Construction machinery

Abstract

To provide a construction machine which appropriately controls charging rate of a power storage device to suppress deterioration of the power storage device.SOLUTION: In a construction machine with a work device driven by pressure oil to be discharged from a hydraulic pump driven by an electric motor, it comprises: a power storage device which stores power; an external power supply device which supplies power from the outside of the construction machine; and a power converter which performs at least one of a power storage device operation for driving the electric motor by the power stored in the power storage device and an external power supply operation for driving the electric motor by the power to be supplied via the external power supply device, drives the electric motor by the power storage device operation or the external power supply operation when charging rate of the power storage device is a preset value or more, and drives the electric motor only by the external power supply operation when the charging rate of the power storage device is the preset value or less in a state in which supply of external power by the external power supply device is allowed.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a construction machine. [Background technology]

[0002] In recent years, there have been calls for global-scale measures to combat natural disasters such as rising sea levels and abnormal weather caused by global warming, which is caused by carbon dioxide emitted by human production activities.

[0003] As one of the countermeasures, efforts are being made rapidly to reduce carbon dioxide emissions and curb global warming by replacing internal combustion engines, which obtain power by burning fossil fuels, with electric motors that are powered by electricity.

[0004] There is also a need to move away from internal combustion engines in construction machinery such as crawler excavators and wheel loaders, and as a measure to achieve this, construction machinery products equipped with electric motors as their power source have been introduced to the market.

[0005] In conventional construction machinery, a hydraulic pump is driven by power generated by burning fuel in an engine, and the hydraulic oil discharged from the hydraulic pump is distributed by a control valve to each hydraulic device to drive it, thereby realizing vehicle movement. Electric construction machinery is one in which the engine that drives the hydraulic pump or each hydraulic device itself is replaced with an electrically driven electric motor or electric actuator, etc.

[0006] Known types of electric construction machinery include those that operate using electricity stored in onboard batteries that have been charged in advance, those that operate while being powered by a cable from a power source installed in the facility, and those that are compatible with both operating methods.

[0007] For example, Patent Document 1 discloses a power supply system having a power supply controller connected to an AC power supply and supplying AC power from the AC power supply, a battery that outputs DC power, an AC-DC conversion unit that converts AC power to DC power, and an inverter unit that converts DC power to AC power of an arbitrary frequency, the AC-DC conversion unit and the inverter unit being connected in series and supplying the AC power converted by the inverter unit to an AC motor, a power supply switching device that can select either connecting the power supply controller to the AC-DC conversion unit or connecting the battery to the inverter unit, and a system controller that controls the power supply switching device. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-228715 Summary of the Invention [Problem to be solved by the invention]

[0009] Meanwhile, while automobiles are used for moving and transporting goods from one destination to another, construction machinery is used for tasks such as excavating and shaping soil and demolishing structures, and is often used without moving or only within a limited area. Furthermore, since there are many environments where it is easy to install power supply equipment, such as in tunnel construction and indoor work at demolition plants, a certain percentage of vehicles are in operation that are powered by a power supply cable from an external power supply facility. However, except when the operating location is fixed to a specific location, many vehicles are designed to be both powered by an external power supply cable and powered by a power storage device, taking into account their versatility so that they can operate in any work environment.

[0010] Today, lithium-ion batteries are widely used in a variety of applications, from portable electronic devices to mobile devices and large plants such as power facilities, due to their high volumetric density in terms of energy output and energy capacity, and the absence of the memory effect caused by repeated charging seen in lead-acid batteries and nickel-metal hydride batteries. They are also beginning to be used as energy storage devices in construction machinery. However, lithium-ion batteries are also subject to degradation, such as a decrease in charge / discharge capacity and a decrease in output due to an increase in the battery's internal resistance, so it is important to operate and store them in a way that prevents this degradation from progressing.

[0011] Generally, lithium-ion batteries are known to have two types of degradation: cycle degradation, which increases with the number of charge / discharge cycles, and storage degradation, which increases over time even if the battery is left unused without charging or discharging. The higher the battery temperature, the greater the degree of degradation. Storage degradation, however, is characterized by the fact that the higher the SOC, the greater the degree of degradation. To efficiently operate lithium-ion batteries, it is important to find ways to reduce degradation.

