMB is equal to or less than the predetermined value 6, and the first map is used when the intake bottom pressure PMB is greater than the predetermined value 6. That is, the second map is used in a range where the load of the engine 1 is low (i.e., the intake bottom pressure PMB is equal to or less than the predetermined value 6). The first map is used in a range where the load of the engine 1 is medium and high (i.e., the intake bottom pressure PMB is greater than the predetermined value 6). The engine rotation speed NE and the intake average pressure PMAV are used as the parameters in the second map. The engine rotation speed NE and the intake bottom pressure PMB are used as the parameters in the first map. Thus, the standard fuel injection amount TP is processed for supplying fuel to the engine 1. The final fuel injection amount TAU can be precisely processed for supplying fuel to the engine 1, using the engine rotation speed NE and the intake pressure PM, such that the final fuel injection amount TAU is valid over the range where the load condition of the engine 1 varies. Thus, emissions can be decreased, and the drivability can be improved. Next, the first variation of processing of the standard fuel injection amount TP is described based on the flow chart shown in FIG. 6. The routine is performed by the CPU 31 of the ECU 30, and used for the fuel injection control apparatus of the internal combustion engine according to one embodiment of the present invention. The standard fuel injection amount processing routine is repeatedly performed by the CPU 31 at a certain interval in every combustion cycle. As shown in FIG. 6, the engine rotation speed NE is stored in step S401. Next, the routine proceeds to step S402, where the intake bottom pressure PMB, which is processed in FIG. 2, is stored. Next, the routine proceeds to step S403, where the intake average pressure PMAV, which is processed in FIG. 3, is stored. Next, the routine proceeds to step S404, where a relation is evaluated, such that whether the intake average pressure PMAV, which is stored in step S403, is equal to or less than a predetermined value e. In the case that the relation makes a positive determination in step S404, that is, that the intake average pressure PMAV is equal to or less than the predetermined value e (i.e., the operation condition of the engine 1 is estimated in the vicinity of the idling rotation speed), the routine proceeds to step S405. The standard fuel injection amount TP is processed based on the engine rotation speed NE, which is stored in step S401, and the intake average pressure PMAV, which is stored in step S403, using the prestored map in ROM 32 in step S405. Subsequently, the routine is terminated. On the other hand, in the case that the relation makes a negative determination in step S404, that is, the intake average pressure PMAV is greater than the predetermined value e ( the operation condition of the engine 1 is estimated away pressure PMAV is greater than the predetermined value e (i.e., from the vicinity of the idling rotation speed), the routine proceeds to step S406. The standard fuel injection amount TP is processed based on the engine rotation speed NE, which is stored in step S401, and the intake bottom pressure PMB, which is stored in step S4 02, using the prestored map in ROM 32 in step S406. Subsequently, the routine is terminated. Various known kinds of compensation are performed to the standard fuel injection amount TP. Thus, the final fuel injection amount TAU is processed for supplying fuel from the injector 5 to the engine 1. The engine controlling means is performed by the CPU 31 of the ECU 30 of the fuel injection control apparatus of the internal combustion engine in this embodiment. The engine controlling means processes the standard fuel injection amount TP using the second map stored in the ROM 32 and the first map stored in the ROM 32 as the load condition of the engine 1. The second map is used when the intake average pressure PMAV is equal to or less than the predetermined value e, and the first map is used when the intake average pressure PMAV is greater than the predetermined value e. That is, the second map is used in a range where the load of the engine 1 is low (i.e., the intake average pressure PMAV is equal to or less than the predetermined value e). The first map is used in a range where the load of the engine 1 is medium and high (i.e., the intake average pressure PMAV is greater than the predetermined value ej. The engine rotation speed NE and the intake average pressure PMAV are used as the parameters in the second map. The engine rotation speed NE and the intake bottom pressure PMB are used as the parameters in the first map. Thus, the standard fuel injection amount TP is processed for supplying fuel to the engine 1. The final fuel injection amount TAU can be precisely processed for supplying fuel to the engine 1 using the engine rotation speed NE and the intake pressure PM, such that the final fuel injection amount TAU is valid over the range where the load condition of the engine 1 varies. Thus, emissions can be decreased, and the drivability can be improved. Next, the second variation of processing of the standard fuel injection amount TP is described based on the flow chart shown in FIG. 7. The routine is performed by the CPU 31 of the ECU 30, and used for the fuel injection control apparatus of the internal combustion engine according to one embodiment of the present invention. The standard fuel injection amount processing routine is repeatedly performed by the CPU 31 at a certain interval in every combustion cycle. As shown in FIG. 7, the engine rotation speed NE is stored in step S501. Next, the routine proceeds to step S502, where the throttle opening degree TA is stored. Next, the routine proceeds to step S503, where the intake bottom pressure PMB is stored. The intake bottom pressure PMB is processed in FIG. 2. Next, the routine proceeds to step S504, where the intake average pressure PMAV is stored. The intake average pressure PMAV is processed in FIG. 3. Next, the routine proceeds tostepS505, where a relation is evaluated, such that whether the throttle opening degree TA, which is stored in step S502, is equal to or less than a predetermined value t,. In the case that the'relation makes a positive determination in step S505, that is the throttle opening degree TA is equal to or less than the predetermined value ^ (i.e., the operation condition of the engine 1 is estimated in the vicinity of the idling rotation speed), the routine proceeds to step S506. The standard fuel injection amount TP is processed based on the engine rotation speed NE, which is stored in step S501, and the intake average pressure PMAV, which is stored in step S504, using the prestoredmap in ROM 32 in step S506. Subsequently, the routine is terminated. Alternatively, in the case that the relation makes a negative determination in step S505, that is, the throttle opening degree TA is greater than the predetermined value t, (i.e., the operation condition of the engine 1 is estimated away from the vicinity of the idling rotation speed), the routine proceeds to step S507. The standard fuel injection amount TP is processed based on the engine rotation speed NE, which is stored in step S501, and the intake bottom pressure PMB, which is stored in step S503, using the prestored map in ROM 3 2 in stepS507 . Subsequently, the routine is terminated. Various known kinds of compensation are performed for the standard fuel injection amount TP. Thus, the final fuel injection amount TAU is processed for supplying fuel from the injector 5 to the engine 1. The fuel injection control apparatus of the internal combustion engine has the throttle-opening sensor 21 as a throttle opening degree detecting means for detecting the throttle opening degree TA of the throttle valve 1, and the engine controlling means, which is performed by the CPU 31 of the ECU 30, in this variation- The engine controlling means processes the standard fuel injection amount TP using the second map stored in the ROM 32 and the first map stored in the ROM 32 as the load condition of the engine 1. The second map is used when the throttle opening degree TA is equal to or less than the predetermined value t,, and the first map is used when the throttle opening degree TA is greater than the predetermined value ^. That is, the second map is used in a range where the load of the engine 1 is low (i.e., the throttle opening degree TA is equal to or less than the predetermined value ^). The first map is used in a range where the load of the engine 1 is medium and high (i.e., the throttle opening degree TA is greater than the predetermined value t,). The engine rotation speed NE and the intake average pressure PMAV are used as the parameters in the second map. The engine rotation speed NE and the intake bottom pressure PMB are used as the parameters in the first map. Thus, the standard fuel injection amount TP is processed for supplying fuel to the engine 1. The final fuel injection amount TAU can be precisely processed for supplying fuel to the engine 1, using the engine rotation speed NE and the intake pressure PM, such that the final fuel injection amount TAU is valid over the range where the load condition of the engine 1 varies. Thus, emissions can be decreased, and the drivability can be improved. Next, the third variation of a processing of the standard fuel