Outer rotor type motor

Abstract

This invention provides an outer rotor type motor that prevents the generation of resin burrs even when insert molding a metal cylindrical bearing housing, which is a pressed product, into a resin housing, and improves the roundness of the bearing housing, as well as the alignment accuracy of a pair of rolling bearings that are assembled concentrically in the cylindrical bore of the bearing housing and the stator assembly that is assembled concentrically on the outer circumference of the bearing housing. [Solution] The bearing housing 8a is press-formed radially to form upper bulges 8e1 and lower bulges 8e2 within the cylindrical hole 8c, respectively, which define the axial position of the rolling bearing 8b, and are provided at multiple locations in the circumferential direction. In the housing housing portion 4e of the resin housing 4b that covers the bearing housing 8a, relief recesses 4g are formed at positions corresponding to the lower bulges 8e2.

Description

Technical Field

[0001] The present invention relates to an outer rotor type motor used as a drive source for in-vehicle devices or HVAC (Heating, Ventilation, and Air Conditioning) devices, for example.

Background Art

[0002] For example, in an outer rotor type axial flow fan motor, the rolling bearings that rotatably support the rotor shaft of the rotor to which the centrifugal fan is assembled are expected to have low noise and a long service life. In a bearing housing in which a pair of rolling bearings are respectively fitted into a metal cylindrical hole and a stator unit (stator assembly) is assembled to the outer periphery of the cylinder, high roundness is required because it is necessary to perform centering of the rolling bearings and centering of the stator assembly for assembly. Also, in order to reduce the manufacturing man-hours and manufacturing costs, products have been proposed that rationalize the assembly by manufacturing a metal cylindrical bearing housing by press working instead of cutting and insert molding it into a resin motor housing (see Japanese Patent No. 4461311; Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the configuration described in Patent Document 1 above, after providing a bearing receiver (upper and lower protrusions) on the inner circumferential surface side of a metal cylindrical bearing housing (bearing liner) by press molding, insert molding is performed. When the area around the bearing receiver is clamped with a mold, a gap is created between the bearing housing and the mold due to the distortion generated around the bearing receiver by press molding. During mold molding, resin may leak out of this gap, potentially causing resin burrs.

[0005] Furthermore, in Patent Document 1, the bearing liner is formed by press working while feeding a metal sheet material into a progressive die. In this case, the upper and lower protrusions formed in the cutting and forming process are arranged at unequal angles in the circumferential direction of the bearing liner, and the upper and lower protrusions are reversed in the axial direction. As a result, stress and strain may occur throughout the circumferential direction of the bearing liner, which may reduce the roundness of the cylindrical metal bearing liner. Moreover, in the punching process following the cutting and forming process, a small-diameter annular flange portion and a notch in the flange portion are formed on one end edge of the bearing liner, which may distort the roundness of the inner diameter of the cylindrical hole of the bearing liner. In addition, because the flange portion is small in diameter, there is a manufacturing challenge in that the bearing liner is susceptible to axial removal and slippage during insert molding. [Means for solving the problem]

[0006] The embodiments described below have been made to solve the above problems, and their purpose is to provide an outer rotor type motor that prevents the generation of resin burrs even when insert molding a metal cylindrical bearing housing, which is a pressed product, into a resin housing, and has high roundness in the bearing housing, and improves the centering accuracy of a pair of rolling bearings that are assembled concentrically in the cylindrical bore of the bearing housing, and a stator assembly that is assembled concentrically on the outer circumference of the bearing housing.

[0007] The embodiments described below have the following configuration in order to achieve the above objective. An outer rotor type motor comprising a stator having stator poles formed thereon, and a rotor having rotor poles made of permanent magnets arranged radially outside the stator opposite to the stator poles, wherein the rotor shaft is formed by integrally assembling the hub and shaft end of a cup-shaped rotor yoke, a metal cylindrical bearing housing is insert-molded into a resin housing and assembled upright, and a pair of rolling bearings are assembled inside the bearing housing and rotatably support the rotor shaft, wherein the bearing housing is press-formed radially to form upper and lower bulges in the cylindrical bore, respectively, which define the axial position of the rolling bearings, and multiple such bulges are provided in the circumferential direction, and relief recesses are formed in the cylindrical portion of the resin housing covering the bearing housing at positions corresponding to the lower bulges. As a result, the metal cylindrical bearing housing has relief recesses formed in the cylindrical portion corresponding to the lower bulge where radial dimensional accuracy is not achieved, and is insert-molded into the resin housing. Therefore, the bearing housing and the mold can be fitted together in the portion where radial dimensional accuracy is achieved, thereby suppressing the generation of resin burrs during insert molding.

