JPH03234403A - Method and device for changing pre-load - Google Patents

Abstract

PURPOSE:To change between a constant position pre-load and a constant pressure pre-load securely and easily by engaging a first and a second rigid, members rigidly for the constant position pre-load, and releasing the rigid engagement and pressing a bearing toward a main shaft axis by a resilient member for the constant pressure pre-load. CONSTITUTION:For rotating a main shaft 3 at a low speed, a piston 26 is moved by an oil pressure cylinder 25 to rotate an operation shaft 23 through an engagement pin 23b in the direction of an arrow E, so a rotation spacer 22 is rotated in the direction of an arrow A through an operation groove 22d. A protruding part 22a is then applied to a protruding part 21a of a fixed spacer 21 to be restrained by contact or rigid members with each other for a distance from an outer race 5b of a bearing 5 to an outer race 9b of a bearing 9. In case of high speed rotation, the piston 26 is moved to rotate the operation shaft 23 in the direction of an arrow F through the engagement pin 23b, so the rotation spacer 22 is rotated in the direction of an arrow B to change the application of the protruding part 22a from that with the protruding part 21a of the fixed spacer 21 to that for moving a protruding member 21d of the fixed spacer 21 in the direction of an arrow C against the resiliency of a spring 21e, so a thrust force is applied to the bearings 5, 6, 7, 9 to make a constant pressure pre-load condition, thereby seizure is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a preload switching method and a preload switching device for a main shaft bearing in a machine tool.

(b), Prior Art FIG. 14 is a sectional view showing an example of a conventional preload switching device.

Conventionally, in machine tools, when the spindle rotates at low speed, the preload on the spindle bearing is preloaded at a fixed position to ensure the positioning of the bearing, thereby increasing the rigidity of the spindle during low-speed heavy cutting and allowing the spindle to rotate at high speed. In some cases, the preload on the main shaft bearing is switched from a fixed position preload to a constant pressure preload to prevent the preload from becoming excessive and causing seizure of the bearing.

That is, in the conventional preload switching device 30 shown in FIG. 14, when rotating the main shaft 3 at low speed, the casing 30a
The hydraulic cylinder 32 provided therein is driven to move the piston 32a and the spacer 33 in the direction of arrow D' against the elasticity of the spring 35.

Then, the spacers 36a and 36b slide against the casing 30a and are pushed in the direction of arrow D' by the spacer 33, so that the spacer 36a.

The hydraulic cylinder 3 is connected to the bearing 37 in contact with the spacer 36b via a spacer 39 fixed to the spacer 36a and the main shaft 3.
2, a predetermined fixed position preload is applied by hydraulic pressure.

Further, when rotating the main shaft 31 at high speed, the oil pressure of the hydraulic cylinder 32 is lowered, and the elasticity of the spring 35 moves the piston 32a and the spacer 33 in the direction of arrow C' force. Then, the contact between the spacer 33 and the spacer 36b is released, and the spacers 36a and 36b are pressed in the direction of the arrow D' by the constant pressure preload spring 36, so that the bearing 37 has no contact with the spacer 36b. A constant constant pressure preload is applied via the seat 36a and the spacer 39 by the elastic force of the constant pressure preload spring 36.

(C) 9 Problems to be Solved by the Invention However, in the conventional preload switching device 30, the hydraulic pressure of the hydraulic cylinder 32 is directly used as the preload load in fixed position preload. Since the hydraulic cylinder 32 is located near the main shaft 31, it is easily affected by heat generation due to the rotation of the main shaft 31, and it is difficult to appropriately control the hydraulic pressure of the hydraulic cylinder 32. Therefore, not only is it difficult to adjust the preload load vR in fixed position preload, but also the bearing 3 is affected by the hydraulic pressure of the hydraulic cylinder 32.
This is because the shape allows 7 to be positioned.

This results in the inconvenience that the bearing 37 cannot be positioned reliably, and that rigidity during low-speed heavy cutting cannot be appropriately ensured. Furthermore, the working fluid such as oil from the hydraulic cylinder 32 may leak into the bearing 37 portion of the main shaft 31, which may adversely affect the bearing 37 and cause seizure or the like.

In view of the above circumstances, an object of the present invention is to provide a preload switching method and a preload switching device that can suitably switch between fixed position preload and constant pressure preload.

