JPS581271B2 - Ignition system for internal combustion engines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ignition device for an internal combustion engine, and more particularly to an ignition device that can supply an optimal ignition spark to the ignition plug of an internal combustion engine.

As a conventionally known ignition device, for example, Japanese Patent Application Laid-Open No. 46-76
There is an ignition device proposed in Publication No. 57.

In the ignition device according to Japanese Patent Application Laid-Open No. 46-7657, the AC output of an AC generator rotating in synchronization with the internal combustion engine is rectified, stored as a DC voltage in a capacitor, and this DC voltage is used as a bias for the AC output. By applying it as a voltage to the waveform shaping circuit, the closing angle at which the ignition coil's primary current is flowing is expanded, and when the ignition coil's primary current reaches a predetermined current, the charge in the capacitor is discharged. The closing angle, that is, the timing at which electricity starts flowing to the ignition coil, is corrected using negative feedback, and the closing angle is controlled so that the ignition timing is reached when the primary current of the ignition coil reaches a predetermined current value.

By the way, before discussing this conventional ignition system, let us explain the required spark voltage v required to ignite the air-fuel mixture of a general internal combustion engine.
2 decreases as the engine speed n increases, as shown in FIG.

This is because the time required for the mixture to ignite and the internal pressure of the combustion chamber to reach its maximum is almost constant, so as the engine speed increases, ignition must occur before the piston reaches top dead center. Since the pressure at the point decreases as the speed increases, the required voltage at the spark plug also decreases.

Therefore, the optimal ignition system is not one that exhibits constant performance against changes in engine speed, but rather one that maintains constant performance against changes in engine speed. The objective is to obtain characteristics with a certain margin of a certain percentage, and for example, in the case of the engine speed mentioned above, the objective is to obtain a characteristic that decreases as the engine speed increases.

By adapting the performance to the engine operating conditions in this way,
The optimal design is one that not only eliminates the unnecessary burden of the ignition coil and its primary current intermittent circuit, but also minimizes the consumption of the onboard power source.

Therefore, the above-mentioned conventionally known ignition system will be discussed to see whether it has the optimal design as described above.

In this conventionally known ignition system, the primary cut-off current of the ignition coil is set to be constant under all operating conditions such as changes in engine speed, so the generated voltage performance of the ignition coil remains constant even in the region of high engine speed. There is a problem in that the voltage generated by the ignition coil is excessive compared to the required voltage especially when the engine speed is high, resulting in wasteful operation.

The present invention solves the problems of the conventional ignition system described above, and by changing the setting value of the ignition coil primary cut-off current, which determines the generated voltage performance of the ignition coil, according to the engine speed. In order to obtain optimal performance, in detail, by decreasing the set value of the primary cut-off current of the 5 ignition coils as the engine speed increases, the generated voltage relative to the required voltage in the high engine speed range is reduced. By optimizing, the purpose is to suppress the temperature rise of the ignition coil and the primary current cutoff circuit, and to suppress wasteful consumption of the vehicle's storage battery as much as possible.

The present invention will be described below with reference to an embodiment shown in the drawings. First, the configuration of an embodiment of the present invention will be explained with reference to the block diagram shown in FIG. 2.

Reference numeral 1 denotes a signal generator that generates a signal in synchronization with the internal combustion engine, and uses, for example, an alternating current generator that rotates in synchronization with the internal combustion engine.

A waveform shaping circuit 100 shapes the waveform of the signal from the front signal generator.

A drive circuit 200 controls the base current of the power transistor 2 which intermittently switches the primary winding current of the ignition coil 3.

A current limiting circuit 600 performs constant current control to suppress the primary winding current of the ignition coil 3 to a predetermined value.

300 is a closed angle expansion circuit, which applies a DC voltage that changes with the rotation speed of the internal combustion engine to the waveform shaping circuit 100, changes the switching level of the waveform shaping circuit 100 with respect to the AC voltage, and controls the primary ignition coil 3. It operates to expand the closing angle where current is flowing.

