JPS60249778A - Operating piston buffer mechanism of hydraulic valve device - Google Patents

Abstract

PURPOSE:To prevent a suction/exhaust valve from jumping by disposing an oil escape path on the end portion of an operating piston and using resistance produced by oil flowing from the oil escape path to a damper port for buffer action. CONSTITUTION:An oil escape path comprising a taper portion 30 is formed on the lower end portion of a hydraulic piston 8 for driving a suction/exhaust valve of an internal-combustion engine. The taper portion 30 is adapted to decrease an open area of a damper port 18 with the descent of the operating piston 8. The length l of the taper portion 30 is a quarter diameter (d) of the damper port 18, or a gap (w) is a quarter the lift of the suction/exhaust valve. In this arrangement, a damping characteristic generating at the taper portion 30 can be strictly controlled. Therefore, a jump phenomenon of the suction/exhaust valve can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an operating piston buffer mechanism of a hydraulic valve operating system in an internal combustion engine that opens intake and exhaust valves using hydraulic pressure, and particularly relates to an operating piston buffer mechanism for a hydraulic valve operating system in an internal combustion engine that uses hydraulic pressure to open intake and exhaust valves. Concerning what prevented jumping.

(Prior Art) As shown in FIG. 4, this type of conventional device has a vertically slidable bridge 4 that presses the pulp 2 of the internal combustion engine downward to open the valve, and the bridge 4Fi hydraulic cylinder 6. The rod 10 of the actuating piston 8, which is fully slidable, is brought into pressure contact with the stopper 4a, thereby being pressed downward. A piping 14 from a hydraulic pump 12 is connected to the hydraulic cylinder 6, and a relief port 16 and a damper boat 18 are provided. 20 is a camshaft for operating the hydraulic pump 12a, and 22 is a feed pump.

By the way, a groove-shaped diagonal notch 24 is formed directly below the damper boat 18 on the inner surface of the hydraulic cylinder 6, and the working piston 8 passes through the damper boat 18 from the diagonal notch 24 as shown in FIG. 5 in the stroke end region. It is braked by the resistance force of the oil flowing out.

However, a groove-like diagonal notch 2 is formed on the inner surface of the hydraulic cylinder 6.
4. It is difficult to perform complete processing, and high precision processing cannot be performed. Therefore, if the lower end surface of the actuating piston 8 collides with the lower surface of the hydraulic cylinder 6 due to insufficient braking of the actuating piston 8, there is a problem in that the valve 2 jumps in the area shown in FIG. 6.

(Object of the Invention) The present invention provides an operating piston for a hydraulic valve system that can prevent the intake and exhaust valves of an internal combustion engine from jumping by generating the full braking force necessary for the operating piston in the final region of its sliding stroke in the valve opening direction. The purpose is to provide a buffer mechanism.

(Structure of the Invention) The present invention relates to a hydraulic valve system for a hydraulic valve type internal combustion engine that utilizes the end of an actuating piston that opens a hydraulic cylinder inner metal contact I-intake and exhaust valve as a damper at maximum lift. , an oil relief passage is formed at the end of the working piston, and the resistance force of the oil flowing from this oil relief passage to the damper boat of the hydraulic cylinder gently pressurizes the working piston to the maximum lift position of the hydraulic cylinder. This is the operating piston buffer mechanism of the hydraulic valve train.

(Example) The entire structure of the Kinai 8A will be explained below with reference to FIGS. 1 to 3. In FIG. 1, parts indicated by the same reference numerals as those in FIGS. 4 and 5 are the same or similar parts.

In FIG. 1 showing the buffer mechanism of the working piston 8 according to the present invention, a taper portion 80 is cut at the lower end of the working piston 8, and a taper s30 and a hydraulic cylinder 6
An oil release passageway with a wedge-shaped cross section is formed between the inner surface and the inner surface. This tapered portion 30 functions to reduce the opening area of the damper boat 18 as the working piston 8 descends, so that the shape of the taper JflS 80 moves downward (D! movement 7,) into the loaf end of the working piston 8. The jump phenomenon of valve 2 is a major factor in the damping characteristics of the valve 2.
This is generated when the force represented by the product of the negative acceleration and the mass of the valve train at the end of the downward sliding stroke of the operating piston 8 (near the maximum lift of the valve 2) exceeds the valve spring force. , the tapered portion has a 3° shape that can attenuate the negative acceleration by the damping force of the actuating piston 8.

