JP2002349653A - Frictional roller system of transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To plan weight reduction in transmission. SOLUTION: A first roller 1 and a second roller 2 are arranged for two shafts, a, b, so that they do not contact each other and a third roller 3 and a fourth roller 4 which contact both of the first and the second rollers are arranged between the first and the second rollers, taking into consideration a specified angle of friction. The pieces of connection plate 16 for connecting a bearing 15, which supports the first roller 1 and the second roller 2 freely rotatably, is constituted from material with almost same coefficient of linear thermal expansion as those of each roller.

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 that transmits torque while changing the speed by a friction roller.

[0002]

2. Related Art In a friction roller type transmission disclosed in Japanese Patent Application No. 2001-141463 filed by the present inventors prior to the present application, two shafts separated in parallel from each other are provided with a first roller centered on each shaft, respectively. A third roller and a fourth roller which are arranged so as not to contact with each other and which contact both of the first and second rollers are disposed between the first and second rollers and the first roller. And the other side of the line connecting the center of the second roller and the tangent line between the first roller and the third roller (or the fourth roller), and the second roller and the third roller (or the The angle formed by the tangent line of the four rollers is set to be not more than twice the friction angle obtained from the friction coefficient between the rollers.

Thus, the transmission path of the first roller → the third roller → the second roller and the first roller → the fourth roller → the second roller
The transmission path of the rollers can be configured, and in a backlashless friction roller type transmission, forward and reverse rotation can be enabled, and operation is performed by generating roller pressing force according to the transmission torque. The increase in torque can be minimized, the efficiency can be improved especially in the area of low transmission torque, and rollers for power transmission are provided for each rotation direction and are always in contact with each other. Even in the case of reversal, torque transmission can be performed without causing delay or hitting sound.

[0004] Specifically, a description will be given with the first roller as an input.

When the first roller is rotated clockwise (CW direction), the tangent line between the third roller and the first roller and the tangent line between the third roller and the second roller have an angle smaller than twice the friction angle. Therefore, the respective contact angles are equal to or smaller than the friction angle, and the third roller and the first roller do not slip relative to each other at the contact portion, so that the third roller is moved closer to the first roller, A counterclockwise (CCW) rotational force is transmitted by the tangential force.

[0006] Even at the contact portion between the third roller and the second roller, the tangent line between the third roller and the first roller and the tangent line between the third roller and the second roller have an angle smaller than twice the friction angle. Therefore, each contact angle is equal to or smaller than the friction angle, and the third roller and the second roller do not slip relative to each other at the contact portion. Therefore, a tangential force acts on the second roller from the third roller, and the rotational force in the CW rotational direction is transmitted. As a reaction, the third roller produces an opposite tangential force. This tangential force is the direction in which the third roller approaches the second roller.

Since the tangential force applied to the third roller is a direction in which the third roller is pressed against the first and second rollers, it is possible to obtain a pressing force corresponding to the transmitted tangential force, that is, the torque. . The operation of the fourth roller is the same except that the rotation direction is different, so that the description is omitted.

[0008]

In the prior application, however, the rollers are housed in a housing made of a material having substantially the same linear expansion coefficient as each roller so that the positional relationship between the rollers does not change due to a temperature change. .

The contact portion between the rollers is pressed with a very strong force, and the stress at the contact portion is several GPa at the maximum. Therefore, the contact portion between the rollers must be made of an iron-based material. I had to.

Therefore, if the entire housing for housing the rollers is made of an iron-based material, it becomes very heavy.
When a device using a conventional speed reducer is mounted on a moving body such as an automobile, an increase in weight becomes a problem.

The present invention has been made in view of the above circumstances, and has as its object to provide a friction roller type transmission that can be reduced in weight.

[0012]

In order to achieve the above object, a friction roller type transmission according to a first aspect of the present invention has two shafts spaced apart in parallel from each other, each centered on each shaft. The first roller and the second roller are arranged so as not to abut each other, and the first roller and the second roller around the respective axes are not abutted on the two shafts separated in parallel from each other. And a third roller and a fourth roller which are in contact with both the first and second rollers, are connected between the first roller and the second roller and between the first roller and the center of the second roller. And an angle formed by a tangent between the first roller and the third roller (or the fourth roller) and a tangent between the second roller and the third roller (or the fourth roller) is Of the friction angle obtained from the friction coefficient between the rollers Times set to become less, the first
The two connecting plates for connecting the roller and the bearing rotatably supporting the second roller at both ends of the two rollers are formed of a material having substantially the same linear expansion coefficient as each roller.

