TWI577897B - Auxiliary bearing device - Google Patents

Description

Auxiliary bearing device

The present invention relates to an auxiliary bearing device that is additionally additionally provided to a support member provided with a bearing that supports a rotatable drive-rotating shaft member.

Conventionally, in the machine tool, as the spindle member provided with the tool, various characteristics are required depending on the workpiece to be processed. And sometimes it may be required to have contradictory characteristics. For example, when performing heavy cutting or re-grinding, high-speed rotatability (that is, easy to rotate (or low rotational resistance)) is required for the spindle to be compared, and high rigidity and high rotation precision are required; and for cutting load or grinding When the load is light, factors such as reduction in working time are more important, so high-speed rotation is required in comparison with high rigidity and high rotation accuracy.

In this regard, in Patent Document 1, a preload applying mechanism is provided for a bearing that supports a main shaft, and the magnitude of the preload is changed in accordance with the number of revolutions (rpm) of the main shaft. That is to say, the following is disclosed: when the heavy cutting is performed at a low speed, the preload is increased, whereby the rolling element of the bearing is crimped to the outer race and the inner race with a large pressure contact force to increase the main shaft. Stiffness or rotation accuracy; and in the case of light cutting at high speed rotation, the above-mentioned crimping force is reduced by reducing the preload to reduce the rotational resistance of the main shaft.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Publication No. 6-15904

However, in the case of Patent Document 1, even if it is a high-speed rotation, since the above-mentioned bearing must support the main shaft, it is necessary to provide a small preload, and it is not possible to greatly reduce the rotational resistance of the bearing. That is, the amount of reduction in the rotational resistance is limited.

Here, for example, if an auxiliary bearing is additionally provided in addition to a common bearing that always supports the main shaft, and the supporting function of the main shaft of the auxiliary bearing can be switched to the effective state and the inactive state, the maximum rigidity that can be achieved can be greatly increased, and at the same time It is also possible to reduce the rotational resistance of the main shaft to the rotational resistance of only the usual bearings when high-speed rotation is required, thereby maximizing the high-speed rotation of the common bearings.

The present invention has been made in view of the foregoing problems as described above, and an object thereof is to substantially increase the maximum achievable rigidity of a main shaft member for driving a rotating shaft, and at the same time, to maximize the bearing supporting the rotatable shaft member. High speed rotation.

The main invention for achieving the above object is an auxiliary bearing device characterized in that it is additionally additionally provided to a support member provided with a bearing for supporting a rotatable drive-rotating shaft member, and has a plurality of rolling elements a shaft member side rolling surface which is annularly provided on the shaft member and is rotatable by the rolling element; and a support member side rolling surface which is annularly provided on the support member and is available for the rolling And a switching mechanism that contacts the rolling element in contact with the support member side rolling surface and the shaft member side rolling surface, and the rolling element floats from the shaft member side rolling surface Switching between the two states of the contact state.

Other features of the present invention will be apparent from the description and the accompanying drawings.

According to the present invention, the maximum achievable rigidity of the main shaft member for driving the rotation can be greatly increased, and at the same time, the high-speed rotation of the bearing supporting the rotatable shaft member can be maximized.

3‧‧‧Shell (support member)

3c‧‧‧Small diameter cylinder

3ea, 440eb‧‧‧ end face

3eb, 440ef, 336e‧‧‧ another end face

3h‧‧‧through hole

3heb‧‧‧opening at the other end

3hs1, 3hs2, 5s1‧‧ ‧ step surface

3k, 3k2, 3ka, 7cka‧‧‧ flow paths

3kae‧‧‧ venting holes

4b, 4m, 6b, 6m‧‧‧ extruded members

5‧‧‧ Spindle (shaft member)

5ea‧‧‧ one end

5h, 60h, 60h', 160h, 260h, 360h‧‧‧ hole

6a‧‧‧ spacers

6c‧‧‧ collar components

6n‧‧‧Nuts

7c‧‧‧covering components

7c1‧‧‧Cylinder

7c1e‧‧‧The other edge

7c2‧‧‧ Cover

7c2h‧‧‧ round hole

10‧‧‧Auxiliary bearing device

11, 111, 211, 311, 311a, 311b‧‧‧ auxiliary bearings

11'‧‧‧ rolling bearing

20, 20', 120, 220, 420, 520‧ ‧ inner seat (equivalent to the inner seat)

20a, 120a, 220a, 320a, 420a‧‧‧ inner race side rolling surface (shaft member side rolling surface)

20a'‧‧‧ rolling surface of the inner race

20b, 60b, 332b, 340a‧‧‧ outer perimeter

30, 30', 130, 230, 330, 430, 530‧‧‧ outer races (equivalent to the components of the outer race)

30a, 130a, 230a, 330a, 430a‧‧‧ outer race side rolling surface (support member side rolling surface)

30a'‧‧‧ rolling surface of the outer race

30b, 60a‧‧‧ inner circumference

30t, 332t‧‧‧ slot

30tb, 332tb‧‧‧ bottom

30ts, 332ts‧‧‧ side

50, 50', 150, 250, 350, 350a, 450, 550‧ ‧ rolling elements

60, 60', 160, 260, 360, 460, 560‧ ‧ keeper

60w1, 60w2‧‧‧ wall

70‧‧‧ buoyancy generating agency

80, 380, 480‧‧‧Pre-stressing institutions

82‧‧‧Actuator

90, 490‧‧‧Control Department

130p1, 130p2‧‧‧ annular segment

320‧‧‧Means equivalent to the inner race

330h, 340h, 440h‧‧‧ supply holes

332‧‧‧Rings

332eb‧‧‧Other end

336‧‧‧Fixed parts (protrusions)

340‧‧‧ ring members

340t, 440t1, 440t2‧‧‧ slots

347, 445, 447 ‧ ‧ washers

410‧‧‧Preload automatic adjustment bearing device

411‧‧‧Special ball bearings

432‧‧‧ inside ring

434‧‧‧ Thin wall

434e1‧‧‧ outer peripheral part

434e2‧‧‧ Inner Periphery

436‧‧‧Outer ring

440‧‧‧Bolt components

482‧‧‧Flow path forming members

485‧‧‧ pump

487‧‧‧pressure adjustment valve

495‧‧‧Retainer speed sensor

497‧‧‧Spindle speed sensor

510‧‧‧General Ball Bearings

Aea‧‧‧ Range from the small diameter cylindrical portion 3c to a specific position in the axial direction

Aeb‧‧‧ Range from the other end side opening 3heb to a specific position in the axial direction

A1, b1, c1‧‧‧ lower limit

A2, b2, c2‧‧‧ upper limit

C5‧‧‧ shaft core

C50‧‧‧Rotation axis

C150, C250, C350a, C450‧‧‧ ball heart

C350‧‧‧Rotary axis

D23, D1213, D3233‧‧‧ interval

D50, D150, D350, D350a‧‧‧ diameter

Fc‧‧‧ centrifugal force

G, G50, G150, G340‧‧‧ gap

G60h‧‧‧Small gap

Ls‧‧‧Distance

Nth‧‧‧ threshold

N ₀ ‧‧‧ theoretical speed

N ₅ ‧‧‧ rpm

N ₅₀ ‧‧‧Roller body 50' speed

N ₆₀ ‧‧‧Retainer 60' speed

V ₅₀ ‧‧ ‧ revolution speed

P1, P2, P3, P4‧‧‧ contact locations

Pb‧‧‧ split position

Pex‧‧‧ discharge location

R‧‧‧rate reduction rate

R70‧‧‧Supply room

R340, R430‧‧‧ pressure chamber

S20‧‧‧inner side clearance

S20e1‧‧‧The size of the inner race side clearance S20 in one end side

S20e2‧‧‧ The size of the inner race side clearance S20 in the other end side

S30‧‧‧Outer seat side clearance

S30e1‧‧‧The size of the outer race side side clearance S30 in the one end side

S30e2‧‧‧The size of the outer race side clearance S30 in the other end side

S90, S490‧‧‧ control signals

SP‧‧‧ Annular space

SP3‧‧‧allowing space

SP510‧‧‧Cylinder space

Α1, α2, α3, α4‧‧‧ contact angle

Fig. 1 is a schematic center cross-sectional view showing a support structure of a shaft member 5 to which the auxiliary bearing device 10 of the first embodiment is applied.

2A is an enlarged view of a portion II in FIG. 1 corresponding to a stopped state of the machine tool, FIG. 2B is a B-B arrow view in FIG. 2A, and FIG. 2C is a C-C arrow view in FIG. 2B.

Fig. 3A is an enlarged view of a portion II in Fig. 1 corresponding to an operating state of the machine tool and an inactive state of the auxiliary bearing device 10, Fig. 3B is a B-B arrow view in Fig. 3A, and Fig. 3C is a C-C arrow view in Fig. 3B.

4A is an enlarged view of a portion II of FIG. 1 corresponding to an operating state of the machine tool and an effective state of the auxiliary bearing device 10, and FIG. 4B is a B-B arrow view of FIG. 4A.

Fig. 5 is a graph showing the relationship between the total value of the preload applied to the main shaft 5 provided with the auxiliary bearing device 10 and the number of revolutions of the main shaft 5.

Fig. 6A shows a first modification of the auxiliary bearing device 10, showing that the bearing is effective The figure of the state is a diagram corresponding to the enlarged view of the portion II in Fig. 1, Fig. 6B is a B-B arrow view in Fig. 6A, and Fig. 6C is a C-C arrow view in Fig. 6B.

Fig. 7A is a view showing a state in which the bearing is ineffective in a first modification of the auxiliary bearing device 10, and is a view corresponding to an enlarged view of a portion II in Fig. 1, and Fig. 7B is a view taken along line B-B in Fig. 7A.

Fig. 8 is an explanatory view showing a second modification of the auxiliary bearing device 10, and corresponds to an enlarged view of a portion II of Fig. 1.

Fig. 9 is a schematic cross-sectional view showing the auxiliary bearing 311 of the second embodiment of the auxiliary bearing device 10.

Fig. 10 is an enlarged view of a portion X in Fig. 9.

Fig. 11 is an explanatory view showing a first modification of the auxiliary bearing device 10 of the second embodiment.

Fig. 12 is an explanatory view showing a second modification of the auxiliary bearing device 10 of the second embodiment.

Fig. 13 is a schematic front cross-sectional view showing a first example of a support structure of the main shaft 5 of the machine tool to which the auxiliary bearing device 10 of the second embodiment is applied.

Fig. 14 is a schematic front cross-sectional view showing a second example of a support structure of the main shaft 5 of the machine tool to which the auxiliary bearing device 10 of the second embodiment is applied.

Fig. 15 is a schematic center sectional view showing a special ball bearing 411.

Figure 16 is an enlarged view of the XVI portion of Figure 15.

Fig. 17A is a schematic center sectional view of a conventional rolling bearing 11', and Fig. 17B is a sectional view taken along line B-B of Fig. 17A.

Fig. 18 is a graph showing the dynamic friction loss characteristics of the rolling bearing 11'.

Fig. 19 is a graph showing the relationship between the reduction rate R of the rotational speed N ₆₀ of the retainer 60' and the dynamic friction coefficient of the rolling bearing 11' obtained by the inventors of the present invention.

Fig. 20 is a schematic view showing the configuration of a preload automatic adjusting bearing device 410 of a common bearing.

Fig. 21A is an explanatory diagram showing an example of a control model for preloading the auxiliary bearing device 10 in cooperation with the preload automatic adjusting bearing device 410, and Fig. 21B is a preloading of the common bearings 411, 510 based on the rotational speed N _{5 of the} main shaft 5. An illustration of an example of a control model for preloading in the case of control.

At least the following matters can be found from the description and the accompanying drawings.

An auxiliary bearing device characterized in that it is additionally provided in a support member provided with a bearing for supporting a rotatable drive-rotating shaft member, and has a plurality of rolling elements; a shaft member side rolling surface, a ring member is disposed on the shaft member and is rotatable by the rolling element; a support member side rolling surface is annularly disposed on the support member and is rotatable by the rolling element; and a switching mechanism is disposed on the rolling body The contact state between the support member side rolling surface and the shaft member side rolling surface is switched between the contact state of the rolling element and the non-contact state in which the rolling element floats from the shaft member side.

According to such an auxiliary bearing device, the switching mechanism can be used to switch the supporting function of the auxiliary bearing device to the shaft member to an active state or an inactive state. That is, such as switching In the contact state described above, the shaft member is supported by the auxiliary bearing device in an effective state; and when the contact state is switched to the non-contact state, the shaft member is not in an inactive state in which the auxiliary bearing device is supported. Further, if the latter is in an inactive state, unnecessary rotational resistance can be added to the shaft member, thereby maximizing the natural high-speed rotation of the bearing provided on the support member, and the former can be maximized. In the effective state, the support rigidity and the rotation accuracy of the shaft member can be greatly improved as compared with the case where only the above-described bearings are supported.

Preferably, the auxiliary bearing device has a ring-shaped member corresponding to the outer race fixed to the support member, and the support member side is formed on an inner circumferential surface of the member corresponding to the outer race. In the rolling surface, the switching mechanism includes: a buoyancy generating mechanism that supplies buoyancy to the rolling element in a direction in which the rolling element is separated from an outer side in a radial direction of the rolling direction of the shaft member; and a preloading mechanism that imparts The above-mentioned support member side rolling contact surface of the outer race corresponds to the inner side in the radial direction, and the rolling element is pressed against the shaft member side rolling surface; and the preload is formed by applying the preload. In the contact state described above, the non-contact state is formed by releasing the application of the preload.

According to such an auxiliary bearing device, the auxiliary bearing device can be easily and surely switched to the active state and the inactive state by the preloading and releasing of the preload by the preloading mechanism.

