JP2001207877A - Valve characteristic control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration in combustion stability caused when a valve lift changes at low vehicle speed time such as an idle state in an internal combustion engine having a variable valve lift mechanism. SOLUTION: When a vehicle speed SP is low, a target shaft position Lt is restricted by processing of Steps S160, S180, S190. Thus, since the valve lift of an intake valve does not largely changes even if a throttle valve opens, even if throttle opening rapidly reduces thereafter, a change is not wholly required in the valve lift, and even if there is a change, it is only a little change. Thus, a large change in the valve lift by the variable valve lift mechanism is not performed to thereby prevent temporary generation of an improper valve lift such as an excessive valve overlap quantity caused by response delay in the intake valve. Thus, when the vehicle speed SP is low, even if the throttle valve is rapidly closed, the combution stability of an engine can be maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve characteristic control device for adjusting a valve lift of an intake valve or an exhaust valve in an internal combustion engine mounted on an automobile or the like.

[0002]

2. Description of the Related Art As a technique for realizing the performance required for an internal combustion engine according to the operating state of an internal combustion engine mounted on an automobile or the like, a technique for controlling valve timing of intake valves and exhaust valves is known. (Japanese Unexamined Patent Publication No. 61-6503
No. 6). In such prior art, in consideration of combustion stability during idling, control is performed by advancing or retarding the valve timing so as to shorten the valve overlap at a low vehicle speed.

In addition to the technique of changing the valve overlap by retarding or advancing the valve timing, the valve characteristics such as the valve timing and the lift amount are adjusted by adjusting the valve lift of the intake valve or the exhaust valve. There are technologies to change.

[0004]

However, it has been found that when the valve lift is adjusted in an operation state at a low vehicle speed such as an idle state, the combustion stability of the internal combustion engine may be reduced.

[0005] For example, in a driving state at a low vehicle speed such as an idling state, when the throttle valve is rapidly closed or the intake air amount sharply decreases, the low vehicle speed at the low vehicle speed accompanying the decrease in the intake air amount. In order to maintain the combustion stability of the valve, the valve overlap is adjusted to a minimum. At this time, the intake air amount is reduced in high response.However, when the valve timing or lift amount of the intake valve or the exhaust valve is changed by adjusting the valve lift, the internal combustion engine depends on the characteristics of the mechanism itself or at idle. Responsiveness is relatively low due to factors such as a low rotational speed of the motor.

[0006] For this reason, even though the intake air amount has already been reduced, an inappropriate valve lift state such as an excessively large valve overlap occurs temporarily. If such a situation occurs in an operation state at a low vehicle speed such as an idling state, misfire or poor combustion may occur due to excessive return of exhaust gas, and combustion stability may be impaired.

Further, in an operation state at a low vehicle speed such as an idling state, the amount of intake air may be increased by turning on an air conditioner or changing a shift position of an automatic transmission. In this case, as the intake air amount increases and the rotational speed of the internal combustion engine further increases, the characteristics associated with valve lift such as valve overlap change from a state suitable for an operation state at a low vehicle speed such as an idle state to an inappropriate state. May be done. As described above, since the valve lift deviates from the valve lift for obtaining a suitable combustion stability for an operation state at a low vehicle speed such as an idling state, a misfire or a poor combustion occurs due to excessive return of the exhaust gas and the combustion stability. May be damaged.

An object of the present invention is to prevent the deterioration of the combustion stability of the internal combustion engine which occurs when the valve lift changes in an operating state at a low vehicle speed such as an idling state. .

[0009]

The means for achieving the above object and the effects thereof will be described below. The valve characteristic control device for an internal combustion engine according to claim 1 includes a variable valve lift mechanism that changes one or both valve lifts of an intake valve and an exhaust valve of an internal combustion engine mounted on an automobile, and the variable valve lift mechanism. A valve characteristic control device for an internal combustion engine, comprising: valve lift control means for adjusting a valve lift in accordance with an operation state of the internal combustion engine, wherein when the vehicle speed is low, the operation state of the internal combustion engine is controlled by the valve lift control means. Valve lift adjustment limiting means for limiting the adjustment of the corresponding valve lift is provided.

[0010] The valve lift adjustment limiting means limits the valve lift adjustment by the valve lift control means in accordance with the operation state of the internal combustion engine when the vehicle speed is low. When the vehicle speed is low, the adjustment of the valve lift is limited, so that the throttle valve opens to increase the amount of intake air,
Even if the number of revolutions is further increased, the valve lift is the same as the initial state or does not significantly change from the initial state.

For this reason, after that, even if the throttle opening rapidly decreases and the valve lift returns to the initial state, the valve lift does not change at all, or even if there is a slight change. is there. Therefore, even if the variable valve lift mechanism has low response, there is no or very little adjustment of the valve lift by the variable valve lift mechanism. In this way, it is possible to prevent an inappropriate valve lift such as an excessive valve overlap amount due to a response delay from temporarily occurring at a low vehicle speed.

Also, at low vehicle speeds, the amount of intake air is increased by turning on the air conditioner or changing the shift position of the automatic transmission. As a result, even if the rotational speed increases, the valve lift changes. There is little change, if any. Therefore, the valve lift state does not change from a state suitable for low vehicle speed to an inappropriate state. For this reason, it is possible to prevent the combustion stability of the internal combustion engine from deteriorating without deviating from the valve lift state for obtaining suitable combustion stability at a low vehicle speed.

According to a second aspect of the present invention, there is provided a variable valve lift mechanism for changing one or both of an intake valve and an exhaust valve of an internal combustion engine mounted on an automobile, and the variable valve. A valve lift control means for adjusting a valve lift according to an operating state of the internal combustion engine by a lift mechanism, wherein the valve lift control means controls the internal combustion engine when the vehicle speed is low. Valve lift adjustment limiting means for limiting the adjustment of the valve lift according to the operating state according to the vehicle speed is provided.

As described above, the valve lift adjustment restricting means includes:
When the vehicle speed is low, the adjustment of the valve lift by the valve lift control means in accordance with the operating state of the internal combustion engine is limited in accordance with the vehicle speed. Therefore, the adjustment of the valve lift can be more reliably restricted. Therefore, even when the throttle valve is opened to increase the intake air amount and further increase the rotation speed, the valve lift is the same as the initial state or does not significantly change from the initial state. After that, even if the throttle opening is rapidly reduced and the valve lift is returned to the initial state, the valve lift is not changed at all, or is slightly changed.

Therefore, even if the variable valve lift mechanism has low response, there is almost no adjustment of the valve lift by the variable valve lift mechanism. Therefore, it is possible to more reliably prevent an inappropriate valve lift from temporarily occurring at a low vehicle speed, such as an excessive valve overlap amount due to a response delay.

Further, the intake air amount is increased by turning on the air conditioner or changing the shift position of the automatic transmission. As a result, even if the rotational speed increases, the valve lift remains unchanged. It is a slight change, if at all. Therefore, it is possible to more reliably prevent the state from changing to an inappropriate valve lift state. Therefore, it is possible to reliably maintain the valve lift state for obtaining a suitable combustion stability at a low vehicle speed, and it is possible to more reliably prevent the deterioration of the combustion stability of the internal combustion engine.

According to a third aspect of the present invention, there is provided a valve characteristic control apparatus for an internal combustion engine according to the second aspect, wherein the valve lift adjustment restriction means restricts a valve lift state according to a vehicle speed. A valve lift restriction range setting means for setting a range, wherein adjustment of a valve lift according to an operation state of the internal combustion engine by the valve lift control means is restricted based on the restriction range set by the valve lift restriction range setting means. By doing so, the valve lift is limited according to the vehicle speed.

The valve lift limit range setting means sets a limit range for limiting the valve lift state according to the vehicle speed.
Then, based on this restriction range, the valve lift adjustment restricting means restricts the adjustment of the valve lift according to the operation state of the internal combustion engine by the valve lift control means.

By providing the limited range of the valve lift according to the vehicle speed in this way, the valve lift can be limited according to the vehicle speed. In this way, it is possible to reliably maintain the valve lift state for obtaining suitable combustion stability at low vehicle speed, and it is possible to more reliably prevent the combustion stability of the internal combustion engine from deteriorating.

According to a fourth aspect of the present invention, there is provided the valve characteristic control device for an internal combustion engine according to any one of the first to third aspects, wherein the valve lift adjustment restricting means is configured to control the vehicle speed to be equal to or less than a reference vehicle speed. The vehicle speed is determined to be low when the vehicle speed becomes low.

As described above, by catching a state in which the vehicle speed is low when the vehicle speed is equal to or lower than the reference vehicle speed, the valve lift adjustment limiting means allows the valve lift control means to adjust the valve lift according to the operating state of the internal combustion engine. Adjustment may be limited. Thus, it is possible to prevent the valve stability from becoming inappropriate at low vehicle speeds and prevent the combustion stability of the internal combustion engine from deteriorating.

According to a fifth aspect of the present invention, there is provided a variable valve lift mechanism for changing one or both of an intake valve and an exhaust valve of an internal combustion engine mounted on a vehicle, and the variable valve. A valve lift control means for adjusting a valve lift according to an operation state of the internal combustion engine by a lift mechanism, wherein the throttle valve of the internal combustion engine has a reference opening degree or less, and When the engine speed and the vehicle speed are low, valve lift adjustment limiting means for limiting the valve lift adjustment by the valve lift control means in accordance with the operating state of the internal combustion engine is provided.

The valve lift adjustment restricting means includes a valve lift control means for controlling the valve lift according to the operating state of the internal combustion engine by the valve lift control means when the throttle valve is not more than the reference opening and the rotation speed and the vehicle speed of the internal combustion engine are low. Limit adjustments. Therefore, when the throttle valve is at or below the reference opening, at a low rotation speed, and at a low vehicle speed, the air intake is increased by turning on the air conditioner or changing the shift position of the automatic transmission, which further increases the rotation speed. As the valve lift increases, the valve lift remains little or no change. Therefore, from a valve lift state suitable for a region where the throttle valve is equal to or less than the reference opening degree and the rotation speed is a low rotation speed and a low vehicle speed range,
It does not change to an inappropriate valve lift state. For this reason, it does not deviate from the valve lift state for obtaining a suitable combustion stability at a low vehicle speed such as an idling state, so that the deterioration of the combustion stability of the internal combustion engine can be prevented.

According to a sixth aspect of the present invention, in the valve characteristic control apparatus for an internal combustion engine according to the fifth aspect of the present invention, the valve lift adjustment restricting means may be arranged so that the rotation speed of the internal combustion engine is equal to or less than a reference rotation speed. When the vehicle speed falls below the reference vehicle speed, it is determined that the rotation speed and the vehicle speed of the internal combustion engine are low.

As described above, the state in which the rotation speed of the internal combustion engine is low when the rotation speed of the internal combustion engine is lower than the reference rotation speed is grasped, and the vehicle speed is low when the vehicle speed is lower than the reference vehicle speed. Thus, the valve lift adjustment limiting means may limit the valve lift adjustment by the valve lift control means according to the operating state of the internal combustion engine. Thus, it is possible to prevent the valve stability from becoming inappropriate at a low vehicle speed such as an idling state and prevent the combustion stability of the internal combustion engine from deteriorating.

