JP6430100B2 - Excavator - Google Patents

Description

  The present invention relates to an excavator having a power storage device including a plurality of power storage cells.

  2. Description of the Related Art Conventionally, there is known an excavator equipped with a power storage device having a plurality of capacitors (cells) connected in series and an equalization circuit provided for each cell (for example, see Patent Document 1).

  The equalization circuit disclosed in Patent Document 1 divides a cell electrode voltage (cell voltage) with a resistor and detects it with a detection element. Then, the equalization circuit determines whether or not the detected cell voltage is equal to or higher than the operating voltage. If the detected cell voltage is equal to or higher than the operating voltage, the equalization circuit turns on the semiconductor switch and leaks current from the corresponding cell via the bypass circuit. Thereby, the voltage of the corresponding cell can be reduced.

  As described above, the equalization circuit disclosed in Patent Document 1 discharges cells whose cell voltage is equal to or higher than the operating voltage individually, and controls the cell voltage of the cells to be the operating voltage to control the cells of a plurality of cells. Equalize the voltage.

JP 2011-30389 A

  The above-described equalization of the cell voltage only consumes the discharge current from the cell by the balance circuit, and can therefore be executed even when the excavator is stopped. That is, when the excavator is keyed off, it is possible to control the cells so that the cell voltage of the cell becomes the predetermined voltage by discharging the cells whose cell voltage is equal to or higher than the predetermined voltage by the equalization circuit. Thereby, the cell voltage is equalized even during the key-off of the shovel so that the cell voltage does not become higher than the predetermined voltage, so that the deterioration of the cell due to the high voltage being maintained even during the key-off can be suppressed.

  Here, when the excavator is keyed off, the cell temperature is maintained in an increased state due to charging / discharging during key-on, and the cell voltage is equalized when the cell temperature is high. When the cell temperature is high, the internal resistance of the cell is small, and the fluctuation range of the cell voltage during charging and discharging is small. Accordingly, the predetermined voltage of the cell voltage set by equalization is normally set to a value close to the upper limit value of the cell voltage.

  However, after a certain amount of time has elapsed after the cell voltage is reduced by the equalization circuit after the key-off, the cell is not charged or discharged during the key-off, so that the cell temperature decreases toward the ambient temperature. At this time, the internal resistance of the cell increases as the cell temperature decreases, and as a result, the fluctuation range of the cell voltage during charge / discharge increases. Therefore, when the excavator is turned on and charge / discharge current flows into the cell with the cell temperature decreasing and the cell voltage fluctuation range increasing, the cell voltage easily exceeds the upper limit (maximum operating voltage). There is a risk that.

  In view of the above problems, an object of the present invention is to provide an excavator in which the cell voltage does not exceed the upper limit even when the key is turned on after the temperature of the cell is lowered at the time of key-off.

In order to achieve the above object, according to one embodiment of the present invention, a lower traveling body, an upper revolving body that is pivotably mounted on the lower traveling body, and a plurality of revolving bodies that are mounted on the upper revolving body. A storage battery having a storage cell, a plurality of discharge circuit portions provided corresponding to the plurality of storage cells, and a control device , wherein the control device is in an operation stop state due to a key-off. When the temperature of the capacitor decreases, the discharge circuit unit is operated to discharge the energy storage cell. The capacitor is configured to be operable by supplying power even when the excavator is stopped. It is determined whether or not the temperature is lower than a predetermined temperature, and when it is determined that the temperature of the battery is lower than the predetermined temperature, whether to discharge the power storage cell or not Lowering the predetermined voltage is a threshold Le voltage, discharging the storage cells of high cell voltage than a predetermined voltage was lowered the shovel is provided.

  According to the embodiment of the present invention, the storage rate of a cell can be reduced until an appropriate cell voltage is reached when the temperature of the cell decreases during key-off. Thus, the cell voltage can be prevented from exceeding the upper limit value even when the key is turned on after the temperature of the cell is lowered at the time of key-off.

It is a side view of an excavator. It is a block diagram which shows the structure of the drive system of the shovel shown in FIG. It is a circuit diagram of a power storage device. It is the schematic which shows the structure of a capacitor. It is a time chart which shows the change of an electrical storage rate (SOC) when a capacitor is charged / discharged in the state where the temperature of a capacitor is high, and the change of a terminal voltage. It is a time chart which shows the change of an electrical storage rate (SOC) when a capacitor is charged / discharged in the state where the temperature of a capacitor is low, and the change of a terminal voltage. It is a time chart which shows the change of an electrical storage rate (SOC) when a capacitor is charged / discharged in the state where the temperature of a capacitor is low, and an electrical storage rate is high, and the change of a terminal voltage. It is a flowchart of an electrical storage rate control process.

  An embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a side view of an excavator according to an embodiment. Although the shovel shown in FIG. 1 is a hybrid excavator, the present invention is not limited to the hybrid excavator, and can be applied to any type of excavator as long as it has a capacitor as a power source for driving an electric load. be able to.

  As shown in FIG. 1, an upper swing body 3 is mounted on a lower traveling body 1 of an excavator via a swing mechanism 2. The upper swing body 3 is provided with a boom 4, an arm 5 and a bucket 6, and a boom cylinder 7, an arm cylinder 8 and a bucket cylinder 9 for hydraulically driving them. The upper swing body 3 is equipped with a cabin 10 and a power source.

  FIG. 2 is a block diagram showing the configuration of the drive system of the shovel shown in FIG. In FIG. 2, the mechanical power system is indicated by a double line, the high-pressure hydraulic line is indicated by a thick solid line, the pilot line is indicated by a broken line, and the electric drive / control system is indicated by a one-dot chain line.

