JPS5821137B2 - Planetary roller type power transmission device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a planetary roller type power transmission device that transmits power by the frictional force of rollers that are in contact with each other.

An example of a conventional planetary roller type power transmission device of this type used as a speed reducer is shown in FIGS. 1 and 2.

In FIG. 1, 1 is a sun roller directly connected to an input shaft 9 that is rotationally driven, 3 is an inner roller fixed to a case T,
Reference numeral 2 designates a plurality of (three in this case) planetary rollers rotatably supported via bearings 5 on a planetary shaft 4 fixed to a carrier 6.

The sun roller 1, the plurality of planetary rollers 2, and the inner roller 3 are pressed against each other by a radial pressing force PN of these rollers, and power is transmitted by the frictional force generated by the PN.

That is, the pressure contact PN is produced by elastically deforming the roller 1°2.3 in the radial direction and making pressure contact.

In this case, there are the following problems.

(1) Since the pressure contact force PN is always constant regardless of the magnitude of the load applied to the output shaft, a constant pressure contact force PN will always act even in the case of a low load rate (for example, no-load operation state). Therefore, the durability of the pressure contact surface of each roller becomes low.

Furthermore, since rolling friction loss is also approximately constant regardless of the load factor, the transmission efficiency in the low load region decreases.

(2) When assembling the device, it is necessary to facilitate the assembly by heating the inner roller 3 to expand it.

Furthermore, when disassembling the device, since this is done with the pressing force PN acting, a resistance force acts along the axial direction of the rollers, making it difficult to disassemble and assemble the device.

As a solution to the above problems, the one shown in FIG. 2 has been proposed.

The one in FIG. 2 uses a torque cam mechanism and a torque cam mechanism interposed between the inner roller 3 and the casing 7 to generate the frictional force necessary to transmit power from the input shaft 9 to the output shaft. The pressing force PN is generated by the action of the inclined pressing surfaces 200 formed on the planetary roller 2 and the inner roller 3, thereby making the pressing force PN proportional to the magnitude of the load on the output shaft.

That is, as shown in FIG. 4, a reaction force P/2 (force between the planetary roller 2 and the inner roller As shown in FIG. 3, a gap 10 is formed between the inner roller 3 and the casing 7 due to the frictional force acting on the pressure contact surface between the inner roller 3 and the casing 7. The torque cam mechanism 80 generates an axial pressing force PT of the roller.

Due to this axial pressing force PT, a radial force PN/2 of the above PT acts on the inclined surfaces 200 formed on both end surfaces of the inner roller 3 and the planetary roller 2, and between the sun roller 1 and the planetary roller 2. is the pressure contact force P as the reaction force of the above radial component force.
N is generated.

Since these pressure contact forces PN/2 and PN have a proportional relationship with the magnitude of the load, the problem in the one shown in FIG. 1 can be solved.

However, the method shown in FIG. 2 also has the following problems.

(1) The pressure contact surface 200 between the planetary roller 2 and the inner roller 3 is
They are parts of a conical surface with P and Q as vertices, respectively.

In this case, since the vertices P and Q of the double-ended cone are not at the same position but are at independent positions, the rolling motion on the pressure contact surface 200 is in a state of slow rolling motion at only one geometric point. With the exception of one, all the others are in a sliding friction state based on the relative speed difference (referred to as differential friction).

For this reason, it is difficult to increase the width of the press-contact surface 200 in order to prevent seizure and abrasion of the press-contact surface 200, and the load capacity of the device is therefore severely limited.

The degree of such restriction increases as the distance between the apex PQ of the double-ended cone, ie, the offset measurement, increases.

(2) Friction loss is large because the pressure contact surfaces 200 are always in a differential state.

Therefore, the transmission efficiency is reduced, and the mechanism is susceptible to seizure on the pressure contact surface 200, making it unsuitable for high-speed operation.

(3) Compared to the one in FIG. 1, the width of the power transmission surface 211 between the sun roller 1 and the planetary roller 2 is narrowed by the width of the pressure contact surface 200, and therefore the load capacity is reduced.

The present invention solves the above problems, and although it is small and lightweight, it has an extremely large load capacity, is highly efficient, and has no operational slip.
It is an object of the present invention to provide a planetary roller type power transmission device which is also highly durable.

