JP2003028092A - Water pump device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and surely press-fit the core of the seal of a bearing device onto the inner peripheral surface of the cylinder of a housing in a water pump device having the bearing device with a rolling surface obtained by quenching the inner peripheral surface of the cylinder of the housing. SOLUTION: In the bearing device 5, local quenching treatment is applied to the cylinder inner peripheral surface 8 of the housing 4 at a rolling groove quenched part 13 and a rolling surface quenched part 14 so that the other portions are not effected by quenching. This seal 28 of the bearing device 5 on an impeller 2 side comprises the core 26 and an elastic lip 27. The elastic lip 27 is allowed to slidably come into contact with the outer peripheral surface of a shaft 1 and a slinger 25 fixed to the outer periphery of the shaft 1 for sealing. On the cylinder inner peripheral surface 8, a large diameter part extending from a pump chamber 16 side is extended near the fixed part of the seal 28 near the position of a step part 15 to the fixed position of the seal 28 so as to shorten the press-fit length L1 of the core 26. Thus a press-fit operation can be facilitated.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water pump device used for a cooling water circulation pump or the like of an internal combustion engine, and more particularly, to an outer ring and a housing of a bearing that supports a shaft of the water pump. The present invention relates to a water pump in which a seal for preventing water or the like from entering a bearing can be easily attached to an integral bearing portion. 2. Description of the Related Art As a water pump device such as a cooling water circulation pump for an internal combustion engine, for example, a water pump device as shown in FIG. 4 is known. In this water pump device 60, as an overall configuration, an impeller 6 is attached to one end of a shaft 61.
2, a pulley 63 is attached to the other end, and an intermediate portion thereof is supported by a bearing device 65 with respect to a housing 64. In the bearing device 65, the shaft 6
The bearing device 65 having a raceway groove 67 formed on the surface of the large diameter portion 66 and press-fitted into the cylindrical inner peripheral surface 68 of the housing 64.
The ball 71 is disposed between the ball 71 and the outer ring 70, and seals 72 and 73 are provided on the side of the ball 71. Furthermore,
A seal device 74 such as a mechanical seal is provided on the outer periphery of the shaft 61 on the side of the impeller 62 fixed to the cylindrical inner surface 68 of the housing 64, and the cooling water of the pump chamber 76 in which the impeller 62 is stored is supplied to the bearing side. The housing 64 is provided with a drainage hole 75 for communicating the space between the seal device 74 and the bearing device 65 with the outside, and cooling water leaking from the seal 74 and flowing into the bearing device 65 side is prevented. At some point, this can be discharged from the drain hole 75. [0004] In the water pump shown in FIG. 4, the raceway groove 67 formed on the surface of the large diameter portion 66 of the shaft 61 as described above, and the outer race 70 of the bearing device 65 pressed into the cylindrical inner peripheral surface 68 of the housing 64. And a ball 71 is arranged between them to form a bearing, and a configuration in which an outer ring is provided is adopted.
When the outer ring is used in this way, the bearing performance is stabilized, but the number of parts is increased, and the outer diameter of the housing at the outer peripheral portion of the bearing is increased, so that the entire apparatus is increased in size and the weight is correspondingly increased. Absent. In the water pump shown in FIG. 4, cooling water leaking from a sealing device 74 such as a mechanical seal is discharged from a drain hole 75 so that cooling water does not enter the bearing device. I can do it. Further, seal fitting grooves 77 and 78 are provided on the inner periphery of both ends of the outer ring 70 of the bearing device 65, and the outer periphery of the seal 72 is fitted and fixed by its elastic force.
Sealing is performed by making sliding contact with the outer periphery of No. 1. [0006] In such a sealing device, water and steam leaking from the sealing device 74 can be discharged to the outside through the drain port 75, but a part of the water and steam is distributed along the outer surface of the shaft. When such a state continues for a long period of time, rust is gradually generated on the shaft surface of this portion, the seal lip portion is damaged by the rust, the durability of the bearing is reduced, and during rotation, There have been various problems that abnormal noise may be generated. As a countermeasure against the above problems, for example, a water pump device as shown in FIG. 5A has been proposed. In this water pump device, the ball 7 is directly provided on the cylindrical inner peripheral surface 80 of the housing 64 without separately providing an outer ring.
One rolling groove 81 is formed, and a peripheral portion of the rolling groove 81 is formed as a rolling groove quenching portion 82 to improve durability as a bearing. In this bearing device 83, a roller 85 is provided adjacent to the ball 71. On the roller 85 side, the outer rolling surface 89 is formed directly on the cylindrical inner peripheral surface 80. Quenching processing unit 86
And In the water pump device shown in FIG. 5A, a slinger 87 is press-fitted into a shaft 91, and an outer peripheral edge of a flange portion 88 is brought close to a drain hole 75 provided in the housing 64. Thereby, the spring 9 is fixed to the ceramic shoe 92 fixed to the impeller 62.
Water and water vapor leaking from the sealing part by sliding the carbon shoe 94 pressed in 3
Guided to the flange portion 88 of the slinger 87, the centrifugal force ensures that the water can be discharged to the outside from the drain hole 75, thereby preventing the rust of the shaft as described above. Further, a seal 97 made of an elastic lip 96 baked on a metal core 95 is press-fitted into the cylindrical inner peripheral surface 80 of the housing facing the outer periphery of the slinger 87, and the elastic lip 96 slides on the outer peripheral surface of the slinger 87. Thereby, a sealing action is performed in this portion. In a conventional water pump device as shown in FIG. 5A, a ball is directly provided on the inner peripheral surface 80 of the housing 64 without using an outer ring as described above. The rolling groove 81 of the roller 71 and the rolling surface 89 of the roller 85 are formed, a hardening process is performed on this portion, and a metal core 95 of a seal 97 is press-fitted into the inner peripheral surface 80 of the cylinder, and water is introduced into the bearing. Etc. are prevented from invading,
The press-fitting of the core bar 95 is performed, for example, as shown in FIG. That is, the seal 97 is still attached to the impeller 6.
2. In a state where the sealing device 74 and the like are not attached,
The housing 64 is inserted from the right opening in the drawing to the fitting step 98 of the sealing device 74. Thereafter, the core metal 95 is attached to the cylindrical inner peripheral surface 8 by the interference between the predetermined inner diameter of the cylindrical inner peripheral surface 80 of the housing 64 and the outer diameter of the core metal 95.
Press into 0. At this time, the metal core 95 is press-fitted from the fitting step 98 of the sealing device to a preset mounting position 99 of the seal ring by a press-fit length L2. In the conventional water pump shown in FIG. 5, since the distance between the fitting step 98 and the predetermined mounting position 99 of the seal 97 is long as described above, the press fitting of the core bar 95 when the seal 97 is mounted. There was a problem that the length L2 was long and workability was poor. In order to solve this problem, seal fitting grooves 77 and 78 are formed in the cylindrical inner peripheral surface 80 of the housing shown in FIG. 5, for example, as in the conventional water pump device shown in FIG. It is also conceivable to fit seals 72 and 73 as shown in FIG. However, the position where this seal is provided is at least the seal 77 located on the impeller side.
Is located at a substantially central position inside the housing 64, and is located far from any opening side of the housing 64.
Therefore, when the seal fitting groove 77 is formed by cutting with a cutting tool, the cutting process must be performed in an unstable cantilever state in which the cutting tool is extended from any opening side of the housing 64, resulting in poor workability. In addition, there is a new problem that machining accuracy is deteriorated. Further, even if such a seal fitting groove 77 is formed, fitting the seal ring at a deep position on the inner peripheral surface of the cylinder in this manner has a problem that workability is poor. As described above, as a measure to shorten the press-fit length of the core metal of the seal ring and to prevent the formation of the seal fitting groove, the fitting of the sealing device shown in FIG. It is conceivable that the stepped portion 98 is located as far back as possible on the inner peripheral surface of the cylinder of the housing, and the press-fit length L2 of the core 95 of the housing is shortened. However, at that time, when finishing the core metal press-fitting portion, the core metal 95
The finishing method must be determined in consideration of performing the quenching process on the raceway groove portion of the ball and the rolling surface of the roller on the cylindrical inner peripheral surface 80 of the housing into which is pressed. That is, when the core inner press-fitting portion is subjected to the finishing process after the entire inner surface 80 of the cylinder is quenched in advance by a method such as sub-hardening, the portion is hardened by quenching. Becomes difficult. In addition, since the press-fitted portion is deformed by quenching, the processing allowance for finishing is increased, and the processing becomes more difficult. On the other hand, if the entire quenching process is performed after finishing the core metal press-fitting part, the finish processing part is deformed due to the quenching process, making it difficult to press-fit. It is conceivable that a gap is formed in a part between the bearing and the inside, and water or water vapor enters the bearing from the part. Therefore, according to the present invention, the outer ring of the bearing supporting the water pump and the housing are integrated with each other, so that water or the like does not enter the bearing at the bearing portion where the inner peripheral surface of the housing is subjected to quenching processing. A main object of the present invention is to provide a water pump device in which a seal can be attached easily and with good sealing properties. In order to solve the above-mentioned problems, the present invention provides a shaft having an impeller and a pulley fixed at both ends, a bearing device provided on the outer periphery of the shaft, and a bearing on the inner peripheral surface of the cylinder. A housing provided with a rolling surface of a rolling element of the device, wherein the rolling surface portion is quenched; and a first seal for sealing leakage of cooling water from the pump chamber to the bearing device side between the bearing device and the impeller. A second seal comprising a cylindrical cored bar between the first seal and the bearing device and a resilient seal fixed to the cored bar and sealing between the housing and the shaft; In the water pump provided with a step, a step where the diameter of the first seal installation side is enlarged is provided on the inner peripheral surface of the cylinder between the first seal and the second seal in the vicinity of the second seal installation position. , At least the quenching process is not performed on the inner peripheral surface of the cylinder from the second seal installation position to the step portion. Embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a water pump device according to an embodiment of the present invention. The overall configuration of the water pump device is the same as that of the conventional water pump device shown in FIG. An impeller 2 is attached to one end of the device 1, a pulley 3 is attached to the other end, and an intermediate portion thereof is rotatably supported by a bearing device 5 with respect to a housing 4. The bearing device 5 in the illustrated example is provided with a raceway groove 7 on the surface of the large diameter portion 6 of the shaft 1, and a ball is provided between the raceway groove 10 and the rolling groove 10 formed directly on the cylindrical inner peripheral surface 8 of the housing 4. 9 are arranged so as to roll freely. In this bearing device 5, a roller 11 is used adjacent to the ball 9;
Like the ball 9, the roller 11 is also arranged so as to roll freely between the surface of the large diameter portion 6 of the shaft 1 and the rolling surface 12 of the cylindrical inner peripheral surface 8 of the housing 4. In this bearing device 5, since the rolling groove 10 is formed directly on the cylindrical inner peripheral surface 8 of the housing 4 and the rolling surface 12 of the roller 11 as described above without using the outer ring, The quenching process is performed to improve the durability of the steel. In this quenching process, in particular, the influence of quenching is applied only to specific portions of the rolling groove quenching portion 13 around the rolling groove 10 and the rolling surface quenching portion 14 around the rolling surface 12. The quenching process is performed so as to be limited, and the other portions are prevented from being affected by the quenching process as much as possible. This prevents the quenching process from affecting the step 15 provided on the inner peripheral surface 8 of the housing 4 on the side of the impeller 2 as described later. The rolling groove 10 of the ball 9 and the rolling surface 12 of the roller 11 are collectively referred to as a rolling surface of a rolling element. The cooling water in the pump chamber 16 is supplied to the bearing device 5.
As a mechanical seal device 20 for preventing the oil from flowing to the side, in the illustrated embodiment, a seal that seals by sliding a carbon shoe 23 pressed by a spring 22 against a ceramic shoe 21 fixed to the impeller 2. Means and the seal 20
When cooling water or steam leaks from the housing, a drain port 24 is formed to penetrate the wall of the cylindrical portion of the housing 4 in order to discharge the cooling water or steam to the outside, as in FIG. In this embodiment, on the side of the impeller 2 of the bearing device 5, as is apparent from an enlarged view of this portion shown in FIG. The slinger 25 having a U-shape is press-fitted and fixed with its opening side facing the bearing. At a position on the cylindrical inner peripheral surface 8 of the housing 4 facing the slinger 25, a seal 28 is provided on a core having a substantially L-shaped cross section and an elastic lip 27 baked thereon.
By press-fitting and fixing the cylindrical portion to the cylindrical inner peripheral surface 8 of the housing 4 and slidingly contacting the elastic seal 27 with the wall surface of the slinger 25, water or the like does not enter the bearing device from this portion. Like that. In this water pump device, the seal device for preventing the cooling water in the pump chamber from entering the bearing device includes the seal device 20 and the seal 28 as described above. Therefore, in the claims, the former is referred to as a first sealing device, and the latter is referred to as a second sealing device. The structure of the peripheral portion of the seal 28 will be described in more detail. As shown in FIG. 1 (b), the slinger 25 having the U-shape has an inner cylindrical portion 30 whose inner surface is a large diameter portion of the shaft 1. 6 and fixed by press-fitting. Further, in the annular portion 31 extending radially outward from the inner cylindrical portion 30, when the cooling water leaks from the sealing device 20 as described above, particularly, the cooling water and the like transmitted along the outer peripheral surface of the shaft 1 The cooling water of the annular portion 31 is radiated along the surface in the outer peripheral direction by centrifugal force generated by the rotation of the annular portion 31 due to the rotation of the shaft 1. Thus, the water can be reliably discharged to the outside from the drain port 24 provided in the radial direction. As described above, the seal 28 is provided with the metal core 26 having a substantially L-shaped cross section. The cylindrical portion 33 of the metal core 26 is press-fitted into the cylindrical inner peripheral surface 8 of the housing 4 from inside and fixed. The elastic seal 27 is fixed to the annular portion 34 extending from the cylindrical portion 33 toward the inner diameter side in the circumferential direction by baking or the like. In the illustrated embodiment, the elastic seal 27 slidably contacts the outer periphery of the inner cylindrical portion 30 of the U-shaped slinger 25 and the first lip portion 35 that slides on the outer peripheral surface of the large-diameter portion 6 of the shaft 1 at its tip. A second lip portion 36 and a lip portion of a third lip portion 37 that is in sliding contact with the outer periphery of the outer cylindrical portion 32 are provided, and reliable sliding is performed by these sliding contacts. Particularly in this embodiment, the housing 4
The outer peripheral rolling groove and the rolling surface of the bearing device are formed on the inner peripheral surface 8 of the cylinder, and a step 15 as a boundary between a small-diameter portion into which the core metal is press-fitted and a large-diameter portion located on the impeller installation side. For example, as apparent from comparison with the conventional step 98 shown in FIG. 5, the seal 28 is formed close to the portion where the seal 28 disposed opposite to the slinger 25 is fixed as described above. Accordingly, when the core 28 is pressed into the inner peripheral surface 8 of the cylinder when the seal 28 is mounted, no step is formed on the inner peripheral surface of the cylinder unlike the conventional water pump shown in FIG. 4, for example. As compared with the case, it is only necessary to press-fit from the step portion, so that the press-fitting length can be shortened, so that the workability of press-fitting can be improved, and the press-fitting jig can be positioned at this step portion. Therefore, the press-fitting operation can be performed in a stable state, and also in this respect, the workability of the press-fitting can be improved. In addition, as compared with the conventional water pump shown in FIG. 5 in which the step 98 exists at a position distant from the mounting portion of the seal 97 and the press-fit length becomes long as L2, FIG. As shown in b), the press-fit length at this time can be shortened to L1.
The workability of the press-fitting operation can be improved. The press-fitted portion on the inner peripheral surface 8 of the cylinder is not subjected to the quenching process as in the rolling groove quenching portion 13 and the rolling surface quenching portion 14, and the influence of the quenching process. Not received. If this part is quenched, it is difficult to finish because the hardness is high, and in particular, the inner surface is deformed by quenching, so the machining allowance must be increased. However, if the quenching process is not performed on this part as described above and the quenching process is not affected, it is easy to finish the press-fitted part. Can be performed at the same time, and the cutting allowance at that time can be reduced. Furthermore, in order to eliminate the difficulty of finishing the press-fitted portion in the case where the quenching process is performed on the entire quenched portion as described above, quenching is performed after the finishing process, and thereafter the entire quenched portion is hardened. In the case of processing, the press-fitting part is deformed by the quenching, so that the press-fitting work of the seal becomes difficult. While there is a possibility that water or steam may enter the inside of the bearing device, in the present embodiment, by configuring as described above, it is possible to perform press-fitting on a portion on which a predetermined finishing process has been performed. The press-fitting is easy and the above-mentioned gap is not generated, so that the sealing property is improved. Further, the fixing of the seal as described above does not depend on press-fitting, but as in the conventional example shown in FIG.
The outer periphery of the seal 72 is sealed by the elastic force of the seal fitting groove 77.
In order to adopt the means of fitting and fixing to, and to configure the housing and the outer ring with the same member without using the outer ring,
It is also conceivable that a seal fitting groove is formed on the inner peripheral surface 8 of the cylinder, and an inner projection formed on the seal is fitted and fixed to this groove. However, in this case, the seal fitting groove is cut by a cutting tool, and the seal fitting groove is located at a substantially intermediate portion of the inner peripheral surface of the cylinder. It is necessary to support the device by holding it and perform cutting, which makes the workability extremely poor. On the other hand, in the above-described embodiment, since the method of press-fitting the cylindrical portion of the core metal into the inner peripheral surface of the housing is adopted, the workability can be improved. In the embodiment shown in FIG. 1B, an example is shown in which the seal press-fitting end 38 at which the step 15 of the cylindrical inner peripheral surface 8 of the housing 4 is formed is formed at an acute angle. As shown in FIG. 1 (c), the chamfer 3
9, the core metal 26 is inserted into the seal press-fitting portion 38.
Can be easily press-fitted into the inner peripheral surface 8 of the cylinder. The water pump according to the invention can also be implemented, for example, as shown in FIG. That is, in this water pump, the bearing device 40 has a configuration of a bearing device having two rows of balls 41 and 42, and rolling grooves 43 and 44 are formed on the inner peripheral surface of the housing. In order to improve the durability of the rolling grooves 43 and 44, a quenching processing part 45 is formed in this part, and the quenching processing part 45 is located at the position where the seal is installed similarly to the embodiment of FIG. The step 46 does not reach the portion where the core metal presses and moves. Further, the step 46 is provided near the seal fixing portion to shorten the press-fitting length and improve the workability of the press-fitting operation, similarly to the embodiment of FIG. As shown in an enlarged view of FIG. 2B, the structure of the vicinity of the seal in this embodiment uses a slinger 47 having a substantially L-shaped cross section, and a core metal 49 having a substantially L-shaped cross section as a seal 48. In contrast, a first seal ship 51 and a second seal lip 52 that are in sliding contact with the outer peripheral surface of the cylindrical portion 50 of the slinger 47 are provided, and the first seal ship 51 is further in sliding contact with the outer peripheral surface of the annular portion 53 that extends in the radial direction of the slinger 47. 3 seal lip 54
Are fixed. Further, in this embodiment, the seal press-fitting portion 38 in the cylindrical inner peripheral surface 8 of the housing 4 is chamfered 39 in the same manner as in FIG.
Has been given. In the above embodiment, similarly to the embodiment shown in FIG. 1, the quenching process is not performed on the seal press-fitting portion and is not affected by the quenching process. Without any deformation of the part
This part can be easily finished, the seal can be easily press-fitted, and the sealing performance is improved. In addition, since the step portion is close to the seal fixing portion, the workability of press-fitting the seal is good, as is the same as the above embodiment. In the embodiment shown in FIG. 2, a bent portion 56 may be formed at the tip of the cylindrical portion 55 of the metal core 49, as shown in FIG. Thereby, at the time of press-fitting the core metal, the pressing tip of the press-fitting tool is received at this portion, so that the press-fitting work can be performed easily and reliably. In the embodiment shown in FIG.
9 inside the annular portion 57, that is, the impeller 2
Although an example in which it is formed so as to extend to the side is shown, this portion may be formed so as to extend outside the annular portion 57, that is, toward the pulley as shown in FIG. In this case, as shown in FIG. 3 (b), a bent portion 58 is formed at the tip of the cylindrical portion 55, that is, at the tip portion which is pushed in at the time of press-fitting, so that the tip portion is formed on the cylindrical inner peripheral surface 8. The press-fitting may be performed smoothly without causing the hooking. In addition, besides forming the bent portion 58 in the manufacturing process, in addition to forming the bent portion in particular, when the core metal is manufactured by a press, if the core metal is automatically formed as a sag of the press, the bent portion is not formed. It can be used as it is. Further, a chamfer for machining or pressing may be provided at the outer diameter side end of the cylindrical portion 55. Further, as shown in FIG. 3C, by chamfering the seal press-fitting portion 38 in the same manner as that shown in FIGS. 1C and 2, the press-fitting of the core of the seal is made easier. You can do it. In the above embodiment, the water pump device according to the present invention is used as a cooling water circulation water pump for an internal combustion engine. However, it can be used for various other cooling water circulation water pumps. Besides, it can be used for various other water pumps. In addition, various types of bearing devices other than the above embodiment can be used for the bearing device, and various types of seals can be used, such as using seals having various types of elastic lips. . According to the present invention having the above-described structure,
Since the quenching process is not performed on the part where the core of the seal is press-fitted, the finishing process of the press-fitted part can be easily performed, and after the finishing process, it is finished as in the case of quenching the whole It is also possible to prevent the processing portion from being deformed to make it difficult to press-fit the core metal or to cause a gap between the core metal and the inner peripheral surface of the cylinder to cause leakage. Further, since the length of press-fitting of the core metal is shortened, the workability of press-fitting can be improved. As a result, the outer ring of the bearing supporting the water pump and the housing are integrated with each other, and in the bearing portion that performs quenching processing on the inner peripheral surface of the housing, a seal that prevents water or the like from entering the bearing can be easily formed, and It can be attached with good sealing properties.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1A and 1B are cross-sectional views of an embodiment of the present invention, in which FIG. 1A is a cross-sectional view of the entire configuration, FIG. 1B is an enlarged cross-sectional view of a portion b in FIG. () Is a sectional view of another embodiment in which a part of the configuration of the seal portion of the bearing device in (b) is changed. FIGS. 2A and 2B are cross-sectional views of another embodiment of the present invention, in which FIG. 2A is a cross-sectional view of the entire structure, FIG. 2B is an enlarged cross-sectional view of a portion b in FIG. FIG. 13 is a cross-sectional view of another embodiment in which a partial configuration of a seal portion of the bearing device in FIG. FIG. 3 is a cross-sectional view showing other various embodiments of a seal portion of the bearing device of the present invention. FIG. 4 is a cross-sectional view of the entire configuration of a conventional example. 5A and 5B are cross-sectional views of another conventional example, in which FIG. 5A is a cross-sectional view of the entire configuration, and FIG. 5B is a cross-sectional view showing a state in which a seal of a bearing device is mounted in FIG. [Description of Signs] 1 Shaft 2 Impeller 3 Pulley 4 Housing 5 Bearing device 6 Large diameter portion 7 Track groove 8 Cylindrical inner peripheral surface 9 Ball 10 Rolling groove 11 Roller 12 Rolling surface 13 Rolling groove quenching portion 14 Rolling Surface hardening part 15 Step part 16 Pump chamber 20 Mechanical seal 21 Ceramic shoe 22 Spring 23 Carbon shoe 24 Drain port 25 Slinger 26 Core bar 27 Elastic lip 28 Seal 30 Inner cylindrical part 31 Ring part 33 Cylindrical part 34 Ring part 35 first lip portion 36 second lip portion 37 third lip portion

   ────────────────────────────────────────────────── ─── Continuation of front page    F-term (reference) 3H022 AA01 BA06 CA12 CA23 CA27                       DA07                 3J016 AA01 BB03 CA03                 3J101 AA01 AA32 AA43 AA52 AA62                       AA72 AA77 BA50 BA53 BA54                       BA70 BA73 DA03 DA05 DA11                       FA44 GA29

Claims (1)

Claims 1. A shaft having an impeller and a pulley fixed to both ends thereof, a bearing device provided on an outer periphery of the shaft, and a rolling surface of a rolling element of the bearing device on an inner peripheral surface of the cylinder. A housing in which a rolling surface portion is quenched; a first seal for sealing leakage of cooling water from the pump chamber to the bearing device side between the bearing device and the impeller; and a first seal between the first seal and the bearing device. A water pump comprising: a press-fitted portion press-fitted into an inner peripheral surface of a cylinder; and a second seal including a cylindrical core and an elastic seal fixed to the core and sealing between a housing and a shaft. A step portion whose diameter is increased on the first seal installation side is provided near the second seal installation position on the inner circumferential surface of the housing between the second seal and the second seal; Water pumping apparatus in the cylindrical inner peripheral surface, characterized in that the hardening processing is not performed in.