Bearing preloading device and rotating electric machine equipped therewith
The bearing preloading device allows for arbitrary switching between constant-pressure and fixed-position preloading in rotating electric machines, addressing preload variability and loss issues by using a combination of permanent magnets and an electromagnet for adjustable preload adjustment.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- IGARASHI ELECTRIC WORKS
- Filing Date
- 2024-12-26
- Publication Date
- 2026-07-08
AI Technical Summary
Existing bearing preloading methods in rotating electric machines lack the ability to arbitrarily switch between constant-pressure and fixed-position preloading based on application and operating conditions, leading to issues such as varying preload with temperature changes, load, and rotational speed, and potential preload loss due to wear.
A bearing preloading device with a cylindrical fixed base, movable constant-pressure and fixed-position bases, an electromagnet assembly, and permanent magnets, allowing for arbitrary switching between constant-pressure and fixed-position preloading via a controller, using magnetic forces to adjust preload.
Enables versatile and cost-effective preload adjustment according to the rotating electric machine's conditions, ensuring appropriate preload regardless of application or operating conditions, with a simple configuration using two sets of permanent magnets and one electromagnet.
Smart Images
Figure 2026114066000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a pressure application device for bearings, and more particularly to a bearing pressure application device capable of arbitrarily switching between constant pressure application and fixed position pressure application, and a rotating electric machine provided with the same.
Background Art
[0002] The rolling bearing device of a rotating electric machine supports both ends of a rotating shaft with respect to a housing by rolling bearings such as ball bearings and tapered roller bearings. As pressure application methods for rolling bearings, constant pressure application and fixed position pressure application are known. Patent Document 1 discloses an invention of a pressure application device that switches between constant pressure application and fixed position pressure application. The invention of Patent Document 1 has a structure in which pressure is applied by two components, a spring component and a holder, in order to solve the situation where the spring component cannot apply pressure, such as when the shaft is subjected to a strong impact or used in an environment with a large temperature difference. Basically, constant pressure is applied by a spring, and when the state exceeds the yield strength of the spring, such as when an impact is applied, it is held by the holder to achieve fixed position pressure application.
[0003] Patent Document 2 discloses an invention of a bearing pressure application device that applies pressure to a bearing using electromagnetic force. According to this invention, when the spindle of a machine tool generates resonance due to a natural frequency under specific conditions, the natural frequency can be changed by adjusting the pressure applied to the bearing using electromagnetic force, thereby avoiding resonance.
[0004] Patent Document 3 also discloses an invention that applies pressure to a bearing using electromagnetic force. According to this invention, pressure can be applied only by electromagnetic force, and the intensity of the pressure can be appropriately controlled.
[0005] Patent Document 4 discloses a bearing pressure application device that applies pressure to a bearing only by the magnetic force of a permanent magnet. That is, in a structure in which a bearing is held using a squeeze film, the thrust surface of the bearing contacts some component, and pressure is applied by magnetic force in order to prevent the squeeze effect from being inhibited by the friction. [Prior art documents] [Patent Documents]
[0006] [Patent Document 1] Japanese Patent Application Publication No. 9-217739 [Patent Document 2] Japanese Patent Publication No. 2009-014101 [Patent Document 3] Japanese Patent Publication No. 2020-026865 [Patent Document 4] Japanese Patent Application Publication No. 58-29407 [Overview of the Initiative] [Problems that the invention aims to solve]
[0007] Generally, fixed-position preloading is suitable for providing higher rigidity (larger preload) compared to constant-pressure preloading. However, it has the disadvantage that the amount of preload changes with temperature changes and bearing deformation due to load. Also, the internal preload increases with rotational speed, so it is not suitable for high-speed rotation. Furthermore, there is a possibility of preload loss due to wear of component parts. On the other hand, constant pressure pre-pressure has the advantage of minimal change in pre-pressure due to temperature changes. However, it has the disadvantage of making it difficult to provide high rigidity.
[0008] In general-purpose rotating electric machines, which are manufactured with the expectation of being used in a variety of applications, the loads applied to the bearings during operation vary. Therefore, it is desirable that manufacturers or users be able to arbitrarily adjust the bearing preloading method so that the appropriate preload is applied to the bearings according to the application and operating conditions of the rotating electric machine. In the invention described in Patent Document 1, the structure switches between constant pressure and fixed position pressure under specific conditions set in advance, and it is not possible to arbitrarily switch between constant pressure and fixed position pressure depending on the application or operating conditions.
