JPH06235305A - Variable valve device for engine - Google Patents

Abstract

PURPOSE:To stabilize combustion and reduce fuel consumption by delaying opening/closing timings of an intake valve during low speed and low load operation time for reducing a lifting rate, advancing the opening/closing timings of the intake valve during low speed and high load operation time for reducing the lifting rate, and delaying the opening/closing timing of the intake valve during high speed operation time for increasing the valve lifting rate. CONSTITUTION:Main rocker arms 1 are provided on a valve lift adjusting mechanism 40 corresponding to two intake valves of each cylinder, which arm l is supported to a cylinder head 69 through a main rocker shaft 3. An adjust screw 10 is arranged between the arm 1 and the intake valve. A sub-rocker arm 2 is provided with a sub-rocker shaft 16 therebetween. A valve timing adjusting mechanism 70 is arranged between a cam shaft 72 and a cam pulley 71 which receives torque from a timing belt 66. A helical gear 73 advances the cam shaft 72 by means of hydraulic pressure in a hydraulic chamber 75. The valve lift adjusting mechanism 40 and the valve timing adjusting mechanism 70 are controlled by means of a control unit 51 through solenoid changeover valves 45, 79.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable valve operating system for controlling a valve lift characteristic of an intake valve according to engine operating conditions.

[0002]

2. Description of the Related Art Conventionally, it has been known to selectively switch the cams involved in the opening / closing operation of the intake valve or the exhaust valve in accordance with operating conditions, thereby controlling the intake / exhaust timing or intake / exhaust amount. (For example, JP-A-63-
167016, JP-A-63-57805, etc.).

To explain this, a rocker shaft for low speed, whose rocking tip abuts against the valve, and a rocker shaft for high speed, which is adjacent to one side of the rocker arm for low speed and has no contact portion with the valve, are common. The low-speed rocker arm is slidably contacted with a low-speed cam, and the high-speed rocker arm is slidably contacted with a high-speed cam having a profile having a larger valve opening angle or valve lift than the low-speed cam.

Further, in a swinging portion separated from the rocker shaft by a predetermined distance, in a direction parallel to the rocker shaft, a plunger responsive to the operating hydraulic pressure is fitted into the fitting hole or is pulled out from the fitting hole. The rocker arm may be connected or disconnected.

[0005]

However, in the conventional device that selectively switches a plurality of cams according to such engine operating conditions, the valve opening period by the low speed cam is different from the valve opening period by the high speed cam. Since it is necessary to set it within the range, for example, in order to prevent the air-fuel mixture sucked into the cylinder in the low rotation and high load range from being discharged to the intake port near the bottom dead center of the intake stroke, the closing timing of the intake valve If the valve is opened earlier, the valve opening period will be shortened and the filling efficiency will deteriorate.
The problem is that a torque drop occurs near the number of revolutions at which the low speed cam switches to the high speed cam.

In view of the above problems, it is an object of the present invention to provide a variable valve operating device that appropriately controls the valve lift characteristic of an intake valve according to operating conditions.

[0007]

According to the present invention, an intake camshaft for opening and closing an intake valve, a valve timing adjusting mechanism for changing the phase angle of the intake camshaft with respect to a crankshaft, and a plurality of profiles each having a different profile. A cam, a valve lift adjusting mechanism for switching between a cam for opening and closing an intake valve, a means for detecting an operating condition of the engine, and a control means for driving the valve timing adjusting mechanism and the valve lift adjusting mechanism according to the operating condition of the engine. In the variable valve operating device of the engine having,
The intake valve opening / closing timing is delayed via the valve timing adjustment mechanism at low rotation and low load, and the lift amount of the intake valve is reduced via the valve lift adjustment mechanism, and intake is performed via the valve timing adjustment mechanism at low rotation and high load. In addition to advancing the opening / closing timing of the valve, the lift amount of the intake valve is reduced via the valve lift adjustment mechanism, and the opening / closing timing of the intake valve is delayed via the valve timing adjustment mechanism at high rotation speeds. The intake valve lift is increased.

According to a second aspect of the present invention, the control means is configured to switch the valve timing adjusting mechanism and the valve lift adjusting mechanism with a time lag during the operation of switching the valve lift characteristic of the intake valve.

