Electric work machine

Abstract

Provided is an electric work machine with which it is possible to improve the accuracy of estimating the remaining charge time or the remaining discharge time of a secondary battery. An electric shovel is provided with a secondary battery, a battery management unit, and a vehicle control unit. The vehicle control unit predicts a change in the temperature of the secondary battery on the basis of the temperature and the charging rate of the secondary battery detected by the battery management unit, predicts a change in the current of the secondary battery on the basis of the predicted change in the temperature of the secondary battery, and controls the vehicle control unit on the basis of the predicted change in the current of the secondary battery. The remaining charge time or the remaining discharge time of the secondary battery is estimated.

Description

Technical Field

[0001] The present invention relates to an electric working machine. Background Art

[0002] An electric excavator, which is one of the electric working machines, has, for example: a secondary battery (specifically, a power storage device composed of a lithium-ion battery or a lead battery, etc.) for storing electric power; an electric motor driven by electric power supplied from the secondary battery via an inverter; a hydraulic pump driven by the electric motor; a hydraulic actuator driven by hydraulic oil from the hydraulic pump; and a charger for charging the secondary battery using electric power supplied from an external power source. In addition, it is recommended that as a configuration for assisting the driver, a controller is provided that calculates the remaining charging time when charging the secondary battery or the remaining discharging time when discharging the secondary battery (in other words, the remaining operating time when the electric excavator is operating); and a display device that displays the remaining charging time or the remaining discharging time calculated by the controller.

[0003] Patent document 1 discloses the following method, which estimates the time (remaining charging time) required to charge a secondary battery by a constant current charging method (specifically, a method of sequentially executing multiple constant current charging steps). In this estimation method, the current charging rate of the secondary battery is obtained. In addition, based on the current temperature of the secondary battery, the achievable charging rate of each constant current charging step is obtained. And, based on the current charging rate of the secondary battery and the achievable charging rate of each constant current charging step, the time required for each constant current charging step is calculated, and the remaining charging time is calculated as the sum of these times.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2020-036393 Summary of the invention

[0007] However, when the secondary battery is charged, the temperature of the secondary battery rises as the charging time passes. In the charging method of Patent Document 1, the current of the secondary battery in each constant current charging step is fixed, and the current of the secondary battery does not change according to the change in the temperature of the secondary battery. However, from the viewpoint of simultaneously suppressing the degradation of the secondary battery and shortening the charging time, it is preferred to change the current of the secondary battery according to the change in the temperature of the secondary battery. In this case, as in the estimation method of Patent Document 1, the change in the temperature of the secondary battery is not taken into account, and the remaining charging time of the secondary battery is estimated only from the current temperature of the secondary battery, and the estimation accuracy will be reduced.

[0008] When the secondary battery is discharged, the temperature of the secondary battery rises as the discharge time passes. In addition, from the viewpoint of simultaneously suppressing the degradation of the secondary battery and increasing the power of the electric motor, it is preferred that the current of the secondary battery be changed according to the change in the temperature of the secondary battery. In this case, if the remaining discharge time of the secondary battery is estimated only from the current temperature of the secondary battery without considering the change in the temperature of the secondary battery, the estimation accuracy will be reduced.

[0009] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electric working machine capable of improving the estimation accuracy of the remaining charging time or the remaining discharging time of a secondary battery.

[0010] In order to achieve the above-mentioned purpose, the electric working machine of the present invention comprises: a secondary battery; and a battery management unit for detecting at least one of the voltage and the charging rate of the secondary battery, and the temperature of the secondary battery, wherein the electric working machine has a vehicle control unit for managing the charging and discharging of the secondary battery, and the vehicle control unit predicts the change of the temperature of the secondary battery based on the temperature and the voltage or the charging rate of the secondary battery detected by the battery management unit, predicts the change of the current of the secondary battery based on the predicted change of the temperature of the secondary battery, and estimates the remaining charging time or the remaining discharging time of the secondary battery based on the predicted change of the current of the secondary battery.

[0011] Effects of the Invention

[0012] According to the present invention, it is possible to improve the estimation accuracy of the remaining charging time or the remaining discharging time of a secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a perspective view showing the structure of the electric excavator in the first embodiment of the present invention.

[0014] Figure 2 It is a block diagram showing the configuration of a battery system in the first embodiment of the present invention.

[0015] Figure 3 This is a diagram showing the relationship between the temperature and the resistance of the secondary battery in the first embodiment of the present invention.

[0016] Figure 4 It is a diagram showing the charging control characteristics in the first embodiment of the present invention.

[0017] Figure 5 This is a flowchart showing a process of estimating the remaining charging time of the secondary battery in the first embodiment of the present invention.

[0018] Fig. 6AIt is a diagram showing the transition of the temperature of the secondary battery in the first embodiment of the present invention.

[0019] Figure 6B It is a diagram showing the transition of the voltage of the secondary battery in the first embodiment of the present invention.

[0020] Figure 6C It is a diagram showing the transition of the current of the secondary battery in the first embodiment of the present invention.

[0021] Figure 7 It is a diagram for explaining the effects of the first embodiment of the present invention.

[0022] Figure 8 This is a diagram showing part of the transition of the current of the secondary battery in a modification of the present invention.

[0023] Fig. 9 This is a flowchart showing a process of estimating the remaining charging time of a secondary battery in the second embodiment of the present invention.

[0024] Fig.10 It is a diagram showing discharge control characteristics in the third embodiment of the present invention.

[0025] Fig.11 This is a flowchart showing a process of estimating the remaining discharge time of a secondary battery in the third embodiment of the present invention.

[0026] Fig.12 This is a flowchart showing a process of estimating the remaining discharge time of a secondary battery in the fourth embodiment of the present invention. DETAILED DESCRIPTION

[0027] A first embodiment of the present invention will be described with reference to the drawings, taking an electric excavator as an example as an applicable object of the present invention.

