JP7704567B2 - Work Machine - Google Patents

Description

The present invention relates to a work machine.

Patent Document 1 describes a hybrid work machine that is equipped with a generator that generates electricity using engine power and an electric motor that outputs power for work. In the work 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, the inverter that sends the generator's power to the DC bus controls the voltage of the DC bus.

JP 2010-178508 A

In hybrid work machines, if an abnormality occurs in the inverter that converts the generator's power, the battery will then run out of charge and the electric motor will no longer be able to operate.

The present invention aims to provide a work machine that can extend the time that the electric motor can be driven even if an abnormality occurs in the inverter that converts the generator's power.

The working machine according to the present invention comprises:
A DC circuit,
a DC/DC converter disposed between the storage battery and the DC circuit and capable of changing a voltage of the DC circuit;
an inverter that converts the electric power generated by a generator and sends the converted electric power to the DC circuit;
an electric motor driven by power supplied from the DC power circuit;
Equipped with
When an abnormality occurs in the inverter, control of the DC/DC converter is switched 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 is abnormal .

According to the present invention, even if an abnormality occurs in the inverter that converts the generator's power, the time that the electric motor can be driven can be extended.

FIG. 2 is a side view showing an example of a shovel. FIG. 2 is a block diagram showing an example of a configuration focusing on a drive system of a shovel. FIG. 2 is a circuit diagram showing an example of an inverter. FIG. 2 is a diagram illustrating the main parts of an electrical drive system of the shovel. 5 is a time chart showing an example of the operation of an inverter connected to a motor generator, a step-up/step-down converter, and an inverter connected to a turning motor. 4 is a flowchart showing an abnormality control process executed by a controller when an abnormality occurs in the inverter. 1A is a schematic front view and FIG. 1B is a schematic side view of a crane system according to an embodiment of the present invention.

Below, we will explain the form for implementing the invention with reference to the drawings.

[Basic configuration of excavator]
First, the basic configuration of the shovel according to this embodiment will be described with reference to Figs.

Figure 1 is a side view showing an example of a shovel according to this embodiment. The shovel corresponds to an example of a work machine according to the present invention.

The excavator according to this embodiment includes a lower carrier 1, an upper rotating body 3 mounted on the lower carrier 1 so as to be rotatable via a rotating mechanism 2, a boom 4, an arm 5, and a bucket 6 as attachments (working devices), and a cabin 10 in which the operator sits.

The lower traveling body 1 includes, for example, a pair of left and right crawlers, each of which is hydraulically driven by traveling hydraulic motors 1A, 1B (see Figure 2) to enable self-propulsion.

The upper rotating body 3 rotates relative to the lower traveling body 1 by being electrically driven by a rotating electric motor 21 (see FIG. 2) described later.

The boom 4 is pivotally attached to the front center of the upper rotating body 3 so that it can be raised and lowered, and an arm 5 is pivotally attached to the tip of the boom 4 so that it can rotate up and down, and a bucket 6 is pivotally attached to the tip of the arm 5 so that it can rotate up and down. The boom 4, arm 5, and bucket 6 are hydraulically driven by a boom cylinder 7, arm cylinder 8, and bucket cylinder 9, which serve as hydraulic actuators, respectively.

The cabin 10 is mounted on the front left side of the upper rotating body 3.

Figure 2 is a block diagram showing an example of the configuration of the excavator, focusing on the drive system, according to this embodiment.

In the diagram, mechanical power lines are indicated by double lines, high-pressure hydraulic lines are indicated by thick solid lines, pilot lines are indicated by dashed lines, and electrical drive and control lines are indicated by thin solid lines.

The hydraulic drive system of the excavator according to this embodiment includes an engine 11, a reduction gear 13, a main pump 14, and a control valve 17. As described above, the hydraulic drive system according to this embodiment also includes traveling hydraulic motors 1A and 1B, a boom cylinder 7, an arm cylinder 8, and a bucket cylinder 9, which hydraulically drive the lower traveling body 1, the boom 4, the arm 5, and the bucket 6, respectively.

