JP3178361B2 - Capacitor discharge type ignition device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitor discharge ignition system for an internal combustion engine.

[0002]

2. Description of the Related Art As is well known, a capacitor discharge type ignition device for an internal combustion engine is provided with an exciter coil provided in a magnet generator driven by the internal combustion engine, an ignition coil, and a primary side of the ignition coil. The ignition energy storage capacitor, which is charged to one polarity by the output of the positive half cycle of the exciter coil, conducts when an ignition signal is given, and discharges the charge stored in the capacitor through the primary coil of the ignition coil. An ignition circuit having a discharge switch provided as described above, and an ignition signal generating unit that provides an ignition signal to the discharge switch at the ignition timing of the internal combustion engine, and a capacitor is provided when the ignition signal is given. By discharging the accumulated charge through the discharge switch and the primary coil of the ignition coil, the secondary coil of the ignition coil is charged with a high ignition voltage. And it is adapted to induce a pressure.
Since the high voltage for ignition is applied to a spark plug attached to a cylinder of the engine, a spark is generated at the spark plug and the engine is ignited.

[0003] In this type of ignition device, the output voltage of the exciter coil increases as the engine speed [rpm] increases, so that the output voltage of the exciter coil is allowed to increase. In addition, the voltage applied from the exciter coil to the ignition circuit during high-speed rotation of the engine increases, and it is necessary to use an expensive capacitor or switch having a high withstand voltage as the capacitor or the discharge switch.

For this reason, an ignition device of this type is often provided with an exciter voltage limiting circuit for limiting the voltage across the exciter coil so that an excessive voltage is not applied to the ignition circuit when the engine is running at high speed.

An exciter voltage limiting circuit conventionally used in a capacitor discharge ignition system for an internal combustion engine divides a voltage Ve across the exciter coil by a predetermined voltage dividing ratio n to correspond to the voltage Ve across the exciter coil. An exciter voltage detecting unit for outputting a voltage detection signal Vs (= n × Ve) having a predetermined magnitude, and conducting when the magnitude of the voltage detection signal reaches a set value to output an output of a positive half cycle of the exciter coil. And an exciter short-circuiting switch for short-circuiting. When the voltage across the exciter coil is lower than the set value, the output voltage of the exciter coil is directly applied to the ignition circuit because the exciter short-circuiting switch is in the cut-off state.

[0006]

Generally, in an internal combustion engine, when starting the engine at a low temperature, an ignition spark having a large energy is required. Since the spark energy is determined by the charging voltage of the capacitor for storing the ignition energy, it is necessary to charge the capacitor to a higher voltage in order to increase the spark energy.

However, in the conventional ignition system for a capacitor discharge type internal combustion engine, the voltage applied to the ignition circuit from the exciter coil is limited in the same manner as when the engine is hot, even when the temperature of the engine is low. When starting the engine at a low temperature, the spark energy could not be increased. Therefore, when a conventional capacitor discharge type internal combustion engine ignition device having an exciter voltage limiting circuit is used, the startability of the engine may be deteriorated when the engine is used in a cold region.

An object of the present invention is to improve the startability of an engine by increasing the voltage applied from an exciter coil to an ignition circuit to increase the energy of an ignition spark when the temperature of the internal combustion engine is low. To provide an ignition device for a capacitor discharge type internal combustion engine capable of preventing an excessive voltage applied from an exciter coil to an ignition circuit in a state where the temperature of the engine becomes high after the engine is started. It is in.

[0009]

SUMMARY OF THE INVENTION The present invention comprises an exciter coil provided in a magnet generator driven by an internal combustion engine, an ignition coil, and a positive half cycle of the exciter coil provided on a primary side of the ignition coil. An ignition circuit comprising: a capacitor charged to one polarity at the output of the switch; and a discharge switch provided to conduct when an ignition signal is supplied and to discharge the charge accumulated in the capacitor through the primary coil of the ignition coil. An ignition signal generating unit for providing an ignition signal to a discharge switch at the time of ignition of the internal combustion engine; and a voltage corresponding to the voltage Ve across the exciter coil by dividing the voltage Ve across the exciter coil by a predetermined voltage division ratio n. Exciter voltage detecting section for outputting a voltage detection signal Vs (= n × Ve), and conducting when the magnitude of the voltage detection signal reaches a set value. Those related to the ignition apparatus for capacitor discharge type internal combustion engine having a switch exciter short for short-circuiting the positive half cycle output of Kisaitakoiru.

