JP2007092865A - One-way clutch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a one-way clutch exerting a torque limiter function certainly in accordance with the size of the input torque in the transmitting direction and free of the risk that dint is generated on the raceway surface by any of sprags. <P>SOLUTION: The one-way clutch is equipped with a plurality of sprags 4 installed in the circumferential arrangement in an annular space 3 between an inner 1 and an outer raceway ring 2, retainers 5 and 6 to hold the sprags 4, and springs 7 for energizing the sprags 4 in the direction of rising within the annular space 3, wherein the sprags 4 are furnished at the outside and inside surfaces with cam faces 41 and 42 contacting with the raceway rings 1 and 2, and one of the cam faces, outer or inner, 42 is composed of a curved surface 42a and a flat surface 42b continued on its lock side to the curved surface 42a. The sprag height Hc when sprag 4 comes into contacts with the corresponding raceway ring 2 at the inflection point 42c between the curved surface 42a and the flat surface 42b is set in J<Hc<J×1.05, where J represents the spacing between the two raceway rings 1 and 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a one-way clutch using a sprag.

  One-way clutches are installed in an annular space formed between inner and outer races, and transmit one-way rotation of the drive raceway to the driven raceway via a sprag. .

  The one-way clutch includes a plurality of sprags arranged along the circumferential direction in an annular space between the inner and outer races, a retainer for holding these sprags, and the sprag standing up in the annular space. And an annular spring body that is urged in the direction of movement.

  Sprag pockets are respectively formed in the cage and the spring body, and the sprags are accommodated in these pockets so as to penetrate in the radial direction.

  In the above configuration, when one of the race rings, for example, the outer ring, rotates in one direction with respect to the inner ring, each sprag stands up along the radial direction in the annular space between the inner and outer rings and stretches between the inner and outer rings. Thus, the locked state is established, and the rotation of the outer ring in one direction is transmitted to the inner ring. When the outer ring rotates in the opposite direction with respect to the inner ring, each sprag is in a posture that falls to follow the rotation of the outer ring, and the outer ring idles with respect to the inner ring (see, for example, Patent Document 1).

  By the way, in the one-way clutch described above, when an excessive torque is applied in the transmission direction, the sprag exceeds the predetermined torque transmission position with respect to both races and further tries to bite between both races. The clutch itself or the inner and outer rings may be deformed or damaged. Further, since excessive torque is transmitted to the driven side of the one-way clutch, the driven member may be damaged.

On the other hand, a flat surface is provided on a part of the cam surface formed on the sprag, and when an excessive torque is applied in the transmission direction, the flat surface comes into contact with the raceway surface of the raceway. There is one in which a sprag is caused to slip with respect to a raceway (see Patent Document 2). This one-way clutch operates like a torque limiter for excessive input torque in the transmission direction, and the driving-side raceway is idled with respect to the driven-side raceway, and the driven-side raceway is excessive. Torque is not transmitted. As a result, the one-way clutch itself or the inner and outer rings can be prevented from being damaged, and the member linked to the driven side of the one-way clutch can also be prevented from being damaged.
JP 2003-28199 A JP-A-60-151426

  However, as described above, in a one-way clutch having a torque limiter function, an indentation may be formed on the raceway surface due to pressure contact and sliding between the flat surface of the cam surface of the sprag and the raceway surface of the raceway ring. As a one-way clutch used in a place where excessive torque is input, it is not preferable.

  In addition, in the conventional one-way clutch having a torque limiter function, there is a large variation in the torque value when slip occurs between the sprag and the raceway with respect to the excessive input torque in the transmission direction. Depending on the size, it may not operate as a torque limiter, and there is a problem in reliably preventing deformation and breakage of the one-way clutch and its driven side members.

  In the present invention, when the torque input in the transmission direction becomes excessive, the torque limiter function is surely exhibited according to the magnitude of the input torque value, and indentations are formed on the raceway surfaces of the inner and outer races by sprags. The challenge is not to stick.

  The inventor of the present invention has studied various operations when the one-way clutch performs the torque limiter function, and as a result, indentations are generated on the raceway surface of the raceway ring, or slip occurs between the flat surface of the sprag and the raceway ring. The large variation in the torque value is mainly caused by the sprag height at the time of locking (the length between the contact point of the sprag with one raceway and the contact point with the other raceway). As a result, the inventors have conducted experiments based on this finding and invented a one-way clutch having the following configuration.

That is, the one-way clutch according to the present invention includes a plurality of sprags arranged along the circumferential direction in an annular space formed between inner and outer races, a cage for holding these sprags, A spring body that urges the sprags in a direction to stand up in the annular space, each sprag having a cam surface that contacts the outer ring side and the inner ring side corresponding to the raceway, and the both cam surfaces One of the cam surfaces is composed of a curved surface and a flat surface continuous to the curved surface on the lock side, and the sprag is in contact with the corresponding raceway at the inflection point between the curved surface and the flat surface. The sprag height Hc is equal to the radial distance J between both race rings.
J <Hc <J × 1.05.

