JPH0419371B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a boost pressure control device for an internal combustion engine, and more specifically, when knocking is detected, the control target boost pressure is reduced to avoid knocking, and The present invention relates to a boost pressure control device for an internal combustion engine configured to protect the engine and improve engine output by quickly increasing the control target boost pressure after avoidance.

(Prior Art) In a supercharged internal combustion engine, when knocking occurs, it is necessary to reduce the supercharging pressure to avoid knocking. One example of this is the technique described in Japanese Patent Application Laid-Open No. 167881/1983.

(Problems to be Solved by the Invention) However, in the conventional example described above, no special consideration is given to speeding up the boost pressure again after reducing the boost pressure to avoid knocking. Depending on the operating state of the engine, there is a problem in that the engine output may not necessarily be fully utilized.

Therefore, an object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, to avoid knocking by calculating a boost pressure control target value and lowering the target value when knocking occurs, and to quickly control the boost pressure control after knocking has been avoided. It is an object of the present invention to provide a boost pressure control device for an internal combustion engine that can increase the target value and improve the engine output to the maximum extent.

Furthermore, as a supercharging pressure control device, JP-A-58-
13127 and Japanese Unexamined Patent Publication No. 16240/1982 are also known, but in these prior art techniques, including the one shown at the beginning, the correction unit amount when increasing or decreasing the boost pressure is calculated based on the internal combustion engine. Since the boost pressure is not changed depending on the operating condition, it is difficult to realize supercharging pressure control that accurately corresponds to the operating condition.

Therefore, the second object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to provide an internal combustion engine which changes the boost pressure increase/decrease correction unit amount according to the operating conditions to more quickly respond to the operating conditions of the internal combustion engine. An object of the present invention is to provide a boost pressure control device for an engine.

(Means and operations for solving the problems) In order to achieve the above object, the present invention, as shown in FIG. Knocking detection means 12 for detecting knocking, control target supercharging pressure calculating means 14 for calculating a control target value of supercharging pressure by inputting the outputs of the knocking detecting means and the operating state detecting means, and the control target supercharging pressure The control target supercharging pressure calculating means includes a supercharging pressure adjusting means 16 that inputs the output of the calculating means to adjust the supercharging pressure, and the control target supercharging pressure calculating means:
When knocking is detected, the control target value is calculated to reduce the boost pressure after a predetermined period of time has elapsed;
After knocking is avoided, a control target value is calculated to increase the boost pressure after a predetermined period of time has elapsed, and the increase/decrease correction unit amount is changed in accordance with the engine speed.

(Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 2 is a block diagram showing the overall configuration of the apparatus according to the present invention. In the figure, an internal combustion engine 20
A crank angle sensor 24 that outputs a crank angle position signal of engine rotation as the piston 22 moves up and down is disposed near the rotating part. Further, an intake temperature sensor 28 for detecting the intake air temperature is disposed at an appropriate location in the intake passage 26 of the internal combustion engine 20, and a water temperature sensor 32 for detecting the temperature of engine cooling water is disposed in the cylinder block 30. These crank angle sensor 24, intake temperature sensor 28 and water temperature sensor 3
2 constitutes the above-mentioned operating state detection means 10. Further, a knock sensor 36 is arranged near the combustion chamber 34 of the internal combustion engine 20 to detect the combustion pressure in the combustion chamber 34.

After the output of the knock sensor 36 is appropriately amplified,
Control unit 1 as the control target boost pressure calculation means
4, where it is input to bandpass filter circuit 3.
After only the knocking frequency component is extracted at step 8, it is input to the next-stage knocking detection circuit 40 consisting of a comparator, a peak hold circuit, etc., where it is compared with a predetermined level to detect whether or not knocking has occurred. The knocking strength is detected from the maximum value. The knocking detection circuit 40, knock sensor 36, and bandpass filter 38 constitute the knocking detection means 12 described above.

The control unit 14 has an input/output interface 1
4a, a CPU 14b, a memory 14c and a clock 14d. CPU 14 of the control unit 14
The output of the knocking detection circuit 40 is input to b via the input/output interface 14a, and the output of the crank angle sensor 24 is also input via the waveform shaping circuit 42. The output is also A/D conversion circuit 44, 46
Input via .

