JPH0544543Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a capacitor discharge type ignition device for a multi-cylinder internal combustion engine.

[Prior Art] A capacitor discharge type ignition device for a multi-cylinder internal combustion engine has electrical continuity between a capacitor charging power supply coil and a capacitor that is provided on the primary side of the ignition coil and is charged by the output of the power supply coil through a diode. A plurality of ignition circuits each having a thyristor are provided so as to discharge the charge of the capacitor through the primary coil of the ignition coil when the ignition occurs, and each of the plurality of ignition circuits ignites a different cylinder.

Figure 4 shows the configuration of one ignition circuit used in a conventional capacitor discharge type ignition system for a multi-cylinder internal combustion engine. In the figure, B is a battery, D _O is a diode, T1 is a transformer, Q1 is a transistor whose collector-emitter circuit is connected in series to the primary coil W11 of the transformer T1, and the output of the battery B is connected to the series circuit of the transformer's primary coil W11 and the transistor Q1 through the diode D _O. Applied to both ends. DC-AC converts the output voltage of battery B into AC voltage using transistor T1 and transistor Q1
Converter circuit DA1 is configured, and transformer T1
The secondary coil W21 is used as a power supply coil for charging the capacitor.

Further, IC1 is an ignition coil, C1 is a capacitor provided on the primary side of the ignition coil and charged from a power supply coil W21 through a diode D11, and S1
is a thyristor provided to discharge the charge of capacitor C1 through the primary coil of the ignition coil when it is conductive, D21 is a diode connected in parallel to the primary coil of the ignition coil, and P1 is a thyristor connected to the cylinder of the engine. The spark plug is installed and connected to the secondary coil of the ignition coil. Thyristor S
A trigger signal is applied to the ignition timing of the internal combustion engine from an ignition timing control circuit (not shown) to the gate No. 1.

When igniting a multi-cylinder internal combustion engine, a plurality of the above ignition circuits are provided. For example, when igniting a two-cylinder internal combustion engine, two ignition circuits each consisting of the converter circuit DA1, diodes D11, D21, ignition coil IC1, capacitor C1, and thyristor S1 are provided, and two of the ignition coils of each ignition circuit are provided. Spark plugs from different cylinders are connected to the next side.

In the ignition circuit shown in Fig. 4, transistor _Q1 is turned on and off in synchronization with the output of an oscillation circuit (not shown) that oscillates at a predetermined frequency (for example, 20KH _Z ), and each time this transistor changes from a conductive state to a cutoff state. The capacitor C1 is charged to the illustrated polarity through the diodes D11 and D21 with a positive voltage induced in the power supply coil W21 (a voltage in which the terminal side of the coil W21 connected to the diode D11 has positive polarity). Then, at the ignition timing of the internal combustion engine, a trigger signal is applied to the thyristor S1 from an ignition timing control circuit (not shown) to make the thyristor conductive, and the charge in the capacitor C1 is discharged through the thyristor S1 and the primary coil of the ignition coil.
This discharge causes a large change in magnetic flux within the ignition coil, inducing a high voltage in the secondary coil of the ignition coil, and producing a spark in the spark plug P1.

[Problem to be solved by the invention] In the ignition circuit shown in Fig. 4, the power supply coil W21
When the polarity of the induced voltage changes from positive to negative, the reverse breakdown voltages of diodes D11 and D21 do not recover immediately, and it takes a predetermined recovery time for the reverse breakdown voltages of these diodes to recover. I need. Therefore diodes D11 and D2
1 is connected to diodes D11 and D during the recovery time after the polarity of the output voltage of the transformer changes from positive to negative.
21 maintains the conductive state, and the power supply coil W21→
Diode D21 and ignition coil primary coil →
A reverse current flows through the path of capacitor C1 → diode D11 → power supply coil W21. After the diode recovery time elapses, the diode D1
1 and D21 rapidly recover the reverse breakdown voltage, the reverse current is suddenly cut off, and this sudden current change generates a large back electromotive force in the power supply coil W21. Therefore, a high voltage, which is the sum of this back electromotive force and the voltage across the capacitor C1, is applied to the diode D11, posing the problem that an expensive high-voltage element must be used as the diode D11.

Further, there was a risk that the back electromotive force caused by the recovery of the diode would become noise and cause the ignition timing control circuit to malfunction.

