Clutch with three ball pins and steering mechanism

Description

Technical area

[0001] The present invention relates to the field of couplings and, in particular, to three ball stud couplings for a steering mechanism of a vehicle. background

[0002] Vehicle steering mechanisms, and in particular electric power steering mechanisms, generally utilize a worm gear and worm gear to amplify motor torque and drive racks to perform steering. Such steering mechanisms include, for example, column and double-pinion steering mechanisms.

[0003] One of the commonly used worm gear systems in the aforementioned steering mechanisms connects the motor output shaft to the worm shaft as the outer shaft and an inner shaft through a coupling, thereby realizing the transmission of motor torque. The motor torque is further transmitted to the worm gear and worm, which are located close to each other and mesh with each other, and is thereby amplified to drive other components in the overall steering system.

[0004] The supporting part of the described worm system comprises a self-aligning bearing on one side of the worm and a deep groove ball bearing on the other side. To ensure continuous and stable engagement of the worm wheel and worm system, a spring is arranged along the vertical direction of the engagement axis of the worm wheel and worm at the part of the worm where the deep groove ball bearing is provided.

[0005] For example, if the worm gear and worm have a gear ratio of 21, the torque transmitted through the coupling to the worm gear is about 100 Nm when the motor torque is 5 Nm (taking into account the efficiency loss of the worm gear and worm during the torque transmission process), and therefore the driving force against the rack is about 10 kN, which is used to drive the wheels to achieve the steering operation. Engineering plastics are generally used as the material for the contact surface between the worm gear and worm to ensure silent torque transmission. However, this plastic contact surface may wear out after long-term use, resulting in the worm shaft axis being subject to worm shaft misalignment at a certain angle under the action of spring force (the misalignment is generally within ±1.5°).to ensure that the worm wheel and worm have essentially the same meshing quality before and after long-term use.

[0006] However, increasing the motor output torque (e.g. from 5 Nm to 8 Nm) to adapt to the drive of vehicles with higher loads leads to greater surface wear of the plastic surface of the worm wheel after long-term use, which in turn requires a larger offset angle (compensation angle) of the worm.

[0007] While the self-aligning bearing located on one side of the worm gear can easily achieve a larger oscillation angle, the coupling located between the motor and the worm gear typically has limited self-alignment capability. Once the offset angle of the worm gear axis exceeds the coupling's designed compensation capability, the system is prone to a number of problems, such as vibration noise, torque transmission hysteresis, and backlash due to wear on the gear meshing profile.

[0008] Therefore, it is urgently necessary to expand the compensation range of the self-alignment angle of the coupling while ensuring the torsional rigidity.

[0009] US 6 074 303 A discloses a coupling with three ball studs, comprising a first connector and a second connector which are connected for rotation therewith, wherein the first connector comprises a stud assembly with three shafts, race assemblies and a cage assembly; the three-shaft stud assembly comprises a shaft and three ball rings surrounding the shaft and arranged at intervals in the circumferential direction of the shaft; three race assemblies are provided; each ball ring is connected to one of the race assemblies; the cage assembly defines the circumferential position of the race assemblies; the race assemblies can provide an elastic force between the ball ring and the cage assembly; and when the ball ring shifts circumferentially relative to the cage assembly, two sides of the race assembly continue to bear circumferentially against the cage assembly.

[0010] WO 2016 / 152667 A1, JP 2005 344737 A, US 5 061 223 A and JP H03 168416 A also show couplings with three ball pins which are connected in a rotationally fixed manner via two connectors. Brief description

[0011] The purpose of the present invention is to provide a three ball stud coupling and steering mechanism to overcome or at least mitigate the above disadvantages of the prior art.

[0012] According to a first aspect of the present invention, a coupling with three ball studs is provided, the coupling with three ball studs comprising a first connector and a second connector which are connected in a rotationally fixed manner, wherein the first connector comprises a three-shaft pin assembly, race assemblies, and a cage assembly; the three-shaft pin assembly comprises a shaft and three ball races surrounding the shaft and spaced circumferentially of the shaft; three race assemblies are present; each ball race is connected to one of the race assemblies; the cage assembly defines the circumferential position of the race assemblies; the race assemblies are capable of providing a resilient force between the ball race and the cage assembly; and when the ball race shifts circumferentially relative to the cage assembly, two circumferential sides of the race assembly continue to bear against the cage assembly.

[0013] In at least one embodiment, the raceway assemblies include raceway frames, inner raceways, outer raceways, and resilient members; Each of the race frames is provided with two inner races and two outer races; two of the inner races are spaced apart from each other to form a ball race mounting portion therebetween; one of the outer races is mounted on one side of each of the inner races remote from the ball race mounting portion; an inner race and an outer race disposed on the same side of the ball race mounting portion form a race pair; the elastic member is provided at least partially between the inner race and the outer race; and the elastic member abuts the inner race and the outer race of each of the race pairs.

[0014] If, in at least one embodiment, the ball ring is located directly in the middle of two of the outer races, the elastic element is moved together by the inner race and the outer race and is thereby elastically deformed.

[0015] In at least one embodiment, the stiffness coefficient of the elastic element changes during elastic deformation of the elastic element.

[0016] In at least one embodiment, a portion of the elastic member between the inner race and the outer race is at least partially undulating.

