JP2023155423A - belt transmission mechanism - Google Patents

Abstract

To provide a belt transmission mechanism which can ensure synchronous rotation even if a speed of a motion accompanied by forward/reverse rotation is increased.SOLUTION: A belt transmission mechanism 1 has an auto tensioner 5 for automatically maintaining the tension of a toothed belt 4 via a first tension roller 51 and a second tension roller 52 which are arranged so as to be turnable in positions for sandwiching a pulley center line PL for connecting a center of a drive pulley 2 and a center of a driven pulley 3, and the auto tensioner 5 has an oscillation shaft 53 which passes a point on the pulley center line PL which is separated to the drive pulley 2 side from a cross point between a roller center line RL for connecting a center of the first tension roller 51 and a center of the second tension roller 52 and the pulley center line PL, and is parallel with a drive shaft 21. The auto tensioner also comprises a spring 54 for energizing the first tension roller 51 and the second tension roller 52 in a direction in which they are attracted to each other, and makes the first tension roller 51 and the second tension roller 52 freely oscillatory with the oscillation shaft 53 as a center.SELECTED DRAWING: Figure 2

Description

The present invention is an auto-tensioner that is incorporated into an arm of an industrial robot, etc., and automatically maintains the tension of a toothed belt at an appropriate level when transmitting the rotational force of a drive pulley to a driven pulley via a toothed belt. The present invention relates to a belt transmission mechanism equipped with a belt transmission mechanism.

In recent years, industrial robots such as vertically articulated robots and horizontally articulated robots (SCARA robots) have been widely used for automobile manufacturing, semiconductor manufacturing, smartphone manufacturing, etc. In industrial robots, toothed belt drive is used instead of gear drive to drive the robot's arm and wrist (hereinafter referred to as "robot arm drive") in order to make it smaller, faster, and lighter. (hereinafter abbreviated as "belt transmission mechanism for driving a robot arm") is being increasingly adopted.

Generally, in a belt transmission mechanism that does not have an auto-tensioner attached, after installing a toothed belt (hereinafter simply referred to as "belt"), it is operated (driving) by running it dry (breaking-in). A process is required to adjust (correct) the belt tension drop that occurs initially. However, due to the structure and manufacturing process, the belt transmission mechanism for driving a robot arm cannot run idle simply by attaching a toothed belt to the pulley in the robot arm. Tension adjustment work is being carried out by operation. Aging involves retensioning the belt (tension adjustment work) by adjusting the distance between the driving pulley and the driven pulley (distance between axes), retightening bolts, etc., and it takes several hours for the robot to be in the correct control state. This had to be done across the country, which caused significant loss costs.

In addition, since the drive of the robot arm involves frequent forward and reverse rotations (the tight side and slack side of the belt are reversed each time it rotates forward and reverse), when switching between forward and reverse directions (starting/stopping forward and reverse), Excessive tension tends to act on the tension side, and loosening tends to occur on the slack side of the belt. If the belt becomes over-tensioned or becomes too loose, the synchronous transmission becomes uncertain (the difference in rotation angle between the drive pulley and the driven pulley is large), and the arm, wrist, etc. It becomes impossible to move the arm accurately to the position (affects the positioning accuracy of the arm, etc.).

In addition, in a belt transmission mechanism where the distance between pulleys is narrow and the reduction ratio (ratio of pulley diameters) is large, the contact angle of the belt becomes small on the drive pulley on the small diameter side, and if the belt becomes loose, the contact angle of the belt becomes small. , there is a concern that belt tooth skipping may occur more easily.

In order to deal with the above problems in synchronous (meshing) transmission using toothed belts, in principle, the belt must be adjusted automatically (including adjusting for the drop in tension that occurs at the beginning of running) and appropriately (to the extent that the belt does not loosen). It is necessary to maintain the tension.

Specifically, in a belt transmission mechanism for driving a robot arm using a toothed belt, even if the tension side and slack side of the belt are reversed each time the belt rotates in forward and reverse directions, the tension side of the belt ( Since it is not necessary to ensure a very high tension at startup (as in the case of friction transmission), it is necessary to suppress tension fluctuations to a low level without applying a damping force.On the other hand, on the slack side of the belt In this case, it is necessary (as in the case of frictional transmission) that the belt does not become loose.

To do this, two tension rollers, which are rotatably installed on both sides of the pulley center line that connects the rotation centers of the drive pulley and the driven pulley, are appropriately biased by springs, etc. By making contact with the inner peripheral surface of the belt, even if the tension side and slack side of the belt are reversed during forward and reverse rotation, the belt will automatically and appropriately (including adjusting the tension drop that occurs at the beginning of running). It is conceivable to adopt a belt transmission mechanism for driving the robot arm that is equipped with an auto-tensioner that can maintain the tension of the belt (to the extent that it does not loosen).

(Conventional technology)
For example, Patent Document 1 (see Figure 1) describes an auto-tensioner installed in a belt transmission mechanism for driving a robot arm, in which both sides of the belt (tension side and slack side) are connected by one spring (tension spring or compression spring). A configuration is disclosed in which the belt is pinched or spread apart by two tension rollers (idlers) by a biasing action to apply tension to the belt. Furthermore, in Patent Document 2 (see Fig. 1), both sides (tension side and slack side) of the belt are sandwiched between two tension rollers (idlers) by a V-shaped swinging arm (no spring biasing), and the belt is A configuration is disclosed in which tension is applied to.

Japanese Patent Application Publication No. 11-33971 Japanese Patent Application Publication No. 2004-156735

However, in recent years, demands for improved productivity in automobile manufacturing, semiconductor manufacturing, smartphone manufacturing, etc. have increased dramatically compared to the past. Therefore, even for industrial robots, there is a demand for further performance improvement in the robot arm drive section. The difference in rotation angle between the driven pulley and the driven pulley can always be kept within the permissible range), synchronous transmission (including adjusting for the drop in tension that occurs at the beginning of running) automatically and appropriately (the belt does not loosen). There is an increasing demand for ``maintaining belt tension to a certain degree''.

The above-mentioned difference in rotation angle in the robot arm drive section is caused by the difference in rotation angle during forward/reverse switching (starting/stopping of forward/reverse) under conditions where the specifications of the belt and pulley (the engagement between the belt teeth and the pulley tooth groove) are fixed. ) is known to reach its maximum (overshoot and undershoot occur during forward/reverse switching).

Therefore, in the belt transmission mechanism for driving a robot arm, in order to repeatedly ensure positioning accuracy (ensure synchronous transmission) even if the speed of movement involving forward and reverse rotation increases, it is necessary to It is important to ensure a high level of responsiveness to driving during forward/reverse switching (start/stop of forward/reverse) (that is, to sufficiently suppress the rotation angle difference mentioned above during forward/reverse switching).

In this regard, as a result of detailed verification in light of the above-mentioned viewpoint, we found that the auto-tensioner (conventional auto-tensioner) provided in the belt transmission mechanism for driving a robot arm, as disclosed above, is not able to reliably meet the above-mentioned recent demands. It turned out to be enough.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a belt transmission mechanism that can ensure synchronous transmission even when the speed of operation involving forward and reverse rotation increases.

The present invention includes a drive pulley fixed to a drive shaft that is rotatably driven in forward and reverse directions by a drive source;
a rotatably supported driven pulley;
a toothed belt wound between the driving pulley and the driven pulley;
Two tension rollers are provided rotatably around their respective base shafts at positions on both sides of the pulley center line connecting the rotation center of the drive pulley and the rotation center of the driven pulley, and are in contact with the toothed belt. an autotensioner that automatically maintains the tension of the toothed belt at an appropriate level through the belt transmission mechanism,
The auto tensioner is
passing through a point on the pulley center line or a point on an extension of the pulley center line that is spaced toward the drive pulley from the intersection of the roller center line connecting the rotation centers of the two tension rollers and the pulley center line; a swing shaft provided to extend in a direction parallel to the drive shaft;
a spring that is stretched between each of the base shaft portions of the two tension rollers and biases the two tension rollers in a direction toward each other or a direction in which they are spaced apart from each other along the roller center line, and
The two tension rollers are configured to be swingable about the swing shaft.

According to the above configuration, in the belt transmission mechanism, it is possible to ensure a high level of responsiveness to the drive during forward/reverse switching (starting/stopping of forward/reverse) (that is, the driving pulley and driven pulley during forward/reverse switching). Even if the speed of movement involving forward and reverse rotation increases, synchronous transmission [(including adjustment of tension drop that occurs at the beginning of running) can be automatically and moderately controlled]. It is possible to ensure that the belt tension is maintained (to the extent that the belt does not loosen).

Further, the present invention provides the above-mentioned belt transmission mechanism,
The auto tensioner is
a first swing arm, one end of which is provided with the base shaft portion of one of the tension rollers, and the other end of which is rotatably supported with respect to the swing shaft;
a second swing arm, one end of which is provided with the base shaft of the other tension roller, and the other end of which is rotatably supported with respect to the swing shaft; have,
The two tension rollers may be characterized in that they swing about the swing shaft via the first swing arm and the second swing arm.

According to the above configuration, two swing arms (a first swing arm and a second swing arm) each having a base shaft of two tension rollers each having a spring tensioned thereon are provided at one end (tip part). Each of the arms) passes through a point on the pulley center line or a point on an extension of the pulley center line, which is spaced away from the intersection of the roller center line and the pulley center line toward the drive pulley, and is parallel to the drive shaft. By being able to freely rotate around the rocking shaft (which extends in the direction), it is possible to concretely realize a mode in which the two tension rollers rock around the rocking shaft in addition to the biasing action of the spring.

