CN216009417U - Tensioner - Google Patents

Abstract

The present application relates to a tensioner comprising: the base, center pin, tensioning arm, belt pulley, coil spring, support and bush, the annular groove of tensioning arm and the uncovered marginal part labyrinth seal of base set up the part that blocks on the contact surface of the uncovered marginal part of base and annular groove contact and/or the annular inslot lateral wall of tensioning arm, and the sectional area in at least one section labyrinth seal clearance has been reduced to the part that blocks. The blocking part is arranged in the labyrinth gap, so that at least one section of passage with the sectional area gradually increased from the outside to the inside is formed in the labyrinth gap, namely the sectional area S1 of the outside is smaller than the sectional area S2 of the inside, and therefore blocking of pollutants is achieved.

Description

Tensioner

Technical Field

The utility model relates to a tensioning ware technical field for the tensioning of belt or similar component or the device of regulation.

Background

The tensioner is a commonly used holding device for a belt transmission system and is characterized by keeping a proper tension of a belt in a transmission process so as to avoid the belt from slipping. In automobile transmission, belt transmission is widely applied, and in order to ensure reliable and effective transmission, a belt tensioner is very necessary to be installed. The tensioner is generally arranged near the automobile tire cover and is easily influenced by the external environment, foreign matters or water enter into the tensioner, so the service life of a bearing on the belt pulley and the sealing performance of the spring cavity are key factors of the service life of the tensioner.

Particularly, in the process of daily use of diesel engine belt tensioning pulleys of engineering and mining machinery, the working environment of the belt tensioning pulleys is very severe compared with that of passenger cars, and the belt tensioning pulleys are often attacked by dust, sewage, slurry and the like; the traditional belt tensioning wheel bearing is dustproof in a clearance mode, the sealing performance of a spring cavity is mainly guaranteed to be sealed through the embedding of a tensioning arm and a spring supporting seat, as shown in figure 1, the opposite surfaces of a sealing gap are basically parallel, the sealing mode can only prevent solid particles with large particle sizes from attacking, the defense capacity to dust, sewage and slurry is poor, the spring in the spring cavity is prone to rusting, pollutants can also affect the damping performance of the tensioner, and the tensioning performance of the belt tensioner is finally affected. Therefore, it is very urgent to design a tensioner having excellent antifouling performance.

Disclosure of Invention

The relatively poor problem of current tensioning ware spring chamber sealing performance has mainly been solved to this application, provides a tensioning ware.

In order to solve the technical problem, the application provides the following technical scheme:

the present application provides a tensioner comprising: the base is internally provided with an open accommodating cavity, and the outer side of the edge part of the open is arranged into a concave structure; the central shaft is coaxially arranged in the accommodating cavity of the base; the tensioning arm comprises a first end and a second end which are opposite, the first end of the tensioning arm closes the open end of the base and rotates around the central shaft, an annular groove for the open edge of the base to be embedded is formed, the annular groove of the tensioning arm is in labyrinth seal with the open edge of the base, a blocking part is arranged on a contact surface of the open edge of the base and the annular groove and/or on the inner side wall of the annular groove of the tensioning arm, and the blocking part reduces the sectional area of at least one section of labyrinth seal gap; the belt pulley is arranged on the second end of the tensioning arm and is used for being tightly attached to an engine belt; the spiral spring is sleeved on the central shaft and coaxially arranged in the accommodating cavity of the base, the spiral spring comprises a first end and a second end which are opposite, the first end of the spiral spring is connected with the base, and the second end of the spiral spring is connected with the first end of the tensioning arm; a bracket which is an annular member having an opening, the bracket being coaxially fitted around the coil spring and an inner surface of the bracket contacting an outer surface of the coil spring; the bushing is an annular bushing, the annular bushing is coaxially sleeved outside the support, the inner surface of the bushing contacts the outer surface of the support, and the outer surface of the bushing contacts the inner wall of the accommodating cavity of the base.

As a further improvement of the present application, the open edge of the base contacting the annular groove comprises a first contact surface, a second contact surface, a third contact surface, a fourth contact surface and a fifth contact surface, and correspondingly, the annular groove inner side wall comprises a first side wall adjacent to the first contact surface, a second side wall adjacent to the second contact surface, a third side wall adjacent to the third contact surface, a fourth side wall adjacent to the fourth contact surface and a fifth side wall adjacent to the fifth contact surface; the blocking part is at least one first blocking block which is arranged on at least one of the first contact surface, the second contact surface, the third contact surface, the fourth contact surface and the fifth contact surface and has a sectional area gradually increased from an inlet to the inside, and/or at least one second blocking block which is arranged on at least one of the first side wall, the second side wall, the third side wall, the fourth side wall and the fifth side wall and has a sectional area gradually decreased from an inlet to the inside.

