Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Naturally occurring carboxylic acid ester wax
Reexamination Certificate
2001-08-09
2002-12-31
McAvoy, Ellen M. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Naturally occurring carboxylic acid ester wax
C508S551000, C508S591000
Reexamination Certificate
active
06500787
ABSTRACT:
FIELD OF THE INVENTOIN
This invention relates to lubricant compositions. The invention is especially concerned with a ball joint comprising a ball seat of synthetic resin and a metal ball stat which ball joint further comprises lubricant composition according to the present invention, and use of a lubricant composition in such ball joint.
BACKGROUND OF THE INVENTION
In ball joints commonly used in automobiles, the basic method of lubrication is the presence of lubricant between the ball seat
1
of synthetic resin and the metal ball stat
2
. Several methods have been proposed for the maintenance and improvement of the performance of ball joints. For example, the hardness was increased in the ball stat to prevent abrasion; molybdenum, graphite or lubricating oil were incorporated in the ball seat so as to increase the gliding property of the resin itself, or a groove was incorporated on the inner surface of the ball seat to act as a reservoir of grease.
However, there is a limit in improvement of the performance of ball joints by these methods. At present, the major opportunity for improvement of performance of ball joints is thought to reside in a lubricant having improved properties.
Ball joints are placed at the extremely important positions in the suspension system and the steering system concerned with the movement of motor vehicles. Direct influence is exerted by the joint on the movement. Therefore, there is a severe problem if the position of the ball stat is altered greatly under load.
In the process of assembling a ball stat, a ball seat and a socket, some load is applied to the ball seat through the ball stat so that the clearance is made as small as possible between the ball stat and the ball seat by taking advantage of iscoelasticity of a synthetic resin. Also it is attempted to limit as much as possible the displacement of the ball stat under a load. Consequently, a certain pressure is maintained in the space between the ball stat and the ball seat, and ordinary lubricating grease tends to be extruded from the space between the ball stat and the ball seat with elapse of time. As the result, the torque upon movement becomes greater and the lubricant membrane is broken during repeated movement, resulting in direct contact between the ball stat and the ball seat, the development of abrasion and an increased displacement of the ball stat.
A lubricant composition to be used in ball joints preferably has the following characteristics: under a load, the lubricant composition preferably adheres strongly to both the ball stat and ball seat to form a membrane with a constant thickness. The lubricant composition preferably flows smoothly at the gliding part when the ball stat moves from the stationary condition to the moving condition, and the grease membrane is preferably maintained without change even after repeated movement of the ball stat so that a stable lubricating function is maintained.
Patent cases concerned with ball joints, are the follows.
Japanese Kokai Patent Application No. Sho 60 [1996]-31598 describes a grease product containing poly-&agr;-olefin type synthetic oil with kinematic viscosity of 500-2000 mm
2
/sec at 40° C., paraffin wax, fatty acid amide wax and urea type thickening agent.
Japanese Kokai Patent Application No. Hei 2[1990]-194095 describes a grease product for ball joints containing urea type thickening agent, hydrogenated mineral oil devoid of wax with the kinematic viscosity of 50-500 mm
2
/sec at 40° C., paraffin wax and fatty acid amide wax.
Japanese Kokai Patent Application No. Hei 6[1994]-116581 describes a lubricating product for ball joints characterized by a content of polyisoprene rubber or polyisoprene rubber viscous material with the viscosity of 3×10
3
-10
5
mN.s/m2 (cP) at 25° C. and aliphatic amide or aliphatic bisamide.
The present invention relates to a further improvement of the technology made public by our Kokai Patent Application No. Hei 6[1994]-116581.
SUMMARY OF THE INVENTION
This invention relates to a lubricant composition comprising
(A) 100 parts by weight of a viscous material having a viscosity from 3×10
3
to 10
5
mN.s/m
2
(cP) at 25° C. which is at least one member chosen from the group consisting of
(i) polyisoprene rubber and
(ii) viscous composition containing polyisoprene rubber
(B) 15-45 parts by weight of at least one compound from the group of aliphatic amides represented by Formula (1)
R
1
CONH
2
(1)
(where R
1
indicates a saturated or unsaturated alkyl group containing 15-17 carbon atoms), and aliphatic bisamides represented by Formula (2)
R
1
CONHR
2
NHCOR
1
(2)
(wherein R
1
represents a saturated or unsaturated alkyl group and R
2
represents methylene or ethylene), and
(C) 5-30 parts by weight of at least one wax chosen from the group of polyethylene wax, paraffin wax and microcrystalline wax.
Lubricant composition according to the present invention was found to give a low torque especially at working conditions (rotatory torque), more especially at working conditions at normal temperature, and to inhibit torque change and to give a ball joint giving good endurance.
Further, the composition was found to inhibit variation in the ball stat after repeated use. A good abrasion resistance was found in durability tests.
Further, the present invention relates to a ball joint comprising a ball seat (1) of synthetic resin and a metal ball stat (2), which ball joint comprises a lubricant composition according to the present invention, and to use of the lubricant composition in such ball joint.
DETAILED DESCRIPTION OF THE INVENTION
Component (A) used as the viscosity agent in this invention has a relation with adhesiveness on the sliding surfaces of ball joints and smooth working property, and its viscosity must be in the range from 3×10
3
to 10
5
mN.s/M
2
(cP) at 25° C. If the viscosity is less than 3×10
3
mN.s/m
2
(cP), the lubricating product has poor adhesive property and the gliding membrane tends to become thin so that the resin and the metal make direct contact at the boundary plane resulting in the increased torque. On the other hand, if the viscosity is greater than 10
5
mN.s/m
2
(cP), the resistance is increased in the lubricating oil itself, resulting in the increased torque of the ball joint.
The aforementioned polyisoprene rubber has the repeating unit
The polyisoprene rubber will generally contain a block of (3) and/or (4) mentioned above. Polymer additives, such as polybutene, polyisobutylene, and polymethacrylate could not achieve the aim of this invention, unlike polyisoprene.
Viscous composition containing polyisoprene rubber can be obtained by addition of mineral oil and/or synthetic oil to polyisoprene rubber. There is no particular limit in the ratio of mixing, and a mixture can be accepted if the viscosity is in the range from 3×10
3
to 10
5
mN.s/m
2
(cP).
Synthetic oil is defined as publicly known oil used as the base oil for production of usual lubricating oil or grease, for example paraffin type mineral oil or naphthene type mineral oil such as the mineral type or poly-&agr;-olefin, cooligomer of &agr;-olefin and ethylene, polyethylene glycol and polypropylene glycol as alklene glycol type; alkyldiphenylether as ether type; and dimethylsilicone as silicone type.
The amide used as component (B) has the function of turning the viscous component (A) into a solid or semisolid and the function of reducing the friction coefficient between the resin and the metal as well as improving the inner fluidity of viscous substance. If the content of this component is less than 15 parts by weight, the lubricant becomes too soft and tends to flow easily so that the effect is weakened for improved gliding property between the resin and the metal. On the other hand, if its content is more than 45 parts by weight, the lubricant becomes too hard and difficult to handle, and the lubricating property is also reduced. Also, there is a possibility that it is too difficult to fill the space between the b
Masumori Ryuichi
Tanaka Keiji
Yatsuzuka Yoshihisa
McAvoy Ellen M.
Shell Oil Company
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