Patent Publication Number: US-2013253781-A1

Title: Shovel

Description:
TECHNICAL FIELD 
     The present invention relates to shovels whose electric working elements are driven with electric power from an electric power accumulator. 
     BACKGROUND ART 
     Shovels that include electric working elements such as a turning mechanism driven by an electric motor are provided with an electric power accumulating unit including an electric power accumulator that supplies electric power for driving the electric working elements. A common electric power accumulating unit is accommodated in a small enclosure. Therefore, the temperature of the electric power accumulator increases because of heat from around or heat generated with the charge and discharge of the electric power accumulator. 
     An increase in the temperature of the electric power accumulator accelerates the degradation of the electric power accumulator, thus shortening the service life of the electric power accumulator. Furthermore, the degradation of the electric power accumulator reduces its power accumulation capacity, so that the reduction rate of the state of charge (SOC) increases. In this case, the amount of accumulated electric power of the electric power accumulator decreases in a short period of time, so that the electric power accumulator is prevented from supplying its electric working elements with necessary electric power. 
     In the case of hybrid shovels, an engine is assisted by driving an assist motor with electric power from an electric power accumulator. Therefore, when the electric power accumulator degrades, the assist motor is often driven with the electric power accumulator being in a low state of charge (SOC). In this case, when the state of charge (SOC) is low, the electric power accumulator may be controlled not to supply electric power, so that the usage rate of the assist motor decreases. As a result, because the driving of the assist motor is prevented, the usage rate of the engine becomes higher than usual, thus resulting in an increase in the amount of fuel consumption of the engine. 
     Therefore, it has been proposed to cool the electric power accumulator by providing a cooling apparatus such as a cooling pump near the electric power accumulator. Cooling the electric power accumulator makes it possible to suppress the degradation of the electric power accumulator due to a temperature increase and to extend the service life of the electric power accumulator. The cooling apparatus such as a cooling pump is electrically driven, so that when the shovel is in operation, it is possible to drive the cooling apparatus by supplying the cooling apparatus with electric power and thereby to cool the electric power accumulator. However, when the operation of the shovel is stopped, electric power is prevented from being supplied, thus preventing the cooling apparatus from being driven. 
     The shovel is often exposed to a high-temperature atmosphere in the open air, so that it is often the case that part of the shovel where an electric power accumulating unit is provided is exposed to direct sunlight so that the electric power accumulating unit is heated. That is, even when the operation of the shovel is stopped, the temperature of the electric power accumulator may increase due to surrounding heat so as to accelerate the degradation of the electric power accumulator. 
     It has been proposed to control an increase in the temperature of an inverter provided in a shovel by performing such control as to reduce the upper limit value of an electric current supplied to an alternating-current electric motor such as a turning electric motor when the temperature of cooling water for cooling the inverter becomes higher than or equal to an output reduction temperature. (For example, see Patent Document 1.) 
     PRIOR ART DOCUMENT 
     Patent Document 
     
         
         [Patent Document 1] Japanese Unexamined Patent Application No. 2010-222815 
       
    
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     It is possible to attach solar cells to a shovel and drive a cooling apparatus with electric power generated by the solar cells. However, when the sunlight is not so strong, the electric power generated by the solar cells is so limited that the cooling apparatus may not be driven with the electric power generated by the solar cells alone. For example, immediately after the operation of the shovel is stopped, a high-temperature state may continue because of heat generated by an electric power accumulating unit and heat generated by other peripheral devices (an engine and a motor). Therefore, desirably, it is possible to cool an electric power accumulator even after the operation of the shovel is stopped. Parts that require cooling include a controller, an inverter, and a converter in addition to the electric power accumulator. 
     For example, a 24 V battery (storage battery) is often provided in a shovel as a power supply for supplying electric power to electrical parts that are kept operating even after the shovel is stopped. Thus, it is desirable to efficiently supply electric power by using both solar cells and a storage battery even after the shovel is stopped. 
     Electric power from the above-described battery may be used in a warmup as well as for driving electrical parts that are kept operating. 
     Means for Solving the Problems 
     According to the present invention, a shovel is provided that includes a lower-part traveling body; an upper-part turning body rotatably provided on the lower-part traveling body; an electrically driven part provided in the upper-part turning body and subjected to temperature control during an operation; a battery provided in the upper-part turning body and configured to supply electric power to a constant electrical load that constantly operates apart from the electrically driven part; a photovoltaic power generation panel provided on the upper-part turning body; a photovoltaic power generator provided in the upper-part turning body, the photovoltaic power generator including a photovoltaic electric power accumulating part configured to accumulate electric power generated by the photovoltaic power generation panel; and a voltage detector configured to detect an output voltage of the photovoltaic electric power accumulating part; a temperature controller connected to the photovoltaic power generator and the battery; a temperature detector configured to detect a temperature of the electrically driven part; a first switch configured to open or close a power supply line connecting the temperature controller and the photovoltaic power generator based on a temperature detection value of the temperature detector; and a second switch configured to open or close a power supply line connecting the temperature controller and the battery based on the temperature detection value of the temperature detector. 
     Effects of the Invention 
     According to the above-described invention, when it is necessary to control the temperature of an electrically driven part that is subjected to temperature control during operation, it is possible to control the temperature of the electrically driven part by driving a temperature controller with electric power from a photovoltaic power generator, and when it is unnecessary to control the temperature of the electrically driven part, it is possible to charge a battery by supplying the battery with electric power from the photovoltaic power generator. Further, when it is necessary to control the temperature of the electrically driven part but the amount of electric power accumulated in the photovoltaic power generator is limited, it is possible to control the temperature of the electrically driven part by driving the temperature controller with electric power from the battery. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a hydraulic shovel. 
         FIG. 2  is a block diagram illustrating a configuration of a drive system of a hydraulic shovel according to an embodiment. 
         FIG. 3  is a block diagram illustrating an electric power accumulation system. 
         FIG. 4  is a block diagram of a drive system of a cooling fan. 
         FIG. 5  is a flowchart of a cooling fan drive control process. 
         FIG. 6  is a block diagram illustrating a state of a cooling fan driving circuit in a normal mode. 
