Working machine power control device

Abstract

To enable a power supply system to be started even when the voltage of a capacitor becomes low at the time of attempting to start the power supply system.SOLUTION: A controller 90 is set with a capacitor voltage determination value th being a voltage of a capacitor 61 required to start a power supply system. When attempting to start the power supply system, the controller 90 performs pre-start charging control being control for charging the capacitor 61 in a case where the voltage of the capacitor 61 is equal to or lower than the capacitor voltage determination value th. When attempting to start the power supply system, if the voltage of the capacitor 61 exceeds the capacitor voltage determination value th, the controller 90 starts the power supply system.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a work machine power control device that controls the power for operating a work machine. [Background technology]

[0002] For example, Patent Document 1 describes a technique for supplying power from a fuel cell and a capacitor to an electric motor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-61212 Summary of the Invention [Problem to be solved by the invention]

[0004] A power supply system that supplies power to an electric motor may be started using power from a capacitor. However, capacitors self-discharge faster than secondary batteries. This can cause the capacitor voltage to drop, potentially making it impossible to start the power supply system (details will be explained later).

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a work machine power control device that can start up a power supply system even if the voltage of the capacitor is low when the power supply system is to be started up. [Means for solving the problem]

[0006] The work machine power control device includes a fuel cell, a capacitor, a capacitor voltage sensor, an electric motor, and a controller. The capacitor voltage sensor detects the voltage of the capacitor. The electric motor is configured to be able to supply power from the fuel cell and the capacitor. The electric motor is for driving the work machine. The controller controls the startup of the power supply system. Starting the power supply system means bringing the electric motor into a state where the electric power supplied to the electric motor can drive the electric motor. A capacitor voltage determination value, which is the voltage of the capacitor required for starting the power supply system, is set in the controller. When attempting to start the power supply system, the controller performs pre-start charge control, which is control to charge the capacitor, if the voltage of the capacitor detected by the capacitor voltage sensor is equal to or lower than the capacitor voltage determination value. When attempting to start the power supply system, the controller starts the power supply system if the voltage of the capacitor detected by the capacitor voltage sensor exceeds the capacitor voltage determination value. [Effects of the Invention]

[0007] The above-described work machine power control device makes it possible to start up the power supply system even if the voltage of the capacitor is low when an attempt is made to start up the power supply system. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a side view of the work machine 10. [Figure 2] FIG. 2 is a circuit diagram of the power control device 40 shown in FIG. [Figure 3] 3 is a flowchart of pre-start charge control by the controller 90 shown in FIG. 2. [Figure 4] FIG. 10 is a circuit diagram of a power control device 240 shown in FIG. 1 according to a second embodiment. [Figure 5] 10 is a flowchart of pre-start charge control and the like by the controller 90 shown in FIG. 2 in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] (First embodiment) A work machine 10 equipped with a power control device 40 (work machine power control device) of a first embodiment will be described with reference to FIGS. 1 to 3.

[0010] As shown in Figure 1, the work machine 10 is a machine that performs work. The work machine 10 may be a construction machine that performs construction work, or a loading and unloading machine that performs loading and unloading work. The work machine 10 may be, for example, a shovel or a crane. The work machine 10 may be a bulldozer or a wheel loader. The work machine 10 is powered by power output from a fuel cell 51 (see Figure 2). The work machine 10 is, for example, a fuel cell shovel. The following description will mainly focus on the case where the work machine 10 is a shovel. The work machine 10 comprises a machine body 10a, an attachment 15, a hydraulic circuit 20 shown in Figure 2, and a power control device 40.

[0011] As shown in FIG. 1, the machine body 10a is the main body of the work machine 10. The machine body 10a includes a lower body 11 and an upper rotating body 13. The lower body 11 supports the upper rotating body 13 so that it can rotate. The lower body 11 may be a lower running body that can run on a running surface (such as the ground). If the lower body 11 is runnable, the lower body 11 may be equipped with crawlers or wheels. The upper rotating body 13 is mounted on the lower body 11 so that it can rotate.

[0012] The attachment 15 is the part that performs work. The attachment 15 is attached to the machine body 10a (more specifically, to the upper rotating body 13). For example, the attachment 15 includes a boom 15a, an arm 15b, and a tip attachment 15c. The boom 15a is rotatably attached to the upper rotating body 13 (capable of rotating in the front-to-back and up-down directions). The arm 15b is rotatably attached to the boom 15a (capable of rotating in the front-to-back and up-down directions). The tip attachment 15c is provided at the tip of the attachment 15. The tip attachment 15c is rotatably attached to the arm 15b (capable of rotating in the front-to-back and up-down directions). The tip attachment 15c may be a bucket that can be used to scoop up work objects and perform excavation, etc. The tip attachment 15c may be equipped with a device for clamping the work object (grapple, nibbler, rotating fork, etc.), a device for crushing the work object (breaker, etc.), or a magnet for attracting metal work objects.

[0013] 2, the hydraulic circuit 20 is a circuit for operating the hydraulic actuator 30. The hydraulic circuit 20 includes a hydraulic pump 21 and the hydraulic actuator 30.

[0014] The hydraulic pump 21 draws hydraulic oil from a tank. The hydraulic pump 21 supplies hydraulic oil to the hydraulic actuator 30. The hydraulic pump 21 is driven (rotationally driven) by an electric motor 77. Only one hydraulic pump 21 may be provided, or multiple hydraulic pumps 21 may be provided. The capacity of the hydraulic pump 21 is variable.

