CN112524204A - Arrangement mode of balance shafts - Google Patents

Abstract

The invention provides an arrangement mode of a balance shaft, and belongs to the technical field of motorcycles. The balance shaft solves the technical problems that the existing balance shaft is easy to loose and make abnormal sound during connection. The arrangement mode of the balance shaft comprises a cylinder cover, the balance shaft and a cam shaft, wherein the balance shaft and the cam shaft are arranged in parallel, a driving gear is fixedly arranged on the outer peripheral surface of the cam shaft in a fixing mode, a balance block and a driven gear meshed with the driving gear are arranged on the balance shaft, the balance block and the driven gear can synchronously rotate, the cylinder cover is of an integrated structure, two ends of the balance shaft are inserted into the cylinder cover, and the balance block and the driven gear are sleeved on the periphery of the balance shaft and can rotate relative to the balance shaft. The invention can not be loosened due to the pulse load when the balance block rotates.

Description

Arrangement mode of balance shafts

Technical Field

The invention belongs to the technical field and relates to an arrangement mode of a balance shaft.

Background

The balance shaft technology is widely applied to the motorcycle engine, has a simple and practical structure, and can effectively reduce the vibration of the whole motorcycle and improve the driving comfort. In order to eliminate vibration, a common mode adopted on a motorcycle engine is to add a balance shaft for solving the problem. The balance shaft is actually a shaft which is provided with the eccentric weight and rotates along with the crankshaft synchronously, the balance shaft drives the eccentric weight to rotate at a high speed when in work, and the engine obtains a good balance effect and reduces the vibration of the engine by utilizing the reverse vibration force generated by the eccentric weight.

For example, patent with publication number CN210637127U discloses a centrifugal balancing device for an engine camshaft, which comprises a driving gear fixed on an intake camshaft or an exhaust camshaft, a rotating shaft rotatably connected inside the engine is arranged between the intake camshaft and the exhaust camshaft, and the length direction of the rotating shaft is parallel to the length direction of the exhaust camshaft or the intake camshaft; the rotating shaft is fixedly provided with a balance block and a connecting gear, the connecting gear is meshed with the driving gear, and the balance block is fan-shaped.

The structure can reduce the problems of bearing wear aggravation, motion noise generation and the like caused by the centrifugal force of the unbalanced bulges on the camshaft, but the applicant finds that the structure has the problems of easy connection loosening and abnormal sound generation at the bearing matching positions at two ends of the rotating shaft in the operation process. To solve this problem, one of ordinary skill in the art can easily consider: 1. the connecting pieces are added to improve the connecting strength of the bearing seats at the two ends of the rotating shaft and the bearing bushes, so that the loosening probability is reduced; 2. the assembly precision of the rotating shaft, the bearing and the bearing seat is improved, and the overlarge fit clearance is avoided as much as possible.

Disclosure of Invention

The invention provides a balance shaft arrangement mode aiming at the problems in the prior art, and the technical problems to be solved by the invention are as follows: how to avoid the balance shaft from loosening and abnormal sound.

The purpose of the invention can be realized by the following technical scheme:

the utility model provides a mode of arrangement of balance shaft, includes cylinder head, balance shaft and camshaft, the balance shaft with camshaft parallel arrangement, the fixed cover in outer peripheral face of this camshaft is equipped with the driving gear, the epaxial balancing piece that is equipped with of this balance and with driven gear that the driving gear engaged with, the balancing piece with driven gear can rotate in step, a serial communication port, cylinder head formula structure as an organic whole, the both ends of balance shaft are all inserted and are located in the cylinder head, the balancing piece with driven gear all overlaps and locates the periphery of balance shaft and this balance shaft rotation relatively.

