JPS593194Y2 - Internal combustion engine ignition control device - Google Patents

Description

[Detailed Description of the Invention] The present invention is an ignition control device for an internal combustion engine, more specifically, an electromagnetic pickup or the like forms a contactless pulse that synchronizes with the rotation of the engine, and based on this pulse, the ignition coil
The present invention relates to a so-called full-transistor type ignition control device that controls opening and closing of an output transistor connected in series to a secondary winding.

Figure 1 is a basic circuit connection diagram of a conventional example of this type of ignition control device, where IG is an ignition coil, Q20 and Q21 are Darlington-connected output transistors, PLG is a spark plug, and R38 is a current detection resistor. The output section is composed of the above parts.

ACR is a signal V from an input section which will be described later.

5 and the current detection signal from the resistor R38, the output transistors Q20 and Q21 are operated in the saturation region when the current rises, and after the current reaches a constant value, for example, 5.5 A, the current is controlled in the active region. This is the circuit.

The input section is a pickup element SG that generates pulses with a waveform as shown by s6 in Fig. 2 in synchronization with the rotation of the engine.
, a bias circuit EvB that forms a predetermined bias voltage from the output of this pickup element, and a transistor Q4. It mainly consists of Q5.

R6, R8, R9 and Rlo are resistors.

This input section includes a bias circuit EvB and a pickup element S.
When the superimposed output with G reaches a predetermined switching level (Vst in FIG. 2), transistor Q4 is turned on.
Transistor Q5 is turned off, and as a result, an input is given to the circuit ACR to make output transistors Q20 and Q2□ conductive, and the superimposed output becomes the switching level ■sL again.
When the voltage drops below, the output transistors Q20 t Q21 are turned off by the opposite action to the above, inducing a steep pulse voltage in the ignition coil 1G, and having the role of supplying this to the spark plug PRG.

The ratio of the output I-transistor conduction period, that is, the duration of the signal ■C5 in Figs. , is called conduction rate or energization rate, but since the time constant of the ignition coil is constant regardless of whether it rotates at low speed or high speed, this energization rate is small at low speeds and large at high speeds, which reduces power loss. This is important in reducing the

For this purpose, according to a proposal published in Japanese Patent Application Laid-Open No. 46-7657, in order to change the switching level VsL according to the rotational speed N, the output of a pickup element SG whose size changes according to the rotational speed N is proposed. A bias voltage is thereby created and this is superimposed on the output of the pickup element SG.

In this way, as the rotation speed increases, the output voltage Vs6 of the pickup element SG exceeds the switching level VsL at a smaller value, and as seen from the bias circuit side terminal of the pickup element, the switching level vsL increases as the rotation speed N increases. It is understood that the energization rate increases from this.

However, the output v of the pickup element SG with respect to the rotational speed N, the positive peak value Vs6-F, the negative peak value v
Figure 3 shows sc-n and switching level sL, and as can be seen from Figure 2, V5°p>
Since the ignition coil is energized only during vst,
Number of revolutions in Figure 3.

□The ignition coil cannot be energized below.

To avoid this, setting the switching level v5L lower will reduce the limit rotation speed.

, will be lower, but this time. >nl, the energization rate increases and the power consumption increases.

Therefore, in the conventional device, it has been a trade-off between reducing power consumption as much as possible and reducing the critical rotational speed at which operation is not possible as much as possible.

Therefore, an object of the present invention is to improve the input section of the circuit shown in FIG. 1 to provide a device that can keep the current conductivity low and operate even at extremely small rotations.

The principle circuit diagram of the input section of the ignition control device of the present invention is shown in FIG.

Terminal V. The circuits after 5 are omitted.

The difference from FIG. 1 is that there is a constant current sink circuit symbolized by an on/off switch S and a constant current source C5 between the base of the input transistor Q4 and the ground GND, a rotation speed N, and a power supply voltage B.
The point is that a circuit C6 for controlling the switch S by + is provided.

When the switch S is closed, a constant current flows through the resistor R6 connected in series with the pickup element SG, so that the level of the signal v8G input to the input transistor Q4 is shifted.

The amount Eb of this level shift is E,=iR6, where i is the magnitude of the current of the constant current source C8. Therefore, the circuit of FIG. 4 can be represented by the equivalent circuit of FIG. 5.

