JP2011236354A - Grease composition for ball-type constant velocity joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grease composition for a constant velocity joint improving abrasion resistance and flaking resistance by the combination of additives in a grease for a ball-type constant velocity joint.SOLUTION: The grease composition for the constant velocity joint includes the following ingredients (a) to (h): (a) a base oil; (b) a diurea-based thickening agent; (c) a zinc dialkyldithiophosphate; (d) a molybdenum dialkyldithiocarbamate; (e) melamine cyanurate; (f) calcium carbonate; (g) a zinc dialkyldithiocarbamate; and (h) a sulfur-nitrogen-based extreme-pressure additive.

Description

  The present invention relates to a grease composition that is excellent in wear resistance and anti-flaking property at a lubrication point of a ball type constant velocity joint of an automobile.

Today, in the automobile industry, miniaturization and weight reduction are progressing from the viewpoint of increasing engine output and securing a living space, and production of FF vehicles is increasing. Also, production of 4WD vehicles is increasing from the viewpoint of its functionality. In these FF vehicles and 4WD vehicles, since power is transmitted and steered by the front wheels, for example, smooth power transmission is required even when the steering wheel is fully turned. For this reason, in the FF vehicle and the 4WD vehicle, a constant velocity joint is indispensable as a component that transmits a rotational motion at a constant speed even when the crossing angle varies between two intersecting axes.
Among these, the ball-type constant velocity joint has a structure in which the ball transmits torque as a rolling element. For this reason, stress is repeatedly applied to the ball and the metal surface in contact with the ball by a complicated rolling and sliding motion under high surface pressure during rotation. Thus, since it becomes a severer lubrication condition, abrasion becomes large and causes the problem of a durability fall and the deterioration of a vibration, and the further improvement in abrasion resistance is calculated | required.

As a grease composition for a constant velocity joint for solving the above-mentioned problems, for example, for the purpose of suppressing wear and preventing flaking, overbased sodium sulfonate, molybdenum dialkyldithiocarbamate, and sulfur phosphorus-based extreme pressure A grease by a combination of agents is known (for example, see Patent Document 1). However, the grease is not sufficient in terms of wear resistance.
In addition, a grease containing melamine cyanurate and molybdenum dithiocarbamate is known in order to effectively reduce wear and friction and effectively prevent flaking (see, for example, Patent Document 2). However, even in the above-mentioned grease, it cannot be said that it is sufficient in terms of wear resistance especially under severe lubrication conditions such as a ball type constant velocity joint.

In addition, it contains sulfur-based extreme pressure additives that do not contain alicyclic or aromatic diurea, melamine cyanurate, molybdenum disulfide and phosphorus for the purpose of optimizing wear of ball-type constant velocity joints and preventing flaking. The grease which performs is known (for example, refer patent document 3). However, the above-mentioned grease is not sufficient in terms of wear resistance and anti-flaking properties even under high load conditions.
In addition, a grease containing zinc dialkyldithiophosphate, molybdenum dialkyldithiocarbamate, zinc dialkyldithiocarbamate, and a sulfur-nitrogen extreme pressure additive is known for the purpose of improving flaking of constant velocity joints (for example, (See Patent Document 4). However, even with the above grease, it cannot be said that the anti-flaking property is sufficient, especially under the condition of a high angle where the complicated rolling and sliding motion of the ball is wide.

Japanese Patent No. 3898912 JP 2006-335876 A Japanese Patent No. 3988895 JP2008-297402

  Accordingly, an object of the present invention is to provide a grease composition for a ball-type constant velocity joint that has improved wear resistance under high surface pressure conditions and improved anti-flaking property.

The inventor has conducted various studies to develop a grease composition that improves wear resistance under high surface pressure conditions such as a ball-type constant velocity joint and prevents joint flaking. The above-described grease performance evaluation for use in lubrication conditions involving complicated rolling and sliding reciprocating motion under high surface pressure conditions was performed using an SRV tester known as a friction and wear tester.
As a result, it has been found that there is a special relationship between the wear resistance and flaking resistance of the constant velocity joint in the durability test and the wear resistance under specific conditions in the SRV test. Furthermore, the present inventor examined the above relationship by using urea grease as a base grease and various combinations of various extreme pressure agents and the like.
As a result, the inventor contains a diurea thickener, base oil, zinc dialkyldithiophosphate, molybdenum dialkyldithiocarbamate, melamine cyanurate, calcium carbonate, zinc dialkyldithiocarbamate, and a sulfur-nitrogen extreme pressure additive. It has been found that the grease composition is very excellent in wear resistance under high surface pressure conditions. Furthermore, it has been found that wear resistance and flaking resistance can be improved even in an endurance test using an actual ball type constant velocity joint.

