JP2008064140A - One-way clutch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a one-way clutch capable of reducing the friction torque in idling by reducing the pressing force of a sprag urging member in advance. <P>SOLUTION: The one-way clutch comprises an inner ring 2 and an outer ring 3, a plurality of sprags 4 arranged in the circumferential direction between the inner and outer rings 2, 3 at a predetermined spacing, and a sprag urging member 5 for urging the sprags 4 in the engaging direction, and the sprags 4 are circumferentially rotated as the outer ring 3 is rotated. The centers G of gravity of at least a part of the sprags 4 out of the plurality of sprags 4 are arranged on the line L of the centrifugal force extending from an outer ring contact point A at which the sprags are brought into contact with the outer ring 3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a one-way clutch.

  A one-way clutch mounted on an automobile transmission or the like is generally one in which a plurality of sprags are arranged at predetermined intervals in the circumferential direction between an inner ring and an outer ring, and the inner ring and the outer ring are relatively in one direction. By rotating, the sprag is engaged between the inner and outer rings and power is transmitted. When the inner ring and the outer ring are relatively rotated in the other direction, the engagement of the sprags is released and the power transmission is interrupted.

  An example of such a one-way clutch is shown in FIG. The one-way clutch 101 is a one-way clutch 101 in which a large number of sprags 104 are arranged in the circumferential direction between an inner ring 102 and an outer ring 103, and each sprag 104 is always in elastic contact with the outer ring 103 on the rotation side. As the sprag 104, an engagement type first sprag 104a and a disengagement type second sprag 104b are arranged in a predetermined ratio in the circumferential direction (see Patent Document 1). Here, the center of gravity G1 of the first sprag 104a is positioned in the idling direction (arrow c direction) of the outer ring 103 with respect to the rotation center O1 of the sprag 104a, and each sprag 104a is centered on rotation by centrifugal force during idling of the outer ring 103. The second sprag 104b is urged to rotate counterclockwise about O1 (engagement direction, arrow A direction). The second sprag 104b has the center of gravity G2 counter-rotating the outer ring 103 with respect to the rotation center O2 of the sprag 104b. Each sprag 104b is urged to rotate clockwise (withdrawal direction, arrow B direction) about the rotation center O2 by centrifugal force when the outer ring 103 is idled.

The one-way clutch 101 urges the sprags 104 in the meshing direction by a return spring 105 that is a sprag urging member, thereby ensuring stable meshing properties, and also connecting the first sprags 104a and the second sprags 104b. When used in combination, the disengagement type second sprags 104b have their inner peripheral surfaces separated from the inner ring 102 as shown by the phantom line in FIG. 4 when idling, and the number of sprags 104 that contact the inner ring 102 during idling. This can reduce the friction torque during idling.
Japanese Utility Model Publication No. 5-89974

However, the one-way clutch 101 described in Patent Document 1 is mounted on an automobile or the like, and the rotational speed of the outer ring 103 is freely changed during use. The centrifugal force also changes in accordance with this change, and the contact force between the sprag 104 and the inner ring 102 also changes due to the change in centrifugal force. Therefore, the one-way clutch 101 takes into account these changes and the pressing force of the return spring 105 is excessive. It was set. For this reason, there was a limit in reducing the friction torque during idling.
The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a one-way clutch capable of reducing the friction torque during idling by previously weakening the pressing force of the sprag urging member. Yes.

The one-way clutch of the present invention includes an inner ring and an outer ring, a plurality of sprags arranged at predetermined intervals in the circumferential direction between the inner and outer rings, and a sprag urging member that urges the sprags in a meshing direction. In the one-way clutch in which the sprag rotates in the circumferential direction as the outer ring rotates,
The center of gravity of at least some of the plurality of sprags is arranged on a centrifugal force direction line extending from an outer ring contact where the sprag contacts the outer ring.

  According to such a configuration, since the center of gravity of at least a part of the sprags is disposed on the centrifugal force direction line extending from the contact point between the sprags and the outer ring, centrifugal force causes the sprags to mesh with each other during idling. Further, even if the centrifugal force changes, the action does not affect the contact force between the sprag and the inner ring. For this reason, since it is not necessary to preliminarily increase the pressing force of the sprag urging member, the pressing force can be set weak. Thereby, since the torque can be made constant at a low value, the friction torque during idling can be reduced.

In the one-way clutch, it is preferable that the centers of gravity of the plurality of sprags are arranged on a centrifugal force direction line extending from the outer ring contact.
In this case, since the pressing force of all the sprag urging members can be set weak, an effect of further reducing the friction torque during idling can be obtained.