Therefore, the planetary roller type power transmission device according to the present invention,
A planetary shaft is supported by a carrier so as to be movable only in the radial direction of the carrier, and rolling elements are inserted into a plurality of rolling grooves provided on the planetary shaft, and a planetary roller formed in a thin-walled cylindrical shape is mounted. By bringing each of the transfer elements into contact with the inner circumferential surface, the planetary roller is supported by the planetary shaft, and the planet is supported by the 1-lux cam mechanism formed by the inner circumferential surface of the planetary roller, the rolling element, and the transfer groove. It is characterized in that a pressing force is generated between the planetary roller and each rotor from the driving force of the load 7 acting on the shaft.

An embodiment of the present invention will be described below with reference to FIGS. 5 to 9.

In FIG. 5, 20 is an input shaft, 22 is a sun roller fixed to the input shaft 20 with a key 21 and a snap ring 23, 24 is a carrier connected to an output shaft 25, and 26 is an inner roller fixed to a stationary member. It's Laura.

27 is a planetary shaft whose both end notches are attached to the carrier 24 in plural pieces (in this case, three pieces) at equal intervals in the circumferential direction of the carrier 24.
It is fitted into the guide groove 28 provided.

The guide groove 28 is shaped so that the planetary shaft 27 can slide only in the radial direction of the carrier 24 along this groove, as shown in FIG.

29 is a planetary roller consisting of a thin cylindrical outer ring 29a, a needle roller bearing 29b, and a thin cylindrical inner ring 29C;
Its outer periphery is brought into contact with the sun roller 22 and the inner roller 26 .

Two transfer grooves 27a are formed in the center of the planetary shaft 27 and are cut out in an arc shape symmetrically with respect to the axis.

As shown in FIG. 6, the center of the notch radius Rs of the transfer groove 27a is located on a line connecting the center notch b22a of the sun roller 22 and the center 27b of the planetary shaft 27.

Note that the radius Rs is formed to be equal to the inner radius Ri of the inner ring 29C.

Reference numeral 30 denotes a transfer element which is fitted into the transfer groove 27a so as to be freely transferable and is brought into contact with the inner periphery of the planetary roller 29.

In this way, the planetary roller 29 is rotatably supported by the planetary shaft 27 via the transfer element 30.

Further, as described above, the inner circumferential surface 29d of the planetary roller 29, the rotor 30, and the rolling groove 27a constitute a torque cam mechanism.

When assembling the planetary roller type power transmission device with the above configuration, the sun roller 22, planetary roller 29, inner roller 2
6. Prepress these to such an extent that a slight pressure force in the radial direction of the carrier 24 acts on their mutual contact surfaces.

When the input shaft 20 rotates, for example, in the direction of arrow Z in FIG. 8, and the output shaft 25 is rotated in the direction of arrow Y and a load is applied thereto, a load driving torque is generated on the axis 27b of the planetary shaft 27. A tangential force PL is applied in the direction shown in FIG.

When the above-mentioned PL acts on the planetary shaft 27, the carrier 24 is moved by the action of the torque cam mechanism constituted by the inner surface 29d of the planetary roller 29, the rotor 30, and the shifting groove 27a of the planetary shaft.
A pressing force FN is generated in the radial direction of the carrier 24, and this FN attempts to expand the planetary roller 29 from the original outer diameter DO to DL in the radial direction of the carrier 24 as shown in FIG. This elastic deformation is restrained by the rollers 22 and inner rollers 26.

Therefore, the pressure contact force PN in the radial direction of the carrier acts on the contact portion ◎ between the planetary roller 29 and the sun roller 22 and the contact portion ◎ between the planetary roller 29 and the inner roller 26 .

This pressing force PN varies depending on the rigidity of the planetary roller 29,
For the same FN, as the rigidity of the planetary roller 29 in the carrier radial direction increases, it decreases.

Therefore, by making the outer ring 29a and inner ring 29c of the planetary roller 29 as thin as possible to reduce the rigidity of the planetary roller 29, it is possible to obtain a pressing force PN close to the pressing force FN generated by the torque cam mechanism.

Therefore, in this embodiment, the outer ring 29a and the inner ring 29
By forming C into a thin cylindrical shape, the above-mentioned rigidity of the planetary roller 29 is made as small as possible.

Therefore, such a planetary roller type power transmission device can obtain a pressing force proportional to the load on the output shaft 25 between each roller.

In addition, both ends of the planetary shaft 2T are fitted into the guide grooves 28 of the carrier to allow the planetary shaft 27 to slide freely in the radial direction of the carrier, so that during load operation, each roller 29 is connected to the planetary roller 29 and the sun roller 22. The pressure contact force PN between the planetary roller 29 and the inner roller 26 is automatically set to a position where the pressure contact force PN between the planetary roller 29 and the inner roller 26 is equal.

