JP2002048200A - Belt transmitting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a belt transmitting apparatus capable of reducing chord- pitch vibration of a toothed belt with interference caused by engagement between the toothed belt and a toothed pulley, and also capable of reducing its noise. SOLUTION: In an assembly of the toothed belt 1 having a cross section of a belt tooth portion 2 in which forward and backward side faces of the belt tooth portion are an arc and a toothed pulley 4 having a cross section of a pulley groove portion 6 in which forward and backward surfaces of the pulley tooth portion are an arc, height of the belt tooth portion 2 is formed longer than the depth of the pulley groove portion 6, and also the belt tooth portion 1 is compressively engaged with the pulley groove portion 6 in the belt transmitting apparatus. The belt tooth portion 2 is formed to compressively engage with the pulley groove portion 6 at a compression ratio of 5 to 10%, and the belt tooth portion 2 is also formed to have 0.05 to 0.15 of a dynamic friction coefficient on the surface against the surface of the pulley groove portion 6 as counter material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a belt transmission using a combination of a toothed belt and a toothed pulley.

[0002]

2. Description of the Related Art In an OHC drive of an automobile engine or the like, a belt transmission device using a combination of a toothed belt and a toothed pulley is used. The toothed belt is formed by alternately providing belt teeth and belt grooves along the belt longitudinal direction, and the toothed pulley is formed by alternately providing pulley teeth and pulley grooves on the outer periphery. The toothed pulley and the toothed belt can be synchronously driven by engaging the belt teeth in the pulley groove and suspending the toothed belt on the toothed pulley.

In such toothed belts and toothed pulleys, the belt teeth and the pulley grooves are often trapezoidal in cross section, but if the belt teeth and pulley grooves have such trapezoidal cross section. When the belt tooth meshes with the pulley groove or when the belt tooth is disengaged, the front and rear side surfaces of the belt tooth and the front and rear surfaces of the pulley groove interfere with each other, and the belt tooth is damaged by shear force. And the life of the belt is significantly shortened.

Therefore, as shown in Japanese Patent Publication No. 57-51589, for example, a toothed belt in which the front and rear side surfaces of a belt tooth portion are formed in an arc shape, and the front and rear surfaces of a pulley groove are formed in an arc shape. A belt transmission device is provided in which the height of the belt teeth is formed to be greater than the depth of the pulley grooves so that the belt teeth are compression-engaged with the pulley grooves. By forming the belt teeth and the pulley grooves in an arc shape in this manner, interference between the belt teeth and the pulley grooves can be reduced, and damage to the belt teeth can be prevented.

[0005]

In such a belt transmission, there is an increasing tendency to require quietness.
One of the causes of noise generated when the belt transmission is driven is string vibration of a linear portion of the toothed belt, which occurs in the toothed belt when the toothed belt meshes with the toothed pulley.

FIG. 1 shows a toothed belt 1 in a belt transmission.
And (a) in FIG. 1 indicate the running direction of the toothed belt 1 (see FIG. 1).
When the belt teeth 2 of the toothed belt 1 mesh with the pulley grooves 6 of the toothed pulley 4 as shown in FIG.
1 and the pulley tooth portion 5 of the toothed pulley 4 are shown in FIG.
From FIG. 1A to FIG. 1B and further to FIG. 1C, the toothed belts 5 interfere with each other as the toothed belt 1 travels, and the toothed pulley 5 pushes up the belt toothed 2 to form a toothed pulley. The toothed belt 1 vibrates a portion where the belt 1 is stretched in a straight line, and this vibration is periodically applied to the toothed belt 1, and the vibration period matches the natural frequency of the linear portion of the toothed belt 1. When you do
The string vibration is amplified by the resonance, and the sound is generated.

The present invention has been made in view of the above points, and a belt transmission capable of reducing string vibration of a toothed belt due to interference at the time of meshing between a toothed belt and a toothed pulley, thereby reducing sound generation. It is intended to provide a device.

