JP2002031133A - Shaft support structure and rotating drum device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cheaply realize a prevention of pre-load removal badness and a shaft falling down without enhancing a pre-load force of a pre-load spring. SOLUTION: In the rotating drum, a rotation shaft 28 is rotatably supported on a fixed drum 21 through two ball bearings 26, 27 axially spaced and a pre- load spring 48 is interposed between outer rings 46, 47 of the two ball bearings 26, 27. A rotation drum 29 is fixed to the rotation shaft 28. The outer ring 46 of one ball bearing 26 is closely contacted with the fixed drum over a large area and the outer ring 47 of the other ball bearing 27 is only closely contacted with a projection 45 having a small area formed on the fixed drum. An axial restriction force at the close contact part 43 between the outer ring 46 of one ball bearing 26 and the fixed drum is sufficiently larger than the pre-load force of the pre-load spring 48. An axial restriction force at the close contact part 44 between the outer ring 47 of the other ball bearing 21 and the fixed drum is approximately the same or smaller than the pre-load force of the pre-load spring 48. An attitude of the other ball bearing is retained by the projection 45 having a small area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel shaft support structure and a rotary drum device. More specifically, the present invention relates to a technique for preventing so-called preload failure and shaft fall without increasing a preload of a preload spring.

[0002]

2. Description of the Related Art A conventional shaft supporting structure, that is, a structure in which a rotating shaft is supported on a supporting base, for example, a fixed drum of a rotating drum device via a ball bearing, is shown in FIG.
It was as shown.

In FIG. 8, a rotating shaft 5 is rotatably supported by a substantially cylindrical shaft supporting portion 2 formed on a fixed drum 1 via two ball bearings 3 and 4 spaced apart in the axial direction. . The ball bearings 3, 4 are formed by arranging a large number of balls 8, 8,... Between grooves 6, 6, which are formed in an annular shape along the rotating shaft 5 in the circumferential direction, and outer rings 7, 7. It has a so-called direct bearing structure, and has two ball bearings 3 and 4 and outer rings 7.
A preload spring 9 is interposed between and.

The shaft supporting portion 2 of the fixed drum 1 has a substantially cylindrical shape, and close contact portions 10 and 11 having inner diameters smaller than other portions are formed at upper and lower ends of an inner peripheral surface.

[0005] Most of the outer peripheral surfaces of the outer rings 7, 7 of the ball bearings 3, 4 are in close contact with the inner peripheral surfaces of the contact portions 10, 11 (see FIG. 8).

[0006] The rotation shaft 5 is supported on the fixed drum 1 via the two ball bearings 3 and 4 as described above, as follows.

First, the outer rings 7 of the ball bearings 3, 4
7 Close contact portion 1 between outer diameters A ₁ and B ₁ and fixed drum 1
The dimensional relationship between the inner diameters A ₂ and B _{2 of} 0 and 11 (see FIG. 9) is such that A ₁ > A ₂ and B ₁ > B ₂ at room temperature, that is, the ball bearings 3 and 4 The ball bearings 11 and 11 are designed so as to be a so-called interference fit, and the two ball bearings 3 and 4 are fixed to the contact portions 10 and 11 by a method called a so-called warm fit shown in FIGS.

That is, first, a rotating shaft assembly 12 in which the rotating shaft 5, the ball bearings 3, 4 and the preload spring 9 are pre-assembled is prepared, and the fixed drum 1 is heated and thermally expanded. The contact portion 1 between the outer diameters A ₁ and B ₁ of the outer rings 7 and 7 and the fixed drum 1
The dimensional relationship between the inner diameters A ₂ and B _{2 of} 0 and 11 is set so that A ₁ <A ₂ and B ₁ <B ₂ (see FIG. 10).
The above-mentioned rotary shaft assembly 12 is inserted into the shaft support portion 2 of FIG.
1), and then the fixed drum 1 is cooled (see FIG. 12).

Then, when the temperature returns to normal temperature, the ball bearings 3 in a so-called tight fit state are obtained from the dimensional relationships A ₁ > A ₂ and B ₁ > B ₂ at the normal temperature.
The outer rings 7, 4 are held by the contact portions 10, 11 of the fixed drum 1 (see FIG. 13).

