JP2009203374A - Grease composition for bevel gear and bevel gear comprising the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grease composition suitable for a bevel gear that improves the steering feeling of the bevel gear by efficiently lubricating the bevel gear to prevent the steering feeling from being worsened. <P>SOLUTION: The grease composition for a bevel gear comprises the following components (a)-(g): (a) a soap-based thickening agent, (b) a base oil, (c) a molybdenum dithiocarbamate, (d) a calcium sulphonate, (e) a calcium phenate, (f) a thiophosphate, and (g) a metal-free sulfur-phosphorus extreme pressure agent other than the thiophosphate. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a grease composition for a bevel gear suitable for a bevel gear provided between a steering wheel and a steering gear in a steering mechanism for a cab-over vehicle, and a bevel gear including the same. In particular, the present invention relates to a grease composition for a bevel gear that can efficiently lubricate the bevel gear, reduce friction, suppress torque fluctuation, and prevent deterioration of steering feeling.

  Conventionally, in order to improve the steering feeling of the bevel gear, a preload is applied to the bevel gear to reduce backlash, and the steering wheel has a flutter and the bevel gear has no backlash.

  However, when the preload of the bevel gear is increased, the meshing force of the bevel gear is increased, the torque fluctuation is increased, and the steering feeling is deteriorated. Further, when the preload of the bevel gear is increased, wear is promoted over time, backlash is increased, the backlash feels and the steering wheel is increased, and the steering feeling is deteriorated due to the decrease of the preload. Therefore, there was a problem that the number of technical services increased.

  Therefore, in the following Patent Document 1 and the like, various devices have been applied to the structure of the bevel gear device or the steering device so as to maintain good steering feeling. In the bevel gear device, a mechanism for applying pressure to the bevel gear input shaft or output shaft in the axial direction is provided, and the backlash is maintained within a predetermined range to solve the problem.

  Also, in Patent Document 2 and the like described below, the steering device is provided with a biasing means for biasing the shaft in the extending direction of the shaft, and this biasing means functions to pressurize the bevel gear. Keep in range and solve the problem.

  Various greases for automobile steering or gears have been developed to prevent seizure, reduce wear, reduce friction, improve low-temperature properties, etc., in order to adapt the grease to severe lubrication conditions. In the following Patent Document 3, in an automotive steering grease composition, (a) a thickener, (b) a base oil having a pour point of −40 ° C. or lower, (c) an organomolybdenum compound, (d) melamine cyanurate, A grease composition containing (e) polytetrafluoroethylene and (f) molybdenum disulfide solves the problems of seizure, wear, and low-temperature fluidity of the steering gear.

  As a grease composition for gear lubrication, in Patent Document 4 below, (a) thickener, (b) synthetic oil, (c) mineral oil, (d) molybdenum dithiocarbamate (MoDTC), and (e) calcium sulfonate Grease composition containing low friction coefficient, excellent wear resistance, and low temperature properties, especially seizure, wear, and low temperature fluidity problems such as rack and pinion parts and pinion assist type electric power steering gear meshing parts. It has been solved.

  Further, in Patent Document 5 below, a grease composition containing a base oil, a thickener, an organic molybdenum compound, and glycerin is used for a gear of an industrial machine that is excellent in wear resistance and requires accuracy. Even in such a case, the decrease in accuracy of the machine is reduced, the reliability of the machine is improved, and the service life is extended.

  As described above, in the steering mechanism of a cab-over vehicle, as a means for maintaining a good steering feeling, conventionally, the bevel gear device or the structural device of the steering device has been used to maintain the backlash within a predetermined range. With an optimal grease composition, the bevel gear is efficiently lubricated, friction is reduced, torque fluctuation is suppressed or aged wear of the bevel gear is suppressed, backlash is reduced, the steering wheel is flat, and the bevel gear is There is no report that it is possible to suppress the rattling of the steering wheel and prevent deterioration of steering feeling over time.

  On the other hand, there are greases that have good seizure resistance, wear resistance, and low temperature fluidity in steering or gears, etc., but their composition does not show the problem of improving the steering feeling that is a problem with bevel gears.

