JPH1136906A - Knocking control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid knocking more effectively through variable control of opening and closing timing of an intake valve. SOLUTION: A variable valve drive mechanism of such a type that the operating angle is changed, is used for an intake valve, and accordingly, the closing timing can be greatly changed while the opening timing is held to be substantially constant. During high temperature and high load operation of an engine, a frequency of knocking detected by a knocking sensor becomes larger, the ignition timing is retarded, and simultaneously, an actuator is operated so as to enlarge the operating angle. As the closing timing of the intake valve is delayed, an actual compression ratio is lowered so as to avoid knocking. When the operating angle is changed up to a desired value, the ignition timing is advanced to its original value, thereby it is possible to prevent the temperature of exhaust gas from rising.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a knocking control device for suppressing knocking of a spark ignition type internal combustion engine typified by an automobile gasoline engine.
The present invention relates to a knocking control device for an internal combustion engine having a variable valve mechanism.

[0002]

2. Description of the Related Art Knocking often occurs under high-temperature and high-load conditions, which are particularly severe conditions in use of an internal combustion engine. In other words, the temperature of the intake air itself rises due to heat exchange with the inner wall of the cylinder, the piston, etc., and while waiting for flame propagation in a compressed state, the unburned mixture spontaneously ignites, and the combustion speed rises abnormally high As a result, a specific knocking sound is generated, and the accelerated flame rapidly raises a local temperature of a piston, a valve, or the like with a high heat transfer coefficient, thereby lowering its durability. As described above, knocking is likely to occur due to an increase in the temperature of the compressed air-fuel mixture, but is particularly likely to occur when the cooling water temperature of the internal combustion engine is increasing due to a continuous high load state.

[0003] In order to avoid such knocking, it is most certain to set the compression ratio of the engine low.
Then, the thermal efficiency decreases and the fuel efficiency deteriorates. Therefore, in recent years, many gasoline engines for automobiles use a relatively high compression ratio, detect the occurrence of knocking with a knock sensor or the like, and retard the ignition timing when knocking occurs, thereby suppressing knocking. Achieving both high compression ratios.

However, avoiding knocking by retarding the ignition timing has good responsiveness and is suitable for avoiding knocking itself. On the other hand, however, deterioration of fuel efficiency due to delay of combustion start from the optimal timing, There are problems such as deterioration of durability of the catalyst and the like due to an increase in the exhaust gas temperature.

[0005] In order to minimize such a problem caused by retardation of the ignition timing, for example, as disclosed in Japanese Patent Application Laid-Open No. 8-338295, to avoid knocking,
The phase of the camshaft on the intake side of the engine is variably controlled, and the phase of the camshaft is delayed with respect to the crankshaft when knocking occurs, in the form of a combination with the retard of the ignition timing. A knocking control device that reduces the compression ratio has been proposed. In other words, as the actual compression ratio is reduced by delaying the closing timing of the intake valve, the charging efficiency is also reduced, the temperature of the air-fuel mixture during compression is reduced, the rise in exhaust temperature is prevented, and knocking is suppressed. is there.

On the other hand, as a variable valve mechanism for variably controlling the opening / closing timing of an intake valve of an internal combustion engine, various types have been proposed in addition to those that change the phase of a camshaft as described above. Some are already in practical use.
In particular, JP-A-6-185321 discloses that the valve lift characteristic can be continuously variably controlled by rotating the cylindrical camshaft at an unequal speed by applying the principle of the unequal speed shaft coupling. A variable valve mechanism is disclosed.

[0007]

The above-mentioned JP-A-8-33
As disclosed in US Pat. No. 8,295, the configuration in which the phase of the camshaft is changed to avoid knocking,
Since not only the closing timing of the intake valve but also the opening timing changes by the same angle at the same time, the amount of phase change is set relatively small so that the intake valve opening timing changes in a narrow range near top dead center. If the closing timing is delayed by more than 20 ° CA in order to avoid knocking, the opening timing of the intake is greatly delayed from the top dead center, and the intake does not enter at the beginning of the intake stroke. Due to the occurrence of pump loss, etc., the decrease in torque cannot be ignored. Also, if the opening angle of the intake valve is set to a wide value in advance to prevent the opening timing of the intake valve from being after the top dead center, an appropriate state may be obtained at the timing retarded to avoid knocking. However, at the normal valve timing without retarding to avoid knocking, the intake valve opening timing was much earlier than the top dead center, the valve overlap expanded, and the intake The high-temperature exhaust gas flows back to the side, which significantly raises the intake air temperature. As a result, the conditions under which knocking occurs under normal valve timing are greatly deteriorated, and knocking is more likely to occur. In addition, when the valve overlap is large as described above, particularly in an internal combustion engine equipped with a turbocharger, when the rotation speed of the turbocharger is in the process of increasing, such as during starting acceleration, the intake pressure (the supercharging pressure ) Is still low and the exhaust pressure is significantly high, there is a problem that the residual gas concentration in the cylinder sharply increases, and not only the charging efficiency deteriorates but also the knock resistance deteriorates.

