JP7466074B1 - Toothed pulley and transmission system - Google Patents

Abstract

A toothed pulley having pulley grooves that mesh with belt teeth of a toothed belt provided at a constant pitch along its outer circumference, the toothed belt being a toothed belt that meshes with a pulley of type S5M defined in JIS B 1857-2 (2015), the toothed pulley having an upper dimension and a lower dimension as a width dimension of the pulley groove in a cross section perpendicular to an axial direction of the pulley groove, the lower dimension being 2.20 mm or less, and a ratio of the upper dimension to the lower dimension being 1.40 or more.

Description

The present invention relates to a toothed pulley and a transmission system.
This application claims priority based on Japanese Application No. 2023-038561 filed on March 13, 2023, and incorporates by reference all of the contents of the above-mentioned Japanese application.

2. Description of the Related Art Transmission systems including toothed belts and toothed pulleys are used in belt transmission systems requiring synchronous transmission in, for example, precision machines such as cameras, computers, and copiers, and general industrial machines such as robots.
These transmission systems are required to have good positioning properties.

In order to improve the positioning accuracy of the transmission system, reducing the backlash can be considered.
Patent Document 1 describes a toothed belt drive device consisting of a toothed belt and a pulley, in which when the belt and pulley are statically engaged to bring the belt teeth into contact with the pulley groove wall, there is no gap between the belt tooth base and the pulley groove wall, and between the belt tooth tip and the pulley groove wall, and a method for designing a toothed pulley, characterized in that when designing the pulley groove, the dimensions of the pulley groove are designed taking into account the molding shrinkage rate of the toothed belt.

JP 2004-308669 A

The invention described in Patent Document 1 is designed to have extremely small backlash, and is therefore expected to improve positioning accuracy.
However, the invention described in Patent Document 1 reduces backlash over the entire meshing portion between the belt and the pulley. Therefore, in a drive device designed by the method described in Patent Document 1, early wear of the belt teeth may occur, or stress may concentrate at the base of the belt teeth, causing damage to the belt teeth. Therefore, the invention described in Patent Document 1 has a problem of significantly reducing the durability of the belt.

The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a toothed pulley that constitutes a transmission system with excellent positioning accuracy and is less likely to reduce the durability of the belt, and a transmission system having such a toothed pulley.

(1) The toothed pulley of the present invention is
A toothed pulley in which pulley grooves that mesh with the belt teeth of a toothed belt are provided at a constant pitch along the outer periphery,
The toothed belt is a toothed belt that meshes with a pulley of type S5M as specified in JIS B 1857-2 (2015),
The toothed pulley has a width dimension of a pulley groove, which has an upper dimension and a lower dimension in a cross section perpendicular to an axial direction of the pulley groove,
the upper dimension is a distance between two intersection points where a perpendicular line to the center line, passing through a point 0.50 mm radially inward from an intersection point between the center line of the pulley groove and the tip circle of the toothed pulley, intersects with a contour line of the pulley groove,
the lower dimension is a distance between two intersection points where a perpendicular line to the center line, passing through a point 1.50 mm radially inward from an intersection point between the center line of the pulley groove and the tip circle of the toothed pulley, intersects with a contour line of the pulley groove,
The lower dimension is 2.20 mm or less,
A ratio of the upper dimension to the lower dimension is greater than or equal to 1.40.

The toothed pulley has a reduced width at the bottom of the pulley groove to reduce backlash at the bottom of the pulley groove in the meshed state, improving positioning accuracy. Furthermore, the toothed pulley has a large ratio of the top dimension to the bottom dimension of the toothed pulley, allowing the belt teeth and pulley groove to smoothly begin meshing with each other.
Therefore, the transmission system including the toothed pulley has excellent positioning accuracy, and the toothed belt is less likely to wear during meshing.

(2) Preferably, in the toothed pulley described in (1) above,
The groove bottom radius _rb of the pulley groove is equal to or greater than 0.40 mm and is equal to or less than 0.50 mm.
This toothed pulley has a groove bottom that is easily narrowed, and is therefore more suitable for improving the positioning accuracy when meshing with a toothed belt.

(3) A transmission system according to the present invention is a transmission system including a toothed belt and a toothed pulley,
The toothed belt is a toothed belt that meshes with a pulley of type S5M as specified in JIS B 1857-2 (2015),
The toothed pulley is the toothed pulley described in (1) or (2) above.
This transmission system has excellent positioning accuracy and the toothed belt is less prone to wear.

According to the present invention, it is possible to provide a transmission system that has excellent positioning accuracy while not compromising the durability of the toothed belt. It is also possible to provide a toothed pulley that constitutes this transmission system.

