JPH06346924A - High speed spindle unit - Google Patents

Abstract

PURPOSE:To provide a high speed spindle unit capable of easily preventing pre-load increase, heating and burning at the time of high speed rotation by way of giving large interference to a bearing inner ring and installing and removing a bearing. CONSTITUTION:This unit is constituted to expand bearing inner rings 5a, 15a in the diametrical direction at the time of installing and removing a bearing by way of giving oil pressure from the shaft side to points to install the bearing inner rings 5a, 15a. Additionally, it is constituted to generate extracting force in the shaft direction on the bearing by pressure oil supplied from the shaft side to the inner peripheral surface of the bearing inner rings 5a, 15a by way of forming a circular stepped part 10 on the inner peripheral surface of the bearing inner rings 5a, 15a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle unit used for a tool spindle of a machine tool, and more particularly to a high speed spindle unit in which a shaft supported by a housing via a rolling bearing rotates at a high speed to a super high speed.

[0002]

2. Description of the Related Art A spindle unit of a machine tool or the like is supported by a housing such that a shaft portion penetrates through a rolling bearing, a tool is mounted in a tapered hole at the tip of the shaft portion, and a rear end of the shaft portion rotates. It is connected to the drive source and rotates at high speed.
In this type of high-speed spindle unit, since the rolling bearing is generally assembled with a fixed position preload, the inner ring of the bearing expands due to the action of centrifugal force when the shaft rotates at an extremely high speed, such as in a machining center. The bearing preload increases, causing heat generation and seizure. In this case, by increasing the tightening margin of the bearing inner ring with respect to the shaft portion, it is possible to prevent an increase in preload due to expansion of the bearing inner ring. However, it is not easy to assemble the bearing on the outer periphery of the shaft portion with a large interference, and if the interference of the bearing is too large, the bearing cannot be removed from the shaft when replacing the bearing. In the case of ultra-high speed rotation, the expansion amount of the inner ring of the bearing is more than 20 μm. However, due to the assembly and removal of the bearing, in the past, only a tightening margin of about 10 μm was given to the calculated value of the inner ring expansion amount of 20 μm. However, heat generation and seizure were dealt with by devising the lubrication of the bearings exclusively (Japanese Patent Application No. 5-19311 and Japanese Patent Application No. 5-19311).
19310).

[0003]

In the conventional high-speed spindle unit, the bearing inner ring cannot be sufficiently tightened with respect to the shaft from the viewpoint of removing and assembling the bearing, and due to the action of centrifugal force during ultra-high speed rotation. Expansion of the bearing inner ring and shaft,
This is one of the factors that increase the bearing preload. A light preload must be used to prevent heat generation and seizure due to increased preload, and to prevent shortening of service life. As a result, rigidity is reduced, chattering and the like occur, and machining accuracy deteriorates. As a means for preventing heat generation and seizure, a so-called under-race lubrication system in which lubricating oil is supplied to the inner ring of the bearing to cool it from the shaft portion side requires a large-scale device, consumes much lubricating oil supply power, and increases running costs. In addition, the tightening margin of the inner ring of the bearing must be set appropriately within a range that does not make it difficult to remove the bearing.Therefore, the dimensional accuracy of the inner ring and shaft is required to be strict, and preload adjustment and bearing tightening adjustment require skilled personnel. There was a problem such as

Therefore, according to the present invention, the bearing inner ring can be easily attached to the outer periphery of the shaft portion with a large tightening margin, and the bearing can be easily removed. It is to provide a high-speed spindle unit that can prevent increase in preload, heat generation, and seizure.

Further, according to the present invention, a stepped portion having a different inner diameter is formed in the bearing inner ring, and even if a large tightening margin is provided as a fixed sleeve type, it can be easily pulled out by the hydraulic pressure from the shaft side, and the tightening adjustment can be made. , It is to provide a high-speed spindle unit that can be easily assembled.