The present invention has been made based on the above findings, and provides the following grease composition for a ball type constant velocity joint and a ball type constant velocity joint in which the grease composition is enclosed.
1. A grease composition for ball-type constant velocity joints comprising the following components (a) to (h):
(A) base oil,
(B) a diurea thickener;
(C) zinc dialkyldithiophosphate,
(D) molybdenum dialkyldithiocarbamate,
(E) Melamine cyanurate,
(F) calcium carbonate,
(G) zinc dialkyldithiocarbamate, and (h) sulfur-nitrogen extreme pressure additive.

  The grease composition for a ball type constant velocity joint of the present invention can improve wear resistance and flaking resistance as compared with a conventional grease composition for a ball type constant velocity joint.

1 shows a fixed-type Zepper type constant velocity joint suitable for enclosing the grease composition of the present invention, wherein (A) is a longitudinal sectional view, (B) is a transverse sectional view thereof, and (C) is a sectional view thereof. It is a partially cutaway sectional view.

As the base oil of component (a) used in the present invention, mineral oils represented by naphthenes and paraffins, ether synthetic oils, ester synthetic oils, hydrocarbon synthetic oils, silicone oils, and fluorinated oils are used. Ordinarily used lubricating oil such as or a mixed oil thereof.
Particularly preferred base oils are those having a kinematic viscosity of 5 mm ² / s or more at 100 ° C., more preferably a mineral oil, a hydrocarbon-based synthetic oil having a kinematic viscosity of 5 to 20 mm ² / s at 100 ° C., Etc.

As the diurea thickener of component (b) used in the present invention, those represented by the following general formula (1), particularly (2) are preferable.
^{R 1 NH-CO-NHR 3} -NH-CO-NHR 2 (1)
^{R 1 NH-CO-NH-} C 6 H 4 -p-CH 2 -C 6 H 4 -p-NH-CO-NHR 2 (2)
Wherein R ¹ and R ² are alkyl groups having 8 to 20 carbon atoms, preferably 8 to 18 carbon atoms, aryl groups having 6 to 12 carbon atoms, preferably 6 to 7 carbon atoms, or 6 to 12 carbon atoms, preferably 6 carbon atoms. A cycloalkyl group having ˜7, and R ³ is a divalent hydrocarbon group having 6 to 15 carbon atoms, such as a diphenylmethane-4,4′-diyl group, a tolylene group or a bitolylene group.)
The diurea thickener of component (b) can be obtained, for example, by reacting a predetermined diisocyanate with a predetermined monoamine.
Preferable specific examples of the diisocyanate are diphenylmethane-4,4′-diisocyanate and tolylene diisocyanate, and particularly preferred is diphenylmethane-4,4′-diisocyanate.
Examples of monoamines include aliphatic amines, aromatic amines, alicyclic amines, and mixtures thereof.

Specific examples of the aliphatic amine include octylamine, dodecylamine, hexadecylamine, octadecylamine and oleylamine.
Specific examples of the aromatic amine include aniline and p-toluidine.
Specific examples of alicyclic amines include cyclohexylamine.
Of the above-mentioned monoamines, the aliphatic diurea thickener of component (b) obtained by using octylamine, dodecylamine, octadecylamine, or a mixture thereof is particularly preferable.
The content of the diurea thickener as the component (b) in the grease composition of the present invention may be an appropriate amount to obtain the required consistency, and is usually based on the total mass of the grease composition. The content is preferably 1 to 25% by mass, and more preferably 3 to 20% by mass. If the content of the diurea thickener is 1% or less, the thickening effect cannot be obtained, so that it is difficult to form a grease. If the content exceeds 25% by mass, the obtained grease composition becomes too hard and the expected effect is obtained. It becomes difficult to obtain.
The consistency of the grease composition for a ball type constant velocity joint of the present invention is preferably 265 to 385, more preferably 285 to 340, as measured by JIS K2220 5.3, for example. Such consistency adjustment can be easily performed by adjusting the amount of the component (b).

