JPS5974313A - Valve head gap eliminating device for tappet valve mechanism - Google Patents

Abstract

PURPOSE:To reduce both oil leakage and the required amount of supplementary oil and to improve responsiveness by providing an eccentric cylinder shaft with a locker arm in such a manner that the arm can be rocked and by rotating the eccentric cylinder shaft through a long operating arm, thereby lowering the oil pressure in a gap eliminating unit. CONSTITUTION:An eccentric cylinder shaft 4 is fitted to a locker shaft 3 in a freely rotatable manner, and locker arms 5i and 5e are installed on the eccentric cylinder shaft 4 in a rocking manner. The eccentric cylinder shaft 4 is provided with an operating arm 6 whose effective length from the center of the locker shaft 3 is greater than the eccentricity of the eccentric cylinder shaft 4, and the arm 6 is connected to a hydraulic gap eliminating unit. The burden of a load to the gap eliminating unit is alleviated according to the ratio between the eccentricity of the eccentric cylinder shaft 4 and the effective length of the operating arm 6. With this contrivance, the value of the maximum oil pressure in an oil pressure chamber can be lowered, thereby reducing the amount of oil leakage and therefore of supplementary oil. Thus, the responsiveness of the unit to the valve head gap is enhnaced so that the valve head gap can surely be eliminated even in high speed operation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a hydraulic valve head gap elimination unit in the engine valve mechanism, automatically eliminates the valve head gap by using hydraulic pressure, and keeps the valve mechanism always quiet. The present invention relates to a valve head gap eliminating device in a valve train which is operated.

Conventionally, in a valve operating mechanism that transmits the valve opening force of a valve operating cam to a valve via a rocker arm, a hydraulic valve head clearance elimination unit has been installed as the rocker arm's rocking axis. Since the valve head gap elimination unit directly supports the valve opening force of the valve drive cam, the load burden on this unit is extremely large (inevitably, the amount of oil leaking from the hydraulic chamber of the unit and The amount of oil supplied to the hydraulic chamber tends to be large, which causes a slow response of the unit to the valve head clearance in the high-speed operating range of the engine.

The present invention has been made in view of the above, and has an object to reduce the load burden on the hydraulic gap elimination unit under the same condition of the valve opening force of the valve train cam, and to enable the unit to operate reliably even when the engine is running at high speed. The object of the present invention is to provide the above-mentioned valve head clearance eliminating device, which is characterized in that an eccentric cylindrical shaft that is eccentric by a certain amount with respect to the center of the rocker shaft is rotatably mounted on the rocker shaft supported by the engine body. A rocker arm that is fitted into the shaft and transmits the valve opening force of the valve drive cam to the valve is swingably supported on the eccentric cylinder shaft, and the effective length from the center of the rocker shaft is attached to the eccentric cylinder sleeve. A hydraulic gap elimination unit is provided with an operating arm larger than the eccentricity of the valve, and rotates the eccentric cylinder shaft in a direction to eliminate the valve head gap when the valve is closed, and prevents rotation of the eccentric cylinder shaft when the valve is opened. is connected to the operating arm.

Hereinafter, one embodiment of the present invention will be explained with reference to the drawings. In Fig. 1, E is an engine body, and there is a gap between the cylinder head 1, which constitutes a part of the engine body, and the camshaft holder 2, which is joined to the upper surface of the engine body. A camshaft C is rotatably held, and this camshaft C is connected to an intake valve cam ci and an exhaust valve cam Ce.
It is equipped with

A pair of rocker shafts 3.3 are attached to the camshaft holder 2, and eccentric cylinder shafts 4.4 are rotatably fitted to these rocker shafts 3.3, respectively. Rocker arms 5j and 5g connecting cams Ci and Ce and intake valves Vi and exhaust valves (not shown) are each supported in a swingable manner (see FIG. 2). Since the intake valve mechanism and the exhaust valve mechanism have essentially the same structure, only the intake valve mechanism will be described below.

A valve closing spring S is connected to the intake valve Vi, which always urges the intake valve in the closing direction.