[0008] Furthermore, it is preferable that the upper bulge and the lower bulge are formed at equally spaced positions in the circumferential direction of the bearing housing and at corresponding positions along the axial direction. As a result, the upper and lower bulges are formed in phase around the bearing housing, reducing stress and strain throughout the circumferential direction, and maintaining the roundness of the cylindrical metal bearing housing even when press-formed in the radial direction.

[0009] Preferably, the bearing housing has an annular flange portion with a larger diameter formed at the upright end of the cylindrical portion, and multiple notches are formed in the circumferential direction on the outer peripheral edge of the annular flange portion, into which the resin of the resin housing enters. Thus, the bearing housing has an annular flange portion with a larger diameter at the upright end of the cylindrical portion, and multiple notches into which resin enters are formed on the outer periphery of the annular flange portion. This maintains the roundness of the inner diameter of the cylindrical hole of the bearing housing, making it difficult to remove the bearing housing axially from the resin housing after insert molding and preventing it from rotating freely. [Effects of the Invention]

[0010] Even when insert molding a metal cylindrical bearing housing, which is a pressed product, into a resin housing, it is possible to prevent the generation of resin burrs and ensure high roundness of the bearing housing. This allows for the provision of an outer rotor type motor with improved centering accuracy for a pair of rolling bearings that are assembled concentrically in the cylindrical bore of the bearing housing, and a stator assembly that is assembled concentrically on the outer circumference of the bearing housing. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a perspective view of a centrifugal blower. [Figure 2] Figure 2 is a perspective view of the centrifugal blower shown in Figure 1 with the top housing removed. [Figure 3] Figure 3 is a vertical cross-sectional view of the main part of the centrifugal blower shown in Figure 1. [Figure 4] Figure 3 is an enlarged cross-sectional view of the motor section. [Figure 5] Figure 5A is a perspective view of the mating portion between the bearing housing and the motor housing, and Figure 5B is an enlarged perspective view of these mating portions. [Figure 6] Figure 6A is a perspective view of the bearing housing, and Figure 6B is a plan view of the bearing housing. [Modes for carrying out the invention]

[0012] Hereinafter, an embodiment of the outer rotor type motor according to the present invention will be described with reference to the attached drawings. First, the general configuration of the outer rotor type motor will be described with reference to Figures 1 to 6. The outer rotor type motor M will be described using a DC brushless motor used in automotive equipment as an example. Hereafter, a centrifugal blower 1 using the outer rotor type motor M as a drive source will be described as an example.

[0013] In Figure 1, the centrifugal blower 1 has a centrifugal fan 2 and a rotor 3 assembled together, and an outer rotor type motor M that rotates them is housed in a blower housing 4 (resin housing). In Figure 2, the blower housing 4 is formed by combining a top housing 4a that covers and is assembled to the centrifugal fan 2 and a bottom housing 4b that rotatably supports the outer rotor type motor M (rotor 3 and stator 5). An intake opening 4c is provided in the center of the top housing 4a, and air is drawn in through the intake opening 4c and pressurized air is exhausted from the radially outer side through an exhaust port 4d provided along the circumferential direction.

[0014] In Figure 2, the centrifugal fan 2 has a hub 2a integrally assembled with the rotor yoke 3a at its radial center. The centrifugal fan 2 is insert-molded with the rotor yoke 3a, and the top surface of the rotor yoke 3a and the hub 2a are integrated. The main plate 2b, which is continuous with the hub 2a, extends radially outward in a stepped manner, and multiple impellers 2c are formed upright on the main plate 2b, curving from the radially inward to the radially outward direction.