(d) Means for solving the zero problem The present invention provides first and second rigid members (21a, 22a) in the casing (2, 2') so as to be able to freely abut and engage with each other. Every other elastic member (21d, 21f, 21e,
22f, 22e) are provided in a form that can press the bearings (5, 6, 7, 9) in the direction of the spindle axis, and
, 7, 9) are to be preloaded in place, the first and second rigid members (21a, 22a) are rigidly engaged and the bearings (5, 6, 7, 9) are preloaded. When the movement in the direction of the spindle axis is restrained by the first and second rigid members (21a, 22a) themselves and the bearings (5, 6, 7, 9) are preloaded with a constant pressure, the first and a second rigid member (21a,
22a), and at the same time, the elastic members (21d, 21f, 21e, 22f, 22e) press the bearings (5, 6, 7, 9) in the direction of the spindle axis. configured.

Further, one aspect of the present invention provides a first spacer (21) and a second spacer (21).
22) are provided in the casing (2, 2') so as to be able to freely rotate relative to each other while in contact with each other and to be engaged with the bearings (5, 6, 7, 9); The first space (
21), on the end face facing the second spacer (22),
A first contact surface (21c) in which a convex part (21a) and a concave part (21b) are formed is provided, and the end face of the second spacer (22) facing the first spacer (21) is provided. , a convex portion (22a
) and a recess (22b) are formed on the second contact surface (22c).
) is provided in the recess (21b or 22b), and elastic protrusion means (21d, 21f, 21e, or 22f, 2
2e) is provided in a form that can come into contact with the convex portion (22a or 21a).

The present invention also provides an operating means (23) for relatively rotating the first spacer (21) and the second spacer (22).
are provided to penetrate the inside and outside of the casing (2), and hydraulic drive means (25, 2) for driving the operation means (23).
6) may be provided outside the casing (2).

Further, in one aspect of the present invention, the bearings (5, 6, 7, 9) are connected to the casing (2, 2') via sliding means (28, 28').
).

Note that the numbers in parentheses are for convenience and indicate corresponding elements in the drawings.

This description is not limited to the description on the drawings.

The same applies to the following columns of ``reaction''.

(e) 0 effect With the above-described configuration, the bearings (5, 6, 7, 9) are rigidly supported via the rigid members (21a, 22a) in the fixed position preload state, and are supported by the elastic members (21a, 22a) in the constant pressure preload state. 21d, 2
1f, 21e, 22f, 22e) so as to be elastically supported.

In addition, in the fixed position preload state, the convex part (21a) of the first contact surface (21c) and the convex part (22a) of the second contact surface (22c)
) are in rigid contact with each other, and in a constant pressure preload state, the convex portion (22a or 21a) and the elastic protrusion means (21d, 21f, 21e, or 22f, 22e) act so as to come into elastic contact with each other.

Additionally, a hydraulic drive means (
25, 26), the hydraulic drive means (25, 26) operates the first spacer (2nd part) and the second spacer in the casing (2, 2') via the operating means (23). The two spacers (22) are rotated relative to each other.

Also, the bearings (5, 6) are connected via the sliding means (28, 28').
, 7, 9), the bearings (5, 9) are supported.
The outer rings 6, 7, and 9) move smoothly in the direction of the spindle axis.

(f), Example Hereinafter, the present invention will be described in detail based on the drawings.

Fig. 1 is a sectional view showing a headstock to which an example of the preload switching device according to the present invention is applied; Fig. 2 is a sectional view taken along the line ■-■ of the headstock shown in the construction drawing; Fig. 3: FIG. 4 is a sectional view taken along the line m-■ of the hydraulic cylinder shown in FIG. 2; FIG. 4 is a perspective view of the fixed spacer shown in FIG. 1;

FIG. 5 is a perspective view of the rotating spacer shown in FIG. 1.

FIG. 6 is a diagram showing an example of the protruding member and the state of contact between the fixed spacer and the rotating spacer in a fixed position preload state. FIG. 7 is a diagram showing the protruding member shown in FIG. 6 and the fixed spacer in a constant pressure preload state FIG. 8 is a diagram showing a contact state between a spacer and a rotating spacer. FIG. 8 is a diagram showing another example of a protruding member, and a diagram showing a contact state between a fixed spacer and a rotating spacer in a fixed position preload state. FIG. 8 is a diagram showing the protruding member shown in FIG. 8, and a state in which the fixed spacer and rotating spacer are in contact with each other in a constant pressure preload state. FIG. 10 is an example of a headstock equipped with a ball bush that supports the outer ring of the bearing. 11 is a sectional view showing the first
FIG. 12 is a sectional view showing another example of a ball bush that supports the outer ring of a bearing; FIG. 13 is a circumferential development view of the ball bush shown in FIG. 12. It is.