FIG. 1 is a side view showing a schematic diagram of a transmission system. FIG. 2 is a perspective view showing an example of a toothed belt included in a transmission system. FIG. 3 is a diagram showing one pulley groove of a toothed pulley. Figure 4 is quoted from JIS B 1857-2 (2015). FIG. 5 is a diagram for explaining a method for evaluating lost motion in the examples and comparative examples. FIG. 6 is a diagram showing an example of the measurement result of lost motion. FIG. 7 is a diagram showing the evaluation results of lost motion. FIG. 8 is a diagram showing a method for evaluating durability (lifespan). FIG. 9 is a diagram showing the evaluation results of durability (lifespan).

Below, embodiments of the present invention are described with reference to the drawings. The present invention is not limited to these embodiments.

(Transmission System)
FIG. 1 is a side view that illustrates a schematic diagram of a transmission system 1 according to an embodiment of the present invention.
The transmission system 1 is suitable for use in applications requiring positioning precision, such as robots, etc. In addition to robots, the transmission system 1 is also suitable for use in precision machinery, such as cameras, computers, and copiers, precision conveying devices, such as banknote conveying devices, machine tools, and printing machines.

As shown in Fig. 1, the transmission system 1 includes a drive pulley 22, a driven pulley 24, and a toothed belt 10. The drive pulley 22 and the driven pulley 24 each have a plurality of pulley grooves 21 formed therein. The toothed belt 10 has a plurality of belt teeth 12 (see Fig. 2) that mesh with the pulley grooves 21, and is stretched across the drive pulley 22 and the driven pulley 24.

Both the drive pulley 22 and the driven pulley 24 have pulley grooves 21 that mesh with the belt teeth 12 of the toothed belt 10 and are evenly spaced along the outer circumference at a predetermined pitch. The pulley grooves 21 of the drive pulley 22 and the pulley grooves 21 of the driven pulley 24 have the same shape. Hereinafter, both the drive pulley 22 and the driven pulley 24 will be referred to simply as toothed pulley 20.

The transmission system 1 transmits power from a driving source to a driven side. In the transmission system 1, the belt running speed is, for example, 10 to 2000 m/min. In the transmission system 1, the transmission capacity is, for example, 0.01 to 50 kW.

(Toothed belt)
2 is a perspective view showing a part of a toothed belt 10 according to an embodiment of the present invention. The toothed belt 10 constitutes a transmission system 1.
The toothed belt 10 employed in this embodiment is a toothed belt that meshes with a pulley of type S5M as defined in JIS B 1857-2 (2015).
An example of such a toothed belt 10 is a toothed belt of type S5M defined in JIS B 1857-1 (2015).
The toothed belt 10 employed in the embodiment of the present invention may be a toothed belt that meshes with a pulley of type S5M as specified in JIS B 1857-2 (2015). All dimensional values of this toothed belt 10 do not necessarily have to match those of the toothed belt of type S5M as specified in JIS B 1857-1 (2015).

2 shows only a portion of the toothed belt 10. The toothed belt 10 is an endless intermeshing power transmission belt.
The belt length of the toothed belt 10 is, for example, not less than 150 mm and not more than 5000 mm.
The belt width of the toothed belt 10 is, for example, not less than 5 mm and not more than 200 mm.

The toothed belt 10 has a plurality of belt teeth 12 on its inner circumferential surface. As shown in Fig. 2, the toothed belt 10 includes a belt body 11, a core wire 13, and a reinforcing fabric 14. The belt teeth 12 of the toothed belt 10 shown in Fig. 2 are straight teeth.
In the embodiment of the present invention, the belt teeth 12 may be helical teeth whose tooth trace is inclined with respect to the belt width direction.

The belt body 11 of the toothed belt 10 has a band shape, a base 11a having a rectangular cross section perpendicular to the belt longitudinal direction, and a plurality of teeth 11b provided on the inner periphery of the base 11a. The teeth 11b are integrated with the base 11a. The teeth 11b are provided at equal intervals at predetermined intervals along the belt longitudinal direction.
In the toothed belt 10, the reinforcing fabric 14 is provided so as to cover the inner peripheral surface of the toothed portion 11b. In the toothed belt 10, the belt tooth 12 is composed of the toothed portion 11b and the reinforcing fabric 14.
Known materials may be used as the respective constituent materials of the belt body 11, the cords 13, and the reinforcing cloth 14. The cords 13 and the reinforcing cloth 14 are both optional constituent members.
The toothed belt 10 can be manufactured by a conventionally known method.

