Machine tool

1. A machine tool comprising:

a retaining member that retains a workpiece or a tool;

a first motor that rotates or moves the retaining member;

an in-machine robot that is provided inside the machine tool and that is an articulated robot having one or more joints; and

a connection mechanism that connects or disconnects a root joint which is placed, among the one or more joints, closest to a base end, and the first motor to or from each other.

2. The machine tool according to claim 1 , further comprising:

a root joint actuator that is provided separately from the first motor and that actuates the root joint.

3. The machine tool according to claim 2 , wherein

during a period in which the root joint and the first motor are connected to each other, the root joint actuator is set in a free state or is disconnected from the root joint.

4. The machine tool according to claim 1 , wherein

the root joint is a rotary joint that rotates, and

the retaining member rotates with actuation of the first motor.

5. The machine tool according to claim 4 , wherein

a rotational axis of the retaining member and a rotational axis of the root joint are non-coincident with each other, and

the root joint is connected to or disconnected from the first motor via a plurality of transmission mechanisms.

6. The machine tool according to claim 4 , wherein

a rotational axis of the retaining member and a rotational axis of the root joint are coincident with each other,

an engagement element is provided on one of the root joint and the retaining member, and

an engaged element that engages or disengages in a circumferential direction with or from the engagement element is provided on the other of the root joint and the retaining member.

7. The machine tool according to claim 1 , wherein

the retaining member is a workpiece spindle which retains the workpiece in a self-rotatable manner.