JPS5856084Y2 - lathe tailstock - Google Patents

Description

[Detailed description of the invention] This invention is a lathe center in which a tailstock shaft fitted with a center is supported by a hydrostatic journal bearing to enable high-speed rotation and axial movement of the tailstock shaft. Regarding the push stand.

When machining shafts, etc. using a lathe, there are conventionally two types of tailstock centers for tailstocking the shaft attached to the headstock: a fixed center and a rotating center, which improve the speed and precision of machining. When required, a rotating center is used.

The following two types of conventional rotation centers are generally used.

(a) A hole is drilled in the axial direction of the tailstock shaft that can only be moved in and out of the tailstock, and a rotation center (commercially available product) having a spindle supported by a rolling bearing is inserted in the direction of the hole. .

(b) A so-called built-in center that rotatably supports the spindle by incorporating a spindle and rolling bearing in the axial center of the tailstock that can only move in and out of the tailstock.

In all of the conventional rotation centers mentioned above, a hole is drilled in the center of the tailstock shaft and the journal part of the center is supported by a rolling bearing. As such, it had no choice but to be small.

For this reason, the center cannot withstand a large load and has a short lifespan.

In addition, since a gap is provided between the tailstock shaft and the main body that supports the tailstock shaft so as to be movable in the axial direction,
When subjected to a load, the tailstock is displaced in the radial direction, or
There was a drawback that the accuracy deteriorated due to long-term use of the tailstock shaft.

In addition, in the case of the conventionally used built-in center, if a hydrostatic bearing, which is a known technology, is used instead of a rolling bearing, the rotational accuracy of the center will be improved, its life will be extended, and the vibration damping characteristics will be improved. Although it is expected to be effective in that it will be advantageous, there will be space limitations due to installing the hydrostatic pressure bearing and the rotating shaft (center) in the Shinshin shaft, and the method of supplying lubricating oil to the hydrostatic bearing and the method of draining oil will be complicated. There are drawbacks, and furthermore, the problem of poor machining accuracy due to the gap provided for sliding the tailstock shaft relative to the main body cannot be solved.

In view of the above, this invention is designed to rotatably support a tailstock shaft by being fitted in a pair of front and rear hydrostatic journal bearings provided in the main body of the Shinshindai, and to move this tailstock shaft forward and backward with respect to the Shinshindai body. The object of the present invention is to provide a lathe tailstock which eliminates the above-mentioned drawbacks.

Next, this invention will be explained based on embodiments shown in the drawings.

The tailstock 1 of a lathe consists of a tailstock main body 2 and a base D that is attached below the main body 2, slides on a bed (not shown) of the lathe, and is fixed at an arbitrary position on the bed. The tailstock main body 2 is provided with a tailstock shaft 3 having a fixed center 4 attached to its front end.

This tailstock shaft 3 has a pair of front and rear ring-shaped hydrostatic journal bearings 5, 6 (
Hereinafter referred to as a hydrostatic bearing.

) is rotatably supported. The front hydrostatic bearing 5 has a plurality of pockets 5a arranged evenly on its inner peripheral surface for storing oil (see FIG. 2).

This front hydrostatic pressure bearing 5 has an outer peripheral surface and a pocket) 5a.
There is a hole 5b that communicates with the main body 2, and an oil passage 2b that communicates with the hole 5b and supplies oil to the front hydrostatic bearing 5 is provided in the main body 2.

The oil supplied to the pocket 5a through the hole 5b is
Land portions 5C on the front and rear inner sides of the front hydrostatic bearing 5
and the outer periphery of the tailstock shaft 3 to the outside.

Similarly to the front fluid static pressure bearing 5, the rear fluid static pressure bearing 6 is also provided with a pocket 6a, a hole 6b, and a land portion 6C, so that oil can flow from the oil passage 2C of the Shinshindai main body 2 to the hole 6b. Supplied.

A cylindrical spacer 7 is attached to the Shinshindai body 2 between the front hydrostatic bearing 5 and the same bearing 6.

A gap S is provided between the inner diameter of this spacer 7 and the outer periphery of the tailstock shaft 3, and the oil accumulated in the gap S is removed by an oil filler 7a that communicates with an oil filler 2d provided in the Shinshindai main body 2. It flows into the oil tank 2e of the Shinshindai main body 2.

As shown in FIG. 4, the piston rod 8 has a rod portion 8.
Near one end of a, there is a flange portion 8b having an outer diameter slightly smaller than the outer diameter of the tailstock shaft 3, and on the opposite side to the flange portion 8b, there is a ring-shaped piston having a smaller diameter than the rod portion 8a. There is a small diameter portion 8C into which the nut 9 is fitted, and a threaded portion 8d into which the nut 10 is screwed following the small diameter portion 8C.

This piston rod 8 has its flange portion 8b attached to the rear end portion of the tailstock shaft 3 with an appropriate number of bolts 20.

The cylinder 11 is provided with an axial hole 11a in its axial center, in which the piston 9 slides in an oil-tight manner.

A disk-shaped cylinder cover 12 having a shaft hole 12a is attached to the front end of the cylinder 11 with an appropriate number of bolts 13.

