Automatic gear shifting mechanism

Abstract

The present invention discloses an automatic shift mechanism, which relates to the field of automobile transmission technology, including a motor, a worm connected to the output end of the motor, a shift shaft provided at intervals and in parallel with the worm, a shift fork provided on a sliding sleeve on the shift shaft, the worm and the shift fork are connected by a connecting member, the connecting member includes a first base, a tooth provided on the side of the first base facing the worm wheel, a shift head provided on the side of the first base facing the shift fork, two opposite shift blocks provided on the shift fork, the shift blocks are used to fix the shift head, and the shift fork is provided with a coaxial assembly at both ends of the shift shaft. The purpose of the present invention is to provide an automatic shift mechanism with good matching effect between the shift fork and the shift shaft and weak torsional force transmission effect of the shift head.

Description

Technical Field

[0001] The invention belongs to the technical field of automobile transmission, and in particular relates to an automatic gear shifting mechanism. Background Art

[0002] As a key component of the automobile transmission system, the traditional shift mechanism realizes the transmission of power and the increase and decrease of speed through multiple components such as clutch gears, shafts and operating levers. In the prior art, the shift mechanism often has many parts, is complex to assemble, and is difficult to repair after sales.

[0003] Prior art includes an invention patent named electric shift actuator, the publication number of which is US20240102554A1. This invention includes a housing assembly, a housing cover assembly covering the housing assembly, and a gear reduction mechanism assembly disposed in the housing assembly. The gear reduction mechanism assembly includes a motor subassembly, a face gear set, a first-stage gear reduction subassembly, and an output gear assembly configured to be connected to a parking mechanism. The output end of the motor subassembly is meshed in parallel with the input end of the first-stage gear reduction subassembly to form a first-stage gear reduction transmission, the output end of the first-stage gear reduction subassembly is meshed vertically with the input end of the face gear set to form a second-stage gear reduction transmission, and the output end of the face gear set is meshed in parallel with the input end of the output gear assembly to form a third-stage gear reduction transmission. The actuator has the functions of emergency stop and manual unlocking, which improves safety and redundancy. However, this invention cannot achieve high-precision control of the fork and its feedback effect on the angle sensor. Summary of the invention

[0004] The object of the present invention is to provide an automatic shifting mechanism with good matching effect between a shift fork and a shift shaft and weak torsional force transmission effect of a shift head.

[0005] The technical solution adopted by the present invention to achieve the above-mentioned purpose is:

[0006] An automatic shifting mechanism comprises a motor, a worm connected to the output end of the motor, a shifting shaft is arranged in parallel with the worm at intervals, a shifting fork is arranged on a sliding sleeve on the shifting shaft, the worm and the shifting fork are connected by a connecting member, the connecting member comprises a first base body, teeth are arranged on the side of the first base body facing the worm wheel, a shifting head is arranged on the side of the first base body facing the shifting fork, two opposite shifting blocks are arranged on the shifting fork, and the shifting blocks are used to fix the shifting head.

[0007] According to an embodiment of the present invention, an angle sensor is disposed on the first substrate.

[0008] According to an embodiment of the present invention, a self-locking device is provided on the shift shaft.

[0009] Through the overall design of an automatic shift mechanism, when the electronically controlled shift actuator receives the control command, the drive motor is the power drive component, the worm helical gear is the power transmission component, the first base is the shift actuator component, the self-locking device fixes the shift shaft position, and the shift angle sensor collects and feeds back the shift position signal in real time, thereby monitoring the shift position in real time. In order to meet the hybrid power shift demand, the device adopts a modular design, which is convenient to replace parts, has a relatively simple structure, high reliability, and fast and accurate control of the shift action, especially for the synchronizer shift, which is easier to achieve precise control.

[0010] According to an embodiment of the present invention, the shift fork sleeve is provided with coaxial components at both ends of the shift shaft, the coaxial components include a coaxial base sleeve, the inner side of the coaxial base sleeve has at least one oil storage groove, and the coaxial base sleeve is connected to the end of the shift fork.

