JP3357487B2 - Engine Valve Actuator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve operating device for an engine, and more particularly, to a valve operating device for an engine in which a valve lift characteristic is switched between a low rotation speed and a high rotation speed of the engine.

[0002]

2. Description of the Related Art Conventionally, in order to achieve both high torque characteristics at low and medium speed operation and improvement of output at high speed operation, lift characteristics of an intake valve or an exhaust valve are varied according to an operation state. It is known to control the timing of intake and exhaust or the amount of intake and exhaust.

As one means for achieving the above object, there is known a valve operating device for an engine which can reduce the cost without requiring high-precision machining and can reduce the moment of inertia. (See, for example, JP-A-5-171909).

[0004] In this method, a sub rocker arm driven by a high-speed cam is interposed with a rocker arm driven by a low-speed cam, which is rotatably supported by a rocker shaft and has a tip linked to a valve. A rockable lever member is provided at a first position supported by a rocker arm to perform a lost motion function and a second position engaged with a sub rocker arm to stop a lost motion function. The drive is switched by a plunger.

[0005]

However, in such a conventional device, the lever member is switched by the operating plunger, so that when the rocker arm and the sub rocker arm are relatively displaced. When the operating plunger is operated and the operating plunger is operated, the lever member also rotates and abuts on the sub rocker arm, or depending on the position of the sub rocker arm, the lever member and the sub rocker arm are partially engaged and the engagement is released. As a result, there is a possibility that a tapping sound may be generated or abnormal wear may occur in an engagement portion between the sub rocker arm and the lever member, and there is still room for improvement.

SUMMARY OF THE INVENTION An object of the present invention is to provide a valve operating device for an engine which solves the above-mentioned conventional problems and does not cause such tapping noise and abnormal wear.

[0007]

In order to achieve the above object, one aspect of the present invention is to form a camshaft which is swingably supported on a rocker shaft and whose tip is linked to an intake valve or an exhaust valve. The first sliding contact with the first cam
A rocker arm, a second rocker arm slidably supported by the first rocker arm and urged to slide against a second cam formed on the camshaft; and a rocker arm supported at a substantially central portion by the first rocker arm; A lever member slidable to a position for connecting and disconnecting the first and second rocker arms, wherein a top surface of one end of the lever member engages a lower surface of a step formed on the second rocker arm at the connection position; A lever member biased by biasing means provided between the first rocker arm and the first rocker arm so that a side surface at the other end abuts on the hydraulically operated plunger. A concave portion is formed in a predetermined section of the base circle, and the second rocker arm and the lever member are connected to each other by the second rocker arm. The position of the linking member can be switched when the sliding member is in sliding contact with the concave portion formed between the concave portions. When the second rocker arm is in sliding contact with a portion other than the concave portion, the rotation thereof is performed by the front surface of the step portion of the second rocker arm. It is characterized by being arranged so as to be blocked by.

[0008]

Further, according to another aspect of the present invention, when the top surface at one end of the lever member and the lower surface of the step portion of the second rocker arm engage with each other, the lever member is turned in the direction of the connection position when both are engaged. It is characterized in that it is formed so that a moving component force acts.

[0010]

According to one embodiment of the present invention, the second rocker arm and the connecting member are connected to each other when the second rocker arm is in sliding contact with a recess formed in a predetermined section of the base circle of the second cam. The switching of the linking member is limited to only a predetermined period of the base circle, and the switching operation is reliably performed.

Further, according to another aspect of the present invention, the lever member urged to abut the hydraulically operated plunger is rotated by the operation of the operation plunger, and the top surface of one end of the lever member is in the connected position. When the second rocker arm is in sliding contact with a portion other than the recess, the side surface of one end of the second rocker arm contacts the front surface of the step portion of the second rocker arm, and rotation is prevented. Therefore, the switching operation is not performed except in the concave portion.

