Construction machinery

Abstract

To perform a conduction troubleshooting of a precharge circuit in a state of blocking a power supply from an inverter.SOLUTION: A motor-driven system 100 comprises: a motor 3 being a power source of a hydraulic pump; a power converter 11 for converting a DC voltage to an AC voltage to be supplied to the motor 3; a capacitor 12 to be connected onto the DC voltage side of the power converter 11; a power supply 14; a precharge circuit 19 for precharging the capacitor 12 by using an electric power supplied from the power supply 14; a power supply 15; a relay switch 17 for blocking an electric current; a precharge circuit 20 for precharging the capacitor 12 by using an electric power supplied from the power supply 15, and supplying the electric power supplied from the power supply 15 to the power converter 11; and a relay switch 16. The system determines whether or not the precharge circuit 20 malfunctions in a state of conduction based on an output voltage from a voltmeter 22 and an output voltage from a voltmeter 23.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a construction machine, and more particularly to a construction machine capable of precharging a capacitor connected to the DC voltage side of a power converter. [Background technology]

[0002] In recent years, construction machinery such as hydraulic excavators has been increasingly electrified in order to be environmentally conscious and improve fuel efficiency. For example, equipment such as a hydraulic pump driven by engine power continues to operate and consume energy as long as the engine is running, regardless of the user's usage status. In contrast, if the equipment is driven by the power of an electric drive source such as an electric motor, it becomes possible to drive the equipment only when and as needed, thereby reducing fuel consumption. In construction machinery equipped with an electric motor, a pre-charge circuit pre-charges (preliminarily charges) the capacitor connected to the power converter that supplies power to the motor at startup to prevent an inrush current from flowing through the capacitor and causing equipment failure.

[0003] If the precharge circuit falls into a conduction fault state, the capacitor will not be precharged and the power supply will be connected to the power converter, which may cause an inrush current to flow and damage the equipment. Therefore, the function to detect the conduction fault state of the precharge circuit is important. Patent Document 1 discloses a method for detecting the conduction fault state of the precharge circuit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-98746 Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 discloses an excavator including an inverter, a smoothing capacitor connected to the DC voltage side of the inverter, a power supply that supplies power to the inverter, and multiple relays arranged between the inverter and the power supply. A positive-side relay is connected to the positive side of the power supply, a negative-side relay is connected to the negative side, and a precharge relay is connected in parallel with the negative-side relay. In Patent Document 1, the relays are sequentially turned on to detect whether other relays are in a continuity fault state. To perform a continuity fault diagnosis (S7, S8) of the precharge circuit (negative-side relay), the positive-side relay is turned on (S6). However, if the precharge circuit (negative-side relay) being diagnosed is in a continuity fault state, the inverter is connected to the power supply without precharging the capacitor, which may cause an inrush current to flow and damage the equipment. To prevent the generation of an inrush current, it is desirable to be able to perform a continuity fault diagnosis of the precharge circuit while the power supply is disconnected from the power converter.

[0006] The present invention provides a technique for diagnosing a continuity fault in a precharge circuit while the power supply is disconnected from the power converter. [Means for solving the problem]

[0007] The construction machine of the present invention comprises an electric motor which is the power source of the hydraulic system, a power converter which converts DC voltage to AC voltage and drives the electric motor, a capacitor connected to the DC voltage side of the power converter, a first power source, a first precharge circuit which precharges the capacitor using power supplied from the first power source, a second power source connected to the power converter, a second precharge circuit which has a first current interruption mechanism which interrupts current and which precharges the capacitor using power supplied from the second power source, a second current interruption mechanism which is provided between the second power source and the second precharge circuit and which interrupts current, and a control device which determines whether the second precharge circuit is faulty while in a conductive state based on the first voltage of the capacitor and the voltage of the second precharge circuit on the opposite side of the capacitor. [Effects of the Invention]

