JPH0735682Y2 - Built-in motor type spindle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a spindle with a built-in motor, and more particularly to a spindle with a built-in motor having an internal cooling structure useful for a machine tool spindle.

[Conventional technology]

This type of motor built-in spindle is shrink fitted directly to the outer circumference of the rotating shaft with respect to the stator attached to the inner circumference of the casing,
Alternatively, a structure in which the rotor is loosely fitted by cold fitting or the like is common, but the rotating shaft holding the rotor is thermally deformed by the heat generation of the built-in motor. . In particular, precision spindles with built-in motors and high-speed rotating spindles lead to shortened bearing life and reduced accuracy. In order to prevent the thermal deformation of the rotating shaft, conventionally, the entire rotating shaft is made of ceramic, and a sleeve inserted through the rotating shaft is fitted with a rotor to reduce the thermal expansion of the shaft (for example, a real one). (Kaisho 64-2565 gazette) or a groove in the circumferential direction is formed on the outer circumference of the rotary shaft, and a sleeve is fixed to the outer circumference of the shaft so as to cover the circumferential groove, and the rotor is fixed via the sleeve. Along with the axial direction of the rotor, the sleeve is formed with radial oil insertion holes that communicate with the circumferential groove, and the hollow portion of the rotary shaft passes through the circumferential groove and the oil passage inside the casing. There is known a structure in which a cooling medium is ejected to spray-cool it (for example, Japanese Utility Model Laid-Open No. 61-88467). The circumferential groove is used as a spiral groove, and the oil mist introduced from the casing side is passed from one radial air hole of the sleeve through the spiral groove of the rotary shaft to the other radial air hole, and the oil mist is passed through the sleeve of the rotor. A structure has also been proposed in which the heat of the motor is cooled so as not to be transferred to the shaft side (No. Shokai 61-88468).

[Problems to be solved by the device]

However, among the conventional spindles with a built-in motor,
The one in which the entire shaft is made of ceramic is cumbersome to manufacture, costly, and does not have a structure that actively cools it.There is no escape area for the heat generated inside, so the sleeve interposed between the shaft and rotor does not undergo thermal deformation. There is a drawback in that the bearing preload changes because the bearing prestrates and the sleeve preloads the bearing via the collar. Further, a groove is formed in the outer circumference of the rotary shaft to form a space between the outer circumference of the shaft and the sleeve, and the fluid is allowed to flow in this portion.
In the case of 88467, the inner circumference side of the sleeve is partially cooled, but since the outer circumference of the sleeve and the rotor are closely fitted, the outer circumference side is not directly cooled, and the heat generated by the rotor is directly applied to the sleeve. Although the temperature of the sleeve can be slightly decreased compared to the above example, the sleeve is deformed and stretched, and the elongation of the sleeve changes the bearing preload in the same manner as in the above example, which causes a change in the bearing preload. . In the case of the rotary electric machine of No. 61-88468, which is described above, it is considered that there is almost no pressure difference between the radial vent holes provided at both ends of the spiral groove, so cooling by the spiral groove cannot be expected and the sleeve temperature The same problem as described above arises because the structure is such that the rise is unavoidable and the elongation of the sleeve changes the bearing preload.

[Means for Solving the Problems]

Therefore, the present invention provides a layer of a heat insulating member having a small linear expansion coefficient on the outer periphery of the rotating shaft and causes the flow of cooling air between the heat insulating member and the rotor, so that heat generation of the rotor is prevented from being transmitted to the shaft side as much as possible. Another object of the present invention is to provide a spindle with a built-in motor that has a structure in which the bearing preload is unlikely to change due to heat generation of the rotor. That is, the present invention is
In a spindle with a built-in motor in which a rotating shaft fitted with a rotor is inserted into a stator attached to the inner circumference of a casing, the outer circumference of the rotating shaft fitted to the rotor has a thick wall of a heat insulating member having a small linear expansion coefficient. The welding molding layer is formed longer than the axial length of the rotor, and the outer surface of the welding molding layer has a plurality of narrow concave grooves extending in the axial direction with a length having at least a portion exceeding the axial length of the rotor. Is formed, the depth of the recessed groove is approximately 1/2 the thickness of the welding molding layer,
A hollow hole having one end closed and the other end opened is formed in the rotary shaft, and a communication hole that connects the hollow hole and the concave groove on the outer periphery of the welding forming layer and an annular groove that connects the communication holes are formed. Cooling gas is sent from the opening of the hollow hole of the rotating shaft so that the cooling gas is brought into contact with the inner surface of the rotor fitted to the outer periphery of the welding-molded layer and flows out to both ends of the rotor.