For example, the auxiliary bearing device is preferably configured to have a ring shape And maintaining in the rotation direction in a state in which the rolling elements adjacent to each other in the rotation direction of the shaft member are arranged in the plurality of rolling elements; the position of the holder in the radial direction is The retainer is limited in contact with the member corresponding to the outer race.

According to the auxiliary bearing device, since the retainer of the auxiliary bearing device contacts the member corresponding to the outer race, the position of the retainer in the radial direction is restricted, so that the retainer is brought into contact with the shaft member to rotate integrally The appropriate components can be used without limiting their position. Thereby, in the inactive state of the auxiliary bearing device, it is possible to effectively prevent the retainer that substantially stops the rotation from interfering with the rotation of the shaft member. As a result, when the inactive state is selected, the inherent high-speed rotation of the bearing can be more reliably exhibited. Performance to the maximum limit.

In the auxiliary bearing device, it is preferable that the retainer has a hole portion penetrating in a radial direction for each of the rolling elements, and the rolling element is inserted into the hole portion and is provided between the hole portion and the hole portion. The gap thereby allows relative movement of the rolling elements relative to the radial direction of the retainer.

According to such an auxiliary bearing device, the rolling system is inserted into the hole portion and has a gap with the hole portion of the holder. Therefore, it is possible to move rapidly in the radial direction corresponding to the preload applied from the preloading mechanism in a state where it is hardly restrained by the retainer, and as a result, the effective state and the invalidity of the auxiliary bearing device can be smoothly performed. Switch between states.

Preferably, the auxiliary bearing device has a structure corresponding to the inner race of the shaft member side rolling surface, and the buoyancy generating mechanism is provided by the upper side. The compressed air is supplied to the gap between the retainer and the member corresponding to the inner race, and the rolling element is given a buoyancy on the outer side in the radial direction.

According to such an auxiliary bearing device, by the simple configuration of supplying compressed air to the gap between the retainer and the member corresponding to the inner race, it is possible to reliably impart the buoyancy of the rolling element to the outer side in the radial direction.

Preferably, the auxiliary bearing device is configured such that the compressed air is supplied to the gap from one end side in the axial direction, and the retainer in the other end side in the axial direction and the member corresponding to the inner race. The gap between the gaps is smaller than the gap between the retainer in the one end side and the member corresponding to the inner race.

According to the auxiliary bearing device, the gap on the other end side in the axial direction is small, so that the compressed air supplied from the one end side is effectively blocked on the other end side, whereby the pressure of the compressed air can be efficiently converted. Buoyancy on the outside of the radial direction. Therefore, it is possible to surely impart the buoyancy of the rolling element to the outer side in the radial direction.

In the auxiliary bearing device, it is preferable that a gap between the retainer on the other end side in the axial direction and a member corresponding to the outer race is larger than the retainer in the other end side and the equivalent The gap between the components of the inner race.

According to such an auxiliary bearing device, it is easy to float the rolling element from the rolling surface of the shaft member in an inactive state. The details are as follows. First, the compressed air supplied between the retainer and the member corresponding to the inner race passes through the gap between the hole portion of the retainer and the rolling body to reach the gap between the retainer and the member corresponding to the outer race. . At this time, if the compressed air stays in the gap, the pressure in the gap increases, and the pressure difference between the retainer and the gap between the members corresponding to the inner race becomes small, so that it is difficult to make The rolling elements float on the outer side in the radial direction. In this regard, according to the above configuration, the gap between the retainer on the other end side and the member corresponding to the outer race is larger than the gap between the retainer in the other end side and the member corresponding to the inner race. Therefore, the compressed air of the gap between the retainer and the member corresponding to the outer race is rapidly discharged from the other end side to the outside of the auxiliary bearing device, and the pressure of the gap becomes low. Therefore, the pressure difference described above is likely to occur, and as a result, the rolling elements are easily floated from the rolling surface of the shaft member side.

Preferably, in the auxiliary bearing device, the one end side in the axial direction is adjacent to the retainer to form a supply chamber for supplying the compressed air in an annular region, and the retainer in the one end side The gap between the member corresponding to the outer race is less than the gap between the retainer in the one end side and the member corresponding to the inner race.

According to such an auxiliary bearing device, the gap between the retainer in one end side and the member corresponding to the outer race is smaller than the gap between the retainer in one end side and the member corresponding to the inner race. Therefore, the supply of compressed air from the supply chamber adjacent to one end side is substantially not between the retainer and the member corresponding to the outer race, and is exclusively between the retainer and the member corresponding to the inner race. The gap is carried out. As a result, the pressure of the gap between the retainer and the member corresponding to the inner race can be effectively increased, and the rolling element can be more easily floated from the shaft member side rolling surface.

Preferably, in the auxiliary bearing device, the one end side in the axial direction is formed in an annular shape adjacent to the retainer to form a supply chamber for supplying the compressed air, and the other end side in the axial direction The gap between the retainer and the member corresponding to the outer race is larger than the retainer and the phase in the one end side As the gap between the components of the outer race.

According to such an auxiliary bearing device, the gap between the retainer in the other end side in the axial direction and the member corresponding to the outer race is larger than the gap between the retainer in the one end side and the member corresponding to the outer race. Therefore, the compressed air of the gap between the retainer and the member corresponding to the outer race is quickly discharged to the outside of the auxiliary bearing device at the other end. Therefore, it is possible to effectively prevent the compressed air existing in the gap between the retainer and the member corresponding to the outer race from flowing back to the supply chamber.

Preferably, the auxiliary bearing device has a control unit that controls the switching mechanism, and when the shaft member rotates at a rotation speed of the first range, the control unit switches the switching mechanism to the contact state. The control unit switches the switching mechanism to the non-contact state when the shaft member rotates at a rotational speed of the second range that is faster than the rotational speed of the first range.

According to such an auxiliary bearing device, for example, when the shaft member is rotated at a low speed as an example of the rotation of the first range, the rigidity and the rotation accuracy of the shaft member are improved by switching to the contact state described above, and the shaft member is used as the shaft member. When one of the rotations of the second range is rotated at a high speed, the shaft member can be easily rotated by switching to the non-contact state described above. The improvement of the support rigidity at the time of the low-speed rotation or the improvement of the rotation performance (the ease of rotation) at the time of high-speed rotation is particularly required in the machine tool, and therefore, as described above, in the contact state and the non-contact state based on the rotational speed of the shaft member. The auxiliary bearing unit for switching is extremely suitable for machine tools.

Preferably, the auxiliary bearing device is configured such that a tool for machining a workpiece is fixed to the shaft member, and the auxiliary bearing device is disposed in an axial direction and is disposed on the shaft member It is closer to the position of the above tool than the above bearing.

According to such an auxiliary bearing device, the auxiliary bearing device is disposed close to the tool. Therefore, in the case where the machining load during machining of the workpiece is large, if the auxiliary bearing device is switched to the above-described contact state, the rigidity of the shaft member can be increased at a position closer to the tool, whereby the bearing member can be firmly supported. Processing load. Therefore, the support stability of the shaft member during processing can be improved.

===First Embodiment ===

Fig. 1 is a schematic center cross-sectional view showing a support structure of a shaft member 5 to which the auxiliary bearing device 10 of the first embodiment is applied. 2A is an enlarged view of a portion II of FIG. 1 showing a stopped state of the machine tool. 2B is a B-B arrow view in FIG. 2A, and FIG. 2C is a C-C arrow view in FIG. 2B. 3A is an enlarged view of a portion II of FIG. 1, but is an operating state of the machine tool and indicates an inactive state of the auxiliary bearing device 10. 3B is a B-B arrow view in FIG. 3A, and FIG. 3C is a C-C arrow view in FIG. 3B. 4A is an enlarged view of a portion II of FIG. 1, but is an operating state of the machine tool and indicates an effective state of the auxiliary bearing device 10. 4B is a B-B arrow view in FIG. 4A.

In the following description, the axial direction of the bearing 11 of the auxiliary bearing device 10 is referred to as "axial direction" or "front-rear direction", and the radial direction of the bearing 11 is referred to as "radial direction" or "inside and outside". The circumferential direction of the bearing 11 is also simply referred to as "circumferential direction". Further, the circumferential direction corresponds to the "rotation direction" of the bearing 11. Further, regarding the cross-sectional view used below, in order to avoid the drawing being too complicated, a part of the hatching originally indicated by the cross-sectional portion is omitted.

In the first embodiment, the auxiliary bearing device 10 is applied to a machine tool The support of the spindle 5 (corresponding to the shaft member). That is, the machine tool has a common bearing 510 that is interposed between the outer casing 3 (corresponding to the supporting member) and the main shaft 5 and always supports the main shaft 5; and the auxiliary bearing device 10 is additionally provided to the common bearing 510. Further, in this example, the one-way contact ball bearing 510, 510 which can support one of the radial load and the axial load is used in the conventional bearing 510, but is not limited thereto. For example, a four-point contact ball bearing or a cylindrical roller bearing can also be used; and, in addition to the rolling bearings, a sliding bearing or an air bearing can also be used.

The auxiliary bearing device 10 has an auxiliary bearing 11 configured such that the position of the tool closer to the main shaft 5 than the support position of the common bearing 510 in the axial direction is the support position; the switching mechanism selectively selects and The auxiliary bearing 11 is switched to support either of the "bearing effective state" of the main shaft 5 and the unsupported "bearing invalid state"; and the control unit 90 controls the switching mechanism.

The auxiliary bearing 11 is as shown in FIGS. 2A to 2C. For example, the rolling element 50 is a cylindrical cylindrical roller bearing, and has an inner race 20 as a member corresponding to the inner race as a member equivalent to the outer race. The outer race 30, the plurality of cylindrically shaped rolling bodies 50, 50, ..., and the retainer 60. The inner race 20 is an annular member, and the main shaft 5 passes through the inner peripheral side thereof, and the inner race 20 is fixed to the main shaft 5 so as to be relatively movable with respect to the core. On the outer circumferential surface of the inner race 20, the inner race side rolling surface 20a (corresponding to the shaft member side rolling surface) for rolling the rolling elements 50 is formed on the entire circumference in the circumferential direction. The outer race 30 is also an annular member and is provided in the through hole 3h of the outer casing 3 (Fig. 1). An annular groove portion 30t is formed on the inner circumferential surface of the outer race 30 in the circumferential direction; the rolling element 50 has the bottom surface 30tb of the groove portion 30t as the outer race side rolling surface 30a (corresponding to the support) Rolling is performed on the member side rolling surface). another Further, the movement of the rolling elements 50 in the axial direction is restricted by one of the grooves 30t to the side faces 30ts, 30ts. The rolling element 50 is a cylindrical body having a perfectly circular cross section, and its direction of the rotation axis C50 is parallel to the axial direction and is interposed between the inner race 20 and the outer race 30. The holder 60 is arranged to prevent the rolling elements 50 and 50 from contacting each other in the circumferential direction (rotation direction) while keeping the rolling elements 50 and 50 spaced apart from each other in the circumferential direction. Specifically, the retainer 60 has a ring-shaped member as a main body; in the retainer 60, a plurality of hole portions 60h into which the rolling elements 50 are inserted correspond to the respective rolling elements 50, and are formed to penetrate in the radial direction. Incidentally, the hole shape of each of the hole portions 60h is such that the rolling element 50 has a cylindrical shape, and thus has a rectangular shape corresponding to the shape of the cylindrical body.

The switching mechanism has a buoyancy generating mechanism 70 that supplies buoyancy to the rolling elements 50 in a direction in which the rolling elements 50 are separated from the outer race side rolling surface 20a toward the outer side in the radial direction, and a preloading imparting mechanism 80 which can be externally The race side rolling surface 30a is provided with a force for pressing the rolling element 50 to the inner side in the radial direction by the outer race side rolling surface 30a as a preload, and the rolling element 50 is pressed against the inner race side rolling surface 20a.

Basically, the buoyancy is given to the rolling bodies 50 during the operation of the machine tool. Further, in a state in which the preload is not applied, as shown in FIGS. 3A and 3B, the inner race 20 and the outer race 30 are formed on the inner race side rolling surface 20a or the outer race side rolling surface 30a. The size of the gap G50 is formed between the rolling bodies 50. For example, the radial direction interval D23 between the inner race side rolling surface 20a and the outer race side rolling surface 30a is set to be slightly larger than the diameter D50 of the rolling body 50.

Therefore, when the rolling element 50 is separated from the inner race side rolling surface 20a by buoyancy as shown in FIG. 3A and FIG. 3B, if the preload is given as shown in FIGS. 4A and 4B, The outer race side rolling surface 30a presses the rolling element 50 against the inner race side rolling surface 20a, so that the rolling element 50 is in contact with the rolling surfaces 30a and 20a at the same time, whereby the auxiliary bearing 11 becomes a supporting spindle. 5 bearing effective state. When the preload is released, as shown in FIG. 3A and FIG. 3B, the outer race side rolling surface 30a is reset to the outside in the radial direction based on the elastic return deformation of the outer race 30, and the rolling element 50 is based on The above buoyancy is in a non-contact state in which the inner race side rolling surface 20a floats, whereby the auxiliary bearing 11 becomes a bearing ineffective state in which the main shaft 5 is not supported. In the former bearing effective state (Fig. 4A and Fig. 4B), not only the bearing 510 is commonly used, but also the auxiliary bearing 11 has great help for the support of the main shaft 5, so that the rigidity of the main shaft 5 can be greatly improved; In the inactive state of the bearing (Fig. 3A and Fig. 3B), the auxiliary bearing 11 does not contribute to the support of the main shaft 5 at all, so that the rotational resistance of the main shaft 5 is not increased by the auxiliary bearing 11, and as a result, the rotational resistance is only The inherent rotational resistance of the conventional bearing 510 can thereby maximize the inherent high-speed rotation performance of the conventional bearing 510. That is, it is possible to achieve high-speed rotation performance as if the auxiliary bearing device 10 is completely absent.

