WO2014041922A1

WO2014041922A1 - Excavator

Info

Publication number: WO2014041922A1
Application number: PCT/JP2013/071100
Authority: WO
Inventors: 英昭湯浅
Original assignee: 住友重機械工業株式会社
Priority date: 2012-09-14
Filing date: 2013-08-05
Publication date: 2014-03-20
Also published as: JP5951027B2; JPWO2014041922A1

Abstract

An engine drives a generator, the electricity generated by the generator is stored in a power storage circuit, and a work-use electric motor is driven by electricity supplied from the power storage circuit. The work-use electric motor causes an upper rotating body to rotate. The power storage circuit has a power storage device and multiple buck-boost converters which are parallel-connected to each other. Each buck-boost converter contains a switching element and a reactor. Induced electromotive force is generated in the reactors by the switching of the switching elements, thereby boosting the voltage of the power storage device, which is then supplied to the work-use electric motor.

Description

Excavator

The present invention relates to an excavator that boosts an output voltage of a power storage device with a buck-boost converter and drives a working electric motor.

A hybrid work machine in which a part of the drive mechanism is electrified and an electric work machine in which all the drive mechanisms are electrified have been proposed. The work machine includes an excavator such as an excavator. In a hybrid work machine or an electric work machine, generally, electric power stored in a power storage device is boosted by a buck-boost converter, and the electric motor is driven by the output of the buck-boost converter.

JP 2010-124568 A

A buck-boost converter usually includes a switching element and a reactor. When using a motor with a large maximum output, a switching element or a reactor of a buck-boost converter must also have a large rated current. When elements having a large rated current are used, the cooling device for cooling these elements is also enlarged. Further, in the hybrid excavator, since the rotation of the revolving body to which the boom is attached is frequently accelerated / decelerated, charging / discharging of the power storage device is frequently switched, and the amount of generated heat is also increased. For this reason, the cooling device used for the hybrid excavator is larger than the cooling device for the buck-boost converter used for the hybrid type general vehicle. In order to be mounted on a hybrid excavator, a step-up / down converter capable of efficiently cooling is desired.

An object of the present invention is to provide an excavator equipped with a step-up / down converter capable of using a switching element or a reactor having a small rated current.

According to one aspect of the invention,
A lower traveling body,
An upper revolving unit mounted on the lower traveling unit so as to be able to swivel;
Engine,
A generator driven by the power of the engine;
A storage circuit for storing electric power;
An inverter connecting the generator and the storage circuit;
Driven by electric power supplied from the power storage circuit, and has a working electric motor for turning the upper turning body,
The storage circuit is
A power storage device;
A plurality of buck-boost converters connected in parallel to each other;
Each of the step-up / step-down converters includes a switching element and a reactor, and generates an induced electromotive force in the reactor by a switching operation of the switching element, thereby boosting a voltage of the power storage device to the working electric motor. A supply excavator is provided.

Since multiple buck-boost converters are connected in parallel with each other, the current flowing through one buck-boost converter is reduced. As a result, it is possible to use a switching element or a reactor having a small rated current. Since the amount of heat generated by each switching element and reactor is reduced, efficient cooling is possible.

FIG. 1 is a side view of an excavator according to an embodiment. FIG. 2 is a block diagram of the excavator according to the embodiment. FIG. 3 is a block diagram of a power storage circuit mounted on the excavator according to the embodiment. FIG. 4 is an equivalent circuit diagram of the buck-boost converter included in the power storage circuit. FIG. 5 is an equivalent circuit diagram of the inverter. FIG. 6 is a cross-sectional view of a power conversion device that houses a buck-boost converter and an inverter. FIG. 7 is a block diagram for explaining the operation of the storage circuit when one buck-boost converter has failed. FIG. 8 is a block diagram showing a control flow of the working electric motor. FIG. 9 is an equivalent circuit diagram of a power storage circuit according to another embodiment. 10A is an equivalent circuit diagram of a storage circuit according to still another embodiment and a block diagram of a control device, and FIG. 10B is an analog value before and after A / D conversion of charge / discharge current by the control device shown in FIG. 10A. It is a graph which shows a response | compatibility with a digital value. 11A is an equivalent circuit diagram of a storage circuit according to a comparative example and a block diagram of a control device, and FIG. 11B shows an analog value and a digital value before and after A / D conversion of charge / discharge current by the control device shown in FIG. 11A. It is a graph which shows correspondence of these.