The perpendicularity and coaxiality between the reference surface c and the outer peripheral surface i of the fixed drum 1 and the inner peripheral surfaces 10 ', 11' of the contact portions 10, 11 can be accurately processed. With such a structure, the outer races 7, 7 of the ball bearings 3, 4 are brought into close contact with the fixed drum 1,
Following the inner peripheral surfaces 10 ′ and 11 ′ of 11, the axis e of the ball bearings 3 and 4 can be assembled without falling with respect to the reference surface c and the outer peripheral surface i of the fixed drum 1.

However, after the heat shrinkage as described above, while the temperature of the fixed drum is high (during cooling), the outer rings 7, 7 of the ball bearings 3, 4 and the upper and lower close contact portions 10, 11 of the fixed drum 1 are connected. Adhesion between them begins to occur, and the two cannot move relatively. As the temperature decreases, the heated fixed drum 1 shrinks in the direction perpendicular to the axis and also shrinks in the axial direction, that is, in the direction to decrease the distance between the ball bearings 3 and 4 (see the arrow in FIG. 12). ). Therefore, when the fixed drum 1 returns to normal temperature, the distance f 'between the ball bearings 3 and 4 (FIG. 13)
(See FIG. 9) is smaller than the interval f (see FIG. 9) when the preload spring 9 is under a normal preload in which it is completely stretched.

As long as the amount of shrinkage (ff ') between the ball bearings 3 and 4 is within the range of the elastic deformation of the outer races 7 and 7, the rotating shaft 5 and the ball 8, no backlash occurs. 5, while the shrinkage (ff ') increases and approaches the limits of the range of elastic deformation of the outer races 7, 7, the rotating shaft 5, and the ball 8, rattling occurs. In addition, the rotation accuracy (non-periodic run-out) of the rotary shaft 5 is remarkably deteriorated, resulting in a so-called preload failure.

Usually, the outer diameter A of the outer rings 7, 7₁, B₁, Fixed
Inner diameter A of contact portions 10 and 11 of ram 1 _Two, B_Two, Preload spring 9
By properly selecting the compression force of
Design so that it does not occur.
Therefore, there is a high probability of occurrence of preload failure.

Therefore, if the spring force of the preload spring 9 is increased to prevent the preload failure, the frictional force between the outer rings 7, 7, the ball 8, and the rotating shaft 5 increases, and the power consumption increases. However, there is also a problem that noise is increased.

In order to avoid the above problems,
As shown in FIGS. 14 and 15, if one of the upper and lower ball bearings 3 and 4 is loosely fitted at room temperature, for example, A ₁ > A ₂ and B ₁ <B _2. Since the axial restraining force between the outer race 7 of the ball bearing 4 and the contact portion 11 (which will be described in detail later) is almost nil, even if the fixed drum 1 shrinks in the axial direction after hot shrinking, it is dragged by it. The distance between the ball bearings 3 and 4 does not shrink, and the state where the preload is normally applied can be maintained.

[0016]

However, since the preload spring 9 is formed in a coil shape and the spring force does not act uniformly on the end faces in the circumferential direction of the outer races 7, FIG.
As shown in FIG. 6, when the rotating shaft assembly 12 exists alone, the axes g, h of the outer rings 7, 7 of the ball bearings 3, 4 do not coincide with the axis e of the rotating shaft 5. Therefore, after the hot shrinkage, the axis e of the rotating shaft 5 is inclined with respect to the reference surface c and the outer peripheral surface i of the rotating drum 1 (FIG. 1).
7). When the axis e of the rotating shaft 5 is greatly inclined, the rotating drum 5 is fixed to the rotating shaft 5 and the magnetic tape running along the outer peripheral surface of the fixed drum 1 is a recording medium supported by the rotating drum. The linearity of the recording track recorded by the head is not maintained, which causes recording and reproduction errors.

