Sealing device

[0002] This is a Divisional of application Ser. No. 08/882,952 filed Jun. 26, 1997 now U.S. Pat. No. 6,102,409 granted Aug. 15, 2000.

[0003] The present invention relates to a sealing device to be used for sealing a shaft of, for example, a cooling water circulating pump (water pump) in an automobile.

[0004] Heretofore, a mechanical seal has generally been used in a seal portion of a cooling water circulating pump in an automobile.

[0005] With the mechanical seal, however, various noises are generated during idling of the automobile because the seal portion is formed as a sliding surface.

[0006] Additionally, the mechanical seal causes an increase of the manufacturing cost because it includes many portions to be precision-machined.

[0007] It is an object of the present invention to provide a sealing device capable of preventing the generation of the aforesaid noises and capable of reducing the manufacturing cost.

[0008] The sealing device of the present invention has a first sealing lip made of rubber and slidable with respect to a shaft and a second sealing lip made of resin and slidable with respect to the said shaft, with a lubricant being held between the first and second sealing lips.

[0009] It is preferable that a spiral groove be formed in the first and/or the second sealing lip, whereby, during rotation of the shaft, the spiral groove if formed in the second sealing lip prevents a fluid from flowing downward. When the shaft is at a standstill, the fluid leaks along the groove because the second sealing lip of a second seal is made of resin and hence the shape of the groove remains intact. However, since the shaft is sealed by a first seal, the fluid is prevented from flowing out downward.

[0010] As the resin there usually is employed a fluorine series inelastic resin such as Teflon for example. As the rubber there is used an elastic body such as, for example, nitrile rubber, acrylic rubber, fluorine-contained rubber, or silicone rubber.

[0011] Since the first sealing lip is made of rubber and the second sealing lip is made of resin, the second sealing lip is more rigid than the first sealing lip. Therefore, the second sealing lip does not undergo any excessive deformation even at an elevated pressure. Thus, it is possible to improve the pressure resistance.

[0012] If the first sealing lip is provided on the side to be sealed by the second sealing lip, variations in pressure against the second sealing lip are diminished and the amount of cooling water (hereinafter referred to as “LLC”) and a foreign matter flowing to the second sealing lip is decreased. As a result, it is possible to attain not only improvement of the pressure resistance but also prevention of wear of both second sealing lip and the shaft.

[0013] Further, since a lubricant is held between the first and second sealing lips, the lubricant is fed effectively to the space between the front end portion of the first sealing lip and the sealing surface of the second sealing lip, so that it is possible to diminish the sliding resistance and improve the wear resistance, with no generation of noise.

[0014] Since the first and second sealing lips are made of rubber and resin, respectively, and there is used a lubricant, it is possible to reduce the manufacturing cost without the need of going through such a precision machining as in the prior art.

[0015] If spiral concaves and convexes are formed on the sealing surface of the first sealing lip, the fluid which has entered under a screw pump action during rotation of the shaft can be excluded to the side to be sealed, so that it is possible to enhance the sealability.

[0016] If spiral concaves and convexes are formed on the sealing surface of the second sealing lip, the fluid which has entered under a screw pump action during rotation of the shaft can be excluded to the side to be sealed, and therefore it is possible to enhance the sealability.

[0017] If the seal portion of the first sealing lip is made generally arcuate in section, an oil film formed between the seal portion and the shaft becomes thicker, whereby not only the wear resistance can be improved but also it is possible to prolong the service life.

[0018] It is preferable that a textile cloth be provided on the sealing surface of the first sealing lip. In the case where the fluid to be sealed is LLC having a high content of water, it is difficult to hold a highly lubricative oil component on the sliding surface of the seal portion, with a likelihood of resulting in deteriorated wear resistance. However, in the presence of a textile cloth, since a lubricant is held in the gaps of the textile cloth, the sealing surface of the first sealing lip slides while forming a thin film of the lubricant. As a result, durability can be improved.

[0019] The textile cloth is impregnated with rubber, then is fed into a mold and is bonded to the first sealing lip simultaneously with vulcanization molding of the first sealing lip. The rubber comes to be present in a crosslinked state within the textile cloth.

[0020] By such a structure of the first sealing lip, a sealability of the sealing surface can be ensured by the rubber, the strength of the sealing lip can be improved by the textile cloth, and the wear resistance can be improved by the lubricant held in the gaps of the textile cloth and the rubbery elastomer.

