Traction drive fluid

Details Traction drive fluid Traction drive fluid

2001-02-27

2001-11-20

Howard, Jacqueline V. (Department: 1764)

Chemistry of hydrocarbon compounds

Compound or reaction product mixture

Alicyclic

C585S022000, C585S253000, C508S110000, C508S591000

Reexamination Certificate

active

06320088

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to traction drive fluids, and more particularly to such traction drive fluids which can be used not only for the driving force transmitting mechanisms but also for hydraulic pressure controlling mechanism and the friction properties controlling mechanisms of the wet clutches of automobiles. The traction drive fluids of the present invention are particularly useful for traction drive type continuously variable transmissions of automobiles.
2. Description of the Prior Art
In the field of industrial machines, traction drive fluids have already been used in traction drive type power transmitting apparatuses which transmit power via oil film. Such traction drive fluids are required to have a high traction coefficient which indicates a power transmission capability.
In recent years, extensive studies and investigations on a traction drive fluid have progressed for its use of the continuously variable transmissions of automobiles. Traction drive fluids to be used for automobiles are expected to be used not only in the power transmitting mechanisms but also in the hydraulic controlling mechanisms and the friction properties controlling mechanisms for the wet clutch.
An automatic transmission fluid (ATF) is known as a lubricating oil used in automobile's transmission hydraulic controlling mechanism and friction properties controlling mechanism of wet clutches. It is a well-known fact that such an ATF is required to have a higher kinematic viscosity at elevated temperatures than a certain level and to be superior in low temperature flowability for performing the role in hydraulic controlling mechanisms. It is also well known that an ATF needs to be blended with additives which have excellent friction properties, particularly anti-shudder properties for fulfilling requirements in performing the role in the friction properties controlling mechanism, particularly the controlling mechanism having in addition thereto slip controlling capabilities.
Therefore, when used in the traction drive type continuous variable transmission of an automobile, a traction drive fluid is required to have driving force transmitting properties which are peculiarly excellent but also properties as a fluid for hydraulic controlling, and friction properties controlling of a wet-type clutch, both of which are required for an ATF.
It is also a well-known fact that a fluid tends to be deteriorated in low-temperature flowability as the traction coefficient increases. Therefore, in the development of a traction drive fluid, it is a major problem how such trade-off relation between traction coefficient and low temperature flowability is deal with.
More specifically, there is a problem that the traction coefficient of a fluid would be reduced if it can achieve the possession of the pour point at −10° C. or below which is required as a traction drive fluid for industrial machines of which usage is limited to indoors or the possession of the low temperature pour point which is required to be also used in the hydraulic controlling mechanisms of traction drive type continuous variable transmissions which have been developed for automobiles.
BRIEF SUMMARY OF THE INVENTION
In view of the current situations, the object of the present invention is to provide a traction drive fluid which is not only superior in power transmitting properties but also can be used in the hydraulic controlling mechanisms of automobiles. Furthermore, the present invention can provide a traction drive fluid which has excellent properties in wet-type clutches which is necessary to be used in automobiles.
Intensive research and efforts made to solve the foregoing problems resulted in the development of a traction drive fluid particularly suitable for use in automobile's traction drive type continuously variable transmission, more specifically a traction drive fluid which can be used not only in hydraulic controlling mechanism and but also the friction properties controlling mechanism of automobile wet clutches.
According to the present invention, there is provided a traction drive fluid which is a saturated polycyclic hydrocarbon compound obtained by hydrogenating a trimeric compound of a cyclopentadiene-based condensed hydrocarbon compound resulting from the Diels-Alder reaction of cyclopentadiene and then isomerizing the resulting hydrogenated compound so as to have a pour point of −10° C. or below.
In addition to the foregoing compound, the traction drive fluid according to the present invention further comprises preferably (A) at least one member selected from the group consisting of a mineral oil and a synthetic oil having a molecular weight of 150 to 800.
Alternatively, the traction drive fluid of the present invention further comprises preferably (B) a viscosity index improver. The viscosity index improver (B) is preferably an ethylene-&agr;-olefin copolymer having a number-average molecular weight of 800 or more and 150,000 or less and hydrides thereof.
Alternatively, the traction drive fluid of the present invention comprises preferably (C) an ashless dispersant and (D) a phosphorus additive.
Further alternatively, the traction drive fluid of the present invention further comprises preferably (E) a friction modifier having at least one alkyl or alkenyl group having 6 to 30 carbon atoms per molecule but having no hydrocarbon group having 31 or more carbon atoms per molecule.
Still further alternatively, the traction drive fluid of the present invention further comprises preferably (E) a metallic detergent having a total base number of 20 to 450 mgKOH/g.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in more details below.
A traction drive fluid according to the present invention is a saturated polycyclic hydrocarbon compound obtained by hydrogenating a trimeric compound of a cyclopentadiene-based condensed hydrocarbon compound resulting from the Diels-Alder reaction of cyclopentadiene and then isomerizing the resulting hydrogenated compound so as to have a pour point of −10° C. or below. In the present invention, the saturated polycyclic hydrocarbon compound if it has a pour point of −10° C. or below, can be used suitably. However, those having a pour point of −20° C. or below are preferred, and those having a pour point of −30° C. or below are more preferred. Lower a pour point, the saturated polycyclic hydrocarbon compound is better. The lower limit is the critical point achieved when the compound of the present invention is used.
The saturated polycyclic hydrocarbon compound of the present invention is synthesized through [A] the Diels-Alder reaction, [B] hydrogenation, and [C] isomerization.
[A] the Diels-Alder reaction
The Diels-Alder reaction of cyclopentadiene results in the formation of a dimeric compound thereof and the reaction when further progressed, results in the reaction of the dimer and cyclopentadiene progressed as indicated by the following formula [I] or [II] thereby obtaining a trimeric compound represented by formula (1) or (2) as the main component.
The Diels-Alder reactions are heat-reaction and thus do not need any catalyst.
Although the cyclopentadiene used in the above-described Diels-Alder reaction may be added in the form of a monomer to the reaction system, dicyclopentadiene which is easily available and produces cyclopentadiene by thermal decomposition may be used as the starting material.
The reaction temperature is arbitrary selected but is usually within the range of 50 to 300° C., preferably 80 to 250° C.
The reaction time is varied depending on the reaction temperature but is usually from 10 minutes to 40 hours, preferably 30 minutes to 30 hours.
In each of the Diels-Alder reactions, if necessary, a polymerization inhibitor such as hydroquinone, p-phenylenediamine, t-butylcatechol may be added so as to suppress the formation of a polymer. These reactions may be conducted in an organic solvent which does n

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