JP2007270884A - Pulley unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pulley unit which has a small and compact structure and prevents the occurrence of an abnormal high-speed rotation state leading to the deterioration of durability by adjusting a power transmission efficiency in a high-speed rotation region. <P>SOLUTION: When rotation speed of an alternator pulley 2 exceeds the set value, centrifugal force acting on a weight 6 of a rotation adjustment mechanism 4 is increased so that the weight 6 moves radially outward against biasing force of a compression coil spring 6a. A slide member 7 follows to move to a wall part 3d side in an axial direction by biasing force of a tension coil spring 7d. As the slide member 7 moves to the wall part 3d side, the clearance L with a magnet 8 is increased to the maximum clearance L2. In magnetic fluid M for filling the clearance L2, shearing stress in a direction orthogonal to a magnetic field is reduced to lower the viscosity with increasing the clearance L2. Power transmission efficiency from the alternator pulley 2 to the alternator shaft 3 by the rotation adjustment mechanism 4 is deteriorated to reduce the rotation speed of the alternator pulley 2 to a set value. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pulley unit.

  For example, when an alternator is driven from a crankshaft (crank pulley) of an automobile engine via a belt, a pulley unit, etc., the alternator also tends to rotate at a higher speed as the engine performance and speed increase ( Patent Document 1). For this reason, it may rotate at a high speed (for example, 18000 rpm) far exceeding the number of rotations (for example, 5000 rpm) required when considering the power generation efficiency. As described above, as a result of being rotated at an unnecessarily high speed, there is a problem that a life reduction due to wear occurs mainly in sliding parts such as a bearing and a brush, and durability (reliability) is lowered.

JP-A-5-263091

  For a pulley unit mainly used in an auxiliary machine such as an alternator, a water pump, an air compressor, and a power steering pump that are driven by an automobile engine, such a severe operating situation in a high speed region is also disclosed in Patent Document 1 and the like. It can be said that this is a new issue that was not anticipated.

  An object of the present invention is to provide a pulley unit having a small and compact structure while preventing occurrence of an abnormal high-speed rotation state that reduces durability by adjusting power transmission efficiency in a high-speed rotation region. There is.

Means for Solving the Problems and Effects of the Invention

In order to solve the above problems, the pulley unit according to the present invention is:
One of the pulley around which the belt is wound and the rotation shaft arranged concentrically with the pulley and capable of rotating integrally is a driving body and the other is a driven body, and a rotation adjusting mechanism between the driving body and the driven body. Is an intervening pulley unit,
The rotation adjusting mechanism is disposed in an annular chamber formed between the driving body and the driven body and enclosing a magnetic fluid,
A slide member having magnetism and movable along the axial direction on the driven body side according to the rotational speed of the driving body;
The slide member and a magnet fixed to the prime mover side so as to face each other so as to form a predetermined interval in the axial direction,
When the rotational speed of the prime mover exceeds a predetermined value, the slide member moves in the axial direction to increase the interval, and as the interval increases, the prime mover to the follower by the rotation adjustment mechanism satisfying the interval. It is characterized in that the power transmission efficiency to is reduced.

  As described above, in the high-speed rotation region, by using the fact that the gap between the magnetic slide member and the magnet is increased and the viscosity of the magnetic fluid is lowered with the increase in the gap, the prime mover ( The power transmission efficiency from the pulley (rotary shaft) to the driven body (rotary shaft or pulley) is reduced. As a result, in a high-speed rotation region of a predetermined value or higher, it is possible to prevent further high-speed rotation by reducing the power transmission efficiency. In other words, it is possible to operate efficiently while maintaining high power transmission efficiency until reaching a predetermined high-speed rotation region.

  Therefore, when used in an auxiliary pulley unit such as an alternator, water pump, air compressor, power steering pump, etc. driven by an automobile engine, the power transmission efficiency from the pulley to the rotating shaft in the high-speed rotation region is reduced. Thus, it is possible to maintain the durability of the bearings on the auxiliary machine side. On the other hand, when used in a pulley unit between a crankshaft and a crank pulley of an automobile engine, the power transmission efficiency from the rotating shaft (crankshaft) to the pulley (crank pulley) in the high-speed rotation region is reduced, and the auxiliary machine is In addition to maintaining the durability of the side bearings and the like, energy (horsepower) generated in the engine can be prevented from being wasted on the auxiliary machine side, which can contribute to an improvement in fuel consumption.