[0017] In at least one embodiment, the elastic member is U-shaped overall; the elastic member includes a connecting portion and two wave-shaped springs connected to two ends of the connecting portion; and two of the wave-shaped springs are each interposed between the inner race and the outer race of one of the race pairs.

[0018] In at least one embodiment, a side of the inner race facing the ball race mounting portion is partially recessed to form a spherical concave surface that is part of a spherical surface and in contact with the ball race.

[0019] In at least one embodiment, a side of the outer race remote from the ball race mounting portion is partially recessed to form a curved surface in contact with the cage assembly.

[0020] According to the invention, the cage assembly includes a cage body and balls; The cage body includes an annular portion and three arms connected to the annular portion; the arms extend along an axial direction of the annular portion; two circumferential sides of the arms are formed with a plurality of notched ball pockets; the balls are housed in the ball pockets and can roll relative to the ball pockets within the ball pockets; each of the arms is interposed between two of the raceway assemblies; and the balls abut against the raceway assemblies.

[0021] In at least one embodiment, a central portion of each of the arms, located circumferentially between two rows of the ball pockets, is radially and inwardly recessed to form an arm recess.

[0022] In at least one embodiment, the second connector includes a tubular sliding sleeve having a first axial end connected to the first connector; an internal cavity of the sliding sleeve includes three projecting ribs in the axial direction near the first end, which project radially and inwardly and are circumferentially spaced; the projecting ribs extend in the axial direction to form a groove between every two adjacent projecting ribs; the arms are circumferentially aligned with the projecting ribs; the balls abut the projecting ribs; and each of the race assemblies is received in one of the grooves.

[0023] In at least one embodiment, two sides of each of the projecting ribs are each formed circumferentially with a depressed curved surface, and the balls abut the curved surfaces.

[0024] In at least one embodiment, a hook portion projecting outward in a radial direction of the annular portion is formed at the end of the arm away from the annular portion; the hook portion hooks into the projecting rib to prevent the cage assembly from detaching from the first end.

[0025] In at least one embodiment, an outer peripheral portion of the annular portion includes a plurality of annular projections projecting radially and outwardly, and the annular projections abut an end surface of the sliding sleeve at the first end to confine the cage assembly in the axial direction.

[0026] In at least one embodiment, the inner cavity of the sliding sleeve does not have the projecting ribs at a second end axially remote from the first end; the second connector further includes a vibration damping assembly mounted at the second end for rotation relative to the sliding sleeve; the vibration damping assembly extends at least partially into the interior cavity of the sliding sleeve; the shaft abuts the vibration damping assembly, an axial end of the shaft proximate the vibration damping assembly forms a spherical surface; and a portion of the vibration damping assembly in contact with the shaft is shaped as a spherical surface.

[0027] In at least one embodiment, the vibration damping assembly includes an adapter, a shell housing, and a buffer; the adapter and the sliding sleeve are connected to each other for rotation; the shell housing is connected to the adapter; the buffer is provided between the shell housing and the adapter; a portion of the shaft in contact with the vibration damping assembly is located on the shell housing; and a portion of the shell housing in contact with the shaft forms a recessed concave spherical portion in the shape of a spherical surface.

[0028] In at least one embodiment, an inner circumferential portion of the adapter forms a splined bore.

[0029] In at least one embodiment, the adapter is embedded in the inner cavity of the sliding sleeve; a central portion of the end surface of the adapter facing the shaft forms a projection by projecting in the direction of the shaft; and the shell housing is pushed onto the projection such that the shell housing is axially movable relative to the projection.

[0030] In at least one embodiment, when the buffer is not compressed, a gap is present between the shell housing and the end surface of the adapter facing the shaft.

[0031] According to a second aspect of the present invention, there is provided a steering mechanism comprising a motor, a clutch, and a worm gear and worm assembly, wherein the clutch is a three-ball stud clutch according to the present invention; the first connector of the three-ball stud clutch and a worm of the worm gear and worm assembly are rotationally connected; and the second connector of the three-ball stud clutch and an output shaft of the motor are rotationally connected.

[0032] The three ball stud coupling according to the present invention can reduce vibrations during the transmission process and can effectively transmit torque when there is axial misalignment between transmission components.

[0033] The steering mechanism according to the present invention is not prone to play and vibration shock during reversing during operation. Brief description of the drawings

[0034] FIG. 1 is a schematic representation of a three ball stud coupling according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of FIG. 1 along the axial direction. FIG. 3 is a schematic structural representation of shaft 11 in FIG. 2 . FIG. 4 is a schematic structural representation of the joint 12 with three bolts and the ball rings 13 in FIG. 2 . FIG. 5 is a schematic structural representation of the race assembly 20 in FIG. 1 . FIG. 6 is a schematic representation of the race frame 21 of the race assembly 20 FIG. 5 . FIG. 7 is a schematic representation of the race 22 of the race assembly 20 in FIG. 5 . FIG. 8 is a schematic representation of the outer race 23 of the race assembly 20 in FIG. 5 . FIG. 9is a schematic representation of the elastic element 24 of the race assembly 20 in FIG. 5 . FIG. 10 is a schematic structural representation of the cage assembly 30 in FIG. 1 . FIG. 11 is a schematic structural representation of the cage body 31 in FIG. 10 . FIG. 12 is a schematic structural representation of the sliding sleeve 40 in FIG. 1 . FIG. 13 is a schematic structural representation of the vibration damping arrangement 50 in FIG. 1 . FIG. 14 is a schematic structural representation of the adapter 51 in FIG. 13 . FIG. 15 is a schematic sectional view of the shell housing 52 and the buffer 53 in FIG. 2 . Detailed description of embodiments

[0035] Exemplary embodiments of the present invention are described below with reference to the drawings. It should be understood that the specific description is intended only to teach those skilled in the art how to implement the present invention and is neither intended to exhaust all possible variations of the present invention nor to limit the scope of the present invention.

