Direct-connection mini-tiller clutch structure and transmission case

Abstract

The invention belongs to the technical field of direct-connection mini-tillers, and particularly discloses a direct-connection mini-tiller clutch structure which comprises a sun gear with the end face provided with multiple sets of ball grooves, the multiple sets of ball grooves are evenly formed in the circumferential direction of the sun gear at intervals, and the ball grooves are used for containing balls; the sun gear shaft sleeve sleeves the outer side of the sun gear; the sun wheel shaft sleeve is provided with a sleeve hole; the clutch sleeve sleeves the outer side of the sun wheel shaft sleeve; an annular groove is formed in the outer side of the clutch sleeve, the clutch sleeve is divided into a first inner ring and a second inner ring, and the inner diameter of the first inner ring is larger than that of the second inner ring. The inner wall of the second inner ring abuts against the outer side of the sun wheel shaft sleeve. The shifting fork assembly is embedded and clamped in the annular groove to drive the clutch sleeve to move up and down along the sun wheel shaft sleeve and drive the balls to move among the clutch sleeve, the sun wheel shaft sleeve and the ball grooves, so that the clutch sleeve and the sun wheel shaft sleeve are rapidly separated or connected without delay, and the clutch structure is small in size and high in reliability. The invention further discloses a transmission case.

Description

Technical Field

[0001] The invention belongs to the technical field of direct-coupled micro-tillage machines, and particularly relates to a clutch structure and a transmission box of a direct-coupled micro-tillage machine. Background Art

[0002] As a type of agricultural machinery, micro-tillers are playing an increasingly important role in agricultural development. Micro-tillers are powered by a diesel or gasoline engine. A clutch transmits torque to a transmission box, which in turn transmits torque to a rotary tiller, which processes the soil. Therefore, in micro-tillers, the clutch controls the separation and engagement of the engine and transmission system.

[0003] Existing direct-connected micro-tiller clutches primarily utilize friction plates. These clutches consist of a pressure plate, a center sleeve, a clutch friction core, a push plate, pressure plate splines, and a spring, resulting in a complex structure. When driving the micro-tiller forward, the push plate pushes the pressure plate, bringing it and the center sleeve together and pressing against the clutch friction core. This allows the friction plates of the clutch friction core to engage with the driven plate, transmitting power through friction. When stopping, the spring force separates the pressure plate from the center sleeve, driving the friction plates and driven plate apart. Even with this design, even if a spring is used to accelerate the separation of the friction plates and driven plate, the oil still adheres strongly to the clutch friction plates, resulting in incomplete separation and adhesion between the clutch friction plates. This can cause the power output shaft to fail to stop within the specified timeframe, posing a significant safety hazard. In particular, if the operator believes the micro-tiller will stop if they release their grip, releasing their grip could result in the micro-tiller continuing to operate without control, potentially causing personal injury or even overturning and damage.

[0004] The clutch of the prior art direct-connected micro-tillage machine also adopts a belt tensioning type, which occupies a large space. Due to the use of the belt tensioning clutch, the belt is always bent back and tensioned, and the belt is continuously heated and easily aged and broken, resulting in poor reliability. Summary of the Invention

[0005] The invention aims to provide a direct-connected micro-tillage machine clutch structure, which can switch between opening and closing quickly without delay, has a small size and high reliability.

[0006] The object of the present invention is achieved through such a technical solution, a direct-connected micro-tillage machine clutch structure, comprising:

[0007] The sun gear has a plurality of ball grooves for accommodating balls on its end surface away from the gear teeth, and the plurality of ball grooves are evenly spaced along the circumference of the sun gear;

[0008] The sun gear sleeve is sleeved on the outside of the sun gear; the sun gear sleeve is provided with sleeve holes that match the balls and ball grooves;

[0009] A clutch sleeve is sleeved on the outer side of the sun gear sleeve; an annular groove is provided on the outer side of the clutch sleeve, and the clutch sleeve is divided into a first inner ring and a second inner ring, the inner diameter of the first inner ring is larger than the inner diameter of the second inner ring; the inner wall of the second inner ring abuts against the outer side of the sun gear sleeve; and

[0010] The shift fork assembly is embedded in the annular groove, and the shift fork assembly drives the clutch sleeve to move up and down along the sun gear sleeve; when the clutch sleeve moves up, the balls are pressed into the second inner ring, the ball groove and the sleeve hole, and the balls are in close contact with the inner wall of the second inner ring, the inner wall of the ball groove and the inner wall of the sleeve hole, and the sun gear sleeve and the sun gear are in an engaged state; when moving down, the balls enter the first inner ring, the balls lean against the inner wall of the first inner ring and away from the inner wall of the ball groove, and the sun gear sleeve and the sun gear are in a separated state.

