CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No. 10-2019-0051687, filed on May 2, 2019, the entire contents of which is incorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an anti-resonance apparatus of a propeller shaft for changing a natural frequency of the propeller shaft depending on a vehicle speed to prevent resonance due to critical revolution of the propeller shaft

Description of Related Art

A propeller shaft transfers driving force between a transmission (or transfer) and a rear differential of a 4WD or FR vehicle. When the length of the propeller shaft is increased, if a critical speed is reached, the excitation frequency (with one time per one revolution of the propeller shaft) due to an imbalanced self-mass of the propeller shaft and the primary bending natural frequency of the propeller shaft are equalized, and thus serious vibration and damage thereof may be caused due to resonance and the propeller shaft needs to be designed in consideration of this.

That is, in the case of a general vehicle with a long wheel base, the length to a rear joint connected to a rear differential from a front joint of the propeller shaft connected to the transmission is excessively increased. Thus, when the propeller shaft is configured in 1-piece type (2-joint & 1-tube structure), the primary component excitation frequency (which has a bending direction due to an imbalanced mass) and the primary bending natural frequency, which are generated via rotation of the propeller shaft within a range of a vehicle operation speed due to the very low primary bending natural frequency of a tube, and thus there is a problem in that serious vibration and damage of the propeller shaft are caused.

To overcome this, conventionally, as shown inFIG. 1, the length of each tube may be reduced while a center joint5is applied to an intermediate portion of the propeller shaft to divide the tube into a front tube1and a rear tube3, and thus the primary bending natural frequency of the tube may be increased. That is, even if the tube is divided, the natural frequency is present, but the length of a separate tube is reduced to excessively increase the natural frequency.

Accordingly, the primary bending natural frequency may be spaced apart to be higher than the revolution imbalanced excitation frequency of the propeller shaft, and thus the primary bending natural frequency and the excitation frequency may not cross each other, preventing resonance from occurring.

FIG. 2andFIG. 3are diagrams showing comparison of a primary bending natural frequency of a propeller shaft between the case in which the propeller shaft includes one tube and the case in which the propeller shaft includes two tubes.

Accordingly, when the propeller shaft includes one tube, the primary bending natural frequency (fnor ωn) of the propeller shaft is present within a maximum driving speed range of the vehicle, as shown inFIG. 2, and thus when a vehicle is continuously driven while the excitation frequency (fcor ωc) (which is proportional to a vehicle driving speed) due to the revolution imbalanced of the propeller shaft is close to the primary bending natural frequency, damage with serious vibration of the propeller shaft may be caused.

However, when the propeller shaft includes two tubes, the primary bending natural frequency (fnor ωn) is present is present above the maximum driving speed range of the vehicle, as shown inFIG. 3, and thus the excitation frequency (fcor ωc) due to revolution imbalance of the propeller shaft is spaced from the primary bending natural frequency (fnor ωn) to prevent influence of resonance.

However, accordingly, when the propeller shaft is divided, components such as a tube and a joint are further required, and thus there is a problem in terms of increased cost and weight and the disadvantageous number of processes.

Needless to say, a method of increasing the bending natural frequency of the propeller shaft includes a method of increasing a diameter of a tube and a method of changing a material of the tube to a material with high specific stiffness as well as the aforementioned method of reducing the length of the propeller shaft via division.

However, in the method of increasing a diameter of a tube, a lower space of a vehicle is narrow and the weight of the vehicle is increased, and thus it is not possible to indefinitely increase the diameter of the tube, and when the tube is formed of a material such as CFRP, specific stiffness is partially increased, but cost is remarkably increased, and when the length of the propeller shaft is further increased, there is also a limit in increasing the natural frequency any longer.

The information included in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and may not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

BRIEF SUMMARY

Various aspects of the present invention are directed to providing an anti-resonance apparatus of a propeller shaft for changing a natural frequency of the propeller shaft depending on a vehicle speed to prevent resonance due to critical revolution of the propeller shaft.

According to an exemplary embodiment of the present invention, an anti-resonance apparatus of a propeller shaft includes a support provided in a tube and configured to be rotated with the tube, and including guide pins arranged at equal angles around a longitudinal axis of the tube and formed in a radial direction of the support, a mass body slidably engaged to the guide pins and guided by the guide pins to be moved along the guide pins, and a return spring configured to provide an elastic force in a moving direction in which the mass body is moved toward the support.

The anti-resonance apparatus may further include flanges formed on opposite end portions of the support, wherein an external circumferential surface of the flanges may be fixed to an internal circumferential surface of the tube, and the support may be rotated with the tube.

The support may be formed in the longitudinal axis of the tube, a plurality of guide pins are formed in the longitudinal direction of the support, and the plurality of guide pins may be paired and a mass body is mounted to each pair of the guide pins.

One end portion of the guide pin may be fixed to an external circumferential surface of the support, a remaining end portion of the guide pin may protrude toward an internal circumferential surface of the tube, and the mass body may be mounted to the guide pin and may be moved between the external circumferential surface of the support and the internal circumferential surface of the tube.

The guide pins may be formed to face each other around a longitudinal axis of the support.

An external surface of the mass body, which faces the internal circumferential surface of the tube, may be formed with an arc shape corresponding to the internal circumferential surface of the tube.

A return spring may be mounted to the guide pin and may be configured to be provided between the external circumferential surface of the support and the mass body.

A single tube may be connected between a transmission and a rear differential.

A natural frequency at which the propeller shaft is operated in a state in which the mass body is spaced from the tube may be spaced apart to be higher than a frequency at a time point of a specific vehicle speed, and a natural frequency at which the propeller shaft is operated in a state in which the mass body contacts with the tube may be spaced apart to be smaller than a frequency at a time point of a specific vehicle speed.

The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description, which together serve to explain certain principles of the present invention.

