Sliding-type constant velocity universal joint

Abstract

To provide a double-offset type sliding-type constant velocity universal joint maintaining strength and durability at a low cost.SOLUTION: Provided is sliding-type constant velocity universal joint 1 which includes: an outer joint member 2 having a plurality of linear track grooves 7 formed therein; an inner joint member 3 having a plurality of linear track grooves 9 formed therein; a plurality of balls 4; and a cage 5 for accommodating the balls 4 in pockets 5a; and in which a center of curvature O1 of a spherical outer peripheral surface 11 of the cage 5 and a center of curvature O2 of the spherical inner peripheral surface 12 are offset from the joint center O on opposite sides in the axial direction, wherein the track grooves 7 of the outer joint member 2 have surfaces that are finished by forging, and the difference in track contact angle α between the track grooves 7 of the outer joint member 2 is 8° or less.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a sliding type constant velocity universal joint used in power transmission systems of automobiles and various industrial machines, for example, in drive shafts and propeller shafts of automobiles. [Background technology]

[0002] Constant velocity universal joints used in automobile drive shafts can be broadly divided into fixed constant velocity universal joints, which only allow angular displacement between two shafts, and sliding constant velocity universal joints, which allow angular and axial displacement. Automobile drive shafts typically use a fixed constant velocity universal joint on the drive wheel side (also called the outboard side) and a sliding constant velocity universal joint on the differential side (also called the inboard side), with these two constant velocity universal joints connected by an intermediate shaft. Various constant velocity universal joints are selected depending on the operating conditions and application.

[0003] Typical sliding-type constant velocity universal joints include double offset constant velocity universal joints (DOJs) and tripod constant velocity universal joints (TJs). DOJ-type sliding-type constant velocity universal joints are widely used due to their low manufacturing costs and the small amount of rotational backlash inside the joint. DOJ-type sliding-type constant velocity universal joints with six or eight balls are known, and Patent Document 1 describes a DOJ with a compact design that uses eight balls, while Patent Document 2 describes a DOJ with a maximum operating angle of 30° or more, which has a higher operating angle and is lighter and more compact.

[0004] A DOJ-type sliding type constant velocity universal joint is composed of an outer joint member, an inner joint member, a cage, and balls. Specifically, the outer joint member has a cylindrical inner peripheral surface on which a plurality of linear track grooves are formed along the axial direction, an inner joint member has a spherical outer peripheral surface on which a plurality of linear track grooves are formed along the axial direction that face the plurality of linear track grooves of the outer joint member, a plurality of balls incorporated between the plurality of linear track grooves of the outer joint member and the plurality of linear track grooves of the inner joint member, and a cage that houses the balls in pockets and has spherical outer and inner peripheral surfaces that are guided in contact with the cylindrical inner peripheral surface of the outer joint member and the spherical outer peripheral surface of the inner joint member, and the centers of curvature of the spherical outer and inner peripheral surfaces of the cage are offset on opposite sides of the joint center in the axial direction. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-73129 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-85488 Summary of the Invention [Problem to be solved by the invention]

[0006] The outer joint member and inner joint member, which are components of a DOJ type sliding type constant velocity universal joint, are generally manufactured by the following process. [Outer joint parts]: Cutting of bar material → Forging → Ironing inside cup → Turning (including rolling of stem part) → Heat treatment (hardening) → Grinding or hard turning of stem part [Inner joint parts]: Cutting bar material → Forging → Turning (including spline broaching) → Heat treatment (hardening) → Outer diameter surface grinding

[0007] As described above, in DOJ-type sliding constant velocity universal joints, the track grooves of the outer joint member and the inner diameter portion and the track grooves of the inner joint member are generally forged to reduce manufacturing costs (no finishing processes such as grinding are performed after the quenching process). As a result, the track grooves of the outer joint member and the inner joint member have large dimensional variations due to forging and variations due to the effects of heat treatment, so the shape differences between the track grooves are larger than in track-ground or hard-milled products. The track groove shapes of the outer joint member and the inner joint member have a significant impact on the strength and durability of the joint.

[0008] Important factors related to the track groove shape are the track contact angle and track contact ratio. The track contact angle and track contact ratio are the main factors that determine the track surface pressure and also affect ball riding at high working angles and under high loads.

[0009] In view of the above problems, an object of the present invention is to provide a double offset sliding type constant velocity universal joint that maintains strength and durability at low cost. [Means for solving the problem]

[0010] The inventors of the present invention have conducted extensive research to achieve the above-mentioned object. As a result, they have noticed that in the case of a forged track product of a DOJ type sliding constant velocity universal joint, it is important to suppress variations in the track contact angle and track contact rate in each track groove in order to stabilize the joint's function, and have come up with the novel idea of ​​determining the degree to which variations in the track contact angle and track contact rate affect durability and strength, and setting the internal specifications of the forged track product, thereby arriving at the present invention.

[0011] As technical means for achieving the aforementioned object, a first invention provides a sliding type constant velocity universal joint comprising: an outer joint member having a plurality of linear track grooves formed on its cylindrical inner peripheral surface along the axial direction; an inner joint member having a plurality of linear track grooves formed on its spherical outer peripheral surface along the axial direction that face the plurality of linear track grooves of the outer joint member; a plurality of balls that are fitted between the plurality of linear track grooves of the outer joint member and the plurality of linear track grooves of the inner joint member to transmit torque; and a cage that houses the balls in pockets and has a spherical outer peripheral surface and a spherical inner peripheral surface that are guided in contact with the cylindrical inner peripheral surface of the outer joint member and the spherical outer peripheral surface of the inner joint member, respectively, wherein the center of curvature of the spherical outer peripheral surface and the center of curvature of the spherical inner peripheral surface of the cage are offset to opposite sides in the axial direction with respect to the joint center, characterized in that the track grooves of the outer joint member have surfaces that are finished by forging, and the difference in track contact angles between the track grooves of the outer joint member is 8° or less. With the above configuration, it is possible to realize a double offset sliding type constant velocity universal joint that maintains strength and durability at low cost.