The cylinder head locates the cylinder body top of engine, the switching of the different steerable combustion chamber air intake and exhaust valves according to the corner state of self when the camshaft rotates, the driving gear is established to the fixed cover in outer peripheral face of balancing axle, balancing axle is parallel and the peripheral cover of balancing axle establishes balancing piece and driven gear, the counter weight of balancing piece self is not evenly arranged around the rotation center, can form centrifugal force when the balancing piece rotates like this and come the unbalanced force and the moment of balanced engine, balancing piece and driven gear synchronous rotation, and the driving gear meshes with driven gear mutually, the camshaft can drive the accurate rotation of balancing piece when rotating like this. Through setting up the cylinder head into integral type structure, make the both ends of balance shaft insert and locate in the cylinder head, and balancing piece and driven gear all overlap the periphery of locating the balance shaft and can rotate balance shaft relatively, balancing piece and driven gear can not drive the balance shaft rotation under synchronous pivoted state like this, therefore balance shaft both ends can form with the cylinder head tight fit and link firmly, eliminate the fit clearance between the two, avoid balance shaft rotation in-process reciprocating swing to produce impact load to the cylinder head, and the both ends of balance shaft are inserted and are established in the cylinder head of integral type, need not to assemble other reinforcement accessories on the radial cooperation department cylinder head of balance shaft, make this cooperation department can not appear the pine and take off the phenomenon because of receiving the impulse load when the balancing piece rotates.

In the arrangement mode of the balance shaft, the cylinder cover is provided with a yielding port, the balance block and the driven gear are both located in the yielding port, the inner edge side wall of the yielding port is provided with two coaxial and opposite installation shaft holes, two ends of the balance shaft are respectively inserted and matched with the two installation shaft holes, and at least one other end of each installation shaft hole penetrates through the cylinder cover along the axial direction. Let the position mouth through setting up on the cylinder head, make weighing apparatus piece and driven gear all be located the position mouth of stepping down, can make the structure compacter and reduce occupation space like this, the inner edge lateral wall that lets the position mouth sets up the both ends cooperation of two coaxial just right installation shaft holes and balance shaft, and make the other end in at least an installation shaft hole link up the cylinder head along the axial, insert through this installation shaft hole translation from the cylinder head outside when assembling balance shaft like this and form the assembly, the installation direction of balance shaft is perpendicular with the centrifugal force direction of balancing piece, the operating condition of guaranteeing the balancing piece can not lead to balance shaft assembly pine to take off.

In the arrangement mode of the balance shaft, a rolling bearing matched with the inner edge of the driven gear is arranged between the balance shaft and the driven gear, and the rolling bearing is sleeved on the peripheral surface of the balance shaft. Through set up antifriction bearing between balance shaft and driven gear to make antifriction bearing's two inside and outside fitting surfaces respectively with balance shaft and driven gear cooperation, reduced driven gear relative balance shaft pivoted frictional resistance and energy loss, guarantee that the motion is smooth and easy accurate.

In the arrangement mode of the balance shaft, the driven gear is provided with a sleeve coaxially arranged, and the balance weight is fixedly sleeved on the outer peripheral surface of the sleeve. Through set up the sleeve of coaxial arrangement on driven gear and make the fixed cover of balancing piece establish at telescopic outer peripheral face, can also guarantee both and the peripheral fitting surface of balanced axle when linking firmly with balancing piece and driven gear like this and be a whole in succession, the balancing piece receives centrifugal force load and driven gear's radial load and all passes through driven gear transmission, makes the unbalance loading that the balanced axle middle section received even, avoids the unbalance loading that two parts caused respectively to cut and lead to the noise.

In the arrangement mode of the balance shaft, an annular gasket is further sleeved on the periphery of the balance shaft and is located between the driven gear and the inner edge side wall of the position yielding opening. The annular gasket is sleeved on the periphery of the balance shaft and is positioned between the driven gear and the side wall of the inner edge of the position yielding opening, so that the phenomenon that the end face of the driven gear is directly contacted and rubbed with the cylinder cover in the rotating process to cause damage can be avoided.

In the arrangement mode of the balance shaft, the two annular gaskets are respectively positioned at two ends of the driven gear, the end faces of the two ends of the driven gear are provided with positioning grooves which are coaxially arranged, the outer contour of each annular gasket is matched with the shape of each positioning groove, and each annular gasket is embedded in each positioning groove and can be abutted against the side wall of the inner edge of each clearance hole. Through setting up two annular gaskets and being located the driven gear both ends respectively, can form better protection to the cylinder head, through all setting up the constant head tank of coaxial arrangement at driven gear's both ends, make annular gasket location inlay establish in the constant head tank and annular gasket's the outside can with let the inner edge lateral wall of a mouthful support and lean on simultaneously, two annular gaskets like this are injectd in the constant head tank along the axial of balance shaft, avoid annular gasket's inner edge and balance shaft surface direct contact and interfere the rotation effect and cause the card to die or the abnormal sound.

