Working machine

Abstract

To provide a work machine that can extend the time in which a motor can be driven even if abnormalities occur in an inverter that converts the power of a generator.SOLUTION: A work machine includes a direct current (DC) circuit (100), a DC / DC converter (110) placed between a storage battery (19) and the DC circuit and capable of changing the voltage of the DC circuit, an inverter (18A) that converts the power generated by a generator (12) and sends the same to the DC circuit (100) and a motor (21) driven by electric power supplied from the DC circuit (100). When abnormalities occur in the inverter (18A), power is sent from the generator (12) to the DC circuit (100) by switching the control of the DC / DC converter (110).SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a working machine.

Background Art

[0002] Patent Document 1 describes a hybrid working machine including a generator that generates electricity using the power of an engine and an electric motor that outputs power for work. In the working machine of Patent Document 1, when an abnormality is detected in a component of the power storage system that maintains the voltage of the DC bus, an inverter that sends the power of the generator to the DC bus performs voltage control of the DC bus.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a hybrid working machine, when an abnormality occurs in an inverter that converts the power of a generator, thereafter, the drive of the electric motor becomes impossible because the remaining charge amount of the storage battery runs out.

[0005] An object of the present invention is to provide a working machine capable of extending the time during which the electric motor can be driven even when an abnormality occurs in an inverter that converts the power of a generator.

Means for Solving the Problems

[0006] The working machine according to the present invention includes a DC circuit, a DC / DC converter disposed between the storage battery and the DC circuit and capable of changing the voltage of the DC circuit, an inverter that converts the power generated by the generator and sends it to the DC circuit, A motor driven by the power supplied from the direct current circuit, is provided with When the inverter malfunctions, the control of the DC / DC converter switches, and power is sent from the generator to the direct current circuit. 、 The DC / DC converter sets the voltage of the DC circuit to a first voltage during normal operation of the inverter, and sets the voltage of the DC circuit to a second voltage lower than the first voltage when the inverter becomes abnormal. .

Advantages of the Invention

[0007] According to the present invention, even when an abnormality occurs in the inverter that converts the power of the generator, the time during which the motor can be driven can be extended.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0009] Hereinafter, modes for carrying out the invention will be described with reference to the drawings.

[0010] [Basic Configuration of the Excavator] First, with reference to FIGS. 1 and 2, the basic configuration of the excavator according to the present embodiment will be described.

[0011] FIG. 1 is a side view showing an example of an excavator according to the present embodiment. The excavator corresponds to an example of a work machine according to the present invention.

[0012] The excavator according to the present embodiment includes a lower traveling body 1, an upper revolving body 3 mounted on the lower traveling body 1 so as to be revolvable via a revolving mechanism 2, a boom 4, an arm 5, and a bucket 6 as an attachment (working device), and a cabin 10 on which an operator rides.

[0013] The lower traveling body 1 includes, for example, a pair of left and right crawlers, and each crawler is self-propelled by being hydraulically driven by traveling hydraulic motors 1A and 1B (see FIG. 2).

[0014] The upper revolving body 3 revolves with respect to the lower traveling body 1 by being electrically driven by a revolving electric motor 21 (see FIG. 2) described later.

[0015] The boom 4 is pivotally attached to the center of the front portion of the upper revolving body 3 so as to be able to pitch, an arm 5 is pivotally attached to the tip of the boom 4 so as to be able to rotate vertically, and a bucket 6 is pivotally attached to the tip of the arm 5 so as to be able to rotate vertically. The boom 4, the arm 5, and the bucket 6 are each hydraulically driven by a boom cylinder 7, an arm cylinder 8, and a bucket cylinder 9 as hydraulic actuators, respectively.

[0016] The cabin 10 is mounted on the left side of the front portion of the upper revolving body 3.

[0017] FIG. 2 is a block diagram showing an example of a configuration centered on the drive system of the excavator according to the present embodiment.

[0018] In the figure, the mechanical power line is shown by a double line, the high-pressure hydraulic line is shown by a thick solid line, the pilot line is shown by a broken line, and the electric drive / control line is shown by a thin solid line.

[0019] The hydraulic drive system of the excavator according to this embodiment includes an engine 11, a speed reducer 13, a main pump 14, and a control valve 17. Further, as described above, the hydraulic drive system according to this embodiment includes travel hydraulic motors 1A and 1B that hydraulically drive the lower traveling body 1, the boom 4, the arm 5, and the bucket 6, respectively, a boom cylinder 7, an arm cylinder 8, a bucket cylinder 9, and the like.