[0036] Unless otherwise stated, A refers to the FIGS. 1 and 2 the axial direction of a three-ball-stud coupling, which coincides with the axial direction of a sliding sleeve 40; and R denotes the radial direction of the three-ball-stud coupling, which coincides with the radial direction of the sliding sleeve 40.

[0037] A three-ball coupling (hereinafter also referred to as a coupling) and a steering mechanism incorporating the coupling according to the present invention will be described with reference to FIGS. 1 to 15 described.

[0038] The steering mechanism according to the present invention includes a motor, a three-ball pin coupling, and a worm gear and worm assembly, wherein the three-ball pin coupling connects an output shaft of the motor and a worm in the worm gear and worm assembly so that torque of the output shaft can be transmitted to the worm.

[0039] With reference to the FIGS. 1 and 2 the three ball stud coupling according to the invention includes a first connector M and a second connector N connected in a torsion-free manner, wherein the first connector M is configured to be connected to the worm gear and the second connector N is configured to be connected to the output shaft of the motor.

[0040] First, the first connector M according to an embodiment of the present invention will be described with reference to the FIGS. 1 to 11described.

[0041] The first connector M includes a bolt assembly 10 with three shafts, race assemblies 20, and a cage assembly 30.

[0042] The three-shaft bolt assembly 10 comprises a shaft 11, a three-bolt joint 12, and ball rings 13.

[0043] The shaft 11 is configured for torsion-free connection to the worm. With reference to FIG. 3 In the present embodiment, a first end (the left end in FIG. 3) of the shaft 11 is provided with a bore 11h that penetrates the shaft 11 in a radial direction R and is used for mating with a bolt. For example, one end of the worm is provided with an inner bore extending in the axial direction and a bolt bore that intersects the inner bore and extends in the radial direction. The first end of the shaft 11 can be inserted into the inner bore, and the bolt is used to pass through the bolt bore and the bore 11h, thereby torsionally connecting the shaft 11 and the worm.

[0044] A second end (the right end in FIG. 3 ) of the shaft 11 has a spherical surface 11s, and the spherical surface 11s is used to mate with the vibration damping assembly 50 (described in detail below) to achieve the function of a universal performance.

[0045] With reference to the FIG. 2 and 4 The three-pin joint 12 comprises a ring 12r arranged in a central portion and three pins 12n connected to an outer peripheral portion of the ring 12r and extending in the radial direction of the ring 12r. Preferably, the three pins 12n are evenly spaced in the circumferential direction of the ring 12r. One of the ball rings 13 is fitted onto the outer periphery of each pin 12n, and the outer peripheral surface of the ball ring 13 is part of a spherical surface. It is understood that a rolling element may be provided between the pin 12n and the ball ring 13. The three-pin joint 12 is fitted onto the outer periphery of the shaft 11 and is connected to the shaft 11 in a torsion-free manner, for example by a press fit.

[0046] With reference to FIG. 1each ball ring 13 is connected to a race assembly 20 and three race assemblies 20 are delimited in the axial direction A and in the circumferential direction of the shaft 11 by the cage assembly 30.

[0047] The race assemblies 20 are described with reference to FIGS. 5 to 9 described.

[0048] In the present embodiment, the race assembly 20 includes a race frame 21, an inner race 22, an outer race 23, and an elastic member 24.

[0049] With reference to FIG. 6The race frame 21 includes two substantially rectangular side frames 211 and a connecting rod 212 connecting the two side frames 211. The central portion of the side frame 211 has a through-hole penetrating in a direction in which the connecting rod 212 extends. Pocket edges 211a are convexly formed on opposite inner surfaces of the two side frames 211. Specifically, four pocket edges 211a are formed on one side frame 211 and are substantially C-shaped, with the main body of the pocket edge 211a located at the central portion of the C-shape extending along one long edge of the side frame 211, and the four pocket edges 211a occupy substantially four corners of the side frame 211.C-shaped openings of two opposite pocket edges 211a on the two long edges of the side frame 211 are opposite each other, defining a pocket slot 211b between the two pocket edges 211a. Each side frame 211 has two pocket slots 211b, each located on two sides of the connecting rod 212, used for mounting the inner race 22 and the outer race 23. The pocket slots 211b of the two side frames 211, which are located on the same side of the connecting rod 212, are opposite each other for mounting a pair of races.

[0050] At the same time, with reference to FIG. 5An inner race 22 and an outer race 23 form a race pair. A race assembly 20 includes two race pairs. The inner race 22 is provided on the inner side of the outer race 23 and is closer to the connecting rod 212. Two ends of each of the inner race 22 and the outer race 23 extend into two pocket slots 211b, respectively, to connect to the race frame 21. The space between the two inner races 22 forms a ball race mounting portion 20s, and the ball race 13 can be embedded in the ball race mounting portion 20s.