Further, the present invention provides the above-mentioned belt transmission mechanism,
the spring is a tension spring;
The two tension rollers may be provided so as to be in contact with the outer peripheral surface of the toothed belt.

According to the above configuration, both sides (tension side and slack side) of the belt are sandwiched between two tension rollers by the biasing action of one spring (tension spring). Therefore, the spring is a compression spring, and the two tension rollers are provided so as to contact the inner peripheral surface of the toothed belt. The contact angle of the belt (the central angle with respect to the circular arc where the belt and the pulley are in contact) becomes larger than that in the case where the belt is pushed out and spread out, thereby suppressing the occurrence of tooth skipping of the belt.

Further, the present invention provides the above-mentioned belt transmission mechanism,
The two tension rollers may be provided on the driving pulley side, or on the pulley side with a smaller diameter among the driving pulley and the driven pulley.

In belt transmission mechanisms, in order to ensure the rotational torque of the driven pulley at a predetermined level, the diameter of the driving pulley is generally smaller than the diameter of the driven pulley (functioning as a so-called speed reduction mechanism). In some cases, the pulley and driven pulley have the same diameter. For example, in a belt transmission mechanism where the distance between pulleys is narrow and the reduction ratio (ratio of pulley diameters) is large, the contact angle of the belt becomes small on the drive pulley on the small diameter side, and if the belt is slack, the belt There is a concern that tooth skipping may easily occur, but according to this configuration, on the drive pulley (including cases where the drive pulley and the driven pulley have the same diameter) or the pulley on the small diameter side (regardless of whether it is driven or driven). Since the contact angle of the belt can be suppressed from becoming small, tooth skipping of the belt can be made less likely to occur.

Further, the present invention provides the above-mentioned belt transmission mechanism,
The drive pulley may have a smaller diameter than the driven pulley.

According to the above configuration (that is, when the belt transmission mechanism is a speed reduction mechanism), the two tension rollers move around the swing shaft during forward/reverse switching, compared to a case where the diameter of the drive pulley is the same as the diameter of the driven pulley. By swinging around the center, the degree of displacement increases.
Therefore, according to this configuration, the two tension rollers are configured to be unable to swing around the swing shaft (a structure in which only the biasing force of the spring acts on the two tension rollers), and are parallel to the drive shaft. Compared to a configuration in which the two tension rollers can only be displaced in a direction perpendicular to the pulley center line when viewed in the direction shown in FIG. By swinging around the swing axis while suppressing displacement, the effect of rapid displacement can be further increased. As a result, in the belt transmission mechanism, it is possible to ensure a higher level of responsiveness to driving during forward/reverse switching (start/stop of forward/reverse).

Moreover, the present invention may be the belt transmission mechanism, in which the drive pulley and the driven pulley are fixed to a robot arm and drive the robot arm.

According to the above configuration, when driving the robot arm, even if the speed of the operation involving forward and reverse rotation increases in the belt transmission mechanism, the positioning accuracy of the robot arm can be repeatedly ensured (that is, the positioning accuracy of the drive pulley and the driven pulley The magnitude of the difference in rotation angle between the two wheels can always be kept within an allowable range), and synchronous transmission can be ensured.

It is possible to provide a belt transmission mechanism that can ensure synchronous transmission even when the speed of operation involving forward and reverse rotation increases.

FIG. 2 is an explanatory diagram of a robot arm drive belt transmission mechanism according to the present embodiment, which is incorporated into a robot arm of a horizontal articulated robot. FIG. 2 is a plan view of the robot arm drive belt transmission mechanism according to the present embodiment (a diagram illustrating a state in which the drive pulley is stopped). 3 is a sectional view/left side view taken along line AA in FIG. 2. FIG. 3 is a sectional view taken along line BB in FIG. 2. FIG. FIG. 2 is a plan view of the belt transmission mechanism for driving a robot arm according to the present embodiment (a diagram illustrating the operating state of the auto tensioner during forward/reverse switching). FIG. 1 is a cross-sectional perspective view of a toothed belt according to the present embodiment. FIG. 2 is an explanatory diagram of a responsiveness evaluation tester related to evaluation (responsiveness test) of the example. FIG. 2 is an explanatory diagram of a test pattern (cycle pattern) of a responsiveness test related to the evaluation (responsiveness test) of the example. 3 is a configuration diagram of an autotensioner according to Comparative Example 4. FIG. FIG. 7 is a plan view of a belt transmission mechanism for driving a robot arm according to another embodiment.

(Embodiment)
This embodiment is incorporated into the second arm 11 of a horizontal articulated robot 10 (industrial robot) called a SCARA robot, and transmits the rotational force of a drive pulley 2 to a driven pulley 3 via a toothed belt 4. A belt transmission mechanism 1 for driving a robot arm (hereinafter sometimes simply referred to as "belt transmission mechanism 1") is provided with an auto-tensioner 5 for automatically maintaining the tension of the toothed belt 4 at an appropriate level. This is an example in which the present invention is applied to.

For example, as shown in FIG. 1, the belt transmission mechanism 1 of this embodiment includes a wrist portion 12 that extends in the vertical direction at the tip of the second arm 11 of the horizontal articulated robot 10 and is detachably attached to the lower end. (details not shown) as a belt-type speed reduction mechanism for driving the ball screw spline shaft 13, which is provided so as to be vertically movable and coaxially rotatable, in forward and reverse rotation via a driven shaft 31 coaxial with the ball screw spline shaft 13. Incorporated. The vertical movement of the ball screw spline shaft 13 is performed by a vertical movement drive mechanism 14. The belt transmission mechanism 1 incorporated as a belt-type reduction mechanism drives the ball screw spline shaft 13 in forward and reverse rotation while allowing the ball screw spline shaft 13 to move up and down by the vertical movement drive mechanism 14 while preventing rotation. can be done.

In addition, in the case of the robot body shown in FIG. 5 of Patent Document 2, the upper and lower arms, which extend in the vertical direction and are provided to be able to move vertically and coaxially, are connected to the T-axis servo motor (T-axis servo motor) at the tip of the second arm. The belt transmission mechanism 1 according to the present embodiment can be incorporated as a T-axis rotation transmission mechanism (second stage mechanism of a two-stage reduction method) that rotates coaxially in the forward and reverse directions by driving the pulley in forward and reverse directions.

(Belt transmission mechanism 1)
As shown in FIGS. 1 and 2, the belt transmission mechanism 1 is connected to a servo motor 20 (drive source: a second stage mechanism of a two-stage reduction system) at the rear side (one end) of the second arm 11. When applied, the driving force of the servo motor provided in the first stage belt type reduction mechanism is applied to the drive shaft 21 (when applied to the second stage mechanism of a two stage reduction system, the driving force is transferred to the first stage belt type reduction mechanism). At the drive pulley 2, which transmits transmission via the drive shaft of the second stage belt-type reduction mechanism (which extends coaxially with the driven shaft (not shown) of the mechanism), and at the front side (the other end) of the second arm 11. , a driven pulley 3 that transmits driving force to a driven shaft 31 connected to a ball screw spline shaft 13 to which the wrist portion 12 is attached, and teeth endlessly wound between the driving pulley 2 and the driven pulley 3. It is composed of a toothed belt 4 and an auto tensioner 5 that automatically maintains the tension of the toothed belt 4 at an appropriate level via a first tension roller 51 and a second tension roller 52 that are rotatably provided.

In FIG. 1, the proximal end side of the second arm 11 (the side connected to the first arm 15) is the rear side (one side), and the distal end side of the second arm 11 (the ball screw to which the wrist portion 12 is attached) is the rear side (one side). The side connected to the spline shaft 13) is defined as the front side (the other side).
Further, in FIG. 2, the left side is defined as the front (the other side), and the right side is defined as the rear (one side). Moreover, in FIG. 3, the radial direction centered on the central axis R of the swing shaft 53 is simply defined as the radial direction, and the circumferential direction centered on the central axis R is simply defined as the circumferential direction. Further, in FIGS. 3 and 4, the up-down direction is defined as the up-down direction, and the left-right direction is defined as the horizontal direction.

(Drive pulley 2 and driven pulley 3)
The drive pulley 2 is fixed to a drive shaft 21 that is driven by the driving force of a servo motor 20 so as to be able to rotate in forward and reverse directions. Further, the driven pulley 3 is fixed to a driven shaft 31 to which the ball screw spline shaft 13 is connected.

The driving pulley 2 and the driven pulley 3 are toothed pulleys. On the outer periphery of the driving pulley 2 and the driven pulley 3, there is a groove (not shown) having a shape corresponding to the shape of the teeth of the toothed belt 4 (for example, the tooth shape called a general straight tooth (Sugba)). It is formed. In this embodiment, the grooves formed on the outer peripheries of the drive pulley 2 and the driven pulley 3 have shapes corresponding to straight teeth, and extend along the direction of the driven shaft 31.

The distance between the axes of the driving pulley 2 and the driven pulley 3 is fixed and cannot be adjusted, and is, for example, about 80 mm to 300 mm (220 mm in this embodiment).
The speed ratio between the driving pulley 2 and the driven pulley 3 (diameter of the driven pulley 3/diameter of the driving pulley 2) is, for example, about 1 to 4. In this embodiment, the driven pulley 3 has a pitch diameter approximately four times larger than that of the driving pulley 2 so that the speed ratio (reduction ratio) is 4.
The belt tension when the toothed belt 4 is stationary (the belt tension when the drive pulley 2 is stopped) is at a level that does not loosen the toothed belt 4, for example, about 1 to 5 N/belt width of 1 mm. (5N/belt 1mm width in this embodiment).
The allowable range of the rotation angle difference between the driving pulley 2 and the driven pulley 3 (maximum at the time of forward/reverse switching) is determined by the design aspect. Note that the above-mentioned "rotation angle difference" is an index (substitute characteristic) representing responsiveness, and refers to "the magnitude of the difference in rotation angle (°) between the driving pulley and the driven pulley."

