JPH08338272A - Valve timing control device - Google Patents

Abstract

PURPOSE: To effectively suppress a knocking while minimizing the deterioration of engine fuel consumption or the rise of exhaust air temperature. CONSTITUTION: This device has an ECU 30 for controlling a variable valve timing device 10 for changing the rotating phase of the cam shaft 1 of an internal combustion engine and regulating the engine valve timing. The ECU 30 controls the variable valve timing device to lag the engine valve timing when a knocking occurs in the engine, and sets the phase lag of the valve timing larger when the knock intensity detected by a knock sensor 50 is higher.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve timing control device, and more particularly to a valve timing control for an internal combustion engine which can suppress engine knocking by continuously changing the closing timing of an internal combustion engine intake valve. Regarding the device.

[0002]

2. Description of the Related Art In an internal combustion engine, it is known that knocking occurs when the ignition timing is advanced or when the engine is operated at a high compression ratio.
When knocking occurs, not only the fuel consumption and vibration of the engine increase, but excessive knocking may cause problems such as melting damage of valves and plugs in extreme cases.

In the conventional internal combustion engine, a method of retarding the ignition timing by retarding the ignition timing from the optimum ignition timing when engine knocking occurs is adopted. However, retarding the ignition timing may cause a problem because it is accompanied by a decrease in engine output, deterioration in fuel consumption, increase in exhaust temperature, and the like. On the other hand, in an engine equipped with a variable valve timing mechanism that makes the engine intake valve closing timing variable, it is known that knocking can be suppressed by changing the intake valve closing timing (hereinafter referred to as valve timing). Has been.

For example, in an ordinary engine, the closing timing of the intake valve is set to a constant crank angle (AB) after the bottom stroke of the intake stroke of each cylinder.
Although fixed to DC), in an engine having a variable valve timing mechanism, knocking can be suppressed by moving the closing timing of the intake valve to the advanced side or the retarded side. That is, if the valve timing is advanced to some extent or more, the intake valve will be closed before the piston reaches the bottom dead center of the intake stroke. Therefore, in a region where the valve timing advance amount is more than a certain amount, the amount of air taken into the engine decreases as the valve timing advances, and the intake volume efficiency and the actual compression ratio of the engine decrease. When the actual compression ratio of the engine decreases, the knock limit of the engine (ignition timing at which knocking occurs) moves toward the advance side. Therefore, by advancing the valve timing to some extent when knocking occurs, the engine does not retard the ignition timing. It becomes possible to suppress the knocking of. Conversely, knocking can also be suppressed by retarding the valve timing. For example, if the valve timing is retarded from the normal state, the intake valve remains open until the beginning of the cylinder compression stroke after the bottom stroke of the intake stroke. in this case,
Since the air-fuel mixture in the cylinder is not compressed while the intake valve is open, the actual compression stroke is started when the intake valve is closed. Therefore, as the intake valve closing timing is retarded, the substantial compression stroke becomes shorter, and the intake volume efficiency and the actual compression ratio of the engine decrease. Therefore, even if the valve timing is retarded, engine knocking can be suppressed without retarding the ignition timing.

As an example of the valve timing control device that suppresses knocking by changing the engine valve timing as described above, for example, the actual opening number is 3-41150.
Is described in Japanese Patent Application Publication No. The device of the publication has a variable valve timing mechanism that switches the closing timing of the intake valve according to the engine operating state, retards the ignition timing when knocking occurs and suppresses knocking, and delays the ignition timing when knocking occurs. When the angle amount exceeds a predetermined amount, in addition to retarding the ignition timing, the closing timing of the intake valve is switched to the retarding side to suppress knocking.

[0006]

However, like the valve timing control device of Japanese Utility Model Laid-Open No. 3-41150, the valve timing is delayed only when the ignition timing retard amount becomes larger than a predetermined amount when knocking occurs. Switching to the corner side may cause a problem. That is, in the above device, the valve timing is controlled by selecting the valve timing on the advance side and the valve timing on the retard side according to the engine operating state, but the ignition timing is a predetermined amount even when knocking occurs. Until the above, the valve timing control is executed. For this reason, for example, when knocking occurs when the valve timing is switched to the retard side according to the engine operating state, even if the knocking suppression is performed by retarding the ignition timing, the ignition timing is retarded. If the angular amount is not equal to or more than the predetermined amount, there is a possibility that the valve timing may be switched to the advanced side according to the change in the engine operating state.

When the valve timing is switched to the advance side, knocking is likely to occur due to an increase in the actual compression ratio. Therefore, when such a situation occurs, knocking, which was suppressed by the ignition timing retardation, occurs again. Becomes
Further, there arises a problem that the ignition timing has to be retarded. That is, in the valve timing control device of the above publication, even when knocking occurs, the engine valve timing is not set in consideration of knocking until the ignition timing retard amount becomes equal to or greater than the predetermined amount, so the valve timing is not set when knocking occurs. On the contrary, there may be a case where the knocking is controlled so that the knocking easily occurs.

In view of the above problems, the present invention performs valve timing control according to the degree of knocking when knocking occurs, so that it is possible to prevent an operation inconsistent with the knocking suppression operation due to ignition timing retard. One aim is to provide a control device. Further, in the device of the above publication, since knocking suppression operations such as ignition timing retard and valve timing retard are executed after knocking occurs during engine operation, the occurrence of knocking itself cannot be prevented.