[0011] The shift fork sleeve is provided with a coaxial assembly at both ends of the shift shaft, and the coaxial assembly realizes the coaxiality of the shift fork and the shift shaft. It should be noted that when the connecting member is driven by the worm, the first base body will rotate, and the first base body will drive the shift head to realize the movement of the shift fork. During the cooperation between the shift head and the shift block, the shift block will be subjected to inconsistent forces. More specifically, when the shift head moves from right to left, the shift head will give a downward force to the left shift block and an upward force to the right shift block, which will cause the shift fork itself to have a tendency to twist; when the shift head moves from left to right, on the contrary, it will also give the shift fork a tendency to twist. The coaxial assembly can realize the coincidence of the axes of the shift fork and the shift shaft, and prevent the shift fork from bending or the uneven oil film between the shift fork and the shift shaft due to the action of the shift head. In addition, the coaxial assembly can also achieve the effect of correcting the bending of the two ends of the shift shaft or the surface straightness of the shift shaft.

[0012] The inner side of the coaxial base sleeve is provided with at least one oil storage groove, which can realize the storage and release of the oil of the reciprocating movement of the shift fork when the shift fork reciprocates in the direction of the shift shaft, which is beneficial to improve the uniformity of the oil film on the shift shaft, thereby improving the accuracy of the shift fork movement and the feedback effect on the angle sensor.

[0013] Moreover, the coaxial base sleeve can make the lubricating oil uniform and promote the displacement of materials on the surface of the shift shaft, thereby solving the problem of gear shifting jamming or not smooth due to the uneven surface of the shift shaft caused by the solidification of the medium on the surface of the shift shaft.

[0014] It should be noted that the oil is used to cool and lubricate the reciprocating motion of the fork.

[0015] According to an embodiment of the present invention, a buffer ring groove is provided in the coaxial base sleeve, a buffer ring is provided in the buffer ring groove, the buffer ring includes no less than three buffer bases, and adjacent buffer bases are connected by elastic plates;

[0016] The buffer base is a protrusion along the radial direction of the coaxial base sleeve.

[0017] By arranging a buffer ring in the coaxial base sleeve, the buffer ring can further achieve the coaxiality of the shift fork and the shift shaft.

[0018] Among them, the elastic plate is connected to the buffer base, which can make it easier for the buffer ring to be placed in the buffer ring groove. When the buffer ring is placed in the buffer ring groove, the outer wall of the buffer ring can be in contact or abutment with the inner wall of the buffer ring groove through the elastic plate, thereby preventing the buffer ring from escaping from the buffer ring groove.

[0019] There are two types of protrusions of the buffer substrate, which will be discussed below.

[0020] When the buffer base body bulges radially inwardly along the coaxial base sleeve, at this time, the outer side of the buffer base body and the elastic plate can be fitted with the buffer ring groove.

[0021] When the shift head applies a torsional force to the shift fork, the force will be transmitted to the buffer ring through the coaxial base sleeve. Since the protrusion of the buffer base is facing the shift shaft, the inner wall of the buffer ring groove will apply pressure to the buffer ring. Since the buffer base has the ability to be compressed, the protrusion of the buffer base will contact the shift shaft, so that the buffer ring can restrict the coaxial base ring and prevent the occurrence of uneven gap between the shift fork and the shift shaft when subjected to torsional force, so as to improve the smoothness of the circumferential movement of the shift fork along the shift shaft when the shift fork is twisted.

[0022] When the buffer matrix protrudes along the radial outer side of the coaxial base sleeve, at this time, the outer side of the buffer matrix will achieve point contact with the inner wall of the buffer ring groove under the action of the elastic plate. Through the above design, the uniformity of the oil in the coaxial base sleeve achieved by the buffer ring can be improved, and the buffer ring can adapt to the shift shaft, that is, when there is solidified oil or other impurities on the shift shaft, the solidified oil and impurities can be collected and cleaned through the buffer ring; and, when the shift head applies a torsional force to the shift fork, it will be transmitted to the buffer ring through the coaxial base sleeve. Since the protrusion of the buffer matrix is ​​toward the inner wall of the buffer ring groove, the inner wall of the buffer ring groove will apply pressure to the buffer ring. Since the buffer matrix has compressibility, the buffer ring can limit the coaxial base ring to prevent the normal and uniform oil film from being formed normally in the case of torsion, and the smoothness of the circumferential movement of the shift shaft when the shift fork is torsion can be improved.

[0023] Preferably, the buffer base body protrudes along the radial outer side of the coaxial base sleeve.

