JP2001082475A - Oil-retaining bearing and motor with oil-retaining bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of abnormal sound due to whirling of a rotating shaft in starting by providing a non-porous abutting part projecting on the inner peripheral surface near a boundary part of adjacent bearing parts in an oil-retaining bearing composed of a center bearing part with its inner peripheral surface parallel with the rotating shaft, and end bearing parts arranged at both ends of the center bearing part. SOLUTION: A rotor of a motor comprises a rotating shaft and an armature assembled almost perpendicularly. The rotating shaft with a driven body such as a fan fitted to the upper end part is rotatably supported in the vertical direction at both ends of the armature by an oil-retaining bearing composed of an upper end side oil- retaining bearing 3a and a lower end side oil-retaining bearing. In this case, the oil- retaining bearing (the upper end side oil-retaining bearing 3a in the figure) is composed of a center bearing part 31a, and one end bearing part 32a and the other end bearing part 33a arranged at both ends of the center bearing part 31a and gradually diameter- enlarged in the inner peripheral surfaces toward the end parts. A non-porous abutting part 38a projected in the inner diameter direction is further formed at a boundary part 34a between the center bearing part 31a and one end bearing part 32a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a porous oil-impregnated bearing having lubricating oil therein and an electric motor using the same.

[0002]

2. Description of the Related Art Conventionally, in an electric motor used for a blower for a vehicle, generally, the electric motor has a rotating shaft arranged in a vertical direction, and an oil-impregnated bearing is formed of a porous sintered alloy impregnated with lubricating oil. The sliding surface is cylindrical. With this configuration, the lubricating oil that has infiltrated the bearing after a long time has passed through the gap between the rotating shaft and the sliding surface may flow out, or may be sucked into the narrow space inside the porous bearing. Therefore, a phenomenon that hardly remains on the sliding surface often occurs.

[0003] In order to solve the above problems, a sintered oil-impregnated bearing disclosed in Japanese Patent Application No. 11-158380 has been proposed. As shown in FIG. 9, two oil-impregnated bearings 3A and 3B are provided above and below the rotating shaft 21 of the electric motor. The oil-impregnated bearings 3A and 3B are provided with central bearings 31A and 31B and end bearings 32A at both ends. , 33A, 32B, and 33B. And the oil-impregnated bearing 3A above the rotating shaft 21
Is provided with a non-porous surface 36A at a boundary 34A between the central bearing 31A and the upper end bearing 32A.
The lower oil-impregnated bearing 3B has a non-porous surface 36 at the boundary 34B between the central bearing 31B and the lower end bearing 32B.
B is provided. In the above configuration, the rotating shaft 2
When the rotation shaft 21 is at the maximum inclination 2θ with respect to the oil-impregnated bearings 3A and 3B, the rotating shaft 21 is moved to the boundary portions 34A and
Contact the non-porous surfaces 36A, 36B of 34B. On the non-porous surfaces 36A and 36B, the lubricating oil
A and 3B are not absorbed inside, so that the rotating shaft 21
Even at a very low temperature, even immediately after startup after a long stop, the rotating shaft can always slide on the oil-impregnated bearing surface while being immersed in the lubricating oil.

[0004]

However, even with the above configuration, as shown in FIG. 9, the rotating shaft 21 is positioned substantially at the center of the inner periphery of the lower oil-impregnated bearing 3B where the non-porous surface 36B is provided. When the upper oil-impregnated bearing 3A and the rotary shaft 21 are stationary in a state of contact (in other words, half of the maximum tilt angle of the rotary shaft, hereinafter referred to as θ), the following problem occurs. At this time, the rotating shaft 21 is the rotating shaft 21 of the oil-impregnated bearing 3B.
The boundary 35B of the porous surface at the opposite end of the rotating shaft 21 in the oil-impregnated bearing 3B is closer than the boundary 34B of the non-porous surface 36B at the end. As a result, the rotating shaft 21
Lubricating oil 100 existing between the oil-impregnated bearing 3B and the lower oil-impregnated bearing 3B
Moves in the direction in which the gap becomes smaller due to the surface tension of the lubricating oil 100. That is, the lubricating oil 100 existing on the non-porous surface 36B moves upward as shown by the arrow in FIG. 9 and moves to the porous surface boundary portion 35B. As a result, when the stationary state as shown in FIG. 9 continues for a long time, the lubricating oil 100 is depleted from the surface of the oil-impregnated bearing 3B. When the electric motor 1 is started in this state, the sliding friction between the oil-impregnated bearings 3A and 3B and the rotary shaft 21 is large, and the static vibration effect due to the lubricating oil cannot be obtained. Then, there is a problem in that a behavior known as backward precession movement is exhibited and an unpleasant sound is generated.