[0006]

According to the present invention, hydraulic pressure is applied to the inner peripheral surface of a bearing inner ring mounted on the outer peripheral surface of the shaft portion from the shaft portion side to expand the bearing inner ring in the radial direction by a tightening margin. While the bearing is attached to or removed from the outer peripheral surface of the shaft portion, an oil passage opening to the outer peripheral surface of the shaft portion at the bearing mounting position is formed in the shaft portion, and pressure is applied from one end of the oil passage through the shaft portion. Oil is applied between the bearing inner ring and the outer peripheral surface of the shaft portion.

Further, according to the present invention, stepped peripheral portions facing each other are formed on the inner peripheral surface of the inner ring of the bearing and the outer peripheral surface of the shaft portion, respectively, and the oil passage is opened between these peripheral portions. There is provided a high-speed spindle unit in which an inner ring of the bearing is attached to the shaft portion by generating an axial withdrawing force in the bearing by the pressurized oil supplied from one end of the oil passage.

[0008]

[Function] By forming an oil passage exposed at a midway position on the inner surface of the bearing inner ring on the shaft portion and applying a hydraulic pressure to the oil passage to expand the bearing inner ring, the bearing is mounted at the bearing mounting position on the outer periphery of the shaft portion. , A large interference can be given to the bearing. Further, when the bearing is removed, the bearing can be easily moved in the axial direction while expanding the inner ring of the bearing by applying hydraulic pressure to the inner ring of the bearing from the opening of the oil passage on the outer circumference of the shaft. In this way, the bearing can be mounted and dismounted with a tightening margin greater than the amount by which the inner ring of the bearing expands due to centrifugal force during high-speed or ultra-high speed rotation. When a radial step is formed on the inner surface of the bearing inner ring, the shaft portion of the portion to which the hydraulic pressure is applied and the bearing inner ring have a cylinder-piston relationship, and the bearing is pushed out in the axial direction. Further, it is possible to adjust the preload and the tightening of the bearing by applying an axial load from the rear side of the bearing to the inner ring side using a hydraulic nut or the like while applying the hydraulic pressure. Since the inner ring of the bearing can be tightened to a large extent, expansion of the shaft portion itself due to high-speed to ultra-high-speed rotation can be prevented.

[0009]

Embodiments of the present invention will now be described with reference to the drawings. The embodiment of FIG. 7 shows the positional relationship between a single rolling bearing incorporated in a high speed spindle unit and a shaft portion. The shaft portion 1 has an axial hole 2 bored in the axial direction within its thickness, a radial hole 3 which is open to the outer peripheral surface of the shaft portion at a bearing mounting position and is connected to the axial hole 2, and the radial direction. An oil passage is formed by a circumferential groove 4 that passes through the opening of the hole 3. Although not shown, one end of the axial hole 2 is pulled out to the shaft end of the shaft portion 1 or an outer peripheral portion near the shaft end and is detachably connected to an external hydraulic pressure supply device. The rolling bearing 5 has its inner ring 5
The inner peripheral surface of a is attached to the outer peripheral surface of the shaft portion so as to close the circumferential groove 4 of the shaft portion 1.

By applying oil pressure to the oil passage of the shaft portion 1 in the closed state of the circumferential groove 4 by the bearing inner ring 5a, the inner ring 5a having a tightening margin expands in the radial direction, and the bearing 5 can be easily attached and detached. However, this embodiment is useful for facilitating the movement of the inner ring 5a for preload adjustment even when a large tightening margin for ultra-high speed rotation is not given. Fine preload adjustment is easy by inflating the inner ring 5a with the oil pressure from the oil passage of the shaft part 1 and tightening with the tightening nut 7 through the inner ring spacer 6 to move the inner ring 5a in the axial direction. Becomes After the assembly of the bearing 5 is completed, the hydraulic pressure in the oil passage is released. When the bearing 5 is removed, the tightening nut 7 and the inner ring spacer 6 that apply a preload to the bearing 5 are removed to supply pressure oil to the axial hole 2 from the outside, and this oil pressure expands the inner ring 5a in the radial direction. While applying force, the bearing 5 is moved to the inner ring spacer 6 side by a known means to form a gap between the outer ring spacer 8 and the bearing 5 on the side opposite to the pulling direction. After that, the bearing 5 is pulled out from the shaft portion 1 by sandwiching the extraction tool from the gap.

