Fan motors and vacuum cleaners

Abstract

The fan motor bearings should be compact and have low mechanical loss. [Solution] A fan motor comprising an electric motor, an impeller that rotates together with the shaft of the electric motor, and two bearings that rotatably support the shaft of the electric motor, wherein the first of the two bearings is a ball bearing and the second of the two bearings is an air bearing.

Description

Technical Field

[0001] The present invention relates to a fan motor and a vacuum cleaner.

Background Art

[0002] Patent Document 1 describes a bearing structure. This bearing structure includes a support shaft erected at the center of a mounting base and a rotating part having a support shaft insertion hole through which the support shaft is inserted at the center. The rotating part is supported by the support shaft via a radial bearing and is also supported by the mounting base via a thrust bearing. The radial bearing and the thrust bearing are each a hydrodynamic bearing. Further, the rotating part is supported by the support shaft via a rolling bearing.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For higher output, the number of fan motors with a rotation speed of 100,000 revolutions per minute or more has been increasing. However, the higher the rotational speed, the greater the mechanical loss of the ball bearing, the worse the efficiency of the fan motor, and the shorter its operating time. Conventionally, it has been known that a hydrodynamic bearing is effective in reducing this mechanical loss. However, when a hydrodynamic bearing is adopted, it is necessary to install a thrust bearing. As a result, due to problems such as the installation location and the thrust of the impeller, the bearing cannot be made compact.

[0005] An object of the present invention is to make the bearing of a fan motor have small mechanical loss and be compact.

Means for Solving the Problems

[0006] To this end, the present invention provides a fan motor comprising an electric motor, an impeller that rotates together with the shaft of the electric motor, and two bearings that rotatably support the shaft of the electric motor, wherein the first of the two bearings is a ball bearing and the second of the two bearings is an air bearing.

[0007] In the fan motor described above, the first bearing may be located on the opposite side of the impeller from the motor, and the second bearing may be located on the impeller side from the motor. In that case, the impeller may be located between the motor and the second bearing.

[0008] In the fan motor described above, the second bearing may be a hydrodynamic air bearing. In that case, the hydrodynamic air bearing may be a bearing that utilizes the wedge effect of the airflow caused by the rotation of the motor shaft.

[0009] The fan motor described above may be one that is used at a rotational speed of 100,000 revolutions per minute or more.

[0010] Furthermore, the present invention also provides a vacuum cleaner equipped with any of the above-described fan motors. [Effects of the Invention]

[0011] According to the present invention, the bearings of a fan motor can be made compact and have low mechanical loss. [Brief explanation of the drawing]

[0012] [Figure 1] This figure shows an example configuration of a stick-type vacuum cleaner to which this embodiment is applied. [Figure 2] This figure shows an example of the fan motor configuration in a stick-type vacuum cleaner to which this embodiment is applied. [Figure 3] This figure shows an example of the configuration of a ball bearing in this embodiment. [Figure 4]Figures (a) and (b) show examples of the configuration of the shaft and radial pneumatic bearing in this embodiment. [Modes for carrying out the invention]

[0013] Embodiments of the present invention will be described in detail below with reference to the attached drawings.

[0014] [Vacuum cleaner] Figure 1 shows an example of the configuration of a stick-type vacuum cleaner 1 to which this embodiment is applied. This vacuum cleaner 1 is a cordless type and is configured to be powered by the power of a built-in battery 8.

[0015] As shown in the figure, the vacuum cleaner 1 comprises a suction section 2, a pipe section 3, a main body section 4, a handle section 5, and a dust case 6.

[0016] The suction section 2 has a suction port 2a on its lower surface and is configured to slide along the floor surface by a rotatable roller 2b. The pipe section 3 consists of an elongated cylindrical member that is expandable and contractible. The lower end of the pipe section 3 is connected to the suction section 2, and the upper end is connected to the main body section 4. The pipe section 3 connects the suction port 2a and the main body section 4.

[0017] The main body 4 is formed to be slightly larger than the pipe section 3. The main body 4 houses the fan motor 7, battery 8, control unit 9, etc. The control unit 9 controls the operation of the fan motor 7. The battery 8 is a rechargeable secondary battery that supplies power to the fan motor 7.

