JP2007224982A - Constant speed universal joint, and its cage - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a constant speed universal joint and its cage, which constant speed universal joint can secure the required depth and surface hardness of a heat treated hardened layer and can prevent the drop of its strength, and can reduce a cost of heat treatment even when the machining of a large allowance should be carried out after heat treatment. <P>SOLUTION: The short cylindrical shape cage 40 is arranged between the inner spherical surface of the outer race and the outer spherical surface of the inner race of the constant speed universal joint, and has a plurality of pockets formed at equal intervals in the circumference so as to retain balls arranged on the ball track between the outer race and the inner race. A heat-treated hardened layer M is formed by induction hardening over the whole range in the thickness direction on the portion including the peripheral portion of the pockets 41 and beam portions 42 between the pockets 41 except both end face portions 43. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is used in power transmission mechanisms of automobiles and various industrial machines, and is, for example, a constant velocity universal joint incorporated in a drive shaft or a propeller shaft used in a 4WD vehicle or an FR vehicle, and components of the constant velocity universal joint This is one of the cages.

  Constant velocity universal joints are used to transmit torque at a constant angular speed by connecting the rotating shaft on the drive side and the rotating shaft on the driven side in the power transmission system of automobiles and various industrial machines. Various types of ball-type constant velocity universal joints such as Barfield type constant velocity universal joints (BJ), double offset type constant velocity universal joints (DOJ) and Lebro (cross groove) type constant velocity universal joints (LJ) is there.

  These constant velocity universal joints include an outer joint member, an inner joint member, a ball, and a cage as main components. Track grooves extending in the axial direction are formed on the inner peripheral surface of the outer joint member, and track grooves extending in the axial direction are also formed on the outer peripheral surface of the inner joint member. A drive-side rotary shaft and a driven-side rotary shaft are connected to the outer joint member and the inner joint member, respectively. The track groove of the outer joint member and the track groove of the inner joint member make a pair to form a ball track, and the ball is incorporated in each ball track. The balls are housed in pockets formed in the circumferential direction of the cage and are held so as to roll freely.

  Therefore, when torque is transmitted with the joint at an operating angle, the ball is always positioned in a plane that bisects the angle formed by the rotation shaft of the outer joint member and the rotation shaft of the inner joint member. Therefore, the constant velocity of the joint is ensured. As described above, the cage, which is one component of the constant velocity universal joint, is incorporated between the outer joint member and the inner joint member, and is an important component that can withstand a large load and hold the ball on the isobaric surface. One is desired to have high strength.

  In order to ensure the high strength of the cage, the cage is subjected to a heat treatment. Generally, carburizing and quenching is used as the heat treatment. This carburizing and quenching is a heat treatment technique suitable for a complicated and thin material such as a cage, but the carburizing and quenching requires a processing time, and thus has poor productivity. In carburizing and quenching, it is difficult to form a heat-treated hardened layer too deep due to its properties. Therefore, when processing is required after carburizing and quenching, particularly in processing that greatly scrapes the surface, it is difficult to ensure the depth of the heat-treated cured layer and the required surface hardness, leading to a decrease in strength. .

  Therefore, when machining with a large machining allowance is required, it was necessary to perform two-stage machining that performs cutting as pre-processing before carburizing and quenching, and further processes to the final finished dimensions after carburizing and quenching. . For such carburizing and quenching and processing of the cage pocket, hard milling has been applied to the cage pocket (see, for example, Patent Document 1).

In other words, the method disclosed in Patent Document 1 is such that after punching a pocket from a short cylindrical shaped member of a cage by press processing, the pocket size is processed to some extent by shaving processing, and further, heat treatment deformation is performed after heat treatment. Pockets that have become inaccurate are processed to the final finished dimensions by hard milling.
JP 2003-49861 A

  By the way, in the conventional carburizing and quenching, it takes time for heat treatment, and it is difficult to make in-line because of batch processing by a furnace. In carburizing and quenching, it is difficult to form a deep heat-treated hardened layer. Therefore, when performing cutting with a large allowance after carburizing and quenching, it is difficult to ensure the necessary depth and surface hardness of the heat-treated hardened layer.

