JPH0514030Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[0001]

[Field of Industrial Application] This invention relates to a planetary roller power transmission device that transmits power by the frictional force of planetary rollers.

[0002]

BACKGROUND OF THE INVENTION As a conventional planetary roller type power transmission device of this type, one used as a speed reducer is known, for example, as shown in FIG. 1 of Japanese Patent Publication No. 58-21137. This known structure consists of a sun wheel made of steel that is directly connected to an input shaft that is rotatably driven, a fixed ring made of steel that is fitted and fixed to the inner periphery of the housing, and an outer periphery of the sun wheel and an inner periphery of the fixed ring. and a plurality of planetary shafts provided in the axial direction at the end of the output shaft. The sun wheel, the plurality of planetary rollers, and the fixed ring are pressed against each other by the contact pressure in the radial direction of each of the planetary rollers, and the frictional force generated by this pressure causes the rotation from the input shaft. The rotational driving force is decelerated and transmitted to the output shaft.

[0003] This type of power transmission device generally has a transmission efficiency of rotational force transmitted from the input shaft to the output shaft.
It is influenced by the magnitude of the maximum contact pressure between the planetary roller, the fixed wheel, and the sun wheel, especially the maximum contact pressure between the planetary roller and the fixed wheel (this point will be discussed in the embodiments of the invention described later). (This will be explained in detail in the description.) The larger the maximum contact pressure between the planetary roller and the fixed ring, the more the efficiency of transmitting rotational force in the device can be improved. However, in order to increase the maximum contact pressure between the planetary rollers and the fixed ring, if the sun ring, planetary rollers, and fixed ring are strongly pressed against each other in the radial direction, the sun ring and the planetary rollers will come into contact with their convex surfaces. Therefore, the maximum contact pressure between the members becomes too excessive, and there is a risk that the device itself may be damaged.

[0004] For this reason, for example, as shown in Japanese Patent Publication No. 56-50140, by providing a groove on the rolling surface (inner peripheral surface) of the fixed ring, the above-mentioned disadvantages can be prevented and the fixed ring and planetary roller The aim is to increase the maximum contact pressure between the two and improve the transmission efficiency of rotational force in the device.

[0005] However, this device adopts a configuration in which a large number of circumferential grooves are provided on the rolling surface of the fixed ring, so it has the disadvantage that the processing of the fixed ring becomes complicated and the processing cost increases. have In addition, the contact pressure increases locally at the boundary between the rolling surface of the fixed ring and the groove, causing local wear on the outer circumferential surface of the planetary roller that comes into contact with this area, resulting in a problem that the life of the device is shortened. be.

[0006] The purpose of this invention is to improve the maximum contact pressure between a fixed wheel and a planetary roller in a planetary roller type power transmission device, and to improve the transmission efficiency of rotational force.

[0007]

[Means for Solving the Problems] According to this invention, in a planetary roller type power transmission device, a fixed ring is formed of a material having a higher modulus of longitudinal elasticity than the sun wheel, such as a ceramic material.

[0008]

[Example] Figures 1 and 2 show an example in which this invention is used as a speed increaser.

[0009] 1 is an input shaft (second rotating shaft), 2 is an output shaft (first rotating shaft), 3 is provided at one end of the output shaft 2 with a key 7, etc., and a sun wheel made of steel (of course The sun ring 3 may be formed integrally with one end of the output shaft 2.), 5 is a fixed ring fitted on the inner peripheral surface of the housing 4, and 6 is a fixed ring fitted on the end surface 1a of the input shaft 1 at equal intervals in the circumferential direction. (Three in this case) are planetary shafts (planetary roller support members) screwed together in the axial direction. As a result, the planetary shafts 6 are arranged at equal intervals in the circumferential direction (in this case, 3
) is fixed to the input shaft 1. 8 is a planetary roller made of steel, and each planetary shaft 6 has a floating bush 9.
The outer periphery thereof is in contact with the cylindrical bottom surface of a circumferential groove 3a for rolling the planetary roller formed on the inner periphery of the fixed ring 5 and the outer periphery of the sun wheel 3. The floating bush 9 is interposed between the circumferential step 6a of the planetary shaft 6 and the planetary roller 8, and is supported in the axial direction by a side surface of the step 6a and a snap ring 10 fixed to the end of the planetary shaft 6. Positioned.

[0010] The fixed ring 5 is made of a ceramic material, for example, Si ₃ N ₄ or SiC. This ceramic material has a longitudinal elastic modulus E of 3 x 10 ⁶ Kgf/cm ² , while the longitudinal elastic modulus E of the bearing steel (SUJ-2), which is the material of the fixed ring of the conventional device, is 2.1 x 10 ⁶ Kgf/cm. ²
It is approximately 1.4 times higher than that of . Of course, fixed wheel 5
may be made of a material having a high modulus of longitudinal elasticity other than ceramic material.