[0021] The term “rubber” is used herein in a broad sense covering various rubbery elastic bodies.

[0022] Embodiments of the present invention will be described hereinunder with reference to the accompanying drawings, in which:

[0023] FIG. 1 is a sectional view showing a principal portion of a sealing device according to the first embodiment of the present invention;

[0024] FIG. 2 is a sectional view of the sealing device of FIG. 1 as attached to a shaft of a water pump;

[0025] FIG. 3 is a sectional view showing a principal portion of a sealing device according to the second embodiment of the present invention;

[0026] FIG. 4 is a sectional view showing a principal portion of a sealing device according to the third embodiment of the present invention; and

[0027] FIG. 5 is a sectional view showing a principal portion of a sealing device according to the fourth embodiment of the present invention.

[0028] FIG. 1 shows a sealing device 1 embodying the present invention.

[0029] The sealing device 1 has a first seal 30 integral with a cylindrical reinforcing ring 20, a seal holding member 40, a second seal 50, and a third seal 60.

[0030] The reinforcing ring 20, which is metallic, is provided with a stepped inward flange 22 on the side (upper side in the figure) to be sealed of a cylindrical portion 21. Also on the side (lower side in the figure) opposite to the side to be sealed there is formed an inward flange 23. The outer periphery of the cylindrical portion 21 of the reinforcing ring 20, the outside surface of the inward flange 22 and the inner end portion of the inward flange 22 are covered with the first seal 30 which is formed of rubber.

[0031] The inner end portion of the inward flange 22 is formed with a first sealing lip 31 as an auxiliary sealing lip extending to the inner side to be sealed and is also formed with a sub lip 32 extending in parallel with the first sealing lip 31.

[0032] In the illustrated embodiment, the first seal 30, the first sealing lip 31 and the sub lip 32 are constituted as an integral body.

[0033] Outside the first sealing lip 31 is mounted an annular spring 33 which urges the first sealing lip inward. By means of the spring 33 a front end portion 31aof the first sealing lip 31 is brought into slidable contact with the outer periphery of a shaft 3 at a predetermined pressure to exhibit a sealing function.

[0034] It is optional whether the sub lip 32 is to be cotacted or not contacted with the outer periphery of the shaft 3. As will be described later, the sub lip 32 functions to hold grease between the first sealing lip 31 and a second sealing lip 52.

[0035] An outer portion 51 of the second seal 50 and a third seal 60, which will be described later, are fixed to the inner periphery of the reinforcing ring 20 in a caulked manner by means of the seal holding member 40, which is metallic and generally V-shaped in section, and the inward flange 23 of the reinforcing ring 20.

[0036] The second seal 50 is formed of a fluorine series inelastic resin, say PTFE, and the whole thereof is in a generally annular shape. The inner end portion of the second seal 50 is integrally formed with the second sealing lip 52 as a main sealing lip extending in the direction to be sealed. On a sealing surface 52aof the second sealing lip 52 are formed spiral concaves and convexes, whereby, during rotation of the shaft 3, a fluid which has entered under a screw pump action is excluded to the side to be sealed, thereby enhancing the sealability. The spiral concaves and convexes are not limited to such a multi-spiral shape as shown in FIG. 1. Even a single and continuous spiral will do. There is no limitation if only it is possible to prevent downward flow and leak of grease 4 during rotation of the shaft 3.

[0037] The third seal 60 is a rubber seal baked integrally to a metallic reinforcing ring 61 of a rectangular section. The third seal 60 covers the end face on the side to be sealed of the reinforcing ring 61 and an inner end portion thereof. At the inner end portion of the third seal 60 is formed a third sealing lip 62 extending inward. The third sealing lip functions to prevent the entry of dust. The front end of the third sealing lip 62 is not limited to such a shape as shown in FIG. 1 wherein the said front end is bent to the side to be sealed. It may be bent to the side opposite to the to-be-sealed side.

[0038] FIG. 2 illustrates the sealing device 1 of FIG. 1 as attached to the water pump shaft 3.

[0039] An outer peripheral portion of the first seal 30 is fitted in the inner surface of a housing 2.