In order to solve the above problem, as shown in FIG. 5, the transformer T1 is provided with a control coil W3 having the opposite polarity to the primary coil W11,
3 is connected in series to the primary coil W11, and a diode D3 is connected between the terminal of the control coil W3 on the opposite side of the primary coil and the ground, thereby suppressing the back electromotive force generated in the power supply coil W21 due to the recovery of the diode D11. Circuits for controlling power have been proposed. However, in this case, the problem arises that the structure of the transformer becomes complicated and the cost increases.

It has also been proposed to connect a resistor R1 in parallel with the power supply coil W21 to suppress the back electromotive force as shown in Figure 6, but in this case, the resistor R1 is a large and expensive This requires a resistor, which raises the problem of increased cost and increased size of the device.

Furthermore, as shown in FIG. 7, a circuit has been proposed in which a diode D4 is connected to both ends of the power supply coil W21, and the back electromotive force is short-circuited by the diode D4. However, in this case, diode D4
Due to the reaction caused by the current flowing through the power supply coil W21, the positive voltage induced in the power supply coil W21 decreases,
There was a problem that the charging voltage of the capacitor C1 decreased.

The purpose of the present invention is to connect a power supply coil for charging a capacitor to a capacitor that is provided on the primary side of the ignition coil and is charged through a rectifying diode using the output of the power supply coil, and when electrical conduction occurs, the electric charge of the capacitor is transferred to the ignition coil. In an ignition system for a multi-cylinder internal combustion engine that is equipped with multiple ignition circuits equipped with a thyristor installed to discharge electricity through the next coil, it is difficult to complicate the configuration, use a high-power resistor, or charge a capacitor. The purpose is to suppress the generation of back electromotive force due to diode recovery without reducing the voltage.

[Means for Solving the Problems] In the present invention, in order to achieve the above object, the diode side terminals of the capacitor charging power supply coils of a plurality of ignition circuits are coupled to each other through an inter-circuit coupling resistor.

[Operation] The back electromotive force caused by the recovery of the rectifier diode for charging the capacitor becomes high when a large current flows through the diode, that is, when the capacitor is being charged. Generally, in an ignition system for a multi-cylinder internal combustion engine, the ignition timing of each ignition circuit (timing when the thyristor conducts) and the charging timing of the capacitor are different, and at each time, the back electromotive force generated by diode recovery in multiple ignition circuits is generated. are different in size. Therefore, as mentioned above,
By connecting the diode-side terminals of the power coils of multiple ignition circuits through an inter-circuit coupling resistor, when an electromotive force is generated in the power coil of each ignition circuit due to recovery of the diode, the circuit between the power coils will be disconnected. The induced voltage in each power supply coil can be lowered by passing a current through the coupling resistor.

Therefore, the voltage applied to the rectifier diode can be lowered, and an inexpensive diode with a low withstand voltage can be used.

Furthermore, since current flows through the inter-circuit coupling resistor only when there is a voltage difference between the power coils of the plurality of ignition circuits, power loss in the resistor is small. Therefore, there is no need to use an expensive high-power resistance as an inter-circuit coupling resistor.

[Embodiments] Examples of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an embodiment of the present invention, in which T1 and T2 are the primary coil W1, respectively.
1 and W12 and secondary coils W21 and W22, and one ends of the secondary coils W21 and W22 are grounded. In each of Q1 and Q2, the collector-emitter circuit is connected to the primary coils W11 and W22 of the transformers T1 and T2, respectively. This is a transistor connected in series to W12, and the emitters of transistors Q1 and Q2 are grounded. The DA converter circuit DA1 is configured by the transformer T1 and the transistor Q1.
Also, by transformer T2 and transistor Q2
Each DA converter circuit DA2 is configured,
The output of battery B is input to these converter circuits via diode D _O and switch SW.

A rectangular wave signal of a predetermined frequency is input from the oscillation circuit OS to the bases of the transistors Q1 and Q2.
Each transistor is conductive while the base current is applied to transistors Q1 and Q2 by the rectangular wave signal. During the period when transistors Q1 and Q2 are conducting, primary coils W1 of transformers T1 and T2
A current flows through W1 and W12. When the rectangular wave signal output from the oscillation circuit OS falls and the base current supply to the transistors Q1 and Q2 is stopped, each transistor is cut off and the transformers T1 and T
A polar voltage is induced in the primary coil of No. 2 that causes the current that had been flowing until then to continue to flow. This voltage is stepped up and high voltages are induced in the secondary coils W21 and W22 of the transformers T1 and T2, respectively.