FIG. 1 shows a side view of an excavator according to the embodiment. An upper turning body 21 is mounted on the lower traveling body 20 so as to be turnable. A boom 23 is connected to the upper swing body 21, an arm 25 is connected to the boom 23, and a bucket 27 is connected to the arm 25. As the boom cylinder 24 expands and contracts, the posture of the boom 23 changes. As the arm cylinder 26 expands and contracts, the posture of the arm 25 changes. Due to the expansion and contraction of the bucket cylinder 28, the posture of the bucket 27 changes. The boom cylinder 24, the arm cylinder 26, and the bucket cylinder 28 are hydraulically driven.

The upper swing body 21 is equipped with a swing motor 22, an engine 30, a motor generator 31, a power storage circuit 40, and a power conversion device 50. The motor generator 31 generates power with the power of the engine 30. The generated power is charged in the storage circuit 40. The turning electric motor 22 is driven by the electric power from the power storage circuit 40 and turns the upper turning body 21. The power conversion device 50 includes a step-up / down converter for performing charge / discharge control of the storage circuit 40, an inverter for driving the swing motor 22, and the like. The motor generator 31 also operates as an electric motor and assists the engine 30. The turning electric motor 22 also operates as a generator and generates regenerative power from the turning kinetic energy of the upper turning body 21.

FIG. 2 shows a block diagram of the excavator according to the first embodiment. In FIG. 2, the mechanical power system is represented by a double line, the high-pressure hydraulic line is represented by a thick solid line, the electric control system is represented by a thin solid line, and the pilot line is represented by a broken line.

The drive shaft of the engine 30 is connected to the input shaft of the torque transmission mechanism 32. The engine 30 is an engine that generates a driving force by a fuel other than electricity, for example, an internal combustion engine such as a diesel engine. The engine 30 is always driven during operation of the work machine.

The drive shaft of the motor generator 31 is connected to the other input shaft of the torque transmission mechanism 32. The motor generator 31 can perform both the electric (assist) operation and the power generation operation. As the motor generator 31, for example, an internal magnet embedded (IPM) motor in which a magnet is embedded in the rotor is used.

The torque transmission mechanism 32 has two input shafts and one output shaft. The output shaft is connected to the drive shaft of the main pump 75.

When the load applied to the engine 30 is large, the motor generator 31 performs an assist operation, and the driving force of the motor generator 31 is transmitted to the main pump 75 via the torque transmission mechanism 32. Thereby, the load applied to the engine 30 is reduced. On the other hand, when the load applied to the engine 30 is small, the driving force of the engine 30 is transmitted to the motor generator 31 via the torque transmission mechanism 32, so that the motor generator 31 is operated for power generation.

The main pump 75 supplies hydraulic pressure to the control valve 77 via the high pressure hydraulic line 76. The control valve 77 distributes hydraulic pressure to the

hydraulic motors

29A and 29B, the boom cylinder 24, the arm cylinder 26, and the bucket cylinder 28 in accordance with a command from the driver. The

hydraulic motors

29A and 29B drive the two left and right crawlers provided in the lower traveling body 20 shown in FIG.

The three-phase AC wiring 60 connects the inverter 51 and the motor generator 31. A DC wiring (bus line) 61 connects the inverter 51 and the storage circuit 40. A three-phase AC wiring 62 connects the turning electric motor 22 and the inverter 52. A DC wiring (bus line) 63 connects the inverter 52 and the storage circuit 40.

Inverters

51 and 52 and power storage circuit 40 are controlled by control device 90.

The inverter 51 controls the operation of the motor generator 31 based on a command from the control device 90. Switching between the assist operation and the power generation operation of the motor generator 31 is performed by the inverter 51.

During the period in which the motor generator 31 is assisted, necessary power is supplied from the power storage circuit 40 to the motor generator 31 through the inverter 51. During the period in which the motor generator 31 is generating, the electric power generated by the motor generator 31 is supplied to the storage circuit 40 through the inverter 51. Thereby, the power storage device in the power storage circuit 40 is charged.

The turning motor 22 is AC driven by the inverter 52 and can perform both power running operation and regenerative operation. For example, an IPM motor is used for the swing motor 22. During the power running operation of the swing motor 22, electric power is supplied from the power storage circuit 40 to the swing motor 22 via the inverter 52. The turning electric motor 22 turns the upper turning body 21 (FIG. 1) via the speed reducer 80. During the regenerative operation, the rotational motion of the upper swing body 21 is transmitted to the swing motor 22 via the speed reducer 80, so that the swing motor 22 generates regenerative power. The generated regenerative power is supplied to the storage circuit 40 via the inverter 52. Thereby, the power storage device in the power storage circuit 40 is charged.

