JPH0568633B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a knock limiting device for an engine, and particularly to measures to prevent erroneous control when the engine is cold.

(Prior art) Conventionally, as an engine knock control device,
For example, as disclosed in Japanese Patent Application Laid-Open No. 60-75730, there is provided a knock detection means for detecting engine knocking, and an engine control such as the ignition timing of the air-fuel mixture when knocking occurs, upon receipt of the output of the knock detection means. By correcting the amount in the direction of suppressing knocking (to the retarded side in terms of ignition timing), knocking is effectively suppressed and good engine durability is ensured.

Since the combustion state of the mixture changes as engine control variables, such as the ignition timing of the air-fuel mixture, are corrected, the maximum amount of correction is usually set in advance, and the ignition timing is adjusted when knocking occurs. If the correction amount exceeds the set maximum amount, it is limited to the set maximum amount to ensure that the combustion state of the air-fuel mixture is at the minimum allowable limit state.

(Problem to be Solved by the Invention) However, in the above conventional system, when the engine is cold, the correction amount of the engine control amount suddenly reaches the set maximum correction amount, and the combustibility of the air-fuel mixture decreases by that amount. As a result, there was a problem that the engine output suddenly decreased.

Therefore, the inventors of the present invention conducted intensive research to find out the cause of the above-mentioned output drop, and found that when the engine is cold, the gap between the piston and the cylinder is relatively large, so the piston hits the cylinder wall during the combustion stroke. It was learned that the noise caused by this collision was mistakenly detected as knocking, and as a result, when the engine was cold, the correction amount suddenly reached its maximum value, causing a decrease in engine output.

Therefore, in order to suppress the output drop when the engine is cold, for example, it may be possible to forcibly stop the knocking control when the engine is cold.
According to this idea, in situations where knocking occurs when the engine is cold, especially during high-load operation where intake supercharging is performed by an exhaust turbo supercharger, etc., it is impossible to prevent piston damage or seizure, and the engine durability is reduced. There is a drawback that it is not possible to ensure a good quality.

In view of the above, the present invention aims to reduce the amount of engine control when the engine is cold, and when noise occurs due to strong hitting of the piston, erroneous detection of knocking due to this is unavoidable. By limiting the maximum correction amount of In addition, when true knocking occurs, the engine control amount is controlled as much as possible in the direction of suppressing knocking, thereby effectively suppressing knocking, and improving the durability and reliability of the engine.

(Means for solving the problem) In order to achieve the above object, the present invention provides the first
As shown in the figure, a knock detecting means 35 for detecting knocking of the engine 1, and a knock detecting means 35 for detecting knocking of the engine 1;
control amount correction means 50 which receives the output of 5 and corrects the control amount of the engine 1 in the direction of suppressing knocking when knocking occurs, and the control amount correction means 50
When the correction amount of the engine control amount exceeds a preset maximum correction amount, the engine control device includes a maximum correction amount limiting means 51 that limits the correction amount of the engine control amount to the preset maximum correction amount. Assumed. Then, an engine temperature detection means 40 detects the temperature of the engine, and a maximum correction amount change that receives the output of the engine temperature detection means 40 and changes the maximum correction amount set by the maximum correction amount limiting means 51 to a smaller value when the engine is cold. The configuration is such that a means 52 is provided.

(Function) With the above configuration, in the present invention, when knocking occurs, the engine control variables such as the ignition timing of the air-fuel mixture and the air-fuel ratio are corrected by the control amount correction means 50 in the direction of suppressing knocking, so that knocking can be effectively prevented. In addition to being suppressed, normal conditions (when the engine is warmed up)
Then, when the correction amount of the engine control amount exceeds the set maximum correction amount, the maximum correction amount limiting means 51
Since this correction amount is limited to the set maximum correction amount, knocking is suppressed as well as possible, and the combustion state of the air-fuel mixture is maintained at a minimum acceptable good combustion state.

