JP4287983B2 - Pulley unit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pulley unit having a one-way clutch. This pulley unit is installed in a crankshaft of an engine such as an automobile or an auxiliary machine driven from the crankshaft via a belt. Examples of the auxiliary machine include an automobile alternator, an air conditioner compressor, a water pump, and a cooling fan.
[0002]
[Prior art]
Conventionally, various one-way clutches using wedge members such as rollers and sprags have been known, but in either configuration, the driven ring is rotated synchronously by changing the biting force of the wedge member. It is configured to switch between a locked state and a free state in which both rings are relatively rotated.
[0003]
Such a one-way clutch may be used in order to prevent the fluctuation of the angular velocity from being transmitted to the driven ring in a situation where the angular velocity of the driving ring is increased or decreased. In other words, the one-way clutch is brought into a locked state or a free state according to fluctuations in the angular velocity of the driving ring, and the rotational power is transmitted to or cut off from the driving ring to the driven ring. Can be absorbed.
[0004]
[Problems to be solved by the invention]
The conventional one-way clutch switches between two states, a locked state for transmitting power and a free state for interrupting power transmission. When an excessive torque is applied in the locked state, a high angular acceleration is increased. In such a case, excessive torque may act on the one-way clutch.
[0005]
In the case of such a structure in which such a one-way clutch is incorporated in a pulley unit mounted on an automobile auxiliary machine or the like, the excessive torque acts as described above, causing the belt to slide against the pulley, Fluctuations increase, leading to a reduction in belt life.
[0006]
In view of such circumstances, it is an object of the present invention to allow a one-way clutch to absorb an excessive torque without causing the excessive torque to be transmitted by sliding the clutch portion when the excessive torque is applied.
[0007]
[Means for Solving the Problems]
According to the pulley unit of the present invention, in accordance with the rotational speed difference between the driving ring and the driven ring arranged concentrically inside and outside in the radial direction in the opposed annular space between the pulley and the shaft inserted through the inner periphery thereof. A one-way clutch that switches between a locked state in which the driven ring is synchronously rotated with respect to the drive ring and a free state in which the driven ring is rotated relative to the driving ring, and a rolling bearing disposed on at least one axial side of the one-way clutch are provided. A pulley unit that is narrower in the circumferential direction on the outer circumferential surface of the annular body on the radially inner side of the two annular bodies and narrower on the other side in the circumferential direction between the inner circumferential surface of the other annular body. A cam surface is formed to form a wedge-shaped space which is widened at the inner surface of the cage, and the rollers are positioned on the inner ring body in a circumferential direction with respect to the inner ring body. An elastic member for pressing the roller in the pocket; and By being accommodated in, one by one in a state of being pressed against the narrow side of the wedge space in a predetermined circumferential direction rolling ranges are arranged, wherein the cam surface is steeply from the outer peripheral surface of the inner ring member The convex spherical surface is formed in a shape having a steep falling portion that falls and a convex spherical portion that is inclined so that the depth gradually increases in one direction in the circumferential direction , and before the steep falling portion. At the position on the part, the wedge angle at that position is set in the range of 4 to 6 degrees so that the roller locks, while the roller moves further to the narrow side of the wedge space and the outer peripheral surface of the inner ring The wedge angle at the abutting position is set to 11 degrees or more so that the roller slides and rotates in a state where it abuts against the corner of the sharply falling portion .
[0012]
As described above, in the pulley unit of the present invention, when the rotational torque exceeding the required value is applied, the wedge member of the one-way clutch is changed from the locked state to the sliding state so as to block transmission of the transmitted rotational torque. ing.
[0013]
In addition, since the pulley unit of the present invention is configured to incorporate the one-way clutch as described above, it is possible to suppress or prevent slipping of the belt wound around the pulley when an excessive rotational torque is input. .
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The details of the present invention will be described based on embodiments shown in the drawings.
[0015]
1 to 5 show a first embodiment of the present invention. 1 is a longitudinal sectional view of a pulley unit, FIG. 2 is an arrow view of a cross section taken along line (2)-(2) in FIG. 1, and FIG. 3 is a developed plan view showing the inside of a pocket of a one-way clutch. These are the perspective views which show the cam surface of the inner ring | wheel in a one way clutch, FIG. 5 is a graph which shows the rotation fluctuation waveform of a pulley unit.