[0024] According to an embodiment of the present invention, the buffer base is provided with an oil guide hole along the axial direction of the coaxial base sleeve.

[0025] Through the above design, the oil guide hole can improve the uniformity of oil distribution, and the buffer matrix can improve its ability to absorb impact force and torsional force through the guide hole, that is, it can be achieved in the case of high-intensity operation. More specifically, when the fork is subjected to a large torsional strength of the shift head, the buffer matrix can absorb the force from the coaxial base sleeve through its own compression.

[0026] According to an embodiment of the present invention, the elastic plate includes a serpentine connection portion.

[0027] Through the above design, the serpentine connection part can improve the elastic force of the elastic plate along its radial direction, thereby achieving the effect of fitting or contacting the elastic base with the inner wall of the buffer ring groove, and preventing the buffer ring from detaching from the buffer ring groove; and the serpentine connection part can further improve the uniformity of the oil, and the solidified oil and impurities can be collected by the elastic plate to prevent the solidified oil and impurities from affecting the stable movement of the shift fork. In addition, the serpentine connection part also has good heat dissipation performance. During long-term use, the serpentine connection part can transfer heat to part of the oil and the shift shaft. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a three-dimensional schematic diagram of an automatic shifting mechanism;

[0029] Figure 2 It is a front view schematic diagram of an automatic shifting mechanism;

[0030] Figure 3 It is a schematic diagram of the coaxial component structure;

[0031] Figure 4 It is a three-dimensional schematic diagram of the coaxial component;

[0032] Figure 5 It is a three-dimensional schematic diagram of a buffer ring;

[0033] Figure 6 It is a schematic diagram of the cooperation between a shift fork and a shift head;

[0034] Figure 7 It is a schematic diagram of another kind of cooperation between the shift fork and the shift head.

[0035] Figure numbers: motor 1, worm 2, shift shaft 3, shift fork 4, connecting piece 5, first base 51, tooth 53, shift head 54, shift block 6, shift block plate 61, first spring 62, connecting plate 63, third spring 64, coaxial assembly 7, coaxial base sleeve 71, buffer ring groove 72, buffer ring 73, buffer base 74, elastic plate 75, oil guide hole 76 angle sensor 8, self-locking device 9. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is further described in detail below in conjunction with specific implementations and drawings:

[0037] Embodiment 1:

[0038] like Figure 1-Figure 5 As shown, an automatic shifting mechanism includes a motor 1, a worm 2 is connected to the output end of the motor 1, a shift shaft 3 is provided with the worm 2 in parallel at intervals, a shift fork 4 is provided on the shift shaft 3, the worm 2 and the shift fork 4 are connected by a connecting member 5, the connecting member 5 includes a first base 51, a tooth 53 is provided on the side of the first base 51 facing the worm 2, a shift head 54 is provided on the side of the first base 51 facing the shift fork 4, and two opposite shift blocks 6 are provided on the shift fork 4, and the shift block 6 is used to fix the shift head 54.

[0039] The angle sensor 8 is provided on the first base body 51 .

[0040] The shift shaft 3 is provided with a self-locking device 9 .

[0041] Through the overall design of an automatic shift mechanism, when the electronically controlled shift actuator receives the control command, the drive motor 1 is the power drive component, the worm 2 helical gear 53 is the power transmission component, the first base 51 is the shift actuator, the self-locking device 9 fixes the position of the shift shaft 3, and the shift angle sensor collects and feeds back the shift position signal in real time, thereby monitoring the shift position in real time. In order to meet the hybrid power shift demand, the device adopts a modular design, which is convenient to replace parts, has a relatively simple structure, high reliability, and fast and accurate control of the shift action, especially for the synchronizer shift, which is easier to achieve precise control.

[0042] The shift fork 4 is sleeved on both ends of the shift shaft 3 and is provided with a coaxial assembly 7, the coaxial assembly 7 includes a coaxial base sleeve 71, the inner side of the coaxial base sleeve 71 has at least one oil storage groove, and the coaxial base sleeve 71 is connected to the end of the shift fork 4.