In the arrangement mode of the balance shaft, the rolling bearings are arranged in sequence along the axial direction of the balance shaft, a gasket sleeved on the periphery of the balance shaft is arranged between every two adjacent rolling bearings, and the outer edge of the gasket is matched with the inner edge of the driven gear. Arrange in proper order through setting up a plurality of antifriction bearings, can improve bearing capacity and support homogeneity, set up the cover between adjacent antifriction bearing and locate the outlying packing ring of balance shaft, the packing ring can inject each antifriction bearing's assembly position, guarantees that support load dispersion is even, and the packing ring does not produce the resistance to the balance shaft of packing into when the assembly in addition, guarantees that the assembly is convenient.

In the arrangement of the balance shaft, the rolling bearing is a needle bearing. By arranging the rolling bearing as a needle bearing piece, the matching distance between the balance shaft and the inner edge of the driven gear can be controlled in a smaller range, so that the structure is more compact.

In the arrangement mode of the balance shaft, the cylinder cover is provided with a mounting hole, the mounting hole is crossed and communicated with the mounting shaft hole, a limit sleeve is inserted and matched in the mounting hole, and the end part of the balance shaft is opposite to the limit sleeve along the axial direction of the balance shaft. Through the mounting hole that sets up and installation shaft hole cross intercommunication on the cylinder head, insert in the mounting hole and establish the spacing sleeve of cooperation and make its just right with the tip of balanced axle, spacing sleeve can provide spacing avoiding it to deviate from the installation shaft hole for balanced axle like this, and installation shaft hole inner wall makes the assembly convenient to the resistance of balanced axle when in addition can also reducing balanced axle assembly.

In the arrangement mode of the balance shaft, two mounting holes are arranged and are respectively positioned at two sides of the yielding position opening, two ends of the balance shaft are respectively opposite to the axial leads of the two limiting sleeves along the axial direction, and the distance between the two mounting holes is slightly larger than the length of the balance shaft. Have two and be located the both sides of letting the position mouth through setting up the mounting hole to make the balance shaft both ends respectively just right with the spacing sleeve axial lead in two mounting holes, if like this can guarantee higher spacing stable effect when balance shaft and spacing sleeve take place to push up to lean on, make the interval size of two mounting holes surpass the length size of balance shaft slightly, balance shaft both ends and spacing sleeve support to lean on or only have certain clearance like this, and then guarantee the stable position of balance shaft.

Compared with the prior art, the invention has the following advantages:

this arrangement of balance shaft is through setting up the cylinder head into integral type structure, make the both ends of balance shaft insert locate the cylinder head in, and balance block and driven gear all overlap locate the periphery of balance shaft and can the rotation of balance shaft relatively, therefore the balance shaft does not participate in the rotation can with the cylinder head stable cooperation and need not to reserve the fit clearance, the bearing assembly is removed from with the cooperation department of cylinder head in balance shaft both ends, the structure is retrencied and more stable, the tip of balance shaft radially receives the parcel of integral type structure cylinder head spacing, there is not the cooperation gap and then difficult emergence pine takes off the abnormal sound because of receiving the vibration of balance block pulsed.

Drawings

Fig. 1 is a schematic perspective view of the present embodiment.

Fig. 2 is a schematic cross-sectional structure diagram of the present embodiment.

Fig. 3 is a schematic view of a partial explosion structure of the present embodiment.

Fig. 4 is a schematic perspective view of the cylinder head in this embodiment.

Fig. 5 is an exploded view of the driven gear, the balance weight, the rolling bearing, the annular washer and the washer in this embodiment.

In the figure, 1, a cylinder head; 11. a let position port; 12. installing the shaft hole; 13. mounting holes;

2. a balance shaft;

3. a camshaft; 31. a driving gear;

4. a counterbalance;

5. a driven gear; 51. a sleeve; 52. positioning a groove;

6. a rolling bearing; 7. an annular gasket; 8. a gasket; 9. and a limiting sleeve.

Detailed Description

The following are specific embodiments of the present invention and are further described with reference to the drawings, but the present invention is not limited to these embodiments.