In the present specification, of the half cycle of one polarity and the half cycle of the other polarity of the AC voltage induced in the exciter coil, the half cycle used for charging the capacitor of the ignition circuit is defined as a positive cycle. Half cycle.

According to the present invention, the exciter voltage detector detects the temperature of the internal combustion engine so as to decrease the voltage division ratio n when the temperature of the internal combustion engine is low and to increase the voltage division ratio n when the temperature of the internal combustion engine is high. It is configured to change the partial pressure ratio n accordingly.

With this configuration, the magnitude of the voltage detection signal corresponding to the same output voltage of the exciter coil decreases when the temperature of the engine is low, and increases when the temperature of the engine increases, so that the temperature of the engine decreases. Sometimes, the exciter short-circuit switch does not conduct unless the output voltage of the exciter coil becomes higher than when the temperature of the engine is high.
Therefore, when the temperature of the engine is low, the voltage applied to the ignition circuit from the exciter coil is set higher than when the temperature of the engine is high, and the capacitor can be charged to a higher voltage than when the temperature of the engine is high. The energy of the spark can be increased.

In practicing the present invention, the voltage dividing ratio n when the temperature of the engine is low is determined by the peak value of the output voltage of the exciter coil when the magnitude of the voltage detection signal reaches a set value.
It is set so as to be equal to or slightly larger than the magnitude corresponding to the charging voltage of the capacitor required at low temperatures.

The voltage dividing ratio n when the temperature of the engine is high is obtained by applying the peak value of the output voltage of the exciter coil when the voltage detection signal reaches a set value to the ignition circuit, as in the prior art. Set to be equal to the voltage limit.

As described above, according to the present invention, when the temperature of the engine is low, the charging energy of the capacitor can be increased and the ignition energy can be increased, so that the ignition performance in a state where the temperature of the engine is low is improved. As a result, the startability of the engine can be improved, and the start of the engine in a cold region can be facilitated.

Further, when the temperature of the engine increases after the engine is started, the voltage division ratio of the exciter voltage detecting section increases, so that the voltage applied from the exciter coil to the ignition circuit does not become excessive as in the prior art. Can be restricted as follows.

The exciter voltage detector comprises a series circuit of first and second resistor branches connected to both ends of the exciter coil, and the first resistor branch has a temperature-sensitive element having a negative temperature coefficient. It can be constituted by a resistance voltage dividing circuit including a resistance element and generating a voltage detection signal at both ends of the second resistance branch.

The above-mentioned exciter voltage detecting section also comprises a series circuit of first and second resistance branches connected to both ends of the exciter coil, and the second resistance branch has a positive temperature coefficient. It can also be constituted by a resistance voltage dividing circuit including a temperature resistance element and generating a voltage detection signal at both ends of the second resistance branch.

In the case where the temperature-sensitive resistance element is provided in a part of the resistance voltage dividing circuit as described above, the resistance value of the temperature-sensitive resistance element changes continuously with the change of the temperature. In order to continuously change the pressure ratio, the limit value of the voltage applied from the exciter coil to the ignition circuit changes continuously, and the high voltage for ignition obtained on the secondary side of the ignition coil is As the temperature rises, the temperature continuously decreases and converges to a certain limit value.

The exciter voltage detecting section may further include a resistor voltage dividing circuit for dividing a voltage between both ends of the exciter coil, and switch means connected in series or parallel to some resistors constituting the resistor voltage dividing circuit. A voltage dividing ratio switching circuit for switching a voltage dividing ratio of a resistance voltage dividing circuit by an on / off operation of the switch means, a temperature sensor for detecting a temperature of the internal combustion engine, and a resistor when the temperature detected by the temperature sensor is lower than a set value. The voltage dividing ratio of the voltage dividing circuit is set to a first value, and when the temperature detected by the temperature sensor is equal to or higher than a set value, the voltage dividing ratio is set to a second value larger than the first value. It can also be constituted by switch control means for controlling the switch means.

