JPH0989047A - Dynamic damper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To hold the degradation of a vibration suppressing effect, caused by the dispersion of a resonance frequency of rotary shaft or the like, to a minimum by alternately arranging in a circumferential direction a high spring part set higher and a low spring part set lower than a specific value, which is a target of spring constant in a shearing direction, in a rubber elastic member. SOLUTION: When a rotary shaft mounting a dynamic damper is rotated, a resonance phenomenon of a mass member 2 is displayed in a diametric direction of high/low spring parts 3a, 3b of a rubber elastic member 3. That is, in a direction in the central part of the low spring part 3b, a resonance characteristic is displayed generating a peak in a frequency a little smaller than a resonance frequency serving as a target of the rotary shaft, and in a direction in the central part of the high spring part 3a, a resonance characteristic is displayed generating a peak in a frequency a little larger than the resonance frequency serving as a target of the rotary shaft. In a direction between the central parts of the low/high spring parts 3b, 3a, a resonance characteristic is displayed in which a peak is generated in an intermediate frequency changed continuously in accordance with a displacement angle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic damper mounted on a rotary shaft such as a drive shaft of an automobile to suppress harmful vibrations generated on the rotary shaft.

[0002]

2. Description of the Related Art In order to suppress harmful vibrations, which should not occur originally, such as bending vibrations and torsional vibrations due to rotational imbalance caused by the rotation of rotary shafts such as drive shafts and propeller shafts of automobiles. In addition, dynamic dampers are often used. These dynamic dampers fulfill their function by matching their natural frequencies with the predominant frequencies of excited harmful vibrations, converting the vibration energy of the rotating shaft into the vibration energy of the dynamic damper by resonance, and absorbing it. There is.

As such a conventional dynamic damper, one shown in FIG. 4 is known. This dynamic damper is located between a pair of ring-shaped fixed members 11 and 11 inserted through and supported by a rotary shaft at a predetermined interval in the axial direction and a pair of fixed members 11 and 11 and is located outside the rotary shaft. A cylindrical mass member 12 coaxially arranged with a space, and the fixing members 11, 11 and respective shaft ends of the mass members 12 adjacent to the fixing members 11, 11 are integrally connected to each other. 12
And a pair of rubber elastic members 13 that elastically support both shaft ends in the shearing direction.

The natural frequency of this dynamic damper is
It is basically determined by the mass of the mass member 12 and the spring constants of the rubber elastic members 13, 13. In this case, since the rubber elastic members 13, 13 receive a load in the shearing direction against the vibration of the mass member 12 in the radial direction, the rubber elastic members 13, 13 are in a direction having a shear spring constant. 12 is elastically supported.

[0005]

By the way, the vibration suppressing effect of the dynamic damper as described above is obtained by the resonance frequency (natural frequency) of the rotary shaft to which the dynamic damper is attached and the resonance frequency (natural frequency) of the dynamic damper.
It becomes the largest when and coincide with each other, and becomes sharply smaller when the respective resonance frequencies deviate beyond a certain small range.

However, the resonance frequency of the rotating shaft varies due to variations in shaft diameter, shaft length, etc., and the resonance frequency of the dynamic damper accompanies variations in rubber hardness of the rubber elastic body and environmental changes such as temperature. Since there are variations due to changes in characteristics, it is extremely difficult to adjust the resonance frequencies of the two so that they completely match, and it is also difficult to adjust within a range that can satisfy all of these variations. .

The present invention has been devised in view of the above circumstances, and it is an object of the present invention to provide a dynamic damper capable of minimizing the reduction of the vibration suppressing effect caused by the variation of the resonance frequency of the rotary shaft and the dynamic damper. This is a problem to be solved.

[0008]

According to the invention of claim 1, which solves the above-mentioned problems, a pair of ring-shaped fixing members inserted into and supported by a rotary shaft at a predetermined interval in the axial direction, and a pair of the fixing members. And a cylindrical mass member that is coaxially arranged outside the rotating shaft with a space therebetween, and each fixing member and each shaft end of the mass member that is adjacent to each fixing member. In a dynamic damper including a pair of rubber elastic members elastically supporting both shaft ends of the mass member in the shearing direction, the rubber elastic member has a spring constant in the shearing direction which is greater than a target specific value. Also has a high spring portion set to be higher and a low spring portion set to be lower than the specific value, and the high spring portions and the low spring portions are alternately arranged in the circumferential direction. It is a thing.

