JP2021011834A - Spindle device - Google Patents

Abstract

To provide a spindle device that, even when load due to imbalance of a rotation shaft or gyroscopic moment due to rotating movement of the rotation shaft occurs, can stably rotate the rotation shaft without losing a clearance of a gas bearing.SOLUTION: A spindle device 10 has a rotation shaft 12 whose gravity center G is set between an axial center C of a radial bearing 20 and an output side end face 20a of the radial bearing 20.SELECTED DRAWING: Figure 1

Description

The present invention relates to a spindle device using an air turbine drive system, and more particularly to a spindle device that can be suitably used for an electrostatic coating machine.

Conventionally, as a spindle device used for a spray gun of an electrostatic coating machine, in Patent Document 1, a radial bearing that supports the rotating shaft in the radial direction, a thrust bearing that supports the rotating shaft in the thrust direction, and a radial shaft are radial. A housing provided with a bearing supported via a bearing and a thrust bearing, and a cover located on the outer peripheral side of the housing are disclosed. Further, it is described that an O-ring is arranged between the housing and the cover in order to absorb vibration due to high-speed rotation and stabilize the operation of the spindle.

In particular, in Patent Document 1, the position of the O-ring is defined starting from the axial center of the housing, and even when a high-strength material is used for the O-ring, the amount of deformation of the O-ring is increased to reduce the vibration. Is stated to be large enough.

Japanese Unexamined Patent Publication No. 2016-223553

By the way, as the performance required for the spindle device for the electrostatic coating machine, the deviation between the center of gravity of the rotating shaft and the center of rotation caused by dirt, scratches, etc. on the bell cup part (hereinafter sometimes referred to as unbalance). And the gyro moment (moment load) that occurs when the robot arm turns while the rotating shaft rotates at high speed (1,000 to 150,000 min ^-1 ) while mounted on the tip of the robot arm, etc. There are two things, tolerance. In particular, due to the specifications of the electrostatic coating machine, it is required to take measures against the case where the robot arm becomes long (the turning radius is large) and a large gyro moment is generated in the spindle device.

However, although the spindle device described in Patent Document 1 describes that it absorbs vibration to stabilize the operation of the spindle, it does not describe measures against a gyro moment.
Further, since the spindle device described in Patent Document 1 has a structure in which the housing is supported by the O-ring, it is necessary to consider not only the cost increase due to the O-ring but also the life of the O-ring.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a rotating shaft without eliminating a gap in a gas bearing even when a large gyro moment is generated due to the turning movement of the rotating shaft. An object of the present invention is to provide a spindle device capable of stable rotation.

The above object of the present invention is achieved by the following configuration.
(1) A rotating shaft in which a plurality of turbine blades are provided across the circumferential direction and a load can be attached to the front end.
A housing for accommodating the rotating shaft and
A radial bearing that is attached to the housing and floats and supports the rotating shaft with respect to the housing by supplying gas.
A spindle device that rotationally drives the rotating shaft by ejecting gas to the plurality of turbine blades.
A spindle device in which the center of gravity of the rotating shaft is set between the axial center of the radial bearing and the output side end surface of the radial bearing.
(2) The spindle device according to (1), wherein the radial bearing is a porous drawing type gas bearing.
(3) The radial bearing is configured such that the ratio of the axial dimension (L) to the inner diameter (D) is 0.5 ≦ L / D ≦ 1.5, (1) or (2). The spindle device described in.
(4) The spindle device according to any one of (1) to (3), wherein the housing has a specific gravity of 4.0 or less, and the radial bearing is fitted with a tightening allowance.
(5) The rotating shaft is provided with a flange portion extending radially outward from the rotating shaft at the rear end portion of the rotating shaft.
A magnet that faces one side surface of the flange portion and exerts an axial attractive force on the flange portion, and is attached to the housing so as to face the one side surface of the flange portion, and is attached to the housing by supplying gas. The spindle device according to any one of (1) to (4), further comprising a gas bearing for blowing compressed air toward a flange portion and a thrust bearing for non-contactly supporting the rotating shaft in the thrust direction.
(6) The spindle device according to (5), wherein the gas bearing constituting the thrust bearing is a self-made drawing type.
(7) The spindle device according to (5) or (6), wherein the housing has a specific gravity of 4.0 or less and the gas bearing is fitted with a tightening allowance.