[0012] As an advantageous configuration, the track grooves of the inner joint member also have surfaces finished by forging, and the difference in track contact angles between the track grooves of the inner joint member is 8° or less. This facilitates the realization of a double offset sliding type constant velocity universal joint that maintains strength and durability at low cost.

[0013] A second invention is a sliding type constant velocity universal joint comprising: an outer joint member having a plurality of linear track grooves formed on its cylindrical inner peripheral surface along the axial direction; an inner joint member having a plurality of linear track grooves formed on its spherical outer peripheral surface along the axial direction that face the plurality of linear track grooves of the outer joint member; a plurality of balls that are fitted between the plurality of linear track grooves of the outer joint member and the plurality of linear track grooves of the inner joint member to transmit torque; and a cage that houses the balls in pockets and has a spherical outer peripheral surface and a spherical inner peripheral surface that are contact-guided by the cylindrical inner peripheral surface of the outer joint member and the spherical outer peripheral surface of the inner joint member, respectively, wherein the center of curvature of the spherical outer peripheral surface and the center of curvature of the spherical inner peripheral surface of the cage are offset to opposite sides in the axial direction with respect to the joint center; characterized in that the track grooves of the outer joint member have surfaces that are finished by forging, and a mutual difference in track contact ratio between the track grooves of the outer joint member is 0.02 or less. With the above configuration, it is possible to realize a double offset sliding type constant velocity universal joint that maintains strength and durability at low cost.

[0014] As an advantageous configuration, the track grooves of the inner joint member also have surfaces finished by forging, and the difference in track contact ratio between the track grooves of the inner joint member is 0.02 or less. This facilitates the realization of a double offset sliding type constant velocity universal joint that maintains strength and durability at low cost. The first and second inventions are collectively referred to as the present invention, and the embodiments described below relating to the first and second inventions are used in common as appropriate.

[0015] Specifically, by setting the number of balls to 5 to 8, it is possible to configure a double offset sliding constant velocity universal joint that is suitable for power transmission systems of automobiles, various industrial machines, and the like. [Effects of the Invention]

[0016] According to the present invention, it is possible to realize a double offset sliding type constant velocity universal joint that maintains strength and durability at low cost. [Brief explanation of the drawings]

[0017] [Figure 1] 3 is a longitudinal sectional view of the sliding type constant velocity universal joint according to the first embodiment of the present invention, taken along line BNB in ​​FIG. 2. FIG. [Figure 2] 2 is a cross-sectional view of the sliding type constant velocity universal joint according to the first embodiment of the present invention, taken along line AA in FIG. 1. FIG. [Figure 3] 3 is an enlarged cross-sectional view of one track groove, balls, and cage taken along line BN in FIG. 2. FIG. [Figure 4] 3 is a schematic view showing a track contact angle between a track groove of the outer joint member in FIG. 2 and a ball. FIG. [Figure 5] 3 is a schematic view showing a track contact angle between a track groove of the outer joint member in FIG. 2 and a ball. FIG. [Figure 6] FIG. 10 is a schematic diagram showing a method for measuring a track contact angle between a track groove of an outer joint member and a ball. [Figure 7] 3 is a schematic view showing a track contact ratio between the track grooves of the outer joint member in FIG. 2 and the balls. FIG. [Figure 8] FIG. 10 is a schematic diagram showing a method for calculating the track contact rate between the track groove and the ball. [Figure 9] FIG. 10 is a schematic diagram showing a method for measuring a track contact rate between a track groove of an inner joint member and a ball. [Figure 10] 1. FIG. 4 is a longitudinal sectional view showing a first modified example of the inner combination body of the sliding type constant velocity universal joint according to the first embodiment of the present invention, taken along line BNB in ​​FIG. [Figure 11] 1. FIG. 4 is a longitudinal sectional view showing a second modified example of the inner combination body of the sliding type constant velocity universal joint according to the first embodiment of the present invention, taken along the line BNB in ​​FIG. [Figure 12] FIG. 12 is an enlarged view of part E in FIG. [Figure 13] 1. FIG. 4 is a longitudinal sectional view showing a third modified example of the inner combination body of the sliding type constant velocity universal joint according to the first embodiment of the present invention, taken along the line BNB in ​​FIG. [Figure 14]16 is a longitudinal sectional view of a sliding type constant velocity universal joint according to a second embodiment of the present invention, taken along line BNB in ​​FIG. 15. FIG. [Figure 15] 15 is a cross-sectional view of a sliding type constant velocity universal joint according to a second embodiment of the present invention, taken along line AA in FIG. 14. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0018] A double offset sliding type constant velocity universal joint according to a first embodiment of the present invention will be described with reference to Figs. 1 to 9. Fig. 1 is a longitudinal sectional view of the sliding type constant velocity universal joint of this embodiment, taken along line BNB in ​​Fig. 2. Fig. 2 is a transverse sectional view of the sliding type constant velocity universal joint of this embodiment, taken along line AA in Fig. 1. Fig. 3 is an enlarged transverse sectional view of one track groove, ball, and cage taken along line BN in Fig. 2.