As described above, in the conventional configuration in which the opening timing and the closing timing of the intake valve are delayed by the same phase simply by changing the phase of the camshaft on the intake valve side,
The effect of avoiding knocking is limited and not sufficient.

[0009]

Therefore, the present invention maximizes the effect of avoiding knocking by variable control of the opening and closing timing of the intake valve by combining with a variable valve mechanism capable of reducing and expanding the operating angle of the intake valve. It is something that you get.

A knocking control apparatus for an internal combustion engine according to a first aspect of the present invention detects occurrence of knocking at a predetermined level in an internal combustion engine having a variable valve mechanism capable of variably controlling the operating angle of an intake valve. Knocking detection means, ignition timing delay means for delaying the ignition timing when the knocking is detected, engine temperature detection means for detecting an engine temperature condition, and load detection means for detecting a load state of the engine. The variable valve mechanism is set such that the change in the closing timing is relatively larger than the change in the opening timing, and the engine temperature and load are in a predetermined region, and knocking at a predetermined level is detected. In this case, the operating angle is expanded so that the closing timing of the intake valve is delayed in addition to the ignition timing retard.

That is, as described above, knocking tends to occur when the temperature of the internal combustion engine is high and the engine is in a high load state. Therefore, when knocking of a predetermined level, for example, predetermined strength or predetermined frequency is detected in a predetermined high temperature state and a high load state, the operation angle is expanded so that the closing timing of the intake valve is delayed.

Here, FIG. 1 shows the above-mentioned JP-A-6-18 / 1994.
5 illustrates an example of a valve lift characteristic obtained by a variable valve mechanism capable of variably controlling an operation angle described in Japanese Patent No. 5321 or the like. The characteristic of FIG. 1 is such that the change of the opening / closing timing of the intake valve occurs symmetrically. When the operating angle is increased, the advance of the opening timing and the retardation of the closing timing are substantially the same. It occurs in quantities. However, with such characteristics, if the operating angle is expanded so that the actual compression ratio is reduced by delaying the intake valve closing timing to avoid knocking, the intake valve opening timing is advanced at the same level at the same time. Although the actual compression ratio decreases, the residual gas ratio increases with the advance of the opening timing, so the effect of improving knock resistance is offset, and it may worsen under conditions of high exhaust pressure, etc. There is also.

Accordingly, in an internal combustion engine in which the valve overlap is set relatively small (the condition of the residual gas ratio is relatively small), as shown in FIG. Is desirably set so that the change of the distance becomes relatively large. With such characteristics,
In order to avoid knocking, the actual compression ratio can be reduced by sufficiently delaying the closing timing of the intake valve, and expansion of the valve overlap can be suppressed as much as possible.

According to a second aspect of the present invention, a supercharger is provided in the intake system, and a supercharging pressure control means for increasing the supercharging pressure in response to the above-mentioned increase in the operating angle is provided.

By increasing the supercharging pressure in response to the expansion of the operating angle in this manner, it is possible to compensate for the decrease in the charging efficiency due to the delay of the closing timing, and to suppress the decrease in the torque.

A knocking control apparatus for an internal combustion engine according to a third aspect of the present invention detects occurrence of knocking of a predetermined level in an internal combustion engine having a variable valve mechanism capable of variably controlling the operating angle of an intake valve. Knocking detection means, ignition timing delay means for retarding the ignition timing when the knocking is detected, engine temperature detection means for detecting the temperature condition of the engine, load detection means for detecting the load state of the engine, The variable valve mechanism is set so that the change in the opening timing is relatively larger than the change in the closing timing, and the temperature and load of the engine are in a predetermined region, and knocking at a predetermined level is performed. When detected, the operating angle is reduced so that the valve overlap is reduced together with the ignition timing retard.

