GB2244527A

GB2244527A - Oil-seal structure of a motor

Info

Publication number: GB2244527A
Application number: GB9011923A
Authority: GB
Inventors: Yasushi Yoshida
Original assignee: Mitsuba Electric Manufacturing Co Ltd
Current assignee: Mitsuba Corp
Priority date: 1990-05-29
Filing date: 1990-05-29
Publication date: 1991-12-04
Anticipated expiration: 2010-05-29
Also published as: GB2244527B; GB9011923D0

Abstract

An oil-sealing structure of a motor including a bearing 9 supporting a motor shaft 5, and an oil seal 15 provided in the space between the motor shaft and a bracket 8 and positioned close to one end of the motor shaft while separated by a predetermined distance from the bearing. An outer peripheral surface of the motor shaft faces, within the space, an inner peripheral surface of the bracket. Steps are formed by recess 5b and oil stopper 19, on the motor-shaft outer peripheral surface and positioned between the bearing and the oil seal, with their diameter increasing in a stepped manner toward the bearing. A stepped groove 17 is formed on the bracket inner peripheral surface and positioned between the bearing and the oil seal, with its diameter decreasing in a stepped manner toward the bearing via stepped portions 16. An oil outlet channel 18 is also formed on the bracket inner peripheral surface for discharging oil which has penetrated beyond the oil seal. The structure is capable of highly secure prevention of oil penetration into the motor. <IMAGE>

Description

OIL-SEALING STRUCTURE OF MOTOR BACKGROUND OF THE INVENTION The present invention relates to an oil-sealing structure of a motor for, e.g., electrical equipment of a vehicle.

A motor of the above-mentioned type is generally such that the motor shaft is dipped in pump oil, as in the case of a motor connected with a pump for actuating an anti-lock brake (ALB) system. The inside of such a motor must be protected from penetration of oil. For this purpose, as shown in Fig. 3, a double oil-sealing structure is adopted, in which, in addition to an oil seal, an oil stopper is provided. However, this structure is still insufficient because it fails to block a small amount of oil which inevitably penetrates into the motor by flowing along the motor shaft.

SUMMERY OF THE INVENTION In view of the above-described circumstances, the present invention has been accomplished in order to provide an oil sealing structure of a motor which is capable of eliminating the above-described problem.

According to the present invention, there is provided an oil-sealing structure of a motor having a motor shaft, a bracket, a bearing provided in the space between the motor shaft and the bracket to support the motor shaft, and an oil seal provided in the space and disposed at a position close to one end of the motor shaft and separated by a predetermined distance from the bearing.The oil-sealing structure comprises: an outer peripheral surface of the motor shaft and an inner peripheral surface of the bracket which face each other within the space; steps formed on the outer peripheral surface of the motor shaft and at a position between the bearing and the oil seal, the diameter of the steps increasing in a stepped manner toward the bearing; a stepped groove formed on the inner peripheral surface of the bracket and at a position between the bearing and the oil seal, the diameter of the stepped groove decreasing in a stepped manner toward the bearing; and an oil outlet channel formed on the inner peripheral surface of the bracket for discharging oil which has penetrated beyond the oil seal.

According to the present invention, the above-specified structure is capable of highly secure prevention of oil penetration to the inside of the motor.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a sectional side view of a motor, showing one embodiment of an oil-sealing structure according to the present invention; Fig. 2 is an enlarged sectional view of essential parts of the structure; and Fig. 3 is a view corresponding to Fig. 2, showing a conventional oil-sealing structure of a motor.

DESCRIPTION OF THE PREFERRED EMBODIMENT One embodiment of the present invention will now be described with reference to the drawings.

Referring to Fig. l, reference numeral 1 denotes a motor for driving a pump which actuates an ALB system. The motor 1 includes, as has been conventionally known, a motor yoke 2, a permanent magnet 3, a rotor 4, a. motor shaft 5, a commutator 6, and a brush 7.

The motor shaft 5 is rotatably supported by bearings 9 which are mounted on the motor yoke 2 and an end bracket 8 integrally assembled onto the yoke 2. One end 5a of the motor shaft 5 projects through the end bracket 8, and a crank shaft 10 is eccentrically connected to this end 5a.

The crank shaft 10 is also connected, through a bearing 11, to a con'rod 13 of a piston 12. Members, such as these, which constitute a pump section P are accommodated in a pump yoke 14. The pump yoke 14 is assembled onto that side of the end bracket 9 which faces the pump section P. The interior of the pump yoke 14 is filled with brake oil.

Referring to Fig. 2, an inner peripheral surface of the end bracket 8, across which the motor shaft 5 extends, is formed with a portion 9a receiving the bearing 9, as well as a portion l5a receiving an oil seal 15. The receiving portion 9a is on the side of the inner peripheral surface which is close to the motor 1, while the receiving portion 15a is separated from the portion 9a by a predetermined distance, and is on the side close to the pump section P.

The oil seal 15, of which the inner periphery is in sliding contact with the motor shaft 5, is fitted in the receiving portion 15a. Between the bearing 9 and the oil seal 15, a part of the inner peripheral surface of the end bracket 8 faces an outer peripheral surface of the motor shaft 5. The end-bracket inner peripheral surface has first to third stepped portions 16 formed thereon, the diameter of the portions 16 decreasing in a stepped manner toward the bearing 9. The stepped portions 16 constitute a stepped annular groove 17 around the motor shaft 5. The end bracket 8 is also formed with an oil outlet channel 18 which extends downward, as viewed in Fig. 2, communicating the annular groove 17 with an oil tank, not shown, disposed outside the end bracket 8.

