JPH09144516A - Valve driving gear for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely and smoothly perform switching operation of the valve driving gear for an internal combustion engine which sets up a cam, provided with a plurality of cam profiles, slidably in an axial direction on a camshaft, displaces this cam in an axial direction of the camshaft, alternatively selects the cam driving a valve from the cam profile and adjusts opening/closing of the valve in accordance with a lift amount of the selected cam profile. SOLUTION: In a valve driving gear for an internal combustion engine of this kind, a second shaft 12 and an operating shaft 13 are parallelly arranged to a camshaft 4, the second shaft 12 is rotated synchronously with the camshaft 4, in the second shaft 12, in a guide groove 17a or the like arranged in an axial direction corresponding to each cam profile A or the like of a cam 5, the guide groove 17a or the like corresponding to an individual part Q of each cam profile A or the like in a peripheral direction is unmovably formed in the axial direction, one end 18a of an operating arm 18 of the operating shaft 13 is connected to the cam 5, also the other end 18b is alternatively engaged with the guide groove 17a or the like of the second shaft 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve drive device for driving an intake valve and an exhaust valve in an internal combustion engine.

[0002]

2. Description of the Related Art In a valve drive device for driving an intake valve and an exhaust valve of an internal combustion engine, a cam having a plurality of cam profiles is installed on a cam shaft so as to be slidable in the axial direction, and the cam is mounted on the cam. One that selectively displaces in the axial direction of the shaft to drive the valve from each of the cam profiles and adjusts the opening and closing of the valve according to the lift amount of the selected cam profile. Some (for example, JP-A-52
-44314).

[0003]

By the way, in such a valve drive device for an internal combustion engine, it is necessary to switch the cam for driving the valve in a timely and reliable manner.

However, since the rotation speed of the cam is high, the switching operation is difficult, and if the switching operation is inappropriate, the valve drive device may be damaged.

The present invention has been made in view of the above circumstances, and a cam having a plurality of cam profiles is installed slidably in the axial direction on the cam shaft, and the cam is mounted on the shaft of the cam shaft. Valve drive of an internal combustion engine for selectively selecting one of the cam profiles that drives the valve by displacing in the direction, and adjusting the opening and closing of the valve according to the lift amount of the selected cam profile. An object of the present invention is to provide a device that can perform the switching operation reliably and smoothly.

[0006]

In order to achieve this object, the invention according to claim 1 is arranged behind a stem portion of a valve of an internal combustion engine in the axial direction without being rotatable in the circumferential direction on a cam shaft. A slidable cam is installed, and the cam has a plurality of cam profiles formed by being arranged in the axial direction of the cam shaft, and each of these cam profiles is a profile common part formed by a common curved surface. And a profile individual part formed of a curved surface different from each other, and by selectively displacing the cam in the axial direction of the cam shaft to drive the valve from among the cam profiles. In the valve drive device for an internal combustion engine, which opens and closes the valve according to the lift amount of the cam profile, the second shaft and the operating shaft are arranged in parallel with the cam shaft, and the second shaft is provided. It is supposed to rotate in synchronization with the cam shaft, and the second shaft has guide grooves arranged in the axial direction corresponding to each cam profile of the cam, and the individual portions of each cam profile in the circumferential direction. Is formed immovably in the axial direction, the operation shaft has an operation arm, one end of the operation arm is connected to the cam, and the other end is the guide groove of the second shaft. Is a valve drive device for an internal combustion engine, characterized in that

[0007]

According to the first aspect of the present invention, in this type of valve drive device for an internal combustion engine, a second shaft that rotates in synchronization with the cam shaft is arranged parallel to the cam shaft, and the second shaft is provided. Has guide grooves arranged in the axial direction corresponding to each cam profile of the cam and formed in the circumferential direction so as to correspond to the individual portions of each cam profile.

The operating shaft has an operating arm. One end of the operating arm is connected to the cam and the other end is selectively engaged with the guide groove of the second shaft. By engaging the operation arm with the guide groove, the cam position on the cam shaft is restricted.

That is, in such a valve drive device for an internal combustion engine, the switching operation is allowed at an appropriate timing, but at an inappropriate timing, the switching is prevented by the engagement between the operation arm and the guide groove. Therefore, the switching operation can be performed reliably and smoothly.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment shown in the drawings will be described below.