In order to avoid the above state,
After one-sided ball bearing 4 is loosely fitted and warmed, the reference surface c and the outer peripheral surface i of the fixed drum 1 are cut with reference to the axis e of the rotating shaft 5, and the axis of the rotating shaft 5 is cut. There is a method of securing the perpendicularity and the coaxiality with respect to e to secure the linearity of the recording track. By doing so, it is possible to achieve both the state in which the preload of the preload spring 9 is normally applied and the assurance of the runout accuracy of the rotary shaft 5. There is a problem that an extra finishing step is required, which causes an increase in cost.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an inexpensive method for preventing so-called preload loss failure and shaft fall without increasing the preload of a preload spring.

[0019]

According to the shaft support structure of the present invention, in order to solve the above-mentioned problems, the outer ring of one ball bearing is in close contact with the support base over a large area.
The outer ring of the other ball bearing is in close contact only with the small-area projection formed on the supporting base, and the axial restraining force at the contact portion between the outer ring of the one ball bearing and the supporting base is the preload of the preload spring. The axial restraining force at the contact portion between the outer ring of the other ball bearing and the support base is substantially the same as or smaller than the preload of the preload spring, and the posture of the other ball bearing is reduced by the small area projection. It is intended to be retained.

Therefore, in the shaft support structure of the present invention, the axial restraining force at the contact portion between the outer race of the other ball bearing and the outer race is substantially the same as or smaller than the preload of the preload spring. The space between the outer rings of the two ball bearings is not reduced more than necessary, and the normal preload state is maintained. Further, the outer ring of the other ball bearing is held in its posture by the small-area projections being in close contact with each other, thereby preventing the ball bearing from falling over.

In order to solve the above-mentioned problems, the rotary drum device of the present invention rotatably supports a rotary shaft on a fixed drum via two ball bearings axially separated from each other, and rotatably supports the two balls. A preload spring is interposed between the outer rings of the bearings, the rotating drum is fixed to the rotating shaft, the outer ring of one ball bearing is in close contact with the fixed drum over a large area, and the outer ring of the other ball bearing is fixed. Only the small-area protrusion formed on the drum is in close contact with the outer ring of the one ball bearing, and the axial restraining force at the contact portion between the fixed drum and the other ball is sufficiently larger than the preload of the preload spring. The axial restraining force at the contact portion between the outer ring of the bearing and the fixed drum is almost the same as or smaller than the preload of the preload spring. Posture of the bearings is that so as to be retained.

Therefore, in the rotary drum device of the present invention, the axial restraining force at the contact portion between the outer ring of the other ball bearing and the outer ring is substantially equal to or smaller than the preload of the preload spring. The space between the outer rings of the two ball bearings is not reduced more than necessary, and the normal preload state is maintained. Also, the outer ring of the other ball bearing is held in its posture by the small-area projections being in close contact with each other, so that the ball bearing is prevented from falling down, and the perpendicularity of the rotating shaft to the reference surface and the outer peripheral surface of the fixed drum and Coaxiality is ensured.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the shaft support structure and the rotary drum device of the present invention will be described below with reference to the accompanying drawings. In the illustrated embodiment, the present invention is applied to a rotating drum device in a video tape recorder.

Referring to FIG. 1, the entire rotary drum device 20 will be briefly described.

The rotary drum device 20 has a fixed drum 21. The fixed drum 21 is formed of a metal material such as aluminum, and has a cylindrical peripheral wall portion 23 that is short from the peripheral edge of the bottom portion 22 and a cylindrical shaft support portion 24 that projects vertically from the center of the bottom portion 22. Are integrally formed. The height of the shaft support portion 24 is higher than the height of the peripheral wall portion 23, and the portion between the shaft support portion 24 and the peripheral wall portion 23 is an arrangement portion 25 that opens upward.

A rotary shaft 28 is rotatably supported on the shaft support 5 of the fixed drum 2 via two ball bearings 26 and 27. The rotating shaft 28 has upper and lower ends projecting from upper and lower ends of the shaft support 24, respectively.

A rotary drum 29 is fixed to the upper end of the rotary shaft 28 projecting upward from the upper end of the shaft support 24.

