JPH02275045A - Knocking controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To perform the accurate judgment of a knock detecting means at all times by changing a sensor fail judging level according to valve timing and/or lift, in a device which is equipped with a variable valve timing mechanism and a knock controlling means. CONSTITUTION:In an internal combustion engine 10 provided with two intake and exhaust valves 54, 56 at each cylinder, a variable valve timing mechanism 60, controlling valve timing and lift of these intake and exhaust valves 54, 56, is connected to these valves 54, 56. In addition, when a knock sensor has detected knock occurrence, an igniter 62 is controlled so sa to compensate ignition timing for its timing delay by the control unit 52. In this case, in the control unit 52, there is provided with a fail judging means which performs a trouble judgment of the knock sensor 44 in comparing output of the knock sensor 44 with a specified fail judging level. Then, the fail judging level is made so as to be changed according to the valve timing and/or lift.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a knock control device for an internal combustion engine, and more specifically, in a knock control device for an internal combustion engine equipped with a variable valve timing mechanism, the present invention relates to a knock control device for an internal combustion engine equipped with a variable valve timing mechanism. The present invention relates to a knock control device for an internal combustion engine that changes the determination level to accurately detect an abnormality in a knock sensor.

(Prior art) When knocking occurs in an internal combustion engine, it causes discomfort to the occupants, and if left untreated, there is a risk of serious damage to the engine. It is common practice to retard the ignition timing, and examples of the prior art include, for example, the Japanese Patent Publication No. 57-12
The technique described in Japanese Patent No. 027 can be mentioned. In such control, knock detection is usually done by installing a vibration sensor in the cylinder block, detecting the background vibration level of the engine at a crank angle that is not directly related to the combustion state, determining the noise level, and then determining the noise level based on the noise level. The occurrence of knock is detected by determining the knock determination level and comparing it with the sensor output during combustion. Furthermore, abnormalities in the vibration sensor itself are monitored by comparing the noise level with a sensor failure determination level appropriately set according to the engine speed.

Recently, in order to meet the high output demands of the engine, a technique has been proposed in which the valve timing of the intake and exhaust valves is made variable according to the operating state of the engine. For example, in that technology, 1
In a four-cylinder, four-valve engine, three cams are mounted in parallel on the camshaft.The cams located at both ends determine the valve timing at low engine speeds, and the cam located in the center determines the valve timing at high speeds. Deciding on timing.

In other words, three rocker arms are arranged in sliding contact with three cams, and the rocker arms at both ends are connected to the intake and exhaust valves, respectively.During low-speed operation, the rocker arm in the center is allowed to idle, and the intake air is activated at the timing determined by the cams at both ends. Open and close the exhaust valve. The three rocker arms can be connected freely by the bin, and during high-speed operation, the bin is moved by hydraulic pressure and the three rocker arms are connected to suck pulp at the high-speed pulp timing specified by the cam in the center position. The exhaust valve is opened and closed, and thus the pulp timing (and lift amount) is changed depending on the operating condition. An example of such a conventional technique is the technique described in Japanese Unexamined Patent Publication No. 121811/1983.

(Problem to be Solved by the Invention) By the way, when performing knock control as described above in an internal combustion engine equipped with the above-mentioned variable valve timing mechanism, when the valve timing changes, the lift amount or rotation characteristic changes, causing valve seating to change. It has recently been discovered that the sound changes and, as a result, the engine's background vibration levels fluctuate. Figure 10 shows experimental data showing changes in the knock sensor output (voltage V) with respect to the engine rotation speed Ne (rpm) conducted on an engine equipped with a variable valve timing mechanism. The output, that is, the noise level, is clearly different (in addition,
In reality, the noise level has a fluctuation range, but it is shown in a simplified manner for ease of understanding).Therefore, the conventional sensor fail judgment level, which is uniquely set, does not accurately detect abnormalities in the knock detection means. Therefore, the present invention solves the above-mentioned drawbacks of the prior art and makes it possible to accurately detect an abnormality in the knock detection means even in an internal combustion engine equipped with a variable valve timing mechanism. An object of the present invention is to provide a knock control device for an internal combustion engine.

