Work machine control method, work machine control program, work machine control system, and work machine

Abstract

To provide a technique capable of shortening a time until an electric motor starts rotating after a predetermined operation is performed when a starting device is in an on-state.SOLUTION: A hydraulic excavator as a work machine includes a battery that stores electric power, an electric motor that is driven by electric power supplied from the battery, and a starter that starts the electric motor. The method for controlling the hydraulic excavator includes performing a discharging process for bringing the battery into a dischargeable state when the activation device is in the ON state, and rotating the electric motor when a predetermined operation is performed after the discharging process is performed.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a control method for a work machine, a control program for a work machine, a control system for a work machine, and a work machine. [Background technology]

[0002] Patent Document 1 discloses a startup process for a hydraulic excavator that includes a battery, an electric motor that generates power using electricity supplied from the battery, and a key switch for starting the electric motor. In the startup process, when the key switch is changed from an on state to a start state, a start signal for the electric motor is generated. Thereafter, it is determined whether or not power can be supplied to the electric motor, and if power can be supplied, a drive command is output to the electric motor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-143453 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, when the key switch (starting device) is on and the electric motor is stopped, such as when the machine is on standby for work, it is desirable for the electric motor to start rotating as quickly as possible in order to start (restart) work as quickly as possible. In this regard, in the configuration of Patent Document 1, the above-mentioned determination process is included between the time when the key switch is turned to the start state (as a predetermined operation) and the time when the electric motor 103 starts rotating, so there is a risk that the start of rotation of the electric motor will be delayed by at least the time required for the determination process.

[0005] The present invention has been made to solve the above-mentioned problems, and its purpose is to provide a technology that can shorten the time from when a specified operation is performed until the electric motor starts to rotate when the starting device is in the on state. [Means for solving the problem]

[0006] A control method for a work machine according to one aspect of the present invention is a control method for a work machine that includes a battery that stores electric power, an electric motor that is driven by receiving electric power from the battery, and a starting device that starts the electric motor, and includes: when the starting device is in an on state, executing a discharge process that puts the battery into a dischargeable state; and when a predetermined operation is performed after executing the discharge process, rotating the electric motor.

[0007] A control program for a work machine according to another aspect of the present invention causes at least one arithmetic device to execute the above control method.

[0008] A work machine control system according to another aspect of the present invention is a work machine control system comprising a battery for storing electric power, an electric motor that is driven by receiving electric power from the battery, and a starting device that starts the electric motor, and further comprising a discharge control unit that executes a discharge process to place the battery in a dischargeable state when the starting device is in an on state, and a rotation control unit that rotates the electric motor when a predetermined operation is performed after the discharge process has been executed.

[0009] A work machine according to another aspect of the present invention includes the above-described control system. [Effects of the Invention]

[0010] According to the above configuration, when the starting device is in the ON state, it is possible to reduce the time from when a predetermined operation is performed until the electric motor starts to rotate. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a side view showing a schematic configuration of a hydraulic excavator, which is an example of a work machine according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram schematically illustrating a configuration of a control system for the hydraulic excavator. [Figure 3] 6 is a flowchart showing a flow up to the start of a discharge process for starting an electric motor provided in the hydraulic excavator. [Figure 4] 10 is a flowchart showing the flow of the discharge process. [Figure 5] 10 is a flowchart showing a process after the discharge process is performed. DETAILED DESCRIPTION OF THE INVENTION

[0012] The following describes an embodiment of the present invention with reference to the drawings.

[0013] [1. General configuration of the work machine] 1 is a side view showing a schematic configuration of a hydraulic excavator 1 (electric excavator) which is an example of a work machine according to an embodiment of the present invention. The hydraulic excavator 1 includes a lower traveling structure 2, a work implement 3, and an upper rotating structure 4.