According to a third aspect of the present invention, the control means is operated to switch the valve lift adjusting mechanism first, and then to operate the valve timing adjusting mechanism, under an operating condition in which the control means shifts from low rotation and high load to high rotation. The valve timing adjusting mechanism is first switched and then the valve lift adjusting mechanism is switched and operated under an operating condition in which the engine speed is changed from high rotation to low rotation and high load.

According to a fourth aspect of the present invention, the control means is operated to switch the valve timing adjusting mechanism after the switching operation of the valve lift adjusting mechanism is completed under the operating condition of shifting from low rotation and high load to high rotation. The valve lift adjusting mechanism is switched after the switching operation of the valve timing adjusting mechanism is completed under the operating condition of shifting from high rotation to low rotation and high load.

[0011]

[Operation] When the rotation speed is low and the load is low, the opening / closing timing of the intake valve is delayed through the valve timing adjusting mechanism, and the lift amount of the intake valve is reduced through the valve lift adjusting mechanism.
By reducing the valve overlap, it is possible to suppress the blowback of the exhaust gas from the exhaust port to the cylinder, reduce the residual gas ratio and stabilize the combustion, improve the idle stability, and reduce the fuel consumption.

By advancing the opening / closing timing of the intake valve via the valve timing adjusting mechanism during low rotation and high load, it is possible to prevent the air-fuel mixture sucked into the cylinder from being discharged to the intake port near the bottom dead center of the intake stroke. Then, the intake charging efficiency can be improved. At this time, by reducing the lift amount of the intake valve via the valve lift adjusting mechanism, it is possible to prevent the valve overlap from becoming too large, reduce the residual gas, and increase the generated torque.

At the time of high speed rotation, the opening / closing timing of the intake valve is delayed via the valve timing adjusting mechanism, and the lift amount of the intake valve is increased via the valve lift adjusting mechanism to utilize the inertia supercharging effect of intake air. The intake charging efficiency can be improved. Moreover, by increasing the valve overlap, the negative pressure wave generated in the exhaust pipe can provide the exhaust gas scavenging effect, and the exhaust loss can be reduced to improve the output. That is, in the latter half of the exhaust stroke, negative pressure is generated by the exhaust gas moving in the exhaust pipe, and during the overlap period, the intake flow flows into the cylinder to enhance the exhaust gas scavenging effect.

According to the second aspect of the present invention, the valve timing characteristic and the valve lift are changed because the valve timing adjusting mechanism and the valve lift adjusting mechanism are switched with a time lag during the operation for changing the valve lift characteristic of the intake valve. By changing the characteristics stepwise, it is possible to reduce the torque shock of the engine that occurs at the time of switching.

According to the third aspect of the present invention, the valve lift adjusting mechanism is first switched and then the valve timing adjusting mechanism is switched and operated under an operating condition in which the rotation speed changes from high load to low rotation. As compared with the case where the valve timing adjusting mechanism having a relatively slow switching operation speed is switched first, the time required for the switching is shortened and the acceleration responsiveness is improved.

Under operating conditions in which the rotation speed changes from a high rotation speed to a low rotation speed and a high load, the valve timing adjustment mechanism is first switched and then the valve lift adjustment mechanism is switched, so that the switching operation speed is relatively high. Compared with the case of switching the fast valve lift adjusting mechanism, the time required for this switching becomes longer, and the shock of sudden deceleration can be alleviated.

According to another aspect of the present invention, after the switching operation of the valve lift adjusting mechanism or the valve timing adjusting mechanism which is first switched according to the operating condition is completed,
By switching and operating the valve timing adjusting mechanism or the valve lift adjusting mechanism, it is possible to ensure that there is a time difference between the operation end timings of the valve timing adjusting mechanism and the valve lift adjusting mechanism.

[0018]

2 and 3 show the mechanical structure of an embodiment of the present invention.

First, the valve lift adjusting mechanism 40 will be described. Each cylinder is provided with a single main rocker arm 1 corresponding to two intake valves 9. The base end of the main rocker arm 1 is swingably supported by the cylinder head 69 via the main rocker shaft 3 common to each cylinder, and the tip of the main rocker arm 1 is brought into contact with the stem tops of the intake valves 9 to adjust screw. 10 is fastened via the nut 11.

