Universal joint

Abstract

A universal joint (10) is provided with: a cross shaft (11) having a trunnion (11a); a bearing cup (12) that supports the trunnion (11a) via a plurality of rollers (15); the fork head (13) is used for mounting the bearing cup (12); a fastening member (14) that fixes the bearing cup (12) to the fork head (13); and a pressure sensor (40). The bearing cup (12) has: a first surface (20) including a first contact surface (22) that comes into contact with the fork head (13) and a key (24) that protrudes from the first contact surface (22); and a through-hole (25) that opens in the first contact surface (22) and through which the fastening member (14) passes. The prong (13) has: a second surface (26) including a second contact surface (30) that comes into contact with the first contact surface (22) and a key groove (23) that is recessed with respect to the second contact surface (30) and into which the key (24) is fitted; a fastening hole (28) that opens in the second contact surface (30) and to which the fastening member (14) is fastened; and a hydraulic chamber (42) filled with a liquid (L). The pressure sensor (40) measures the pressure of the liquid (L). At least a portion of the hydraulic chamber (42) is located between the key groove (23) and the fastening hole (28).

Description

Technical Field

[0001] The present invention relates to a universal joint. Background Art

[0002] Patent Document 1 discloses a large universal joint used for a drive shaft of a rolling mill or the like.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2006-77873 Summary of the invention

[0006] Problems to be solved by the invention

[0007] In order to measure the torque acting on the drive shaft of the rolling mill using the universal joint, for example, a strain gauge may be mounted on the drive shaft. The torque acting on the drive shaft is measured based on the output of the strain gauge.

[0008] However, torque measurement based on strain gauges requires the connection of a transmitter and a bridge circuit, etc., in addition to the strain gauge, to obtain the output of the strain gauge when the drive shaft rotates. In addition, multiple cables are required to connect these devices, so the structure of the equipment used for torque measurement is often complicated. In addition, there is the possibility that the strain gauge may be damaged by the excessive torque generated instantly.

[0009] The universal joint connected to the drive shaft is constructed by including a plurality of parts.

[0010] The inventors of the present application focused on this point and considered that the torque of the drive shaft can be measured with a relatively simple structure by simply measuring the stress acting on some of the multiple components included in the universal joint, thereby creating the embodiment involved in the present disclosure.

[0011] Means for solving problems

[0012] The universal joint of this embodiment comprises: a cross shaft having an ear shaft; a bearing cup supporting the ear shaft via a plurality of rollers; a fork head for mounting the bearing cup; a fastening member for fixing the bearing cup to the fork head; and a pressure sensor. The bearing cup comprises: a first surface including a first abutting surface abutting against the fork head and a key protruding relative to the first abutting surface; and a through hole opening in the first abutting surface and allowing the fastening member to pass through. The fork head comprises: a second surface including a second abutting surface abutting against the first abutting surface and a keyway recessed relative to the second abutting surface and allowing the key to be inserted; a fastening hole opening in the second abutting surface and allowing the fastening member to be fastened; and a hydraulic chamber filled with liquid. The pressure sensor measures the pressure of the liquid. At least a portion of the hydraulic chamber is located between the keyway and the fastening hole.

[0013] Effects of the Invention

[0014] According to the present disclosure, it is possible to obtain a universal joint capable of measuring torque with a simple structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a diagram showing a universal joint according to an embodiment.

[0016] Figure 2 It is an exploded perspective view of the universal joint according to the embodiment.

[0017] Figure 3 yes Figure 1 Partial cross-sectional view taken along line III-III.

[0018] Figure 4 yes Figure 3 Partial cross-sectional view taken along line IV-IV.

[0019] Figure 5 This is a block diagram showing a configuration example of a pressure sensor and a data processing device.

[0020] Figure 6 It is a diagram showing a universal joint according to a modified example. DETAILED DESCRIPTION

[0021] First, the contents of the embodiment will be listed and described.

