JP2001187924A - Constant velocity joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a constant velocity joint that comprises structural members of a material resistant to fatigue cracking and excellent in durability. SOLUTION: Major structural members are a tripod member having three radially projecting leg shafts, an outer joint member having three axial track grooves in the internal surface and having an axial roller guide surface on each side of each track groove, and rolling members interposed between the leg shafts of the tripod member and the outer joint member to transmit torque. The rolling members comprise a steel material including as its alloy elements at least, by mass %, C of 0.6% to 1.3%, Si of 0.3% to 3.0%, Ni of 0.1% to 3.0%, Mn of 0.2% to 1.5% and Cr of 0.3% to 5.0%, and have surface hardness of HRC 58 or more in Rockwell hardness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a constant velocity joint, and more particularly, to a constant velocity joint such as various tripod joints used in a power transmission unit of an automobile, an aircraft, a ship, an industrial machine, or the like.

[0002]

2. Description of the Related Art For example, an apparatus used as a means for transmitting a rotational force from an engine of an automobile to a wheel at a constant speed has a structure in which two shafts on a driving side and a driven side are connected and there is an angle between the two axes. There is a tripod joint that is a type of constant velocity joint that can transmit a rotational force at a constant velocity.

This tripod joint has a tripod member having three leg shafts protruding in the radial direction, and three axial track grooves formed in an inner peripheral portion thereof. An outer joint member having a roller guide surface, and a structure in which a rolling member that transmits rotational torque and is interposed between a leg shaft of the tripod member and the outer joint member is used as a main component. The components described in (1) slide and move in the axial direction while transmitting rotational torque under a large load condition, and oscillate and swing. Due to its mechanism, rotational torque (rotational load) and rocking (axial motion)
Receive at the same time.

[0004]

By the way, there are various types of tripod joints described above. Recently, tripod joints as shown in FIGS. 1A and 1B and FIG. 2 have been proposed. I have. This tripod joint is of a sliding type in which relative axial displacement between two axes is made possible by plunging the joint, and is a tripod member 2 having three leg shafts 1 protruding in the radial direction.
Is connected to one shaft, and a hollow cylindrical outer joint member 4 having three track grooves 3 extending in the axial direction is connected to the other shaft, and a tripod member is provided in the track groove 3 of the outer joint member 4. The two leg shafts 1 are accommodated to transmit torque.

An annular inner roller 5 externally fitted on the outer peripheral surface of the leg shaft 1 and an outer joint member 4 accommodated in the track groove 3 of the outer joint member 4 while rolling on the roller guide surface 6. The outer roller 7 that moves in the axial direction is unitized through a plurality of needle rollers 8 and is a roller assembly 9 that can be relatively rotated.
Is composed. The cylindrical outer peripheral surface of the inner roller 5 is used as an inner raceway surface, and the cylindrical inner peripheral surface of the outer roller 7 is used as an outer raceway surface.

In this tripod joint, in order to reduce the torque loss, the inner surface of the inner roller 5 is formed into a convex R shape to make point contact with the leg shaft 1, and the cross section of the leg shaft 1 is made substantially elliptical to form the inner roller. By providing a predetermined clearance between the inner roller 5 and the inner roller 5, not only the inner roller 5 can move in the axial direction of the leg shaft 1, but also the roller assembly 9 including the inner roller 5 and the outer roller 7 can be moved by the leg shaft. 1 is swingable.

Since the roller assembly 9 is swingable and swingable, when the outer joint member 4 and the tripod member 2 transmit a rotational force in an operating angle, the roller assembly 9 is rotated by the outer joint member 4. Can be rolled only in the axial direction, and the exciting force of the outer joint member 4 can be received by the rolling of the needle rollers 8, so that the slide resistance can be reduced.

Further, as described above, the inner surface of the inner roller 5 is formed in a convex R shape so that the load point becomes the center, and
The point of contact with the inner roller 5 is made substantially elliptical (the load point is on the long axis side), so that the moment of tilting the roller assembly 9 during operation is reduced, thereby reducing the roller assembly. 9 can maintain the posture, and the resistance between the rotating outer joint member 4 and the roller assembly 9 during rotation is reduced, thereby reducing the induced thrust.

The components of this joint are mainly SUJ
2 (JIS G 4805) or other high carbon chromium bearing steel. However, the inner roller 5 of the roller assembly 9 described above has a point contact structure with the leg shaft 1 so that a large surface pressure is applied. This causes a sliding movement and a swinging and swinging movement at the contact portion, causing a large slip and galling, making it difficult to satisfy the durability and crack fatigue life as functions that the joint should have. Was. Therefore, it has been desired that the constituent members of the tripod joint be made of a material having excellent durability and crack fatigue strength.

