JP2001193744A - Spindle support device for machine tool spindles - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize, at low cost, a structure hardly causing skidding damage to a base end rolling bearing 6b supporting a base end of a spindle 1. SOLUTION: A cylindrical roller bearing with an outer ring raceway track 14 or the like having a non-circular cross section is used as the base end rolling bearing 6b. Preload is applied to some cylindrical rollers 16, 16 to diminish revolution sliding, so that the skidding damage is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle, which is incorporated in various types of machine tools such as a machining center and rotates at a high speed while a tool or a workpiece is supported and fixed at a tip end thereof, with respect to a fixed housing. The present invention relates to an improvement of a rotation supporting device for freely supporting.

[0002]

2. Description of the Related Art The main shaft of a machine tool rotates at a high speed during use and is affected by heat generated at a contact portion (working portion) between a tool and a workpiece, so that the entire length thereof expands and contracts.
That is, the main shaft is elastically deformed in a direction in which the entire length is reduced instead of the diameter thereof being increased based on the centrifugal force accompanying the high-speed rotation. Further, due to the influence of the heat, the entire length of the main shaft becomes longer due to thermal expansion or becomes shorter due to thermal contraction. On the other hand, it is important for precision machining that the position of the tip portion of the spindle is not displaced irrespective of changes in the rotation speed or temperature of the spindle.

In the case of a so-called motor-built-in type machine tool, in particular, a rotor of an electric motor is fixed to an outer peripheral surface of an intermediate portion of a spindle, and the spindle itself functions as a rotation axis of the electric motor. The rotation speed of the spindle is high, and the speed of change (acceleration, deceleration) is remarkable. Therefore, in the case of such a main shaft of a motor built-in machine tool, it is necessary to use a rolling bearing for supporting the main shaft that can withstand high-speed operation. Further, due to the change in the operating condition of the machine tool and the heat generated by the rotor and the stator constituting the electric motor,
Since the change in the total length of the main shaft becomes remarkable, it is necessary to adopt a structure that can smoothly absorb the change.

For this reason, conventionally, the tip of the main shaft is prevented from being displaced in the axial direction of the main shaft with respect to the housing by a front-end rolling bearing unit, and a radial load applied to the front end of the main shaft is supported so as to be freely supported. At the same time, the base end side of the main shaft is supported by a base end side rolling bearing to support a radial load applied to the base end portion of the main shaft, but the main shaft is allowed to freely displace in the axial direction. FIGS. 3 and 4 show a conventional structure of a rotary support device for a main shaft of a machine tool having such a function.
An example is shown.

[0005] First, in the case of the first example shown in FIG. 3, the tip (the left end in FIG. 3) of the main shaft 1 is connected to a pair of angular (or deep groove) ball bearings 2, 2. It is supported on a fixed housing 4 by a tip side rolling bearing unit 3 combined with a back surface. The inner races of the ball bearings 2 and 2 are externally fitted and fixed to the outer peripheral surface of the front end portion of the main shaft 1 by interference fit, and the outer race is similarly internally fixed to the inner peripheral surface of the housing 4 by interference fit. I have. Therefore, the distal-end-side rolling bearing unit 3 supports the distal end of the main shaft 1 so as to prevent axial displacement and to support a radial load applied to the distal end of the main shaft 1. On the other hand, the base end side (the right end side in FIG. 3) of the main shaft 1 is fixed by a base end side rolling bearing 6 formed by combining a pair of angular type (or deep groove type) ball bearings 5 on the back side. Of the housing 4a. This housing 4a is
It may be one body or separate body. The inner races of the ball bearings 5 and 5 are externally fitted and fixed to the outer peripheral surface of the base end portion of the main shaft 1 by interference fit. Similarly, the outer race is internally fitted to the inner peripheral surface of the housing 4a by a clearance fit. I have. Therefore, the base-side rolling bearing 6 supports the base end of the main shaft 1 for a radial load applied to the base end, but supports the main shaft 1 in an axially displaceable manner. Further, a rotor 9 is fixed between the distal-end rolling bearing unit 3 and the proximal-end rolling bearing 6 at an intermediate portion of the main shaft 1, and is supported by an outer peripheral surface of the rotor 9 and a fixed portion such as a housing. Stator 10
The electric motor 11 is configured so as to face the inner peripheral surface of the electric motor 11. During operation of the machine tool, the stator 10 is energized to rotate the spindle 1 at high speed.