A roller 14 is rotatably connected to the shaft 13 of the main rocker arm 1 via a needle bearing, and a low speed cam 21 is brought into rolling contact with the roller 14.

The main rocker arm 1 is formed in a substantially rectangular shape in plan view, and the main rocker arm 1 is provided with a sub-rocker arm 2 along with the roller 14. The base end of the sub rocker arm 2 is connected to the main rocker arm 2 via a sub rocker shaft 16 so as to be relatively rotatable. The sub-rocker shaft 16 is slidably fitted in a hole 17 formed in the sub-rocker arm 2, and is press-fitted into a hole 18 formed in each main rocker arm 1.

The sub-rocker arm 2 does not have a portion that comes into contact with the intake valve 9, and a cam follower portion 23 that slidably contacts the high-speed cam 22 is formed at the tip thereof so as to project in an arc shape, and the cam follower portion 23 is provided below it. A lost motion spring 25 that presses against the high speed cam 22 is interposed.

The main rocker arm 1 is located immediately below the sub rocker arm 2 and has a lost motion spring 25.
A cylindrical concave portion 26 for interposing is formed integrally. The lower end of the coiled lost motion spring 25 has a recess 26.
Is seated on a bottom surface 26a of the sub-rocker arm 2 and its upper end abuts on a follower portion 28 formed integrally with the sub-rocker arm 2 via a retainer 27 slidably fitted in the recess 26.

The low-speed cam 21 and the high-speed cam 22 are integrally formed on a common cam shaft 72, and have different shapes (sizes are different from each other) so as to satisfy the required valve lift characteristics at low engine speed and high engine speed. (Including similar shapes). In this embodiment, as shown in FIG. 4, the high speed cam 22 has a profile in which both the valve lift amount and the valve opening period are larger than those of the low speed cam 21. Here, the valve lift amount and the valve opening period are both increased. If the lift amount of the cam that drives the exhaust valve is h ₁ , the lift amount of the high speed cam 22 is h ₃ , and the lift amount of the low speed cam 21 is h ₂ , then there is a relationship of h ₃ > h ₁ > h _2. There is.

Plungers 33, 31, 3 are provided across the main rocker arm 1 and the sub-rocker arm 2 as a connecting drive means capable of locking the relative rotation of both rocker arms 1, 2.
4 is slidably fitted, the hydraulic passage 43 is connected behind the plunger 33, and the return spring 38 is interposed behind the plunger 34.

When the operating hydraulic pressure introduced from the hydraulic passage 43 is low, the plungers 33 and 31 are accommodated in the sub-rocker arm 2 and the main rocker arm 1 by the urging force of the return spring 38 and do not restrain the swing of both. on the other hand,
When the operating hydraulic pressure introduced from the hydraulic passage 43 rises, the plungers 33 and 31 slide while compressing the return spring 38, and are fitted over the main rocker arm 1 and the sub-rocker arm 2 so that they are integrated. Rock.

The hydraulic passage 43 is provided through the insides of the main rocker arm 1 and the main rocker shaft 3, and the discharge hydraulic pressure of the oil pump 57 is guided through the electromagnetic switching valve 45 at a predetermined high rotation speed.

Next, the valve timing adjusting mechanism 70 will be described. The valve timing adjusting mechanism 70 is provided between the cam shaft 72 and the cam pulley 71, and changes the phase angle between the two according to operating conditions to change the opening / closing timing of the intake valve 9. Rotational force from a crankshaft (not shown) is transmitted to the cam pulley 71 via the timing belt 66.

At the end of the camshaft 72, a cylindrical inner housing 65 is fastened via bolts 64. A cylindrical outer housing 63 that is rotatably fitted to the inner housing 65 is provided, and a cam pulley 71 is formed integrally with the outer housing 63.

A ring-shaped helical gear 73 is interposed between the inner housing 65 and the outer housing 63. Helical splines are formed on the inner and outer circumferences of the helical gear 73, and the helical splines mesh with the outer circumference of the inner housing 65 and the inner circumference of the outer housing 63, and the helical gear 73 moves axially against the return spring 74. As the inner housing 65 rotates relative to the outer housing 63, the cam pulley 7
The phase angle in the rotation direction of the camshaft 72 with respect to 1 changes.

