Electric construction machine

Abstract

The purpose of the present invention is to provide a construction machine capable of achieving both operability and working time. Thus, the electric construction machine comprises: an operation device for instructing the operation of the hydraulic actuator; a motor rotation speed setting device for instructing the rotation speed of the electric motor; and a controller that controls the rotational speed of the electric motor, the controller reducing the rotational speed of the electric motor from the indicated rotational speed indicated by the motor rotational speed setting device to an idle rotational speed determined in accordance with the charging rate of the battery when the non-operating state of the operating device continues for a certain period of time.

Description

Technical Field

[0001] This invention relates to electric construction machinery such as hydraulic excavators. Background Technology

[0002] Most construction machinery, such as hydraulic excavators, uses diesel engines as their power source. Pressurized oil supplied by a hydraulic pump connected to the diesel engine actuates the hydraulic actuators, thus performing the work. However, in recent years, from the perspectives of improved fuel economy, better exhaust characteristics, and reduced noise, electric construction machinery, such as electric hydraulic excavators, has been developed and is gradually becoming practical. These machines are equipped with batteries that replace diesel engines and use electric motors as their power source, with the batteries serving as the power supply for the electric motors.

[0003] Furthermore, most of the aforementioned hydraulic excavators and other construction machinery are equipped with a function (automatic idling) to switch from normal operation to idling operation and reduce the engine speed to a specified low speed in order to improve fuel economy. Prior art documents disclosing such construction machinery include, for example, Patent Document 1.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Publication No. 60-038561 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] In the aforementioned electric hydraulic excavators and other electric construction machinery, in order to reduce the power consumption of the electric motor, it is preferable to install the following function (automatic idling): the speed of the electric motor is indicated by a speed input device (e.g., a motor speed dial), the operator operates the speed input device to set the target speed of the electric motor, and after a predetermined time has elapsed from the moment when all operating devices (e.g., operating levers) indicating the action of the hydraulic actuator are held in the neutral position, the motor speed is controlled to a predetermined speed (idling speed) that is lower than the speed indicated by the speed input device.

[0009] However, installing existing automatic idle systems on electric construction machinery presents the following problems. In existing automatic idle systems, because the idle speed is constant, when the idle speed is set low, the operational response time when resuming from automatic idle state becomes longer, reducing the operability of the electric construction machinery. Conversely, when the idle speed is set high, battery power consumption increases, shortening the operating time of the electric construction machinery.

[0010] The present invention was proposed in view of the above-mentioned problems, and its purpose is to provide an electric engineering machine that can balance operability and working time.

[0011] Methods for solving problems

[0012] To achieve the above objectives, the engineering machinery of the present invention includes: a battery; an electric motor driven by electricity supplied from the battery; a hydraulic pump driven by the electric motor; a hydraulic actuator driven by pressurized oil supplied from the hydraulic pump; an operating device that instructs the operation of the hydraulic actuator; a motor speed setting device that instructs the speed of the electric motor; and a controller that controls the speed of the electric motor, wherein, if the operating device remains in an inactive state for a certain period of time, the controller causes the speed of the electric motor to decrease from the indicated speed instructed by the motor speed setting device to an idle speed determined corresponding to the charging rate of the battery.

[0013] Invention Effects

[0014] According to the electric construction machinery of the present invention, by reducing the speed of the electric motor from the indicated speed to the idle speed when the operating device remains in an inactive state for a certain period of time, the power consumption of the battery can be suppressed, thereby extending the working time of the electric construction machinery. Furthermore, by adjusting the idle speed according to the battery's state of charge (SOC), the time it takes for the electric motor speed to recover from the idle speed to the indicated speed when operation of the operating device resumes can be shortened, thus suppressing any reduction in the operability of the electric construction machinery. Attached Figure Description

[0015] Figure 1 This is a side view of the electric hydraulic excavator according to an embodiment of the present invention.

[0016] Figure 2 This is a top view of the electric hydraulic excavator according to an embodiment of the present invention.

[0017] Figure 3 This is a configuration diagram of the drive system of the electric hydraulic excavator according to an embodiment of the present invention.