400 is a closing angle reduction circuit, which connects the power transistor 2
The switching level of the waveform shaping circuit 100 with respect to the alternating current voltage is changed in accordance with the time width during which the constant current is controlled, thereby operating to reduce the closing angle at which the primary current of the ignition coil 3 is flowing.

500 is a current setting circuit, and in this embodiment, as the rotation speed of the internal combustion engine increases, the power transistor 2
It operates to lower the constant current setting value.

Next, the block diagram explained in FIG. 2 will be explained with reference to a specific circuit shown in FIG. 3.

The waveform shaping circuit 100 includes a capacitor 101 that absorbs noise in the output signal of the signal generator 1, a resistor 102 and a Zener diode 103 for obtaining a constant voltage, an input transistor 104, its base resistor 105, and the input transistor 104. a resistor 106 for driving the
A diode-connected transistor 107 for compensating the temperature characteristics of the saturation voltage between the base and emitter of the input transistor 104, and a diode 108 for preventing reverse bias damage between the base and emitter of the input transistor 104.
, a resistor 109 connected to the collector of the input transistor 104, a transistor 110 that outputs a phase-inverted output of the input transistor 104, an output resistor 111 connected to its emitter, a transistor 112 operating in the same phase as the transistor 110, and Base-emitter resistance 113 and collector resistance 1 of this transistor 112
14, a resistor 115 for providing negative feedback to the input transistor 104 by the output of the transistor 112,
A resistor 11 connected to the collector of the transistor 112
6, an output transistor 117 that outputs a phase-inverted output from the transistor 112, a collector resistor 118 thereof, and an output resistor 119.

The drive circuit 200 includes a transistor 201 driven by a signal passed through a resistor 119 from the output transistor 117 of the waveform shaping circuit 100, and a collector resistor 202 of the transistor 201.
, a transistor 203 that outputs a phase inverted output of the transistor 201 to drive the final stage power transistor 2, a collector resistor 204 thereof, a resistor 205 configured as a resistance between the base and emitter of the final stage power transistor 2, and Zener diode 2 for protecting the breakdown voltage between the collector and emitter of the final stage power transistor 2
It consists of 06.

Next, the closing angle expansion circuit 300 includes a diode 301 that rectifies the AC output of the signal generator 1 and a charging resistor 303 that charges the rectified output to a capacitor 302. One end of the transistor 304 applies a bias to the base of the input transistor 104 of the waveform shaping circuit 100 via a resistor 305, and the other end applies a bias to the base of the input transistor 104 of the waveform shaping circuit 100.
It is connected to a current limiting circuit 600 via a resistor 501 of 0.00.

The current limiting circuit 600 is connected between the emitter of the final stage power transistor 2 and the negative terminal of the power supply, and detects the primary winding current of the ignition coil 3 flowing through the final stage power transistor 2 with a current detection resistor 601. , the current detection resistor 6
By applying the terminal voltage of 01 through the resistor 602 and the diode-connected transistor 603 to the connection point between the resistors 604 and 605, when the primary current of the ignition coil 3 increases beyond a predetermined value, the terminal of the current detection resistor 601 The voltage increases, raising the potential at the connection point between the resistors 604 and 605, biasing the transistor 201 of the drive circuit 200 from the non-conducting state to the active region, and the drive circuit 2
By changing the transistor 203 of 00 from a conductive state to an active region operation and the final stage power transistor 2 from a conductive state to an active region operation, an increase in the primary winding current of the ignition coil 3 is prevented, and eventually the current reaches a predetermined value. This is a pressing motion.

The closing angle reduction circuit 400 is connected to the final stage power transistor 2.
A resistor 401 for detecting the collector potential of the power transistor 2, a Zener diode 402 for clipping the high voltage when the final stage power transistor 2 is cut off, and a capacitor 403.
A charging resistor 404 is connected to the capacitor 403, and a diode 405 for preventing reverse flow of the charge of the capacitor 403 is used to transfer the collector potential of the final stage transistor 2 to the capacitor 403 through the charging resistor 404 only when the primary current is applied to the ignition coil 3. Resistor 406 and transistor 40 for charging operation
7.