The target specific value here is used when setting the resonance frequency of the dynamic damper, which is determined by the mass of the mass member and the spring constant of the rubber elastic member, corresponding to the target resonance frequency of the rotating shaft. The value of the spring constant of. The two resonance frequencies of the dynamic damper set by the high spring portion and the low spring portion of the rubber elastic body are preferably set within a range of ± 10% with respect to the target resonance frequency of the rotating shaft.

[0010]

In the dynamic damper of the present invention, the pair of rubber elastic members elastically supporting both axial ends of the mass member in the shearing direction is a high spring whose spring constant in the shearing direction is set higher than a target specific value. The high spring portion and the low spring portion are alternately arranged in the circumferential direction, each having a portion and a low spring portion set to be lower than the specific value.

As a result, when the rotary shaft equipped with the dynamic damper of the present invention rotates, the resonance phenomenon of the mass member as shown in FIG. 3 occurs in the radial direction of the high spring portion and the low spring portion of the rubber elastic member. appear. That is, in the direction of the central portion of the low spring portion, a resonance characteristic (shown by a solid line) that has a peak at a frequency slightly smaller than the target resonance frequency of the rotary shaft appears, and in the direction of the central portion of the high spring portion, , Resonance characteristics (shown by a dotted line) having a peak at a frequency slightly higher than the target resonance frequency of the rotary shaft appear. Then, in the direction between the central portion of the low spring portion and the central portion of the high spring portion, a resonance characteristic having a peak at an intermediate frequency that continuously changes according to the displacement angle appears.

Therefore, in the dynamic damper of the present invention, a plurality of resonance frequencies are set in a wide range so as to straddle one resonance frequency which is a target of the rotation axis, and variations in the resonance frequency of the rotation axis and the dynamic damper. The reduction of the vibration suppression effect caused by the reduction is minimized.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of the dynamic damper according to the present embodiment taken along the axial direction, and FIG. 2 is a side view thereof. The dynamic damper of the present embodiment includes a pair of ring-shaped fixing members 1, which are inserted and supported on an outer peripheral surface of a columnar portion of a rotation shaft (not shown) such as a drive shaft at predetermined intervals in the axial direction. 1 and a cylindrical mass member 2 located between the pair of fixing members 1 and 1 and coaxially arranged outside the rotating shaft with a space therebetween. Each of the fixing members 1 and 1 and the mass member 2. It is composed of a pair of rubber elastic members 3, 3 which are integrally connected to the shaft end and have high spring portions 3a, 3a and low spring portions 3b, 3b.

The fixing members 1 and 1 are used as a pair in a ring shape and are made of a rubber material such as natural rubber.
The diameter of the inner peripheral surface forming the central axis hole of the ring-shaped fixing member 1 is formed to be slightly smaller than the diameter of the outer peripheral surface of the drive shaft. Further, on the outer peripheral surface of the fixing member 1, a ring-shaped locking groove 1a for fastening the fixing band is formed.

The mass member 2 is formed by coating a rubber material such as natural rubber on an outer peripheral surface and an inner peripheral surface of a cylindrical metal mass body such as a thick-walled steel pipe. A space is formed between the inner peripheral surface of the mass member 2 and the outer peripheral surface of the rotary shaft so that the mass member 2 can be displaced in the radial direction. It should be noted that if this void is about 1 to 2 mm, its function can be sufficiently fulfilled.

The rubber elastic members 3, 3 are made of a rubber material such as natural rubber and have a substantially hollow truncated cone shape. The small diameter side is connected to the fixing member 1 and the large diameter side is the mass member 2. It is connected to the shaft end. Each of the rubber elastic members 3, 3 has two high spring portions 3a, 3a whose spring constant in the shearing direction is set higher than a target specific value, and two low spring portions 3 which are set lower than the specific value.
b, 3b, and the high spring portions 3a, 3a and the low spring portions 3b, 3b are formed with a width substantially quadrant in the circumferential direction and are alternately arranged.