(Toothed belt 4)
As shown in FIG. 6, the toothed belt 4 includes a back part 43 in which a core wire 42 is embedded spirally along the belt longitudinal direction, and an inner circumferential surface of the back part 43 (corresponding to one surface of the back part 43). The belt has a plurality of teeth 44 arranged at predetermined intervals along the longitudinal direction of the belt. In this embodiment, the plurality of teeth 44 are integrally molded on the inner circumferential surface of the back portion 43. Further, the tooth portion 44 extends along the belt width direction (that is, the tooth portion 44 is a straight tooth). In addition, the inner circumferential surface of the toothed belt 4, that is, the surface of the toothed portion 44 and a part of the inner circumferential surface of the back portion 43 (the portion where the toothed portion 44 is not provided) are constituted (covered) with a tooth cloth 45. has been done. Note that the outer peripheral surface of the back portion 43 (corresponding to the other surface of the back portion 43) is not covered with cloth or the like (back cloth).

The interval (tooth pitch Pt) between the teeth 44 adjacent to each other in the belt longitudinal direction is determined from the viewpoint of repeatedly ensuring positioning accuracy (ensuring synchronous transmission) even when the speed of operations involving forward and reverse rotation increases. It is better to set it to a relatively small value, for example, about 2 mm to 5 mm (3 mm in this embodiment). Note that the numerical value of the tooth pitch Pt also corresponds to the scale of the tooth portion 44 (the length of the tooth portion 44 in the belt longitudinal direction and the tooth height Ht of the tooth portion 44). That is, as the tooth pitch Pt becomes larger, the scale of the tooth portion 44 similarly becomes larger.

The length (circumferential length) of the toothed belt 4 in the belt longitudinal direction is, for example, about 200 mm to 800 mm (about 600 mm in this embodiment).
The length (width) of the toothed belt 4 in the belt width direction is, for example, about 6 mm to 35 mm (10 mm in this embodiment).

(back part 43 and tooth part 44)
The back portion 43 and tooth portions 44 of the toothed belt 4 are made of a rubber composition, and the rubber components of this rubber composition include chloroprene rubber (CR), nitrile rubber, hydrogenated nitrile rubber (HNBR), and ethylene-propylene. Copolymers (EPM), ethylene-propylene-diene terpolymer (EPDM), styrene-butadiene rubber, butyl rubber, chlorosulfonated polyethylene rubber, etc. are used. These rubber components can be used alone or in combination. The rubber component of the rubber composition constituting the back portion 43 and the tooth portions 44 is preferably chloroprene rubber, especially from the viewpoint of low cost (this embodiment also uses chloroprene rubber). Note that the rubber compositions forming the tooth portion 44 and the back portion 43 may be the same or different. The rubber composition constituting the back portion 43 and the tooth portions 44 may contain various conventional additives (or compounding agents) as necessary. The hardness of the rubber composition (tooth rubber) constituting the toothed portion 44 is determined based on JIS K6253 (2012) from the viewpoint of ensuring the transmission performance (particularly tooth skipping resistance) of the toothed belt 4, and the hardness is determined based on the ambient temperature. The hardness is preferably about 73° to 83° as measured using a type A durometer at 23° C. (23±2° C.).

(Tooth shape of tooth portion 44)
As long as synchronous transmission (meshing transmission) is possible, the tooth shape of the tooth portion 44 of the toothed belt 4 may be a general straight tooth shape, or a helical tooth shape (with a contact angle of the tooth surface). A tooth shape called a diagonal tooth shape may also be used. The toothed belt 4 used in the belt transmission mechanism 1 of this embodiment has straight teeth.

As the tooth shape belonging to the straight teeth, it is possible to select a tooth shape suitable for the purpose of the belt transmission mechanism, such as the well-known tooth shapes listed below, modified shapes thereof, or special shapes. For example, the H-tooth profile is a shape with a substantially semi-circular cross section, the T-tooth profile is a trapezoidal cross-section, and the S-tooth profile (STPD type) is a convex curved surface (arc surface) that bulges outward. Examples include a shape in which two sides are connected by a flat surface. From the viewpoint of ensuring the transmission performance (particularly transmission capacity and tooth skip resistance) of the toothed belt 4, it is better to increase the rigidity of the tooth portion 44, and it is better to increase the rigidity of the tooth portion 44. It is preferable to do so (this embodiment also has an H tooth profile).

(core wire 42)
The core wire 42 is composed of a twisted cord formed by twisting a plurality of strands together. One strand may be formed by bundling and aligning filaments (long fibers). From the viewpoint of improving responsiveness to driving during forward/reverse switching in the belt transmission mechanism 1, the material of the filament is preferably one with high strength (high modulus of elasticity) and low elongation, such as alkali-free glass fiber (E glass fiber). ), high strength glass fiber or carbon fiber. From the viewpoint of low cost, alkali-free glass fiber (E-glass fiber) is more preferable. The diameter of the core wire 42 is determined from the viewpoint of improving the flexibility of the toothed belt 4 (the flexibility of the toothed belt 4 when it is wound around the drive pulley 2 or the driven pulley 3), that is, the belt pitch. From the viewpoint of suppressing the speed unevenness of the toothed belt 4 due to vertical movement of the line and ensuring high positioning accuracy, it is preferable that the diameter is small. The diameter of the core wire 42 is, for example, about 0.15 mm to 0.60 mm. is 0.53 mm).

As the high-strength glass fiber, for example, one having a tensile strength of 300 kg/cm ² or more, particularly a glass fiber having a composition shown in Table 1, which has a higher Si content than alkali-free glass fiber (E glass fiber), can be suitably used. .
Note that Table 1 also shows the composition of E glass fiber for comparison. Such high-strength glass fibers include K glass fiber, U glass fiber (both manufactured by Nippon Glass Fiber Co., Ltd.), T glass fiber (manufactured by Nittobo Co., Ltd.), R glass fiber (manufactured by Vetrotex), S glass fiber, and S glass fiber. -2 glass fiber, ZENTRON glass fiber (all manufactured by Owens Corning Fiberglass), and the like.

Examples of carbon fibers include pitch-based carbon fibers, polyacrylonitrile (PAN)-based carbon fibers, phenolic resin-based carbon fibers, cellulose-based carbon fibers, and polyvinyl alcohol-based carbon fibers. Commercially available carbon fiber products include, for example, "Torayca (registered trademark)" manufactured by Toray Industries, Inc., "Tenax (registered trademark)" manufactured by Toho Tenax Co., Ltd., and "Dialead (registered trademark)" manufactured by Mitsubishi Chemical Corporation. ” etc. can be used. These carbon fibers can be used alone or in combination of two or more. Among these carbon fibers, pitch-based carbon fibers and PAN-based carbon fibers are preferred, and PAN-based carbon fibers are particularly preferred.

It is preferable that the twisted cord used as the core wire 42 is subjected to an adhesive treatment in order to improve its adhesion to the back portion 43. As the adhesive treatment, for example, a method is employed in which a twisted cord is immersed in a resorcinol-formalin-latex treatment liquid (RFL treatment liquid) and then heated and dried to form an adhesive layer uniformly on the surface. The RFL treatment liquid is a latex mixed with an initial condensate of resorcinol and formalin, and the latex used here includes chloroprene, styrene-butadiene-vinylpyridine terpolymer (VP latex), hydrogenated Examples include nitrile and NBR. Note that, as the adhesion treatment, there is also a method of pre-treatment with an epoxy or isocyanate compound and then treatment with an RFL treatment liquid.

The core wires 42 are spirally embedded in the back portion 43 along the belt longitudinal direction at predetermined intervals in the belt width direction. That is, the core wires 42 are arranged on the back portion 43 at predetermined intervals in the belt width direction.

(Tooth cloth 45)
From the viewpoint of wear resistance, it is preferable that the tooth cloth 45 is made of a woven fabric in which the warp and the weft are intertwined vertically and horizontally according to a certain rule. The tooth cloth 45 is preferably arranged such that the warp of the woven fabric extends in the belt width direction and the weft thread extends in the belt longitudinal direction. Thereby, elasticity of the tooth cloth 45 in the belt longitudinal direction can be ensured. In addition, the tooth cloth 45 may be arranged so that the weft of the woven fabric extends in the belt width direction and the warp threads of the woven fabric extend in the belt longitudinal direction. In this case, elastic threads having stretchability may be used as the warp threads. As the material of the fibers constituting the tooth cloth 45, any one of nylon, aramid, polyester, polybenzoxazole, cotton, etc. or a combination thereof can be used.
The woven fabric used as the tooth cloth 45 may be subjected to an adhesive treatment in order to improve adhesiveness with the back portion 43 and the tooth portions 44. A common method of adhesion treatment is to immerse a woven fabric in resorcinol-formalin-latex (RFL liquid) and then heat and dry it to form an adhesive layer uniformly on the surface.

(Method for manufacturing toothed belt 4)
The toothed belt 4 according to the present embodiment is manufactured, for example, by the following construction method (press-fit construction method). First, the fiber fabric forming the tooth cloth 45 is wound around the outer peripheral surface of a cylindrical mold having a plurality of grooves (concave lines) corresponding to the teeth 44 of the toothed belt 4. Subsequently, the twisted cord constituting the core wire 42 is spirally wound around the outer peripheral surface of the wound fiber fabric at a predetermined pitch (so as to have a predetermined pitch in the axial direction of the cylindrical mold). Furthermore, an unvulcanized rubber sheet forming the back portion 43 and tooth portions 44 is wrapped around the outer circumferential side to form an unvulcanized belt molded body (unvulcanized laminate).