According to a seventh aspect of the present invention, in the valve characteristic control apparatus for an internal combustion engine according to the fifth or sixth aspect, the state where the throttle valve is not more than the reference opening degree is a fully closed state. A valve characteristic control device for an internal combustion engine, comprising:

As described above, when the throttle valve of the internal combustion engine is fully closed and the rotation speed and the vehicle speed of the internal combustion engine are low, the valve lift adjustment restricting means changes the operating state of the internal combustion engine by the valve lift control means. Adjustment of the corresponding valve lift may be limited. Thus, it is possible to prevent the valve stability from becoming inappropriate at a low vehicle speed such as an idling state and prevent the combustion stability of the internal combustion engine from deteriorating.

According to an eighth aspect of the present invention, there is provided a valve characteristic control apparatus for an internal combustion engine according to any one of the fifth to seventh aspects, wherein the valve lift adjustment restricting means is controlled by the valve lift control means. The adjustment of the valve lift is restricted by stopping the adjustment of the valve lift according to the operating state of the internal combustion engine.

The restriction on the adjustment of the valve lift according to the operating state of the internal combustion engine by the valve lift control means may be executed by stopping the adjustment of the valve lift. As described above, the adjustment of the valve lift is limited by fixing the valve lift in the form in which the adjustment of the valve lift is stopped. For this reason, the intake air amount is increased by turning on the air conditioner or changing the shift position of the automatic transmission, and the valve lift does not change even if the rotation speed increases. Therefore, there is no change from a suitable valve lift state to an inappropriate valve lift state. Therefore, the vehicle does not deviate from the valve lift state for obtaining a suitable combustion stability at a low vehicle speed such as an idle state.

As described above, the valve lift does not become inappropriate at a low vehicle speed such as an idle state, so that the deterioration of the combustion stability of the internal combustion engine can be prevented. The valve characteristic control device for an internal combustion engine according to claim 9,
9. The valve characteristic control device for an internal combustion engine according to claim 8, wherein the valve lift adjustment limiting unit stops adjusting the valve lift according to the operating state of the internal combustion engine by the valve lift control unit. The valve lift is set in accordance with a state quantity other than the operation state of (1).

As described above, when the adjustment of the valve lift is stopped, the valve lift adjustment limiting means sets the valve lift in accordance with a state quantity other than the operating state of the internal combustion engine used by the valve lift control means for adjusting the valve lift. Set.
From this, the valve lift set when adjustment is stopped is
The valve lift control means is not affected by changes in the operating state of the internal combustion engine used for adjusting the valve lift. Therefore, at the time of low vehicle speed such as an idling state, there is no change from a suitable valve lift state to an inappropriate valve lift state, and deterioration of combustion stability of the internal combustion engine can be prevented.

In particular, since the valve lift is set in accordance with a state quantity other than the operation state of the internal combustion engine, even at a low vehicle speed such as an idling state, a more appropriate valve lift is set in accordance with the situation at that time. The lift can be set, and the combustion stability of the internal combustion engine can be further improved.

According to a tenth aspect of the present invention, in the valve characteristic control device for an internal combustion engine according to any one of the first to ninth aspects, the variable valve lift mechanism continuously adjusts a valve lift. It is characterized in that it is possible.

As described above, by using a structure for continuously adjusting the valve lift as the variable valve lift mechanism, the valve lift can be adjusted with higher accuracy. The valve characteristic control device for an internal combustion engine according to claim 11 is the valve characteristic control device for an internal combustion engine according to claim 10, wherein one or both of the intake valve and the exhaust valve are lifted by cams having different profiles in the rotation axis direction. When driven, the variable valve lift mechanism can continuously adjust the valve lift by adjusting the position in the rotation axis direction with respect to the cam having a different profile in the rotation axis direction. And

As a configuration for continuously adjusting the valve lift, there is a configuration in which the lift is driven by cams having different profiles in the rotation axis direction. As a result, the valve lift can be adjusted with high accuracy. One or both of the intake valve and the exhaust valve have different profiles in the rotation axis direction, and the variable valve lift mechanism adjusts a position in the rotation axis direction with respect to the valve having a different profile in the rotation axis direction. The valve lift can be continuously adjusted.

A valve characteristic control device for an internal combustion engine according to a twelfth aspect is the valve characteristic control device for an internal combustion engine according to any one of the first to eleventh aspects, wherein the valve lift control means sets the operating state of the internal combustion engine as an internal combustion engine. The valve lift is adjusted by a variable valve lift mechanism in accordance with the rotation speed and load of the internal combustion engine, and the valve lift other than at full load in the adjustment is adjusted at full load at the rotation speed of the internal combustion engine. The adjustment amount for shifting to is set to be a value within the followable range.

The adjustment of the valve lift by the valve lift control means is performed when the amount of adjustment for shifting to the valve lift adjusted at the full load at the rotation speed of the corresponding internal combustion engine is a value within the range in which the valve lift can be followed except at the time of full load. It is to be.

The limitation of being within the following range is as follows.
Since it is imposed on the adjustment of the valve lift, even if the internal combustion engine rapidly shifts from the partial load operation state to the full load state, it can immediately shift to the valve lift set for the full load state. . For this reason, the adjustment of the valve lift suitable for the operation state of the internal combustion engine at the time of acceleration can always be performed with high responsiveness.

Therefore, in addition to the functions and effects described in any one of the first to eleventh aspects, the valve lift control can be made highly responsive without increasing the cost for speeding up the variable valve lift mechanism. In addition, a suitable valve lift state can be quickly realized during acceleration.

According to a thirteenth aspect of the present invention, in the valve characteristic control device for an internal combustion engine according to any one of the first to eleventh aspects, the valve lift control means sets the operating state of the internal combustion engine as an internal combustion engine. The valve lift is adjusted by a variable valve lift mechanism in accordance with the rotation speed and the load of the valve lift control, and the valve lift control is performed when the valve lift adjustment limiting means does not limit the valve lift adjustment by the valve lift control means. If the valve lift adjusted by the means is not within the range that can be adjusted to shift to the valve lift adjusted at full load at the rotation speed of the internal combustion engine, the adjustment amount can follow. A valve lift for correcting a valve lift adjusted by the valve lift control means so as to fall within a range. Characterized by comprising a positive means.

Here, in the adjustment of the valve lift by the valve lift control means, the adjustment amount for shifting to the valve lift adjusted at the full load is not set to a value within the followable range. Alternatively, when the valve lift adjustment restricting means does not restrict the valve lift adjustment by the valve lift control means, the valve lift correction means adjusts the valve lift control means so that the adjustment amount is within the operable range. The corrected valve lift is corrected.

This also imposes a restriction on the adjustment of the valve lift within the range that can be followed. Therefore, even when the internal combustion engine rapidly shifts from the partial load operation state to the full load state, it can immediately shift to the valve lift set for the full load state, and is adapted to the operation state of the internal combustion engine. The adjusted valve lift can always be performed with high responsiveness.

Further, the correction of the valve lift by the valve lift correction means is executed when the valve lift adjustment limiting means does not limit the adjustment of the valve lift by the valve lift control means. For this reason, the function and effect described in any of claims 1 to 11 is not inhibited.

According to a fourteenth aspect of the present invention, in the valve characteristic control apparatus for an internal combustion engine according to the twelfth or thirteenth aspect, the followable range is set to be narrower as the rotational speed of the internal combustion engine is higher. It is characterized by having.

The change in the output of the internal combustion engine with respect to the change in the valve lift increases as the rotational speed of the internal combustion engine increases. That is, in acceleration in a state where the rotation speed of the internal combustion engine is low, even if the valve lift is shifted to the valve lift at full load, the increase in the output of the internal combustion engine is relatively small. Conversely, in acceleration in a state where the rotation speed of the internal combustion engine is high, the increase in the output of the internal combustion engine when the valve lift is shifted to the valve lift at full load is relatively large.

For this reason, when the internal combustion engine is rapidly accelerated at a low rotational speed, the output of the internal combustion engine originally rises only slightly.
Even if the time required to reach the valve lift at full load is somewhat longer, the acceleration is hard to deteriorate. However, during rapid acceleration with the internal combustion engine rotating at a high speed, if the time to reach the valve lift at full load is long, the difference between the full load output operation and the actual internal combustion engine output will increase, and the acceleration performance will increase. The deterioration becomes remarkable.

For this reason, in the present invention, the following range is set narrower as the rotational speed of the internal combustion engine increases.
The valve lift at full load can be obtained in a shorter time when the internal combustion engine is rapidly accelerated with a high rotational speed. Therefore, it is possible to more reliably prevent an output shortage from occurring during acceleration in a state where the rotation speed of the internal combustion engine is high.

According to a fifteenth aspect of the present invention, in the valve characteristic control apparatus for an internal combustion engine according to any one of the twelfth to fourteenth aspects, the followable range is:
The temperature is set narrower as the temperature of the internal combustion engine is lower.

When the temperature of the internal combustion engine is low, the viscosity of the lubricating oil is high and the sliding resistance of each part is large, so that the operating speed of the variable valve lift mechanism is lower than at the time of high temperature. If the variable valve lift mechanism is hydraulically driven, the flow resistance of the working oil increases, and the operating speed tends to further decrease. Therefore, when the temperature of the internal combustion engine is low, the time required for shifting to the valve lift at full load increases.

For this reason, in the present invention, the following range is set narrower as the temperature of the internal combustion engine is lower, so that even if the operating speed of the variable valve lift mechanism decreases in a state where the temperature of the internal combustion engine is low, An increase in the time required to shift to the valve lift at full load is prevented. Therefore, it is possible to more reliably control an appropriate valve lift state at all times.

The valve characteristic control device for an internal combustion engine according to claim 16 is the valve characteristic control device for an internal combustion engine according to claim 10 or 11, wherein the amount of lift is reduced while the fuel cut processing is being executed in the internal combustion engine. Is provided with a valve lift adjusting means at the time of fuel cut to make the valve lift minimum or close to the minimum.

As described above, at the time of fuel cut, the valve lift is adjusted to a minimum or a valve lift close to the minimum by the fuel cut valve lift adjusting means. Therefore,
The resistance to intake or exhaust is increased, so that the action of the engine brake can be improved. In addition, the amount of air sent to the catalyst during the exhaust stroke decreases, and the deterioration of the catalyst can be reduced.

[0053]

[First Embodiment] FIG. 1 is a schematic structural explanatory view of an engine 11 incorporating a valve characteristic control device to which the above-described invention is applied. FIG. 1 also shows a block diagram of an electronic control unit (hereinafter, referred to as “ECU”) 80 as a control system.

The engine 11 is an in-line four-cylinder gasoline engine, and is mounted on an automobile to drive the automobile with its output. The engine 11 includes a cylinder block 13 provided with a reciprocating piston 12.
And an oil pan 13 a provided below the cylinder block 13, and a cylinder head 14 provided above the cylinder block 13.

