Belt wheel and transmission device

Abstract

The utility model relates to a belt wheel and a transmission device, the belt wheel comprises a plurality of gear teeth used for being meshed with belt teeth of a cog belt, the gear teeth comprise gear tooth tops and gear tooth groove bottoms, the belt teeth comprise belt tooth tops and belt tooth groove bottoms, and the axial width of the gear tooth tops is larger than that of the gear tooth groove bottoms. The axial width of the bottoms of the gear tooth grooves is smaller than that of the belt tooth tops, and the bottoms of the gear tooth grooves are used for abutting against the axial middle parts of the belt tooth tops. Compared with the prior art, due to the fact that the width of the bottoms of the gear tooth grooves of the gear teeth is smaller than that of the wide gear teeth of the gear teeth, the tooth top face portions of the belt teeth abut against the bottoms of the gear tooth grooves with the smaller width, torque balance is formed on the two sides of the abutting position, the self-centering effect is achieved, and meanwhile the tooth width of the belt teeth is close to that of the gear teeth; the roots of the belt teeth can make contact with the tooth surfaces of the tops of the gear teeth with the large width, the bearing capacity is greatly improved and stress is dispersed under the condition that self-centering is achieved, and transmission precision and stability are further improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to transmission technical field especially a kind of pulley and transmission device. BACKGROUND

[0002] In the transmission system of vehicle, belt drive can buffer load impact, run smoothly, and noise is lower, so it is gradually concerned. Especially the transmission system of high-end two-wheeled bicycle or motorcycle pursues more pursuit of silence, maintenance-free and durability.

[0003] However, the transmission belt deviation is a common problem in belt drive system. During the movement of the transmission belt, it may deviate from the center position of the pulley, causing uneven contact between the belt and the pulley, aggravating local wear and shortening the service life.

[0004] However, the transmission belt deviation is a common problem in belt drive system. During the movement of the transmission belt, it may deviate from the center position of the pulley due to various factors, causing uneven contact between the belt and the pulley, aggravating local wear and shortening the service life. With the development of technology, the acceleration requirement of vehicle is higher, and the instantaneous power of transmission device is larger, so the vehicle belt drive mechanism needs to have greater carrying capacity.

[0005] Therefore, it is necessary to develop a new type of pulley and transmission device to improve the above-mentioned problems in the related art. UTILITY MODEL CONTENT

[0006] The utility model aims at providing a kind of pulley, which can increase the carrying capacity of belt drive mechanism on the basis of re-alignment after the position of belt deviates during transmission.

[0007] The purpose of the utility model can be realized by the following technical solutions:

[0008] The utility model provides a kind of pulley including a plurality of teeth, for being engaged with the teeth of toothed belt, the tooth includes tooth top and tooth groove bottom, the teeth include tooth top and tooth groove bottom, the axial width of the tooth top is greater than the axial width of the tooth groove bottom, the axial width of the tooth groove bottom is less than the axial width of the tooth top, and the tooth groove bottom is used to abut the axial middle part of the tooth top.

[0009] Further, the axial both sides distance of the tooth changes from wide to narrow monotonous transition from tooth top to tooth groove bottom.

[0010] Further, the axial both sides distance of the tooth changes from wide to narrow monotonous transition from tooth top to tooth groove bottom.

[0011] Further, the tooth thickness of the tooth changes from thin to thick monotonous transition from tooth top to tooth groove bottom.

[0012] Further, the axial width of the tooth top is greater than or equal to the axial width of the tooth groove bottom.

[0013] Further, the tooth profile of the tooth is involute or circular arc.

[0014] Further, the curve of the tooth profile of the tooth includes a first arc and a second arc connected in sequence in the direction of the tooth top extending to the tooth groove bottom, the radius of the first arc is greater than that of the second arc, and the center of the first arc is closer to the tooth top than the center of the second arc.

[0015] Further, the tooth groove bottom is provided with a groove for contacting the top end surface of the toothed top.

[0016] Further, the inner profile of the groove is U-shaped.

[0017] The utility model also provides a kind of transmission device, including two transmission wheels and toothed belt, at least one of two transmission wheels is the pulley described above.

