JP2002372067A - Constant velocity universal coupling for propeller shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a constant velocity universal coupling for a propeller shaft having excellent heat-resistant dimensional stability, usable even under the operating condition of a large N-θ value and having excellent durability. SOLUTION: In this constant velocity universal coupling for the propeller shaft with a ball 4 interposed between an inner ring 1 and an outer ring 2, the outer ring 2 has a plurality of linear track grooves 9 axially extending on a cylindrical inner peripheral surface, and the inner ring 1 has a plurality of linear track grooves 8 on a convex outer peripheral surface opposedly to the track grooves 9 of the outer ring 2. Both track grooves 8, 9 are provided in cross arrangement, and the ball 4 is built in the cross part of the track grooves 8, 9. The ball 4 is held by the cage 3 arranged between the outer peripheral surface of the inner ring 1 and the inner peripheral surface of the outer ring 2. The ball 4 is formed of heat resistant steel, and the surface hardness after quenching or carbonitriding is 58HRC or more, and the maximum carbon substance dimension is 8 μm or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a constant velocity universal joint mainly used for a propeller shaft of an automobile.

[0002]

2. Description of the Related Art As a constant velocity universal joint of this type, there is a cross groove constant velocity universal joint in which track grooves of inner and outer rings cross each other. In the cross groove type joint, the shape of the track groove is an elliptical or gothic arch shape, the curvature ratio of the contact point to the ball curvature is 1.02 to 1.05, and the contact angle is 35 to 45 ° and the angular contact is formed. I have.
For this reason, a slight vertex clearance VC (Vertex Clearance) is provided at the bottom of the track groove of the inner and outer wheels with the ball interposed therebetween. Further, in this constant velocity universal joint, the ball is controlled at the intersection of the track grooves of the inner and outer rings, and it is easy to roll in the axial direction. Therefore, it is mainly used for a propeller shaft that requires good high-speed rotation.

[0003]

In such a cross-groove type constant velocity universal joint to which such a ball preload is applied, the temperature rise (T) has a correlation with the rotational speed (N) and the operating angle (θ). That is, as the number of rotations / angle value (N · θ), which is the value of the number of rotations (N) × the operating angle (θ), increases, the temperature rises. The limit value of the rotation speed / angle value (N · θ) is N · θ> 20000
~ 22000 is a guide. Increasing the limit rotational speed / angle value (N · θ) as much as possible is a problem of the cross groove constant velocity universal joint. Normally, the ball used for the cross groove type constant velocity universal joint is tempered at about 180 ° C. after quenching. Changes the retained austenite, and the size increases.
As a result, the preload amount is further increased, the temperature rise of the constant velocity universal joint is further increased, and a remarkable peak temperature is exhibited. In the past example, a ball having a hardness of typically HRC 60 or higher may have a H
In some cases, it dropped to near RC40.

As means for solving such a problem, there has been proposed a ball subjected to a heat treatment temperature stabilization treatment at a high tempering temperature (Japanese Patent Laid-Open No. 2000-74082). However, increasing the tempering temperature inevitably lowers the hardness of the ball, causing a new problem of impairing the durability of the constant velocity universal joint.

In the conventional cross-groove type constant velocity universal joint, since the track groove curvature of the inner and outer rings is small and the gap at the groove bottom apex is small, when the temperature of the constant velocity universal joint rises, the ball is deformed due to thermal deformation. There is also a problem that a hit occurs and the temperature rise is further increased in combination with deterioration of the intervening property of the lubricant. The bottom contact of the ball hinders the smooth operation of the constant velocity universal joint.

SUMMARY OF THE INVENTION An object of the present invention is to provide a constant-speed universal propeller shaft which has excellent heat-resistant dimensional stability, can be used even under a large number of rotations and angle values (N.theta. Values), and has excellent durability. It is to provide a joint. Another object of the present invention is to reduce the possibility of the ball interfering with the bottom of the track groove even under a driving condition with a large number of rotations / angle value (N · θ value). It is to be excellent.

