outer rotor motor

Abstract

To provide a small-sized outer rotor type motor that neither loses mechanical strength of a bearing, nor generates oil film shortage even when using an oil refilling member together with the oil-impregnated sintered bearing.SOLUTION: According to an outer rotor type motor M whose rotor 3 is rotatably supported with a rotor shaft 3c inserted in an oil-impregnated sintered bearing 8 as a center, a porous metal sintered felt 9 for feeding a lubricant to the oil-impregnated sintered bearing 8 is concentrically engaged to a one end side outer-periphery in a shaft direction of the oil-impregnated sintered bearing 8 in a range of not being overlapped in a radial direction with a stator core 7 assembled on an outer-periphery of a stator housing 6, and is stored inside the stator housing 6.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an outer rotor motor used as a drive source for, for example, seat air conditioning or HVAC (Heating, Ventilation, and Air Conditioning) equipment. [Background technology]

[0002] Sintered oil-impregnated bearings are used to support the rotation of the rotor shaft, as they are less expensive to manufacture than rolling bearings. Sintered oil-impregnated bearings use porous sintered metal materials (for example, iron and copper materials that have been sintered and hardened) and are impregnated with lubricating oil inside.

[0003] When using sintered oil-impregnated bearings, if the amount of lubricating oil impregnated inside them becomes insufficient, the oil film that exists in the sliding area between the rotor shaft and the bearing will disappear, which could cause seizure, vibration, or noise. Furthermore, if the amount of lubricating oil is increased, the sintered oil-impregnated bearing will become larger, which could lead to lubricating oil leakage.

[0004] The following oil-impregnated bearing mechanism has been proposed to increase the amount of lubricant retained in an oil-impregnated bearing and prevent the leakage and evaporation of lubricant from the oil-impregnated bearing: It comprises a concentric inner bearing and an outer bearing, each made of a porous material containing lubricant and having a substantially hollow cylindrical shape, and a plurality of communication grooves, which communicate with the outside and are formed by parts of the outer surface of the inner bearing and parts of the inner surface of the outer bearing, are formed between the outer surface of the inner bearing and the inner surface of the outer bearing, and these communication grooves communicate between a space on one axial end of the inner bearing and a space on the other axial end (see JP 2009-85355 A; Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-85355 Summary of the Invention [Problem to be solved by the invention]

[0006] The oil-impregnated bearing in Patent Document 1 has a hollow cylindrical inner bearing and an outer bearing made of a porous metal material containing lubricating oil, which are arranged concentrically. Therefore, increasing the oil content increases the radial dimension. Also, since recesses must be formed at multiple locations along the axial direction on the inner peripheral surface of the outer bearing, processing costs increase.

[0007] In contrast to this, a sintered oil-impregnated bearing containing lubricant (porous metal material: oil content 15 to 30 vol%) is used as the inner bearing, and a sintered oil-impregnated bearing with an oil supply mechanism (sintered felt: oil content 30 vol% or more) is used as the outer bearing, in which felt metal is arranged concentrically. Sintered oil-impregnated bearings and sintered felt are similar in composition (a mixture of mainly iron and copper), but their spatial density is different, with sintered felt being sparser than sintered oil-impregnated bearings. Therefore, sintered felt has a greater capacity to store lubricating oil (lubricating oil content per unit volume) than sintered oil-impregnated bearings. However, although sintered felt is made of porous sintered metal like sintered oil-impregnated bearings, its mechanical properties make it a hard sponge-like material that undergoes plastic deformation, and it cannot be subjected to stress like ordinary metal materials. That is, sintered felt is pressed onto the outer periphery of the sintered oil-impregnated bearing (reference pressure: 20N to 50N), and the sintered oil-impregnated bearing is then pressed into the stator housing via the sintered felt (reference pressure: 200N to 300N) to secure it to the motor base. Therefore, if the structure is such that the sintered felt is pressed onto the outer diameter of the bearing and the outer diameter of the sintered felt is pressed into the inner diameter of the stator housing, the fixing force of the sintered oil-impregnated bearing to the stator housing may be weak.

