JPH11241724A - Sintered alloy bearing for capstan shaft, and capstan motor with this bearing applied to it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the bearing load of a sintered oil-retaining bearing for rotatably supporting a capstan shaft. SOLUTION: In a sintered alloy bearing 5 for a capstan shaft being pressed into the hole of a bearing holder to rotatably support a capstan shaft 11 in operating a capstan, while a recording medium 12 is pressed to the rotatably shaft 11 by a pinch roller 20; first and second circular arc contact parts 5a1 and 5a2 , circular arcingly formed respectively on the inner diameter part 5a of the bearing 5 over a given angle range of θ1 and θ2, with respective positions, distanced about 180 deg. and 270 deg., in the rotation direction of the shaft 11 from the contact part S between the shaft 11 and the medium 12, as centers; and first and second recessed parts 5a3 and 5a4 formed hollower than the contact parts 5a1 and 5a2 for connecting between these contact parts 5a1 and 5a2 .

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 unit that rotatably supports a capstan shaft when a recording medium is run at a constant speed while being pressed against a capstan shaft rotating at a constant speed by a pinch roller. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sintered alloy bearing for a capstan shaft with an improved bearing load, and a capstan motor to which the sintered alloy bearing is applied.

[0002]

2. Description of the Related Art Generally, when a recording medium such as a magnetic tape used for a video tape recorder or a recording paper used for a printer is driven at a constant speed along a predetermined path, the recording medium is rotated at a constant speed. The recording medium is run while being pressed against a capstan shaft to be pressed by a pinch roller. In this case, as a bearing for rotatably supporting the capstan shaft, an inexpensive sintered oil-impregnated bearing or a high-precision ball bearing is used, but in the following description, the sintered oil-impregnated bearing is used. A general capstan shaft bearing structure will be described.

FIGS. 3A and 3B are views showing a general capstan shaft bearing structure, wherein FIGS. 3A and 3B are a plan view and a longitudinal sectional view, and FIG. 4 is a view for the capstan shaft shown in FIG. It is the top view which expanded and showed the vicinity of the sintered oil-impregnated bearing.

In the general capstan shaft bearing structure shown in FIG. 3, a bearing holder 101 formed by using a polycarbonate material, a die-cast material or the like is fixedly installed on a base table (not shown). This bearing holder 101 has a central hole 1 that is penetrated vertically.
Copper-based sintered oil-impregnated bearings 102, 102 are press-fitted above and below 01a. These sintered oil-impregnated bearings 102, 102 rotatably support a capstan shaft 103 heat-treated using SUS420J2 material. I have. At this time, a cup-shaped thrust washer 104 made by pressing the capstan shaft 103 upward to the upper side of the sintered oil-impregnated bearing 002 inside the bearing holder 101 and pressing and barrel-polishing a SUS304 material having a thickness of 0.5 mm. Bearing holder 101
And the capstan shaft 1
The thrust ring 105 is fitted into the shaft 03 so that the capstan shaft 103 does not come down.

[0005] Although a method of driving the rotation of the capstan shaft 103 is not shown in the figure, it is not limited to the structure described above (capstan motor) directly connected to the rotor of the motor or the lower end of the capstan shaft 103. Or a structure in which a flywheel is attached to the motor and indirectly connected to a motor via a belt, or a capstan shaft 103
A gear is attached to the lower end of the motor, and the motor is indirectly connected to the motor via a gear train.

On the other hand, a pinch roller 106 using a rubber material
The recording medium 1 is supported by a rotatable arm 107 so as to be rotatable about a shaft 108, and is biased by a spring 109.
10 is pressed against the capstan shaft 103.

Accordingly, the recording medium 110 pressed by the pinch roller 106 can run at a constant speed by rotating the capstan shaft 103 at a constant rotation speed.

