JPS6314191B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ignition timing control method for an engine.

An example of an ignition timing control device for an engine installed in a vehicle such as an automobile is shown in FIG.

To explain this simply, a vibration sensor 1 attached to an engine cylinder block (not shown), etc.
A knocking detection circuit 2, which is shown surrounded by a broken line, is detected from the detection signal S by detecting engine vibration.
(including the fail-safe circuit 13) detects the presence or absence of knocking.

That is, from the detection signal S of the vibration sensor 1, the ignition noise mixed in at the time of ignition is cut out by the gate circuit 3, which is closed for a certain period of time immediately after ignition, using a signal SF having a predetermined pulse width periodic to the ignition signal ST.
The signal is amplified by a predetermined amount by a buffer amplifier 4, and a signal Sa of a predetermined frequency (6 to 8 KHz) is extracted via a bandpass filter 5.

Next, this signal Sa is smoothed and amplified by a smoothing/amplifying circuit 6, and then is sent to an offset setting circuit 7.
The DC signal Sb is obtained by adding the offset voltage V ₀ from
After obtaining the signal Sb, the sample and hold circuit 8 samples and holds the signal Sb to obtain a comparison signal Sr. Note that this sample hold circuit 8 holds the signal Sb immediately before the signal S _{N is output while the knocking detection signal S N is} output from the comparator 12 described later, and when the signal S _N is not output. continues sampling continuously.

This comparison signal Sr and the output signal Sa of the bandpass filter 5 are input to the comparator 9 and compared, and Sa≧
Pulse signal Sp that becomes high level “H” when Sr
is output to the integrator 10. The integrator 10 integrates the pulse signal Sp and outputs a voltage signal Vp according to the number of pulses. Incidentally, this integrator 10 is reset every time the engine is ignited by the ignition signal _ST .

Next, this voltage signal Vp and the reference voltage generation circuit 1
The reference voltage Vr from 1 is input to the comparator 12 and compared, and when Vp≧Vr, it is assumed that knocking has occurred, and a knocking detection signal S _N that remains at a high level “H” for a predetermined period is output. do.

In this way, the presence or absence of knocking is detected, but due to a failure of the vibration sensor 1, etc., the signal level of the comparison signal Sr from the sample and hold circuit 8 becomes extremely high, or becomes zero, and the presence or absence of knocking is detected. When this becomes impossible, the fail-safe circuit 13 detects this and outputs a signal S _M that becomes "H" only at that time.

When the signal S _M output from the fail-safe circuit 13 is "L", the retard voltage generation circuit 14 outputs the knocking detection signal S _N from the comparator 12.
is output continuously, a corresponding retard control voltage V _D is output, and when the knocking detection signal S _N is no longer output, the retard control voltage V _D is gradually attenuated at a constant speed.

Further, when the signal S _M from the fail-safe circuit 13 becomes “H”, the retard voltage generation circuit 14
The retard control voltage V _D is determined in advance by the signal S _K and the signal S _M output from the rotation speed detection circuit 15 when the rotation speed is detected by the ignition signal S T and the rotation speed _exceeds a predetermined value. is held at a predetermined value.

Then, the angle control circuit 16 retards the basic ignition timing timing signal S _H determined by the distributor 17 according to the operating state of the engine in accordance with the voltage level of the retard control voltage V _D. to form an ignition signal S _T and output the ignition signal S _T to the ignition circuit 18 . Note that the retard voltage generation circuit 1
4 and the angle control circuit 16 constitute an ignition timing correction means.

Then, the ignition circuit 18 controls the energization of an ignition coil (not shown) so that ignition can be performed at the timing of the ignition signal _ST , and controls the firing via the distributor 17 and the spark plugs (not shown) for each cylinder. The ignition is performed in such a way that the occurrence is suppressed or avoided, or a slight knocking occurs.

Incidentally, the ignition timing correction range in the knocking control device described above is determined by the maximum retard control voltage that the retard voltage generation circuit 14 can output, and is constant.