As a further improvement of the present application, the number of the first blocking blocks is several, and several first blocking blocks are staggered on at least one of the first contact surface, the second contact surface, the third contact surface, the fourth contact surface, and the fifth contact surface; the number of the second blocking blocks is a plurality, and the plurality of the second blocking blocks are arranged on at least one of the first side wall, the second side wall, the third side wall, the fourth side wall and the fifth side wall in a staggered mode.

As a further improvement of the present application, the blocking portion further comprises a first protrusion disposed on the first blocking tab adjacent to the inner portion, and/or a second protrusion disposed on the second blocking tab adjacent to the inner portion.

As a further improvement of the present application, the blocking portion further includes a third protrusion disposed on at least one of the first contact surface, the second contact surface, the third contact surface, the fourth contact surface, and the fifth contact surface, and/or a fourth protrusion disposed next to the inside and disposed on at least one of the first sidewall, the second sidewall, the third sidewall, the fourth sidewall, and the fifth sidewall; the first end of the third projection is adjacent to the inner part, and the second end of the third projection is adjacent to the first stop block; a first end of the fourth protrusion is proximate the interior and a second end of the fourth protrusion is proximate the second stop.

As a further improvement of the present application, the open edge of the base contacting the annular groove comprises a first contact surface, a second contact surface, a third contact surface, a fourth contact surface and a fifth contact surface, and correspondingly, the annular groove inner side wall comprises a first side wall adjacent to the first contact surface, a second side wall adjacent to the second contact surface, a third side wall adjacent to the third contact surface, a fourth side wall adjacent to the fourth contact surface and a fifth side wall adjacent to the fifth contact surface; the blocking portion is a fifth protruding portion arranged on at least one of the first contact surface, the second contact surface, the third contact surface, the fourth contact surface and the fifth contact surface, and/or a sixth protruding portion arranged on at least one of the first side wall, the second side wall, the third side wall, the fourth side wall and the fifth side wall.

As a further improvement of the present application, the fifth protrusion includes a plurality of fifth protrusions, and the plurality of fifth protrusions are staggered on at least one of the first contact surface, the second contact surface, the third contact surface, the fourth contact surface, and the fifth contact surface; the sixth protrusions include a plurality of sixth protrusions, and the plurality of sixth protrusions are arranged in a staggered manner on at least one of the first side wall, the second side wall, the third side wall, the fourth side wall, and the fifth side wall.

As a further improvement of the application, the bottom of the accommodating cavity is provided with an axial through hole penetrating through the base, and the central shaft is installed on the base through the axial through hole.

As a further improvement of the application, a holding part for fixing the central shaft extends from the edge of the axial through hole.

As a further improvement of the present application, a bushing is further disposed between the holding portion and the central shaft.

The application has the advantages that the tensioner comprises: the base, center pin, tensioning arm, belt pulley, coil spring, support and bush, the annular groove of tensioning arm and the uncovered marginal part labyrinth seal of base set up the part that blocks on the contact surface of the uncovered marginal part of base and annular groove contact and/or the annular inslot lateral wall of tensioning arm, and the sectional area in at least one section labyrinth seal clearance has been reduced to the part that blocks. The blocking part is arranged in the labyrinth gap, so that at least one section of passage with the sectional area gradually increased from the outside to the inside is formed in the labyrinth gap, namely the sectional area S1 of the outside is smaller than the sectional area S2 of the inside, and therefore blocking of pollutants is achieved.