The engine 11 is the main power source in the hydraulic drive system, and is mounted, for example, at the rear of the upper rotating body 3. The engine 11 rotates at a constant speed at a preset target speed under the control of an engine control module (ECM: Engine Control Module) 11A. The engine 11 is, for example, a diesel engine that uses diesel as fuel, and drives a main pump 14 and a pilot pump 15 via a reduction gear 13. The engine 11 also drives a motor generator 12 via the reduction gear 13, causing the motor generator 12 to generate electricity.

In addition, a clutch 11B is provided on the power transmission path between the engine 11 and the reduction gear 13. As described below, the operation of the clutch 11B is controlled by the controller 30, and the engine 11 and the reduction gear 13 can be switched between a connected state and a non-connected state. The clutch 11B may be, for example, an electromagnetic type that is directly controlled by a signal from the controller 30.

The clutch 11B may be omitted.

The reduction gear 13 is mounted on the rear of the upper rotating body 3, for example, like the engine 11, and has two input shafts to which the engine 11 and the motor generator 12 described below are connected, and one output shaft to which the main pump 14 and pilot pump 15 are coaxially connected in series. The reduction gear 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. The reduction gear 13 can also 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.

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

The control valve 17 is, for example, mounted in the center of the upper rotating body 3, and is a hydraulic control device that controls the hydraulic drive system in response to the operation of the operating device 26 by the operator. As described above, the control valve 17 is connected to the main pump 14 via the high-pressure hydraulic line 16, and selectively supplies hydraulic oil supplied from the main pump 14 to the traveling hydraulic motors 1A (for the right) and 1B (for the left), boom cylinder 7, arm cylinder 8, and bucket cylinder 9, which are hydraulic actuators, in response to the operating state of the operating device 26. Specifically, the control valve 17 is a valve unit that includes multiple hydraulic control valves (directional control 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.

The electric drive system according to this embodiment also includes a motor generator 12, a turning motor 21, a turning reducer 24, a current sensor 21s, a resolver 22, a mechanical brake 23, and an electricity storage system 120.

The motor generator 12 (an example of a first motor) is an assist power source for the hydraulic drive system that assists the engine 11 to drive the main pump 14, and is mounted, for example, together with the engine 11 and the reduction gear 13 at the rear of the upper rotating body 3. Since the motor generator 12 is an assist power source, the output of the motor generator 12 is usually relatively smaller than the output of the engine 11, for example, the output of the motor generator 12 is about 20% of the output of the engine 11. The motor generator 12 is connected to the power storage system 120 including the storage battery 19 via the inverter 18A, and operates with three-phase AC power supplied from the storage battery 19 and the swing motor 21 via the inverter 18A, and drives the main pump 14 and the pilot pump 15 via the reduction gear 13. The motor generator 12 also operates to generate electricity by being driven by the engine 11, and can supply the generated power to the storage battery 19 and the swing motor 21. The motor generator 12 is controlled to switch between power running and power generation by the controller 30, which will be described later, controlling the drive of the inverter 18A.

The turning motor 21 (an example of a second motor or actuator) drives the turning mechanism 2 that connects the upper turning body 3 to the lower traveling body 1 for free turning. The turning motor 21 performs power running to turn the upper turning body 3 and regenerative running to generate regenerative power and brake the upper turning body 3 under the control of the controller 30. The turning 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 motor generator 12 via the inverter 18B. The turning motor 21 also supplies regenerative power to the storage battery 19 or the motor generator 12 via the inverter 18B. This allows the storage battery 19 to be charged or the motor generator 12 to be driven with the regenerative power. The switching control between power running and regenerative running of the turning motor 21 is realized by the controller 30 controlling the drive of the inverter 18B. A resolver 22, a mechanical brake 23, and a rotation reducer 24 are connected to the rotating shaft 21A of the rotation motor 21.

The slewing reduction gear 24 is connected to the rotating shaft 21A of the slewing motor 21, and reduces the output (torque) of the slewing motor 21 at a predetermined reduction ratio, thereby increasing the torque and driving the upper slewing body 3 to rotate. That is, during power running, the slewing motor 21 drives the upper slewing body 3 to rotate via the slewing reduction gear 24. The slewing reduction gear 24 also increases 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 regenerative operation, the slewing motor 21 generates regenerative power using the inertial rotational force of the upper slewing body 3 transmitted via the slewing reduction gear 24, and brakes the upper slewing body 3 to rotate.