[0051] At the same time, with reference to FIG. 7opposite surfaces of the two inner races 22 are partially recessed to form a concave surface 22s, which is preferably part of a spherical surface. When the ball race 13 is embedded in the ball race mounting portion 20s, the ball race 13 is clamped by the two concave surfaces 22s. The ball race 13 can vibrate in all directions within a small range relative to the concave surface 22s, but cannot detach from the race assembly 20 because the spherical surface of the ball race 13 mates with the spherical surface of the concave surface 22s. The position of the race assembly 20 in the axial direction A and in the circumferential direction relative to the shaft 11 can be determined such that the ball race 13 mates with the two concave surfaces 22s of the race assembly 20 because the position of the ball race 13 relative to the joint 12 is determined with three bolts (orto the shaft 11) in axial direction A and in circumferential direction.

[0052] With reference to the FIG. 5 and 9 The elastic element 24 is substantially U-shaped and comprises a connecting portion 242 and two wave-shaped springs 241 connected to both ends of the connecting portion 242. The two wave-shaped springs 241 are each inserted between the inner race 22 and the outer race 23 of a race pair, wherein the connecting portion 242 extends through a bore in the central portion of the side frame 211, and preferably the connecting portion 242 is entirely housed in the bore in the central portion of the side frame 211.

[0053] Both sides of the wave-shaped spring 241 abut against the inner race 22 and the outer race 23, respectively. Preferably, in the initial state (when the coupling is not mounted on the motor shaft and the worm gear, and the ball race 13 is positioned exactly in the center of the two outer races 23), the wave-shaped spring 241 is slightly deformed downward, slightly compressing the inner race 22 and the outer race 23. At this time, the elastic force generated by the wave-shaped spring 241 presses the inner race 22 and the outer race 23 against the contour edge of the pocket slot 211b, that is, the inner race 22 and the outer race 23 abut against the pocket edges 211a to fill the pocket slots 211b in the direction in which the long edges of the side frames 211 extend.

[0054] During operation of the steering mechanism, the ball ring 13 pushes one of the inner races 22 in a certain direction (this state will be described below), causing the wave-shaped spring 241 to deform under compression.

[0055] The wave-shaped spring 241 has a wave shape and falls under the category of a non-linear spring. This means that the stiffness coefficient (also called elastic constant) of the wave-shaped spring 241 changes when the wave-shaped spring is deformed by compression. Since the wave-shaped spring 241 deforms to different degrees, the force exerted by the wave-shaped spring 241 on the inner race 22 and the outer race 23 is also non-linear, which is beneficial for maintaining a certain transmission stiffness.

[0056] With reference to the FIG. 5 and 8the central portion of the outer race 23 side away from the ball ring mounting portion 20s is recessed to form a curved surface 23a in contact with balls 32 of the cage assembly 30, which will be described below.

[0057] With reference to the FIG. 1 , 10 and 11 The specific structure of the cage assembly 30 and its limitation to the race assembly 20 are described as follows.

[0058] The cage assembly 30 includes a cage body 31 and balls 32. The cage body 31 includes an annular portion 311 and three arms 312 connected to the annular portion 311, the three arms 312 being equally spaced circumferentially of the annular portion 311 and extending axially of the annular portion 311. The arms 312 engage both the race assembly 20 and projecting ribs 41 of the sliding sleeve 40 of the second connector N (described further below).

[0059] With reference to FIG. 11 each arm 312 is formed with two rows of notches on both sides in the circumferential direction of the annular portion 311, and each row of notches includes a plurality (three in the figure) of ball pockets 31b in the shape of a large semicircle (a semicircle corresponding to a main arc).

[0060] With reference to FIG. 10Each ball pocket 31b accommodates a ball 32, which is preferably a steel ball. The balls 32 are floatingly received in the ball pockets 31b, meaning that the balls 32 can roll in the ball pockets 31b without rolling out of the ball pockets 31b.

[0061] With further reference to FIG. 11The central portion of each arm 312, located in the circumferential direction between two rows of ball pockets 31b, is recessed radially and inwardly to form an arm recess 312a. A hook portion 31h, projecting radially and outwardly, is formed at one end of the arm 312 away from the annular portion 311. Preferably, the outer peripheral portion of the annular portion 311 also has three radially and outwardly projecting annular projections 311a arranged between two adjacent arms 312 in the circumferential direction.The arm recess 312a is configured to mate with the protruding rib 41 (described below) of the sliding sleeve 40 located on the second connector N to define a position between the first connector M and the second connector N in the circumferential direction; the hook portion 31h is configured to hook into the protruding rib 41 to define a position between the first connector M and the second connector N in the axial direction A; and the annular projections 311a are configured to abut against an end surface (described below) of a first end 401 of the sliding sleeve 40 in the axial direction A to define a position between the first connector M and the second connector N in the axial direction A.

[0062] With further reference to FIG. 1With respect to the first connector M, a race assembly 20 is housed between two adjacent arms 312, and the balls 32 abut against the curved surface 23a of the outer race 23 of the race assembly 20. In addition, the race assembly 20 (in particular, the race frame 21 of the race assembly 20) abuts against the cage body 31 of the cage assembly 30 in the axial direction A, so that the race assembly 20 is prevented from deviating from the FIG. 1 shown left side.