(Means and effects for solving the problem) In order to achieve the above object, the present invention provides a variable valve that changes the pulp timing and/or lift amount of at least one of the intake and exhaust valves according to the operating state of the internal combustion engine. A knock control device for an internal combustion engine, comprising a timing mechanism and a knock control means for detecting the occurrence of knock through a knock detection means and retarding the ignition timing when knock occurs, wherein the knock control device comprises: a timing mechanism; The means includes a sensor fail determination means for comparing the output of the knock detecting means with a predetermined sensor fail determination level to determine an abnormality of the knock detecting means, and also compares the predetermined sensor fail determination level with the valve timing and/or It is configured to change according to the amount of lift.

(Example) Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. 1st
FIG. 1 is a schematic diagram showing the entire knock control device for an internal combustion engine according to the present invention. To explain according to the same figure, reference numeral 10
1 shows a multi-cylinder internal combustion engine for a vehicle consisting of four cylinders or the like, and is equipped with an intake pipe 12. The Fk intake pipe 12 is equipped with a throttle valve 14 at an appropriate position, and the intake air introduced from an air cleaner (not shown) attached to the tip of the intake pipe is
The flow rate is adjusted by the throttle valve 14, and fuel is supplied to the cylinder head 18 by a fuel injection valve (not shown).
The air is fed into the combustion chamber 22 through an intake boat 20 provided in the air. In the combustion chamber 22, the air-fuel mixture passes through the piston 24.
After being compressed, it is ignited by the spark plug 26 and explodes.
The piston 24 is driven downward, and the air is discharged outside the engine through the exhaust boat 28 and the exhaust pipe 30.

Here, a throttle position sensor 32 for detecting the opening degree of the throttle valve 14 provided in the intake pipe 12 is provided at an appropriate position of the engine, and a throttle position sensor 32 is provided in the intake pipe 12 to detect the opening degree of the throttle valve 14.
A pipe (not shown) is connected and branched downstream of 4, and an intake pressure sensor 34 that measures the pressure of intake air in absolute value is provided near the end of the branched path. An intake temperature sensor 36 for detecting the temperature of intake air is provided at an appropriate position. Further, a water temperature sensor 42 is provided near the cooling water passage 40 in the cylinder block 38 of the internal combustion engine 10 to detect the temperature of the engine cooling water, and to detect vibrations caused by knocks generated from the combustion chamber 22. A piezoelectric knock sensor 44 for detection is provided. Further, a distributor 46 is provided at an appropriate position of the internal combustion engine 10, and a piston 2 is installed inside the distributor 46.
A crank angle sensor 48 consisting of a magnet that rotates in synchronization with the rotation of a crankshaft (not shown) that rotates as the crankshaft 4 moves up and down, and a rotating body that is disposed facing the magnet, is housed therein. Outputs a pulse signal every time. In addition, a vehicle speed sensor 5 is located at an appropriate position on the vehicle to detect the traveling speed.
0 is set. The outputs of sensors 3234.36, 42.44.48.50, such as the throttle position sensor described above, are sent to control unit 52.

Therefore, the internal combustion engine 10 has one cylinder and four valves,
The intake boat 20 described above is provided with two intake valves 54 for opening and closing the boat, and the exhaust boat 28 is also provided with two exhaust valves 56 for opening and closing the boat (only the valve on the near side is shown in the figure). ), and the intake and exhaust valves 54.5
The above-mentioned variable valve timing mechanism 60 is connected to 6, and the intake and exhaust valves 54 and 5 are connected in accordance with commands from the control unit 52.
The pulp timing and lift amount of No. 6 are variably driven.

That is, as will be described later, the control unit 52 inputs the output of the oil pressure switch 600 provided in the variable pulp timing mechanism 60, and adjusts the pulp timing and lift amount according to the operating state determined from the output of the crank angle sensor 48, etc. is determined to control the operation of the variable valve timing mechanism 60. Further, an ignition device 62 consisting of an igniter or the like is connected to the control unit 52, and the ignition device 62 inputs the output of the control unit 52, and discharges the spark plug 26 via the distributor 46 at the determined ignition timing to cause the air-fuel mixture to ignite.

