JP4626103B2 - Power transmission belt - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power transmission device that transmits power between two pulleys by a belt wound around them, and more particularly to the belt.
[0002]
[Prior art]
A power transmission device is known in which a belt that fits into the groove is wound between two pulleys having a substantially V-shaped groove in the circumferential direction, and power is transmitted between the pulleys via the belt. For example, in recent years, a belt type CVT (continuous variable ratio transmission) that has been adopted for vehicles is known as the aforementioned power transmission device.
[0003]
In this belt type CVT, the pulley is constituted by two sheaves having substantially conical surfaces, and the conical surfaces are faced to form the V-shaped groove. The belt is configured by arranging a plurality of blocks in the belt longitudinal direction, and these blocks are bundled by a hoop extending in the belt longitudinal direction. The side surface of this block contacts the side surface of the V-shaped groove of the pulley. Further, the hoop has a thin strip shape so that it can be bent in a plane perpendicular to the rotation axis of the pulley around which the hoop is wound. By changing the sheave interval, the wrapping diameter of the belt with respect to the pulley changes, whereby the input / output speed ratio can be varied.
[0004]
[Problems to be solved by the invention]
The belt of the above-described power transmission device extends linearly between the pulleys, but is curved at a portion wound around the pulley. Similarly, the hoop has a straight portion and a curved portion, but the cross-sectional shape orthogonal to the longitudinal direction of the hoop strip shape is affected by the above-described curvature and is different for each portion. If the hoop cross-sectional shape is inappropriate, wear or the like may occur due to interference with other parts, and durability may be reduced.
[0005]
An object of this invention is to provide the cross-sectional shape of the hoop which can improve the durability of a belt.
[0006]
[Means for Solving the Problems]
In order to solve the above-described problems, the belt of the power transmission device according to the present invention has a hoop shape that is a curved shape that protrudes outward from the belt in a cross section orthogonal to the longitudinal direction of the hoop. The shape is represented by a 1.7 to 2.2 degree function. Thereby, the deformation of the cross-sectional shape in the portion where the belt is wound around the pulley and curved is suppressed, and the durability of the belt is improved.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram illustrating an example of a belt-type CVT that is a belt-type power transmission device. An input pulley 16 and an output pulley 18 that rotate together with the shaft are provided on the input shaft 12 and the output shaft 14 of the CVT 10. The input pulley 16 includes an input fixed sheave 20 and an input movable sheave 22, and these sheaves 20, 22 have a substantially frustoconical shape whose opposing surfaces are part of a conical surface with the central axis of the input shaft 12 as an axis. is doing. The fixed sheave 20 is fixed to the input shaft 12 not only in the rotational direction but also in the axial direction. The movable sheave 22 is restricted in the rotational direction with respect to the input shaft 12 and is allowed to move in the axial direction. A fluid pressure cylinder 24 is arranged behind the movable sheave 22, that is, on the side opposite to the fixed sheave 20 in the axial direction. The movable sheave 22 itself functions as a piston and forms an actuator together with the fluid pressure cylinder 24. A working fluid is supplied from a fluid pressure line (not shown) to a fluid pressure chamber 26 formed by a fluid pressure cylinder 24 and a movable sheave 22 as a piston, and is discharged from the fluid pressure chamber 26, whereby the movable sheave 22. Moves along the input shaft 12.
[0008]
The output pulley 18 has a configuration substantially similar to that of the input pulley 16. That is, the output pulley 18 includes an output fixed sheave 28 whose movement is restricted in the rotational direction and the axial direction, and an output movable sheave 30 whose movement is restricted in the rotational direction and allowed in the axial direction. A fluid pressure cylinder 32 is disposed behind the movable sheave 30 and the movable sheave 30 as a piston constitutes an actuator including a fluid pressure chamber 34. The movement of the movable sheave 30 is controlled by this actuator.
[0009]
The two sheaves 20 and 22 of the input pulley and the two sheaves 28 and 30 of the output pulley respectively hold the belt 36 by the facing surfaces of the two sheaves, and the pulleys 16 and 18 engage with the belt 36.
[0010]
