JP2018021593A - Preload adjustment structure of bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a preload adjustment structure of a bearing having proper bearing surface pressure and high bearing rigidity.SOLUTION: Ring-shaped members 11, 12 are fitted to an outer peripheral side of a rotational shaft 2 so as to rotate integrally with the rotational shaft 2. Consequently, between the ring-shaped members 11, 12 and the outer periphery of the rotational shaft 2, formed are pressurized spaces 17, 18 whose both axial sides are sealed. On the rotational shaft, provided are radial holes (centrifugal pressurization spaces) 13, 14 extending in a radial direction and opened to the pressurized spaces 17, 18, and into the pressurized spaces 17, 18 and the centrifugal pressurization spaces 13, 14, liquid is sealed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a bearing preload adjusting structure used in a rotating device such as a spindle device of a machine tool.

  FIG. 4 shows an example of a spindle device of a machine tool. The spindle device (1) of a machine tool supports the spindle (2) and the spindle (2) via a bearing (4) on the front side (left side in the figure) and a bearing (5) on the rear side (right side in the figure). And a housing (3). Each bearing (4) (5) is an angular bearing having an inner ring (4a) (5a), an outer ring (4b) (5b) and a plurality of balls (4c) (5c). ) Between the outer rings (4b) and (5b) and the outer ring spacer (7).

  The spindle (2) is provided with a receiving part (2a) that prevents the front bearing (4) from moving to the front side of the inner ring (4a), and the male thread part provided on the spindle (2) is threaded. The fitted nut (8) presses the inner ring (5a) of the rear bearing (5) forward, so that the inner rings (4a) (5a) of the front and rear bearings (4) (5) It is fixed to 2).

  In some rotating devices such as the spindle device (1) of such machine tools, there is a demand to rotate the bearings (4) and (5) having a large diameter and high rigidity at high speed. In such a device (1), the inner ring (4a) (5a) of the bearings (4) and (5) expands due to the influence of centrifugal force and heat generation during rotation, so that the surface pressure of the rolling contact surface increases significantly and the bearings (4) Fatigue fracture of (5) becomes a problem. As a countermeasure against this, various preload adjustment structures have been developed so far in order to keep the bearing surface pressure during rotation appropriate.

  As a conventional preload adjusting structure, for example, as disclosed in Patent Document 1, there is a structure that reduces an increase in surface pressure by using an elastic body. This is generally called a constant pressure preload method, and is widely used for high-speed spindles and the like.

  In addition, as in Patent Document 2, for example, by applying an external force using hydraulic pressure or the like, the positions of the outer rings (4b) and (5b) of the bearings (4) and (5) are controlled and actively preloaded. There is a method of changing the pressure and optimizing the surface pressure.

  There is also a method of reducing the initial preload at the time of incorporation in advance so that the surface pressure becomes appropriate when rotated.

  In order to avoid an increase in surface pressure due to the influence of heat generation during rotation, it is sufficient that there is no temperature increase on the inner ring (4a) (5a) side of the bearings (4) and (5). As disclosed in Patent Document 3, there has been developed one that can reduce the increase in surface pressure by cooling the main shaft (2) side.

  In order to avoid an increase in surface pressure due to centrifugal force during rotation, the mass of the inner rings (4a) and (5a) of the bearings (4) and (5), which are rotating bodies, should be reduced. Some are made of lightweight materials such as ceramics. In addition, as in Patent Document 4, there is a type that adjusts a preload by using a tapered spacer and converting a force due to a centrifugal force into an axial force.

Japanese Utility Model 3-62702 microfilm JP-A-3-79205 Japanese Examined Patent Publication No. 7-106534 JP 2002-235740 A

  The conventional bearing preload adjusting structure has the following problems.

  Although the constant pressure preload method using an elastic body as in Patent Document 1 mitigates an increase in bearing surface pressure, it is easily deformed by a load from outside the spindle device. This means that the machine tool spindle has low rigidity against the cutting force, and the machining capability is low.