Next, the variable valve timing mechanism 60 will be explained with reference to FIGS. 2 and 3.

FIG. 2 is an enlarged sectional view showing in detail the interior of the cylinder head of the internal combustion engine 10 shown in FIG. The two valve operating systems 6021e, which are composed of the side valve operating system 602i and the exhaust side valve operating system 602e that opens and closes the exhaust valve 56, have basically the same structure, so the intake side members in the drawings are The subscript i is given to the exhaust side member, and the subscript e is given to the exhaust side member, and the following description will be made for both without the subscript.

The dual valve gear 602 includes a camshaft 604 that is rotationally driven by an engine crankshaft (not shown) at a reduction ratio of 1/2. On the camshaft 604, each cylinder has
A first low-speed cam 606 and a second low-speed cam 608 are mounted in parallel with an interval between them, and a high-speed cam 610 is disposed between them. Here, the cam shapes of the first and second low-speed cams 606 and 608 are configured to have a gap between the cams, and the high-speed cam 610 is configured to have a cam shape that protrudes relatively in the radial direction. A rocker shaft 612 is provided parallel to the camshaft 604, and a first rocker arm 614 and a second rocker arm 6 are mounted on the rocker shaft 612, as best shown in FIG.
16 and a free rocker arm 618 are rotatably disposed. These three rocker arms are provided corresponding to the cams, and the tenth lock arm 614 is in sliding contact with the first low speed cam 606, the twentieth lock arm 616 is in sliding contact with the second low speed cam 608, and the free rocker arm 618 is in sliding contact with the second low speed cam 608. are arranged so as to be in sliding contact with the high speed cam 610. As shown in FIG.
Tappet screws 620 are screwed into the valves 6 so as to be movable back and forth, and these tappet screws 620 contact the upper ends of the intake and exhaust valves 54 and 56 to open and close them. Moreover, the free rocker arm 618 in the central position is swingably supported by the lost motion mechanism 622, and does not itself participate in opening or closing the valve unless connected to an adjacent rocker arm. Therefore, these 3
A coupling mechanism 630 is provided to couple the rocker arms 614,616,618. In addition, camshaft 6
A timing pulley 624 is fixed to the end of 04e, and is connected to a crankshaft (not shown) by a timing belt 626.

FIG. 3 shows the details of the coupling mechanism 630, that is, three rocker arms 614, 616, and 618 are bored transversely through the interior thereof, and holes 6632 and holes 634, and 636 are continuously formed. A first connecting pin 640, a second connecting pin 642, and a regulating pin 644 are slidably housed there. One end of the first connecting pin 640 has a reduced diameter and an oil chamber 646 is formed therein, and the oil chamber 646 communicates with an oil passage 650 via a branch passage 648 . Further, the regulation bin 644 is provided with a spring 652, and the regulation bin 644 is connected to the second connecting pin 652.
42 side. That is, when high pressure oil is introduced into the oil chamber 646, the first and second connecting bottles 640 and 642 protrude against the spring force, press the regulating bottle 644, bridge and connect the rocker arms, and When the oil pressure decreases, the spring 652 is configured to return to the illustrated position by the biasing force of the spring 652 and release the connection.

A hydraulic switching mechanism 660 shown in the upper part of FIG. 3 is inserted between the oil passage 650 and a hydraulic source (not shown). The hydraulic switching mechanism 660 includes a spool valve 662 that controls the flow rate between an inlet boat 664 that communicates with the hydraulic pressure source and an outlet boat 666 that communicates with the oil passage 650 via a communication passage 654. That is, when spool valve 662 is in the closed position shown, pressure oil flowing from inlet boat 664 flows through orifice hole 668 to outlet boat 6.
It flows to 66. At this time, part of the pressure oil is transferred to the bypass port 6.
Coupled with the fact that the oil flows out through the oil passage 650 and acts on the oil chamber 646, the oil pressure flowing into the oil passage 650 and acting on the oil chamber 646 is low, so the three rocker arms 614, 616, 118 swing separately,
The intake and exhaust valves 54 and 56 are opened and closed at low speed valve timing.