  According to the one-way clutch of the present invention, the friction torque during idling can be reduced by previously weakening the pressing force of the sprag urging member.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following, “radial direction” and “circumferential direction” mean the radial direction and the circumferential direction in the one-way clutch (or inner and outer rings).
FIG. 1 is a side view of a one-way clutch 1 according to an embodiment of the present invention, and FIG. 2 is an enlarged cross-sectional view of the one-way clutch 1. The one-way clutch 1 includes an inner ring 2 and an outer ring 3, a plurality of sprags 4 equally spaced between the inner and outer rings 2 and 3 in the circumferential direction, and a sprag that urges the sprags 4 in the meshing direction. And a ribbon spring 5 as an urging member. Further, each sprag 4 is held by an inner holder 6 and an outer holder 7. In FIG. 1, the inner ring 2 and the outer ring 3 are indicated by two-dot chain lines in order to avoid the drawing from being complicated.

  Ribbon springs 5 (shown by thick lines in FIGS. 1 and 2) are generally annular, and are provided at predetermined intervals in the circumferential direction to accommodate sprags 4 and to the inside of the pockets 5p. And a tongue-like leaf spring portion 5a protruding toward the top (see FIG. 2). The ribbon spring 5 rotates with the sprag 4 rotating. The tip of the leaf spring portion 5a is always in contact with the sprag 4 regardless of the posture of the sprag 4, and is urged to rotate in the meshing direction with the sprag 4.

  Each of the inner cage 6 and the outer cage 7 has a substantially annular shape as a whole, and has sprag pockets at predetermined intervals in the circumferential direction. Of these, the inner cage 6 holds the radially inner portion of the sprag 4 by sprag pockets 6p (see FIG. 2) provided at predetermined intervals in the circumferential direction. Moreover, the outer holder | retainer 7 hold | maintains the radial direction outer side part of the sprag 4 by the sprag pocket 7p provided at the circumferential direction predetermined space | interval. Then, the sprags 4 are held while being inclined in the mesh release direction by making the phases of the sprag pockets 6p, 7p different between the inner and outer holders 6, 7.

  In the one-way clutch 1, the outer cage 7 is fixed to the outer ring 3. That is, as shown in FIG. 1, the outer retainer 7 has flanges (projections) 7a provided on the outer peripheral edge thereof at predetermined intervals in the circumferential direction and extending radially outward. The maximum diameter of the outer cage 7 formed by the above is set to be slightly larger than the inner diameter of the outer ring 3. Then, the outer retainer 7 is fitted to the inner peripheral surface 3 a of the outer ring 3 while the outer retainer 7 is fitted to the inner peripheral surface 3 a of the outer ring 3 with the outer surface of the flange 7 a pressed against the inner peripheral surface 3 a of the outer ring 3. Is fixed. Since the outer cage 7 is fixed to the outer ring 3 in this way, when the outer ring 3 rotates, the outer cage 7 rotates with the rotation, and the sprag 4 held by the outer cage 7 also extends in the circumferential direction. Rotates (moves in the circumferential direction).

  The inner cage 6 is not fixed to the inner ring 2, and the inner cage 6 and the inner ring 2 can freely rotate relative to each other. Further, the inner cage 6 is not fixed to the outer cage 7. However, since the inner retainer 6 and the outer retainer 7 both hold the common sprag 4, when the outer retainer 7 rotates due to the rotation of the outer ring 3, the inner retainer 6 also rotates accordingly.

  The one-way clutch 1 is engaged when the inner ring 2 and the outer ring 3 are relatively rotated in one direction (for example, the outer ring 3 is rotated in the direction of arrow a in FIG. 2), and power is transmitted between the inner and outer rings 2 and 3. The On the other hand, when the inner ring 2 and the outer ring 3 are rotated relative to each other in the other direction (for example, the inner ring 2 is rotated in the direction of arrow b in FIG. 2), the sprag 4 is tilted to disengage the sprag 4 from the inner ring 2. 3 and the inner ring 2 idle with each other.

  In the one-way clutch 1, the center of gravity G of all of the plurality of sprags 4 is a centrifugal force direction line L extending from the outer ring contact A where the sprag 4 contacts the inner peripheral surface 3a of the outer ring 3, that is, the outer ring contact A and the inner ring. It is arranged on a line connecting the two centers O. By arranging the center of gravity G of the sprag 4 on the centrifugal force direction line L extending from the outer ring contact A, the centrifugal force Mr at the time of idling causes the sprag 4 to move in either the meshing direction (arrow a direction) or the idling direction (arrow b direction). Therefore, even if the centrifugal force Mr changes, the action does not affect the contact force between the sprag 4 and the inner ring 2 at the inner ring contact B where the sprag 4 contacts the inner ring 2.

