Bearing support structure and electric pump

Abstract

To provide a structure that effectively prevents fretting and creep with a simple configuration. [Solution] A rolling bearing is provided, comprising an inner ring positioned radially inward, an outer ring positioned radially outward, and a plurality of rotating bodies located between the inner and outer rings and capable of rotational movement in the circumferential direction; a bearing holding portion having a circular inner wall into which the outer ring is fitted by clearance fitting, the inner wall having a groove that extends circumferentially and has a depth toward the radially outward direction; and a sealing material disposed in the groove, the radially inward inner surface of which contacts the radially outward outer surface of the outer ring.

Description

Technical Field

[0001] The present invention relates to a bearing support structure and an electric pump.

Background Art

[0002] Conventionally, rolling bearings have been known as bearings for a rotating shaft. A typical rolling bearing includes a plurality of rotating bodies between an inner ring and an outer ring, and the inner ring supports the rotating shaft. For example, Patent Document 1 discloses a configuration in which O-rings are disposed in two O-ring grooves formed on the outer peripheral surface of the outer ring at substantially the same interval as the width of the rolling elements in the axial direction.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the conventional technology, since the O-ring is small, a plurality of O-rings are required to prevent fretting and creep between the outer ring and the housing. Specifically, in the conventional technology, an O-ring groove is formed in the outer ring of the rolling bearing. However, since rolling elements exist on the inner side in the radial direction of the outer ring, in order to avoid interference with the rolling elements, the O-ring groove is formed at a distance substantially the same as the width of the rolling elements in the axial direction. Therefore, two O-rings are required. Furthermore, since it is difficult to form a large O-ring groove in the outer ring of the rolling bearing, the O-ring disposed in the O-ring groove becomes small. For this reason, the effect of preventing fretting and preventing creep may be reduced over time due to wear of the O-ring or the like.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide a structure that effectively prevents fretting and creep with a simple configuration. [Means for solving the problem]

[0006] A bearing support structure according to one embodiment comprises a rolling bearing having a plurality of rotating bodies that can rotate in the circumferential direction between an inner ring and an outer ring in the radial direction; a bearing holding portion having a circular inner wall into which the outer ring is fitted by clearance fitting, and having a groove in the inner wall that extends in the circumferential direction and has a depth toward the radially outward direction; and a sealing material disposed in the groove, the radially inward inner surface of which contacts the radially outward outer surface of the outer ring.

[0007] In other words, in a structure in which a rolling bearing is supported by a bearing holder, if the outer ring of the rolling bearing and the inner wall of the bearing holder are in a clearance fit, the outer ring becomes rotatable relative to the inner wall, and fretting or creep may occur at the point where the two contact. Therefore, a groove is formed in the inner wall of the bearing holder, and a sealing material is placed in the groove so that the radially inward inner surface of the sealing material contacts the radially outward outer surface of the outer ring. With this configuration, the possibility of contact between the outer ring of the rolling bearing and the inner wall of the bearing holder is reduced, and the possibility of fretting or creep occurring is reduced. [Brief explanation of the drawing]

[0008] [Figure 1] This is a diagram illustrating an electric pump. [Figure 2] This is a diagram showing the bearing support structure. [Modes for carrying out the invention]

[0009] Here, embodiments of the present invention will be described in the following order. (1) Electric pump configuration: (2) Bearing support structure: (3) Other embodiments, etc.:

[0010] (1) Electric pump configuration: This description will use the configuration of an electric pump having a bearing support structure as shown in this embodiment. The electric pump according to this embodiment is, for example, a pump that circulates a fluid (refrigerant) to cool an engine, motor, or inverter mounted on a vehicle. Figure 1 is a cross-sectional view showing the electric pump 1 cut in half along a plane containing the rotation axis Ax of the shaft 10 of the electric pump 1. In Figure 1, structures other than the bearing support structure are omitted and shown in gray. In the example shown in Figure 1, the rotation axis Ax is oriented in the vertical direction of the drawing, but the electric pump 1 can be used in any orientation. In this specification, the direction along the rotation axis Ax is referred to as the "axial direction," and the direction along the circumference of a circle centered on the rotation axis Ax is referred to as the "circumferential direction." Furthermore, the direction perpendicular to the rotation axis Ax is referred to as the "radial direction," and in the radial direction, the direction approaching the rotation axis Ax is referred to as the radially inward direction, and the direction moving away from the rotation axis Ax is referred to as the radially outward direction.