  Moreover, the rotation adjusting mechanism may be provided with a magnetic slide member and a magnet in an annular chamber in which a magnetic fluid is sealed. As a result, the pulley unit can be made compact and compact.

  Here, the magnetic fluid is a suspension in which solid fine particles of a ferromagnetic material such as magnetite are uniformly dispersed in a liquid using a surfactant, as is generally well known. The ferrofluid in the magnetic field (magnetic field) generates shear stress in the direction perpendicular to the magnetic field (shear slip in the direction perpendicular to the magnetic field) because the solid particles form clusters (chain structure) along the direction of the magnetic field. Internal stress for increasing the viscosity) and the viscosity increases. Since the variable viscosity magnetic fluid has a property that the viscosity greatly changes with the strength of the magnetic field, for example, the viscosity varies greatly only by changing the interval between the magnetic bodies. MR fluid (Magneto Rheological Fluid) is also considered as a kind of variable viscosity magnetic fluid.

  Therefore, it is only necessary that the magnetic slide member is disposed opposite to the magnet, and the magnetic fluid satisfies the axial distance between them. The slide member includes a ferromagnetic material (eg, Fe, Ni, Co and alloys thereof), a paramagnetic material (eg, Al, Mn, Pb, Pt, K, Na and alloys thereof), and a diamagnetic material (eg, Cu, Ag). , Bi, Sb, and alloys thereof). However, in order to increase the fluctuation range of the viscosity of the magnetic fluid, it is desirable that the slide member is made of a ferromagnetic material.

  By the way, the slide member is arranged so that a movable body that generates a centrifugal force according to the number of rotations of the prime mover and can move in the radial direction is always in contact, and the slide member is arranged in the radial direction by the centrifugal force. It is desirable to move in the axial direction following the movement. By following and moving a moving body (for example, a spherical weight) that can move in the radial direction by the centrifugal force during rotation, the slide member can move smoothly in the axial direction.

  Further, the moving body includes a wall portion that extends in a radial direction from the driven body and forms an end surface on one side of the annular chamber, and a slide member that is disposed in the annular chamber and is biased toward the wall portion. It is desirable to hold it in between. Thus, since the moving body is held using the wall portion that forms a part of the annular chamber, the annular chamber and the inside thereof can be formed in a compact and compact manner.

  Furthermore, in order to move the moving body in the radial direction and move the slide member in the axial direction, the separation distance increases as the opposing surface of the wall portion of the driven body and the slide member moves outward in the radial direction. It is good to form. Thus, since the opposing surface of a wall part and a slide member is formed so that it may spread toward the outer side, the movement to the radial direction outer side of a moving body can be performed smoothly. Specifically, by making the wall portion side a vertical surface and the slide member side a tapered surface, the moving body can move more smoothly in the radial direction while sufficiently securing the volume of the annular chamber. .

  By the way, the magnet is fixed to the driving body side on the side opposite to the side where the driven body is positioned with respect to the sliding member, and the sliding member increases the distance from the magnet when moving in the direction approaching the wall portion. Can do. As described above, the magnet and the slide member can be compactly accommodated in the annular chamber, and the distance between the two can be easily followed by the change in the rotational speed in order to change the viscosity of the magnetic fluid. As a result, the pulley unit can be further reduced in size.

Example 1
Hereinafter, embodiments of the present invention will be described with reference to examples shown in the drawings. FIG. 1 is a half sectional view showing an example of a pulley unit according to the present invention, and FIG. 2 is a half sectional view showing an operation at the time of high speed rotation. FIG. 1 shows a pulley unit 1 of an alternator (not shown) driven by an automobile engine (not shown), and an alternator pulley 2 (pulley) as a driving body to which driving force from the engine is transmitted from a belt B. An alternator shaft 3 (rotary shaft) as a follower that is arranged concentrically with the alternator pulley 2 and can rotate integrally, and a rotation adjusting mechanism 4 interposed between the alternator pulley 2 and the alternator shaft 3; It is equipped with. Therefore, in FIG. 1, the driving force of the engine is transmitted from belt B → alternator pulley 2 → rotation adjustment mechanism 4 → alternator shaft 3.