On the other hand, when the engine is cold, the piston makes strong contact with the cylinder wall, causing noise, which makes it easy for knocking to be falsely detected. Since the maximum value of the correction amount of the engine control amount is changed to a smaller value by the correction amount changing means 52 than when the engine is warmed up, the combustion state of the air-fuel mixture remains unchanged even when knocking is erroneously detected due to noise generation. The situation will not get worse and an unexpected drop in engine output will be prevented. Furthermore, even when true knocking occurs, the engine control amount is corrected in the direction of suppressing knocking, so knocking can be suppressed as much as possible, ensuring good engine durability and reliability.

(Example) Hereinafter, an example of the present invention will be described based on the drawings from FIG. 2 onwards.

FIG. 2 shows the overall schematic configuration of an engine knock control device according to the present invention, which is applied to knock control of an engine using high octane fuel (high octane gasoline) or low octane fuel (regular gasoline) as the fuel used. It is. In the figure, 1 is an engine, 2 is a combustion chamber formed by a piston 4 that is slidably inserted into a cylinder 3 of the engine, 5 is a combustion chamber whose one end is connected to the atmosphere via an air cleaner 6, and whose other end is the combustion chamber mentioned above. Opening to chamber 2,
An intake passage 7 that supplies intake air to the combustion chamber 2 is an exhaust passage that opens into the combustion chamber 2 at one end and opens to the atmosphere at the other end to discharge exhaust gas. In the middle of the intake passage 5, there is a throttle valve 10 that controls the amount of intake air, and a fuel injection valve 11 that injects fuel toward the combustion chamber 2 downstream of the throttle valve 10.
A catalyst device 12 for purifying exhaust gas is interposed in the exhaust passage 7. Further, an ignition plug 13 for igniting the air-fuel mixture in the combustion chamber 2 is disposed at the top of the combustion chamber 2, and an intake valve 14 is disposed at the opening of the intake passage 5 to the combustion chamber 2. An exhaust valve 15 is arranged at each opening of the passage 7 into the combustion chamber 2 . Further, a fuel tank 19 is connected to the fuel injection valve 11 through a fuel supply passage 18 in which a fuel filter 17 is interposed. Fuel (regular gasoline) is supplied arbitrarily at different times.

In addition, the intake passage 5 on the upstream side of the throttle valve 10 and the exhaust passage 7 on the upstream side of the catalyst device 12 include:
An exhaust turbo supercharger 20 is arranged astride.
The exhaust turbo supercharger 20 includes a turbine 20a disposed in an exhaust passage 7, and a compressor 2 which is drivingly connected to the turbine 20a via a connecting shaft 20c and disposed on the upstream side of the throttle valve 10 in the intake passage 5.
0b, and a compressor 20b is rotationally driven by a turbine 20a rotated by the exhaust gas flow to perform supercharging of intake air.

A bypass passage 22 that bypasses the exhaust turbo supercharger 20 is provided in the exhaust passage 7 near the exhaust turbo supercharger 20, and an upstream opening of the bypass passage 22 is configured to open and close the opening. A waste gate 23 is arranged. The waste gate valve 23 includes a diaphragm device 25 for opening and closing the waste gate valve 23.
The diaphragm device 25 includes a pressure chamber 25b and a spring chamber 25c which are partitioned left and right in the figure by a diaphragm 25a, and a spring 25d is compressed in the spring chamber 25c.
A duty solenoid valve 26 is communicatively connected to 5b. The duty electromagnetic valve 26 receives the pressure of the intake passage 5 downstream of the compressor 20b of the exhaust turbo supercharger 20, that is, supercharging pressure, through the pressure passage 27, and also introduces the pressure into the compressor 20b through the open passage 28. When the intake passage 5 on the upstream side is opened and the duty ratio is 0%, the open passage 28 is closed and the supercharging pressure itself is applied directly to the pressure chamber 25b of the diaphragm device 25, thereby reducing the overcharging. Unbalanced supply pressure value where the supply pressure is greater than the biasing force of the spring 25d
When the temperature rises to P _L , the diaphragm 25a is biased while contracting the spring 25d to open the waste gate valve 23, while at the same time, when the duty ratio is 100%, the pressure passage 27 is opened to the maximum opening area. 28, the pressure value acting on the pressure chamber 25b is lowered, and the waste gate valve 23 is opened accordingly even at a boost pressure value PH higher than the boost pressure value _PL . In addition, 29 is the exhaust turbocharger 20
intercooler for cooling supercharged air, 30
is an igniter that adjusts the ignition timing of the spark plug 13.