[0018] Compared with the prior art, the utility model has the following beneficial effects:

[0019] 1, the pulley in the utility model is matched with the belt, the toothed width is similar to the tooth width of the tooth, and the width of the tooth groove bottom is less than the tooth width of the tooth; when engaging, the engagement point gradually moves to the tooth root of smaller width and makes the tooth top surface part of the tooth abut on the tooth groove bottom of smaller width, so that the abutment forms a support area to resist tension and pre-tightening force, forms stress area on both sides of the abutment under the action of tension and pre-tightening force, forms two side moments with the support area as center; when the belt and the pulley are stably matched, the two side moments keep balance; when external interference force acts on the belt, the external interference force participates in one side moment to break the moment balance, the position of the support area moves, the width of the stress area of the side participating in the external interference force increases, and the width of the stress area of the other side decreases, the offset amount continuously increases until the two side moments under the participation of external interference force reach balance; when the external interference force is removed, the side participating in the original external interference force decreases, the two side moments balance is broken again, and the position of the support area returns to the initial position, so that self-centering of the belt transmission is realized. And, since the toothed width is similar to the tooth width of the tooth, the tooth root can contact the tooth surface of the tooth top of larger width when engaging, so that the load-carrying capacity is greatly improved under the condition of self-centering, the stress is dispersed, and the transmission precision and stability are also improved.

[0020] 2, the axial two side edges of the tooth in the utility model are monotonically transitioned from wide to narrow from tooth top to tooth groove bottom, so that the engagement width is avoided from suddenly changing, and the stability of transmission is improved.

[0021] 3. The utility model discloses a wheel tooth thickness monotone transition from the tooth top to the tooth groove bottom thin to thick, and the tooth thickness increases to make the tooth root position thickness of the key area of the bending stress, thereby effectively improving the bending strength of the tooth root, and improving the carrying capacity of the belt drive.

[0022] 4. The utility model discloses the axial width of the wheel tooth top is greater than or equal to the axial width of the tooth groove bottom, and the meshing width at the wheel tooth top position is the tooth width of the tooth, and the width of the tooth profile is fully utilized to improve the carrying capacity of the transmission.

[0023] 5. The utility model discloses the tooth profile shape of the wheel tooth is set as involute or circular arc, which can improve the stability of the transmission and increase the carrying capacity.

[0024] 6. The utility model discloses the tooth profile of the wheel tooth is composed of multiple arc lines, and when the tooth engages with the wheel tooth, the stress direction of the tooth is directed to the center of the second arc line on the tooth profile. Since the center of the second arc line is closer to the wheel tooth top, i.e. closer to the tooth groove bottom, the stress concentration area is closer to the core rope layer of the toothed belt, so that the stress concentration on the tooth is reduced when the smaller width of the wheel tooth root engages with the tooth, thereby improving the service life of the belt on the basis of torque balance.

[0025] 7. The utility model discloses the structure form that the groove is set in the tooth groove bottom of the wheel to form the axial width of the tooth groove bottom less than the axial width of the tooth top, which realizes the self-centering principle and makes the belt wheel have better integrity, easy processability and economy.

[0026] 8. The groove shape of the tooth groove bottom of the belt wheel in the utility model is U-shaped, which can increase the tooth width of the wheel tooth near the root to a greater extent on the basis of the same tooth groove bottom width, and has better carrying capacity. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is the schematic diagram of the transmission device of example 1.

[0028] Figure 2 It is the schematic diagram of the engagement of the belt wheel and the toothed belt in example 1.

[0029] Figure 3 It is Figure 2 the schematic diagram of the stress in the A direction section in the utility model.

[0030] Figure 4 It is Figure 2 the schematic diagram of the stress in the A direction section of the toothed belt after the offset under the action of the external interference force.

[0031] Figure 5 It is the structural schematic diagram of the belt wheel in example 1.

[0032] Figure 6 Structure diagram of the tooth of the belt wheel in Example 1;

[0033] Figure 7 Structure diagram of the tooth of the belt wheel in Example 1;

[0034] Figure 8 Structure diagram of the tooth of the belt wheel in Example 2;

[0035] Figure 9 Structure diagram of the tooth of the belt wheel in Example 3;

[0036] Figure 10 Structure diagram of the tooth profile of the tooth in Example 1;

[0037] Figure 11 Structure diagram of the tooth of the belt wheel in Example 4;

[0038] Figure 12 Structure diagram of the tooth of the belt wheel in Example 5;

[0039] Figure 13 Structure diagram of the tooth profile in Example 6;

[0040] Figure 14 Stress diagram of the tooth profile in Example 6.