Further, according to another aspect of the present invention, when the top surface of one end of the lever member and the lower surface of the step portion of the second rocker arm are engaged with each other, the lever member is moved in the connecting position direction. The lever member is rotated in the direction of the coupling position by the component force even if the operating plunger is operated when the second rocker arm is in sliding contact with the recess because the component force is formed so that the component force rotates. The incompletely engaged state is instantaneously eliminated.

[0013]

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

FIGS. 1 to 4 show an engine equipped with two valves having the same function for one cylinder (either an intake valve or an exhaust valve, the illustrated one being an intake valve). 1 shows an embodiment in which the invention is applied.

To explain this, each cylinder is provided with a single main rocker arm (first rocker arm) 1 corresponding to two intake valves V, V. The base end of the main rocker arm 1 is swingably supported by a cylinder head via a hollow main rocker shaft 3 common to each cylinder.
Abuts the stem top.

The main rocker arm 1 is formed substantially bifurcated in a plan view. The main rocker arm 1 is provided with a single sub rocker arm (second rocker arm) 2 substantially above the center thereof. And in FIG.
Low-speed cams 2 serving as first cams formed on camshafts 20 are provided on both sides of sub rocker arm 2.
Cam follower portions 11 and 11 with which sliding contact are provided are provided. The base end of the sub rocker arm 2 is rotatably supported by the main rocker arm 1 via a sub rocker shaft 16. The sub rocker shaft 16 is slidably fitted in a hole formed in the sub rocker arm 2, and is press-fitted and supported in a hole in a support wall 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 V, and a cam follower portion 2A that slides on a high-speed cam 22 as a second cam is formed at the tip of the sub-rocker arm 2 so as to protrude in an arc shape.

In the main rocker arm 1, a space 1 A around the distal end of the sub rocker arm 2 and a lever member to be described later is located near the main rocker shaft 3.
B is formed so as to form B, whereby the distance between the main rocker shaft 3 and the valve shaft of the intake valve V can be shortened, that is, the main rocker arm 1 can be made compact. Further, a cylindrical concave portion 27 for accommodating the lost motion mechanism 25 is formed below the sub rocker arm 2. The base end of the coil-shaped lost motion spring 26 is supported by the bottom surface of the concave portion 27, and the distal end thereof biases a bottomed cylindrical lost motion plunger 29 slidably fitted in the concave portion 27. Accordingly, the head of the lost motion plunger 29 abuts on the step 1B, and the sub rocker arm 2 is biased to abut on the base circle of the second cam 22.

Further, the sub rocker arm 2 has a stepped portion 2B formed below the cam follower portion 2A with which a later-described lever member 7 is engaged.
And a stepped front surface 2Bb that engages with the top surface 7A at one end of the lever member 7 and a stepped front surface 2Bb that is connected to the lower surface 2Ba and that abuts a side surface 7B of one end of the lever member 7 at a predetermined time. The top surface 7A and the stepped lower surface 2Ba are formed so as to be inclined, respectively, so that when they are engaged, a component force for rotating the lever member 7 in the connecting position direction acts.

Below the main rocker arm 1, the above-mentioned lever member 7 is provided as a linking member which is swingably supported by a pin 6 parallel to the side of the rocker shaft 3. A protrusion 12 is integrally formed on the upper side of the lever member 7 (see FIG. 3), and a return spring 9 and a return plunger 10 (see FIG. 4) housed in a cylindrical recess 8 formed in the main rocker arm 1. Thus, the lever member 7 is urged via the protrusion 12 in a direction in which the engagement with the step portion 2B of the sub rocker arm 2 is released.

On the other hand, the lower end of the lever member 7 is in contact with the operating plunger 31 of the hydraulic drive unit 30 provided at the lower center of the main rocker arm 1. That is, the main rocker arm 1 is formed with a columnar concave portion 32 in 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. A hydraulic chamber 34 is formed between the two.