As described above, according to the present invention, the two connecting plates for connecting the bearings rotatably supporting the first roller and the second roller at both ends of both rollers are substantially the same as those of the rollers. Since it is formed from a material having a linear expansion coefficient of, the weight can be reduced.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A friction roller type transmission (reduction gear) according to an embodiment of the present invention will be described below with reference to the drawings. (Basic Structure) FIG. 1A is a side view of a friction roller type transmission (reduction gear) according to the basic structure of the present invention.
(B) is a schematic perspective view of the friction roller type transmission shown in (a). FIG. 2A is a side view of the friction roller type transmission according to the basic structure of the present invention (first roller → fourth roller).
FIG. 2 is a diagram showing a transmission path from a roller to a second roller), FIG.
(B) is a side view of the same (first roller → third roller →
FIG. 7 is a diagram illustrating a transmission path of a second roller).

In this basic structure, in a friction roller type transmission (reduction gear), as shown in FIGS. 1 and 2, two shafts parallel to and separated from each other have a first roller centered on each shaft. The first roller 1 and the second roller 2 are arranged such that the first roller 1 and the second roller 2 are not in contact with each other, and the third roller 4 and the fourth roller 4 are in contact with both the first and second rollers. Between the first roller 1 and the third roller 3 (or the fourth roller 4); and a tangent line between the first roller 1 and the third roller 3 (or the fourth roller 4). The second roller 2 and the third roller 3 (or the fourth roller 3)
The angle between the tangent of the roller 4) and the tangent of the roller 4) is set to be no more than twice the friction angle determined from the coefficient of friction between the rollers, and the friction portion is outside the roller.

In other words, the center of each roller is P1
ＰP4, the sum of the angle between the line P1P2 and the line P1P3 (α1: ＰP2P1P3), the angle between the line P1P2 and the line P2P3 (α2: ∠P1P2P3), and the line P1P2
(Α3: ∠P2P1P4) and the angle (α4: ∠P1P2P) formed by the line P1P2 and the line P2P4
4) is set to be equal to or less than twice the friction angle (θ = tan ⁻¹ μ).

In this arrangement, since the friction angle is small, the third and fourth rollers 3 and 4 have to be located at positions overlapping in the axial direction.

According to the above configuration, a pressing force corresponding to the transmission torque can be obtained. Therefore, there is no need for a pressing force (pressing the third and fourth rollers 3 and 4 toward the first and second rollers 1 and 2) required for friction transmission. However, in the non-rotating state,
It is better to apply a small pressing force for securing the initial contact state. Further, each roller is constituted by one, but plural rollers may be employed.

Hereinafter, the operation will be described 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 smaller than twice the friction angle, the respective contact angles are smaller than the friction angle. , Third
Since the 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 third roller 3 is transmitted with a counterclockwise (CCW) rotational force by the tangential force.

In the contact portion between the third roller 3 and the second roller 2, the tangent between the third roller 3 and the first roller 1 and the tangent between the third roller 3 and the second roller 2 have a friction angle of 2 Since the angle is less than twice, each contact angle is less than the friction angle, and the third roller 3 and the second roller 2 do not slip relative to each other at the contact portion. Therefore, a 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, the third roller 3 generates a tangential force opposite thereto. This tangential force is
This is a direction in which the roller 3 is brought closer to the second roller 2.

The tangential force acting on the third roller 3 is
Since the direction is the direction in which the third roller 3 is pressed against the first and second rollers 2, a pressing force corresponding to the transmitted tangential force, that is, the torque, can be obtained.

At this time, as shown in FIG. 2A, since the relative sliding does not occur in the contact portion of the fourth roller 4, the fourth roller 4 is separated from the first and second rollers 1 and 2. A tangential force is applied, but the direction is a direction in which the fourth roller 4 is separated from the first and second rollers 1 and 2, and the fourth roller 4 contacts the first roller 1 and the second roller 2. It is just rolling.

Next, as shown in FIGS. 1 (b) and 2 (a), when the first roller 1 is rotated in the CCW direction by reverse rotation, the action of the fourth roller 4 and the third roller 3 is effected. In other words, since the fourth roller 4 has already contacted the first roller 1 and the second roller 2, the power transmission direction can be smoothly changed when the rotation direction is reversed.

