JP2557920Y2 - 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 and a high rotation 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 (see, for example,
167,016, JP-A-63-57806, etc.).

In these, a low-speed rocker arm whose swinging end contacts the valve and a high-speed rocker arm which is a free cam fore 3 provided between the low-speed rocker arm and having no contact portion with the valve are common. The low speed rocker arm is swingably supported by the rocker shaft, and the low speed rocker arm is provided with a low speed cam, and the high speed rocker arm is provided with a high speed cam having a profile in which the valve opening angle or valve lift is larger than that of the low speed cam. Touched.

In the rocker arm for high speed and the rocker arm for low speed, a fitting hole is formed in a swinging part separated from the rocker shaft by a predetermined distance in a direction parallel to the rocker shaft. A plunger is fitted in the fitting hole, and the two rocker arms are connected or disconnected when the plunger is fitted into or removed from the fitting hole in response to the operating oil pressure. There is provided a connection switching mechanism.

By the way, in such a conventional device,
The plurality of plungers fitted in the respective fitting holes are configured such that when the fitting holes are aligned coaxially, the plunger receiving the hydraulic pressure fits into the mating hole of the other while pushing the other plunger. Therefore, extremely high machining accuracy is required between the plunger and the fitting holes of the high-speed rocker arm and the low-speed rocker arm, which contributes to an increase in cost. This is because, if the machining accuracy is reduced and the clearance between the two is greatly allowed, first, the holding of the working oil pressure is not guaranteed, and furthermore, abrasion and noise due to the one-side contact between the fitting hole and the plunger are not preferable. .

Therefore, the applicant of the present invention does not use a conventional structure in which a plunger is inserted into a fitting hole and connects the same, but switches the connection between the rocker arm and the free cam follower to the free cam follower via a lost motion mechanism provided in the rocker arm. A valve operating device for an engine using an axially movable link member has been proposed (Japanese Patent Application No. 3-97238).

[0007]

In the above proposal, it is not necessary to form a fitting hole for inserting a plunger as in the prior art, and the machining accuracy of the connection switching mechanism between the rocker arm and the free cam follower is not so much considered. Although good manufacturing cost can be reduced, the linking member that performs the above connection switching has a structure that slides inside the free cam follower, so both sliding surfaces need to be machined and precision is also required. This is an obstacle to reducing the manufacturing cost.

An object of the present invention is to solve such a problem.
In addition, it is an object of the present invention to provide a valve operating device for an engine that can accurately perform connection switching between a rocker arm and a free cam follower and that can sufficiently support a rotational force acting on a linking member.

[0009]

In order to achieve the above object, the present invention provides a rocker arm having one end linked to an intake valve or an exhaust valve and driven by a first cam, and swingably supported by the rocker arm. A free cam follower driven by a second cam, a lost motion mechanism associated with the free cam follower, provided on the rocker arm, and a first position associated with the lost motion mechanism, the spline or serration engaging the free cam follower. When,
A link member movable to a second position connected to the rocker arm, and link switching means capable of switching linking of the link member to the rocker arm and the lost motion mechanism are provided.

[0010]

According to the present invention, the connection switching between the rocker arm and the free cam follower is performed by the link member splined or serrated on the free cam follower.
It can be performed accurately without special machining finish of the sliding surface, and the rotational force acting on the connecting member can be sufficiently supported by splines or serrations.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIGS. 1 to 4 show an engine provided 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 to which the present invention is applied.

To explain this, each cylinder is provided with a single rocker arm 1 corresponding to two intake valves 9. A base end of the rocker arm 1 is swingably supported by a cylinder head via a rocker shaft 3 common to each cylinder, and a tip end of the rocker arm 1 abuts on a stem top of the intake valve 9.

The rocker arm 1 is formed in a substantially rectangular shape in a plan view, and the rocker arm 1 is provided with a single free cam follower 2 substantially on the upper surface of the center thereof. In FIG. 2, the first cam follower 2
A cam follower portion 1A made of a wear-resistant material with which the low-speed cam 21 as a cam contacts is provided, and a hydraulic drive portion 30 for driving a prop 4 described later is formed on the right side. The base end of the free cam follower 2 is supported by the rocker arm 1 via a sub rocker shaft 16 so as to be swingable (relatively rotatable). The sub rocker shaft 16 is slidably fitted in a hole 17 formed in the free cam follower 2, while a hole 1 formed in a support wall 18 formed in the rocker arm 1.
9 is press-fitted and supported.

The free cam follower 2 does not have a portion that comes into contact with the intake valve 9, 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 free cam follower so as to protrude in an arc shape.

