Press brake and table driving method for press brake

A table driving method for a press brake, the press brake comprising:

• a fixed table;
• a movable table that is disposed opposite to the fixed table in an up-down direction;
• an electric motor provided with an electric motor shaft;
• a speed reducer that includes a mechanical paradox planetary gear mechanism, and outputs a rotation of the electric motor shaft by reducing the rotation of the electric motor shaft at either a first reduction ratio or a second reduction ratio larger than the first reduction ratio;
• and
• a clutch that switches a reduction ratio in the speed reducer between the first reduction ratio and the second reduction ratio;
• and
• a conversion mechanism that moves the movable table in the up-down direction by converting a rotation motion transmitted from the speed reducer into a linear motion,
• wherein the clutch includes:
• a first clutch tooth that is connected to a first rotation element included in the speed reducer and rotates integrally with the first rotation element;
• a second clutch tooth that is connected to a second rotation element included in the speed reducer and rotates integrally with the second rotation element;
• and
• a rotationally fixed clutch tooth that is provided between the first clutch tooth and the second clutch tooth disposed to be opposite to each other such that a tooth structure of the first clutch tooth and a tooth structure of the second clutch tooth face each other, and axially moves between the first clutch tooth and the second clutch tooth, and
• when driving the movable table in either an upward direction or a downward direction,
• the table driving method for the press brake includes:
• a first step of operating the speed reducer at the second reduction ratio by meshing the fixed clutch tooth only with the first clutch tooth to fix the first rotation element;
• a second step of operating the speed reducer at the first reduction ratio by meshing the fixed clutch tooth only with the second clutch tooth to fix the second rotation element;
• and
• a third step of meshing the fixed clutch tooth with each of the first clutch tooth and the second clutch tooth when changing a step between the first step and the second step.