[0043] The coaxial components 7 are provided at both ends of the shift fork 4 sleeved on the shift shaft 3. The coaxial components 7 realize the coaxiality of the shift fork 4 and the shift shaft 3. It should be noted that when the connecting member 5 is driven by the worm 2, the first base 51 will rotate, and the first base 51 will drive the shift head 54 to realize the movement of the shift fork 4. During the cooperation between the shift head 54 and the shift block 6, the shift block 6 will be subjected to inconsistent forces. More specifically, when the shift head 54 moves from right to left, the shift head 54 will give a downward force to the left shift block 6 and an upward force to the right shift block 6, which will cause the shift fork 4 to have a tendency to twist; when the shift head 54 moves from left to right, on the contrary, it will also give the shift fork 4 a tendency to twist. The coaxial components 7 can realize the coincidence of the axes of the shift fork 4 and the shift shaft 3, and prevent the shift fork 4 from bending or the uneven oil film between the shift fork 4 and the shift shaft 3 due to the action of the shift head 54. In addition, the coaxial component 7 can also achieve the effect of correcting the bending of the two end portions of the shift shaft 3 or the surface straightness of the shift shaft 3 .

[0044] The inner side of the coaxial base sleeve 71 is provided with at least one oil storage groove, which can realize the storage and release of the oil of the reciprocating movement of the shift fork 4 when the shift fork 4 reciprocates in the direction of the shift shaft 3, which is beneficial to improve the uniformity of the oil film on the shift shaft 3, and further improve the movement accuracy of the shift fork 4 and the feedback effect on the angle sensor 8.

[0045] Furthermore, the coaxial base sleeve 71 can make the lubricating oil uniform and promote the displacement of the material on the surface of the shift shaft 3, thereby solving the problem of the medium solidifying on the surface of the shift shaft 3 and causing the uneven surface of the shift shaft 3 to cause the shifting to be stuck or not smooth.

[0046] It should be noted that the oil is used to cool and lubricate the reciprocating motion of the shift fork 4.

[0047] A buffer ring groove 72 is provided in the coaxial base sleeve 71, a buffer ring 73 is provided in the buffer ring groove 72, and the buffer ring 73 includes no less than three buffer bases 74, and adjacent buffer bases 74 are connected by elastic plates 75;

[0048] The buffer base 74 is a protrusion along the radial direction of the coaxial base sleeve 71 .

[0049] By arranging a buffer ring 73 in the coaxial base sleeve 71 , the buffer ring 73 can further achieve the coaxiality of the shift fork 4 and the shift shaft 3 .

[0050] Among them, the elastic plate 75 is connected to the buffer base 74, which can make it easier for the buffer ring 73 to be placed in the buffer ring groove 72, and when the buffer ring 73 is placed in the buffer ring groove 72, the outer wall of the buffer ring 73 can be in contact or abutment with the inner wall of the buffer ring groove 72 through the elastic plate 75, thereby reducing the possibility of the buffer ring 73 escaping from the buffer ring groove 72.

[0051] There are two types of protrusions of the buffer substrate 74, which will be discussed below.

[0052] When the buffer base 74 protrudes radially inwardly of the coaxial base sleeve 71 , at this time, the outer side of the buffer base 74 and the elastic plate 75 can be fitted with the buffer annular groove 72 .

[0053] When the shift head 54 applies a torsional force to the shift fork 4, the torsional force will be transmitted to the buffer ring 73 through the coaxial base sleeve 71. Since the protrusion of the buffer base 74 is toward the shift shaft 3, the inner wall of the buffer ring groove 72 will apply pressure to the buffer ring 73. Since the buffer base 74 has the ability to be compressed, the protrusion of the buffer base 74 will contact the shift shaft 3, that is, the buffer ring 73 can limit the coaxial base ring to prevent the occurrence of uneven gap between the shift fork 4 and the shift shaft 3 when subjected to torsional force, so as to improve the smoothness of the circumferential movement of the shift fork 4 along the shift shaft 3 when the shift fork 4 is twisted.

