JPH06235307A - Variable valve timing device for engine - Google Patents

Abstract

PURPOSE:To stabilize combustion and reduce fuel consumption by delaying opening/closing timings of an intake valve while advancing an exhaust valveduring low speed and low load operation time, advancing the opening/ closing timings of both the intake valve and the exhaust valve during low speed and high load operation time, and delaying the opening/closing timing of both the intake valve and the exhaust valve during high speed operation time. CONSTITUTION:Valve timing mechanisms 1i, 1e are arranged between cam shafts 2i, 2e and cam pulleys 3i, 3e, while opening/closing timings of an exhaust valve is independently varied while varying phase angles. The valve timing adjust mechanism 1i of an intake valve is, for instance, provided with an inner housing 4i, an outer housing, a helical gear 6i, and a spline 17i. With the engagement thereof, a positional angle of the cam shaft 2i is varied in a rotational direction in respect to the cam pulley 3i. Such driving is performed by opening/ closing of a solenoid valve 7i which is controlled according to an operation condition by means of a control unit 31, with a hydraulic pressure in a hydraulic chamber 12i being varied. The same is true for the valve timing mechanism 1e of the exhaust valve.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable valve timing device for controlling the opening / closing timing of intake / exhaust valves in accordance with engine operating conditions by changing the phase angle of a camshaft with respect to a crankshaft.

[0002]

2. Description of the Related Art As a variable valve timing device of this type, as shown in, for example, Japanese Utility Model Application Laid-Open No. 2-72305, a cam pulley and a cam shaft are connected via a helical gear that responds to hydraulic pressure to form a helical gear. There is a valve timing adjusting mechanism that moves the helical gear in the direction of the rotation axis and controls the crankshaft and the camshaft to rotate relative to each other by controlling the hydraulic pressure acting on the gear according to the operating state of the engine.

Conventionally, however, such a valve timing adjusting mechanism is provided only on the intake side camshaft, and by reducing the valve overlap at low rotation and low load, the residual gas ratio is reduced and combustion is stabilized. ,
By advancing the opening and closing timing of the intake valve at low rotation and high load, it is possible to suppress the mixture mixture drawn into the cylinder from being discharged to the intake port near the bottom dead center of the intake stroke, thereby improving the intake charging efficiency. ing.

However, in such a device that adjusts only the opening / closing timing of the intake valve, for example, the closing timing of the intake valve is advanced at low rotation and high load, so that if the opening / closing timing is advanced, the valve overlap becomes too large. However, the residual gas ratio increases and the combustibility is impaired. Further, it is impossible to delay the opening / closing timing of the intake valve while increasing the valve overlap at the time of high rotation, so that there is a problem that a sufficient output cannot be obtained.

Further, conventionally, there is known a device for controlling the intake / exhaust timing or the intake / exhaust amount, which is provided with a valve operation adjusting mechanism for selectively switching a plurality of cams according to engine operating conditions. In this case, it is necessary to provide a valve operation adjusting mechanism for switching the cam corresponding to the intake / exhaust valve of each cylinder, which causes a problem of cost increase (for example, Japanese Patent Laid-Open Nos. 63-167016 and 63-167016). 63-57
805, etc.).

It is an object of the present invention to provide a device for controlling intake / exhaust timing by using a valve timing adjusting mechanism for changing a phase angle of a camshaft with respect to a crankshaft, focusing on the above problems.

[0007]

According to the present invention, there are provided an intake side camshaft for opening and closing an intake valve, an exhaust side camshaft for opening and closing an exhaust valve, an intake side camshaft and an exhaust side camshaft with respect to a crankshaft. A variable valve timing device for an engine, comprising a valve timing adjusting mechanism for independently changing a phase angle, a means for detecting an engine operating condition, and a control means for driving the valve timing adjusting mechanism according to the engine operating condition. Therefore, the control means delays the opening and closing timing of the intake valve at low rotation and low load, advances the opening and closing timing of the exhaust valve, and advances the opening and closing timing of the intake valve at low rotation and high load, and the opening and closing timing of the exhaust valve. The valve timing adjustment mechanism to delay the opening / closing timing of the intake valve and the opening / closing timing of the exhaust valve at high rotation speed. A configuration in which dynamic.

According to the second aspect of the present invention, in the valve timing adjusting mechanism, the maximum displacement amount of the phase angle of the intake side camshaft with respect to the crankshaft is set smaller than the maximum displacement amount of the phase angle of the exhaust side camshaft.