[0009] The invention described in Patent Document 2 aims to change the natural frequency of the main shaft (or its surrounding structure), and is different from both the generally known constant-position pre-pressure and constant-pressure pre-pressure. Therefore, it is not possible to arbitrarily switch between constant-pressure pre-pressure and constant-position pre-pressure depending on the application or operating conditions. The invention described in Patent Document 3 has a structure that variably controls the magnetic force of the electromagnet over the entire operating range, and it is not possible to arbitrarily switch between constant pressure pre-pressure and fixed position pre-pressure depending on the application and operating conditions. The invention described in Patent Document 4 is based on a structure that uses a squeeze membrane to hold the bearing, which lacks versatility and does not allow for arbitrary switching between constant pressure pre-pressure and fixed position pre-pressure depending on the application and operating conditions.
[0010] The object of the present invention is to provide a versatile bearing preloading device and a rotating electric machine equipped therewith, which allows the manufacturer or user to arbitrarily adjust the preloading method so that appropriate preload is applied to the bearing according to the application and operating conditions of the rotating electric machine in which the bearing is installed. [Means for solving the problem]
[0011] The bearing preloading device of the present invention is A cylindrical fixed base provided spaced apart from the bearing in the axial direction, A constant-pressure pre-pressure base is held in the hollow portion of the fixed base so as to be movable in the axial direction, A fixed-position pressure base is provided, on the side opposite to the bearing with respect to the constant-pressure pressure base, and is movably arranged in the axial direction. An electromagnet assembly fixed to the motor case has an electromagnet located on the opposite side of the constant-pressure base, with the constant-position pressure base in between, The system includes a spring member that, on the side facing the bearing, contacts the constant pressure base and applies the constant pressure to the bearing, The aforementioned fixed-position pressure base has an arm portion for applying fixed-position pressure to the bearing, The constant pressure application base is provided with a first permanent magnet, and the fixed position pressure application base is provided with a second permanent magnet having a polarity opposite to that of the first permanent magnet at a position facing the first permanent magnet. The electromagnet includes means for switching the current in the forward and reverse directions, and is configured to be capable of generating a magnetic force greater than the magnetic force between the first permanent magnet and the second permanent magnet in the forward and reverse directions between the electromagnet and the second permanent magnet.
[0012] Another feature of the present invention is a rotating electric machine including the bearing of the pressure application structure as a bearing for supporting a rotating shaft.
[0013] According to the present invention, according to the use and operating conditions of the rotating electric machine to which the bearing is mounted, by controlling the electromagnet, a bearing pressure application device and a rotating electric machine provided with the same that can be arbitrarily adjusted by a manufacturer or a user so that an appropriate pressure is applied to the bearing can be provided. In particular, since the preloading method can be easily switched only by the controller even after the pressure application device is incorporated into the unit, the preloading method can be switched according to the required rotational speed and load. Further, the present invention has a simple configuration using two sets of permanent magnets and one electromagnet, and can provide a versatile bearing pressure application device.
Brief Description of Drawings
[0014] [Figure 1] It is a longitudinal sectional view of a brushless motor including a bearing with a bearing pressure application device according to an embodiment of the present invention. [Figure 2] It is an exploded perspective view of the bearing pressure application device of FIG. 1. [Figure 3A] It is a side view of the constant pressure application base shown in FIG. 2. [Figure 3B] It is a front view of the constant pressure application base shown in FIG. 2. [Figure 3C] It is a rear view of the constant pressure application base shown in FIG. 2. [Figure 4A] It is a front view of the fixed position pressure application base shown in FIG. 2. [Figure 4B]It is a perspective view of the fixed-position pressure-applying base shown in FIG. 2. [Figure 5] It is a longitudinal sectional view of the bearing with a pressure-applying device of FIG. 1. [Figure 6] It is a diagram for explaining the operation of the electromagnet shown in FIG. 2. [Figure 7] It is a diagram showing an example of the relationship of the pressure-applying characteristics in the bearing pressure-applying device of the present invention. [Figure 8A] It is a diagram for explaining the function of constant-pressure application in the bearing pressure-applying device of the present invention. [Figure 8B] It is a diagram for explaining the function of constant-pressure application in the bearing pressure-applying device of the present invention. [Figure 9A] It is a diagram for explaining the function of fixed-position pressure application in the bearing pressure-applying device of the present invention. [Figure 9B] It is a diagram for explaining the function of fixed-position pressure application in the bearing pressure-applying device of the present invention.