injection amount TP is described based on the flowchart shown in FIG. 8. The routine is performed by the CPU 31 of the ECU 30, and used for the fuel injection control apparatus of the internal combustion engine according to one embodiment of the present invention. The standard fuel injection amount processing routine is repeatedly performed by the CPU 31 at a certain interval in every combustion cycle. As shown in FIG. 8, the engine rotation speed NE is stored in step S601. Next, the routine proceeds to step S602, where the intake bottom pressure PMB is stored. The intake bottom pressure PMB is processed in FIG. 2. Next, the routine proceeds to step S603, where the intake average pressure PMAV is stored. The intake average pressure PMAV is processed in FIG. 3. Next, the routine proceeds tostepS604, where the position of the idle SWis evaluated to be ON or not. In the case that the evaluation makes a positive determination in step S604, that is, the position of the idle SW is ON (i.e., the operation condition of the engine 1 is estimated in the idling rotation speed), the routine proceeds to step S605. The standard fuel injection amount TP is processed based on the engine rotation speed NE, which is stored in step S601, and the intake average pressure PMAV, which is stored in step S603, using the prestored map in ROM 32 in step S605. Subsequently, the routine is terminated. On the other hand, in the case that the evaluation makes a negative determination in step S604, that is, the position of the idle SW is OFF (i.e., the operation condition of the engine 1 is estimated away from the idling rotation speed), the routine proceeds to step S606. The standard fuel injection amount TP is processed based on the engine rotation speed NE, which is stored in step S601, and the intake bottom pressure PMB, which is stored in step S602, using the prestored map in ROM 32 in step S606. Subsequently, the routine is terminated. Various kinds of known compensation are performed for the standard fuel injection amount TP. Thus, the final fuel injection amount TAU is processed for supplying fuel from the injector 5 to the engine 1. The fuel injection control apparatus of the internal combustion engine has the idle SW (not shown) as an idle detecting means for detecting a condition where the throttle valve 11 is near its fully closed state, and the engine controlling means, which is performed by the CPU 31 of the ECU 30, in this variation. The engine controlling means processes the standard fuel injection amount TP using the second map stored in the ROM 32 and the first map stored in the ROM 32 as the load condition of the engine 1. The second map is used when the position of the idle SW is ON (i.e., the throttle valve 11 is in the vicinity of the fully closed condition), and the first map is used when the position of the idle SW is OFF (i.e., the throttle valve 11 is not in the vicinity of the fully closed condition). That is, the second map is used in a range where the load of the engine 1 is low (i.e., the position of the idle SW is ON). The first map is used in a range where the load of the engine 1 is medium and high (i.e., the position of the idle SW is OFF). The engine rotation speed NE and the intake average pressure PMAV are used as the parameters in the second map. The engine rotation speed NE and the intake bottom pressure PMB are used as the parameters in the first map. Thus, the standard fuel injection amount TP is processed for supplying fuel to the engine 1. The final fuel injection amount TAU can be precisely processed for supplying fuel to the engine 1, using the engine rotation speed NE and the intake pressure PM, such that the final fuel injection amount TAU is valid over the range where the load condition of the engine 1 varies. Thus, emissions can be decreased, and the drivability can be improved• Here, the above embodiments and the above variations are described in the case that the engine is the single-cylinder engine. However, the use of the present invention is not limited to that as described above. In the case that the engine is an individual, intake-type, multi-cylinder engine that intakes air individually into each cylinder, similar functions and effects can be expected. That is, variation of the intake pressure in every combustion cycle of the engine is apt to distinctly appear. Thus, the intake bottom pressure and the intake average pressure can be precisely processed. Here, the above embodiments and the above variations are described in the case that the intake bottom pressure PMB is processed based on the intake pressure PM in or at a certain interval • However, the use of the present invention is not limited to that described above. The intake bottom pressure PMB can be processed every time the crank angle signal is generated from the crank angle , sensor 24. The intake bottom pressure PMB can be processed by providing a peak hold circuit in the ECU 30. Similarly/ various modifications and alternations may be made to the above embodiments without departing from the spirit of the present invention. Claims: 1. A fuel injection control apparatus for an internal combustion engine, the fuel injection control apparatus comprising: means for detecting rotation speed of the internal combustion engine; means for detecting pressure of an intake passage, which is downstream of a throttle valve of the internal combustion engine; means for processing intake bottom pressure, which is minimum intake pressure in every combustion cycle of the internal combustion engine; means for processing intake average pressure, which is averaged pressure over a predetermined period in every combustion cycle of the internal combustion engine, the predetermined period includes at least a compression stroke or an expansion stroke; means for storing a first map, which is used for processing an injection amount of fuel into the internal combustion engine, wherein the first map storing means uses the engine rotation speed and the intake bottom pressure as parameters of the first map; means for storing a second map, which is used for processing the fuel injection amount into the internal combustion engine, wherein the second map storing means uses the engine rotation speed and the intake average pressure as parameters of the second map; and means for controlling an operation condition of the internal combustion engine utilizing the fuel injection amount, which is processed based on one of the first map and the second map that are switched in accordance with a load condition of the internal combustion engine. 2. A fuel injection control apparatus for an internal combustion engine according to claim 1, wherein the engine controlling means processes the fuel injection amount utilizing the second map as a basis of the load condition of the internal combustion engine when the intake bottom pressure is equal to or less than a predetermined value, and the engine controlling means processes the fuel injection amount utilizing the first map as a basis of the load condition of the internal combustion engine when the intake bottom pressure is greater than the predetermined value. 3- A fuel injection control apparatus for an internal combustion engine according to claim 1, wherein the engine controlling means processes the fuel injection amount utilizing the second map as a basis of the load condition of the internal combustion engine when the intake average pressure is equal to or less than a predetermined value, and the engine controlling means processes the fuel injection amount utilizing the first map as a basis of the load condition of the internal combustion engine when the intake average pressure is greater than the predetermined value. 4. A fuel injection control apparatus for an internal combustion engine according to claim 1, further comprising: means for detecting a throttle opening degree, wherein the engine controlling means processes the fuel injection amount utilizing the second map as a basis of the load condition of the internal combustion engine when the throttle opening degree is equal to or less than a predetermined value, and the engine controlling means processes the fuel injection amount utilizing the first map as a basis of the load condition of the internal combustion engine when the throttle opening degree is greater than the predetermined value. 5. A fuel injection control apparatus for an internal combustion engine according to claim 1, further comprising: means for detecting an idle condition in which the throttle valve is in the vicinity of a fully closed state, wherein the internal combustion engine controlling means processes the fuel injection amount utilizing the second map as a basis of the load condition of the internal combustion engine when the idle detecting means detects a condition in which the throttle valve is in the vicinity of a fully closed condition, and the engine controlling means processes the fuel injection amount utilizing the first map as a basis of the load condition of the internal combustion engine when the idle detecting means detects a condition in which the throttle valve is out of the vicinity of a fully closed condition. 6. A fuel injection control apparatus for an internal combustion engine according to claim 1, wherein the internal combustion engine has at least one cylinder that intakes air. 7. A fuel injection control apparatus substantially as herein described with reference to the accompanying drawings.

