JP2002213477A - Tripod constant velocity universal joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the strength of rollers for directly participating in the transmission of rotational torque of a tripod constant velocity universal joint, prolong the service life, and reduce the weight and size of the whole joint. SOLUTION: This tripod constant velocity universal joint has an outside joint member 10, having three track grooves 12 which extend in the shaft direction on the inner periphery, and forming a roller guide surface 14 on opposed sidewalls of the respective track grooves 12, a tripod member 20 having three trunnions 22 projecting in the radial direction, and the rollers 30 freely rotatable via a plurality of needle rollers 31 in respective trunnions 22, and housed in the track grooves 12 of the outside joint member 10, and guides these rollers 30 by the roller guide surface 14 on an outer peripheral surface. The rollers 30 are composed of carbon steel, having a carbon content of 0.50 to 0.85 wt.%, and are quenched up to the core part to obtain prescribed hardness, and when the collapse strength is set to F (kN) and a sectional modulus is Z (mm3), that ratio F/Z is set to 0.7 (kN/mm3) or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding tripod type constant velocity universal joint used for a power transmission shaft of an automobile, an industrial machine or the like.

[0002]

2. Description of the Related Art In general, a sliding tripod type constant velocity universal joint is used as one of means for transmitting a rotational torque at a constant speed with relative angular displacement and axial displacement between two axes. And connected to one axis as shown in FIG.
An outer joint member 1 having three track grooves 2 extending in the axial direction on an inner periphery thereof and having a roller guide surface 3 formed on an opposing side wall of each track groove 2, and being coupled to the other shaft and projecting in the radial direction. A tripod member 4 having three trunnions 5
Each trunnion 5 is provided with a roller 7 rotatable via a plurality of needle rollers 6 and housed in the track groove 2 of the outer joint member 1. It is configured to be guided.

[0003]

In order to reduce the weight and size of the joint, it is necessary to reduce the PCD (diameter at the torque transmitting position) of the joint or to reduce the size of the roller 7 itself. However, by adopting these countermeasures, the load applied to the roller 7 becomes larger than that of the related art. Therefore, it is necessary for the roller 7 to take measures for higher strength and longer life. The roller 7 is usually manufactured by turning, heat-treating, grinding or the like from a pipe material or a forged product of bearing steel (SUJ2 material or the like). In addition, the management of the heat treatment at that time mainly specifies the hardness of the roller 7, but does not particularly specify the hardness at a specific position. The strength of the roller 7 is evaluated in terms of static torsional strength. When the roller 7 is damaged, the form of the damage starts from the inner diameter part, and all the damage starting points in the crush test are as follows.
The inner diameter of the roller 7. This is because the load applied to the roller 7 is slightly different from the static torsional strength and the crushing strength. However, since the maximum tensile stress is generated in the inner diameter portion of the roller 7 and the roller 7 is broken starting from there, It has been found that it is important to improve the strength of the inner diameter portion of the roller 7 and extend the life thereof.

Accordingly, an object of the present invention is to improve the strength and extend the life of a roller directly involved in the transmission of rotational torque of a tripod type constant velocity universal joint, and to reduce the weight and size of the entire joint. is there.

[0005]

According to a first aspect of the present invention, a tripod type constant velocity universal joint includes three track grooves extending in an axial direction on an inner periphery thereof, and has a pair of track grooves on opposite side walls of each track groove. An outer joint member forming a roller guide surface, and a tripod member having three trunnions protruding in the radial direction,
A roller rotatably supported on each trunnion via a plurality of needle rollers, and a roller housed in a track groove of the outer joint member, wherein the roller is guided by the roller guide surface. In the speed universal joint, the roller is provided with a carbon content of 0.50 to 0.85 wt%.
When the crushing strength is F (kN) and the section modulus is Z (mm ³ ), the ratio F / Z is 0.7 (kN / mm ^3). ) Is characterized by the above.