On the other hand, the ignition timing at which knocking may occur varies depending on engine operating conditions such as engine speed. That is, as shown in Fig. 2, for example, the engine speed characteristic at the knocking limit is a curve (equal knocking line) A shown by a broken line, and the engine speed characteristic at an ignition timing where no knocking occurs is also a curve B shown by a dashed-dotted line. become that way.

Furthermore, although it is desirable to set the basic ignition timing determining characteristic of the distributor 17 in conjunction with the equal notching line A, in reality, it is approximated by a simple straight line as shown by the solid line C in FIG. That's all I can do.

Therefore, regardless of the frequency of occurrence of knocking, there are operating regions where knocking cannot be suppressed or avoided unless it is significantly retarded from the basic ignition timing determined by the distributor, and conversely, it is better to advance the ignition timing. An area is created, and as a result,
There have been cases where proper knocking control has become impossible, and engine output and fuel efficiency have deteriorated more than necessary.

In recent years, the ignition timing has been determined by detecting engine operating conditions such as engine speed and suction negative pressure, and calculating the ignition advance angle using an electronic circuit. In order to prevent this from occurring, it has also been proposed to retard the ignition timing at a predetermined speed based on the ignition advance angle calculated as above, and to correct the ignition timing so that it is advanced at a predetermined speed when knocking does not occur. ing.

However, even if you do this, it is important to always maintain the engine at the most efficient operating state in terms of engine output and fuel efficiency, which is the boundary between whether or not knocking occurs, or at a state where slight knocking occurs. However, there was a problem that it was difficult to control the ignition timing.

Furthermore, in the conventional knocking control device as described above, when the fail-safe circuit is activated, the basic ignition timing is retarded to the ignition timing that suppresses or avoids knocking to some extent under any operating condition. If the engine continues to operate at high load and high rotation speed for a long time, the exhaust gas temperature will rise considerably, damaging the durability of the exhaust pipe, and the temperature in the engine room will rise, resulting in poor restartability. It was hot.

Therefore, in the past, the air-fuel ratio was set low (large amount of fuel) in advance to prevent the exhaust gas temperature from rising even if the fail-safe circuit was activated and the ignition timing was delayed to a certain extent. Even when the engine is not operating, the air-fuel ratio decreases, resulting in poor fuel efficiency.

This invention was made in view of the above-mentioned problem, and is designed to enable the engine to be operated constantly near the boundary between knocking and not occurring, or in a state where knocking is so slight that it is not detected as occurring. In addition to controlling the ignition timing, the air-fuel ratio is also controlled to the optimum value to improve engine output and fuel efficiency, and even if an abnormality occurs in the knocking detection means and the fail-safe circuit is activated, the exhaust gas temperature will not be abnormal. The purpose of this invention is to prevent the occurrence of problems due to high temperatures.

Therefore, the engine ignition timing control method according to the present invention adjusts the ignition timing to the basic advance value of the ignition timing and the ignition timing when no knocking occurs, depending on the engine operating condition (for example, engine speed and fuel injection amount). The maximum value that can be advanced from the basic advance value, the advance speed when advancing the ignition timing, and the retardation speed when retarding the ignition timing are calculated respectively, and when the engine speed is below a predetermined value or a fail-safe circuit. When the engine is operating, the ignition timing is controlled to the above-mentioned basic advance value, and when the engine speed is not below a predetermined value and the fail-safe circuit is not operating, it is determined whether or not knocking is occurring. If knocking does not occur, the ignition timing is controlled to be advanced from the basic advance value at the advance speed, with the maximum value that can be advanced as the limit, and if knocking occurs, the ignition timing is controlled to advance. By controlling the advance angle value at that time to be retarded at the above-mentioned retardation speed with the above-mentioned basic advance value as a limit, the ignition timing can be adjusted between the basic advance angle value according to the engine operating condition and the maximum value that can be advanced. Control is performed at the most advanced time while preventing the occurrence of knocking.

If the exhaust gas temperature rises above a predetermined temperature, an increase in fuel is corrected to reduce the air-fuel ratio by a predetermined amount. Prevent exhaust gas temperature from becoming abnormally high.

Embodiments of the present invention will be described below with reference to FIG. 3 and subsequent figures of the accompanying drawings. In FIG. 3, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and explanations of those parts will be omitted.

