Title of Invention

LOAD DEPENDENT ADVANCE-RETARD TIMING MECHANISM IN CASE OF IN-LINE FUEL INJECTION PUMP

Abstract

The invention relates to a fuel injection pump mechanism, wherein the fuel timing and fuel quantity are controlled. The distance travelled by plunger from BDC to port closure i.e. the pre-stroke is varied by varying the top land of plunger surface, such that input port dose not close at the same plunger height. The top land plunger surface grooves thereby determine the LLA and LLR. The other sloping groove (Helix) connected to output port varies the end of injection depending on CRP. Any change in CRP 'causes change in delivery quantity,. hence load and also the change in pre-stroke due to presence of grooves on top land surface.

Full Text

Field Of Invention The Diesel engine technology has made great progress on the way qf continuous improvement to reduce the key pollutants from on-road, off-road and stationary diesel engines. Diesel engine has some environmental advantages over other type of engines, and is more fuel efficient. The pollutants like Hydrocarbons(HC), carbon monoxide (CO) and carbon dioxide (C02)are very less in amount in diesel engines. Only challenge is to reduce Particulate matter (PM) and oxides of nitrogen (NOx). Now diesel technology has reduced 83% of particulate matter and 63% of NOx generation from diesel engine since 1988 by various phases of development. For optimizing the engine performance, fuel has to be injected at very high pressure for complete burning. Also begin of injection and injection duration has to be achieved up to desired level under different operating conditions. All these requirements can be achieved with the help of modem fuel injection equipment. This will help engine manufacturer to optimize engine emission performance with optimum SFC and power, and without much modifications on engine. By retarding the injection timing, we can retard the process of combustion. NOx formation occurs later, so concentration of peak temperatures and NOx are lesser. At higher loads with higher temperature and higher peak pressures, the process forms larger regions that are close to stoichiometric burned gases. Also non-uniform fuel distribution causes NOx formation. NOx emissions are more or less proportional to the mass of fuel injected in controlled conditions. A number of techniques are available for control of emissions. But most of them are more complex and expensive. Light Load retard (LLRl feature is very simple and less expensive. In recent days static timing of engine is retarded to achieve NOx emission, and this retardation results in start of injection at no load getting closer to Top Dead Centre. With increasing speed, start of injection at no-load even goes beyond Top Dead Centre. However, this retardation causes unstable combustion at cold conditions resulting in misfiring and white smoke when engine is accelerated immediately after starting. This white smoke and misfiring tendency can be improved by using features like LLA 8& LLR on element, and also by increasing compression ratio of engine. Light load advance (LLA) element, which advances timing at lower part loads, is now used in many tractor/Vehicular engines to over come the no load misfiring and white smoke problem at cold conditions. The element with LLA advances the dynamic timing only at light loads, without significantiy affecting NOx Emission. It is possible to overcome problem of part load NOx without changing the static timing at full-load, by LLR feature which retards the d3niainic timing only at part loads. This results in reducing combustion temperature and therefore NOx. For heavy and medium range of engines percentage of NOx emission reduction will be higher. In this case static timing retardation as well as part load retardation is required. So problem of bluish white puff and misfiring at cold condition can exist, because of static timing retardation with lesser compression ratio. Combination of Light load advance and part load retard (LLA-LLR) feature is desired for optimum results. Prior Art Currently LLA and LLR are two separate features and are used separately for light load advance and part load retard applications. So far emission norms were not stringent, and the existing features serve the purpose. But the emerging scenario is different, and therefore the need for a fuel injection pump with advance and retard features being simultaneously present. Disadvantages Of The Prior Art 1. With LLA, generation of NOx at light loads is high. 2. With LLR, incidence of white puff or misfiring is high. Objects of the current Invention; In no load conditions, the quantity of fuel injected is required to just overcome friction and keep the engine running. In this invention, as shown in Fig-4, this is accomplished by appropriately designing the grooves to yield this result. The resultant engine embodying and the fuel system with this invention operates