The resolver 81 detects the position of the rotating shaft of the turning electric motor 22 in the rotational direction. The detection result of the resolver 81 is input to the control device 90. By detecting the position of the rotating shaft in the rotational direction before and after the operation of the turning electric motor 22, the turning angle and the turning direction are derived.

The mechanical brake 82 is connected to the rotating shaft of the turning electric motor 22 and generates a mechanical braking force. The braking state and the release state of the mechanical brake 82 are controlled by the control device 90 and switched by an electromagnetic switch.

The pilot pump 78 generates a pilot pressure necessary for the hydraulic operation system. The generated pilot pressure is supplied to the operating device 83 via the pilot line 79. The operation device 83 includes a lever and a pedal and is operated by a driver. The operating device 83 converts the primary side hydraulic pressure supplied from the pilot line 79 into a secondary side hydraulic pressure in accordance with the operation of the driver. The secondary side hydraulic pressure is transmitted to the control valve 77 via the hydraulic line 84 and to the pressure sensor 86 via the other hydraulic line 85.

The detection result of the pressure detected by the pressure sensor 86 is input to the control device 90. Thereby, the control apparatus 90 can detect the operation state of the lower traveling body 20, the turning electric motor 22, the boom 23, the arm 25, and the bucket 27 (FIG. 1).

FIG. 3 shows a block diagram of the storage circuit 40. A plurality, for example, two step-up / down converters 41 are connected in parallel to each other. A power storage device 45 is connected to an input terminal of the step-up / down converter 41 connected in parallel with each other through a disconnection circuit 35. For the power storage device 45, for example, an electric double layer capacitor, a lithium ion capacitor, a lithium ion secondary battery, or the like is used. Isolation circuit 35 includes a relay 36 disposed corresponding to each of step-up / down converters 41. The relay 36 is controlled by the control device 90. When relay 36 is turned off, buck-boost converter 41 is electrically disconnected from power storage device 45. Further, the step-up / down converters 41 connected in parallel to each other are electrically disconnected. The voltmeter 56 measures the voltage between the terminals of the power storage device 45. The measurement result is input to the control device 90.

The output terminals of the step-up / down converter 41 connected in parallel to each other are connected to the DC bus line 55. A voltmeter 57 and a capacitor 46 for smoothing voltage and current are connected between the power supply line of the DC bus line 55 and the ground line. The voltmeter 57 measures the voltage between the output terminals of the buck-boost converter 41 (that is, the voltage of the DC bus line 55). The measurement result is input to the control device 90. The output terminal of the step-up / down converter 41 is connected to the

inverters

51 and 52 via

DC wirings

61 and 63. The step-up / down converter 41 controls charging / discharging of the power storage device 45 (FIG. 3).

The control device 90 monitors the normality of each operation state of the buck-boost converter 41. The normality of the operation is performed, for example, by measuring a charge / discharge current flowing through the buck-boost converter 41. When it is determined that the operation state of at least one step-up / down converter is abnormal, the control device 90 controls the disconnection circuit 35 so that the step-up / step-down converter 41 whose operation state is determined to be abnormal is Disconnect from the pressure converter. Even after the abnormal step-up / down converter 41 is disconnected, the operation of the step-up / down converter having the normal operation state is continued. For this reason, even if one buck-boost converter 41 breaks down, excavation work can be continued.

FIG. 4 shows an equivalent circuit diagram of the buck-boost converter 41. Between the output terminals of the step-up / down converter 41, a series circuit of a step-up switching element 42A and a step-down switching element 42B is connected. For example, insulated gate bipolar transistors (IGBT) are used as the

switching elements

42A and 42B. The emitter of the step-up IGBT 42A is connected to the negative output terminal, and the collector of the step-down IGBT 42B is connected to the positive output terminal. An interconnection point between the step-up IGBT 42 </ b> A and the step-down IGBT 42 </ b> B is connected to the positive input terminal via the reactor 44. Both the negative output terminal and the negative input terminal are grounded. A parallel circuit of the relay 48 and the resistor 49 is connected to the reactor 44 in series. The control device 90 performs on / off control of the relay 48. During normal operation, the relay 48 is on.

Commutation diodes (free wheel diodes) 43A and 43B are connected in parallel to the step-up IGBT 42A and the step-down IGBT 42B, respectively, with the direction from the emitter toward the collector being the forward direction. The control device 90 applies a control pulse width modulation (PWM) signal to the gate electrodes of the step-up IGBT 42A and the step-down IGBT 42B. Generally, the

switching elements

42A and 42B and the

commutation diodes

43A and 43B are modularized to form the switching module 42.