Further, the buoyancy generating mechanism 70 has, for example, a supply chamber R70 that supplies compressed air to a gap S20 (hereinafter also referred to as an inner race side gap S20) between the retainer 60 and the inner race 20 (FIG. 3A). . On the other hand, the supply chamber R70 is supplied with compressed air at a specific pressure, for example, via appropriate flow paths 3ka and 7cka (Fig. 13). Therefore, the pressure of the compressed air in the inner race side clearance S20 acts on the rolling element 50 as the buoyancy on the outer side in the radial direction, whereby the rolling is performed as shown in FIGS. 3A and 3B under the release of the preload. The body 50 is moved to the outside in the radial direction and becomes a non-contact state in which the inner race side rolling surface 20a is lifted up. In addition, in the following, the holder is held in accordance with the "inner race side clearance S20" described above. The gap S30 between the 60 and the outer race 30 is also referred to as "outer race side clearance S30".

The supply chamber R70 described above is an annular space formed by arranging one of the end faces in the axial direction adjacent to the retainer 60 and the outer race 30 (and sometimes including the inner race 20). Further, as shown in FIG. 3A, the size S20e2 of the inner race side clearance S20 in the other end side in the axial direction is set to be smaller than the size S20e1 of the inner race side clearance S20 in the one end side. Therefore, the compressed air supplied through the inner race side clearance S20 on the one end side is effectively blocked on the other end side, whereby the pressure of the compressed air can be efficiently converted into the buoyancy on the outer side in the radial direction. In the structure in which the inner race side clearance S20 is reduced at the other end side, for example, the other end portion of the inner circumferential surface 60a of the retainer 60 in the axial direction is provided with an annular shape protruding inward in the radial direction. Wall portion 60w2. This example is used here.

Further, as described above, in the holder 60, the hole portion 60h into which the rolling elements 50 are inserted is formed for each of the rolling elements 50. Further, as shown in FIGS. 3A to 3C, the hole portion 60h is a straight hole whose shape is the same shape in the radial direction, and is provided with a minute gap G60h between the rolling element 50 and the rolling element 50. Therefore, the rolling elements 50 are relatively movable in the radial direction with respect to the hole portion 60h. Therefore, when the outer race side rolling surface 30a is pressed by the application of the preload, the rolling elements 50 are smoothly inwardly seated. The side rolling surface 20a moves.

However, the compressed air supplied to the inner race side side gap S20 leaks to the outer race side clearance S30 through the minute gap G60h of the hole portion 60h, and stays in the outer race side clearance S30, so that it is inside and outside. Since the pressure difference is less likely to occur between the race side side gaps S20, the rolling elements 50 are less likely to rise from the inner race side scroll surface 20a. Therefore, the size S30e2 of the outer race side side gap S30 in the other end side in the axial direction is set larger than the size S20e2 of the inner race side side gap S20 in the other end side, thereby causing leakage to the outer race side. Gap S30 The compressed air is quickly discharged to the outside of the auxiliary bearing 11.

Moreover, in order to prevent the compressed air of the outer race side clearance S30 from flowing back to the supply chamber R70, the size S30e1 of the outer race side side clearance S30 at one end side is smaller than the size S30e2 of the outer race side clearance S30 of the other end side. In other words, the annular wall portion 60w1 that protrudes outward from the outer peripheral surface 60b of the retainer 60 in the radial direction is provided in one end portion, whereby the outer race side side gap S30 is contracted at one end side. Therefore, the compressed air of the outer race side side gap S30 is effectively blocked at one end side, whereby the compressed air of the outer race side side gap S30 is quickly discharged to the outside of the auxiliary bearing 11 from the other end side.

In addition, the size of the outer race side side gap S30 in the one end side is set to be smaller than the size S20e1 of the inner race side side gap S20 in the one end side by the wall portion 60w1. Therefore, the compressed air in the supply chamber R70 is exclusively supplied to the inner race side clearance S20, whereby the pressure in the inner race side clearance S20 can be effectively increased, and as a result, the radial direction of the rolling elements 50 can be efficiently imparted. Buoyancy.

By the wall portion 60w1, the size S30e1 of the outer race side side gap S30 on the one end side is set smaller than the size S20e2 of the inner race side side gap S20 in the other end side. That is, as described above, the other end side is also provided with an annular wall portion 60w2 which protrudes inward in the radial direction from the inner circumferential surface 60a of the retainer 60; the inner race side of the position of the wall portion 60w2 The size S20e2 of the gap S20 is set to be larger than the size S30e1 of the seat-side gap S30 at the position of the wall portion 60w1 on the one end side. Thereby, the movement of the retainer 60 in the radial direction is mainly restricted by the abutment of the wall portion 60w1 of the retainer 60 and the inner peripheral surface 30b of the outer race 30, without the retainer 60 and the inner race. 20 outer peripheral surface 20b abuts. Therefore, in the state in which the bearing is ineffective, the holder 60 that can prevent the rotation from substantially stopping can be surely prevented. The inner race 20 is rotated integrally with the main shaft 5 to prevent the rotation of the inner race 20; this point also contributes to the high-speed rotation performance inherent to the conventional bearing 510 in the inactive state of the auxiliary bearing 11.

Further, lubricating oil may be contained in the above-mentioned compressed air, so that damage of the auxiliary bearing 11 can be effectively prevented.

The preload applying mechanism 80 has, for example, an actuator 82 that can apply a force to the auxiliary bearing 11 to move the outer race side rolling surface 30a inward in the radial direction as a preload. The rolling element 50 is pressed against the inner race side rolling surface 20a by the movement of the outer race side rolling surface 30a due to the application of the preload, whereby the outer race 30, the rolling element 50, and the inner seat are provided. Circle 20 is crimped. The actuator 82 described above operates based on the pre-compression control signal S90 transmitted from the control unit 90 described below. Further, various well-known structures can be used in the preload applying mechanism 80. Description of the well-known structure is omitted here; and the structure of the new preloading mechanism 380 will be described below.

The control unit 90 mainly controls the operation of the preload applying unit 80, and for example, a computer or a PLC (Programmable Logic Control) can be used. Further, an operation panel (not shown) is attached to the control unit 90. The operation panel has a bearing effective mode button corresponding to the bearing effective state, and a bearing invalid mode button corresponding to the bearing ineffective state, and two types of operation buttons. When the operator operates the button to select the bearing effective mode, the control unit 90 transmits, for example, a value of a predetermined magnitude of preload to the preload applying mechanism 80 as a preload control signal S90. Then, the actuator 82 of the preload applying mechanism 80 applies a preload to the auxiliary bearing 11, and the auxiliary bearing 11 becomes a bearing effective state for supporting the main shaft 5. On the other hand, if the bearing ineffective mode is selected, the control unit 90 transmits, for example, a zero value as a preload control to the preload applying mechanism 80. Signal S90. Then, the actuator 82 of the preload applying mechanism 80 releases the preload of the auxiliary bearing 11, and the auxiliary bearing 11 becomes a bearing ineffective state in which the spindle 5 is not supported.

Further, the switching operation is not limited to the button operation of the operator, and the control unit 90 may be automatically performed. For example, as shown in the graph of FIG. 5, it is also possible to automatically switch in conjunction with the rotational speed of the spindle 5. In detail, first, a rotation speed detecting sensor such as a pulse generator or an encoder that detects the rotation speed of the spindle 5 is provided, and the measurement data of the rotation speed of the spindle 5 measured by the sensor is instantaneously transmitted to the control unit 90. Then, when the measured value of the rotational speed of the measurement data is stored in advance in the memory N of the control unit 90 or less, the control unit 90 selects the bearing effective mode and transmits the actuator 82 of the preload applying mechanism 80. The value of the preload of a specific size is used as the pre-compression control signal S90. On the other hand, when the number of revolutions exceeds the threshold value Nth, the control unit 90 selects the bearing ineffective mode and transmits a zero value as the preload control signal S90 to the actuator 82 of the preload applying mechanism 80. In this way, the main shaft 5 can be automatically switched to a high rigidity for heavy cutting which is usually performed by low-speed rotation, and can be automatically switched to the rotation resistance of the main shaft 5 for light cutting which is usually performed by high-speed rotation. status.

As a result, the support structure of the main shaft 5 having the auxiliary bearing 11 and the common bearing 510 can exhibit the rigidity characteristics shown in the graph of Fig. 5. The vertical axis of the graph contributes to the total value of the preload of the support of the main shaft 5, and the horizontal axis represents the rotational speed of the main shaft 5. In the high-speed rotation region, based on the so-called fixed-position pre-compression method, only the preload of the common bearing 510 has an effect, so that the total value of the pre-compression becomes low, thereby ensuring high-speed rotation performance; but in the low-speed rotation region, In addition to this, the preload of the auxiliary bearing 11 also acts, so that the total value of the preload is greatly increased, so that the reinforcement is high rigidity rather than high speed rotation.

6A to 7B are explanatory views of a first modification of the auxiliary bearing device 10. Fig. 6A is a view corresponding to an enlarged view of a portion II of Fig. 1, showing a bearing effective state. 6B is a B-B arrow view in FIG. 6A, and FIG. 6C is a C-C arrow view in FIG. 6B. In addition, FIG. 7A is a view corresponding to an enlarged view of a portion II in FIG. 1, but shows a state in which the bearing is ineffective. 7B is a B-B arrow view in FIG. 7A.

In the first modification, a four-point contact ball bearing is used as the auxiliary bearing 111, and mainly in this point, unlike the first embodiment, the other structure is substantially the same as that of the first embodiment. Therefore, in the following description, the differences will be mainly described, and the description of the same contents will be omitted.

As shown in FIGS. 6A to 6C, a four-point contact ball bearing is used, so that the spherical rolling elements 150 are recessed in the inner circumference of the inner race 120 (corresponding to the member corresponding to the inner race). In the ring side rolling surface 120a, the positions of the two portions in the axial direction are the contact positions P1, P2, and are respectively contacted by the contact angles α1 and α2; and are recessed in the outer race 130 (and the equivalent outer race) In the outer race side rolling surface 130a other than the inner peripheral surface of the member, the two portions in the axial direction are also in contact with each other at the contact angles α3 and α4. The contact positions P1 and P2 of the inner race side rolling surface 120a (corresponding to the shaft member side rolling surface) are set so as to sandwich the position of the center C150 of the rolling element 150 from both sides in the axial direction; The contact positions P3 and P4 of the race side rolling surface 130a (corresponding to the support member side rolling surface) are also set so as to sandwich the position of the center C150 of the rolling element 150 from both sides in the axial direction. Therefore, the radial load acting on the main shaft 5 can be supported, and the axial load in both directions can also be supported.

Moreover, in the first variation, it is also continuously operated in the operation of the machine tool. The rolling bodies 150 impart buoyancy. The inner race 120 and the outer race 130 are formed such that the inner race side rolling surface 120a or the outer race side rolling surface 130a and the rolling element are formed in a state where no preload is applied as shown in FIGS. 7A and 7B. A size of the gap G150 is formed between 150. For example, the interval D1213 between the inner race side rolling surface 120a and the outer race side rolling surface 130a, that is, the interval D1213 on the straight line passing through the position of the center of the core 150 of the rolling element 150 is designed to be slightly larger than the rolling body 150. Diameter D150. Therefore, in the state in which the bearing is not biased, the rolling element 150 can be surely floated from the inner race side rolling surface 120a by the action of the compressed air of the buoyancy generating mechanism 70, whereby the roller body 150 can be surely made The auxiliary bearing 111 is in a state in which the bearing is ineffective.

Moreover, from the viewpoint of assembling the inner race 120, the outer race 130, the retainer 160, and the rolling element 150 in the state of FIG. 6A, it is preferable that two The position between the contact positions P1 and P2 (P3, P4) is defined as the division position Pb, and is divided into one of the two portions to form the annular divided bodies 130p1 and 130p2 to constitute the inner race 120 or the outer race 130. At least one. In the example of FIG. 6A, the outer race 130 is divided into two portions, but the inner race 120 may be divided into two portions.

Further, the retainer 160 is different from the retainer 60 of the first embodiment except that the hole portion 160h of each of the rolling elements 150 and the shape of the rolling element 150, that is, the spherical hole corresponding to the spherical shape, are formed in a circular shape. The description is omitted for the same configuration.

Fig. 8 is an explanatory view showing a second modification of the auxiliary bearing device 10, and corresponds to an enlarged view of a portion II of Fig. 1. In the second modification, the angular contact ball bearing is used as the auxiliary bearing 211, and mainly in this respect, the configuration is different from that of the first embodiment, and the other configuration is substantially the same as that of the first embodiment. Therefore, in the following description, mainly The different aspects will be described, and the description of the same contents will be omitted.

Since the ball bearings are angularly contacted, each of the rolling elements 250 is formed in a substantially arc-shaped inner race side rolling surface 220a on the outer circumferential surface of the inner race 220, and the position of one portion in the axial direction is the contact position. P1 is in contact with the contact angle α1; and the inner circumferential surface of the outer race 230 (corresponding to the member corresponding to the outer race) is formed in a substantially arc shape, and the raceway side rolling surface 230a is also axially One of the directions is the contact position P4 and is in contact with the contact angle α4. The contact position P1 between the inner race side rolling surface 220a (corresponding to the shaft member side rolling surface) and the outer race side rolling surface 230a (corresponding to the support member side rolling surface) is set to be self-axial. The positions of the center C250 of the rolling elements 250 are sandwiched on both sides of the direction. Therefore, the radial load acting on the main shaft 5 can be supported, and the axial load in one direction can also be supported.