  Among these, the alternator pulley 2 has a cylindrical pulley body 2b in which a wavy groove 2a for winding the belt B is formed on the outer periphery. An annular flange portion 2c is integrally formed so as to extend inward in the radial direction on one end side (left end side) in the axial direction of the pulley body 2b.

  On the other hand, the alternator shaft 3 has a cylindrical shaft body 3a, and an alternator input shaft (not shown) is screwed and fixed to a mounting shaft hole 3b formed on the inner surface side thereof. Further, a ball bearing 11 (rolling bearing; bearing portion) is interposed at the other axial end side (right end side) of the shaft body 3a and the pulley body 2b. The ball bearing 11 includes an annular inner ring 11a (inner raceway) fixed to the outer peripheral surface 3c of the shaft body 3a and an annular outer ring 11b (outer raceway) fixed to the inner peripheral surface 2d of the pulley body 2b. Wheel) and a plurality of balls (rolling elements) that roll between the inner ring 11a and the outer ring 11b. The ball bearing 11 is supported by an annular wall portion 3d that is integrally extended from the central portion of the outer peripheral surface 3c of the shaft body 3a toward the outer side in the radial direction on one end side (left end side) in the axial direction. ing. Therefore, the relative movement in the axial direction between the alternator pulley 2 and the alternator shaft 3 is restricted by the ball bearing 11 and the wall 3d.

  Next, the rotation adjusting mechanism 4 is disposed in the annular chamber 5 in which the magnetic fluid M is enclosed. The annular chamber 5 has a rectangular cross section due to the inner peripheral surface 2d of the pulley body 2b and the outer peripheral surface 3c of the shaft body 3a, and the flange portion 2c of the pulley body 2b and the wall portion 3d of the shaft body 3a. Thus, it is formed in a donut shape from the central part of the pulley unit 1 to one end part side (left end part side). Reference numeral 12 denotes a circle interposed between the inner peripheral surface 2d of the pulley main body 2b and the tip of the wall 3d, and between the outer peripheral surface 3c of the shaft main body 3a and the tip of the flange 2c. An annular sealing seal is shown.

  Inside the annular chamber 5 are a weight 6 (moving body) that can move in the radial direction by a centrifugal force accompanying rotation, and a slide member 7 that can move along the axial direction on the outer peripheral surface 3c of the shaft body 3a. The magnet 8 fixed to the flange portion 2c of the pulley body 2b is housed.

  Among these, the weights 6 are formed in a spherical shape, and a plurality (for example, four) of weights 6 are arranged at predetermined angular intervals (for example, 90 ° intervals) in the circumferential direction. Each weight 6 is formed in a radial direction by a compression coil spring 6a (biasing member) on an inner surface of an annular flange 3e formed to project from the tip of the wall 3d toward one end in the axial direction (left end). The center side is biased and supported. Each weight 6 is sandwiched and held so as to always contact the wall 3d and the slide member 7.

  The slide member 7 is formed of a ferromagnetic material (for example, steel) in an annular shape, and a bush 7b, which is a slide bearing, is fixed to the inner diameter portion 7a of the slide member 7 so as to be movable along the axial direction. The slide member 7 is formed in a tapered surface shape so that the facing surface 7c facing the vertical wall portion 3d is separated toward the outside in the radial direction (the separation distance becomes large). The slide member 7 and the weight 6 are urged and supported on the wall 3d side by a tension coil spring 7d (biasing member) spanned between the wall 3d and the slide member 7.

  Therefore, when the rotation of the alternator pulley 2 becomes high speed, the weight 6 generates a centrifugal force according to the rotational speed, and moves outward in the radial direction against the urging force of the compression coil spring 6a. The slide member 7 follows the movement of the weight 6 outward in the radial direction, and moves to the axial wall 3d side by the biasing force of the tension coil spring 7d (see FIG. 2).