The cylinder cover 12 has an outer diameter slightly smaller than the inner diameter of the shaft hole 2a of the Shinshindai main body 2, and an O-nong 14 is fitted into a groove provided on the outer periphery of the attachment portion to the cylinder 11.

The cylinder cover 12 has a shaft hole 12a in which a rod portion 8a of the piston rod 8 can slide, and a protrusion 12b having the same outer diameter as the piston 9 is formed at the rear end. has been done.

The throttle valve 15 is screwed into the cylindrical body 16 and the cylindrical body 16,
The valve stem 17 has a tapered front end (see FIG. 5).

The barrel 16 has at its rear end a flange 16a, which is followed by an externally threaded threaded section 16b having a smaller diameter than the flange 16a.

The cylindrical body 16 has a tapered portion 16C at the front of its shaft hole, and an oil filler 16d is bored perpendicularly to the cylindrical body 16 near the rear end of the tapered portion 16C.

The throttle valve 15 can be adjusted from the front to the cylindrical body 16 by turning the valve stem 17 screwed into the threaded part provided in the shaft hole at the rear end of the cylindrical body 16.
By moving it in the rearward direction, it is possible to increase or decrease the flow path resistance of the oil supplied to the cylindrical body 16 from the oil filler 16d while it exits from the tip of the tapered portion 16C.

The hydrostatic bearings are formed as described above and paired with each pocket,
The same number of throttle valves 15 as the hydrostatic bearing pockets are installed in the cylinder 1.
The threaded portion 16b of the cylinder 11 is screwed into the rear end of the cylinder 11 at equal center angles on a circumference having a predetermined radius from the center C of the shaft hole 11a (see FIG. 6).

The cylinder 11 is provided with an oil supply port 1B on its outer periphery, and oil flowing from this supply port 18 is supplied to all the throttle valves 15 through an oil groove 19 formed in the circumferential direction.

As described above, the cylinder 11 with the throttle valve 15 attached to the front cylinder cover 12 and the rear part is inserted into the outside of the piston rod 8 attached to the rear end of the tailstock shaft 3 from the cylinder cover 12 side. An appropriate number of bolts 21 are screwed in from the rear end of the cylinder 11 (see Fig. 6).
It can be attached to the Shinshindai main body 2 by.

At this time, the cylinder cover 12 is oil-tight with respect to the shaft hole 2a of the Shinshindai main body 2 by the O-nong 14.

Note that 22 is a spacer, which is provided between the rear hydrostatic bearing 6 and the cylinder cover 12.

Next, after inserting the piston 9 into the piston rod 8,
The piston 9 is attached to the piston rod 8 by tightening the nut 10 on the threaded portion 8d of the rod 8, and the rear end of the shaft hole 11a of the cylinder 11 is oil-tightly covered with a cap 23. 23 is attached to the cylinder 11 with an appropriate number of bolts 24.

The cylinder 11 attached to the rear end of the Shinshindai main body 2 as described above and the piston 8 attached to the rear end of the Shinshinshaft 3 are arranged between the cylinder cover 12 and the piston 9 to provide front hydraulic pressure. A chamber A and a rear hydraulic chamber B are formed between the piston 9 and the cap 23.

The front hydraulic chamber A is connected to an external hydraulic system (not shown) through an oil passage 25 and the rear hydraulic chamber B through an oil passage 26.

Each throttle valve 15 has an oil reservoir 16 d in the cylinder body 16 communicating with each oil passage 27 of the cylinder 11 that is connected to an external hydraulic device, and each throttle valve 15 has an oil passage 28 connected to the cylinder 11 . , and communicates with the oil passage 2b or 2C of the Shinjindai main body 2.

That is, the pressure oil supplied from the external hydraulic system to each throttle valve 15 via each oil passage 27 passes through each throttle valve 15 adjusted to have an appropriate flow resistance, and then passes through each oil passage 28 of the cylinder 11 and the It is supplied to each pocket 6a of the rear hydrostatic bearing 6 via each oil passage 2b of the stand body 2, to each corresponding pocket 5a of the front hydrostatic bearing 5, and through the oil passage 2C.

A non-contact type sealing device 29 that surrounds the Shinshin axis 3 is provided at the front end of the Shinshindai main body 2.

This sealing device 29 includes an inner air static pressure bearing 30 fitted in the front end of the shaft hole 2a of the Shinshindai body 2, and an outer air static pressure bearing 30 fitted in the front end of the Shinshindai body 2. It is formed of a thrust bearing 31 and a ring 32 fitted on the outside of the center shaft 3 between the outer hydrostatic thrust bearing 31 and the inner hydrostatic thrust bearing 30.

The inner diameters of the inner hydrostatic thrust bearing 30 and the outer hydrostatic thrust bearing 31 are slightly larger than the outer diameter of the shinshaku 3.

The ring 32 can airtightly slide in the axial direction relative to the Shinshin axis 3, and on both sides and the outer circumference of the ring 32,
Inner hydrostatic thrust bearing 30 and outer hydrostatic thrust bearing 3
A gap is formed between 1 and 1.