This spool valve 662 is connected to a solenoid valve 680 via pipes 672 and 674, and the pressure oil that flows in from the inlet port 664 is sent to the solenoid valve 680 via the pipe 672, and the valve is demagnetized, as shown in the figure. When in the closed position, it is grounded there. Thus, when the solenoid valve 680 is energized, it opens, and the pressure oil passes through the second pipe line 674 to the spool valve 662.
act on the top of the valve to drive the spare valve to the open position shown in phantom. As a result, the pressure oil flowing from the inlet boat 664 not only passes through the above-described orifice hole 668 but also passes through the gap formed between the annular recess and the housing wall of the spool valve 662 as shown by the arrow (imaginary line) to the output port 666. and flows into the oil passage 650. This increases the oil pressure in the oil passage 650, moves the connecting pins 640, 642, connects the three rocker arms 614, 616, and 618 in a skewered manner, and drives the intake and exhaust valves to open and close at high-speed valve timing.

At this high speed valve timing, the overlap time and lift amount are increased compared to when the valve timing is at low speed. The above-mentioned oil pressure switch 600 is provided near the spool valve 662 to detect the pressure in the oil passage 650 and turn it on (H level) when the pressure is low and off (L level) when the pressure is high.
level) and sends it to the control unit 52.

Now, to explain the control unit 52 with reference to FIG. 4, the analog output of the throttle position sensor 32, etc. is input to a level conversion circuit 64 in the control unit, converted to a predetermined level, and input to the microcomputer 66. be done. The microcomputer includes an A/D conversion circuit 66a, an l1066b, a CPU 66c, and a ROM6.
6d, RAM 66e, arithmetic registers, and a timer (the registers and timers are not shown), and the level conversion circuit output is converted into a digital value by the A/D conversion circuit 66a in accordance with the command from the CPU 66c. After that, it is temporarily stored in the RAM 66e. In addition, the digital output of the crank angle sensor 48, etc. is waveform-shaped by the waveform shaping circuit 6, and then sent to the micro-
entered into the computer.

Further, the output of the knock sensor 44 described above is sent to the control unit 52 and then input to the knock detection circuit 70. The knock detection circuit 70 includes a filter means 70a, a comparator means 70b, and a D/A conversion means Toe, and the filter means 70a is connected to a non-inverting input terminal of the comparator means 70b, and its inverting input terminal is
/A conversion means 70c is connected. Further, the comparator means 70b is connected to the microcomputer 66, and the microcomputer 66 is connected to the D/A conversion means 7.
Connected to 0c. It should be noted that if a resonance type sensor that generates an output by resonating at a frequency based on the knock is used as the above-mentioned knock sensor 44, the filter means 70a becomes unnecessary, as shown by the imaginary line.

In this knock detection circuit 70, the sensor output is sent to the microcomputer 6 in the comparator means 70b.
The noise level is calculated and knock is determined by comparing it with the reference value set by the microcomputer 66, and to explain this point with reference to the timing chart in FIG. In the angular range (for example, ATDC 120 to 140 degrees), the noise level VNOISf!, which is the background value of engine vibration, for the D/A conversion means 70c. is output as a comparison reference value. This angular range is shown as a "noise gate" in FIG.
It is compared in. The microcomputer 66 changes this noise level based on the comparison result. The noise level is set to be approximately near the peak value of the sensor output level.

Further, the microcomputer 66 calculates a predetermined coefficient GAMP (depending on the operating state) based on the noise level VNOISE in an appropriate rank angle range (ATDCIO to 50 degrees) including the combustion state shown as "knock gate" in FIG. A knock determination level is calculated by multiplying the knock determination level by an appropriately set value), and the calculated knock determination level is output to the comparator means 70b via the D/A converting means 70c.

The comparator means 70b compares the sensor output level with the knock determination level, and determines that a knock has occurred when the sensor output exceeds the knock determination level.