  According to the above configuration, in response to an excessive input torque in the transmission direction, the contact portion between the cam surface of the sprag and the corresponding bearing ring moves from the curved surface of the cam surface to the flat surface beyond the inflection point. When the flat surface contacts the raceway almost entirely over a wide range, slip occurs between the sprag and the raceway, and the entire one-way clutch operates as a torque limiter.

  In this case, the flat surface of the sprag is in pressure contact with the race and slides, but there is no indentation on the race. This has been confirmed by experiments, and the height of the sprags that are stretched between the two races when shifting from the locked state to the slipping state as the torque limiter is greater than the spacing between the two races. This is presumably because the contact surface pressure against the raceway of the flat surface of the sprag is suppressed to an appropriate value without becoming excessive.

  Moreover, in the said structure, there is no big dispersion | variation in the input torque value at the time of exhibiting a torque limiter function. This is also confirmed by experiments. As described above, since the sprag height at the inflection point of the cam surface is not excessive, it is considered that the transition from the locked state to the sliding state is smoothly performed without being caught or having a large resistance.

  As a more desirable configuration, the sprag height at the inflection point of the cam surface is set to 1.03 or less of the radial interval between the inner and outer races. In this configuration, the one-way clutch operates the torque limiter with an input torque less than three times the rated torque, and the torque exceeding three times the rated torque is transmitted to the driven side of the one-way clutch. Therefore, deformation and breakage of the driven member can be reliably prevented.

  According to the present invention, for excessive input torque in the transmission direction, the torque limiter function can be surely exhibited according to the magnitude of the input torque value, and indentations can be applied to the race. Is prevented.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 to FIG. 3 show the best embodiment of the present invention. FIG. 1 is a front view showing a one-way clutch according to the best embodiment in a partial cross section along the radial direction. 1 is a cross-sectional view taken along the axial direction of the one-way clutch in FIG. 1, and FIG. 3 is an enlarged front view of a sprag that is a part of the one-way clutch in FIG.

  As shown in FIGS. 1 and 2, the one-way clutch of the present embodiment is provided between an outer ring (outer raceway) 1 and an inner ring (inner raceway) 2 that are arranged concentrically inside and outside in the radial direction. A plurality of sprags 4, 4... That are arranged along the circumferential direction in an annular space 3 formed between the inner and outer wheels 1, 2, and these sprags 4. An outer cage 5 that holds the sprag 4 on the outer circumferential side, an inner cage 6 that holds the sprag 4 on the inner circumferential side of the annular space 3, and a direction in which the sprag 4 rises along the radial direction between the inner and outer wheels 1 and 2. And a ribbon spring 7 which is a spring body to be urged.

  The outer cage 5, the inner cage 6 and the ribbon spring 7 are respectively formed with pockets 5a, 6a and 7a for accommodating the sprags 4, and the sprags 4 are radially formed in these pockets 5a, 6a and 7a. It is housed in a penetrating state.

  Each sprag 4 has cam surfaces 41 and 42 that contact the outer ring 1 and the inner ring 2 on the outer diameter side and the inner diameter side. As shown in FIG. 3, the cam surface 41 on the outer diameter side is a curved surface composed of an arc with the point Qo set at the midway in the radial direction of the sprag 4 as the center (arc center) and the radius as Ro. . This curved surface is formed over a range So before and after in the circumferential direction.

  The cam surface 42 on the inner diameter side includes a curved surface 42a and a flat surface 42b continuous with the curved surface 42a. The curved surface 42a is formed on the free side of the cam surface 42 on the inner diameter side (specifically, when the sprag 4 is in a posture that is largely inclined with respect to the radial direction and becomes free with respect to the inner and outer rings 1 and 2, the inner ring 2 3 is formed on the close contact side and on the right side in FIG. 3 and is formed of a circular arc. The circular arc center Qi is set to a position deviated in the circumferential direction from the circular arc center Qo of the cam surface 41 on the outer diameter side. Has been. The curved surface 42a is formed over a range Si before and after the circumferential direction as a radius Ri.

  The flat surface 42b of the cam surface 42 on the inner diameter side is on the lock side of the cam surface 42 (specifically, the sprag 4 is in an upright position along the radial direction, and is locked with respect to the inner and outer rings 1 and 2). Sometimes, it is formed on the side close to and in contact with the inner ring 2 and on the left side in FIG. 3, and smoothly continues to the curved surface 42a via an inflection point 42c. The flat surface 42b is formed over a range Sc from the inflection point 42c to the lock side.

