WO2007117076A1

WO2007117076A1 - Universal joint

Info

Publication number: WO2007117076A1
Application number: PCT/KR2007/000367
Authority: WO
Inventors: Jai-Bok Sung
Original assignee: Sejong Metal Co., Ltd.
Priority date: 2006-04-10
Filing date: 2007-01-22
Publication date: 2007-10-18
Also published as: KR20070101017A

Abstract

A universal joint is disclosed. The universal joint includes a first shaft including a shaft body, and a ball groove formed in the shaft body to extend inwardly from an end of the shaft body, a second shaft including a joint ball, the joint ball being received in the ball groove of the first shaft, and a support protrusion or a forcibly-fitting groove provided at the ball groove of the first shaft. The support protrusion or forcibly-fitting groove causes the joint ball to be forcibly fitted in the ball groove while preventing the fitted joint ball from being separated from the ball groove. In accordance with this configuration, the assembly structure of the universal joint is simple. Also, the joint connecting structure of the universal joint provides an enhanced re¬ liability. It is also possible to minimize wear even after prolonged use, and thus to achieve enhanced durability.

Description

Description UNIVERSAL JOINT

Technical Field

[1] The present invention relates to a universal joint for use in a model car or the like, and more particularly to a universal joint wherein a joint ball is coupled in a forcibly fitted manner by a protrusion or a groove, thereby capable of simplifying the overall structure, and achieving enhanced durability. Background Art

[2] Generally, universal joints are adapted to connect a propeller shaft arranged between differential gears to an output shaft of a transmission. Such a universal joint is used to achieve transmission of power between two shafts connected to each other while allowing the angle between the shafts to be variable.

[3] FIG. 1 is an exploded perspective view of a conventional universal joint. FIG. 2 is a partially-sectioned side view illustrating a coupled state of the conventional universal joint. FIGS. 1 and 2 illustrate an example in which the conventional universal joint is used in a model car.

[4] As shown in FIGS. 1 and 2, the conventional universal joint connects a first shaft 10 corresponding to an output shaft of a transmission and a second shaft 20 corresponding to a propeller shaft. The conventional universal joint will be described hereinafter in conjunction with only the first and second shafts 10 and 20, without description of a universal joint portion connected to a differential gear via the second shaft 20.

[5] The first shaft 10 includes a shaft body 12, and a joint 14 formed at one end of the shaft body 12. The joint 14 has a groove structure such that it receives an end of the second shaft 20. That is, the joint 14 is provided with a ball groove 16, and an inclined groove 17 arranged outwardly of the ball groove 16.

[6] The joint 14 is also provided with a slit 18 extending inwardly from an outer end of the joint 14 while being laterally opened, in order to receive joint shafts 26 fixed to the second shaft 20. A plurality of pin holes 19 are formed at the joint 14, in order to receive joint pins 30, and thus to prevent a joint ball 24 of the second shaft 20 from being separated from the joint 14. The joint pins 20 will be described later.

[7] The joint ball 24, which is included in the second shaft 20, is formed at one end of a shaft body 22 included in the second shaft 20. The joint shafts 26 extend from opposite sides of the joint ball 24 in a direction perpendicular to the shaft body 22, respectively. The joint ball 24 is received in the ball groove 16 of the first shaft 10. In this state, the joint shafts 26 are received in the slit 18 of the first shaft 10.

[8] A joint ball 28 and a joint shaft are provided at the other end of the second shaft 20, in order to connect the second shaft 20 to another shaft included in the differential gear or the like, using a universal joint structure.

[9] The joint pins 30 are inserted into the pin holes 19 in a state in which the joint ball

24 of the second shaft 20 has been received in the ball groove 16 of the first shaft 10. Accordingly, the joint pins 30 connect the joint ball 24 to the ball groove 16 while preventing separation of the joint ball 24 from the ball groove 16.

[10] In the conventional universal joint having the above-mentioned configuration, the second shaft 20 can transmit rotating power received from the first shaft 10 to the differential gear or the like while being freely rotatable with respect to the first shaft 10 within a certain angle.