[0015] As shown in Figure 3, the outer rotor type motor M comprises a rotor 3 and a stator 5. The rotor 3 has a rotor shaft 3b mounted on the hub of a cup-shaped rotor yoke 3a. An annular rotor magnet 3c is provided on the inner circumferential surface of the rotor yoke 3a. The rotor magnet 3c has rotor magnetic poles formed by permanent magnets with alternating north and south poles in the circumferential direction. The rotor 3 is mounted radially outward of the stator 5 such that the rotor magnetic poles formed by the rotor magnet 3c are positioned opposite the stator magnetic poles.

[0016] In FIG. 3, in the stator 5, a motor coil 5d is wound around the periphery of a plurality of salient poles 5c protruding radially outward from the core back portion 5b of an annular stator core 5a via an insulator 7 to form stator poles. In this embodiment, a single-phase coil is wound, but a three-phase coil or the like may also be used. Further, two coil pins (not shown) for connecting to the motor coil 5d are provided on the insulator 7. Coil leads drawn from the motor coil 5d are respectively connected to the coil pins.

[0017] In FIG. 3, in the bottom housing 4b of the blower housing 4, a metal cylindrical bearing housing 8a is insert-molded and concentrically assembled in a cylindrical housing accommodation portion 4e (cylindrical portion). The upper end portion 4f of the housing accommodation portion 4e defines the axial assembly position of the stator core 5a (core back portion 5b). The bearing housing 8a has a cylindrical portion 8a1 and an annular flange portion 8g having a larger diameter than that at its lower end. In the cylindrical hole 8c of the bearing housing 8a, a pair of rolling bearings (bearing bearings 8b) are inserted and assembled from both longitudinal sides of the bearing housing 8a. The axial positions of the pair of bearing bearings 8b in the cylindrical hole 8c are respectively defined by a plurality of bulging portions as will be described later. The rotor shaft 3b is rotatably supported by a pair of bearing bearings 8b assembled in the cylindrical hole 8c of the bearing housing 8a. Further, a retaining washer 8d is fitted on the rotor shaft 3b at the shaft end side, and the axial movement is restricted by the bearing bearing 8b at the lower end side in the axial direction. Further, the bearing housing 8a assembled upright on the bottom housing 4b has an annular flange portion 8g having a larger diameter than the cylindrical portion 8a1 at the upright base end portion. As will be described later, the annular flange portion 8g is insert-molded so that the bearing housing 8a is prevented from coming off and rotating with respect to the bottom housing 4b.

[0018] In Fig. 3, the motor substrate 6 is assembled to the blower housing 4 (bottom housing 4b). Also, a coil pin (not shown) connected to the motor coil 5d wound around the pole teeth 5c of the stator core 5a is inserted into the substrate terminal hole and soldered. The motor substrate 6 is provided with a magnetic pole detection element (not shown) such as a Hall IC for detecting the magnetic pole position of the rotor 3. By detecting the magnetic pole position of the rotor 3 with the magnetic pole detection element and switching the direction of the current flowing through the motor coil 5d, the rotor 3 is biased and rotated. Note that in a sensorless motor, the magnetic pole detection element may be omitted.

[0019] As shown in Fig. 3, the stator core 5a is assembled by integral molding with the insulator 7. The insulator 7 is formed by insert molding the stator core 5a using, for example, PBT (polybutylene terephthalate) resin. Note that, without insert formation, only the insulator 7 may be molded and assembled around the pole teeth 5c of the stator core 5a.

[0020] On the radially inner side of the stator core 5a of the insulator 7, cylindrical portions 7a project axially on both sides. As will be described later, the motor substrate 6 is assembled to one of the cylindrical portions 7a (see Fig. 4), and the cylindrical portion 7a of the stator 5 and the motor substrate 6 (stator assembly) is concentrically fitted to the outer peripheral side of a housing accommodation portion 4e that houses the metal cylindrical bearing housing 8a, and is assembled to the bottom housing 4b (see Fig. 2).

