JP3123377B2 - Variable valve train for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable valve apparatus for variably controlling a valve lift characteristic of an intake valve or an exhaust valve of an internal combustion engine (both are generally referred to as intake and exhaust valves) in accordance with engine operating conditions. .

[0002]

2. Description of the Related Art In general, a valve train for an internal combustion engine transmits a cam lift to intake and exhaust valves via a rocker arm and a swing arm, and pushes open and exhaust valves urged in a closing direction by a valve spring. However, since, for example, preferable valve lift characteristics are different between a low-speed region and a high-speed region of the engine, various variable valve operating devices capable of switching the valve lift characteristics depending on operating conditions have been proposed. One example is disclosed in, for example, JP-A-63-167016.
In Japanese Unexamined Patent Application Publication No. H10-207, a low-speed cam and a high-speed cam having different profiles are arranged side by side on a camshaft, and a driven main rocker arm and a sub-rocker arm are switched to a connected state or a disconnected state as necessary. Configurations are known. In general, a high-speed cam is set to have both a larger cam lift and a longer valve opening period than a low-speed cam.

[0003] In addition, some variable valve actuating devices using a valve timing adjustment mechanism for delaying the valve timing of opening and closing the intake and exhaust valves by changing the phase of the camshaft with respect to the crankshaft have been conventionally used. Has been put to practical use. That is, in this case, the operating center angle (the crank angle that is the center between the opening timing and the closing timing) changes without changing the shape of the valve lift characteristic.

[0004] Further, there has also been proposed a variable valve actuation device in which a former valve lift adjusting mechanism by cam switching and a latter valve timing adjusting mechanism are combined. By combining the two, the valve lift can be changed in magnitude, and at the same time, the opening timing and the closing timing can be variably controlled, so that the requirements can be further adapted to the requirements under each operating condition.

[0005]

The variable valve mechanisms such as the valve lift adjustment mechanism and the valve timing adjustment mechanism described above are generally of a hydraulic drive type, and apply a lubricating oil pressure of the internal combustion engine to an actuator section. It is switched by supplying or stopping.

[0006] If the temperature of the lubricating oil becomes excessively high, the viscosity of the lubricating oil decreases, and the hydraulic pressure supplied to the actuator unit decreases, so that normal operation may not be guaranteed. Therefore, when the oil pressure of the lubricating oil becomes lower than the predetermined oil pressure, the supply of the oil pressure to the variable valve mechanism is prohibited,
It has been proposed to keep the variable valve mechanism in an initial state regardless of operating conditions (for example, Japanese Patent Publication No. 5-240).
No. 8).

However, in an internal combustion engine having a plurality of variable valve mechanisms such as the above-described valve lift adjustment mechanism and valve timing adjustment mechanism, the supply of hydraulic pressure to each variable valve mechanism is suddenly stopped as the oil pressure decreases. If so, an extremely large torque change occurs as a whole, and there is a possibility that the driver may feel uncomfortable.

In particular, when the mechanism for changing the valve lift characteristics in a stepwise manner by switching between a high-speed cam and a low-speed cam is unexpectedly switched, a sense of step occurs in the torque.

[0009]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a plurality of variable valves which continuously or stepwise change the valve lift characteristics of an intake valve or an exhaust valve in response to supply and stop of hydraulic pressure to an actuator. Mechanism, a plurality of hydraulic control valves for respectively controlling hydraulic pressure supply to the actuator section of each variable valve mechanism, control means for outputting a control signal to each hydraulic control valve according to engine operating conditions, and lubrication of the internal combustion engine. A variable valve actuation device for an internal combustion engine, comprising: hydraulic pressure detecting means for detecting a hydraulic pressure; and hydraulic supply inhibiting means for inhibiting hydraulic pressure supply by the hydraulic control valve when the detected hydraulic pressure is lower than a set hydraulic pressure. In the plurality of variable valve mechanisms, for the plurality of variable valve mechanisms that may be supplied with hydraulic pressure under the same engine operating condition, the set hydraulic pressures are different from each other. It is a symptom.