The rotary drum 29 has a press-fitting hole 30 formed at the center, and the upper end of the rotary shaft 28 is press-fitted into the press-fitting hole 30. Thus, the rotating drum 29 is rotatably supported by the fixed drum 21.

A plurality of rotating magnetic heads 31, 31, 31 (only one is shown in FIG. 1) are supported at a position near the peripheral edge of the lower surface of the rotating drum 29.
Notches 32, 32, 32 formed at the lower surface of the outer peripheral portion of the rotating drum 29 with the tips of 31, 31 (only one is shown in FIG. 1)
From the outside.

The lower surface of the portion of the lower portion of the rotating drum 29 projecting into the arrangement portion 25 of the fixed drum 21 and the fixed drum 21
The rotary transformer 33 is arranged in the arrangement section 25 of the first embodiment. That is, the stator portion 33s of the rotary transformer 33 is disposed in the disposition portion 25 of the fixed drum 21 in a state where the stator portion 33s of the rotary transformer 33 is disposed on the lower surface of the rotary drum 29 at a small interval. Is arranged. Then, the rotating magnetic head 3
1, 31, 31 are the rotor units 3 of the rotary transformer 33
3r.

The stator 33 of the rotary transformer 33
s below the flexible circuit board 3 for transmitting video signals
A signal transmission line (not shown) formed on the flexible circuit board 14 is connected to a predetermined channel of the stator section 33s. Then, the connection portion 35 of the flexible circuit board 34 is drawn out from a drawing hole 36 formed in the peripheral wall portion 23 of the fixed drum 21, and is connected to a signal processing circuit (not shown) via the connection portion 35. Then, the recording signal sent from the signal processing circuit passes through the flexible circuit board 34 and the rotary transformer 3.
3, and is recorded on a magnetic tape (not shown) running while being wound around the outer peripheral surfaces of the fixed drum 21 and the rotating drum 29 by the rotating magnetic heads 31, 31, 31; The signals recorded on the magnetic tape are transmitted to the rotating magnetic heads 31, 3
1 and 31, and the read signal is sent to the flexible circuit board 3 via the rotary transformer 33.
The signal is sent to the signal processing circuit via 4, and is processed by the signal processing circuit and sent to the output device.

A rotor 38 of a motor 37 is fixed to a portion of the rotary shaft 28 protruding from the lower end of the shaft support 24 of the fixed drum 21. The rotor 38 has a press-fit hole 38b formed in the center of a disk-shaped rotor case 38a, an annular rotor magnet 38c fixed on the upper surface, and a rotating yoke 38d attached thereto. The rotation shaft 28 is inserted into the press-fit hole 38b of the rotor case 38a.
Is press-fitted. The stator substrate 39 on which a coil (not shown) is mounted is mounted on the rotor magnet 38.
The motor 37 is configured to be fixed to the fixed drum 21 so as to be located between the rotation y and the rotating yoke 38d.

The details of the shaft support 24 of the fixed drum 21 and the support of the rotating shaft 28 on the shaft support 24 will be described with reference to FIGS.

The shaft support 24 of the fixed drum 21 is
A tall upper cylindrical portion 4 protruding upward from the upper surface of the central portion of 2
0, a lower cylindrical portion 41 that is short and protrudes downward from the lower surface of the central portion of the bottom portion 22 and an insertion hole 42 that is formed through the central portion of the bottom portion 22. At the upper and lower ends of the insertion hole 42, contact portions 43 and 44 having an inner diameter smaller than the other portions are provided.
Are formed. The inner diameter of the contact portion 43 is a
_2, and the inner diameter of the contact portion 44 is b ₂ . Further, a narrow ridge 45 is formed at a position near the lower end of the lower contact portion 44, and the inner diameter of the ridge 45 is b _{2 ′} (see FIG. 3).

Further, the outer diameter of the outer ring 45 of the ball bearing 26 which is attached to the adhesion portion 43 is a _{a 1,} the outer diameter of the outer ring 46 of the ball bearing 27 which is attached to the contact portion 44 _{b 1} and is, these dimensional relationships in normal temperature is to be _{a 1> a 2, b 2} > a 2> b 2 '.

