Electric construction machinery

Abstract

To provide an electric construction machine that can suppress the deterioration of the energy storage device due to use in a low-charge state while minimizing the reduction in the amount of time that can be used for work. [Solution] The electric construction machine 1 includes an electric motor 31 as a drive source, a power storage device 32 which is a power source for the electric motor 31, an inverter 33 which adjusts the power supplied from the power storage device 32 to the electric motor 31, a state detection device 35 which detects the internal state of the power storage device 32, and a control device 40 which 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 control device 40 sets the limit value according to the charge state (SOC) of the power storage device 32 obtained from the state detection device 35 if the charge state obtained from the state detection device 35 is above a predetermined value, and sets the limit value according to the voltage of the power storage device 32 obtained from the state detection device 35 if the charge state obtained from the state detection device 35 is below a predetermined value.

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, which serves as a drive source for enabling the operation of the construction machine, is driven by electricity supplied from a power storage device. [Background technology]

[0002] In construction machinery such as hydraulic excavators and wheel loaders, electric versions have been developed that use electric motors instead of engines to drive the hydraulic pumps, with the aim of being environmentally conscious. Some electric construction machines use energy storage devices as the power source to drive the electric motors.

[0003] Regarding the use of energy storage devices, State of Charge (SOC), which represents the amount of energy stored in the device as a percentage, is used as one indicator of the charge state. SOC is expressed as a range from 0% to 100%, with 100% representing a fully charged state and 0% representing a completely discharged state. Generally, SOC is estimated from various information such as the voltage and temperature of the energy storage device based on logic devised by the battery manufacturer, and therefore includes estimation errors. For this reason, even if the estimated SOC is a few percent, the actual charge state (true value of SOC) may be 0%.

[0004] It is known that energy storage devices, especially lithium-ion batteries, can deteriorate significantly and increase the risk of malfunctions if they continue to discharge while the actual charge level (true value of SOC) is very low, and the actual charge level (true value of SOC) approaches a state of complete discharge (0%). Therefore, energy storage devices are generally used only when the estimated value of SOC, which is the result of calculations, is within a predetermined range that is narrower than 0-100%, taking into account the estimation error of SOC, so that the actual charge level (true value of SOC) does not reach 0%.

[0005] Furthermore, lithium-ion batteries are susceptible to accelerated degradation and malfunctions even when the battery voltage drops below a predetermined value (open-circuit voltage equivalent to SOC 0%) due to the flow of high current. To avoid these risks, batteries must be used with a limit on the upper limit of the discharge current.

[0006] Regarding the control of energy storage devices, a technology for setting an upper limit on charge and discharge power is disclosed in Patent Document 1. The charge and discharge control device for an energy storage device of construction machinery described in Patent Document 1 sets an upper limit on the charge and discharge power of the energy 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 the multiple energy storage modules that make up the energy storage device, in order to suppress overvoltage or overheating of the energy storage device during charging and discharging. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2015-35841 [Overview of the project] [Problems that the invention aims to solve]

[0008] As mentioned above, energy storage devices are generally used with a limited range for the State of Charge (SOC) (estimated value) to avoid being used when the actual charge state (true value of SOC) is 0%. The usable range of SOC (lower and upper limits) is set taking into account the estimation error of SOC. If the usable range of SOC is limited to, for example, 10-90%, the discharge of the energy storage device will stop when the SOC falls below 10%. However, in electric construction machinery, power consumption is high and the space available for battery installation is limited, making it difficult to install a power storage device with a capacity sufficient to handle the machinery's daily workload. Therefore, if the lower limit of the SOC usage range is raised to ensure that the actual charge state (true value of SOC) remains above 0%, the operating time of the construction machinery on a single charge is limited and shortened, which is undesirable from the standpoint of work efficiency. In other words, there is a demand to maximize the SOC usage range to allow electric construction machinery to operate for extended periods.

[0009] The present invention is based on the above-mentioned matters and aims to provide an electric construction machine that can suppress deterioration of the energy storage device due to use in a low-charge state while suppressing a reduction in the working time. [Means for solving the problem]

[0010] The present invention includes multiple means for solving the above problems. One example of a solution provided by the present invention is an electric construction machine comprising an electric motor as a drive source, a power storage device which is a power source for the electric motor, an inverter which adjusts the power supplied from the power storage device to the electric motor, a state detection device which detects the internal state of the power storage device including the charge state and voltage of the power storage device, and a control device which sets a limit value for the 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 according to the charge state obtained from the state detection device when the SOC of the power storage device obtained from the state detection device is greater than or equal to a predetermined value, and to set the limit value according to the voltage of the power storage device obtained from the state detection device when the charge state obtained from the state detection device is less than the predetermined value. [Effects of the Invention]

[0011] According to one example of the solution of this invention, when the charge state of the energy storage device is below a predetermined value (low charge state), the limit value of the discharge current of the energy storage device is set according to the actual voltage value (detected value) of the energy storage device, rather than the estimated charge state. This makes it possible to avoid the voltage of the energy storage device falling below a predetermined voltage value (a voltage value defined based on the open-circuit voltage equivalent to a 0% charge state). Furthermore, even when operating an electric construction machine while the energy storage device is in a low charge state, it is possible to avoid the voltage of the energy storage device falling below a predetermined voltage value, thus eliminating the need to narrow the normal operating range of the charge state. In other words, it is possible to suppress deterioration of the energy storage device due to use in a low charge state while suppressing a reduction in the working time of the electric construction machine. Other issues, configurations, and effects not mentioned above will be clarified by the following description of the embodiments. [Brief explanation of the drawing]

[0012] [Figure 1] This is an external view showing an electric excavator as an electric construction machine according to one embodiment of the present invention. [Figure 2] This is a block diagram showing the main configuration of the drive system of an electric construction machine according to one embodiment shown in Figure 1. [Figure 3] Figure 2 shows an example of a first map (first characteristic information that defines the current limit value in response to changes in the State of Charge (SOC) of the energy storage device) used by the vehicle controller of an electric construction machine according to one embodiment shown in Figure 2 for calculating the current limit value (when the temperature of the energy storage device is divided into three temperature ranges: high temperature range, normal temperature range, and low temperature range). [Figure 4A] Figure 2 shows an example of a second map (second characteristic information that defines the current limit value in relation to changes in the potential of the energy storage device) used by the vehicle body controller of an electric construction machine according to one embodiment shown in Figure 2 for calculating the current limit value (when the temperature of the energy storage device is divided into three temperature ranges: high temperature range, normal temperature range, and low temperature range), and this figure shows the map corresponding to the high temperature range. [Figure 4B] This diagram shows an example of the second map (where the temperature of the energy storage device is divided into three temperature ranges: high temperature, normal temperature, and low temperature), specifically the map corresponding to the normal temperature range. [Figure 4C] This diagram shows an example of the second map (where the temperature of the energy storage device is divided into three temperature ranges: high temperature, normal temperature, and low temperature), specifically the map corresponding to the low temperature range. [Figure 5] Figure 2 shows a state transition diagram illustrating the conditions (timing) for switching maps (Figures 3 and 4A to 4) used by the vehicle controller of an electric construction machine according to one embodiment for limiting the discharge current of the energy storage device. [Figure 6] Figure 2 is a flowchart showing an example of a processing procedure for limiting the discharge current of a power storage device in a vehicle controller of an electric construction machine according to one embodiment. [Figure 7] This is a time chart showing the relationship between the state of the energy storage device in an electric construction machine according to one embodiment and the control of the inverter output limit (limit of the discharge current of the energy storage device) by the vehicle controller. [Modes for carrying out the invention]

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

[0014] [One Embodiment] First, the configuration of an electric excavator as an electric construction machine according to one embodiment will be explained using Figure 1. Figure 1 is an external view showing an electric excavator as an electric construction machine according to one embodiment.

