Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Silicon dioxide – silicic acid – orthosilicate – or...
Reexamination Certificate
1999-05-12
2001-05-01
Medley, Margaret (Department: 1714)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Silicon dioxide, silicic acid, orthosilicate, or...
C508S138000, C508S144000, C508S137000, C074S467000
Reexamination Certificate
active
06225265
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a miniature electric motor with reduction worm gear unit and more particularly to a miniature electric motor with reduction worm gear unit used for driving an electric window device of an automotive vehicle.
2. Description of the Related Art
A miniature electric motor with reduction worm gear unit (hereinafter simply referred to as a motor) has been conventionally and extensively used for driving the electric window device, an electric sunroof device or the like. The motor has a motor portion and a reduction worm gear unit for producing an output of the motor portion through the reduction worm gear unit.
Lubricant (mainly, grease) having good wear resistance is used for lubricating worm gears of the reduction worm gear unit.
By the way, the electric window device performs opening/closing operations of a window glass of an automotive vehicle. The motor used in the electric window device requires such reverse rotation proof that the motor is never reversed for burglar proof and security even if an external force is applied in an opening direction to the window glass.
In general, an automotive vehicle is used in a wide range of temperature (for example, −30° C. to +80° C.). Therefore, the motor for the electric window device always requires the reverse rotation proof in this environmental temperature range.
Conventionally, there have been proposed a variety of lubricants having general reverse rotation proof. However, there are almost no lubricants for which the reverse rotation proof of the worm gears is taken into consideration. Namely, in the case where conventional lubricant is used for the worm gears, a transmission efficiency of gears is largely changed when the environmental temperature changes.
For this reason, there is a possibility that the window glass of the automotive vehicle might be opened from the outside by the external force in some environmental temperature range. This is disadvantageous in the aspect of the burglar proof and security. In order to solve this problem, it is necessary to ensure the gear transmission efficiency so that the reverse rotation proof may be always maintained even in the worst environmental temperature range.
Therefore, in the conventional motor, the first countermeasure thereof is that a lead angle of a worm is extremely decreased, or the second countermeasure is that a brake device is installed within an interior of the motor, or the third countermeasure is that mat finishing is effected to rough mesh tooth surfaces of the gears in a mat finish manner to increase a frictional coefficient, thereby maintaining the reverse rotation proof.
However, as in the first countermeasure, if the lead angle of the worm is decreased, an outer diameter of the worm is naturally increased so that it is difficult to miniaturize the motor as a whole. If the brake device is provided as in the second countermeasure, the number of the parts of the motor and the number of the steps for assembly are increased, resulting in increased cost.
The third countermeasure is proposed by the present applicant or assignee (Japanese Patent No. 2636958). The mat finishing for increasing the frictional coefficient of the mesh surfaces of the gears and the maintenance work thereof are required.
Thus, with the first to third countermeasures, since the gear transmission efficiency is decreased so that the reverse rotation proof is always maintained in the environmental temperature range, it is difficult to miniaturize the motor. Also, the conventional methods suffer from the difficulty in temperature characteristics.
SUMMARY OF THE INVENTION
In order to solve the above-noted defects, an object of the present invention is to provide a miniature electric motor with reduction worm gear unit, which always may maintain reverse rotation proof while always keeping a desired gear transmission efficiency in a wide environmental temperature range, thereby making it possible to miniaturize an overall size of the motor.
In order to attain this and other objects, according to the present invention, there is provided a miniature electric motor with reduction worm gear unit in which a reduction worm gear unit is mounted on a motor portion and an output of the motor portion is subjected to a speed reduction through the reduction worm gear unit, characterized in that: in lubricant for lubricating worm gears of the reduction worm gear unit, fine silica grain is added and mixed to base oil, and a content of the fine silica grain is in a range of about 3 to about 10 wt. (weight) %.
Incidentally, it is preferable that a granular size of the fine silica grain is in a range of about 7 to about 40 nm. It is preferable that at least one selected from the group of oiliness improver, viscosity improver, solid lubricant and consistency increasing agent is added and mixed to the lubricant into which the fine silica grain is added.
It is preferable that the oiliness improver is at least one selected from the group of sorbitan fatty acid ester and ester structured of copolymer; the viscosity improver is at least one selected from the group of polyisobutylene, polybutene, low molecular weight polyethylene, polybutadiene and poly methacrylate; the solid lubricant is selected from the group of melamine resin, silicone resin, paraffin and fluorocarbon resin; and the consistency increasing agent is selected from the group of lithium soap, bentonite and polyurea resin.
For example, the oiliness improver is sorbitan monooleate or oiliness improver mixed with pentaerythritol ester and dipentaerythritol ester. Also, the solid lubricant contains boron nitride and fine electric black lead powder.
It is preferable that at least one selected from the group of the oiliness improver, the viscosity improver, the solid lubricant and the consistency increasing agent is added and mixed to the lubricant into which the fine silica grain is added is in a range of about 0.2 to about 20.0 wt. %. For example, the content of the consistency increasing agent is in a range of about 0.5 to about 2.5 wt. %.
It is preferable that the base oil is chemical synthetic hydrocarbon oil or mineral oil that is superior in low temperature characteristics, attacked resin and corrosiveness. Also, it is preferable that chemical synthetic hydrocarbon oil is ethylene-&agr;-olefin copolymer or poly-&agr;-olefin.
For example, the reduction worm gear unit drives an electric window device for automatically opening/closing a window glass of an automotive vehicle. For example, the worm gears are composed of a worm formed out of carbon steel and a worm wheel formed out of synthetic resin.
The worm gears exhibit the first function that reverse rotation proof is maintained by a predetermined static frictional force so that the window glass is not opened by an external force when the electric window device is kept under a static condition, and the second function that the worm gears are smoothly rotated with a small frictional force equal to or less than a maximum value of a dynamic frictional force while the dynamic frictional force is abruptly reduced during the rotation after the miniature electric motor is turned on to a dynamic friction from a static friction for keeping the reverse rotation proof. For example, an environmental temperature range of the miniature electric motor is in a range of −30° C. to +80° C.
According to the present invention, with the above-noted arrangement and composition, it is possible to always maintain the reverse rotation proof while always keeping a desired gear transmission efficiency in a wide environmental temperature range. As a result, it is possible to miniaturize a motor and also to increase a life cycle number to prolong service life of the motor. The miniature electric motor may be applied to an electric window device of an automotive vehicle.
REFERENCES:
patent: 2968999 (1961-01-01), Breton
patent: 3595789 (1971-07-01), Coshburn
patent: 3775317 (1973-11-01), Inami et al.
patent: 4396514 (1983-08-01), Randi
Kurata Junya
Shibuya Isao
Armstrong Westerman Hattori McLeland & Naughton LLP
Mabuchi Motor Co. Ltd.
Medley Margaret
LandOfFree
Miniature electric motor with reduction worm gear unit does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Miniature electric motor with reduction worm gear unit, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Miniature electric motor with reduction worm gear unit will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2504100