[0016]
The illustrated pulley unit 1 includes a pulley 2, a hollow shaft 3, a one-way clutch 4, and two rolling bearings 5 and 5.
[0017]
The pulley 2 is rotationally driven via a V-rib shaped belt 6 by, for example, a crankshaft of an automobile engine, and a wave-like groove around which the belt 6 is wound is formed on the outer periphery thereof.
[0018]
The hollow shaft 3 is inserted into the inner periphery of the pulley 2 and is fixed to an input shaft (for example, a rotor of an alternator) of an auxiliary machine of an automobile engine (not shown).
[0019]
The one-way clutch 4 is interposed in the axial center of the opposed annular space between the pulley 2 and the hollow shaft 3, and includes an inner ring 10, an outer ring 11, a synthetic resin annular retainer 12, and a plurality of rollers 13. An elliptical coil spring 14 is provided as an elastic member.
[0020]
The two rolling bearings 5 and 5 are interposed one by one on both sides in the axial direction of the opposed annular space between the pulley 2 and the hollow shaft 3, and in this embodiment, a general deep groove type ball bearing is used. It has been. Seals (not shown) are attached to the outer ends of the rolling bearings 5 and 5, respectively, and a lubricant such as grease is enclosed. In addition, a seal ring 7 made of an annular plate is attached to the outside of the outer rolling bearing 5 in order to prevent further muddy water and the like from being directly applied to the rolling bearing 5.
[0021]
Each component of the one-way clutch 4 will be described.
[0022]
The inner ring 10 is externally fitted to the hollow shaft 3 by press fitting, and concave cam surfaces 10a are provided at several circumferential positions on the outer circumferential surface thereof. The cam surface 10a is formed in a concave shape so that the depth gradually increases toward one circumferential direction, and the facing portion between the cam surface 10a and the inner circumferential surface of the outer ring 11 faces one circumferential direction. It becomes a wedge-shaped space that becomes narrower. Since the shape of each cam surface 10a is characteristic, it will be described in detail later.
[0023]
The outer ring 11 is fitted into the pulley 2 by press fitting, and an inner peripheral surface thereof is formed in a cylindrical shape.
[0024]
The cage 12 is disposed in the annular space facing the inner and outer rings 10 and 11 and is externally positioned with respect to the inner ring 10 in a circumferential direction and an axial direction. In a region corresponding to the cam surface 10a, a pocket 12a penetratingly formed inside and outside in the radial direction is provided.
[0025]
One roller 13 is accommodated in each pocket 12a of the cage 12 in a state where the circumferential rolling range is restricted.
[0026]
The coil spring 14 is attached to a protrusion 12b protruding from the inner wall surface of each pocket 12a of the cage 12, and the wedge-shaped space forming the roller 13 by the cam surface 10a and the inner peripheral surface of the outer ring 11 is narrow. It pushes to the side (lock side).
[0027]
The positioning of the cage 12 in the axial direction and the circumferential direction is performed by fitting a convex portion 12c provided at one axial end of the cage 12 with a concave portion 10b provided at one axial end of the inner ring 10. It is done.
[0028]
Next, the operation of the pulley unit 1 will be described. Here, the pulley 2 is rotationally driven by the belt 6, and power is transmitted from the pulley 2 to the hollow shaft 3. Here, when the rotational speed of the pulley 2 is relatively higher than that of the hollow shaft 3, the roller 13 of the one-way clutch 4 is rolled to the narrow side of the wedge-shaped space and is locked. The shaft 3 and the shaft 3 are integrally rotated. However, when the rotational speed of the pulley 2 becomes relatively slower than that of the hollow shaft 3, the rollers 13 of the one-way clutch 4 are rolled to the wide side of the wedge-shaped space and become free. The transmission of the rotational power to 3 is cut off, and the hollow shaft 3 continues to rotate only with the rotational inertia force.
[0029]
And in the said Embodiment 1, when the rotational torque input from the pulley 2 exceeds the required value about the one-way clutch 4 used for the pulley unit 1, the pulley 2 and the hollow shaft are arranged on the narrow side of the wedge-shaped space. The power transmission from the pulley 2 to the hollow shaft 3 is cut off by sliding with respect to the shaft 3.
