Electric construction machinery

Abstract

Provided is an electric construction machine that can suppress deterioration of a power storage device due to use in a low-charged state while suppressing a reduction in the time during which work can be performed. [Solution] An electric construction machine 1 includes an electric motor 31 as a drive source, a power storage device 32 as a power source for the electric motor 31, an inverter 33 that adjusts the power supplied from the power storage device 32 to the electric motor 31, a state detection device 35 that detects the internal state of the power storage device 32, and a control device 40 that sets a limit value for the discharge current of the power storage device 32 and limits the output power of the inverter 33 based on the set limit value. If the state of charge (SOC) of the power storage device 32 acquired from the state detection device 35 is equal to or greater than a predetermined value, the control device 40 sets the limit value according to the state of charge, and if the state of charge acquired from the state detection device 35 is less than the predetermined value, sets the limit value according to the voltage of the power storage device 32 acquired from the state detection device 35.

Description

[Technical Field]

[0001] The present invention relates to an electric construction machine, and more particularly to an electric construction machine in which an electric motor serving as a drive source for operating the construction machine is driven by electric power supplied from an electricity storage device. [Background technology]

[0002] For construction machinery such as hydraulic excavators and wheel loaders, electric models that use electric motors instead of engines as the drive source for driving hydraulic pumps have been developed with environmental considerations in mind. Some electric construction machinery uses a power storage device as the power source for driving the electric motor.

[0003] When using a power storage device, one indicator of the state of charge is the State of Charge (SOC), which indicates the amount of power stored in the power storage device as a percentage. The SOC is expressed as a range from 0% to 100%, with a fully charged state being 100% and a completely discharged state being 0%. The SOC is generally estimated from various information such as the voltage and temperature of the power storage device based on logic designed by the battery manufacturer, and is subject to estimation error. For this reason, even if the estimated SOC value is a few percent, the actual state of charge (true SOC value) may be 0%.

[0004] It is known that when a power storage device, particularly a lithium-ion battery, continues to discharge while its actual state of charge (true SOC value) is extremely low, and the actual state of charge (true SOC value) approaches a completely discharged state where the actual state of charge (true SOC value) is 0%, deterioration is significantly accelerated and the risk of abnormalities increases. Therefore, taking into consideration SOC estimation errors, power storage devices are generally used only when the estimated SOC value, which is the calculation result, is within a predetermined range that is set narrower than 0 to 100%, so that the actual state of charge (true SOC value) does not reach 0%.

[0005] Furthermore, lithium-ion batteries are at risk of accelerated deterioration and malfunctions even if the battery voltage drops below a certain value (open circuit voltage equivalent to 0% SOC) due to a large current flow. To avoid these risks, the battery must be used with an upper limit on the discharge current.

[0006] Regarding the control of a power storage device, a technology for setting an upper limit of charge / discharge power is disclosed in Patent Document 1. The power storage device charge / discharge control device for construction machinery described in Patent Document 1 sets an upper limit of charge / discharge power of the power storage device based on the lowest temperature (lowest module temperature) and state of charge (SOC) or the highest temperature (highest module temperature) and state of charge (SOC) of multiple power storage modules that make up the power storage device, in order to prevent overvoltage or overheating of the power storage device during charging / discharging. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-35841 Summary of the Invention [Problem to be solved by the invention]

[0008] As described above, to avoid using a power storage device when its actual state of charge (true SOC value) is 0%, the range of its SOC (estimated value) is generally limited. The SOC usage range (lower and upper limits) is set taking into account SOC estimation errors. If the SOC usage range is limited to 10 to 90%, for example, discharging of the power storage device will be stopped if the SOC falls below 10%. However, because electric construction machinery consumes a lot of power and there is limited space for installing batteries, it is difficult to install a power storage device with a capacity that corresponds to the construction machinery's daily work volume. Therefore, if the lower limit of the SOC usage range is raised and the usage range is narrowed to ensure that the actual state of charge (true SOC value) is maintained above 0%, the amount of time the construction machinery can work on a single charge will be limited and shortened, which is undesirable from the perspective of work efficiency. In other words, there is a demand for the SOC usage range to be as wide as possible so that electric construction machinery can operate for long periods of time.

[0009] The present invention has been made based on the above-mentioned matters, and its object is to provide an electric construction machine that can suppress deterioration of the storage device due to use in a low-charge state while suppressing a reduction in the amount of time that work can be performed. [Means for solving the problem]

[0010] The present application includes multiple means for solving the above-mentioned problems. One example of the means for solving the problems of the present application is an electric construction machine including an electric motor as a drive source, a power storage device as a power source for the electric motor, an inverter that adjusts the power supplied from the power storage device to the electric motor, a state detection device that detects an internal state of the power storage device including the charge state and voltage of the power storage device, and a control device that sets a limit value for a discharge current of the power storage device and limits the output power of the inverter based on the set limit value, wherein the control device is configured to set the limit value in accordance with the charge state of the power storage device acquired from the state detection device when the SOC of the power storage device acquired from the state detection device is equal to or greater than a predetermined value, and to set the limit value in accordance with the voltage of the power storage device acquired from the state detection device when the charge state acquired from the state detection device is less than the predetermined value. [Effects of the Invention]

[0011] According to one example of the solution of the present application, when the state of charge of the power storage device is less than a predetermined value (when the state of charge is low), the limit value for the discharge current of the power storage device is set according to the actual voltage value (detected value) of the power storage device rather than the estimated state of charge, making it possible to prevent the voltage of the power storage device from falling below a predetermined voltage value (a voltage value defined based on an open circuit voltage equivalent to a 0% state of charge). Furthermore, since it is possible to prevent the voltage of the power storage device from falling below a predetermined voltage value even when an electric construction machine is operated when the power storage device is in a low state of charge, there is no need to narrow the normal operating range of the state of charge. In other words, it is possible to prevent a reduction in the workable time of the electric construction machine while also suppressing deterioration of the power storage device due to use in a low state of charge. Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is an external view showing an electric shovel as an electric construction machine according to an embodiment of the present invention. [Figure 2] 2 is a block diagram showing the main configuration of a drive system provided in the electric construction machine according to the embodiment shown in FIG. 1. FIG. [Figure 3] FIG. 3 is a diagram showing an example of a first map (first characteristic information that defines a current limit value in response to changes in the SOC of the power storage device) used by the vehicle controller of the electric construction machine according to the embodiment shown in FIG. 2 in calculating a current limit value (when the temperature of the power storage device is divided into three temperature ranges: a high temperature range, a normal temperature range, and a low temperature range). [Figure 4A] FIG. 10 is a diagram showing an example of a second map (second characteristic information that defines the current limit value in response to changes in the potential of the power storage device) used by the vehicle controller of the electric construction machine according to the embodiment shown in FIG. 2 to calculate the current limit value (when the temperature of the power storage device is divided into three temperature ranges: a high temperature range, a normal temperature range, and a low temperature range), showing a map corresponding to the high temperature range. [Figure 4B] FIG. 10 is a diagram showing a map corresponding to the normal temperature range in an example of a second map (when the temperature of the power storage device is divided into three temperature ranges: a high temperature range, a normal temperature range, and a low temperature range). [Figure 4C] FIG. 10 is a diagram showing a map corresponding to a low temperature range in an example of a second map (when the temperature of the power storage device is divided into three temperature ranges: a high temperature range, a normal temperature range, and a low temperature range). [Figure 5] 4A to 4D are state transition diagrams showing conditions (timing) for switching maps (FIGS. 3 and 4A to 4D) used by the vehicle controller of the electric construction machine according to the embodiment shown in FIG. 2 to limit the discharge current of the power storage device. [Figure 6] 3 is a flowchart showing an example of a processing procedure for limiting control of the discharge current of the power storage device in the vehicle body controller of the electric construction machine according to the embodiment shown in FIG. 2. [Figure 7] 10 is a time chart showing the relationship between the state of the power storage device in an electric construction machine according to one embodiment and the control of inverter output limitation (limitation of discharge current of the power storage device) by a vehicle controller. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of an electric construction machine of the present invention will be described with reference to the drawings. In this embodiment, an electric shovel will be described as an example of an electric construction machine. Note that the front, rear, left, and right directions described in this specification refer to directions as seen from the perspective of an operator riding on the electric construction machine.

[0014] [One embodiment] First, the configuration of an electric shovel as an electric construction machine according to one embodiment will be described with reference to Fig. 1. Fig. 1 is an external view showing an electric shovel as an electric construction machine according to one embodiment.

[0015] 1, an electric shovel 1 as an electrically powered construction machine is roughly composed of a self-propelled running body 2, a rotating body 3 rotatably mounted on the running body 2, and a working device 4 rotatably provided in the front part of the rotating body 3. The rotating body 3 is configured to rotate relative to the running body 2 by a rotating device including a swing hydraulic motor 5 which is a hydraulic actuator.

[0016] The traveling body 2 is provided with crawler-type traveling devices 6 on both the left and right sides (only one is shown). Each traveling device 6 is configured to be driven by a traveling hydraulic motor 7, which is a hydraulic actuator.

