JPH0631603B2 - Ignition timing control device for internal combustion engine - Google Patents

Description

TECHNICAL FIELD The present invention relates to an ignition timing control device for an internal combustion engine.

Background Art A cylinder pressure change is obtained as a so-called finger pressure signal by forming a through hole communicating with a combustion chamber in a member forming a combustion chamber such as a cylinder head of an internal combustion engine and inserting a pressure sensor using a piezoelectric element or the like into the through hole. You can Further, a method of obtaining a finger pressure signal by interposing a pressure gauge at the connecting portion between the cylinder head and the cylinder block is also conceivable.

It can be seen that the change in the engine cylinder internal pressure in the operating state of the internal combustion engine is as shown by the curve A in FIG. When the ignition system is triggered at the ignition angle θ _{IG, the} air-fuel mixture is ignited with an ignition delay θd, and the cylinder pressure then rises sharply and follows a maximum pressure peak P (hereinafter referred to as a finger pressure peak).

It is known that the crank rotation angle position of this acupressure peak is related to the state where the engine exhibits the maximum output, and the crank rotation angle position of the acupressure peak that can give this maximum output is as shown in the figure. After the dead point (hereinafter A
It was experimentally confirmed that the angle is in the range of 12 ° to 13 ° (referred to as TDC). Therefore, with ATDC 12 ° to 13 ° as the ideal crank rotation angle position, the finger pressure peak is set to ATDC.
The applicant has already proposed an ignition timing control device of a finger pressure detection type that controls the ignition timing θ _IG so as to obtain an ideal crank rotation angle position of 12 ° to 13 °.

Such an ignition timing control device directly detects the cylinder internal pressure and obtains the finger pressure peak position data for each engine cycle by a finger pressure signal representing the cylinder internal pressure, and compares it with the crank reference position data to advance or advance the ignition timing for each engine cycle. It is designed to be retarded. By the way, in such a finger pressure detection type ignition timing control device, a top dead center (hereinafter referred to as TDC) position is usually used as a crank reference position, and a reference position signal at the TDC position is used to detect the crank reference position. A reference position signal generating circuit for generating is generated. On the other hand, a clock generation circuit for generating a clock pulse in synchronization with crank rotation is provided, and the finger pressure peak position is detected by counting the clock pulse from the generation time point to the finger pressure peak time point every time the reference position signal is generated. Both the reference position signal generating circuit and the clock generating circuit need to be provided with a detection unit such as a pulsar in the engine in order to obtain a signal synchronized with the crank rotation. However, the detector requires a relatively large space, and when two detectors are provided, the layout of the engine becomes difficult and the cost becomes high.

SUMMARY OF THE INVENTION Therefore, the present invention provides an ignition timing control device of a finger pressure detection system that can generate a reference position signal and a clock pulse to control the ignition timing at low cost without making the layout of the engine difficult. With the goal.

Since it has been confirmed that the peak position of the finger pressure is equal to the reference position (TDC position) when the engine is started, the ignition timing control device according to the present invention determines the crank rotation angular position from the reference angular position to the reference angular position again. A number of clock pulses are generated in synchronization with the crank rotation by the clock pulse generation means, and when the acupressure signal reaches the maximum peak immediately after the engine start operation starts, a peak signal is generated and the reference position is generated at the time of the peak signal generation. It is characterized in that a reference position signal is generated every time a signal is generated and then a predetermined number of clock pulses are counted.