That is, all the planetary rollers 29 are operated in a state where the pressure contact force is always equal between them and the sun roller 22 and the inner roller 26.

Although the above embodiment is a speed reduction device in which input is input from the sun roller 22 side and output is output from the carrier 24 side, the present invention can also be applied to a speed increase device in which input is input from the carrier 24 side and output is output from the sun roller 22 side. Applicable.

As described above, in the planetary roller type power transmission device according to the present invention, the planetary shaft is supported by the carrier so as to be movable only in the radial direction of the carrier, while the thin-walled cylindrical planetary roller is engraved on the planetary shaft. The inner circumference of the planetary roller, the transfer element,
A torque cam mechanism consisting of a transfer groove is formed, and the torque cam mechanism generates a pressure contact force in the radial direction of the carrier between the planetary roller and the transfer element from the load driving force acting on the planetary shaft, and the pressure contact force causes the sun roller to , the planetary roller, and the inner roller are brought into pressure contact with each other, so there are the following advantages.

(1) It is possible to obtain a pressing force that is approximately proportional to the magnitude of the load, and by making the planetary shaft movable only in the radial direction of the carrier, the pressing force between each roller is equalized.

Therefore, the durability of the pressure contact surface (that is, the transfer surface of the roller) is improved.

(2) Since the transfer surface of the roller is cylindrical, (2-1)
There is no differential slip, and rolling friction loss is small.

This improves the transmission effect and prevents seizure of transfer surfaces and accidents during high-speed operation.

(2-2) Since the transfer surface is extremely easy to process, the manufacturing cost of the device is reduced.

(2-3) Since no axial moment acts on the sun roller, planetary roller, and inner roller during operation, high-speed operation can be easily achieved.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view taken along the axial line showing one example of a conventional planetary roller type reducer, and Figs. 2 to 4 show another example of a conventional planetary roller type reducer. A view corresponding to Figure 1, Figure 3 is a view seen in the direction of arrow A in Figure 2, and Figure 4 is a view corresponding to Figure 2.
FIG. 3 is a sectional view taken along line BB in the figure. 5 to 9 show one embodiment of the present invention, FIG. 5 is a diagram corresponding to FIGS. 1 and 2, and FIG. 6 is a diagram corresponding to FIG.
7 is a sectional view taken along line C, FIG. 7 is a view taken in the direction of arrow D in FIG. 5, and FIGS. 8 and 9 are explanatory views of the operation. 20...Input shaft, 22...Sun roller, 24...
Carrier, 25... Output shaft, 26... Inner roller, 2
7... Planetary shaft, 27a... Rolling groove, 28... Guide groove, 29... Planetary roller, 29a... Outer ring, 29
b...Needle roller bearing, 29c...Inner ring, 30
...transfer child.

Claims (1)

[Claims] 1. A plurality of planetary rollers 29 that are in contact with the outer periphery of the sun roller 22 connected to the first rotating shaft 20 and the inner periphery of the inner roller 26 fixed to a stationary member, respectively, are connected to the second rotating shaft 25. Planetary shaft 2 supported by carrier 24 to be connected
7, the planetary shaft 27 is supported on the carrier 24 so as to be movable only in the radial direction of the carrier, and the planetary shaft 27 , a plurality of transfer grooves 27a are arranged at substantially symmetrical positions with respect to the axis 27b, and the center of the radius of curvature Rs at the bottom thereof is located approximately on the line connecting the axis 22a of the sun roller 22 and the axis 27b of the planetary shaft 27. A transfer element 30 is inserted into each of the transfer grooves 27a so that the transfer element 30 can be freely transferred by contacting the inner circumferential surface 29d of the planetary roller 29, and the planetary roller 29 is formed into a thin cylindrical shape. At the same time, the planetary shaft 27 is transferred through each transfer element 30.
The planetary roller 29 is rotatably supported by the planetary roller 29 from the load driving force acting on the planetary shaft 27 at the inner peripheral surface of the planetary roller 29, the rotor 30, and the rolling groove 27a.
forming a torque cam mechanism for generating a pressure contact force in the radial direction of the carrier 24 between and each of the rolling elements 30;
The sun roller 22, planetary roller 29 and inner roller 26
A planetary roller type % type % characterized by generating a pressing force between them in proportion to the magnitude of the load on the rotating shaft.