The current sensor 21s detects the current of each of the three phases (U-phase, V-phase, and W-phase) of the turning motor 21. The current sensor 21s is provided, for example, in the power path between the turning motor 21 and the inverter 18B. The detection signal corresponding to the current of each of the three phases of the turning motor 21 detected by the current sensor 21s is taken into the inverter 18B and transmitted from the inverter 18B to the controller 30.

The resolver 22 detects the rotational position (rotational angle) of the turning motor 21. The resolver 22 transmits a detection signal corresponding to the detected rotational angle to the controller 30.

Under the control of the controller 30, the mechanical brake 23 mechanically generates a braking force on the upper rotating body 3 (specifically, the rotating shaft 21A of the rotating motor 21), braking the upper rotating body 3 from rotating and maintaining the upper rotating body 3 in a stopped state.

In FIG. 2, the slewing reducer 24 and the mechanical brake 23 are shown as separate block elements for simplicity, but the mechanical brake 23 may be, for example, a hydraulic brake that is incorporated between multiple reducers included in the slewing reducer 24, or an electromagnetic brake that is provided separately from the slewing reducer 24.

The power storage system 120 includes a storage battery 19, a DC bus 100, and a step-up/step-down converter (corresponding to a DC/DC converter) 110, and is mounted, for example, together with inverters 18A and 18B on the front right side of the upper rotating body 3.

The storage battery 19 (an example of a power storage device) supplies power to the motor generator 12 and the turning motor 21, and also charges the generated power of the motor generator 12 and the turning motor 21, which is supplied via the DC bus 100 and the step-up/step-down converter 110.

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

The DC bus 100 is disposed between the inverters 18A, 18B and the step-up/step-down converter 110, and transmits power between the storage battery 19, the motor generator 12, and the turning motor 21. The DC bus 100 is a DC circuit (DC bus) having a positive power line and a negative power line that transmit DC voltage.

The step-up/step-down converter 110 switches between step-up and step-down operation depending on the operating state of the motor generator 12 and the turning motor 21 so that the voltage value of the DC bus 100 falls within a certain range. The step-up/step-down converter 110 switches between step-up and step-down operation 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, and is controlled by the controller 30.

The operating system of the excavator in this embodiment also includes a pilot pump 15, an operating device 26, a pressure sensor 29, etc.

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

The operating device 26 includes levers 26A, 26B and a pedal 26C. The operating device 26 is provided near the cockpit of the cabin 10, and is an operation input means for the operator to operate each operating element (lower traveling body 1, upper rotating body 3, boom 4, arm 5, bucket 6, etc.). In other words, the operating device 26 is an operation input means for operating each hydraulic actuator (travel hydraulic motor 1A, 1B, boom cylinder 7, arm cylinder 8, bucket cylinder 9, etc.) and electric actuator (swing electric motor 21, etc.) that drive each operating element. The operating device 26 (levers 26A, 26B, and pedal 26C) are each connected to the control valve 17 via a hydraulic line 27. As a result, a pilot signal (pilot pressure) corresponding to the operating state of the lower traveling body 1, boom 4, arm 5, 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. The operating device 26 is also connected to a pressure sensor 29 via a hydraulic line 28.

As described above, the pressure sensor 29 is connected to the operating device 26 via the hydraulic line 28, and detects the secondary pilot pressure of the operating device 26, i.e., the pilot pressure corresponding to the operating state of each operating element 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 state of the lower traveling body 1, upper rotating body 3, boom 4, arm 5, bucket 6, etc. in the operating device 26 is input to the controller 30.

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 any hardware, software, or a combination thereof, and may be, for example, configured as a microcomputer including a CPU, ROM, RAM, I/O, etc., and various functions are realized by executing various programs stored in the ROM on the CPU. The controller 30, the ECM 11A, etc. are connected to each other by a communication network (LAN: Local Area Network) based on a communication standard such as CAN (Controller Area Network) or Ethernet (registered trademark).

The controller 30 controls the drive of the shovel. For example, the controller 30 controls the drive of the electric drive system based on a detection value transmitted from the pressure sensor 29 that corresponds to the operating state of the operating device 26.

