JPH11101331A - Pulley with built-in clutch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pulley with a built-in clutch whereby without tumbling a sprag even when excessive torque is applied, a clutch function is prevented from being damaged. SOLUTION: A cam surface 12 of a sprag 5 in contact with a cylindrical surface 10 of an outer member 2 is formed by a first/second circular arc surface 12a, 12b of R1 , R2 radius of curvature and a third circular arc surface 12c of R3 radius of curvature considerably larger than these R1 , R2 , radius of curvature, so that load torque is increased, when a contact point B with the cylindrical surface 10 of the cam surface 12 is moved to the third circular arc surface 12c, so as to rapidly increase a wedge angle, in the case of momentarily applying excessive torque, between the sprag 5 and the cylindrical surface 10, a slip is generated, the sprag 5 is prevented from tumbling.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulley with a built-in clutch, and more particularly to a pulley with a built-in clutch used for driving an AC generator of an automobile.

[0002]

2. Description of the Related Art A pulley used for transmitting the rotation of a crankshaft of an automobile to an AC generator has a built-in clutch in order to rotate the rotating shaft of the AC generator having a large inertial force at a constant speed as much as possible. What was used is used. That is, the pulley with a built-in clutch transmits rotation when the rotation of the crankshaft is faster than the rotation of the AC generator, and when the rotation of the crankshaft becomes slower than the rotation of the AC generator, the pulley with a one-way clutch is engaged. By canceling the combination, the rotating shaft of the alternator is freely rotated.

[0003] A pulley with a built-in clutch used for driving an alternator of an automobile of this type or the like is disclosed in Japanese Patent Application No. Hei 8-25 filed by the present applicant for the purpose of compact design.
No. 6,630, there is a pulley with a built-in clutch.

The basic structure of the clutch built-in pulley is as follows:
A description will be given based on FIGS. 1 and 2 showing an embodiment of the present application. The pulley with a built-in clutch includes an inner member 1 attached to a shaft, a cylindrical outer member 2 disposed outside the inner member 1, and a retainer 3 interposed between these two members 1 and 2 to be incorporated. A plurality of steel balls 4 and sprags 5, and a pulley 6 fitted on the outer diameter surface of the outer member 2.

[0005] The outer diameter surface of the inner member 1 and the inner diameter surface of the outer member 2 have track grooves 7 and 8 extending in the circumferential direction of an arc-shaped cross section, and cylindrical surfaces 9 on both sides of each of the track grooves 7 and 8. ,
10 are provided. The plurality of steel balls 4 are fitted into the two raceway grooves 7 and 8 to form a bearing. The plurality of sprags 5 are arranged so as to straddle both the raceway grooves 7 and 8.

As shown in FIG. 5 (a), the sprags 5 have cam surfaces 11, 12 in contact with the cylindrical surfaces 9, 10 of the inner member 1 and the outer member 2, respectively.
₁ , R ₂ and R ₁ ′, R ₂ ′.
The holder 13 is pressed against the wall of the retainer 3 by the spring piece 13 to maintain its posture.

When the driving force is transmitted to the pulley 6 by a belt, and the outer member 2 fitted to the pulley 6 rotates in the direction of the arrow, the sprags 5 have their cam surfaces 12 and the cylindrical shape of the outer member 2. Upon contact with the surface 10, a clockwise rotation moment is received, and the cam surfaces 11, 12 formed by the circular arc surfaces engage the respective cylindrical surfaces 9, 10 of the inner member 1 and the outer member 2. Therefore, the shaft rotates together with the inner member 1, and the driving force is transmitted.

When the rotation speed of the shaft is higher than the rotation speed of the pulley 6, the pulley 6
As a result, the sprag 5 receives a counterclockwise rotational moment, and is disengaged from the cylindrical surfaces 9 and 10. Therefore, in this case, the shaft and the inner member 1 rotate freely without being restricted by the rotation of the pulley 6.

[0009]

The pulley with a built-in clutch of the type described above is composed of the cam surfaces 11 and 1 of the sprag 5.
2 is formed by two arc surfaces, and in FIG. 5A, when the sprag 5 rotates clockwise to increase the sprag height, the wedge angle gradually increases (FIG. 6). That is, when the load torque from the belt increases, the sprag height increases, and accordingly, the wedge angle increases to withstand the load.

Here, the sprag height H is (D−d) / 2, where d is the outer diameter of the inner member 1 and D is the inner diameter of the outer member 2, and the wedge angle α is 1
1 and a straight line connecting the contact point B of the cam surface 12 with the cylindrical surface 10 and a straight line extending through the contact point A from the rotation center O of the inner member 1. The intersection angle.