Full Text

FUEL INJECTION CONTROL APPARATUS FOR INTERNAL COMBUSTION ENGINE HAVING FUEL INJECTION AMOUNT SWITCHING FUNCTION
Description
The present invention relates to a fuel injection control apparatus of an internal combustion engine that controls the fuel injection amount of the injection operation, which is in accordance with the load condition of the internal combustion engine.
Generally, in some known injection systems, in order to control the engine, the fuel injection amount is controlled according to the rotational speed of the internal combustion engine (engine) and variation of the intake pressure.
According to JP-A-10-280995 (page 2 to page 3), emissions can be decreased and overall engine and driving performance, hereafter, "drivability, " canbeimprovedby accurately processing a fuel injection amount for each cylinder of a two-cylinder engine using an output signal from one intake pressure sensor. In this document, the fuel injection amount is processed using the engine rotation speed and the difference in pressure between atmospheric pressure and the intake bottom pressure, as parameters. However, emissions are increased and drivability is decreased in a specific range, that is, when the throttle opening degree of the throttle valve is substantially small, hereinafter known as "the range." Here, the intake bottom pressure is measured in the vicinity of the end of the intake stroke of the engine, that is, near bottom dead center. The intake bottom pressure varies very little, even though the intake airflow rate changes throughout the intake stroke.

Accordingly, variation of the intake airflow rate is not reflected in the fuel injection amount. As a result, a lean air-fuel ratio exists, thereby increasing emissions and reducing drivability. Additionally, variation of the intake pressure is more pronounced in the compression stroke, which is immediately after the intake stroke, or during an expansion (combustion) stroke, than the variation of the intake bottom pressure when the throttle opening degree of the throttle valve is substantially small.
To solve the above problems, embodiments of the present invention pertain to a fuel injection control apparatus of an internal combustion engine so that engine emissions can be decreased and drivability can be improved. The fuel injection amount can be precisely processed based on the engine rotation speed and the intake pressure, over a range where the load condition varies. The range includes a condition where the throttle of the throttle valve of the engine is substantially closed.
An engine rotation speed detection means detects the engine rotation speed. An intake pressure detection means detects the pressure of an intake passage, which is located downstream of a throttle valve. An engine controlling means controls an operation condition of the engine using the fuel injection amount, which is processed based on one of the first map and the second map that are switched in accordance with a load condition of the internal combustion engine. A first map storing means stores a first map, which is defined using the engine rotation speed and the intake bottom pressure as parameters. A second map storing means stores a second map, which is defined using the engine rotation speed

and the intake average pressure as parameters. An intake bottom pressure processing means processes the intake bottom pressure, which is the minimum intake pressure in every combustion cycle of the internal combustion engine. An intake average pressure processing means processes the intake average pressure, which is averaged intake pressure over a predetermined period in every combustion cycle of the internal combustion engine.
The predetermined period includes at least a compression stroke or an expansion (combustion) stroke. That is, the first map and the second map are switched when the fuel injection amount is processed, so that the fuel injection amount is precisely processed. The fuel injection amount is validover the range where the load condition of the engine varies. The first map corresponds to a range where the load of the engine is medium to high, and the second map corresponds to a range where the load of the engine is low. Thus, emissions can be reduced and drivability can be improved.
The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings, wherein:
FIG. 1 is apartialcross-sectionalviewof partof an internal combustion engine and a diagram of peripheral devices showing a fuel feed control apparatus of the internal combustion engine according to an embodiment of the present invention;
FIG. 2 is a flowchart of an intake bottom pressure processing procedure performed in a CPU of an ECU that is used in the fuel

injection control apparatus of the internal combustion engine according to an embodiment of the present invention;
FIG. 3 is a flowchart showing an intake average pressure processing procedure performed in a CPU of an ECU that is used in the fuel injection control apparatus of the internal combustion engine according to an embodiment;
FIG. 4 is a graph showing transitions of various sensor signals and various control amounts corresponding to the flowcharts of FIG. 2 and FIG. 3;
FIG. 5 is a flowchart of a standard fuel injection amount processing procedure performed in a CPU of an ECU that is used in the fuel injection control apparatus of the internal combustion engine according to an embodiment;
FIG. 6 is a flowchart of a first variation of a standard fuel injection amount processing procedure performed in a CPU of an ECU that is used in the fuel injection control apparatus of the internal combustion engine according to an embodiment;
FIG. 7 is a flowchart showing a second variation of a standard fuel injection amount processing procedure performed in a CPU of an ECU that is used in the fuel injection control apparatus of the internal combustion engine according to an embodiment; and
FIG. 8 is a flowchart showing a third variation of a standard fuel injection amount processing procedure performed in a CPU of an ECU that is used in the fuel injection control apparatus of the internal combustion engine according to an embodiment.
As shown in FIG. 1/ an engine 1 is an internal combustion