Accordingly, the present invention has been proposed in view of the above problems, and an object of the present invention is to provide a constant velocity joint made of a constituent member made of a material which is resistant to fatigue cracking and has excellent durability. It is in.

[0011]

SUMMARY OF THE INVENTION As a technical means for achieving the above object, the present invention provides a tripod member having three leg shafts protruding in a radial direction, and a three-portion member having an inner peripheral portion having three axially extending legs. An outer joint member having a track groove formed thereon and having an axial roller guide surface on each side of each track groove,
A rolling member for transmitting rotational torque, which is interposed between a leg shaft of the tripod member and an outer joint member, is used as a main constituent member. , C (carbon) at 0.6% or more.
3% or less, Si (silicon) is 0.3% or more and 3.0%
Hereinafter, Ni (nickel) is 0.1% or more and 3.0% or less, Mn (manganese) is 0.2% or more and 1.5% or less,
It is formed of a steel material containing 0.3% or more and 5.0% or less of Cr (chromium), and its surface hardness is defined as Rockwell hardness HRC5.
8 or more.

[0012] The rolling member constituting the constant velocity joint of the present invention has at least C of 0.6% or more and 1.3% or less;
Si is 0.3% or more and 3.0% or less, Ni is 0.1% or more and 3.0% or less, Mn is 0.2% or more and 1.5% or less, and Cr is 0.3% or more. The durability and crack fatigue characteristics can be improved by forming the steel material containing not more than 5.0% and setting the surface hardness to Rockwell hardness HRC58 or more.

[0013] The steel material is V
(Vanadium) is 0.05% or more and 1.0% or less, Mo
(Molybdenum) is desirably added at 0.05% or more and less than 0.25%. It is desirable that the steel material be manufactured by induction hardening. Further, it is desirable that a carbonitrided layer be formed on the surface, and the amount of retained austenite in the carbonitrided layer be 10% by volume or more.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a constant velocity joint according to the present invention will be described in detail below. The constant velocity joint of the present invention
As shown in FIGS. 1 (a) and 1 (b) and FIG. 2, the cross-sectional shape of each leg shaft 1 of the tripod member 2 is made elliptical, and the inner roller 5 and the outer roller 7 are unitized via needle rollers 8. The present invention can be applied to a tripod joint provided with the roller assembly 9 described above. In addition to this, for example, as shown in FIGS. A spherical ring 14 is provided on the outer peripheral surface of the shaft 11 via a needle roller 13, and is accommodated in a track groove 16 of an outer joint member 15 on the outer side of the spherical ring 14 to roll on a roller guide surface 17. However, the present invention can also be applied to a tripod joint having a roller 18 that moves in the axial direction of the outer joint member 15.

Rolling members constituting the tripod joint, that is, the inner roller 5, the outer roller 7, and the needle rollers 8
At least about 0.6 to 1.3% of C, 0.6% or more of 3.0% and 3.0% of Ni, and 0.1% or more of 3.0% of Ni. Hereinafter, Mn is 0.2% or more and 1.5% or less, and Cr is 0.3% or less.
% And not more than 5.0%, and the surface hardness thereof is Rockwell hardness HRC 58 or more. By manufacturing from a steel material having the above-described composition and surface hardness, durability and crack fatigue characteristics can be improved.

The reason why the content of C is set to 0.6% or more and 1.3% or less is as follows. That is, C is an essential element for securing strength as a constant velocity joint, and 0.6% for maintaining hardness after a predetermined heat treatment.
Therefore, the lower limit of the content of C is set to 0.
Limited to 6%. In addition, carbides play an important role in durability, but when the content of C exceeds 1.3%, it has been found that large-sized carbides are generated and durability is lowered. Was limited to 1.3%.

The reason why the content of Si is set to 0.3% or more and 3.0% or less is as follows. That is, since Si has the effect of suppressing softening at high temperatures and improving heat resistance, the effect cannot be obtained at less than 0.3%, and the lower limit is limited to 0.3%. Although the heat resistance improves with an increase in the content of Si, the effect is saturated even if it is contained in a large amount exceeding 3.0%, and the hot workability and machinability decrease. Therefore, the upper limit was limited to 3.0%.

Ni forms a solid solution in the steel to strengthen the matrix, and also improves the toughness against cracking. Therefore,
Ni has the effect of improving the fatigue cracking strength. In order to obtain these effects, it is necessary to contain Ni at 0.1% or more, so the lower limit was made 0.1%. But,
If 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.
The upper limit was limited to 3.0%.

Mn is an element used for deoxidation in the production of steel, and forms a solid solution in the steel to strengthen the steel and improve the hardenability. Cr is an element that forms carbides and strengthens the steel, and is used for improving hardenability, securing hardness by the carbides, and improving the life. 0.2% Mn content
The reason why the content of Cr is set to 0.3% or more is to obtain these effects. Further, the content of Mn is 1.5
% Or less in order to avoid a decrease in machinability.
The content of r is set to not more than 5.0% in order to prevent embrittlement due to generation of large carbides. According to these elements, improvement in crack fatigue strength can be achieved by containing a suitable amount.