[0011] Preferably, an annular arc groove communicating with the ball groove is provided on the outer side of the sun gear.

[0012] Preferably, the first inner ring and the second inner ring are provided with a transition portion, which is an inclined surface, the upper end surface diameter is equal to the inner diameter of the first inner ring, and the lower end surface diameter is equal to the inner diameter of the second inner ring.

[0013] Preferably, the distance from the inner wall of the second inner ring to the inner wall of the ball groove is equal to the outer diameter of the ball, and the inner diameter of the sleeve hole is equal to the outer diameter of the ball.

[0014] Preferably, the shift fork assembly includes a shift fork and a shift fork shaft, the shift fork is installed in the shift fork shaft, and the shift fork is embedded in the annular groove.

[0015] Preferably, the shift fork is C-shaped and is provided with two sets of shift fork posts. The shift fork posts are symmetrically arranged on the shift fork with respect to the axis of the clutch sleeve, and the shift fork posts are installed in the annular groove by interference fit.

[0016] Due to the adoption of the above technical solution, the present invention has the following beneficial effects:

[0017] The present invention uses balls as the torque transmission medium, resulting in a low ball friction coefficient and improved motion efficiency. A shift fork drives the clutch sleeve along the sun gear sleeve, and the balls move between the sun gear sleeve and the clutch sleeve to achieve torque separation and engagement. Compared to traditional friction plate or belt tensioning clutches, the present invention offers high torque tolerance, reliable engagement, and a compact clutch structure. The shift fork assembly moves the clutch sleeve, allowing the balls to quickly engage and disengage with the inner wall of the ball groove, allowing the clutch structure to rapidly switch between engagement and disengagement without delay, resulting in high reliability.

[0018] Another object of the present invention is to provide a transmission box that utilizes a direct-connected micro-tiller clutch structure to quickly connect or disconnect the engine power to the micro-tiller's transmission system.

[0019] It includes a box body, a planetary gear train, a planetary carrier, a ring gear and a direct-connected micro-tiller clutch structure. The direct-connected micro-tiller clutch structure, planetary gears and ring gears are installed in the box body, and the fork assembly is exposed outside the box body. The planetary gears are engaged with the sun gear, and the inner teeth of the ring gear are engaged with the planetary gears. The planetary gear train is installed on one end of the planetary carrier, and the other end of the planetary carrier is connected to the transmission member.

[0020] Preferably, the box body is provided with a positioning column, the gear ring is installed on the positioning column, the box body is also provided with a buffer groove, the buffer groove is provided with a buffer member, one end of the buffer member abuts against the inner wall of the buffer groove, and the other end of the buffer member abuts against the outer end face of the positioning column, and the abutting end faces of the positioning column and the buffer member are flat.

[0021] Preferably, the box body includes a box cover, and a return spring is provided between the box cover and the clutch sleeve. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the specific embodiments of the present invention, the following briefly introduces the drawings required for use in the specific embodiments. In all the drawings, each element or part is not necessarily drawn according to the actual scale.

[0023] Figure 1 This is a schematic structural diagram of a direct-coupled micro-tillage machine clutch structure according to the present invention;

[0024] Figure 2 It is a schematic diagram of the overall structure of the direct-connected micro-tiller's clutch structure;

[0025] Figure 3 This is a schematic diagram of the clutch structure of a direct-connected micro-tiller;

[0026] Figure 4 This is a schematic diagram of the separation of the clutch structure of the direct-connected micro-tillage machine;

[0027] Figure 5 It is a structural schematic diagram of a transmission box;

[0028] Figure 6 This is a structural schematic diagram of a transmission box with the box cover removed;

[0029] Figure 7 Schematic diagram of the planetary gear train and ring gear.

