JP2014100771A - Tail stock - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tail stock capable of holding a workpiece without retraction of a tailstock spindle even when oil pressure supply is blocked.SOLUTION: In the tail stock including a tailstock spindle for holding a center which supports a center hole of an object to be supported, a hydrostatic bearing for supporting so that rotation and movement toward an axial direction are possible, an oil pressure cylinder for reciprocating the tailstock spindle toward the axial direction, and a pressure oil supply device for supplying pressure oil to the oil pressure cylinder are provided. When pressure oil supply is stopped, a fastening device fastens the tailstock spindle and the tailstock body so that the tailstock spindle does not move.

Description

  The present invention relates to a tailstock for a machine tool.

  In a machine tool that rotates and supports a long workpiece, one end of the workpiece is rotationally driven and held by the headstock, and a center is inserted into a center hole provided on the end surface of the other end. A supporting arrangement is used. In order to reduce rotational frictional resistance between the center hole and the center, the tailstock shaft that holds the center is held rotatably by a hydrostatic bearing with low frictional resistance, and the tailstock shaft is driven forward and backward by a hydraulic cylinder. (For example, Patent Document 1).

JP-A-61-241050

Since the tailstock of Patent Document 1 is driven by a hydraulic cylinder to move the tailstock shaft back and forth, when the hydraulic supply is interrupted when the machine tool is stopped, the tailstock is driven by the axial force acting on the center hole. The shaft retracts and can no longer hold the workpiece.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a tailstock that can hold a workpiece without the tailstock shaft moving backward even when the hydraulic pressure supply is interrupted.

In order to solve the above problems, the features of the invention according to claim 1 are:
A tailstock,
A center that is held by the tailstock and supports a center hole of a supported object;
A hydrostatic bearing that is held by the tailstock main body and supports the tailstock shaft so that the tailstock shaft can rotate and move in the axial direction;
A hydraulic cylinder for reciprocating the tailstock shaft in the axial direction;
A pressure oil supply device for supplying pressure oil to the hydraulic cylinder;
When the supply of the pressure oil is stopped, a fastening device for fastening the tailstock shaft and the tailstock body so as not to move relative to each other is provided.

The invention according to claim 2 is characterized in that, in the invention according to claim 1, the fastening device comprises:
An annular flange portion, an extension portion extending from the inner diameter portion of the flange portion in the direction of the central axis of the flange portion, and a taper formed on the outer diameter side of the distal end portion of the extension portion and tapering in the direction of the central axis And an elastic ring fixed to the tailstock main body so that the inner peripheral surface has a predetermined gap with the outer peripheral surface of the tailstock shaft. When,
A pressing ring having a tapered surface circumscribing the tapered portion, and being held so as to be slidable in the axial direction of the tailstock shaft;
An elastic member for pressing the pressing ring with an elastic force in an axial direction of the tailstock shaft so that the tapered surface contacts the tapered portion;
When pressure oil is supplied from the pressure oil supply device, the pressing ring is pressed with a force larger than the elastic force in the axial direction of the tailstock shaft such that the tapered portion and the tapered surface have a gap, When the supply of pressure oil is stopped, a pressure oil chamber is provided in which the force becomes smaller than the elastic force.

  According to the first aspect of the present invention, when the pressure oil supply device is stopped and no pressure oil is supplied to the hydraulic cylinder, the tailstock is fastened and fixed to the tailstock body by the fastening device. The axis does not retract. Even if a force acting to retract the tailstock due to the weight of the supported object acts on the center at the center hole, the tailstock does not retract, and thus a tailstock that does not drop the supported object can be realized.

  According to the second aspect of the present invention, when the pressure oil supply device is stopped and no pressure oil is supplied to the pressure oil chamber, the axial force of the tailstock shaft acting on the pressing ring by the elastic member is reduced to the taper of the pressing ring. The force can be increased by converting into the radial direction of the tailstock through the surface and the tapered portion of the elastic ring. By this increased force, the inner peripheral surface of the elastic ring is pushed in the inner diameter direction to hold the outer peripheral surface of the tailstock, thereby realizing a tailstock that can fasten the tailstock to the tailstock body.

It is a top view of the grinding machine of this embodiment. It is the schematic of the tailstock of this embodiment. It is detail drawing of the fastening device of this embodiment. It is detail drawing which shows the time of the fastening operation | movement of the fastening apparatus of this embodiment. It is a figure which shows the fastening device of the deformation | transformation aspect of this embodiment.