In view of this problem, the present invention determines the possibility of knocking from the operating state that affects the occurrence of knocking, and controls the valve timing based on the possibility of knocking to prevent knocking. It is another object to provide a valve timing control device that can be effectively prevented.

[0010]

According to the invention as set forth in claim 1, a valve timing setting means for setting a target value of the engine intake valve closing timing according to an operating condition of the internal combustion engine, and the engine timing control means are provided in the engine. Knock strength detection means for detecting the strength of knocking, correction means for correcting the intake valve closing timing target value as the detected knock strength is larger, in the direction in which the actual compression ratio of the engine decreases, and There is provided a valve timing control device comprising: a valve timing control means for controlling the valve closing timing to a target value after being corrected by the correction means.

According to the second aspect of the present invention, the valve timing setting means for setting the target value of the engine intake valve closing timing according to the operating conditions of the internal combustion engine, and the operating condition parameters involved in the occurrence of engine knocking. The parameter detection means for detecting the engine intake valve closing timing, the more the value of the operating state parameter is a value at which knocking easily occurs,
Valve timing control provided with a correction means for largely correcting in the direction in which the actual engine compression ratio decreases and a valve timing control means for controlling the closing timing of the engine intake valve to a target value after being corrected by the correction means. A device is provided.

According to the third aspect of the present invention, the parameter detecting means includes means for detecting a deposit accumulation amount in the engine combustion chamber, and the correcting means closes the intake valve as the deposit accumulation amount increases. The valve timing control device according to claim 2, wherein the timing is largely corrected in the direction in which the actual compression ratio of the engine decreases. According to the invention described in claim 4, the internal combustion engine is an automobile internal combustion engine having a transmission, the parameter detecting means includes shift position detecting means for detecting a transmission shift position, and the correcting means is The valve timing control device according to claim 2, wherein the intake valve closing timing is corrected so that the actual engine compression ratio is greatly reduced as the transmission shift position is closer to the low speed gear side.

[0013]

In the valve timing control device according to the first aspect of the present invention, the correction means corrects the engine valve timing target value in such a direction that the actual compression ratio of the engine is greatly reduced as the detected knock strength is increased. Since the valve timing control means controls the engine valve timing to the corrected target value,
When knocking occurs, the actual compression ratio of the engine is controlled according to the knock strength.

In the valve timing control device according to the second aspect of the present invention, the correction means largely corrects the valve timing in a direction in which the actual engine compression ratio decreases as the value of the engine operating condition parameter is a value at which knocking easily occurs. . Since the valve timing control means controls the engine valve timing to the corrected target value, the actual engine compression ratio is greatly reduced in an operating state in which knocking is likely to occur in the engine.

In the valve timing control device according to the third aspect, the deposit accumulation amount in the engine combustion chamber is used as the engine operating condition parameter according to the second aspect, and the actual engine compression ratio is greatly reduced as the deposit accumulation amount is larger. . In the valve timing control device according to the fourth aspect, the transmission shift position is used as the engine operating state parameter according to the second aspect, and the actual engine compression ratio is reduced as the transmission shift position is closer to the low speed gear.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing a main part configuration of an embodiment in which a knocking control device of the present invention is applied to a four-cycle internal combustion engine for automobiles. In this embodiment, a double overhead camshaft (DOHC) type engine having separate camshafts for opening and closing the intake valve and the exhaust valve is used, and the intake valve of this DOHC type engine is shown in FIG. Only one portion of the drive camshaft (intake camshaft) is shown.

In this embodiment, a variable valve timing device 10, which will be described later, is connected to the end portion of the intake camshaft 1. The variable valve timing device 10 is shown in FIG.
It operates by the hydraulic pressure supplied by the linear solenoid valve shown by, and the intake valve opening / closing timing of the engine can be adjusted steplessly. Variable valve timing device 1
The configuration and operation of 0 will be described later in detail.

Reference numeral 30 in FIG. 1 denotes a control circuit (ECU) of the engine. In this embodiment, the ECU 30 includes a read only memory (ROM) 32, a random access memory (RAM) 33, a microprocessor (CPU) 34,
A backup RAM that is directly connected to the input port 35, the output port 36, and the battery and that can store and retain data even when the engine is stopped
It is a digital computer having a known structure in which 37 are mutually connected by a bidirectional bus 31. In addition to performing basic control of the fuel injection amount of the engine, ignition timing, etc., valve timing control described below is performed to suppress engine knock.

For these controls, various parameters representing the operating state of the engine are input to the input port 35 of the ECU 30 from the sensors described below.
Indicated at 41 in FIG. 1 is an air flow meter arranged in an intake passage (not shown) of the engine. As the air flow meter 41, a movable vane type is used, for example, and generates a voltage signal proportional to the engine intake air amount. The voltage signal from the air flow meter 41 is an AD with a built-in multiplexer.
It is supplied to the input port of the ECU 30 via the converter 38. Reference numeral 43 is an air-fuel ratio sensor arranged in the exhaust passage (not shown) of the engine. The air-fuel ratio sensor 43 detects the oxygen concentration in the exhaust gas and outputs a voltage signal corresponding to the engine air-fuel ratio. This signal is sent to the ECU 30 via the AD converter 38.
Is supplied to the input port of. This air-fuel ratio signal is used for engine fuel injection control and calculation of the deposit accumulation amount in the combustion chamber described later.