  The engine 11 as the mechanical drive unit and the motor generator 12 as the assist drive unit are both connected to the input shaft of the transmission 13. A main pump 14 and a pilot pump 15 are connected 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 control device that controls the hydraulic system. Connected to the control valve 17 are hydraulic motors 1A (for right) and 1B (for left), a boom cylinder 7, an arm cylinder 8, and a bucket cylinder 9 for the lower traveling body 1 via a high-pressure hydraulic line.

  The motor generator 12 is connected via an inverter 18 to a power storage device 120 including a power storage capacitor or a battery that is a battery. In this embodiment, the power storage device 120 includes a capacitor such as an electric double layer capacitor (EDLC) as a power storage device. In addition, a turning electric motor 21 is connected to the power storage device 120 via an inverter 20. In the above description, a capacitor is shown as an example of a capacitor. However, instead of a capacitor, a rechargeable secondary battery such as a lithium-ion battery (Lithium Ion Battery (LIB)) or other form capable of receiving and transferring power. May be used as a battery.

  A resolver 22, a mechanical brake 23, and a turning speed reducer 24 are connected to the rotating shaft 21 </ b> A of the turning electric motor 21. An operation device 26 is connected to the pilot pump 15 through a pilot line 25.

  A control valve 17 and a pressure sensor 29 as a lever operation detection unit are connected to the operating device 26 via hydraulic lines 27 and 28, respectively. The pressure sensor 29 is connected to a controller 30 that performs electric system drive control.

  The inverter 18 is provided between the motor generator 12 and the power storage device 120 as described above, and controls the operation of the motor generator 12 based on a command from the controller 30. Thus, the inverter 18 can supply necessary electric power from the power storage device 120 to the motor generator 12 when the motor generator 12 performs a power running operation. Further, when the motor generator 12 performs a regenerative operation, the electric power generated by the motor generator 12 can be stored in the battery of the power storage device 120.

  The power storage device 120 is disposed between the inverter 18 and the inverter 20. Thereby, when at least one of the motor generator 12 and the turning electric motor 21 is performing a power running operation, the power storage device 120 can supply electric power necessary for the power running operation. In addition, when at least one of the power storage devices 120 is performing a regenerative operation, the regenerative power generated by the regenerative operation can be stored as electric energy.

  The inverter 20 is provided between the turning electric motor 21 and the power storage device 120 as described above, and controls the operation of the turning electric motor 21 based on a command from the controller 30. Thereby, the inverter 20 can supply necessary electric power from the power storage device 120 to the turning electric motor 21 when the electric turning motor 21 performs a power running operation. Further, when the turning electric motor 21 performs the regenerative operation, the electric power generated by the turning electric motor 21 can be stored in the electric storage device 120.

  The charge / discharge control of the battery of the power storage device 120 is based on the charge state of the battery, the operation state of the motor generator 12 (powering operation or regenerative operation), and the operation state of the turning motor 21 (powering operation or regenerative operation). This is done by the controller 30.

  The controller 30 is a control device that performs drive control of the shovel, and includes a drive control unit 32, an electric turning control unit 40, and a main control unit 60. The controller 30 is composed of an arithmetic processing unit including a CPU (Central Processing Unit) and an internal memory. The drive control unit 32, the electric turning control unit 40, and the main control unit 60 are functional elements that are realized when the CPU of the controller 30 executes a drive control program stored in an internal memory.

  Further, the controller 30 includes an arithmetic processing unit (not shown) that converts a signal input from the pressure sensor 29 into a speed command. Thereby, the operation amount of the lever 26A is converted into a speed command (rad / s) for rotating the turning electric motor 21. This speed command is input to the drive control unit 32, the electric turning control unit 40, and the main control unit 60.

  The drive control unit 32 is a control device for performing operation control of the motor generator 12 (switching between power running operation or regenerative operation) and charge / discharge control of the battery. The drive control unit 32 switches between the power running operation and the regenerative operation of the motor generator 12 according to the load state of the engine 11 and the charge state of the battery. The drive control unit 32 performs charge / discharge control of the battery via the inverter 18 by switching between the power running operation and the regenerative operation of the motor generator 12.

  FIG. 3 is a circuit diagram of the power storage device 120. Power storage device 120 includes a capacitor 19 as a power storage, a buck-boost converter 100, and a DC bus 110. The DC bus 110 controls transmission and reception of electric power among the capacitor 19, the motor generator 12, and the turning electric motor 21. The capacitor 19 is provided with a capacitor voltage detector 112 for detecting a capacitor voltage value and a capacitor current detector 113 for detecting a capacitor current value. The capacitor voltage value and the capacitor current value detected by the capacitor voltage detection unit 112 and the capacitor current detection unit 113 are supplied to the controller 30.

  The step-up / step-down converter 100 performs control to switch between the step-up operation and the step-down operation so that the DC bus voltage value falls within a certain range according to the operating state of the motor generator 12 and the turning electric motor 21. The DC bus 110 is disposed between the inverters 18 and 20 and the step-up / down converter 100, and transfers power between the capacitor 19, the motor generator 12, and the turning electric motor 21.

  Switching control between the step-up / step-down operation of the buck-boost converter 100 is performed by the DC bus voltage value detected by the DC bus voltage detection unit 111, the capacitor voltage value detected by the capacitor voltage detection unit 112, and the capacitor current detection unit 113. This is performed based on the detected capacitor current value.

  In the configuration as described above, the electric power generated by the motor generator 12 as an assist motor is supplied to the DC bus 110 of the power storage device 120 via the inverter 18 and supplied to the capacitor 19 via the step-up / down converter 100. . The regenerative power generated by the regenerative operation of the turning electric motor 21 is supplied to the DC bus 110 of the power storage system 120 via the inverter 20 and supplied to the capacitor 19 via the step-up / down converter 100.