In the rocker arm 1, a hollow space 1C is provided around the tip of the free cam follower 2, and a cylindrical step for accommodating the lost motion mechanism 25 is provided at a position slightly deviated from directly below the free cam follower 2. A partial arc portion 1B having a perforated hole 27 is formed. The lower end of the coiled lost motion spring 26 has a hole 2
7 is supported by a lower spring retainer 28 locked by a locking ring 27A mounted on an annular groove formed at the upper end of the upper spring retainer 29 having a bottomed cylindrical shape and slidably fitted in the hole 27. It is energizing.

Further, the upper spring retainer 29 has a flange 29A formed at the edge thereof.
A engages the step 27B formed in the hole 27 to form a stopper, and the amount of protrusion of the upper spring retainer 29 from the hole 27 is regulated. Thus, the height between the upper surface of the upper spring retainer 29 and the upper end surface of the partial arc portion 1B of the rocker arm 1 is maintained equal.

On the other hand, the above-mentioned free cam follower 2 has a form in which a keyhole-shaped cavity parallel to the axis of the sub rocker shaft 16 is provided below the cam follower portion 2A, and a prop 4 as a linking member is provided inside the cavity. It is provided movably in the direction. Prop 4 basically has a bottomed cylindrical shape,
A first leg 4A and a second leg 4B that protrude in the radial direction are provided on the outer peripheral portion. And the inner hole 4C of the prop 4
A guide tube 5 whose one end is in contact with the rocker arm 1 is slidably fitted to the head of the guide tube 5 and the inner hole 4C.
2, a return spring 6 for urging the prop 4 rightward in FIG. 2 is contracted.

In the present invention, a spline or serration is used as a mechanism for guiding the axial movement of the prop 4, as shown in FIG. That is, the outer periphery (sliding portion) 4D of the cylindrical portion of the prop 4 has several spline teeth cut in parallel with the axis, and the sliding portion 2B of the free cam follower 2 formed by the cavity has a spline groove. Provided. With such a structure of the linking member, the outer periphery 4D of the cylindrical portion of the prop 4 and the free cam follower 2
The sliding portion 2B is slidable in the axial direction, and the second
Prop 4 via free cam follower 2 by cam 22
Is sufficiently supported by the spline engagement between the sliding portion 2B and the outer periphery 4D of the cylindrical portion.

In this embodiment, as shown in FIG. 5, a gap L is formed between the keyhole-shaped cavity of the free cam follower 2 and the opposing surfaces of the legs 4A and 4B of the prop 4.
In the spline engagement between the sliding portion 2B of the free cam follower 2 and the outer peripheral portion 4D of the cylindrical portion of the prop 4, when the L is meshed with one tooth deviated from the normal position, the leg 4A,
4B is set so that the prop 4 cannot be inserted into the free cam follower 2 by colliding with the side surface of the keyhole-shaped cavity of the free cam follower 2. Therefore, the setting of L has a function of preventing the prop 4 from being inserted at an incorrect position when the prop 4 is incorporated into the free cam follower 2.

On the other hand, the operating plunger 31 of the hydraulic drive unit 30 provided on the rocker arm 1 is in contact with the bottom of the prop 4. That is, the rocker arm 1 is provided with a stepped through hole 32 that opens into the space 1C in parallel with the axis of the main rocker shaft 3 described above, and the operation plunger 31 described above is slidably fitted on the small diameter side thereof. On the large diameter side, a plug 33 having a projection formed at the center is fitted. A hydraulic chamber 34 is formed between the operating plunger 31 and the plug 33.

An oil passage for guiding the operating oil pressure to the hydraulic chamber 34 is provided through the inside of the rocker arm 1 and the main rocker shaft 3. The rocker arm 1 has one end opening to the hydraulic chamber 34 and a through hole 41 having the other end passing through a bearing surface for the main rocker shaft 3. An oil gallery 42 is formed in the main rocker shaft 3 in the axial direction. The oil gallery 42 communicates with the through hole 41 of the rocker arm 1 through the through hole 43 and the annular groove 44. Here, the prop hydraulic pressure is introduced into the hydraulic chamber 34 and the return spring 6 described above, so that the prop 4
Of the link switching means.

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. The switching between the low-speed cam 21 and the high-speed cam 22, which will be described later, is performed smoothly while suppressing the rapid fluctuation of the engine torque based on the detected value of

The low-speed cam 21 and the high-speed cam 22 adjacent thereto are integrally formed on a common camshaft, respectively, so as to satisfy the valve lift characteristics required when the engine is running at a low speed and at a high speed. They are formed in different shapes (including similar shapes having 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.