The ECM 11A controls the engine 11, specifically the various devices included in the engine 11 (e.g., fuel injection device, etc.), and rotates the engine 11 at a constant speed (constant speed control).

In addition, the ECM 11A transmits detection signals from sensors (e.g., an RPM sensor, not shown) that detect various conditions of the engine 11 to the controller 30. The ECM 11A also has a function (diagnosis function) to detect faults in the engine 11 based on the detection signals from the sensors, and if a fault that causes the engine 11 to stop occurs, it transmits a signal (fault signal) to the controller 30 indicating that a fault has occurred.

When an abnormality occurs in the inverter 18A connected to the motor generator 12, the shovel according to this embodiment switches control of the step-up/step-down converter 110 to perform abnormal operation to extend the time during which the rotation motor 21 can be driven. The shovel according to this embodiment includes a display device 32 that displays the occurrence of an abnormality and that abnormal operation is being performed, as a configuration related to the abnormal operation described above. By looking at the display, the operator can operate the rotation motor 21, but can also recognize that an abnormality has occurred in the inverter 18A and that maintenance is required. The shovel may further include an abnormal operation switch 36 that switches between starting and stopping abnormal operation, so that abnormal operation can be started or stopped by the operator's operation.

The display device 32 is communicatively connected to the controller 30 and displays various information for the operator, etc. (e.g., guidance information regarding operation guidance during abnormal operation of the excavator, which will be described later) under the control of the controller 30. The display device 32 is, for example, a liquid crystal display.

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. The abnormal operation switch 36 may also be an existing hardware switch that performs other functions in the normal operation mode.

<Inverter 18A>
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 units 181 each connected to a three-phase coil of the motor generator 12. Each circuit unit 181 includes a current path leading to a negative output terminal TON via a lower switching element SN, and a current path leading to a positive output terminal TOP via an upper switching element SP. In each circuit unit 181, a 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 connected to a positive power line 100P and a negative power line 100N of the DC bus 100, respectively.

The upper switching element SP switches between on and off two terminals through which current flows depending on the voltage at the control terminal. The lower switching element SN switches between on and off two terminals through which current flows depending on the voltage at 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 current flows of the upper switching element SP in a direction that allows current to flow from node N to the positive output terminal TOP. The diode DP is connected between the two terminals through which current flows of the lower switching element SN in a direction that allows current to flow from the negative output terminal TON to node N.

The controller 30 converts the AC power generated in the three-phase coil of the motor generator 12 into DC power by controlling the switching of the three upper switching elements SP and the three lower switching elements SN in accordance with the rotation phase of the motor generator 12. The DC power is then sent to the DC bus 100 from the negative output terminal TON and the positive output terminal TOP. The controller 30 controls the inverter 18A so that a current flows with a phase angle shifted relative to the phase of the induced electromotive force generated in the coil of the motor generator 12, thereby increasing the regenerative torque of the motor generator 12 and generating large power.

The controller 30 detects the AC current flowing through the three-phase coils and controls the inverter 18A so that the AC current matches a target value.

<Abnormality in inverter 18A>
If an abnormality occurs in the inverter 18A, the controller 30 stops switching control of the inverter 18A. The inverter 18A may have sensors for detecting the voltage, current, temperature, etc. of each component, and when the sensor values indicate an abnormality, a signal indicating the abnormality is sent to the controller 30, which then determines that the inverter 18A is abnormal. Alternatively, the controller 30 may determine that the inverter 18A is abnormal when the currents flowing through the three-phase coils of the motor generator 12 deviate from target values.

When the controller 30 determines that there is an abnormality in the inverter 18A and stops controlling 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 AC induced electromotive force generated in the three-phase coils of the motor generator 12 is output to each node N.

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, and no current is generated from the motor generator 12 to the DC bus 100. No reverse current is generated 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 a current flows from the motor generator 12 to the DC bus 100. In other words, the generated power is sent from the motor generator 12 to the DC bus 100.

<Control operation>
FIG. 4 is a diagram illustrating the main parts of the electric drive system of the shovel.