[0007]

SUMMARY OF THE INVENTION A constant velocity universal joint for a propeller shaft according to the present invention comprises an outer ring having a plurality of linear track grooves extending in the axial direction on a cylindrical inner peripheral surface, and a plurality of opposing rings facing the track grooves. An inner ring having a linear track groove on the convex spherical outer peripheral surface, the two track grooves are provided in a crossed arrangement with each other, and a ball is incorporated in a crossing portion of the two track grooves. And a constant velocity universal joint for a propeller shaft held by a cage disposed between the outer ring and an inner peripheral surface of the outer ring, wherein the ball is made of heat-resistant steel, and has a configuration in which the ball is quenched or carbonitrided and tempered. The surface hardness after the treatment is HRC 58 or more, and the maximum carbonaceous material size is 8 μm or less.

[0008] Heat-resistant steel is a type of steel in which dimensional changes due to structural changes at high temperatures are small and surface hardness is small in comparison with general steel materials. As the above heat resistant steel, compared to general steel materials used for constant velocity universal joints (for example, high carbon chromium steel, etc.), heat resistant steel is used under a high temperature generated during operation of a cross groove type constant velocity universal joint for a propeller shaft. It is preferable to have excellent dimensional stability and high-temperature softening resistance. By using such heat-resistant steel, due to its excellent heat-resistant dimensional stability, even if the joint temperature becomes high under the operating conditions where the rotation speed and angle value (N · θ value) are large, the ball will not There is no increase in dimensions due to structural change, and a sharp rise in joint temperature due to an increase in the amount of preload can be avoided. In addition, the use of heat-resistant steel prevents the balls from softening at high temperatures and reducing the durability. The ball is made of the above-mentioned heat-resistant steel, is hardened by quenching or carbonitriding, and is tempered. Since the surface hardness after the tempering is HRC58 or more, the ball has a long fatigue life. . A correlation is recognized between the surface hardness of the ball and the fatigue life, and the higher the surface hardness, the longer the fatigue life tends to be. When the surface hardness is less than 58, the fatigue life tends to be rapidly shortened, and the life variation becomes large. Improves life at high temperatures,
In order to reduce the variation, it is necessary to have a hardness of HRC 58 or more. Therefore, it was limited to HRC 58 or more. The carbide in the steel material maintains the hardness during the tempering treatment, suppresses the structural change during the fatigue of the ball, and is effective in improving the fatigue life. At this time, regarding the relationship between the maximum size of the carbide and the ball fatigue life, the life tends to be reduced in the presence of a large carbide, and the life sharply decreases when a large carbide having a maximum size of more than 8 μm remains. It turns out. For this reason, the maximum size of the carbide is set to 8 μm.

In the present invention, the heat-resistant steel has an alloying element content of mass%, C of 0.6% or more and 1.3% or less, Si of 0.3% or more and 3.0% or less, and Mn of 0.2%
1.5% or less, P is 0.03 or less, S is 0.03%
Hereinafter, Cr is 0.3% or more and 5.0% or less, and Ni is 0.1% or less.
% Or more, 3.0% or less, Al: 0.050% or less, Ti: 0.003% or less, O: 0.0015% or less, and N: 0.
015% or less, and the balance preferably contains Fe and inevitable impurities. By making the components of the heat-resistant steel, which is the material of the ball, in this way, the heat-resistant dimensional stability of the ball is improved, and the ball can be used under operating conditions with a large N · θ value. The degree of decrease in surface hardness due to high-temperature tempering is small, and the durability is excellent. Even when tempering is performed at a high temperature (for example, 350 ° C.), the HRC
High hardness of 58 or more can be obtained. Since the amount of retained austenite can be reduced by performing the tempering treatment at such a high temperature, dimensional stability in a high temperature environment can be obtained, and a high hardness of HRC 58 or more can be obtained. Therefore, the fatigue life and wear resistance in a high temperature environment can be improved as compared with the conventional example.