(Toothed pulley)
The toothed pulley 20 employed in the embodiment of the present invention is a toothed pulley that meshes with the above-mentioned toothed belt 10. In the toothed pulley 20, the pulley groove 21 has a specific shape in a side view.
Therefore, the transmission system 1 including the toothed pulley 20 has excellent positioning accuracy and the toothed belt 10 is less likely to wear.

The toothed pulley 20 is made of, for example, stainless steel.
The toothed pulley 20 has pulley grooves 21 that mesh with the belt teeth 12 of the toothed belt 10 and are provided at a predetermined pitch along the outer periphery.
The outer diameter of the toothed pulley 20 is, for example, not less than 15 mm and not more than 300 mm.
The toothed pulley 20 may be provided with a flange.

Fig. 3 is a diagram showing one of the pulley grooves 21 of the toothed pulley 20. Fig. 3 shows the shape of the pulley groove 21 in a side view.
In FIG. 3 , the dashed dotted line CL is the center line of the pulley groove 21 , and a point P is the intersection point between the center line CL of the pulley groove 21 and the tip circle TC of the toothed pulley 20 .
In FIG. 3 , point PU is a point 0.50 mm radially inward from point P, point PM is a point 1.00 mm radially inward from point P, and point PL is a point 1.50 mm radially inward from point P.

In FIG. 3 , WU, WM and WL are width dimensions of the pulley groove 21 .
The width dimension WU is the upper dimension of the pulley groove 21. When the intersections IU1 and IU2 of the perpendicular line to the center line CL passing through the point PU and the contour line 25 of the pulley groove 21 are defined as the intersection points IU1 and IU2, the upper dimension WU is the distance between the intersection points IU1 and IU2.
The width dimension WL is the bottom dimension of the pulley groove 21. This bottom dimension WL is the distance between the intersection points IL1 and IL2, where IL1 and IL2 are the intersection points between a perpendicular line to the center line CL passing through the point PL and the contour line 25 of the pulley groove 21.
The width dimension WM is the median dimension of the pulley groove 21. When the intersections IM1 and IM2 of the perpendicular line to the center line CL passing through the point PM and the contour line 25 of the pulley groove 21 are defined as the intersection points IM1 and IM2, the median dimension WM is the distance between the intersection points IM1 and IM2.

In the toothed pulley 20, the bottom dimension WL of the pulley groove 21 is 2.20 mm or less.
In this case, since the width of the bottom side of the pulley groove 21 of the toothed pulley 20 is narrow, there is little backlash at the bottom side of the pulley groove 21 when meshing with the toothed belt 10. Therefore, the transmission system 1 including the toothed pulley 20 can ensure excellent positioning accuracy.
On the other hand, if the lower dimension WL exceeds 2.20 mm, backlash becomes large at the groove bottom side of the pulley groove 21 of the toothed pulley 20 when meshing with the toothed belt, and the positioning accuracy of the transmission system 1 equipped with the toothed pulley 20 decreases.
The lower dimension WL is preferably equal to or greater than 2.00 mm.

In the pulley groove 21 of the toothed pulley 20, the ratio (WU/WL) of the upper dimension WU to the lower dimension WL is 1.40 or more.
In this case, the width dimension (upper dimension) on the tooth tip side of the pulley groove 21 of the toothed pulley 20 is not narrowed. Therefore, when the pulley groove 21 meshes with the belt teeth 12 of the toothed belt 10, stress concentration is unlikely to occur at the base of the belt teeth 12 at the start and end of meshing, and early wear of the belt teeth 12 can be avoided.
If the lower dimension WL is set to 2.20 mm or less and WU/WL is set to less than 1.40, the positioning accuracy can be ensured, but the belt teeth 12 will wear out early and the belt life of the toothed belt 10 will be shortened.
WU/WL is preferably equal to or less than 1.60, and more preferably equal to or less than 1.45.

The pulley groove 21 preferably has a groove bottom radius r _b of 0.40 mm or greater and 0.50 mm or less.
The groove bottom radius r _b of the toothed pulley 20 is one of the dimensions of the S-tooth groove defined in JIS B 1857-2 (2015) (see FIG. 4).
The groove bottom radius _{r_b} being in the above range is suitable for improving the positioning accuracy of the transmission system 1 including the pulley 21.
On the other hand, if the groove bottom radius r _b is less than 0.40 mm, the positioning accuracy may be insufficient, and if the groove bottom radius r _b exceeds 0.50 mm, the toothed belt 10 of the transmission system 1 is likely to wear out early, and the toothed belt 10 will have poor durability.