[0020] The engine 11 is the main power source in the hydraulic drive system and is mounted, for example, at the rear of the upper slewing body 3. The engine 11 rotates at a constant speed at a preset target rotational speed under the control of an engine control module (ECM) 11A. The engine 11 is, for example, a diesel engine that uses light oil as fuel, and drives the main pump 14 and the pilot pump 15 via the speed reducer 13. Further, the engine 11 drives the motor generator 12 via the speed reducer 13 to generate electricity in the motor generator 12.

[0021] Also, a clutch 11B is provided on the power transmission path between the engine 11 and the speed reducer 13. As will be described later, the operation of the clutch 11B is controlled by a controller 30, and it can be switched between a connected state and a disconnected state between the engine 11 and the speed reducer 13. The clutch 11B may be, for example, an electromagnetic type directly controlled by a signal from the controller 30.

[0022] Note that the clutch 11B may be omitted.

[0023] The speed reducer 13 is mounted, for example, at the rear of the upper slewing body 3 like the engine 11, and has two input shafts to which the engine 11 and the motor generator 12 described later are connected, and one output shaft to which the main pump 14 and the pilot pump 15 are coaxially connected in series. The speed reducer 13 can transmit the power of the engine 11 and the motor generator 12 to the main pump 14 and the pilot pump 15 at a predetermined reduction ratio. Further, the speed reducer 13 can distribute and transmit the power of the engine 11 to the motor generator 12, the main pump 14, and the pilot pump 15 at a predetermined reduction ratio.

[0024] The main pump 14 is mounted, for example, at the rear of the upper swing body 3 in the same manner as the engine 11, and supplies hydraulic oil to the control valve 17 through the high-pressure hydraulic line 16. The main pump 14 is driven by the engine 11, or the engine 11 and the motor generator 12. The main pump 14 is, for example, a variable displacement hydraulic pump. Under the control of a controller 30 described later, a regulator (not shown) controls the angle of the swash plate (tilt angle) to adjust the stroke length of the piston, thereby controlling the discharge flow rate (discharge pressure).

[0025] The control valve 17 is mounted, for example, at the center of the upper swing body 3, and is a hydraulic control device that controls the hydraulic drive system in response to an operation of an operating device 26 by an operator. As described above, the control valve 17 is connected to the main pump 14 via the high-pressure hydraulic line 16, and supplies the hydraulic oil supplied from the main pump 14 to the traveling hydraulic motors 1A (for right) and 1B (for left), which are hydraulic actuators, the boom cylinder 7, the arm cylinder 8, and the bucket cylinder 9 according to the operation state of the operating device 26. Specifically, the control valve 17 is a valve unit including a plurality of hydraulic control valves (direction change valves) that control the flow rate and flow direction of the hydraulic oil supplied from the main pump 14 to each of the hydraulic actuators.

[0026] In addition, the electric drive system according to the present embodiment includes a motor generator 12, a swing motor 21, a swing speed reducer 24, a current sensor 21s, a resolver 22, a mechanical brake 23, and a power storage system 120.

[0027] The electric generator 12 (an example of the first electric motor) is an assist power source for the hydraulic drive system that assists the engine 11 to drive the main pump 14. For example, it is mounted integrally with the engine 11 and the speed reducer 13 at the rear part of the upper swing body 3. Since the electric generator 12 is an assist power source, usually, the output of the electric generator 12 is relatively smaller than the output of the engine 11. For example, the electric generator 12 is about 20% of the output of the engine 11. The electric generator 12 is connected to the power storage system 120 including the storage battery 19 via the inverter 18A, performs power running operation with three-phase AC power supplied from the storage battery 19 or the swing electric motor 21 via the inverter 18A, and drives the main pump 14 and the pilot pump 15 via the speed reducer 13. Further, the electric generator 12 performs power generation operation by being driven by the engine 11, and can supply the generated electric power to the storage battery 19 or the swing electric motor 21. The switching control between the power running operation and the power generation operation of the electric generator 12 is realized by the inverter 18A being driven and controlled by the controller 30 described later.

[0028] The swing electric motor 21 (an example of the second electric motor and an actuator) drives the swing mechanism 2 that rotatably connects the upper swing body 3 to the lower traveling body 1. The swing electric motor 21 performs a power running operation of swing-driving the upper swing body 3 and a regeneration operation of generating regenerative power to swing-brake the upper swing body 3 under the control of the controller 30. The swing electric motor 21 is connected to the power storage system 120 via the inverter 18B and is driven by three-phase AC power supplied from the storage battery 19 or the electric generator 12 via the inverter 18B. Further, the swing electric motor 21 supplies the regenerative power to the storage battery 19 or the electric generator 12 via the inverter 18B. Thereby, the storage battery 19 can be charged or the electric generator 12 can be driven with the regenerative power. The switching control between the power running operation and the regeneration operation of the swing electric motor 21 is realized by the inverter 18B being driven and controlled by the controller 30. A resolver 22, a mechanical brake 23, and a swing speed reducer 24 are connected to the rotating shaft 21A of the swing electric motor 21.

