JP2006009901A - Power transmission device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power transmission device having excellent absorption performance of rotation fluctuation. <P>SOLUTION: This power transmission device (a pulley unit 1) transmits power between a pulley 2 and a rotor shaft 3 which are two ring bodies arranged coaxially in the inside and the outside in the radial direction. An annular transmission body 6 is arranged between the pulley 2 and the rotor shaft 3, and torsion coil springs 8, 9 are arranged on both sides in the axial direction of the annular transmission body 6 in a compressed condition. The annular transmission body 6 is fitted into the pulley 2 by splines 2b, 6b in the axial direction. A screw groove 6a in the axial direction is provided on an inner peripheral side of the annular transmission body 6, and a screw groove 3a in the axial direction is formed on an outer peripheral side of the rotor shaft 3. A plurality of balls 12 are provided between both grooves 6a and 3a to connect the annular transmission body 6 with the rotor shaft 3 through the balls 12. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power transmission device that transmits rotational power between two annular bodies arranged concentrically inside and outside in the radial direction. This type of power transmission device can be installed in, for example, an engine crankshaft or accessories driven from the crankshaft via a belt. Examples of the auxiliary machines include an automobile alternator, an air conditioner compressor, a water pump, and a cooling fan.

  Vehicles such as automobiles are equipped with auxiliary equipment such as an alternator, an air conditioner compressor, a water pump, and a cooling fan that are driven from a crankshaft of an engine via a belt. When the rotational power of the engine is transmitted from the crankshaft to the auxiliary machine via the belt, the belt tends to slip due to fluctuations in the rotational speed of the crankshaft, and abnormal noise tends to be generated. This will be explained by taking an alternator as one of the auxiliary machines as an example. Due to the operation process of the engine, the rotation speed of the crankshaft always varies during the rotation. On the other hand, since the rotor of the alternator has a large rotational inertia, inertia torque is applied to the rotor. For this reason, when the alternator rotor is driven by a crankshaft with fluctuations in rotational speed, the slack side and the tension side of the belt are alternately switched to generate a fluctuation in tension, while the inertia torque of the rotor is applied to the belt. As a result, the belt tends to slip and generate abnormal noise, or the durability tends to decrease.

Therefore, conventionally, a power transmission device using a one-way clutch as a power transmission member between a rotor shaft of an alternator and a pulley around which the belt is wound has been proposed (see Patent Document 1). However, in the one-way clutch type power transmission device, the locked state and the free state of the clutch are repeated according to the fluctuation of the input rotation, and the non-power transmission state is interposed between the power transmission states. When switching from the free state to the locked state due to large rotational fluctuations on the input side, the rollers and sprags as the wedge members suddenly engage with each other, so relatively large fluctuations appear in the rotation on the output side, and the effect of absorbing rotational fluctuations Is insufficient.
JP 2001-90751 A

  Therefore, a problem to be solved by the present invention is to provide a power transmission device that is excellent in the absorption performance of the rotation fluctuation.

  A power transmission device according to the present invention is a power transmission device that performs power transmission between two annular bodies arranged concentrically inside and outside in the radial direction, and an annular transmission is arranged between the two annular bodies, and the annular transmission Screw grooves formed on the inner ring body, with springs arranged on both sides in the axial direction, and the annular transmission body coupled to the outer ring body so as to be integrally rotatable and axially displaceable. It is characterized in that a plurality of balls are interposed in the inside. As a mode of coupling between the annular transmission body and the outer ring body, male and female axial splines are provided in each of the outer ring body and the annular transmission body, and the outer ring body and the annular transmission body are coupled via these splines. Also good. Alternatively, instead of providing a spline on the annular transmission body, a rolling element capable of rolling in the axial direction within the spline of the outer annular body is provided, and the outer annular body and the annular ring are formed by the spline of the outer annular body and the rolling element of the annular transmission body. You may couple | bond with a transmission body.

  The spring includes not only a metal but also a resin spring. The above-mentioned spring is not limited to a coil spring but may have any name or shape as long as it has a function as a spring. For example, even if it is expressed as an elastic body, It is construed to be included in the spring of the invention.

  To explain the process up to the completion of the present invention, the present inventors have intensively studied a power transmission device using a spring instead of a one-way clutch inferior in the ability to absorb rotational fluctuations. Among them, it is composed of a transmission body that can be displaced in the axial direction between the pulley and the rotor shaft in a state of fitting with both in the rotational direction, and coil springs arranged on both sides in the axial direction of the transmission body, and input rotation As a result, a spring-type power transmission device has been conceived in which the transmission body is displaced in the axial direction against the spring force of the coil spring in accordance with the fluctuations of the coil spring to absorb the rotation fluctuation. In accordance with this idea, the present applicant has already proposed the power transmission device of Japanese Patent Application No. 2004-88950. However, in the case of such a spring-type power transmission device, in particular, since the structure for transmitting rotational power from the annular transmission to the inner ring is a spline structure, friction loss between the annular transmission and the inner ring is lost. Is big. Thus, an invention has been completed that can provide a power transmission device that can reduce friction loss during rotational power transmission between the annular transmission and the inner ring.

