JPS588841A - Shock absorber - Google Patents

Abstract

PURPOSE:To make high frequency micro-vibrations absorbable, by installing a subpiston with an orifice relatively small in diameter on a piston rod only when a relative displacement between a main piston and its axial thrust exceeds limitation of a certain value. CONSTITUTION:At a lower end setting part 2, a piston rod 4 is inserted through into the inside of a tube 1 to be installed on the car body side and an outer tube 7 serving as bushing for the tube 1 is clamped thereto. At the lower end of the piston 4, main pistons 31 and 32 to be secured to that end part a subpiston 33 which loosely fitted to the piston rod 4 between both pistons 31 and 32 are fitted with some play. To these main pistons 31 and 32, orifices 61 and 62 relatively large in diameter are formed and to the subpiston 3, they 61 and 62 are made up of smaller diameters than the above case. In addition, at space between the subpiston 33 and the main pistons 31 and 32, slightly larger clearances 10 and 11 than amplitude of a high frequency vibration to be inputted are provided to house springs 12 and 13 in this space.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a shock absorber that is interposed between a vehicle body and a movable member such as a power unit.

Generally, in an automobile, a windshield is installed between the vehicle body and the axle, between the vehicle body top power unit, and the like. This shock absorber attenuates and absorbs the vertical vibration of the vehicle body relative to the axle and the vibration of the power unit relative to the vehicle body, thereby preventing vibrations in the vehicle and transmission of vibrations to the knocker unit, improving overall ride comfort. The aim is to

As a conventional shock absorber used for such a purpose, for example, one shown in FIG. 1 is known. That is, a tube 1 filled with working fluid is attached to the vehicle body at a mounting portion 2 at its lower end, and a piston rod 4 having a piston 3 fixed at its lower end that slides on the inner surface thereof is connected to a mounting portion 5 at its upper end. It can be installed on the power unit. An orifice 6 is opened in the piston 3, and communicates the upper chamber in the tube 1 with the royal chamber. 7 is an outer cylinder fixed to the piston rod 4; 8 is an outer cylinder fixed to the piston rod 4;
The end cover 9 that closes the upper end of the tube 1 is a rod guide that guides the movement of the piston rod 4.
The upper end of the tube 1 is liquid-tightly sealed by the end cap 8 and the end cap 8.

Therefore, when vibrations are input to the shock absorbers, displacement occurs between the tube 1 and the piston rod 4, and the piston 3 moves within the tube 1. At this time, the working fluid at the front of the piston 3 flows through the orifice 6 to the rear, and due to the flow resistance when passing through the orifice 6, kinetic energy is converted into thermal energy, thereby damping the input vibration.

However, in such a conventional shock absorber, the flow cross-sectional area of the orifice 6 is always unchanged;
In addition, its area was relatively small so as to cause the above-mentioned flow resistance, so when the high-frequency micro-vibration generated on the power unit side is input, the working fluid flows into the orifice 6.
A phenomenon occurs that does not pass through. This is because the piston 3 moves up and down at high speed due to fine imaging, so the working fluid tries to pass through the orifice 6 at high speed, and as a result, the orifice 6 receives high flow resistance. This is because it becomes impossible to pass through. Then, the working fluid is restricted in both chambers partitioned by the piston 3,
When the piston 3 vibrates slightly in this state, the pressure of the working fluid changes accordingly, so the fine vibration of the piston 3 is directly transmitted to the tube 1 via the working fluid, which causes the attachment part 2 to The noise is transmitted to the vehicle body through the noise source, resulting in a problem that causes muffled noise inside the vehicle interior.

The present invention was made by focusing on these conventional problems, and fixes a main piston having an orifice with a relatively large flow cross-sectional area to the piston/rod, and also fixes the main piston with an orifice with a relatively large flow cross-sectional area to the piston/rod. By attaching a sub-piston with an orifice to the piston rod in such a way that it interlocks with the main piston only when the relative displacement in the axial direction with the main piston exceeds a certain value, only the main piston can be operated when high-frequency micro-motion is input. The purpose of this invention is to operate the piston to absorb the vibration, and when a low frequency vibration is input, also operate the sub-piston to damp the vibration, thereby solving the above-mentioned problems of the prior art.

Hereinafter, the present invention will be explained based on the drawings. FIG. 2 is a diagram showing a first embodiment of the present invention.

First, to explain the structure, numeral 1 is a tube filled with working fluid, and is attached to the vehicle body side at a lower end attachment portion 2. 4 is a piston rod, which is attached to the power unit at an attachment portion 5 at the upper end. 7 is an outer cylinder;
It is fixed to the mounting part 5 and the piston/rod 4, and is placed outside the tube 1 and superimposed on the pup. The upper end of the tube 1 is liquid-tightly sealed by a rod guide 9 and an end cap 8.

At the lower end of the piston rod 4 are two main pistons 31.3.
2 and one sub-piston 33 are attached. The main piston 31, 32 is fixed to the piston rod 4,
Orifices 61, 62 each having a relatively large flow cross section
is formed.

A sub-piston 33 is loosely fitted onto the piston rod 4 between the main pistons 31 and 32. The sub-piston 33 includes a cylindrical portion 33a that fits loosely into the piston rod 4 and a main body 33b, and the main body 33b includes an orifice 63 having a relatively small flow cross-sectional area. Between both end surfaces of the cylindrical portion 33a and the main pistons 31 and 32, gaps 10 and 11 are provided that are slightly larger than the amplitude of the input high-frequency micro-vibration. In addition, the main piston 31, 32 and the main body 33b of the sub piston 33
Coil springs 12 and 13 are interposed as elastic bodies between the two to maintain the same distance 10 and 11. Instead of the coil springs 12 and 13, rubber or other elastic bodies may be used. Such coil springs 12, 13 or an elastic body replacing them are arranged so that when the piston rod 4 is stopped, the distance 10.
11, and its spring constant is set small so that it expands and contracts when the piston rod 4 moves due to vibration input.

