JPS63227955A - Knocking control device for engine with supercharger - Google Patents

Abstract

PURPOSE:To eliminate the possibility of generating engine damage, by providing a limiting means which limits correction of the ignition timing to its advance timing side after knocking disappears, when a supercharge pressure control means comes to be substantially unable to control a supercharge pressure to be decreased. CONSTITUTION:An engine B is equipped with a turbosupercharger A, and the engine B, having an ignition timing control means C and a supercharge pressure control means D, controls the ignition timing to be retarded by the ignition timing control means C, when generation of knocking is detected, while the ignition timing so as to be advanced to the regular ignition timing when the knocking disappears. While the engine controls the knocking, when it is generated, so as to decrease a supercharge pressure by the supercharge pressure control means D. In a device such as in the above, an advance timing amount limiting means E is further provided, and when a decrease of the supercharge pressure comes to be substantially unable to be controlled by the supercharge pressure control means D, the engine is controlled so as to restrict correction of the ignition timing to its advance timing side by the ignition timing control means C after the knocking disappears.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a knocking control device for a supercharged engine.

(Prior Art) Generally, in a supercharged engine, knocking is more likely to occur when the supercharging pressure is high. This is because knocking itself is caused by spontaneous ignition of the end gas (unburned air-fuel mixture at the end of the flame propagation direction) before the flame propagation after ignition, causing high combustion pressure in the engine combustion chamber and temporarily causing rapid combustion. (in the case of spark-ignition engines), when the compression pressure in the engine combustion chamber is high and the boost pressure is high, spontaneous ignition is more likely to occur, and detonation as described above is more likely to occur. It depends. Therefore, as a means for suppressing knocking in a supercharged engine, the knock intensity is generally detected by a knock sensor, and the ignition timing is retarded according to the detected knock intensity to prevent combustion near the top dead center of the piston. The pressure is reduced by a predetermined amount to suppress an increase in the compression pressure of the end gas, and a supercharging pressure control means is provided to reduce the supercharging pressure of the supercharger when the knocking is detected (for example, (See Japanese Patent Publication No. 61-9503).

(Problem to be Solved by the Invention) However, in a control system that simply uses ignition timing retard control and supercharging pressure reduction control as means for suppressing knocking, such as the above-mentioned conventional technology, the knock sensor detects the knock state. As long as it is detected, the control will automatically continue to retard the ignition timing and reduce the boost pressure, and even if there is an uncontrollable state where the boost pressure cannot be lowered any further (for example, the actuator's duty cycle is Even if the ratio is at its maximum (caused by the wastegate actuator, stick in the exhaust gas relief passage, etc.), at least the ignition timing correction control will continue as is.

Therefore, in this state, once the knocking disappears due to the retardation of the ignition timing, the ignition timing is advanced in accordance with the amount of retardation and corrected to the proper ignition timing.

However, if the ignition timing is advanced in response to the above-mentioned retard skip in a state where the boost pressure cannot be reduced as described above, the state will return to the state where knocking is likely to occur, and the new strength will be increased. When knocking occurs, it is not possible to control the reduction in boost pressure itself due to the above reasons, so the knocking must be suppressed only by retarding the ignition timing, and depending on the boost pressure value at that time, the ignition timing may change. There are cases where it is impossible to actually suppress knocking with just the retard, and there is a problem in that it causes considerable damage to the engine.

(Means for Solving the Problems) The present invention has been made for the purpose of solving the above problems, and includes an ignition timing control means and a supercharging pressure control means, and when knocking occurs, the above-mentioned The ignition timing control means retards the ignition timing of the engine, and when the knocking disappears, the ignition timing is controlled to be advanced to the normal ignition timing, and when the knocking occurs, the boost pressure is controlled. In a supercharged engine in which the supercharging pressure is reduced by a means, when it becomes substantially impossible to control the reduction of supercharging pressure by the supercharging pressure control means, after the knocking by the ignition timing control means disappears. An advance angle limiter is provided for limiting the correction of the ignition timing toward the advance side.

(Function) According to the above means, in a state where boost pressure reduction control cannot be performed, the amount of advance of the ignition timing after knocking disappears is limited to a value smaller than the original correction value. The engine operating state after the engine is turned on is an operating state in which knocking is not likely to occur or, even if knocking occurs, the level of knocking is relatively low. Therefore, there is no risk of engine damage even if the operation is continued when the supercharging pressure reduction control is impossible as described above.

(Embodiment) FIGS. 2 to 4 show a knocking control device for a supercharged engine according to an embodiment of the present invention.

First, FIG. 2 is a schematic diagram of the control system of the apparatus of the above embodiment, and reference numeral 1 in the figure indicates an engine equipped with a turbocharger 6. In FIG.

The turbo supercharger 6 includes a compressor wheel 6a and a turbine wheel 6b, and these wheels are interconnected by a rotating shaft 7.

In the intake passage 2 that communicates with the intake manifolds 31 to 34 of each cylinder of the engine body 1, from the intake upstream side to the intake downstream side, an air cleaner 3, an air flow meter 4, and a compressor wheel of the turbo supercharger 6 are sequentially installed. 6a and a surge tank 5 are provided respectively.