  The magnet 8 is formed in an annular shape, and is fixed to the inner surface (the annular chamber 5 side) of the flange portion 2c of the pulley body 2b on one end side (left end portion side) in the axial direction of the alternator pulley 2. That is, the magnet 8 is disposed opposite to the slide member 7 with an interval L (L1) filled with the magnetic fluid M in the axial direction. Accordingly, when the slide member 7 moves toward the axial wall 3d side, the distance L from the magnet 8 increases to L2 (see FIG. 2).

  Next, the operation of the pulley unit 1 configured as described above will be described with reference to FIGS. 1 and 2. As shown in FIG. 1, when the alternator pulley 2 rotates at a set value (for example, 5000 rpm), the interval L between the slide member 7 and the magnet 8 is maintained at the initial interval L1. At this time, in the magnetic fluid M satisfying the distance L1, shear stress (internal stress for causing shear slip in the direction perpendicular to the magnetic field) across the magnetic field between the slide member 7 and the magnet 8 is increased, and the viscosity is maintained high. (See FIG. 5). Therefore, the power transmission efficiency from the alternator pulley 2 to the alternator shaft 3 by the rotation adjusting mechanism 4 is kept high, and the power is efficiently transmitted.

  As shown in FIG. 2, when the rotational speed of the alternator pulley 2 exceeds the set value, the centrifugal force acting on the weight 6 of the rotation adjusting mechanism 4 increases, and the weight 6 resists the biasing force of the compression coil spring 6a. Then, it moves outward in the radial direction while being slidably guided by the vertical wall portion 3d and the tapered opposing surface 7c of the slide member 7. At the same time, the slide member 7 follows and moves toward the wall 3d side in the axial direction by the biasing force of the tension coil spring 7d. As the slide member 7 moves to the wall 3d side, the interval L with the magnet 8 increases to the maximum interval L2.

  As the distance L2 between the magnet 8 and the slide member 7 increases, in the magnetic fluid M satisfying the distance L2, the shear stress in the direction orthogonal to the magnetic field decreases and the viscosity decreases (see FIG. 5). Therefore, the power transmission efficiency from the alternator pulley 2 to the alternator shaft 3 by the rotation adjusting mechanism 4 decreases, and the rotation speed of the alternator pulley 2 decreases to the set value.

  As described above, when the rotation speed of the alternator pulley 2 exceeds the set value, the power transmission efficiency from the alternator pulley 2 to the alternator shaft 3 by the rotation adjusting mechanism 4 decreases, so that the rotation of the alternator pulley 2 after a predetermined time elapses. The number drops again to the set value. Therefore, the alternator pulley 2 is prevented from rotating abnormally at high speed, and the durability of the bearing 11 and the brush (not shown) is maintained. The maximum interval L2 may be set within a range in which power generation (charging) by the alternator can be performed without hindrance.

(Example 2)
FIG. 3 is a half sectional view showing another example of the pulley unit according to the present invention, and FIG. 4 is a half sectional view showing the operation at the time of high speed rotation. FIG. 3 shows a pulley unit 101 of an automobile engine (not shown) for driving an alternator (not shown), an engine output shaft 103 (rotary shaft) as a prime mover directly connected to the crankshaft of the engine, and the engine An engine pulley 102 (pulley) as a driven body that is arranged concentrically with the output shaft 103 and can rotate integrally, and a rotation adjusting mechanism 4 interposed between the engine output shaft 103 and the engine pulley 102. I have. Therefore, in FIG. 3, the driving force of the crankshaft of the engine is transmitted from the engine output shaft 103 → the rotation adjusting mechanism 4 → the engine pulley 102 → the belt B.

  Among these, the engine pulley 102 has a cylindrical pulley body 102b in which a wavy groove 102a for winding the belt B is formed on the outer periphery. An annular flange portion 102c is integrally formed to extend inward in the radial direction on one end side (left end side) in the axial direction of the pulley body 102b.