  The preload variable mechanism using external force as in Patent Document 2 can increase the rigidity while maintaining a proper surface pressure. However, the structure becomes complicated, the cost increases, and the reliability of the structure itself decreases. In addition, it is difficult in terms of control to accurately follow a transient surface pressure change due to a temperature change and to accurately follow a surface pressure change due to a centrifugal force. Further, since the external force has to be controlled, there is a drawback that a power failure or the like occurs during the rotation, and the surface pressure cannot be maintained properly while the main shaft rotates by inertia.

  Although the method of lowering the initial preload in advance can maintain an appropriate surface pressure during high-speed rotation, the surface pressure is excessively low during low-speed rotation, which causes problems such as a decrease in the rigidity of the main shaft and damage due to sliding of the bearing. For this reason, the rotation speed which can be used is limited.

  The method of cooling the inner ring of the bearing as in Patent Document 3 can reduce the temperature rise and reduce the surface pressure rise. However, it has no effect on increasing the surface pressure due to centrifugal force. Although it is conceivable to cool the inner ring side excessively so that the centrifugal force can be offset, the temperature change is transient, whereas the centrifugal force change is instantaneous, so it is difficult to follow. When the surface pressure increase due to centrifugal force is large, it is necessary to combine with another method.

  As a method for reducing the centrifugal force by lightening the rotating body, a rolling element made of ceramics or the like is widely used and has a certain effect. However, the inner ring and the main shaft rotating at the highest speed are difficult to be made of ceramics due to manufacturing problems, and even if possible, the increase in surface pressure cannot be made zero.

  In the method of changing the centrifugal force to the axial force as in Patent Document 4, an axial force can be generated, but a force enough to shift the fit of the bearing cannot be generated. Also, as a practical matter, since the bearing is strongly tightened in the axial direction with a nut or the like, the friction force between the spacer and the taper portion of the bearing is large, and it is not easy to shift, so the effect of adjusting the preload cannot be so great. . Further, it cannot be used for bearings with a contact angle of 0 degrees, such as deep groove ball bearings and cylindrical roller bearings.

  An object of the present invention is to provide a bearing preload adjusting structure that solves the above-described problems and achieves both an appropriate bearing surface pressure and high bearing rigidity.

  A bearing preload adjusting structure according to the present invention is a bearing preload adjusting structure provided in a rotating device having a rotating shaft rotatably supported by a plurality of bearings, and is provided on both sides in the axial direction between the outer periphery of the rotating shaft. A ring-shaped pressurized space forming member for forming a pressurized space in which the pressure is sealed is fitted so as to rotate integrally with the rotary shaft, and extends in the radial direction to open into the pressurized space. A centrifugal pressurizing space is provided in the rotating shaft, and a liquid is sealed in the pressurized space and the centrifugal pressurizing space.

  The pressurized space is an annular space, and the centrifugal pressurized space is a plurality of holes formed at equal intervals in the circumferential direction and extending in the radial direction or an annular groove extending in the circumferential direction. The centrifugal pressurizing space is more preferably a plurality of holes.

  According to the bearing preload adjusting structure of the present invention, when the rotating shaft rotates, the centrifugal force acts on the liquid sealed in the pressurized space and the centrifugal pressure space, and all the centrifugal force generated in the liquid on the inner diameter side is reduced. Since the liquid on the outer diameter side is pressurized, a large pressure is generated in the liquid on the outer diameter side. In the pressurized space that becomes a large pressure generation location, the liquid exerts pressure in all directions, and the diameter of the rotating shaft and the bearing can be reduced by pressurizing the rotating shaft from the outer diameter side to the inner diameter side. Thereby, the centrifugal expansion effect of the rolling surface at the time of rotation is offset and the increase in surface pressure is mitigated.