[0014] Here, the directions used in the description of this embodiment are defined as follows. The direction in which an operator (operator, driver) seated in the driver's seat 44a arranged in the control section 44 of the upper rotating body 4 faces forward is defined as "forward," and the opposite direction is defined as "rearward." When the upper rotating body 4 is not rotating relative to the lower running body 2 (swing angle 0 degrees), the fore-and-aft direction of the upper rotating body 4 coincides with the fore-and-aft direction of the lower running body 2. In the drawings, the hydraulic excavator 1 is shown in a state in which the upper rotating body 4 is not rotating relative to the lower running body 2. Furthermore, the left side as viewed from the operator seated in the driver's seat 44a is defined as "left," and the right side is defined as "right." Furthermore, the direction of gravity, which is perpendicular to the fore-and-aft direction and the left-and-right direction, is defined as the up-and-down direction, and the upstream side of the direction of gravity is defined as "up," and the downstream side is defined as "down." In the drawings, where necessary, the following symbols are used to indicate front: "F", rear: "B", right: "R", left: "L", top: "U", and bottom: "D".

[0015] The lower traveling structure 2 is equipped with a pair of left and right crawlers 21, a pair of left and right travel motors 22, and a blade 23. The left and right travel motors 22 drive the left and right crawlers 21, respectively, to move the hydraulic excavator 1 forward and backward. The travel motors 22 are configured as hydraulic motors. The blade 23, which performs ground leveling work, earth removal work, etc., is provided on the front side of the lower traveling structure 2. The blade 23 is rotated by a blade cylinder 23a. The blade cylinder 23a is configured as a hydraulic cylinder. The base end of the blade cylinder 23a is connected to the blade 23, and the tip end is connected to the front part of the lower traveling structure 2.

[0016] The work implement 3 includes a boom 31, an arm 32, and a bucket 33. By independently driving the boom 31, the arm 32, and the bucket 33, it is possible to perform work of excavating earth and sand, etc.

[0017] The boom 31 is rotated by a boom cylinder 31a. The boom cylinder 31a is composed of a hydraulic cylinder. The base end of the boom cylinder 31a is supported on the front part of the upper rotating body 4, and the boom cylinder 31a moves freely in an extendable and retractable manner. When the boom cylinder 31a extends and retracts, the boom 31 rotates in the up-down and back-to-front directions relative to the upper rotating body 4.

[0018] The arm 32 is rotated by an arm cylinder 32a. The arm cylinder 32a is composed of a hydraulic cylinder. The base end of the arm cylinder 32a is supported by the boom 31 and is movable so as to be extendable and retractable. When the arm cylinder 32a extends and retracts, the arm 32 rotates in the up-down and back-to-front directions relative to the boom 31.

[0019] The bucket 33 is rotated by a bucket cylinder 33a. The bucket cylinder 33a is composed of a hydraulic cylinder. The base end of the bucket cylinder 33a is supported by the arm 32 and is movable so as to be able to extend and retract. When the bucket cylinder 33a extends and retracts, the bucket 33 rotates up and down and back and forth relative to the arm 32.

[0020] The upper rotating body 4 is located above the lower traveling body 2 and is rotatable relative to the lower traveling body 2 via a swivel bearing (not shown). The upper rotating body 4 includes a swivel frame 41, a swivel motor 42, a machine room 43, and a control unit 44. The upper rotating body 4 rotates relative to the lower traveling body 2 by driving the swivel motor 42 arranged on the swivel frame 41. The swivel frame 41 is configured to include multiple metal members joined by welding or the like. The swivel motor 42 is configured as a hydraulic motor. The machine room 43 accommodates a battery unit 101, an inverter unit 102 (see FIG. 2), etc., which will be described later.

[0021] The control unit 44 is provided at the top of the upper rotating body 4. A driver's seat 44a is arranged in the control unit 44. A plurality of control members 44b are arranged around the driver's seat 44a. The plurality of control members 44b are configured to include levers, switches, pedals, etc. An operator sits in the driver's seat 44a and operates the plurality of control members 44b to drive the left and right traveling motors 22, the boom cylinder 31a, the swing motor 42, etc. This allows the lower traveling body 2 to travel, the blade 23 to perform earth removal work, the work implement 3 to perform excavation work, the upper rotating body 4 to rotate, etc.

[0022] At least one of the plurality of operating members 44b is included in a control system 100 that controls the hydraulic excavator 1. In other words, the hydraulic excavator 1 is equipped with the control system 100. The configuration of the control system 100 will be described below.