The high spring portions 3a, 3a are set to have a predetermined spring constant higher than the specific value by forming the high spring portions 3a, 3a so as to have a short axial length and a large radial thickness. Further, the low spring portions 3b, 3b are set to have a predetermined spring constant lower than the specific value by increasing the length in the axial direction and thinning in the radial direction. In addition, the axial length of the space that allows the mass member 2 to be displaced in the radial direction is set to the high spring 3a. 3a is short, and the low spring portion 3b. 3b
The intervals are set to be long so that the spring constants are different.

The rubber elastic bodies 3 and 3 are formed by integral vulcanization molding together with the coating rubber of both the fixing members 1 and 1 and the mass member 2. The dynamic damper of the present embodiment configured as described above is used as follows. First, when attaching the dynamic damper to the drive shaft, before the drive shaft is attached to the vehicle body of the automobile, the inner holes of the fixing members 1 and 1 of the dynamic damper are expanded and press-fitted from the axial end of the drive shaft, Place the dynamic damper in place. Then, the dynamic damper is attached to the drive shaft by fastening the fixing band in the locking grooves 1a, 1a of the both fixing members 1, 1.

When harmful vibrations are excited with the rotation of the drive shaft, the mass member 2 of the dynamic damper in which the natural frequency is adapted to the frequency of the harmful vibrations.
Resonates through the shear deformation of the rubber elastic members 3 and 3, whereby the vibration energy of the drive shaft is absorbed,
Excited harmful vibrations are suppressed. In this case, the resonance frequency of the dynamic damper is set in a wide range so as to have a plurality of resonance frequencies so as to straddle one target resonance frequency of the drive shaft. Even if there is some variation, it is unlikely that the resonance frequency of the drive shaft and the resonance frequency of the dynamic damper will greatly shift due to variations or the like. Therefore, the resonance frequency of the drive shaft and the resonance frequency of the dynamic damper are in a matched state, and a state in which the maximum vibration suppressing effect of the dynamic damper can be exhibited is ensured.

As described above, in the dynamic damper of the present embodiment, a plurality of resonance frequencies are set in a wide range so as to straddle one target resonance frequency of the rotary shaft, so that the rotary shaft and the dynamic damper are It is possible to minimize the reduction of the vibration suppressing effect caused by the variation of the resonance frequency. In the present embodiment, the rubber elastic member 3
The high spring portion 3a and the low spring portion 3b are provided at two locations in the circumferential direction, but they may be provided at three or more locations.

Further, in the present embodiment, the high spring portion 3a and the low spring portion 3b of the rubber elastic member 3 are configured to have different spring constants by varying their lengths and thicknesses. As an embodiment of the above, the spring constant may be made different by making the rubber hardness different.

[0022]

According to the dynamic damper of the present invention,
The rubber elastic member has a high spring portion whose spring constant in the shearing direction is set higher than a target specific value and a low spring portion which is set lower than the specific value. Since they are arranged alternately in the circumferential direction, it is possible to set multiple resonance frequencies of the dynamic damper in a wide range by straddling one resonance frequency that is the target of the rotation axis. It is possible to minimize the reduction of the vibration suppression effect caused by the variation of the resonance frequency of the damper.

[Brief description of drawings]

FIG. 1 is a sectional view taken along an axial direction of a dynamic damper according to an embodiment of the present invention.

FIG. 2 is a side view of the dynamic damper according to the embodiment of the present invention.

FIG. 3 is a graph showing the relationship between the acceleration level and the frequency of the mass member of the dynamic damper according to the present invention.

FIG. 4 is a sectional view taken along the axial direction of a conventional dynamic damper.

[Explanation of symbols]

1 ... Fixing member 1a ... Locking groove 2 ... Mass member 3
... Rubber elastic member 3a ... High spring portion 3b ... Low spring portion

Claims (1)

[Claims] 1. A pair of ring-shaped fixing members that are inserted through and supported by a rotary shaft at a predetermined interval in the axial direction, and coaxially spaced from the rotary shaft and located between the pair of fixing members. Cylindrical members arranged in a fixed manner, the fixing members and the shaft ends of the mass members adjacent to the fixing members are integrally connected to each other, and both shaft end portions of the mass member are arranged in the shearing direction. In a dynamic damper provided with a pair of rubber elastic members that elastically support, the rubber elastic member is configured such that a high spring portion in which a spring constant in a shearing direction is set higher than a target specific value and a value lower than the specific value are set. And a low spring portion that is formed, the high spring portion and the low spring portion being alternately arranged in the circumferential direction.