In the case of the second example shown in FIG. 4, the tip of the main shaft 1 (the left end in FIG. 4) is connected to a pair of angular (or deep groove) ball bearings 2, 2. It is supported on a fixed housing 4 by a tip side rolling bearing unit 3a formed in parallel combination. The inner races of the ball bearings 2 and 2 are externally fitted and fixed to the outer peripheral surface of the front end portion of the main shaft 1 by interference fit, and the outer race is similarly internally fixed to the inner peripheral surface of the housing 4 by interference fit. I have. Therefore, the tip side rolling bearing unit 3 a
Axial displacement to the proximal end (right side in FIG. 4) is prevented, and the radial load applied to the distal end of the main shaft 1 is supported so as to be freely supported. On the other hand, the base end side of the main shaft 1 (the right end side in FIG. 4)
And a pair of angular (or deep groove) ball bearings 5, 5
Are supported on the fixed housing 4a by a base-side rolling bearing 6a formed by combining in parallel. The directions of the contact angles of the ball bearings 5 and 5 are opposite to the directions of the contact angles of the ball bearings 2 and 2. The inner races forming the respective ball bearings 2 and 2 are externally fitted and fixed to the outer peripheral surface of the front end portion of the main shaft 1 by interference fit, and the outer race is similarly internally fitted to the inner peripheral surface of the housing 4a by a clearance fit. Sleeve 7
Is fixed inside. Further, a spring 8 is provided between the sleeve 7 and the housing 4a so that the sleeve 7
The ball bearings 5 and 5 are provided with elasticity in a direction in which a preload is applied. Therefore, the base-side rolling bearing 6a supports the base end of the main shaft 1 in a radial load applied to the base end, but supports the main shaft 1 in an axially displaceable manner. The fact that the electric motor 11 is assembled to the intermediate portion of the main shaft 1 is the same as in the case of the first example shown in FIG.

As described above, in the case of the conventional rotary support device for the main shaft of a machine tool, the ball bearings 5, 5 are used for the base side rolling bearings 6, 6a for supporting the base side of the main shaft 1. are doing. The reason for this is that in the case of a rotary support device for a main shaft of a motor built-in type machine tool, the base-side rolling bearing 6,
This is because the load applied to 6a is small, and skidding damage is likely to occur when a general roller bearing is used.
That is, the load (cutting force) generated at the contact portion between the tool or the workpiece supported by the tip of the spindle 1 and the workpiece or the tool and generated by the processing of the workpiece is almost at the tip side. The rolling bearing units 3 and 3a support and hardly transmit to the base-side rolling bearings 6 and 6a. Most of the load transmitted to the base-end rolling bearings 6 and 6a is in the case of a horizontal machine tool in which the spindle 1 is arranged in a horizontal direction, and is only a part of the own weight of the spindle 1. . Furthermore,
In the case of a vertical machine tool in which the main shaft 1 is disposed in the vertical direction, the main shaft 1 is mounted on the base-side rolling bearings 6 and 6a.
Even the own weight is not applied, and only the unbalanced load is applied, resulting in an extremely light load.

As described above, when a general roller bearing is used as the base-side rolling bearing 6, 6a to which only a light load is applied at the time of high-speed rotation, the rolling of the roller that does not rotate while being pressed against the outer ring raceway by centrifugal force. The above-mentioned skidding damage occurs in which the surface is worn by rubbing against the inner raceway. Such skidding damage occurs not only in the roller bearing but also in the ball bearing. In the case of the ball bearing, the occurrence of the skidding damage is prevented by applying a preload, and the support of the main spindle 1 rotating at a high speed. Can be performed. Conventionally, ball bearings have been used as the base-side rolling bearings 6 and 6a. Conversely, in general, in the case of a roller bearing, if a preload is applied (negative internal clearance) to prevent the occurrence of skidding damage, damage such as seizure occurs with high-speed rotation. Conventionally, spindle 1 of high-speed machine tool
Roller bearings have not been used as base-end rolling bearings for supporting the base end of the roller.

