Tripod joint and inner joint portion of tripod joint

Abstract

The present invention relates to a tripod joint (1). The tripod joint (1) comprises at least an outer joint portion (2), an inner joint portion (3), and a plurality of rotating bodies (4). The outer joint portion (2) has a receiving portion (6) for the inner joint portion (3) extending along a first rotation axis (5), and three raceways (9) extending along the first rotation axis (5) and distributed in the circumferential direction (7, 8). The inner joint portion (3) has a central body (11) extending along a second rotation axis (10), and three journals (14) extending from the central body (11) along the radial direction (12). Each journal has a journal axis (13) and is distributed in the circumferential direction (7, 8). One of the plurality of rotating bodies (4) is disposed on each of the journals (14), and the rotating body (4) contacts the journal (14) with an inner circumferential surface (15) and contacts each raceway (9) with an outer circumferential surface (16). The present invention further relates to the inner joint portion (3).

Description

Technical Field

[0001] The present invention relates to a tripod joint and an inner joint portion of a tripod joint, particularly to the inner joint portion of the described tripod joint.

Background Art

[0002] A tripod joint generally includes at least an outer joint portion having a first rotation axis and an inner joint portion having a second rotation axis. The inner joint portion includes a central body having three integrally formed journals. A rotating body is disposed on each journal. In particular, the inner joint portion can move relative to the outer joint portion along the first rotation axis. Further, the inner joint portion can tilt relative to the outer joint portion, i.e., the first rotation axis and the second rotation axis can be arranged relative to each other at a so-called bending angle.

[0003] This type of joint is known, for example, from Patent Document 1. The outer joint portion has a longitudinal axis (first rotation axis) and a cavity (receptacle) that extends along the longitudinal axis and has at least one open end, and three recesses (raceways) that extend parallel to the longitudinal axis are formed in the outer joint portion. The inner joint portion has a (different) longitudinal axis (second rotation axis) and a central body on which three journals are formed. Each journal has a journal axis that extends radially from the longitudinal axis. A rotating body is disposed on each journal. The rotating bodies are respectively received in the recesses of the outer joint portion and move longitudinally. The rotating bodies can be disposed on the journals via a bearing body (rolling element) or via a further inner ring. In particular, the rotating body has at least one outer ring and a bearing body, and may optionally have an inner ring, whereby the bearing body is disposed between the outer ring and the inner ring.

[0004] Tripod joints have been manufactured and sold by the applicant for a long time under the name of, for example, AAR tripod joints. These tripod joints are used for the side shafts of automobiles and, in particular, serve as a drive connection between the differential gear and the drive wheel. On the wheel side, a so-called constant velocity ball joint is usually used, and the AAR tripod joint mentioned here is used as a sliding joint arranged adjacent to the differential gear. The AAR tripod joint is designed in particular for bending angles on the order of 23 to 26° (or less).

[0005] The journal contacts each support body or the inner ring of the rotating body via a so-called sliding surface (contact surface). Each sliding surface is designed in the shape of a spherical segment in particular. These sliding surfaces are aligned in the circumferential direction, and the torque acting around the plurality of longitudinal axes of the joint is transmitted from the journal to the rotating body via each sliding surface of the journal and then from the rotating body to the recess (or vice versa).

[0006] In the traction operation of an automobile, i.e., when the automobile is driven by a drive unit, the journal contacts one sliding surface of the rotating body, and the rotating body contacts only one side of the recess in particular. In the engine braking state or when the automobile is in a coasting state, i.e., when the driving torque from the wheel is introduced and the drive unit is still connected (engine braking state) or disconnected (coasting state), the journal contacts the other sliding surface of the rotating body, and the rotating body contacts only the opposite side of the recess. In the engine braking state or coasting state, the direction of the applied torque and the direction of rotation of the joint are opposite to each other, and in the traction state, they are in the same direction.

[0007] In order to achieve particularly advantageous guiding characteristics, an offset is provided between the first pitch radius of the sliding surface of each journal and the second pitch radius of each recess.

[0008] The pitch radius of each journal is the so-called effective radius. This is defined for an extended (unbent) joint, i.e., when each longitudinal axis or each rotational axis is arranged coaxially with respect to each other. The effective radius determines the lever arm of the resultant force when torque is transmitted. Therefore, the pitch circle radius of each journal is the radius starting from the longitudinal axis of the inner joint part. For example, when the joint is extended, the center of each sliding surface of the spherical base of the journal is arranged on this radius.

[0009] The pitch radius of the outer joint part or the recess is also the so-called effective radius. This is defined for an extended joint, i.e., when each longitudinal axis or each rotational axis is arranged coaxially with respect to each other. The effective radius determines the lever arm of the resultant force when torque is transmitted.

[0010] The definition of the pitch circle radius (also known as Pitch Circle Radius (PCR)) is generally known, especially for tripod joints.

[0011] Therefore, the offset of each pitch circle radius is the difference between these pitch circle radii.

[0012] Also, the characteristics of the tripod joint are determined, in particular, by the so-called ACFG value (Axial Cyclic Force Generation, the unwanted axial force generated by the joint). This value is given as the root mean square value of the force, and the unit is Newton root mean square value [Nrms]. The value varies as a function of the bending angle of the joint, and thus the transition of the value can be defined or determined for each joint as a function of the bending angle. The range in which the joint is used is thus limited by the maximum bending angle. At this maximum bending angle, the ACFG value does not exceed an amount considered acceptable.