  The buck-boost converter 100 includes a reactor 101, a boosting IGBT (Insulated Gate Bipolar Transistor) 102A, a step-down IGBT 102B, a power supply connection terminal 104 for connecting the capacitor 19, and an output terminal 106 for connecting the inverters 18 and 20. Is provided. The output terminal 106 of the buck-boost converter 100 and the inverters 18 and 20 are connected by a DC bus 110.

  One end of the reactor 101 is connected to an intermediate point between the step-up IGBT 102 </ b> A and the step-down IGBT 102 </ b> B, and the other end is connected to the power supply connection terminal 104. Reactor 101 is provided in order to supply induced electromotive force generated when boosting IGBT 102 </ b> A is turned on / off to DC bus 110.

  The step-up IGBT 102A and the step-down IGBT 102B are semiconductor elements (switching elements) that are composed of bipolar transistors in which MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) are incorporated in a gate portion and can perform high-power high-speed switching. The step-up IGBT 102A and the step-down IGBT 102B are driven by the controller 30 by applying a PWM voltage to the gate terminal. Diodes 102a and 102b, which are rectifier elements, are connected in parallel to the step-up IGBT 102A and the step-down IGBT 102B.

  Capacitor 19 may be a chargeable / dischargeable capacitor so that power can be exchanged with DC bus 110 via buck-boost converter 100. 3 shows a capacitor 19 as a capacitor. Instead of the capacitor 19, a secondary battery that can be charged and discharged, such as a lithium ion battery, or another type of power source that can exchange power is used. Also good.

  The power connection terminal 104 may be a terminal to which the capacitor 19 can be connected, and the output terminal 106 may be a terminal to which the inverters 18 and 20 can be connected. A capacitor voltage detection unit 112 that detects a capacitor voltage is connected between the pair of power supply connection terminals 104. A DC bus voltage detector 111 that detects a DC bus voltage is connected between the pair of output terminals 106.

  The capacitor voltage detector 112 detects the voltage value Vcap of the capacitor 19. The DC bus voltage detection unit 111 detects the voltage value Vdc of the DC bus 110. The smoothing capacitor 107 is a power storage element that is inserted between the positive terminal and the negative terminal of the output terminal 106 and smoothes the DC bus voltage. The smoothing capacitor 107 maintains the voltage of the DC bus 110 at a predetermined voltage.

  The capacitor current detection unit 113 is detection means for detecting the value of the current flowing through the capacitor 19 on the positive terminal (P terminal) side of the capacitor 19. That is, the capacitor current detection unit 113 detects the current value I1 flowing through the positive terminal of the capacitor 19.

  In the buck-boost converter 100, when boosting the DC bus 110, a PWM voltage is applied to the gate terminal of the boosting IGBT 102A, and the boosting IGBT 102A is turned on / off via the diode 102b connected in parallel to the step-down IGBT 102B. The induced electromotive force generated in the reactor 101 when the power is turned off is supplied to the DC bus 110. Thereby, the DC bus 110 is boosted.

  When the DC bus 110 is stepped down, a PWM voltage is applied to the gate terminal of the step-down IGBT 102B, and regenerative power supplied via the inverters 18 and 20 is supplied from the DC bus 110 to the capacitor 19 through the step-down IGBT 102B. Is done. As a result, the electric power stored in the DC bus 110 is charged in the capacitor 19 and the DC bus 110 is stepped down.

  In the present embodiment, a relay 130-1 is provided as a circuit breaker capable of interrupting the power line 114 on the power line 114 that connects the positive terminal of the capacitor 19 to the power connection terminal 104 of the buck-boost converter 100. Relay 130-1 is arranged between connection point 115 of capacitor voltage detection unit 112 to power supply line 114 and the positive terminal of capacitor 19. The relay 130-1 is operated by a signal from the controller 30, and the capacitor 19 can be disconnected from the step-up / down converter 100 by cutting off the power supply line 114 from the capacitor 19.

  In addition, a relay 130-2 is provided as a circuit breaker capable of interrupting the power line 117 on the power line 117 that connects the negative terminal of the capacitor 19 to the power connection terminal 104 of the buck-boost converter 100. The relay 130-2 is disposed between the connection point 118 of the capacitor voltage detection unit 112 to the power supply line 117 and the negative terminal of the capacitor 19. The relay 130-2 is operated by a signal from the controller 30, and the capacitor 19 can be disconnected from the step-up / down converter 100 by cutting off the power supply line 117 from the capacitor 19. Note that the relay 130-1 and the relay 130-2 may be a single relay, and both the power line 114 on the positive terminal side and the power line 117 on the negative terminal side may be simultaneously cut off to disconnect the capacitor 19.

  In practice, a drive unit that generates a PWM signal for driving the boosting IGBT 102A and the step-down IGBT 102B exists between the controller 30 and the step-up IGBT 102A and the step-down IGBT 102B, but is omitted in FIG. Such a driving unit can be realized by either an electronic circuit or an arithmetic processing unit.

  FIG. 4 is a schematic diagram showing the configuration of the capacitor 19. As shown in FIG. 4, the capacitor 19 as a capacitor includes n capacitor cells (hereinafter referred to as “power storage cells” or simply “cells”) 19-1 to 19 -n (n Is an integer greater than or equal to 2) and the power storage management device 140. In FIG. 4, the electric drive system is indicated by a solid line, and the electric control system is indicated by a broken line.

  The power storage management device 140 is a device that manages the power storage of the capacitor 19, and includes discharge circuit units 141-1 to 141-n and a power storage rate control unit 142. In the present embodiment, when the excavator is in the key-off state, the power storage management device 140 is operable by receiving power supplied from the capacitor 19 at regular time intervals. The power storage management device 140 may be supplied with power from an external battery such as a 24V battery. The power storage management device 140 is arranged away from the controller 30 and is connected to the controller 30 via a communication line 145 conforming to a communication standard such as CAN. The power storage management device 140 and the controller 30 may be connected via wireless communication.

