JPH05115146A - Oil impregnated sintered bearing for small-size motor - Google Patents

Abstract

PURPOSE:To allow an oil impregnated sintered bearing for small-size motor to have a dynamic pressure bearing function and a low abrasion function and to generate low noise. CONSTITUTION:On the inner surface of a bearing hole to face a rotating shaft 13, the plurality of rectangular staged parts 92 having a slidable surface which forms a concentric circle with the rotating shaft 13 are formed in the circumference direction of the rotary shaft 13. A space surrounded by the adjacent staged parts 92, the inner surface of the bearing hole between the adjacent staged parts 92 and the rate shaft 13 is practically formed in the rectangular shape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sintered oil-impregnated bearing for a small motor, and more particularly to a sintered oil-impregnated bearing for a small motor in which an oil film on a sliding surface is formed into a substantially rectangular shape instead of a wedge shape.

[0002]

2. Description of the Related Art In a sintered oil-impregnated bearing, a viscous oil film is constantly interposed between two relatively sliding surfaces to support the load acting on the shaft by the pressure of the oil film. This oil is the lubricating oil impregnated in the pores of the bearing, which is a sintered body, leaching on the sliding surface due to the suction force due to the shaft rotation and the temperature rise of the bearing.

FIG. 19 shows the structure of a conventional sintered oil-impregnated bearing. This bearing 9 is an example in which a dynamic pressure bearing is obtained by providing a spiral groove 20 on the inner peripheral surface of the bearing hole of the bearing that slides relative to the rotary shaft so as to obtain sufficient hydraulic pressure during use. (Japanese Patent Publication No. 63-60247).

20 to 23 show the structure of another conventional sintered oil-impregnated bearing. This bearing 9 has a wedge-shaped void (that is, an oil film) S formed by providing a protrusion 21 on the inner peripheral surface of the bearing hole of the bearing that slides relative to the rotary shaft 13, and a sufficient hydraulic pressure is obtained during use. Is an example of a dynamic pressure bearing (Japanese Patent Laid-Open No. 3-107612).

FIG. 24 shows the structure of still another conventional sintered oil-impregnated bearing, that is, the structure of a general sintered oil-impregnated bearing. In this bearing, the rotary shaft 13 and the inner circumference of the bearing hole of the bearing 9 that slides relative to the rotary shaft 13 are formed concentrically.

[0006]

In the case of the example shown in FIG. 19 described above, since the shape of the groove 20 is spiral and special, it is difficult to process the groove 20 and a high level technique is required. Therefore, there is a problem that the bearing 9 becomes expensive.

In the case of the examples shown in FIGS. 20 to 23, it is necessary to form the protrusion 21 so that the wedge shape S is formed between the rotary shaft 13 and the protrusion 21, and therefore the following problems occur. Occurs. That is, if the angle of the tip of the wedge shape S is too large, the pressure (dynamic pressure) of the oil film is reduced, and the effect of providing the protrusion 21 is reduced. In addition, the space between the protrusion 21 and the rotary shaft 13 is 2 to 3 in a narrow space.
Since the clearance needs to be about μm, the clearance and wedge-shaped angle values and tolerances must be highly accurate. Further, when the shape of the protrusion 21 is triangular, arcuate, trapezoidal, etc., the shape of the bearing hole of the bearing 9 becomes complicated, making it difficult to process and making the bearing 9 expensive. Furthermore, when the rotation speed is low,
The rotating shaft 13 and the protruding portion 21 are in local contact with each other, and are easily worn.

In the case of the example shown in FIG. 24, the structure is simple and there is no problem in terms of processing, but if the rotating shaft 13 contacts the entire inner circumference of the bearing hole, the pores of the sintered body will become inner circumference. There is a problem that the surface is crushed, oil is prevented from leaching to the inner peripheral surface, and seizure occurs due to oil film breakage. As a measure against this, even when the surface of the rotary shaft 13 and / or the inner peripheral surface of the bearing hole is coated (or adhered) with the solid lubricant, the solid lubricant may get into the pores of the sintered body due to various causes and the fineness of As a result of the pores being sealed, oil leaching is hindered and seizure occurs.