In the present invention, the cross-sectional shape of the track grooves of the inner and outer rings is an ellipse or a gothic arch, and at least the ratio of the groove radius of curvature at the contact point between the inner groove track grooves and the ball to the ball radius is 1.05. ~ 1.10.
It is preferable that If the cross-sectional shape of the track groove is an ellipse or a gothic arch, the ball comes into point contact on both sides of the groove. In this case, by defining the ratio between the groove radius of curvature and the ball radius at the contact point in the range of 1.05 to 1.10.
The groove bottom apex gap between the track groove and the ball is, for example, 1.7 to 1.9 times larger than that of about 1.0 to less than (less than). Therefore, even under the operating condition with a large N · θ value, it is possible to reduce the interference of the ball with the bottom of the track groove due to the thermal deformation due to the rise in the joint temperature. Further, since the gap is maintained in the groove floor of the track groove, the lubricant is easily interposed, and the temperature suppressing performance is excellent.

In the present invention, of the track grooves of the inner and outer rings, the contact angle between at least the track groove of the inner ring and the ball may be 35 to 45 °. When the contact angle changes, the contact point between the track groove and the ball changes. If the contact angle is too large, a contact ellipse serving as a contact point may run on the shoulder of the track groove, which is not preferable in terms of durability. If it is too small, the ball tends to interfere with the groove bottom. Therefore, the contact angle is usually in the range of 35 to 45 °. In the range of the contact angle of 35 to 45 °, as described above, the ratio of the radius of curvature of the groove at the contact point to the radius of the ball is set to 1.
In the case where the ratio is from 0.05 to 1.10.

The reasons for limiting the chemical components of the heat-resistant steel ball will be described. (1) About the content of C (0.6% or more and 1.3% or less). C is an essential element for securing the strength of the ball,
In order to maintain the hardness after a predetermined heat treatment, it is necessary to contain C in an amount of 0.6% or more. Therefore, the lower limit of the C content is limited to 0.6%. Further, as described above, the carbide plays an important role in the fatigue life of the ball. However, when the C content exceeds 1.3%, a large carbide is generated, and the fatigue life is reduced. Therefore, the upper limit of the C content was limited to 1.3%.

(2) Si content (0.3% or more and 3.0% or more)
% Or less). Si is desirably added because it has an effect of suppressing softening in a high temperature range and improving heat resistance of the ball. But,
Since the effect cannot be obtained if the Si content is less than 0.3%, the lower limit of the Si content is limited to 0.3%. Also, S
The heat resistance improves with the increase in the i content, but is 3.0%.
If the content exceeds a large amount, the effect is saturated and the hot workability and machinability are reduced. Therefore, the upper limit of the Si content is limited to 3.0%.

(3) Mn content (from 0.2% to 1.5%)
% Or less). Mn is an element used for deoxidation in the production of steel and is an element that improves hardenability. To obtain this effect, it is necessary to add 0.2% or more of Mn.
The lower limit of the content was limited to 0.2%. But 1.5%
If the content exceeds a large amount, the machinability is greatly reduced. Therefore, the upper limit of the Mn content is limited to 1.5%.

(4) Regarding the content of P (0.03% or less). P segregates at the austenite grain boundaries of steel and causes a decrease in toughness and rolling fatigue life. Therefore, the upper limit of the content of P is set to 0.03%.

(5) S content (0.03% or less). S impairs the hot workability of steel and forms nonmetallic inclusions in the steel to reduce toughness and fatigue life.
The upper limit of the content was set. In addition, S has a harmful surface as described above, but also has an effect of improving machinability. Therefore, it is desirable to reduce S as much as possible, but 0.005%
If it is contained up to, it is acceptable.