Drawings

FIG. 1 is a schematic view of a prior art spring chamber seal arrangement for a tensioner;

FIG. 2 is a schematic of the cracking configuration of the tensioner of the present application;

FIG. 3 is a schematic view of a spring cavity seal structure of an embodiment of the tensioner of the present application;

FIG. 4 is an enlarged partial schematic view of a spring chamber seal structure of an embodiment of the tensioner of the present application;

FIG. 5 is a schematic view of a spring chamber seal structure of another embodiment of the tensioner of the present application;

in the figure:

1. a base; 11. a blocking portion; 12. a first contact surface; 13. a second contact surface; 14. a third contact surface; 15. a fourth contact surface; 16. a fifth contact surface; 17. a third protrusion;

2. a central shaft; 21. a mounting seat;

3. a tensioning arm; 31. a first side wall; 32. a second side wall; 33. a third side wall; 34. a fourth side wall; 35. a fifth side wall;

4. a belt pulley; 5. a coil spring; 6. a support; 7. a bushing; 8. and a shaft sleeve.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be described in detail and completely with reference to the following specific embodiments of the present application and the accompanying drawings. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

The application provides a tensioning ware, this tensioning ware's spring chamber sealing performance is excellent, can effectually block the pollutant to get into the spring chamber.

The tensioner of the present application will be described in detail below with reference to fig. 2-5.

Referring to the schematic structural views of fig. 2 to 5, the present embodiment provides a tensioner comprising: base 1, center pin 2, tensioning arm 3, belt pulley 4, coil spring 5, support 6 and bush 7, wherein: an open accommodating cavity is arranged in the base 1, and the outer side of the edge of the open is arranged to be a concave structure; the central shaft 2 is coaxially arranged in the accommodating cavity of the base 1; the tensioning arm 3 comprises a first end and a second end which are opposite, the first end of the tensioning arm 3 closes the open end of the base 1 and rotates around the central shaft 2, an annular groove for embedding the open edge of the base 1 is formed, the annular groove of the tensioning arm 3 is in labyrinth seal with the open edge of the base 1, a blocking part 11 is arranged on a contact surface of the open edge of the base 1 and the annular groove and/or the inner side wall of the annular groove of the tensioning arm 3, and the blocking part 11 reduces the sectional area of at least one section of labyrinth seal gap; the belt pulley 4 is arranged on the second end of the tensioning arm 3 and is used for being tightly attached to an engine belt; the spiral spring 5 is sleeved on the central shaft 2 and coaxially arranged in the accommodating cavity of the base 1, the spiral spring 5 comprises a first end and a second end which are opposite, the first end of the spiral spring 5 is connected with the base 1, and the second end of the spiral spring 5 is connected with the first end of the tensioning arm 3; the bracket 6 is a ring-shaped member with an opening, the bracket 6 and the shaft sleeve 8 are arranged outside the spiral spring 5, the inner surface of the bracket 6 contacts the outer surface of the spiral spring 5, and the bracket 6 mainly and effectively transmits the radial extrusion force of the spiral spring 5; the bush 7 is an annular bush 7, the annular bush 7 and the shaft sleeve 8 are arranged outside the bracket 6, the inner surface of the bush 7 contacts the outer surface of the bracket 6, and the outer surface of the bush 7 contacts the inner wall of the accommodating cavity of the base 1.

The working principle of the tensioner of the present application is as follows: when the first end of the tensioning arm 3 makes a rotary motion, the first end of the tensioning arm 3 applies pressure to the second end of the coil spring 5, and the bottom of the base 1, under the action of the extrusion force of the coil spring 5, also applies a reverse acting force to the second end of the coil spring 5, so that the coil spring 5 is compressed integrally, and a force for pressing the belt is provided for tensioning the engine belt.

In some embodiments, referring to the schematic structural diagrams of fig. 3 to 5, the open edge of the base 1 contacting with the annular groove may be configured to include a first contact surface 12, a second contact surface 13, a third contact surface 14, a fourth contact surface 15 and a fifth contact surface 16, wherein the first contact surface 12, the second contact surface 13, the third contact surface 14, the fourth contact surface 15 and the fifth contact surface 16 are sequentially connected end to end; correspondingly, the annular groove inner side wall comprises a first side wall 31 adjacent to the first contact surface 12, a second side wall 32 adjacent to the second contact surface 13, a third side wall 33 adjacent to the third contact surface 14, a fourth side wall 34 adjacent to the fourth contact surface 15 and a fifth side wall 35 adjacent to the fifth contact surface 16, and the first side wall 31, the second side wall 32, the third side wall 33, the fourth side wall 34 and the fifth side wall 35 are sequentially connected end to end.