[0008] According to the present invention, it is possible to perform a continuity fault diagnosis of the precharge circuit while the power supply is disconnected from the power converter. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram showing the overall configuration of a construction machine according to a first embodiment. [Figure 2] 1 is a configuration diagram of an electric power system of a construction machine according to a first embodiment. [Figure 3] FIG. 2 is a hardware block diagram of a vehicle body controller. [Figure 4A] 1 is a flowchart illustrating a method for precharging a capacitor. [Figure 4B] 1 is a flowchart illustrating a method for precharging a capacitor. [Figure 5] FIG. 10 is a timing chart of the power supply system when the precharge circuit 20 is normal. [Figure 6] FIG. 10 is a timing chart of the power supply system when the precharge circuit 20 is abnormal. [Figure 7] FIG. 10 is a configuration diagram of an electric power system of a construction machine according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] The embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, it goes without saying that the components (including steps, etc.) are not necessarily essential unless otherwise specified or considered to be obviously essential in principle.

[0011] Example 1 (Construction Machinery 1) As shown in FIG. 1, the construction machine 1 is a machine used at a construction site, and is a hybrid hydraulic excavator in which an engine 2 and an electric motor 3 drive a hydraulic pump (hydraulic system) 4. The engine 2 and the electric motor 3 are the power sources for the hydraulic pump 4. The hydraulic pressure generated by the hydraulic pump 4 is distributed by a control valve 5 and supplied to multiple hydraulic actuators (a bucket cylinder 6, an arm cylinder 7, a boom cylinder 8, a swing hydraulic motor 9, and a traveling hydraulic motor 10). By driving the multiple hydraulic actuators, the construction machine 1 performs excavation operations, swing operations, and traveling operations.

[0012] (Electric System 100) As shown in Fig. 2, the electric system 100 includes an electric motor 3 connected to the hydraulic pump 4 and the engine 2, a power converter 11 that drives the electric motor 3, a capacitor 12 connected to the DC voltage side of the power converter 11, and a vehicle controller (control device) 13 that monitors the status of each part of the construction machine 1 and issues commands to control the operation of each part of the construction machine 1. The power converter 11 is an inverter circuit that converts DC voltage into AC voltage. The capacitor 12 is a smoothing capacitor that stabilizes the DC voltage of the inverter circuit (power converter 11).

[0013] The electric power system 100 also includes a precharge circuit 19 and a precharge circuit 20 that precharge the capacitor 12. In the electric power system 100 of the first embodiment, each of the two precharge circuits 19 and 20 can precharge the capacitor 12. The electric power system 100 also includes a power supply 14 that supplies power to the power converter 11 via the precharge circuit 19, and a power supply 15 that supplies power to the power converter 11 via the precharge circuit 20.

[0014] A voltmeter 22 that measures and outputs the voltage of capacitor 12 is connected in parallel to capacitor 12. Furthermore, a voltmeter 23 that measures and outputs the voltage of precharge circuit 20 on the opposite side of capacitor 12 is connected in parallel to precharge circuit 20. Each of voltmeter 22 and voltmeter 23 outputs the measured voltage to vehicle body controller 13.

[0015] The electric power system 100 includes a relay switch 16 provided between the power source 15 and the pre-charge circuit 20. The relay switch 16 interrupts the current flowing between the power source 15 and the power converter 11. The pre-charge circuit 20 includes a relay switch 17, and a relay switch 18 and a resistor (step-down element) 21 connected in parallel with the relay switch 17. The relay switch 17 and the relay switch 18 interrupt the current flowing between the power source 15 and the power converter 11. The relay switches 16, 17, and 18 are controlled by the vehicle body controller 13 to be in a conductive state (closed circuit state) or a cut-off state (open circuit state).

[0016] The power converter 11 drives the electric motor 3 by converting the DC voltage to an AC voltage after the capacitor 12 connected to the DC voltage side is precharged. The power supply 14 is connected to the DC voltage side of the power converter 11 via a precharge circuit 19. The vehicle controller 13 outputs a precharge command to the precharge circuit 19. The precharge circuit 19 precharges the capacitor 12 in accordance with the precharge command. In the first embodiment, the power supply 14 is, for example, a lead battery, and the precharge circuit 19 is, for example, a DC-DC converter that converts the voltage of the power supply 14 to a voltage similar to that of the power supply 15. The DC-DC converter precharges the capacitor 12 by constant current control to prevent inrush current from flowing.