According to a third aspect of the present invention, an intake side hydraulic actuator that changes the phase angle of the intake side camshaft with respect to the crankshaft in a direction in which the opening / closing timing of the intake valve advances in response to a rise in hydraulic pressure, and the intake side hydraulic actuator when it is not energized An intake-side solenoid valve that lowers the hydraulic pressure that is guided to the hydraulic hydraulic actuator, and an exhaust-side hydraulic actuator that changes the phase angle of the exhaust-side camshaft with respect to the crankshaft so that the opening / closing timing of the exhaust valve is delayed in response to the increase in hydraulic pressure. An exhaust side solenoid valve that reduces the hydraulic pressure guided to the exhaust side hydraulic actuator when the power is not supplied.

According to a fourth aspect of the present invention, there is provided control means for switching the opening / closing timing of the exhaust valve after switching the opening / closing timing of the intake valve under operating conditions that change from low rotation and high load to high rotation.

[0011]

[Function] By advancing the opening / closing timing of the exhaust valve and delaying the opening / closing timing of the intake valve to reduce the valve overlap at the time of low rotation and low load, the blowback of the exhaust gas from the exhaust port to the cylinder is suppressed, and the residual The gas ratio is lowered to stabilize combustion, and idle stability is enhanced, thereby reducing fuel consumption.

By advancing the opening / closing timing of the intake valve at low rotation and high load, it is possible to suppress the mixture mixture sucked into the cylinder from being discharged to the intake port near the bottom dead center of the intake stroke, thereby improving the intake charge efficiency. Can be increased. At this time, the opening / closing timing of the exhaust valve is also advanced to prevent the valve overlap from becoming too large, reduce the residual gas, and increase the generated torque.

By delaying the opening / closing timing of the intake valve at the time of high rotation, it is possible to enhance the intake charging efficiency by utilizing the inertia supercharging effect of intake air.

According to the second aspect of the present invention, the maximum displacement amount of the phase angle of the intake side camshaft with respect to the crankshaft is set smaller than the maximum displacement amount of the phase angle of the exhaust side camshaft. The valve overlap can be increased at the time of high rotation in which both the opening and closing timings of the valves are delayed. As a result, the negative pressure wave generated in the exhaust pipe provides the scavenging effect of the exhaust gas, which reduces the extrusion loss of the exhaust gas and improves 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.

According to the third aspect of the present invention, the hydraulic pressure introduced to the valve timing adjusting mechanism is reduced to delay the opening / closing timing of the intake valve and advance the opening / closing timing of the exhaust valve. Therefore, it is possible to secure the switching responsiveness that reduces the valve overlap when the discharge oil pressure of the oil pump is low and at low rotation and low load, and it is possible to maintain the startability and idle stability. Also,
If sufficient hydraulic pressure is not generated due to a hydraulic system failure,
Stable drivability can be ensured by delaying the opening / closing timing of the intake valve and advancing the opening / closing timing of the exhaust valve to reduce the valve overlap.

According to the fourth aspect of the present invention, the two opening / closing timings of the exhaust valve are changed after the opening / closing timing of the intake valve is changed under the operating condition changing from low rotation / high load to high rotation. Is simultaneously energized to prevent an oil hammering action in which the hydraulic pressure introduced to each valve timing adjustment mechanism is momentarily increased, and damage to the lubrication system is prevented.

[0017]

FIG. 2 shows the mechanical structure of an embodiment of the present invention.

In the figure, 2i is a cam shaft for opening and closing an intake valve (not shown), 2e is a cam shaft for opening and closing an exhaust valve (not shown), 3i and 3e are crankshafts via a timing belt 16. It is a cam pulley to which the rotational force from (not shown) is transmitted.

The valve timing adjusting mechanisms 1i and 1e are provided between the camshafts 2i and 2e and the cam pulleys 3i and 3e, respectively, and the phase angle between the camshafts 2i and 2e is changed according to operating conditions to open and close the intake valve and the exhaust valve. To change independently.

At the ends of the camshafts 2i and 2e, the cylindrical inner housings 4i and 4e are attached to the bolts 15i and 15 respectively.
It is concluded via e.

Cylindrical outer housings 5i and 5e are rotatably fitted to the outer circumferences of the inner housings 4i and 4e, and the cam pulleys 3i and 3e are integrally formed on the outer housings 5i and 5e.