Reference numeral 50 in FIG. 1 denotes a knock sensor for detecting the strength of knocking generated in the engine. The knock sensor 50 is a vibration sensor attached to a cylinder block of the engine for detecting vibration of a specific frequency. When knocking occurs in the cylinder, the pressure fluctuates in the cylinder to cause a unique frequency (for example, 5 to 20 KHz).
Vibration occurs. The knock sensor 50 detects the amplitude of the vibration of the above frequency transmitted to the cylinder block and converts it into a voltage signal. If the knock intensity is high, the amplitude of the knocking vibration transmitted to the cylinder block is also high, so that the knock intensity can be detected from the voltage signal of the knock sensor 50. The output of knock sensor 50 is also AD
It is supplied to the input port of the ECU 30 via the converter 38.

In this embodiment, the vibration detection type knock sensor 50 is used. However, in an engine having a combustion pressure sensor for detecting the combustion pressure in the cylinder, the knock intensity is determined based on the output of the combustion pressure sensor. It is also possible to detect
When a knock occurs, the combustion pressure fluctuation of the above-mentioned natural frequency occurs after the combustion pressure in the cylinder reaches a peak. Therefore, by filtering the output of the combustion pressure sensor and detecting the amplitude of the pressure fluctuation of the above-mentioned natural frequency, the knock intensity can be detected as in the vibration detection type knock sensor.

At the input port 35 of the ECU 30, a pulse signal indicating a rotation angle CMA of the camshaft 1 from a camshaft rotation angle sensor 45 provided on the intake camshaft 1 and a crankshaft rotation angle sensor provided on the crankshaft. A pulse signal indicating the crankshaft rotation angle CA is input from each. The pulse signal from the crankshaft rotation angle sensor 46 is composed of an N1 signal indicating a reference position of the crankshaft, which is output every 720 degrees of crankshaft rotation, and an NE signal which is output every 30 degrees of crankshaft rotation. From the camshaft rotation angle sensor 45, a CN1 pulse signal indicating that the camshaft has reached the reference position is generated every 360 degrees of camshaft rotation. The ECU 30 calculates the engine speed NE from the pulse interval of the NE signal at regular time intervals, and uses this engine speed NE to determine the rotational phase of the camshaft 1 from the time interval between the N1 signal and the CN1 signal (intake valve described later). Valve timing) VT is calculated. The calculation result is stored in a predetermined area of the RAM 33.

Further, a signal indicative of a gear shift state (used gear) of a transmission (not shown) connected to an engine output shaft is input to the input port 35 of the ECU 30 by a shift position sensor 47.
It is input from. In this embodiment, the intake air amount signal from the air flow meter 41 and the air-fuel ratio signal from the air-fuel ratio sensor 43 are AD-converted by an AD conversion routine that is performed at regular intervals, and stored in a predetermined area of the RAM 33.

That is, the engine speed data NE, the valve timing VT, the intake air amount data G, the air-fuel ratio data, the knock intensity NK, and the data of the transmission use gear SP stored in the RAM 33 are updated at regular intervals. The latest value is always stored in the RAM 33. On the other hand, the output port 36 of the ECU 30 is connected to the linear solenoid actuator 25b of the above-mentioned linear solenoid valve 25 via the drive circuit 48, and controls the operation of the variable valve timing device 10.

Next, the variable valve timing device 10 of this embodiment will be described. As shown in FIG. 1, the variable valve timing device 10 includes a timing pulley 12 having a cylindrical sleeve 13 and a cover 14 that covers an end portion of the camshaft 1. The timing pulley 12 includes the cylindrical sleeve 13. The camshaft 1 is rotatably attached to the periphery of the intake camshaft 1 via.
Further, the cover 14 is attached to the timing pulley 12 with bolts 15
It is fixed by and is rotated integrally with the pulley 12.

A piston member 17 is provided inside the cover 14. The piston member 17 includes an annular piston portion 19 and a cylindrical portion 21 extending from the piston portion 19. The outer peripheral surface and the inner peripheral surface of the piston portion 19 are
The inner peripheral surface of the cover 14 and the outer peripheral surface of the sleeve 13 of the pulley 12 are in sliding contact with each other. In addition, the piston member 17
An outer helical gear 21a and an inner helical gear 21b, each having a predetermined twist angle, are engraved on the outer peripheral surface and the inner peripheral surface of the cylindrical portion 21, and the outer helical gear 21a is formed on the inner peripheral surface of the cover 14. Inner tooth helical gear 22a and inner helical gear 21
b is a ring-shaped external tooth helical gear 22b integrally mounted on the end surface of the camshaft 1 by a bolt 1a and a pin 1b.
Are in mesh with each other.

Variable valve timing device 10 of the present embodiment
Then, the rotation of the crankshaft (not shown) of the engine is transmitted to the timing pulley 12 via the timing belt 12a. When the pulley 12 rotates, the cover 14 rotates together with the pulley 12, and the piston member 17 connected to the cover 14 via the helical gears 22a and 21a rotates together with the cover 14. The piston member 17 is connected to the camshaft 1 via the helical gears 21b and 22b, so that the camshaft 1 rotates integrally with the pulley 12.

That is, in the variable valve timing apparatus 10 of this embodiment, the rotational driving force of the camshaft 1 is transmitted from the crankshaft to the timing pulley 12 via the timing belt 12a, and the pulley 12 covers the cover 14 and the helical gear 22a. It is transmitted to the camshaft 1 via 21a, the piston member 17 and the helical gears 21b and 22b.

