Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic compound containing boron
Reexamination Certificate
2001-06-05
2003-09-09
Howard, Jacqueline V. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic compound containing boron
Reexamination Certificate
active
06617286
ABSTRACT:
This application claims priority to Japanese Patent Application No. 167144/00 filed Jun. 5, 2000.
FIELD OF THE INVENTION
This invention relates to a lubricating oil composition for continuously variable transmission, and more particularly, to a lubricating oil composition used in a push belt type of continuously variable transmission. More specifically, the invention relates to a lubricating oil composition which ensures a high coefficient of boundary lubrication friction and an enhanced wear preventing property in a push belt-type continuously variable transmission.
BACKGROUND OF THE INVENTION
The push belt-type continuously variable transmission (which may be sometimes referred to as belt-type CVT hereinafter) rapidly increases in number because it is effective in improving a fuel cost and also drivability of automobiles. However, the belt-type CVT is difficult in obtaining a large transmission torque capacity, and has been mounted only on a small automobile whose displacement is 1600 cc or below. The improvement in the-transmission torque capacity is a serious problem on the belt-type CVT.
With the belt-type CVT, a torque is transmitted by means of a friction force between a belt element and a pulley. Thus, the transmission torque capacity is determined depending on the coefficient of friction between the metals of the belt element and the pulley and the urging force of the pulley. The coefficient of friction between the metals is influenced by the property of a lubricating oil. The shortage of the coefficient of friction between the metals may lead to the slippage between the belt and the pulley and may cause a disadvantage in that the belt is broken out.
On the other hand, an electromagnetic clutch has been hitherto used as a starting mechanism of the belt-type CVT. In order to cope with an increasing transmission torque accompanied by the tendency toward a great displacement and improve the drivability, there has been now used a wet clutch or and a torque converter with a lock-up clutch. These wet clutch, torque converter and CVT make use of a common lubricating oil. Accordingly, it has become important how to adapt the lubricating oil for continuously variable transmission (CVT oil) to the wet clutch or torque converter.
Under these circumstances, an automatic transmission oil (which may be referred to as ATF) has been frequently used for the CTV oil. This is because with an existing automobile of a small displacement, the transmission torque is so small that a required level of the coefficient of friction between metals is not so high, under which if an oil having a relatively high coefficient of friction between metals is selected among ATFs, the performance can be satisfied. The merit of making use of ATF includes actual results on the adaptability with a wet clutch and also on adaptability on other types of materials. However, if the belt-type CVT is mounted in an automobile of a large displacement, a required level of the coefficient of friction between metals increases. The mere use of ATF does not result in a satisfactory performance, and an oil only for the CVT has to be used.
Hitherto, lubricating oils for continuously variable transmission have been proposed including, for example, a lubricating oil composition of Japanese Patent Application Laid-open No. Hei 2-175794 wherein a wear preventive, a metal detergent and a carboxyl group-bearing friction modifier are formulated, a composition for continuously variable transmission of Japanese Patent Application Laid-open No. Hei 9-100487 wherein a sulfur-based extreme pressure agent, a phosphorus-based extreme pressure agent, and a metal-based detergent are formulated, a lubricating oil composition for continuously variable transmission of Japanese Patent Application Laid-open No. Hei 10-8081 wherein an ashless dispersant, a sulfur-based extreme pressure agent and a phosphorus-based extreme pressure agent are formulated, a lubricating oil composition for belt-type CVT automatic transmission of Japanese Patent Application Laid-open No. Hei 10-306292 wherein a Ca sulfonate and a phosphite ester having a specified range of a total base number are formulated, a lubricating oil composition for belt-type continuously variable transmission of Japanese Patent Application Laid-open No. Hei 11-80772 which has a coefficient of friction within a specified range and wherein a metal detergent and a zinc dialkyldithiophosphate are formulated, and a lubricating oil composition for continuously variable transmission of Japanese Patent Application Laid-open No. Hei 11-181464 wherein a polymethacrylate or the like, an imide compound and a zinc alkyldithiophosphate are formulated.
In spite of these proposals, however, there are few oils which provide an adequate, high level of a coefficient of friction between metals and an excellent oxidation stability. Especially, in order to obtain a required high coefficient of friction between metals, it is effective to formulate a combination of a wear preventive and a metal detergent in a belt-type continuously variable transmission lubricating oil (CVT oil). If it is intended to obtain a high coefficient of friction between metals only by use of the combination thereof, the amounts of a wear preventive and a metal detergent become too great, thus presenting the problem that oxidation stability becomes unsatisfactory, and thus, the transmission does not stand long-term use. Applicants' invention addresses these needs.
SUMMARY OF THE INVENTION
Applicants have found that when at least three additives including a wear preventive (A), a metal detergent (B) and an ashless dispersant (C) are formulates as essential components in a lubricating base oil, there is obtained a lubricating oil composition having a high coefficient of friction between metals required for a lubricating oil for continuously variable transmission and enhanced oxidation stability providing the performance over a long time.
More particularly, according to the invention, there is provided a lubricating oil composition for continuously variable transmission of the type which comprises a lubricating base oil made of a mineral oil and/or a synthetic oil formulated with a wear preventive (A), a metal detergent (B), and an ashless dispersant (C), characterized in that said ashless dispersant (C) consists of an succinimide having boron at a rate of one or more atoms in one molecule of the ashless dispersant.
As stated above, the invention relates to a lubricating oil composition wherein at least three specific types of compounds are formulated in a lubricating base oil. Preferred embodiments include those set forth below.
(1) A lubricating oil composition for continuously variable transmission, wherein the wear preventive is made of a phosphorus-based wear preventive.
(2) A lubricating oil composition for continuously variable transmission, wherein the phosphorus-based wear preventive is made of at least one phosphorus-based wear preventive selected from an acid phosphate ester, an acid phosphite ester and phosphoric acid and mixtures thereof.
(3) A lubricating oil composition for continuously variable transmission, wherein the phosphorus-based wear preventive is made of a zinc dialkyldithiophosphate whose alkyl groups are primary, secondary or a mixture thereof or a thiophosphate ester and mixtures thereof.
(4) A lubricating oil composition for continuously variable transmission, wherein the amount of the wear preventive ranges 200-500 ppm as phosphorus (P) based on the total weight of the composition.
(5) A lubricating oil composition for continuously variable transmission, wherein the amount of the metal detergent ranges 100-1000 ppm as a metal based on the total weight of the composition.
(6) A lubricating oil composition for continuously variable transmission, wherein the metal detergent has a total base number of 400 mg KOH/g or below.
(7) A lubricating oil composition for continuously variable transmission, wherein the metal detergent is made of an alkaline earth metal salt of an alkylbenzene or alkylnaphthalenesulfonic ac
Kugimiya Takanori
Sato Takehisa
Howard Jacqueline V.
Scuorzo Linda M.
Tonen General Sekiyu K.K.
LandOfFree
Lubricating oil composition for continuously variable... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Lubricating oil composition for continuously variable..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Lubricating oil composition for continuously variable... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3026094