In this embodiment, as shown in FIG. 5, the left end of the first leg 4A and the edge of the upper spring retainer 29, that is, the hole 27 of the rocker arm 1 are enlarged.
Is determined so that the distance LA from the outer edge of the second leg 4B to the outer edge of the circular arc portion 1B of the rocker arm 1 is larger than the distance LA from the peripheral edge of the second leg 4B. In other words, the second
The leg 4B is set such that the connection with the rocker arm 1 is achieved earlier than the first leg 4A.

In this embodiment having the above-described structure, when the engine is running 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 9. At this time, the free cam follower 2 is
The prop 4 is slid in the cavity of the free cam follower 2 at the position shown in FIG. 2 by the urging force of the return spring 6, and only the first leg 4A is moved by the lost motion mechanism 25. In contact with the upper spring retainer 29 at the first position. Accordingly, even when the rocker arm 1 is input from the first leg 4A to the upper spring retainer 29, the movement of the rocker arm 1 is not hindered only by the bending of the lost motion spring 26.

On the other hand, when the engine is running at a high speed,
When the operating hydraulic pressure is guided to the hydraulic chamber 34 via the oil gallery 42 and the oil passage 41, the operating plunger 31 moves the prop 4 in the cavity against the return spring 6 and moves to the second position shown in FIG. Bring. In this state, the first leg 4A and the second leg 4B of the prop 4
The rocker arm 1 and the free cam follower 2 are connected and integrated with each other by engaging with the upper end surface of the partial arc portion 1B of the rocker arm 1, and swing around the main rocker shaft 3.

Here, the high speed cam 22 is
The cam follower portion 1A of the rocker arm 1 rises from the low-speed cam 21 when swinging integrated with the free cam follower 2 because both the valve opening and the valve lift amount are formed larger than Each intake valve 9 is driven to open and close according to the profile of the high-speed cam 22, and both the valve opening and the valve lift are increased.

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 prop 4 and the operating plunger 31 are moved by the elastic restoring force of the return spring 6. The rocker arm 1 is moved to the original position, and the restraint of the rocker arm 1 is released.

As a result, 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.

In the above-described embodiment,
Even when the operating hydraulic pressure is not sufficiently generated and the movement of the prop 4 from the first position to the second position is insufficient,
Since the second leg 4B is preferentially connected to the rocker arm 1, the free cam follower 2 is less likely to tilt. This is because the connecting portion of the second leg 4B to the rocker arm 1 is located closer to the center of the free cam follower 2 than the connecting portion of the first leg 4A. As a result, the free cam follower 2 is prevented from hitting one side, and the occurrence of abnormal noise is reduced.

[0032]

As is apparent from the above description, according to the present invention, since the connecting member using the spline or the serration is employed for the connection switching mechanism between the rocker arm and the free cam follower, the mechanical characteristics of the sliding surface are improved. Not only does processing finish become unnecessary, contributing to the reduction of manufacturing costs,
The rotational force acting on the connecting member can be sufficiently supported by the grooved sliding mechanism.

[Brief description of the drawings]

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

FIG. 2 is a longitudinal sectional view taken along the line II-II of FIG. 1 and shows a state in which the rocker arm and the free cam follower are disconnected from each other (during low-speed operation).

FIG. 3 is a transverse sectional view taken along the line III-III in FIG. 1;

FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG.

FIG. 5 is an enlarged view of the lost motion mechanism section of FIG. 2;

FIG. 6 is a longitudinal sectional view taken along the line II-II of FIG. 1, and shows a connection state between the rocker arm and the free cam follower (during high-altitude operation).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rocker arm 2 Free cam follower 2B Sliding part 3 Main rocker shaft 4 Prop (coupling member) 4A 1st leg 4B 2nd leg 4D Peripheral outer periphery of prop 6 Return spring 9 Intake valve 16 Sub rocker shaft 25 Lost motion mechanism 26 Lost Motion Spring 27 Stepped Hole 28 Lower Spring Retainer 29 Upper Spring Retainer 30 Hydraulic Drive 31 Operating Plunger

Claims (1)

(57) [Scope of request for utility model registration] 1. A rocker arm having one end linked to an intake valve or an exhaust valve and driven by a first cam, a free cam follower slidably supported by the rocker arm and driven by a second cam, and a free cam follower. A lost motion mechanism provided in the rocker arm; a spline or serration engaged with the free cam follower; and a movable position linked to the lost motion mechanism and a second position coupled to the rocker arm. A valve operating device for an engine, comprising: a member; and link switching means capable of switching a link of the link member to the rocker arm and the lost motion mechanism.