[0010] In particular, according to the second aspect of the present invention, the set hydraulic pressure of the variable valve mechanism in which the valve lift characteristic changes continuously is set higher than the set hydraulic pressure of the variable valve mechanism in which the valve lift characteristic changes stepwise. .

According to the third aspect of the present invention, while the oil pressure is lower than the set oil pressure of the variable valve mechanism in which the valve lift characteristic continuously changes, the valve lift characteristic of the variable valve mechanism changes stepwise. Switching from the hydraulic stop state to the hydraulic supply state was prohibited.

The variable valve mechanism in which the valve lift characteristic continuously changes is, for example, a valve timing adjusting mechanism that changes the phase of a camshaft with respect to a crankshaft. The variable valve mechanism that changes stepwise is, for example, a valve lift adjustment mechanism that transmits a lift of one of a low-speed cam and a high-speed cam to an intake / exhaust valve.

According to the fifth aspect of the present invention, a variable valve mechanism is provided for each of the intake valve and the exhaust valve, and the set hydraulic pressure of the variable valve mechanism on the exhaust side is set by the variable valve mechanism on the intake side. It was set higher than the oil pressure.

[0014]

According to the first aspect of the present invention, if the lubricating oil pressure is excessively reduced while the hydraulic pressure is being supplied to the actuator section of each variable valve mechanism, the supply of the hydraulic pressure to each variable valve mechanism is prohibited, Although the lift characteristics will change, the set hydraulic pressures for inhibiting the supply of hydraulic pressure are different from each other, and the inhibition of the supply of hydraulic pressure is sequentially executed by each variable valve mechanism. In other words,
The plurality of variable valve mechanisms do not switch at the same time as the oil pressure decreases, and the change in torque is reduced.

[0015] In particular, according to the second aspect of the present invention, when the hydraulic pressure decreases,
First, the supply of hydraulic pressure to the variable valve mechanism in which the valve lift characteristic changes continuously is cut off, and then the supply of hydraulic pressure to the variable valve mechanism in which the valve lift characteristic changes stepwise is cut off. When the valve lift characteristic changes, the output of the internal combustion engine decreases.If the decrease in oil pressure is caused by an increase in oil temperature, the oil temperature decreases due to the first stop of oil pressure supply to the variable valve mechanism, and the oil pressure decreases. May recover. When the hydraulic pressure is recovered in this way, switching of the variable valve mechanism in which the valve lift characteristics change stepwise is avoided.

According to the third aspect of the present invention, when the hydraulic valve is stopped at the variable valve mechanism in which the former valve lift characteristic continuously changes, the latter valve lift characteristic changes stepwise. When the hydraulic pressure is not supplied to the mechanism, the supply of the hydraulic pressure is not started even if the operating condition changes.

According to a fourth aspect of the present invention, there is provided a valve timing adjusting mechanism.
By changing the phase of the camshaft with respect to the crankshaft, the valve lift characteristics are changed stepwise. The valve lift adjusting mechanism changes the valve lift characteristics in a stepwise manner by selectively transmitting either one of the low-speed cam and the high-speed cam to the intake / exhaust valve.

According to the fifth aspect of the present invention, when the hydraulic pressure decreases,
First, the supply of hydraulic pressure to the variable valve mechanism on the exhaust side, which has little effect on torque, is cut off, and then the supply of hydraulic pressure to the variable valve mechanism on the intake side is cut off.

[0019]

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

FIG. 1 shows an embodiment of a variable valve apparatus in which a valve lift adjusting mechanism 40 and a valve timing adjusting mechanism 70 are provided as variable valve operating mechanisms on the intake valve 9 side.

