JP2003028251A - Friction roller type transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep increase of operation torque as small as possible by generating roller pressing force in proportion to transmitting torque. SOLUTION: A first roller 1 and a second roller 2 which have centers on two parallel separate shafts a, b respectively are arranged not to get into contact with each other. A third roller 3 and a fourth roller 4 getting into contact with both of the first and the second rollers 1, 2 are arranged between the first roller 1 and the second roller 2. Angles between a tangential line of the first roller 1 and the third roller 3 (or the fourth roller 4) and a tangential line of the second roller 2 and the third roller 3 (or the fourth roller 4) are twice or less of friction angles found from a friction coefficiency between the respective rollers, and friction parts are positioned outside the rollers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction roller type transmission.

[0002]

2. Description of the Related Art As a transmission for transmitting power between shafts, a gear transmission is common and widely used. In a gear transmission, proper backlash is indispensable for smooth operation due to a shape error in manufacturing gears. However, when the gear transmission is applied to the purpose of rotating the transmission in a complicated manner, the backlash of the gear transmission hits the tooth flanks when reversing the rotation direction, which causes noise.

In order to cope with this, as a playless (backlashless) power transmission means, a friction roller type transmission has been known for a long time which attempts to transmit power by pressing a roller and utilizing its frictional force. ing. For example, in a planetary roller type speed reducer, a planetary roller arranged around the center roller and a ring roller inscribed with the planetary roller are assembled with a tightening margin by shrink fitting, etc. The force is transmitted by generating a pressing force.

[0004]

In a general friction roller type transmission, a constant inter-roller pressing force is applied to generate a friction force for power transmission. Therefore, power can be transmitted only up to the initially set pressing force range, and it is necessary to initially apply a very large pressing load equivalent to the maximum possible transmission torque.

However, in a general friction roller type transmission, since an extremely large pressing load is always applied, internal loss due to repeated elastic deformation during rotation is generated regardless of the actual transmission torque. And a loss occurs due to an increase in the operating torque of the bearing that receives the load. As a result, the operating torque becomes very large,
In a region where the transmission torque is small, there is a problem that the loss is large and the transmission efficiency is extremely poor.

Further, in Japanese Unexamined Patent Publication No. 6-135339, torque is transmitted between an input side friction roller and an output side friction roller, and when a torque larger than a predetermined value is applied, the rollers are separated. A torque limiting intermediate roller is interposed. Thus, when a torque of a predetermined value or more is applied, the intermediate roller is separated from both rollers, so that excessive torque does not act on each roller.

Further, Japanese Patent Laid-Open No. 6-288453 discloses a torque cam system (orthogonal type rolling transmission device) as a device for applying a pressing load according to a transmission torque. This is effective in adjusting the pressing force in one rotation, but in the case where the transmission direction is reversed, when the rotation direction of the torque cam is switched, a large displacement of the roller for switching the cam surface accompanies the transmission. There is a problem in that a delay and a tapping sound between the cam surface and the roller occur.

Further, in JP-A-2000-16313 and JP-A-2000-16314, in a planetary roller type transmission, the ring roller and the sun roller are slightly decentered so that the planetary roller has a wedge effect. hand,
Although a wedge roller type transmission that obtains a pressing force according to torque has been disclosed, there is a problem that power can be transmitted only in one rotation.

The present invention has been made in view of the above circumstances, and provides a friction roller type transmission capable of transmitting torque without causing a delay or a tapping sound even in the case of reversing the rotation direction. The purpose is to provide.

[0010]

In order to achieve the above object, a friction roller type transmission according to the present invention has two shafts separated from each other, a first roller and a second roller centered on each shaft. The rollers are arranged so as not to contact each other, and a third roller and a fourth roller which contact both the first and second rollers are provided between the first roller and the second roller and between the first roller and the second roller. It is arranged on the opposite side of the line connecting the centers of the first roller and the second roller, and the tangent line of the first roller and the third roller (or the fourth roller), the second roller and the third roller.
The angle formed by the tangent line of the roller (or the fourth roller) is 2 of the friction angle obtained from the coefficient of friction between the rollers.
It is characterized in that it is set to be equal to or less than twice.