FIG. 6 shows operating waveforms of the circuit shown in FIG. 5, and the potential relationship is based on the reference terminal (2) of the pickup element SG.

First, as shown in a, the switching level V5L is set so that the motor operates at an appropriate energization rate during extremely low speed rotation.

The energization period is indicated by Da.

As the rotation speed increases, as mentioned above, the pickup element SG
As the frequency of the output increases, the peak value also increases, so that it becomes as shown by V'5G-b of b, and the energization period D-b becomes longer than necessary.

Then, when the switch S in FIG. 4 is closed and a level shift is carried out, ■, 6-b moves downward by E, and becomes v'56-b.

Accompanying this, the energization period also decreases from D-b to D'-b.

Therefore, it is possible to achieve the objectives of reducing power consumption and operating even during extremely low speed rotation.

FIG. 7 shows the input signals vsG-P and v56' of the input transistor Q4 when the level is not shifted and when the level is shifted, and the rotational speed N.

Switching level ■The transition is as shown in the diagram.

As can be seen from this figure, if the circuit constants of the circuit CC in Fig. 4 are selected so that the level shift is performed at the lowest rotational speed n3 at which the necessary energization rate can be obtained at ■5'G-1. This means that a good energization rate can always be obtained.

The above is an explanation from the perspective of performing a level shift according to the rotation speed, but in addition to this, when the DC power supply (usually a battery) voltage B+ changes, the time required to flow a constant current to the ignition coil IG changes (almost inversely proportional), it is preferable to make the conduction rate inversely proportional to the power supply voltage B+.

Therefore, by changing the current i in proportion to B+, the level shift amount E
By making b proportional to B+, control can be taken into account so that power consumption does not increase even when the power supply voltage fluctuates.

FIG. 8 is a specific circuit diagram of an embodiment of the present invention.

EvB is a bias circuit, and at the output voltage of pickup element SG, resistor R4, diode D1, capacitor C1
, diode D9, and resistor R2.
1 is charged, and this potential is impedance-converted by transistors Q1 and Q2 to raise the potential of the reference terminal (2) of the pickup element SG.

■C1 is an input stage and connects the base input of input transistor Q4 to transistor Q5. Q6. Q7 performs waveform shaping and level conversion to apply to control transistor Q18.

The control transistor Q18 further includes a current negative feedback circuit ■C2
A signal is supplied from the output stage transistor Q8.

Q19 and Q20 are Darlington-connected output transistors, which are connected in series with the primary winding of the ignition coil IG, and further in series with the current detection resistor to connect to the battery power supply B.
+ and ground GND.

The power supply feedback circuit C2 divides the voltage drop across the current detection resistor R38 using resistors R36 and R3, and when the voltage drop reaches a predetermined value, increases the conductivity of the differentially connected transistor Q17. Engineering.

Transistor Q16 reduces the conductivity of Q16, thereby increasing
In response to a rise in the collector potential of transistor Q9. Q8
increases the base current of control transistor QI8, resulting in control transistor QI8
by increasing the base current of the output transistor Q19,
The function is to suppress the increase in the collector current of Q20 and control it to a constant value.

On the other hand, due to the increase in the collector voltage of the transistor Q16 due to the soil removal, the transistor Q15 is made conductive, and the capacitor C1 of the bias circuit EvB is discharged, and the bias voltage for the output of the pickup wife and child SG is decreased, and the conduction rate of the next cycle is We are trying to reduce the number of people.

The above is an explanation of circuit parts that are not directly related to the present invention, but are considered necessary for understanding the role of the constant current sink circuit according to the present invention, which will be described below.

Now, the constant current sink circuit according to the present invention is mainly composed of a transistor Q3 and a diode D3, forming a so-called current mirror circuit.

The current flowing into diode D3 via resistor R7 is determined by the battery voltage B+ and the resistance value of resistor R7, and since this and the amount of sinking are the same value, transistor Q3 is B+
A constant current proportional to is drawn in, and the level shift amount E5 is determined by the product of this and the resistance value of the resistor R6.