[0012] Regarding the installation of power storage devices, the mainstream for electric vehicles and hybrid vehicles is to install them in the frame space under the vehicle seats. This limits the effects of the vehicle's outside temperature and radiant heat from onboard equipment such as the engine, and the air conditioning and heating in the passenger compartment can be used to cool and heat the power storage device as needed, making it an excellent thermal environment for the power storage device. In contrast, construction machinery typically installs power storage devices inside or outside the upper rotating body rather than inside the cab where the operator is located. This means that the power storage device is exposed to sunlight, outside air, and radiant heat from onboard equipment such as the engine inside the rotating body, creating a poor thermal environment for the power storage device, a major difference.

[0013] In terms of operation, the way construction machinery is used and its operating conditions vary greatly depending on the location and purpose for which it is deployed, and construction periods are often long, ranging from several months to several years, so it is not uncommon for machinery to be used in the same way in the same location (environment) for long periods of time.

[0014] In such a characteristic use of construction machinery, in a conventional construction machinery that is compatible with both external power feeding operation and power storage device operation, when the external power feeding is in operation, the power storage device is electrically disconnected to stop the vehicle and then left installed in the vehicle. Therefore, in a conventional vehicle, when the external power feeding is in operation, the storage battery state at the time the power storage device was electrically disconnected is maintained, and if the storage battery's charge rate at that time is high, that state is maintained while the external power feeding is in operation.

[0015] As mentioned above, the storage deterioration of lithium-ion batteries tends to increase as the charge rate increases, so the higher the charge rate of a lithium-ion battery, the more rapidly the storage deterioration of the lithium-ion battery will progress even if it is not in use.

[0016] Although lithium-ion batteries have become commonplace, replacement costs are high. Therefore, if degraded lithium-ion batteries are continued to be used without replacement, the battery operating time will be shortened, output will be reduced, and the convenience of construction machinery vehicles will be reduced.

[0017] The present invention has been made in view of the above, and has an object to provide a construction machine that can appropriately control the charging rate of a power storage device to suppress deterioration of the power storage device. [Means for solving the problem]

[0018] The present application includes multiple means for solving the above-mentioned problems, and one example thereof is a construction machine having a hydraulic pump driven by an electric motor and a work implement driven by pressurized oil discharged from the hydraulic pump, the construction machine being equipped with a power storage device that stores electric power, an external power supply device that supplies electric power from outside the construction machine, a power converter that performs at least one of power storage device operation to drive the electric motor with electric power stored in the power storage device and external power supply operation to drive the electric motor with electric power supplied via the external power supply device, and a controller, wherein, in a state where external electric power can be supplied from the external power supply device, when the charge rate of the power storage device is equal to or higher than a preset value, the controller drives the electric motor by operating the power storage device or the external power supply operation, and when the charge rate of the power storage device is lower than the preset value, the controller drives the electric motor only by operating the external power supply operation. [Effects of the Invention]

[0019] According to the present invention, the charging rate of the power storage device can be appropriately controlled to suppress deterioration of the power storage device. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a side view schematically illustrating the appearance of an electric crawler excavator, which is an example of a construction machine. [Figure 2] FIG. 2 is a diagram illustrating a configuration related to power supply of the electric crawler excavator, extracted from the diagram and showing related configurations. [Figure 3] FIG. 1 is a diagram schematically illustrating a configuration of a power storage device. [Figure 4] 10 is a flowchart showing the processing contents of mode determination of the power storage device. [Figure 5] 10 is a diagram showing a time chart of operation mode switching control, illustrating a case where the state of charge (SOC) of the power storage device is higher than the SOC reduction determination threshold value. FIG. [Figure 6] 10 is a diagram showing a time chart of operation mode switching control, illustrating a case where the state of charge (SOC) of the power storage device is lower than the SOC reduction determination threshold value. FIG. [Figure 7] 5 is a flowchart showing the processing contents of the power storage device maintenance when the external power feeding in FIG. 4 is in operation. [Figure 8] 10 is a time chart of the power storage device maintenance control when external power feeding is in operation. DETAILED DESCRIPTION OF THE INVENTION

[0021] An embodiment of the present invention will be described below with reference to the drawings. In this embodiment, an electric crawler excavator will be described as an example of a construction machine, but the present invention can also be applied to other electric construction machines such as an electric wheel loader.

