JPH06212925A - Valve operating device for engine - Google Patents

Abstract

PURPOSE:To reduce the cost and increase the degree of freedom of control by providing a linkage-switching means for switching a linking member supported on a rocker arm to a first position and to a second position. CONSTITUTION:A linking member 7 is supported on a rocker arm 1, and is oscillated to a first position where a lost motion mechamism 25 exhibits its function, and to a second position where the lost motion mechanism 25 stops its function. Since the lever member 7 is linked to the first position where the lost motion mechanism 25 exhibits its function at the time when the engine is operated at a low speed, the motion of the rocker arm 1 is not disturbed. When the engine is operated at a high speed, an operating plunger 31 oscillates the lever member 7 against a return spring to move it to the second position. The linkage-switching is performed by the engagement and disengagement of the end part of the lever member 7 with and from the step part 2B of a free cam-follower 2. Thus, since there is no need to drill fitting holes, the machining accuracy can be low. Further, the free cam-follower, the linking member, etc., can be arranged close to the rocker shaft center.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve actuating device for an engine, and more particularly to a valve actuating device for an engine adapted to switch a valve lift characteristic when the engine is running at low speed and when it is running at high speed.

[0002]

2. Description of the Related Art Conventionally, the lift characteristic of an intake valve or an exhaust valve is made different according to the operating state for the purpose of achieving both high torque characteristics at low and medium speed operation and improved output at high speed operation. It is known to control the timing of intake / exhaust or the amount of intake / exhaust.
-167016, JP-A-63-57805, etc.).

These rocker arms have a common low-speed rocker arm whose rocking tip comes into contact with the valve, and a high-speed rocker arm which is a free cam follower provided between the low-speed rocker arms and having no contact portion with the valve. The low-speed rocker arm is slidably supported by the shaft, and the high-speed rocker arm is slidably contacted with the high-speed cam having a profile with a larger valve opening angle or valve lift than the low-speed cam. Has been done.

Fitting holes are formed in the rocker arm for high speed and the rocker arm for low speed in a direction parallel to the rocker shaft at rocking portions separated from the rocker shaft by a predetermined distance. The plunger is fitted in the fitting hole, and the two rocker arms are connected or released when the plunger fits into the fitting hole or comes out of the fitting hole in response to the hydraulic pressure. A connection switching mechanism is provided.

[0005]

However, in such a conventional one, the plurality of plungers fitted in the respective fitting holes receive the hydraulic pressure when the fitting holes are coaxially aligned. Since the plunger is configured to fit into the mating hole of the mating body while pushing the mating plunger, extremely high processing accuracy is required between the plunger and the mating holes of the high-speed rocker arm and the low-speed rocker arm, which increases costs. It is one of the causes. Because, if the machining accuracy is lowered and the clearance between both is allowed to be large,
First of all, the hydraulic oil pressure is not guaranteed, the arm is not connected smoothly, wear and noise occur due to the contact between the fitting hole and the plunger, and the opening / closing characteristics of the valve are unstable. This is because the combustion conditions deteriorate and are not preferable. Further, there is a problem that the rocker arms are inevitably increased in size and the moment of inertia of the entire valve train is increased.

Further, in the structure in which a plurality of valves are driven simultaneously when they are connected, there is a problem that the respective valves cannot be driven individually and the degree of freedom of control is limited.

An object of the present invention is to solve the conventional problems described above, reduce the cost without requiring high-precision machining, reduce the moment of inertia, and increase the degree of freedom in control. It is to provide a valve actuating device for an engine.

[0008]

In order to achieve the above object, the present invention provides a first cam which is rockably supported by a rocker shaft and whose tip is linked to each of an intake valve and an exhaust valve. , A free cam follower rockably supported by each of the rocker arms and driven by a second cam, a lost motion mechanism provided for the free cam follower, and the lost motion supported by the rocker arm. A linking member swingable between a first position for exhibiting the function of the mechanism and a second position for stopping the function of the lost motion mechanism, and switching of the linking member between the first position and the second position. And a link switching means.

[0009]

According to the present invention, the linking member supported by the rocker arm, the tip of which is linked to each of the intake valve and the exhaust valve, is moved to the first position where the linking switching means exerts the lost motion function. By doing so, the connection between the rocker arm and the free cam follower is released, and by moving the rocker arm to the second position where the function of the lost motion mechanism is stopped, the rocker arm and the free cam follower are connected. Therefore, a plunger and a fitting hole, which are required in the related art, are unnecessary, high-precision machining of each component is not required, and the opening / closing characteristics of each valve can be set individually.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings.