A crankshaft 15 as an output shaft is rotatably supported below the engine 11, and a piston 12 is connected to the crankshaft 15 via a connecting rod 16. The reciprocating motion of the piston 12 is converted by the connecting rod 16 into a rotational motion of the crankshaft 15.

The combustion chamber 17 is located above the piston 12.
The combustion chamber 17 is connected to an intake port 18 and an exhaust port 19. The intake port 18 and the combustion chamber 17 are communicated and shut off by an intake valve 20, and the exhaust port 19 and the combustion chamber 17 are communicated and shut off by an exhaust valve 21.

In the cylinder head 14, an intake camshaft 22 and an exhaust camshaft 23 are arranged in parallel. The intake-side camshaft 22 is supported on the cylinder head 14 so as to be rotatable and movable in the axial direction, and the exhaust-side camshaft 23 is supported on the cylinder head 14 so as to be rotatable but not movable in the axial direction. ing.

At one end of the intake camshaft 22, a variable valve lift mechanism 24 having a timing sprocket 24a is provided. A timing sprocket 25 is attached to one end of the exhaust side camshaft 23. The timing sprocket 25 and the timing sprocket 2 of the variable valve lift mechanism 24
4a is connected via a timing chain 26 to a sprocket 15a attached to the crankshaft 15. The rotation of the crankshaft 15 as the output shaft is transmitted via the sprocket 15a and the timing chain 26 to the timing sprockets 24a and 24a.
5 is transmitted. As a result, the intake camshaft 22 and the exhaust camshaft 23 rotate in synchronization with the rotation of the crankshaft 15.

The variable valve lift mechanism 24 acts on the intake side camshaft 22 by making a configuration as described later, and is controlled by the ECU 80 as necessary to control the position of the intake side camshaft 22 in the rotation axis direction. Has been adjusted.

The intake cam shaft 22 is provided with an intake cam 27 which comes into contact with a valve lifter 20 a provided at the upper end of the intake valve 20. The exhaust camshaft 23 is provided with an exhaust cam 28 which comes into contact with a valve lifter 21a provided at the upper end of the exhaust valve 21. When the intake camshaft 22 rotates in synchronization with the crankshaft 15, the intake valve 20 is opened and closed according to the cam profile of the intake cam 27, and when the exhaust camshaft 23 rotates, the cam profile of the exhaust cam 28 rotates. The exhaust valve 21 is driven to open and close according to.

Here, the cam profile of the exhaust cam 28 is a flat cam that is constant with respect to the rotation axis direction of the exhaust cam shaft 23. However, the cam profile on the cam surface 27a of the intake cam 27 shown in FIG. 2 continuously changes in the rotation axis direction (the direction of the arrow S) of the intake camshaft 22. That is, the intake cam 27 is configured as a three-dimensional cam. Details of the profile of the intake cam 27 will be described later. The arrow C in FIG.
2 shows the rotation direction.

The variable valve lift mechanism 24, the intake camshaft 22, the intake cam 27, and the ECU 80 adjust the valve lift of the intake valve 20 according to the operating state of the engine 11. The variable valve lift mechanism 24 will be described in detail with reference to FIG.

In the variable valve lift mechanism 24, the timing sprocket 24 a includes a cylindrical portion 51 through which the intake camshaft 22 penetrates, a disk portion 52 protruding from the outer peripheral surface of the cylindrical portion 51, and an outer periphery of the disk portion 52. And a plurality of external teeth 53 provided on the surface. The cylindrical portion 51 of the timing sprocket 24a is connected to the journal bearing 14a of the cylinder head 14 and the camshaft bearing cap 1
4b rotatably supported. Then, the intake side camshaft 22 is moved so that it can move in the axial direction.
1 through.

Further, a cover 54 provided so as to cover the end of the intake side camshaft 22 is fixed to the timing sprocket 24 a with bolts 55. At a position corresponding to the end of the intake-side camshaft 22 on the inner peripheral surface of the cover 54, a plurality of internal teeth 57 spirally extending in the rotation axis direction of the intake-side camshaft 22 are arranged along the circumferential direction. Is provided.

On the other hand, a cylindrical ring gear 62 is fixed to the tip of the intake side camshaft 22 by a hollow bolt 58 and a pin 59. Ring gear 6
A spiral tooth 63 that meshes with the internal teeth 57 of the cover 54 is provided on the outer peripheral surface of the cover 2. Thus, the ring gear 6
Numeral 2 is integrated with the intake-side camshaft 22 in the rotation axis direction of the intake-side camshaft 22 and is movable while rotating the phase relative to the cover 54.

In the variable valve lift mechanism 24 configured as described above, the crankshaft 15 is rotated by the driving of the engine 11, and the rotation is controlled by the timing chain 2.
6, the intake camshaft 22 is rotated via the variable valve lift mechanism 24. With the rotation of the intake camshaft 22, the intake cam 27 drives the intake valve 20 to open and close.

When the ring gear 62 moves toward the timing sprocket 24a (in the direction indicated by the arrow R) while rotating the phase relative to the cover 54 by a mechanism described later, the intake camshaft 22 is also integrated. Then, it moves in the direction R while rotating the phase relative to the cover 54.

As a result, the contact position of the cam follower 20b provided on the valve lifter 20a can be shifted from the surface on the direction R side to the surface on the direction F side of the cam surface 27a of the intake cam 27 while changing the phase. Can be. Further, when the ring gear 62 moves toward the cover 54 (arrow direction F) while relatively changing the phase, the intake side camshaft 22 also moves in the direction F while relatively changing the phase as a unit. Thus, the contact position of the cam follower 20b can be moved from the surface on the direction F side to the surface on the direction R side while changing the phase on the cam surface 27a of the intake cam 27.

Next, the structure of the variable valve lift mechanism 24 for hydraulically controlling the movement of the ring gear 62 will be described. Since the outer peripheral surface of the disc-shaped ring portion 62a of the ring gear 62 is slidably adhered to the inner peripheral surface of the cover 54, the inside of the cover 54
It is partitioned into a lift pattern side hydraulic chamber 65 and a first lift pattern side hydraulic chamber 66. The second lift pattern control oil passage 67 and the first lift pattern control oil are connected to the second lift pattern side hydraulic chamber 65 and the first lift pattern side hydraulic chamber 66, respectively, inside the intake side camshaft 22. Road 68 passes.

The second lift pattern control oil passage 67 communicates with the second lift pattern side hydraulic chamber 65 through the interior of the hollow bolt 58 and the oil control through the camshaft bearing cap 14 b and the cylinder head 14. Connected to valve 70. The first lift pattern control oil passage 68 communicates with the first lift pattern side hydraulic chamber 66 through an oil passage 72 in the cylindrical portion 51 of the timing sprocket 24a, and the camshaft bearing cap 14b and the cylinder head 14
And connected to the oil control valve 70.

On the other hand, a supply passage 74 and a discharge passage 76 are connected to the oil control valve 70. The supply passage 74 is connected to the oil pan 13a via the oil pump 13b, and the discharge passage 76 is directly connected to the oil pan 13a.

The oil control valve 70 includes an electromagnetic solenoid 70a. When the electromagnetic solenoid 70a is in a demagnetized state, the oil control valve 70 communicates with an internal port.
Hydraulic oil in the oil pan 13a is supplied to the first lift pattern side hydraulic chamber 66 of the variable valve lift mechanism 24 via the supply passage 74, the oil control valve 70, and the first lift pattern control oil passage 68 as shown by the arrows in the figure. Is done. Further, the oil in the second lift pattern side hydraulic chamber 65 of the variable valve lift mechanism 24 is supplied to the oil pan 13 through the second lift pattern control oil passage 67, the oil control valve 70, and the discharge passage 76 as shown by arrows in the figure.
Returned to a. As a result, inside the cover 54, the ring gear 62 is moved toward the second lift pattern side hydraulic chamber 65 while changing the phase relative to the cover 54, and moves the intake camshaft 22 in the direction F while changing the phase. Let it. As a result, the contact position of the cam follower 20b with respect to the cam surface 27a is changed to the end face in the direction R of the intake cam 27 as shown in FIG.
27c).

On the other hand, when the electromagnetic solenoid 70a is excited, the hydraulic oil in the oil pan 13a is supplied to the supply passage 74, the oil control valve 70, The oil is supplied to the second lift pattern side hydraulic chamber 65 of the variable valve lift mechanism 24 via the second lift pattern control oil passage 67. Also, the variable valve lift mechanism 24
The hydraulic oil in the first lift pattern side hydraulic chamber 66 of the first lift pattern control oil passage 6 is opposite to the illustrated arrow.
8. Oil control valve 70 and discharge passage 76
Through the oil pan 13a. As a result, the ring gear 62 is moved toward the first lift pattern side hydraulic chamber 66 while changing the phase relative to the cover 54, and moves the intake side camshaft 22 in the direction R while changing the phase. As a result, the contact position of the cam follower 20b with respect to the cam surface 27a changes in the direction F of the intake cam 27.
(Hereinafter, referred to as a “second end surface”) 27d.

Further, when the power supply to the electromagnetic solenoid 70a is controlled and the movement of the hydraulic oil between the ports inside the oil control valve 70 is prohibited, the hydraulic chamber 65 on the second lift pattern side and the hydraulic chamber 66 on the first lift pattern side are controlled. On the other hand, supply and discharge of hydraulic oil are not performed. Therefore, the hydraulic oil is filled and held in the second lift pattern side hydraulic chamber 65 and the first lift pattern side hydraulic chamber 66, and the ring gear 62 is fixed. As a result, the contact position of the cam follower 20b in the axial direction with respect to the cam surface 27a is maintained, so that the valve lift of the intake valve 20 is maintained at the state when the ring gear 62 is fixed.

The ECU 80 controlling the oil control valve 70 described above, as shown in FIG.
It is configured as a logical operation circuit including a CPU 82, a ROM 83, a RAM 84, a backup RAM 85, and the like.

Here, the CPU 82 executes necessary arithmetic processing based on various control programs stored in the ROM 83. The ROM 83 is a memory that stores various control programs and maps that are referred to when the various control programs are executed. The RAM 84 is a CPU 8
2 is a memory for temporarily storing the result of the calculation in step 2, data input from each sensor, and the like. Backup RAM 85
Is a nonvolatile memory for storing data to be stored when the engine 11 is stopped. And the CPU 82 and the ROM
The RAM 83, the RAM 84, and the backup RAM 85 are connected to each other via a bus 86, and are also connected to an external input circuit 87 and an external output circuit 88.

The external input circuit 87 includes a crank-side electromagnetic pickup 90 for detecting the engine speed, an intake-cam-side electromagnetic sensor for detecting the cam angle of the intake cam 27 and the amount of movement of the intake camshaft 22 in the rotation axis direction. Pickup 92, starter switch 9 for turning on / off starter
3. a water temperature sensor 94 for detecting the temperature of the cooling water of the engine 11, an air conditioner switch 95 for detecting a driving state of the air conditioner, and a vehicle speed sensor 9 for detecting a traveling speed of the vehicle.
6. Throttle opening sensor 97 for detecting the opening degree and fully closed state of the throttle valve, air flow meter 98 for detecting the intake air amount GA, shift position sensor 99 for detecting the shift position of the automatic transmission,
An electric load switch 100 for detecting a driving state of a device that generates various other electric loads and the like and another ECU are connected to receive signals from these.

