JP2011042747A - Grease composition for speed reducer and speed reducer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grease composition for a speed reducer, which reduces damages of metal contact part at a high temperature and makes the part have a long life and a speed reducer having a long life at a high temperature. <P>SOLUTION: The grease composition for a speed reducer comprises (a) a base oil, (b) a thickener, (c) molybdenum dithiophosphate and (d) at least one of calcium salt selected from the group consisting of a calcium salt of a petroleum sulfonic acid, a calcium salt of an alkyl aromatic sulfonic acid, a calcium salt of an oxidized wax, a perbasic calcium salt of a petroleum sulfonic acid, a perbasic calcium salt of an alkyl aromatic sulfonic acid and a perbasic calcium salt of an oxidized wax. The speed reducer uses the same. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention particularly relates to a grease composition suitably used for a reduction gear having a large reduction ratio and a low backlash (1 arc.min. Or less) used for driving a robot, an industrial machine, and the like, and a reduction speed in which the grease composition is enclosed. Related to the machine.

The inside of the decelerator is composed of a plurality of sliding portions and rolling portions. When torque is applied to the input side, the torque is transmitted to the output side by decelerating or increasing the speed. It is preferable that the output side torque is constant for a long time and does not change. The output side torque is greatly changed due to a change in the shape of the internal parts.
Lubricating oils and greases in which calcium salt is blended with molybdenum dithiocarbamate, which has a high friction reduction effect, have been proposed as lubricant compositions for reduction gears (for example, Patent Document 1). However, lubricants containing molybdenum dithiocarbamate and calcium salts are not sufficient to reduce damage to metal contact areas in high temperature environments, and there is a problem that the lifespan of reduction gears used in high temperature environments is shortened. Therefore, it is necessary to change the lubricant in a short cycle.

JP2004-339411

Accordingly, an object of the present invention is to provide a grease composition for a speed reducer that reduces damage to a metal contact portion at a high temperature and has a long life.
Another object of the present invention is to provide a reduction gear having a long life at high temperatures.

In order to achieve the above object, the present invention provides the following grease composition for a reduction gear and a reduction gear using the same.
1. A reduction gear grease composition comprising the following components (a) to (d):
(A) base oil,
(B) a thickener;
(C) molybdenum dithiophosphate, and (d) calcium salt of petroleum sulfonic acid, calcium salt of alkyl aromatic sulfonic acid, calcium salt of oxidized wax, overbased calcium salt of petroleum sulfonic acid, excess of alkyl aromatic sulfonic acid. At least one calcium salt selected from the group consisting of basic calcium salts and overbased calcium salts of oxidized waxes.
2. ^{2. The} grease composition for a reducer according to the above 1, wherein the kinematic viscosity at 40 ° C. of the component (a) base oil is 20 to 300 mm ² / s.
3. 3. The grease composition for a reducer according to 1 or 2 above, wherein the thickener of component (b) is a urea thickener.
4). Any one of said 1-3 whose content of (c) molybdenum dithiophosphate is 0.1-10 mass% and (d) calcium salt content is 0.1-20 mass% in all the compositions. The grease composition for a reduction gear as described.
5). A speed reducer in which the grease composition according to any one of the above 1 to 4 is enclosed.

  The grease composition for a speed reducer of the present invention has a higher wear reduction effect than a conventional grease composition for a speed reducer, and can improve the life of the speed reducer at high temperatures. Therefore, the speed reducer of the present invention in which this is enclosed has a long life at high temperatures.

As the base oil (a) used in the present invention, any lubricant that is usually used as a base oil of a grease composition such as mineral oil, synthetic hydrocarbon oil, ester oil, phenyl ether, polyglycol can be used. Preferably, mineral oil and synthetic hydrocarbon oil are used.
The kinematic viscosity at 40 ° C. of the (a) base oil used in the present invention is preferably 20 to 300 mm ² / s, more preferably 30 to 220 mm ² / s. If it is less than 20 mm ² / s, the lifetime tends to be insufficient, and if it exceeds 300 mm ² / s, there is a tendency for problems to occur at low temperatures.

  Examples of the thickener (b) used in the present invention include all thickeners. For example, soap thickeners represented by Li soap and composite Li soap, urea thickeners represented by diurea, inorganic thickeners represented by organic clay and silica, and organic materials represented by PTFE. Examples of such a thickener include urea-based thickeners. The amount of the thickener in the grease composition of the present invention is preferably 0.5 to 20% by mass, more preferably 1 to 10% by mass. If the amount is less than 0.5% by mass, the thickening effect is lost, and if it exceeds 20% by mass, the grease composition becomes too hard, and there is a tendency that it becomes difficult to obtain a sufficient effect because it does not flow into the lubrication part.

Preferable examples of (c) molybdenum dithiophosphate (= MoDTP) used in the present invention include those represented by the following formula (1).
[(R ¹ O) (R ² O) PS-S] ₂ Mo ₂ O _{m Sn}
Wherein R ¹ and R ² are each independently an alkyl group having 1 to 24 carbon atoms or an aryl group having 6 to 30 carbon atoms, m is 0 to 3, n is 4 to 1, and m + n = 4)
Content in the grease composition of the component (c) MoDTP used for this invention becomes like this. Preferably it is 0.1-10 mass%, More preferably, it is 0.1-5.0 mass%. If it is less than 0.1% by mass, the life tends to be insufficient, and if it exceeds 10% by mass, no further improvement in the effect is observed.