The present invention solves such a problem. Even when assembled in a substantially vertical direction, lubricating oil can be retained on the sliding surface for a long period of time, and the rotating shaft wobbles at start-up, and abnormal noise is generated. It is an object of the present invention to provide an oil-impregnated bearing and a motor using the oil-impregnated bearing, which can reliably prevent the occurrence of such a situation.

[0006]

According to a first aspect of the present invention, there is provided a central bearing having an inner peripheral surface parallel to a rotating shaft, and an inner peripheral surface at one end at both ends of the central bearing. In a porous oil-impregnated bearing including a lubricating oil composed of an end bearing portion gradually expanding toward the inside, an inner peripheral surface near a boundary between the central bearing portion and the end bearing portion has a non-porous inner diameter direction. An oil-impregnated bearing characterized by having an abutting portion protruding from the bearing.

According to a second aspect of the present invention, there is provided a central bearing having an inner peripheral surface parallel to the rotating shaft, a one-end bearing having an inner peripheral surface which gradually widens toward an end of the rotating shaft, and an inner peripheral surface having an inner peripheral surface. In a porous oil-impregnated bearing including lubricating oil comprising a bearing at the other end gradually expanding toward the opposite end of the rotating shaft, an inner periphery near a boundary between the central bearing and the bearing at the one end is provided. The oil-impregnated bearing is characterized in that the surface has a nonporous abutting portion projecting in the inner diameter direction.

In a third aspect of the present invention, in addition to the second aspect, the axial length of the central bearing portion is L, and a half of the maximum inclination angle of the rotating shaft without the contact portion is θ °. And when
The oil-impregnated bearing is characterized in that the amount of protrusion in the inner diameter direction at the contact portion is not less than L × tan θ. Also, the fourth
The present invention is an electric motor using the oil-impregnated bearing according to any one of the first to third inventions.

[0009]

According to the oil-impregnated bearing according to the first and second aspects of the present invention and the electric motor according to the fourth aspect, when the rotary shaft is rotating, the contact between the rotary shaft and the inner peripheral surface of the bearing is achieved. Lubricating oil overflows from the inner peripheral surface of the porous central bearing portion due to frictional heat. Then, the lubricating oil travels along the rotating shaft or the inner peripheral surface to reach the boundary of the non-porous surface provided between the central bearing and the end bearing. Even after the rotary shaft is stopped and left for a long time, the boundary is a non-porous surface, so that the lubricating oil does not permeate into the inside and is always immersed. As a result, even if the rotating shaft is operated after the rotating shaft is stopped and left for a long time, the rotating shaft is inclined as shown in FIG. Is covered with the lubricating oil and no backward precession occurs, and the generation of unpleasant noise can be prevented. Further, even when the rotating shaft is inclined at a very low temperature for a long time as shown in FIG. 4, the portion where the rotating shaft and the surface of the oil-impregnated bearing are closest is the contact portion of the non-porous surface. Lubricating oil is not depleted by being absorbed inside the bearing.

[0010] In particular, according to the oil-impregnated bearing according to claim 2 of the present invention and the electric motor according to claim 4 using the oil-impregnated bearing, if two oil-impregnated bearings are provided above and below the rotary shaft, the oil-impregnated upper bearing will be described. The bearing is provided with a non-porous portion at the boundary between the upper end bearing portion and the central bearing portion, and the lower oil-impregnated bearing is provided with a non-porous portion at the boundary portion between the lower end bearing portion and the central bearing portion. Provided. As a result, since the portion where the rotating shaft is inclined and the closest portion becomes the protruding portion, even if one non-porous portion is provided at two boundary portions in one oil-impregnated bearing, there is an effect that the lubricating oil is not efficiently absorbed.

