Title of Invention

IGNITION DEVICE OF CAPACITOR CHARGING AND DISCHARGING TYPE

Abstract

An ignition device of the capacitor charging/ discharging type in which an engine is started only when an ignition key switch is operated. The ignition device includes a driving power source, a DC-DC converter, an ignition key switch, an ignition capacitor, a thyristor, an ignition coil, a pulser coil and a key switch operation detecting circuit. A second switch is provided in the ignition key switch so as to perform the off/on operation in an interlocking relation with the on/off operation of a first switch and a nonlinear element is also provided which is connected across terminals of the second switch and in which one end is connected to the output side of the first switch. The key switch operation detecting circuit includes first and second voltage detecting circuits for detecting a desired voltage developed across terminals of the nonlinear element and a smoothing circuit. The igniting operation is controlled by the voltage developed across the terminals of the nonlinear element Z1 when the ignition key switch is operated.

Full Text

- 1A- BACKGROUND OF THE INVENTION Field of the Invention The invention relates to an ignition device of a capacitor charging/discharging type in which an engine is started only when an ignition key switch for starting the engine of an automobile, a motor-bicycle, or the like is operated by the key. Description of the Related Art As a conventional ignition device of the capacitor charging/discharging type, for example, there are a device disclosed in JP-A-59-165864 and a device disclosed in JP-U-3-27881. A/The conventional device will now be described with reference to Fig. 1 showing a fundamental circuit construction of those devices. In Fig. 1, reference numeral 1 denotes a DC power source (battery); 2 an ignition key switch having a switch X to turn on/off the circuit between terminals A and B; and 3 a DC-DC converter constructed by a rectifying diode Dl, a smoothing capacitor C1, a transformer Tl, a switching transistor Ql, and a switching circuit 4 comprising a high frequency switching oscillator. Reference numeral 5 denotes an ignition coil; 6 a pulser coil for detecting a timing for ignition; D2 and D3 rectifying diodes; S1 a thyristor for ignition; - 2 - C2 a capacitor for ignition; 7 an overvoltage detecting circuit for detecting an overcharging when the capacitor C2 for ignition is overcharged; and 8 a control circuit for controlling a trigger operation of the thyristor S1 for ignition by signal of the pulser coil 6 and for controlling the operation of the switching circuit 4 on the basis of an output signal of the overvoltage detecting circuit 7. The circuit operates in a manner such that when the ignition key switch 2 is turned on to close the contact X, the DC power source 1 is connected to the DC-DC converter 3 through the terminals A and B, the switching circuit 4 is made active by the control circuit 8, the switching transistor Ql is allowed to perform the switching operation, and the capacitor C2 for ignition is charged through the transformer Tl. When the capacitor C2 for ignition reaches a specified voltage by the charging, the overvoltage detecting circuit 7 operates, thereby stopping the operation of the switching transistor Ql via the control circuit 8. When the engine subsequently starts to rotate, an ignition signal is input from the pulser coil 6 to the control circuit 8, the thyristor S1 for ignition is triggered, and an energy in the capacitor C2 for ignition is discharged to the ignition coil 5, thereby igniting the engine. However, according to the conventional ignition device of the capacitor charging/discharging - 3 – type, by closing (ON state) the contact X by the ON operation of the ignition key switch 2, the engine can be started. Therefore, particularly in a motor-bicycle among automobiles, the number of wirings around the engine is small and the wirings can be easily changed, so that by directly connecting a circuit between the connection wires arranged across the terminals A and B of the ignition key switch 2 by using another electric wire, the same state as the ON state of the contact X of the ignition key switch 2 can be obtained. SUMMARY OF THE INVENTION The present invention is made to solve the above drawbacks and intends to provide an ignition device of the capacitor charging/discharging type in which an engine is not started even if a circuit between the terminals A and B of an ignition key switch is connected by using another connection wire. More particularly, the invention provides an ignition device of the capacitor charging/discharging type which can certainly accomplish its function even when a driving power source of an engine uses an AC generator in addition to a DC power source. According to the invention, there is provided an ignition device comprising: a power source including a DC power source and/or a generator; a DC voltage generating circuit for generating a DC voltage in accordance with a control signal when an electric power - 4 – is supplied from the power source; a capacitor for charging or discharging an output voltage of the DC voltage generating circuit; an ignition coil for performing an igniting operation by a discharge current of the capacitor; an ignition key switch including a first switch for turning on/off a connection between the power source and the DC voltage generating circuit and a second switch for performing the on/off operation in an interlocking relation with the on/off operation of the first switch; an impedance element which has first and second terminals connected respectively to two terminals of the second switch and in which the second terminal is connected to a connecting point between the first switch and the DC voltage generating circuit; voltage detecting means for detecting voltages at the first and second terminals of the impedance element and for generating an output signal on the basis of the voltage detected; and control means for controlling the operation of the DC voltage generating circuit and/or the discharge of the capacitor on the basis of an output signal of the voltage detecting means. According to the above construction, the voltages across the terminals of the impedance element which are detected at the times of the ON operation of the first switch and the OFF operation of the second switch by the operation of the ignition key switch are detected and the igniting operation of the engine is controlled, so that only when the ignition key switch is - 5 - merely short-circuited, the engine cannot be started. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Fig. 1 is a circuit diagram showing an example of a conventional ignition device; Fig. 2 is a circuit diagram of an ignition device according to an embodiment of the invention; Fig. 3A is a circuit diagram showing an inactive state of an ignition key switch included in the ignition device of Fig. 2; Fig. 3B is a circuit diagram showing an active state of an ignition key switch included in the ignition device of Fig. 2; Fig. 4 is a diagram showing a signal waveform in each portion in a key switch operation detecting circuit in case of using an AC generator as a power source in the ignition device of the invention; Fig. 5 is a diagram showing the operation in case of forcibly short-circuiting or releasing the ignition key switch in the ignition device of the invention; Figs. 6A and 6B are circuit diagrams showing other examples of nonlinear elements which can be used in the ignition key switch in the ignition device of the invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 2 shows a circuit according to an - 6 – embodiment of the invention and the same component elements as those in the circuit diagram of the conventional device shown in Fig. 1 are designated by the same reference numerals and their descriptions are omitted. In Fig. 2, reference numeral 11 denotes an AC generator having coils L1 and L2 of the generator. The AC generator 11 has a function for supplying an electric power as a driving power source to the ignition device in place of the DC power source 1 or charging the DC power source 1 and, further, lighting on a lamp 12. Reference numeral 13 denotes a control unit for supplying an electric power for each of the foregoing applications . Reference numeral 14 denotes an ignition key switch. In addition to a switch X between the terminals A and B, a switch Y for performing the operation opposite to the ON/OFF operation of the switch X is provided between terminals C and D. A Zener diode Zl is provided as an impedance element, preferably, a nonlinear element between the terminals C and D. A cathode side of the Zener diode Zl is connected to the terminal B on the output side of the ignition key switch 14. As shown in Figs. 3A and 3B, both of the operations of the switches X and Y of the ignition key switch 14 are switched by an ignition key (not shown) in an interlocking relation such that when the ignition key switch 14 is OFF (Fig. 3A), the switch X is turned off and the switch Y is turned ON and, when the ignition key switch 14 is ON (Fig. 3B), the switch X is ON and the switch Y is OFF. - 7 - Therefore, when the ignition key switch 14 is turned off, the Zener diode Zl provided between the terminals C and D is short-circuited. When the ignition key switch 14 is turned on, the short circuit is released and the Zener diode Zl is connected to the circuit between the terminal B and a Z terminal. Reference numeral 15 denotes a key switch operation detecting circuit for checking whether or not the ignition key switch 14 normally operates as shown in Fig. 3B. The detecting circuit 15 is made up of a first voltage detecting circuit 16, a second voltage detecting circuit 17, and a smoothing circuit 18. By turning on the ignition key switch 14, the switch X is turned on to close the circuit across the terminals A and B. When the switch Y is turned off to open the circuit across the terminals C and D, the key switch operation detecting circuit 15 is made active, thereby allowing the control circuit 8 to operate by an output of the key switch operation detecting circuit 15. A Zener diode Z2 of the second voltage detecting circuit 17 is a protecting circuit for protecting each element of the key switch operation detecting circuit 15 from a high voltage when an AC half wave voltage is input in so called a battery open state in which the AC generator is connected as a power voltage. First, the operation in the ON state of the ignition key switch 14 shown in Fig. 3B will be described. By the ON operation of the ignition key - 8 – switch 14, a voltage VB is applied to a BAT terminal (power source terminal) of the second voltage detecting circuit 17 of the key switch operation detecting circuit 15 through the DC power source 1 or AC generator 11 and a voltage Vz is applied to the Z terminal {detecting terminal) of the first voltage detecting circuit 16 through the terminal A of the switch X - terminal B -Zener diode Zl - terminal D of the switch Y. As for the voltage at the BAT terminal, the voltage VB is applied to an emitter terminal of a transistor Q2 through a resistor Rl. The voltage at the Z terminal turns on a transistor Q3 through a resistor R5 and is applied to a resistor R3. Thus, a collector voltage of the transistor R3 is almost equal to the voltage Vz at the Z terminal. Therefore, so long as a condition of (VB > Vz) due to a voltage drop of the Zener diode Zl is satisfied, the transistor Q2 is turned on and a capacitor C5 is charged through a resistor R6. When the capacitor C5 has a voltage of a predetermined level, a transistor Q4 is turned on and issues a permission of an igniting operation to the control circuit 8. This state corresponds to a result in which it is determined that the ignition key switch 14 normally operates. Next, the operation of the key switch operation detecting circuit 15 in the case where the DC power source 1 is open, the ignition key switch 14 is in the normal operating state, and the AC half wave voltage of - 9 – the output of the AC generator 11 is applied to the BAT terminal (power source terminal) and the Z terminal (detecting terminal) will now be described with reference to an operating waveform diagram of Fig. 4. The AC half wave voltage of Fig. 4 (a) is applied to the BAT terminal and the 2 terminal. The AC half wave voltage is smoothed as shown in Fig. 4 (b) by the capacitor C1 and is