It is an object of the present invention to provide a sintered oil-impregnated bearing for a small motor which has a simple structure and has a dynamic pressure bearing function, a low noise and a low wear function.

[0010]

In order to achieve the above object, the present invention provides a sintered oil-impregnated bearing for a small motor,
On the inner peripheral surface of the bearing hole that slides on the rotary shaft, a plurality of substantially rectangular stepped portions having sliding surfaces that are concentric with the rotary shaft are provided in the circumferential direction, and the stepped portions that are adjacent to each other are provided. A gap surrounded by the attachment portion and the inner peripheral surface of the bearing hole between the attachment portion and the rotating shaft is substantially rectangular. Further, a solid lubricant is coated on the sliding surface of the stepped portion.

[0011]

According to the above-mentioned means, the stepped portion provided on the bearing is
Since it has a simple structure of a substantially rectangular shape having a sliding surface that is concentric with the rotary shaft, it can be obtained by simple processing, and the bearing does not become expensive. Further, the groove formed by the stepped portions adjacent to each other and the inner peripheral surface of the bearing hole between them is always ensured, so that the oil leaches and collects from the pores of the bearing which is the sintered body. This allows
A sufficient pressure (dynamic pressure) of the oil film can be generated in the space surrounded by the groove portion and the rotary shaft, and can be supported even when a large load is applied to the rotary shaft.

Further, the solid lubricant on the sliding surface of the stepped portion has a lubricating action and a buffering action when the rotating shaft comes into contact with the stepped portion, causing seizure on the rotating shaft and the bearing. Can be prevented, these can be prevented from being worn, and noise can be prevented from being generated by contact.

[0013]

EXAMPLE A small motor using the sintered oil-impregnated bearing for a small motor of the present invention is shown in FIG. FIG. 1 is a sectional view of an essential part showing an example of a small motor. In FIG. 1, a housing 1 is formed of a metal material such as soft iron into a hollow cylindrical shape with a bottom, and an arc segment-shaped permanent magnet 2 is fixed to the inner peripheral surface thereof. Inside the housing 1, a rotor 5 including an armature 3 facing the permanent magnet 2 and a commutator 4 is provided. The end plate 6 is made of, for example, a metal material similar to that of the housing 1, and is fitted into the opening of the housing 1. The brush arm 7 is provided so as to slide on the commutator 4, and is provided on the end plate 6 together with the input terminal 8 electrically connected to the brush arm 7. The sintered oil-impregnated bearing 9 is fixed in a bearing holding portion 11 formed by projecting the bottom portion of the housing 1 and the end plate 6, and supports the rotating shaft 13 integrated with the rotor 5.

With the above structure, by supplying a current from the input terminal 8 to the armature 3 via the brush arm 7 and the commutator 4, the permanent magnet 2 fixed to the inner peripheral surface of the housing 1 is formed. A rotating force is applied to the armature 3 existing in the existing magnetic field to rotate the rotor 5 and drive an external device (not shown) via the rotating shaft 13.

FIG. 2 shows the structure of the sintered oil-impregnated bearing 9. The cross section shown in FIG. 2 shows the structure of the cross section taken along the section line XX of FIG. 1, in which the rotary shaft 13 is also shown, while the bearing holding portion 11 is omitted.

The sintered oil-impregnated bearing 9 is made of a sintered body, and is sintered so that the inside thereof has a large number of pores and most of the pores communicate with the outside, and is impregnated with lubricating oil. The rotary shaft 13 penetrates through the bearing hole 90 of the sintered oil-impregnated bearing 9. In the bearing hole inner peripheral surface 91 facing the rotating shaft 13,
A plurality of (six in the figure) stepped portions 92 are provided in the circumferential direction. The stepped portion 92 has a sliding surface that is concentric with the rotary shaft 13, and slides relative to the rotary shaft 13.
The inner peripheral surface 91 of the bearing hole also forms a concentric circle with the rotary shaft 13.