The ammeter 38 measures the charge / discharge current flowing through the reactor 44. The measurement result is input to the control device 90. The control device 90 determines the normality of the operation of the buck-boost converter 41 based on the measurement result of the ammeter 38.

Hereinafter, the boosting operation (discharging operation) will be described. A PWM voltage is applied to the gate electrode of the boosting IGBT 42A. During the switching operation of the boosting IGBT 42A, the inter-terminal voltage of the power storage device 45 is boosted by the induced electromotive force generated in the reactor 44, and the discharge current flows out from the output terminal via the commutation diode 43B.

Next, the step-down operation (charging operation) will be described. A PWM voltage is applied to the gate electrode of the step-down IGBT 42B. The power storage device 45 (FIG. 3) is charged via the commutation diode 43A by the induced electromotive force generated in the reactor 44 during the switching operation of the step-down IGBT 42B.

The control device 90 synchronously controls the plurality of step-up / down converters 41 based on the measurement results of the voltmeters 56 and 57 (FIG. 3). That is, the plurality of step-up / down converters 41 are synchronously controlled based on the same input information. Specifically, the pulse width of the PWM voltage applied to the gate electrodes of the

switching elements

42A and 42B is changed under the condition that the pulse widths of the PWM voltages applied to the plurality of buck-boost converters 41 are equal. The control of the plurality of step-up / down converters 41 is performed independently of the control of the

inverters

51 and 52.

The phase of the PWM voltage applied to the plurality of step-up / down converters 41 may be shifted. By shifting the phase of the PWM voltage, the ripple of the voltage output from the plurality of step-up / down converters 41 to the DC bus line 55 (FIG. 3) can be reduced. When n buck-boost converters 41 are connected, it is preferable to shift the phase of the PWM voltage applied to the n buck-boost converters 41 by 360 ° / n. For example, when two buck-boost converters 41 are connected in parallel, it is preferable to shift the phase of the PWM voltage by 180 °. When the three buck-boost converters 41 are connected in parallel, it is preferable that the phases of the PWM voltages are shifted from each other by 120 °.

When the voltage between the output terminals of the buck-boost converter 41 is lower than the voltage between the input terminals, that is, the voltage between the terminals of the power storage device 45 (FIG. 3), the relay 48 is turned off. At this time, the power storage device 45 is discharged via the resistor 49, the reactor 44, and the commutation diode 43B, and a discharge current flows out from the output terminal. The resistor 49 prevents an excessive discharge current from flowing.

When the primary battery is used for the power storage device 45 and only the discharge control of the power storage device 45 is performed, the step-down IGBT 42B is not necessary. Further, the commutation diode 43A connected in parallel to the boosting IGBT 42A is not necessary.

FIG. 5 shows an equivalent circuit diagram of the inverter 52 (FIG. 2) for the swing motor 22. The inverter 51 for the motor generator 31 has the same configuration as the inverter 52 for the swing motor 22.

Between the DC wiring 63, a U-phase switching module 53U, a V-phase switching module 53V, and a W-phase switching module 53W are inserted in parallel. Each of these switching modules includes two IGBTs connected in series, and a commutation diode inserted in parallel with each of the IGBTs. The interconnection points of the two IGBTs are connected to the U-phase, V-phase, and W-phase terminals of the swing electric motor 22, respectively. A control signal subjected to pulse width modulation (PWM) is applied from the control device 90 to the gate electrode of each IGBT.

FIG. 6A shows a cross-sectional view of the power conversion device 50 (FIG. 1). In the housing 65, the step-up / down converter 41 shown in FIG. 3, the

inverters

51, 52 shown in FIG. The housing 65 includes a side wall 66, a partition wall 67, a first lid 68, and a second lid 69. The flat cross section of the side wall 66 is, for example, a rectangle, and its top and bottom are open. The upper and lower open portions of the side wall 66 are closed with a first lid 68 and a second lid 69, respectively. A partition wall 67 is provided at substantially the center of the side wall 66 in the height direction. The partition wall 67 is orthogonal to the height direction of the side wall 66 and partitions the internal space of the housing 65 into two spaces. Of the two spaces partitioned by the partition wall 67, the space on the first lid 68 side is referred to as a “first space” 91, and the space on the second lid 69 side is referred to as a “second space” 92. And

A flow path (cooling mechanism) 94 is formed inside the partition wall 67. The cooling medium flowing through the flow path 94 cools the partition wall 67. The partition plate 67 partitions the space in the housing 65 and also functions as a cooling plate.