  On the other hand, the engine output shaft 103 has a cylindrical shaft main body 103a, and a crankshaft (not shown) is screwed and fixed to a mounting shaft hole 103b formed on the inner surface side thereof. Further, a ball bearing 11 (rolling bearing; bearing portion) is interposed at the other axial end side (right end side) of the shaft main body 103a and the pulley main body 102b. The ball bearing 11 includes an annular inner ring 11a (inner raceway) fixed to the outer peripheral surface 103c of the shaft main body 103a and an annular outer ring 11b (outer raceway) fixed to the inner peripheral surface 102d of the pulley main body 102b. Wheel) and a plurality of balls (rolling elements) that roll between the inner ring 11a and the outer ring 11b. The ball bearing 11 is supported at one end (left end) in the axial direction by an annular wall portion 102e integrally extending from the center of the inner peripheral surface 102d of the pulley body 102b toward the inside in the radial direction. Has been. Therefore, the relative movement of the engine pulley 102 and the engine output shaft 103 in the axial direction is restricted by the ball bearing 11 and the wall 102e.

  Next, the rotation adjusting mechanism 4 is disposed in the annular chamber 5 in which the magnetic fluid M is enclosed. The annular chamber 5 is surrounded by the inner peripheral surface 102d of the pulley main body 102b and the outer peripheral surface 103c of the shaft main body 103a and the flange portion 102c and the wall portion 102e of the pulley main body 102b so as to have a rectangular cross section. Thus, the pulley unit 101 is formed in a donut shape from the center to one end (left end).

  Inside the annular chamber 5, there are a weight 6 (moving body) movable in the radial direction by a centrifugal force accompanying rotation, and a slide member 7 movable along the axial direction on the inner peripheral surface 102d of the pulley body 102b. And the magnet 8 fixed to the outer peripheral surface 103c of the shaft main body 103a are housed.

  Among these, the weights 6 are formed in a spherical shape, and a plurality (for example, four) of weights 6 are arranged at predetermined angular intervals (for example, 90 ° intervals) in the circumferential direction. Each weight 6 is radially formed by a compression coil spring 6a (biasing member) on an inner surface of an annular flange portion 102f formed to project from the base end portion of the wall portion 102e to one end side (left end portion side) in the axial direction. It is biased and supported at the center of the direction. Each weight 6 is sandwiched and held so as to always contact the wall 102e and the slide member 7.

  The slide member 7 is formed of a ferromagnetic material (for example, steel) in an annular shape, and a bush 7b, which is a slide bearing, is fixed to the inner diameter portion 7a of the slide member 7 so as to be movable along the axial direction. The slide member 7 is formed in a tapered surface shape so that the facing surface 7c facing the vertical wall portion 102e is separated toward the outside in the radial direction (the separation distance becomes large). The slide member 7 and the weight 6 are urged and supported on the side of the wall portion 102e by a tension coil spring 7d (biasing member) spanned between the wall portion 102e and the slide member 7.

  Therefore, the weight 6 generates a centrifugal force according to the rotational speed when the engine output shaft 103 rotates at a high speed, and moves outward in the radial direction against the urging force of the compression coil spring 6a. The slide member 7 moves toward the wall portion 102e in the axial direction by the urging force of the tension coil spring 7d following the weight 6 moving outward in the radial direction (see FIG. 4).

  The magnet 8 is formed in an annular shape, and is fixed to the inner peripheral surface 103 c on one end side (left end portion side) in the axial direction of the engine output shaft 103. That is, the magnet 8 is disposed opposite to the slide member 7 with an interval L (L1) filled with the magnetic fluid M in the axial direction. Therefore, when the slide member 7 moves toward the axial wall portion 102e, the distance L from the magnet 8 increases to L2 (see FIG. 4).

  Next, the operation of the pulley unit 101 configured as described above will be described with reference to FIGS. 3 and 4. As shown in FIG. 3, when the engine output shaft 103 rotates at a set value (for example, 5000 rpm), the interval L between the slide member 7 and the magnet 8 is maintained at the initial interval L1. At this time, in the magnetic fluid M satisfying the distance L1, shear stress (internal stress for causing shear slip in the direction perpendicular to the magnetic field) across the magnetic field between the slide member 7 and the magnet 8 is increased, and the viscosity is maintained high. (See FIG. 5). Therefore, the power transmission efficiency from the engine output shaft 103 to the engine pulley 102 by the rotation adjusting mechanism 4 is kept high, and power transmission is performed efficiently.