408 is a resistor for charging and discharging the capacitor 403, and the voltage charged to the capacitor 403 is further applied to transistors 409 and 410 of the Darlington-connected emitter follower circuit.
A voltage corresponding to the charging voltage is applied to a resistor 413 via a resistor 416, Turlington-connected transistors 409 and 410, a resistor 411, and a diode 412.

The resistor 414 and the transistor 415 are connected to each other when the ignition coil 3 is energized.
The operation configuration is such that the capacitor 403 is made conductive and the application of voltage to the resistor 413 is blocked according to the charging voltage of the capacitor 403.

The circuit configuration and the existing operation described above with reference to FIG. 3 will be further explained with reference to the operation waveform diagrams shown in FIGS. 4 and 5.

First, FIG. 4 shows operation waveforms of each part when the engine speed is low, and FIG. 5 shows similar operation waveforms of each part when the engine speed is high.

Further, in FIGS. 4 and 5, a indicates the output waveform of the signal generator 1, and b indicates the input transistor 1 of the waveform shaping circuit 100.
04, C shows the primary winding current waveform of the ignition coil 3, d shows the collector waveform of the final stage power transistor 2, and e shows the collector waveform of the transistor 407 of the closing angle reduction circuit 400. , f similarly indicate the charging voltage waveform of the capacitor 403 of the closing angle reduction circuit 400.

Now, to explain the case where the engine speed is low, the AC output of the signal generator 1 is very small during low speed rotation, so the charging voltage of the capacitor 302 of the closing angle expansion circuit 300 is almost zero, and the closing angle is reduced. In the absence of the circuit 400, the signal generator switches the transistor 104 at a point determined by the zero cross point of the AC output (points X1, Y, in the case of the waveform diagram a shown in FIG. 4), but the closing angle Because of the reduction circuit 400, the transistor 407 is made non-conductive only during the period when the final stage power transistor 2 is conducting or non-saturated in the waveform diagram d shown in FIG. 4, which is the collector output of the final stage power transistor 2. , the collector voltage of the collector waveform during non-saturated operation is charged to the capacitor 403, and a charging waveform as shown in FIG. 4f is obtained.

The charging voltage is applied to the transistors 409 and 410 of the Turlington-connected emitter follower circuit, and is negatively fed back to the resistor 411, the diode 412, and the emitter resistor 413 of the input transistor 104 of the waveform shaping circuit 100. Since the transistor 415 is limited by the collector waveform of the transistor 112, the negative feedback is limited only to the period in which the primary current to the ignition coil 3 is not energized.

Therefore, the input transistor 104 is connected to the closed angle expansion circuit 30.
Since it is not biased from 0, it turns off at point P1 of the waveform a shown in FIG. It operates to delay the start of energization to reduce the non-saturated operating period of the final stage power transistor 2.

Next, the operation in a high engine speed range will be explained with reference to FIG.

When the engine speed is sufficiently high, the output of the signal generator 1 is sufficiently large, so the capacitor 302 of the closing angle expansion circuit 300 is charged with a DC voltage corresponding to the engine speed, and the transistor 10
4 is supplied with a forward bias through an emitter follower transistor 304 and a resistor 305.

Therefore, the switching level of the transistor 104 is lowered by V1' in the a waveform shown in FIG. 5, and the transistor 104 is turned off at P2. ON in Q2
and turns off at P3.

The period between Q2 and P3 on this a waveform becomes the energized section of the ignition coil 3.

In other words, the closing angle is expanded by the closing angle expansion circuit 300.

During this energization period, the primary current of the ignition coil 3 has a waveform as shown in waveform C shown in FIG.