[0040] The space defined by the shaft 3, the front end portion 31aof the first sealing lip 31 and the sub lip 32, the spaced defined by the shaft 3, the sub lip 32 and the second sealing lip 52, and the space defined by the shaft 3, the second sealing lip 52 and the third sealing lip 62, are filled with grease 4 as a lubricant.

[0041] The following description is now provided about the function of the sealing device illustrated in FIGS. 1 and 2.

[0042] The sealing device 1 includes a combination of the first sealing lip 31 made of rubber and the second sealing lip 52 made of resin (say PTFE). The second sealing lip 52 mainly fulfills a sealing function. The first sealing lip 31 functions to temporarily prevent the entry of LLC and a foreign matter contained therein and also functions to hold grease between the first and second sealing lips 31, 52.

[0043] With the above construction, it is possible to attain the reduction of the manufacturing cost without the need of precision machining for components which has been required in the conventional mechanical seal.

[0044] The second sealing lip 52 made of say PTFE is small in sliding resistance and possesses rigidity, so even at an elevated pressure there is no fear of seizure or deformation and it is possible to improve the pressure resistance.

[0045] Moreover, since the first sealing lip 31 is disposed on the to-be-sealed side of the second sealing lip 52, it is possible to diminish variations in pressure against the second sealing lip 52. Consequently, it is possible to improve the pressure resistance.

[0046] Further, extending the inward flange 22 of the reinforcing ring 20 up to a position near the outer periphery of the shaft 3 as in the illustrated embodiment is advantageous in that even at an elevated pressure there is no fear of easy deformation of the first seal 30 and it is possible to further improve the pressure resistance.

[0047] The space defined by the shaft 3 and the first and second sealing lips 31,52, and the space defined by the shaft 3 and the second and third sealing lips 52,62, are filled with grease 4, and the grease 4 is fed effectively to the front end portion 31aof the first sealing lip 31 and also to the sealing surface 52aof the second sealing lip 52. Therefore, it is possible to diminish the sliding resistance and improve the wear resistance, with no generation of such noise as mechanical noise.

[0048] Constituting the second sealing lip 52 with such a resin as PTFE is advantageous over the use of rubber in that there are attained improvement in both wear resistance and chemicals resistance.

[0049] As mentioned above, moreover, since the amount of LLC and a foreign matter contained therein reaching the second sealing lip 52 is decreased by the first sealing lip 31 made of rubber, it is possible to prevent wear of the second sealing lip 52 and that of the shaft 3.

[0050] By forming the front end portion 31aof the first scaling lip 31 in an arcuate shape in section, the contact pressure of the front end-portion 31adecreases and the thickness of an oil film formed between the front end portion 31aand the shaft 3 becomes thicker, so that not only it is possible to improve the wear resistance but also the service life of the sealing lip can be prolonged.

[0051] Since the entry of dust or the like and the leak of grease 4 can be prevented by the third sealing lip 62, it is possible to prevent damage and wear of the second sealing lip 52 and improve the sealing function.

[0052] Although the above description is directed to the case where the sealing device embodying the present invention is applied to the shaft 3 of water pump, the invention is not limited thereto.

[0053] FIG. 3 illustrates a sealing device 100 according to the second embodiment of the present invention.

[0054] As to the same portions as in the first embodiment are indicated by the same reference numerals as in the first embodiment and explanations thereof are here omitted.

[0055] The sealing device 100 of the second embodiment uses a first sealing lip different from that used in the sealing device 1 of the first embodiment.

[0056] The first sealing lip, indicated at 131, used in the sealing device 100 has a sharp front end portion 131a, with spiral concaves and convexes being formed on a sealing surface 131b, whereby, during rotation of the shaft 3, a fluid which has entered the body of the sealing device 100 is discharged to the exterior of the body by virtue of a screw pump action. Thus, it is possible to further improve the sealing performance.

[0057] The spiral concaves and convexes are not limited to such a multi-spiral shape as shown in FIG. 3. Even a single and continuous spiral will do.

[0058] FIG. 4 illustrates a sealing device 200 according to the third embodiment of the present invention.

[0059] The same portions as in the first embodiment arc indicated by the same reference numerals as in the first embodiment and explanations thereof are here omitted.

[0060] The sealing device 200 of the third embodiment uses a first sealing lip different from that used in the sealing device 1 of the first embodiment.