[0028] Figure 1 It is a perspective view showing the structure of the electric excavator in this embodiment.

[0029] The electric excavator of this embodiment includes a traveling body 11 capable of traveling, a swing body 12 provided on the upper side of the traveling body 11 so as to be swingable, and a working device 13 connected to the front side of the swing body 12. The traveling body 11 and the swing body 12 constitute a vehicle body. The traveling body 11 travels by the rotation of the left and right traveling motors 14, and the swing body 12 swings by the rotation of a swing motor (not shown).

[0030] The working device 13 is used for excavation and loading operations, and includes a boom 15 rotatably connected to the front of the swing body 12, an arm 16 rotatably connected to the front end of the boom 15, and a bucket 17 rotatably connected to the front end of the arm 16. The boom 15 is rotated by the extension and contraction of the boom cylinder 18, the arm 16 is rotated by the extension and contraction of the arm cylinder 19, and the bucket 17 is rotated by the extension and contraction of the bucket cylinder 20.

[0031] The revolving body 12 includes a cab 21 in which a driver can sit, and an engine room 22 formed in a portion other than the cab 21. A plurality of operating levers (not shown) that can be operated by the driver, and a display device 23 (for details, a display, etc., see the following description) that can be visually confirmed by the driver are provided in the cab 21 of the revolving body 12. Figure 2 ).

[0032] An electric motor 24 (see below) is provided in the machine room 22 of the rotary body 12. Figure 2 ), a hydraulic pump (not shown) driven by an electric motor 24, and a plurality of control valves (not shown) that work according to the operation of a plurality of operating levers and control the flow (in detail, direction and flow rate) of hydraulic oil from the hydraulic pump to a plurality of hydraulic actuators (in detail, the above-mentioned travel motor 14, swing motor, boom cylinder 18, arm cylinder 19, and bucket cylinder 20).

[0033] Furthermore, a battery system for supplying electric power to the electric motor 24 and controlling the electric motor 24 is provided in the machine room 22 of the revolving body 12 . Figure 2 It is a diagram showing the configuration of a battery system in this embodiment.

[0034] The battery system of the present embodiment includes a secondary battery (power storage device) 25 for storing electric power, an inverter 26 and a charger 27 connected to the secondary battery 25 , a battery management unit (BMU) 28 , and a vehicle control unit (VCU) 29 .

[0035] The secondary battery 25 is composed of, for example, a plurality of battery modules 30 connected in series, and each battery module 30 is composed of a plurality of battery cells 31 (specifically, lithium-ion batteries or lead batteries, etc.) connected in series.

[0036] The battery management unit 28 is a microcontroller having a processing device and a storage device. The processing device executes processing according to the program, and is a CPU (Central Processing Unit), MPU (Micro Processing Unit) or DSP (Digital Signal Processor). The storage device stores programs and data, and is a non-volatile memory such as ROM (Read Only Memory), flash memory and hard disk drive, or a volatile memory such as RAM (Random Access Memory).

[0037] The battery management unit 28 detects the state of the secondary battery 25 described later and stores its detection history. The battery management unit 28 detects the current of the battery cells constituting the secondary battery 25, that is, the current of the secondary battery 25, using the current sensor 32. The battery management unit 28 detects the temperature of the multiple battery cells constituting the secondary battery 25 using a plurality of temperature sensors (not shown), and detects the temperature of the secondary battery 25 as the average value or the minimum value of these temperatures. The battery management unit 28 detects the voltage of the multiple battery cells constituting the secondary battery 25 using a plurality of voltage sensors (not shown), and detects the voltage of the secondary battery 25 as the sum of these voltages. The battery management unit 28 detects the external air temperature using a temperature sensor (not shown).

[0038] The battery management unit 28 detects the charge rate (SOC: State Of Charge) of the secondary battery 25 based on the voltage of the secondary battery 25. To explain in detail, for example, when the battery management unit 28 is switched from off to on, the charge rate of the secondary battery 25 is obtained from the voltage of the secondary battery 25 detected as described above using a graph showing the correspondence between the voltage of the secondary battery 25 and the charge rate of the secondary battery 25. Then, the current of the secondary battery 25 detected as described above is accumulated, and the change amount of the charge rate of the secondary battery 25 is calculated based on the accumulated value, and the charge rate of the secondary battery 25 is updated.

[0039] The battery management unit 28 detects the capacity degradation rate (SOHQ: State Of Health Quantity) of the secondary battery 25. To explain in detail, for example, the difference between the previous charging rate and the current charging rate of the secondary battery 25 acquired using the graph as described above is calculated, and the current of the secondary battery 25 detected between the previous and current times is accumulated. In addition, based on the ratio between the difference in the charging rate of the secondary battery 25 and the accumulated current value, the current value of the capacity of the secondary battery 25 is calculated. In addition, the ratio between the current value of the capacity of the secondary battery 25 and the initial value is calculated to obtain the capacity degradation rate of the secondary battery 25.

[0040] The battery management unit 28 detects the resistance degradation rate (SOHR: State Of Health Resistance) of the secondary battery 25. To explain in detail, for example, the resistance is calculated from the voltage and current of the secondary battery 25 before a predetermined time has passed, and the resistance is calculated from the voltage and current of the secondary battery 25 after a predetermined time has passed, and the current value of the change in resistance of the secondary battery 25, which is the difference between these resistances, is obtained. In addition, the ratio of the current value of the change in resistance of the secondary battery 25 to the initial value is calculated to obtain the resistance degradation rate of the secondary battery 25.

[0041] The vehicle control unit 29 is a microcontroller having a processing device and a storage device. The processing device executes processing according to a program, and is a CPU, MPU, or DSP, etc. The storage device stores programs and data, and is a non-volatile memory such as a ROM, flash memory, a hard disk drive, or a volatile memory such as a RAM.