The spindle metalwork shown in the drawing is installed in a machine tool such as a machining center (not shown), and the headstock 1 has a casing 2, and the casing 2 has a cylindrical spindle mounting hole 2a. It is set up. In the spindle mounting hole 2a, a spindle 3, which has a tapered mounting hole 3a drilled at the left end in the figure into which a rotary tool or the like can be mounted, is inserted and mounted between the spindle 3 and the spindle mounting hole 2a. Multiple bearings 5.6.
7.9, etc., and is rotatably driven in the directions of arrows A and B at an arbitrary rotation speed by a drive motor (not shown). And between the bearings 6 and 7,
A preload switching device 20 is provided that includes two fixed spacers, a rotating spacer 22, and the like.

That is, on the outer circumferential surface 3c of the main shaft 3, between the contact surface 3b on the left side in FIG. 1 and the upper spacer 5 fixed on the outer circumferential surface 3c of the main spindle 3 on the right side in FIG. Spacer 10, inner race 5a of bearing 5, spacer 11, inner race 6a of bearing 6, spacer 12, inner race 7a of bearing 7, spacer 13, inner race 9a of bearing 9
are in close contact with the outer peripheral surface 3c of the main shaft 3, respectively,
They are provided in such a manner that they are in contact with each other and are restrained from sliding in the direction of the spindle axis, that is, in the directions of arrows C and D. Further, on the inner circumferential surface of the spindle mounting hole 2a, between the abutment surface 2b on the left side of the drawing and the abutment surface 20 on the right side of FIG. 1, there is a spacer 16, an outer race 5b of the bearing 5, Spacer 17, outer race 6b of bearing 6, fixed spacer 2
1. Rotating spacer 22, spacer 18, outer race 7b of bearing 7,
Maza 19. The outer race 9b of the bearing 9 is connected to the main shaft mounting hole 2.
They are provided in such a manner that they are in contact with the inner surface of a, and are able to abut each other and slide a predetermined distance in the directions of arrows C and D.

Furthermore, the rotary spacer 22 is provided rotatably in the directions of arrows A and B over a predetermined angular range.

Then, the right end face in FIG. 1 of the fixed spacer 21, that is,
As shown in FIG. 4, on the end face facing the rotating spacer 22, a plurality of convex portions 21a and concave portions 21b are formed alternately at equal angular intervals (in the case of FIG. 21a,l
! Twelve seven portions 21b are formed at 30° intervals. ) A fixed abutment surface 21c is provided. Then, in a predetermined recess 21b among the plurality of recesses 21b,
As shown in FIGS. 6 and 7, the protruding member 21d is biased in the direction of the arrow by a spring 21e provided inside the rotating spacer 22 and protrudes toward the contact surface 21c. There is.

The protruding member 21d is provided with a stopper 21d' to limit the amount of protrusion of the protruding member 21d in the direction of the arrow. That is, the protruding member 21d is provided in such a manner that it can come into contact with a convex portion 22a of the rotating spacer 22, which will be described later, but cannot come into contact with a concave portion 22b.

Further, as shown in FIG. 5, a plurality of convex portions 22a and a plurality of concave portions 22b are formed alternately on the end surface of the rotary spacer 22 on the left side of the drawing, that is, the end surface facing the fixed spacer 21. Rotating contact surfaces 22c are provided at equal angular intervals (in the case of FIG. 5, twelve convex portions 22a and twelve concave portions 22b are formed at 15° intervals). An operating groove 22d is formed in the upper part of the outer peripheral surface of the one-turn spacer 22 in the left-right direction in the figure.

Then, the casing 2 in the upper part of FIG. 1 of the rotating spacer 22
A communication hole 2d is formed to pass through the spindle mounting hole 2a and the outside of the casing 2, and a substantially cylindrical operating shaft 23 is rotatable in the directions of arrows E and F in the communication hole 2d. It is set in.

An operation bin 23 is located at the bottom of the operation shaft 23 in the figure.
a is provided eccentrically with respect to the axis CT, and the operation pin 23a is connected from the communication hole 2d to the main shaft mounting hole 2.
a, and is slidably inserted into and engaged with the operating groove 22d of the rotary spacer 22. Furthermore, an engagement pin 23b is provided at the upper part of the operating shaft 23 in the drawing in an eccentric manner with respect to the axis CT, and the engagement pin 23b protrudes from the communication hole 2d to the outside of the casing 2. ing.

A hydraulic cylinder 25 is provided outside the casing 2 above the operating shaft 23 in FIG. 1, and the hydraulic cylinder 25 has a piston 2 as shown in FIG.
6 is provided so as to be freely movable and driveable in the directions of arrows G and H.

In the lower part of the piston 26 in FIG. 2, that is, in the portion facing the operating shaft 23, an engagement groove 26a is formed, as shown in FIG.
, are drilled in the D direction. Then, the engagement groove 2
The engagement pin 23b of the operating shaft 23 is slidably inserted into and engaged with the engagement pin 6a.