[0006] The material of the roller directly involved in the transmission of the rotational torque of the tripod type constant velocity universal joint is a conventional bearing steel (SUJ).
From 2), to carbon steel having the above carbon content range, the core is quenched to a predetermined hardness to obtain a predetermined hardness, and the ratio F / Z of crushing strength to section modulus is set to 0.7 (kN / mm ³ ) or more. By doing so, the strength of the roller can be improved, thereby making it possible to reduce the weight and size of the entire joint. If the carbon content of the carbon steel constituting the roller is 0.50% by weight or less, the predetermined strength, wear resistance and rolling fatigue life cannot be obtained, and 0.85% or less.
If it exceeds wt%, cold workability, warm workability, machinability, and toughness decrease. Further, by quenching the core, the hardness of the entire roller can be uniformly improved, which can contribute to the improvement of the strength. If the ratio F / Z between the crushing strength and the section modulus is less than 0.7 (kN / mm ³ ), predetermined static torsional strength and crushing strength cannot be obtained, and the roller is likely to be damaged.

In the tripod type constant velocity universal joint according to a second aspect of the present invention, the surface hardness of the inner diameter portion of the roller is at least 61.5 HRC (Rockwell hardness C scale).
The features are as described above.

According to a third aspect of the present invention, in the tripod type constant velocity universal joint, the roller has a C content of 0.70 wt% or more and less than 0.80 wt%, a Si content of 0.50 wt% or more,
1.0 wt% or less, Mn: 0.10 wt% or more, 2.0
wt% or less, Cr: 0.40 wt% or more, 0.95 wt%
%, Al: 0.050 wt% or less, O: 0.003%
It is characterized in that it contains 0 wt% or less and the balance consists of carbon steel having Fe and unavoidable impurities.

[0009] The carbon steel constituting the above-mentioned roller improves the forging formability as the spheroidization of the carbide increases. In order to improve the spheroidization rate of this carbide, it is necessary to specify the constituent elements of carbon and chromium in a specific range with respect to the spheroidizing annealing conditions. I do.

[0010] The C content is 0.70 wt% or more, 0.80 wt%
The reason is set as below. C is an element effective for improving the cold workability and the spheroidization ratio, and is based on the proportion of chromium. Further, it is dissolved in the base material (Fe) to strengthen martensite, thereby improving strength, abrasion resistance and rolling resistance. In order to improve the dynamic fatigue life, it is necessary to add at least 0.70 wt% or more. On the other hand, if 0.80 wt% or more is added, cold workability, warm workability, machinability, and toughness decrease, and diffusion annealing cannot be omitted due to the relationship with other elements. Therefore, the C content is set to 0.70 wt% or more and less than 0.80 wt%.

[0011] The Si content is 0.50 wt% or more, 1.0 wt%
The reason is set as follows. In addition to deoxidation, Si is a necessary element as a solid solution in the base material to improve the rolling fatigue life. If the content is less than 0.50% by weight, this effect is small, while if it exceeds 1.0% by weight, the hardness after spheroidization is increased, and the machinability and workability are significantly reduced. Therefore, the amount of Si is 0.5
The range is 0 wt% or more and 1.0 wt% or less.

When the Mn content is 0.10 wt% or more, 2.0 wt%
The reason is set as follows. Mn enhances the toughness of the base material martensite by improving the hardenability of steel, and effectively contributes to the improvement of rolling fatigue life. However, if it is less than 0.10 wt%, the effect of addition is poor. On the other hand, if it exceeds 2.0 wt%, the machinability, toughness and workability are significantly reduced.
% To 2.0 wt% or less. In addition, it is preferable that the content be in the range of 0.50 to 1.20 wt%.

When the Cr content is 0.40 wt% or more, 0.95 w
The reason is set to t% or less for the following reason. Cr is an element that not only improves the hardenability of steel and improves the strength and toughness of the base material, but also is effective in improving the spheroidization rate, which is closely related to the improvement in cold workability. If the content is less than 0.40 wt%, these effects are small. On the other hand, if the content exceeds 0.95 wt%, it becomes impossible to omit diffusion annealing due to the relationship with other elements. It should be noted that such an effect of Cr is almost saturated at 0.80 wt%, and at 0.80 wt% or more, a giant carbide is easily generated at the time of smelting due to the relationship between other elements, particularly C and Si. Therefore, the amount of Cr added is 0.40 to 0.1.
95 wt% or less, preferably 0.40 to 0.80
wt% range.