Prior Art Documents

Patent Documents

[0013]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0014] The object of the present invention is to at least partially solve the problems described in relation to the prior art. In particular, a tripod type joint or an inner joint portion of a tripod type joint that exhibits particularly advantageous behavior with respect to the ACFG value is proposed.

Means for Solving the Problems

[0015] A tripod type joint having the features according to claim 1 and an inner joint portion having the features according to claim 10 contribute to the solution of these problems. Advantageous developments are the subject matter of the dependent claims. The features listed in the claims can be combined in technically feasible ways and may be complemented by the explanatory technical content of this specification and the details of the figures, which disclose further embodiments of the present invention.

[0016] A tripod type joint (hereinafter referred to as a joint) is proposed. This joint comprises at least an outer joint portion, an inner joint portion, and a plurality of rotating bodies. In particular, the tripod type joint is a sliding joint, and the inner joint portion is movable along a first rotation axis with respect to the outer joint portion.

[0017] The outer joint portion has a receiving portion for the inner joint portion that extends along the first rotation axis and three raceway surfaces that extend along the first rotation axis and are (equally) distributed in the circumferential direction.

[0018] The inner joint portion has a central body extending along the second rotation axis and three journals extending from the central body along the radial direction. Each journal has a journal axis and is (equally) distributed in the circumferential direction.

[0019] The rotating bodies are arranged on each of the journals. The rotating bodies are in contact with the journals on the inner circumferential surfaces and in contact with the respective raceways on the outer circumferential surfaces. Each journal has respective contact surfaces for contacting the inner circumferential surface. The first contact surface faces at least in the first circumferential direction, and the second contact surface faces at least in the second circumferential direction. The second circumferential direction faces in a direction opposite to the first circumferential direction. When the rotation axes are arranged coaxially with respect to each other, the first contact surface has a first pitch circle radius, the second contact surface has a second pitch circle radius, the raceway has a third pitch circle radius, and at least the first pitch circle radius and the second pitch circle radius have different values from each other.

[0020] In particular, the outer circumferential surface of the rotating body is rotatable with respect to the inner circumferential surface of the rotating body. The inner circumferential surface is formed, for example, by a journal or an inner ring in contact with the respective contact surfaces or each rolling element. When the inner circumferential surface is formed by an inner ring, each rolling element is arranged between the inner ring and the outer circumferential surface, thereby enabling relative rotation.

[0021] By the rotation of the inner circumferential surface with respect to the outer circumferential surface, the rotating body can roll along the raceway, whereby the inner joint portion can be displaced along the first rotation axis with respect to the outer joint portion.

[0022] When the inner joint portion tilts, the rotating body is further guided via the raceway, whereby at least each journal tilts with respect to each rotating body.

[0023] In particular, each rotating body is guided via the raceway so that the rotating body does not tilt with respect to the raceway.

[0024] Alternatively, when the inner joint portion tilts, the rotating body also tilts with respect to the raceway.

[0025] In particular, the inner circumferential surface and the outer circumferential surface do not perform any further relative movement with respect to each other, apart from the relative rotation.

[0026] As defined above, the pitch circle radius of each journal is, in particular, the so-called effective radius. This is defined for an extended joint, i.e., when the respective axes of rotation are arranged coaxially with respect to each other. The effective radius determines the lever arm of the resultant force when torque is transmitted. Therefore, the pitch circle radius of each journal is a radius starting from the second axis of rotation. For example, when the joint is extended, the center of each sliding surface of the spherical seat of the journal is arranged on this radius.

[0027] As defined above, the pitch radius of the outer joint part or the raceway surface is the so-called effective radius, which is defined for an extended joint, i.e., when the respective longitudinal axes or the respective axes of rotation are arranged coaxially with respect to each other. The effective radius determines the lever arm of the resultant force when torque is transmitted.

[0028] The pitch circle radius is defined in particular with respect to the spherical surface (of the journal or the outer joint part). If the shape deviates from a spherical surface (for example, when the surface or its contour is elliptical, or has a spline contour or a torus contour), the actual contact point of the resultant force can be used on that surface.

[0029] The offset provided in a known joint is between the first pitch radius of the sliding surface of the journal and the second pitch radius of the recess. When the joint is used in the engine braking state / coasting state or the traction state, it has been found that the ACFG value or its transition varies according to the bending angle. However, in these joints, the offset can only be set at the best compromise point, so that an ACFG value that is equally suitable for both the engine braking state / coasting state and the traction state can be obtained.

[0030] The proposed tripod joint has different pitch circle radii on each contact surface. With this tripod joint, on the one hand, it can adapt to the engine braking state or the coasting state, and on the other hand, it can adapt to the traction state. Therefore, the contact surfaces oriented in different circumferential directions have different characteristics, that is, different pitch circle radii. Therefore, by adapting one (for example, the first) pitch radius, the ACFG value of the joint can be designed specifically for the engine braking state or the coasting state, and by adapting the other (for example, the second) pitch radius, the ACFG value can be designed specifically for the traction state.

[0031] The first pitch circle radius and the second pitch circle radius differ by a factor of at least 1.001, preferably by a factor of at least 1.005, and particularly preferably by a factor of at least 1.01.

[0032] In particular, the first pitch circle radius is smaller or larger than the third pitch circle radius.

