GB2219475A

GB2219475A - Seal assembly for water pump bearing

Info

Publication number: GB2219475A
Application number: GB8910604A
Authority: GB
Inventors: Nobuhiko Miyake
Original assignee: NSK Ltd
Current assignee: NSK Ltd
Priority date: 1988-05-12
Filing date: 1989-05-09
Publication date: 1989-12-13
Also published as: KR890017461A; GB8910604D0; JPH01285699A

Abstract

A bearing seal assembly which is mounted between the rolling bearing (10, 25, 21; 26) and the mechanical seal 27 of a water pump bearing includes first and second seal members 41, 44 forming a labyrinth seal unit. The first labyrinth seal members 41 includes a cylindrical portion 42 and at least one annular fin 43 extending radially from the cylindrical portion, and is mounted on the rotary shaft 10 of the water pump bearing. The second labyrinth seal member 44 includes a cylindrical portion 45 and at least two annular fins 46 extending inwardly radially from the cylindrical portion 45. The second seal member 44 is mounted on the inner surface of a housing 30 so that the fins 43, 46 of the first and second seal members are interdigitated. Instead of extending radially, the seal members can be orientated so that the fins extend axially, Fig. 4 (not shown). <IMAGE>

Description

SEAL ASSEMBLY FOR WATER PUMP BEARING The present invention relates to the seals of the water pump bearing for automobiles, and in particular, to a seal assembly of improved sealing property.

Typically, a water pump comprises a shaft with a driven pulley on one end and a water impeller on the other. The shaft rotates within a liner and is spaced from this liner by rollers or balls rolling within a lubricated space. This space and its lubricant are sealed off at each end by a rubber seal rotary with the shaft and sliding inside the liner.

Although the impellers are mechanically sealed from the drive shaft. some water always penetrates behind the impeller. Conveniently, therefore, a deflector plate is located around the shaft so that water reaching the shaft is barred by the plate and is flung outward by centrifugal force into peripheral drainage ports.

There is always however a gap between the edge of this plate and the surrounding housing, so that some water always arrives behind the plate, and some of this will penetrate the end seals. This gap cannot effectively be sealed. Also, with the current demand for smaller, i.e. shorter pumps, and thus smaller zones between the impeller and bearing, the problem of water contamination and loss of lubricant effect is more noticeable still.

The present invention sets out to solve the above problems and provide a bearing seal assembly for a water pump having a sealing function of higher performance due to a staggered type labyrinth structure.

The invention consists in a bearing seal assembly for a water pump; the water pump comprising a driven shaft carrying an impeller and surrounded by rotary units located within a stationary bearing member inside a pump shaft housing there already being (a) a mechanical seal adjacent the impeller and (b) sealing pieces, spaced therefrom, sealing between the shaft and the stationary bearing member to enclose the rotary units; the bearing seal assembly being located in the space between the mechanical seal and the nearer sealing piece and having a labyrinthine nature.

In one form, such an assembly may comprise a first generally circular labyrinth seal member attached to the shaft, with at least one annular fin extending radially from the shaft and a second generally circular labyrinth seal member comprising at least two fins attached to and extending inwardly from the pump shaft housing, fins of the first1 rotary, labyrinth seal member being received within those of the second, stationary labyrinth seal member.

For convenience, at least one (preferably the second) of said labyrinth seal members may be divided into halves about a plane containing when assembled the central shaft axis. The two halves can be assembled in use by a surrounding 0- ring or elastic band. The contacting faces of the two halves may comprise respectively one or more locating projections and one or more complementary localising recesses.

In another form, the assembly may comprise a first generally cylindrical labyrinth seal member attached to the shaft with at least one cylindrical fin extending lengthwise, and a second generally cylindrical labyrinth seal member comprising at least two cylindrical fins extending lengthwise and attached to be stationary in respect of the stationary bearing member, fins of the first, rotary, labyrinth seal member being received within those of the second, stationary, labyrinthine seal member in use.