In the friction roller type transmission according to the present invention, preferably, the shaft of the first roller and the shaft of the second roller may be parallel to each other.

In the friction roller type transmission according to the present invention, the diameter of the third roller and the diameter of the fourth roller can be made larger than the shortest distance between the peripheral surfaces of the first roller and the second roller.

Further, in the friction roller type transmission according to the present invention, preferably, the friction portion is located outside each roller.

Furthermore, in the friction roller type transmission according to the present invention, the friction portion can be inside either one of the first roller and the second roller.

The friction roller type transmission according to the present invention can also be used in an electric power steering system.

Further, in the friction roller type transmission according to the present invention, it is preferable that the linear expansion coefficient of the housing is equal to that of each roller.

The friction roller type transmission according to the present invention is the third one.
The fourth and fourth rollers can be overlapped, and the first and second rollers can be commonly used in forward and reverse rotation.

According to the present invention, the transmission path of the first roller → the third roller → the second roller and the first roller → the fourth roller →
By forming the transmission path of the second roller, it is possible to perform forward and reverse rotation in the backlashless friction roller type transmission, and by generating the roller pressing force according to the transmission torque. The increase in operating torque can be minimized, the efficiency can be improved especially in the area of low transmission torque, and the roller for power transmission is provided in each rotation direction so as to be in contact with each other. Even in the case of reversing, torque can be transmitted without causing delay or tapping sound.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION A friction roller type transmission (speed reducer) according to an embodiment of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 (a) is a side view of a friction roller type transmission (speed reducer) according to a first embodiment of the present invention, and FIG. It is a schematic perspective view of the shown friction roller type transmission. FIG. 2A is a side view of the friction roller type transmission according to the first embodiment of the present invention (a diagram showing a transmission path of a first roller → a fourth roller → a second roller), FIG. FIG. 2B is a side view of the same (a diagram showing a transmission path of the first roller → the third roller → the second roller).

In the first embodiment, in the friction roller type transmission (speed reducer), as shown in FIGS. 1 and 2, two shafts a and b which are separated from each other in parallel are respectively provided. A small diameter first roller 1 and a large diameter second roller 2 as the center
And are arranged so as not to abut each other.

Between the first roller 1 and the second roller 2 and on the opposite side of the line connecting the centers of the first roller and the second roller, preferably the third roller and the fourth roller having the same diameter are parallel to each other. Is arranged so as to contact both the first and second rollers 1 and 2.

The diameters of the third and fourth rollers are both the first
It is larger than the shortest distance between the peripheral surfaces of the roller and the second roller.

The tangent line between the first roller 1 and the third roller 3 (or the fourth roller 4) and the second roller 2 and the third roller 3
The angle formed by the tangent line of (or the fourth roller 4) is set to be equal to or less than twice the friction angle obtained from the friction coefficient between the rollers, and the friction portion is outside the rollers.

In other words, the center of each roller is P1.
.About.P4, the sum of the angle (α1: ∠P2P1P3) formed by the lines P1P2 and P1P3 and the angle (α2: ∠P1P2P3) formed by the lines P1P2 and P2P3 and the line P1P2.
And the line P1P4 form an angle (α3: ∠P2P1P4) and the line P1P2 forms a line P2P4 (α4: ∠P1P2P
The sum of 4) is set to be less than twice the friction angle (θ = tan ⁻¹ μ).