[Action]

In the present invention, a thick layer of a material such as ceramic having a small coefficient of linear expansion and a high heat insulating property, which is shown in the drawing, is interposed between the rotor and the rotating shaft, and the heat insulating layer is axially arranged in the axial direction. Since a large number of recessed grooves are formed to reduce the contact area with the rotor, and cooling gas is circulated from the outside to the recessed grooves through the rotating shaft to perform forced gas cooling, heat to the rotating shaft is reduced. Since the transmission can be extremely reduced and the rotor is supported only by the heat insulating material layer having a small linear expansion coefficient, the fluctuation of the bearing preload is small. In this invention, ceramic can be used as the heat insulating member and the outer circumference of the shaft can be adhered by means such as welding.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

Referring to FIG. 1, a stator 2 of a motor is fixed to an inner peripheral portion of a spindle casing 1, and a rotary shaft 3 is rotatably supported by bearings 4 and 5 so as to penetrate the center of the casing 1. Has been done. The outer diameter of the rotating shaft 3 is small over a required length in the portion inside the casing 1, and a material having a small linear expansion coefficient and a high heat insulating property such as ceramic is filled by means such as thermal spraying so as to fill the small diameter portion. It is welded and molded. The thickness of the welding molding layer 6 has a certain thickness as shown in the drawing, and the length of the welding molding layer 6 is longer than the axial length of the rotor 7 of the motor fitted thereon. After welding again, a plurality of recessed grooves 8 extending in the axial direction are formed on the outer periphery of the welding molding layer 6 as shown in an enlarged view in FIGS. 2 and 3. As shown in FIGS. 1 and 2, the depth of each recessed groove 8 is almost half that of the welding molding layer 6, and the length of each recessing groove 8 is shorter than the length of the welding molding layer 6. It is formed to be short but at least longer than the axial length of the rotor 7. Therefore, both ends of each groove 8 are exposed in the casing 1 from both end faces of the rotor 7 in a state where the rotor 7 is fixed to the outer periphery of the welding layer 6. is doing.

The rotary shaft 3 is formed with a hollow hole 9 concentric with the rotary shaft from one end thereof to the vicinity of the other end thereof, and further, at a midway position of the hollow hole 9 in the axial direction, from the hollow hole 9 to the welding molding layer 6. A radial communication hole 10 is formed to connect to the groove 8. Communication hole
An annular groove 11 is formed on the outer periphery of the welded layer 6 at the position 10 so as to connect all the axial recessed grooves 8. Therefore, each concave groove 8 communicates with the hollow hole 9 of the rotary shaft 3 through the annular groove 11. As shown in FIG. 1, a nozzle member 13 attached to a bearing retainer 12 is inserted into the open end of the hollow hole of the rotary shaft 3 so as not to interfere with the rotating operation of the rotary shaft. A supply pipe connected to a cooling air supply source (not shown) is connected to the nozzle member 13.