[0018] Figure 4 This is a flowchart illustrating the automatic idling-related processing of the controller in an embodiment of the present invention.

[0019] Figure 5 This is a block diagram illustrating the automatic idling-related functions of the controller in an embodiment of the present invention.

[0020] Figure 6 This is a graph showing the relationship between the SOC of the battery and the idle speed in an embodiment of the present invention. Detailed Implementation

[0021] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the same reference numerals are used to label the same parts in each figure, and repeated descriptions are omitted where appropriate.

[0022] Figure 1 This is a side view of the electric hydraulic excavator in this embodiment. Figure 2 This is its top view. It should be noted that the application of this invention is not limited to electric hydraulic excavators, but can be applied to all electric construction machinery.

[0023] exist Figure 1 and Figure 2 The electric hydraulic excavator 100 includes a tracked lower traveling body 1, an upper slewing body 2 rotatably mounted on the lower traveling body 1, and a working device 5. The upper slewing body 2 has a slewing frame 3 forming the foundation substructure and a swing column 4 rotatably mounted on the front side of the slewing frame 3. The working device 5 is rotatably connected to the swing column 4 in the vertical direction. A canopy-type cab 6 is provided on the front side of the slewing frame 3. A battery storage 7 is provided on the rear side of the slewing frame 3. Figure 3 The drive battery unit mounting unit 8 (shown) can be connected to an external power source (not shown) via an external power connection cable 26. The electric hydraulic excavator 100 is driven by electricity supplied from the battery 7 or an external power source.

[0024] The lower traveling body 1 includes: a track frame 9 that is roughly H-shaped when viewed from above; left and right drive wheels 10A and 10B that are rotatably supported near the rear ends of the left and right sides of the track frame 9; left and right driven wheels (idler wheels) 11A and 11B that are rotatably supported near the front ends of the left and right sides of the track frame 9; and left and right tracks 12A and 12B that are wound around the left and right drive wheels 10A and 10B and the driven wheels 11A and 11B. The left drive wheel 10A (i.e., the left track 12A) is driven to rotate by a left travel hydraulic motor 13A, and the right drive wheel 10B (i.e., the right track 12B) is driven to rotate by a right travel hydraulic motor 13B.

[0025] A scraper 14 for discharging soil is provided on the front side of the track frame 9, which can move up and down. The scraper 14 moves up and down by the extension and retraction drive of the scraper hydraulic cylinder (not shown).

[0026] A slewing wheel 15 is provided at the center of the track frame 9. The slewing frame 3 is rotatably mounted by means of the slewing wheel 15. The slewing frame 3 (i.e., the upper slewing body 2) is driven by a slewing hydraulic motor (not shown).

[0027] The swing column 4 is rotatably mounted on the front side of the rotating frame 3, and rotates in the left and right directions by the extension and retraction of the swing hydraulic cylinder (not shown). As a result, the working device 5 swings left and right.

[0028] The working device 5 includes: a boom 16 rotatably connected to a swing column 4; a stick 17 rotatably connected to the front end of the boom 16; and a bucket 18 rotatably connected to the front end of the stick 17. The boom 16, stick 17, and bucket 18 are rotated in the vertical direction by a boom hydraulic cylinder 19, a stick hydraulic cylinder 20, and a bucket hydraulic cylinder 21. It should be noted that the bucket 18 can be replaced, for example, with an auxiliary device (not shown) equipped with an optional hydraulic actuator.

[0029] The driver's cab 6 is equipped with a driver's seat 22. In front of the driver's seat 22 are a left-moving control lever 23A and a right-moving control lever 23B, which are operated in the forward and backward directions to respectively indicate the operation of the left and right moving hydraulic motors 13A and 13B (i.e., the left and right tracks 12A and 12B). Further to the left of the left-moving control lever 23A, at the foot, is a selection pedal (not shown) that is operated in the left and right directions to indicate the operation of a selected hydraulic actuator (i.e., an auxiliary device). Further to the right of the right-moving control lever, at the foot, is a swing control pedal (not shown) that is operated in the left and right directions to indicate the operation of a swinging hydraulic cylinder (i.e., the swing column 4).

