JP2016204502A - Traction grease composition and traction drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a traction grease composition capable of achieving high heat resistance, high traction coefficient and long life, and a traction drive device in which the traction grease composition is encapsulated.SOLUTION: The traction grease composition is provided which contains a base oil composed of a synthetic hydrocarbon oil and a thickener composed of silica, and in which the base oil has a kinetic viscosity of 25000 mm/s to 32000 mm/s(40°C) and the thickener is contained in an amount of 5 mass% to 20 mass%.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a traction grease composition and a traction drive device using the traction grease composition.

Greases known as lubricating oils are used for friction parts such as bearings, brakes, clutches, etc., and various grease compositions have been conventionally provided.
For example, Patent Document 1 contains Botryococcus oil (base oil) having a kinematic viscosity of 14.3 mm ² / s (40 ° C.) represented by the molecular formula C ₃₄ H ₅₈ and a thickener made of silica. A grease composition for a clutch is disclosed.

Patent Document 2 discloses a grease composition for preventing brake noise, which contains a silicone oil (base oil) having a kinematic viscosity of 5000 mm ² / s (25 ° C.), a polyimide resin as a thickener, and silica. .
A traction drive device is known as one of the uses of a grease composition. The traction drive device includes, for example, a sun shaft and a plurality of planetary rollers provided in pressure contact with the sun shaft. When the sun shaft is connected to the power source, the rotation of the power source is decelerated through the planetary roller, and the torque is amplified and transmitted to the low speed shaft. On the other hand, when the low speed shaft is connected to the power source, the rotation of the power source is accelerated through the planetary roller and transmitted to the sun shaft.

The planetary roller type traction drive device having such a configuration has the advantages shown in the following (1) to (4), and is therefore used for driving machine tools, other transmissions, power steering of automobiles, and the like. Yes.
(1) Smooth rotation with low noise and vibration.
(2) High-speed rotation is possible compared to gears.
(3) Almost no backlash and highly accurate rotation can be obtained.
(4) Since the structure is simple, it is inexpensive and compact.

JP 2013-170230 A JP 2012-236929 A

Since the traction drive device always receives a pressure contact force, the temperature tends to rise. In particular, when used in a high temperature environment such as an automobile engine room, the temperature may rise to 100 ° C. or more due to the influence of the surrounding environment.
However, at present, no grease composition is provided that has high heat resistance that can withstand use in an environment exceeding 100 ° C. while exhibiting a high traction coefficient required for the traction grease composition. For example, there are grease compositions prepared using synthetic naphthenes such as 2,4-dicyclohexyl-2-methylpentane and dibenzyltoluene hydride, and base oils such as alkylbenzene. This type of grease composition has a cyclic structure and can exhibit a relatively high traction coefficient, but has the disadvantages of low heat resistance, high oil separation and evaporation.

  Accordingly, an object of the present invention is to provide a traction grease composition capable of realizing high heat resistance, a high traction coefficient and a long life, and a traction drive device in which the traction grease composition is enclosed.

Traction grease composition of the present invention comprises a base oil of a synthetic hydrocarbon oil, and a thickening agent consisting of silica, kinematic viscosity of the base oil is 25000mm ² / s~32000mm ² / in s (40 ° C.) Yes, containing 5 to 20% by mass of the thickener (Claim 1).
The traction drive device of the present invention includes a first rotator (3), a traction drive mechanism including a second rotator (4) disposed in pressure contact with the first rotator (3), and the traction drive mechanism. And the traction grease composition (G) encapsulated in (Claim 2).

  In the traction drive device of the present invention, the traction drive mechanism includes a fixed wheel (2), and a sun shaft (3) as the first rotating portion disposed concentrically inside the fixed wheel (2). A plurality of planetary rollers (4) as the second rotating portion provided in a pressure contact state between the sun shaft (3) and the fixed ring (2), and each planetary roller (4) can be rotated. And a supporting carrier (5).

According to the present invention, the kinematic viscosity of the base oil of a synthetic hydrocarbon oil is ^{25000mm 2 / s~32000mm 2 / s (} 40 ℃), thickener consisting of silica contained 5 wt% to 20 wt% Therefore, high heat resistance, high traction coefficient and long life can be realized.