In particular, according to the oil-impregnated bearing according to the third aspect of the present invention and the electric motor according to the fourth aspect using the same, according to the above configuration, the half of the maximum inclination angle of the rotating shaft when there is no contact portion is θ and θ. Assuming that the central bearing portion is L, the amount of protrusion of the contact portion is L × tan θ or more. With this set value, the rotating shaft does not come into contact with the other end bearing portion which is not a non-porous surface.

[0012]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a motor according to a first embodiment of the present invention, FIG. 2 is a cross-sectional view of an upper end side oil-impregnated bearing of the first embodiment of the present invention, and FIG. 3 is a first embodiment of the present invention. It is sectional drawing of the lower end side oil-impregnated bearing of FIG. In FIG. 1, which is the electric motor 1, the rotor 2 that is driven to rotate includes a rotating shaft 21 and an armature 22 that are assembled in a substantially vertical direction. A driven body such as a blower fan (not shown) is attached to the upper end of the rotating shaft 21. The oil-impregnated bearing 3 is provided with an upper-end oil-impregnated bearing 3a and a lower-end oil-impregnated bearing 3b so as to support the rotating shaft 21 in the vertical direction. The commutator 4 is fixed to the rotating shaft 21 and rectifies the power supply of the electric motor 1. As a stator, a yoke housing 5 and a magnet 6 fixed to an inner wall of the yoke housing 5 are provided, and a brush 7 is used for power supply.

The upper oil-impregnated bearing 3a shown in FIG. 2 and the lower oil-impregnated bearing 3b shown in FIG. 3 are made of a porous material obtained by compressing and pressing a powder metal conventionally used in an electric motor of this type and further sintering it. is there.

Here, first, the upper end side oil-impregnated bearing 3a of FIG.
Will be described. The upper end side oil-impregnated bearing 3a is provided with a rotating shaft 21 of the electric motor 1 which is arranged vertically as shown in FIG.
And an armature 22 serving as a rotor 2 main body.
Are provided on the upper side. Upper end side oil-impregnated bearing 3
a is mainly composed of three members, which are a central bearing portion 31a, one end bearing portion 32a, and another end bearing portion 33a. The central bearing 31a is parallel to the rotating shaft 21. The one-end bearing portion 32a is provided at an upper end of the central bearing portion 31a, and has an inner peripheral surface that forms a linear tapered surface that gradually expands outward in the axial longitudinal direction. The other end bearing portion 33a is provided at a lower end portion of the center bearing portion 31a, and has an inner peripheral surface that forms a linear tapered surface that gradually expands outward in the longitudinal direction of the shaft. The positional relationship between the upper end side oil-impregnated bearing 3a and the rotating shaft 21 is determined by the one-end bearing portion 32.
a is a direction away from the armature 22 and the other end bearing portion 33
a is a direction approaching from the armature 22.

Next, the central bearing portion 31a and the one-end bearing portion 32
a one end boundary portion 34a serving as a boundary with the center bearing portion 31
a and a linearly tapered inner peripheral surface of the one end bearing portion 32a has a circular refraction shape. Similarly, the other end boundary portion 35a, which is the boundary between the central bearing portion 31a and the other end bearing portion 33a, has a parallel inner peripheral surface of the central bearing portion 31a and a linear tapered inner peripheral surface of the other end bearing portion 32a. From this, it has a circular refraction shape. The one end boundary portion 32a and its vicinity are non-porous surfaces 36a, respectively, and this portion is formed by crushing the porous oil-impregnated bearing surface. Although the one end boundary portion 34a is a circular line, since this non-porous portion is also provided near the one end boundary portion,
The inner peripheral surface of the central bearing portion 31a and the one end bearing portion 32a are also partially provided. The non-porous surface 36a is a non-porous surface in all circumferential directions, and becomes a contact portion 38a slightly projecting in the inner diameter direction from the surfaces of the central bearing portion 31a and the one-end bearing portion 32a. ing. If the amount of protrusion of the contact portion 38a in the inner diameter direction is larger than the value shown below, the other end boundary portion 35a will not contact the rotating shaft 21. The value is L × tan θ, where L is the axial length of the central bearing portion 31a and θ is half the maximum inclination angle of the rotating shaft 21 without the contact portion 38a.
Therefore, for example, half of the tiltable angle of the rotating shaft 21 when there is no contact portion 38a is 1 °, and the center bearing portion 31a is 7 °.
mm, the projecting amount of the contact portion 38a is at least 0.12 mm
is necessary.