A hydraulic chamber 75 is defined between the inner housing 65, the outer housing 63 and the helical gear 73. When the hydraulic pressure guided to the hydraulic chamber 75 rises above a predetermined value, the helical gear 73 moves from the initial position to the right in the figure against the return spring 74.
The cam shaft 72 is adapted to rotate in a direction that advances the opening / closing timing of the intake valve 9.

As a result, when the helical gear 73 is in the initial position, the opening / closing timing of the intake valve 9 is delayed as shown by the solid line in FIG. 4, and when the helical gear 73 is displaced to the maximum, the broken line in FIG. As shown by, the opening / closing timing of the intake valve 9 is advanced.

The hydraulic chamber 75 is provided with an oil through a shaft hole 78 formed inside the camshaft 72, an oil gallery 59 formed on the cylinder head 69, an orifice 77, and a main gallery 58 formed on the cylinder block 68. The discharge hydraulic pressure from the pump 57 is introduced.

At the other end of the camshaft 72 is provided an electromagnetic switching valve 79 which is controlled to open / close in accordance with engine operating conditions. The electromagnetic switching valve 79 opens the shaft hole 78 when not energized to reduce the hydraulic pressure introduced to the hydraulic chamber 75 as shown in the figure, and closes the shaft hole 78 when energized to increase the hydraulic pressure introduced to the hydraulic chamber 75. ing.

As a control means for the valve lift adjusting mechanism 40 and the valve timing adjusting mechanism 70, a control unit 51 for controlling the energization of the electromagnetic switching valve 45 and the electromagnetic switching valve 79 is provided.

The control unit 51 inputs an engine rotation signal, an engine load signal, a cooling water temperature signal, a lubricating oil temperature signal, an intake supercharging pressure signal by a supercharger, etc., and based on these detected values. The valve lift characteristics are smoothly switched while suppressing a sudden change in engine torque.

As shown in FIG. 1, the control unit 51 delays the opening / closing timing of the intake valve 9 at the time of low rotation and low load, and reduces the lift amount of the intake valve 9 via the low speed cam 21 to reduce the low rotation and high load. At the same time, the opening / closing timing of the intake valve 9 is advanced, the lift amount of the intake valve 9 is reduced via the low speed cam 21, the opening / closing timing of the intake valve 9 is delayed during high rotation, and the intake valve 9 is opened via the high speed cam 22. The valve timing adjusting mechanism 70 and the valve lift adjusting mechanism 40 are driven so as to increase the lift amount.

The control unit 51 switches the valve timing adjusting mechanism 70 and the valve lift adjusting mechanism 40 with a time lag during the operation of switching the valve lift characteristic of the intake valve 9 to reduce the torque shock of the engine generated during the switching. To do.

That is, the control unit 51 is
Under an operating condition that shifts from low rotation and high load to high rotation, the solenoid switching valve 45 of the valve lift adjustment mechanism 40 is turned off first.
After switching from ON to ON, the valve timing adjustment mechanism 70
The electromagnetic switching valve 79 is switched from OFF to ON. Then, under an operating condition that shifts from high rotation to low rotation and high load, the electromagnetic switching valve 7 of the valve timing adjustment mechanism 70 is first.
After switching 9 from ON to OFF, the electromagnetic switching valve 45 of the valve lift adjusting mechanism 40 is switched from ON to OFF.

Next, the operation will be described.

When the engine speed is low and the load is low, the opening / closing timing of the intake valve is delayed via the valve timing adjusting mechanism 70.
By reducing the lift amount of the intake valve 9 and reducing the valve overlap via the valve lift adjusting mechanism 40, blowback of exhaust gas from the exhaust port to the cylinder can be suppressed, and the residual gas ratio can be reduced to perform combustion. It stabilizes and enhances idle stability, while reducing fuel consumption.

By advancing the opening / closing timing of the intake valve 9 via the valve timing adjusting mechanism 70 at low rotation and high load, the air-fuel mixture sucked into the cylinder is discharged to the intake port near the bottom dead center of the intake stroke. Can be suppressed, and the intake charging efficiency can be improved. At this time, by reducing the lift amount of the intake valve via the valve lift adjusting mechanism, it is possible to prevent the valve overlap from becoming too large, reduce the residual gas, and increase the generated torque.