[0030]
In order to realize such an operation, the shape of the cam surface 10 of the inner ring 10 is as follows.
[0031]
The cam surface 10a has a steeply falling portion 10a1 that sharply falls from the outer peripheral surface of the inner ring 10, and a convex spherical portion 10a2 that is inclined so that the depth gradually increases from the outer circumferential surface toward one side in the circumferential direction. It is formed into a shape. As shown in FIG. 4, the convex spherical portion 10 a 2 is formed by securing the curvature center O <b> 1 at a position shifted from the curvature center of the inner ring 10.
[0032]
In such a cam surface 10a, the wedge angle θ1 at the lock position P1 of the convex spherical surface portion 10a2 is a small angle so that the roller 13 is strongly bitten, and the wedge angle θ2 at the sliding rotation position P2 of the corner portion 10a3 is The angle is large enough to slide 13. However, it is preferable that the wedge angle θ1 is set in a range of 4 to 6 degrees, for example, and the wedge angle θ2 is set to be 11 degrees or more, for example.
[0033]
The roller 13 is set to be locked when it is positioned at the required position P1 on the shallow side of the cam surface 10a. When the roller 13 moves further to the shallower side from the lock position P1, the roller 13 moves to the outer periphery of the inner ring 10. The roller 13 is set to slide and rotate when the roller 13 is received by contacting the corner 10a3 between the surface and the cam surface 10a and reaches the position P2.
[0034]
Here, the torque at which the roller 13 slides and rotates can be set based on the separation interval between the lock position P1 and the sliding rotation position P2 and the spring constants of the inner ring 10 and the outer ring 11.
[0035]
In addition to the wedge angles θ1 and θ2, the roller 13 is engaged with the friction between the inner peripheral surface of the outer ring 11 forming the wedge-shaped space and the steeply falling portions 10a1 and the corner portions 10a3 of the cam surface 10a. The factor μ is also relevant. That is, a condition necessary for torque transmission at the time of locking is generally known, but can be expressed by a relational expression of μ> tan θ / 2. θ is the wedge angle.
[0036]
With such a configuration, the operation of the one-way clutch 4 is such that when the roller 13 is locked, that is, in the power transmission state, a rotational torque greater than a predetermined specified value is applied to the pulley 2 as the belt 6 rotates. When added, the roller 13 will be pushed further into the narrow side of the wedge-shaped space. At this time, when the roller 13 is moved to the position P2 where it abuts against the corner portion 10a3, the roller 13 slides and rotates, so that the pulley 2 and the hollow shaft 3 rotate relatively. The power transmission from 2 to the hollow shaft 3 is cut off. As a result, the belt 6 does not slide on the pulley 2 and does not slip and does not slide, so the tension on the tension side (the upstream side in the rotational direction) of the belt 6 becomes stronger and the belt 6 on the loose side (the downstream side in the rotational direction). Tension fluctuations such as weakening of tension can be suppressed, and moreover, no extra stress is applied to the belt 6, which can contribute to the improvement of the life of the belt 6.
[0037]
However, when the rotational torque applied from the belt 6 to the pulley 2 becomes less than a predetermined specified value, the roller 13 is separated from the corner portion 10a3 and returned to the lock position P1, and the roller 13 is locked again. Therefore, power transmission from the pulley 2 to the hollow shaft 3 is performed.
[0038]
Thus, in addition to the original lock and free operation of the one-way clutch 4, the above-described operation of sliding rotation is enabled, so that the upper limit value of the rotational torque for transmitting power can be regulated. The lower limit value and the upper limit value of the rotational torque for transmitting power can be defined.
[0039]
For reference, the rotation fluctuation and tension fluctuation of the pulley unit 1 of the first embodiment are examined, and will be described.
[0040]
The test conditions are such that the pulley unit 1 as a sample is mounted on an alternator attached to the engine, the alternator speed is 2000 rpm, and the load current of the alternator is set to 5A.