The external output circuit 88 is provided with an intake side camshaft 2 by hydraulic control of the variable valve lift mechanism 24.
2 is connected to an oil control valve 70 for adjusting the position in the axial direction.

In the first embodiment, the EC
Through U80, valve characteristic control is performed by adjusting the valve lift of the intake valve 20. That is, the ECU
80 detects the operating state of the engine 11 based on detection signals from various sensors. Then, the oil control valve 70 is drive-controlled in order to bring the valve lift of the intake valve 20 of the engine 11 into an appropriate state according to the detection result. In this valve lift adjustment, feedback control is performed so that a target valve lift state of the intake valve 20 is realized. That is, the position of the intake camshaft 22 is detected by the intake cam-side electromagnetic pickup 92, and the variable valve lift mechanism 24 is driven by the oil control valve 70 so that the target shaft position is realized. Adjust the rotation axis position.

Further, other ECs communicating with the ECU 80
In U, various controls such as fuel injection amount control, fuel injection timing control, and ignition timing control are performed on the engine 11. Then, necessary information is transmitted to the ECU 80.

Here, the cam profile of the intake cam 27 shown in FIG. 2 will be described. As described above, the intake cam 27 is configured as a three-dimensional cam in which the profile of the cam surface 27a changes in the rotation axis direction.
Here, the height of the cam nose 27b on the front end face 27d on the direction F side in the arrow S direction is the rear end face 2 on the direction R side.
The height is higher than the height of the cam nose 27b on the 7c side. Then, as the position shifts from the rear end face 27c to the front end face 27d, the working angle with respect to the intake valve 20 also increases, as shown in FIG. 4, at the rear end face 27c (shown by a solid line).
The working angle dθmin gradually increases from the minimum working angle dθmin on the side to the maximum working angle dθmax on the side of the front end face 27d (indicated by a dashed line).

FIG. 5 shows a graph of the valve lift with respect to the rotation angle of the intake cam 27. As illustrated, the lift pattern of the intake cam 27 includes a second lift (hereinafter, referred to as a sub-lift) in addition to a normal lift (hereinafter, referred to as a main lift). However, the sub-lift is sufficiently present on the front end face 27d side, but not on the rear end face 27c side. Therefore, as shown in FIG. 4, the operating angle of the intake cam 27 in the rotation axis direction increases and decreases particularly on the valve opening side than on the valve closing side.

Then, the front end face 27d and the rear end face 27c
The cam profile changes continuously between and.
As described above, the intake cam 27 has a lift characteristic in which the main lift and the sub-lift are combined, and is configured as a composite lift three-dimensional cam in which the main lift and the sub-lift continuously change in the rotation axis direction. . This change in valve lift is as shown in FIG.

Accordingly, when the intake side camshaft 22 is moved in the direction R by the variable valve lift mechanism 24, the contact position of the intake valve 20 with respect to the valve lifter 20a is moved toward the front end face 27d to increase the working angle of the intake valve 20. (Lmax in FIG. 5). Conversely, when the intake side camshaft 22 is moved in the direction F, the contact position of the intake valve 20 with the valve lifter 20a is moved toward the rear end face 27c, and the working angle of the intake valve 20 can be reduced (FIG. 5).
Lmin). In addition, as the contact position approaches the front end surface 27d, the opening timing of the intake valve 20 is rapidly advanced by the action of the sublift.

As described above, since the internal teeth 57 of the cover 54 and the teeth 63 of the ring gear 62 that are engaged with each other are spiral, the variable valve lift mechanism 24 can move the intake-side camshaft 22 in the direction R. In conjunction with this, the rotational phase of the intake side camshaft 22 is changed to the crankshaft 1
5 is advanced. Embodiment 1
As shown in FIG. 6, the intake cam 2 is different between when the rear end face 27c is in contact with the valve lifter 20a and when the front end face 27d is in contact with the valve lifter 20a.
7, a phase difference of θx (° CA: crank angle) occurs. In FIG. 6, the moving amount of the intake side camshaft 22 in the direction R is 0 mm (rear end face 27 c side) to the front end face 27.
The four states up to the d side are shown. In practice, the variable valve lift mechanism 24 indicates that the area between these four states is:
The valve lift is adjusted continuously, that is, continuously. A broken line Ex indicates a valve lift of the exhaust valve 21.

Here, the valve lift is a general term for the opening / closing timing, lift amount, and operating angle of the intake valve 20. Therefore, the variable valve lift mechanism 2
No. 4 can continuously adjust the opening / closing timing of the intake valve 20, the lift amount, and the operating angle.

Next, the valve lift control processing executed by the ECU 80 will be described. The contents of this processing are shown in the flowchart of FIG. This processing is repeatedly executed at a predetermined control cycle (every time or every crank angle rotation).

Although not shown in the flow chart, the ECU 80 controls the intake cam side electromagnetic pickup 92
By detecting the actual shaft position at, the movable position feedback control of the intake camshaft 22 by the variable valve lift mechanism 24 is performed. In this movement position feedback control, the variable valve lift mechanism 24 is driven by PID control or the like so that the actual shaft position matches the target shaft position Lt obtained in the valve lift control process, and the rotation of the intake side camshaft 22 is rotated. It adjusts the axial position.

When the valve lift control process (FIG. 7) is started, it is first determined whether or not the starter signal ST is "OFF", that is, whether or not the engine 11 is being started (S110). Here, the starter signal ST is "ON"
If the engine is being started ("NO" in S110), the starting shaft position Lbase is set to the target shaft position Lt (S120). This starting shaft position Lbas
e is a fixed value (for example, Lba) for obtaining a valve lift that realizes necessary valve overlap or the like during startup.
(se = 0 mm) is set in advance.

If the starter signal ST is "OFF", it is determined that the start of the engine 11 has been completed (S110).
Is "YES"), a map Lx corresponding to the current operation mode is selected from the plurality of maps L shown in FIG. 8 (S13).
0). The plurality of maps L include a map of the target shaft position Lt using the engine load (here, the intake air amount GA) and the engine speed NE as parameters, and include an idle operation before warm-up, an idle operation after warm-up, and a stoichiometric operation. A map is provided for each operation mode such as a combustion operation and a lean combustion operation.

The distribution of the value of the target shaft position Lt in each of the maps shown in FIG. 8 is classified into regions as shown in FIG. That is, (1) in the idle range, the valve overlap is minimized, the exhaust gas is prevented from returning, the combustion is stabilized, and the engine rotation is stabilized. (2) In the light load region, the valve overlap is minimized to suppress the blowback of exhaust gas, stabilize combustion, and stabilize engine rotation. (3) In the medium load region, the valve overlap is slightly increased, the internal EGR rate is increased, and the pumping loss is reduced. (4) In the high-load low-medium-speed rotation region,
Maximize valve overlap to increase volumetric efficiency and increase torque. (5) In a high-load, high-speed rotation region, the volume efficiency is improved by setting the valve overlap to medium to large.

Next, using the map Lx selected in step S130, the target shaft position Lt is determined based on the engine speed NE detected by the crank side electromagnetic pickup 90 and the intake air amount GA detected by the air flow meter 98. Is calculated (S140).

Step S120 or S140
When the target shaft position Lt is obtained at the step S, the cooling water temperature THW of the engine 11 detected by the water temperature sensor 94 is obtained.
Then, the water temperature correction amount Lw is calculated based on the one-dimensional map Fw (S150). An example of this one-dimensional map Fw is shown in FIG.
0 is shown in the graph. As shown in the drawing, the water temperature correction amount Lw is set to increase as the temperature decreases.

Next, the limited shaft position Lsp is calculated based on the one-dimensional map Fsp from the vehicle speed SP detected by the vehicle speed sensor 96 (S160). This one-dimensional map F
An example of sp is shown in the graph of FIG. As shown in the figure, in a region lower than the reference vehicle speed SPc, the vehicle speed SP
Is set such that the limit shaft position Lsp becomes smaller as the value becomes lower. Further, in a region where the speed is higher than the reference vehicle speed SPc, the limit shaft position Lsp is fixed to the maximum shaft position regardless of the value of the vehicle speed SP.
That is, it is shown that the shaft position is not substantially restricted in a region where the speed is higher than the reference vehicle speed SPc.

Next, as shown in the following equation 1, the target shaft position Lt is corrected by the water temperature correction amount Lw (S170).

[0096]

Lt ← Lt−Lw (Equation 1) With this correction calculation, the target shaft position Lt is corrected to a smaller value as the cooling water temperature THW of the engine 11 is lower.

Next, it is determined whether the target shaft position Lt calculated in step S170 is larger than the limit shaft position Lsp calculated in step S160 (S180). If Lt ≦ Lsp (“NO” in S180), since the target shaft position Lt is within the limit shaft position Lsp, the process is temporarily terminated as it is. On the other hand, if Lt> Lsp (“YE
S "), the target shaft position Lt is the limit shaft position Ls
Since the value exceeds p, the target shaft position Lt is set to the target shaft position Lt to limit the target shaft position Lt (S190), and the process is once ended.

Thus, steps S180 and S190
By the processing described in the above, the processing for limiting the target shaft position Lt to within the limited shaft position Lsp is performed. In the first embodiment described above, steps S110 to S150, S1
70 corresponds to the processing as the valve lift control means.
Steps S160, S180, and S190 correspond to processing as valve lift adjustment limiting means, and among them, step S160 corresponds to processing as valve lift restriction range setting means.

According to the first embodiment described above, the following effects can be obtained. (I). In the valve lift control process by the ECU 80, if the vehicle speed SP is low by the processes of steps S160, S180, and S190, steps S110 to S1 are performed.
50, the target shaft position Lt calculated by the processing of S170 is limited. This allows the intake valve 20
The adjustment of the valve lift with respect to is restricted.

As described above, when the vehicle speed SP is low, the adjustment of the valve lift of the intake valve 20 is limited. Therefore, when the vehicle speed SP is low, the throttle valve is rapidly closed by the driver's operation of the accelerator pedal or the like. Even so, the combustion stability of the engine 11 can be maintained. That is, first, when the throttle valve is opened, the intake air amount G
Even if A is increased and the engine speed NE is further increased, the valve lift of the intake valve 20 is the same as the initial state or does not significantly change from the initial state. For this reason, even if the throttle opening rapidly decreases thereafter and the valve lift of the intake valve 20 returns to the initial state, the valve lift of the intake valve 20 changes little if not at all. It is.

Therefore, even if the variable valve lift mechanism 24 has a low response, the variable valve lift mechanism 24 does not significantly change the valve lift of the intake valve 20. For this reason, it is possible to prevent an inappropriate valve lift such as an excessive valve overlap amount due to a response delay from occurring at the intake valve 20 temporarily at a low vehicle speed such as an idle state.

