Bearing assembly for an electric machine and electric machine
By designing a specific shape gap between the transition surface and the inner wall of the floating bearing outer ring and end cover in the motor bearing assembly, the problem of wave spring breakage under resonance is solved, improving the durability of the bearing assembly and the design efficiency of the motor.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- BOSCH POWERTRAIN SYSTEMS CO LTD
- Filing Date
- 2025-06-11
- Publication Date
- 2026-06-16
AI Technical Summary
Motor shafts and rotors are prone to resonance under external impacts and vibrations, which can cause wave springs to break, thereby affecting the motor's NVH performance and potentially damaging the entire machine.
Design a bearing assembly in which the outer ring of the floating bearing has a specific axial clearance between the transition surface and inner wall of the end cap, which can limit the axial movement of the motor shaft during resonance, prevent the wave spring from directly bearing the impact force, and thus prevent the wave spring from breaking.
It effectively prevents wave spring breakage, improves the durability of bearing assemblies, reduces the design requirements for wave springs, improves motor design efficiency, and saves design time.
Smart Images
Figure CN224367638U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of motors, and more specifically, to a bearing assembly for a motor and a motor. Background Technology
[0002] An electric motor (e.g., a vehicle drive motor) typically includes a motor shaft, a rotor to which the motor shaft is torsionally connected (e.g., coaxially mounted), and a stator mounted around the rotor on the inner side of a motor housing. Additionally, bearing assemblies can be provided at both axial ends of the motor shaft to support smooth motor operation. For example, the bearing assemblies may include: an end cap including an inner peripheral wall and a bottom wall extending radially from the inner peripheral wall; a floating bearing (e.g., a rolling ball bearing) having an inner ring and an outer ring, the inner ring being configured to be mounted around one of the axial ends of the motor shaft, and the inner peripheral wall of the end cap being mounted around the outer ring of the floating bearing; and a wave spring, a first axial end abutting against the outer ring of the floating bearing and a second axial end abutting against the bottom wall of the end cap to provide a preload force to the outer ring of the floating bearing relative to the end cap, thereby allowing axial movement of the outer ring of the floating bearing within a certain range. This prevents the floating bearing from seizing due to external shocks and vibrations or excessive temperature differences.
[0003] However, during motor operation, especially under external impacts and vibrations, the motor shaft and rotor may resonate. This can cause the large-scale axial movement of the motor shaft and rotor to repeatedly and violently impact the wave spring, leading to its breakage. The consequences of a broken wave spring are very serious: First, the wave spring will no longer be able to provide preload to the floating bearing, resulting in NVH (noise, vibration, and harshness) problems in the motor, and the floating bearing will also be quickly damaged. Second, the broken wave spring may be sucked into the air gap between the stator and rotor, causing damage to the entire motor. Utility Model Content
[0004] One object of this invention is to provide an improved bearing assembly and motor for an electric motor that can prevent wave spring breakage.
[0005] According to one aspect of the present invention, a bearing assembly for an electric motor is provided, comprising an end cap, a wave spring, and a floating bearing. The floating bearing has an inner ring and an outer ring, the inner ring being configured to be assembled around a motor shaft of the motor. The outer ring includes an axial end face, an outer peripheral surface, and a transition surface connecting the axial end face and the outer peripheral surface. The end cap includes a first inner peripheral wall, a second inner peripheral wall, and a transition inner wall connecting the first inner peripheral wall and the second inner peripheral wall. The second inner peripheral wall of the end cap is assembled around the outer peripheral surface of the outer ring, and the axial end face of the outer ring abuts against a first axial end face of the wave spring, such that the wave spring provides a preload force to the outer ring relative to the end cap. The floating bearing is configured in a first state having the transition surface of the outer ring spaced apart from the transition inner wall of the end cap, and in a second state having a portion of the transition surface of the outer ring abutting against the transition inner wall of the end cap.
[0006] Optionally, the end cap includes a bottom wall extending radially from the first inner peripheral wall, the bottom wall abutting against a second axial end side of the wave spring opposite to the first axial end side, and in the second state of the floating bearing, the axial distance between the bottom wall and the axial end face is equal to or greater than the minimum working height of the wave spring.
[0007] Optionally, in the second state of the floating bearing, a portion of the transition surface of the outer ring abuts against the transition inner wall of the end cap in a face-to-face contact manner.