The eccentric cylinder shaft 4 is eccentric by a certain amount ε with respect to the center of the rocker shaft 3, and when it rotates around the rocker shaft 3 in the direction of the arrow α, it displaces the rocker arm 5i toward the valve drive cam Ci and the intake valve Vi. ing. This eccentric cylinder shaft 4 is integrally formed with an actuation arm 6 that protrudes laterally from one end thereof, and the effective length L from the center of the rocker shaft 3 is equal to the eccentricity of the eccentric cylinder shaft 4. The hydraulic gap elimination unit Z is connected to this operating arm 6.

The main components of the hydraulic gap elimination unit Z are a cylinder 7 and a plunger 9 that slides on the inner circumferential surface of the cylinder 7 to define a hydraulic chamber 8 therein, as is conventionally the case. 7 is fitted into a support hole 10 provided in the camshaft holder 2 so as to be able to rise and fall freely, and the lower spherical end 7α is engaged with the hemispherical oil reservoir 11 on the upper surface of the operating arm 6. Thus, the operating arm 6 A gap eliminating unit Z is connected to the gap eliminating unit Z.

The upper end of the support hole 10 is closed by a cover 12 joined to the camshaft holder 2, and the upper end of the plunger 9 is supported by this cover 12. The plunger 9 is provided with an oil reservoir chamber 13 and a valve hole 14 that communicates the oil reservoir chamber 13 with the hydraulic chamber 8. It communicates with an oil supply passage 17 through an oil hole 16 in the side wall, so that the oil supply passage 17 is always filled with oil supplied from an oil pump (not shown).

A hat-shaped valve cage 18 is fitted to the lower end of the plunger 9, and a spherical check pulp 19 for opening and closing the valve hole 14 is accommodated in the valve cage 18. The valve opens and closes when pressure increases.

A push-out spring 20 is provided between the cylinder 7 and the plunger 9 and exerts a resilient force so as to push the cylinder 7 downward. The elastic force of this spring 20 is much weaker than that of the valve-closing spring S described previously, and its elastic force acts on the actuating arm 6 via the cylinder 7 as a couple in the direction of the arrow a. It is designed to act as a.

Next, to explain the operation of this embodiment, when the intake valve Vi is closed, the operating arm 6 rotates in the direction of arrow α together with the eccentric cylinder shaft 4 by the force couple received from the extrusion spring 20, so that the rocker arm 5i to valve drive cam C7 and intake valve V
s, thereby increasing the valve head gap, that is, the valve Vi
The gap between the connecting portion between the rocker arm 5i and the rocker arm 5i is eliminated.

At this time, if the pressure in the hydraulic chamber 8 is reduced due to the pushing action of the pushing spring 20 against the cylinder 7, the check valve 19
Since the valve is opened, oil in the oil reservoir chamber 13 is supplied to the hydraulic chamber 8 through the valve hole 14, and the hydraulic chamber 8 is reliably filled with oil.

Next, the rocker arm 5i is lifted by the lift action of the valve train cam Ci.
The valve opening force acts on the eccentric cylinder shaft 4 (and the valve opening force also acts on the eccentric cylinder shaft 4 as shown by arrow a).
acts as a couple in the opposite direction, and this couple presses the cylinder 7 toward the plunger 9 via the actuating arm 6,
Since the check valve 19 closes at the same time as the pressure in the hydraulic chamber 8 increases, a high hydraulic pressure corresponding to the pressing force from the operating arm 6 is generated in the hydraulic chamber 8. This hydraulic pressure prevents the cylinder 7 from sliding, and the eccentric cylinder shaft 4 is also prevented from rotating. As a result, the rocker arm 5i swings about the eccentric cylinder shaft 4, and the valve closing spring S
Open the intake valve Vi against the force of. During this time, the oil in the hydraulic chamber 8 leaks slightly from between the sliding surfaces of the cylinder 7 and the plunger 9, but the leaked amount is replenished from the oil reservoir chamber 13 the next time the intake valve Vi is closed. On the other hand, some of the leaked oil flows down between the sliding surfaces of the support hole 10 and the cylinder 7 and flows into the operating arm 6.
” The oil collects in the oil reservoir 11 on two sides, and the spherical end 7a of the cylinder I
This is used to lubricate the joint between the actuating arm 6 and the actuating arm 6.