First, the valve lift adjusting mechanism 40 will be described. As shown in FIGS. 2 and 3, each cylinder is provided with one main rocker arm 1 corresponding to a pair of intake valves 9. The base end of the main rocker arm 1 is swingably supported by a cylinder head 69 via a main rocker shaft 3 common to each cylinder. An adjusting screw 10 that is in contact with the stem top of each intake valve 9 is fastened to the tip of the main rocker arm 1 via a nut 11.

The main rocker arm 1 has a shaft 13
The roller 14 is rotatably supported via a needle bearing, and the low-speed cam 21 is in contact with the roller 14.

The main rocker arm 1 is formed in a substantially rectangular shape in plan view, and the sub rocker arm 2 is provided in an opening formed alongside the roller 14. The base end of the sub rocker arm 2 is connected to the main rocker arm 1 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, while being press-fitted into a hole 18 formed in the main rocker arm 1.

The sub rocker arm 2 does not have a portion that comes into contact with the intake valve 9, and as shown in FIG. 3, a cam follower portion 23 that slides on the high-speed cam 22 is formed at the tip thereof in a circular arc shape, and is formed thereunder. On the side, a lost motion spring 25 for pressing the cam follower portion 23 against the high-speed cam 22 is interposed.

A lost motion spring 25 is located on the main rocker arm 1 immediately below the sub rocker arm 2.
Are formed integrally with each other. The lower end of the coiled lost motion spring 25 has a concave portion 26.
Of the sub rocker arm 2 via a retainer 27 that slidably fits into the recess 26.

The low-speed cam 21 and the high-speed cam 22 are integrally formed on a common camshaft 72, and have different shapes (sizes) so as to satisfy the valve lift characteristics required when the engine is running at a low speed and at a high speed. Are also included. In this embodiment, as shown in FIG. 5, the high-speed cam 22 has a profile in which both the valve lift and the operating angle (valve opening period) are larger than the low-speed cam 21.

To properly connect the two rocker arms 1 and 2, plungers 33, 31, and 34 are slidably fitted over the main rocker arm 1 and the sub rocker arm 2. A hydraulic passage 43 is connected to the rear of the plunger 33 serving as an actuator section.
A return spring 38 is provided behind the back.

When the operating oil pressure guided from the hydraulic passage 43 is low, the plungers 33 and 31 are respectively accommodated in the sub rocker arm 2 and the main rocker arm 1 by the urging force of the return spring 38, so that the swinging of both is not restrained. That is, both are in the detached state. On the other hand, when the operating oil pressure guided 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 integrally formed. Rocks.

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

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

As shown in FIG. 4, a cylindrical inner housing 65 is fixed to an end of the camshaft 72 via a bolt 64. A cylindrical outer housing 63 rotatably fitted to the outer periphery of 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. The helical gear 73 has helical splines formed on the inner and outer circumferences. Each helical spline meshes with the outer circumference of the inner housing 65 and the inner circumference of the outer housing 63, and when the helical gear 73 moves in the axial direction, the outer housing 63 Inner housing 6
5, the phase of the cam shaft 72 with respect to the cam pulley 71 changes.

A hydraulic chamber 75 is defined between the inner housing 65, the outer housing 63, and the helical gear 73, which are actuator portions. When the hydraulic pressure guided to the hydraulic chamber 75 rises above a predetermined value, the helical gear 73
Moves from the initial position in the axial direction against the return spring 74, so that the camshaft 72 rotates in a direction to advance the opening / closing timing of the intake valve 9.

That is, when the helical gear 73 is in the initial position, the opening and closing timing of the intake valve 9 is relatively late as shown in the upper and lower parts of FIG.
Is maximized, the opening / closing timing of the intake valve 9 is relatively advanced, as shown in the middle part of FIG.

The hydraulic chamber 75 includes a shaft hole 78 formed in the camshaft 72, an oil gallery 59 formed in the cylinder head 69, an orifice 77, and a main gallery 58 formed in the cylinder block 68. Through this, the discharge oil pressure from the oil pump 57 is introduced.