By the action of these alloy components, it is possible to form a joint material having excellent durability and crack fatigue strength.
By adding Mo in an amount of 0.05% or more and less than 0.25%, the characteristics can be further improved. The contents of V and Mo are limited as described above for the following reasons.

V combines with carbon to precipitate fine carbides, promotes the refinement of crystal grains, improves strength and toughness, and suppresses softening at high temperatures. Therefore, N
Like i, V has the effect of improving durability. To obtain this effect, the content of V is set to 0.05% or more. The reason why the upper limit is limited to 0.1% is that 1.0%
%, The machinability and the hot workability decrease.

Mo improves the hardenability of steel and
By forming a solid solution in the carbide, temper embrittlement is prevented, and softening in a high temperature range is also suppressed. Therefore, Mo also has the effect of improving durability. To achieve this effect,
The content of o was set to 0.05% or more. When the Mo content is 0.25% or more, the hardness does not decrease during the softening treatment for facilitating the cutting process, so that the machinability decreases and the steel material cost increases. Limited to less than 25%.

By the action of each of the above-mentioned alloy elements, a material having high crack fatigue strength and excellent durability can be obtained.

A carbonitrided layer is formed on the surface layer of the component having the above composition, and the amount of retained austenite in the carbonitrided layer is set to 10% by volume or more, thereby imparting high toughness to the surface layer. The generation and propagation of cracks can be suppressed, and the crack fatigue strength can be further increased.

That is, when the nitrogen content of the surface layer is increased by carbonitriding, the Ms point (martensite transformation start temperature) of the surface layer is lowered, and when this is quenched, a large amount of untransformed austenite remains in the surface layer. I do. Retained austenite has high toughness and work hardening characteristics, and functions to suppress crack generation and propagation. In the surface layer having a lowered Ms point, the martensitic transformation starts later than the inside and the amount of transformation is larger than the inside, so that residual compressive stress is formed in the surface layer, and the fatigue strength of the surface layer is reduced. As a result, the crack fatigue strength is improved. The reason why the amount of retained austenite in the carbonitrided layer is set to 10% by volume or more is to obtain these effects. The intrusion of nitrogen by carbonitriding is also advantageous in terms of imparting heat resistance.

Further, in order to apply a favorable effect of compressive stress on surface damage under a condition where a tangential force (tensile stress) acts, the steel material of the component is induction hardened to form a larger compressive stress in the surface layer. This prevents the occurrence of surface-initiated damage and improves crack resistance.

There is a correlation between the surface hardness and durability of the component made of the above composition, and the higher the surface hardness, the more the durability tends to be improved. Therefore, the durability is improved by setting the surface hardness to Rockwell hardness HRC 58 or more. When the surface hardness is less than Rockwell hardness HRC58, the life tends to be sharply reduced, and the life variability increases.

[0028]

EXAMPLES Examples and comparative examples of the present invention will be described below.

[0029]

[Table 1]

Durability obtained by subjecting steels having six kinds of chemical components shown in Table 1 to quenching and tempering described below,
Test specimens for crack life strength evaluation (Examples 1 to 6 in Table 1) were prepared. Specimens (Examples 7 to 10 in Table 1) obtained by subjecting some of the steel materials shown in Examples 1 to 6 to carbonitriding and test pieces subjected to induction hardening (Example 11 in Table 1) were also prepared. . The heat treatment of the test piece without carbonitriding is 840-860.
℃, then quenched into oil, Rockwell hardness H
Tempered at a temperature up to 350 ° C. so as to obtain an RC of 58 or more. In some examples, heating before quenching was performed in a carburizing atmosphere to which ammonia gas was added, and carbonitriding was also performed. The tempering temperature of the carbonitrided steel was 230 ° C. The induction hardened product was cured to a depth of 1 mm below the surface, and tempered so that the surface layer could secure Rockwell hardness of HRC 58 or more.

As a comparative example, high carbon chromium bearing steel SUJ
2. Test pieces (Comparative Examples 1 to 4 in Table 1) prepared by quenching and tempering SUJ3 and steels having two kinds of chemical components deviating from the range of the chemical components of the present invention. For SUJ2 and two kinds of steels deviating from the chemical composition of the present invention, test pieces (Comparative Examples 5 to 7 in Table 1) which were also subjected to carbonitriding were also prepared.