[0015] In Figure 1, the electric excavator 1, as an electric construction machine, is broadly composed of a self-propelled vehicle 2, a slewing body 3 mounted on the vehicle 2 so as to be rotatable, and a working device 4 provided at the front of the slewing body 3 so as to be rotatable in the vertical direction. The slewing body 3 is configured to rotate relative to the vehicle 2 by a slewing device including a slewing hydraulic motor 5, which is a hydraulic actuator.

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

[0017] The slewing body 3 consists of a slewing frame 9 as a support structure rotatably mounted on the traveling body 2, a cab 10 installed on the left front side of the slewing frame 9, a counterweight 11 installed at the rear end of the slewing frame 9, and a machine room 12 provided between the cab 10 and the counterweight 11. The cab 10 is where the operator who operates the electric excavator 1 sits. The cab 10 houses a driver's seat for the operator and operating devices (neither shown) for operating the electric excavator 1. The counterweight 11 is for balancing the weight with the working device 4. The machine room 12 houses the hydraulic equipment 21, 22 and electrical equipment 31, 32, 33 (both shown in Figure 2 below) for operating the electric excavator 1.

[0018] The work device 4 is a multi-jointed device composed of multiple link members connected vertically so as to be rotatable for performing excavation work, etc. The multiple link members include, for example, a boom 14, an arm 15, and a bucket 16 as a work tool. The base end of the boom 14 is rotatably connected to the front of the slewing body 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, namely a boom cylinder 17, an arm cylinder 18, and a bucket cylinder 19, respectively.

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

[0020] In Figure 2, the electric excavator 1 is equipped with a hydraulic system 20 and an electric system 30 as a drive system that drives the traveling body 2, the rotating body 3, and the working device 4 (see Figure 1 for all).

[0021] The hydraulic system 20 comprises a plurality of hydraulic actuators driven by pressurized oil, a hydraulic pump 21 that supplies pressurized oil to the plurality of hydraulic actuators, and a control valve unit 22 that controls the flow of pressurized oil supplied from the hydraulic pump 21 to the plurality of hydraulic actuators. The plurality of hydraulic actuators in the hydraulic system 20 include the aforementioned swing hydraulic motor 5, travel hydraulic motor 7, boom cylinder 17, arm cylinder 18, and bucket cylinder 19 (see Figure 1 for all). The swing hydraulic motor 5 drives the swinging body 3 to perform a swinging motion. The travel hydraulic motor 7 drives the travel device 6 to perform a travel motion. The combined drive of the boom cylinder 17, arm cylinder 18, and bucket cylinder 19 allows the work device 4 to perform excavation and other operations. The control valve unit 22 distributes the pressurized oil discharged from the hydraulic pump 21 to the plurality of hydraulic actuators 5, 7, 17, 18, and 19, and is an assembly of control valves corresponding to each hydraulic actuator 5, 7, 17, 18, and 19. Each control valve in the control valve unit 22 controls the flow of pressurized oil supplied from the hydraulic pump 21 to the corresponding hydraulic actuators 5, 7, 17, 18, and 19.

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

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

[0024] The energy storage device 32 is a device that discharges the 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 energy storage device 32 is equipped with a voltage sensor 32c for detecting the voltage of the energy storage device 32, a current sensor 32d for detecting the current of the energy storage device 32, and a temperature sensor 32e for detecting the temperature of the energy storage device 32.

[0025] Furthermore, the energy storage device 32 is equipped with an energy storage device controller 35 that monitors the internal state of the energy storage device 32 and detects abnormalities in the energy storage device 32. The energy storage device controller 35 monitors the state of the energy storage device 32 and detects abnormalities by collecting sensor information detected by multiple sensors 32c, 32d, and 32e. The internal state of the energy storage device 32 includes, for example, the charge state, voltage, current, and temperature. The charge state is, for example, the State of Charge (SOC), which is the amount of energy stored in the energy storage device 32 as a ratio to its rated capacity (full charge capacity). SOC is expressed as 0% to 100%, with 100% representing a fully charged state, 50% representing half of the rated capacity, and 0% representing a completely discharged state. SOC cannot be directly measured and is estimated by the energy storage device controller 35 based on sensor information detected by each of the sensors 32c, 32d, and 32e installed in the energy storage device 32. The energy storage device controller 35 transmits information such as the internal state of the energy storage device 32 and whether or not there are any abnormalities to the vehicle body controller 40, which will be described later. For example, the energy 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 energy storage device controller 35 in this embodiment functions as a state detection device that detects the internal state of the energy storage device 32.

[0026] The inverter 33 converts the DC power output from the energy storage device 32 into desired AC power so that the electric motor 31 can be driven according to the command of 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 rotational speed or torque of the electric motor 31 corresponds to the command of 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 according to the output limiting signal Cl of the vehicle body controller 40, which will be described later.

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

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

[0029] In summary, the vehicle controller 40, if the State of Charge (SOC signal Ss) of the energy storage device 32 obtained from the energy storage device controller 35 is equal to or greater than a predetermined value, sets a limit value for the discharge current of the energy storage device 32 according to the SOC, and limits the output power of the inverter 33 to the electric motor 31 based on the set discharge current limit value. If the SOC (SOC signal Ss) obtained from the energy storage device controller 35 is less than the predetermined value mentioned above, the vehicle controller 40 sets a limit value for the discharge current of the energy storage device 32 according to the voltage (voltage signal Sv) of the energy storage device 32 obtained from the energy storage device controller 35, and limits the output power of the inverter 33 to the electric motor 31 based on the set discharge current limit value.

[0030] The predetermined value described above can be, for example, the lower limit of the SOC usage range recommended in advance by the manufacturer for the energy storage device 32. Alternatively, the predetermined value can be set considering the estimation error of the SOC of the energy storage device 32. In this case, the predetermined value can be set, for example, to a value obtained by adding the estimation error of the SOC to 0% of the SOC. The estimation error of the SOC can be a value provided by the manufacturer of the energy storage device 32 or a value measured experimentally in advance. Furthermore, the predetermined value can be set based on both the lower limit of the SOC usage range recommended for the energy storage device 32 and the estimation error of the SOC.

[0031] The vehicle controller 40 has a hardware configuration consisting of a storage device 41 made up of RAM, ROM, etc., and a processing device 42 made up of a CPU, MPU, etc. The storage device 41 has programs and various information (for example, see Figures 3 and 4 described later) necessary for limiting the discharge current of the energy storage device 32 stored in advance. The processing device 42 reads programs and various information from the storage device 41 as appropriate and receives status information of the energy storage device 32 (various signals Ss, Sv, St) from the energy storage device controller 35, and executes processing according to the program to output an output limit signal Cl to the inverter 33 that commands the limiting of the output power of the inverter 33.

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

[0033] If the vehicle body controller 40 obtains the State of Charge (SOC signal Ss) of the energy storage device 32 from the energy storage device controller 35 and it is equal to or greater than the predetermined value described above, the vehicle body controller 40 calculates the limit value of the discharge current of the energy storage device 32 using first characteristic information that defines the limit value of the discharge current of the energy storage device in response to changes in the SOC of the energy storage device. The first characteristic information is, for example, stored in advance in the memory device 41. The vehicle body controller 40 refers to the first characteristic information and calculates the limit value of the discharge current of the energy storage device 32 based on the SOC obtained from the energy storage device controller 35.

[0034] On the other hand, if the State of Charge (SOC) obtained from the energy storage device controller 35 falls below the predetermined value mentioned above, the vehicle controller 40 calculates the discharge current limit value of the energy storage device 32 using second characteristic information that defines the discharge current limit value (current limit value) of the energy storage device in response to changes in the voltage of the energy storage device. The second characteristic information is stored in advance in the memory device 41, for example. The vehicle controller 40 refers to this second characteristic information and calculates the discharge current limit value of the energy storage device 32 based on the voltage (voltage signal Sv) of the energy storage device 32 obtained from the energy storage device controller 35.