Moreover, in the second modification, buoyancy is continuously applied to the rolling elements 250 during the operation of the machine tool. In the state in which the preload is not applied, the inner race 220 and the outer race 230 are formed such that the inner race side rolling surface 220a or the outer race side is rolled, as in the case of the first modification described above. A dimension of the gap is formed between the face 230a and the rolling body 250. Therefore, the rolling element 250 can be surely floated from the inner race side rolling surface 220a by the action of the compressed air of the buoyancy generating mechanism 70, whereby the auxiliary bearing 211 can be surely brought into a bearing ineffective state.

Further, the retainer 260 is the same as the retainer 60 of the first embodiment except that the hole portion 260h of each of the rolling elements 250 and the shape of the rolling element 250, that is, a straight hole which is formed in a spherical shape in a spherical shape, is inserted. The description is omitted for the same configuration.

=== Second embodiment ===

9 and 10 are explanatory views of the second embodiment of the auxiliary bearing device 10. In the second embodiment, a part of the preload applying mechanism 380 that applies the preload to the auxiliary bearing 311 is incorporated in the auxiliary bearing 311, and is mainly different from the first embodiment in this point, and other configurations are also employed. The system is substantially the same as the first embodiment. Therefore, in the following description, the different aspects will be mainly described, and the description of the same contents will be omitted.

Fig. 9 is a schematic center sectional view of the auxiliary bearing 311. 10 is an enlarged view of a portion X in FIG. 9.

The auxiliary bearing 311 belongs to the category of so-called single row cylindrical roller bearings. That is, since it is a single row, a plurality of rolling elements 350 are arranged between the inner race side rolling surface 320a and the outer race side rolling surface 330a so as to be aligned in a row in the circumferential direction. Further, since the cylindrical roller bearing 311 is used, a cylindrical body having a circular cross-sectional shape is used as the rolling element 350, and the rotating shaft C350 of the rolling element 350 is parallel to the axial direction. Thereby, the higher support capacity of the radial load can be exerted. In addition, the circumferentially adjacent rolling elements 350, 350 are prevented from contacting each other by the annular retainer 360. For example, the retainer 360 has a hole portion 360h for accommodating the rolling bodies 350 for each of the rolling bodies 350, thereby preventing the rolling bodies 350, 350 from coming into contact with each other.

As shown in FIG. 9, the inner race side rolling surface 320a (corresponding to the shaft member side rolling surface) is formed directly on the outer peripheral surface of the main shaft 5 having a substantially circular cross section. That is, in this example, the inner race is omitted, whereby the rotation accuracy and rigidity of the spindle 5 can be improved. The inner race side rolling surface 320a is parallel to the axial direction; the rolling body 350 rolls on the rolling surface 320a. Further, a portion in which the inner race side rolling surface 320a is formed on the outer peripheral surface of the main shaft 5 corresponds to "a member equivalent to the inner race" in the patent application, and the spindle 5 is also hereinafter. The outer peripheral surface is referred to as "a member 320 equivalent to the inner race". Moreover, in this example, the inner race is omitted, but the inner race may be provided.

The outer race 330 (corresponding to the member corresponding to the outer race) is a steel cylinder having a substantially circular cross section. Specifically, it has an annular annular portion 332 at the inner circumference. The surface has a rolling surface 330a for rolling the rolling body 350; and a fixing portion 336 that fixes the outer race 330 to the outer casing 3 of the machine tool. The fixing portion 336 is integrally extended to the other end portion 332eb of the annular portion 332 in the axial direction and protrudes in an annular shape toward the outer side in the radial direction, for example, the axial direction of the protruding portion 336 The other end surface 336e abuts against one end surface of the outer casing 3 in the axial direction to fix the outer race 130 to the outer casing 3. In this fixed state, the radial load acting on the main shaft 5 is sequentially transmitted to the annular portion 332 and the fixed portion 336 of the outer race 330 via the member 320 corresponding to the inner race and the rolling elements 350 (the projection 336 And is quickly transmitted to the outer casing 3 by the fixing portion 336 (refer to FIG. 13). Therefore, the outer casing 3 can be surely supported to support the radial load of the main shaft 5.

As shown in FIG. 10, a concave groove portion 332t is formed on the inner circumferential surface of the annular portion 332 over the entire circumference in the circumferential direction. Further, the bottom surface 332tb of the groove portion 332t is formed in parallel with the axial direction, and the rolling element 350 is rolled by the bottom surface 332tb as the outer race side rolling surface 330a (corresponding to the support member side rolling surface). Further, since the side faces 332ts and 332ts of the groove portion 332t are provided on both sides of the outer race side rolling surface 330a in the axial direction, the end faces of the rolling elements 350 abut against the respective side faces 332ts and 332ts to restrict the axial direction of the rolling elements 350. The direction of movement.

A portion of the preload applying mechanism 380 is provided on the outer circumferential surface 332b of the annular portion 332. One part of the preloading mechanism 380 is a body made of a metal ring member 340 that is disposed to face the outer peripheral surface 332b of the annular portion 332 with a predetermined gap G340; An annular pressure chamber R340 is defined between the annular member 340 and the annular portion 332. Therefore, by supplying the pressurized fluid to the pressure chamber R340 to reduce the diameter of the annular portion 332, the rolling element 350 is passed to the member 320 corresponding to the inner race due to the race-side rolling surface 330a of the annular portion 332. (It has been described above that the outer peripheral surface of the main shaft 5 which directly forms the inner race side rolling surface 320a is pressed), and as a result, the rolling element 350 is crimped to the outer race 330 and the inner race. The state of the member 320.

From the above, it can be seen that in the pressure bonding process, almost no metal contact portions move relative to each other, so that a so-called slip phenomenon is less likely to occur. Therefore, the pressure contact force between the rolling element 350 and the outer race 330 and the member 320 corresponding to the inner race is smoothly and rapidly changed in conjunction with the increase and decrease of the supply pressure of the pressurized fluid. As a result, the pressure contact force can be accurately supplied, and the change in the pressure contact force (change in the preload) can be accurately performed.

Further, in a state where the pre-compression is not applied, that is, the pressurized fluid is not supplied to the pressure chamber R340, the inner race side rolling surface 320a of the main shaft 5 and the annular portion 332 of the outer race 330 are formed to have a size of A gap is formed between the race-side rolling surface 320a of the main shaft 5 or the annular portion 332 of the outer race 330 and the race-side rolling surface 330a and the rolling element 350. For example, the radial direction interval D3233 between the inner race side rolling surface 320a and the outer race side rolling surface 330a is designed to be slightly larger than the diameter D350 of the rolling body 350. Therefore, in the state where the preload is not applied, the rolling element 350 can be surely floated from the inner race side rolling surface 320a by the action of the compressed air of the buoyancy generating mechanism 70 described above, whereby the rolling element 350 can be surely made This auxiliary bearing 311 becomes a bearing ineffective state.

As shown in Fig. 10, washers 347, 347 for preventing the pressurized fluid from leaking from the pressure chamber R340 to the outside are provided at both end portions of the annular member 340 in the axial direction. also In other words, grooves 340t and 340t are formed on both ends of the inner circumferential surface of the annular member 340, and an annular gasket 347 is inserted into each groove 340t. The washer 347 is in contact with both the outer circumferential surface 332b of the annular portion 332 and the bottom surface of the groove 340t, and is interposed between the annular portion 332 and the annular member 340 in a state of being slightly elastically compressed and deformed. Therefore, it is possible to effectively prevent leakage of pressurized fluid from the pressure chamber R340. Further, the annular portion 332 and the annular member 340 are kept in a non-contact state by the insertion of the gasket 347, and the gasket 347 is made of rubber or resin. Therefore, in the case where both the annular portion 332 and the annular member 340 are made of metal, it is possible to surely avoid the occurrence of slippage due to the metal contact between the two.

The supply of the pressurized fluid to the pressure chamber R340 is performed by the supply hole 330h which is perforated in the outer race 330. That is, in the example of Fig. 10, in the annular portion 332 and the fixing portion 336, a supply hole 330h is formed along the axial direction, one end of the supply hole 330h is open to the pressure chamber R340, and the other end is fixed. The other end 336e of the portion 336. The other end opening of the supply hole 340h is connected to the flow path 3k (Fig. 13) of the pressurized fluid perforated in the outer casing 3, whereby the pressurized fluid can be supplied to the pressure chamber R340. The number of the supply holes 340h may be one or plural. Further, a supply hole may be formed in the annular member 340 instead of the supply hole 330h described above. The pressurized fluid is usually a hydraulic oil for oil pressure, but may be compressed air or a fluid other than the above.

Further, a flow path 3k (Fig. 13) of the pressurized fluid perforated in the outer casing 3 described above is also formed as a part of the preload applying mechanism 380 in the same manner as the above-described annular member 340. In detail, the preload applying mechanism 380 includes the above-described annular member 340, the flow path 3k in the above-described outer casing 3, a suitable piping such as a suitable pipe connected to the flow path 3k, and the like, and is connected to The flow path forming member is a pump (not shown) that supplies a pressurized fluid, And a pressure regulating valve (not shown) provided in one of the flow path forming members. The pressure regulating valve adjusts the supply pressure to the pressure chamber R340 based on the control signal S90 of the preload transmitted from the control unit 90 described above. Therefore, by the adjustment of the supply pressure, the pressure contact force between the rolling element 350 and the outer race 330 and the member 320 corresponding to the inner race can be adjusted to a desired arbitrary value. That is, the bearing 311 can be given a preload of a specific size.

In addition, since the retainer 360 has the same structure as the retainer 60 of the first embodiment, the description thereof will be omitted. Further, the supply chamber R70 of the buoyancy generating mechanism 70 is adjacent to one end side of the retainer 360 or the outer race 330 in the axial direction, and the retainer 360 and the inner race from the supply chamber R70. The fact that the inner race side clearance S20 between the members 320 supplies compressed air is also the same as that of the first embodiment, and therefore the description thereof will be omitted.

Fig. 11 is an explanatory view showing a first modification of the auxiliary bearing device 10 of the second embodiment. In the first modification, the auxiliary bearing 311 of the second embodiment is changed to belong to the category of a four-point contact ball bearing; and mainly in this respect, the second embodiment is different from the second embodiment. 2 The embodiment is the same. Therefore, in the following description, the different aspects will be mainly described, and the same reference numerals will be given to the same components, and the description thereof will be omitted.

As shown in FIG. 11, since the ball bearing is a four-point contact, each of the spherical rolling elements 350a is formed in the inner race side rolling surface 320a which is formed in a concave shape on the outer peripheral surface of the main shaft 5, in the axial direction. The positions of the two portions are the contact positions P1 and P2, which are respectively contacted by the contact angles α1 and α2, and are also recessed in the outer race side rolling surface 330a of the inner circumferential surface of the annular portion 332 of the outer race 330. The position of the two parts in the axial direction is the contact position P3 and P4 are contacted by contact angles α3 and α4, respectively. The contact positions P1, P2 of the inner race side rolling surface 320a are set such that the positions of the center of the core C350a of the rolling element 350a are sandwiched from both sides in the axial direction; and the contacts of the outer race side rolling surface 330a are contacted. The positions P3 and P4 are also set so as to sandwich the position of the center C350a of the rolling element 350a from both sides in the axial direction. Therefore, the radial load acting on the main shaft 5 can be supported, and the axial load in both directions can also be supported.

Further, in a state where the pre-compression is not applied, that is, the pressurized fluid is not supplied to the pressure chamber R340, the inner race side rolling surface 320a of the main shaft 5 and the annular portion 332 of the outer race 330 are formed to have a size of A gap is formed between the race-side rolling surface 320a of the main shaft 5 or the annular portion 332 of the outer race 330, and the race-side rolling surface 330a and the rolling element 350a. For example, the interval D3233 between the inner race side rolling surface 320a and the outer race side rolling surface 330a, that is, the interval D3233 on the straight line passing through the position of the spherical center C350a of the rolling element 350a is set to be slightly larger than that of the rolling body 350a. Diameter D350a. Therefore, the rolling element 350a can be surely floated from the inner race side rolling surface 320a by the action of the compressed air of the buoyancy generating mechanism 70 in a state where the preload is not applied, whereby the assist can be surely made The bearing 311a is in a state in which the bearing is ineffective.

Fig. 12 is an explanatory view showing a second modification of the auxiliary bearing device 10 of the second embodiment. In the second modification, the auxiliary bearing 311 of the second embodiment is changed to belong to the category of the angular contact ball bearing, and mainly differs from the second embodiment in that the configuration is substantially the same as that of the second embodiment. The second embodiment is the same. Therefore, in the following description, the different aspects will be mainly described, and the same reference numerals will be given to the same components, and the description thereof will be omitted.

As shown in Fig. 12, since the ball bearings are angular contact, the balls are rolled. The movable body 350a is formed in the inner race side rolling surface 320a which is formed in a substantially arc shape on the outer circumferential surface of the main shaft 5, and the position of one portion in the axial direction is the contact position P1, and is contacted by the contact angle α1; The inner circumferential surface of the annular portion 332 of the outer race 330 is formed in a substantially circular arc shape, and the position of one portion in the axial direction is the contact position P4 at the contact angle α4. . The contact position P4 between the contact position P1 of the inner race side rolling surface 320a and the outer race side scroll surface 330a is set so as to sandwich the position of the center C350a of the rolling element 350a from both sides in the axial direction. Therefore, the radial load acting on the main shaft 5 can be supported, and the axial load in one direction can also be supported.

