JP4338983B2 - Constant velocity universal joint - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a constant velocity universal joint, and more particularly to a tripod type constant velocity universal joint suitable for use in a power transmission unit of an automobile, an aircraft, a ship, various industrial machines, and the like.
[0002]
[Prior art]
For example, a tripod type constant velocity universal joint is one type of constant velocity universal joint used as a means for transmitting rotational force from an automobile engine to wheels at a constant speed. This tripod type constant velocity universal joint connects two shafts on the drive side and the driven side, transmits rotational torque at a constant speed even if the two shafts take an operating angle, and also allows relative displacement in the axial direction. It has a structure that can
[0003]
In general, the tripod type constant velocity universal joint has three track grooves 1 in the axial direction formed in the inner peripheral portion as shown in FIG. 8, and the axial roller guide surfaces on both sides of each track groove 1. 2, a tripod member 5 having three leg shafts 4 projecting in the radial direction, and between the leg shaft 4 of the tripod member 5 and the roller guide surface 2 of the outer joint member 3. The roller 6 accommodated rotatably is comprised as a main member. One of the two shafts is connected to the outer joint member 3 and the other is connected to the tripod member 5.
[0004]
In this way, the leg shaft 4 of the tripod member 5 and the roller guide surface 2 of the outer joint member 3 are engaged with each other in the biaxial rotational direction via the roller 6, so that the rotational torque is constant from the drive side to the driven side. Communicated in Further, as each roller 6 rolls on the roller guide surface 2 while rotating with respect to the leg shaft 4, relative axial displacement and angular displacement between the outer joint member 3 and the tripod member 5 are absorbed. Is done.
[0005]
The tripod member 5 constituting this tripod type constant velocity universal joint has a configuration in which serrations 8 for torque transmission are formed on the inner diameter surface of a boss portion 7 having three leg shafts 4 as shown in FIGS. The serrations 8 are engaged with serrations 10 formed on the outer peripheral surface of the rotary shaft 9 press-fitted inside the tripod member 5 as shown in FIG. Torque is transmitted. Since the tripod member 5 is required to have strength, the hardness is usually increased by performing a heat treatment such as quenching (see, for example, Patent Document 1).
[0006]
[Patent Document 1]
Japanese Utility Model Laid-Open No. 5-1028 (paragraph numbers [0002] to [0004], FIGS. 3 to 5)
[0007]
[Problems to be solved by the invention]
By the way, the tripod member 5 in the tripod type constant velocity universal joint described above has a large thickness in the radial direction at the formation portion m of the leg shaft 4 and a small thickness in the radial direction at the cylindrical portion n between the leg shafts 10. Therefore, in the heat treatment of the tripod member 5, the shrinkage amount of the material is not uniform in the circumferential direction of the boss portion 7 in the cooling process after quenching, and the inner diameter surface of the cylindrical portion n having a large shrinkage amount is the formation portion m of the leg shaft 4. The inner surface of the boss portion 7 is deformed inwardly as shown by a chain line p in FIG. 9.
[0008]
For this reason, when the rotary shaft 9 is press-fitted into the tripod member 5 and coupled to each other, the interference of the serration 8 on the inner diameter surface of the cylindrical portion n is the portion where the leg shaft 4 is formed. The clearance of serration 8 at m is larger than that of the serration 8, and if the clearance fit is fitted, the clearance of serration 8 at cylindrical portion n is smaller than the clearance of serration 8 at formation portion m of leg shaft 4. As a result, there is a problem that a large load is applied to the serration 8 on the inner diameter surface of the cylindrical portion n during torque transmission, and the thin cylindrical portion n is weak in strength. Further, even on the rotating shaft side press-fitted into the tripod member 5, a large load is applied to the serration that fits into the serration 8 of the tripod member 5, and the strength of the rotating shaft 9 is also reduced.
[0009]
Therefore, the present invention has been proposed in view of the above-described problems, and an object of the present invention is to provide a constant velocity universal joint capable of improving durability in a cylindrical portion of a tripod member by simple means. It is in.