  In the present embodiment, all of the n cells 19-1 to 19-n are connected in series, and one power storage management device 140 is provided for all the cells. However, cells connected in series may be one group, a plurality of groups may be connected in series or in parallel, and one power storage management device may be provided for each group. Further, an upper power storage management device that controls a plurality of power storage management devices may be provided.

  In the following description, for convenience, all the cells 19-1 to 19-n may be collectively referred to as a cell 19-n, and each cell may be referred to as 19-n. Discharge circuit units 141-1 to 141-n, and later-described balance switches 146-1 to 146-n, discharge resistors 148-1 to 148-n, which are components of each discharge circuit unit 141-n, voltage measurement The same applies to the units 149-1 to 149-n and the temperature sensors 150-1 to 150 n.

  The discharge circuit unit 141-n is an electric circuit that realizes an SOC reduction function that reduces the storage rate (SOC) of each cell as necessary. The cell storage rate (SOC) is related to the cell voltage, and “reducing the storage rate” is synonymous with “reducing the cell voltage”. In the present embodiment, the discharge circuit unit 141-n performs the SOC reduction function under the control of the power storage rate control unit 142-n. The SOC reduction function is a function of discharging part or all of the cells 19-1 to 19-n in order to reduce the cell voltages of the cells 19-1 to 19-n.

  Specifically, each of the discharge circuit units 141-n is connected to both ends of the corresponding one cell 19-n. For example, as shown in FIG. 4, two electrodes of a specific cell 19-m (m is an integer of 1 to n) are connected to an equalization circuit unit 141-m. The discharge circuit unit 141-m includes a balance switch 146-m and a discharge resistor 148-m. The discharge circuit unit 141-m connects the balance switch 146-m and the discharge resistor 148-m in series between the two electrodes of the cell 19-m and in parallel to the cell 19-m. . Moreover, the discharge circuit unit 141-m includes a voltage measurement unit 149-m that measures the interelectrode voltage of the cell 19-m. Each of the discharge circuit units 141-n may be connected to both ends of one or a plurality of cell groups. The cell group is a group of a plurality of cells 19-n connected in series.

  The balance switch 146-n is a switch that controls the discharge of the cell 19-n, and discharges the cell 19-n when in the ON (conducting) state, and discharges the cell 19-n when in the OFF (cut-off) state. Stop discharging. In the present embodiment, the balance switch 146-n is configured by an FET (field effect transistor), and is switched between an ON (conducting) state and an OFF (blocking) state in accordance with a control signal from the power storage rate control unit 142.

  Each of the cells 19-1 to 19-n is provided with temperature sensors 150-1 to 150-n made of, for example, a thermistor. The temperature sensors 150-1 to 150-n measure the temperatures of the cells 19-1 to 19-n, and supply measurement signals to the storage rate control unit 142. When a thermistor is used as the temperature sensors 150-1 to 150-n, the measurement signal is the resistance value of the thermistor. The storage rate control unit 142 obtains the cell temperature of the corresponding cell from the measurement signals supplied from the temperature sensors 150-1 to 150-n, and uses it for the storage rate control. One temperature sensor may be provided, or a plurality of temperature sensors may be provided. Further, not the cell temperature but the air temperature in the vicinity of the cell may be measured.

  The storage rate control unit 142 is a device that controls the storage rate (SOC) by controlling the voltage Vn of the cell 19-n. In the present embodiment, the storage rate control unit 142 controls each of the discharge circuit units 141-1 to 141-n. Specifically, the power storage rate control unit 142 individually acquires the cell voltage measurement values of the capacitor cells 19-1 to 19-n from the discharge circuit units 141-1 to 141-n. The measured values (detected values) of the cell voltages of the capacitor cells 19-1 to 19-n are individually measured (detected) by the voltage measuring units 149-1 to 149-n. Further, the storage rate control unit 142 outputs a control signal to the balance switches 146-1 to 146-n, and switches the balance switches 146-1 to 146-n to the ON (conductive) / OFF (cutoff) state. Control individually.

  More specifically, the power storage rate control unit 142 is connected to each of the discharge circuit units 141-1 to 141-n via communication conforming to a communication standard such as CAN. And the electrical storage rate control part 142 acquires a cell voltage measured value from each of the discharge circuit parts 141-1 to 141-n with a predetermined period. Then, the power storage rate control unit 142 calculates statistical values such as the maximum value, the minimum value, and the average value of the acquired one set of cell voltage measurement values.

  In addition, the power storage rate control unit 142 acquires a measurement signal indicating the cell temperature from each of the temperature sensors 150-1 to 150-n at a predetermined cycle, and obtains a cell temperature measurement value. Then, the storage rate control unit 142 calculates a statistical value such as the maximum value, the minimum value, and the average value of the acquired one set of cell temperature measurement values.

  Then, based on the measured cell temperature values of the capacitor cells 19-1 to 19-n, the power storage rate control unit 142 selects a balance switch 146 corresponding to a cell that satisfies a predetermined condition among the capacitor cells 19-1 to 19-n. A discharge start signal is output for -n. For example, the storage rate control unit 142 outputs a discharge start signal to the balance switch 146-n corresponding to the capacitor cell 19-n whose cell voltage is higher than the predetermined voltage Vth. The predetermined voltage Vth is a voltage value set in advance, and is a voltage value that is variable depending on temperature as will be described later.

  Upon receiving the discharge start signal, the balance switch 146-n switches to the ON (conducting) state, and discharges the corresponding capacitor cell 19-n.