[0022] FIG. 1 is a side view that schematically shows the appearance of an electric crawler excavator, which is an example of a construction machine according to this embodiment.

[0023] In FIG. 1, the electric crawler excavator 100 (construction machinery) is composed of a self-propelled crawler-type lower running body 109, a slewing device 10 provided on the lower running body 109, an upper rotating body 110 mounted on the lower running body 109 so as to be able to rotate via the slewing device 10, and a multi-jointed working device 100A provided in front of the upper rotating body 110 and used for excavation work, etc.

[0024] The working device 100A is made up of a boom 111, an arm 112, and a bucket 113 as a working implement, which are connected to each other by a pin, and a boom cylinder 11, an arm cylinder 12, and a bucket cylinder 13 as a working implement actuator, which drive these.

[0025] Furthermore, a connector 2 is provided on the upper rear side of the upper revolving body 110 to connect a power cable that supplies power to the electric crawler excavator 100 from a commercial power source 1 (described later).

[0026] FIG. 2 is a diagram that schematically illustrates the configuration related to the power supply of the electric crawler excavator, along with related configurations.

[0027] In FIG. 2, the electric crawler excavator 100 includes a hydraulic pump 6 that is driven by the mechanical power of an electric motor 5, sucks in hydraulic oil stored in a hydraulic oil tank 8, and discharges it at a predetermined pressure; a traveling hydraulic motor 9, a swing device 10, a boom cylinder 11, an arm cylinder 12, and a bucket cylinder 13 that are hydraulic actuators driven by the pressure oil discharged from the hydraulic pump 6; a hydraulic control valve 7 that distributes the hydraulic oil discharged from the hydraulic pump 6 to the hydraulic devices (hydraulic actuators 9 to 13); a connector 2 that is detachably provided with a harness connected to a commercial power source 1 that is an external power source for the electric crawler excavator 100, and that connects to the commercial power source 1 to supply power from outside the electric crawler excavator 100; an AC / DC converter 3 that converts AC power supplied from the commercial power source 1 via the connector 2 into DC power; and a charging relay 111 that converts the DC power supplied via the AC / DC converter 3 into a charging relay 121. The external power supply includes a charger 14 that charges the power storage device 17 via a connector 15, an inverter 4 (power converter) that converts DC power supplied from the AC / DC converter 3 or DC power supplied from the power storage device 17 via a discharge relay 16 into AC power to drive the electric motor 5, or converts AC power generated by the electric motor 5 into DC power to charge the power storage device 17 via the discharge relay 16, a main controller 20 that controls the AC / DC converter 3, the inverter 4, the hydraulic control valve 7, the charger 14, the charge relay 15, the discharge relay 16, a cooling device (cooling fan) 18 that cools the power storage device 17, and the power storage device 17 and monitors a thermistor 19 that measures the housing temperature (ambient temperature) of the power storage device 17, and a console 20a that is an input / output device such as a switch panel, keyboard, mouse, and display that inputs and outputs (displays) various information and settings to the main controller 20. Here, the connector 2 and the AC / DC converter 3 constitute an external power supply device.

[0028] In the main controller 20, an operator or the like sets, via the console 20a, a power supply mode that specifies, for example, the source of power supply to the electric crawler excavator 100. The power supply mode includes an external power feeding operation that instructs the electric motor 5 to be driven mainly by power supplied from the commercial power source 1 via the connector 2 and the AC / DC converter 3 (external power supply device), and this driving by external power feeding can be set to enabled (ON) or disabled (OFF). Note that when the external power feeding operation is disabled (OFF), power storage device operation is set that instructs the electric motor 5 to be driven mainly by power stored in the power storage device 17. Furthermore, the setting of the external power feeding operation may be performed by providing a setting switch on the console 20a of the vehicle driver's seat, and the state of the switch may be observed when the vehicle is started to determine whether the external power feeding operation is set.

[0029] FIG. 3 is a diagram schematically illustrating the configuration of the power storage device.