[0014]
[Means for Solving the Problems]
As technical means for achieving the above-mentioned object , the present invention forms a plurality of track grooves on the inner peripheral surface along the axial direction at equal intervals in the circumferential direction, and is fixed to the end of the first rotating shaft. The outer joint member and the outer circumferential surface of the outer joint member are alternately formed with a radially thick portion and a radially thin portion at equal intervals in the circumferential direction so as to form a pair with the track groove of the outer joint member. A heat-treated inner joint member that is fixed to the end portion by serration fitting, and a plurality of members that are interposed between the outer joint member and the inner joint member and transmit torque between the first rotating shaft and the second rotating shaft. In the constant velocity universal joint provided with the rolling element, the inner joint member has three leg shafts that protrude radially on the outer peripheral surface of the boss portion fixed to the end of the second rotating shaft. formed in equidistant, a tripod member which has its trunnion forming site and the radially thick portion, the second The end of the rotating shaft has a shaft hole for serration fitting, and the shaft hole is shaped by heat treatment so that the inner diameter dimension of the radially thin part is smaller than the inner diameter dimension of the radially thick part. The formation of a serration forms a perfect circle that matches the outer diameter of the second rotating shaft, and an abnormal layer due to heat treatment is eliminated .
[0015]
In this invention, since the serration was formed in the inner diameter of the shaft hole after the heat treatment of the inner joint member, as described above, even when the heat treatment was performed to increase the hardness of the inner joint member, Since the deformed portion due to the contraction of the second portion can be eliminated by forming serrations, it can be a perfect circle that matches the outer diameter shape of the second rotating shaft that is press-fitted into the shaft hole.
[0016]
As a result, the load applied to the serration of the inner diameter surface of the shaft hole becomes uniform during torque transmission, the strength of the inner joint member can be ensured, and the abnormal layer generated on the inner diameter surface by heat treatment can be eliminated. Therefore, the serration strength can be further improved.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment in which the present invention is applied to a tripod type constant velocity universal joint will be described in detail below.
[0020]
The tripod type constant velocity universal joint of the embodiment shown in FIG. 2 and FIG. 3 is composed mainly of an outer joint member 11, a tripod member 12 which is an inner joint member, and a roller 13 which is a rolling element. The first rotary shaft, which is one of the two shafts to be connected on the driven side, is connected to the outer joint member 11, and the second rotary shaft 14 which is the other is connected to the tripod member 12, so that the operating angle is constant. Is provided with a configuration capable of transmitting rotational torque and also allowing relative displacement in the axial direction.
[0021]
The outer joint member 11 has a substantially cylindrical cup shape with one end opened and the other end closed, and a first rotating shaft (not shown) is integrally provided at the other end, and an axial direction is provided at the inner peripheral portion. Three track grooves 15 are formed around the central axis at intervals of 120 °. Each track groove 15 is formed with a concave curved roller guide surface 16 in the axial direction on the side walls facing each other in the circumferential direction. The tripod member 12 has three leg shafts 17 protruding in the radial direction, and is held on the second rotating shaft 14 by serration fitting. The roller 13 is rotatably mounted on the leg shaft 17 via a plurality of needle rollers 18 and is accommodated between the leg shaft 17 of the tripart member 12 and the roller guide surface 16 of the outer joint member 11.
[0022]
The outer peripheral surface of the leg shaft 17 is an inner raceway surface of the needle roller 18, and the inner peripheral surface of the roller 13 is an outer raceway surface of the needle roller 18. The outer peripheral surface of the roller 13 is a convex spherical surface that fits the roller guide surface 16. The needle roller 18 is assembled in a full roller state, and is prevented from coming off by a circlip 19 attached near the tip of the leg shaft 17.
[0023]
In this tripod type constant velocity universal joint, the leg shaft 17 of the tripod member 12 and the roller guide surface 16 of the outer joint member 11 are engaged with each other in the biaxial rotation direction via the roller 13, so that the driven side is driven to the driven side. Rotational torque is transmitted at a constant speed. In addition, as each roller 13 rolls on the roller guide surface 16 while rotating with respect to the leg shaft 17, relative axial displacement and angular displacement between the outer joint member 11 and the tripod member 12 are absorbed. Is done.
[0024]
The tripod member 12 constituting a part of the tripod type constant velocity universal joint includes a cylindrical boss portion 20 and the above-described leg shaft integrally projecting around the central axis of the boss portion 20 at intervals of 120 °. 17 and has a shaft hole 21 penetrating the shaft center of the boss portion 20 and into which the second rotating shaft 14 is press-fitted. A serration 22 is formed on the inner diameter surface of the shaft hole 21 of the tripod member 12, and a serration 23 is formed on the outer diameter surface of the end portion of the second rotating shaft 14. Torque can be transmitted by engaging the serrations 22 and 23 of the rotary shaft 14 by press-fitting. Since the tripod member 12 is required to have strength, the hardness is usually increased by performing a heat treatment such as quenching.