In some specific embodiments, the blocking portion 11 may be at least one first blocking piece provided on at least one of the first contact surface 12, the second contact surface 13, the third contact surface 14, the fourth contact surface 15, and the fifth contact surface 16, and having a sectional area gradually increasing from the inlet to the inner portion. The longitudinal sectional shape of the first stopper may be, but not limited to, a trapezoid, a triangle, etc. As a preferred embodiment, the number of the first stoppers may be several, and several first stoppers may be staggered on at least one of the first contact surface 12, the second contact surface 13, the third contact surface 14, the fourth contact surface 15, and the fifth contact surface 16. As another preferred embodiment, the first stopper may be a first annular cone provided on at least one of the first contact surface 12, the second contact surface 13, the third contact surface 14, the fourth contact surface 15, and the fifth contact surface 16. Further, the blocking portion 11 may further include a first protrusion disposed on the first blocking piece adjacent to the inside. Furthermore, the blocking portion 11 may further include a third protrusion 17 provided on at least one of the first contact surface 12, the second contact surface 13, the third contact surface 14, the fourth contact surface 15, and the fifth contact surface 16. Preferably, a first end of the third protrusion 17 is adjacent to the inside, and a second end of the third protrusion 17 is adjacent to the first stopper. In addition, the schematic structural diagrams of fig. 3 and 4 show that the blocking portion 11 is a first blocking block which is arranged on the third contact surface 14 and the sectional area of which is gradually increased from the inlet to the inner part. The schematic structure of fig. 5 shows that the blocking portion 11 is a first blocking piece and a third protrusion 17, which are arranged on the third contact surface 14, the cross-sectional area of which is gradually increased from the inlet to the inner part, the first end of the third protrusion 17 is adjacent to the inner part, and the second end of the third protrusion 17 is adjacent to the first blocking piece. The technical scheme of the present application can be further understood by the schematic structural diagrams of fig. 3 to 5.

In some specific embodiments, the blocking portion 11 may be at least one second blocking piece provided on at least one of the first sidewall 31, the second sidewall 32, the third sidewall 33, the fourth sidewall 34, and the fifth sidewall 35, and having a sectional area gradually decreasing from the inlet toward the inside. The longitudinal sectional shape of the second stopper may be, but not limited to, a trapezoid, a triangle, etc. As a preferred embodiment, the number of the second stoppers may be several, and several second stoppers may be staggered on at least one of the first, second, third, fourth, and fifth sidewalls 31, 32, 33, 34, and 35. As another preferred embodiment, the second stopper may be a second annular cone provided on at least one of the first, second, third, fourth, and fifth sidewalls 31, 32, 33, 34, and 35. Further, the blocking portion 11 may further include a second protrusion disposed on the second blocking piece adjacent to the inside. In addition, the blocking portion 11 may further include a fourth protrusion disposed on at least one of the first, second, third, fourth, and fifth sidewalls 31, 32, 33, 34, and 35, adjacent to the inside. Preferably, a first end of the fourth projection is proximate the interior and a second end of the fourth projection is proximate the second stop.

In some embodiments, as a preferred embodiment, the blocking portion 11 may be a fifth protrusion portion disposed on at least one of the first contact surface 12, the second contact surface 13, the third contact surface 14, the fourth contact surface 15, and the fifth contact surface 16. Preferably, the fifth projection comprises a plurality of fifth projections. Further, a plurality of fifth protrusions are staggered on at least one of the first contact surface 12, the second contact surface 13, the third contact surface 14, the fourth contact surface 15 and the fifth contact surface 16. As another preferred embodiment, the blocking portion 11 may be a sixth protrusion provided on at least one of the first, second, third, fourth, and fifth sidewalls 31, 32, 33, 34, and 35. Preferably, the sixth protrusion includes a plurality of sixth protrusions. Further, a plurality of sixth protrusions are staggered on at least one of the first sidewall 31, the second sidewall 32, the third sidewall 33, the fourth sidewall 34, and the fifth sidewall 35.

It should be further noted that the first blocking block and the second blocking block or the second blocking block and the second protrusion or the second blocking block and the fourth protrusion may be combined, on the basis, the first blocking block and the first protrusion may be combined, or the first blocking block and the third protrusion may be combined, so as to achieve better blocking of the contaminants. Preferably, the first blocking block and the base 1 are integrally formed, or the first blocking block and the first protrusion are integrally formed with the base 1, or the first blocking block and the third protrusion are integrally formed with the base 1, or the fifth protrusion is integrally formed with the base 1; and/or; the second stop block and the tensioning arm 3 are integrally formed, or the second stop block and the second protrusion and the tensioning arm 3 are integrally formed, or the second stop block and the fourth protrusion and the tensioning arm 3 are integrally formed, or the sixth protrusion and the tensioning arm 3 are integrally formed.