In order to appropriately release the hydraulic pressure, an electromagnetic switching valve 79 is provided at the other end of the camshaft 72, and is controlled to open and close according to engine operating conditions.
The electromagnetic switching valve 79 opens the shaft hole 78 as shown in the drawing when the electric power is not supplied to reduce the hydraulic pressure guided to the hydraulic chamber 75, and closes the shaft hole 78 when the electric power is supplied to increase the hydraulic pressure guided to the hydraulic chamber 75. ing.

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

The control unit 51 receives an engine rotation signal, an engine load signal, a cooling water temperature signal, a supercharging pressure signal of intake air from a supercharger, a lubricating oil temperature, and the like. The switching of the valve lift characteristics is performed smoothly while suppressing the rapid fluctuation of the valve lift characteristics.

Further, at an appropriate position in the lubrication system of the internal combustion engine,
An oil pressure sensor 80 for detecting the lubricating oil pressure is provided,
The detection signal is input to the control unit 51. The lubricating oil pressure may not be directly detected as described above, but may be indirectly estimated from other parameters.

Further, a warning light 81 is provided to call the driver's attention when the oil pressure drops.

Next, the operation of the above embodiment will be described.

FIG. 5 is an explanatory view showing the control state of the valve lift adjusting mechanism 40 and the valve timing adjusting mechanism 70 with respect to the engine operating conditions. As shown in FIG. The cam 22 is selected, and the valve timing adjusting mechanism 70 controls the opening / closing timing to be delayed. This increases the valve overlap. The electromagnetic switching valve 45 of the valve lift adjustment mechanism 40
ON corresponds to the high-speed cam 22 and OFF corresponds to the low-speed cam 21. The valve timing adjusting mechanism 70
ON of the electromagnetic switching valve 79 of the
Correspond to the lag side, respectively. That is, in the engine high speed range, the electromagnetic switching valve 45 is turned on and the electromagnetic switching valve 79 is turned off.

In the low engine speed region and on the high load side, the electromagnetic switching valve 45 is turned off and the electromagnetic switching valve 79 is turned on, so that the low-speed cam 21 is opened and closed.

Further, in the low engine speed region and on the low load side, both solenoid-operated directional control valves 45 and 79 are turned off, and the low-speed cam 21 and the opening / closing timing are delayed.

When the electromagnetic switching valves 45 and 79 are turned on,
The OFF control is performed based on the engine operating conditions, that is, the engine load and the rotation speed, with reference to a control map given to the control unit 51 in advance. Since the electromagnetic switching valve 45 and the electromagnetic switching valve 79 are controlled based on respective control maps, the rough classification in FIG. 5 shows that both are not turned on at the same time. However, actually, the ON regions partially overlap, and both can be turned ON at the same time.

On the other hand, the control unit 51 constantly monitors whether the lubricating oil pressure is excessively reduced based on the oil pressure detected by the oil pressure sensor 80. When the hydraulic pressure is lower than the set hydraulic pressure, the warning light 81 is turned on and the ON operation of the electromagnetic switching valves 45 and 79 is prohibited.

The flowcharts shown in FIG. 6 and FIG.
This shows a specific control flow. In step 1 of the main flowchart of FIG. 6, the engine operating conditions represented by the engine load and rotation speed are read, and in step 2, the valve timing adjusting mechanism 70, ie, the electromagnetic switching valve It is determined whether or not it is the ON area of No. 79. Here, if it is outside the ON region, the process proceeds to step 3 and the electromagnetic switching valve 79 is turned off. On the other hand, if it is in the ON region, the process proceeds to step 4, and the state of the first permission flag FT based on the hydraulic pressure is determined. As for the permission flag FT, “1” indicates a state in which the ON of the electromagnetic switching valve 79 is permitted, and “0” indicates a state in which the ON is prohibited.
Therefore, only when the permission flag FT is "1" in step 4, the process proceeds to step 5, and the electromagnetic switching valve 79 is turned on. If the permission flag FT is "0", the process proceeds to step 3, where the electromagnetic switching valve 79 is turned off. Similarly, in step 6, the engine operating condition is changed to the valve lift adjusting mechanism 40.
That is, it is determined whether or not it is in the ON region of the electromagnetic switching valve 45,
If it is in the ON region, the electromagnetic switching valve 45 is turned ON on condition that the second permission flag FL is "1" indicating the ON permission state (steps 8 and 9). Otherwise, in step 7, the electromagnetic switching valve 45 is turned off.