[0017] The power supply 15 is connected to the DC voltage side of the power converter 11 via a relay switch 16 and a precharge circuit 20. The relay switch 16 is provided between the precharge circuit 20 and the power supply 15 and is turned on or off in response to a conduction command or a cutoff command from the vehicle body controller 13. The relay switches 17 and 18 inside the precharge circuit 20 are turned on or off in response to a conduction command or a cutoff command from the vehicle body controller 13. When precharging the capacitor 12, the relay switch 17 is turned off and the relay switch 18 is turned on. This connects the power supply 15 to the capacitor 12 via the resistor 21, thereby precharging the capacitor 12. When connecting the power supply 15 to the power converter 11, the relay switch 17 is turned on and the relay switch 18 is turned off. This connects the power supply 15 to the power converter 11 without the resistor 21. In the first embodiment, the power supply 15 is, for example, a lithium-ion battery.

[0018] (Vehicle Controller 13) As shown in FIG. 3, the vehicle body controller 13 has a processor 31, a communication interface (hereinafter, interface will be abbreviated as I / F) 32, a main memory device 33, an auxiliary memory device 34, an input / output I / F 35, and a bus 36 that communicatively connects each of the above-mentioned units.

[0019] The processor 31 is a central processing unit that controls the operation of each part of the vehicle body controller 13. The processor 31 is, for example, a central processing unit (CPU), a digital signal processor (DSP), or an application-specific integrated circuit (ASIC). The processor 31 deploys programs stored in the auxiliary storage device 34 in an executable manner in a work area of ​​the main storage device 33. The main storage device 33 stores programs executed by the processor 31, data processed by the processor, and the like. The main storage device 33 is, for example, a flash memory, a random access memory (RAM), or a read-only memory (ROM). The auxiliary storage device 34 stores various programs and various data. The auxiliary storage device 34 stores, for example, an operating system (OS), various programs, various tables, and the like. The auxiliary storage device 34 is, for example, a silicon disk including a non-volatile semiconductor memory (flash memory, erasable programmable ROM (EPROM)), a solid-state drive device, or a hard disk drive (HDD). The input / output I / F 35 is communicably connected to the relay switch 16, the precharge circuit 19, and the precharge circuit 20. The input / output I / F 35 outputs various commands from the processor 31 to the relay switch 16, the precharge circuit 19, and the precharge circuit 20.

[0020] (Precharge of capacitor 12) A method for precharging the capacitor 12 in the first embodiment will be described with reference to Figures 4A and 4B. The main memory device 33 stores program code for executing the steps of Figures 4A and 4B, and the processor 31 executes the program code stored in the main memory device 33 to execute the steps of the flowcharts of Figures 4A and 4B. The processor 31 may be a single processor or a multiprocessor.

[0021] In step S1, when the key switch of the construction machine 1 is operated, a key-on signal indicating that the key switch has changed from off to on is input to the processor 31. When the key-on signal is input, the processor 31 pre-charges the capacitor 12 as a start-up process, as shown below. In step S2, the processor 31 outputs a shut-off command to the relay switches 16, 17, and 18 so that the relay switches 16, 17, and 18 are turned off. The processor 31 also outputs a pre-charge command to the pre-charge circuit 19. The relay switches 16, 17, and 18 are turned off in accordance with the shut-off command from the processor 31. Then, in accordance with the pre-charge command, the pre-charge circuit 19 passes a current suitable for pre-charging through the capacitor 12 by constant current control, thereby pre-charging the capacitor 12.

[0022] In step S3, after a predetermined time has elapsed since the precharge circuit 19 started precharging the capacitor 12, the processor 31 determines whether the voltage of the capacitor 12 is equal to or greater than a first threshold. The voltage of the capacitor 12 is measured by the voltmeter 22, which outputs the measured voltage to the processor 31. If the processor 31 determines that the voltage input from the voltmeter 22 is equal to or greater than the preset first threshold, it determines that the precharging of the capacitor 12 by the precharge circuit 19 has been completed, and the process proceeds to step S4. On the other hand, if the processor 31 determines that the voltage input from the voltmeter 22 is less than the first threshold, it determines that the precharging of the capacitor 12 by the precharge circuit 19 has not been completed, and the process proceeds to step S9 (FIG. 4B). The first threshold used in the determination in step S3 is set to a voltage at which the capacitor 12 is considered to be sufficiently charged. The predetermined time is set to a time required for precharging the capacitor 12.