Embodiments for Carrying Out the Invention
[0015] Hereinafter, embodiments of the bearing pressure-applying device according to the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view of a brushless motor as a rotating electric machine 1 provided with the bearing pressure-applying device according to the first embodiment of the present invention. The motor cases 2A and 2B of the DC motor 1 are cup-shaped metal cases such as iron with openings at their respective ends. A laminated iron core 1A constituting the stator of the DC motor is fixed to the motor cases 2A and 2B. A laminated iron core 1B constituting the rotor of the DC motor and a multi-pole permanent magnet magnetized in the circumferential direction are integrally formed with the rotating shaft 4, and this rotating shaft is rotatably supported by a pair of rolling bearings 3A and 3B on the metal motor cases 2A and 2B. A cylindrical magnet is adhesively fixed to the laminated iron core 1B, generating a magnetic field. The rolling bearing 3A side of the rotating shaft 4 is connected to the driven member.
[0016] The rotating electric machine 1 to which the present invention applies may be any other type of electric device or generator, as long as it comprises a stator and a rotor, and the rotating shaft of the rotor is supported by a pair of bearings. In the case of a generator, the rolling bearing 3A side of the rotating shaft 4 is connected to a power source. The rolling bearings 3A and 3B consist of an inner ring, an outer ring, and rolling elements between them. The bearing preloading device 5 applies a constant preload to the outer ring of the rolling bearing 3B, thereby providing the rotating electric machine 1 with predetermined bearing rigidity and stable rotation.
[0017] Next, the bearing preloading device 5 of the present invention will be described with reference to Figures 2 to 4B. First, Figure 2 is an exploded perspective view of the bearing preloading device 5. This bearing preloading device 5 is provided with a cylindrical fixed base 7 made of a non-magnetic material, spaced apart from the bearing 3B in the axial direction. The fixed base 7 has an annular body 70, a hollow portion 71, a guide hole 72, and a stopper portion 73, and is fixed to the motor case 2B by screws or press-fitting. A constant-pressure preloading base 8 made of a non-magnetic material is held within the hollow portion 71 of the fixed base 7 so as to be movable in the axial direction. Furthermore, within the fixed base 7, a fixed-position preloading base 9 made of a non-magnetic material is movably arranged on the side opposite to the bearing 3B relative to the constant-pressure preloading base 8. A cup-shaped electromagnet assembly 10 is arranged on the side opposite to the constant-pressure preloading base 8, sandwiching the fixed-position preloading base 9. This electromagnet assembly 10 is fixed to the motor case 2B by screws or press-fitting. Furthermore, on the side facing the bearing 3B, a wave washer 6, acting as a spring member, is positioned between the hollow portion 71 of the fixed base 7 and the constant-pressure / pre-pressure base 8. This wave washer 6 has a washer body 61 and a relief portion 62, and has the function of applying constant pressure / pre-pressure to the bearing 3B. The electromagnet assembly 10 has an iron core 102 fixed within a cup-shaped base 101 made of a non-magnetic material, an electromagnetic coil 103 wound around this iron core 102, and a controller 11 including a switch positioned between the coil 103 and its power supply. The controller 11 may be integrated with the controller of the rotating electric machine 1.
[0018] Next, the constant-pressure pressurized base 8 will be explained with reference to Figures 3A to 3C. Figure 3A is a side view of the constant-pressure pressurized base, Figure 3B is a front view of the constant-pressure pressurized base, and Figure 3C is a rear view of the constant-pressure pressurized base. The constant-pressure pre-pressure base 8 comprises a cylindrical base portion 80 having a surface perpendicular to the axial direction, and a cylindrical washer holding portion 81 having a smaller diameter than the base portion. A pair of first permanent magnets (82, 83) are embedded in the base portion 80 at positions symmetrical with respect to its center. These pair of permanent magnets are, for example, disc-shaped magnets with S poles and N poles stacked in the axial direction, and are installed so that each S pole and N pole is located on the same side with respect to the base portion 80.
