JPS6131124Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a variable valve lift device with a buffer mechanism that makes the valve lift variable in a valve device for an internal combustion engine and absorbs the impact force when the valve is seated.

The valve timing of the intake and exhaust valves in an internal combustion engine is set to a constant value that corresponds to maximum output, but because the valve timing is constant, the valve overlap is long in the engine's low speed range, making it impossible to use combustion energy effectively. Since the air-fuel mixture blows through, fuel consumption increases, and the intake efficiency decreases and the exhaust backflow phenomenon occurs, which is extremely disadvantageous in terms of exhaust gas purification measures.

Therefore, a hydraulic lash adjuster, such as an oil tappet, is installed as part of the mechanical transmission mechanism that transmits the movement of the cam to the valve, and absorbs a portion of the cam lift without contributing to the valve lift. A method has also been proposed in which the valve timing is substantially controlled by reducing the valve timing.

However, when the valve lift is made variable using a hydraulic latch adjuster, the rising and falling parts of the cam profile no longer contribute to the valve lift, and in actual valves, the buffer curve (base circle of the cam) formed on the cam profile The curve that smoothly connects the cam profile and the boundary area of the cam profile does not function, and the shock when the valve opens and closes becomes large.Especially when the seat is seated, a large impact force is applied between the valve and the seat, increasing noise. This leads to decreased durability due to increased wear and tear.

Therefore, a shock absorbing mechanism has been proposed to absorb this impact force, but since it is installed independently from the hydraulic latch adjuster such as an oil tappet, its structure is complicated, has many parts, and is expensive. It is something.

The present invention has been made in view of the prior art, and aims to provide a variable valve lift device with a shock absorbing mechanism that has a simple configuration, can vary the valve lift, and can also absorb shock when seating. shall be. The configuration of the present invention that achieves this object includes a plunger and a first hydraulic chamber as part of a mechanical transmission mechanism that converts the movement of a cam into reciprocating motion to open and close a valve, and also includes a plunger and a first hydraulic chamber. A hydraulic latch adjuster is installed to make the valve lift variable by releasing oil supplied to the hydraulic chamber according to the rotational speed of the engine, while a fixed member fixed to the engine and the mechanical transmission mechanism A buffer mechanism is provided between the valve piston and a second hydraulic chamber to absorb shock when the valve is seated, and a throttle is provided to supply and buffer oil escaping from the first hydraulic chamber to the second hydraulic chamber. It is characterized in that the first hydraulic chamber and the second hydraulic chamber are communicated through an oil passage.

Hereinafter, one embodiment of the present invention will be described in detail based on FIGS. 1 to 5.

1 to 4 show the case where the variable valve lift device with a shock absorbing mechanism of the embodiment is applied to a rocker arm.

At the rear of the rocker arm 1 is a push rod 2.
A hydraulic latch adjuster 3 is provided to adjust the clearance between the valve and the upper end and to vary the valve lift. This hydraulic lash adjuster 3
is constructed as follows. First, Rotsuker Arm 1
A plunger 4 is slidably installed in a recess formed in the recess, thereby forming a first hydraulic chamber 5. A spring 6 is interposed in the first hydraulic chamber 5 to bias the tip of the plunger 4 toward the push rod 2 side. Further, in order to supply engine oil as hydraulic oil to the first hydraulic chamber 5, an oil passage 7 communicating with the bearing part of the rocker shaft is bored in the rocker arm 1, and an air vent 8 and a check valve 9 are provided from the upper part of the rocker arm 1. A check valve main body 10 connected by a T-shaped oil passage is installed, and the oil supplied from the oil passage 7 passes through the check valve 9, which is only allowed to flow into the first hydraulic chamber 5. 1 is sent to the hydraulic chamber 5.
Further, a hole is formed in the side wall of the plunger 4 in order to relieve pressure oil from the first hydraulic chamber 5 according to the rotational speed of the engine.

On the other hand, a buffer mechanism 11 for absorbing shock when the valve is seated is provided at the rear end of the rocker arm 1 than the hydraulic latch adjuster 3, and a buffer piston 12 is slidably mounted in a recess formed in the rocker arm 1. Then, the second hydraulic chamber 13 is formed. This second hydraulic chamber 13 includes a buffer piston 12.
A spring 14 is interposed to urge the hydraulic latch adjuster 3 upward.
In order to supply the pressure oil relieved from the hydraulic chamber 5, an oil passage 16 is formed which includes an orifice 15 as a throttle. 17 is a plug buried after drilling the oil passage 16. Further, the tip of the buffer piston 12 faces a fixed member 18 fixedly installed on the upper surface of the cylinder head, which is the fixed side of the engine, and a buffer material 19 is provided on the opposing surface of the fixed member 18 to absorb shock. It is installed.

In the variable valve lift device with a shock absorbing mechanism configured as described above, when the valve is not operating (when the push rod 2 is not pushed up), part of the engine oil flows from the bearing of the rocker shaft through the oil passage 7 and the check valve 9. is introduced into the first hydraulic chamber 5 and pushes down the plunger 4 together with the spring 6 to make the clearance zero.