(D) Calcium salts used in the present invention include all calcium sulfonates (Ca sulfonates) used as lubricants and rust inhibitors for lubricating oils such as engine oils, and calcium salts of oxidized waxes. An overbased calcium salt of oxidized wax can be used. For example, calcium salt of petroleum sulfonic acid obtained by sulfonation of aromatic hydrocarbon component in lubricating oil fraction, calcium salt of alkyl aromatic sulfonic acid such as dinonylnaphthalene sulfonic acid and alkylbenzene sulfonic acid, oxidized wax Examples include calcium salts, overbased calcium salts of petroleum sulfonic acids, overbased calcium salts of alkyl aromatic sulfonic acids, and overbased calcium salts of oxidized waxes. Particularly preferred are alkyl aromatic sulfonic acids. A calcium salt is mentioned.
The amount of component (d) calcium salt in the grease composition used in the present invention is preferably 0.1 to 20% by mass, more preferably 0.5 to 10% by mass. If it is less than 0.1% by mass, the lifetime tends to be insufficient, and if it exceeds 20% by mass, no further improvement in the effect is observed.

  Various additives can be added to the grease composition of the present invention as necessary. Examples of such additives include rust preventives other than the calcium salt of component (d), detergents and dispersants other than the calcium salt of component (d), antioxidants, metal corrosion inhibitors, oily agents, and wear resistance. Agents, extreme pressure agents, solid lubricants and the like.

Hereinafter, the present invention will be described more specifically with reference to examples.
Examples 1-6, Comparative Examples 1-4
The components shown in Table 1 were mixed at the ratio shown in Table 1 to prepare grease compositions of Examples 1 to 6 and Comparative Examples 1 to 4. In addition, a commercially available grease composition for reduction gears was used as Comparative Example 5.
These grease compositions were subjected to an SRV test under the following conditions to measure the ball wear scar diameter.
Moreover, the grease composition was enclosed in an eccentric rocking planetary gear type reduction gear (manufactured by Nabtesco Corporation, RV-70F), a life test was performed under the following conditions, and the output side torque was measured. The results are shown in Table 1.
<Test method>
SRV test <br/> Test piece Ball diameter: 17.5mm
Plate material: SUJ2
Plate roughness: Rz = 0.8 μm
Condition Load: 100N
Amplitude: 1.0 mm
Frequency: 50Hz
Test temperature: 80 ° C
Endurance test Conditions Reducer model: RV-70F
Rotation speed: 10rpm
Temperature: 80 ° C
Life time ratio: Relative time ratio when the time until the fluctuation of the output side torque exceeds the allowable value when using a commercially available product (Comparative Example 5) is 1.

Base oil: Mineral oil (mixed and adjusted to a kinematic viscosity of 80 mm ² / s at 40 ° C.)
Urea thickener: (a) In 4000 g of mineral oil (mixed and adjusted to a kinematic viscosity of 80 mm ² / s at 40 ° C.), 250 g (1 mol) of diphenylmethane-4, 4′-diisocyanate, 258 g of octylamine ( 2 mol) is a diurea compound obtained by reaction.
Li soap thickener: 140 g of 50% aqueous lithium hydroxide is added to 2500 g of mineral oil (mixed and adjusted to a kinematic viscosity of 80 mm ² / s at 40 ° C.) and 500 g of 12-hydroxystearic acid, and then reacted. Li soap compound obtained by heating to 210 ° C and then cooling to 100 ° C or lower.
MoDTP: Asahi Denka Kogyo Co., Ltd., trade name: Sakura Rube 300
Ca sulfonate: Calcium salt of alkyl aromatic sulfonic acid (manufactured by KING INDUSTRIES, trade name: NA-SUL729)
Overbased Ca sulfonate: Overbased calcium salt of alkyl aromatic sulfonic acid (manufactured by CHEMTURA CORPOR, trade name: BRYTON C-400C KY)
ZnDTP: zinc dithiophosphate, manufactured by Nippon Lubrizol, trade name: LUBRIZOL1375
MoDTC: Molybdenum dithiocarbamate, manufactured by Asahi Denka Kogyo, trade name Sakura Rube 515

  As shown in Tables 1 and 2, the grease compositions of Examples 1 to 6 according to the present invention include Component (c) Comparative Example 1 not including MoDTP, Component (d) Comparative Example 2 including no calcium salt, Component ( d) Compared with Comparative Example 3 using ZnDTP instead of calcium salt, Comparative Example 4 using MoDTC corresponding to Patent Document 1, and Comparative Example 5 using a commercial product to which an SP extreme pressure agent or the like was added Thus, it can be seen that the wear scar diameter of the SRV test is small, and the lifetime of the reduction gear is long.

Claims (5)

A reduction gear grease composition comprising the following components (a) to (d):
(A) base oil,
(B) a thickener;
(C) molybdenum dithiophosphate, and (d) calcium salt of petroleum sulfonic acid, calcium salt of alkyl aromatic sulfonic acid, calcium salt of oxidized wax, overbased calcium salt of petroleum sulfonic acid, excess of alkyl aromatic sulfonic acid. At least one calcium salt selected from the group consisting of basic calcium salts and overbased calcium salts of oxidized waxes. The grease composition for a speed reducer according to claim 1, wherein the kinematic viscosity at 40 ° C of the component (a) base oil is 20 to 300 mm ² / s.   The grease composition for a speed reducer according to claim 1 or 2, wherein the thickener of component (b) is a urea thickener.   The content of (c) molybdenum dithiophosphate is 0.1 to 10% by mass in the total composition, and (d) the content of calcium salt is 0.1 to 20% by mass. The grease composition for a reduction gear according to the item.   A speed reducer in which the grease composition according to any one of claims 1 to 4 is enclosed.