[0015] The hydraulic actuator 30 is a device that moves the work machine 10. The hydraulic actuator 30 is hydraulically driven by hydraulic oil supplied from the hydraulic pump 21. The hydraulic actuator 30 may be equipped with a hydraulic motor for rotational drive, or may be equipped with a hydraulic cylinder (telescopic cylinder) for telescopic drive. As shown in FIG. 1 , the hydraulic actuator 30 is equipped with a travel motor 31, a swing motor 33, a boom cylinder 35a, an arm cylinder 35b, and a tip attachment cylinder 35c. The travel motor 31 drives the lower body 11 to travel. The travel motor 31 is a hydraulic motor (as is the swing motor 33). The swing motor 33 drives the upper swing body 13 to swing relative to the lower body 11. The boom cylinder 35a drives (raise and lower) the boom 15a relative to the upper swing body 13. The boom cylinder 35a is a hydraulic cylinder (as are the arm cylinder 35b and the tip attachment cylinder 35c). The arm cylinder 35b rotates the arm 15b relative to the boom 15a. The tip attachment cylinder 35c rotates the tip attachment 15c relative to the arm 15b. If the tip attachment 15c itself is drivable, for example, as a device for clamping an object, a hydraulic actuator 30 may be provided to drive the tip attachment 15c.

[0016] The power control device 40 (work machine power control device) is a device (power control system) that controls the power used to operate the work machine 10. The power control device 40 controls the power (power system) used to drive the work machine 10. The power control device 40 may also control the power used to drive an auxiliary machine 277 (described below) (see FIG. 4). The power control device 40 is mounted on the machine main body 10a (specifically, the upper rotating body 13).

[0017] As shown in FIG. 2, this power control device 40 includes a fuel cell 51 and a capacitor 61 (a hybrid system of the fuel cell 51 and the capacitor 61). The drive source of the work machine 10 (see FIG. 1) is the fuel cell 51 and the capacitor 61. Therefore, compared to when the drive source of the work machine 10 is an engine (motor) alone, it is possible to reduce or eliminate carbon dioxide emissions from the work machine 10. The power control device 40 is a fuel cell control system that controls the output of the fuel cell 51, and a capacitor control system that controls the output of the capacitor 61. The power control device 40 includes a fuel cell 51, a fuel cell converter 53, a capacitor 61, and a capacitor converter 63. Furthermore, the power control device 40 includes a motor inverter 71, a high-voltage DC unit 73, an AC unit 75, an electric motor 77, a sensor 80, and a controller 90.

[0018] The fuel cell 51 (FC) is a device that generates electrical energy through a chemical reaction between a fuel and an oxidant. The fuel for the fuel cell 51 may be hydrogen or alcohol (e.g., methanol, ethanol, etc.). The oxidant for the fuel cell 51 is, for example, oxygen. The portion between the fuel cell 51 and the fuel cell converter 53 (between them in the electrical circuit) is referred to as the fuel cell output DC section 51o (DC; Direct Current). The fuel cell output DC section 51o is the section through which direct current flows.

[0019] The fuel cell converter 53 is a device that controls the power output by the fuel cell 51. The fuel cell converter 53 is a device (power conversion device) that converts the power output by the fuel cell 51. The fuel cell converter 53 is connected to the fuel cell 51. "Connected" means electrically connected (the same applies to "connected" below). The fuel cell converter 53 is connected to the high-voltage DC unit 73. The fuel cell converter 53 is a DC-DC converter that converts direct current to direct current (the same applies to the capacitor converter 63 and the battery converter 253 (see FIG. 4) described later). The fuel cell converter 53 is equipped with semiconductor elements (switch elements, power elements) that perform switching (the same applies to the capacitor converter 63 and the battery converter 253 (see FIG. 4)).

[0020] The fuel cell converter 53 controls the voltage (output voltage) output by the fuel cell converter 53 to a specific voltage (set voltage). The fuel cell converter 53 is a step-up / step-down converter. Specifically, the fuel cell converter 53 functions as a step-up converter, increasing the voltage output by the fuel cell 51 and outputting it to the high-voltage DC unit 73. The fuel cell converter 53 can increase the voltage of the high-voltage DC unit 73 relative to the voltage of the fuel cell output DC unit 51o. After the power supply system is started (described below), when power is supplied from the fuel cell 51 to the electric motor 77 or the capacitor 61, the fuel cell converter 53 functions as a step-up converter. The fuel cell converter 53 functions as a step-down converter, decreasing the voltage output by the fuel cell 51 and outputting it to the high-voltage DC unit 73. The fuel cell converter 53 can decrease the voltage of the high-voltage DC unit 73 relative to the voltage of the fuel cell output DC unit 51o. When the power supply system is started (described below), when power is supplied from the fuel cell 51 to the capacitor 61, the fuel cell converter 53 functions as a step-down converter.

[0021] The capacitor 61 is a power storage device that stores electric power. The capacitor 61 is an electric double layer capacitor (electric double layer condenser). Compared to secondary batteries (lead-acid batteries, lithium-ion batteries, etc.), the capacitor 61 has a faster charge / discharge response and is capable of instantaneous charging and discharging (inputting and outputting) of electric power. For this reason, the capacitor 61 is more suitable than a secondary battery as a power storage device that stores electric power for operating the work machine 10 (see FIG. 1) (for example, to drive the electric motor 77). More specifically, the work machine 10 shown in FIG. 1 may be subjected to sudden operations or may come into contact with a work target (such as soil). For this reason, the load acting on the work machine 10 fluctuates more drastically (for example, the load time constant is on the order of approximately 0.1 seconds) than, for example, an automobile. This causes a sudden change in the pressure of the hydraulic oil discharged by the hydraulic pump 21 shown in FIG. 2. This causes a sudden change in the load (required electric power) on the electric motor 77 that drives the hydraulic pump 21. This requires instantaneous charging and discharging (releasing and absorbing) of power, so a capacitor 61 is more suitable than a secondary battery as a power storage device for storing power to operate the work machine 10 (see FIG. 1).