In the embodiment shown in FIG. 1, the oil passage formed by the axial portion 2, the radial hole 3 and the circumferential groove 4 formed in the shaft portion 1 is the same as that shown in FIG. A circumferential step portion 10 having a different inner diameter is formed on the inner peripheral surface of the inner ring 5a, and the outer diameter of the shaft portion 1 has a different outer diameter corresponding to the inner diameter of the bearing inner ring 5a on both sides of the circumferential groove 4. . When the bearing 5 is mounted in a predetermined position, the oil chamber 11 is formed between the large-diameter inner peripheral surface of the bearing inner ring 5a and the circumferential groove 4 on the outer peripheral surface of the shaft portion.
In the case of FIG. 7, it is easy to mount the bearing 5 having a tightening margin by applying hydraulic pressure to the oil passage of the shaft portion 1 at the time of mounting the bearing 5 and adjusting the preload to give a radial expansion force to the inner ring 5a. In the embodiment of FIG. 1, the hydraulic pressure of the oil chamber 11 further acts on the stepped portion 10 of the inner ring 5a to push out in the axial direction (smaller diameter side of the stepped portion 10) in the embodiment of FIG. Occurs, which causes the outer ring spacer 8 on the opposite side to the bearing 5 in the extracting direction.
A gap is formed between the bearing 5 and the bearing 5, and the bearing 5 can be easily removed even when the bearing has a large interference. The embodiment of FIG. 2 has a bearing 5
Inner ring 5 of cylindrical roller bearing 5 using rollers as rolling elements
This is an example in which the step portion 10 described in FIG. 1 is formed in a. In order to prevent the inner ring 5a from inclining in the axial direction and expanding when a hydraulic pressure is applied to the oil passage of the shaft part 1, the circumferential groove 4 of the shaft part 1 is provided with the bearing 5 at the mounting position of the inner ring 5a. The step portion 10 of the inner ring 5a is formed so as to face the substantially axial center position, and is formed at the approximately axial center position of the inner peripheral surface of the inner ring 5a.

In the embodiment shown in FIGS. 3 and 4, the outer rings 5b and 5 are separate bodies.
It is an example in which the present invention is applied to the DB or DT combination bearing 5 in which the inner ring 5a is integrated with c and the split outer ring spacer 12 is inserted between the outer rings 5b and 5c. Suitable for giving a large closing margin as a type. The inner ring 5a has a stepped portion 10 having a large diameter and a small diameter inner circumferential surface at a substantially axial center position, and the shaft portion 1 on which the bearing 5 is mounted has the inner ring 5a as described in FIG. 5
An oil passage having an outer peripheral surface having a different outer diameter corresponding to the inner peripheral surface of a and having a circumferential groove 4 facing the position of the inner ring step portion 10, a radial hole 3 and an axial hole 2 is formed. There is. Inner ring 5
With the large inner diameter portion of a and the large outer diameter portion of the shaft portion 1 fitted, pressure oil is sent to the oil passage of the shaft portion 1 to expand the inner ring 5a and move the bearing 5 to a predetermined assembly position. After that, the bearing 5 can be mounted with a large interference by removing the hydraulic pressure, and at the time of removal, the oil chamber 11 between the large inner diameter portion of the inner ring 5a and the large outer diameter portion of the shaft portion 1 can be removed through the oil passage. The hydraulic pressure given to the bearing acts on the step portion 10 and the bearing 5 moves to the extraction side.