1 to 5 relate to an embodiment of the present invention, two valves having the same function for one cylinder (either an intake valve or an exhaust valve may be used, and the illustrated valve is an intake valve). It shows a case where the present invention is applied to an engine provided with.

Explaining this, each cylinder is provided with two rocker arms 1, 1 corresponding to two intake valves V, V in parallel in a plane-symmetrical relationship. That is, both rocker arms 1 and 1 are configured in a mirror-symmetrical relationship with respect to a plane existing in the center of the two intake valves V. Therefore, in the following description, only one side (including a cam described later) will be described, and the other side will be denoted by the same reference numeral and will not be described. However, when it is necessary to distinguish between the left and right ones, the suffixes L and R will be attached and described.

The base end of the rocker arm 1 is swingably supported by the cylinder head via a main rocker shaft 3 arranged in pairs for each cylinder, and the tip end of the rocker arm 1 contacts the stem top of the intake valve V.

The rocker arm 1 is formed into a substantially bifurcated shape in a side view, and the rocker arm 1 is provided with a free cam follower 2 approximately above the center thereof. Further, on one side of the free cam follower 2, a roller 11 with which a low speed cam 21 as a first cam abuts is provided. The roller 11 is provided with a bearing shaft 12 inserted into a through hole 13 provided in the rocker arm 1 and a needle bearing 1
It is rotatably supported via 4. The base end of the free cam follower 2 is swingably (relatively rotatable) supported by the rocker arm 1 via a sub-rocker shaft 16. The sub-rocker shaft 16 is slidably fitted in a hole 17 formed in the free cam follower 2, and is press-fitted and supported in holes 19, 19 of support walls 18, 18 formed in the rocker arm 1.

The free cam follower 2 does not have a portion that comes into contact with the intake valve V, and a cam follower portion 2A that is slidably contacted with a high speed cam 22 as a second cam is formed at the tip of the free end to project in an arc shape.

In the rocker arm 1, a space 1A for accommodating a tip end portion of the free cam follower 2 and a lever member 7 described later is formed by cutting until the rocker shaft 3 is exposed, whereby the rocker shaft 3 and the intake valve V are formed. It is possible to shorten the distance from the valve shaft of, that is, to make the rocker arm 1 compact. A columnar recess 27 for accommodating the lost motion mechanism 25 is formed below the free cam follower 2. The base end of the coiled lost motion spring 26 is supported by the bottom surface of the recess 27, and the tip thereof urges a bottomed cylindrical spring retainer 29 slidably fitted in the recess 27. The head of the spring retainer 29 is in contact with the rocker shaft 3 in the above-described exposed state.

Further, the above-mentioned free cam follower 2 includes:
Below the cam follower portion 2A, a step portion 2B with which a later-described lever member 7 is engaged and an inclined portion 2C continuous with the step portion 2B are formed. Further, below the rocker arm 1, there is provided a lever member 7 as a linking member that is swingably supported by a pin 6 on the side of the rocker shaft 3.

A protrusion 7A is integrally formed on the upper side of the lever member 7 (see FIG. 2), and a return spring 9 and a spring retainer 10 (FIG. 4) accommodated in a cylindrical recess 8 formed in the rocker arm 1. (See reference), the free cam follower 2 is urged in a direction in which the engagement with the free cam follower 2 is released.

On the other hand, at the lower end of the lever member 7, an operating plunger 3 of a hydraulic drive unit 30 provided on the rocker arm 1 is provided.
1 is in contact. That is, the rocker arm 1 is formed with a cylindrical recess 32 into which the above-mentioned operating plunger 31 is slidably fitted in a direction orthogonal to the axis of the above-mentioned main rocker shaft 3, and the operating plunger 31 and the recess 32 are formed.
A hydraulic chamber 34 is formed between

An oil passage for guiding the working hydraulic pressure to the hydraulic chamber 34 is provided through the insides of the rocker arm 1 and the main rocker shaft 3. The rocker arm 1 is formed with a through hole 41 having one end opened to the hydraulic chamber 34 and the other end penetrating a bearing surface for the main rocker shaft 3. Inside the main rocker shaft 3, an oil gallery 42 whose one end is closed by a closing plate 45 is formed in the axial direction, and the oil gallery 42 communicates with the through hole 41 of the rocker arm 1 through the through hole 43. At the same time, it communicates with the passage 46 in which a switching valve described later is interposed via the through hole 44.
Here, the working hydraulic pressure guided to the hydraulic chamber 34 and the above-mentioned return spring 9 constitute a linkage switching means of the lever member 7.