[0009]

Of the conventional structures shown in FIGS. 3 and 4, in the case of the first example shown in FIG. 3, the shafts of the outer rings of the ball bearings 5, 5 accompanying the expansion and contraction of the main shaft 1 are shown. The directional displacement may not always be performed smoothly. That is, the entire length of the main shaft 1 expands and contracts with a change in rotation speed and temperature, and the outer rings of the ball bearings 5 and 5 move with the expansion and contraction.
However, since the outer peripheral surface of the outer ring and the inner peripheral surface of the housing 4a are not necessarily smooth surfaces and the lubrication state may not be good, the axial displacement of the outer ring May not be performed smoothly. In particular,
When the rotation speed of the main shaft 1 changes suddenly, the possibility that such axial displacement becomes defective increases. And
If this axial displacement is not performed smoothly, the outer peripheral edge of each outer ring meshes with the inner peripheral surface of the housing 4a to generate stick, and the preload of each of the ball bearings 5, 5 is reduced. It becomes excessively large, and there is a possibility that damage such as seizure may occur in these ball bearings 5, 5.

On the other hand, in the case of the second example shown in FIG. 4, in addition to the problem that the axial displacement cannot always be performed smoothly as described above, the resonance at the base-side rolling bearing 6a is caused. And the problem that the structure is complicated and the cost increases. That is, the sleeve 7, which is axially pressed by the spring 8 with a constant elastic force, resonates at a specific rotational speed based on the minute vibration of the main shaft 1 rotating at a high speed, and axial vibration is likely to occur. Further, the provision of the sleeve 7 and the spring 8 complicates the structure and increases the cost. In order to smoothly perform the axial displacement of the sleeve 7 due to the expansion and contraction of the main shaft 1, a ball spline may be provided between the outer peripheral surface of the sleeve 7 and the inner peripheral surface of the housing 4a. The structure becomes more and more complicated and the cost becomes higher. The rotary support device for a spindle of a machine tool according to the present invention has been invented in view of such circumstances.

[0011]

A rotary support device for a main shaft of a machine tool according to the present invention comprises a main shaft rotating about its axis, like the above-described rotary support device for a main shaft of a conventional high-speed machine. A tip-side rolling bearing unit provided between an outer peripheral surface of a distal end portion of a main shaft and an inner peripheral surface of a fixed housing, for preventing axial displacement of the main shaft and supporting a radial load applied to a front end portion of the main shaft; Provision is made between the base outer peripheral surface of the main shaft and the inner peripheral surface of the fixed housing to support the radial load applied to the base end of the main shaft, but to allow the axial displacement of the main shaft. And a bearing.
In particular, in the rotary support device for a main shaft of a machine tool according to the present invention, the base rolling bearing is a cylindrical roller bearing. Then, at least one of the outer raceway and the inner raceway constituting the cylindrical roller bearing is non-circular at least when assembled to the outer peripheral surface of the main shaft and the inner peripheral surface of the housing.

[0012]

According to the rotary support device for a main shaft of a machine tool of the present invention having the above-described structure, the following operations and effects can be obtained. It is possible to prevent the occurrence of skidding damage on the base-end rolling bearing that rotates at a high speed under a light load state. That is, since at least one of the outer raceway and the inner raceway of the cylindrical roller bearing that is the base rolling bearing is made non-circular,
The interval between these two orbits is reduced in a part of the circumferential direction, so that the rolling surface of the cylindrical roller existing in the portion is elastically pressed against these two orbits simultaneously (in a state where a preload is applied). . For this reason, the plurality of cylindrical rollers constituting the cylindrical roller bearing do not revolve without rotating, that is, so-called revolving sliding, so that the occurrence of the skidding damage can be prevented. The axial displacement on the base end side of the main shaft accompanying the expansion and contraction of the main shaft is smoothly performed, so that the occurrence of stick can be prevented. That is, the rolling surfaces of the plurality of cylindrical rollers and the outer raceway and the inner raceway that slide with respect to each other at the time of the axial displacement are finished smoothly and are sufficiently lubricated. Accordingly, the resistance to the axial displacement is extremely small, and the axial displacement can be smoothly performed, thereby preventing the occurrence of stick. The provision of the base-end rolling bearing does not require a sleeve, a spring, or a ball spline, so that the structure can be simplified and the cost can be reduced. Since the preload by the spring is not applied to the base-end rolling bearing, regardless of the rotational speed fluctuation of the main shaft, the minute vibration of the main shaft and the base-end rolling bearing do not resonate, and the chatter noise is reduced. And other harmful vibrations and noises can be prevented.