A knock sensor 35 is arranged around the cylinder 3 of the engine 1 as a knock detection means for detecting knocking, and its detection signal is inputted via a knock adapter 36 to a controller 37 containing a built-in CPU, etc. .

Further, 38 is an air flow sensor disposed directly downstream of the air cleaner 6 to measure the amount of intake air; 39
40 is a cooling water temperature sensor that detects the engine temperature based on the engine cooling water temperature. 41 is the opening degree of the throttle valve 10. Opening sensor that detects
Reference numeral 42 denotes a distributor serving as an engine rotation speed sensor, and the detections from each of the sensors 38 to 42 are input to the controller 37. Then, the controller 37 controls the fuel injection valve 1
1. The duty solenoid valve 26 and the igniter 30 are each operated and controlled. In FIG. 2, reference numeral 43 indicates a starter switch that is turned on when starting the engine 1.

Next, the control of the fuel injection amount, ignition timing, and maximum boost pressure by the controller 37 will be explained based on the flowcharts shown in FIGS. 3A and 3B. Starting from Figure 3A, after turning on the power by turning on the ignition switch in step _S1 , assuming that the fuel to be used is high octane fuel, in step _S2 , the duty solenoid valve 26 is turned on. The duty ratio signal value D _REG of the control signal is set to 10%, the maximum boost pressure of the exhaust turbo supercharger 20 is initially set to the boost pressure value PH, and the ignition timing of the spark plug 13 is set in step _S3 . Initialize the retard amount θ _K to the reference value (0°cA). Further, in step _S4 , the engine coolant temperature is detected from the coolant temperature sensor 40, and in step _S5 , the engine coolant temperature is detected from the intake air temperature sensor 3.
Let us detect the intake air temperature from 9.

After that, turn on the starter switch 43 in step _S6 .
If the ON operation is YES, step _S7 determines that the engine is starting and remains on standby. After the engine is turned OFF and complete explosion, the engine is disabled in step _S8 . The engine speed Ne from the user 42 is detected, and the step
In step _S9 , the intake air amount Q per engine rotation is calculated based on the detection signal from the air flow sensor 38, and based on these values, the fuel injection amount T _P from the fuel injection valve ₁₁ is calculated in step S10. .

Then, in step _S11 , the engine speed Ne is compared with a very low speed value (for example, 500 rpm), and the engine speed Ne is
If YES is <500 rpm, it is determined in step _S7 that the engine is starting or stalled, and the process returns to step _S6 . On the other hand, after the start is completed, first, in order to determine whether or not the knock control and maximum boost pressure control are performed,
In step _S12 , the engine speed Ne is compared, and in step _S13 , the fuel injection amount (injection pulse width) _Tp is compared, and if Ne<1500rpm and _Tp <2msec, it is not within the control range. In step _S14 , the duty control value _DWG of the duty solenoid valve 26 is set to "0" value, and in step _S15 in Fig. 3B,
Repeat the above steps until the engine stops when the ignition switch is turned off.