[0008] Furthermore, due to capillary action acting in the tiny gap between the rotor shaft and the bearing and the pumping effect generated by the rotation of the rotor shaft, the lubricating oil inside the sintered oil-impregnated bearing forms an oil film near the sliding area between the rotor shaft and the bearing. Furthermore, the lubricating oil has a higher coefficient of expansion than the sintered oil-impregnated bearing. Therefore, at low temperatures such as -30°C, the lubricating oil contracts more than the bearing, causing a shortage of lubricating oil in the sliding area, which can lead to the oil film breaking down in the oil film formed between the rotor shaft and the sintered oil-impregnated bearing, which can cause abnormal noise. [Means for solving the problem]

[0009] The present invention has been made to solve these problems, and its purpose is to provide an outer rotor type motor that is small and does not suffer from oil film shortage, even when an oil supply member is used together with a sintered oil-impregnated bearing without losing the mechanical strength of the bearing.

[0010] In order to achieve the above object, the present invention has the following configuration. An outer rotor motor has a stator in which a stator core is assembled to the outer periphery of a cylindrical stator housing and a sintered oil-impregnated bearing made of porous sintered metal is assembled concentrically to the inner periphery of the stator housing, and a rotor is supported rotatably around a rotor shaft inserted into the sintered oil-impregnated bearing, and an annular oil supply member made of porous sintered metal that supplies lubricating oil to the sintered oil-impregnated bearing is concentrically fitted to the outer periphery of one axial end of the sintered oil-impregnated bearing within a range that does not overlap radially with the stator core assembled to the outer periphery of the stator housing, and a gap of 0.05 mm to 0.5 mm is provided radially between the outer periphery of the oil supply member and the inner periphery of the stator housing. and axially 5.0 mm or more The stator is housed in the stator housing with a gap formed therebetween. As a result, when the rotor shaft rotates while sliding against the sintered oil-impregnated bearing, the lubricating oil inside the sintered oil-impregnated bearing made of porous sintered metal moves to the sliding part with the rotor shaft, and the lubricating oil moves from the porous sintered metal oil supply member into the sintered oil-impregnated bearing, preventing oil film breakdown in the sliding part with the rotor shaft and the sintered oil-impregnated bearing. When the rotor shaft stops rotating, the lubricating oil in the sliding part returns to the sintered oil-impregnated bearing, and the lubricating oil inside the sintered oil-impregnated bearing returns to the oil supply member. In this way, the oil supply member functions as a buffer for the lubricating oil of the sintered oil-impregnated bearing. Furthermore, since the oil supply member is fitted concentrically onto the outer periphery of one axial end of the sintered oil-impregnated bearing without radially overlapping with the stator core assembled to the outer periphery of the stator housing, the outer diameter of the sintered oil-impregnated bearing is not larger than necessary, and since it is fitted so as to partially overlap one axial end of the sintered oil-impregnated bearing, the sintered oil-impregnated bearing does not become larger in the axial direction. Moreover, since only the stator housing and the sintered oil-impregnated bearing are present on the inner periphery of the stator core, the central hole of the stator core can be made small, allowing for a more compact motor. Furthermore, since the oil supply member is not deformed when the stator core is assembled to the stator housing, its mechanical strength is not impaired. In particular, while the rotor shaft is stopped, the gap between the outer circumferential surface of the oil supply member and the inner circumferential surface of the stator housing can be used as an additional buffer for the lubricating oil, so that sufficient lubricating oil can be supplied even if the oil supply member is small. Furthermore, at the other axial end of the sintered oil-impregnated bearing where no oil supply member is provided, the space between the inner surface of the stator housing and the outer surface of the sintered oil-impregnated bearing can be used as a buffer space for lubricating oil. Furthermore, when the oil supply member is assembled to the sintered oil-impregnated bearing, interference with the stator housing can be avoided.

