Sliding type constant velocity universal joint

Abstract

Provided is a double-offset sliding constant velocity universal joint that maintains strength and durability at low cost. A sliding constant velocity universal joint (1) is provided with an outer joint member (2) in which a plurality of linear track grooves (7) are formed, an inner joint member (3) in which a plurality of linear track grooves (9) are formed, a plurality of balls (4), and a cage (5) that houses the balls (4) in grooves (5a). The center of curvature (O1) of the spherical outer peripheral surface (11) of the cage (5) and the center of curvature (O2) of the spherical inner peripheral surface (12) of the cage (5) are offset on the opposite sides in the axial direction with respect to the joint center (O), and the outer joint member (2) is characterized in that the track groove (7) of the outer joint member (2) is configured from a surface that has been finished by forging; the difference between the track grooves (7) of the track contact angle (alpha) of the outer joint member (2) is 8 DEG or less.

Description

Technical Field

[0001] The present invention relates to a sliding type constant velocity universal joint used in power transmission systems of automobiles, various industrial machines, and the like, for example, a drive shaft or a propeller shaft of an automobile. Background Art

[0002] Constant velocity universal joints used in automotive drive shafts can be broadly categorized into fixed-type constant velocity joints, which only allow angular displacement between the two shafts, and sliding-type constant velocity joints, which allow both angular and axial displacement. A typical automotive drive shaft configuration consists of a fixed constant velocity universal joint on the drive wheel side (also known as the outboard side) and a sliding constant velocity universal joint on the differential side (also known as the inboard side), with the two constant velocity universal joints connected by an intermediate shaft. The type of constant velocity universal joint selected varies depending on the operating conditions and application.

[0003] Representative sliding constant velocity universal joints include double-offset constant velocity universal joints (DOJ) and tripod constant velocity universal joints (TJ). DOJ-type sliding constant velocity universal joints are widely used due to their low manufacturing costs and minimal internal rotational directional play. DOJ-type sliding constant velocity universal joints with six or eight balls are also known. Patent Document 1 describes a compact DOJ design with eight balls, while Patent Document 2 describes a DOJ with a maximum operating angle of 30° or greater, achieving a higher operating angle and a lighter, more compact design.

[0004] A DOJ-type sliding constant velocity universal joint consists of an outer joint member, an inner joint member, a retainer, and balls. Specifically, the structure includes: an outer joint member having a plurality of linear raceway grooves formed axially on its cylindrical inner circumference; an inner joint member having a plurality of linear raceway grooves formed axially on its spherical outer circumference, which oppose the plurality of linear raceway grooves of the outer joint member; a plurality of balls assembled between the plurality of linear raceway grooves of the outer joint member and the plurality of linear raceway grooves of the inner joint member; and a retainer that accommodates the balls in grooves and has a spherical outer circumferential surface and a spherical inner circumferential surface that are contact-guided by the cylindrical inner circumferential surface of the outer joint member and the spherical outer circumferential surface of the inner joint member. The centers of curvature of the retainer's spherical outer circumferential surface and the centers of curvature of the spherical inner circumferential surface are offset axially to opposite sides relative to the center of the joint.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 10-73129

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2007-85488 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] The outer joint member and the inner joint member, which are components of a DOJ type sliding constant velocity universal joint, are generally manufactured in the following steps.

[0011] [Outer coupling component]: Bar cutting → Forging → Cup-thinning forging → Turning (including rod rolling) → Heat treatment (quenching) → Rod grinding or hard turning

[0012] [Inner coupling component]: Bar cutting → Forging → Turning (including spline broaching) → Heat treatment (quenching) → OD grinding

[0013] In DOJ-type sliding constant velocity universal joints, as mentioned above, the raceway grooves and inner diameter portion of the outer joint member, as well as the raceway grooves of the inner joint member, are typically forged and finished to reduce manufacturing costs (no finishing, such as grinding, is performed after the quenching process). Consequently, the raceway grooves of the outer and inner joint members experience significant dimensional fluctuations due to forging and heat treatment, leading to greater differences in shape between the individual raceway grooves compared to raceway-ground or hard-milled products. The shape of the raceway grooves of the outer and inner joint members significantly impacts the strength and durability of the coupling.

[0014] Important factors related to the ball groove shape include the ball contact angle and the ball contact ratio. These factors are the primary factors determining the ball surface pressure and also affect ball climbing at high operating angles and high loads.

[0015] In view of the above-mentioned problems, an object of the present invention is to provide a double-offset sliding constant velocity universal joint that maintains strength and durability at low cost.

[0016] Solutions to Problems

[0017] The present inventors conducted extensive research to achieve the aforementioned objectives. As a result, they focused on the importance of suppressing fluctuations in the raceway contact angle and raceway contact ratio within each raceway groove in a DOJ-type sliding constant velocity universal joint's raceway forging product for maintaining stable coupling function. This invention was achieved through a novel concept based on identifying how fluctuations in the raceway contact angle and raceway contact ratio affect durability and strength and setting internal specifications for the raceway forging product.

[0018] As a technical solution for achieving the above-mentioned purpose, the first invention is a sliding constant velocity universal joint, which includes: an outer coupling member, which has a plurality of linear rolling grooves formed along the axial direction on the cylindrical inner peripheral surface; an inner coupling member, which has a plurality of linear rolling grooves formed along the axial direction on the spherical outer peripheral surface and is opposite to the plurality of linear rolling grooves of the outer coupling member; a plurality of balls, which are assembled between the plurality of linear rolling grooves of the outer coupling member and the plurality of linear rolling grooves of the inner coupling member and transmit torque; and a retainer, which holds the The ball is accommodated in the groove and has a spherical outer peripheral surface and a spherical inner peripheral surface which are contacted and guided by the cylindrical inner peripheral surface of the outer coupling member and the spherical outer peripheral surface of the inner coupling member respectively. The curvature center of the spherical outer peripheral surface of the retaining frame and the curvature center of the spherical inner peripheral surface are offset to opposite sides of the axial direction relative to the coupling center. The sliding constant velocity universal joint is characterized in that the raceway groove of the outer coupling member is composed of a surface that has been finely processed by forging, and the difference between the raceway contact angles of the raceway grooves of the outer coupling member is less than 8°.