In some embodiments, an axial through hole is provided through the base 1 at the bottom of the receiving cavity, and the central shaft 2 is mounted to the base 1 through the axial through hole. Preferably, the shape of the axial through hole is matched with that of the central shaft, so that the central shaft 2 is in close contact with the side wall of the axial through hole, and the purpose that the central shaft 2 can be firmly fixed on the base 1 is achieved. Further, the sectional area of the axial through hole is gradually increased when extending from the bottom of the base 1 to the direction of the accommodating cavity, so that the production and assembly of the tensioner are facilitated. In addition, the central shaft 2 comprises a first end and a second end which are opposite, the first end of the central shaft extends into the first end of the tensioning arm 3, and the second end of the central shaft is provided with a mounting seat 21, the mounting seat 21 can prevent the central shaft 2 from moving up and down along the axial through hole relative to the base 1, so that the fixed position between the central shaft 2 and the base 1 is kept consistent. Preferably, mount pad 21 imbeds the bottom of base 1, and the bottom of base 1 is equipped with the recess that is used for imbedding mount pad 21, and this kind of structural design is favorable to carrying out axial spacing to center pin 2 on the one hand, is convenient for on the one hand with center pin 2 and base 1 fixed mounting together. Preferably, the mounting seat 21 is integrally formed with the central shaft 2.

In some embodiments, a holding portion for fixing the central shaft is extended from the edge of the axial through hole. Wherein, the holding part can be one or more. Preferably, the holding portion is integrally formed with the base 1. Further, a shaft sleeve 8 is arranged between the holding part and the central shaft 2, and the shaft sleeve 8 is in interference fit with the central shaft 2. The shape setting of axle sleeve 8 matches with the center pin appearance, if: when the central shaft 2 is a cylinder, the shaft sleeve 8 is a ring-shaped element matched with the cylinder; when the central shaft 2 is a convex cylinder, the shaft sleeve 8 is a ring-shaped member matching with the convex cylinder.

In summary, the present application provides a tensioner comprising: the base 1, center pin 2, tensioning arm 3, belt pulley 4, coil spring 5, support 6 and bush 7, the annular groove of tensioning arm 3 and the uncovered marginal part labyrinth seal of base 1 set up on the contact surface of the uncovered marginal part of base 1 and annular groove contact and/or the annular inslot lateral wall of tensioning arm 3 and block 11, block 11 has reduced the sectional area of at least one section labyrinth seal clearance. Utilize the hydrodynamics principle, the formula Q of flow is SV (Q is the flow, and S is cross sectional area, and V is fluid speed), and when the fluid passes through little cross sectional area passageway, the flow resistance that receives increases, and flow Q reduces, realizes that the pollutant blocks, otherwise, when the fluid passes through big cross sectional area passageway, the flow resistance that receives reduces, and flow Q increases, is difficult to block the pollutant. The blocking part 11 is arranged in the labyrinth gap, so that at least one section of cross section difference of the inner and outer large-opening passages (refer to fig. 4: A1< A2) is formed in the labyrinth gap, namely the cross section area S1 of the outer gap is less than the cross section area S2 of the inner gap, and therefore blocking of pollutants is achieved.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, many modifications and improvements can be made without departing from the inventive concept, and all of them belong to the protection scope of the present invention.

Claims (10)

1. A tensioner, comprising:

the base is internally provided with an open accommodating cavity, and the outer side of the edge part of the open is arranged into a concave structure;

the central shaft is coaxially arranged in the accommodating cavity of the base;

the tensioning arm comprises a first end and a second end which are opposite, the first end of the tensioning arm closes the open end of the base and rotates around the central shaft, an annular groove for the open edge of the base to be embedded is formed, the annular groove of the tensioning arm is in labyrinth seal with the open edge of the base, a blocking part is arranged on a contact surface of the open edge of the base and the annular groove and/or on the inner side wall of the annular groove of the tensioning arm, and the blocking part reduces the sectional area of at least one section of labyrinth seal gap;

the belt pulley is arranged on the second end of the tensioning arm and is used for being tightly attached to an engine belt;

the spiral spring is sleeved on the central shaft and coaxially arranged in the accommodating cavity of the base, the spiral spring comprises a first end and a second end which are opposite, the first end of the spiral spring is connected with the base, and the second end of the spiral spring is connected with the first end of the tensioning arm;

a bracket which is an annular member having an opening, the bracket being coaxially fitted around the coil spring and an inner surface of the bracket contacting an outer surface of the coil spring;

the bushing is an annular bushing, the annular bushing is coaxially sleeved outside the support, the inner surface of the bushing contacts the outer surface of the support, and the outer surface of the bushing contacts the inner wall of the accommodating cavity of the base.