Valve timing adjusting mechanism 70 at high rotation speed
By delaying the opening / closing timing of the intake valve 9 via the valve and increasing the lift amount of the intake valve 9 via the valve lift adjusting mechanism 40, the intake supercharging effect can be utilized to increase the intake charging efficiency. Moreover, by increasing the valve overlap, the negative pressure wave generated in the exhaust pipe can provide the exhaust gas scavenging effect, and the exhaust loss can be reduced to improve the output. That is, in the latter half of the exhaust stroke, the negative pressure is generated by the exhaust gas moving in the exhaust pipe, and the intake flow flows into the cylinder during the overlap period, so that the scavenging effect of the exhaust gas is enhanced.

The valve lift adjusting mechanism 40 completes switching of the cams 21 and 22 instantly by turning on / off the electromagnetic switching valve 45. However, by turning on / off the electromagnetic switching valve 79, the valve lift adjusting mechanism 70 causes the camshaft 72 to move. It takes about 0.2 to 1 second to complete the rotation.

The control unit 51 turns on / off the electromagnetic switching valve 45 and the electromagnetic switching valve 79 with a predetermined time difference.
By performing FF and switching the valve timing characteristic and the valve lift characteristic stepwise, it is possible to mitigate the torque shock of the engine that occurs at the time of switching.

Under an operating condition of shifting from low rotation and high load to high rotation, the electromagnetic switching valve 45 is first switched from OFF to ON, and the valve lift adjusting mechanism 40 is instantaneously switched to operate. Hold and turn off the solenoid switching valve 79
By switching the valve timing adjusting mechanism 70 from ON to ON, the valve timing adjusting mechanism 70 is switched and operated, so that the time required for switching is shortened as compared with the case where the valve timing adjusting mechanism 70 having a relatively slow switching operation speed is switched first, and the acceleration responsiveness is increased. Can be increased.

Under an operating condition that shifts from high rotation to low rotation and high load, the electromagnetic switching valve 79 is first switched from ON to OFF, the valve timing adjusting mechanism 70 is switched and operated, and then the electromagnetic switching valve 45 is turned ON. By switching from OFF to OFF and instantaneously switching the valve lift adjusting mechanism 70, the time required for this switching becomes longer than in the case where the valve lift adjusting mechanism 70 having a relatively high switching operation speed is switched first. It is possible to reduce the shock of sudden deceleration.

Further, the control unit 51 turns off the electromagnetic switching valve 79 of the valve timing adjusting mechanism 70 after the switching operation of the valve lift adjusting mechanism 40 is completed under the operating condition of shifting from low rotation and high load to high rotation. Is changed from ON to OFF, and after the switching operation of the valve timing adjusting mechanism 70 is completed under the operating condition of shifting from high rotation to low rotation and high load, the electromagnetic switching valve 45 of the valve lift adjusting mechanism 40 is switched from ON to OFF. Also good.

As a result, the valve timing adjusting mechanism 7
It is possible to ensure that there is a time difference between 0 and the operation end timing of the valve lift adjusting mechanism 40. In the valve timing adjusting mechanism 70, the electromagnetic switching valve 79 is actually turned from ON to OFF.
It takes a maximum of about 1 second until the operation is completed after the switching to No. 1, but the valve timing adjusting mechanism 70 has a predetermined time of one second or more after the electromagnetic switching valve 79 is switched from ON to OFF. After a lapse of time, the electromagnetic switching valve 45 of the valve lift adjusting mechanism 40 may be switched from ON to OFF.

