JPS6245919A - Valve timing adjuster - Google Patents

Abstract

PURPOSE:To obtain variable valve timing through a simple and low-cost structure by disposing an abutment portion of a valve arm above a stem end portion of a valve member and supporting a valve arm shaft in an inclined manner so as to adjust the valve space between the two portions in response to the axial displacement of the valve-arm. CONSTITUTION:In a support structure of an intake valve 1 constituting a valve member, a support pedestal 9 for supporting a valve arm 8 is protruded upwardly from the upper surface 6 of a cylinder head, and the support pedestal 9 supports a valve arm shaft 10 in an inclined manner with respect to the upper surface 6 of the cylinder head. A valve arm boss 11 is fitted over the extreme end of the valve arm shaft 10 swingingly movably in the circumferential direction of the valve arm shaft 10, and the valve arms boss 11 has an abutment 12 projecting forwardly and disposed above the stem end portion 4. The abutment 12 is swingingly movable in the vertical direction on a fulcrum of the valve arm shaft 10 by a valve actuating mechanism of the engine provided oppositely to the valve arm boss 11. This permits the valve arm 8 to be moved on the valve arm shaft 10 by appropriate means, resulting in variable valve timing.

Description

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

BACKGROUND OF THE INVENTION In recent years, internal combustion engines have become faster. In this type of high-speed engine, in order to prevent the intake air amount from decreasing during high-speed operation,
It tends to delay the closing timing of the intake valve. However, simply delaying the valve closing timing can cause inconveniences such as a decrease in intake flow rate at low speeds and high loads, resulting in performance deterioration, and a decrease in effective compression ratio, resulting in deterioration in starting performance and low-power combustion performance. be. In this case, if the valve timing is changed between low speed and high speed, the above-mentioned inconvenience can be solved.

Conventionally, such valve timing variable mechanisms include the following. For example, Utsukai Showa 55-17700
In the device disclosed in Publication No. 7, the valve arm is attached eccentrically to the valve arm shaft, and the valve arm shaft is rotated in the circumferential direction to move the fulcrum of the valve arm, thereby adjusting the valve timing. I'm trying to change it. Furthermore, in the method disclosed in Japanese Patent Application Laid-Open No. 59-23007, two types of cams are provided, one for high speed and one for low speed, and the valve timing is changed by selectively moving the valve arms of both of them. There is.

Problems to be Solved by the Invention In the former case, since the valve arm shaft has a variable structure, there is a problem in that it becomes mechanically complex and is prone to failure. The latter method requires two types of cams, which poses a problem in that it is expensive.

The present invention aims to solve the above problems.

Means for Solving the Problems The present invention provides a valve arm (10) swingably supported on a valve arm shaft (10).
8) so as to be movable in the axial direction of the valve arm shaft (10), and the abutting portion (12) of the valve arm (8) is placed above the stem end portion (4) of the valve member (1). The valve arm shaft (lO) is supported in an inclined manner so that the valve gap between the two can be changed by the axial displacement device of the valve arm (8).

Operation By moving the valve arm (8) on the valve arm axis (lO) by an appropriate means, the valve gap increases or decreases and the valve timing changes.

Example Hereinafter, one embodiment of the present invention will be described based on the drawings.

In FIG. 1, (1) shows an intake valve as a valve member of the present invention. Pulp stem (2) of this intake valve (1)
) extends upward through the cylinder head (3). A valve spring (7) is interposed between the valve spring receiver (5) attached to the stem end portion (4) at the upper end of the pulp stem (2) and the upper surface (6) of the cylinder head.

Further, a valve arm support stand (9) for supporting the valve arm (8) is provided to protrude above the second surface (6) of the cylinder head. A valve arm shaft (10) is supported on the valve arm support base (9) so as to be inclined with respect to the upper surface (6) of the cylinder head. The valve arm shaft (10) is arranged at the rear of the intake valve (1) as shown in FIG.

Near the tip of the valve arm shaft (10), there is a valve arm boss portion (
11) is fitted around the valve arm shaft (10) so as to be swingable in the circumferential direction. A contact portion (I2) projecting forward from the valve arm boss portion (11) is arranged above the stem end portion (4). The contact portion (12) is configured to swing in the vertical direction about the valve arm shaft (10) as a fulcrum by a valve operating mechanism of an engine provided on the opposite side of the valve arm boss portion (11). It has become. In addition, the valve arm boss portion (1
1) is adapted to slide in the axial direction of the valve arm shaft (10).

A cylindrical spring guide (13) is fixed to the inside of the valve arm boss portion (11), that is, to the side of the valve arm support base (9). The spring guide (13) has a valve arm shaft (10).
A return spring (14) fitted externally is installed inside, and
A first stopper portion (15) is provided at its tip. One end side of the return spring (14) is attached to a valve arm support stand (
9), thereby making contact with the side wall surface of the valve arm (9).
8) is urged in a direction away from the valve arm support base (9).