         FIG. 7  is a block diagram illustrating a state of the cooling fan driving circuit in a first electric power accumulator cooling mode. 
         FIG. 8  is a block diagram illustrating a state of the cooling fan driving circuit in a second electric power accumulator cooling mode. 
         FIG. 9  is a plan view of the hybrid shovel, illustrating locations for attaching solar panels. 
         FIG. 10  is a diagram of an overall configuration of a cooling apparatus. 
         FIG. 11  is a block diagram of a drive system of a pump motor. 
         FIG. 12  is a flowchart of a pump drive control process. 
         FIG. 13  is a block diagram illustrating a state of a pump motor driving circuit in a normal mode. 
         FIG. 14  is a block diagram illustrating a state of the pump motor driving circuit in a first electrically driven part cooling mode. 
         FIG. 15  is a block diagram illustrating a state of the pump motor driving circuit in a second electrically driven part cooling mode. 
         FIG. 16  is a block diagram of a drive system of an electric motor. 
         FIG. 17  is a flowchart of an electric heater drive control process. 
         FIG. 18  is a block diagram illustrating a state of an electric heater driving circuit in a normal mode. 
         FIG. 19  is a block diagram illustrating a state of the electric heater driving circuit in a first electric power accumulator warmup mode. 
         FIG. 20  is a block diagram illustrating a state of the electric heater driving circuit in a second electric power accumulator warmup mode. 
         FIG. 21  is a block diagram illustrating a configuration of a hybrid shovel where a turning mechanism is driven by a turning hydraulic motor. 
         FIG. 22  is a block diagram illustrating a configuration of a drive system of an electric shovel. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Next, a description is given of embodiments, referring to the drawings. 
       FIG. 1  is a side view illustrating a hybrid shovel, which is an example of a shovel to which the present invention is applied. 
     An upper-part turning body  3  is mounted through a turning mechanism  2  on a lower-part traveling body  1  of the hybrid shovel. A boom  4  as an attachment is attached to the upper-part turning body  3 . An arm  5  is attached to the end of the boom  4 . A bucket  6  is attached to the end of the arm  5 . The boom  4 , the arm  5 , and the bucket  6  are hydraulically driven by a boom cylinder  7 , an arm cylinder  8 , and a bucket cylinder  9 , respectively. A cabin  10  is provided and power sources such as an engine are mounted on the upper-part turning body  3 . Thus, the cabin and the attachment are configured as part of the upper-part turning body  3 . 
       FIG. 2  is a block diagram illustrating a configuration of a drive system of the hybrid shovel according to an embodiment of the present invention. In  FIG. 2 , a double line, a solid line, a broken line, and a solid line indicate a mechanical power system, a high-pressure hydraulic line, a pilot line, and an electric drive and control system, respectively. 
     An engine  11  as a mechanical drive part and a motor generator  12  as an assist drive part are connected to a first input shaft and a second input shaft, respectively, of a transmission  13 . A main pump  14  and a pilot pump  15  are connected as hydraulic pumps to the output shaft of the transmission  13 . A control valve  17  is connected to the main pump  14  via a high-pressure hydraulic line  16 . 
     The control valve  17  is a controller configured to control a hydraulic system in the hybrid shovel. Hydraulic motors  1 A (right) and  1 B (left) for the lower-part traveling body  1 , the boom cylinder  7 , the arm cylinder  8 , and the bucket cylinder  9  are connected to the control valve  17  via high-pressure hydraulic lines. 
     An electric power accumulation system  120  including a capacitor as an electric power accumulator is connected to the motor generator  12  via an inverter  18 A. A turning electric motor  21  as an electric working element is connected to the electric power accumulation system  120  via an inverter  20 . A resolver  22 , a mechanical brake  23 , and a turning transmission  24  are connected to a rotation shaft  21 A of the turning electric motor  21 . Furthermore, an operation apparatus  26  is connected to the pilot pump  15  via a pilot line  25 . The turning electric motor  21 , the inverter  20 , the resolver  22 , the mechanical brake  23 , and the turning transmission  24  constitute a load drive system. 
     The operation apparatus  26  includes a lever  26 A, a lever  26 B, and a pedal  26 C. The lever  26 A, the lever  26 B, and the pedal  26 C are connected to the control valve  17  and a pressure sensor  29  via hydraulic lines  27  and  28 , respectively. The pressure sensor  29  is connected to a controller  30  that controls the driving of an electric system. 
     According to this embodiment, a boom regeneration motor  300  (also referred to as “motor generator  300 ”) for acquiring boom regenerated electric power is connected to the electric power accumulation system  120  via an inverter  18 C. The motor generator  300  is driven by a hydraulic motor  310  that is driven with hydraulic fluid discharged from the boom cylinder  7 . The motor generator  300  converts the potential energy of the boom  4  into electrical energy using the pressure of hydraulic fluid discharged from the boom cylinder  7  as the boom  4  is lowered in accordance with gravity. In  FIG. 2 , the hydraulic motor  310  and the motor generator  300  are illustrated at separate positions for convenience of description. Actually, however, the rotation shaft of the motor generator  300  is mechanically connected to the rotation shaft of the hydraulic motor  310 . 
     That is, the hydraulic motor  310  is configured to rotate with hydraulic fluid discharged from the boom cylinder  7  when the boom  4  is lowered, and is provided to convert energy at the time of the boom  4  being lowered in accordance with gravity into a rotating force. The hydraulic motor  310  is provided in a hydraulic pipe  7 A between the control valve  17  and the boom cylinder  7 . The hydraulic motor  310  may be attached to an appropriate part in the upper-part turning body  3 . 
     The electric power generated in the motor generator  300  is supplied as regenerated electric power to the electric power accumulation system  120  via the inverter  18 C. The motor generator  300  and the inverter  18 C constitute a boom regeneration system. 
     According to this embodiment, a boom angle sensor  7 B for detecting the angle of the boom  4  is attached to the support shaft of the boom  4 . The boom angle sensor  7 B feeds a detected boom angle θB to the controller  30 . 