  Further, when the cell voltage of the capacitor cell 19-n that has started discharging becomes less than the predetermined voltage Vth, the equalization control unit 142 outputs a discharge stop signal to the corresponding balance switch 146-n. Upon receiving the discharge stop signal, the balance switch 146-n switches to the OFF (cut-off) state and stops the discharge of the corresponding capacitor cell 19-n.

  Here, the fluctuation of the terminal voltage of the capacitor 19 when charging and discharging the capacitor 19 in the excavator having the above configuration will be described.

  FIG. 5 is a time chart showing a change in the storage rate (SOC) and a change in the terminal voltage when the capacitor is charged and discharged in a state where the temperature of the capacitor is high. During the operation of the shovel, the capacitor 19 is normally used in a range where the terminal voltage of the capacitor 19 is high by setting the target storage rate (SOC) of the capacitor 19 high. This is to increase the charge / discharge efficiency by using the capacitor 19 in a state where the terminal voltage of the capacitor 19 is high. For example, during operation of the excavator, as shown in FIG. 5B, the target power storage rate is set to, for example, about 70% of the maximum power storage rate. As a result, as shown in FIG. 5B, when the capacitor 19 is discharged, the storage rate (SOC) decreases, and the fluctuation is repeated in which it is charged and then increased again to recover the storage rate.

  When charging / discharging is repeated in this way, the terminal voltage of the capacitor 19 varies on the side close to the maximum voltage in the range between the maximum voltage and the minimum voltage, as shown in FIG. Here, the maximum voltage is the maximum operating voltage determined from the characteristics of the capacitor, and the minimum voltage is the minimum operating voltage determined from the characteristics of the capacitor. The fluctuation range of the terminal voltage of the capacitor 19 at this time is small because the temperature of the capacitor 19 rises and the internal resistance is small. This is because even when the same current flows through the capacitor 19, the internal resistance is smaller and the voltage fluctuation is smaller when the temperature is higher. Therefore, when the temperature of the capacitor 19 is high, the terminal voltage fluctuates on the side close to the maximum voltage, but does not exceed the maximum voltage and is maintained below the maximum voltage.

  On the other hand, when the temperature of the capacitor 19 is low, the internal resistance of the capacitor 19 increases, so that the fluctuation range of the terminal voltage also increases. FIG. 6 is a time chart showing a change in the storage rate (SOC) and a change in the terminal voltage when the capacitor is charged and discharged in a state where the temperature of the capacitor is low.

  When the temperature of the capacitor 19 is low, as shown in FIG. 6A, the fluctuation range of the terminal voltage when the charge / discharge current flows through the capacitor is large. Therefore, the target power storage rate is set low so that the maximum voltage is not exceeded when the terminal voltage rises. In the example shown in FIG. 6, as shown in FIG. 6B, the target storage rate is set to, for example, about 40% of the maximum storage rate, and the fluctuation range of the terminal voltage is reduced overall, so that the terminal voltage The maximum value does not exceed the maximum voltage.

  Here, let us consider a case where the storage rate of the capacitor 19 is high regardless of the temperature of the capacitor 19 being low. FIG. 7 is a time chart showing a change in the storage rate (SOC) and a change in the terminal voltage when the capacitor is charged and discharged in a state where the temperature of the capacitor is low and the storage rate is high.

  Under such conditions, the fluctuation range of the terminal voltage increases, and as shown in FIG. 7A, the maximum value of the terminal voltage when switching from discharging to charging exceeds the maximum voltage. If the terminal voltage exceeds the maximum voltage or has risen to a voltage value close to the maximum voltage for a long time, the deterioration of the capacitor 19 is promoted. Further, the terminal voltage may reach the allowable terminal voltage of the capacitor 19 and cause a problem.

  Such a condition may occur, for example, immediately after the operation of the excavator is stopped in a state where the storage rate of the capacitor 19 is high, the temperature of the capacitor decreases during the operation stop, and then the operation of the excavator is started.

  Therefore, in the present embodiment, the above-described power storage rate control unit 142 monitors the cell temperature of the capacitor cells 19-1 to 19-n while the excavator is stopped, and responds to the temperature decrease when the cell temperature decreases to some extent. To control the cell to discharge. By reducing the storage rate of each capacitor cell 19-1 to 19-n while the excavator is stopped (key-off state), the maximum value of the terminal voltage does not exceed the maximum voltage even immediately after starting the next operation. Thus, the storage rate control process can be achieved.

  Hereinafter, the storage rate control process executed while the excavator is stopped will be described with reference to FIG. FIG. 8 is a flowchart of the storage rate control process performed by the above-described storage rate control unit 142 using the discharge circuit units 141-1 to 141-n.

  The power storage rate control process is performed while the excavator is stopped, that is, when the excavator is keyed off. For example, when the excavator is stopped, it means that the excavator is keyed off after the excavator is turned off and the excavator is keyed off the next day. is there. The storage rate control process is repeatedly performed at predetermined time intervals while the excavator is stopped.

  The start timing of the storage rate control process is managed so that the excavator controller 30 is repeatedly performed at predetermined time intervals based on a time such as a timer. If it is determined that it is time to start the storage rate control process while the excavator is stopped, the power from the capacitor 19 is supplied to the storage management device 140 to start the storage management device 140. As a result, the power storage management device 140 that has been in the sleep state is activated (step S1).

  The storage ratio control unit 142 of the activated power storage management device 140 first checks the cell temperature of each of the capacitor cells 19-1 to 19-n, and determines whether or not the minimum temperature among the cell temperatures is equal to or lower than the high temperature threshold Thi. Is determined (step S2).