Next, while the unvulcanized belt molded body is placed around the outer periphery of the cylindrical mold, a rubber jacket serving as a vapor barrier material is placed over the outside of the molded body. Subsequently, the jacketed belt molded body and the cylindrical mold are housed inside a vulcanization device such as a vulcanization can. Then, when the belt molded body is heated and pressurized inside the vulcanization device, the rubber composition of the unvulcanized rubber sheet and the fiber fabric are press-fitted into the grooves (concave stripes) of the cylindrical mold, forming the teeth of the desired shape. is formed, and the rubber composition of the unvulcanized rubber sheet is vulcanized to form a sleeve-shaped vulcanized product (vulcanized belt sleeve) in which the rubber composition, fiber fabric, and core wire are integrated. be done. At this time, the fiber fabric is stretched to follow the contour shape of the toothed portion 44, and becomes a tooth cloth 45 disposed on the surface of the toothed portion 44. A plurality of toothed belts 4 are obtained by cutting the vulcanized belt sleeve removed from the cylindrical mold into a predetermined width. In this construction method (press-in construction method), the same rubber composition is used for the back portion 43 and the tooth portion 44.

(Auto tensioner 5)
As shown in FIGS. 2 to 4, the auto tensioner 5 includes a swing shaft 53 fixed to the casing of the second arm 11, and a tip 561 (corresponding to one end of the first swing arm 56). A first base shaft portion 51A on which the first tension roller 51 is rotatably supported is provided, and a base end portion 562 (corresponding to the other end of the first swing arm 56) is connected to the swing shaft 53. A first swing arm 56 is rotatably supported on the other hand, and a second tension roller 52 is rotatably supported on a tip end 571 (corresponding to one end of the second swing arm 57). A second swing arm 57 is provided with a base shaft portion 52A, and a base end portion 572 (corresponding to the other end of the second swing arm 57) is rotatably supported with respect to the swing shaft 53; The first base shaft portion 51A and the second base shaft portion 52A are urged in a direction in which they are drawn toward each other along the roller center line RL connecting the rotation center 51C of the first tension roller 51 and the rotation center 52C of the second tension roller 52. The spring 54 has a spring 54.

In this embodiment, the auto tensioner 5 has two tension rollers (a first tension roller 51 and a second tension roller 52) provided not on the driven pulley 3 side but on the drive pulley 2 side. Note that the auto tensioner 5 may have two tension rollers (the first tension roller 51 and the second tension roller 52) provided on the pulley side with the smaller diameter of the drive pulley 2 and the driven pulley 3. Here, "the two tension rollers are provided on the drive pulley 2 side" means that the intersection of the roller center line RL and the pulley center line PL is located closer to the drive pulley 2 than the center of the pulley center line PL. It means to do.

(First tension roller 51 and second tension roller 52)
The first tension roller 51 is a cylindrical roller member that is rotatably supported by the first base shaft portion 51A via a rolling bearing (not shown) about the central axis R2. The second tension roller 52 is also a cylindrical roller member rotatably supported by the second base shaft portion 52A via a rolling bearing (not shown) around the center axis R3.

As shown in FIG. 2, the first tension roller 51 and the second tension roller 52 sandwich a pulley center line PL connecting the rotation center 22 of the drive pulley 2 and the rotation center 32 of the driven pulley 3 on the drive pulley 2 side. The first tension roller 51 and the second tension roller 52 are provided rotatably around a first base shaft portion 51A and a second base shaft portion 52A at positions on both sides, respectively, so that the first tension roller 51 and the second tension roller 52 can contact the outer peripheral surface of the toothed belt 4. ing.

(First base portion 51A and second base portion 52A)
As shown in FIGS. 3 and 4, the first base shaft portion 51A is a base end portion that supports the first tension roller 51 rotatably about the central axis R2 via a rolling bearing (not shown).
The first base shaft portion 51A has a male threaded portion extending downward to be inserted into a hole (female threaded portion) provided in a tip portion 561 of the first swing arm 56, which will be described later.
Similarly, the second base shaft portion 52A is a base end portion that supports the second tension roller 52 rotatably about the central axis R3 via a rolling bearing (not shown), as shown in FIG.
The second base shaft portion 52A has a male threaded portion extending downward to be inserted into a hole (female threaded portion) provided in a tip portion 571 of a second swing arm 57, which will be described later.
A spring 54, which will be described later, is stretched between the first base portion 51A and the second base portion 52A.

(oscillating shaft 53)
As shown in FIG. 3, the swing shaft 53 includes a cylindrical body portion 531 extending in the vertical direction, a flange portion 532 extending radially outward from the upper end of the body portion 531, and a lower end surface of the body portion 531. It has a fastening portion 533 extending downward from the center portion (lower end surface), and is a metal component integrally formed.

As shown in FIG. 2, the swing shaft 53 has a center axis R (swing center point) that is aligned with the rotation center 51C of the first tension roller 51 and the rotation center 52C of the second tension roller 52. Passing through a point on the pulley center line PL (or a point on an extension of the pulley center line PL) that is spaced away from the drive pulley 2 side from the intersection of the roller center line RL and the pulley center line PL that connect the It is fixed to the casing (female threaded portion) of the second arm 11 of the horizontal articulated robot 10 via a fastening portion 533 (male threaded portion) so as to extend in parallel directions. Further, in the swing shaft 53, the outer circumferential surface of the body portion 531 and the lower end surface of the flange portion 532 are in surface contact with a sliding member 55 (bearing), and via this sliding member 55 (bearing), The first swing arm 56 and the second swing arm 57 are rotatably supported.

(Spring 54)
The spring 54 is a tension spring in this embodiment.
The tension spring is stretched between the first base portion 51A and the second base portion 52A in a state where it is stretched in a direction in which it becomes longer than its natural length (a state in which self-elastic recovery force acts in the direction of contraction), The first base shaft portion 51A and the second base shaft portion 52A are urged in a direction to draw them toward each other along the roller center line RL. That is, the spring 54 moves the first tension roller 51 rotatably provided on the first base portion 51A and the second tension roller 52 rotatably provided on the second base portion 52A along the roller center line RL. and bias them in the direction of drawing them together.

A tension spring is employed when the first tension roller 51 and the second tension roller 52 are used in a manner in which they are in contact with the outer circumferential surface of the toothed belt 4, as shown in FIG.

Note that a compression spring may be used as the spring 54. The compression spring is attached between the first base shaft portion 51A and the second base shaft portion 52A in a state where it is compressed in a direction in which it becomes shorter than its natural length (a state in which a self-elastic recovery force acts in the direction of extension), and the compression spring is attached between the first base shaft portion 51A and the second base shaft portion 52A. It is used when urging the portion 51A and the second base portion 52A in a direction to separate them from each other along the roller center line RL. Specifically, in the compression spring, a first tension roller 51 and a second tension roller 52 are arranged on the inner peripheral side of the toothed belt 4, and the first tension roller 51 and the second tension roller 52 are arranged on the inner peripheral side of the toothed belt 4. This is adopted when the device is used in a manner in which it contacts the inner circumferential surface of the device.

If a tension spring is used as the spring 54 as in this embodiment, the biasing action of one spring 54 (tension spring) will cause the two tension rollers (first tension roller 51 and second tension roller 52) to , so that both sides (tension side and slack side) of the toothed belt 4 are sandwiched. Therefore, the spring 54 is a compression spring, and two tension rollers (first tension roller 51 and second tension roller 52) are provided so as to contact the inner peripheral surface of the toothed belt 4 (one The contact angle of the toothed belt 4 (the center of the arc where the belt and pulley are in contact) is By increasing the angle), it is possible to suppress tooth skipping of the toothed belt 4.

The spring 54 is preferably a coil spring so that predetermined spring characteristics can be repeatedly obtained for each belt transmission mechanism 1, and a coil spring is also used in this embodiment.
The spring wire is preferably an oil-tempered wire for springs with a circular cross-section or the like in accordance with JIS G3560:1994, and this embodiment employs an oil-tempered wire for springs with a circular cross-section that conforms to the above standard.
The diameter of the spring wire, as well as the winding diameter and winding length (natural length) of the spring are designed and determined so that predetermined spring characteristics can be repeatedly obtained for each belt transmission mechanism 1 (especially for each level of belt tension). Ru.

In this embodiment, in order to make it easier to tension the spring 54 between the first base portion 51A and the second base portion 52A, both ends of the spring 54 (hereinafter referred to as “ Both ends of the spring end portions 541A and 541B are bent approximately 90 degrees in the same direction.

(First swing arm 56 and second swing arm 57)
The first swing arm 56 and the second swing arm 57 are mutually independent metal parts made of aluminum alloy casting (for example, ADC 12).
As shown in FIG. 3, the base end portion 562 of the first swing arm 56 is rotatably supported by the swing shaft 53 (via a sliding member 55 (bearing) to be described later).
Similarly, the base end portion 572 of the second swing arm 57 is also rotatably supported by the swing shaft 53 (via a sliding member 55 (bearing) to be described later), as shown in FIG.
As shown in FIG. 2, the first swing arm 56 and the second swing arm 57 have a substantially C-shaped overall shape when viewed from above when they are installed in the belt transmission mechanism 1 as the auto tensioner 5. It is formed like this.

