JPH0788705A - Spindle supporting structure for lathe - Google Patents

Abstract

PURPOSE:To improve the natural vibration of a spindle in a lathe by journalling the spindle by bearings in two places spaced in the axial direction, supporting a rotary joint in the overhanging state at the rear end of the spindle, and fixing the casing of this rotary joint through insulating cushioning material. CONSTITUTION:A spindle 1 is journalled to a spindle casing 11 by a first bearing 5 formed of a radial bearing 2 and two angular bearings 3, 4, and a second bearing 7 formed of one radial bearing 6. A hydraulic chuck 12 is mounted to the tip of the spindle 1, and a hollow rod 13 for opening/closing the claw of the chuck 12 is provided piercing the axis of the spindle 1. The pulley 14 of a belt transmission gear is fixed to the rear end side of the spindle 1, and a chuck cylinder 17 rotated along with the spindle 1 is fixed to the rear side face of the pulley 14 through a flange 18. The lower end of the casing 28 of a rotary joint 24 is bolt-fixed to a bracket 32, extended to the rear of the rear side face of the spindle casing 11, through insulating cushioning material 34.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for supporting a spindle of a lathe, and more particularly to a rotary joint for supplying hydraulic pressure to a chuck cylinder for opening and closing a chuck mounted on the tip of the spindle. The present invention relates to a supporting structure for a main shaft provided.

[0002]

2. Description of the Related Art When a chuck cylinder is incorporated in a main shaft of a lathe to automatically open and close the chuck, a rotary joint is provided at a rear end of the main shaft and a hydraulic pressure is supplied to the chuck cylinder through the rotary joint. It 4 and 5
1 shows a conventional shaft support structure in the main shaft 1 having a structure in which a rotary joint 24 is provided at the rear end of the main shaft 1 and a rotational driving force is transmitted to the main shaft 1 via a belt pulley 14.

In the conventional structure shown in FIG. 4, the main shaft casing 11 is made up of two bearings 25 and 26 which separate the main shaft 1 in the axial direction.
The belt pulley 14 and the rotary joint 24 on the main shaft 1
In the structure shown in FIG. 5, the main shaft 1 is axially supported by the main shaft casing 11 by three bearings 25, 26 and 41 which are separated from each other in the axial direction. Is disposed between the intermediate bearing 26 and the rear end bearing 41, and the rotary joint 24 is supported by overhanging behind the rear end bearing 41.

The rotary joint 24 is provided with a casing which does not rotate on the outer side thereof, but the thermal expansion of the main shaft 1 is released rearward to maintain the processing accuracy, and a large thermal deformation is not transmitted to the inside of the rotary joint 24. In order to prevent the heat generated on the side of the rotary joint 24 from being transmitted to the main shaft casing 11, a structure in which only the rotational movement of the casing is normally restrained by a slightly flexible member is adopted.

[0005]

Currently, the main spindle of a lathe has a rotation speed of about 6000 rpm, but it is desired to perform the processing at a higher spindle rotation speed in order to improve the processing efficiency and the processing surface accuracy. . In order to realize higher rotation of the main shaft 1, it is necessary to make the resonance frequency of the main shaft 1 higher than that at present, and it is necessary to further increase the support rigidity of the main shaft 1.

The presently desired spindle speed is 1000
Although it is about 0 rpm, when looking at the conventional support structure on the premise of such a rotation speed, the structure shown in FIG. 4 lacks the support rigidity of the main shaft, and the structure shown in FIG. 5 has three bearings 25, The positional accuracy of 26 and 41, especially the positional accuracy maintenance when thermal deformation occurs during operation, cannot be dealt with unless it is higher than at present.

When the support rigidity of the main shaft is to be increased with the structure shown in FIG. 4, the bearings 25 and 26 become large,
This time, it becomes impossible to increase the spindle speed due to the restriction on the bearing side, and eventually it becomes impossible to achieve the desired rotation speed. In addition, in the case of FIG. 5, the device becomes expensive in order to improve the positional accuracy of the bearing,
Care must be taken to suppress thermal deformation, and with a structure in which the main shaft is driven using a belt, maintenance work such as belt replacement is very troublesome.

The present invention has been made to solve the above problems, and can increase the natural frequency of the main shaft of a lathe having a rotary joint at the rear end with a simple structure and can be used for belt replacement or the like. The problem is to obtain a support structure for the spindle of a lathe that does not hinder maintenance work.

[0009]

A main shaft supporting structure for a lathe according to the present invention is a main shaft 1 supporting structure having a rotary joint 24 for a fluid pressure device built in the main shaft at the rear end thereof. The main shaft 1 is axially supported by the main shaft casing 11 by bearings 5 and 7 at two locations spaced apart in the axial direction, and a rotary joint 24 is supported at the rear end of the main shaft 1 in an overhang state. The casing 28 is fixed to a bracket 32 extending from the main shaft casing 11 via a heat insulating cushioning material 34.

[0010]

The rotary joint 24, which is supported on the rear end of the main shaft 1 in an overhanging state, has a large inertial mass against bending vibration of the main shaft 1 and reduces the natural frequency of the main shaft 1. On the other hand, when the casing 28 of the rotary joint 24 is fixed to the main shaft casing 11 with a metal member or the like, the main shaft 1 is substantially supported at three points, and the heat from the rotary joint 24, which generates a large amount of heat, is applied to the main shaft 1 and the main shaft casing 11. And a complicated thermal deformation is caused to the both sides of the main shaft 1 and a trouble due to a large thermal stress is applied to the rotary joint 24 composed of delicate parts compared to the main shaft 1 side (for example, seizure due to metal contact between the rotary side and the stationary side) ), And a decrease in machining accuracy due to an increase in thermal deformation of the main shaft casing 11 poses a problem.