In FIG. 3, an intake air amount sensor 20 measures the intake air amount of the engine and outputs an analog signal _S0 corresponding to the amount of intake air. The starter switch 21 outputs a signal _S1 which is "H" when the engine is cranking and is "L" otherwise. The crank angle sensor 22 outputs a reference pulse signal S ₂ at every constant crank angle (for example, 66 degrees) before top dead center depending on the number of cylinders of the engine during one revolution of the crankshaft, and Angle (e.g. 2°)
Outputs an angle pulse signal _S3 every time it rotates.

The exhaust gas temperature sensor 23 is installed in the exhaust manifold, detects the exhaust gas temperature, and outputs an analog signal _S4 corresponding to the exhaust temperature. Cooling water temperature sensor 24
detects the engine cooling water temperature and outputs an analog signal _S5 corresponding to the temperature. Fuel injection circuit 25
The fuel injection valve (electromagnetic valve) is driven and opened according to the pulse width of the pulse signal S _I outputted from the input/output interface 26 and indicating the fuel injection amount.

The input/output interface 26 consists of an A/D converter, a latch circuit, a counter circuit, a register, etc., and receives signals from each sensor and switch for detecting the engine operating state described above, as well as the knocking detection explained in FIG. Reading of signals etc. from the circuit 2, fail-safe circuit, signal conversion, temporary storage, measurement of engine rotation speed, data transfer to the calculation circuit 27, and formation of driving signals for each load based on calculation data from the calculation circuit 27 etc.

That is, the input/output interface 26 converts analog signals S ₀ , S ₄ , and S ₅ from the intake air amount sensor 20 , exhaust temperature sensor 23 , and cooling water temperature sensor 24 into digital signals using an A/D converter. or the angle pulse signal from the crank angle sensor 22.
S ₃ is counted for a certain period of time to measure the engine speed, and signals from other knocking detection circuits 2, fail-safe circuits 13 and starter switch 21 are used.
After reading S _N , S _M , and S ₁ , they are temporarily stored in the latch circuit.

Then, the various data stored in the latch circuit are transferred to a predetermined circuit in the arithmetic circuit 27 via the data bus line DB ₁ as appropriate in response to a command input from the arithmetic circuit 27 via the address bus line AB ₁ . . Note that a clock signal ck from a clock generator 28 is input to the input/output interface 26, and this clock signal ck is input to the A/D.
Used for conversion and engine speed measurement.

Further, the reference pulse signal S ₂ from the crank angle sensor 22 is inputted to the arithmetic circuit 27 via the input/output interface 26 at any time.

Furthermore, the input/output interface 26 forms a pulse signal S _{I of a pulse width according to the calculation result of the fuel injection amount from the calculation circuit 27, and generates the pulse signal S I.}
S _I is output to the fuel injection circuit 25, and the arithmetic circuit 2
An ignition signal _ST is formed based on the dwell angle calculation result and the ignition timing calculation result from 7, and is output to the ignition circuit 18. Note that the clock signal ck from the clock generator 28 is also used to form the pulse signal S _I.

The arithmetic circuit 27 has an input/output interface 26
various data from and non-volatile semiconductor memory.
Based on the data stored in the ROM29,
It calculates the fuel injection amount, ignition timing, etc., and outputs the results to the input/output interface 26.

Note that the ROM 29 is addressed by the arithmetic circuit 27 via the address bus line _AB2 ,
Data at the address specified by the address specification is output to the arithmetic circuit 27 via the data bus line _DB2 . Further, the RAM 30 serving as a data memory temporarily stores data in the middle of _an operation by the arithmetic circuit 27 and the result of the operation at an address specified via the address bus line AB ₃ , or vice versa. It is provided so that it can be read out via the

Next, the configuration and operation of the arithmetic circuit 27 will be explained with reference to FIG.

The arithmetic circuit 27 can be composed of one microprocessor, but from a functional perspective, as shown in FIG.
ADV (advanced angle value) calculation circuit 273, variable ADV (advanced angle value) calculation circuit 274, lead angle/retard angle speed calculation circuit 2
75, an exhaust gas temperature determination circuit 276, an ignition timing clamp circuit 277, and a fail-safe signal reading circuit 278.