(Tip portion 561 and tip portion 571)
As illustrated in FIG. A convex portion 561A is formed to protrude downward in a cylindrical shape (below the lower end surface of). A female threaded portion is formed in a hole in the tip portion 561, including the convex portion 561A, that penetrates in the vertical direction centering on the axis R2. Further, a spring end portion 541A of the spring 54 is inserted into the convex portion 561A from below and is locked to the outer peripheral portion of the upper end (base) of the convex portion 561A.
As a result, at the distal end portion 561 of the first swinging arm 56, the first base portion 51A (mainly the male thread portion) is fixed from above by the hinge, so that the spring end portion 541A is inserted into the first base portion through the convex portion 561A. It will be locked to the first base shaft portion 51A.

As illustrated in FIG. A convex portion 571A is formed to protrude upward in a cylindrical shape (from the upper end surface). A female threaded portion is formed in a hole in the tip portion 571, including the convex portion 571A, that penetrates in the vertical direction centering on the axis R3. Further, the spring end 541B of the spring 54 is inserted into the convex portion 571A from above and is locked to the outer peripheral portion of the lower end (base) of the convex portion 571A.
As a result, the second base portion 52A (mainly the male thread portion) is fixed from above at the tip portion 571 of the second swing arm 57, so that the spring end portion 541B is attached to the second base portion 52A through the convex portion 571A. It will be locked to the second base shaft portion 52A.

With the above configuration, the first base shaft portion 51A, on which the first tension roller 51 is rotatably supported, is immovably fixed (hinged) to the distal end portion 561 of the first swing arm 56.
Similarly, the second base shaft portion 52A, on which the second tension roller 52 is rotatably supported, is immovably fixed (hinged) to the distal end portion 571 of the second swing arm 57.
The spring end portion 541A is inserted into the first base portion 51A, and the spring end portion 541B is inserted through the second base portion 52A, so that the spring 54 is The first base shaft portion 51A and the second base shaft portion 52A are connected in such a manner that the locking positions are on the same plane in side view (not shifted in the vertical direction), and the spring ends 541A and 541B cannot fall off from each other. (See Figure 3).

(Proximal end portion 562 and proximal end portion 572)
The base end portion 562 of the first swing arm 56 has a flange shape extending upward, and is formed into a cylindrical shape when viewed from above. Specifically, as shown in FIG. 3, the upper end surface of the base end portion 562 is radially outward from the upper end of a cylindrical portion 551A extending in the vertical direction in the upper cylindrical sliding portion 551 of the sliding member 55, which will be described later. The lower end surface of the proximal end portion 562 contacts the upper end surface of the plate-like sliding portion 552 of the sliding member 55, which will be described later. ing.
Further, the base end portion 562 extends radially inward to a position where it can come into contact with the outer peripheral surface of the vertically extending cylindrical portion 551A of the upper cylindrical sliding portion 551. The diameter (inner diameter) of the radially inner end surface of the base end portion 562 is the same as or slightly larger than the diameter (outer diameter) of the outer peripheral surface of the cylindrical portion 551A of the upper cylindrical sliding portion 551 (see FIG. 3).

The base end portion 572 of the second swing arm 57 has a flange shape extending downward, and is formed into a cylindrical shape when viewed from above. Specifically, as shown in FIG. 3, the lower end surface of the base end portion 572 is radially outward from the lower end of a cylindrical portion 553A extending in the vertical direction in the lower cylindrical sliding portion 553 of the sliding member 55, which will be described later. The upper end surface of the base end portion 572 contacts the lower end surface of the plate-like sliding portion 552 of the sliding member 55, which will be described later. ing.
Furthermore, the base end portion 572 extends radially inward to a position where it can come into contact with the outer peripheral surface of the vertically extending cylindrical portion 553A of the lower cylindrical sliding portion 553. The diameter (inner diameter) of the radially inner end surface of the base end portion 572 is the same as or slightly larger than the diameter (outer diameter) of the outer peripheral surface of the cylindrical portion 553A of the lower cylindrical sliding portion 553 (see FIG. 3).

With the above configuration, the base end 562 of the first swing arm 56 and the base end 572 of the second swing arm 57 swing independently in the vertical direction via the sliding member 55 (bearing) described below. It is rotatably supported on a shaft 53.

(Sliding member 55 (bearing))
As shown in FIG. 3, the sliding member 55 has an upper cylindrical sliding part 551, a plate-like sliding part 552, and a lower cylindrical sliding part 553, which are formed separately. There is. The upper cylindrical sliding part 551 and the lower cylindrical sliding part 553 have the same configuration (shape, size).

The upper cylindrical sliding portion 551 has a cylindrical portion 551A that extends in the vertical direction, and a plate-shaped portion 551B that extends radially outward from the upper end of the cylindrical portion 551A.
The plate-shaped sliding portion 552 has a plate-shaped portion 552A formed in an annular plate shape, and a cylindrical portion 552B extending upward and downward on the radially inner side of the plate-shaped portion 552A. .
The lower cylindrical sliding portion 553 has a cylindrical portion 553A that extends in the vertical direction, and a plate-shaped portion 553B that extends radially outward from the lower end of the cylindrical portion 553A.

The sliding member 55 is fitted onto the body portion 531 of the swing shaft 53 . Specifically, the upper cylindrical sliding part 551, the base end 562, the plate-like sliding part 552, the base end 572, and the lower cylindrical sliding part 553 are fitted onto the body 531 of the swing shaft 53 in this order. The upper cylindrical sliding part 551, the plate-like sliding part 552, and the lower cylindrical sliding part 553 are arranged in the vertical direction between the flange part 532 of the swing shaft 53 and the housing of the second arm 11. It is fixed in a pinched manner.

The sliding member 55 has a cylindrical portion 551A of the upper cylindrical sliding portion 551 and a cylindrical portion 552B of the plate-like sliding portion 552 on the inner circumferential surface of the base end portion 562 with respect to the first swing arm 56. The plate-like portion 551B of the upper cylindrical sliding portion 551 is in surface contact with the upper end surface of the proximal end portion 562, and the upper end surface of the plate-like portion 552A of the plate-like sliding portion 552 is in surface contact with the proximal end portion 551B. By coming into surface contact with the lower end surface of 562, it functions as a sliding bearing that slides on the first swing arm 56.

Similarly, the sliding member 55 has a cylindrical portion 553A of the lower cylindrical sliding portion 553 and a cylindrical portion 552B of the plate-like sliding portion 552 with respect to the second swing arm 57. The plate-shaped portion 553B of the lower cylindrical sliding portion 553 is in surface contact with the inner peripheral surface, and the lower end surface of the plate-shaped portion 552A of the plate-shaped sliding portion 552 is in surface contact with the lower end surface of the base end portion 572. By coming into surface contact with the upper end surface of the base end portion 572, it functions as a sliding bearing that slides on the second swing arm 57.

With the above configuration, the first swing arm 56 and the second swing arm 57 are independently rotatably supported by the swing shaft 53 via the sliding member 55 (bearing).

The sliding member 55 (bearing) of this embodiment is a hard thermal bearing with a Rockwell R scale (based on JIS K7202-2:2001) of 80 to 130 from the viewpoint of low friction sliding properties and wear resistance. A plastic resin (for example, polyacetal resin) was formed by injection molding.

(Operation of auto tensioner 5: tension side of toothed belt 4)
(motion)
In the belt transmission mechanism 1 for driving the robot arm,
i. When the drive pulley 2 is stopped, the two tension rollers are aligned in such a manner that the roller center line RL and the pulley center line PL are perpendicular to each other when viewed in a direction parallel to the drive shaft 21 (hereinafter viewed from above). (the first tension roller 51 and the second tension roller 52) and the outer peripheral surface of the toothed belt 4 are in contact with each other and are balanced (see FIG. 2).

ii. When switching forward/reverse (starting/stopping forward/reverse) (when drive pulley 2 rotates in the direction of arrow Z in Figure 5)
First, the tension of the toothed belt 4 increases on the tension side of the toothed belt 4, and the first tension roller 51, which is one tension roller located on the tension side of the toothed belt 4, increases the tension of the toothed belt 4. When pushed by the toothed belt 4 and displaced in the tension direction of the toothed belt 4, in this configuration, the first swing arm 56 and the second swing arm 57 are respectively rotatable around the swing shaft 53. In addition, the two tension rollers (first tension roller 51 and second tension roller 52) connected (energized) by a spring 54 between the first base shaft portion 51A and the second base shaft portion 52A are oscillated. Since it is configured to be able to swing freely in a plane around the moving shaft 53 (center axis R), as the tension of the toothed belt 4 increases, the first tension roller 51 is pushed by the toothed belt 4 and When viewed from above, the first The direction of the arrow (1) about the swing axis 53 is on a trajectory with a swing radius r1 between the rotation center 51C of the tension roller 51 and the center point of swing (center axis R) of the swing shaft 53. The first swing arm 56 starts rotating in the direction of the arrow X and rotates around the swing shaft 53 in the direction of the arrow X while resisting the biasing force of the spring 54. By swinging in the direction 1), the belt is quickly displaced to the equilibrium position, that is, the belt position where the toothed belt 4 reaches a tensioned state on the tension side (see FIG. 5).