[0023] In step S4, the processor 31 calculates the potential difference across the precharge circuit 20. Specifically, the processor 31 calculates the difference between the voltage input from the voltmeter 22 and the voltage input from the voltmeter 23. This difference is the potential difference across the precharge circuit 20. In step S5, the processor 31 compares the potential difference calculated in step S4 with a preset second threshold value and determines whether the potential difference across the precharge circuit 20 is equal to or greater than the second threshold value. If the potential difference across the precharge circuit 20 is equal to or greater than the second threshold value, the processor 31 determines that the precharge circuit 20 is in a normal state and proceeds to step S7. On the other hand, if the potential difference across the precharge circuit 20 is less than the second threshold value, the processor 31 determines that the precharge circuit 20 is in a conduction fault state and proceeds to step S6.

[0024] In step S6, the processor 31 records the continuity fault of the precharge circuit 20 in the auxiliary storage device 34, and then proceeds to step S7. The location for recording the continuity fault is not limited to the auxiliary storage device 34, as long as it is a non-volatile storage unit. In step S7, the processor 31 sets the closing prohibition flag of the relay switch 16 to "permitted" to bring the relay switch 16 into a conductive state. Then, in step S8, the processor 31 outputs a conduction command to each of the relay switch 16 and the relay switch 17, bringing the relay switch 16 and the relay switch 17 into a conductive state. This connects the power supply 15 to the DC voltage side of the power converter 11. The flow of precharging the capacitor 12 by the precharge circuit 19 is completed in step S8, and the vehicle body controller 13 can drive the electric motor 3 using the power converter 11.

[0025] If it is determined in step S3 that the precharging of the capacitor 12 by the precharge circuit 19 is incomplete, then in step S9, as shown in FIG. 4B , the processor 31 calls up the record of the continuity failure of the precharge circuit 20 from the auxiliary storage device 34. The record of the continuity failure is not cleared even when the key switch is turned off, the operation of the construction machine 1 stops, and the supply of power from the power supply 14 to the vehicle body controller 13 is stopped. The record of the continuity failure is cleared, for example, upon completion of maintenance such as replacement of a part of the precharge circuit 20. In step S10, the processor 31 checks whether or not there is a record of the continuity failure of the precharge circuit 20. If there is a record of the continuity failure of the precharge circuit 20, precharging of the capacitor 12 by the precharge circuit 20 is impossible, and the process proceeds to step S13. The processor 31 does not precharge the capacitor 12 by the precharge circuit 20. In step S13, the processor 31 sets the circuit closing prohibition flag of the relay switch 16 to prohibition. The flow in which the capacitor 12 is not precharged by the precharge circuit 19 and the precharge circuit 20 is completed at step S13.

[0026] On the other hand, if there is no record of a continuity failure in the precharge circuit 20 in step S10, the process proceeds to step S11. Then, in step S11, the processor 31 determines that precharging of the capacitor 12 by the precharge circuit 20 is possible, and therefore precharges the capacitor 12 by the precharge circuit 20. Specifically, in step S11, the processor 31 outputs a conduction command to each of the relay switch 16 and the relay switch 18, bringing the relay switch 16 and the relay switch 18 into a conducting state. The relay switch 17 remains in a cut-off state. As a result, the precharge circuit 20 passes a current suitable for precharging through the resistor 21, thereby precharging the capacitor 12.

