SHOVEL

Abstract

A shovel includes an electrically driven part subjected to temperature control during operation, a battery that supplies electric power to a constant electrical load that constantly operates apart from the electrically driven part, a first switch, and a second switch. The first switch opens or closes a power supply line between a temperature controller that controls the temperature of the electrically driven part and a photovoltaic power generator based on the temperature detection value of a temperature detector that detects the temperature of the electrically driven part. The second switch opens or closes a power supply line between the temperature controller and the battery based on the temperature detection value of the temperature detector.

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 1A (right) and 1B (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 18A. 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 21A 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 26A, a lever 26B, and a pedal 26C. The lever 26A, the lever 26B, and the pedal 26C 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 18C. 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 7A 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 18C. The motor generator 300 and the inverter 18C constitute a boom regeneration system.

According to this embodiment, a boom angle sensor 7B for detecting the angle of the boom 4 is attached to the support shaft of the boom 4. The boom angle sensor 7B 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 18A, 18C, 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 18A 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 18C, 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 7B 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 S1, a temperature Tc inside the electric power accumulating unit box 50 is detected with the temperature detection sensor 54. In step S2, 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 S3.

In step S3, 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>Tlmt) in step S2, the process proceeds to step S4. In step S4, 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 S4 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 S5. In step S5, 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 S4 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 S6. In step S6, 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 m², the upper surface 3-1 of the counterweight of the upper-part turning body is, for example, 4.4 m², and the area of the upper surface 4-1 of the boom 4 is, for example, 0.8 m². The total of these areas shows that the area to which the solar panels 62 may be attached is 6.9 m². It is said that an area of approximately 7 m² 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 m²), 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 m² 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 m² 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 18A, 18C, 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 18A, 18C, 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 18A, 18C, 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 18A, 18C, and 20, the step-up/step-down converter 100, etc., in parallel. Furthermore, all of the controller 30, the inverters 18A, 18C, 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 S11, 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 18A, 18C 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 S12, 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 S13.

In step S13, 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>Tlmt) in step S12, the process proceeds to step S14. In step S14, 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 S14 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 S15. In step S15, 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 S14 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 S16. In step S16, 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 18A, 18C, 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 S21, the temperature Tc inside the electric power accumulating unit box 50 is detected with the temperature detection sensor 54. In step S22, it is determined whether the temperature Tc inside the electric power accumulating unit box 50 is lower than a predetermined temperature Tlmt2. If the temperature Tc inside the electric power accumulating unit box 50 is higher than or equal to the predetermined temperature Tlmt2 (Tc≧Tlmt2), the process proceeds to step S23.

In step S23, 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 Tlmt2 (Tc>Tlmt2) in step S22, the process proceeds to step S24. In step S24, 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 S24 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 S25. In step S25, 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 S24 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 S26. In step S26, 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 18A. An external power supply 500 may be connected to the electric power accumulation system 120 via a converter 120A. 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
  • 1A, 1B hydraulic motor
  • 2 turning mechanism
  • 3 upper-part turning body
  • 4 boom
  • 5 arm
  • 6 bucket
  • 7 boom cylinder
  • 7A hydraulic pipe
  • 7B 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, 18A, 18B, 20 inverter
  • 19 capacitor
  • 21 turning electric motor
  • 22 resolver
  • 23 mechanical brake
  • 24 turning transmission
  • 25 pilot line
  • 26 operation apparatus
  • 26A, 26B lever
  • 26C pedal
  • 26D 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
  • 120A 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

Claims

1. A shovel, comprising:

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;

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; and

a controller configured to be supplied with a voltage detection value from the voltage detector and the temperature detection value from the temperature detector and to transmit signals to the first switch and the second switch.

2. The shovel as claimed in claim 1, further comprising:

a third switch configured to open or close a power supply line between the photovoltaic power generator and the first and second switches based on the voltage detection value of the voltage detector.

3. The shovel as claimed in claim 2, wherein the first switch is closed, the second switch is open, and the third switch is closed when the temperature detection value of the temperature detector is higher than a predetermined temperature value and the voltage detection value of the voltage detector is higher than a predetermined voltage value.

4. The shovel as claimed in claim 2, wherein the first switch is closed, the second switch is closed, and the third switch is open when the temperature detection value of the temperature detector is higher than a predetermined temperature value and the voltage detection value of the voltage detector is lower than or equal to a predetermined voltage value.

5. The shovel as claimed in claim 2, wherein the first switch is open, the second switch is closed, and the third switch is closed when the temperature detection value of the temperature detector is lower than or equal to a predetermined temperature value and the voltage detection value of the voltage detector is higher than a predetermined voltage value.

6. The shovel as claimed in claim 2, wherein the first switch is closed, the second switch is open, and the third switch is closed when the temperature detection value of the temperature detector is lower than a predetermined temperature value and the voltage detection value of the voltage detector is higher than a predetermined voltage value.

7. The shovel as claimed in claim 2, wherein the first switch is closed, the second switch is closed, and the third switch is open when the temperature detection value of the temperature detector is lower than a predetermined temperature value and the voltage detection value of the voltage detector is lower than or equal to a predetermined voltage value.

8. The shovel as claimed in claim 2, wherein the first switch is open, the second switch is closed, and the third switch is closed when the temperature detection value of the temperature detector is higher than or equal to a predetermined temperature value and the voltage detection value of the voltage detector is higher than a predetermined voltage value.

9. The shovel as claimed in claim 1, wherein the electrically driven part is a main electric power accumulating unit.

10. The shovel as claimed in claim 1, wherein the electrically driven part includes at least one of an inverter, a converter, and a controller.