Variable valve timing device 10 of the present embodiment
Changes the valve timing of the intake valve by moving the piston member 17 in the axial direction of the camshaft 1. That is, the piston members 17 mesh with each other,
Helical gears 22a, 21a each having a predetermined twist angle
And 21b, 22b are connected to the cover 14 and the camshaft 1. Therefore, the piston member 17
Moves in the direction of the camshaft axis, the helical gear 2
The meshing positions of 2a, 21a and 21b, 22b move in the axial direction along the respective tooth traces. However, since the tooth flanks of the respective gears have different twist angles with respect to the camshaft axial direction, when the meshing position moves in the axial direction, the cover 14 and the piston member 17, and the piston member 17 and the camshaft 1 are separated from each other. Each of them relatively moves in the circumferential direction along the tooth trace of the helical gear. Therefore, as the piston member 17 moves in the axial direction, the cover 14 and the piston member 17, and the piston member 17 and the camshaft 1 rotate relatively. Therefore, by moving the piston member 17 in the axial direction of the camshaft 1 during operation of the engine, the rotational phase of the timing pulley 12, that is, the rotational phase of the camshaft 1 with respect to the rotational phase of the crankshaft can be advanced (or delayed). Therefore, the opening / closing timing of the intake valve driven by the camshaft 1 can be advanced (or retarded).

As described above, the variable valve timing device 10 of this embodiment changes only the rotational phase of the intake camshaft 1. Therefore, when the valve timing is changed, the opening timing and closing valve of the intake valve are changed. The timing always changes by the same amount, and the intake valve opening period itself is maintained constant. In the present embodiment, the piston member 17 is hydraulically operated during engine operation.
The valve timing of the intake valve is changed by moving. As shown in FIG. 1, two oil passages 2 and 3 are bored in the camshaft 1 along the axial direction. The oil passage 2 is provided at the center of the cam shaft 1, and the shaft end side of the oil passage 2 is formed between the inner surface of the cover 14 and the end surface of the piston 17 on the shaft end side via a port 2a formed in the bolt 1a. Communicating with the hydraulic chamber 5. In addition, the oil passage 2
The other end is connected to a linear solenoid valve 25, which will be described later, through a port 2b formed in the cam shaft 1 in the radial direction. On the other hand, the end portion on the shaft end side of the oil passage 3 is closed by the ring-shaped external tooth helical gear 22b. Further, the oil passage 3 communicates with a hydraulic chamber 8 defined by the end face of the piston 17, the timing pulley 12 and the cover 14 via a port 3a formed in the radial direction, and a linear solenoid valve via the port 3b. It communicates with 25.

The linear solenoid valve 25 is a spool valve having a spool 26, and has a hydraulic port 26a connected to the port 2b of the oil passage 2 through a pipe,
A hydraulic port 26b connected to the port 3b of the oil passage 3 through a pipe, a port 26c connected to a pressure oil supply source 28 such as an engine lubricating oil pump, and two drain ports 26.
d and 26e. The spool 26 of the valve 25 has one of the ports 26a and 26b connected to the port 26c.
And operates to connect the other to the drain port.

That is, when the spool 26 moves to the left in FIG. 1, the port 26a communicating with the port 2b of the hydraulic passage 2 is connected to the hydraulic pressure supply source 28 via the port 26c, and the drain port 26d is closed. Also,
At this time, the port 26b connected to the port 3b of the hydraulic passage 3 simultaneously communicates with the drain port 26e. For this reason, in the hydraulic chamber 5 of the variable valve timing device 10, the hydraulic passage 2 from the hydraulic pressure supply source 28 such as the lubricating oil pump of the engine,
Lubricating oil flows in through the port 2a and presses the piston 19 to the right in FIG. At this time, the lubricating oil in the hydraulic chamber 8 passes from the port 3a to the oil passage 3, the port 3b, the port 26b of the linear solenoid valve 25, etc.
It is discharged from 6e. Therefore, the piston member 17 moves rightward in FIG.

On the contrary, when the spool 26 moves to the right in FIG. 1, the port 26b is connected to the port 26c and the port 26a is connected to the drain port 26d. As a result, the lubricating oil flows into the hydraulic chamber 8 through the oil passage 3 and is discharged from the hydraulic chamber 5 through the oil passage 2 to the drain port 26d.
7 moves to the left in FIG.

A linear solenoid actuator for driving the spool 26 is shown at 25b in FIG. The linear solenoid actuator 25b receives a control signal from the ECU 30 and moves the spool 26 by an amount proportional to the magnitude of the control signal to change the position of the piston member 17, that is, the valve timing of the intake valve.

FIG. 2 is a diagram for explaining the valve timing setting of this embodiment. is there. In FIG. 2, TDC indicates the top dead center of the piston stroke, BDC indicates the bottom dead center, and IO and IC respectively indicate the opening timing and closing timing of the intake valve.
In the present embodiment, the valve timing VT is defined as the reference state (VT = 0) when the intake valve valve timing is most retarded by the variable valve timing device 10, and the intake valve valve timing advance amount with respect to the reference state is defined as VT. To do.

As shown in FIG. 2, VT = 0 in this embodiment.
In this state, the intake valve opens after the exhaust stroke top dead center (TDC) (indicated by IO ₀ in FIG. 2), and the intake stroke bottom dead center (BD
After C), the valve is closed, for example, at about 70 ° (ABDC 70 °) (indicated by IC ₀ in FIG. 2). On the other hand, although not shown, in the present embodiment, the opening timing and closing timing of the exhaust valve are fixed, and the exhaust valve always opens before the bottom dead center (BDC) of the explosion stroke and rises on the exhaust stroke. Close the valve after dead center (TDC).

