Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic compound containing boron
Reexamination Certificate
1999-04-02
2001-02-06
Johnson, Jerry D. (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
06184185
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of The Invention
This invention relates to a lubricant oil composition, more particularly, the composition characterized by high transmission torque capacity and good anti-shudder property, and useful for an automatic and continuously variable transmission (e.g., belt or traction type) with a built-in torque converter equipped with a lock-up clutch, the transmission being used in an automobile.
2. Description of The Related Art
A lubricant oil for an automatic or continuously variable transmission can be used in an automobile equipped with a torque converter, gear and hydraulic mechanisms, wet type clutch, and so on. This type of lubricant is required to have a variety of properties, because it functions as the power transmission medium for the torque converter, and hydraulic and control systems; as the lubricant and temperature-controlling medium for the gears, bearings, wet type clutch, and so on; and as the lubricant medium and the medium to maintain the function-related characteristics of the friction material, in order to smoothly operate the transmission.
Recently, lock-up clutches have been built in torque converters in many automobiles to improve mileage. In this mechanism, a transmission is built in a torque converter. A lock-up clutch is a device that directly transmits the engine driving force to the transmission under varying running conditions. Torque converter efficiency can be enhanced, when switching between torque converter driving and direct driving is well timed.
However, a conventional lock-up clutch mechanism works only in a high speed range, and not in a low speed range where engine torque widely varies.
Recently, slip control is adopted to help the lock-up clutch work in the low speed range of an automatic transmission. However, abnormal vibration of the car body, known as shudder, has been frequently observed at the lock-up clutch's surface, when the lock-up mechanism is operated in a low speed range. Such a phenomenon is more pronounced, when coefficient of friction decreases as relative sliding velocity increases at the slip-controlled lock-up clutch. In order to prevent the shudder phenomenon, the lubricant is required to have good &mgr;(coefficient of friction)−V (sliding velocity) characteristics. In other words, it is required to have a coefficient of friction which increases as sliding velocity increases, i.e., positive &mgr;−V relationship, for an automatic and continuously variable transmission.
Esters of phosphates, aliphatic acids and fatty amides have been proposed as friction modifiers for automatic transmission lubricants, as disclosed by Japanese Laid-open Patent application No. 63-254196. However, these modifiers have disadvantages which result in a decreasing coefficient of friction at the lock-up clutch in a low sliding velocity range, and in insufficient transmission torque when the clutch is connected.
Use of metallic detergents and ashless depressants has been proposed, as disclosed by Japanese Laid-open Patent application Nos. 5-105892, 6-271883, 8-127789 and 8-319494, to increase transmission torque capacity. Nevertheless, however, few lubricants have exhibited sufficient friction-related properties, even in the presence of the above additives.
As discussed above, the &mgr;−V characteristics trade off with transmission torque capacity, and it is necessary to increase transmission torque capacity while keeping a positive &mgr;−V relationship. As a result, there have been demands increasingly for the technique to increase coefficient of friction in a high sliding velocity.
DESCRIPTION OF THE INVENTION
It is an object of the present invention to provide a lubricant oil composition for an automatic and continuously variable transmission, which exhibits a sufficient coefficient of friction in a high sliding velocity range in an automatic and continuously variable transmission with a built-in torque converter equipped with a lock-up clutch.
It has been discovered that the lubricant composition for an automatic and continuously variable transmission exhibits a sufficient coefficient of friction in a high sliding velocity range while keeping the lubricant characteristics required by these transmissions, when the lubricant base oil is incorporated with an adequate but minor quantity of an additive which contains at least one type of cyclic carboxylic acid imide having boron in the molecule and substituted by hydrocarbyl groups selected from the group consisting of alkyl group(s), alkenyl group(s), and mixtures thereof.
The present invention provides a lubricant oil composition for an automatic and continuously variable transmissions equipped with a slip-controlled, lock-up clutch, which exhibits a sufficient coefficient of friction in a high sliding velocity range by incorporating in the base oil an additive which contains at least one type of cyclic carboxylic acid imide, containing a specific boron species in the molecule and substituted by hydrocarbyl group(s) selected from the group consisting of alkyl or alkenyl group(s) and mixtures thereof.
The present invention relates, as described above, to a lubricant oil composition comprising a major amount of a base oil incorporated with a minor amount of specific additive. Some of the preferred embodiments are described below:
(1) A lubricant oil composition for an automatic and continuously variable transmission, characterized by incorporating in the base oil at least one type of cyclic dicarboxylic acid imide having boron in the molecule and substituted by alkyl and/or alkenyl group(s), at 0.1 to 12 wt % based on the whole composition.
(2) A lubricant oil composition for an automatic and continuously variable transmission, characterized by incorporating in the base oil at least one type of cyclic dicarboxylic acid imide, shown by one of the general formulae (1) through (4) described below, having boron in the molecule, at 0.1 to 12 wt % based on the whole composition.
(3) A lubricant oil composition for an automatic and continuously variable transmission as described in (1) or (2) above, wherein the hydrocarbyl group substituted onto the boron containing cyclic carboxylic acid imide is an alkyl or alkenyl group having a carbon number of 6 to 300 (molecular weight of 80 to 4200).
(4) A lubricant oil composition for an automatic and continuously variable transmission as described in (1) to (3) above, wherein B/N ratio, i.e., the molar ratio of boron to nitrogen in the cyclic dicarboxylic acid imide is 0.01 to 0.5.
(5) A lubricant oil composition for an automatic and continuously variable transmission, containing the above composition, is further incorporated with at least one type of additives selected from the group consisting of viscosity index improver, pour depressant, ashless dispersant, metallic detergent, oxidation inhibitor, wear inhibitor, extreme-pressure agent, metal deactivator, corrosion inhibitor, anti-foaming agent and other additives required for the lubricant oil composition for an automatic and continuously variable transmission.
THE PRESENT INVENTION
The present invention is described in more detail, below:
(1) Lubricant Base Oil
The base oil for the lubricant oil composition of the present invention for an automatic and continuously variable transmission is not limited, and any oil commonly used as a base oil can be used. It may be a mineral or synthetic oil, or a mixture thereof.
The mineral oil may be a raffinate derived from a naphthenic or paraffinic crude oil, where the lubricant stock from the atmospheric or vacuum residue is extracted with an adequate aromatic solvent, e.g., phenol, furfural or N-methylpyrrolidone to produce the raffinate. It may be a hydrotreated oil, derived from the above lubricant stock which is subjected to a hydrotreatment process including hydrocracking, or isomerate obtained by bringing wax into contact with hydrogen under isomerization conditions in the presence of an isomerization catalyst. It may be also a lubricant fraction which is treated by solvent extraction combined
Kugimiya Takanori
Nakanishi Hiroshi
Taguchi Shigeko
Allocca Joseph J.
Dvorak Joseph J.
Johnson Jerry D.
Tonen Corporation
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