When the valve overlap of the internal combustion engine is set to be relatively large, for example, the residual gas is positively increased by enlarging the valve overlap by using a variable valve operating mechanism. In an internal combustion engine or the like in which the NOx is suppressed by the effect, although the NOx is reduced due to the high residual gas concentration,
The temperature of the unburned mixture increases with an increase in the residual gas ratio,
Knocking is likely to occur. In such a case, in order to avoid knocking, the opening timing is retarded rather than the retarding of the intake valve closing timing to reduce the residual gas ratio, whereby a greater effect can be obtained.

However, in this case, with the characteristic that changes symmetrically as shown in FIG. 1, if the intake valve opening timing is delayed to reduce the valve overlap in order to avoid knocking,
At the same time, the intake valve closing timing is advanced by the same level, so that the closing timing approaches the bottom dead center and the actual compression ratio increases, thereby canceling the knock resistance improvement effect due to the reduction of the valve overlap. Therefore, in such a case, as shown in FIG. 4, it is desirable to set the variable valve mechanism so that the change in the opening timing is relatively larger than the change in the closing timing. With such characteristics, the valve overlap can be reduced by advancing the opening timing of the intake valve to avoid knocking, and at the same time, the change in the closing timing of the intake valve can be suppressed as much as possible.

According to the fourth aspect of the present invention, the expansion and contraction of the operating angle is maintained even after knocking is suppressed, and the desired characteristics are restored on condition that the load on the engine becomes equal to or less than a predetermined value. It is characterized by doing.

Under the condition that the internal combustion engine is continuously operated under a high load condition and each part becomes high temperature due to an increase in the temperature of the cooling water, there is a high possibility that knocking will occur. Under such conditions, when knocking is avoided by variably controlling the operating angle of the intake valve, if the operating angle is returned to a normal state when knocking is no longer detected, knocking occurs again, and the engine operates again. The operation of enlarging or reducing the corner is repeated. In the case of knocking control based on ignition timing, responsiveness is high, and it is possible to maintain a state in which weak knocking is occurring by fine control, that is, a so-called trace knocking state, but variable control of the operating angle of the intake valve. In the case of, since a mechanical drive system is interposed,
Since the response time is long and the torque changes with the change in the charging efficiency, frequent increase and decrease of the operating angle is liable to cause deterioration of drivability. Therefore, as in claim 4, once the operating angle is changed, even if knocking is suppressed, the knocking is suppressed until the operating angle deviates from a predetermined high load region.
It is desirable not to return the operating angle.

The knocking control by retarding the ignition timing is as follows.
As described above, although the responsiveness is high, if a large retardation is continued, there is a concern that the exhaust gas temperature rises and deterioration of the catalyst and the like is accelerated. Therefore, a fifth aspect of the present invention is characterized in that there is provided a means for detecting the operating angle, and the retard of the ignition timing is released when the amount of change in expansion or contraction of the operating angle reaches a predetermined value. .

Further, the invention of claim 6 is characterized in that when the retard of the ignition timing is released, the ignition timing is immediately returned to the advance level immediately before the retard, and thereafter the advance is gradually advanced. And That is, when the expansion or reduction of the operating angle is completed, the ignition timing is promptly returned to the original level, and thereafter the angle is gradually advanced and the trace knock state is maintained.

A seventh aspect of the present invention is based on the premise of the second aspect. When the retarded ignition timing is restored, the supercharging pressure control means responds accordingly. It is characterized in that the pressure is reduced to a predetermined level. Further, in the present invention, when the ignition timing that has been retarded is returned, the ignition timing is returned to the ignition timing that is delayed from the advance level immediately before the retardation in response to the increase in the supercharging pressure. Features. That is, when the boost pressure is high, the knocking occurrence condition becomes severe. Therefore, when the ignition timing is advanced, the boost pressure is reduced as in claim 7, or the ignition timing is slightly reduced as in claim 8. On the lag side, it is desirable to suppress the occurrence of knocking.