Further, in a state where the pre-compression is not applied, that is, the pressurized fluid is not supplied to the pressure chamber R340, the inner race side rolling surface 320a of the main shaft 5 and the annular portion 332 of the outer race 330 are formed to have a size of A gap is formed between the race-side rolling surface 320a of the main shaft 5 or the annular portion 332 of the outer race 330, and the race-side rolling surface 330a and the rolling element 350a. For example, the interval D3233 between the inner race side rolling surface 320a and the outer race side rolling surface 330a, that is, the interval D3233 on the straight line passing through the position of the spherical center C350a of the rolling element 350a is set to be slightly larger than that of the rolling body 350a. Diameter D350a. Therefore, the rolling element 350a can be surely floated from the inner race side rolling surface 320a by the action of the compressed air of the buoyancy generating mechanism 70 in a state where the preload is not applied, whereby the assist can be surely made The bearing 311b is in an ineffective state of the bearing.

Fig. 13 is a schematic front cross-sectional view showing a first example of a support structure of the main shaft 5 of the machine tool to which the auxiliary bearing device 10 of the second embodiment is applied. Further, the shaft core C5 of the main shaft 5 is along the axial direction of the auxiliary bearing 311 of the auxiliary bearing device 10, and the side of the tool (the left side in FIG. 13) is attached to both ends of the axial direction. "one end The side is referred to as the "other end side" on the opposite side (the right side in Fig. 13).

As shown in FIG. 13, in the support structure of the main shaft 5, a pair of single-row angular contact ball bearings 510, 510 are used in a back-side combination as a common bearing for always supporting the main shaft 5. Therefore, basically, the main shaft 5 is supported by the equiangular contact ball bearings 510, 510. That is, the radial load and the axial load acting on the main shaft 5 are supported by the pair of angular contact ball bearings 510, 510.

However, in the machine tool, a tool (not shown) is attached to one end portion 5ea of the main shaft 5 in the axial direction. Therefore, in the case of heavy cutting or the like, a large radial load acts on the one end portion 5ea. Hey. Therefore, the auxiliary bearing 311 of the auxiliary bearing device 10 is provided at a position closer to one end of the axial direction than the support position of the above-described angular contact ball bearings 510, 510 as a support position. More specifically, the main shaft 5 has a conical conical hole portion 5h for receiving a conical conical retaining portion (not shown) of the fixing tool on one end side; and the auxiliary bearing 311 is configured to be The position of the hole portion 5h corresponding to the axial direction is its support position. The auxiliary bearing 311 is as described above and belongs to the category of single row cylindrical roller bearings. Therefore, the auxiliary bearing 311 is specialized to support the radial load, whereby in the case where the radial load such as heavy cutting is large, if the auxiliary bearing 311 is switched to the bearing effective state, the auxiliary bearing 311 can be surely supported. Large radial load.

Incidentally, in the example of FIG. 13, the pair of angular contact ball bearings 510 and 510 are disposed by the back surface combination, but the invention is not limited thereto. That is, a pair of single-row angular contact ball bearings 510, 510 may be disposed in the same manner as the back-side combination, in a front-side combination that can support axial loads in both directions. Incidentally, the angular contact ball bearing 510 has an inner race 520, an outer race 530, and the inner races at respective corresponding contact angles. A plurality of spherical rolling bodies 550 of 520 and outer race 530. In this example, the pair of angular contact ball bearings 510, 510 are formed by pressing members 4m, 6m such as nut members and by a fixed position preloading method (by fixing the inner race 520 and the outer race 530 to The pre-compression is given to the method of pre-pressing the fixed position, but since the fixed-position pre-compression method is a well-known technique, the description thereof is omitted.

Hereinafter, the support structure of the spindle 5 of the first example will be described in detail.

The outer casing 3 of the machine tool has a through hole 3h from one end to the other end in the axial direction as a through hole 3h into which the main shaft 5 is inserted. In a state in which the main shaft 5 is inserted into the through hole 3h, the angular contact ball bearing 510 provided at one end of the through hole 3h and the angular contact ball bearing 510 provided at the other end portion are wound around the main shaft 5 C5 rotates freely.

In addition, one of the end faces 3ea of the outer casing 3 in the axial direction is integrally protruded in the axial direction from the small-diameter cylindrical portion 3c having the same core as the through hole 3h, and is disposed on the inner peripheral surface of the small-diameter cylindrical portion 3c. There is an angular contact ball bearing 510 at one of the above ends. Further, the space on the outer side in the radial direction of the small-diameter cylindrical portion 3c serves as an arrangement space for a part of the auxiliary bearing 311. That is, the small-diameter cylindrical portion 3c is integrally connected to one end surface 3ea of the outer casing 3 at the other end edge portion of the outer casing 3, and the one end surface 3ea of the outer casing 3 and the fixed portion of the outer race 330 of the auxiliary bearing 311 The other end surface 336e of 336 abuts and is fixed by relative movement without a screw or the like. This fixing causes the outer race 330 to be disposed in the same core as the through hole 3h of the outer casing 3.

Further, since the inner side of the annular portion 332 of the outer race 330 has no small diameter cylindrical portion 3c on the inner side in the radial direction, the annular portion 332 and the outer peripheral surface of the main shaft 5 are used for the division. To configure the annular space of the rolling body 350. Therefore, the rolling body 350 It is configured in this space. Further, as described above, since the auxiliary bearing 311 of the second embodiment has no inner race, the inner race side rolling surface 320a is directly formed on the outer peripheral surface of the main shaft 5. Further, a retainer 360 is disposed between the outer race 330 and the inner race side rolling surface 320a, and a preload applying mechanism is formed on the outer side in the radial direction of the annular portion 332 of the outer race 330. An annular member 340 of one portion of 380.

Further, in order to adjoin the outer race 330 and the retainer 360 from one end side in the axial direction, the supply chamber R70 of the compressed air of the annular buoyancy generating mechanism 70 is formed, and one end side and the diameter from the axial direction are provided. The cover member 7c of the auxiliary bearing 311 is surrounded by the outer side of the direction. That is, the cover member 7c has a cylindrical portion 7c1 provided with a space between the outer peripheral surface of the annular member 340 of the auxiliary bearing 311, and an annular cover portion 7c2 from the cylindrical portion. One end edge portion of the axial direction of 7c1 protrudes inward in the radial direction; a circular hole 7c2h for exposing one end surface of the main shaft 5 to the outside of the cover member 7c is formed at the center of the cover portion 7c2. Further, the other end edge portion 7c1e of the tubular portion 7c1 abuts against one end surface of the fixing portion 336 of the outer race 330 and is fixed by a screw or the like, whereby the auxiliary bearing 311 is self-contained by the cover portion 7c2 and the cylindrical portion 7c1. One end side of the axial direction and the outer side of the radial direction are surrounded. Thereby, a substantially closed space R70 is formed on the side of the outer race 330 and the one end side of the retainer 360, and the space R70 serves as the supply chamber R70 for the compressed air described above. Further, the supply of the compressed air to the supply chamber R70 is via a flow path 7cka of compressed air perforated in the lid portion 7c2 or a flow path 3ka of compressed air perforated in the outer casing 3, and is suitably used. It is carried out by a compressed air source such as a pump.

Incidentally, the compressed air supplied from the supply chamber R70 to the auxiliary bearing 311 is used for cooling the auxiliary bearing 311 in addition to the use for floating the rolling element 350. material. The compressed air is discharged from the other end side to the outside of the auxiliary bearing 311 by the inner race side clearance S20 between the retainer 360 and the outer peripheral surface of the main shaft 5 which is the member 320 corresponding to the inner race, but the above A common bearing, that is, an angular contact ball bearing 510, is located on the other end side than the discharge position Pex. Therefore, the angular contact ball bearing 510 also uses compressed air as a cooling material. Further, another angular contact ball bearing 510 is located on the other end side of the angular contact ball bearing 510, and a cylindrical space SP510 is provided between the ball bearings 510, 510. Therefore, the compressed air passes through the cylindrical space SP510 and reaches the angular contact ball bearing 510 on the other end side for cooling. Then, it is discharged to the outside of the outer casing 3 through an appropriate gap which the outer casing 3 has, or a vent hole 3kae or the like which is perforated in the outer casing 3.

Further, as shown in the lower part of Fig. 13, the cover member 7c is disposed such that a space SP3 is left between the outer peripheral surface of the annular member 340 of the race 330 other than the auxiliary bearing 311; and the space SP3 is allowed The space in which the annular member 340 is elastically expanded and deformed (hereinafter also referred to as the allowable space SP3) is used. In other words, when the pressurized fluid is supplied to the pressure chamber R340 in order to apply the pressure contact force in the radial direction to the rolling elements 350, the annular member 340 is elastically expanded in diameter accompanying the reduction of the diameter of the annular portion 332 of the outer race 330. The size of the allowable space SP3 is set in advance so that the elastic expansion deformation at this time can be accommodated in the allowable space SP3. Thereby, the outer peripheral surface 340a of the annular member 340 is not brought into contact with the inner peripheral surface of the cover member 7c. Therefore, the outer side of the outer peripheral surface 340a of the annular member 340 does not have any member capable of obtaining a reaction force. Therefore, when the pressurized fluid is supplied to the pressure chamber R340, the supply pressure of the pressurized fluid in the pressure chamber R340 is faithfully Converted to a crimping force in the radial direction. Thereby, the annular portion 332 is reduced in diameter only by the supply pressure of the pressurized fluid, and therefore the annular portion 332 is substantially uniformly reduced in diameter over the entire circumference thereof. As a result, the rolling elements 350 are given Since the pressure contact force is also substantially uniform over the entire circumference of the auxiliary bearing 311, the rotation accuracy and the rotational rigidity of the auxiliary bearing 311 can be improved.

Fig. 14 is a schematic front cross-sectional view showing a second example of a support structure of the main shaft 5 of the machine tool to which the auxiliary bearing device 10 of the second embodiment is applied. In the first example described above, the pre-pressure is applied to the angular contact ball bearings 510 and 510 as one of the usual bearings by the fixed position preloading method, and the magnitude of the preload cannot be arbitrarily changed. In this regard, in the second example, the biggest difference is that the preloading automatic adjustment bearing device 410 is replaced with the preloading automatic adjustment bearing device 410 while monitoring the state of the common bearing 411 while replacing the normal bearing 411. The corner of the law contacts the ball bearing 510. That is, the auxiliary bearing device 10 is the same as the first example; however, the configuration of the common bearing is different. Therefore, the following description will be made in detail with respect to the preload automatic adjustment bearing device 410 for a common bearing, and the description of the auxiliary bearing device 10 will be omitted.

As shown in Fig. 14, the diagonal contact ball bearings 411, 510, which are one of the common bearings, are arranged in a so-called back combination, whereby the radial load and the axial load in both directions can be supported. For the angular contact ball bearing 510 of one of the end faces, a general-purpose angular contact ball bearing 510 is used in the same manner as in the first example, but the angular contact ball bearing 411 on the other end side uses a special angular contact ball bearing 411, which is built-in. A portion of the preloading mechanism 480, that is, the rolling element 450 is crimped to one of the inner race 420 and the crimping mechanism 480 of the outer race 430. Since the pressure-bonding operation is performed by supplying a pressurized fluid to the pressure chamber R430 in the outer race 430 to elastically deform the thin portion 434 described below, the supply pressure of the pressurized fluid can be adjusted. The rolling element 450 is crimped to the outer race 430 and the inner race 420 at a pressure contact force of the supply pressure. That is, the magnitude of the preload value can be changed to an arbitrary value.

Further, the details will be described below, and the component of the axial direction of the crimping force is transmitted to the one end side angular contact ball bearing 510 via the outer casing 3 or the spacer 6a of FIG. Therefore, with the provision of the preload by the preload applying mechanism 480 described above, the angular contact ball bearing 510 on the one end side is also preloaded, and the value of the preload is in contact with the angular contact ball bearing 411 on the other end side. The value of the preload is changed in conjunction with the change.

Further, hereinafter, a single-row angular contact ball bearing 510 which is provided on one end side of a pair of angular contact ball bearings 510 and 411 is also referred to as a "general ball bearing 510", and will also be provided at a special corner on the other end side. The contact ball bearing 411 is referred to as a "special ball bearing 411".

Fig. 15 is a schematic cross-sectional view showing a center of a special ball bearing 411, and Fig. 16 is an enlarged view of a portion XVI of Fig. 15. As shown in Fig. 15, the inner race 420 is made of a steel cylindrical body. Further, as shown in FIG. 16, an inner race side rolling surface 420a having a groove shape in which the rolling elements 450 are rolled is provided on the entire circumference of the outer circumferential surface of the inner race 420. The inner race side rolling surface 420a is a concave curved surface 420a having a substantially arc-shaped cross-sectional shape; the substantially circular arc shape is formed such that the rolling element 50 contacts at a position P1 of one of the axial directions in the circular arc shape. The angle α1 is in contact. Thereby, the rolling element 450 is attached to the rolling surface 420a, and is in contact with the inner race 420 at a position where the angle α1 is inclined from the radial direction toward the other end side as the contact position P1.

The outer race 430 has an inner annular portion 432 having a race side rolling surface 430a for rolling the rolling element 450, and a disk-shaped thin portion 434 provided from the inner annular portion 432 toward The outer side of the radial direction is integrally extended and is coaxial with the inner annular portion 432; and the outer annular portion 436 is integrally formed with the inner annular portion 432 and is disposed coaxially with the outer peripheral portion 434e1 of the thin portion 434. Supporting the inner annular portion through the thin portion 434 432, the inner annular portion 432 is movable in the axial direction. The thin portion 434 is provided at a substantially central position of the outer annular portion 436 in the axial direction, and the inner annular portion 432 is provided with the inner peripheral portion 434e2 of the thin portion 434 as the starting end. It extends toward one end side of the direction. Thereby, the annular space SP is defined by the outer annular portion 436, the thin portion 434, and the inner annular portion 432 at a position closer to the one end side of the thinner portion 434; the annular space SP is used as The pressure chamber R430 which imparts a crimping force to the rolling elements 450 is used.