[0029] The slewing reducer 24 is connected to the rotating shaft 21A of the slewing motor 21, and increases the torque by reducing the output (torque) of the slewing motor 21 at a predetermined reduction ratio, thereby driving the upper slewing body 3 to slewing. That is, during the power running operation, the slewing motor 21 drives the upper slewing body 3 to slewing via the slewing reducer 24. Further, the slewing reducer 24 increases the speed of the inertial rotational force of the upper slewing body 3 and transmits it to the slewing motor 21 to generate regenerative power. That is, during the regenerative operation, the slewing motor 21 performs regenerative power generation by the inertial rotational force of the upper slewing body 3 transmitted via the slewing reducer 24, and slewing brakes the upper slewing body 3.

[0030] The current sensor 21s detects the currents of the three phases (U phase, V phase, W phase) of the slewing motor 21. The current sensor 21s is provided, for example, in the power path between the slewing motor 21 and the inverter 18B. Detection signals corresponding to the currents of the three phases of the slewing motor 21 by the current sensor 21s are taken into the inverter 18B and transmitted from the inverter 18B to the controller 30.

[0031] The resolver 22 detects the rotational position (rotation angle) etc. of the slewing motor 21. The resolver 22 transmits a detection signal corresponding to the detected rotation angle to the controller 30.

[0032] The mechanical brake 23 mechanically generates a braking force on the upper slewing body 3 (specifically, the rotating shaft 21A of the slewing motor 21) under the control of the controller 30, slewing brakes the upper slewing body 3, and maintains the stopped state of the upper slewing body 3.

[0033] In addition, in FIG. 2, the slewing reducer 24 and the mechanical brake 23 are described as separate block elements for simplicity, but the mechanical brake 23 may be, for example, a hydraulic brake incorporated between a plurality of speed reducers included in the slewing reducer 24, or an electromagnetic brake provided separately from the slewing reducer 24.

[0034] The power storage system 120 includes a storage battery 19, a DC bus 100, and a boost - buck converter (equivalent to a DC / DC converter) 110, and is mounted, for example, on the right front part of the upper swing body 3 together with the inverters 18A and 18B.

[0035] The storage battery 19 (an example of a power storage device) supplies power to the motor - generator 12 and the swing motor 21, and also charges the generated power of the motor - generator 12 and the swing motor 21 supplied via the DC bus 100 and the boost - buck converter 110.

[0036] In addition, the excavator according to this embodiment usually uses the engine 11 as the main power source of the hydraulic drive system, and the energy consumed by the motor - generator 12 is relatively small. Also, the swing motor 21 can return most of the energy consumed during swing drive as regenerative energy generated by regenerative power generation during swing braking to the storage battery 19. Therefore, the capacity of the storage battery 19 is often relatively small.

[0037] The DC bus 100 is disposed between the inverters 18A and 18B and the boost - buck converter 110, and transmits power among the storage battery 19, the motor - generator 12, and the swing motor 21. The DC bus 100 is a DC circuit (DC bus bar) having a positive - side power line and a negative - side power line for transmitting a DC voltage.

[0038] The boost - buck converter 110 switches between a boosting operation and a bucking operation so that the voltage value of the DC bus 100 falls within a certain range according to the operating states of the motor - generator 12 and the swing motor 21. The switching control of the boosting operation and the bucking operation of the boost - buck converter 110 is realized by the controller 30 based on the voltage detection value of the DC bus 100, the voltage detection value of the storage battery 19, and the current detection value of the storage battery 19.

[0039] Also, the operation system of the excavator according to this embodiment includes a pilot pump 15, an operation device 26, a pressure sensor 29, etc.

[0040] The pilot pump 15 is mounted on the rear part of the upper slewing body 3 and supplies pilot pressure to the operating device 26 via the pilot line 25. The pilot pump 15 is, for example, a fixed displacement hydraulic pump and is driven by the engine 11, or the engine 11 and the motor generator 12.

[0041] The operating device 26 includes levers 26A and 26B and a pedal 26C. The operating device 26 is provided near the driver's seat in the cabin 10 and is an operation input means for the operator to operate each operating element (the lower traveling body 1, the upper slewing body 3, the boom 4, the arm 5, the bucket 6, etc.). In other words, the operating device 26 is an operation input means for operating each hydraulic actuator (traveling hydraulic motors 1A and 1B, boom cylinder 7, arm cylinder 8, bucket cylinder 9, etc.) and electric actuator (slewing motor 21, etc.) that drive each operating element. The operating device 26 (levers 26A and 26B, and pedal 26C) is respectively connected to the control valve 17 via the hydraulic line 27. Thereby, a pilot signal (pilot pressure) corresponding to the operating states of the lower traveling body 1, the boom 4, the arm 5, the bucket 6, etc. in the operating device 26 is input to the control valve 17. Therefore, the control valve 17 can drive each hydraulic actuator according to the operating state in the operating device 26. Further, the operating device 26 is connected to the pressure sensor 29 via the hydraulic line 28.