Here, sintered oil-impregnated bearings 102, 102 press-fitted above and below a center hole 101a of a bearing holder 101.
As shown in an enlarged view in FIG. 4, the inner diameter portion 102a of the capstan shaft 103, which is in contact with the outer diameter portion 103a, is formed in a perfect circle slightly larger in diameter than the capstan shaft 103, The rotation speed of the shaft 103 and the pinch roller 1
The optimum clearance is designed by the value of the pressing force of 06. Accordingly, the recording medium 110 is sandwiched between the capstan shaft 103 and the pinch roller 106.
Is pressed against the capstan shaft 103 by the pinch roller 106, and the pressing force of the pinch roller 106 causes the outer diameter portion 103a of the capstan shaft 103 to contact the inner diameter portion 102a of the sintered oil-impregnated bearing 102 as shown by the dotted line. First, the capstan shaft 103 is rotated to apply tension to the recording medium 110, and as shown by a solid line, the outer diameter portion 103a of the capstan shaft 103 is
The second inner diameter portion 102a has moved from the contact point to the contact point.

[0009]

By the way, in a general capstan shaft bearing structure, as described with reference to FIG. 4, the capstan shaft 103 is pressed by the pinch roller 106 into contact with the sintered oil-impregnated bearing 102. The first contact is made at the contact point of the inner diameter portion 102a, and the contact surface is moved to the contact point while the recording medium 110 is running by the rotation of the capstan shaft 103. Here, the contact position of the capstan shaft 103 with the sintered oil-impregnated bearing 102 changes periodically or irregularly due to a change in the tension with the recording medium 110 or a change in the friction of the pinch roller 106, and the position of the contact point 1 moves. I do. In other words, the travel of the recording medium 110 causes the capstan shaft 10 to move.
Numeral 3 vibrates along the inner diameter portion 102a of the sintered oil-impregnated bearing 102 in a range of approximately 90 ° when viewed from the upper surface of the capstan shaft 103. Therefore, the axis of the capstan shaft 102 changes by Δd in the running direction of the recording medium 110 and by Δd ′ in the direction of the pinch roller 106, and gives these changes of Δd and Δd ′ to the running of the recording medium 110. As a result, uneven rotation due to the axial movement of the capstan shaft 103 appears, and when the recording medium 110 runs at a constant speed, vibrations are transmitted to the recording medium 110 and the speed of the recording medium 110 fluctuates. Has occurred.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a first invention is to provide a bearing when a recording medium is run while being pressed against a rotatable capstan shaft by a pinch roller. In a sintered alloy bearing for a capstan shaft press-fit into a hole of a holder and rotatably supporting the capstan shaft, an inner peripheral portion of the sintered alloy bearing to which an outer peripheral portion of the capstan shaft fits, First and second concentric arcs are formed over a predetermined angle range around respective positions approximately 180 ° and approximately 270 ° apart in the rotation direction of the capstan shaft from the contact portion between the capstan shaft and the recording medium. It has a second arc-shaped contact portion, and first and second concave portions formed to be more concave than the first and second arc-shaped contact portions for connecting the first and second arc-shaped contact portions. Characterized by A sintered alloy bearings for Yapusutan axis.

Further, in the sintered alloy bearing for a capstan shaft according to the first aspect of the present invention, a predetermined angle range of the first and second arc-shaped contact portions is set to approximately 180 ° in a rotation direction of the capstan shaft. And ± 5 ° to ± 44 ° about the respective positions separated by approximately 270 °.

Further, in the sintered alloy bearing for a capstan shaft according to the first invention, the depth of the first and second concave portions is set to 5 μm to 100 μm. .