  When such a process is required, a two-stage process including a pre-process before carburizing and quenching (shaving process) and a post-process after carburizing and quenching (hard milling process) may be performed as in Patent Document 1. By doing so, it is possible to prevent a reduction in cage strength due to excessive cutting of the heat-treated hardened layer after carburizing and quenching.

  However, in the case of two-stage processing consisting of pre-processing before carburizing and quenching and post-processing after carburizing and quenching, the processing must be performed twice before and after carburizing and quenching. There is a problem that the time is increased and the cost of the product is increased.

  Therefore, the present invention has been proposed in view of the above-mentioned problems, and the object is to ensure the necessary depth and surface hardness of the heat-treated hardened layer even when a large machining allowance is applied after heat treatment. It is an object of the present invention to provide a constant velocity universal joint and its cage that can prevent a decrease in strength and can reduce heat treatment costs.

  As a technical means for achieving the above-mentioned object, the present invention is arranged between the inner spherical surface of the outer joint member of the constant velocity universal joint and the outer spherical surface of the inner joint member, and between the outer joint member and the inner joint member. A cage having a short cylindrical shape in which a plurality of pockets for accommodating balls arranged on the ball track are formed at equal intervals in the circumferential direction, including a pocket peripheral portion and a column portion between the pockets, and both end surface portions. A heat-treated hardened layer is formed over the entire region in the thickness direction at a portion excluding.

  In the present invention, by forming the heat treatment hardened layer over the entire thickness direction of the cage, it is possible to ensure the necessary depth and surface hardness of the heat treated hardened layer even when a large machining allowance is applied after the heat treatment. It is possible to prevent the strength from being lowered.

  The reason why the heat treatment hardened layer is formed is that the peripheral portion of the pocket and the part including the pillars between the pockets are the largest load due to contact with the ball. To ensure proper strength. Further, the reason why the heat-treated hardened layer is not formed on the both end surface portions of the cage is to alleviate the crack sensitivity at the end surface portions, thereby improving the strength of the cage.

  The heat-treated cured layer in the present invention is desirably formed by induction hardening. By using induction hardening as the heat treatment, a deep heat treatment hardened layer can be formed, so that the heat treatment hardened layer can be easily formed over the entire region in the thickness direction.

  The cage of the present invention preferably uses a material made of medium carbon steel. Since the medium carbon steel contains a predetermined amount of carbon, it is easy to form a deep heat treatment hardened layer by induction hardening.

  According to the present invention, an outer joint member, an inner joint member, and a ball that is rotatably held by the cage and transmits torque between the outer joint member and the inner joint member are added to the cage configured as described above. It is possible to configure a constant velocity universal joint.

  The present invention includes an outer joint member formed in the axial direction in a state where a plurality of linear track grooves are inclined with respect to the axis on the inner peripheral surface, and an outer joint with a plurality of linear track grooves on the outer peripheral surface with respect to the axis. An inner joint member formed in the axial direction in a state inclined in the opposite direction to the track groove of the member, a ball incorporated in a crossing portion of the track groove of the outer joint member and the track groove of the inner joint member, and the outer joint member A constant velocity universal joint provided with a cage disposed between the inner peripheral surface of the inner joint member and the outer peripheral surface of the inner joint member and holding the ball between the track groove of the outer joint member and the track groove of the inner joint member, It is preferable to apply to a Lebro (cross groove) type constant velocity universal joint.

  According to the present invention, since the heat-treated hardened layer is formed by induction hardening over the entire thickness direction of the cage, the required depth and surface hardness of the heat-treated hardened layer even when a large machining allowance is applied after the heat treatment. Can be ensured, and strength reduction can be prevented. In addition, since the heat-treated hardened layer is not formed on both end surface portions of the cage, the sensitivity of the end surface portion to cracks can be alleviated, so that the strength of the cage can be improved. Furthermore, by using induction hardening, the heat treatment time can be shortened, the heat treatment cost can be reduced, and the in-line process can be realized.

  5 to 7 show an embodiment of a constant velocity universal joint cage according to the present invention, and illustrate a Lebro (cross groove) type constant velocity universal joint (LJ) incorporating the cage. The present invention is also applicable to other types of constant velocity universal joints such as a double offset type constant velocity universal joint (DOJ) and a Barfield type constant velocity universal joint (BJ).