[0008]

SUMMARY OF THE INVENTION A belt transmission according to the present invention is formed of an elastic elastomer that extends along a pitch line 7 and is thereby reinforced by a reinforcing member 8 that defines the pitch line 7. A series of belt teeth 2 of the same shape are spaced at the same pitch via the belt groove 3, and most or all of the front and rear side surfaces of each belt tooth 2 are shaped as an arc having a radius W. And a plurality of pulley tooth portions of the same shape formed between the pulley groove 6 and the toothed belt 1 in which both of the arcs are located on the pitch line 7 at a distance W apart from each other. 5, and most or all of the front and rear surfaces of the pulley groove 6 are shaped in cross section as an arc centered on the pitch circle 9, and the radius of the pitch circle 9 passes through the tip of the pulley tooth 5. Radius of pulley outer diameter circle 10 A combination with the toothed pulley 4 which is the sum of the distance from the bottom of the belt groove 3 to the pitch line 7 in the toothed belt 1, wherein the toothed belt 1 is suspended on the toothed pulley 4 and In the belt transmission device in which the height of the portion 2 is formed to be larger than the depth of the pulley groove portion 6 so that the belt teeth portion 1 is compression-engaged with the pulley groove portion 6, the belt teeth between the belt tooth portion 2 and the pulley groove portion 6 are formed. The portion 2 is formed so as to be compression-engaged at a compression ratio of 5 to 10%, and the kinetic friction coefficient of the surface of the belt tooth portion 2 becomes 0.05 to 0.15 with the surface of the pulley groove 6 as a mating member. It is characterized by being formed in.

[0009]

Embodiments of the present invention will be described below.

[0010] The basic construction of the belt transmission, that is, a series of identical elastomers formed by an elastic elastomer extending along the pitch line 7 and thereby reinforced by a reinforcing member 8 defining the pitch line 7. The belt tooth portions 2 having the same shape are separated at the same pitch via the belt groove portion 3, and most or all of the front and rear side surfaces of each belt tooth portion 2 are shaped as an arc having a radius W, and the cross section is formed. Both arcs have a toothed belt 1 whose center is located on the pitch line 7 at a distance W and a plurality of pulley teeth 5 of the same shape formed between the pulley grooves 6. Most or all of the front and rear surfaces of the pulley groove 6 have a cross section shaped as an arc centered on the pitch circle 9,
The toothed pulley 4 whose radius of the pitch circle 9 is the sum of the radius of the pulley outer diameter circle 10 passing through the tip of the pulley tooth portion 5 and the distance from the bottom of the belt groove 3 to the pitch line 7 in the toothed belt 1. The toothed belt 1 is suspended on the toothed pulley 4, and the height of the belt teeth 2 is formed to be greater than the depth of the pulley groove 6, and the belt teeth 2 are engaged with the pulley groove 6. The points that are combined are the same as those described in the above-mentioned Japanese Patent Publication No. 57-51589, but these components will be described first.

FIG. 2 shows an example of the embodiment of the toothed belt 1. The toothed belt 1 has an annular belt back portion 16 in which a reinforcing member 8 is embedded along the longitudinal direction of the belt.
Belt teeth 2 and belt grooves 3 formed by alternately arranging a large number of belt teeth on the inner peripheral surface of the belt back 16 in the longitudinal direction of the belt.
It is formed from Belt back 16 and belt teeth 2
Is formed by an elastic elastomer, and rubber can be used as the elastic elastomer. Examples of such rubber include natural rubber, butyl rubber, styrene-butadiene rubber, chloroprene rubber, ethylene-propylene rubber, and alkylated chloro rubber. A rubber material such as a sulfonated polyethylene, a hydrogenated nitrile rubber, a mixed polymer of a hydrogenated nitrile rubber and an unsaturated metal carboxylate alone or a mixture of these rubber materials can be used.
The reinforcing member 8 can be a core 17. As the core 17, a cord obtained by treating a cord of polyester fiber, aramid fiber, glass fiber, or the like with an RFL solution can be used. In addition, back 1
6, a reinforcing cloth 18 may be laminated on the surface from the belt tooth portion 2 to the belt groove portion 3. As such a reinforcing cloth 18, cotton, polyester fiber,
A canvas in which a nylon fiber or the like is woven in a plain weave, a twill weave, a satin weave, or the like can be used. After being treated with an RFL solution, the rubber composition is used as a rubber-coated canvas obtained by fiction coating. The RFL solution is obtained by mixing an initial condensate of resorcinol and formalin with a latex such as chloroprene, styrene / butadiene / vinylpyridine terpolymer, hydrogenated nitrile rubber (H-NBR), or NBR.