[0019] With the above-described structure, a double-offset sliding constant velocity universal joint that maintains strength and durability can be realized at low cost.

[0020] An advantageous feature of the structure is that the raceway grooves of the inner coupling member also have a surface that has been finished by forging, and the difference in raceway contact angle between the raceway grooves of the inner coupling member is also 8° or less. This facilitates the realization of a double-offset sliding constant velocity universal joint that maintains strength and durability at low cost.

[0021] The second invention is a sliding constant velocity universal joint, which includes: an outer coupling member having a plurality of linear rolling grooves formed along the axial direction on a cylindrical inner peripheral surface; an inner coupling member having a plurality of linear rolling grooves formed along the axial direction on a spherical outer peripheral surface, the plurality of linear rolling grooves being opposed to the plurality of linear rolling grooves of the outer coupling member; a plurality of balls assembled between the plurality of linear rolling grooves of the outer coupling member and the plurality of linear rolling grooves of the inner coupling member to transmit torque; and a retainer that accommodates the balls in grooves , and has a spherical outer peripheral surface and a spherical inner peripheral surface that are respectively contacted and guided by the cylindrical inner peripheral surface of the outer coupling member and the spherical outer peripheral surface of the inner coupling member, the curvature center of the spherical outer peripheral surface of the retaining frame and the curvature center of the spherical inner peripheral surface are offset to opposite sides of the axial direction relative to the coupling center, and the sliding constant velocity universal joint is characterized in that the raceway groove of the outer coupling member is composed of a surface that has been finished by forging, and the mutual difference between the raceway grooves of the outer coupling member in the raceway contact rate is less than 0.02.

[0022] With the above-described structure, a double-offset sliding constant velocity universal joint that maintains strength and durability can be realized at low cost.

[0023] An advantageous feature of the structure is that the raceway grooves of the inner coupling member also have a surface that has been finished by forging, and the difference in raceway contact ratio between the raceway grooves of the inner coupling member is also 0.02 or less. This facilitates the realization of a double-offset sliding constant velocity universal joint that maintains strength and durability at low cost.

[0024] The first invention and the second invention are also collectively referred to as the present invention, and the embodiments of the first invention and the second invention described later are used in common as appropriate.

[0025] Specifically, by setting the number of the balls to 5 to 8, a double-offset sliding constant velocity universal joint suitable for power transmission systems of automobiles, various industrial machines, and the like can be constructed.

[0026] Effects of the Invention

[0027] According to the present invention, a double-offset sliding constant velocity universal joint that maintains strength and durability can be realized at low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a longitudinal sectional view of a sliding constant velocity universal joint according to a first embodiment of the present invention, and is Figure 2 A longitudinal cross-sectional view of the BNB line.

[0029] Figure 2 is a cross-sectional view of a sliding constant velocity universal joint according to a first embodiment of the present invention, and is Figure 1 Cross-sectional view of line AA.

[0030] Figure 3 It will Figure 2 An enlarged cross-sectional view of a BN line raceway groove, ball, and cage.

[0031] Figure 4 It shows Figure 2 Schematic diagram of the contact angle between the raceway groove and the ball of the outer coupling component.

[0032] Figure 5 It shows Figure 2 Schematic diagram of the contact angle between the raceway groove and the ball of the outer coupling component.

[0033] Figure 6 This is a schematic diagram showing a method for measuring the contact angle between the raceway groove of the outer joint member and the ball.

[0034] Figure 7 It shows Figure 2 Schematic diagram of the contact ratio between the raceway groove and the ball raceway of the outer coupling component.

[0035] Figure 8 This is a schematic diagram showing a method for calculating the rolling contact ratio between the rolling groove and the ball.

[0036] Figure 9 This is a schematic diagram showing a method for measuring the rolling contact ratio between the rolling grooves of the inner joint member and the balls.

[0037] Figure 10 is a longitudinal sectional view showing a first modified example of the inner assembly of the sliding constant velocity universal joint according to the first embodiment of the present invention, and is Figure 1 A longitudinal cross-sectional view of the BNB line.

[0038] Figure 11 is a longitudinal sectional view showing a second modified example of the inner assembly of the sliding constant velocity universal joint according to the first embodiment of the present invention, and is Figure 1 A longitudinal cross-sectional view of the BNB line.

[0039] Figure 12 yes Figure 11 An enlarged view of part E of FIG.

[0040] Figure 13 is a longitudinal sectional view showing a third modified example of the inner assembly of the sliding constant velocity universal joint according to the first embodiment of the present invention, and is Figure 1 A longitudinal cross-sectional view of the BNB line.

[0041] Figure 14 is a longitudinal sectional view of a sliding constant velocity universal joint according to a second embodiment of the present invention, and is Figure 15 A longitudinal cross-sectional view of the BNB line.

[0042] Figure 15 is a cross-sectional view of a sliding constant velocity universal joint according to a second embodiment of the present invention, and is Figure 14 Cross-sectional view of line AA.

[0043] Description of Reference Numerals

[0044] 1 Sliding constant velocity universal coupling

[0045] 2 Outer coupling member

[0046] 3 Inner coupling member

[0047] 4 balls

[0048] 5 Cage

[0049] 6 Cylindrical inner surface

[0050] 7 Roller groove

[0051] 8 Spherical outer surface

[0052] 9 Roller groove

[0053] 11 Spherical outer surface

[0054] 12 Spherical inner surface

[0055] F offset

[0056] O Coupling Center

[0057] O1 center of curvature

[0058] O2 center of curvature

[0059] R1 ball radius

[0060] R2 Curvature radius of the cross section of the raceway groove

[0061] α raceway contact angle

[0062] φ Raceway contact ratio. DETAILED DESCRIPTION

[0063] based on Figures 1 to 9 A double offset sliding constant velocity universal joint according to a first embodiment of the present invention will be described. Figure 1 is a longitudinal sectional view of the sliding constant velocity universal joint of this embodiment, and is Figure 2 A longitudinal cross-sectional view of the BNB line. Figure 2 is a cross-sectional view of the sliding constant velocity universal joint of this embodiment, and is Figure 1 Cross-sectional view of line AA. Figure 3 It will Figure 2 An enlarged cross-sectional view of a BN line raceway groove, ball, and cage.