engine that has one cylinder (single-cylinder engine). Air is supplied from an air cleaner 3 toward an air intake passage 2 of the engine 1. A throttle valve 11 is provided midstream of the air intake passage 2. The throttle valve 11 is opened and closed by operation of an accelerator pedal (not shown) or the like, in accordance with the demand of the driver, so that the intake air flow rate toward the air intake passage 2 is controlled. Fuel is injected with the intake air from an injector (fuel injection valve) 5. The fuel injection valve 5 is provided in the air intake passage 2 of the engine 1, near an intake port 4. The fuel is press-transferred from a fuel tank (not shown) by a fuel pump. The pressure of the fuel is controlled by a pressure regulator. A predetermined amount of the fuel injection and a predetermined amount of the intake air becomes an air-fuel mixture. Subsequently, the air-fuel mixture is supplied toward a combustion chamber through the intake valve 6.
The throttle valve 11 is disposed midstream of the air intake passage 2 - A throttle opening sensor 21 is provided on the throttle valve 11 for detecting the throttle opening degree TA, which corresponds to a stepping degree of an accelerator pedal or the like. The throttle-opening sensor 21 includes an idle SW (not shown) for detecting a condition, where the throttle valve 11 is substantially fully closed. An intake pressure sensor 22 is provided downstream of the throttle valve 11 for detecting the intake pressure PM in the air intake passage 2. A water temperature sensor 23 is provided in the engine 1 for detecting the cooling water temperature THW. A crank angle sensor 24 is provided

proximate the crankshaft 13 of the engine 1 for detecting the crank angle [^CA] in accordance with the rotation of the crankshaft 13. The engine rotation speed NE of the engine 1 is processed based on the crank angle, which is detected by the crank angle sensor
24.
A spark plug or ignition plug 14 is provided so as to be oriented toward the inside of a combustion chamber 7 of the engine 1. The ignition plug 14 is supplied with high voltage from an ignition coil / igniter 15, so that the mixture gas in the combustion chamber 7 is ignited and burned. The ignition plug 14 is energized based on an ignition signal, which is synchronized with a crank angle detected by the crank angle sensor 24. The ignition signal is produced by an ECU (Electronic Control Unit) 30- Thus, the mixture gas in the combustion chamber 7 is burned (expanded), so that driving power is obtained. The exhaust gas after combustion is led from an exhaust valve 8 toward an exhaust passage 9 through an exhaust manifold- Subsequently, the exhaust gas is discharged into the outside air-
The ECU 30 comprises a CPU 31, a ROM 32, a RAM 33, a B/U RAM 34 (back-up RAM), an I/O circuit 35 and a bus line 36. The CPU 31 is a central processing unit for performing a wide variety of arithmetic processing. The ROM 32 stores control programs and control data- The RAM 33 stores various data or the like. The bus line 36 internally wires the components in the ECU 30 described above. The ECU 30 retrieves the throttle opening degree TA from the throttle opening sensor 21, the intake pressure PM from the intake pressure sensor 22, the cooling water temperature THW from

the water temperature sensor 23, the engine rotation speed NE from the crank angle sensor 24 and the like. The ECU 30 delivers control signals that are based on the above various kinds of the sensor signal toward the injector 5, the ignition plug 14, the ignition coil/igniter 15 and the like. The injector 5 is controlled based on the fuel injection time and the fuel injection amount. The ignition plug 14 and the ignition coil/igniter 15 are controlled based on ignition time.
Next, a processing routine of the intake bottom pressure PMB is described based on the flow chart shown in FIG. 2 with reference to FIG. 4. The intake bottom pressure is the minimum intake pressure in every combustion cycle of the internal combustion engine. The routine is performed by the CPU 31 of the ECU 30, and used for the fuel injection control apparatus of the internal combustion engine according to one embodiment of the present invention. Here, FIG. 4 is a graph or time chart showing transitions of various kinds of the sensor signal and various kinds of the control amount, corresponding to a processing routine shown in FIG. 2 and FIG. 3 (described later). As shown in FIG. 4, each engine stroke, that is, intake compression - expansion (combustion) • exhaust is measured based on a cam angle signal from the cam angle sensor (not shown) and the crank angle signal from the crank angle sensor 24. The position of the triangular pointer indicates maximum compression or TDC (Top Dead Center) of the cylinder of the engine 1. This intake bottom pressure processing routine is repeatedly performed by the CPU 31 at a certain interval.

As shown in FIG. 2, the present intake pressure PM is stored in step SlOl. Next, the routine proceeds to step S102, where a relation is evaluated whether a crank angle signal counter NNUM is equal to a predetermined value a. As shown in FIG. 4, for example, '*!" is the predetermined value a (Fig. 2), which represents the completion point of the expansion (combustion) stroke. The crank angle signal counter NNUM indicates a crank angle position. For example, the crank angle signal counter NNUM is set to "0" at a standard crank angle position, corresponding to a cam angle signal that is generated by the cam angle sensor (not shown) . The standard crank angle position is detected by the crank angle sensor 24, which is provided at the crank shaft 13 of the engine 1. One combustion cycle consists of four strokes or cycles (intake -> compression -^ expansion (combustion) -* exhaust), and is equivalent to 720 [** CA] (crank angle). The crank angle signal is generated every 30 [° CA] so as to increase the crank angle position in increments of +1, so that the crank angle position varies from 0 to 23 with respect to one combustion cycle. The incremental counting is repeatedly performed such that the crank angle position is reset to 0 when the crank angle exceeds 23.
In the case that the relation makes a positive determination in step S102 (i.e., the crank angle counter NNUM equals the
predetermined value a, which is at time tO and at time t2 in FIG. 4 ), the routine proceeds to step S103. The intake bottom pressure
PMB is initialized at a predetermined maximum value in step S103.
On the other hand, in the case that the relation makes a negative
determination in step S102, (i.e., the crank angle signal counter

NNUM is other than the predetermined value a), step SI03 is skipped.
Next, the routine proceeds to step SI04, where a relation is evaluated to determine whether the intake bottom air pressure PMB is greater than the present intake pressure PM. In the case that the relation makes a positive determination in step SI 04 (i.e., the intake bottom air pressure PMB is greater than the present intake pressure PM), the routine proceeds to step S105. Step S105 replaces the intake bottom pressure PMB with the present intake pressure PM, and returns the routine.
On the other hand, in the case that the relation makes a negative determination in step SI04, (i.e., the intake bottom air pressure PMB is equal to or less than the present intake pressure PM), step S105 is skipped, so that the intake bottom air pressure PMB is not replaced by the present intake pressure PM. Subsequently, the routine is terminated.
As shown in FIG. 4, a detection system of the intake pressure is used in the engine 1, such as a single-cylinder engine ( including, a multi-cylinder engine) in this embodiment. The intake pressure PM becomes negative in the intake stroke, subsequently; it gradually increases, and approaches atmospheric pressure by flowing air into the intake passage 2 from an opening of the throttle valve 11 after finishing the intake stroke. The intake bottom pressure processing routine replaces the intake bottom pressure PMB one after another. The intake bottom pressure PMB at the time tl (shown in FIG. 4) is measured as the intake bottom pressure
PMB [kPa: kilopascal] of the present combustion cycle (720 [° CA]).