(effect)
In this configuration, when viewed from above, the center point of the swing (center axis R) is a point on the pulley center line PL that is spaced toward the drive pulley 2 from the intersection of the roller center line RL and the pulley center line PL. Therefore, the tension of the toothed belt 4 increases on the tension side of the toothed belt 4, and the first tension roller 51 located on the tension side of the toothed belt 4 increases the tension of the toothed belt 4 due to the tension of the toothed belt 4. When the toothed belt 4 is displaced in the tension direction by being pushed by the toothed belt 4, the first swing arm 56 and the second swing arm 57 are respectively rotatable around the swing shaft 53, and are connected to the first base portion 51A. Two tension rollers (a first tension roller 51 and a second tension roller 52) connected (energized) with a second base shaft portion 52A by a spring 54 are configured to be able to swing freely around a swing shaft 53. Therefore, while resisting the biasing force of the spring 54, the first tension roller 51 connects (biases) the first base shaft portion 51A and the second base shaft portion 52A with the spring 54. For each tension roller (first tension roller 51 and second tension roller 52), the swing radius r1 of the first tension roller 51 and the swing radius r2 of the second tension roller 52 (the rotation center 52C of the second tension roller 52 and the swing radius The tension direction of the toothed belt 4 (in the direction of arrows (1) and (2) in FIG. 5) is on an orbit whose swing radius is the center point of swing of the moving shaft 53 (distance between the swing center point (center axis R)). By swinging around the swing shaft 53, the first tension roller 51 can be quickly displaced to the equilibrium position.

Therefore, the two tension rollers (the first tension roller 51 and the second tension roller 52) cannot swing around the swing shaft 53 (a structure in which only the urging force of the spring acts on the two tension rollers). Compared to a configuration in which the two tension rollers can only be displaced in a direction perpendicular to the pulley center line PL when viewed from above (for example, the configuration shown in FIG. 1 of Patent Document 1), the tension side of the toothed belt 4 is The first tension roller 51 is rotated in the direction of arrow X around the swing shaft 53 while suppressing damping by the spring 54 (displacement in the direction against the biasing force of the spring 54) through the first swing arm 56. By swinging around the swing shaft 53, the first tension roller 51 can be quickly displaced to the balanced position, and as a result, the responsiveness (operating speed) of the first tension roller 51 on the tension side of the toothed belt 4 is improved due to forward and reverse rotation. , it is possible to suppress excessive tension in the toothed belt 4 (tension fluctuations can be suppressed to a low level).

(Operation of auto tensioner 5: Loose side of toothed belt 4)
(action, action)
iii. Next, on the slack side of the toothed belt 4, the tension of the toothed belt 4 decreases, causing the toothed belt 4 to become slack, but the above operation on the tension side of the toothed belt 4 In (ii), the first tension roller 51 on the tension side resists the biasing force of the spring 54 while connecting (biasing) the first base shaft portion 51A and the second base shaft portion 52A with the spring 54. In addition, for each of the two tension rollers (the first tension roller 51 and the second tension roller 52), a trajectory whose swing radius is the swing radius r1 of the first tension roller 51 and the swing radius r2 of the second tension roller 52, respectively. In response to the above movement being swung in the direction of arrow (1) about the swiveling shaft 53, the other second tension roller 52 on the loosened side of the toothed belt 4 automatically moves to loosen the toothed belt 4. centering on the swinging shaft 53 via the second swinging arm 57 which is rotated in the direction of the arrow X around the swinging shaft 53 while being biased by the spring 54 in the direction in which the By swinging to , it is quickly displaced in the direction of arrow (2) (see FIG. 5).

Therefore, even when the toothed belt 4 is slack, the responsiveness (operating speed) of the second tension roller 52 is improved, and the second tension roller 52 remains in contact with the outer peripheral surface of the toothed belt 4. By being able to maintain the tension of the toothed belt 4, the tension of the toothed belt 4 can be automatically maintained at an appropriate level without causing the toothed belt 4 to loosen.

iv. In this configuration, the spring 54 is stretched between the first base shaft portion 51A and the second base shaft portion 52A of the two tension rollers (the first tension roller 51 and the second tension roller 52).
Therefore, even if the two tension rollers (first tension roller 51 and second tension roller 52) are configured to be able to swing freely around the swing shaft 53 (along a plane perpendicular to the swing shaft 53), , a configuration in which the spring 54 is not tensioned between the base shafts of the two tension rollers [for example, the spring 54 is not stretched between the members connecting the base shafts of the two tension rollers and the swing shaft (two arms that are independent of each other)] When viewed in a direction parallel to the drive shaft 21, the center point of the swing (center axis R: toothed belt) The distance between the "fulcrum" on the slack side of the toothed belt 4) and the point where the biasing force of the spring 54 is applied on the slack side of the toothed belt 4 (that is, the "point of force" on the slack side of the toothed belt 4) is long. . Therefore, on the slack side of the toothed belt 4, a larger force is applied at the point where the second tension roller 52 and the toothed belt 4 on the slack side contact each other (that is, the "point of action" on the slack side of the toothed belt 4). Therefore, the responsiveness (operating speed) of the second tension roller 52 is further improved on the slack side of the toothed belt 4.

v. In the configuration of Patent Document 2, the biasing action of a spring or the like does not work between the two tension rollers in the first place. Therefore, it is not possible to adjust the tension drop that occurs at the beginning of running.

(When the drive pulley 2 rotates in the direction opposite to the arrow Z direction in Fig. 5)
Next, when the drive pulley 2 is rotationally driven in the direction opposite to the arrow Z direction in FIG. In the case where the toothed belt 4 is rotationally driven in the Z direction), the second tension roller 52 is first pushed by the toothed belt 4 on the tension side of the toothed belt 4 and is displaced in the tension direction of the toothed belt 4. At this time, the second swing arm 57 is rotated around the swing shaft 53 in the direction opposite to the arrow X direction while resisting the biasing force of the spring 54. As a result, the first tension roller 51 is quickly displaced from the position shown in FIG. 5 to the balanced position in the direction opposite to the direction of arrow (2) in FIG. The first swing arm 56 rotates about the swing shaft 53 in the direction opposite to the direction of the arrow By swinging around the shaft 53, it is quickly displaced from the position shown in FIG. 5 in the direction opposite to the direction of arrow (1) in FIG.
As a result, the responsiveness (operating speed) of the second tension roller 52 is improved on the tension side of the toothed belt 4, and excessive tension in the toothed belt 4 can be suppressed (tension fluctuations can be kept low). In addition, the responsiveness (operating speed) of the first tension roller 51 is improved on the slack side of the toothed belt 4, and the first tension roller 51 is brought into contact with the outer peripheral surface of the toothed belt 4. By maintaining the same state, the tension of the toothed belt 4 can be automatically maintained at an appropriate level without loosening the toothed belt 4.

As described above, according to the present configuration, in the belt transmission mechanism 1 for driving a robot arm, regardless of whether the drive pulley 2 rotates in the forward or reverse direction, the driving force at the time of forward/reverse switching (start/stop of forward/reverse) is It is possible to ensure a high level of responsiveness (that is, to sufficiently suppress the rotation angle difference between the drive pulley 2 and the driven pulley 3 when switching between forward and reverse directions), increasing the speed of operations involving forward and reverse rotation. synchronous transmission [maintaining the tension of the toothed belt 4 automatically and appropriately (to the extent that the toothed belt 4 does not loosen)] can be taken as a thing.

Further, the two tension rollers (the first tension roller 51 and the second tension roller 52) are provided on the drive pulley 2 side, or on the pulley side with a smaller diameter among the drive pulley 2 and the driven pulley 3.
In order to ensure the rotational torque of the driven pulley 3 at a predetermined level, the robot arm driving belt transmission mechanism 1 is used when the diameter of the driving pulley 2 is smaller than the diameter of the driven pulley 3 (when functioning as a so-called deceleration mechanism). Generally, the diameter of the driving pulley 2 and the driven pulley 3 may be the same. For example, in a belt transmission mechanism 1 in which the distance between the drive pulley 2 and the driven pulley 3 is narrow and the reduction ratio (ratio of pulley diameters) is large, the contact angle of the toothed belt 4 on the drive pulley 2 on the small diameter side is If the toothed belt 4 becomes smaller and the toothed belt 4 has a large amount of slack, there is a concern that tooth skipping of the toothed belt 4 will easily occur. or by suppressing the contact angle of the toothed belt 4 from becoming small on the pulley on the small diameter side (regardless of whether it is driven or driven), it is possible to make the tooth skipping of the toothed belt 4 less likely to occur. can.

Furthermore, if the diameter of the driving pulley 2 of the belt transmission mechanism 1 is smaller than the diameter of the driven pulley 3 (in other words, when the belt transmission mechanism 1 is a reduction mechanism), the diameter of the driving pulley 2 is the same as the diameter of the driven pulley 3. Compared to the diameter case, the two tension rollers swing about the swing shaft 53 during forward/reverse switching, resulting in a greater degree of displacement.
Therefore, according to this configuration, the two tension rollers (the first tension roller 51 and the second tension roller 52) cannot swing around the swing shaft 53 (only the urging force of the spring is applied to the two tension rollers). In comparison with a configuration in which the two tension rollers can only be displaced in a direction perpendicular to the pulley center line when viewed in a direction parallel to the drive shaft, the tension rollers on the tension side of the toothed belt 4 are By swinging the tension roller 51 around the swing shaft 53 while suppressing damping by the spring 54 (displacement in a direction that resists the biasing force of the spring 54), it is possible to further increase the effect of quickly displacing the tension roller 51. As a result, in the robot arm drive belt transmission mechanism 1, a higher level of responsiveness to driving during forward/reverse switching (start/stop of forward/reverse) can be ensured.

