JPS61169309A - Suspension device - Google Patents

Abstract

PURPOSE:To restrain resonance to enhance the characteristic of control stability in a suspension device having a longitudinal rod member, by forming liquid chambers in rubber bushings, and by communicating the chambers with each other through a communication passage in the rod member. CONSTITUTION:When an exciting force due to the dynamic unbalance of wheels and the like, is applied having a frequency which is equal to the frequency of a resonant vibration frequency (f), a relative displacement occurs between an axle casing and a vehicle body, and therefore, the supporting span (l) of a rod 4 is changed thereby. Accordingly, the rubber bushings 11, 12 are deformed in accordance with variations in the span (l), and therefore, one of liquid chambers 15, 16 is enlarged while the other is contracted so that liquid W flows between both liquid chambers 15, 16. Thereby, the exciting force is converted into fluid energy and absorbed. With this arrangement, it is possible to restrain resonance to enhance the characteristic of control stability.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a suspension device for a vehicle, and particularly to a technology for damping low frequency vibrations in the longitudinal direction of a vehicle.

(Prior Art) As a conventional suspension device, for example, Fig. 4.4 on page 116 of Automotive Engineering Complete Book Volume 11: Steering Suspension (Sankaido Co., Ltd., published August 1980)
6 is known.

The tension rod of this conventional device has a
A solid rubber bush as shown in Figure 3.11 on page 60 of the circular is provided in each case, and the rubber bush damps vibrations transmitted from the wheel side to the vehicle body side.

(Problems to be Solved by the Invention) However, in such conventional suspension devices, vibrations input from the wheel side are attempted to be damped only by the damping action of the rubber bushes themselves. Therefore, when the suspension system resonates with the input vibration frequency, there is a problem in that the damping effect against the vibration input to the vehicle body is low, and the damping function is also low.

Due to this problem, when a rod with a conventional structure is used as a suspension rod for a rear suspension, vibrations of 1 OHZ to 40 H2 that are input to the wheels when driving on rough paved roads are transmitted to the vehicle body, resulting in harshness. This caused the phenomenon and worsened the noise inside the vehicle.In addition, when using a rod of the conventional structure as the suspension rod of the front suspension, the 20H2
The following vibrations were transmitted to the steering system, causing a shimmy phenomenon and reducing steering stability.

(Means for Solving the Problems) The present invention has been made for the purpose of solving the above-mentioned problems, and in order to achieve this purpose, in the present invention, one end is attached to the vehicle body side member, and the other end is attached to the vehicle body side member. is connected to a wheel side member via a rubber bushing, and is provided with a rod member disposed in the longitudinal direction of the vehicle. The chambers are formed so that the volume of one fluid chamber expands and the volume of the other fluid chamber decreases as the mounting span changes, and the first fluid chamber and the second fluid chamber are communicated by a communication path inside the rod member. A dynamic damper was constructed by

(Function) Therefore, in the suspension device of the present invention, by employing the above-mentioned means, the fluid flowing between the first fluid chamber and the second fluid chamber in the rubber bush and the communication path inside the support rod can be reduced in mass. A dynamic damper (dynamic vibration absorber) is formed using the elasticity of the rubber bush as a spring as the fluid chamber expands and contracts.By tuning the resonance frequency of this fluid dynamic damper to the resonance frequency range of the suspension, the suspension Resonance can be suppressed by dynamic damper action.

Note that this damping action occurs when the fluid flows violently, and the fluid vibration during the damping action has a maximum phase shift component of 90° with respect to the input vibration.

In addition, the present invention does not simply aim at the damping effect by a restriction such as an orifice (damping force is generated in proportion to the speed of fluid restriction, but the damping effect is not high); The aim is to achieve a damping effect using a dynamic damper that is effective against steady excitation forces.

(Example) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In describing this embodiment, a rear suspension system (first embodiment) and a front suspension system N (second embodiment) of an automobile will be taken as examples.

First, the configuration of the first embodiment shown in FIGS. 1 and 2 will be explained.

1 is a rear suspension device, as shown in FIG. 2, it includes a rear axle case 2, upper rods (also referred to as upper links) 3, 3, lower rods (also referred to as lower links) 4, 4, coil springs 5, 5. Shock absorber 6.6, mounting insulator 7.7
It is equipped with

The rear axle case 2 houses a differential gear and a drive shaft therein, and wheels are mounted on both ends thereof.