Next, a processing routine of the intake average pressure PMAV is described based on the flow chart shown in FIG. 3 with reference to FIG. 4. The intake average pressure is averaged pressure over a predetermined period in every combustion cycle of the internal combustion engine, the predetermined period including at least a compression stroke or an expansion stroke. The routine is performed by the CPU 31 of the ECU 30, and used for the fuel injection control apparatus of the internal combustion engine according to one embodiment of the present invention. The intake average pressure processing routine is repeatedly performed by the CPU 31 for a predetermined period at a certain interval in every combustion cycle of the engine 1. The predetermined period includes at least a compression stroke and an expansion (combustion) stroke.
As shown in FIG. 3, a relationship is evaluated in step S201, such as whether the crank angle signal counter NNUM is equal to
or greater than a predetermined value p (for example,"19" which represents the starting point of the compression stroke in FIG.
4). In the case that the relation makes a negative determination
in step S201 (i.e., the crank angle signal counter NNUM is less
than the predetermined value p), the routine proceeds to step S204 .
A relation is evaluated in step S204 to determine whether the
crank angle signal counter NNUM is less than a predetermined value
Y (for example,"?" which represents the ending point of the expansion (combustion) stroke in FIG. 4). In the case that the relation makes a negative determination in step S204 (i.e., the crank angle signal counter NNUM is equal to or greater than the

predetermined value y), the routine proceeds to step S208, A relation is evaluated in step S208 to determine whether the crank
angle signal counter NNUM is equal to the predetermined value y. In the case that the relation makes a negative determination in step S208 (i.e., the crank angle signal counter NNUM is greater
than the predetermined value y) / the routine proceeds to step S202. An intake pressure summation counter C is reset to "0" in step S202. Next, the routine proceeds to step S203, where an intake pressure summation value PMSM is reset to "0," subsequently the routine is terminated.
On the other hand, in the case that the relation makes a positive determination in step S204 (i.e., the crank angle signal
counter NNUM is less than the predetermined value y), the routine proceeds to step S205. The intake pressure PM, which is currently detected, is added to the intake pressure summation value PMSMO, which is integrated up to the previous processing, so that the intake pressure summation value PMSM is processed in step 5205. On the other hand, in the case that the relation makes a positive determination in step S201 (i.e., the crank angle signal counter NNUM is equal to or greater than the predetermined value
(5), the routine proceeds to step S205 as well. The intake pressure PM, which is currently detected, is added to the intake pressure summation value PMSMO, which is integrated up to the previous processing, so that the intake pressure summation value PMSM is processed in step S205.
The range, where the crank angle signal counter NNUM is equal to or greater than the predetermined value p and equal to or less

than the predetermined value y, is defined within a crank angle range in the intake stroke, the compression stroke and the expansion (combustion) stroke, in this embodiment. The range corresponds to the predetermined period in every combustion cycle of the engine 1. The predetermined period at least includes the combustion stroke and the expansion (combustion) stroke. Next, the routine proceeds to step S206, where the intake pressure summation counter C is increased in increments of +1. Then, the routine is terminated.
On the other hand, in the case that the relation makes a positive determination in step S208 (i.e., the crank angle signal
counter NNUM becomes equal to the predetermined value y), the routine proceeds to step S207. The intake pressure summation value PMSM, which is processed in step S205, is divided by the summation counter C, which is processed in step S206, so that the intake average pressure PMAV is processed. Subsequently, the routine is terminated.
Next, a processing routine of a standard fuel injection amount TP is described based according to the flow chart shown in FIG. 5. The routine is performed by the CPU 31 of the ECU 30, and used for the fuel injection control apparatus of the internal combustion engine according to one embodiment of the present invention. The standard fuel injection amount processing routine is repeatedly performed by the CPU 31 at a certain interval, in every combustion cycle of the engine 1.
As shown in FIG. 5, the engine rotation speed NE is stored in step S301. Next, the routine proceeds to step S302, where the

intake bottom pressure PMB is stored. The intake bottom pressure PMB is processed in FIG. 2 as described above. Next, the routine proceeds to step S303, where the intake average pressure PMAV is stored. The intake average pressure PMAV is processed in FIG. 3 as described above. Next, the routine proceeds to step S304 where a relation is evaluated, such as whether the intake bottom
pressure PMB is equal to or less than a predetermined value 6. In the case that the relation makes a positive determination in step S304 (i.e., the intake bottom pressure PMB is equal to or
less than the predetermined value 6), the operation condition of the engine 1 is estimated to be near or at the idling rotation speed/ so that the routine proceeds to step S305. The standard fuel injection amount TP is processed based on the engine rotation speed NE and the intake average pressure PMAV, using a map that is stored in the ROM 32 in step S305. Subsequently, the routine is terminated. The engine rotation speed NE is stored in step S301, and the intake average pressure PMAV is stored in step S303. On the other hand, in the case that the relation makes a negative determination in step S304 (i.e., the intake bottom
pressure PMB is greater than the predetermined value 6), the operating condition of the engine 1 is estimated to be away from the vicinity of the idling rotation speed. Subsequently, the routine proceeds to step S306. The standard fuel injection amount TP is processed in step S306 based on the engine rotation speed NE and the intake bottom pressure PMB using another map, which is stored in the ROM 32. Subsequently, the routine is terminated. The engine rotation speed NE is stored at step S301, and the intake