[0064] like Figure 1 、 Figure 2As shown, the sliding constant velocity universal joint 1 is a so-called double-offset sliding constant velocity universal joint (sometimes referred to as a DOJ or DOJ-type sliding constant velocity universal joint). Its main components are an outer joint member 2, an inner joint member 3, balls 4 for transmitting torque, and a retainer 5. Six ball bearing grooves 7 are formed on the cylindrical inner circumferential surface 6 of the outer joint member 2, spaced evenly along the circumference and arranged linearly in the axial direction. On the spherical outer circumferential surface 8 of the inner joint member 3, ball bearing grooves 9 are formed at equal intervals along the circumference and arranged linearly in the axial direction, opposing the ball bearing grooves 7 of the outer joint member 2. Six balls 4 are assembled one-to-one between the ball bearing grooves 7 of the outer joint member 2 and the ball bearing grooves 9 of the inner joint member 3. The balls 4 are accommodated in grooves 5a of the retainer 5.

[0065] The retainer 5 has a spherical outer peripheral surface 11 and a spherical inner peripheral surface 12. The spherical outer peripheral surface 11 engages with the cylindrical inner peripheral surface 6 of the outer coupling member 2 for contact guidance, while the spherical inner peripheral surface 12 engages with the spherical outer peripheral surface 8 of the inner coupling member 3 for contact guidance. The spherical outer peripheral surface 11 of the retainer 5 is formed with a curvature radius Rc1 with the center of curvature set to O1, and the spherical inner peripheral surface 12 is formed with a curvature radius Rc2 with the center of curvature set to O2. The spherical outer peripheral surface 8 of the inner coupling member 3 is formed with a curvature radius Ri with the center of curvature set to O2. The centers of curvature O1 and O2 are located on the axis N and are offset by an equal distance F in opposite axial directions relative to the coupling center O. Thus, when the coupling takes the operating angle, the balls 4 are always guided on a plane bisecting the angle formed by the axes of the outer coupling member 2 and the inner coupling member 3, and are rotated at a constant speed between the two axes.

[0066] A retaining ring groove 15 is provided at the open end of the outer coupling member 2, and a retaining ring 17 is mounted in the retaining ring groove 15 to prevent the outer coupling member 2 from being loosened. Figure 1 The inner assembly 1 including the inner coupling member 3, the balls 4, and the retainer 5 is shown as being released from the open end of the outer coupling member 2. A shield mounting groove 16 is provided on the outer periphery of the open end of the outer coupling member 2. The rod portion (shaft portion) 2b is integrally formed on the opposite side of the open end of the outer coupling member 2 (see FIG. Figure 14 ), and is connected to a differential (not shown).

[0067] The inner coupling member 3 has linear raceway grooves 9 formed on its spherical outer peripheral surface 8. The depth of the raceway grooves 9 decreases as it moves from the axial center toward the ends of the inner coupling member 3. A spline (including serrations, the same applies hereinafter) 14 is formed in the connecting hole 13 of the inner coupling member 3. The shaft end of an intermediate shaft (not shown) is splined and engaged with the spline, and the intermediate shaft is axially fixed to the inner coupling member 3 via an intermediate shaft shoulder and a retaining ring (not shown).

[0068] exist Figure 1 The axial center of the retainer 5 shown by the line AA is provided with six grooves 5a at equal intervals along the circumferential direction, and the adjacent grooves 5a form a column portion 5b (refer to Figure 2 ). A notch portion 5c for assembling the inner coupling member 3 is provided on the inner periphery of the large diameter side end portion of the retainer 5. The limiting surface 5d of the retainer 5 is formed into a conical shape connected to the spherical outer peripheral surface 11 as a tangent. In the sliding constant velocity universal joint 1 of the present embodiment, the maximum working angle is set to 25°, for example. When the coupling takes a working angle, the retainer 5 is tilted by half the angle formed by the two axes of the outer coupling member 2 and the inner coupling member 3, so the inclination angle S of the limiting surface 5d is set to 12.5°. In this way, the maximum allowable angle of the sliding constant velocity universal joint 1 can be limited.

[0069] based on Figure 3 Next, the contact state between the ball rolling groove 7 of the outer joint member 2, the ball rolling groove 9 of the inner joint member 3, and the ball 4 will be described. Figure 3 Show Figure 2 A raceway groove 7, 9, a ball 4 and a cage 5 of the BN line.

[0070] like Figure 3 As shown, the cross-sections of the raceway grooves 7 of the outer coupling member 2 and the raceway grooves 9 of the inner coupling member 3 are formed into an apex shape formed by combining two circular arcs. Therefore, the balls 4 make angular contact with the raceway grooves 7 and 9 at two points, C1, C2, C3, and C4, respectively. The cross-sectional shape of the raceway grooves 7 and 9 is not limited to the aforementioned apex shape; an elliptical shape is also acceptable.

[0071] The raceway grooves 7 and 9 contact the balls 4 at a raceway contact angle α. The raceway contact angle α is Figure 3 The angle α formed by the straight line La and the straight line Lb. The straight line La is the center line of the cross section of the raceway grooves 7 and 9 and is aligned with Figure 2 The straight line Lb connects the contact points C1, C2, C3, and C4 of the ball 4 on the side surfaces of the raceway grooves 7 and 9 with the center Ob of the ball 4. The raceway contact angles used in this specification and the patented technical solution have the aforementioned meaning. The radius of curvature of the cross section of the raceway grooves 7 and 9 is R2, and the radius of the ball 4 is R1. The raceway contact ratio φ is the ratio R2 / R1. The raceway contact ratios used in this specification and the patented technical solution have the aforementioned meaning.