The second (stationary) labyrinthine seal member may in either case be firmly attached to the stationary bearing member inside the pump shaft housing.

In the seal device in the invention, the labyrinth unit formed by combining the first labyrinth seal member and the second labyrinth seal member can be inserted and fitted in an annular space between the housing and the rotary shaft before assembly into the water pump.

The invention will be further described with reference to the accompanying drawings, which: Figure 1 is a longitudinal section of part of a water pump showing a first embodiment of bearing seal assembly; Figure 2A is aside view from the joining face of one of the two halves of a second seal member; Figure 2B is a front view of the half seal member of Fig. 2a; Figure 3 is a longitudinal section of part of a water pump showing a second embodiment of bearing seal assembly Figure 4 is a longitudinal section of part of a water pump showing a third embodiment of bearing seal assembly; Figure 5 is a longitudinal section of a prior art water pump showing the general arrangement of bearing and seals; and Figure 6 is a longitudinal section, analogous to Figures 1, 3 and 4 of prior art bearing seals as used in Figure 5.

It will be found convenient to describe firstly the prior art water pump, and its bearings and seal, as shown in Figures 5 and 6 respectively.

The prior art water pump for automobiles as shown in Figure 5 has a rotary shaft 10 with an impeller 2 at one axial end. The shaft 10 is supported by a housing 30 via a rolling bearing 20, a drive pulley seat 4, press fitted at the other end of the rotary shaft 10, carries a driving pulley 5. This pulley is coupled by an endless belt to a crankshaft of an engine, but none of these components are shown.

The bearing 20 has an outer stationary bearing member as a liner or ring 21 fitted into the housing 30, and rotary units including a single row of cylindrical rollers 23 and a single row of balls 25, which are respectively held and guided by retainers 22 and 24, disposed between the outer stationary bearing member 4, aroung the rotary shaft 10. The rotary shaft 10 itself thus functions as an inner ring for these rotary units.

For sealing a water pump bearing 20, seal pieces 26 are fastened within the outer ring 21 at opposite ends thereof and slidingly contact the outer surface of the rotary shaft 10 thereby to seal off a lubricant (such as oil or grease) contained inside the water pump bearing 20, as shown on an enlarged scale in Figure 6.

Furthermore, and also within the housing 30, a mechanical seal 27 (the detailed structure of which is not shown) is attached to the inner surface between the bearing 20 and the impeller 2 to seal between pump chamber 3 and the pump bearing 20, and moreover, a deflector (or slinger) 28 having an L-shaped cross section is fixed to a shoulder of rotary shaft 10 thereby further to provide a barrier effective in use between the mechanical seal 27 and the pump bearing 20.

In the prior art water pump described. any arrival of water at the inside of the housing 30 from the pump chamber 30 is interrupted first by the mechanical seal 27. Any water passing through the mechanical seal 27 is received by the deflector 28 and deflected outwardly in a radial direction due to centrifugal force. The deflected water is discharged by a drain hole 31 in the housing 30.

The deflector 28 thus functions to prevent water from approaching the water pump bearing 20.

However, it is impossible to completely interrupt the intrusion of water through the gap between the deflector 28 and the housing 30. As a result, water will enter the bearing and service life will be reduced due to deterioration of the lubricant sealed therein.

In more recent designs of pump, the axial distance between the water pump bearing 20 and the mechanical seal 27 has been decreased due to requirements for compact and light weight automobile engines. The water pump bearing is then in an environment wherein it tends to be influenced by water more than before.

To turn now to the present invention, Figure 1 is analogous to Figure 6. However, labyrinth seal members generally referenced at 40 are mounted between the water pump bearing and the mechanical seal 27 (like parts in Figures 1 and 6 are designated by like numerals, and descriptions thereof are omitted).

