One-way clutch

Abstract: The present invention provides a one-way clutch having rollers (4) individually disposed in wedge-shaped spaces formed at some positions on a circumference between two inner (1) and outer (2) annular bodies disposed concentrically with each other, in which a wedge angle (α) of each the wedge-shaped space is fixed at of 4° to 8°. As a result, an engagement position of the roller becomes relatively shallow when the roller (4) is positioned on a narrower side of the wedge-shaped space and gaps between the roller and the two inner (1) and outer (2) annular bodies become relatively small when the roller (4) is positioned on a wider side of the wedge-shaped space. Therefore, the rollers move smoothly in switching between the lock state and the free state.

Description: The present invention relates to a one-way clutch of a type employing rollers according to the preamble of claim 1. This one-way clutch is built into a pulley mounted to auxiliary machinery driven by a crankshaft of an engine of an automobile or the like through a belt, for example. The U.S.-A-5,482,144 discloses a one-way clutch of the above kind having a cam surface on the inner periphery of an outer rotary ring forming a wedge angle with the outer peripheral surface of an inner ring. Springs are provided to push rollers into the wedge-shaped gaps formed by the inner and outer ring. The Japanese unexamined patent publication No. Hei-3-249435 discloses a cam surface of the inner ring being formed as a flat surface, and rollers being provided between the inner ring and the outer ring. A conventional one-way clutch of this type will be described. An inner annular body and an outer annular body are disposed inside and outside each other in a diameter direction and concentrically with each other. Wedge-shaped spaces each with a gap in a diameter direction narrowing in one direction in a circumferential direction are formed at some positions on a circumference in a gap through which both the annular bodies face each other. A roller is individually disposed in each the wedge-shaped space. Between both the annular bodies, a cage having pockets extending to open inside and outside in a diameter direction at positions in phase with the wedge-shaped spaces is provided. Each roller is individually housed by each corresponding pocket. An elastic member is housed by each pocket. Each roller is elastically biased by each elastic member toward a narrower side (lock side) in one direction in the circumferential direction in the wedge-shaped space. The wedge-shaped spaces are formed by providing cam faces to one of the annular bodies (an outer peripheral face of the inner annular body or an inner peripheral face of the outer annular body) and a wedge angle of the wedge-shaped space is generally set at 9° to 11°. The wedge angle is an angle (α, β which will be described later) at which two tangents intersect each other, one of the tangents being a tangent at a point of contact at which the roller contacts the outer peripheral face of the inner annular body and the other of the tangents being a tangent at a point of contact at which the roller contacts the inner peripheral face of the outer annular body when the roller rolls to the lock side. In the above structure of the one-way clutch, when each the roller rolls to the narrower side in one direction in the circumferential direction of the wedge-shaped space, the clutch is brought into a lock state in which the inner annular body and the outer annular body are integrated with each other through the rollers and rotate synchronously. When each the roller rolls to a wider side on the other direction in the circumferential direction of the wedge-shaped space, the clutch is brought into a free state in which the inner annular body and the outer annular body rotate with respect to each other. In this manner, depending on a position in the wedge-shaped space to which each the roller rolls, the clutch is switched between the lock state and the free state. By the above wedge angle in the conventional one-way clutch, a lock malfunction may occur and a response property of a clutch operation is degraded when the roller rolls to the narrower side of the wedge-shaped space to bring the clutch into the lock state. SUMMARY OF THE INVENTION Therefore, it is a main object of the present invention to provide a one-way clutch in which generation of a lock malfunction is prevented and a response property of a clutch operation is improved. It is another object of the invention to provide a one-way clutch in which a wedge angle of each wedge-shaped space is set at a proper value, switching between a lock state and a free state is made smooth, and the response property of the clutch operation is improved. Other objects, features, and advantages of the invention will become apparent from the following descriptions. To