[0042] The vehicle control unit 29 outputs a command to drive the electric motor 24 (in other words, a command to discharge the secondary battery 25) to the inverter 26. In response to the command, the inverter 26 converts the DC power of the secondary battery 25 into AC power and supplies it to the electric motor 24, thereby driving the electric motor 24.

[0043] The vehicle control unit 29 outputs a command to charge the secondary battery 25 by, for example, a constant current charging method to the charger 27. The charger 27 charges the secondary battery 25 using electric power supplied from an external power source (not shown).

[0044] When the secondary battery 25 is charged, the temperature of the secondary battery 25 increases as the charging time passes. Figure 3 As shown in FIG. 1 , when the temperature of the secondary battery 25 is low, the resistance of the secondary battery 25 is greater than when the temperature of the secondary battery 25 is high. Therefore, the change in the voltage of the secondary battery 25 is likely to be large, and degradation is likely to progress. Therefore, in order to suppress the degradation of the secondary battery 25, it is preferred to reduce the current of the secondary battery 25. On the other hand, when the temperature of the secondary battery 25 is high, in order to shorten the charging time of the secondary battery 25, it is preferred to increase the current of the secondary battery 25. Therefore, as Figure 4 As shown, the vehicle control unit 29 outputs a command to the charger 27 to change the current of the secondary battery 25 stepwise according to the temperature of the secondary battery 25 detected by the battery management unit 28. Specifically, the vehicle control unit 29 outputs a command to the charger 27 to increase the current of the secondary battery 25 stepwise according to the increase in the temperature of the secondary battery 25.

[0045] The vehicle control unit 29 manages the charging and discharging of the secondary battery 25. The vehicle control unit 29 outputs a command to the charger 27 to change the current of the secondary battery 25 stepwise according to the charging rate (or voltage) of the secondary battery 25 detected by the battery management unit 28. Specifically, the command to the charger 27 to decrease the current of the secondary battery 25 stepwise according to the increase of the charging rate (or voltage) of the secondary battery 25 is output.

[0046] As a feature of this embodiment, the vehicle control unit 29 estimates the remaining charging time of the secondary battery 25 when the secondary battery 25 is charged, and displays it on the display device 23. Figure 5 The process of estimating the remaining charging time of the secondary battery 25 in the present embodiment will be described. Figure 5 : is a flowchart showing the process of estimating the remaining charging time of the secondary battery in this embodiment.

[0047] In step S11, the vehicle control unit 29 predicts the change in the temperature of the secondary battery 25 based on the temperature and the charging rate of the secondary battery 25 detected by the battery management unit 28 (see Fig. 6A ). To explain in detail, for example, for each condition consisting of the temperature of the secondary battery 25 and the charging rate at the start of charging of the secondary battery 25, the data of the change in the temperature of the secondary battery 25 acquired in advance are stored, and the data of the change in the temperature of the secondary battery 25 corresponding to the temperature of the secondary battery 25 and the charging rate detected at the start of charging of the secondary battery 25 are extracted. The following Table 1 shows the data of the change in the temperature of the secondary battery 25 when the temperature of the secondary battery 25 is 0°C and the charging rate is 20% at the start of charging of the secondary battery 25. In Table 1, for convenience, the case where the time interval is 10 minutes is taken as an example, but it is not limited to this.

[0048]

Table 1

[0049] Elapsed time [min] 0 10 20 30 40 50 Temperature [℃] 0 10 18 23 26 28

[0050] In step S12, the vehicle control unit 29 predicts the change in voltage of the secondary battery 25 based on the temperature and charging rate of the secondary battery 25 detected by the battery management unit 28 (see Figure 6B). If described in detail, for example, for each condition consisting of the temperature of the secondary battery 25 and the charging rate at the start of charging of the secondary battery 25, the data of the change of the voltage of the secondary battery 25 acquired in advance is stored, and the data of the change of the voltage of the secondary battery 25 corresponding to the temperature of the secondary battery 25 and the charging rate detected at the start of charging of the secondary battery 25 are extracted. The following Table 2 shows the data of the change of the voltage of the secondary battery when the temperature of the secondary battery 25 is 0°C and the charging rate is 20% at the start of charging of the secondary battery 25. In Table 2, for convenience, the case where the time interval is 10 minutes is used as an example, but it is not limited to this.

[0051]

Table 2

[0052] Elapsed time [min] 0 10 20 30 40 50 Voltage [V] 320 335 345 360 370 375

[0053] The process proceeds to step S13, and the vehicle control unit 29 predicts the change in the current of the secondary battery 25 based on the change in the temperature of the secondary battery 25 predicted in step S11 and the change in the voltage of the secondary battery 25 predicted in step S12 (see Figure 6C In detail, using the above Figure 4 The change in the current of the secondary battery 25 is predicted based on the charging control characteristics described above.

[0054] Proceeding to step S14, the vehicle control unit 29 estimates the remaining charging time of the secondary battery 25 based on the change in the current of the secondary battery 25 predicted in step S13. Specifically, based on the change in the current of the secondary battery 25, the change in the voltage of the secondary battery 25 is calculated again. In addition, in the present embodiment, since the secondary battery 25 is charged by a constant current charging method, for example, the time until the voltage of the secondary battery 25 becomes equal to or greater than a set value is calculated as the remaining charging time. Alternatively, based on the change in the current of the secondary battery 25, the change in the charging rate of the secondary battery 25 is calculated, for example, the time until the charging rate of the secondary battery 25 becomes equal to a set value is calculated as the remaining charging time.