[0011] The other axial end side of the stator housing where the oil supply member is not provided is formed to have a diameter smaller than the outer diameter of the stator housing to which the stator core is assembled, and a space is provided between the outer periphery of the sintered oil-impregnated bearing and the inner periphery of the stator housing, and the space may have a radial width of 0.05 mm or more and 0.3 mm or less if the axial length is 1.5 mm or more, or a radial width of 0.05 mm or more and 0.2 mm or less if the axial length is 1.0 mm or more. As a result, at the other axial end of the sintered oil-impregnated bearing where no oil supply member is provided, the space between the inner surface of the stator housing and the outer surface of the sintered oil-impregnated bearing can be used as a buffer space for lubricating oil. [Effects of the Invention]

[0014] It is possible to provide an outer rotor motor equipped with a small, oil-impregnated sintered bearing that does not lose its mechanical strength even when an oil supply member is used, and that does not suffer from oil film shortage. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a perspective view of a centrifugal blower. [Figure 2] FIG. 2 is a partial cross-sectional view of the centrifugal fan and motor of FIG. 1. [Figure 3] 1 is a vertical cross-sectional view of an outer rotor motor according to a first embodiment. [Figure 4] FIG. 10 is a vertical cross-sectional view of an outer rotor motor according to a second embodiment. [Figure 5] FIG. 10 is an explanatory diagram of an experiment to confirm the state of lubricating oil retention in the gap between the sintered oil-impregnated bearing and the stator housing. DETAILED DESCRIPTION OF THE INVENTION

[0016] [First Example] An embodiment of an outer rotor motor according to the present invention will be described below with reference to the accompanying drawings. First, the schematic configuration of the outer rotor motor will be described with reference to Figures 1 to 3. In this embodiment, an outer rotor motor used as a drive source for a centrifugal blower will be described as an example.

[0017] As shown in Figure 1, centrifugal blower 1 is configured by assembling centrifugal fan 2 and rotor 3 (see Figure 2) together, and an outer rotor type motor M that rotates and drives these is housed in case body 4. Air is drawn in from the upper center of the axial direction of case body 4, and the compressed air that has been centrifugally pressurized inside case body 4 is exhausted from an exhaust port provided on the outer peripheral side of case body 4.

[0018] The configuration of the outer rotor motor M will be described with reference to FIGS. The rotor 3 is integrally assembled by press-fitting, gluing, shrink-fitting, or a combination of these methods into the hub 3b of the cup-shaped rotor yoke 3a, at one end of the rotor shaft 3c. An annular rotor magnet 3d, magnetized with alternating north and south poles, is assembled to the inner peripheral surface of the rotor yoke 3a. The rotor yoke 3a may be insert-molded together with the centrifugal fan 2.

[0019] The stator 5 has a stator core 7 adhesively fixed to the outer periphery of the axial center of a cylindrically molded stator housing 6. The stator core 7 is assembled by inserting the stator housing 6 into the center hole of an annular core back portion 7a. The stator core 7 is positioned axially by abutting against a stepped portion 6g provided on the stator housing 6. The stator core 7 has multiple pole teeth 7b protruding radially outward from the core back portion 7a. The pole teeth 7b are covered with an insulator 7c, and motor coils 7d are wound around them.

[0020] A sintered oil-impregnated bearing 8 made of porous sintered metal and formed into a cylindrical shape is press-fitted inside the stator housing 6. The sintered oil-impregnated bearing 8 is impregnated with lubricating oil. A sintered felt 9 (oil replenishment member) made of porous metal that supplies lubricating oil to the sintered oil-impregnated bearing is concentrically fitted onto the outer periphery of one axial end (lower end) of the sintered oil-impregnated bearing 8, which is extended on the opposite side from the rotor yoke 3a, so as to partially overlap in the axial direction. A gap 10 of 0.05 mm to 0.5 mm is provided between the outer circumferential surface of the sintered felt 9 and the inner circumferential surface of the stator housing 6, and the sintered felt 9 is housed in the cylindrical hole of the stator housing 6.

[0021] As a result, while the rotor shaft 3c is stopped, the gap 10 between the outer circumferential surface of the sintered felt 9 and the inner circumferential surface of the stator housing 6 can be used as an additional buffer for lubricating oil, so that a sufficient amount of lubricating oil can be supplied even if the sintered felt 9 is small. In addition, when the sintered felt 9, which has low mechanical strength, is assembled into the sintered oil-impregnated bearing 8, interference with the stator housing 6 can be avoided.