(6) Cr content (from 0.3% to 5.0)
% Or less). Cr is an element that plays an important role in the present invention,
It is added to improve hardenability, secure hardness by carbide and improve life. 0.3 to obtain the required carbide
%, The lower limit of the Cr content is limited to 0.3%. However, if it is contained in a large amount exceeding 5.0%, large-sized carbides are formed and the fatigue life is reduced, so the upper limit of the Cr content is limited to 5.0%.

(7) Al content (less than 0.050%)
about. Although Al is used as a deoxidizing agent in the production of steel, it is desirable to reduce Al to form hard oxide-based inclusions and reduce the fatigue life. In addition, exceeding 0.050%
When a large amount of was contained, a noticeable decrease in fatigue life was observed, so the upper limit of the Al content was limited to 0.050%.
In addition, if the Al content is less than 0.005%, the production cost of steel increases, so the lower limit of the Al content is preferably limited to 0.005%.

(8) Ti content (0.003% or less), O content (0.0015% or less), and N content (0.015% or less). Ti, O, and N form oxides and nitrides in the steel and serve as nonmetallic inclusions, which are the starting points of fatigue fracture and reduce the fatigue life. Therefore, Ti: 0.003%, O: 0.0015
%, N: 0.015% was set as the upper limit of each element.

(9) Ni content (0.1% or more and 3.0% or more)
% Or less). Ni is an element that plays an important role in the present invention,
Particularly, it has an effect of suppressing a change in the structure during a fatigue process when used in a high-temperature environment, and suppressing a decrease in hardness in a high-temperature region to thereby improve the fatigue life. In addition, Ni improves the toughness, improves the life under a foreign substance environment, and is effective in improving the corrosion resistance. Therefore, Ni is 0.1%
Therefore, the lower limit of the Ni content is limited to 0.1%. However, if a large amount of Ni is contained in excess of 3.0%, a large amount of retained austenite is generated during the quenching treatment, and a predetermined hardness cannot be obtained, and the cost of steel material increases. 0.0%
Limited to.

Next, the temper hardness and carbide of the ball will be described. (10) Temper Hardness In order to stabilize the dimensions under the use environment, it is general that a joint used in a high temperature range is subjected to a temper treatment at a temperature equal to or higher than the environmental temperature. The present inventors have conducted a study on the tempering hardness and fatigue life at a temperature environment of 200 ° C. As a result, a correlation was found between the tempering hardness and the fatigue life,
It was confirmed that the higher the tempering hardness, the longer the fatigue life tends to be. In particular, when the tempering hardness is the same, it has been found that a ball whose tempering treatment is performed at a higher temperature has a longer life, and a ball whose tempering hardness is higher even at a high temperature has a longer life. Was done. Further, it has been found that when the hardness after the tempering treatment is less than HRC 58, the life tends to be sharply reduced, and the life variation increases. In order to improve the life at high temperature and reduce the variation, it is necessary to maintain a hardness of HCR 58 or more, and the tempering temperature at this time is preferably higher.

(11) Carbide Carbide was found to have the effect of maintaining the hardness during the tempering treatment, suppressing the structural change during ball fatigue, and improving the fatigue life. At this time, as a result of investigating the maximum size of the carbide and the fatigue life at a depth of 0.1 mm from the surface layer of the ball, the life tends to be reduced in the presence of a large-sized carbide. Since it was found that the life would suddenly decrease when remaining, the maximum dimension of the carbide was set to 8 μm.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. The constant velocity universal joint A for a propeller shaft of this embodiment is a cross-groove type constant velocity universal joint in which a plurality of balls 4 held by a cage 3 are interposed between an inner ring 1 and an outer ring 2, and an inner and outer ring The angle at which the axes 1 and 2 intersect freely changes to transmit rotation between the inner and outer rings 1 and 2. Inner ring 1 is the propeller shaft 5 of the car
, And the outer ring 2 is connected to the drive-side rotating body 6 by bolts 7. The drive-side rotating body 6 is composed of a companion flange and is connected to an output shaft of a transmission and an input shaft of a differential.