  As shown in FIGS. 5 and 6, the constant velocity universal joint includes an inner ring 10 as an inner joint member, an outer ring 20 as an outer joint member, a plurality of balls 30 and a cage 40 as main components. The inner ring 10 has a shaft (not shown) connected to the center hole 11 thereof by spline fitting, and a plurality of linear track grooves 12 are formed in the axial direction on the outer peripheral surface. The outer ring 20 is positioned on the outer periphery of the inner ring 10, and the same number of linear track grooves 22 as the track grooves 12 of the inner ring 10 are formed in the axial direction on the inner peripheral surface. A cylindrical cage 40 that is short in the axial direction is disposed between the inner ring 10 and the outer ring 20. The plurality of balls 30 are respectively accommodated in a plurality of pockets 41 formed at equal intervals in the circumferential direction of the cage 40.

  The track groove 12 of the inner ring 10 and the track groove 22 of the outer ring 20 form an angle (track crossing angle α) inclined in the opposite direction with respect to the axis L as shown in FIG. 7 (the cage 40 is not shown). A ball 30 is incorporated at the intersection of the track groove 12 of the inner ring 10 and the track groove 22 of the outer ring 20.

  Since the cage 40 incorporated in the Lebro (cross groove) type constant velocity universal joint receives the greatest load at the peripheral portion of the pocket 41 that contacts the ball 30 and the portion including the column portion 42 between the pockets 40, Heat treatment is applied to the part. As this heat treatment, induction hardening capable of forming a deep heat treatment hardened layer is employed.

  In the conventional carburizing and quenching, all the parts of the cage are hardened, and after that treatment, a grain boundary oxide layer is generated as a surface abnormal layer on the surface layer part, which causes a problem of strength variation. In addition, since carburizing and quenching diffuses a high concentration of carbon on the surface, there is a problem in that a large amount of carbides cause coarsening of crystal grains that precipitate at grain boundaries, causing deformation and reducing strength. Although the grain boundary oxide layer can be removed by processing in a later step, it usually remains on the peripheral edge of the pocket and the end surface of the cage without processing.

  Therefore, in this embodiment, by adopting induction hardening, it is possible to suppress the generation of the grain boundary oxide layer in the entire region of the cage 40. Therefore, the strength of the cage 40 is not reduced by the grain boundary oxide layer, and the cage The strength of 40 can be improved. In addition, by adopting induction hardening, the heat treatment time can be shortened and the heat treatment cost can be reduced, the process can be inlined, and the product cost can be reduced.

  FIGS. 1 and 2 show two examples of heat treatment patterns in the cage 40 incorporated in the constant velocity universal joint of FIGS. 3A is a cross section taken along line AA in FIG. 1, FIG. 3B is a cross section taken along line BB in FIG. 1, and FIG. 4A is taken along line CC in FIG. 4B is a cross section taken along the line DD of FIG. In addition, as a raw material of the cage 40, medium carbon steel is used. Since this medium carbon steel contains a predetermined amount of carbon, it is easy to form a deep heat treatment hardened layer by induction hardening.

  In the cage 40 shown in FIG. 1 and FIG. 2, a portion subjected to the largest load in contact with the ball 30, that is, a portion including the peripheral portion of the pocket 41 and the column portion 42 between the pockets 41 is heat-treated and hardened by induction hardening. M and N are formed. The heat treatment hardened layers M and N are formed deeply by adopting induction hardening, and are formed over the entire region in the thickness direction of the cage 40 as shown in FIGS. The hatched portion in the figure indicates the portion where the heat-treated hardened layers M and N are formed.

  Thus, by forming the heat treatment hardened layers M and N over the entire region in the thickness direction of the cage 40, the necessary heat treatment hardened layer of the heat treatment hardened layer can be obtained even when a large machining allowance is applied after the induction hardening. Depth and surface hardness can be ensured and strength reduction can be prevented.

  Here, when processing with a large allowance after heat treatment is performed, conventionally, after punching a pocket from a short cylindrical shaped material of a cage by press processing, the pocket size is processed to a certain extent by shaving processing, and further after heat treatment A pocket whose dimensional accuracy has deteriorated due to heat treatment deformation has been processed into a final finished dimension by hard milling or the like (see Patent Document 1).