[0008] Optionally, a portion of the transition surface of the outer ring and the transition inner wall of the end cap have the same arc shape, the same parabolic shape, or the same slope shape.
[0009] Optionally, the range of desired axially movable distances of the motor shaft and the motor rotor is set within the range of variation of the axial clearance between the transition surface of the outer ring and the transition inner wall of the end cap in the first state of the floating bearing.
[0010] Optionally, the axial clearance can vary from 0 to 0.5 mm.
[0011] Optionally, in the first state of the floating bearing, another portion of the transition surface of the outer ring extends axially beyond the transition inner wall of the end cap.
[0012] Optionally, the inner ring is configured to be mounted around a first axial end of the motor shaft, and the bearing assembly for the motor also includes a fixed bearing configured to be mounted around a second axial end of the motor shaft.
[0013] According to another aspect of the present invention, an electric motor is provided, comprising: a motor shaft; and a bearing assembly for the electric motor as described above, mounted around the motor shaft.
[0014] Optionally, the motor shaft includes a first radially projecting surface that supports the inner ring from a first axial direction, and the preload force provided by the wave spring to the outer ring is in a second axial direction opposite to the first axial direction.
[0015] During the operation of the motor provided by this utility model, if the motor shaft (and rotor) resonates due to external impacts and vibrations, or if the external impact is too large, a portion of the transition surface of the outer ring will abut against the transition inner wall of the end cover to restrict the axial movement of the motor shaft and directly transmit a large part of the impact force generated by the axial movement of the motor shaft to the end cover, rather than the wave spring. This not only prevents the wave spring from breaking and increases the durability of the bearing assembly, but also reduces the design requirements or restrictions on the wave spring, improves the design efficiency of the motor, and saves design time.
[0016] Other features and advantages of the present invention will become clear from the following detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings. Attached Figure Description
[0017] The accompanying drawings, which form part of this specification, illustrate embodiments of the present invention and, together with the specification, serve to explain the principles of the present invention.
[0018] Figure 1 This is a cross-sectional schematic diagram of a portion of a motor according to one embodiment of the present invention.
[0019] Figure 2 It is used in Figure 1 A cross-sectional schematic diagram of the bearing assembly of the motor.
[0020] Figure 3 yes Figure 2 A partial enlarged view of the bearing assembly. Detailed Implementation
[0021] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values of the components and steps set forth in these embodiments do not limit the scope of the present invention.
[0022] Technologies and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such technologies and equipment should be considered part of the specification.
[0023] In all the examples shown and discussed herein, any specific values should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.
[0024] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.
[0025] refer to Figure 1 The motor 10, such as a vehicle drive motor 10, includes a motor housing (not shown) and other components of the motor 10 housed within the motor housing. The other components of the motor 10 include: a motor shaft 12, which includes a first axial end 12a and a second axial end 12b, and a shaft body 12c located between the first axial end 12a and the second axial end 12b; a rotor 14 torsionally connected to the motor shaft 12, for example, the rotor 14 being coaxially mounted around the shaft body 12c via a balance disc 16; a stator (not shown) mounted around the rotor 14 on the inner side of the motor housing; and a bearing assembly, which may include a floating bearing 18 disposed at the first axial end 12a and a fixed bearing 20 disposed at the second axial end 12b to support smooth operation of the motor 10.
[0026] refer to Figure 2 The bearing assembly may further include a first end cap 22 and a wave spring 24 for use with the floating bearing 18. The floating bearing 18 has a first inner ring 18a, a first outer ring 18b, and rolling balls (not shown for clarity) located between the first inner ring 18a and the first outer ring 18b. Generally, a relative axial offset between the first inner ring 18a and the first outer ring 18b can occur within an allowable range, for example, 0.3-0.5 mm. The first inner ring 18a is configured to assemble around a first axial end 12a of the motor shaft 12. For example, the first axial end 12a of the motor shaft 12 forms a first radially projecting surface 12a1, the first inner ring 18a has a first axial end face 18a1 and a second axial end face 18a2 opposite to the first axial end face 18a1, the first radially projecting surface 12a1 supporting the second axial end face 18a2 from a first axial direction (as shown by arrow A1).