[0030] In FIG. 3 , the power storage device 17 is configured with a lithium-ion secondary battery 30 composed of a plurality of lithium-ion batteries (battery cells) connected in series and in parallel, a current sensor 31 that measures the charge and discharge current of the lithium-ion secondary battery 30, a battery controller (BCU) 32 that determines, estimates, and controls the state of the lithium-ion secondary battery 30 based on the voltage and temperature of the lithium-ion secondary battery 30 and the current value measured by the current sensor 31, a relay 33 that is connected to the positive electrode side of the charging relay 15 and the discharging relay 16 and performs connection and disconnection between the positive electrode of the lithium-ion secondary battery 30 and the positive electrode on the DC side of the inverter 4, and a relay 34 that is connected to the negative electrode side of the charging relay 15 and the discharging relay 16 and performs connection and disconnection between the negative electrode of the lithium-ion secondary battery 30 and the negative electrode on the DC side of the inverter 4.

[0031] The operation of the present embodiment configured as above will now be described.

[0032] FIG. 4 is a flowchart showing the processing for determining the mode of the power storage device.

[0033] As shown in FIG. 4, when the starter (start key) of the electric crawler excavator 100 is turned on (KEY-ON), first, the main controller 20 is put into a start-up state (step S100).

[0034] Next, the battery controller (BCU) 32 receives a start signal from the main controller 20 and starts up, starting the power storage device 17 (step S110), and performs a fault diagnosis, measures the open circuit voltage (OCV) of the installed battery, and determines whether cell balancing should be performed based on the measured open circuit voltage (OCV).At this time, if the cell balancing execution determination determines that cell balancing should be performed, cell balancing begins.

[0035] Here, cell balancing is a process for keeping the voltages of multiple battery cells mounted on the power storage device 17 within a certain voltage range and making the state and performance of each battery cell uniform. In this embodiment, the battery cell with the lowest voltage is used as the reference, and resistances are connected to battery cells with higher voltages, and the discharge time is controlled according to the voltage difference with the lowest voltage battery cell, thereby adjusting the voltage variation of each battery cell to within a certain voltage difference.

[0036] The decision to perform cell balancing can be made in two cases: when the function is already implemented in the battery controller (BCU) 32 installed in the power storage device 17, or when the function is implemented separately; however, in this embodiment, it is assumed that the battery controller (BCU) 32 is already equipped with a cell balancing implementation decision function and a cell balancing function.

[0037] After the process of step S110 is completed, it is then determined whether or not the power supply cable is connected (step S120). The determination of whether or not the power supply cable is connected is made by the main controller 20 based on the state of the connector 2.

[0038] Here, the determination method will be explained. First, terminals for determining connection (for example, terminal a, terminal b) are provided on each of the socket on the electric crawler excavator 100 side (vehicle side) of the connector 2 and the plug on the commercial power source 1 side (power supply cable side). When the connector 2 is in a connected state (i.e., when the plug is connected to the socket), terminal a of the socket and terminal a of the plug are connected and conductive, and terminal b of the socket and terminal b of the plug are connected and conductive.

[0039] Here, terminals a and b of the plug of connector 2 are connected by wiring to establish electrical continuity, and an arbitrary voltage is applied to terminal a provided on the socket of connector 2, and terminal b is connected to the input terminal of the main controller. When a plug is connected to the socket in this state, the arbitrary voltage applied to terminal a of the socket is input to main controller 20 via terminals a and b of the plug and terminal b of the socket, and the connection of the power supply cable is detected. If a plug is not connected to the socket, terminal b of the socket remains open, and no voltage is input to main controller 20, detecting that the power supply cable is not connected.

[0040] In this embodiment, the main controller 20 determines whether the power supply cable is connected or not. However, the AC / DC converter 3 may make the determination, and the main controller 20 may receive the resulting information to determine whether the power supply cable is connected or not and manage the state transition.

[0041] If the determination result in step S120 is NO, that is, if it is determined that the power supply cable is not connected, the vehicle is operated with the power storage device in operation (step S121), and the process ends.

[0042] If the determination result in step S120 is YES, that is, if it is determined that the power supply cable is connected, it is then determined whether or not external power supply operation is set (step S130).