Then, a notch mark 37a is formed on the shaft end surface in the direction in which the non-porous surface 34a is provided at the one end boundary portion 34a of the upper end side oil-impregnated bearing 3a so as to penetrate from the inner peripheral surface to the outer peripheral surface. Is provided. This allows the arrangement of the non-porous surface 36a to be determined from the appearance. By providing the mark 37a to the outside of the rotor 22, the non-porous surface 36a is arranged on the upper end side of the rotating shaft 21 away from the rotor 22, so that
The operation of the present invention when inclined as shown in FIG. 4 can be reliably produced. The outer peripheral side surface of the upper end side bearing 3a has a curved surface shape with respect to the axis. The outer peripheral side surface is a portion fixed to a housing case 50 which is a stator of the electric motor. When the rotating shaft 21 is inclined with respect to the rotating shaft 21 as shown in FIG. This is a structure that can be finely adjusted so as to be in contact with the surface 36a.

Similarly, the lower end side oil-impregnated bearing 3b in FIG. 3 will be described. The lower end-side oil-impregnated bearing 3b supports the rotating shaft 21 of the electric motor 1 arranged in the vertical direction as shown in FIG. 1, and is disposed in the lower end side direction of the armature 22, which is the main body of the rotor 2. Is provided. Lower end side oil-impregnated bearing 3b
Is mainly composed of three members, a central bearing portion 31b, one end bearing portion 32b, and another end bearing portion 33b. The central bearing portion 31b is parallel to the rotating shaft 21. The one-end bearing portion 32b is provided at a lower end portion of the center bearing portion 31b, and has an inner peripheral surface that forms a linear tapered surface that gradually expands outward in the longitudinal direction of the shaft. The other end bearing portion 33b is provided at the lower end of the central bearing portion 31b, and has an inner peripheral surface that forms a linear tapered surface that gradually expands outward in the longitudinal direction of the shaft. The positional relationship between the lower end side oil-impregnated bearing 3b and the rotating shaft 21 is determined by the one-end bearing portion 32b.
Is a direction away from the armature 22, and the other end bearing portion 33b
Is a direction approaching from the armature 22.

Next, the central bearing portion 31b and the one-end bearing portion 32
The one end boundary portion 34b serving as the boundary with the center bearing portion 31b
b and a linear tapered inner surface of the one end bearing portion 32b form a circular refraction shape. Similarly, the other end boundary portion 35b which is a boundary between the central bearing portion 31b and the other end bearing portion 33b is formed by a parallel inner peripheral surface of the central bearing portion 31b and a linear tapered inner peripheral surface of the other end bearing portion 32b. From this, it has a circular refraction shape. The one end boundary portion 32b and its vicinity are non-porous surfaces 36b, respectively, and these portions are formed by crushing the porous oil-impregnated bearing surface. Although the one end boundary portion 34b is a circular line, since this non-porous portion is also provided near the one end boundary portion,
The inner peripheral surface of the central bearing portion 31b and the one end bearing portion 32b are also partially provided. The non-porous surface 36b has a non-porous surface in all circumferential directions,
The contact portion 38b slightly projects in the inner diameter direction from the surfaces of the central bearing portion 31b and the one end bearing portion 32b. If the amount of protrusion of the contact portion 38b in the inner diameter direction is larger than the value shown below, the other end boundary portion 35b will not contact the rotating shaft 21. The value is L when the axial length of the central bearing portion 31b is L and the rotating shaft 21 when there is no contact portion 38b.
If half of the maximum inclination angle is θ, then L × tan θ. Therefore, for example, the rotation shaft 2 when there is no contact portion 38a
Half of the tiltable angle of 1 is 1 ° and the central bearing portion 31b
Is 7 mm, the amount of protrusion of the contact portion 38b is at least 0.12.
mm is required.