Embodiment FIG. 2 shows an ignition timing control device for a two-cycle engine according to the present invention. In this device, a through hole is formed in a member such as a cylinder head forming a combustion chamber of an engine (not shown). This includes a finger pressure signal generating circuit 1 obtained by inserting a pressure sensor such as a piezoelectric element in close contact so that the detection head is exposed in the combustion chamber. The output terminal of the acupressure signal generating circuit 1 is connected to a waveform shaping circuit 2 that outputs a high level when the acupressure signal level is equal to or higher than a predetermined level. The clock generation circuit 3 generates a clock pulse synchronized with the engine rotation. As a means for obtaining a clock pulse, a disc that rotates in response to the rotation of a crankshaft, and a pulse coupler that obtains a clock pulse by an output signal of the photocoupler by combining a photocoupler with a slit disc having 64 slits at equal intervals Is known. The one-shot pulse generation circuit 4 generates a high level pulse having a predetermined time width when the engine start switch 5 is turned on. The AND circuit 6 takes the logical product of the output levels of the waveform shaping circuit 2, the clock generation circuit 3, and the one-shot pulse generation circuit 4. The ring counter 7 for measuring the crank angle position counts clock pulses and is reset to a count value 0 by a high level signal output from the AND circuit 6 6
It is a quaternary counter. Reference position signal generation circuit 8 is NO
It is composed of an R circuit 9 and an AND circuit 10 and has a count value of 0 in the ring counter 7 and generates a reference position signal when a clock pulse is generated. The peak hold circuit 11 holds the maximum value of the acupressure signal after being cleared by the reference position signal, and the comparison circuit 12 generates a peak detection signal when the acupressure signal itself falls below the maximum value. Latch circuit 1
Reference numeral 3 latches the count value of the ring counter 7 every time the peak detection signal from the comparison circuit 12 is supplied to its gate terminal g. On the other hand, the decoder 14
When the count value of the ring counter 7 reaches 12, for example, a read command signal is supplied to the ignition angle setting circuit 15. The count value 12 corresponds to a crank angle that is larger than the crank angle at which the acupressure peak value is predicted to occur, and obtains a reading timing that is not affected even if valve seating noise of the exhaust valve is mixed in the acupressure signal. ing. In response to this, the ignition angle setting circuit 15 reads the contents of the latch circuit 13 and determines the contents of this latch as the peak position data θ _px on the crank angle. A configuration in which the latch contents are supplied to the ignition angle setting circuit 15 via a gate circuit that opens the gate in response to a read command signal from the decoder 14 is also conceivable. The ignition angle setting circuit 15 is configured by a microprocessor or the like, and has a desired ignition angle θIG according to a program described later based on the supplied peak position data θ _px.
Data is supplied to the ignition command circuit 16. Ignition command circuit 1
6 knows the crank angle current value θ _ig by counting clock pulses with reference to the reference position signal, and determines the current value θ _{ig.
When ig} matches the input θIG, the ignition switch SW is opened, whereby an ignition current flows through the secondary coil of the ignition transformer T, and ignition is performed by an ignition plug (not shown). The ignition angle setting circuit 15 and the ignition command circuit 16 form ignition command means. Further, the ignition angle setting circuit 15 uses various engine parameters from the engine parameter sensor 17, that is, the engine speed Ne and the suction negative pressure P.
A mode that operates based on _{B 1} , throttle opening θ _th , engine cooling water temperature Tw, etc. may also be provided.

In the ignition timing control device according to the present invention, when the starter switch 5 is turned on at the time of starting the engine, the one-shot pulse generation circuit 4 increases the predetermined time width indicating the starting state of the engine as shown in FIG. 3 (A). Generate level pulse. When the crankshaft is rotated by a starter motor (not shown) to increase the pressure in the combustion chamber and the finger pressure signal level output from the finger pressure signal generating circuit 1 as shown in FIG. 3 (B) exceeds a predetermined level, waveform shaping is performed. The output level of the circuit 2 becomes high level as shown in FIG. 3 (C),
This high level is the peak signal. On the other hand, when the crankshaft rotates, the clock pulse is generated from the clock generating circuit 3 as shown in FIG. When the output level of the waveform shaping circuit 2 becomes a high level and a clock pulse is generated while a high level pulse is being generated from the one-shot pulse generating circuit 4, the AND circuit 6 outputs a clock signal as shown in FIG. 3 (E). A reset pulse having the same pulse width as the pulse is supplied to the ring counter 7. Since the reset pulse resets the count width of the ring counter 7 to 0, the ring counter 7 counts up from 0. When the count value of the ring counter 7 becomes 0, the reference position signal is generated from the reference position signal generating circuit 8 at the same time as the clock pulse generated at that time, as shown in FIG. That is, when the engine speed is low, the peak of the finger pressure signal coincides with the TDC position, so that the reference position of the crank rotation angle is when the reset pulse is generated. Therefore, the reference position signal is generated at the reference position every time the clock pulse is counted 64 with the reset pulse generation time as the prime.

After the engine is started, when the reference position signal and the clock pulse are generated as shown in FIGS. 4 (A) and 4 (B), the acupressure signal changes as shown by the solid line in FIG. 4 (C). The output of the peak hold circuit 11 is as shown by the dotted line in FIG. Comparison circuit 1
2 generates a peak detection signal as shown in FIG. 4D for each maximum point of the acupressure signal. FIG. 4 (E) shows the ring counter 7.
The state of change in the count value of is shown by numbers.

FIG. 4 (F) shows the states of changes in the latch contents of the latch circuit 13 by numbers. FIG. 4 (G) shows a decoder 14
Of the read command signal. In this case, the high level is the read command signal.