[0055] As described above, in this embodiment, the change of the temperature of the secondary battery 25 is predicted, the change of the current of the secondary battery 25 is predicted based on the change of the temperature of the secondary battery 25, and the remaining charging time of the secondary battery 25 is estimated based on the change of the current of the secondary battery 25. Figure 7 As shown, compared with the case (comparative example) where the remaining charging time of the secondary battery 25 is estimated based only on the current temperature of the secondary battery 25 without considering the change in the temperature of the secondary battery 25, the error of the estimated value of the remaining charging time of the secondary battery 25 (the difference from the actual measured value) can be reduced. In other words, the estimation accuracy of the remaining charging time of the secondary battery 25 can be improved.

[0056] In addition, in the first embodiment, the vehicle control unit 29 predicts the change of the temperature of the secondary battery 25 based on the temperature and the charging rate of the secondary battery 25 detected by the battery management unit 28, but the present invention is not limited to this. The vehicle control unit 29 may predict the change of the temperature of the secondary battery 25 based on the temperature and the voltage of the secondary battery 25 detected by the battery management unit 28. To explain in detail, for example, for each condition consisting of the temperature and the voltage of the secondary battery 25 at the start of charging of the secondary battery 25, the data of the change of the temperature of the secondary battery 25 acquired in advance may be stored, and the data of the change of the temperature of the secondary battery 25 corresponding to the temperature and the voltage of the secondary battery 25 detected by the battery management unit 28 at the start of charging of the secondary battery 25 may be extracted.

[0057] Alternatively, the vehicle control unit 29 may predict the change in the temperature of the secondary battery 25 based on the temperature, charge rate, or voltage, and degradation rate of the secondary battery 25 detected by the battery management unit 28. To be more specific, for example, for each condition consisting of the temperature, charge rate, or voltage, and degradation rate (specifically, capacity degradation rate or / and resistance degradation rate) of the secondary battery 25 at the start of charging of the secondary battery 25, the data on the change in the temperature of the secondary battery 25 acquired in advance may be stored, and the data on the change in the temperature of the secondary battery 25 corresponding to the temperature, charge rate, or voltage, and degradation rate (specifically, capacity degradation rate or / and resistance degradation rate) of the secondary battery 25 detected by the battery management unit 28 at the start of charging of the secondary battery 25 may be extracted.

[0058] In addition, in the first embodiment, the vehicle control unit 29 predicts the change of the voltage of the secondary battery 25 based on the temperature and the charging rate of the secondary battery 25 detected by the battery management unit 28, but the present invention is not limited thereto. The vehicle control unit 29 may predict the change of the voltage of the secondary battery 25 based on the temperature and the voltage of the secondary battery 25 detected by the battery management unit 28. To explain in detail, for example, for each condition consisting of the temperature and the voltage of the secondary battery 25 at the start of charging of the secondary battery 25, the data of the change of the voltage of the secondary battery 25 acquired in advance may be stored, and the data of the change of the voltage of the secondary battery 25 corresponding to the temperature and the voltage of the secondary battery 25 detected by the battery management unit 28 at the start of charging of the secondary battery 25 may be extracted.

[0059] Alternatively, the vehicle control unit 29 may predict the change in the voltage of the secondary battery 25 based on the temperature, charge rate (or voltage), and degradation rate of the secondary battery 25 detected by the battery management unit 28. To be specific, for example, for each condition consisting of the temperature, charge rate (or voltage), and degradation rate (specifically, capacity degradation rate or / and resistance degradation rate) of the secondary battery 25 at the start of charging of the secondary battery 25, the data on the change in the voltage of the secondary battery 25 acquired in advance may be stored, and the data on the change in the voltage of the secondary battery 25 corresponding to the temperature, charge rate (or voltage), and degradation rate (specifically, capacity degradation rate or / and resistance degradation rate) of the secondary battery 25 at the start of charging of the secondary battery 25 detected by the battery management unit 28 may be extracted.

[0060] In addition, in the first embodiment, the vehicle control unit 29 predicts the change in temperature and voltage of the secondary battery 25 and predicts the change in current of the secondary battery 25 based on the change in temperature and voltage of the secondary battery 25. However, the present invention is not limited to this. The vehicle control unit 29 may estimate the change in charging rate of the secondary battery 25 instead of estimating the change in voltage of the secondary battery 25 and predict the change in current of the secondary battery 25 based on the change in temperature and charging rate of the secondary battery 25.

[0061] In addition, in the first embodiment, the vehicle control unit 29 is described as an example in which the current of the secondary battery 25 is changed stepwise according to the charge rate (or voltage) of the secondary battery 25 detected by the battery management unit 28 when the secondary battery 25 is charged, but the present invention is not limited thereto. The vehicle control unit 29 may also be configured not to change the current of the secondary battery 25 according to the charge rate (or voltage) of the secondary battery 25 detected by the battery management unit 28 when the secondary battery 25 is charged. In this modified example, the vehicle control unit 29 may not predict the change of the voltage (or charge rate) of the secondary battery 25, but may predict the change of the current of the secondary battery 25 based on the change of the temperature of the secondary battery 25.

[0062] In addition, in the first embodiment, the case where the secondary battery 25 is charged by the constant current charging method is described as an example, but the present invention is not limited to this. Alternatively, the secondary battery 25 may be charged by the constant current and constant voltage charging method (in detail, the method is as follows: a constant current charging step is performed, for example, after the voltage of the secondary battery 25 reaches a predetermined value, a constant voltage charging step is performed). In this modified example, the current of the secondary battery 25 in the constant current charging step is determined by the above-mentioned Figure 6C As shown by the solid line. Figure 8As shown, the current of the secondary battery 25 in the constant voltage charging step decreases as the constant voltage charging time passes. The vehicle control unit 29 predicts the change of the current of the secondary battery 25 in the constant voltage charging step using, for example, a mathematical model. Alternatively, for example, the change of the current of the secondary battery 25 in the constant voltage charging step is predicted using the change of the reduction rate of the current acquired in advance. Furthermore, the change of the current of the secondary battery 25 in the constant voltage charging step may be corrected based on the temperature and degradation rate of the secondary battery 25.