[0023] [2. Control system configuration] Fig. 2 is a block diagram that schematically illustrates the configuration of the control system 100. Note that Fig. 2 illustrates components necessary for explaining the features of this embodiment, and omits descriptions of general components.

[0024] The control system 100 includes a battery unit 101, an inverter unit 102, an electric motor 103, a DC-DC converter 104, a lead battery 105, a control device 106, a starting device 107, a rotation speed setting device 108, and a switching device 109. In other words, the hydraulic excavator 1 includes the battery unit 101, the inverter unit 102, the electric motor 103, the DC-DC converter 104, the lead battery 105, the control device 106, the starting device 107, and the switching device 109.

[0025] The battery unit 101 is configured to include a battery 101a. The battery 101a is configured, for example, as a lithium-ion battery. The battery 101a may be configured by unitizing a plurality of battery cells, or may be configured as a single battery cell. Therefore, the battery 101a is configured to be able to store electricity. In other words, the hydraulic excavator 1 is equipped with the battery 101a that stores electricity. The battery 101a is electrically connected via a power feed port (not shown) that is configured to be connectable to an external power source (not shown), such as a commercial power source, and a charger (not shown). The charger converts AC voltage supplied from the external power source into DC voltage. Therefore, the battery 101a can be charged by connecting the power feed port to the external power source.

[0026] The battery 101a is connected to the electric motor 103 via a first connection circuit C1 that includes the inverter unit 102. That is, the hydraulic excavator 1 is provided with the first connection circuit C1 that electrically connects the battery 101a and the electric motor 103. In addition to the inverter unit 102, the first connection circuit C1 includes a pair of first and second electric circuits E1 and E2, and a pair of third and fourth electric circuits E3 and E4. The pair of first and second electric circuits E1 and E2 connect the battery 101a and the inverter unit 102. The pair of third and fourth electric circuits E3 and E4 connect the inverter unit 102 and the electric motor 103.

[0027] The inverter unit 102 is configured to include an inverter 102a. That is, the hydraulic excavator 1 is equipped with the inverter 102a. The inverter 102a is connected to the battery 101a via a second connection circuit C2 that includes a pair of a first electric circuit E1 and a second electric circuit E2. That is, the hydraulic excavator 1 is equipped with the second connection circuit C2 that electrically connects the battery 101a and the inverter 102a. The second connection circuit C2 constitutes the first connection circuit C1.

[0028] The inverter 102a converts the DC voltage supplied from the battery 101a into AC voltage and supplies it to the electric motor 103. This drives the electric motor 103. That is, the inverter 102a supplies the electric power supplied from the battery 101a to the electric motor 103. The electric motor 103 is driven by receiving the electric power supplied from the battery 101a. The electric motor 103 is configured as a synchronous motor, an induction motor, or the like.

[0029] The battery unit 101 includes a battery 101a, a first inrush current prevention circuit 101b, and a BMU (Battery Management Unit) 101c. The inverter unit 102 includes an inverter 102a, a second inrush current prevention circuit 102b, a relay control unit 102c, and a capacitor 102d.

[0030] The first inrush current prevention circuit 101b is provided on the second electrical path E2. That is, the first connection circuit C1 including the second electrical path E2 has the first inrush current prevention circuit 101b. The first inrush current prevention circuit 101b has a first path R1 and a second path R2 that are arranged in parallel with each other on the second electrical path E2.

[0031] The first path R1 includes a first relay RL1. The first relay RL1 (also referred to as a battery relay or a PDU relay) is provided in the first inrush current prevention circuit 101b, i.e., on the second electric circuit E2, as well as on the first electric circuit E1. Therefore, in this embodiment, two first relays RL1 are provided. That is, the first connection circuit C1 including the first electric circuit E1 and the second electric circuit E2 has a first relay RL1. Note that, hereinafter, the first relay RL1 on the first electric circuit E1 may be referred to as one first relay RL1, and the first relay RL1 on the second electric circuit E2 may be referred to as the other first relay RL1.