(Other embodiments)
In the above embodiment, the center axis R (the center point of the swing) of the swing shaft 53 is the roller center line RL connecting the rotation center 51C of the first tension roller 51 and the rotation center 52C of the second tension roller 52, and the pulley It is configured to extend in a direction parallel to the drive shaft 21 through a point on the pulley center line PL that is spaced away from the intersection with the center line PL toward the drive pulley 2 side.
However, the center axis R of the swing shaft 53 (the center point of swing) is the roller center line RL connecting the rotation center 51C of the first tension roller 51 and the rotation center 52C of the second tension roller 52, and the pulley center line PL. The configuration may be such that the line passes through a point on an extension of the pulley center line PL, which is spaced away from the intersection with the drive pulley 2 side.
Specifically, the drive shaft 21 may be arranged between two tension rollers (the first tension roller 51 and the second tension roller 52) of the auto tensioner 5 and the swing shaft 53.
Further, as shown in FIG. 10, the center axis R (center point of swing) of the swing shaft 53 is a roller center connecting the rotation center 51C of the first tension roller 51 and the rotation center 52C of the second tension roller 52. A point on the pulley center line PL that is spaced toward the drive pulley 2 from the intersection of the line RL and the pulley center line PL, passing through the center axis of the drive shaft 21 (rotation center 22 of the drive pulley 2), 21 (that is, the drive shaft 21 also serves as the swing shaft 53). In this case, the first swing arm 56 and the second swing arm 57 are rotatably supported by the existing drive shaft 21 via the sliding member 55 (bearing: not shown in FIG. 10). , it is possible to simplify the belt transmission mechanism 1 (reducing parts and improving ease of assembly).

Further, in the above embodiment, the belt transmission mechanism according to the present invention has been described as a robot arm driving belt transmission mechanism that drives a robot arm, but the present invention is not limited to this. For example, the belt transmission mechanism according to the present invention can be used in injection molding machines (belt transmission mechanism parts that are electrically driven by independent motors in each operating section such as injection, metering, mold opening/closing, etc.) and other general industrial applications. It can be applied to belt transmission mechanisms of equipment, devices, etc.

In the belt transmission mechanism of the present invention, even if the speed of operation involving forward and reverse rotation increases, positioning accuracy can be repeatedly ensured [i.e., response to drive during forward and reverse switching (starting/stopping of forward and reverse)]. Synchronous transmission It is necessary to ensure that the tension of the belt is maintained automatically and appropriately (to the extent that the belt does not loosen) (including adjusting the tension drop that occurs at the beginning of running).

Therefore, in this example, belt transmission mechanisms according to Examples 1 to 3 and Comparative Examples 1 to 4 (hereinafter referred to as each specimen) were fabricated, and a response test [during forward/reverse switching (forward/reverse start/stop) ) and conducted comparative verification.
The present invention will be explained in more detail below based on Examples, but the present invention is not limited to these Examples.

[Belt transmission mechanism]
(Common for each specimen)
(Toothed belt: Figure 6)
- Shape of tooth: The tooth shape was an H tooth shape (approximately semi-circular cross section) belonging to straight teeth.
・Number of teeth: 200
・Tooth pitch: 3mm
・Belt length: 600mm
・Belt width: 10mm

[Materials used]
(core wire)
- Structure: Twisted cords A1 to A3 having the structure shown in Table 2 were prepared as core wires to be used for each toothed belt of each specimen.
・A1 core wire (twisted cord) was created using the following procedure.
Filaments (9 micron diameter) of glass fibers (E glass fibers) with the name ECG-150 described in JIS R 3413 (2012) were bundled and aligned to form three strands. These three strands were immersed in RFL liquid (18-23°C) having the composition shown in Table 3 by passing it through for 3 seconds, and then heated and dried at 200-280°C for 3 minutes to form an adhesive layer uniformly on the surface. was formed. After this adhesive treatment, the three strands were pre-twisted at a twist rate of 12 twists/10 cm to prepare a single-twisted cord having a diameter of about 0.35 mm without any final twist.
The core wire (twisted cord) of A2 was made in the same manner as A1 except that the glass fiber was changed to KCG150.
The A3 core wire (twisted cord) was created using the same procedure as the A1 and A2 core wires, except that the strand used was a single strand made by bundling and aligning carbon fiber filaments (3K). A twisted cord with a diameter of 0.53 mm was made with one twist.

(Modulus of elasticity of core wire)
Here, a method for measuring the elastic modulus (tensile modulus) of the core wire (longitudinal direction) shown in Table 2 will be explained.
Attach chucks to the lower fixed part and upper load cell connection part of the Autograph ("AGS-J10kN" manufactured by Shimadzu Corporation), and grip both ends of the core wire with the chucks.
Next, in the stress-strain curve measured when the cord was pulled at a speed of 250 mm/min until it was cut, the slope of the straight line in a relatively linear region (100 to 200 N) was calculated as the tensile elasticity of the cord. Calculated as a percentage.

(tooth cloth)
- The composition of the fiber fabric used for the tooth cloth of each specimen was one of the following types.
The composition is 66 nylon for the weft and 66 nylon for the warp. The yarn structure is woolly textured yarn with a weft of 44 dtex and a warp of 44 dtex. The weave structure is a twill weave. Then, the tooth cloth having the above configuration was subjected to RFL treatment using the RFL treatment liquid shown in Table 3. Thereafter, the same rubber composition as the unvulcanized rubber sheet shown in Table 4 was bonded with rubber glue dissolved in toluene, and further, rubber composition sheets with the composition shown in Table 4 were laminated and coated. went.

(Rubber composition)
- A rubber composition having the composition shown in Table 4 [rubber component: chloroprene rubber (CR)] was kneaded using a Banbury mixer, and the kneaded rubber was passed through a calender roll to form a rolled rubber sheet of a predetermined thickness. An unvulcanized rubber sheet for forming the back and teeth of a toothed belt was produced.
- The hardness of the vulcanized rubber sheet obtained by press-curing the prepared rubber composition (unvulcanized rubber sheet) at 165 ° C for 30 minutes is based on JIS K 6253 (2012), The hardness was approximately 81 as measured using a type A durometer at an ambient temperature of 23°C (23±2°C).
・The ingredients marked with * in Table 4 are as follows.

※１ デンカ社製「ＰＭ－４０」
※２ 大内新興化学工業社製「ノクラックＭＢ」
※３ 大内新興化学工業社製「Ｎ－シクロヘキシル－２ベンゾチアゾールスルフェンアミド」
※４ 東海カーボン社製「シースト３」
※５ 正同化学工業社製「酸化亜鉛３種」

*1 “PM-40” manufactured by Denka
*2 “Nocrack MB” manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
*3 “N-cyclohexyl-2benzothiazole sulfenamide” manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
*4 “Seest 3” manufactured by Tokai Carbon Co., Ltd.
*5 “3 types of zinc oxide” manufactured by Seido Kagaku Kogyo Co., Ltd.

[Manufacture of toothed belt]
・Using the core wire (adhesive treated product), tooth cloth (adhesive treated product), and rubber composition (unvulcanized rubber sheet) explained in the materials used above, the normal method described in the above embodiment mode can be produced. Each toothed belt for each specimen was manufactured using the press-in method. In addition, vulcanization was performed at 161° C. for 25 minutes. In addition, in order to configure the back part to a predetermined thickness, the back side of the belt sleeve obtained by vulcanization was polished to a certain thickness, and then cut to a certain width, and each toothed belt of each specimen was Obtained.
・Because the toothed belt was manufactured using the normal press-fitting method, the back and teeth are made of the same rubber composition. Therefore, in each toothed belt, the hardness of the rubber composition constituting the back portion and the hardness of the rubber composition constituting the toothed portion are approximately the same.

(Pulley layout)
・The belt transmission mechanisms of Examples 1 to 3 (Fig. 2) and Comparative Examples 1 to 4 (Comparative Examples 1 to 3 are not shown, and Comparative Example 4 is shown in Fig. 9) each have a driving pulley and a driven pulley. is a pulley with straight teeth, has a two-axis layout with fixed shafts, and is equipped with a shaft load detector (load cell) that can be connected to the rotating shaft of one (drive pulley).
・Number of teeth of drive pulley/pulley diameter (assuming core line): 21 teeth/20.054mm
・Number of teeth of driven pulley/Pulley diameter (assuming core line): 84 teeth/80.214mm
・Reduction ratio: 4 (The pitch diameter of the driven pulley is 4 times larger than that of the driving pulley)
- Belt installation tension: The level of belt installation tension required was approximately 5N/mm width (5N per 1mm belt width).
In this specification, the belt tension measured in a stationary state immediately before actual driving [after dry running (break-in driving)] is treated as "belt attachment tension."
The belt attachment tension was calculated from the shaft load detected by a shaft load detector (load cell) connected to one (drive pulley) rotating shaft.
- The distance between the axes was 220 mm (standard value).

(auto tensioner)
(Examples 1 to 3)
- The autotensioner described in the above embodiment (see FIGS. 3 and 4) was attached to the belt transmission mechanism in the manner shown in FIG. In other words, the autotensioners of Examples 1 to 3 all have the same configuration, and the two tension rollers have a biasing action of a spring (tension spring) tensioned between the base shaft portions of the two tension rollers. This is an auto tensioner configured so that both the oscillating motion and the oscillating motion around the oscillating shaft work together.

(Comparative example 1)
- The belt transmission mechanism has a configuration without an auto-tensioner (that is, a configuration with only a driving pulley, a driven pulley, and a toothed belt) (not shown).

(Comparative example 2: equivalent to the configuration of Patent Document 1)
・Based on the auto tensioner of Example 1 (see Figures 3 and 4), only the biasing action of the spring (tension spring) acts on the two tension rollers, and the oscillation around the oscillation axis is performed. An autotensioner (not shown) configured to be inoperative was provided to the belt drive mechanism in the layout shown in FIG.

(Comparative example 3: equivalent to the configuration of Patent Document 2)
- Based on the auto tensioner of Example 1 (see Figures 3 and 4), the spring biasing action does not work on the two tension rollers, and only the swinging action around the swinging axis works. The configured autotensioner (not shown) was attached to the belt transmission mechanism in the manner (layout) shown in FIG.

