JP6458402B2 - Friction roller reducer - Google Patents

Description

  The present invention relates to a friction roller type speed reducer.

  In order to improve the convenience of electric vehicles that have begun to spread in recent years, there is a strong demand for improving the efficiency of electric motors in order to increase the travelable distance per charge. In order to improve the efficiency of the electric motor, it is desirable to use a small electric motor that rotates at high speed and to reduce the rotation of the motor output shaft before transmitting it to the drive wheels of the vehicle. In this case, the speed reducer connected to the motor output shaft has a very high operating speed and is likely to generate vibration and noise. Therefore, in order to suppress vibration and noise during operation, it is considered to use a friction roller type speed reducer. As a conventional friction roller type speed reducer, for example, one described in Patent Document 1 is known.

  As shown in FIG. 10, a friction roller type speed reducer 200 described in Patent Document 1 includes an input shaft 111, an output shaft 113, a sun roller 117, a ring roller 119, a plurality of intermediate rollers 121, and a loading. The cam mechanism 123 includes a connecting portion 133 that connects the ring roller 119 and the output shaft 113. The sun roller 117 includes a pair of sun roller elements 137A and 137B divided in the axial direction.

  The loading cam mechanism 123 is disposed at the end of the sun roller element 137A opposite to the sun roller element 137B. As shown in FIG. 11, the base end surface of the sun roller element 137 </ b> A facing the cam ring 149 and the one side surface of the cam ring 149 facing the sun roller element 137 </ b> A are arranged at a plurality of locations along the circumferential direction on the sun roller element 137 </ b> A side. A driven cam surface 153 and a driving cam surface 155 on the cam ring 149 side are provided. Balls 157 are disposed between the cam surfaces 153 and 155, respectively. Each of the cam surfaces 153 and 155 has a shape in which the groove depth in the axial direction becomes gradually shallower toward both ends in the circumferential direction.

  In the loading cam mechanism 123 configured as described above, in a state where the input shaft 111 is stopped, each ball 157 has a cam surface 153, as shown in FIG. It is located at the deepest part of 155. When the input shaft 111 is driven to rotate, the balls 157 move to the shallow portions of the cam surfaces 153 and 155 as shown in FIG. Then, the distance Lc between the sun roller element 137A and the cam ring 149 is increased, and the sun roller element 137A is pressed toward the sun roller element 137B. As a result, the sun roller element 137A is rotationally driven while being pressed toward the sun roller element 137B.

  Thus, when the friction roller type speed reducer is activated from the state shown in FIG. 13A where no rotational torque is input to the input shaft 111, as shown in FIG. 13B, the loading cam mechanism The distance between the sun roller elements 137A and 137B is reduced by the axial thrust generated by the shaft 123. Therefore, the contact surface pressure of each rolling contact portion is changed according to the magnitude of torque to be transmitted between the input shaft 111 and the output shaft 113.

Japanese Patent No. 4948968

  However, in the friction roller type speed reducer 200 disclosed in Patent Document 1, since the loading cam mechanism 123 is disposed on the sun roller 117 side, the sun roller elements 137A and 137B are rotated from the rotation center of the input shaft 111 shown in FIG. The radius of rotation to the rolling contact area (contact ellipse) between the outer peripheral surface and the outer peripheral surface of the intermediate roller 121 is short. Therefore, the peripheral speed difference increases in accordance with the difference between the radial distance at both ends in the axial direction of the contact area in the rolling contact portion and the radial distance at the central portion. As a result, slipping occurred at the rolling contact portion, and the power transmission efficiency of the friction roller type reduction gear was reduced.

  On the other hand, although not shown, there is known a friction roller type speed reducer in which a loading cam mechanism is provided on the ring roller side. In this speed reducer, by providing the loading cam mechanism on the ring roller side, the radius of rotation from the rotation center of the input shaft to the rolling contact portions of the inner peripheral surface of the ring roller and the outer peripheral surface of each intermediate roller can be increased. . Thereby, the radial distance difference between the axial both ends of the contact area in the rolling contact portion and the central portion can be reduced with respect to the radial distance, and the generated peripheral speed difference can be suppressed to be small.