[0022] The rotor shaft 3c is inserted into a cylindrical hole 6a of the stator housing 6 and fixed. child The rotor shaft 3c is press-fitted into a cylindrical hole 8a of a sintered oil-impregnated bearing 8 press-fitted into the housing 6. The insertion end of the rotor shaft 3c is supported by a thrust receiver 6c supported by a closing member 6b that closes the cylindrical hole 6a of the stator housing 6. The closing member 6b is abutted against a recess 6d of the stator housing 6 and assembled together. A retaining washer 6e is fitted near the insertion end of the rotor shaft 3c to prevent the rotor shaft 3c from coming off in the axial direction. The closing member 6b is sealed by a sealant 6f that is filled in the recess 6d of the stator housing 6.

[0023] The stator housing 6 is fixed to and assembled integrally with a sheet metal base plate 11 that covers the bottom of the motor. A motor board 12 is assembled on top of the base plate 11 with the stator housing 6 inserted into a board through-hole 12a. A current-carrying circuit is formed on the motor board 12, and the coil lead of the motor coil 7d is electrically connected to the terminal portion.

[0024] As shown in Figure 2, the rotor shaft 3c and the sintered oil-impregnated bearing 8 slide against each other at both axial ends of the sintered oil-impregnated bearing 8 (the upper end indicated by oval A and the lower end indicated by oval B). A gap is formed between both axial ends of the sintered oil-impregnated bearing 8 and the inner wall of the stator housing 6. Furthermore, a sintered felt 9 is press-fitted onto the outer periphery of the lower axial end of the sintered oil-impregnated bearing 8. Therefore, when the rotor shaft 3c rotates while sliding against the sintered oil-impregnated bearing 8, lubricating oil in the sintered oil-impregnated bearing 8 (made of porous sintered metal) moves to the sliding area. To compensate for the lubricating oil that has moved, lubricating oil moves from the sintered felt 9 (made of porous metal) into the sintered oil-impregnated bearing 8. In this way, oil film breakdown at the sliding area between the rotor shaft 3c and the sintered oil-impregnated bearing 8 is prevented. When the rotor shaft 3c stops rotating, the lubricating oil in the sliding area returns to the sintered oil-impregnated bearing 8, and the lubricating oil that overflows from the sintered oil-impregnated bearing 8 is collected by the sintered felt 9. In this way, the sintered felt 9 functions as a buffer for the lubricating oil of the sintered oil-impregnated bearing 8 .

[0025] Furthermore, the sintered felt 9 is press-fit concentrically so as to partially overlap the sintered oil-impregnated bearing 8 at the axial lower end. For this reason, as shown by oval C in Fig. 2, the stator core 7 is assembled to the outer periphery of the stator housing 6 so as to directly overlap the sintered oil-impregnated bearing 8 in the radial direction. In other words, the sintered felt 9 is arranged in a position that does not affect the radial dimension of the stator core 7, within a range that does not overlap the stator core 7 assembled to the outer periphery of the stator housing 6 in the radial direction. For this reason, since only the stator housing and the sintered oil-impregnated bearing are present on the inner periphery of the stator core, the central hole of the stator core 7 can be made small in diameter, which contributes to the miniaturization of the motor. Figure Furthermore, since the sintered felt 9 is not deformed when the stator core 7 is attached to the stator housing 6, the mechanical strength is not impaired. Furthermore, since the sintered felt 9 is accommodated with a gap 10 between it and the inner wall of the stator housing 6, the gap 10 can be used as a buffer for the lubricating oil, and the diameter of the sintered felt 9 can also be made small.

[0026] To assemble the outer rotor motor M described above, as shown in Fig. 3, the sintered oil-impregnated bearing 8 is press-fitted into the cylindrical hole 6a of the stator housing 6. Then, a sizing process is performed to align the inner diameters of the cylindrical holes 8a of the sintered oil-impregnated bearings 8.