[0030] On the left side of the driver's seat 22 is a cross-shaped stick / slewing lever 24, which functions as an operating device. Operating it in the forward / backward direction instructs the movement of the stick hydraulic cylinder 20 (i.e., stick 17), and operating it in the left / right direction instructs the movement of the slewing hydraulic motor (i.e., upper slewing body 2). On the right side of the driver's seat 22 is a cross-shaped boom / bucket operating lever 25, which functions as an operating device. Operating it in the forward / backward direction instructs the movement of the boom hydraulic cylinder 19 (i.e., boom 16), and operating it in the left / right direction instructs the movement of the bucket hydraulic cylinder 21 (i.e., bucket 18). Additionally, on the right side of the driver's seat 22 is a scraper operating lever (not shown), which functions as an operating device that instructs the movement of the scraper hydraulic cylinder (i.e., scraper 14) by operating it in the forward / backward direction.

[0031] Figure 3 This is a diagram illustrating the drive system configuration of an electric hydraulic excavator 100. The drive system 200 includes an electric motor 33 as a power source, a variable-capacity hydraulic pump 38 driven by the electric motor 33, and a fixed-capacity pilot pump 40.

[0032] Each hydraulic actuator 13A, 13B, and 19-21 is driven by pressurized oil injected from hydraulic pump 38. The flow (direction and flow rate) of the pressurized oil supplied from hydraulic pump 38 to each hydraulic actuator 13A, 13B, and 19-21 is controlled by a directional control valve (not shown). Each directional control valve is operated by a pilot pressure output from each operating lever 23A, 23B, 24, and 25. Each operating lever 23A, 23B, 24, and 25 is equipped with a pilot valve that generates a pilot pressure corresponding to the lever's tilting amount, using the injection pressure (pilot primary pressure) of pilot pump 40 as the base pressure.

[0033] The hydraulic pump 38 is equipped with an adjuster piston 41 and a spring 42 that opposes the adjuster piston 41. The pressure of the pressure oil supply line 35, which supplies the pressure oil ejected from the hydraulic pump 38, is introduced into the adjuster piston 41. As a result, if the pressure of the pressure oil supply line 35 increases, the tilt of the hydraulic pump 38 decreases, and the power absorbed by the hydraulic pump 38 decreases.

[0034] The electric motor 33 is electrically connected to the inverter 32 via a high-voltage wire. The inverter 32 is electrically connected to the battery 7 via a high-voltage wire. The inverter 32 converts the high-voltage DC current input from the battery 7 into high-voltage AC current and outputs it to the electric motor 33, thereby controlling the speed of the electric motor 33.

[0035] Battery 7 is equipped with a battery control controller 36. The battery control controller 36 controls battery 7 and obtains the state of charge (SOC) of battery 7.

[0036] Monitor 31 is installed in the cab 6 and displays various information related to the electric hydraulic excavator 100 in response to the operator's actions.

[0037] The motor speed setting device 34 is installed in the cab 6 and indicates the speed of the electric motor 33 corresponding to the operator's operation to the controller 37 (indicating speed).

[0038] An automatic idle switch 39 is located on the monitor 31 and instructs the controller 37 whether automatic idle is enabled in response to operator input. Automatic idle functions as follows: when all operating levers 23A, 23B, 24, and 25 are in the neutral position for a certain period of time, the speed of the electric motor 33 is reduced to a predetermined low speed (idle speed) regardless of the indication from the motor speed setting device 34. The operating state of the electric hydraulic excavator 100 performing automatic idle will be referred to as the automatic idle state, and all other operating states will be referred to as the normal state.

[0039] The hydraulic sensor 30 converts the pilot pressure output from each operating lever 23A, 23B, 24, and 25 into an analog signal and outputs it to the controller 37.

[0040] The controller 37 calculates the motor speed command value of the electric motor 33 based on the signals from the motor speed setting device 34, the automatic idle switch 39 and the hydraulic sensor 30 and outputs it to the inverter 32.

[0041] The inverter 32 controls the speed of the electric motor 33 in accordance with the motor speed command value input from the controller 37.