  However, in the friction roller type speed reducer configured as described above, since the loading cam mechanism is provided on the ring roller side, the number of large-diameter parts is increased, the weight of the speed reducer itself is increased, and the inertial force during rotational driving increases. Thus, there is a disadvantage that the rotational responsiveness is lowered. Also, the work of assembling the ring roller and the loading cam mechanism to the connecting portion has become complicated.

  Accordingly, the present invention provides a friction roller type speed reducer capable of reducing the number of parts, reducing the weight and reducing the inertial force, while suppressing the friction loss and ensuring high power transmission efficiency, and having good assemblability. Objective.

The present invention has the following configuration.
(1) A sun roller disposed concentrically with the input shaft, a ring roller disposed concentrically with the sun roller on an outer peripheral side of the sun roller, and between an outer peripheral surface of the sun roller and an inner peripheral surface of the ring roller, A plurality of intermediate rollers that are rotatably supported around a rotation axis parallel to the input shaft and are in rolling contact with the outer peripheral surface of the sun roller and the inner peripheral surface of the ring roller, and the ring roller and the output shaft are connected. A friction roller type speed reducer comprising: a connecting portion; and a loading cam mechanism for changing a contact surface pressure of a rolling contact surface of each roller,
The ring roller is composed of a pair of ring roller elements arranged side by side in the axial direction of the input shaft, and the inner peripheral surface of each of the ring rollers is from the opposite end face where the ring roller elements face each other. It is formed with a slope whose inner diameter decreases toward the outer end surface on the opposite side,
The coupling portion includes a base end portion connected to the output shaft, and a roller holding portion that extends from the base end portion and holds the pair of ring roller elements,
The loading cam mechanism is disposed only on the outer end face side of one of the pair of ring roller elements, and presses the outer end face in the axial direction according to the input rotational torque, thereby the ring roller element. To bring them closer together,
The roller holding portion has a retaining ring fitted in a ring groove formed on an inner peripheral surface of an axial end opposite to the base end ,
The retaining ring includes an outer peripheral portion and a plurality of spring portions that protrude radially inward from the outer peripheral portion and are inclined in the axial direction. The spring portions are elastically deformed in the axial direction, and the pair of ring rollers Preload the other of the elements in the axial direction, and restrict the position of the other ring roller element in the axial direction when the entire outer end surface of the other ring roller element is in contact with the side surface of the retaining ring. Friction roller speed reducer characterized by
(2) The spring portion has a certain amount of elastic deformation in the axial direction according to the axial displacement of the loading cam mechanism proportional to the rotational torque from the input shaft, and the other ring roller element The friction roller type reduction gear according to (1), wherein an axial displacement is allowed only by the elastic deformation allowance, and when the elastic deformation allowance is exceeded, the other ring roller element is fixed in the axial direction. .
( 3 ) The loading cam mechanism
A first cam groove formed on the outer end face of the one ring roller element and provided at a plurality of locations along the circumferential direction;
A second cam groove formed at the plurality of locations corresponding to the first cam groove, formed in the connecting portion facing the first cam groove;
Rolling elements sandwiched between the first cam groove and the second cam groove,
Each of the first cam groove and the second cam groove has a shape in which an axial depth gradually changes along a circumferential direction and becomes shallower toward a circumferential end of the cam groove. The friction roller type speed reducer according to (1) or (2) .

According to the present invention, it is possible to reduce the number of parts and reduce the weight and the inertial force while suppressing friction loss and ensuring high power transmission efficiency. Further, the assembly work can be simplified.
Further, according to the present invention, the loading cam mechanism is formed in the ring roller element disposed on the base end side of the connecting portion and the connecting portion facing the ring roller element, thereby further reducing the ring roller element. It can be pressed with a simple mechanism.