[0027] Next, sintered felt 9 is superimposed and press-fit onto the outer periphery of one end (lower end) of the sintered oil-impregnated bearing 8. The sintered felt 9 is housed in the cylindrical hole 6a of the stator housing 6 with a gap 10 formed therein.

[0028] Next, the flange portion of the stator housing 6 is placed on the bottom surface of the base plate 11 and resistance-welded to assemble them together. Next, the motor board 12 is placed on the base plate 11 with the stator housing 6 inserted through the board through-hole 12a, and the protrusions on the base plate 11 are crimped to assemble them.

[0029] The stator core 7 is inserted into the central hole of the core back portion 7a and fixed with adhesive through the stator housing 6. The stator core 7 is positioned in the axial direction by the stepped portion 6g of the stator housing 6 and assembled. The coil leads drawn out from the motor coil 7d wound around the pole teeth 7b of the stator core 7 are soldered to the terminal portions of the motor board 12 for electrical connection.

[0030] Next, the rotor shaft 3c of the rotor 3 integrated with the centrifugal fan 2 is inserted into the cylindrical hole of the stator housing 6 and press-fitted into the cylindrical hole 8a of the sintered oil-impregnated bearing 8. A retaining washer 6e is attached to the insertion end of the rotor shaft 3c exposed from the sintered oil-impregnated bearing 8 to prevent it from coming off. The thrust receiver 6c supported by the closing member 6b is placed on top of the end of the rotor shaft 3c so that it abuts against the end of the rotor shaft 3c, and a sealant 6f (a resin material such as an adhesive) is filled into the recess 6d to cover and seal the closing member 6b.

[0031] According to experiments, the effect of the sintered oil-impregnated bearing 8 on the generation of abnormal noise during low-temperature operation is as follows: An outer rotor type motor M was driven for 30 minutes in an 85°C environment and then stopped for 30 minutes, repeatedly, to carry out a durability test for a total of 1000 hours. In the product without the sintered felt 9, no abnormal noise was heard at temperatures above -30°C before the durability test, and no abnormal noise was heard at temperatures above 0°C after the durability test. On the other hand, the product to which sintered felt 9 was assembled produced no abnormal noise at temperatures above -40°C before the durability test, and no abnormal noise at temperatures above -30°C after the durability test. In this way, it was found that the durability of the outer rotor type motor M in low temperature environments was improved.

[0032] As explained above, when the rotor shaft 3c rotates while sliding against the sintered oil-impregnated bearing 8, the lubricating oil inside the sintered oil-impregnated bearing 8 made of porous sintered metal moves to sliding parts A and B shown in Figure 2, and the lubricating oil moves from the sintered felt 9 made of porous metal into the sintered oil-impregnated bearing 8, preventing the oil film from running out at sliding parts A and B between the rotor shaft 3c and the sintered oil-impregnated bearing 8. When the rotation of the rotor shaft 3c stops, the lubricating oil at sliding parts A and B returns to the sintered oil-impregnated bearing 8, and any lubricating oil that has overflowed from the sintered oil-impregnated bearing 8 returns to the sintered felt 9. In this way, the sintered felt 9 functions as a buffer for the lubricating oil of the sintered oil-impregnated bearing 8. Furthermore, since the sintered felt 9 is partially overlapped and concentrically fitted onto the outer periphery of one axial end of the sintered oil-impregnated bearing 8, the outer diameter of the sintered oil-impregnated bearing 8 does not become larger than necessary, and the sintered oil-impregnated bearing 8 does not become larger in the axial direction. Furthermore, since the sintered felt 9 is housed in the cylindrical hole 6a with a gap 10 between it and the inner wall of the stator housing 6, the mechanical strength of the sintered oil-impregnated bearing 8 is not impaired, the gap 10 can be used as a buffer for the lubricating oil, and the diameter of the sintered felt 9 can also be made small.

