Patent ID: 12234868

EMBODIMENT FOR CARRYING OUT THE INVENTION

In the following, a ratchet type one-way clutch apparatus (herein after, simply called as “one-way clutch”) according to the embodiment of the present invention will be described with referring to the accompanying drawings.

At first, some terms relating to directions about the one-way clutch according to the embodiment shown inFIG.1will be defined. In the description of the embodiment, the terms “axial direction”, “radial direction” and “circumferential direction” of the one-way clutch1respectively refer to the axial direction, radial direction, and circumferential direction with respect to the central axis O of the one-way clutch1(that is, the central axis of the outer race2or the inner race3). In the axial direction, the front side of the plane of the drawing sheets is referred to as one axial side, and the back side of the plane of the drawing sheets is referred to as the other axial side. In the circumferential direction, the clockwise direction towards the plane of the drawing sheets is referred to as one circumferential side (or clockwise direction) and the counterclockwise direction towards the plane of the drawing sheets is referred to as the other circumferential side (or counterclockwise direction). Meanwhile, regarding rotation of the one-way clutch1, rotation of the inner race3relative to the outer race2will be explained, but it is noted that the rotation of the outer race2and the rotation of the inner race3are relative to each other.

As shown inFIG.1, the one-way clutch1comprises a circular cylindrical outer race2, a circular cylindrical inner race3that is rotatable relative to the outer race2, and a torque transmitting mechanism for carrying out torque transmission from the inner race3to the outer race2. The torque transmitting mechanism of the one-way clutch1, adopts a ratchet mechanism that includes the first to third pawl members4ato4cprovided at the inner circumferential portions of the outer race2.

The inner race3is spaced apart on inner side in the radial direction from the outer race2and is smaller in diameter than the outer race2and coaxial with the outer race2. On the outer circumferential surface of the inner race3, a plurality of tooth portions5projected radially outwardly and extended in the axial direction are provided over the entire circumferential surface and equi-distantly in the circumferential direction. The plurality of tooth portions5each have, viewed from the one axial side, a trapezoidal shape in cross section, and constitute the ratchet teeth to be meshed with the first to third pawl members4ato4c. In detail, with the wall surfaces6on the one circumferential side (clockwise side) of the tooth portions5, the first to third pawl members4ato4care brought into engagement and are meshed each other. Here, areas between the adjacent tooth portions5on the outer circumferential surface of the inner race3are referred to as the bottom surfaces7, and entering of the pawl members4ato4cinto between the tooth portions5respectively is referred to as dropping onto or arriving at the bottom surface7.

The inner circumferential surface of the outer race3constitutes a shaft hole8. In the shaft hole8, a shaft9that is coaxial with the inner race3, is fitted, and the inner race3and the shaft9are rotatable as one body. The shaft9is connected to an unillustrated drive mechanism through an unillustrated gear mechanism, for example. The shaft9and the shaft hole8may be spline-fitted.

On the outer circumferential surface of the outer race2, a plurality of the projected portions11projected radially outwardly and extended in the axial direction are provided along the circumferential direction. The projected portions11each have, viewed from the one axial side, a trapezoidal cross section, and are fitted in an unillustrated shaft connected to an unillustrated driven mechanism, for example.

On the inner circumferential portions of the outer race2, the first to third pawl member holding portions12ato12cextended in the axial direction are formed at substantially equal intervals in the circumferential direction (refer toFIGS.2A to2C). The afore mentioned first to third pawl members4ato4care respectively held in the first to third pawl member holding portions12ato12c.

The first pawl member holding portion12ais a concaved portion opened radially inwardly on the inner circumferential surface of the outer race2. The first pawl member holding portion12ais comprised of a first concave portion13aand a second concave portion14acontinuously neighboring to the first concave portion13aon the other circumferential side thereof.

The first concave portion13aof the first pawl member holding portion12ais, viewed from the one axial side, a circular portion concaved towards one circumferential side and radially outwardly from the inner circumferential surface of the outer race2, thereby holding the first pawl member4ato allow the swinging movement therein.