[0072] The overall structure of the double offset sliding constant velocity universal joint 1 of this embodiment is as described above. Next, the characteristic structure will be described.

[0073] <Characteristic Structure of the First Invention>

[0074] (1) In a double offset sliding constant velocity universal joint, the raceway grooves of the outer joint member are formed of a surface finished by forging, and the difference in raceway contact angle between the raceway grooves of the outer joint member is 8° or less.

[0075] As an advantageous configuration, the raceway grooves of the inner joint member also have surfaces finished by forging, and the difference in raceway contact angle between the raceway grooves of the inner joint member is also 8° or less.

[0076] <Characteristic Structure of the Second Invention>

[0077] (2) In a double offset sliding constant velocity universal joint, the raceway grooves of the outer joint member are formed of a surface finished by forging, and the difference in raceway contact ratio between the raceway grooves of the outer joint member is 0.02 or less.

[0078] As an advantageous configuration, the raceway grooves of the inner joint member also have surfaces finished by forging, and the difference in raceway contact ratio between the raceway grooves of the inner joint member is also 0.02 or less.

[0079] By the characteristic structure (1) of the first invention and the characteristic structure (2) of the second invention, a DOJ type sliding constant velocity universal joint that maintains strength and durability at low cost can be realized.

[0080] The characteristic structure (1) of the first invention and the characteristic structure (2) of the second invention were achieved through the following research process. That is, the present inventors focused on the fact that suppressing the fluctuation of the raceway contact angle and the raceway contact rate in each raceway groove in the raceway forging finished product of the DOJ type sliding constant velocity universal joint is important for stabilizing the function of the joint. By finding out the influence of the fluctuation of the raceway contact angle and the raceway contact rate on the durability and strength and setting the internal specifications of the raceway forging finished product, the present inventors achieved the characteristic structures (1) and (2) mentioned above.

[0081] The impact of fluctuations in the raceway contact angle and raceway contact ratio on durability and strength was studied. Sliding constant velocity universal joints are sized based on load capacity, and a 1-inch difference in size results in approximately a 5% difference in raceway surface pressure.

[0082] <Raceway contact angle>

[0083] When the raceway contact angle between the raceway grooves of a sliding constant velocity universal joint fluctuates by ±4°, the raceway surface pressure fluctuates by approximately ±4%. It was discovered that when the raceway contact angle fluctuates by more than ±4%, a sliding constant velocity universal joint of one size larger must be used. Thus, as a characteristic structure (1) of the first invention, it was derived that the difference in the raceway contact angle between the raceway grooves of the outer coupling member is 8° or less, and as an advantageous structure, it was derived that the difference in the raceway contact angle between the raceway grooves of the inner coupling member is also 8° or less.

[0084] <Raceway contact ratio>

[0085] When the raceway contact ratio between the raceway grooves of a sliding constant velocity universal joint fluctuates by ±0.01, the raceway surface pressure fluctuates by approximately ±3%. It was discovered that when the raceway contact ratio fluctuates by more than ±3%, a sliding constant velocity universal joint of one size larger must be used. Thus, as a characteristic feature (2) of the second invention, it was derived that the difference between the raceway contact ratios of the outer coupling member and the raceway grooves is 0.02 or less, and as an advantageous feature, it was derived that the difference between the raceway contact angles of the inner coupling member and the raceway grooves is also 0.02 or less.

[0086] In addition, in the raceway forging finished product of the DOJ type sliding constant velocity universal joint, the following technical solution was created to realize the above structure in order to suppress the mutual difference between the raceway grooves in the raceway contact angle to less than 8° and the mutual difference between the raceway grooves in the raceway contact rate to less than 0.02.

[0087] (1) As a forming method, cold forging using a high-precision die is performed to achieve high precision and stability of the formed product.

[0088] (2) As a heat treatment method, high-frequency soaking heating using rotational heating of the workpiece is performed to suppress heat treatment deformation.

[0089] Regarding the characteristic structure (1) of the first invention, based on Figures 4 to 6 Let’s explain in detail. Figure 4 as well as Figure 5 It shows Figure 2 Schematic diagram showing the contact angle between the raceway groove of the outer coupling member and the ball. Figure 6 This is a schematic diagram showing a method for measuring the contact angle between the raceway groove of the outer joint member and the ball.

[0090] The raceway grooves 7 of the outer coupling member 2 and the raceway grooves 9 of the inner coupling member 3, components of the double-offset sliding constant velocity universal joint 1, are typically finished by cold forging (without finishing by grinding or other processes after quenching). In other words, the raceway grooves 7 and 9 have surfaces that have been finished by forging. The term "surfaces that have been finished by forging" is used in this specification and patent application.

[0091] Next, regarding the fluctuation of the contact angle between the raceway groove and the ball, based on Figure 4 、 Figure 5 The following description will be given using the outer coupling member as an example. Figure 4 The sliding constant velocity universal joint 1 of this embodiment is illustrated with an exaggerated fluctuation in the contact angle α between the raceway grooves 7 of the outer joint member 2 and the balls 4. Figure 4 The position of the vertex is set to phase angle β = 0°, and the rolling groove 7 with phase angle β = 0° is set as rolling groove 7 (1). Rotating left (counterclockwise) from rolling groove 7 (1), rolling groove 7 (2) with phase angle β = 60°, rolling groove 7 (3) with phase angle β = 120°, rolling groove 7 (4) with phase angle β = 180°, rolling groove 7 (5) with phase angle β = 240°, and rolling groove 7 (6) with phase angle β = 300° are set.