It is a figure for demonstrating embodiment of this invention, and is a partial cross section perspective view of a friction roller type reduction gear. It is principal part sectional drawing of the friction roller type reduction gear shown in FIG. It is a perspective view of the retaining ring shown in FIG. (A) is sectional drawing of the retaining ring in the state in which the projection part was compressed, (B) is sectional drawing of the retaining ring in the state to which the elastic deformation allowance was provided. It is a graph showing the correlation between the axial displacement amount of the retaining ring and the rotational torque. It is principal part sectional drawing as a reference figure of a loading cam mechanism. It is principal part sectional drawing of the loading cam mechanism provided with the retaining ring in which the projection part curved. It is a perspective view of the retaining ring shown in FIG. It is operation | movement explanatory drawing of a retaining ring. It is sectional drawing of the conventional friction roller type reduction gear. It is a top view of the cam ring which shows the cam surface of a loading cam mechanism. It is AA sectional drawing of FIG. 11, Comprising: It is sectional drawing which each shows the state (A) in which the loading cam mechanism is not generating thrust, and the state (B) which is generating thrust. It is a schematic diagram of the friction roller type reduction gear which shows the state where an intermediate roller is displaced based on the action of the loading cam mechanism, when torque is not transmitted (A) and when transmitted (B).

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
<First configuration example>
FIG. 1 is a diagram for explaining an embodiment of the present invention. FIG. 2 is a partially sectional perspective view in which a part of the friction roller type speed reducer 100 is cut out, and FIG. 2 is a schematic view of the friction roller type speed reducer 100 shown in FIG. FIG.
The friction roller type speed reducer 100 includes a sun roller 15 concentric with the input shaft 11, a ring roller 17, a plurality of intermediate rollers 19, a connecting portion 21 that connects the ring roller 17 and the output shaft 13, and loading. And a cam mechanism 23.

  The sun roller 15 is a solid structure roller integrally formed with the input shaft 11 at one end of the input shaft 11. The sun roller 15 is formed by cutting and grinding the input shaft 11, and its outer peripheral surface is in rolling contact with the intermediate roller 19.

  The ring roller 17 is a pair of ring roller elements arranged side by side in the axial direction, and includes a first ring roller element 27 and a second ring roller element 29. These ring roller elements 27 and 29 are arranged concentrically with the sun roller 15 on the outer peripheral side of the sun roller 15 in a state of being accommodated inside the cup-shaped connecting portion 21.

  As shown in FIG. 2, the inner peripheral surfaces 27 a and 29 a of the first ring roller element 27 and the second ring roller element 29 are opposite to each other in the axial direction from the opposite end face 24 where the ring roller elements 27 and 29 face each other. It becomes the inclined surface where an internal diameter becomes small toward the outer side end surfaces 30 and 34 of this. Each of these inclined surfaces becomes a rolling contact surface on which the intermediate roller 19 rolls. The inner peripheral surfaces 27a and 29a are not limited to the inclined surfaces, but may be concave curved surfaces in which the outer edge shape of the axial cross section is a single arc-shaped concave curve.

  The first ring roller element 27 is formed with a plurality of radial projections 28 at a plurality of locations on the outer peripheral surface, and engages with the connecting portion 21 as will be described later.

  The plurality of intermediate rollers 19 are supported on a support shaft (spinning shaft) 31 parallel to the input shaft 11 via a needle bearing (not shown), and are rotatably supported in the axial direction. It is arranged between the inner peripheral surface 17 a of the roller 17. Both ends of the support shaft 31 are supported by a roller holder 32 as shown in FIG. The roller holder 32 is supported by the carrier 33 so that the intermediate roller 19 can move (swing) in the radial direction of the input shaft 11. The carrier 33 is fixed to a motor body (not shown) by a fastening member.

  The outer peripheral surface of each intermediate roller 19 is a convex curve having a single circular arc outer edge shape in axial section, and is in rolling contact with the outer peripheral surface of the sun roller 15 and the inner peripheral surface of the ring roller 17.

  The connecting portion 21 is formed in a substantially disc shape and has a base end portion 37 whose central portion is connected to the output shaft 13, and extends in the axial direction from the outer peripheral edge of the base end portion 37. And a cylindrical roller holding portion 39 to be held.