The second concave portion14aof the first pawl member holding portion12ais, viewed from the one axial side, a rectangular portion concaved towards the other circumferential side and radially outwardly from the inner circumferential surface of the outer race2. At the bottom surface of the second concave portion14ais further formed with a concave portion concaved radially outwardly shown by dotted line inFIGS.2A to2C, in which concaved portion an elastic member15ais set as a biasing member for biasing or pushing the first pawl member4aonto the inner race3side. Meanwhile, the bottom surface of the concaved portion on which the elastic member15ais set is referred as a setting surface of the elastic member15a.

Meanwhile, the second and third pawl member holding portions12band12chave similar configurations to the first pawl member holding portion12a, and include respectively the first concave portions13b,13c, the second concave portions14b,14cand the elastic members15b,15c. The elastic members15a,15b,15cmay be coil springs, for example.

A first pawl member4ahas a predetermined circumferential length and is a metal member elongated in the axial direction. The first pawl member4acomprises, viewed from the one axial side, a circular portion16a, and a rectangular pawl portion17aprojected integrally from the circular portion16atowards the other circumferential side.

The circular portion16aof the first pawl member4ais held in the first concave portions13aof the first pawl member holding portion12a, as shown inFIG.2Aand is rotatable (swingable) about the center18aof the circular portion16a.

The pawl portion17aof the first pawl member4ais disposed in the second concave portion14aof the first pawl member holding portion12a, and is always forced towards the inner race3side (radially inwardly) by the elastic member15aprovided in the second concave portions14a. The pawl portion17aof the first pawl member4ais projected from through the opening on the inner race3side of the second concave portions14ato the circumferential other side and to the inner race3side.

Meanwhile, the second and third pawl members4band4chave similar configuration to the first pawl member4a, and include respectively the circular portions16b,16cand the pawl portions17b,17c.

The tooth portions5of the inner race3, the first to third pawl member holding portions12ato12cof the outer race2, the first to third pawl members4ato4cheld in the first to third pawl member holding portion12ato12cand the elastic members15ato15ccompose a rachet mechanism of the one-way clutch1.

In the one-way clutch1configured as described above, when the inner race3is rotated in the clockwise direction together with the shaft9driven by an unillustrated driving device, the relative rotation of the inner race3to the outer race2is fixed, and the inner race3and the outer race2and the unillustrated shaft fitted on the outer race2are rotated as one body. On the other hand, when the inner race3is rotated in the counterclockwise direction, the inner race3freely rotates relative to the outer race2.

In detail, upon the inner race3rotating clockwise, the first to third pawl members4ato4cin the outer race2respectively mesh with the tooth portions5of the inner race3. Concretely, the tips of the pawl portions17ato17cof the first to third pawl members4ato4cin the outer race2are brought into engagement with the wall surfaces6on the one circumferential side of the tooth portions5. As described, the wall surfaces6on the one circumferential side of the tooth portions5constitute the meshing surfaces of the tooth portions5which mesh respectively with the first to third pawl members4ato4c. By meshing the first to third pawl members4ato4cwith the respective tooth portions5, the inner race2and the outer race3rotate together as one body so that torque is transmitted from the inner race3to the outer race2. Meanwhile, in a case where the outer race2is fixed, the one-way clutch1functions as backstop that impedes clockwise rotation of the inner race3.

On the other hand, upon the inner race3rotating counterclockwise, the first to third pawl members4ato4cdo not mesh with the tooth portions5of the inner race3. Specifically, when the tooth portions5of the inner race3come in contact with the first to third pawl members4ato4c, the inner race3rotates while the tooth portions5push the first to third pawl members4ato4cradially outwardly against biasing forces of the elastic members15ato15c. Thus, the inner race3rotates freely from the outer race2, so no torque is transmitted from the inner race3to the outer race2.