The component (c) zinc dialkyldithiophosphate used in the present invention is preferably represented by the following general formula (3).
_{^{[(R 4 O) 2 SP}} -S] 2 -Zn (3)
(Wherein R ⁴ is a primary or secondary alkyl group having 1 to 24 carbon atoms or an aryl group having 6 to 30 carbon atoms, particularly preferably a primary or secondary alkyl group having 3 to 8 carbon atoms. .)
The content of the component (c) in the grease composition of the present invention is preferably 0.1 to 10% by mass, more preferably 0.1 to 5% by mass. If the amount is less than 0.1% by mass, the effect tends to be insufficient, and if the amount exceeds 10% by mass, no further improvement in the effect is observed.

The component (d) molybdenum dialkyldithiocarbamate used in the present invention is preferably represented by the following general formula (4).
_{^{[R 5 2 N-CS-}} S] 2 -Mo 2 O m S n (4)
(In the formula, R ⁵ is a primary or secondary alkyl group having 1 to 24 carbon atoms, preferably 3 to 18 carbon atoms, m is 0 to 3, n is 1 to 4, and m + n = 4.)
The content of the component (d) in the grease composition of the present invention is preferably 0.1 to 10% by mass, more preferably 0.1 to 5% by mass. If the amount is less than 0.1% by mass, the effect tends to be insufficient, and if the amount exceeds 10% by mass, no further improvement in the effect is observed.

The component (e) melamine cyanurate used in the present invention is an adduct of melamine and cyanuric acid. Cyanuric acid is in a tautomeric relationship with isocyanuric acid, and commercially available melamine cyanurate is an adduct of 1 mol of melamine and 1 mol of cyanuric acid, and is in the form of melamine isocyanurate. In this specification, melamine cyanurate refers to an adduct of melamine and cyanuric acid or isocyanuric acid. Melamine cyanurate is easily deposited as a white precipitate when, for example, a melamine aqueous solution and a cyanuric acid or isocyanuric acid aqueous solution are mixed. Melamine cyanurate is usually marketed as a white fine powder with an average particle size of 1 to 2 μm. Melamine molecules having a 6-membered ring structure and cyanuric acid molecules are strongly bonded by hydrogen bonds and arranged on a plane. It is presumed that the planes overlap each other with a weak bonding force and are cleaved in the same manner as molybdenum disulfide and give excellent lubricity.
The content of the component (e) in the grease composition of the present invention is preferably 0.1 to 10% by mass, more preferably 0.1 to 5% by mass. If the amount is less than 0.1% by mass, the effect tends to be insufficient, and if the amount exceeds 10% by mass, no further improvement in the effect is observed.

The component (f) calcium carbonate used in the present invention has various crystal structures and particle sizes depending on purification and processing methods. In the present invention, these are not particularly limited, but the particle diameter is preferably 100 μm or less, more preferably 50 μm or less, in order to exert an effect by intervening in the lubrication part.
The content of the component (f) in the grease composition of the present invention is preferably 0.1 to 10% by mass, more preferably 0.1 to 5% by mass. If the amount is less than 0.1% by mass, the effect tends to be insufficient, and if the amount exceeds 10% by mass, no further improvement in the effect is observed.

The component (g) zinc dialkyldithiocarbamate used in the present invention is preferably represented by the following general formula (5).
[R ⁶ ₂ N-CS-S] ₂ —Zn (5)
In the formula, R ⁶ is a primary or secondary alkyl group having 1 to 24 carbon atoms or an aryl group having 6 to 30 carbon atoms. Particularly preferred is a primary or secondary alkyl group having 3 to 8 carbon atoms. )
The content of the component (g) in the grease composition of the present invention is preferably 0.1 to 10% by mass, more preferably 1 to 5% by mass. If the amount is less than 0.1% by mass, the effect tends to be insufficient, and if the amount exceeds 10% by mass, no further improvement in the effect is observed.

As a sulfur-nitrogen system extreme pressure additive of the component (h) used for this invention, a sulfur content of 5-20% mass% and a nitrogen content of 1-10 mass% are preferable.
The content of component (h) in the grease composition of the present invention is preferably 0.05 to 5% by mass. If it is less than 0.05% by mass, the effect tends to be insufficient, and if it exceeds 5% by mass, no further improvement in the effect is observed.