[0022] The capacitor converter 63 is a device that controls the charging and discharging power of the capacitor 61. The capacitor converter 63 is a device (power conversion device) that converts the charging and discharging power of the capacitor 61. The capacitor converter 63 is configured to be able to both charge and discharge the capacitor 61. The capacitor converter 63 is connected to the capacitor 61. The capacitor converter 63 is connected to the high-voltage DC unit 73.

[0023] This capacitor converter 63 is a bidirectional (step-up / step-down) converter. For example, after the power supply system is started (described later), when the capacitor 61 supplies power to the electric motor 77, the capacitor converter 63 functions as follows. At this time, the capacitor converter 63 functions as a step-up converter that increases the voltage from the capacitor 61 toward the high-voltage DC unit 73 so that a current flows from the capacitor 61 to the high-voltage DC unit 73. When the power of the fuel cell 51 is charged into the capacitor 61, the capacitor converter 63 functions as a step-down converter that decreases the voltage from the high-voltage DC unit 73 toward the capacitor 61 so that a current flows from the high-voltage DC unit 73 to the capacitor 61.

[0024] This capacitor converter 63 is configured to be able to freely control (within a predetermined range) the power charged and discharged to and from the capacitor 61. The capacitor converter 63 can respond to a sudden change in the load on the electric motor 77 while the work machine 10 (see FIG. 1) is operating after the power supply system has been started (described later). Specifically, if the load on the electric motor 77 increases suddenly, the capacitor converter 63 can supply the electric power (discharged power) output by the capacitor 61 to the electric motor 77. Furthermore, if the load on the electric motor 77 decreases suddenly, the capacitor converter 63 can charge the electric power output by the fuel cell 51 to the capacitor 61.

[0025] The motor inverter 71 is a device (motor drive device) that drives the motor 77. The motor inverter 71 is configured to be able to receive power from the fuel cell 51 and the capacitor 61. The motor inverter 71 converts the power received from the fuel cell 51 and the capacitor 61 and supplies the converted power to the motor 77. More specifically, the motor inverter 71 converts a direct current input from the high-voltage DC unit 73 into an alternating current. The motor inverter 71 outputs the alternating current to the motor 77 via the AC unit 75.

[0026] High voltage DC section 73 (high voltage DC section) is a section configured to be able to supply power from fuel cell 51 and capacitor 61 to motor inverter 71. High voltage DC section 73 is a section through which direct current (DC) flows.

[0027] The AC section 75 is a section between the motor inverter 71 and the motor 77, through which an alternating current (AC) flows.

[0028] The electric motor 77 is configured to be able to receive power from the fuel cell 51 and the capacitor 61. The electric motor 77 is driven by the power output by the fuel cell 51 and the capacitor 61. The electric motor 77 is a load (power load) that consumes the power output by the fuel cell 51 and the capacitor 61. The electric motor 77 is driven by the electric motor inverter 71. The electric motor 77 is used to drive the work machine 10 (see FIG. 1 ). Specifically, the electric motor 77 drives the hydraulic pump 21. When the hydraulic pump 21 is driven, the hydraulic pump 21 discharges hydraulic oil, which is supplied to the hydraulic actuator 30, which moves the hydraulic actuator 30, thereby moving the work machine 10. Note that an electric motor 77 that moves something other than the hydraulic pump 21 may also be provided. For example, the electric motor 77 may move the work machine 10 without going through the hydraulic circuit 20. Specifically, the electric motor 77 may be the rotation motor 33 that rotates the upper rotating body 13 relative to the lower body 11 shown in Fig. 1. Only one electric motor 77 shown in Fig. 2 may be provided, or multiple electric motors 77 may be provided.

[0029] The sensors 80 detect various types of information. The sensors 80 detect information used for processing (control, etc.) by the controller 90. The sensors 80 output the detected information (signals) to the controller 90. The sensors 80 include, for example, a fuel cell current sensor 85i, a fuel cell voltage sensor 85v, a capacitor temperature sensor 86t, a capacitor current sensor 86i, a capacitor voltage sensor 86v, and a high-voltage DC voltage sensor 87v. Note that sensors 80 other than these may also be provided.

[0030] The fuel cell current sensor 85i detects the current output by the fuel cell 51. The fuel cell current sensor 85i detects the current flowing in the fuel cell output DC unit 51o. The fuel cell voltage sensor 85v detects the voltage output by the fuel cell 51. The fuel cell voltage sensor 85v detects the voltage (voltage between the positive and negative poles) of the fuel cell output DC unit 51o. The capacitor temperature sensor 86t detects the temperature of the capacitor 61. The capacitor voltage sensor 86v detects the voltage (voltage between the positive and negative poles) of the capacitor 61. The capacitor current sensor 86i detects the current (charge / discharge current) flowing in the capacitor 61. The capacitor current sensor 86i detects the current flowing in the circuit between the capacitor 61 and the capacitor converter 63. The high-voltage DC voltage sensor 87v detects the voltage (voltage between the positive and negative poles) of the high-voltage DC unit 73.

[0031] The controller 90 is a computer that inputs and outputs signals, performs calculations (processing), stores information, etc. The functions of the controller 90 are realized by executing a program stored in a storage unit of the controller 90 in a calculation unit of the controller 90. The controller 90 and other devices may be connected by wireless communication or by wired communication. For example, information is input to the controller 90 from the sensor 80.

