JP2008095864A - One-way clutch sprag and one-way clutch - Google Patents

Abstract

A sprag for a one-way clutch and a one-way clutch capable of reducing the disengagement speed and improving the meshing life of a sprag and an inner ring without changing the contour shape of the sprag.
In the sprag, a cut portion is formed with respect to the sprag having a uniform thickness on both sides of the outer cam surface side half portion 41, the outer cam surface side half portion 41 is thin, and the inner cam surface side is formed. The half part 42 is a thick stepped shape. Both side surfaces of the outer cam surface side half 41 are provided so as to be flat and symmetrical with respect to a surface orthogonal to the axial direction. Thus, the outer cam surface side half 41 is lighter than the inner cam surface side half 42.
[Selection] Figure 1

Description

  The present invention relates to a sprag for a one-way clutch used in a power transmission device such as a transmission mechanism of an automobile and a one-way clutch provided with the sprag.

  Conventionally, as a one-way clutch using sprags, the inner ring and outer ring, a plurality of sprags formed with cam surfaces in contact with the outer peripheral surface of the inner ring and the inner peripheral surface of the outer ring, and the circumferential position of the sprags must be regulated. A cage having a plurality of pockets for individually accommodating sprags and a ribbon spring that is formed with a pocket for accommodating sprags and urges the sprags in a direction to lock the inner and outer rings is known ( Patent Document 1).

The sprag is manufactured by cold forging or the like, and its thickness (dimension in the axial direction) is constant (uniform thickness) regardless of the location.
JP 2001-330062 A

  The sprag for a one-way clutch as described above generates a centrifugal force required for the sprag to float above the inner ring by the rotation of the outer ring. If the outer ring rotation speed (hereinafter referred to as “disengage speed”) required for the sprags to rise is lowered, the friction between the sprags and the inner ring is reduced and the engagement life is extended.

  Therefore, in the past, in order to reduce the disengagement speed, the sprag contour shape (the shape viewed from the axial direction of the one-way clutch) was changed. However, the sprag contour shape is different from the interference with the cage. There is a limit to reducing the disengagement speed because the design freedom is low due to constraints such as the interference with the ribbon spring.

  An object of the present invention is to provide a sprag for a one-way clutch and a one-way clutch capable of reducing the disengagement speed and improving the engagement life between the sprag and the inner ring without changing the contour shape of the sprag. .

The sprag for a one-way clutch according to claim 1 is formed between an inner ring and an outer ring with an inner cam surface in contact with the outer peripheral surface of the inner ring and an outer cam surface in contact with the inner peripheral surface of the outer ring, and rotates integrally with the outer ring. A sprag for a one-way clutch that floats from an inner ring when centrifugal force increases, wherein the outer cam surface side half is lighter than the inner cam surface side half.
The sprag side view shape (the shape seen from the axial direction) is the same as a known one, and is a shape (so-called saddle shape) in which the substantially central portion between the inner cam surface and the outer cam surface is constricted. The outer cam surface side half is the outer cam surface side half and the inner side portion is the inner cam surface side half of the constricted portion, and the outer cam surface side half is the inner cam surface side while maintaining the side profile. The weight is reduced (thinned) relative to the half. The line separating the two halves is not limited to a straight line connecting the constricted portions, but may be a curved line (for example, an arc shape convex toward the inner cam surface).

  The sprag is rotated synchronously with the outer ring. When this rotation causes a centrifugal force to act on the sprag, and when shifting from the locked state to the free state, the outer cam contact point (the sprag outer cam surface and the outer ring ) Contact moment) (hereinafter referred to as “disengage moment”), the inner cam surface of the sprag is detached from the inner ring. To reduce the disengage speed, the disengage moment can be increased.

  The sprag may have a stepped shape with a thin half on the outer cam surface side and a thick wall on the inner cam surface side. A cut portion such as a through hole or a notch may be provided on the cam surface side half.

    Preferably, the sprag has a stepped shape in which the outer cam surface side half is thin and the inner cam surface side half is thick (Claim 2).