[0063] At this point, the reader can understand how the three-pin shaft assembly 10, the raceway assemblies 20, and the cage assembly 30 are connected to form an integral whole. The first connector M of the whole can transmit torque in the circumferential direction. In other words, the cage assembly 30 can transmit torque to the shaft 11 via the raceway assemblies 20, the ball races 13, and the three-pin joint 12. Each component of the first connector M can absorb vibration during the process of mutually transmitting torque (described below).

[0064] Next, the second connector N according to the present invention and the connection relationship between the second connector N and the first connector M will be described with reference to FIG. FIGS. 1, 2 and 12 to 15 described.

[0065] The second connector N comprises a sliding sleeve 40 and a vibration damping arrangement 50, which are connected in a torsion-free manner.

[0066] With reference to FIG. 1 (the dotted line in FIG. 1 indicates the sliding sleeve 40), FIG. 2 and FIG. 12 The sliding sleeve 40 has a substantially tubular shape. A first end 401 (a left end in FIG. 12 ) of the sliding sleeve 40 in the axial direction A is connected to the first connector M and a second end 402 (a right end in FIG. 12 ) of the sliding sleeve 40 is connected in axial direction A to the vibration damping arrangement 50.

[0067] The inner cavity of the sliding sleeve 40 is formed at the first end 401 with three ribs 41 that are evenly distributed in the circumferential direction and project radially inward, wherein the projecting ribs 41 extend in the axial direction A to form a groove 42 between each two adjacent projecting ribs 41.

[0068] Two sides of each protruding rib 41 are each formed with a recessed curved surface 41a in the circumferential direction, and each curved surface 41a abuts a row of balls 32 mounted on an arm 312. In other words, each protruding rib 41 mates with a corresponding arm 312. The protruding rib 41 has a length in the axial direction A that is approximately equal to the length of the arm 312.

[0069] With reference to the FIG. 1 and 11the projecting portion of the projecting rib 41 is provided relative to the arm recess 312a, and the balls 32 abut against the curved surface 41a; the arms 312 have a certain elasticity in the radial direction R, so that when the first connector M is inserted into the sliding sleeve 40 from the first end 401 of the sliding sleeve 40, the hook portion 31h is pressed by the projecting rib 41 to be elastically deformed radially and inwardly, and the first connector M continues to extend into the sliding sleeve 40 until the annular projections 311a abut against the end surface of the sliding sleeve 40 at the first end 401, at which point the first connector M is mounted in place.At this time, the hook portions 31h extend just beyond the area covered by the protruding ribs 41 in the axial direction A and are ejected radially and outwardly, and therefore, the arms 312 are returned to their original shape. Hook portions 31h hook into the end surface in the axial direction of the protruding ribs 41 away from the first end 401 such that the annular projections 311a and hook portions 31h define the position of the cage assembly 30 and the sliding sleeve 40 relative to each other at both ends of the axial direction A.

[0070] At this time, the raceway assemblies 20 are received in the grooves 42, the raceway assemblies 20 are positioned in the circumferential direction by the balls 32, and the balls 32 are positioned in the circumferential direction by the curved surfaces 41a, thereby realizing the mutual positioning of the first connector M and the second connector N in the circumferential direction.

[0071] With further reference to FIG. 12 the inner cavity of the sliding sleeve 40 does not have any protruding ribs 41 near the second end 402, but instead forms a smooth cylindrical surface.

[0072] Preferably, the inner cavity of the sliding sleeve 40 of the structure described above can be machined, for example, by machining the three projecting ribs penetrating the inner cavity of the sliding sleeve 40 in the axial direction A, using rotary deep drawing in the inner cavity, and then removing a part of the projecting ribs near the second end 402 by machining to form the FIG. 12 shown projecting ribs 41.

[0073] With reference to FIGS. 1 and 2 The second end 402 of the sliding sleeve 40 is configured to mount the vibration damping assembly 50. The vibration damping assembly 50 includes an adapter 51, a shell housing 52, and a buffer 53. The adapter 51 is connected to the sliding sleeve 40 in a torsion-free manner.

[0074] With reference to the FIGS. 13 and 14The adapter 51 includes a main body 511 and a projection 512. The main body 511 is shaped like a disc, the cylindrical projection 512 is convexly formed in the center of the main body 511 facing the end surface of the first end 401, and the projection 512 is configured for mounting the shell housing 52. The central portion of the adapter 51 is also provided with a splined hole 51h configured to be connected to the output shaft of the motor of the steering mechanism. For example, an external spline is provided on the output shaft to mate with the splined hole 51h.

[0075] Preferably, the adapter 51 is made of an engineering plastic with suitable deformability. The adapter 51 is embedded in the inner cavity of the sliding sleeve 40, and the torsion-free connection between the adapter 51 and the sliding sleeve 40 is realized by a press fit between the base body 511 and the sliding sleeve 40. When the splined bore 51h mates with the external spline, the splined bore 51h is slightly enlarged by the external spline, thereby achieving a backlash-free fit between the adapter 51 and the external spline.

[0076] With reference to the FIG. 2 and 15The shell housing 52 has the shape of a shell and is formed, for example, by stamping. The shell housing 52 is slid onto the projection 512 of the adapter 51 and can move within a small range in the axial direction A relative to the projection 512 (it would be easier for the reader to understand this small range of movement if a gap G is described below). In the axial direction A, a buffer 53 is provided in the inner cavity of the shell housing 52, or actually between the shell housing 52 and the adapter 51. The buffer 53 is made of rubber, for example, and the rubber buffer 53 is molded into the inner cavity of the shell housing 52, for example, by a vulcanization process.