The internal combustion engine 20 is provided with a turbo charger 48 and a turbine 52 disposed within the exhaust passage 50.
is driven by exhaust gas to drive a compressor 54 provided in the intake passage 26, and the compressed air is sent to the combustion chamber 3.
Send it within 4. A bypass 56 is attached to the exhaust path 50, and a waste gate valve 58 is provided at a branch position of the bypass 56. The valve 58 is opened and closed by a wastegate valve actuator 60 to adjust the boost pressure. The wastegate valve actuator 60 controls the opening/closing operation of the wastegate valve by driving a solenoid (not shown) on and off in response to the output of the control unit 14. This waste gate valve actuator 60 and waste gate valve 5
8 constitutes the supercharging pressure adjusting means 16 described above. A supercharging pressure sensor 62 for detecting supercharging pressure is disposed at an appropriate location in the intake passage 26, and its output is sent to the control unit 14 via an A/D conversion circuit 64.
It is input to the CPU 14b.

Next, the operation of the apparatus according to the present invention will be explained with reference to the flow chart of FIG.

First, in step 70, the crank angle sensor 2
4 and the engine speed Ne and intake temperature Ta detected through the intake temperature sensor 28.
Calculate PT. Since the control target value PT is stored as a map value in the memory 14c of the control unit, it is searched based on the detected engine speed Ne, etc.

Next, in step 72, the water temperature sensor 32
Control target value is determined based on the engine cooling water temperature Tw, atmospheric pressure Pa, etc. detected through a barometric pressure sensor (not shown), etc.
Correct PT.

Subsequently, in step 74, knocking correction is further applied to the control target value PT corrected as described above. Figure 4 shows the sub-system that calculates the knocking correction.
1 is a flow chart showing the routine.

This knocking correction subroutine is performed repeatedly at predetermined time intervals, and first, in steps 74a to 74i, the engine rotational speed Ne at that time is determined.
is compared with predetermined rotational speeds N1, N2, N3, N4, and N5, and one of the control regions Z1, Z2, Z3, and Z4 is selected. The fifth control area Z1-Z4
As shown in the figure, the control values are different. This control value is
It is stored as a table value in the memory 14c of the control unit 14.

Subsequently, in step 74j, it is determined whether or not the boost pressure control flag FT is "1". The knock supercharging pressure control flag FT and other flag groups to be described later are built into the control unit 14, and are set to "1" when the knocking detection circuit 40 detects knocking. In addition, if the ignition timing calculated by the ignition timing calculation means (not shown) exceeds a predetermined retard amount, or if the knocking occurrence frequency exceeds a predetermined value, a temperature sensor is activated to detect the wall temperature of the combustion chamber 34. The flag FT may be set to "1" in case the wall temperature exceeds a predetermined value.

If the knock boost pressure control flag FT is "1" in step 74j, then step 74j
At 74k, it is determined whether the supercharging pressure down control flag FTD is "1" at knock time. Since the initial value of this flag FTD is "0", if it is the first time, the flag FTD is set to "1" in step 74l. If not, then in step 74m, it is determined whether the count value TD of the boost pressure down time constant timer at the time of knock is greater than or equal to the predetermined value TDR. This judgment step is for checking whether a predetermined delay time has elapsed to prevent hunting.

If the predetermined delay time has elapsed in step 74m, a knocking correction value ΔPK (initial value "0") is calculated in step 74n. This work calculates the reduction unit correction pressure ΔPKD for pressure drop,
As shown in FIG. 5, selection is made from among ΔPKD1-ΔPKD4 according to control regions Z1-Z4. Since this reduction unit correction pressure differs depending on the control region divided by the engine speed, it is possible to perform knocking correction optimally depending on the engine operating state. It is to be noted that it is more effective if the decreasing unit correction pressure ΔPKD in FIG. 5 is further varied stepwise according to the knocking strength. The calculated knocking correction value ΔPK is the minimum corrected supercharging pressure ΔPKMi1
-ΔPKMi4, the minimum corrected supercharging pressure ΔPKMi1-ΔPKMi4 is set as the correction value (steps 74o and 74p). Also, if the delay time has not elapsed at step 74m, add a predetermined amount n to the timer value TD and return (step
74q).