  If the minimum cell temperature is not equal to or lower than the high temperature threshold Thi (NO in step S2), the process proceeds to step S17. In step S <b> 17, the power storage management device 140 including the power storage rate control unit 142 is set in the sleep state, and the current power storage rate control process ends.

  On the other hand, when the minimum cell temperature is equal to or lower than the high temperature threshold Thi (YES in step S2), the process proceeds to step S3. In step S3, the power storage rate control unit 142 determines whether or not the minimum temperature among the cell temperatures is equal to or higher than the medium temperature threshold Tmd (step S3).

  When the minimum cell temperature is equal to or higher than the medium temperature threshold Tmd (YES in step S3), the process proceeds to step S4.

  In step S4, the cell voltage of each capacitor cell 19-1 to 19-n is checked, and the storage rate control unit 142 determines whether or not the cell voltage Vn is equal to or higher than the high voltage threshold Vhi (step S4). The determination of the cell voltage Vn is performed for each of the capacitor cells 19-1 to 19-n. Note that the condition for determining whether or not the cell voltage Vn is equal to or higher than the high voltage threshold Vhi is defined as (Condition A).

  If the cell voltage Vn is equal to or higher than the high voltage threshold Vhi (YES in step S4), the process proceeds to step S5. In step S5, the balance switch 146-n corresponding to the cell 19-n in which (Condition A) is satisfied is turned on (ON). As a result, the cell 19-n is discharged through the balance switch 146-n, and the discharge current is consumed by the heat generated by the discharge resistor 148-n.

  Due to the consumption of the cell 19-n, the cell voltage of the cell 19-n decreases, and as a result, the storage rate (SOC) of the cell 19-n also decreases. The storage rate control unit 142 monitors the cell voltage Vn of the cell 19-n, and when the cell voltage Vn becomes less than the high voltage threshold Vhi, the balance switch 146-n is turned off (OFF). As a result, the cell voltage Vn of the cell 19-n is reduced to the high voltage threshold Vhi or lower, and the storage rate of the cell 19-n is also reduced to a value corresponding to the high voltage threshold Vhi.

  Subsequently, the process proceeds to step S7, and the power storage rate control unit 142 determines whether the balance switches 146-1 to 146-n corresponding to all the cells 19-1 to 19-n are in the non-conduction state (OFF). Determine whether or not. If it is determined that the balance switches 146-1 to 146-n corresponding to all the cells 19-1 to 19-n are not non-conductive (OFF) (NO in step S7), the process returns to step S4. The processing is continued for the next cell 19-n. If it is determined that the balance switches 146-1 to 146-n corresponding to all the cells 19-1 to 19-n are in the non-conductive state (OFF) (YES in step S7), the process proceeds to step S17. Then, the power storage management device 140 including the power storage rate control unit 142 is set in the sleep state, and the current power storage rate control process ends.

  Here, although the example in which the controller 30 activates the power storage management device 140 has been described in the present embodiment, an activation management unit for activating the power storage rate control unit 142 may be provided in the power storage management device 140. In this case, when it is determined that the activation management unit provided in the storage rate management device 140 has reached the timing for starting the storage rate control process, the power from the capacitor 19 is supplied to the storage rate management control unit 142, and the storage rate The control unit 142 is activated. Thereby, the power storage rate control part 142 which was in a sleep state can be made into an operation state (step S1). Thereby, the controller 30 can be put into a sleep state simultaneously with the key-off.

  On the other hand, if it is determined in step S4 that the cell voltage Vn is less than the high voltage threshold Vhi (NO in step S4), the process proceeds to step S6. In step S6, the balance switch 146-n corresponding to the cell 19-n in which (Condition A) is not satisfied is set in a non-conductive state (OFF). Subsequently, the process proceeds to step S7, and the power storage rate control unit 142 determines whether the balance switches 146-1 to 146-n corresponding to all the cells 19-1 to 19-n are in the non-conduction state (OFF). Determine whether or not.

  If it is determined that the balance switches 146-1 to 146-n corresponding to all the cells 19-1 to 19-n are not non-conductive (OFF) (NO in step S7), the process returns to step S4. The processing is continued for the next cell 19-n. If it is determined that the balance switches 146-1 to 146-n corresponding to all the cells 19-1 to 19-n are in the non-conductive state (OFF) (YES in step S7), the process proceeds to step S17. Then, the power storage management device 140 including the power storage rate control unit 142 is set in the sleep state, and the current power storage rate control process ends.

  If it is determined in step S3 described above that the minimum cell temperature is less than the medium temperature threshold Tmd (NO in step S3), the process proceeds to step S8. In step S8, the power storage rate control unit 142 determines whether or not the minimum temperature among the cell temperatures is equal to or higher than the low temperature threshold Tlo (step S8).

  If the minimum cell temperature is equal to or higher than the low temperature threshold Tlo (YES in step S8), the process proceeds to step S9. In step S9, the storage rate control unit 142 checks the cell voltage of each of the capacitor cells 19-1 to 19-n, and determines whether or not the cell voltage Vn is equal to or higher than the medium voltage threshold value Vmd (step S9). The determination of the cell voltage Vn is performed for each of the capacitor cells 19-1 to 19-n. Note that the condition for determining whether or not the cell voltage Vn is equal to or higher than the medium voltage threshold Vmd is (Condition B).

  If the cell voltage Vn is equal to or higher than the medium voltage threshold Vmd (YES in step S9), the process proceeds to step S10. In step S10, the balance switch 146-n corresponding to the cell 19-n in which (Condition B) is satisfied is turned on (ON). As a result, the cell 19-n is discharged through the balance switch 146-n, and the discharge current is consumed by the heat generated by the discharge resistor 148-n.