The secondary voltages of transformers T1 and T2 are in opposite phase to the primary voltage, and transistors Q1 and Q2
The moment transformers T1 and T2 are cut off, respectively,
A voltage of a polarity in the direction of the arrow shown in each of the secondary coils (the potential of the non-grounded side terminal of the secondary coil has a positive polarity with respect to the ground) is induced.

The non-grounded terminal of the secondary coil (capacitor charging power supply coil) W21 of the transformer T1 is connected to one end of the capacitor C1 via a diode D11 with its anode facing the secondary coil, and the other end of the capacitor C1 is It is connected to one end of the primary coil of the ignition coil IC1. Ignition coil CI1-1
The other end of the primary coil is grounded, and a diode D21 with its cathode facing the ground is connected to both ends of the primary coil. Capacitor C1 and diode D
The anode of the thyristor S1 is connected to the connection point with the thyristor S1, and the cathode of the thyristor is grounded. A spark plug P1 attached to a cylinder of an engine (not shown) is connected to the secondary coil of the ignition coil IC1. A protective resistor R11 is connected to both ends of the thyristor S1. Power coil W
21, diode D11, capacitor C1, ignition coil C1, diode D11, thyristor S
1. The resistor R11 and the spark plug P1 constitute a first ignition circuit IG1 that ignites the first cylinder.

Similarly, on the DA converter circuit DA2 side, the secondary coil (power supply coil) W22 of the transformer T2,
Diode D12, capacitor C2, ignition coil
IC2, diode D22, thyristor S2, resistor R12, and spark plug P2 constitute a second ignition circuit IG2 that ignites the second cylinder.

In the present invention, the non-grounded terminals of the power supply coils W21 and W22 are coupled to each other via an inter-circuit coupling resistor Rc having a relatively small resistance value.

The operating waveforms of this embodiment are shown in FIGS. 2A to 2D. FIGS. 2A and 2B show temporal changes in the voltages Vc2 and Vd2 across the capacitor C2 and diode 12 of the second ignition circuit IG1, respectively, and FIGS.
The voltages Vc1 and Vd1 across the capacitor C1 and diode D11 of IG1 are shown. Figure 2B
In and D, the broken line waveform shows the case where the resistor Rc is not provided, and the solid line waveform shows the case where the resistor Rc is provided.

In this embodiment, the first and second ignition circuits
Capacitors C1 and C2 of IG1 and IGI are charged through diodes D11 and D12 by the output voltages of power supply coils W21 and W22, respectively.

In addition, in Fig. 2 A and C, capacitor C2
The voltages Vc2 and Vc1 across the capacitor C1 and C1 are shown in a smoothly rising waveform.
1 and C2 are charged by the voltage intermittently generated in the secondary coils of the transformers T1 and T2 each time the transistors Q1 and Q2 turn from the on state to the off state, so when viewed microscopically, the capacitors C1 and C2 The terminal voltage of will have a waveform that increases stepwise.

Capacitors C1 and C2 are thyristors S1 and S2
Even when the capacitor C is in the cut-off state, a small amount of discharge occurs through the resistors R11 and R12, so the capacitor C
1 and C2 continue to be charged until the ignition timing. That is, in the capacitor terminal voltage waveforms of FIGS. 2A and 2C, even in the region that appears to be saturated, the capacitors C1 and C2 are actually being charged.

A trigger signal is applied to the thyristors S1 and S2 from an ignition timing control circuit (not shown) to the ignition timing of the first and second cylinders, respectively. Thyristor S
When 1 and S2 are conductive, the charges in capacitors C1 and C2 are transferred to thyristors S1 and S2 and ignition coil IC1,
It is discharged through the primary coil of IC2, and an ignition operation is performed.