[0018] The handle portion 5 is the part that the user grips and is provided integrally with the main body portion 4. The handle portion 5 is provided so as to protrude backward from the rear side of the main body portion 4. The vacuum cleaner 1 is configured so that the user can operate it while holding the handle portion 5 with one hand.

[0019] The dust case 6 is installed below the handle part 5. The dust case 6 is configured to be detachable from the main body part 4. The fan motor 7 is disposed at a position adjacent to the dust case 6. The fan motor 7 is driven by the electric power supplied from the battery 8 according to the control of the control part 9. When the fan motor 7 is driven, a strong suction force is formed. Thereby, the dust sucked from the suction port 2a is accumulated in the dust case 6 through the pipe part 3.

[0020] [Fan motor] The fan motor 7 is a small device in which a fan and a motor (electric motor) are integrally formed. The fan is a so-called centrifugal fan. As the impeller (described later) rotates around the rotation axis, air is sucked in from the intake port (described later) and discharged toward the outer side in the radial direction. The outer diameter and the overall height of the fan motor 7 are designed to be very small so that they can be accommodated in the main body part 4.

[0021] FIG. 2 is a diagram showing a configuration example of the fan motor 7 in the cleaner 1 of FIG. 1. As shown in the drawing, the fan motor 7 includes a ball bearing 10, a motor 20, an impeller 30, and a radial air dynamic pressure bearing 40. And these are connected to a single shaft 50 in this order from the upper side.

[0022] Generally, in such a fan motor 7, a cheap and easy-to-use ball bearing is used as a bearing for rotatably supporting the shaft 50. On the other hand, in recent years, the motor 20 rotates at a rotation speed of 100,000 revolutions per minute or more due to high speed. And for miniaturization and high output, further high speed of the motor 20 is aimed at. In this case, since the motor 20 becomes a high-speed low-torque type, the mechanical loss of the ball bearing affects the performance of the motor 20.

[0023] Therefore, it is conceivable to adopt a low-loss radial air dynamic pressure bearing instead of the ball bearing. Thereby, the mechanical loss is reduced and high efficiency is achieved.

[0024] However, when using radial pneumatic bearings, thrust is generated in the upward direction as the impeller 30 rotates, so it is necessary to provide low-loss thrust pneumatic bearings. However, when a thrust air dynamic bearing is installed, the thrust of the impeller 30 increases as the rotation speed increases, and the thrust air dynamic bearing is pressed against it. This makes it difficult to lift off using air compression. Furthermore, during operation, the vacuum cleaner's body changes position and moves. As a result, the thrust pneumatic bearing frequently comes into contact with other parts, which can hinder rotation, cause it to lock up, or lead to the generation of abnormal noises. Furthermore, when using two radial pneumatic bearings, conical mode runout occurs in the shaft 50, making the shaft 50 more prone to vibration. As a result, the impeller 30 vibrates radially, increasing the likelihood of contact with the shroud, making it impossible to reduce the tip clearance, and potentially leading to performance degradation.

[0025] Therefore, in this embodiment, in order to avoid this phenomenon, one of the two bearings is a ball bearing, and the other of the two bearings is a radial pneumatic bearing. By fixing the outer ring of the ball bearing, the movement of the impeller 30 in the thrust direction and radial direction is restricted. By eliminating the thrust pneumatic bearing in this way, it is possible to prevent the generation of abnormal noise and locking due to changes in the posture of the main body. In addition, the radial pneumatic bearing reduces mechanical loss, and the ball bearing suppresses the generation of conical mode runout, preventing the generation of abnormal noise and locking, thereby improving the efficiency and performance of the fan motor 7.

[0026] In other words, let's assume that in Figure 2, the ball bearing 10 is replaced with a radial pneumatic bearing. In that case, since the restriction in the thrust direction is removed, it is usually necessary to add two thrust pneumatic bearings, or at least one additional one. However, due to the thrust of the impeller 30 and the change in the posture of the main body generated during high-speed rotation, friction or locking of the thrust pneumatic bearing may occur.