The permission flags FT and FL are set according to the flowchart of FIG. That is, the hydraulic pressure P detected by the hydraulic pressure sensor 80 in step 11 is read, and
The set hydraulic pressure P1 and the second set hydraulic pressure P2 are compared with each other in Steps 12 and 16, respectively. When the actual oil pressure P is higher than the first set oil pressure P1, the first permission flag F
T is set to "1" (step 13). When the pressure is equal to or less than the first set hydraulic pressure P1, the first permission flag FT is set to “0”.
(Step 14), and a warning lamp 81 is turned on to notify a decrease in hydraulic pressure (step 15). Similarly, when the actual oil pressure P is higher than the second set oil pressure P2, the second permission flag FL is set to "1" (step 1).
7) If the oil pressure is equal to or less than the second set oil pressure P2, the second permission flag FL is set to "0" (step 18). Here, the valve timing adjusting mechanism 70, that is, the electromagnetic switching valve 79 is turned on.
The first set oil pressure P1, which is the prohibited oil pressure, is set higher than the second set oil pressure P2, which is the ON prohibited oil pressure of the valve lift adjusting mechanism 40, that is, the electromagnetic switching valve 45.

Therefore, in this embodiment, when the oil pressure drops excessively due to an increase in the lubricating oil temperature, the electromagnetic switching valve 79 first returns to the OFF state, and then the electromagnetic switching valve 4
5 returns to the OFF state. Therefore, since the two variable valve mechanisms, that is, the valve timing adjustment mechanism 70 and the valve lift adjustment mechanism 40 are not switched at the same time, a slight time difference is given, so that the torque fluctuation is reduced.

The former valve timing adjusting mechanism 70
Is turned off to change the valve lift characteristics, thereby suppressing the output of the internal combustion engine and preventing the lubricating oil from further rising in oil temperature. Further, a decrease in lubricating oil temperature is promoted. Therefore, when the decrease in oil pressure is caused by an increase in oil temperature, the electromagnetic switching valve 7 of the valve timing adjustment mechanism 70
There is a possibility that the oil pressure may be recovered at the stage when the valve 9 is turned off, and the OF of the electromagnetic switching valve 45
There is a possibility that F operation can be avoided. In particular, the valve timing adjustment mechanism 70 in which the valve lift characteristics continuously change
Is turned off first, so that a sudden change in torque can be further alleviated, and switching of the valve lift adjusting mechanism 40 having a relatively large change in torque can be avoided as much as possible.

FIG. 8 shows another embodiment in which the setting of the permission flags FT and FL is different. In this embodiment, step 21
And reads the oil pressure P detected by the oil pressure sensor 80, and compares it with the first set oil pressure P1 in step 22. Also in this embodiment, the first set oil pressure P1 that is the ON-inhibited oil pressure of the electromagnetic switching valve 79 is set higher than the second set oil pressure P2 that is the ON-inhibited oil pressure of the electromagnetic switching valve 45. If the actual oil pressure P is higher than the first set oil pressure P1, the process proceeds to step 23, where the first permission flag FT and the second permission flag FL are set to "1". When the pressure is equal to or lower than the first set oil pressure P1, the first permission flag FT is set to “0” in step 24, and the warning light 81 is turned on in step 25. Then, in step 26, it is determined whether or not the engine operating condition is in the OFF region of the valve lift adjusting mechanism 40, that is, the electromagnetic switching valve 45.
The permission flag FL is set to “0”. Outside the OFF area, that is, O
If it is in the N range, the hydraulic pressure P is further compared with the second set hydraulic pressure P2 in step 28, and if it is lower than the second set hydraulic pressure P2, the second permission flag FL is set to "0" in step 27.