In addition to the above components, the grease composition of the present invention may contain other extreme pressure additives, antioxidants, rust inhibitors, anticorrosives, and other additives usually used in grease compositions.
The grease composition for the ball type constant velocity joint of the present invention uses components (a) to (h) as essential components at a desired blending ratio, and optionally uses the various additives as optional components. It can be manufactured easily. For example, the component (a) and the component (b) are mixed to prepare a urea grease as a base in advance, and the components (c) to (h) can be appropriately added thereto.

  The grease composition for the ball type constant velocity joint of the present invention can be used without any limitation as long as it is a ball type constant velocity joint. For example, the effect is remarkable with respect to a fixed type constant velocity joint.

Hereinafter, a constant velocity joint suitable for enclosing the grease composition of the present invention will be described.
FIG. 1 shows a fixed type Rzeppa constant velocity joint. The Rzeppa constant velocity joint includes an outer joint member 10, an inner joint member 20, a ball 30, and a cage 40 as shown in FIGS. Eight curved track grooves 12 are provided on the spherical inner surface 11 of the outer joint member 10 at an interval of 45 °. On the other hand, eight curved track grooves 22 are similarly formed on the spherical outer surface 21 of the inner joint member 20 at an interval of 45 °, and the center of curvature A of the inner joint member track groove 22 and the outer joint member track are formed. The center of curvature B of the groove 12 is offset from the angle center O of the joint by an equal distance from side to side. When the outer joint member 10 and the inner joint member 20 are angularly displaced by an angle θ, the torque transmission ball 30 guided by the cage 40 is divided into two halves (θ / 2) of the angle θ at an arbitrary operating angle θ. The constant velocity of the joint is ensured as is well known.
The ball 30 is assembled between the outer joint member track groove 12 and the inner joint member track groove 22, while the cage 40 is assembled between the outer joint member 10 and the inner joint member 20. The cage 40 has a spherical surface 41 that is guided in contact with the spherical inner surface 11 of the outer joint member 10 and the spherical outer surface 21 of the inner joint member 20 inside and outside. The cage 40 is formed with eight pockets 43 for receiving the balls 30 at equal intervals in the circumferential direction.
The shaft 1 is fitted to the inner joint member 20. The outer periphery of the outer joint member 10 and the outer periphery of the shaft 1 are covered with the boot 2, and the outer joint member 10, the inner joint member 20, the outer joint member track groove 12, the inner joint member track groove 22, and the torque transmission ball 30. The grease 3 of the present invention is enclosed in a space surrounded by the cage 40 and the shaft 1.

  Hereinafter, although it demonstrates more concretely based on an Example and a comparative example, this invention is not limited to the following Examples at all.

<Preparation of grease composition>
Examples 1-5, Comparative Examples 1-11
In 4000 g of component (a) base oil (mineral oil having a kinematic viscosity of 13.2 mm ² / s at 100 ° C.), 250 g (1 mol) of diphenylmethane-4,4′-diisocyanate and 258 g (2 mol) of octylamine were added. The base grease was obtained by making it react and disperse | distributing the diurea type compound of the produced | generated component (b) uniformly.
Add additives to the base grease in the formulations shown in Table 1, Table 2, and Table 3, and add JIS consistency No. 1 with a three-stage roll mill while adding component (a) base oil as appropriate. It adjusted to 1 grade (consistency 310-340).
Comparative Example 12
Component (a) A base oil (mineral oil having a kinematic viscosity of 13.2 mm ² / s at 100 ° C.) in 8200 g is reacted with 1012 g of diphenylmethane-4,4′-diisocyanate, 563 g of cyclohexylamine, and 225 g of aniline. The base grease was obtained by uniformly dispersing the diurea compound of component (b).
To this base grease, an additive was added according to the formulation shown in Table 3, and a JIS consistency No. 1 was added with a three-stage roll mill while appropriately adding the component (a). It adjusted to 1 grade (consistency 310-340).

<SRV test>
About each grease composition of Examples 1-5 of Table 1, Comparative Examples 1-9 of Table 2, and Comparative Examples 10-12 of Table 3, the magnitude | size of the wear trace of a ball was evaluated by the SRV friction abrasion test.
・ Measurement conditions (Measurement method conforms to ASTM D5707)
Surface pressure: 2.2 GPa
Sliding speed: 180mm / s
・ Evaluation method The wear diameter of the ball is measured with a microscope.