[0050]

As described above, according to the present invention, the intake side camshaft for opening and closing the intake valve, the valve timing adjusting mechanism for changing the phase angle of the intake side camshaft with respect to the crankshaft, and the plurality of profiles having different profiles from each other. Lift valve, a valve lift adjusting mechanism that switches the cam that opens and closes the intake valve, a means that detects the operating condition of the engine, and a control means that drives the valve timing adjusting mechanism and the valve lift adjusting mechanism according to the operating condition of the engine. And a control means for delaying the opening / closing timing of the intake valve via a valve timing adjusting mechanism at the time of low rotation and low load, and for lifting the intake valve via the valve lift adjusting mechanism. The amount is reduced and the intake valve opening / closing timing is advanced through the valve timing adjustment mechanism during low rotation and high load. At the same time, the lift amount of the intake valve is reduced via the valve lift adjustment mechanism, the opening / closing timing of the intake valve is delayed via the valve timing adjustment mechanism at high rotation speed, and the lift amount of the intake valve is reduced via the valve lift adjustment mechanism. Since the configuration is increased, the valve lift characteristic of the intake valve can be appropriately controlled over a wide operating range, and it is possible to improve the torque at low and medium speeds and improve the output at high speeds.

According to the second aspect of the present invention, the valve timing characteristic and the valve lift are changed because the valve timing adjusting mechanism and the valve lift adjusting mechanism are switched with a time lag during the operation for changing the valve lift characteristic of the intake valve. By changing the characteristics stepwise, it is possible to reduce the torque shock of the engine that occurs at the time of switching.

According to the third aspect of the invention, the valve lift adjusting mechanism is first switched and operated, and then the valve timing adjusting mechanism is switched and operated under the operating condition of transition from low rotation and high load to high rotation. Under the operating condition that shifts from rotation to low rotation and high load, the valve timing adjustment mechanism is first switched and then the valve lift adjustment mechanism is switched and operated, so acceleration response is enhanced and deceleration is rapidly performed. The shock can be alleviated.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing control contents for switching valve lift characteristics in an embodiment of the present invention.

FIG. 2 is a mechanical configuration diagram showing an embodiment of the present invention.

FIG. 3 is a sectional view taken along line XX of FIG.

FIG. 4 is a switching characteristic diagram of valve lift characteristics.

[Explanation of symbols]

 40 Valve Lift Adjusting Mechanism 45 Electromagnetic Intake Valve 51 Control Unit 70 Valve Timing Adjusting Mechanism 79 Electromagnetic Switching Valve

Claims (4)

[Claims] 1. An intake side camshaft for opening / closing driving an intake valve, a valve timing adjusting mechanism for changing a phase angle of the intake side camshaft with respect to a crankshaft, a plurality of cams having different profiles, and an opening / closing drive for the intake valve. Variable valve operating mechanism provided with a valve lift adjusting mechanism for switching the cams to be operated, means for detecting the operating condition of the engine, and control means for driving the valve timing adjusting mechanism and the valve lift adjusting mechanism according to the operating condition of the engine. In the device, the control means delays the opening / closing timing of the intake valve via the valve timing adjusting mechanism at the time of low rotation and low load, and reduces the lift amount of the intake valve via the valve lift adjusting mechanism to reduce the low rotation and high load. At the same time as advancing the opening and closing timing of the intake valve via the valve timing adjustment mechanism,
The lift amount of the intake valve is reduced via the valve lift adjustment mechanism, the opening / closing timing of the intake valve is delayed via the valve timing adjustment mechanism at high revolutions, and the lift amount of the intake valve is increased via the valve lift adjustment mechanism. A variable valve operating system for an engine, which is characterized in that it has a structure. 2. The control means is configured to switch the valve timing adjusting mechanism and the valve lift adjusting mechanism with a time lag during the operation of switching the valve lift characteristic of the intake valve. Variable valve operating system for engine. 3. The control means switches and operates the valve lift adjusting mechanism first and then the valve timing adjusting mechanism under the operating condition of shifting from low rotation and high load to high rotation. 3. The variable valve operating valve for an engine according to claim 2, wherein the valve timing adjusting mechanism is first switched and then the valve lift adjusting mechanism is switched and operated under an operating condition that shifts to a low rotation and high load. apparatus. 4. The control means switches the valve timing adjusting mechanism after the switching operation of the valve lift adjusting mechanism is completed under an operating condition of transitioning from low rotation and high load to high rotation, and switches the valve timing adjusting mechanism to switch from high rotation to low rotation. 4. The variable valve operating system for an engine according to claim 3, wherein the valve lift adjusting mechanism is switched after the switching operation of the valve timing adjusting mechanism is completed under an operating condition that shifts to a high rotational load.