[0041] Reference signs:

[0042] 1, tooth; 11, top of the tooth; 12, bottom of the tooth groove; 121, groove; 101, tooth profile; 102, wheel end face; 103, tooth flank;

[0043] 2, belt tooth; 21, top of the belt tooth; 22, bottom of the belt tooth groove;

[0044] 41, support area; 42, stress area;

[0045] 51, first arc; 52, second arc; 53, third arc;

[0046] 61, first arc center; 62, second arc center;

[0047] 7, stress concentration area. DETAILED DESCRIPTION

[0048] The utility model will be explained in detail below in combination with the drawings and specific embodiments. The embodiments are implemented on the premise of the technical scheme of the utility model, and detailed implementation modes and specific operation processes are given, but the protection scope of the utility model is not limited to the following embodiments.

[0049] Example 1

[0050] This utility model provides a transmission device, such as... Figure 1 , Figure 5 and Figure 7 As shown, this device can be specifically applied to two-wheeled bicycles or two-wheeled electric bicycles. The transmission device includes two mating pulleys and a toothed belt. The toothed belt is tensioned on the two pulleys, forming a belt drive. At least one of the pulleys is the driving pulley, and its diameter is smaller than the other pulley, used to connect the pedals or engine of the two-wheeled vehicle. Figure 1 As shown, a belt has several teeth 1, which mesh with the teeth 2 of a toothed belt. Each tooth 1 includes a tooth top 11 and a tooth groove bottom 12. Each tooth 2 includes a tooth top 21 and a tooth groove bottom 22. The tooth width of the teeth 1 varies radially. The tooth top 11 monotonically changes as it transitions to the tooth groove bottom 12, decreasing in width on both sides simultaneously, resulting in a symmetrically decreasing overall tooth width. This ensures that the axial width of the tooth top 11 is greater than the axial width of the tooth groove bottom 12, and the axial width of the tooth groove bottom 12 is less than the axial width of the tooth top 21. The tooth groove bottom 12 abuts against the axial middle portion of the tooth top 21. The other pulley connects to one wheel of the two-wheeled vehicle, thus driving the vehicle. It should be noted that both pulleys can serve as driving pulleys. The two pulleys can have the same or different shapes. The two pulleys can have the same size or a difference in diameter.

[0051] like Figure 2 As shown, the gear tooth 1 includes a tooth groove bottom 12 and a tooth top 11, and the belt tooth 2 includes a belt tooth groove bottom 22 and a belt tooth top 21. The axial width of the tooth groove bottom 12 of the gear tooth 1 is smaller than the axial width of the belt tooth top 21, causing the middle portion of the tooth groove bottom 12 and the belt tooth top 21 to abut. Simultaneously, a certain gap remains between the tooth top 11 and the tooth groove bottom 22. The pulley and the toothed belt primarily engage and transmit power through the abutting portion. In another embodiment, the tooth top 11 and the tooth groove bottom 22 can be in a form of partial contact, where they are in contact but do not exert any force on each other.

[0052] like Figure 3 and Figure 4As shown, when the pulley is engaged with the toothed belt, the toothed belt is subjected to the pre-tightening force and the pulling force. Due to the abutting of the bottom of the tooth groove 12 to the partial area of the top of the belt tooth 21, the pre-tightening force and the pulling force on the abutting area, i.e. the support area 41, are counteracted by the reaction force provided by the bottom of the tooth groove 12, and the force areas 42 on both sides of the abutting area are subjected to the pre-tightening force and the pulling force. When engaged, the top of the belt tooth 21 is partially abutted to the bottom of the tooth groove 12, and the bottom of the tooth groove 12 supports the local belt tooth 231, the abutting position is the support area 41, which can resist the pulling force and the pre-tightening force; the force areas 42 on both sides of the abutting position are subjected to the pulling force and the pre-tightening force, and form a torque on both sides with the support area 41 as the center; when the toothed belt is in cooperation with the pulley, the torques on both sides are balanced, and the belt is kept at the target position. When an external interference force acts on the belt, the external interference force participates in one side torque to break the torque balance, the position of the support area 41 moves, the width of the force area 42 on one side participating in the external interference force increases, and the width of the force area 42 on the other side decreases, and the offset amount continuously increases until the torque balance on both sides under the participation of the external interference force is reached; when the external interference force is removed, the torque on the side participating in the original external interference force decreases, the torque balance on both sides is broken again, and the position of the support area 41 returns to the original position, thereby realizing the self-centering effect of the belt transmission. It should be noted that when the external interference force gradually increases, the greater the offset amount of the toothed belt, the greater the torque for returning the toothed belt to the target position.