  A tangential force represented by (outer ring load torque) ÷ (outer ring raceway radius) acts on the outer cam surface of the sprag, and (inner ring reaction torque) ÷ (inner ring raceway radius) on the inner cam surface. A tangential force expressed by Here, the load torque and the reaction torque are the same magnitude, and the outer ring raceway radius (the radius of the outer peripheral surface of the outer ring) is larger than the inner ring raceway radius (the radius of the outer peripheral surface of the inner ring). The surface tangential force is greater than the outer cam surface tangential force, and the inner cam surface contact surface pressure is greater than the outer cam surface contact surface pressure. That is, the inner cam surface receives a larger force than the outer cam surface, and is relatively easily damaged.

  Therefore, as in the case of the sprag according to claim 2, the inner cam surface side half is relatively easily damaged by forming a stepped shape in which the outer cam surface side half is thin and the inner cam surface side half is thick. As the part becomes thicker, durability against frictional contact on the inner cam side is improved, and not only the disengagement speed is reduced due to the movement of the center of gravity, but also damage due to wear of the sprag and the inner ring can be reduced. And the meshing life can be increased.

The sprag for a one-way clutch according to claim 3 is formed between an inner ring and an outer ring, with an inner cam surface in contact with the outer peripheral surface of the inner ring and an outer cam surface in contact with the inner peripheral surface of the outer ring, and rotates integrally with the outer ring. A sprag for a one-way clutch that floats from the inner ring when the centrifugal force increases. The distance between the outer cam contact point where the outer cam surface contacts the outer ring and the sprag center of gravity is R, and the centrifugal force direction and the outer cam contact point direction at the sprag center of gravity position With reference to a sprag having a uniform thickness with an angle of θ being the angle, the contour shape is maintained and a part of the sprag is cut off. The distance between the outer cam contact point and the sprag center of gravity is R ′, The angle formed by the centrifugal force direction and the outer cam contact point direction at the sprag center of gravity is θ ′, and Rsinθ <R′sinθ ′.
When the distance between the outer cam contact point where the outer cam surface contacts the outer ring and the sprag center of gravity is R, and the angle between the centrifugal force direction and the outer cam contact point direction at the sprag center of gravity is θ, the disengage moment is the centrifugal force It is expressed as × R × sin θ, and by increasing this, the disengagement speed can be reduced.

  As described above, in order to cut off a part of the sprag, it suffices to provide a notch or a through hole. At this time, as in claim 2, the outer cam surface side half of the sprag is thin and the inner cam surface The side half is preferably thick and stepped. However, in order to reduce the disengagement speed, the disengage moment may be increased. Therefore, R ′ and θ ′ satisfying Rsinθ <R′sinθ ′. It is also possible to cut the sprags so that In this case, it is possible to make only a part thick without reducing the thickness of the entire outer cam surface half, and it is not limited to cutting only the outer cam surface half. A part of the surface side half may be cut off, which increases the degree of design freedom.

  The sprags can be manufactured by cold forging, and can also be manufactured by drawing.

  In the one-way clutch according to claim 4, the inner ring and the outer ring, a plurality of sprags formed with cam surfaces in contact with the inner ring outer circumferential surface and the outer ring inner circumferential surface, and the sprags individually to regulate the circumferential positions of the sprags. Each sprag is claimed in a one-way clutch in which a plurality of pockets for receiving the sprags and a ribbon spring for forming the pockets for receiving the sprags and urging the sprags in a direction to lock the inner and outer rings are arranged. Any one of Items 1 to 3 is used.

  According to the sprag for a one-way clutch and the one-way clutch of this invention, the outer cam surface side half is lighter than the inner cam surface side half, so that the inner cam of the outer ring sprag can be rotated at a lower rotational speed than in the prior art. Since the surface can be lifted, the friction torque between the sprag and the inner ring can be reduced. Further, by providing a stepped shape in which the outer cam surface side half is thin and the inner cam surface side half is thick, the service life of the sprag and the inner ring can be further extended.

  The present invention will be described below with reference to the drawings.

  FIG. 1 shows a one-way clutch according to the present invention, and FIGS. 2 to 4 show a sprag according to the present invention.