Accordingly, in this embodiment, when the lubricating oil pressure drops abnormally, the electromagnetic switching valve 79 of the valve timing adjusting mechanism 70 immediately turns off the OF at the stage where P1 ≧ P.
The state returns to the F state, and the output of the internal combustion engine is suppressed. And
The electromagnetic switching valve 45 of the valve lift adjustment mechanism 40 has a value of P1 ≧
While P> P2, as long as the operating conditions do not deviate from the ON region,
Once held in the ON state and once in the OFF region,
Fixed to the FF state. Therefore, there is no possibility that the torque of the internal combustion engine suddenly drops suddenly during high-speed running and gives an uncomfortable feeling. Further, since switching from OFF to ON is prohibited, when P2 ≧ P, O
The possibility of switching from N to OFF is reduced, and unintended torque change can be prevented as much as possible.

As described above, the embodiment in which the present invention is applied to an internal combustion engine having two variable valve mechanisms on the intake side has been described. However, the present invention relates to an internal combustion engine having more variable valve operating mechanisms. Applicable to institutions. In the case where three or more variable valve mechanisms are provided, the set hydraulic pressure may be made different only for those which are likely to be simultaneously turned ON under the same operating conditions.

The present invention can also be applied to a case where variable valve mechanisms are provided on each of the intake side and the exhaust side. FIG.
10 and FIG. 10 show an example of control in the case where variable valve mechanisms are provided on both the intake side and the exhaust side. FIG. 9 is a main flowchart for controlling ON / OFF of the electromagnetic switching valve of the intake-side variable valve mechanism and the electromagnetic switching valve of the exhaust-side variable valve mechanism, and is substantially the same as the flowchart of FIG. Based on the determination of the ON region on the exhaust side (steps 32 and 36) and the determination of the intake side permission flag Fi and the exhaust side permission flag Fe (steps 34 and 38), the ON / OFF of each electromagnetic switching valve is determined. I have decided.

FIG. 10 is a flowchart similar to FIG. 7 for setting the permission flags Fi and Fe.
The hydraulic pressure P detected by the hydraulic pressure sensor 80 is read, and is compared with the exhaust-side set hydraulic pressure Pe and the intake-side set hydraulic pressure Pi in steps 42 and 46, respectively. If the actual oil pressure P is higher than the exhaust-side set oil pressure Pe, the exhaust-side permission flag Fe is set to "1" (step 43). If the actual oil pressure P is lower than the exhaust-side set oil pressure Pe, the exhaust-side permission flag Fe is set to "0". And turns on the warning lamp 81 (steps 44 and 45). Similarly, if the actual oil pressure P is higher than the intake-side set oil pressure Pi, the intake-side permission flag Fi is set to "1" (step 47). If the actual oil pressure P is equal to or lower than the intake-side set oil pressure Pi, the intake-side permission flag Fi is set. Is set to "0" (step 48). Here, ON of the variable valve mechanism on the exhaust valve side is performed.
The exhaust-side set oil pressure Pe that is the prohibited oil pressure is set higher than the intake-side set oil pressure Pi that is the ON-inhibited oil pressure of the intake valve-side variable valve mechanism.

Therefore, in this embodiment, when the lubricating oil pressure drops abnormally, the exhaust-side variable valve mechanism first returns to the OFF state, and then the intake-side variable valve mechanism turns off.
Return to the state. Therefore, the output of the internal combustion engine is suppressed, and an increase in the oil temperature that causes a decrease in the oil pressure of the lubricating oil is prevented. At this time, since the variable valve mechanism on the exhaust side and the variable valve mechanism on the intake side are not switched at the same time, a slight time difference is given, so that torque fluctuation is reduced. In particular, since the exhaust valve side that has less influence on the torque is first switched to the OFF state, the driver feels less uncomfortable.