When the voltage detection circuit is configured as described above,
When the temperature of the engine reaches the set value, the peak value of the voltage applied from the exciter coil to the ignition circuit decreases stepwise, and when the temperature of the engine reaches the set value, the secondary voltage of the ignition coil decreases. The voltage obtained on the side will drop stepwise.

As described above, a temperature sensor for detecting the temperature of the internal combustion engine is provided instead of connecting the temperature-sensitive resistance element to a part of the resistance voltage dividing circuit, and the temperature sensor is provided in accordance with the temperature detected by the temperature sensor. If the partial pressure ratio is switched, the temperature of the engine can be detected more accurately, so that the control of the spark energy according to the temperature of the engine can be performed more accurately.

[0023]

FIG. 1 shows an example of the configuration of an ignition device for a capacitor discharge type internal combustion engine according to the present invention.
In the figure, 1 is an ignition circuit, 2 is an exciter coil,
Reference numeral 3 denotes an ignition signal generator, and reference numeral 4 denotes an exciter voltage limiting circuit. The ignition circuit 1 includes: an ignition coil 101 having one end of a primary coil 101a and a secondary coil 101b grounded; an ignition energy storage capacitor 102 having one end connected to a non-grounded terminal of the primary coil 101a of the ignition coil; A thyristor 103 having a cathode connected to the ground side between the other end of the capacitor 102 and ground;
2 and a diode 1 having a cathode connected to the other end of the primary coil 101a of the ignition coil and a cathode connected to the ground.
05, and a resistor 106 and a capacitor 107 connected in parallel between the gate and cathode of the thyristor 103 to prevent false triggering of the thyristor 103 due to noise. The non-ground side terminal of the secondary coil 101b of the ignition coil 101 is connected to a spark plug 1 attached to a cylinder of the engine.
08 is connected through a high-voltage cord to the non-ground side terminal. In this example, the thyristor 103 forms a discharge switch.

The exciter coil 2 is provided on the stator side of a magnet generator having a rotor mounted on the output shaft of the internal combustion engine, and outputs an AC voltage in synchronization with the rotation of the engine. One end of the exciter coil 2 is grounded, and the other end is connected to the anode of the diode 104.

The ignition signal generating section 3 is a section for giving an ignition signal Vi to the gate of the thyristor 103 constituting a discharge switch at the time of ignition of the internal combustion engine. This ignition signal generating section 3 is a signal normally attached to the internal combustion engine. The rotation angle information of the engine is obtained from a signal output by the generator at a predetermined rotation angle position, and an ignition signal (a thyristor trigger signal) is given to the gate of the thyristor 103 at the ignition timing of the engine. The ignition signal generating unit 3 may be configured to provide the output of the signal generator to the thyristor 103 as an ignition signal directly or through a waveform shaping circuit or the like, or to obtain rotation angle information obtained from the output signal of the signal generator. In some cases, the ignition timing is determined by performing a predetermined calculation using the rotation speed information and the ignition signal is supplied to the thyristor 103 at the determined ignition timing.

The exciter voltage limiting circuit 4 divides the voltage Ve at both ends of the exciter coil 2 by a predetermined voltage dividing ratio n to generate a voltage detection signal Vs (= n × Ve) having a magnitude corresponding to the voltage Ve at both ends of the exciter coil. ), And an exciter short-circuit switch 402 that conducts when the voltage detection signal Vs reaches a set value and short-circuits the output of the positive half cycle of the exciter coil.