[0035] Specifically, when the SOC acquired from the power storage device controller 35 is greater than or equal to the above-mentioned predetermined value, the vehicle body controller 40 calculates, for example, the limit value of the discharge current of the power storage device 32 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 such that, for example, the definition of the current limit value Is of the power storage device with respect to the SOC of the power storage device varies according to the difference in the temperature of the power storage device. Specifically, 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 corresponds to the map for the high temperature range, the characteristic diagram shown by the broken line corresponds to the map for the normal temperature range, and the characteristic diagram shown by the one-dot chain line corresponds to the map for the low temperature range. When using the first map shown in FIG. 3 having maps corresponding to the three temperature ranges respectively, the vehicle body controller 40 is configured to select the map of the corresponding temperature range among the three temperature ranges according to the temperature (temperature signal St) of the power storage device 32 acquired from the power storage device controller 35.

[0036] In the map of the high temperature range shown by the solid line in the first map shown in FIG. 3, when the SOC is greater than SOC max1 or less than SOC min1 , the current limit value Is is defined as 0. When the SOC is greater than SOC min1 and less than SOC max1 to the set value, and up to SOC max1 , the current limit value Is is defined as a constant value Is high . When the SOC is in the range from SOC min1 to the above-mentioned set value, the current limit value Is is defined to increase linearly to reach Is high . That is, the first map corresponding to the high temperature range restricts the use range of the SOC to the range from SOC min1 to SOC max1 .

[0037] SOC min1 and SOC max1These are, for example, the lower and upper limits of the manufacturer's recommended SOC usage range when the temperature of the energy storage device 32 is in the high-temperature range. min1 This can also be set by considering at least one of the manufacturer's recommended lower limit of the SOC usage range when the temperature of the energy storage device 32 is in the high-temperature range, and the estimation error of the SOC obtained from the energy storage device controller 35. Furthermore, it is possible to use a map provided by the manufacturer of the energy storage device 32 as the first map corresponding to the high-temperature range.

[0038] In the map of the room temperature range shown by the dashed line in the first map, SOC is SOC max2 If it is greater than or SOC min2 For cases where the SOC is smaller than the SOC value, the current limit value Is is specified as 0. min2 Larger than SOC max2 From a setting value smaller than that, SOC max2 For the range up to , the current limit value Is is a constant value Is med It is stipulated in the SOC. min2 For the range from the above-mentioned set value, the current limit value Is increases linearly. med It is stipulated that it should reach [a certain value]. In other words, the first map corresponding to the ambient temperature range defines the usage range of SOC as [a certain value]. min2 From SOC max2 It is limited to the range up to that point.

[0039] SOC min2 and SOC max2 These are, for example, the lower and upper limits of the manufacturer's recommended SOC usage range when the temperature of the energy storage device 32 is in the normal temperature range. min2 This can also be set by considering at least one of the manufacturer's recommended lower limit of the SOC usage range when the temperature of the energy storage device 32 is in the ambient temperature range, and the estimation error of the SOC obtained from the energy storage device controller 35. Furthermore, it is possible to use a map provided by the manufacturer of the energy storage device 32 as the first map corresponding to the ambient temperature range.

[0040] In the low-temperature region shown by the dashed line in the first map, SOC is SOCmax3 If it is greater than or SOC min3 For cases where the SOC is smaller than the SOC value, the current limit value Is is specified as 0. min3 Larger than SOC max3 From a setting value smaller than that, SOC max3 For the range up to , the current limit value Is is a constant value Is low It is stipulated in the SOC. min3 For the range from the above-mentioned set value, the current limit value Is increases linearly. low It is stipulated that it should reach [a certain value]. In other words, the first map corresponding to the low-temperature range defines the usage range of SOC as [a certain value]. min3 From SOC max3 It is limited to the range up to that point.

[0041] SOC min3 and SOC max3 These are, for example, the lower and upper limits of the manufacturer's recommended SOC usage range when the temperature of the energy storage device 32 is in the low temperature range. min3 This can also be set by considering at least one of the manufacturer's recommended lower limit of the SOC usage range when the temperature of the energy storage device 32 is in the low temperature range and the estimation error of the SOC obtained from the energy storage device controller 35. Furthermore, it is possible to use a map provided by the manufacturer of the energy 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) in the room temperature range is med (including) the current limit value Is (constant value Is) in the high temperature range high It is specified to be smaller than the current limit value Is (including) in the low temperature range (constant value Is low (including) the current limit value I (constant value Is) in the room temperature range. med It is specified that the voltage of the energy storage device 32 should be smaller than (including). This is to prevent the voltage of the energy storage device 32 from falling below a predetermined value (open circuit voltage equivalent to SOC 0%), as the internal resistance of the energy storage device 32 increases as its temperature decreases.

[0043] Furthermore, in the first map, the lower limit of the usable range of SOC in the normal temperature range is shown. min2 This is the lower limit of the usable range of SOC in the high-temperature range. min1 It is set to be greater than the lower limit of the usable SOC range in the low-temperature range. min3 The lower limit of the usable range of SOC in the room temperature range is SOC min2 It is set to be greater than this. This is because the lower the temperature of the energy storage device 32, the higher the risk that the voltage of the energy storage device 32 will fall below a predetermined value (open-circuit voltage equivalent to SOC 0%), and therefore the intended purpose is to narrowly limit the usable range of SOC on the safe side.

[0044] Furthermore, the predetermined value mentioned above, which is an indicator used by the vehicle controller 40 to switch between the first map and the second map for calculating the current limit value, corresponds to the lower limit of the usable range of SOC as defined in the first map. That is, the predetermined value mentioned above is the SOC when the temperature of the energy storage device 32 is in the high temperature range. min1 If the temperature of the energy storage device 32 is in the room temperature range, then SOC min2 If the temperature of the energy storage device 32 is in the low temperature range, then SOC min3 It corresponds to this.

[0045] The vehicle controller 40 determines that the SOC obtained from the energy storage device controller 35 is the lower limit of the SOC usage range specified in the first map for the temperature range (high temperature range, normal temperature range, or low temperature range) corresponding to the temperature of the energy storage device 32 (SOC min1 SOC min2 , or SOC min3 If the temperature is above 0, the vehicle controller 40 calculates the limit value of the discharge current of the energy storage device 32 using the first map of the temperature range corresponding to the temperature of the energy storage device 32. The vehicle controller 40 refers to the first map and calculates the limit value of the output power of the inverter 33 based on the current limit value Is set according to the SOC obtained from the energy storage device controller 35, and outputs an output limit signal Cl to the inverter 33 according to the calculation result.

[0046] Furthermore, if the State of Charge (SOC) obtained from the energy storage device controller 35 falls below the predetermined value mentioned above, the vehicle body controller 40 calculates a limit value for the discharge current of the energy storage device 32 using, for example, a second map shown in any of Figures 4A to 4C as second characteristic information. In Figures 4A to 4C, the horizontal axis V represents the voltage of the energy storage device, and the vertical axis Iv high , Iv med , Iv low This indicates the current limit value of the energy storage device.

[0047] The second map shown in Figures 4A to 4C, like the first map shown in Figure 3, is set so that the current limit value of the energy storage device is specified differently depending on the temperature of the energy storage device. Specifically, the second map shown in Figures 4A to 4C divides the temperature of the energy storage device into three temperature ranges: high temperature, ambient temperature, and low temperature, and has a map with different characteristics corresponding to each temperature range. The characteristic diagram shown by the solid line in Figure 4A is the map corresponding to the high temperature range of the second map, the characteristic diagram shown by the dashed line in Figure 4B is the map corresponding to the ambient temperature range of the second map, and the characteristic diagram shown by the dashed line in Figure 4C is the map corresponding to the low temperature range of the second map. When using the second map shown in Figures 4A to 4C, which has maps corresponding to three temperature ranges, the vehicle controller 40 is configured to select the map corresponding to the appropriate temperature range from the three temperature ranges according to the temperature (temperature signal St) of the energy storage device 32 obtained from the energy storage device controller 35.

