JPS5893965A - Ignition device in internal-combustion engine - Google Patents

Abstract

PURPOSE:To make it possible to control as occasion demands the ignition energy of an ignition device in an internal-combustion engine, in which high DC voltage is applied to the secondary winding of an ignition coil so that ignition energy is intensified, by controlling the output voltage of a DC/DC converter in accordance with the operating condition of the engine. CONSTITUTION:High DC voltage generated by a DC/DC converter 20 is applied to the secondary winding 46 of an ignition coil 4. A partial voltage Ve is changed by turning a rotary switch 29 in accordance with the opening degree of a throttle valve 28. Accordingly, the output voltage of the DC/DC converter 20 is lowered with the increase of load. With this arrangement, ignition energy may be controlled in accordance with the operating condition of the engine.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ignition system for an internal combustion engine in which a high DC voltage is applied to a secondary winding of an ignition coil to strengthen the ignition force.

Conventional ignition devices for internal combustion engines that enhance the ignition efficiency include those described in, for example, Japanese Patent Laid-Open No. 52-22667 and Japanese Patent Laid-Open No. 53-14242.

To explain this simply, as shown in FIG. Power is supplied to one end of the primary winding 4a of the ignition coil 4 via the current limiting resistor Rt, and this primary winding 4
The other end of a is an all-transistor switching circuit (
(hereinafter referred to as "Full Torra Ignition Unit") 5, and the Full Torra Ignition Unit 5 has a pickup rotor 6.
An ignition signal from the electromagnetic pickup 7 generated by the rotation of the ignition coil 4 is applied, and the current flowing through the primary winding 4a of the ignition coil 4 is interrupted in accordance with the ignition timing.

One end of the secondary winding 4b of the ignition coil 4 is connected to the rotor terminal of the distributor 9 via the center coil 18, and the other end is connected to the high voltage output terminal 13 of the DC/I)C converter 6. - The valley distribution terminal of the cylinder 9 is connected to the spark plug 11 of the valley cylinder by a high tension cord 10.

The J)C/I)C converter 6 is a DC booster circuit that generates a DC high voltage of about 2KV to be applied to the secondary winding 4bf2 of the ignition coil 4, and an example of the circuit is shown in FIG. .

This applies the battery voltage supplied to the power supply terminal A to the midpoint terminal of the primary winding 12a of the step-up transformer 12, and connects transistors Ql and Q2 inserted between both terminals of the primary winding 12a and ground, respectively. , the tertiary winding 12-b of the step-up transformer 12 oscillates in opposite directions to each other, and the direction of the excitation current of the step-up transformer 12 is reversed to the receiving direction.
(Two high voltage alternating voltages are generated, and this alternating voltage is converted to direct current by a voltage doubler rectifier circuit consisting of diodes DI, D2 and capacitors C1, C2, and is taken out from output terminal B as a direct current high voltage.) .

Note that capacitors C3 and C4 and inductance L in FIG. 2 constitute a filter circuit for noise prevention, and resistors 1-t2 to 1(
, 4 gradually discharges the capacitor C>, (::2cr) for safety when the ignition switch 'f2 is off.

The conventional ignition device configured in this way cuts off the current flowing through the primary winding 4a+2 of the ignition coil 4 according to the ignition timing by switching the full-torque ignition unit 5 (2). The high voltage generated in the spark plug 11 starts spark discharge between the electrodes of the spark plug 11.

When this spark discharge starts, the capacitor C connected to the output terminal B of the DC/DC" converter 6
If the high voltage of approximately 2 KV charged in I and C2 flows between the electrodes of the spark plug 11, resulting in a sustained discharge and a spark discharge, and the resistance between the electrodes continues to be destroyed by this high voltage, During that time, the discharge continues and the ignition is strengthened.

However, the combustion conditions in an internal combustion engine generally vary depending on its operating condition, and as shown in Figures 3 and 4, the lower the load or rotation, the greater the ignition energy required, and the higher the load or rotation. As a result, the ignition light and lugi can be made smaller.