[0077] When the shell housing 52 is pushed onto the projection 512, the projection 512 abuts the buffer 53 in the initial state, but the shell housing 52 does not abut the main body 511, that is, there is a gap G in the axial direction A between the shell housing 52 and the main body 511 (see FIG. 2 ). The buffer 53 can deform elastically in the axial direction A, so that the shaft 11 can be displaced in the axial direction A relative to the adapter 51 within a small range.

[0078] The central portion of the shell housing 52, facing the end surface of the shaft 11 in the axial direction A, is recessed to form a concave spherical portion 52s in the shape of a spherical surface. Accordingly, an elastic member tightly abutting the shell housing 52 also forms a spherical concave portion 53s at a corresponding position. The concave spherical portion 52s is configured to abut the spherical surface 11s of the shaft 11. Preferably, the radius of the sphere corresponding to the spherical surface 11s is slightly smaller than the radius of the sphere corresponding to the concave spherical portion 52s.

[0079] The spherical surface 11s abuts the concave spherical portion 52s, so that when the shaft 11 is offset relative to the axial direction A, the concave spherical portion 52s can still achieve effective centering on the shaft 11.

[0080] Accordingly, when the first connector M and the second connector N are connected in the axial direction A as a connecting end of the coupling, the shaft 11 abuts against the shell housing 52 on one side and is thereby restricted relative to the second connector N, and the shaft 11 is restricted by the raceway assemblies 20 connected to the shaft 11 (the raceway assemblies 20 are restricted by the cage body 31 in the axial direction A) on the other side and is thereby restricted relative to the first connector M.

[0081] With further reference to the FIGS. 1 and 2The self-aligning and vibration-damping capabilities of the coupling according to the present invention are described. If the axial play of a self-aligning bearing located on one side of the worm gear is too small at the time of steering reversal, the worm gear and the worm gear will transition from a static friction engagement to a sliding friction engagement, resulting in a sudden increase and decrease in friction torque. One way to prevent or mitigate this sudden increase or decrease in friction torque is to increase the axial play of the self-aligning bearing, which leads to axial acceleration between parts of the bearing. The vibration caused by the axial acceleration can then be absorbed by the coupling according to the present invention.

[0082] For example, when the axial acceleration generated by the self-aligning bearing is transmitted to the shaft 11, the shaft 11 abuts against the vibration damping assembly 50, so that the shock of the shaft 11 against the shell housing 52 is absorbed by the buffer 53.

[0083] In addition, the distance between the teeth of the worm gear increases when the worm gear wears under high torque, causing the worm meshing with the worm gear to vibrate and be displaced in all directions. The vibration can be absorbed by the coupling according to the invention, and the displacement can be adjusted by the coupling according to the invention.

[0084] For example, when the axis of the shaft 11 is offset relative to the sliding sleeve 40 (this offset may involve axial displacement of the shaft 11 relative to the sliding sleeve 40 and / or circumferential deflection of the shaft 11 relative to the sliding sleeve 40), the ball race 13 presses on the inner race 22, so that the distance between the inner race 22 and the outer race 23 changes, and the vibration generated by the change in distance can be absorbed by the elastic member 24. When the race assemblies 20 are offset relative to the cage assembly 30, the six rows of balls 32 roll on the cage assembly 30 relative to the curved surfaces 23a of six outer races arranged on the three race assemblies 20, so that sudden increases and decreases in friction are less likely to occur.

[0085] Finally, an assembly method for a three ball stud coupling according to the present invention is introduced as follows.

[0086] An inner race 22, an outer race 23, and an elastic member 24 are mounted on a race frame 21 to form a race assembly 20. Three race assemblies 20 are then mounted on a three-shaft pin assembly 10 to form a three-pin universal pivot module.

[0087] A shell housing 52 with a buffer 53 is connected to an adapter 51 to form a vibration damping assembly 50.

[0088] Balls 32 are mounted in ball pockets 31b of a cage body 31 to form a cage assembly 30.

[0089] The vibration damping assembly 50 is press-fitted to a sliding sleeve 40; then, the cage assembly 30 drives the universal pivot module into the sliding sleeve 40 with three bolts in an axial direction A; and when a hook portion 31h and an annular projection 311a of the cage assembly 30 are fitted in place on the sliding sleeve 40 and the shaft 11 abuts the shell housing 52, the assembly is complete.

[0090] It is understood that the order of execution of each sub-step of the arrangement described above can be adapted.