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. Furthermore, the controller 30 controls the inverter 18B in response to the driving operation, so that power is sent from the DC bus 100 to the turning motor 21, which drives the turning motor 21. Furthermore, the step-up/step-down converter 110 operates to maintain the voltage of the DC bus 100, so that if the generated power of the motor generator 12 is greater than the power used by the turning motor 21, the step-up/step-down 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 turning motor 21, the step-up/step-down converter 110 sends the discharge current of the storage battery 19 to the DC bus 100.

Next, we will explain the operation of the above electrical drive system when inverter 18A is normal and when control of inverter 18A is stopped due to an abnormality.

Figure 5 is a time chart showing an example of the operation of an inverter connected to a motor generator, a step-up/step-down converter, and an inverter connected to a turning motor. In Figure 5, at timing t1, control of inverter 18A is stopped due to an abnormality.

During normal operation (period T1), the controller 30 sets the target voltage of the step-up/step-down converter 110 to a first voltage V1 (e.g., 360 V). By setting the target voltage, the voltage of the DC bus 100 is adjusted to the first voltage V1.

Furthermore, the controller 30 limits the output power of the electric motor 21 to a first upper limit power _Pmax1 or less. The output power of the electric motor 21 varies depending on the operation of the operator and the rotation load of the upper rotating body 3. The controller 30 calculates the current of the electric motor 21 so that the electric motor 21 outputs a predetermined power according to the operation and load, and controls the inverter 18B to obtain the calculated current. Note that the output power is a concept that includes the output torque and the rotation speed. The output power may be interpreted as the output torque, the rotation speed, or both.

Furthermore, the controller 30 changes the power generated by the motor generator 12 according to the output power of the motor 21. Alternatively, the controller 30 may control the power generated according to the remaining charge of the storage battery 19 so that the power generated by the motor generator 12 is increased when the remaining charge is low and decreased when the remaining charge is high. The power generated by the motor generator 12 is changed by changing the target current of the inverter 18A. The target current of the inverter 18A means the effective value of the AC current flowing through the coil of the motor generator 12.

During normal operation (period T1), when the amount of power generated by the motor generator 12 is smaller than the output power of the turning motor 21, the step-up/step-down 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 amount of power generated by the motor generator 12 is greater than the output power of the turning motor 21, the step-up/step-down converter 110 draws current from the DC bus 100 to the storage battery 19 in order to maintain the voltage of the DC bus 100 at the first voltage V1, thereby charging the storage battery 19. This action causes the remaining charge of the storage battery 19 to fluctuate up and down.

When an abnormality occurs in the inverter 18A and the inverter 18A switches to abnormal operation, the controller 30 changes the target voltage of the step-up/step-down converter 110 to a second voltage V2 (e.g., 220 V) lower than the first voltage V1 (e.g., 360 V) (period T2a). In accordance with 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 when 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, the motor generator 12 rotates and a current flows from the inverter 18A to the DC bus 100. Therefore, the generated power is sent from the motor generator 12 to the DC bus 100.

Furthermore, the controller 30 limits the output power of the turning electric motor 21 to a second upper limit power _Pmax2 or less. The second upper limit power _Pmax2 is lower than the first upper limit power _Pmax1 , which is the upper limit during normal operation. Due to the above-mentioned limitation, even if an operation that exceeds the second upper limit power _Pmax2 is performed, the controller 30 keeps the output power of the inverter 18B at the second upper limit power _Pmax2 . As the voltage of the DC bus 100 (the input voltage of the inverter 18B) decreases, the upper limit of the output power of the turning electric motor 21 decreases, making it possible to prevent an excessive load from being applied to the inverter 18B.

Furthermore, when the remaining charge of the storage battery 19 becomes greater than the first threshold TH1 (timing t2), the controller 30 switches the target voltage of the step-up/step-down converter 110 to a third voltage V3 (e.g., 300 V) higher than the second voltage V2 (e.g., 220 V) (period T2b). When the remaining charge of the storage battery 19 becomes less than the second threshold TH2 (timing t3), the controller 30 returns the target voltage of the step-up/step-down converter 110 to the second voltage V2 (period T2c). The third voltage V3 is lower than the first voltage V1, which is the target voltage in the normal state.

The third voltage V3 is a value higher than the induced electromotive force generated in the coil of the motor generator 12 when the inverter 18A is stopped, but may be a lower 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 when the inverter 18A is stopped and the motor generator 12 is rotating can be made zero (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 turning motor 21, it is possible to prevent a charging current from being sent to the storage battery 19 and to suppress a decrease in the remaining charge of the storage battery 19.