  On the other hand, in this embodiment, since the heat treatment hardened layers M and N can be formed deeply by induction hardening, even when processing a large machining allowance after induction hardening, even if processing at a stretch by hard milling, The necessary depth and surface hardness of the heat-treated cured layer can be ensured. Therefore, the shaving process can be abolished while ensuring high pocket dimensional accuracy by hard milling, and the heat treatment cost can be reduced.

  The portion that includes the peripheral portion of the pocket 41 and the column portion 42 between the pockets 41 as the portion for forming the heat treatment hardened layers M and N has the largest load due to contact with the ball 30 as described above. Because. Therefore, it is not necessary to form the heat treatment hardened layers M and N by induction hardening on the both end surface portions 43 of the cage 40 because they do not receive a large load due to contact with the balls 30 (see FIGS. 1 and 2). By not forming the heat treatment hardened layers M and N on the both end face portions 43 of the cage 40, the crack sensitivity at the end face portion 43 can be reduced, and the strength of the cage 40 is improved.

  In the above embodiment, the case where the present invention is applied to a Lebro (cross groove) type constant velocity universal joint has been described. However, the present invention is not limited to a double offset type constant velocity universal joint (DOJ) or a Barfield type constant velocity universal joint (BJ). It is also applicable to. However, the application of the present invention is optimally a Lebro (cross groove) type constant velocity universal joint. The reason is as follows.

  In the double offset type constant velocity universal joint (DOJ) and the barfield type constant velocity universal joint (BJ), when the joint takes an operating angle, the outer diameter of the inner ring is tilted while being in contact with the inner diameter of the cage. Therefore, it is necessary to reduce the spherical clearance between the cage inner diameter and the inner ring outer diameter. On the other hand, in a Lebro (cross groove) type constant velocity universal joint, there is no contact between the cage inner diameter and the inner ring outer diameter. Therefore, it is not necessary to completely heat-treat the inner and outer diameters of the cage, and heat treatment that leaves uncured portions on both end surfaces of the cage is possible.

In embodiment of this invention, it is sectional drawing which shows an example of the heat processing pattern in a cage. In other embodiment of this invention, it is sectional drawing which shows the other example of the heat processing pattern in a cage. (A) is sectional drawing which follows the AA line of FIG. 1, (b) is sectional drawing which follows the BB line of FIG. (A) is sectional drawing which follows the CC line of FIG. 2, (b) is sectional drawing which follows the DD line | wire of FIG. It is sectional drawing which shows schematic structure of the Lebro (cross groove) type constant velocity universal joint to which this invention is applied. FIG. 6 is a side view of FIG. 5. FIG. 6 is a partial front view for explaining a track crossing angle α in the inner ring and the outer ring in FIG. 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Outer ring 12 Track groove 20 Inner ring 22 Track groove 30 Ball 40 Cage 41 Pocket 42 Column part 43 End surface part

Claims (5)

  A plurality of pockets that are disposed between the inner spherical surface of the outer joint member of the constant velocity universal joint and the outer spherical surface of the inner joint member, and that contain balls disposed on the ball track between the outer joint member and the inner joint member, are circular. A short cylindrical cage formed at equal intervals in the circumferential direction, including a pocket peripheral portion and a column portion between the pockets, and a heat treatment hardened layer over the entire thickness direction at a portion excluding both end surface portions. A constant velocity universal joint cage characterized by being formed.   The constant velocity universal joint cage according to claim 1, wherein the heat-treated hardened layer is formed by induction hardening.   The constant velocity universal joint cage according to claim 1 or 2, comprising medium carbon steel.   The outer joint member, the inner joint member, the cage according to any one of claims 1 to 3, and the outer joint member and the inner joint member are rotatably held by the cage and transmit torque. A constant velocity universal joint provided with   The outer joint member formed in the axial direction with a plurality of linear track grooves inclined with respect to the axis on the inner peripheral surface, and the outer joint member formed with the plurality of linear track grooves on the outer peripheral surface with respect to the axis. An inner joint member formed in an axial direction in a state inclined in the opposite direction to the track groove, a ball incorporated in a crossing portion of the track groove of the outer joint member and the track groove of the inner joint member, and the outer joint member And a cage that is disposed between the inner peripheral surface of the inner joint member and the outer peripheral surface of the inner joint member and holds the ball between the track groove of the outer joint member and the track groove of the inner joint member. Constant velocity universal joint.

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