[0019] As shown in Figures 1 and 2, the sliding type constant velocity universal joint 1 is a so-called double offset sliding type constant velocity universal joint (sometimes referred to as DOJ or DOJ-type sliding type constant velocity universal joint), and is mainly composed of an outer joint member 2, an inner joint member 3, balls 4 for transmitting torque, and a cage 5. Six track grooves 7 are formed on a cylindrical inner peripheral surface 6 of the outer joint member 2 at equal intervals in the circumferential direction and linearly along the axial direction. Track grooves 9 opposing the track grooves 7 of the outer joint member 2 are formed on a spherical outer peripheral surface 8 of the inner joint member 3 at equal intervals in the circumferential direction and linearly along the axial direction. Six balls 4 are incorporated between the track grooves 7 of the outer joint member 2 and the track grooves 9 of the inner joint member 3, one each. The balls 4 are accommodated in pockets 5a of the cage 5.

[0020] The cage 5 has a spherical outer peripheral surface 11 and a spherical inner peripheral surface 12. The spherical outer peripheral surface 11 fits into and is in contact with the cylindrical inner peripheral surface 6 of the outer joint member 2, and the spherical inner peripheral surface 12 fits into and is in contact with the spherical outer peripheral surface 8 of the inner joint member 3. The spherical outer peripheral surface 11 of the cage 5 is formed with a radius of curvature Rc1 with a center of curvature O1, and the spherical inner peripheral surface 12 is formed with a radius of curvature Rc2 with a center of curvature O2. The spherical outer peripheral surface 8 of the inner joint member 3 is formed with a radius of curvature Ri with a center of curvature O2. The centers of curvature O1 and O2 are located on the axis N and are offset by an equal distance F on the opposite side of the axial direction from the joint center O. As a result, when the joint has an operating angle, the balls 4 are always guided on a plane that bisects the angle formed by the axes of the outer joint member 2 and the inner joint member 3, and rotation is transmitted between the two shafts at a constant speed.

[0021] A retaining ring groove 15 is provided at the open end of the outer joint member 2, and a retaining ring 17 is fitted in this retaining ring groove 15 to prevent the inner assembly I, consisting of the inner joint member 3, balls 4, and cage 5 shown in Figure 1, from slipping out of the open end of the outer joint member 2. A boot mounting groove 16 is provided on the outer periphery of the open end of the outer joint member 2. A stem portion (shaft portion) 2b is formed integrally with the outer joint member 2 on the side opposite the open end (see Figure 14), and is connected to a differential (not shown).

[0022] Linear track grooves 9 are formed on the spherical outer peripheral surface 8 of the inner joint member 3, and the depth of the track grooves 9 becomes shallower from the center to both ends in the axial direction of the inner joint member 3. A spline (including serrations, the same applies hereinafter) 14 is formed in the connecting hole 13 of the inner joint member 3, and the axial end of an intermediate shaft (not shown) is spline-fitted thereto, and the intermediate shaft is fixed in the axial direction to the inner joint member 3 by a shoulder portion of the intermediate shaft and a retaining ring (not shown).

[0023] Six pockets 5a are provided at equal intervals in the circumferential direction at the axial center of the cage 5, indicated by line AA in FIG. 1, with pillar portions 5b (see FIG. 2) between adjacent pockets 5a. A notch 5c is provided on the inner periphery of the large-diameter end of the cage 5 for assembling the inner joint member 3. The stopper surface 5d of the cage 5 is formed in a conical shape that connects tangently to the spherical outer peripheral surface 11. In the sliding type constant velocity universal joint 1 of this embodiment, the maximum operating angle is set to, for example, 25°. When the joint takes an operating angle, the cage 5 is inclined by half the angle formed by the axes of the outer joint member 2 and the inner joint member 3, so the inclination angle S of the stopper surface 5d is set to 12.5°. This makes it possible to restrict the maximum allowable angle of the sliding type constant velocity universal joint 1.

[0024] The contact states between the track grooves 7 of the outer joint member 2 and the track grooves 9 of the inner joint member 3 and the balls 4 will be described with reference to Figure 3. Figure 3 shows one track groove 7, 9, ball 4, and cage 5 taken along line BN in Figure 2.

[0025] 3, the cross sections of the track grooves 7 of the outer joint member 2 and the track grooves 9 of the inner joint member 3 are formed in a Gothic arch shape, which is a combination of two circular arcs. Therefore, the balls 4 come into angular contact with the track grooves 7, 9 at two points C1, C2, C3, and C4, respectively. The cross section shape of the track grooves 7, 9 is not limited to the Gothic arch shape described above, and may be an elliptical shape.

[0026] The track grooves 7, 9 and the ball 4 are in contact with each other at a track contact angle α. The track contact angle α refers to the angle α formed by the lines La and Lb in FIG. 3. The line La is the center line of the cross section of the track grooves 7, 9, and corresponds to the line BN in FIG. 2. The line Lb is a line connecting the contact points C1, C2, C3, and C4 of the ball 4 on the side surfaces of the track grooves 7, 9 with the center Ob of the ball 4. In this specification and claims, the track contact angle has the above meaning. The radius of curvature of the cross section of the track grooves 7, 9 is R2, and the radius of the ball 4 is R1. The track contact ratio φ refers to the ratio R2 / R1. In this specification and claims, the track contact ratio has the above meaning.