[0042] The pressure sensor 29 is connected to the operating device 26 via the hydraulic line 28 as described above, and detects the pilot pressure on the secondary side of the operating device 26, that is, the pilot pressure corresponding to the operating states of the respective operating elements in the operating device 26. The pressure sensor 29 is connected to the controller 30, and a pressure signal (pressure detection value) corresponding to the operating states of the lower traveling body 1, the upper slewing body 3, the boom 4, the arm 5, the bucket 6, etc. in the operating device 26 is input to the controller 30.

[0043] In addition, the control system of the excavator according to this embodiment includes a controller 30, an ECM 11A, etc. The functions of the controller 30 and the ECM 11A may be realized by arbitrary hardware, software, or a combination thereof. For example, they are composed of a microcomputer including a CPU, a ROM, a RAM, an I / O, etc., and various functions are realized by executing various programs stored in the ROM on the CPU. Also, the controller 30, the ECM 11A, etc. are mutually connected by a communication network (LAN: Local Area Network) based on a communication standard such as CAN (Controller Area Network), Ethernet (registered trademark), etc.

[0044] The controller 30 performs drive control of the excavator. For example, the controller 30 performs drive control of the electric drive system based on the detection value corresponding to the operation state of the operation device 26 transmitted from the pressure sensor 29.

[0045] The ECM 11A controls the engine 11, specifically, various devices (for example, a fuel injection device, etc.) included in the engine 11, and rotates the engine 11 at a predetermined rotational speed (constant rotational speed control).

[0046] Also, the ECM 11A transmits detection signals of sensors (for example, a rotational speed sensor, etc.) not shown in the figure that detect various states of the engine 11 to the controller 30. Further, the ECM 11A has a function (diagnostic function) of detecting a failure of the engine 11 based on the detection signals of the sensors, and when a failure that causes the engine 11 to stop occurs, it transmits a signal (failure signal) indicating that a failure has occurred to the controller 30.

[0047] When an abnormality occurs in the inverter 18A connected to the electric generator 12, the excavator according to this embodiment performs an abnormal operation to extend the time during which the swing electric motor 21 can be driven by switching the control of the boost converter 110. The excavator according to this embodiment includes a display device 32 as a configuration related to the above-described abnormal operation, which displays the occurrence of the abnormality and the fact that the abnormal operation is being performed. By viewing this display, the operator can move the swing electric motor 21, but can recognize that an abnormality has occurred in the inverter 18A and that maintenance is required. The excavator may further include an abnormal operation switch 36 for switching the start and stop of the abnormal operation, so that the operator can start or stop the abnormal operation by operating it.

[0048] The display device 32 is communicably connected to the controller 30 and displays various information (for example, guidance information regarding operation guidance in the abnormal operation of the excavator described later) for the operator and the like under the control of the controller 30. The display device 32 is, for example, a liquid crystal display.

[0049] The abnormal operation switch 36 may be, for example, a push-button type hardware switch, or may be a software switch as a virtual button (icon) displayed on the screen of the display device 32. Further, the abnormal operation switch 36 may be configured to also serve as an existing hardware switch that performs other functions in the normal operation mode.

[0050] <Inverter 18A> FIG. 3 is a circuit diagram showing an example of an inverter connected to a motor generator. The inverter 18A connected to the motor generator 12 includes three circuit portions 181 respectively connected to the three-phase coils of the motor generator 12. Each circuit portion 181 includes a current path leading to the negative output terminal TON through the lower switching element SN and a current path leading to the positive output terminal TOP through the upper switching element SP. In each circuit portion 181, the node N between the upper switching element SP and the lower switching element SN is connected to the coil of each phase of the motor generator 12. The positive output terminal TOP and the negative output terminal TON are respectively connected to the positive power line 100P and the negative power line 100N of the DC bus 100.

[0051] The upper switching element SP switches between on and off the two terminals through which current flows according to the voltage of the control terminal. The lower switching element SN switches between on and off the two terminals through which current flows according to the voltage of the control terminal. The upper switching element SP includes a diode DP. The lower switching element SN includes a diode DN. The diode DP is connected between the two terminals through which the current of the upper switching element SP flows in the direction of flowing current from the node N to the positive output terminal TOP. The diode DP is connected between the two terminals through which the current of the lower switching element SN flows in the direction of flowing current from the negative output terminal TON to the node N.