[0043] If the determination result in step S130 is NO, i.e., if the external power supply operation is disabled (OFF), charging of the power storage device 17 is performed (step S131), and the process ends. Charging of the power storage device 17 ends when the voltage of at least one of the multiple battery cells constituting the power storage device 17 reaches a preset battery cell charging end threshold (voltage V2). Here, the charging rate may be calculated from the threshold voltage at which charging ends, and compared with the charging rate of the battery cell with the highest voltage to determine whether charging should end.

[0044] If the determination result in step S130 is YES, that is, if the setting of external power feeding operation is enabled (ON), it is then determined whether or not long-term external power feeding operation is set (step S140).

[0045] The long-term external power supply operation setting is set to enabled (ON) when vehicle operation with external power supply operation for a long period of time is planned. In this way, when there is no long-term external power supply, that is, when operation with the power storage device in operation is planned from the next day, for example, and it is not desired to lower the charge rate of the power storage device 17 in order to save on charging time, by setting the long-term external power supply operation setting to ON, the vehicle can be operated with the power storage device in operation without performing operation (discharging) to lower the charge rate of the power storage device 17. Note that, like the setting of the external power supply operation, this long-term external power supply operation setting can be set by inputting settings into the console 20a or operating a dedicated switch, and the main controller 20 can determine whether or not long-term external power supply operation is set from these setting states.

[0046] If the determination result in step S140 is YES, it is then determined whether the state of charge (SOC) of the power storage device 17, which is calculated from the average voltage of all battery cells of the power storage device 17, is equal to or greater than a preset SOC reduction determination threshold V1 (step S150).

[0047] If the determination result in step S150 is YES, the vehicle is then started to operate by operating the power storage device (step S160).

[0048] Next, it is determined whether or not the state of charge SOC of the power storage device 17 is smaller than the SOC reduction determination threshold V1 (step S170). If the determination result in step S170 is NO, the process returns to step S160.

[0049] Furthermore, if the determination result in step S170 is YES, the power storage device 17 is stopped to stop power supply to the electric crawler excavator 100 (step S180), the vehicle starts to move with external power supply operating (step S190), and the process ends.

[0050] If the determination results in steps S140 and S150 are NO, the process proceeds to step S180.

[0051] Here, the processing of steps S150 to S190 indicated by the dashed lines in FIG. 4 is referred to as operation mode switching control.

[0052] When the processing of steps S121, S131, and S190 is completed and the vehicle key is turned off, the maintenance control ends and the vehicle is stopped.

[0053] 5 and 6 are diagrams showing time charts of the operation mode switching control.

[0054] 5 and 6 show the transition of the state of each device from the vehicle KEY-ON, the comparison and determination of the charge rate of the power storage device, and the transition of the vehicle operation mode according to the result over time.

[0055] FIG. 5 is a time chart showing a case where the state of charge SOC of the power storage device 17 is higher than the SOC reduction determination threshold V1.

[0056] When the vehicle key is turned ON, the main controller 20 starts up (ON), and the power storage device starts up (ON) in response to a start signal from the main controller 20. This causes a fault diagnosis of the power storage device 17, an OCV measurement (SOC estimation), and a cell balancing implementation determination. The states of the power supply cable connection, the external power feeding operation setting, and the long-term external power feeding operation setting are then determined. If all of the determination results are "Yes," the charging rate of the power storage device (power storage device SOC) is compared with a preset SOC reduction determination threshold V1. Since the power storage device SOC is higher than the SOC reduction determination threshold V1, the vehicle operation mode is transitioned to power storage device operation, and the vehicle is operated using power supplied from the power storage device 17. If the charging rate of the power storage device 17 (power storage device SOC) subsequently drops below the SOC reduction determination threshold V1 as a result of the vehicle being operated, the vehicle operation mode is transitioned to external power feeding operation, and the vehicle is operated using power supplied from the external power feeding device. The state transitions of the vehicle operation mode are shown in chronological order.

[0057] FIG. 6 is a time chart showing a case where the state of charge SOC of the power storage device 17 is lower than the SOC reduction determination threshold V1.

[0058] The transition is the same as in Figure 5 up to the comparison of the charging rate of the storage device 17 (storage device SOC) with the preset SOC reduction judgment threshold V1, and since the storage device SOC is lower than the SOC reduction judgment threshold V1, the vehicle operation mode is set to external power supply operation, and the state transition of the vehicle operation mode in which the vehicle is operated by external power supply is shown in chronological order.