As shown in fig. 1-5, the arrangement of the balance shaft includes a cylinder cover 1, a balance shaft 2 and a camshaft 3, the balance shaft 2 is parallel to the camshaft 3, a driving gear 31 is fixedly sleeved on the outer peripheral surface of the camshaft 3, a balance block 4 and a driven gear 5 engaged with the driving gear 31 are arranged on the balance shaft 2, the balance block 4 and the driven gear 5 can synchronously rotate, the cylinder cover 1 is of an integrated structure, the end of the balance shaft 2 is provided with a guiding conical surface, the two ends of the balance shaft 2 are inserted into the cylinder cover 1 to form a tight fit, and the balance block 4 and the driven gear 5 are sleeved on the periphery of the balance shaft 2 and can rotate relative to the balance shaft 2. Cylinder head 1 locates the cylinder body top of engine, the switching of the different steerable combustion chamber intake and exhaust valves according to the corner state of self when camshaft 3 rotates, driving gear 31 is established to the fixed cover in outer peripheral face of balancing axle, balancing axle 2 is parallel and balancing axle 2 periphery cover establishes balancing piece 4 and driven gear 5 with camshaft 3, the counter weight of balancing piece 4 self is not evenly arranged around the rotation center, can form centrifugal force when balancing piece 4 rotates like this and come the unbalanced force and the moment of balanced engine, balancing piece 4 and driven gear 5 rotate in step, and driving gear 31 meshes with driven gear 5 mutually, camshaft 3 can drive the accurate rotation of balancing piece 4 when rotating like this. Through setting up cylinder head 1 to the integral type structure, make the both ends of balance shaft 2 insert and locate in cylinder head 1, and balance block 4 and driven gear 5 all overlap the periphery of locating balance shaft 2 and can rotate 2 synchronous relatively, balance block 4 and driven gear 5 can not drive balance shaft 2 under synchronous pivoted state and rotate like this, therefore 2 both ends of balance shaft can form with cylinder head 1 tight fit and link firmly, eliminate the fit clearance between the two, avoid 2 rotation in-process reciprocal swings of balance shaft to produce impact load to cylinder head 1, and the both ends of balance shaft 2 insert and establish in the cylinder head 1 of integral type, need not to assemble other reinforcement accessories on 2 radial cooperation department cylinder head 1 of balance shaft, make the cooperation department can not appear the pine because of receiving the pulse load when balance block 4 rotates and take off the phenomenon. Further, the cylinder cover 1 is provided with a yielding port 11, the balance block 4 and the driven gear 5 are both located in the yielding port 11, the side wall of the inner edge of the yielding port 11 is provided with two coaxially opposite mounting shaft holes 12, two ends of the balance shaft 2 are respectively inserted and matched in the two mounting shaft holes 12, and the other end of at least one mounting shaft hole 12 axially penetrates through the cylinder cover 1. Through set up on cylinder head 1 and let position mouth 11, make weighing apparatus piece and driven gear 5 all be located let position mouth 11, can make the structure compacter and reduce occupation space like this, set up two coaxial dead right installation shaft hole 12 and the both ends cooperation of balanced axle 2 at the inner edge lateral wall of the mouth of stepping down 11, and make the other end of at least one installation shaft hole 12 link up cylinder head 1 along the axial, insert through installation shaft hole 12 translation from cylinder head 1 outside when assembling balanced axle 2 like this and form the assembly, the installation direction of balanced axle 2 is perpendicular with the centrifugal force direction of balancing piece 4, guarantee that the operating condition of balancing piece 4 can not lead to balancing axle 2 to assemble the pine and take off. When the balance weight is installed, the balance weight 4, the driven gear 5 and other parts are assembled and then are placed in the position-giving opening 11, and then the balance shaft 2 is pressed into the cylinder cover 1 from the outer side of the cylinder cover 1 through the installation shaft hole 12 to form matching. A rolling bearing 6 matched with the inner edge of the driven gear 5 is arranged between the balance shaft 2 and the driven gear 5, and the rolling bearing 6 is sleeved on the peripheral surface of the balance shaft 2. Through set up antifriction bearing 6 between balance shaft 2 and driven gear 5 to make antifriction bearing 6's two inside and outside fitting surfaces respectively with balance shaft 2 and driven gear 5 cooperation, reduced driven gear 5 relative balance shaft 2 pivoted frictional resistance and energy loss, guarantee that the motion is smooth and easy accurate. The driven gear 5 is provided with a sleeve 51 coaxially arranged, and the balance weight 4 is fixedly sleeved on the outer peripheral surface of the sleeve 51. Through set up coaxial arrangement's sleeve 51 on driven gear 5 and make the fixed cover of balancing piece 4 establish at sleeve 51's outer peripheral face, can also guarantee both and 2 outlying fitting surfaces of balanced axle and be continuous and be a whole with balancing piece 4 when linking firmly with driven gear 5 like this, balancing piece 4 receives centrifugal force load and driven gear 5's radial load and all passes through driven gear 5 transmission, the unbalance loading that makes 2 middle sections of balanced axle receive is even, the unbalance loading that avoids two parts to cause respectively is cuted and is leaded to the noise. The periphery of the balance shaft 2 is also sleeved with an annular gasket 7, and the annular gasket 7 is positioned between the driven gear 5 and the inner edge side wall of the abdicating opening 11. The annular gasket 7 is sleeved on the periphery of the balance shaft 2, so that the annular gasket 7 is positioned between the driven gear 5 and the inner edge side wall of the abdicating opening 11, and the phenomenon that the end surface of the driven gear 5 is directly contacted and rubbed with the cylinder cover 1 in the rotating process to cause damage can be avoided. Preferably, two annular gaskets 7 are respectively located at two ends of the driven gear 5, the size of the inner edge of each annular gasket 7 is larger than the diameter size of the balance shaft 2, the end faces of the two ends of the driven gear 5 are provided with positioning grooves 52 which are coaxially arranged, the outer contour of each annular gasket 7 is matched with the shape of each positioning groove 52, and each annular gasket 7 is embedded in each positioning groove 52 and can be abutted against the side wall of the inner edge of the corresponding abdicating opening 11. Through setting up two annular gaskets 7 and being located 5 both ends of driven gear respectively, can form better protection to cylinder head 1, through all setting up the constant head tank 52 of coaxial arrangement at the both ends of driven gear 5, make annular gasket 7 fix a position inlay establish in constant head tank 52 and annular gasket 7's the outside can support with the inner edge lateral wall of stepping down the mouth 11 simultaneously and lean on, two annular gaskets 7 are injectd in constant head tank 52 along the axial of balance shaft 2 like this, avoid annular gasket 7's inner edge and balance shaft 2 surface direct contact and interfere the rotation effect and cause the card to die or the abnormal sound. The two rolling bearings 6 are sequentially arranged along the axial direction of the balance shaft 2, a gasket 8 sleeved on the periphery of the balance shaft 2 is arranged between the two rolling bearings 6, and the outer edge of the gasket 8 is matched with the inner edge of the driven gear 5. Arrange in proper order through setting up two antifriction bearing 6, can improve bearing performance and support homogeneity, set up the cover between two antifriction bearing 6 and locate balanced axle 2 outlying packing ring 8, packing ring 8 can inject each antifriction bearing 6's assembly position, guarantees that support load dispersion is even, and packing ring 8 does not produce the resistance to the balanced axle 2 of packing into when the assembly in addition, guarantees that the assembly is convenient. Preferably, the rolling bearing 6 is a needle bearing. By arranging the rolling bearing 6 as a needle bearing, the fit distance between the balance shaft 2 and the inner edge of the driven gear 5 can be controlled in a small range, and the structure is more compact.