Japanese Utility Model Publication No. 63-11014 JP 2001-213330 A JP 2001-64665 A JP 2004-269722 A JP-A-5-313184

  The structural idea of the conventional bevel gear device or the steering device leads to an increase in manufacturing cost. In addition, with the conventional steering or the grease having improved seizure resistance, wear resistance, low temperature fluidity, etc. with a gear or the like, the steering feeling of the bevel gear cannot be improved.

  Therefore, an object of the present invention is to improve the steering feeling of the bevel gear by efficiently lubricating the bevel gear with a grease composition suitable for the bevel gear and preventing the deterioration of the steering feeling.

  The present inventors have found that the above problems can be solved by a grease composition having a specific composition, and have reached the present invention.

That is, first, the present invention is an invention of a grease composition for bevel gears, and includes at least the following components (a) to (g).
(A) soap thickener (b) base oil (c) molybdenum dithiocarbamate (MoDTC)
(D) Calcium sulfonate (e) Calcium phenate (f) Thiophosphate (g) Sulfur-phosphorus extreme pressure agent containing no metal other than thiophosphate

  The grease composition for a bevel gear according to the present invention is suitably used for a bevel gear provided between a steering wheel and a steering gear in a steering mechanism for a cab-over vehicle. The grease composition for a bevel gear of the present invention can efficiently lubricate the bevel gear, reduce friction, suppress torque fluctuation, and prevent deterioration of steering feeling. Further, the bevel gear can be efficiently lubricated, the bevel gear can be prevented from wearing over time, the backlash can be reduced, the steering wheel can be prevented from being fluffed and the bevel gear can be loosened, and the steering feeling can be prevented from deteriorating over time.

  The grease composition for bevel gears of the present invention can be used by appropriately changing the amounts of the above components (a) to (g). Specifically, in the whole composition, the content of molybdenum dithiocarbamate is 0.1 to 10% by mass, the content of calcium sulfonate is 0.5 to 15% by mass, and the content of calcium phenate is 0.1. ~ 15 mass%, content of thiophosphate is 0.1 to 10 mass%, and content of sulfur-phosphorus extreme pressure agent not containing metal other than thiophosphate is preferably 0.1 to 10 mass% Illustrated.

  Preferred examples of the soap thickener (a) used in the bevel gear grease composition of the present invention include lithium stearate and / or lithium 12 hydroxystearate.

  Second, the present invention is a bevel gear lubricated with the above-described grease composition for bevel gear. Specifically, a bevel gear provided between a steering wheel and a steering gear is preferably exemplified in a steering mechanism of a cab-over vehicle.

  The grease composition of the present invention is a grease composition suitable for a bevel gear provided between a steering wheel and a steering gear in a cabover vehicle steering mechanism. In particular, the bevel gear can be efficiently lubricated, friction can be reduced, torque fluctuation can be suppressed, and deterioration of steering feeling can be prevented. Further, the bevel gear can be efficiently lubricated, the bevel gear can be prevented from wearing over time, the backlash can be reduced, the steering wheel can be prevented from being fluffed and the bevel gear can be loosened, and the steering feeling can be prevented from deteriorating over time.

  Accordingly, the bevel gear is efficiently lubricated, the friction is reduced, the torque fluctuation is suppressed, and the deterioration of the steering feeling is prevented by the grease composition without increasing the manufacturing cost.

  Hereinafter, the essential components (a) to (g) contained in the grease composition for bevel gears of the present invention will be described.

(A) Component: Thickener The soap-based thickener of component (a) used in the present invention is lithium soap, metal soap typified by calcium soap, calcium complex soap, lithium complex soap, aluminum: complex soap. Examples include complex soaps.

  Of these, lithium soap is preferred. Lithium soap, when used with a bevel gear over time, shows that the grease undergoes shearing and the grease tends to soften moderately. Therefore, oil (grease) can be stably supplied to the lubrication part over a long period of time, and wear due to aging of the gear can be prevented. On the other hand, urea grease, etc. has good shear stability, so it is difficult to soften due to shear and the inflow property of grease is poor, so it is difficult for grease removed from the lubrication part due to centrifugal force or vibration to return to the lubrication part again . Accordingly, the wear resistance over time is inferior to that of lithium soap grease.