[11] However, the above-mentioned conventional universal joint has a problem.

Although the conventional universal joint uses the joint pins 30 to prevent the joint ball 24 of the second shaft 10 from being separated from the ball groove 16 of the first shaft 10, it is difficult to form the pin holes 19 for receiving the joint pins 30 because the pin holes 19 have a very small diameter. In particular, if the pin holes 19 are inaccurately formed, the second shaft 20 may be easily separated from the first shaft 10. Otherwise, the second shaft 20 connected to the first shaft 10 cannot be freely moved. In either case, the function of the universal joint can be considerably degraded.

[12] In particular, in the above-mentioned conventional universal joint, the support structure for the joint ball 24 is weak because the joint pins 30, which have a rectilinear structure, supports the joint ball 24, which has a spherical shape, in a point contact manner. Furthermore, the joint pins 30 may be easily worn. Thus, the durability of the universal joint is degraded. Disclosure of Invention

Technical Problem

[13] The present invention has been made in view of the above mentioned problems, and an object of the invention is to provide a universal joint which includes a support protrusion or a fitting groove formed in an area where a joint ball is positioned, to support the joint ball, and thus enabling the joint ball to be coupled in a forcibly fitted manner, thereby being capable of simplifying the overall structure, and achieving enhanced durability. Technical Solution

[14] In order to accomplish this object, the present invention provides a universal joint comprising: a first shaft including a shaft body, and a ball groove formed in the shaft body to extend inwardly from an end of the shaft body; a second shaft including a joint ball, the joint ball being received in the ball groove of the first shaft; and forcibly- fitting means provided at the ball groove of the first shaft, the forcibly-fitting means causing the joint ball to be forcibly fitted in the ball groove while preventing the fitted joint ball from being separated from the ball groove. [15] The forcibly-fitting means may comprise a support protrusion formed near an inlet of the ball groove, and adapted to prevent the joint ball from being separated from the ball groove. [16] The support protrusion may be protruded from an inner surface of the ball groove in the form of a circular ring. [17] The forcibly-fitting means may comprise a forcibly-fitting groove formed at an inner surface of the ball groove. The forcibly-fitting groove receives a part of the joint ball while preventing the joint ball from being separated from the ball groove. [18] The forcibly-fitting groove may have a radius of curvature larger than a radius of the joint ball.

Brief Description of the Drawings [19] The above objects, and other features and advantages of the present invention will become more apparent after reading the following detailed description when taken in conjunction with the drawings, in which:

[20] FIG. 1 is an exploded perspective view of a conventional universal joint;

[21] FIG. 2 is a partially-sectioned side view illustrating a coupled state of the conventional universal joint; [22] FIG. 3 is a sectional view illustrating a first shaft included in a universal joint according to an exemplary embodiment of the present invention; [23] FIG. 4 is a sectional view illustrating a state of the universal joint according to the illustrated embodiment of the present invention before connection of the universal joint; [24] FIG. 5 is a sectional view illustrating a connected state of the universal joint according to the illustrated embodiment of the present invention. [25] FIG. 6 is a sectional view illustrating a first shaft included in a universal joint according to another embodiment of the present invention; [26] FIG. 7 is a sectional view illustrating a state of the universal joint according to the embodiment of the present invention illustrated in FIG. 6 before connection of the universal joint; and [27] FIG. 8 is a sectional view illustrating a connected state of the universal joint according to the embodiment of the present invention illustrated in FIG. 6.

Mode for the Invention [28] Hereinafter, preferred embodiments of the present invention will be described with reference to the annexed drawings. [29] FIG. 3 is a sectional view illustrating a first shaft included in a universal joint according to an exemplary embodiment of the present invention. FIG. 4 is a sectional view illustrating a state of the universal joint according to the illustrated embodiment of the present invention before connection of the universal joint. FIG. 5 is a sectional view illustrating a connected state of the universal joint according to the illustrated embodiment of the present invention.

[30] The universal joint according to the illustrated embodiment of the present invention mainly includes a first shaft 50, and a second shaft 60 connected to the first shaft 50 in a universal joint manner.