noticeably more efficiently between zero fuel to full load operation. Besides the improved fuel economy, exhaust emissions are also reduced. Description of Invention with reference to Drawings Fig 1 illustrates the grooves of a typical LLA, LLR arrangement simultaneously existing in the same plunger. Groove depth defines the extent of advance and retard of timing. Fig 2 illustrates the Plunger-stroke phases in a complete injection cycle on the developed view of plunger, (1) Bottom Dead Center (BDC) (2) Pre-stroke. (3) Retraction Stroke. (4) Effective Stroke. (5) Residual Stroke. (6) Top Dead Center (TDC) Control rack(ll) is connected to control lever as illustrated in Fig-3 through governor linkage and also to accelerator pedal. Pump element and control rack are in contact with each other by means of a rack and pinion arrangement. Control collar (Pinion) is mounted on plunger of element, which helps in metering the desired quantity at desired speed 3. As per the prior art, a plunger(9) which is housed in the barrel(7) is in contact with the cam through some intermediate components. During an intake process the cam disc when driven by the drive shaft causes the plunger to reciprocate within the barrel in the vertical direction, plunger reciprocates in one direction, fuel flows into a compression space that is enclosed in the barrel(7) and plunger(9) via intake port(8). Further during subsequent movement of plunger, a helix formed on plunger will communicate with the output port to create a drop in fuel pressure which causes the end of fuel delivery and end of injection. Effective stroke controls the delivery by determining the end of injection as illustrated in Fig-2. Typically this is achieved by a sloping groove (Helix), which varies the end of injection depending on the Control Rack Position (CRP). Altering the CRP causes change in delivery quantity (and hence load) as well as change in the pre-stroke due to presence of groove. During upward movement of the plunger, as shown in 'T of fig. 2, the fuel flows from the pump chamber into a compression space in the barrel above the plunger via the intake port of the barrel (in the direction of arrow). As the plunger moves further up, as in '2' of fig. 2, the fuel entrapped in the barrel is delinked from the intake port of the barrel and starts to get pressurized. In this condition the flat plunger top seals off the inlet port. As the plunger continues to move further up as in '3' of fig-2 the fuel pressure builds up further causing the delivery valve (which is on top of the plunger and barrel assembly ) to open against the opposing force of the valve spring. The conunued upward motion of the plunger drastically rises the fuel pressure and causes the fuel to be injected at very high pressure inside the combustion chamber overcoming the nozzle spring force. As the plunger continues to move up, the high pressure fuel finds an easy path through the plunger helix back into the fuel gallery through the inlet port (see arrow in " 51. This causes the fuel pressure on top of the plunger to drop drastically and results in "end of injection" as the nozzle needle now sits back on the nozzle seat arresting the injection of fuel into the combustion chamber. It is to be understood that although the plunger now continues to move upwards as in '6', the fuel above the plunger is no longer pressurized since the intake port of the barrel which is at low pressure is linked to the high pressure" chamber on top of the plunger by the helix and the vertical groove on the plunger. To sum up, injection of fuel commences shortly after the plunger top during the upward motion, seals off the inlet port of the barrel and ends as soon as the helix uncovers the inlet port. Therefore the effective fuel delivered is dependent on the distRnce traveled by the plunger between these two sections. Although the begin of injection is kept the same, depending on when the plunger helix uncovers the inlet port, the end of injection can be varied by causing a different portion of the helix to make contact with the inlet port. This is accomplished by rotating the plunger with respect to the barrel depending on the volume of fuel delivery required. This is shown in fig 3. where the control rack '11' which governs the rotation of the plunger causes the end of injection to be delayed and therefore causes a higher volume of fuel to be injected. As described above it is noted that until now the beginning of the delivery is constant only the ending of the delivery is variable. The main piirpose of this invention is to have a variable beginning of the injection alongwith the controlled quantity of the fuel injected. This has been achieved in this invention by creating additional grooves on the top land of the plunger. Due to these grooves the intake port does not close at the same plunger height which leads to varying beginning of delivery so as to achieve the advance and retardation