In the first space 91, the switching module 42 of the buck-boost converter 41 (FIG. 3), the U-phase switching module 53U, the V-phase switching module 53V, and the W-phase switching module 53W of the inverter 52 (FIG. 4). Contained. The switching

modules

42, 53 U, 53 V, and 53 W are mounted on the surface of the partition wall 67 on the first space 91 side and are thermally coupled to the partition plate 67. For this reason, the switching

modules

42, 53 U, 53 V, and 53 W are cooled by the cooling medium flowing through the flow path 94.

In the second space 92, the reactor 44, the relay 48, and the resistor 49 of the step-up / down converter 41 (FIG. 3) are accommodated. Specifically, the reactor 44, the relay 48, and the resistor 49 are mounted on the surface of the partition wall 67 on the second space 92 side, and are thermally coupled to the partition plate 67. For this reason, the reactor 44, the relay 48, and the resistor 49 are cooled by the cooling medium flowing through the flow path 94.

Openings

95 and 96 are formed in the partition wall 67. The smoothing capacitor 46 is accommodated in the housing 65 so as to penetrate the opening 96. As the capacitor 46, for example, an electrolytic capacitor is used. The outer shape of the electrolytic capacitor is generally larger than that of the switching

modules

42, 53U, 53V, 53W, the reactor 44, and the like. For this reason, when the capacitor 46 is accommodated only in one of the first space 91 and the second space 92, the space for accommodating the capacitor 46 must be enlarged. By disposing the capacitor 46 so as to pass through the opening 96 formed in the partition wall 67, an increase in the size of the housing 65 can be avoided. Furthermore, by providing the partition wall 67 that partitions the space in the housing 65 into the first space 91 and the second space 92, the overall rigidity of the power conversion device 50 can be increased.

The capacitor 46 is supported by the partition wall 67 through the tray 97. The tray 97 is attached to the partition wall 67 so as to close the opening 96 from the second space 92 side. By adjusting the depth of the tray 97, a sufficient space for wiring or the like can be secured between the capacitor 46 and the first lid 68. The condenser 46 is thermally coupled to the partition plate 67 via the tray 97 and is cooled via the tray 97 by the cooling medium flowing through the flow path 94.

The connector 98 is attached to the side wall 66. The switching module 42, the reactor 44, the relay 48, the resistor 49, and the connector 98 are connected to each other by a wiring 99. Some of the wirings 99 connect the components in the first space 91 and the components in the second space 92 through the opening 95.

FIG. 6B is a plan sectional view taken along one-dot chain line 6B-6B in FIG. 6A.

Switching modules

42, 53 U, 53 V, and 53 W are mounted on the partition wall 67. Furthermore, the switching

modules

54U, 54V, 54W constituting the inverter 51 (FIG. 2) are also mounted on the surface of the partition wall 67 on the first space 91 (FIG. 5A) side. Further, the switching module 47 of another step-up / down converter 41 (FIG. 3) different from the step-up / down converter 41 including the switching module 42 is also mounted on the surface of the partition wall 67 on the first space 91 (FIG. 5A) side. Has been. A capacitor 46 is disposed in the opening 96. A plurality of connectors 98 are attached to the side wall 66.

A cooling medium flow path 94 is formed in the partition wall 67. The flow path 94 advances in a direction orthogonal to the direction from the opening 95 toward the opening 96 as a whole while meandering between the opening 95 and the opening 96. Both ends of the flow path 94 are open to the outer surface of the same side surface of the side wall 66 as the surface to which the connector 98 is attached. The channel 94 overlaps the switching

modules

53U, 53V, 53W, 54U, 54V, 54W, 42, and 47 in plan view. Thereby, a switching module etc. can be cooled efficiently. Since the connector 98 and the openings at both ends of the flow path 94 are disposed on the same surface of the side wall 66, the power converter 50 can be installed more freely than in a configuration in which both are disposed on different surfaces. The degree increases. In addition, maintenance inspection and repair of the power conversion device 50 can be easily performed.

In the configuration in which the flow path 94 is disposed inside the outer wall of the housing 65, the outer surface of the outer wall cannot be used for cooling the switching module or the like. In the embodiment, since the flow path 94 is disposed in the partition wall 67 disposed in the internal space of the housing 65, both surfaces of the partition wall 67 can be used for cooling the switching module or the like. For this reason, the mounting density of components to be cooled can be increased. In other words, the power conversion device 50 can be downsized.