[0091] Some of the advantageous effects of the above embodiments of the present invention will be briefly described below. (i) A first connector M of a three-ball-stud coupling according to the present invention uses a three-shaft stud assembly 10. A ball race 13 of the three-shaft stud assembly 10 forms a spherical fit with an inner race 22 of a race assembly 20, and that of a race assembly 20 fits into a sliding sleeve 40 of a second connector N, thereby achieving universal oscillation of the first connector M relative to the second connector N. When a large angle misalignment (e.g., ±1.5°) occurs between the first connector M and the second connector N, torque can still be transmitted between the first connector M and the second connector N. In other words, the misalignment angle of the worm can be dynamically compensated even under high load, for example, when the plastic worm wheel is severely worn and the worm axis is severely offset.(ii) The race assembly 20 includes a non-linear wave spring 241 having two sides that flexibly fix the inner race 22 and the outer race 23. The three race assemblies 20 are arranged around the three-wave pin assembly 10, so that backlash-free transmission between the first connector M and the second connector N in the circumferential direction can be realized. The elastic member 24 can compensate for the tolerance, and this not only ensures the transmission rigidity but also lowers the tolerance requirements for the production of related parts to improve production robustness, thereby avoiding backlash and vibration shock during reversing by meeting the requirements for gapless torque transmission between transmission elements.(iii) A cage assembly 30 includes floating balls 32, and the balls 32 form a linear race pair with the sliding sleeve 40 and the outer race 23, thereby eliminating sudden increases and decreases in friction during transmission. Furthermore, the processing and assembly of the balls 32 and a cage body 31 are technically simple because the balls 32 can be first mounted on the cage body 31 and then assembled together with the cage body 31 into the inner cavity of the sliding sleeve 40. (iv) The second connector N of the three-ball coupling according to the present invention includes a vibration damping assembly 50, so that the transmission elements are not subjected to axial vibration, and the requirement for controlling the axial play of the self-aligning bearing of the steering gear is reduced.(v) The steering mechanism according to the present invention is not liable to backlash and vibration shock during reversing, and to system shock due to friction fluctuations during the operation of reversing reverse and forward and continuous starting and stopping.

[0092] It should be understood that the above embodiments are merely exemplary and are not intended to limit the present invention. Those skilled in the art may make various modifications and changes to the above embodiments in accordance with the teachings of the present invention without departing from the scope of the present invention. For example: (i) the adapter 51 need not be an insert embedded in the sliding sleeve 40, but may be connected to the sliding sleeve 40, for example, by a screw connection, a threaded connection, or fusion welding; (ii) the joint 12 may be formed with three bolts as an integral part of the shaft 11; (iii) the race frame 21 may be in other frame shapes and is not limited to the shape described herein; and (iv) the two wave-shaped springs 241 of the same race assembly 20 need not be connected by the connecting portion 242, thereby forming two independent elastic elements. LIST OF REFERENCE SYMBOLS

[0093] M.first connector; N.second connector; 10.three-shaft pin assembly; 11.shaft; 11s.spherical surface; 11h.pin hole; 12.three-pin joint; 12n.trunnion; 13.ball race; 20.race assembly; 20s.ball race mounting portion; 21.race frame; 211.side frame; 211a.pocket edge; 212.connecting rod; 22.inner race; 22s.spherical concave surface; 23.outer race; 23a.curved surface; 24.elastic element; 241.wave spring; 242.connecting portion; 30.cage assembly; 31.cage body; 311.annular portion; 311a.annular projection; 312.arm; 312a.arm recess; 31b.ball pocket; 31h.hook portion; 32.ball; 40.sliding sleeve; 401.first end; 402.second end; 41.projecting rib; 41a.curved surface; 42.groove; 50.vibration damping assembly; 51.adapter; 511.main body; 512.projection; 51h.spline bore; 52.shell housing; 52s.concave spherical portion; 53.buffer; 53s.concave spherical portion; A.axial direction; R.radial direction; G.Gap.

Claims

1. A three ball stud-type coupling, comprising a first connector (M) and a second connector (N), which are non-rotatably connected, wherein the first connector (M) comprises a stud assembly with three shafts (10), race assemblies (20) and a cage assembly (30); the three-shaft stud assembly (10) comprises a shaft (11) and three ball rings (13) surrounding the shaft (11) and spaced apart in the circumferential direction of the shaft (11); three race assemblies (20) are provided; each ball ring (13) is connected to one of the race assemblies (20); the cage assembly (30) defines the circumferential position of the race assemblies (20); the race assemblies (20) can provide an elastic force between the ball ring (13) and the cage assembly (30); and when the ball ring (13) shifts relative to the cage assembly (30) in the circumferential direction, two sides of the race assembly (20) continue to bear against the cage assembly (30) in the circumferential direction, characterised in that the cage assembly (30) comprises a cage body (31) and balls (32); the cage body (31) comprises an annular section (311) and three arms (312) connected to the annular section (311); the arms (312) extend along an axial direction (A) of the annular section (311); two sides of the arms (312) are formed with a plurality of notched ball pockets (31b) in the circumferential direction; the balls (32) are accommodated in the ball pockets (31b) and are capable of rolling relative to the ball pockets (31b) within the ball pockets (31b); each of the arms (312) is inserted between two of the race assemblies (20); and the balls (32) bear against the race assemblies (20).

2. The three ball stud-type coupling according to claim 1, characterised in that the race assemblies (20) comprise race frames (21), inner races (22), outer races (23) and elastic elements (24); each of the race frames (21) is provided with two inner races (22) and two outer races (23); two of the inner races (22) are spaced apart from each other to form a ball ring mounting section (20s) therebetween; one of the outer races (23) is mounted on one side of each of the inner races (22) spaced apart from the ball ring mounting section (20s); an inner race (22) and an outer race (23) arranged on the same side of the ball ring mounting section (20s) form a race pair; the elastic element (24) is provided at least partially between the inner race (22) and the outer race (23); and the elastic element (24) bears against the inner race (22) and the outer race (23) of each of the race pairs.