[0048] In the second map (solid line) corresponding to the high-temperature region shown in Figure 4A, the open-circuit voltage X0 corresponds to SOC 0% to the open-circuit voltage X0 corresponds to SOC 100%. 100 For the range up to, the current limit value Iv high This is specified. Voltage X min1 and voltage X max1 These are SOCs, respectively. min1 Equivalent open-circuit voltage and SOC max1 This indicates a considerable open-circuit voltage.

[0049] The voltage of the energy storage device changes from voltage X0 to voltage X min1 For the range up to this point, the current limit value Iv highIt is specified that it increases steeply from 0. min1 From voltage X max1 For the range up to this point, the current limit value Iv high It is stipulated that the voltage should be approximately constant. max1 From voltage X 100 For the range up to this point, the current limit value Iv high From voltage X0 to voltage X min1 It is stipulated that the increase should be slower compared to the case up to a certain range.

[0050] The current limit value Iv is shown by the solid line in Figure 4A. high For example, this is defined as the value obtained by dividing the difference obtained by subtracting the open-circuit voltage equivalent to SOC0% (a predetermined voltage value) from each voltage of the energy storage device on the horizontal axis V by the internal resistance (DCR) of the energy storage device 32 in the high-temperature range. This is to avoid the voltage of the energy storage device 32 falling below the open-circuit voltage equivalent to SOC0% (a predetermined voltage value), and is basically defined based on the following equation 1.

[0051] Energy storage device voltage = Open-circuit voltage - Internal resistance of energy storage device × Current ... Equation 1 In the second map (dashed line) corresponding to the room temperature range shown in Figure 4B, the open-circuit voltage X0 corresponds to SOC 0% to the open-circuit voltage X100%. 100 For the range up to this point, the current limit value Iv of the discharge current of the energy storage device. med This is specified. Voltage X min2 and voltage X max2 These are SOCs, respectively. min2 Equivalent open-circuit voltage and SOC max2 This indicates a considerable open-circuit voltage.

[0052] The voltage of the energy storage device changes from voltage X0 to voltage X min2 For the range up to this point, the current limit value Iv med It is specified that it increases steeply from 0. min2 From voltage X max2 For the range up to this point, the current limit value Iv med It is stipulated that the voltage should be approximately constant.max2 from voltage X 100 to the range of, the current limit value Iv med is defined to increase slowly compared to the case of the range from voltage X0 to voltage X min2 up to.

[0053] The current limit value Iv indicated by the dashed line in FIG. 4B med is defined as, for example, a value obtained by dividing the difference obtained by subtracting the open - circuit voltage (predetermined voltage value) corresponding to SOC0% from each voltage of the power storage device on the horizontal axis V by the internal resistance in the normal temperature range of the power storage device 32. This is to avoid the voltage of the power storage device 32 from becoming lower than the open - circuit voltage (predetermined voltage value) corresponding to SOC0%, and is basically defined based on the above - mentioned formula 1.

[0054] In the second map (dashed - dotted line) corresponding to the low - temperature range shown in FIG. 4C, for the range from the open - circuit voltage X0 corresponding to SOC0% to the open - circuit voltage X corresponding to SOC100% 100 of the power storage device, the current limit value Iv of the discharge current of the power storage device low is defined. The voltage X min3 and the voltage X max3 respectively indicate the open - circuit voltage corresponding to SOC min3 and the open - circuit voltage corresponding to SOC max3 respectively.

[0055] For the range of the voltage of the power storage device from voltage X0 to voltage X min3 up to, the current limit value Iv low [[ID=​​​​​​​​​​​​​​​​​​low For example, this is defined as the value obtained by dividing the difference obtained by subtracting the open-circuit voltage equivalent to SOC0% (a predetermined voltage value) from each voltage of the energy storage device on the horizontal axis V by the internal resistance of the energy storage device 32 in the low-temperature range. This is to prevent the voltage of the energy storage device 32 from falling below the open-circuit voltage equivalent to SOC0% (a predetermined voltage value), and is basically defined based on the above-mentioned Equation 1.

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

[0058] In the second map, the voltage X shown in Figure 4A is min1 The voltage X shown in Figure 4B min2 The voltage X shown in Figure 4C min3 These are SOCs, respectively. min1 SOC min2 SOC min3 Since it is a considerable open-circuit voltage, it is generally a different value. Similarly, the voltage X shown in Figure 4A max1 The voltage X shown in Figure 4B max2 The voltage X shown in Figure 4C max3 These are SOCs, respectively. max1 SOC max2 SOC max3 Since it represents a considerable open-circuit voltage, it generally has a different value.

[0059] Furthermore, in the second map shown in Figures 4A to 4C, the current limit value Iv in the room temperature range is shown.med The current limit value Iv in the high-temperature range hig It is specified to be smaller than, and the current limit value Iv in the low-temperature range low The current limit value Iv in the room temperature range med It is specified to be smaller than (except when the open-circuit voltage X0 is equivalent to SOC0%). This is to prevent the voltage of the energy storage device 32 from falling below a predetermined voltage value (open-circuit voltage equivalent to SOC0%), as the internal resistance of the energy storage device 32 increases as its temperature decreases.

[0060] The vehicle controller 40 determines that the SOC of the energy storage device 32 obtained from the energy storage device controller 35 is the lower limit of the SOC usage range specified in the first map for the temperature range (high temperature range, normal temperature range, or low temperature range) corresponding to the temperature of the energy storage device 32 (SOC min1 SOC min2 , or SOC min3 If the temperature falls below a certain level, the second map of the temperature range corresponding to the temperature of the energy storage device 32 is used to set a limit on the discharge current of the energy storage device 32. The vehicle controller 40 refers to the second map and calculates a limit on the output power of the inverter 33 based on the current limit value Iv set according to the voltage of the energy storage device 32 obtained from the energy storage device controller 35, and outputs an output limit signal Cl to the inverter 33 according to the calculation result.

[0061] Next, the conditions for switching the map used by the vehicle controller of an electric construction machine according to one embodiment for limiting the discharge current of the energy storage device will be explained using Figure 5. Figure 5 is a state transition diagram showing the conditions for switching the map used by the vehicle controller of an electric construction machine according to one embodiment shown in Figure 2 for limiting the discharge current of the energy storage device.

[0062] As described above, the vehicle controller 40 calculates the discharge current limit value of the energy storage device 32 by switching between a first map that defines a current limit value for changes in the state of charge (SOC) of the energy storage device and a second map that defines a current limit value for changes in the voltage of the energy storage device, according to predetermined conditions. The first map and the second map each divide the temperature of the energy storage device into three temperature ranges: high temperature, normal temperature, and low temperature, and have maps with different characteristics corresponding to each temperature range (see Figures 3 and 4A to 4C).

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

[0064] When the current limit value is set using the ambient temperature map from the first map, if the energy storage controller 35 receives a high-temperature signal St, that is, if the temperature of the energy storage device 32 becomes high-temperature (T==high temperature), the vehicle body controller 40 changes from the ambient temperature map (dashed line) to the high-temperature map (solid line) in the first map (Figure 3) and sets the current limit value. This corresponds to the transition from the left-center box to the upper-left box in Figure 5. Also, when the ambient temperature map is being used, if the energy storage controller 35 receives a low-temperature signal St, that is, if the temperature of the energy storage device 32 becomes low-temperature (T==low temperature), the vehicle body controller 40 changes from the ambient temperature map (dashed line) to the low-temperature map (dotted line) in the first map (Figure 3) and sets the current limit value. This corresponds to the transition from the left-center box to the lower-left box in Figure 5.