[0017] The rotating body 3 is configured to include a rotating frame 9 as a support structure rotatably mounted on the traveling body 2, a cab 10 installed on the left front side of the rotating frame 9, a counterweight 11 installed at the rear end of the rotating frame 9, and a machine room 12 provided between the cab 10 and the counterweight 11. The cab 10 is where an operator who operates the electric shovel 1 rides. The cab 10 is equipped with a driver's seat where the operator sits and operating devices (neither of which are shown) for operating the electric shovel 1. The counterweight 11 is used to achieve a weight balance with the working device 4. The machine room 12 houses hydraulic equipment 21, 22 and electric equipment 31, 32, 33 (both of which are shown in FIG. 2) to operate the electric shovel 1, which will be described later.

[0018] The working device 4 is an articulated device configured by connecting multiple link members for rotatably moving in the vertical direction for performing excavation work and the like. The multiple link members include, for example, a boom 14, an arm 15, and a bucket 16 as a working implement. The base end of the boom 14 is rotatably connected to the front of the revolving unit 3. The base end of the arm 15 is rotatably connected to the tip of the boom 14. The base end of the bucket 16 is rotatably connected to the tip of the arm 15. The boom 14, arm 15, and bucket 16 are driven by hydraulic actuators: a boom cylinder 17, an arm cylinder 18, and a bucket cylinder 19, respectively.

[0019] Next, the schematic configuration of a drive system provided in an electric construction machine according to one embodiment will be described with reference to Fig. 2. Fig. 2 is a block diagram showing the main configuration of the drive system provided in the electric construction machine according to one embodiment shown in Fig. 1.

[0020] In FIG. 2, the electric excavator 1 includes a hydraulic system 20 and an electric system 30 as a drive system for driving the traveling body 2, the revolving body 3, and the working device 4 (all of which are shown in FIG. 1).

[0021] The hydraulic system 20 is configured to include multiple hydraulic actuators driven by pressurized oil, a hydraulic pump 21 that supplies pressurized oil to the multiple hydraulic actuators, and a control valve unit 22 that controls the flow of pressurized oil supplied from the hydraulic pump 21 to the multiple hydraulic actuators. The multiple hydraulic actuators of the hydraulic system 20 include the swing hydraulic motor 5, traveling hydraulic motor 7, boom cylinder 17, arm cylinder 18, and bucket cylinder 19 (all of which are shown in FIG. 1 ). The swing hydraulic motor 5 is driven to cause the swing body 3 to perform a swing operation. The traveling hydraulic motor 7 is driven to cause the traveling device 6 to perform a traveling operation. The combined drive of the boom cylinder 17, arm cylinder 18, and bucket cylinder 19 causes the working device 4 to perform an excavation operation, etc. The control valve unit 22 distributes pressurized oil discharged from the hydraulic pump 21 to the multiple hydraulic actuators 5, 7, 17, 18, and 19, and is an assembly of control valves corresponding to the respective hydraulic actuators 5, 7, 17, 18, and 19. Each control valve of the control valve unit 22 controls the flow of pressure oil supplied from the hydraulic pump 21 to the corresponding hydraulic actuators 5, 7, 17, 18, and 19.

[0022] The electric system 30 uses electric power to drive the hydraulic pump 21 of the hydraulic system 20. Specifically, the electric system 30 includes an electric motor 31 mechanically connected to the hydraulic pump 21, an electricity storage device 32 as a power source that supplies electric power to the electric motor 31, and an inverter 33 that adjusts the power supplied from the electricity storage device 32 to the electric motor 31.

[0023] The electric motor 31 is a prime mover that drives the hydraulic pump 21, and functions as a drive source that enables the operation of the electric shovel 1. The electric motor 31 is configured, for example, such that the inverter 33 is separate from the electric motor 31, but it is also possible for the inverter 33 to be integrated into the electric motor 31.

[0024] The power storage device 32 is a device that discharges stored power to the electric motor 31 via the inverter 33, and is, for example, a secondary battery such as a lithium-ion battery. The power storage device 32 is provided with a voltage sensor 32c that detects the voltage of the power storage device 32, a current sensor 32d that detects the current of the power storage device 32, a temperature sensor 32e that detects the temperature of the power storage device 32, and the like.

[0025] The power storage device 32 is also provided with a power storage device controller 35 that monitors the internal state of the power storage device 32 and detects abnormalities in the power storage device 32. The power storage device controller 35 monitors the state and detects abnormalities in the power storage device 32 by collecting sensor information detected by multiple sensors 32c, 32d, and 32e. The internal state of the power storage device 32 is, for example, the state of charge, voltage, current, and temperature. The state of charge is, for example, State of Charge (SOC), which indicates the amount of power charged in the power storage device 32 as a ratio to its rated capacity (fully charged capacity). The SOC is expressed as a range from 0% to 100%, with 100% representing a fully charged state, 50% representing half the rated capacity, and 0% representing a completely discharged state. The SOC cannot be directly measured and is estimated by the power storage device controller 35 based on sensor information detected by the sensors 32c, 32d, and 32e provided in the power storage device 32. The power storage device controller 35 transmits information such as the internal state of the power storage device 32 and the presence or absence of an abnormality to the vehicle body controller 40, which will be described later. For example, the power storage device controller 35 transmits an SOC signal Ss corresponding to the estimated SOC, a voltage signal Sv corresponding to the voltage value detected by the voltage sensor 32c, and a temperature signal St corresponding to the temperature detected by the temperature sensor 32e to the vehicle body controller 40. The power storage device controller 35 according to this embodiment functions as a state detection device that detects the internal state of the power storage device 32.

[0026] The inverter 33 converts the DC power output from the power storage device 32 into desired AC power so that the electric motor 31 can be driven in accordance with a command from the vehicle body controller 40. That is, the inverter 33 controls the output voltage and output current to the electric motor 31 so that the rotation speed or torque of the electric motor 31 corresponds to a command from the vehicle body controller 40. The inverter 33 according to this embodiment is configured to limit the output power supplied to the electric motor 31 in accordance with an output limit signal Cl from the vehicle body controller 40, which will be described later.

[0027] The vehicle body controller 40 controls the operation of the electric shovel 1. The vehicle body controller 40 is configured to control the drive of the multiple hydraulic actuators 5, 7, 17, 18, and 19 by controlling the control valve unit 22 of the hydraulic system 20 and also controlling the output (rotation speed and torque) of the electric motor 31 via the inverter 33.

[0028] The vehicle body controller 40 according to this embodiment acquires various signals Ss, Sv, and St (status information of the power storage device 32) transmitted from the power storage device controller 35, and limits the discharge current of the power storage device 32 based on the acquired status information (various signals Ss, Sv, and St) of the power storage device 32. However, the vehicle body controller 40 is configured to indirectly limit the discharge current of the power storage device 32 by performing limit control on the output (rotation speed and torque) of the electric motor 31 via the inverter 33.

[0029] In summary, when the SOC (SOC signal Ss) of the power storage device 32 acquired from the power storage device controller 35 is equal to or greater than a predetermined value, the vehicle body controller 40 sets a limit value for the discharge current of the power storage device 32 in accordance with the SOC, and limits the output power of the inverter 33 to the electric motor 31 based on the set limit value for the discharge current. Also, when the SOC (SOC signal Ss) acquired from the power storage device controller 35 is below the above-mentioned predetermined value, the vehicle body controller 40 sets a limit value for the discharge current of the power storage device 32 in accordance with the voltage (voltage signal Sv) of the power storage device 32 acquired from the power storage device controller 35, and limits the output power of the inverter 33 to the electric motor 31 based on the set limit value for the discharge current.

[0030] The predetermined value may be, for example, the lower limit of the SOC usage range recommended in advance by the manufacturer of the power storage device 32. The predetermined value may also be set taking into account an estimation error of the SOC of the power storage device 32. In this case, the predetermined value may be set to, for example, a value obtained by adding the SOC estimation error to 0% SOC. The SOC estimation error may be a value provided by the manufacturer of the power storage device 32 or a value experimentally measured in advance. The predetermined value may also be set based on both the lower limit of the SOC usage range recommended for the power storage device 32 and the SOC estimation error.

[0031] The vehicle body controller 40 includes, as its hardware configuration, a storage device 41 including RAM, ROM, etc., and a processing device 42 including a CPU, MPU, etc. The storage device 41 stores in advance programs and various information (see, for example, FIGS. 3 and 4 described below) required for limiting and controlling the discharge current of the power storage device 32. The processing device 42 reads the programs and various information from the storage device 41 as appropriate, receives status information (various signals Ss, Sv, St) of the power storage device 32 from the power storage device controller 35, and executes processing in accordance with the programs to output an output limit signal Cl to the inverter 33, instructing the inverter 33 to limit the output power of the inverter 33.

[0032] Next, a method for calculating a limit value for the discharge current of the power storage device in the vehicle body controller of the electric construction machine according to one embodiment will be described with reference to Fig. 3 and Figs. 4A to 4C. Fig. 3 is a diagram showing an example of a first map (when the temperature of the power storage device is divided into three temperature ranges: high temperature range, normal temperature range, and low temperature range) used by the vehicle body controller of the electric construction machine according to one embodiment shown in Fig. 2 to calculate the current limit value. Figs. 4A to 4C are diagrams showing an example of a second map (when the temperature of the power storage device is divided into three temperature ranges: high temperature range, normal temperature range, and low temperature range) used by the vehicle body controller of the electric construction machine according to one embodiment shown in Fig. 2 to calculate the current limit value.