The oil passage for guiding the operating oil pressure to the oil pressure chamber 34 includes the main rocker arm 1 and the main rocker shaft 3.
It is provided through the inside. The main rocker arm 1 has an opening in the hydraulic chamber 34 at one end, and a through hole 41 formed at the other end through a bearing surface for the main rocker shaft 3. An oil gallery 42 is formed inside the main rocker shaft 3 in the axial direction, and the oil gallery 42 communicates with the through hole 41 of the main rocker arm 1 through a through hole 43. Here, the operating pressure guided to the hydraulic chamber 34, the operating plunger 31 including the return spring 35, and the above-described return spring 9 constitute the link switching means of the lever member 7.

To the oil gallery 42, the discharge oil pressure of the oil pump is guided at a predetermined high-speed operation via a switching valve (not shown). The control unit, which electronically controls the operation of the switching valve, receives an engine rotation signal, a cooling water temperature signal, a lubricating oil temperature signal, a supercharging pressure signal of intake air from a supercharger, a throttle valve opening signal, and the like. A switching signal is issued to the switching valve while suppressing a sudden change in the engine torque based on the detected value of the low speed cam 21.
The switching between the high-speed cam 22 and the high-speed cam 22 is performed smoothly.

The low-speed cams 21 and 21 and the high-speed cam 22 therebetween are integrally formed on a common camshaft 20 to satisfy the valve lift characteristics required at low and high engine speeds. In different shapes (including similar shapes of different sizes). That is, the high-speed cam 22 has a profile that makes at least one of the valve lift amount and the valve opening period larger than the low-speed cam 21. Here, the valve lift and the valve opening period are both increased. And sub rocker arm 2
A concave portion 22A is formed in a predetermined section of the base circle of the high-speed cam 22 with which the cam 22 slides. This recess 22
The section where A is formed is, for example, the time required for the lever member 7 to start engaging with the sub rocker arm 2 from the end of the lift of the sub rocker arm 2 while considering the magnitude of the operating oil pressure and the strength of the return spring 9. It is preferable to set the rotation angle to the corresponding rotation angle range of the camshaft 20.

In this embodiment having the above-described structure, the camshaft 20 is driven at half the rotation speed of the crankshaft of the engine. Correspondingly, the rocker arms 1 and 2 are respectively swung. Therefore, during low-speed operation of the engine, the main 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 sub rocker arm 2 is
However, the lever member 7 is at a position separated from the step front surface 2Bb of the sub rocker arm 2 shown in FIGS. 4 and 5 by a predetermined gap due to the urging force of the return spring 9, and the lost motion mechanism 25 Is in a non-connected state in which it functions. Therefore, even if there is an input from the sub rocker arm 2, the lost motion spring 2
The movement of the main rocker arm 1 is not hindered only by bending of the arm 6.

On the other hand, when the engine is running at a high speed,
When the operating oil pressure is guided to the hydraulic chamber 34 via the oil gallery 42 and the oil passage 41, the operating plunger 31 swings the lever member 7 against the return spring 9 and brings the lever member 7 to the connection position shown in FIG. In this state, the top surface 7A at one end of the lever member 7 is completely engaged with the lower surface 2Ba of the step portion of the sub rocker arm 2, so that the main rocker arm 1 and the sub rocker arm 2 are connected and integrated to form the main rocker shaft. 3 will be oscillated.

Here, the high speed cam 22 is
In this case, the cam follower 1A of the main rocker arm 1 is moved from the low-speed cam 21 at the time of swinging integrated with the sub rocker arm 2 because both the valve opening and the valve lift are formed to be larger than those of FIG. When the intake valve V rises, the intake valve V is opened and closed according to the profile of the high-speed cam 22, and both the valve opening and the valve lift are increased.

Next, switching timing control will be described. It is not clear when the above-mentioned request for switching to the valve lift by the high speed or low speed cam is generated depending on the state of the engine. To reliably connect and disconnect the sub rocker arm 2, the lever member 7 must be set to a predetermined position. It is necessary to move at the timing.