of the injection. Fig 5 shows a few details alongwith the nomenclature explained on the developed view of the plunger. In all the subsequent figures for the sake of ease of explanation, contrary to actual condition, the plunger is shown stationary, while the barrel intake port is shown in different positions with respect to plunger. A simple LLA arrangement as known in prior art will have grooves on full load region and a simple LLR arrangement will have groove on Light Load region. A simple LLR arrangement as known in prior art will have grooves on Light Load region which causes beginning of delivery to be delayed at Light Load while the Full Load continues to operate at normal timing. A simple LLA arrangement as known in prior art will have grooves on Full Load region which causes beginning of delivery to be delayed at Full Load while the Light Load continues to operate at normal timing. However in this invention, plunger has two grooves, one short groove and one long groove as in Fig 4. Keeping the reference as full load timing, the invention achieves a retard in certain portions/regions of Light Load i.e., LLR effect is achieved. However in certain other portions/regions of Light Load although the timing continues to be normal timing , with respect to Full Load timing, the timing in these regions is advanced i.e., LLA effect is achieved. The main characteristic feature of the invention is the combination of LLA and LLR feature in the same element. Fig-4: illustrates the plunger(9) as per the invention showing the grooves on the surface of the body which controls the quantity of the fuel and also the grooves on the top land of the plunger(9) which controls the advance or the retardation of the injection. It illustrates a first set of grooves and second groove (10) which determines the beginning and end of fuel delivery, thereby achieving the effect of LLA and LLR. Fig 5 shows the development view of plunger, on which various parameters of the element are illustrated -top of plunger, bottom helix full and light load regions, barrel inlet ports, begin and end of delivery corresponding to different load regions of the plunger, and finally the effective stroke. Begin of delivery is the point on the upward motion of plunger, at which the plunger top covers the inlet port of barrel causing the pressurization of fuel entrapped at the top of plunger. The distance traveled by the plunger from the bottom dead centre point to the begin of delivery point is called the pre-stroke. Joining the delivery begin point at all load regions you arrive at a horizontal line which is offset with respect to top of plunger by a distance of half the inlet port diameter. End of delivery is the point at which the bottom helix of plunger uncovers the inlet port causing the fuel pressure drop above the plunger and hence causing the end of delivery. This line is again offset with respect to helix by half the port diameter. The distance traveled by the plunger between the begin of delivery and end of delivery points is called the effective stroke. Effective stoke together with the cross-sectional area of the plunger determines the amount of fuel delivered. The different load regions - full load(13), light loads(14) etc., on the element have different delivery requirements. To vary the volume of fuel delivered we only need to alter the effective stroke, by varying the slope and position of the helix. Any groove on the top of the plunger causes the begin of delivery (prestroke) to be delayed/ retarded, because the plunger has to travel a farther distance for the inlet port to be covered. This ultimately causes a change in timing of injection. Fig 6 shows a simple LLR arrangement where a groove is made only on the light load region of the plunger. This causes the begin of delivery (PS) to be delayed / retarded when the plunger is operating at the light load region. Considering reference point as full load region, we say that the timing is retarded at light load region(14) with respect to full load region(13). Hence the name Light Load Retardation - LLR Fig 7 shows a simple LLA arrangement where a groove is made only on the full load region and NOT on the light load region. This groove causes the beginning of delivery to be delayed at the full load region(13) only, while the light load region continues to operate at normal timing. However, once again considering the full load region as reference, we can say that the timing is advanced at light load region(14) "with respect to full load region". Hence the name light load Advance - LLA. All timing features are usually named keeping the full load timing as the reference timing. Fig 8 shows an execution of plunger where two grooves are present - one short groove similar to LLR groove and other longer one similar to LLA groove simultaneously on the same plunger. Here full load timing is retarded compared to normal timing. But keeping reference point as full load