Since the headstock 1 has one or more configurations, when rotating the main shaft 3 at low speed, the hydraulic cylinder 25 is appropriately driven to apply preload at a fixed position to the bearings 5, 6, 7, and 9. Multiply.

That is, the piston 26 is moved to the third position by the hydraulic cylinder 25.
Move it in the direction of arrow C in the figure. Then, the piston 26
, the engagement pin 23b engaged with the engagement groove 26a is shown in the direction of arrow G.

That is, the operating shaft 23 is rotated in the direction of arrow E by being pushed to the left in the figure. When the operating shaft 23 rotates in the direction of arrow E, the operating pin 23a moves in the direction of arrow C in FIG. , the rotating spacer 22 is indicated by arrow A
Rotate in the direction.

Then, when the rotating spacer 22 rotates in the direction of arrow C in FIG. Face 21
It comes into contact with the convex portion 21a of c. At this time, the stopper 21d'
The protrusion member 2 whose protrusion amount in the direction of the arrow is limited by
1d does not come into contact with the recess 22b of the rotating spacer 22. Then, as shown in the construction drawing, since the distance between the contact surface 3b of the main shaft 3 and the upper spacer 5 is constant, the fixed spacer 21 is
The rotating spacer 22 presses the rotating spacer 22 in the direction of the arrow C via the protrusions 22a and 21a, and the rotating spacer 22 is pushed in the direction of the arrow C by the fixed spacer 21 via the protrusions 21a and 22a. Pressed in the direction. The fixed spacer 2 presses the outer race 6b of the bearing 6 in the direction of arrow C in FIG. 1, and further pushes the outer race 5b of the bearing 5 in the direction of arrow C in FIG. , press through the spacer 17. Further, the rotating spacer 22 presses the outer race 7b of the bearing 7 in the direction of the arrow in FIG. 1 via the upper spacer 8, and further,
Move the outer race 9b of the bearing 9 in the direction of the arrow in FIG.
It is pressed through the outer race 7b of the bearing 7 and the spacer 19.

Each bearing 5.6, 7.9 has an inner race 5a, 6a.
, 7a, 9a are contact surfaces 3b, spacers 10.11.12, 1
Since the movement in the direction of arrow C or D is restricted by 3.15, a thrust force, that is, a preload load acts on each of the bearings 5.6.7.9, and further movement in the direction of arrow C or D is applied. It becomes a fixed position preloaded state where the movement of is completely restricted. That is,
The distance in the main shaft axis direction from the outer race 5b of the bearing 5 to the outer race 9b of the bearing 9 is the distance between the contact surface 3b engaged with the inner race 5a of the bearing 5 and the spacer engaged with the inner race 9a of the bearing 9. 1
5 restrains expansion, and the convex portion 21
a and the convex portion 22a come into contact with each other to rigidly engage with each other. That is, the rigid members (nearly rigid bodies) were engaged in an inelastic manner by contact with each other. The fixed spacer 21 and the rotating spacer 22 restrain the spacer from shrinking. Therefore, in this state, the rigidity of the main shaft 3 is ensured higher than when the outer race of the bearing is locked by conventional hydraulic pressure.
It is possible to perform heavy cutting, etc. still.

In the above case, the hydraulic pressure is changed by switching the preload, that is, the rotating spacer 2
It is used to rotationally drive 2, -dan,
When switched to the fixed position preload state, the bearing is restrained regardless of the hydraulic pressure.

Next, when rotating the main shaft 3 at high speed, the hydraulic cylinder 25 is appropriately driven to apply a constant pressure preload to the bearings 5, 6.7°9. That is, by the hydraulic cylinder 25, the piston 2
6 in the direction of arrow C in FIG. Then, the piston 26 pushes the engagement pin 23b that is engaged with the engagement groove 26a in the direction of arrow H, that is, to the right in the figure.
Rotate in the direction of arrow F. When the operating shaft 23 rotates in the direction of arrow F, the operating pin 23a moves in the direction of arrow C in FIG. , rotate the rotating spacer 22 in the direction of arrow B.