[0032] The first relay RL1 can switch between electrical connection and disconnection between the battery 101a and the electric motor 103. More specifically, the first relay RL1 is configured to be switchable between a connected state (closed state) and a disconnected state (open state). When one of the first relays RL1 is in the connected state, the first electric circuit E1 electrically connects the battery 101a and the electric motor 103 (via the inverter unit 102 and the third electric circuit E3 or the fourth electric circuit E4). On the other hand, when the other of the first relays RL1 is in the disconnected state, the first electric circuit E1 electrically disconnects the battery 101a and the electric motor 103.

[0033] When the other first relay RL1 is in a connected state, the second electric circuit E2 electrically connects the battery 101a and the electric motor 103 (via the inverter unit 102 and the third electric circuit E3 or the fourth electric circuit E4). On the other hand, when the other first relay RL1 is in a disconnected state, the second electric circuit E2 electrically disconnects the battery 101a and the electric motor 103.

[0034] The second path R2 includes a first inrush current prevention relay R2a and a first inrush current prevention resistor R2b. The first inrush current prevention relay R2a and the first inrush current prevention resistor R2b are arranged in series on the second path R2. In this embodiment, the first inrush current prevention relay R2a is arranged on the battery 101a side, and the first inrush current prevention resistor R2b is arranged on the inverter 102a (electric motor 103) side, but this configuration is not limited to this. For example, the first inrush current prevention relay R2a may be arranged on the inverter 102a (electric motor 103) side, and the first inrush current prevention resistor R2b may be arranged on the battery 101a side. The first inrush current prevention relay R2a is configured to be switchable between a connected state and a disconnected state. The first inrush current prevention resistor R2b is provided to reduce the magnitude of the inrush current flowing through the second path R2.

[0035] The first inrush current prevention circuit 101b including the other first relay RL1 and the one first relay RL1 configure a PDU (Power Drive Unit) 101d. That is, the battery unit 101 includes the PDU 101d.

[0036] The BMU 101c monitors the state of the battery 101a and controls the battery 101a, and also controls the first relay RL1 and the first inrush current prevention relay R2a to control the input and output of the battery 101a. Note that the control of the first relay RL1 and the first inrush current prevention relay R2a may be performed by the control device 106 instead of or in addition to the BMU 101c.

[0037] The second inrush current prevention circuit 102b is provided on the first electrical circuit E1. That is, the second connection circuit C2 including the first electrical circuit E1 has the second inrush current prevention circuit 102b. The second inrush current prevention circuit 102b has a third path R3 and a fourth path R4 that are arranged in parallel with each other on the first electrical circuit E1.

[0038] The third path R3 includes the second relay RL2. Therefore, it can be said that the second relay RL2 is provided on the first electrical path E1. That is, the second connection circuit C2, which includes the first connection circuit C1, has the second relay RL2.

[0039] The second relay RL2 (also referred to as an inverter relay) can switch between electrical connection and disconnection between the battery 101a and the inverter 102a. More specifically, the second relay RL2 is configured to be switchable between a connected state and a disconnected state, similar to the first relay RL1. When the second relay RL2 is in the connected state, the first electrical circuit E1 electrically connects the battery 101a and the inverter 102a. On the other hand, when the second relay RL2 is in the disconnected state, the first electrical circuit E1 electrically disconnects the battery 101a and the inverter 102a.

[0040] The fourth path R4 includes a second inrush current prevention relay R4a and a second inrush current prevention resistor R4b. The second inrush current prevention relay R4a and the second inrush current prevention resistor R4b are arranged in series on the fourth path R4. In this embodiment, the second inrush current prevention relay R4a is arranged on the inverter 102a (electric motor 103) side, and the second inrush current prevention resistor R4b is arranged on the battery 101a side, but this configuration is not limited to this. For example, the second inrush current prevention relay R4a may be arranged on the battery 101a side, and the second inrush current prevention resistor R4b may be arranged on the inverter 102a (electric motor 103) side. The second inrush current prevention relay R4a is configured to be switchable between a connected state and a disconnected state. The second inrush current prevention resistor R4b is provided to reduce the magnitude of the inrush current flowing through the fourth path R4.

[0041] The relay control unit 102c controls switching between the connected state and the disconnected state of the second relay RL2 and the second inrush current prevention relay R4a. In the present embodiment, the relay control unit 102c is provided separately from the inverter 102a, but this is not limiting. For example, the relay control unit 102c may be built into the inverter 102a. Furthermore, the switching of the second relay RL2 and the second inrush current prevention relay R4a may be performed by the control device 106 instead of or in addition to the relay control unit 102c.