       FIG. 3  is a block diagram illustrating the electric power accumulation system  120 . The electric power accumulation system  120  includes a capacitor  19  as an electric power accumulator, a step-up/step-down converter  100 , and a DC bus  110 . The DC bus  110  as a second electric power accumulator controls the transfer of electric power among the capacitor  19  as a first electric power accumulator, the motor generator  12 , and the turning electric motor  21 . The capacitor  19  is provided with a capacitor voltage detecting part  112  for detecting a capacitor voltage value and a capacitor electric current detecting part  113  for detecting a capacitor electric current value. The capacitor voltage value and the capacitor electric current value detected by the capacitor voltage detecting part  112  and the capacitor electric current detecting part  113 , respectively, are fed to the controller  30 . 
     The step-up/step-down converter  100  performs such control as switching a step-up operation and a step-down operation in accordance with the operating states of the motor generator  12 , the motor generator  300 , and the turning electric motor  21 , so that the DC bus voltage value falls within a certain range. The DC bus  110  is provided between the inverters  18 A,  18 C, and  20  and the step-up/step-down converter  100  to transfer electric power among the capacitor  19 , the motor generator  12 , the motor generator  300 , and the turning electric motor  21 . 
     Here, a description is given, taking the capacitor  19  as an example. However, in place of the capacitor  19 , a rechargeable battery capable of being charged and discharged, such as a lithium-ion battery, or other form of power supply capable of transferring electric power, may be used as an electric power accumulator. 
     Referring back to  FIG. 2 , the controller  30  is a control unit serving as a main control part that controls the driving of the hybrid shovel. The controller  30  includes a processor including a CPU (Central Processing Unit) and an internal memory. The controller  30  is implemented by the CPU executing a drive control program contained in the internal memory. 
     The controller  30  converts a signal fed from the pressure sensor  29  into a speed command, and controls the driving of the turning electric motor  21 . The signal fed from the pressure sensor  29  corresponds to a signal representing the amount of operation in the case of operating the operation apparatus  26  to turn the turning mechanism  2 . 
     The controller  30  controls the operation (switches the electric motor [assist] operation and the generator operation) of the motor generator  12 . The controller  30  also controls the charge and discharge of the capacitor  19  by controlling the driving of the step-up/step-down converter  100  as a step-up/step-down control part. The controller  30  controls the charge and discharge of the capacitor  19  by controlling the switching of the step-up operation and the step-down operation of the step-up/step-down converter  100  based on the state of charge of the capacitor  19 , the operating state (electric motor [assist] operation or generator operation) of the motor generator  12 , and the operating state (power running operation or regenerative operation) of the turning electric motor  21 . 
     This control of the switching of the step-up operation and the step-down operation of the step-up/step-down converter  100  is performed based on the DC bus voltage value detected by a DC bus voltage detecting part  111 , the capacitor voltage value detected by the capacitor voltage detecting part  112 , and the capacitor electric current value detected by the capacitor electric current detecting part  113 . 
     In the above-described configuration, the electric power generated by the motor generator  12 , which is an assist motor, is supplied to the DC bus  110  of the electric power accumulation system  120  via the inverter  18 A to be supplied to the capacitor  19  via the step-up/step-down converter  100 . The electric power regenerated by the regenerative operation of the turning electric motor  21  is supplied to the DC bus  110  of the electric power accumulation system  120  via the inverter  20 , to be supplied to the capacitor  19  via the step-up/step-down converter  100 . Furthermore, the electric power generated by the motor generator  300  for boom regeneration is supplied to the DC bus  110  of the electric power accumulation system  120  via the inverter  18 C, to be supplied to the capacitor  19  via the step-up/step-down converter  100 . 
     The rotational speed (angular velocity w) of the turning electric motor  21  is detected by the resolver  22 . Furthermore, the angle of the boom  4  (boom angle θB) is detected by the boom angle sensor  7 B such as a rotary encoder provided on the support shaft of the boom  4 . 
     According to a first embodiment of the present invention, a cooling fan is provided as a cooling apparatus for cooling the above-described capacitor  19 . The cooling fan is driven with electric power generated by a solar photovoltaic power generator.  FIG. 4  is a block diagram illustrating a drive system of the cooling apparatus. 
     The capacitor, which is an example of a main electric power accumulating unit, corresponds to an electrically driven part that is subjected to temperature control such as cooling during operation. Furthermore, the cooling fan is an example of a temperature controller that controls the temperature of the electrically driven part. 
     The capacitor  19 , serving as a main electric power accumulating unit, is accommodated in an electric power accumulating unit box  50  provided in the upper-part turning body  3 . A cooling fan  52  for cooling the capacitor  19  is attached to the electric power accumulating unit box  50 , and cools the capacitor  19  by introducing outside air into the electric power accumulating unit box  50 . A temperature detection sensor  54  is provided in the electric power accumulating unit box  50  as a temperature detector. The temperature detection sensor  54  detects temperature inside the electric power accumulating unit box  50 , and feeds a temperature detection value to the controller  30 . 
     A photovoltaic power generator  60  is provided as an apparatus that supplies the cooling fan  52  with electric power. The photovoltaic power generator  60  includes solar panels  62  and a solar cell electric power accumulator  64  as a photovoltaic electric power accumulating part that accumulates electric power generated in the solar panels  62 . The electric power that the solar panels  62  generate by receiving solar radiation is accumulated in the solar cell electric power accumulator  64 , so that the electric power is supplied from the solar cell electric power accumulator  64  to the cooling fan  52 . A voltmeter  66  is provided in the solar cell electric power accumulator  64  as a voltage detector. The voltmeter  66  detects a voltage across the solar cell electric power accumulator  64 . 
     In addition to electrically driven parts that include electric working elements and electrical parts for electrically driving electrical working elements, a constant electrical load  70  is provided in the hybrid shovel. The constant electrical load  70  is an electrical load that is supplied with electric power to keep on operating even when the shovel is not in operation, that is, even when the engine is not rotating and the inverters and the converter are not activated. Examples of the constant electrical load  70  include a communications device, a lighting apparatus, and a memory data retention device. The constant electrical load  70  is constantly supplied with electric power from a battery  72  as a dedicated electric power accumulating unit. This allows the constant electrical load  70  to operate even when the operation of the shovel is stopped. Electrical parts for driving electric working elements include the CPU of a controller, an inverter and a converter that transfer electric power, and an electric power accumulator or a battery. 