bottom pressure PMB is stored at step S302. Various kinds of known compensation are performed to the standard fuel injection amount TP, which is processed by this routine, so that a final fuel injection amount TAU is processed. The fuel is supplied from the injector 5 to the engine 1 using the final fuel injection amount TAU.
The fuel injection control apparatus of the internal combustion engine includes the crank angle sensor 24, the intake pressure sensor 22, the intake bottom pressure processing means, the intake average pressure processing means, the ROM 32 of the ECU 3 0,and the engine controlling means. The crank angle sensor 24 is an engine rotation speed detection means for detecting the rotation speed of the engine 1. The intake pressure sensor 22 is an intake pressure detection means for detecting the intake pressure PM in the intake passage 2, which is provided downstream of the throttle valve 11 of the engine 1.
The intake bottom pressure processing means is performed by the CPU 31 of the ECU 30 for processing the intake bottom pressure PMB, which is the minimum intake pressure in every combustion cycle of the engine 1. The intake average pressure processing means is performed by the CPU 31 of the ECU 30 for processing the intake average pressure PMAV, which is the averaged intake pressure over the predetermined period in every combustion cycle of the engine 1. The predetermined period includes at least a compression stroke or the expansion (combustion) stroke.
The ROM 32 of the ECU 30 is the first map storing means and the second map storing means. The first map storing means stores the first map which is used for processing the standard fuel

injection amount TP for supplying fuel to the engine 1, xising the engine rotation speed NE and the intake bottom pressure PMB as parameters. The second map storing means stores the second map, which is used for processing the standard fuel injection amount TP for supplying fuel to the engine 1, using the engine rotation speed NE and the intake average pressure PMAV as parameters. The engine controlling means is performed by the CPU 31 of the ECU 3 0 for controlling the operating condition o*f the engine 1 using the final fuel injection amount TAU.
The final fuel injection amount TAU is obtained by performing various kinds of compensation to the standard fuel injection amount TP. The standard fuel injection amount TP is obtained from one of the first map and the second map that are switched in accordance with the load condition of the engine 1. Additionally, the engine 1 is a single-cylinder engine.
The final fuel injection amount TAU can be precisely processed for supplying fuel to the engine 1, using the engine rotation speed NE and the intake pressure PM, by switching the first map and the second map when the standard fuel injection amount TP is processed. The amount TP is processed such that the final fuel injection amount TAU for supplying fuel to the engine 1 is valid over the range where the load condition of the engine 1 varies. Thus, emissions can be decreased, and the drivability can be improved. The engine rotation speed NE and the intake average pressure PMAV are used as the parameters in the second map. The engine rotation speed NE and the intake bottom pressure PMB are used as the parameters in the first map. In the case that the

engine 1 is a single-cylinder engine, variation of the intake pressure is apt to explicitly appear, so that the intake bottom pressure PMB and the intake average pressure PMAV can be precisely
processed.
The engine controlling means is performed by the CPU 31 of the ECU 30 of the fuel injection control apparatus of the internal combustion engine in this embodiment. The engine controlling means processes the standard fuel injection amount TP using the second map stored in the ROM 32 and the first map stored in the ROM 32 as the load condition of the engine 1. The second map is used when the intake bottom pressure PMB is equal to or less than the predetermined value 6, and the first map is used when the intake
bottom pressure PMB is greater than the predetermined value 6.
That is, the second map is used in a range where the load
of the engine 1 is low (i.e., the intake bottom pressure PMB is
equal to or less than the predetermined value 6). The first map is used in a range where the load of the engine 1 is medium and
high (i.e., the intake bottom pressure PMB is greater than the
predetermined value 6). The engine rotation speed NE and the intake average pressure PMAV are used as the parameters in the second map. The engine rotation speed NE and the intake bottom pressure PMB are used as the parameters in the first map. Thus, the standard fuel injection amount TP is processed for supplying fuel to the engine 1. The final fuel injection amount TAU can be precisely processed for supplying fuel to the engine 1, using the engine rotation speed NE and the intake pressure PM, such that the final fuel injection amount TAU is valid over the range where the load

condition of the engine 1 varies. Thus, emissions can be decreased, and the drivability can be improved.
Next, the first variation of processing of the standard fuel injection amount TP is described based on the flow chart shown in FIG. 6. The routine is performed by the CPU 31 of the ECU 30, and used for the fuel injection control apparatus of the internal combustion engine according to one embodiment of the present invention. The standard fuel injection amount processing routine is repeatedly performed by the CPU 31 at a certain interval in every combustion cycle.
As shown in FIG. 6, the engine rotation speed NE is stored in step S401. Next, the routine proceeds to step S402, where the intake bottom pressure PMB, which is processed in FIG. 2, is stored. Next, the routine proceeds to step S403, where the intake average pressure PMAV, which is processed in FIG. 3, is stored. Next, the routine proceeds to step S404, where a relation is evaluated, such that whether the intake average pressure PMAV, which is stored
in step S403, is equal to or less than a predetermined value e. In the case that the relation makes a positive determination in step S404, that is, that the intake average pressure PMAV is equal
to or less than the predetermined value e (i.e., the operation condition of the engine 1 is estimated in the vicinity of the idling rotation speed), the routine proceeds to step S405. The standard fuel injection amount TP is processed based on the engine rotation speed NE, which is stored in step S401, and the intake average pressure PMAV, which is stored in step S403, using the prestored map in ROM 32 in step S405. Subsequently, the routine is

terminated.
On the other hand, in the case that the relation makes a negative determination in step S404, that is, the intake average
pressure PMAV is greater than the predetermined value e ( the operation condition of the engine 1 is estimated away
pressure PMAV is greater than the predetermined value e (i.e.,
from the vicinity of the idling rotation speed), the routine proceeds to step S406. The standard fuel injection amount TP is processed based on the engine rotation speed NE, which is stored in step S401, and the intake bottom pressure PMB, which is stored in step S4 02, using the prestored map in ROM 32 in step S406. Subsequently, the routine is terminated. Various known kinds of compensation are performed to the standard fuel injection amount TP. Thus, the final fuel injection amount TAU is processed for supplying fuel from the injector 5 to the engine 1.
The engine controlling means is performed by the CPU 31 of the ECU 30 of the fuel injection control apparatus of the internal combustion engine in this embodiment. The engine controlling means processes the standard fuel injection amount TP using the second map stored in the ROM 32 and the first map stored in the ROM 32 as the load condition of the engine 1. The second map is used when the intake average pressure PMAV is equal to or less
than the predetermined value e, and the first map is used when the intake average pressure PMAV is greater than the predetermined
value e.
That is, the second map is used in a range where the load of the engine 1 is low (i.e., the intake average pressure PMAV
is equal to or less than the predetermined value e). The first