[0063] In the above modification, the secondary battery 25 is charged by constant current and constant voltage charging. Figure 5 In step S14, the vehicle control unit 29 calculates, for example, the time until the voltage of the secondary battery 25 reaches a predetermined value in the constant current charging step as the constant current charging time, and calculates the time until the current of the secondary battery 25 becomes less than the set value in the constant voltage charging step as the constant voltage charging time, and calculates the total charging time as the sum of these times. And, the remaining charging time is calculated by subtracting the time elapsed from the start of charging of the secondary battery 25 from the total charging time.

[0064] In this embodiment, the same reference numerals are used for the same parts as those in the first embodiment, and the description thereof will be omitted as appropriate.

[0065] The vehicle control unit 29 of this embodiment estimates the remaining charging time of the secondary battery 25 when the secondary battery 25 is charged and displays it on the display device 23, but the estimation method is different from that of the first embodiment. Fig. 9 The process of estimating the remaining charging time of the secondary battery 25 in the present embodiment will be described. Fig. 9 : is a flowchart showing the process of estimating the remaining charging time of the secondary battery in this embodiment.

[0066] In step S21, the vehicle control unit 29 is initialized to operator k=1. The process proceeds to step S22, and the temperature of the secondary battery 25 after X minutes is predicted using the heat balance model. As shown in the following formula (1), the heat balance of the secondary battery 25 is expressed using the heat generated Qb, the radiant heat Qr, the surface area S, and the temperature T of the secondary battery 25, the temperature Tm of the external air (refrigerant) cooling the secondary battery 25, and the heat transfer coefficient α. The radiant heat Qr and the surface area S of the secondary battery 25 are fixed values. The heat transfer coefficient α is a fixed value, but it can also be changed according to the change of the cooling method such as natural cooling or forced cooling. As shown in the following formula (2), the heat generated Qb of the secondary battery is calculated using the resistance value (specifically, the difference between the voltage V and the open circuit voltage OCV) and the current I of the secondary battery 25. The open circuit voltage OCV is a fixed value. As shown in the following formula (3), the temperature rise ΔT of the secondary battery 25 is calculated using the heat Q and the heat capacity C of the secondary battery 25. The heat capacity C is a fixed value. Therefore, the vehicle control unit 29 uses equations (1) to (3) to predict the temperature of the secondary battery 25 X minutes later based on the current temperature, voltage, and current of the secondary battery 25 detected by the battery management unit 28 and the outside air temperature.

[0067]

Number 1

[0068] Q=Q b -Q r -α×S×(TT m )…(1)

[0069]

Number 2

[0070] Q b =(V-OCV)×I…(2)

[0071]

Number 3

[0072]

[0073] In step S23, the vehicle control unit 29 uses the electrical circuit model to predict the voltage of the secondary battery 25 after X minutes. As shown in the following formula (4), the voltage V of the secondary battery 25 is calculated using the open circuit voltage OCV, current I, instantaneous resistance Ro, resistance degradation rate SOHR, and polarization voltage Vp of the secondary battery 25. The instantaneous resistance Ro is calculated using the charging rate SOC and temperature T. As shown in the following formula (5), the polarization voltage Vp is calculated using the current I, polarization resistance Rp, elapsed time t, and time constant τ. The polarization resistance Rp is calculated using the charging rate SOC and temperature T. The time constant τ is a fixed value. Therefore, the vehicle control unit 29 uses formulas (4) to (5) to predict the voltage of the secondary battery 25 after X minutes based on the current temperature, charging rate, resistance degradation rate, and current of the secondary battery 25 detected by the battery management unit 28.

[0074]

Number 4

[0075] V=OCV+I×R o (SOC, T)×SOHR+Vp(SOC, T)…(4)

[0076]

Number 5

[0077]

[0078] The vehicle control unit 29 proceeds to step S24, and predicts the current of the secondary battery 25 after X minutes based on the temperature of the secondary battery 25 after X minutes predicted in step S22 and the voltage of the secondary battery 25 after X minutes predicted in step S23, using the operator k=1. Figure 4 The charging control characteristics described above predict the current of the secondary battery 25 after X minutes. However, the predicted current of the secondary battery 25 is set to be less than the current current of the secondary battery 25 detected by the battery management unit 28 .

[0079] The process proceeds to step S25, where the vehicle control unit 29 predicts the temperature of the secondary battery 25 after (X×2) minutes using the heat balance model from the operator k=1. Specifically, the temperature of the secondary battery 25 after (X×2) minutes is predicted based on the temperature, voltage, and current of the secondary battery 25 after X minutes and the outside air temperature using equations (1) to (3). In addition, the outside air temperature after X minutes is assumed to be the same as the current outside air temperature.

[0080] In step S26, the vehicle control unit 29 predicts the voltage of the secondary battery 25 after (X×2) minutes using the electric circuit model from the operator k=1. Specifically, the voltage of the secondary battery 25 after (X×2) minutes is predicted based on the temperature, charging rate, resistance degradation rate, and current of the secondary battery 25 after X minutes using equations (4) to (5). In addition, the charging rate of the secondary battery 25 after X minutes is obtained using the current charging rate and current of the secondary battery 25. The resistance degradation rate of the secondary battery 25 after X minutes is set to be the same as the resistance degradation rate of the current secondary battery 25.

[0081] The process proceeds to step S27, and the vehicle control unit 29 determines whether the secondary battery 25 has been fully charged after (X×2) minutes. When the secondary battery 25 is charged by a constant current charging method, for example, it is determined whether the secondary battery 25 has been fully charged based on whether the voltage of the secondary battery 25 is above a set value. When the secondary battery 25 is charged by a constant current and constant voltage charging method, for example, it is determined whether the secondary battery 25 has been fully charged based on whether the current of the secondary battery 25 in the constant voltage charging step is less than a set value. If the secondary battery 25 has not been fully charged after (X×2) minutes, the process proceeds to step S28.