The arithmetic control circuit 270 is provided to control the flow of arithmetic operations in each of the circuits described above. This arithmetic control circuit 270 usually includes a basic ADV arithmetic circuit 273, a variable ADV arithmetic circuit 274, an advance/retard angle speed arithmetic circuit 275, and an exhaust gas temperature determination circuit 27.
6. The ignition timing clamp circuit 277 and the fail-safe signal reading circuit 278 send and receive a computation start signal and a computation end signal in this order to proceed with computation control.

Then, every time the reference pulse signal _S2 is input from the input/output interface 26, the ignition timing calculation circuit 271 is activated by an interrupt, and the clock signal
The time is measured by ck, and the fuel injection amount calculation circuit 272 is activated by an interrupt every 10 msec, for example. Note that if another arithmetic circuit or the like is in operation when the above two interrupts occur, the interrupt is masked until the operation is completed.

When activated by an interrupt, the fuel injection amount calculation circuit 272 reads data on the engine speed and intake air amount measured at the input/output interface 26 from the latch circuit of the input/output interface 26, and calculates the basic fuel from both data. The injection amount (basic fuel injection amount∝intake air amount/rotational speed) is calculated and the calculation result is stored in the RAM 30.

Then, according to the cooling water temperature data from the input/output interface 26 and the judgment result of the exhaust gas temperature judgment circuit 276 (described later), that is, the judgment data when the exhaust gas temperature rises above a predetermined temperature.
The basic fuel injection amount data stored in the RAM 30 is corrected to increase the air-fuel ratio by a predetermined amount, and the result is stored in the RAM 30 and used for storing the fuel injection amount data in the input/output interface 26. Transfer to register. When these operations are completed, a computation end signal is output to the computation control circuit 270.

The basic ADV calculation circuit 273 converts the basic ADV value stored in advance in the ROM 29 in the form of a two-dimensional table of engine speed and fuel injection amount into engine speed data and basic fuel injection amount data stored in the RAM 30. Therefore, the table is searched up, and if there is corresponding data, its value is stored in the RAM 30, and if not, the value calculated from the table by linear approximation interpolation is stored in the RAM 30.
The dwell angle according to the ADV is also calculated and stored in the RAM 30. Then, when these operations are completed, a computation end signal is output to the computation control circuit 270.

Note that the basic ADV value stored in the ROM 29 is a value that can suppress or avoid knocking even when the partial pressure of water vapor in the intake air decreases, such as in winter.

The variable ADV calculation circuit 274 converts the variable ADV value stored in advance in the ROM 29 in the form of a two-dimensional table of engine speed and fuel injection amount into engine speed data and basic fuel injection amount data stored in the RAM 30. Then, pull up the table and select the relevant data if there is, or if there is not,
After storing the value calculated from the table by the linear approximation interpolation method in the RAM 30, a computation end signal is output to the computation control circuit 270. Note that this variable ADV value is the maximum value that can be advanced from the basic ADV value when knocking does not occur.

The advance angle/retard angle speed calculation circuit 275 is also
The advance angle and retard angle speeds, which are stored in advance in the ROM 29 in the form of a two-dimensional table of engine speed and fuel injection amount, are retrieved from the table based on the engine speed data and basic fuel injection amount data, and the corresponding data is retrieved. If there is, then its value, if not, the value calculated from the table by linear approximation interpolation method,
After storing in the RAM 30, a computation end signal is output to the computation control circuit 270.

The advance angle speed is defined as the amount of time it takes to advance the ignition timing by one degree, and the retard angle speed is defined as the amount of retard for one knocking occurrence. Stored in ROM29.

The exhaust gas temperature determination circuit 276 reads the exhaust gas temperature data latched in the latch circuit of the input/output interface 26, determines whether the value is greater than or equal to a predetermined value, and outputs the determination result. Store in RAM30. Then, a determination end signal is output to the arithmetic control circuit 270.