The pulley groove 21 preferably has a depth _Hg of 1.74 mm or more and 1.80 mm or less.
The depth _Hg of the toothed pulley 20 is one of the dimensions of the tooth space of an S-tooth type defined in JIS B 1857-2 (2015) (see FIG. 4).
The depth _Hg being within the above range is suitable for improving the positioning accuracy of the transmission system 1 and for ensuring the durability of the toothed belt 10 that engages with it.
On the other hand, if the depth _Hg is less than 1.74 mm, the positioning precision of the transmission system 1 becomes insufficient. If the depth _Hg is less than 1.74 mm, the toothed belt 10 included in the transmission system 1 is likely to wear out early, resulting in poor durability of the toothed belt 10. If the depth _Hg exceeds 1.80 mm, the belt teeth of the toothed belt 10 included in the transmission system 1 are likely to be damaged due to stress concentration at the belt tooth root portion, resulting in poor durability of the toothed belt 10.

A method for manufacturing the toothed pulley 20 will now be described.
The toothed pulley 20 can be manufactured by a conventionally known method. For example, the toothed pulley 20 can be manufactured by preparing a dedicated hob cutter according to the tooth groove shape of the toothed pulley, then subjecting a metal material to gear cutting using the hob cutter, and further performing drilling, external processing, flange attachment, and the like as necessary.

Hereinafter, the embodiments of the present invention will be described in more detail with reference to examples, but the embodiments of the present invention are not limited to the following examples.
Stainless steel toothed pulleys having different pulley groove shapes were produced for each of Example 1 and Comparative Examples 1 to 3. The specific pulley groove shapes are as shown in Table 1.

A driving pulley and a driven pulley were each produced in each of Example 1 and Comparative Examples 1 to 3. In this case, the shape of the pulley groove of the driving pulley and the shape of the pulley groove of the driven pulley were the same.
The manufactured drive pulley had a tooth tip radius of 12.8 mm, 16 teeth, and a width of 20 mm.
The produced driven pulley had a tooth tip radius of 38.2 mm, 48 teeth, and a width of 20 mm.

The toothed pulleys of Example 1 and Comparative Examples 1 to 3 were produced by a known method.
Here, a dedicated hob cutter was created according to the pulley groove shape of each toothed pulley, and the gears were manufactured through a manufacturing process that included gear cutting using this hob cutter.

In Table 1, "WU", "WM", and "WL" are the dimensions mentioned above (see FIG. 3).
In Table 1, "B _g ", "H _g ", "R ₂ ", "r _b ", "r _t ", "a", "R ₁ " and "Y ₁ " are the dimensions of the tooth space of an S-type tooth defined in JIS B 1857-2 (2015) (see Figure 4).

The toothed pulleys (drive pulley and driven pulley) produced in the examples and comparative examples were combined with a toothed belt to form a transmission system, and the performance of the transmission system was evaluated.
As the toothed belt, a toothed belt of type S5M as specified in JIS B 1857-1 (2015) was used.

The toothed belt has a belt width of 15 mm and a belt length of 415 mm.
The toothed belt has a belt body made of chloroprene rubber, a core wire 13 made of glass fiber, and a reinforcing cloth 14 made of a woven nylon fiber.

(evaluation)
In order to evaluate the positioning accuracy of the transmission system, the amount of lost motion was measured, and in order to evaluate the life of the toothed belt, a durability test was performed.

<Measurement of the amount of lost motion>
FIG. 5 is a diagram for explaining a method for measuring the amount of lost motion.
The lost motion was measured using a test device 3 to which the transmission systems of the embodiment and the comparative example were attached.
The test device 3 includes a toothed belt 30 , a driving pulley 32 , a driven pulley 34 , a load application handle 37 , and a laser displacement meter 38 .
The drive pulley 32 is fixed to a fixed shaft 35 that does not rotate, and the driven pulley 34 is fixed to a rotatable rotating shaft 36. A load application handle 37 is also fixed to this rotating shaft 36. The load application handle 37 has a handle body 37a that extends radially outward. The load application handle 37 can be rotated about the rotating shaft 36 by applying a load to the handle body 37a, and when the load application handle 37 is rotated, the driven pulley 34 also rotates about the rotating shaft 36 by the same rotation angle.
The test device 3 is also configured to be capable of adjusting the belt installation frequency (belt tension).