[0092] When a torque is applied from the inner coupling member (not shown) in the direction of rotation indicated by the hollow arrow, Figure 4 As shown, the contact angle of the raceway of the raceway groove 7 (1) is extremely small at α (1), while the contact angle of the raceway of the raceway groove 7 (4) is relatively large at α (4). The smaller the raceway contact angle, the greater the surface pressure of the raceway groove, and the larger the raceway contact angle, the smaller the surface pressure of the raceway groove. Therefore, the surface pressure of the raceway groove 7 (1) increases, and the life becomes shorter, while the surface pressure of the raceway groove 7 (4) decreases, and the life becomes longer. However, as for the life of the coupling, it is determined by the life of the raceway groove 7 (1) where the surface pressure increases the most, and thus the life becomes shorter.

[0093] The raceway contact angles α(2), α(3), α(5), and α(6) of the remaining raceway grooves 7(2), 7(3), 7(5), and 7(6) are intermediate between the raceway contact angle α(1) of the aforementioned raceway groove 7(1) and the raceway contact angle α(4) of the raceway groove 7(4), and the values ​​of the raceway contact angles α(2), α(3), α(5), and α(6) are also approximately the same.

[0094] Here, the difference between the rolling contact angles α between the rolling grooves 7 is defined. The difference between the rolling contact angles α between the rolling grooves 7 is Figure 4The difference between the maximum value of the raceway contact angle α (4) and the minimum value of the raceway contact angle α (1) is shown. The difference between the raceway contact angles of the raceway grooves in this specification and the patent technical solution has the above meaning. Although omitted from the figure, the difference between the raceway contact angles α of the raceway grooves 9 of the inner coupling member 3 is also the same.

[0095] exist Figure 4 In the figure, the differences between the raceway contact angles α of the outer joint member 2 are exaggerated for ease of understanding. In this embodiment, even if the raceway contact angle α of the outer joint member 2 fluctuates, the differences between the raceway contact angles α of the outer joint member 2 are suppressed to 8° or less. Similarly, even if the raceway contact angle α of the inner joint member 2 fluctuates, the differences between the raceway contact angles α of the inner joint member 3 are suppressed to 8° or less.

[0096] Figure 5 The figure shows a case where the difference between the contact angles α between the raceway grooves 7 of the outer joint member 2 and the balls 4 is small. Figure 5 The reference numerals for the phase angle β, the raceway groove 7, and the raceway contact angle α are given in the same manner as Figure 4 The contact angles are approximately the same in all the raceway grooves 7, so the surface pressures in the raceway grooves 7 are approximately the same, resulting in no difference in lifespan between the raceway grooves 7 and satisfactory durability. In this case, the raceway contact angles α of the outer coupling member 2 naturally differ by 8° or less between the raceway grooves 7.

[0097] Next, based on Figure 6 The method for measuring the contact angle α of the rolling groove 7 and the ball 4 is described using the case of the outer coupling member 7. A coating material (e.g., brightener) for contact inspection is applied to the entire area of ​​the rolling groove 7. Thereafter, the reference ball 4 is pressed against the rolling groove 7 and dragged over the entire area of ​​the rolling groove 7. As a result, the brightener of the contact portion between the rolling groove 7 and the ball 4 is peeled off. The length L between the ball contact tracks is measured using a vernier caliper, etc., and the contact angle α is calculated using the formula (1) described later. Although the case of the outer coupling member 2 is shown in the figure, the measurement method for the inner coupling member 3 is the same.

[0098]

Mathematical formula 1

[0099]

[0100] Next, based on Figures 7 to 9 The characteristic structure (2) of the second invention will be described in detail. Figure 7 It shows Figure 2Schematic diagram of the fluctuation state of the raceway contact ratio between the raceway groove and the ball of the outer coupling member. Figure 8 This is a schematic diagram showing a method for calculating the rolling contact ratio between the rolling groove and the ball. Figure 9 This is a schematic diagram showing a method for measuring the raceway contact ratio of the inner joint member.

[0101] based on Figure 7 The fluctuation in the rolling contact ratio between the rolling groove and the ball will be described. Figure 7 The fluctuation of the raceway contact ratio φ between the raceway groove 7 of the outer joint member 2 and the ball 4 is exaggerated in the figure. Figure 4 Likewise, Figure 7 The position of the vertex is set to phase angle β = 0°, and the rolling groove 7 with phase angle β = 0° is set as rolling groove 7 (1). The rolling groove 7 (2) with phase angle β = 60°, the rolling groove 7 (3) with phase angle β = 120°, the rolling groove 7 (4) with phase angle β = 180°, the rolling groove 7 (5) with phase angle β = 240°, and the rolling groove 7 (6) with phase angle β = 300° are set.

[0102] The raceway contact ratio φ is the ratio R2 / R1 of the curvature radius R2 of the cross section of the raceway groove 7 to the radius R1 of the ball 4 (see Figure 3 ).exist Figure 7 Among them, the rolling contact rate φ(1) of the rolling groove 7(1) is large, and the rolling contact rate φ(4) of the rolling groove 7(4) is small. As for the rolling contact rates φ(2), φ(3), φ(5), and φ(6) of the remaining rolling grooves 7(2), 7(3), 7(5), and 7(6), they are intermediate between the rolling contact rate angle φ(1) of the rolling groove 7(1) and the rolling contact rate φ(4) of the rolling groove 7(4), and the values ​​of the rolling contact angles φ(2), φ(3), φ(5), and α(6) are also approximately the same.

[0103] When a torque is applied from the inner coupling member (not shown) in the direction of rotation indicated by the hollow arrow, Figure 7 In the case of the rolling groove 7 (1), the rolling contact rate of the rolling groove 7 (1) is the largest at φ (1), while the rolling contact rate of the rolling groove 7 (4) is the smallest at φ (4). As for the contact between the ball and the rolling groove, when the rolling contact rate is large, the contact ellipse becomes smaller and the surface pressure becomes higher, but it is advantageous in terms of the contact ellipse climbing up to the end of the rolling groove. On the contrary, when the rolling contact rate is small, the contact ellipse becomes larger and the surface pressure becomes lower, but it is disadvantageous in terms of the contact ellipse climbing up to the end of the rolling groove. Therefore, in the rolling groove 7 (1), the surface pressure becomes higher, but it is advantageous in terms of climbing up, while in the rolling groove 7 (4), the surface pressure decreases, but it is disadvantageous in terms of climbing up. However, in order to ensure the life of the coupling, there is an allowable range for both the surface pressure and the climbing up, and in order to stabilize the life of the coupling, it is necessary to suppress the fluctuation of the rolling contact rate φ.