     A solar cell power supply line  80  is extended from the photovoltaic power generator  60 . The solar cell power supply line  80  branches off into a cooling fan power supply line  82  and a battery power supply line  84 . The cooling fan power supply line  82  is connected to the cooling fan  52 , so that electric power from the solar cell electric power accumulator  64  may be supplied to the cooling fan  52  via the solar cell power supply line  80  and the cooling fan power supply line  82  so as to drive the cooling fan  52 . Meanwhile, the battery power supply line  84  is connected to the battery  72  for the constant electrical load  70 , so that electric power from the solar cell electric power accumulator  64  may be supplied to the battery  72  via the solar cell power supply line  80  and the battery power supply line  84  so as to be accumulated in the battery  72 . Furthermore, because the cooling fan power supply line  82  and the battery power supply line  84  are connected at the branch point, electric power may be supplied from the battery  72  to the cooling fan  52  via the battery power supply line  84  and the cooling fan power supply line  82  so as to drive the cooling fan  52 . 
     A first switch  90  formed of, for example, an electromagnetic make-and-break switch, is provided in the cooling fan power supply line  82 , so that the first switch  90  controls the feeding of electric power to the cooling fan  52 . Furthermore, a second switch  92  formed of, for example, an electromagnetic make-and-break switch, is provided in the battery power supply line  84 , so that the second switch  92  controls the feeding of electric power to the battery  72 . Furthermore, a third switch  94  formed of, for example, an electromagnetic make-and-break switch, is provided in the solar cell power supply line  80 , so that the third switch  94  controls the feeding of electric power from the solar cell electric power accumulator  64  of the photovoltaic power generator  60 . The make and break of the first and second switches  90  and  92  is controlled by signals from the controller  30 . The make and break of the third switch  94  is controlled based on a voltage detection value from the voltmeter  66  provided in the solar cell electric power accumulator  64 . Alternatively, the voltage detection value from the voltmeter  66  may be fed to the controller  30  so as to cause the controller  30  to control the make and break of the third switch  94 . 
     A description is given below of control of the driving of a cooling fan performed in the above-described cooling fan drive system. 
       FIG. 5  is a flowchart of a cooling fan drive control process. First, in step S 1 , a temperature Tc inside the electric power accumulating unit box  50  is detected with the temperature detection sensor  54 . In step S 2 , it is determined whether the temperature Tc inside the electric power accumulating unit box  50  is higher than a predetermined temperature Tlmt. If the temperature Tc inside the electric power accumulating unit box  50  is lower than or equal to the predetermined temperature Tlmt (Tc≦Tlmt), the process proceeds to step S 3 . 
     In step S 3 , a normal mode is set, and the second and third switches  92  and  94  are closed (ON) and the first switch  90  is opened (OFF) as illustrated in  FIG. 6 . That is, when the temperature Tc inside the electric power accumulator box is low, the temperature of the capacitor  19  is also low, so that there is no need for cooling. Therefore, the first switch  90  is opened (OFF) to break the cooling fan power supply line  82 , thereby preventing the cooling fan  52  from operating. 
     At this point, the second and third switches  92  and  94  are closed (ON). As a result, when the solar panels  62  generate electric power, and the electric power is accumulated in the solar cell electric power accumulator  64  so that the voltage of the solar cell electric power accumulator  64  becomes higher than a preset voltage value (that is, the state of charge (SOC) of the solar cell electric power accumulator  64  exceeds a predetermined state of charge), electric power is supplied from the solar cell electric power accumulator  64  to the battery  72  via the solar cell power supply line  80  and the battery power supply line  84 , so that the battery  72  is charged with the electric power. Accordingly, when there is no need to cool the capacitor  19 , electric power generated by the solar panels  62  is accumulated in the battery  72  without being wasted. 
     Referring back to  FIG. 5 , if the temperature Tc inside the electric power accumulating unit box  50  is higher than the predetermined temperature Tlmt (Tc&gt;Tlmt) in step S 2 , the process proceeds to step S 4 . In step S 4 , it is determined whether a voltage Vs of the solar cell electric power accumulator  64  is higher than a preset voltage Vlmt. That is, it is determined whether the state of charge (SOC) of the solar cell electric power accumulator  64  is higher than a predetermined state of charge. The voltage Vs of the solar cell electric power accumulator  64  is a voltage detected with the voltmeter  66 . 
     If it is determined in step S 4  that the voltage Vs of the solar cell electric power accumulator  64  is higher than the preset voltage Vlmt (that is, if it is determined that the state of charge (SOC) of the solar cell electric power accumulator  64  is higher than a predetermined state of charge), the process proceeds to step S 5 . In step S 5 , a first electric power accumulator cooling mode is set, and the first and third switches  90  and  94  are closed (ON) and the second switch  92  is opened (OFF) as illustrated in  FIG. 7 . That is, by closing the first and third switches  90  and  94  (ON), the electric power of the solar cell electric power accumulator  64  is supplied to the cooling fan  52  via the solar cell power supply line  80  and the cooling fan power supply line  82 . As a result, the cooling fan  52  operates, so that it is possible to cool the capacitor  19 . At this point, the second switch  92  is opened (OFF). Therefore, the battery  72  is supplied with no electric power, so that the entire electric power of the solar cell electric power accumulator  64  is used to drive the cooling fan  52 . 
     Referring back to  FIG. 5 , if it is determined in step S 4  that the voltage Vs of the solar cell electric power accumulator  64  is lower than or equal to the preset voltage Vlmt (that is, if it is determined that the state of charge (SOC) of the solar cell electric power accumulator  64  is lower than or equal to a predetermined state of charge), the process proceeds to step S 6 . In step S 6 , a second electric power accumulator cooling mode is set, and the first and second switches  90  and  92  are closed (ON) and the third switch  94  is opened (OFF) as illustrated in  FIG. 8 . That is, by opening the third switch  94  (OFF), no electric power is supplied from the solar cell electric power accumulator  64 . Furthermore, by closing the first and second switches  90  and  92  (ON), electric power accumulated in the battery  72  is supplied to the cooling fan  52  via the battery power supply line  84  and the cooling fan power supply line  82 , so that the cooling fan  52  is driven to cool the capacitor  19 . Thus, when the state of charge of the solar cell electric power accumulator  64  is low, the cooling fan  52  may be driven with electric power from the battery  72 . Therefore, it is possible to cool the capacitor  19  even when the shovel is in such a location where sunlight is insufficient. 