  The one-way clutch (1) includes an inner ring (2) and an outer ring (3), an inner cam surface (4a) that contacts the outer peripheral surface of the inner ring (2), and an outer cam surface (4b) that contacts the inner peripheral surface of the outer ring (3). Inner cage in which a plurality of formed sprags (4) and a plurality of pockets (P1) (P2) for individually accommodating the sprags (4) to regulate the mutual circumferential position of the sprags (4) are formed (5) and the outer cage (6), and a pocket (P3) that is located between the inner cage (5) and the outer cage (6) and accommodates the sprag (4) is formed, and the inner and outer rings (2 ) (3) and a ribbon spring (7) for urging the sprag (4) in the locking direction.

  The outer cage (6) is fixed to the outer ring (3), and the inner cage (5) is not fixed to either the inner ring (2) or the outer ring (3).

  This one-way clutch (1) is used for outer ring rotation drive, and the sprag (4) is formed so that its inner cam surface (4a) floats above the inner ring (2) when centrifugal force increases. Has been.

  According to this one-way clutch (1), when the inner ring (2) rotates relative to the outer ring (3) in the direction of arrow A, the sprag (4) is brought into frictional contact with the inner ring (2), thereby As shown in FIG. 1, the spring (7) moves in a standing direction while being urged by elasticity, and is engaged between the inner ring (2) and the outer ring (5). The inner and outer rings (2) and (3) rotate together. Thus, when the rotational speed of the outer ring (3) moved in the direction C increases and the inner ring (2) rotates relative to the outer ring (3) in the direction opposite to the arrow A, the sprag (4) becomes It moves as indicated by arrow B against the elasticity of the ribbon spring (7), thereby releasing the locked state between the inner ring (2) and the outer ring (3), and the outer ring (3) is moved to the inner ring (2). Continue to rotate in a disconnected state.

  As shown in FIG. 2, the sprag (4) has cut portions (41a) and (41b) formed on the entire side surfaces of the outer cam surface side half (41) with respect to the uniform thickness sprags indicated by the two-dot chain line. The outer cam surface side half (41) is thin and the inner cam surface side half (42) is thick. The cut portions (41a) and (41b) are formed so that the boundary between the thin wall portion and the thick wall portion becomes a convex curve toward the inner cam surface (4a), as shown in FIG. As shown in FIG. 4B, both side surfaces of the outer cam surface side half (41) are provided so as to be flat and symmetrical with respect to a surface orthogonal to the axial direction. Thus, the outer cam surface side half (41) is lighter than the inner cam surface side half (42).

  FIG. 3 schematically shows the disengage moment acting on the sprag (4) in comparison with the disengage moment acting on the uniform thickness sprag. In the figure, the force acting on the uniform thickness sprag is indicated by a two-dot chain line, the center of gravity is O, the distance between the outer cam contact point and the sprag center of gravity O is R, and the centrifugal force acting on the center of gravity O is F. When the angle between the centrifugal force direction and the outer cam contact point direction at the center of gravity O is θ, the disengage moment = F × R × sin θ. On the other hand, according to the sprag (4) of the present invention, since the outer cam surface side half (41) is lighter than the inner cam surface side half (42), the center of gravity O 'is the inner cam surface ( As a result, the distance R ′ between the outer cam contact point and the center of gravity O ′ increases, and the disengage moment = F × R ′ × sin θ ′ can be increased. The inner cam surface (4a) of the sprag (4) is in frictional contact with the inner ring (2) until it is lifted, but the sprag (4) is larger than the sprag with a uniform thickness. ) Is easily lifted, so that the sprag (4) can be prevented from being damaged by frictional contact.