The oil pressure discharged from the oil pump is guided to the oil gallery 42 through a switching valve (not shown) during a predetermined high speed operation. The control unit that electronically controls the operation of the switching valve inputs the engine rotation signal, the cooling water temperature signal, the lubricating oil temperature signal, the intake supercharging pressure signal by the supercharger, the throttle valve opening signal, etc. Based on the detected value, the rapid change of the engine torque is suppressed and the switching between the low speed cam 21 and the high speed cam 22 described later is smoothly performed.

The low speed cam 21 and the high speed cam 22 are integrally formed on a common cam shaft 20 and have different shapes so as to satisfy the valve lift characteristics required at low engine speed and high engine speed ( (Similar shapes with different sizes are also included.) That is, the high speed cam 22
Has a profile in which at least one of the valve lift amount and the valve opening period is larger than that of the low speed cam 21. Here, both the valve lift amount and the valve opening period are increased.

In this embodiment having the above-described structure, when the engine is operating at a low speed, the rocker arm 1 swings according to the profile of the low speed cam 21 to open and close each intake valve V. At this time, the free cam follower 2 moves to the high speed cam 22.
Although the lever member 7 is swung by the return spring 9, the lever member 7 is in the position shown by the solid line in FIG. 3 and is in the first position where the lost motion mechanism 25 performs its function. Even if there is an input from the cam follower 2, only the lost motion spring 26 bends and the movement of the rocker arm 1 is not hindered.

On the other hand, when the engine is operating at high speed,
When the operating oil pressure is introduced into the oil pressure chamber 34 through the oil gallery 42 and the oil passage 41, the operating plunger 31 swings the lever member 7 against the return spring 9 to the second position shown by the broken line in FIG. Bring In this state, the end portion of the lever member 7 engages with the step portion 2B of the free cam follower 2, so that the rocker arm 1 and the free cam follower 2 are connected and integrated, and swing around the main rocker shaft 3. It will be.

Here, the high-speed cam 22 is the low-speed cam 21.
In comparison with the above, since the valve opening and the valve lift amount are both large, when the free cam follower 2 is integrated with the rocker arm 1, the roller 11 of the rocker arm 1 causes the roller 11 of the low speed cam 21 to move. And each intake valve V is opened and closed according to the profile of the high speed cam 22,
Both the valve opening and the valve lift amount increase.

On the other hand, when the engine moves from the high speed region to the low speed region again, the hydraulic pressure introduced into the hydraulic chamber 34 is lowered by the operation of the switching valve, and the elastic restoring force of the return spring 9 causes the lever member 7 and the operating plunger 31 to move. Moves to the original position, and the locker arm 1 is released from the restraint.

Thus, the torque characteristic based on the profile of the low speed cam 21 and the torque characteristic based on the profile of the high speed cam 22 are combined, and the torque can be increased from the low rotation range to the high rotation range.

By the way, in the above-mentioned embodiment,
Even if the hydraulic pressure is not sufficiently generated and the movement of the lever member 7 from the first position to the second position is insufficient, the end portion of the lever member 7 does not move the inclined portion 2C of the free cam follower 2. Since the lever member 7 swings while sliding, it is possible to mitigate the collision between the roller 11 and the low speed cam 21.
Generation of abnormal noise is reduced.

Further, according to this embodiment, the lever member 7
Since linkage switching is performed by engaging and disengaging the end portion of the free cam follower 2 with the step portion 2B of the free cam follower 2, it is possible to perform stable operation without requiring high precision.
Further, since the accuracy in the height direction of the upper surface of the roller 11 and the upper surface of the free cam follower 2 can be easily obtained by exchanging the lever member 7, the number of steps can be reduced and the cost can be reduced. .

Further, the free cam follower 2 is compact, and the recess 2 for accommodating the lost motion mechanism 25 therein.
7, the weight of the spring retainer 2 is reduced, and the lost motion spring 26 may be weak.
The cam 2 can be provided without providing a stroke restricting unit 9 or the like.
2 and the free cam follower 2 can be reduced in friction.

