Drive power transmission device and control program therefor

1. A drive power transmission device comprising:

a first rotation shaft configured to rotate in only one direction;

a second rotation shaft;

an elastic member having a first end and a second end, the first end of the elastic member being fixed to the second rotation shaft; and

a vibration element fixed to the second end of the elastic member, the vibration element being configured to be disposed in one of a first state of being connected to the first rotation shaft, a second state of being disconnected from the first rotation shaft, a third state of being locked to a fixed member, and a fourth state of being released from the locking to the fixed member.

2. The drive power transmission device according to claim 1 , further comprising a control unit configured to perform:

a first control of placing the vibration element in the first state; and

a second control of placing the vibration element in the second state.

3. The drive power transmission device according to claim 2 , wherein the control unit is configured to perform the first control in response to a velocity difference between rotational velocity of the first rotation shaft and movement velocity of the vibration element being smaller than or equal to a predetermined value.

4. The drive power transmission device according to claim 2 , wherein the control unit is configured to:

perform a third control of placing the vibration element in the third state and a fourth control of placing the vibration element in the fourth state;

execute the second control after the first control;

execute the third control after the second control; and

execute the fourth control after the third control.

5. The drive power transmission device according to claim 4 , wherein the control unit is configured to:

receive input requirement information denoting requirement for the first rotation shaft or the second rotation shaft, and

in response to receiving the requirement information, control any one of an amplitude of the vibration element, a period of time from execution of the first control to execution of the second control, and a period of time from execution of the third control to execution of the fourth control.

6. The drive power transmission device according to claim 5 , wherein:

a rotational velocity of the second rotation shaft is higher than a rotational velocity of the first rotation shaft;

the first control is executed with respect to the vibration element when the elastic member urges the second rotation shaft in a rotation direction of the second rotation shaft, and, concurrently, the second rotation shaft receives transmission of elastic energy released from the elastic member in addition to drive power of the first rotation shaft; and

the third control is executed with respect to the vibration element when the elastic member urges the second rotation shaft in an opposite direction from the rotation direction of the second rotation shaft, and, concurrently, the second rotation shaft causes elastic energy urging in the opposite direction to further accumulate in the elastic member.

7. The drive power transmission device according to claim 5 , wherein:

the second rotation shaft rotates in a direction counter to rotation of the first rotation shaft;

when the elastic member urges the second rotation shaft in an opposite direction from the rotation direction of the second rotation shaft, the vibration element is placed in the first state, and the mutually counter-rotating first rotation shaft and the second rotation shaft cause further accumulation in the elastic member of elastic energy urging in the opposite direction; and

when the elastic member urges the second rotation shaft in the rotation direction of the second rotation shaft, the vibration element is placed in the third state in which the third control is executed, and the second rotation shaft is urged in the rotation direction whereby elastic energy is released.

8. A drive power transmission device comprising:

a first rotation shaft configured to rotate in only one direction;

a second rotation shaft; and

a transmission member configured to accumulate and release elastic energy by deformation, the transmission member being fixed relative to the second rotation shaft in a shaft circumferential direction of the second rotation shaft, and the transmission member being configured to be placed in one of a first state of being connected to the first rotation shaft, a second state of being disconnected from the first rotation shaft, a third state of being locked to a fixed member, and a fourth state of being released from the locking to the fixed member.

9. The drive power transmission device according to claim 8 , wherein:

the first state is a state to accumulate energy transmitted from the first rotation shaft as elastic energy in the transmission member, and

the third state is a state to transmit the elastic energy of the transmission member to the second rotation shaft.