FIG. 1 is a schematic cross-sectional view of a planetary roller type power transmission device according to an embodiment of the present invention. 2 is a cross-sectional view taken along line (2)-(2) in FIG. FIG. 3 is a diagram showing the degree of oil separation in Examples and Comparative Examples. FIG. 4 is a diagram showing the oil separation degree of the comparative example. FIG. 5 is a diagram showing traction coefficients of the example and the comparative example. FIG. 6 is a diagram illustrating the traction coefficient of the comparative example.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic cross-sectional view of a planetary roller type power transmission device according to an embodiment of the present invention. 2 is a cross-sectional view taken along line (2)-(2) in FIG.
The planetary roller type power transmission device as an example of the traction drive device of the present invention includes a housing 1, a fixed wheel 2 fixed to the housing 1, and a first of the present invention disposed concentrically inside the fixed wheel 2. The sun shaft 3 as an example of the rotating portion, and a plurality (four in FIG. 1) of planetary rollers as an example of the second rotating portion of the present invention provided in a pressure contact state between the sun shaft 3 and the fixed ring 2. 4 and a carrier 5 that rotatably supports each planetary roller 4 and rotates by the revolution of the planetary roller 4. Grease G is filled inside the fixed ring 2 so as to be in contact with the sun shaft 3 and the planetary roller 4.

The fixed ring 2 is fixed to the housing 1 by screws 7 together with the guide rings 6 and 6 on both sides thereof. Each planetary roller 4 is rotatably supported by a roller shaft 8 protruding from the carrier 5. The carrier 5 is formed in a bottomed cylindrical shape, and a low-speed input / output shaft 9 is inserted and coupled into the cylindrical shape.
Between the adjacent planetary rollers 4 and 4, a plurality of (four in FIG. 1) oil-impregnated rollers 10 that are in contact with the planetary rollers 4 are arranged. The oil-impregnated roller 10 is, for example, a mixture of a thermoplastic resin such as ultra high molecular weight polyethylene, nylon or polypropylene and a lubricating oil such as naphthenic mineral oil or silicone oil heated to the melting temperature of each of the above resins, and solidified by cooling. What was obtained by forming into a cylindrical shape. A small hole inside the oil-impregnated roller 10 is impregnated with the lubricating oil. The oil-impregnated roller 10 may be produced by pressure-molding resin powder and lubricant powder. The support state of the oil-impregnated roller 10 with respect to the support 11 is preferably rotatable but may be set to non-rotation.

The support 11 is a member provided on the end surface of the carrier 5 separately from the carrier 5. The support 11 has an engaging recess 11a, and the roller shaft 8 is engaged with the engaging recess 11a.
When the sun shaft 3 rotates, the planetary roller 4 revolves while rotating, and the carrier 5 rotates along with this revolution. At this time, since the support 11 is engaged with the roller shaft 8 of the planetary roller 4, it rotates together with the carrier 5. The oil-impregnated roller 10 supported by the support 11 revolves to follow the planetary roller 4 and rotates while contacting the planetary roller 4. As a result, an oil film is formed on the rolling surfaces of the fixed ring 2 and the planetary roller 4. At this time, each oil-impregnated roller 10 is kept in a constant radial position by the support 11 so that it is not caught between the fixed ring 2 and the planetary roller 4.

Next, the grease composition constituting the grease G will be described in detail.
The grease composition contains a base oil and a thickener.
Synthetic hydrocarbon oil is used as the base oil. More specifically, examples of the synthetic hydrocarbon oil include those obtained by polymerizing α-olefins produced using ethylene, propylene, butene, and derivatives thereof as raw materials alone or in combination of two or more. Preferred examples of the α-olefin include those having 6 to 18 carbon atoms, and more preferable examples include 1-decene and poly-α-olefin (PAO) which is an oligomer of 1-dodecene.

The content rate of base oil is 80 mass%-95 mass%, for example.
About the physical property of a base oil, the following range is preferable. In other words, the kinematic viscosity (according to JIS K 2283) ^{is 25000mm 2 / s~32000mm 2 / s (} 40 ℃), ^{preferably, 28000mm 2 / s~30000mm 2 / s} (40 ℃).
If the kinematic viscosity of the base oil is less than 25000 mm ² / s, the oil film holding ability is lowered, the shear resistance is lowered, and it is difficult to obtain a high traction coefficient. In the planetary roller type power transmission device, it is preferable that a traction coefficient of 0.060 or more, preferably 0.065 to 0.1 can be expressed. On the other hand, when the kinematic viscosity of the base oil exceeds 32000 mm ² / s, the low temperature fluidity of the grease composition is lowered. For this reason, it is difficult to use in a harsh environment where the ambient temperature constantly changes from below zero to a high temperature exceeding 100 ° C. due to the air temperature, the operating heat of each part, etc. That is, by the kinematic viscosity of the base oil and ^{25000mm 2 / s~32000mm 2 / s (} 40 ℃), greater than 100 ° C. from a low temperature range up to (e.g., about 120 ° C.) higher temperature range, a wide range of temperatures High traction performance can be demonstrated in the area.