  The pressurized space forming member and the member positioned on the inner diameter side thereof (the rotating shaft or a ring-shaped member separate from the rotating shaft) are connected only by a seal member such as an O-ring. By doing so, the pressurized space forming member swells to the outer diameter side when pressurized by centrifugal force, but this influence does not affect the rotating shaft or the bearing inner ring.

  Thus, an increase in surface pressure due to centrifugal force can be reduced without relying on control by external force, and both appropriate bearing surface pressure and high bearing rigidity can be achieved.

  The portion on the rotating shaft side facing the pressurized space forming member may be a ring-shaped member separate from the rotating shaft.

  The rotating shaft is thick and has little deformation. By receiving the pressure of the liquid in the pressurized space by a thin ring member separate from the rotating shaft, the rotating shaft side The diameter can be easily reduced.

  The ring-shaped member that is separate from the rotating shaft may be integrated with a rotating wheel of the bearing.

  If it does in this way, the rotating wheel (inner ring) of a bearing will receive the pressure of the liquid of a to-be-pressurized space directly, and it will be pressurized to offset that a rolling surface expands with the centrifugal force at the time of rotation. The pressure of the liquid in the space can be more appropriately applied to the rotating wheel of the bearing.

  As the centrifugal force acting on the liquid increases, the centrifugal expansion effect at the time of rotation can be offset and the force for reducing the increase in surface pressure can be increased. Therefore, the liquid is preferably a high specific gravity liquid. Examples of the high specific gravity liquid include mercury.

  The rotating shaft or the rotating wheel of the bearing is preferably cooled by a cooling fluid.

  Bearing preload is built-in preload + centrifugal force increase + temperature increase. In addition to adjusting the centrifugal force increase, the temperature increase is adjusted by cooling, so the change in preload is further suppressed. Can do. That is, when the influence of heat generation is large, more appropriate preload adjustment can be performed by combining with the cooling structure of the rotating shaft.

  According to the bearing preload adjusting structure of the present invention, the radial expansion contraction effect can be generated and canceled out with respect to the centrifugal expansion on the rotating shaft side using the fluid pressurized by the centrifugal force. Since centrifugal force is used, there is no delay in the pressurized fluid, and it can cope with instantaneous changes in centrifugal force. Further, since control is not required, the preload adjustment is always performed stably, and the surface pressure can be optimized even if a power failure occurs and the inertia rotates. Since this method can handle the bearing with a fixed position preload, the bearing rigidity can always be kept high, and when applied to a machine tool, its cutting performance can be increased. Further, since the structure is simple, the cost can be kept low and the reliability of the structure can be increased.

FIG. 1 is a longitudinal sectional view of one side of a center line of a main part of a bearing preload adjusting structure showing a first embodiment of the present invention. FIG. 2 is a longitudinal sectional view of one side of the center line of the main part of the bearing preload adjusting structure showing the second embodiment of the present invention. FIG. 3 is a longitudinal sectional view of one side of the center line of the main part of the bearing preload adjusting structure showing the third embodiment of the present invention. FIG. 4 is a longitudinal sectional view on one side of the center line of the main part of a conventional rotating device to which the bearing preload adjusting structure of the present invention is applied.

  Hereinafter, an embodiment of a bearing preload adjusting structure according to the present invention will be described with reference to the drawings. In the following description, the left of each figure is the front and the right is the rear.

  FIG. 1 shows a first embodiment in which the bearing preload adjusting structure of the present invention is applied to a spindle device of a machine tool.

  In FIG. 1, a spindle device (rotating device) (1) of a machine tool includes a spindle (rotating shaft) (2) and a spindle (2) through a front bearing (4) and a rear bearing (5). A supporting housing (3) is provided, and a bearing preload adjusting structure (10) is provided for the rear bearing (5).

  Each bearing (4) (5) is an angular bearing having an inner ring (4a) (5a), an outer ring (4b) (5b) and a plurality of balls (4c) (5c). ) Between the outer rings (4b) and (5b) and the outer ring spacer (7).