In the one-way clutch1according to the present embodiment, when the first to third pawl members4ato4cmesh with the tooth portions5respectively, no first to third pawl members4ato4care bounced radially outwardly in the non-engagement direction by the meshing surfaces6of the tooth portions5, that is, and ride up on the tooth portions5, so the first to third pawl members4ato4ccan be brought into engagement with the tooth portions5securely.

The configuration of the ratchet mechanism of the present embodiment, which achieves these effects, is described in detail below.

In the present embodiment, the second and third pawl member holding portions12band12care provided respectively at positions deviating by arbitrary angles α1and α2degrees from the positions dividing the inner circumferential surface of the outer race2into three equal parts in the circumferential direction, as viewed from the central axis O of the outer race2.

In detail, on the inner circumferential surface of the outer race2, the second pawl member holding portion12bis provided so that, with reference to the center21aof the first concave portion13ain the first pawl member holding portion12a(=the center of rotation of the first pawl member4a), the center21bof the first concave portion13bin the second pawl member holding portion12bis located at a position displaced or deviating by an arbitrary angle di degrees in one circumferential side (clockwise direction) from the position trisecting the inner circumferential surface of the outer race2in the circumferential direction as viewed from the central axis O. In other words, the angle in the clockwise direction between the center21aof the first concave portion13ain the first pawl member holding portion12aand the center21bof the first concave portion13bin the second pawl member holding portion12b, centered on the central axis O, is (120+α1) degrees. Meanwhile, it is desirable that the arbitrary angle α1should be set in consideration of the amount of deformation when each component of the one-way clutch1, namely the outer race2, inner race3and first to third pawl members4ato4care elastically deformed under torque load and the mounting clearances during assembly.

On the inner circumferential surface of the outer race2, the third pawl member holding portion12cis provided so that, with reference to the center21aof the first concave portion13aof the first pawl member holding portion12a, the center21cof the first concave portion13cin the third pawl member holding portion12cis located at the position displaced or deviating by an arbitrary angle α2degrees in the clockwise direction from another position trisecting the inner circumferential surface of the outer race2in the circumferential direction as viewed from the central axis O. In other words, the angle in the clockwise direction between the center21aof the first concave portion13ain the first pawl member holding portion12aand the center21cof the first concave portion13cin the third pawl member holding portion12c, centered on the central axis O, is (240+α2) degrees. Meanwhile, it is desirable that the arbitrary angle α2like the aforementioned arbitrary angle α1should be set in consideration of the amount of deformation when each component of the one-way clutch1is elastically deformed under torque load and the mounting clearances during assembly, and the arbitrary angle α1degrees may be equal to the arbitrary angle α2degrees (α2=α1). Hereinafter, the configuration on the first to third pawl member holding portion12ato12cas described above is called as “first configuration”.

According to the first configuration, when the inner race3is rotated in the clockwise direction, at first the pawl portion17aof the first pawl member4ain the outer race2drops onto or arrive at the bottom surface7of the inner race3and is engaged with the meshing surface6of the tooth portion5, as shown inFIG.2A.

At this time, the pawl portion17bof the second pawl member4bdrops on or arrives at the bottom surface7of the inner race3. Since the location of the second pawl member holding portion12bin the inner circumferential surface of the outer race2is displaced or deviated by the arbitrary angle α1degrees circumferentially from the position trisecting the inner circumferential surface of the outer race2in the circumferential direction, as described above, a circumferential clearance is generated between the tip end face on the other circumferential side (counterclockwise direction side) of the pawl portion17bof the second pawl member4band the meshing surface6of the tooth portion5, as shown inFIG.2B. Accordingly, the pawl portion17bof the second pawl member4bcan drop onto or arrive at the bottom surface7of the inner race3, without the pawl portion17briding up on the tooth portion5. And, by further rotation of the inner race3in the clockwise direction, or by elastic deformation of the constituent elements due to torque load or presence of mounting play (looseness) for assembling, the circumferential clearance disappears, and the pawl portion17bof the second pawl member4bcan be brought into engagement with the meshing surface6of the tooth portion5. Meanwhile, the pawl portion17cof the third pawl member4cacts in the same way as the pawl portion17bof the second pawl member4bat the time when the inner race3rotates in the clockwise direction.