[0022] [Overview of Embodiments]

[0023] (1) The universal joint of this embodiment comprises: a cross shaft having an ear shaft; a bearing cup supporting the ear shaft via a plurality of rollers; a fork head for mounting the bearing cup; a fastening member for fixing the bearing cup to the fork head; and a pressure sensor. The bearing cup comprises: a first surface including a first abutting surface abutting against the fork head and a key protruding relative to the first abutting surface; and a through hole opening in the first abutting surface and allowing the fastening member to pass through. The fork head comprises: a second surface including a second abutting surface abutting against the first abutting surface and a keyway recessed relative to the second abutting surface and allowing the key to be inserted; a fastening hole opening in the second abutting surface and allowing the fastening member to be fastened; and a hydraulic chamber filled with a liquid. The pressure sensor measures the pressure of the liquid. At least a portion of the hydraulic chamber is located between the keyway and the fastening hole.

[0024] When torque acts on the universal joint via the drive shaft or the like, stress corresponding to the torque acts on the fork through the bearing cup. The fork is slightly elastically deformed by the stress. At this time, the pressure of the liquid in the hydraulic chamber provided in the fork changes according to the magnitude of the stress acting on the fork. That is, the pressure of the liquid in the hydraulic chamber changes according to the magnitude of the torque acting on the universal joint.

[0025] In particular, compressive stress acts on the keyway of the fork head. The compressive stress is generated by the keyway being pressed by the key or the key being pressed by the keyway.

[0026] In this embodiment, at least a portion of the hydraulic chamber is located between the keyway and the fastening hole. Therefore, the hydraulic chamber is located near the keyway. The compressive stress acts on the hydraulic chamber. As a result, the stress change caused by the torque acting on the universal joint is manifested as a pressure change of the liquid.

[0027] Therefore, the universal joint of the present embodiment can measure the torque acting on the universal joint based on the output of the pressure sensor.

[0028] Thus, the universal joint of this embodiment can measure torque by measuring the pressure of the liquid in the hydraulic chamber. Therefore, compared with the universal joint described in the above-mentioned subject that uses a strain gauge for torque measurement, a bridge circuit or the like is not required, and the processing of wiring or the like is also simplified. As a result, the universal joint of this embodiment can measure torque with a simple structure. In addition, the universal joint of this embodiment will not damage the hydraulic chamber due to the excessive torque generated instantly.

[0029] (2) In the above-mentioned universal joint, it is preferable that the hydraulic chamber is located between the bottom surface of the key groove and the second contact surface in an axial direction parallel to the central axis of the universal joint.

[0030] In this case, the hydraulic chamber can be reliably provided between the key groove and the fastening hole.

[0031] (3) In the universal joint of the present embodiment, compressive stress in the circumferential direction acts on the key groove. Therefore, in the universal joint of the present embodiment, compressive stress acts on the key groove over the entire region in the longitudinal direction of the key groove.

[0032] In this regard, in the above-mentioned universal joint, preferably, when the key and the key groove extend in a radial direction orthogonal to the central axis, the hydraulic chamber includes a cylindrical hole along a longitudinal direction of the key groove.

[0033] In this case, the universal joint of this embodiment can ensure a large range in which the hydraulic chamber and the key groove are arranged in the vicinity along the length direction of the key groove. Therefore, the universal joint of this embodiment can generate a more significant pressure change of the liquid caused by the stress change.

[0034] [Details of implementation method]

[0035] Hereinafter, preferred embodiments will be described with reference to the drawings.

[0036] [About the overall structure]

[0037] Figure 1 It is a diagram showing a universal joint according to an embodiment. Figure 2 It is an exploded perspective view of the universal joint according to the embodiment.

[0038] The universal joint 10 is used, for example, in a rolling mill of an ironworks. More specifically, the universal joint 10 is disposed between the input shaft and the drive shaft of the roll, and between the output shaft and the drive shaft of the drive motor, and connects a pair of shafts to each other so that they can rotate as one. The universal joint 10 transmits rotational force from one of the pair of shafts to the other.

[0039] The universal joint 10 includes a cross shaft 11 , four bearing cups 12 , a pair of yokes 13 , and a plurality of fastening members 14 .

[0040] The plurality of fastening members 14 are members for fixing the bearing cup 12 to the fork head 13. The plurality of fastening members 14 are, for example, bolts.

[0041] The cross shaft 11 has four trunnions 11 a.

[0042] Each bearing cup 12 supports each trunnion 11a via a plurality of rollers 15. All the bearing cups 12 have the same structure.

[0043] Each bearing cup 12 is mounted on a pair of forks 13 .

[0044] The pair of forks 13 are connected to a pair of shafts (not shown) in the rolling mill so as to be rotatable as one with the other.