Here, as shown in FIG. 3, the valve train cam Ci is
Fa, the gap elimination unit Z applies the valve opening force to the operating arm 6.
When the reaction force given to is Fr, the following equation holds true. In the figure, 03 is the center of the rocker shaft 3, and 04 is the center of the eccentric cylinder shaft 4.

Fa-ε=Fr・l Fr=Fa-1 As is clear from the above equation, the valve opening force Fa applied by the valve drive cam ci to the eccentric cylinder shaft 4 is determined by the eccentricity ε of the eccentric cylinder shaft 4 and the actuating arm 6. effective length t
Since it is transmitted to the gap elimination unit Z, the load burden on the unit Z is reduced, and the maximum hydraulic pressure in the hydraulic chamber 8 can be lowered accordingly.

In addition, in the illustrated example, since the gap elimination unit Z is provided at the top of the camshaft holder 2, the influence of heat from the cylinder head 1 having a combustion chamber to the gap elimination unit Z is small (the heat of the unit Z is It is possible to prevent performance deterioration due to

Furthermore, since the upper end of the support hole 10 for mounting the gap elimination unit Z provided in the camshaft holder 9-2 is closed with the cover 12, the gap elimination unit Z can be taken out simply by removing the cover 12. At that time, there is no need to disassemble the valve mechanism, so the maintainability of the unit Z is extremely good.

As described above, according to the present invention, an eccentric cylindrical shaft that is eccentric by a certain amount with respect to the center of the rocker shaft supported by the engine body is rotatably fitted, and the valve opening force of the valve drive cam is applied to the rocker shaft. A rocker arm for transmitting transmission to the valve is swingably supported on the eccentric cylinder shaft, and the eccentric cylinder shaft is provided with an operating arm whose effective length from the center of the rocker shaft is larger than the amount of eccentricity of the eccentric cylinder shaft. A hydraulic gap elimination unit is connected to the operating arm, which rotates the eccentric cylinder shaft in a direction to eliminate the gap between the valve heads when the valve is closed, and prevents rotation of the eccentric cylinder shaft when the valve opens, so that the eccentricity of the eccentric cylinder sleeve is reduced. The load on the gap elimination unit can be reduced depending on the ratio between the amount and the effective length of the working arm (10-), and as a result, the maximum oil pressure in the hydraulic chamber in the unit is reduced, reducing the amount of oil leaking from the hydraulic chamber. The amount of replenishing oil to the hydraulic chamber is reduced, and the responsiveness of the unit to the valve head gap is significantly improved, and the valve head gap can be reliably eliminated even when the engine is operated at high speed.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional front view of a valve mechanism of an engine showing an embodiment of the device of the present invention, Fig. 2 is a sectional view taken along line I-■ in Fig. 1, and Fig. 3 is an explanatory diagram of the operation of the device of the present invention. be. C...Camshaft, Ci, Ce...Valve train cam, E.
...Engine body, Vs...Valve, Z...Gap elimination unit, l...Effective length, ε...Eccentricity, meter...Rocker shaft, 4...Eccentric cylinder shaft, 5z, 5g...rocker arm, 6...operating arm 11-

Claims (1)

[Claims] An eccentric cylindrical shaft that is eccentric by a certain amount with respect to the center of the rocker shaft supported by the engine body is rotatably fitted, and a rocker arm that transmits the valve opening force of the valve drive cam to the valve is attached to the eccentric cylindrical shaft. The eccentric cylinder shaft is supported so as to be swingable, and the eccentric cylinder shaft is provided with an operating arm whose effective length from the center of the rocker shaft is larger than the amount of eccentricity of the eccentric cylinder shaft, so that the valve head gap is eliminated when the valve is closed. A valve head gap eliminating device in a valve operating mechanism, comprising a hydraulic gap eliminating unit connected to the operating arm, which rotates the eccentric cylinder shaft when the valve is opened, and prevents rotation of the eccentric cylinder shaft when the valve is opened.