Here, regarding the constant current setting value, since a voltage corresponding to the engine speed is added to the resistor 501 of the current setting circuit 500 from the transistor 304 of the emitter follower of the closing angle expansion circuit 300, the current limiting circuit 600 resistance 6
The bias potential at the connection point between 04 and 605 increases as the engine speed increases, and the collector potential of transistor 201 similarly decreases.
The base current of the final power transistor 2 flowing through the ignition coil 3 decreases, and the primary current of the ignition coil 3 also decreases as the engine speed increases, and the ignition plug connected to the secondary side of the ignition coil 3 This corresponds to the required voltage drop in .

Therefore, as shown by the C waveform shown in FIG. 5, the constant current setting value decreases by Δ■1 compared to the low speed rotation range.

When the constant current region is reached, the capacitor 403 of the closing angle reduction circuit 400 is charged with the collector voltage of the final stage power transistor 2, and a charging waveform shown in the f waveform shown in FIG. 5 is obtained.

Then, due to this charging pressure, the final stage power transistor 2
The emitter resistor 4 of the transistor 104 only during the OFF period of
Since the negative feedback bias V2' is applied to the transistor 104, the time point when the transistor 104 is turned ON again is Q3, and the closing angle of the current-carrying section up to the next OFF point P4 is reduced, and the non-saturation region of the final stage power transistor 2 is reduced. operating time can be reduced.

As can be seen from the above, according to the present invention, the constant current setting value of the energizing current of the ignition coil 3 is changed according to the engine speed, so that the shaded portion as shown in the waveform C shown in FIG. Excellent effects can be expected in that wasteful power consumption can be suppressed, unnecessary temperature rises of the ignition coil 3 and final stage power transistor 2 can be suppressed as much as possible, and power consumption can also be suppressed as much as possible.

In the above-described practical example, an alternating current generator is used as the signal generator 1, but the present invention is not limited to this, and a signal generator that outputs a rectangular wave may be used.

Similarly, the closing angle expansion circuit 300 and the closing angle reduction circuit 4
Although we have described an example in which a control circuit equipped with It goes without saying that it can be done.

As described above, the present invention includes a signal generator that generates a signal synchronized with the rotational speed of an internal combustion engine, a waveform processing circuit that performs waveform processing on the output signal of the signal generator, and a waveform processing circuit that processes the output signal of the signal generator. An ignition device comprising a switching element that is driven to cut off the primary current of the ignition coil, and a current limiting circuit that controls the primary current of the ignition coil at a constant current,
Since the constant current setting value of the current limiting circuit is decreased as the engine speed increases, the minimum necessary ignition performance that is optimal for the voltage required for sparking at the ignition plug in the engine high speed range can be supplied. Not only can unnecessary power consumption of the primary current interrupting element of the ignition coil be suppressed. An excellent effect can be expected in that unnecessary power consumption can be suppressed as much as possible.

[Brief explanation of drawings]

Fig. 1 is a characteristic diagram of the voltage required for sparking at the spark plug of a general internal combustion engine, Fig. 2 is a block diagram showing an actual case of the device of the present invention, Fig. 3 is a specific electric circuit diagram of the above embodiment, and Fig. 4 and 5 are waveform diagrams of various parts at low speed and high speed for explaining the operation of the above-mentioned actual case. DESCRIPTION OF SYMBOLS 1... Signal generator, 2... Power transistor as a switching element, 3... Ignition coil, 100, 200
, 300, 400...Waveform shaping circuit constituting the waveform processing circuit. Dry circuit, closing angle expansion circuit, closing angle reduction circuit, 500... current setting circuit constituting constant current setting value changing means, 600... current limiting circuit.

Claims (1)

[Claims] 1. A signal generator that generates a signal synchronized with the rotational speed of the internal combustion engine, a waveform processing circuit that processes the output signal of the signal generator into a waveform, and a primary current of the ignition coil driven by the output signal of the waveform processing circuit. In an ignition device for an internal combustion engine, the constant current setting value of the current limiting circuit changes as the engine speed increases, and the current limiting circuit controls the primary current of the ignition coil at a constant current. An ignition device for an internal combustion engine, comprising means for changing a constant current setting value that decreases.