[0045] A pair of forks 13 Figure 1 and Figure 2 The first fork 13a shown on the right side of FIG. 1 is included in the first shaft 16. The first fork 13a is rotatable integrally with the first shaft 16. The first shaft 16 is connected to one of a pair of shafts in the rolling mill.

[0046] A pair of forks 13 Figure 1 and Figure 2 The second fork 13b shown on the left side is included in the second shaft 17. The second fork 13b is rotatable integrally with the second shaft 17. The second shaft 17 is connected to the other shaft of the pair of shafts in the rolling mill.

[0047] The first fork 13a and the second fork 13b have the same structure.

[0048] Here, the central axis of the first shaft 16 (the first fork 13 a ) and the central axis of the second shaft 17 (the second fork 13 b ) are arranged in a straight line ( Figure 1 In the state shown in the figure), the direction along the central axis C is the "axial direction". In the invention disclosed in the present invention, the "axial direction" also includes the direction parallel to the central axis C.

[0049] In addition, the direction orthogonal to the central axis C is the “radial direction”. The direction of rotation about the central axis C is the “circumferential direction”.

[0050] like Figure 2 As shown, each bearing cup 12 has a first surface 20 opposite to the fork head 13 and a plurality of through holes 25 .

[0051] The first surface 20 includes a first abutting surface 22 that abuts against the fork 13 and a key 24 .

[0052] The key 24 protrudes in a rectangular shape relative to the first contact surface 22 .

[0053] The plurality of through holes 25 are provided parallel to the axial direction. The plurality of through holes 25 penetrate between the first surface 20 and the first opposite surface 19. The first opposite surface 19 is a surface facing the opposite side of the first surface 20 in the bearing cup 12.

[0054] In this embodiment, three through holes 25 are provided on both sides of the bearing cup 12 in the circumferential direction, and a total of six through holes 25 are provided. The plurality of through holes 25 open in two regions 22a adjacent to both sides of the key 24 in the circumferential direction of the first abutting surface 22. The three through holes 25 open in two regions 22a respectively.

[0055] The two sets of a pair of bearing cups 12 are mounted on a pair of forks 13. The following description will describe the structure of the first fork 13a. On the other hand, the structure of the second fork 13b is the same as that of the first fork 13a.

[0056] The first prong 13 a has a second surface 26 opposite to the first surface 20 of the bearing cup 12 and a plurality of fastening holes 28 .

[0057] The second surface 26 includes a pair of second abutting surfaces 30 and a pair of key grooves 23. The pair of second abutting surfaces 30 are surfaces that abut against the first abutting surface 22 of one of the bearing cups 12 in the pair.

[0058] The pair of second contact surfaces 30 are provided on both sides of the second surface 26 in the radial direction with the central axis C interposed therebetween.

[0059] The pair of key grooves 23 are recessed relative to the pair of second abutment surfaces 30. The keys 24 of the pair of bearing cups 12 are inserted into the pair of key grooves 23.

[0060] The pair of key grooves 23 extend radially from the outer peripheral surface 13g of the first fork 13a, respectively. Therefore, the key grooves 23 are provided so as to cut out the outer peripheral surface 13g.

[0061] The plurality of fastening holes 28 are respectively disposed on the pair of second abutting surfaces 30 .

[0062] The plurality of fastening holes 28 are opened in two regions 30a adjacent to both sides in the circumferential direction of the key groove 23 in the second contact surface 30. The three fastening holes 28 are opened in the two regions 30a, respectively.

[0063] An internal thread is formed on the inner peripheral surface of the fastening hole 28. An external thread provided on the front end of the fastening member 14 is screwed into the internal thread.

[0064] The fastening member 14 is inserted into the through hole 25 from the first opposite surface 19 side of the bearing cup 12 , and is screwed into the fastening hole 28 .

[0065] Thus, the bearing cup 12 is fixed to the second surface 26 of the first fork 13a. At this time, the first abutting surface 22 of the bearing cup 12 and the second abutting surface 30 of the first fork 13a abut against each other.

[0066] The universal joint 10 of the present embodiment further includes a pressure sensor 40 .

[0067] The pressure sensor 40 measures the pressure of the fluid filled in the hydraulic chamber 42 provided in the first fork 13 a .

[0068] [About the hydraulic chamber]

[0069] The above-mentioned hydraulic chamber 42 is provided in the first fork head 13a of the present embodiment.