Further, at low vehicle speeds such as an idle state, the air conditioner (not shown) may be turned on or the shift position of the automatic transmission (not shown) may change. At this time, the intake air amount GA is increased, which further increases the engine speed NE. In such a case, even if the valve lift of the intake valve 20 is not changed or is slight, it is slight. It is a change.
Therefore, there is no change from a valve lift state suitable for low vehicle speed to an inappropriate valve lift state. In this way, it is possible to prevent the combustion stability of the engine 11 from deteriorating without deviating from the valve lift state for obtaining suitable combustion stability at a low vehicle speed such as an idling state. For this reason, problems such as undershoot of the engine 11, engine stall, and deterioration of emission due to unstable combustion can be prevented.

(B). In the process of step S160, the restricted shaft position Ls for restricting the valve lift state according to the vehicle speed SP is determined based on the one-dimensional map shown in FIG.
p (corresponding to the limit range) is set. Then, based on the limited shaft position Lsp, a step S18 is performed.
At 0, S190, the adjustment of the target shaft position Lt set according to the operating state of the engine 11 is restricted by the normal valve lift control.

Since the valve lift is limited in accordance with the vehicle speed SP, the intake valve 20 is set to a more appropriate state.
Can be limited. In this way, it is possible to reliably maintain the valve lift state of the intake valve 20 to obtain a suitable combustion stability at a low vehicle speed such as an idling state, and to more reliably reduce the combustion stability of the engine 11. Can be prevented.

[Embodiment 2] In Embodiment 2, E
In the CU 80, as a valve lift control process, FIG.
Is different from the first embodiment in that the control shown in the flowchart of FIG. The other configuration is basically the same as that of the first embodiment.

When the valve lift control process (FIG. 12) is executed, it is first determined whether or not the starter signal ST is "OFF", that is, whether or not the engine 11 is being started (S210). Here, the starter signal ST becomes “O
N "and the engine 11 is being started (S210
Then, the starting shaft position Lbase is set to the target shaft position Lt (S220). As described in the first embodiment, a fixed value (for example, Lbase = 0 mm) for obtaining the valve overlap required during the start is set in the shaft position Lbase during the start, as described in the first embodiment.

If the starter signal ST is "OFF", it is determined that the start of the engine 11 has been completed (S210).
Then, it is determined whether or not the throttle valve is fully closed based on the detection of the throttle opening sensor 97 (S230). If the throttle valve is fully closed ("YES" in S230), then the vehicle speed sensor 9
It is determined whether the vehicle speed SP detected at 6 is equal to or lower than the reference vehicle speed SPx indicating a low vehicle speed (S240). The reference vehicle speed SPx is set to, for example, “10 km / h”.

If SP ≦ SPx (“YE” in S240)
S "), it is then determined whether or not the engine speed NE detected by the crank side electromagnetic pickup 90 is equal to or lower than a reference speed NEx indicating low rotation (S250).
The reference rotation speed NEx is set to, for example, “2000 rpm”.

If NE ≦ NEx (“YE” in S250)
S "), the idle shaft position Lid is set as the target shaft position Lt (S260). The idling shaft position Lid is determined by the position of the intake camshaft 22 that realizes a valve lift such as a valve overlap necessary for maintaining a suitable combustion stability in the idle region shown in FIG. 9 of the first embodiment. Represents the axial position.
For example, Lid = 0 mm is set.

On the other hand, the throttle valve is not fully closed (S
230, “NO”, vehicle speed SP> reference vehicle speed SPx (S2
If “NO” at 40, or if the engine speed NE> the reference speed NEx (“NO” at S250),
A map Lx corresponding to the current operation mode is selected from the plurality of maps L shown in FIG. 8 of the first embodiment (S
265).

Next, the target shaft position Lt is calculated from the engine speed NE detected by the crank side electromagnetic pickup 90 and the intake air amount GA detected by the air flow meter 98 using the map Lx selected in step S265. (S270).

When the target shaft position Lt is obtained in step S220, S260 or S270, the engine 1 detected by the water temperature sensor 94
Based on the one-dimensional map Fw, a water temperature correction amount Lw is calculated from the cooling water temperature THW (S280). An example of the one-dimensional map Fw is as shown in FIG. 10 of the first embodiment.

Next, as shown in equation 1 of the first embodiment, the target shaft position Lt is corrected by the water temperature correction amount Lw (S290). Thus, the process is once ended. As described above, the target shaft position L is determined by the valve lift control process.
By calculating t, E is set so that the shaft position of the intake-side camshaft 22 becomes the target shaft position Lt.
Feedback control is performed by the CU 80 via the variable valve lift mechanism 24.

In the second embodiment, as described above, the throttle valve is fully closed, the vehicle speed SP is equal to or lower than the reference vehicle speed SPx, and the engine speed NE is equal to the reference engine speed NEx.
In the following cases, the calculation of the target shaft position Lt based on the engine speed NE and the intake air amount GA is stopped. And the valve lift is the shaft position Li at idle.
The state is fixed to the state corresponding to d.

In the second embodiment, steps S210, S220, S265, S270 to S290 correspond to the processing as the valve lift control means. Also,
Steps S230 to S260 correspond to the processing as the valve lift adjustment restricting means.

According to the second embodiment described above, the following effects can be obtained. (I). The ECU 80 determines in steps S230 to S260 that the throttle valve is fully closed and the engine speed NE and the vehicle speed SP are equal to the reference values SPx and NEx.
If it is lower than step S220 or step S2
65, valve lift control in S270 is stopped.
Instead, the idling shaft position Lid as a fixed value is set to the target shaft position Lt for the shaft position control of the intake camshaft 22, thereby fixing the valve lift state appropriate at a low vehicle speed such as an idling state. ing. This completely restricts the adjustment of the valve lift.

Therefore, when the throttle valve is fully closed and the engine speed is low and the vehicle speed is low, the intake air amount GA is increased by turning on the air conditioner or changing the shift position of the automatic transmission. Further, even when the engine speed NE increases, the valve lift of the intake valve 20 does not change. Therefore, there is no change from a valve lift state suitable for a low vehicle speed such as an idle state to an inappropriate valve lift state for a low vehicle speed such as an idle state. Therefore, the deterioration of the combustion stability of the engine 11 can be prevented, and the deterioration of the fuel consumption and the emission at the time of a low vehicle speed such as an idle state can be prevented.

[Embodiment 3] In the present embodiment 3, E
In the CU 80, the valve lift control process shown in FIG.
The second embodiment is different from the second embodiment in that the control shown in the flowchart of FIG. The other configuration is basically the same as that of the second embodiment.

The processes in steps S310 to S390 of the valve lift control process (FIG. 13) are the same as steps S260 and S360 in FIG. 12 of the second embodiment than in steps S210 to S290. All are the same except for the differences.

Here, in step S360, the throttle valve is fully closed and the vehicle speed SP is equal to or lower than the reference vehicle speed SPx,
Further, when the engine speed NE is equal to or lower than the reference speed NEx, the target shaft position Lt is set.
However, unlike step S260 of the second embodiment,
The target shaft position Lt is set to a fixed value provided corresponding to a state quantity other than the throttle opening, the vehicle speed SP, and the engine speed NE.

The process of setting the target shaft position Lt in step S360 is shown in the flowchart of FIG. When the process of step S360 is started, first, it is determined whether or not the range of the automatic transmission detected by the shift position sensor 99 is the D range (S36).
1). If it is in the D range ("YES" in S361), the idling first shaft position Li is shifted to the target shaft position Lt.
d1 is set (S362). The idling first shaft position Lid1 is necessary for maintaining the combustion stability suitable for the load at this time when the automatic transmission is in the D range in the idle region shown in FIG. 9 of the first embodiment. 3 shows the axial position of the intake-side camshaft 22 that realizes a valve lift such as a simple valve overlap.

On the other hand, if it is not the D range ("NO" in S361), it is next determined whether or not the air conditioner state detected by air conditioner switch 95 is on (S36).
3). If the air conditioner is on ("YE" in S363)
S "), the idle second shaft position Lid2 is set as the target shaft position Lt (S364). When the air conditioner is on in the idle region shown in FIG. 9 of the first embodiment, the second shaft position Lid at the time of idling is a valve required to maintain combustion stability suitable for the load at this time. It shows the axial position of the intake side camshaft 22 that realizes a valve lift such as overlap.

If the air conditioner is not on (S36)
If "3" is "NO"), it is determined whether or not an electric load detected by various electric load on / off switches, for example, a headlamp is on (S365). If the electric load is on ("YES" in S365), step S364
As in the case where the air conditioner is on, the idling second shaft position Lid2 is set to the target shaft position Lt. This is because when the air conditioner is on and when the electric load is on, the valve lifts such as valve overlap necessary for maintaining suitable combustion stability are almost the same.

On the other hand, when the electric load is off (S3
If “NO” at step 65, the idling third shaft position Lid is set to the target shaft position Lt (S36).
6). The idling third shaft position Lid is determined by a valve such as a valve overlap necessary for maintaining a suitable combustion stability when various loads are not present in the idle region shown in FIG. 9 of the first embodiment. It shows the axial position of the intake side camshaft 22 that realizes the lift. For example, the same value as the idling shaft position Lid used in step 260 of the second embodiment is set.

When the target shaft position Lt is obtained in step S362, S364, or S366, the process is temporarily exited, and step S380 in FIG.
Move to

Thus, when the throttle valve is fully closed,
When the vehicle speed SP is equal to or less than the reference vehicle speed SPx and the engine speed NE is equal to or less than the reference speed NEx, the setting of the target shaft position Lt based on the engine speed NE and the intake air amount GA is stopped. The target shaft position Lt has a fixed value, i.e., the idling shaft position Lid.
Either 1, Lid2, or Lid3 is set according to the state of the load, and the valve lift is fixed in a state corresponding to this position.

In the third embodiment described above, steps S310, S320, S365, S370 to S390 correspond to the processing as the valve lift control means. Also,
Steps S330 to S360 correspond to the processing as the valve lift adjustment restricting means.

According to the third embodiment described above, the following effects can be obtained. (I). The ECU 80 produces the effects described in (a) of the second embodiment by the processing of steps S330 to S360.

(B). In setting a fixed value for the target shaft position Lt in step S360, the map L
The shift state of the automatic transmission, the on / off state of the air conditioner, or the state of the electric load as a state quantity other than the engine speed NE and the intake air amount GA which are parameters of x are obtained. Then, a fixed value is selected according to these load conditions, and a suitable target shaft position Lt is set.

Therefore, even at a low vehicle speed such as an idle state, a more appropriate valve lift can be set in accordance with the situation at that time, and the combustion stability of the engine 11 can be further improved.

[Embodiment 4] In Embodiment 4, the EC
The difference from the first embodiment is that the control shown in the flowcharts of FIGS. 15 and 16 is periodically executed as the valve lift control processing in U80. The other configuration is basically the same as that of the first embodiment.

Steps S410 to S490 of the valve lift control process (FIG. 15) are the same as steps S110 to S190 of the first embodiment shown in FIG. However, the difference from the first embodiment is that the target shaft position Lt correction processing shown in FIG. 16 is executed when it is determined that the target shaft position Lt ≦ the limit shaft position Lsp (“NO” in S480).

The target shaft position Lt correction process shown in FIG. 16 is performed when the target shaft position Lt set in step S470 is not restricted in step S490 (S4
This is a process for correcting the target shaft position Lwot in the full load state at the current engine speed NE so as to be within the followable range ("NO" at 80).