Next, the action will be explained.

When high-frequency microvibrations are input, the piston rod 4 causes high-frequency microvibrations in the axial direction with respect to the tube 1, and the main pistons 31 and 32 vibrate together with this.

/ Since the amplitude is small, the coil spring 12°13
expands and contracts, causing a relative displacement in the axial direction between the width piston 33 and the main piston 31.32, but the distance 10.11 does not become O. This is because the secondary piston 33 is loosely fitted into the piston rod 4 in the cylindrical portion 33a, and the flow cross-sectional area of the orifice 63 is small, so that the secondary piston 33 is caused by the flow resistance of the working fluid that is trying to pass through at high speed. This is because the auxiliary piston 33 does not move together with the piston rod 4 due to the difficulty of movement, and the distance 10° 11 is set to be slightly larger than the amplitude of the high frequency microvibration. Therefore, at this time, the main piston 31.
Only 32 vibrates, and at this time its orifice 61.62
Vibration is damped by the flow resistance of the hydraulic fluid flowing through. The orifices 61 and 62 have a relatively large flow cross-sectional area, so the imaging attenuation rate is not very large, but due to high frequency vibrations, even if the hydraulic fluid flow rate is low, Therefore, high-frequency micro-vibrations of the piston rod 4 are absorbed by the vibrations of the main pistons 31 and 32 and are not transmitted to the tube 1, and low-frequency vibrations with large amplitudes such as rolling of the power unit are When input, the amplitude of the main pistons 31, 32 becomes larger than the interval 10.11, and the main pistons 31, 32 compress the coil springs 12, 13, alternately press the secondary pistons 33, and The piston 33 is forcibly moved.

Due to this, the hydraulic fluid is forced to flow through the orifice 63 of the sub-piston 33, and the flow resistance converts kinetic energy into thermal energy, so that inputted low frequency vibrations are attenuated. The vibrations are then additionally damped by the orifice 61.62 of the main piston 31.32. In addition, the main piston 31, 32 of the sub piston 33
This movement is not only caused by the main pistons 31° and 32 directly pressing the cylindrical portion 33a, but also by the spring force of the compressed coil spring 12.13 acting on the main piston 31.32 at the beginning of the movement. A smooth transition is made from a not-so-great damping characteristic due to the orifices 61, 62 to a high damping characteristic due to the orifice 63 of the secondary piston 33.

FIG. 3 shows a second embodiment of the present invention, in which the sub-piston 33 is comprised of a large-diameter cylindrical portion 33C and upper plates 3 at both ends of the auxiliary piston 33.
3.1 and the lower plate 33θ, and the upper plate 33d
was loosely fitted onto the piston rod 4, the lower end of the piston rod 4 was exposed to the sub-piston 33, and the main piston 31 was fixed to the piston rod 4 within the sub-piston 33. A small diameter orifice 63 is provided in the cylindrical portion 330 of the sub-piston 33.
On the other hand, a coil spring 12. is formed between the raw piston 31 and the upper plate 33d1 and the lower plate 33e. Interpose i, 3.

In this second embodiment, a distance equal to one-half of the sum of the distances over which the coil springs 12 and 13 can expand and contract corresponds to the interval 10.11 in the first embodiment.

The other configurations are the same as in the first embodiment.

Thus, the main piston 31 vibrates when high-frequency slight vibrations are input, and the coil springs 12 and 13 are alternately compressed to vibrate the sub-piston 33 as the main piston 31 vibrates when low-frequency vibrations are input. Including orifice 61.63,
Other operations are the same as in the previous embodiment.

As explained above, according to the present invention, a main piston having an orifice with a relatively large flow cross-sectional area is fixed to the piston rod, and a sub-piston having an orifice with a relatively small flow cross-sectional area is fixed to the piston rod. The structure is such that it is attached to the piston rod so that it operates in conjunction with the main piston only when the relative displacement in the axial direction with respect to the main piston exceeds a certain value.

Therefore, when high-frequency micro-vibrations are input, displacement of the piston rod is allowed under a small photographic damping force by operating only the main piston, so that high-frequency micro-vibrations can be absorbed. Therefore, it is possible to prevent muffled noise in the vehicle interior. Furthermore, when low-frequency vibrations are input, the low-frequency vibrations can be attenuated mainly by the orifice action of the secondary piston due to the operation of the main piston and the sub-piston, thereby preventing transmission of the low-frequency vibrations to the vehicle body. Thus, according to the present invention, it is possible to prevent vibrations in a wide frequency range from being transmitted to the vehicle body, thereby contributing to improving the ride comfort of the vehicle.

[Brief explanation of the drawing]

FIG. 1 is a partially broken front view of a conventional example, FIG. 2 is a partially broken pressure surface view showing a first embodiment of the present invention, and FIG. 3 is a partially broken front view showing a second embodiment of the invention. . 1...Tube, 4...Piston rod, 7...
Outer cylinder 10.11... Spacing %12.13... Coil spring (elastic body) 31. 32... Main piston, 33...
I11 piston, 61, 62, 63... orifice Patent applicant: Nissan Motor Co., Ltd. Representative Patent attorney: Tetsuya Mori, patent attorney
Yoshiaki Naito, Patent Attorney Shimizu
Positive

Claims (1)

[Claims] A main piston having an orifice with a relatively large flow cross-sectional area is fixed to the piston rod, and a sub-piston having a relatively small flow cross-sectional area and an orifice is fixed in axial relative displacement with the main piston. A shock absorber characterized by being attached to the piston rod so that it interlocks with the main piston only when the value exceeds the specified value.