(B) Component: Base oil The base oil of component (b) used in the present invention is a lubricating oil that is usually used as a base oil for grease, such as mineral oil, ester oil, synthetic hydrocarbon oil, phenyl ether, polyglycol, and the like. , And a mixture of two or more of these, but are not limited thereto, and a wide variety of known base oils for grease compositions can be used.

(C) Component: Molybdenum dithiocarbamate (MoDTC)
Preferred examples of the component (c) molybdenum dithiocarbamate used in the present invention include those represented by the following general formula (1).
^{_{(R 1 R 2 N-CS}} -S) 2 -Mo 2 O m S n ···· (1)
(Wherein R ¹ and R ² independently represent an alkyl group having 1 to 24 carbon atoms, preferably 3 to 18 carbon atoms, m is 0 to 3, n is 4 to 1, and m + n = 4)

(D) Component: Calcium sulfonate The calcium sulfonate of the (d) component used for this invention is known as a metal-type detergent dispersing agent and rust preventive agent used for lubricating oils, such as an engine oil. For example, calcium of petroleum sulfonic acid obtained by sulfonation of aromatic hydrocarbon component in lubricating oil fraction, synthetic sulfonic acid calcium such as alkyl aromatic sulfonic acid such as dinonylnaphthalene sulfonic acid and alkylbenzene sulfonic acid At least one selected from the group consisting of a salt, a calcium salt of oxidized wax, an overbased calcium salt of petroleum sulfonic acid, an overbased calcium salt of alkyl aromatic sulfonic acid, and an overbased calcium salt of oxidized wax .

  Particularly preferred calcium sulfonates are dinonyl naphthalene sulfonic acid calcium salt and alkyl aromatic sulfonic acid calcium salt.

(E) Component: Calcium Phenate The component (e) calcium phenate used in the present invention is a calcium salt of sulfurized alkylphenol, and is commercially available as a detergent dispersant.

(F) Component: Thiophosphate Preferable examples of the thiophosphate of component (f) used in the present invention include those represented by the following general formula (2).
(R ³ O) (R ⁴ O) P (= S) (OR ⁵ ) (2)
(In the formula, R ³ is an alkyl group having 1 to 24 carbon atoms, a cycloalkyl group having 5 to 6 carbon atoms, an alkylcycloalkyl group having 6 to 30 carbon atoms, an aryl group having 1 to 3 rings, or a carbon atom. An alkylaryl group having 6 to 30 carbon atoms, or an arylalkyl group having 6 to 30 carbon atoms, wherein R ⁴ and R ⁵ are a hydrogen atom or an alkyl group having 1 to 24 carbon atoms and a cyclohexane having 5 to 6 carbon atoms; An alkyl group, an alkylcycloalkyl group having 6 to 30 carbon atoms, an aryl group having 1 to 3 rings, an alkylaryl group having 6 to 30 carbon atoms, and an arylalkyl group having 6 to 30 carbon atoms).

Particularly preferred thiophosphates are trialkylthiophosphates and tri (alkylphenyl) thiophosphates in which R ³ , R ⁴ and R ⁵ are alkyl groups having 12 or 13 carbon atoms.

(G) Component: Sulfur-phosphorus extreme pressure agent containing no metal other than thiophosphate The sulfur-phosphorus extreme pressure agent containing no metal other than thiophosphate as the component (g) used in the present invention is zinc, molybdenum. And those containing no metal such as antimony.

  In particular, those having a sulfur content of 10 to 40% and a phosphorus content of 0.5 to 5% are preferred. By adjusting the contents of sulfur and phosphorus within this range, excellent wear prevention performance and seizure prevention performance can be effectively exhibited. If the sulfur component exceeds the above range, the gear tends to corrode, and if the phosphorus component exceeds the above range, the gear wear prevention effect tends to be insufficient. Moreover, when both are less than the said range, abrasion prevention performance and seizure prevention performance may not fully be exhibited.