In FIG. 2, reference numeral 1 denotes an intake valve, which is a poppet valve, and opens and closes the intake passage provided in the cylinder head of the internal combustion engine and the combustion chamber.

In the intake valve 1, a coil spring 3 is interposed between a spring receiver 2 installed at the upper end of the stem portion 1a and a cylinder head, and the intake valve 1 is elastically urged to close. There is.

On the other hand, such a stem portion 1a of the intake valve 1
A cam shaft 4 for driving the intake valve 1 is arranged behind the engine, and a rocker arm 6 is arranged below a cam 5 installed on the cam shaft 4.

The rocker arm 6 is swingably supported by a rocker arm shaft 7, and the tip end portion 6a of the rocker arm 6 is always in contact with the tip end upper surface of the stem portion 1a of the intake valve 1.

A roller 11 pivotally supported by a pivot 8 is mounted on the rocker arm 6 thus arranged, and the roller 11 is always in contact with the cam surface 5a of the cam 5.

Therefore, the intake valve 1 has the cam surface 5a of the cam 5 via the rocker arm 6 and the roller 11.
It is designed to be opened and closed by.

In such an internal combustion engine, as shown in FIG. 1, four cam profiles A, B, C and D are integrally formed on the cam surface 5a of the cam 5 in a state where they are arranged in the axial direction of the cam shaft 4. Is formed in.

Each of these cam profiles A, B, C,
As shown in FIG. 2, D is each cam profile A, B,
C and D have the same cylindrical surface and are common (hereinafter referred to as profile common portion P), and the tip end of each cam profile A, B, C, D is the cam profile A, B, Each of C and D is formed by a separate curved surface having a different cam lift amount or the like (hereinafter referred to as profile individual portion Q).

In this embodiment, in the profile individual portion Q of each cam profile A, B, C, D, both side edges in the axial direction thereof are formed as ridges so that the guide wall 5c is formed.
With this guide wall 5c, each cam profile A,
The rollers 11 rolling B, C and D are prevented from deviating from the required cam profile.

Such a cam 5 is mounted on the spline shaft portion 4b of the cam shaft 4, and is mounted on the cam shaft 4 such that it cannot rotate in the circumferential direction but can slide in the axial direction.

Then, as shown in FIG.
A second shaft 12 and an operating shaft 13 are arranged in parallel with.

The second shaft 12 is a drive gear 4a of the cam shaft 4.
It is driven to rotate synchronously at the same rotation speed via a driven gear 12a that meshes with (see FIG. 2).

A guide sleeve 14 is provided on the second shaft 12 so as to be immovable in the axial direction and rotatable in the circumferential direction.
When the external force is applied to the guide sleeve 14 in the circumferential direction, the guide sleeve 14 is appropriately rotationally displaced. However, when the external force is removed, the return spring 15 elastically urges the guide sleeve 14 to the initial proper position. It is supposed to come back.

On the peripheral surface of the guide sleeve 14, the cam profiles A, B, C, D of the cam 5 are provided.
Corresponding to the profile individual portion Q of the four guide grooves 17a, 17b, 17 divided by the side wall 16 extending in the circumferential direction.
c, 17d are formed. That is, in these guide grooves 17a, 17b, 17c, 17d, the side wall 6 is formed in the portion where the phase is in agreement with the profile individual portion Q of the cam 5, but in the portion where the phase is in agreement with the common profile portion P. The side wall 16 is not formed. This is due to the cam profiles A, B,
In the profile common part P of C and D, the operation arm 1
This is because the switching operation among the cam profiles A, B, C, D by 8 is performed.

On the other hand, the operating shaft 13 is operated to switch the cam profiles A, B, C and D by moving it back and forth in the axial direction. The operation arm 18 is mounted so as to be slidable in the circumferential direction, and the operation arm 18 is located at a predetermined position in a state of having a habit of returning by the coil spring 21.

The one end 18a of the operating arm 18
Holds the cam 5 rotatably by being engaged with a holding groove 5b formed at the end of the cam 5. In addition, the operation arm 1
The other end 18b of the guide groove 17 is the guide groove 17 of the guide sleeve 14.
It is selectively engaged with a, 17b, 17c and 17d.

Therefore, when the roller 11 is positioned at the profile common portion P of the cam profiles A, B, C and D and the axial displacement of the operating shaft 18 is given at an appropriate timing, the operating shaft 13 is operated. The other end 18 of the arm 18
b passes through a portion of the guide grooves 17a, 17b, 17c, 17d where the side wall 16 is absent, and the adjacent guide grooves 17a, 17b,
Reach 17c and 17d.