[0104] Here, the difference between the rolling contact ratio φ between the rolling grooves 7 is defined. The difference between the rolling contact angle φ between the rolling grooves 7 is Figure 7 The difference between the maximum value of the raceway contact ratio φ (1) and the minimum value of the raceway contact ratio φ (4) is shown. The difference between the raceway contact ratios of the raceway grooves in this specification and the patented technical solution has the above-mentioned meaning. Although omitted from the illustration, the difference between the raceway contact ratios φ of the raceway grooves 9 of the inner coupling member 3 is also the same.

[0105] In addition, Figure 7 In the figure, the difference between the raceway contact ratio φ of the outer joint member 2 is exaggerated for ease of understanding. In this embodiment, the difference between the raceway contact ratio φ of the outer joint member 2 and the raceway grooves 7 is suppressed to 0.02 or less, and the difference between the raceway contact ratio φ of the inner joint member 3 and the raceway grooves 9 is also suppressed to 0.02 or less.

[0106] Next, based on Figure 8 、 Figure 9 The calculation method and measurement method of the rolling contact ratio between the rolling groove and the ball are explained below. The rolling contact ratio φ is the ratio R2 / R1 of the curvature radius R2 of the cross section of the rolling groove 7, 9 to the radius R1 of the ball 4. Figure 8 As shown, the curvature radius R2 of the cross section of the raceway grooves 7 and 9 can be expressed as the radius R1 of the reference ball × the raceway contact ratio φ. The raceway grooves 7 and 9 contact the ball 4 at a raceway contact angle α. A vertex gap Vc is provided at the groove bottom of the raceway grooves 7 and 9.

[0107] based on Figure 9 The following describes the method for measuring the raceway contact ratio φ. Figure 9 The inner coupling member 3 is shown. The measuring device 20 for measuring the raceway contact ratio φ mainly comprises a reference ball 21, a measuring pin 22, a pressing member 23, and a dial indicator 24. The measuring pin 22 is slidably inserted into the through-hole in the center of the reference ball 21, with the tip of the measuring pin 22 protruding from the through-hole. The base 22a of the measuring pin 22 is guided by the pressing member 23, and the tip abuts the dial indicator 24. The reference ball 21 is mounted on the pressing member 23.

[0108] When the reference ball 21 and the measuring pin 22 of the measuring device 20 are pressed against the raceway groove 9, the measuring pin 22 descends, and the amount of descent of the measuring pin 22 is read using the dial gauge 24. This gives the vertex clearance Vc, and the raceway contact ratio φ is calculated using the calculation described below.

[0109]

Mathematical formula 2

[0110]

[0111] based on Figure 10 A first variation of the inner assembly of the sliding constant velocity universal joint according to the first embodiment of the present invention will be described. The inner assembly of this variation differs from the first embodiment in that a positive axial clearance is provided between the retainer grooves and the balls. The remaining structure is the same as the first embodiment, so parts with the same functions are denoted by the same reference numerals, and only the key points will be described.

[0112] Figure 10 1 is a longitudinal sectional view of a first modified example of the inner assembly I of the sliding constant velocity universal joint of the first embodiment. Figure 10 As shown, the inner assembly I includes the inner coupling member 3, the retainer 5, and the ball 4. A positive axial clearance δ2 is formed between the wall 5d of the groove 5a of the retainer 5 that is opposite in the axial direction of the coupling and the ball 4. When the diameter of the ball 4 is set to D BALL When the width between the wall surfaces 5d of the groove 5a of the retainer 5 facing each other in the axial direction of the coupling is Lw, the axial gap δ2 becomes δ2=Lw-D BALL , is about +0.001mm~+0.050mm. Thus, the ball 4 can roll smoothly in the groove 5a, achieving a reduction in sliding resistance.

[0113] based on Figure 11 、 Figure 12 The following describes a second variation of the inner assembly of the sliding constant velocity universal joint of the first embodiment of the present invention. The inner assembly of this variation differs from the first embodiment in that a positive axial clearance is provided between the retainer grooves and the balls, and an axial clearance is provided that enables axial relative movement between the inner coupling member and the retainer. The remaining structure is identical to the first embodiment, so components with the same functions are designated by the same reference numerals, and only the key points will be described.

[0114] Figure 11 1 is a longitudinal sectional view of a second modified example of the inner assembly of the sliding constant velocity universal joint of the first embodiment. Figure 12 yes Figure 11 An enlarged view of part E. Figure 11As shown, the inner assembly I comprises an inner coupling member 3, a retainer 5, and balls 4. A positive axial clearance δ2 is formed between the axially opposing walls 5d of the retainer 5's groove 5a and the balls 4. The retainer 5's spherical outer peripheral surface 11 is formed with a curvature radius Rc1, with the center of curvature being Oc1, and the spherical inner peripheral surface 12 is formed with a curvature radius Rc2, with the center of curvature being Oc2. The inner coupling member 3's spherical outer peripheral surface 8 is formed with a curvature radius Ri, with the center of curvature being Oi2. The centers of curvature Oc1 and Oi2 are located on the axis N and are offset axially by an equal distance F from the coupling center O. Furthermore, the center of curvature Oc2 of the retainer 5's spherical inner peripheral surface 12 is radially offset from the axis N relative to the center of curvature Oi2, such that Rc2 > Ri, and is axially offset by a distance F from the coupling center O.