[0070] Figure 3 yes Figure 1 Partial cross-sectional view taken along line III-III.

[0071] like Figure 3 As shown, the hydraulic chamber 42 is formed by the hole portion 44 and the internal space of the adapter 46 .

[0072] The hole 44 opens at the outer peripheral surface 13g of the first fork 13a. The hole 44 has a first cylindrical surface 44a and a bottom surface 44b. The first cylindrical surface 44a is a surface connecting the outer peripheral surface 13g and the bottom surface 44b. The first cylindrical surface 44a is along the longitudinal direction of the key groove 23.

[0073] Figure 4 yes Figure 3 Partial cross-sectional view taken along line IV-IV.

[0074] exist Figure 4 In the embodiment, the key groove 23 has a bottom surface 23 a and a pair of stepped surfaces 23 b. The pair of stepped surfaces 23 b are surfaces connecting a pair of long sides of the bottom surface 23 a and two regions 30 a on both sides of the key groove 23 .

[0075] like Figure 3 and Figure 4 As shown, the hole portion 44 is provided between the key groove 23 and the fastening hole 28. Therefore, the hydraulic chamber 42 is located between the key groove 23 and the fastening hole 28.

[0076] And, if Figure 4 As shown, the hole portion 44 is provided in the axial direction between the bottom surface 23a and the region 30a (second abutment surface 30) of the key groove 23. Therefore, the hydraulic chamber 42 is located between the bottom surface 23a and the second abutment surface 30 in the axial direction.

[0077] When torque is transmitted between the key 24 and the key groove 23, the step surface 23b on the torque source side presses the key 24. The key 24 on the side receiving the torque presses the step surface 23b. As a result, compressive stress acts on the surface portion with the step surface 23b as the surface, generating a slightly plastically deformed area.

[0078] Therefore, in Figure 4 In the embodiment, the interval W between the step surface 23 b and the hole portion 44 is set to a value at which no plastic deformation occurs in the hole portion 44 .

[0079] Thus, the plastic deformation generated in the surface layer portion of the step surface 23 b does not affect the hydraulic chamber 42 .

[0080] like Figure 3 As shown, the adapter 46 is mounted on the outer end portion 44a1 of the first cylindrical surface 44a.

[0081] like Figure 2 As shown, the adapter 46 is a T-type connector. The adapter 46 has a first tube 46a extending in the radial direction and a second tube 46b extending in the axial direction.

[0082] The first tube 46a and the second tube 46b are connected to each other at substantially the center in the longitudinal direction. In addition, the first tube 46a and the second tube 46b are connected to each other.

[0083] like Figure 3 As shown, the front end portion 46a1 of the first tube 46a facing radially inward is pressed into the outer end portion 44a1.

[0084] like Figure 1 As shown in FIG. 1 , the pressure sensor 40 is provided at the front end portion 46 b 1 of the second tube 46 b facing the second fork 13 b . The pressure sensor 40 is fixed to the outside of the bearing cup 12 .

[0085] The valve 48 is provided at the front end portion 46b2 of the second tube 46b in the opposite direction to the front end portion 46b1. The valve 48 can be opened and closed, and can be switched to connect and disconnect the inside of the hydraulic chamber 42 with the outside.

[0086] like Figure 3 As shown, the liquid L fills the interior of the hydraulic chamber 42. In addition, the connection between the hole 44 and the adapter 46, the connection between the adapter 46 and the pressure sensor 40, and the connection between the adapter 46 and the valve 48 are sealed. The liquid L in the hydraulic chamber 42 does not leak from these connection parts.

[0087] The liquid L is, for example, hydraulic oil.

[0088] The fluid L is filled in the hydraulic chamber 42 so as to have a predetermined pressure.

[0089] The liquid L is injected into the interior of the hydraulic chamber 42 from the valve 48 .

[0090] For example, an injection pipe for injecting the liquid L is connected to the valve 48. Next, the valve 48 is opened, and the interior of the hydraulic chamber 42 becomes a negative pressure.

[0091] Thereafter, the liquid L is injected into the hydraulic chamber 42 , and when the liquid L reaches a predetermined pressure, the valve 48 is closed. In this way, the liquid L is filled into the hydraulic chamber 42 .

