TECHNICAL FIELD

This disclosure relates to a machine tool capable of friction-welding a pair of workpieces.

BACKGROUND

Conventionally, there is known a machine tool capable of friction-welding a pair of workpieces, including a pair of spindles for holding respective workpieces and a pair of drive sources for moving the respective spindles in the axial direction, wherein the workpieces held by the respective spindles are brought into contact with each other while being relatively rotated so as to frictionally heat the pair of workpieces, and then the relative rotation is stopped to carry out the friction-welding (refer, for example, to JPH 08-206926 A (PTL 1)).

CITATION LIST

Patent Literature

PTL 1: JPH 08-206926 A

SUMMARY

Technical Problem

There is known a machine tool wherein both of the above-mentioned conventional spindles are provided as being movable in the axial direction, though it is often difficult to smoothly carry out the friction-welding by means of the above-mentioned machine tool.

The present disclosure has been made in view of the above-mentioned problem, and it is an object of the present disclosure to provide a machine tool capable of smoothly friction-welding a pair of workpieces.

Solution to Problem

According to the present disclosure, there is provided a machine tool comprising a first spindle for holding a workpiece, a first drive source for moving the first spindle in an axial direction, a second spindle for holding a workpiece, a second drive source for moving the second spindle in the axial direction, and a control means for controlling the rotation of the first spindle, the rotation of the second spindle and the operation of the second drive source, so as to bring the workpiece held by the first main shaft and the workpiece held by the second main shaft into contact with each other while rotating them relative to each other, thereby to carry out the friction-heating, and to stop the relative rotation of the pair of workpieces and move only the second main shaft in the axial direction while holding the first main shaft stationary, thereby to carry out friction-welding of the pair of workpieces, characterized in that the control means is adapted to control the operation of the first drive source so as to maintain the axial position of the first spindle upon friction-welding of the pair of the workpieces.

Preferably, in the machine tool of the present disclosure with the above-mentioned configuration, the inertia of a members driven by the first drive source and moving in the axial direction together with the first spindle, as a whole, is larger than the inertia of a members driven by the second drive source and moving in the axial direction together with the second spindle, as a whole.

Preferably, in the machine tool of the present disclosure with the above-mentioned configuration, the first drive source is an electric motor, and the machine tool further comprises torque detecting means for detecting the torque applied to the first drive source, and wherein the control means is adapted to control the operation of the first drive source upon the friction-welding of the pair of workpieces, so as to resist the torque detected by the torque detecting means.

Preferably, in the machine tool of the present disclosure with the above-mentioned configuration, the machine tool comprises a tool that can be moved under the control by the control means, and the control means is adapted to control the rotation of the first spindle, the rotation of the second spindle and the relative movement of the tool so that, after the pair of workpieces have been friction-welded, the first spindle and the second spindle are rotated in the same direction at the same rotation speed, while the tool is moved relative to the workpieces, thereby to carry out cutting process for cutting the workpiece by means of the tool.

Preferably, in the machine tool of the present disclosure with the above-mentioned configuration, the control means is adapted to control the operation of the second drive source so that, after stopping the relative rotation of the pair of the workpieces and while maintaining the first spindle stationary. only the second spindle is moved to an axial position predetermined in consideration of an upset distance.

Advantageous Effect

The present disclosure thus provides a machined tool wherein, when friction-welding is carried out, one of the spindles is moved while the other of the spindles is maintained stationary to carry out the friction-welding, thereby allowing the friction-welding to be carried out smoothly, even when both spindles are movable in the axial direction.