The upper rod 3 has one end supported by the rear axle case 2 and the other end supported by the vehicle body. support.

Similar to the upper rod 3.3, the lower rods 4, 4 have one end supported by the rear axle case 2 and the other end supported by the vehicle body, and the two lower rods 4, 4 are arranged parallel to the longitudinal direction of the vehicle. Mainly supports the load in the longitudinal direction of the vehicle.

The coil spring 5 and shock absorber 6 are
Both are arranged coaxially to support the vertical load of the vehicle, and a mounting insulator 7.7 is interposed in the supporting portion with the vehicle body.

In the first embodiment, a rod structure (link structure) according to the present invention is applied to the lower rod 4, and the structure of the lower rod 4 will be explained with reference to FIG.

The lower rod 4 includes a rod 8, a vehicle-side outer cylinder 9, a wheel-side outer cylinder 10, a vehicle-side rubber bushing 11, and a wheel-side rubber bushing 1.
2, vehicle body side inner cylinder 13, wheel side inner cylinder 14, first liquid chamber 15,
It is composed of a second liquid chamber 16, a communication passage 17, and a sealed fluid W.

The rod 8 has a vehicle body-side outer cylinder 9 and a wheel-side outer cylinder IO integrally fixed to both ends thereof.

The vehicle body side inner tube 13 and the wheel side inner tube 14 are provided concentrically with the outer tubes 9 and 10 via both rubber bushes 11 and 12, and the vehicle body side inner tube 13 is connected to the vehicle body side bolt 1.
8 to the vehicle body, and the wheel side inner cylinder 14 is fixed to the rear axle case 2 by a wheel side port 19.

The first liquid chamber 15 is formed inside the rubber bushing 11 on the vehicle body side, and its position is in the rubber bushing 11.
This is the rod side position of No. 1.

The second liquid chamber 16 is formed inside the wheel-side rubber bushing 12, and its position is in the rubber bushing 12.
This is the position opposite to the rod in No. 2.

Note that when the wheel-side inner cylinder 14 moves in the direction of the arrow in FIG. 1 due to the front-back movement of the rear axle case 2 (the support span becomes longer), the first liquid chamber 15 expands and the second liquid chamber 16 is contracted, the enclosed fluid W flows in the direction opposite to the moving direction A (in the direction of arrow A'), and when the wheel-side inner cylinder 14 moves in the direction of arrow B in Fig. 1 (the support span is short). ), the first liquid chamber 15 is contracted and the second liquid chamber 16 is expanded,
The sealed fluid W flows in a direction opposite to the moving direction B (arrow B' direction).

The communication passage 17 communicates the first liquid chamber 15 and the second liquid chamber 16, and is formed in the rod 8, the outer cylinder 9.10, and both rubber bushes 11.12.

Note that as the sealed fluid W sealed in the first liquid chamber 15, the second liquid chamber 16, and the communication path 17, incompressible antifreeze or the like is used.

Moreover, the mass of the enclosed fluid W is m, and the first and second liquid chambers 15
．． The resonant frequency of the fluid dynamic damper, which uses the elasticity of both rubber bushes 11 and 12 as a spring K (which also serves as a damping C) as the rubber bushes 11 and 16 expand and contract, is the rear It is tuned to almost match the resonance frequency of the suspension system 511.

Next, the operation of the first embodiment will be explained.

First, the schematic diagram of the vibration system in the first embodiment is a two-degree-of-freedom vibration system as shown in FIG.
A main vibration system is formed by the springs such as 12, and the mass m due to the enclosed fluid W, and the spring K (damping (including C) to form an auxiliary vibration system.

Therefore, the principle of a dynamic damper can be applied, in which the mass M of the main vibration system can be brought close to stationary by causing the sub-vibration system to resonate.

Specifically, when an excitation force due to unevenness of the road surface or dynamic unbalance of the wheels is applied at the same frequency as the longitudinal resonance frequency f of the rear suspension device l, the resonance causes the longitudinal vibration between the rear axle case 2 and the vehicle body. A relative displacement in the direction occurs.

This relative displacement in the longitudinal direction directly becomes a length displacement of the support span of the lower rod 4, and both rubber bushings 11 and 12 deform in response to the displacement, allowing the first fluid chamber 15 and the second fluid chamber 16 to expand and contract. Then, a flow of the sealed fluid W occurs.