[0021] The bearing housing 8a is formed into a metal cylinder by transfer forming, for example, when a galvanized steel sheet is used as the base material (workpiece), and the workpiece is press-formed while being transported between press dies. At this time, multiple upper bulges 8e1 and lower bulges 8e2 are provided in the circumferential direction (three at 120-degree intervals in the circumferential direction) that bulge into the cylindrical hole 8c of the cylindrical portion 8a1. The upper bulges 8e1 and lower bulges 8e2 define the axial positions of a pair of bearing bearings 8b that are fitted into the cylindrical hole 8c of the bearing housing 8a from both ends. The bearing housing 8a is insert-molded into the bottom housing 4b and assembled concentrically with the lower half of the cylindrical portion 8a1 covered by the housing housing portion 4e (cylindrical portion). Furthermore, the upper half of the cylindrical portion 8a1 of the bearing housing 8a is exposed from the housing compartment 4e, but as shown in Figure 4, the stator core 5a is fitted onto the outer circumference of the upper half of the cylindrical portion 8a1, and the core back portion 5b abuts against the upper end portion 4f of the housing compartment 4e, thereby assembling the stator assembly. In addition, a preload spring 8f is fitted around the rotor shaft 3b in a compressed state from its natural length between the hub 3a1 of the rotor yoke 3a and the bearing bearing 8b (inner ring) on ​​the axial upper end side, which is positioned opposite in the axial direction, in order to improve the rotational stability of the rotor 3.

[0022] An example of the press forming process for the bearing housing 8a is as follows: The workpiece, which will be the base material (e.g., galvanized steel sheet), is transported between multiple press die devices and subjected to transfer press forming. First, the cylindrical portion 8a1 is press-formed in the first pressing process. This determines the roundness of the cylindrical portion 8a1. Next, in the second pressing process, upper bulges 8e1 and lower bulges 8e2 are formed on the cylindrical portion 8a1 at multiple locations (for example, three locations at 120-degree intervals in the circumferential direction). At this time, a radial pressing force is applied to the cylindrical portion 8a1, so the roundness of the cylindrical portion 8a1 where the upper bulges 8e1 and lower bulges 8e2 are formed decreases. Next, in the third pressing process, an annular flange portion 8g is press-formed at one end of the cylindrical portion 8a1, using the cylindrical portion 8a1 as a reference. This third pressing process has no effect on the roundness of the cylindrical portion 8a1. Next, in the fourth pressing step, notches 8h are formed at multiple locations in the circumferential direction (for example, three locations at 120-degree intervals in the circumferential direction) on the outer edge of the annular flange portion 8g. At this time, the annular flange portion 8g is processed by applying an axial pressing force, so there is no particular effect on the roundness of the cylindrical portion 8a1. Finally, the bearing housing 8a having the cylindrical portion 8a and the annular flange portion 8g is press-formed by cutting off the unnecessary parts from the base material (see Figure 6A).

[0023] As shown in Figures 5A and 5B, relief recesses 4g are formed at the upper end of the housing portion 4e that covers the bearing housing 8a, at positions corresponding to the lower bulge portion 8e2. As a result, the press-formed metal cylindrical bearing housing 8a is insert-molded into the resin bottom housing 4b with relief recesses 4f formed at positions corresponding to the lower bulge portion 8e2, where radial dimensional accuracy is not achieved. This allows the bearing housing 8a to be fitted with the mold at locations where radial dimensional accuracy is achieved, thereby suppressing the generation of resin burrs during insert molding.

[0024] Furthermore, as shown in Figure 6A, the upper bulge 8e1 and the lower bulge 8e2 provided on the bearing housing 8a are formed at equally spaced positions in the circumferential direction of the bearing housing 8a (for example, three locations at 120-degree intervals in the circumferential direction) and at corresponding positions along the axial direction. That is, the upper bulge 8e1 and the lower bulge 8e2 are formed axially separated with the same phase along the circumferential direction of the bearing housing 8a. As a result, stress and strain after press working are reduced throughout the circumferential direction of the bearing housing 8a, and the roundness of the cylindrical metal bearing housing 8a can be maintained even after press working. Therefore, a pair of bearings 8b can be assembled concentrically with high precision into the cylindrical bore 8c of the bearing housing 8a.