[0054] When the buffer base 74 protrudes radially outwardly of the coaxial base sleeve 71 , the outer side of the buffer base 74 will achieve point contact with the inner wall of the buffer ring groove 72 under the action of the elastic plate 75 . Through the above design, the buffer ring 73 can improve the uniformity of the oil in the coaxial base sleeve 71, and the buffer ring 73 can adapt to the shift shaft 3, that is, when there is solidified oil or other impurities on the shift shaft 3, the solidified oil and impurities can be collected and cleaned through the buffer ring 73; and, when the shift head 54 applies a torsional force to the shift fork 4, it will be transmitted to the buffer ring 73 through the coaxial base sleeve 71. Since the protrusion of the buffer base 74 is toward the inner wall of the buffer ring groove 72, that is, the inner wall of the buffer ring groove 72 will apply pressure to the buffer ring 73, and since the buffer base 74 has compressible ability, the buffer ring 73 can limit the coaxial base ring to prevent the failure to form a normal and uniform oil film in the event of torsion, and can improve the smoothness of the circumferential movement of the shift fork 4 along the shift shaft 3 when the shift fork 4 is torsion.

[0055] It is preferred that the buffer base 74 protrudes along the radial outer side of the coaxial base sleeve 71 .

[0056] The buffer base 74 is provided with an oil guide hole 76 along the axial direction of the coaxial base sleeve 71 .

[0057] Through the above design, the oil guide hole 76 can improve the uniformity of oil distribution, and the buffer base 74 can improve the absorption capacity of impact force and torsional force through the guide hole, that is, it can be achieved in the case of high-intensity operation. More specifically, when the torsional strength of the shift fork 4 is large by the shift head 54, the buffer base 74 can absorb the force from the coaxial base sleeve 71 through its own compression.

[0058] The elastic plate 75 includes a serpentine connection portion.

[0059] Through the above design, the serpentine connection part can improve the elastic force of the elastic plate 75 along its radial direction, thereby achieving the effect of fitting or contacting the elastic base with the inner wall of the buffer ring groove 72, and preventing the buffer ring 73 from being separated from the buffer ring groove 72; and, the serpentine connection part can further improve the uniformity of the oil, and the solidified oil and impurities can be collected by the elastic plate 75, preventing the solidified oil and impurities from affecting the moving stability of the shift fork 4. In addition, the serpentine connection part also has good heat dissipation performance. During long-term use, the serpentine connection part can transfer heat to part of the oil and the shift shaft 3.

[0060] Embodiment 2:

[0061] like Figure 6 and Figure 7 As shown, an automatic shifting mechanism according to another embodiment of the present invention is different from that of Example 1 in that the shift block 6 includes two opposite shift block plates 61 , and a first spring 62 is disposed between the two opposite shift block plates 61 .

[0062] It should be noted that when the shift head 54 cooperates with the two opposite shift blocks 6 , the first spring 62 is in a compressed state.

[0063] When the shift head 54 drives the shift fork 4 to move, that is, the shift head 54 realizes the movement of the shift fork 4 by driving the shift block 6. In this process, the setting of the first spring 62 can ensure that the cooperation between the shift block plate 61 and the shift head 54 is always in a close state, thereby improving the connection between the shift head 54 and the shift block plate 61 and preventing the shift head 54 and the shift block 6 from separating during the gear shifting process; the shift blocks 6 on both sides can be used to control the stability of the shift head 54, and the movement of the shift blocks 6 on both sides can be in opposite directions, that is, when the shift head 54 moves, the torsional force is controlled or eliminated by the longitudinal movement of the shift block 6, thereby reducing the torque transmitted to the shift fork 4, further improving the smoothness of the movement of the shift fork 4 on the shift shaft 3 and the ability to control the moving distance of the shift fork 4, and preventing the cooperation between the shift block 6 and the shift head 54 from changing with the change of the angle, thereby improving the movement accuracy of the shift fork 4 and the feedback effect of the angle sensor 8.

[0064] The shift block plate 61 is connected to the shift fork 4 via a connecting plate 63 .

[0065] The connecting plate 63 may be arranged vertically.

[0066] The connecting plate 63 can be arranged tilted. Further, the connecting plates 63 of the two opposite shifting blocks 61 are arranged symmetrically.

[0067] The connecting plates 63 of the two opposite shifting block plates 61 are disposed to be inclined toward each other.

[0068] The connecting plates 63 of the two opposite shifting block plates 61 are arranged to be inclined away from each other.