The belt 36 is formed in such a manner that a large number of thin plate blocks 38 having the shape shown in the figure are arranged, and these endless and flexible two hoops 40 are folded. The belt 36 is stretched over the input / output pulleys 16 and 18, and the side surface of the block 38 is engaged with the sheave. Since the width of the belt 36, that is, the width of the side surface of the block 38 is constant, the winding position of the belt 36 with respect to the pulleys 16 and 18, that is, the winding radii Rin and Rout are determined. . The transmission ratio is determined by the input / output wrapping radius ratio. Further, the wrapping radius can be changed by moving the movable sheaves 22 and 30, whereby the transmission ratio can be changed. Specifically, when the winding radius Rin of the input pulley 16 is to be increased, the working fluid is supplied into the fluid pressure chamber 26 and the actuator is operated in the direction in which the movable sheave 22 is advanced. Due to the pressing force, the winding radius Rin increases as the belt 36 is pushed out as the pulley 16 and the belt 36 rotate. When the winding radius Rin is reduced, the movable sheave 22 moves in the reverse direction, and the belt 36 moves so as to fall in the valley between the sheaves, and the winding radius Rin is reduced. The winding radius Rout is changed in the same manner on the output pulley 18 side, but the sheave movement is opposite in the input / output pulleys 16 and 18. That is, when trying to increase the winding radius by narrowing the sheave interval on one shaft, the other shaft is controlled synchronously to increase the winding radius by increasing the sheave interval. The
[0011]
FIG. 2 is a diagram showing a detailed structure of the belt 36. The blocks 38 are arranged by being bundled by a hoop 40 in the belt longitudinal direction. The left and right hoops 40 are each formed by laminating thin steel bands 42. The number of the steel bands 42 is mainly determined by the maximum transmission torque of the CVT, and of course it can be set to one if sufficient strength is achieved.
[0012]
FIG. 3 shows a cross-sectional shape of the hoop 40 perpendicular to the longitudinal direction of the belt. In the figure, the upper side is the outside of the belt wound around the pulleys 16 and 18. As shown in the drawing, the hoop 40 is given a curved or warped shape so as to be convex toward the outside of the belt. This is because the same shape is given to the individual steel bands 42 constituting the hoop 40.
[0013]
FIG. 4 is a diagram showing some examples of curved shapes of the hoop 40 or the steel band 42 (hereinafter simply referred to as a hoop). The curved shape of the hoop 40 is expressed by the following equation, where x is the width direction and y is the thickness direction, and each value is shown by substituting several values for the order n of x. The origin is the center of the hoop 40 in the width direction.
[0014]
[Expression 1]
y = x ⁿ
[0015]
FIG. 5 is a diagram showing a state of deformation of the cross-sectional shape of the hoop 40 at a portion where the hoop 40 having each cross-sectional shape shown in FIG. 4 is actually wound around the pulley and wound around the pulley. is there. It can be seen that the deformation of the hoop 40 is reduced within a certain range of the order n.
[0016]
FIG. 6 is a graph summarizing the width of the displacement in the thickness direction shown in FIG. 5, that is, the difference between the maximum value and the minimum value of the displacement with respect to the order n. As shown in this graph, it can be seen that the hoop displacement is small in the vicinity of the order n = 2. The allowable displacement in terms of durability performance is shown as TH in FIG. The range of the order n satisfying this is a range of 1.7 to 2.2. Preferably, the range of the order n is in the range of 1.8 to 2.1. More preferably, the range of the order n is in the range of 1.9 to 2.0.
[0017]
As described above, when the hoop 40 is in a straight state, the cross-section when the hoop 40 is curved is obtained by bending the cross-sectional shape to be expressed by a function of 1.7 to 2.2. Shape deformation can be reduced. And since this deformation | transformation is small, malfunctions, such as contacting only a specific site | part, with respect to the surrounding components which contact a hoop, such as a block, can be prevented.
[0018]
Although the present embodiment has been described with respect to the belt of the belt type CVT, the present invention is not limited to this, and the same structure is applied to a power transmission device that does not continuously change the gear ratio and does not have a gear shifting function. The present invention can also be applied to a belt having the same.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a belt type CVT.
FIG. 2 is a view showing a detailed structure of a belt.
FIG. 3 is a view showing a cross section in the longitudinal direction of a hoop or a steel band.
4 is a diagram illustrating an example of a function indicating a shape of an orthogonal cross section in FIG. 3. FIG.
5 is a diagram showing a deformed state in a belt bending portion such as a hoop having an orthogonal cross section shown in FIG. 4; FIG.
FIG. 6 is a diagram showing the relationship between the order of a function representing the cross-sectional shape of the hoop and the amount of deformation at the belt curved portion.
[Explanation of symbols]
36 belts, 38 blocks, 40 hoops, 42 steel belts.

Claims (2)

Between the two pulleys, the belt of the power transmission device that transmits power through the belt wound around them,
A plurality of blocks arranged in the longitudinal direction of the belt;
A hoop having a belt shape extending in the longitudinal direction of the belt, and bundling the blocks in a belt shape;
Have
When the belt is linear, the hoop is curved so as to be convex toward the outer periphery of the belt in a cross section orthogonal to the longitudinal direction of the belt, and the curved shape is 1.7 to 2.2. Is the following function,
Power transmission belt. The belt of the power transmission device according to claim 1, wherein the hoop is formed by stacking a plurality of bands, and the band has a curved shape similar to that of the hoop.

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