[0027] Similarly, the first outer ring 18b has a first axial end face 18b1 and a second axial end face 18b2 opposite to the first axial end face 18b1. The first axial end face 18b1 of the first outer ring 18b is on the same side as the first axial end face 18a1 of the first inner ring 18a, and the second axial end face 18b2 of the first outer ring 18b is on the same side as the second axial end face 18a2 of the first inner ring 18a. The first axial end face 18b1 of the first outer ring 18b, or its outer periphery, has a first outer diameter. The first outer ring 18b also includes an outer peripheral surface 18b3 with a second outer diameter and a transition surface 18b4 connecting the first axial end face 18a1 and the outer peripheral surface 18b3. The first outer diameter is smaller than the second outer diameter. That is, the transition surface 18b4 is located between the first axial end face 18b1 and the outer peripheral surface 18b3 of the first outer ring 18b, and the outer diameter of the transition surface 18b4 changes along the axial direction.
[0028] The first end cap 22 is configured to be fixed to the motor housing to help shield other components of the motor 10 within the housing. The first end cap 22 includes a first inner peripheral wall 22a having a first inner diameter, a second inner peripheral wall 22b having a second inner diameter, and a transition inner wall 22c connecting the first inner peripheral wall 22a and the second inner peripheral wall 22b. The first inner diameter is between a first outer diameter and a second outer diameter, and the second inner diameter is substantially equal to the second outer diameter. Thus, the second inner peripheral wall 22b of the first end cap 22 can be assembled around the outer peripheral surface 18b3 of the first outer ring 18b. In other words, the transition inner wall 22c is located between the first inner peripheral wall 22a and the second inner peripheral wall 22b, and the inner diameter of the transition inner wall 22c changes axially.
[0029] The first end cap 22 also includes an annular bottom wall 22d extending radially from the first inner peripheral wall 22a, whereby the annular bottom wall 22d, the first inner peripheral wall 22a, and the first axial end face 18b1 of the first outer ring 18b together define a space for accommodating the wave spring 24. The first axial end face 18b1 of the first outer ring 18b abuts against the first axial end side of the wave spring 24, and the annular bottom wall 22d abuts against the second axial end side of the wave spring 24 opposite to the first axial end side, thereby compressing the wave spring 24 to provide a preload force to the floating bearing 18 relative to the first end cap 22 in a second axial direction opposite to the first axial direction (as shown by arrow A2).
[0030] It can be understood that the wave spring 24 forms a continuous wavy ring structure. In this wavy ring structure, crests and troughs alternate between the first and second axial ends of the wave spring 24, so that the wave spring 24 has a certain stiffness. Figure 2In the cross-section shown, the wave spring 24 is neither in contact with the first axial end face 18b1 of the first outer ring 18b nor with the annular bottom wall 22d. However, viewed from the perspective of the entire wave spring 24, the first axial end face 18b1 of the first outer ring 18b abuts against the first axial end side of the wave spring 24, and the annular bottom wall 22d abuts against the second axial end side of the wave spring 24. Generally speaking, the stiffness of the wave spring 24 is greatly affected by process parameters, and the error can be ±20%.
[0031] In this invention, the floating bearing 18 is configured in a first state in which the transition surface 18b4 of the first outer ring 18b is separated from the transition inner wall 22c of the first end cover 22, and in a second state in which a portion of the transition surface 18b4 of the first outer ring 18b (i.e., a portion of the outer peripheral surface 18b3 of the transition surface 18b4 near the first outer ring 18b) abuts against the transition inner wall 22c of the first end cover 22.
[0032] For example, in the initially assembled motor 10, or during the stable operation of the motor 10, the floating bearing 18 may have a first state in which the wave spring 24 is compressed to have a first (axial) working height.
[0033] Optionally, in the first state of the floating bearing 18, another portion of the transition surface 18b4 of the first outer ring 18b (i.e., a portion of the axial end face of the transition surface 18b4 near the first outer ring 18b) protrudes axially beyond the transition inner wall 22c of the first end cover 22 to prevent the wave spring 24 from contacting the transition inner wall 22c and thus causing mutual interference.