FIG. 11 shows another embodiment in which the setting of the permission flags Fi and Fe is different. This embodiment corresponds to FIG.
Is similar to that of FIG.
0 reads the detected oil pressure P, and compares it with the exhaust-side set oil pressure Pe in step 52. Also in this embodiment, the exhaust-side set oil pressure Pe that becomes the ON-inhibited oil pressure of the exhaust valve-side variable valve mechanism is higher than the intake-side set oil pressure Pi that becomes the ON-inhibited oil pressure of the intake valve-side variable valve mechanism. It is set high. When the actual oil pressure P is higher than the exhaust-side set oil pressure Pe, the routine proceeds to step 53, where the exhaust-side permission flag Fe and the intake-side permission flag Fi are set to "1". If the oil pressure is equal to or lower than the exhaust-side set oil pressure Pe, the exhaust-side permission flag Fe is set to "0" in step 54, and the warning lamp 81 is turned on in step 55. Then, in step 56, the engine operating conditions are:
It is determined whether or not it is in the OFF region of the electromagnetic switching valve of the intake-side variable valve mechanism. If it is in the OFF region, the intake-side permission flag Fi is set to “0” in step 57. If it is outside the OFF area, that is, if it is the ON area, the hydraulic pressure P is further compared with the intake-side set oil pressure Pi in step 58.
And

Therefore, in this embodiment, when the lubricating oil pressure drops abnormally, the exhaust-side variable valve mechanism having a relatively small torque change is immediately turned off when Pe ≧ P.
Returning to the state, the output of the internal combustion engine is suppressed. Then, as long as the operating condition does not deviate from the ON region of the intake-side variable valve mechanism during Pe ≧ P> Pi,
Once held in the ON state and once in the OFF region,
Fixed to the FF state. Therefore, there is no possibility that the torque of the internal combustion engine suddenly drops suddenly during high-speed running and gives an uncomfortable feeling. Further, since switching from OFF to ON is prohibited, when Pi ≧ P, O
The possibility of switching from N to OFF is reduced, and unintended torque change can be prevented as much as possible.

[0059]

As is apparent from the above description, according to the present invention, when the lubricating oil pressure is excessively reduced, the variable valve mechanism is returned to the initial state, and malfunctions due to insufficient oil pressure can be prevented. Then, at this time, the plurality of variable valve mechanisms do not switch at the same time based on the oil pressure, but switch sequentially, so that the torque change can be reduced.

In particular, according to the second aspect of the present invention, the variable valve mechanism in which the valve lift characteristic continuously changes is preferentially switched, and the variable valve mechanism in which the valve lift characteristic changes stepwise is provided later. Since the switching is performed, the torque change can be made more gentle. Further, there is a possibility that the hydraulic pressure may be recovered due to the decrease in the output, and the switching of the variable valve mechanism in which the valve lift characteristic changes stepwise can be avoided as much as possible.

According to the third aspect of the present invention, the supply of hydraulic pressure to the variable valve mechanism in which the valve lift characteristic changes stepwise is prohibited, so that unintended switching after that is prevented.

In particular, in the apparatus having a mechanism for changing the valve lift characteristics by switching between the low-speed cam and the high-speed cam as in the fourth aspect, the switching caused by the decrease in the hydraulic pressure of the mechanism is avoided as much as possible. Abrupt torque fluctuation can be prevented.

According to the fifth aspect of the present invention, the exhaust valve having less influence on the torque is switched first, so that the torque fluctuation can be suppressed.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory view showing one embodiment of a variable valve apparatus according to the present invention.