In the above-mentioned toothed belt 1, the center line of the reinforcing member 8 formed by the core wire 17 becomes the pitch line 7, and the belt tooth portion 2 formed in the same shape has the pitch P
Only separated. Each of the belt teeth 2 is formed such that the front side surface and the rear side surface in the belt running direction have a cross-sectional shape cut in the belt longitudinal direction into an arc having a radius W. The center O ₂₁ of the arc on the front side and the center O ₂₂ of the arc on the rear side are both located on the pitch line 7, and the centers O ₂₁ and O ₂₂ are separated by a distance W. Here, the radius W of the arc is preferably set to the tooth thickness dimension of the belt tooth portion 2 in the belt longitudinal direction.

FIGS. 3A and 3B show the implementation of the toothed pulley 4. FIG.
It shows an example of the form, and is an iron (steel) disc
Pulley tooth portions 5 and pulley groove portions 6 are alternately arranged on the outer circumference in the circumferential direction.
It is formed by arranging a large number of
Pulley teeth 5 are separated by a pitch P. Again
The pulley groove 6 formed in one shape is oriented in the pulley rotation direction.
The front side and the rear side in parallel with the pulley surface direction.
The cut cross-section is centered on the pitch circle 9₆₁, O₆₂To
It is formed so as to have a circular arc. This pitch circle 9
Is the center of the pulley outer diameter circle 10 passing through the tip of the pulley tooth portion 5
O is the same circle as the center, and the radius r of the pitch circle 9₁Is
Radius r of the outer diameter circle 10_TwoAnd bell in toothed belt 1
And the distance d from the bottom of the groove 3 to the pitch line 7
Is defined. Here, the front side surface of the pulley groove 6
And the center O of the arc on the rear side₆₁, O ₆₂Is separated by distance W
Is preferably set on the pitch circle 9,
Also, the radius r of this arc_ThreeAdded the factor xc to W
It is preferable to set the dimensions. c is the side of the belt tooth 2
And the desired spacing between the surface of the pulley groove 6 and x
A numerical coefficient that can be selected and must be 0.5 or 1
Preferred (particularly 0.5 is preferred).

A belt transmission is formed by combining the toothed belt 1 formed as described above and the toothed pulley 4 and suspending the toothed belt 1 on the toothed pulley 4. The height H of the belt teeth 2 is changed to the pulley groove 6
Is formed so as to be larger than the depth D, and when the toothed belt 1 is engaged with the toothed pulley 4, the belt teeth 2 are compression-engaged with the pulley groove 6. The height H of the belt teeth 2 and the depth D of the pulley grooves 6 are set so that the belt teeth 2 are compression-engaged at a compression ratio of 5 to 10% between the belt teeth 2 and the pulley grooves 6. is there. That is, by setting the height H of the belt teeth 2 and the depth D of the pulley groove 6 so that D / H = 90 to 95%, the belt teeth 2 can be compressed at a compression ratio of 5 to 10%. It is designed to engage in compression.

Further, in the present invention, the surface of the belt tooth portion 2 of the toothed belt 1 is formed so that the coefficient of kinetic friction is 0.05 to 0.15 with the surface of the pulley groove 6 as a mating member. Since the toothed pulley 4 is generally made of iron (steel), it may be formed so that the kinetic friction coefficient of the surface of the belt tooth portion 2 becomes 0.05 to 0.15 with iron as a mating material.
The friction coefficient of the surface of the belt tooth portion 2 is determined by the reinforcing cloth 18 when the surface is covered with the reinforcing cloth 18, so that the 15 mm × 60 mm square reinforcing cloth 18 is placed on a flat iron plate. Put a weight of mass w = 500g on top,
The load (f) at that time is read by pulling the reinforcing cloth 18 at a speed of 30 mm / s, and the numerical value calculated as the dynamic friction coefficient μ = f / w can be adopted as the dynamic friction coefficient of the surface of the belt tooth portion 2. .

According to the present invention, as described above, when the toothed belt 1 is engaged with the toothed pulley 4 and the belt tooth 2 is compression-engaged with the pulley groove 6, the belt tooth 2 is 5 to 10 %, The interference at the time of engagement with the toothed pulley 4 can be reduced, and the exciting force applied to the toothed belt 1 can be reduced. By setting the kinetic friction coefficient of the belt tooth portion 2 of the synchronous belt 1 in the range of 0.05 to 0.15, interference at the time of meshing between the synchronous belt 1 and the synchronous pulley 4 is smoothly eliminated, The vibration force applied to the toothed belt 1 can be reduced, and as a result, the string vibration generated in the toothed belt 1 can be reduced, and the sound generation can be reduced. In particular, the vibration period of the toothed belt 1 can be changed,
String vibration of toothed belt 1, toothed belt 1 and toothed pulley 4
The resonance point of the meshing sound can be shifted to a high rotation speed range where sound generation is not so problematic in an engine or the like, so that sound generation can be suppressed particularly in a low rotation speed range where quietness is required.