Then, when the rotating spacer 22 rotates in the direction of arrow C in FIG. 1, as shown in FIG. 21c
The contact with the convex part 21a of the rotary spacer 22 is released, and the convex part 22a of the rotary abutting surface 22c of the rotary spacer 22 is removed from the protruding member 2 provided in the concave part 21b of the fixed abutting surface 21c of the fixed spacer 21.
1d and the protruding member 21d are brought into contact with each other in such a manner that they are moved in the direction of arrow C against the elasticity of the spring 21e. Then, the fixed rJJ/! ! ! 21 and the rotating spacer 22 have a convex portion 22a.
They are elastically engaged via the protruding member 21d and the elastic force of the spring 2e acts between them via the protruding member 21d and the convex portion 22a. Therefore, the fixed spacer 2 is pressed in the direction of arrow C by the elasticity of the spring 21e, and the rotating spacer 22 is pushed in the direction of the arrow C by the elasticity of the spring 21e via the protruding member 21d and the convex portion 22a. Pressed in the direction. Then, the fixed spacer 21 presses the outer race 6b of the bearing 6 in the direction of arrow C in FIG.
Press the outer race 5b of the bearing 6 in the direction of arrow C in FIG. 1 via the outer race 6b of the bearing 6 and the spacer F.

Further, the rotating spacer 22 presses the outer race 7b of the bearing 7 in the direction indicated by the arrow in FIG. It is pressed through the seat 18, the outer race 7b of the bearing 7, and the spacer 19.

And each bearing 5.6.7.9 has an inner race 5a, 6a
, 7a, 9a are the contact surface 3b, spacer top 0.11.12.1
3.15 restricts movement in the direction of arrow C or D, each of the bearings 5.6.7, 9 is provided with a spring 21e.
A thrust force due to the elastic force of , that is, a preload load acts, resulting in a constant pressure preload state. Therefore, in this state, each bearing 5.6.7.9 generates heat as the main shaft 3 rotates at high speed, and each bearing 5.6.7.9, each spacer 16.17, 8 and 9 ,
When the fixed spacer 2 and the rotating spacer 22 undergo thermal expansion, the spring 21a contracts and the fixed spacer 2
1 moves in the direction of arrow C, and the rotating spacer 22 moves in the direction of arrow C. Therefore, since excessive thrust force, that is, preload load is not applied to each bearing 5.6.7.9, seizure of each bearing 5.6.7, 9 is prevented, and the main shaft 3
High-speed rotation is possible.

In the above-mentioned embodiment, when rigid members (near rigid bodies) are to be rigidly engaged during fixed position preloading, that is, when the rigid members are brought into contact with each other, contact surfaces (with a constant distance) are used. A convex portion (first rigid member) 21a and a convex portion (second rigid member) whose movement in the spindle axis direction is restricted within a predetermined range by a rigid member) 3b, a spacer (rigid member) 15, etc.
22a, but the invention is not limited to this, and a pin (first rigid member) whose movement in the axial direction of the main shaft is restricted from the casing (rigid member) 2 side is inserted in the radial direction of the main shaft. What would it be like to restrain movement of the bearing in the direction of the spindle axis through contact between rigid members, such as by engaging with a spacer (second rigid member) in the form of It may be configured as follows.

Furthermore, in the above-described embodiment, a case was described in which the protruding member 21d is provided with a stopper 21d' to prevent the protruding member 21d from coming into contact with the recess 22b of the rotating spacer 22 in the fixed position preload state. The member does not necessarily have to be provided with a stopper. That is, the protruding member 21f shown in FIGS. 8 and 9 is not provided with a stopper. Therefore, the protruding member 2 provided on the fixed spacer 21a
If is in contact with the recess 22b of the rotating spacer 22 in the preloaded state shown in FIG. 8, the elastic force of the spring 21e acts between the fixed spacer 21 and the rotating spacer 22. At this time, at the same time, the protrusion 21a of the fixed spacer 2 and the protrusion 2 of the rotating spacer 22 are
2a is also in contact with each other, so the fixed spacer 21 and the rotating spacer 22
The relative movement in the directions of arrows C and D is completely restrained,
It becomes a fixed position preload state. In addition, in the constant pressure preload state shown in FIG.
1a and the recess 22b of the rotating spacer 22 do not come into contact with each other. Therefore, only the elastic force of the spring 21e acts between the fixed spacer 2 and the rotating spacer 22, resulting in a constant preload state.

Further, in the above-described embodiment, the case where only the rotary spacer 22 is rotated in the directions of arrows A and B has been described, but the convex portion 22a of the rotary spacer 22 is the convex portion of the fixed spacer 2. 21a
Alternatively, it may be possible to selectively abut the protruding parts i' 21 d and 21 f.

As long as the fixed spacer 21 and the rotary spacer 22 can rotate relative to each other, they may be arranged in any manner 41.

Further, although the case has been described in which the protruding members 21d, 21f and the spring 21e are provided in the recess 21b of the fixed spacer 21, the protruding member and the spring are provided in the recess 22b of the rotating spacer 22,
The convex portion 21a of the fixed spacer 2] is the convex portion 2 of the rotating spacer 22.
Of course, the structure may be such that it can selectively come into contact with 2a or the protruding member.