[0065] When the current limit value is set using the low-temperature region map of the first map, if the energy storage controller 35 receives a high-temperature region temperature signal St, that is, if the temperature of the energy storage device 32 becomes high-temperature (T==high-temperature region), the vehicle body controller 40 changes from the low-temperature region map (dotted line) to the high-temperature region map (solid line) in the first map (Figure 3) and sets the current limit value. This corresponds to the transition from the lower left box to the upper left box in Figure 5. Also, when the low-temperature region first map is being used, if the energy storage controller 35 receives a normal temperature region temperature signal St, that is, if the temperature of the energy storage device 32 becomes normal temperature (T==normal-temperature region), the vehicle body controller 40 changes from the low-temperature region map (dotted line) to the normal temperature region map (dashed line) in the first map (Figure 3) and sets the current limit value. This corresponds to the transition from the lower left box to the left-center box in Figure 5.

[0066] Furthermore, when the vehicle controller 40 sets the current limit value using the high-temperature region map of the first map, it receives the SOC from the energy storage device controller 35. min1When an SOC signal Ss corresponding to a SOC less than 0 is received, the system switches from the high-temperature region map in the first map based on SOC (shown by the solid line in Figure 3) to the high-temperature region map in the second map based on voltage (shown by the solid line in Figure 4A) and sets the current limit value. This corresponds to the transition from the upper left box to the upper right box in Figure 5. Also, when the current limit value is set using the room temperature region map of the first map, the energy storage device controller 35 receives the SOC signal. min2 When an SOC signal Ss corresponding to a SOC less than a certain value is received, the system switches from the SOC-based first map for the room temperature range (shown by the dashed line in Figure 3) to the voltage-based second map for the room temperature range (shown by the dashed line in Figure 4B) and sets the current limit value. This corresponds to the transition from the box in the left center to the box in the right center in Figure 5. Also, when the current limit value is set using the low-temperature range map of the first map, the energy storage device controller 35 receives the SOC signal. min3 When an SOC signal Ss corresponding to a SOC less than a certain value is received, the system switches from the low-temperature region map in the first map based on SOC (shown by the dashed line in Figure 3) to the low-temperature region map in the second map based on voltage (shown by the dashed line in Figure 4C) to set the current limit value. This corresponds to the transition from the bottom left box to the bottom right box in Figure 5.

[0067] Furthermore, when the vehicle body controller 40 is setting the current limit value using the high-temperature region map (Figure 4A) of the second map, if it receives a temperature signal St in the normal temperature range from the energy storage device controller 35, that is, if the temperature of the energy storage device 32 becomes normal temperature (T==normal temperature range), the vehicle body controller 40 changes from the high-temperature region map (Figure 4A) in the second map to the normal temperature region map (Figure 4B) and sets the current limit value. This corresponds to a transition from the upper right box to the right center box in Figure 5. Also, when using the high-temperature region second map, if it receives a low-temperature region temperature signal St from the energy storage device controller 35, that is, if the temperature of the energy storage device 32 becomes low temperature (T==low temperature range), the vehicle body controller 40 changes from the high-temperature region map (Figure 4A) in the second map to the low-temperature region map (Figure 4C) and sets the current limit value. This corresponds to a transition from the upper right box to the lower right box in Figure 5.

[0068] When the current limit value is set using the ambient temperature map of the second map, if the energy storage controller 35 receives a high-temperature signal St, that is, if the temperature of the energy storage device 32 becomes high-temperature (T==high temperature), the vehicle body controller 40 changes from the ambient temperature map (Figure 4B) in the second map to the high-temperature map (Figure 4A) and sets the current limit value. This corresponds to a transition from the box in the center right to the box in the upper right of Figure 5. Also, when the ambient temperature map of the second map is being used, if the energy storage controller 35 receives a low-temperature signal St, that is, if the temperature of the energy storage device 32 becomes low-temperature (T==low temperature), the vehicle body controller 40 changes from the ambient temperature map (Figure 4B) in the second map to the low-temperature map (Figure 4C) and sets the current limit value. This corresponds to a transition from the box in the center right to the box in the lower right of Figure 5.

[0069] When the current limit value is set using the low-temperature map of the second map, if the energy storage controller 35 receives a high-temperature signal St, that is, if the temperature of the energy storage device 32 becomes high-temperature (T==high-temperature), the vehicle body controller 40 changes from the low-temperature map (Figure 4C) in the second map to the high-temperature map (Figure 4A) and sets the current limit value. This corresponds to a transition from the bottom right box to the top right box in Figure 5. Also, when the low-temperature second map is being used, if the energy storage controller 35 receives a normal temperature signal St, that is, if the temperature of the energy storage device 32 becomes normal temperature (T==normal-temperature), the vehicle body controller 40 changes from the low-temperature map (Figure 4C) in the second map to the normal temperature map (Figure 4B) and sets the current limit value. This corresponds to a transition from the bottom right box to the right-center box in Figure 5.

[0070] In this way, the vehicle controller 40 sets the current limit value by changing the map to one corresponding to the temperature range, according to the temperature of the energy storage device 32 obtained from the energy storage device controller 35. In addition, the lower limit of the usage range of the first map for the temperature range in which the SOC obtained from the energy storage device controller 35 corresponds is set. min1 SOC min2 SOC min3 If the value falls below this level, the system switches from the first map based on SOC to the second map based on voltage to set the current limit.

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

[0072] In Figure 6, the vehicle controller 40 first determines which of the three temperature ranges (low temperature range, ambient temperature range, high temperature range) the temperature signal St (temperature of the energy storage device 32) from the energy storage device controller 35 falls into (steps S10 to S30). Note that the order of processing in steps S10 to S30 can be changed. However, the later steps must also be changed according to the change in order.

[0073] The vehicle body controller 40 determines, for example, whether the temperature (temperature signal St) of the energy storage device 32 obtained from the energy storage device controller 35 is in the low temperature range (step S10). If the vehicle body controller 40 determines that the temperature of the energy storage device 32 is in the low temperature range (YES), it proceeds to step S40. If it determines that the temperature of the energy storage device 32 is not in the low temperature range (NO), it proceeds to step S20 to determine whether the temperature (temperature signal St) of the energy storage device 32 is in the normal temperature range. In step S20, if it determines that the temperature of the energy storage device 32 is in the normal temperature range (YES), it proceeds to step S90. If it determines that the temperature of the energy storage device 32 is not in the normal temperature range (NO), it proceeds to step S30 to determine whether the temperature (temperature signal St) of the energy storage device 32 is in the high temperature range. In step S30, if it is determined that the temperature of the energy storage device 32 is in the high temperature range (YES), the process proceeds to step S140. However, if it is determined that the temperature of the energy storage device 32 is not in the high temperature range (NO), the process returns to step S10, and steps S10 to S30 are repeated until it is determined that the temperature of the energy storage device 32 (temperature signal St) falls within one of the low temperature, normal temperature, or high temperature ranges (YES).

[0074] If step S10 determines YES (the temperature of the energy storage device 32 is in the low temperature range), the vehicle controller 40 will determine that the SOC (SOC signal Ss) of the energy storage device 32 obtained from the energy storage device controller 35 is in the low temperature range. min3 It is determined whether the SOC is less than (the lower limit of the SOC usage range in the first map of the low-temperature region (dotted line in Figure 3)) (step S40). The SOC of the energy storage device 32 is SOC min3If it is determined to be less than (YES), the vehicle controller 40 selects the low-temperature region map (Figure 4C) from the second map based on the voltage of the energy storage device as the map to be used to set the current limit value (step S50), and calculates the output power limit value of the inverter 33 based on the discharge current limit value of the energy storage device 32 set according to the voltage of the energy storage device 32 obtained from the energy storage device controller 35 by referring to the second map in the low-temperature region, and outputs the output limit signal Cl generated according to the calculation result to the inverter 33 (step S60). Meanwhile, if the SOC of the energy storage device 32 is min3 If the result is determined to be NO, the low-temperature region map (dotted line in Figure 3) from the first map based on the State of Charge (SOC) of the energy storage device is selected as the map to be used to set the current limit value (step S70). The output power limit value of the inverter 33 is calculated based on the discharge current limit value of the energy storage device 32 set according to the SOC of the energy storage device 32 obtained from the energy storage device controller 35 by referring to the first map in the low-temperature region, and an output limit signal Cl generated according to the calculation result is output to the inverter 33 (step S80).