The exciter voltage detecting section 401 includes a resistor R having one end connected to a non-ground side terminal of the exciter coil 2.
1, a resistor R2 having one end connected to the other end of the resistor R1,
It comprises a resistor R3 connected between the other end of the resistor R2 and the ground, and a temperature-sensitive resistance element Rt1 connected in parallel to both ends of the resistor R2. In this exciter voltage detecting section, a first resistor branch of a resistor voltage dividing circuit is constituted by the resistors R1 and R2 and the temperature-sensitive resistor Rt1, and a second resistor of the resistor voltage dividing circuit is constituted by a resistor R3. A branch is formed. The exciter voltage detector 401 divides the voltage (output voltage) Ve across the exciter coil 2 by a predetermined voltage division ratio n,
A voltage detection signal Vs (= n × Ve) is generated at both ends of the resistor R3. Here, the resistance values of the first resistance branch (resistances R1, R2
If the combined resistance value of R2 and Rt1) is r1 and the resistance value of the second resistor branch (resistance value of resistor R3) is r2, the voltage division ratio n
Is given by r2 / (r1 + r2).

Since the ignition device is usually arranged near the internal combustion engine, the temperature-sensitive resistance element Rt1 changes its resistance value under the influence of the temperature of the engine. In this example, since a temperature-sensitive resistance element Rt1 having a negative temperature coefficient whose resistance value decreases as the temperature rises is used, when the temperature of the engine rises, the first resistance of the resistance voltage dividing circuit is increased. Resistance r of the branch
1 decreases and the partial pressure ratio n increases. Therefore, when the voltage Ve at both ends of the exciter coil is constant, the voltage detection signal Vs obtained at both ends of the resistor R3 (second resistor branch) of the resistor voltage dividing circuit rises as the engine temperature rises. And
It decreases as the temperature decreases.

As shown in FIG. 1, the first resistor branch of the resistor voltage dividing circuit constituting the exciter voltage detecting section 401 is constituted by a plurality of resistors R1 and R2, and a temperature-sensitive resistor element is partially provided. If they are connected in parallel, the resistors R1 and R2
By adjusting the resistance value, the temperature characteristic of the resistance value of the first resistance branch of the resistance voltage dividing circuit can be finely adjusted, so that the range of selection of the temperature-sensitive resistance element Rt1 can be expanded. . However, in this case, the first of the resistance voltage dividing circuits
The resistance value of the entire resistance branch may be decreased as the temperature rises. Therefore, if a temperature-sensitive resistance element Rt1 having an appropriate resistance value can be obtained, the first resistance element Rt1 may be used. The branch may be constituted only by the temperature-sensitive resistance element Rt1. When the circuit is configured as shown in FIG. 1, the resistor R2 may be omitted depending on the characteristics of the temperature-sensitive resistance element Rt1.

In the present invention, when the temperature of the engine is low, the magnitude of the voltage detection signal is reduced with respect to the output voltage Ve of the same exciter coil, and the magnitude of the voltage detection signal increases as the temperature rises. Therefore, instead of providing the temperature-sensitive resistance element Rt1 having a negative temperature coefficient in the first resistance branch of the resistance voltage dividing circuit, as shown by a broken line in FIG. The second resistance branch of the voltage circuit may be provided with a temperature-sensitive resistance element Rt2 having a positive temperature coefficient whose resistance increases with an increase in temperature. In this case, the temperature-sensitive resistor Rt2 may be connected in parallel to the resistor R3 as shown in the figure, or may be connected in series to the resistor R3.

The exciter short-circuiting switch 402 comprises a thyristor Th connected to both ends of the exciter coil 2 with the cathode facing the ground, and a resistor R4 and a capacitor between the gate and cathode of the thyristor Th for preventing false triggering. C1 are connected in parallel. Thyristor T
The gate of h is connected to the non-ground side terminal of the resistor R3 (the output terminal of the exciter voltage detection unit 401) through a Zener diode ZD1 whose anode is directed to the thyristor Th side.

In the exciter voltage limiting circuit 4, when the voltage detection signal Vs obtained from the exciter voltage detecting section 401 reaches the Zener voltage of the Zener diode ZD1, the thyristor Th conducts and the positive half cycle of the exciter coil 2 becomes active. Short the output voltage. Therefore, the maximum value of the voltage applied from the exciter coil 2 to the ignition circuit 1 depends on whether the voltage detection signal Vs is equal to the Zener diode ZD1.
Is limited to the peak value of the output voltage of the exciter coil when the Zener voltage (set value) is reached.