Ring-shaped helical gears 6i, 6e are interposed between the inner housings 4i, 4e and the outer housings 5i, 5e. The helical splines 17i and 18i are formed on the inner and outer circumferences of the helical gear 6i, and the helical splines 17e and 18e are formed on the inner and outer circumferences of the helical gear 6e. Each helical spline 17i,
17e meshes with the outer circumferences of the inner housings 4i, 4e,
The helical splines 18i and 18e mesh with the inner circumferences of the outer housings 5i and 5e, and the helical gears 6i and 6e.
As the e moves in the axial direction, each outer housing 5
The inner housings 4i, 4e rotate relative to the i, 5e, and the phase angle in the rotational direction of the cam shafts 2i, 2e with respect to the cam pulleys 3i, 3e changes.

The helical splines 17e and 18e of the helical gear 6e are formed by being twisted in opposite directions with respect to the helical splines 17i and 18i of the helical gear 6i. As a result, the helical gears 6i and 6e rotate in opposite directions by moving in the right direction in the figure against the return springs 13i and 13e from the desired positions, and the intake side camshaft 2i opens and closes the intake valve. And the exhaust side camshaft 2e rotates in a direction to retard the opening / closing timing of the exhaust valve.

Each return spring 13 is provided between each helical gear 6i, 6e and each inner housing 4i, 4e.
i, 13e are interposed, each return spring 13i,
The helical gears 6i and 6e are biased leftward in the figure by 13e and are held at the initial positions.

Hydraulic chambers 12i and 12e are defined between the inner housings 4i and 4e, the outer housings 5i and 5e and the helical gears 6i and 6e. Hydraulic chamber 12i, 12
When the hydraulic pressure introduced to e rises above a predetermined value, the helical gears 6i, 6e move to the return springs 12i, 1e.
While moving 2e, it moves to the right in the figure.

As a result, when the helical gears 6i and 6e are in the initial positions, the intake valve opening / closing timing is delayed and the exhaust valve opening / closing timing is advanced, as shown by the solid line in FIG. When 6i and 6e are displaced to the maximum, the opening / closing timing of the intake valve is advanced and the opening / closing timing of the exhaust valve is delayed as shown by the broken line in FIG.

The maximum displacement θi of the phase angle of the intake camshaft 2i with respect to the crankshaft is set smaller than the maximum displacement θe of the phase angle of the exhaust camshaft 2e by a predetermined amount.

The hydraulic chambers 12i, 12e are respectively provided with shaft holes 21i, 21e formed inside the camshafts 2i, 2e.
And the oil gallery 2 formed on the cylinder head 22.
The hydraulic pressure discharged from the oil pump 29 is introduced through the nozzle 3, the orifice 26, and the main gallery 25 formed in the cylinder block 24.

At the other ends of the camshafts 2i and 2e, solenoid valves 7i and 7e are opened / closed according to engine operating conditions.
Is provided. When the solenoid valves 7i, 7e are not energized, the shaft holes 21i, 21e are opened as shown in the figure to open the hydraulic chambers 12i, 1e.
2e reduces the hydraulic pressure introduced to each shaft hole 21 when energized.
i and 21e are closed to increase the hydraulic pressure introduced to the hydraulic chambers 12i and 12e.

An energization control unit 31 for controlling energization of each solenoid valve 7i, 7e is provided as a control means of each valve timing adjusting mechanism 1i, 1e.

The control unit 31 inputs an engine rotation signal, an intake air amount signal, a water temperature signal, a throttle valve switch signal, etc., and controls the energization of each solenoid valve 7i, 7e according to these engine operating conditions. The valve timing adjusting mechanisms 1i and 1e are operated.

As shown in FIG. 1, the control unit 31 controls each solenoid valve 7 during low rotation and low load including idling.
i and 7e are both turned off to delay the opening / closing timing of the intake valve and advance the opening / closing timing of the exhaust valve to minimize the valve overlap in which the intake valve and the exhaust valve open simultaneously, and to reduce electromagnetic interference at low rotation and high load. Turn on the valve 7i to turn on the solenoid valve 7
By turning off e, advancing the opening / closing timing of the intake valve and advancing the opening / closing timing of the exhaust valve, the valve overlap is set to an intermediate value, the solenoid valve 7i is turned off at high rotation, and the solenoid valve 7e is turned on. Each valve timing adjusting mechanism 1 delays the opening / closing timing of the intake valve and delays the opening / closing timing of the exhaust valve to increase the valve overlap.
Drive i, 1e.