[0027] Therefore, in this embodiment, one of the two bearings is a ball bearing 10. This allows for restriction of thrust direction, simplifies the configuration, and reduces costs. Furthermore, since one side of the shaft 50 is fixed by the ball bearing 10, the wobble in conical mode is suppressed, preventing the generation of abnormal noises and locking. It also prevents the generation of abnormal noises and locking due to changes in the posture of the main unit.

[0028] As shown in the diagram, an inverter circuit 60 that drives the motor 20 is installed on the fan motor 7 at the upstream end of the airflow F1, F2. A ball bearing 10 is also attached to the fan motor 7 below it as the first bearing.

[0029] Furthermore, a motor 20 is mounted below the fan motor 7. The motor 20 includes a rotor 21 and a stator 22. The rotor 21 consists of magnets directly fixed to the shaft 50 with adhesive. The stator 22 is positioned to surround the rotor 21 with an air gap, and rotates the rotor 21 by the magnetic force generated when current flows through the winding coil.

[0030] Furthermore, an impeller 30 is installed on the fan motor 7. In addition, a radial pneumatic bearing 40 is installed on the fan motor 7 as a second bearing. Moreover, a diffuser 70 is installed on the fan motor 7 to recover the swirling component produced by the impeller 30.

[0031] With this configuration, the uncompressed, unheated airflow F1 and F2 drawn in from the intake port 81 can cool the circuit board of the inverter circuit 60 and the motor 20. As a result, more power can be supplied to the fan motor 7, enabling higher output.

[0032] Furthermore, as will be described later, the ball bearing 10 is designed to handle ultra-high-speed rotation, and since its outer ring is fixed to the bearing housing 11, it also functions as a thrust bearing. In addition, the motor 20 is positioned directly below the ball bearing 10, and an air passage 80 is provided around it to facilitate cooling by uncompressed air.

[0033] Then, the impeller 30 is mounted on the shaft 50 at a certain distance from the motor 20. The impeller 30 is rotationally driven by the motor 20. In other words, the impeller 30 rotates at high speed in one direction together with the shaft 50 of the motor 20. As a result, the impeller 30 creates a high-speed, powerful swirling flow in the centrifugal or diagonally downward direction.

[0034] A diffuser 70 is positioned behind the impeller 30 to recover the swirling component of this swirling flow and convert it into suction force. In this embodiment, a two-stage diffuser 70 is used to recover the swirling component more powerfully. A radial pneumatic bearing 40 is also positioned directly below the impeller 30.

[0035] In this fan motor 7, one of the bearings is a ball bearing 10, which restricts the thrust direction. Therefore, this fan motor 7 does not require a thrust pneumatic bearing. In addition, by fixing one side of the shaft 50, conical mode runout is suppressed, and the tip clearance can be reduced. As a result, it becomes a compact, low-loss (high-efficiency), and high-output fan motor.

[0036] By the way, in order to handle ultra-high-speed rotation, each component is made to a specification that can withstand it.

[0037] In particular, the ball bearing 10 is important, and it is preferable that it suppresses conical mode runout and can handle ultra-high speed rotation. Figure 3 shows an example configuration of a ball bearing 10. As shown, the ball bearing 10 includes an inner ring 12, an outer ring 13, balls 14, and a retainer 15. The inner ring 12 is fitted onto the shaft 50. The outer ring 13 is concentrically positioned on the outer circumference of the inner ring 12 and fixed to the bearing housing 11. The multiple balls 14 are housed in the annular space between the inner ring 12 and the outer ring 13. The retainer 15 holds these balls 14.

[0038] Of these, the retainer 15 should be made of a heat-resistant material. A heat-resistant material could be, for example, PEEK (Poly Ether Ketone) material. Furthermore, by making the radial and axial gaps between each component of the ball bearing 10 small, conical mode runout is suppressed, enabling it to handle high-speed rotation. Furthermore, the ball 14 may sometimes need to be made of ceramic.