[0052] The controller 30 switches and controls the three upper switching elements SP and the three lower switching elements SN in accordance with the rotational phase of the motor generator 12, thereby converting the alternating current generated power generated in the three-phase coils of the motor generator 12 into direct current power. Then, the direct current power is sent from the negative output terminal TON and the positive output terminal TOP to the DC bus 100. The controller 30 controls the inverter 18A so that a current with a phase angle shifted with respect to the phase of the dielectric electromotive force generated in the coil of the motor generator 12 flows, thereby increasing the regenerative torque of the motor generator 12 and generating a large amount of power.

[0053] The controller 30 detects the alternating current flowing through the three-phase coil and controls the inverter 18A so that the alternating current matches the target value.

[0054] <Abnormality of the inverter 18A> When an abnormality occurs in the inverter 18A, the controller 30 stops the switching control of the inverter 18A. The inverter 18A has sensors that detect the voltage, current, temperature, etc. of each part. When the value of the sensor indicates an abnormality, a signal indicating the abnormality is sent to the controller 30, and the controller 30 may determine that the inverter 18A is abnormal. Alternatively, the controller 30 may determine the abnormality of the inverter 18A by the current flowing through the three-phase coil of the motor generator 12 deviating from the target value.

[0055] When the controller 30 determines that there is an abnormality in the inverter 18A and stops the control of the inverter 18A, the upper switching element SP and the lower switching element SN remain off (open). At this time, when the motor generator 12 rotates, the alternating induced electromotive force generated in the three-phase coil of the motor generator 12 is output to each node N.

[0056] Here, if the voltage of the DC bus 100 (the potential difference between the positive power line and the negative power line) is higher than the above-mentioned induced electromotive force, a reverse voltage is applied to the diodes DP and DN, so no current flows from the motor generator 12 to the DC bus 100. No reverse current flows either. On the other hand, if the voltage of the DC bus 100 is lower than the above-mentioned induced electromotive force, a forward voltage is applied to the diodes DP and DN, and current flows from the motor generator 12 to the DC bus 100. That is, the generated power is sent from the motor generator 12 to the DC bus 100.

[0057] <Control operation> FIG. 4 is a diagram extracting the main part of the electrical drive system of the excavator.

[0058] As described above, the power of the engine 11 is transmitted to the motor generator 12, and the controller 30 controls the inverter 18A, so that the generated power of the motor generator 12 is output to the DC bus 100. Further, the controller 30 controls the inverter 18B according to the operation operation, so that power is sent from the DC bus 100 to the slewing motor 21 and the slewing motor 21 is driven. Further, the buck-boost converter 110 operates to maintain the voltage of the DC bus 100. If the generated power of the motor generator 12 is greater than the power used by the slewing motor 21, the buck-boost converter 110 sends a charging current to the storage battery 19. Conversely, if the generated power of the motor generator 12 is less than the power used by the slewing motor 21, the buck-boost converter 110 sends the discharge current of the storage battery 19 to the DC bus 100.

[0059] Subsequently, the operation when the inverter 18A is normal and when the control of the inverter 18A stops abnormally in the above electrical drive system will be described.

[0060] FIG. 5 is a time chart showing an example of the operation of the inverter connected to the motor generator, the buck-boost converter, and the inverter connected to the slewing motor. In FIG. 5, the control of the inverter 18A has stopped based on an abnormality at timing t1.

[0061] During normal operation (period T1), the controller 30 sets the target voltage of the buck-boost converter 110 to the first voltage V1 (for example, 360V). By setting the target voltage, the voltage of the DC bus 100 is adjusted to the first voltage V1.

[0062] Furthermore, the controller 30 limits the output power of the motor 21 to a first upper limit power P max1 described below. The output power of the motor 21 varies depending on the operation of the operator and the slewing load of the upper slewing body 3. The controller 30 calculates the current of the motor 21 so that a predetermined power corresponding to the operation and the load is output from the motor 21, and controls the inverter 18B so that the current is obtained. The output power is a concept including the output torque and the rotational speed. The output power may be read as the output torque, the rotational speed, or both.

[0063] Furthermore, the controller 30 changes the power generation power of the motor generator 12 according to the output power of the electric motor 21. Alternatively, the controller 30 may control the power generation power so that, according to the remaining charge of the storage battery 19, the power generation power of the motor generator 12 is increased when the remaining charge is low and the power generation power of the motor generator 12 is decreased when the remaining charge is high. The change in the power generation power of the motor generator 12 is realized by changing the target current of the inverter 18A. The target current of the inverter 18A means the effective value of the alternating current flowing through the coil of the motor generator 12.