[0033] In particular, the second pitch circle radius is larger or smaller than the third pitch circle radius.

[0034] In particular, the value of the first pitch circle radius or the second pitch circle radius corresponds to the value of the third pitch circle radius.

[0035] In particular, the third pitch circle radius is larger or smaller than the first pitch circle radius and the second pitch circle radius.

[0036] In particular, all ratios between the pitch circle radii are possible, whereby the first pitch circle radius and the second pitch circle radius are always different from each other or have different values.

[0037] In particular, the contact surface is spherical. However, the contour of each contact surface can also deviate from the spherical shape. For example, each contact surface can be formed by several different radii of curvature. The starting point of the radius may or may not be arranged on each journal axis. The contact surface can also be elliptical or toroidal.

[0038] In particular, the inner circumferential surface contacts the surface of each contact surface only at one point in a cross-section extending in a direction transverse to the second axis of rotation.

[0039] In particular, each raceway surface is curved in a cross-section extending in a direction transverse to the first axis of rotation. In particular, the shape of the raceway surface in this cross-section is formed by one or more radii. In particular, the curvature is concave with respect to the outer circumferential surface of the rotating body. In particular, the transition of the curvature is in the shape of a pointed arch, also known as a cusp arch. In particular, the outer circumferential surface contacts the surface of each raceway surface 9 at only one point, or at two points, or along a line, in the cross-section.

[0040] The contact between each of the above-mentioned surfaces is described only in an idealized form. For example, when a convexly curved surface contacts a cylindrical surface, due to the elastic deformation of each surface, a linear contact may actually occur, but from an idealized perspective, it contacts only at one point.

[0041] In particular, each rotating body includes an inner ring having an inner circumferential surface, an outer ring having an outer circumferential surface, and a plurality of rolling elements between the inner ring and the outer ring.

[0042] In particular, the outer circumferential surface has a convex shape with respect to each raceway surface.

[0043] In particular, the inner circumferential surface is cylindrical.

[0044] In particular, the inner peripheral surface is concave with respect to each contact surface. In this context, concave means that the inner peripheral surface has a central region that recedes with respect to each contact surface and an outer region that is adjacent to the central region and protrudes towards each contact surface.

[0045] The central region can be cylindrical or concave. In particular, the curvature of the concave surface of the central region may extend to the outer region with a constant radius or a varying radius. The outer region may have a conical shape starting from the (curved or cylindrical) central region.

[0046] Due to the inner peripheral surface being designed to be concave, the rotating body or the inner ring can be fixed on the journal during the operation of the tripod joint. In particular, this means that it is not necessary to fix the inner ring with respect to the outer ring.

[0047] Normally, for example, such a fixation is provided so that the inner ring can only rotate with respect to the outer ring. However, this fixation is usually made with a retaining / locking ring on the outer ring or the inner ring. When the inner joint part is displaced along the first rotation axis, only the outer ring performs a rotational movement around the journal axis, resulting in frictional losses.

[0048] The fact that the inner peripheral surface is designed to be concave serves to fix the inner ring on each journal respectively, and the outer peripheral surface is guided by the raceway surface or is fixed by the raceway surface (for example, with respect to the circumferential direction and the radial direction centered on the first rotation axis).

[0049] In particular, each contact surface extends over an angular range that spreads around each journal axis. The angular range has an angle of less than 180 degrees, in particular, an angle of less than 150 degrees, and preferably an angle of less than 130 degrees.

[0050] In particular, the inner joint portion has a central cross-section that extends transversely to the second axis of rotation and intersects the center of mass of the inner joint portion. In this cross-section, the inner joint portion has a minimum thickness (the sum of the first thickness and the second thickness) between the central body and each contact surface, along the radial direction or along each journal axis respectively. The first thickness that extends from the journal axis to the first surface of the inner joint portion disposed adjacent to the first contact surface is smaller than or larger than the second thickness that extends from the journal axis to the second surface of the inner joint portion disposed adjacent to the second contact surface. The difference between the first thickness and the second thickness is at least 1 percent of the larger thickness, preferably at least 5 percent.

[0051] An inner joint portion for a tripod joint is further proposed. In particular, an inner joint portion for the tripod joint described above is proposed. In particular, the inner joint portion comprises at least a central body extending along the second axis of rotation and three journals extending radially from the central body, each journal having a journal axis and being circumferentially distributed. Each journal has a respective contact surface for contacting the rotating body of the tripod joint. The first contact surface faces at least in a first circumferential direction, the second contact surface faces at least in a second circumferential direction, and the second circumferential direction faces in a direction opposite to the first circumferential direction. The first contact surface has a first pitch circle radius, the second contact surface has a second pitch circle radius, and the first pitch circle radius and the second pitch circle radius have different values from each other.

[0052] The inner joint portion or at least each contact surface can be manufactured by machining (e.g., turning, milling, grinding) or forming (e.g., forging) processes.

[0053] The description regarding the tripod joint is particularly applicable to the inner joint portion, and vice versa.

[0054] The described tripod joint, or the tripod joint with the described inner joint part, is particularly applicable to the side shaft of an automobile. In particular, the side shaft is connected to the drive unit of the automobile, whereby the torque of the drive unit can be transmitted to the wheel of the automobile via the tripod joint.

