JPS61189363A - Rolling friction transmission - Google Patents

Abstract

PURPOSE:To prevent production of abnormal wear and to provide a high traction rate, by a method wherein the surface of a roller is coarsened and proper flatness is provided. CONSTITUTION:The surface of at least the one roller 12 of roller 10 and 12 is coarsened. Surface coarseness of the coarsened surface is 5mum or more in 10 point average coarseness. This constitution causes an oil film bottom to be partially divided, and since power transmission, in which a power transmission, produced by viscosity of a oil film F, is combined with power transmission produced by contact between the rollers 10 and 12, the coefficient of traction can be sharply improved.

Description

[Detailed description of the invention] [Industrial application field] This invention relates to a rolling friction transmission.

[Conventional technology]

In rolling friction transmissions using contacting rollers,
A preload is applied to each other such that at least one of the rollers bites into the other, thereby causing frictional rotation of the rollers. In order to maximize the friction area and eliminate slippage, the surface of the roller is formed to be flat and have as little surface roughness as possible.
Lubricating oil is interposed between the roller surfaces, and power is transmitted in a fluid lubrication state. In other words, as the rollers rotate at high speed, the squee-winter effect causes the lubricating oil to be squeezed between the rollers, forming a thin film of lubricating oil between the contact surfaces, and the viscous force that resists the shearing force of this film inhibits power transmission. It will be done.

[Problem that the invention seeks to solve]

In the conventional structure, the contact surface of the roller is flattened because power is transmitted under fluid lubrication.

However, in power transmission under fluid lubrication, the traction coefficient is small, so effective transmitted power cannot be obtained unless the rollers are rotated at high speed. However, when driving at high rpm,
The influence of the centrifugal force of the rollers makes it difficult to manage the gap between the rollers, and the high rotation speed also causes problems such as heat generation in the bearings and the need for a cooling device.

JP-A-55-86949 and JP-A-59-113357
The paper proposes forming grooves on the surface of the roller.

The grooves on the surface of the roller appear to be aimed at improving oil supply characteristics. However, even with this prior art, power transmission is basically performed under fluid lubrication, and the traction coefficient is small. Therefore, there is a problem in that effective transmission power cannot be obtained unless the rollers are rotated at high speed.

[Means for solving problems]

This invention includes at least a pair of rollers that are in contact with each other, the contact surfaces are preloaded to cause frictional rotation of the rollers, the contact surfaces of the rollers are formed as flat surfaces, and lubricating oil is interposed between the contact surfaces. In a rolling friction transmission device that transmits power between rollers, the contact surface of at least one of the rollers is roughened.

Preferably, the roughened surface has a 10-point average roughness of 5 μm or more.

Preferably, the roughened surface is partially planarized to remove only abnormal protrusions on the surface.

[For production]

By roughening the surface of at least one of the rollers, power transmission is changed from conventional hydrodynamic lubrication to mixed or boundary lubrication.

That is, by partially dividing the lubricating oil film between the rollers by roughening the surface, power transmission can be performed by combining the shearing of the viscous oil film and the contact of the rollers. Therefore, the traction coefficient can be improved.

〔Example〕

FIG. 1 is an axial sectional view of a planetary roller mechanism as an embodiment of the present invention, in which 10 is a sun roller, 12 is a planetary roller, and 14 is a ring roller.

A carrier 15 rotatably holds four planetary rollers 12 at equal intervals in the circumferential direction. The planetary roller 12 is formed as a hollow body, and includes a sun roller 1o and a ring roller 14.
The rollers are arranged so as to be appropriately elastically deformed in a compressed state between them, thereby ensuring rolling frictional contact between the sun roller 10 and the planetary rollers 1-2 and between the planetary rollers 12 and the ring roller 14. It is designed so that The carrier 15 that rotatably holds the planetary roller 12 has four axially cantilevered protrusions g15a, and the planetary roller 12 is rotatably held between adjacent protrusions 15a. The sun roller 10 extends as a first shaft 18 , while the carrier 15 extends as a second shaft 20 , the first shaft 18 and the second shaft 20 being rotatably supported in a housing 22 . has been done. When the transmission is used, as is well known, one of the three rollers 10, 12, 14 is restrained by a brake (not shown), and the first
One of the shaft 18 and the second shaft 20 serves as an input shaft, and the other serves as an output shaft, and a speed ratio corresponding to the roller diameter is obtained. Although not shown, means for supplying lubricating oil between the rollers is provided.