[0075] If step S20 determines YES (the temperature of the energy storage device 32 is in the normal temperature range), the vehicle controller 40 will determine that the SOC obtained from the energy storage device controller 35 is the SOC min2 It is determined whether the SOC is less than (the lower limit of the SOC usage range in the first map of the ambient temperature range (dashed line shown in Figure 3)) (step S90). The SOC of the energy storage device 32 is SOC min2 If it is determined to be less than (YES), the vehicle controller 40 selects the ambient temperature range map (Figure 4B) from the second map based on the voltage of the energy storage device as the map to be used to set the current limit value (step S100), and calculates the output power limit value of the inverter 33 based on the discharge current limit value of the energy storage device 32 set according to the voltage obtained from the energy storage device controller 35 by referring to the second map in the ambient temperature range, and outputs the output limit signal Cl generated according to the calculation result to the inverter 33 (step S110). Meanwhile, if the SOC of the energy storage device 32 is min2If the result is determined to be NO, the system selects the room temperature range map (dashed line in Figure 3) from the first map based on the battery's SOC as the map to be used for calculating the current limit value (step S120). The system then refers to the first map in the room temperature range and calculates the output power limit value of the inverter 33 based on the discharge current limit value of the energy storage device 32 set according to the SOC obtained from the energy storage device controller 35. The system then outputs the generated output limit signal Cl to the inverter 33 according to the calculation result (step S130).

[0076] If step S30 determines YES (the temperature of the energy storage device 32 is in the high temperature range), the vehicle controller 40 will determine that the SOC obtained from the energy storage device controller 35 is in the high temperature range. min1 It is determined whether the SOC is less than (the lower limit of the SOC usage range in the first map of the high-temperature region (solid line shown in Figure 3)) (step S140). The SOC of the energy storage device 32 is SOC min1 If it is determined to be less than (YES), the vehicle controller 40 selects the high-temperature region map (Figure 4A) from the second map based on the voltage of the energy storage device as the map to be used to set the current limit value (step S150), and calculates the output power limit value of the inverter 33 based on the discharge current limit value of the energy storage device 32 set according to the voltage obtained from the energy storage device controller 35 by referring to the high-temperature region second map, and outputs the output limit signal Cl generated according to the calculation result to the inverter 33 (step S160). Meanwhile, if the SOC of the energy storage device 32 is less than (YES) min1 If the result is determined to be NO, the high-temperature region map (solid line in Figure 3) from the first map based on the State of Charge (SOC) of the energy storage device is selected as the map to be used to set the current limit value (step S170). The output power limit value of the inverter 33 is calculated based on the discharge current limit value of the energy storage device 32 set according to the SOC obtained from the energy storage device controller 35 by referring to the first map in the high-temperature region, and an output limit signal Cl generated according to the calculation result is output to the inverter 33 (step S180).

[0077] Thus, the vehicle body controller 40 in this embodiment first makes a first determination of which of the three temperature ranges (low temperature range, ambient temperature range, high temperature range) the temperature (temperature signal St) of the energy storage device 32 acquired from the energy storage device controller 35 falls into. Next, it determines whether the SOC (SOC signal Ss) of the energy storage device 32 acquired from the energy storage device controller 35 falls into the lower limit of the SOC usage range corresponding to the temperature range of the first determination result (SOC min3 SOC min2 SOC min1 A second determination is made to determine if the value is less than the lower limit (predetermined value). If the result of the second determination is determined to be less than the lower limit (predetermined value), the map corresponding to the temperature range of the first determination result is selected from the second map based on the voltage of the energy storage device and the output limit value of the inverter 33 is calculated. On the other hand, if the result of the second determination is determined to be greater than or equal to the lower limit, the map corresponding to the temperature range of the first determination result is selected from the first map based on the SOC of the energy storage device and the output limit value of the inverter 32 is calculated.

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

[0079] At time t0, the operator starts operating the electric excavator 1. At the start of operation, the State of Charge (SOC) of the energy storage device 32 (first stage in Figure 7) is close to the upper limit of the operating range, and the temperature of the energy storage device 32 (third stage in Figure 7) is in the low temperature range. The energy storage device controller 35 outputs a low temperature range temperature signal St (fourth stage in Figure 7) to the vehicle controller 40 according to the temperature of the energy storage device 32. When the vehicle controller 40 receives the low temperature range temperature signal St, it sets the current limit value Is (seventh stage in Figure 7) based on the low temperature range map (solid line in Figure 3) of the first map based on the SOC. That is, when the SOC of the energy storage device 32 is greater than or equal to the lower limit (predetermined value) of the operating range of the temperature range corresponding to the temperature of the energy storage device 32, the first map is selected, and the second map is disabled. The inverter 33's output is limited based on the current limit value Is set using the first map of the low temperature range (ninth stage in Figure 7).

[0080] From time t1 onward, the state of charge (SOC) of the energy storage device 32 will reach a predetermined value due to continued operation by the operator. d3 When the SOC falls below the threshold (see the horizontal axis in Figure 3), the current limit value Is is set to change linearly in accordance with the decrease in SOC, based on the first map in the low-temperature range (the dashed line in Figure 3). As a result, the output of the inverter 33 is limited to correspond to the current limit value Is, which changes in a derating manner.

[0081] At time t2, if the temperature of the energy storage device 32 rises due to continued operation by the operator and moves from the low temperature range to the ambient temperature range, the energy storage device controller 35 outputs an ambient temperature signal St. When the vehicle body controller 40 receives the ambient temperature signal St, it changes from the low temperature map (dotted line in Figure 3) to the ambient temperature map (dashed line in Figure 3) among the first maps and sets the current limit value Is. That is, the first map of the temperature range selected according to the temperature of the energy storage device 32 is used to set the current limit value Is. The output of the inverter 33 is limited according to the current limit value Is set using the first map of the ambient temperature range. As shown in Figure 3, the current limit value Is defined in the first map is higher in the ambient temperature range than in the low temperature range for the same SOC. Therefore, the output limit of the inverter 33 is relaxed when changing from the first map of the low temperature range to the first map of the ambient temperature range.

[0082] At time t3, due to continued operation by the operator, the State of Charge (SOC) of the energy storage device 32 reaches the lower limit of the operating range in the normal temperature range. min2 When the current falls below (see the horizontal axis in Figure 3), the vehicle controller 40 disables the first map for the ambient temperature range and uses the ambient temperature map (Figure 4B) of the second map based on the voltage of the energy storage device to set the current limit value Iv med (The 8th row in Figure 7) is set. That is, when the State of Charge (SOC) of the energy storage device 32 falls below the lower limit of the operating range of the temperature range corresponding to the temperature of the energy storage device 32, the map used to set the current limit value is switched from the first map based on SOC to the second map based on voltage. The output of the inverter 33 is set to the current limit value Iv set using the second map for the normal temperature range. med It is restricted accordingly.

[0083] At time t4, if the temperature of the energy storage device 32 rises further due to continued operation by the operator and moves from the ambient temperature range to the high temperature range, the energy storage device controller 35 outputs a high temperature signal St. When the vehicle body controller 40 receives the high temperature signal St, it changes from the ambient temperature map (Figure 4B) to the high temperature map (Figure 4A) of the second map and sets the current limit value Iv highThis is set. In other words, the second map of the temperature range selected according to the temperature of the energy storage device 32 is used to set the current limit value Is. The output of the inverter 33 is set using the current limit value Iv set using the second map of the high temperature range. high It is restricted accordingly.

[0084] Generally, energy storage devices are used with a limited range of State of Charge (SOC) to avoid being used when the actual charge state (true value of SOC) is 0%. In other words, the usable range of SOC is limited to a predetermined range (e.g., 10-90%). When the SOC falls below the lower limit of the predetermined range (e.g., 10%), the discharge of the energy storage device stops. In this case, the electric construction machine equipped with the energy storage device will enter a stopped state, and depending on its stopping position, it may interfere with other construction machines. Considering this situation, it is preferable that electric construction machines can operate for a short period of time even when the SOC is below the lower limit of the normal usable range.