In order to realize the above-described variable control of the closing timing of the intake valve, the knocking control device according to the ninth aspect is characterized in that the variable valve mechanism includes a drive shaft that rotates in synchronization with the rotation of the engine. A camshaft arranged coaxially with the drive shaft and having a cam on the outer periphery for driving the intake valve;
A flange portion provided at an end of the camshaft and having an engagement groove formed in a radial direction, and provided on the drive shaft side so as to face the one flange portion; and The other flange portion having an engagement groove formed along the same, an annular disk disposed swingably between the two flange portions, and projecting in opposite directions on both sides of the annular disk. A pin engaged with each of the engagement grooves of the flange portions, and a drive mechanism for swinging the annular disk in accordance with an engine operating state.

In this configuration, when the center of rotation of the annular disk is concentric with the center of the drive shaft and the camshaft, the drive shaft and the camshaft rotate at a constant speed, and the annular disk is at an eccentric position. In such a case, the two rotate unequally. Therefore, the valve lift characteristic of the intake valve changes continuously according to the position of the annular disk, and the opening / closing timing and operating angle of the intake valve change. It should be noted that a different characteristic as described in claim 1 or 3 can be realized by the positional relationship of the same phase point where the phases of the drive shaft and the camshaft always coincide.

[0026]

As described above, according to the present invention, the knocking is avoided by using a variable valve mechanism capable of variably controlling the operating angle of the intake valve, thereby changing the phase of the conventional camshaft. In this case, it is possible to more effectively avoid knocking in a high-temperature and high-load state while avoiding problems such as occurrence of pump loss in the initial stage of the intake stroke and excessive expansion of valve overlap. In particular, the invention of claim 1 is suitable for an internal combustion engine in which the valve overlap is set relatively small, and the invention of claim 3 is
This is suitable for an internal combustion engine having a relatively large valve overlap.

According to the second aspect, it is possible to suppress a decrease in torque due to an increase in the operating angle, and to reduce adverse effects on drivability.

According to the fourth to eighth aspects of the present invention, it is possible to prevent frequent enlargement and reduction of the operating angle, and
Excessive rise in exhaust gas temperature due to continuation of the retard of the ignition timing can be avoided.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 2 shows a configuration of a gasoline engine equipped with a turbocharger as one embodiment of the internal combustion engine according to the present invention. In FIG. 2, a plurality of cylinders 2 are arranged in series in a cylinder block 1; A piston 3 is slidably fitted in each cylinder 2. An intake port 6 opened and closed by an intake valve 5 and an exhaust port 8 opened and closed by an exhaust valve 7 are formed in the cylinder head 4 covering the top of the cylinder 2. On the upstream side of an intake passage connected to the intake port 6, a turbocharger 9, specifically, a compressor 9a thereof is provided. This compressor 9a
The exhaust turbine 9 b for driving the exhaust gas is interposed in an exhaust passage downstream of the exhaust port 8. The exhaust turbine 9b
An exhaust bypass passage 10 is provided between the outlet side and the inlet side of the vehicle, and an electronically controlled wastegate valve 11 is interposed here. Further, a supercharging pressure sensor 12 for detecting a supercharging pressure is disposed on the outlet side of the compressor 9a, that is, on the upstream side of the intake port 6.

The waste gate valve 11 is opened on the high speed side of the engine so as to maintain the supercharging pressure at a predetermined characteristic, and is controlled by a control unit 13. Detection signals such as the engine speed, load, cooling water temperature, lubricating oil pressure, and supercharging pressure by the supercharging pressure sensor 12 are input to the control unit 13, and the supercharging pressure is adjusted to characteristics according to the engine operating conditions. Controlling.

A knocking sensor 14 for detecting knocking vibration of a predetermined frequency is mounted on the cylinder block 1, and a knocking detection signal is input to the control unit 13. Note that, for example, an in-cylinder pressure sensor may be provided in the washer portion of the ignition plug, and knocking may be detected based on a change in the in-cylinder pressure. The control unit 13 variably controls the ignition timing of an unillustrated spark plug and the operating angle of the intake valve 5 described later based on the detection of the knocking.

The exhaust valve 7 is opened and closed at a fixed valve timing by an exhaust camshaft (not shown). On the other hand, the intake valve 5 is configured such that the opening and closing timing thereof can be variably controlled together with the operating angle by a variable valve mechanism described later.