The control unit 31 stops energization of at least one of the intake side solenoid valve 7i and the exhaust side solenoid valve 7e during the operation of switching the opening / closing timing of the intake valve or the exhaust valve. That is, when switching from the low rotation and high load state where the solenoid valve 7i is turned on to the high rotation state where the solenoid valve 7e is turned on, the solenoid valve 7i is turned off first and then the solenoid valve 7e is turned on. To do. On the contrary, when the electromagnetic valve 7e is turned on at a high rotation speed and the electromagnetic valve 7i is turned on at a low rotation and high load at a predetermined time difference, the electromagnetic valve 7e is turned off first, Solenoid valve 7 with a time difference of
Turn i on.

Next, the operation will be described.

By minimizing the valve overlap at low rotation and low load, blowback of exhaust gas from the exhaust port to the cylinder can be suppressed and the residual gas ratio can be reduced. As a result, combustion is stabilized, fuel consumption is reduced, and idle stability is enhanced.

Further, each valve timing adjusting mechanism 1i,
1e is an initial position where the hydraulic pressure introduced to the hydraulic chambers 12i, 12e decreases, and delays the opening / closing timing of the intake valve,
Since the exhaust valve opening / closing timing is advanced, switching responsiveness can be secured during low rotation and low load when the discharge hydraulic pressure of the oil pump is low, including during startup, and startability and idle stability can be maintained. . Also, when sufficient hydraulic pressure is not generated due to a hydraulic system failure, the intake valve opening / closing timing is delayed and the exhaust valve opening / closing timing is advanced to reduce valve overlap and ensure stable operability. can do.

By advancing the opening / closing timing of the intake valve at low rotation and high load, it is possible to suppress the mixture mixture sucked into the cylinder from being discharged to the intake port near the bottom dead center of the intake stroke, thereby improving the intake charging efficiency. Can be increased. At this time, the opening / closing timing of the exhaust valve is also advanced to prevent the valve overlap from becoming too large, reduce the residual gas, and increase the generated torque.

By delaying the opening / closing timing of the intake valve at the time of high rotation, the intake supercharging efficiency can be improved by utilizing the inertia supercharging of the intake air.

Since the maximum displacement θi of the phase angle of the intake camshaft 2i with respect to the crankshaft is set to be smaller than the maximum displacement θe of the phase angle of the exhaust camshaft 2e by a predetermined amount, the intake valve and the exhaust valve are It is possible to increase the valve overlap at the time of high rotation in which both the opening and closing timings of are delayed. By increasing the valve overlap at the time of high rotation, the scavenging effect by the negative pressure wave generated in the exhaust pipe is obtained, and the output loss is reduced by reducing the extrusion loss of the exhaust. That is, in the latter half of the exhaust stroke, 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,
Exhaust gas scavenging effect is enhanced.

During operation for switching the opening / closing timing of the intake valve or the exhaust valve, the energization of at least one of the intake side solenoid valve 7i and the exhaust side solenoid valve 7e is stopped, so that the intake side solenoid valve 7i and the exhaust side solenoid valve 7e are simultaneously operated. This prevents the oil hammering action in which the oil pressure is energized and guided to each valve timing adjusting mechanism 1i, 1e is momentarily increased to prevent the lubricating system from being damaged.

[0041]

As described above, according to the present invention, the intake side camshaft that opens and closes the intake valve, the exhaust side camshaft that opens and closes the exhaust valve, the intake side camshaft and the exhaust side camshaft with respect to the crankshaft. Variable valve timing apparatus including a valve timing adjusting mechanism that independently changes the phase angle of the engine, a unit that detects an operating condition of the engine, and a control unit that drives the valve timing adjusting mechanism according to the operating condition of the engine Therefore, the control means delays the opening / closing timing of the intake valve at the time of low rotation and low load, advances the opening / closing timing of the exhaust valve, advances the opening / closing timing of the intake valve at low rotation and high load, and opens / closes the exhaust valve. A valve timing adjuster that advances the timing and delays the opening / closing timing of the intake valve at the time of high rotation and delays the opening / closing timing of the exhaust valve. Because it is configured to be driven and to properly control the timing of intake and exhaust over a wide operating range,
It is possible to improve the torque at low and medium speeds and the output at high speeds. Further, as compared with a conventional device including a valve operation adjusting mechanism that selectively switches a plurality of cams in accordance with engine operating conditions, the same performance can be obtained while a significant cost reduction is achieved.