[0033] When the SOC (SOC signal Ss) of the power storage device 32 acquired from the power storage device controller 35 is equal to or greater than the predetermined value, the vehicle body controller 40 calculates a limit value for the discharge current of the power storage device 32 using first characteristic information that defines a limit value (current limit value) for the discharge current of the power storage device in response to changes in the SOC of the power storage device. The first characteristic information is pre-stored in, for example, the storage device 41. The vehicle body controller 40 refers to the first characteristic information and calculates the limit value for the discharge current of the power storage device 32 based on the SOC acquired from the power storage device controller 35.

[0034] On the other hand, when the SOC acquired from the power storage device controller 35 is lower than the predetermined value, the limit value of the discharge current of the power storage device 32 is calculated using second characteristic information that defines the limit value (current limit value) of the discharge current of the power storage device in response to changes in the voltage of the power storage device. The second characteristic information is pre-stored in, for example, the storage device 41. The vehicle body controller 40 refers to the second characteristic information and calculates the limit value of the discharge current of the power storage device 32 based on the voltage (voltage signal Sv) of the power storage device 32 acquired from the power storage device controller 35.

[0035] Specifically, when the SOC acquired from the power storage device controller 35 is equal to or greater than the predetermined value, the vehicle body controller 40 calculates a limit value for the discharge current of the power storage device 32, for example, using the first map shown in FIG. 3 as the first characteristic information. In FIG. 3, the horizontal axis B represents the SOC of the power storage device, and the vertical axis Is represents the current limit value of the power storage device. The first map shown in FIG. 3 is set, for example, so that the current limit value Is for the power storage device relative to the SOC of the power storage device varies depending on the temperature of the power storage device. In detail, the first map shown in FIG. 3 divides the temperature of the power storage device into three temperature ranges: a high temperature range, a normal temperature range, and a low temperature range, and has maps with different characteristics corresponding to each temperature range. The characteristic diagram shown by the solid line is the map corresponding to the high temperature range, the characteristic diagram shown by the dashed line is the map corresponding to the normal temperature range, and the characteristic diagram shown by the dashed line is the map corresponding to the low temperature range. When using the first map shown in Figure 3, which has maps corresponding to three temperature ranges, the vehicle body controller 40 is configured to select the map for the corresponding temperature range from among the three temperature ranges depending on the temperature (temperature signal St) of the storage device 32 obtained from the storage device controller 35.

[0036] In the first map shown in Fig. 3, the map of the high temperature range indicated by the solid line shows that the SOC is max1 or SOC min1 The current limit value Is is set to 0 when the SOC is less than SOC min1 Larger than SOC max1 SOC from a set value smaller than max1 For the range up to, the current limit value Is is constant high SOC is defined in min1 From the range to the above setting, the current limit value Is increases linearly until Is high In other words, the first map, which corresponds to the high temperature range, specifies the range of SOC usage as SOC min1 From SOC max1 is limited to the range.

[0037] SOC min1 and SOC max1are, for example, the lower and upper limits of the range of SOC recommended by the manufacturer when the temperature of the power storage device 32 is in the high temperature range. min1 It is also possible to set the first map taking into consideration at least one of the lower limit of the SOC usage range recommended by the manufacturer when the temperature of the power storage device 32 is in the high temperature range and the estimation error of the SOC acquired from the power storage device controller 35. Note that it is possible to use a map provided by the manufacturer of the power storage device 32 as the first map corresponding to the high temperature range.

[0038] In the first map, which is shown by the dashed line in the normal temperature range, the SOC is max2 or SOC min2 The current limit value Is is set to 0 when the SOC is less than SOC min2 Larger than SOC max2 SOC from a set value smaller than max2 For the range up to, the current limit value Is is constant med SOC is defined in min2 From the range to the above setting, the current limit value Is increases linearly until Is med In other words, the first map, which corresponds to the normal temperature range, specifies the range of SOC usage as SOC min2 From SOC max2 is limited to the range.

[0039] SOC min2 and SOC max2 are, for example, the lower and upper limits of the SOC range recommended by the manufacturer when the temperature of the power storage device 32 is in the normal temperature range. min2 It is also possible to set the first map taking into consideration at least one of the lower limit of the SOC usage range recommended by the manufacturer when the temperature of the power storage device 32 is in the normal temperature range and the estimation error of the SOC acquired from the power storage device controller 35. Note that it is possible to use a map provided by the manufacturer of the power storage device 32 as the first map corresponding to the normal temperature range.

[0040] In the first map, the low temperature range indicated by the dashed line, the SOC ismax3 or SOC min3 The current limit value Is is set to 0 when the SOC is less than SOC min3 Larger than SOC max3 SOC from a set value smaller than max3 For the range up to, the current limit value Is is constant low SOC is defined in min3 From the range to the above setting, the current limit value Is increases linearly until Is low In other words, the first map, which corresponds to the low temperature range, specifies the range of SOC usage as SOC min3 From SOC max3 is limited to the range.

[0041] SOC min3 and SOC max3 are, for example, the lower and upper limits of the SOC range recommended by the manufacturer when the temperature of the power storage device 32 is in the low temperature range. min3 It is also possible to set the first map taking into consideration at least one of the lower limit of the SOC usage range recommended by the manufacturer when the temperature of the power storage device 32 is in the low temperature range and the estimation error of the SOC acquired from the power storage device controller 35. Note that it is possible to use a map provided by the manufacturer of the power storage device 32 as the first map corresponding to the low temperature range.

[0042] In the first map, the current limit value I (constant value Is med (including) is the current limit value Is in the high temperature range (constant value Is high It is specified that the current limit value Is in the low temperature range (constant value Is low (including) is the current limit value I (constant value Is med This is because the internal resistance of the power storage device 32 increases as the temperature of the power storage device 32 decreases, and therefore the voltage of the power storage device 32 is prevented from falling below a predetermined value (open circuit voltage equivalent to an SOC of 0%).

[0043] In addition, in the first map, the lower limit of the SOC range in the normal temperature range is SOC min2 is the lower limit of the SOC range in high temperature ranges. min1 It is set to be larger than the lower limit of the SOC range in the low temperature range. min3 is the lower limit of the SOC range in normal temperature range. min2 This is because the lower the temperature of the power storage device 32, the higher the risk that the voltage of the power storage device 32 will fall below a predetermined value (open circuit voltage equivalent to 0% SOC), and therefore the intended use range of the SOC is narrowly limited to a safe range.

[0044] The predetermined value, which is an index for switching between the first map and the second map used by the vehicle controller 40 to calculate the current limit value, corresponds to the lower limit of the SOC range defined in the first map. That is, when the temperature of the power storage device 32 is in the high temperature range, the predetermined value is set to the lower limit of the SOC range. min1 When the temperature of the power storage device 32 is in the normal temperature range, the SOC min2 When the temperature of the power storage device 32 is in the low temperature range, the SOC min3 is equivalent to

[0045] The vehicle body controller 40 determines whether the SOC acquired from the power storage device controller 35 is equal to or lower than the lower limit (SOC min1 , SOC min2 , or SOC min3 ), the vehicle body controller 40 calculates a limit value for the discharge current of the power storage device 32 using a first map of a temperature range corresponding to the temperature of the power storage device 32. The vehicle body controller 40 refers to the first map to calculate a limit value for the output power of the inverter 33 based on the current limit value Is set according to the SOC acquired from the power storage device controller 35, and outputs an output limit signal Cl according to the calculation result to the inverter 33.

[0046] Furthermore, when the SOC acquired from the power storage device controller 35 falls below the predetermined value, the vehicle body controller 40 calculates a limit value for the discharge current of the power storage device 32 using, for example, the second map shown in any one of Figures 4A to 4C as the second characteristic information. In Figures 4A to 4C, the horizontal axis V represents the voltage of the power storage device, and the vertical axis Iv high , IV med , IV low indicates the current limit value of the power storage device.

[0047] Similar to the first map shown in FIG. 3, the second maps shown in FIGS. 4A to 4C are set so that the current limit value for the power storage device with respect to the voltage of the power storage device varies depending on the temperature of the power storage device. Specifically, the second maps shown in FIGS. 4A to 4C divide the temperature of the power storage device into three temperature ranges: a high temperature range, a normal temperature range, and a low temperature range, and each map has a different characteristic corresponding to each temperature range. The characteristic diagram shown by the solid line in FIG. 4A is the map corresponding to the high temperature range in the second map, the characteristic diagram shown by the dashed line in FIG. 4B is the map corresponding to the normal temperature range in the second map, and the characteristic diagram shown by the dashed line in FIG. 4C is the map corresponding to the low temperature range in the second map. When the second maps shown in FIGS. 4A to 4C, which have maps corresponding to three temperature ranges, are used, vehicle body controller 40 is configured to select a map corresponding to a corresponding temperature range from among the three temperature ranges depending on the temperature of power storage device 32 (temperature signal St) acquired from power storage device controller 35.

[0048] In the second map (solid line) corresponding to the high temperature range shown in FIG. 4A, the open circuit voltage X0 corresponding to SOC 0% to the open circuit voltage X1 corresponding to SOC 100% 100 The current limit value Iv high is specified. Voltage X min1 and voltage X max1 are SOC min1 Equivalent open circuit voltage and SOC max1 A significant open circuit voltage is shown.