A durability test and a crack fatigue test were performed on the test piece samples of the above-mentioned Examples and Comparative Examples. The outline and results of each test are as follows. (1) Endurance Test In the endurance test, a sample was rotatably connected to a drive shaft, and torque and torque were applied while taking an angle through the drive shaft to evaluate the rotation durability. The test was performed under the following test conditions.・ Operating angle: 0 to 10 ° ・ Rotational speed: 250 rpm ・ Load torque: 60 kg ・ m

[0033]

[Table 2]

Table 2 shows the test results. Comparative Example 1 is 100
Damage to the extent that operation is possible occurs in time, and damage that cannot be operated in 150 hours. On the other hand, in Examples 1 and 5, even after 100 hours, there is no abnormality, and even after 150 hours, only operable damage occurs. Furthermore, in Examples 3 and 4, even after 150 hours, there is no abnormality, and even after 200 hours, only operable damage occurs. From these results, Examples 1, 3, 4, and 5 have excellent durability. (2) Crack fatigue test From the materials of the examples and comparative examples, φ45 × φ60 × L15
Was heat-treated under the same conditions as the above φ12 cylindrical test piece, and then subjected to a rotational crack fatigue test under the following test conditions. -Test load: 9.8 kN-Lubricating oil: Turbine oil VG68-Specimen load speed: 8000 times / minute-Evaluation: Number of times of load until breaking (times)

[0035]

[Table 3]

The test results are shown in Table 3. Each of the test pieces of the examples has a long crack life, and the induction hardened product has a longer life because of the compressive stress of the surface layer. Each test piece of the comparative example has a life of about 80% or less of that of the example in the standard heat-treated product. The crack strength is improved by carbonitriding in both the comparative example and the example, but the carbonitrided product of the example has a longer life.

From the above test results, those of the examples are as follows.
It shows that it exhibits excellent crack fatigue characteristics and has performance suitable for a joint with excellent durability.

[0038]

According to the present invention, the rolling member can be used as an alloy element in the following manner.
3% or less, Si is 0.3% or more and 3.0% or less, Ni is 0.1% or more and 3.0% or less, Mn is 0.2% or more and 1.5% or less, and Cr is 0.2% or less. It is formed of a steel material containing 3% or more and 5.0% or less, and its surface hardness is defined as Rockwell hardness HR
By setting C58 or more, durability and crack fatigue characteristics can be excellent, and the durability life and reliability of a joint used under high load and sliding conditions can be improved.

Further, the steel material is expressed as a mass% as an alloying element.
V is 0.05% or more and 1.0% or less, and Mo is 0.0% or more.
When added in an amount of 5% or more and less than 0.25%, durability and crack fatigue characteristics can be further improved, and the durability and reliability of the joint used under high load and sliding conditions can be improved. Properties can be further improved.

Further, when a carbonitrided layer is formed on the surface and the amount of retained austenite in the carbonitrided layer is set to 10% by volume or more, high toughness is imparted to the surface layer to suppress the generation and propagation of cracks, and to improve the durability life. Can be further improved. In addition, by forming a compressive stress on the surface layer by combining induction hardening, it is possible to further increase the life and the high cracking strength.

[Brief description of the drawings]

1 (a) is an example of a tripod joint to which the present invention is applied, and FIG. 1 (b) is an end view showing a part of the roller assembly of FIG. 1 (a).

FIG. 2 is a longitudinal sectional view showing a relationship between a leg shaft and a roller assembly.

FIG. 3 is an end view partially sectioned in another example of a tripod joint to which the present invention is applied.

FIG. 4 is an end view partially sectioned in another example of a tripod joint to which the present invention is applied.

[Explanation of symbols]

 2 Tripod member 4 Outer joint member 5 Rolling member (inner roller) 7 Rolling member (outer roller) 8 Rolling member (needle roller)

Claims (4)

[Claims] 1. A tripod member having three leg shafts protruding in a radial direction, and three axial track grooves formed in an inner peripheral portion, and an axial roller guide surface on each side of each track groove. An outer joint member having: and a rolling member that is interposed between a leg shaft of the tripod member and the outer joint member and transmits a rotational torque as a main constituent member, wherein the rolling member is At least C is 0.6% or more and 1.3% or less, and Si is 0.3% by mass% as an alloying element.
% Or more and 3.0% or less, Ni is 0.1% or more and 3.0% or less.
Hereinafter, Mn is 0.2% or more and 1.5% or less, and Cr is 0.2% or more.
A constant velocity joint formed of a steel material containing 3% or more and 5.0% or less, and having a surface hardness of Rockwell hardness HRC 58 or more. 2. The steel material is, as an alloying element, in mass%,
V is 0.05% or more and 1.0% or less, Mo is 0.05%
The constant velocity joint according to claim 1, wherein less than 0.25% is added. 3. The constant velocity joint according to claim 1, wherein a carbonitrided layer is formed on the surface, and a residual austenite amount of the carbonitrided layer is set to 10% by volume or more. 4. A constant velocity joint, wherein the steel material according to claim 1 or 2 is manufactured by induction hardening.