In FIG. 2, tVT is the optimum valve timing (basic valve timing) determined by the engine operating condition. The basic valve timing tVT is a valve timing determined from the engine load (for example, the intake air amount per engine revolution) and the number of revolutions. In this embodiment, as the value of tVT increases, tVT advances. It will be set as square.

Further, VKNK in FIG. 2 indicates the valve timing retard amount (however, VKNK ≧ 0), and VTCAL indicates the actual (after retard) valve timing. That is, the actual valve timing VTCAL is VTC.
Expressed as AL = tVT-VKNK. Next, knocking suppression by retarding the valve timing will be described.

As described above, when the valve timing is retarded (that is, when VT becomes smaller), the intake valve opens until the compression stroke. For example, in the example shown in FIG. 2, the larger the valve timing retard amount VKNK with respect to the basic valve timing tVT, the later the intake valve is closed in the compression stroke. Therefore, if the valve timing is retarded, the piston stroke from the time of closing the intake valve to the top dead center of the compression stroke is shortened, and the actual compression ratio of the engine is reduced. Therefore, it is possible to suppress the knocking by delaying the valve timing when the knocking occurs, and when the engine is operated in a state where the knocking easily occurs, the valve timing is retarded to prevent the knocking. Occurrence can be prevented.

The valve timing control of the present invention will be described below. In this embodiment, when the knocking occurs, the valve timing delay amount VKNK is determined according to the knock intensity.
(See FIG. 2) is set, and the basic valve timing tVT is corrected by using the retard amount VKNK to retard the valve timing of the engine to suppress knocking. Further, the higher the engine compression ratio, the higher the knock strength. Therefore, the higher the knock strength, the lower the actual engine compression ratio in order to suppress knocking. Therefore, the retard amount VKNK is set to a larger value as the knock intensity NK detected by the knock sensor 50 is larger.

FIG. 3 is a flow chart showing an embodiment of the valve timing control of the present invention. This routine is E
It is executed by the CU 30 at regular intervals. When the routine starts in FIG. 3, in step 301, the intake air amount data G, the rotation speed data NE, and the knock intensity NK are set to R.
It is read from a predetermined area of AM33. Next, at step 303, the intake air amount G / NE per engine revolution is calculated from the intake air amount G and the revolution speed NE read as described above, and the engine revolution speed NE and the intake air amount G per revolution of the engine G are calculated. Optimal valve timing (basic valve timing) tV according to engine operating conditions using / NE
T is set.

The basic valve timing tVT is obtained in advance by experiments or the like, and G / NE and N of the type shown in FIG.
ECU 30 in the form of a numerical table (map) using E and
Stored in the ROM 32. In step 303,
The basic valve timing tVT is determined from the values of G / NE and NE based on the map of FIG. Next, at step 305, it is judged if the engine is currently knocking. Whether or not knocking has occurred is determined by the knock intensity NK detected by the knock sensor 50 being a predetermined value NK.
It is judged by whether it is ₀ or more. Here, NK ₀ is a determination value as to whether knocking has occurred, and is set to a value as small as possible within a range that does not cause an erroneous determination.

If NK <NK ₀ in step 305, it is determined that knock has not occurred, and step 3
At 07, the control target value VTCAL of valve timing is set to the same value as the basic valve timing tVT set at step 303, and VTCAL set at step 313.
The value of is stored in a predetermined area of the RAM 33, and the routine ends.

When the value of VTCAL is stored in the RAM 33, the linear solenoid actuator 25b is controlled by a routine (not shown) executed separately, and the variable valve timing device 10 is controlled so that the actual valve timing VT becomes the control target value VTCAL. The hydraulic pressure supplied to is feedback-controlled. Since this feedback control is a known PID (proportional, integral, differential) control based on the deviation between the target value VTCAL and the actual VT, detailed description thereof will be omitted.

By executing step 307, when the engine is not knocked, the engine valve timing is controlled to be the optimum valve timing (basic valve timing) according to the operating conditions. On the other hand, knocking has occurred in step 305 (NK ≧ NK ₀ ).
If it is determined that the valve timing retard amount VKNK is set in step 309 according to the knock intensity NK. FIG. 5 is a diagram showing a relationship between the valve timing retard amount VKNK and the knock intensity NK in the present embodiment.
As shown in FIG. 5, the retard amount VKNK is set to a larger value as the knock intensity NK is larger.

Next, at step 311, the basic valve timing tVT is increased by the retard amount VKNK calculated above.
Is set as the value of the control target value VTCAL, and in step 313, the value of this VTCAL is set in the RAM 3
The value is stored in 3, and this routine ends. According to the above routine, when knocking occurs, the valve timing is retarded according to the knock strength, and the actual compression ratio of the engine decreases according to the knock strength.

The above embodiment shows the case where the knocking is suppressed by retarding the valve timing when the knocking occurs. However, when the knocking occurs, the normal ignition timing retarding may be executed together with the valve timing retarding. good. Generally, the change of the ignition timing is completed in a shorter time than the change of the valve timing. Therefore, if the ignition timing retard and the valve timing retard are simultaneously executed when knocking occurs, the ignition timing retard is completed first. Therefore, as the knock intensity (steps 305 and 309) when the valve timing control routine is executed, the knock intensity in the state where the ignition timing retard is completed is used. Therefore, according to the present embodiment, even when the valve timing retard and the ignition timing retard are simultaneously executed when knocking occurs, the ignition timing control and the valve timing control do not perform control in opposite directions, and It is possible to effectively suppress knocking. Next, another embodiment of the present invention will be described with reference to FIG. In the present embodiment, the magnitude of knock intensity is divided into two regions, low level knock and high level knock, and the valve timing is retarded according to the respective knock intensity levels.