[0059] FIG. 7 is a flowchart showing the processing contents of the power storage device maintenance when the external power feeding is in operation in FIG.

[0060] As shown in Fig. 7, when maintenance of the power storage device is started while the external power supply is operating (see step S190 in Fig. 4), it is first determined whether or not an arbitrarily set time (e.g., 24 hours) has elapsed since the vehicle key was turned on or the previous determination in step S200 (step S200). The purpose of the set time here is to accurately measure the open circuit voltage (OCV) of the battery cells. A necessary condition is that the battery be in a rest state (power storage device stopped state) required to eliminate polarization or an increase in internal resistance within the battery caused by charging and discharging, and this is determined based on the characteristics of the battery cells installed.

[0061] If the determination result in step S200 is NO, the process proceeds to step S260.

[0062] If the determination result in step S200 is YES, the power storage device 17 is started (step S210). At this time, in the power storage device 17, a fault diagnosis is performed, the battery open circuit voltage (OCV) is measured, and a determination is made as to whether or not cell balancing should be performed based on the measured open circuit voltage (OCV), and cell balancing is performed when the determination is made.

[0063] After the process in step S210 is completed, it is then determined whether supplementary charging is being performed (step S220).

[0064] If the determination result in step S220 is NO (supplementary charging is not being performed), it is determined whether the voltage of the lowest battery cell of power storage device 17 (hereinafter referred to as the minimum voltage) is greater than a predetermined supplementary charging start threshold V3 (step S221).

[0065] If the determination result in step S221 is YES (the minimum voltage is greater than the supplemental charging start threshold V3), the process proceeds to step S260.

[0066] If the determination result in step S221 is NO (the minimum voltage is less than or equal to the recharge start threshold value V3), recharge is started (step S222), and the process proceeds to step S260. Here, the current value during recharge may be any value as long as the charging is completed within the time set in step S200 (the next startup of the power storage device).

[0067] If the determination result in step S220 is YES (recharge is in progress), it is determined whether the minimum battery cell voltage (minimum voltage) is greater than a predetermined recharge end threshold value V4 (step S230).

[0068] If the determination result in step S230 is NO (the minimum voltage is less than or equal to the recharge end threshold value V4), recharge is continued (step S231), and the process proceeds to step S260.

[0069] If the determination result in step S230 is YES (the minimum voltage is greater than the recharge end threshold value V4), recharge is stopped (step S240), and the power storage device 17 is stopped (step S250).

[0070] Note that the magnitude relationship between the recharge start threshold value V3 and the recharge end threshold value V4 is set such that V3 < V4.

[0071] Here, in the present embodiment, charging is performed based on the minimum value of the voltage of the battery cells of the power storage device 17, but it may be configured to perform charging based on the charge rate of the power storage device.

[0072] When the process in step S250 ends, subsequently, it is determined whether the cooling device 18 is operating (ON) (step S260).

[0073] If the determination result in step S260 is NO (the cooling device 18 is stopped), it is determined whether the measured temperature around the power storage device is less than a predetermined power storage device cooling start threshold value T1 (step S261).

[0074] If the determination result in step S261 is YES (smaller than power storage device cooling start threshold T1), the process proceeds to step S290.

[0075] If the determination result in step S261 is NO (equal to or greater than power storage device cooling start threshold T1), cooling device 18 is operated to start cooling (step S262), and the process proceeds to step S290.

[0076] If the determination result in step S260 is YES (cooling device 18 is operating), it is then determined whether the ambient temperature of power storage device 17 is lower than a predetermined power storage device cooling end threshold T2 (step S270).

[0077] If the determination result in step S270 is NO (the ambient temperature is equal to or higher than power storage device cooling end threshold T2), cooling of power storage device 17 continues (step S271), and the process proceeds to step S290.

[0078] If the determination result in step S270 is YES (the ambient temperature is lower than the power storage device cooling end threshold T2), the cooling of power storage device 17 is ended and cooling device 18 is stopped (step S280), and the process proceeds to step S290.

[0079] The magnitude relationship between the power storage device cooling start threshold T1 and the power storage device cooling end threshold T2 is set so that T1>T2.