According to a second aspect of the present invention, there is provided a sintered alloy bearing press-fitted into a hole of a bearing holder when a recording medium is run while being pressed against a rotatable capstan shaft fixed to a rotor of a motor by a pinch roller. In a capstan motor rotatably supporting a capstan shaft, an inner peripheral portion of the sintered alloy bearing to which an outer peripheral portion of the capstan shaft fits is provided by a capstan shaft from a contact portion between the capstan shaft and the recording medium. About 180 ° and about 270 in the rotational direction of the shaft
第 First and second arc-shaped contact portions formed concentrically over a predetermined angular range around each of the separated positions, and the first and second arc-shaped contact portions for connecting the first and second arc-shaped contact portions. A capstan motor characterized by having first and second concave portions formed respectively in a concave shape from the first and second arc-shaped contact portions.

Further, in the capstan motor according to the second aspect of the present invention, a predetermined angle range of the first and second arc-shaped contact portions is separated by approximately 180 ° and approximately 270 ° in the rotation direction of the capstan shaft. ± 5 ゜ ~ ± around each position
The angle is set to 44 °.

[0015] In the capstan motor according to the second aspect of the present invention, the depth of the first and second concave portions is 5 μm to 5 μm.
The thickness is set to 100 μm.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a sintered alloy bearing for a capstan shaft according to the present invention and a capstan motor to which the sintered alloy bearing is applied will be described in detail with reference to FIGS. explain.

FIG. 1 is a structural view for explaining a capstan motor to which a sintered alloy bearing for a capstan shaft according to the present invention is applied, and FIG. 2 is a sintered oil-impregnated bearing for a capstan shaft shown in FIG. It is the top view which expanded and showed the vicinity.

As shown in FIG. 1, a capstan motor 1 employing a sintered alloy bearing for a capstan shaft according to the present invention is applied to a well-known video tape recorder (VTR) or the like. .

The capstan motor 1 is roughly divided into a stator S side fixedly installed on a base table (not shown) and a rotor R side rotating with respect to the stator S side.

First, on the stator S side, the printed circuit board 3 is attached to the back surface 2b of the metal plate 2 except for a hole 2a formed substantially at the center of the metal plate 2 formed flat using an iron or silicon steel plate or the like. A bearing holder 4 formed of a polycarbonate material, a die-cast material or the like is positioned and mounted in the hole 2 a of the metal plate 2 so as to protrude upward and downward from the metal plate 2.

The bearing holder 4 is press-fitted with upper and lower copper-based sintered oil-impregnated bearings 5, 5 which are vertically penetrated and drilled. In order to rotatably support the stun shaft 11, the inner diameter portions 5a are formed in a special shape as described later with reference to FIG.

At the lower end of the bearing holder 4, a laminated circular core 6 is screwed coaxially with the capstan shaft 11.
And 24 slots are arranged by 24 coils 8 along the circumference of the circular core 6. At this time, the printed circuit board 3 has mounted thereon the coil 8, an electric component for driving the voltage applied to the coil 8, a Hall element 9 for detecting the rotational position, an MR element 10 for detecting the rotational speed of the rotor R, and the like. I have.

On the other hand, the rotor R side has sintered oil-impregnated bearings 5, 5
The long capstan shaft 11 that fits with SUS420J
Heat treatment is performed using two materials, and the hardness is set to 50 ° or more HRC. When a magnetic tape is used as the recording medium 12 attached to the capstan shaft 11, the outer diameter portion 11a of the capstan shaft 11 is
The surface roughness of the contacted portion contacted with is 0.3S or less, and the surface roughness of the contacted portion contacting the sintered oil-impregnated bearings 5, 5 is 0.8S or less.
It is processed below. At the lower end of the capstan shaft 11, a pulley 14 caulked with a cup-shaped rotor yoke 13 is press-fitted coaxially with the capstan shaft 11.
At this time, the inner periphery of the cup-shaped rotor yoke 13
A driving magnet 15 for three-phase driving is bonded to an eight-pole pair (16 poles) so as to face the four coils 8. Then, with the thrust washer 16 fitted into the capstan shaft 11, the capstan shaft 11 is inserted from the sintered oil-impregnated bearing 5 side below the bearing holder 4, and the capstan shaft 11
Of the SUS 30 having a thickness of 0.5 mm is protruded from the upper part of the bearing holder 4 on the side of the sintered oil-impregnated bearing 5.
Pressed and barrel polished four materials cup-shaped thrust washer 1
7 is fixed to the step portion 4b of the bearing holder 4, and a thrust ring 18 is fitted into the capstan shaft 11 so that the capstan shaft 11 does not fall down.