As described above, when the inner race3is rotated in the clockwise direction, the respective pawl portions17ato17cof the first to third pawl members4ato4ccan be engaged with the tooth portions5surely. For this reason, upon transmitting torque from the inner race3to the outer race2, the torque load can be shared by the first to third pawl members4ato4c. Accordingly, the one-way clutch1can ensure the maximum torque transmittable between the inner race3and the outer race2. Further, it is possible to eliminate an occurrence of a case where any pawl member can not engage the tooth portion5, so the one-way clutch1can be prevented from reducing in torque capacity and from being damaged. Furthermore, it is not necessary to increase the number of pawl members to secure the safety of the one-way clutch1, and it is not required to enlarge diameter of the one-way clutch1.

In the present embodiment, a position in which the elastic member15ais set in the second concave portion14aof the first pawl member holding portion12ais deviated or displaced on the other circumferential side, viewed from the central axis O, compared to a position in which the elastic member15bor15cis set in the second concave portion14bor14cof the second or third pawl member holding portion12b,12c. For this reason, a position25ain the pawl portion17aof the first pawl member4a, which receives the biasing force of the biasing member15a(the last mentioned position is referred to as “point of action of load by the elastic member”) is deviated on the other circumferential side viewed from the central axis O, compared to a position25bor25cin the pawl portion17bor17cof the second or third pawl member4bor4c, which receives the biasing force of the biasing member15bor15c(point of action of load by the elastic member). Refer toFIG.2AtoFIG.2C. In other words, the position25a,25bor25cis point of action onto which the biasing force of the elastic member15a,15bor15cacts.

According this configuration, an interval between the position25a(the point of action of load by the elastic member) in the first pawl member4aand the rotation center18aof the first pawl member4a(that is, the center18aof the circular portion16aof the first pawl member4a), that is, the interval D1in the circumferential direction viewed from the one axial side, is larger than the interval D2between the position25b(the point of action of load by the elastic member) in the second pawl member4band the rotation center18bof the second pawl member4b, or the interval D3between the position25c(the point of action of load by the elastic member) in the third pawl member4cand the rotation center18cof the third pawl member4c(D1>D2, D1>D3). Here, it is noted that the interval D2is the same as the interval D3(D2=D3). This configuration of the first to third pawl members4ato4cand the first to third pawl member holding portions12ato12c, are called as “second configuration”.

Meanwhile, in the present embodiment, the same elastic members having the same elastic force (load) are used for the elastic members15ato15cin the first to third pawl member holding portions12ato12c.

As described above, according to the configuration that the interval D1between the position25a(the point of action of load by the elastic member) in the first pawl member4aand the rotation center18aof the first pawl member4ais larger than the interval D2between the position25b(the point of action of load by the elastic member) in the second pawl member4band the rotation center18bof the second pawl member4b, or the interval D3between the position25c(the point of action of load by the elastic member) in the third pawl member4cand the rotation center18cof the third pawl member4c. Therefore, in the pawl member4a, the action of the biasing force of the elastic member15a, in the moment causing the rotational movement of the first pawl member4a, is larger than that of the second or third pawl member4bor4c. In other words, the first pawl member4ais rotatable more easily than the second or third pawl member4bor4c.

According to the above mentioned second configuration, when the inner race3is rotated in the clockwise direction and the pawl portions17ato17cof the first to third pawl members4ato4cdrop onto or arrive at the bottom surfaces7in the inner race3, the dropping speed of the pawl portion17aof the first pawl member4aarriving at the bottom surface7can be made larger than the dropping speed of the pawl portions17bor17cof the second or third pawl member4bor4c.