On the other hand, in the structure of the present invention, since the casing 28 of the rotary joint 24 is fixed to the spindle casing 11 by the simple bracket 32 via the heat insulating cushioning material 34, the bending vibration of the spindle 1 is affected. Rotary joint 24
Only a part of the mass of the main shaft 1 is supported by the main shaft 1, and the heat insulating cushioning material 34 prevents the heat from the rotary joint 24 from being transferred to the main shaft casing 11. Since the bending vibration of the main shaft 1 is suppressed, the natural frequency of the main shaft 1 can be considerably increased, and the displacement of the rotary joint 24 with respect to the main shaft casing 11 is absorbed by the deformation of the heat insulating cushioning material 34. Since a large stress is prevented from acting on the inside, the adverse effect caused by fixing the rotary joint 24 can be avoided.

[0012]

EXAMPLES Next, examples shown in FIGS. 1 to 3 will be described. The main shaft 1 is composed of one radial bearing 2 and two angular bearings 3 and 4, and is a first bearing 5 on the tip side of the main shaft.
And a second bearing 7 on the rear end side composed of one radial bearing 6 are axially supported by the spindle casing 11 at two locations 5 and 7 axially spaced from each other. A hydraulic chuck 12 is attached to the tip of the main shaft 1, and a hollow rod 13 for opening and closing its claw penetrates the shaft center of the main shaft 1. On the rear end side of the main shaft 1, a pulley 14 of a belt transmission device for transmitting the rotational force of a main shaft motor (not shown) to the main shaft 1 is fixed. The first bearing 5 is the first nut 1 screwed onto the main shaft 1.
5, the second bearing 7 and the pulley 14 are fixed in the axial direction by a second nut 16 screwed to the rear end of the main shaft.

A chuck cylinder 17 rotating with the main shaft 1 is fixed to the rear side surface of the pulley 14 via a flange 18. A piston 19 that drives the rod 13 in the axial direction is installed in the chuck cylinder 17, and two oil passages 21 and 21 that supply and discharge hydraulic pressure to and from the hydraulic chambers on both sides of the piston 19 are provided in the chuck cylinder 17. An opening is formed in the peripheral surface of a rotor shaft 23 extending from the rear end of the cylinder body 22 into the rotary joint 24. Inside the rotary joint 24, a short cylindrical oil supply block 27 is supported on the rotor shaft 23 by two bearings 25 and 26, and a casing 28 of the rotary joint is fixed to the oil supply block 27. In the casing 28,
A drain receiver 29 for receiving hydraulic oil leaking from the sliding contact surface between the rotor shaft 23 and the oil supply block 27 is formed, and a drain pipe 31 communicates with a hydraulic oil tank (not shown) from the drain receiver 29.

On the other hand, a base end of a bracket 32 extending rearward is fixed to a rear side surface of the main shaft casing 11, and a seat surface 33 facing upward is formed at a rear end of the bracket 32.
The lower end of the casing 28 of the rotary joint is fixed to the seat surface 33 by a bolt 35 via a heat insulating cushioning material 34.
This heat insulating cushioning material 34 is, for example, Turkite (trade name)
The casing 28 is made of a synthetic resin block having a heat insulating property, a vibration absorbing property and a small elastic modulus.
A concave portion 36 is provided on the joint surface with and so that heat transmitted from the rotary joint 24 to the bracket 32 is reduced.
The heat insulating cushioning material 34 does not necessarily have to be composed of one block, and may have a combined structure of a member having a heat insulating property and a member having a shock absorbing property.

The casing 2 of the rotary joint 24 mounted in an overhang state at the rear end of the main shaft 1 which is axially supported by the main casing 11 by two points 5 and 7 which are axially separated in the above structure.
8 is to be supported by the main shaft casing 11 via the heat insulating cushioning material 34, and most of the mass of the rotary joint 24 that causes the natural frequency of the main spindle 1 to decrease is the heat insulating cushioning material 3.
It was possible to increase the natural frequency of the main shaft 1 including the rotary joint 24 and the chuck cylinder 17 by 30 to 50 Hertz (1800 to 3000 rpm in the main shaft rotation speed) supported by the main shaft casing 11 via the No. 4 and the bracket 32.

[0016]

Therefore, by adopting the structure of the present invention, the main shaft of a lathe having a rotary joint at the rear end thereof does not require an increase in the size of the bearing and the accuracy of machining around the main shaft is high. The number of revolutions can be increased on the order of thousands of revolutions, and a high-speed lathe equipped with a hydraulic chuck can be provided more economically.

[Brief description of drawings]

FIG. 1 is a partial sectional plan view showing an embodiment of the present invention.

FIG. 2 is a schematic front view showing only a rear end portion of FIG.

FIG. 3 is a schematic side view of FIG.

FIG. 4 is a side view schematically showing a first conventional structure.

FIG. 5 is a side view schematically showing a second conventional structure.

[Explanation of symbols]

 1 Spindle 5 1st bearing 7 2nd bearing 11 Spindle casing 24 Rotary joint 32 Bracket 34 Insulation cushioning material

Claims (1)

[Claims] 1. A support structure for a spindle, comprising a rotary joint (24) for a fluid pressure device built in the spindle at the rear end of the spindle (1), wherein the spindle (1) is axially spaced apart from each other. Bearings (5) and (7) are supported in the main shaft casing (11) at
A rotary joint (24) is supported at the rear end of the main shaft (1) in an overhanging state, and a casing (28) of the rotary joint (24) is attached to a bracket (32) extending from the main shaft casing (11) with a heat insulating cushioning material.
A structure for supporting a main shaft of a lathe, which is fixed via (34).