The ignition timing clamp circuit 277 reads the signal _S1 from the starter switch 21 and the engine speed data from the latch circuit of the input/output interface 26, and determines whether the signal _S1 is "H" or whether the engine speed is below a predetermined value. and store the judgment results in RAM.
Store at 30. Then, a determination end signal is output to the arithmetic control circuit 270.

The fail-safe signal reading circuit 278 reads the signal S _M of the fail-safe circuit 13 from the latch circuit of the input/output interface 26, determines whether the signal S _M is "H", and stores the determination result in the RAM 3.
0 and sends the determination end signal to the arithmetic control circuit 27.
Output to 0.

As described above, the ignition timing calculation circuit 271 is activated when the reference pulse signal _S2 is input to the calculation control circuit 270, and performs calculations according to the flow shown in FIG. 5, for example.

That is, first, when an interrupt occurs, the knock tires of the ignition timing calculation circuit 271 are activated. This knob timer. It is used to measure the advance angle velocity value (time data) stored in the RAM 30.

Next, in STEP 1 to 3, the ignition timing clamp circuit 2
77 and the fail-safe signal reading circuit 278 are read from the RAM 30, and whether the starter switch 21 is on or the engine speed is below a predetermined speed (for example, 400 rpm), the fail-safe circuit 1 is read.
3 is operating.

Then, if any one of the judgment conditions is satisfied, clear the knock timer in STEP 4,
In STEP 5, the ignition timing is set to the basic ADV value stored in the RAM 30, and in STEP 6, the ignition timing data and corresponding dwell angle data are transferred to the register of the input/output interface 26.

In this way, even if vibrations not caused by knocking occur during cranking or at low engine speeds, it will not be determined as knocking and the ignition timing will not be retarded. Of course, if the fail-safe circuit 13 operates, it means that an abnormality has occurred in the vibration sensor 1 or the knocking detection circuit 2, so the ignition timing is fixed at the basic ADV value to suppress or avoid the occurrence of knocking.

If the starter switch 21 is off, the engine speed exceeds a predetermined value, and the failsafe circuit 13 does not operate, check the latch circuit of the input/output interface 26 in STEP 7 to see if the knocking detection signal S _N is latched. Depending on whether or not knocking occurs, it is determined whether or not knocking occurs.

If knocking does not occur, it is determined in STEP 8 whether the time measured by the knocking timer is equal to or greater than the advance angle velocity value (time data) stored in the RAM 30. If the advance angle speed is higher than that, go to STEP 9 and change the ignition timing to the basic ADV stored in RAM30.
Advance the value by one degree and clear the knock timer in STEP10. Also, if the time measured by the knock timer is less than the advance angle speed value, steps 9 and 10 are jumped.

Next, STEP 11 and 12 are steps to determine whether the ignition timing is within the range of the basic ADV value to the basic ADV value + variable ADV value. Since it advances step by step, do not proceed to STEP 14 or 15.
Proceeding to STEP 6, ignition timing = basic ADV value + 1 degree and corresponding dwell angle data are transferred to the register of the input/output interface 26. Then, if knocking does not occur, the reference pulse signal S ₂
Each time an interrupt occurs, the ignition timing is advanced by one degree to the maximum basic ADV value + variable ADV value according to the given advance speed according to the flow described above. However, if it is determined in STEP 12 that the ignition timing has exceeded the basic ADV value + variable ADV value,
The ignition timing is delayed once in STEP 15, and the delayed ignition timing data is transferred to the register of the input/output interface 26 in STEP 6.

When it is determined that knocking has occurred in STEP 7, the basic ADV value, variable ADV value, and retardation speed value stored in the RAM 30 are read out in STEP 13, and the ignition timing is set to the basic ADV value + (variable
ADV value - retarded velocity value). and,
The ignition timing data is transferred to the register of the input/output interface 26 in STEP 6 together with corresponding dwell angle data via STEP 10, 11, and 12.

Note that the calculation in STEP 13 is performed every time knocking occurs, so if knocking occurs continuously, the ignition timing may be delayed from the basic ADV value. Therefore, if it is determined in STEP 11 that the ignition timing is delayed from the basic ADV value,
In STEP14, set the ignition timing to the basic ADV value.