When the knock intensity decreases due to the retarded valve timing, the valve timing approaches (advances) the basic valve timing in accordance with the reduced knock intensity.
Although the operation is performed, if the valve timing is advanced only by a slight decrease in the knock strength, the knock strength once decreased may increase again. Therefore, in this embodiment,
Even if the knock strength is decreased due to the retarded valve timing, the valve timing is not advanced immediately, but the valve timing is advanced after waiting until the knock strength is decreased to some extent.

When the routine starts in FIG. 6,
In steps 601 and 603, the intake air amount G, the engine speed NE, and the knock intensity NK are read and the basic valve timing tVT (FIG. 4) is set as in the routine of FIG. Next, at step 605, it is judged if the knock intensity NK exceeds a low level predetermined value NK _L, and if NK> NK _L , then step 607.
The value of the history flag XL is set to 1. Where X
L is a flag indicating that the knock intensity NK once exceeds a low level predetermined value NK _L.

Next, at step 609, the knock strength NK
Exceeds a high level predetermined value NK _H, and if NK> NK _H , the value of the history flag XH is set to 1 in step 611. XH is a flag that indicates that the knock intensity NK has once exceeded a high level predetermined value NK _H and has increased. Further, in this case, step 613 is executed next, and the control target value VTCAL of the engine valve timing is the basic valve timing tVT.
Is retarded by a relatively large fixed amount VKNK _{H, and the} value of VTCAL for which the retard is set is RAM3 in step 631.
3 is stored in a predetermined area.

On the other hand, if it is determined in step 609 that the knock strength NK is between the low level predetermined value NK _L and the high level predetermined value NK _H (NK _L ≤NK ≤NK _H ), the routine proceeds to step 615, where It is determined based on the value of the history flag XH whether or not the knocking intensity of the knocking is once the knocking intensity of a high level and then the knocking is attenuated. Step 6
If XH = 1 at 15, that is, if the knock intensity NK is the predetermined value NK of high level during the previous routine execution.
_Since it means that the engine had risen above _H , immediately advance the valve timing, the knock strength may increase again. Therefore, in step 617, it is determined whether or not the knock intensity NK is lower than the high level predetermined value NK _H by a predetermined amount β or more, and the valve timing is not advanced unless NK <NK _H −β.

That is, when the current knock intensity NK is NK ≧ NK _H −β in step 617, the routine proceeds to step 613, where the valve timing retard when the knock intensity is high is continued. It On the other hand, when the knock intensity has decreased to NK <NK _H −β in step 617, the flag XH is set to 0 in step 619 and then step 621 is executed, and the control target value VTCAL of the engine valve timing is Valve timing tVT
To a relatively small constant value VKNK _L (VKNK _H > VK
NK _L ). Also, in step 615, XH
Even if ≠ 1, step 621 is similarly executed.

By executing steps 609 to 621, it is possible to prevent the engine valve timing from frequently repeating the retard angle and the advance angle in the vicinity of the high level predetermined value of the knock intensity. If NK is less than or equal to the low level predetermined value NK _{L in} step 605 (that is, NK ≦ NK _L ), the same operation as in steps 609 to 621 is performed in steps 623 to 629. That is, when the knock intensity has once exceeded the low level predetermined value NK _L (step 62
3 is XL = 1), and if the knock intensity is not lower than the low level predetermined value NK _L by the predetermined amount α or more (NK> NK _L −α), step 621 is executed and the knock intensity is the low level. The valve timing retardation of the
Only when ≦ NK−α, the value of the flag XL is set to 0, and the valve timing control target value VTCAL is set to the basic valve timing tVT. That is, the valve timing returns to the basic valve timing. Further, even if XL ≠ 1 in step 623, VTCAL is set to the basic valve timing tVT in step 629.

The value of VTCAL set in any of steps 613, 621 and 629 is the RA of step 631.
It is stored in M33. In the present embodiment, when the valve timing retard amount is set according to the knock intensity as described above, the knock intensity (N
K _L, NK _H) and knock magnitude to initiate valve timing advance _{(NL L -α, NK H -β} ) and were set to different values (i.e., provided with a hysteresis in the valve timing control) by the above Knock strength judgment value (N
K _L, NK _H) is prevented and frequent advance and retard in the vicinity is performed, the valve timing control can be stabilized.

Next, another embodiment of the present invention will be described. In the present embodiment, the valve timing retard amount is not set according to the knock intensity, but an operating state parameter that affects the occurrence of knocking of the engine is detected, and the value of this parameter is a value at which knocking easily occurs. The valve timing is retarded. That is, in the above-described embodiment, the knocking is suppressed by delaying the valve timing after the occurrence of knocking. However, in the embodiments described below, the actual compression ratio of the engine increases as the knocking easily occurs. To prevent knocking from occurring.

FIG. 7 is a flow chart showing an embodiment of valve timing control for retarding the valve timing according to the operating condition parameter. In this embodiment, the deposit amount in the combustion chamber is used as the operating state parameter that affects the occurrence of knocking, and the valve timing is retarded as the deposit amount increases.