[0033] [Second Example] Next, another example of an outer rotor type motor will be described with reference to FIG. The same members as in the first embodiment are given the same numbers and their explanations will be incorporated, and the following description will focus on the different configurations. The outer diameter of the stator housing 6 is formed to be even smaller at the other axial end (rotor 3 side) where the sintered felt 9 (oil supply member) is not provided than the outer diameter where the stator core 7 is assembled, and a space 13 is provided between the other axial end and the tip of the sintered oil-impregnated bearing 8. This space 13 has a gap of at least 0.05 mm to 0.3 mm in the radial direction, and this gap is capable of retaining lubricating oil. This allows the space 13 formed between the inner surface of the stator housing 6 and the sintered oil-impregnated bearing 8 on the other axial end side of the sintered oil-impregnated bearing 8 where the sintered felt 9 is not provided to be used as a buffer space for the lubricating oil.

[0034] In order to ensure robustness against environmental temperatures, etc., and to ensure that the sintered oil-impregnated bearing 8 performs stably over the long term, it is desirable to have excess lubricating oil around the sintered oil-impregnated bearing 8 and the sintered felt 9 (oil-replenishing member), and it is also necessary to prevent this excess lubricating oil from leaking. As described above, in the present invention, the "gap 10 between the sintered felt 9 and the stator housing 6" and the "space 13 between the sintered oil-impregnated bearing 8 and the stator housing 6" have the function of retaining excess lubricating oil. An experiment was conducted to confirm whether the "gap 10 between the sintered felt 9 (oil supply member) and the stator housing 6" and the "space 13 between the sintered oil-impregnated bearing 8 and the stator housing 6" could retain lubricating oil, regarding them as gaps.

[0035] First, the gap that retains the lubricating oil was defined as the "gap width W," which is the distance between the sintered oil-impregnated bearing 8 and the stator housing 6, and the "gap length L," which is the distance of the gap in the longitudinal direction of the cylinder of the sintered oil-impregnated bearing 8, as shown in Figures 5A and 5B. The use of an oil-replenishing member will be discussed later. Multiple values for the gap width W and multiple values for the gap length L were selected, and multiple experimental members with approximately the same shape as the stator housing 6 and corresponding inner dimensions were created. Transparent resin was used for the experimental members, making it easier to observe the state of lubricating oil retention. Sintered oil-impregnated bearings 8 were fitted to these multiple experimental components, and the lubricating oil used in the sintered oil-impregnated bearings 8 was dripped onto them to verify whether the gap between the sintered oil-impregnated bearings 8 and the stator housing 6 could retain the lubricating oil.

[0036] Table 1 below shows the change in kinematic viscosity of the lubricating oil used in the dropping experiment with respect to the change in temperature. [Table 1] Assuming that the end of the sintered oil-impregnated bearing 8 with the space 13 in the cylindrical longitudinal direction is the tip, the test piece was placed with the tip side facing downwards, and lubricating oil was dripped from the rear end (upper part in Figure 5A) of the sintered oil-impregnated bearing 8 (see arrow in Figure 5A) to check whether the lubricating oil leaked out beyond (downward from) the gap (space 13). The amount of lubricating oil dripped was 50 μL, which is the standard amount for the sintered oil-impregnated bearing 8 used. The test environment was room temperature (20°C) and 80°C. During the experiment, the rotor shaft 3c was inserted into the sintered oil-impregnated bearing 8, and verification was performed under conditions where no lubricating oil leakage occurred through the inner periphery of the sintered oil-impregnated bearing 8 (see FIG. 5A). As shown in FIG. 5C, the outer circumferential surface of the sintered oil-impregnated bearing 8 is provided with an air vent groove. 8b Since a plurality of lubricating oil gaps are provided, the dropped lubricating oil immediately falls down to the gap (space portion 13).

[0037] Tables 2 and 3 below show the results of dripping experiments when the gap width W and gap length L are changed. The gap with no leakage further down (lubricant retained in the gap) is the desired state and is marked as OK, while the gap with leakage further down is not desirable and is marked as NG. [Table 2] [Table 3]

[0038] The results of this experiment showed that if the gap length L is 1.5 mm or more, the gap width W should be 0.3 mm or less to prevent lubricant leakage, and if the gap length L is 1.0 mm or more, the gap width W should be 0.2 mm or less to prevent lubricant leakage. This confirmed that the gap can function effectively as a buffer (retention space) for lubricant. Furthermore, regarding the gap length L and gap width W, experimental results indicate that the gap has the ability to retain lubricant if the relationship is "gap width W ≦ (1 / 5) gap length L." If the gap in this experiment is applied to the space 13 between the outer periphery of the sintered oil-impregnated bearing 8 and the inner periphery of the stator housing 6, it becomes "0.05 mm to 0.3 mm in the radial direction, and 1.5 mm or more in the axial direction" or "0.05 mm to 0.2 mm in the radial direction, and 1.0 mm or more in the axial direction." The minimum radial gap width of 0.05 mm is an allowable tolerance based on the machining accuracy of the parts.