[0013]

1 and 2 show an embodiment of the present invention. Tip of spindle 1 (left end in FIG. 1)
And a pair of angular (or deep groove) ball bearings 2, 2
Side rolling bearing unit 3 which is composed of
, And is supported with respect to the fixed housing 4. The inner races of the ball bearings 2 and 2 are externally fitted and fixed to the outer peripheral surface of the front end portion of the main shaft 1 by interference fit, and the outer race is similarly internally fixed to the inner peripheral surface of the housing 4 by interference fit. I have. Therefore, the distal-end-side rolling bearing unit 3 prevents the distal end portion of the main shaft 1 from being displaced in the axial direction.
The bearing supports the radial load applied to the tip of the.

On the other hand, the base end side of the main shaft 1 (FIG. 1)
Is supported by a base-side rolling bearing 6b with respect to the fixed housing 4a. This housing 4a
May be integral with or separate from the housing 4. In the case of the rotary support device for a main shaft of a machine tool according to the present invention, the base-side rolling bearing 6b has a cylindrical inner raceway 1 on its outer peripheral surface.
2, an outer ring 15 having a cylindrical outer raceway 14 on the inner peripheral surface thereof, and a plurality of cylindrical rollers 16, 1 provided so as to be able to roll between the inner raceway 12 and the outer raceway 14.
6) a cylindrical roller bearing. Among the components of the base-side rolling bearing 6b, flanges 17 are formed at both ends of the outer peripheral surface of the inner ring 13 so as to sandwich the inner raceway 12 from both sides in the axial direction. Each of the above cylindrical rollers 16, 16
Are arranged between the flanges 17 to prevent the cylindrical rollers 16 from being displaced in the axial direction with respect to the inner ring 13. In contrast, the outer ring 15
No flange is formed on the inner peripheral surface of the cylindrical roller, and the cylindrical rollers 16, 16 can be freely displaced in the axial direction with respect to the outer ring 15.
Therefore, the axial displacement between the inner ring 13 and the outer ring 15 is free.

[0015] Of the base-end rolling bearing 6b as described above,
The inner ring 13 is externally fitted and fixed to the outer peripheral surface of the tip portion of the main shaft 1 by interference fit, and the outer ring 15 is similarly internally fixed to the inner peripheral surface of the housing 4a by interference fit. Accordingly, the base-side rolling bearing 6b supports the base end of the main shaft 1 with a radial load applied to the base end, and the shaft of the main shaft 1 is based on the axial displacement between the inner ring 13 and the outer ring 15. It supports directional displacement freely.

The cross-sectional shape of the inner raceway 12 provided on the outer peripheral surface of the inner race 13 constituting the cylindrical roller bearing which is the base rolling bearing 6b, and the outer raceway 14 similarly formed on the inner peripheral surface of the outer race 15 Are each substantially circular. However, the cross-sectional shape of at least one track is slightly non-circular in a state where at least the proximal rolling bearing 6b is assembled to the outer peripheral surface of the main shaft 1 and the inner peripheral surface of the housing 4a. That is, Technical Journal "Lubrication" Vol. 28, No. 6, pp. 435-436, or "Rolling Bearing Engineering" 1st Edition, published by Yokendo Co., Ltd. As described on page 105, pages 363 to 364, and the like, a non-circular cylindrical roller bearing conventionally used for forming a rotary support portion of a jet engine is used as the base-side rolling bearing 6b. use.