[0092] As described above, the pressure sensor 40 has a function of measuring the pressure of the liquid L filling the inside of the hydraulic chamber 42. In addition, the pressure sensor 40 has a function of wirelessly transmitting the measured output to a data processing device.

[0093] [About pressure measurement and torque measurement]

[0094] When torque is transmitted from one of the first shaft 16 or the second shaft 17 to the other and acts on the universal joint 10, stress corresponding to the torque acts on the fork 13 through the bearing cup 12. The fork 13 is slightly elastically deformed by the stress. At this time, the pressure of the liquid L in the hydraulic chamber 42 provided in the first fork 13a changes according to the magnitude of the stress acting on the first fork 13a. That is, the pressure of the liquid L in the hydraulic chamber 42 changes according to the magnitude of the torque acting on the universal joint 10.

[0095] In particular, compressive stress acts on the keyway 23 of the fork 13. The compressive stress is generated by the keyway 23 being pressed by the key 24 or the key 24 being pressed by the keyway 23.

[0096] In this embodiment, the hydraulic chamber 42 is located between the key groove 23 and the fastening hole 28. Therefore, the hydraulic chamber 42 is located near the key groove 23. The above-mentioned compressive stress acts on the hydraulic chamber 42. Thus, the stress change caused by the torque acting on the universal joint 10 appears as a pressure change of the liquid L.

[0097] Therefore, the torque acting on the universal joint 10 can be measured based on the output of the pressure sensor 40 .

[0098] Figure 5 It is a block diagram showing a configuration example of the pressure sensor 40 and a data processing device.

[0099] exist Figure 5 In the embodiment, the pressure sensor 40 is capable of wirelessly communicating with the data processing device 50 .

[0100] The pressure sensor 40 includes a communication unit 40 a and a sensor unit 40 b .

[0101] The sensor unit 40 b has a function of measuring the pressure of the liquid L in the hydraulic chamber 42 and a function of providing an output indicating the measurement result to the communication unit 40 a .

[0102] The communication unit 40a has a function of performing wireless communication based on a wireless WAN (Wide Area Network) or the like, and transmits and receives information to and from the data processing device 50 via the network. The communication unit 40a transmits an output indicating a measurement result to the data processing device 50.

[0103] The data processing device 50 includes a communication unit 50a and a processing unit 50b.

[0104] The communication unit 50 a has a function of wirelessly communicating with the communication unit 40 a of the pressure sensor 40 and receiving an output indicating a measurement result transmitted from the pressure sensor 40 .

[0105] The processing unit 50 b is a computer including a CPU (Central Processing Unit) and a storage unit such as a memory and a hard disk.

[0106] The processing unit 50 b has a function of obtaining the torque acting on the universal joint 10 based on the output indicating the measurement result.

[0107] The processing unit 50b stores the conversion table 50b1 in the storage unit.

[0108] Data indicating the correlation between the output from the pressure sensor 40 and the torque are registered in the conversion table 50b1. The conversion table 50b1 is prepared in advance using a test device or the like, for example, before the universal joint 10 is installed on an actual machine. The data serving as a reference for the data indicating the correlation is obtained by applying a known torque to the universal joint 10 by the test device and measuring the pressure of the liquid L at that time. Different known torques are applied to the universal joint 10. The pressure of the liquid L when different known torques are applied is measured by the pressure sensor 40. The output from the pressure sensor 40 (measured value of the pressure) and the data indicating the correlation with the torque are registered in the conversion table 50b1.

[0109] The output from the pressure sensor 40 is provided to the processing unit 50b. The processing unit 50b performs processing for converting the output from the pressure sensor 40 into a torque value using data indicating the correlation registered in the conversion table 50b1.

[0110] As described above, the universal joint 10 according to the embodiment can measure the torque acting on the universal joint 10 .

[0111] Thus, according to the present embodiment, torque can be measured by measuring the pressure of the liquid L in the hydraulic chamber 42. Therefore, compared with the universal joint using a strain gauge for torque measurement described in the above-mentioned subject, a bridge circuit or the like is not required, and the processing of wiring or the like is also simplified. As a result, the universal joint 10 of the present embodiment can measure torque with a simple structure. In addition, the universal joint 10 of the present embodiment will not damage the hydraulic chamber due to the excessive torque generated instantly.