It is determined as "NO" in step S480, and target shaft position Lt correction processing (S500: FIG. 16)
Is started, first, it is determined whether or not the vehicle speed SP detected by the vehicle speed sensor 96 exceeds the reference vehicle speed SPc (S501). If SP ≦ SPc (“NO” in S501), the process once exits as it is. This is because if SP ≦ SPc, the target shaft position Lt is restricted according to the vehicle speed SP as shown in FIG. 11, so that the target shaft position Lt is not changed.

If SP> SPc ("YE" in S501)
S "), and then a target shaft position Lwot in a full load state corresponding to the current engine speed NE is calculated (S).
502). This corresponds to the full load position (the position of the line indicated by "full load" in FIG. 9) at the current engine speed NE in the map Lx using the engine speed NE and the intake air amount GA shown in FIG. By calculating the target shaft position Lt, the full load target shaft position Lwo is obtained.
t is obtained.

Next, the full load target shaft position Lwot and the target shaft position L obtained in step S470
The absolute value “| Lwot−Lt |” of the difference from t is the allowable value α.
Is determined (S504). The allowable value α is an adjustment amount for shifting from the valve lift corresponding to the target shaft position Lt to the valve lift at the time of full load, and a followable range in which “| Lwot−Lt |” provides a sufficient responsiveness. It is a value for determining whether or not it is within. For example, the allowable value α is the variable valve lift mechanism 24
Is set based on the maximum operating speed of the motor so as not to deteriorate the acceleration performance at the time of rapid acceleration.

When | Lwot−Lt | ≦ α is satisfied (S5
("NO" in 04), even if the intake-side camshaft 22 moves to the target shaft position Lt, the process can be maintained within the range in which the intake-side camshaft 22 can follow the full-load target shaft position Lwot.

On the other hand, if | Lwot−Lt |> α (“YES” in S504), the intake side camshaft 2
When 2 moves to the target shaft position Lt, it means that the target shaft position Lt is out of the followable range with respect to the full load target shaft position Lwot.

Therefore, it is determined whether the full load target shaft position Lwt is larger than the target shaft position Lt (S506). If Lwot> Lt (S50
6 "YES"), the target shaft position L as in the following equation 2.
t is set (S508).

[0140]

Lt ← Lwot−α (Equation 2) On the other hand, if Lwt <Lt (“N” in S506)
O "), the target shaft position Lt is set as in the following Expression 3 (S510).

[0141]

Lt ← Lwot + α (Equation 3) After the target shaft position Lt is corrected to be within the allowable value α with respect to the full load target shaft position Lwt in step S508 or step S510, Exit this process.

As described above, when the target shaft position Lt is less than the limit shaft position Lsp and the target shaft position Lt
Is not necessary ("NO" in S480),
And when the vehicle speed SP exceeds the reference vehicle speed SPc (S5
01 "YES"), taking into account the response during acceleration,
The valve lift is corrected so as to be within the range that can follow the valve lift at the time of full load.

In the above-described fourth embodiment, steps S410 to S450 and S470 correspond to processing as valve lift control means. Steps S460 and S460
Steps 480 and S490 correspond to the processing as the valve lift adjustment restricting means, and among them, step S460 corresponds to the processing as the valve lift restriction range setting means. Step S500 corresponds to a process as a valve lift correction unit.

According to the fourth embodiment described above, the following effects can be obtained. (I). The effects described in (a) and (b) of the first embodiment are obtained. (B). In the process of step S500, the amount of adjustment to the valve lift of the full load, that is, the difference between the target shaft position Lt and the full load target shaft position Lwot is calculated in the processes up to step S470 so as to be within the followable range. The corrected target shaft position Lt is corrected.

As a result, the restriction that the valve can be followed is imposed on the adjustment of the valve lift. Therefore, even when the engine 11 rapidly shifts from the partial load operation state to the full load state, it is possible to immediately shift from the current valve lift to the valve lift set for the full load state. The adjustment of the valve lift suitable for the operation state at the time of acceleration 11 can always be performed with high responsiveness. Therefore, the valve lift control can be made highly responsive without incurring an increase in cost for speeding up the variable valve lift mechanism 24, and a suitable valve lift state during acceleration can be quickly realized.

[Fifth Embodiment] A fifth embodiment is different from the first embodiment only in the map itself shown in FIGS. 8 and 9 used in the valve lift control process. Is basically the same as in the first embodiment.

FIG. 17 shows an example of the map in the fifth embodiment.
Shown in In the map other than the correction area indicated by cross-hatching in the map of FIG. 17, the same target shaft position Lt as the map of FIGS.
Are distributed.

On the other hand, the correction region of FIG. 17 is the same as that of the fourth embodiment described with respect to the full load target shaft position Lwot at the same engine speed NE in FIGS. > Α ”. In the correction area of FIG. 17, the target shaft position Lt set within an allowable range from the full load target shaft position Lwot at the same engine speed NE is set.

For example, the target shaft position Lt set within the correction region at a certain engine speed NEi
Is set to a value of “Lwoti ± α” with respect to the full load target shaft position Lwoti at the engine speed NEi. In the example of FIG. 17, since the target shaft position Lt (the value in FIGS. 8 and 9)> the full load target shaft position Lwoti, the value is set to Lt = Lwoti + α.

Therefore, the target shaft positions Lt obtained from the map of FIG. 17 are all within the allowable range from the full load target shaft position Lwot at the corresponding engine speed NE.

According to the fifth embodiment described above, the following effects can be obtained. (I). The effects described in (a) of the fourth embodiment are obtained. (B). The target shaft position Lt map is set so that the adjustment amount of the full load to the valve lift, that is, the difference between the target shaft position Lt and the full load target shaft position Lwot is within the followable range.

As a result, the restriction that the valve can be followed is imposed on the adjustment of the valve lift. Therefore, even when the engine 11 rapidly shifts from the partial load operation state to the full load state, it is possible to immediately shift from the current valve lift to the valve lift set for the full load state. The adjustment of the valve lift suitable for the operation state at the time of acceleration 11 can always be performed with high responsiveness. Therefore, the valve lift control can be made highly responsive without incurring an increase in cost for speeding up the variable valve lift mechanism 24, and a suitable valve lift state during acceleration can be quickly realized.

(C). The map itself of the target shaft position Lt is set such that the difference between the target shaft position Lt and the full load target shaft position Lwot falls within the followable range. For this reason, the target shaft position Lt obtained based on the map is used to correct the target shaft position Lt and the full load target shaft position Lwot in the target shaft position Lt correction processing.
It is not necessary to make correction so that the difference is within the followable range.

Therefore, there is an advantage that the processing of the ECU 80 is simplified. [Embodiment 6] Embodiment 6 is directed to Embodiment 4 of the present invention.
The difference is that the allowable value α used in the valve lift control process is determined based on the engine speed NE. Therefore, the processing shown in the flowchart of FIG. 18 is executed as the target shaft position Lt correction processing. Here, the processes of steps S601 to S610 other than step S603 are the same as steps S501 to S510 of the target shaft position Lt correction process (FIG. 16) of the fourth embodiment. The other configuration is basically the same as that of the fourth embodiment.

Target shaft position Lt correction processing (FIG. 18)
In, a process of setting the allowable value α is performed next to the calculation of the full load target shaft position Lwot corresponding to the engine speed NE (S602) (S603). here,
From the allowable value one-dimensional map shown in FIG.
The allowable value α is calculated based on E.

As shown in FIG. 19, the allowable value α is set so as to gradually decrease as the engine speed NE increases. In order to increase the output of the engine 11 during acceleration or the like, it is necessary to advance the ignition timing as the actual compression ratio increases. However, if the ignition timing is advanced to a certain extent, knock occurs. For this reason, the ignition timing cannot be advanced beyond the advance amount at which knock occurs. Further, the ignition timing advance amount (knock limit) at which this knock occurs becomes smaller as the engine speed NE is lower.

For this reason, during acceleration when the engine speed NE is in the low speed range, even if the valve lift is set to the optimum valve lift at full load in a short time to increase the actual compression ratio of the engine 11, The ignition timing is limited to a knock limit, cannot be advanced to an optimum value for the compression ratio, and cannot obtain an output corresponding to the actual compression ratio at full load. Therefore, when the engine is running at a low speed, the increase in the engine output obtained at the time of rapid acceleration is smaller than that at the time of high speed rotation. Therefore, even if the follow-up of the valve lift is slightly delayed, the acceleration is not significantly affected.

That is, during acceleration when the engine speed NE is low, since the engine output is originally limited by the knock limit of the ignition timing, the output is significantly increased even when shifting to the optimum valve lift at full load. Does not rise, and the sensitivity of the output change to the change in the valve lift is low. For this reason, even if the optimum valve lift at the time of full load is slightly delayed, the deterioration of the acceleration performance is not so large in practice. Therefore, even if the allowable value α is increased, the effect when the operation amount of the variable valve lift mechanism 24 increases is reduced.

On the other hand, when the engine speed NE is high, the knock limit becomes large, so that the ignition timing can be advanced to a value suitable for the actual compression ratio at full load, and the engine output during rapid acceleration can be reduced. The rise is great. For this reason, the output change depends on the valve lift, and the sensitivity of the output change to the valve lift change is increased. Therefore, in the acceleration in the high rotation region, if the shift of the valve lift is delayed, the increase in the output of the engine is delayed, and the deterioration of the acceleration performance is increased.

For this reason, in the sixth embodiment, as shown in FIG. 19, the allowable value α is increased in the low rotation region where the influence on the acceleration is small, so that the more optimal valve lift can be obtained at medium load. In addition, the allowable value α is reduced in the high rotation region where the influence on the acceleration is large, so that the optimum valve lift at full load can be reached in a short time.

In Embodiment 6 described above, the target shaft position Lt correction processing in FIG. 18 corresponds to the processing as the valve lift correction means. Embodiment 6 described above
According to the above, the following effects can be obtained.

(A). (B) of the fourth embodiment;
The effect described in (b) is obtained. (B). As described above, since the allowable value α is set in accordance with the engine speed NE, the acceleration performance in the entire operation range can be improved while maintaining the output characteristics and emission at low and medium speeds even better.

[Seventh Embodiment] A seventh embodiment is different from the sixth embodiment in that the allowable value α in the sixth embodiment is set (S603).
The map of FIG. 20 is used instead of the map of FIG. The other configuration is basically the same as that of the sixth embodiment.

In FIG. 20, the allowable value α is set based on the state of the cooling water temperature THW of the engine 11 other than the engine speed NE. In FIG. 20, the value of the allowable value α is set to be smaller when the engine 11 is at a low temperature than when the engine 11 is at a high temperature even at the same rotational speed.

That is, when the engine temperature is low, the lubricating oil temperature is low, and the flow resistance of the lubricating oil is large. Therefore, even if the operation amount of the variable valve lift mechanism 24 is the same, the operation time becomes long. For this reason, by setting the value of the allowable value α to be smaller at a low engine temperature than at a high temperature, the operation amount of the variable valve lift mechanism 24 is generally reduced so that the same operation time as at a high temperature can be obtained. I have.