[0030] Reference numerals:

[0031] 1-sun gear, 11-ball groove, 111-circular arc groove, 112-cone groove, 12-annular arc groove, 2-ball, 3-sun gear sleeve, 31-hole, 32-power gear, 4-clutch sleeve, 41-annular groove, 42-first inner ring, 43-second inner ring, 44-transition part, 5-shift fork assembly, 51-shift fork, 511-shift fork column, 52 shift fork shaft, 6-box, 61-box cover, 62-rotating shaft seat, 63-return spring, 64-positioning column, 65-buffer groove, 66-buffer, 7-planetary gear train, 8-planet carrier, 9-ring gear. DETAILED DESCRIPTION

[0032] See also Figure 1 、 Figure 2 、 Figure 3 and Figure 4 A direct-connected micro-tiller clutch structure includes: a sun gear 1, a ball bearing 2, a sun gear sleeve 3, a clutch sleeve 4 and a fork assembly 5.

[0033] The end face of the sun gear 1, facing away from the gear teeth, is equipped with multiple sets of ball grooves 11 for accommodating the balls 2. These sets of ball grooves 11 are evenly spaced along the circumference of the sun gear 1. A sun gear sleeve 3 is sleeved onto the outside of the sun gear 1; it has holes 31 that mate with the balls 2 and the ball grooves 11. A clutch sleeve 4 is sleeved onto the outside of the sun gear sleeve 3; it has an annular groove 41 on its outside. The clutch sleeve 4 is divided into a first inner ring 42 and a second inner ring 43. The inner diameter of the first inner ring 42 is larger than that of the second inner ring 43. The inner wall of the second inner ring 43 abuts the outside of the sun gear sleeve 3. The shift fork assembly 5 is embedded in the annular groove 41, and the shift fork assembly 5 drives the clutch sleeve 4 to move up and down along the sun gear sleeve 3; when the clutch sleeve 4 moves upward, the ball 2 is pressed into the second inner ring 43, the ball groove 11 and the sleeve hole 31, and the ball 2 is in close contact with the inner wall of the second inner ring 43, the inner wall of the ball groove 11 and the sleeve hole 31, and the sun gear sleeve 3 and the sun gear 1 are in an engaged state; when moving downward, the ball 2 enters the first inner ring 42, and the ball 2 leans against the inner wall of the first inner ring 42 and away from the inner wall of the ball groove 11, and the sun gear sleeve 3 and the sun gear 1 are in a separated state.

[0034] Specifically, a power gear 32 is provided on the inner wall of the end of the sun gear sleeve 3 away from the sun gear 1. The power gear 32 is connected to the engine output shaft of the micro-tiller, and the sun gear 1 is connected to the transmission system of the micro-tiller. Each set of ball grooves 11 is divided into arc grooves 111 and truncated cone grooves 112. The arc grooves 111 are located near the axis, and the inner diameter of the arc grooves 111 is equal to the outer diameter of the ball 2. This structure ensures that the ball 2 is fully in contact with the inner wall of the arc grooves 111; the truncated cone grooves 112 are located near the sun gear sleeve 3. The radius gradually increases from the inside to the outside, and the arc grooves 111 and the truncated cone grooves 112 transition in an arc. This structure facilitates the installation of the ball 2 in the ball grooves 11 through the sleeve hole 31. Preferably, there are five sets of ball grooves 11, and the depth of the ball grooves 11 is half the diameter of the ball 2. The diameter of the sleeve hole 31 is equal to the diameter of the ball 2.