The above variable valve mechanism is disclosed in Japanese Patent Laid-Open No. 6-1853.
As disclosed in Japanese Patent No. 21365 and US Pat. No. 5,365,896, the cylindrical camshaft 22 of each cylinder is rotated at a non-constant speed by applying the principle of a non-constant speed shaft coupling. Thus, the valve lift characteristics can be continuously variably controlled.

Since this mechanism itself is known, it will be briefly described with reference to FIGS.
Is a drive shaft to which rotational force is transmitted from an unillustrated engine crankshaft via a timing chain 23, and 22 is the drive shaft 21
Is a hollow cylindrical camshaft rotatably fitted on the outer periphery of the camshaft. The camshaft 22 is divided for each cylinder.

The camshaft 22 is rotatably supported by a cam bearing at the upper end of the cylinder head 4 and has a pair of cams 26 formed on the outer periphery thereof for opening the pair of intake valves 5 of each cylinder. . Also, the camshaft 22
Is divided into a plurality of pieces as described above, and a first flange portion 27 is provided at one of the divided ends. A sleeve 28 and an annular disk 29 are arranged between the ends of the plurality of divided camshafts 22, respectively. The first flange portion 27 is formed with an elongated engagement groove extending in the radial direction.

The sleeve 28 is fixed to the drive shaft 21. The sleeve 28 has a second flange 32 facing the first flange 27. The second flange portion 32 is also formed with an elongated engagement groove along the radial direction.

The annular disk 29 located between the flange portions 27 and 32 has an annular plate shape, and has a drive shaft 21.
And has an annular gap with the outer peripheral surface of the disk housing 34, and is rotatably held on the inner peripheral surface of the disk housing 34. Further, a pair of pins 36 and 37 projecting to opposite sides are provided at opposite positions on diameter lines different from each other by 180 °, and the pins 36 and 37 are engaged with the respective engagement grooves.

The disk housing 34 has a substantially triangular shape. The circular disk 29 is held in a circular opening thereof, and a cam fitting hole 38 and a bush fitting hole 39 are provided at two places at the top of the triangle. Are formed through.

An eccentric cam 41 formed integrally with the control shaft 42 is rotatably fitted in the cam fitting hole 38, and a support shaft 4 is provided in the bush fitting hole 39.
The eccentric bush 43 supported by the rotary member 4 is rotatably fitted.

The eccentric bush 43 is rotatably supported on a support shaft 44. The eccentric cam 41 is
A control shaft 42 that is continuous over a plurality of cylinders along the engine front-rear direction is provided for each cylinder. At one end of the control shaft 42 located at one end of the engine, a rotary hydraulic actuator 46 is attached as a drive mechanism. A sensor such as a potentiometer (not shown) is provided to detect the rotational position of the control shaft 42, that is, the phase of the eccentric cam 41.

In the above-described variable valve mechanism, the eccentric position of the annular disk 29 is variably controlled through the eccentric cam 41, so that the camshaft 22 rotates at an irregular speed, and the camshaft 22 rotates between the camshaft 22 and the drive shaft 21. A phase difference occurs according to the amount of eccentricity.
For example, as shown in FIG.
When the center Y of the drive shaft 21 coincides with the center X of the drive shaft 21, the camshaft 22 rotates synchronously with the drive shaft 21 at a constant speed, so that valve lift characteristics along the cam profile can be obtained. On the other hand, as shown in FIG. 6B, when the center Y of the annular disk 29 is eccentric to one side, a phase difference occurs according to the eccentricity Δ, and the operating angle is enlarged or reduced accordingly. The valve lift characteristics can be obtained in such a shape.

During one rotation of the drive shaft 21, a phase difference in the positive direction and a phase difference in the negative direction occur, and the same phase point exists in the middle. Then, the characteristic as shown in FIG. 3 or FIG. 4 can be obtained by the position of the in-phase point. According to the characteristics shown in FIG. 3, even when the center of the annular disk 29 is eccentric and the valve operating angle is increased or decreased, the opening timing hardly changes and only the closing timing changes.
Conversely, in the characteristics of FIG. 4, even when the operating angle changes, the closing timing hardly changes, and only the opening timing changes.

The hydraulic pressure supplied to the hydraulic actuator 46 is controlled via a hydraulic control valve (not shown) based on a control signal from the control unit 13 described above.
Various signals indicating the engine operating conditions are input to the control unit 13 as described above, and the operating angle (opening / closing timing) of the intake valve 5 is variably controlled based on these signals.