In order to transmit torque, the third
The fourth and third rollers 3 and 4 only need to be 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 with the first and second rollers 1, 2,
A very small pressing force may be obtained.

As described above, according to this basic structure, 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 In a backlashless friction roller type transmission (reduction gear), forward and reverse rotation can be enabled, and the roller pressing force is generated in accordance with the transmission torque to operate the transmission. The increase in torque can be minimized, the efficiency can be improved especially in the area of low transmission torque, and rollers for power transmission are provided for each rotation direction and are always in contact with each other. Even in the case of reversal, torque transmission can be performed without causing delay or hitting sound. (Embodiment of the present invention) FIG. 3 is a view of a friction roller type transmission (reduction gear) according to an embodiment of the present invention, (a) is a side sectional view, and (b) is
It is sectional drawing along the bb line of (a), (c) is
It is sectional drawing along the cc line of (b).

FIG. 4 is an exploded sectional view of the friction roller type transmission (reduction gear) shown in FIG.

FIG. 5 (a) is a plan sectional view of the friction roller type transmission (reduction gear) shown in FIG. 3, and FIG. 5 (b) is a friction roller type transmission (reduction gear) according to a modification. It is a plane sectional view.

In this embodiment, the above basic structure is embodied, and the arrangement, contact angle and friction angle of the first to fourth rollers 1 to 4 are the same as those of the basic structure.

As shown in FIGS. 3 and 4, a unit body 11 is housed in a housing frame 10, and a cover 12 is attached to the housing body 10 with bolts 13. The housing frame 10 is made of a lightweight material such as an aluminum alloy and can be formed by casting such as die casting.

A seal member 14 is provided on the support portion of the housing frame 10 for the output shaft b and the support portion of the cover 12 for the input shaft a. Since the sliding diameter of the seal can be made smaller than when a sealed bearing is used, an increase in operating torque due to seal friction can be reduced.

The unit body 11 includes first and second rollers 1 and 2.
2 connecting plates 1 for connecting a pair of bearings 15 supporting
6 are provided. The connecting plate 16 is formed of a material having substantially the same linear expansion coefficient as the third and fourth rollers 3 and 4.

The surface of the connecting plate 16 is also used as a sliding surface for the third and fourth rollers 3 and 4, but in the conventional integrated housing, the bottom surface of the insertion hole of the third and fourth rollers 3 and 4 is used. Is a sliding surface, which makes finishing difficult. However, in the present embodiment, the two connecting plates 16 have a simple plate shape, so that finishing of the sliding surface is easy. Can be done. In addition, punching can be performed from a plate material by press molding or the like, and finishing processing itself can be omitted. Further, the same components can be used face-to-face, so that the cost can be reduced.

As described above, in the present embodiment, the first and second
The two connecting plates 16 for connecting the rollers 1 and 2 at both ends thereof via the bearings 15 are made of a unit body 11 made of a material having substantially the same linear expansion coefficient as that of the rollers. As a configuration for housing in the housing frame 10 made of a material, weight reduction can be achieved.

Further, as shown in FIG.
6, an injection hole 17 for injecting lubricating oil is provided.
Alternatively, as shown in FIG.
In addition, an injection hole 17 for injecting lubricating oil is provided.

Further, as shown in detail in FIG.
The holder 20 includes a flange portion 21 and a shaft portion 22. The flange portion 21 and the shaft portion 22 are eccentric by a predetermined amount, and the flange portion 21 has a substantially semicircular cross section. The holder 20 can be fitted by reversing the shaft portion 22, has a mating surface stopper surface 23, and has an annular groove 24 on the outer peripheral surface which becomes one when combined. A wire ring 25 as a spring element is fitted into the annular groove 24, and an elastic force is applied in a direction in which the distance between the two shaft portions 22 is reduced, so that they are integrated. The third and fourth rollers 3 and 4 are rotatably supported by shafts 22 of the respective holders 20 via bearings 26.

Further, a backup roller 30 is provided in contact with the third and fourth rollers 3, 4 to limit the displacement of the third and fourth rollers 3, 4 to a predetermined amount. For example, a rolling bearing having an outer ring as a contact surface. As described above, in the present embodiment, the displacement of the third and fourth rollers 3 and 4 is limited to a predetermined amount to prevent the rollers 3 and 4 from climbing over. Thus, it is possible to prevent the torque transmission path from being damaged due to excessive torque.