[0041]
FIG. 5 shows the results relating to the present embodiment, and FIG. 6 shows the results relating to the conventional example in which the one-way clutch is not used. As is apparent from these figures, in the case of the conventional example, the angular velocity of the pulley 2 fluctuates slightly like a sine curve and is transmitted to the hollow shaft 3 as it is. In the case of the present embodiment, it has been confirmed that even if the angular velocity of the pulley 2 fluctuates slightly like a sine curve, the rotational fluctuation width of the hollow shaft 3 becomes small. Further, in the case of the conventional example, the tension variation between the tension side (downstream in the rotation direction) and the loose side (upstream in the rotation direction) of the belt 6 wound around the pulley 2 is increased. In the case of a form, it has confirmed that those tension | tensile_strength fluctuation amounts are suppressed small.
[0042]
7 to 11 show reference examples of the present invention. 7 is a longitudinal sectional view of the upper half of the pulley unit, FIG. 8 is a sectional view taken along the line (8)-(8) in FIG. 7, and FIG. 9 is an explanatory view showing the operation of the sprag in the one-way clutch. FIG. 10 is a perspective view showing a spring body in the one-way clutch, and FIG. 11 is an explanatory diagram showing the design requirements for the sprags in the one-way clutch.
[0043]
The pulley unit 1 of this reference example is different from the first embodiment in that a one-way clutch 20 using a sprag is used.
[0044]
The one-way clutch 20 here has a generally well-known configuration, and includes a pair of annular plates 21 and 22, a plurality of sprags 23, a retainer 24, and a spring body 25.
[0045]
The sprag 23 has a shape having a drum-shaped cross section, and is disposed between the pair of annular plates 21 and 22.
[0046]
The cage 24 is formed in an annular shape with, for example, a synthetic resin, and is provided with pockets 24a through which the sprags 23 are inserted at several places on the circumference. The cage 24 is interposed between the pair of annular plates 21 and 22.
[0047]
The spring body 25 is formed in an annular shape with a thin spring steel material or the like, and as shown in FIG. 10, through holes 25a through which the sprags 23 are inserted are provided at several places on the circumference thereof. A holding piece 25b that presses the sprag 23 in an upright position is provided in the through hole 25a. The spring body 25 is fitted and attached to the inner diameter side of the cage 24.
[0048]
In this one-way clutch 20, in order to provide the same function as that of the first embodiment described above, the strut angles α and β of the sprags 23 with respect to the pulley 2 and the hollow shaft 3 are inclined so as to exceed the required angles in the lock direction. Sometimes set to change from locked to slipping.
[0049]
Specifically, when the sprag 23 is tilted so as to be in an upright position and its radial dimension becomes the largest, the sprag 23 is in a locked state. In this state, when a rotational torque exceeding a predetermined specified value is applied, When it further falls from the standing posture in the locked state and its radial dimension becomes slightly smaller, it enters a sliding rotation state and power transmission is interrupted.
[0050]
In the state where the sprag 23 is in a sliding state, when the input rotational torque is less than a predetermined specified value, the sprag 23 is returned to the locked state by the reaction force of the elastic deformation of the sprag 23, the pulley 2 and the hollow shaft 3. It will be.
[0051]
Here, the design conditions of the one-way clutch 20 using the sprag 23 will be described.
[0052]
First, as shown in FIG. 11, assuming that the points where the sprags 23 are in contact with the pulley 2 and the hollow shaft 3 are A and B, respectively, the straight line AB and the center O of the track diameter of the pulley 2 and the hollow shaft 3 are drawn. The angles α and β formed by the straight lines OA and OB are called Strat angles. If the angle formed by the straight lines OA and OB is γ, α = β + γ, and α> β is always satisfied.
[0053]
In order for the sprag 23 to engage with the race and transmit torque, tan α must be smaller than the friction coefficient μ of the contact surface. That is, tan α <μ.
[0054]
When the sprag 23 receives torque, a force Q is generated on the strat straight lines A and B. At the contact point A, the vertical component force is P and the contact component force is F.
F = P · tan α.
[0055]
The transmission torque T at this time is
T = N · P · tan α · R1 · l.
[0056]
Here, N is the number of sprags 23, R1 is the orbit radius of the hollow shaft 3, and l is the effective length of the sprags 23.