On the other hand, in steps _S12 and _S13 above, Ne≧
In the case of YES at 1500 rpm and T _P ≧2 msec, it is determined in step _S16 that it is in the knock control and maximum boost pressure control region, and the duty ratio signal value D _REG to the duty solenoid valve 26 is set in step _S17 . After setting the initial setting value (100%), knocking control is performed using the ignition timing and maximum boost pressure from step _S18 onwards.

That is, first, in step _S18 , the knob sensor 35 is
Since the number of pulses is proportional to the knock intensity, the number of knock pulses is counted, and if the number of knock pulses = 0, the duration is determined in step _S19 in order to advance the ignition timing. T is measured, and if T≦60 msec, the ignition timing retard amount θ _K (i) is set and held at the previous value θ _K (i-1) in step _S20 to prevent erroneous control. On the other hand, if T > 60 msec, step _S21 changes the previous value θ _K (i-1) to a minute value (for example, 0.234°).
After subtracting the amount and advancing the angle by that amount, step
In S ₂₂ , grasp the value of this current retard amount θ _K (i),
If θ _K (i)<0, in order to prevent advance angle control beyond the reference value, in step S ₂₃ the process is particularly corrected to θ _K (i) = 0, and the process proceeds to step S ₂₅ .

Also, in step _S18 above, the number of knock pulses≠0
In this case, knocking is occurring, so the ignition timing is retarded, and in step _S24 , the retard amount θ _K (i-1) of the previous ignition timing is calculated as follows:
After increasing the current retard amount θ _K (i) by adding the per-time retard amount θ _RET that increases as the number of knock pulses increases, the process proceeds to step _S25 .

Then, in step _S25 , the ignition timing retard amount θ _K is compared with a limit value (for example, 6°cA), and it is determined that θ _K ≦6°cA.
In this case, it is determined that knocking can be sufficiently suppressed with ignition timing control, and steps are taken immediately.
Proceeding to _S37 , in step _S37 , the duty ratio signal value D _REG of the duty solenoid valve 26 at that time (initially 100
%), the intake air temperature correction coefficient has a characteristic that gradually decreases as the intake air temperature increases as shown in Figure 4.
After multiplying C _AT to calculate the duty control value D _WG of the duty solenoid valve 26 and correcting the maximum boost pressure value so that it becomes low at high intake air temperature in order to ensure engine reliability, in step _S15 . If it is determined that the engine is running, return to step _S4 and repeat the above operations.

On the other hand, if θ _K > 6°cA in step S ₂₅ , it is determined that maximum boost pressure control is necessary to suppress knocking, and the ignition timing retard amount θ _K limit value is determined in step S ₂₆ . (6°cA), then in step _S27 of Figure 3B, subtract 25% from the duty ratio signal D _REG (initially 100%) of the duty solenoid valve 26, and adjust the maximum boost pressure by that amount. By lowering the value, knocking can be effectively suppressed.

After that, the maximum boost pressure value will be lowered by one step, so after determining how many steps it can be lowered according to the engine coolant temperature, in order to return the ignition timing to the reference value after a predetermined time, first, in step _S28 , the cooling water is lowered. Temperature sensor 4
Grasp the cooling water temperature T _W from 0 and calculate the cooling water temperature
T _W is compared with a predetermined temperature value (e.g. 85°C) corresponding to engine warm-up, and since normally T _W ≧85°C during engine warm-up, the duty ratio signal value D after the above subtraction is determined in step _S29 . Understand the value of _REG , D _REG ≧
In the case of 0, the duty ratio signal value after subtraction D _REG
Then, the duty solenoid valve 26 is actually operated to lower the maximum boost pressure, and at the same time, in step S ₃₀
After setting a timer for a predetermined time (for example, 100 msc), step _S31 sequentially counts down the timer value, step _S32 waits for the timer value to become 0, and step _S33 sets the ignition timing retard amount. Reset θ _K to the reference value (“0” value) and return the ignition timing to its original value. On the other hand, if the control to lower the maximum boost pressure value is repeated several times and finally becomes D _REG <0 in step _S29 , it is determined that the knock control is at its limit, and the duty ratio signal value is lowered in step _S34 .
Correct D _REG to “0” value and install exhaust turbo supercharger 2.
The maximum boost pressure of 0 is maintained at the boost pressure value _PL , and the ignition timing at that time is also maintained.