[0049] The voltage of the storage device changes from voltage X0 to voltage X min1 For the range up to, the current limit value Iv highis specified to increase sharply from 0. min1 to voltage X max1 For the range up to, the current limit value Iv high The voltage is set to be approximately constant. max1 to voltage X 100 For the range up to, the current limit value Iv high voltage X0 to voltage X min1 It is specified that the increase is slower than in the range up to

[0050] The current limit value Iv shown by the solid line in Figure 4A high is defined as a value obtained by, for example, dividing the difference obtained by subtracting the open circuit voltage (predetermined voltage value) equivalent to SOC 0% from each voltage of the power storage device on the horizontal axis V by the internal resistance (DCR) of the power storage device 32 in the high temperature range. This is to prevent the voltage of the power storage device 32 from falling below the open circuit voltage (predetermined voltage value) equivalent to SOC 0%, and is basically defined based on the following formula 1.

[0051] Voltage of the storage device = Open circuit voltage - Internal resistance of the storage device × Current ... Equation 1 In the second map (dashed line) corresponding to the normal temperature range shown in FIG. 4B, the open circuit voltage X0 corresponding to SOC 0% to the open circuit voltage X1 corresponding to SOC 100% 100 The current limit value Iv of the discharge current of the storage device for the range up to med is specified. Voltage X min2 and voltage X max2 are SOC min2 Equivalent open circuit voltage and SOC max2 A significant open circuit voltage is shown.

[0052] The voltage of the storage device changes from voltage X0 to voltage X min2 For the range up to, the current limit value Iv med is specified to increase sharply from 0. min2 to voltage X max2 For the range up to, the current limit value Iv med The voltage is set to be approximately constant.max2 to voltage X 100 For the range up to, the current limit value Iv med voltage X0 to voltage X min2 It is specified that the increase is slower than in the range up to

[0053] The current limit value Iv shown by the dashed line in Figure 4B med is defined as, for example, a value obtained by subtracting the open circuit voltage (predetermined voltage value) equivalent to SOC 0% from each voltage of the power storage device on the horizontal axis V, and dividing the difference by the internal resistance of the power storage device 32 in the normal temperature range. This is to prevent the voltage of the power storage device 32 from falling below the open circuit voltage (predetermined voltage value) equivalent to SOC 0%, and is basically defined based on the above-mentioned formula 1.

[0054] In the second map (dashed line) corresponding to the low temperature range shown in FIG. 4C, the open circuit voltage X0 corresponding to SOC 0% to the open circuit voltage X1 corresponding to SOC 100% 100 The current limit value Iv of the discharge current of the storage device for the range up to low is specified. Voltage X min3 and voltage X max3 are SOC min3 Equivalent open circuit voltage and SOC max3 A significant open circuit voltage is shown.

[0055] The voltage of the storage device changes from voltage X0 to voltage X min3 For the range up to, the current limit value Iv low is specified to gradually increase from 0. min3 to voltage X max3 For the range up to, the current limit value Iv low The voltage is set to be approximately constant. max3 to voltage X 100 For the range up to, the current limit value Iv low voltage X0 to voltage X min3 It is specified that the increase is slower than in the range up to

[0056] The current limit value Iv shown by the dashed line in FIG.low is defined as, for example, a value obtained by dividing the difference obtained by subtracting the open circuit voltage (predetermined voltage value) equivalent to SOC 0% from each voltage of the power storage device on the horizontal axis V by the internal resistance of the power storage device 32 in the low temperature range. This is to prevent the voltage of the power storage device 32 from falling below the open circuit voltage (predetermined voltage value) equivalent to SOC 0%, and is basically defined based on the above-mentioned formula 1.

[0057] The internal resistance of the power storage device 32 generally depends at least on the temperature of the power storage device 32, and the current limit value Iv of the power storage device in the second map shown in FIGS. 4A to 4C is calculated using data on the internal resistance value provided by the manufacturer of the power storage device 32. high , IV med , IV low Furthermore, if the power storage device controller 35 is configured to be able to detect the internal resistance value of the power storage device 32, the vehicle body controller 40 can also be configured to acquire the internal resistance value of the power storage device 32 from the power storage device controller 35. In this case, the vehicle body controller 40 can calculate the current limit value Iv of the power storage device 32 from the voltage and internal resistance of the power storage device 32 acquired from the power storage device controller 35, without using the second maps of FIGS. 4A to 4C .

[0058] In the second map, the voltage X shown in FIG. min1 , the voltage X shown in Figure 4B min2 , the voltage X shown in Figure 4C min3 are SOC min1 , SOC min2 , SOC min3 Similarly, the voltage X shown in Figure 4A is max1 , the voltage X shown in Figure 4B max2 , the voltage X shown in Figure 4C max3 are SOC max1 , SOC max2 , SOC max3 Since it is an equivalent open circuit voltage, it will generally be a different value.

[0059] In the second map shown in FIGS. 4A to 4C, the current limit value Ivmed is the current limit value Iv in the high temperature range hig The current limit value Iv low is the current limit value Iv in the normal temperature range med (except when the open circuit voltage is X0 corresponding to an SOC of 0%). This is because the internal resistance of the power storage device 32 increases as the temperature of the power storage device 32 decreases, and this prevents the voltage of the power storage device 32 from becoming less than a predetermined voltage value (open circuit voltage corresponding to an SOC of 0%).

[0060] The vehicle body controller 40 determines whether the SOC of the power storage device 32 acquired from the power storage device controller 35 is equal to or lower than the lower limit (SOC min1 , SOC min2 , or SOC min3 ), the vehicle body controller 40 sets a limit value for the discharge current of the power storage device 32 using a second map of a temperature range corresponding to the temperature of the power storage device 32. The vehicle body controller 40 refers to the second map to calculate a limit value for the output power of the inverter 33 based on the current limit value Iv that is set according to the voltage of the power storage device 32 obtained from the power storage device controller 35, and outputs an output limit signal Cl according to the calculation result to the inverter 33.

[0061] Next, the conditions under which the vehicle controller of the electric construction machine according to one embodiment switches the map used in limit control of the discharge current of the power storage device will be described with reference to Fig. 5. Fig. 5 is a state transition diagram showing the conditions under which the vehicle controller of the electric construction machine according to one embodiment shown in Fig. 2 switches the map used in limit control of the discharge current of the power storage device.

[0062] As described above, the vehicle body controller 40 switches between the first map, which defines the current limit value in response to changes in the SOC of the power storage device, and the second map, which defines the current limit value in response to changes in the voltage of the power storage device, in accordance with predetermined conditions, to calculate the limit value for the discharge current of the power storage device 32. The first map and the second map each divide the temperature of the power storage device into three temperature ranges: a high temperature range, a normal temperature range, and a low temperature range, and have maps with different characteristics corresponding to each temperature range (see FIG. 3 and FIGS. 4A to 4C).

[0063] When the temperature signal St from the power storage device controller 35 is in the high temperature range, the vehicle body controller 40 sets the limit value of the discharge current of the power storage device 32 using the map for the high temperature range (solid line) of the first map (FIG. 3) based on the SOC. When the vehicle body controller 40 receives the temperature signal St for the normal temperature range from the power storage device controller 35 while using the first map for the high temperature range, that is, when the temperature of the power storage device 32 falls into the normal temperature range (T==normal temperature range), the vehicle body controller 40 changes from the map for the high temperature range (solid line) in the first map (FIG. 3) to the map for the normal temperature range (dashed line) and sets the current limit value. This corresponds to a transition from the box in the upper left to the box in the center left in FIG. 5. Furthermore, when the first map for the high temperature range is used and a temperature signal St for the low temperature range is received from the power storage device controller 35, that is, when the temperature of the power storage device 32 falls into the low temperature range (T=low temperature range), the vehicle body controller 40 changes from the map for the high temperature range (solid line) in the first map (FIG. 3) to the map for the low temperature range (dotted line) and sets the current limit value. This corresponds to a transition from the upper left box to the lower left box in FIG. 5.

[0064] When the vehicle body controller 40 receives a temperature signal St in the high temperature range from the power storage device controller 35 while setting the current limit value using the normal temperature range map of the first map, that is, when the temperature of the power storage device 32 falls into the high temperature range (T== high temperature range), the vehicle body controller 40 changes the map from the normal temperature range map (dashed line) in the first map (FIG. 3) to the high temperature range map (solid line) and sets the current limit value. This corresponds to a transition from the center left box to the top left box in FIG. 5. Also, when the vehicle body controller 40 receives a temperature signal St in the low temperature range from the power storage device controller 35 while using the normal temperature range first map, that is, when the temperature of the power storage device 32 falls into the low temperature range (T== low temperature range), the vehicle body controller 40 changes the map from the normal temperature range map (dashed line) in the first map (FIG. 3) to the low temperature range map (dash-dotted line) and sets the current limit value. This corresponds to a transition from the center left box to the bottom left box in FIG. 5.

[0065] When the vehicle body controller 40 receives a temperature signal St in the high temperature range from the power storage device controller 35 while setting the current limit value using the map for the low temperature range of the first map, that is, when the temperature of the power storage device 32 falls into the high temperature range (T==high temperature range), the vehicle body controller 40 changes the map for the low temperature range (dashed line) in the first map (FIG. 3) to the map for the high temperature range (solid line) and sets the current limit value. This corresponds to a transition from the lower left box to the upper left box in FIG. 5. Also, when the vehicle body controller 40 receives a temperature signal St in the normal temperature range from the power storage device controller 35 while using the first map for the low temperature range, that is, when the temperature of the power storage device 32 falls into the normal temperature range (T==normal temperature range), the vehicle body controller 40 changes the map for the low temperature range (dashed line) in the first map (FIG. 3) to the map for the normal temperature range (dashed line) and sets the current limit value. This corresponds to a transition from the lower left box to the middle left box in FIG. 5.