[0053] In the embodiment, the root depth of the tooth 10 is less than or equal to 0 mm, so that the bottom of the tooth groove of the tooth 10 and the top of the belt tooth 2 are not top clearances when engaged.

[0054] Specifically, the root depth can be -0.2, -0.18, -0.16, -0.14, -0.12, -0.1, -0.08, -0.06, -0.04, -0.02 or 0 mm.

[0055] In the embodiment, the tooth of the pulley and the wheel body can be integrally formed, combined, detachable, inlaid or welded, and the utility model does not limit this.

[0056] In the embodiment, as shown in the figure, Figure 10 The tooth profile 101 of the tooth 10 is in the shape of a circular arc.

[0057] In the embodiment, the curvature of the circular arc can be positive or negative, i.e. the tooth profile 101 of the tooth 10 can be in the shape of a concave circular arc or an outward convex circular arc.

[0058] In the embodiment, as shown in the figure, Figure 10 The tooth profile 101 of the tooth 10 is in the shape of a concave circular arc, and the two opposite tooth profiles 101 on the two adjacent teeth 10 and the bottom of the tooth groove 12 together form a circular arc-shaped tooth groove to cooperate with the circular arc-shaped tooth 2.

[0059] In another embodiment, the tooth profile 101 of the gear tooth 10 is shaped as a concave circular arc, and the two opposite tooth profiles 101 of the two adjacent gear teeth 10 together form a circular arc-shaped tooth groove to match the circular arc-shaped tooth profile 101 of the toothed belt 2.

[0060] In this embodiment, as shown in the figure, the toothed belt has equal-width teeth, that is, the width of the toothed belt 2 is equal during the transition from the tooth top 21 to the tooth groove bottom 22, and the axial width of the gear tooth top 11 is greater than or equal to the axial width of the tooth groove bottom 22, so that the two sides of the gear tooth top 11 protrude from the two sides of the toothed belt 2. Figure 6 In this embodiment, as shown in the figure, the tooth thickness of the gear tooth 10 gradually increases during the transition from the tooth top to the tooth groove bottom.

[0061] Figure 10 In this embodiment, as shown in the figure, the tooth thickness of the gear tooth 10 gradually increases during the transition from the tooth top to the tooth groove bottom.

[0062] Embodiment 2

[0063] As shown in the figure, the basic structure of the belt wheel in this embodiment is the same as that in Embodiment 1, and the difference lies in that the tooth width of the gear tooth 11 first remains a certain value and then gradually decreases during the transition from the gear tooth top 11 to the gear tooth groove bottom 12. Specifically, Figure 8 In this embodiment, the tooth profile 101 of the gear tooth 10 is involute.

[0064] Embodiment 3

[0065] As shown in the figure, the basic structure of the belt wheel in this embodiment is the same as that in Embodiment 1, and the difference lies in that the tooth width of the gear tooth 10 decreases on one side in the width direction and remains unchanged on the other side, so that the overall tooth width gradually decreases on both sides asymmetrically.

[0066] Figure 9 Embodiment 4

[0067] As shown in the figure, in this embodiment, a groove 121 is provided on the wheel end surface 102 of the belt wheel 1, the groove 121 is located between the adjacent gear teeth 10, the axial width of the gear tooth top is greater than the axial width of the gear tooth groove bottom, and the tooth thickness of the gear tooth 10 gradually increases during the transition from the tooth top to the tooth root.

[0068] In this embodiment, as shown in the figure, the gear tooth 10 includes a tooth flank 103, the tooth flank 103 of the gear tooth 10 is two surfaces facing away from each other in the tooth width direction, the belt wheel 1 includes a wheel end surface 102, the wheel end surface 102 of the belt wheel 1 is two surfaces facing away from each other in the axial direction of the belt wheel 1, and the groove 121 is provided on the wheel end surface 102 in the axial direction of the belt wheel 1. Figure 11 In this embodiment, as shown in the figure, the gear tooth 10 includes a tooth flank 103, the tooth flank 103 of the gear tooth 10 is two surfaces facing away from each other in the tooth width direction, the belt wheel 1 includes a wheel end surface 102, the wheel end surface 102 of the belt wheel 1 is two surfaces facing away from each other in the axial direction of the belt wheel 1, and the groove 121 is provided on the wheel end surface 102 in the axial direction of the belt wheel 1.