Therefore, the upper ball bearing 26 is in a tightly fitted state in the close contact portion 43, that is, most of the outer peripheral surface of the outer ring 46 is in close contact with the close contact portion 43, and the lower ball bearing 27 is in a clearance gap. In other words, the outer ring 47 is brought into close contact with the contact portion 44 and the ridge 45 only. A preload spring 48 is interposed between the outer rings 46 and 47 of the ball bearings 26 and 27.

Therefore, as described above, the rotary shaft 28, the ball bearings 26, 27 (the grooves 26a, 27a and the balls 26b,
, 27b, 27b,...) And a preload spring 48 are integrally assembled.
9 (direct bearing) is prepared (see FIG. 3), and the rotating shaft assembly 49 is assembled to the fixed drum 21 by so-called hot shrinkage (see FIGS. 4 and 5).

The fitting pressure Pm between the outer ring 47 of the lower ball bearing 27 and the ridge 45 of the contact portion 44 is expressed by the following equation (1).

[0039]

(Equation 1)

The axial constraint force F between the outer ring 47 and the ridge 45 of the contact portion 44 is given by the following equation (2).

[0041]

(Equation 2)

Therefore, the axial restraining force F is applied to the preload spring 48.
If the width j and the inner diameter b _{2 ′} of the ridge 45 are selected so as to be smaller than the preload caused by the above, the distance between the outer rings 46 and 47 of the ball bearings 26 and 27 and the fixed drum 21 during the cooling after the hot shrinkage. Even if the fitting starts to occur, the preload spring 48 is not contracted by the contraction of the fixed drum 21 at the time of cooling.
The state where the preload is normally applied to 6, 27 can be maintained.

Further, since the outer ring 47 of the ball bearing 27 is held so that the axis d of the fixed drum 21 and the axis h of the outer ring 47 coincide with each other at the position of the ridge 45 of the contact portion 44, Rotation accuracy can be maintained.

The position at which the ridge 45 of the contact portion 44 is formed may be determined as follows. That is, the ball bearing 27 is rotated while the rotating shaft 28 is fixed, and the runout of the outer peripheral surface of the outer ring 47 is measured at several places, and the position where the touch accuracy is good, that is, the position where the runout of the outer peripheral surface is the smallest (see FIG. 4) may be pressed by the ridge 45. Thereby, the axis e of the rotating shaft 28 and the axis d of the fixed drum 21 are made to coincide with each other, and high rotational accuracy can be obtained.

Then, after warm shrinking, the ridge 4 of the contact portion 44 is formed.
5 and the outer ring 47 of the ball bearing 27 are fixed with an adhesive or the like.

The small-area projections that support the outer ring 47 of the ball bearing 27 so that the shaft does not fall down during warm-up are not limited to the above-described one ridge 45 extending in the circumferential direction.

For example, as shown in FIG.
The two ridges 50 and 51 are vertically separated from each other at the close contact portion 44.
Are formed at the contact portion 44, and the protrusions 50, 51
Only the outer ring 47 of the ball bearing 27 (not shown in FIG. 6) may be in close contact with the outer ring 47, or FIG.
, A large number of minute projections 52, 52,... Are scattered all over the contact portion 44, and only the minute projections 52, 52,. The outer ring 47 may be in close contact with the outer ring 47 (not shown in FIG. 6). In short, the axial restraining force between the ridges 50, 51 and the minute projections 52, 52,... Is equal to or smaller than the preload of the preload spring 48 (not shown in FIG. 6). The shape of the small-area projection is not limited.

As shown in FIG. 6, the outer ring 47 of the ball bearing 27 is supported by two upper and lower ridges 50 and 51, or as shown in FIG. Small protrusions 52, 5 scattered over
When supported by 2,..., The shaft fall of the outer ring 47 can be more reliably prevented.

In the above-described shaft support structure according to the present invention, it is possible to avoid poor preloading by basically making one of the ball bearings a loose fit, so that the spring force of the preload spring is increased. It is not necessary to reduce the loss torque in the ball bearing, power saving can be achieved, and noise can be reduced.