The center of gravity of the rotating shaft means the center of gravity of the rotating shaft when a mounted object such as a bell cup for an electrostatic coating machine is attached to the front end of the rotating shaft. To do.
Further, the axial center of the radial bearing means the axial center of the output side end face and the counter-output side end face in the range that functions as a radial bearing (supports the load in the radial direction).

According to the spindle device of the present invention, the center of gravity of the rotating shaft is set between the axial center of the radial bearing and the output side end face of the radial bearing, so that the center of gravity of the rotating shaft and the radial bearing mainly receive an unbalanced load. Between the center of gravity of the rotating shaft, which mainly receives the gyro moment generated due to the turning movement of the rotating shaft during high-speed rotation, and the opposite end face of the radial bearing with respect to the length between the bearing and the output side end face. The length of is increased. As a result, even when a large gyro moment acts on the rotating shaft, the gap between the gas bearings is not eliminated, and the rotating shaft can rotate stably.

It is sectional drawing of the spindle device which concerns on one Embodiment of this invention.

Hereinafter, the spindle device according to the embodiment of the present invention will be described in detail with reference to the drawings. In the following description, the left side, which is the output side shown in FIG. 1, is referred to as the front side, and the right side, which is the non-output side, is referred to as the rear side.

As shown in FIG. 1, the spindle device 10 of the present embodiment is an air turbine drive type spindle device used for an electrostatic coating machine. The spindle device 10 includes a rotating shaft 12 in which a plurality of turbine blades 11 are provided across the circumferential direction, a radial bearing 20 which is a gas bearing that supports the rotating shaft 12 in the radial direction, and a rotating shaft 12 in the thrust direction. It mainly includes a thrust bearing 21 which is a composite bearing of a gas bearing 21A and a magnetic bearing 21B, and a housing 30 for accommodating a rotating shaft 12.

The rotating shaft 12 extends radially outward from a cylindrical portion 15 to which a bell cup (loading object) 1 for atomizing and spraying paint is attached to the front end portion side and a rear end portion of the cylindrical portion 15. The flange portion 16 is provided, and is formed in a hollow cylindrical shape. The front end side of the cylindrical portion 15 to which the bell cup 1 is attached is formed in a tapered shape that gradually narrows toward the front end, and by fitting with the tapered hole 1a of the bell cup 1, the bell is formed on the front end side of the cylindrical portion 15. Cup 1 is attached. Further, the plurality of turbine blades 11 are formed by processing the outer peripheral surface of the flange portion 16.

Since the rotating shaft 12 rotates at high speed, it is important to suppress imbalance during rotation. Therefore, the rotating shaft 12 reduces the resistance during rotation by processing the hollow portion 15a to correct the balance.

The housing 30 has a housing main body 31, a substantially disk-shaped front lid portion 32 fixed to the front portion of the housing main body 31, and a rear housing 33 fixed to the rear portion of the housing main body 31.

In the present embodiment, aluminum (specific gravity 2.7) is used as the material of the housing body 31, the front lid 32, and the rear housing 33, but these materials are not limited to aluminum, for example. A material having a specific gravity of 4.0 or less (about half or less of iron having a specific gravity of 7.85) such as ceramic is preferable. Further, a material having a specific gravity of 3.0 or less, such as resin or CFRP, is more preferable. Further, the housing 30 may be formed by combining these materials. As a result, the weight of the spindle device 10 can be reduced, so that the weight of the robot equipped with the spindle device 10 can be reduced and energy consumption can be suppressed (energy saving).

The housing body 31 is provided around the cylindrical portion 15 of the rotating shaft 12, has a small diameter cylindrical portion 34 to which the radial bearing 20 is attached to the inner peripheral surface 34a, and is provided in front of the flange portion 16 of the rotating shaft 12 to form a cylinder. A large-diameter disc portion 35 extending outward in the radial direction from the rear end portion of the portion 34 is provided, and is formed in a hollow and stepped shape. The disk portion 35 is formed with an annular groove 36 having a rectangular cross section that opens rearward so as to accommodate the gas bearing 21A of the thrust bearing 21. Further, the disk portion 35 is formed with a magnet mounting portion 37 that opens rearward so as to accommodate the magnet 50 on the inner diameter side of the annular groove 36.