2. The tensioner as in claim 1, wherein the open edge of the base that contacts the annular groove comprises a first contact surface, a second contact surface, a third contact surface, a fourth contact surface, and a fifth contact surface, and wherein the annular groove inner sidewall comprises, respectively, a first sidewall adjacent the first contact surface, a second sidewall adjacent the second contact surface, a third sidewall adjacent the third contact surface, a fourth sidewall adjacent the fourth contact surface, and a fifth sidewall adjacent the fifth contact surface;

the blocking part is at least one first blocking block which is arranged on at least one of the first contact surface, the second contact surface, the third contact surface, the fourth contact surface and the fifth contact surface and has a sectional area gradually increased from an inlet to the inside, and/or at least one second blocking block which is arranged on at least one of the first side wall, the second side wall, the third side wall, the fourth side wall and the fifth side wall and has a sectional area gradually decreased from an inlet to the inside.

3. The tensioner as in claim 2, wherein the first stop is a plurality of first stops, the plurality of first stops being staggered on at least one of the first contact surface, the second contact surface, the third contact surface, the fourth contact surface, and the fifth contact surface;

the number of the second blocking blocks is a plurality, and the plurality of the second blocking blocks are arranged on at least one of the first side wall, the second side wall, the third side wall, the fourth side wall and the fifth side wall in a staggered mode.

4. The tensioner as in claim 2 or 3, wherein the blocking portion further comprises a first protrusion disposed on the first blocking tab proximate the inside and/or a second protrusion disposed on the second blocking tab proximate the inside.

5. The tensioner as in claim 2 or 3, wherein the blocking portion further comprises a third protrusion disposed on at least one of the first contact surface, the second contact surface, the third contact surface, the fourth contact surface, the fifth contact surface, and/or a fourth protrusion disposed immediately inwardly on at least one of the first sidewall, the second sidewall, the third sidewall, the fourth sidewall, the fifth sidewall;

the first end of the third projection is adjacent to the inner part, and the second end of the third projection is adjacent to the first stop block; a first end of the fourth protrusion is proximate the interior and a second end of the fourth protrusion is proximate the second stop.

6. The tensioner as in claim 1, wherein the open edge of the base that contacts the annular groove comprises a first contact surface, a second contact surface, a third contact surface, a fourth contact surface, and a fifth contact surface, and wherein the annular groove inner sidewall comprises, respectively, a first sidewall adjacent the first contact surface, a second sidewall adjacent the second contact surface, a third sidewall adjacent the third contact surface, a fourth sidewall adjacent the fourth contact surface, and a fifth sidewall adjacent the fifth contact surface;

the blocking portion is a fifth protruding portion arranged on at least one of the first contact surface, the second contact surface, the third contact surface, the fourth contact surface and the fifth contact surface, and/or a sixth protruding portion arranged on at least one of the first side wall, the second side wall, the third side wall, the fourth side wall and the fifth side wall.

7. The tensioner as in claim 6, wherein the fifth lobe comprises a plurality of fifth lobes that are staggered on at least one of the first contact surface, the second contact surface, the third contact surface, the fourth contact surface, the fifth contact surface;

the sixth protrusions include a plurality of sixth protrusions, and the plurality of sixth protrusions are arranged in a staggered manner on at least one of the first side wall, the second side wall, the third side wall, the fourth side wall, and the fifth side wall.

8. The tensioner as in claim 1, wherein an axial through hole is provided through the base at the bottom of the housing, the central shaft being mounted to the base through the axial through hole.

9. The tensioner as in claim 8, wherein a retaining portion for fixing the central shaft extends from an edge of the axial through hole.

10. The tensioner as in claim 9, further comprising a bushing between the retaining portion and the central shaft.

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