map is used in a range where the load of the engine 1 is medium and high (i.e., the intake average pressure PMAV is greater than
the predetermined value ej. The engine rotation speed NE and the intake average pressure PMAV are used as the parameters in the second map. The engine rotation speed NE and the intake bottom pressure PMB are used as the parameters in the first map. Thus, the standard fuel injection amount TP is processed for supplying fuel to the engine 1. The final fuel injection amount TAU can be precisely processed for supplying fuel to the engine 1 using the engine rotation speed NE and the intake pressure PM, such that the final fuel injection amount TAU is valid over the range where the load condition of the engine 1 varies. Thus, emissions can be decreased, and the drivability can be improved.
Next, the second variation of processing of the standard fuel injection amount TP is described based on the flow chart shown in FIG. 7. The routine is performed by the CPU 31 of the ECU 30, and used for the fuel injection control apparatus of the internal combustion engine according to one embodiment of the present invention. The standard fuel injection amount processing routine is repeatedly performed by the CPU 31 at a certain interval in every combustion cycle.
As shown in FIG. 7, the engine rotation speed NE is stored in step S501. Next, the routine proceeds to step S502, where the throttle opening degree TA is stored. Next, the routine proceeds to step S503, where the intake bottom pressure PMB is stored. The intake bottom pressure PMB is processed in FIG. 2. Next, the routine proceeds to step S504, where the intake average pressure

PMAV is stored. The intake average pressure PMAV is processed in FIG. 3. Next, the routine proceeds tostepS505, where a relation is evaluated, such that whether the throttle opening degree TA, which is stored in step S502, is equal to or less than a predetermined
value t,. In the case that the'relation makes a positive determination in step S505, that is the throttle opening degree
TA is equal to or less than the predetermined value ^ (i.e., the operation condition of the engine 1 is estimated in the vicinity of the idling rotation speed), the routine proceeds to step S506. The standard fuel injection amount TP is processed based on the engine rotation speed NE, which is stored in step S501, and the intake average pressure PMAV, which is stored in step S504, using the prestoredmap in ROM 32 in step S506. Subsequently, the routine is terminated.
Alternatively, in the case that the relation makes a negative determination in step S505, that is, the throttle opening degree
TA is greater than the predetermined value t, (i.e., the operation condition of the engine 1 is estimated away from the vicinity of the idling rotation speed), the routine proceeds to step S507. The standard fuel injection amount TP is processed based on the engine rotation speed NE, which is stored in step S501, and the intake bottom pressure PMB, which is stored in step S503, using the prestored map in ROM 3 2 in stepS507 . Subsequently, the routine is terminated. Various known kinds of compensation are performed for the standard fuel injection amount TP. Thus, the final fuel injection amount TAU is processed for supplying fuel from the injector 5 to the engine 1.

The fuel injection control apparatus of the internal
combustion engine has the throttle-opening sensor 21 as a throttle
opening degree detecting means for detecting the throttle opening
degree TA of the throttle valve 1, and the engine controlling means,
which is performed by the CPU 31 of the ECU 30, in this variation-
The engine controlling means processes the standard fuel injection
amount TP using the second map stored in the ROM 32 and the first
map stored in the ROM 32 as the load condition of the engine 1.
The second map is used when the throttle opening degree TA is equal
to or less than the predetermined value t,, and the first map is used when the throttle opening degree TA is greater than the
predetermined value ^.
That is, the second map is used in a range where the load
of the engine 1 is low (i.e., the throttle opening degree TA is
equal to or less than the predetermined value ^). The first map is used in a range where the load of the engine 1 is medium and
high (i.e., the throttle opening degree TA is greater than the
predetermined value t,). The engine rotation speed NE and the intake average pressure PMAV are used as the parameters in the second map. The engine rotation speed NE and the intake bottom pressure PMB are used as the parameters in the first map. Thus, the standard fuel injection amount TP is processed for supplying fuel to the engine 1. The final fuel injection amount TAU can be precisely processed for supplying fuel to the engine 1, using the engine rotation speed NE and the intake pressure PM, such that the final fuel injection amount TAU is valid over the range where the load condition of the engine 1 varies. Thus, emissions can be decreased,

and the drivability can be improved.
Next, the third variation of a processing of the standard fuel injection amount TP is described based on the flowchart shown in FIG. 8. The routine is performed by the CPU 31 of the ECU 30, and used for the fuel injection control apparatus of the internal combustion engine according to one embodiment of the present invention. The standard fuel injection amount processing routine is repeatedly performed by the CPU 31 at a certain interval in every combustion cycle.
As shown in FIG. 8, the engine rotation speed NE is stored in step S601. Next, the routine proceeds to step S602, where the intake bottom pressure PMB is stored. The intake bottom pressure PMB is processed in FIG. 2. Next, the routine proceeds to step S603, where the intake average pressure PMAV is stored. The intake average pressure PMAV is processed in FIG. 3. Next, the routine proceeds tostepS604, where the position of the idle SWis evaluated to be ON or not. In the case that the evaluation makes a positive determination in step S604, that is, the position of the idle SW is ON (i.e., the operation condition of the engine 1 is estimated in the idling rotation speed), the routine proceeds to step S605. The standard fuel injection amount TP is processed based on the engine rotation speed NE, which is stored in step S601, and the intake average pressure PMAV, which is stored in step S603, using the prestored map in ROM 32 in step S605. Subsequently, the routine is terminated.
On the other hand, in the case that the evaluation makes a negative determination in step S604, that is, the position of

the idle SW is OFF (i.e., the operation condition of the engine 1 is estimated away from the idling rotation speed), the routine proceeds to step S606. The standard fuel injection amount TP is processed based on the engine rotation speed NE, which is stored in step S601, and the intake bottom pressure PMB, which is stored in step S602, using the prestored map in ROM 32 in step S606. Subsequently, the routine is terminated. Various kinds of known compensation are performed for the standard fuel injection amount TP. Thus, the final fuel injection amount TAU is processed for supplying fuel from the injector 5 to the engine 1.
The fuel injection control apparatus of the internal combustion engine has the idle SW (not shown) as an idle detecting means for detecting a condition where the throttle valve 11 is near its fully closed state, and the engine controlling means, which is performed by the CPU 31 of the ECU 30, in this variation. The engine controlling means processes the standard fuel injection amount TP using the second map stored in the ROM 32 and the first map stored in the ROM 32 as the load condition of the engine 1. The second map is used when the position of the idle SW is ON (i.e., the throttle valve 11 is in the vicinity of the fully closed condition), and the first map is used when the position of the idle SW is OFF (i.e., the throttle valve 11 is not in the vicinity of the fully closed condition).
That is, the second map is used in a range where the load of the engine 1 is low (i.e., the position of the idle SW is ON). The first map is used in a range where the load of the engine 1 is medium and high (i.e., the position of the idle SW is OFF).