That is, β = α1 + α2 ≦ 2 · tan ⁻¹ μ
β = α3 + α4 ≦ 2 · tan ⁻¹ μ The contact angle can be defined as an angle formed by a perpendicular line (s: reference line) connecting the centers of the first roller and the second roller.
However, since the magnitudes of the contact forces acting on the contact portions are equal, the resultant force is in the direction of the bisector (n) of the angle formed by each tangent line. The directions of the reference line (s) defining the contact angle and the bisector (n) match if the diameters of the entrance and exit rollers are equal, but they slightly deviate if there is a diameter difference. The forces acting in the two normal directions (directions connecting the centers) acting on the wedge roller from the input / output rollers at the contact portion have the same angle with the preceding bisector (n), so the bisector ( A balance can be achieved by considering (a surface including n,) as a reference. Considering the force acting on the wedge roller as a reference, the contact angle should be defined with reference to the line (plane) in which the normal direction force of the contact portion balances.

When this arrangement is adopted, since the friction angle is small, the third and fourth rollers 3 and 4 are inevitably positioned so as to overlap each other in the axial direction.

With the above structure, a pressing force corresponding to the transmitted torque can be obtained. Therefore, the pressing force (pressing the third and fourth rollers 3 and 4 toward the first and second rollers 1 and 2) necessary for friction transmission is not required. However, in the non-rotating state,
It is better to apply a slight pressing force that secures the initial contact state. Further, each roller is composed of one, but a plurality of rollers may be used.

The operation will be described below with the first roller as an input.

As shown in FIGS. 1 (b) and 2 (b),
When the first roller 1 is rotated clockwise (CW direction),
Since the tangent line between the third roller 3 and the first roller 1 and the tangent line between the third roller 3 and the second roller 2 are at an angle of twice the friction angle or less, each contact angle is equal to or less than the friction angle. Since the third roller 3 and the first roller 1 do not slide relative to each other at the contact portion, a tangential force is applied to the third roller 3 from the first roller 1. The tangential force is a direction in which the third roller 3 approaches the first roller 1, and the tangential force causes the third roller 3 to transmit a counterclockwise (CCW direction) rotational force.

Also at the contact portion between the third roller 3 and the second roller 2, the tangent line between the third roller 3 and the first roller 1 and the tangent line between the third roller 3 and the second roller 2 have a friction angle of 2 °. Since the angles are not more than double, the contact angle of each is less than the friction angle, and the third roller 3 and the second roller 2 do not cause relative sliding at the contact portion. Therefore, the tangential force is applied to the second roller 2 from the third roller 3, and the rotational force in the CW rotational direction is transmitted. As a reaction, a tangential force opposite to that is generated on the third roller 3. This tangential force is a direction that brings the third roller 3 closer to the second roller 2.

The tangential force acting on the third roller 3 is
Since it is the direction in which the third roller 3 is pressed against the first and second rollers 2, it is possible to obtain a pressing force according to the transmitted tangential force, that is, torque.

At this time, as shown in FIG. 2A, even in the fourth roller 4, relative sliding does not occur at the abutting portion thereof, so that the fourth roller 4 is separated from the first and second rollers 1 and 2. Although a tangential force is applied, the direction is a direction in which the fourth roller 4 is separated from the first and second rollers 1 and 2, so that the fourth roller 4 is in contact with the first roller 1 and the second roller 2. It is just rolling around.

Next, as shown in FIGS. 1 (b) and 2 (a), when the first roller 1 rotates in the reverse direction and rotates in the CCW direction, the action of the fourth roller 4 and the third roller 3 works. Although they are replaced, the fourth roller 4 is already in contact with the first roller 1 and the second roller 2, so that the power transmission direction can be smoothly converted when the rotation direction is reversed.

In order to transmit the torque, the third
It suffices that the fourth and third rollers 3 and 4 are in contact with the first and second rollers 1 and 2. In order to secure the contact state,
The third and fourth rollers 3, 4 are replaced by the first and second rollers 1, 2,
A slight pressing force may be obtained.