[0025]
In the first embodiment, as shown in FIG. 1, the shape of the shaft hole 21 before heat treatment is such that the inner diameter dimension of the cylindrical portion X (radially thin portion) of the boss portion 20 located between the leg shafts 17 is the boss portion 20. This is a rice ball shape that is larger than the leg-shaft forming portion Y (the radially thick portion). The difference between the inner diameter dimension of the cylindrical part X of the boss portion 20 and the inner diameter dimension of the leg shaft forming part Y is desirably 10 μm at the maximum. The serration 22 of the shaft hole 21 of the tripod member 12 is generally formed by broaching, but the above-mentioned rice ball-shaped pre-heat treatment shape can be obtained by broaching simultaneously with serration formation.
[0026]
As described above, the shape before the heat treatment of the shaft hole 21 of the tripod member 12 is a rice bowl shape in which the inner diameter dimension of the cylindrical portion X of the boss portion 20 is larger than the inner diameter dimension of the leg shaft forming portion Y. Even if deformation occurs when heat treatment is performed to increase the hardness of 12, the post-heat treatment shape of the shaft hole 21 is a perfect circle that matches the outer diameter shape of the second rotating shaft 14 (a in FIG. 1). reference).
[0027]
That is, in the cooling process after quenching in the heat treatment of the tripod member 12, the cylindrical portion X of the boss portion 20 has a larger amount of contraction than the leg shaft forming portion Y, so that the inner diameter surface of the cylindrical portion X is the leg shaft forming portion. Deforms inward from the inner diameter surface of Y. Here, as described above, since the inner diameter dimension of the cylindrical portion X is made larger than the inner diameter dimension of the leg shaft forming portion Y, the shape after the heat treatment of the shaft hole 21 after the deformation due to the shrinkage during the heat treatment is second. It becomes a perfect circle that matches the outer diameter shape of the rotary shaft 14.
[0028]
As a result, the load applied to the serrations 22 on the inner diameter surface of the shaft hole 21 during torque transmission is uniform, and the strength of the tripod member 12 can be ensured. Thus, if the load applied to the serration 22 of the tripod member 12 becomes uniform, the load applied to the serration 23 fitted to the serration 22 of the tripod member 12 becomes uniform even on the rotary shaft side press-fitted into the tripod member 12. Also, the strength of the rotating shaft 14 can be ensured.
[0029]
In the first embodiment described above, the shape of the shaft hole 21 of the tripod member 12 before the heat treatment is formed into a round shape taking into account the amount of deformation caused by the heat treatment in advance, so that the shape of the shaft hole after the heat treatment is a perfect circle. However, the present invention is not limited to this, and as a second embodiment, serrations 22 are formed in the inner diameter of the shaft hole 21 of the tripod member 12 after heat treatment as shown in FIG. You may do it.
[0030]
That is, as described above, when heat treatment is performed to increase the hardness of the tripod member 12, even if the shaft hole 21 is deformed into a dog-like shape as shown by a broken line b in FIG. Therefore, the shape of the shaft hole 21 can be a perfect circle that matches the outer diameter shape of the second rotating shaft 14.
[0031]
As a result, the load applied to the serration 22 on the inner diameter surface of the shaft hole 21 becomes uniform during torque transmission, the strength of the tripod member 12 can be secured, and an abnormal layer generated on the inner diameter surface of the shaft hole 21 by heat treatment. Can also be eliminated, and the serration strength can be further improved.
[0032]
In the above-described embodiment, the tripod member in which the three leg shafts 17 protruding in the radial direction are formed at equal intervals in the circumferential direction on the outer peripheral surface of the boss portion 20 fixed to the end portion of the second rotating shaft 14. Although the case where it applied to the tripod type constant velocity universal joint which used 12 as the inner joint member was demonstrated, as another embodiment, the track which makes a pair with the track groove 15 of the outer joint member 11 as shown in FIG. The present invention is also applicable to a constant velocity universal joint in which an inner ring 12 ′ in which grooves 24 are formed at equal intervals in the circumferential direction along the axial direction is used as an inner joint member. In this case, the track groove forming portion X is a radially thin portion.
[0033]
In the embodiment shown in FIG. 5, when heat treatment is performed, even if the shaft hole 21 is deformed into a polygon as shown by a broken line c in FIG. Since it can be deleted by formation, the shape of the shaft hole 21 can be a perfect circle that matches the outer diameter shape of the second rotating shaft 14.
[0034]
As a result, the load applied to the serration 22 on the inner diameter surface of the shaft hole 21 becomes uniform during torque transmission, the strength of the tripod member 12 can be secured, and an abnormal layer generated on the inner diameter surface of the shaft hole 21 by heat treatment. Can also be eliminated, and the serration strength can be further improved.