[31] Typically, the first shaft 50 may correspond to an output shaft included in a transmission of, for example, a model car, or a portion connected to the output shaft, whereas the second shaft 60 may correspond to a propeller shaft adapted to transmit power to a differential gear or the like. Of course, such a connecting configuration is only illustrative. Various mechanical mechanisms may be applicable to the present invention, as long as they must transmit rotating power between two shafts under the condition in which the angle defined between the shafts is variable.

[32] Hereinafter, the constituent elements of the universal joint according to the present invention will be described in detail.

[33] The first shaft 50 includes a shaft body 52, and a joint 54 provided at one end of the shaft body 52. The joint 54 has an enlarged cylindrical structure. The joint 54 is inwardly formed with an inclined groove 57 and a ball groove 56, in this order, in the form of a continuous groove structure, in order to receive the second shaft 60, and thus to connect the second shaft 60 to the first shaft 50.

[34] The ball groove 56 is a portion for receiving a joint ball 64 of the second shaft 60, whereas the inclined groove 57 is a portion having an enlarged structure for allowing the second shaft 60 to rotate within a predetermined angle without any interference.

[35] The joint 54 also is provided with a flange 55 formed at an outer end of the joint 54 to have an enlarged structure. Elongated slits 58 are formed at opposite sides of the joint 54, to receive joint shafts 65 fixed to the second shaft 60, respectively.

[36] In particular, a forcibly-fitting means is provided at an inner surface of the ball groove 56, in order to cause the joint ball 64 to be forcibly fitted in the ball groove 56, and thus to prevent the joint ball 64 from being separated from the ball groove 56 after being fitted in the ball groove 56. In the illustrated embodiment, the forcibly-fitting means comprises a support protrusion 80 formed at the ball groove 56 near an inlet of the ball groove 56.

[37] Preferably, the support protrusion 80 is protruded in the form of a circular ring structure. Under the given practical condition, the support protrusion 80 may have a discrete circular ring structure including a plurality of spaced support protrusions.

[38] Preferably, the support protrusion 80 is protruded to a certain height such that it can prevent the joint ball 64 from being separated from the ball groove 56 after being forcibly fitted in the ball groove 56 using a fitting machine. The support protrusion 80 may be protruded from the inner surface of the ball groove 56 to a height of 0.2 to 0.3 mm.

[39] The second shaft 60 includes a shaft body 62. The joint ball 64, which is also included in the second shaft 60, is provided at an end of the shaft body 62 facing the first shaft 50. The joint ball 64 is received in the ball groove 56 after being forcibly fitted into the ball groove 56.

[40] The joint shafts 65 are protruded from the joint ball 64 at opposite sides of the joint ball 64 in a direction perpendicular to the shaft body 62, respectively. The joint shafts 65 are received in and coupled with the slits 58 of the first shaft 50, respectively.

[41] Meanwhile, a backup ball 70 is provided at an inner central portion of the ball groove 56 of the first shaft 50. The backup ball 70 rolls while being in contact with the joint ball 64, to reduce a resistance generated during the movement of the joint ball 64.

[42] Now, the assembly procedure for the universal joint having the above-described configuration according to the illustrated embodiment of the present invention will be described.

[43] The backup ball 70 is inserted into the ball groove 56 of the first shaft 50.

[44] Thereafter, the second shaft 60 is moved toward the first shaft 50, using a fitting machine in a state in which the joint ball 64 of the second shaft 60 is positioned in front of the ball groove 56 of the first shaft 50. As a result, the joint ball 64 is forcibly fitted into the ball groove 56 after being moved beyond the support protrusion 80.

[45] In this state, the joint ball 64 is firmly received in the ball groove 56 while being forcibly fitted in the support protrusion 80. Accordingly, the second shaft 60 can transmit rotating power while being freely rotatable with respect to the first shaft 50 within a predetermined angle under the condition in which the joint ball 64 is stably coupled with the ball groove 56 without a possibility of separation.