[0011] The electric pump 1 comprises a shaft 10, and a fluidizing section 20 is provided on one end of the shaft 10 in the axial direction. The fluidizing section 20 is the part that causes fluid to flow as the shaft 10 rotates. The configuration of the fluidizing section 20 is not limited, but for example, it can be realized by a configuration that includes an impeller (not shown) connected to the shaft 10 and rotating with the shaft 10, and a housing (not shown) that houses the impeller. The housing is connected to an inlet passage for introducing fluid into the housing and an outlet passage for releasing fluid to the outside of the housing. When the impeller rotates due to the shaft 10, fluid flows into the housing from the inlet passage and out of the housing from the outlet passage. As a result, the electric pump 1 can circulate fluid within the piping.

[0012] The electric pump 1 comprises a motor 11 having a rotor 12 that rotates around a rotation axis Ax, and a stator 13 positioned radially outward from the rotor 12. The motor 11 is electrically connected to a circuit board (not shown) located in the control unit 14, and the rotation of the motor 11 is controlled by a circuit on the circuit board. The shaft 10 rotates in conjunction with the rotor 12.

[0013] (2) Bearing support structure: In this embodiment, the shaft 10 is supported by rolling bearings at two locations in the axial direction. Specifically, the shaft 10 is supported by a rolling bearing 30 at the end opposite to the fluidized section 20, and by a second rolling bearing 40 at the end on the fluidized section 20 side.

[0014] Figure 2 is a diagram showing the rolling bearing portion extracted from Figure 1. The second rolling bearing 40 comprises a second inner ring 41 positioned radially inward, a second outer ring 42 positioned radially outward, and a plurality of second rotating bodies 43 located between the second inner ring 41 and the second outer ring 42, which are rotatable in the circumferential direction.

[0015] The second rolling bearing 40 is housed in a second bearing retaining portion 44 formed in the housing that accommodates the motor 11. Specifically, the second bearing retaining portion 44 has a second inner wall 44a that extends in the axial direction. The second inner wall 44a has a circular cross-section in the direction perpendicular to the axial direction. Furthermore, the circular shape formed by the second inner wall 44a is the same in the axial direction, and a cylindrical space is formed radially inside the second inner wall 44a. The second rolling bearing 40 is positioned radially inside the second inner wall 44a.

[0016] In this embodiment, the axial lengths of the second inner ring 41 and the second outer ring 42 are smaller than the axial length of the second inner wall 44a of the second bearing retaining portion 44. Therefore, the second rolling bearing 40 is housed in the second bearing retaining portion 44 with the radially outer surface of the second outer ring 42 in contact with the radially inner surface of the second inner wall 44a of the second bearing retaining portion 44. Furthermore, in this embodiment, the diameter of the radially outer surface of the second outer ring 42 is slightly larger than the diameter of the radially inner surface of the second inner wall 44a. For this reason, the second outer ring 42 is fitted into the second inner wall 44a by interference fit. Therefore, the second outer ring 42 and the second inner wall 44a do not move relative to each other in response to the operation of the electric pump 1 accompanied by the rotation of the shaft 10. For this reason, fretting and creep do not occur in the second inner wall 44a.

[0017] On the one hand, the rolling bearing 30 according to the present embodiment is a clearance fit. Specifically, the rolling bearing 30 includes an inner ring 31 disposed on the radially inner side, an outer ring 32 disposed on the radially outer side, and a plurality of rotors 33 existing between the inner ring 31 and the outer ring 32 and rotatable in the circumferential direction.

[0018] The rolling bearing 30 is housed in a bearing holding portion 34 formed in a housing that houses the motor 11. Specifically, the bearing holding portion 34 has an inner wall 34a extending in the axial direction. The inner wall 34a has a circular cross-section in a direction perpendicular to the axial direction. Further, except for a groove 34b described later, the circles formed by the inner wall 34a have the same shape in the axial direction, and a cylindrical space is formed inside the inner wall 34a in the radial direction. The rolling bearing 30 is disposed inside the inner wall 34a in the radial direction.

[0019] A groove 34b is formed at the axial center of the inner wall 34a. The groove 34b extends over the entire circumference in the circumferential direction on the inner wall 34a. Further, the groove 34b is a recess directed radially outward from the inner wall 34a and has a constant depth in the radially outward direction. Furthermore, on any plane perpendicular to the circumferential direction, the three surfaces constituting the groove 34b are perpendicular to each other, and a rectangular groove is formed.