The intake air taken in by the air cleaner 3 is measured by an air flow meter 4, compressed and pressurized by the compressor wheel 6a, and then supplied to the engine.

Further, a turbine wheel 6b of the turbocharger 6 is provided in the middle of the exhaust passage 9 of the engine l,
The rotation of the turbine wheel 6b due to exhaust gas energy drives the compressor wheel 6a to supercharge the intake air. Further, the exhaust passage 9 is connected from the inlet side 8A to the outlet side 8A in the turbine housing portion of the turbine wheel 6b.
The inlet side 8A and outlet side 8B of the curved portion bypass the turbine housing and are provided with an exhaust gas relief passage IO, and the outlet 8B side end of the relief passage IO A waste gate valve 11 is installed in the section. The wastegate valve 11 is connected via a link lever 12 to an operating shaft of a wastegate actuator 13 made of a diaphragm, and the valve state is controlled by the wastegate actuator 13 during this time. Further, the wastegate actuator 13 is connected to an intake pressure introduction passage 14 and an intake relief passage 1 to the downstream and upstream sides of the compressor wheel 6a of the intake passage 2, respectively, via an electrically controlled three-way soresoid valve t5.
6, and the opening time of the three-way solenoid valve 5 is controlled by the boost pressure control signal Sp (FIG. 5C) from the engine control unit 24, which will be described later. The opening period of the waste gate valve 11, that is, the amount of relief of exhaust gas is adjusted according to the duty ratio) to control the supercharging pressure of the intake air by the intake passage side compressor wheel 6a.

On the other hand, the reference numeral 22 is a distributor equipped with an engine speed and ignition timing pickup, and applies a high-voltage secondary current from an igniter (not shown) to the spark plugs 20, 20, etc. of the engine side number cylinders at a predetermined ignition timing. The actual engine speed Nε and ignition timing G detected by the engine speed pickup and ignition timing pickup of the distributor 22 are as follows:
Each is input to the engine control unit 24. The engine control unit 24 is composed of a microcomputer, and includes a knocking detection signal Vf detected by the knock sensor 21 along with the above detection signal, an ON signal of the idle contact of the intake air amount Q1 detected by the air flow meter 4, and 0 ．． Sensor output Vo, engine boost pressure B, throttle opening signal T
Control parameters required for various controls such as engine air-fuel ratio such as VO, engine cooling water @TW, ignition timing, and knocking suppression control are input.

Next, the ignition timing control operation of the engine by the engine control unit 24 will be explained in detail with reference to the flowchart of FIG.

First, in step S, an ON signal of the ignition switch IGSW is input as a control start trigger signal, and it is determined whether the ON state is the same as the OFF state.

If the result is YES, that is, when starting the engine, first, the retard amount of the ignition timing and the knock occurrence memory value (knock intensity) in the RAM in the engine control unit 24 are sequentially reset (step S!+53). ). Then, the process proceeds to step S, where the intake air amount Q1 and engine speed loss Nε are newly read, and in step Ss, the basic advance value of the ignition timing corresponding to the engine operating state at that time is calculated according to these values. . The calculation of this basic advance angle value is, of course, performed in consideration of the octane number of the fuel (gasoline) used for the engine.

Next, in step S, the output Vf of the knock sensor 21 (FIG. 5a) is read, and the process proceeds to step S7, where it is determined whether or not a knock has occurred.

If knocking has occurred (YES), the process further proceeds to step S, where the three-way solenoid, which is a supercharging pressure control means for controlling the supercharging pressure of the supercharger 6, is activated. Boost pressure control signal to valve 15 (Fig. 5C
) It is determined whether the boost pressure is saturated (see FIG. 5d) from the value of the duty ratio.

If the result is YES, the process proceeds to step S, where it is determined whether or not there is a memory of the fact that a knock occurred before that, and if there is no memory of the fact that a knock occurred (No), the process further proceeds to step SIG. The current knock occurrence value is memorized.

Then, in the next step S, the amount of retard of the ignition timing is calculated according to the knock intensity at that time, and then in step S1! Then, the calculated value (retard amount) is stored. Subsequently, in step S13, the actual ignition advance value is calculated (corrected) by subtracting the calculated value from the basic advance value determined by the engine operating state at that time, and finally, in step S14, a corresponding value is calculated. Outputs the ignition timing signal (Fig. 5b) I gc.