[0042] The capacitor 102d is arranged in parallel with the inverter 102a and is connected to the first electric circuit E1 and the second electric circuit E2. The capacitor 102d is configured to be able to store electricity and smoothes the DC voltage supplied to the inverter 102a.

[0043] The DC-DC converter 104 is connected to the second connection circuit C2. The DC-DC converter 104 reduces a high DC voltage supplied from the battery 101a via the second connection circuit C2 to a low voltage. The lead battery 105 is connected to the DC-DC converter 104. The lead battery 105 stores low DC voltage power and outputs the stored (low voltage) power. Note that the lead battery 105 is different from the battery 101a.

[0044] The low-voltage DC power output from the DC-DC converter 104 and the lead battery 105 is supplied as control power to, for example, the control device 106. The control power is also supplied between the control device 106 and the inverter unit 102. The power is also supplied between the inverter unit 102 and the battery unit 101.

[0045] The control device 106 controls each part of the hydraulic excavator 1. More specifically, the control device 106 is a computer device configured to include an arithmetic device 106a and a storage unit 106b. The arithmetic device 106a is, for example, a processor or a microprocessor. Note that, as an example, FIG. 2 illustrates one arithmetic device 106a in the control device 106, but the number of arithmetic devices 106a may be two, or three or more.

[0046] The storage unit 106b is a main storage device such as a read-only memory (ROM) or a random access memory (RAM). The storage unit 106b may further include an auxiliary storage device such as a hard disk drive (HDD) or a solid state drive (SSD). The storage unit 106b stores various programs, data, etc. The various programs include a control program 106b1 related to a method for starting the electric motor 103. The arithmetic unit 106a reads, for example, the control program 106b1 from the storage unit 106b and executes arithmetic processing in accordance with the control program 106b1.

[0047] The above-described hardware and software can cooperate to cause the control device 106 to operate as a discharge control unit 106c and a rotation control unit 106d. That is, the control system 100 includes the discharge control unit 106c and the rotation control unit 106d. The functions of the discharge control unit 106c and the rotation control unit 106d will be described later. The control device 106 may be configured as a single piece of hardware, or may be configured as multiple pieces of hardware that can communicate with each other.

[0048] As described above, the functional units 106c and 106d of the control device 106 may be implemented by causing the arithmetic unit 106a to execute arithmetic processing in accordance with the control program 106b1, i.e., by software, but may also be implemented by other methods. At least one of the functional units 106c and 106d may be implemented using, for example, an application-specific integrated circuit (ASIC) or a field-programmable gate array (FPGA). That is, at least one of the functional units 106c and 106d may be implemented by hardware using a dedicated IC or the like. At least one of the functional units 106c and 106d may also be implemented by a combination of software and hardware. The functional units 106c and 106d are conceptual structures. Therefore, the functions performed by one component may be distributed among multiple components, or the functions of multiple components may be integrated into one component.

[0049] The control device 106 is connected to the battery unit 101 and the inverter unit 102 so as to be able to communicate with each other. In this embodiment, the battery unit 101 and the control device 106 communicate with each other using CAN communication. The inverter unit 102 and the control device 106 also communicate with each other using the same CAN communication. Note that the communication method is not limited to CAN communication.

[0050] An activation device 107, a rotation speed setting device 108, and a switching device 109 are connected to the control device 106. The activation device 107, the rotation speed setting device 108, and the switching device 109 are included in a plurality of operation members 44b (see FIG. 1). Therefore, the activation device 107, the rotation speed setting device 108, and the switching device 109 are arranged around the driver's seat 44a (see FIG. 1).

[0051] The activation device 107 is, for example, a key switch. The key switch includes a key cylinder and a key. The activation device 107 (particularly the key cylinder) is disposed, for example, to the right of the driver's seat 44a. Note that the configuration of the activation device 107 is not limited to the above, and may be, for example, a momentary switch that can be pressed.