Furthermore, the microcomputer 66 determines the sensor fail judgment level V F which will be described in detail later in the crank angle range shown as "sensor fail judgment gate" in the figure.
Set SVT and compare with noise level VNOISE,
When the noise level falls below the determination level, it is determined that the sensor is abnormal. Note that calculation of the noise level and knock judgment level in such a knock detection method is performed using a software method in the microcomputer 66, but it may also be detected in an analog manner using a hardware circuit. Various methods may be used to generate the sensor output, such as using the average value of the sensor output.

In addition, in a microcomputer, the CPU 66c is
As will be described later, the pulp timing range is determined from the engine speed, intake pressure, etc., and the solenoid valve 680 is energized/demagnetized via the output circuit 72 and a solenoid valve drive circuit (not shown) to adjust the pulp timing (and lift amount). Control. Furthermore, based on the determined valve timing, the CPU 66c in the microcomputer controls the crank angle sensor 48.
The engine speed is calculated from the output of the intake pressure sensor 34, and the engine load condition is determined from the output of the intake pressure sensor 34.
The basic ignition timing map for the relevant valve timing stored in is searched to calculate the basic ignition timing, the basic ignition timing is corrected from other operating parameters such as water temperature and intake air temperature, and the basic ignition timing is corrected from the output of the comparator means 70b described above. When it is determined that a knock condition exists, the ignition timing is further corrected for advance/retardation to calculate the final ignition timing, and the second
The ignition device 62 is commanded to ignite through the output circuit 74 of the spark plug 2 of a predetermined cylinder through the distributor 46.
6 to ignite the air-fuel mixture in the combustion chamber 22.

This variable valve timing control will be briefly explained with reference to the flow chart in FIG.
Parameters indicating the operating state of the engine including the water temperature T- and the like are read, and it is determined in S12 whether or not a condition for prohibiting valve timing switching is satisfied. Examples of the prohibition conditions include that the engine is in the process of warming up, that the vehicle speed is extremely low, and so on.

When it is determined in 312 that the prohibition condition is not satisfied, the process proceeds to 514, where the engine speed Ne and intake pressure Pba are determined.
(load) and searches the map stored in the ROM 66d to determine the valve timing zone. FIG. 7 is an explanatory diagram showing this valve timing zone, and as shown in the figure, a switching point is set from an appropriate engine speed and load, and the switching point shifts to a higher rotation side as the load is lower. is set to In step 314, it is determined from the sensor output whether the valve timing on the low speed side or the high speed side should be selected.

Next, the process proceeds to 316 to determine whether or not the determined valve timing is on the high speed side, and if it is the high speed side, the process proceeds to 31B to energize the solenoid valve 680, and if it is the low speed side, the process proceeds to S20 to energize the solenoid valve 680. Demagnetize 680.

When the high speed side is determined and the solenoid valve is excited, the process proceeds to 322, where it is determined whether the oil pressure switch 600 has been turned off. Since it takes time for the solenoid valve to be energized and the oil pressure to rise and turn off the oil pressure switch, the judgment in S22 is denied and the process moves to 324, and the timer t LVTDLY is turned off.
It is determined whether the value of (down counter) is zero. This timer will be described later, but the judgment there is usually affirmative and goes to S26, where the second tie? t HVTDL
Start Y (down counter), proceed to 328, reset the valve timing zone determination flag FVT to zero, and display that the timing is on the low speed side for the time being.

Then, when the program is started from the next time onward, if it is determined at 322 that the oil pressure switch is off, the process goes to 330, and after confirming that the second timer value started earlier has reached zero, the process goes to 322.
Step 334 starts the first timer and sets the flag FVT to 1 to indicate that it is in the high-speed timing range. Note that even if the solenoid valve is demagnetized in S20 due to low speed timing, S36
S30°332 until it is determined that the oil pressure switch is on.
, the zone determination flag is left set to 1 in S34, the oil pressure switch is determined to be on in S36, and only after it is confirmed in S24 that the first timer value has reached zero, the zone determination flag FVT is set in S328. is reset to zero to indicate that the timing has been switched to the low speed timing range. First timer tLVTDLY and second timer tHVTDL
As is clear from the above, Y is for compensating for the delay in the operation of the hydraulic mechanism when changing the valve timing. still,
Since the charging efficiency or combustion characteristics differ depending on the valve timing, the ignition timing is selected from the basic characteristics of the low speed side or the high speed side as described above according to the timing determined in 328 and 334, and the fuel injection is also handled. characteristics are selected.