[0082] In step S28, the vehicle control unit 29 updates the operator k=2. The process proceeds to step S24, and the vehicle control unit 29 predicts the current of the secondary battery 25 (X×2) minutes later based on the temperature of the secondary battery 25 (X×2) minutes later and the voltage of the secondary battery 25 (X×2) minutes later. The process proceeds to step S25, and the vehicle control unit 29 predicts the temperature of the secondary battery 25 (X×3) minutes later based on the temperature, voltage, and current of the secondary battery 25 (X×2) minutes later and the outside air temperature from the operator k=2. In step S26, the voltage of the secondary battery 25 (X×3) minutes later is predicted from the operator k=2 based on the temperature, charging rate, resistance degradation rate, and current of the secondary battery 25 (X×2) minutes later. The process proceeds to step S27, and it is determined whether the secondary battery 25 is fully charged (X×3) minutes later.

[0083] Before it is determined in step S27 that the secondary battery 25 has completed charging after (X×k) minutes, the operator k is updated in step S28, and steps S24, S25, and S26 are repeatedly executed. If it is determined that the secondary battery 25 has completed charging after (X×k) minutes, the process proceeds to step S29. In step S29, the vehicle control unit 29 estimates that the remaining charging time of the secondary battery 25 is (X×k) minutes.

[0084] In the present embodiment described above, the remaining charging time of the secondary battery 25 can be estimated with higher accuracy than when the remaining charging time of the secondary battery 25 is estimated only from the current temperature of the secondary battery 25 without considering the change in the temperature of the secondary battery 25 .

[0085] In addition, in the present embodiment, the heat balance model and the electrical circuit model (specifically, the above-mentioned equations (1) to (5)) are used, so the burden of preparation can be reduced compared to the case where the data of the secondary battery 25 acquired in advance for each condition of the secondary battery 25 is used as in the first embodiment. In addition, the estimation accuracy of the remaining charging time of the secondary battery 25 can be improved compared to the first embodiment.

[0086] A third embodiment of the present invention will be described. In this embodiment, the same reference numerals are used for the same parts as those in the first embodiment, and the description thereof will be omitted as appropriate.

[0087] When the secondary battery 25 is discharged, the temperature of the secondary battery 25 rises as the discharge time passes. When the temperature of the secondary battery 25 is low, as described above, Figure 3 As shown in FIG. 1 , the resistance of the secondary battery 25 is larger than when the temperature of the secondary battery 25 is high, so the change in the voltage of the secondary battery 25 is likely to be large, and degradation is likely to progress. Therefore, it is preferable to reduce the current of the secondary battery 25 in consideration of the suppression of degradation of the secondary battery 25. On the other hand, when the temperature of the secondary battery 25 is high, it is preferable to increase the current of the secondary battery 25 in consideration of the increase in the power of the electric motor 24. Therefore, as Fig.10 As shown, the vehicle control unit 29 of this embodiment outputs a command to the inverter 26 to change the current of the secondary battery 25 according to the temperature of the secondary battery 25 detected by the battery management unit 28. Specifically, the inverter 26 outputs a command to increase the current of the secondary battery 25 according to the increase in the temperature of the secondary battery 25.

[0088] The vehicle control unit 29 outputs a command to the inverter 26 to change the current of the secondary battery 25 according to the charge rate (or voltage) of the secondary battery 25 detected by the battery management unit 28. Specifically, the vehicle control unit 29 outputs a command to the inverter 26 to reduce the current of the secondary battery 25 according to the decrease in the charge rate (or voltage) of the secondary battery 25.

[0089] As a feature of the present embodiment, the vehicle control unit 29 estimates the remaining discharge time of the secondary battery 25 (in other words, the remaining operating time of the electric excavator) when the secondary battery 25 is discharged, and displays it on the display device 23. Fig.11 The process of estimating the remaining discharge time of the secondary battery 25 in the present embodiment will be described. Fig.11: is a flowchart showing the process of estimating the remaining discharge time of the secondary battery in this embodiment.

[0090] In step S31, the vehicle control unit 29 predicts the change in the temperature of the secondary battery 25 based on the temperature and the charging rate of the secondary battery 25 detected by the battery management unit 28. To be more specific, for example, for each condition consisting of the temperature and the charging rate of the secondary battery 25 at the start of discharge of the secondary battery 25, the data on the change in the temperature of the secondary battery 25 acquired in advance is stored, and the data on the change in the temperature of the secondary battery 25 corresponding to the temperature and the charging rate of the secondary battery 25 detected at the start of discharge of the secondary battery 25 is extracted.

[0091] In step S32, the vehicle control unit 29 predicts the change in the voltage of the secondary battery 25 based on the temperature and the charging rate of the secondary battery 25 detected by the battery management unit 28. To be more specific, for example, for each condition consisting of the temperature and the charging rate of the secondary battery 25 at the start of discharge of the secondary battery 25, the data on the change in the voltage of the secondary battery 25 acquired in advance is stored, and the data on the change in the voltage of the secondary battery 25 corresponding to the temperature and the charging rate of the secondary battery 25 detected when the charging of the secondary battery 25 starts is extracted.

[0092] The process proceeds to step S33, and the vehicle control unit 29 predicts the change in the current of the secondary battery 25 based on the change in the temperature of the secondary battery 25 predicted in step S31 and the change in the voltage of the secondary battery 25 predicted in step S32. Fig.10 The discharge control characteristics described above predict the transition of the current of the secondary battery 25 .