supplied as a power source of the ignition device. In the AC half wave voltage waveform at the Z terminal, the voltage is lower by a level of AVZ1 corresponding to a voltage drop by the Zener diode Zl than the AC half wave voltage waveform at the BAT terminal and is as shown in Fig. 4 (a). The voltage applied to the BAT terminal is clamped by the Zener diode Z2 for protecting an input overvoltage of the second voltage detecting circuit 17 in the battery open state when it is equal to or higher than a predetermined voltage, for example, 30V. After that, each input voltage is held for a predetermined time by capacitors C3 and C4 of the second and first voltage detecting circuits 17 and 16. They are shown in Fig. 4 (c). In a state in which the AC half wave voltage of the AC generator 11 is higher than the foregoing predetermined voltage and is clamped by the Zener diode Z2, namely, for an interval during which a current is flowing in the Zener diode Z2, the transistor Q2 is inversely biased, so that the transistor Q2 never operates. The other operations are similar to those - 10 – when the DC power source 1 exists. As shown in Fig. 4 (d), as for those timings, when the AC half wave voltage rises, a period of time during which the transistor Q2 operates, namely, a period of time during which a potential difference between the capacitors C3 and C4 corresponds to the voltage drop of the Zener diode Zl is equal to an extremely short time tl. However, when the AC half wave voltage trails, since each input voltage waveform of the capacitors C3 and C4 (preferably, a capacitance value of C4 > a capacitance value of C3) is held for a predetermined time, a period of time during which the transistor Q2 operates is equal to a long period t2 and the charging and smoothing operations of the capacitor C5 are executed at timings shown in Fig. 4 (e). Therefore, even when the AC half wave voltage is input, the transistor Q4 does not perform an unstable operation. That is, at this time point, as a smoothed voltage VC5 keeps a voltage that is equal to or higher than a threshold level at which the transistor Q4 can operate. The subsequent operation is similar to that in the case where the DC power source 1 exists. Consequently, even in the battery open state, the stable operation can be performed in a manner similar to the case where the DC power source 1 is used. A phenomenon that the ignition device does not operate even if somebody tries to start the ignition device by forcibly short-circuiting the ignition key - 11 - switch 14 from the external terminal by a wire or the like or by releasing it in a state where the ignition key switch 14 is not operated (state of Fig. 3A) will now be described with reference to Fig, 5. A state of No. 1 in Fig. 5 shows a case where the ignition key switch 14 is normally operated as mentioned above. An emitter voltage of the transistor Q2 is equal to VB and a collector voltage of the transistor Q3 is equal to (VB - Vz) . Therefore, a voltage of the capacitor C5 is equal to V0N of a predetermined value or more, the transistor Q4 is turned on, a start signal is output to the control circuit 8, and the ignition device can be made operative. A state of No. 2 in Fig. 5 relates to the case where the circuit across the terminals A and D is short-circuited by a wire or the like. In this case, since the Zener diode Zl is short-circuited by the switch X, both voltages at the BAT terminal and the Z terminal are the same potential VB, so that the emitter voltage of the transistor Q2 and the collector voltage of the transistor Q3 are also the same potential and the transistor Q2 is not turned on. Thus, no voltage is applied to the capacitor C5 and no start signal is transmitted from the key switch operation detecting circuit 15 to the control circuit 8, so that the ignition device is not started. A state of No. 3 in Fig. 5 relates to the case where the circuit across the terminals A and B is short- _ 12 – circuited. In this case as well, in a manner similar to the case of No, 2 mentioned, above, the voltages at the BAT terminal and the Z terminal are the same potential VB and the ignition device is not started. A state of No. 4 in Fig. 5 relates to the case where the circuit across the terminals B and D is short-circuited by a wire or the like. In this case, since the voltage from the DC power source 1 or AC generator 11 is not applied, the voltages at the BAT terminal and the Z terminal are equal to the zero potential and the ignition device is not started. A state of No. 5 in Fig. 5 relates to the case where the circuit across the terminals A and D and the circuit between the terminals A and B are short-circuited by wires or the like. In this case as well, in a manner similar to the cases of Nos. 2 and 3 mentioned above, the voltages at the BAT terminal and the z terminal are set to the same potential VB and the ignition device is not started. A state of No. 6 in Fig. 5 relates to the case where the circuit across the terminals A and D and the circuit between the terminals B and D are short-circuited by wires or the like. In this case as well, in a manner similar to the case of No. 2 mentioned above, the voltages at the BAT terminal and the Z terminal are set to the same potential V8 and the ignition device is not started. A state of No. 7 in Fig. 5 relates to the case - 13 – where the circuit across the terminals A and D is short-circuited and the BAT terminal is opened. In this case as well, in a manner similar to the case of No. 2 mentioned above, the voltages at the BAT terminal and the Z terminal are set to the same potential VB and the ignition device is not started. A state of No. 8 in Fig. 5 relates to the case where the circuit across the terminals A and B is short-circuited and the Z terminal is opened. In this case as well, in a manner similar to the case of No. 2 mentioned above, the voltages at the BAT terminal and the Z terminal are set to the same potential VB and the ignition device is not started. In each of states of Nos. 9 to 12 in Fig. 5, in a manner similar to the case of No. 4, since the voltage from the DC power source 1 or AC generator 11 is not applied, the voltages at the BAT terminal and the Z terminal are equal to the zero potential