[0039] Figures 4(a) and 4(b) show examples of the configuration of the shaft 50 and the radial pneumatic bearing 40. Figure 4(a) shows the shaft 50. Herringbone grooves 51 are arranged at equal intervals around the entire circumference of the tip of the shaft 50. The angle and number of herringbone grooves are determined by the rotational speed and load. The grooves 51 are approximately 10 μm deep and are generally created by etching.

[0040] Figure 4(b) shows a radial pneumatic bearing 40. The radial pneumatic bearing 40 includes a sleeve 41, a frame 42, and an elastic member 43. The sleeve 41 is positioned with a gap between it and the shaft 50. Here, the gap between the sleeve 41 and the shaft 50 should be about 5 μm on each side. The frame 42 is positioned concentrically around the outer circumference of the sleeve 41 and is fixed to the fan motor 7. The elastic member 43 is a member that provides elasticity between the sleeve 41 and the frame 42, and is made of, for example, rubber.

[0041] With this configuration, the radial pneumatic bearing 40 becomes a bearing that utilizes the wedge effect of the airflow caused by the rotation of the motor shaft 50.

[0042] In addition to the above, foil bearings are also used for pneumatic bearings. However, with foil bearings, the deformation of the corrugated bump foil creates a gas film, resulting in a large amount of deformation of the shaft 50. In particular, the clearance at the tip narrows in some areas during startup, and in the worst case, contact with the impeller 30 may occur. For this reason, the adoption of foil bearings is difficult.

[0043] [summary] This embodiment can be understood as follows: A fan motor according to the first embodiment comprises an electric motor, an impeller that rotates together with the shaft of the electric motor, and two bearings that rotatably support the shaft of the electric motor, wherein the first of the two bearings is a ball bearing and the second of the two bearings is an air bearing. The second embodiment of the fan motor is a fan motor in which, in the first embodiment, the first bearing is located on the opposite side of the impeller with respect to the motor, and the second bearing is located on the side of the impeller with respect to the motor. The third embodiment of the fan motor is a fan motor in which, in the second embodiment, an impeller is positioned between the electric motor and the second bearing. The fourth embodiment of the fan motor is a fan motor in which, in any of the first to third embodiments, the second bearing is a dynamic pressure type air bearing. The fifth embodiment of the fan motor is a fan motor in which, in the fourth embodiment, the dynamic pressure type air bearing is a bearing that utilizes the wedge effect of the airflow caused by the rotation of the motor shaft. The sixth embodiment of the fan motor is a fan motor used in any of the first to fifth embodiments at a rotational speed of 100,000 revolutions per minute or more. The vacuum cleaner of the first embodiment is a vacuum cleaner equipped with a fan motor of any of the first to sixth embodiments. [Explanation of Symbols]

[0044] 1...Vacuum cleaner, 2...Suction section, 3...Pipe section, 4...Main body, 5...Handle section, 6...Dust case, 7...Fan motor, 8...Battery, 9...Control unit, 10...Ball bearing, 20...Motor, 30...Impeller, 40...Radial pneumatic bearing, 50...Shaft, 60...Inverter circuit, 70...Diffuser, 80...Airflow path

Claims

1. Electric motor and, An impeller that rotates together with the shaft of the aforementioned electric motor, Two bearings that rotatably support the shaft of the aforementioned electric motor, Equipped with, A fan motor in which the first of the two bearings is a ball bearing, and the second of the two bearings is an air bearing.

2. The first bearing is positioned on the opposite side of the impeller with respect to the electric motor. The fan motor according to claim 1, wherein the second bearing is positioned on the impeller side with respect to the electric motor.

3. The fan motor according to claim 2, wherein the impeller is arranged between the electric motor and the second bearing.

4. The fan motor according to claim 1, wherein the second bearing is a dynamic pressure type air bearing.

5. The fan motor according to claim 4, wherein the dynamic pressure type air bearing is a bearing that utilizes the wedge effect of the airflow caused by the rotation of the motor shaft.

6. The fan motor according to claim 1, which is used at a rotational speed of 100,000 revolutions per minute or more.

7. A vacuum cleaner equipped with a fan motor according to any one of claims 1 to 6.

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