If the boost pressure control flag FT is not "1" in step 74j, step 74r
At the time of knock, it is determined whether or not the supercharging pressure up control flag FTU is "1". The flag FTU is set to “1” to correct the knocking when there is a remaining knocking correction amount and the knocking is avoided.
The device is configured so that When the flag FTU is "1", in step 74s, the value TU of the boost pressure up time constant timer at the time of knocking is changed to a predetermined time constant TUR provided to prevent sudden boost pressure changes.
Determine whether or not the limit has been exceeded, and if it has exceeded the step
At 74t, the knocking correction value ΔPK is determined by selecting one of the incremental unit correction pressures ΔPKU1-ΔPKU4 according to the control region Z1-Z4. that time,
If the knocking correction value ΔPK is larger than the maximum corrected boost pressure ΔPKMa1-ΔPKMa4, it is fixed at the maximum pressure ΔPKMa1-ΔPKMa4 (step
74u, 74v). In addition, in step 74r, the boost pressure up control flag FTU is set to "1".
If not, if the state is such that an increase correction is required after knocking has been avoided, the flag FTU is set to "1" and the timer value TU is reset (steps 74w, 74x). This is also to prevent a sudden increase in supercharging pressure. Furthermore, if the delay time has not elapsed in step 74s, the timer value
Add a predetermined amount n to TU and return (step 74y). Furthermore, when the engine speed Ne is greater than or equal to the maximum rotation speed N1 or less than the minimum rotation speed N5, the knocking correction value is set to a predetermined fixed value ΔPKF (step
74z).

Returning to the flow chart in Figure 3 again, in the final step 76, the control target value corrected as above
PT is output to the wastegate valve actuator 60 to open and close the wastegate valve 58 to adjust the supercharging pressure.

FIG. 6 is a flowchart showing a second embodiment of the present invention.
This is a chart, and only the differences from the first embodiment will be explained. After knocking correction is added to the control target value PT in step 84, the actual supercharging pressure P2 is detected via the supercharging pressure sensor 62 in step 86. After that, in step 88, the difference from the actual supercharging pressure P2 is determined, and if there is a difference, the supercharging pressure is re-corrected in step 90 according to the difference, and is output in step 100, thereby performing feedback control of the supercharging pressure. be.

(Effects of the Invention) The present invention is configured to reduce the control target boost pressure when knocking is detected to avoid knocking, and to quickly increase the control target boost pressure after knocking is avoided. This system has the advantage that the engine can be protected by reliably avoiding knocking, and that the supercharging pressure can be immediately increased after knocking has been avoided to increase the engine output to the maximum limit.

[Brief explanation of drawings]

Fig. 1 is a diagram corresponding to the claims of the present invention, Fig. 2 is a block diagram of the device according to the present invention, Fig. 3 is a flow chart showing its operation, and Fig. 4 is a subroutine of the flow chart in Fig. 3. FIG. 5 is an explanatory diagram showing calculation values used in the flow chart of FIG. 4, and FIG. 6 is a flow chart showing a second embodiment of the present invention. 10... Operating state detection means (crank angle sensor 2
4, intake temperature sensor 28, water temperature sensor 32), 12
...Knocking detection means (knock sensor 36, bandpass filter 38, knocking detection circuit 40),
14... Control target boost pressure calculation means (control unit),
16...Supercharging pressure adjustment means (wastegate valve actuator 60, wastegate valve 58).

Claims (1)

[Scope of Claims] 1 a. Operating state detecting means for detecting the operating state of the engine; b. Knocking detecting means for detecting knocking occurring in the combustion chamber of the engine; c. Inputting the outputs of the knocking detecting means and the operating state detecting means. a control target supercharging pressure calculation means for calculating a control target value of the supercharging pressure according to the control target supercharging pressure calculation means; and d supercharging pressure adjusting means for adjusting the supercharging pressure by inputting the output of the control target supercharging pressure calculation means. In preparation, the control target supercharging pressure calculation means calculates the control target value in order to reduce the supercharging pressure after a predetermined period of time when knocking is detected, and after knocking is avoided, the control target boost pressure is reduced for a predetermined period of time. A supercharging pressure control device for an internal combustion engine, characterized in that it calculates a control target value to increase after waiting for the elapse of time, and changes its increase/decrease correction unit amount in accordance with the engine speed. 2. The boost pressure control device for an internal combustion engine according to claim 1, characterized in that when calculating the control target value when knocking is detected, the unit amount of decrease in the control target value is changed according to the intensity of knocking. .