  In the illustrated embodiment, the flat surface 42b is formed in a shape along the tangent line of the curved surface 42a at the inflection point 42c, thereby smoothly continuing to the curved surface 42a. In addition, by forming a small-diameter curved surface having a shorter radius of curvature than the curved surface 42a on the lock side (left side in FIG. 3) of the curved surface 42a, the curved portion of the cam surface 42 has a two-stage curved configuration, and the tangent to the small-diameter curved surface The flat surface 42b may be smoothly continuous with the curved surface 42a by forming the flat surface 42b along the shape.

  In the sprag 4, the length between the point where the outer diameter side cam surface 41 contacts the outer ring 1 and the point where the inner diameter side cam surface 42 contacts the inner ring 2 is the sprag height. For example, when the inflection point 42c between the curved surface 42a and the flat surface 42b of the cam surface 42 on the inner diameter side is in contact with the inner ring 2, the cam surface 41 on the outer diameter side is in contact with the outer ring 1 at the point 41c. Then, the length between the point 42c and the point 41c becomes the sprag height Hc at this time. Further, the radial line Rr passing through the contact point between the sprag 4 and the inner ring 2 (inflection point 42c in the illustrated example of FIG. 3) from the rotation center Or of the inner and outer rings 1 and 2 is the inner and outer rings 1 and 2 of the sprag 4. The angle θ formed with the line segment connecting the contact points with 2 (the line segment S connecting the point 42c and the point 41c in FIG. 3) is a strat angle (also referred to as a wedge angle) at this time.

  In the one-way clutch configured as described above, any of the inner and outer wheels 1 and 2 may be a driving wheel. Hereinafter, an operation when the outer wheel 1 is a driving wheel will be described.

  When the outer ring 1 rotates in one direction with respect to the inner ring 2 (the clockwise direction indicated by the arrow A in FIGS. 1 and 3), each sprag 4 is in a tilted position so as to follow the rotation of the outer ring 1 and is free. The outer ring 1 is idled with respect to the inner ring 2.

  When the outer ring 1 rotates in the opposite direction with respect to the inner ring 2 (counterclockwise direction indicated by an arrow B in FIGS. 1 and 3), each sprag 4 follows the radial direction in the annular space 3 between the inner and outer rings 1 and 2. As a result, the inner ring 1 and the outer ring 1 are stretched to be locked, and the rotation of the outer ring 1 in the direction of arrow B is transmitted to the inner ring 2. In this case, on the inner diameter side of the sprag 4, the curved surface 42 a of the cam surface 42 is in pressure contact with the raceway surface of the inner ring 2.

  Next, when an excessive torque is applied to the outer ring 1 in the direction of the arrow B which is the transmission direction, the sprag 4 rises along the radial direction, and the inner ring 2 of the cam surface 42 is located on the inner diameter side of the sprag 4. Is moved from the curved surface 42a over the inflection point 42c to the flat surface 42b, and the flat surface 42b comes into contact with the raceway surface of the inner ring 2. Therefore, the sprag 4 slips with respect to the inner ring 2, and the outer ring 1 idles with respect to the inner ring 2. Thus, the one-way clutch operates like a torque limiter and excessive torque is not transmitted to the inner ring 2.

  In this case, in the conventional one-way clutch, the flat surface 42b of the cam surface 42 of the sprag 4 is pressed against and slides on the raceway surface of the raceway such as the inner ring 2 to cause indentation on the raceway surface or the sprag 4 There may be a large variation in the torque value when slippage occurs between the flat surface 42b and the raceway surface. The inventor of the present invention considers that the occurrence of such a problem is related to the sprag height at the time of locking, and the sprag height at the time of locking is constant relative to the radial interval J between the inner and outer rings 1 and 2. A number of different sprags 4 are prepared, and a transmission experiment is performed with a one-way clutch including these sprags 4, and the minimum input torque at which slip occurs between the flat surface 42b of the sprag 4 and the inner ring 2 is measured. Thereafter, it was inspected whether or not there was any indentation on the raceway surface of the inner ring 2.

  Specifically, as the sprag 4 used for the experiment, the sprag height Hc when contacting the inner ring 2 at the inflection point 42c of the cam surface 42 on the inner diameter side thereof is relative to the gap J between the inner and outer rings 1 and 2. 21 samples having various values were prepared.

  The results of the experiment are shown in the relationship diagram of FIG. In the relationship diagram of FIG. 4, the horizontal axis represents the ratio (Hc / J) of the sprag height Hc at the inflection point 42 c to the radial interval J between the inner and outer rings 1, 2, Magnification (T / To) of input torque T when slip occurs with respect to rated torque To of one-way clutch (a torque that can be applied to one-way clutch and is determined by the number of sprags 4 and the axial width of sprags 4) Is shown. In the relationship diagram, a circle mark (◯) indicates a case where no indentation occurs, and a cross mark (×) indicates a case where an indentation occurs.

