JPS6026803A - Piston type hydraulic cylinder - Google Patents

Abstract

PURPOSE:To provide compact design and high buffing ability for a hydraulic cylinder of a hydraulic circuit which converts an impact into an effort of compressing gas inside an accumulator and prevents damage of the hydraulic cylinder or the like by boring the piston of the hydraulic cylinder inside. CONSTITUTION:A hydraulic circuit converts a kinetic energy produced by collision of objects into an effort of compressing gas inside an accumulator 2, so as to prevent damages of a hydraulic cylinder 1, piping and so on. If the kinetic energy is so great that the accumulator 2 cannot bear it, a relief valve 3 releases working oil outside the circuit to restrict increase of pressure. For the purpose of the release, a hollow part 4a is formed inside a piston 4 of the cylinder 1, whereby achieving reduced spring constant of a hydraulic spring inside the cylinder 1 without increasing the stroke of the piston 4. Consequently, impact buffing ability may be enhanced without need of reducing the output of the cylinder and elongating the full length of the cylinder 1 or other redesigning requiring enlarged installation space.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic cylinder whose shock absorption capacity is increased by making the piston circular portion hollow.

(Prior art) Conventionally, the first
A hydraulic circuit as shown in Figure 2 is constructed using a single-acting cylinder as shown in the figure. This circuit converts the kinetic energy of a collision or fall of an object into work that compresses the gas inside the accumulator 2, suppressing the generation of nerge pressure due to impact force and preventing damage to hydraulic cylinders, piping, etc. It is something. Furthermore, when the accumulator 2 is unable to buffer the severe impact force and the pressure rises, the relief valve 3 releases the hydraulic oil to the outside of the circuit to suppress the pressure rise. M in the figure is a motor. However, if the collision speed of the object is high, hydraulic cylinder 1 and accumulator 2
Measures must be taken such as increasing the diameter of the piping between them, bringing the hydraulic cylinder 1 and accumulator 2 closer together, and lengthening the stroke of the hydraulic cylinder, which requires a large space. The purpose of lengthening the cylinder stroke is to convert the interlocking energy of the collision of an object into work that compresses the hydraulic oil inside the cylinder, thereby suppressing the generation of surge pressure. By making the cylinder hollow, a cylinder with a short stroke can have the same shock-absorbing ability as a cylinder with a long stroke.

(Structure and operation of the invention) As described above, when absorbing the impact due to a collision or falling of an object, or when the collision speed is high, surge pressure is generated even in a circuit equipped with an accumulator as shown in FIG. 2. This is because the fluid inside the cylinder is compressed and absorbs the energy of the collision as a fluid spring.

Here, the spring constant 1k of the fluid spring inside the cylinder with the normal piston shown in FIG. 1 is expressed by the following equation (1).

K: Bulk elastic modulus of hydraulic oil S Cross-sectional area of cylinder tube LS: Siege pressure P when the stroke of the piston and the energy of collision are absorbed by the deflection of the fluid spring, is expressed by equation (2).

Po: Hydraulic source pressure E: Collision energy As can be seen from equation (2), the smaller the spring constant is 1, the smaller the surge pressure becomes. Either make it larger or make the cross-sectional area S of the cylinder tube smaller.

However, the cylinder tube Itl "Face S/J-S<
As a result, the cylinder output also decreases, and the cylinder stroke LS must be increased unnecessarily.
k.

The 15-day solution to reduce the
When the stone stroke Ls is increased, the total length of the cylinder is also increased, and a larger installation space is required. Here, in order to increase the piston stroke Ls, a method of decreasing the nokune constant is to make the inside of the piston hollow.

A full cylinder with a hollow piston? negative precepts) 3
In the figure, 04 indicates a hollow piston, and 5 indicates a tube.At this time, when entering the piston hollow 4a, the spring constant of the piston becomes the formula (3) 1, So: Cross-sectional area of the piston hollow part Lo: Depth of the hollow part of the piston, and 1 for the total fluid spring constant inside the cylinder with a hollow piston becomes equation (4). Since k2=spring constant of the hollow part of the piston, and obviously )kζ, as shown in equation (2)K, when the inside of the piston is made hollow, the surge pressure is lower than that in a solid piston.

(Effects of the Invention) By configuring and using the above-described structure, the present invention can achieve a simple arrangement of grooves without reducing the cylinder output or increasing the installation space such as increasing the total length of the cylinder. Succeeded in increasing street noise absorption capacity (Industrial application field) The present invention can be widely used as a shock absorbing device for the purpose of shock absorption.

[Brief explanation of drawings]

FIG. 1 is a schematic vertical cross-sectional view of a conventional single-acting cylinder; FIG. 2 is an example of a hydraulic circuit diagram; FIG. 3 is a schematic vertical cross-sectional view of an embodiment of a piston-type hydraulic cylinder according to the present invention.

Claims (1)

[Claims] Hollow piston type hydraulic cylinder with inner cavity formed in the rod