  For example, the base end portion 37 of the connecting portion 21 is formed by cutting such as lathe processing, and the roller holding portion 39 is formed by plastic processing such as press molding. By forming the base end portion 37 and the roller holding portion 39 as a single unit and then joining them together, it is possible to achieve a configuration in which the axes are aligned with high accuracy at low cost. Further, the base end portion 37 and the roller holding portion 39 are joined by beam welding. As a result, it is possible to perform heat bonding with a narrow bead and in a short time, and it is possible to suppress the occurrence of misalignment by minimizing thermal distortion.

  As a specific example, a low carbon steel such as chrome molybdenum steel SCM420 (JIS G 4053 alloy steel for machine structure) is used for the base end portion 37 of the connecting portion 21, and the welded surface is subjected to a carbon-proof treatment. Heat treatment is performed. As a result, it is possible to ensure the hardness of a cam groove to be described later formed on the base end portion 37 while ensuring weldability. In addition, the said process is not restricted to a charcoal-proof process, What is necessary is just the process which suppresses the carbon content of a welding part, such as shaping | molding a welding surface by a cutting process after a plating process or heat processing.

  A ball 51, a second ring roller element 29, a first ring roller element 27, and a retaining ring 47 are inserted in this order from the base end 37 side into the roller holding part 39 of the connecting part 21. The roller holding unit 39 is assembled.

  On the inner peripheral surface of the roller holding portion 39, a plurality of torque transmitting concave grooves 43 are formed along the axial direction. The concave groove 43 of the roller holding portion 39 engages with the protrusion 28 of the first ring roller element 27 and transmits the rotational torque from the first ring roller element 27 to the roller holding portion 39. In addition, a ring groove 45 is formed on the inner circumferential surface of the end portion in the axial direction opposite to the base end portion 37 side of the roller holding portion 39 in the entire circumferential direction. A retaining ring 47 for supporting the first ring roller element 27 in the axial direction is fitted in the ring groove 45.

  The retaining ring 47 regulates the position of the first ring roller element 27 in the axial direction, prevents the first ring roller element 27 from falling off the roller holding portion 39, and applies a preload to the first ring roller element 27. .

<Loading cam mechanism>
Here, a specific configuration of the loading cam mechanism 23 will be described.
The second ring roller element 29, the base end portion 37 of the connecting portion 21, and the ball 51 constitute a loading cam mechanism 23. The loading cam mechanism 23 changes the contact surface pressure of each rolling contact surface of the sun roller 15, the ring roller 17, and the intermediate roller 19 shown in FIG. A plurality of first cam grooves 53 are formed in the outer end surface 30 facing the base end portion 37 of the second ring roller element 29 along the circumferential direction.

  A plurality of second cam grooves 55 are formed in the base end portion 37 at circumferential positions corresponding to the first cam grooves 53. The first cam groove 53 and the second cam groove 55 are the same as the cam surfaces 153 and 155 shown in FIG. 11, and are formed at three locations at equal intervals along the circumferential direction.

  The balls 51 are sandwiched between the first cam groove 53 and the second cam groove 55, respectively.

  The loading cam mechanism 23 includes a first cam groove 53, a second cam groove 55, and a ball 51. The first cam grooves 53 are formed on the outer end surface 30 of the second ring roller element 29 disposed on the base end portion 37 side of the connecting portion 21 and are provided at a plurality of locations along the circumferential direction. The second cam groove 55 is formed at the base end portion 37 of the connecting portion 21 facing the first cam groove 53, and is provided at a plurality of locations corresponding to the first cam groove 53.

  One ball 51 is sandwiched between the first cam groove 53 and the second cam groove 55. The first cam groove 53 and the second cam groove 55 are formed in a shape in which the axial depth gradually changes along the circumferential direction and becomes shallower toward the circumferential end of the cam groove.