As shown in fig. 1-4, the cylinder head 1 has a mounting hole 13, the mounting hole 13 intersects and communicates with the mounting shaft hole 12, a limiting sleeve 951 is inserted and fitted in the mounting hole 13, and the end of the balance shaft 2 is opposite to the limiting sleeve 951 along the axial direction of the balance shaft 2. Through set up on cylinder head 1 with the mounting hole 13 of mounting shaft hole 12 cross intercommunication, it is just right to insert the tip that matches limiting sleeve 951 made it and balanced axle 2 in mounting hole 13, and limiting sleeve 951 can provide spacing avoiding it to deviate from mounting shaft hole 12 for balanced axle 2 like this, and the resistance of mounting shaft hole 12 inner wall to balanced axle 2 when in addition can also reducing balanced axle 2 assembly makes the assembly convenient. Preferably, two mounting holes 13 are respectively located at two sides of the relief opening 11, two ends of the balance shaft 2 are respectively opposite to the axial lines of the two limiting sleeves 951 along the axial direction, and the distance between the two mounting holes 13 is slightly larger than the length of the balance shaft 2. Have two and be located the both sides that let position mouth 11 through setting up mounting hole 13 to make 2 both ends of balance shaft respectively with two mounting holes 13 in spacing sleeve 951 axial lead just right, if balance shaft 2 takes place to guarantee higher spacing stable effect when leaning on with spacing sleeve 951 like this, make the interval size of two mounting holes 13 slightly exceed the length size of balance shaft 2, 2 both ends of balance shaft support with spacing sleeve 951 and lean on or only have certain clearance like this, and then guarantee the stable in position of balance shaft 2.