The labyrinth members 40 comprise a first seal member 41 fitted to rotary shaft 10, a second seal member 44 fitted to housing 30, both seal members 41 and 44 being molded in a material such as synthetic polymer or rubber.

The first seal member 41 has a cylindrical portion 42 reinforced by a metal core 42, and three equispaced annular fins 43 all molded as a unitary body.

The second seal member 44 has a cylindrical portion 45, and three annular fins 46 extending inwardly at equal axial intervals to and intercalated with fins 43.

An attachment portion 47 is formed at an axially inner end of the cylindrical portion 45, and a peripheral groove 48 is formed around the outer surface of the cylindrical portion 47.

The second seal member 44 is constituted as two halves 44a, divided by a plane containing the center axis of the cylindrical portion 45. Figs. 2A and 2B show one of the two halves. One half member 44a has projections at the joining surface, and the other half member (not shown) has complementary recesses, the recesses being engageable with the projections 49 upon proper assembly.

To assemble this labyrinthine seal assembly the first seal member 41 and the second seal member 44 are combined in such a way that the fins 46 of each half of the second seal member 44 are respectively inserted in recessed between the fins 43 of the first seal member 41. Then the joining surfaces of the two halves 44a of the second seal member 44 are engaged with each other.

Then an O-ring or a rubber band 50 is fitted into the peripheral groove 48 of the second seal member 44 so as to couple the two halves 44a firmly together.

The labyrinth members 40 are thus combined as a unit which is first assembled to the outer ring 21 of the water pump bearing 20 by fitting the attachment portion 47 of the second seal member 44 into a groove 21a provided in the outer ring 21 for that purpose. The assembly of the outer ring 21 and the labyrinth unit 40 is then inserted in the space between the housing 30 and the rotary shaft 10 and fitted to the inner surface of the housing 30, as the first seal member 41 becomes fitted around the outer surface of the rotary shaft 10.

The labyrinth unit 40 comprises three labyrinths of a staggered shape formed by the fins 43 and 46. As a result, a seal having a very high sealing effect is achieved due to the multiplication effect of substantially extending the axial distance between the water pump bearing 20 and the mechanical seal 27. The water arriving at the inside of the housing 30, i.e.

passing the mechanical seal 27 is thus essentially prevented from entering towards the bearing 20.

Furthermore, the 0 ring 50 seals between the housing 30 and second seal member 44, so that any water leaking through the mechanical seal 27 cannot enter towards the bearing 20 via the outer periphery of the laybrinth unit 40.

Figure 3 shows a second embodiment of seal, similar to that of Figure 1.

In this embodiment, a first seal member 410 of a labyrinth unit 400 includes a cylindrical portion 420, and a single annular fin 430 extending from one end of the cylindrical portion 420. The cylindrical portion 420 and the fin 430 are formed integrally e.g. out of metal. A second seal member 440 is of a similar structure to member 44 in the first embodiment except that the second has only two annular fins 460 extending from the cylindrical portion 420.

In this embodiment, the assembled labyrinth seal unit 400 has one labyrinth of a staggered shape formed therein.

Alternatively (but not shown) first and second seal members may be formed so that the fins 430 and 460 extend in the converse directions to those of the first and second seal members 410 and 440. That seal member then having the shape of the second seal member 44 i.e.

having fins extending radially is formed integrally and fitted to the rotary shaft 10. The other seal member having the shape of the first seal member 41 can be formed in two halves and fitted to the housing 30.

Furthermore, in each of the above embodiments, the first seal member 41 or 410 may if desired be formed in two halves, in which case the second seal member 44 or 440 may be formed integrally.

Figure 4 shows a third embodiment of a seal similar to that of Figure 1. Identical parts to those shown in Figure 1 are again indicated by identical reference numerals.