For example, when the cooling water temperature THW is equal to or lower than the reference temperature (for example, 70 ° C.), it is determined that the engine 11 is at a low temperature, and the allowable value α is determined using a low-temperature map (dashed line in FIG. 20). To determine. If the temperature exceeds the reference temperature, it is determined that the engine 11 is at a high temperature, and a high temperature map (FIG. 20)
Is determined by using the solid line of FIG.

According to the seventh embodiment described above, the following effects can be obtained. (I). The effects described in (a) and (b) of the sixth embodiment are obtained. (B). Furthermore, since the allowable value α is changed in accordance with the engine temperature, regardless of the temperature state of the engine 11, a good acceleration performance in the entire operation range while maintaining the output characteristics and the emission at low and medium speeds even better. Obtainable.

(C). In addition, by setting the value of the allowable value α to be smaller when the engine 11 is at a low temperature than when the engine 11 is at a high temperature, the internal EGR amount is reduced at a low and medium load, and at the same time, the combustion deteriorates when the engine is at a low temperature. Can be prevented.

[Eighth Embodiment] In the eighth embodiment, E
In the CU 80, the valve lift control process is performed as shown in FIG.
Is different from the first embodiment in that the control shown in the flowchart of FIG. Further, a fuel cut process as shown in FIG. 22 is performed in another ECU which executes the fuel injection amount control. The other configuration is basically the same as that of the first embodiment.

In the valve lift control process (FIG. 21), except for steps S725 and S795, steps S710 to S710 are performed.
Each process of S790 is the same as steps S110 to S190 shown in FIG. 7 of the first embodiment.

In the valve lift control process (FIG. 21), when the starter signal ST is "OFF"("YES" in S710), the fuel cut execution flag Fca is then set based on the transmission data from another ECU. It is determined whether it is "OFF" (S725). Fuel cut execution flag Fc
a is a flag set by another ECU in a fuel cut process described later. If the fuel cut execution flag Fca is “ON”, it is understood that the fuel cut process is being executed, and “OFF” If there is, it is understood that the fuel cut processing has not been performed.

Here, if Fca = “OFF”, (S
“YES” at 725), and thereafter, steps S730-S79
0 is executed. The processing of this part is as described in steps S130 to S190 in the first embodiment.

On the other hand, if Fca = “ON” (S72)
5, "NO", the target shaft position Lt is set to the minimum lift amount of the shaft position Ls (S79).
5), once terminate the process. Specifically, the minimum lift amount shaft position Ls corresponds to the shaft position 0 mm (Lmin) where the lift amount and the operating angle of the intake valve 20 are minimized as shown in FIG.

Next, the fuel cut process is shown in the flowchart of FIG. This process is a process executed by another ECU in a time cycle. First, it is determined whether a fuel cut condition is satisfied (S810). If the fuel cut condition is satisfied ("YES" in S810), "ON" is set in fuel cut execution flag Fca (S82).
0), once terminate the process. If the fuel cut condition is not satisfied ("NO" in S810), "OFF" is set in the fuel cut execution flag Fca (S83).
0), once terminate the process.

Here, the fuel cut condition means, for example, that the vehicle needs to be decelerated on the basis of the accelerator opening ACCP detected by the accelerator opening sensor (not shown) or the vehicle speed SP detected by the vehicle speed sensor 96. State,
A state in which the engine speed NE detected from the crank side electromagnetic pickup 90 is higher than the fuel cut speed,
Alternatively, the vehicle speed SP is higher than the maximum regulation speed. Then, “O” is set in the fuel cut execution flag Fca.
If "N" is set, the other ECU stops fuel injection from the fuel injection valve to the intake port 18.

By performing the processing described above, the EC
U80 controls the valve lift of the intake valve 20 to a position where the lift amount and the operating angle are minimized when the fuel cut is being executed.

In the above-described eighth embodiment, steps S710, S720, S730-S750, and S770 correspond to processing as valve lift control means. Also,
Steps S760, S780, and S790 correspond to processing as valve lift adjustment limiting means, and among them, step S760 corresponds to processing as valve lift restriction range setting means. Steps S725 and S795 correspond to the processing as the valve lift adjusting means at the time of fuel cut.

According to the eighth embodiment described above, the following effects can be obtained. (I). The effects described in (a) and (b) of the first embodiment are obtained. (B). By the processing of steps S725 and S795, during fuel cut, the valve lift and the valve operating angle are adjusted to the minimum valve lift. Therefore, the intake resistance increases, the function of the engine brake can be improved, and the amount of air sent to the catalyst during the exhaust stroke decreases, so that the deterioration of the catalyst can be reduced.

[Other Embodiments] In each of the above embodiments, the one-dimensional map for obtaining the water temperature correction amount Lw shown in FIG. 10 or the one-dimensional map for obtaining the restricted shaft position Lsp shown in FIG. The dimension map may be provided for each operation mode in order to correspond to the operation mode described in step S130.

In the above-described embodiments, the intake valve 2 is moved by moving the intake camshaft 22 in the rotation axis direction.
Although the valve lift of 0 is adjusted, the valve lift of the exhaust valve 21 may be adjusted by moving the exhaust camshaft 23 in the rotation axis direction with the exhaust cam 28 being a three-dimensional cam. Furthermore, both the intake side camshaft 22 and the exhaust side camshaft 23 may be movable in the direction of the rotation axis, and the valve lift of both the intake valve 20 and the exhaust valve 21 may be adjusted.

In each embodiment, the profile of the cam surface 27a of the intake cam 27 has a sub-lift as shown in FIG. 5, but may have no sub-lift as shown in FIG. . In this case, for example, FIG.
As shown in FIG. 7, the valve overlaps with the exhaust cam 28 (shown by a broken line Ex).

The profile of the cam surface 27a of the intake cam 27 may be such that the sub-lift greatly changes and the peak MP of the main lift is constant as shown in FIG. In this case, the variable valve lift mechanism 24 causes a valve overlap with the exhaust cam 28 (shown by a broken line) as shown in FIG. 26, for example.

In each of the above embodiments, since the inner teeth 57 of the cover 54 and the teeth 63 of the ring gear 62 are spiral, the variable valve lift mechanism 24 moves the intake-side camshaft 22 in the direction R. , The rotational phase of the intake camshaft 22 is changed to the crankshaft 15.
It was configured to advance with respect to. Besides this,
Inner teeth 5 of cover 54 in variable valve lift mechanism 24
27 and the teeth 63 of the ring gear 62 are formed straight, so that the rotation of the intake-side camshaft 22 regardless of the movement of the intake-side camshaft 22 in the direction R by the variable valve lift mechanism 24 as shown in FIG. The phase may be kept constant with respect to the crankshaft 15.

In the above embodiments, the valve lift of the intake valve 20 is adjusted by adjusting the position of the intake camshaft 22 in the direction of the rotation axis by the variable valve lift mechanism 24. In addition to the configuration, a configuration for adjusting the rotation phase of the intake side camshaft 22 with respect to the crankshaft 15 may be added. This makes it possible to more precisely adjust the valve timing and valve overlap by advancing or retarding the entire valve lift.

In each of the above embodiments, a gasoline engine of the type in which fuel is injected into the intake port 18 has been described. However, the present invention is also applicable to a direct injection type in which fuel is directly injected into the combustion chamber 17. Also applicable to gasoline engines. It can also be applied to diesel engines.

The embodiments of the present invention have been described above. It should be noted that the embodiments of the present invention include the following embodiments. (1). A variable valve lift mechanism for changing one or both valve lifts of an intake valve and an exhaust valve of an internal combustion engine mounted on an automobile, and a valve for adjusting the valve lift according to the operating state of the internal combustion engine by the variable valve lift mechanism A valve characteristic control device for an internal combustion engine, comprising: a lift control unit; and a valve according to an operation state of the internal combustion engine by the valve lift control unit when the internal combustion engine is in an idle state or an operation state near the idle state. A valve characteristic control device for an internal combustion engine, comprising valve lift adjustment limiting means for limiting lift adjustment.

(2). A variable valve lift mechanism for changing one or both valve lifts of an intake valve and an exhaust valve of an internal combustion engine mounted on an automobile, and a valve for adjusting the valve lift according to the operating state of the internal combustion engine by the variable valve lift mechanism A valve characteristic control device for an internal combustion engine, comprising: a lift control unit; and a valve according to an operation state of the internal combustion engine by the valve lift control unit when the internal combustion engine is in an idle state or an operation state near the idle state. A valve characteristic control device for an internal combustion engine, comprising valve lift adjustment limiting means for limiting the adjustment of a lift according to a vehicle speed.

(3). 17. The valve characteristic control device for an internal combustion engine according to claim 1, wherein a phase difference between a rotation phase of one or both of an intake valve and an exhaust valve and a rotation phase of a crankshaft is continuously adjusted. A valve characteristic control device for a direct injection type internal combustion engine, comprising a variable valve timing mechanism for continuously changing one or both valve timings of an intake valve and an exhaust valve.

(4). The valve characteristic control device for an internal combustion engine according to claim 9, wherein the valve lift control means includes:
As the operating state of the internal combustion engine, using a load and a rotation speed of the internal combustion engine, a variable valve lift mechanism adjusts a valve lift according to the load and the rotation speed of the internal combustion engine, and the valve lift adjustment limiting unit includes: When stopping the adjustment of the valve lift according to the operation state of the internal combustion engine by the valve lift control means, the valve lift is set according to the drive state of an air conditioner driven by the internal combustion engine. Engine valve characteristic control device.

(5). The valve characteristic control device for an internal combustion engine according to claim 9, wherein the valve lift control means includes:
As the operating state of the internal combustion engine, using a load and a rotation speed of the internal combustion engine, a variable valve lift mechanism adjusts a valve lift according to the load and the rotation speed of the internal combustion engine, and the valve lift adjustment limiting unit includes: When the adjustment of the valve lift according to the operating state of the internal combustion engine by the valve lift control means is stopped, the valve lift according to the shift position of the automatic transmission is set. apparatus.

(6). The valve characteristic control device for an internal combustion engine according to claim 9, wherein the valve lift control means includes:
As the operating state of the internal combustion engine, using a load and a rotation speed of the internal combustion engine, a variable valve lift mechanism adjusts a valve lift according to the load and the rotation speed of the internal combustion engine, and the valve lift adjustment limiting unit includes: When the adjustment of the valve lift according to the operating state of the internal combustion engine by the valve lift control means is stopped, the valve lift according to the degree of electric load on the internal combustion engine is set. Characteristic control device.

[Brief description of the drawings]

FIG. 1 is a schematic configuration explanatory diagram of an engine and a control system in which a valve characteristic control device according to a first embodiment is incorporated.

FIG. 2 is a perspective view of an intake cam according to the first embodiment.

FIG. 3 is an explanatory view of a longitudinal section and a hydraulic system of the variable valve lift mechanism according to the first embodiment.

FIG. 4 is an explanatory view of a profile of an intake cam according to the first embodiment.

FIG. 5 is an explanatory view of a valve lift by the intake cam according to the first embodiment.