[0032] This controller 90 controls, for example, the power output by the fuel cell 51 and the power charged and discharged by the capacitor 61. After the power supply system is started (described later), the controller 90 calculates the power distribution (output power distribution) between the fuel cell 51 and the capacitor 61 when power is supplied from the fuel cell 51 and the capacitor 61 to the electric motor 77. For example, the controller 90 outputs commands to the fuel cell converter 53 and the capacitor converter 63. The controller 90 (functions of the controller 90) includes a fuel cell converter control means 95 and a capacitor converter control means 96.

[0033] The fuel cell converter control means 95 controls the fuel cell converter 53. By controlling the fuel cell converter 53, the fuel cell converter control means 95 controls the power output by the fuel cell 51. The fuel cell converter control means 95 controls the voltage output by the fuel cell converter 53. The fuel cell converter control means 95 controls the step-up and step-down of the voltage output by the fuel cell 51. The fuel cell converter control means 95 controls the current output by the fuel cell 51. Specifically, for example, the fuel cell converter control means 95 instructs the fuel cell converter 53 on power (outputs a power command). Then, the fuel cell converter 53 controls the current output by the fuel cell converter 53 (output current) so that the fuel cell converter 53 outputs the power instructed by the fuel cell converter control means 95. The fuel cell converter control means 95 outputs a switching signal (a command to turn the switch on and off) to the switch element of the fuel cell converter 53.

[0034] The capacitor converter control means 96 controls the capacitor converter 63. The capacitor converter control means 96 controls the charging and discharging of the capacitor 61 by controlling the capacitor converter 63. At the start-up of the power supply system and after the start-up (described later), the capacitor converter control means 96 controls the voltage of the high-voltage DC unit 73. The capacitor converter control means 96 controls the capacitor converter 63 so that the voltage of the high-voltage DC unit 73 is constant (so that it is stabilized at a specific voltage). The capacitor converter control means 96 may control the current output by the capacitor 61 based on the current detected by the capacitor current sensor 86i. The capacitor converter control means 96 outputs a switching signal (a command to turn the switch on and off) to the switch element of the capacitor converter 63.

[0035] (Activated) Work machine 10 (see FIG. 1) is configured to operate as follows.

[0036] As described above, the electric motor 77 is driven to rotate by the electric power output by the fuel cell 51 and the capacitor 61. The electric motor 77 is controlled by the controller 90. More specifically, the controller 90 outputs a command to the electric motor inverter 71, and the electric motor inverter 71 drives the electric motor 77 in accordance with the command. The electric motor 77 is controlled (speed controlled) by the controller 90 so as to drive to rotate at a speed set in the controller 90. The electric motor 77 drives the hydraulic pump 21. The hydraulic pump 21 draws hydraulic oil from a tank, discharges the hydraulic oil, and supplies the hydraulic oil to the hydraulic actuator 30. A control valve (not shown) controls the flow rate and direction of the hydraulic oil supplied from the hydraulic pump 21 to the hydraulic actuator 30. The hydraulic actuator 30 moves (drives) when hydraulic oil is supplied from the hydraulic pump 21. Movement of the hydraulic actuator 30 moves the work machine 10 (see FIG. 1 ).

[0037] (Normal power system startup) The controller 90 controls the startup of the power supply system. Starting up the power supply system means putting the electric motor 77 into a state where the electric power (electric power supplied to the electric motor inverter 71) can be supplied to the electric motor 77. Starting up the power supply system means raising (rising) the voltage of the high voltage DC unit 73 from 0 V (or approximately 0 V) ​​to the voltage (set voltage) to be supplied to the electric motor inverter 71, thereby putting the electric motor 77 into a state where it can be driven. The "voltage (set voltage) to be supplied to the electric motor inverter 71" is set in advance in the controller 90 (before starting up the power supply system). Starting up the power supply system is performed, for example, when starting up the work machine 10 (see FIG. 1). Specifically, starting up the power supply system is performed when the key switch of the work machine 10 is turned on, etc.

[0038] Here, the startup of the power supply system will be described in the case where (normally) the voltage of capacitor 61 exceeds a capacitor voltage judgment value th (specifically, a charge start judgment value th1 ("judgment value th1" in FIG. 3)) which will be described later when the power supply system is started up. The case where the voltage of capacitor 61 is equal to or lower than the capacitor voltage judgment value th when the power supply system is started up will be described later.

[0039] When the power supply system is started, the electrical energy stored in the capacitor 61 is used to raise the voltage of the high-voltage DC unit 73 to the set voltage. Specifically, the controller 90 controls the capacitor converter 63 to boost the voltage output by the capacitor 61 and adjust the voltage of the high-voltage DC unit 73 to the set voltage. At this time, the controller 90 controls the capacitor converter 63 to stabilize the voltage of the high-voltage DC unit 73 at the set voltage (constant voltage). Thereafter, the controller 90 starts the fuel cell 51. Specifically, the controller 90 supplies fuel to the fuel cell 51 and controls the fuel cell 51 to output power. The controller 90 then connects the fuel cell 51 to the high-voltage DC unit 73. Specifically, the controller 90 boosts the voltage output by the fuel cell 51 and controls the fuel cell converter 53 to adjust the voltage output by the fuel cell converter 53 to the set voltage. This makes it possible to supply power output by the fuel cell 51 to the high-voltage DC unit 73. As a result, the power supply system is started. Specifically, the voltage of the high voltage DC unit 73 reaches the set voltage (rises), power can be supplied from the fuel cell 51 and the capacitor 61 to the electric motor 77, and the electric motor 77 enters a state where it can be driven.