On Figure 4 a labyrinth unit 60 comprises a first seal member 61 and a second seal member 64. The first seal member 61 fits on a rotary shaft 10 and includes an annular portion 62, and three equispaced cylindrical fins 63. A portion of the inner fin 63 and a portion of the annular portion 62 are reinforced by a metal core 63a. The second seal member 64 fitted to the housing 30 includes an annular portion 65. and two cylindrical fins 66 extending towards the mechanical seal 27 respectively from outer and inner peripheral edges and the center thereof at radially equal intervals to that of the fins 63 of the first seal member 61. The annular portion 65 has an attachment portion 67 formed at an outer peripheral edge and has a peripheral groove 68 formed in the peripheral surface.

Each of the first and second seal member 61 and 64 can be integrally molded by using a material such as polymer or rubber.

For assembly, the first and second seal members 61 and 64 are combined in advance so that the fins 66 of the second seal member 64 are respectively inserted in the recesses between the fins 63 of the first seal members 61 and the fins 66 of the second seal member 64 of the labyrinth seal unit 60, and a seal assembly having a similar function to that of the first and second embodiments is formed.

As described in the foregoing, there is in the present invention at least one labyrinth of a staggered shape formed between the water pump bearing and the mechanical seal by a combination of the first and second seal members. As a result, a labyrinth seal unit having a high sealing property is achieved, and furthermore, the maximum distance between the water pump bearing and the mechanical seal is extended substantially so that the water pump bearing is less influenced by water.

Accordingly, the service life of the bearing is extended, and a highly reliable sealing device can be obtained.

Furthermore, in the present invention. it is possible to form a labyrinth of a staggered shape quite simply merely by combining the first and second seal members, and assembling the combined seal members to an annular space between the housing and the rotary shaft.

Thus, there is no need to employ special housing of a divided type or to perform machining for a complicated groove, and the present invention can be applied to a water pump having a conventional housing.

Claims

1. A bearing seal assembly for a water pump: the water pump comprising a driven shaft carrying an impeller and surrounded by rotary units located within a stationary bearing member inside a pump shaft housing there already being (a) a mechanical seal adjacent the impeller and (b) sealing pieces. spaced therefrom, sealing between the shaft and the stationary bearing member to enclose the rotary units the bearing seal assembly being located in the space between the mechanical seal and the nearer sealing piece and having a labyrinthine nature.

2. A bearing seal assembly for a water pump, as claimed in claim 1, comprising a first generally circular labyrinth seal member attached to the shaft, with at least one annular fin extending radially from the shaft and a second generally circular labyrinth seal member comprising at least two fins attached to and extending inwardly from the pump shaft housing, fins of the first, rotary, labyrinth seal member being received within those of the second, stationary labyrinth seal member.

3. A bearing seal assembly as claimed in claim 2 wherein at least one of said labyrinth seal members is divided into halves about a plane containing when assembled the central shaft axis.

4. A bearing seal assembly as claimed in claim 3 in which the second, stationary, labyrinth seal member is divided into two halves.

5. A bearing seal assembly as claimed in claim 3 or 4 in which the two halves of the divided labyrinth seal member are assembled in use by a surrounding 0- ring or rubber band.

6. A bearing seal assembly as claimed in any one of claims 3, 4 or 5 in which contacting faces of the two halves comprise respectively one or more localising projections and one or more complementary localising recesses.

7. A bearing seal assembly as claimed in any one preceding claim wherein the second, stationary, labyrinth seal member is firmly attached to the stationery bearing member inside the pump shaft housing.

8. A bearing seal assembly for a water pump as claimed in claim 8, comprising a first generally cylindrical labyrinth seal member attached to the shaft with at least one cylindrical fin extending lengthwise, and a second generally cylindrical labyrinth seal member comprising at least two cylindrical fins extending lengthwise and attached to be stationary in respect of the stationary bearing member, fins of the first, rotary, labyrinth seal member being received within those of the second, stationary, labyrinthine seal member in use.

9. A bearing seal assembly as claimed in claim 8 in which the second, stationary, labyrinthine seal member is firmly attached to the stationary bearing member inside the pump shaft housing.