  Here, the relationship between the centrifugal force Mr and the contact force F between the sprag 4 and the inner ring 2 will be specifically described with reference to FIG. In a state where the sprag 2 is in contact with the outer peripheral surface 2a of the inner ring 2, the radius from the center O of the inner ring 2 to the center of gravity Go of the sprag is assumed to be Ro. Further, the outer ring contact where the sprag 4 contacts the inner peripheral surface 3a of the outer ring 3 is A, the inner ring contact where the sprag 4 contacts the outer peripheral surface 2a of the inner ring 2 is B, and the center of gravity Go of the sprag 4 and the outer ring contact A Let the horizontal distance be hr. When the outer ring 3 rotates with the sprag 4 at a predetermined speed, the centrifugal force Mr acting on the sprag 4 is M, and the rotational speed of the outer ring is ω.

It is expressed. In FIG. 3, the contact force F between the sprag 4 and the inner ring 2 can be represented by a vertical component of the reaction force received by the sprag 4 at the inner ring contact B. The pressing force of the ribbon spring 5 is P, the perpendicular distance between the parallel line of the pressing force vector of the ribbon spring 5 and the outer ring contact A is hp, the perpendicular length in the F vector direction of the distance between the contacts AB is h1, and the projection length When the height is h2 and the dynamic friction coefficient between the inner ring 2 and the sprag 4 is μ, the contact force F is given by the balance of the moment of the sprag 4 as follows:

It is expressed. Here, if hr is 0, that is, if the center of gravity Go of the sprag 4 is arranged on the centrifugal force direction line L extending from the outer ring contact A, the centrifugal force Mr becomes 0, and the contact force F becomes the centrifugal force Mr. It turns out that it is not influenced by. In this case, the centrifugal force Mr is balanced with the reaction force at the outer ring contact A. Therefore, by arranging the center of gravity G of the sprag 4 on the centrifugal force direction line L extending from the outer ring contact A, the contact force F between the sprag 4 and the inner ring 2 is influenced by the centrifugal force Mr that freely changes during use. Therefore, it is not necessary to set the pressing force of the sprag urging member 5 to be strong with the change of the centrifugal force Mr, and the pressing force of the sprag urging member 5 can be set to be weak beforehand. Thereby, since the torque can be made constant at a low value, the friction torque during idling can be reduced. Here, all the gravity centers G of the plurality of sprags 4 are arranged on the centrifugal force direction line L extending from the outer ring contact A, and the pressing force of all the sprag urging members 5 can be set to be weak. Therefore, the effect of reducing the friction torque during idling can be obtained.

The one-way clutch of the present invention is not limited to the above-described embodiment, and can be appropriately changed within the scope of the present invention.
For example, in the above-described embodiment, the case where the sprag 4 is rotated together with the outer ring 3 is shown. However, a method that does not involve a cage, for example, pivotally supports the sprag 4 to the outer ring 3 side is adopted. You can also In FIG. 1, the outer cage 7 is fixed to the outer ring 3 by the projection 7 a, but the shape is not limited, and a method of fixing to the outer ring 3 using another part is adopted. May be. The retainer that holds the sprag 4 has a double structure including an outer retainer 7 that is radially outer and an inner retainer 6 that is smaller in diameter than either of the outer retainer 7 and the inner retainer 6. Either of them may be omitted to form a single structure. Further, these cages may be divided into a plurality in the circumferential direction.
Further, the center of gravity G of all the sprags 4 does not have to be arranged on the centrifugal force direction line L extending from the outer ring contact A, and at least a part of the centers of gravity G of the sprags 4 are arranged at the above positions. Good. Also in this case, the friction torque during idling can be reduced. If the engagement type is used for the remaining sprags 4, the engagement can be ensured and the safety can be further improved.

1 is a side view of a one-way clutch according to an embodiment of the present invention. It is an expanded sectional view of the one-way clutch of FIG. It is explanatory drawing of the one-way clutch used in order to demonstrate the relationship between the centrifugal force and the contact force of a sprag and an inner ring. It is an expanded sectional view of the conventional one-way clutch.

Explanation of symbols

1 one-way clutch 2 inner ring 3 outer ring 4 sprag 5 ribbon spring (sprag urging member)
G Center of gravity A Outer ring contact L Centrifugal force direction line Mr Centrifugal force acting on sprag

Claims (2)

An inner ring and an outer ring; a plurality of sprags arranged at predetermined intervals in the circumferential direction between the inner and outer rings; and a sprag urging member that urges the sprags in a meshing direction. In a one-way clutch that rotates in a direction,
The one-way clutch, wherein a center of gravity of at least some of the plurality of sprags is disposed on a centrifugal force direction line extending from an outer ring contact point where the sprag contacts the outer ring.   2. The one-way clutch according to claim 1, wherein the center of gravity of all of the plurality of sprags is disposed on a centrifugal force direction line extending from the outer ring contact.

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