Further, a pinch roller 20 using a rubber material
Is rotatably supported about a shaft 22 by a rotatable arm 21 and presses the recording medium 12 against the capstan shaft 11 by the urging force of a spring (not shown).

Therefore, the capstan shaft 11 is connected to the stator S
The recording medium 12 pressed by the pinch roller 20 can run at a constant speed by rotating at a constant rotation speed by a driving force generated between the recording medium 12 and the rotor R side.

Here, the shape of the inner diameter of the sintered oil-impregnated bearings 5, 5 which are press-fitted above and below the bearing holder 4, which is the main part of the present invention, will be described with reference to FIG.

As shown in an enlarged manner in FIG. 2, the inner diameter portion 5a of the sintered oil-impregnated bearing 5 has an outer diameter portion 11a of the capstan shaft 11.
Two first and second arc-shaped contact portions 5 formed concentrically with the capstan shaft 11 so as to make smooth contact.
a ₁ , 5a ₂ and the first and second arc-shaped contact portions 5a ₁ , 5a so that the outer diameter portion 11a of the capstan shaft 11 does not contact the a ₁ , 5a _2.
The first was formed in a concave shape with respect to _2, the second recess _5a 3, 5
It is made from a ₄ Metropolitan. At this time, the first and second arc-shaped contact portions 5 with which the outer diameter portion 11a of the capstan shaft 11 contacts
Although the surface roughness of a ₁ and 5a ₂ is formed smoothly, the surface roughness of the first and second recessed portions 5a ₃ and 5a ₄ which escape without contacting the outer diameter portion 11a of the capstan shaft 11 Is formed without any particular problem.

Here, the first arc-shaped contact portion 5 a ₁ formed on the inner diameter portion 5 a of the sintered oil-impregnated bearing 5 is connected to the capstan shaft 11.
The recording medium 12 is formed in an arc shape over a predetermined angle range θ1, θ1 around a position approximately 180 ° apart in the rotation direction of the capstan shaft 11 from the contact portion S with the recording medium 12. The second arc-shaped contact portion 5a ₂ formed on the inner diameter portion 5a of the oil-impregnated sintered bearing 5, substantially from the contact portion S between the capstan shaft 11 and the recording medium 12 in the rotational direction of the capstan shaft 11 27
A predetermined angle range θ2, θ2 around a position separated by 0 °
Are formed in an arc shape. In other words, the pressing force of the pinch roller 20 against the capstan shaft 11 is received by the first and second arc-shaped contact portions 5a ₁ and 5a ₂ formed on the inner diameter portion 5a of the sintered oil-impregnated bearing 5.

At this time, the first and second arc-shaped contact portions 5a ₁ ,
Predetermined angle range θ1 of forming a 5a _2, .theta.2 is approximately 180 ° in the rotational direction of the capstan shaft 11, which is ± 5 ° ~ ± 44 ° set as the center position of each of spaced substantially 270 °, In the embodiment, the predetermined angle ranges θ1 and θ2 are approximately ±
It is set at 30 ° (approximately 60 ° at 2 × θ1, 2 × θ2), but the predetermined angle range θ1, θ2 is ± 5 ° to ± 44 ° (10 ° at 2 × θ1, 2 × θ2) depending on the situation. However, if the predetermined angle ranges θ1 and θ2 are less than ± 5 °, lubrication between the oil-impregnated sintered bearing 5, the capstan shaft 11 and the oil is not sufficiently performed, and the load current is reduced. Increase. On the other hand, the predetermined angle ranges θ1 and θ2 are ± 4.
Sintered oil-impregnated bearing 5 and capstan shaft 1 in a range exceeding 4 mm
When 1 is in contact, the frictional resistance increases, and the load current similarly increases. Therefore, the capstan shaft 11
The predetermined angle ranges θ1 and θ2 that are familiar with ± 5 ° ~
± 44 ° (10 ° to 88 ° at 2 × θ1 and 2 × θ2).

