JP3995073B2 - Silencing structure of propeller shaft - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is a propeller shaft having a double pipe connection structure that is connected to an inner pipe attached to a joint by being externally inserted through an elastic body so as to be connected to a differential gear via the joint. The present invention relates to a muffler structure of a propeller shaft for absorbing resonance vibration.
[0002]
[Prior art]
There is a phenomenon that vibrations of the engine, transmission, differential gear, and the like are amplified by air column resonance of air in the propeller shaft closed at both ends. This increases the noise of the propeller shaft, and when the propeller shaft has a center bearing, the vibration propagates to the floor. In order to reduce the vibration of such a propeller shaft, for example, in Japanese Patent Laid-Open No. 9-169221, a double pipe connection structure in which an anti-vibration rubber is interposed in a universal joint or an inner pipe is inserted into a propeller shaft. It is also well known that a vibration-proof rubber is interposed between the pipes. Instead of using such an elastic body, a method of absorbing resonance vibration in the propeller shaft by paper mounted along its inner peripheral surface is also well known.
[0003]
[Problems to be solved by the invention]
However, none of these methods attempt to suppress the occurrence of the propeller shaft resonance phenomenon itself.
[0004]
In view of the above, the present invention has an object to provide a noise reduction structure for a propeller shaft in which a silencer is configured in the inner pipe on the premise of a double pipe connection structure for the propeller shaft.
[0005]
[Means for Solving the Problems]
In order to achieve this object, the present invention provides, according to claim 1, a propeller connected in an extrapolated state via an elastic body to an inner pipe attached to a joint in order to connect to a differential gear via the joint. In the shaft silencer structure, the end of the inner pipe on the side opposite to the joint is configured so that the inner pipe is configured as a Helmholtz-type silencer that absorbs the resonance frequency of the resonance frequency with the closed ends on both sides of the propeller shaft as an antinode. It was closed with a closing plate, and the end of the pipe-shaped neck portion on the side opposite to the joint was attached to this closing plate with an opening formed in the closing plate portion surrounded by this end portion. It is characterized by that.
[0006]
By configuring a Helmholtz type silencer in the propeller shaft, resonance vibration of air inside the propeller shaft is canceled, and generation of noise or vibration amplification is suppressed.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Based on FIG. 1, a noise reduction structure of a propeller shaft according to an example of an embodiment of the present invention will be described. The end of the propeller shaft 1 opposite to the transmission side is connected to the differential gear 3 via the joint 2. The propeller shaft 1 is connected to the universal joint 2 with a well-known double pipe connection structure, and the inner pipe 5 is welded to the flange portion 21a of the propeller shaft side yoke 21, and the anti-vibration rubber mounted on the outer peripheral surface thereof. 7, the end of the propeller shaft 1 is joined as an outer pipe in an extrapolated state. A companion flange portion 3 a of the differential gear 3 is screwed to the flange portion 22 a of the differential gear side yoke 22.
[0008]
According to the present invention, the end portion on the side opposite to the joint of the inner pipe 5 is a circular closing plate so as to constitute a Helmholtz type silencer that absorbs resonance sound having the closed ends on both sides of the propeller shaft 1 as the belly in the inner pipe 5. 11 is welded to form a closing surface, and the end of the pipe-shaped neck portion 10 inserted into the inner pipe 5 is welded to the closing plate. A circular opening 11a having a corresponding shape is formed in the closing plate portion surrounded by the end so that the inner pipe 5 communicates with the propeller shaft 1.
[0009]
Here, if the length of the neck portion 10 is L, the inner diameter d of the neck portion 10 and the volume of the inner pipe 5 is v, the silencing frequency f by Helmholtz resonance is as follows.
[0010]
f = (c / 2π) × √ (G / v) (1)
Here, c is the speed of sound, and G = πd ² / (L + d × π / 2).
[0011]
The operation of the Helmholtz silencer configured as described above is as follows. When the length of the propeller shaft 1 with both ends closed is 450 mm, the primary resonance frequency (n = 1) is given by fo = (n / 2) × (c / Lo) with the air column resonance frequency being fo. 378 Hz. Here, n is a natural number, c is the speed of sound, and Lo is the length of the propeller shaft 1.
[0012]
Accordingly, the dimensions of the respective parts related to the above-described formula (1) are set such that L is 25 mm, d is 10 mm, the length of the inner pipe 5 defining the volume v of the inner pipe 5 is 100 mm, and the inner diameter is 45 mm.
[0013]
Thereby, in addition to the suppression of vibration propagation by the anti-vibration rubber 7, the resonance vibration of the internal air to be generated in the propeller shaft 1 closed at both ends is canceled by the resonance in the inner pipe 5. Noise due to the resonance vibration of 1 is silenced and vibration amplification is also suppressed.
[0014]
Further, when the propeller shaft 1 has a center bearing, vibrations of the engine, transmission, differential gear, etc. are prevented from being amplified and propagated to the body floor.
[0015]
In addition, by providing the center bearing in this way, when the propeller shaft is partitioned on both sides in a closed state, the above formula (1) corresponds to the length between the closed end and the joint side closed end of the propeller shaft. Set the dimensions of each related part.
[0016]
【The invention's effect】
According to the present invention, a silencer is formed with a simple configuration using an inner pipe with a double pipe connection structure, noise generation due to resonance in the propeller shaft is reduced, and amplification of drive system vibration is also avoided. Is done.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a muffler structure of a propeller shaft according to an embodiment of the present invention.
[Explanation of symbols]
1 Propeller shaft 2 Joint 3 Differential gear 5 Inner pipe 7 Anti-vibration rubber 10 Neck part 11 Closing plate 11a Opening part

Claims (1)

In a muffler structure for a propeller shaft that is connected to an inner pipe attached to the joint in an extrapolated state via an elastic body in order to connect to the differential gear via the joint, the inner pipe has closed ends on both sides in the propeller shaft. The end of the inner pipe opposite to the joint is closed with a closing plate so as to be configured as a Helmholtz-type silencer that absorbs the resonance frequency of the resonance frequency with the belly. The propeller shaft silencing structure, wherein an end portion of the neck portion on the side opposite to the joint is attached to the inner pipe by forming an opening portion in the closing plate portion surrounded by the end portion.

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