[0085] When operating electric construction machinery for short periods when the State of Charge (SOC) is below the lower limit of the normal operating range, it is necessary to avoid the risk of the energy storage device deteriorating significantly and malfunctioning due to the voltage of the energy storage device falling below the open-circuit voltage equivalent to SOC 0%. In this case, if the discharge current of the energy storage device is limited based on the estimated SOC, there is a concern that, due to estimation errors in SOC, the energy storage device may actually continue to be used at a voltage value below the open-circuit voltage equivalent to SOC 0%.

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

[0087] As described above, in the electric excavator 1 according to this embodiment, if the State of Charge (SOC) of the energy storage device 32 falls below the lower limit (predetermined value) of the operating range corresponding to the temperature range at that time, the vehicle controller 40 switches from the first map based on the SOC of the energy storage device to the second map based on the voltage of the energy storage device and sets the discharge current limit value of the energy storage device 32 from the voltage of the energy storage device 32 obtained from the energy storage device controller 35. As a result, even if the electric excavator 1 is operated for a short time when the SOC of the energy storage device 32 is below the lower limit of the operating range, the discharge current limit value of the energy storage device 32 is set according to the actual voltage value (detected value) of the energy storage device 32 rather than the estimated SOC, so it is possible to avoid deterioration of the energy storage device 32 due to the voltage of the energy storage device 32 falling below a predetermined voltage value (open circuit voltage equivalent to SOC 0%).

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

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

[0090] If the current limit is set using the voltage-based second map instead of the SOC-based first map, the following drawbacks occur: The voltage value of the energy storage device 32 tends to fluctuate more rapidly instantaneously than the SOC (the horizontal axis values ​​in Figures 4A to 4C fluctuate more than the horizontal axis values ​​in Figure 3), so large fluctuations in the current limit (vertical axis values ​​in Figures 4A to 4C) are likely to occur. As a result, even though there is actually a sufficient charge, the voltage value of the energy storage device 32 instantaneously approaches voltage X0, causing the current limit Iv to fluctuate. med The rapid increase and decrease in this force repeatedly causes the drive limit of the electric excavator 1 to be restricted, worsening the operability of the electric excavator 1.

[0091] On the other hand, in the configuration of the electric excavator 1 according to this embodiment, only in an emergency situation where the SOC is low, below the lower limit of the operating range, i.e., when the battery is about to run out, is it possible to change the posture of the work device 4 and travel without interfering with other machines, even if it means allowing a deterioration in operability. In other words, when the electric excavator 1 is not in an emergency situation where the battery is about to run out, even if it performs an operation with large voltage fluctuations, it is possible to avoid deterioration in operability due to sudden fluctuations in the current limit value caused by the use of the voltage-based second map. As a result, the operator can operate it for a long time without compromising operability. Furthermore, since the electric excavator 1 can be operated even in an emergency situation where the battery is about to run out, it is expected that this will lead to ensuring safety for other construction machines and avoiding a decrease in work efficiency. In addition, unless it is an operation that involves a high load such as excavation work, the fluctuation of the voltage value is relatively suppressed, so the increase or decrease in the current limit value is small, and the deterioration in operability is minimized.

[0092] As described above, the electric excavator 1 (electric construction machine) according to one embodiment comprises an electric motor 31 as a drive source, a power storage device 32 which is a power source for the electric motor 31, an inverter 33 which adjusts the power supplied from the power storage device 32 to the electric motor 31, a power storage device controller 35 (state detection device) which detects the internal state of the power storage device 32, including the state of charge (SOC) and voltage of the power storage device 32, and a vehicle controller 40 (control device) which 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 body controller 40 (control device) is configured to set the above-mentioned limit value according to the SOC (charge state) of the energy storage device 32 obtained from the energy storage device controller 35 (state detection device) if the SOC (charge state) of the energy storage device 32 obtained from the energy storage device controller 35 (state detection device) is above a predetermined value, and to set the above-mentioned limit value according to the voltage of the energy storage device 32 obtained from the energy storage device controller 35 (state detection device) if the SOC (charge state) obtained from the energy storage device controller 35 (state detection device) is below the predetermined value.

[0093] With this configuration, when the State of Charge (SOC) of the energy storage device 32 is below a predetermined value (in a low-charge state), the limit value of the discharge current of the energy storage device 32 is set according to the actual voltage value (detected value) of the energy storage device 32, rather than the estimated SOC (charge state). This prevents the voltage of the energy storage device 32 from falling below a predetermined voltage value (a voltage value defined based on the open-circuit voltage equivalent to an SOC (charge state) of 0%). Furthermore, even when the electric excavator 1 (electric construction machine) is operated while the energy storage device 32 is in a low-charge state, the voltage of the energy storage device 32 can be prevented from falling below a predetermined voltage value, so there is no need to narrow the normal operating range of the SOC (charge state). In other words, it is possible to suppress the reduction in the working time of the electric excavator 1 (electric construction machine) while suppressing the deterioration of the energy storage device 32 due to use in a low-charge state.

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

[0095] With this configuration, the limit value of the discharge current of the energy storage device 32 is set based on the temperature of the energy storage device 32 in addition to the State of Charge (SOC) or voltage of the energy storage device 32. Therefore, the limit value of the discharge current of the energy storage device 32 can be set considering the temperature dependence of the internal resistance of the energy storage device 32. Accordingly, the vehicle controller 40 (control device) can more accurately perform control to prevent the voltage of the energy storage device 32 from falling below a predetermined voltage value (a voltage value defined based on the open-circuit voltage equivalent to a SOC (charge state) of 0%).

[0096] Furthermore, in the electric excavator 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 energy storage device relative to the State of Charge (SOC) of the energy storage device by dividing it into a plurality of temperature ranges of the energy storage device, and a plurality of second maps (second characteristic information) that define the limit value of the discharge current of the energy storage device relative to the voltage of the energy storage device by dividing it into the plurality of temperature ranges of the energy storage device. Furthermore, the vehicle body controller 40 (control device) determines which of the above-mentioned temperature ranges the temperature obtained from the energy storage device controller 35 (state detection device) falls into. If the SOC (charge state) obtained from the energy storage device controller 35 (state detection device) is equal to or greater than the predetermined value, the vehicle body controller 40 sets the above-mentioned limit value using the first map (first characteristic information) corresponding to the determined temperature range from among the multiple first maps (first characteristic information). If the SOC (charge state) obtained from the energy storage device controller 35 (state detection device) is below the predetermined value, the vehicle body controller 40 sets the above-mentioned limit value using the second map (second characteristic information) corresponding to the determined temperature range from among the multiple second maps (second characteristic information). The predetermined value is set based on the lower limit of the usable range of the energy storage device's SOC (charge state) as defined in the first map (first characteristic information) corresponding to the determined temperature range from among the multiple first maps (first characteristic information).

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

[0098] Furthermore, by setting the predetermined value described above, which functions as a threshold for switching between the first map (first characteristic information) and the second map (second characteristic information), based on the lower limit of the usable range of the State of Charge (SOC) of the energy storage device specified in the first map (first characteristic information) corresponding to the temperature range of the judgment result, the predetermined value described above can be set to a different value depending on the temperature range of the energy storage device 32. This makes it possible to set the usable range of the SOC (charge state) as wide as possible according to the temperature range of the energy storage device 32, while avoiding the voltage of the energy storage device 32 falling below a predetermined voltage value (a voltage value specified based on the open-circuit voltage equivalent to an SOC (charge state) of 0%).

[0099] Furthermore, in the electric excavator 1 (electric construction machine) according to this embodiment, a first temperature range (low temperature range) in which multiple temperature ranges indicate temperatures within a predetermined range, and a second temperature range (high temperature range) which is a temperature range higher than the first temperature range. In addition, the first characteristic information corresponding to the second temperature range (high temperature range) is defined so that the lower limit of the usable range of the charge state of the energy storage device 32 is lower than that of the first characteristic information corresponding to the first temperature range (low temperature range).