At this time, the one end 18a of the operating arm 18 is also moved in the axial direction similarly with the cam 5. Since the roller 11 is located in the profile common portion P of the cam 5 at this point, the roller 11 is not obstructed by the guide wall 5c and is adjacent to another cam profile A, B, or another cam profile.
Switching is performed by moving to C and D.

Thereafter, the other end 18a of the operating arm 18 is
Is engaged with the appropriate guide grooves 17a, 17b, 17c, 17d and is restrained by the side wall 16, and the corresponding cam profiles A, B, C, on the cam surface 5a of the cam 5 are also provided.
The roller 11 installed on the rocker arm 6 faces the roller D and rolls while being positioned between the guide walls 16 on both sides.

When the operating shaft 18 is operated at an improper timing, the other end 18b of the operating arm 18 comes into contact with the side surface of the side wall 16 of the guide sleeve 14 or the tip of the side wall 16, and thus the side wall. The operation force 18 is pushed back by the reaction force from 16, and the execution of switching is prevented.

In this embodiment, since the tip of the side wall 16 is formed as a tapered taper surface, when the other end 18b of the operating arm 18 comes into contact with the tip of the side wall 16, the tip of the side wall 16 is formed. The tapered taper surface that forms the
It is possible to reliably push back b to the original guide groove side.

As described above, when the operation of the operation shaft 18 is performed at an improper timing, the switching is prevented from being executed. In this state, the coil spring 21 on the operation shaft 13 is bent. In this state, execution of the switching operation of the cam profiles A, B, C, D waits until the next appropriate timing, and the other end 18b of the operation arm 18 becomes the side wall 16
The switching is executed by the spring force of the coil spring 21 at an appropriate timing when it reaches a portion where there is no.

The return spring 15 has a function of smoothly performing the standby operation for switching as described above.

In such an embodiment, the phase relationship between the cam profiles A, B, C, D and the guide sleeve 14 is as shown in FIG. 3, for example.

In FIG. 3, diagrams X and Y show guide grooves 17a, 17b, 17c and 17d in the guide sleeve 14.
Shows the phase state of engagement and disengagement between the operating arm 18 and the other end 18b of the operating arm 18. The line X shows the case where the coil spring 21 is not bent and the guide sleeve 14 is in a predetermined position, and the line Y shows the guide sleeve 14. This is a case of a standby state in which an external force acts on the coil spring 21 to cause the coil spring 21 to bend.

The diagram Z shows the phase state of engagement and disengagement between the roller 11 and the profile individual portion Q of the cam profiles A, B, C and D on the cam surface 5a.

First, when the guide spring 14 is located at a predetermined position without any bending of the coil spring 21, comparing the line X with the line Z, the engagement between the guide sleeve 14 and the cam surface 5a is reached at the time point G. Since they are released at the same time, the operation arm 18 can be moved in the axial direction from this time point G, and the cam profile switching operation can be executed.

After that, the engagement of the guide sleeve 14 is started before the time point J and the engagement of the cam surface 5a is started at the time point L, so that the switching of the cam profile is performed from the time point G to the time point J. Is possible.

From the time point J to the time point L, the guide sleeve 14 restrains the other end 18b of the operating arm 18, so that the roller 11 is required even at this portion without the guide wall 5c on the cam surface 5a. Is prevented from deviating from the cam profile.

Next, in the case where the coil spring 21 is bent, comparing the diagram Y with the diagram Z,
The phase of the guide sleeve 14 is delayed by M, which corresponds to the amount of the deflection, as compared with the case described above.

Therefore, the engagement between the guide sleeve 14 and the cam surface 5a is released at the time point H, and from this time point H, the cam profile can be switched.

After that, the engagement of the guide sleeve 14 starts before the time point L of the engagement of the cam surface 5a at the time point K which is delayed by the phase M from the time point J, so that the switching of the cam profile is started from the time point H. Until time point K.

From time point K to time point L, and time point G
From the time to the time H, the engagement of the guide sleeve 14 prevents the roller 11 from deviating from the required cam profile on the cam surface 5a.

In the phase relationship between the engagement of the guide sleeve 14 and the engagement of the cam surface 5a, the engagement states of both are partially overlapped with each other, and both are in the disengaged state. The period is preferably set to the minimum necessary for the cam profile switching operation.