[0025] Furthermore, as shown in Figure 6B, an annular flange portion 8g, which is larger in diameter than the cylindrical portion 8a1, is formed on the base end side of the bearing housing 8a, which is assembled upright on the bottom housing 4b. Multiple notches 8h are provided on the outer peripheral edge of this annular flange portion 8g in the circumferential direction (for example, three notches at 120-degree intervals in the circumferential direction). The resin of the bottom housing 4b is inserted into these notches 8h and formed by insert molding. As described above, an annular flange portion 8g with a larger diameter than the cylindrical portion is formed at the upright end of the bearing housing 8a, and multiple notches 8h are formed in the annular flange portion 8g by axial press working, so that the roundness of the inner diameter of the cylindrical bore of the bearing housing 8a can be maintained. In addition, since resin enters into the multiple notches 8h when the bottom housing 4b is insert molded, it is possible to prevent the bearing housing 8a from being removed axially from the bottom housing 4b after insert molding and to prevent it from rotating freely.

[0026] As explained above, when insert molding the metal cylindrical bearing housing 8a, which is a press-formed product, into the bottom housing 4b, the bearing housing 8a and the mold can be fitted together in areas where radial dimensional accuracy is achieved, thus suppressing the generation of resin burrs during insert molding. Furthermore, because the cylindrical portion 8a1 of the press-formed bearing housing 8a has high roundness, the alignment accuracy of the pair of bearing bearings 8b, which are assembled concentrically in the cylindrical bore 8c of the bearing housing 8a, and the stator assembly, which is assembled concentrically on the outer circumference of the bearing housing 8a, can be improved, making it possible to provide a low-cost, high-performance outer rotor type motor.

[0027] In the embodiment described above, a magnetic pole detection element 6a such as a Hall IC was provided on the motor board 6, but a sensorless type DC brushless motor in which the magnetic pole detection element is omitted may also be used. Furthermore, the insulator 7 does not have to be integrally molded with the stator core 5a; it may be molded separately and assembled. Furthermore, the number of upper bulges 8e1 and lower bulges 8e2 provided on the bearing housing 8a may be more than three, and the number of notches 8h provided on the annular flange portion 8g may be more or less than three. [Explanation of symbols]

[0028] 1 Centrifugal blower 2 Centrifugal fan 2a Hub 2b Main plate 2c Impeller M Outer rotor type motor 3 Rotor 3a Rotor yoke 3a1 Hub 3b Rotor shaft 3c Rotor magnet 4 Blower housing 4a Top housing 4b Bottom housing 4c Intake opening 4d Exhaust port 4e Housing storage section 4f Upper end 4g Relief recess 5 Stator 5a Stator core 5b Core back section 5c Pole teeth 5d Motor coil 6 Motor board 7 Insulator 7a Cylindrical section 8a Bearing housing 8a1 Cylindrical section 8b Bearing 8c Cylindrical hole 8d Retaining washer 8e1 Upper bulge section 8e2 Lower bulge section 8f Preload spring 8g Annular flange section 8h Notch section

Claims

1. An outer rotor type motor comprising a stator on which stator poles are formed, and a rotor on the radially outer side of the stator, in which rotor poles formed by permanent magnets are arranged opposite to the stator poles, A rotor shaft in which the hub and shaft end of a cup-shaped rotor yoke are assembled integrally, A metal cylindrical bearing housing is formed upright by insert molding into a resin motor housing, The system comprises a pair of rolling bearings assembled within the bearing housing and rotatably supporting the rotor shaft, An outer rotor type motor characterized in that the bearing housing is press-formed and has multiple upper and lower bulging portions that bulge into a cylindrical bore at various locations in the circumferential direction, and the cylindrical portion of the motor housing that covers the bearing housing has relief recesses formed at positions corresponding to the lower bulging portions.

2. The outer rotor type motor according to claim 1, wherein the upper bulge and the lower bulge are formed in equidistant positions in the circumferential direction of the bearing housing and along the axial direction.

3. The outer rotor type motor according to claim 1 or claim 2, wherein the bearing housing has a flange portion with a larger diameter formed at the end of the cylindrical housing portion, and multiple notches are formed in the circumferential direction on the outer peripheral edge of the flange portion, into which the resin of the resin motor housing enters.

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