[0011] In the planetary roller type power transmission device, which is a speed increaser with the above configuration, the sun wheel 3, the planetary rollers 8, and the fixed wheel 5 are arranged so that radial contact pressure acts on their mutual contact surfaces. As a result, when the input shaft 1 rotates, for example, in the direction of the arrow X in FIG.
Rotate in the direction of the arrow. At this time, as the maximum contact pressure P _Anax (described later) between the fixed ring 5 and the planetary roller 8 increases, the slippage between the two members 5 and 8 decreases, so that the rotational force from the input shaft 1 to the output shaft 2 increases. Transmission efficiency can be improved.

[0012] Next, in this invention, the reason why the fixed ring 5 is made of a ceramic material having a high longitudinal elastic modulus will be described.

[0013] Generally, in this type of planetary roller type power transmission device, the maximum contact pressure P _Anax generated when the planetary roller 8 and the fixed ring 5 come into contact is:

[0014]

[Math 1] ■■■ Tortoise shell [0001] ■■■

[0015] According to the formula, on the other hand, the maximum contact pressure P _Bnax caused by the contact between the planetary roller 8 and the sun ring 3 is:

[0016]

[Math 2]■■■ Turtle shell [0002] ■■■

[0017] Each is determined by the following equations.

[0018] In each of the above equations, P: Contact pressure applied to the planetary roller r ₁ : Outer radius of the planetary roller r ₂ : Inner radius of the fixed ring r ₃ : Radius of the solar ring E ₁ : Longitudinal elastic modulus of the planetary roller E ₂ : Longitudinal elastic modulus of fixed ring E ₃ : Longitudinal elastic modulus of solar ring L: Indicates the effective length of the planetary roller.

[0019] As is clear from the above equations (1) and (2), the maximum contact pressure is P _Anax < P _Bnax , so the slip between the two members 5 and 8 is reduced, and the rotational force in the device is transmitted. To improve efficiency, it is necessary to make the maximum contact pressure P _Anax between the planetary roller 8 and the fixed ring 5 as high as possible. However, when the planetary roller 8 and the fixed ring 5 are strongly pressed against each other to increase the maximum contact pressure P _Anax , an equivalent pressing force is applied to the planetary roller 8 and the sun wheel 3, and these are in a convex surface-to-convex contact state. Therefore, the maximum contact pressure P _Bnax between the members 8 and 3 becomes too excessive,
The device itself may be damaged.

[0020] Therefore, in this invention, the fixed wheel 5
By using a ceramic material with a higher modulus of longitudinal elasticity than bearing steel, even if the pressing force between the fixed ring 5 and the planetary roller 8 and between the sun ring 3 and the planetary roller 8 is the same, the pressure between the fixed ring 5 and the planetary roller 8 is reduced. The maximum contact pressure between P _Anax is increased.

[0021]

[Effects of the invention] Since this invention has the above configuration, it has the following effects.

[0022] When the contact pressure between the planetary roller and the fixed ring is the same, the longitudinal elastic modulus E of the ceramic material is approximately 1.4 times larger than that of bearing steel, so the maximum contact between the planetary roller and the fixed ring is Pressure increases by approximately 10%.

[0023] Therefore, the transmission efficiency of rotational force in the device is improved.

[0024] When trying to obtain the same transmission efficiency as the conventional device, there is no need to strongly press the planetary rollers, the fixed ring, and the sun wheel against each other, so the life of the entire device is improved.

[0025] By simply making the fixed ring a material with a high modulus of longitudinal elasticity, special processing such as grooves is not required, and therefore the processing process of the fixed ring is simplified, which does not increase the processing cost. Nor. Further, since no groove is required on the inner circumferential surface of the fixed ring, contact pressure is not locally increased and local wear on the planetary rollers does not occur, and the life of the entire device is improved.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a main part of an embodiment of this invention.

FIG. 2 is a sectional view taken along the - line in FIG. 1;

[Explanation of symbols]

1...Input shaft (second rotating shaft) 2...Output shaft (first rotating shaft) 3...solar ring 4...Housing 5...Fixed wheel 6... Planetary shaft (planetary roller support member) 8... Planetary roller 9...Floating bush.

Claims (1)

[Scope of utility model registration request] Claim 1: A plurality of planetary rollers are disposed between the outer periphery of a sun ring provided on a first rotating shaft and the inner periphery of a fixed ring fitted and fixed to a housing, each abutting both circumferential surfaces. are provided, and each planetary roller is
In a planetary roller type power transmission device in which power is transmitted between the two rotating shafts by being supported by a planetary roller support member fixed to a second rotating shaft, the fixed ring is higher than the sun wheel. A planetary roller type power transmission device characterized in that it is made of a material having a longitudinal elastic modulus.