The reason for setting the Al content to 0.050 wt% or less is as follows. Al is added as a deoxidizer,
Since it combines with O to form hard oxide-based inclusions, the rolling fatigue life is reduced. Therefore, it is desirable that the amount is as small as possible, and the upper limit is 0.050 wt%.

The reason for setting the O content to 0.0030% by weight or less is as follows. O combines with Al to form hard oxide-based nonmetallic inclusions, thereby reducing the rolling fatigue life. Therefore, it is desirable that the number is as small as possible.
030 wt% is the upper limit.

Although the basic components have been described above, the balance is Fe and carbon steel having unavoidable impurities.

A tripod-type constant velocity universal joint according to a fourth aspect of the present invention is characterized in that an outer peripheral surface of the roller has a convex spherical surface.

A tripod type constant velocity universal joint according to a fifth aspect of the present invention is characterized in that a ring is mounted on an outer peripheral surface of the trunnion, and the outer peripheral surface of the ring is an inner raceway surface of the needle roller. And According to this configuration, it is possible to improve the strength of the roller in the tripod type constant velocity universal joint of the type shown in FIG. 3, thereby making it possible to reduce the weight and size of the entire joint.

[0019]

FIG. 1 is a block diagram showing an embodiment of the present invention.
A description will be given based on FIG. Here, FIG. 1A shows a cross section of a sliding tripod type constant velocity universal joint.
(B) shows a longitudinal section of the joint, and FIG. 1 (C) shows a section of the roller. As shown in FIG. 1, the sliding tripod type constant velocity universal joint includes an outer joint member 10 and a tripod member 20. One of two shafts to be connected is connected to the outer joint member 10, and the other is a tripod. Connected to member 20.

The outer joint member 10 has three track grooves 12 extending in the axial direction on the inner peripheral surface. Each track groove 12
A roller guide surface 14 is formed on the circumferentially opposite side wall of the roller guide surface 14. The axis of the roller guide surface 14 is the outer joint member 1.
It is composed of a part of a cylindrical surface parallel to the zero axis. The tripod member 20 includes three trunnions 22 protruding in a radial direction, and a roller 30 is rotatably mounted on each trunnion 22 via a plurality of needle rollers 31.
The roller 30 is accommodated in the track groove 12 of the outer joint member 10. The outer peripheral surface of the trunnion 22 is an inner raceway surface of the needle roller 31, and the inner peripheral surface of the roller 30 is an outer raceway surface of the needle roller 31. The outer peripheral surface of the roller 30 is a convex spherical surface that fits the roller guide surface 14.
The needle rollers 31 are incorporated in a full-roller state, and are prevented from falling off by a circlip 32 mounted near the tip of the trunnion 22.

The roller 30 has a carbon content C of 0.5.
It is composed of carbon steel in the range of 0 to 0.85 wt%.
More preferably, C: 0.70 wt.
% Or more, less than 0.80 wt%, Si: 0.50 wt% or more, 1.0 wt% or less, Mn: 0.10 wt% or more,
2.0 wt% or less, Cr: 0.40 wt% or more, 0.9
5 wt% or less, Al: 0.050 wt% or less, O: 0.
0030 wt% or less, and the balance is made of Fe and carbon steel having unavoidable impurities. Then, the core portion is hardened, and the surface hardness of the inner diameter portion of the roller 30 is
At least 61.5 HRC or more. When the crushing strength is F (kN) and the section modulus is Z (mm ³ ), the ratio F / Z is 0.7 (kN / mm ³ ) or more.