and the ignition device is not started. In the foregoing embodiment shown in Fig. 2, although the Zener diode Zl has been used as a nonlinear element provided in the ignition key switch 14, similar function and effect can be also derived even if a transistor Q5 or a diodes Za to 2c other than the Zener diode is used as shown in Fig. 6A or 6B. As mentioned above, according to the invention, even when the driving power source of the ignition device is any one of the DC power source 1 and/or the AC - 14 – generator 11, so long as the ignition key switch 14 is normally operated and the switch X is turned on and the switch Y is turned off, the potential difference across the terminals of the nonlinear element provided in the ignition key switch 14 is detected by the key switch operation detecting circuit 15 constructed by the first voltage detecting circuit 16, second voltage detecting circuit 17, and smoothing circuit 18, thereby starting the igniting circuit. It is extremely difficult to start the igniting circuit by short-circuiting the circuit across the terminals of the ignition key switch 14, by connecting each terminal to the ground, or the like. In other words, in a state where the operating characteristics of the nonlinear element built in the ignition key switch 14 are not known, the igniting circuit cannot be started. The characteristics of the nonlinear element largely differ when a parameter such as a voltage to be applied or the like changes and it is remarkably difficult to know its operating characteristics . According to the invention as described in detail above, even when the driving power source of the ignition device is the DC power source or AC generator, the engine is started in a state where the ignition key switch 14 is normally operated. However, it is fairly difficult to start the engine by a method of short-circuiting or opening the circuit across the external terminals of the ignition key switch or the like. -15- WE CLAIM 1. An ignition device comprising: a power source comprising one of a DC power source (1) and a generator (11); a DC voltage generating circuit (3, D2) for generating a DC voltage in accordance with a control signal when an electric power is supplied from said power source; a capacitor (C2) for charging or discharging an output voltage of said DC voltage generating circuit; an ignition coil (5) for performing an igniting operation by a discharge current of said capacitor; an ignition key switch (14) having a first switch (X) for turning on/off a connection between said-power source and said DC voltage generating circuit, characterized in that: - a second switch (Y) is provided for performing the off/on operation in an interlocking relation with the on/off operation of said first switch; an impedance element (Zl1 having first and second terminals (Z, BAT) is connected respectively to two terminals (D,C) of said second switch (Y), said second terminal (BAT) being connected to a connecting point between said first switch (X) and said DC voltage generating circuit; - voltage detecting means (15) is arranged for detecting voltages at the first and second terminals of said impedance element (Zl) and for generating an output signal on the basis of the detected voltage; and - control means (8) is disposed for controlling one of operation of said DC voltage generating circuit and discharge of a capacitor (CI) on the basis of an output signal of said voltage detecting means. 2. A device as claimed in claim 1, wherein said control means comprises a thyristor (SI) for discharging electric charge in said capacitor (CI) on the basis of an output signal of a pulser coil (6). -16- 3. A device as claimed in claim 1 or 2, wherein said impedance element (Z comprises a nonlinear element. 4. A device as claimed in any one of claims 1 to 3, wherein said voltag detecting means (15) comprises : a first voltage detecting circuit (16) having a first holding capacitor (C4 for holding a voltage at said first terminal (Z) of said impedance elemen (Zl) when said voltage has an AC half wave form and a first transistor (Q3) which operates when the voltage at said first terminal is equal to c higher than a predetermined voltage; a second voltage detecting circuit (17) having a Zener diode (Z2) for clamping a voltage at said second terminal (BAD) of said impedance element (Zl) to a predetermined voltage when said voltage has an AC half wave form, a second holding capacitor (C3) for holding said clamping voltage, and a second transistor (Q2) which operates when the voltage a said first terminal (Z) is lower than the voltage at said second terminal (BAT) substantially by a voltage drop due to said impedance element (Zl); and a smoothing circuit (18) having a smoothing capacitor (C5) for smoothing an output voltage of said second voltage detecting circuit (17) when said output voltage has a pulsating wave form and a third transistor (Q4) which operates in accordance with the smoothed voltage. 5. A device as claimed in claim 4, wherein said second transistor (Q2) of said second voltage detecting circuit (17) is made operative in response to a trailing edge of said AC half wave form so as to charge said smoothing capacitor (C5). An ignition device of the capacitor charging/ discharging type in which an engine is started only when an ignition key switch is operated. The ignition device includes a driving power source, a DC-DC converter, an ignition key switch, an ignition capacitor, a thyristor, an ignition coil, a pulser coil and a key switch operation detecting circuit. A second switch is provided in the ignition key switch so as to perform the off/on operation in an interlocking relation with the on/off operation of a first switch and a nonlinear element is also provided which is connected across terminals of the second switch and in which one end is connected to the output side of the first switch. The key switch operation detecting circuit includes first and second voltage detecting circuits for detecting a desired voltage developed across terminals of the nonlinear element and a smoothing circuit. The igniting operation is controlled by the voltage developed across the terminals of the nonlinear element Z1 when the ignition key switch is operated.

