Mixer drum driving apparatus including a plurality of motors configured to drive an auxiliary fluid pressure pump to rotate

1. A mixer drum driving apparatus, comprising:

a mixer drum carried on a frame of a concrete mixer truck to be free to rotate;

a fluid pressure motor that drives the mixer drum to rotate;

a fluid pressure pump that is driven by power from an engine of the concrete mixer truck in order to supply a working fluid to the fluid pressure motor;

at least one auxiliary fluid pressure pump that is provided independently of the fluid pressure pump and is capable of supplying the working fluid to the fluid pressure motor so as to cause the mixer drum to perform agitation rotation;

a plurality of motors configured to drive the at least one auxiliary fluid pressure pump to rotate;

a control unit that controls rotation of the mixer drum,

wherein, when the engine is stopped during the agitation rotation of the mixer drum, the control unit drives the at least one auxiliary fluid pressure pump to rotate by operating the plurality of motors selectively so that an agitation rotation speed of the mixer drum comes to be a predetermined speed,

wherein, a load of the mixer drum is detected by detecting a pressure of the working fluid discharged from the at least one auxiliary fluid pressure pump, and

wherein, the control unit controls a number of the motors selectively driving the at least one auxiliary fluid pressure pump to rotate in accordance with the load of the mixer drum; and

a pressure sensor for detecting the pressure of the working fluid discharged from the at least one auxiliary fluid pressure pump to detect the load of the mixer drum.

2. The mixer drum driving apparatus as defined in claim 1 , wherein the at least one auxiliary fluid pressure pump includes a plurality of auxiliary fluid pressure pumps, and the motors are each connected to a corresponding one of the auxiliary fluid pressure pumps.

3. The mixer drum driving apparatus as defined in claim 1 , wherein the at least one auxiliary fluid pressure pump is provided singly, and the plurality of motors are connected to the auxiliary fluid pressure pump.

4. The mixer drum driving apparatus as defined in claim 1 , further comprising:

a connecting pipe that connects the fluid pressure pump to the fluid pressure motor;

a switch valve that is provided in the connecting pipe and blocks the connection between the fluid pressure pump and the fluid pressure motor when the engine is stopped;

a supply pipe configured to supply the working fluid discharged from the at least one auxiliary fluid pressure pump to the fluid pressure motor through the connecting pipe;

a check valve that allows the working fluid to flow only from the at least one auxiliary fluid pressure pump to the connecting pipe;

a discharge pipe configured to discharge a part of the working fluid, that is discharged into the connecting pipe from the fluid pressure motor, to a tank; and

an opening/closing valve configured to open and close the discharge pipe.

5. The mixer drum driving apparatus as defined in claim 4 , wherein, when the engine is stopped, the switch valve is switched from an open position to a blocking position and the opening/closing valve is switched from a blocking position to an open position, and

the fluid pressure motor is driven to rotate by working fluid supplied from the at least one auxiliary fluid pressure pump, which is driven by the selectively operated motors, via the check valve.

6. The mixer drum driving apparatus as defined in claim 5 , wherein, when the engine is restarted after being stopped, the switch valve is switched from the blocking position to the open position and the opening/closing valve is switched from the open position to the blocking position, and

the fluid pressure motor is driven to rotate by the working fluid discharged from the fluid pressure pump driven by the engine.

7. The mixer drum driving apparatus as defined in claim 1 , further comprising:

a connecting pipe that connects the fluid pressure pump to the fluid pressure motor;

a switch valve that is provided in the connecting pipe and blocks the connection between the fluid pressure pump and the fluid pressure motor when the engine is stopped;

a supply pipe configured to supply the working fluid discharged from the at least one auxiliary fluid pressure pump to the fluid pressure motor through the connecting pipe;

a discharge pipe configured to discharge a part of the working fluid, that is discharged into the connecting pipe from the fluid pressure motor, to a tank; and

a control valve configured to control a communication condition between the supply pipe and the connecting pipe and a communication condition between the discharge pipe and the connecting pipe.

8. The mixer drum driving apparatus as defined in claim 7 , wherein, when the engine is stopped, the switch valve is switched from an open position to a blocking position and the control valve is switched from a blocking position to an open position, and

the fluid pressure motor is driven to rotate by working fluid supplied from the at least one auxiliary fluid pressure pump, which is driven by the selectively operated motors, via the control valve.

9. The mixer drum driving apparatus as defined in claim 8 , wherein, when the engine is restarted after being stopped, the switch valve is switched from the blocking position to the open position and the control valve is switched from the open position to the blocking position, and

the fluid pressure motor is driven to rotate by the working fluid discharged from the fluid pressure pump driven by the engine.