[0100] With this configuration, the higher the temperature of the energy storage device 32, the lower the risk that the voltage of the energy storage device 32 will fall below a predetermined value (open-circuit voltage equivalent to SOC 0%). Therefore, it becomes possible to expand the usable range of SOC in the second temperature range (high temperature range) compared to the usable range of SOC in the first temperature range (low temperature range).

[0101] Furthermore, in the electric excavator 1 (electric construction machine) according to this embodiment, multiple temperature ranges include a first temperature range (low temperature range) where temperatures are within a predetermined range, and a second temperature range (high temperature range) where temperatures are higher than the first temperature range. In addition, the second characteristic information corresponding to the second temperature range (high temperature range) is defined such that, when the voltage of the energy storage device 32 is the same, the limit value of the discharge current of the energy storage device 32 is higher than that of the second characteristic information corresponding to the first temperature range (low temperature range).

[0102] With this configuration, the higher the temperature of the energy storage device 32, the lower the risk of the voltage of the energy storage device 32 falling below a predetermined value (open-circuit voltage equivalent to SOC 0%). Therefore, it is possible to increase the discharge current limit when the temperature of the energy storage device 32 is high. As a result, when the temperature of the energy storage device 32 is high, the drive limit of the electric excavator 1 is relaxed, and deterioration of the operability of the electric excavator 1 is suppressed.

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

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

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

[0106] With this configuration, the limit value of the discharge current of the energy storage device 32 is calculated based on the relationship between the voltage, current, and internal resistance of the energy storage device 32, so it is possible to reliably avoid the voltage of the energy storage device 32 falling below a predetermined voltage value (a voltage value defined based on the open-circuit voltage equivalent to SOC 0%). In addition, since the temperature-dependent internal resistance value is determined according to the actual temperature, the vehicle controller 40 (control device) can more accurately perform control to avoid the voltage of the energy storage device 32 falling below a predetermined voltage value (a voltage value defined based on the open-circuit voltage equivalent to SOC (charge state) 0%).

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

[0108] With this configuration, the predetermined value described above, which functions as a threshold for switching between the State of Charge (SOC), which is the internal state of the energy storage device used when setting the limit value of the discharge current of the energy storage device 32, and the voltage, is set based on the estimation error of the SOC (charge state) obtained from the energy storage device controller 35 (state detection device). Therefore, there is no need to narrow the normal operating range of the SOC (charge state).

[0109] [Other embodiments] In the embodiments described above, an example of applying the present invention to an electric excavator 1 was shown. However, the present invention can be broadly applied to various types of electric construction machinery, such as electric hydraulic cranes.

[0110] Furthermore, the present invention is not limited to the embodiments described above, and various modifications are included. The embodiments described above are explained in detail for the purpose of clearly illustrating the present invention, and are not necessarily limited to those having all the configurations described. It is also possible to add, delete, or replace some of the configurations of these embodiments with other configurations.

[0111] For example, in this embodiment, as the first and second characteristic information used to set the limit value of the discharge current of the energy storage device 32, an example was shown in which the temperature of the energy storage device 32 is divided into three temperature ranges: a high temperature range, a normal temperature range, and a low temperature range, and a first map and a second map corresponding to the three temperature ranges are used. However, it is also possible to configure the first and second characteristic information to divide the temperature of the energy storage device 32 into four or more temperature ranges and use a first map and a second map corresponding to four or more temperature ranges. Furthermore, it is also possible to configure the first and second characteristic information to not divide the temperature of the energy storage device 32 and to use a first map and a second map without temperature range divisions.

[0112] Furthermore, in this embodiment, an example was shown in which the vehicle body controller 40 sets a limit value for the discharge current of the energy 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 energy storage device 32. However, it is also possible to configure the vehicle body controller to directly calculate the 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 the limit value for the output current of the inverter with respect to the State of Charge (SOC) of the energy storage device, and the second map (second characteristic information) defines the limit value for the output current of the inverter with respect to the voltage of the energy storage device. For example, if the power supplied from the energy storage device 32 to the electric motor 31 is sufficiently greater than the power supplied from the energy storage device 32 to other electrical equipment of the electric shovel 1, the output current of the inverter 33 can be considered as the discharge current of the energy storage device 32. [Explanation of Symbols]

[0113] 1…Electric excavator (electric construction machine), 31…Electric motor, 32…Energy storage device, 33…Inverter, 35…Energy storage device controller (status detection device), 40…Vehicle controller (control device)

Claims

1. An electric motor as a power source, The power storage device is the power source for the aforementioned electric motor, An inverter that adjusts the power supplied from the energy storage device to the electric motor, A state detection device for detecting the internal state of the energy storage device, including the charge state and voltage of the energy storage device, An electric construction machine comprising a control device that sets a limit value for the discharge current of the energy storage device and limits the output power of the inverter based on the set limit value, The control device is If the charge state of the energy storage device obtained from the state detection device is greater than or equal to a predetermined value, the limit value is set according to the charge state obtained from the state detection device. If the charge state obtained from the state detection device is less than the predetermined value, the limit value is set according to the voltage of the energy storage device obtained from the state detection device. An electric construction machine characterized by the following features.

2. In the electric construction machine according to claim 1, The state detection device is configured to detect the temperature of the energy storage device as an internal state of the energy storage device. The control device is If the charge state obtained from the state detection device is greater than or equal to the predetermined value, the limit value is set according to the temperature of the energy storage device obtained from the state detection device in addition to the charge state. If the charge state obtained from the state detection device is less than the predetermined value, the limit value is set according to the temperature obtained from the state detection device in addition to the voltage obtained from the state detection device. An electric construction machine characterized by the following features.

3. In 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 charge state of the energy storage device by dividing it into a plurality of temperature ranges of the energy storage device, and a plurality of second characteristic information that defines the limit value for the voltage of the energy storage device by dividing it into the plurality of temperature ranges. The control device is The system determines which of the multiple temperature ranges the temperature obtained from the state detection device corresponds to. If the charge state obtained from the state detection device is greater than or equal to the predetermined value, the limit value is set using the first characteristic information corresponding to the determined temperature range from among the plurality of first characteristic information. If the charge state obtained from the state detection device is less than the predetermined value, the limit value is set using the second characteristic information corresponding to the determined temperature range from among the plurality of second characteristic information. The predetermined value is set based on the lower limit of the usable range of the charge state of the energy storage device, which is defined in the first characteristic information corresponding to the temperature range determined among the plurality of first characteristic information. An electric construction machine characterized by the following features.

4. In the electric construction machine according to claim 3, The plurality of temperature ranges include a first temperature range that represents 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 defined such that the lower limit of the usable range of the charge state of the energy storage device is lower than that of the first characteristic information corresponding to the first temperature range. An electric construction machine characterized by the following features.

5. In the electric construction machine according to claim 3, The plurality of temperature ranges include a first temperature range that represents 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 such that, when the voltage of the energy storage device is the same, the limit value of the discharge current of the energy storage device is higher than that of the second characteristic information corresponding to the first temperature range. An electric construction machine characterized by the following features.

6. In the electric construction machine according to claim 1, The control device is configured to set the limit value as the difference obtained by subtracting a predetermined voltage value from the voltage obtained from the state detection device, divided by the internal resistance value of the energy storage device, if the charge state obtained from the state detection device is less than the predetermined value. An electric construction machine characterized by the following features.

7. In the electric construction machine according to claim 2, The control device is configured such that, if the charge state obtained from the state detection device is less than the predetermined value, it sets the limit value as the difference obtained by subtracting a predetermined voltage value from the voltage obtained from the state detection device and dividing that difference by the internal resistance value of the energy storage device. The internal resistance value is determined based on the temperature obtained from the state detection device. An electric construction machine characterized by the following features.

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

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