[0027] After a predetermined time has elapsed since the precharge circuit 20 started precharging the capacitor 12, the processor 31 outputs a conduction command to the relay switch 17, causing the relay switch 17 to be in a conducting state. The processor 31 also outputs a cut-off command to the relay switch 18, causing the relay switch 18 to be in a cut-off state. This connects the power supply 15 to the DC voltage side of the power converter 11 without passing through the resistor 21. The predetermined time is set to a time sufficient for the precharge circuit 20 to precharge the capacitor 12. The flow for precharging the capacitor 12 by the precharge circuit 20 is completed in step S12, and the vehicle body controller 13 is then able to drive the electric motor 3 using the power converter 11.

[0028] 5, a timing chart of the power supply system when the precharge circuit 20 is normal will be described. Below, the case where the precharge circuit 20 is normal will be described separately for the case where the precharge circuit 19 is normal and the case where it is abnormal.

[0029] (When the precharge circuit 19 is normal) 5, precharge circuit 19 precharges capacitor 12. First, at time T11, the key switch is operated to switch the key signal from off to on, and at time T12, processor 31 outputs a precharge command to precharge circuit 19. As a result, current flows through capacitor 12 due to constant current control by precharge circuit 19, and the voltage of capacitor 12 (voltmeter 22) rises. Note that from time T11 to time T15, relay switch 16, relay switch 17, and relay switch 18 are each in a cutoff state (open-circuit state).

[0030] At time T13, a predetermined time after time T12, processor 31 stops issuing a precharge command to precharge circuit 19 and determines the precharge state of capacitor 12. At time T13, the voltage of capacitor 12 (voltmeter 22) is equal to or greater than the first threshold, so processor 31 determines that precharging of capacitor 12 by precharge circuit 19 has been completed. At time T14, processor 31 calculates the potential difference across precharge circuit 20 from the difference between the voltage output by voltmeter 22 and the voltage output by voltmeter 23. At this time, precharge circuit 20 is controlled to be in an off state, so the voltage of voltmeter 23 does not increase. Meanwhile, the voltage of capacitor 12 (voltmeter 22) is increasing, so the potential difference across precharge circuit 20 becomes equal to or greater than the second threshold. If the potential difference across precharge circuit 20 becomes equal to or greater than the second threshold, processor 31 determines that precharge circuit 20 is in a normal state.

[0031] At time T15, processor 31 outputs a conduction command to relay switch 16 and relay switch 17, turning relay switch 16 and relay switch 17 into a conductive state. This connects power supply 15 to the DC voltage side of power converter 11. This state is maintained until time T16 when the key signal is switched from on to off by operating the key switch.

[0032] (If the precharge circuit 19 is abnormal) 5, precharge circuit 19 does not precharge capacitor 12. First, at time T21, when the key signal is switched from off to on by operating the key switch, processor 31 outputs a precharge command to precharge circuit 19 at time T22. Here, it is assumed that even if the precharge command is output, current from precharge circuit 19 does not flow to capacitor 12, and the voltage of capacitor 12 (voltmeter 22) does not increase. Note that from time T21 to time T25, relay switch 16, relay switch 17, and relay switch 18 are each in an interrupted state.

[0033] At time T23, a predetermined time after time T22, processor 31 stops issuing the precharge command to precharge circuit 19 and determines the precharge state of capacitor 12. At time T23, because the voltage of capacitor 12 (voltmeter 22) is less than the first threshold, processor 31 determines that precharging of capacitor 12 by precharge circuit 19 is incomplete. Next, at time T24, processor 31 calls up the record of a continuity failure of precharge circuit 20 and determines whether precharge circuit 20 can precharge capacitor 12. Here, it is assumed that there is no record of a continuity failure of precharge circuit 20. If processor 31 determines that precharge circuit 20 can precharge capacitor 12, at time T25, processor 31 outputs a precharge command to precharge circuit 20 and also outputs conduction commands to relay switch 16 and relay switch 18. As a result, a precharge current flows from the precharge circuit 20 to the capacitor 12, and the voltage of the capacitor 12 (voltmeter 22) rises.

[0034] At time T26, when a predetermined time has elapsed since time T25, processor 31 stops issuing the precharge command to precharge circuit 20. Processor 31 also outputs a conduction command to relay switch 17 and an interruption command to relay switch 18. This connects power supply 15 to the DC voltage side of power converter 11. This state is maintained until time T27, when the key signal is switched from on to off by operating the key switch.