[0027] The overall configuration of the double offset sliding type constant velocity universal joint 1 of this embodiment has been described above. Next, the characteristic configuration will be described. <Characteristic configuration of the first invention> (1) In a double offset type sliding constant velocity universal joint, the track grooves of the outer joint member have surfaces that are finished by forging, and the difference in the track contact angles between the track grooves of the outer joint member is 8° or less. Advantageously, the track grooves of the inner joint member also have surfaces finished by forging, and the difference in track contact angles between the track grooves of the inner joint member is also 8° or less. <Characteristic configuration of the second invention> (2) In a double offset type sliding constant velocity universal joint, the track grooves of the outer joint member have surfaces that are finished by forging, and the difference in the track contact rate between the track grooves of the outer joint member is 0.02 or less. Advantageously, the track grooves of the inner joint member also have surfaces finished by forging, and the difference in track contact ratio between the track grooves of the inner joint member is 0.02 or less. The characteristic configuration (1) of the first invention and the characteristic configuration (2) of the second invention make it possible to realize a DOJ type sliding constant velocity universal joint that maintains strength and durability at low cost.

[0028] The above-mentioned characteristic feature (1) of the first invention and the characteristic feature (2) of the second invention were arrived at through the following investigation process: The inventors of the present invention noticed that in the track forged product of a DOJ-type sliding constant velocity universal joint, suppressing variations in the track contact angle and track contact rate in each track groove is important for the stability of joint function, and they came up with the novel idea of ​​determining the degree to which variations in the track contact angle and track contact rate affect durability and strength and setting the internal specifications of the track forged product, thereby arriving at the above-mentioned characteristic features (1) and (2).

[0029] We investigated the extent to which variations in track contact angle and track contact rate affect durability and strength. The size of sliding constant velocity universal joints is determined by load capacity, and a difference of one size results in a difference of approximately 5% in track surface pressure. <Track contact angle> When the track contact angle varies by ±4° between the track grooves of a single sliding type constant velocity universal joint, the track surface pressure varies by approximately ±4%. We found an indicator that if the track contact angle varies beyond this, a sliding type constant velocity universal joint one size larger must be used. This led to a characteristic configuration (1) of the first invention in which the difference in track contact angle between track grooves of the outer joint member is 8° or less, and an advantageous configuration in which the difference in track contact angle between track grooves of the inner joint member is also 8° or less. <Truck contact rate> When the track contact ratio varies by ±0.01 between the track grooves of a single sliding-type constant velocity universal joint, the track surface pressure varies by approximately ±3%. A guideline was found that if the track contact ratio varies beyond this, a sliding-type constant velocity universal joint one size larger must be used. This led to a characteristic configuration (2) of the second invention, in which the difference in track contact ratio between track grooves of the outer joint member is 0.02 or less, and an advantageous configuration in which the difference in track contact angle between track grooves of the inner joint member is also 0.02 or less.

[0030] In addition, in the track forged finish of DOJ type sliding constant velocity universal joints, the following technical means were created and achieved to suppress the difference in track contact angle between track grooves to 8° or less, and the difference in track contact rate between track grooves to 0.02 or less. (1) As a forming method, cold forging is performed using high-precision dies to ensure high precision and stability of the formed products. (2) As a heat treatment method, high-frequency uniform heating is performed by rotating the workpiece to suppress heat treatment deformation.

[0031] The characteristic configuration (1) of the first invention will be specifically described with reference to Fig. 4 to Fig. 6. Fig. 4 and Fig. 5 are schematic diagrams showing the state of the track contact angle between the track grooves of the outer joint member and the balls in Fig. 2. Fig. 6 is a schematic diagram showing a method for measuring the track contact angle between the track grooves of the outer joint member and the balls.

[0032] The track grooves 7 of the outer joint member 2 and the track grooves 9 of the inner joint member 3, which are components of the double offset sliding type constant velocity universal joint 1, are generally finished by cold forging (no finishing process such as grinding after the quenching process is performed). In other words, the track grooves 7 and 9 have surfaces that are finished by forging. In this specification and the claims, the term "surfaces finished by forging" is used in this sense.

[0033] Next, the variation in the track contact angle between the track grooves and the balls will be described for the outer joint member with reference to Figures 4 and 5. Figure 4 shows the sliding-type constant velocity universal joint 1 of this embodiment, but the variation in the track contact angle α between the track grooves 7 of the outer joint member 2 and the balls 4 is exaggerated for explanation. The position of the vertex in Figure 4 is defined as phase angle β = 0°, and the track groove 7 with phase angle β = 0° is defined as track groove 7(1). Rotating left (counterclockwise) from track groove 7(1), the following are defined: track groove 7(2) with phase angle β = 60°, track groove 7(3) with phase angle β = 120°, track groove 7(4) with phase angle β = 180°, track groove 7(5) with phase angle β = 240°, and track groove 7(6) with phase angle β = 300°.

[0034] When torque is applied from the inner joint member (not shown) in the rotational direction indicated by the white arrow, as shown in FIG. 4, the track contact angle of track groove 7(1) is extremely small at α(1), while the track contact angle of track groove 7(4) is large at α(4). The smaller the track contact angle, the larger the surface pressure of the track groove, and vice versa. As a result, the surface pressure of track groove 7(1) increases, resulting in a short lifespan, but the surface pressure of track groove 7(4) decreases, resulting in a long lifespan. However, the joint lifespan is determined by the lifespan of track groove 7(1), where the surface pressure increases the most, resulting in a short lifespan.

[0035] The track contact angles α(2), α(3), α(5), and α(6) of the remaining track grooves 7(2), 7(3), 7(5), and 7(6) are intermediate in size between the track contact angle α(1) of track groove 7(1) and the track contact angle α(4) of track groove 7(4), and the values ​​of the track contact angles α(2), α(3), α(5), and α(6) are also approximately the same.