[0055] The indefinite articles ("ein", "eine", "einer", "eines") are not intended to be used as numerals, especially in the claims and the descriptions that reproduce these claims, and should be understood as such. Accordingly, the terms and components introduced correspondingly are intended to be understood as being present at least once, but in particular, may also be present several times.

[0056] For the sake of avoiding doubts, the ordinal numbers ("first", "second", etc.) used in this specification are mainly provided only for distinguishing several similar objects, numerical values, and processes. That is, in particular, these ordinal numbers do not necessarily define any dependency relationships or orders among these objects, numerical values, and processes. If dependency relationships or orders are required, this will be specified in this specification or will become clear to those skilled in the art by examining the actually described configurations. If dependency relationships or orders are required, this will be specified in this specification or will become clear to those skilled in the art by examining the actually described configurations.

[0057] Hereinafter, with reference to the accompanying drawings, the present invention and the technical environment will be described in more detail. It should be noted that the present invention is not limited by the described design change examples. In particular, it should be noted that the drawings and especially the illustrated ratios are merely schematic.

Brief Description of the Drawings

[0058]

Figure 1

Figure 2

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Figure 8

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Figure 11

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Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

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Figure 24

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Figure 26

Figure 27

DETAILED DESCRIPTION OF THE INVENTION

[0059] Fig. 1 shows the side shaft 26 of the automobile 27 in the traction state. The side shaft 26 connects the wheel 30 of the automobile 27 to the drive unit 28 or the gearbox 38. The side shaft 26 has a tripod joint 1 on the drive unit 28 side or the gearbox 38 side, and further has a joint 29 on the wheel 30 side. In the traction state, the direction of the applied torque 31 and the rotation direction of the side shaft 26 are in the same direction (refer to the arrow).

[0060] FIG. 2 shows the side shaft 26 according to FIG. 1 in the engine braking state or the coasting state. Refer to the description regarding FIG. 1. In the engine braking state or the coasting state, the direction of the applied torque 31 and the rotation direction of the side shaft 26 are opposite to each other.

[0061] FIG. 3 shows a known tripod joint 1 from a perspective along the coaxial rotation shafts 5 and 10. FIG. 4 shows the tripod joint 1 according to Patent Document 2. FIGS. 3 and 4 will be collectively described below. Refer to the description regarding FIGS. 1 and 2.

[0062] The tripod joint 1 includes an outer joint portion 2, an inner joint portion 3, and a plurality of rotating bodies 4. The tripod joint 1 is a sliding joint, and the inner joint portion 3 is movable along the first rotation axis 5 with respect to the outer joint portion 2. The outer joint portion 2 has a receiving portion 6 for the inner joint portion 3 extending along the first rotation axis 5, and three raceway surfaces 9 extending along the first rotation axis 5 and evenly distributed in the circumferential directions 7 and 8. The inner joint portion 3 has a central body 11 extending along the second rotation axis 10 and three journals 14 extending from the central body 11 along the radial direction 12. Each journal has a journal axis 13 and is evenly distributed in the circumferential directions 7 and 8.

[0063] The rotating bodies 4 are arranged on each journal 14. The rotating bodies 4 are in contact with the journals 14 on the inner circumferential surfaces 15 and in contact with the respective raceway surfaces 9 on the outer circumferential surfaces 16. Each journal 14 has contact surfaces 17 and 18 for contacting the inner circumferential surface 15. The first contact surface 17 faces at least the first circumferential direction 7, and the second contact surface 18 faces at least the second circumferential direction 8, which is opposite to the first circumferential direction 7. When the rotation shafts 5 and 10 are arranged coaxially with respect to each other, the first and second contact surfaces 17 and 18 have a first pitch radius 19, and the raceway surfaces 9 have a third pitch radius 21.

[0064] In order to achieve particularly advantageous guiding characteristics, an offset 32 is provided between the first pitch radius 19 of the contact surfaces 17, 18 of each journal 14 and the third pitch radius 21 of the raceway surface 9.

[0065] Each rotating body 4 includes an inner ring 22 having an inner circumferential surface 15, an outer ring 23 having an outer circumferential surface 16, and a plurality of rolling elements 24 between the inner ring 22 and the outer ring 23.

[0066] When the vehicle 27 is in a traction state, that is, when the vehicle 27 is driven by the drive unit 28, the journal 14 contacts the rotating body 4 on one of the contact surfaces 17, 18, and the rotating body 4 contacts only one side of the raceway surface 9. In the engine braking state or the coasting state of the vehicle 27, that is, when the driving torque is introduced from the wheel 30 and the drive unit 28 is still connected (engine braking state) or disconnected (coasting state), the journal 14 contacts the rotating body 4 on the other of the contact surfaces 18, 17, and the rotating body 4 contacts only the other side of the raceway surface 9.

[0067] FIG. 5 shows the first figure. FIG. 6 shows the second figure. FIGS. 5 and 6 will be described together. The ACFG value 34 is plotted on each vertical axis in [Nrms], and the bending angle 33 of the tripod joint 1 is plotted on the horizontal axis in [degrees].

[0068] The ACFG value 34 changes as a function of the bending angle 33 of the tripod joint 1, whereby the transition 35 of the value as a function of the bending angle 33 is determined and can be obtained for each tripod joint 1. Therefore, the applicable range of the tripod joint 1 is limited by the maximum bending angle 33. This maximum bending angle 33 is the bending angle when the ACFG value 34 exceeds the maximum value 36 that is considered acceptable.