In FIG. 2, section A indicates a section where capacitors C1 and C2 of the first and second ignition circuits have both been fully charged and no ignition operation is performed in any of the ignition circuits, and section B indicates the section where the capacitors C1 and C2 of the first and second ignition circuits are both completed and no ignition operation is performed in any of the ignition circuits. The section in which the thyristor S1 of the first ignition circuit is conductive is shown. Further, section C indicates a section where capacitor C1 is charged after thyristor S1 is cut off (section until thyristor S2 of the second ignition circuit becomes conductive), and section D indicates a section where thyristor S2 of the second ignition circuit is charged.
indicates the section where conduction occurs. Furthermore, section E indicates a section where capacitor C2 is charged after thyristor S2 is cut off.

In the state where the charging of the capacitors of the first ignition circuit and the second ignition circuit is completed and before the ignition operation of both ignition circuits is performed (section A in Figure 2), the terminal voltage Vc1 of capacitor C1 and the terminal voltage Vc2 of capacitor C2 are at approximately the same level, so almost no current flows through resistor Rc.
In addition, in this section, the charging of the capacitors C1 and C2 is almost completed, so the diode D11
The current flowing through D11 and D12 is small. Therefore, in this section, a large counter electromotive force is not generated in the power coils W21 and W22 due to the recovery of the diodes D11 and D12.

Next, in section B where the thyristor S1 of the first ignition circuit is conductive, the positive direction output of the power supply coil W22 (output with the polarity in the direction of the arrow in the figure) causes the power supply coil W22→resistance Rc→diode D
A current flows through the path 11→thyristor S1→power coil W22. Therefore, at this time, the positive direction output of the power supply coil W22 decreases due to the voltage versus current characteristic of the transformer T2. In this embodiment, the inter-circuit coupling resistor Rc is designed to flow the current necessary to make the positive voltage of the power supply coil W22 lower than the terminal voltage of the capacitor C2, which has already received power.
It is desirable to set a resistance value of . If the voltage across the power supply coil W22 is set to be lower than the terminal voltage of the capacitor C2 in this way, no current will flow from the power supply coil W22 through the diode D12.
The generation of back electromotive force due to the recovery of No. 12 can be eliminated.

Further, when the power supply coil W22 generates a negative direction output, the power supply coil W22 → the power supply coil W21
A current flows through the path of →resistance Rc →power coil W22. Therefore, due to the voltage versus current characteristic of the transformer T2, the voltage across the power supply coil W22 becomes low, and the voltage applied to the diode D12 becomes low.

Next, in section C, thyristor S1 shuts off and charging of capacitor C1 starts;
Since Vc2>Vc1, when transformer T2 generates a positive output, power coil W22 → resistor
The path of Rc→power coil W21→power coil W22, the path of power coil W22→resistance Rc→power coil W21→power coil W22, and the path of power coil W22→resistor Rc→diode D11 capacitor C1→diode D21→power coil W22 A current flows, and almost no current flows through the diode D12. Therefore, the problem of generation of back electromotive force due to recovery of diode D12 does not occur. On the other hand, since the diode D11 is energized, a back electromotive force is generated in the power supply coils W21 and W22 due to the recovery of the diode D11, but at this time, the back electromotive force induced in the power supply coil W21 is more induced in the secondary coil W22. Since it is higher than the back electromotive force, the current flows from power coil W21 → power coil W22 → resistor
It flows through the path from Rc to power coil W21. Therefore, due to the voltage vs. current characteristics of the transformer T1, the voltage across the power supply coil W21 decreases, causing the diode D11 to drop.
The applied voltage to decreases. That is, power coil W2
1 and W22 due to diode recovery, the back electromotive force of each power supply coil is suppressed by the current flowing through the inter-circuit coupling resistor Rc due to the difference in the back electromotive force induced in both power supply coils.

Next, in section D, since the thyristor S2 is conductive, a current flows in the path of the power coil W21→resistance R1→diode D2→thyristor S2→power coil W21 due to the positive direction output of the power supply coil W21. As a result, the output voltage of the power supply coil W21 becomes lower than the terminal voltage of the capacitor C2, so that no current flows through the diode D11. Therefore, due to the recovery of the diode D11, the secondary coil W21
No back electromotive force is induced. Moreover, at this time, power supply coil W21 → power supply coil W22 → resistance
Since a current flows through the path from Rc to power supply coil W21, the voltage across both ends of power supply coil W21 decreases, and the voltage applied to diode D11 decreases.