Then, a notch mark 37a is formed on the shaft end surface in the direction in which the non-porous surface 34b is provided at the one end boundary portion 34b of the lower end side oil-impregnated bearing 3b so as to penetrate from the inner peripheral surface to the outer peripheral surface. Is provided. This allows the arrangement of the non-porous surface 36b to be determined from the appearance. By providing the mark 37b toward the outside of the rotor 22, the non-porous surface 36b is arranged on the lower end side of the rotating shaft 21 away from the rotor 22, so that
The operation of the present invention when inclined as shown in FIG. 4 can be reliably produced. Further, the outer peripheral side surface of the lower end side bearing 3b has a curved surface shape with respect to the axis. The outer peripheral side surface is a portion fixed to a housing case 50 which is a stator of the electric motor. When the rotating shaft 21 is inclined with respect to the rotating shaft 21 as shown in FIG. This is a structure that can be finely adjusted so as to be in contact with the surface 36b.

Next, a mechanism for suppressing the generation of unpleasant sounds with the above configuration will be described. Due to the positional relationship between the rotor 22, the rotating shaft 21, the upper end-side oil-impregnated bearing 3a, and the lower end-side oil-impregnated bearing 3b schematically shown in FIG.
May be inclined. At this time, the collision at the point A between the rotating shaft 21 and the inner peripheral surface of the one end boundary portion 34a of the upper end side oil-impregnated bearing 3a, and the inner peripheral surface of the one end boundary portion 34b of the rotating shaft 21 and the lower end side oil-impregnated bearing 3b. Collision (not shown) is one of the causes of the vibration, especially when the lubricating oil is not sufficiently supplied to the non-porous surface at the time of restart during long-term stop. Generates a behavior known as backward precession, which produces an unpleasant sound.

However, the one end boundary 34a of the upper end oil-impregnated bearing 3a, which is the end side of the rotary shaft 21, and the one end boundary 34b of the lower end oil-impregnated bearing 3b have a non-porous surface. The lubricating oil can be immersed in this part even during restarting during a long-term stop. Therefore,
It eliminates the problem of generating a behavior known as backward precession and generating unpleasant sounds.

Next, the operation of the electric motor 1 having the oil-impregnated bearing 3 (the upper-end oil-impregnated bearing 3a and the lower-end oil-impregnated bearing 3b) during normal rotation will be described. First, when a drive switch (not shown) is turned on, a brush 7, a commutator 4,
Power is supplied to the rotor 22, and the rotor 22 rotates, transmitting the rotational driving force to the rotating shaft 21 to rotate the non-driving body.

Next, the lubricating oil and the upper end side oil-impregnated bearing 3a while the rotating shaft is rotating will be described with reference to the upper diagram of FIG. The lubricating oil that has infiltrated the sliding surface falls along the gravity in the gap between the tapered portion of the bearing portion 32a and the rotating shaft 21 at one end. Then, the lubricating oil is immersed on the non-porous surface 36a (arrow C). On the other hand, the lubricating oil that has permeated into the oil-impregnated bearing 3a is absorbed and supplied from the surface of the central bearing portion 31a (arrow D). It should be noted that the angle of the one end bearing portion 32a has such an angle that the surface of the one end bearing portion 32a does not come into contact even if the rotating shaft 21 is maximally inclined with respect to the axis of the oil-impregnated bearing 3 due to runout or the like. The state is as shown in FIG. Therefore, the lubricating oil is less likely to be absorbed from the bearing portion 32a during rotation, and is often supplied.