The rear housing 33 is formed in a hollow cylindrical shape, and is fastened and fixed to the rear end surface of the housing body 31 by bolts (not shown). Further, the housing main body 31 is formed with a bearing gas supply path 40 formed so as to penetrate in the radial direction from the outer peripheral surface 34b of the cylindrical portion 34 toward the inner peripheral surface 34a. The bearing gas supply path 40 supplies compressed air from a compressed air supply source (not shown) to the radial bearing 20 arranged on the inner peripheral surface 34a.

Further, the housing main body 31 and the rear housing 33 are provided with a bearing gas supply path 41 formed in the axial direction from the rear end surface of the rear housing 33 and further bent inward in the radial direction at the disk portion 35. .. The bearing gas supply path 41 supplies compressed air from a compressed air supply source (not shown) to the gas bearing 21A arranged in the annular groove 36.
The front lid portion 32 is also fastened and fixed to the front end surface of the housing body 31 by bolts (not shown).

The radial bearing 20 is a cylindrical porous member made of graphite, and is fitted and fixed to the inner peripheral surface 34a of the housing body 31 with a tightening allowance. The inner peripheral surface of the radial bearing 20 faces the outer peripheral surface of the cylindrical portion 15 of the rotating shaft 12. The radial bearing 20 blows compressed air supplied from the bearing gas supply path 40 toward the outer peripheral surface of the cylindrical portion 15 of the rotating shaft 12.

As a result, the radial bearing 20 floats and supports the rotating shaft 12 with respect to the housing 30 due to the pressure difference generated in the gap between the rotating shaft 12 and the radial bearing 20.
The radial bearing 20 is composed of a porous drawing type gas bearing made of graphite. A gas bearing using a porous member can easily secure rigidity, and therefore, sufficient rigidity can be secured even when the flow rate of gas is small.
Further, the radial bearing 20 is not limited to a single member, and may be divided into a plurality of members and arranged as needed.

The gas bearing 21A constituting the thrust bearing 21 is a substantially cylindrical porous member made of graphite, so that the axial rear end surface 22 of the gas bearing 21A faces the front side surface 16a of the flange portion 16 of the rotating shaft 12. Then, it is fitted and fixed to the annular groove 36 with a tightening margin. The gas bearing 21A is configured by a self-made drawing method, and a plurality of small diameter holes (not shown) communicating with the bearing gas supply path 41 are opened in the axial rear end surface 22 of the gas bearing 21A. The gas bearing 21A blows compressed air supplied from the bearing gas supply path 41 from a plurality of small-diameter holes toward the front side surface 16a of the flange portion 16 into the gap between the front side surface 16a of the flange portion 16 and the gas bearing 21A. The generated pressure difference pulls the rotating shaft 12 backward with respect to the housing 30.

Further, the magnetic bearing 21B constituting the thrust bearing 21 has a magnet 50 held by the magnet yoke 51. The magnet yoke 51 is screwed and attached to the magnet attachment portion 37 formed on the rear end surface 35a of the disk portion 35 of the housing 30. In this state, the magnet 50, which is a permanent magnet, is in close contact with the front side surface 16a of the flange portion 16. Therefore, the flange portion 16 is attracted forward by the magnetic force of the magnet 50.

As a result, in the thrust bearing 21 of the present embodiment, the magnetic bearing 21B blows the attractive force (magnetic force) of the magnet 50 and the gas bearing 21A blows compressed air toward the front side surface 16a of the flange portion 16. The rotating shaft 12 is supported in the thrust direction without contacting the housing 30 by the reaction force, and the rotating shaft 12 is pulled out to the rear by the magnet 50 (the rotating shaft 12 is separated from the housing 30). Is prevented.

Supporting the rotating shaft 12 in the thrust direction with the thrust bearing 21 made of such a composite bearing has a smaller bearing loss than the case where the rotating shaft 12 is supported only with the gas bearing.
Further, when the rotating shaft 12 is supported only by the gas bearing, it is necessary to blow gas from both sides of the flange portion 16, so that the axial length of the spindle device 10 becomes long, but when the magnet 50 is used, the axial length of the spindle device 10 becomes long. Since gas is blown and attracted by the magnet 50 to one of the two side surfaces of the flange portion 16, the axial length of the spindle device 10 can be shortened.