Further, in order to connect the first and the inner arcuate contact portion 5a ₁ formed in the inner diameter portion 5a of the oil-impregnated sintered bearing 5, between the second inner arcuate contact portion 5a _2, first recess Part 5a
₃ are formed over a small angular range. Furthermore, the outside of the first arc-shaped contact portion 5a ₁ and the second arc-shaped contact portion 5a
To connect between the _second outer, second recess 5a ₄ is formed over a wide angular range. These first and second
The depths of the recesses 5a ₃ and 5a ₄ affect the reliability of the sintered oil-impregnated bearing 5. If the depth is 5 μm or less, the amount of oil necessary for lubrication is not maintained, and the friction increases. There is a step with the first and second arc-shaped contact portions 5a ₁ and 5a ₂ , vibration occurs, and the deflection of the capstan shaft 11 increases, so that performance with sufficient accuracy cannot be obtained. Therefore, the first relative to the outer diameter 11a of the capstan shaft 11, which controls the depth of the second recess _5a 3, 5a ₄ to 5 m to 100 m.

Although the internal diameter of the upper oil-impregnated bearing 5 close to the recording medium is particularly described here, the lower oil-impregnated bearing 5 has the same shape and the upper oil-impregnated bearing 5 has the same shape. A further accurate effect can be obtained by mounting by rotating the capstan shaft 180 around the center of the capstan shaft 180 °. This is because the upper sintered oil-impregnated bearing 5 acts as a fulcrum with respect to the capstan shaft 11, so that the stress on the lower sintered oil-impregnated bearing 5 acts in the opposite direction to the upper sintered oil-impregnated bearing 5. .

In the embodiment, the sintered oil-impregnated bearing 5 for a capstan shaft according to the present invention is applied to the capstan motor 1, but the drive of the capstan shaft 11 is performed as described in the prior art. The present invention can be applied to a case where the motor is transmitted from another motor.

With the above configuration, the capstan shaft 1
1 has a smaller contact area between the outer diameter portion 11a and the first and second arc-shaped contact portions 5 of the sintered oil-impregnated bearing 5 than conventional sintered alloy bearings, so that shaft loss is small and sufficient lubricating oil is provided. Can be supplied to the sintered oil-impregnated bearing 5 for a long period of time, so that not only can the highly reliable sintered oil-impregnated bearing 5 be obtained, but also because the axial center of the capstan shaft 11 does not move, the recording medium 12 can be reliably moved at a constant speed. No vibration is transmitted to the recording medium 12 at the time of traveling, and the speed of the recording medium 12 does not fluctuate. Further, the current consumption of the motor for driving the capstan shaft 11 is small, and the other motors for indirectly driving the capstan shaft 11 as well as the capstan motor 1 for directly driving the capstan shaft 11 have a long life. Performance can be stabilized.

[0034]

According to the sintered alloy bearing for a capstan shaft and the capstan motor to which the sintered alloy bearing according to the present invention described in detail above is applied, the outer diameter portion of the capstan shaft and the sintered oil-impregnated bearing are used. Since the contact area with the first and second arc-shaped contact portions is smaller than that of the conventional sintered alloy bearing, the shaft loss is small, and sufficient lubricating oil can be supplied to the sintered oil-impregnated bearing for a long period of time. In addition to obtaining a sintered oil-impregnated bearing with a high speed, there is no movement of the axis of the capstan shaft, so vibration is not transmitted to the recording medium when the recording medium is reliably run at a constant speed. There is no speed fluctuation of the medium. In addition, the current consumption of the capstan shaft is small, and the capstan motor that drives the capstan shaft directly and the other motor that drives the capstan shaft indirectly have long life and stable performance. Can be.