[0040] (When the charge level of capacitor 61 is low) The capacitor 61 self-discharges (naturally discharges) faster (the amount of self-discharge is larger) than secondary batteries (lead-acid batteries, lithium-ion batteries, etc.). Furthermore, the capacitor 61 can store less electric power than secondary batteries (the amount of electric power that can be stored is smaller when compared with batteries of the same volume). Therefore, if the power control device 40 is not used, such as when the power supply to the work machine 10 is turned off, for example, after one to three weeks, the charge amount (charge amount, remaining energy) of the capacitor 61 will become empty or nearly empty. Then, when an attempt is made to start the power supply system, the electric energy remaining in the capacitor 61 may not be enough to raise the voltage of the high-voltage DC section 73 to the set voltage.

[0041] (Pre-start charge control) Therefore, the controller 90 performs pre-start charge control, which is a control for charging the capacitor 61 when the power supply system is about to be started (before start-up) to bring the power supply system into a startable state.

[0042] The processing of the controller 90, such as pre-start charge control, will be described with reference to the flowchart shown in Figure 3. Unless otherwise specified, the processing will be described in the order of the processing. Note that the order of the processing can be changed in various ways. Each component of the power control device 40 will be described with reference to Figure 2, and each step of the flowchart shown in Figure 3 will be described with reference to Figure 3.

[0043] In step S1, the controller 90 (for example, the capacitor converter control means 96) shown in FIG. 2 acquires the voltage of the capacitor 61 (capacitor voltage) detected (measured) by the capacitor voltage sensor 86v.

[0044] In step S2 (see FIG. 3 ), the controller 90 determines the charge amount (amount of charge) of the capacitor 61. Because there is a correlation between the voltage of the capacitor 61 and the charge amount of the capacitor 61, the charge amount of the capacitor 61 can be detected by the capacitor voltage sensor 86v detecting the voltage of the capacitor 61. For example, the controller 90 determines whether the voltage of the capacitor 61 (acquired in step S1) is equal to or less than a capacitor voltage determination value th (specifically, a charge start determination value th1). The capacitor voltage determination value th is the voltage of the capacitor 61 required to start up the power supply system (details will be described later). If the voltage of the capacitor 61 is equal to or less than the charge start determination value th1 (YES in step S2), the controller 90 advances the process flow to step S3. If the voltage of the capacitor 61 exceeds the charge start determination value th1 (NO in step S2), the power supply system is in a state where it can be started up (the above-mentioned “normal state”). In this case, the controller 90 starts up the power supply system (details will be described above).

[0045] The capacitor voltage judgment value th is the voltage of the capacitor 61 required to start up the power supply system. The capacitor voltage judgment value th may be the minimum voltage of the capacitor 61 required to start up the power supply system (minimum required voltage). The capacitor voltage judgment value th may be a value close to the "minimum required voltage" but greater than the minimum required voltage. More specifically, as described above, when the power supply system starts up, the capacitor converter 63 boosts the voltage of the capacitor 61, and the voltage of the high-voltage DC unit 73 becomes the set voltage. However, if the voltage of the capacitor 61 is too low, the voltage of the high-voltage DC unit 73 cannot become the set voltage, and the power supply system cannot start up. If the voltage of the capacitor 61 is equal to or higher than the "minimum required voltage," the capacitor converter 63 boosts the voltage of the capacitor 61, making it possible to make the voltage of the high-voltage DC unit 73 become the set voltage. Therefore, the capacitor voltage judgment value th is set to this "minimum required voltage" or a value close to the minimum required voltage but greater than the minimum required voltage.

[0046] This capacitor voltage judgment value th may be a constant value that is set in advance (at least before the judgment in step S2) in the controller 90. The controller 90 may change the capacitor voltage judgment value th depending on the conditions.

[0047] The capacitor voltage determination value th may be set to a charge start determination value th1 (see step S2) and a charge stop determination value th2 (see step S4). The charge start determination value th1 is the capacitor voltage determination value th when the determination in step S2 is made. The charge stop determination value th2 is the capacitor voltage determination value th when the determination in step S4 (described later) is made. The charge start determination value th1 and the charge stop determination value th2 may be the same value or different values ​​(described later).

[0048] The controller 90 may change the capacitor voltage determination value th according to the temperature of the capacitor 61. Specifically, the controller 90 acquires the temperature detected by the capacitor temperature sensor 86t. The lower the temperature of the capacitor 61, the lower the current that the capacitor 61 can output and the higher the voltage required to start the power supply system. Therefore, the controller 90 increases the capacitor voltage determination value th as the temperature of the capacitor 61 decreases. For example, the controller 90 may increase the capacitor voltage determination value th continuously (e.g., proportionally or approximately proportional to the temperature) as the temperature of the capacitor 61 decreases. The controller 90 may increase the capacitor voltage determination value th in stages as the temperature of the capacitor 61 decreases. The controller 90 decreases the capacitor voltage determination value th as the temperature of the capacitor 61 increases. For example, if the temperature of the capacitor 61 differs between when step S2 is performed and when step S4 is performed, the charge start determination value th1 and the charge stop determination value th2 may differ.