FIG. 7 is a timing chart showing a first embodiment of the knocking avoidance control according to the present invention. This embodiment is based on the premise that the variable valve mechanism changes with characteristics as shown in FIG.

In FIG. 7, (a) shows the output signal of the knocking sensor 14. While the knocking signal is at a relatively small level, the ignition timing is set to a so-called trace as shown in (c). The knock point is controlled. In other words, by advancing as far as possible within a range in which knocking does not occur, a state in which extremely weak knocking occurs is maintained. On the other hand, when the frequency of the knocking signal exceeding the slice level becomes equal to or higher than a predetermined value when the internal combustion engine is in a predetermined high temperature and high load region, knocking that combines ignition timing retarding and intake valve operating angle control is performed. It is determined that the avoidance control should be started (the timing of T1 in the figure corresponds to this). This allows
The ignition timing is retarded to a predetermined level. In addition, since this retarding can be performed with good responsiveness, knocking is quickly suppressed. At the same time, as shown in (d), the hydraulic actuator 46 of the variable valve mechanism is controlled so that the operating angle of the intake valve increases. Since the control of the operating angle involves a mechanical delay, the actual operating angle gradually changes depending on the operating speed of the hydraulic actuator 46 as shown in FIG. By increasing the operating angle in this way, as is apparent from FIG. 3, the closing timing of the intake valve 5 is delayed and the actual compression ratio is reduced, so that knocking is less likely to occur. Then, when it is detected that the expansion of the operating angle has reached the target value, the ignition timing is advanced to the original level (T2 in the figure). As a result, a rise in the exhaust gas temperature is avoided. After that, the ignition timing resumes the trace knock control, but since the knocking is suppressed by the operation angle control, the ignition timing is gradually advanced to the trace knock level.

FIGS. 11 and 12 are flowcharts showing the control flow of the first embodiment executed by the control unit 13. First, in step 1, a control map of the intake valve closing timing (IVC) and the ignition The control map of the timing (Adv) is read. As the control map, a map for a normal temperature condition, a map for a cold state, and a map for a high temperature are set in advance. Next, in step 2, the cooling water temperature tw is compared with a predetermined reference temperature (temperature at which the warm-up is considered to be completed) t0. In step 3, the target values of the intake valve closing timing and the ignition timing corresponding to the load, engine speed, and the like at that time are determined using a control map for cold time (not shown). If the warm-up is completed and the cooling water temperature tw is higher than the reference temperature t0, the process proceeds to step 4. In step 4, the cooling water temperature tw is further compared with a predetermined high-temperature-side reference temperature (a temperature at which knocking is a problem) th. In step 5, the target values of the intake valve closing timing and the ignition timing corresponding to the load, engine speed, and the like at that time are determined using the control map of the normal temperature condition for after warm-up. In addition, the cooling water temperature tw is maintained due to the continuation of the high load operation.
Is higher than the high-temperature-side reference temperature th, the routine proceeds to step 6, where the target values of the intake valve closing timing and the ignition timing corresponding to the load and the engine speed at that time are determined using the high-temperature control map. I do. Then, in the case of such a high temperature state, the process further proceeds to step 7 to execute the knocking avoidance control shown in FIG.

In this knocking avoidance control, first, at step 11, the output signal of knocking sensor 14 is read, and at step 12, it is determined whether or not the frequency of occurrence of knocking above the slice level is below a predetermined value. Here, if it is equal to or less than the predetermined value, the knocking avoidance control routine ends. That is, the intake valve operating angle and the ignition timing are controlled in accordance with the characteristics of the above-described high-temperature control map. On the other hand, if the knocking occurrence frequency is larger than the predetermined value, the ignition timing retard amount necessary for avoiding knocking is determined in step 13 and this retardation is executed in step 14. Further, in step 15, the amount of increase in the operating angle of the intake valve necessary for avoiding knocking is determined, and the hydraulic actuator 46 is operated in step 16 in order to execute the expansion of the operating angle. In step 17, it is determined whether the operating angle has reached the target value determined in step 15,
The operation of the actuator 46 is continued until the target value is reached. Then, when the operating angle reaches the target value, the routine proceeds to step 18, where the ignition timing is returned to the value before correction.