[0036] Here, the difference in track contact angle α between the track grooves 7 will be defined. The difference in track contact angle α between the track grooves 7 is the difference between the track contact angle α(4) having the maximum value and the track contact angle α(1) having the minimum value shown in FIG. 4. The difference in track contact angle between the track grooves in this specification and claims has the above meaning. Although not shown in the drawings, the same applies to the difference in track contact angle α between the track grooves 9 of the inner joint member 3.

[0037] 4 exaggerates the difference in track contact angle α between the track grooves 7 of the outer joint member 2 to make it easier to understand. In the present embodiment, even if the track contact angle α of the outer joint member 2 varies, the difference in track contact angle α between the track grooves 7 of the outer joint member 2 is kept to 8° or less, and similarly, even if the track contact angle α of the inner joint member 2 varies, the difference in track contact angle α between the track grooves 9 of the inner joint member 3 is also kept to 8° or less.

[0038] Fig. 5 shows a case where the difference between the track contact angles α between the track grooves 7 of the outer joint member 2 and the balls 4 is small. The symbols used to designate the phase angle β, track grooves 7, and track contact angles α in Fig. 5 are the same as those in Fig. 4. Because the magnitude of the contact angle is almost the same for all track grooves 7, the surface pressure of the track grooves 7 is almost the same, there is no difference in lifespan between the track grooves 7, and the desired durability is achieved. In this case, of course, the difference between the track contact angles α of the track grooves 7 of the outer joint member 2 is 8° or less.

[0039] Next, a method for measuring the track contact angle α between the track grooves 7 and the balls 4 will be explained for the outer joint member 7 with reference to Figure 6. A paint used for contact inspection (for example, rouge) is applied to the entire area of ​​the track groove 7. Then, the reference ball 4 is pressed against the track groove 7 and dragged across the entire area of ​​the track groove 7. As a result, the rouge at the contact area between the track groove 7 and the ball 4 peels off. The length L between the ball contact marks is measured with a vernier caliper or the like, and the contact angle α is calculated using equation (1) described below. Although the case of the outer joint member 2 is illustrated, the measurement procedure is the same for the inner joint member 3.

number

[0040] Next, a characteristic configuration (2) of the second invention will be specifically described with reference to Figs. 7 to 9. Fig. 7 is a schematic diagram showing variations in the track contact ratio between the track grooves of the outer joint member and the balls in Fig. 2. Fig. 8 is a schematic diagram showing a method for calculating the track contact ratio between the track grooves and the balls. Fig. 9 is a schematic diagram showing a method for measuring the track contact ratio of the inner joint member.

[0041] The variation in the track contact ratio between the track grooves and the balls will be explained with reference to Fig. 7. Fig. 7 illustrates an exaggerated variation in the track contact ratio φ between the track grooves 7 of the outer joint member 2 and the balls 4. As with Fig. 4 for the track contact angle α, the position of the vertex in Fig. 7 is set to phase angle β = 0°, and the track groove 7 with phase angle β = 0° is designated as track groove 7(1). The track grooves 7 with phase angle β = 60° are designated as track groove 7(2), phase angle β = 120°, phase angle β = 180°, phase angle β = 240°, and phase angle β = 300° are designated as track groove 7(6).

[0042] The track contact ratio φ is the ratio R2 / R1 of the radius of curvature R2 of the cross section of the track groove 7 to the radius R1 of the ball 4 (see Figure 3). In Figure 7, the track contact ratio φ(1) of track groove 7(1) is large, and the track contact ratio φ(4) of track groove 7(4) is small. The track contact ratios φ(2), φ(3), φ(5), and φ(6) of the remaining track grooves 7(2), 7(3), 7(5), and 7(6) are intermediate between the track contact ratio angle φ(1) of track groove 7(1) and the track contact ratio φ(4) of track groove 7(4), and the values ​​of the track contact angles φ(2), φ(3), φ(5), and α(6) are also similar.

[0043] When torque is applied from the inner joint member (not shown) in the rotational direction indicated by the white arrow, in Figure 7, the track contact ratio of track groove 7(1) is largest at φ(1), and conversely, the track contact ratio of track groove 7(4) is smallest at φ(4). When the ball contacts the track groove, if the track contact ratio is large, the contact ellipse becomes small, resulting in high surface pressure, but this is advantageous for the contact ellipse to ride over the track groove end. Conversely, if the track contact ratio is small, the contact ellipse becomes large, resulting in low surface pressure, but this is disadvantageous for the contact ellipse to ride over the track groove end. Therefore, track groove 7(1) has high surface pressure, but is advantageous for ride-over, while track groove 7(4) has low surface pressure, but is disadvantageous for ride-over. However, there is an allowable range for both surface pressure and ride-over to ensure joint life, and it is necessary to suppress variation in the track contact ratio φ to stabilize joint life.

[0044] Here, the difference in track contact ratio φ between the track grooves 7 will be defined. The difference in track contact angle φ between the track grooves 7 is the difference between the track contact ratio φ(1) having the maximum value and the track contact ratio φ(4) having the minimum value shown in FIG. 7. The difference in track contact ratio between the track grooves in this specification and claims has the above meaning. Although not shown in the drawings, the same applies to the difference in track contact ratio φ between the track grooves 9 of the inner joint member 3.

[0045] 7 exaggerates the difference in track contact ratio φ between the track grooves 7 of the outer joint member 2 for ease of understanding. In the present embodiment, the difference in track contact ratio φ between the track grooves 7 of the outer joint member 2 is suppressed to 0.02 or less, and the difference in track contact ratio φ between the track grooves 9 of the inner joint member 3 is also suppressed to 0.02 or less.