Next, a second embodiment shown in FIGS. 4 and 5 will be described. The second embodiment is different from the first embodiment described above mainly in the cam profile A formed on the cam surface 5a.
The shapes of B, C, and D are different, in particular, the guide wall 5c is not formed, and other points are substantially the same.

Therefore, in the following, only matters related to this difference will be described.

That is, the cam profiles A, B, C and D formed on the cam surface 5a of this embodiment are different from those of the first embodiment and are different from each other.
The guide walls 5c made of ridges are not formed on both sides of C and D, and the cam profiles A, B, C, and D are formed on the camshaft 4 respectively.
It is formed by a quadric surface parallel to.

Therefore, the guide wall 5c of the cam surface 5a and the roller 1 which can be expected in the first embodiment are provided.
It is difficult to expect the position of the operation arm 18 to be regulated by engaging with 1.

In consideration of this point, in the second embodiment, the guide groove 17a formed in the guide sleeve 14 is
The side walls 16 of 17b, 17c and 17d are set to be long in the circumferential direction so that the side walls 16 do not exist and the cam profiles A, B,
The cam surface 5 sets the period (phase) during which the switching operation between C and D is possible
It is set to be performed at an extremely short phase at the midpoint of the profile common portion P of a.

Also in this embodiment, the operation arm 18 is restrained by the side wall 16 of the guide sleeve 14 over a long phase other than the phase in which the switching operation of the cam profiles A, B, C, D is possible. Operation arm 1
8 does not deviate from the required cam profile excessively, and the switching operation is reliable and smooth as in the first embodiment.

[0051]

As described above, according to the invention described in claim 1, in the valve drive device of this kind of internal combustion engine,
A second shaft that rotates in synchronism with the cam shaft is arranged in parallel with the cam shaft, and the second shaft has guide grooves arranged in the axial direction corresponding to each cam profile of the cam. Guide grooves are formed corresponding to individual portions of each cam profile in the circumferential direction.

The operation shaft has an operation arm. One end of the operation arm is connected to the cam and the other end is selectively engaged with the guide groove of the second shaft. By engaging the operation arm with the guide groove, the cam position on the cam shaft is restricted.

That is, in such a valve drive device for an internal combustion engine, switching operation is permitted at an appropriate timing, but at inappropriate timing, switching is prevented by engagement between the operation arm and the guide groove. Therefore, the switching operation can be performed reliably and smoothly.

[Brief description of the drawings]

FIG. 1 is an exploded top view of a valve drive device of a first embodiment.

FIG. 2 is an overall side view of the valve drive system of the first embodiment.

FIG. 3 is an explanatory diagram of a phase relationship between a cam and a guide sleeve in the first embodiment.

FIG. 4 is a developed top view of the valve drive system of the second embodiment.

FIG. 5 is an overall side view of the valve drive system of the second embodiment.

[Explanation of symbols]

 A, B, C, D Cam profile P Profile common part Q Profile individual part 1 Intake valve (valve) 4 Cam shaft 5 Cam 12 Second shaft 13 Operation shaft 17a, 17b, 17c, 17d Guide groove 18 Operation arm 18a One end 18b the other end

Claims (1)

[Claims] 1. A cam, which is not rotatable in the circumferential direction but slidable in the axial direction on the cam shaft, is installed behind the stem portion of a valve of an internal combustion engine, and the cam is in the axial direction of the cam shaft. A plurality of cam profiles formed by arranging in a row, each of these cam profiles having a profile common part formed by a common curved surface and a profile individual part formed by a curved surface different from each other. Is displaced in the axial direction of the cam shaft to selectively select one that drives the valve from each of the cam profiles,
In a valve drive device for an internal combustion engine that opens and closes the valve according to the lift amount of the cam profile, a second shaft and an operating shaft are arranged in parallel with the cam shaft, and the second shaft is a cam shaft. It is supposed to rotate in synchronism, and the second shaft has guide grooves arranged in the axial direction corresponding to the cam profiles of the cam and corresponding to the individual portions of each cam profile in the circumferential direction. A guide groove is formed immovably in the axial direction, the operation shaft has an operation arm, one end of the operation arm is connected to the cam, and the other end is selected as a guide groove of the second shaft. Valve drive device for an internal combustion engine, characterized in that the valve drive device is internally engaged.