[0069] Figure 5 shows the transition 35 of the traction state of the tripod joint 1 in FIGS. 3 and 4. Figure 6 shows the transition 35 of the engine braking state / coasting state of this tripod joint 1. The applicable range of the tripod joint 1 is limited by the bending angle 33, and it can be seen that this bending angle 33 exceeds the maximum value 36 regarded as acceptable of the ACFG value 34 in the engine braking state / coasting state.

[0070] Figure 7 shows the tripod joint 1 in FIG. 3 having a driven outer joint portion 2. The arrow indicates the resultant torque 31 acting on the effective radius of the outer joint portion 2.

[0071] Figure 8 shows the tripod joint 1 having a driven outer joint portion 2 from the perspective along the coaxially arranged rotating shafts 5 and 10. The tripod joint 1 includes an outer joint portion 2, an inner joint portion 3, and a plurality of rotating bodies 4. The tripod joint 1 is a sliding joint, and the inner joint portion 3 is movable along the first rotating shaft 5 with respect to the outer joint portion 2. The outer joint portion 2 has a receiving portion 6 for the inner joint portion 3 extending along the first rotating shaft 5, and three raceway surfaces 9 extending along the first rotating shaft 5 and evenly distributed in the circumferential directions 7 and 8. The inner joint portion 3 has a central body 11 extending along the second rotating shaft 10 and three journals 14 extending from the central body 11 along the radial direction 12. Each journal has a journal shaft 13 and is evenly distributed in the circumferential directions 7 and 8.

[0072] The rotating bodies 4 are arranged on each journal 14. The rotating bodies 4 are in contact with the journal 14 on the inner peripheral surface 15 and in contact with the respective raceway surfaces 9 on the outer peripheral surface 16. Each journal 14 has contact surfaces 17 and 18 for contacting the inner peripheral surface 15. The first contact surface 17 faces at least the first circumferential direction 7, and the second contact surface 18 faces at least the second circumferential direction 8 opposite to the first circumferential direction 7.

[0073] Each of the rotating bodies 4 includes an inner ring 22 having an inner peripheral surface 15, an outer ring 23 having an outer peripheral surface 16, and a plurality of rolling elements 24 between the inner ring 22 and the outer ring 23.

[0074] When the rotating shafts 5 and 10 are coaxially arranged with respect to each other, the first contact surface 17 has a first pitch circle radius 19, the second contact surface 18 has a second pitch circle radius 20, the raceway surface 9 has a third pitch circle radius 21, and at least the first pitch circle radius 19 and the second pitch circle radius 20 have different values from each other.

[0075] The outer peripheral surface 16 of the rotating body 4 is rotatable with respect to the inner peripheral surface 15 of the rotating body 4. The inner peripheral surface 15 is formed by the journal 14 or the inner ring 22 that contacts the contact surfaces 17 and 18. The rolling elements 24 are arranged between the inner ring 22 and the outer peripheral surface 16, thereby enabling relative rotation.

[0076] By the rotation of the inner peripheral surface 15 with respect to the outer peripheral surface 16, the rotating body 4 can roll along the raceway surface 9, whereby the inner joint portion 3 can be displaced along the first rotating shaft 5 with respect to the outer joint portion 2.

[0077] When the inner joint portion 3 tilts, the rotating body 4 is further guided via the raceway surface 9, whereby the journal 14 tilts with respect to the rotating body 4.

[0078] The inner peripheral surface 15 and the outer peripheral surface 16 do not perform any further relative movement with respect to each other, apart from the relative rotation.

[0079] The pitch circle radii 19, 20 of each journal 14 are so-called effective radii. These are defined for the case of an extended tripod joint 1, i.e., when the rotational axes 5, 10 are arranged coaxially with respect to each other. The effective radius determines the lever arm of the resultant force when torque 31 (see the arrow in Fig. 8) is transmitted. Therefore, the pitch circle radii 19, 20 of each journal 14 are radii starting from the second rotational axis 10, and when the tripod joint 1 is extended, the centers of the spherical contact surfaces 17, 18 of the journal 14 are arranged on this radius.

[0080] The proposed tripod joint 1 has different pitch circle radii 19, 20 for each contact surface 17, 18. With this tripod joint 1, on the one hand, it becomes possible to adapt to the engine braking state or the coasting state, and on the other hand, it becomes possible to adapt to the towing state. Therefore, the contact surfaces 17, 18 directed in different circumferential directions 7, 8 have different characteristics, i.e., different pitch circle radii 19, 20. Therefore, by adapting the first pitch radius 19, the ACFG value 34 of the tripod joint 1 can be designed specifically for the engine braking state or the coasting state, and by adapting the second pitch radius 20, the ACFG value 34 can be designed specifically for the towing state.

[0081] Here, the second pitch circle radius 20 is smaller than the third pitch circle radius 21, and the first pitch circle radius 19 is larger than the third pitch circle radius 21.

[0082] Fig. 9 shows the tripod joint 1 in Figs. 3 and 7 having a driven inner joint part 3. Refer to Fig. 7. The arrow indicates the resultant torque 31 acting on the effective radius of the outer joint part 2, the third pitch radius 21.

[0083] Fig. 10 shows the tripod joint 1 in Fig. 8 having a driven inner joint part 3. Refer to Fig. 8. The arrow indicates the resultant torque 31 acting on the effective radius of the outer joint part 2, the third pitch circle radius 21.