In the ignition device shown in FIG. 1, the exciter coil 2 → the diode 104 → the capacitor 102 →
Primary coil 101a of diode 105 and ignition coil
→ By the circuit of the exciter coil 2, the capacitor 102 is driven by the output voltage of the positive half cycle of the exciter coil 2.
Is configured to charge the capacitor. When the exciter coil 2 generates an output voltage of a positive half cycle in the direction of the arrow shown in the figure, the capacitor 102 is charged to the polarity shown by the capacitor charging circuit. After the capacitor 102 is charged, the ignition signal generator 3 outputs the ignition signal V
When i occurs, the thyristor 103 constituting the discharge switch becomes conductive. When the thyristor 103 is turned on, the electric charge accumulated in the capacitor 102 is discharged through the thyristor 103 and the primary coil 101a of the ignition coil, so that a large magnetic flux change occurs in the core of the ignition coil. A high voltage V2 for ignition is induced in the next coil 101b. Since the high voltage V2 is applied to the spark plug 108, a spark is generated at the spark plug and the engine is ignited. This spark energy is determined by the charging voltage of the capacitor 102, and the higher the charging voltage, the greater the spark energy.

When the temperature of the engine is low, the magnitude of the voltage detection signal Vs for the same output voltage Ve of the exciter coil 2 is smaller than when the temperature of the engine is high.
The peak value of the output voltage Ve of the exciter coil when the magnitude of the voltage detection signal Vs reaches the set value becomes larger than when the engine temperature is high. Therefore, when the temperature of the engine is low, the maximum value (limit value) of the voltage applied from the exciter coil 2 to the ignition circuit 1 is higher than when the temperature of the engine is high, and the maximum value of the charging voltage of the capacitor 102 at the time of low temperature is high. The value is higher than at high temperatures. Therefore, the spark energy when the engine temperature is low can be made larger than the spark energy when the engine temperature is high, and the startability of the engine in a cold region can be improved.

When the temperature of the engine increases after the engine starts, the voltage division ratio n of the exciter voltage detector 401 increases, and the limit value of the voltage applied from the exciter coil to the ignition circuit decreases. Therefore, by selecting the resistance value and the temperature characteristic of the temperature-sensitive resistance element Rt1 so that the voltage dividing ratio n of the exciter voltage detecting section 401 at a high temperature of the engine is set to an appropriate value, the exciter during steady operation of the engine is The voltage applied to the ignition circuit 1 from the coil 2 can be limited to the magnitude required to obtain the spark energy required for igniting the engine, so that excessive voltage is not applied to the ignition circuit 1. Can be prevented.

FIG. 4 shows the waveform of the output voltage Ve of the exciter coil 2 when the rotation speed of the engine is constant and the waveform of the voltage detection signal Vs1 when the temperature of the engine is low in the ignition device of FIG. Voltage detection signal V when engine temperature is high
In the figure, Vz is the Zener voltage of the Zener diode ZD1 (set value of the voltage detection signal).
And Ve1 and Ve2 indicate the limit value of the voltage applied from the exciter coil to the ignition circuit when the engine temperature is low and high, respectively. That is, when the temperature of the engine is low, the voltage detection signal Vs becomes lower than the output voltage Ve of the exciter coil as shown in FIG.
The delay of the voltage detection signal reaching the set value Vz is delayed, and the limit value of the voltage applied from the exciter coil to the ignition circuit becomes a high value Ve1. On the other hand, when the temperature of the engine is high, the voltage detection signal Vs becomes higher as shown in FIG. 2 for the same output voltage Ve of the exciter coil, so that the voltage detection signal reaches the set value Vz earlier, The limit value of the voltage applied from the exciter coil to the ignition circuit becomes a low value Ve2.

In the ignition device for an internal combustion engine shown in FIG. 1, since the division ratio of the exciter voltage detecting section 401 changes continuously with a change in temperature, the ignition coil is not affected by the lapse of time t from the start of the engine. The change of the voltage V2 obtained in the secondary coil is shown by a curve a shown by a solid line in FIG. That is, the secondary voltage V2 of the ignition coil decreases from the initial value V2i at the start of the engine over time (as the temperature of the engine rises), and finally converges to the steady value V2s. I do.