[0034] Simultaneously, based on the desired range of axial movement of the motor shaft 12 and rotor 14 (typically determined by the allowable range of relative axial offset between the first inner ring 18a and the first outer ring 18b), an axial clearance S is set between the transition surface 18b4 of the first outer ring 18b and the transition inner wall 22c of the first end cover 22 (especially as...). Figure 3 The range of variation is shown in the figure. For example, the axial clearance S varies between 0 and 0.5 mm. That is, for the same bearing assembly, when the transition surface 18b4 of the first outer ring 18b is maximally separated from the transition inner wall 22c of the first end cover 22, the axial clearance S is approximately 0.5 mm. When the transition surface 18b4 of the first outer ring 18b is not maximally separated from the transition inner wall 22c of the first end cover 22 under normal external impact, the axial clearance S is less than 0.5 mm.
[0035] For example, in cases where external impacts and vibrations cause resonance between the motor shaft 12 and the rotor 14, or in cases where the external impact is excessive, the floating bearing 18 can have a second state. In this second state, the wave spring 24 is further compressed to have a second (axial) working height, which must be equal to or greater than the minimum or limit (axial) working height of the wave spring 24. That is, the axial distance between the annular bottom wall 22d and the axial end face of the first outer ring 18b must be equal to or greater than the minimum working height of the wave spring 24. In this second state, a portion of the transition surface 18b4 of the first outer ring 18b abuts against the transition inner wall 22c of the first end cover 22 to restrict the axial movement of the motor shaft 12 and directly transmit the impact force generated by the axial movement of the motor shaft 12 to the first end cover 22, rather than the wave spring 24. This not only prevents the wave spring 24 from breaking and increases the durability of the bearing assembly, but also reduces the design requirements or limitations on the wave spring 24 (as mentioned above, the stiffness of the wave spring 24 is greatly affected by process parameters), improving the design efficiency of the motor 10 and saving design time.
[0036] Optionally, in the second state of the floating bearing 18, a portion of the transition surface 18b4 of the first outer ring 18b abuts against the transition inner wall 22c of the first end cap 22 in a face-to-face contact manner.
[0037] from Figure 3 As can be seen in the cross-sectional schematic diagram, a portion of the transition surface 18b4 of the first outer ring 18b can be an arc shape with a first curvature, which can be a single curvature or a composite curvature (i.e., including at least two different curvatures). The transition inner wall 22c of the first end cap 22 can also be an arc shape with a second curvature. The second curvature can be the same as or similar to the first curvature.
[0038] In fact, the shape of the portion of the transition surface 18b4 of the first outer ring 18b and the shape of the transition inner wall 22c of the first end cap 22 are not restricted, as long as care is taken to prevent stress concentration when the floating bearing 18 transitions from the first state to the second state.
[0039] For example, a portion of the transition surface 18b4 of the first outer ring 18b can be a first parabolic shape. The transition inner wall 22c of the first end cap 22 can also be a second parabolic shape. The second parabolic shape can be the same as or similar to the first parabolic shape.
[0040] For example, a portion of the transition surface 18b4 of the first outer ring 18b can be a ramp shape having a first slope relative to the axial direction. The transition inner wall 22c of the first end cap 22 can also be a ramp shape having a second slope relative to the axial direction. The second slope can be the same as or similar to the first slope.
[0041] In practice, the shape of the transition inner wall 22c of the first end cap 22 is generally designed based on the shape of a portion of the transition surface 18b4 of the first outer ring 18b.
[0042] Return to Figure 1 The bearing assembly may further include a second end cap 26, a retaining ring 28, and a snap ring 30 for securing the bearing 20. The secured bearing 20 has a second inner ring 20a, a second outer ring 20b, and rolling balls (not shown for clarity) located between the second inner ring 20a and the second outer ring 20b. The second inner ring 20a of the secured bearing 20 is configured to assemble around a second axial end 12b of the motor shaft 12. For example, the second axial end 12b of the motor shaft 12 forms a second radially projecting surface 12b1, the second inner ring 20a has a first axial end face and a second axial end face opposite to the first axial end face, the second radially projecting surface 12b1 supporting the first axial end face of the second inner ring 20a from the second axial direction, and the retaining ring 28 supporting the second axial end face of the second inner ring 20a from the first axial direction (as shown by arrow A1) to secure the second inner ring 20a. Similarly, the second outer ring 20b of the fixed bearing 20 has a first axial end face and a second axial end face opposite to the first axial end face. The first axial end face of the second outer ring 20b is on the same side as the first axial end face of the second inner ring 20a, and the second axial end face of the second outer ring 20b is on the same side as the second axial end face of the second inner ring 20a.