[0084] Figure 11 shows the outer joint portion 2 of the tripod joint 1 in FIGS. 3, 4, 7 to 10. The outer joint portion 2 has a receiving portion 6 for the inner joint portion 3 that extends along the first rotation axis 5, and three raceways 9 that extend along the first rotation axis 5 and are evenly distributed in the circumferential directions 7 and 8.

[0085] Each raceway 9 extends in a lateral direction with respect to the first rotation axis 5 and is curved in the illustrated cross section. The shape of the raceway 9 in this cross section is formed by a plurality of radii. The curvature is concave with respect to the outer peripheral surface 16 of the rotating body 4. The transition of the curvature is in a pointed arch shape, which is also known as a pointed arch. The outer peripheral surface 16 contacts the surface of the raceway 9 at two points in the cross section (see also FIGS. 7 to 10).

[0086] The outer joint portion 2 has each raceway 9 disposed on the third pitch circle radius 21.

[0087] Figure 12 shows a first design modification example of the inner joint portion 3 from the perspective along the second rotation axis 10. Refer to the description and illustration of the inner joint portion 3 in FIG. 10.

[0088] Each journal 14 has contact surfaces 17, 18 for contacting the inner peripheral surface 15. The first contact surface 17 faces at least the first circumferential direction 7, and the second contact surface 18 faces at least the second circumferential direction 8, which is in the direction opposite to the first circumferential direction 7. The first contact surface 17 has a first pitch circle radius 19, the second contact surface 18 has a second pitch circle radius 20, and the first pitch circle radius 19 is larger than the second pitch circle radius 20.

[0089] Figure 13 shows a second design modification example of the inner joint portion 3 from the perspective along the second rotation axis 10. Refer to the description regarding FIG. 12.

[0090] In contrast to the first design modification example, here the first pitch circle radius 19 is smaller than the second pitch circle radius 20.

[0091] FIG. 14 shows a third figure. FIG. 15 shows a fourth figure. Refer to the descriptions regarding FIGS. 5 and 6. FIGS. 14 and 15 will be described together.

[0092] The ACFG values 34 are plotted on the respective vertical axes in [Nrms], and the bending angle 33 of the tripod joint 1 is plotted on the horizontal axis in [degrees].

[0093] The ACFG value 34 changes as a function of the bending angle 33 of the tripod joint 1, thereby determining the transition 35 of the value as a function of the bending angle 33, which can be determined for each tripod joint 1. Therefore, the applicable range of the tripod joint 1 is limited by the maximum bending angle 33. This maximum bending angle 33 is the bending angle when the ACFG value 34 exceeds the maximum value 36 considered acceptable.

[0094] FIG. 14 shows the transition 35 of the traction state of the tripod joint 1 in FIGS. 8 and 10 to 13. FIG. 15 shows the transition 35 of the engine braking state / coasting state of this tripod joint 1. The applicable range of the tripod joint 1 is only limited by a fairly large value of the bending angle 33, and it can be seen that in both operating states, the ACFG value 34 exceeds the maximum value 36 considered acceptable.

[0095] FIG. 16 shows a part of the inner joint portion 3 in the third design modification example from the viewpoint along the second rotation axis 10. Here, the journal 14 is manufactured by a machining manufacturing process. The rotation axis 37 of the journal geometry (Zapfengeometrie) used in the manufacturing process can be seen.

[0096] FIG. 17 shows a part of the inner joint portion 3 in a fourth design modification example from the viewpoint along the second rotation axis 10. Here, the journal 14 is manufactured by a forging process.

[0097] FIG. 18 shows the inner joint portion 3 from the viewpoint along the second rotation axis 10. FIG. 19 shows the inner joint portion 3 in FIG. 18 from the viewpoint along the journal axis 13. FIG. 20 shows the inner joint portion 3 in FIGS. 18 and 19 in a side view. FIGS. 18 to 20 will be collectively described below. Refer to the descriptions of FIGS. 8 and 10 to 17.

[0098] Each journal 14 has contact surfaces 17, 18 for contacting the inner peripheral surface 15. The first contact surface 17 faces at least the first circumferential direction 7, and the second contact surface 18 faces at least the second circumferential direction 8 which is opposite to the first circumferential direction 7.

[0099] Each of the contact surfaces 17, 18 extends over an angular range 25 that spreads around the respective journal axis 13, and this angular range has an angle of less than 150 degrees.

[0100] The inner joint portion 3 has a central cross-section 41 which extends in a lateral direction with respect to the second rotation axis 10 and intersects the mass center 42 of the inner joint portion 3. In this central cross-section 41, the inner joint portion 3 has a minimum thickness (the sum of the first thickness 43 and the second thickness 45) along the radial direction 12 or along each journal axis 13 between the central body 11 and each of the contact surfaces 17, 18. The first thickness 43 that spreads from the journal axis 13 to the first surface 44 of the inner joint portion 3 disposed adjacent to the first contact surface 17 is smaller than the second thickness 45 that spreads from the journal axis 13 to the second surface 46 of the inner joint portion 3 disposed adjacent to the second contact surface 18.