FIG. 5 shows an example of a program relating to ignition control of the ignition angle setting circuit 15 of the device shown in FIG. That is,
The ignition angle setting circuit 15 performs the ignition control operation,
First, the ignition angle θ _IG is set to the initial value θ _IGO , the read command signal from the decoder 11 is waited, and when the read command signal is received, the latch content of the latch circuit 10 is fetched as peak position data θ _px ( Step S ₁ ,
S ₂ ). Next, it is judged whether or not this peak position data θ _px is larger or smaller than the sum of the top dead center angle θ _TDC (here, θ _TDC = 0 °) and the angle α of 12 ° (step S ₃ ), and it is judged to be large. If so, the ignition angle θ _IG is advanced by Δθ (step S ₄ ), and if it is smaller, the ignition angle θ _IG is retarded by Δθ (step S ₅ ). The operation of one cycle of steps S ₁ to S ₅ from the start to the end is sequentially executed according to the clock pulse, and the cycle operation is repeated. The following programs are similar in this respect.

FIG. 6 shows an example of an operation program when the ignition command circuit 16 is formed by a microprocessor. That is, when the ignition command circuit 16 detects a datum signal (step S _11), the crank angle current value of the internal register θ
_ig is set to θ _TDC (or a predetermined value) (step S ₁₂ ). Next, the ignition angle data θ _IG from the ignition angle setting circuit 15 is fetched (step ₁₂ ), and this is compared with the current crank angle value θ _ig, and an ignition command is issued immediately when the condition of θ _ig = θ _IG is satisfied ( step S _14, S _15), allowed to open the ignition switch SW. On the other hand, when θ _ig ≠ θ _IG , the unit crank angle δθ is added to θ _ig to prepare for the next program cycle (step S ₁₆ ). In step S ₁₄ , it is not a judgment as to whether or not θ _ig = θ _IG , but θ _ig and θ _IG
It may be possible to determine whether the difference from _IG is smaller than δθ.

In the above example, the peak position data θ _px is obtained every engine cycle, and the ignition angle θ _IG for the next cycle is determined by θ _px in each cycle.

In the above-described embodiment of the present invention, the starting state of the engine is detected by turning on the start switch, but the invention is not limited to this. For example, when the generation interval of the clock pulse is a predetermined time or more, The engine start start state may be set when the number of revolutions is equal to or lower than the predetermined number of revolutions.

As is apparent from the above, according to the ignition timing control device of the present invention, it is confirmed that the peak position of the finger pressure coincides with the reference position (TDC position) at the time of engine start. The reference position signal is generated when the acupressure signal reaches the maximum peak, and then the reference position signal is generated every time the clock pulse is counted by the number corresponding to one cycle of the engine. The ignition timing can be accurately controlled by detecting the reference position without providing a dedicated pulser or the like. Therefore, since only one pulsar is required, the pulsar can be easily provided on the engine and the cost of the entire apparatus can be reduced.

[Brief description of drawings]

FIG. 1 is a graph illustrating changes in internal pressure of an engine cylinder, FIG. 2 is a circuit diagram showing an embodiment of the present invention, and FIGS. 3 and 4 are signal waveform diagrams showing the operation of the apparatus of FIG. FIG. 5 and FIG. 6 are flowcharts showing an operation program of a portion constituted by the microprocessor of the apparatus shown in FIG. Explanation of symbols of main parts 7 ... Ring counter 8 ... Reference position signal generation circuit 13 ... Latch circuit 14 ... Decoder 15 ... Ignition setting circuit 16 ... Ignition command circuit SW ... Ignition switch T ... Ignition Trance

Claims (1)

[Claims] 1. A reference position signal generating means for generating a reference position signal each time the crank rotation angular position of an internal combustion engine reaches the reference angular position, and a finger pressure signal generating means for generating a finger pressure signal representing an engine combustion chamber pressure. Peak position detecting means for generating a finger pressure peak data signal representing the maximum peak position of the finger pressure signal from the generation of one reference position signal to the generation of the next reference position signal, and engine ignition at an ignition angle corresponding to the finger pressure peak data signal. And an ignition timing control device for instructing the ignition timing control device, wherein the reference position signal generation means outputs a predetermined number of clock pulses to crank rotation until the crank rotation angular position reaches the reference angular position again. When a clock pulse generating means that is generated in synchronization with the acupressure signal reaches its maximum peak immediately after the engine start operation is started. And a counting means for generating a reference position signal at the time of generation of the peak signal and thereafter generating the reference position signal each time the clock pulse is counted by a predetermined number. A characteristic ignition timing control device for an internal combustion engine.