  The spindle (2) is provided with a receiving part (2a) that prevents the front bearing (4) from moving to the front side of the inner ring (4a), and the male thread part provided on the spindle (2) is threaded. The fitted nut (8) presses the inner ring (5a) of the rear bearing (5) forward, so that the inner rings (4a) (5a) of the front and rear bearings (4) (5) It is fixed to 2).

  On the inner periphery of the inner ring spacer (6), there are provided recesses (6a) that open to the inner diameter side and the rear side. In the inner periphery of the nut (8), there are provided recesses (8a) that open to the inner diameter side and the rear side.

  The bearing preload adjustment structure (10) includes a front ring-shaped member (pressurized space forming member) (11) fitted in the recess (6a) of the inner ring spacer (6) and a recess of the nut (8). The rear ring-shaped member (pressurized space forming member) (12) fitted in the place (8a) and the front and rear radial directions in which a plurality of circumferentially arranged spindles (2) are provided at equal intervals. Holes (front and rear centrifugal pressure spaces) (13) and (14).

  O-rings (seal means) (15) are provided at the front and rear ends of the front ring-shaped member (11) to seal between the outer peripheral surface of the main shaft (2). O-rings (seal means) (16) are also provided at the front and rear ends of the rear ring-shaped member (12) to seal between the outer peripheral surface of the main shaft (2).

  The front and rear ring-shaped members (11) and (12) are connected to the main shaft (2) via O-rings (15) and (16), and thus rotate integrally with the main shaft (2).

  The inner ring (5a) of the rear bearing (5) is sandwiched between the inner ring spacer (6) and the nut (8), and rotates integrally with the main shaft (2). Therefore, when a radially outward force is applied to the inner ring spacer (6) or the nut (8), the inner ring (5a) of the rear bearing (5) receives an outward force therefrom. On the other hand, the front and rear ring-shaped members (11) and (12) are not in contact with the inner ring (5a) of the rear bearing (5), and therefore the front or rear ring-shaped members (11 ) Even if a radially outward force acts on (12), the inner ring (5a) of the rear bearing (5) does not receive an outward force therefrom.

  The inner peripheral surface of the front ring-shaped member (11) is cut away between the front and rear O-rings (15), so that the outer periphery of the main shaft (2) and the front ring-shaped member (11) A pressure-receiving space (17) on the front side in which both sides in the axial direction are sealed is formed.

  The inner peripheral surface of the rear ring-shaped member (12) is cut away between the front and rear O-rings (16), so that the outer periphery of the main shaft (2) and the rear ring-shaped member ( 12), a pressurized space (18) on the rear side in which both sides in the axial direction are sealed is formed.

  The front radial hole (13) provided in the main shaft (2) has one end opened on the outer peripheral surface of the main shaft (2) and faced to the front end of the front pressurized space (17), and the other end It extends in the radial direction to the vicinity of the center of the main shaft (2), and forms a front centrifugal pressurizing space that leads to the front pressurized space (17) while increasing the diameter. Similarly, the rear radial hole (14) provided in the main shaft (2) has one end opened to the outer peripheral surface of the main shaft (2) and formed in the rear end portion of the rear pressurized space (18). The other end extends in the radial direction to the vicinity of the center of the main shaft (2), forming a rear centrifugal pressurizing space that leads to the rear pressurized space (18) while increasing the diameter. .

  In the front and rear pressurized spaces (17) (18) and front and rear radial holes (front and rear centrifugal pressure spaces) (13) (14), mercury as a high specific gravity liquid Is enclosed.