The test procedure will be described below.
(1) The belt attachment frequency is adjusted by adjusting the position of the fixed shaft 35.
(2) The position of point MP, which was 100 mm away from the rotation axis 36 of the handle body 37a, was measured by the laser displacement meter 38, and the position of point MP was set as a reference point BP (amount of displacement 0). During the following operations, the position of point MP was continuously measured by the laser displacement meter 38.
(3) A force of 100 N was applied to a point EP 140 mm from the rotation axis 36 of the handle body 37a, and the operation of rotating the handle body 37a in the forward direction was repeated 10 times. The load was released for the 10th time, and the position of point MP was calculated after 20 seconds had elapsed. This position was designated as the first displacement point CP1.
(4) After 30 seconds had elapsed, a force of 100 N was applied to point EP of the handle body 37a, and the handle body 37a was rotated in the reverse direction 10 times. The load was released for the tenth time, and the position of point MP after 20 seconds had elapsed was calculated. This position was designated as the second displacement point CP2.
(5) After calculating the first displacement point CP1 and the second displacement point CP2, the distance between them (see L1 in FIG. 6) is calculated as the amount of lost motion.

FIG. 6 is a diagram showing an example of the measurement result of lost motion.
In FIG. 6, the horizontal axis indicates the measurement time (seconds) and the vertical axis indicates the amount of displacement.

The evaluation results are shown in FIG.
FIG. 7 is a diagram showing the evaluation results of lost motion, and is a graph with the belt fastening frequency on the horizontal axis and the amount of lost motion (mm) on the vertical axis.
As shown in FIG. 7, it has become clear that the transmission system (Example 1) using the toothed pulley according to the embodiment of the present invention has a small amount of lost motion and is excellent in positioning accuracy.

<Durability test>
FIG. 8 shows the pulley layout of a belt running test machine for durability testing.
The transmission systems prepared in the examples and comparative examples were arranged in the pulley layout shown in Fig. 8 to form a belt running test machine 5. In this belt running test machine 5, a driving pulley 52 and a driven pulley 54 are disposed at a distance from each other in the lateral direction, and a toothed belt 50 is wound between the two pulleys.
The driven pulley 54 is configured so that a lateral shaft load (SW) can be applied thereto.

In this durability test, a belt running test was conducted under conditions of a rotation speed of the drive pulley 52 of 5,000 rpm and an axle load (SW) of 500 N, and the running time until the belt teeth broke was measured.

The results are shown in Figure 9.
In FIG. 9, the running time of Comparative Example 1 is set to 100, and the running times of Comparative Examples 2 and 3 and Example 1 are shown as relative values to the running time of Comparative Example 1.

As shown in Figures 7 and 9, it has become clear that a transmission system equipped with a toothed pulley according to an embodiment of the present invention can ensure the durability of the toothed belt and excellent positioning accuracy.

REFERENCE SIGNS LIST 1 Transmission system 3 Test device 5 Belt running tester 10, 30, 50 Toothed belt 11 Belt body 11a Base 11b Toothed portion 12 Belt teeth 13 Core wire 14 Reinforcing cloth 20 Toothed pulley 21 Pulley groove 22, 32, 52 Driving pulley 24, 34, 54 Driven pulley 25 Contour line 35 Fixed shaft 36 Rotating shaft 37 Load application handle 37a Handle body 38 Laser displacement meter WU Upper dimension WL Lower dimension WM Middle dimension

Claims (3)

A toothed pulley in which pulley grooves that mesh with the belt teeth of a toothed belt are provided at a constant pitch along the outer periphery,
The toothed belt is a toothed belt that meshes with a pulley of type S5M as defined in JIS B 1857-2 (2015),
The toothed pulley has a width dimension of a pulley groove that is an upper dimension and a lower dimension in a cross section perpendicular to an axial direction of the pulley groove,
the upper dimension is a distance between two intersection points where a perpendicular line to the center line, passing through a point 0.50 mm radially inward from an intersection point between a center line of the pulley groove and a tooth tip circle of the toothed pulley, intersects with a contour line of the pulley groove;
the lower dimension is a distance between two intersection points where a perpendicular line to the center line, passing through a point 1.50 mm radially inward from an intersection point between a center line of the pulley groove and a tooth tip circle of the toothed pulley, intersects with a contour line of the pulley groove;
The lower dimension is 2.20 mm or less,
a ratio of said upper dimension to said lower dimension is greater than or equal to 1.40. 2. The toothed pulley according to claim 1, wherein the pulley groove has a groove bottom radius _rb of 0.40 mm or more and 0.50 mm or less. A transmission system comprising a toothed belt and a toothed pulley,
The toothed belt is a toothed belt that meshes with a pulley of type S5M as defined in JIS B 1857-2 (2015),
A transmission system, wherein the toothed pulley is a toothed pulley according to claim 1 or 2.

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