[0064] During normal times (period T1), when the power generation amount of the motor generator 12 is smaller than the output power of the rotation electric motor 21, the buck-boost converter 110 discharges current from the storage battery 19 to the DC bus 100 in order to maintain the voltage of the DC bus 100 at the first voltage V1. Conversely, when the power generation amount of the motor generator 12 is larger than the output power of the rotation electric motor 21, the buck-boost converter 110 draws current from the DC bus 100 to the storage battery 19 to charge the storage battery 19 in order to maintain the voltage of the DC bus 100 at the first voltage V1. By such an action, the remaining charge of the storage battery 19 fluctuates up and down.

[0065] When an abnormality occurs in the inverter 18A and the operation switches to abnormal operation, the controller 30 changes the target voltage of the buck-boost converter 110 to a second voltage V2 (for example, 220V) lower than the first voltage V1 (for example, 360V) (period T2a). According to the change in the target voltage, the voltage of the DC bus 100 drops to the second voltage V2. The second voltage V2 is set to a value smaller than the induced electromotive force generated in the coil of the motor generator 12 in a state where the inverter 18A is stopped. Since the voltage of the DC bus 100 is the second voltage V2, even when the inverter 18A is stopped, current flows from the motor generator 12 to the DC bus 100 side due to the rotation of the motor generator 12. Therefore, the power generation power is sent from the motor generator 12 to the DC bus 100.

[0066] Furthermore, the controller 30 sets the output power of the rotation electric motor 21 to the second upper limit power Pmax2 is limited as follows. The second upper limit power P max2 is lower than the first upper limit power P max1 which is the upper limit during normal operation. Due to the above limitation, even if an operation exceeding the second upper limit power P max2 is performed, the controller 30 restricts the output power of the inverter 18B to the second upper limit power P max2 . As the voltage of the DC bus 100 (input voltage of the inverter 18B) decreases and the upper limit of the output power of the motor 21 for rotation decreases, it is possible to prevent an excessive load from being applied to the inverter 18B.

[0067] Furthermore, the controller 30 switches the target voltage of the buck-boost converter 110 to a third voltage V3 (e.g., 300 V) higher than the second voltage V2 (e.g., 220 V) when the remaining charge of the storage battery 19 becomes more than the first threshold TH1 (timing t2) according to the remaining charge of the storage battery 19 (period T2b). Also, the controller 30 returns the target voltage of the buck-boost converter 110 to the second voltage V2 when the remaining charge becomes less than the second threshold TH2 (timing t3) (period T2c). The third voltage V3 is lower than the first voltage V1 which is the target voltage during normal operation.

[0068] The third voltage V3 is a value higher than the dielectric electromotive force generated in the coil of the motor generator 12 in a state where the inverter 18A is stopped, but it may also be a low value. When the voltage of the DC bus 100 becomes the third voltage V3 higher than the second voltage V2, the generated power sent from the motor generator 12 to the DC bus 100 side can be made zero when the inverter 18A is stopped and the motor generator 12 is rotating (period T2b). Alternatively, by setting the third voltage V3 to a value lower than the above-mentioned induced electromotive force, the generated power sent from the motor generator 12 to the DC bus 100 side can be reduced. By making the small generated power equal to or smaller than the power consumption of the motor 21 for rotation, it is possible to prevent a charging current from being sent to the storage battery 19 and suppress a decrease in the remaining charge of the storage battery 19.

[0069] The first voltage V1 to the third voltage V3 may be set to a voltage higher than the voltage of the storage battery 19. According to such a setting, since the buck-boost converter 110 only performs a boosting operation, the circuit configuration of the buck-boost converter 110 can be simplified.

[0070] According to such control, as shown in periods T2a, T2b, and T2c, when the remaining charge amount of the storage battery 19 decreases, the power sent from the motor generator 12 to the DC bus 100 increases, while when the remaining charge amount of the storage battery 19 increases, the power sent from the motor generator 12 to the DC bus 100 decreases. Therefore, the storage battery 19 can maintain the function of buffering the difference between the generated power and the used power for a long time.

[0071] During abnormal operation, the controller 30 causes the display device 32 to display information on abnormal operation. The information to be displayed may include that the upper limit power of the swing motor 21 has dropped to the second upper limit power P max2 and that although operation can continue, maintenance of the inverter 18A is required. Based on the information displayed on the display device 32, the operator can continue to operate the excavator while requesting maintenance. Alternatively, the operator can request maintenance and move the excavator from the work site to a maintenance location, reducing the situation where the excavator with the abnormality remains at the work site.

[0072] <Control Process> FIG. 6 is a flowchart showing the abnormal operation process executed by the controller. When starting up, the controller 30 starts the abnormal operation process. When the abnormal operation process is started, the controller 30 reads the detected values of the state (currents, voltages, temperatures, etc. of each part) of the inverter 18A and determines whether an abnormality has occurred in the inverter 18A (step S1). If there is no abnormality, the controller 30 returns the process to step S1 and repeats the determination in step S1.