The engine rotation speed NE and the intake average pressure PMAV are used as the parameters in the second map. The engine rotation speed NE and the intake bottom pressure PMB are used as the parameters in the first map. Thus, the standard fuel injection amount TP is processed for supplying fuel to the engine 1. The final fuel injection amount TAU can be precisely processed for supplying fuel to the engine 1, using the engine rotation speed NE and the intake pressure PM, such that the final fuel injection amount TAU is valid over the range where the load condition of the engine 1 varies. Thus, emissions can be decreased, and the drivability can be improved•
Here, the above embodiments and the above variations are described in the case that the engine is the single-cylinder engine. However, the use of the present invention is not limited to that as described above. In the case that the engine is an individual, intake-type, multi-cylinder engine that intakes air individually into each cylinder, similar functions and effects can be expected. That is, variation of the intake pressure in every combustion cycle of the engine is apt to distinctly appear. Thus, the intake bottom pressure and the intake average pressure can be precisely processed.
Here, the above embodiments and the above variations are described in the case that the intake bottom pressure PMB is processed based on the intake pressure PM in or at a certain interval • However, the use of the present invention is not limited to that described above. The intake bottom pressure PMB can be processed every time the crank angle signal is generated from the crank angle

,
sensor 24. The intake bottom pressure PMB can be processed by providing a peak hold circuit in the ECU 30. Similarly/ various modifications and alternations may be made to the above embodiments without departing from the spirit of the present invention.

Claims:
1. A fuel injection control apparatus for an internal combustion engine, the fuel injection control apparatus comprising:
means for detecting rotation speed of the internal combustion engine;
means for detecting pressure of an intake passage, which is downstream of a throttle valve of the internal combustion engine;
means for processing intake bottom pressure, which is minimum intake pressure in every combustion cycle of the internal combustion engine;
means for processing intake average pressure, which is averaged pressure over a predetermined period in every combustion cycle of the internal combustion engine, the predetermined period includes at least a compression stroke or an expansion stroke;
means for storing a first map, which is used for processing an injection amount of fuel into the internal combustion engine, wherein the first map storing means uses the engine rotation speed and the intake bottom pressure as parameters of the first map;
means for storing a second map, which is used for processing the fuel injection amount into the internal combustion engine, wherein the second map storing means uses the engine rotation speed and the intake average pressure as parameters of the second map; and
means for controlling an operation condition of the internal combustion engine utilizing the fuel injection amount, which is processed based on one of the first map and the second map that

are switched in accordance with a load condition of the internal combustion engine.
2. A fuel injection control apparatus for an internal combustion engine according to claim 1, wherein
the engine controlling means processes the fuel injection amount utilizing the second map as a basis of the load condition of the internal combustion engine when the intake bottom pressure is equal to or less than a predetermined value, and the engine controlling means processes the fuel injection amount utilizing the first map as a basis of the load condition of the internal combustion engine when the intake bottom pressure is greater than the predetermined value.
3- A fuel injection control apparatus for an internal combustion engine according to claim 1, wherein
the engine controlling means processes the fuel injection amount utilizing the second map as a basis of the load condition of the internal combustion engine when the intake average pressure is equal to or less than a predetermined value, and the engine controlling means processes the fuel injection amount utilizing the first map as a basis of the load condition of the internal combustion engine when the intake average pressure is greater than the predetermined value.
4. A fuel injection control apparatus for an internal combustion engine according to claim 1, further comprising:

means for detecting a throttle opening degree, wherein the engine controlling means processes the fuel injection amount utilizing the second map as a basis of the load condition of the internal combustion engine when the throttle opening degree is equal to or less than a predetermined value, and the engine controlling means processes the fuel injection amount utilizing the first map as a basis of the load condition of the internal combustion engine when the throttle opening degree is greater than the predetermined value.
5. A fuel injection control apparatus for an internal combustion engine according to claim 1, further comprising:
means for detecting an idle condition in which the throttle valve is in the vicinity of a fully closed state, wherein
the internal combustion engine controlling means processes the fuel injection amount utilizing the second map as a basis of the load condition of the internal combustion engine when the idle detecting means detects a condition in which the throttle valve is in the vicinity of a fully closed condition, and the engine controlling means processes the fuel injection amount utilizing the first map as a basis of the load condition of the internal combustion engine when the idle detecting means detects a condition in which the throttle valve is out of the vicinity of a fully closed condition.
6. A fuel injection control apparatus for an internal combustion engine according to claim 1, wherein

the internal combustion engine has at least one cylinder that intakes air.

7. A fuel injection control apparatus substantially as herein described with reference to the accompanying drawings.

Documents:

1042-che-2003-abstract.pdf

1042-che-2003-claims duplicate.pdf

1042-che-2003-claims original.pdf

1042-che-2003-correspondence others.pdf

1042-che-2003-correspondence po.pdf

1042-che-2003-description complete duplicate.pdf

1042-che-2003-description complete original.pdf

1042-che-2003-drawings.pdf

1042-che-2003-form 1.pdf

1042-che-2003-form 26.pdf

1042-che-2003-form 3.pdf

1042-che-2003-form 5.pdf

1042-che-2003-other documents.pdf

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Patent Number

202963

Indian Patent Application Number

1042/CHE/2003

PG Journal Number

05/2007

Publication Date

02-Feb-2007

Grant Date

09-Nov-2006

Date of Filing

22-Dec-2003

Name of Patentee

M/S. DENSO CORPORATION

Applicant Address

1-1, SHOWA-CHO, KARIYA-CITY, AICHI-PERF 448-8661,

Inventors:

#	Inventor's Name	Inventor's Address
1	OKOCHI, YASUHIRO	C/O DENSO CORPORATION, 1-1, SHOWA-CHO, KARIYA-CITY, AICHI-PERF 448-8661,
2	KOBAYASHI, FUMIO	C/O DENSO CORPORATION, 1-1, SHOWA-CHO, KARIYA-CITY, AICHI-PERF 448-8661,
3	DOMYO, MASAHISA	C/O DENSO TRIM CO., LTD, 2460 AKASAKA OGOHARA, KOMONO-CHO, MIE-GUN, MIE-PREF., 510-1222,

PCT International Classification Number

F02D 41/36

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	2002-375255	2002-12-25	Japan
2	2003-363523	2003-10-23	Japan