The resonant frequency fO of the fluid dynamic damper formed by the sealed fluid W and both rubber bushes 11 and 12 is made approximately equal to the resonant frequency f of the rear suspension device l, so that the excitation force is applied to the rear suspension device l. Most of the work is converted into kinetic energy that causes the enclosed fluid W to flow, causing the enclosed fluid W to flow violently.

Due to the intense flow of the enclosed fluid W, the longitudinal resonance vibration of the rear suspension device I is attenuated in a short time,
Thereafter, even if the excitation force is continuously applied, the rear suspension device 1 hardly vibrates, and instead only the enclosed fluid W flows violently.

As shown in FIG. 4, the damping force by this fluid dynamic damper is determined by the resonance frequency fo of the fluid dynamic damper.
As for the vibration transmission characteristics, as shown in graph D in Figure 5, compared to the case of conventional suspension rods (graph E), the vehicle body transmission force immediately after vibration is small, and the convergence time is also short. It will be extremely short.

It is considered that the sealed fluid W during the damping action is flowing in an opposite phase with a phase shift of 900 relative to the vibration of the rear suspension device (2) caused by the excitation force.

In this way, the vibration damping effect of the fluid dynamic damper reduces the vibration (l O
Hz~40H2) vehicle body transmission can be significantly reduced, thereby preventing the harshness phenomenon.

In addition, since the damping effect is performed by a fluid dynamic damper, the damping coefficient of both rubber bushings 11 and 12 itself is increased.
There is no need to listen to noise, and road noise can be prevented from worsening.

Next, a second embodiment shown in FIGS. 6 to 8 will be described.

This second embodiment is an example in which a damper rod 21 as a fluid dynamic damper is added to the front suspension device 20.

The first embodiment is an example in which a fluid dynamic damper is incorporated into the lower rod 4 of the rear suspension device 1.

20 is a front suspension device, as shown in FIG. 8, suspension member 22, transverse link 23, 23, strut device 24, 24, stabilizer 25, tension rod 26, 26, damper rod 21, 21, vehicle body Equipped with side boot ticket 1-27.27.

The vehicle vertical load is supported by the strut devices 24 and 24, and the lateral load is supported by the transverse link 23.
．． 23, and the longitudinal load is supported by tension rods 26 and 26.

Further, the tension rods 26, 26 are provided with low-damping rubber bushings in order to improve high-frequency vibration transmission characteristics in order to prevent road noise.

In the second embodiment, the rod structure according to the present invention is applied to the damper rod 21, and the structure of the damper rod 21 will be explained with reference to FIGS. 6 and 7.

The damper rod 21 includes a rod 28 and a first outer cylinder 29 on the vehicle body side.
, a second outer cylinder 30 on the vehicle body side, an inner cylinder 31 on the vehicle body side, a rubber bushing 32 on the vehicle body side, a first outer cylinder 33 on the wheel side, and a second outer cylinder 34 on the wheel side
, wheel side inner cylinder 35, wheel side rubber bush 36, first liquid chamber 37. It is composed of a second liquid chamber 38, a communication path 39, and an inlet fluid W.

The outer cylinder has a double outer cylinder structure consisting of a first outer cylinder 29.33 and a second outer cylinder 30, 34, and a rubber bushing 32.36 is bonded (vulcanized adhesive) to the inner second outer cylinder 30.34. etc.)
I'm letting you do it.

The wheel-side inner cylinder 35 is fixed to the outside of the wheel-side first outer cylinder 33 by welding or the like.

The vehicle-side rubber bush 32 is provided in the rod-side half of the vehicle-side inner cylinder 31 and the vehicle-side second outer cylinder 30, and the first liquid chamber 37 therein is configured to adjust the height of the mounting span according to changes in the mounting span height. to zoom in and out.

The wheel-side rubber bushing 36 is provided throughout the inside of the wheel-side second outer cylinder 34, and the volume of the second liquid chamber 38 inside the wheel-side rubber bushing 36 increases as the enclosed fluid W flows.
6 expands and contracts by elastically deforming.

Note that the damper rod 21 of the second embodiment is provided as a fluid dynamic damper and is not intended to support the load in the longitudinal direction of the vehicle. The structure ensures a wide enclosure volume.

In addition, the resonant frequency of the fluid dynamic damper, which uses the enclosed fluid W as the mass and the elasticity of both rubber bushes 32 and 36 as the liquid chamber expands and contracts as a spring, is within the frequency range (20 Hz or less) that causes the shimmy phenomenon. It is tuned to almost match the resonance frequency of the front suspension device 20.