In the example shown in FIG. 1, the temperature-sensitive resistance element Rt1 is provided inside the ignition device, but in order to more accurately control the spark energy according to the temperature of the internal combustion engine, the temperature-sensitive resistance element Rt1 is provided. Rt1 may be arranged at a position close to the internal combustion engine and connected to the exciter voltage detector 401 through a lead wire.

In the example shown in FIG. 1, the voltage division ratio of the exciter voltage detecting section 401 is continuously changed with the change of the engine temperature, and the limit value of the voltage applied from the exciter coil 2 to the ignition circuit is reduced. Although the pressure is changed continuously, the pressure division ratio may be increased stepwise when the temperature of the engine reaches a set value.

FIG. 2 shows an example of the configuration of an ignition device in which the partial pressure ratio is increased stepwise when the temperature of the engine reaches a set value. In this example, the terminal on the non-ground side of the exciter coil 2 is shown. A first resistor branch of the resistor voltage dividing circuit constituting the exciter voltage detecting unit 401 is formed by a resistor R1 having one end connected to the resistor R1, and resistors R31 and R32 having one end commonly connected to the other end of the resistor R1. A second resistor branch of the voltage divider is formed. The other ends of the resistors R31 and R32 are respectively connected to the collectors of NPN transistors TR1 and TR2 whose emitters are grounded. A connection point between the other end of the resistor R1 and one end of the resistors R31 and R32 is connected to the gate of the thyristor Th through a Zener diode ZD1.

In this example, the ignition signal generator 3 is constituted by a microcomputer. The microcomputer calculates the ignition timing at each rotation speed using the rotation angle information and the rotation speed information of the engine obtained from a signal generated by a signal generator (not shown) at a predetermined rotation angle position of the engine. The microcomputer also performs a detection operation for detecting the calculated ignition timing, and supplies an ignition signal to the thyristor 103 of the ignition circuit 1 when the calculated ignition timing is detected.

In the example shown in FIG. 2, in order to detect the temperature of the internal combustion engine, a temperature sensor Rts composed of a temperature-sensitive resistance element is arranged near the internal combustion engine. The detected value of the temperature by the temperature sensor Rts is input to the CPU of the microcomputer constituting the ignition signal generating unit 3, and a base current is supplied from the output port of the CPU to the transistors TR1 and TR2 through a predetermined interface circuit. I have. The microcomputer compares the temperature of the engine detected by the temperature sensor Rts with the set value, and applies a base current to the transistor TR1 to make the transistor TR1 conductive when the temperature of the engine is lower than the set value. The microcomputer also applies a base current to the transistor TR2 to turn on the transistor TR2 when the detected engine temperature is equal to or higher than the set value. Accordingly, the exciter voltage detector 401 turns on the transistor TR1 when the temperature of the engine is lower than the set value, divides the output voltage of the exciter coil at a division ratio determined by the resistors R1 and R31, and outputs a voltage detection signal Vs. Then, when the temperature of the engine becomes equal to or higher than the set value, the output voltage of the exciter coil is divided at a voltage division ratio determined by the resistors R1 and R32, and a voltage detection signal Vs is output.

In this example, the resistance value of the resistor R31 is
And the magnitude of the voltage detection signal Vs when the engine temperature is lower than the set value when the output voltage Ve of the exciter coil is constant and the engine temperature is lower than the set value. The magnitude of the voltage detection signal Vs at the time of the above is smaller than the magnitude of the voltage detection signal Vs. When the temperature of the engine is lower than the set value (when the transistor TR1 is turned on and the transistor TR2 is turned off), the peak value of the output voltage of the exciter coil becomes smaller than that of the capacitor 102 required when the engine is cold. When the voltage is equal to or slightly higher than the charging voltage, the voltage detection signal Vs obtained across the resistor R31 reaches a set value (the zener voltage Vz of the zener diode ZD1) and the thyristor Th
In the state where the temperature of the engine is equal to or higher than the set value (when the transistor TR1 is turned off and the transistor TR2 is turned on), the peak value of the output voltage of the exciter coil is required when the temperature of the engine is high. Capacitor 10
2, the voltage detection signal Vs obtained at both ends of the resistor R32 reaches a set value when the charging voltage becomes equal to the charging voltage (the limit value of the voltage applied to the ignition circuit 1 in the steady state), and the thyristor Th is made conductive. The resistance value of the resistor R1 and the resistance values of the resistors R31 and R32 are set.