FIG. 6 is a diagram illustrating valve characteristics of an intake valve according to the first embodiment.

FIG. 7 is a flowchart of a valve lift control process according to the first embodiment.

FIG. 8 is an explanatory diagram of a map for setting a target shaft position Lt used in the first embodiment.

FIG. 9 is a graph showing an example of the configuration of the map shown in FIG. 8;

FIG. 10 is a configuration explanatory diagram of a one-dimensional map Fw for obtaining a water temperature correction amount Lw from a cooling water temperature THW in the first embodiment.

FIG. 11 is a configuration explanatory diagram of a one-dimensional map Fsp for obtaining a limited shaft position Lsp from a vehicle speed SP in the first embodiment.

FIG. 12 is a flowchart of a valve lift control process according to the second embodiment.

FIG. 13 is a flowchart of a valve lift control process according to the third embodiment.

FIG. 14 is a flowchart of target shaft position Lt setting processing according to the third embodiment.

FIG. 15 is a flowchart of a valve lift control process according to the fourth embodiment.

FIG. 16 is a flowchart of a target shaft position Lt correction process according to the fourth embodiment.

FIG. 17 is an explanatory diagram of a configuration of a map for setting a target shaft position Lt used in the fifth embodiment.

FIG. 18 is a flowchart of a target shaft position Lt correction process according to the sixth embodiment.

FIG. 19 is a configuration explanatory diagram of an allowable value one-dimensional map for obtaining an allowable value α from an engine speed NE used in the sixth embodiment.

FIG. 20 is a diagram illustrating a configuration of a map used to determine an allowable value α from an engine speed NE and a coolant temperature THW used in the seventh embodiment.

FIG. 21 is a flowchart of a valve lift control process according to the eighth embodiment.

FIG. 22 is a flowchart of a fuel cut process according to the eighth embodiment.

FIG. 23 is an explanatory view of a valve lift by an intake cam according to another embodiment.

FIG. 24 is an explanatory diagram of valve characteristics of the intake valve of FIG. 23;

FIG. 25 is an explanatory view of a valve lift by an intake cam according to another embodiment.

FIG. 26 is an explanatory diagram showing valve characteristics of the intake valve shown in FIG. 25;

FIG. 27 is an explanatory diagram of valve characteristics of an intake valve according to another embodiment.

[Explanation of symbols]

11 ... Engine, 12 ... Piston, 13 ... Cylinder block, 13a ... Oil pan, 13b ... Oil pump, 1
4: Cylinder head, 14a: Journal bearing, 14b
... Camshaft bearing cap, 15 ... Crankshaft, 15a ... Sprocket, 16 ... Connecting rod, 1
7: combustion chamber, 18: intake port, 19: exhaust port, 2
0: intake valve, 20a: valve lifter, 20b: cam follower, 21: exhaust valve, 21a: valve lifter,
22: intake camshaft, 23: exhaust camshaft, 24: variable valve lift mechanism, 24a, 25: timing sprocket, 26: timing chain, 27
... intake cam, 27a ... cam surface, 27b ... cam nose, 2
7c: rear end face, 27d: front end face, 28: exhaust cam,
51: cylindrical portion, 52: disk portion, 53: external teeth, 54: cover, 55: bolt, 57: internal teeth, 58: hollow bolt, 5
Reference numeral 9: pin, 62: ring gear, 62a: disk-shaped ring portion, 63: tooth, 65: hydraulic chamber on the second lift pattern side, 6
6 ... first lift pattern side hydraulic chamber, 67 ... second lift pattern control oil passage, 68 ... first lift pattern control oil passage,
70: oil control valve, 70a: electromagnetic solenoid, 72: oil passage in 74, supply passage, 76: discharge passage, 80: ECU, 82: CPU, 83: ROM, 84
... RAM, 85 ... Backup RAM, 86 ... Bus, 8
7 ... External input circuit, 88 ... External output circuit, 90 ... Crank side electromagnetic pickup, 92 ... Intake cam side electromagnetic pickup, 93 ... Starter switch, 94 ... Water temperature sensor, 9
5: air conditioner switch, 96: vehicle speed sensor, 97: throttle opening sensor, 98: air flow meter, 99: shift position sensor, 100: electric load switch.

Continued on front page F-term (reference) 3G016 AA08 AA19 BA03 BA06 BA23 BA28 BA37 BA39 BB04 CA24 DA06 DA22 DA23 GA08 GA10 3G084 BA23 CA03 CA04 DA08 DA16 DA34 EB14 EB15 FA05 FA06 FA07 FA10 FA18 FA20 FA33 FA38 3G092 AA01 AA01 DA11 DA12 DF04 DG05 DG09 EA01 EA02 EA09 EA13 EA14 EA22 EA28 EA29 EB02 EB03 EC01 EC10 FA03 FA09 FA15 FA20 FA21 FA25 FA34 FA40 FA50 GA04 GA12 GB02 HA01Z HA09Z HA11Z HA13X HA13Z HE01Z HE03Z HE08ZHFZ HF04 JA33 KA07 KA08 KA13 KA24 KA26 KB04 LA01 LA07 LB02 LC01 LC08 MA24 NA03 NA04 NA05 NA08 NB18 NC04 ND03 ND04 NE01 NE06 NE18 PA01Z PA14Z PA17Z PE01Z PE03Z PE08Z PE10A PE10Z PF01Z PF03Z PF07Z PF13Z

Claims (16)

[Claims] 1. A variable valve lift mechanism for changing one or both valve lifts of an intake valve and an exhaust valve of an internal combustion engine mounted on an automobile, and the variable valve lift mechanism sets the valve lift to an operating state of the internal combustion engine. A valve characteristic control device for an internal combustion engine, comprising: a valve lift control unit that adjusts the valve lift according to an operating state of the internal combustion engine when the vehicle speed is low. A valve characteristic control device for an internal combustion engine, comprising a valve lift adjustment restricting means. 2. A variable valve lift mechanism for changing one or both valve lifts of an intake valve and an exhaust valve of an internal combustion engine mounted on an automobile, and the variable valve lift mechanism sets the valve lift to an operating state of the internal combustion engine. And a valve lift control means for adjusting the valve lift according to the operating state of the internal combustion engine by the valve lift control means when the vehicle speed is low. A valve characteristic control device for an internal combustion engine, comprising: a valve lift adjustment restricting means for restricting the valve characteristic according to the condition. 3. The valve characteristic control device for an internal combustion engine according to claim 2, wherein said valve lift adjustment limiting means includes a valve lift limiting range setting means for setting a limiting range for limiting a valve lift state according to a vehicle speed. Limiting the valve lift according to the vehicle speed by restricting the adjustment of the valve lift by the valve lift control means in accordance with the operating state of the internal combustion engine based on the restriction range set by the valve lift restriction range setting means. A valve characteristic control device for an internal combustion engine, comprising: 4. The valve characteristic control device for an internal combustion engine according to claim 1, wherein said valve lift adjustment limiting means determines that the vehicle speed is low when the vehicle speed falls below a reference vehicle speed. A characteristic valve control device for an internal combustion engine. 5. A variable valve lift mechanism for changing one or both valve lifts of an intake valve and an exhaust valve of an internal combustion engine mounted on an automobile, and the variable valve lift mechanism sets the valve lift to an operating state of the internal combustion engine. A valve characteristic control device for an internal combustion engine, comprising: a valve lift control means that adjusts the throttle valve in accordance with the internal combustion engine. A valve characteristic control device for an internal combustion engine, comprising valve lift adjustment limiting means for limiting adjustment of a valve lift according to an operation state of the internal combustion engine by the valve lift control means. 6. The valve characteristic control device for an internal combustion engine according to claim 5, wherein said valve lift adjustment restricting means is provided when the rotational speed of the internal combustion engine is lower than the reference rotational speed and the vehicle speed is lower than the reference vehicle speed. A valve characteristic control device for an internal combustion engine, which determines that the rotation speed and the vehicle speed of the internal combustion engine are low. 7. The valve characteristic control device for an internal combustion engine according to claim 5, wherein the state in which the throttle valve is equal to or less than the reference opening is a fully closed state. 8. The valve characteristic control device for an internal combustion engine according to claim 5, wherein said valve lift adjustment limiting means adjusts a valve lift according to an operation state of the internal combustion engine by said valve lift control means. A valve characteristic control apparatus for an internal combustion engine, wherein the valve lift is stopped to limit adjustment of a valve lift. 9. The valve characteristic control device for an internal combustion engine according to claim 8, wherein said valve lift adjustment limiting means is adapted to stop adjusting the valve lift according to the operating state of the internal combustion engine by said valve lift control means. A valve characteristic control device for an internal combustion engine, wherein a valve lift is set according to a state quantity other than an operation state of the internal combustion engine. 10. The internal combustion engine according to claim 1, wherein said variable valve lift mechanism is capable of continuously adjusting a valve lift. Valve characteristic control device. 11. A valve characteristic control apparatus for an internal combustion engine according to claim 10, wherein one or both of said intake valve and said exhaust valve are lift-driven by cams having different profiles in the direction of a rotation axis, and said variable valve lift is controlled. A valve characteristic control device for an internal combustion engine, wherein the mechanism is capable of continuously adjusting a valve lift by adjusting a position in the rotation axis direction with respect to the cam having a different profile in the rotation axis direction. . 12. The valve characteristic control device for an internal combustion engine according to claim 1, wherein said valve lift control means controls a variable valve lift according to a rotational speed and a load of the internal combustion engine as an operation state of the internal combustion engine. The valve lift is adjusted by the mechanism, and the valve lift other than at the time of full load in the adjustment is within the range in which the adjustment amount for shifting to the valve lift adjusted at the full load at the rotation speed of the corresponding internal combustion engine can follow. A valve characteristic control device for an internal combustion engine, wherein the valve characteristic control device is set to have a value of: 13. The valve characteristic control device for an internal combustion engine according to claim 1, wherein said valve lift control means controls a variable valve lift according to an operation speed of the internal combustion engine and a load of the internal combustion engine. The valve lift is adjusted by a mechanism, and when the valve lift adjustment limiting means does not limit the adjustment of the valve lift by the valve lift control means, the valve lift adjusted by the valve lift control means corresponds to the internal combustion engine. When the adjustment amount for shifting to the valve lift adjusted at the full load at the engine speed is not a value within the followable range, the valve lift control unit controls the adjustment amount to be within the followable range. A valve for an internal combustion engine, comprising valve lift correction means for correcting a valve lift to be adjusted. Control device. 14. The valve characteristic control apparatus for an internal combustion engine according to claim 12, wherein the followable range is set narrower as the rotation speed of the internal combustion engine increases. Control device. 15. The internal combustion engine valve characteristic control apparatus according to claim 12, wherein the followable range is set narrower as the temperature of the internal combustion engine is lower. Valve characteristic control device. 16. The valve characteristic control apparatus for an internal combustion engine according to claim 10 or 11, wherein the fuel cut is performed such that the lift amount is a minimum or a valve lift close to the minimum during a period in which the fuel cut processing is executed in the internal combustion engine. A valve characteristic control device for an internal combustion engine, comprising: a valve lift adjusting means.