[0069] Figure 11 In this embodiment, as shown in the figure, the gear tooth 10 includes a tooth flank 103, the tooth flank 103 of the gear tooth 10 is two surfaces facing away from each other in the tooth width direction, the belt wheel 1 includes a wheel end surface 102, the wheel end surface 102 of the belt wheel 1 is two surfaces facing away from each other in the axial direction of the belt wheel 1, and the groove 121 is provided on the wheel end surface 102 in the axial direction of the belt wheel 1.

[0070] ​​​In this embodiment, as shown in Figure 11 The grooves 121 are symmetrically arranged on the two opposite wheel end faces 102 of the belt wheel 1.

[0071] In this embodiment, as shown in Figure 11 The tooth flanks 103 of the gear teeth 10 coincide with the wheel end faces 102 of the belt wheel 1, i.e. there is no height difference between the tooth flanks 103 of the gear teeth 10 and the wheel end faces 102 of the belt wheel 1, the grooves 121 are arranged on the wheel end faces 102 of the belt wheel 1 between the adjacent gear teeth 10, the grooves 121 are recessed downward from the wheel end faces 102 of the belt wheel 1, the groove walls of the grooves 121 extend from the tooth top edges of the gear teeth 10 to the edges of the gear tooth groove bottoms 12101, and thus the width of the gear teeth 10 is greater than the width of the gear tooth groove bottoms 12101.

[0072] In another embodiment, there is a height difference between the tooth flanks 103 of the gear teeth 10 and the wheel end faces 102 of the belt wheel 1, i.e. the tooth flanks 103 of the gear teeth 10 protrude from the wheel end faces 102 of the belt wheel 1, the grooves 121 are arranged on the wheel end faces 102 of the belt wheel 1 between the adjacent gear teeth 10, the grooves 121 are recessed downward from the wheel end faces 102 of the belt wheel 1, the groove walls of the grooves 121 extend from the tooth top edges of the gear teeth 10 to the edges of the gear tooth groove bottoms 12101, and thus the width of the gear teeth 10 is greater than the width of the gear tooth groove bottoms 12101.

[0073] Embodiment 5

[0074] This embodiment is improved on the basis of Embodiment 4, and the main improvement point is that, as shown in Figure 12 The inner contour of the groove 121 is in the shape of a U, and specifically, in the radial view of the belt wheel 1, the inner contour of the groove 121 is in the shape of a U.

[0075] In another embodiment, in the radial view of the belt wheel 1, the inner contour of the groove 121 can also be in the shape of a rectangle, a V, or a trapezoid, and the utility model does not limit this.

[0076] Embodiment 6

[0077] The basic structure of the belt wheel in this embodiment is the same as that in Embodiment 1, and the difference is that the tooth profile 101 of the gear tooth 1 is composed of multiple arc lines. As shown in Figure 13 The curve of the tooth profile 101 of the gear tooth 1 includes a first arc line 51 and a second arc line 52 connected in sequence in the direction in which the tooth top 11 extends to the gear tooth groove bottom 12, the radius of the first arc line 51 is greater than that of the second arc line 52, and the center of the first arc line 51 is closer to the tooth top than the center of the second arc line 52.

[0078] As shown in Figure 13As shown, in the embodiment, the tooth profile 101 of the gear tooth 1 is sequentially connected with the third arc line 53, the first arc line 51 and the second arc line 52 in the process of extending from the gear tooth top 11 to the gear tooth groove bottom 12, the third arc line 53 is close to the gear tooth top 11, the second arc line 52 is close to the gear tooth groove bottom 12, and the first arc line 51 is located between the second arc line 52 and the third arc line 53, that is, the third arc line 53 is located in the middle section of the tooth profile 101.

[0079] As shown in the drawings, Figure 13 As shown, in the embodiment, the first arc center 61 is the center of the circle to which the first arc line 51 belongs, and the second arc center 62 is the center of the circle to which the second arc line 52 belongs.