In other words, when the inner race3is rotated in the clockwise direction, the pawl portion17aof the first pawl member4acan drop onto or arrive at the bottom surface7of the inner race3more quickly than the pawl portion17bor17cof the second or third pawl member4bor4c, and the pawl portion17aof the first pawl member4acan be brought into engagement firstly with the tooth portion5. And, subsequent to the first pawl member4a, the pawl portion17bor17cof the second or third pawl member4bor4cdrops onto or arrives at the bottom portion7of the inner race3and is brought into engagement with the tooth portion5.

Thus, the one-way clutch1can attain the effects by the above mentioned first configuration of the first to third pawl member holding portions12ato12cmore surely.

According to the present embodiment, it is possible to realize the one-way clutch1in which all of the first to third pawl members4ato4ccan be engaged with the tooth portions5safely and transmit maximum torque thereto without causing any damage.

In the above embodiment, the one-way clutch1is equipped with three pawl members (first to third pawl members4ato4c) and three pawl member holding portions (first to third pawl member holding portions12ato12c), but the number of the pawl members or the number of the pawl member holding portions is not limited to three.

For example, assuming a case where the number of the pawl members and the number of the pawl member holding portions is “n” each (n is an integer that is not less than 2), the second to nth pawl member holding portions may be respectively provided at positions displaced by an arbitrary angle from positions where the inner circumferential surface of the outer race2is divided into n equal parts in the circumferential direction with the first pawl member holding portion as reference, viewed from the central axis O of the outer race2. More specifically, the second to nth pawl member holding portions may be provided on the inner circumferential surface of the outer race2so as to satisfy the following conditional expression (1). Meanwhile, the arbitrary angles α1to αn-1shall be set respectively for the second to nth pawl member holding portions.
A=(360/n)×(m−1)+αm-1(1)where “A” denotes angle (unit: degree) between the arc from the position of the first pawl member holding portion to the position of the second to nth pawl member holding portions on the inner circumferential surface of the outer race2and the central axis O of the outer race2;“n” denotes the number of the first to nth pawl member holding portions (n is an integer not less than 2);“m” denotes order of the second to nth pawl member holding portions counted from the first pawl member holding portion as the first one (m is an integer); and“αm-1” denotes an arbitrary angle (unit: degree) of the second to nth pawl member holding portions.

In the one-way clutch1according to the above embodiment, the inner race3is on the input side, the outer race2is on the output side, and torque is transmittable from the inner race3to the outer race2. However, the present invention is not limited to such embodiment, and is applicable to a one-way clutch in which an outer race is on the input side, an inner race is on the output side, and torque is transmitted from the outer race to the inner race.

In the one-way clutch1according to the above embodiment, the first to third pawl members4ato4care brought into engagement with the wall surfaces6on the one circumferential side of the tooth portions5, and thereby the clockwise rotation of the inner race3is transmitted to the outer race2. However, the present invention is not limited to this, and the present invention can be applied to a so-called ratchet type torque transmitting direction change-over one-way clutch which comprises further a plurality of pawl members that are engageable with wall surfaces on the other circumferential side of the tooth portions5and in which a state where clockwise rotation of the inner race3is transmitted to the outer race2and a state where counterclockwise rotation of the inner race3is transmitted to the outer race2are selectively changed over by changing over between the last-mentioned the plurality of pawl members and the first to third pawl members4ato4c.

EXPLANATION OF REFERENCES

1: one-way clutch2: outer race3: inner race4ato4c: first to third pawl members5: tooth portion of inner race6: wall surface (meshing surface) of tooth portion12ato12c: first to third pawl member holding portions13ato13c: first concave portions of first to third pawl member holding portions14ato14c: second concave portions of first to third pawl member holding portions15ato15c: elastic members in first to third pawl member holding portions16ato16c: circular portions of first to third pawl members17ato17c: pawl portions of first to third pawl members18ato18c: centers of circular portions of first to third pawl members21ato21c: centers of first concave portions of first to third pawl member holding portions25ato25c: the point of action of load by the elastic memberO: central axis of inner race and outer race