     Here, consideration is given to a position for attaching the solar panels  62 .  FIG. 9  is a plan view of the above-described hybrid shovel, where locations to which the solar panels  62  may be attached are shaded with oblique lines. The locations to which the solar panels  62  may be attached include an upper surface (the outside of a ceiling)  10 - 1  of the cabin  10 , an upper surface  3 - 1  of the counterweight of the upper-part turning body  3  (engine hood), and an upper surface  4 - 1  of the boom  4 . 
     In common shovels, the area of the upper surface  10 - 1  of the cabin  10  is, for example, 1.7 m 2 , the upper surface  3 - 1  of the counterweight of the upper-part turning body is, for example, 4.4 m 2 , and the area of the upper surface  4 - 1  of the boom  4  is, for example, 0.8 m 2 . The total of these areas shows that the area to which the solar panels  62  may be attached is 6.9 m 2 . It is said that an area of approximately 7 m 2  is necessary to obtain electric power of 1 kW with currently available solar panels. Accordingly, when solar panels are attached to the entirety of the above-described area (6.9 m 2 ), it is possible to obtain electric power of approximately 1 kW. Assuming 1000 hours of fine weather, the annual generation of electric power is approximately 1000 kWh. That is, in the case of generating electric power by attaching the solar panels  62  to the locations illustrated in  FIG. 9 , the generation of electric power of approximately 1000 kWh may be expected in a year. 
     Meanwhile, letting the electric power consumed by the cooling fan  52  be, for example, 36 W, the annual consumption of electric power is 36 kWh in the case of annual utilization of 1000 hours. This is far less than the annual electric power generation of 1000 kWh of solar panels, thus showing that the amount of electric power generated by solar panels is sufficient to cover the amount of electric power supplied to the cooling fan  52 . 
     In the above-described embodiment, the cooling fan  52  that ventilates the electric power accumulating unit box  50  is used as a cooling apparatus, but it is also possible to use other cooling apparatuses. As long as it is possible to cover consumed electric power, for example, a heat exchanger using a refrigerant or an electronic cooling device such as a Peltier device may be used to cool the capacitor  19 . Furthermore, electric power of approximately 250 kWh may be annually obtained even with the 1.7 m 2  area of the upper surface of the cabin  10 . Likewise, electric power of approximately 640 kWh may be annually obtained even with the 4.4 m 2  area of the upper surface of the counterweight  3 - 1 . Therefore, by placing solar panels on at least one of the upper surface of the cabin  10  and the upper surface of the counterweight  3 - 1 , it is possible to obtain electric power necessary to cool the electric power accumulating part. 
     Next, a description is given of a second embodiment. In the second embodiment, a cooling apparatus for cooling electrically driven parts is provided. Here, as described above, the electrically driven parts include the controller  30 , the inverters  18 A,  18 C, and  20 , the step-up/step-down converter  100 , the capacitor  19 , the turning electric motor  21 , and the motor generator  12 . Furthermore, a cooling apparatus is an example of a temperature controller that controls the temperatures of electrically driven parts. 
       FIG. 10  is a diagram of an overall configuration of a cooling apparatus. The cooling apparatus includes a tank  200 , a pump  201 , a pump motor  202 , a radiator  203 , and a water temperature gauge  204  (a temperature detection part). Cooling water (a refrigerant) in the cooling apparatus is stored in the tank  200 , and is conveyed to the radiator  203  by the pump  201 , which is driven by the pump motor  202 . The cooling water cooled by the radiator  203  is conveyed to the inverters  18 A,  18 C, and  20 , the step-up/step-down converter  100 , and the capacitor  19  via the controller  30  through pipes. The cooling water is returned to the tank  200  via the turning electric motor  21 , the motor generator  12 , and the transmission  13 . The water temperature gauge  204  detects the temperature of the cooling water conveyed from the radiator  203 , and transmits information on the detected temperature to the controller  30 . 
     Furthermore, the pipe for cooling water to the controller  30  is directly connected to the radiator  203 . This makes it possible to ensure cooling performance with respect to the CPU inside the controller  30 , so that the reliability of the shovel is ensured. In  FIG. 10 , the pipes are connected so that the cooling water used to cool the controller  30  is used to cool the inverters  18 A,  18 C, and  20 , the step-up/step-down converter  100 , etc. Alternatively, however, the pipe from the radiator  203  may be connected to the controller  30 , the inverters  18 A,  18 C, and  20 , the step-up/step-down converter  100 , etc., in parallel. Furthermore, all of the controller  30 , the inverters  18 A,  18 C, and  20 , the step-up/step-down converter  100 , the capacitor  19 , the turning electric motor  21 , and the motor generator  12  may not be cooled by liquid, and one or more of the electrically driven parts may be cooled by air using a fan. In this case, the fan may be driven with electric power supplied from the battery  72  or the solar cell electric power accumulator  64 . 
     In this embodiment, in place of the fan  52  in the first embodiment, the pump motor  202  is driven with electric power from the solar cell electric power accumulator  64  or electric power from the battery  72 , thereby cooling electrically driven parts during the suspension of the operation of the shovel (during the stoppage of the engine  11 ) as well. 