[0039] In this invention, the axial length of the oil supply member (sintered felt 9; see Figure 3) is 5.0 mm. Because the oil-impregnated capacity of a sintered oil-impregnated bearing and an oil supply member differs, a safety factor of 2.0 is used. Therefore, based on the aforementioned relationship of "gap width W ≦ (1 / 5) gap length L," the size of the gap 10 between the outer circumferential surface of the oil supply member and the inner circumferential surface of the stator housing 6, when applied to the gap size in this experiment, is "0.05 mm to 0.5 mm in the radial direction, and 5.0 mm or more in the axial direction." The minimum radial gap width of 0.05 mm is a tolerance based on the machining accuracy of the part. As mentioned above, the oil-impregnated capacity of the sintered oil-impregnated bearing 8 and the oil supply member differ, so a safety factor of 2.0 was multiplied and the gap width W was set to "0.5 mm or less" instead of "1.0 mm or less." If the axial length of the oil supply member is set to a value other than 5.0 mm, it is also possible to select a gap width W that satisfies the relationship "gap width W ≦ (1 / 5) gap length L × (1 / safety factor)."

[0040] The above-described embodiment of the outer rotor motor has been described using an in-vehicle seat air conditioner as an example, but the invention is not limited to this and may also be used in centrifugal fans for HVAC (heating, ventilation, and air conditioning) etc. It goes without saying that the present invention is equally effective in places other than vehicles where there is little spare space and it is difficult to secure space for installing a conventional air conditioning fan. [Explanation of symbols]

[0041] REFERENCE SIGNS LIST 1 centrifugal blower 2 centrifugal fan 3 rotor 3a rotor yoke 3b hub 3c rotor shaft 3d rotor magnet M outer rotor type motor 4 case body 5 stator 6 stator housing 6a, 8a cylindrical hole 6b closing member 6c thrust receiver 6d recess 6e retaining washer 6f sealing material 6g stepped portion 7 stator core 7a core back portion 7b pole teeth 7c insulator 7d motor coil 8 sintered oil-impregnated bearing 9 sintered felt 10 gap 11 base plate 12 motor board 12a board through-hole 13 space portion

Claims

1. An outer rotor type motor having a stator in which a stator core is assembled to the outer periphery of a cylindrical stator housing and a sintered oil-impregnated bearing made of porous sintered metal is concentrically assembled to the inner periphery of the stator housing, and a rotor is rotatably supported around a rotor shaft inserted into the sintered oil-impregnated bearing, An outer rotor type motor is characterized in that an annular oil supply member made of porous sintered metal that supplies lubricating oil to the sintered oil-impregnated bearing is concentrically fitted onto the outer periphery of one axial end of the sintered oil-impregnated bearing to the extent that it does not overlap radially with the stator core assembled to the outer periphery of the stator housing, and the motor is housed within the stator housing with a gap of 0.05 mm to 0.5 mm radially and 5.0 mm axially formed between the outer periphery of the oil supply member and the inner periphery of the stator housing.

2. 2. The outer rotor motor of claim 1, wherein the other axial end of the stator housing where the oil supply member is not provided is formed to have a smaller diameter than the outer diameter of the stator housing to which the stator core is assembled, and a space is provided between the outer periphery of the sintered oil-impregnated bearing and the inner periphery of the stator housing, and the space has a radial width of 0.05 mm to 0.3 mm if the axial length is 1.5 mm or more, and a radial width of 0.05 mm to 0.2 mm if the axial length is 1.0 mm or more.

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