Hereinafter, the embodiment of the present invention will be described using a case where a tailstock is mounted on a grinding machine.
The cylindrical grinding machine 1 includes a bed 2, and includes a grindstone base 3 that can reciprocate in the X-axis direction on the bed 2 and a table 4 that can reciprocate in the Z-axis direction orthogonal to the X-axis. The grinding wheel base 3 includes a rotation motor (not shown) that rotatably supports the grinding wheel 7 and rotates the grinding wheel 7. On the table 4, a spindle 5 that grips and rotatably supports one end of a workpiece (supported object) W, and is rotated by a spindle motor (not shown), and a center hole at the other end of the workpiece W Is supported by the spindle 5 and the tailstock 6 and is rotationally driven during the grinding process. A dressing device 9 is fixed on the main shaft 5 and further includes a hydraulic unit (pressure oil supply device) 10 that supplies pressure oil to the tailstock 6 and the like.

  The cylindrical grinding machine 1 includes a control device 30 that executes automated grinding and dressing by executing a predetermined program. As a functional configuration of the control device 30, an X-axis control unit 31 that controls the feed of the grindstone table 3, a Z-axis control unit 32 that controls the feed of the table 4, a spindle control unit 33 that controls the spindle 5, and a tailstock 6 And a tailstock control unit 34 for controlling the operation.

The tailstock 6 will be described with reference to FIG.
The tailstock main body 61 includes two hydrostatic journal bearings 61a and 61b, and the hydrostatic journal bearing supports the tailstock shaft 62 so as to be able to rotate and move in the axial direction. A fastening device 66 is built in the rear end portion of the tailstock body 61 and is positioned by a cap 67. The tailstock 62 has a center 63 at the front end and a piston 64 at the rear end. A cylinder body 65 is mounted on the outer periphery of the piston 64 and fastened to a cap 67 to constitute the cylinder 600.
The hydrostatic journal bearings 61 a and 61 b are connected to the hydraulic unit 10 via the throttle valve and the conduit 23, the cylinder 600 is connected via the conduit 22 and the switching valve 21, and the fastening device 66 is connected via the conduit 23. Pressure oil is supplied from the pump 101.

The fastening device 66 will be described in detail based on FIG.
After the flange portion of the elastic ring 661 is fixed to the countersink hole 61a at the rear end of the tailstock body 61, the pressing ring 662 is slidably inserted into the countersink hole 61a and positioned by the cap 67. . The inner peripheral surface of the end portion 662a of the pressing ring 662 is slidably engaged with the flange outer peripheral surface 661a of the elastic ring 661. Thereby, an annular pressure oil chamber 664 surrounded by the counterbore 61a, the flange outer peripheral surface 661a, and the end 662a is configured.
The end portion 662c of the pressing ring 662 is provided with a plurality of spring holding holes 662d, and a compressed spring (elastic member) 663 is held inside. The pressure of the pressure oil supplied to the pressure oil chamber 664 is set to a size that allows the end portion 662 c of the pressing ring 662 to contact the cap 67 against the elastic force of the spring 663.
The outer periphery of the distal end portion of the thin portion extending in the axial direction from the inner diameter portion of the flange portion of the elastic ring 661 forms a tapered portion 661b. A tapered surface 662b is provided at a position near the tapered portion 661b on the inner circumference of the pressing ring 662. In a state where the end portion 662c of the pressing ring 662 is in contact with the cap 67, the tapered portion 661b and the tapered surface 662b are provided with a gap. In this state, the inner peripheral surface 661c on the inner diameter side of the tapered portion 661b and the outer peripheral surface 62a of the tailstock shaft 62 also have a gap.