       FIG. 11  is a block diagram of a drive system of a pump motor. Like in the first embodiment, the solar cell power supply line  80  is extended from the photovoltaic power generator  60 . The solar cell power supply line  80  branches off into a pump motor power supply line  86  and the battery power supply line  84 . The pump motor power supply line  86  is connected to the pump motor  202 , so that electric power from the solar cell electric power accumulator  64  may be supplied to the pump motor  202  via the solar cell power supply line  80  and the pump motor power supply line  86  so as to drive the pump  201 . Meanwhile, the battery power supply line  84  is connected to the battery  72  for the constant electrical load  70 , so that electric power from the solar cell electric power accumulator  64  may be supplied to the battery  72  via the solar cell power supply line  80  and the battery power supply line  84  so as to be accumulated in the battery  72 . Furthermore, because the pump motor power supply line  86  and the battery power supply line  84  are connected at the branch point, electric power may be supplied from the battery  72  to the pump motor  202  via the battery power supply line  84  and the pump motor power supply line  86  so as to drive the pump  201 . When the pump  201  is thus driven, the cooling water cooled in the radiator  203  is supplied to individual electrically driven parts. Here, the cooling fan  52  illustrated in  FIG. 4  may be further provided as a cooling fan for the radiator  203 , and the cooling fan may be driven with electric power supplied from the battery  72  or the solar cell electric power accumulator  64 . 
     Like in the first embodiment, the first switch  90  formed of, for example, an electromagnetic make-and-break switch, is provided in the pump motor power supply line  86 , so that the first switch  90  controls the feeding of electric power to the pump motor  202 . Furthermore, the second switch  92  formed of, for example, an electromagnetic make-and-break switch, is provided in the battery power supply line  84 , so that the second switch  92  controls the feeding of electric power to the battery  72 . Furthermore, the third switch  94  formed of, for example, an electromagnetic make-and-break switch, is provided in the solar cell power supply line  80 , so that the third switch  94  controls the feeding of electric power from the solar cell electric power accumulator  64  of the photovoltaic power generator  60 . The make and break of the first and second switches  90  and  92  is controlled by signals from the controller  30 . The make and break of the third switch  94  is controlled based on a voltage detection value from the voltmeter  66  provided in the solar cell electric power accumulator  64 . Alternatively, the voltage detection value from the voltmeter  66  may be fed to the controller  30  so as to cause the controller  30  to control the make and break of the third switch  94 . 
     A description is given below of control of the driving of a pump performed in the above-described drive system of the pump  201 . 
       FIG. 12  is a flowchart of a pump drive control process. First, in step S 11 , a temperature Te of an electrically driven part is detected with a temperature detection sensor  56 . The temperature detection sensor  56  is a temperature sensor provided in the controller  30 , the inverter  18 A,  18 C or  20 , the step-up/step-down converter  100 , the capacitor  19 , the turning electric motor  21 , the motor generator  12  or the like. Then, in step S 12 , it is determined whether the temperature Te of the electrically driven part is higher than a predetermined temperature Tlmt. If the temperature Te of the electrically driven part is lower than or equal to the predetermined temperature Tlmt (Te≦Tlmt), the process proceeds to step S 13 . 
     In step S 13 , a normal mode is set, and the second and third switches  92  and  94  are closed (ON) and the first switch  90  is opened (OFF) as illustrated in  FIG. 13 . That is, when the temperature Te of the electrically driven part is low, the temperature of the electrically driven part is also low, so that there is no need for cooling. Therefore, the first switch  90  is opened (OFF) to break the pump motor power supply line  86 , thereby preventing the pump motor  202  from operating. 
     At this point, the second and third switches  92  and  94  are closed (ON). As a result, when the solar panels  62  generate electric power, and the electric power is accumulated in the solar cell electric power accumulator  64  so that the voltage of the solar cell electric power accumulator  64  becomes higher than a preset voltage value (that is, the state of charge (SOC) of the solar cell electric power accumulator  64  exceeds a predetermined state of charge), electric power is supplied from the solar cell electric power accumulator  64  to the battery  72  via the solar cell power supply line  80  and the battery power supply line  84 , so that the battery  72  is charged with the electric power. Accordingly, when there is no need to cool the electrically driven part, electric power generated by the solar panels  62  is accumulated in the battery  72  without being wasted. 
     Referring back to  FIG. 12 , if the temperature Te of the electrically driven part is higher than the predetermined temperature Tlmt (Te&gt;Tlmt) in step S 12 , the process proceeds to step S 14 . In step S 14 , it is determined whether the voltage Vs of the solar cell electric power accumulator  64  is higher than a preset voltage Vlmt. That is, it is determined whether the state of charge (SOC) of the solar cell electric power accumulator  64  is higher than a predetermined state of charge. The voltage Vs of the solar cell electric power accumulator  64  is a voltage detected with the voltmeter  66 . 
     If it is determined in step S 14  that the voltage Vs of the solar cell electric power accumulator  64  is higher than the preset voltage Vlmt (that is, if it is determined that the state of charge (SOC) of the solar cell electric power accumulator  64  is higher than a predetermined state of charge), the process proceeds to step S 15 . In step S 15 , a first electrically driven part cooling mode is set, and the first and third switches  90  and  94  are closed (ON) and the second switch  92  is opened (OFF) as illustrated in  FIG. 14 . That is, by closing the first and third switches  90  and  94  (ON), the electric power of the solar cell electric power accumulator  64  is supplied to the pump motor  202  via the solar cell power supply line  80  and the pump motor power supply line  86 , so that the pump motor  202  operates to drive the pump  201 . As a result, cooling water is supplied to the electrically driven part, so that it is possible to cool the electrically driven part. At this point, the second switch  92  is opened (OFF). Therefore, the battery  72  is supplied with no electric power, so that the entire electric power of the solar cell electric power accumulator  64  is used to drive the pump motor  202 . 