[0019] Next, the fixed-position pressurized base 9 will be explained with reference to Figures 4A and 4B. Figure 4A is a front view of the fixed-position pressure base, and Figure 4B is a perspective view of the fixed-position pressure base. The fixed-position pressure base 9 has a base portion 90 having a surface perpendicular to the axial direction, a pair of arm portions 91 extending axially from the base portion 90, and a pair of second permanent magnets (92, 93) embedded in the base portion 90. The pair of arm portions 91 are members for applying fixed-position pressure to the bearing 3B. The pair of second permanent magnets (92, 93) are each positioned opposite the pair of first permanent magnets (82, 83), and are disc-shaped magnets with S poles and N poles stacked in the axial direction, and are installed so that each S pole and N pole is on the same side with respect to the base portion 90. However, the polarity of the pair of second permanent magnets (92, 93) is such that the opposing magnetic poles repel each other with respect to the pair of first permanent magnets (82, 83). For example, the first permanent magnets (82, 83) are a pair of permanent magnets positioned symmetrically with respect to the center of the constant-pressure pre-pressure base 8, and the second permanent magnets (92, 93) are permanent magnets positioned symmetrically with respect to the center of the constant-position pre-pressure base 9 and opposite the pair of first permanent magnets.
[0020] Figure 5 is a longitudinal cross-sectional view showing the state of bearing 3B with the bearing preloading device 5 incorporated. In particular, Figure 5 shows the relative positional relationships between bearing 3B, bearing constant pressure preloading base 8, fixed position preloading base 9, and electromagnet assembly 10. Here, bearing 3B is in a constant pressure preloading state, and fixed position preloading base 9 is attracted to base 101 by the electromagnet of electromagnet assembly 10. Due to the magnetic repulsion force between the first permanent magnets (82, 83) and the second permanent magnets (92, 93), the constant pressure preloading base 8 is separated from the fixed position preloading base 9 and positioned closer to bearing 3B. That is, due to the magnetic repulsion forces between the first and second permanent magnets, and between the first permanent magnet and the electromagnet assembly 10, the base portion 80 of the constant pressure preloading base 8 is pressed against the stopper portion 73 of the fixed base 7, and the constant pressure preloading base 8 is integrally held within the fixed base 7. As a result, the base portion 80 of the constant-pressure pre-pressure base 8 presses against the wave washer 6, and its spring force presses against the outer ring of the rolling bearing 3B, thereby applying a constant pre-pressure between the washer and the rolling elements of the rolling bearing 3B.
[0021] Next, the operation of the electromagnet assembly 10 will be explained with reference to Figures 6(A) and 6(B). The central axis of the iron core 102 of the electromagnet assembly 10 lies on the line connecting the centers of the constant-pressure pre-pressure base 8 and the fixed-position pre-pressure base 9. The direction of the current flowing through the electromagnetic coil 103, controlled by the controller 11, changes the north and south poles of the iron core 102, and is controlled to generate a magnetism that imparts either an attractive or repulsive force to the first and second permanent magnets. Furthermore, the magnetic force generated between the electromagnet assembly 10 and the second permanent magnet is greater than the magnetic force between the first permanent magnet and the second permanent magnet.
[0022] Next, the preloading characteristics of the bearing preloading device of the present invention will be explained with reference to Figure 7. Figure 7(a) shows an example of the relationship between the spring characteristics of the wave washer, F=kx, and the magnetic force of an electromagnet, etc. Figures 7(b) and (c) show the relationship between the force F applied to the bearing, the constant preloading by the wave washer, and the repulsive forces between the electromagnet and the permanent magnetic forces 82 and 83. In the constant pressure pre-pressure state, the wave washer applies a constant pressure pre-pressure to the bearing that is greater than the force F applied to the bearing under normal operating conditions. When the magnetic force of the electromagnet assembly 10 is increased to achieve a fixed position pre-pressure state, the bearing is held in place by an axial force greater than the force applied by the wave washer.
[0023] Next, the operation of the bearing preloading device of the present invention during constant pressure preloading will be explained with reference to Figures 8A and 8B. In the following, it will be assumed that the first permanent magnets (82, 83) are configured so that the bearing 3B side is the north pole, and the second permanent magnets (92, 93) are configured so that the bearing 3B side is the south pole. In this state, when the electromagnet assembly 10 is controlled to generate a magnetism such that the bearing 3B side is the south pole, the same state as described in Figure 5 will occur, the second permanent magnets (92, 93) of the constant-position preloading base 9 will be attracted to the electromagnet of the electromagnet assembly 10, the first permanent magnets (82, 83) of the constant-pressure preloading base 8 will be repelled by the electromagnet of the electromagnet assembly 10 and will move away from the constant-position preloading base 9, the wave washer 6 will be pushed by the base portion 80 of the constant-pressure preloading base 8, and a constant preload will be applied to the rolling bearing 3B.