  FIG. 4 shows forces acting on the cam surfaces (4a) and (4b) of the sprag (4). In the figure, the sprag (4) has a load torque T at the outer cam contact point (contact point between the sprag outer cam surface (4b) and the outer ring (3)), and the inner cam contact point (sprag inner cam surface (4a ) And the inner ring (2) at the contact point), the reaction force torque T acts respectively. As a result, a tangential force Fe expressed by (load torque T) / (outer ring raceway radius Re) acts on the outer cam surface (4b) of the sprag (4), and the inner cam surface (4a) A tangential force Fi expressed by (reaction torque T ′) ÷ (inner ring race radius Ri) acts. Here, the load torque T (= Fe × Re) and the reaction force torque T ′ (= Fi × Ri) have the same magnitude, and the outer ring raceway radius Re is larger than the inner ring raceway radius Ri. The tangential force Fi of the inner cam surface (4a) is greater than the tangential force Fe of the outer cam surface (4b), and the contact surface pressure of the inner cam surface (4a) is greater than the contact surface pressure of the outer cam surface (4b). growing. That is, the inner cam surface (4a) receives a larger force than the outer cam surface (4b), and is relatively easily damaged. According to the above sprag (4), the inner cam surface side half (42), which is relatively susceptible to damage, is made thick, and as a result, durability against frictional contact on the inner cam surface (4a) side is increased. As a result, not only can the disengage speed be reduced due to the movement of the center of gravity, but also damage due to wear of the sprag (4) and the inner ring (2) can be reduced, and the engagement life can be increased.

  In FIG. 3, in order to increase the disengage moment = F × R ′ × sin θ ′, the shape of the sprag (4) is not limited to that shown in FIG. In the range satisfying Rsinθ <R′sinθ ′, where R ′ is the distance between the outer cam contact point and the sprag centroid, and θ ′ is the angle formed by the centrifugal force direction and the outer cam contact point direction at the sprag centroid position, Various ablation shapes are possible.

  In the above embodiment, the sprag (4) is held by the inner cage (5) and the outer cage (6), and the ribbon spring (7) is interposed between the inner cage (5) and the outer cage (6). Although the arrangement example is shown, the present invention can also be applied to a one-way clutch having a structure in which the sprag (4) is held by one cage and the ribbon spring (7) is arranged inside the cage. .

FIG. 1 is a cross-sectional view showing a main part of a one-way clutch according to the present invention. 2A and 2B are views showing a sprag for a one-way clutch according to the present invention, in which FIG. 2A is a side view, and FIG. 2B is a cross-sectional view taken along line bb in FIG. FIG. 3 is a diagram schematically showing the force acting on the center of gravity of the sprag. FIG. 4 is a diagram schematically showing the force acting on the cam surface of the sprag.

Explanation of symbols

(1) One-way clutch
(2) Inner ring
(3) Outer ring
(4) Sprag
(5) Inner cage
(6) Outer cage
(7) Ribbon spring
(41) Outer cam surface side half
(42) Inner cam surface side half

Claims (4)

For a one-way clutch that has an inner cam surface that contacts the outer peripheral surface of the inner ring and an outer cam surface that contacts the inner peripheral surface of the outer ring, is arranged between the inner ring and the outer ring, rotates together with the outer ring, and rises above the inner ring when centrifugal force increases Sprags,
A sprag for a one-way clutch, characterized in that the outer cam surface side half is lighter than the inner cam surface side half.   The sprag for a one-way clutch according to claim 1, wherein the outer cam surface side half is thin and the inner cam surface side half is thick. For a one-way clutch that has an inner cam surface that contacts the outer peripheral surface of the inner ring and an outer cam surface that contacts the inner peripheral surface of the outer ring, is arranged between the inner ring and the outer ring, rotates together with the outer ring, and rises above the inner ring when centrifugal force increases Sprags,
Based on sprags of uniform thickness where the distance between the outer cam contact point where the outer cam surface contacts the outer ring and the sprag center of gravity is R, and the angle between the centrifugal force direction and the outer cam contact point direction is θ at the sprag center of gravity position. The distance between the outer cam contact point and the sprag center of gravity is R ′, and the centrifugal force direction and the outer cam contact point direction are formed at the sprag center of gravity position. A sprag for a one-way clutch, wherein the angle is θ ′ and Rsinθ <R′sinθ ′.   Inner and outer rings, a plurality of sprags formed with cam surfaces in contact with the inner ring outer peripheral surface and the outer ring inner peripheral surface, respectively, and a plurality of pockets for individually accommodating the sprags to regulate the circumferential position of the sprags are formed. And a ribbon spring for energizing the sprags in a direction in which the inner and outer rings are locked, and each sprag is defined in any one of claims 1 to 3. One-way clutch characterized by that.

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