[0101] FIG. 21 shows the tripod joint 1 having the inner joint portion 3 in FIGS. 18 to 20 from a viewpoint along the rotation axes 5 and 10, and is shown partially in cross section. FIG. 22 shows the inner joint portion 3 having the rotating body 4 in FIG. 21 from a viewpoint along the journal axis 13. FIG. 23 shows the inner joint portion 3 having the rotating body 4 in FIG. 22 from a viewpoint along the second rotation axis 10, and is shown partially in cross section. FIG. 24 shows the tripod joint in FIG. 21 in a side view and a cross-sectional view. FIGS. 21 to 24 will be described below in summary. Refer to the descriptions regarding FIGS. 8 and 10 to 20.

[0102] The tripod joint 1 includes an outer joint portion 2, an inner joint portion 3, and a plurality of rotating bodies 4. The tripod joint 1 is a sliding joint, and the inner joint portion 3 is movable along the first rotation axis 5 with respect to the outer joint portion 2. The outer joint portion 2 has a receiving portion 6 for the inner joint portion 3 extending along the first rotation axis 5, and three raceway surfaces 9 extending along the first rotation axis 5 and evenly distributed in the circumferential directions 7 and 8. The inner joint portion 3 has a central body 11 extending along the second rotation axis 10 and three journals 14 extending from the central body 11 along the radial direction 12. Each journal has a journal axis 13 and is evenly distributed in the circumferential directions 7 and 8.

[0103] The rotating bodies 4 are arranged on each journal 14. The rotating bodies 4 are in contact with the journals 14 on the inner peripheral surfaces 15 and with the respective raceway surfaces 9 on the outer peripheral surfaces 16. Each journal 14 has the contact surfaces 17 and 18 described in relation to FIGS. 18 to 20 for contacting the inner peripheral surface 15. The first contact surface 17 faces at least the first circumferential direction 7, and the second contact surface 18 faces at least the second circumferential direction 8 which is opposite to the first circumferential direction 7.

[0104] The outer peripheral surface 16 of the rotating body 4 is rotatable with respect to the inner peripheral surface 15 of the rotating body 4. The inner peripheral surface 15 is formed by an inner ring 22 that contacts the journal 14 or the contact surfaces 17, 18. Rolling elements 24 are arranged between the inner ring 22 and the outer peripheral surface 16, thereby enabling relative rotation.

[0105] By the rotation of the inner peripheral surface 15 with respect to the outer peripheral surface 16, the rotating body 4 can roll along the raceway surface 9, whereby the inner joint portion 3 can be displaced along the first rotation axis 5 with respect to the outer joint portion 2.

[0106] When the inner joint portion 3 tilts, the rotating body 4 is further guided via the raceway surface 9, whereby the journal 14 pivots with respect to the rotating body 4. The bending angle 33 set between the first rotation axis 5 and the second rotation axis 10 is shown in FIG. 24.

[0107] The inner peripheral surface 15 and the outer peripheral surface 16 do not perform further relative movement with respect to each other, apart from relative rotation.

[0108] The proposed tripod joint 1 has different pitch circle radii 19, 20 on each contact surface 17, 18. With this tripod joint 1, on the one hand, it is possible to adapt to the engine braking state or the coasting state, and on the other hand, it is possible to adapt to the traction state.

[0109] Here, the second pitch circle radius 20 is smaller than the third pitch circle radius 21, and the first pitch circle radius 19 is larger than the third pitch circle radius 21.

[0110] Each rotating body 4 includes an inner ring 22 having an inner peripheral surface 15, an outer ring 23 having an outer peripheral surface 16, and a plurality of rolling elements 24 between the inner ring 22 and the outer ring 23. The outer peripheral surface 16 has a convex shape with respect to the raceway surface 9. The inner peripheral surface 15 is cylindrical.

[0111] FIG. 25 shows a third design modification example of the inner joint portion 3 from the perspective along the second rotation axis 10. FIG. 26 shows details of the inner joint portion 3 in FIG. 26 from the perspective along the second rotation axis 10. FIG. 27 shows details of a fourth design modification example of the inner joint portion 3 from the perspective along the second rotation axis 10.

[0112] In contrast to the first and second design modification examples, here, the inner peripheral surface 15 is concave with respect to each contact surface 17, 18. In this context, concave means that the inner peripheral surface 15 has a central region 39 that recedes with respect to each contact surface 17, 18 and an outer region 40 that is adjacent to the central region 39 and protrudes toward each contact surface 17, 18.

[0113] In the third and fourth design modification examples, the central region 39 is cylindrical. In the third design modification example, each outer region 40 has a curved shape (see FIG. 26). In the fourth design modification example, each outer region 40 has at least a partially conical shape starting from the cylindrical central region 39.

[0114] Since the inner peripheral surface 15 is designed to be concave, the rotating body 4 or the inner ring 22 can be fixed on the journal 14 during the operation of the tripod joint 1. This means that it is not necessary to fix the inner ring 22 with respect to the outer ring 23.

[0115] Normally, for example, such fixation is provided so that the inner ring 22 can only rotate with respect to the outer ring 23. However, this fixation is usually made with a retaining / locking ring on the outer ring 23 or the inner ring 22. However, when the inner joint portion 3 is displaced along the first rotation axis 5, only the outer ring 23 performs a rotational movement around the journal axis 13, resulting in frictional losses.

[0116] The fact that the inner peripheral surface 15 is designed to be concave serves to fix the inner ring 22 on each journal 14, and the outer peripheral surface 16 is guided by the raceway surface 9 or is fixed by the raceway surface 9 (for example, with respect to the circumferential directions 7, 8 centered on the first rotation axis 5 and with respect to the radial direction 12).