[0046] Next, methods for calculating and measuring the track contact ratio between the track groove and the ball will be explained with reference to Figs. 8 and 9. The track contact ratio φ is the ratio R2 / R1 of the radius of curvature R2 of the cross section of the track grooves 7 and 9 to the radius R1 of the ball 4. As shown in Fig. 8, the radius of curvature R2 of the cross section of the track grooves 7 and 9 can be expressed as the radius R1 of the reference ball × the track contact ratio φ. The track grooves 7 and 9 and the ball 4 are in contact with each other at a track contact angle α. A vertex gap Vc is provided at the groove bottom of the track grooves 7 and 9.

[0047] A method for measuring the track contact ratio φ will be described with reference to Figure 9. Figure 9 shows the case of the inner joint member 3. A measuring device 20 for the track contact ratio φ mainly comprises a reference ball 21, a measuring pin 22, a pressing member 23, and a dial gauge 24. The measuring pin 22 is slidably inserted into a through hole in the center of the reference ball 21, and the tip of the measuring pin 22 protrudes from the through hole. A base 22a of the measuring pin 22 is guided by the pressing member 23, and the end abuts against the dial gauge 24. The reference ball 21 is provided in the pressing member 23.

[0048] When the reference ball 21 and measuring pin 22 of the measuring device 20 are pressed against the track groove 9, the measuring pin 22 moves down and the amount of this movement is read with a dial gauge 24. This gives the apex clearance Vc, and the track contact ratio φ can be calculated as follows:

[0049]

number

[0050] A first modified example of the inner assembly of the sliding type constant velocity universal joint according to the first embodiment of the present invention will be described with reference to Fig. 10. The inner assembly I of this modified example is a combination of the cage pocket and the ball. The difference from the first embodiment is that a positive axial clearance is provided between them. The other configurations are the same as those of the first embodiment, so parts having similar functions are given the same reference numerals and only the main points will be explained.

[0051] FIG. 10 shows a first modified example of the inner combination body I of the sliding type constant velocity universal joint according to the first embodiment. As shown in FIG. 10, the inner assembly I includes an inner joint member 3, a cage 5, , and a ball 4, and a positive axial clearance δ2 is formed between the ball 4 and a wall surface 5d of the pocket 5a of the cage 5 facing in the joint axial direction. The diameter of the ball 4 is D BALL , If the width between the wall surfaces 5d of the pocket 5a of the cage 5 facing each other in the joint axial direction is Lw, the axial clearance δ2 is δ2 = Lw - D BALL This is about +0.001 mm to +0.050 mm, which allows the balls 4 to roll smoothly within the pockets 5a, thereby reducing the sliding resistance.

[0052] A second modified example of the inner assembly of the sliding type constant velocity universal joint according to the first embodiment of the present invention will be described with reference to Figures 11 and 12. The inner assembly of this modified example differs from the first embodiment in that a positive axial clearance is provided between the cage pockets and the balls, and that an axial clearance is provided that allows relative axial movement between the inner joint member and the cage. As the other configurations are the same as those of the first embodiment, parts having similar functions are given the same reference numerals, and only the main points will be described.

[0053] Fig. 11 is a longitudinal sectional view of a second modified example of the inner combination body of the sliding type constant velocity universal joint according to the first embodiment, and Fig. 12 is an enlarged view of part E in Fig. 11. As shown in Fig. 11, the inner combination body I is composed of the inner joint member 3, the cage 5, and the balls 4. A positive axial clearance δ2 is formed between the balls 4 and the wall surface 5d that faces each other in the joint axial direction. The spherical outer peripheral surface 11 of the cage 5 is formed with a curvature radius Rc1 with a center of curvature Oc1, and the spherical inner peripheral surface 12 is formed with a curvature radius Rc2 with a center of curvature Oc2. The spherical outer peripheral surface 8 of the inner joint member 3 is formed with a curvature radius Ri with a center of curvature Oi2. The centers of curvature Oc1 and Oi2 are located on the axis N and are offset from the joint center O by an equal distance F in the axial direction. Furthermore, the curvature center Oc2 of the spherical inner peripheral surface 12 of the cage 5 is offset from the axis N in the radial direction with respect to the center of curvature Oi2 so that Rc2 > Ri, and is offset from the joint center O by a distance F in the axial direction.

[0054] As shown in Figure 12, a spherical clearance δ3 is formed at the axial center of the spherical outer peripheral surface 8 of the inner joint member 3, allowing contact and guiding with the spherical inner peripheral surface 12 of the cage 5. On both sides of the center, an axial clearance δ4 is formed, allowing relative axial movement between the inner joint member 3 and the cage 5. The median value of the spherical clearance δ3 is approximately 0.050 mm. The axial clearance δ4 is approximately 1 mm. The axial movement of the inner joint member 3 relative to the outer joint member 2 is approximately 2 mm, which is twice the axial clearance δ4 (approximately 1 mm). Vibrations are absorbed within this range of axial movement. In other words, sliding resistance can be reduced under commonly used vibration conditions. The spherical clearance δ3 and the axial clearance δ4 are exaggerated in the illustration.

[0055] The axial gap δ4 between the cage 5 and the inner joint member 3 and the positive axial gap δ2 between the ball 4 and the wall surface 5d of the pocket 5a of the cage 5 facing in the joint axial direction can combine to reduce sliding resistance.

[0056] A third modified example of the inner assembly of the sliding type constant velocity universal joint according to the first embodiment of the present invention will be described with reference to Fig. 13. The inner assembly of this modified example differs from that of the second modified example in the shape of the spherical inner peripheral surface of the cage. As the other configurations are the same as those of the first embodiment and the second modified example, parts having similar functions are given the same reference numerals and only the main points will be described.