Next, the lubricating oil and the lower end side oil-impregnated bearing 3b will be described with reference to the lower diagram of FIG. The lubricating oil that has infiltrated the sliding surface is once held against the gravity in the gap between the tapered portion of the bearing portion 32b and the rotating shaft 21. This phenomenon is generally called capillary action, and a force calculated by the surface tension of the liquid and the size of the gap acts. Incidentally, the liquid surface is raised to a height of about 50 cm in the gap of 10 μm. Therefore, a desirable angle of the tapered portion is 1 ° to 10 °. The tapered surface of the lower end bearing portion 32b has an effect of preventing the lubricating oil in the sliding surface from dripping. More specifically, the upper end bearing portion 33b may have an angle of 1 ° to 10 °, but the lower end bearing portion 32b may preferably have an angle smaller than 1 ° to 5 °. With this range, it is particularly effective to prevent the lubricant oil from dripping downward. The angle of the one end bearing portion 32b is such that the surface of the one end bearing portion 32b does not come into contact even if the rotating shaft 21 is inclined at the maximum with respect to the axis of the oil-impregnated bearing 3 due to runout or the like. The state is as shown in FIG. on the other hand,
The lubricating oil dropped from the lower end bearing portion 32b non-porous surface 36b is absorbed from the porous one end side oil-impregnated bearing 32b into the oil-impregnated bearing 3b (arrow E). Then, the lubricating oil is supplied to the sliding surface of the rotating shaft 21 via the surface of the central bearing portion 31b and the surface of the other end bearing portion 33b (arrow F), and the lubricating oil supplied from the sliding surface is supplied near the boundary portion 33b. It is supplied so as to fall on the inner peripheral surface of the non-porous surface 34b (arrow G).

The operation of the contact portions 38a and 38b in a state where the rotating shaft is stopped for a long time under cryogenic temperature, which is the point of the present invention, will be described with reference to FIG. In this figure, the contact portions 38a and 38b are projected more than necessary, but this is for easy understanding. In this state, the rotating shaft 21 is closest to the boundary portions 38a, 38b of the non-porous surface due to the presence of the contact portions 38a, 38b. Therefore, when the lubricating oil existing between the rotating shaft 21 and the oil-impregnated bearings 3a, 3b is stationary for a long time, the non-porous surfaces 36a, 3b
Move to 6b. As a result, the lubricating oil is not absorbed into the oil-containing bearing.

Next, after the long-time rotating shaft of the present invention stops,
Fig. 6 shows the microscopic action of lubricating oil when operating
It will be described according to the following. FIG. 6A is an explanatory diagram showing the surface of the rotating shaft 21 and the oil-impregnated bearing 3 made of porous material. The porous oil-impregnated bearing 3 has a myriad of fine holes 30,
After the stop of 1, the lubricating oil 100 is absorbed into the oil-impregnated bearing 3 main body by the capillary phenomenon, and the lubricating oil 100 does not exist on the sliding surface around the opening of the fine hole 30. However, FIG.
In the oil-impregnated bearing 3 according to the first embodiment of the present invention shown in (B), the surface near the one end boundaries 34a and 34b has a fine hole 30.
Since the lubricating oil 100 is formed on the non-porous surfaces 36a and 36b, the lubricating oil 100 continues to be held on the sliding surface.

As a result, even if the rotating shaft 21 is operated after the rotating shaft 21 is stopped and left for a long time, when the rotating shaft 21 is inclined as shown in FIG. One end boundaries 34a, 34 of the rotating shaft 21 and the oil-impregnated bearing 3
Since the lubricating oil is covered between the inner peripheral surface and the inner peripheral surface of the rotating shaft b, the coefficient of sliding friction between the rotating shaft 21 and the oil-impregnated bearing 3 does not increase, so that there is no backward precession movement, which is unpleasant. It is possible to prevent the generation of unpleasant sounds. In particular, since the porous surfaces 36a and 36b are provided, the probability that the non-porous surfaces 36a and 36b are immersed in the lubricating oil increases.

FIG. 7 shows the results of a comparison experiment between the case where the oil-impregnated bearing in which all the sliding surfaces are formed of porous material is used and the case where the first embodiment is used. In the experiment, we used a high-viscosity lubricating oil to repeatedly start and stop after a short period of operation, and examined the power consumption at startup. If a large amount of lubricating oil is held, power consumption will increase because of high viscosity. In the experiment, the bearing of the present invention showed no change even after the repetition. On the other hand, when the whole surface was porous, the power consumption was reduced every time the experiment was repeated, indicating that the lubricating oil was reduced.