An example of a high speed spindle unit for a machining center incorporating the DB combination bearing 5 of FIG. 3 will be described with reference to FIG. The front end plate 14 and the front combined bearing 5 are mounted on the outer peripheral portion of the hollow shaft portion 1 having the taper hole 13 for tool fitting at the front end, and the preload is applied by the front inner ring spacer 16 and the front tightening nut 17. In the applied state, the shaft portion 1 is inserted into the housing 18 from the front end side of the housing 18. The axial holes 2 and 19 of the shaft portion 1 on both the front side and the rear side are provided symmetrically on the diameter of the shaft portion 1 in order to balance during rotation. In this case, when the combined bearing 5 is press-fitted into the shaft portion 1, the front side axial hole 2 is pulled out to the front end of the shaft portion 1.
One side is connected to a hydraulic pressure supply device (not shown), and the other front side axial hole 2 that is diametrically symmetrical to this is plugged and closed, and the pressure oil introduced from the one axial hole 2 is connected. Allows the bearing inner ring 5 to move from the circumferential groove 4 through the radial hole 3.
By applying hydraulic pressure to the large-diameter inner peripheral surface of a, the inner ring 5a is expanded,
At the same time, the two split outer ring spacers 12a and 12b shown in FIG. 6 are inserted from the radial direction between the outer rings 5b and 5c, the front inner ring spacer 16 and the front tightening nut 17 are tightened to push the inner ring 5a, The preload is adjusted between the front end plate 14 and the outer ring spacers 12a and 12b to assemble them.

Although the rear rolling bearing 15 has a smaller diameter than the front bearing 5 in this embodiment, the rear rolling bearing 15 is a DB combination bearing having the same type and structure as the front bearing, and has a step of different inner diameter on the inner peripheral surface of the inner ring 15a. It has a section 10. Similarly to the front bearing 5, the rear bearing 15 also has the other rear axial hole 19 in which one of the rear axial holes 19 is pulled out to the rear end side of the shaft portion 1 while the other rear axial hole 19 is closed.
To the inner ring 15a through the radial hole 20 and the circumferential groove 21 to apply hydraulic pressure from the shaft side to expand the inner ring 15a by the tightening margin.
The outer ring spacers 12a and 12b (FIG. 6), which are split in two, are attached to the outer ring 15
The rear end plate 22 is inserted into the shaft portion 1 after being sandwiched between b and 15c, and then the preload adjustment and assembly are performed by tightening the rear inner ring spacer 23 and the rear tightening nut 24. After assembling the bearings 5 and 15, the front and rear end plates 14 and 22 are bolted to the housing 18. Also, the axial holes 2, 19 on one side that were plugged when pressure oil was supplied
Remove the stopper.

A lubricating oil supply passage 25 passing through the inside of the housing is provided in one of the outer ring spacers 12a of the split outer ring spacers 12a and 12b.
A nozzle 26 is formed which communicates with the inner and outer races of the bearings 5 and 15 and provides lubricating oil between the inner and outer races, and the other outer race spacer 12b guides the lubricating oil between the inner and outer races to a lubricant discharge passage 28 of the housing 18. 29 are formed. The rear end of the shaft portion 1 projects more than the housing 18, and is connected to the outer peripheral portion of the shaft portion 1 to a rotary drive source of the shaft portion. Further, a drawbar device (not shown) for fixing and releasing the tool mounted in the taper hole at the front end of the shaft portion is incorporated in the hollow portion of the shaft portion 1.