[0080] Here, the temperature of the storage device 17 used to determine cooling may be a measurement value monitored by a higher-level or other controller than the battery controller (BCU) in the storage device 17 (a temperature that can grasp the temperature status of the storage device, such as the temperature of the storage device's housing, the temperature inside the storage device's housing, or the temperature of a specific battery cell).

[0081] After the processes in steps S262, S271, and S280 are completed, the state of the vehicle key (start-on or stop-off) is checked to determine whether the key is in the key-off state (step S290).

[0082] If the determination result in step S290 is NO (KEY-ON state), the process returns to step S200, and the process for maintaining the power storage device is repeated.

[0083] If the determination result in step S290 is YES (key-off state), the control of external power supply operation (see step S190 in FIG. 4) ends.

[0084] Next, the operation of the power storage device maintenance control will be described.

[0085] FIG. 8 is a time chart of the maintenance control of the power storage device when the external power feeding is in operation.

[0086] In FIG. 8, when the vehicle key is turned on at time t0, the main controller 20 starts up and determines whether 24 hours have passed since the vehicle key was turned on or the previous check (see step S200 in FIG. 7).

[0087] At time t1, immediately after startup, the power storage device is started (see step S210 in FIG. 7), and then it is determined whether supplementary charging is being performed (see step S220 in FIG. 7). Since supplementary charging is not being performed here, it is next determined whether the lowest battery cell voltage of power storage device 17 is greater than supplementary charging start threshold V3 (see step S221 in FIG. 7). Here, the lowest battery cell voltage of the power storage device is lower than supplementary charging start threshold V3, so supplementary charging is started (see step S222 in FIG. 7). As a result, the lowest battery cell voltage of power storage device 17 begins to rise.

[0088] At time t2, it is determined whether the lowest battery cell voltage is greater than the supplementary charging termination threshold V4 (see step S230 in FIG. 7). Here, since the lowest battery cell voltage is greater than the supplementary charging termination threshold V4, supplementary charging is terminated (see step S240 in FIG. 7), and then the power storage device is shut down (see step S250 in FIG. 7).

[0089] At time t3, the operation status of cooling device 18 is checked (see step S260 in FIG. 7). Here, cooling device 18 is stopped, so it is then determined whether or not the ambient temperature of power storage device 17 is lower than a predetermined power storage device cooling start threshold T1 (see step S261 in FIG. 7). Here, the ambient temperature of power storage device 17 is higher than power storage device cooling start threshold T1, so the cooling device is operated (step S262 in FIG. 7). As a result, the temperature around the power storage device starts to decrease.

[0090] At time t4, it is determined whether the ambient temperature of the power storage device is lower than power storage device cooling completion threshold T2 (see step S270 in FIG. 7). Here, since the ambient temperature of power storage device 17 is lower than power storage device cooling completion threshold T2, cooling device 18 is stopped (see step S280 in FIG. 7).

[0091] In this way, when the vehicle is operated on external power supply for a long period of time, the vehicle is operated with the charge rate of the storage device at a low level, which prevents the charge rate of the storage device from being maintained at a high level during operation, and as a result, deterioration of the storage device can be reduced.

[0092] Furthermore, there are concerns that storage deterioration may increase further when construction machinery is used in hot environments such as under the blazing summer sun, indoors in the summer without air conditioning, or in high temperature environments caused by radiant heat from other onboard equipment. However, in this embodiment, when the power storage device is not in use (when external power supply is operating) and the ambient temperature around the power storage device is high (the power storage device is exposed to high temperatures), the vehicle's cooling mechanism is activated to lower the ambient temperature around the power storage device, thereby reducing the effect of temperature on storage deterioration of the power storage device.

[0093] Furthermore, if the vehicle continues to operate on external power supply for a long period of time, the power storage device will not be started during that time, and therefore it will not be possible to respond to the self-discharge of the battery cells that occurs during startup (adjusting cell voltage variations and supplementary charging to prevent over-discharge). As a result, it will be necessary to start the vehicle periodically to perform maintenance work on the power storage device, which poses problems in terms of maintainability. However, in this embodiment, when the external power supply is operating (when the power storage device is stopped), the system automatically determines whether cell balancing adjustment is necessary due to natural discharge of the power storage device battery cells, performs this adjustment, and monitors for voltage drops and supplementary charging, thereby improving maintainability and preventing the risk of the power storage device becoming unusable due to forgetting to perform this work, etc.