In addition, since the outer ring of the ball bearing is supported by the small-area projection while having a small area in which the axial restraining force is equal to or smaller than the preload of the preload spring, it is possible to prevent the outer ring from tipping over. This eliminates the need for post-processing to maintain the squareness and coaxiality between the rotating shaft and the reference surface and outer peripheral surface of the fixed drum, thereby reducing costs.

In the above embodiment, the present invention is applied to a rotary drum device of a video tape recorder. However, the present invention is widely applied to a supporting shaft structure in other devices. Can be done. Although the above-mentioned rotary drum device is used for a video tape recorder, it can be widely applied to a rotary drum device in a digital audio tape recorder and other devices.

Further, the shapes and structures of the respective parts shown in the above-described embodiments are merely examples of the specific embodiments to be carried out when carrying out the present invention, and the technical scope of the present invention is not limited thereto. Should not be interpreted restrictively.

[0053]

As is apparent from the above description, the shaft supporting structure of the present invention supports the rotating shaft rotatably on the supporting base via two ball bearings axially separated from each other. A ball bearing having a preload spring interposed between outer races of the ball bearing, wherein the outer race of one ball bearing is in close contact with the support base over a large area, and the outer race of the other ball bearing is the support base. Only the small-area projection formed on the outer surface of the one ball bearing, the axial restraint force at the contact portion between the outer ring of the one ball bearing and the support base is sufficiently larger than the preload of the preload spring, and the other ball bearing The axial restraint force at the contact portion between the outer ring and the support base is substantially the same as or smaller than the preload of the preload spring, and the posture of the other ball bearing is reduced by the small area protrusion. Characterized in that it is lifting.

Therefore, in the shaft support structure of the present invention, the axial restraining force at the contact portion between the outer race of the other ball bearing and the outer race is substantially the same as or smaller than the preload of the preload spring. The space between the outer rings of the two ball bearings is not reduced more than necessary, and the normal preload state is maintained. Further, the outer ring of the other ball bearing is held in its posture by the small-area projections being in close contact with each other, thereby preventing the ball bearing from falling over.

According to the second aspect of the present invention, since the small-area protrusions are two ridges which are located apart from each other in the axial direction and extend in the circumferential direction, the outer race of the other ball bearing is formed. Shaft fall can be more reliably prevented.

Further, the rotary drum device of the present invention is a rotary drum device in which the rotary drum is disposed rotatably with respect to the fixed drum, wherein the rotary drum device is provided on the fixed drum via two ball bearings spaced in the axial direction. A rotating shaft is rotatably supported, a preload spring is interposed between the outer rings of the two ball bearings, and a rotating drum is fixed to the rotating shaft. The outer ring of one of the ball bearings extends over a large area with the fixed drum. The outer ring of the other ball bearing is in close contact only with the small-area projection formed on the fixed drum, and the axial restraint force at the contact portion between the outer ring of the one ball bearing and the fixed drum is as described above. Is sufficiently larger than the preload of the preload spring, and is the axial restraining force at the contact portion between the outer ring of the other ball bearing and the fixed drum substantially equal to the preload of the preload spring? Small, characterized in that the attitude of the other ball bearing by a projection of the small area is maintained.

Therefore, in the rotary drum device according to the present invention, the axial restraining force at the contact portion between the outer ring of the other ball bearing and the outer ring is substantially the same as or smaller than the preload of the preload spring. The space between the outer rings of the two ball bearings is not reduced more than necessary, and the normal preload state is maintained. Also, the outer ring of the other ball bearing is held in its posture by the small-area projections being in close contact with each other, so that the ball bearing is prevented from falling down, and the perpendicularity of the rotating shaft to the reference surface and the outer peripheral surface of the fixed drum and Coaxiality is ensured.

[Brief description of the drawings]

FIG. 1 shows an embodiment in which the present invention is applied to a rotary drum device in a video tape recorder together with FIGS. 2 to 5, and FIG. 1 is a longitudinal sectional view of the rotary drum device.

FIG. 2 is a longitudinal sectional view showing a state where a rotating shaft is attached to a fixed drum.

FIG. 3 is a longitudinal sectional view showing a state before a rotating shaft is attached to a fixed drum.