  As described above, the first cam groove 53 is formed on the back surface of the second ring roller element 29, and the axial thrust proportional to the torque input to the rotating shaft is applied to the second ring roller element 29. It has become. The second ring roller element 29 is not in direct contact with the connecting portion 21 but is positioned by being supported by the ball 51 and the intermediate roller 19.

  The loading cam mechanism 23 presses the outer end surface 30 of the second ring roller element 29 in the axial direction in accordance with the rotational torque input from the input shaft 11, so that the second ring roller element 29 and the first ring The contact surface pressure of the rolling contact surface can be increased by bringing the roller element 27 closer.

<Retaining ring>
Next, the retaining ring 47 will be described.
FIG. 3 is a perspective view of the retaining ring 47 shown in FIG. The retaining ring 47 is formed by omitting a part of the ring, and includes an outer peripheral portion 50 and a plurality of projecting portions 48 that protrude radially inward from the outer peripheral portion 50 and are inclined in the axial direction. The plurality of protrusions 48 function as spring portions that are elastically deformed in the axial direction, and restrict the axial position of the first ring roller element 27 by the elasticity.

  4A is a cross-sectional view of the retaining ring 47 in a state where the protrusion 48 is compressed, and FIG. 4B is a sectional view of the retaining ring 47 in a state where an elastic deformation allowance is applied. As shown in FIG. 4B, the protrusion 48 is inclined toward the preload urging side, and performs a spring function by the bending of the protrusion 48. The first ring roller element 27 is moved axially by the intermediate roller 19 from a state having an elastic deformation allowance δ between the outer periphery of the retaining ring 47 and the first ring roller element 27 shown in FIG. The force is displaced as shown in FIG. Then, the entire outer end surface 34 of the first ring roller element 27 comes into contact with the side surface of the retaining ring 47, and the displacement of the first ring roller element 27 is restricted here.

  FIG. 5 is a graph showing the correlation between the amount of axial displacement of the retaining ring 47 and the rotational torque. In the initial stage of the axial displacement, the amount of axial displacement of the loading cam mechanism 23 (see FIG. 2) increases in proportion to the rotational torque from the input shaft 11. When the axial displacement amount increases, the protrusion 48 of the retaining ring 47 is compressed from the state shown in FIG. 4B to the state shown in FIG. When the retaining ring 47 is compressed by a certain amount (elastic deformation allowance δ), the retaining ring 47 reaches a region (state shown in FIG. 4A) that functions as the retaining ring 47 that prevents further axial displacement.

<Effects of friction roller reducer and retaining ring>
According to the friction roller type speed reducer 100 of this configuration, the preload is applied to the first ring roller element 27 by the spring structure of the retaining ring 47, so that the surface pressure of the rolling contact portion is ensured to the minimum necessary. This prevents the occurrence of slip during light torque transmission. However, the retaining ring 47 can stabilize the behavior of the traction component when the torque region functioning as a spring is as small as possible with respect to fluctuations in the input rotational torque. Therefore, the displacement of the first ring roller element 27 is allowed by a predetermined elastic deformation allowance δ provided in advance, and when the elastic deformation allowance δ is exceeded, the first ring roller element 27 is fixed in the axial direction. As a result, it is possible to prevent a reduction in power transmission efficiency when the rotational torque is small and to stabilize the behavior of the reduction gear when the rotational torque is large.

  Further, in the friction roller type speed reducer 100 of this configuration example, since the loading cam mechanism 23 is provided on the ring roller 17 side, each rolling is performed from the rotation center of the ring roller 17 as compared with the case where it is provided on the sun roller 15 side. The distance (rotation radius) to the contact portion can be increased. For this reason, even when the crowning shape of each roller is the same as that of the conventional structure, the circumferential speed difference can be kept small at both ends in the axial direction in the contact area (contact ellipse) of each rolling contact portion. As a result, the friction loss at each rolling contact portion can be reduced, and the transmission efficiency of the friction roller type speed reducer 100 can be easily secured.