According to the present invention, in addition to the embodiment shown in FIG.
As shown in FIG. 3A, a ring 33 is mounted on the outer peripheral surface of the trunnion 22 so as to be slidable in the axial direction.
The roller 30 may be rotatably supported by using the outer peripheral surface of the roller 30 as an inner raceway surface of the needle roller 31. Further, according to the present invention, as shown in FIG.
2 has a convex spherical outer peripheral surface, and a ring 33 having a cylindrical inner peripheral surface attached to this portion, or a ring 33 having a convex inner spherical surface as shown in FIG. May be applied to a form mounted on the outer peripheral surface of the trunnion 22.
In the case of the embodiment shown in FIG. 3C, the outer peripheral surface of the trunnion 22 has a substantially elliptical cross section as shown by a chain line in FIG. However,
In this case, the direction of the major axis of the ellipse of the trunnion 22 is set on the direction contributing to the transmission of the rotational torque, that is, on the plane perpendicular to the axis of the tripod member 20, and the direction of the minor axis is the direction of the tripod member 20. Set in the axial direction. The present invention may be applied to a configuration in which steel balls are arranged in the circumferential direction of the trunnion 22 instead of the needle rollers 31 interposed between the ring 33 and the roller 30.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The strength of the sliding tripod type constant velocity universal joint to which the present invention is applied is actually evaluated in terms of static torsional strength. Roller 3
0 is the inner diameter part. This is static torsional strength, crush strength,
Although the load applied to the roller 30 is slightly different, the maximum tensile stress is generated in the inner diameter portion of the roller 30 and the roller 30 is broken at the starting point. , Was evaluated. The A, B, and C3 type rollers 30 are forged, turned, heat-treated (subbu-yaki), and made of the above-described carbon steel (hereinafter, referred to as the present carbon steel) and conventional bearing steel (hereinafter, referred to as SUJ2). In the grinding step, each was manufactured in the same shape as shown in FIG. 1 (C), and Table 1 shows the relationship between the crushing strength results of SUJ2 and the carbon steel of the present invention and the inner diameter part hardness. In Table 1, the outer diameter D is shown in FIG.
It corresponds to the dimensions of the part described in (C). The heat treatment conditions were as follows: heating (quenching) → oil cooling → tempering.

Among these, in the heating (quenching) step, if the heating temperature is high, the coarseness of γ (austenite) crystal grains, excessive γ grains (decrease in hardness), and the viscosity after tempering are inferior. Usually, the optimum heating temperature is 780 ° C (C: 0.85 wt%) to 850 ° C (C:
(0.37 wt%), and the heating time is the time required until the γ grains become uniform. When the heating time is prolonged, coarsening of γ grains, oxidation, and decarburization occur. Basically, as the volume increases, the heating time also increases. It is generally known that the relationship between the heating temperature and the heating time is shorter if the temperature is higher.
The quenching hardness is determined not by the simple amount of C but by the amount of C which forms a solid solution in martensite (the hardness increases as the amount of C increases, but the amount of C is up to 0.6 wt%).

In the oil cooling step, stirring (stop, weak, strong) and injection (presence / absence) are simultaneously performed. If the cooling rate is high, γ tends to be martensitic.

In the tempering step, the temperature is 150 ° C. to 250 ° C.
Perform within the range. If the temperature is high, the hardness decreases. When the temperature is low, the hardness increases (however, up to a minimum of 100 ° C.). When the breaking load increases (the amount of deformation is large), the temperature is eutectoid steel (C
The amount is about 200 ° C. in the amount of 0.8 wt%). The time was 60 minutes. This time is not fixed and can be changed as appropriate. However, the degree of influence on the hardness is as follows: temperature> time.

[0027]

[Table 1]

The test was applied by an Amsler type testing machine until the static load was destroyed. As for the crushing strength of the carbon steel of the present invention, the strength tends to increase as the surface hardness of the inner diameter portion, which is the fracture starting point, increases, and it can be seen that there is a correlation between hardness and strength. SUJ2
Does not show that tendency. FIG. 2 shows the ratio F / Z (kN) between the crushing strength F (kN) of each type and the section modulus Z (mm ³ ).
/ Mm ³ ) on the vertical axis and the horizontal axis on the surface hardness (H
(RC). The above Z is Z = I /
e, where I is a roller 30 shown in FIG.
Is the second moment of area, and e is the distance from the center of the cross section of the roller 30 of FIG. From FIG. 2, it can be seen that if the inner diameter hardness of the carbon steel of the present application is 61.5 HRC or more, a strength of SUJ2 or more can be obtained.