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

Note that the programs shown in this flow chart and the flow chart in FIG.
6 at a predetermined crank angle.

First, at 5100, the engine speed Ne, the noise level VNOISEO value, and the zone determination flag FVTO value detected through the sensor are read, and at 5102, the ROM 66 d is searched, and the sensor fail determination level V is determined according to the determined low speed or high speed valve timing. F
Search SVT according to engine speed. FIG. 9 is an explanatory diagram showing the characteristics of this sensor fail judgment level VPSVT. As shown, the judgment level is set to be different from VFSVT-Hi or VFSVT-Lo depending on the pulp timing. This level is appropriately set based on the experimental data shown in Fig. 10 and stored in the ROM66d, and since the knock sensor output increases in proportion to the engine speed, it can be searched freely according to the engine speed. . In addition, in Figures 10 and 9, the noise level during low-speed valve timing is higher than that during high-speed valve timing, but - for boat fishing, the lift amount is larger during high-speed valve timing. Therefore, the vibration during valve seating will also be larger than during low-speed valve timing, and therefore the noise level will also be larger. However, this varies depending on the angular range in which the noise level is measured, the opening/closing interval of each valve, the magnitude of the valve seating noise due to the magnitude of the lift amount, and the magnitude of vibration determined from the relationship with the cam profile. However, the results are not necessarily the same in experiments. However, in any case, it can be seen from the experimental data that the noise level is different between the low-speed timing and the high-speed timing. Therefore, sensor fail determination levels were individually set as shown in the figure, depending on the different noise levels. Therefore, in 5100, the noise level V N0TSt! calculated at the current valve timing. -VTLo or VNOISE-
VT old is read, and in 5102, the corresponding sensor fail judgment value VPSVT-Lo or VFSVT-
Select HL.

Subsequently, in 5104, the fail judgment flag FKC
After confirming that FS is not set to 1, that is, a fail determination has not already been made, the process proceeds to 5106;
Then, it is determined whether the detected engine speed exceeds a predetermined value NFS. This is to determine whether the engine is in the idle speed range or not.As mentioned above, the knock sensor output increases or decreases in proportion to the engine speed, so when the engine is in a low speed range such as an idle state, the knock sensor output itself This is to avoid the risk of erroneous determination if a fail determination is made. Therefore, this predetermined value NFS is set to an appropriate value such as 11000 rp.

When it is determined in 8106 that the rotation speed is not in the idle range, the process moves to 310B, where the noise level VNOIS is determined.
E-VTLo (old) and sensor fail judgment value V FSV
T-LO (old) is compared, and if the noise level exceeds, it is determined that the sensor is normal, and the process proceeds to 5110, where the fail judgment counter CFS is reset, and in 5112, the fail judgment flag FKC['S is set to zero. Reset and exit the program. Also, when 3106 determines that it is in the idle speed range, it immediately jumps to 5110,
The program ends through step 5112.

If it is determined in step 5108 that the noise level is below the sensor fail judgment value, the process proceeds to step 5114, where the fail judgment counter CFS is incremented, and in step 3116, the counter value is set to a predetermined value CTFSJ.
The loop continues until it is determined that the sensor has reached 3118, and when it is confirmed that the sensor has reached 3118, the fail determination flag is set to 1 and it is determined that the sensor is abnormal. It goes without saying that the reason for counting the number of failure determinations in the above and determining a sensor failure only when a predetermined value is reached is to avoid false detections, taking into account delays in valve timing switching operations, etc. . Incidentally, the microcomputer 66 mentioned above
Appropriate warning display means may be connected to 8118 to display when a sensor failure is detected.

In this embodiment, as described above (when determining an abnormality of a knock sensor in an internal combustion engine equipped with a variable valve timing mechanism, the sensor fail judgment value is changed depending on the valve timing range, so noise that differs depending on the valve timing) It is possible to accurately set the sensor fail judgment value in accordance with the level, and it becomes possible to accurately judge the abnormality of the knock sensor.