As described above, according to the first embodiment,
A transmission path of the first roller 1 → the third roller 3 → the second roller 2 and a transmission path of the first roller 1 → the fourth roller 4 → the second roller 2 can be configured, and a backlash-less friction roller type In the transmission (reduction gear), forward and reverse rotations can be made possible, and by increasing the roller pressing force according to the transmission torque, the increase in operating torque can be made as small as possible. Efficiency can be improved in the torque range, and since rollers for power transmission are provided in each rotation direction and are always in contact, there is no delay or tapping sound even when reversing the rotation direction. , Torque transmission can be performed. (Second Embodiment) FIG. 3 (a) is a side view of a friction roller type transmission (speed reducer) according to a second embodiment of the present invention, and FIG. It is a schematic perspective view of the shown friction roller type transmission. FIG. 4A is a side view of a friction roller type transmission according to a second embodiment of the invention (a diagram showing a transmission path of a first roller → a fourth roller → a second roller), FIG. 4B is a side view of the same (a diagram showing a transmission path of the first roller → the third roller → the second roller).

Also in the friction roller type transmission (speed reducer) according to the second embodiment, as shown in FIGS. 3 and 4,
A first roller 1 and a second roller 2 centered on the respective axes are arranged so as not to abut each other on the two axes a and b spaced apart from each other in parallel, and the first and second rollers 1 and 2 are provided. The third roller 4 and the fourth roller 4 that come into contact with both
It is arranged between the first roller 1 and the second roller 2. First
Between the roller 1 and the second roller 2 and between the first roller and the second roller
The third roller and the fourth roller are arranged parallel to each other on the side opposite to the line connecting the centers of the rollers so as to abut both the first and second rollers 1 and 2. The diameters of the third roller and the fourth roller are both larger than the shortest distance between the peripheral surfaces of the first roller and the second roller. The angle formed by the tangent line between the first roller 1 and the third roller 3 (or the fourth roller 4) and the tangent line between the second roller 2 and the third roller 3 (or the fourth roller 4) is
The friction angle is set to be equal to or less than twice the friction angle obtained from the friction coefficient between the rollers, and the friction portion is inside the rollers.

That is, the wedge roller is expanded to be compatible with both rotations, the axial distance is made smaller than the sum of the radii of the first roller 1 and the second roller 2, and the second roller 2 is considered to be the inner peripheral surface. It was The concept of the friction angle and the contact angle is the same if the angle formed by each tangent to the perpendicular of the line connecting the centers of the first roller 1 and the second roller 2 is the contact angle.

Thus, also in the second embodiment, the transmission path of the first roller 1 → the third roller 3 → the second roller 2 and the transmission path of the first roller 1 → the fourth roller 4 → the second roller 2 The transmission path can be configured to enable forward and reverse rotation in a backlash-less friction roller type transmission (speed reducer), and by generating roller pressing force according to the transmission torque. Since the increase in operating torque can be made as small as possible, the efficiency can be improved especially in the low transmission torque region, and the rollers for power transmission are provided in each rotation direction and are always in contact with each other. Even in the case of reversing the rotation direction, torque can be transmitted without causing a delay or a tapping sound. (Third Embodiment) FIG. 5 is a diagram of a friction roller type transmission (speed reducer) according to a third embodiment of the present invention.
Is a front sectional view, and (b) is a side sectional view.

The third embodiment is a concrete embodiment of the first embodiment, and the arrangement, contact angle and friction angle of the first to fourth rollers 1 to 4 are the same as those of the first embodiment. In this example, the idle rollers (third and fourth rollers) are not slightly pressed.

The input shaft a is attached to the pair of housings 10 and 11.
Is rotatably supported by a pair of bearings 12 and 13, and the output shaft b is rotatably supported on the housings 10 and 11 by a pair of bearings 14 and 15.

The pair of housings 10, 11 and the first
Thru / or the fourth rollers 1 to 4 have the same linear expansion coefficient.