timing, we can say that timing at Light Load timing region 1 is retarded or LLR effect is visible. Coming to Light load region 2, although the timing continues to be normal timing, with respect to full load timing the Light load timing at region 2 is advanced.. Hence LLA effect is also seen. The unique feature of the invention is the combination of LLA and LLR features on the same element to give selected timing at different load points. Need for Load Dependeiit Advance-Retard Timing Mechanism In Case Of In-Line Fuel Injection Pump : The invention attempts to achieve the combination of two features on a single element i.e. advance and retard of timing. This will serve the purpose of meeting for small and medium range of engines with In-Line FIP. At certain higher load condition, production of NOx is high, therefore by retarding the timing we can reduce the NOx. But at lower loads, retardation of timing will lead to problems of high smoke and puffing which will result in higher particulate matter. So, it is essential to balance the advance and retard of timing, in order to thereby the balance on NOx and particulate matter. Combination of advance and retard feature in element is therefore desirable. It is always most generally desirable to have injection timing retarded during start up but during the warm-up period and thereafter it is desirable that fuel injection timing be advanced in proportion to speed increase. This increases the time between end of injection and start of combustion. Depending on the extent of advance or retard required, the grooves are positioned on the plunger at the appropriate place to get a combination of load and required timing. In this invention the plunger not only has the control edge helix with the groove or controlling the quantity of the fuel injected as known in the prior art, it is specially novel and characterized in that it has upper grooves on the top land surface by which the beginning of the effective stroke varies as the plunger is rotated due to the fact that the top edge which closes the inlet port is no more flat but is grooved. The plunger has two sets of grooves as herein described above to achieve both a variable beginning and the variable end of the delivery of the fuel. The plunger allows the control of the start of the injection as per requirement by providing both advance and retard at part loads which is hitherto unknown to be operable from the same plunger, which plunger controls the quantity of the fuel injected by varying the end of the fuel delivery. The advantages of this inventions are: 1. No misfiring or white smoke problem at low loads. 2. Controlled formation of NOx emission at light loads. 3. Improved SFC. 4. Better emission, which all have been achieved in this invention in a very cost effective and in a simple manner. We Claim; L A fuel injector with a load dependent advanced and retard timing mechanism of the internal combustion engine comprising a moveable grooved plunger(9) rotatable and reciprocable in a plunger barrel(7), having formed thereon a chamber with the vertical groove (12a) and a control helix (12b) edge communicating with the said vertical groove, said control helix inclined with the respect to the plunger axis, the intersection of the control helix edge with the output port determining the end of the pumping stroke for the plunger and thereby the quantity of the fuel pump, the supply range of the said control helix edge being adapted for full load to no load idle engine operation, means for reciprocating and rotating the plunger to vary the effective stroke, and the said plunger characterized in having a set of two grooves(lO) one short and one long groove on the top land, the intersection of any of the said two the grooves with the intake port determining the beginning of the effective pumping of the plunger(9) over the range of engine operation from full load to no load idle, wherein the said control edge helix controls the quantity of the fuel injected and the end of the injection, and wherein the said grooves on the top land of the plunger advances or retards the beginning of the injections. 2. A fuel injector as claimed in claim-1, wherein the control mechanism comprising of fuel metering control and injection timing control with a single plunger with a set of two grooves. 3. A fuel injector as claimed in claim-1, wherein plunger of the fuel injector having grooves to control the quantity of the fuel injector and to control the advance and retardation of the injection, first groove shorter than the second groove.

Documents:

0720-che-2003-abstract.pdf

0720-che-2003-claims.pdf

0720-che-2003-correspondnece-others.pdf

0720-che-2003-correspondnece-po.pdf

0720-che-2003-description(complete).pdf

0720-che-2003-description(provisional).pdf

0720-che-2003-drawings.pdf

0720-che-2003-form 1.pdf

0720-che-2003-form 26.pdf

0720-che-2003-form 3.pdf

0720-che-2003-form 4.pdf

0720-che-2003-form 5.pdf