When the push rod 2 starts to be pushed up from this state, the plunger 4 in the first hydraulic chamber 5 is also pushed up and the oil pressure increases, but if the engine rotation speed is in a low speed range, the rotation speed of the cam is slow and the first oil pressure The rising speed dp/dt of the oil pressure in the chamber 5 (where p is the oil pressure and t is the time) is small, and the pressure oil in the first oil pressure chamber 5 flows into the oil path 16 through the orifice 15 as a throttle.
relief from the second hydraulic chamber 13. For this reason,
The valve lift is not performed until the bottom of the plunger 4 comes into contact with the first hydraulic chamber 5, so that the valve opening timing is delayed and the valve closing timing is accelerated, so that the amount of valve lift is also reduced. Also, when the valve is operated, the pressure oil relieved from the first hydraulic chamber 5 is transferred to the second hydraulic chamber 1.
3 to push down the buffer piston 12 against the spring 14. Then, just before the valve is seated, the tip of the buffer piston 12 comes into contact with the buffer material 19 of the fixed member 18, and when the cam further rotates and the rocker arm 1 rotates, the buffer piston 12 is pushed up and the second hydraulic chamber 13 is opened. Increase oil pressure. At this time, since the plunger 4 is lowered in the first hydraulic chamber 5, the oil passage 16 communicates the second hydraulic chamber 13 and the first hydraulic chamber 5 via the orifice 15, so the flow rate is restricted by the orifice 15 and the pressure is Since the oil escapes to the first hydraulic chamber 5, it is possible to absorb the impact force when the valve is seated. The operating ranges of the first hydraulic chamber 5 and the second hydraulic chamber 13 in this case can be expressed by the rotation angles of the cams in FIG. 5 and θ ₁ and θ ₂ ,
The valve lift characteristic can be shown by a solid line A.
In addition, the broken line B in the figure shows the case where the pressure oil of the hydraulic lash adjuster 3 is not relieved.

The operating range θ ₁ of the first hydraulic chamber 5 and the operating range θ ₂ of the second hydraulic chamber 13 are determined by setting the diameter d ₁ of the first hydraulic chamber 5 and the diameter d ₂ of the second hydraulic chamber 13 to appropriate values. Adjust with.

On the other hand, when the rotational speed of the engine is in a high speed range, the rotational speed of the cam is also high, and the rising speed dp/dt of the hydraulic pressure in the first hydraulic chamber 5 is also large, so that the oil pressure is transferred from the oil passage 16 to the second hydraulic chamber via the orifice 15. 13, the oil passage 16 is closed by the plunger 4, the first hydraulic chamber 5 is sealed, and the valve lift is not absorbed by the hydraulic lash adjuster 3, resulting in a valve lift characteristic based on the cam profile. .
When the valve is seated in this state, the second hydraulic chamber 13
Since no oil is supplied to the cam, there is no cushioning effect, and the cushioning curve provided on the cam allows the cam to sit smoothly.

In the above embodiment, a variable valve lift device with a shock absorbing mechanism was installed on the rocker arm, but the rocker arm is not limited to this.It is possible to use an oil tappet as a hydraulic latch adjuster, and to use a shock absorber operated by oil relieved from a hydraulic chamber formed in the oil tappet. The same effect can be obtained by having the shock absorbing piston of the mechanism come into contact with a part of the mechanical transmission mechanism, such as a push rod.

As explained above in detail along with the embodiments, according to the present invention, it is possible to make the valve lift variable, absorb the shock when the valve is seated, prevent the generation of noise, and at the same time reduce wear and durability. improves. Further, it is possible to achieve engine performance in a low-speed rotation range, such as reduction in fuel consumption and purification of exhaust gas, without affecting engine performance in a high-speed rotation range. Furthermore, since the hydraulic latch adjuster and the buffer mechanism are configured to work together and the buffer mechanism is operated by oil from the hydraulic latch adjuster, the structure is simple and has a small number of parts, making it inexpensive.

[Brief explanation of the drawing]

Figures 1 to 5 show an embodiment of the variable valve lift device with shock absorbing mechanism of the present invention applied to a rocker arm, with Figure 1 being a front view, Figure 2 being a right side view, and Figure 3 being a right side view. FIG. 4 is a cross-sectional view along the - arrow in FIG. 3, and FIG. 5 is an explanatory diagram of valve lift characteristics. In the drawing, 1 is a rocker arm, 2 is a push rod, 3 is a hydraulic latch adjuster, 4 is a plunger, 5 is a first hydraulic chamber, 6 is a spring, 7 is an oil passage, 8
1 is an air vent, 9 is a check valve, 10 is a check valve body, 11 is a buffer mechanism, 12 is a buffer piston, 1
3 is a second hydraulic chamber, 14 is a spring, 15 is an orifice, 16 is an oil passage, 17 is a plug, 18 is a fixing member, and 19 is a buffer material.

Claims (1)

[Scope of utility model registration request] A part of the mechanical transmission mechanism that converts the movement of the cam into reciprocating motion to open and close the valve includes a plunger and a first hydraulic chamber, and the oil supplied to the first hydraulic chamber via the check valve is used to rotate the engine. A hydraulic latch adjuster is installed to make the valve lift variable by releasing the valve according to the speed, and a buffer piston and a second hydraulic chamber are provided between the fixed member fixed to the engine and the mechanical transmission mechanism. A buffer mechanism is provided to absorb the shock when the valve is seated, and an oil passage is provided with a throttle that supplies and buffers oil escaping from the first hydraulic chamber to the second hydraulic chamber. A variable valve lift device with a buffer mechanism, characterized in that two hydraulic chambers are communicated with each other.