The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the invention as defined in the appended claims.

Claims (10)

1. The utility model provides an arrangement mode of balance shaft, includes cylinder head (1), balance shaft (2) and camshaft (3), balance shaft (2) with camshaft (3) parallel arrangement, the fixed cover in outer peripheral face of this camshaft (3) is equipped with driving gear (31), be equipped with on this balance shaft (2) balancing piece (4) and with driven gear (5) that driving gear (31) engaged with, balancing piece (4) with driven gear (5) can synchronous rotation, a serial communication port, cylinder head (1) formula structure as an organic whole, the both ends of balance shaft (2) are all inserted and are located in cylinder head (1), balancing piece (4) with driven gear (5) all overlap and are located the periphery of balance shaft (2) and can rotate relative this balance shaft (2).

2. The arrangement of the balance shaft according to claim 1, wherein the cylinder head (1) is provided with a position-giving opening (11), the balance weight (4) and the driven gear (5) are both located in the position-giving opening (11), the inner edge side wall of the position-giving opening (11) is provided with two coaxially opposite mounting shaft holes (12), two ends of the balance shaft (2) are respectively inserted and fitted in the two mounting shaft holes (12), and the other end of at least one mounting shaft hole (12) axially penetrates through the cylinder head (1).

3. The arrangement of the balance shaft according to claim 1 or 2, wherein a rolling bearing (6) matched with the inner edge of the driven gear (5) is arranged between the balance shaft (2) and the driven gear (5), and the rolling bearing (6) is sleeved on the outer peripheral surface of the balance shaft (2).

4. The arrangement of the balance shaft according to claim 3, wherein the driven gear (5) is provided with a sleeve (51) which is coaxially arranged, and the balance weight (4) is fixedly sleeved on the outer peripheral surface of the sleeve (51).

5. Arrangement of a balance shaft according to claim 2, characterized in that the balance shaft (2) is further sleeved with an annular gasket (7), and the annular gasket (7) is located between the driven gear (5) and the inner edge side wall of the abdicating opening (11).

6. The balance shaft arrangement manner according to claim 5, wherein two annular gaskets (7) are respectively arranged at two ends of the driven gear (5), the end faces of the two ends of the driven gear (5) are provided with positioning grooves (52) which are coaxially arranged, the outer contour of each annular gasket (7) is matched with the shape of each positioning groove (52), and each annular gasket (7) is embedded in each positioning groove (52) and can be abutted against the inner edge side wall of each relief opening (11).

7. The arrangement mode of the balance shaft according to claim 4, wherein a plurality of rolling bearings (6) are sequentially arranged along the axial direction of the balance shaft (2), a gasket (8) sleeved on the periphery of the balance shaft (2) is arranged between every two adjacent rolling bearings (6), and the outer edge of the gasket (8) is matched with the inner edge of the driven gear (5).

8. Arrangement of a balance shaft according to claim 3, characterized in that the rolling bearing (6) is a needle bearing piece.

9. The arrangement of the balance shaft according to claim 2, wherein the cylinder head (1) is provided with a mounting hole (13), the mounting hole (13) is crossed with and communicated with the mounting shaft hole (12), a limiting sleeve (9) (51) is inserted and matched in the mounting hole (13), and the end part of the balance shaft (2) is opposite to the limiting sleeve (9) (51) along the axial direction of the balance shaft (2).

10. The arrangement mode of the balance shaft according to claim 9, wherein two mounting holes (13) are respectively located at two sides of the relief opening (11), two ends of the balance shaft (2) are respectively opposite to the axial leads of the two limiting sleeves (9) (51) along the axial direction, and the distance between the two mounting holes (13) is slightly larger than the length of the balance shaft (2).

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