It is preferable that the gas is sprayed and the magnet 50 is attracted to the front side surface 16a of the two side surfaces of the flange portion 16. As a result, the gas bearing 21A (gas ejection portion) and the magnetic bearing 21B are arranged on the front end side of the flange portion 16, so that the axial length of the spindle device 10 is longer than that on the rear end side of the flange portion 16. Can be shortened. Further, when the radial bearing 20 and the gas bearing 21A of the thrust bearing 21 are separately configured, the magnet 50 is arranged on the inner diameter side with respect to the gas bearing 21A to lay out the bearing gas supply path 41 of the gas bearing 21A. Can be easily configured.

In the rear housing 33, a turbine air supply path (not shown) for supplying compressed air for operation to the turbine blades 11 is formed in a phase different from that of the bearing gas supply paths 40 and 41. Further, a plurality of nozzles (not shown) communicating with the turbine air supply path are formed in the rear housing 33 so as to face the turbine blades 11 and open on the inner peripheral surface. Therefore, by controlling the flow rate of the air supplied to the turbine air supply path, the rotating shaft 12 can obtain a predetermined rotational speed.

In the spindle device 10 configured in this way, the rotating shaft 12 is rotatably supported by the housing 30 in a non-contact manner by supplying gas (compressed air) to the gas bearing 21A of the radial bearing 20 and the thrust bearing 21. It becomes a state. Further, by ejecting gas from the plurality of nozzles toward the plurality of turbine blades 11, the kinetic energy of the jet stream is converted into the rotational driving force of the rotating shaft 12, and the rotating shaft 12 is rotationally driven.

Further, in the spindle device 10 of the present embodiment, the axial position of the center of gravity G of the rotating shaft 12 is between the axial center C of the radial bearing 20 and the output side end surface 20a which is the front end surface of the radial bearing 20. It is set. The axial position of the center of gravity G of the rotating shaft 12 is set within the above range by adjusting the wall thickness, the diameter dimension, etc. of the cylindrical portion 15 and the flange portion 16.

Here, the center of gravity G of the rotating shaft 12 means that the bell cup 1 is attached to the rotating shaft 12 when a bell cup (loading object) 1 for an electrostatic coating machine is attached to the front end of the rotating shaft 12. It means the center of gravity in the state of being.
Further, the axial center C of the radial bearing 20 means the axial center of the output side end surface 20a and the opposite output side end surface 20b in the range functioning as the radial bearing 20. Therefore, even when the radial bearing 20 is divided into a plurality of parts, the axial center C of the radial bearing 20 means the axial center of the output side end face and the counter-output side end face in the range functioning as the radial bearing 20. To do.

When the spindle device 10 of the present embodiment is used for electrostatic coating, the spindle device 10 is attached to the tip of a robot arm. Then, a paint discharge tube is inserted into the hollow portion 15a of the rotating shaft 12, and compressed air is ejected from a plurality of nozzles toward the turbine blades 11 via the turbine air supply path to rotate the rotating shaft 12 at high speed. , The paint is atomized and painted.

At that time, the unbalance of the rotating shaft 12 can be corrected by processing the hollow portion 15a, but if the unbalance remains on the rotating shaft 12, the rotating shaft 12 becomes unbalanced with rotation. The load is generated in the radial direction. Further, when the rotating shaft 12 is rotating at high speed and the spindle device 10 is swiveled by the robot arm, a gyro moment is generated on the rotating shaft 12.

In the spindle device 10 having a configuration as in this embodiment, the radial bearing 20 receives both an unbalanced load and a gyro moment load, but the radial bearing 20 is unbalanced on the output side with respect to the center of gravity G of the rotating shaft 12. The ratio of receiving the balance load is large, and the ratio of receiving the load of the gyro moment on the counter-output side with respect to the center of gravity G of the rotating shaft 12 is large.

In the present embodiment, the center of gravity G of the rotating shaft 12 is set on the output side of the radial bearing 20 (between the axial center C of the radial bearing 20 and the output side end surface 20a of the radial bearing 20). Therefore, the gyro moment of the rotating shaft 12 is relative to the length L1 of the output side portion of the radial bearing 20 (between the center of gravity G of the rotating shaft 12 and the output side end surface 20a of the radial bearing 20) that mainly receives the unbalanced load. The length L2 of the counter-output side portion of the radial bearing 20 (between the center of gravity G of the rotating shaft 12 and the counter-output side end surface 20b of the radial bearing 20) is increased. As a result, the non-output side portion of the radial bearing 20 has a large residual force for receiving the load of the gyro moment.