[0049] The controller 90 may change the capacitor voltage judgment value th according to the deterioration level of the capacitor 61. The higher the deterioration level of the capacitor 61, the lower the current that the capacitor 61 can output, and the higher the voltage required to start up the power supply system. Therefore, the controller 90 increases the capacitor voltage judgment value th as the deterioration level of the capacitor 61 increases. The controller 90 may increase the capacitor voltage judgment value th continuously or in stages as the deterioration level of the capacitor 61 increases. The controller 90 may decrease the capacitor voltage judgment value th as the deterioration level of the capacitor 61 decreases. The controller 90 may calculate the deterioration level of the capacitor 61 from various parameters. The controller 90 may calculate the deterioration level of the capacitor 61 based on the usage time of the capacitor 61 from a new state, or may calculate it based on the total power input and output to the capacitor 61. Controller 90 may calculate the degree of deterioration of capacitor 61 based on the amount by which the voltage of capacitor 61 exceeds the upper limit voltage (for example, the difference between the actual voltage and the upper limit voltage, the number of times it exceeds the upper limit voltage, etc.), or may calculate the degree of deterioration of capacitor 61 based on the amount by which the voltage of capacitor 61 falls below the lower limit voltage. For example, if the degree of deterioration of capacitor 61 differs between when step S2 is performed and when step S4 is performed, charging start determination value th1 and charging stop determination value th2 may differ.

[0050] In step S3 (see FIG. 3), controller 90 performs pre-startup charge control. Pre-startup charge control is control for charging (pre-charging) capacitor 61 when attempting to start up the power supply system (before startup). Pre-startup charge control is performed when the voltage of capacitor 61 is equal to or lower than charge start determination value th1 (capacitor voltage determination value th) (NO in step S2). Hereinafter, it is assumed that charging of capacitor 61 is not charging after the power supply system has started up, but charging during pre-startup charge control.

[0051] The power source (pre-charge power source) for charging the capacitor 61 is preferably a power source mounted on the work machine 10 (see FIG. 1). In this case, there is no need to use an external power source (a power source external to the work machine 10) as the pre-charge power source. Specifically, the pre-charge power source is the fuel cell 51. The controller 90 uses pre-start charge control to charge the capacitor 61 with the power output by the fuel cell 51. The pre-charge power source may be a battery 251 (see FIG. 4), which will be described later. However, the pre-charge power source may also be an external power source.

[0052] If the charging power of the capacitor 61 is too large, there is a risk of deterioration (including damage) of the capacitor 61. When the voltage of the capacitor 61 is low (specifically, a state equal to or lower than the capacitor voltage judgment value th), there is a risk of deterioration of the capacitor 61 if the power output by the pre-charge power supply is supplied to the capacitor 61 as is. Therefore, the controller 90 gradually increases the charging power of the capacitor 61.

[0053] A specific example of charging the capacitor 61 with the power output by the fuel cell 51 will be described. For example, the controller 90 outputs an instruction to the fuel cell converter 53 to step down the voltage output by the fuel cell 51 (causing the fuel cell converter 53 to perform a step-down operation). The controller 90 outputs an instruction to the fuel cell converter 53 so that the voltage output by the fuel cell converter 53 (output to the high-voltage DC unit 73) becomes a voltage that can suppress deterioration of the capacitor 61. The controller 90 also controls the current output by the fuel cell 51, thereby controlling the current input to the capacitor 61. Specifically, the controller 90 controls the current output by the fuel cell 51 to a predetermined current value (set current value) based on the current detected by the fuel cell current sensor 85i (by current feedback control). The current feedback control is, for example, PI control (proportional integral control). The controller 90 outputs an instruction to a switch element of the fuel cell converter 53 and controls the switch element using PWM (pulse width modulation).

[0054] In step S4 (see FIG. 3), the controller 90 determines whether or not to stop charging the capacitor 61. Specifically, the controller 90 determines whether or not the voltage of the capacitor 61 has reached a voltage at which the power supply system can be started. More specifically, the controller 90 determines whether or not the voltage of the capacitor 61 exceeds a capacitor voltage determination value th (specifically, a charging stop determination value th2). If the voltage of the capacitor 61 is equal to or lower than the charging stop determination value th2 (NO in step S4), the controller 90 continues charging the capacitor 61. In this case, the flow returns to step S3. If the voltage of the capacitor 61 exceeds the charging stop determination value th2 (YES in step S4), the controller 90 stops charging the capacitor 61 (step S5). That is, the controller 90 ends the pre-start charging control. After stopping the charging of the capacitor 61 (after step S5), the controller 90 starts up the power supply system.

[0055] (Program, Method) The power control device 40 shown in FIG. 2 is configured to perform each of the above operations. A power control program may be set to cause a controller 90 (computer) to execute the process of performing each of the above operations. A power control method may be implemented to perform each of the above operations. Each of the above operations may be considered a "step" in the program and method. For example, the pre-start charge control by the controller 90 may be considered a "pre-start charge step."

[0056] (Effects of the first invention) The effects of the power control device 40 (work machine power control device) shown in Figure 2 are as follows. The power control device 40 includes a fuel cell 51, a capacitor 61, a capacitor voltage sensor 86v, an electric motor 77, and a controller 90. The capacitor voltage sensor 86v detects the voltage of the capacitor 61. The electric motor 77 is configured to be able to receive power from the fuel cell 51 and the capacitor 61. The electric motor 77 is used to drive the work machine 10 (see Figure 1). The controller 90 controls the startup of the power supply system. Starting up the power supply system means bringing the electric motor 77 into a state where it can be driven by the power supplied to the electric motor 77.

[0057] [Configuration 1A] A capacitor voltage determination value th (see step S2 in FIG. 3) which is the voltage of capacitor 61 required to start up the power supply system is set in controller 90. When attempting to start up the power supply system, if the voltage of capacitor 61 detected by capacitor voltage sensor 86v is equal to or lower than capacitor voltage determination value th (YES in step S2 in FIG. 3), controller 90 performs the following process. In this case, controller 90 performs pre-startup charge control which is control to charge capacitor 61 (step S3 in FIG. 3).