[0069] By setting the connecting plate 63, the connecting plate 63 can achieve a relatively small swing, so when the shift head 54 drives the shift block 6 to move the shift fork 4, the torsional force of the shift head 54 on the shift block plate 61 will drive it to swing or move, thereby reducing the strength of the torsional force transmitted to the shift fork 4. In addition, the shift block plate 61 can also improve the tightness of the fit between the shift fork 4 and the shift block 6, reducing the possibility of the shift fork 4 and the shift block 6 falling off.

[0070] A third spring 64 is disposed between the two shifting blocks 6 , and the third spring 64 faces the shifting head 54 .

[0071] By providing the third spring 64, the third spring 64 can abut against the shift head 54 to prevent the shift head 54 from vibrating during movement or twisting, that is, the stability and accuracy of the stop process of the shift head 54 after positioning or moving to the desired position can be achieved, thereby achieving the shift action without retraction, thereby ensuring that the shift action is quick and stable.

[0072] Secondly, when the shift head 54 has a torsional force, the third spring 64 can reduce or offset the torsional force, thereby reducing the influence of the shift head 54 on the shift fork 4 when it is twisted, which is beneficial to the stability of the shift fork 4 during its movement along the shift shaft 3, and is beneficial to the formation of an oil film between the shift fork 4 and the shift shaft 3 and the realization of uniformity of the oil film, thereby achieving precise control of the gear shift and rapid action.

[0073] The embodiments described above provide a detailed description of the technical solutions of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements or similar substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An automatic shift mechanism, comprising a motor (1), wherein the output end of the motor (1) is connected to a worm (2), the worm (2) is provided with a shift shaft (3) spaced in parallel, and a shift fork (4) is provided on a sliding sleeve on the shift shaft (3), characterized in that: The worm (2) and the shift fork (4) are connected via a connecting member (5), the connecting member (5) comprising a first base (51), a side of the first base (51) facing the worm (2) being provided with teeth (53), a side of the first base (51) facing the shift fork (4) being provided with a shift head (54), the shift fork (4) being provided with two opposing shift blocks (6), the shift blocks (6) being used to fix the shift head (54); The shift fork (4) is sleeved on both ends of the shift shaft (3) and is provided with a coaxial assembly (7), the coaxial assembly (7) comprising a coaxial base sleeve (71), the inner side of the coaxial base sleeve (71) having at least one oil storage groove, the coaxial base sleeve (71) and the end of the shift fork (4) being connected; A buffer ring groove (72) is provided in the coaxial base sleeve (71), a buffer ring (73) is provided in the buffer ring groove (72), the buffer ring (73) comprises no less than three buffer base bodies (74), and adjacent buffer base bodies (74) are connected via elastic plates (75).

2. The automatic shifting mechanism according to claim 1, characterized in that: An angle sensor (8) is provided on the first substrate (51).

3. The automatic shifting mechanism according to claim 1, characterized in that: The shift shaft (3) is provided with a self-locking device (9).

4. The automatic shifting mechanism according to claim 1, characterized in that: The buffer base (74) protrudes inwardly or outwardly in the radial direction of the coaxial base sleeve (71); When the buffer base (74) protrudes radially inwardly of the coaxial base sleeve (71), the outer side of the buffer base (74) and the elastic plate (75) can be fitted with the buffer annular groove (72); When the buffer base (74) protrudes radially outwardly of the coaxial base sleeve (71), the outer side of the buffer base (74) will achieve point contact with the inner wall of the buffer ring groove (72) under the action of the elastic plate (75).

5. An automatic shift mechanism according to claim 4, characterized in that: The buffer base (74) is provided with an oil guide hole (76) along the axial direction of the coaxial base sleeve (71).

6. The automatic shift mechanism according to claim 4, characterized in that: The elastic plate (75) comprises a serpentine connecting portion.

7. The automatic shifting mechanism according to claim 1, characterized in that: The shift block (6) comprises two opposing shift block plates (61), a first spring (62) is provided between the two opposing shift block plates (61), and the shift block plates (61) are connected to the shift fork (4) via a connecting plate (63).

8. An automatic shift mechanism according to claim 7, characterized in that: The connecting plate (63) is arranged vertically.

9. The automatic shift mechanism according to claim 7, characterized in that: The connecting plate (63) is arranged obliquely, and the two connecting plates (63) relative to the shifting block plate (61) are arranged symmetrically; A third spring (64) is provided between the two shifting blocks (6), and the third spring (64) faces the shifting head (54).

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