  According to the bearing preload adjusting structure (10), when the main shaft (2) rotates at a high speed, the diameter of the inner ring (5a) of the bearing (5) is expanded by centrifugal force. On the other hand, a large centrifugal force acts on the liquid sealed in the centrifugal pressurizing spaces (13) and (14), and a larger pressure is generated on the outer diameter side. The pressurized space (17) (18) provided between the ring-shaped members (11) (12) and the main shaft (2) is connected to the outer diameter side of the centrifugal pressurized space (13) (14). Therefore, high pressure is generated inside the pressurized spaces (17) and (18). Due to this high pressure, the ring-shaped members (11) and (12) are deformed to the outer diameter side, and the main shaft (2) is deformed to the inner diameter side. As a result, the rolling surface of the inner ring (5a) can be deformed to the inner diameter side, the expansion due to the centrifugal force and the reduction due to the liquid pressure are offset, and the increase in the surface pressure due to the rotation can be eliminated.

  In the above embodiment, by using an elastic body such as an O-ring as the sealing means, the ring-shaped members (11), (12) and the main shaft (2) can be freely separated in the radial direction. Moreover, since a large centrifugal force is generated by using a liquid having a high specific gravity such as mercury as the liquid sealed inside, the rolling surface of the inner ring (5a) can be more effectively deformed toward the inner diameter side.

  In the above embodiment, the ring-shaped members (11) and (12) are arranged on the inner diameter side of the inner ring spacer (6), nut (8), etc., but these are arranged on the inner ring spacer (6) and nut. It may be arranged on the outer diameter side of (8), and the diameter of the main shaft (2) may be reduced through the inner ring spacer (6) and the nut (8).

  FIG. 2 shows a second embodiment in which the bearing preload adjusting structure of the present invention is applied to a spindle device of a machine tool.

  The bearing preload adjusting structure (20) of the second embodiment includes a front ring-shaped member (pressurized space forming member) (11) fitted in the recess (6a) of the inner ring spacer (6), and a nut. The rear ring-shaped member (pressurized space forming member) (12) fitted in the recess (8a) of (8), and the rear ring shape from the vicinity of the front end of the front ring-shaped member (11) The main shaft side ring-shaped member (21) provided so as to face the part (12) up to the vicinity of the rear end portion from the inside in the radial direction, and a plurality of the main shaft (2) are provided at equal intervals in the circumferential direction. The front-side and rear-side radial holes (22), (23) and the front-side and rear-side radial holes (22), (23) of the spindle (2) are connected to the spindle-side ring-shaped member (21 ) And front and rear through holes (24) and (25).

  An annular recess (2b) is formed on the outer periphery of the main shaft (2), and the main shaft side ring-shaped member (21) is fitted into the recess (2b). That is, the main shaft (2) in the first embodiment is formed by the main shaft (2) in which the recess (2b) is formed and the main shaft side ring-shaped member (21) separate from this.

  At the front and rear ends of the front ring-shaped member (11), O-rings (seal means) (15) are provided for sealing between the outer peripheral surface of the main shaft-side ring-shaped member (21). At the front and rear ends of the rear ring member (12), O-rings (seal means) (16) are provided for sealing between the outer peripheral surface of the main shaft ring member (21).

  The ring members (11) and (12) on the front and rear sides are connected to the main ring member (21) via the O-rings (15) and (16), so that the main ring member (21 ) And rotate together.

  The main shaft (2) includes a front O-ring (26) for sealing between the peripheral edge of the butted portion of the front radial hole (22) and the through hole (24) and the outer peripheral surface of the main shaft (2), and the rear A rear O-ring (27) that seals between the peripheral edge of the butted portion of the side radial hole (23) and the through hole (25) and the outer peripheral surface of the main shaft (2) is provided.

  The main shaft side ring-shaped member (21) is connected to the main shaft (2) via the O-rings (26) and (27), and thus rotates integrally with the main shaft (2).

  The inner peripheral surface of the front ring-shaped member (11) is cut off at the portion located between the front and rear O-rings (15), so that the outer periphery of the spindle-side ring-shaped member (21) and the front ring-shaped member A pressure-receiving space (28) on the front side in which both sides in the axial direction are sealed is formed between the member (11).

  The inner peripheral surface of the rear ring-shaped member (12) is cut away between the front and rear O-rings (16). A pressurized space (29) on the rear side is formed between the ring-shaped member (12) and both sides in the axial direction are sealed.