[0035] The present invention is a direct-connected micro-tillage machine clutch structure, please refer to Figure 3 Under the action of external force, the shift fork assembly 5 drives the clutch sleeve 4 upward along the sun gear sleeve 3. The inner wall of the clutch sleeve 4 drives the ball 2 into the sleeve hole 31 of the sun gear sleeve 3 and then into the ball groove 11. The ball 2 contacts and rubs against the sleeve hole 31 and the inner wall of the ball groove 11. At this time, the external force drives the sun gear sleeve 3 to rotate. The sun gear sleeve 3 transmits the rotational motion to the sun gear 1 through the ball 2. The sun gear 1 continues to transmit torque through the gear shift. This process is the engagement state. Please refer to Figure 4 , under the action of external force, the fork assembly 5 causes the clutch sleeve 4 to move downward along the sun gear sleeve 3; the ball 2, under the action of centrifugal force, separates from the inner wall of the ball groove 11 and leans against the inner wall of the first inner ring 42. At this moment, the sun gear sleeve 3 continues to rotate, but the sun gear 1 stops rotating. This process is a separation state. The present invention uses the ball 2 as a torque transmission medium, and achieves the clutch effect of torque transmission by moving the ball 2 between the sun gear sleeve 3 and the clutch sleeve 4. The ball 2 has a relatively low friction coefficient, can withstand large torque, and has reliable connection, thereby improving movement efficiency. Compared with traditional friction plate or belt tensioning types, the clutch method of the present invention is small in size. The clutch sleeve 4 is driven by the fork assembly 5, and the ball 2 quickly contacts or disengages from the inner wall of the ball groove 11, so that the clutch structure quickly switches between opening and closing without delay and with high reliability.

[0036] See also Figure 1 Furthermore, in order to facilitate the movement of the ball 2, an annular arc groove 12 communicating with the ball groove 11 is provided on the outer side of the sun gear shaft.

[0037] See also Figure 3 and Figure 4The first inner ring 42 and the second inner ring 43 are provided with a transition portion 44. This transition portion 44 is an inclined surface with an upper end surface diameter equal to the inner diameter of the first inner ring 42 and a lower end surface diameter equal to the inner diameter of the second inner ring 43. Specifically, the second inner ring 43 is located near the teeth of the sun gear 1, that is, the second inner ring 43 is located below the first inner ring 42. The transition portion 44 is inclined downward. When the clutch sleeve 4 moves up or down, the balls 2, aided by the transition portion 44, smoothly and quickly engage or disengage with the inner wall of the ball groove 11. Preferably, the distance from the inner wall of the second inner ring 43 to the inner wall of the ball groove 11 is equal to the outer diameter of the balls 2. When the sun gear sleeve 3 is engaged with the sun gear 1, half of the balls 2 are in the ball groove 11, fully contacting the sun gear 1; the other half are in the sleeve hole 31, fully contacting the sun gear sleeve 3. This ensures smooth and reliable rotation without slipping.

[0038] See also Figure 1 and Figure 2 Furthermore, the shift fork assembly 5 includes a shift fork 51 and a shift fork shaft 52. The shift fork 51 is mounted on the shift fork shaft 52 and is embedded in the annular groove 41. Specifically, the shift fork is C-shaped and has two sets of shift fork posts 511. The shift fork posts 511 are symmetrically arranged on the shift fork 51 about the axis of the clutch sleeve 4 and are installed in the annular groove 41. The shift fork 51 is fixed to the center of the shift fork shaft 52 by bolts. The shift fork posts 511 are respectively provided at the C-shaped open ends of the shift fork. The diameter of the shift fork posts 511 is slightly larger than the width of the annular groove 41. The shift fork posts 511 are installed in the annular groove 41 through an interference fit, enabling the shift fork 51 to smoothly move the clutch sleeve 4.

[0039] See also Figure 5 、 Figure 6 and Figure 7A transmission box includes a box body 6, a planetary gear train 7, a planetary carrier 8, a ring gear 9 and a direct-connected micro-tiller clutch structure. The direct-connected micro-tiller clutch structure, the planetary gear train 7, the planetary carrier 8 and the ring gear 9 are installed in the box body 6, the fork assembly 5 is exposed to the box body 6, the planetary gear train 7 is engaged with the sun gear 1, and the inner teeth of the ring gear 9 are engaged with the planetary gear train 7. The planetary gear train 7 is installed at one end of the planetary carrier 8, and the other end of the planetary carrier 8 is connected to the transmission member. Specifically, a removable box cover 61 is provided on the top of the box body 6 to facilitate the installation, maintenance or replacement of the components inside the box body 6. The planetary gear train 7 is provided with a plurality of planetary gears, and the plurality of planetary gears are evenly spaced along the circumference of the inner ring of the ring gear 9. Each planetary gear is engaged with the inner teeth of the sun gear 1 and the ring gear 9 at the same time. When the clutch structure of the direct-coupled micro-tiller is engaged, external power drives the sun gear 1 to rotate, while the ring gear 9 remains stationary. The sun gear 1 drives the planetary gear train 7 to rotate, which in turn rotates around the ring gear 9. The planetary gear train 7 drives the planetary carrier 8 to rotate, which in turn drives the transmission components of the micro-tiller to operate, thereby achieving power transmission. A rotating shaft seat 62 is provided on the housing 6. One end of the shift fork shaft 52 is rotatably mounted on the rotating shaft seat 62, while the other end is exposed outside the housing 6 to facilitate the application of external force to the shift fork shaft 52.