The inner ring 1 has an outer peripheral surface formed in a convex spherical shape, and the outer ring 2 has an inner peripheral surface formed in a cylindrical shape. These inner rings 1
The outer ring 2 has a plurality of linear track grooves 8 and 9 which extend in the axial direction and are inclined in directions opposite to each other with respect to the axis and arranged in a cross shape (see FIG. 2). Both track grooves 8,
Numerals 9 are opposed to each other, and the ball 4 is incorporated in the intersection of the track grooves 8, 9 between the track grooves 8, 9 with a negative gap, that is, in a preloaded state. Cage 3
Is a member disposed between the outer peripheral surface of the inner ring 1 and the inner peripheral surface of the outer ring 2, and is a spherical ring-shaped member corresponding to the outer diameter surface of the inner ring 1. 10 are formed and hold the ball 4 in each pocket 10.

On one side surface of the outer ring 2, a flange 11 a provided at the rear end of the support cylinder 11 is fixed by tightening the bolt 7, and between the tip of the support cylinder 11 and the propeller shaft 5. A diaphragm 12 having a U-shaped cross section is provided. The inside of the constant velocity universal joint A is sealed by the diaphragm 12 and the grease cover 13 having an outer diameter portion supported on the other side surface of the outer race 2, and leakage of grease (not shown) sealed therein is prevented. Preventing.

The constant velocity universal joint A for a propeller shaft according to this embodiment has a structure in which the ball 4 is made of heat-resistant steel, quenched or carbonitrided and tempered, and the surface after tempering Hardness is HRC 58 or more, and maximum carbonaceous material size is 8 μm or less. The heat-resisting steel, which is the material of the ball 4, has an alloying element content of
C is 0.6% or more and 1.3% or less, Si is 0.3% or more and 3.0% or less, Mn is 0.2% or more and 1.5% or less, P
0.03% or less, S 0.03% or less, Cr 0.3%
Not less than 5.0%, Ni is not less than 0.1% and not more than 3.0%,
Al: 0.050% or less, Ti: 0.003% or less, O
Is 0.0015% or less, N is 0.015% or less, and the balance is Fe and steel having unavoidable impurities. A heat-resistant steel having this chemical composition, with a tempering temperature of, for example, 200 to 300 ° C. and a surface hardness of HRC5
8 or more. The reasons for limiting each chemical component in this heat-resistant steel are as described above.

The heat-resistant steel which is the material of the ball 4 has the above-mentioned chemical composition, and more preferably, in mass%,
Mo of at least 0.05% and less than 0.25% and 0.05%
It is preferable to further contain at least one of V of 1.0% or less. Thereby, the fatigue life in a foreign substance mixed environment and a high temperature environment can be further improved, and the hardness after tempering can be improved.

The reason for limiting the additional chemical component will be described. (12) Mo content (0.05% or more and less than 0.25%). Mo has the effect of improving the hardenability of steel and preventing softening during tempering by forming a solid solution in carbide. In particular, Mo has been found to have an effect of improving the fatigue life in a high-temperature range, and is therefore added. However, 0.
When Mo is contained in a large amount of 25% or more, the cost of steel material increases, and the machinability is greatly deteriorated without a decrease in hardness at the time of softening treatment for facilitating machining. Was limited to less than 0.25%. Also Mo
If the content of is less than 0.05%, there is no effect on carbide formation, so the lower limit of the Mo content was limited to 0.05%.

(13) V content (0.05% or more;
0% or less). V combines with carbon to precipitate fine carbides, promotes the refinement of crystal grains, and has the effect of improving strength and toughness. The addition of V improves the heat resistance of steel materials and softens after high-temperature tempering. To suppress rolling, improve rolling fatigue life, and reduce life variability. V at which this effect is obtained
Is 0.05% or more, so the lower limit of the V content is limited to 0.05%. However, when V is contained in a large amount exceeding 1.0%, machinability and hot workability are reduced, so the upper limit of the V content is limited to 1.0%.