The first voltage V1 to the third voltage V3 may be set to a voltage higher than the voltage of the storage battery 19. With such a setting, the step-up/step-down converter 110 only performs step-up operation, so that the circuit configuration of the step-up/step-down converter 110 can be simplified.

According to this control, as shown in periods T2a, T2b, and T2c, if the remaining charge of the storage battery 19 decreases, the power sent from the motor generator 12 to the DC bus 100 increases, whereas if the remaining charge 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 for a long time the function of buffering the difference between the generated power and the power used.

During abnormal operation, the controller 30 causes the display device 32 to display information about the abnormal operation. The displayed information may include information such as that the upper limit power of the swing electric motor 21 has been reduced to the second upper limit power _Pmax2 , that operation can be continued but maintenance of the inverter 18A is necessary, and the like. The operator can continue operating the excavator while requesting maintenance based on the information displayed on the display device 32. Alternatively, the operator can request maintenance and move the excavator from the site to a maintenance location, thereby reducing the situation in which an excavator with an abnormality remains at the site.

<Control Processing>
6 is a flow chart showing the abnormal operation process executed by the controller. The controller 30 starts the abnormal operation process when it is started. When the abnormal operation process starts, the controller 30 reads the detected values of the state of the inverter 18A (current, voltage, temperature, etc. of each part) and determines whether or not an abnormality has occurred in the inverter 18A (step S1). If no abnormality is found, the controller 30 returns to the process in step S1 and repeats the determination in step S1.

On the other hand, if it is determined that there is an abnormality, the controller 30 stops the control of the inverter 18A (step S2), and switches the target voltage of the step-up/step-down converter 110 to the second voltage V2 (step S3). Furthermore, the set value of the upper limit power of the turning electric motor 21 is reduced to the second upper limit power _Pmax2 (step S4). By setting the upper limit power, the output power of the inverter 18B is limited to the second upper limit power _Pmax2 or less in the control process of the inverter 18B.

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

The controller 30 further determines whether the target voltage of the buck-boost converter 110 is the third voltage V3 and the remaining charge of the storage battery 19 is less than the second threshold TH2 (step S7), and if NO, 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 returns to step S5.

This abnormal operation process realizes the control operation shown in Figure 5.

As described above, according to the excavator of this embodiment, even if an abnormality occurs in the inverter 18A connected to the motor generator 12, the control of the step-up/step-down 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 turning motor 21 can be driven can be extended by the amount of power sent from the motor generator 12.

Furthermore, according to the excavator of this embodiment, when an abnormality occurs in the inverter 18A, the target voltage of the step-up/step-down 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 via the inverter 18A, whose control has been stopped.

Furthermore, according to the excavator of this embodiment, the target voltage of the step-up/step-down converter 110 is switched between the second voltage V2 and a higher third voltage V3 based on the remaining charge of the storage battery 19. By switching the target voltage to the third voltage V3, it is possible to reduce the generated power sent from the motor generator 12 to the DC bus 100 via the inverter 18A whose control has been stopped. Therefore, when the power used 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.

Furthermore, according to the excavator of this embodiment, when an abnormality occurs in the inverter 18A, the upper limit power of the turning electric motor 21 is switched to the second upper limit power _Pmax2 which is lower than the first upper limit power _Pmax1 in the normal state. Therefore, it is possible to prevent an excessive load from being applied to the inverter 18B due to a drop in the input voltage of the inverter 18B.

In the above embodiment, an example was shown in which the equipment driven by the electric power generated by the motor generator 12 is the electric motor 21 for rotating the upper rotating body 3. However, the hydraulic cylinders for driving the boom 4, arm 5, and bucket 6 can be replaced with electric motors. In this case, the boom 4, arm 5, or bucket 6 may be applied as the equipment driven by the electric power generated by the motor generator 12.

In addition, in the above embodiment, the motor generator 12 is configured to have the function of assisting the driving of the engine 11 by using the power of the storage battery 19, but the motor generator 12 may be changed to a generator dedicated to generating electricity.