[0061] The first sealing lip, indicated at 231, of the sealing device 200 has a sharp front end portion 231a, and a reinforcing member 233 formed of an inelastic resin, say PTFE, is baked to the sealing surface of the first sealing lip, whereby it is possible to improve the wear resistance of the first sealing lip 231.

[0062] FIG. 5 illustrates a sealing device 300 according to the fourth embodiment of the present invention.

[0063] The same portions as in the first embodiment are indicated by the same reference numerals as in the first embodiment and explanations thereof are here omitted.

[0064] The sealing device 300 permits a more positive lubrication with grease 4 between a sliding surface of a first sealing lip 301 and that of the shaft 3 which is in opposed abutment with the sliding surface of the first sealing lip. Even in the case where the fluid to be sealed is one containing much water such as LLC for example, it is possible to prevent breaking of an oil film at the lip front end portion and improve the durability.

[0065] In the sealing device 300, a textile cloth 302 is bonded to the sealing surface on the grease holding side of the first sealing lip 301.

[0066] As the textile cloth 302 there may be used a so-called nonwoven cloth or a fabric obtained by using strong fibers. The textile cloth is applied to impregnated with a petroleum solvent solution (rubber cement) which contains several percent of a rubber component and which is utilized for bonding rubber. Alternatively, a powdery rubber component is deposited on the textile cloth. Thereafter, the textile cloth is placed in a mold for molding the first sealing lip 301 and is bonded to the first sealing lip simultaneously with vulcanization molding of the same sealing lip, to form the structure shown in FIG. 5. Now, rubber is present in a crosslinked state in the interior of the textile cloth.

[0067] The textile cloth 302, by the action of the rubber present in the interior thereof, exhibits the sealability of its sealing surface to the same extent as that of the sealing surface not provided with the textrile cloth.

[0068] Further, there can be attained improvement of strength by the textile cloth and improvement of wear resistance by the lubricant held in the gaps of the textile cloth and rubber.

[0069] Also in this fourth embodiment, as in the first embodiment illustrated in FIG. 2, the grease 4 is sealed in the space defined by the shaft 3 and the first and second sealing lips 301,52 and in the space defined by the shaft 3 and the second and third sealing lips 52,62, and the grease is fed to and held at a front end portion 301aof the first sealing lip as the front end portion of the textile cloth 302 and between the sealing surface 52aof the second sealing lip 52 and the shaft 3.

[0070] In the present invention, a first sealing lip made of rubber and a second sealing lip made of resin are combined slidably with respect to a shaft of a water pump for example. Thus, the second sealing lip is more rigid than the first sealing lip, so even at an elevated pressure there is no fear of deformation and it is possible to improve the pressure resistance.

[0071] Besides, since the first sealing lip is provided on the side to be sealed of the second sealing lip, not only variations in pressure against the first sealing lip are diminished but also the amount of LLC and a foreign matter reaching the second sealing lip is reduced. Thus, it is possible to attain both improvement of the pressure resistance and prevention of wear of the second seating lip and the shaft.

[0072] Further, with a lubricant held between the first and second sealing lips, the lubricant is fed effectively to between the front end portion of the first sealing lip and the sealing surface of the second sealing lip, whereby the sliding resistance can be diminished and the wear resistance can be improved, with no generation of such noise as mechanical noise.

[0073] Since there are provided the second sealing lip made of resin, the first sealing lip made of rubber, and the lubricant held between the first and second sealing lips, such a precision machining as in the prior art is not required, and it is possible to reduce the manufacturing cost.

[0074] Since spiral concaves and convexes are formed on the sealing surface of at least one of the first and second sealing lips, fluid can be excluded to the side to be sealed by the action of a screw pump during rotation of the shaft. That is, the sealability can be enhanced.

[0075] By forming the seal portion of the first sealing lip generally in an arcuate shape in section, the thickness of an oil film formed between the seal portion and the shaft becomes larger, so that not only the wear resistance can be improved but also it is possible to prolong the service life.

[0076] With a textile cloth provided on the sealing surface of the first sealing lip, since a lubricant is held in small gaps of the textile cloth, the sealing surface of the first sealing lip slides while forming a thin film of the lubricant, whereby the durability can be improved.

[0077] Further, when rubber is present in a crosslinked state within the textile cloth, the sealability of the sealing surface can be kept high by the rubber, the strength of the sealing lip can be improved by the textile cloth, and wear resistance can be improved by the lubricant held in the gaps of the textile cloth and rubber.