According to the constant velocity universal joint for a propeller shaft having this configuration, the heat-resistant steel used as the material of the ball 4 is a steel material excellent in heat-resistant dimensional stability and high-temperature softening resistance. The dimensional change underneath is small and the decrease in hardness is also small. As a result, in the constant velocity universal joint A, the heat resistance dimensional stability of the ball 4 is improved as compared with the conventional product, so that the ball 4 can be used even under an operating condition having a large N · θ value. In addition, the degree of hardness reduction due to high-temperature tempering can be reduced, so that durability is improved as compared with conventional products.

The track grooves 8, 9 of the inner and outer rings 1, 2 are provided.
Has a shape of a gothic arch as shown in FIG. 3 and at least a ratio of a groove curvature radius at a contact point between the track groove 8 of the inner ring 1 and the ball 4 to a radius R of the ball 4 is 1.05 to 1.05. 1.10. In this example, the ratio between the radius of curvature of the groove 4 at the contact point between the track groove 9 of the outer race 2 and the ball 4 and the radius R of the ball 4 is also 1.05-1.
It is assumed to be 10. In addition, the shape of the track grooves 8 and 9 may be an ellipse instead of the gothic arch.

In this embodiment, the track grooves 8,
The specifications of 9 are different from those of the conventional product as shown in Table 1. Thereby, the groove bottom apex gap VC between the track grooves 8, 9 and the ball 4 is 1.7 to 1.7 times smaller than that of the conventional product.
As a result, the ball 4 can be prevented from interfering with the bottoms of the track grooves 8 and 9 even under an operating condition having a large N · θ value. In addition, since a gap is formed at the bottom of the track grooves 8, 9, the lubricant is easily interposed, and the temperature suppressing performance is improved.

[0033]

[Table 1]

The track grooves 8, 9 of the Gothic arch
In the case of the above, the groove bottom vertex gap VC between the groove and the ball is geometrically determined by the ball radius (r), the track groove contact ratio (ψ) and the contact angle α, but the contact angle α is small and the contact ratio 小 is small. , And becomes maximum when the contact angle α is large and the contact ratio ψ is large. When the contact ratio is large, the surface pressure on the inner surface of the track groove is increased, but it is advantageous for running over the track shoulder contact ellipse. In the case of a propeller shaft, since the torque is low and the rotation is high, the surface pressure on the inner surface of the track groove does not matter. Therefore, in the constant velocity universal joint for a propeller shaft, it is often advantageous to increase the contact ratio.

Although different from the present invention, the material of the heat resistant steel in the ball 4 is not limited to the cross groove type. For example, as shown in various examples in FIGS. The present invention can be applied to a constant velocity universal joint for a propeller shaft in which balls 4 and 4D are interposed between the outer ring 2 and the angle at which the axes of the inner and outer rings 1 and 2 intersect freely to transmit rotation.

The example shown in FIG. 4 is a so-called bar field type constant velocity universal joint. The constant velocity universal joint B shown in FIG.
The inner diameter of the outer ring 2 and the inner diameter of the outer ring 2 are both spherical, and the track grooves 8A and 9A of the inner and outer rings 1 and 2 are all parallel to the axis, and the groove bottom has a cross section along the axial direction. The shape is an arc shape. Other configurations are the same as the embodiment of FIG.

The example shown in FIG. 5 is a so-called double offset type constant velocity universal joint. In the constant velocity universal joint C shown in the figure, the track grooves 8C and 9C provided in the inner ring 1 and the outer ring 2
It is a straight line parallel to the axis. The cage 3 plays a role of controlling the movement of the ball 4, but has a cylindrical surface portion formed on the inner diameter surface to make the ball 4 easily roll. In other words, the inner diameter surface of the cage 3 is configured such that both side portions in the axial direction are spherical portions whose spherical center positions are offset from each other, and the space between the two spherical portions is a cylindrical surface portion. Other configurations are the same as those in the example of FIG.