[0035]
【Example】
FIG. 6 shows the relationship between the amount of distortion of the shape before heat treatment of the shaft hole 21 (triple shape) of the tripod member 12 and the number of repetitions by the swing fatigue strength test in the first embodiment. Here, the swing fatigue strength test is a test for determining the number of repetitions until breakage when twisted with a certain swing torque of 0 to + T, and the higher the number of repetitions, the higher the number of repetitions that is the test result, the higher the strength. Means. The amount of strain is the difference between the circumscribed circle radius A and the inscribed circle radius B of the rice ball shape by measuring the shape of the serrated inner diameter surface of the shaft hole 21 as shown in FIG.
[0036]
In the result of the one-sided fatigue strength test shown in FIG. 6, the second rotating shaft side is broken, and the tripod member 12 is in an unbroken state. From this test result, it is clear that as the amount of strain increases, the number of repetitions until the second rotating shaft 14 is damaged decreases and the strength decreases. Therefore, when the strain amount is 10 μm at the maximum, the number of repetitions increases and the strength increases.
[0038]
【The invention's effect】
According to the present invention, since the serration is formed on the inner diameter of the shaft hole after the heat treatment of the inner joint member, even if deformation occurs when the heat treatment is performed to increase the hardness of the inner joint member as described above, Since the deformed part due to shrinkage during heat treatment can be eliminated by forming serrations, the shape of the shaft hole can be a perfect circle that matches the outer diameter shape of the second rotating shaft, and the inner diameter surface of the shaft hole can be transmitted during torque transmission. The load applied to the serration becomes uniform, the strength of the inner joint member can be secured, and the abnormal layer generated on the inner diameter surface by the heat treatment can be deleted, so that the serration strength can be further improved. It is possible to provide a constant-velocity universal joint with high reliability and long life.
[Brief description of the drawings]
FIG. 1 is a front view showing a tripod member of a tripod constant velocity universal joint according to an embodiment of the present invention.
FIG. 2 is a front sectional view showing a tripod type constant velocity universal joint according to an embodiment of the present invention.
FIG. 3 is a side sectional view showing a tripod type constant velocity universal joint according to an embodiment of the present invention.
FIG. 4 is a front view showing a tripod member according to another embodiment of the present invention.
FIG. 5 is a front view showing an inner ring in another embodiment of the present invention.
FIG. 6 is a characteristic diagram showing the relationship between the amount of distortion of the shape before the heat treatment (rice ball shape) of the center hole of the tripod member and the number of repetitions by the swing fatigue strength test.
FIG. 7 is a schematic diagram for explaining the difference between the circumscribed circle radius and the inscribed circle radius of the rice ball shape.
FIG. 8 is a side sectional view showing a tripod type constant velocity universal joint in a conventional example of a constant velocity universal joint.
FIG. 9 is a front view showing a tripod member in a conventional example of a constant velocity universal joint.
FIG. 10 is an enlarged partial front view showing serrations formed in a center hole of a tripod member in a conventional example of a constant velocity universal joint.
[Explanation of symbols]
11 Outer joint member 12 Inner joint member (tripod member)
12 'Inner joint member (inner ring)
13 Rolling elements (rollers)
14 Second rotating shaft 15 Track groove 17 Leg shaft 20 Boss portion 21 Center hole 22 Serration 24 Track groove X Radial thin portion Y Radial thick portion

Claims (1)

A plurality of track grooves are formed on the inner peripheral surface along the axial direction at equal intervals in the circumferential direction, and the outer joint member is fixed to the end of the first rotating shaft, and the track grooves of the outer joint member are formed on the outer peripheral surface. A heat-treated inner joint member that is alternately formed with a radially thick portion and a radially thin portion at equal intervals in the circumferential direction so as to be paired with each other and fixed to the end of the second rotating shaft by serration fitting And a constant velocity universal joint comprising a plurality of rolling elements that are interposed between the outer joint member and the inner joint member and transmit torque between the first rotating shaft and the second rotating shaft,
The inner joint member is formed with three leg shafts projecting radially on the outer peripheral surface of the boss portion fixed to the end of the second rotating shaft at equal intervals in the circumferential direction, and the leg shaft forming portion is formed. This is a tripod member having a radially thick portion, and the end of the second rotating shaft has a shaft hole for serration fitting, and the shaft hole has a radially thick inner diameter dimension due to heat treatment. The shape is smaller than the inner diameter of the part, and the formation of serrations after the heat treatment forms a perfect circle that matches the outer diameter shape of the second rotating shaft, and the abnormal layer due to the heat treatment is deleted. Constant velocity universal joint.

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