[0066] Furthermore, when the vehicle body controller 40 sets the current limit value using the map for the high temperature range of the first map, the vehicle body controller 40 receives the SOC min1When an SOC signal Ss corresponding to an SOC less than 1000 kJ / s is received, the controller 35 switches from the map for the high temperature range in the first map based on SOC (map shown by the solid line in FIG. 3) to the map for the high temperature range in the second map based on voltage (map shown by the solid line in FIG. 4A) and sets the current limit value. This corresponds to a transition from the box in the upper left to the box in the upper right in FIG. 5. Also, when the map for the normal temperature range in the first map is used to set the current limit value, the controller 35 sends the SOC min2 When an SOC signal Ss corresponding to an SOC less than 0.001 is received, the current limit value is set by switching from the map for the normal temperature range in the first map based on SOC (map shown by the dashed line in FIG. 3) to the map for the normal temperature range in the second map based on voltage (map shown by the dashed line in FIG. 4B). This corresponds to a transition from the box in the middle left to the box in the middle right in FIG. 5. Also, when the current limit value is set using the map for the low temperature range in the first map, the power storage device controller 35 min3 When an SOC signal Ss corresponding to an SOC less than 0.05 is received, the current limit value is set by switching from the low temperature range map in the first map based on SOC (map shown by the dashed line in FIG. 3) to the low temperature range map in the second map based on voltage (map shown by the dashed line in FIG. 4C). This corresponds to a transition from the box in the lower left to the box in the lower right in FIG. 5.

[0067] Furthermore, when the vehicle body controller 40 receives a temperature signal St for the normal temperature range from the power storage device controller 35 while setting the current limit value using the map for the high temperature range of the second map (FIG. 4A), that is, when the temperature of the power storage device 32 falls into the normal temperature range (T==normal temperature range), the vehicle body controller 40 changes the second map from the map for the high temperature range (FIG. 4A) to the map for the normal temperature range (FIG. 4B) and sets the current limit value. This corresponds to a transition from the box at the top right to the box at the center right in FIG. 5. Furthermore, when the vehicle body controller 40 receives a temperature signal St for the low temperature range from the power storage device controller 35 while using the second map for the high temperature range, that is, when the temperature of the power storage device 32 falls into the low temperature range (T==low temperature range), the vehicle body controller 40 changes the second map from the map for the high temperature range (FIG. 4A) to the map for the low temperature range (FIG. 4C) and sets the current limit value. This corresponds to a transition from the box at the top right to the box at the bottom right in FIG. 5.

[0068] When the current limit value is set using the normal temperature range map of the second map, and a temperature signal St in the high temperature range is received from the power storage device controller 35, that is, when the temperature of the power storage device 32 falls into the high temperature range (T== high temperature range), the vehicle body controller 40 changes the second map from the normal temperature range map (FIG. 4B) to the high temperature range map (FIG. 4A) and sets the current limit value. This corresponds to a transition from the center right box to the top right box in FIG. 5. Also, when the second map for the normal temperature range is used, and a temperature signal St in the low temperature range is received from the power storage device controller 35, that is, when the temperature of the power storage device 32 falls into the low temperature range (T== low temperature range), the vehicle body controller 40 changes the second map from the normal temperature range map (FIG. 4B) to the low temperature range map (FIG. 4C) and sets the current limit value. This corresponds to a transition from the center right box to the bottom right box in FIG. 5.

[0069] When the current limit value is set using the low temperature range map of the second map, and a temperature signal St in the high temperature range is received from the power storage device controller 35, that is, when the temperature of the power storage device 32 falls into the high temperature range (T==high temperature range), the vehicle body controller 40 changes the second map from the map for the low temperature range (FIG. 4C) to the map for the high temperature range (FIG. 4A) and sets the current limit value. This corresponds to a transition from the lower right box to the upper right box in FIG. 5. Also, when the second map for the low temperature range is used, and a temperature signal St in the normal temperature range is received from the power storage device controller 35, that is, when the temperature of the power storage device 32 falls into the normal temperature range (T==normal temperature range), the vehicle body controller 40 changes the second map from the map for the low temperature range (FIG. 4C) to the map for the normal temperature range (FIG. 4B) and sets the current limit value. This corresponds to a transition from the lower right box to the middle right box in FIG. 5.

[0070] In this way, the vehicle body controller 40 changes the map to one corresponding to the temperature range in accordance with the temperature of the power storage device 32 acquired from the power storage device controller 35, and sets the current limit value. Also, the vehicle body controller 40 changes the map to one corresponding to the temperature range in accordance with the temperature of the power storage device 32 acquired from the power storage device controller 35, and sets the current limit value. min1 , SOC min2 , SOC min3 ), the current limit value is set by switching from the first map based on the SOC to the second map based on the voltage.

[0071] Next, a processing procedure for limiting control of the discharge current of the power storage device by the vehicle controller of the electric construction machine according to one embodiment will be described with reference to Fig. 6. Fig. 6 is a flowchart showing an example of a procedure for limiting control of the discharge current of the power storage device by the vehicle controller of the electric construction machine according to one embodiment shown in Fig. 2.

[0072] 6, vehicle body controller 40 first determines which of three temperature ranges (low temperature range, normal temperature range, high temperature range) temperature signal St (temperature of power storage device 32) from power storage device controller 35 belongs to (steps S10 to S30). The order of steps S10 to S30 can be changed. However, if the order is changed, the subsequent steps must also be changed.

[0073] For example, the vehicle body controller 40 determines whether the temperature (temperature signal St) of the power storage device 32 acquired from the power storage device controller 35 is in the low temperature range (step S10). If the vehicle body controller 40 determines that the temperature of the power storage device 32 is in the low temperature range (YES), the process proceeds to step S40. If the vehicle body controller 40 determines that the temperature of the power storage device 32 is not in the low temperature range (NO), the process proceeds to step S20, where the vehicle body controller 40 determines whether the temperature (temperature signal St) of the power storage device 32 is in the normal temperature range. If the vehicle body controller 40 determines in step S20 that the temperature of the power storage device 32 is in the normal temperature range (YES), the process proceeds to step S90. If the vehicle body controller 40 determines that the temperature of the power storage device 32 is not in the normal temperature range (NO), the process proceeds to step S30, where the vehicle body controller 40 determines whether the temperature (temperature signal St) of the power storage device 32 is in the high temperature range. In step S30, if it is determined that the temperature of the storage device 32 is in the high temperature range (YES), the process proceeds to step S140. On the other hand, if it is determined that the temperature of the storage device 32 is not in the high temperature range (NO), the process returns to step S10, and the processes of steps S10 to S30 are repeated until it is determined that the temperature (temperature signal St) of the storage device 32 is in the low temperature range, normal temperature range, or high temperature range (YES).

[0074] If the determination in step S10 is YES (the temperature of the power storage device 32 is in the low temperature range), the vehicle body controller 40 determines whether the SOC (SOC signal Ss) of the power storage device 32 acquired from the power storage device controller 35 is SOC min3 It is determined whether the SOC of the power storage device 32 is less than the lower limit of the SOC use range in the first map (the dashed line in FIG. 3) in the low temperature range (step S40). min3If it is determined that the SOC is less than SOC 1 (YES), the vehicle body controller 40 selects the map for the low temperature range (FIG. 4C) from the second maps based on the voltage of the power storage device as the map to be used for setting the current limit value (step S50), and calculates the limit value of the output power of the inverter 33 based on the limit value of the discharge current of the power storage device 32 set according to the voltage of the power storage device 32 acquired from the power storage device controller 35 by referring to the second map for the low temperature range, and outputs an output limit signal Cl generated according to the calculation result to the inverter 33 (step S60). min3 If the result is NO, the low temperature range map (dashed line in FIG. 3) of the first map based on the SOC of the power storage device is selected as the map to be used for setting the current limit value (step S70), and the limit value of the output power of the inverter 33 is calculated based on the limit value of the discharge current of the power storage device 32 set according to the SOC of the power storage device 32 obtained from the power storage device controller 35 by referring to the first low temperature range map, and an output limit signal Cl generated according to the calculation result is output to the inverter 33 (step S80).

[0075] If the determination in step S20 is YES (the temperature of the power storage device 32 is in the normal temperature range), the vehicle body controller 40 determines whether the SOC acquired from the power storage device controller 35 is SOC min2 It is determined whether the SOC of the power storage device 32 is less than the lower limit of the SOC use range in the first map (the broken line shown in FIG. 3) for the normal temperature range (step S90). min2 If it is determined that the SOC of the power storage device 32 is less than SOC 1 (YES), the vehicle body controller 40 selects the map for the normal temperature range (FIG. 4B) from the second maps based on the voltage of the power storage device as the map to be used for setting the current limit value (step S100), and calculates the limit value of the output power of the inverter 33 based on the limit value of the discharge current of the power storage device 32 set according to the voltage acquired from the power storage device controller 35 by referring to the second map for the normal temperature range, and outputs an output limit signal Cl generated according to the calculation result to the inverter 33 (step S110). min2If the answer is NO, the controller 100 selects the normal temperature range map (dashed line in FIG. 3) from the first maps based on the SOC of the storage battery as the map to be used in calculating the current limit value (step S120), and calculates the limit value of the output power of the inverter 33 based on the limit value of the discharge current of the storage device 32 set according to the SOC obtained from the storage device controller 35 by referring to the normal temperature range map, and outputs an output limit signal Cl generated according to the calculation result to the inverter 33 (step S130).