In addition, in step _S28 above, if the engine is cold and T _W <85°C, it is determined that the noise caused by the strong contact of the piston 4 against the cylinder 3 is likely to lead to erroneous detection of knocking. , in order to suppress the drop in maximum boost pressure, the duty ratio signal value D _REG after _subtraction is set to a predetermined value (for example, 50
%) or more, and if D _REG ≧50%, it is determined that it is within the permissible range, and the duty solenoid valve 26 is actually operated and controlled using the duty ratio signal value D _REG after the subtraction. While lowering the maximum boost pressure, return to step _S30 and set the ignition timing retard amount _θK.
is reset to the reference value (“0” value) after a predetermined time. On the other hand, if D _REG <50%, it is determined that the limit of boost pressure reduction control is exceeded, and the step is
In _S36 , the duty ratio signal value D _REG after subtraction is held at 50% value, and the maximum boost pressure is maintained as it is.

After that, in step _S37 , the duty ratio signal value D _REG of the duty solenoid valve 26 is multiplied by the intake air temperature correction coefficient C _AT shown in FIG. 4 to calculate the duty control value D _WG , and then in step _S15 If it is determined that the engine is running, return to step _S4 and repeat the above operations.

Therefore, in the control flow shown in FIG. 3, in steps S ₁₈ , S ₂₄ to _{S 27} , and S ₂₉ to S ₃₃ , the output of the knock sensor 35 is received, and when knocking occurs, the ignition timing retard amount θ _K reaches the limit value. (6°cA), the duty ratio signal value D _REG of the duty solenoid valve 26 is decreased by 25% from 100%, and the maximum boost pressure value (engine control amount) of the exhaust turbo supercharger 20 is set. A control amount correction means 50 is configured to correct the boost pressure value PH in a stepwise direction to suppress knocking (in a direction of decrease).

In addition, in step _S34 of FIG _. The amount of decrease (correction amount) is the preset maximum correction amount (100
% to 0%), the maximum correction amount limiting means 51 is configured to limit this correction amount to 100% of the set maximum correction amount, that is, to limit the duty ratio signal value D _REG to 0%. are doing.

Furthermore, according to steps S ₂₈ , S ₃₅ and S ₃₆ in the same figure,
In response to the output of the cooling water temperature sensor 40, when the engine temperature is less than 85°C, which corresponds to warm-up, when the engine is cold, the maximum boost pressure value of the exhaust turbo supercharger 20 (the duty ratio signal value D _REG of the duty solenoid valve 26) is determined. )
is limited to 50%, and the maximum correction amount limiting means 51
The maximum correction amount changing means 52 is configured to reduce the set maximum correction amount from 100% to 50%.

Therefore, in the above embodiment, as shown in FIG. 5, when the engine is warmed up when the engine cooling water temperature is 85° C. or higher, as the number of knock pulses of the knock sensor 35 increases, the ignition timing retard amount θ _K
increases, the ignition timing is retarded, and knocking is suppressed. When knocking disappears, the ignition timing is advanced, and when knocking occurs again, the above-mentioned ignition timing retard control is repeated until the retard amount θ _K finally reaches the limit value (6°cA). , this time, the duty ratio signal value D _REG of the duty solenoid valve 26 is controlled to be smaller by 25%,
Accordingly, the maximum boost pressure by the exhaust turbo supercharger 20
As the pH decreases, the ignition timing reaches the reference value (θ _K =
0) is repeatedly performed, and knocking is effectively suppressed. Even if the above operation is repeated every time knocking occurs and the duty ratio signal value D _REG finally becomes D _REG <0, the maximum correction amount limiting means 5 as shown by the broken line in the same figure.
1, the maximum supercharging pressure of the exhaust _turbo supercharger 20 is maintained at the supercharging pressure value _PL .

