JPH10274013A - Valve spring load adjustment device - Google Patents

Abstract

(57) [Problem] To increase a set load of a valve spring on an exhaust valve side when an exhaust brake is operated, to prevent the exhaust valve from being forcibly opened, and to obtain a large braking effect. To SOLUTION: An inclined cam plate 11 whose upper surface is inclined in a circumferential direction is horizontally rotatable between a seat plate 13 for receiving a lower end of a valve spring 7 on an exhaust valve 3 side of an engine and a cylinder head 1. By rotating the inclined cam plate 11 when the exhaust brake is operated,
The seat plate 13 is raised.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve spring load adjusting device which increases the load of a valve spring on the exhaust valve side when an exhaust brake is operated.

[0002]

2. Description of the Related Art Generally, in a large vehicle equipped with a diesel engine, an exhaust brake provided for closing the exhaust shutter provided in an exhaust pipe to perform a negative work using the engine as a compressor to brake the vehicle. The device is mounted. The effectiveness of the exhaust brake depends on the pressure in the exhaust pipe (exhaust manifold) when the exhaust brake is activated, and the greater the pressure, the greater the braking effect.

However, when the pressure in the exhaust pipe exceeds a certain pressure, as shown in FIG. 4, the exhaust valve is set to a timing other than the valve timing (a) according to the cam profile.
(b) That is, the forcible opening is forcibly reopened in the suction process, and the pressure in the exhaust pipe flows back into the cylinder and the intake port, thereby impairing the braking effect. The reason why the exhaust valve is opened in the intake stroke as described above is as follows.

When the engine is in the compression and combustion strokes, the pressure in the cylinder is high (positive pressure), so that the exhaust valve is not opened by the pressure in the exhaust pipe. However, during the suction stroke, the pressure inside the cylinder becomes negative, so the pressure difference between the exhaust pipe and the cylinder becomes large.When the pressure inside the exhaust pipe exceeds the set load of the valve spring, the exhaust valve is forcibly turned on. The valve is opened.

If the exhaust valve is opened at a timing other than a predetermined timing, in a multi-cylinder engine having four or more cylinders, since any one of the cylinders is always in the intake stroke, the pressure in the exhaust pipe escapes to the intake port side and is reduced. As a result, the braking effect is reduced. In order to solve such a problem, the set load is increased by increasing the spring constant of the valve spring of the exhaust valve, and the exhaust valve is easily opened even if the pressure in the exhaust pipe increases during the operation of the exhaust brake. It is effective to avoid this.

[0006]

However, as described above, if the set load is increased by increasing the spring constant of the valve spring, the usefulness of the exhaust brake is improved, but the mechanical loss increases and the output decreases. At the same time, the wear of the valve face and valve seat of the exhaust valve, and the sliding contact surfaces such as the cam, the rocker arm, and the valve shaft end are accelerated.

[0007] In view of the above, there is naturally a limit to increasing the spring constant of the valve spring. Usually, the exhaust gas is exhausted in consideration of both the strength of the exhaust brake and the mechanical loss. The fact is that the spring constant (set load) of the valve spring of the valve is optimally set.

[0008] Therefore, there is a limit to the effectiveness of the exhaust brake, and it is difficult to expect a greater braking effect.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and increases the set load of a valve spring only when an exhaust brake is actuated, thereby minimizing mechanical loss and wear of various parts, thereby achieving a large braking effect. It is an object of the present invention to provide a valve spring load adjusting device capable of obtaining the following.

[0010]

According to the present invention, the above-mentioned problem is solved as follows. (1) An inclined cam plate having an upper surface inclined in a circumferential direction is provided between a seat plate for receiving a lower end of a valve spring on an exhaust valve side of an engine and a cylinder head so as to be horizontally rotatable, and an exhaust brake is operated. In some cases, the seat plate is raised by rotating the inclined cam plate.

(2) In the above item (1), two inclined cam plates are provided so as to face each other with the upper surfaces inclined in opposite directions, and are rotated in synchronization with each other in the same direction.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows an exhaust-side valve train, in which a vertically oriented valve guide (2) press-fitted into a cylinder head (1) has a shaft portion (3a) of an exhaust valve (3).
Are slidably held up and down.

An umbrella (3) connected to the lower end of the exhaust valve (3)
The valve face portion (3c) of (b) is in contact with the valve seat (5) fitted to the lower end of the opening of the exhaust port (4), and always closes the exhaust port (4).

(6) is a spring retainer, which is an exhaust valve.
It is fixed to the shaft end of (3) via a pair of cotters (not shown). A valve spring (7) is contracted between the spring retainer (6) and a washer (14) mounted on a piston (12), which will be described later.
It is always biased upward.

(8) A rocker arm which is swung up and down by a cam (not shown). The adjuster bolt (9) screwed to the tip of the rocker arm pushes the shaft end of the exhaust valve (3) to open and close it. Is performed.