The rotor 7 is closely fitted to the outer peripheral surface of the ridge that defines the groove 8 so as to surround the groove 8 of the welding layer 6, and in this state, the rotor outer surface has a predetermined gap with the stator. Two
Faces the inner surface of the. When the rotor 7 and the rotating shaft 3 are rotated by the power supply to the stator 2, the nozzle member
A cooling gas, for example, air is fed into the hollow hole 9 of the rotary shaft 3 through 13. The cooling gas flows through the communication hole 10 and the annular groove 11 to both sides in the axial direction in each groove 8, and then flows into the casing 1 from both ends thereof. When the cooling gas flows through each groove 8, the inner peripheral surface of the rotor 7 is directly cooled. Further, the contact area between the rotor 7 and the welding molding layer 6 is reduced by the respective concave grooves 8, and since the welding molding layer itself is a heat insulating material such as ceramic, heat transfer from the rotor 7 to the rotary shaft 3 is reduced. ,
As a result, the temperature rise of the rotary shaft is prevented, and the change of the bearing preload and the accuracy reduction of the spindle due to the thermal deformation as in the conventional case are prevented. The cooling gas flowing from the groove 8 into the casing 1 is discharged to the outside through the bearings 4 and 5 and the power supply line portion of the stator 2, and the heat is not trapped in the casing 1. In the present embodiment, the concave groove formed in the fusion-molded layer of the heat insulating member is an axial groove, but it may be a spiral groove. Further, although the molding layer is formed in the small diameter portion provided on the rotary shaft, the small diameter portion may not be provided.

[Effect of device]

As described above, according to the present invention, a heat-insulating welding forming layer is formed by ceramic spraying or the like between the rotor and the rotating shaft, and a groove is formed on the outer periphery of the heat insulating welding forming layer, and the outer surface thereof is formed. Since the rotor was fitted and the cooling gas was circulated from the outside into the groove to directly cool the rotor, the rotor was supported by the rotating shaft through the heat insulating molding layer having a small linear expansion coefficient. As a result, the contact area of the fitting portion of the rotor is also reduced, the heat transfer from the rotor to the rotary shaft is reduced, and the temperature rise of the rotary shaft is prevented. Since the thermal deformation of the rotating shaft is suppressed, the spindle accuracy is improved and high speed is secured. Further, the heat insulating layer can be easily formed, which brings many advantages that have not been obtained in the past.

[Brief description of drawings]

1 is a vertical sectional view of a spindle with a built-in motor according to an embodiment of the present invention, FIG. 2 is a partially enlarged vertical sectional view of a rotor fitting portion of the embodiment shown in FIG. 1, and FIG. Figure III-III
A partial cross-sectional view along the line, FIG. 4 is IV-IV of FIG.
FIG. 4 is a partial cross-sectional view taken along the line. 1 ... Casing, 2 ... Stator, 3 ... Rotating shaft, 4,5 ... Bearing, 6 ... Welding forming layer, 7 ... Rotor, 8 ... Recessed groove, 9 ... Hollow hole, 10 ... Communication hole, 11 ... Annular groove, 12 ... bearing retainer, 13 ... nozzle member.

Claims (2)

[Scope of utility model registration request] 1. In a spindle with a built-in motor in which a rotary shaft fitted with a rotor is inserted into a stator mounted on the inner circumference of a casing, the outer circumference of the rotary shaft fitted with the rotor has a small thermal expansion coefficient. A thick weld forming layer of the member is formed longer than the axial length of the rotor, and the outer surface of the weld forming layer has a plurality of narrow axially extending lengths having at least a portion exceeding the axial length of the rotor. A groove having a width is formed, and the depth of the groove is approximately 1/2 of the thickness of the welding molding layer.
And a hollow hole having one end closed and the other end open to the rotary shaft, and a communication hole that connects the hollow hole and the concave groove on the outer periphery of the welding molding layer and an annular shape that connects the communication holes. A groove is formed so that cooling gas is sent from the hollow hole opening of the rotary shaft so that the cooling gas is brought into contact with the inner surface of the rotor fitted to the outer periphery of the welding layer and flows out to both ends of the rotor. Built-in motor type spindle. 2. The spindle with a built-in motor according to claim 1, wherein the welding molding layer is a ceramic welding molding layer.