comply with these objects, the one-way clutch according to the invention is characterized by the features of claim 1. According to the invention, there is provided a one-way clutch including an inner annular body, an outer annular body which is disposed outside the inner annular body and concentrically with the inner annular body and constitutes wedge-shaped spaces at some positions in a circumferential direction between the inner annular body and the outer annular body, each the wedge-shaped space being narrowing in one direction in the circumferential direction, and a plurality of rollers each disposed in each the wedge-shaped space for switching between a lock state in which each the roller rolls to a narrower side of the wedge-shaped space to integrate both the annular bodies with each other to allow both the annular bodies to rotate synchronously and a free state in which each the roller rolls to a wider side of the wedge-shaped space to cancel the lock state to allow both the annular bodies to rotate with respect to each other, wherein the inner annular body and the outer annular body have a structure in which a wedge angle of each the wedge-shaped space is set at 4° to 8°. If the wedge angle of the wedge-shaped space is set at the above value, an engagement position of each the roller is at a position in the wedge-shaped space with the narrowest wedge angle and is relatively shallow when the roller is positioned on the narrower side of the wedge-shaped space and gaps between each the roller and both the annular bodies are relatively small when the roller is positioned on the wider side of the wedge-shaped space. Therefore, the rollers move smoothly in switching between the lock state and the free state. BRIEF DESCRIPTION OF THE DRAWINGS These and other objects as well as advantages of the invention will become clear by the following description of preferred embodiments of the invention with reference to the accompanying drawings, wherein: FIG. 1 is a sectional side view of an upper half of a one-way clutch according to a preferred embodiment of the present invention; FIG. 2 is a sectional view taken along a line (2)-(2) and in a direction shown by arrows in FIG. 1; FIG. 3 is a plan developed view of a pocket portion of a cage in FIG. 1; FIG. 4 is an explanatory view showing wedge angles in one wedge-shaped space in FIG. 1; and FIG. 5 is a sectional view of an upper half of a pulley unit for which the one-way clutch of the invention is used. In all these figures, like components are indicated by the same numerals. DETAILED DESCRIPTION OF THE INVENTION A one-way clutch according to a preferred embodiment of the present invention will be described below with reference to FIGs. 1 to 4. The one-way clutch A has, as its components, an inner ring 1, an outer ring 2, a cage 3, rollers 4, and coil springs 5 as elastic members. The roller 4 rolls to a narrower side (lock side) or a wider side (free side) in a wedge-shaped space described later according to a rotation difference between the inner ring 1 and the outer ring 2. If the roller 4 rolls to the lock side, the inner ring 1 and the outer ring 2 are brought into a lock state in which the inner ring 1 and the outer ring 2 are integrated with each other through the roller 4 and rotate synchronously and power is transmitted. If the roller 4 rolls to the free side, the lock state of the inner ring 1 and the outer ring 2 is canceled and the inner ring 1 and the outer ring 2 are brought into a free state in which the inner ring 1 and the outer ring 2 rotate with respect to each other and power transmission is interrupted. In this manner, the inner and outer rings are switched between the lock state and the free state depending on the position to which the roller 4 rolls. The components of the one-way clutch A will be described below in detail. The inner ring 1 is provided with cam faces 6 constructed of flat key-shaped notches at some positions in a circumferential direction of an inner peripheral face. At two positions facing each other through 180° on one end face of the inner ring 1, slit-shaped notches 1a, 1a are provided. The outer ring 2 is formed to have cylindrical inner and outer peripheral faces and disposed concentrically with the inner ring 1 to face an outer periphery of the inner ring 1 through a required gap. By the inner peripheral face of the outer ring 2 and the cam faces 6 of the inner ring 1, wedge-shaped spaces are formed at some positions on a circumference in the gap through which the inner ring 1 and outer ring 2 face each other. A gap in a diameter direction of each wedge-shaped space is narrow on the lock side on one side in the circumferential direction and wide on the free side on the other side in the circumferential direction. The cage 3 is mounted between the inner ring 1 and outer ring 2 and fitted to the outer peripheral face of the inner