[0042] Figure 4 This is a flowchart illustrating the processing related to automatic idling of controller 37. Regardless of whether there is an external power connection cable 26 ( Figure 1 or Figure 2 The connections shown are all executed within a specified computation cycle. Figure 4 The processing shown.

[0043] The controller 37 first determines whether the automatic idle switch 39 is ON (step S1).

[0044] If the determination result in step S1 is FALSE, the automatic idle switch 39 is ON and the variable (time counter) representing the duration of the state in which all operating levers 23A, 23B, 24, and 25 are in the neutral position is cleared (reset to zero) (step S2).

[0045] Next, in step S2, the motor speed (indicated speed) indicated by the motor speed setting device 34 is output to the inverter 32 as a command value (step S3), ending the process. Thus, when the automatic idle switch 39 is OFF, the motor speed is controlled to the indicated speed.

[0046] If the result of step S1 is TRUE, determine whether all control levers are in the neutral position (step S4). If the result of step S4 is FALSE, proceed to step S2.

[0047] If the determination result in step S4 is TRUE, the time counter will start counting (step S5).

[0048] Next, in step S5, it is determined whether the time counter has reached a non-operational time constant (e.g., 5 minutes) or more (step S6). If the determination result in step S6 is FALSE, proceed to step S3.

[0049] If the determination result in step S6 is TRUE, the idle speed is calculated based on SOC (step S7).

[0050] Next, in step S7, it is determined whether the idle speed is lower than the indicated speed (step S8). If the determination result in step S8 is FALSE, the process proceeds to step S3. Thus, when the indicated speed is lower than the idle speed, since the motor speed is maintained at the indicated speed which is lower than the idle speed, the power consumption of battery 7 can be suppressed compared to the case where the speed is controlled at idle.

[0051] If the determination result in step S8 is TRUE, the idle speed is output as a command value to the inverter 32 (step S9), and the process ends. This reduces the motor speed to idle speed, suppressing power consumption by the battery 7.

[0052] Figure 5 This is a block diagram illustrating the functions related to automatic idling of the controller 37. The controller 37 includes a pressure conversion unit 50a, an operation determination unit 50b, an automatic idling determination unit 50c, a constant / table storage unit 50d, and a motor speed calculation unit 50e. The controller 37 has an arithmetic unit such as a CPU, storage units such as ROM and RAM, and an input / output interface for signal input / output with external devices. The functions of each part are implemented by executing programs stored in the ROM, etc. It should be noted that... Figure 5 In this diagram, the functions related to control other than electric motor 33 are omitted from the illustration.

[0053] The pressure conversion unit 50a converts the analog signal input from the hydraulic sensor 30 into pilot pressure information for each operating lever 23A, 23B, 24, and 25 and outputs it.

[0054] The operation determination unit 50b determines whether the operation of the operating levers 23A, 23B, 24, and 25 is performed based on the pilot pressure information input from the pressure conversion unit 50a and outputs the determination result. Specifically, the determination is made by comparing the determination threshold stored in the constant / table storage unit 50d with the pilot pressure information calculated by the pressure conversion unit 50a.

[0055] The automatic idle speed determination unit 50c determines whether the electric hydraulic excavator 100 is in an automatic idle speed state based on the information input from the automatic idle speed switch 39 (automatic idle speed switch information), the determination result input from the operation determination unit 50b, and the no-operation time constant input from the constant / table storage unit 50d, and outputs the determination result. Specifically, if the automatic idle speed switch 39 is ON and the determination result of the operation determination unit 50b is no operation (all operating levers 23A, 23B, 24, and 25 are in the neutral position) and the state continues for a no-operation time constant or more, it is determined to be in an automatic idle speed state; otherwise, it is determined to be in a normal state.

