SEALING DEVICE

Abstract: A sealing device is adapted to be disposed between a stationary part (2) and a rotary shaft (1) in the stationary part (2) so as to provide a seal in the gap between the stationary (2) part and the rotary shaft (1). The sealing device has a slinger (3) secured to one of the stationary part and the rotary shaft and a rubber seal (5) secured to the other of the stationary part and the rotary shaft and provided with a lip (5a) which makes a resilient pressure contact with the slinger (3). When the rotation speed of the rotary shaft (1) is increased, centrifugal force is increased to cause a tendency to decrease the pressure of contact between the lip (5a) and the slinger (3) so that the wear of the lip is prevented to improve the durability of the sealing device. In addition, the resistance torque produced by the sealing device is not increased substantially even when the speed of rotation of the rotary shaft is increased.

Description: The present invention relates to a sealing device and, more particularly, to a sealing device which suffers from reduced wear and which is capable of improving sealing effect. In general, a sealing device is disposed between a stationary part and a rotary shaft such that the sealing device is penetrated by the rotary shaft so as to provide a seal in the gap between the rotary shaft and the stationary part. Figs. 3 to 5 illustrate the construction of a typical example of the sealing device of the kind described. The sealing device shown in these Figures has a slinger 43 composed of a tubular portion 43b through which the rotary shaft 41 extends and a radial portion 43a provided on one axial end of the tubular portion 43b and extending radially outwardly therefrom, and a rubber seal 45 which is disposed on the outer side of the tubular portion 43b of the slinger 43. The rubber seal 45 has a reinforcement member 44 embedded therein. The reinforcement member has a substantially L-shaped cross-section with one leg 44a thereof being directed towards the slinger 43. The rubber seal 45 has outer peripheral surface fitting in the bore in the stationary part 42, and is provided, at its portion near the end of the reinforcement member 44 adjacent the slinger 43, with a lip 45a contacting the radial portion 43a of the slinger 43 and a lip 45b which is directed towards the tubular portion 43b on the rotary shaft 41. In order to impart a high oil-gathering effect produced by the lips 45a and 45b, a spiral groove 46 starting at the center and terminating at the peripheral end is formed in the surface of the radial portion 43a of the slinger 43 facing the lip 45a. In operation, the slinger 43 rotates together with the rotary shaft 41 as a unit therewith, with the lip 45a of the rubber seal 45 keeping a sliding contact with the radial portion 43a of the slinger 43 thereby attaining a sealing effect. This known sealing device, however, suffers from the following disadvantages. In operation, the spiral groove 46 formed in the radial portion 43a of the slinger 43 serves to displace the oil radially outwardly during rotation of the slinger 43 as shown in Fig. 5. In addition, the pressure at which the lip 45a contacts with the slinger 43 is kept constant regardless of the rotation speed 41 of the rotary shaft 41. In consequence, the lip 45a is rapidly worn down due to sliding contact with the radial portion 43a of the slinger 43 during rotation of the rotary shaft 41, thus impairing durability of the sealing device, and the load torque is undesirably increased as the rotation speed increases. British Patent publication No. GB-A-2028440 discloses a sealing device having a flexible sealing ring for mounting on a shaft and sealing against a fixed element through which the shaft passes. However, the material of this sealing ring must be sufficiently hard to prevent excessive wear; therefore the sealing ring is not easily deformable by centrifugal force. The present invention aims to provide a sealing device in which the sliding frictional resistance between the lip and the slinger is reduced to suppress the wear of the lip. The present invention also aims to provide a sealing device in which the load torque produced by the sealing device is reduced during high-speed rotation of the rotary shaft. To this end, according to the present invention, there is provided a sealing device for disposal between a stationary part and a rotary shaft which extends through said stationary part, so as to provide a seal for the gap between said stationary part and said rotary shaft, said sealing device comprising a slinger and a rubber seal having a lip, characterised in that said rubber seal is adapted to be secured to said stationary part and includes a reduced-diameter outer peripheral portion for fitting in said stationary part, and a reinforcement member embedded therein, and in that said slinger is adapted for attachment to said rotary shaft, and includes a tubular member for attachment to said rotary shaft such that said rotary shaft extends through said tubular member, and a ring member connected to said tubular member through a resilient member, whereby, when said rotary shaft rotates, said lip of said rubber seal makes a sliding contact with said ring member of said slinger and said ring member is moved in the direction of axis of said rotary shaft due to centrifugal force so as to reduce the pressing force. Preferably, said ring member of said slinger is connected to said tubular member through said resilient member so as to be positioned radially outward of said tubular member. Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings, in which:- Fig. 1 is a sectional view of a first embodiment of the sealing device in accordance with the present invention, taken at a plane which includes the axis of a rotary shaft on which the sealing device is set; Fig. 2 is a sectional view of the sealing device shown in Fig. 1 in a state under the influence of centrifugal force generated as a result of high-speed rotation; Fig. 3 is a sectional view of a known sealing device; Fig. 4 is a bottom plan view of a slinger incorporated in the sealing device of Fig. 3; and Fig. 5 is an illustration of the relationship between the slinger and the rubber seal lip. Figs. 1 and 2 show a first embodiment of the sealing device in accordance with the present invention. The sealing device is composed of a slinger 3 and a rubber seal 5. The slinger 3 has a tubular member 14 through which a rotary shaft 1 extends, a ring member 13 on the radially outer side of the tubular member 14 and an resilient member 15 which interconnects the tubular member 14 and the ring member 13. The resilient member 15, which interconnects the ring member 13 and the slinger 14, does not extend in the direction perpendicular to the axis of the rotary shaft 1 but extends in a direction which is inclined at a predetermined angle to the direction which is perpendicular to the axis of the rotary shaft 1. The rubber seal 5 is provided with a reinforcement member 4 embedded therein. The reinforcement member 4 has a substantially L-shaped cross-section with its one leg 4a directed towards the tubular member 14 of the slinger 3. The rubber seal 5 surrounds the tubular member 14 of the slinger 3, and has a stepped outer peripheral surface the reduced-diameter portion 5d of which fits in the stationary part 2. The rubber seal 5 is provided at its portion adjacent to the slinger 3 with a lip 5a which resiliently contacts with the ring member 13 of the slinger 3 and also with a lip 5b which is directed towards the tubular member 14 of the slinger. In operation, the rotation of the rotary shaft 1 causes the ring member 13 of the slinger 3 to rotate in sliding contact with the lip 5a of the rubber seal 5 so as to provide a high sealing effect. As the speed of rotation of the rotary shaft 1 increases, the resistance torque tends to increase. In the sealing device of the invention, however, centrifugal force acts on the slinger 3 which rotates as a unit with the rotary shaft 1 so that the ring member 13 of the slinger 3 so as to be displaced from the position indicated by broken lines to the position shown by the solid lines in Fig. 2, overcoming the resilient force of the resilient member 15. Thus, the ring member 13 tends to move away from the lip 5a of the rubber seal 5. On the other hand, the lip 5a of the rubber seal 5 also deflects from the state shown by broken lines to the state shown by solid lines so as to be kept in contact with the ring member 13 of the slinger 3. In this state, however, the pressure of contact between the lip 5a and the ring member 13 is small as compared with the case where the speed of rotation of the rotary shaft 1 is low. It is therefore possible to maintain the resistance torque at a sufficiently low level even when the rotation speed of the rotary shaft 1 is increased. In addition, since only the reduced-diameter portion 5d of the rubber seal 5 fits in the stationary part 2 while the large-diameter portion 5c contacts with a side surface of the stationary part 2, the rubber seal 5 is prevented from moving axially even when a force is generated in the axial direction of the rotary shaft 1, thus preventing undesirable axial shift of the sealing device. The provision of the step on the outer peripheral surface of the rubber seal 5 is not essential. Namely, the rubber seal 5 may have a straight outer peripheral surface, i.e., only the reduced-diameter portion 5d which fits in the stationary part 2.