[0024] Next, the function of the bearing preloading device of the present invention will be explained with reference to Figures 9A and 9B. When the state of the current flowing through the electromagnet of the electromagnet assembly 10 is reversed from the constant pressure preloading state, a magnetism is generated in the electromagnet assembly 10 with the bearing 3B side being the north pole. The first permanent magnets (82, 83) of the constant pressure preloading base 8 are attracted to the electromagnet assembly side by the magnetic force of the electromagnet assembly 10, but the second permanent magnets (92, 93) of the constant pressure preloading base 9 receive a greater repulsive force from the magnetic force of the electromagnet assembly 10. As a result, the constant pressure preloading base 9 moves away from the electromagnet assembly 10, and the constant pressure preloading base 9 moves further toward the bearing 3B side, beyond the position of the wave washer 6, to a position where it is in contact with the constant pressure preloading base 8, against the magnetic repulsive force between it and the constant pressure preloading base 8. As a result, the wave washer 6 is released, and the tips of the pair of arm portions 91 of the fixed-position pre-pressure base 9, which are pushed by the magnetic force of the electromagnet assembly 10, come into direct contact with the rolling bearing 3B, resulting in a fixed-position pre-pressure state.
[0025] In addition, other types of springs, such as conical coil springs, can be used for the spring member depending on the required characteristics, but they must have a shape that allows clearance for the column portion 91 of the constant-pressure / pre-pressure base and can support the outer ring of the rolling bearing 3B.
[0026] According to the present invention, a simple configuration using two sets of permanent magnets and one electromagnet allows for arbitrary switching between constant-pressure preloading and fixed-position preloading simply by switching the direction of the electromagnet's current. In other words, the present invention provides a versatile and inexpensive bearing preloading device. This allows for easy switching of the preloading method using only a controller, even after the preloading device has been incorporated into a unit. This enables switching of the preloading method according to the desired rotational speed and load. [Explanation of Symbols]
[0027] 2B Motor Case 3B bearing 5. Bearing preloading device 6 Wave Washers 7 Fixed base 73 Stopper part 8 Constant pressure / pressure base 80 Base section 82, 83 First permanent magnet 9. Fixed-position pressurized base 90 Base section 91 Arm section 92, 93 Second permanent magnet 10 Electromagnet Assembly 102 Iron Heart 103 Electromagnetic coil 11 Controllers
Claims
1. A cylindrical fixed base provided spaced apart from the bearing in the axial direction, A constant-pressure pre-pressure base is held in the hollow portion of the fixed base so as to be movable in the axial direction, A fixed-position pressure base is provided, on the side opposite to the bearing with respect to the constant-pressure pressure base, and is movably arranged in the axial direction. An electromagnet assembly fixed to the motor case has an electromagnet located on the opposite side of the constant-pressure base, with the constant-position pressure base in between, The system includes a spring member that, on the side facing the bearing, contacts the constant pressure base and applies the constant pressure to the bearing, The aforementioned fixed-position pressure base has an arm portion for applying fixed-position pressure to the bearing, The constant-pressure base is provided with a first permanent magnet, and the fixed-position pressure base is provided with a second permanent magnet positioned opposite to the first permanent magnet and having the opposite polarity to the first permanent magnet. The bearing preloading device is characterized in that the electromagnet includes means for switching the current in the forward and reverse directions, and is configured to generate a magnetic force in the forward and reverse directions greater than the magnetic force between the first permanent magnet and the second permanent magnet between the electromagnet and the second permanent magnet.
2. In claim 1, The fixed base has a stopper portion that restricts the movement of the constant-pressure base in the bearing direction. A bearing preloading device characterized in that, with the fixed-position preloading base attracted to the electromagnet assembly by the magnetic force of the electromagnet, the constant-pressure preloading base is pressed against the stopper portion by the magnetic repulsive force between the first permanent magnet and the electromagnet, and the constant-pressure preloading base presses against the spring member, thereby providing the constant-pressure preloading.
3. In either claim 1 or 2, The aforementioned fixed-position pressurizing base has a base portion extending in a direction perpendicular to the axial direction and a guide hole for making the arm portion movable in the bearing direction. A bearing pressure device characterized in that the magnetic force of the electromagnet moves the constant pressure base toward the electromagnet assembly, and moves the fixed-position pressure base toward the bearing against the magnetic repulsive force between the second permanent magnet and the first permanent magnet, and the arm portion applies the fixed-position pressure to the bearing.
4. A rotating electric machine comprising a stator and a rotor, wherein the rotation axis of the rotor is supported by a bearing, A rotating electric machine characterized in that the bearing comprises a bearing having the pre-pressurized structure described in any one of claims 1 to 3.