Table 2 shows a φ12 × L22 cylindrical test piece of the same shape made of the carbon steel of the present invention and SUJ2, and φ1.
The results of a rolling life test performed using a counterpart steel ball of 9.05 mm (median value of the Weibull probability distribution of n = 16) are shown. The test conditions are as follows.

Maximum contact stress: Pmax = 5.88 GPa Load speed: 46240 cpm Lubricating oil: Turbine VG68 oil supply

[0031]

[Table 2]

From this, it is understood that the carbon steel of the present invention is superior in life to the conventional SUJ2.

As described above, when the carbon steel of the present invention is applied to the roller 30, if the surface hardness of the inner diameter portion is set to 61.5 HRC or more, it is possible to achieve higher strength and longer life than the conventional SUJ2.

[0034]

According to the present invention, the material of the roller directly involved in the transmission of the rotational torque of the tripod type constant velocity universal joint is changed from conventional bearing steel (SUJ2) to carbon steel having a predetermined carbon content range, and its core is changed. Part is quenched to a predetermined hardness, and the ratio F / Z of crushing strength to section modulus is 0.7 (kN /
mm ³ ) or more, it is possible to improve the strength and extend the life of the roller, thereby making it possible to reduce the weight and size of the entire joint.

[Brief description of the drawings]

1A is a cross-sectional view of a sliding tripod type constant velocity universal joint according to an embodiment of the present invention, FIG. 1B is a longitudinal sectional view of the joint, and FIG. 1C is a cross-sectional view of a roller. is there.

FIG. 2 is a graph showing the relationship between the crushing strength / section modulus and the inner diameter hardness of the roller according to the present invention and a conventional roller.

3 (A), 3 (B), and 3 (C) are partial cross-sectional views of main parts of a sliding tripod type constant velocity universal joint showing another different embodiment of the present invention.

FIG. 4A is a cross-sectional view of a conventional sliding-type tripod constant velocity universal joint, and FIG. 4B is a longitudinal cross-sectional view of the joint of FIG.

[Explanation of symbols]

 Reference Signs List 10 outer joint member 12 track groove 14 roller guide surface 20 tripod member 22 trunnion 30 roller 31 needle roller 33 ring

Claims (5)

[Claims] 1. An outer joint member having three track grooves extending in the axial direction on an inner periphery thereof and a roller guide surface formed on a side wall facing each track groove, and three trunnions protruding in a radial direction. A tripod member, and a roller rotatably supported on each trunnion via a plurality of needle rollers and accommodated in a track groove of the outer joint member, wherein the roller is guided by the roller guide surface. In the tripod-type constant velocity universal joint, the roller is made of carbon steel having a carbon content of 0.50 to 0.85 wt%, quenched up to its core, and has a crushing strength of F (kN) and a section modulus. Wherein the ratio F / Z is 0.7 (kN / mm ³ ) or more, where Z is the size of Z (mm ³ ). 2. The tripod-type constant velocity universal joint according to claim 1, wherein the inner surface of the roller has a surface hardness of at least 61.5 HRC or more. 3. The roller according to claim 1, wherein C: 0.70% by weight or more, less than 0.80% by weight, Si: 0.50% by weight or more,
1.0 wt% or less, Mn: 0.10 wt% or more, 2.0
wt% or less, Cr: 0.40 wt% or more, 0.95 wt%
%, Al: 0.050 wt% or less, O: 0.003%
The tripod-type constant velocity universal joint according to claim 1, wherein the tripod-type constant velocity universal joint comprises 0 wt% or less, and the balance is made of carbon steel having Fe and unavoidable impurities. 4. The tripod type constant velocity universal joint according to claim 1, wherein an outer peripheral surface of said roller has a convex spherical surface. 5. The tripod type according to claim 1, wherein a ring is mounted on an outer peripheral surface of the trunnion, and the outer peripheral surface of the ring is an inner raceway surface of the needle roller. Constant velocity universal joint.