Hereinafter, the operation of the tailstock 6 will be described.
First, when the hydraulic unit 10 is activated and pressure oil is supplied to the pressure oil chamber 664 of the fastening device 66, the end portion 662c of the pressing ring 662 contacts the cap 67 as shown in FIG.
When pressure oil is supplied to the hydrostatic bearings 61a and 61b, the tailstock 62 is lifted and held in a state where only the viscous resistance of the oil becomes resistance. When the switching valve 21 is switched in the direction in which the piston 64 is retracted, the tailstock shaft 62 is positioned at the retracted position.
When the workpiece is carried in, the switching valve 21 is switched, the tailstock 62 is advanced by the cylinder 600, the center 63 is inserted into the center hole at one end of the workpiece W, and the other end of the workpiece W by the main shaft. The workpiece W is rotatably held by gripping.
When the main shaft 5 rotates the workpiece W, the tailstock shaft 62 has almost no frictional resistance, and thus rotates integrally with the workpiece W by the frictional force acting on the center hole.
When the grinding of the workpiece W is completed, the switching valve 21 is switched in the direction in which the piston 64 moves backward, the tailstock 62 is positioned in the retracted position, and the workpiece W is carried out.

By the way, when an abnormality occurs and the operation of the hydraulic unit 10 is stopped, the tailstock 6 operates as follows.
When the operation of the hydraulic unit 10 is stopped and the supply of the pressure oil is stopped, the holding force in the axial direction of the tailstock shaft 62 is lost due to the pressure drop of the cylinder 600, and at the same time, the pressure in the pressure oil chamber 664 of the fastening device 66. Decreases.
When the pressure in the pressure oil chamber 664 decreases, the force that pushes the pressing ring 662 toward the cap 67 decreases from the elastic force of the spring 663. The pressing ring 662 moves in the direction of the elastic ring 661 by the elastic force of the spring 663, and the tapered portion 661b of the elastic ring 661 and the tapered surface 662b of the pressing ring 662 come into contact with each other. When the pressing ring 662 further moves, the tapered portion 661b of the elastic ring 661 is pushed and bent in the inner diameter direction, as shown in FIG. Pressed against. The tailstock shaft 62 is fastened and fixed to the tailstock body 61 via the elastic ring 661 by the frictional force acting between the inner peripheral face 661c and the outer peripheral face 62a.

When the fastening device 66 is not provided, the holding force in the axial direction of the tailstock shaft 62 is lost, and the tailstock shaft 62 is retracted by the axial force acting on the center 63 due to the weight of the workpiece W. Can no longer hold and drops.
As described above, by using the tailstock of the present embodiment, even if the hydraulic unit stops during an emergency stop, the workpiece can be held without dropping.

  In this embodiment, a taper is used for the fastening device 66. However, as shown in FIG. 5, when the pressure in the pressure oil chamber 74 decreases, the end surface 72a of the pressing rod 72 is pushed by the elastic force of the spring 73. You may press against the axis | shaft 62.

5: Main shaft 6: Tailstock 10: Hydraulic unit 61: Tailstock body 61a, 61b: Hydrostatic bearing 62: Tailstock 63: Center 66: Fastening device 67: Cap 600: Hydraulic cylinder 661: Elastic ring 662: Pressing ring 663: Spring 664: Pressure oil chamber W: Workpiece

Claims (2)

The tailstock body,
A tailstock,
A center that is held by the tailstock and supports a center hole of a supported object;
A hydrostatic bearing that is held by the tailstock main body and supports the tailstock shaft so that the tailstock shaft can rotate and move in the axial direction;
A hydraulic cylinder for reciprocating the tailstock shaft in the axial direction;
A pressure oil supply device for supplying pressure oil to the hydraulic cylinder;
A tailstock comprising a fastening device that fastens the tailstock shaft and the tailstock main body so that they cannot move relative to each other when supply of the pressure oil is stopped. The fastening device is
An annular flange portion, an extension portion extending from the inner diameter portion of the flange portion in the direction of the central axis of the flange portion, and a taper formed on the outer diameter side of the distal end portion of the extension portion and tapering in the direction of the central axis And an elastic ring fixed to the tailstock main body so that the inner peripheral surface has a predetermined gap with the outer peripheral surface of the tailstock shaft. When,
A pressing ring having a tapered surface circumscribing the tapered portion, and being held so as to be slidable in the axial direction of the tailstock shaft;
An elastic member for pressing the pressing ring with an elastic force in an axial direction of the tailstock shaft so that the tapered surface contacts the tapered portion;
When pressure oil is supplied from the pressure oil supply device, the pressing ring is pressed with a force larger than the elastic force in the axial direction of the tailstock shaft such that the tapered portion and the tapered surface have a gap, The tailstock according to claim 1, further comprising a pressure oil chamber in which the force becomes smaller than the elastic force when the supply of the pressure oil is stopped.

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