Next, in section E, thyristor S2 shuts off and charging of capacitor C2 starts;
Since Vc1>Vc2, when transformer T1 generates a positive output, the current flows from power supply coil W21→
Resistor Rc → Power coil W22 → Power coil W21
Path and power supply coil W21 → Resistor Rc → Diode D12 → Capacitor C2 → Diode D22
→Flows through the path of power supply coil W21 and diode D
In most cases, no current flows through 11. Therefore, almost no back electromotive force is generated in the power supply coil W21 due to the recovery of the diode D11.
The voltage applied to diode D11 decreases.

At this time, since the diode D12 is energized, a back electromotive force is generated in the power supply coil W22 due to the recovery of the diode D12, but at this time, the voltage across the power supply coil W22 is higher than that of the power supply coil W2.
1, the current flows through the path of power coil W22→power coil W21→resistance Rc→power coil W21. Therefore, transformer T2
Due to the voltage versus current characteristic of , the output voltage of power supply coil W22 decreases, and the voltage applied to diode D2 decreases.

As described above, when the power supply coils W21 and W22 are coupled by the inter-circuit coupling resistor Rc, the voltage induced in the power supply coil can be suppressed by recovery of the diode.

The power supply coil W2 is used for the above inter-circuit coupling resistor Rc.
Since power is applied only when there is a difference between the terminal voltages of terminals 1 and W22, power loss in the resistor can be reduced compared to the case where resistors are connected to both ends of the power supply coil as shown in FIG. Therefore, it is not necessary to use a high-power resistor as the resistor Rc, and an inexpensive resistor can be used.

In the above embodiment, the secondary coil of the transformer of the DC-AC converter circuit was used as the power source coil for charging the capacitor, but as shown in FIG. The present invention can be applied in exactly the same way when used as a coil. Even when the exciter coils L1 and L2 are used as power supply coils, the voltage across the exciter coils L1 and L2 is in the negative direction at the time when the current has finished charging the capacitors C1 and C2, so the diodes D11 and D12 A reverse current flows through the coils L1 and L2, and a high voltage is induced in the coils L1 and L2 due to the recovery of both diodes. By connecting the resistor Rc as shown, it is possible to suppress the electromotive force induced in the coils L1 and L2 by recovery of the diodes D11 and D12.

[Effect of the invention] As described above, according to the invention, by connecting the diode side terminals of the power coils of the plurality of ignition circuits through the inter-circuit coupling resistor, the diode can be connected to the power coils of the plurality of ignition circuits. When an electromotive force is generated due to recovery, current is passed between the power supply coils through the inter-circuit coupling resistor to reduce the induced voltage in each power supply coil, making it possible to lower the voltage applied to the rectifier diode. I can do it,
There is an advantage that an inexpensive diode with a low breakdown voltage can be used.

In addition, current flows through the inter-circuit coupling resistor only when there is a voltage difference between the power coils of multiple ignition circuits, so the power loss in the resistor is small, and the inter-circuit coupling resistor There is no need to use one for high power.

Therefore, according to the present invention, there is an advantage that the electromotive force due to recovery of the diode can be suppressed and malfunction of the ignition circuit can be prevented without using expensive elements.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is an operation waveform diagram of the embodiment of Fig. 1, Fig. 3 is a circuit diagram showing another embodiment of the invention, and Figs. FIG. 7 is a circuit diagram showing different conventional examples. B...Battery, D _O ...Diode, T1,
T2...Transformer, W11, W12...Primary coil, W21, W22...Secondary coil (power supply coil), D11, D12...Rectifier diode, C
1, C2... Capacitor, IC1, IC2... Ignition coil, P1, P2... Spark plug, OS... Oscillator circuit, L1, L2... Exciter coil, Rc
...Resistance for coupling between circuits.

Claims (1)

[Claims for Utility Model Registration] A power supply coil for charging a capacitor; a capacitor provided on the primary side of an ignition coil and charged by the output of the power supply coil through a rectifying diode;
An ignition device for a multi-cylinder internal combustion engine comprising a plurality of ignition circuits each including a thyristor provided to discharge the electric charge of the capacitor through the primary coil of the ignition coil when conductive, the plurality of ignition circuits An ignition device for a multi-cylinder internal combustion engine, characterized in that terminals on the diode side of the capacitor charging power supply coil are coupled to each other through an inter-circuit coupling resistor.