[0017]

Next, the present invention will be described specifically with reference to examples.

Example 1 A toothed belt 1 as shown in FIG. 2 was manufactured. The elastic elastomer constituting the back portion 16 and the belt tooth portion 2 of the toothed belt 1 was formed of the rubber compound shown in Table 1.

[0019]

[Table 1]

The reinforcing cloth 18 covering the back 16 of the toothed belt 1, the belt teeth 2 and the belt groove 3 includes
A canvas having the composition shown in Table 2 was rubber-treated and used. That is, the RFL treatment liquid in Table 3 is obtained by adding “Fluon AD1” (aqueous dispersion of polytetrafluoroethylene, manufactured by Asahi ICI Fluoropolymers Co., Ltd.), which is a fluororesin powder, to a commonly used RFL treatment liquid. Average particle diameter 0.25 μm, solid content 60% by mass). The canvas shown in Table 2 was immersed in this RFL treatment liquid, dried at 120 ° C., and then heat-treated at 180 ° C. for 2 minutes. . Next, a polyaryl polyisocyanate (PAP) was added to the rubber paste treating solution shown in Table 4.
The canvas after the RFL treatment was immersed in the treatment liquid prepared by adding I) to form a first rubber layer. Table 4
20 parts per 100 parts by weight of rubber compound
Parts by weight of an antioxidant ("Nocrack N" manufactured by Ouchi Shinko Chemical Co., Ltd.)
BC ”), MEK was added so that“ Nocrack NBC ”was 15% by mass of the whole, and graphite was further added thereto with 6 parts per 100 parts by mass of the rubber compound.
A treatment liquid was prepared by adding and mixing 3.9 parts by mass, and the canvas on which the first rubber layer was formed was immersed in the treatment liquid and dried at 80 ° C. for 4 minutes to form a second rubber layer. Was formed. This was used as the reinforcing cloth 18.

[0021]

[Table 2]

[0022]

[Table 3]

[0023]

[Table 4]

As the cord 17 constituting the reinforcing member 8, a cord having a composition shown in Table 5 was used, and the cord was treated with a treatment liquid prepared by mixing isocyanate with the RFL treatment liquid shown in Table 3.

[0025]

[Table 5]

The dimensions of the toothed belt 1 of Example 1 were as follows. Belt width 30mm, number of teeth 2
53, the pitch P of the belt teeth 2 = 8 mm, the tooth thickness W (= radius of the side surface of the belt teeth 2) = 5.2 mm, d = 0.68
6 mm, height H of the belt tooth portion 2 = 3.01 mm. Further, the coefficient of kinetic friction of the surface of the belt teeth 2 formed of the reinforcing cloth 18 against iron (steel) was 0.13.

On the other hand, the toothed pulley 4 was made of iron (steel) having 26 teeth and had the following dimensions.
Pitch P of pulley teeth 5 = 8 mm, radius r of pitch circle 9
₁ = 66.21 mm, radius r ₂ of pulley outer diameter circle 10 = 3
2.42 mm, radius r ₃ of the side surface of the pulley groove 6 = 5.3
0 mm, the depth D of the pulley groove 6 is 2.83 mm.

Therefore, in the first embodiment, D / H = 94%, and the belt teeth 2 are compression-engaged with the pulley groove 6 at a compression ratio of 6%.

(Comparative Example 1) As a reinforcing cloth 18, a cloth having the composition shown in Table 6 was used, and a rubber-treated cloth was used in the same manner as in Example 1 except that "Fluon AD1" was not used. Others are the same as Example 1, and the toothed belt 1 as shown in FIG.
Was prepared. The dimensions of the toothed belt 1 of Comparative Example 1 were almost the same as those of Example 1, but the height H of the belt tooth portion 2 was set to 2.90 mm. The coefficient of kinetic friction of iron (steel) on the surface of the belt teeth 2 formed by the reinforcing cloth 18 was 0.17.