Further, in the present embodiment, since the arm length of the rocker arm 1 and the fitting portion length of the rocker arm 1 and the rocker shaft 3 are provided with the extension portion E (see FIG. 1), they are appropriately set. It is possible to prevent the rocker arm 1 from falling, and thus prevent uneven wear of the cams 21 and 22. That is, as shown in FIG. 1, P and D are intersections with the axis of the rocker shaft 3 at both ends of the rocker arm 1, Q is a contact point with the valve shaft of the rocker arm 1, and the high-speed cam 22 of the free cam follower 2.
When the load center point is defined as C, the load center point C is set to be located inside the line segment PQ connecting P and Q. If the end point of the rocker arm 1 is P'without providing the extension E, the load center point C is located outside the line segment P'Q, and the point D rises. A collapse of 1 occurs.

Further, in the present embodiment, since the hydraulic pressure supply paths to the left valve actuation mechanism M _L including the left rocker arm 1 _L and the right valve actuation mechanism M _R including the right rocker arm 1 _R are independent, the oil gallery is independent. 42 _L , 42 _R
Is independently supplied with operating hydraulic pressure. This makes it possible to switch the torque characteristics of the engine in three stages.

That is, in the low rotation range, the hydraulic chambers 34 _L , 3
The hydraulic pressure is not supplied to 4 _R , and the intake valves V _L and V _R have a torque characteristic driven by the low speed cams 21 _L and 21 _R. Further, in the middle rotation range, for example, the left side hydraulic chamber 34 _L is left as it is, and the working hydraulic pressure is supplied only to the right side hydraulic chamber 34 _R , so that the left side intake valve _VL is the low speed cam 21 _L and the right side intake valve _VL. V _R will be driven by the high-speed cam 22 _R, torque increases somewhat. Further, in the high rotation range, the working hydraulic pressure is supplied to both hydraulic chambers 34 _L and 34 _R , and both intake valves V
_L, V _R is driven together with the high-speed cam 22 _L, 22 _R,
The torque increases further. As described above, by making the torque characteristic switchable in three stages, the torque drop is less than in the case of two stages, and a smooth and flat torque characteristic can be obtained.

[0034]

As is apparent from the above description, according to the present invention, compared with the conventional one in which a plunger is inserted into a fitting hole for connection, it is not necessary to form a fitting hole, and the processing accuracy thereof is higher. Since it may be low, the cost can be reduced. Further, the free cam follower, the linking member, and the like can be arranged close to the center of the rocker shaft, so that the equivalent inertial mass can be reduced and the degree of freedom of control can be increased.

[Brief description of drawings]

FIG. 1 is a plan view of a valve train system showing an embodiment of the present invention.

FIG. 2 is a vertical sectional view taken along the line II-II in FIG.

3 is a cross-sectional view taken along the line III-III in FIG. 2, showing a state where the rocker arm and the free cam follower are disconnected from each other.

FIG. 4 is a partial cross-sectional view taken along the line IV-IV of FIG. 2, showing a state in which a free cam follower is removed.

FIG. 5 is a sectional view showing a main rocker shaft portion of an embodiment of the present invention.

[Explanation of symbols] 1 rocker arm 2 free cam follower 3 main rocker shaft 7 lever member (coupling member) 9 return spring 10 spring retainer 21 low speed cam (first cam) 22 high speed cam (second cam) 25 lost motion mechanism 26 Lost motion spring 29 Spring retainer 30 Hydraulic drive unit 31 Actuating plunger 34 Hydraulic chamber V Intake valve

Claims (2)

[Claims] 1. A rocker arm which is rockably supported by a rocker shaft and whose tip is linked to an intake valve or an exhaust valve and is driven by a first cam, and a rocker arm which is rockable to each of the rocker arms. A free cam follower supported and driven by a second cam, a lost motion mechanism provided for the free cam follower, a first position supported by the rocker arm and exerting the function of the lost motion mechanism, and a lost motion mechanism of the lost motion mechanism. A valve actuation of an engine, comprising: a linkage member swingable to a second position for stopping the function; and a linkage switching means for switching the linkage member between the first position and the second position. apparatus. 2. The valve actuating device for an engine according to claim 1, wherein a plurality of the intake valves or the exhaust valves are provided for each cylinder, and the linkage switching means are independently controlled.