FIG. 4 is an exaggerated view of the gist of the present invention, together with FIG. 5, which is a schematic longitudinal sectional view showing a state before a rotary shaft is attached to a fixed drum.

FIG. 5 is a schematic longitudinal sectional view showing a state where a rotating shaft is attached to a fixed drum.

FIG. 6 is a schematic longitudinal sectional view showing a modified example of the fixed drum in which main parts are exaggerated.

FIG. 7 is a schematic longitudinal sectional view showing another modified example of the fixed drum in which main parts are exaggerated.

8 shows an example of a fixed drum in a conventional rotary drum device together with FIG. 9, and FIG. 8 is a longitudinal sectional view.

FIG. 9 is a longitudinal sectional view showing a state before the rotation shaft is attached to the fixed drum.

FIG. 10 shows a conventional problem together with FIGS. 11 to 13, and is a schematic longitudinal sectional view showing a state before a rotary shaft is attached to a fixed drum.

FIG. 11 is a schematic longitudinal sectional view showing a state immediately after a rotating shaft is inserted into a shaft supporting portion of the fixed drum together with a ball bearing after heating the fixed drum.

FIG. 12 is a schematic longitudinal sectional view showing a state in which the fixed drum is being cooled.

FIG. 13 is a schematic longitudinal sectional view showing a state after the fixed drum is cooled.

14 shows an improvement example together with FIG. 15, and is a schematic longitudinal sectional view showing a state before the rotation shaft is attached to the fixed drum.

FIG. 15 is a schematic longitudinal sectional view showing a state after the rotation shaft is fixed to the fixed drum.

FIG. 16 is a schematic longitudinal sectional view showing a state of the improvement example together with FIG. 17 and showing a state before the rotation shaft is attached to the fixed drum.

FIG. 17 is a schematic longitudinal sectional view showing a state after the rotation shaft is fixed to the fixed drum.

[Explanation of symbols]

Reference numeral 20: rotating drum device, 21: fixed drum (support base), 26: one ball bearing, 27: other ball bearing, 29: rotating drum, 43: one contact portion, 44: other contact portion, 45 ... Ridge (projection of small area), 46: outer ring, 47: outer ring, 48: preload spring, 50
… Ridges (small area projections), 51… ridges (small area projections)
52 ... minute projection (projection with small area)

Claims (3)

[Claims] A rotary shaft is rotatably supported on a supporting base via two ball bearings spaced apart in the axial direction.
A shaft support structure in which a preload spring is interposed between outer rings of individual ball bearings, wherein the outer ring of one ball bearing is in close contact with the support base over a large area, and the outer ring of the other ball bearing is supported. Only the small-area protrusion formed on the base is in close contact with the outer ring of one of the ball bearings, and the axial constraint force at the contact portion between the outer ring of the one ball bearing and the support base is sufficiently larger than the preload of the preload spring, and the other ball is The axial restraining force at the contact portion between the outer ring of the bearing and the support base is substantially the same as or smaller than the preload of the preload spring, and the attitude of the other ball bearing is maintained by the small area projection. Shaft support structure. 2. The shaft support structure according to claim 1, wherein the small-area protrusions are two ridges which are located apart from each other in the axial direction and extend in the circumferential direction. 3. A rotary drum device in which a rotary drum is rotatably disposed with respect to a fixed drum, wherein the rotary shaft is rotatably supported on the fixed drum via two ball bearings spaced apart in the axial direction. A preload spring is interposed between the outer rings of the two ball bearings, and a rotating drum is fixed to the rotating shaft. The outer ring of one of the ball bearings is in close contact with the fixed drum over a large area. The outer ring of the ball bearing is in close contact with only a small area projection formed on the fixed drum, and the axial restraining force at the contact portion between the outer ring of one of the ball bearings and the fixed drum is more than the preload of the preload spring. And the axial restraining force at the contact portion between the outer ring of the other ball bearing and the fixed drum is substantially the same as or smaller than the preload of the preload spring, and the small area projection is used. Rotary drum apparatus characterized by orientation of the other ball bearing is held by.