The outer race side rolling surface 430a on which the rolling elements 450 are rolled is directly formed on the entire circumference of the inner circumferential surface of the inner annular portion 432. The outer race side rolling surface 430a is a concave curved surface 430a having a substantially arc-shaped cross-sectional shape. The substantially circular arc shape is formed such that the rolling elements 450 are in contact with each other at a contact angle α4. Thereby, the rolling surface 430a can engage the rolling elements 450 from both sides in the radial direction and the axial direction at the contact angles α1, α4 while cooperating with the rolling surface 420a of the inner race 420.

More specifically, the inner annular portion 432 is provided on the one end side of the substantially central position of the outer annular portion 436 in the axial direction as described above, whereby the contact position P4 with the rolling element 450 is located at a relatively rolling position. The center of the core C450 of the body 450 is closer to one end side in the axial direction; and the contact position P1 of the inner race 420 is located closer to the other end side than the substantially central position of the axial direction, whereby the contact position P1 is located at a more rolling side. The core C450 of the body 450 is further on the other end side. Therefore, the outer race 430 and the inner race 420 can sandwich the rolling elements 450 from the inner side and the outer side in the radial direction at the respective contact angles α4 and α1.

Further, in the annular space SP of the pressure chamber R430 shown in Fig. 16, an annular plug member 440 is inserted from one end side in the axial direction and fixed to the outer race 430, whereby the annular space can be The other end side area of the SP ensures the size of the pressure chamber R430 The volume is sealed at the same time. Here, the fixing of the plug member 440 to the outer race 430 is performed only on the outer annular portion 436, and the inner annular portion 432 is not performed. In other words, the plug member 440 is fixed to the inner circumferential surface of the outer annular portion 436 so as to be relatively movable by screwing or the like, but is opposed to the inner annular portion 432 by a specific gap G, that is, The plug member 440 and the inner annular portion 432 are in a non-contact state.

Therefore, when the thin portion 434 is elastically deformed in the axial direction by the supply and pressurization of the pressurized fluid to the pressure chamber R430, the inner annular portion 432 smoothly moves in the axial direction in response to the elastic deformation. The pressure contact operation of the rolling elements 450 is smoothly performed by the movement of the inner annular portion 432 in the axial direction.

In other words, when the supply pressure of the pressurized fluid is increased and the thin portion 434 is elastically deformed toward the other end side in the axial direction, the inner annular portion 432 is moved to the other end side, whereby the inner annular portion 432 is illustrated. The contact angle α4 shown at 16 presses the rolling element 450, and the rolling element 450 is pressed to the rolling surface 420a of the inner race 420 at the contact angle α1. As a result, the rolling body 450 is crimped to the outer race. The state of 430 and inner race 420.

When the supply pressure of the pressurized fluid is lowered, the elastic deformation of the other end side of the thin portion 434 in the axial direction is reduced, and the inner annular portion 432 is returned to one end side in the axial direction, and the rolling element 450 is rolled. The crimping state is alleviated, and if the supply pressure of the pressurized fluid is reduced to zero, the crimping state of the outer race 430 and the inner race 420 of the rolling element 450 is completely released, that is, the non-crimping state is obtained. .

In the pressure bonding process, as described above, the thin portion 434 is elastically deformed in the axial direction and the inner annular portion 432 is moved in the axial direction, but at this time, as described above, the metal contact portion hardly occurs. Relative to each other. So, a few can be completely Prevent slippage. Therefore, the pressure contact force between the rolling element 450 and the outer race 430 and the inner race 420 is smoothly and rapidly changed in conjunction with the increase and decrease of the supply pressure, whereby the pressure contact force can be accurately imparted and the pressure can be accurately performed. Change of relay (change of preload). Further, since the pressure contact force is smoothly changed in conjunction with the supply pressure of the pressurized fluid, the pressure contact force can be smoothly and freely adjusted to an arbitrary target value.

The supply of the pressurized fluid to the pressure chamber R430 is performed by the supply hole 440h which is perforated in the plug member 440. In the example of FIG. 16, the supply hole 440h is formed to penetrate the plug member 440 in the axial direction, that is, at the other end surface 440ef of the plug member 440, one of the supply holes 440h is exposed to the pressure chamber R430. One end face 440eb of the plug member 440 is exposed on the outer side of the outer race 430. A pipe or a manifold member or the like as a flow path of the pressurized fluid is connected to the mouth of the latter to supply a pressurized fluid to the pressure chamber R430. Details of this content are described below. The number of the supply holes 440h may be one or plural. Further, the pressurized fluid is usually a hydraulic oil for hydraulic pressure, but may be compressed air or a fluid other than the above.

Further, in the second example, in order to prevent the pressurized fluid from leaking from the pressure chamber R430, as shown in Fig. 16, a ring is interposed between the inner circumferential surface of the outer annular portion 436 and the outer peripheral surface of the plug member 440. The gasket 445 is further provided with an annular gasket 447 between the inner circumferential surface of the plug member 440 and the outer circumferential surface of the inner annular portion 432. Here, as for the latter washer 447, a rubber or a resin can be used, whereby the inner circumferential surface and the inner annular portion 432 of the washer 447 that relatively slide when the inner annular portion 432 moves in the axial direction. The contact of the outer peripheral surface also becomes a non-metallic contact, so that the occurrence of the slip phenomenon can be completely suppressed. Incidentally, in order to prevent the washer 445 and the washer 447 from coming off the plug member 440, the plug member 440 A groove 440t1 of the locking washer 445 and a groove 440t2 of the locking washer 447 are formed on the outer circumference and the inner circumference, respectively.

A special ball bearing 411 having a part of such a preloading mechanism 480 is incorporated with reference to Fig. 14, as described above, on the other end side of the through hole 3h of the outer casing 3, and on the one end side. There is a universal ball bearing 510. The ball bearings 411 and 510 rotatably support the main shaft 5 inserted into the through hole 3h around the axis C5 of the main shaft 5.

As shown in FIG. 14, the universal ball bearing 510 has an inner race 520, an outer race 130, a plurality of spherical rolling bodies 550 that are lined up between the two, and the rolling bodies 550 are held to each other. A holder 560 in a non-contact state. Further, the general-purpose ball bearing 510 is disposed in a so-called back combination with the special ball bearing 411 as described above. Therefore, the radial load and the axial load in both directions can be supported by the special ball bearing 411 and the universal ball bearing 510. For example, when an axial load toward the one end side (right side) acts on the main shaft 5, the axial load is supported by the special ball bearing 411; and the shaft is oriented toward the other end side (the left side in the drawing). When the load acts, the axial load is supported by the universal ball bearing 510.

The outer race 530 of the universal ball bearing 510 is inserted into the through hole 3h of the outer casing 3 and disposed at a specific position on one end side in the axial direction. Further, the outer casing 3 is fixed to the outer casing 3 so as not to be movable relative to the outer casing 3 in the radial direction and the axial direction. Further, the inner race 520 of the universal ball bearing 510 is disposed such that the inner peripheral side thereof is inserted with the main shaft 5 at a specific position on one end side in the axial direction. Further, the spindle 5 is fixed to the spindle 5 so as not to be relatively movable in the radial direction and the axial direction with respect to the spindle 5.

On the other hand, the outer race 430 of the special ball bearing 411 is inserted into the through hole 3h of the outer casing 3 and disposed at a specific position on the other end side in the axial direction. Further, the outer casing 3 is fixed to the outer casing 3 so as not to be movable relative to the outer casing 3 in the radial direction and the axial direction. Further, the inner race 420 of the special ball bearing 411 is disposed such that the inner peripheral side is inserted with the main shaft 5 at a specific position on the other end side in the axial direction. Further, the spindle 5 is fixed to the spindle 5 so as not to be relatively movable in the radial direction and the axial direction with respect to the spindle 5.

In this configuration, when the pressurized fluid is supplied to the pressure chamber R430 of the special ball bearing 411 and the preload is applied, the preload is applied to the special ball bearing 510 not only to the special ball bearing 411. The following is explained.

First, the special ball bearing 411 is disposed on the other end side in the axial direction by the back surface combination, and therefore, the direction thereof is a direction in which the axial load toward the one end side can be supported. That is, it is configured such that when the pressurized fluid is supplied to the pressure chamber R430, the thin portion 434 of the outer race 430 is elastically deformed toward the other end side and the inner annular portion 432 is moved in the direction.

When the pressurized fluid is supplied to the pressure chamber R430 of the special ball bearing 411, as described above, the elastic deformation of the thin portion 434 toward the other end side is transmitted, and the inner annular portion 432 presses the rolling element 450 toward the other end side. The rolling body 450 presses the inner race 420 toward the other end side at the contact angle α1. Therefore, first, the rolling element 450 of the special ball bearing 411 is in a state of being pressed by the inner race 420 and the outer race 430. That is, the special ball bearing 411 is in a state of being preloaded.

On the other hand, since the inner race 420 is fixed to the main shaft 5, the inner race 420 is pressed toward the other end side, so that the main shaft 5 is also pressed toward the other end side. borrow Therefore, the inner race 520 of the universal ball bearing 510 fixed to the main shaft 5 is also pressed toward the other end side, and the inner race 520 presses the rolling body 550 toward the other end side at the contact angle α1. As a result, the rolling elements 550 are pressed against the race 530 fixed to the outer casing 3 at the contact angle α4. As a result, the rolling element 550 of the universal ball bearing 510 is in a state of being pressed by the inner race 520 and the outer race 530, and the preload is also applied to the universal ball bearing 510.

Incidentally, in the second example, the outer races 530 and 430 of the respective ball bearings 510 and 411 are fixed to the outer casing 3, and the inner races 520 and 420 of the respective ball bearings 510 and 411 are fixed to the main shaft 5 This is done, for example, in the following manner.

First, the outer race 530 of the universal ball bearing 510 is inserted into the through hole 3h from the small-diameter cylindrical portion 3c which protrudes from the one end surface 3ea of the outer casing 3. Here, the inner diameter of the through hole 3h is in the range Aea from the small diameter cylindrical portion 3c to a specific position in the axial direction, and is substantially the same as the outer diameter of the outer race 530, and the fitting tolerance is set. Therefore, in the operation of the machine tool, the inner circumferential surface of the through hole 3h and the outer circumferential surface of the outer race 530 abut on the entire circumference. Thereby, the seat ring 530 inserted into the through hole 3h is fixed to the outer casing 3 so as not to be relatively movable in the radial direction. Further, at the specific position of the through hole 3h, a step surface 3hs1 in which the inner diameter of the through hole 3h is reduced in diameter is formed. Therefore, the other end surface of the outer race 530 abuts against the step surface 3hs1. Thereby, the outer race 530 is fixed relative to the outer casing 3 so as not to be movable relative to each other in the axial direction.

On the other hand, the main shaft 5 is inserted into the inner peripheral side of the inner race 520 of the universal ball bearing 510. Here, the outer diameter of the main shaft 5 is within a range from the substantially other end of the main shaft 5 to a specific position on one end side in the axial direction, and is substantially the same as the inner diameter of the inner race 520, and the fitting tolerance thereof is adopted. Is set to be within the inner race 520 under the operation of the machine tool The circumferential surface and the outer peripheral surface of the main shaft 5 abut on the entire circumference. Thereby, the inner race 520 into which the main shaft 5 is inserted is fixed relative to the main shaft 5 so as not to be relatively movable in the radial direction. Further, at the specific position of the main shaft 5, a step surface 5s1 in which the outer diameter of the main shaft 5 is expanded is formed. Therefore, one end surface of the inner race 520 abuts against the step surface 5s1, and the other end surface of the inner race 520 abuts against the spacer 6a described below. Thereby, the inner race 520 is fixed relative to the main shaft 5 so as not to be movable relative to each other in the axial direction.

Similarly, the outer race 430 of the special ball bearing 411 is inserted into the through hole 3h from the other end side opening portion 3heb of the other end surface 3eb of the outer casing 3. Here, the inner diameter of the through hole 3h is in the range Aeb from the other end side opening portion 3heb to a specific position in the axial direction, and is substantially the same as the outer diameter of the outer race 430, and the fitting tolerance is set. Therefore, in the operation of the machine tool, the inner circumferential surface of the through hole 3h and the outer circumferential surface of the outer race 430 abut on the entire circumference. Thereby, the seat ring 430 is inserted into the through hole 3h, and the seat ring 430 is fixed relative to the outer casing 3 so as not to be relatively movable in the radial direction. Further, at the specific position of the through hole 3h, a step surface 3hs2 in which the inner diameter of the through hole 3h is reduced in diameter is formed. Therefore, one end surface of the outer race 430 abuts against the step surface 3hs2, and the pressing member 4b for stopping is abutted against the other end surface of the outer race 430 from the side of the other end side opening portion 3heb. Thereby, the outer race 430 is fixed relative to the outer casing 3 so as not to be movable relative to each other in the axial direction. Further, the pressing member 4b is fixed to the outer casing 3 so as not to be movably by screwing or screwing or the like.

On the other hand, the main shaft 5 is inserted into the inner peripheral side of the inner race 420 of the special ball bearing 411. Here, the outer diameter of the main shaft 5 is at least in the range from the other end of the main shaft 5 to the specific position, and is substantially the same as the inner diameter of the inner race 420, and the fitting tolerance is set to Under the operation of the machine tool, the inner circumference of the inner race 420 is outside the main shaft 5 The circumference is in full contact throughout the week. Thereby, the inner race 420 into which the main shaft 5 is inserted is fixed so as not to be relatively movable with respect to the main shaft 5 in the radial direction. Further, in a portion between the inner race 520 of the universal ball bearing 510 in the main shaft 5 and the inner race 420 of the special ball bearing 411, the cylindrical spacer 6a is configured to cover the outer peripheral surface of the main shaft 5, the spacer The total length of the axial direction of 6a is set to be substantially the same value as the distance Ls between the step surface 3hs1 and the step surface 3hs2 of the through hole 3h. Therefore, the other end surface of the inner race 520 of the universal ball bearing 510 abuts against one end surface of the spacer 6a, and one end surface of the inner race 420 of the special ball bearing 411 abuts against the other end surface of the spacer 6a. The other end surface of the inner race 420 abuts against a suitable stopper pressing member 6b having a nut 6n or a collar member 6c. Thereby, the inner race 420 is fixed relative to the main shaft 5 so as not to be movable relative to each other in the axial direction. Further, the pressing member 6b is fixed to the main shaft 5 so as not to be movable by screwing or the like.