As described above, also in the third embodiment, the transmission path of the first roller 1 → the third roller 3 → the second roller 2 and the first roller 1 → the fourth roller 4 → the second roller 2 are transmitted. The transmission path can be configured to enable forward and reverse rotation in a backlash-less friction roller type transmission (speed reducer), and by generating roller pressing force according to the transmission torque. Since the increase in operating torque can be made as small as possible, the efficiency can be improved especially in the low transmission torque region, and the rollers for power transmission are provided in each rotation direction and are always in contact with each other. Even in the case of reversing the rotation direction, torque can be transmitted without causing a delay or a tapping sound. (Fourth Embodiment) FIG. 6 is a diagram of a friction roller type transmission (speed reducer) according to a fourth embodiment of the present invention.
Is a side sectional view, (b) is a sectional view taken along line bb of (a), (c) is a sectional view taken along line cc of (b), (D) is a perspective view of a spring.

The fourth embodiment embodies the first embodiment, and the arrangement, contact angle and friction angle of the first to fourth rollers 1 to 4 are the same as those of the first embodiment. In this example, the idle rollers (third and fourth rollers) are slightly pressed.

The input shaft a is attached to the pair of housings 10 and 11.
Is rotatably supported by a pair of bearings 12 and 13, and the output shaft b is rotatably supported on the housings 10 and 11 by a pair of bearings 14 and 15.

Ring-shaped springs 20 are engaged with the third and fourth rollers 3 and 4, respectively.
Applying a slight pressing force to the third and fourth rollers 3 and 4,
Ensures initial contact.

The pair of housings 10, 11 and the first
Thru / or the fourth rollers 1 to 4 have the same linear expansion coefficient.

Thus, also in the fourth embodiment, the transmission path of the first roller 1 → the third roller 3 → the second roller 2 and the transmission of the first roller 1 → the fourth roller 4 → the second roller 2 The transmission path can be configured to enable forward and reverse rotation in a backlash-less friction roller type transmission (speed reducer), and by generating roller pressing force according to the transmission torque. Since the increase in operating torque can be made as small as possible, the efficiency can be improved especially in the low transmission torque region, and the rollers for power transmission are provided in each rotation direction and are always in contact with each other. Even in the case of reversing the rotation direction, torque can be transmitted without causing a delay or a tapping sound. (Fifth Embodiment) FIG. 7 is a diagram of a friction roller type transmission (speed reducer) according to a fifth embodiment of the present invention.
Is a side sectional view, (b) is a sectional view taken along line bb of (a), (c) is a sectional view taken along line cc of (b), (D) is sectional drawing which followed the dd line of (b).

The fifth embodiment is a concrete embodiment of the first embodiment. The arrangement, contact angle and friction angle of the first to fourth rollers 1 to 4 are the same as those of the first embodiment. In this example, the idle rollers (third and fourth rollers) are slightly pressed.

The input shaft a is attached to the pair of housings 10 and 11.
Is rotatably supported by a pair of bearings 12 and 13, and the output shaft b is rotatably supported on the housings 10 and 11 by a pair of bearings 14 and 15.

Each of the third and fourth rollers 3 and 4 is provided with a pressing portion. A roller 31 is rotatably attached to the tip of an oscillating arm 30 in each of the pressing portions.
Alternatively, it is elastically pressed against the fourth rollers 3 and 4. As a result, a slight pressing force is applied to the third and fourth rollers 3, 4 to ensure the initial contact.

The pair of housings 10, 11 and the first
Thru / or the fourth rollers 1 to 4 have the same linear expansion coefficient.

