JPH0422115Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to the structure of a needle valve used as a damping force generating mechanism in a vehicle shock absorber or the like.

(Prior Art) As a device for adjusting the damping force of a shock absorber, a device using a needle valve is conventionally known.

FIG. 3 shows a conventional example in which a needle valve is combined with a temperature compensation chamber, in which a piston 102 is fixed to a hollow rod 101 inserted into a cylinder 100, and a flow path 103 during compression and a flow path during expansion are connected to the piston 102. 104, a leaf valve 105 is provided at the outlet of the flow path 103, a leaf valve 106 is provided at the outlet of the flow path 104, and the flow path 104 and the hollow rod 10 are connected.
A piston 109 is connected to the piston 107 in the hollow rod 101 by a passage 108, and the piston 109 is moved in the axial direction by an adjustment rod.
A needle valve 111 defining a temperature compensation chamber 110 between the needle valve 9 and the needle valve 111 and a valve seat 112 constricting the flow path between the needle valve 111 and the tip thereof are provided.

Here, the shock absorber converts input from the road surface into heat and absorbs it, so if the shock absorber is operated frequently, the temperature of the hydraulic oil increases, the viscosity of the hydraulic oil decreases, and the damping force also decreases. Become. In order to compensate for this, a temperature compensation chamber is provided, and the needle valve 11
1 is advanced in the direction of the valve seat 112, the flow path area between the needle valve 111 and the valve seat 112 is narrowed, and a decrease in damping force is suppressed.

By the way, the relationship between the temperature and viscosity of hydraulic oil is
As shown in the figure, there is no linear proportional relationship, but a quadratic curve. Therefore, if the shape of the tip 111a of the needle valve 111 is made into a simple conical shape, appropriate temperature compensation cannot be achieved. Therefore, the tip 111a of the needle valve 111 is made to have a quadratic curved surface.

(Problems to be Solved by the Invention) To create the needle valve 111 having the above-mentioned shape, as shown in FIG.
14, the needle valve tip 111a is cut, but since the diameter of the needle valve 111 is small, the needle valve tip 111a is deformed during cutting.

(Means for solving the problem) In order to solve the above problem, the present invention leaves the tip of the needle valve in the shape of a rod without cutting, and the valve seat facing the tip is cut using a cutting tool. It was then processed into a quadratic curved surface.

(Function) Since the relationship between the area of the annular flow path formed between the needle valve and the valve seat and the forward and backward stroke of the needle valve is a quadratic curve, the flow follows the viscosity change of the hydraulic oil due to temperature change. The road area changes and a constant damping force is obtained.

(Example) An example of the present invention will be described below based on the accompanying drawings.

FIG. 1 is a cross-sectional view of a main part of a shock absorber to which the needle valve structure according to the present invention is applied. A hollow rod 2 is inserted into the cylinder 1 from below, and the upper end of the hollow rod 2 A piston 3 is fixed in sliding contact with the piston 3. A flow path 4 for compression and a flow path 5 for expansion are bored in the piston 3, a leaf valve 8 is seated at the outlet of the flow path 4, a leaf valve 7 is seated at the outlet of the flow path 5, These leaf valves 6, 7 are fixed to the hollow rod 2 with a nut 9 through a seat 8.

In addition, there is a push rod 10 inside the hollow rod 2.
A piston 11 that moves in the axial direction is slidably provided via a seal ring 12, and above the piston 11, a needle valve 14 defining a temperature compensation chamber 13 with the piston 11 is also sealed. Provided to be slidable via a ring 15,
A cylindrical valve seat 16 is fixed in the tip of the hollow rod 2 above the needle valve 14, and the oil chamber S above the piston 3 is guided through the valve seat 16.
This flow path 17 and the elongated flow path 5 formed in the piston 3 are communicated by a flow path 18. Note that the flow path 4 and the flow path 17 may be communicated with each other.

Further, the tip 14a of the needle valve 14 is in the shape of a rod without cutting, and the lower end opening of the valve seat 16 is a quadratic curved surface 16a that expands downward.
A narrowed annular flow path 17a is formed between the valve seat 4a and the quadratic curved surface 16a of the valve seat. In order to form the quadratic curved surface 16a on the valve seat 16, as shown in FIG. 2, cutting is carried out using a full-form cutting tool 19 whose blade portion 19a forms a concave quadratic curved surface.

In the above, when the temperature of the hydraulic oil increases due to the operation of the buffer, the hydraulic oil in the temperature compensation chamber 13 expands, the needle valve 14 moves upward by that amount, and the area of the annular flow path 17a also decreases. becomes.
The viscosity of the hydraulic oil decreases in a quadratic curve as the temperature rises, but the area of the annular flow path 17a also decreases in a quadratic curve as the temperature rises, so the shock absorber as a whole The damping force of is kept constant.

(Effects of the invention) As explained above, according to the invention, among the needle valve and valve seat that form the flow path for damping force adjustment, the needle valve is made into a rod shape without being cut with a cutting tool, and the valve Since the seat is machined with a full-form cutting tool, the machining accuracy can be increased compared to conventional machining on needle valves, and when used as a needle valve for temperature compensation. Appropriate damping force adjustment can be performed.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of the main parts of a shock absorber to which the needle valve structure of the present invention is applied, Figure 2 is a diagram showing the state in which the valve seat is cut, and Figure 3 is a diagram showing the conventional needle valve structure. FIG. 4 is a graph showing the relationship between the temperature and viscosity of the hydraulic oil, and FIG. 5 is a diagram showing the needle valve being machined. In addition, in the drawing, 1 is a cylinder, 2 is a hollow rod,
3, 11 is a piston, 13 is a temperature compensation chamber, 14 is a needle valve, 14a is the tip of the needle valve, 16 is a valve seat, 16a is a quadratic curved surface of the valve seat, 17a is between the needle valve and the valve seat The annular channel 19 formed is a full-length cutting tool.

Claims (1)

[Claims for Utility Model Registration] (1) A rod-shaped needle valve moves back and forth with respect to a valve seat formed by hole machining, thereby changing the flow path area between the valve seat and the needle valve and creating a damping force. In the needle valve structure for adjustment, the tip of the needle valve is formed substantially perpendicular to the axis, and the cross-sectional shape of the opening at one end of the valve seat facing the tip of the needle valve is on the side of the needle valve, which is the valve body. A needle valve structure in a shock absorber characterized by forming a quadratic curve bulging toward. (2) The needle valve structure in a shock absorber according to claim 1, wherein the needle valve moves forward and backward in response to changes in volume of the temperature compensation chamber.