FIG. 2 is an enlarged plan view of the rocker arm.

FIG. 3 is a sectional view of a rocker arm portion.

FIG. 4 is a sectional view of a valve timing adjustment mechanism.

FIG. 5 is a valve lift characteristic diagram of this embodiment.

FIG. 6 is a flowchart showing a flow of control of each variable valve mechanism according to engine operating conditions.

FIG. 7 is a flowchart illustrating a process of setting a permission flag based on a hydraulic pressure.

FIG. 8 is a flowchart showing another embodiment.

FIG. 9 is a flowchart showing an embodiment in which variable valve mechanisms are provided on both the intake valve side and the exhaust valve side.

FIG. 10 is a flowchart showing a process for setting an intake side and exhaust side permission flags based on hydraulic pressure.

FIG. 11 is a flowchart showing another embodiment in which the setting of the intake side and exhaust side permission flags is different.

[Explanation of symbols]

 40: Valve lift adjusting mechanism 45: Electromagnetic switching valve 51: Control unit 70: Valve timing adjusting mechanism 79: Electromagnetic switching valve 80: Oil pressure sensor

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Shin Shin Nakamura 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd. (56) References JP-A-3-217610 (JP, A) JP-A-2- 248608 (JP, A) Fully open 1987-61907 (JP, U) Fully open 1979-54, 130 (JP, U) Fully open, 59-186431 (JP, U) (58) Field surveyed (Int. ⁷ , DB name) F01L 13/00 301 F01L 1/34

Claims (5)

(57) [Claims] 1. A plurality of variable valve mechanisms for continuously or stepwise changing a valve lift characteristic of an intake valve or an exhaust valve according to supply and stop of hydraulic pressure to an actuator section, and an actuator of each variable valve mechanism. A plurality of hydraulic control valves for respectively controlling the supply of hydraulic pressure to the unit, and control means for outputting a control signal to each hydraulic control valve according to the engine operating conditions,
Hydraulic pressure detecting means for detecting the lubricating oil pressure of the internal combustion engine, and hydraulic pressure supply inhibiting means for inhibiting hydraulic pressure supply by the hydraulic pressure control valve when the detected oil pressure is lower than a set oil pressure,
In the variable valve operating device for an internal combustion engine, comprising: a plurality of variable valve mechanisms, among a plurality of variable valve mechanisms that may be supplied with hydraulic pressure under the same engine operating conditions, the set hydraulic pressure is set to A variable valve gear for an internal combustion engine, wherein the variable valve gears are different from each other. 2. The method according to claim 1, wherein the set hydraulic pressure of the variable valve mechanism in which the valve lift characteristic changes continuously is set higher than the set hydraulic pressure of the variable valve mechanism in which the valve lift characteristic changes stepwise. Item 4. The variable valve train for an internal combustion engine according to Item 1. 3. While the hydraulic pressure is lower than the set hydraulic pressure of the variable valve mechanism in which the valve lift characteristic changes continuously, the hydraulic pressure is supplied from the hydraulic stop state of the variable valve mechanism in which the valve lift characteristic changes stepwise. 3. The variable valve apparatus for an internal combustion engine according to claim 2, wherein switching to the state is prohibited. 4. The variable valve mechanism in which the valve lift characteristic changes continuously is a valve timing adjustment mechanism that changes the phase of a camshaft with respect to a crankshaft, and the valve lift characteristic changes stepwise. 4. The internal combustion engine according to claim 2, wherein the variable valve mechanism is a valve lift adjusting mechanism that selectively transmits a lift of one of a low-speed cam and a high-speed cam to an intake / exhaust valve. Variable valve gear. 5. A variable valve mechanism is provided for each of the intake valve and the exhaust valve, and the set hydraulic pressure of the variable valve mechanism on the exhaust side is set higher than the hydraulic pressure set for the variable valve mechanism on the intake side. The variable valve train for an internal combustion engine according to claim 1, wherein