ring 1. The cage 3 has pockets 3a extending to open inside and outside in the diameter direction at positions corresponding to the respective cam faces 6 of the inner ring 1. To two positions facing each other through 180° on an inner peripheral face of a wall portion 3b on one side of the axial direction of the pocket 3a in the cage 3, projecting chips 3c, 3c, to be press-fitted into the notches 1a, 1a of the inner ring 1 are provided. The projecting chips 3c, 3c are fitted into the notches 1a, 1a. As a result, the cage 3 is positioned in the circumferential direction and the axial direction with respect to the inner ring 1 having the cam faces 6. Each the roller 4 is individually housed for rolling in the circumferential direction by the corresponding pocket 3a in the cage 3. In this housed state, each the roller 4 is individually disposed on each the wedge-shaped space formed between the corresponding cam face 6 of the inner ring 1 and the inner peripheral face of the outer ring 2. The coil spring 5 is individually housed by the pocket 3a of the cage 3 in a compressed state. The coil spring 5 elastically biases the roller 4 toward the narrower side (lock side) in the wedge-shaped space by its extension restoring force. The coil spring 5 is fitted to an outside of a projection 3d integrally formed on an inner diameter side on one side of a side wall of a circumferential direction of an inner face of the pocket 3a in the cage 3 such that an expanding/contracting direction (along axis AS) of the coil spring 5 is orthogonal to a rolling axis center of the roller 4 and that one end of the coil spring 5 abuts on an intermediate area in the axial direction of the roller 4 (axis of roller AR). The coil spring 5 is an angularly wound spring wound to have a substantially rectangular prism in section and one end of the coil spring 5 in the expanding/contracting direction abuts on a half or more, e.g., two-thirds of a length of the roller in an axial direction at the intermediate area of the roller 4 in the axial direction. The coil spring 5 elastically biases the roller 4 toward the inner peripheral face of the outer ring 1 substantially in a direction along the cam face 6 of the inner ring. A wedge angle α of the wedge-shaped space in the invention is set at 4° to 8°, and preferably at 5° to 7°. If a lower limit value of the wedge angle α is set at a value smaller than 4°, a dimensional deviation of the narrower side and the wider side of the wedge-shaped space from each other becomes too small and the roller 4 is liable to remain locked in switching from the lock state to the free state. If an upper limit value of the wedge angle is set at a value greater than 8°, a dimensional deviation of the narrower side and the wider side of the wedge-shaped space from each other becomes too large and a lock malfunction may occur to delay the switching operation in switching from the free state to the lock state. A difference between the wedge angle α of the invention and the wedge angle β of prior art is shown in FIG. 4. In FIG. 4, a solid line and a broken line respectively show the lock state (the narrower side of the wedge-shaped space) and the free state (the wider side of the wedge-shaped space) of the roller 4 in the invention. A two-dot dashed line and a one-dot dashed line respectively show the lock state and the free state of the roller 4C in the prior art. FIG. 4 is for facilitating understanding of the invention and shows that an engagement position of the roller 4 is shallower in the lock state and gaps between the roller 4 and the inner ring 1 and outer ring 2 are smaller in the free state in the invention as compared with the prior art. Consequently, if the wedge angle is set at a proper value, the roller 4 can move smoothly and stably in switching between the lock state and the free state. Therefore, in the invention, switching of the state is carried out swiftly without delay. Furthermore, in the invention, because the rollers 4 move smoothly, wearing of the inner ring 1 and outer ring 2 which the rollers 4 contact is suppressed. In the invention, coil springs 5 each having a circular shape or a shape of an ellipse of an end face may be used. In the invention, other elastic members such as leaf springs or Belleville springs may be used instead of the coil springs 5. The one-way clutch A of the invention is built in the pulley mounted to auxiliary machinery driven by the crankshaft of the engine of the automobile or the like through the belt, for example. Examples of other auxiliary machinery for which the one-way clutch A of the invention can be used are a compressor for an air conditioner, a water pump, an alternator, a cooling fan, crank pulley, and the like. To be more concrete, a case in which the one-way clutch A is incorporated into a pulley of an alternator as auxiliary machinery is shown in FIG. 5 and will be