[0057] Fig. 13 is a longitudinal sectional view of a third modified example of the inner combination body of the sliding type constant velocity universal joint according to the first embodiment. As shown in Fig. 13, the spherical inner peripheral surface 12 of the cage 5 is composed of a spherical portion 12a with a center of curvature Oc2 and a radius of curvature Rc2, a spherical portion 12b with a center of curvature Oc3 and a radius of curvature Rc2, and a cylindrical portion 12c connecting the spherical portion 12a and the spherical portion 12b by a tangent. The centers of curvature Oc2 and Oc3 are located on the axis N, and the axial center point of the centers of curvature Oc2 and Oc3 is offset by F from the joint center O. The spherical outer peripheral surface 8 of the inner joint member 3 is formed with a center of curvature Oi2 and a radius of curvature Ri. In the arrangement state of FIG. 13, the axial midpoint between the centers of curvature Oc2 and Oc3 of the spherical inner peripheral surface 12 of the cage 5 coincides with the center of curvature Oi2 of the spherical outer peripheral surface 8 of the inner joint member 3.

[0058] A spherical clearance δ3 is formed in the axial center of the spherical outer peripheral surface 8 of the inner joint member 3, allowing contact and guiding with the cylindrical portion 12c of the cage 5, and axial clearances δ4 are formed on both sides of the center, allowing relative axial movement between the inner joint member 3 and the cage 5. The length of the cylindrical portion 12c is about 1 mm, and the axial clearance δ4 corresponds to the length of the cylindrical portion 12c. The amount of axial movement of the inner joint member 3 relative to the outer joint member 2 is about 2 mm, which is twice the length of the cylindrical portion 12c (about 1 mm), and vibrations are absorbed within this range of axial movement. In other words, sliding resistance can be reduced under commonly used vibration conditions.

[0059] In this modification, the spherical inner peripheral surface 12 of the cage 5 is composed of a spherical portion 12a with a radius of curvature Rc2 and a center of curvature Oc2, a spherical portion 12b with a center of curvature Oc3 and a radius of curvature Rc2, and a cylindrical portion 12c connecting the spherical portions 12a and 12b by a tangent. Since the radius of curvature Rc2 and the radius of curvature Ri are substantially the same, smooth and stable contact and guidance is achieved between the spherical inner peripheral surface 12 of the cage 5 and the spherical outer peripheral surface 8 of the inner joint member 3. As in the first and second modifications, a positive axial clearance δ2 is formed between the balls 4 and wall surfaces 5d of the pockets 5a of the cage 5 facing each other in the joint axial direction.

[0060] The double offset type sliding constant velocity universal joint 1 consisting of the inner combination bodies of the first to third modified examples also has the following characteristic configuration (1) of the first invention and the characteristic configuration (2) of the second invention, similar to the double offset type sliding constant velocity universal joint 1 according to the first embodiment described above. <Characteristic configuration of the first invention> (1) In a double offset type sliding constant velocity universal joint, the track grooves of the outer joint member have surfaces that are finished by forging, and the difference in the track contact angles between the track grooves of the outer joint member is 8° or less. Advantageously, the track grooves of the inner joint member also have surfaces finished by forging, and the difference in track contact angles between the track grooves of the inner joint member is also 8° or less. <Characteristic configuration of the second invention> (2) In a double offset type sliding constant velocity universal joint, the track grooves of the outer joint member have surfaces that are finished by forging, and the difference in the track contact rate between the track grooves of the outer joint member is 0.02 or less. Advantageously, the track grooves of the inner joint member also have surfaces finished by forging, and the difference in track contact ratio between the track grooves of the inner joint member is 0.02 or less.

[0061] The characteristic configuration (1) of the first invention and the characteristic configuration (2) of the second invention described above make it possible to realize a DOJ type sliding constant velocity universal joint that maintains strength and durability at low cost. The contents of the characteristic configurations (1) and (2) described above for the double offset sliding constant velocity universal joint 1 of the first embodiment are also applicable to the double offset sliding constant velocity universal joint 1 consisting of the inner combination body of the first to third modified examples, and therefore apply mutatis mutandis.

[0062] A sliding type constant velocity universal joint according to a second embodiment of the present invention will be described with reference to Figs. 14 and 15. The double offset sliding type constant velocity universal joint of this embodiment has eight balls, which is different from the number of balls in the sliding type constant velocity universal joint of the first embodiment. Since the other configurations are the same as those of the first embodiment, parts having similar functions will be given the same reference numerals, and only the main points will be described. Fig. 14 is a longitudinal cross-sectional view of the sliding type constant velocity universal joint according to this embodiment, taken along line BNB in ​​Fig. 15. Fig. 15 is a transverse cross-sectional view of the sliding type constant velocity universal joint according to this embodiment, taken along line AA in Fig. 14.

[0063] 14 and 15 , in a double offset sliding type constant velocity universal joint 1 according to this embodiment, eight track grooves 7 are formed on a cylindrical inner peripheral surface 6 of an outer joint member 2 at equal intervals in the circumferential direction and linearly along the axial direction. Track grooves 9 opposing the track grooves 7 of the outer joint member 2 are formed on a spherical outer peripheral surface 8 of the inner joint member 3 at equal intervals in the circumferential direction and linearly along the axial direction. Eight balls 4 are incorporated between the track grooves 7 of the outer joint member 2 and the track grooves 9 of the inner joint member 3, one each.

