JP2007162875A - Constant velocity universal joint and its internal member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate the need for machining of a shaft hole internal diameter face before heat treatment to be carried out in consideration of deformation of the shaft hole internal diameter face by the heat treatment, and to secure strength of an inner ring. <P>SOLUTION: The constant velocity universal joint transmitting torque while allowing angular displacement with an outer ring is provided with the inner ring 22, wherein a shaft is inserted into a shaft hole 32 formed in an internal diameter to carry out spline fitting. An internal diameter face shape of the shaft hole 32 is polygonally formed after the heat treatment forming a spline 33. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is used in power transmission systems of automobiles and various industrial machines, for example, fixed or sliding constant velocity universal joints incorporated in drive shafts and propeller shafts used in 4WD vehicles, FR vehicles, and the like. The present invention relates to an inner member that constitutes a part of a quick universal joint.

  Sliding constant velocity universal joints that allow both angular displacement and axial displacement are used in the power transmission systems of automobiles and various industrial machines, such as the drive shafts of front-wheel drive vehicles and independent-suspension-type rear-wheel drive vehicles. ing. As this sliding type constant velocity universal joint, a ball type double offset constant velocity universal joint (DOJ) using a ball as a torque transmission element is well known.

  This type of double offset type sliding constant velocity universal joint includes an outer ring as an outer member, an inner ring as an inner member, and a plurality of balls incorporated between the outer ring and the inner ring to transmit torque. A cage that holds the ball interposed between the outer ring and the inner ring is a main component (see, for example, Patent Document 1). In this constant velocity universal joint, the drive-side shaft described above is connected to the outer ring, and the shaft as the driven-side shaft is connected to the inner ring.

  The outer ring has a cylindrical shape in which a plurality of linear track grooves parallel to the axis are formed on the inner diameter surface at equal intervals in the circumferential direction. The inner ring is formed with a plurality of linear track grooves parallel to the axis on the outer surface corresponding to the track grooves of the outer ring. A ball for transmitting torque is arranged on a ball track formed by cooperation between the track groove of the outer ring and the track groove of the inner ring. Each ball is accommodated in a cage pocket interposed between the inner diameter of the outer ring and the outer diameter surface of the inner ring.

  The inner ring constituting the constant velocity universal joint has a configuration in which a spline for torque transmission is formed in the shaft hole, and the spline is engaged with a spline formed on the outer diameter surface of the shaft press-fitted into the inner ring. Then, torque transmission is performed at the engaging portion of both splines. Since the inner ring is required to have strength, the inner ring is usually subjected to a heat treatment such as quenching to increase the hardness.

  On the other hand, as another sliding type constant velocity universal joint, there is a tripod type constant velocity universal joint (TJ) (for example, see Patent Document 2).

  Generally, a tripod type constant velocity universal joint has three track grooves formed on the inner diameter surface in the axial direction, and an outer ring as an outer member having an axial roller guide surface on each side of each track groove; A main component is a tripod member as an inner member having three leg shafts protruding in the radial direction, and a roller rotatably accommodated between the leg shaft of the tripod member and the roller guide surface of the outer ring. It is said. In this constant velocity universal joint, the drive side shaft described above is connected to the outer ring, and the shaft as the driven side shaft is connected to the tripod member.

The tripod member constituting the constant velocity universal joint has a configuration in which a spline for torque transmission is formed in the shaft hole, and the spline includes a spline formed on the outer diameter surface of the shaft press-fitted into the tripod member. Engaged and torque transmission is performed at the engaging portions of both splines. Since the tripod member is required to have strength, the hardness is usually increased by performing a heat treatment such as quenching.
Japanese Utility Model Publication No. 4-117926 Japanese Patent Laid-Open No. 2004-232697

  By the way, in the double offset type constant velocity universal joint and the tripod type constant velocity universal joint disclosed in Patent Documents 1 and 2 described above, the inner ring or the tripod member before the inner ring or the heat treatment such as quenching can be easily formed so that splines can be formed in the tripod member. Usually, a spline is formed on the inner surface of the shaft hole of the tripod member.

  In particular, in the case of the tripod type constant velocity universal joint disclosed in Patent Document 2, in consideration of deformation of the inner diameter surface of the shaft hole due to heat treatment, a spline is formed on the inner diameter surface of the shaft hole that has been processed into a predetermined shape in advance. . Thereby, the shape of the inner diameter surface of the shaft hole after the heat treatment in which the spline is formed is a perfect circle that matches the shape of the shaft, thereby preventing a decrease in strength.

  However, it is quite difficult to pre-process the inner diameter surface of the shaft hole into a predetermined shape in anticipation of deformation of the inner diameter surface of the shaft hole due to heat treatment, and the phase of the shaft hole relative to the processing tool is determined during the processing. It is necessary to perform positioning so that there is no deviation, and it takes time and effort to reduce workability.

  Therefore, the present invention has been proposed in view of the above-described problems, and the object of the present invention is to eliminate the need for machining the inner diameter surface of the shaft hole before heat treatment in anticipation of deformation of the inner diameter surface of the shaft hole due to heat treatment. Another object is to provide a constant velocity universal joint that can secure the strength of the inner member and the inner member thereof.