[0040] See also Figure 6 Furthermore, a return spring 63 is provided between the case cover 61 and the clutch sleeve 4. The return spring 63 is sleeved on the outside of the sun gear sleeve 3. The sun gear sleeve 3 prevents the return spring 63 from deflecting and limits the position and direction of the return spring 63's expansion and contraction. One end of the return spring 63 abuts the case cover 61, and the other end abuts the top of the clutch sleeve 4. When the shift fork 51 drives the clutch sleeve 4 up or down, the return spring 63 acts to cause the clutch sleeve 4 to move smoothly along the sun gear sleeve 3.

[0041] See also Figure 6 and Figure 7Furthermore, the housing 6 is provided with a positioning post 64, on which the gear ring 9 is mounted. The housing 6 is also provided with a buffer groove 65, which is provided with a buffer member 66. One end of the buffer member 66 abuts against the inner wall of the buffer groove 65, and the other end of the buffer member 66 abuts against the outer end surface of the positioning post 64. The abutting end surfaces of the positioning post 64 and the buffer member 66 are flat. Specifically, the positioning post 64 is provided with a step for positioning and supporting the gear ring 9. There are multiple groups of positioning posts 64, which are evenly spaced along the circumference of the inner wall of the housing 6. Preferably, there are six groups of positioning posts 64. The end surface of the positioning post 64 that faces the buffer member 66 is flat to increase the contact area with the buffer member 66. When the transmission components are suddenly subjected to an external force opposite to the driving force, such as a micro-tiller suddenly coming to a stop upon encountering a large rock, the planetary carrier 8 may suddenly slow down or stop due to the external force, but the planetary gear train 7 may continue to rotate at the original speed driven by the sun gear 1. The planetary gear train 7 and the ring gear 9 are a rigid connection in the transmission. When the ring gear 9 encounters an impact load, it may be easily damaged due to excessive force. A buffer 66 is provided to convert the original rigid connection into an elastic connection, forming a damping between the ring gear 9 and the inner wall of the housing 6, forming a compression buffer to reduce the force on the transmission components, play a buffering role, and protect the ring gear 9. Preferably, the buffer 66 is a spring.

[0042] The present invention provides a transmission case, wherein the clutch structure of the direct-connected micro-tiller adopts balls 2 as a torque transmission medium. The balls 2 have a small friction coefficient, are subjected to a large torque, are reliably coupled, and have improved motion efficiency. The clutch sleeve 4 is driven to move along the sun gear sleeve 3 by the shift fork 51. The balls 2 are quickly brought into contact with or disengaged from the inner wall of the ball groove 11 by utilizing the inclined surface provided on the clutch sleeve 4, so that the clutch structure can quickly switch between opening and closing without delay and with high reliability. A buffer member 66 is provided between the ring gear 9 and the housing 6. When the micro-tiller is suddenly subjected to an external force, a damping is formed between the ring gear 9 and the inner wall of the housing 6, forming a compression buffer to reduce the force borne by the transmission parts, thereby playing a buffering role and protecting the ring gear 9.

[0043] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above is only a specific implementation method of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the scope of the present invention should be included in the scope of protection of the present invention.