[0020] In the present embodiment, the lengths of the inner ring 31 and the outer ring 32 in the axial direction are smaller than the length of the inner wall 34a of the bearing holding portion 34 in the axial direction. Therefore, the rolling bearing 30 is housed in the space formed inside the inner wall 34a of the bearing holding portion 34 in the radial direction. Further, in the present embodiment, the diameter of the outer surface on the radially outer side of the outer ring 32 is slightly smaller than the diameter of the inner surface on the radially inner side of the inner wall 34a. For this reason, the outer ring 32 is fitted to the inner wall 34a by a clearance fit.

[0021] As described above, in the case where the rolling bearing 30 is held by the bearing holder 34 by clearance fitting, when the outer ring 32 and the inner wall 34a relatively move in accordance with the operation of the electric pump 1 accompanied by the rotation of the shaft 10, fretting or creep may occur on the inner wall 34a. Therefore, in the present embodiment, the outer ring 32 and the inner wall 34a are configured not to relatively move.

[0022] Specifically, in the present embodiment, the sealing material 35 is disposed in the groove 34b. In the present embodiment, the sealing material 35 is an annular square gasket. That is, in the sealing material 35, the shape of the cross section in the direction perpendicular to the circumferential direction is rectangular, and the shape of the cross section is the same over the entire circumference in the circumferential direction. The sealing material 35 is made of an elastic body. The material of the sealing material 35 is not limited, and it can be made of various resins, for example, EPDM (ethylene propylene diene rubber), etc.

[0023] The diameter of the outer surface 35b on the radially outer side of the sealing material 35 is slightly larger than or substantially the same as the diameter of the inner surface 34b1 on the radially inner side of the groove 34b. Therefore, in the state where the sealing material 35 is disposed in the groove 34b, the sealing material 35 is not in a state where it can freely rotate in the circumferential direction.

[0024] The diameter of the inner surface 35a on the radially inner side of the sealing material 35 is smaller than the diameter of the outer surface 32a on the radially outer side of the outer ring 32. Therefore, when the rolling bearing 30 is fitted into the inner surface 35a of the sealing material 35, the outer ring 32 is fitted into the sealing material 35 while the outer surface 32a of the outer ring 32 expands the diameter of the inner surface 35a of the sealing material 35. For this reason, in the state where the rolling bearing 30 is fitted into the inner surface 35a of the sealing material 35, the outer ring 32 and the sealing material 35 do not relatively rotate. Therefore, although the outer ring 32 is fitted into the inner wall 34a by clearance fitting, the outer ring 32 does not relatively rotate with respect to the inner wall 34a. For this reason, the possibility of fretting or creep occurring on the inner wall 34a can be reduced.

[0025] In this embodiment, the sealing material 35 has a rectangular cross-section in the direction perpendicular to the circumferential direction. Therefore, compared to sealing materials with other cross-sectional shapes, such as circular ones, the contact area with the outer ring 32 can be increased. If the contact area between the outer ring 32 and the sealing material 35 is small, the effect of suppressing relative rotation between the outer ring 32 and the inner wall 34a will be reduced. However, in this embodiment, since a sealing material 35 with a rectangular cross-section is used, the outer ring 32 and the sealing material 35 can be configured to make contact with a sufficient contact area.

[0026] Furthermore, when comparing a sealing material with a circular cross-section and a sealing material with a rectangular cross-section 35 that can be placed in the same groove 34b, the sealing material with a circular cross-section has a smaller volume and is more prone to breakage. However, since the sealing material 35 in this embodiment has a rectangular cross-section, the possibility of breakage can be reduced compared to other sealing materials with a circular cross-section.

[0027] Furthermore, in this embodiment, the groove 34b is formed at one location on the inner wall 34a in the axial direction. Therefore, there is only one sealing material 35 between the outer ring 32 and the bearing retaining portion 34. Thus, compared to a configuration in which two O-rings are fitted to the outer ring, as in Patent Document 1, fretting and creep can be prevented with a simpler configuration.

[0028] Furthermore, in configurations such as Patent Document 1, where grooves are formed on the outer ring, it is necessary to form the grooves at a distance approximately equal to the diameter of the rotating body in the axial direction in order to avoid interference with the rotating body. Moreover, even if grooves are formed while avoiding the area where the rotating body is located, forming large grooves on the outer ring 32 will cause interference with the rotating body. However, in this embodiment, since grooves 34b are formed on the inner wall 34a of the bearing holder 34, it is not necessary to form grooves on the outer ring 32 of the rolling bearing 30.