[Brief description of the drawings]

FIG. 1 is a configuration diagram for explaining a capstan motor to which a sintered alloy bearing for a capstan shaft according to the present invention is applied.

FIG. 2 is an enlarged plan view showing the vicinity of a sintered oil-impregnated bearing for a capstan shaft shown in FIG. 1;

FIG. 3 is a view showing a bearing structure of a general capstan shaft.

FIG. 4 is an enlarged plan view showing the vicinity of a sintered oil-impregnated bearing for the capstan shaft shown in FIG. 3;

[Explanation of symbols]

1. Capstan motor, 4. Bearing holder, 4a
... Center hole, 5 ... Sintered oil-impregnated bearing, 5a ... Inner diameter part, 5a ₁ ,
5a _2, first and second arc-shaped contact portions, 5a ₃ , 5a ₄ , first and second concave portions, 11: capstan shaft, 11a: outer diameter portion, 12: recording medium, 20: pinch roller, θ1 , Θ2
... A predetermined angle range of the first and second arc-shaped contact portions 5a ₁ and 5a ₂ , S: a contact portion between the capstan shaft 11 and the recording medium 12.

Claims (6)

[Claims] When a recording medium is run while being pressed against a rotatable capstan shaft by a pinch roller, the capstan shaft is press-fitted into a hole of a bearing holder and rotatably supports the capstan shaft. In the gold bearing, an inner peripheral portion of the sintered alloy bearing to which an outer peripheral portion of the capstan shaft fits is substantially 180 ° and approximately 180 ° in a rotational direction of the capstan shaft from a contact portion between the capstan shaft and the recording medium. The first and second arc-shaped contact portions formed concentrically over a predetermined angle range around the respective positions separated by 270 °, and the first and second arc-shaped contact portions are connected to connect the first and second arc-shaped contact portions. A sintered alloy bearing for a capstan shaft, comprising: first and second concave portions each formed more concavely than first and second arc-shaped contact portions. 2. A predetermined angle range of the first and second arc-shaped contact portions is ± 5 ° to ± 5 ° centered on respective positions separated by approximately 180 ° and approximately 270 ° in the rotation direction of the capstan shaft.
The sintered alloy bearing for a capstan shaft according to claim 1, wherein the bearing is set at 44 °. 3. The depth of each of the first and second concave portions is 5 μm to 5 μm.
The sintered alloy bearing for a capstan shaft according to claim 1 or 2, wherein the diameter is set to 100 µm. 4. When a recording medium is run while being pressed against a rotatable capstan shaft fixed to a rotor of a motor by a pinch roller, the capstan shaft is rotatable on a sintered alloy bearing pressed into a hole of a bearing holder. In the capstan motor supported in the above, an outer peripheral portion of the capstan shaft is fitted to an inner diameter portion of the sintered alloy bearing, and a contact portion between the capstan shaft and the recording medium is substantially rotated in a rotation direction of the capstan shaft. First and second arc-shaped contact portions formed concentrically over a predetermined angular range around respective positions 180 ° and approximately 270 ° apart, and between the first and second arc-shaped contact portions. A capstan motor comprising: first and second recessed portions each formed more concavely than the first and second arc-shaped contact portions for connection. 5. A predetermined angular range of the first and second arc-shaped contact portions is ± 5 ° to ± 5 ° centered on respective positions separated by approximately 180 ° and approximately 270 ° in the rotation direction of the capstan shaft.
The capstan motor according to claim 4, wherein the angle is set to 44 °. 6. The depth of the first and second recesses is 5 μm or less.
The capstan motor according to claim 4, wherein the capstan motor is set to 100 μm.