<Durability test>
About each grease composition of Examples 1-5 of Table 1, Comparative Examples 1-9 of Table 2, and Comparative Examples 10-12 of Table 3, it encloses in an actual joint (fixed type constant velocity joint), and uses this The joint durability test was conducted, and the wear state of the joint and the occurrence time of flaking were evaluated.
・ Evaluation method and evaluation criteria Joint wear state: Compare the occurrence of abnormal wear in each part of the joint (outer ring, inner ring, cage, ball) in the endurance test for a predetermined time. (For example, climbing to the edge due to wear of the inner ring and outer ring, abnormal wear of the cage pocket, etc.)
○: No abnormal wear ×: Flaking occurred with abnormal wear: Check for occurrence of flaking in each part of the joint (outer ring, inner ring, cage, ball).
○: No flaking occurred ×: Flaking occurred

* 1) LUBRIZOL 1395 manufactured by Nippon Lubrizol
* 2) MOLYVAN A manufactured by RTVANDERBILT
* 3) MELAPUR MC25 manufactured by Ciba Japan
* 4) MCA manufactured by Mitsubishi Chemical Corporation
* 5) Sankyo Seisaku Co., Ltd. Escalon 2000
* 6) OMYA OMYALITE 95T
* 7) VANLUBE AZ made by RTVANDERBILT
* 8) VANLUBE 601 made by RTVANDERBILT
* 9) Industrial No. 1 castor oil manufactured by Toyokuni Oil Co., Ltd. * 10) LUBRIZOL 810 manufactured by Nippon Lubrizol Co., Ltd.
* 11) Japanese Patent Application Laid-Open No. 2008-297402, Example 1 * 12) LUBRIZOL 5318A manufactured by Nippon Lubrizol Corporation
* 13) Asahi Denka Kogyo's SakuraLube 600
* 14) Anglamol 99 manufactured by Nippon Lubrizol
* 15) NICHIMOLY SF-0 manufactured by Daizo
* 16) Anglamol 33 manufactured by Nippon Lubrizol
* 17) Japanese Patent No. 39898912, Example 1 * 18) Japanese Patent Application Laid-Open No. 2006-335876, Example 1 * 19) Japanese Patent No. 3988895, Example 1

Examples 1-5 are shown in Table 1, Comparative Examples 1-9 are shown in Table 2, and Comparative Examples 10-12 are shown in Table 3.
The grease compositions of Examples 1 to 5 of the present invention containing the components (a) to (h) have a ball wear scar size of less than 0.80 mm in the SRV test. There is no abnormal wear in each part, and no flaking occurs. It can be seen that the combination of the components (a) to (h) can improve the wear resistance and flaking resistance.
On the other hand, Comparative Example 1 to Comparative Example 6 not including each of the additives (c) to (h), and Comparative Example 7 not including any of the component (e) and component (f) 4), Comparative Example 8 in which an oily agent was blended with Comparative Example 7, Comparative Example 9 in which a sulfur-phosphorus extreme pressure agent was blended with Comparative Example 7, and Comparative Examples 10 to 10 prepared with reference to Patent Documents 1 to 3 In the grease composition of No. 12, the size of the ball wear scar in the SRV test was more than 0.80 mm, and abnormal wear and flaking occurred in each part of the joint in the endurance test for a predetermined time.

DESCRIPTION OF SYMBOLS 1 Shaft 2 Boot 3 Grease 10 Outer joint member 11 Spherical inner surface 12 Outer joint member track groove 20 Inner joint member 21 Spherical outer surface 22 Inner joint member track groove 30 Torque transmission ball 40 Cage 41 Spherical surface 43 Pocket

Claims (1)

A grease composition for ball-type constant velocity joints comprising the following components (a) to (h):
(A) base oil,
(B) a diurea thickener;
(C) zinc dialkyldithiophosphate,
(D) molybdenum dialkyldithiocarbamate,
(E) Melamine cyanurate,
(F) calcium carbonate,
(G) zinc dialkyldithiocarbamate, and (h) sulfur-nitrogen extreme pressure additive.

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