Then, compressed air is supplied from the conduit 33;) (When this compressed air is supplied, the compressed air is supplied to the outer hydrostatic thrust bearing 31 and the inner hydrostatic thrust bearing 30, respectively. When the Shinshinshaft 3 moves in the front-rear direction relative to the Shinshindai main body 2, air flows between the ring 32 and both hydrostatic thrust bearings 30 and 31. A space created by compressed air is maintained, and pressure oil from the front hydrostatic bearing 5 side is prevented from leaking to the outside.

Next, the operation of this embodiment will be explained.

After fixing the base D of Shinshindai 1 to the appropriate position on the bed,
When pressure oil is supplied from the supply port 18, this pressure oil passes through each throttle valve 15 that has been adjusted to an appropriate flow resistance in advance, passes through the oil passage 28, oil passages 2b, and 2C, and is then supplied to each of the front hydrostatic bearings 5. After being supplied to the pocket) 5a and each pocket) 6a of the rear hydrostatic bearing 6, it flows out from each land 5C of the front hydrostatic bearing 5 and each land 6C of the rear hydrostatic bearing 6.

As a result, the cardiac axis 3 having the fixed center 4 floats according to the principle of hydrostatic bearings and is supported on the center line of the front and rear hydrostatic bearings 5 and 6.

The oil flowing out from the lands 5C and 6C of the hydrostatic bearings 5 and 6 flows into the oil tank 2e through the oil reservoirs 2d of the Shinshindai main body 2, and then is discharged to the outside.

Further, oil leaking from the land 5C at the front of the front hydrostatic bearing 5 is prevented from leaking to the outside by the sealing device 29.

In the above state, when pressure oil is supplied from the oil passage 26 into the rear hydraulic chamber B, the piston 9 is pushed and moves forward. Advance.

When the Shinshin axis 3 moves forward and the fixed center 4 hits a workpiece (not shown) attached to the headstock,
The center shaft 3 stops, and a tailstock force is generated by the thrust of the piston 9 to support the workpiece.

When the workpiece rotates, the shaft 3 rotates together with the workpiece and supports the load applied to the workpiece by the cutting tool.

Then, when the cardiac axis 3 and the piston rod 8 rotate in this manner, both rotate with no contact points.

When processing of the workpiece is completed, the cylinder 1 is opened from the oil passage 25.
When pressurized oil is supplied into the front hydraulic chamber A of 1 and the oil passage 26 of the rear hydraulic chamber B is opened to the atmosphere, the piston 9 is pushed rearward and the piston rod 8 and the center shaft 3 retreat, so that the headstock Remove the workpiece from the

As mentioned above, this invention is based on a center stand for a lathe in which a center shaft with a fixed center attached to the front end is rotatably supported by a hydrostatic journal bearing provided in the shaft hole and movable in the axial direction of the shaft hole. A piston fixed to the rear end of the cardiac axis and a cylinder that accommodates this piston and forms hydraulic chambers in front and behind the piston are provided, and when hydraulic pressure acts on the rear or front hydraulic chamber, the cardiac axis moves forward. Or, since it is configured so that it can be moved backward, the following effects can be obtained.

(a) By forming the drive device that moves the Shinshin axis in the forward and backward directions integrally with the Shinshindai, the structure of the Shinshindai, including the drive device, can be made very compact.

(b) Since hydraulic pressure acts on the front and rear surfaces of the piston in the cylinder, the cylinder and piston serve as thrust bearings for the center shaft.

Therefore, there is no need to specifically provide a thrust bearing for the Shinshin shaft.

(c) Since there are no contact points in the Shinshin axis and the pistons, etc. that actuate the Shinshin axis when the Shinshin axis advances or retreats, its life and accuracy can be maintained semi-permanently even when used at high speed rotation.

[Brief explanation of drawings]

The figures show one embodiment of this invention, in which Fig. 1 is a longitudinal sectional view of the headstock, Fig. 2 is a sectional view taken along the line II-II in Fig. 1, and Fig. 3 is a sectional view taken along the line III-III in Fig. 1. Figure 4 is a front view of the cylinder, Figure 5 is an enlarged sectional view of the throttle part, and Figure 6 is the front view of the cylinder.
It is a view taken along arrow C in the figure. DESCRIPTION OF SYMBOLS 1...Shinshindai, 2...Shinshindai main body, 2a...Shaft hole, 3...Shinjinshaft, 4...Fixed center, 5...Front fluid static pressure journal bearing, 6. ...Rear hydrostatic journal bearing, 9...Piston, 11...Cylinder, A
...Front hydraulic chamber, B...Rear hydraulic chamber.

Claims (1)

[Scope of utility model registration request] A tailstock for a lathe that supports a tailstock shaft having a fixed center attached to a front end thereof in a static pressure journal bearing provided in a shaft hole so as to be rotatable and movable in the axial direction of the shaft hole. It has a piston fixed to the rear end of the shaft, and a cylinder that accommodates this piston and forms hydraulic chambers in front and behind the piston, and the tailstock shaft is moved by the hydraulic pressure acting on the rear or front hydraulic chambers. A lathe tailstock characterized in that it can be moved forward or backward.