[0073] On the other hand, if an abnormality is detected, the controller 30 stops the control of the inverter 18A (step S2) and switches the target voltage of the buck-boost converter 110 to the second voltage V2 (step S3). Further, the set value of the upper limit power of the swing motor 21 is reduced to the second upper limit power P max2 (step S4). By setting the upper limit power, in the control process of the inverter 18B, the output power of the inverter 18B is limited to be equal to or less than the second upper limit power P max2 .

[0074] Subsequently, the controller 30 determines whether the target voltage of the buck-boost converter 110 is the second voltage V2 and the remaining charge amount of the storage battery 19 is greater than the first threshold TH1 (step S5). If NO, the process proceeds directly to step S7. On the other hand, if YES, the controller 30 switches the target voltage of the buck-boost converter 110 to the third voltage V3 (step S6) and then proceeds with the process to step S7.

[0075] Furthermore, the controller 30 determines whether the target voltage of the buck-boost converter 110 is the third voltage V3 and the remaining charge amount of the storage battery 19 is less than the second threshold TH2 (step S7). If NO, the process returns to step S5. On the other hand, if YES, the controller 30 switches the target voltage of the buck-boost converter 110 to the second voltage V2 (step S8) and then returns the process to step S5.

[0076] Such abnormal operation processing realizes the control operation shown in FIG. 5.

[0077] As described above, according to the excavator of the present embodiment, even if an abnormality occurs in the inverter 18A connected to the motor generator 12, the control of the buck-boost converter 110 is switched, so that power is sent from the motor generator 12 to the DC bus 100. Therefore, the period during which the swing motor 21 can be driven can be extended by the amount of power sent from the motor generator 12.

[0078] Furthermore, according to the excavator of the present embodiment, when an abnormality occurs in the inverter 18A, the target voltage of the buck-boost converter 110 is switched to a second voltage V2 that is lower than the first voltage V1 during normal operation. By switching the target voltage, the induced electromotive force generated in the coil of the motor generator 12 becomes higher than the voltage of the DC bus 100, and power can be sent from the motor generator 12 to the DC bus 100 through the inverter 18A in which the control has stopped.

[0079] Furthermore, according to the excavator of the present embodiment, based on the remaining charge of the storage battery 19, the target voltage of the buck-boost converter 110 is switched between a second voltage V2 and a third voltage V3 that is higher than the second voltage V2. By switching the target voltage to the third voltage V3, the generated power sent from the motor generator 12 to the DC bus 100 can be reduced through the inverter 18A in which the control has stopped. Therefore, when the power consumption is less than the power sent from the motor generator 12 to the DC bus 100 and the remaining charge of the storage battery 19 increases, the generated power can be reduced, and the power buffering function of the storage battery 19 can be maintained.

[0080] Furthermore, according to the excavator of the present embodiment, when an abnormality occurs in the inverter 18A, the upper limit power of the swing motor 21 is switched to a second upper limit power P max1 that is lower than the first upper limit power P max2 during normal operation. Therefore, it is possible to prevent an excessive load from being applied to the inverter 18B as the input voltage of the inverter 18B decreases.

[0081] In the above embodiment, an example is shown in which the device driven by the power generated by the motor generator 12 is the swing motor 21 that swings the upper swing body 3. However, the hydraulic cylinders that drive the boom 4, the arm 5, and the bucket 6 can be replaced with electric motors. In this case, the boom 4, the arm 5, or the bucket 6 may be applied as the device driven by the power generated by the motor generator 12.

[0082] In the above-described embodiment, the motor generator 12 is configured to have a function of assisting the driving of the engine 11 by using the power of the storage battery 19. However, the motor generator 12 may be changed to a generator dedicated for power generation.

[0083] In the above-described embodiment, the buck-boost converter 110 that controls the voltage of the DC bus 100 may be a DC / DC converter that only boosts the voltage, or may be a DC / DC converter that only steps down the voltage depending on the voltage of the storage battery 19.

[0084] (Other application examples) Subsequently, an example in which the work machine according to the embodiment of the present invention is applied to a crane system will be described.

[0085] FIGS. 7A and 7B are a schematic front view and a schematic side view of a crane system according to the present embodiment. A plurality of columns 40 support a girder 41. The column 40 and the girder 41 constitute a gantry frame. Wheels 42 are attached to the lower ends of the columns 40, and the gantry frame travels along a rail 43. The direction perpendicular to the plane of FIG. 7A and the left-right direction of FIG. 7B correspond to the traveling direction. A trolley 45 is mounted on the girder 41. A hoisting machine 46 is mounted on the trolley 45.