Incidentally, in the example of Fig. 14, in the outer casing 3, a flow path 3k2 for supplying a pressurized fluid to the supply hole 440h of the plug member 440 is formed in a bifurcated tubular shape, whereby the pressure chamber for the special ball bearing 411 is obtained. R430 supplies pressurized fluid.

Further, the value of the preload of the common bearing formed by the special ball bearing 411 and the universal ball bearing 510 is changed to an appropriate value while monitoring the state of the common bearing. This point has been described above, but the following will be described in detail.

<<<Basic ideas about preload control of common bearings>>

Fig. 17A is a schematic center sectional view of a conventional rolling bearing 11', and Fig. 17B is a BB sectional view of Fig. 17A. Further, Fig. 18 is a graph showing the dynamic friction loss characteristics of the rolling bearing 11' which is generally known. The vertical axis of the graph is the dynamic friction loss (W) of the rolling bearing 11', and the horizontal axis is the rotational speed of the spindle 5 (rpm (min ^-1 )) supported by the rolling bearing 11'.

As shown in Fig. 18, if the rotational speed N _{5 of the} main shaft 5 becomes larger due to the driving rotation of the main shaft 5, the dynamic friction loss of the rolling bearing 11' also becomes large; and the reason is that the rolling is accompanied by the increase of the rotational speed N ₅ of the main shaft 5 The relative sliding between the body 50' and the rolling surface 20a' of the inner race 20' or the rolling surface 30a' of the outer race 30' becomes larger. In other words, if the rotational speed N ₅ (rpm) of the main shaft 5 becomes large, the rotational speed N ₅₀ (hereinafter also referred to as the revolution speed V ₅₀ ) of the rolling elements 50 ′ around the main shaft 5 shown in FIG. 17B also becomes large, so that rolling The centrifugal force Fc of the body 50' also becomes large, but in this way, the rolling element 50' is easily separated from the rolling surface 20a' of the inner race 20' which rotates integrally with the main shaft 5, so that the rolling body 50' becomes It is difficult to obtain the driving force from the inner race 20'. As a result, the rolling element 50' is largely slid on the side delayed with respect to the rolling surface 20a' of the inner race 20', and the dynamic friction loss is increased.

Therefore, it is necessary to pay attention to relative sliding when monitoring the state of the rolling bearing 11'.

On the other hand, from the perspective of the giant view, the effect of the relative sliding can be understood as the retardation N ₆₀ of the retainer 60' is delayed relative to the rotational speed N _{5 of the} main shaft 5. The details are as follows. As described above, the retainer 60' has an annular member that accommodates the hole portion 60h' of the rolling element 50' for each of the rolling elements 50'. Further, the retainer 60' is rotated about the main shaft 5 integrally with the rolling element 50' by the rolling element 50' which is rolled by the inner race 20' to obtain a driving force about the main shaft 5. That is, the holder 60 'based equivalent rolling bodies 50' of the revolution speed N ₅₀ of the speed V ₅₀ rotates. Thus, the rolling body 50 'of the system affect the relative sliding movement through the rolling bodies 50' of the revolution speed of ₅₀ V decreases, while the holder 60 'is drawn up of the rotational speed N ₆₀ of the reduced form presented, therefore, maintained by monitoring The rotational speed N _{60 of the} device 60' can grasp the state of relative sliding between the rolling element 50' and the rolling surface 20a' of the inner race 20', that is, the state of the rolling bearing 11'.

Fig. 19 is a graph showing the relationship between the reduction rate R of the rotational speed N ₆₀ of the retainer 60' and the dynamic friction coefficient of the rolling bearing 11' obtained by the inventors of the present invention. The dynamic friction coefficient of the rolling bearing 11' on the vertical axis has the same meaning as the dynamic friction loss of the above-described rolling bearing 11'. Moreover, the rate of decrease R (%) of the number of revolutions N ₆₀ of the retainer 60' on the horizontal axis is obtained by the following formula 1. That is, if the rotational speed of the ideal state in which the retainer 60' is rotated without delay relative to the main shaft 5 is set to the theoretical rotational speed N ₀ (rpm) of the retainer 60', the actual rotational speed of the retainer 60' is N ₆₀ (rpm). The ratio of how much is reduced compared to the theoretical rotational speed N ₀ . Incidentally, the theoretical rotational speed N ₀ is obtained by converting the actual rotational speed N ₅ (rpm) of the main shaft 5 into the rotational speed of the retainer 60' by the following Equation 2, and "d" in the following Equation 2 For the diameter of the rolling element 50', "α" is the contact angle between the inner race 20' of the bearing 11' and the outer race 30' and the rolling body 50, and "Dp" is the pitch diameter of the rolling body 50'.

In Fig. 19, the curve shows the number of revolutions N ₅ of the spindles 5 of the three levels of high-speed rotation, medium-speed rotation, and low-speed rotation, and the respective curves are obtained as follows. First, the rotational speed is selected from the above three levels to maintain the rotational speed N _{5 of the} main shaft 5 at the rotational speed. Then, under the condition that the rotation speed N _{5 is} fixed, the magnitude of the preload applied to the bearing 11' is gradually increased, and in the increasing process, the reduction rate R of the rotation speed N ₆₀ of the holder 60' is corresponding thereto. The power value (W) of the drive motor of the spindle 5 is recorded, thereby obtaining the curves of Fig. 19. Further, the value of the dynamic friction coefficient of the vertical axis is obtained by converting the dynamic value (W) of the above-described drive motor into a dynamic friction coefficient using a well-known conversion formula. Therefore, as described above, the longitudinal axis of the curve has the same meaning as the dynamic friction loss.

Referring to Fig. 19, it is understood that the dynamic friction coefficient is extremely small when the rate of decrease R of the rotational speed N ₆₀ of the retainer 60' is within a specific range as a whole. For example, in the range where the reduction rate R of the rotational speed N ₆₀ is greater than 0% and less than 10%, the dynamic friction coefficient, that is, the dynamic friction loss is extremely small.

Further, in Fig. 19, the direction in which the preload is increased is also indicated by an arrow, and the preloading area where the preload is relatively small, the preloading excess area having a relatively large preload, and the preloading amount are The appropriate pre-compression area between the two is illustrated. It can be seen that the rate of decrease R of the rotational speed N ₆₀ of the retainer 60' is substantially reduced with the increase of the pre-pressure, except for the excess pre-pressure region at the left end in FIG. small. Therefore, the reduction rate R of the rotation speed N ₆₀ of the adjustment holder 60' can be increased or decreased by the increase/decrease adjustment of the preload.

Further, based on the findings obtained above, in the preload automatic adjusting bearing device 410 of the conventional bearing of the second example described above, in order to maintain the state of the common bearing well, the magnitude of the preload is controlled so that the retainer 60 is The rate of decrease R of the number of revolutions is within a predetermined specific range.

Incidentally, when the curve of the low-speed rotation, the curve of the medium-speed rotation, and the curve of the high-speed rotation of FIG. 19 are compared in detail, it is understood that the rate of decrease of the dynamic friction coefficient is extremely small because the number of revolutions N _{5 of the} spindle 5 is different. For example, in the low-speed rotation, the dynamic friction coefficient is extremely small in the range of the reduction rate a1 to a2; in the medium-speed rotation, the dynamic friction coefficient is extremely small in the range of the reduction rate b1 to b2; and in the case of the high-speed rotation, The dynamic friction coefficient is extremely small in the range of the reduction rate c1 to c2. Therefore, it is preferable that the respective ranges of the rotational speed N ₅ of the main shaft 5 are respectively set to the target range to be maintained at the lowering rate R of the rotational speed N ₆₀ of the retainer 60'; and the insight is also reflected in the common bearing described below. The preload is automatically adjusted in the bearing device 410.

<<<Pre-pressure automatic adjustment bearing device 410 for common bearings>>>

Fig. 20 is a schematic view showing the configuration of a preload automatic adjusting bearing device 410 for a common bearing, and a portion of the special ball bearing 411 is shown by a schematic center cross section.

The preload automatic adjustment bearing device 410 has a special ball bearing 411 as a common bearing, which supports the main shaft 5 to the outer casing 3, a preload applying mechanism 480 which imparts a preload to the special ball bearing 411, and a control portion 490 whose control pre The pressure applying mechanism 480; and various sensors 495, 497 that measure the state of the bearing 411 and output the measurement data to the control unit 490.

As shown in FIG. 20, the common bearing of the so-called preload control object is a special ball bearing 411 having an inner race 420, a race 430 having a built-in pressure chamber R430, a rolling body 450, and a retaining body. 460. However, as described above, when the preload of the special ball bearing 411 is changed, the preload of the universal ball bearing 510 of FIG. 14 is also changed by the transmission of the force in the axial direction by the spacer 6a or the like. The ball bearing 510 is also indirectly controlled by the preload.

The preloading mechanism 480 has, for example, an actuator that can bias the outer race side rolling surface 430a with a force that causes the outer race side rolling surface 430a to press the rolling element 450 toward the inner side in the radial direction. In this example, there is a pressure built into the outer race 430. The force chamber R430 serves as the actuator. In addition to the actuator, the preload applying mechanism 480 has a flow path 3k2 for pressurizing fluid formed in the outer casing 3, a flow path forming member 482 (not shown) connected to the flow path, and the like; The flow path forming member 482 is a pump 485 which is a supply source of pressurized fluid, and a pressure regulating valve 487 provided in a part of the flow path forming member 482. The pressure regulating valve 487 adjusts the supply pressure to the pressure chamber R430 based on the pre-pressure control signal S490 transmitted from the control unit 490. Therefore, by the adjustment of the supply pressure, the pressure contact force between the rolling element 450 and the outer race 430 and the inner race 420 can be adjusted to a desired arbitrary value.

The various sensors 495, 497 include: a holder rotational speed sensor 495 that measures the rotational speed of the retainer 460 and outputs the measured data of the measured rotational speed N ₆₀ ; and a spindle rotational speed sensor 497, which is The rotational speed N _{5 of the} main shaft 5 is measured, and the measured data of the measured rotational speed N _{5 is} immediately output. The holder rotation speed sensor 495 is disposed in the vicinity of the holder 460; the spindle rotation speed sensor 497 is disposed in the vicinity of the main shaft 5. Further, the sensors 495 and 497 use, for example, a pulse generator or an encoder, and each measurement data is sequentially transmitted to the control unit 490.

The control unit 490 is, for example, a computer or a PLC (Programmable Logic Control), and has a processor and a memory. The processor reads and executes the control program stored in the memory in advance, thereby functioning as various functional blocks shown in FIG.

In other words, the control unit 490 includes a holder theoretical rotation speed calculation unit, a holder rotation speed reduction rate calculation unit, and a holder rotation speed reduction rate quality determination unit as the functional blocks.

The spindle rotational speed sensor 497 instantaneously and sequentially transmits the measurement data of the rotational speed N ₅ of the main shaft 5 to the retainer theoretical rotational speed computing unit. Then, the arithmetic unit substitutes the measured value of the rotational speed N ₅ indicated by the measurement data into the above formula 2, and calculates the theoretical value of the rotational speed of the retainer 460, that is, the theoretical rotational speed N ₀ .

The holder rotation speed sensor 495 sequentially transmits the measurement data of the rotation speed of the holder 460 to the holder rotation speed reduction rate calculation unit; further, the above-described holder theoretical rotation speed calculation unit sequentially transmits the theoretical rotation speed N ₀ to the holder rotation speed reduction rate calculation unit. . Then, the holder rotation speed reduction rate calculation unit substitutes the measured value of the rotation speed N ₆₀ indicated by the measurement data and the theoretical rotation speed N ₀ into the above-described formula 1, and sequentially calculates the reduction rate R of the rotation speed of the holder 460 (%). ).

In the holder rotation speed reduction rate determination unit, the reduction rate R (%) successively calculated by the holder rotation speed reduction rate calculation unit is compared with the specific threshold data stored in the memory in advance, thereby The reduction rate R (%) is judged whether or not it is good or bad. Further, when the determination result is "good", that is, when the reduction rate R% is within the accuracy range determined by the upper limit value and the lower limit value of the threshold data, the value of the current preload is maintained. When the determination result is "NO", that is, when the reduction rate R% deviates from the above accurate range, the pre-compression control signal S490 is transmitted to the preload applying means 480 so that the reduction rate R (%) converges. The exact range specified by the upper and lower limits of the above threshold data.

For example, when the reduction rate R deviates to a positive "No" determination on the side greater than the upper limit of the accurate range, it is determined that the preload is insufficient, and the value of the preload is increased by a specific value. It is transmitted to the preloading mechanism 480; and when the lowering rate R deviates to a negative "No" side of the side lower than the lower limit of the accurate range, it is determined that the preloading has occurred. The control signal S490, which is smaller than the current value of the preload, is reduced to a specific value, and is transmitted to the preloading mechanism 480.

The transmission processing of the quality determination processing and the control signal S490 is repeatedly executed in a specific control cycle of several milliseconds to several tens of milliseconds, whereby the preload is frequently adjusted in accordance with the state of the bearing 11.