A deposit of carbon or the like is deposited in the engine combustion chamber as it is used, but since the deposited deposit has a relatively rough surface, burned gas after combustion tends to be retained on the deposit surface. For this reason, when deposits are accumulated in the combustion chamber, combustion is less likely to occur in the vicinity of the deposit accumulation portion, and knocking is likely to occur in the engine. Therefore, knocking is more likely to occur as the deposit amount in the combustion chamber increases. In this embodiment, the amount of deposit accumulated in the combustion chamber is estimated, and the valve timing is retarded as the amount of deposit accumulated increases, thereby preventing knocking in the engine due to deposit accumulation.

Next, the estimation of the deposit accumulation amount in the combustion chamber in this embodiment will be described. In this embodiment, the deposit accumulation amount in the combustion chamber is estimated based on the value of the deposit learning correction amount KDPC of the fuel injection amount set by a routine (not shown) executed separately. The deposit learning correction amount KDPC is a correction amount for correcting that the amount of fuel attached to and retained on the intake port wall surface changes according to the amount of deposit accumulated on the intake port wall surface. In other words, if the amount of deposits accumulated on the wall surface of the intake port increases, the amount of fuel that adheres to the wall surface of the intake port of the fuel injected into the intake port increases, so even if the fuel injection amount is increased during acceleration, for example, A part of the burned fuel is consumed to increase the amount of fuel adhering to the wall of the intake port and does not reach the combustion chamber. Therefore, if the amount of deposit accumulated on the wall surface of the intake port increases, the air-fuel ratio becomes lean during engine acceleration. Therefore, in the present embodiment, the ECU 30
By a routine (not shown) executed separately, the deposit learning correction amount KDPC is updated based on the degree to which the air-fuel ratio becomes lean during engine acceleration during operation, and is stored in the backup RAM 37 of the ECU 30. The ECU 30 increases the fuel increase amount during acceleration as the value of KDPC increases, and prevents the air-fuel ratio from becoming a lean air-fuel ratio during acceleration. That is, the deposit learning correction amount KDPC is set to a value corresponding to the amount of deposit accumulated on the wall surface of the intake port.

On the other hand, it is considered that the deposit amount on the wall surface of the combustion chamber increases in proportion to the deposit amount on the wall surface of the intake port. Therefore, in the present embodiment, the value of the deposit learning correction amount KDPC is used as a parameter representing the deposit accumulation amount on the wall surface of the combustion chamber, and the valve timing retard amount VKNK is set according to the value of KDPC. When the routine starts in FIG. 7, step 701
Then, from the RAM 33, the engine intake air amount G and the engine speed N
E and E are read, and in this embodiment, the deposit learning correction amount KDPC is read from the backup RAM 37.

In step 703, G / NE and N
Using E and E, the basic valve timing tVT is set from the map of FIG. Further, in step 705, the valve timing delay amount VKNK is premised on the basis of the value of the deposit learning correction amount KDPC read in step 701. FIG. 8 is a deposit learning correction amount KDP of this embodiment.
It is a figure which shows the relationship between C and valve-timing retard amount VKNK. As shown in FIG. 8, in this routine, the larger the value of the deposit learning correction amount KDPC, that is, the larger the deposit accumulation amount and the more easily knocking occur, the larger the valve timing retard amount VKNK is set.

Next, at step 707, the valve timing control target value VTCAL is set to the basic valve timing t.
VT is set to a value that is retarded by the retard amount VKNK, and in step 709, the target value VTCAL that is retarded is set to R.
It is stored in AM33. By executing the above routine, the valve timing control target value VTCAL is retarded with respect to the basic valve timing tVT as the deposit amount in the combustion chamber increases, and knocking due to deposit accumulation is effectively prevented. It

FIG. 9 is a flowchart showing another embodiment of setting the retard amount VKNK according to the deposit learning correction amount KDPC. In this embodiment, similarly to the embodiment of FIG. 6, the value of the deposit learning correction amount KDPC is divided into a high level region and a low level region, and the retard angle amount is set according to each level and the valve timing is set. Hysteresis is provided for control. The flowchart of FIG. 9 corresponds to the step of replacing the knock intensity NK of each step of the flowchart of FIG. 6 with the deposit learning correction amount KDPC, and the operation of each step is substantially the same as that of FIG. Detailed description is omitted. In FIG. 9, KD _L and KD _H (steps 905 and 909) are the determination values of the deposit learning correction amount KDPC on the low level side and the high level side, respectively, γ and δ (steps 925 and 917).
Are respectively α and β in FIG. 6 (steps 625 and 61 in FIG. 6).
It is a constant value corresponding to 7).

Next, another embodiment of the valve timing control for delaying the valve timing according to the operating condition parameter will be described with reference to FIG. In this embodiment, as the operating state parameter that affects the occurrence of knocking,
By using the gear used during traveling, the valve timing is retarded as the gear used is on the lower gear side.
For example, when the vehicle is traveling using a low speed gear having a large gear ratio, the vehicle is in a driving state in which the engine speed is relatively high and the traveling speed is low. In such a case, the traveling wind hitting the engine tends to be smaller and the engine temperature and the intake air temperature tend to be higher than when traveling in a high speed gear having a small gear ratio. On the other hand, as the engine temperature and the intake air temperature increase, the engine is more likely to knock. Therefore, the closer the gear used during traveling is to the low speed gear side, the more easily the engine is knocked. That is, the gear used during traveling can be used as an operating state parameter indicating the ease with which knocking occurs.

In the embodiment of FIG. 10, as the traveling gear detected by the shift position sensor 47 is at a lower speed (the gear gear ratio is larger), the valve timing retard amount VKNK is increased.
Is set to a large value to prevent engine knock. When the routine starts in FIG. 10, in step 1001, the engine intake air amount G, the engine speed NE, and the used gear SP detected by the shift position sensor 47 are read from the RAM 33.