  FIG. 6 is a cross-sectional view of an essential part shown as a reference diagram of the loading cam mechanism provided on the ring roller 17 side. In the loading cam mechanism 61, a spring portion 69 that presses the ring roller element 63 in the direction of the ring roller element 67 is provided between the ring roller element 63 and the roller holding portion 65. An anchor plate 71 is provided outside the ring roller element 67 in the axial direction. The anchor plate 71 is restricted from moving in the axial direction by a stopper 73 fixed to the roller holding portion 65. A first cam groove 53 and a second cam groove 55 similar to the above are formed on the opposing surface of the anchor plate 71 and the ring roller element 67, and a ball 51 is disposed between the grooves.

  In the case of this loading cam mechanism 61, since the number of large-diameter parts (stopper 73, anchor plate 71, spring portion 69) increases, an increase in the weight of the entire apparatus and an increase in inertial force are inevitable.

  On the other hand, in the friction roller type speed reducer 100 of this configuration, as shown in FIG. 2, the spring portion (protrusion portion 48) for preload is integrated with the retaining ring 47 that regulates the position of the ring roller element 27. Since it is provided, the preload mechanism can be simplified by omitting the spring portion 69. Further, by providing the second cam groove 55 integrally with the connecting portion 21, the anchor plate 71 can also be omitted. For this reason, the number of parts is reduced, and the weight of the entire apparatus can be reduced. Further, since the weight of the large-diameter part is reduced, an effect of reducing the inertial force can be obtained. Furthermore, the fixing of the ring roller 17 by the retaining ring 47 and the preload adjustment can be performed simultaneously, so that the apparatus can be made compact and the assembly workability can be improved.

  By connecting the input shaft 11 of the friction roller type reduction gear 100 of this configuration to the output shaft of the electric motor for driving the vehicle and connecting the output shaft 13 to the drive device for the electric vehicle, quietness and power transmission efficiency are high. Therefore, it is possible to construct a high-quality electric vehicle having a good acceleration response.

<Second configuration example>
Next, a second configuration example of the friction roller type speed reducer will be described.
The friction roller type speed reducer 110 of this configuration example is the same as the above-described configuration except that the retaining ring 47 in the first configuration example is changed to a retaining ring having a curved protrusion.

  FIG. 7 is a cross-sectional view of a main part of a loading cam mechanism 81 provided with a retaining ring 79 having a curved projection 77, and FIG. 8 is a perspective view of the retaining ring 79 shown in FIG. The retaining ring 79 of this configuration has an outer peripheral portion 80 and a plurality of protrusions 77 formed to protrude radially inward from the outer peripheral portion 80. Each of the plurality of protrusions 77 includes a base end side protrusion 85 and a distal end side inclined portion 87. The proximal-side protruding portion 85 is formed to protrude radially inward from the outer peripheral portion 80 of the retaining ring 79, and the distal-side inclined portion 87 is inclined in the axial direction and exceeds the axial center position of the outer peripheral portion 80. It is extended to. As shown in FIG. 7, the retaining ring 79 has an outer peripheral portion 80 fitted in the ring groove 45, and a distal end portion 87 a of the distal end side inclined portion 87 abuts on the first ring roller element 27, and the first ring roller element 27. Are arranged so as to be pressed in the axial direction.

  In the case of the shape of the retaining ring 47 shown in FIG. 3 described above, the protrusion 48 is not inclined in the state shown in FIG. 4A, and the retaining ring 47 is flat with respect to the axial direction. Although accurate design of the spring load in this state is difficult, in the retaining ring 79 of this configuration example, the tip side inclined portion 87 does not become flat in the axial direction but always maintains a curved shape. Therefore, as shown in FIG. 9, an elastic repulsive force (preload) having a substantially constant spring constant is generated until the retaining ring 79 changes from the state before deformation indicated by the dotted line to the state after change indicated by the solid line. To do. Further, even after the protrusion 77 reaches the post-deformation state indicated by the solid line, the pre-pressure that presses the first ring roller element 27 is accurately generated as an elastic repulsive force according to the shape of the tip side inclined portion 87. be able to. That is, the protrusion 77 always maintains the curvature of the tip side inclined portion 87, so that it functions as a spring portion that can accurately generate a desired preload, and the design of the spring load is facilitated.