[0058] [Configuration 1B] When attempting to start the power supply system, if the voltage of capacitor 61 detected by capacitor voltage sensor 86v exceeds capacitor voltage determination value th, controller 90 performs the following process: In this case, controller 90 starts up the power supply system (see the case of NO in step S2 and the case of YES in step S4).

[0059] The above [Configuration 1A] and [Configuration 1B] provide the following effects. Capacitor 61 self-discharges faster than a secondary battery. Therefore, when capacitor 61 is left uncharged, the voltage of capacitor 61 is likely to become lower than the voltage required to start the power supply system. If the power supply system cannot be started and the electric motor 77 cannot be driven, the work machine 10 will not move. Therefore, in the above [Configuration 1A], when attempting to start the power supply system, if the voltage of capacitor 61 is equal to or lower than the capacitor voltage determination value th (YES in step S2 of FIG. 3), the controller 90 charges capacitor 61 (step S3 of FIG. 3). On the other hand, if the voltage of capacitor 61 exceeds the capacitor voltage determination value th, the power supply system is in a state where it can be started. Therefore, in the above [Configuration 1B], when attempting to start the power supply system, if the voltage of capacitor 61 exceeds the capacitor voltage determination value th (NO in step S2, YES in step S4), the controller 90 starts the power supply system. Therefore, even if the voltage of capacitor 61 is low when attempting to start the power supply system, the power supply system can be started. As a result, electric motor 77 can be driven, and working machine 10 can be operated.

[0060] (Effects of the second invention) [Configuration 2] The controller 90 causes the capacitor 61 to be charged with the power output by the fuel cell 51 through pre-start charge control (see step S3).

[0061] In the above [Configuration 2], the capacitor 61 can be charged in the pre-start charge control without using an external power supply (a power supply external to the power supply system including the fuel cell 51 and the capacitor 61).

[0062] (Effect of the fourth invention) [Configuration 4] The power control device 40 includes a capacitor temperature sensor 86t that detects the temperature of the capacitor 61. The controller 90 changes the capacitor voltage determination value th according to the temperature of the capacitor 61 detected by the capacitor temperature sensor 86t.

[0063] The above [Configuration 4] achieves the following effect. The current that the capacitor 61 can output varies depending on the temperature of the capacitor 61, and as a result, the voltage required to start the power supply system varies. Therefore, in the above [Configuration 4], the controller 90 changes the capacitor voltage determination value th depending on the temperature of the capacitor 61. Thus, the controller 90 can determine an appropriate capacitor voltage determination value th according to the temperature of the capacitor 61. More specifically, if the capacitor voltage determination value th is too low relative to the voltage actually required to start the power supply system, the power supply system cannot be started and the electric motor 77 cannot be driven. On the other hand, if the capacitor voltage determination value th (the charge stop determination value th2 in FIG. 3 ) is too high relative to the voltage actually required to start the power supply system, the charging time to the capacitor 61 in the pre-start charge control becomes long. By setting the capacitor voltage determination value th to an appropriate value, the power supply system can be started appropriately and the charging time to the capacitor 61 can be prevented from becoming long.

[0064] (Second embodiment) 4 and 5, the differences between the power control device 240 of the second embodiment and the power control device 40 of the first embodiment will be described. Note that, among the power control device 240 of the second embodiment, the commonalities with the power control device 40 of the first embodiment will not be described. The difference is the power source (pre-charge power source) for charging the capacitor 61 in the pre-start charge control (see step S203 in FIG. 5). The pre-charge power source is a fuel cell 51 in the example shown in FIG. 2, but is a battery 251 in the example shown in FIG. 4. The details of the differences are as follows:

[0065] The power control device 240 includes a battery 251, a battery converter 253, and an auxiliary device 277. The sensor 80 includes a battery current sensor 285i. The controller 90 includes a battery converter control means 295.

[0066] The battery 251 is a power source (auxiliary battery) for the auxiliary device 277. The battery 251 is a secondary battery. The battery 251 may include a lead-acid battery or a lithium-ion battery. Usually, the power that the battery 251 can output is smaller than the power that the fuel cell 51 can output. On the other hand, the rise in voltage of the battery 251 is faster than the rise in voltage of the fuel cell 51. The battery 251 is connected to the high-voltage DC unit 73 via a battery converter 253. The battery 251 is connected to the capacitor 61 via the battery converter 253 (and further via a capacitor converter 63).

[0067] The battery converter 253 controls the power of the battery 251. The battery converter 253 controls the power output (discharged) by the battery 251. The battery converter 253 may be capable of controlling the power charged to the battery 251. The battery converter 253 has a function of a step-down converter that reduces the voltage output by the battery 251 and outputs it to the high-voltage DC unit 73. The battery converter 253 may have a function of a step-up converter that increases the voltage output by the battery 251 and outputs it to the high-voltage DC unit 73. The battery converter 253 may be a step-up / step-down (bidirectional) converter.

[0068] The auxiliary device 277 is a device (electrical load) that consumes electric power. The auxiliary device 277 is a device different from the electric motor 77 (main engine). For example, the auxiliary device 277 may include a computer (e.g., a controller 90) or a cooling fan (e.g., a fan that cools the electric motor 77, etc.). The auxiliary device 277 may include the fuel cell converter 53, the capacitor converter 63, the electric motor inverter 71, or the battery converter 253. The auxiliary device 277 may include a pump that supplies fuel to the fuel cell 51, etc. The auxiliary device 277 may include a sensor 80.