As described above, also in the fifth embodiment, the transmission path of the first roller 1 → the third roller 3 → the second roller 2 and the transmission of the first roller 1 → the fourth roller 4 → the second roller 2 The transmission path can be configured to enable forward and reverse rotation in a backlash-less friction roller type transmission (speed reducer), and by generating roller pressing force according to the transmission torque. Since the increase in operating torque can be made as small as possible, the efficiency can be improved especially in the low transmission torque region, and the rollers for power transmission are provided in each rotation direction and are always in contact with each other. Even in the case of reversing the rotation direction, torque can be transmitted without causing a delay or a tapping sound. (Sixth Embodiment) FIG. 8 is a diagram of a friction roller type transmission (speed reducer) according to a sixth embodiment of the present invention.
Is a side sectional view, (b) is a sectional view taken along line bb of (a), and (c) is a sectional view taken along line cc of (b).

The sixth embodiment is a concrete example of the first embodiment, and the arrangement, contact angle and friction angle of the first to fourth rollers 1 to 4 are the same as those of the first embodiment. In this example, the idle rollers (third and fourth rollers) are slightly pressed.

The input shaft a is attached to the pair of housings 10 and 11.
Is rotatably supported by a pair of bearings 12 and 13, and the output shaft b is rotatably supported on the housings 10 and 11 by a pair of bearings 14 and 15.

In order to slightly press the third and fourth rollers 3 and 4, the supporting member 4 is attached to each of the housings 10 and 11.
0 is fitted, and the support shaft 4 provided on the support member 40
1, the third and fourth rollers 3 and 4 are rotatably supported via bearings 42, respectively. Further, a spring 43 for adjusting the positions of the support member 40 and the support shaft 41 is provided. As a result, a slight pressing force is applied to each of the third and fourth rollers 3 and 4 to ensure the initial contact.

The pair of housings 10, 11 and the first
Thru / or the fourth rollers 1 to 4 have the same linear expansion coefficient.

As described above, also in the sixth embodiment, the transmission path of the first roller 1 → the third roller 3 → the second roller 2 and the transmission path of the first roller 1 → the fourth roller 4 → the second roller 2 The transmission path can be configured to enable forward and reverse rotation in a backlash-less friction roller type transmission (speed reducer), and by generating roller pressing force according to the transmission torque. Since the increase in operating torque can be made as small as possible, the efficiency can be improved especially in the low transmission torque region, and the rollers for power transmission are provided in each rotation direction and are always in contact with each other. Even in the case of reversing the rotation direction, torque can be transmitted without causing a delay or a tapping sound. (Seventh Embodiment) Next, referring to FIG. 9 and FIG. 10, a seventh embodiment of the present invention will be described in which the above-described sixth embodiment of the present invention is applied to an electric power steering apparatus for a vehicle. explain.

FIG. 9 is a sectional structural view of an electric power steering apparatus showing a seventh embodiment of the present invention, and FIG. 10 (a) is a sectional view taken along line AA of FIG. 9 showing a portion of a friction roller transmission which is a rotation speed reducing means. FIG. 10B is a vertical cross-sectional view taken along the line BB of FIG.

In FIG. 9, the first roller 1 is fixed to the output rotary shaft 52 on the same axis as the output rotary shaft of the electric motor 50 which is an electric motor unit.

The second roller 2 is externally fitted and fixed to the nut-shaped ball screw nut 53, or is formed integrally therewith. The ball screw nut 53 is the housing 1
It is rotatably supported on bearings 0, 11 via bearings 58, 58 and 63, and is provided with the rack shaft 51 fitted therein, that is, around it. The rack shaft 51 is provided with a thread groove 51b that indirectly engages with the thread groove 53a of the ball screw nut 53 via the ball 54. That is, this ball screw nut 53
The rack shaft 51 and the rack shaft 51 are indirectly engaged with each other through a large number of spherical balls 54 that are rotatably fitted in the troughs of the thread groove 53a and the thread groove 51b. The ball screw nut 53 is fitted on a part of the direction. The ball screw nut 53 and the ball 54 constitute a known so-called ball screw or ball screw.