[0076] If the determination in step S30 is YES (the temperature of the power storage device 32 is in the high temperature range), the vehicle body controller 40 determines whether the SOC acquired from the power storage device controller 35 is SOC min1 It is determined whether the SOC of the power storage device 32 is less than the lower limit of the SOC use range in the first map (solid line shown in FIG. 3) in the high temperature range (step S140). min1 If it is determined that the SOC of the power storage device 32 is less than SOC 1 (YES), the vehicle body controller 40 selects the map for the high temperature range (FIG. 4A) from the second maps based on the voltage of the power storage device as the map to be used for setting the current limit value (step S150), and calculates the limit value of the output power of the inverter 33 based on the limit value of the discharge current of the power storage device 32 set according to the voltage acquired from the power storage device controller 35 by referring to the second map for the high temperature range, and outputs an output limit signal Cl generated according to the calculation result to the inverter 33 (step S160). min1 If the result is NO, the high temperature range map (solid line in FIG. 3) of the first maps based on the SOC of the power storage device is selected as the map to be used for setting the current limit value (step S170), and the high temperature range map is referenced to calculate the limit value of the output power of the inverter 33 based on the limit value of the discharge current of the power storage device 32 set according to the SOC obtained from the power storage device controller 35, and an output limit signal Cl generated according to the calculation result is output to the inverter 33 (step S180).

[0077] As described above, the vehicle body controller 40 of this embodiment first performs a first determination as to which of the three temperature ranges (low temperature range, normal temperature range, high temperature range) the temperature (temperature signal St) of the power storage device 32 acquired from the power storage device controller 35 falls. Next, the vehicle body controller 40 determines whether the SOC (SOC signal Ss) of the power storage device 32 acquired from the power storage device controller 35 falls within the lower limit value (SOC min3 , SOC min2 , SOC min1 If the result of the second determination is determined to be less than the lower limit value (predetermined value), a map corresponding to the temperature range of the first determination result is selected from among the second maps based on the voltage of the power storage device, and an output limit value for inverter 33 is calculated, whereas if the result of the second determination is determined to be equal to or greater than the lower limit value, a map corresponding to the temperature range of the first determination result is selected from among the first maps based on the SOC of the power storage device, and an output limit value for inverter 32 is calculated.

[0078] Next, current limitation of the power storage device in accordance with changes in the state of the power storage device in an electric construction machine according to one embodiment will be described using Figure 7. Figure 7 is a time chart showing the relationship between the state of the power storage device in an electric construction machine according to one embodiment and the control of inverter output limitation (limitation of the discharge current of the power storage device) by the vehicle controller. The time chart shown in Figure 7 shows, from top to bottom, the SOC, voltage, and temperature of the power storage device 32, the temperature signal St from the power storage device controller 35, a first map (a map in which a current limit value is defined with respect to changes in the voltage of the power storage device), a second map (a map in which a current limit value is defined with respect to changes in the SOC of the power storage device), the current limit value according to the first map, the current limit value according to the second map, and the output of the inverter 33.

[0079] At time t0, the operator starts operating the electric shovel 1. At the start of operation, the SOC of the power storage device 32 (first row in FIG. 7) is close to the upper limit of the usage range, and the temperature of the power storage device 32 (third row in FIG. 7) is in the low temperature range. The power storage device controller 35 outputs a temperature signal St (fourth row in FIG. 7) for the low temperature range to the vehicle body controller 40 in accordance with the temperature of the power storage device 32. Upon receiving the temperature signal St for the low temperature range, the vehicle body controller 40 sets a current limit value Is (seventh row in FIG. 7) based on the map for the low temperature range (solid line in FIG. 3) of the first map based on the SOC. That is, when the SOC of the power storage device 32 is equal to or higher than the lower limit (predetermined value) of the usage range of the temperature range corresponding to the temperature of the power storage device 32, the first map is selected, while the second map is disabled. The inverter 33 limits its output based on the current limit value Is set using the first map for the low temperature range (ninth row in FIG. 7).

[0080] After time t1, the SOC of the power storage device 32 is increased to a predetermined value SOC d3 When the SOC falls below the first map (see the horizontal axis in FIG. 3), the current limit value Is is set to change while being linearly derated in accordance with the decrease in SOC based on the first map for the low temperature range (the dashed-dotted line in FIG. 3). As a result, the output of the inverter 33 is limited to correspond to the current limit value Is that changes while being derated.

[0081] At time t2, when the temperature of the power storage device 32 rises due to continued operation by the operator and transitions from the low temperature range to the normal temperature range, the power storage device controller 35 outputs a temperature signal St for the normal temperature range. Upon receiving the temperature signal St for the normal temperature range, the vehicle body controller 40 changes the first map from the low temperature map (dashed line in FIG. 3 ) to the normal temperature range map (broken line in FIG. 3 ) and sets the current limit value Is. That is, to set the current limit value Is, the first map for the corresponding temperature range selected according to the temperature of the power storage device 32 is used. The output of the inverter 33 is limited according to the current limit value Is set using the first map for the normal temperature range. As shown in FIG. 3 , the current limit value Is specified in the first map is higher in the normal temperature range than in the low temperature range for the same SOC. For this reason, the output limit of the inverter 33 is relaxed when switching from the first map for the low temperature range to the first map for the normal temperature range.

[0082] At time t3, the SOC of the power storage device 32 reaches the lower limit SOC of the normal temperature range due to the continued operation of the operator. min2 (see the horizontal axis of FIG. 3), the vehicle body controller 40 disables the first map for the normal temperature range and uses the map for the normal temperature range (FIG. 4B) among the second maps based on the voltage of the power storage device to set the current limit value Iv med In other words, when the SOC of the power storage device 32 falls below the lower limit of the usage range of the temperature range corresponding to the temperature of the power storage device 32, the map used to set the current limit value is switched from the first map based on the SOC to the second map based on the voltage. The output of the inverter 33 is controlled by the current limit value Iv set using the second map for the normal temperature range. med is limited accordingly.

[0083] At time t4, when the temperature of the power storage device 32 rises further due to continued operation by the operator and shifts from the normal temperature range to the high temperature range, the power storage device controller 35 outputs a temperature signal St for the high temperature range. Upon receiving the temperature signal St for the high temperature range, the vehicle body controller 40 changes the second map from the map for the normal temperature range (FIG. 4B) to the map for the high temperature range (FIG. 4A) and adjusts the current limit value Iv highThat is, the current limit value Is is set using the second map for the temperature range selected according to the temperature of the power storage device 32. The output of the inverter 33 is controlled by the current limit value Iv set using the second map for the high temperature range. high is limited accordingly.

[0084] Generally, power storage devices are used with a limited range of SOC (estimated value) to avoid being used when the actual state of charge (true SOC value) is 0%. In other words, the usable range of SOC is limited to a predetermined range (for example, 10 to 90%). If the SOC falls below the lower limit of the predetermined range (for example, 10%), discharging of the power storage device is stopped. In this case, an electric construction machine equipped with a power storage device will transition to a stopped state, and depending on its stopped position, it may interfere with other construction machines. In light of this situation, it is preferable that an electric construction machine be able to operate for a short period of time even when the SOC is below the lower limit of the normal usable range.

[0085] When operating an electric construction machine for a short time when the SOC is below the lower limit of the normal operating range, it is necessary to prevent the voltage of the power storage device from dropping below the open circuit voltage equivalent to 0% SOC, which would significantly accelerate deterioration of the power storage device and increase the risk of abnormalities. In this case, if the discharge current of the power storage device is limited based on the estimated SOC, there is a concern that the power storage device may continue to be used at a voltage value below the open circuit voltage equivalent to 0% SOC due to an error in the SOC estimation, etc.

[0086] To address these concerns, one possible approach is to raise the lower limit of the normal SOC range (for example, from 10% to 15%) and limit the range near the lower limit of the normal SOC range (10-15%) to exceptional use for short-term operation of electric construction machinery. Setting the SOC range in this way ensures that the power storage device can be used when the actual state of charge (true SOC value) is above 0%. However, because electric construction machinery consumes a lot of power and there is limited space available for installing batteries, it is difficult to install a power storage device with a capacity that can handle the amount of work required in a day. Therefore, raising the lower limit of the normal SOC range to narrow the range would shorten the amount of time the construction machinery can work on a single charge, which is undesirable from the perspective of work efficiency.