[0086] A plurality of electric actuators drive their respective operating parts. For example, a traveling motor 51 mounted on the gantry frame drives the wheels 42. A traversing motor 52 mounted on the trolley 45 moves the trolley 45 in the traversing direction. The left-right direction of FIG. 7A and the direction perpendicular to the plane of FIG. 7B correspond to the traversing direction. A hoisting motor 53 mounted on the hoisting machine 46 winds up and pays out a wire having a suspension tool 47 such as a hook attached to its tip. In this way, electric actuators such as the hoisting motor 53, the traversing motor 52, and the traveling motor 51 drive the operating parts of the suspension tool 47, the trolley 45, and the wheels 42, respectively.

[0087] An AC power source 60, a power conversion device (DC-DC converter) 65, a power storage device 67, and a power conversion device (DC-DC converter) 68 are mounted on a portal frame. The AC power source 60 includes an engine 61 and a generator 62. The AC power source 60 supplies driving power to a hoisting motor 53, a traversing motor 52, and a traveling motor 51. Further, the power storage device 67 is charged with the power supplied from the AC power source 60.

[0088] An inverter 62I for converting the generated power into DC power is connected to the generator 62, and an inverter 53I for driving the hoisting motor 53 is connected to the hoisting motor 53. The inverter 62I, the inverter 53I, and the power conversion device 68 are connected via a DC bus. The controller 70 of the crane system performs the same control on the inverter 62I, 53I, and the power conversion device 68 as the controller 30 of the above-described embodiment. At this time, the inverter 62I corresponds to the inverter 18A of the embodiment, the inverter 53I corresponds to the inverter 18B of the embodiment, and the power conversion device 68 corresponds to the buck-boost converter 110 of the embodiment.

[0089] An inverter 52I for driving the traversing motor 52 is connected to the traversing motor 52, and an inverter 51I for driving the traveling motor 51 is connected to the traveling motor 51. And the controller 70 may perform the same control on the traversing motor 52 and the inverter 52I, and the traveling motor 51 and the inverter 51I as the control performed by the controller 30 of Embodiment 1 on the slewing motor 21 and the inverter 18B.

[0090] In the crane system of the present embodiment, a configuration in which the wheels 42 are driven by the power of the engine 61 may be adopted, or a configuration in which the trolley 45 moves in the traversing direction by the power of the engine 61 may be adopted.

[0091] As described above, also in the crane system, when an abnormality occurs in the inverter 62I that converts the generated power, power can be sent from the generator 62 to the DC bus, so that the same effects as those of the above-described embodiment are achieved.

[0092] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and the matters shown in the embodiments can be appropriately changed without departing from the gist of the invention.

Description of Reference Numerals

[0093] 3 Upper slewing body 4 Boom 5 Arm 6 Bucket 11 Engine 12 Electric generator (generator) 18A Inverter 19 Storage battery 21 Slewing motor 30 Controller 32 Display device 36 Abnormal operation switch 100 DC bus (DC circuit) 110 Step-up / down converter SP Upper switching element SN Lower switching element DP, DN Diode V1 First voltage V2 Second voltage V3 Third voltage P max1 First upper limit power P max2 Second upper limit power 45 Trolley 46 Hoist 47 Suspension tool 51 Travel motor (electric motor) 52 Sideways travel motor (electric motor) 53 Hoisting motor (electric motor) 61 Engine 62 Generator 62I Inverter 68 Power conversion device (DC-DC converter) 70 Controller

Claims

1. A DC circuit, a DC / DC converter disposed between the storage battery and the DC circuit and capable of changing the voltage of the DC circuit, an inverter that converts the power generated by the generator and sends it to the DC circuit, a motor driven by the power supplied from the DC circuit, and comprising, when the inverter malfunctions, the control of the DC / DC converter switches so that power is sent from the generator to the DC circuit, the DC / DC converter sets the voltage of the DC circuit to a first voltage when the inverter is normal, and sets the voltage of the DC circuit to a second voltage lower than the first voltage when the inverter malfunctions, a working machine.

2. When the inverter malfunctions, the DC / DC converter switches the voltage of the DC circuit between the second voltage and a third voltage higher than the second voltage based on the remaining charge of the storage battery, The working machine according to Claim 1.

3. When the inverter malfunctions, at least one of the output power, rotational speed, and output torque of the motor is limited to a value lower than when the inverter is normal, The working machine according to Claim 1 or Claim 2.

4. A hoisting tool for lifting a load, and a hoisting machine for winding up a wire to which the hoisting tool is connected, the motor drives the hoisting machine, The working machine according to any one of Claims 1 to 3.

5. An upper slewing body that supports a bucket via an arm and a boom, and comprising, the motor drives at least one of the bucket, the arm, the boom, and the upper slewing body, The working machine according to any one of Claims 1 to 3.

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