[0035] Next, a timing chart of the power supply system when the precharge circuit 20 is abnormal will be described with reference to Fig. 6. Below, the case where the precharge circuit 20 is abnormal will be described separately for the case where the precharge circuit 19 is normal and the case where the precharge circuit 19 is abnormal. The abnormality of the precharge circuit 20 is assumed to be a continuity failure of the relay switch 17.

[0036] (When the precharge circuit 19 is normal) 6, precharge circuit 19 precharges capacitor 12. First, at time T31, the key switch is operated to switch the key signal from off to on, and at time T32, processor 31 outputs a precharge command to precharge circuit 19. As a result, current flows through capacitor 12 under constant current control by precharge circuit 19, and the voltage of capacitor 12 (voltmeter 22) rises. Note that, from time T31 to time T35, interruption commands are output to each of relay switch 16, relay switch 17, and relay switch 18, but relay switch 17 is actually in a conductive state due to a continuity fault.

[0037] At time T33, a predetermined time after time T32, processor 31 stops issuing a precharge command to precharge circuit 19 and determines the precharge state of capacitor 12. At time T33, the voltage of capacitor 12 (voltmeter 22) is equal to or greater than the first threshold, so processor 31 determines that precharging of capacitor 12 by precharge circuit 19 has been completed. At time T34, processor 31 calculates the potential difference across precharge circuit 20 from the difference between the voltage output by voltmeter 22 and the voltage output by voltmeter 23. At this time, relay switch 17 is in a conduction fault state, so the voltage of voltmeter 23 rises in accordance with the voltage of capacitor 12 (voltmeter 22), and the potential difference across precharge circuit 20 becomes less than the second threshold. If the potential difference across precharge circuit 20 is less than the second threshold, processor 31 determines that precharge circuit 20 is in a conduction fault state.

[0038] When the processor 31 determines that the precharge circuit 20 is in a continuity fault state, it records the continuity fault of the precharge circuit 20 in the auxiliary storage device 34. The closing prohibition flag of the relay switch 16 remains enabled and is not changed. Then, at time T35, the processor 31 outputs a continuity command to the relay switch 16 and the relay switch 17 to connect the power supply 15 to the power converter 11. Because the relay switch 17 is in a continuity fault state, it remains in a conducting state even without a continuity command. This connects the power supply 15 to the DC voltage side of the power converter 11. This state is maintained until time T36 when the key signal is switched from on to off by operating the key switch.

[0039] (If the precharge circuit 19 is abnormal) 6, precharge circuit 19 does not precharge capacitor 12. First, at time T41, when the key signal is switched from off to on by operating the key switch, processor 31 outputs a precharge command to precharge circuit 19 at time T42. Here, it is assumed that current from precharge circuit 19 does not flow to capacitor 12, and the voltage of capacitor 12 (voltmeter 22) does not increase. Note that, from time T41 to time T46, interruption commands are output to relay switch 16, relay switch 17, and relay switch 18, but relay switch 17 is actually in a conductive state due to a continuity fault.

[0040] At time T43, a predetermined time after time T42, processor 31 stops issuing the precharge command to precharge circuit 19 and determines the precharge state of capacitor 12. At time T43, because the voltage of capacitor 12 (voltmeter 22) is less than the first threshold, processor 31 determines that precharging of capacitor 12 by precharge circuit 19 is incomplete. At time T44, processor 31 calls up the record of a continuity failure of precharge circuit 20 and determines whether precharging of capacitor 12 by precharge circuit 20 is possible. Here, it is assumed that there is a record of a continuity failure of precharge circuit 20. If processor 31 determines that there is a record of a continuity failure of precharge circuit 20, it determines that precharging of capacitor 12 by precharge circuit 20 is impossible.

[0041] Then, at time T45, processor 31 sets the circuit closing prohibition flag of relay switch 16 to prohibition, prohibiting relay switch 16 from entering a conductive state. This prevents power supply 15 from being connected to the DC voltage side of power converter 11. Because power supply 15 is not connected to power converter 11 while precharging of capacitor 12 is not complete, no inrush current flows to capacitor 12, etc. This state is maintained until time T46 when the key switch is operated to switch the key signal from on to off.