     Referring back to  FIG. 12 , if it is determined in step S 14  that the voltage Vs of the solar cell electric power accumulator  64  is lower than or equal to the preset voltage Vlmt (that is, if it is determined that the state of charge (SOC) of the solar cell electric power accumulator  64  is lower than or equal to a predetermined state of charge), the process proceeds to step S 16 . In step S 16 , a second electrically driven part cooling mode is set, and the first and second switches  90  and  92  are closed (ON) and the third switch  94  is opened (OFF) as illustrated in  FIG. 15 . That is, by opening the third switch  94  (OFF), no electric power is supplied from the solar cell electric power accumulator  64 . Furthermore, by closing the first and second switches  90  and  92  (ON), electric power accumulated in the battery  72  is supplied to the pump motor  202  via the battery power supply line  84  and the pump motor power supply line  86 , so that the pump motor  202  operates to drive the pump  201 . As a result, cooling water is supplied to the electrically driven part, so that it is possible to cool the electrically driven part. Thus, when the state of charge of the solar cell electric power accumulator  64  is low, the pump motor  202  may be driven with electric power from the battery  72 . Therefore, it is possible to cool electrically driven parts (an electric motor, a motor generator, a controller, an inverter, a converter, etc.) even when the shovel is in such a location where sunlight is insufficient. Furthermore, there is no need to cool the controller  30 , the inverters  18 A,  18 C, and  20 , the step-up/step-down converter  100 , the capacitor  19 , the turning electric motor  21 , and the motor generator  12 , which are electrically driven parts, with a single cooling circuit as in the case illustrated in  FIG. 10 . The cooling circuit may be formed with a capacitor alone, the cooling circuit may be formed with an inverter alone, or individual cooling circuits may be combined. Furthermore, in place of water, oil may be used as a refrigerant. 
     Next, a description is given of a third embodiment. In the third embodiment, the electric power of the solar cell electric power accumulator  64  is used to warm up the capacitor  19 . 
     In this embodiment, as illustrated in  FIG. 16 , an electric heater  58  is provided around the capacitor  19 . The electric heater  58  is provided with electric power to generate heat, so that it is possible to warm up the capacitor  19 . The capacitor  19 , which is an example of a main electric power accumulating unit, corresponds to an electrically driven part that is subjected to temperature control such as a warmup. Furthermore, the electric heater  58  is an example of a temperature controller that controls the temperature of the electrically driven part. 
     Like in the first and the second embodiment, the solar cell power supply line  80  is extended from the photovoltaic power generator  60 . The solar cell power supply line  80  branches off into a heater power supply line  88  and the battery power supply line  84 . The heater power supply line  88  is connected to the electric heater  58  provided around the capacitor  19 , so that electric power from the solar cell electric power accumulator  64  may be supplied to the electric heater  58  via the solar cell power supply line  80  and the heater power supply line  88  so as to cause the electric heater  58  to generate heat. On the other hand, the battery power supply line  84  is connected to the battery  72  for the constant electrical load  70 , so that electric power from the solar cell electric power accumulator  64  may be supplied to the battery  72  via the solar cell power supply line  80  and the battery power supply line  84  so as to be accumulated in the battery  72 . Furthermore, because the heater power supply line  88  and the battery power supply line  84  are connected at the branch point, electric power may be supplied from the battery  72  to the electric heater  58  via the battery power supply line  84  and the heater power supply line  88  so as to drive the electric heater. 
     Like in the first and the second embodiment, the first switch  90  formed of, for example, an electromagnetic make-and-break switch, is provided in the heater power supply line  88 , so that the first switch  90  controls the feeding of electric power to the electric heater  58 . Furthermore, the second switch  92  formed of, for example, an electromagnetic make-and-break switch, is provided in the battery power supply line  84 , so that the second switch  92  controls the feeding of electric power to the battery  72 . Furthermore, the third switch  94  formed of, for example, an electromagnetic make-and-break switch, is provided in the solar cell power supply line  80 , so that the third switch  94  controls the feeding of electric power from the solar cell electric power accumulator  64  of the photovoltaic power generator  60 . The make and break of the first and second switches  90  and  92  is controlled by signals from the controller  30 . The make and break of the third switch  94  is controlled based on a voltage detection value from the voltmeter  66  provided in the solar cell electric power accumulator  64 . Alternatively, the voltage detection value from the voltmeter  66  may be fed to the controller  30  so as to cause the controller  30  to control the make and break of the third switch  94 . 
     A description is given below of control of the driving of a heater performed in the above-described drive system of the electric heater  58 . 
       FIG. 17  is a flowchart of an electric heater drive control process. First, in step S 21 , the temperature Tc inside the electric power accumulating unit box  50  is detected with the temperature detection sensor  54 . In step S 22 , it is determined whether the temperature Tc inside the electric power accumulating unit box  50  is lower than a predetermined temperature Tlmt 2 . If the temperature Tc inside the electric power accumulating unit box  50  is higher than or equal to the predetermined temperature Tlmt 2  (Tc≧Tlmt 2 ), the process proceeds to step S 23 . 
     In step S 23 , a normal mode is set, and the second and third switches  92  and  94  are closed (ON) and the first switch  90  is opened (OFF) as illustrated in  FIG. 18 . That is, when the temperature Tc inside the electric power accumulator box is high, the temperature of the capacitor  19  is also high, so that there is no need for performing a warmup. Therefore, the first switch  90  is opened (OFF) to break the heater power supply line  88 , thereby preventing the electric heater  58  from operating. 
     At this point, the second and third switches  92  and  94  are closed (ON). As a result, when the solar panels  62  generate electric power, and the electric power is accumulated in the solar cell electric power accumulator  64  so that the voltage of the solar cell electric power accumulator  64  becomes higher than a preset voltage value (that is, the state of charge (SOC) of the solar cell electric power accumulator  64  exceeds a predetermined state of charge), electric power is supplied from the solar cell electric power accumulator  64  to the battery  72  via the solar cell power supply line  80  and the battery power supply line  84 , so that the battery  72  is charged with the electric power. Accordingly, when there is no need to warm up the capacitor  19 , electric power generated by the solar panels  62  is accumulated in the battery  72  without being wasted. 
     Referring back to  FIG. 17 , if the temperature Tc inside the electric power accumulating unit box  50  is higher than the predetermined temperature Tlmt 2  (Tc&gt;Tlmt 2 ) in step S 22 , the process proceeds to step S 24 . In step S 24 , it is determined whether the voltage Vs of the solar cell electric power accumulator  64  is higher than a preset voltage Vlmt. That is, it is determined whether the state of charge (SOC) of the solar cell electric power accumulator  64  is higher than a predetermined state of charge. The voltage Vs of the solar cell electric power accumulator  64  is a voltage detected with the voltmeter  66 . 