  In the power transmission device according to the present invention, for example, even if the outer ring rotates, the rotation change is absorbed by the annular transmission being displaced in one axial direction against the spring, and the inner ring is absorbed. Since it is hardly transmitted to the body, it is possible to prevent the action of a sudden tension on the belt due to rotational fluctuations, and to extend the life of the belt and the outer ring. In addition, according to the power transmission device of the present invention, transmission of rotational power between the annular transmission body and the inner ring body is performed not via spline fitting but via a ball, and therefore, between the annular transmission body and the inner ring body. As a result of greatly reducing the friction loss, the rotational power transmission performance is excellent.

  ADVANTAGE OF THE INVENTION According to this invention, the power transmission device excellent in the absorption performance of rotation fluctuation can be provided.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the accompanying drawings. In this embodiment, the power transmission device is applied to a pulley unit used for an auxiliary machine of a vehicle. FIG. 1 is a side sectional view showing the overall configuration of the pulley unit, and FIG. 2 is a perspective view of an annular transmission in the pulley unit. Referring to these drawings, reference numeral 1 denotes the entire pulley unit. The pulley unit 1 includes a pulley 2 as an outer ring and a rotor shaft 3 as an inner ring.

  The pulley 2 has a pulley groove 2a around which a belt (not shown) that is fed in conjunction with the crankshaft of the engine is wound on the outer peripheral side, and a female spline 2b that is linear in the axial direction on the inner peripheral side. .

  The rotor shaft 3 is disposed on the radially inner side of the pulley 2 and includes two spiral thread grooves 3a parallel to each other in the middle of the outer peripheral side in the axial direction. The number of the thread grooves 3a may be one, or three or more, and is not limited to the number of the thread grooves 3a.

  The rolling bearing 4 is a deep groove ball bearing that supports the rotor shaft 3 on the pulley 2. The rolling bearing 4 is fixed in the axial direction by a step 3 b on the outer peripheral side of the rotor shaft 3 and a retaining ring 5. 2 is positioned in the axial direction.

  The annular transmission body 6 is provided in an annular space 7 between the outer peripheral side of the rotor shaft 3 and the inner peripheral side of the pulley 2 in a state that can be displaced within a certain range in the axial direction, and is included in the input rotation to the pulley 2. The rotational power of the pulley 2 can be transmitted to the rotor shaft 3 while absorbing fluctuations such as pulsation. The annular transmission 6 is provided with a male spline 6b having an axial linear shape corresponding to the spline 2b of the pulley 2 on the outer peripheral side, and two corresponding to the thread groove 3a of the rotor shaft 3 on the inner peripheral side. Two spiral thread grooves 6a are provided substantially in parallel. The number of the thread grooves 6a may be one, or three or more, and is not limited to the number of the thread grooves 3a. A large number of balls 12 are interposed in a ball transfer path formed by the threaded grooves 6 a and 3 a of the annular transmission 6 and the rotor shaft 3. The rotor shaft 3 constitutes a screw shaft, the annular transmission 6 constitutes a nut, and these and the ball 12 constitute a ball screw. Accordingly, the annular transmission 6 is moved in the axial direction by rotation around the rotor shaft 3, and since a more detailed configuration and operation of such a ball screw are well known, a more detailed description is omitted.

  With the above configuration, the annular transmission 6 is coupled to the pulley 2 so as to be integrally rotated and axially displaceable by coupling the spline 6b and the spline 2b of the pulley 2, and the thread groove 6a and the rotor shaft 3 are coupled. The screw groove 3a and the ball 12 interposed between them can be displaced in the axial direction while rotating around the rotor shaft 3.

  Torsion coil springs 8 and 9 are arranged in a compressed state on both axial sides of the annular transmission 6. The outer end of one torsion coil spring 8 is received by a spring receiver 10 that is in contact with the inner end of the rolling bearing 7. The outer end of the other torsion coil spring 9 is received by a radially inward flange portion 2 c of the pulley 2. The spring that presses the annular transmission 6 in the axial direction is not limited to the torsion coil springs 8 and 9, and other types of springs can be used.