[0064] The cage 5 has a spherical outer peripheral surface 11 and a spherical inner peripheral surface 12. The spherical outer peripheral surface 11 fits into and is in contact with the cylindrical inner peripheral surface 6 of the outer joint member 2, and the spherical inner peripheral surface 12 fits into and is in contact with the spherical outer peripheral surface 8 of the inner joint member 3. The spherical outer peripheral surface 11 of the cage 5 is formed with a radius of curvature Rc1 with a center of curvature O1, and the spherical inner peripheral surface 12 is formed with a radius of curvature Rc2 with a center of curvature O2. The spherical outer peripheral surface 8 of the inner joint member 3 is formed with a radius of curvature Ri with a center of curvature O2. The centers of curvature O1 and O2 are located on the axis N and are offset equidistantly from the joint center O on the opposite side in the axial direction. As a result, when the joint has an operating angle, the balls 4 are always guided on a plane that bisects the angle formed by the axes of the outer joint member 2 and the inner joint member 3, and rotation is transmitted between the two shafts at a constant speed.

[0065] The double offset type sliding constant velocity universal joint 1 of this embodiment, like the double offset type sliding constant velocity universal joint 1 of the first embodiment described above, also has the following characteristic configuration (1) of the first invention and the characteristic configuration (2) of the second invention. <Characteristic configuration of the first invention> (1) In a double offset type sliding constant velocity universal joint, the track grooves of the outer joint member have surfaces that are finished by forging, and the difference in the track contact angles between the track grooves of the outer joint member is 8° or less. Advantageously, the track grooves of the inner joint member also have surfaces finished by forging, and the difference in track contact angles between the track grooves of the inner joint member is also 8° or less. <Characteristic configuration of the second invention> (2) In a double offset type sliding constant velocity universal joint, the track grooves of the outer joint member have surfaces that are finished by forging, and the difference in the track contact rate between the track grooves of the outer joint member is 0.02 or less. Advantageously, the track grooves of the inner joint member also have surfaces finished by forging, and the difference in track contact ratio between the track grooves of the inner joint member is 0.02 or less.

[0066] The characteristic configuration (1) of the first invention and the characteristic configuration (2) of the second invention described above make it possible to realize a DOJ type sliding constant velocity universal joint that maintains strength and durability at low cost. The contents of the characteristic configurations (1) and (2) described above for the double offset sliding constant velocity universal joint 1 of the first embodiment are also applicable to the double offset sliding constant velocity universal joint 1 according to this embodiment, and therefore apply mutatis mutandis.

[0067] The present invention is not limited to the above-described embodiments and modifications, and can of course be embodied in various other forms without departing from the spirit of the present invention. The scope of the present invention is indicated by the claims, and further includes the equivalent meanings set forth in the claims, and all modifications within the scope of the claims. [Explanation of symbols]

[0068] 1. Sliding constant velocity universal joint 2 Outer joint member 3 Inner joint member 4 balls 5 cages 6 Cylindrical inner surface 7 Track groove 8 Spherical outer surface 9 Track groove 11 Spherical outer surface 12 Spherical inner surface F offset amount O Joint center O1 center of curvature O2 center of curvature R1 ball radius R2 Radius of curvature of the cross section of the track groove α track contact angle φ Truck contact rate

Claims

1. a sliding type constant velocity universal joint comprising: an outer joint member having a cylindrical inner peripheral surface on which a plurality of linear track grooves are formed along the axial direction; an inner joint member having a spherical outer peripheral surface on which a plurality of linear track grooves facing the plurality of linear track grooves of the outer joint member are formed along the axial direction; a plurality of balls that are fitted between the plurality of linear track grooves of the outer joint member and the plurality of linear track grooves of the inner joint member to transmit torque; and a cage that houses the balls in pockets and has a spherical outer peripheral surface and a spherical inner peripheral surface that are guided in contact with the cylindrical inner peripheral surface of the outer joint member and the spherical outer peripheral surface of the inner joint member, respectively, wherein the centers of curvature of the spherical outer peripheral surface and the spherical inner peripheral surface of the cage are offset to opposite sides in the axial direction with respect to a joint center, a sliding type constant velocity universal joint, characterized in that the track grooves of the outer joint member have surfaces finished by forging, and a difference in track contact angle between the track grooves of the outer joint member is 8° or less.

2. 2. The sliding type constant velocity universal joint according to claim 1, wherein the track grooves of the inner joint member also have surfaces finished by forging, and a mutual difference in track contact angles between the track grooves of the inner joint member is 8° or less.

3. a sliding type constant velocity universal joint comprising: an outer joint member having a cylindrical inner peripheral surface on which a plurality of linear track grooves are formed along the axial direction; an inner joint member having a spherical outer peripheral surface on which a plurality of linear track grooves facing the plurality of linear track grooves of the outer joint member are formed along the axial direction; a plurality of balls that are fitted between the plurality of linear track grooves of the outer joint member and the plurality of linear track grooves of the inner joint member to transmit torque; and a cage that houses the balls in pockets and has a spherical outer peripheral surface and a spherical inner peripheral surface that are guided in contact with the cylindrical inner peripheral surface of the outer joint member and the spherical outer peripheral surface of the inner joint member, respectively, wherein the centers of curvature of the spherical outer peripheral surface and the spherical inner peripheral surface of the cage are offset to opposite sides in the axial direction with respect to a joint center, a sliding type constant velocity universal joint, characterized in that the track grooves of the outer joint member have surfaces finished by forging, and a difference in track contact ratio between the track grooves of the outer joint member is 0.02 or less.

4. 4. The sliding type constant velocity universal joint according to claim 3, wherein the track grooves of the inner joint member also have surfaces finished by forging, and a mutual difference in track contact ratios between the track grooves of the inner joint member is 0.02 or less.

5. 5. The sliding type constant velocity universal joint according to claim 1, wherein the number of the balls is 5 to 8.

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