[0057]
In the pulley unit including the sprag type one-way clutch 20 as described above, the strut angles α and β of the sprag 23 with respect to the pulley 2 and the hollow shaft 3 are set in the locked state when the posture is inclined more than the required angle in the lock direction. If it is set so as to be changed to the slipping state, the above-described slipping operation can be made possible in addition to the original locking and free operation of the one-way clutch 20 as described in the first embodiment. Therefore, the lower limit value and the upper limit value of the rotational torque for transmitting power can be defined. In this way, by preventing an excessive rotational torque from being transmitted, slippage between the belt 6 and the pulley 2 can be eliminated, fluctuations in the tension of the belt 6 can be suppressed, and the life of the belt 6 can be improved. You can contribute.
[0058]
In addition, this invention is not limited only to Embodiment 1 mentioned above, A various application and deformation | transformation can be considered.
[0060]
(1) The detailed configuration of the one-way clutches 4 and 20 in the above embodiment is not limited, and various modifications are conceivable.
[0061]
【The invention's effect】
The pulley unit of the present invention is configured so that the wedge member can be operated in a sliding rotation state or a sliding state in addition to the original locking and free operation of the one-way clutch provided in the pulley unit. The upper limit value of can be regulated. Accordingly, since the lower limit value and upper limit value of the rotational torque for transmitting power can be severely specified, it is possible to select an optimum one according to the object of use, thereby improving usability.
[0062]
Since the pulley unit of the present invention includes the one-way clutch configured so as not to transmit excessive rotational torque as described above, the transmission of power can be cut off when excessive rotational torque is input. It is possible to eliminate slippage between the pulley and the pulley wound around the belt, and to suppress fluctuations in belt tension, thereby contributing to improvement in belt life.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of an upper half of a pulley unit according to Embodiment 1 of the present invention. FIG. 2 is a sectional view taken along line (2)-(2) in FIG. FIG. 4 is a perspective view showing the cam surface of the inner ring in the one-way clutch of the first embodiment. FIG. 5 is a graph showing the rotational fluctuation waveform of the pulley unit of the first embodiment. FIG. 7 is a vertical sectional view of the upper half of a pulley unit according to a reference example of the present invention. FIG. 8 (8) in FIG. )-(8) A cross-sectional view taken along the line [FIG. 9] An explanatory view showing the operation of the sprag in the one-way clutch of the reference example . FIG. 10 is a perspective view showing a spring body in the one-way clutch of the reference example . It shows the design requirements of the sprag in the one-way clutch of reference example Illustration

Claims (1)

Driven with respect to the drive ring according to the difference in rotational speed between the drive ring and the driven ring arranged concentrically inside and outside in the radial direction in the opposite annular space between the pulley and the shaft inserted through the inner circumference thereof A pulley unit in which a one-way clutch that switches between a locked state in which a ring body rotates synchronously and a free state in which a ring body rotates relatively, and a rolling bearing that is disposed on at least one axial side of the one-way clutch are provided. And
A wedge-shaped space that is narrower in the circumferential direction and narrower in the circumferential direction is formed between the annular body and the inner circumferential surface of the other annular body at several places on the outer circumferential surface of the annular body on the radially inner side. A cam surface is provided, and the roller is accommodated in the wedge-shaped space together with an elastic member that presses the roller in a pocket of a cage that is positioned in the circumferential direction with respect to the inner ring. Are arranged one by one in a state of being pressed to the narrow side of the wedge space within the circumferential rolling range of
The cam surface, comprises a steep falling portion falling sharply from the outer peripheral surface of the inner ring member, and a convex spherical surface portion that is inclined so as gradually becomes deeper toward the depth from which the one circumferential direction , Formed into a shape recessed from the outer peripheral surface of the inner ring body to the inner diameter side ,
At the position on the convex spherical surface before the steeply falling portion, the wedge angle at that position is set in the range of 4 to 6 degrees so that the roller is locked, while the roller is further narrow in the wedge space. The wedge angle at the abutment position is set to 11 degrees or more so that the roller slides and rotates in a state where it is in contact with the corner of the outer peripheral surface of the inner ring body and the steeply falling part. Being
Pulley unit characterized by that.

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