  Grease is applied to the splines 2b and 6b of the annular transmission body 6 and the pulley 2, and the thread grooves 3a and 6a of the annular transmission body 6 and the rotor shaft 3, respectively, or for friction reduction such as fluorine coating. A coating is applied. A seal 11 that seals the annular space 7 from the outside is provided between the inner peripheral side of the flange portion 2 c of the pulley 2 and the outer peripheral side of the rotor shaft 3.

  In the above configuration, the rotational power of the pulley 2 is applied to the spline 2b of the pulley 2 and the spline 6b of the annular transmission 6 and in the screw grooves 3a and 6a between the annular transmission 6 and the rotor shaft 3. It is transmitted to the rotor shaft 3 by the balls 12 and the torsion coil springs 8 and 9. When the pulley 2 is rotating in a steady state, the annular transmission 6 is positioned in the middle in the axial direction. However, when the pulley 2 suddenly increases in speed, for example, the annular transmission 6 rotates to rotate the rotor shaft 3. Although the rotor shaft 3 is difficult to rotate due to its inertia, the annular transmission 6 is against the rotor shaft 3 against the spring force of the torsion coil springs 8 and 9 on one axial side. To one side in the axial direction. While the annular transmission 6 is displaced in one axial direction, a delay occurs in the rotation of the rotor shaft 3 with respect to the pulley 2. It is hardly transmitted. In short, the rotational fluctuation included in the input rotation is absorbed as energy for displacing the annular transmission 6 in the axial direction. Therefore, the action of a sudden tension on the belt due to the rotation fluctuation can be prevented, and the life of the belt and the pulley 2 can be extended. When the rotation of the pulley 2 suddenly fluctuates in the deceleration direction, for example, the annular transmission 6 tries to follow the rotation of the pulley 2 and resists the spring force of the torsion coil springs 8 and 9 along the screw grooves 3a and 6a. It moves in the decelerating direction and is displaced in the other axial direction, and the displacement included in the rotation of the pulley 2 is absorbed by this displacement. As a result, the rotational fluctuation included in the rotation of the pulley 2 is absorbed as energy that the annular transmission 6 is displaced in the axial direction, so that an abrupt tension action on the belt accompanying the rotational fluctuation can be prevented. And the life of the pulley 2 can be extended. In addition, according to the pulley unit 1, by changing the number and arrangement of the torsion coil springs 8 and 9 in which the annular transmission 6 is arranged on both sides in the axial direction, the springs of the torsion coil springs 8 and 9 as a whole are changed. The spring force that easily presses the annular transmission 9 can be set to a desired value by changing the constant, and the required spring strength can be set when changing the spring constant to improve the rotational fluctuation absorbing performance. Can be secured, and an increase in the size can be suppressed.

(Other forms)
A pulley unit as a power transmission device according to another embodiment of the present invention will be described with reference to FIG. In the pulley unit 1 shown in FIG. 3, no axial male spline is provided on the outer peripheral side of the annular transmission 10, and a plurality of balls 21 held by the cage 20 are arranged on the outer peripheral side of the annular transmission 6. The balls 21 can be axially rolled in the axial spline 2b on the inner peripheral side of the pulley 2, and the other configurations are the same as those in the above-described embodiment. In the pulley unit 1 shown in FIG. 3, the annular transmission 6 is rotationally integrated with the pulley 2 by the ball 21 by the axial spline 2 b of the pulley 2 and can be axially displaced. In the form of FIG. 1, when the annular transmission 6 is displaced in the axial direction, the spline 6b of the annular transmission 6 slides in the spline 2b of the pulley 2 so that both the splines 2b and 6b are likely to wear friction. However, in the embodiment of FIG. 3, when the annular transmission 6 is displaced in the axial direction, the ball 21 rolls in the spline 2b of the pulley 2 and the annular transmission 6 is displaced in the axial direction. Wear can be eliminated, the life and performance of the power transmission device can be improved, and the same effects as the pulley unit 1 according to FIG. 1 can be obtained.

Side surface sectional drawing which shows the whole structure of the pulley unit which concerns on the best form of this invention 1 is a perspective view of the annular transmission body of FIG. Side surface sectional drawing which shows the whole structure of the pulley unit which concerns on the other form of this invention.

Explanation of symbols

2 Pulley (outer ring)
2b Spline 3 Rotor shaft (inner ring)
3a Thread groove 6 Annular transmission 6a Thread groove 6b Spline 8, 9 Torsion coil spring 12 Ball

Claims (1)

  A power transmission device for transmitting power between two annular bodies concentrically arranged inside and outside in a radial direction, wherein an annular transmission is arranged between the two annular bodies and springs are arranged on both axial sides of the annular transmission. In addition, the annular transmission body is coupled to the outer ring body so as to be integrally rotatable and axially displaceable, and a plurality of balls are interposed in thread grooves respectively formed with respect to the inner ring body. A power transmission device characterized by being coupled together.

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