The present invention is not limited to the above-described embodiment, but can be variously modified. The friction roller type transmission (reduction gear) according to the present invention can be used, for example, in an electric power steering device for a vehicle.

Next, a second embodiment of the present invention in which the above-described first embodiment of the present invention is applied to an electric power steering apparatus for a vehicle will be described with reference to FIGS.

FIG. 6 is a sectional view of an electric power steering apparatus according to a second embodiment of the present invention, and FIG. 7 (a) shows a portion of a friction roller transmission which is a rotation reducing means, and FIG.
7A is a cross-sectional view taken along a line BB in FIG. 7A.

In FIG. 6, 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 a nut-shaped ball screw nut 53, or is formed integrally therewith. The ball screw nut 53 is the housing 1
Bearings 58, 58 and 15, 15 for 0, 11
The rack shaft 51 is rotatably supported via a rack shaft 51, that is, is provided around the rack shaft 51. Rack shaft 51
Is formed 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 5
3 and the rack shaft 51 are indirectly engaged via a number of spherical balls 54 rotatably fitted into the valleys of the thread grooves 53a and the thread grooves 51b. A ball screw nut 53 is externally fitted in a part of the axial direction. The ball screw nut 53 and the ball 54 constitute a known ball screw or ball screw.

As in FIGS. 3 and 4, the housing frame 10
, A unit body 11 is housed.

The unit body 11 includes first and second rollers 1 and 2.
Connecting plates 1 for connecting a pair of bearings 15 supporting
6 are provided. The connecting plate 16 is formed of a material having substantially the same linear expansion coefficient as the third and fourth rollers 3 and 4.

The surface of the connecting plate 16 is also used as a sliding surface for the third and fourth rollers 3, 4. In the present embodiment, since the two connecting plates 16 have a simple plate shape, the finishing of the sliding surface can be easily performed. In addition, punching can be performed from a plate material by press molding or the like, and finishing processing itself can be omitted. Further, the same components can be used face-to-face, so that the cost can be reduced.

As described above, in the present embodiment, the first and second
The two connecting plates 16 for connecting the rollers 1 and 2 at both ends thereof via the bearings 15 are made of a unit body 11 made of a material having substantially the same linear expansion coefficient as that of the rollers. As a configuration for housing in the housing frame 10 made of a material, weight reduction can be achieved.

Further, as shown in detail in FIG.
The holder 20 includes a flange portion 21 and a shaft portion 22. The flange portion 21 and the shaft portion 22 are eccentric by a predetermined amount, and the flange portion 21 has a stepped cross section. The holder 20 can be fitted by reversing the shaft portion 22, has a mating surface stopper surface 23, and has an annular groove 24 on the outer peripheral surface which becomes one when combined. A wire ring 25 as a spring element is fitted into the annular groove 24, and an elastic force is applied in a direction in which the distance between the two shaft portions 22 is reduced, so that they are integrated. The third and fourth rollers 3 and 4 are rotatably supported by shafts 22 of the respective holders 20 via bearings 26.

Further, a backup roller 30 is provided in contact with the third and fourth rollers 3 and 4 to limit the displacement of the third and fourth rollers 3 and 4 to a predetermined amount. For example, a rolling bearing having an outer ring as a contact surface. As described above, in the present embodiment, the displacement of the third and fourth rollers 3 and 4 is limited to a predetermined amount to prevent the rollers 3 and 4 from climbing over. Thus, it is possible to prevent the torque transmission path from being damaged due to excessive torque.

As described above, also in the second 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 A transmission path can be configured, and in a backlashless friction roller type transmission (reduction gear), forward and reverse rotations can be enabled, and by generating a roller pressing force according to the transmission torque, Since the increase in the operating torque can be minimized, the efficiency can be improved especially in the region of low transmission torque, and the rollers for power transmission are provided for each rotation direction and are always in contact. Even in the case of reversal of the rotation direction, torque transmission can be performed without delay or hitting sound.

The electric motor 50 includes a stator (not shown), a rotor having a rotating shaft (not shown), and the like. In the case of the present 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 disposed at an appropriate inclination depending on the installation space. One end of the rack shaft 51 is connected to a tie rod 65 via a ball joint 59.