Claims

1. A direct-connected micro-tillage machine clutch structure, characterized in that: include: A sun gear (1), wherein the end surface of the sun gear (1) away from the gear teeth is provided with a plurality of groups of ball grooves (11) for accommodating balls (2), and the plurality of groups of ball grooves (11) are evenly spaced along the circumference of the sun gear (1); The sun gear shaft sleeve (3) is sleeved on the outer side of the sun gear (1); the sun gear shaft sleeve (3) is provided with a sleeve hole (31) that matches the ball (2) and the ball groove (11); A clutch sleeve (4) is sleeved on the outer side of the sun gear sleeve (3); an annular groove (41) is provided on the outer side of the clutch sleeve (4); the clutch sleeve (4) is divided into a first inner ring (42) and a second inner ring (43); the inner diameter of the first inner ring is larger than the inner diameter of the second inner ring (43); the inner wall of the second inner ring (43) abuts against the outer side of the sun gear sleeve (3); and The shift fork assembly (5) is embedded in the annular groove (41), and the shift fork assembly (5) drives the clutch sleeve (4) to move up and down along the sun gear shaft sleeve (3); when the clutch sleeve (4) moves up, the ball (2) is pressed into the second inner ring (43), the ball groove (11) and the sleeve hole (31), and the ball (2) is in close contact with the inner wall of the second inner ring (43), the inner wall of the ball groove (11) and the inner wall of the sleeve hole (31), and the sun gear shaft sleeve (3) and the sun gear (1) are in an engaged state; when moving down, the ball (2) enters the first inner ring (42), the ball (2) is close to the inner wall of the first inner ring (42) and away from the inner wall of the ball groove (11), and the sun gear shaft sleeve (3) and the sun gear (1) are in a separated state.

2. The direct-connected micro-tillage machine clutch structure according to claim 1, characterized in that: An annular arc groove (12) communicating with the ball groove (11) is provided on the outer side of the sun gear (1).

3. The direct-connected micro-tillage machine clutch structure according to claim 1 or 2, characterized in that: The first inner ring (42) and the second inner ring (43) are provided with a transition portion (44), which is an inclined surface, with an upper end surface diameter equal to the inner diameter of the first inner ring (42) and a lower end surface diameter equal to the inner diameter of the second inner ring (43).

4. The direct-connected micro-tillage machine clutch structure according to claim 1 or 2, characterized in that: The distance from the inner wall of the second inner ring (43) to the inner wall of the ball groove (11) is equal to the outer diameter of the ball (2), and the inner diameter of the sleeve hole (31) is equal to the outer diameter of the ball (2).

5. The direct-connected micro-tillage machine clutch structure according to claim 3, characterized in that: The distance from the inner wall of the second inner ring (43) to the inner wall of the ball groove (11) is equal to the outer diameter of the ball (2), and the inner diameter of the sleeve hole (31) is equal to the outer diameter of the ball (2).

6. The direct-connected micro-tillage machine clutch structure according to claim 1, 2 or 5, characterized in that: The shift fork assembly (5) comprises a shift fork (51) and a shift fork shaft (52). The shift fork (51) is installed in the shift fork shaft (52), and the shift fork (51) is embedded in the annular groove (41).

7. The direct-connected micro-tillage machine clutch structure according to claim 6, characterized in that: The shift fork (51) is C-shaped and is provided with two groups of shift fork columns (511). The shift fork columns (511) are symmetrically arranged on the shift fork (51) with respect to the axis of the clutch sleeve (4). The shift fork columns (511) are installed in the annular groove (41) by interference fit.

8. A transmission box, characterized in that: The invention comprises a housing (6), a planetary gear train (7), a planetary carrier (8), a ring gear (9) and a direct-connected micro-tillage machine clutch structure as claimed in any one of claims 1 to 7, wherein the direct-connected micro-tillage machine clutch structure, the planetary gear train (7), the planetary carrier (8) and the ring gear (9) are installed in the housing (6), the fork assembly (5) is exposed outside the housing (6), the planetary gear train (7) is meshed with the sun gear (1), the inner teeth of the ring gear (9) are meshed with the planetary gear train (7), the planetary gear train (7) is installed on one end of the planetary carrier (8), and the other end of the planetary carrier (8) is connected to the transmission part of the micro-tillage machine.

9. The transmission box according to claim 8, characterized in that: The housing (6) is provided with a positioning column (64), the gear ring (9) is mounted on the positioning column (64), the housing (6) is further provided with a buffer groove (65), the buffer groove (65) is provided with a buffer member (66), one end of the buffer member (66) abuts against the inner wall of the buffer groove (65), the other end of the buffer member (66) abuts against the outer end surface of the positioning column (64), and the abutting end surfaces of the positioning column (64) and the buffer member (66) are plane.

10. The transmission box according to claim 8 or 9, characterized in that: The box body (6) comprises a box cover (61), and a return spring (63) is provided between the box cover (61) and the clutch sleeve (4).

Images