  As a technical means for achieving the above-mentioned object, the present invention is provided in a constant velocity universal joint that transmits torque while allowing angular displacement with an outer member, and in a shaft hole formed in an inner diameter. An inner member into which a shaft is inserted to be fitted into a spline, wherein the shape of the inner surface of the shaft hole after heat treatment in which the spline is formed is a polygon.

  The inner member in the configuration described above preferably has a plurality of track grooves on the outer diameter surface that form a ball track with the outer member, and the number of the track grooves is eight or more.

  In the present invention, the shaft hole inner diameter surface shape after heat treatment in which the spline is formed is made to be a polygon, particularly an octagon or more, so that the shaft hole inner diameter surface shape after the heat treatment is approximated to a perfect circle as much as possible. Accordingly, when the inner member is spline-fitted with the shaft to transmit torque, the spline teeth can transmit the load evenly, and the strength of the inner member and the shaft can be easily improved.

  A constant velocity universal joint can be constructed by adding an outer member and a ball for transmitting torque interposed between the outer member and the inner member to the inner member having the above-described configuration. It becomes.

  According to the present invention, the shaft hole inner diameter surface shape after heat treatment in which the spline is formed is made to be a polygon, particularly an octagon or more, so that the shaft hole inner diameter surface shape after the heat treatment is approximated to a perfect circle as much as possible. Accordingly, when the inner member is spline-fitted with the shaft to transmit torque, the spline teeth can transmit the load evenly, and the strength of the inner member and the shaft can be easily improved.

  As a result, the product life can be improved and the reliability of the product can be greatly improved. Also, if the strength of the inner member and the shaft is maintained as they are, the constant velocity universal joint can be made compact. Further, the machining of the shaft hole inner diameter surface before the heat treatment performed in anticipation of the deformation of the shaft hole inner diameter surface by the heat treatment as in the prior art becomes unnecessary, and the work efficiency can be improved by saving the labor of the processing.

  As an embodiment of the present invention, a double offset type (DOJ) sliding constant velocity universal joint will be described in detail below. Since the present invention is applicable to any ball type constant velocity universal joint, as another embodiment, a fixed type constant velocity universal joint of a Zepper type (BJ) or an undercut free type (UJ), Or it is applicable also to a cross groove type (LJ) sliding type constant velocity universal joint.

  3 and 4 illustrate a basic configuration of a general double offset type constant velocity universal joint. The constant velocity universal joint includes an outer ring 1 as an outer member, an inner ring 2 as an inner member, a plurality of torque transmission balls 3 incorporated between the outer ring 1 and the inner ring 2, as shown in FIG. A cage 4 that is interposed between the outer ring 1 and the inner ring 2 and holds the ball 3 is a main component.

  The outer ring 1 has a cylindrical shape in which a plurality of linear track grooves 5 parallel to the axis are formed on the inner diameter surface 6 at equal intervals in the circumferential direction. The inner ring 2 is formed with a plurality of linear track grooves 7 parallel to the axis line on the outer diameter surface 8 so as to correspond to the track grooves 5 of the outer ring 1. A ball 3 for transmitting torque is disposed on a ball track formed by the track groove 5 of the outer ring 1 and the track groove 7 of the inner ring 2 in cooperation. Each ball 3 is accommodated in a pocket 9 of a cage 4 interposed between an inner diameter surface 6 of the outer ring 1 and an outer diameter surface 8 of the inner ring 2.

The outer diameter surface 10 and the inner diameter surface 11 of the cage 4 are each composed of a partial spherical surface. The center of curvature O ₁ of the outer diameter surface 8 of the inner ring 2 and the center of curvature O ₂ of the partial spherical surface of the outer diameter surface 10 of the cage 4 are axially equal to the joint center plane P including the center O _{3 of the} ball 3. It is offset by a distance f. The partial spherical surface of the inner diameter surface 11 of the cage 4 has a center of curvature O ₁ that coincides with the outer diameter surface 8 of the inner ring 2.

  In this constant velocity universal joint, when an operating angle is given between the outer ring 1 and the inner ring 2, the cage 3 controls the ball 3 on the bisecting plane of the operating angle to maintain the constant velocity of the joint. It has a structure. Even in the state where there is an angular displacement between the outer ring 1 and the inner ring 2, the axial displacement of the inner ring 2 is made smoothly.

  The inner ring 2 constituting the constant velocity universal joint has a configuration in which a torque transmission spline 13 is formed in the shaft hole 12, and the spline 13 is formed on the outer side of a shaft (not shown) press-fitted into the inner ring 2. The splines are engaged with the splines formed on the radial surfaces, and torque is transmitted at the engaging portions of both splines. Since the inner ring 2 is required to have strength, the inner ring 2 is usually subjected to a heat treatment such as quenching to increase the hardness.

  Therefore, the inner ring 2 is made of a steel material that can be hardened by quenching, for example, carbon steel for machine structure. The inner ring 2 is formed with a spline 13 on the inner diameter surface of the shaft hole 12 before heat treatment such as quenching so that the spline 13 can be easily formed, and then subjected to heat treatment such as quenching to improve the strength.