  Examples of sulfur-phosphorus extreme pressure agents other than thiophosphate include sulfurized fats and oils containing only sulfur, polysulfide and the like, and phosphates and phosphites containing only phosphorus.

  Various additives can be added to the grease composition of the present invention as necessary. Examples of such additives include antioxidants, rust inhibitors, metal corrosion inhibitors, oiliness agents, antiwear agents, extreme pressure agents, solid lubricants, and the like.

  Next, the present invention will be described with reference to examples and comparative examples.

[Examples 1-5, Comparative Examples 1-6]
Add 500 g of 12-hydroxystearic acid to 2500 g of mineral oil (trade name: Super Oil K40 (manufactured by Nippon Oil Corporation)), heat to 80 ° C., add 140 g of 50% aqueous lithium hydroxide and stir for 30 minutes. The reaction was followed by heating to 210 ° C.

  After heating, the mixture was cooled to 160 ° C., 1930 g of the above mineral oil was further added, and the mixture was cooled to 100 ° C. or lower with stirring. This was designated as “base grease A”.

  Various additives were added to the base grease A in the formulations shown in Tables 1 and 2 below, mineral oil was added as appropriate, and the blending degree was set to No. 3 using a three-stage roll mill. Adjusted to 1 grade (310-340).

[Example 6, Comparative Examples 7 and 8]
To 2500 g of a synthetic hydrocarbon oil (trade name: Spectran 6 (manufactured by ExxonMobil Chemical Co., Ltd.)), 500 g of lithium 12-hydroxystearate was added and stirred, and then heated to 210 ° C. After heating, the mixture was cooled to 160 ° C., 1000 g of the above synthetic hydrocarbon oil was added, and the mixture was cooled to 100 ° C. or lower with stirring. This was designated as “base grease B”.

  To this base grease B, additives shown in the following Tables 1 and 2 were added, and a synthetic hydrocarbon oil was added as appropriate. Adjusted to 2 grades (265-295).

[Comparative Example 9]
To a reaction vessel, 323 g of diphenylmethane 4,4′-diisocyanate was added to 1200 g of mineral oil (trade name: Super Oil K40 (manufactured by Shin Nippon Oil Co., Ltd.)) and heated to 70 to 80 ° C. with stirring. In a separate container, add 277 g of paratoluidine to 1200 g of mineral oil (trade name: Super Oil K40 (manufactured by Nippon Oil Co., Ltd.)), heat to 70-80 ° C. while stirring, add to the reaction container, and stir and react well. This was designated as “base grease C”.

  Various additives were added to this base grease C in the proportions shown in Table 2 below, mineral oil was added as appropriate, and the blending consistency was set to No. 3 using a three-stage roll mill. Adjusted to 1 grade (310-340).

  In Tables 1 and 2, molybdenum dithiocarbamate A is trade name: Polyvan A (manufactured by RT Vanderbilt), and molybdenum dithiocarbamate B is trade name: Polyvan 822 (manufactured by RT Vanderbilt). And the calcium sulfonate is a neutral alkyl aromatic calcium sulfonate, the phosphorothionate is tri (alkylphenyl) thiophosphate, the SP extreme pressure agent has a sulfur content of 31.5%, The phosphorus content is 1.7%, molybdenum disulfide is trade name: Polysulfide (manufactured by CLYMAX MOLYBDENUM COMPANY), melamine cyanurate is trade name: MCA (manufactured by Ciba Japan Co., Ltd.), poly Tetrafluoroethylene is trade name: Lub L-5F (manufactured by Daikin Industries, Ltd.), mineral oil is Super Oil K40 (manufactured by Nippon Oil Corporation), and synthetic hydrocarbon oil is trade name: Spectran 6 (Exxon Mobil Chemical Co., Ltd.) Company-made). The number in the grease composition is the content (mass%) in the grease.