(10) is a lip seal for preventing oil from falling. A pair of fan-shaped inclined cam plates (11) and (11) are provided on both sides of the valve guide (2) on the upper surface of the cylinder head (1) so as to be horizontally rotatable by pins (12). A seat plate (13) for receiving the lower end of the valve spring (7) is mounted on the upper surface thereof. The seat plate (13)
The valve guide (2) is fitted to the cylinder head (1) so as to be slidable up and down on a cylindrical portion (1a) surrounding the outer peripheral surface of the valve guide (2).

As shown in FIG. 3, the contact surface between each inclined cam plate (11) and the seat plate (13) is an inclined surface facing in the circumferential direction, and the inclined cam plate (11) is rotated. At this time, the seat plate (13) moves up and down. In addition, the inclination direction of the inclined surface is
It is preferable that the right and left sides are reversed. Both inclined cam plates (11) are synchronously rotated by a drive rod (14) linked to an actuator (not shown).

When the two inclined cam plates (11) are rotated in the same direction simultaneously with the operation of the exhaust brake, the seat plate
By raising (13), the set load of the valve spring (7) is increased, and the upward urging force (valve closing force) of the exhaust valve (3) increases.

As a result, even if the pressure in the exhaust pipe (exhaust manifold) including the exhaust port (4) rises due to the operation of the exhaust brake, the exhaust valve (3) remains in the conventional state.
However, there is no possibility that the valve will be forcibly opened at a time other than the predetermined timing (intake stroke), and the pressure in the exhaust pipe is prevented from flowing back to the suction port side and reduced, so that a large braking effect is obtained. can get.

Further, the set load of the valve spring (7) increases only when the exhaust brake is operated and decreases during normal operation, so that the mechanical loss of the valve train is reduced and the engine performance is improved. In addition, as in the prior art, the valve spring (7)
It is not necessary to make the spring constant excessively large, so that, similarly to the above, the mechanical loss is reduced, the frictional resistance of each contact portion of the valve train components is reduced, and the engine performance is improved.

Further, since the exhaust valve (3) does not open and close by impact except at a predetermined valve timing, wear of the valve face part (3c) and the valve seat (5) is small, and the umbrella part (3b) and The load applied to the shaft (3a) is also reduced.

Further, since a part of the exhaust gas in the exhaust pipe immediately after the operation of the exhaust brake does not flow backward to the cylinder and the suction port side, not only is the intake shutter unnecessary, but also the residual exhaust gas in the cylinder is eliminated. The reduction in volume leads to a smooth re-acceleration after the release of the exhaust brake, in addition to an increase in fuel consumption and a reduction in black smoke particles.

The present invention is not limited to the above embodiment. In the embodiment, the case where the valve spring (7) is single has been described, but the present invention can also be applied to a double-spring type valve operating mechanism including large and small valve springs inside and outside. At this time, the set load of one or both of the inner and outer valve springs may be increased by the seat plate (13).

Also, a valve spring (7) formed by a seat plate (13).
Can be arbitrarily adjusted by changing the inclination angle of the contact surface between the inclined cam plate (11) and the seat plate (13).

[0025]

According to the present invention, the following effects can be obtained. (A) When the exhaust brake is operated, the exhaust valve is forcibly opened to prevent the pressure in the exhaust pipe from being reduced, so that a great braking effect can be obtained.

(B) Also, only when the exhaust brake is operated, the set load of the valve spring increases and normally decreases, so that the wear of each part of the valve train decreases and the mechanical loss decreases. To improve engine performance.

(C) According to the second aspect, the seat plate can be raised and lowered stably without rotating the seat plate.

[Brief description of the drawings]

FIG. 1 is a central longitudinal sectional front view of an exhaust-side valve gear to which the present invention is applied.

FIG. 2 is a cross-sectional plan view taken along the line II-II of FIG.

FIG. 3 is an enlarged vertical sectional side view taken along line III-III of FIG. 2;

FIG. 4 is an explanatory view showing an example of movement of a conventional exhaust valve.

[Explanation of symbols]

 (1) Cylinder head (2) Valve guide (3) Exhaust valve (3a) Shaft (3b) Head (3c) Valve face (4) Exhaust port (5) Valve seat (6) Spring retainer (7) Valve Spring (8) Rocker arm (9) Adjuster bolt (10) Lip seal (11) Inclined cam plate (12) Pin (13) Seat plate (14) Drive rod

Claims (2)

[Claims] An inclined cam plate having an upper surface inclined in a circumferential direction is provided between a seat plate for receiving a lower end of a valve spring on an exhaust valve side of an engine and a cylinder head so as to be horizontally rotatable, and an exhaust brake is provided. Wherein the seat plate is raised by rotating the inclined cam plate at the time of the operation of (1). 2. The load adjustment of a valve spring according to claim 1, wherein two inclined cam plates are provided so as to face each other with the upper surfaces inclined in opposite directions, and are rotated synchronously in the same direction. apparatus.