Further, in step 1003, the basic valve timing tVT is set from the map of FIG. 4 using G / NE and NE. Further, in step 1005, the valve timing delay amount VKNK is premised on the basis of the value of the used gear SP read in step 1001. FIG.
FIG. 1 is a diagram showing the relationship between the used gear SP and the valve timing retard angle amount VKNK in this embodiment. 5 is a flowchart illustrating another embodiment of the valve timing control of the present invention. As shown in FIG. 11, in this routine, the valve timing retard amount VKNK is set larger as the value of the used gear SP is closer to the low speed gear, that is, the knocking is more likely to occur due to the engine temperature rise.

Next, at step 1007, the valve timing control target value VTCAL is set to a value obtained by retarding the basic valve timing tVT by the retard amount VKNK, and at step 1009, the retard target setting value VTCAL is set.
Are stored in the RAM 33. By executing the above routine,
The valve timing control target value VTCAL is set to a retard angle with respect to the basic valve timing tVT as the gear used is at a lower speed side, and knocking during low speed traveling is effectively prevented.

The example of the valve timing control in which the valve timing retard amount VKNK is set according to the value of the engine operating condition parameter has been described above.
Can be set according to parameters other than the engine operating state parameters described above. For example, the values of other engine operating state parameters that affect the occurrence of knocking, such as engine intake temperature and atmospheric pressure, are detected, and the valve timing retard amount VKNK increases as the values of these parameters tend to cause knocking. You may set so that it may become large.

In each of the above embodiments, the knocking is suppressed by retarding the closing timing of the intake valve, but as described above, the knocking is also prevented by advancing the closing timing of the intake valve. It is possible to suppress. Therefore, in the above embodiment, the actual volumetric efficiency of the engine may be reduced and the knocking may be suppressed by advancing the valve timing according to the knocking strength or the value of the engine operating state parameter.

[0069]

[Effects of the Invention] According to the inventions described in the claims, the effect that the knocking of the engine can be effectively suppressed can be obtained. According to the first aspect of the present invention, the valve timing retard amount is set according to the knock intensity, so that in addition to the common effect described above, knocking suppression by ignition timing retard is performed at the same time. Also, it is possible to prevent knocking from easily occurring due to execution of the valve timing control.

According to the invention described in claims 2 to 4, the valve timing retard amount is set to be larger as the engine operating condition is such that knocking is more likely to occur. In addition to this, it is possible to effectively prevent the occurrence of knocking even in an operating state where knocking is likely to occur.

[Brief description of drawings]

FIG. 1 is a diagram showing a main part configuration of an embodiment in which the present invention is applied to an internal combustion engine for automobiles.

FIG. 2 is a diagram illustrating the definition of valve timing in the embodiment of FIG.

FIG. 3 is a flowchart illustrating an example of valve timing control according to the present invention.

FIG. 4 is a diagram showing a format of a map used in the routine of FIG.

FIG. 5 is a diagram showing a relationship between knock intensity and a valve timing delay amount.

FIG. 6 is a flowchart illustrating another embodiment of valve timing control according to the present invention.

FIG. 7 is a flowchart illustrating another embodiment of valve timing control of the present invention.

8 is a diagram showing a relationship between a deposit learning correction amount and a valve timing delay amount in the embodiment of FIG.

FIG. 9 is a flowchart illustrating another embodiment of valve timing control of the present invention.

FIG. 10 is a flowchart illustrating another embodiment of valve timing control of the present invention.

FIG. 11 is a diagram showing a relationship between a used gear and a valve timing delay amount.

[Explanation of symbols]

 1 ... Camshaft 10 ... Variable Valve Timing Device 30 ... ECU 47 ... Shift Position Sensor 50 ... Knock Sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location F02D 29/00 F02D 29/00 H 45/00 368 45/00 368A

Claims (4)

[Claims] 1. A valve timing setting means for setting a target value of an engine intake valve closing timing according to an operating condition of an internal combustion engine, and a knock intensity detecting means for detecting the intensity of knocking occurring in the engine, A correction means that largely corrects the intake valve closing timing target value in the direction in which the actual compression ratio of the engine decreases as the knock strength increases, and a target value after the closing timing of the engine intake valve is corrected by the correction means. A valve timing control device comprising: 2. A valve timing setting means for setting a target value of an engine intake valve closing timing according to an operating condition of an internal combustion engine, and a parameter detecting means for detecting an operating state parameter involved in engine knocking occurrence. As the value of the operating condition parameter is such that knocking tends to occur, the correction means for correcting the engine intake valve closing timing to a direction in which the actual compression ratio of the engine is decreased, and the closing timing of the engine intake valve are corrected as described above. A valve timing control device comprising: a valve timing control device that controls the target value after being corrected by the device. 3. The parameter detecting means includes means for detecting a deposit accumulation amount in the engine combustion chamber, and the correcting means decreases the intake valve closing timing and the engine actual compression ratio as the deposit accumulation amount increases. The valve timing control device according to claim 2, wherein the valve timing control device largely corrects the valve timing. 4. The internal combustion engine is a vehicle internal combustion engine having a transmission, the parameter detection means includes shift position detection means for detecting a transmission shift position, and the correction means determines a transmission shift position. The lower the gear side, the closer the intake valve closing timing,
The correction is performed so that the actual compression ratio of the engine is greatly reduced.
Valve timing control device.