Based on the ignition timing data and dwell angle data calculated in this way and transferred to the register of the input/output interface 26, the input/output interface 26 forms the ignition signal S _T.

That is, the ignition timing data and dwell angle data (determining ignition energy) are calculated every time the reference pulse signal _S2 shown in FIG. It is set in the ADV register and dwell register of the input/output interface 26 (see C and D in FIG. 6).

And ADV of input/output interface 26
As shown in FIG. 6C, the counter starts counting the angle pulse signal _S3 when the reference pulse signal _S2 is input, and is reset when the count value matches the data in the ADV register.
In addition, the dwell counter is as shown in Figure 6 D.
When the ADV counter is reset, counting of the angle pulse signal _S3 is started, and when the count value matches the data in the dwell register, it is reset.

Then, for example, by setting and resetting the flip-flop circuit based on the reset timing of the ADV counter and dwell counter, the ignition signal _ST corresponding to the data from the arithmetic circuit 27 as shown in FIG. Obtained from the terminal.

The ignition signal S _T thus obtained is output to the ignition circuit 18 as shown in FIG. 3, thereby causing the desired ignition.

As explained above, in the engine ignition timing control method according to the present invention, the engine ignition timing is adjusted according to the engine operating state, except when the engine speed is below a predetermined value or when the failsafe circuit is activated. Between the basic advance value and the maximum advance value calculated by
When knocking occurs, the engine is controlled to be retarded at a retardation speed that corresponds to the operating conditions, so the engine can be operated efficiently near the boundary between whether knocking occurs or not, improving engine output and fuel efficiency. In addition, it is possible to prevent problems caused by knocking.

Furthermore, when the exhaust gas temperature rises above a predetermined temperature, the fuel amount is corrected to reduce the air-fuel ratio by a predetermined amount, so there is normally no need to reduce the air-fuel ratio, so In addition, even if high-speed, high-load operation continues after the fail-safe circuit is activated, the exhaust gas temperature may become abnormally high, causing deterioration of the exhaust pipe, etc. It is possible to prevent the occurrence of inconveniences such as deterioration of startability.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional ignition timing control device. FIG. 2 is a diagram for explaining the operation of FIG. 1. FIG. 3 is a block diagram showing an embodiment of an ignition timing control device to which the present invention is applied.
FIG. 4 is a block diagram of the arithmetic circuit in FIG. 3. FIG. 5 is a flowchart showing the flow of calculations by the ignition timing calculation circuit in FIG. 4. FIGS. 6A to 6E are timing charts showing the process of forming an ignition signal. 1...Vibration sensor, 2...Knocking detection circuit, 1
3...Fail safe circuit, 18...Ignition circuit, 20
...Intake air amount sensor, 21...Starter switch,
22... Crank angle sensor, 23... Exhaust gas temperature sensor, 24... Cooling water temperature sensor, 25... Fuel injection circuit, 26... Input/output interface, 27... Arithmetic circuit.

Claims (1)

[Scope of Claims] 1. In an engine equipped with a knocking detection means, the basic advance value of the ignition timing and when knocking does not occur, the ignition timing is advanced from the basic advance value according to the operating state of the engine. In addition to calculating the maximum possible value, the advancing speed when advancing the ignition timing, and the retarding speed when retarding the ignition timing, it also determines whether the engine speed is below a predetermined value and when an abnormality occurs in the knocking detection means. It is determined whether or not the fail-safe circuit is operating, and when the engine speed is below a predetermined value or when the fail-safe circuit is operating, the ignition timing is controlled to the basic advance value, and the engine speed is controlled. is not below the predetermined value and the fail-safe circuit is not operating, it is determined whether or not knocking has occurred based on the detection signal of the knocking detection means, and if knocking has not occurred, the ignition is stopped. The ignition timing is controlled to be advanced from the basic advance value at the advance angle speed up to the maximum value that can be advanced, and if knocking occurs, the ignition timing is changed from the advance value at that time to the basic advance value. Control is performed to retard the angle at the retardation speed with the angle value as a limit, and when the exhaust gas temperature rises above a predetermined temperature, an increase in fuel is corrected to reduce the air-fuel ratio by a predetermined amount. This is an engine ignition timing control method.