[0087] Therefore, as described above, in the electric shovel 1 according to the present embodiment, when the SOC of the power storage device 32 falls below the lower limit (predetermined value) of the usage range corresponding to the temperature range at that time, the vehicle body controller 40 switches from the first map based on the SOC of the power storage device to the second map based on the voltage of the power storage device, and sets the limit value of the discharge current of the power storage device 32 from the voltage of the power storage device 32 acquired from the power storage device controller 35. As a result, even if the electric shovel 1 is operated for a short time when the SOC of the power storage device 32 is below the lower limit of the usage range, the limit value of the discharge current of the power storage device 32 is set according to the actual voltage value (detected value) of the power storage device 32 rather than the estimated SOC value, and it is therefore possible to avoid deterioration of the power storage device 32 caused by the voltage of the power storage device 32 falling below the predetermined voltage value (open circuit voltage equivalent to 0% SOC).

[0088] Furthermore, since the estimated SOC generally has an unknown error, it is usually necessary to provide a margin when setting the lower limit of the SOC usage range to prevent the voltage of the power storage device 32 from falling below a predetermined voltage value (open circuit voltage equivalent to 0% SOC). In contrast, in this embodiment, it is possible to set the lower limit of the SOC usage range without providing a margin. This allows the SOC usage range to be wider than usual.

[0089] Furthermore, in the electric shovel 1 according to this embodiment, the setting of the current limit value of the storage device 32 using the second map based on the voltage of the storage device is limited to short-term operation of the electric shovel 1 when the power supply is about to run out, and at other times the current limit value is set using the first map based on the SOC.

[0090] If the current limit value is set by always using the second map based on voltage without using the first map based on SOC, the following drawback occurs. The voltage value of the power storage device 32 tends to fluctuate more instantaneously than the SOC (the horizontal axis values ​​in FIGS. 4A to 4C tend to fluctuate more than the horizontal axis values ​​in FIG. 3), so the current limit value (the vertical axis values ​​in FIGS. 4A to 4C) is likely to fluctuate more. As a result, even if there is actually a sufficient amount of charge, the voltage value of the power storage device 32 may momentarily become close to voltage X0, resulting in the current limit value Iv med If the load increases or decreases sharply, the drive of the electric shovel 1 is restricted repeatedly, and the operability of the electric shovel 1 deteriorates.

[0091] On the other hand, the configuration of the electric shovel 1 according to this embodiment allows for a deterioration in operability only when the SOC is low, below the lower limit of the operating range, i.e., only in an emergency when power is about to run out, and allows the working implement 4 to change its posture or travel without interfering with other machinery. In other words, even when the electric shovel 1 performs an operation with large voltage fluctuations, deterioration in operability due to a sudden fluctuation in the current limit value resulting from the use of the second map based on voltage can be avoided. This allows the operator to operate the electric shovel 1 for long periods of time without impairing operability. Furthermore, since the electric shovel 1 can be operated even in an emergency when power is about to run out, it is expected that this will ensure the safety of other construction machinery and prevent a decline in work efficiency. Furthermore, unless the operation involves a high load, such as excavation work, fluctuations in the voltage value are relatively suppressed, and fluctuations in the current limit value are small, resulting in minimal deterioration in operability.

[0092] As described above, the electric shovel 1 (electric construction machine) according to one embodiment includes the electric motor 31 as a drive source, the power storage device 32 as a power source for the electric motor 31, the inverter 33 that adjusts the power supplied from the power storage device 32 to the electric motor 31, the power storage device controller 35 (state detection device) that detects the internal state of the power storage device 32 including the SOC (state of charge) and voltage of the power storage device 32, and the vehicle controller 40 (control device) that sets a limit value for the discharge current of the power storage device 32 and limits the output power of the inverter 33 based on the set limit value. The vehicle controller 40 (control device) is configured to set the above-mentioned limit value according to the SOC (state of charge) acquired from the storage device controller 35 (state detection device) when the SOC (state of charge) of the storage device 32 acquired from the storage device controller 35 (state detection device) is equal to or greater than a predetermined value, and to set the above-mentioned limit value according to the voltage of the storage device 32 acquired from the storage device controller 35 (state detection device) when the SOC (state of charge) acquired from the storage device controller 35 (state detection device) is less than the above-mentioned predetermined value.

[0093] According to this configuration, when the SOC of the power storage device 32 is below a predetermined value (in the case of a low state of charge), the limit value of the discharge current of the power storage device 32 is set according to the actual voltage value (detected value) of the power storage device 32, rather than the estimated SOC (state of charge). This makes it possible to prevent the voltage of the power storage device 32 from falling below a predetermined voltage value (a voltage value determined based on an open-circuit voltage equivalent to an SOC (state of charge) of 0%). Furthermore, even if the electric shovel 1 (electric construction machine) is operated when the power storage device 32 is in a low state of charge, it is possible to prevent the voltage of the power storage device 32 from falling below a predetermined voltage value, so there is no need to narrow the normal operating range of the SOC (state of charge). In other words, it is possible to prevent a reduction in the workable time of the electric shovel 1 (electric construction machine) while also suppressing deterioration of the power storage device 32 due to use in a low state of charge.

[0094] Moreover, in the electric shovel 1 (electric construction machine) according to this embodiment, the power storage device controller 35 (state detection device) is configured to detect the temperature of the power storage device 32 as the internal state of the power storage device 32. Furthermore, when the SOC (state of charge) acquired from the power storage device controller 35 (state detection device) is equal to or greater than the predetermined value, the vehicle body controller 40 (control device) is configured to set the above-mentioned limit value in accordance with the temperature of the power storage device 32 acquired from the power storage device controller 35 (state detection device) in addition to the SOC (state of charge), and when the SOC (state of charge) acquired from the power storage device controller 35 (state detection device) is less than the predetermined value, the vehicle body controller 40 is configured to set the above-mentioned limit value in accordance with the temperature acquired from the power storage device controller 35 (state detection device) in addition to the voltage acquired from the power storage device controller 35 (state detection device).

[0095] According to this configuration, the limit value of the discharge current of the power storage device 32 is set based on the temperature of the power storage device 32 in addition to the SOC (state of charge) or voltage of the power storage device 32, so that the limit value of the discharge current of the power storage device 32 can be set taking into consideration the temperature dependency of the internal resistance of the power storage device 32. Therefore, the vehicle body controller 40 (control device) can more accurately execute control to prevent the voltage of the power storage device 32 from falling below a predetermined voltage value (a voltage value defined based on an open circuit voltage equivalent to an SOC (state of charge) of 0%).

[0096] Furthermore, in the electric shovel 1 (electric construction machine) according to this embodiment, the vehicle controller 40 (control device) has a plurality of first maps (first characteristic information) that define the limit value of the discharge current of the power storage device relative to the SOC (state of charge) of the power storage device by dividing it into a plurality of temperature ranges of the power storage device, and a plurality of second maps (second characteristic information) that define the limit value of the discharge current of the power storage device relative to the voltage of the power storage device by dividing it into the above-mentioned plurality of temperature ranges. Furthermore, vehicle body controller 40 (control device) is configured to determine which of the plurality of temperature ranges the temperature acquired from power storage device controller 35 (state detection device) falls within, and if the SOC (state of charge) acquired from power storage device controller 35 (state detection device) is equal to or greater than the predetermined value, set the limit value using one of a plurality of first maps (first characteristic information) that corresponds to the determined temperature range, and if the SOC (state of charge) acquired from power storage device controller 35 (state detection device) is below the predetermined value, set the limit value using one of a plurality of second maps (second characteristic information) that corresponds to the determined temperature range. The predetermined value is set based on the lower limit of the usage range of the SOC (state of charge) of the power storage device, which is defined in the first map (first characteristic information) that corresponds to the determined temperature range among the plurality of first maps (first characteristic information).

[0097] According to this configuration, the limit value of the discharge current of the storage device 32 is set based on a plurality of first maps (first characteristic information) and second maps (second characteristic information) defined according to the temperature of the storage device 32, which is divided into a plurality of temperature ranges, so that the limit value of the discharge current of the storage device 32 can be easily calculated taking into account the temperature dependency of the internal resistance of the storage device 32.

[0098] Furthermore, by setting the above-mentioned predetermined value, which functions as a threshold value for switching between the first map (first characteristic information) and the second map (second characteristic information), based on the lower limit value of the usable range of the SOC (state of charge) of the power storage device defined in the first map (first characteristic information) corresponding to the temperature range of the determination result, it is possible to define the above-mentioned predetermined value to a different value depending on the temperature range of the power storage device 32. This makes it possible to prevent the voltage of the power storage device 32 from becoming equal to or lower than a predetermined voltage value (a voltage value defined based on an open circuit voltage equivalent to an SOC (state of charge) of 0%), and to define the usable range of the SOC (state of charge) as broadly as possible depending on the temperature range of the power storage device 32.

[0099] Furthermore, in the electric shovel 1 (electric construction machine) according to this embodiment, the multiple temperature ranges include a first temperature range (low temperature range) indicating a predetermined range of temperatures, and a second temperature range (high temperature range) that is a temperature range higher than the first temperature range. Furthermore, the first characteristic information corresponding to the second temperature range (high temperature range) is specified so that the lower limit value of the usable range of the state of charge of the power storage device 32 is lower than that of the first characteristic information corresponding to the first temperature range (low temperature range).

[0100] According to this configuration, the higher the temperature of the storage device 32, the lower the risk that the voltage of the storage device 32 will fall below a predetermined value (open circuit voltage equivalent to 0% SOC), so it is possible to expand the range of use of SOC in the second temperature range (high temperature range) more than the range of use of SOC in the first temperature range (low temperature range).

