JPH0130568Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a variable valve timing mechanism for an internal combustion engine.

Background of the Technology In order to change the opening/closing timing and lift amount of intake valves, exhaust valves, etc. of an internal combustion engine according to the operating condition of the engine, for example, two intake cams with different cam profiles are provided per cylinder. A cam piece moving type variable valve timing mechanism has been known that operates the intake valve by switching to a low-speed intake cam at low speeds and a high-speed cam at high speeds to improve fuel efficiency and output.

In this type of variable valve timing mechanism,
Regarding the timing of switching the cam, it is necessary to quickly complete the switching within a short time from the time when the cam starts to close the on-off valve to the time when the on-off valve starts to open next. In particular, when switching from a low-speed cam to a high-speed cam, it is necessary to quickly move the cam piece when the engine speed increases, that is, when the vehicle is accelerating. In order to move the cam piece quickly in this way, the cam piece has conventionally been attached to the camshaft via a ball slide bearing.

By the way, since the outer side (cam surface) of the cam piece slides on the rocker arm, it is required to have high wear resistance against slipping. On the other hand, the ball groove inside the cam piece is required to withstand high contact surface pressure with the ball and to not cause fatigue or peeling due to rolling of the ball. However, conventionally, cam pieces were made of a single material, so if cast iron, which is resistant to slippage and wear, was used, the ball grooves would not be hard enough and there was a risk of dents forming in the ball grooves during operation. . Furthermore, if the cam piece is made of bearing steel that can withstand high contact surface pressure, there is a problem in that the cam surface and the rocker arm do not contact well and pitting occurs.

Purpose of the invention The present invention uses a cam piece moving type variable valve timing mechanism as described above, in which the outside of the cam piece is made of cast iron, etc., which is resistant to slippage, and the inside is made of bearing steel, etc., which can withstand high surface pressure. The purpose of this combination is to prevent dents in the ball groove and improve the contact and wear resistance of the cam piece surface.

Structure of the Invention In order to achieve the above object, in the present invention, a cam piece having at least two drive cams with different cam profiles for one on-off valve is movable in the axial direction via a slide bearing. A variable internal combustion engine, which is mounted on a camshaft so as not to move in the rotational direction, and by moving the cam piece in the axial direction, the at least two driving cams are selectively switched to operate an on-off valve. In the valve timing mechanism, the cam piece is made of a metal material that can withstand high contact surface pressure on the inside including the inner surface that contacts the slide bearing, and is made of a metal material with high wear resistance on the outside. A variable valve timing mechanism is proposed which is characterized in that it is integrally coupled.

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a cam piece moving type variable valve timing mechanism that employs a slide bearing mechanism. In FIG. 1, 1 is a cylinder head of an engine, 2 is an intake port, 3 is an intake valve, 4 is a valve retainer, 5 is a valve spring, 6 is a latch adjuster, and 7 is a rocker arm. An intake cam piece 12 is supported by a slide bearing 20 on a camshaft 10 that rotates in synchronization with the rotation of a crankshaft (not shown) of an engine, so that it cannot rotate relative to the camshaft 12 but can move in the axial direction.

As shown in detail in FIG. 2, the outer peripheral surface of the camshaft 10 has grooves 10 extending in the axial direction at equal intervals in the circumferential direction.
a is formed, while the intake cam piece 12
Grooves 12a extending in the axial direction are also formed at equal intervals in the circumferential direction on the inner peripheral surface. The slide bearing 20 includes a large number of balls 21 and these balls 21.
It is composed of a cylindrical retainer 22 with a number of holes for rotatably retaining the retainer 22. The balls 21 of the slide bearing 20 are inserted between the groove 10a of the camshaft 10 and the groove 12a of the intake cam piece 12 so as to be preloaded in advance.

As shown in FIGS. 3 and 4, the intake cam piece 12 includes a low-speed cam 13a and a high-speed cam 13b, which have different cam profiles and are spaced apart from each other in the axial direction. A circular collar 13c is provided. The low-speed cam 13a and the high-speed cam 13b have a common base circular portion and a lift portion having different profiles. That is, in the high-speed operating range of the engine, the opening time of the intake valve 3 (Fig. 1) is made longer than in the low-speed operating range, and by increasing the lift amount, it is possible to take in a large amount of intake air, and the output is improved. and aims to reduce fuel consumption. 3 shows a state in which the high-speed cam 13b is in contact with the rocker arm 7 (the cam piece 12 has moved to the left end with respect to the camshaft 10), and FIG. 4 shows a state in which the low-speed cam 13a is in contact with the rocker arm 7. (a state in which the cam piece 12 has moved to the right end with respect to the cam shaft 10). In this way, the intake cam piece 12 is connected to the low-speed cam 13a and the high-speed cam 13b by a fork (not shown) that engages with the flange 13c.
It is moved in the axial direction by a distance corresponding to the interval of .