Thus, the rotary shaft 13 and the bearing hole inner peripheral surface 9
1 and the stepped portion 92 are concentric, the clearance between the rotary shaft 13 and the bearing hole inner peripheral surface 91 is C2, and the rotary shaft 1 is
If the gap between 3 and the stepped portion 92 is C1, C2 = C
1 + hd is established. Here, hd is the height of the sliding surface of the stepped portion 92 from the bearing hole inner peripheral surface 91. Since the height hd is sufficiently smaller than the diameter of the bearing hole 90, each stepped portion 92
Has a substantially rectangular shape. Further, the groove formed by the two stepped portions 92 adjacent to each other and the bearing hole inner peripheral surface 91 between them is also a groove portion that forms a part of a substantially rectangular shape.
Therefore, the space surrounded by the groove and the rotary shaft 13 has a substantially rectangular shape.

The reason why the stepped portion 92 is formed in a rectangular shape in this way is to generate a maximum peak pressure (dynamic pressure) as the pressure of the oil film during use and support a large load. The shape of the plain bearings is wedge-shaped, step-shaped,
There are various types such as an arc shape and the above combination, but it is known that a rectangular step shape produces the maximum peak pressure (for example, P277 of "Tribology", published by Modern Science Co., Ltd.).

Further, by forming the stepped portion 92 into a rectangular shape which is concentric with the rotary shaft 13, the shape of the mold can be made concentric when the sintered oil-impregnated bearing 9 is sintered. This shape is
Since the structure is simpler than the wedge shape and the like, it is effective for reducing the manufacturing cost of the sintered oil-impregnated bearing 9 and for mass production.

Further, since the bottom of the groove formed by the stepped portion 92, that is, the bearing hole inner peripheral surface 91 does not come into contact with the rotary shaft 13, the air permeability φ is always constant at the bearing hole inner peripheral surface 91.
You get ₂ . Therefore, the suction / discharge of the oil of the sintered oil-impregnated bearing 9 is smoothly circulated, the cooling of the oil and the lubricity of the sliding surface can be improved, and the seizure of the rotary shaft 13 can be prevented.

FIG. 3 shows the distribution of pressure generated in the oil film when the stepped portion 92 has a substantially rectangular shape. Figure 3
One stepped portion 92 is shown as a rectangular shape. The pressure P becomes maximum at one end of the stepped portion 92 when the rotary shaft 13 and the stepped portion 92 relatively slide in the direction of the arrow in the figure.

The pressure distribution as shown in FIG.
Is an example in which the bearing has no eccentricity, and it is necessary to consider the eccentricity in actual use. For example, as shown in FIG. 4, the position of the rotary shaft 13 when there is no eccentricity with respect to the bearing is as shown by the dotted line, as compared with the actual rotary shaft 1
Since 3 has eccentricity, its position is shown by the solid line. Here, when the axial eccentricity amount is represented by e and the radial clearance is represented by C1, the eccentricity is obtained by e / C1.

FIGS. 5 to 7 show a circumferential clearance distribution H (μm) between the rotary shaft 13 and the sintered oil-impregnated bearing 9 when eccentricity is taken into consideration. In particular, FIG. 5 shows the case where the number of stepped portions 92 (step number) is 0, FIG. 6 shows the case where the step number is 3, and FIG. 7 shows the case where the step number is 6. In any case, the radius clearance C1 is 0.005 mm and the eccentricity is 0.9 (e = 4.5 μm). Furthermore, FIG. 6 and FIG.
In, the height (groove depth) hd of the stepped portion 92 is 20 μm.
Is. Note that FIG. 6 corresponds to the case of FIG.
The distribution of gaps in the direction is shown.