[46] FIG. 6 is a sectional view illustrating a first shaft included in a universal joint according to another embodiment of the present invention. FIG. 7 is a sectional view illustrating a state of the universal joint according to the illustrated embodiment of the present invention before connection of the universal joint. FIG. 8 is a sectional view illustrating a connected state of the universal joint according to the illustrated embodiment of the present invention.

[47] In the following description, constituent elements identical or similar to those of the above-described embodiment will be designated by the same reference numerals, and no detailed description thereof will be given.

[48] In accordance with this embodiment, the forcibly-fitting means of the universal joint comprises a forcibly-fitting groove 90 formed at the ball groove 56 near a central portion of the ball groove 56, different from the above-mentioned embodiment in which the forcibly-fitting means comprises the support protrusion 80.

[49] The forcibly-fitting groove 90 is formed in the inner surface of the ball groove 56 at a position where the joint ball 64 comes into contact with the ball groove 56 in a state in which the joint ball 64 is completely received in the ball groove 56.

[50] The ball groove 56 has a diameter slightly smaller than the diameter of the joint ball

64, whereas the forcibly-fitting groove 90 has a diameter equal to or slightly larger than the diameter of the joint ball 64.

[51] Also, it is preferred that the radius of curvature of the forcibly-fitting groove 90 be larger than the radius of the joint ball 64. This is because, when the radius of curvature of the forcibly-fitting groove 90 is smaller than the radius of the joint ball 64, increased resistance may be generated during movement of the joint ball 64 at inflection points where the inner surface of the ball groove 56 meets the forcibly-fitting groove 90.

[52] Preferably, the forcibly-fitting groove 90 is finely formed to have a depth of about

0.2 to 0.3 mm.

[53] In the universal joint according to this embodiment, the circumferential surface of the joint ball 64 is partially received in the forcibly-fitting groove 90 of the ball groove 56 when the joint ball 64 is forcibly fitted into the ball groove 56. Accordingly, the joint ball 64 is firmly received in the ball groove 56 without a possibility of separation, similarly to the above-described embodiment.

[54] In the assembled state as described above, the second shaft 60 can transmit rotating power while being freely rotatable with respect to the first shaft 50 within a predetermined angle. Industrial Applicability

[55] As apparent from the above description, the universal joint having the above- described configuration and function according to the present invention can assemble the joint ball in a forcibly-fitted manner in accordance with the provision of the forcibly-fitting means, which comprises the support protrusion or forcibly-fitting groove in an area where the joint ball is to be received. Accordingly, there are advantages in that the assembly structure is simple, and the machining of essential parts can be easily achieved by virtue of elimination of pin holes, the machining of which is difficult.

[56] In accordance with the present invention, the forcibly-fitting means is formed in the ball groove of the first shaft such that it stably supports the joint ball in a linear contact manner, different from the conventional point contact manner. Accordingly, there are advantages in that it is possible to achieve an enhancement in the reliability of the joint connecting structure, and to minimize wear even after prolonged use, and thus to achieve enhanced durability.

[57] Although the preferred embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

[ 1 ] A universal joint comprising: a first shaft including a shaft body, and a ball groove formed in the shaft body to extend inwardly from an end of the shaft body; a second shaft including a joint ball, the joint ball being received in the ball groove of the first shaft; and forcibly-fitting means provided at the ball groove of the first shaft, the forcibly- fitting means causing the joint ball to be forcibly fitted in the ball groove while preventing the fitted joint ball from being separated from the ball groove.

[2] The universal joint according to claim 1, wherein the forcibly-fitting means comprises a support protrusion formed near an inlet of the ball groove, and adapted to prevent the joint ball from being separated from the ball groove.

[3] The universal joint according to claim 2, wherein the support protrusion is protruded from an inner surface of the ball groove in the form of a circular ring.

[4] The universal joint according to claim 1, wherein the forcibly-fitting means comprises a forcibly-fitting groove formed at an inner surface of the ball groove, the forcibly-fitting groove receiving a part of the joint ball while preventing the joint ball from being separated from the ball groove.

[5] The universal joint according to claim 4, wherein the forcibly-fitting groove has a radius of curvature larger than a radius of the joint ball.