According to the second aspect of the present invention, the maximum displacement amount of the phase angle of the intake side camshaft with respect to the crankshaft is set smaller than the maximum displacement amount of the phase angle of the exhaust side camshaft, whereby the intake valve and the exhaust gas are exhausted. The valve overlap can be increased at the time of high rotation in which both the opening and closing timings of the valves are delayed. As a result, the negative pressure wave generated in the exhaust pipe provides the scavenging effect of the exhaust gas, which reduces the extrusion loss of the exhaust gas and improves the output.

According to the third aspect of the present invention, the hydraulic pressure introduced to the valve timing adjusting mechanism is reduced to delay the opening / closing timing of the intake valve and advance the opening / closing timing of the exhaust valve. Therefore, it is possible to secure the switching responsiveness that reduces the valve overlap at the time of low rotation and low load when the discharge hydraulic pressure of the oil pump is low, and it is possible to maintain startability and idle stability. Also,
If sufficient hydraulic pressure is not generated due to a hydraulic system failure,
Stable drivability can be ensured by delaying the opening / closing timing of the intake valve and advancing the opening / closing timing of the exhaust valve to reduce the valve overlap.

According to the fourth aspect of the present invention, the two opening / closing timings of the exhaust valve are changed after the opening / closing timing of the intake valve is changed under the operating condition changing from low rotation / high load to high rotation. Is simultaneously energized to prevent an oil hammering action in which the hydraulic pressure introduced to each valve timing adjustment mechanism is momentarily increased, and damage to the lubrication system is prevented.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing control contents for switching valve timings 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 characteristic diagram of valve timing switching.

[Explanation of symbols]

 1i Valve timing adjusting mechanism 1e Valve timing adjusting mechanism 2i Intake side camshaft 2e Exhaust side camshaft 7i Intake side solenoid valve 7e Exhaust side solenoid valve 12i Hydraulic chamber 12e Hydraulic chamber 13i Return spring 13e Return spring 31 Control unit

Claims (4)

[Claims] Claim: What is claimed is: 1. An intake side camshaft that opens and closes an intake valve, an exhaust side camshaft that opens and closes an exhaust valve, and a valve that independently changes the phase angles of the intake side camshaft and the exhaust side camshaft with respect to a crankshaft. A variable valve timing device for an engine, comprising: a timing adjusting mechanism; a means for detecting an operating condition of the engine; and a control means for driving the valve timing adjusting mechanism according to the operating condition of the engine. The intake valve opening and closing timing is delayed when the rotation speed is low, and the exhaust valve opening and closing timing is advanced, and the intake valve opening and closing timing is advanced when the low rotation and high load is applied, and the exhaust valve opening and closing timing is advanced. The valve timing adjustment mechanism is driven so that the opening / closing timing of the valve is delayed and the opening / closing timing of the exhaust valve is delayed. A variable valve timing device for the engine to be considered. 2. The valve timing adjusting mechanism sets the maximum displacement amount of the phase angle of the intake side camshaft with respect to the crankshaft smaller than the maximum displacement amount of the phase angle of the exhaust side camshaft. Variable valve timing device for the engine described. 3. An intake-side hydraulic actuator that changes the phase angle of the intake-side camshaft with respect to the crankshaft in a direction in which the opening / closing timing of the intake valve advances in response to an increase in hydraulic pressure, and is guided to the intake-side hydraulic actuator when it is not energized. An intake-side solenoid valve that lowers the oil pressure, an exhaust-side hydraulic actuator that changes the phase angle of the exhaust-side camshaft with respect to the crankshaft so that the opening / closing timing of the exhaust valve is delayed in response to an increase in the hydraulic pressure, and the exhaust-side hydraulic actuator when it is not energized. The variable valve timing device for an engine according to claim 1, further comprising an exhaust-side solenoid valve that lowers a hydraulic pressure guided to a hydraulic actuator. 4. The control means for switching the opening / closing timing of the exhaust valve after switching the opening / closing timing of the intake valve under operating conditions changing from low rotation and high load to high rotation. Variable valve timing device for engines.