Description of Symbols

[0117] 1 Tripod joint 2 Outer joint part 3 Inner joint part 4 Rotating body 5 First rotation axis 6 Receiving part 7 First circumferential direction 8 Second circumferential direction 9 Raceway surface 10 Second rotation axis 11 Central body 12 Radial direction 13 Journal shaft 14 Journal 15 Inner peripheral surface 16 Outer peripheral surface 17 First contact surface 18 Second contact surface 19 First pitch circle radius 20 Second pitch circle radius 21 Third pitch circle radius 22 Inner ring 23 Outer ring 24 Rolling element 25 Angular region 26 Side shaft 27 Automobile 28 Drive unit 29 Joint 30 Wheel 31 Torque 32 Offset 33 Bending angle 34 ACFG value 35 Transition 36 Maximum value 37 Rotation axis 38 Gear 39 Central region 40 Outer region 41 Central cross-section 42 Center of mass 43 First thickness 44 First surface 45 Second thickness 46 The second surface

Claims

1. A tripod joint (1) comprising at least an outer joint portion (2), an inner joint portion (3), and a plurality of rotating bodies (4), wherein the outer joint portion (2) has a receiving portion (6) for the inner joint portion (3) extending along a first rotation axis (5), and three raceways (9) extending along the first rotation axis (5) and distributed in the circumferential directions (7, 8), and the inner joint portion (3) has a central body (11) extending along a second rotation axis (10), and three journals (14) extending from the central body (11) along the radial direction (12), each of the journals having a journal axis (13) and being distributed in the circumferential directions (7, 8), one of the plurality of rotating bodies (4) being disposed on each of the journals (14), the rotating body (4) contacting the journal (14) at an inner circumferential surface (15) and contacting each of the raceways (9) at an outer circumferential surface (16), each journal (14) having contact surfaces (17, 18) for contacting the inner circumferential surface (15), the first contact surface (17) facing at least the first circumferential direction (7), the second contact surface (18) facing at least the second circumferential direction (8), the second circumferential direction (8) facing in a direction opposite to the first circumferential direction (7), when the rotation axes (5, 10) are coaxially arranged with respect to each other, the first contact surface (17) having a first pitch circle radius (19), the second contact surface (18) having a second pitch circle radius (20), the raceway (9) having a third pitch circle radius (21), at least the first pitch circle radius (19) and the second pitch circle radius (20) having different values from each other, a tripod joint (1).

2. The tripod joint (1) according to Claim 1, wherein the first pitch circle radius (19) is smaller or larger than the third pitch circle radius (21). A tripod joint (1) characterized by this.

3. The tripod joint (1) according to Claim 1 or 2, wherein the second pitch circle radius (20) is larger or smaller than the third pitch circle radius (21). A tripod joint (1) characterized by this.

4. The tripod joint (1) according to any one of Claims 1 to 3, ​ ​ The value of the first pitch circle radius (19) or the second pitch circle radius (20) corresponds to the value of the third pitch circle radius (21). Tripod joint (1), characterized in that.

5. The tripod joint (1) according to claim 1, wherein the third pitch circle radius (21) is larger or smaller than the first pitch circle radius (19) and the second pitch circle radius (20). Tripod joint (1), characterized in that.

6. The tripod joint (1) according to any one of claims 1 to 5, wherein each of the rotating bodies (4) respectively comprises an inner ring (22) having the inner peripheral surface (15), an outer ring (23) having the outer peripheral surface (16), and a plurality of rolling elements (24) between the inner ring (22) and the outer ring (23). and is provided with Tripod joint (1), characterized in that.

7. The tripod joint (1) according to any one of claims 1 to 6, wherein the outer peripheral surface (16) has a convex shape with respect to each of the raceway surfaces (9). Tripod joint (1), characterized in that.

8. The tripod joint (1) according to any one of claims 1 to 7, wherein the inner peripheral surface (15) is cylindrical. Tripod joint (1), characterized in that.

9. The tripod joint (1) according to any one of claims 1 to 7, wherein the inner peripheral surface (15) is concave with respect to each of the contact surfaces (17, 18). Tripod joint (1), characterized in that.

10. The tripod joint (1) according to any one of claims 1 to 9, wherein each of the contact surfaces (17, 18) extends over an angular range (25) that spreads around the respective journal shaft (13), and the angular range (25) has an angle less than 180 degrees. Tripod joint (1), characterized in that.

11. An inner joint portion (3) for a tripod joint (1), comprising a central body (11) extending along the second rotation axis (10), and three journals (14) extending from the central body (11) along the radial direction (12). and at least comprising each of the journals (14) has a journal shaft (13) and is distributed in the circumferential direction (7, 8) in a dispersed manner. Each of the journals (14) has contact surfaces (17, 18) for contacting a rotating body (4) of the tripod joint (1), which rotating body (4) can be arranged on the journal (14). The first contact surface (17) faces at least in a first circumferential direction (7). The second contact surface (18) faces at least in a second circumferential direction (8). The second circumferential direction (8) faces in a direction opposite to the first circumferential direction (7). The first contact surface (17) has a first pitch circle radius (19). The second contact surface (18) has a second pitch circle radius (20). The first pitch circle radius (19) and the second pitch circle radius (20) have different values from each other. Inner joint part (3).

Images