Further, as a driving means for rotating the rotating spacer 22, an operating shaft 23. Although the case where the hydraulic cylinder 25 and the piston 26 are used is described, it goes without saying that any driving means may be used as long as it can drive the rotary spacer 22 to rotate. When the hydraulic cylinder 25 is used as the driving means as in the above-mentioned embodiment, the hydraulic cylinder 25 is installed outside the casing 2, so that working fluid such as oil can reach the bearing part. leaking bearing 5
．． In addition, in the above embodiment, switching between fixed position preload and constant pressure preload is performed using the outer races 5b, 6b of each bearing 5, 6.7.9. ,7
The outer races 5b, 6b, 7b, and 9b are moved slightly in the direction of arrows C and D in FIG.
, it slides against the casing 2 when moving in the D direction. However, due to the high speed rotation of the main shaft 3, the bearing 5.6.7
．． When 9 thermally expands, the outer races 5b, 6b, 7b, 9b
is crimped to the casing 2, and the outer race 5b,
Movement of 6b, 7b, and 9b in the directions of arrows C and D may be restricted, and switching between fixed position preload and constant pressure preload may not be performed smoothly. Therefore, as shown in the headstock 1' shown in Fig. 10, by rubbing the outer races 7b and 9b of the bearings 7.9 in the directions of arrows C and D, smooth preload switching can be achieved. The preload load can be set to a constant value immediately after switching to constant pressure preload. The headstock 1' shown in FIG. 10 is substantially the same as the headstock 1 shown in FIG. 1, so the same components will be given the same numbers and their explanation will be omitted.

That is, the headstock l' has a casing 2', and a spindle 3' is connected to the spindle 3' in a spindle mounting hole 2a' formed in the casing 2'. It is supported by the casing 2' via a plurality of bearings 5, 6, 7, 9, etc. fitted therebetween, and is rotatably movable in the directions of arrows A and B. That is, the inner races 5a, 6a, 7a, 9a of the bearing 5.6.7.9 are in close contact with the outer circumferential surface 3C of the main shaft 3', and the contact surfaces 3b'1 and the spacers 11.12.
13.15, it is held in position with respect to the directions of arrows C and D. In addition, the outer race 5b of the bearing 5.6,
6b is supported by the casing 2' in contact with the inner peripheral surface of the spindle mounting hole 2a'.

The outer races 7a and 9a of the bearings 7 and 9 are connected to a bearing side ring 29, a ball bush 28 . Casing side ring 2
7, it is supported by the casing 2' so as to be movable in the directions of arrows C and D. That is, the bearing side ring 29, the ball bush 28, and the casing side ring 27 are each formed in an annular shape, the casing side ring 27 is fixed to the casing 2', and the inner peripheral surface of the bearing side ring 29 is attached to the bearing 7.9. The outer races 7b and 9b are in contact with each other. The ball bush 28 provided between the bearing side ring 29 and the casing side ring 27 is protected from a large number of balls 28b and the retainer 28a, as shown in FIG. 29 and the casing side ring 27, and is held in an annular shape by a retainer 28a so as to be freely removable. Therefore, bearing 7
．． The outer races 7b and 9b of 9 can smoothly move together with the bearing side ring 29 in the directions of arrows C and D in FIG. 10 with respect to the casing 2' via the ball bush 28. Although the ball bush 28 is movable in the direction of arrow C1D, it is restricted in the directions of arrows A and B (circumferential direction). The outer races 5b, 6b, 7b, 9b of each bearing 5.6.7.9 are connected in the directions of arrows C and D via the spacer 17.14, the rotating spacer 22, the fixed spacer 211, and the spacer 19. It is held in a form that allows it to move by a predetermined amount.

In addition, in the rotating spacer 22 and the fixed spacer 21 of the headstock 1', a protruding member 22f and a spring 22e are provided in the recess 22b on the one-rotation spacer 22 side, and a protruding member 22e is provided on the fixed spacer 2 side. Although a spring is not provided, switching between fixed position preload and constant pressure preload is performed in the same manner as in the case of the spindle metalwork described above. That is, by driving the hydraulic cylinder 25, the rotary spacer 22 is operated in the directions of arrows A and B via the piston 26 and the operating shaft 23, and the convex portion 22a of the rotary spacer 22 and the convex portion of the fixed spacer 21 are moved. When 21a is brought into contact with the bearing 5.6.7
, 9 are in a fixed position preloaded state due to rigid body contact, and when the protruding member 22f of the rotating spacer 22 and the convex portion 21a of the fixed spacer 21 are brought into contact, the bearing 5.6.7°9 is preloaded with a constant pressure due to the elasticity of the spring 22a. state.