[0101] Furthermore, in the electric shovel 1 (electric construction machine) according to this embodiment, the multiple temperature ranges include a first temperature range (low temperature range) indicating a predetermined range of temperatures, and a second temperature range (high temperature range) that is a temperature range higher than the first temperature range. Furthermore, the second characteristic information corresponding to the second temperature range (high temperature range) is specified so that, when the voltage of the power storage device 32 is the same, the limit value of the discharge current of the power storage device 32 is higher than that of the second characteristic information corresponding to the first temperature range (low temperature range).

[0102] According to this configuration, the higher the temperature of the power storage device 32, the lower the risk that the voltage of the power storage device 32 will fall below a predetermined value (open circuit voltage equivalent to SOC 0%), and therefore it is possible to increase the limit value of the discharge current when the temperature of the power storage device 32 is high. Therefore, when the temperature of the power storage device 32 is high, the drive limit on the electric shovel 1 is relaxed, and deterioration in the operability of the electric shovel 1 is suppressed.

[0103] Furthermore, in the electric shovel 1 (electric construction machine) according to this embodiment, when the SOC (state of charge) acquired from the power storage device controller 35 (state detection device) is less than the above-mentioned predetermined value, the vehicle controller 40 (control device) is configured to set the above-mentioned limit value as a value obtained by subtracting a predetermined voltage value from the voltage acquired from the power storage device controller 35 (state detection device) and dividing the difference by the internal resistance value of the power storage device 32.

[0104] According to this configuration, the limit value of the discharge current of the storage device 32 is calculated based on the relationship between the voltage, current, and internal resistance of the storage device 32, so that it is possible to reliably prevent the voltage of the storage device 32 from falling below a predetermined voltage value (a voltage value defined based on an open circuit voltage equivalent to an SOC (state of charge) of 0%).

[0105] Furthermore, in the electric shovel 1 (electric construction machine) according to this embodiment, when the SOC (state of charge) acquired from the power storage device controller 35 (state detection device) is less than the above-mentioned predetermined value, the vehicle controller 40 (control device) is configured to set as the above-mentioned limit value a value obtained by subtracting a predetermined voltage value from the voltage acquired from the power storage device controller 35 (state detection device) and dividing the difference by the internal resistance value of the power storage device 32. The internal resistance value is determined based on the temperature acquired from the power storage device controller 35 (state detection device).

[0106] According to this configuration, the limit value of the discharge current of the power storage device 32 is calculated based on the relationship between the voltage, current, and internal resistance of the power storage device 32, so it is possible to reliably prevent the voltage of the power storage device 32 from falling below a predetermined voltage value (a voltage value defined based on an open circuit voltage equivalent to an SOC of 0%). Furthermore, because the temperature-dependent internal resistance value is determined according to the actual temperature, the vehicle body controller 40 (control device) can more accurately execute control to prevent the voltage of the power storage device 32 from falling below a predetermined voltage value (a voltage value defined based on an open circuit voltage equivalent to an SOC (state of charge) of 0%).

[0107] Furthermore, in the electric shovel 1 (electric construction machine) according to this embodiment, the above-mentioned predetermined value is set based on the estimation error of the SOC (state of charge) acquired from the power storage device controller 35 (state detection device).

[0108] According to this configuration, the SOC (state of charge), which is the internal state of the storage device used when setting the limit value of the discharge current of the storage device 32, and the above-mentioned predetermined value that functions as a threshold for switching voltage are set based on the estimation error of the SOC (state of charge) obtained from the storage device controller 35 (state detection device), so there is no need to narrow the normal usage range of the SOC (state of charge).

[0109] [Other embodiments] In the above-described embodiment, an example has been shown in which the present invention is applied to the electric shovel 1. However, the present invention can be widely applied to various types of electric construction machinery such as an electric hydraulic crane.

[0110] Furthermore, the present invention is not limited to the above-described embodiment, but includes various modifications. The above-described embodiment has been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. It is also possible to add, delete, or replace part of the configuration of the present embodiment with other configurations.

[0111] For example, in the present embodiment, an example has been shown in which the temperature of the power storage device 32 is divided into three temperature ranges, namely, a high temperature range, a normal temperature range, and a low temperature range, and first and second maps corresponding to the three temperature ranges are used as the first characteristic information and second characteristic information used to set the limit value of the discharge current of the power storage device 32. However, a configuration is also possible in which the temperature of the power storage device 32 is divided into four or more temperature ranges and first and second maps corresponding to the four or more temperature ranges are used as the first characteristic information and second characteristic information. Also, a configuration is possible in which the temperature of the power storage device 32 is not divided and first and second maps without temperature range divisions are used as the first characteristic information and second characteristic information.

[0112] Furthermore, in the present embodiment, an example has been shown in which the vehicle body controller 40 sets a limit value for the discharge current of the power storage device 32 using the first map (first characteristic information) and the second map (second characteristic information), and limits the output power of the inverter 33 based on the set limit value for the discharge current of the power storage device 32. However, a configuration is also possible in which the vehicle body controller directly calculates a limit value for the output current of the inverter 33 using the first map (first characteristic information) and the second map (second characteristic information). That is, the first map (first characteristic information) defines a limit value for the inverter output current relative to the SOC of the power storage device, and the second map (second characteristic information) defines a limit value for the inverter output current relative to the voltage of the power storage device. For example, when the power supplied from the power storage device 32 to the electric motor 31 is sufficiently greater than the power supplied from the power storage device 32 to other electrical devices of the electric shovel 1, the output current of the inverter 33 can be considered to be the discharge current of the power storage device 32. [Explanation of symbols]

[0113] 1... electric shovel (electric construction machine), 31... electric motor, 32... power storage device, 33... inverter, 35... power storage device controller (state detection device), 40... vehicle controller (control device)

Claims

1. an electric motor as a drive source; an electricity storage device that is a power source for the electric motor; an inverter that adjusts the power supplied from the power storage device to the electric motor; a state detection device that detects an internal state of the power storage device, including a charge state and a voltage of the power storage device; a control device that sets a limit value for a discharge current of the power storage device and limits the output power of the inverter based on the set limit value, The control device When the state of charge of the power storage device acquired from the state detection device is equal to or greater than a predetermined value, the limit value is set according to the state of charge acquired from the state detection device; When the state of charge acquired from the state detection device is less than the predetermined value, the limit value is set according to the voltage of the power storage device acquired from the state detection device. An electric construction machine characterized by:

2. The electric construction machine according to claim 1, the state detection device is configured to detect a temperature of the power storage device as the internal state of the power storage device; The control device When the state of charge acquired from the state detection device is equal to or greater than the predetermined value, the limit value is set according to the temperature of the power storage device acquired from the state detection device in addition to the state of charge; When the state of charge acquired from the state detection device is less than the predetermined value, the limit value is set according to the temperature acquired from the state detection device in addition to the voltage acquired from the state detection device. An electric construction machine characterized by:

3. The electric construction machine according to claim 2, the control device has a plurality of first characteristic information that defines the limit value for the state of charge of the power storage device by dividing it into a plurality of temperature ranges of the power storage device, and a plurality of second characteristic information that defines the limit value for the voltage of the power storage device by dividing it into a plurality of temperature ranges, The control device determining which of the plurality of temperature ranges the temperature acquired from the state detection device falls within; When the state of charge acquired from the state detection device is equal to or greater than the predetermined value, the limit value is set using first characteristic information corresponding to the determined temperature range among the plurality of first characteristic information; When the state of charge acquired from the state detection device is less than the predetermined value, the limit value is set using second characteristic information corresponding to the determined temperature range among the plurality of second characteristic information, The predetermined value is set based on a lower limit value of a usable range of the state of charge of the power storage device, which is defined in the first characteristic information corresponding to the determined temperature range, among the plurality of first characteristic information. An electric construction machine characterized by:

4. The electric construction machine according to claim 3, the plurality of temperature ranges include a first temperature range indicating a predetermined range of temperatures and a second temperature range that is a temperature range higher than the first temperature range, The first characteristic information corresponding to the second temperature range is specified so that the lower limit value of the usable range of the state of charge of the power storage device is lower than the first characteristic information corresponding to the first temperature range. An electric construction machine characterized by:

5. The electric construction machine according to claim 3, the plurality of temperature ranges include a first temperature range indicating a predetermined range of temperatures and a second temperature range that is a temperature range higher than the first temperature range, The second characteristic information corresponding to the second temperature range is defined so that, when the voltage of the power storage device is the same, the limit value of the discharge current of the power storage device is higher than that of the second characteristic information corresponding to the first temperature range. An electric construction machine characterized by:

6. The electric construction machine according to claim 1, The control device is configured to, when the state of charge acquired from the state detection device is less than the predetermined value, set the limit value to a value obtained by subtracting a predetermined voltage value from the voltage acquired from the state detection device and dividing the difference by an internal resistance value of the power storage device. An electric construction machine characterized by:

7. The electric construction machine according to claim 2, the control device is configured to, when the state of charge acquired from the state detection device is less than the predetermined value, set the limit value to a value obtained by subtracting a predetermined voltage value from the voltage acquired from the state detection device and dividing the result by an internal resistance value of the power storage device; The internal resistance value is determined based on the temperature obtained from the state detection device. An electric construction machine characterized by:

8. The electric construction machine according to claim 1, The predetermined value is set based on an estimation error of the state of charge obtained from the state detection device. An electric construction machine characterized by:

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