[0093] Proceeding to step S34, the vehicle control unit 29 estimates the remaining discharge time of the secondary battery 25 based on the change in the current of the secondary battery 25 predicted in step S33. Specifically, based on the change in the current of the secondary battery 25, the change in the voltage of the secondary battery 25 is calculated again. And, for example, the time until the voltage of the secondary battery 25 becomes less than the set value is calculated as the remaining discharge time. Alternatively, based on the change in the current of the secondary battery 25, the change in the charging rate of the secondary battery 25 is calculated, for example, the time until the charging rate of the secondary battery 25 becomes less than the set value is calculated as the remaining discharge time.

[0094] As described above, in the present embodiment, the change of the temperature of the secondary battery 25 and the like is predicted, the change of the current of the secondary battery 25 is predicted based on the change of the temperature of the secondary battery 25 and the like, and the remaining discharge time of the secondary battery 25 is estimated based on the change of the current of the secondary battery 25. Therefore, the estimation accuracy of the remaining discharge time of the secondary battery 25 can be improved compared with the case where the remaining discharge time of the secondary battery 25 is estimated only from the current temperature of the secondary battery 25 without considering the change of the temperature of the secondary battery 25.

[0095] In addition, similarly to the above-mentioned modification of the first embodiment, the third embodiment can also be modified. Furthermore, since the discharge condition of the secondary battery 25 changes according to the driving condition of the electric motor 24, the current of the secondary battery 25 can also be added as a parameter. That is, the vehicle control unit 29 can also predict the change of the temperature of the secondary battery 25 and the change of the voltage or charging rate of the secondary battery 25 based on the temperature and charging rate or voltage and current (or the average current within a predetermined time) of the secondary battery 25 detected by the battery management unit 28. In addition, the vehicle control unit 29 can also predict the change of the temperature of the secondary battery 25 and the change of the voltage or charging rate of the secondary battery 25 based on the temperature and charging rate or voltage and deterioration rate and current (or the average current within a predetermined time) of the secondary battery 25 detected by the battery management unit 28.

[0096] In this embodiment, the same reference numerals are used for the parts equivalent to those in the third embodiment, and the description thereof will be omitted as appropriate.

[0097] The vehicle control unit 29 of this embodiment estimates the remaining discharge time of the secondary battery 25 when the secondary battery 25 is discharged and displays it on the display device 23, but the estimation method is different from that of the third embodiment. Fig.12 The process of estimating the remaining discharge time of the secondary battery 25 in the present embodiment will be described. Fig.12 : is a flowchart showing the process of estimating the remaining discharge time of the secondary battery in this embodiment.

[0098] In step S41, the vehicle control unit 29 is initialized to operator k = 1. The process proceeds to step S42, and the temperature of the secondary battery 25 after X minutes is predicted using the heat balance model. Specifically, the temperature of the secondary battery 25 after X minutes is predicted based on the current temperature, voltage, and current of the secondary battery 25 detected by the battery management unit 28 and the outside air temperature using the above equations (1) to (3).

[0099] In step S43, the vehicle control unit 29 uses the electric circuit model to predict the voltage of the secondary battery 25 after X minutes. Specifically, the voltage of the secondary battery 25 after X minutes is predicted based on the current temperature, charging rate, resistance degradation rate, and current of the secondary battery 25 detected by the battery management unit 28 using the above equations (4) to (5).

[0100] The vehicle control unit 29 proceeds to step S44, and predicts the current of the secondary battery 25 after X minutes based on the temperature of the secondary battery 25 after X minutes predicted in step S42 and the voltage of the secondary battery 25 after X minutes predicted in step S43, using the operator k=1. Fig.10 The discharge control characteristic described above predicts the current of the secondary battery 25 after X minutes.

[0101] Proceeding to step S45, the vehicle control unit 29 uses the heat balance model to predict the temperature of the secondary battery 25 after (X×2) minutes from the operator k=1. Specifically, the temperature of the secondary battery 25 after (X×2) minutes is predicted based on the temperature, voltage, and current of the secondary battery 25 after X minutes and the outside air temperature using equations (1) to (3).

[0102] In step S46, the vehicle control unit 29 predicts the voltage of the secondary battery 25 after (X×2) minutes using the electric circuit model from the operator k=1. Specifically, the voltage of the secondary battery 25 after (X×2) minutes is predicted based on the temperature, charging rate, resistance degradation rate, and current of the secondary battery 25 after X minutes using equations (4) to (5).

[0103] The process proceeds to step S47, and the vehicle control unit 29 determines whether the secondary battery 25 stops discharging after (X×2) minutes. Specifically, for example, the process determines whether the secondary battery 25 stops discharging based on whether the voltage of the secondary battery 25 is less than a set value. If the secondary battery 25 does not stop discharging after (X×2) minutes, the process proceeds to step S48.

[0104] In step S48, the vehicle control unit 29 updates the operator k=2. The process proceeds to step S44, and the vehicle control unit 29 predicts the current of the secondary battery 25 (X×2) minutes later based on the temperature of the secondary battery 25 (X×2) minutes later and the voltage of the secondary battery 25 (X×2) minutes later, from the operator k=2. The process proceeds to step S45, and the vehicle control unit 29 predicts the temperature of the secondary battery 25 (X×3) minutes later based on the temperature, voltage, and current of the secondary battery 25 (X×2) minutes later and the outside air temperature, from the operator k=2. In step S46, the voltage of the secondary battery 25 (X×3) minutes later is predicted based on the temperature, charging rate, resistance degradation rate, and current of the secondary battery 25 (X×2) minutes later, from the operator k=2. The process proceeds to step S47, and it is determined whether the discharge of the secondary battery 25 (X×3) minutes later has stopped.

[0105] In step S47, before it is determined that the secondary battery 25 stops discharging after (X×k) minutes, the operator k is updated in step S48, and steps S44, S45, and S46 are repeatedly executed. If it is determined that the secondary battery 25 stops discharging after (X×k) minutes, the process proceeds to step S49. In step S49, the vehicle control unit 29 estimates that the remaining discharge time of the secondary battery 25 is (X×k) minutes.