Semiconductor elements such as switching

modules

42, 47, 53U, 53V, and 53W are accommodated in the first space 91, and passive elements such as the reactor 44 and the resistor 49 are accommodated in the second space 92. Semiconductor elements are more prone to failure than passive elements. Since components that are relatively susceptible to failure are collectively stored in the first space 91, it is possible to perform repair by removing the first lid 68 when the semiconductor element fails. It is preferable that the power converter 50 is mounted on the excavator so that the maintenance person can access the first lid 68 more easily than the second lid 69. Thereby, maintenance inspection work and repair can be performed easily.

Since a plurality of buck-boost converters 41 are connected in parallel to each other, the current flowing through one buck-boost converter 41 is reduced. For this reason, the thing with small current capacity can be used as the switching module 42 and the reactor 44 (FIG. 4). When a configuration in which a plurality of step-up / step-down converters 41 are connected in parallel is employed, more switching is used than when a single step-up / step-down converter having a large rated current is used. For example, as shown in FIG. 3, the configuration in which two buck-boost converters 41 are connected in parallel includes two switching modules 42 and 47 (FIG. 6B). As the number of switching modules increases, the total contact area between the partition wall 67 acting as a cooling plate and the switching modules increases. For this reason, the cooling efficiency of a switching module can be improved. Similarly, the cooling efficiency of the reactor 44 (FIG. 4, FIG. 6A) can be improved.

FIG. 7 shows a block diagram of the storage circuit 40 when one of the two buck-boost converters 41 fails. The failed buck-boost converter 41F is disconnected from the normal buck-boost converter 41. Specifically, the control device 90 turns off the relay 36 corresponding to the failed buck-boost converter 41F. The relay 36 corresponding to the normal step-up / down converter 41 is turned on. Only normal buck-boost converter 41 is operated to charge / discharge power storage device 45.

FIG. 8 is a block diagram for explaining the flow of control of the turning electric motor 22. The operating device 83 is operated by the driver. The pressure sensor 86 detects the operation amount of the lever or the like of the operation device 83. The detected lever operation amount is input to the control device 90. The case where the turning operation of the upper turning body 21 (FIG. 1) is performed will be described. The amount of operation of the lever of the operating device 83 corresponds to the required value of the turning speed of the turning electric motor 22. The amount of operation of the turning lever is referred to as “requested output value Preq” for the turning electric motor 22.

The control device 90 generates an output control value Pcon based on the output request value Preq. The control device 90 sends a control signal to the inverter 52 so that the turning electric motor 22 outputs power corresponding to the output control value Pcon. The signs of the output control value Pcon and the output request value Preq indicate the rotation direction of the turning electric motor 22. For example, the positive output control value Pcon and the output request value Preq represent a right turn, and the negative output control value Pcon and the output request value Preq represent a left turn.

When the two buck-boost converters 41 are operating normally, the output control value Pcon is equal to the output request value Preq. However, the maximum absolute value of the output control value Pcon is limited by Pmax0. When one buck-boost converter 41 is out of order and only one buck-boost converter 41 is operating, the maximum absolute value of the output control value Pcon is Pmax1 which is smaller than the normal maximum value Pmax0. Limited.

When at least one step-up / down converter 41 is out of order, the maximum value Pmax1 of the output control value Pcon is limited to be smaller than the maximum value Pmax0 at normal time, whereby the step-up / down converter 41 operating normally Therefore, it is possible to prevent an excessive discharge current from flowing.

When the storage circuit 40 is composed of three or more buck-boost converters 41, it is preferable to vary the maximum value Pmax1 of the output control value Pcon according to the number of failed buck-boost converters 41.

Not only when the buck-boost converter 41 fails, but also when the electrical load of the storage circuit 40 is light, one buck-boost converter 41 may be stopped and only the other buck-boost converter 41 may be operated. For example, when the control device 90 detects that the electrical load of the power storage circuit 40 has become less than the reference value, control for stopping some of the step-up / down converters 41 may be performed.

With reference to FIG. 9, a power storage circuit according to another embodiment will be described. FIG. 9 shows an equivalent circuit diagram of a storage circuit according to another embodiment. Hereinafter, differences from the embodiment shown in FIGS. 3 to 6 will be described, and description of the same configuration will be omitted.

The power storage circuit 40 according to the embodiment shown in FIG. 3 includes two buck-boost converters 41 connected in parallel to each other. However, in the embodiment shown in FIG. 9, only one buck-boost converter 41 stores power. It is connected between the device 45 and the DC bus line 55. In the buck-boost converter 41 of the embodiment shown in FIG. 3, the inductance for generating the induced electromotive force is constituted by one reactor 44. In the embodiment shown in FIG. 9, the inductance for generating the induced electromotive force is constituted by a plurality of reactors 44 connected in parallel to each other. FIG. 9 shows an example in which two reactors 44 are connected in parallel.