As shown in FIGS. 2, 3, and 4, the cam piece 12 has an inner side 121 including the inner surface (ball groove 12a) of the cam piece 12 that contacts a large number of balls 21, and a rocker arm 7 (see FIG. 1). The outer side 122 including the low-speed cam 13a and the high-speed cam 13b that come in contact with each other are made of different materials. That is, the inner side 121 is made of a metal material that can withstand high contact pressure, such as bearing steel, and the outer side 122 is made of a metal material that has high wear resistance, such as cast iron. These inner portion 121 and outer portion 122 are joined by welding,
Alternatively, the inner part 121 is integrally coupled by press-fitting the outer part.

The retaining ring 31 contacts the left end ball 21a of the slide bearing 20 at the left stroke end position in FIG. 3, and the right end ball 21 of the slide bearing 20 at the right stroke end position in FIG.
A retaining ring 32 that contacts b is attached to the outer periphery of the camshaft 10, which is a shaft member. These retaining rings 31 and 32 are of a normal type that are fitted into ring grooves, but their outer diameters are not so large that they do not come into contact with the retainer 22 of the slide bearing 20. In addition, a retaining ring 33 is in contact with the right end 22a of the retainer of the slide bearing 20 at the left stroke end position in FIG. 3, and a retaining ring 34 is in contact with the left end 22b of the retainer of the slide bearing 20 in the right stroke end position in FIG. It is attached to the inner circumference of the intake cam piece 12, which is a shaft fitting member. These retaining rings 3
3 and 34 are also of a normal type that are fitted into the ring grooves, but their inner diameters are the same as those of the retaining rings 31 and 32.
shall be larger than the outer diameter of

According to such a structure, the retaining rings 31, 32, 3 can be attached at any position shown in FIG.
3 and 34 act as stoppers for the slide bearing 20, so even if a radial load or torque is applied to the intake cam piece 12 and the slide bearing 20 attempts to move in the axial direction, it cannot move.
When the intake cam piece 12 moves rightward from the position shown in FIG. 3 to the position shown in FIG. 4, or conversely, when it moves leftward from the position shown in FIG. 4 to the position shown in FIG.
Since the balls 21 of the slide bearing 20 can roll throughout the entire stroke of travel, the intake cam piece 12 can move smoothly and quickly. During the movement, the retaining rings 33 and 34 of the intake cam piece 12 are attached to the retaining rings 31 and 3 of the camshaft 10.
Each exceeds 2. Further, at the end of the movement stroke, the retainer end 22a or 22b abuts the retaining ring 33 or 34, and the end ball 21a or 21b abuts the retaining ring 31 or 32, forming a stopper.

In this way, the shaft fitting member (intake cam piece) 12
By stopping the movement of the slide bearing 20 at both end positions of the movement stroke, the necessary movement distance of the slide bearing 20 accompanying the movement of the shaft fitting member (intake cam piece) 12 can always be secured. Therefore, the slide bearing 20 always maintains a constant sliding amount, and the balls 21 reliably roll without slipping over the entire movement stroke. Also, camshaft 1
Even when assembling the No. 0 assembly into the engine, the cam piece 12 is prevented from falling off, and the assembling work efficiency is improved. In the embodiment shown in FIGS. 3 and 4, the retaining rings 31 and 32 are attached to the retainer end 22.
a, 22b, and the retaining rings 33, 34 may be brought into contact with the end balls 21a, 21b.

Effects of the invention When forming a cam piece using a conventional uniform material, it was very difficult to find a material that could withstand both sliding wear and contact wear, so various surface hardening treatments were tried to find compatibility. It was necessary to find a good surface treatment method through trial and error. In contrast, the cam piece 1 adopted in this invention
According to 2, materials suitable for rolling wear (known)
By combining this with a material (known) suitable for sliding wear, the optimal material can be selected in a short time without trial and error. Further, special processing such as heat treatment of the cam piece 12 is not required, resulting in lower cost.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a cam piece moving type variable valve timing mechanism having a slide bearing of the present invention, Fig. 2 is a detailed sectional view of the slide bearing mechanism, and Figs. 3 and 4 are axial directions showing the state of movement of the cam piece. FIG. 3...Intake valve, 10...Camshaft, 12...
Intake cam piece, 20...Slide bearing,
121... Inner part of the cam piece, 122... Outer part of the cam piece.

Claims (1)

[Scope of utility model registration request] At least two drive cams 13a, 13b with different cam profiles for one on-off valve 3
The cam piece 12 with the sliding bearing 2
0, the at least two drive cams are mounted on a cam shaft 10 so as to be movable in the axial direction but not in the rotational direction, and the at least two drive cams are selectively moved by moving the cam piece 12 in the axial direction. In a variable valve timing mechanism for an internal combustion engine in which an on-off valve is operated by switching, the cam piece 12
The inner side 121 including the inner surface that contacts the slide bearing 20 is made of a metal material that can withstand high contact surface pressure, and the outer side 122 is made of a metal material with high wear resistance.
22 is a variable valve timing mechanism characterized in that it is integrally coupled.