However, in the conventional ignition system as described above, I)C
/I) So that the output voltage of the C converter is always constant (
Due to the charge response characteristics of capacitors C1 and C2 in the voltage doubler rectifier circuit, the ignition energy tended to decrease at high speeds, but sufficient ignition energy was obtained even at low loads or low speeds. I) C/DC so that
If the output voltage of the converter is set high, when the load or rotational speed increases, more ignition energy than necessary will be provided, resulting in wasteful power consumption (Second).

If the output voltage of the DC/DC converter is set to a low level C2 to prevent this, there is a problem that there may be cases where sufficient ignition energy cannot be obtained at low loads and low rotations, resulting in a misfire. Ta.

This invention was made in view of the above points, and the DC/
A voltage control means is provided to change the output voltage of the DC converter according to the operating conditions of the internal combustion engine (engine). An ignition system that reduces the charging pressure of the capacitor as the rotation or high load increases (2) provides the necessary ignition energy according to the operating conditions and eliminates wasteful power consumption to improve fuel efficiency. It provides:

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 5 is a circuit diagram of an ignition device showing one practical example of the present invention, and parts corresponding to those of the conventional example shown in FIG. 1 are given the same reference numerals.

In this embodiment, the DC/DC converter 20 that generates a high voltage to be applied to the secondary winding 4b of the ignition coil 4 is powered from the middle point f of the primary winding 21a of the step-up transformer 21 (supplied from the Transistors Q3, Q4 and C5, C are inserted between the terminals at both ends of this primary winding 21a and the ground.
6 is controlled by the output voltage of the oscillator 24 via emitter follower circuits 22 and 23, and is alternately switched to generate a high-voltage alternating voltage in the secondary winding 21b of the step-up transformer 21.

Then, this alternating voltage is rectified by a bridge rectifier circuit including diodes D3 to D6 to charge a capacitor C5, and the charging voltage of this capacitor C5 is taken out from the output terminal B1 and applied to the secondary winding 4b of the ignition coil 4. It looks like this.

Furthermore, transistors Q3. to which the outputs of the emitter follower circuits 22.23 are applied Diodes D7. with their respective anodes connected to the base of Q5. Connect the cathode side of D8 to the collector of a common NPN l-transistor Q7,
The emitter of this transistor Q7 is grounded, and its base (common itC emitter resistor R5 of the two transistors Q4 and Q6)
, R6 is applied to each transistor Q3.
- Controls the switching time of Q6.

Therefore, in this embodiment, the pass voltage of the transistor Q7 is controlled by the voltage control means 25, and the DC/D
The output voltage of the C converter 20 is changed according to the operating conditions of the internal combustion engine.

The single voltage control means 25 includes a comparator 26, a voltage regulator 27, and a throttle valve 28 provided in the intake pipe of the engine. It consists of a voltage dividing circuit 30 and the like.

Voltage regulator 2 controls the voltage of battery 1 (1,2V
) is a stabilizing circuit that keeps the output voltage (8V) constant even if the voltage changes, and the output voltage is connected to the resistor Rs.

The voltage is divided by about 9 and applied to the inverting input terminal of the comparator 26 as the reference voltage Vr.

On the other hand, the non-inverting input terminal of the comparator 26 has DC/
The output terminal B1 of the DC converter 20 is connected to the output terminal B2 via the resistor R7 (2. The variable voltage divider circuit 60
The movable contact e of the rotary switch 29 is connected.

Therefore, at the non-inverting input terminal of the comparator 26,
The output voltage of the DC/DC converter 20 is
A voltage Ve divided by one of the resistors R and a-Rd is applied. The output of the comparator 26 is applied to the base of the transistor Q7 of the -/- DC/DC converter 20 via the diode D9.

Therefore, the charging voltage of the capacitor C5 on the output side of the DC/DC converter 20, that is, the output high voltage VH becomes higher, and the voltage Ve obtained by dividing it by the resistor R7 and the variable voltage divider circuit 60 becomes higher than the reference voltage Vr. When the voltage becomes high, the output of the comparator 26 becomes a high level "H"', making the transistor Q7 conductive.

Thereby, transistors Q3 to Q6 are all kept off, the boosting operation of DC/DC converter 20 is stopped, and output high voltage VH is controlled so that divided voltage Ve becomes equal to reference voltage Vr.