     If it is determined in step S 24  that the voltage Vs of the solar cell electric power accumulator  64  is higher than the preset voltage Vlmt (that is, if it is determined that the state of charge (SOC) of the solar cell electric power accumulator  64  is higher than a predetermined state of charge), the process proceeds to step S 25 . In step S 25 , a first electric power accumulator warmup mode is set, and the first and third switches  90  and  94  are closed (ON) and the second switch  92  is opened (OFF) as illustrated in  FIG. 19 . That is, by closing the first and third switches  90  and  94  (ON), the electric power of the solar cell electric power accumulator  64  is supplied to the electric heater  58  via the solar cell power supply line  80  and the heater power supply line  88 . As a result, the electric heater  58  may generate heat, so that it is possible to warm up the capacitor  19 . At this point, the second switch  92  is opened (OFF). Therefore, the battery  72  is supplied with no electric power, so that the entire electric power of the solar cell electric power accumulator  64  is used to drive the electric heater  58 . 
     Referring back to  FIG. 17 , if it is determined in step S 24  that the voltage Vs of the solar cell electric power accumulator  64  is lower than or equal to the preset voltage Vlmt (that is, if it is determined that the state of charge (SOC) of the solar cell electric power accumulator  64  is lower than or equal to a predetermined state of charge), the process proceeds to step S 26 . In step S 26 , a second electric power accumulator warmup mode is set, and the first and second switches  90  and  92  are closed (ON) and the third switch  94  is opened (OFF) as illustrated in  FIG. 20 . That is, by opening the third switch  94  (OFF), no electric power is supplied from the solar cell electric power accumulator  64 . Furthermore, by closing the first and second switches  90  and  92  (ON), electric power accumulated in the battery  72  is supplied to the electric heater  58  via the battery power supply line  84  and the heater power supply line  88 , so that the electric heater  58  generates heat to warm up the capacitor  19 . Thus, when the state of charge of the solar cell electric power accumulator  64  is low, the electric heater  58  may be driven with electric power from the battery  72 . Therefore, it is possible to warm up the capacitor  19  even when the shovel is in such a location where sunlight is insufficient. 
     A description is given above of three embodiments—the first through third embodiments—in sequence, while these embodiments may be suitably combined into a single embodiment. For example, by combining the first embodiment and the third embodiment, it is possible to use electric power from the solar cell electric power accumulator  64  in both cooling and warming up a capacitor. In this case, the capacitor  19  may be provided with the electric heater  58 , and the heater power supply line  88  may be connected to the solar cell power supply line  80  so as to be parallel to the cooling fan power supply line  82  in the first embodiment. Any two of the embodiments may be combined in the same manner. Furthermore, all of the first through third embodiments may also be combined. 
     In the above-described first through third embodiments, the turning mechanism  2  is driven by the turning electric motor  21 , but the turning mechanism  2  may alternatively be driven by a turning hydraulic motor  40  as illustrated in  FIG. 21 . In this case, the turning hydraulic motor  40  is connected to the control valve  17 , and the load drive system including the turning electric motor  21  is removed. 
     Furthermore, the present invention is not limited to hydraulic shovels, and may also be applied to an electric shovel driven by electric motors alone as illustrated in  FIG. 22 . No engine is provided in the electric shovel illustrated in  FIG. 22 , and all working elements are driven by electric motors. Electric power to the individual electric motors is all provided by electric power from the electric power accumulation system  120 . A pump electric motor  400  for driving the main pump  14  as well is driven with electric power supplied from the electric power accumulation system  120  via the inverter  18 A. An external power supply  500  may be connected to the electric power accumulation system  120  via a converter  120 A. Electric power is supplied from the external power supply  500  to the electric power accumulation system  120 , so that an electric power accumulator is charged with the electric power and the electric power is supplied from the electric power accumulator to each of the electric motors. 
     The present application is based on and claims the benefit of priority of Japanese Patent Application No. 2010-279902, filed on Dec. 15, 2010, the entire contents of which are incorporated herein by reference. 
     INDUSTRIAL APPLICABILITY 
     The present invention may be applied to working machines in which electric working elements are driven with electric power from an electric power accumulator. 
     DESCRIPTION OF THE REFERENCE NUMERALS 
     
         
         
           
               1  lower-part traveling body 
               1 A,  1 B hydraulic motor 
               2  turning mechanism 
               3  upper-part turning body 
               4  boom 
               5  arm 
               6  bucket 
               7  boom cylinder 
               7 A hydraulic pipe 
               7 B boom angle sensor 
               8  arm cylinder 
               9  bucket cylinder 
               10  cabin 
               11  engine 
               12  electric motor 
               13  transmission 
               14  main pump 
               15  pilot pump 
               16  high-pressure hydraulic line 
               17  control valve 
               18 ,  18 A,  18 B,  20  inverter 
               19  capacitor 
               21  turning electric motor 
               22  resolver 
               23  mechanical brake 
               24  turning transmission 
               25  pilot line 
               26  operation apparatus 
               26 A,  26 B lever 
               26 C pedal 
               26 D button switch 
               27  hydraulic line 
               28  hydraulic line 
               29  pressure sensor 
               30  controller 
               35  display unit 
               40  turning hydraulic motor 
               50  electric power accumulating unit box 
               52  cooling fan 
               54 ,  56  temperature detection sensor 
               58  electric heater 
               60  photovoltaic power generator 
               62  solar panel 
               64  solar cell electric power accumulator 
               70  constant electrical load 
               72  battery 
               80  solar cell power supply line 
               82  cooling fan power supply line 
               84  battery power supply line 
               86  pump motor power supply line 
               88  heater power supply line 
               90  first switch 
               92  second switch 
               94  third switch 
               100  step-up/step-down converter 
               110  DC bus 
               111  DC bus voltage detecting part 
               112  capacitor voltage detecting part 
               113  capacitor electric current detecting part 
               120  electric power accumulation system 
               120 A converter 
               300  boom regeneration motor (motor generator) 
               310  boom regeneration hydraulic motor 
               200  tank 
               201  pump 
               202  pump motor 
               203  radiator 
               204  water temperature gauge 
               400  pump electric motor 
               500  external power supply