Silica is used as the thickener. Since silica is an inorganic substance, deterioration due to heat is small as compared with organic substances such as diurea compounds generally used as thickeners in grease compositions. Therefore, it contributes to the improvement of the heat resistance of the grease composition.
The silica to be used is not particularly limited, and for example, the primary particles having an average particle diameter of about 1.5 μm to 100 μm may be used. As the specific surface area by BET method of the silica, for ^example, it may be 50m ² / g~900m 2 / g. Further, the shape of the primary particles of silica may be any shape such as a spherical shape, a needle shape, a cubic shape, a scale shape, and an indefinite shape.

The content ratio of the thickener (silica) is 5% by mass to 20% by mass, and preferably 6% by mass to 7% by mass.
When the content ratio of silica is less than 5% by mass, the grease composition has a high consistency (60 W) (softened), excessively high fluidity, and the grease cannot be maintained. On the other hand, when the content ratio of silica exceeds 20% by mass, the consistency (60W) becomes small (cured), and an appropriate oil film formation and fluid state cannot be maintained in the traction drive mechanism.

In addition to the base oil and the thickener, the grease composition includes, as an optional component, for example, an extreme pressure agent, an oily agent, a rust preventive agent, a friction modifier, an oxidation agent at a ratio of about 1% by mass to 5% by mass. Various additives such as an inhibitor, an antiwear agent, a dye, a hue stabilizer, a structural stabilizer, a metal deactivator, and a viscosity index improver may be contained.
The above grease composition is, for example, a synthetic hydrocarbon oil (base oil) and a silica thickener as essential components, and further mixed with other additives as necessary, and then passed through a roll mill or the like. Can be obtained by:

Thus the grease composition thus obtained has a kinematic viscosity of the base oil of a synthetic hydrocarbon oil is ^{25000mm 2 / s~32000mm 2 / s (} 40 ℃), thickener consisting of silica 5 wt% Since it is contained in an amount of ˜20% by mass, high heat resistance, high traction coefficient and long life can be realized. For example, a traction coefficient of 0.060 or more and an oil separation degree of 0.10 to 0.30 can be achieved. Therefore, by using the above grease composition, a traction drive device such as the planetary roller type power transmission device of FIGS. 1 and 2 can be driven well even under a high temperature environment exceeding, for example, 100 ° C. . Particularly preferably, it can be used favorably in a temperature environment of 120 ° C. or less. Moreover, since the oil separation degree of 0.10 to 0.30 can be achieved, an oil film can be formed over a long period of time while suppressing excessive oil loss (long life), and high heat resistance is ensured. You can also

As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented with another form.
The traction drive device of the present invention in which the traction grease composition is used is not limited to the configuration of the planetary roller type power transmission device of FIGS. 1 and 2, for example, a traction drive device for driving an automobile power steering, It can be used for a traction drive device for driving a supercharger that supercharges an engine of an automobile or the like, a traction drive device for driving an auxiliary machine such as an air conditioner compressor or an alternator in an engine room of an automobile or the like.

  In addition, various design changes can be made within the scope of matters described in the claims.

Next, although this invention is demonstrated based on an Example and a comparative example, this invention is not limited by the following Example.
<Examples 1-3 and Comparative Examples 1-13>
Test grease compositions were prepared by blending base oil, thickener and additives in the formulations shown in Table 1 for each Example and each Comparative Example. The oil separation degree and traction coefficient of the obtained grease composition for test were measured. The evaluation results are shown in Table 1 and FIGS.

  In Table 1, the kinematic viscosity of the base oil is a value measured according to JIS K 2283. The oil separation degree is a value measured according to JIS K 2220, and the traction coefficient is a value measured using an EHL tester (“EHD2” manufactured by PCS Instruments).

  From Table 1 and FIGS. 3 and 4, it was found that the grease compositions of Examples 1 to 3 showed an appropriate degree of oil separation and could realize high heat resistance and long life. Further, from Table 1 and FIGS. 5 and 6, it was found that all of the grease compositions of Examples 1 to 3 satisfied a traction coefficient of 0.060 or more.

  2 ... fixed wheel, 3 ... sun shaft, 4 ... planetary roller, 5 ... carrier, G ... grease

Claims (3)

A base oil made of synthetic hydrocarbon oil;
A thickener made of silica,
Kinematic viscosity of the base oil is ^{25000mm 2 / s~32000mm 2 / s (} 40 ℃),
A traction grease composition containing 5 to 20% by mass of the thickener. A traction drive mechanism including a first rotating part and a second rotating part arranged in pressure contact with the first rotating part;
A traction drive device comprising the traction grease composition according to claim 1 enclosed in the traction drive mechanism. The traction drive mechanism is
A fixed ring,
A sun axis as the first rotating part disposed concentrically inside the fixed ring;
A plurality of planetary rollers as the second rotating part provided in a pressure contact state between the sun shaft and the fixed wheel;
The traction drive device according to claim 2, further comprising a carrier that rotatably supports each planetary roller.

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