In the prior art, the surfaces of the sun roller 10, the planetary rollers 12, and the ring roller 4 are usually finished as flat surfaces with the surface roughness suppressed as much as possible. This is to obtain a power transmission effect in a so-called fluid lubrication state, in which lubricating oil is supplied between the rollers to form an oil film, and power is transmitted by the shear force applied to the oil film as the rollers rotate. However, power transmission based on this principle only yields a small traction coefficient, and there is a problem in that effective power transmission cannot be achieved unless the speed of the rollers is increased. The present invention attempts to solve this conventional problem by providing the contact surface of the roller with the following structure.

That is, as shown schematically in an enlarged view of the contact portion of the rollers in FIG. 3, the surface of one of the rollers, the planetary roller 12 in this embodiment, is roughened.

Incidentally, the surfaces of the sun roller 10 and the ring roller 14 are formed into flat surfaces with as small a surface roughness as possible (10-point average roughness of 1.0 .mu.m or less) by polishing and finishing as in the prior art. Power transmission between the planetary roller 12 and the sun roller 10 (or ring roller 14) is performed while lubricating oil is supplied between the contact surfaces of these rollers as indicated by arrow r. By roughening one of the contact surfaces of the rollers as in this invention, the oil film F between the rollers is partially separated, and power transmission by the viscosity of the oil film and power transmission by contact between the rollers are combined. In addition, power is transmitted in a mixed or boundary lubrication state, making it possible to increase the traction coefficient.

Any known method may be used to roughen the surface of the roller; for example, there is a method of roughening using alumina particles as abrasive grains. Figure 4 shows the experimental conditions in which the roller contact load was 27 kgf, the ring roller rotation speed was 200 rpm, and lubricating oil ATF D-II was supplied at a rate of 10 drops/min using the apparatus shown in Figure 1. ,
This is the relationship between the slip rate and traction coefficient when the surface roughness changes. The surface roughness is expressed as the average size of 10 points. The slip rate is
It is expressed as However, this is a case where the gear ratio is assumed to be 1. The traction coefficient is expressed as: The larger the traction coefficient, the higher the transmitted force. From Figure 4, from about 5 μm to 25
Looking at the data for surface roughness in the micrometer range, it is clear that the traction coefficient can be significantly improved compared to the conventional surface roughness of 1 micrometer.

As shown in FIG. 3, it is preferable that the roughened surface of the roller 00 be partially flattened by removing abnormal protrusions on the surface. This is to prevent abnormal wear between the rollers.

The degree of flattening of the surface is the flatness ratio, z, +j! ,+...+A! 7 Plane ratio = X 100X ・
...(3)! can be represented by Here l is a certain arbitrary length, and 17 is the length of each flat portion. For measuring flatness, it is possible to use a relative load curve produced by a recently developed instrument called a universal surface profilometer with roughness analyzer. To explain the principle of surface measurement using this device, in FIG. 5 (a) schematically shows the uneven shape of the surface to be measured. Assuming a certain depth CVm from the reference point P, the length of the actual part of the sample at that depth is 2. ,
Il.

...17, and the percentage tpm relative to the total length of the sample is obtained. Such measurements are performed over each depth, resulting in a curve as shown in (o). This is called a relative load curve, and the roughness state of the sample can be evaluated. It can also be used to evaluate flat conditions. In other words, if the surface protrusions (broken line) are removed by making a certain cut as shown in Figure 6 (a), the relative load curve will be flat from 0% to tpa+% as shown in Figure 6 (0). , and tpm can be adopted as the planarity ratio in equation (3).

FIG. 7 shows the relationship between the flatness ratio and the traction coefficient measured by the relative load curve in this manner.