Such a non-circular cylindrical roller bearing generally has a non-circular cross-sectional shape of the outer raceway 14 in a use state. The following three types (1) to (3) are known. (1) In a free state, the cross-sectional shape of the outer surface of the outer ring is made non-circular such as an ellipse, the cross-sectional shape of the outer ring raceway is made a perfect circle, and this outer ring is fitted inside a housing whose cross-sectional shape of the inner peripheral surface is a perfect circle In this state, the cross-sectional shape of the outer raceway is made non-circular. In the case of this type, no preload is applied to any of the cylindrical rollers in the free state, but in the state where the outer ring is fixedly fitted in the housing, the major axis of the ellipse having a sectional shape of the outer peripheral surface of the outer ring in the free state is set. The cylindrical rollers existing in the direction are pressed between the outer raceway and the inner raceway (preload is applied). (2) In a free state, the outer peripheral surface of the outer race and the cross-sectional shape of the outer raceway are both non-circular. In the case of this type, a preload is applied to the cylindrical rollers from the free state, the outer ring is fitted in the housing, and even when the non-circular shape of the outer ring has returned to a perfect circle, some cylindrical members are still present. A state is obtained in which a preload is applied to the roller. (3) In a free state, make the cross-sectional shape of the outer peripheral surface of the outer ring a perfect circle,
The cross-sectional shape of the outer raceway is made non-circular, and the outer race is fitted in a housing whose inner peripheral surface has a perfect circular cross-sectional shape. In the case of this type, a preload is applied to some of the cylindrical rollers from the free state, and even when the outer ring is fitted inside the housing,
As a result, a preload is applied to some of the cylindrical rollers.

In addition, even if the above-mentioned non-circular shape is used, FIG.
Elliptical shape (Bilobe bearing) as exaggerated in (A)
And a triangular conical shape (Trilobe bearing) as shown exaggeratedly in FIG. Any shape can be used for the main shaft rotation support device of the machine tool of the present invention. FIG.
Indicates the type of (2) among the above (1) to (3). In the case of this type, in a state where the outer ring 15 is fixedly fitted inside the housing 4a by interference fit, the outer ring 15 is formed between the outer peripheral surface of a portion of the outer ring 15 having a reduced diameter and the inner peripheral surface of the housing 4a. There are slight gaps 18, 18. Then, a preload having a size indicated by an arrow in FIG. 2 is applied to the cylindrical rollers 16, 16 existing on the inner diameter side of the gaps 18, 18. Therefore, each of these gaps 1
Cylindrical rollers 16, 16 existing on the inner diameter side portions of 8, 18
With the rotation of the inner ring 13, the rolling surfaces revolve while rotating, with the respective rolling surfaces pressed against the inner ring track 12 and the outer ring track 14, and no revolving slip occurs.

Further, in the illustrated example, a rotor 9 is fixed between the distal-end rolling bearing unit 3 and the proximal-end rolling bearing 6b at an intermediate portion of the main shaft 1, and the outer peripheral surface of the rotor 9 is Stator 1 supported on a fixed part such as a housing
The electric motor 11 is configured so as to face the inner peripheral surface of the electric motor 11. During operation of the machine tool, the stator 10 is energized to rotate the spindle 1 at high speed.

According to the rotary support device for a spindle of a machine tool of the present invention configured as described above, the following functions and effects can be obtained. It is possible to prevent skidding damage from occurring in the base-end rolling bearing 6b that rotates at a high speed under a light load state. That is,
Outer ring raceway 1 of cylindrical roller bearing which is base end rolling bearing 6b
4 is a non-circular shape such as an elliptical shape or a triangular conical shape, as shown in FIG. 2, the distance between the outer raceway 14 and the inner raceway 12 on the outer peripheral surface of the inner race 13 is determined by the clearances 18, 18. It becomes narrower at a part of the circumferential direction where it matches. Then, the rolling surfaces of the cylindrical rollers 16, 16 existing in the portion correspond to the two orbits 14,
At the same time, the cylindrical rollers 16 are elastically pressed against the cylindrical rollers 12, so that a preload is applied to these cylindrical rollers 16. For this reason, a plurality of cylindrical rollers 16, 16 constituting the cylindrical roller bearing are provided.
However, the so-called revolving slip, which revolves without rotating, can be sufficiently suppressed, and the occurrence of the skidding damage can be prevented.