[0056] The motor speed calculation unit 50e calculates the motor speed based on the SOC information of the battery 7 input from the battery control controller 36, the indicated speed information input from the motor speed setting device 34, and the determination result input from the automatic idle speed determination unit 50c. Specifically, when the determination result input from the automatic idle speed determination unit 50c indicates an automatic idle state, the idle speed is calculated based on the SOC information. If the calculated idle speed is lower than the motor speed indicated by the motor speed setting device 34 (indicated speed), the idle speed is output as a motor speed command value to the inverter 32. If the idle speed is higher than or equal to the indicated speed, the indicated speed is output as a motor speed command value. When the determination result input from the automatic idle speed determination unit 50c indicates a normal state, the indicated speed is output as a motor speed command value to the inverter 32.

[0057] Figure 6 This is a graph showing the relationship between the state of charge (SOC) of battery 7 and idle speed (SOC-idle speed table). The SOC-idle speed table 60 is stored in the constant / table storage unit 50d and is referenced when the motor speed calculation unit 50e calculates the idle speed based on the SOC. Figure 6 In the example shown, when the SOC is above 50% (the first threshold), the idle speed is constant at 1800 rpm. When the SOC is below 30% (the second threshold), the idle speed is constant at 1200 rpm. Between 50% and 30% SOC, the idle speed continuously decreases from 1800 rpm to 1200 rpm as the SOC decreases.

[0058] The upper limit of the idle speed (1800 rpm) is set between the maximum indicated speed (2400 rpm) and the minimum indicated speed (1200 rpm). The lower limit of the idle speed (1200 rpm) is set to be the same as the minimum indicated speed (1200 rpm). The minimum indicated speed is equal to the minimum value of the permissible speed range of the hydraulic pump 38.

[0059] like Figure 6 As shown, by not excessively reducing the idle speed when the SOC is high, the operability of recovering from automatic idle state can be improved. Furthermore, by reducing the idle speed as the SOC decreases, the power consumption of battery 7 can be suppressed, thereby extending the battery 7's operating time.

[0060] In the SOC-idle speed gauge 60 of this embodiment, a range is set where the idle speed is constant and independent of SOC (SOC is above 50% or below 30%). However, the idle speed can also be proportionally reduced from the upper limit (1800 rpm) to the lower limit (1200 rpm) according to the SOC. In this embodiment, the idle speed is kept constant at the upper limit (1800 rpm) until the SOC falls below 50%, thus improving operability when resuming from automatic idle compared to the case where the idle speed is proportionally reduced according to the SOC. Furthermore, if the SOC is below 30%, the idle speed is kept constant at the lower limit (1200 rpm), thus extending the battery 7's lifespan compared to the case where the idle speed is proportionally reduced according to the SOC.

[0061] (Summarize)

[0062] In this embodiment, the electric construction machinery 100 includes: a battery 7; an electric motor 33 driven by electricity supplied from the battery 7; a hydraulic pump 38 driven by the electric motor 33; hydraulic actuators 13A, 13B, 19-21 driven by pressurized oil supplied from the hydraulic pump 38; operating devices 23A, 23B, 24, 25 indicating the operation of the hydraulic actuators 13A, 13B, 19-21; a motor speed setting device 34 indicating the speed of the electric motor 33; and a controller 37 that controls the speed of the electric motor 33. When the operating devices 23A, 23B, 24, 25 remain in an inactive state for a certain period of time, the controller 37 reduces the speed of the electric motor 33 from the indicated speed indicated by the motor speed setting device 34 to an idle speed determined corresponding to the charging rate of the battery 7.

[0063] According to this embodiment configured as described above, by reducing the speed of the electric motor 33 from the indicated speed to the idle speed when the operating devices 23A, 23B, 24, and 25 have been in an inactive state for a certain period of time, the power consumption of the battery 7 can be suppressed, thereby extending the working time of the electric construction machinery 100. Furthermore, by adjusting the idle speed according to the state of charge (SOC) of the battery 7, the time it takes for the speed of the electric motor 33 to recover from the idle speed to the indicated speed when the operation of the operating devices 23A, 23B, 24, and 25 resumes can be shortened, thus suppressing any decrease in the operability of the electric construction machinery 100.