[0069] The battery current sensor 285i detects the current output from the battery 251. The battery current sensor 285i detects the current flowing through the circuit between the battery 251 and the battery converter 253.

[0070] The battery converter control means 295 controls the battery converter 253. The battery converter control means 295 controls the discharge of the battery 251. The battery converter control means 295 may control the charging of the battery 251. The battery converter control means 295 controls the voltage output by the battery converter 253 (see the description of the fuel cell converter 53 for a specific example). The battery converter control means 295 may control the current output by the battery 251 based on the current detected by the battery current sensor 285i.

[0071] (Activated) The operation of the power control device 240 will be described below in terms of differences from the operation of the power control device 40 shown in FIG. 2. In the power control device 40 shown in FIG. 2, the controller 90 charges the capacitor 61 with the power output from the fuel cell 51 through pre-start charge control (step S3 in FIG. 3). In this embodiment, the controller 90 shown in FIG. 4 charges the capacitor 61 with the power output from the battery 251 through pre-start charge control (step S203 in FIG. 5). For example, the controller 90 (specifically, the battery converter control means 295) reduces the voltage output from the battery 251 and outputs it to the high-voltage DC unit 73. The controller 90 also controls the current output from the battery 251, thereby controlling the current input to the capacitor 61. Specifically, the controller 90 controls the current output from the battery 251 to be a predetermined current value (set current value) based on the current detected by the battery current sensor 285i (through current feedback control (a specific example is described above)).

[0072] (Effect of the third invention) 4 provides the following effects: The power control device 240 includes a battery 251 that is a power source for an auxiliary device 277 that is a device different from the electric motor 77 .

[0073] [Configuration 3] The controller 90 causes the capacitor 61 to be charged with the power output by the battery 251 through pre-start charge control (see step S203 in FIG. 5).

[0074] With the above [Configuration 3], the capacitor 61 can be charged using the power of the battery 251. Here, the voltage of the battery 251 rises faster than the voltage of the fuel cell 51. Therefore, the charging time for the capacitor 61 can be shortened compared to when the capacitor 61 is charged with the power of the fuel cell 51. As a result, the start-up time of the power supply system can be shortened. As a result, the work machine 10 can be started up sooner.

[0075] (Variation) The above-described embodiments (including modified examples within the embodiments (the same applies hereinafter)) may be modified in various ways. All or part of different embodiments may be combined in various ways. For example, the number of components of the above-described embodiments may be changed, or some of the components may not be provided. For example, the connections between the components shown in FIGS. 2 and 4 may be changed. For example, the inclusion relationships between the components may be changed in various ways. For example, a component described as a lower-level component included in a higher-level component may not be included in this higher-level component, but may be included in another component. For example, what is described as multiple different components may be combined into a single component. For example, what is described as a single element may be provided as multiple different elements. For example, the order of the steps in the flowcharts shown in FIGS. 3 and 5 may be changed, some steps may not be performed, or steps in different flowcharts may be combined. For example, various information (values, ranges, etc.) may be preset in the controller 90, or may be set by being read into the controller 90 from an external storage device of the controller 90. The various information may be set directly by manual operation by an operator, or may be set in the controller 90 based on information set by manual operation by the operator. The various pieces of information may be set in the controller 90 based on information detected by the sensor 80. For example, the various pieces of information may not be changeable, may be changeable by manual operation, or may be automatically changed by the controller 90 in response to certain conditions. For example, the controller 90 may perform substantially the same processing (calculation, determination, etc.) as that of the above-described embodiment. Specifically, the controller 90 may perform processing using information that can be converted into the various pieces of information used in the above-described embodiment. The processing performed by the controller 90 may be combined in various ways. For example, each component may have only a part of its characteristics (function, arrangement, shape, operation, etc.). [Explanation of symbols]

[0076] 10. Work Machinery 40, 240 Power control device (work machine power control device) 51 Fuel Cell 61 Capacitor 77 Electric motor 86t Capacitor Temperature Sensor 86v Capacitor Voltage Sensor 90 Controller 251 Battery 277 Auxiliary Machinery th Capacitor voltage judgment value

Claims

1. A fuel cell; A capacitor; a capacitor voltage sensor for detecting a voltage of the capacitor; an electric motor configured to be able to receive power from the fuel cell and the capacitor and for driving a work machine; A controller; Equipped with the controller controls activation of a power supply system that supplies power to the electric motor so that the electric motor can be driven; a capacitor voltage determination value, which is a voltage of the capacitor required to start up the power supply system, is set in the controller; the controller performs pre-startup charge control, which is control to charge the capacitor, when the voltage of the capacitor detected by the capacitor voltage sensor is equal to or lower than the capacitor voltage determination value when attempting to start up the power supply system; the controller starts the power supply system if the voltage of the capacitor detected by the capacitor voltage sensor exceeds the capacitor voltage determination value when attempting to start the power supply system; Work machine power control device.

2. 2. The work machine power control device according to claim 1, the controller causes the capacitor to be charged with the power output by the fuel cell through the pre-start charge control; Work machine power control device.

3. 2. The work machine power control device according to claim 1, a battery that is a power source for an auxiliary device that is a device different from the electric motor; the controller causes the capacitor to be charged with power output from the battery through the pre-start charge control; Work machine power control device.

4. 2. The work machine power control device according to claim 1, a capacitor temperature sensor for detecting the temperature of the capacitor; the controller changes the capacitor voltage determination value in accordance with the temperature of the capacitor detected by the capacitor temperature sensor; Work machine power control device.

Images