[0038]

The constant velocity universal joint for a propeller shaft according to the present invention is a cross-groove type constant velocity universal joint having a structure in which balls are made of heat-resistant steel, quenched or carbonitrided, and tempered. The surface hardness after treatment is 58
HRC or more, and the maximum carbon material size is 8 μm or less, so it has excellent heat resistance dimensional stability, can be used even under operating conditions with large N · θ values, and has excellent durability. Become. In particular, when the material of the heat-resisting steel of the ball is the material of claim 2, the ball has good heat-resistant dimensional stability, a small reduction in surface hardness due to high-temperature tempering, and a high hardness of 58 or more HRC. And excellent durability. When the shape of the track grooves of the inner and outer rings is an ellipse or a gothic arch, and at least the ratio of the radius of curvature of the grooves at the contact point between the track grooves of the inner ring and the ball and the radius of the ball is 1.05 to 1.10. In addition, the groove bottom apex gap between the track groove and the ball becomes larger than that of the conventional example, so that the ball can be prevented from interfering with the track groove bottom even under an operation condition having a large N · θ value. Further, the lubricant easily intervenes at the groove bottom, and the temperature suppressing performance can be improved.

[Brief description of the drawings]

FIG. 1 is a cutaway front view of a constant velocity universal joint according to an embodiment of the present invention.

FIG. 2 is an explanatory view of track grooves showing inner and outer races of the equivalent speed universal joint in a developed view.

FIG. 3 is an enlarged sectional view showing a part of an equivalent speed universal joint.

FIG. 4 is a cutaway front view of a constant velocity universal joint according to a proposal example.

FIG. 5 is a cutaway front view of a constant velocity universal joint according to another proposed example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Inner ring 2 ... Outer ring 3 ... Cage 4 ... Ball 5 ... Propeller shaft 8, 9 ... Track groove

Claims (4)

[Claims] 1. An outer ring having a plurality of linear track grooves extending in the axial direction on a cylindrical inner peripheral surface, and an inner ring having a plurality of linear track grooves opposed to the track grooves on a convex spherical outer peripheral surface. The two track grooves are provided in an intersecting arrangement with each other, a ball is incorporated in a crossing portion of the two track grooves, and the ball is held by a cage arranged between the outer peripheral surface of the inner race and the inner peripheral surface of the outer race. In the constant velocity universal joint for a propeller shaft, the ball is made of heat-resistant steel, has a configuration of being tempered by quenching or carbonitriding, has a surface hardness after tempering of HRC 58 or more, and has a maximum carbon Object size is 8μ
m, a constant velocity universal joint for a propeller shaft. 2. The heat-resistant steel according to claim 1, wherein the content of alloying elements is% by mass, C is 0.6% or more and 1.3% or less, and Si is 0.3% or less.
Not less than 3.0%, Mn is not less than 0.2% and not more than 1.5%,
P is 0.03 or less, S is 0.03% or less, and Cr is 0.3
% To 5.0%, Ni is 0.1% to 3.0%, Al is 0.050% or less, Ti is 0.003% or less, O is 0.0015% or less, and N is 0.015%. %. The constant velocity universal joint for a propeller shaft according to claim 1, wherein the steel is a steel material containing Fe and unavoidable impurities. 3. The cross-sectional shape of the track grooves of the inner and outer rings is an ellipse or a gothic arch, and at least the ratio of the groove radius of curvature and the ball radius at the contact point between the track grooves of the inner ring and the ball is 1.05 to 1.05. 3. The constant velocity universal joint for a propeller shaft according to claim 1, wherein the constant velocity universal joint is 1.10. 4. A contact angle between at least a track groove of the inner race and a track groove of the inner race of the inner and outer races is set to 35 to
The constant velocity universal joint for a propeller shaft according to any one of claims 1 to 3, wherein the angle is 45 °.