That is, by changing the voltage dividing ratio of variable voltage dividing circuit 60 (-), it is possible to control the output voltage of DC/I)C converter 20, that is, the charging voltage of capacitor C5.

In this embodiment, when the opening degree of the throttle valve 28 is small,
That is, when the load is low, the rotary switch 29 is switched so that the resistor ad with the smallest resistance value is connected, and as the opening degree of the throttle valve 28 becomes wider (8-), that is, as the load becomes larger,
The rotary switch 29 is switched so that the resistors Be, l(, b, and a) with larger resistance values are connected in sequence, and as the opening degree of the throttle valve 28 becomes larger, the divided voltage e is increased, and the DC voltage is increased. /Lower the output voltage of the DC converter 20.

In this way, for example, load 1. shown in FIG. II.

1 (at the point 1

1) If you switch to ("+c4d), it will become as shown by the broken line A-D in the same figure. As a result, step-like characteristics as shown by the solid line in the figure can be obtained.

By doing so, it is possible to supply a sufficiently large ignition energy at low loads, and for example, under operating conditions where the interelectrode breakdown voltage Vs, sustained discharge voltage VAI, and sustained discharge time Dsl of the spark plug were conventionally shown in FIG. (load condition), the sustained discharge voltage is set to VA2 (VA2
> VAI ) (2 high, continuous discharge time DS2 (Ds2
) I) It is possible to increase the ignition efficiency by increasing the length as shown in st), thereby improving the ignitability.

Then, as the load increases, the ignition energy can be reduced to prevent wasteful power consumption.

Note that the variable pressure dividing circuit 60 is connected to the throttle valve 2 in this example.
Rotary switch 29 whose contacts change according to the opening degree of 8.
By switching fixed resistors FLaxRd with different resistance values, the partial pressure ratio was changed stepwise.However, by using a potentiometer that interlocks with the throttle valve (2), the partial pressure ratio can be changed steplessly according to the throttle valve opening (2). You may change it.

Further, the voltage division ratio of the output voltage of the DC/DC converter 20 which is input to the comparator 26 is kept constant, and the reference voltage Vr
may be changed according to the throttle opening.

Although the opening degree of the throttle valve 28 has been taken up as representing the operating conditions of the internal combustion engine, the operating conditions can also be detected by the engine speed, intake pipe negative pressure, airflow meter output, etc. The above-mentioned voltage division ratio or reference voltage may be changed depending on the detection result.

u J-As explained above, according to the present invention, the output voltage of the C/J) C converter is controlled under operating conditions (I), and the capacitor is increased as the combustion worsens at low rotation speeds or low loads. By increasing the charging voltage of the fuel and igniting it with high energy, it is possible to promote fire propagation and improve fuel efficiency.

Furthermore, at high speeds or high loads where small ignition energy is required, the ignition energy can be minimized to minimize power consumption due to ignition, further improving vehicle fuel efficiency.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an example of a conventional ignition system for an internal combustion engine, Fig. 2 is a circuit diagram showing a specific example of a DC/DC converter, and Figs. A curve diagram showing the relationship between the load or rotational speed and ignition energy in the engine, FIG. 5 is a circuit diagram showing one embodiment of the present invention, and FIGS.
FIG. 3 is an explanatory diagram for explaining the operation of the actual paper example shown in the figure. 6.20...DC/DC converter (DC voltage booster circuit) 28...Throttle valve 29...Rotary switch 60...Variable voltage divider circuit C5...Capacitor 12- Fig. 1 Fig. 2 2 Figure 5-333- Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] 1. It has a DC voltage booster circuit for applying a high voltage to the secondary winding of the ignition coil, and after the spark plug starts discharging, it is connected to the output side of the DC voltage booster circuit between the electrodes of the spark plug. Spark ignition is performed by discharging the electric charge stored in the capacitor, and in the ignition device between the twisting machines, a high voltage control means is provided for changing the output voltage of the DC voltage boosting circuit according to the operating conditions of the internal combustion engine, Internal combustion engine 1
An internal combustion engine characterized in that the charging voltage of the capacitor is increased as the vehicle running conditions become lower rotation or load, and conversely, the charging voltage of the capacitor is decreased as the rotation or load becomes higher. Ignition device.