described in this case, between the pulley 20 of the alternator and a rotor 21, the one-way clutch A of the above-described embodiment is mounted and rolling bearings 22, 22 such as deep groove ball bearings are disposed on opposite sides of the one-way clutch A in an axial direction. In this case, the one-way clutch A is switched between the free state and the lock state according to a rotation difference between the pulley 20 and the rotor 21, thereby transmitting rotation power from the pulley 20 to the rotor 21 or interrupting the transmission of the rotation power. In the alternator, because the pulley 20 is driven for rotation by the crankshaft of the engine through a belt 23, power generation efficiency of the alternator decreases conventionally if a rotation speed of the crankshaft decreases. However, if the one-way clutch A is built in, the one-way clutch A can be functioned such that a rotation speed of the rotor 21 is kept high by an inertial force of the rotor 21 itself when a rotation speed of the pulley 20 decreases, which contributes to improvement of the power generation efficiency. Moreover, by a variation in rotation from the crankshaft and an inertial force of a rotor shaft of the alternator, it is possible to prevent shortening of life of the belt due to stress applied to the belt and generation of noise due to a slip. In such usage, by an excellent clutch function of the one-way clutch A of the invention, it is possible to stably switch between transmission of power between the pulley 20 and the rotor 21 of the alternator and interruption of the transmission and a function peculiar to the alternator using the above one-way clutch A is reliably carried out. While there has been described what is at present considered to be preferred embodiments of this invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the scope of this invention as defined by the appended claims.

Claims: A one-way clutch comprising: an inner annular body (1); an outer annular body (2) which is disposed outside said inner annular body and concentrically with said inner annular body and constitutes wedge-shaped spaces at some positions in a circumferential direction between said inner annular body (1) and said outer annular body (2), each said wedge-shaped space being narrowing in one direction in said circumferential direction; and a plurality of rollers (4) each disposed in each said wedge-shaped space for switching between a lock state in which each said roller rolls to a narrower side of said wedge-shaped space to integrate both said annular bodies (1,2) with each other to allow both said anular bodies to rotate synchronously and a free state in which each said roller rolls to a wider side of said wedge-shaped space to cancel said lock state to allow both said annular bodies to rotate with respect to each other, characterized in that said inner annular body (1) has cam faces (6) constructed of flat key-shaped notches at some positions in a circumferential direction of an outer peripheral face, said outer annular body (2) has an inner peripheral face having a circular shape in section, and each said wedge-shaped space is formed in a gap through which each said cam face (6) of said inner annular body (1) and said inner peripheral face of said outer annular body (2) face each other, said inner annular body (1) and said outer annular body (2) have a structure in which a wedge angle of said wedge-shaped space being formed by the intersection angle of a extension of a cam face (6) of said inner annular body (1) with a tangent line which touches the inner circumferential surface of the outer annular body (2) at the point of contact, where the roller (4) is locked, is set at 4° to 8°. The one-way clutch according to claim 1, characterized by a cage (3) disposed in a gap through which both said annular bodies (1,2) face each other and having pockets corresponding to said respective wedge-shaped spaces and extending to open inside and outside in a diameter direction, each said pocket individually housing each said roller (4); and elastic members (5) each disposed individually in each said pocket for elastically biasing said roller (4) in said pocket toward a lock side of said wedge-shaped space. A one-way clutch as claimed in claim 1, characterized in that the pockets (3a) of the cage are provided in positions facing each other through 180° of the inner peripheral face of the wall portion (3b).

Inventors: FUJIWARA HIDEKI, NAKAGAWA YOSHITAKA, TAZUMI HAJIME, TERADA TADAHIRO, FUJIWARA, HIDEKI, NAKAGAWA, YOSHITAKA, TAZUMI, HAJIME, TERADA, TADAHIRO, Fujiwara, Hideki, c/o Koyo Seiko Co., Ltd., Nakagawa, Yoshitaka, c/o Koyo Seiko Co., Ltd., Tazumi, Hajime, c/o Koyo Seiko Co., Ltd., Terada, Tadahiro, c/o Koyo Seiko Co., Ltd.
Applicants: KOYO SEIKO CO, KOYO SEIKO CO., LTD.
Application year: 2000
Main classification: F16D41
IPC codes: F16D41