In the example shown in FIG. 2, the transistor TR1
And TR2 constitute switch means connected in series to some of the resistors R31 and R32 constituting the resistor voltage divider circuit. These switch means switch the voltage divider ratio of the resistor voltage divider circuit. The circuit is configured.
Further, according to the microcomputer and a predetermined program executed by the microcomputer, when the temperature detected by the temperature sensor Rts is lower than the set value, the voltage dividing ratio of the resistance voltage dividing circuit is set to the first value, and the temperature sensor detects the voltage. Switch control means for controlling the switch means of the voltage division ratio switching circuit so that the voltage division ratio becomes a second value larger than the first value when the temperature is equal to or higher than the set value.

When the voltage limiting circuit 4 is configured as shown in FIG. 2, as shown by a curve b shown by a broken line in FIG.
After a certain period of time has elapsed after the engine has started in a low temperature state, when the temperature of the engine reaches the set value, the limit value of the voltage applied from the exciter coil to the ignition circuit decreases stepwise, and the ignition coil Is obtained in which the secondary voltage V2 is gradually reduced.

In the example shown in FIG. 2, the second resistor branch of the resistor voltage dividing circuit constituting the exciter voltage detector 401 is
By providing two resistors R31 and R32 in parallel, the transistor T
The voltage dividing ratio is switched by selecting one of these resistors by turning on and off the switch means composed of R1 and TR2. As shown in FIG. 3, the voltage dividing ratio of the resistive voltage dividing circuit constituting the exciter voltage detecting unit 401 is changed. Two resistors R31 and R32 may be provided in series in the two resistor branches, and one of these resistors may be short-circuited or opened by switch means to switch the voltage division ratio.

In the example shown in FIG. 3, the second resistor branch of the resistor voltage dividing circuit constituting the exciter voltage detecting section 401 is constituted by resistors R31 and R32 connected in series, and the second resistor is connected to the second resistor branch. N is connected to both ends of a resistor R32 provided on the ground side of the branch.
By connecting the collector-emitter circuit of the PN transistor TR1 in parallel and turning on the transistor TR1 when the temperature of the engine is lower than the set value, the voltage dividing ratio of the resistance voltage dividing circuit is reduced to reduce the output voltage of the exciter coil. The limit value is increased, and the transistor TR1 is turned off when the temperature of the engine becomes equal to or higher than the set value, thereby increasing the voltage division ratio and lowering the limit value of the output voltage of the exciter coil. Other configurations of the ignition device shown in FIG. 3 are the same as those of the example shown in FIG.

In the above example, the capacitor 10 of the ignition circuit
2 is connected in series with the primary coil of the ignition coil 101, but the capacitor 102 only needs to be provided on the primary side of the ignition coil and be charged by the output of the exciter coil. However, they need not be connected in series. For example, in FIG. 1, a known ignition circuit in which the positions of the capacitor 102 and the thyristor 103 are interchanged may be used.

In the above example, the diodes 105 are connected to both ends of the primary coil of the ignition coil 101.
This diode 105 can be omitted.

In the example shown in FIG. 3, the second resistor branch of the resistor voltage dividing circuit constituting the exciter voltage detecting section 401 is constituted by two resistors R31 and R32 connected in series. Is short-circuited or opened to switch the voltage dividing ratio. However, the first resistor branch of the resistor voltage dividing circuit is constituted by a plurality of resistors connected in series, and the plurality of resistors are connected. The voltage division ratio may be switched by short-circuiting or opening a part of the resistor.

In the examples shown in FIGS. 2 and 3, the voltage dividing ratio of the exciter voltage detecting section is switched in two stages. However, the voltage dividing ratio can be switched in more stages if necessary.