[0112] In addition, in the universal joint 10 of the present embodiment, as described above, the hydraulic chamber 42 is located between the bottom surface 23 a and the second contact surface 30 in the axial direction. Therefore, the hydraulic chamber 42 can be reliably provided between the key groove 23 and the fastening hole 28 .

[0113] In the universal joint 10 of the present embodiment, compressive stress in the circumferential direction acts on the step surface 23b of the key groove 23. Therefore, in the universal joint 10 of the present embodiment, compressive stress acts on the key groove 23 over the entire region in the longitudinal direction of the key groove 23.

[0114] In this regard, in the present embodiment, the hydraulic chamber 42 includes the cylindrical hole portion 44 along the length direction of the key groove 23, so the universal joint 10 of the present embodiment can ensure a wide range in which the hydraulic chamber 42 and the key groove 23 are arranged in the vicinity along the length direction of the key groove 23. Therefore, the universal joint 10 of the present embodiment can generate a more significant pressure change of the liquid L caused by the stress change.

[0115] 〔other〕

[0116] The embodiments disclosed this time are to be considered in all respects as illustrative and non-restrictive.

[0117] For example, in the above-described embodiment, the hole 44 is opened in the outer peripheral surface 13 g of the first fork 13 a , and the pressure sensor 40 is fixed to the outside of the bearing cup 12 .

[0118] However, if Figure 6 As shown, the hole portion 44 may also have a first cylindrical surface 44a and a second cylindrical portion 44c. Figure 6 The first cylindrical surface 44a shown does not have an opening on the outer peripheral surface 13g. After the first cylindrical surface 44a forms an opening on the outer peripheral surface 13g, the opening is closed by a plug or welding. In addition, the second cylindrical portion 44c extends in the axial direction. The second cylindrical portion 44c is connected to the first cylindrical surface 44a and opens at the end surface 13t of the fork 13 (second fork 13b). Therefore, the second cylindrical portion 44c connects the first cylindrical surface 44a with the outside.

[0119] The adapter 46 composed of a single tube is connected to the open end of the second cylindrical portion 44c. The pressure sensor 40 is provided at the front end of the adapter 46.

[0120] In this case, the pressure sensor 40 is fixed to the outer peripheral surface of the second shaft 17 .

[0121] exist Figure 6 In the case of the illustrated structure, as in the case of the structure of the above-described embodiment, torque measurement can be performed with a simple structure.

[0122] The scope of rights of the present invention is not limited to the above-described embodiments, and includes all modifications within the scope equivalent to the configurations described in the claims.

[0123] Description of Reference Numerals

[0124] 10 Universal joint

[0125] 11 Cross Axle

[0126] 11a Trunnion

[0127] 12 Bearing cup

[0128] 13 Fork

[0129] 13a First Fork

[0130] 14 Fastening components

[0131] 15 Roller

[0132] 20 Page 1

[0133] 22 first contact surface

[0134] 23 Keyway

[0135] 23a Bottom

[0136] 24 keys

[0137] 25 Through hole

[0138] 26 Side 2

[0139] 28 Fastening holes

[0140] 30 Second contact surface

[0141] 40 Pressure Sensor

[0142] 42 Hydraulic Room

[0143] L Liquid

Claims

1. A universal joint, comprising: A cross-axis with trunnions; a bearing cup supporting the trunnion via a plurality of rollers; a fork head for mounting the bearing cup; A fastening member, fixing the bearing cup to the fork; and Pressure sensor, The bearing cup has: A first surface including a first abutting surface abutting against the fork head and a key protruding relative to the first abutting surface; and a through hole, opening in the first abutting surface and allowing the fastening member to pass through, The fork head has: The second surface comprises a second abutting surface abutting against the first abutting surface and a keyway recessed relative to the second abutting surface and for the key to be inserted into; A fastening hole, opening on the second abutting surface and being fastened by the fastening member; and The hydraulic chamber is filled with liquid. The pressure sensor measures the pressure of the liquid. At least a portion of the hydraulic chamber is located between the keyway and the fastening hole.

2. The universal joint according to claim 1, wherein: The hydraulic chamber is located between the bottom surface of the key groove and the second abutment surface in an axial direction parallel to the central axis of the universal joint.

3. The universal joint according to claim 1, wherein: The key and the keyway extend along a radial direction orthogonal to the central axis. The hydraulic chamber includes a cylindrical hole along the length direction of the key groove.

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