  From the relationship diagram, when the sprag height Hc to distance ratio (Hc / J) is 1.05, that is, when the sprag height Hc is 5% greater than the radial distance J between the inner and outer rings 1 and 2, It can be assumed that no indentation is generated in the inner ring 2 in any of the samples if the indentation is generated in the inner ring 2 of some samples and the ratio of the sprag height Hc to the spacing (Hc / J) is less than 1.05.

  Further, from the relationship diagram, as the ratio of the sprag height Hc to the distance (Hc / J) increases, the magnification (T / To) of the torque T at the time of slippage with respect to the rated torque To increases almost directly. In addition, for each value of the sprag height Hc to spacing ratio (Hc / J), there is no great variation in the value of the torque T at the time of occurrence of slipping, and when the sprag height Hc is constant, It can be seen that the magnification (T / To) of the torque T at the time of slippage to the rated torque To is within the range of 0.5 to 0.6 points from the lowest value.

  From the above, in order to prevent indentation on the raceway surface of the raceway and to prevent a large variation in the torque value when slipping occurs, the inflection point 42c of one cam surface 42 of the sprag 4 is used. It is understood that the sprag height Hc may be less than 1.05 times the radial interval J between the inner and outer rings 1 and 2. When the sprag 4 contacts the inner ring 2 at the inflection point 42c of the one cam surface 42, the sprag 4 must be locked between the inner and outer rings 1 and 2, so that the inflection of the sprag 4 Needless to say, the sprag height Hc at the point 42c is larger than the radial distance J between the inner and outer rings 1 and 2.

  By the way, when the input torque T when operating as a torque limiter is relatively large, a relatively excessive torque several times the rated torque To is transmitted to the driven side of the one-way clutch, and the driven side of the one-way clutch is It has a great influence on the members.

  Considering the strength of the driven side member of the one-way clutch, the sprag height Hc at the inflection point 42c of the cam surface 42 of the sprag 4 is 1.03 times or less the radial interval between the inner and outer rings 1 and 2. Is desirable.

  In the relationship diagram of FIG. 4, in the range where the sprag height Hc to spacing ratio (Hc / J) is from 1.02 to more than 1.03, the rated torque of the input torque T is proportional to the increase in the spacing ratio. It can be assumed that the magnification (T / To) with respect to To has increased. As described above, when the ratio of the sprag height Hc to the spacing is 1.03 or less, slip occurs between the sprag 4 and the inner ring 2 with respect to the input torque that is three times or less of the rated torque To, and the torque It will act as a limiter. Therefore, a torque exceeding three times the rated torque To is not transmitted to the driven side of the one-way clutch, and deformation and breakage of the driven side member can be reliably prevented.

  In the above embodiment, the cam surface 42 on the inner diameter side of the sprag 4 is configured by the curved surface 42a and the flat surface 42b, but the cam surface 41 on the outer diameter side may be configured by a curved surface and a flat surface. In that case, against the excessive input torque in the transmission direction, the flat surface of the cam surface 41 on the outer diameter side comes into contact with the raceway surface of the outer ring 1 and slip occurs therebetween. In the illustrated embodiment, the two cages 5 and 6 are provided inside and outside, but the cage can be single.

The front view which showed the one-way clutch which concerns on the best form of this invention in a partial cross section along radial direction. FIG. 2 is a cross-sectional view taken along the axial direction of the one-way clutch in FIG. 1. The enlarged front view of the sprag which is a part of one-way clutch of FIG. The relationship figure which shows the relationship between the sprag height obtained by experiment, and input torque.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Outer ring 2 Inner ring 3 Annular space 4 Sprag 41 Outer diameter side cam surface 42 Inner diameter side cam surface 42a Curved surface 42b Flat surface 42c Inflection point 5 Outer cage 6 Inner cage 7 Ribbon spring (annular spring body)
Hc Sprag height at inflection point J Radial distance between inner and outer rings

Claims (1)

A plurality of sprags arranged along the circumferential direction in an annular space formed between the inner and outer races, a holder for holding these sprags, and a direction in which the sprags stand up in the annular space And a spring body biasing the
Each sprag has a cam surface that contacts the corresponding raceway on its outer diameter side and inner diameter side,
Of the two cam surfaces, one cam surface is composed of a curved surface and a flat surface continuous to the curved surface on the lock side,
The sprag height Hc when the sprag is in contact with the corresponding raceway at the inflection point between the curved surface and the flat surface is the radial distance J between the raceways,
J <Hc <J × 1.05
One-way clutch characterized by being.

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