FIG. 8 is a timing chart showing a second embodiment of the knocking avoidance control according to the present invention.
This embodiment is based on the premise that the variable valve mechanism changes with the characteristics shown in FIG. 3 as in the first embodiment.

In this embodiment, in order to avoid knocking, the boost pressure of the turbocharger 9 is increased as shown in FIG. To gradually increase. This compensates for a decrease in the charging efficiency due to an increase in the operating angle of the intake valve 5. If the boost pressure is increased in this manner, the knocking occurrence condition becomes severer accordingly. Therefore, the return of the ignition timing at the time point T2 when the operating angle reaches the predetermined value, as shown in FIG. It is set to the retard side from the level.

FIG. 9 is a timing chart showing a third embodiment of the knocking avoidance control according to the present invention. This embodiment is also based on the premise that the variable valve mechanism changes with characteristics as shown in FIG.

In this embodiment, similarly to the second embodiment, in order to avoid knocking, in response to the expansion of the intake valve operating angle as shown in FIG. The supercharging pressure of the supercharger 9 is gradually increased. Then, at T2 when the operating angle reaches a predetermined value, the ignition timing is advanced and, at the same time, the supercharging pressure is reduced. As a result, knocking due to a high boost pressure can be prevented, and the ignition timing can be advanced to the initial level. It is not always necessary to reduce the supercharging pressure to the original level, and it is possible to reduce the torque reduction by returning the supercharging pressure to a somewhat higher level as shown in the figure while considering the possibility of knocking. Further, since the reduction of the supercharging pressure appears at a certain speed as shown in (b), the advance of the ignition timing is changed at a speed corresponding to this.

Next, FIG. 10 is a timing chart showing a fourth embodiment of the knocking avoidance control according to the present invention. This embodiment is different from the above-described first to third embodiments on the assumption that the variable valve mechanism changes with characteristics as shown in FIG. This is suitable when operating with large valve overlap at partial load,
Knocking is avoided by reducing the operating angle of the intake valve 5 and delaying the opening timing of the intake valve 5.

That is, while the knocking signal shown in (a) is at a relatively small level, the ignition timing is controlled to a so-called trace knock point as shown in (c). In other words, by advancing as far as possible within a range in which knocking does not occur, a state in which extremely weak knocking occurs is maintained. On the other hand, when the frequency of the knocking signal exceeding the slice level becomes equal to or higher than a predetermined value when the internal combustion engine is in a predetermined high temperature and high load region, knocking that combines ignition timing retarding and intake valve operating angle control is performed. As avoidance control, the ignition timing is retarded to a predetermined level. In addition, since this retarding can be performed with good responsiveness, knocking is quickly suppressed. At the same time, as shown in (d), the hydraulic actuator 46 of the variable valve mechanism is controlled so that the intake valve operating angle is reduced. Since the reduction in the operating angle involves a mechanical delay, the actual operating angle gradually changes depending on the operating speed of the hydraulic actuator 46 as shown in FIG. By reducing the operating angle in this way, as is apparent from FIG. 4, the opening timing of the intake valve 5 is delayed, and the valve overlap is reduced as shown in FIG. . Then, when it is detected that the reduction of the operating angle has reached the target value, the ignition timing is advanced to the original level (T2 in the figure). As a result, a rise in the exhaust gas temperature is avoided. After that, the ignition timing resumes the trace knock control, but since the knocking is suppressed by the operation angle control, the ignition timing is gradually advanced to the trace knock level.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing an example of a change in a valve lift characteristic according to an increase and a decrease in an operating angle.

FIG. 2 is a configuration explanatory diagram showing a configuration of an internal combustion engine according to the present invention.

FIG. 3 is a characteristic diagram showing an example of a change in a valve lift characteristic according to an increase and a decrease in an operating angle.

FIG. 4 is a characteristic diagram showing an example of a change in a valve lift characteristic according to an increase and a decrease in an operating angle.

FIG. 5 is a perspective view of a main part showing a configuration of a variable valve mechanism.

FIGS. 6A and 6B are explanatory views showing the operation of the variable valve mechanism, wherein FIG. 6A is an explanatory view showing a concentric state, and FIG. 6B is an explanatory view showing an eccentric state.