(Comparative example 4)
・As shown in Figure 9, based on the autotensioner of Example 1 (see Figures 3 and 4), the biasing action of a spring (tension spring) and the pivoting axis are applied to two tension rollers. However, the spring is not stretched between the base shafts of the two tension rollers, and the springs are not stretched between the base shafts of the two tension rollers and the rocking shaft. An autotensioner configured to be stretched between each member (between two mutually independent arm members) was provided to the belt transmission mechanism in the same manner (layout) as in FIG. 2.

[Evaluation of belt transmission mechanism: items, methods, criteria]
For each specimen (Examples 1 to 3, Comparative Examples 1 to 4), in order to determine whether or not a belt transmission mechanism capable of solving the problems of the present application was obtained, the necessity of aging [automatic reduction of tension at the beginning of belt running] was determined. Adjustment (correction) possible] and responsiveness (responsiveness to driving during forward/reverse switching) were verified.

[Need for aging]
(Method, criteria)
To ensure the specified belt installation tension (approximately 5 N/mm width) without aging [belt retensioning (tension adjustment work) by adjusting the center distance after dry running (breaking-in)] If this is possible, it is evaluated that the decrease in tension at the initial stage of belt running can be automatically adjusted (corrected), and a rating of A is given.
In order to secure the specified belt installation tension (approximately 5 N/mm width), aging [belt retensioning (tension adjustment work) by adjusting the center distance, etc. after dry running (breaking-in)] is necessary. In this case, it was evaluated that it was not possible to automatically adjust (correct) the decrease in tension at the beginning of belt running, and a rating of b was given, and the subsequent test (responsiveness test) was postponed.
From the viewpoint of suitability for actual use in this application (need for aging), the belt transmission mechanism that was rated a was set to an acceptable level.

[responsiveness]
(exam name)
Responsiveness test (testing machine)
A responsiveness evaluation tester was used for the test (see Figure 7).
The test machine runs a toothed belt wrapped between pulleys on two axes in a test pattern (cycle pattern) with frequent forward and reverse rotations, and a pair of rotary encoders (rotation) attached to each axis. The vehicle is configured to be able to detect time-series changes in the rotation angle difference (rotation angle of the drive shaft - rotation angle of the driven shaft) during running using the rotation pulse signal output by the angle detector).
The pulley layout is the same as the belt transmission mechanism described above (FIG. 2). That is, the pulley layout of the test machine included a driving pulley and a driven pulley, and the distance between the axes was fixed at 220 mm.
In addition, assuming this application (for driving a robot arm), a flywheel was attached to the driven side so that a predetermined load torque could be applied.
In addition, assuming this application (for driving a robot arm), a pair of rotary encoders, both of which have excellent resolution of the rotation angle, are used to detect the rotation angle of the drive pulley and the rotation angle of the driven pulley with high precision. An encoder (R-1L manufactured by CANON) with an angular resolution of 0.0044° was used.

(Test method)
At room temperature, a toothed belt was wound around the pulleys (fixed center distance) with a predetermined belt mounting tension (approximately 5 N/mm width) under the test conditions shown in Table 5 (only the number of rotations of the drive pulley was variable). The vehicle was run in a test pattern (cycle pattern) shown in FIG. 8 in which frequent forward and reverse rotations were repeated for 250 cycles. From the obtained graph (not shown) of time-series changes in the rotation angle difference, the level of the rotation angle difference (maximum absolute value) is determined as the test result for each variable number of rotations of the drive pulley (1, 2, 5 rps). I read it as.
In addition, the rotation angle difference causes overshoot and undershoot when switching between forward and reverse [forward/reverse start (acceleration)/stop (deceleration)] when viewed in time series, so its absolute value is: It is maximum when switching between forward and reverse (frequency: 4 times per cycle). Table 6 shows the acceleration/deceleration speed at the time of forward/reverse switching, which corresponds to each rotational speed of the drive pulley.

(Judgment criteria)
In order to judge the responsiveness (responsiveness to driving during forward/reverse switching), which is most important for a belt transmission mechanism in this application, the rotation angle difference between the driving pulley and the driven pulley during forward/reverse switching is used as an index (the absolute value is (The smaller the value, the higher the responsiveness, ensuring repeatable positioning accuracy, and ensuring synchronous transmission), and the rotation angle difference (absolute value) for each rotation speed of the drive pulley is always within 0.2°. A case where the angle was greater than 0.2° was judged as a, and a case where it exceeded 0.2° even once was judged as b.
From the viewpoint of suitability (responsiveness) for actual use in this application, the belt transmission mechanism that was judged as a was determined to be an acceptable level.

[Comprehensive judgment]
The criteria for comprehensive judgment (ranking) as a belt transmission mechanism capable of solving this problem were as follows based on the judgment results for the above two test items (need for aging and responsiveness).
Rank A: If all of the above evaluations (need for aging, responsiveness) were evaluated as A, the product was ranked as fully satisfactory as a solution to this problem (passed).
Rank B: If even one of the above evaluations (need for aging, responsiveness) was judged as b, it was ranked as insufficient as a solution to the problem (fail).

[inspection result]
The verification results are shown in Table 6.

(Comparison where the auto tensioner configuration was changed: Example 1, Comparative Examples 1 to 4)
The auto tensioner of Embodiment 1 (so that the biasing action of the spring tensioned between the base shafts of the two tension rollers and the swinging action about the swinging shaft work together on the two tension rollers) The configuration of the auto-tensioner (including whether or not an auto-tensioner is installed) was changed and compared. When the belt transmission mechanism has an auto-tensioner that applies a spring biasing action to the two tension rollers (Example 1, Comparative Examples 2 and 4), aging is not necessary (judgment a), and the two tension rollers In Example 1, where the roller not only has a spring biasing action, but also a rocking action around the rocking axis, the responsiveness was also rated a (rank A in the overall rating), but the two In Comparative Example 2, only the biasing action of the spring acts on the tension roller, and the oscillating action around the swing axis does not work, and in addition to the urging action of the spring on the two tension rollers. Comparative example 4, which also works for rocking motion around the rocking axis, but in which the spring is not stretched between the respective base shafts of the two tension rollers, has a response rating of B (ranked B in the overall rating). became.
On the other hand, in Comparative Example 1 in which the belt transmission mechanism does not have an auto-tensioner in the belt transmission mechanism, and the two tension rollers, the biasing action of the spring does not work, and only the oscillating action around the oscillating axis works. Comparative Example 3, which had an auto-tensioner in the belt transmission mechanism, required aging (b rating) and was ranked B in the overall rating.

(Comparison of toothed belts with different core types: Examples 1 to 3)
Based on the toothed belt (E glass fiber: A1) of Example 1, the fiber material (filament material) constituting the core of the toothed belt was changed and compared. Example 2 uses a cord made of high-strength glass fiber (K glass fiber: A2), which has a higher elastic modulus than Example 1, and uses a cord made of carbon fiber (A3), which has an even higher elastic modulus than Example 2. In Example 3, the higher the modulus of elasticity and the lower the elongation of the core wire (i.e., the belt), the smaller the level of the rotation angle difference (maximum absolute value) for each rotation speed of the drive pulley, and the response. There was a tendency for the performance (responsiveness to driving during forward/reverse switching) to increase, and under these conditions (Examples 1 to 3), it was ranked A.

(obtained effect)
From the above verification results, when the belt transmission mechanism of Examples 1 to 3 is applied to a belt transmission mechanism that can be rotated in forward and reverse directions, such as for driving a robot arm, two tension rollers can be Equipped with an auto-tensioner configured to work together with the biasing action of a spring (tension spring) tensioned between each base shaft of the roller and the swinging action around the swinging shaft, aging [ After dry running (breaking-in), you can secure the specified belt installation tension (approximately 5 N/mm width) without having to retension the belt (tension adjustment work) by adjusting the distance between the shafts, etc. It is possible to automatically adjust (correct) the drop in tension at the beginning of running, and the rotation angle difference (absolute value), which is an index of responsiveness to drive when switching between forward and reverse, is within the permissible range (within 0.2°). This shows that even if the speed of motion involving forward and reverse rotation increases, positioning accuracy can be repeatedly ensured and synchronous transmission can be ensured.

1 Belt transmission mechanism 11 Second arm 2 Drive pulley 21 Drive shaft 22 Rotation center 3 Driven pulley 31 Driven shaft 32 Rotation center 4 Toothed belt 5 Auto tensioner 51 First tension roller 51A First base shaft portion 52 Second tension roller 52A 2 base shaft portion 53 Swing shaft 54 Spring 55 Sliding member 56 First swing arm 561 Tip portion 562 Base end portion 57 Second swing arm 571 Tip portion 572 Base end R Center axis PL Pulley center line RL Roller center line

Claims (1)

a drive pulley fixed to a drive shaft that is rotatably driven in forward and reverse directions by a drive source;
a rotatably supported driven pulley;
a toothed belt wound between the driving pulley and the driven pulley;
Two tension rollers are provided rotatably around their respective base shafts at positions on both sides of the pulley center line connecting the rotation center of the drive pulley and the rotation center of the driven pulley, and are in contact with the toothed belt. an autotensioner that automatically maintains the tension of the toothed belt at an appropriate level through the belt transmission mechanism,
The auto tensioner is
The drive pulley and the having a swing shaft that is independent of the driven pulley and extends in a direction parallel to the drive shaft;
a spring that is stretched between each of the base shaft portions of the two tension rollers and biases the two tension rollers in a direction toward each other or a direction in which they are spaced apart from each other along the roller center line, and
A belt transmission mechanism, wherein the two tension rollers are configured to be able to swing freely around the swing shaft.

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