The method of determining the upper limit value and the lower limit value of the reduction rate R is determined in advance, for example, from the curve of FIG. 19, in which the dynamic friction coefficient is read to a specific range of the minimum reduction rate R. For example, in the case of low-speed rotation, the dynamic friction coefficient is extremely small in the range of the reduction rate a1 to a2. Therefore, the lower limit value is determined in advance as a1, and the upper limit value is determined in advance as a2, and is stored in the memory as a threshold in advance. data. Incidentally, the relationship of the graph of FIG. 19 is obtained by performing a preliminary experiment or the like on the special ball bearing 411 of the object.

Further, as described above with reference to Fig. 19, the range in which the dynamic friction coefficient is extremely small, that is, the range of accuracy, that is, the accurate range changes in accordance with the rotational speed N _{5 of the} main shaft 5. That is, in the low-speed rotation, the dynamic friction coefficient is extremely small in the range of the reduction rate R from a1 to a2; but in the medium-speed rotation, the dynamic friction coefficient is extremely small in the range of the reduction rate R from b1 to b2; In the case of rotation, the dynamic friction coefficient is extremely small in the range where the reduction rate R is c1 to c2.

Therefore, in the memory of the control unit 490, the threshold data lower limit value and the upper limit value for the above-described quality determination processing are stored in accordance with the respective rotational speed levels of the low speed rotation, the medium speed rotation, and the high speed rotation. For example, in low speed rotation, the lower limit is a1 and the upper limit is a2; in the medium speed rotation, the lower limit is b1 and the upper limit is b2; in addition, in high speed rotation, the lower limit is c1 and upper The limit is c2.

In the holder rotation speed reduction rate determination unit, the upper limit value and the lower limit value are obtained from the memory based on the measurement data of the rotation speed N ₅ of the spindle 5 transmitted from the autonomous axis rotation speed sensor 497. The above-mentioned good or bad determination process. For example, when the measurement data of the rotational speed N ₅ of the main shaft 5 corresponds to the low-speed rotation, a1 is selected as the lower limit value a1, b1, c1 and the upper limit values a2, b2, and c2 from the threshold data of the memory. The limit value is selected and a2 is selected as the upper limit value, and the above-described goodness determination processing is performed.

Further, the low-speed rotation, the medium-speed rotation, and the high-speed rotation are not predetermined as precise punctuation but are determined in advance by the range of the rotational speed N ₅ . For example, the rotation at a low speed is N ₅ <N1, the medium-speed rotation is N1≦N ₅ <N2, the high-speed rotation is N2≦N _{5 ,} and the like, and is determined in advance by the range of the rotation speed N ₅ .

Further, in the above examples, the threshold data is provided as a numerical value expressed in percentages such as a1 and a2, but the present invention is not limited thereto. For example, the threshold data may be provided by a ratio of a1 or a2 divided by a specific reference value a0. That is, for the threshold data of the low-speed rotation, a1/a0 may be the lower limit value, or a2/a0 may be the upper limit value. In this case, the reduction rate R is also changed to the reference value a0 and is changed to R/a0 for the quality determination process.

Further, in the above example, as shown in Figs. 14 and 20, the spindle rotational speed sensor 497 is disposed in the vicinity of the main shaft ₅ to measure the rotational speed N ₅ of the main shaft 5, and is output from the sensor 497. The measurement data of the rotational speed N ₅ of the spindle 5 is calculated for the theoretical rotational speed N ₀ of the retainer 460, but is not limited thereto. For example, the main shaft 5 is normally driven to rotate by an electric motor. In the electric motor, generally, in order to control the rotational speed N _{5 of the} main shaft ₅ , a sensor such as an encoder that measures the rotational speed N ₅ is provided. Therefore, the measurement data outputted from the sensor can be transmitted to the control unit 490 described above for the calculation of the theoretical rotational speed N ₀ ; or sometimes the rotational speed N ₅ for controlling the rotational speed of the electric motor can be used. The command signal is transmitted to the above-described control unit 490 and is used for the calculation of the theoretical rotational speed N ₀ . Moreover, the spindle speed sensor 497 can be omitted as such.

21A is a view showing a state in which the control unit 90 of the auxiliary bearing device 10 and the control unit 490 of the preload automatic adjustment bearing device 410 cooperate with each other in the support structure (FIG. 14) of the spindle 5 of the second example described above. The control model of the preload that is obtained. The horizontal axis is the number of revolutions of the main shaft 5, and the vertical axis is the total value of the preload applied to the main shaft 5 by the common bearings 411 and 510 and the auxiliary bearing 11.

In the low-speed rotation region, the auxiliary bearing 11 is in an effective state of the bearing. Therefore, in addition to the preload of the common bearings 411 and 510, the preload of the auxiliary bearing 11 is also acted upon, and the preload is in a large state. On the other hand, if the rotational speed N _{5 of the} main shaft 5 exceeds the threshold value Nth, the auxiliary bearing 11 is switched to the bearing ineffective state, and the preload is reduced only based on the usual bearings 411, 510.

And, in relation to common bearing preload 411,510, the train is controlled, so that the retainer to reduce the ratio R 460 corresponding to a specific range and the rotational speed N ₅ decision a1 ~ a2, b1 ~ b2, c1 ~ c2 Therefore, the result is a curve depicting the model as shown in Fig. 21A. Incidentally, the magnitude of the preload in the high-speed rotation region is gradually increased because the centrifugal force Fc acting on the rolling elements 450 becomes large and the relative sliding between the rolling elements 450 and the inner race 420 becomes conspicuous. That is, the reason is that the preload of the usual bearings 411, 510 is automatically increased based on the reduction rate R in order to suppress the relative slip.

Further, the pre-compression of the common bearings 411 and 510 may be controlled based on the rotation speed N _{5 of the} main shaft 5 instead of the reduction ratio R of the retainer 460 described above. Fig. 21B is an explanatory diagram showing an example of the control model of the preload.

The situation of Fig. 21B is also rotated at a low speed as in the case of Fig. 21A. Since the auxiliary bearing 11 in the region is in an effective state of the bearing, in addition to the preload of the common bearings 411 and 510, the preload of the auxiliary bearing 11 is also actuated, so that the preload is in a large state. Further, in this example, with respect to the preload applied to the common bearings 411, 510, the preload in the medium-speed rotation region is more stepwise reduced than in the low-speed rotation region; and compared with the medium-speed rotation region. The preload in the high-speed rotation region is stepped down more, because the medium-speed rotation region and the high-speed rotation region are more preferentially compared with the rigidity of the main shaft 5, so the rotation resistance is required. Reduced.

===Other implementations ===

The embodiment of the present invention has been described above, but the present invention is not limited to the embodiment, and the following modifications can be made without departing from the spirit and scope of the invention.

In the above-described embodiment, the support structure of the spindle 5 of the power tool is exemplified as an application example of the auxiliary bearing device 10 of the present invention. However, the present invention is not limited thereto, and may be applied as long as it supports the shaft member.

In the above-described embodiment, the buoyancy generating mechanism 70 is exemplified by a mechanism for supplying compressed air to the inner race side clearance S20 between the retainer 60 and the inner race 20, but the present invention is not limited thereto. For example, in the case where the rolling element 50 is made of iron or the like, if the outer race 30 is formed by a strong magnet, the rolling element 50 can be floated from the inner race 20 by the magnetic force thereof, and the configuration is also included in the present invention. Within the scope. However, in this case, the material of the rolling element 50 is limited to the material that reacts to the magnetic force, and therefore, the buoyancy generating mechanism 70 that is still compressed air is preferable.

In the above embodiment, the inner race in one of the axial end directions The size S20e1 of the side gap S20, the size S20e2 of the inner race side clearance S20 in the other end side in the axial direction, the size S30e1 of the outer race side side gap S30 in one end side in the axial direction, and the other axial direction The magnitude relationship of the size S30e2 of the outer race side side gap S30 in one end side is described. However, if the definition of the size of each of the gaps is described in more detail, it means a gap in the position as described below. size. First, the size S20e1 of the inner race side clearance S20 in one end side in the axial direction means a position closer to one end side in the axial direction than the rolling elements 50 (150, 250, 350, 350a) (for example, one end portion) The size of the inner race side clearance S20 in the position); the size S20e2 of the inner race side clearance S20 in the other end side in the axial direction means the shaft is closer to the shaft than the rolling elements 50 (150, 250, 350, 350a) The size of the inner race side side gap S20 on the other end side of the direction (for example, the position of the other end portion). Similarly, the size S30e1 of the outer race side side gap S30 in one end side in the axial direction means a position closer to one end side in the axial direction than the rolling element 50 (150, 250, 350, 350a) (for example, one end portion) The position of the outer race side side gap S30; the size of the outer race side clearance S30 in the other end side of the axial direction S30e2 means that the rolling element 50 (150, 250, 350, 350a) is more The position of the other end side of the axial direction (for example, the position of the other end portion) is the size of the outer race side side gap S30.

3‧‧‧Shell (support member)

5‧‧‧ Spindle (shaft member)

11‧‧‧Auxiliary Bearing

20‧‧‧ inner seat (equivalent to the inner seat)

20a‧‧‧Inside race side rolling surface (shaft member side rolling surface)

20b, 60b‧‧‧ outer perimeter

30‧‧‧Outer seat (equivalent to the components of the outer race)

30a‧‧‧Outer race side rolling surface (support member side rolling surface)

30b, 60a‧‧‧ inner circumference

50‧‧‧ rolling elements

60‧‧‧keeper

60h‧‧‧ hole department

60w1, 60w2‧‧‧ wall

D23‧‧‧ interval

D50‧‧‧ diameter

G50‧‧‧ gap

G60h‧‧‧Small gap

R70‧‧‧Supply room

S20‧‧‧inner side clearance

S20e1‧‧‧The size of the inner race side clearance S20 in one end side

S20e2‧‧‧ The size of the inner race side clearance S20 in the other end side

S30‧‧‧Outer seat side clearance

S30e1‧‧‧The size of the outer race side side clearance S30 in the one end side

S30e2‧‧‧The size of the outer race side clearance S30 in the other end side

Claims (10)

An auxiliary bearing device characterized in that it is additionally provided in a support member provided with a bearing for supporting a rotatable drive-rotating shaft member, and has a plurality of rolling elements; a shaft member side rolling surface, a ring member is disposed on the shaft member and is rotatable by the rolling element; a support member side rolling surface is annularly disposed on the support member and is rotatable by the rolling element; and the member is fixed to the support member The annular ring corresponds to the member of the outer race, and the support member side rolling surface is formed on the inner circumferential surface of the member corresponding to the outer race; and the switching mechanism is in contact with the support member side. The contact state between the rolling surface and the rolling surface of the shaft member side is switched between the two states of the non-contact state in which the rolling element floats from the rolling surface of the shaft member, and the switching mechanism includes a buoyancy generating mechanism. The rolling element provides a buoyancy of the rolling element in a direction away from the outer side in the radial direction of the rolling direction of the shaft member side; and a preload applying mechanism; The rolling element is pressed against the shaft member side rolling surface by applying a preload to move the support member side rolling surface of the member corresponding to the outer race to the inner side in the radial direction; The contact state is formed by pressing, and the non-contact state is formed by releasing the application of the preload. An auxiliary bearing device according to claim 1, wherein An annular retainer that is held in the rotation direction in a state in which a space between the rolling elements adjacent to each other in the rotation direction of the shaft member is arranged in the plurality of rolling elements; The position of the retainer is limited by the contact of the retainer with the member corresponding to the outer race. The auxiliary bearing device according to claim 2, wherein each of the retainers has a hole portion penetrating in a radial direction, and the rolling element is inserted into the hole portion to have a gap with the hole portion. Thereby, the relative movement of the rolling elements with respect to the radial direction of the retainer is allowed. The auxiliary bearing device of claim 2, wherein the buoyancy generating mechanism has a member corresponding to the inner race, and the buoyancy generating mechanism is configured by the retainer and the member corresponding to the inner race. The gap between the two is supplied with compressed air to impart buoyancy to the rolling element on the outer side in the radial direction. The auxiliary bearing device of claim 4, wherein the compressed air is supplied to the gap from one end side in the axial direction, and the retainer in the other end side in the axial direction is between the member corresponding to the inner race and the member corresponding to the inner race The gap is smaller than the gap between the retainer in the one end side and the member corresponding to the inner race. The auxiliary bearing device of claim 4 or 5, wherein a gap between the retainer in the other end side in the axial direction and the member corresponding to the outer race is larger than the retainer in the other end side The above corresponds to the gap between the members of the inner race. The auxiliary bearing device according to any one of claims 4 to 5, wherein the one end side of the axial direction is adjacent to the retainer to form a supply chamber for supplying the compressed air in an annular region, the one end side The gap between the retainer and the member corresponding to the outer race is smaller than a gap between the retainer in the one end side and the member corresponding to the inner race. The auxiliary bearing device according to any one of claims 4 to 5, wherein the one end side in the axial direction is adjacent to the retainer to form a supply chamber for supplying the compressed air in an annular region, the axial direction The gap between the retainer on the other end side and the member corresponding to the outer race is larger than a gap between the retainer in the one end side and the member corresponding to the outer race. The auxiliary bearing device according to any one of claims 1 to 5, further comprising: a control unit that controls the switching mechanism, wherein the control unit switches the switching mechanism when the shaft member rotates at a rotation speed of a first range In the contact state, when the shaft member rotates at a rotation speed of the second range which is faster than the rotation speed of the first range, the control unit switches the switching mechanism to the non-contact state. The auxiliary bearing device according to any one of claims 1 to 5, wherein a tool for machining a workpiece is fixed to the shaft member, and the auxiliary bearing device is disposed at an axial direction closer to the tool than the bearing. .