On the other hand, if it is determined in step S7 that there is no knock occurring at this time (No), there is no need to retard the ignition timing, so first step S'
Then, it is determined whether or not the retard amount of the ignition timing at that time (the amount of retardation with respect to the reference value SL) h (0) is determined. , Proceed directly to step S+a and, as in the case of step S6 above, check the saturated state of the supercharging pressure (Fig. 5 d). This includes an uncontrollable state in which the supercharging pressure cannot be lowered any further, including cases due to failure. ) to judge. If the supercharging pressure is saturated (YES), in which it is virtually impossible to control the reduction of the supercharging pressure, then in the next step S+7, it is determined whether or not knocking occurred last time. If not (No), it is determined that the knock has disappeared, and the process further proceeds to step srs, where an appropriate amount of retard of the ignition timing is calculated according to the current operating state. In the above case, the ignition timing retard amount is calculated based on the fact that there is no knocking (knocking has disappeared), so the ignition timing is normally advanced in response, but this advance is based on the current ignition timing. Simply from the retard amount! The actual advance angle correction is stopped by only subtracting a predetermined amount of attenuation, which is an integral value for a cycle (see FIG. 5). Then, proceed to steps S and t above.

On the other hand, if the determination in step StS is YES, meaning that the current ignition timing retard amount is 0, the process directly proceeds to step Sat.

Also, if the supercharging pressure is not saturated in step S1# above, N
In the case of O, the process directly proceeds to step SI6, while in the case of YES in the above step S+t where knock occurred last time, it is acknowledged that knocking is still being suppressed and the current ignition timing retard amount is held as is in step StS. After doing so, the process proceeds to step 5lffi described above.

Next, the supercharging pressure control operation performed in response to the above-mentioned ignition timing control will be explained in detail with reference to the flowchart of FIG. 4.

First, in step SI, turn on the ignition switch I.
Determine whether the GSW has changed from OFF to ON, and select YES.
If S, then step S.

Proceed to and first reset the boost pressure control signal supplied to the three-way solenoid valve I5 (initial set).
.

Then, the process further advances to step S, where the amount of retardation of the ignition timing in the flow shown in FIG. The level of knocking caused by the ignition timing is J111.11. ?
I have to decide whether or not to ask because my husband is still alive.

If the result is YES, it is recognized that boost pressure reduction control is necessary, and the process proceeds to the next step Ss. (target value to be lowered). After that, first, it is determined whether or not the current supercharging pressure reduction control is possible, that is, the saturated state of the supercharging pressure, and if YES, the process proceeds to step S7, where the state (saturated state) is memorized. The process proceeds to step S, while if NO, the process directly proceeds to step S8, where the three-way solenoid valve 1
5, a supercharging pressure control signal corresponding to the above-mentioned calculated value is output, and the supercharging pressure is controlled to decrease to suppress knocking.

On the other hand, in the case of NO in each of the above steps Ss and Ss,
The process directly proceeds to step S8. Then, normal supercharging pressure control that is different from knocking control is performed. In addition, in this embodiment, when the boost pressure reduction control is suppressed (when disabled)
Although advancing the ignition timing is prohibited in , the ignition timing may be advanced with a small control gain, that is, gradually advancing the ignition timing.

(Effects of the Invention) As explained above, the present invention includes an ignition timing control means and a supercharging pressure control means, and when knocking occurs, the ignition timing control means retards the ignition timing of the engine. , with a supercharger that controls the ignition timing so as to advance it to the normal ignition timing when the knocking disappears, and also reduces the supercharging pressure by the supercharging pressure control means when the knocking occurs. In the engine, when control to reduce the boost pressure by the boost pressure control means becomes substantially impossible, an advance angle that limits the correction of the ignition timing to the advance side by the ignition timing control means after knocking disappears. It is characterized by being provided with a quantity limiting means.

In other words, according to the present invention, in a state in which boost pressure reduction control cannot be performed, the amount of advance of the ignition timing after knocking disappears is limited to a value smaller than the original correction value. The operating state of the engine is such that knocking is not likely to occur or, even if knocking occurs, the level of knocking is relatively low. Therefore, there is no risk of engine damage even if the operation is continued when the supercharging pressure reduction control is impossible as described above.

[Brief explanation of drawings]

Fig. 1 is a diagram corresponding to claims of the present invention, Fig. 2 is a control system diagram of a knocking control device for a supercharged engine according to an embodiment of the present invention, and Fig. 3 is an ignition timing control operation of the same device. FIG. 4 is a flowchart showing the supercharging pressure control operation of the device, and FIG. 5 is a time chart showing signal waveforms of each part in the control operation of the device. ! ... Engine 2 ... Intake passage 6 ... Turbocharger 9 ... Exhaust passage lO ... Exhaust gas relief passage ■! ...Wastegate valve 13...Wastegate actuator 15...
・Three-way solenoid valve 20...Spark plug 21...Knock sensor

Claims (1)

[Claims] 1. Equipped with an ignition timing control means and a boost pressure control means, and when knocking occurs, the ignition timing control means retards the ignition timing of the engine, and when the knocking disappears, the ignition timing is returned to the normal ignition timing. In a supercharged engine in which the ignition timing is controlled to advance the ignition timing and the supercharging pressure is reduced by the supercharging pressure control means when knocking occurs, the supercharging pressure is controlled by the supercharging pressure control means. A supercharger characterized in that a supercharger is provided with advance amount limiting means that limits the ignition timing control means from correcting the ignition timing to the advance side after knocking disappears when lowering control becomes substantially impossible. Knocking control device for the attached engine.