Q is a transistor that controls the operation of the current mirror according to the battery voltage. When the battery voltage B+ exceeds a certain value, it is detected by a voltage divider consisting of resistors R23 and R24, and transistor Q14 is made conductive. Q13 is made non-conductive to take advantage of the level shift caused by constant current absorption.

Transistors QIO to Q1° are transistors that control the operation of the current mirror according to the rotation speed N.
It works like this:

That is, the capacitor C3 is charged via the resistor R2□, and the charging voltage is applied to the diode D5. The capacitor C3 is connected to the transistor Q1□ so that when it exceeds a predetermined value determined by the weir layer voltage between the base and emitter of the transistor Q1□, the transistor Q1□ becomes conductive to kill the current mirror operation. □ to the specified rotation speed (
When the rotation speed is higher than na in FIG. 7, the rotation speed is bypassed so as not to reach the predetermined value.

For this purpose, a transistor QIO is provided, which is supplied with a base current via a resistor R1□ from the collector voltage of the transistor Q5, which is at a high value during the conduction period of the output transistor. The circuit is configured to discharge the capacitor C2.

When the number of circuits is higher than R3, transistor QIO
The conduction period of transistor Q1 also becomes shorter, and along with this, the conduction period of transistor Q1 becomes shorter.
Since the conduction period of □ is also shortened, capacitor C3' cannot reach the above-mentioned predetermined value, and therefore transistor Q1□ remains off and the current mirror operation is utilized.

On the other hand, when the rotation speed becomes less than n3, the conduction period of transistor QIO becomes longer, capacitor C2 in the base circuit of transistor Q1° completes charging, transistor Q11 becomes cut-off, and therefore capacitor 0
3 will be charged to a predetermined value, transistor Q1□ will become conductive, and the current mirror operation will be killed.

Since the level shift caused by the current mirror operation is meaningful before the output transistor is turned on, that is, before the transistor Q1o is turned on, the above operation causes the transistor Q1□ to control the current mirror according to the rotation speed N. That will be understood.

At the input section of the circuit explained above, the battery voltage B+
When the current application time was measured at =12V, the following results were obtained.

Engine rotation speed Conventional device Device of the present invention 200r, p
, m, 80 ms□ 10 m56003
0〃7.5〃 1.000 18〃6〃 2.000 9°3〃5. O7/ 3.000 6.5〃5. The optimum energization time for O〃 B-2 12V is always 5.5V in this rotational speed range. Qms, it can be said that the device of the present invention is extremely superior to the conventional device (one based on the circuit principle shown in FIG. 1).

Furthermore, during the above measurement, the device of the present invention uses 3Q r , p
Reliable operation was obtained even when rotating at extremely low speeds such as , m.

When starting with the starter motor, the engine is driven to a rotation speed that far exceeds this rotation speed, so it has been confirmed that the device of the present invention has no practical problems at all.

[Brief explanation of the drawing]

Figure 1 is the principle circuit diagram of the conventional device, Figures 2 and 3 are explanatory waveform diagrams and characteristic diagrams, Figure 4 is the principle circuit diagram of the present invention, Figure 5 is its equivalent circuit diagram, Figures 6 and 7
The figures are an explanatory waveform diagram and characteristic diagram, and FIG. 8 is a circuit connection diagram of an embodiment of the present invention. In FIG. 4, SG is a pickup element, EvB is a bias circuit, S is a switch, C5 is a constant current source, and C6 is a switch control circuit.

Claims (1)

[Scope of utility model registration request] An electromagnetic pickup element SG that generates a pulse signal synchronized with the rotation of the engine, and an input transistor Q4 that inputs the output of this electromagnetic pickup element via a resistor R6.
and an output transistor Q19, which is controlled to be turned on or off according to the output of the input transistor Q4. Q20, the ignition coil IG and series resistor R38 connected in series to the output transistors Q19 and Q20, and the series resistor R38.
A current negative feedback circuit IC2 that performs negative feedback control on the output transistor based on the voltage drop of Constant current sink circuit Q3 controlled according to voltage. D3 is inserted between the resistor R6 and the input transistor Q4, and this constant current sink circuit is operated only at a predetermined engine speed or higher, and the voltage drop due to the sink current in the resistor R6 is converted into a level shift signal with respect to the pulse signal. An ignition control device for an internal combustion engine, characterized in that: