JP7503458B2 - water pump - Google Patents

Description

The present invention relates to a water pump driven by a pulley.

The cooling water for cooling the engine is circulated by a water pump. Prior art related to water pumps is disclosed in Patent Document 1.

The water pump disclosed in Patent Document 1 has a support part in which a bearing chamber that supports a bearing is formed in a horizontal direction, an impeller drive shaft that is rotatably supported by the bearing and passes through the bearing chamber, a pulley that is attached to one end of the impeller drive shaft and driven by a belt, an impeller that is attached to the other end of the impeller drive shaft, and a mechanical seal that is attached between the impeller and the bearing. When the pulley is driven by the belt, the impeller attached to the impeller drive shaft rotates and coolant is pumped out.

Japanese Utility Model Application Publication No. 3-65891

The pulley is cylindrical with a bottom and surrounds an annular support. An annular gap is formed between the outer circumferential surface of the support and the inner circumferential surface of the pulley's cylindrical portion.

In the operating environment in which the water pump operates, dirt, dust, mud, sand, water and oil (hereafter referred to as dust) can get into the annular gap formed between the pulley and the support. If the dust gets inside the bearing, it shortens the life of the bearing.

A disk-shaped partition plate is provided on the outer circumferential surface of the support part. By providing the partition plate, the gap between the pulley and the support part is narrowed, preventing dust from entering the inside of the pulley.

This partition plate is fixed to the outer peripheral surface of the support part by pressing or crimping. As mentioned above, the support part is the part that supports the bearing. If an external force acts on the support part when pressing or crimping the partition plate, a load is applied to the bearing, which may shorten the life of the bearing.

The objective of this invention is to provide technology that extends the life of water pumps.

According to the invention of claim 1, a rotor has a support portion in which a bearing hole that supports a bearing is formed, a rotating shaft that is rotatably supported by the bearing and passes through the bearing hole, a cylindrical pulley with a bottom provided at one end of the rotating shaft, an impeller provided at the other end of the rotating shaft, and a seal member disposed between the impeller and the bearing,
a communication hole is formed in the support portion to allow communication between a space between the seal member and the bearing in the bearing hole and an outside of the support portion;
the support portion has an annular small diameter portion having the bearing hole formed at its center, and an annular large diameter portion having an outer circumferential surface with a diameter larger than that of an outer circumferential surface of the small diameter portion, the outer circumferential surface of the annular large diameter portion being centered on the bearing hole,
At least a portion of the small diameter portion is located closer to the pulley than the large diameter portion,
a first annular gap is formed between the cylindrical portion of the pulley and the large diameter portion,
A water pump is provided, characterized in that a second cylindrical portion is provided at the bottom of the pulley, and a second annular gap is formed between this second cylindrical portion and the small diameter portion.

As described in claim 2, preferably, a dimension in an axial direction where the cylindrical portion of the pulley and the large diameter portion of the support portion overlap each other is defined as a first dimension,
If the axial dimension of the overlapping portion between the second cylindrical portion and the small diameter portion of the support portion is defined as a second dimension,
The first dimension is less than the second dimension.

As described in claim 3, the radial dimension of at least one of the first gap or the second gap is set to be narrower toward the impeller side with respect to the direction in which the center line of the bearing hole extends.

As described in claim 4, the support portion has a facing surface facing the bottom portion of the pulley, and in addition to the communication hole, a recess is formed on this facing surface.

As described in claim 5, the large diameter portion surrounds the small diameter portion, the thickness of the large diameter portion is thinner than the thickness of the small diameter portion based on the radial direction, and the recess is formed by the space between the small diameter portion and the large diameter portion.

As described in claim 6, multiple ribs are formed from the outer peripheral surface of the small diameter portion to the inner peripheral surface of the large diameter portion.

As described in claim 7, the center line of the bearing hole extends horizontally, and at least a portion of the recess formed in the opposing surface is located above the upper end of the bearing.

In claim 1, the water pump has a support portion that supports a rotating shaft and a cylindrical pulley with a bottom provided at one end of the rotating shaft. The support portion has an annular small diameter portion with a bearing hole formed in the center, and an annular large diameter portion whose outer circumferential surface has a larger diameter than the outer circumferential surface of the small diameter portion.

At least a portion of the small diameter portion is located closer to the pulley than the large diameter portion. A first annular gap is formed between the tubular portion of the pulley and the large diameter portion. A second tubular portion is provided at the bottom of the pulley. A second annular gap is formed between the second tubular portion and the small diameter portion.

In other words, two gaps are formed between the pulley and the support to prevent dust from entering. This makes it difficult for dust to reach the inside of the bearing.

In addition, the second cylindrical portion is provided at the bottom of the pulley. Because the second cylindrical portion is not fitted to the support portion, no external force is applied to the support portion. As a result, no load is applied to the bearing provided in the support portion. This contributes to a longer life for the bearing.

In addition, the second cylindrical portion is provided on the pulley, which is a rotating body. When the pulley rotates, the second cylindrical portion also rotates. Air flow is more likely to occur in the second gap between the second cylindrical portion and the small diameter portion of the support portion. Dust is less likely to enter the second gap.

In claim 2, the axial dimension where the tubular portion of the pulley and the large diameter portion of the support overlap is defined as the first dimension. The axial dimension where the second tubular portion provided on the pulley and the small diameter portion overlap is defined as the second dimension. The first dimension is shorter than the second dimension.

In addition, the first gap is both an entrance for dust into the pulley and an exit for dust that has entered the pulley. By shortening the first dimension, even if dust enters the pulley through the first gap, it becomes easier for the dust to be discharged to the outside of the pulley through the first gap.

In claim 3, the radial dimension of at least one of the first gap and the second gap is set to be narrower toward the impeller side, based on the direction in which the center line of the bearing hole extends. Since the gap on the impeller side, which is the side through which dust can enter, is set to be narrower, the intrusion of dust can be suppressed. The life of the water pump can be extended.

In claim 4, dust that has entered through the first gap can reach the edge of the opposing surface that faces the bottom of the pulley. The pulley is cylindrical with a bottom, and when the pulley rotates, an air flow occurs inside the pulley. Therefore, the dust is also subjected to a radially outward external force caused by the air flow. In addition to the communication hole, the opposing surface is formed with a recess. Some of the dust enters the recess. The dust that enters the recess will move away from the bearing. Dust can be kept away from the bearing, making it more difficult for the dust to enter the bearing.

Even if dust that has entered a recess moves toward the bearing, the distance it travels to reach the bearing will be longer than if it moved on a flat surface where no recesses were formed. Dust will have a harder time reaching the bearing.

For the same reasons as above, dust is less likely to reach the outlet of the communication hole. This helps to extend the life of the water pump.

In claim 5, the thickness of the large diameter portion is thinner than the thickness of the small diameter portion, based on the radial direction of the small diameter portion and the large diameter portion. The recess is formed by the space between the small diameter portion and the large diameter portion. Therefore, a larger recess can be formed between the small diameter portion and the large diameter portion. Dust can more easily penetrate the recess. Dust can be moved away from the bearing, making it more difficult for dust to reach the bearing. The life of the water pump can be extended.

In claim 6, multiple ribs are formed from the outer peripheral surface of the small diameter portion to the inner peripheral surface of the large diameter portion. In other words, the recess formed by the space between the small diameter portion and the large diameter portion is partitioned by multiple ribs. Therefore, when dust that has entered the recess moves along the surface of the recess toward the communication hole, the ribs impede the movement of the dust. This makes it possible to prevent the dust from approaching the communication hole.

In addition, the formation of the ribs makes it easier for turbulent air to occur inside the pulley as it rotates. This makes it easier for the external force caused by the turbulent air to act on the dust, making it even harder for the dust to reach the bearings. This can extend the life of the water pump.

In claim 7, the center line of the bearing hole extends horizontally, and at least a portion of the recess formed in the opposing surface is located above the upper end of the bearing. When dust moves toward the bearing due to the action of gravity, the dust enters the recess formed in the upper end of the bearing, making it difficult for the dust to reach the bearing. As a result, dust is less likely to enter the bearing, and the life of the water pump can be extended.

1 is a cross-sectional view of a water pump according to an embodiment of the present invention. FIG. 2 is an exploded perspective view of the water pump shown in FIG. 1 . 3 is a diagram illustrating a support portion of the water pump shown in FIG. 2. FIG. 2 is an enlarged view of a portion of the water pump shown in FIG. 1 .

The embodiment of the present invention will be described below with reference to the attached drawings.

<Example>
1 shows a water pump 10 according to an embodiment. The water pump 10 circulates cooling water for cooling an engine 11. The water pump 10 is fixed by fastening members 13 to an engine block 12 of a vehicle or heavy machinery such as a power shovel.

Refer to Figures 1 and 2. The housing 20 of the water pump 10 is a cast product, and is composed of a plate-shaped fixing part 22 in which multiple (e.g., five) fastening holes 21 through which the fastening members 13 pass, and a support part 40 in which a bearing hole 41 that supports the bearing 30 is formed.

The center line L1 of the bearing hole 41 of the support part 40 extends horizontally. A coolant flow path 23 is formed on the inner surface of the fixed part 22 (the surface facing the engine block 12). A seal member 24 is provided between the housing 20 and the side surface 14 of the engine block 12.

Hereinafter, "inside (In)" refers to the side of the impeller 15 (described later) with respect to the horizontal direction, and "outside (Ou)" refers to the side of the pulley 60 (described later). "Down (Dn)" refers to the vertically downward direction, and "up (Up)" refers to the vertically upward direction.

The bearing 30 is composed of an annular member 31 that fits into the bearing hole 41, and a cylindrical rolling element 32 and a spherical rolling element 33 that are arranged inside the annular member 31.

A rotating shaft 50 rotatably supported by the bearing 30 is provided in the bearing hole 41 of the support part 40. The rotating shaft 50 passes through the bearing hole 41 in the axial direction. A pulley 60 driven by a belt is provided at the outer end 51 (one end) of the rotating shaft 50. An impeller 15 is provided at the inner end 52 (the other end) of the rotating shaft 50. When the pulley 60 is driven, the impeller 15 provided on the rotating shaft 50 rotates, and the cooling water is sent out through the flow path 23.

A mechanical seal 16 (sealing member) is provided between the impeller 15 and the bearing 30. The mechanical seal 16 fills the gap between the rotating shaft 50 and the bearing hole 41 to prevent cooling water from entering the inside of the bearing hole 41. A detailed description of the mechanical seal 16 is omitted. Instead of the mechanical seal 16, a sealing member such as a packing or an oil seal may be used.

The pulley 60 is generally cylindrical with a bottom, and is made up of a disk-shaped bottom 61 and a hollow cylindrical tube portion 62 (first tube portion) that extends inward from the periphery 61a of the bottom 61. The bottom 61 is formed with a fixing hole 63 into which the outer end portion 51 of the rotating shaft 50 is press-fitted and fixed.

A cylinder 65 is provided on the inner surface 64 of the bottom 61. The cylinder 65 is composed of an annular flange portion 66 welded to the inner surface 64 of the bottom 61 of the pulley 60, and a hollow cylindrical second cylinder portion 67 extending inward from the radially inner inner peripheral edge 66a of the flange portion 66. The second cylinder portion 67 may be formed integrally with the pulley 60.

See Figure 3. When viewed in the direction along the center line L1 (also called the axial direction), the support portion 40 has an annular small diameter portion 42 with a bearing hole 41 formed in the center, and an annular large diameter portion 45 with an outer circumferential surface 44 having a larger diameter than the outer circumferential surface 43 of the small diameter portion 42.

The large diameter portion 45 surrounds the small diameter portion 42 with the center line L1 as the center. Based on the radial direction of the small diameter portion 42 and the large diameter portion 45, the thickness T1 of the large diameter portion 45 is thinner than the thickness T2 of the small diameter portion 42 (T1<T2).

See FIG. 1. The end face 46 of the small diameter portion 42 is located on the outside (pulley side) of the end face 47 of the large diameter portion 45. The outer peripheral surface 44 of the large diameter portion 45 is inclined so that the diameter of the outer peripheral surface 44 decreases as it moves outward (inclination angle θ1). Similarly, the outer peripheral surface 43 of the small diameter portion 42 is inclined so that the diameter of the outer peripheral surface 43 decreases as it moves outward (inclination angle θ2).

Refer to Figure 3. The annular space surrounded by the outer circumferential surface 43 of the small diameter portion 42, the inner circumferential surface 48 of the large diameter portion 45, and the bottom surface 25 of the fixed portion 22 is called the recess 70. This recess 70 is divided into six sections by a plurality of ribs 81-84 (e.g., four sets) described below. The ribs 81-84 are formed radially from the outer circumferential surface 43 of the small diameter portion 42 to the inner circumferential surface 48 of the large diameter portion 45. The ribs 81-84 are positioned at equal intervals from one another in the circumferential direction.

Of the ribs 81 to 84, the one that extends downward from the lower end 43a of the outer circumferential surface 43 of the small diameter portion 42 is referred to as the first rib 81. The first rib 81 is block-shaped and is set to have a thicker circumferential dimension than the other ribs 82 to 84.

Refer to Figures 1 and 3. The first rib 81 has a communication hole 39 formed therein that allows communication between the space 38 between the mechanical seal 16 and the bearing 30 in the bearing hole 41 and the outside of the support part 40. The communication hole 39 is made up of a first hole 35 that extends radially outward from the space 38, and a second hole 36 that communicates with the first hole 35 and also extends outward. The outlet of the communication hole 39 is located at the end face 86 of the first rib 81.

Of the ribs 82-84, the ribs extending diagonally downward from the outer peripheral surface 43 of the small diameter portion 42 are referred to as second ribs 82, 82, the ribs extending diagonally upward from the outer peripheral surface 43 of the small diameter portion 42 are referred to as third ribs 83, 83, and the rib extending upward from the upper end 43b of the outer peripheral surface 43 of the small diameter portion 42 is referred to as fourth rib 84.

The fourth rib 84 consists of a cylindrical portion 91 located approximately in the radial center, an inner wall portion 92 located radially inward from the cylindrical portion 91, and an outer wall portion 93 located radially outward from the cylindrical portion 91.

The end face 94 of the inner wall portion 92 is located inside the end face 95 of the cylindrical portion 91. The end face 96 of the outer wall portion 93 is inclined inward as it moves radially outward. The end face 95 of the cylindrical portion 91 is the surface that is pressed when the housing 20 is released from the mold.

The second rib 82 and the third rib 83 have the same size and shape as the fourth rib 84. Explanation is omitted. Furthermore, except for the first rib 81 that constitutes the communication hole 39, the second rib 82 to the fourth rib 84 do not need to be provided.

Refer to FIG. 3. The support portion 40 has a symmetrical configuration with respect to a line L2 that is perpendicular to the center line L1 and extends vertically. Below, the configuration to the right of the line L2 will be described. This description also applies to the configuration to the left of the line L2.

The space 38 between the first rib 81 and the second rib 82 is the first recess 71. The space 38 between the second rib 82 and the third rib 83 is the second recess 72. The space 38 between the third rib 83 and the fourth rib 84 is the third recess 73. This explanation also applies to the configuration on the left side of the line L2. Explanation will be omitted.

Refer to FIG. 2. Of the outer peripheral surface 43 of the small diameter portion 42, the surface that constitutes part of the first recess 71 is referred to as the first curved surface 74, the surface that constitutes part of the second recess 72 is referred to as the second curved surface 75, and the surface that constitutes part of the third recess 73 is referred to as the third curved surface 76. Of the outer peripheral surface 43 of the small diameter portion 42, the surface that is outside the ribs 81-84 is referred to as the annular surface 77. The annular surface 77 can also be said to be a surface that does not constitute the recess 70.

Refer to FIG. 4. A first annular gap C1 is formed between the inner peripheral surface 68 of the tubular portion 62 of the pulley 60 and the outer peripheral surface 44 of the large diameter portion 45. The annular surface 77 is located outside (Ou) relative to the outer peripheral surface 44 of the large diameter portion 45. A second annular gap C2 is formed between the inner peripheral surface 67a of the second tubular portion 67 and the annular surface 77 of the small diameter portion 42.

The outer peripheral surface 44 of the large diameter portion 45 is inclined so that the diameter of the outer peripheral surface 44 increases toward the inside (impeller 15 side) (inclination angle θ (see FIG. 1)). Therefore, the radial dimension B1 of the first gap C1 becomes narrower toward the inside (impeller 15 side (see FIG. 1)). It is narrow on the inside and wide on the outside (pulley 60 side). Since the side where dust penetrates is narrow, the intrusion of dust can be suppressed. The outer peripheral surface 43 of the small diameter portion 42 is also inclined in the same way, and the same effect as above is achieved. Furthermore, the outer peripheral surface 43 of the small diameter portion 42 is inclined so that the diameter of the outer peripheral surface 43 increases toward the inside (impeller 15 side) (inclination angle θ2 (see FIG. 1)). Therefore, the radial dimension B2 of the second gap C2 becomes narrower toward the inside (impeller 15 side (see FIG. 1)). It is narrow on the inside and wide on the outside (pulley 60 side). The side through which dust can enter is narrow, preventing dust from entering.

Based on the horizontal direction (the direction in which the center line L1 of the rotating shaft 50 extends), the dimension where the cylindrical portion 62 of the pulley 60 and the large diameter portion 45 of the support portion 40 overlap is defined as a first dimension A1. The dimension where the second cylindrical portion 67 and the small diameter portion 42 overlap is defined as a second dimension A2. The first dimension A1 is shorter than the second dimension A2.

The second tubular portion 67 is located radially inward of the rotating shaft 50 relative to the cylindrical portion 91. This allows the axial dimension of the water pump 10 to be shortened. The end face 69 of the second tubular portion 67 is located axially outward (Ou) relative to the end face 47 of the large diameter portion 45. Similarly, the end face 69 is located axially outward (Ou) relative to the end faces 94 to 96. The second tubular portion 67 and the cylindrical portion 91 may be configured to overlap in the axial direction of the rotating shaft 50 (see line L3).

See Figures 1 and 3. In addition, the bearing hole 41, the small diameter portion 42, the large diameter portion 45, the rotating shaft 50, the pulley 60, and the second cylindrical portion 67 are positioned concentrically about the center line L1.

The effects of the embodiment are explained.

Refer to FIG. 4. A first annular gap C1 is formed between the inner peripheral surface 68 of the tubular portion 62 of the pulley 60 and the outer peripheral surface 44 of the large diameter portion 45. A tubular body 65 is provided at the bottom 61 of the pulley 60. A second annular gap C2 is formed between the second tubular portion 67 of the tubular body 65 and the small diameter portion 42. In other words, two gaps C1 and C2 that suppress the intrusion of dust are formed between the pulley 60 and the support portion 40. Therefore, dust is less likely to reach the inside of the bearing 30.

In addition, the second cylindrical portion 67 is provided on the bottom portion 61 of the pulley 60. Because the second cylindrical portion 67 is not fitted to the support portion 40, no external force is applied to the support portion 40. As a result, no load is applied to the bearing 30 provided on the support portion 40, and the life of the bearing 30 can be extended.

In addition, the second tubular portion 67 is provided on the pulley 60, which is a rotating body. When the pulley 60 rotates, the second tubular portion 67 also rotates. Air flow is easily generated in the second gap C2 between the second tubular portion 67 and the small diameter portion 42 of the support portion 40. Dust is less likely to enter the second gap C2.

In addition, the first dimension A1 is shorter than the second dimension A2. The first gap C1 is both the entrance of dust into the pulley 60 and the exit of dust that has entered the pulley 60. By shortening the first dimension A1, even if dust has entered the pulley 60 from the first gap C1, it is easier to discharge the dust from the first gap C1 to the outside of the pulley 60. The radial dimension B1 of the first gap C1 is smallest at the innermost side. This smallest dimension is defined as dimension B11. The radial dimension B2 of the second gap C2 is largest at the outermost side. This largest dimension is defined as dimension B21. For example, if dimension B11 is set larger than dimension B21 (B11<B21), even if dust has entered the pulley 60 from the first gap C1, it is easier to discharge the dust from the first gap C1 to the outside of the pulley 60.

See FIG. 1. In addition, the outer peripheral surface 44 of the large diameter portion 45 is inclined (inclined angle θ) so that the diameter of the outer peripheral surface 44 decreases as it moves outward (toward the pulley 60). Therefore, dust that adheres to the surface of the outer peripheral surface 44 below the center line L1 moves inward and away from the bearing 30. This makes it difficult for dust to enter the bearing 30.

Explain other effects.

Refer to Figures 1 and 3. A first annular gap C1 is formed between the cylindrical portion 62 of the pulley 60 and the support portion 40 that supports the rotating shaft 50.

The end face of the support portion 40 that faces the bottom portion 61 of the pulley 60 is the facing surface 40a (the facing surface 40a can be said to include the end face 46 of the small diameter portion 42, the end face 47 of the large diameter portion 45, and the end faces 86 of the first rib 81 to 89 of the fourth rib 84). If dust penetrates, it may reach the edge of the facing surface 40a (the end face 47 of the large diameter portion 45).

In addition to the communication hole 39, the opposing surface 40a is formed with a recess 70. The recess 70 includes a third recess 73 that is located above the upper end 30a of the bearing 30 (see line L4). Because the opposing surface 40a faces horizontally, dust moves downward. However, the pulley 60 is cylindrical with a bottom, and air flows inside the pulley 60 when the pulley 60 rotates.

Dust is subject to not only gravity but also external forces due to air flow. Some of the dust enters the third recess 73 (recess 70). Dust that enters the third recess 73 moves away from the bearing 30. The dust can be moved away from the bearing 30 in the horizontal direction, making it difficult for the dust to penetrate into the bearing 30.

Even if dust that has entered the third recess 73 (recess 70) moves toward the bearing 30, the distance it travels to reach the bearing 30 will be longer than if it moved along a plane on which the third recess 73 (recess 70) is not formed. The dust will be less likely to reach the bearing 30.

The same effect as above also makes it difficult for dust to reach the outlet of the communication hole 39. As a result, the life of the water pump 10 can be extended.

In addition, the radial thickness T1 of the large diameter portion 45 is thinner than the thickness T2 of the small diameter portion 42. Therefore, a larger recess 70 can be formed between the small diameter portion 42 and the large diameter portion 45. Dust can more easily penetrate into the recess 70. Dust can be separated from the bearing 30, making it more difficult for dust to reach the bearing 30. The life of the water pump 10 can be extended.

In addition, the recess 70 is partitioned by the first rib 81 to the fourth rib 84, and the second rib 82 to the fourth rib 84 are located above the communication hole 39 (see line L5). Even if dust that has entered the recess 70 moves along the surface of the recess 70 toward the communication hole 39, the second rib 82 to the fourth rib 84 impede the flow of dust. This makes it possible to prevent dust from entering the communication hole 39.

In addition, the formation of the second rib 82 to the fourth rib 84 makes it easier for turbulent air to occur within the pulley 60. This also makes it easier for external forces caused by turbulent air to act on dust, making it more difficult for the dust to reach the bearing 30. This makes it possible to extend the life of the water pump 10.

As long as the action and effect of the present invention is achieved, the present invention is not limited to the examples. For example, the center line L1 of the bearing hole 41 of the support part 40 is described as extending horizontally, but the direction in which the center line L1 extends is not limited to this. The present invention achieves the same effect even if the center line L1 is set to extend vertically or in an oblique direction halfway between the vertical and horizontal directions.

The water pump of the present invention is suitable for installation in engines of power shovels, vehicles, etc.

10... Water pump 15... Impeller 16... Mechanical seal (sealing member)
30: bearing; 30a: upper end; 39: communication hole; 40: support portion; 40a: opposing surface; 41: bearing hole; 42: small diameter portion; 43: outer peripheral surface; 45: large diameter portion; 44: outer peripheral surface; 50: rotating shaft; 51: outer end portion (one end);
52: Inner end (other end)
60...pulley 61...bottom, 64...inner surface 62...tubular portion, 68...inner peripheral surface 65...tubular body 66...flange portion 67...second cylindrical portion, 67a...inner peripheral surface 70...recess 71...first recess 72...second recess 73...third recess 81...first rib 82...second rib 83...third rib 84...fourth rib A1...first dimension (horizontal overlap dimension)
A2: Second dimension (horizontal overlap dimension)
B1: Radial dimension of the first gap B2: Radial dimension of the second gap C1: First gap C2: Second gap

Claims (6)

The rotating shaft has a support portion in which a bearing hole that supports a bearing is formed, a rotating shaft that is rotatably supported by the bearing and passes through the bearing hole, a bottomed cylindrical pulley provided at one end of the rotating shaft, an impeller provided at the other end of the rotating shaft, and a seal member disposed between the impeller and the bearing,
a communication hole is formed in the support portion to allow communication between a space between the seal member and the bearing in the bearing hole and an outside of the support portion;
the support portion has an annular small diameter portion having the bearing hole formed at its center, and an annular large diameter portion having an outer circumferential surface with a diameter larger than that of an outer circumferential surface of the small diameter portion, the outer circumferential surface of the annular large diameter portion being centered on the bearing hole,
At least a portion of the small diameter portion is located closer to the pulley than the large diameter portion,
a first annular gap is formed between the cylindrical portion of the pulley and the large diameter portion,
a second cylindrical portion is provided at a bottom of the pulley, and a second annular gap is formed between the second cylindrical portion and the small diameter portion ,
a first dimension is an axial dimension of an overlap between the cylindrical portion of the pulley and the large diameter portion of the support portion,
If the axial dimension of the overlapping portion between the second cylindrical portion and the small diameter portion of the support portion is defined as a second dimension,
The water pump , wherein the first dimension is less than the second dimension . 2. The water pump according to claim 1, wherein a radial dimension of at least one of the first gap or the second gap is set to become narrower toward the impeller side, based on a direction in which a center line of the bearing hole extends. the support portion has an opposing surface facing the bottom portion of the pulley,
3. The water pump according to claim 1, wherein the opposing surface is formed with a recess in addition to the communication hole. the large diameter portion surrounds the small diameter portion,
A thickness of the large diameter portion is smaller than a thickness of the small diameter portion based on a radial direction,
4. The water pump according to claim 3 , wherein the recess is defined by a space between the small diameter portion and the large diameter portion. 5. The water pump according to claim 4, wherein a plurality of ribs are formed from an outer circumferential surface of the small diameter portion to an inner circumferential surface of the large diameter portion. The centerline of the bearing hole extends horizontally,
6. The water pump according to claim 3, wherein at least a portion of the recess formed in the opposing surface is located above an upper end of the bearing.

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