  As shown in FIG. 4, when the rotational speed of the engine output shaft 103 exceeds the set value, the centrifugal force acting on the weight 6 of the rotation adjusting mechanism 4 becomes large, and the weight 6 acts on the urging force of the compression coil spring 6a. On the contrary, it moves outward in the radial direction while being slidably guided by the vertical wall portion 102e and the tapered opposing surface 7c of the slide member 7. At the same time, the slide member 7 follows and moves toward the wall portion 102e in the axial direction by the urging force of the tension coil spring 7d. Then, as the slide member 7 moves to the wall 102e side, the interval L with the magnet 8 increases to the maximum interval L2.

  As the distance L2 between the magnet 8 and the slide member 7 increases, in the magnetic fluid M satisfying the distance L2, the shear stress in the direction orthogonal to the magnetic field decreases and the viscosity decreases (see FIG. 5). Therefore, the power transmission efficiency from the engine output shaft 103 to the engine pulley 102 by the rotation adjusting mechanism 4 decreases, and the rotation speed of the engine output shaft 103 decreases to the set value.

  As described above, when the rotational speed of the engine output shaft 103 exceeds the set value, the power transmission efficiency from the engine output shaft 103 to the engine pulley 102 by the rotation adjusting mechanism 4 decreases. The number of revolutions 103 decreases to the set value again. Therefore, the engine output shaft 103 is prevented from rotating at an abnormally high speed, and the durability of the bearing 11 and the brush (not shown) is maintained. Further, it is possible to prevent energy (horsepower) generated in the engine from being wasted on the alternator side and contribute to improvement in fuel consumption. The maximum interval L2 may be set within a range in which power generation (charging) by the alternator can be performed without hindrance.

The half sectional view showing an example of the pulley unit concerning the present invention. FIG. 2 is a half cross-sectional view showing the operation of the pulley unit of FIG. 1 during high-speed rotation. The half sectional view showing other examples of the pulley unit concerning the present invention. FIG. 4 is a half sectional view showing the operation of the pulley unit of FIG. 3 during high-speed rotation. The graph which shows the relationship between the space | interval of a magnet and a slide member, the viscosity of a magnetic fluid, and power transmission efficiency.

Explanation of symbols

1 Pulley unit 2 Alternator pulley (pulley)
3 Alternator shaft (rotating shaft)
4 Rotation adjustment mechanism 5 Annular chamber 6 Weight (moving body)
7 Slide member 8 Magnet 101 Pulley unit 102 Engine pulley (pulley)
103 Engine output shaft (rotary shaft)
B Belt M Magnetic fluid L Interval

Claims (5)

One of the pulley around which the belt is wound and the rotation shaft arranged concentrically with the pulley and capable of rotating integrally is a driving body and the other is a driven body, and a rotation adjusting mechanism between the driving body and the driven body. Is an intervening pulley unit,
The rotation adjusting mechanism is disposed in an annular chamber formed between the driving body and the driven body and enclosing a magnetic fluid,
A slide member having magnetism and movable along the axial direction on the driven body side according to the rotational speed of the driving body;
The slide member and a magnet fixed to the prime mover side so as to face each other so as to form a predetermined interval in the axial direction,
When the rotational speed of the prime mover exceeds a predetermined value, the slide member moves in the axial direction to increase the interval, and as the interval increases, the viscosity of the magnetic fluid that satisfies the interval decreases. A pulley unit that reduces power transmission efficiency from the driving body to the driven body by a rotation adjusting mechanism. The slide member is arranged so that a movable body that generates a centrifugal force according to the number of rotations of the prime mover and is movable in a radial direction is always in contact,
The pulley unit according to claim 1, wherein the slide member moves in the axial direction following the movement of the moving body in the radial direction by centrifugal force.   The movable body includes a wall portion that extends in a radial direction from the follower to form an end surface on one side of the annular chamber, and the slide that is disposed in the annular chamber and is biased toward the wall portion. The pulley unit according to claim 2 held between members.   In order to move the movable body in the radial direction and move the slide member in the axial direction, the facing surface between the wall portion of the driven body and the slide member becomes larger in the radial direction outward. The pulley unit according to claim 3 formed as described above. The magnet is fixed to the prime mover side on the side opposite to the side where the follower is positioned with respect to the slide member,
The pulley unit according to claim 3 or 4, wherein the slide member increases a distance between the slide member and the magnet when the slide member moves in a direction approaching the wall portion.

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