FIG. 7 is a timing chart showing a first embodiment of knocking avoidance control according to the present invention.

FIG. 8 is a timing chart showing a second embodiment of knocking avoidance control according to the present invention.

FIG. 9 is a timing chart showing a third embodiment of knocking avoidance control according to the present invention.

FIG. 10 is a timing chart showing a knocking avoidance control according to a fourth embodiment of the present invention.

FIG. 11 is a flowchart corresponding to a first embodiment of knocking avoidance control of the present invention.

FIG. 12 is a flowchart showing details of the main part.

[Explanation of symbols]

 5 ... intake valve 9 ... turbocharger 14 ... knocking sensor

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 43/00 301 F02D 43/00 301Z 45/00 368 45/00 368A F02P 5/152 F02P 5/15 D 5/153

Claims (9)

[Claims] In an internal combustion engine having a variable valve mechanism capable of variably controlling the operating angle of an intake valve, a knocking detecting means for detecting occurrence of knocking of a predetermined level, and an ignition timing being delayed when the knocking is detected. Ignition timing retarding means for turning, engine temperature detecting means for detecting engine temperature conditions, and load detecting means for detecting a load state of the engine. When the change in the closing timing is set to be relatively large, and when the engine temperature and the load are in a predetermined region and knocking of a predetermined level is detected, the ignition valve is retarded together with the ignition timing. A knocking control device for an internal combustion engine, characterized in that the operating angle is increased so that the closing timing of the engine is delayed. 2. The system according to claim 1, further comprising a supercharger in the intake system, and supercharging pressure control means for increasing the supercharging pressure in response to the increase in the operating angle. Knocking control device for internal combustion engine. 3. An internal combustion engine having a variable valve mechanism capable of variably controlling the operating angle of an intake valve, a knocking detecting means for detecting occurrence of knocking of a predetermined level, and an ignition timing being delayed when the knocking is detected. An ignition timing retarding means for correcting the angle, an engine temperature detecting means for detecting a temperature condition of the engine, and a load detecting means for detecting a load state of the engine. Also, the change in the opening timing is set to be relatively large, and when the engine temperature and load are in a predetermined region and knocking of a predetermined level is detected, the ignition timing is retarded and the valve timing is adjusted. A knocking control device for an internal combustion engine, wherein the operating angle is reduced so that the overlap is reduced. 4. The method according to claim 1, wherein the increase or decrease in the operating angle is maintained even after knocking is suppressed, and the expected characteristic is restored on condition that the load on the engine becomes equal to or less than a predetermined value. A knocking control device for an internal combustion engine according to any one of claims 1 to 3. 5. The apparatus according to claim 1, further comprising means for detecting the operating angle, wherein the retard of the ignition timing is released when a change amount of the expansion or reduction of the operation angle reaches a predetermined value. 4. The knocking control device for an internal combustion engine according to claim 1. 6. The method according to claim 5, wherein upon releasing the retard of the ignition timing, the ignition timing is immediately returned to an advance level immediately before the retard and is gradually advanced thereafter. Knocking control device for an internal combustion engine. 7. When returning the retarded ignition timing,
3. The knocking control apparatus for an internal combustion engine according to claim 2, wherein the supercharging pressure control means reduces the supercharging pressure to a predetermined level. 8. When returning the retarded ignition timing,
3. The knocking control device for an internal combustion engine according to claim 2, wherein the ignition timing is returned to an ignition timing that is delayed from the advance level immediately before the retardation in response to an increase in the supercharging pressure. 9. The variable valve mechanism, comprising: a drive shaft that rotates in synchronization with rotation of the engine; and a camshaft disposed coaxially with the drive shaft and having a cam that drives an intake valve on an outer periphery. A flange portion provided at an end of the camshaft and having an engagement groove formed in a radial direction;
The other flange portion, which is provided on the drive shaft side so as to face the one flange portion and has an engagement groove formed in the radial direction, is swingably disposed between the two flange portions. The annular disc thus formed, pins protruding from both sides of the annular disc in opposite directions to engage in respective engagement grooves of the flange portions, and the annular disc is swung according to engine operating conditions. The knocking control device for an internal combustion engine according to any one of claims 1 to 8, further comprising a driving mechanism for moving the intake disk, wherein the operating angle of the intake valve changes according to the position of the annular disk.