Claims: A sealing device for disposal between a stationary part (2) and a rotary shaft (1) which extends through said stationary part (2), so as to provide a seal for the gap between said stationary part (2) and said rotary shaft (1), said sealing device comprising a slinger (3) and a rubber seal (5) having a lip (5a), characterised in that said rubber seal (5) is adapted to be secured to said stationary part (2) and includes a reduced-diameter outer peripheral portion (5d) for fitting in said stationary part (2), and a reinforcement member (4) embedded therein, and in that said slinger (3) is adapted for attachment to said rotary shaft (1), and includes a tubular member (14) for attachment to said rotary shaft (1) such that said rotary shaft (1) extends through said tubular member (14), and a ring member (13) connected to said tubular member (14) through a resilient member (15), whereby, when said rotary shaft (1) rotates, said lip (5a) of said rubber seal (5) makes a sliding contact with said ring member (13) of said slinger (3) and said ring member (13) is moved in the direction of axis of said rotary shaft (1) due to centrifugal force so as to reduce the pressing force. A sealing device according to claim 1, wherein said ring member (13) of said slinger (3) is connected to said tubular member (14) through said resilient member (15) so as to be positioned radially outward of said tubular member (14).

Inventors: ANZUE, KAORU, ISOMOTO, JUN, TAKEI, NOBUO
Applicants: MITSUBISHI JIDOSHA KOGYO KABUSHIKI KAISHA, NOK CORPORATION
Application year: 1989
Main classification: F16J15
IPC codes: F16J15