At this time, the outer races 7b and 9b of the bearings 7 and 9 are connected to the main shaft 3'
Even if the bearing side ring 29 is pressed into contact with the bearing side ring 29 due to thermal expansion due to high speed rotation, it can be smoothly moved in the direction of arrow C1D together with the bearing side ring 29 via the ball bushing 28, so that preload switching can be performed smoothly. . In addition, the outer race 7b due to the rolling contact of the ball bush 28,
By moving 9b in the directions of arrows C and D, the preload load can be made to be a constant value as soon as the welding method is switched to constant pressure preload, so the preload adjustment can be easily performed.

Note that the ball bushings are located at the arrows C and D on the bearing side ring 29.
The shape etc. may be configured in any way as long as the movement in the direction can be made smooth, and as in the case of the ball bush 28' shown in FIG. may be configured.

Furthermore, a piece 2e is provided in the main shaft mounting hole 2a' of the casing 2' of the main spindle metalwork shown in FIG. , bearing 6
The load acting on the bearing 5.6 in the direction of the arrow can be supported by contacting the piece 14a protruding from the spacer 14 inserted behind the outer race 6b. That is, in the spindle metalwork shown in FIG. 1, when a load is applied from the spindle 3 to the bearing 5.6 in the direction of the arrow, the load is
is supported by the casing 2 by the rear spring 22e and the further rear contact surface 2C of the protruding member 22f, but in the headstock 1' shown in FIG.
When a load in the direction of the arrow is applied to the main shaft 3', it is supported by the casing 2' by the spring 22e and the front piece 2e of the protruding member 22f, so the main shaft 3' has high rigidity and the cutting ability can be improved.

(g) Effects of the 1 Invention As explained above, according to the present invention, the casing 2
．． 2', first and second rigid members such as a convex portion 21a and a convex portion 22a are provided so as to be able to abut and engage with each other, and include protruding members 21d, 21f, a spring 21e, a protruding member 22f,
An elastic member such as a spring 22e is provided in such a manner as to be able to press the bearing 5.6.7.9 in the direction of the spindle axis.
．． 7.9 as a fixed position preload, the first and second rigid members are rigidly engaged (in this specification,
"Rigidly engaging" means "engaging through contact between rigid members without using an elastic material or the like." ), the movement of the bearing 5, 6.7.9 in the direction of the main axis axis is restrained by the first and second rigid members themselves, and the bearing 5.6.7
, 9 are to be preloaded with a constant pressure, the first and second rigid members are released from the rigidly engaged state, and the elastic member moves the bearing 5.6.7.9 in the direction of the spindle axis. Since the bearing 5.6.7.9 is configured to be pressed, the bearing 5.6.7.9 is elastically supported via the elastic member in the constant pressure preload state, and has a rigid structure that restricts movement in the direction of the spindle axis in the fixed position preload state. It is rigidly supported via a member. Therefore, in the fixed position preload state, the bearing 5.6.7
．． 9 displacement can be suitably prevented, and the main shaft 3.3'
It is possible to improve the rigidity of the

Further, the present invention provides a first spacer such as the fixed spacer 21 and a second spacer such as the rotating spacer 22, which are relatively rotatably movable while in contact with each other and bearings 5.6. .7.9 are provided in the casing 2 in a form that engages with the second spacer, and a convex portion 21a and a concave portion 21b are provided on the end surface of the first spacer facing the second spacer.
A second contact surface, such as a fixed contact surface 21c formed thereon, is provided on an end surface of the second spacer facing the first spacer.

A rotating contact surface 22c in which a convex portion 22a and a concave portion 22b are formed.
etc., and furthermore, protruding members 21d, 21f, springs 21e (
Alternatively, since the elastic protruding means such as the protruding member 22f and the spring 22e are provided in a form that can come into contact with the convex part 22a (or 21a), in the preloaded position state, the convex part 21a of the first contact surface and The convex portion 22a of the second contact surface is in rigid contact, and in the constant pressure preload state, the convex portion 22a (or 21a) and the elastic protruding means are in elastic contact. Therefore, by simply rotating the ↓-th spacer and the second spacer relative to each other, it is possible to easily switch between the normal position fa-'P pressure and the constant pressure preload.

Furthermore, in the fixed position preload state, there is no relative movement between the spacer for the first work and the second spacer, so the bearing can be positioned reliably and rigidity during low-speed heavy cutting can be suitably ensured. I can do it. In addition, in a constant preload state, the relative movement of the first spacer and the second spacer prevents the preload load from becoming excessive and causing seizure of the bearing, and allows the main shaft to rotate at high speed. It becomes possible.