On the other hand, when the engine is cold and the engine cooling water temperature is less than 85°C, the gap between the piston 4 and the cylinder 3 is relatively large, and the strong contact between the two tends to generate noise, and this noise is detected by the knock sensor 35 as knocking. Since the situation is such that erroneous detection is likely to occur, the duty ratio signal value D _REG is immediately limited to D _REG =0, and the maximum boost pressure suddenly decreases to the boost pressure value _PL . However, when the engine is cold, the reduction range (correction amount) of the duty ratio signal value D _REG
is changed from 100% to 50%, and as shown by the solid line in the same figure, the duty ratio signal value D _REG is reduced to its maximum value.
Stay at 50%. Due to this, the maximum boost pressure is
A boost pressure value located between the boost pressure value PH corresponding to 100% and the boost pressure value P _L corresponding to 0% {PH+
P _L }/2 and does not decrease to the minimum supercharging pressure value P _L , so that a sudden decrease in engine output is prevented as much as possible. Moreover, even if knocking truly occurs, the maximum boost pressure value has decreased from the boost pressure value PH to the boost pressure value {PH + P _L }/2, so knocking can be prevented as effectively as possible. This effectively ensures engine durability and reliability.

In the above embodiment, if the ignition timing retard control is not sufficient, the maximum boost pressure value is gradually lowered to a value corresponding to a low octane value (supercharge pressure value P _L ), but knocking control is not used. Of course, the engine control amount for suppressing knocking may be performed by controlling the boost pressure only, and the engine control amount for suppressing knocking may be the ignition timing or the air-fuel ratio of the air-fuel mixture in addition to the boost pressure. In that case, for example, in knocking control using ignition timing, the maximum value of the ignition timing retard amount θ _K (set maximum correction amount) can be changed from 6°cA when the engine is warmed up to 2°cA when the engine is cold. .

(Effects of the Invention) As explained above, according to the knock control device of the present invention, the set maximum correction amount at engine warm-up of the correction amount of the engine control amount to be corrected in the direction of suppressing knocking when knocking occurs. Since the change is made small when the engine is cold, even if knocking is erroneously detected due to noise when the engine is cold, over-correction of the engine control amount due to this can be prevented, and an unexpected drop in engine output can be effectively prevented. Even if knocking does occur, it can be effectively suppressed and the durability and reliability of the engine can be improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention. Figures 2 to 5 show embodiments of the present invention, with Figure 2 being a general schematic diagram, Figures 3A and 3B being a flowchart showing the operation of the controller, and Figure 4 being the maximum excess temperature with respect to intake air temperature. A characteristic diagram of the supply pressure correction coefficient and FIG. 5 are operation explanatory diagrams. 1...Engine, 13...Spark plug, 20...
...Exhaust turbo supercharger, 23...Wastegate valve, 26...Duty solenoid valve, 35...Knock sensor, 37...Controller, 40...Cooling water temperature sensor, 50...Controlled amount correction means, 51...
Maximum correction amount limiting means, 52... Maximum correction amount changing means.

Claims (1)

[Claims] 1 Knock detection means for detecting knocking of the engine; control amount correction means for receiving the output of the knock detection means and correcting the control amount of the engine in the direction of suppressing knocking when knocking occurs; The correction amount of the engine control amount is
Maximum correction amount limiting means for limiting the correction amount of the engine control amount to the preset maximum correction amount when the preset maximum correction amount is exceeded, and engine temperature detection means for detecting the temperature of the engine;
A knock control device for an engine, comprising: maximum correction amount changing means that receives the output of the engine temperature detection means and changes the maximum correction amount set by the maximum correction amount limiting means to a smaller value when the engine is cold.