Documents:

02304-cal-1997-abstract.pdf

02304-cal-1997-assignment.pdf

02304-cal-1997-claims.pdf

02304-cal-1997-correspondence.pdf

02304-cal-1997-description(complete).pdf

02304-cal-1997-drawings.pdf

02304-cal-1997-form-1.pdf

02304-cal-1997-form-2.pdf

02304-cal-1997-form-3.pdf

02304-cal-1997-form-5.pdf

02304-cal-1997-p.a.pdf

02304-cal-1997-priority document others.pdf

02304-cal-1997-priority document.pdf

2304-CAL-1997-ASSIGNMENT 1.1.pdf

2304-CAL-1997-CORRESPONDENCE 1.1.pdf

2304-CAL-1997-FORM 16.pdf

2304-cal-1997-granted-abstract.pdf

2304-cal-1997-granted-claims.pdf

2304-cal-1997-granted-correspondence.pdf

2304-cal-1997-granted-description (complete).pdf

2304-cal-1997-granted-drawings.pdf

2304-cal-1997-granted-examination report.pdf

2304-cal-1997-granted-form 1.pdf

2304-cal-1997-granted-form 2.pdf

2304-cal-1997-granted-form 3.pdf

2304-cal-1997-granted-form 5.pdf

2304-cal-1997-granted-letter patent.pdf

2304-cal-1997-granted-pa.pdf

2304-cal-1997-granted-priority document.pdf

2304-cal-1997-granted-reply to examination report.pdf

2304-cal-1997-granted-specification.pdf

2304-cal-1997-granted-translated copy of priority document.pdf