Since a plurality of reactors 44 are connected in parallel, the current flowing through each reactor 44 is reduced as compared with the case where one reactor is used. For this reason, the reactor 44 having a small rated current can be used. As the reactor 44, a reactor having an inductance such that the combined inductance of a plurality of reactors 44 connected in parallel has a desired value is selected.

Generally, a reactor with a small rated current is accommodated in a flat package rather than a reactor with a large rated current. Contact when two reactors 44 having a small rated current are mounted compared to the contact area between the reactor 44 and the partition wall 67 when one reactor 44 having a large rated current is mounted on the partition wall 67 shown in FIG. 6A. The area can be increased. For this reason, the cooling efficiency of the reactor 44 can be improved.

With reference to FIG. 10A and FIG. 10B, the electrical storage circuit 40 by another Example is demonstrated. Hereinafter, differences from the power storage circuit 40 illustrated in FIGS. 3 and 4 will be described, and description of the same configuration will be omitted.

FIG. 10A shows a block diagram of the storage circuit 40. Although FIG. 10A shows one buck-boost converter 41, a plurality of buck-boost converters 41 may be connected in parallel as shown in FIG. In the configuration shown in FIGS. 3 and 4, one ammeter 38 is arranged in one charge / discharge current path. A bidirectional ammeter is used as the ammeter 38, and the ammeter 38 can measure the discharge current and the charging current.

In the example shown in FIG. 10A, two unidirectional ammeters 38A and 38B are arranged in one charge / discharge current path. One ammeter 38A measures the discharge current, and the other ammeter 38B measures the charging current. The outputs of the ammeters 38A and 38B are respectively input to the analog input terminals of the A / D converter 93 of the control device 90 via operational amplifiers.

The A / D converter 93 has a plurality of analog input terminals, converts an analog signal input to one selected analog input terminal into a digital signal, and outputs the digital signal. When the power storage device 45 is discharged, an analog terminal to which an output signal from the discharge ammeter 38A is input is selected. When the power storage device 45 is charged, the analog terminal to which the output signal from the charging ammeter 38B is input is selected.

FIG. 10B shows the correspondence between the analog value Ia and the digital value Id before and after the A / D conversion of the charge / discharge current. The horizontal axis represents the analog value Ia of the charge / discharge current, and the vertical axis represents the digital value Id of the charge / discharge current. The analog value Ia when the analog input terminal to which the output of the charging ammeter 38B is input is selected is defined as negative. A case where the A / D converter 93 has a resolution of 12 bits will be described. For each of the discharge current and the charge current, 12-bit resolution, that is, 4096-level resolution from 0 to 4095 can be ensured.

FIG. 11A shows a block diagram of a power storage circuit 40 according to a comparative example. In the comparative example, a bidirectional ammeter 38 is used. The output of the ammeter 38 is input to one input terminal of the comparator, and the output of the comparator is input to the analog input terminal of the A / D converter 93. A reference voltage Ref is applied to the other input terminal of the comparator. The reference voltage Ref corresponds to the output of the ammeter 38 when the maximum charging current is flowing.

FIG. 11B shows the correspondence between the analog value Ia and the digital value Id before and after the A / D conversion of the charge / discharge current. The horizontal axis represents the analog value Ia of the charge / discharge current, and the vertical axis represents the digital value Id of the charge / discharge current. The range from the maximum value of the discharge current to the negative maximum value of the charge current is digitally converted with a resolution of 12 bits. Therefore, for each of the discharge current and the charge current, only 12-bit resolution, that is, 2048 resolutions from 0 to 2047 can be ensured.

In the embodiment shown in FIG. 10A, a discharge ammeter 30A and a charge ammeter 30B are arranged in the charge / discharge current path. Further, the output of the discharging ammeter 38A and the output of the charging ammeter 38B are input to different analog input terminals. For this reason, each of the discharge current and the charging current can be converted into a digital value with the maximum resolution of the A / D converter 93. Thereby, the precision of various control based on charging / discharging electric current can be raised.

The discharge ammeter 38 </ b> A and the charge ammeter 38 </ b> B may be disposed corresponding to each of the buck-boost converters 41 illustrated in FIG. 3, or may be disposed corresponding to the power storage device 45.

Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

20 Lower traveling body 21 Upper revolving body 22 Swing motor (working motor)
23 Boom 24 Boom cylinder 25 Arm 26 Arm cylinder 27 Bucket 28 Bucket cylinder 29A, 28B Hydraulic motor 30 Engine 31 Motor generator 32 Torque transmission mechanism 35 Disconnect circuit 36 Relay 38 Ammeter 38A Discharge ammeter 38B Charging ammeter 40 power storage circuit 41 step-up / down converter 42 switching module 42A step-up switching element 42B step-down

switching element

43A, 43B commutation diode 44 reactor 45 power storage device 46 capacitor 47 switching module 48 relay 49 resistor 50

power conversion device

51, 52

inverter

53U , 54U U-phase switching

module

53V, 54V V-

phase switching module

53W, 54W W-phase switching module 55 DC bus line 56 57 Voltmeter 60 Three-phase AC wiring 61 DC wiring 62 Three-phase AC wiring 63 DC wiring 65 Housing 66 Side wall 67 Partition wall 68 First lid 69 Second lid 75 Main pump 76 High-pressure hydraulic line 77 Control valve 78 Pilot pump 79 Pilot line 80 Reducer 81 Resolver 82 Mechanical brake 83

Operating device

84, 85 Hydraulic line 86 Pressure sensor 90 Control device 91 First space 92 Second space 93 A / D converter 94

Flow path

95, 96 Opening 97 Receptacle 98 Connector 99 Wiring

Claims

A lower traveling body,
An upper revolving unit mounted on the lower traveling unit so as to be able to swivel;
Engine,
A generator driven by the power of the engine;
A storage circuit for storing electric power;
An inverter connecting the generator and the storage circuit;
Driven by electric power supplied from the power storage circuit, and has a working electric motor for turning the upper turning body,
The storage circuit is
A power storage device;
A plurality of buck-boost converters connected in parallel to each other;
Each of the step-up / step-down converters includes a switching element and a reactor, and generates an induced electromotive force in the reactor by a switching operation of the switching element, thereby boosting a voltage of the power storage device to the working electric motor. Excavator to supply.
The excavator according to claim 1, wherein the step-up / step-down converter is charged by supplying electric power generated by the generator to the power storage device.
The excavator according to claim 2, further comprising a cooling plate that is thermally coupled to each switching element of each of the plurality of step-up / step-down converters and cools the switching element.
The excavator according to claim 2 or 3, further comprising a separation circuit for electrically separating the plurality of step-up / down converters.
And a control device for monitoring the normality of each operating state of the buck-boost converter,
When the operation state of at least one step-up / step-down converter is determined to be abnormal, the control device controls the disconnection circuit so that the step-up / down converter whose operation state is determined to be abnormal is The excavator according to claim 4, wherein the excavator is separated from the pressure converter.
6. The excavation according to claim 5, wherein the control device continues the operation of the buck-boost converter whose operation state is normal after disconnecting the buck-boost converter whose operation state is determined to be abnormal from the buck-boost converter whose operation state is normal. Machine.
When the operation state of at least one of the plurality of step-up / step-down converters is determined to be abnormal among the plurality of step-up / step-down converters, the control device determines the maximum value of the output of the working motor as the operation state of the plurality of step-up / down converters. The excavator according to claim 5 or 6, wherein the excavator is made smaller than a maximum value of the output of the working electric motor when the power is normal.
The excavator according to any one of claims 5 to 7, wherein the control device synchronously controls the plurality of buck-boost converters and controls the inverter independently of the control of the buck-boost converter.
The storage circuit is
An ammeter for discharge that is disposed in a charge / discharge current path of the power storage device and measures a discharge current;
An ammeter for charging that is disposed in a charging / discharging current path of the power storage device and measures a charging current;
2. An A / D converter having an analog input terminal to which an output from the discharging ammeter is input and another analog input terminal to which an output from the charging ammeter is input. The excavator according to any one of 8.
signal
A lower traveling body,
An upper revolving unit mounted on the lower traveling unit so as to be able to swivel;
Engine,
A generator driven by the power of the engine;
A storage circuit for storing electric power;
An inverter connecting the generator and the storage circuit;
Driven by electric power supplied from the power storage circuit, and has a working electric motor for turning the upper turning body,
The storage circuit is
A power storage device;
A buck-boost converter,
The step-up / down converter includes a switching element and a plurality of reactors connected in parallel to each other, and generates an induced electromotive force in the reactor by a switching operation of the switching element, thereby generating a voltage of the power storage device. An excavator that pressurizes and supplies the work electric motor.