8 to 10 show the distribution of the oil film pressure P (kgf / cm ² ) in the circumferential direction when eccentricity is taken into consideration. In particular, FIGS. 8, 9 and 10 show cases where the number of steps is 0, 3 and 6, respectively, that is, FIGS.
Shows the case. In any case, the eccentricity is 0.9
(C1 = 5 μm, e = 4.5 μm), shaft rotation speed is 600
0 rpm, the air permeability φ ₁ at the stepped portion 92 is 3 × 10 ^-10 c
m ² , the air permeability φ ₂ at the inner peripheral surface 91 of the bearing hole is 30 × 10
^-10 cm ² (Thus, in the case of FIG. 8, φ ₁ = φ ₂ = 30 ×
10 ^-10 cm ² at a), the height hd of the stepped portions 92 0.
02 mm, radius clearance C1 = 0.005 mm, bearing diameter 5 mm, bearing length 4.5 mm, bearing thickness 4.25.
mm.

As shown by hatching in FIGS. 9 and 10, a negative pressure portion (hatched portion) is generated corresponding to the stepped portion 92, and oil flows into this. That is, the oil suction force due to the shaft rotation increases due to the generation of the negative pressure portion. Thereby, the dynamic pressure due to the oil film can be increased, and the rotating shaft 13 can be supported with a larger force. Therefore, it is possible to withstand a larger axial load, the metal contact between the rotary shaft 13 and the sintered oil-impregnated bearing 9 is reduced, and the wear of these can be reduced. Further, since the gap between the rotary shaft 13 and the sintered oil-impregnated bearing 9, that is, the clearance C1 shown in FIG. 2 can be increased, the dimensional accuracy and tolerances of these can be easily controlled, and the assembling thereof can be facilitated. it can.

11 and 12 show an example in which the stepped portion 92 has a plurality of steps (two steps in the case of the figure) to generate a larger dynamic pressure by the oil film. As shown in the drawing, an intermediate stepped portion 92 'having an intermediate height hd / 2 between the stepped portion 92 having the height hd and the bearing hole inner peripheral surface 91 (height 0) is provided. The intermediate stepped portion 92 'is provided only on one side in the circumferential direction of the bearing hole inner circumferential surface 91 in FIG. 11, and is provided on both sides in the circumferential direction of the bearing hole inner circumferential surface 91 in FIG. Therefore, FIG. 11 is for one rotation (in the direction of the arrow in the figure), and FIG. 12 is for both rotations. A larger dynamic pressure can be obtained by providing an intermediate stepped portion 92 'along with each of the stepped portions 92 or a predetermined one.

FIG. 13 shows the height hd (μm) of the stepped portion 92.
And bearing load FT (kgf) are shown.
Here, the eccentricity is 0.9 and the shaft rotation speed is 30,000 rp.
m, air permeability φ ₁ is 5 × 10 ⁻¹⁰ cm ² , air permeability φ ₂ is 7
0 × 10 ^-10 cm ² , step number 3, radius clearance 0.005 mm, bearing diameter 5 mm, bearing length 4.5
mm, the bearing thickness is 4.25 mm. Height hd is 0
To 180 μm.

In FIG. 13, for comparison, a dotted line a and
And b in the conventional bearing without the stepped portion 92
Indicates the applied load. In particular, the dotted line a is the air permeability φ₁= Φ₂= 5
0x10^-Tencm²And the dotted line b indicates the air permeability φ.₁
= Φ₂= 70 × 10^-Tencm ²Shows the case.

As can be seen from FIG. 13, when the height hd is a certain value or more, the force for supporting the shaft due to the generated oil film pressure becomes smaller than that without the stepped portion 92 shown by the broken line a. .. That is, from FIG. 13, the height hd for obtaining the supporting force of the shaft equivalent to the case where the stepped portion 92 is not provided is 6
It is required to be 0 to 80 μm. Therefore, the stepped portion 9
In order to obtain a larger bearing capacity of the shaft than without 2.
The height hd needs to be 60 to 80 μm or less.