Since increasing the flatness ratio lowers the traction coefficient, it is necessary to determine an appropriate flatness ratio within a range that can prevent abnormal wear and that can obtain the desired traction coefficient.

As a means for flattening, there is a method in which a roller with a roughened surface whose surface condition is extremely small is brought into pressure contact with the roller, and the roller is rubbed and rotated by applying an arbitrary load.

〔example〕

In the friction planetary roller mechanism shown in FIG. 1.2, shot blasting was applied to the surface of the planetary roller 12 to roughen the surface. The obtained roughened surface looked as shown in FIG. 8(a) on the chart of a universal shape measuring device with a roughness analyzer. The measurement conditions in this case were as follows.

Sample length L: 2.5mm Vertical magnification V: 1000 Horizontal magnification H: 20 Cut length C: 0.8m+w The measurement results were as follows.

Average roughness Ra: 3.1 μm Maximum roughness Rmax: 21.2 μm 10-point average roughness Rz: 16.5 #m The obtained relative load curve is shown in FIG. 8(o).

Next, an extremely flattened small roller was pressed against the thus roughened surface of the roller to partially flatten the roughened surface of the roller. The state of the surface after planarization was as shown in FIG. 9(a) on the chart. The measurement conditions were the same.

The measurement results were as follows.

Average roughness Ra: 2.1 μm Maximum roughness Rt: 18.5 μm 10-point average roughness RZ: 14.5. The relative load curve obtained is shown in FIG. 9 (b). When the planetary roller 12 thus partially flattened was incorporated into the apparatus shown in FIGS. 1-2 and operated, it became possible to operate for a long time without causing abnormal wear to the sun roller 10 and the ring roller 14.

〔Effect of the invention〕

According to this invention, by roughening the surface of the roller and giving it an appropriate flatness rate, it is possible to construct a friction true speed device that does not cause abnormal wear and has a high traction rate. The high traction coefficient improves the transmission ability, and if the same power is transmitted as before, the rotational speed can be reduced accordingly. Therefore, centrifugal force is reduced, the bearing can maintain an appropriate temperature, durability is improved, and the cooling means can be simplified.

[Brief explanation of the drawing]

Fig. 1 is an axial sectional view of a planetary roller device which is an embodiment of the transmission device of the present invention, Fig. 2 is a transverse sectional view taken along line nn in Fig. 1, and Fig. 3 shows the contact portion of the rollers. Figure 4 is an enlarged schematic diagram showing the relationship between slip rate and traction coefficient with various surface roughness changes, and Figures 5 and 6 are relative loads measured by a universal shape measuring device with a roughness analyzer. A diagram explaining how to measure a curve, Figure 7 is a relationship diagram between flatness ratio and traction coefficient, Figures 8 and 9 are after roughening and after the part is flattened, respectively, with a roughness analyzer attached. A diagram showing a surface shape chart (A) and a relative load curve actually obtained by a universal shape measuring device. 10... Sun roller, 12... Planetary roller, 14.
...Ring roller, 15...Carrier. ~14--1ν Ning roller 18.20-11 Rotating shaft Fig. 3 1z Fig. 4 Slip rate al. Figure 5 (a)
(B) Plane ratio = ^ρm Figure 7 Plane ratio o1゜ Figure 8 (A)
(b) and relative load curve (b) Figure 9 (a)
(b) and relative load curve (b)

Claims (1)

[Claims] 1. At least a pair of contacting rollers are provided, the contact surfaces are preloaded to cause frictional rotation of the rollers, the contact surfaces of the rollers are formed as flat surfaces, and there is a gap between the contact surfaces. A rolling friction transmission device that transmits power between rollers using lubricating oil, wherein the contact surface of at least one of the rollers is roughened. 2. The surface roughness of the roughened surface is 5 as a 10-point average roughness.
The rolling friction device according to claim 1, wherein the rolling friction device has a diameter of μm or more. 3. The rolling friction device according to claim 1, wherein the roughened surface is partially flattened to remove abnormal protrusions.