FIG. 8 shows a second embodiment. In the oil-impregnated bearing 3c of the second embodiment, the non-porous surfaces 36c and 36d are located near the upper and lower boundaries 34c and 34d where the rotating shaft 21 is closest, so that the lubricating oil moves to either side. It is not absorbed. Therefore, the effect of the present invention can be obtained by providing the oil-impregnated bearing 3c only below the rotating shaft 21, or both above and below the rotating shaft 21. Moreover, since it has a vertically symmetrical shape, it can be easily assembled without particularly providing a mark when assembling.

[0030]

As is apparent from the above description, according to the present invention, the lubricating oil oozing out of the sintered oil-impregnated bearing is prevented from traveling along the rotating shaft and dripping outside the bearing. Lubricating oil can be retained on the sliding surface of the bearing immediately after startup after being stopped for a long time by preventing accumulation in the narrow spaces in the bearing. In particular, the friction between the oil-impregnated bearing and the rotating shaft when the rotating shaft is inclined, which causes vibration, can be reduced, so that uncomfortable noise during startup can be prevented. Moreover, the certainty is improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of an electric motor according to a first embodiment.

FIG. 2 is a cross-sectional view of an upper end side oil-impregnated bearing in the first embodiment.

FIG. 3 is a sectional view of a lower end side oil-impregnated bearing in the first embodiment.

FIG. 4 is an explanatory view when the rotating shaft is inclined with respect to the oil-impregnated bearings on the upper end side and the lower end side.

FIG. 5 is an explanatory diagram showing movement of lubricating oil in the first embodiment.

FIG. 6 is an explanatory diagram showing movement of lubricating oil in an oil-impregnated bearing.

FIG. 7 is a result of a comparative experiment between the present invention and a conventional bearing.

FIG. 8 is a sectional view of an oil-impregnated bearing according to a second embodiment.

FIG. 9 is an explanatory view when the rotating shaft is inclined with respect to the conventional upper and lower oil-impregnated bearings.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electric motor, 21 ... Rotating shaft, 22 ... Rotor, 3 ... Oil-impregnated bearing, 4 ... Commutator, 5 ... Yoke housing, 6 ... Magnet, 7 ... Brush, 30 ... Fine hole of conventional bearing, 3a ... Upper end Part-side oil-impregnated bearings, 3b: Lower end-side oil-impregnated bearings, 31a, 31b, 31c: Central bearing part, 32
a, 32b, 32c: One end bearing portion, 33a, 33b, 3
3c: other end bearing, 34a, 34b, 34c: one end boundary, 35a, 35b, 35c: other end boundary, 36a, 3
6b, 36c, 36d: non-porous surface, 38a, 38
b, 38c, 38d: abutting part 100: lubricating oil

Claims (4)

[Claims] 1. A porous material containing lubricating oil comprising a central bearing portion having an inner peripheral surface parallel to the rotation axis, and an end bearing portion whose inner peripheral surface gradually widens toward both ends at both ends of the central bearing portion. An oil-impregnated bearing comprising: an oil-impregnated bearing, wherein an inner peripheral surface near a boundary between the central bearing section and the end bearing section has a nonporous abutment portion projecting in an inner diameter direction. 2. A central bearing having an inner peripheral surface parallel to the rotating shaft, a one-end bearing having an inner peripheral surface gradually expanding toward an end of the rotating shaft, and an inner peripheral surface being an opposite end of the rotating shaft. In a porous oil-impregnated bearing including a lubricating oil composed of a bearing at the other end that gradually spreads in the direction of the part, an inner peripheral surface near a boundary between the central bearing and the bearing at one end is non-porous. An oil-impregnated bearing having a contact portion protruding in the inner diameter direction of the bearing. 3. An axial length of the central bearing portion is L, and a half of a maximum inclination angle of the rotating shaft without the contact portion is θ.
°, the amount of protrusion in the inner diameter direction at the contact portion is:
3. The oil-impregnated bearing according to claim 2, wherein L × tan θ. 4. An electric motor using the oil-impregnated bearing according to claim 1.