[0115] like Figure 12 As shown, a spherical clearance δ3 is formed in the axial center of the spherical outer peripheral surface 8 of the inner coupling member 3, which can contact and guide the spherical inner peripheral surface 12 of the retaining frame 5. An axial clearance δ4 is formed on both sides of the center to enable axial relative movement of the inner coupling member 3 and the retaining frame 5. The median value of the spherical clearance δ3 is approximately 0.050 mm. The axial clearance δ4 is approximately 1 mm. The axial movable amount of the inner coupling member 3 relative to the outer coupling member 2 is approximately 2 mm, which is approximately twice the 1 mm of the axial clearance δ4. Vibration is absorbed within this range of axial movable amount. In other words, it is possible to reduce sliding resistance relative to general vibration conditions. The spherical clearance δ3 and the axial clearance δ4 are shown in exaggerated form.

[0116] The axial gap δ4 between the retainer 5 and the inner joint member 3 and the positive axial gap δ2 between the axially opposing wall surfaces 5d of the groove 5a of the retainer 5 and the balls 4 combine to reduce sliding resistance.

[0117] based on Figure 13 Next, a third variation of the inner assembly of the sliding constant velocity universal joint according to the first embodiment of the present invention will be described. The shape of the spherical inner circumferential surface of the retainer of the inner assembly of this variation differs from that of the second variation. The remaining structure is the same as that of the first and second variations, so parts with the same functions are denoted by the same reference numerals, and only the key points will be described.

[0118] Figure 13 1 is a longitudinal sectional view of a third modified example of the inner assembly of the sliding constant velocity universal joint of the first embodiment. Figure 13As shown, the spherical inner peripheral surface 12 of the retainer 5 is composed of a spherical portion 12a with a curvature radius Rc2 and a curvature center Oc2, a spherical portion 12b with a curvature radius Rc2 and a curvature center Oc3, and a cylindrical portion 12c connected by a tangent line between the spherical portion 12a and the spherical portion 12b. The curvature center Oc2 and the curvature center Oc3 are located on the axis N, and the axial center point of the curvature center Oc2 and the curvature center Oc3 is offset by F relative to the coupling center O. The spherical outer peripheral surface 8 of the inner coupling member 3 is formed by a curvature radius Ri with a curvature center Oi2. Figure 13 In the arranged state, the axial center point of the curvature center Oc2 and the curvature center Oc3 of the spherical inner peripheral surface 12 of the retainer 5 coincides with the curvature center Oi2 of the spherical outer peripheral surface 8 of the inner joint member 3 .

[0119] A spherical gap δ3 is formed in the axial center of the spherical outer peripheral surface 8 of the inner coupling member 3, allowing contact and guidance with the cylindrical portion 12c of the retainer 5. Axial gaps δ4 are formed on either side of the center to enable axial relative movement between the inner coupling member 3 and the retainer 5. The length of the cylindrical portion 12c is approximately 1 mm, and the axial gap δ4 corresponds to the length of the cylindrical portion 12c. The axial movable range of the inner coupling member 3 relative to the outer coupling member 2 is approximately 2 mm, which is twice the length of the cylindrical portion 12c, approximately 1 mm. Vibration is absorbed within this axial movable range. In other words, sliding resistance can be reduced under common vibration conditions.

[0120] In this modified example, the spherical inner circumferential surface 12 of the retainer 5 is composed of a spherical portion 12a having a radius of curvature Rc2 with a center of curvature at Oc2, a spherical portion 12b having a radius of curvature Rc2 with a center of curvature at Oc3, and a cylindrical portion 12c connecting the spherical portion 12a and the spherical portion 12b by a tangent line. The radius of curvature Rc2 is substantially the same as the radius of curvature Ri, ensuring smooth and stable contact and guidance between the spherical inner circumferential surface 12 of the retainer 5 and the spherical outer circumferential surface 8 of the inner joint member 3. Similar to the first and second modified examples, a positive axial clearance δ2 is formed between the wall surfaces 5d of the groove 5a of the retainer 5, which oppose each other in the coupling axial direction, and the ball 4.

[0121] In the double-offset sliding constant velocity universal joint 1 including the inner assembly of the first to third modified examples, similarly to the double-offset sliding constant velocity universal joint 1 of the aforementioned first embodiment, it has the characteristic structure (1) of the first invention and the characteristic structure (2) of the second invention as shown below.

[0122] <Characteristic Structure of the First Invention>

[0123] (1) In a double offset sliding constant velocity universal joint, the raceway grooves of the outer joint member are formed of a surface finished by forging, and the difference in raceway contact angle between the raceway grooves of the outer joint member is 8° or less.

[0124] As an advantageous configuration, the raceway grooves of the inner joint member also have surfaces finished by forging, and the difference in raceway contact angle between the raceway grooves of the inner joint member is also 8° or less.

[0125] <Characteristic Structure of the Second Invention>

[0126] (2) In a double offset sliding constant velocity universal joint, the raceway grooves of the outer joint member are formed of a surface finished by forging, and the difference in raceway contact ratio between the raceway grooves of the outer joint member is 0.02 or less.

[0127] As an advantageous configuration, the raceway grooves of the inner joint member also have surfaces finished by forging, and the difference in raceway contact ratio between the raceway grooves of the inner joint member is also 0.02 or less.

[0128] By the characteristic structure (1) of the first invention and the characteristic structure (2) of the second invention, a DOJ type sliding constant velocity universal joint that maintains strength and durability at low cost can be realized. The characteristic structures (1) and (2) described in the double offset sliding constant velocity universal joint 1 of the first embodiment are the same as those described in the double offset sliding constant velocity universal joint 1 of the inner assembly of the first to third modified examples and can therefore also be applied.

[0129] based on Figure 14 、 Figure 15 The following describes a sliding constant velocity universal joint according to a second embodiment of the present invention. The double-offset sliding constant velocity universal joint of this embodiment has eight balls, which differs from the sliding constant velocity universal joint of the first embodiment. The remaining structure is the same as that of the first embodiment, so parts with the same functions are denoted by the same reference numerals, and only the key points will be described. Figure 14 is a longitudinal sectional view of the sliding constant velocity universal joint of this embodiment, and is Figure 15 A longitudinal cross-sectional view of the BNB line. Figure 15 is a cross-sectional view of the sliding constant velocity universal joint of this embodiment, and is Figure 14 Cross-sectional view of line AA.

