Patent ID: 12224643

DETAILED DESCRIPTION

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

A composite oil seal according to an embodiment may perform both an oil-sealing function and a grounding function for discharging current induced in a shaft to a motor housing, thereby preventing damage to a bearing due to static electricity.

Such a composite oil seal is realized merely by adding a grounding function to an oil seal, which is essentially mounted in a motor. Therefore, it is possible to completely resolve inconveniences in mounting a conventional ground ring.

FIG.1is a view showing a motor10to which a composite oil seal300having an electric corrosion prevention function according to an embodiment of the present invention is applied, andFIG.2is a cross-sectional view of the composite oil seal shown inFIG.1.

As shown in the drawings, a shaft15is mounted in a motor housing11constituting the motor10. The shaft15rotates in the state of being supported by a bearing13and transmits rotational torque to a reducer20. One end portion of the shaft15extends so as to be exposed to the outside of the motor housing11.

In addition, the composite oil seal300is located beside the bearing13.

The composite oil seal300includes a rigid frame305, a seal main body310, and an electrical path fabric330.

The rigid frame305is made of a rigid material such as metal. The seal main body310is formed of an elastic material, and is bonded to and supported by the rigid frame305. The seal main body310has an outer circumferential surface that is in contact with the inner circumferential surface of the motor housing11and at least one lip protruding inwards so as to be in contact with the outer circumferential surface of the shaft15.

The lip may include a main lip312and a dust lip314. The main lip312is a protruding portion that is located farther inward than the dust lip314and protrudes toward the outer circumferential surface of the shaft15. The main lip312resiliently presses the outer circumferential surface of the shaft to prevent leakage of a working fluid.

The dust lip314serves to block entrance of external foreign substances.

The main lip312has a pocket portion formed in the outer side portion thereof, and a spring320is mounted in the pocket portion. The spring320constricts the main lip312so that the main lip312is in tighter contact with the outer circumferential surface of the shaft.

The electrical1path fabric330functions to transmit electricity remaining in the shaft15in a direction indicated by the arrow a to discharge the electricity to the motor housing11. As described above, if electricity remains in the shaft15, the electricity leaks to the bearing13and thus causes the occurrence of arc, leading to damage to the bearing13.

The electrical path fabric330may be fixed to the seal main body310in a bonding manner. This means that the electrical path fabric330is capable of being applied to any of various general oil seals. It is possible to use an oil seal having only a sealing function not only as a general sealing element but also as a grounding element exhibiting a greatly improved grounding function merely by attaching the electrical path fabric330to the oil seal.

The electrical path fabric330is made by weaving metallic yarns. Accordingly, the shape or size of the electrical path fabric330may be varied freely. Since the electrical path fabric330is made by weaving metallic yarns, the electrical path fabric330is flexible, and thus is hardly worn by friction caused by contact with the shaft that rotates. Therefore, the electrical path fabric330has a longer lifespan than the oil seal.

As shown inFIG.3, the electrical path fabric330has a shape of a hollow disc having a shaft hole330aformed in the center thereof. The shaft hole330ais a hole through which the shaft15passes. The inner diameter of the shaft hole330ais smaller than the diameter of the shaft15, and the outer periphery of the electrical path fabric330is in contact with the inner circumferential surface of an opening11aformed in the motor housing11.

The metallic yarns forming the electrical path fabric330may be unit stainless yarns331and332, each of which is formed by combining a plurality of stainless yarns336, as shown inFIG.3(b). A fabric structure is formed by weaving the unit stainless yarns.

In this case, as shown inFIGS.3and5, the electrical path fabric330may be a twill fabric formed by weaving the unit stainless yarns in such a manner that warps331and wefts332cross each other. The twill fabric is referred to as a twill weave, which has diagonal twill lines on the surface thereof. For example, as shown inFIG.3(a), the twill fabric is composed of three warps and three wefts, and may be a 2-up and 1-down (2/1) or 1-up and 2-down (1/2) twill weave.

The twill fabric has various surface structures depending on variation in twill lines. Further, because the twill fabric has a small number of weave points, the threads thereof move freely, and thus the twill fabric is highly resistant to wrinkles and is flexible. For these reasons, the twill fabric is suitable for the electrical path fabric330.

Alternatively, as shown inFIG.4, the electrical path fabric330according to the present invention may be a plain weave formed by weaving the unit stainless yarns in such a manner that a warp and a weft cross over and under one another.

The shaft hole330aand the outer peripheral portion330bof the electrical path fabric330may be formed through a cutting process using a laser or a knife.

Meanwhile, the electrical path fabric may be coated with a protective film339made of a conductive coating material. The protective film339prevents the metallic yarns of the electrical path fabric from unraveling after the shaft hole and the outer peripheral portion of the electrical fabric is formed through a cutting process.

In this case, the protective film339may be made of a polyimide or silicone coating liquid. The protective film339may be coated on the electrical path fabric through impregnation of the electrical path fabric with the coating liquid or by spraying the coating liquid onto the electrical path fabric.

The electrical path fabric330may be formed such that the center portion thereof is adhered to the seal main body310, one end thereof is in contact with the inner surface of the motor housing, and the other end thereof is in contact with the outer surface of the shaft.

According to the present invention, since the electrical path fabric is manufactured through processes of weaving and cutting metallic yarns and is attached to the seal main body, the electrical path fabric may be used irrespective of the diameter of the shaft or a gap between the shaft and the inner circumferential surface of the motor housing. Because the inner diameter of the conventional shaft ground ring is not adjusted, the conventional shaft ground ring has poor versatility. That is, if the conventional shaft ground ring does not fit the specifications of the shaft, it is impossible to mount the same to the shaft.

As is apparent from the above description, the composite oil seal having an electric corrosion prevention function of the present invention configured as described above transmits current induced in a shaft to the outside while performing a basic sealing function in the state of being mounted to the shaft, thereby preventing damage to a bearing, preventing electrical defects of a motor, and increasing the lifespan of the motor.

In addition, since the electrical path fabric is made of a low-priced fiber material, the electrical path fabric may be used semi-permanently, and it may not be necessary to machine a motor housing in order to mount the electrical path fabric.

In addition, since elongation of the electrical path fabric is increased in both the circumferential direction and the radial direction about the center of the seal main body, the durability and electrical conductivity thereof are increased.

In addition, it is possible to ensure oil sealing and to prevent electric corrosion using the integrated-type oil seal without using a conventional high-priced shaft ground ring (SGR). Accordingly, it is economical.

In addition, since it is not necessary to mount the shaft ground ring (SGR), the size of an available space in the motor is increased, the assemblability thereof is improved, and the weight thereof is reduced.

Although specific embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions, and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.