[0030]

[Table 6]

On the other hand, the same pulley 4 as in Example 1 was used as the toothed pulley 4, and the depth D of the pulley groove 6 was 2.83 mm. Therefore, in Comparative Example 1, D / H = 97.5%, and the belt teeth 2 are compression-engaged with the pulley groove 6 at a compression ratio of 2.5%.

The belt transmission device comprising the combination of the toothed belt 1 and the toothed pulley 4 in the above-mentioned Example 1 and Comparative Example 1 was driven, and its sound was measured by frequency analysis.
FIG. 7 shows an OHC drive belt transmission device used for the measurement. In addition to the toothed pulley 4, a 26-tooth clamp pulley 20, a water pump pulley 21, a tensioner pulley 22, and an idler pulley 23 are arranged. hand,
The toothed belt 1 was suspended between them. As the clamp pulley 20, the one having the same tooth shape as the toothed pulley 4 of the first embodiment was used. Then, the belt transmission was driven at 700 to 2000 rpm, which is the normal rotation speed range of the automobile engine, the sound was captured by a microphone, and the captured sound was subjected to FFT to perform frequency analysis. Table 7
The compression ratio and the kinetic friction coefficient of the belt teeth 2 of Example 1 and Comparative Example 1 are compared and displayed.

[0033]

[Table 7]

FIG. 4 is a graph showing the results of the frequency analysis of the pronunciations of Example 1 and Comparative Example 1 performed as described above. FIG. 4A shows the relationship between the noise level and the frequency of the sound around 700 rpm, and FIG. 4B shows the relationship between the noise level and the frequency of the sound near 1200 rpm.
(C) shows the relationship between the noise level and the frequency of sound generation near 1400 rpm, and it is confirmed that the sound of Example 1 is lower in sound generation than that of Comparative Example 1. In particular, at around 700 rpm, the reduction of the 26th-order (mesh primary) component as the first peak and the 52nd (mesh secondary) component as the second peak in the graph of FIG. It is large, and around 1400 rpm, which is the first peak 26 in the graph of FIG.
It can be seen that the reduction of the sound of the next (engagement primary) component is large, and is effective in reducing the sound generation in the normal rotation range.

Comparative Example 2 A toothed belt 1 as shown in FIG. 2 was produced in the same manner as in Comparative Example 1. The size of the toothed belt 1 of Comparative Example 2 was almost the same as that of Example 1, but the height H of the belt tooth portion 2 was set to 3.01 mm. Further, the coefficient of kinetic friction of the surface of the belt tooth portion 2 with respect to iron (steel) is 0.17 as in Comparative Example 1.

On the other hand, the toothed pulley 4 is the same as that of the first embodiment, and the depth D of the pulley groove 6 is 2.83 mm. Therefore, in Comparative Example 2, D / H = 94%, and the belt tooth portion 2 is compression-engaged with the pulley groove 6 at a compression ratio of 6%.

A belt transmission device comprising a combination of the toothed belt 1 and the toothed pulley 4 in the comparative example 2 was driven, and its sound was frequency-analyzed and measured in the same manner as described above. FIG. Table 8 shows a comparison between the compression ratio and the kinetic friction coefficient of the belt teeth 2 of Example 1 and Comparative Example 2.

[0038]

[Table 8]

FIG. 5A shows the relationship between the noise level and the frequency of the sound at around 700 rpm, and FIG.
The relationship between the noise level and the frequency of the sound at around rpm,
FIG. 5C shows the relationship between the noise level and the frequency of sound generation at around 1400 rpm, and it is confirmed that the sound of Example 1 is lower in sound generation than that of Comparative Example 2.

Example 2 A toothed belt 1 as shown in FIG. 2 was produced in the same manner as in Example 1. The dimensions of the toothed belt 1 of Comparative Example 2 were almost the same as those of Example 1, but the height H of the belt tooth portion 2 was set to 2.97 mm. Further, the coefficient of kinetic friction of the surface of the belt tooth portion 2 with respect to iron (steel) is 0.13 as in the first embodiment.

On the other hand, the same pulley 4 as in Example 1 was used as the toothed pulley 4, and the depth D of the pulley groove 6 was 2.83 mm. Accordingly, in the second embodiment, D / H = 95%, and the belt teeth 2 are compression-engaged with the pulley groove 6 at a compression ratio of 5%.