[0052]

As described above, according to the present invention, the voltage dividing ratio of the resistance voltage dividing circuit constituting the voltage detecting section of the circuit for limiting the output voltage of the exciter coil is changed according to the temperature of the internal combustion engine. As a result, when the temperature of the engine is low, the charging voltage of the capacitor is increased to increase the ignition energy, so that the ignition performance when the engine temperature is low can be improved, and the startability of the engine can be improved. There is.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration example of an ignition device according to the present invention.

FIG. 2 is a circuit diagram showing another configuration example of the ignition device according to the present invention.

FIG. 3 is a circuit diagram showing still another configuration example of the ignition device according to the present invention.

FIG. 4 is a voltage waveform diagram for explaining the operation of the ignition device of FIG. 1;

5 is a diagram showing a comparison between a temporal change of a secondary voltage of an ignition coil of the ignition device of FIG. 1 and a temporal change of a secondary voltage of an ignition coil of the ignition device of FIG. 2;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Ignition circuit 101 Ignition coil 102 Capacitor 103 Thyristor 104 Diode 2 Exciter coil 3 Ignition signal generation part 4 Exciter voltage limiting circuit 401 Exciter voltage detection part 402 Exciter short circuit switch R1, R2 The first resistance branch of the voltage dividing circuit is constituted. Resistances R3, R31, R32 Resistances Rt1, Rt2 constituting the second resistance branch of the voltage dividing circuit Rt1, Rt2 Temperature-sensitive resistance element Rts Temperature sensor

Claims (4)

(57) [Claims] An exciter coil provided in a magnet generator driven by an internal combustion engine, an ignition coil, and one polarity charged by an output of a positive half cycle of the exciter coil provided on a primary side of the ignition coil. An ignition circuit having a capacitor to be turned on and a discharge switch provided so as to conduct when an ignition signal is given and to discharge the electric charge stored in the capacitor through the primary coil of the ignition coil; and An ignition signal generating unit for providing an ignition signal to the discharge switch at a time; and a voltage having a magnitude corresponding to the voltage Ve across the exciter coil by dividing the voltage Ve across the exciter coil by a predetermined voltage dividing ratio n. An exciter voltage detecting section for outputting a detection signal Vs (= n × Ve); An exciter short-circuit switch for short-circuiting the output of the positive half cycle of the exciter coil, comprising: an exciter short-circuit switch; and an exciter voltage detection unit, wherein when the temperature of the internal combustion engine is low, the division ratio n A capacitor discharge internal combustion engine configured to change the partial pressure ratio n according to the temperature of the internal combustion engine so as to decrease the internal pressure and increase the partial pressure ratio n when the temperature of the internal combustion engine is high. Ignition device. 2. The exciter voltage detector comprises a series circuit of first and second resistance branches connected to both ends of the exciter coil, and includes at least a part of the first resistance branch. 2. The ignition device for a capacitor discharge internal combustion engine according to claim 1, further comprising a temperature-sensitive resistance element having a negative temperature coefficient, wherein the voltage detection signal is generated at both ends of the second resistance branch. 3. 3. The exciter voltage detecting section comprises a series circuit of first and second resistance branches connected to both ends of an exciter coil, wherein at least a part of the second resistance branch is positively connected. Including a temperature-sensitive resistance element having a temperature coefficient of
The ignition device according to claim 1, wherein the voltage detection signal is generated at both ends of the second resistance branch. 4. An exciter voltage detecting section, comprising: a resistive voltage dividing circuit for dividing a voltage between both ends of an exciter coil; and a switch connected in series or parallel to a part of the resistors constituting the resistive voltage dividing circuit. Means for switching the voltage dividing ratio of the resistance voltage dividing circuit by on / off operation of the switch means, a temperature sensor for detecting a temperature of the internal combustion engine, and a temperature detected by the temperature sensor being a set value. When the temperature is lower than the first value, the voltage dividing ratio of the resistance voltage dividing circuit is set to a first value, and when the temperature detected by the temperature sensor is equal to or higher than a set value, the voltage dividing ratio is set to a second value larger than the first value. 2. A capacitor discharge type internal combustion engine ignition device according to claim 1, further comprising: switch control means for controlling switch means of said voltage division ratio switching circuit.