[0042] 6, precharge circuit 19 precharges capacitor 12. First, at time T51, the key switch is operated to switch the key signal from off to on, and at time T52, processor 31 outputs a precharge command to precharge circuit 19. As a result, current flows through capacitor 12 under constant current control by precharge circuit 19, and the voltage of capacitor 12 (voltmeter 22) rises. Note that, from time T51 to time T55, interruption commands are output to each of relay switch 16, relay switch 17, and relay switch 18, but relay switch 17 is actually in a conductive state due to a continuity fault.

[0043] At time T53, a predetermined time after time T52, processor 31 stops issuing a precharge command to precharge circuit 19 and determines the precharge state of capacitor 12. At time T53, the voltage of capacitor 12 (voltmeter 22) is equal to or greater than the first threshold, so processor 31 determines that precharging of capacitor 12 by precharge circuit 19 has been completed. At time T54, processor 31 calculates the potential difference across precharge circuit 20 from the difference between the voltage output by voltmeter 22 and the voltage output by voltmeter 23. At this time, relay switch 17 is in a conduction fault state, so the voltage of voltmeter 23 rises in accordance with the voltage of capacitor 12 (voltmeter 22), and the potential difference across precharge circuit 20 becomes less than the second threshold. If the potential difference across precharge circuit 20 is less than the second threshold, processor 31 determines that precharge circuit 20 is in a conduction fault state.

[0044] When processor 31 determines that precharge circuit 20 is in a continuity fault state, it records the continuity fault of precharge circuit 20 in auxiliary storage device 34. At time T55, processor 31 sets the circuit closing prohibition flag of relay switch 16 to "permitted." Because precharging of capacitor 12 is complete, it is possible to turn relay switch 16 into a conductive state without damaging capacitor 12 or the like due to an inrush current.

[0045] Then, processor 31 outputs a conduction command to relay switch 16 and relay switch 17 to connect power supply 15 to the DC voltage side of power converter 11. This state is maintained until time T56 when the key signal is switched from on to off by operating the key switch.

[0046] (Effects of Example 1) In the electric power system 100 of the first embodiment, by comparing the potential difference across the precharge circuit 20 with a threshold value, it is possible to perform a continuity fault diagnosis of the precharge circuit 20 while the power supply 15 is disconnected from the power converter 11. This makes it possible to prevent the power supply 15 from being connected to the power converter 11 before the precharge of the capacitor 12 is completed.

[0047] The electric power system 100 of the first embodiment is provided with two precharge circuits 19 and 20, so that if one of them fails, the other precharge circuit can precharge the capacitor 12. This reduces the risk that the construction machine 1 will stop operating due to a failure in one of the precharge circuits.

[0048] In the electric power system 100 of the first embodiment, the precharge circuit 19 is instructed to precharge the capacitor 12 while the relay switch 16 is controlled to be in the off state. This allows the capacitor 12 to be precharged before the power source 15 is connected to the power converter 11, even if the precharge circuit 20 (relay switch 17) is in the conductive state and has a fault.

[0049] In the electric power system 100 of the first embodiment, the precharge circuit 19 is a DC-DC converter, so that the capacitor 12 can be precharged with a desired voltage.

[0050] In the electric power system 100 of the first embodiment, a precharge circuit 20 is provided, which includes a relay switch 17, and a relay switch 18 and a resistor 21 arranged in parallel with the relay switch 17. This allows the voltage supplied to the power converter 11 to be stepped down by the resistor 21, thereby precharging the capacitor 12. That is, in the first embodiment, the capacitor 12 can be precharged by the precharge circuit 20, which has a simple configuration and does not use a DC-DC converter.

[0051] <Example 2> In the first embodiment, a hybrid hydraulic excavator in which the hydraulic pump 4 is driven by the engine 2 and the electric motor 3 is described, but in the second embodiment, an electric hydraulic excavator in which the hydraulic pump 4 is driven only by the electric motor 3 is described. Fig. 7 is a configuration diagram of an electric system of a construction machine in the second embodiment. Description of the same configuration as in the first embodiment will be omitted as appropriate.