  Therefore, according to the friction roller type speed reducer 110 of this configuration example, the friction loss can be reduced and high transmission efficiency can be easily ensured as in the case of the first configuration example. Pressure can be applied more accurately. Thereby, the power transmission performance from the low load torque to the high load torque can be stably maintained.

  As described above, the present invention is not limited to the above-described embodiments, but can be modified by those skilled in the art based on combinations of the configurations of the embodiments, descriptions in the specification, and well-known techniques. Application is also within the scope of the present invention and is within the scope of protection.

DESCRIPTION OF SYMBOLS 11 Input shaft 13 Output shaft 15 Sun roller 17 Ring roller 19 Intermediate roller 21 Connecting part 23, 61 Loading cam mechanism 24 Opposite side end surface 27 First ring roller element 29 Second ring roller element 30, 34 Outer end surface 31 Support shaft (spinning shaft) )
37 Base end part 39 Roller holding part 47 Retaining ring 48, 77 Projection part (spring part)
51 balls (rolling elements)
53 First cam groove 55 Second cam groove 100, 110 Friction roller type speed reducer δ Elastic deformation allowance

Claims (3)

A sun roller disposed concentrically with the input shaft; a ring roller disposed concentrically with the sun roller on an outer peripheral side of the sun roller; and the input shaft between an outer peripheral surface of the sun roller and an inner peripheral surface of the ring roller. A plurality of intermediate rollers that are rotatably supported around a rotation axis parallel to the outer periphery of the sun roller and that are in rolling contact with the outer peripheral surface of the sun roller and the inner peripheral surface of the ring roller, and a connecting portion that connects the ring roller and the output shaft. A friction roller type speed reducer comprising a loading cam mechanism for changing the contact surface pressure of the rolling contact surface of each roller,
The ring roller is composed of a pair of ring roller elements arranged side by side in the axial direction of the input shaft, and the inner peripheral surface of each of the ring rollers is from the opposite end face where the ring roller elements face each other. It is formed with a slope whose inner diameter decreases toward the outer end surface on the opposite side,
The coupling portion includes a base end portion connected to the output shaft, and a roller holding portion that extends from the base end portion and holds the pair of ring roller elements,
The loading cam mechanism is disposed only on the outer end face side of one of the pair of ring roller elements, and presses the outer end face in the axial direction according to the input rotational torque, thereby the ring roller element. To bring them closer together,
The roller holding portion has a retaining ring fitted in a ring groove formed on an inner peripheral surface of an axial end opposite to the base end ,
The retaining ring includes an outer peripheral portion and a plurality of spring portions that protrude radially inward from the outer peripheral portion and are inclined in the axial direction. The spring portions are elastically deformed in the axial direction, and the pair of ring rollers Preload the other of the elements in the axial direction, and restrict the position of the other ring roller element in the axial direction when the entire outer end surface of the other ring roller element is in contact with the side surface of the retaining ring. Friction roller speed reducer characterized by The spring portion has a certain amount of axial elastic deformation according to the amount of axial displacement of the loading cam mechanism proportional to the rotational torque from the input shaft, and the axial displacement of the other ring roller element. The friction roller type reduction gear according to claim 1, wherein only the elastic deformation allowance is allowed, and when the elastic deformation allowance is exceeded, the other ring roller element is fixed in the axial direction. The loading cam mechanism is
A first cam groove formed on the outer end face of the one ring roller element and provided at a plurality of locations along the circumferential direction;
A second cam groove formed at the plurality of locations corresponding to the first cam groove, formed in the connecting portion facing the first cam groove;
Rolling elements sandwiched between the first cam groove and the second cam groove,
Each of the first cam groove and the second cam groove has a shape in which an axial depth gradually changes along a circumferential direction and becomes shallower toward a circumferential end of the cam groove. The friction roller type speed reducer according to claim 1 or 2 .

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