  Due to the consumption of the cell 19-n, the cell voltage of the cell 19-n decreases, and as a result, the storage rate (SOC) of the cell 19-n also decreases. The storage rate control unit 142 monitors the cell voltage Vn of the cell 19-n, and when the cell voltage Vn becomes less than the medium voltage threshold value Vmd, the balance switch 146-n is turned off (OFF). As a result, the cell voltage Vn of the cell 19-n is reduced to the medium voltage threshold value Vmd or less, and the storage rate of the cell 19-n is also reduced to a value corresponding to the medium voltage threshold value Vmd.

  Subsequently, the process proceeds to step S12, and the power storage rate control unit 142 determines whether the balance switches 146-1 to 146-n corresponding to all the cells 19-1 to 19-n are in the non-conduction state (OFF). Determine whether or not. If it is determined that the balance switches 146-1 to 146-n corresponding to all the cells 19-1 to 19-n are not non-conductive (OFF) (NO in step S12), the process returns to step S9. The processing is continued for the next cell 19-n. If it is determined that the balance switches 146-1 to 146-n corresponding to all the cells 19-1 to 19-n are in the non-conductive state (OFF) (YES in step S12), the process proceeds to step S17. Then, the power storage management device 140 including the power storage rate control unit 142 is set in the sleep state, and the current power storage rate control process ends.

  On the other hand, if it is determined in step S9 that the cell voltage Vn is less than the medium voltage threshold Vmd (NO in step S9), the process proceeds to step S11. In step S11, the balance switch 146-n corresponding to the cell 19-n in which (Condition B) is not satisfied is set in a non-conductive state (OFF). Subsequently, the process proceeds to step S12, and the power storage rate control unit 142 determines whether the balance switches 146-1 to 146-n corresponding to all the cells 19-1 to 19-n are in the non-conduction state (OFF). Determine whether or not.

  If it is determined that the balance switches 146-1 to 146-n corresponding to all the cells 19-1 to 19-n are not non-conductive (OFF) (NO in step S12), the process returns to step S9. The processing is continued for the next cell 19-n. If it is determined that the balance switches 146-1 to 146-n corresponding to all the cells 19-1 to 19-n are in the non-conductive state (OFF) (YES in step S12), the process proceeds to step S17. Then, the power storage management device 140 including the power storage rate control unit 142 is set in the sleep state, and the current power storage rate control process ends.

  If it is determined in step S8 described above that the minimum cell temperature is less than the low temperature threshold Tlo (NO in step S8), the process proceeds to step S13. In step S13, the storage rate control unit 142 checks the cell voltages of the capacitor cells 19-1 to 19-n, and determines whether or not the cell voltage Vn is equal to or higher than the low voltage threshold Vlo (step S13). The determination of the cell voltage Vn is performed for each of the capacitor cells 19-1 to 19-n. Note that the condition for determining whether or not the cell voltage Vn is equal to or higher than the low voltage threshold Vlo is defined as (Condition C).

  When the cell voltage Vn is equal to or higher than the low voltage threshold Vlo (YES in step S13), the process proceeds to step S14. In step S14, the balance switch 146-n corresponding to the cell 19-n in which (Condition C) is satisfied is turned on (ON). As a result, the cell 19-n is discharged through the balance switch 146-n, and the discharge current is consumed by the heat generated by the discharge resistor 148-n.

    Due to the consumption of the cell 19-n, the cell voltage of the cell 19-n decreases, and as a result, the storage rate (SOC) of the cell 19-n also decreases. The power storage rate control unit 142 monitors the cell voltage Vn of the cell 19-n, and when the cell voltage Vn becomes less than the low voltage threshold Vlo, the balance switch 146-n is turned off (OFF). As a result, the cell voltage Vn of the cell 19-n is reduced to the low voltage threshold Vlo or less, and the storage rate of the cell 19-n is also reduced to a value corresponding to the low voltage threshold Vlo.

  Subsequently, the process proceeds to step S16, and the power storage rate control unit 142 determines whether the balance switches 146-1 to 146-n corresponding to all the cells 19-1 to 19-n are in the non-conduction state (OFF). Determine whether or not. If it is determined that the balance switches 146-1 to 146-n corresponding to all the cells 19-1 to 19-n are not non-conductive (OFF) (NO in step S16), the process returns to step S13. The processing is continued for the next cell 19-n. If it is determined that the balance switches 146-1 to 146-n corresponding to all the cells 19-1 to 19-n are in the non-conductive state (ON) (YES in step S16), the process proceeds to step S17. Then, the power storage management device 140 including the power storage rate control unit 142 is set in the sleep state, and the current power storage rate control process ends.

  On the other hand, when it is determined in step S13 that the cell voltage Vn is the low voltage threshold Vlo (NO in step S13), the process proceeds to step S15. In step S15, the balance switch 146-n corresponding to the cell 19-n in which (Condition C) is not satisfied is set in a non-conductive state (OFF). Subsequently, the process proceeds to step S16, and the power storage rate control unit 142 determines whether the balance switches 146-1 to 146-n corresponding to all the cells 19-1 to 19-n are in the non-conduction state (OFF). Determine whether or not.

  If it is determined that the balance switches 146-1 to 146-n corresponding to all the cells 19-1 to 19-n are not non-conductive (OFF) (NO in step S16), the process returns to step S13. The processing is continued for the next cell 19-n. If it is determined that the balance switches 146-1 to 146-n corresponding to all the cells 19-1 to 19-n are non-conductive (OFF) (YES in step S16), the process proceeds to step S17. Then, the power storage management device 140 including the power storage rate control unit 142 is set in the sleep state, and the current power storage rate control process ends.