Next, the operation of the second embodiment will be explained.

When the excitation force due to the dynamic imbalance of the wheels is applied at the same frequency as the longitudinal resonance frequency of the front suspension device 20 (resonance caused by the mass of the transverse link etc. and mainly the rubber bush of the tension rod 26 as a spring), A relative displacement occurs between the front suspension device 20 and the vehicle body in the longitudinal direction, and the length of the mounting span of the damper rod 21 also changes accordingly.

Due to this change in the length of the mounting span intersection, a damping effect is performed by the same mechanism as in the first embodiment, and the resonance of the front suspension device 20 is damped in a short time.

The damping effect of this fluid dynamic damper reduces the vibration (20Hz) caused by the resonance of the front suspension system M20.
(below) can be significantly reduced in transmission to the steering system and to the vehicle body, thereby preventing the shimmy phenomenon of the steering system and also preventing deterioration of cabin noise. In the second embodiment, since the damper rod 21 is added, vibration transmission in the high frequency range can be reduced by the retention rod 26 as before, and the vibration transmission characteristics in other frequency ranges are reduced. I won't let you.

Next, the embodiment shown in FIG. 9 and FIG. In the modified example shown in FIG. 9, the peripheral outer cylinders 29A and 33A of the damper rod 21A are installed in a vertical state, and in contrast to the modified example shown in FIG. An example is
The peripheral outer cylinders 29B and 33B of the damper rod 21B are attached in an orthogonal state (one horizontally and the other vertically).

Such a mounting state is an example for selecting a mounting state that can exhibit the most fluid dynamic damper effect depending on the direction of vibration input.

Although the embodiments of the present invention have been described above in detail with reference to the drawings, the specific configuration is not limited to these embodiments, and the present invention may be modified without departing from the gist of the present invention. included.

For example, as in the first embodiment, a fluid chamber or a communication passage may be provided in the suspension rod that supports the load in the longitudinal direction, and a fluid dynamic damper may be incorporated, or as in the second embodiment, the suspension rod that supports the load in the longitudinal direction of the vehicle may be provided with a fluid dynamic damper. A rod constituting a fluid dynamic damper may be added at the position.

(Effects of the Invention) As explained above, in the suspension device of the present invention, the first
A sealed fluid sealed in the fluid chamber, the second fluid chamber, and the communication path;
Since a fluid dynamic damper is formed by the elasticity of the rubber bushings accompanying the expansion and contraction of both fluid chambers, this fluid dynamic damper action has the effect of damping the resonance of the suspension.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a lower rod applied to a rear suspension device according to a first embodiment of the present invention, FIG. 2 is a perspective view showing a rear suspension device according to a first embodiment, and FIG.
A schematic diagram of the vibration system of the device of the embodiment, FIG. 4 is a damping characteristic diagram of the fluid dynamic damper of the device of the first embodiment, FIG. 5 is a diagram of vibration transmission characteristics of the device of the first embodiment, and FIG. 6 is a diagram of the vibration transmission characteristic of the device of the first embodiment. FIG. 7 is a cross-sectional view taken along line I-I in FIG. 6, FIG. 8 is a perspective view showing the front suspension device of the second embodiment, and FIG. 9 and 10 are perspective views showing a modification of the device of the second embodiment. l...Rear suspension device 4...Lower rod (rod member) 11...Vehicle side rubber bushing 12...Wheel side rubber bushing 15...First liquid chamber 16...Second liquid chamber 17... Communication path or...support span (mounting span) 21...damper rod (rod member) 32...vehicle body side rubber bushing 36...heavy wheel side rubber bushing 37...first fluid chamber (first fluid chamber) ) 38...Second fluid chamber (second fluid chamber) 39...Communication passage text'...Mounting span Patent application Nissan Motor Co., Ltd. Figure 8 Figure 9 Zll:S

Claims (1)

[Claims] 1) A suspension device including a rod member arranged in the longitudinal direction of the vehicle, with one end connected to a vehicle body side member and the other end connected to a wheel side member via rubber bushes, respectively.
A first fluid chamber and a second fluid chamber are provided in each of the rubber bushes, and both fluid chambers are formed so that the volume of one fluid chamber expands and the volume of the other fluid chamber decreases as the mounting span changes, and . A suspension device, wherein the first fluid chamber and the second fluid chamber are communicated with each other by a communication path inside the rod member.