In FIG. 10, the third and fourth rollers 3, 4
In order to slightly press, the support member 40 is fitted in each of the housings 10 and 11, and the support shaft 41 provided in the support member 40 is provided with the bearings 42 by the third and fourth rollers 3 and 4, respectively. It is rotatably supported via. Also,
A spring 43 for adjusting the positions of the support member 40 and the support shaft 41 is provided. As a result, a slight pressing force is applied to each of the third and fourth rollers 3 and 4 to ensure the initial contact.

The pair of housings 10, 11 and the first
Thru / or the fourth rollers 1 to 4 have the same linear expansion coefficient.

As described above, also in the seventh embodiment, the transmission path of the first roller 1 → the third roller 3 → the second roller 2 and the first roller 1 → the fourth roller 4 → the second roller 2 are transmitted. The transmission path can be configured to enable forward and reverse rotation in a backlash-less friction roller type transmission (speed reducer), and by generating roller pressing force according to the transmission torque. Since the increase in operating torque can be made as small as possible, the efficiency can be improved especially in the low transmission torque region, and the rollers for power transmission are provided in each rotation direction and are always in contact with each other. Even in the case of reversing the rotation direction, torque can be transmitted without causing a delay or a tapping sound.

The electric motor 50 is composed of a stator (not shown), a rotor having a rotary shaft (not shown), and the like. In this embodiment, the electric motor 50 is arranged in an axial direction substantially parallel to the rack shaft 51. ing. The electric motor 50 may be tilted as appropriate depending on the installation space. One end of the rack shaft 51 has a tie rod 6 through a universal joint 59.
It is connected with 5.

In the drawing of the rack shaft 51, a rack (not shown) is formed on the left side portion (tip portion) of the thread groove 51b. This rack is externally fitted and fixed to a pinion shaft (not shown) connected to a lower end of a steering shaft (not shown) connected to a handle (not shown), and is incorporated in a pinion gear box (not shown). It meshes with a pinion gear (not shown). The steering shaft and the pinion shaft constitute rotary shaft means, and the rack and the pinion gear constitute rack and pinion means. The rack and pinion means itself is a well-known means for drivingly connecting the rotating shaft means and the rack shaft 51.

The operation of the above configuration will be briefly described. Although the driver controls the electric motor 50 based on the torque applied to the steering wheel, the vehicle speed, or the like, a detailed description of the control circuit is omitted because it is not directly related to the present invention. The control device controls the output of the electric motor 50 so as to obtain an appropriate assisting force according to the detected torque and vehicle speed.

The rotating shaft of the electric motor 50 and the shaft of the first roller 1 are connected. In this case, the rotation of the first roller 1 is transmitted to the ball screw nut 53 via the third roller 3, the fourth roller 4, and the second roller 2 to rotate the ball screw nut 53, and this rotation causes the rack shaft 5 to rotate.
The steering wheel is steered by driving 1 in either direction of arrow D. At this time, the torque of the steering shaft and the vehicle speed according to the load received by the rack shaft 51 and the vehicle speed are detected, and the electric motor 50 is detected according to these detected values.
By controlling the output of, the electric assist force is appropriately added to the manual steering force.

The present invention is not limited to the above-mentioned embodiments, but can be variously modified.

[0069]

As described above, according to the present invention,
A backlash-less friction roller type transmission (speed reducer) can be constituted by a transmission path of a first roller → a third roller → a second roller and a transmission path of a first roller → a fourth roller → a second roller. In the above, the forward and reverse rotations can be made possible, and by increasing the roller pressing force according to the transmission torque, it is possible to minimize the increase in the operating torque, and particularly in the area of low transmission torque. Can be improved,
Further, since the roller for power transmission is provided for each rotation direction and is always in contact with the roller, torque transmission can be performed without causing delay or tapping sound even when the rotation direction is reversed.

[Brief description of drawings]

FIG. 1A is a side view of a friction roller type transmission (speed reducer) according to a first embodiment of the present invention, and FIG.
It is a schematic perspective view of the friction roller type transmission (speed reducer) shown to (a).