  FIG. 2 shows a six-ball inner ring 2 which is a part of the components of the constant velocity universal joint of FIGS. 3 and 4 and is a premise of the present invention. The inner ring 2 has six track grooves 7 formed on its outer diameter surface 8 at equal intervals in the circumferential direction. When the shaft hole 12 of the inner ring 2 into which a shaft (not shown) is press-fitted by spline fitting is subjected to a heat treatment such as quenching in a state where the shape of the inner diameter surface before the heat treatment is a true circle (see the broken line m in the figure). The shape of the inner diameter surface of the shaft hole after the heat treatment is a hexagon.

  That is, the inner ring 2 is thin in the radial direction at the portion where the track grooves 7 are formed and thick in the radial direction at the portion between the track grooves 7. The amount of shrinkage of the material is not uniform in the circumferential direction, and the inner diameter surface of the thin portion where the track groove 7 is formed is deformed inward more than the inner diameter surface of the thick portion between the track grooves 7. As a result, the shape of the inner diameter surface of the shaft hole 12 that was a perfect circle before the heat treatment becomes a hexagon after the heat treatment.

  In the inner ring 2 of FIG. 2 described above, since the amount of deformation (strain) of the inner diameter surface of the shaft hole by heat treatment is large, in the present invention, the number of track grooves of the inner ring is eight or more. FIG. 1 illustrates an embodiment of the present invention. In the inner ring 22 in this embodiment, as shown in the figure, eight track grooves 27 are formed on the outer diameter surface 28 at equal intervals in the circumferential direction. .

  As described above, when the inner ring 22 having the eight track grooves 27 is subjected to heat treatment such as quenching after the spline 33 is formed on the inner surface of the shaft hole 32 into which the shaft is press-fitted by spline fitting, the inner ring 2 described above is applied. As described in the above, since the radial thickness at the portion where the track grooves 27 are formed is thin and the radial thickness at the portion between the track grooves 27 is thick, the material shrinks during the cooling process after quenching in the heat treatment. The amount does not become uniform in the circumferential direction, and the inner diameter surface of the thin portion where the track groove 27 is formed is deformed inward larger than the inner diameter surface of the thick portion between the track grooves 27.

  As a result, the shape of the inner diameter surface of the shaft hole 32 (see the broken line n in the figure) that was a perfect circle before the heat treatment becomes an octagon after the heat treatment. The octagon has an inner diameter surface of the thin portion where the track grooves 27 are formed as one side and an inner diameter surface of the thick portion between the track grooves 27 as the apex.

  Here, when compared with the inner ring 2 (see FIG. 2) having the hexagonal inner diameter surface shape described above, the inner ring 22 (see FIG. 1) having the octagonal inner diameter surface shape is the shaft hole inner diameter surface by heat treatment. The amount of deformation of (a> b) is small, and the shape of the inner diameter surface of the shaft hole after the heat treatment more closely approximates a perfect circle.

  As a result, in the inner ring 22 shown in FIG. 1, when the torque is transmitted by fitting the shaft with the spline, the spline teeth can transmit the load evenly, and the strength of the inner ring 22 and the shaft can be easily improved. If the same strength as that of the inner ring 2 of FIG. 2 is maintained, the constant velocity universal joint can be made compact while maintaining the strength. Furthermore, the processing of the inner diameter surface of the shaft hole before the heat treatment performed in anticipation of the deformation of the inner diameter surface of the shaft hole due to the heat treatment as in the prior art becomes unnecessary.

  In addition, the polygon which becomes the shape of the inner diameter surface of the shaft hole after the heat treatment corresponds to the number of track grooves of the inner ring, and as the number of the track grooves is increased, the inner diameter surface of the shaft hole after the heat treatment is increased. Since the number of corners of the polygon increases, it becomes remarkable that the shape of the inner diameter surface of the shaft hole after heat treatment approximates a perfect circle.

In the embodiment of the present invention, it is a side view showing an inner ring having eight track grooves on the outer diameter surface. As a premise of the present invention, it is a side view showing an inner ring having six track grooves on the outer diameter surface. FIG. 5 is a cross-sectional view taken along line A-O-A in FIG. 4, illustrating a general double offset type sliding constant velocity universal joint. FIG. 4 is a left side view of FIG. 3.

Explanation of symbols

1 Outer member (outer ring)
3 ball 22 inner member (inner ring)
27 Track groove 28 Outer diameter surface 32 Shaft hole 33 Spline

Claims (3)

  An inner member that is equipped with a constant velocity universal joint that transmits torque while allowing angular displacement with an outer member, and that is inserted into a shaft hole formed in an inner diameter and is spline-fitted, An inner member of a constant velocity universal joint, characterized in that a shaft hole inner diameter surface shape after heat treatment in which a spline is formed is a polygon.   The inner member of the constant velocity universal joint according to claim 1, wherein a plurality of track grooves forming a ball track with the outer member are provided on an outer diameter surface, and the number of the track grooves is eight or more.   A constant velocity universal joint comprising an outer member, the inner member according to claim 1, and a ball that is interposed between the outer member and the inner member to transmit torque.

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