First, for simplicity, we tentatively achieved the following conditions.

■ The valve spring force is constant with respect to the lift amount near the maximum lift ■ The flow coefficient is constant even if the flow path shape changes ■ The force that the working piston 8 receives from the hydraulic pump 12 is constant At this time, the flow rate flowing out from the damper boat 18 is Since it is proportional to the opening area of the damper bow) 18, it becomes: Flow iQ, opening area A, ゛Pressure P of the oil chamber, constant C, then Q-CAJ] 10,000...■. Differentiating both sides of this equation 0 with respect to time t gives the following equation.

Dividing both sides of equation 0 by the effective cross-sectional area a of the oil chamber gives the moving speed of the working piston 8.

,=cJ, embryo! 19. .

a dt ■Type 9723 "-K (CQnSt,) トL te ICR
11J] t When differentiated by T, the acceleration α becomes C1,A. Here, the conditions for preventing the valve 2 from jumping are as follows, assuming that the valve spring force is t-F1 and the valve train mass is 2 m. The tapered portion 30 may have a shape that satisfies this formula 0.

As shown in FIG. 1, the diameter of the damper boat 18 is
When the length of the taper part 80 is 'cl' and the distance between the taper part 30 and the cylinder 6 is PliftW, the gap W is from the position where the working piston 8 does not overlap the damper bow) 18 at all.
It is necessary to change the opening area continuously as shown in characteristic 40 of the A'tjigZ diagram (because if it changes continuously as in formula 0, the acceleration α becomes infinite).

The length l of the tapered portion 80 is such that the kinetic energy of the valve train at the start of the damping force is the absorbed energy of the valve spring.]
Valve 2 must also be made small.
Next, the operation will be explained assuming that the amount of glue=kH. When the valve 2 is opened by the working piston 8 of the present invention, the tapered portion 80 of the working piston 8 gradually reduces the opening area Ai of the damper boat 18 as the working piston 8 descends, cutting off the flow path of the outflowing oil. Increase the amount of area reduction. Therefore, the valve 2 smoothly converges to the maximum lift value near the maximum lift as shown in region R in FIG. 8, and the valve 2 is prevented from causing a jump phenomenon.

(Effects of the Invention) As explained above, according to the present invention, the tapered portion 80 is formed on the outer circumferential surface of the lower end of the operating piston 8, so that a diagonal notch is formed on the inner surface of the hydraulic cylinder 6 as in the conventional case. It is much easier to process (compared to forming), it can be processed with high precision, and the damping characteristics occurring in the tapered portion 80 can be tightly controlled. Therefore, the valve 2 does not cause a jump phenomenon, making it possible to reduce the operating noise of the internal combustion engine and extend the life of the valve train.

(Another embodiment) The shape of the oil relief passage of the working piston 18 is a tapered part 80.
However, as shown in FIG.

[Brief explanation of the drawing]

Fig. 1 is a schematic front view showing the working piston buffer mechanism according to the present invention, Fig. 2 is a characteristic diagram showing the reduction characteristic of the opening area of the oil seepage passage by the working piston, and Fig. M3 is a valve by the working piston buffer mechanism according to the present invention. Figure 4 is a structural diagram of a conventional hydraulic valve system, Figure 5 is an enlarged view of the V section in Figure 4, and Figure 6 is a diagram showing the valve opening characteristics of a conventional valve. Characteristic diagram, FIG. 7 (Z) (/j: Partially cutaway front view showing different embodiments. 6...Hydraulic cylinder, 8... Operating piston, 18... Damper boat , 3o...Taper part ◇ Figure V (X) (Y) (ZJ R

Claims (1)

[Claims] In a hydraulic valve system for a hydraulic valve-operated internal combustion engine that uses the end of the working piston that slides completely inside the hydraulic cylinder to open the intake and exhaust valves as a damper at maximum lift, an oil relief passage is provided at the end of the working piston. , and the operating piston is gently seated at the maximum position of the hydraulic cylinder by the resistance force of the oil flowing from the oil relief passage to the damper boat of the hydraulic cylinder. Working piston damping mechanism.