[0080] As shown in the drawings, Figure 14 As shown, in the embodiment, the distance from the first arc center 61 to the top circle of the gear tooth 1 is closer than the distance from the second arc center 62 to the top circle of the gear tooth 1, when the toothed belt 2 is engaged with the gear tooth 1, the stress direction of the toothed belt 2 abutting the first arc line 51 on the tooth profile 101 points to the first arc center 61, and the stress direction is the direction of the arrow shown in the figure. Since the first arc center 61 is closer to the gear tooth top 11, that is, the first arc center 61 is closer to the tooth root of the toothed belt, the stress concentration area 7 is shifted upward, closer to the layer where the core rope of the toothed belt is located, which is beneficial to protect the toothed belt 2 and improve the service life of the toothed belt.

[0081] As shown in the drawings, Figure 13 As shown, in the embodiment, in the plane perpendicular to the belt wheel axis, the first arc center 61 can be directly above, left above or right above the second arc center 62.

[0082] In the description of the utility model, it is understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the utility model and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements indicated must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the utility model.

[0083] In addition, the terms "first" and "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first" and "second" can explicitly or implicitly include at least one of the features. In the description of the utility model, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise specifically limited.

[0084] In the present application, unless otherwise expressly specified and limited, the terms "mounting", "connecting", "connecting", "fixing" and the like should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship of two elements, unless otherwise expressly limited. For ordinary skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0085] In the present application, unless otherwise expressly specified and limited, the first feature is "on" or "under" the second feature. The first and second features can be in direct contact, or the first and second features can be in indirect contact through an intermediate medium. Moreover, the first feature "above", "above" and "above" the second feature can be directly above or obliquely above the first feature, or only indicate that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "below" and "below" the second feature can be directly below or obliquely below the first feature, or only indicate that the horizontal height of the first feature is less than that of the second feature.

[0086] It should be noted that when an element is referred to as "fixed to" or "disposed on" another element, it can be directly on another element or there can be a middle element. When an element is considered to be "connected" to another element, it can be directly connected to another element or there can be a middle element. The terms "vertical", "horizontal", "up", "down", "left", "right" and similar expressions used herein are for illustrative purposes only and are not the only embodiment.

[0087] The above describes the preferred embodiments of the present application in detail. It should be understood that those skilled in the art can make many modifications and changes without creative labor according to the concept of the present application. Therefore, any technical solution obtained by logical analysis, reasoning or limited experiment on the basis of the prior art according to the concept of the present application shall be within the protection scope determined by the claims.

Claims

1. A pulley characterized by comprising a plurality of teeth (1) for engaging with teeth (2) of a toothed belt, said teeth (1) comprising a tooth top (11) and a tooth groove bottom (12), said teeth (2) comprising a tooth top (21) and a tooth groove bottom (22), an axial width of said tooth top (11) is greater than an axial width of said tooth groove bottom (12), an axial width of said tooth groove bottom (12) is less than an axial width of said tooth top (21), said tooth groove bottom (12) being configured to abut an axial middle portion of said tooth top (21). axial side distances of said tooth (1) monotonously transition from wide to narrow from a tooth top to a tooth groove bottom.

2. The wheel of claim 1, wherein axial side distances of said tooth (1) monotonously transition from a constant value to wide to narrow from a tooth top to a tooth groove bottom.

3. The wheel of claim 1, wherein a tooth thickness of said tooth (1) monotonously transitions from thin to thick from a tooth top to a tooth groove bottom.

4. The wheel of claim 2, wherein an axial width of said tooth top (11) is greater than or equal to an axial width of said tooth groove bottom (22).

5. The wheel of claim 1, wherein a tooth profile (101) of said tooth (1) is involute or circular arc.

6. The wheel of claim 1, wherein a curve of said tooth profile (101) of said tooth (1) comprises, in an extension direction of said tooth top (11) toward said tooth groove bottom (12), a first arc and a second arc connected in sequence, a radius of said first arc is greater than a radius of said second arc, and a center of said first arc is closer to a tooth top than a center of said second arc.

7. The wheel of claim 1, wherein said tooth groove bottom (12) is provided with a groove (121) for contacting a top end surface of said tooth top (21).

8. The wheel of claim 1, wherein an inner profile of said groove (121) is U-shaped.

9. The wheel of claim 8, wherein at least one of two transmission pulleys is the pulley as claimed in any one of claims 1 to 9.

10. A transmission comprising two transmission wheels and a toothed belt, characterized in that ​

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