Therefore, the radial bearing 20 receives an unbalanced load, and even if a large gyro moment is generated due to the turning movement of the spindle device 10, the radial bearing 20 can receive the load of the gyro moment, and while securing a gap between the gas bearings, It is possible to maintain stable high-speed rotation.

Further, the radial bearing 20 is configured such that the ratio of the axial dimension (L) to the inner diameter (D) is 0.5 ≦ L / D ≦ 1.5. This is because if the L / D is smaller than 0.5, the load capacity of the radial bearing 20 is insufficient, and the radial bearing 20 and the rotating shaft 12 may come into contact with each other due to an imbalance of the rotating shaft 12. .. Further, when the L / D is larger than 1.5, the effect of downsizing and weight reduction (energy saving) of the spindle device 10 is small.

The present invention is not limited to the above-described embodiment, and can be appropriately modified, improved, and the like.
For example, in the present embodiment, the spindle device 10 of the present invention has been described as being used for an electrostatic coating machine, but the present invention is not limited to this, and a semiconductor manufacturing device (wafer outer peripheral chamfering machine) or a machined product is used. It can also be applied to the edge deburring machine of.

Further, in the present embodiment, the thrust bearing 21 is formed by the gas bearing 21A and the magnetic bearing 21B to support the rotating shaft 12 in the thrust direction. However, the present invention is not limited to this, and a plurality of gas bearings are used. Therefore, the rotating shaft 12 may be supported in the thrust direction by supplying gas.

Further, the radial bearing 20 of the present invention is not limited to the porous drawing method, and the gas bearing 21A of the thrust bearing 21 of the present invention is not limited to the self-drawing method, and all of them are gases of other types. Bearings may be applied.

Further, although it has been described that the radial bearing 20 and the gas bearing 21A of the thrust bearing 21 are formed separately and fitted to the housing 30 with a tightening allowance, the gas bearing 21A of the radial bearing 20 and the thrust bearing 21 has been described. May be integrally molded and fitted to the housing 30 with a tightening allowance.

1 Bell cup (loaded)
10 Spindle device 11 Turbine blade 12 Rotating shaft 16 Flange portion 16a Front side surface (one side surface of flange portion)
20 Radial bearing 20a Output side end face 20b Non-output side end face 21 Thrust bearing 21A Gas bearing 21B Magnetic bearing 30 Housing 50 Magnet C Axial center of radial bearing D Inner diameter of radial bearing G Center of gravity of rotating shaft L Axial dimension of radial bearing

Claims (7)

A rotating shaft with multiple turbine blades installed across the circumference and a load can be attached to the front end.
A housing for accommodating the rotating shaft and
A radial bearing that is attached to the housing and floats and supports the rotating shaft with respect to the housing by supplying gas.
A spindle device that rotationally drives the rotating shaft by ejecting gas to the plurality of turbine blades.
A spindle device in which the center of gravity of the rotating shaft is set between the axial center of the radial bearing and the output side end surface of the radial bearing. The spindle device according to claim 1, wherein the radial bearing is a porous drawing type gas bearing. The spindle device according to claim 1 or 2, wherein the radial bearing is configured such that the ratio of the axial dimension (L) to the inner diameter (D) is 0.5 ≦ L / D ≦ 1.5. .. The spindle device according to any one of claims 1 to 3, wherein the housing has a specific gravity of 4.0 or less, and the radial bearing is fitted with a tightening allowance. The rotating shaft is provided with a flange portion extending radially outward from the rotating shaft at the rear end portion of the rotating shaft.
A magnet that faces one side surface of the flange portion and exerts an axial attraction on the flange portion, and is attached to the housing so as to face the one side surface of the flange portion, and is attached to the housing by supplying gas. The spindle device according to any one of claims 1 to 4, further comprising a thrust bearing that has a gas bearing that blows compressed air toward a flange portion and supports the rotating shaft in the thrust direction in a non-contact manner. The spindle device according to claim 5, wherein the gas bearing constituting the thrust bearing is a self-made drawing type. The spindle device according to claim 5 or 6, wherein the housing has a specific gravity of 4.0 or less, and the gas bearing is fitted with a tightening allowance.

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