The axial displacement on the base end side of the main shaft 1 along with the expansion and contraction of the main shaft 1 is smoothly performed, so that sticking can be prevented. That is, the rolling surfaces of the plurality of cylindrical rollers 16, 16 and the outer raceway 14 and the inner raceway 12, which slide with respect to each other at the time of the axial displacement, are finished smoothly and are sufficiently lubricated. I have. Accordingly, the resistance to the axial displacement is extremely small, and the axial displacement can be smoothly performed, thereby preventing the occurrence of stick.

In order to provide the base-side rolling bearing 6b, a sleeve 7, a spring 8, and a ball spline are not required as in the second example of the conventional structure shown in FIG. Can be simplified to reduce costs. Since the preload by the spring is not applied to the base-side rolling bearing 6b, the base-side rolling bearing 6b resonates based on the minute vibration of the main shaft 1 irrespective of the rotational speed fluctuation of the main shaft 1. Therefore, generation of harmful vibration and noise can be prevented.

As described above, the rotary support device for a spindle of a machine tool according to the present invention facilitates axial displacement by using a cylindrical roller bearing as the base-side rolling bearing 6b, and causes harmful vibration and noise. Is prevented, and a preload is applied to some of the cylindrical rollers 16 to prevent the occurrence of skidding damage. In this case, in order to prevent skidding damage, the preload applied to some of the cylindrical rollers 16, 16 is small, and it is easy to manage (prevention of excessive preload). Even when the base-side rolling bearing 6b, which is a roller bearing, is operated at a high speed, it is possible to sufficiently prevent the base-side rolling bearing 6b from being damaged such as seizure.

[0024]

The rotary support device for a main shaft of a machine tool according to the present invention is constructed and operates as described above. Therefore, even when the rotational speed of the main shaft is increased in order to increase work efficiency, the rotary support device for the main shaft is supported. The reliability and durability of the part can be sufficiently ensured. In addition, the cost does not increase.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of an embodiment of the present invention.

FIG. 2 is a view corresponding to an enlarged sectional view taken along the line AA of FIG. 1, showing two examples of the proximal rolling bearing in a state in which the distortion of the shape of the outer ring is exaggerated.

FIG. 3 is a schematic sectional view showing a first example of a conventional structure.

FIG. 4 is a schematic sectional view showing the second example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main shaft 2 Ball bearing 3, 3a Tip side rolling bearing unit 4, 4a Housing 5 Ball bearing 6, 6, a, 6b Base end side rolling bearing 7 Sleeve 8 Spring 9 Rotor 10 Stator 11 Electric motor 12 Inner ring track 13 Inner ring 14 Outer ring track 15 Outer ring 16 Cylindrical roller 17 Flange 18 Clearance

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Naoki Matsuyama 1-5-150 Kugenuma Shinmei, Fujisawa-shi, Kanagawa F-term in NSK Ltd. (reference) 3J101 AA13 AA24 AA42 AA52 AA62 BA53 BA54 BA55 FA01 FA33 FA44 FA55 GA31

Claims (1)

[Claims] 1. A main shaft rotating about its axis,
A tip-side rolling bearing unit that is provided between an outer peripheral surface of a distal end portion of the main shaft and an inner peripheral surface of a fixed housing and that prevents axial displacement of the main shaft and supports a radial load applied to a distal end portion of the main shaft; A base end provided between the base outer peripheral surface of the main shaft and the inner peripheral surface of the fixed housing to support a radial load applied to the base end of the main shaft, but permitting axial displacement of the main shaft. In a rotary support device for a main shaft of a machine tool having a rolling bearing, the base-end rolling bearing is a cylindrical roller bearing, and at least one of an outer ring raceway and an inner ring raceway constituting the cylindrical roller bearing. Orbit
A rotary support device for a main shaft of a machine tool, wherein the main body is non-circular at least when assembled to an outer peripheral surface of the main shaft and an inner peripheral surface of the housing.