[0094] <Additional Notes> The present invention is not limited to the above-described embodiments, and includes various modifications and combinations within the scope of the gist thereof. Furthermore, the present invention is not limited to those including all of the configurations described in the above-described embodiments, and includes those in which some of the configurations are omitted. Furthermore, the above-described configurations, functions, etc. may be realized in part or in whole by designing them as, for example, integrated circuits. Furthermore, the above-described configurations, functions, etc. may be realized in software by a processor interpreting and executing a program that realizes each function. [Explanation of symbols]

[0095] 1...Commercial power supply, 2...Connector, 3...AC / DC converter, 4...Inverter, 5...Electric motor, 6...Hydraulic pump, 7...Hydraulic control valve, 8...Hydraulic oil tank, 9...Travel hydraulic motor, 10...Slewing device, 11...Hydraulic actuator, 11...Boom cylinder, 12...Arm cylinder, 13...Bucket cylinder, 14...Charger, 15...Charging relay, 16...Discharging relay, 17...Electric storage device, 18...Cooling device (cooling fan), 19...Thermistor, 20...Main controller, 20a...Console, 21...Current sensor, 30...Lithium-ion secondary battery, 31...Current sensor, 32...Battery controller (BCU), 33...Relay, 34...Relay, 100...Electric crawler excavator, 100A...Work device, 109...Undercarriage, 110...Uppercarriage, 111...Boom, 112...Arm, 113...Bucket

Claims

1. a hydraulic pump driven by an electric motor; In a construction machine equipped with a working device driven by pressure oil discharged from the hydraulic pump, a power storage device that stores power; an external power supply device that supplies power from outside the construction machine; a power converter that performs at least one of a power storage device operation in which the electric motor is driven by power stored in the power storage device and an external power supply operation in which the electric motor is driven by power supplied via the external power supply device; a controller; The controller In a state where the external power supply device is capable of supplying external power, When the charging rate of the power storage device is equal to or higher than a preset value, the power storage device or the external power supply is operated to drive the electric motor; When the charging rate of the power storage device is lower than a preset value, the electric motor is driven only by the external power supply operation, and a construction machine configured to charge the power storage device until the battery cell voltage of the power storage device reaches a predetermined supplementary charging termination threshold when the battery cell voltage of at least one of the plurality of battery cells constituting the power storage device drops below a predetermined supplementary charging determination threshold while the electric motor is being driven by the external power supply operation.

2. 2. The construction machine according to claim 1, a setting device that presets a drive method of the electric motor to either one of the power storage device operation and the external power supply operation; The controller When the external power supply operation is preset, if the charging rate of the power storage device is equal to or higher than a preset value, the charging rate of the power storage device is reduced to or below the preset value by driving the electric motor with the power storage device before driving the electric motor with the external power supply operation, and then the driving of the electric motor is switched to external power supply operation.

3. 2. The construction machine according to claim 1, The controller a construction machine configured to charge the power storage device until the charging rate of the power storage device becomes equal to or greater than a predetermined supplementary charging termination threshold when the charging rate of the power storage device falls below a predetermined supplementary charging determination threshold while the electric motor is being driven by the external power supply operation.

4. 2. The construction machine according to claim 1, The controller a construction machine characterized in that, when the electric motor is driven by the external power supply, if the voltage difference among the plurality of battery cells constituting the power storage device increases to or exceeds a predetermined threshold, each battery cell is discharged individually, and balancing is performed so that the voltage difference among the plurality of battery cells decreases to a voltage difference smaller than the predetermined value.

5. 2. The construction machine according to claim 1, The controller a cooling device that, when the ambient temperature, the temperature of the housing, the temperature inside the housing of the power storage device, or the temperature of the battery cells that constitute the power storage device reaches a temperature equal to or higher than a preset cooling start threshold while the electric motor is being driven by the external power supply, cools the ambient temperature, the temperature of the housing, the temperature inside the housing of the power storage device, or the temperature of the battery cells until the ambient temperature, the temperature of the housing, the temperature inside the housing of the power storage device, or the temperature of the battery cells reaches a temperature equal to or lower than a preset cooling end threshold.

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