[Grease composition evaluation test method]
The evaluation test method of the grease composition is as follows.
・ Mixture penetration: JIS K2220 7
・ High-speed 4-ball wear resistance: ASTM D 2266
・ Evaluation of actual vehicle steering feeling: Apply sample grease to the steering bevel gear of a commercially available cab-over vehicle, and run a specified distance. The steering feeling after traveling a specified distance is determined according to the following criteria. As for the judgment criteria, a case where none of the following applies to the initial stage was determined to be acceptable (O), and a case where even one of the conditions was satisfied was determined to be unacceptable (x). Here, “Aging 1” indicates that the actual vehicle steering feeling is confirmed after traveling 1000 to 3000 km, and “Aging 2” indicates that the actual vehicle steering feeling is verified after traveling 10,000 to 20000 km. .
i) There is a feeling of rattling ii) Steering is heavy. Roll stability: A test is conducted at 100 ° C. for 24 hours according to ASTM D 1831, and a blending consistency at 25 ° C. (JIS K22207) is measured.

  From the results of Table 1, it can be seen that the grease composition having each component of the present invention is excellent in actual vehicle steering feeling after traveling 1000 to 3000 km and in actual vehicle steering feeling after traveling 10,000 to 20000 km. Further, from the results of Table 2, the grease composition lacking each component of the present invention has a problem in the actual vehicle steering feeling after traveling 1000 to 3000 km or the actual vehicle steering feeling after traveling 10,000 to 20000 km. I understand.

  In the grease composition of the present invention, the calcium phenate content is 0.1 to 15% by mass, preferably 1 to 10% by mass, and the molybdenum dithiocarbamate content is based on the total mass of the grease composition. 0.1 to 10% by mass, preferably 0.5 to 5% by mass, calcium sulfonate content is 0.5 to 15% by mass, preferably 1 to 10% by mass, thiophosphate content is preferable Is 0.1 to 10% by mass, preferably 0.2 to 5% by mass, and the content of the sulfur-phosphorus extreme pressure agent containing no metal other than thiophosphate is 0.1 to 10% by mass, preferably 0 2 to 5% by mass.

  The calcium phenate content is less than 0.1% by mass, the molybdenum dithiocarbamate content is less than 0.1% by mass, the calcium sulfonate content is less than 0.5% by mass, and the thiophosphate content is 0. When the content of the sulfur-phosphorus extreme pressure agent containing less than 0.1% by mass and containing no metal other than thiophosphate is less than 0.1% by mass, it is difficult to obtain the desired effect sufficiently.

  On the other hand, the content of calcium phenate exceeds 15% by mass, the content of molybdenum dithiocarbamate exceeds 10% by mass, the content of calcium sulfonate exceeds 15% by mass, and the content of thiophosphate is 10% by mass. Even if the content of the sulfur-phosphorus extreme pressure agent exceeding 10% and containing no metal other than thiophosphate exceeds 10% by mass, no increase in effect is observed.

  The grease composition of the present invention is used for a bevel gear provided between a steering wheel and a steering gear in a steering mechanism of a cab-over vehicle. The grease composition efficiently lubricates the bevel gear and reduces friction. Torque fluctuation is suppressed to prevent deterioration of steering feeling. Further, since the steering mechanism is not changed, the manufacturing cost is not increased.

Claims (5)

A grease composition for bevel gears comprising at least the following components (a) to (g).
(A) soap-based thickener (b) base oil (c) molybdenum dithiocarbamate (d) calcium sulfonate (e) calcium phenate (f) thiophosphate (g) sulfur containing no metal other than thiophosphate Phosphorus extreme pressure agent   In the total composition, the content of molybdenum dithiocarbamate is 0.1 to 10% by mass, the content of calcium sulfonate is 0.5 to 15% by mass, the content of calcium phenate is 0.1 to 15% by mass, The content of the thiophosphate is 0.1 to 10% by mass, and the content of the sulfur-phosphorus extreme pressure agent not containing a metal other than thiophosphate is 0.1 to 10% by mass. The grease composition for bevel gears as described.   The grease composition for bevel gears according to claim 1 or 2, wherein the component (a) is lithium stearate and / or lithium 12 hydroxystearate.   The bevel gear lubricated with the grease composition for bevel gears of any one of Claims 1-3.   The bevel gear according to claim 4, wherein the bevel gear is a bevel gear provided between a steering wheel and a steering gear in a steering mechanism for a cab-over vehicle.