[0029] Therefore, in this embodiment, a larger sealing material 35 can be used compared to the configuration described in Patent Document 1. As a result, the possibility of damage to the sealing material 35 can be reduced compared to a configuration using a small O-ring. Furthermore, since the possibility of fretting and creep occurring can be reduced by a single sealing material 35, the possibility of fretting and creep occurring can be reduced with a simple configuration.

[0030] (3) Other embodiments, etc.: The embodiments described above are merely examples for carrying out the present invention and are not limited thereto; various other embodiments can be adopted. A rolling bearing only needs to have a plurality of rotating bodies that can rotate in the circumferential direction between an inner ring and an outer ring in the radial direction. That is, it is sufficient that the friction between the shaft on the inner ring side and the bearing holder on the outer ring side is configured to be rolling friction. The shape of the rotating bodies is not limited; in addition to spheres as in the embodiments described above, they may be composed of cylinders, columns, etc. The inner ring and outer ring only need to be parts that can hold the plurality of rotating bodies in between, and their size and shape are not limited.

[0031] The bearing holder has a circular inner wall into which the outer ring is fitted by clearance fitting, and the inner wall has a groove formed therein that extends in the circumferential direction and has a depth that is directed radially outward. In other words, the bearing holder is the part that supports the rolling bearing by clearance fitting. However, if the rolling bearing is able to rotate while in contact with the inner diameter by clearance fitting, fretting and creep will occur, so a groove for placing a sealing material is formed in the inner wall of the bearing holder.

[0032] The groove only needs to be formed to accommodate a sealing material that contacts the outer surface of the outer ring. Therefore, the groove is formed to extend circumferentially on the inner wall. Furthermore, since the groove is formed in the bearing retaining portion, it has a depth on the inner wall that is directed radially outward. Typically, the groove has a constant depth and is formed around the entire circumference in the circumferential direction.

[0033] The sealing material can be any member that is placed in the groove and whose radially inner surface contacts the radially outer surface of the outer ring. In other words, by being placed in the groove, the radially inner surface of the sealing material is located radially inward from the inner wall of the bearing retaining part, and by contacting the radially outer surface of the outer ring, the possibility of direct contact between the inner wall and the outer ring can be reduced. Furthermore, the shape of the sealing material is not limited to a rectangular cross-section in the direction perpendicular to the circumferential direction, and may be circular or other shapes. Even a circular sealing material can be used as a sealing material if it deforms upon contact with the outer ring, increasing the contact area, and if the contact area becomes large enough to suppress relative rotation between the outer ring and the inner wall. [Explanation of symbols]

[0034] 1…Electric pump, 10…Shaft, 11…Motor, 12…Rotor, 13…Stator, 14…Control unit, 20…Fluid section, 30…Rolling bearing, 31…Inner ring, 32…Outer ring, 32a…Outer surface, 33…Rotating body, 34…Bearing holder, 34a…Inner wall, 34b…Groove, 34b1…Inner surface, 35…Sealing material, 35a…Inner surface, 35b…Outer surface, 40…Second rolling bearing, 41…Second inner ring, 42…Second outer ring, 43…Second rotating body, 44…Second bearing holder, 44a…Second inner wall

Claims

1. A rolling bearing comprising an inner ring positioned radially inward, an outer ring positioned radially outward, and a plurality of rotating bodies located between the inner and outer rings and capable of rotational movement in the circumferential direction, The bearing retaining portion has a circular inner wall into which the outer ring is fitted by clearance fitting, and the inner wall has a groove that extends in the circumferential direction and has a depth that is directed radially outward, A sealing material is disposed in the groove, the inner surface of which is radially inward contacts the outer surface of which is radially outward of the outer ring, A bearing support structure equipped with the following features.

2. The aforementioned sealing material is The cross-section perpendicular to the circumferential direction is rectangular. The bearing support structure according to claim 1.

3. The groove is formed at one location on the inner wall, One of the sealing materials is placed in the groove. The bearing support structure according to claim 1.

4. The bearing support structure according to claim 1, A second rolling bearing comprising: a second inner ring positioned radially inward; a second outer ring positioned radially outward; and a plurality of second rotating bodies located between the second inner ring and the second outer ring, which are circumferentially rotatable; The second bearing retainer has a circular second inner wall into which the second outer ring is fitted by interference fit, The shaft is supported at two points in the axial direction by the aforementioned rolling bearing and the aforementioned second rolling bearing, and rotates with the rotational driving force of the motor, A fluid section that causes fluid to flow by the rotation of the shaft, An electric pump equipped with [a specific feature].

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