In addition, in the above embodiment, the step-up/step-down converter 110 that controls the voltage of the DC bus 100 may be a DC/DC converter that only steps up the voltage, or a DC/DC converter that only steps down the voltage depending on the voltage of the storage battery 19.

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

Figures 7A and 7B are schematic front and side views of a crane system according to this embodiment. A plurality of pillars 40 support a girder 41. The pillars 40 and the girder 41 form a portal frame. Wheels 42 are attached to the lower ends of the pillars 40, and the portal frame runs along rails 43. The direction perpendicular to the paper surface of Figure 7A and the left-right direction of Figure 7B correspond to the running direction. A trolley 45 is mounted on the girder 41. A hoist 46 is mounted on the trolley 45.

A number of electric actuators drive the respective operating parts. For example, a travel motor 51 mounted on the portal frame drives the wheels 42. A traverse motor 52 mounted on the trolley 45 moves the trolley 45 in the traverse direction. The left-right direction in FIG. 7A and the direction perpendicular to the paper surface in FIG. 7B correspond to the traverse direction. A hoist motor 53 mounted on the hoist 46 winds up and pays out a wire with a hanging device 47, such as a hook, attached to its tip. In this way, electric actuators such as the hoist motor 53, traverse motor 52, and travel motor 51 drive the operating parts of the hanging device 47, the trolley 45, and the wheels 42, respectively.

An AC power supply 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 the portal frame. The AC power supply 60 includes an engine 61 and a generator 62. The AC power supply 60 supplies driving power to the hoisting motor 53, the traverse motor 52, and the travel motor 51. Furthermore, the power storage device 67 is charged by the power supplied from the AC power supply 60.

An inverter 62I that converts the generated power into DC power is connected to the generator 62, and an inverter 53I that drives the hoisting motor 53 is connected to the hoisting motor 53. The inverters 62I, 53I, and the power conversion device 68 are connected via a DC bus. The controller 70 of the crane system controls the inverters 62I, 53I, and the power conversion device 68 in the same manner as the controller 30 of the above-mentioned embodiment. In this case, 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 step-up/step-down converter 110 of the embodiment.

The traverse motor 52 is connected to an inverter 52I that drives the motor, and the travel motor 51 is connected to an inverter 51I that drives the motor. The controller 70 may also perform control over the traverse motor 52 and the inverter 52I, and the travel motor 51 and the inverter 51I in the same manner as the controller 30 of the first embodiment performs control over the turning motor 21 and the inverter 18B.

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

As described above, in the crane system, if 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 the same effect as in the above-mentioned embodiment can be achieved.

The above describes an embodiment of the present invention. However, the present invention is not limited to the above embodiment, and the details shown in the embodiment can be modified as appropriate without departing from the spirit of the invention.

3 Upper rotating body 4 Boom 5 Arm 6 Bucket 11 Engine 12 Motor generator (generator)
18A inverter 19 storage battery 21 turning motor 30 controller 32 display device 36 abnormal operation switch 100 DC bus (direct current 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 device 51 Travel motor (electric motor)
52 Traverse motor (electric motor)
53 Hoisting motor (electric motor)
61 Engine 62 Generator 62I Inverter 68 Power conversion device (DC-DC converter)
70 Controller

Claims (5)

A DC circuit,
a DC/DC converter disposed between the storage battery and the DC circuit and capable of changing a voltage of the DC circuit;
an inverter that converts the electric power generated by a generator and sends the converted electric power to the DC circuit;
an electric motor driven by power supplied from the DC power circuit;
Equipped with
When an abnormality occurs in the inverter, control of the DC/DC converter is switched 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 is abnormal;
Working machinery. When the inverter becomes abnormal, 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.
2. The work machine according to claim 1 . When the inverter becomes abnormal, at least one of the output power, the rotation speed, and the output torque of the motor is limited to a value lower than that when the inverter is normal.
A work machine according to claim 1 or 2 . A lifting device for lifting a load;
a hoist that hoists the wire to which the suspending tool is connected,
The electric motor drives the hoist.
A work machine according to any one of claims 1 to 3 . an upper rotating body that supports the bucket via an arm and a boom;
Equipped with
The electric motor drives at least one of the bucket, the arm, the boom, and the upper rotating body.
A work machine according to any one of claims 1 to 3 .

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