On the other hand, a sleeve (16) is fitted onto the shaft end side of the valve arm shaft (10). The sleeve (16) is attached to the valve arm boss portion (11
), and a cylinder chamber (17) is formed at the inner end thereof between the valve arm boss portion (11) and the valve arm boss portion (11). Further, at the outer end portion of the sleeve (16),
A second stopper portion (18) is provided which projects laterally. A portion of the second stopper (18) has a valve arm boss portion (
11) to restrict movement in the axial direction. Note that (19) is a circlip for preventing removal that is integrally attached to the valve arm shaft (10) on the outside of the sleeve (16).

Further, an oil passage (20) is provided inside the valve arm shaft (10) along the axial direction of the valve arm shaft (10). This oil passage (20) and the cylinder chamber (17) communicate with each other via a communication hole (21) formed in the valve arm shaft (10). Further, this oil passage (20) is connected to the valve arm support base (
9) is connected to a hydraulic power source (not shown) for lubricating the valve arm such as a hydraulic pump via a valve arm lubricating oil passage (22) provided in the valve arm lubricating oil passage (22). The oil pressure supplied from this valve arm lubrication oil pressure source increases or decreases in proportion to the engine speed.

That is, when the engine is stopped, no hydraulic pressure acts on the cylinder chamber (IT), so the valve arm (8) is moved by the return spring (
14) in the axial direction of the valve arm shaft (10) and moves to the left, and is regulated by a portion of the second stopper (18) as shown in FIGS. 1 and 2. In this state, the abutting portion (12) of the valve arm (8) and the stem end portion (
4) is the maximum clearance (
1+).

When the engine is started from the above state, the oil pressure of the valve arm lubrication oil pressure source increases, and accordingly, the oil pressure is supplied to the cylinder via the oil passage (20) connected to the valve arm lubrication oil passage (22). The hydraulic pressure supplied to the chamber (17) also increases. As a result, the valve arm (8) moves from left to right along the axial direction of the valve arm shaft (10) against the return spring (14), and the valve gap gradually decreases during this time.

Since the valve clearance differs between low speed and high speed, the stem end (4) due to the abutting portion (12)
A shift occurs in the impact timing of the intake valve (1), and the valve closing timing of the intake valve (1) changes. Therefore, by appropriately selecting the parameters, the valve closing timing can be set to an optimum state so that the volumetric efficiency increases both at low speed and high load and at high speed and high load. Furthermore, since the valve closing timing during low speed rotation can be set later than during high speed rotation, the effective compression ratio during low speed rotation can be increased, and low power combustion performance and starting performance can be improved.

In the high oil pressure state during high-speed operation, the spring guide (1
3), the first stopper part (15) is regulated by coming into contact with the valve arm support base (9) as shown in FIGS. 3 and 4.

In this state, the valve clearance is the minimum clearance (t2).

In addition, during low-speed operation, the contact portion (12) at the tip of the valve arm (8)
) moves outward from the lower stem end (4),
Part of the second stopper (
18) on the valve arm axis (10), the valve arm (8) enters a so-called missed state and the intake valve (1) is at rest. Therefore, in a multi-cylinder engine, by selecting a certain cylinder and having the structure as described above, it is possible to reduce the number of cylinders during low-speed operation.

Effects of the Invention As described above, in the present invention, the abutting portion of the valve arm is arranged above the stem end portion of the valve member, so that the valve gap between the two changes depending on the amount of movement of the valve arm in the axial direction. By supporting the valve arm shaft in an inclined manner, the valve arm can be moved on the valve arm shaft by appropriate means (for example, hydraulic pressure that increases or decreases depending on the engine speed as in this embodiment). For example, this causes the valve timing to change depending on the operating state of the engine. Therefore, since there is no need to make the valve arm shaft a variable structure, there is an advantage that the support structure is simplified and durability is improved. Furthermore, since there is no need to provide two types of cams, one for high speed and one for low speed, there is an advantage that manufacturing costs can be reduced.

[Brief explanation of drawings]

Fig. 1 is a partially cutaway front view showing a state in which the valve clearance is at its maximum in an embodiment of the present invention, Fig. 2 is a cross-sectional view of the main part of Fig. 1, and Fig. 3 is a valve FIG. 4 is a partially cutaway front view showing a state in which the gap is at its minimum, and FIG. 4 is a cross-sectional view of the main part of FIG. 3. (1)...Intake valve, (4)...Stem end, (
8)...Valve arm, (10)...Valve armlet, (12)...
・Abutment part.

Claims (1)

[Claims] A valve arm is swingably supported on a valve arm shaft, and the valve arm is movably supported in the axial direction of the valve arm shaft, and the abutment portion of the valve arm is disposed above the stem end portion of the valve member, so that both A variable valve timing device characterized in that the valve arm shaft is supported in an inclined manner so that the valve gap between the valve arms changes depending on the amount of movement of the valve arm in the axial direction.