  The through-hole (24) on the front side of the main ring member (21) has a radially outer opening facing the front end of the pressurized space (28) on the front side. The radial hole (22) has one end opened to the bottom surface of the recess (2b) of the main shaft (2) and the other end connected to the front through hole (24) of the main ring side ring-shaped member (21). It extends in the radial direction to near the center of the main shaft (2). These radial holes (22) and through holes (24) form a front centrifugal pressurizing space (30) that leads to the front pressurized space (28) while increasing the diameter.

  The through-hole (25) on the rear side of the main shaft side ring-shaped member (21) has an opening on the outer side in the radial direction facing the front end of the pressurized space (29) on the rear side. The rear radial hole (23) has one end opened to the outer peripheral surface of the main shaft (2) and the other end connected to the rear through hole (25) on the main shaft side ring-shaped member (21). It extends in the radial direction to near the center of the main shaft (2). These radial holes (23) and through-holes (25) form a rear centrifugal pressurizing space (31) that communicates with the rear pressurized space (29) while increasing the diameter.

  Mercury as a high specific gravity liquid is enclosed in the front and rear pressurized spaces (28) and (29) and the front and rear centrifugal pressurized spaces (30) and (31).

  According to the bearing preload adjusting structure (20) of the second embodiment, when the main shaft (2) rotates at a high speed, the inner ring (5a) of the bearing (5) expands in diameter due to centrifugal force. On the other hand, a large centrifugal force acts on the liquid sealed in the centrifugal pressurizing spaces (30) and (31), and a larger pressure is generated on the outer diameter side. The pressurized space (28) (29) provided between the ring-shaped members (11), (12) and the main shaft-side ring-shaped member (21) is the outer diameter side of the centrifugal pressurized space (30), (31). Therefore, high pressure is generated inside the pressurized spaces (28) and (29). Due to this high pressure, the ring-shaped members (11) and (12) are deformed to the outer diameter side, and the main shaft side ring-shaped member (21) is deformed to the inner diameter side. As a result, the rolling surface of the inner ring (5a) can be deformed to the inner diameter side, the expansion due to the centrifugal force and the reduction due to the liquid pressure are offset, and the increase in the surface pressure due to the rotation can be eliminated.

  According to the second embodiment, the main shaft side ring-shaped member (21), which is a thin ring-shaped member that is more easily deformed than the main shaft (2), is provided on the inner diameter side of the pressurized space (28) (29). As a result, the amount of reduction in the radial direction can be increased, the rolling surface of the inner ring (5a) can be easily deformed to the inner diameter side, and the surface pressure increase due to rotation can be further eliminated.

  FIG. 3 shows a third embodiment in which the bearing preload adjusting structure of the present invention is applied to a spindle device of a machine tool.

  The bearing preload adjusting structure (40) of the third embodiment includes a front ring-shaped member (pressurized space forming member) (41) and a rear ring-shaped member (pressurized space forming member) (42). An inner ring member (43) having a front extension part (52) and a rear extension part (53), and a plurality of front and rear radial holes provided at equal intervals in the circumferential direction on the main shaft (2) ( 44) (45) and the front extension part (52) and the rear extension part of the inner ring member (43) provided to be connected to the front and rear radial holes (44) (45) of the main shaft (2). (53) are provided with front and rear through holes (46), (47) penetrating in the radial direction.

  Both the inner ring spacer (48) and the nut (49) are shorter than those of the first and second embodiments.

  The inner ring member (43) includes a main body part (51) on which a transfer surface of the ball (5c) is formed, a front extension part (52) integrally provided on the front side of the main body part (51), and a main body part (51 ) And a rear extending portion (53) provided integrally on the rear side.

  The rear bearing (5) is an angular bearing having an inner ring, an outer ring (5b) and a plurality of balls (5c) formed by the main body (51) of the inner ring member (43).