However, in the conventional sprag 5 having the characteristics as shown in FIG. 6, when an unexpectedly large torque is applied, the wedge angle α exceeds the limit value,
As shown in (b), there is a problem of falling clockwise. If the sprags 5 fall over in this way, even if the load is released, it cannot be returned to the original posture, and the clutch function is destroyed.

As a measure against the excessive torque as described above,
Although it is possible to design the clutch with a very large safety factor for the normal torque, this method is not preferable because it increases the size of the clutch and increases the cost.

An object of the present invention is to provide a pulley with a built-in clutch in which a sprag does not fall even when an excessive torque is applied and a clutch function is not destroyed.

[0014]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is directed to an inner race which has a raceway groove extending in the circumferential direction and an outer diameter surface provided with cylindrical surfaces on both sides thereof. A member and the outer member,
An outer member having a raceway groove extending in the circumferential direction and an inner diameter surface provided with a cylindrical surface on both sides thereof, a pulley fitted to the outer diameter surface of the outer member, and both raceway grooves of the inner member and the outer member. A plurality of rolling elements fitted and held, and a cam that is held between the cylindrical surfaces of the inner member and the outer member across the two raceway grooves and is formed to be able to engage with these cylindrical surfaces. In a pulley with a built-in clutch composed of a plurality of sprags having a surface, a cylindrical surface of the inner member or the outer member of the sprag or a cam surface facing both cylindrical surfaces is formed with a first arc surface whose wedge angle is gradually reduced. A second arc surface having a gradually increasing wedge angle, and a third arc surface connected to an end of the second arc surface on the side where the wedge angle is gradually increased and having a sharply increasing wedge angle. It was adopted.

A raceway groove extending in the circumferential direction and an outer diameter surface having cylindrical surfaces on both sides thereof; an inner member attached to the shaft; and an outer member disposed outside the inner member.
A pulley having a raceway groove extending in the circumferential direction and an inner diameter surface having cylindrical surfaces provided on both sides thereof; a plurality of rolling elements fitted and held in both raceway grooves of the inner member and the pulley; A clutch built-in pulley comprising a plurality of sprags having a cam surface formed so as to be engaged with the inner member and the pulley and held between the inner member and the pulley while straddling the same as described above. Can be employed.

That is, by providing a third arcuate surface having a sharply increasing wedge angle on the cam surface of the sprag facing the cylindrical surface of the outer member or the pulley, when a momentary excessive torque is applied to the pulley. Since the contact point of the sprag cam surface with the cylindrical surface moves from the second arc surface to the third arc surface and the wedge angle sharply increases, the movement of the contact point stops, Sliding occurs between the sprag and the cylindrical surface. At this time, the clutch slips, but the function can be restored if the excessive torque is released.

The same effect can be obtained even if the third arc surface is provided on the cam surface of the sprag facing the cylindrical surface of the inner member, or on both cam surfaces facing the two cylindrical surfaces. .

[0018]

Embodiments of the present invention will be described below. As shown in FIGS. 1 and 2, the clutch built-in pulley of the embodiment is incorporated with an inner member 1, a cylindrical outer member 2, and a retainer 3 held between these two members 1, 2. Steel balls 4 and sprags 5
And a pulley 6 fitted on the outer diameter surface of the outer member 2. The outer diameter surface of the inner member 1 and the inner diameter surface of the outer member 2 are connected in a circumferential direction of an arc-shaped cross section. The raceway grooves 7, 8 are provided with cylindrical surfaces 9, 10 on both sides of the raceway grooves 7, 8. The plurality of steel balls 4 are fitted into the two raceway grooves 7 and 8 to form a bearing portion, and the plurality of sprags 5 are arranged across the two raceway grooves 7 and 8.

The sprag 5 of this embodiment is shown in FIG.
As shown in FIG. 3, the cam surface 12 which comes into contact with the cylindrical surface 10 of the outer member 2 includes first and second circular arc surfaces 12a, 12b having radii of curvature R ₁ , R ₂ , and a radius of curvature R ₁ ,
Third circular arc surface 1 having a radius of curvature R ₃ which is considerably larger than R ₂
2c. The cylindrical surface 9 of the inner member 1
Is formed by two arc surfaces having a radius of curvature R ₁ ′ and R ₂ ′. The sprag 5 is a spring piece 1
At 3, it is pressed against the wall of the retainer 3 to maintain its posture.

The sprag height H of the sprag 5 described above.
The characteristic curve of the wedge angle α is as shown in FIG. 4, and the sprag height H _C when the contact point B of the cam surface 12 with the cylindrical surface 10 shifts from the arc surface 12b to the arc surface 12c. The wedge angle α sharply increases.