Comparative Example 3 A toothed belt 1 as shown in FIG. 2 was produced in the same manner as in Comparative Example 1. The size of the toothed belt 1 of Comparative Example 3 was almost the same as that of Example 1, but the height H of the belt tooth portion 2 was set to 2.97 mm. Further, the coefficient of kinetic friction of the surface of the belt tooth portion 2 with respect to iron (steel) is 0.17 as in Comparative Example 1.

On the other hand, the same pulley 4 as in Example 1 was used as the toothed pulley 4, and the depth D of the pulley groove 6 was 2.83 mm. Therefore, in Comparative Example 3, D / H = 95%, and the belt teeth 2 are compression-engaged with the pulley groove 6 at a compression ratio of 5%.

The belt transmission device composed of the combination of the toothed belt 1 and the toothed pulley 4 in the above-described Example 2 and Comparative Example 3 was driven, and its sound was frequency-analyzed and measured in the same manner as described above. As shown in FIG. Table 9 shows Example 2.
And the compression ratio and the kinetic friction coefficient of the belt tooth portion 2 of Comparative Example 3 are displayed.

[0045]

[Table 9]

FIG. 6A shows the relationship between the noise level and the frequency of sound generation at around 700 rpm, and FIG.
The relationship between the noise level and the frequency of the sound at around rpm,
FIG. 6C shows the relationship between the noise level and the frequency of sound generation near 1400 rpm, and it is confirmed that the sound of Example 2 is lower than that of Comparative Example 3.

[0047]

As described above, according to the present invention, the belt teeth are formed so as to be compression-engaged at a compression ratio of 5 to 10% between the belt teeth and the pulley grooves, and the surface of the belt teeth is formed. The coefficient of kinetic friction is 0.05-0.
15 so that the interference at the time of meshing with the toothed pulley can be reduced and the exciting force applied to the toothed belt can be reduced, and the string vibration generated in the toothed belt can be reduced. Then, the pronunciation can be reduced.

[Brief description of the drawings]

FIG. 1 shows engagement of a toothed belt and a toothed pulley, and (a) to (c) are partial front views.

FIG. 2 is a partial front view showing the toothed belt.

3A and 3B show a toothed pulley, wherein FIG. 3A is a front view, and FIG. 3B is a partially enlarged front view.

FIG. 4 is a graph showing the results of frequency analysis of pronunciation of Example 1 and Comparative Example 1.

FIG. 5 is a graph showing the results of frequency analysis of pronunciations of Example 1 and Comparative Example 2.

FIG. 6 is a graph showing the results of frequency analysis of pronunciations of Example 2 and Comparative Example 3.

FIG. 7 is a schematic diagram of a belt transmission device for sound generation measurement.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Toothed belt 2 Belt tooth part 3 Belt groove part 4 Toothed pulley 5 Pulley tooth part 6 Pulley groove part 7 Pitch line 8 Reinforcement member 9 Pitch circle 10 Pulley outer diameter circle

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F16H 55/36 F16H 55/36 H 55/38 55/38 A

Claims (1)

[Claims] 1. A series of identically shaped belt teeth formed of an elastic elastomer reinforced by one or more reinforcing members extending along the pitch line and thereby defining the pitch line. In addition to being separated by a belt groove portion, most or all of the front and rear side surfaces of each belt tooth portion are shaped as an arc having a radius W, and the center of both arcs is separated by a distance W. It has a toothed belt positioned on the pitch line and a plurality of pulley teeth of the same shape formed between the pulley grooves, and most or all of the front and rear surfaces of the pulley grooves are pitched. The cross section is shaped as an arc centered on a circle, and the radius of the pitch circle is the sum of the radius of the pulley outer diameter circle passing through the tip of the pulley tooth and the distance from the bottom of the belt groove to the pitch line in the toothed belt. In The toothed pulley is suspended on the toothed pulley, the height of the belt tooth is formed larger than the depth of the pulley groove, and the belt tooth is compression-engaged with the pulley groove. In the belt transmission device, the belt tooth portion is formed so as to be compression-engaged at a compression ratio of 5 to 10% between the belt tooth portion and the pulley groove portion, and the kinetic friction coefficient of the surface of the belt tooth portion is reduced by the pulley. A belt transmission device characterized in that the surface of the groove portion is formed so as to be 0.05 to 0.15 as a mating material.