  The inner peripheral surfaces of the main body part (51), the front extension part (52) and the rear extension part (53) are flush with each other, and the inner diameter thereof is substantially equal to the inner diameter of the main shaft (2). The inner ring member (43) is sandwiched between the rear end face of the inner ring spacer (48) and the front end face of the nut (49).

  The front ring-shaped member (41) has a front end received in a recess provided in the outer peripheral portion of the inner ring spacer (48), and a rear end of the front ring-shaped member (43). Received at the rear end. The rear ring-shaped member (42) has a rear end portion received in a recess provided in an outer peripheral portion of the nut (49), and a front end portion of the rear ring-shaped member (43) of the inner ring member (43). Received at the front end.

  O-rings (seal means) (54) are provided at the front and rear end portions of the front ring-shaped member (41) to seal between the outer peripheral surface of the front extension portion (52) of the inner ring member (43). Yes. O-rings (seal means) (55) are also provided at the front and rear end portions of the rear ring-shaped member (42) to seal between the outer ring surface of the rear extended portion (53) of the inner ring member (43). It has been.

  The front and rear ring-shaped members (41) and (42) are connected to the inner ring member (43) via O-rings (54) and (55), and thus rotate integrally with the inner ring member (43). .

  The inner peripheral surface of the front ring-shaped member (41) has a portion that is located between the front and rear O-rings (54), and thereby, the outer periphery of the front extended portion (52) of the inner ring member (43) Between the front ring-shaped member (41), a pressurized space (56) on the front side in which both sides in the axial direction are sealed is formed.

  The inner circumferential surface of the rear ring-shaped member (42) is cut away at the portion located between the front and rear O-rings (55), thereby the rear extension portion (53) of the inner ring member (43). Between the outer periphery and the rear ring-shaped member (42), there is formed a rear pressurized space (57) in which both sides in the axial direction are sealed.

  The main shaft (2) includes a front O-ring (58) that seals between the peripheral edge of the butted portion of the front radial hole (44) and the through hole (46) and the outer peripheral surface of the main shaft (2), and the rear An O-ring (59) is provided for sealing between the peripheral edge of the butted portion of the side radial hole (45) and the through hole (47) and the outer peripheral surface of the main shaft (2).

  The inner ring member (43) rotates integrally with the main shaft (2) by being connected to the main shaft (2) via O-rings (58) and (59). An annular shallow recess (2b) is formed on the outer periphery of the main shaft (2) corresponding to the inner ring member (43).

  The front through hole (46) that penetrates the front extension part (52) of the inner ring member (43) has a radially outer opening facing the front end of the front pressurized space (56), and the main shaft The front radial hole (44) of (2) has one end opened to the outer peripheral surface of the main shaft (2) so as to be connected to the front through hole (46) that penetrates the front extension part (52), and the other. The end extends in the radial direction to the vicinity of the center of the main shaft (2). These radial holes (44) and through-holes (46) form a front centrifugal pressurizing space (60) communicating with the front pressurized space (56) while increasing the diameter.

  The rear through hole (47) that passes through the rear extension (53) of the inner ring member (43) has a radially outer opening facing the rear end of the rear pressurized space (57). The rear radial hole (45) of the main shaft (2) is connected to the rear through hole (47) penetrating the rear extending portion (53), and one end of the outer periphery of the main shaft (2). Opened to the surface, the other end extends in the radial direction to near the center of the main shaft (2). These radial holes (45) and through-holes (47) form a rear centrifugal pressurizing space (61) communicating with the rear pressurized space (57) while increasing the diameter.

  Mercury as a high specific gravity liquid is enclosed in the front and rear pressurized spaces (56) and (57) and the front and rear centrifugal pressurized spaces (60) and (61).