As described above, the combined bearings 5 and 15 have the front side,
Since the inner rings 5a, 15a are fixed sleeve type and are radially expanded and pressed in by hydraulic pressure from the shaft side on both the rear side, mounting and preload adjustment with a large tightening margin of 20 μm or more are possible, but when removing Also, it can be easily removed by the axial force acting on the stepped portion 10 of the inner rings 5a, 15a as the inner rings 5a, 15a are expanded by the hydraulic pressure supplied from the shaft side. More specifically, in order to disassemble the spindle unit, first, the radial notch 30 of the rear end plate 22 is used to loosen the screw 31 of the rear tightening nut 24 to remove the tightening nut 24, and then the front end plate 14 is attached. When the bolts are removed and the rear inner ring spacer 23 and the rear end plate 22 are removed, hydraulic pressure is applied from one of the rear axial holes 19 of the shaft 1 (the other hole 19
The housing 18 and the rear bearing 15 are integrally pulled out from the shaft portion 1 to the rear side while generating an axial force toward the rear end side in the rear bearing 15. In this case, the inner diameter portion 18a of the housing middle portion between the two bearings 5 and 15 is smaller than the outer diameter of the rear bearing 15, so that the inner diameter portion 18 of the housing 18 is
It becomes easy to bring the outer ring 15b of the rear bearing 15 into contact with the step of "a" and extract it. After removing the housing 18, similarly, the front tightening nut 17 and the front inner ring spacer 16 are removed, and hydraulic pressure is applied from one (the other is closed) of the front axial hole 2 to move the front bearing 5 to the shaft portion. Remove from 1.

Although the above embodiment is an example of a high speed spindle unit assembled with a DB combined bearing, it goes without saying that a spindle unit having another type of combined bearing or a single rolling bearing may be used.

[0018]

As described above, according to the present invention, since the hydraulic pressure is applied from the shaft side to the mounting position of the inner ring of the bearing, the tightening margin of the bearing inner ring with respect to the shaft portion can be increased. It is easy to install and remove the bearing.
In the case of the fixed sleeve type in which the inner peripheral surface of the inner ring is stepped, hydraulic force can generate a force in the removing direction in addition to the expansion of the inner ring. Since the tightening margin of the inner ring can be increased, the preload does not increase even if the inner ring expands due to centrifugal force during rotation. According to the present invention, the factor of increase in preload is reduced, so that high-speed rotation can be performed during fixed position preload. Furthermore, the tightening margin of the inner ring can be increased to prevent expansion of the shaft due to high speed rotation, and a highly durable high speed spindle unit that does not generate heat or seizure can be realized.

[Brief description of drawings]

FIG. 1 is a partial vertical cross-sectional view showing an assembled state of a shaft portion and a bearing having a stepped inner ring to which the present invention is applied.

FIG. 2 is a partial vertical sectional view of a cylindrical roller bearing having a stepped inner ring according to another embodiment of the present invention.

FIG. 3 is a partial vertical cross-sectional view showing a mounted state of a DB combined bearing having a fixed sleeve type stepped inner ring according to an embodiment of the present invention.

FIG. 4 is a partial vertical sectional view of a DT combined bearing according to another embodiment of the present invention.

5 is a vertical cross-sectional view of a high speed spindle unit using the DB combined bearing having the stepped inner ring shown in FIG.

FIG. 6 is a front view of a split outer ring spacer of the combined bearing.

FIG. 7 is a vertical cross-sectional view showing a positional relationship between a single rolling bearing and a shaft portion of the spindle unit according to the embodiment of the invention.

[Explanation of symbols]

 1 Shaft part 2,19 Axial hole 3,20 Radial hole 4,21 Circumferential groove 5,15 DB combination bearing 5a, 15a Inner ring 7,17,24 Tightening nut 10 Step part 11 Oil chamber 12 Two outer rings Spacer 18 Housing

Claims (2)

[Claims] 1. An oil passage, which opens to the outer peripheral surface of the shaft portion of a portion where the inner ring of the bearing is fitted, is formed in the shaft portion, and pressurized oil is supplied from one end of the oil passage to a diameter of the inner ring of the bearing. A high-speed spindle unit, wherein an inner ring of the bearing is attached to a shaft portion by generating a directional expansion force. 2. An inner peripheral surface of the inner ring of the bearing and an outer peripheral surface of the shaft portion are respectively formed with stepped peripheral portions facing each other, and the oil passage is opened between these stepped peripheral portions, and one end of the oil passage is formed. The high-speed spindle unit according to claim 1, wherein an axial extracting force is generated in the bearing by pressurized oil supplied from the bearing.