FIG. 2A is a side view of the friction roller type transmission (speed reducer) according to the first embodiment of the present invention (first roller → fourth roller → second roller transmission path). FIG. 3B is a side view of the same (a diagram showing a transmission path of the first roller → the third roller → the second roller).

FIG. 3A is a side view of a friction roller type transmission (speed reducer) according to a second embodiment of the present invention, and FIG.
It is a schematic perspective view of the friction roller type transmission (speed reducer) shown to (a).

FIG. 4A is a side view of a friction roller type transmission (speed reducer) according to a second embodiment of the present invention (first roller → fourth roller → second roller transmission path). FIG. 3B is a side view of the same (a diagram showing a transmission path of the first roller → the third roller → the second roller).

FIG. 5 is a diagram of a friction roller type transmission (speed reducer) according to a third embodiment of the present invention, (a) is a front sectional view, and (b) is a side sectional view.

FIG. 6 is a diagram of a friction roller type transmission (speed reducer) according to a fourth embodiment of the present invention, (a) is a side sectional view, and (b) is b- of (a). It is sectional drawing which followed the b line, (c) is sectional drawing which followed the cc line of (b), (d) is a perspective view of a spring.

FIG. 7 is a diagram of a friction roller type transmission (speed reducer) according to a fifth embodiment of the present invention, in which (a) is a side sectional view and (b) is (b) of (a). It is sectional drawing along line b, (c) is sectional drawing along line cc of (b), (d) is sectional drawing along line dd of (b). is there.

FIG. 8 is a diagram of a friction roller type transmission (speed reducer) according to a sixth embodiment of the present invention, (a) is a side sectional view, and (b) is a b- portion of (a). It is sectional drawing which followed the b line, (c) is sectional drawing which followed the cc line of (b).

FIG. 9 is a cross-sectional configuration diagram of a vehicle power steering device according to a seventh embodiment of the present invention.

10A is a sectional view taken along line AA of FIG. 9, and FIG. 10B is a sectional view taken along line BB of FIG.

[Explanation of symbols]

a Input axis b Output shaft 1st roller 2 Second roller 3rd roller 4th roller 10,11 housing 12, 13 bearings 14,15 bearing 20 spring 30 arms 31 Laura 32 spring 40 Support member 41 Support shaft 42 bearing 43 spring 50 electric motor 51 rack shaft 51a, 53a Thread groove 53 ball screw nut 54 balls 59 Universal joint 65 tie rod

Claims (8)

[Claims] 1. A first roller and a second roller centering on each of the two shafts separated from each other are arranged so as not to abut each other, and contact with both the first and second rollers. A third roller and a fourth roller which come into contact with each other are arranged between the first roller and the second roller and on the opposite side of a line connecting the centers of the first roller and the second roller, The angle formed by the tangent line of the third roller (or the fourth roller) and the tangent line of the second roller and the third roller (or the fourth roller) is obtained from the coefficient of friction between the rollers. A friction roller type transmission characterized in that the friction angle is less than twice the friction angle. 2. The friction roller type transmission according to claim 1, wherein a shaft of the first roller and a shaft of the second roller are parallel to each other. 3. The friction roller according to claim 1, wherein the diameter of the third roller and the diameter of the fourth roller are larger than the shortest distance between the peripheral surfaces of the first roller and the second roller. Type transmission. 4. The friction roller type transmission according to claim 1, wherein the friction portion is outside the roller. 5. The friction roller type transmission according to claim 1, wherein the friction portion is inside one of the first roller and the second roller. 6. An electric power steering apparatus using the friction roller type transmission according to any one of claims 1 to 3. 7. The friction roller type transmission according to claim 1, wherein the linear expansion coefficient of the housing is equal to that of each roller. 8. The third and fourth rollers are overlapped with each other, and the first and second rollers are commonly used for forward and reverse rotations. Friction roller type transmission.