A rack (not shown) is formed at a part of the rack shaft 51. This rack was 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 was built in a pinion gear box (not shown). It is in mesh with a pinion gear (not shown). The rotating shaft means is constituted by the steering shaft and the pinion shaft, and the rack and pinion means is constituted by the rack and the pinion gear. The rack and pinion means itself is a known means for drivingly connecting the rotating shaft means and the rack shaft 51.

The operation in the above configuration will be briefly described. Although the electric motor 50 is controlled based on information such as the torque applied to the steering wheel by the driver or the vehicle speed, 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 rotation 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.
When the wheel 1 is driven in one of the directions indicated by the arrow D, the steered wheels are steered. At this time, the torque of the steering shaft and the vehicle speed corresponding to the load received by the rack shaft 51 are detected, and the electric motor 50 is determined in accordance with the detected values.
, The electric assist force is appropriately applied to the manual steering force.

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

[0055]

As described above, according to the present invention,
Since the two connecting plates that connect the bearings that rotatably support the first roller and the second roller at both ends of both rollers are formed from a material having a linear expansion coefficient substantially equal to that of each roller, The weight of the housing material can be reduced by using a lighter material.

[Brief description of the drawings]

FIG. 1A is a side view of a friction roller type transmission (reduction gear) according to a basic structure of the present invention, and FIG. 1B is a side view of FIG.
FIG. 2 is a schematic perspective view of the friction roller type transmission (reducer) shown in FIG.

FIG. 2A is a side view of a friction roller type transmission (reduction gear) according to a basic structure of the present invention (first roller → fourth roller).
FIG. 7 is a diagram showing a transmission path from a roller to a second roller),
(B) is a side view of the same (first roller → third roller →
FIG. 6 is a diagram illustrating a transmission path of a second roller).

FIG. 3 is a view of a friction roller type transmission (reduction gear) according to the embodiment of the present invention, (a) 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).

FIG. 4 is an exploded sectional view of the friction roller type transmission (reduction gear) shown in FIG. 3;

5 (a) is a plan sectional view of the friction roller type transmission (reduction gear) shown in FIG. 3, and FIG. 5 (b) is a plan view of a friction roller type transmission (reduction gear) according to a modified example. It is sectional drawing.

FIG. 6 is a sectional configuration diagram of a vehicle power steering device according to a second embodiment of the present invention.

7A is a cross-sectional view taken along line AA of FIG. 6, and FIG. 7B is a cross-sectional view taken along line BB of FIG.

[Explanation of symbols]

 a Input shaft b Output shaft 1 First roller 2 Second roller 3 Third roller 4 Fourth roller 10 Housing frame 11 Unit body 12 Cover 13 Bolt 14 Seal member 15 Bearing 16 Connection plate 17 Injection hole 20 Holder 21 Flange 22 Shaft 23 Stopper surface 24 Annular groove 25 Wiring 26 Bearing 30 Backup roller

Claims (7)

[Claims] 1. A first roller and a second roller, each of which is centered on two axes, which are spaced apart in parallel from each other, are arranged so as not to abut each other, and are disposed on both the first and second rollers. A third roller and a fourth roller that are in contact with each other are disposed 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 between the tangent to the third roller (or the fourth roller) and the tangent to the second roller and the third roller (or the fourth roller) is a friction angle determined from a coefficient of friction between the rollers. And two connecting plates for connecting the bearings for rotatably supporting the first roller and the second roller at both ends of these rollers, respectively. It is characterized by being formed from materials with the same linear expansion coefficient. Friction roller type transmission to. 2. The friction roller type transmission according to claim 1, wherein a unit body in which each roller is assembled to a connecting plate is housed in a housing. 3. The friction roller type transmission according to claim 1, wherein the housing for housing the unit body is made of a lighter material than the unit body. 4. The friction roller type transmission according to claim 1, wherein a bearing is disposed between the roller and the shaft portion. 5. The friction roller type transmission according to claim 1, wherein a seal member is provided between the housing and the input / output shaft. 6. A lubricating oil injection hole is provided in a portion of the connecting plate or the housing to be sealed.
2. The friction roller type transmission according to claim 1. 7. A friction transmission according to any one of claims 1 to 6, an electric motor that outputs rotation to said first roller, a ball screw nut that rotates with rotation of said second roller, An electric power steering device, comprising: a ball screw nut; a ball screw; and a nut shaft that reciprocates linearly with the rotation of the ball screw nut to steer the steered wheels.