[0106] In the present embodiment described above, the remaining discharge time of the secondary battery 25 can be estimated with higher accuracy than when the remaining discharge time of the secondary battery 25 is estimated only from the current temperature of the secondary battery 25 without considering the change in the temperature of the secondary battery 25 .

[0107] In addition, in this embodiment, the heat balance model and the electrical circuit model (specifically, the above-mentioned equations (1) to (5)) are used, so the burden of preparation can be reduced compared to the case where the data of the secondary battery 25 acquired in advance for each condition of the secondary battery 25 is used as in the third embodiment. In addition, compared with the third embodiment, the estimation accuracy of the remaining discharge time of the secondary battery 25 can be improved.

[0108] In the first to fourth embodiments, the secondary battery 25 is described as an example in which the secondary battery 25 is composed of a plurality of battery modules 30 connected in series, but the present invention is not limited thereto. The secondary battery 25 may be composed of a plurality of battery modules 30 connected in parallel, for example.

[0109] In the first to fourth embodiments, the vehicle control unit 29 predicts the change of the temperature of the secondary battery 25, predicts the change of the current of the secondary battery 25 based on the change of the temperature of the secondary battery 25, and estimates the remaining charge time or remaining discharge time of the secondary battery 25 based on the change of the current of the secondary battery 25. However, the vehicle control unit 29 may use a map that reflects the change of the temperature of the secondary battery 25 and the change of the current of the secondary battery 25, and indicates the correspondence between the condition composed of the temperature and voltage or the charging rate of the secondary battery 25 (in detail, the capacity degradation rate or resistance degradation rate of the secondary battery 25, or the outside air temperature) and the remaining charge time or remaining discharge time of the secondary battery 25, and acquires the remaining charge time or remaining discharge time of the secondary battery 25 based on the condition composed of the temperature and voltage or the charging rate of the secondary battery 25 detected by the battery management unit 28. As a specific example, as shown in Table 3 below, using a graph showing the correspondence between the conditions consisting of the temperature and the charging rate of the secondary battery 25 and the remaining charging time of the secondary battery 25, if the temperature of the secondary battery 25 at the start of charging of the secondary battery 25 is 0°C and the charging rate is 20%, it is estimated that the remaining charging time is 100 minutes. According to this modification, the estimation accuracy of the remaining charging time or the remaining discharging time of the secondary battery 25 can also be improved.

[0110]

Table 3

[0111]

[0112] In addition, the present invention has been described above by taking the case where the present invention is applied to an electric excavator as an example, but is not limited thereto. That is, the present invention may also be applied to other electric working machines such as an electric wheel loader, an electric dump truck, or an electric road machine.

[0113] Description of Reference Numerals

[0114] 25 Secondary battery

[0115] 28 Battery Management Unit

[0116] 29 Vehicle control unit.

Claims

1. An electric working machine, comprising: Secondary batteries; and a battery management unit for detecting at least one of a voltage and a charging rate of the secondary battery and a temperature of the secondary battery, The electric working machine is characterized in that A vehicle control unit is provided for managing the charging and discharging of the secondary battery, The vehicle control unit is configured as follows: predicting a change in the temperature of the secondary battery based on the temperature and the voltage or the charging rate of the secondary battery detected by the battery management unit, predicting a change in the current of the secondary battery based on the predicted change in the temperature of the secondary battery, Based on the predicted change in the current of the secondary battery, a remaining charge time or a remaining discharge time of the secondary battery is estimated.

2. The electric working machine according to claim 1, characterized in that: The battery management unit detects a degradation rate of the secondary battery, The vehicle control unit predicts a change in the temperature of the secondary battery based on a degradation rate, a temperature, and a voltage or a charging rate of the secondary battery detected by the battery management unit.

3. The electric working machine according to claim 1, characterized in that: The battery management unit detects the current of the secondary battery, The vehicle control unit predicts a change in the temperature of the secondary battery based on the current, the temperature, and the voltage or the charging rate of the secondary battery detected by the battery management unit.

4. The electric working machine according to claim 1, wherein: The vehicle control unit changes the current of the secondary battery according to the voltage or charging rate of the secondary battery detected by the battery management unit when the secondary battery is charged or discharged. The vehicle control unit is configured as follows: predicting a change in the voltage or charging rate of the secondary battery based on the temperature, voltage or charging rate of the secondary battery detected by the battery management unit, Based on the predicted change in the temperature of the secondary battery and the predicted change in the voltage or the charging rate of the secondary battery, a change in the current of the secondary battery is predicted.

5. The electric working machine according to claim 4, characterized in that: The battery management unit detects a degradation rate of the secondary battery, The vehicle control unit predicts a change in voltage or charging rate of the secondary battery based on a degradation rate, a temperature, and a voltage or charging rate of the secondary battery detected by the battery management unit.

6. The electric working machine according to claim 4, characterized in that: The battery management unit detects the current of the secondary battery, The vehicle control unit predicts a change in a voltage or a charging rate of the secondary battery based on the current, the temperature, and the voltage or the charging rate of the secondary battery detected by the battery management unit.

7. The electric working machine according to claim 1, wherein: The battery management unit detects the current and degradation rate of the secondary battery and the external air temperature, The vehicle control unit changes the current of the secondary battery according to the voltage or charging rate of the secondary battery detected by the battery management unit when the secondary battery is charged or discharged. The vehicle control unit is configured as follows: using a heat balance model, predicting the change in the temperature of the secondary battery based on the temperature, voltage, and current of the secondary battery detected by the battery management unit and the outside air temperature, using an electrical circuit model, predicting a change in voltage or charging rate of the secondary battery based on the temperature, charging rate, degradation rate, and current of the secondary battery detected by the battery management unit, Based on the predicted change in the temperature of the secondary battery and the predicted change in the voltage or the charging rate of the secondary battery, a change in the current of the secondary battery is predicted.

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