[0043] The second end cap 26 is configured to be fixed to the motor housing to help shield other components of the motor 10 in the motor housing, and the second end cap 26 supports the first axial end face of the second outer ring 20b from the second axial direction, and the retaining ring 30 fixed to the second end cap 26 supports the second axial end face of the second outer ring 20b from the second axial direction (as shown by arrow A2).
[0044] While specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of the present invention. The scope of the present invention is defined by the appended claims.
Claims
1. A bearing assembly for an electric motor (10), comprising an end cap (22), a wave spring (24), and a floating bearing (18) having an inner ring (18a) and an outer ring (18b), the inner ring (18a) being configured to assemble around a motor shaft (12) of the electric motor (10), characterized in that: The outer ring (18b) includes an axial end face (18b1), an outer peripheral surface (18b3), and a transition surface (18b4) connecting the axial end face (18b1) and the outer peripheral surface (18b3). The end cap (22) includes a first inner peripheral wall (22a), a second inner peripheral wall (22b), and a transition inner wall (22c) connecting the first inner peripheral wall (22a) and the second inner peripheral wall (22b). The second inner peripheral wall (22b) of the end cap (22) is assembled around the outer peripheral surface (18b3) of the outer ring (18b), and the axial end face (18b1) of the outer ring (18b) abuts against the first axial end side of the wave spring (24) so that the wave spring (24) provides a preload force to the outer ring (18b) relative to the end cap (22), and the floating bearing (18) is configured in a first state having the transition surface (18b4) of the outer ring (18b) separated from the transition inner wall (22c) of the end cap (22) and a second state having a portion of the transition surface (18b4) of the outer ring (18b) abutting against the transition inner wall (22c) of the end cap (22).
2. The bearing assembly for the motor (10) according to claim 1, characterized in that, The end cap (22) includes a bottom wall extending radially from the first inner peripheral wall (22a), which abuts against the second axial end side of the wave spring (24) opposite to the first axial end side. In the second state of the floating bearing (18), the axial distance between the bottom wall and the axial end face (18b1) is equal to or greater than the minimum working height of the wave spring (24).
3. The bearing assembly for a motor (10) according to claim 1 or 2, characterized in that, In the second state of the floating bearing (18), a portion of the transition surface (18b4) of the outer ring (18b) abuts against the transition inner wall (22c) of the end cap (22) in a face-to-face contact manner.
4. The bearing assembly for the motor (10) according to claim 3, characterized in that, The portion of the transition surface (18b4) of the outer ring (18b) and the transition inner wall (22c) of the end cap (22) have the same arc shape, the same parabolic shape, or the same slope shape.
5. The bearing assembly for a motor (10) according to claim 1 or 2, characterized in that, The desired range of axially movable distance of the rotor (14) of the motor shaft (12) and the motor (10) is set within the range of axial clearance between the transition surface (18b4) of the outer ring (18b) and the transition inner wall (22c) of the end cap (22) in the first state of the floating bearing (18).
6. The bearing assembly for the motor (10) according to claim 5, characterized in that, The axial clearance varies from 0 to 0.5 mm.
7. The bearing assembly for an electric motor (10) according to claim 1 or 2, characterized in that, In the first state of the floating bearing (18), another portion of the transition surface (18b4) of the outer ring (18b) extends axially beyond the transition inner wall (22c) of the end cap (22).
8. The bearing assembly for an electric motor (10) according to claim 1 or 2, characterized in that, The inner ring (18a) is configured to be mounted around the first axial end (12a) of the motor shaft (12), and the bearing assembly for the motor (10) also includes a fixed bearing (20) configured to be mounted around the second axial end (12b) of the motor shaft (12).
9. An electric motor (10), characterized in that, include: Motor shaft (12); and A bearing assembly for a motor (10) according to any one of claims 1 to 8, assembled around the motor shaft (12).
10. The motor (10) according to claim 9, characterized in that, The motor shaft (12) includes a first radial protruding surface (12a1) that supports the inner ring (18a) from a first axial direction, and the preload provided by the wave spring (24) to the outer ring (18b) is in a second axial direction opposite to the first axial direction.