Incidentally, specifically, the height hd is determined by the stepped portion 9
2 must be taken into consideration in consideration of wear and the like, and it is desirable to select in the range of 5 μm to 80 μm.
FIG. 14 shows the air permeability φ ₁ of the stepped portion 92 and the bearing load FT.
The relationship with (kgf) is shown. Here, the eccentricity is 0.9, the shaft speed is 30,000 rpm, the number of steps is 3, the air permeability φ ₂ is 50 × 10 ⁻¹⁰ cm ² , the height hd is 0.02 mm, the radial clearance is 0.005 mm, and the bearing is Diameter 5mm, bearing length 4.5mm, bearing thickness 4.25
mm. Air permeability φ ₁ is 5 × 10 ^-10 to 50 × 10
It is changed to ^-10 cm ² .

In FIG. 14, for comparison, a dotted line c and
And d in the conventional bearing without the stepped portion 92
Indicates the applied load. Especially, the dotted line c indicates the air permeability φ₁= Φ₂= 5
0x10^-Tencm²The dotted line d indicates the air permeability φ.₁
= Φ₂= 70 × 10^-Tencm ²Shows the case.

As can be seen from FIG. 14, when the air permeability φ ₁ is smaller than the air permeability φ _2, the force for supporting the shaft due to the generated oil film pressure is larger than that without the stepped portion 92. That is, from the comparison with the dotted line c, φ ₁ = about 23 × 10
^{When -10} cm ² and φ ₂ = 50 × 10 ^-10 cm ² , φ
_{When 1} = φ ₂ = 50 × 10 ⁻¹⁰ cm ^2, a larger shaft supporting force can be obtained. Further, from the comparison between the dotted lines _{d, φ 1 = 40 × 10} -1 0 cm 2 cutlet φ ₂ = 50 × 10
^{When -10} cm ² , φ ₁ = φ ₂ = 70 × 10 ^-10 cm ²
It is possible to obtain a larger shaft supporting force than in the case of a large air permeability.

From the above, the air permeability φ ₁ particularly on the sliding surface (the surface facing the rotating shaft 13) of the stepped portion 92 is higher than the air permeability φ ₂ on the rotating shaft 13 and the bearing hole inner peripheral surface 91. Made smaller. An example in which the air permeabilities φ ₁ and φ ₂ are set in this way is shown in FIGS. 16 and 17. Further, FIG. 15 shows a case where the air permeability is φ ₁ = φ ₂ for comparison. That is, FIG.
5 is φ ₁ = φ ₂ = 30 × 10 ⁻¹⁰ cm ² , and in FIGS. 16 and 17, φ ₁ = 3 × 10 ⁻¹⁰ c
m ² and φ ₂ = 30 × 10 ⁻¹⁰ cm ² . 15,
16 and 17, the number of steps is 0, 3 and 6, respectively.
Shows the case.

16 and 17, the rotary shaft 13 may come into contact with the sliding surface of the stepped portion 92, but does not come into contact with the bearing hole inner peripheral surface 91, that is, the bottom of the groove. .. Therefore, by increasing the air permeability φ ₂ , it is possible to secure a certain amount of oil suction / discharge according to the size, and
The amount of oil in the bearing hole 90 can also be secured.

In order to reduce the air permeability φ ₁ particularly on the sliding surface of the stepped portion 92, it is necessary to close or seal the pores on the sliding surface of the stepped portion 92. As a means for this, a method of sealing by plating or coating is adopted. As the plating, for example, hard chrome plating is used. As the coating, for example, a solid lubricant such as Teflon or molybdenum disulfide is used.
In addition, there is a method of sizing at the time of sintering, superoll processing, etc.

FIG. 18 shows an example in which a film 93 is formed by coating or coating the above-mentioned solid lubricant on the sliding surface of the stepped portion 92. The thickness t of the film 93 is 3 to 15 μm, and usually about 10 μm in order to obtain the adhesion strength. When the thickness is more than 15 μm, the film 93 is easily peeled off, while the thickness of one spray is about 3 μm.
Is.