[0052] As shown in Fig. 7 , an electric power system 400 of the second embodiment includes a precharge circuit 419 that precharges the capacitor 12, and a power supply 414 that supplies power to the power converter 11 via the precharge circuit 419. In the first embodiment, the power supply 14 is, for example, a lead battery, but in the second embodiment, the power supply 414 is a system power supply that supplies AC power. Also, in the first embodiment, the precharge circuit 19 is, for example, a DC-DC converter, but in the second embodiment, the precharge circuit 419 is an AC-DC converter that converts AC to DC voltage. The precharge circuit 419 converts the voltage of the power supply 414 to a voltage similar to that of the power supply 15.

[0053] The electric hydraulic excavator of the second embodiment can also achieve the same effects as those of the first embodiment.

[0054] It should be noted that the present invention is not limited to the above-described embodiment, and includes various modifications. The above-described embodiment has been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to an embodiment having all of the described configurations.

[0055] For example, in the first and second embodiments, a hydraulic excavator has been described as an example of the construction machine of the present invention, but the hydraulic excavator in the first and second embodiments may be a construction machine such as a wheel loader, a truck, or road machinery.

[0056] Furthermore, in the first embodiment, the precharge circuit 19, which is a DC-DC converter, precharges the capacitor 12. However, the precharge circuit 19 may be an AC-DC converter that is connected to a system power supply that supplies AC power and charges the power.

[0057] It is also possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment, or to add, delete, or replace part of the configuration of each embodiment with the configuration of another embodiment. [Explanation of symbols]

[0058] 1: Construction machine 2: Engine 3: Electric motor 4: Hydraulic pump (hydraulic system) 11: Power converter 12: Capacitor 13: Vehicle controller (control device) 14: Power supply (first power supply) 15: Power supply (second power supply) 16: Relay switch (second current interruption mechanism) 17: Relay switch (first current interruption mechanism) 18: Relay switch (third current interruption mechanism) 19: Precharge circuit (first precharge circuit) 20: Precharge circuit (second precharge circuit) 21: Resistor (step-down element) 100: Electric system 400: Electric system 414: Power supply (first power supply) 419: Precharge circuit (first precharge circuit)

Claims

1. An electric motor that is the power source of the hydraulic system; a power converter that converts a DC voltage into an AC voltage and drives the electric motor; a capacitor connected to a DC voltage side of the power converter; a first power source; a first precharge circuit that precharges the capacitor using power supplied from the first power supply; a second power source connected to the power converter; a second precharge circuit having a first current interruption mechanism that interrupts a current and that precharges the capacitor using power supplied from the second power supply; a second current cutoff mechanism that is provided between the second power supply and the second precharge circuit and cuts off current; a control device that determines whether the second precharge circuit is in a conductive state and has a failure based on a first voltage of the capacitor and a voltage of the second precharge circuit on an opposite side of the capacitor; Equipped with instructing the first precharge circuit to precharge the capacitor while the first current interruption mechanism and the second current interruption mechanism are controlled to be in an interruption state, and after the instruction, determining whether or not the second precharge circuit is faulty in a conductive state based on a first voltage of the capacitor and a voltage of the second precharge circuit on the opposite side of the capacitor; Construction machinery characterized by:

2. The control device 2. The construction machine according to claim 1, wherein when it is determined that the precharging of the capacitor by the first precharge circuit has not been completed and the second precharge circuit is in a conductive state and has not failed, the construction machine instructs the second precharge circuit to precharge the capacitor.

3. 3. The construction machine according to claim 1, wherein the first precharge circuit includes a DC-DC converter or an AC-DC converter.

4. 3. The construction machine according to claim 1, wherein the second precharge circuit has a third current interruption mechanism and a step-down element arranged in parallel with the first current interruption mechanism, and precharges the capacitor using power output via the third current interruption mechanism and the step-down element.

5. the first power supply is a system power supply that supplies AC power, 3. The construction machine according to claim 1, wherein the first precharge circuit is an AC-DC converter.

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