First, during the low-speed operation of the engine described above, at the rest position shown in FIG. 5 where both the main rocker arm 1 and the sub rocker arm 2 are in contact with the base circles of the cams 21 and 22, the hydraulic pressure is applied to the hydraulic chamber 34. The operating plunger 31 is not operating and the return spring 9
Is pushed back by the lever member 7.
In this state, since the top surface 7A at one end of the lever member 7 is located above the step lower surface 2Bb of the sub rocker arm 2, when the main rocker arm 1 and the sub rocker arm 2 are in contact with the base circle. Even if the switching signal is received and the operating hydraulic pressure acts on the operating plunger 31,
During the contact with the base circle, the lever member 7 is allowed to rotate only for a gap until the side surface 7B at one end thereof contacts the step front surface 2Bb, and does not perform the engaging operation.

In this state, when the cams 21 and 22 rotate and the main rocker arm 1 and the sub rocker arm 2 are pushed down, the cam ridge of the high-speed cam 22 is larger than the cam ridge of the low-speed cam 21. Only by increasing the amount of contact between the side surface 7B at one end of the member 7 and the step front surface 2Bb, the standby state is maintained as it is. Of course, even when the switching signal is input during the valve lift, the engagement operation is not performed and the standby state is maintained.

When the cams 21 and 22 are further rotated and the valve lift is completed and the section of the concave portion 22A of the base circle is reached, the sub rocker arm 2 is urged by the lost motion spring 28 so as to slide on the concave portion 22A. Become. Then, since the lever member 7 and the sub rocker arm 2 do not interfere with each other, the lever member 7 is pressed by the operating plunger 31 and pivots until the projection 12 abuts on the main rocker arm 1, as shown in FIG. , One end of which enters under the step 2B of the sub rocker arm 2.
When the sub rocker arm 2 comes into sliding contact with the base circle other than the concave portion 22A, the sub rocker arm 2
Slightly rotates, and as shown in FIG.
Is supported by the lever member 7, that is, the connected state.

As described above, the concave portion 22A of the base circle
The operation of connecting the lever member 7 is performed only while the sub rocker arm 2 is in sliding contact with the concave portion by the action of, so that a tapping sound due to connection failure and abnormal wear of the connection portion are prevented.

When a switching signal is generated while the sub rocker arm 2 is in sliding contact with the concave portion and hydraulic pressure is applied, the top surface 7A at one end of the lever member 7 partially engages with the step lower surface 2Ba. In some cases, the base circle section may be reached in an incompletely engaged state. In this case, when the top surface 7A of the lever member 7 and the stepped lower surface 2Ba of the sub rocker arm 2 are engaged with each other, the lever member 7 is disengaged. Since they are formed to be inclined so that a component force rotating in the direction of the connection position acts, there is no problem without disengagement.

On the other hand, when the engine shifts from the high rotation range to the low rotation range again, the hydraulic pressure guided to the hydraulic chamber 34 is reduced by the operation of the switching valve, and the elastic member of the return spring 9 restores the lever member 7 and the operating plunger 31. Moves to the original position and the restraint of the main rocker arm 1 is released. Timing control at this time will be described.

When a switching signal is issued in a state where the sub rocker arm 2 and the lever member 7 are engaged and connected to each other, the operating oil pressure in the hydraulic chamber 34 is reduced. If it is in contact, the main rocker arm 1 and thus the lever member 7 pivotally supported by the main rocker arm 1
Since the load of the return spring of the intake valve V is applied, the engagement between the sub rocker arm 2 and the lever member 7 is not immediately released.

When the cams 21 and 22 further rotate and the sub rocker arm 2 comes into sliding contact with the concave portion 22A of the base circle, the lever member 7 and the sub rocker arm 2 do not interfere with each other as described above. 9 allows the lever member 7 to move the operating plunger 3
Move 1 to return to the original unconnected position.

As described above, the concave portion 22A of the base circle
The operation of releasing the connection of the lever member 7 is performed only during the sliding contact of the sub rocker arm 2 with the concave portion 22A by the action of the sub rocker arm 2, so that the hitting sound due to the failure of the return of the lever member and the abnormal wear of the connection portion are prevented. You.

As described above, the torque characteristics based on the profile of the low-speed cam 21 and the torque characteristics 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.