As described above, when the stepped portion 92 is coated with a solid lubricant, the film 93 has a buffering action,
Vibration, noise, and wear due to contact between the rotary shaft 13 and the sintered oil-impregnated bearing 9 can be prevented. Further, even if a part of the film 93 is peeled off and attached to the rotary shaft 13, the rotary shaft 13
Since there is no contact between the bearing hole inner peripheral surface 91 and the bearing hole inner peripheral surface 91, the film 93 attached to the rotating shaft 13 does not seal the pores of the bearing hole inner peripheral surface 91. This is the same when the rotary shaft 13 is coated with a solid lubricant or the like.

[0038]

As described above, according to the present invention,
In a sintered oil-impregnated bearing for small motors, by providing a plurality of substantially rectangular stepped portions on the inner peripheral surface of the bearing hole, a sufficiently large oil film pressure can be obtained, so that a large bearing load can be supported. Moreover, even if the rotating shaft contacts the stepped portion, it is possible to prevent the pores at the bottom of the groove from being sealed, so that a certain amount of oil suction / discharge can always be ensured and seizure can be prevented. It can be prevented.

[Brief description of drawings]

FIG. 1 is a diagram showing a small motor.

FIG. 2 is a diagram showing a structure of a sintered oil-impregnated bearing.

FIG. 3 is a diagram showing an oil film pressure distribution.

FIG. 4 is an explanatory diagram of eccentricity.

FIG. 5 is a diagram showing a gap distribution.

FIG. 6 is a diagram showing a gap distribution.

FIG. 7 is a diagram showing a gap distribution.

FIG. 8 is a diagram showing an oil film pressure distribution.

FIG. 9 is a diagram showing an oil film pressure distribution.

FIG. 10 is a diagram showing an oil film pressure distribution.

FIG. 11 is a diagram showing an example of a plurality of steps.

FIG. 12 is a diagram showing an example of a plurality of steps.

FIG. 13 is a diagram showing the relationship between height and bearing load.

FIG. 14 is a relationship diagram between air permeability and bearing load.

FIG. 15 is a diagram showing a ventilation distribution.

FIG. 16 is a diagram showing a ventilation distribution.

FIG. 17 is a diagram showing a ventilation distribution.

FIG. 18 is a diagram showing an example in which a solid lubricant is coated.

FIG. 19 is a diagram illustrating a conventional technique.

FIG. 20 is a diagram illustrating another conventional technique.

FIG. 21 is a diagram illustrating another conventional technique.

FIG. 22 is an explanatory view of another conventional technique.

FIG. 23 is another prior art explanatory diagram.

FIG. 24 is a view for explaining still another conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Housing 2 Permanent magnet 3 Armature 4 Commutator 5 Rotor 6 End plate 7 Brush arm 8 Input terminal 9 Sintered oil-impregnated bearing 11 Bearing holding portion 13 Rotating shaft 90 Bearing hole 91 Bearing hole inner peripheral surface 92 Stepped portion 93 Membrane

Claims (5)

[Claims] 1. A substantially rectangular stepped portion having a sliding surface that is concentric with the rotating shaft (13) in the inner peripheral surface of the bearing hole facing the rotating shaft (13) in the circumferential direction thereof. (9
The stepped portions (92) adjacent to each other are provided with a plurality of 2).
A sintered oil-impregnated bearing for a small motor, characterized in that a space surrounded by the inner peripheral surface of the bearing hole and the rotating shaft (13) therebetween is substantially rectangular. 2. The sintered oil-impregnated bearing for a small motor according to claim 1, wherein the sliding surface of the stepped portion (92) is coated with a solid lubricant. 3. The small motor according to claim 1, wherein the air permeability of the sliding surface of the stepped portion (92) is smaller than the air permeability of the inner peripheral surface of the bearing hole. Sintered oil-impregnated bearing. 4. The burner for a small motor according to claim 1, wherein the height of the sliding surface of the stepped portion (92) from the inner peripheral surface of the bearing hole is 5 to 80 μm or less. Oil-impregnated bearing. 5. The sintered oil-impregnated bearing for a small motor according to claim 1, wherein the stepped portion (92) has a plurality of steps.