On the other hand, the outer peripheral surface of the motor shaft 5 which faces the above-described inner peripheral surface of the end bracket 8 has a recess 5b formed thereon positioned close to the oil seal 15. A cylindrical oil stopper 19 is fitted on the motor shaft 5 and positioned slightly distant from the recess 5b. The oil stopper 19 has a funnel-shaped peripheral edge 19a which is on the side close to the bearing 9, the edge 19a diverging toward the bearing 9.Thus, on the outer peripheral surface of the motor shaft 5, the rising inner wall of the recess 5b on the side close to the bearing 9, the end face of the oil stopper 19 on the side close to the oil seal 15 which forms a step rising from the shaft 5, and the diverging peripheral edge 19a of the stopper 19 together form steps which make the outer peripheral surface of the motor shaft increase in diameter toward the bearing 9.

In the embodiment of the present invention having the above-described construction, the inside of the pump yoke 14 and the inside of the motor 1 are sealed from each other by the oil seal 15 provided in the end bracket 8. However, a small amount of oil may enter the inside of the motor 1 by flowing along the motor shaft 5. In such cases, with the oil-sealing structure of the invention, the oil which has entered is prevented from reaching the bearing 9 by the recess 5b formed on the motor shaft 5 and the oil stopper 19 fitted thereon. The oil is further subjected to centrifugal force generated by the rotation of the motor shaft 5, whereupon the oil is blown radially outward to be received in the stepped annular groove 17 formed in the end bracket 8. Thereafter, the oil within the groove 17 is returned therefrom to the oil tank through the outlet channel 18.

In this way, according to the present invention, when a part of the oil in the pump section P has entered beyond the oil seal 15, the oil-sealing structure provides the following function. The oil which has entered is blocked, first by the rising inner wall of the recess 5b on the side of the bearing 9, and then by the end face of the oil stopper 19 on the side of the oil seal 15. Even when a small portion of the oil flows inward over the oil stopper 19, the peripheral edge 19a located on the side of the bearing 9 prevents further inward advancement. In brief, an outer peripheral surface of the motor shaft 5 which is formed by the above-described members has its diameter increasing in a stepped manner toward the bearing 9, thereby effectively preventing inward penetration of oil. The oil thus prevented from penetration and maintained on the outer peripheral surface of the motor shaft 5 is blown by centrifugal force caused by the rotation of the motor shaft 5 toward the annular groove 17 on the inner peripheral surface of the end bracket 8, to be received in the groove 17. Since the annular groove 17 is stepped and has its diameter decreasing in a stepped manner toward the bearing 9, the oil blown is positively received by the stepped surfaces of the first to third stepped portions 16 whose diameters decrease in a stepped manner. As a result, the amount of oil present on the inner peripheral surface of the end bracket 8 is decreased toward the bearing 9 until there is substantially no oil in the end.In brief, the inner peripheral surface of the end bracket 8 serves, in cooperation with the outer peripheral surface of the motor shaft 5, to enable highly secure prevention of oil penetration to the inside of the motor 1, thereby rendering the motor 1 free of oil adhered to the commutator 6, the brush 7, etc., hence, rendering it capable of exhibiting high reliability. The oil received in the annular groove 17 is discharged to the outside of the end bracket 8 by flowing through the channel 18. Accordingly, there is no risk that oil may remain in the end bracket 8. Another advantage is that it is possible to detect, from the amount of oil discharged, any damage or the degree of wear of the oil seal 15.

To summarize, the present invention has the following advantageous features.

Even when oil has entered beyond the oil seal, heading toward the bearing, the plurality of steps formed on the outer peripheral surface of the motor shaft, with diameters increasing in a stepped manner toward the bearing, serve to block the oil a number of times and securely.

When the oil is blown toward the inner peripheral surface of the bracket by centrifugal force generated by the motor shaft rotation, the stepped annular groove having its diameter decreasing in a stepped manner toward the bearing cause the oil to be received by the plurality of stepped surfaces of the groove a number of the times, so that the oil amount decreases toward the bearing until there is substantially no oil in the end. Thus, highly secure prevention of oil penetration into the motor is possible, thereby rendering the inside of the motor free from oil adhesion to various members, hence, rendering the motor highly reliable.

The oil in the groove is discharged to the outside of the bracket through the oil outlet channel. This is advantageous in that oil is prevented from remaining in the bracket, and that any breakage or the degree of wear of the oil seal can be detected from the amount of discharged oil.

Claims

What is claimed is:

1. An oil-sealing structure of a motor having a motor shaft, a bracket, a bearing provided in the space between said motor shaft and said bracket to support said motor shaft, and an oil seal provided in said space and disposed at a position close to one end of said motor shaft and separated by a predetermined distance from said bearing, said oil-sealing structure comprising: : an outer peripheral surface of said motor shaft and an inner peripheral surface of said bracket which face each other within said space; steps formed on said outer peripheral surface of said motor shaft and at a position between said bearing and said oil seal, the diameter of said steps increasing in a stepped manner toward said bearding; a stepped groove formed on said inner peripheral surface of said bracket and at a position between said bearing and said oil seal, the diameter of said stepped groove decreasing in a stepped manner toward said bearing; and an oil outlet channel formed on said inner peripheral surface of said bracket for discharging oil which has penetrated beyond said oil seal.

2. An oil-sealing structure of a motor substantially as hereinbefore described with reference to the accompanying drawings.