[0130] like Figure 14 、 Figure 15As shown, the double-offset sliding constant velocity universal joint 1 of this embodiment has eight ball bearing grooves 7 formed on the cylindrical inner circumferential surface 6 of the outer joint member 2 at equal intervals along the circumferential direction and in a straight line along the axial direction. Ball bearing grooves 9 are formed on the spherical outer circumferential surface 8 of the inner joint member 3 at equal intervals along the circumferential direction and in a straight line along the axial direction, opposing the ball bearing grooves 7 of the outer joint member 2. Eight balls 4 are assembled one-to-one between the ball bearing grooves 7 of the outer joint member 2 and the ball bearing grooves 9 of the inner joint member 3.

[0131] The retainer 5 has a spherical outer peripheral surface 11 and a spherical inner peripheral surface 12. The spherical outer peripheral surface 11 engages with the cylindrical inner peripheral surface 6 of the outer coupling member 2 for contact guidance, while the spherical inner peripheral surface 12 engages with the spherical outer peripheral surface 8 of the inner coupling member 3 for contact guidance. The spherical outer peripheral surface 11 of the retainer 5 is formed with a curvature radius Rc1 with the center of curvature set to O1, and the spherical inner peripheral surface 12 is formed with a curvature radius Rc2 with the center of curvature set to O2. The spherical outer peripheral surface 8 of the inner coupling member 3 is formed with a curvature radius Ri with the center of curvature set to O2. The centers of curvature O1 and O2 are located on the axis N and are offset equidistantly in opposite directions in the axial direction relative to the coupling center O. Thus, when the coupling takes the operating angle, the balls 4 are always guided on a plane bisecting the angle formed by the axes of the outer coupling member 2 and the inner coupling member 3, and are rotated at a constant speed between the two axes.

[0132] The double offset sliding constant velocity universal joint 1 of this embodiment also has the characteristic structure (1) of the first invention and the characteristic structure (2) of the second invention as shown below, similarly to the double offset sliding constant velocity universal joint 1 of the first embodiment.

[0133] <Characteristic Structure of the First Invention>

[0134] (1) In a double offset sliding constant velocity universal joint, the raceway grooves of the outer joint member are formed of a surface finished by forging, and the difference in raceway contact angle between the raceway grooves of the outer joint member is 8° or less.

[0135] As an advantageous configuration, the raceway grooves of the inner joint member also have surfaces finished by forging, and the difference in raceway contact angle between the raceway grooves of the inner joint member is also 8° or less.

[0136] <Characteristic Structure of the Second Invention>

[0137] (2) In a double offset sliding constant velocity universal joint, the raceway grooves of the outer joint member are formed of a surface finished by forging, and the difference in raceway contact ratio between the raceway grooves of the outer joint member is 0.02 or less.

[0138] As an advantageous configuration, the raceway grooves of the inner joint member also have surfaces finished by forging, and the difference in raceway contact ratio between the raceway grooves of the inner joint member is also 0.02 or less.

[0139] By the characteristic structure (1) of the first invention and the characteristic structure (2) of the second invention, a DOJ type sliding constant velocity universal joint that maintains strength and durability at low cost can be realized. The characteristic structures (1) and (2) described in the double offset sliding constant velocity universal joint 1 of the first embodiment are the same as those described in the double offset sliding constant velocity universal joint 1 of the present embodiment and can also be applied.

[0140] The present invention is not limited to the aforementioned embodiments and modifications, and can of course be implemented in various ways without departing from the spirit of the present invention. The scope of the present invention is shown by the patent technical solution, and also includes the equivalent meanings and all changes within the scope recorded in the patent technical solution.

Claims

1. A sliding constant velocity universal coupling comprising: The outer ring of the wheel shaft is annularly fixed to the outer ring of the wheel shaft, and the inner ring of the wheel shaft is provided with an axially extending inner ring of the wheel shaft, and the axially extending inner ring of the wheel shaft is provided with an axially extending inner ring of the wheel shaft, and the axially extending inner ring of the wheel shaft is provided with an axially extending outer ring of the wheel shaft, and the axially extending inner ring of the wheel shaft is provided with an axially extending inner ... The sliding constant velocity universal joint is characterized in that: The raceway grooves of the outer joint member are formed of surfaces finished by forging, and the difference in raceway contact angles between the raceway grooves of the outer joint member is 8° or less.

2. The sliding constant velocity universal joint according to claim 1, characterized in that: The raceway grooves of the inner joint member also have surfaces that have been finished by forging, and the difference in raceway contact angles between the raceway grooves of the inner joint member is also 8° or less.

3. A sliding constant velocity universal coupling comprising: The outer ring of the wheel shaft is annularly fixed to the outer ring of the wheel shaft, and the inner ring of the wheel shaft is provided with an axially extending inner ring of the wheel shaft, and the axially extending inner ring of the wheel shaft is provided with an axially extending inner ring of the wheel shaft, and the axially extending inner ring of the wheel shaft is provided with an axially extending outer ring of the wheel shaft, and the axially extending inner ring of the wheel shaft is provided with an axially extending inner ... The sliding constant velocity universal joint is characterized in that: The raceway grooves of the outer joint member are formed of surfaces finished by forging, and a difference in raceway contact ratio between the raceway grooves of the outer joint member is 0.02 or less.

4. The sliding constant velocity universal joint according to claim 3, characterized in that: The raceway grooves of the inner joint member also have surfaces that have been finished by forging, and the difference in raceway contact ratio between the raceway grooves of the inner joint member is also 0.02 or less.

5. The sliding constant velocity universal joint according to any one of claims 1 to 4, characterized in that: The number of the balls is 5 to 8.

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