3. The three ball stud-type coupling according to claim 2, characterised in that when the ball ring (13) is arranged exactly in the middle of two of the outer races (23), the elastic element (24) is compressed by the inner race (22) and the outer race (23) and is thereby elastically deformed.

4. The three ball stud-type coupling according to claim 2, characterised in that a stiffness coefficient of the elastic element (24) changes during an elastic deformation of the elastic element (24).

5. The three ball stud-type coupling according to claim 4, characterised in that a section of the elastic element (24) between the inner race (22) and the outer race (23) is at least partially wave-shaped.

6. The three ball stud-type coupling according to claim 5, characterised in that the elastic element (24) is U-shaped overall; the elastic element (24) comprises a connecting section (242) and two wave-shaped springs (241) connected to two ends of the connecting section (242); and two of the wave-shaped springs (241) are each inserted between the inner race (22) and the outer race (23) of one of the race pairs.

7. The three ball stud-type coupling according to claim 2, characterised in that a side of the inner race (22) facing the ball ring mounting section (20s) is partially recessed to form a spherical concave surface (22s) which is part of a spherical surface and is in contact with the ball rings (13).

8. The three ball stud-type coupling according to claim 2, characterised in that a side of the outer race (23) facing away from the ball ring mounting section (20s) is partially recessed to form a curved surface (23a) in contact with the cage assembly (30).

9. The three ball stud-type coupling according to claim 1, characterised in that a central section of each of the arms (312) located in the circumferential direction between two rows of the ball pockets (31b) is recessed radially and inwardly to form an arm recess (312a).

10. The three ball stud-type coupling according to claim 1, characterised in that the second connecting piece (N) comprises a tubular sliding sleeve (40) having a first end (401) in the axial direction (A) connected to the first connecting piece (M); an inner cavity of the sliding sleeve (40) comprises three projecting ribs (41) in the axial direction (A) near the first end (401), which project radially and inwardly and are spaced apart in the circumferential direction; the projecting ribs (41) extend in the axial direction (A) to form a groove (42) between each two adjacent projecting ribs (41); the arms (312) are circumferentially aligned with the projecting ribs (41); the balls (32) bear against the projecting ribs (41); and each of the race assemblies (20) is received in one of the grooves (42).

11. The three=ball stud-type coupling according to claim 10, characterised in that two sides of each of the projecting ribs (41) in the circumferential direction are each formed with a depressed curved surface (41a), and the balls (32) bear against the curved surfaces (41a).

12. The three=ball stud-type coupling according to claim 10, characterised in that a hook section (31H) projecting outward in a radial direction of the annular section (311) is formed at the end of the arm (312) away from the annular section (311), and the hook section (31H) hooks into the projecting rib (41) to prevent the cage assembly (30) from detaching from the first end (401).

13. The three ball stud-type coupling according to claim 10, characterised in that an outer peripheral section of the annular section (311) includes a plurality of annular projections (311a) projecting radially and outwardly, and the annular projections (311a) bear against an end surface of the sliding sleeve (40) at the first end (401) to delimit the cage assembly (30) in the axial direction (A).

14. The three ball stud-type coupling according to claim 10, characterised in that the inner cavity of the sliding sleeve (40) has no projecting ribs (41) in the axial direction (A) at a second end (402) spaced apart from the first end (401); the second connector (N) further comprises a vibration-damping assembly (50) non-rotatably mounted at the second end (402) relative to the sliding sleeve (40); the vibration-damping assembly (50) extends at least partially into the interior cavity of the sliding sleeve (40); the shaft (11) bears against the vibration-damping assembly (50), an axial end of the shaft (11) near the vibration-damping assembly (50) forms a spherical surface (11s); and a section of the vibration-damping assembly (50) which is in contact with the shaft (11) is shaped as a spherical surface.

15. The three ball stud-type coupling according to claim 14, characterised in that the vibration-damping assembly (50) comprises an adapter (51), a shell housing (52) and a buffer (53); the adapter (51) and the sliding sleeve (40) are non-rotatably connected to each other; the shell housing (52) is connected to the adapter (51); the buffer (53) is provided between the shell housing (52) and the adapter (51); a section of the shaft (11) which is in contact with the vibration-damping assembly (50) is located on the shell housing (52); and a section of the shell housing (52) which is in contact with the shaft (11) forms a recessed concave ball section (52s) in the shape of a spherical surface.

16. The three ball stud-type coupling according to claim 15, characterised in that an inner peripheral section of the adapter (51) forms an interlocking bore (51h).

17. The three ball stud-type coupling according to claim 15, characterised in that the adapter (51) is embedded in the inner cavity of the sliding sleeve (40); a central section of the end surface of the adapter (51) facing the shaft (11) forms a projection (512) by projecting in the direction of the shaft (11); and the shell housing (52) is pushed onto the projection (512) such that the shell housing is axially movable relative to the projection.

18. The three ball stud-type coupling according to claim 17, characterised in that, when the buffer (53) is not compressed, a gap (G) exists between the shell housing (52) and the end surface of the adapter (51) facing the shaft (11).

19. A steering mechanism comprising a motor, a coupling, and a worm gear and worm assembly, characterised in that the coupling is a three ball stud-type coupling according to any one of claims 1 to 18; the first connector (M) of the three ball stud-type coupling and a worm of the worm gear and worm assembly are non-rotatably connected; and the second connector (N) of the three ball stud-type coupling and an output shaft of the motor are non-rotatably connected.