[0064] Furthermore, when the charge rate of battery 7 is above the first threshold (50%), the controller 37 in this embodiment sets the idle speed to the first speed (1800 rpm). When the charge rate of battery 7 is below the second threshold (30%), which is smaller than the first threshold, the idle speed is set to the second speed (1200 rpm), which is lower than the first speed. When the charge rate of battery 7 is below the first threshold but above the second threshold, the idle speed is monotonically reduced from the first speed to the second speed in response to the decrease in the charge rate of battery 7. Thus, the idle speed remains constant at the first speed (1800 rpm) until the state of charge (SOC) falls below the first threshold (50%). Therefore, compared to the case where the idle speed is reduced proportionally to the SOC, the operability when recovering from automatic idle is improved. In addition, if the SOC is lower than the second threshold (30%), the idle speed is kept constant at the second speed (1200 rpm). Therefore, compared with the case where the idle speed is reduced proportionally to the SOC, the power consumption of battery 7 can be suppressed.

[0065] Furthermore, when the indicated speed is lower than the idle speed, the controller 37 in this embodiment maintains the speed of the electric motor 33 at the indicated speed. Thus, when the indicated speed, as indicated by the motor speed setting device 34, is lower than the idle speed, the speed of the electric motor 33 is controlled to be lower than the idle speed indicated speed, thereby further suppressing the power consumption of the battery 7.

[0066] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the above embodiments, but includes various modifications. For example, the detailed description has been provided for the purpose of clearly explaining the present invention, but the above embodiments are not necessarily limited to having all the described configurations. Explanation of reference numerals in the attached figures

[0067] 1…Lower traveling body, 2…Upper slewing body, 3…Slewing frame, 4…Swing column, 5…Working device, 6…Cab, 7…Battery, 8…Drive battery unit mounting unit, 9…Track frame, 10A, 10B…Drive wheels, 11A, 11B…Driven wheels, 12A, 12B…Tracks, 13A, 13B…Traveling hydraulic motors (hydraulic actuators), 14…Scraper, 15…Slewing wheel, 16…Boom, 17…Stick, 18…Bucket, 19…Boom hydraulic cylinder (hydraulic actuator), 20…Stick hydraulic cylinder (hydraulic actuator), 21…Bucket hydraulic cylinder (hydraulic actuator), 22…Cab seat, 23A, 23B…Traveling control levers (operating devices) 24… Stick / slewing lever (operating device), 25… Boom / bucket lever (operating device), 30… Hydraulic sensor, 31… Monitor, 32… Inverter, 33… Electric motor, 34… Motor speed setting device, 35… Pressure oil supply line, 36… Battery control controller, 37… Controller, 38… Hydraulic pump, 39… Automatic idle switch, 40… Pilot pump, 41… Regulator piston, 42… Spring, 50a… Pressure conversion unit, 50b… Operation determination unit, 50c… Automatic idle speed determination unit, 50d… Constant / table storage unit, 50e… Motor speed calculation unit, 60… Idle speed gauge, 100… Electric hydraulic excavator (electric construction machinery).

Claims

1. An electric engineering machine, comprising: Battery; An electric motor, which is driven by electricity supplied from the battery; A hydraulic pump, which is driven by the electric motor; A hydraulic actuator, which is driven by pressurized oil supplied from the hydraulic pump; An operating device that instructs the action of the hydraulic actuator; A motor speed setting device that indicates the speed of the electric motor; and The controller controls the rotational speed of the electric motor. The electric engineering machinery is characterized by the following features: If the inactive state of the operating device continues for a certain period of time, the controller causes the speed of the electric motor to decrease from the indicated speed indicated by the motor speed setting device to the idle speed determined corresponding to the charging rate of the battery.

2. The electric engineering machinery according to claim 1, characterized in that, When the battery's charging rate is above a first threshold, the controller sets the idle speed to the first speed. If the battery charging rate is lower than a second threshold that is smaller than the first threshold, the idle speed is set to a second speed that is lower than the first speed. When the battery charging rate is lower than the first threshold and higher than the second threshold, the idle speed is monotonically reduced from the first speed to the second speed in response to the decrease in the battery charging rate.

3. The electric engineering machinery according to claim 1, characterized in that, When the indicated speed is lower than the idle speed, the controller maintains the speed of the electric motor at the indicated speed.

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