Therefore, when an instantaneous excessive torque is applied to the pulley 6, the sprag 5 rotates clockwise from the normal clutch state shown in FIG.
As shown in FIG. 5, in a state where the circular arc surface 12c is in contact with the cylindrical surface 10, the clockwise rotation is stopped to cause slippage between the circular surface 12c and the cylindrical surface 10, and as shown in FIG. Never.

In the above-described embodiment, the third arc surface has a large radius of curvature. However, the radius of curvature may be infinite and the third arc surface may be a flat surface.

Examples and comparative examples will be described below.

[0024]

EXAMPLE A pulley with a built-in clutch having a rated torque capacity of 4.45 kgfm incorporating a sprag having the shape shown in FIG. 3A was prepared.

[0025]

[Comparative Example] With the same rated torque capacity as the embodiment, FIG.
A pulley with a built-in clutch incorporating a sprag having the shape shown in (1) was prepared.

The pulleys with built-in clutches of the above Examples and Comparative Examples were mounted on shafts, and the load torque was gradually increased to investigate the limit torque at which the sprags would fall.

As a result, the pulley with a built-in clutch of the comparative example fell over at a load torque of 15 kgf · m, whereas the pulley with a built-in clutch of the embodiment fell over even when the load torque was increased to 25 kgf · m. Did not.

[0028]

As described above, according to the pulley with a built-in clutch of the present invention, the cylindrical surface of the inner member or the outer member of the sprag or the cam surface opposed to both cylindrical surfaces is formed by the first arc having a wedge angle gradually reduced. Surface, a second arc surface having a gradually increasing wedge angle, and a third arc surface connected to an end of the second arc surface on the side where the wedge angle is gradually increasing and having a sharply increasing wedge angle. Therefore, even if an instantaneous excessive torque is applied to the pulley, the clutch function can be restored again if the excessive torque is released without the sprags falling over.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of a pulley with a built-in clutch.

FIG. 2 is a partially omitted cross-sectional view along the line II-II in FIG.

FIGS. 3A and 3B are cross-sectional views illustrating an operation state of the sprag according to the embodiment;

FIG. 4 is a graph showing the relationship between the sprag height and the wedge angle of the sprag of FIG. 3;

FIGS. 5A and 5B are cross-sectional views illustrating an operation state of a conventional sprag.

6 is a graph showing the relationship between the sprag height and the wedge angle of the sprag of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inner member 2 Outer member 3 Cage 4 Steel ball 5 Sprag 6 Pulley 7, 8 Track groove 9, 10 Cylindrical surface 11, 12 Cam surface 12a, 12b, 12c Arc surface 13 Spring piece

Claims (2)

[Claims] 1. An orbiting groove having a circumferentially continuous raceway groove and an outer diameter surface having cylindrical surfaces on both sides thereof, an inner member attached to a shaft, and a raceway arranged outside the inner member and continuous in a circumferential direction. An outer member having an inner diameter surface having a groove and a cylindrical surface on both sides thereof; a pulley fitted to the outer diameter surface of the outer member; and being fitted into and held by both the raceway grooves of the inner member and the outer member. A plurality of rolling elements and a plurality of cam surfaces having a cam surface formed so as to be engaged with the cylindrical surfaces of the inner member and the outer member so as to straddle the two raceway grooves. In the clutch built-in pulley composed of a sprag, a cam surface facing the cylindrical surface of the inner member or the outer member of the sprag or a cylindrical surface of both of the sprag and the first arc surface having a wedge angle gradually reduced. , A second arc surface having a wedge angle gradually increasing, and a third arc surface connected to the end of the second arc surface on the side where the wedge angle is gradually increased and the wedge angle increasing rapidly. A pulley with a built-in clutch. 2. An orbital groove having a circumferentially continuous raceway groove and an outer diameter surface having cylindrical surfaces on both sides thereof, an inner member attached to a shaft, and a raceway arranged outside the inner member and continuous in a circumferential direction. A groove and a pulley having an inner diameter surface provided with a cylindrical surface on both sides thereof; a plurality of rolling elements fitted and held in both the raceway grooves of the inner member and the pulley; A clutch built-in pulley comprising a plurality of sprags having a cam surface formed to be able to engage with the inner member and the pulley held between the inner surface of the inner member and the pulley; The cam surface facing the cylindrical surface or both cylindrical surfaces has a first arc surface with a gradually decreasing wedge angle, a second arc surface with a gradually increasing wedge angle, and the wedge of the second arc surface. A pulley with a built-in clutch, wherein the pulley is provided with a third arcuate surface connected to the end on the side where the angle gradually increases and the wedge angle sharply increases.