  According to the bearing preload adjusting structure (40) of the third embodiment, when the main shaft (2) rotates at a high speed, the inner ring member (43) expands in diameter due to centrifugal force. On the other hand, a large centrifugal force acts on the liquid sealed in the centrifugal pressurizing spaces (60) and (61), and a larger pressure is generated on the outer diameter side. The pressurized space (56) (57) provided between the ring-shaped member (41) (42) and the inner ring member (43) is connected to the outer diameter side of the centrifugal pressurized space (60) (61). Therefore, a high pressure is generated inside the pressurized space (56) (57). Due to this high pressure, the ring-shaped members (41) and (42) are deformed to the outer diameter side, and the inner ring member (43) is deformed to the inner diameter side. Thereby, the rolling surface of the main body portion (51) of the inner ring member (43) can be deformed to the inner diameter side, and the expansion due to the centrifugal force and the reduction due to the liquid pressure are offset, and the increase in the surface pressure due to the rotation is eliminated. Can do.

  According to the third embodiment, the main shaft side ring-shaped member (21) (a thin ring-shaped member that is easier to deform than the main shaft (2)) and the inner ring (5a) of the bearing (5) , The effect of pressure by the liquid acts more directly on the rolling surface of the main body part (51) of the inner ring member (43) corresponding to the inner ring (5a), effectively centrifugal contraction effect Can be generated.

  In each of the above embodiments, the bearing preload adjustment structure (10), (20), (40) is applied only to the rear bearing (5), but this is one of the angular contact ball bearings ( This is because if the preload of 5) is lowered, the preload is reduced by averaging with the other bearing (4). However, this structure (10), (20), and (40) may be applied to all bearings (4) and (5), and this structure is also applied to the bearing provided in the main shaft (2) not shown. (10) (20) (40) may be applied. It is necessary to apply this structure (10), (20) and (40) to bearings with a contact angle of 0 degrees, such as deep groove ball bearings and cylindrical roller bearings.

  Although not shown, the main shaft (2) and / or the bearing inner ring (5a) may be cooled by flowing a cooling fluid into the main shaft (2), for example. The bearing preload also changes depending on the temperature, and the preload fluctuation due to this temperature is suppressed by cooling, and the preload fluctuation due to centrifugal force is suppressed by the bearing preload adjustment structure (10) (20) (40) above. Therefore, it is possible to adjust the preload of the bearing with extremely high accuracy.

(2): Main shaft (rotating shaft)
(4) (5): Bearing
(10): Bearing preload adjustment structure
(11) (12): Ring-shaped member (Pressurized space forming member)
(13) (14): Radial hole (centrifugal pressure space)
(17) (18): Pressurized space
(20): Bearing preload adjustment structure
(21): Spindle side ring-shaped member (ring-shaped member)
(28) (29): Pressurized space
(30) (31): Centrifugal pressurization space
(40): Bearing preload adjustment structure
(43): Inner ring member
(56) (57): Pressurized space
(60) (61): Centrifugal pressure space

Claims (5)

A preload adjusting structure for a bearing provided in a rotating device having a rotating shaft rotatably supported by a plurality of bearings,
A ring-shaped pressurized space forming member for forming a pressurized space sealed on both sides in the axial direction between the outer periphery of the rotating shaft is fitted so as to rotate integrally with the rotating shaft, and has a diameter. A centrifugal pressurizing space that extends in the direction and opens to the pressurized space is provided in the rotating shaft, and a liquid is sealed in the pressurized space and the centrifugal pressurized space. Preload adjustment structure.   The bearing preload adjusting structure according to claim 1, wherein a portion on the rotating shaft side facing the pressurized space forming member is a ring-shaped member separate from the rotating shaft.   The bearing preload adjustment structure according to claim 1 or 2, wherein the ring-shaped member separate from the rotating shaft is integrated with a rotating wheel of the bearing.   The bearing preload adjusting structure according to claim 1, wherein the liquid is a high specific gravity liquid.   The bearing preload adjusting structure according to any one of claims 1 to 4, wherein the rotating shaft or the rotating wheel of the bearing is cooled by a cooling fluid.

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