[0039]

As is apparent from the above description, according to one embodiment of the present invention, the second rocker arm and the connecting member are
Since the second rocker arm is arranged so that the position of the linking member can be switched when the second rocker arm is in sliding contact with a concave portion formed in a predetermined section of the base circle of the second cam, a switching signal is generated at any time. The switching of the linking member is limited to only a predetermined period of this base circle,
The switching operation is performed reliably. Therefore, it is possible to prevent occurrence of a tapping sound and abnormal wear.

According to another aspect of the present invention, the lever member biased to abut the hydraulically operated plunger is rotated by the operation of the operation plunger, and the top surface at one end thereof is in the connected position. When the second rocker arm is in sliding contact with a portion other than the recess, the side surface of one end of the second rocker arm contacts the front surface of the step portion of the second rocker arm, and rotation is prevented. Therefore, the switching operation is not performed except in the concave portion, and the connected and disconnected states can be reliably obtained.

Further, according to another aspect of the present invention, when the top surface at one end of the lever member and the lower surface of the step portion of the second rocker arm engage with each other, the lever member is moved in the direction of the connecting position when both are engaged. Since the rotating component is formed to act, even if the switching signal is issued and the operating plunger is operated when the second rocker arm is in sliding contact with the recess, the lever member is connected by the component force. It is rotated in the position direction, and the incompletely engaged state is instantaneously canceled. Therefore, it is possible to more reliably prevent the occurrence of a tapping sound due to the engagement failure.

[Brief description of the drawings]

FIG. 1 is a side view of a valve train showing one embodiment of the present invention.

FIG. 2 is a plan view of a valve train showing one embodiment of the present invention.

FIG. 3 is a front view of a valve train showing one embodiment of the present invention.

FIG. 4 is a cross-sectional view taken along the line AA of FIG. 2, showing a state in which a main rocker arm and a sub rocker arm are disconnected.

FIG. 5 is a transverse sectional view corresponding to FIG. 4, wherein (A) shows a state in which the lever member and the sub rocker arm are not connected,
(B) is a partially enlarged view thereof.

6 is a cross-sectional view corresponding to FIG. 4, in which (A) shows a state immediately before the lever member and the sub rocker arm are connected, and (B) is a partially enlarged view thereof.

FIG. 7 is a transverse sectional view corresponding to FIG. 4, in which (A) shows a state in which the lever member and the sub rocker arm are connected,
(B) is a partially enlarged view thereof.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main rocker arm 2 Sub rocker arm 3 Main rocker shaft 7 Lever member (coupling member) 9 Return spring 16 Sub rocker shaft 21 Low speed cam 22 High speed cam 22A Recess of base circle 25 Lost motion mechanism 31 Operating plunger

Claims (2)

(57) [Claims] A first rocker arm slidably supported by a rocker shaft and having a distal end linked to an intake valve or an exhaust valve and slidably contacting a first cam formed on a cam shaft; A second rocker arm movably supported and urged to slide against a second cam formed on the camshaft; and a second rocker arm supported at a substantially central portion by the first rocker arm;
A lever member slidable to a position at which the first and second rocker arms are connected and disconnected , wherein
A top surface is formed on the second rocker arm at the connection position.
And the other side surface is hydraulically operated.
It is installed between the first rocker arm and the
A lever member biased by a beam biasing means , wherein a recess is formed in a predetermined section of a base circle of the second cam, and the second rocker arm and the lever member are said second rocker arm Ri is Do allow switching of the position of the linkage member when it is in sliding contact with the concave portion formed in a predetermined section of the base circle of the second cam, said second rocker arm
Is in sliding contact with the portion other than the concave portion,
Serial valve operating system for an engine, characterized in that disposed on so that is blocked by the stepped portion front surface of the second rocker arm. 2. A top surface at one end of the lever member and the second surface.
The stage lower surface of the rocker arm, when both are engaged, the engine according to claim 1, characterized in that component force for rotating the lever member to the connecting position direction is formed so as to act Valve actuator.