Further, in the present invention, an operating means such as an operating shaft 23 for relatively rotationally driving the first spacer and the second spacer is provided so as to pass through the inside and outside of the casing 2, and the operating means is Since the hydraulic drive means such as the hydraulic cylinder 25° piston 26 to be driven is provided outside the casing 2,
The first spacer and the second spacer inside the casing 2 are relatively rotationally driven from outside the casing 2 by the hydraulic drive means via the operating means. Therefore, the working fluid such as oil of the hydraulic opening means does not leak into the casing 2.2' and cause an adverse effect such as seizure on the bearing 5.6.7.9.

Furthermore, in the present invention, the bearing 5.6.7.9 is supported on the casing 2.2' via a sliding means such as a ball bush 28.28', so that even if the bearing 5.6.7.9 undergoes thermal expansion, The outer ring of the bearing 5.6.7.9 can be smoothly moved in the direction of the main shaft axis. Therefore, the preload can be switched smoothly and the preload of constant pressure preload can be quickly brought to a constant value, so that the preload U! 4 adjustments can be done easily.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a headstock to which an example of a preload switching device according to the present invention is applied. Figure 2 is a cross-sectional view of the headstock shown in Figure 1 taken along the line ■-■ Figure 3 is a cross-sectional view of the hydraulic cylinder shown in Figure 2 taken along the line ■-m Figure 4 is the construction drawing The perspective view of the fixed spacer shown in Fig. 5 is as follows.
FIG. 6 is a perspective view of the rotating spacer shown in FIG. 1, FIG. Figure 8 shows another example of the protruding member and the contact state between the fixed spacer and the rotating spacer in the fixed position preload state. FIG. 9 is a diagram showing a state in which the protruding member shown in FIG. 8 and a fixed spacer and a rotating spacer are in contact with each other in a constant pressure preload state. FIG. 10 is a sectional view showing an example of a headstock equipped with a ball bush that supports the outer ring of the bearing, and FIG.
FIG. 12 is a sectional view showing another example of a ball bush that supports the outer ring of a bearing; FIG. 13 is a circumferential development view of the ball bush shown in FIG. 12. . FIG. 4 is a sectional view showing an example of a conventional preload switching device. 2. 3. 5. 2 Work 1 1 2'...Casing 3'...Main shaft 6.7.9...Bearing...First spacer (fixed spacer) a... ... Rigid member, convex portion 1) ... Concave portion 21c ... First contact surface (fixed contact surface) 21d.
...Elastic member, elastic protrusion means (protrusion member) 21e...Elastic member 1 elastic protrusion means (spring) 21
f...Elastic member, elastic protruding means (protruding member) 22... Second spacer (rotating spacer) 22a...
... Rigid member, convex portion 22b, ... concave portion 22c, ... second contact surface (rotating contact surface) 22e,
...Elastic member, elastic protruding means (spring) 22f...
...Elastic member, elastic protruding means (protruding member) 23... Operating means (operating shaft) 25... Hydraulic thigh movement means (hydraulic cylinder) 26...
...Hydraulic drive means (piston) 28.28'...
・Sliding means (ball bush)

Claims (4)

[Claims] (1) A bearing structure having a casing, and a main shaft rotatably supported in the casing via two or more bearings having inner and outer rings, wherein first and second rigid members are disposed within the casing. , are provided so as to be able to abut and engage with each other, and an elastic member is provided in a form that can press the bearing in the direction of the spindle axis, and when the bearing is preloaded in a fixed position, the first and the first When the two rigid members are rigidly engaged and the movement of the bearing in the direction of the main shaft axis is restrained by the first and second rigid members themselves, and the bearing is preloaded with a constant pressure, 1st and 2nd
A preload switching method comprising: releasing the rigidly engaged state of the rigid member, and pressing the bearing in the direction of the spindle axis using the elastic member. (2) A bearing structure having a casing, in which the main shaft is rotatably supported via two or more bearings having inner and outer rings, wherein the first spacer and the second spacer are mutually connected. A convex portion is provided in the casing so as to be relatively rotationally driveable in a state of contact and engaged with the bearing, and a convex portion is provided on an end surface of the first spacer facing the second spacer. a first abutment surface having a recess formed therein; and an end surface of the second spacer facing the first spacer,
A preload switching device comprising: a second contact surface having a convex portion and a concave portion; and an elastic protruding means provided in the concave portion in a form capable of coming into contact with the convex portion. (3) An operating means for relatively rotationally driving the first spacer and the second spacer is provided so as to pass through the inside and outside of the casing, and a hydraulic drive means for driving the operating means is provided as described above. The preload switching device according to claim 2, which is configured to be provided outside the casing. (4) The preload switching device according to claim 2, wherein the bearing is supported by a casing via a sliding means.