  According to the power storage rate control process described above, the cell voltage can be reduced by discharging the cell of the capacitor and reducing the power storage rate during excavator key-off. The degree of reduction of the power storage rate is determined based on the cell temperature. That is, in the power storage rate control process described above, if the minimum cell temperature exceeds the high temperature threshold Thi, the cell storage rate control is not performed because it is not necessary to reduce the power storage rate because the cell temperature is high. .

  On the other hand, when the minimum temperature of the cell is not more than the high temperature threshold Thi and not less than the medium temperature threshold Tmd, that is, if the temperature is between the high temperature threshold and the medium temperature threshold, the cell voltage is high (above the high voltage threshold Vhi). The cell voltage is reduced by performing a process (discharge process) for reducing the storage rate on the cell. When the cell temperature is a temperature between the high temperature threshold value Thi and the intermediate temperature threshold value Tmd, the cell temperature is low, but the decrease in temperature is not so large, and the storage rate of the cell having a high cell voltage is set to the temperature. The cell voltage is lowered by a reduction corresponding to the decrease in the cell voltage.

  When the minimum temperature of the cell is equal to or lower than the medium temperature threshold Tmd and equal to or higher than the low temperature threshold Tlo, that is, when the temperature is between the medium temperature threshold Tmd and the low temperature threshold Tlo, the cell voltage is high (the medium voltage threshold Vmd). The cell voltage is reduced by performing a process (discharge process) for reducing the power storage rate on the above cells. When the cell temperature is between the middle temperature threshold value Tmd and the low temperature threshold value Tlo, it is assumed that the cell temperature is low, and the power storage rate of the cell having a high cell voltage is reduced in proportion to the decrease in temperature. Therefore, the cell voltage is lowered.

  Further, when the minimum temperature of the cell is lower than the low temperature threshold Tlo, the cell voltage is reduced by performing a process (discharge process) for reducing the storage rate on a cell having a high cell voltage (more than the low voltage threshold Vlo). Reduce. If the cell temperature is lower than the low temperature threshold Tlo, the cell temperature is assumed to be very low, and the cell voltage is lowered to reduce the storage rate of the cell having a high cell voltage in proportion to the temperature drop. Yes.

  In the above processing, the minimum temperature among the measured temperatures of all cells is set as the cell temperature, and the condition for reducing the power storage rate is used. However, an average value of the measured temperatures of all cells may be used. Alternatively, instead of obtaining the cell temperature from the temperature of all the cells, for example, a predetermined cell representing all the cells is determined, and only the temperature of the predetermined cell is measured and used as the cell temperature. it can.

  In the above-described processing, the three-stage temperature thresholds, ie, the high-temperature threshold Thi, the intermediate-temperature threshold Tmd, and the low-temperature threshold Tlo, are set. The storage rate may be controlled with a finer width with respect to the decrease in temperature, or only one stage may be used.

  DESCRIPTION OF SYMBOLS 1 ... Lower traveling body 1A, 1B ... Hydraulic motor 2 ... Turning mechanism 3 ... Upper turning body 4 ... Boom 5 ... Arm 6 ... Bucket 7 ... Boom cylinder 8 ... arm cylinder 9 ... bucket cylinder 10 ... cabin 11 ... engine 12 ... motor generator 13 ... transmission 14 ... main pump 15 ... pilot pump 16 ... High pressure hydraulic line 17 ... Control valve 18, 20 ... Inverter 19 ... Capacitor 19-1 to 19-n ... Capacitor cell 21 ... Rotating motor 22 ... Resolver 23 ... Mechanical Brake 24 ... Swivel transmission 25 ... Pilot line 26 ... Operating device 26A, 26B ... Lever 26C ... Pedal 27 ..Hydraulic line 28 ... Hydraulic line 29 ... Pressure sensor 30 ... Controller 32 ... Drive control unit 40 ... Electric turning control unit 60 ... Main control unit 101 ... Reactor 102A .. Boost IGBT 102B ... Buck IGBT 104 ... Power supply connection terminal 106 ... Output terminal 107 ... Capacitor 110 ... DC bus 111 ... DC bus voltage detector 112 ... Capacitor Voltage detection unit 113 ... Capacitor current detection unit 114, 117 ... Power supply line 120 ... Power storage device 140 ... Power storage management device 141-1 to 141-n ... Discharge circuit unit 142 ... Power storage Rate control unit 146-1 to 146 -n ... balance switch 148-1 to 148 -n ... discharge resistance 149-1 to 149- ... Voltage measuring unit 150-1 to 150-n ... Temperature sensor

Claims (3)

A lower traveling body,
An upper swing body that is rotatably mounted on the lower traveling body;
A storage battery having a plurality of storage cells mounted on the upper swing body;
A plurality of discharge circuit portions provided corresponding to the plurality of power storage cells;
A control device,
In the case where the excavator is in an operation stop state due to key-off, when the temperature of the battery is lowered, the control device operates the discharge circuit unit to discharge the battery cell,
It is configured to be operable by supplying power even when the excavator is stopped, and it is determined whether or not the temperature of the battery is lower than a predetermined temperature during key-off, and the temperature of the battery is lower than the predetermined temperature. If it is determined, a predetermined voltage that is a threshold value of a cell voltage for determining whether or not to discharge the storage cell is lowered, and the storage cell having a cell voltage higher than the decreased predetermined voltage is discharged.
Excavator. The excavator according to claim 1,
A plurality of the predetermined temperatures are set,
The control device discharges the storage cell to a lower voltage as the predetermined temperature is lower.
Excavator. The excavator according to claim 1,
The control device enters a sleep state by a key-off of an excavator, is activated at predetermined time intervals, determines whether or not the temperature of the capacitor has become lower than a predetermined temperature, and the temperature of the capacitor is the predetermined value. If it is determined that the temperature has become lower, the storage cell is discharged;
Excavator.

Images