(Effects of the Invention) The present invention includes a variable valve timing mechanism that changes the valve timing and/or lift amount of at least one of the intake and exhaust valves according to the operating state of the internal combustion engine, and
In a knock control device for an internal combustion engine, the knock control device includes a knock control device that detects the occurrence of knock through a knock detection device and retards the ignition timing when knock occurs, wherein the knock control device is configured to A sensor fail determination means is provided for determining an abnormality of the knock detection means by comparing the output with a predetermined sensor fail determination level, and the predetermined sensor fail determination level is changed in accordance with the valve timing and/or lift amount. With this configuration, it is possible to accurately set the sensor fail judgment level in response to the background noise level of the engine that varies depending on the valve timing and/or lift amount, and it is possible to accurately judge an abnormality in the knock detection means. I can do it.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the overall knock control device for an internal combustion engine according to the present invention, FIG. 2 is an explanatory cross-sectional view of the cylinder head section showing its variable valve timing mechanism, and FIG. 3 is an explanatory diagram of its coupling mechanism and hydraulic pressure. 4 is an explanatory block diagram showing details of the control unit in the device shown in FIG. 1; FIG. 5 is an explanatory waveform diagram showing the operation of the knock detection circuit therein; FIG. FIG. 7 is an explanatory flow chart generally showing the control operation of variable valve timing, FIG. 7 is an explanatory diagram showing its switching characteristics, FIG. 8 is an explanatory flow chart showing the operation of the device according to the present invention, and FIG. The figure is an explanatory diagram showing the characteristics of the sensor fail judgment level used therein, and FIG. 10 is experimental data showing the fluctuation of the noise level according to the valve timing. DESCRIPTION OF SYMBOLS 10... Internal combustion engine, 12... Intake pipe, 14... Throttle valve, 18... Cylinder head, 22... Intake boat, 22... Combustion chamber, 24... Piston, 2
6...Spark plug, 28...Exhaust port, 30...
・Exhaust pipe, 32... Throttle position sensor, 34...
・Intake pressure sensor, 36... Intake temperature sensor, 38...
・Cylinder block, 40...Cooling water passage, 42...
・Water temperature sensor, 44...Knock sensor, 46...Distributor, 48...Crank angle sensor, 50
...Vehicle speed sensor, 52...Control unit, 54...
- Intake valve, 56... Exhaust valve, 60... Variable valve timing mechanism, 62... Ignition device, 64... Level conversion circuit, 66... Micro computer, 68...
. . . Waveform shaping circuit, 70 . . . Knock detection circuit, 72.
74... Output circuit, 600... Oil pressure switch, 60
2... Suction (wandering) air side valve train, 604... Camshaft, 606, 608... Low speed cam, 610...
High-speed cam, 612...Rocker shaft, 614,6
16,618... Rocker arm, 620... Tappet screw, 622... Lost motion mechanism, 630...
...Connection mechanism, 632... Hole, 634, 636...
Hole, 640.642... Connecting pin, 644... Regulating bottle, 646... Oil chamber, 648... Branching path, 650
... Oil path, 652 ... Spring, 654 ... Communication path,
660... Hydraulic switching mechanism, 662... Spool valve,
664... Entrance boat, 666... Exit boat, 6
68... Orifice hole, 670... Bypass port Figure 1 pjiε? Figure 6 Figure 7 Figure 8 O Figure 9 e

Claims (1)

[Claims] The engine is equipped with a variable valve timing mechanism that changes the valve timing and/or lift amount of at least one of the intake and exhaust valves according to the operating state of the internal combustion engine, and detects the occurrence of knock through a knock detection means. In the knock control device for an internal combustion engine, the knock control device includes a knock control means for retarding ignition timing, wherein the knock control means compares the output of the knock detection means with a predetermined sensor failure determination level. 1. A knock control device for an internal combustion engine, comprising a sensor fail determination means for determining an abnormality in the engine, and a predetermined sensor fail determination level thereof is changed in accordance with the valve timing and/or the lift amount.