[0052] The starting device 107 is configured to be switchable between an OFF state (also referred to as a key-OFF state), an ON state (also referred to as a key-ON state), and a START state. For example, when the operator inserts the key into the key cylinder and rotates the key to the OFF position of the key cylinder, the starting device 107 is in the OFF state. When the operator rotates the key to the ON position of the key cylinder, the starting device 107 is in the ON state. When the operator rotates the key to the START position of the key cylinder, the starting device 107 is in the START state. When the starting device 107 is in the START state, the electric motor 103 is started. In other words, the starting device 107 makes it possible to start the electric motor 103. Note that when the operator releases the key while rotating it to the START position of the key cylinder, the key returns to the ON position of the key cylinder. The starting device 107 also outputs to the control device 106 whether it is in the OFF state, ON state, or START state.

[0053] The rotation speed setting device 108 enables the setting of the rotation speed (target rotation speed) of the electric motor 103. The rotation speed setting device 108 is, for example, a dial. For example, when the operator operates (rotates) the rotation speed setting device 108 clockwise, the rotation speed of the electric motor 103 increases. On the other hand, when the operator operates the rotation speed setting device 108 counterclockwise, the rotation speed of the electric motor 103 decreases. The rotation speed setting device 108 outputs the set rotation speed of the electric motor 103 to the control device 106. The rotation speed setting device 108 is, for example, disposed to the right front of the driver's seat 44a. Note that the configuration of the rotation speed setting device 108 is not limited to that described above and may be, for example, a lever.

[0054] The switching device 109 enables operation of a cutoff valve 115, which will be described later. The switching device 109 includes a cutoff lever 109a and a cutoff switch 109b. The cutoff lever 109a is provided, for example, to the left of the driver's seat 44a so as to be rotatable in the vertical direction. The cutoff switch 109b detects the rotation position of the cutoff lever 109a and outputs (information on) the detected rotation position to the cutoff valve 115 and the control device 106. Note that the configuration of the cutoff lever 109a is not limited to the above, and may be, for example, a pressable alternate switch. Details of the operation of the cutoff valve 115 by the switching device 109 will be described later.

[0055] The control system 100 further includes a plurality of hydraulic pumps 111, a hydraulic actuator 112, a control valve 113, a remote control valve 114, and a cut-off valve 115. The plurality of hydraulic pumps 111 include a main pump 111a and a pilot pump 111b.

[0056] The main pump 111a is configured as a variable displacement pump, but is not limited to this and may be configured as a fixed displacement pump, for example. The main pump 111a is connected to the rotating shaft (output shaft) of the electric motor 103. The main pump 111a is driven by the rotation of the rotating shaft of the electric motor 103.

[0057] The pilot pump 111b is configured as a fixed displacement pump, but is not limited to this and may be configured as a variable displacement pump, for example. Like the main pump 111a, the pilot pump 111b is connected to the rotating shaft of the electric motor 103. The pilot pump 111b is driven by the rotation of the rotating shaft of the electric motor 103. The main pump 111a and the pilot pump 111b are each connected to a hydraulic oil tank (not shown) that stores hydraulic oil.

[0058] 2 shows one main pump 111a and one pilot pump 111b as an example, there may be two or more main pumps 111a and two or more pilot pumps 111b. The number of main pumps 111a and the number of pilot pumps 111b may be different from each other. For example, there may be two main pumps 111a and one pilot pump 111b.

[0059] The hydraulic actuator 112 has hydraulic motors (for example, the left and right travel motors 22, the swing motor 42) and hydraulic cylinders (for example, the blade cylinder 23a, the boom cylinder 31a, the arm cylinder 32a, and the bucket cylinder 33a) (see FIG. 1).

[0060] When the main pump 111a is driven by the electric motor 103, the hydraulic oil in the hydraulic oil tank is supplied to the hydraulic actuator 112 via the control valve 113. As a result, the hydraulic actuator 112 is driven.

[0061] The control valve 113 is a directional switching valve that controls the flow direction and flow rate of the hydraulic oil supplied from the main pump 111a to the hydraulic actuator 112. More specifically, the flow direction and flow rate of the hydraulic oil are controlled based on the hydraulic oil (also called pilot oil) supplied to the control valve 113 from the pilot pump 111b via a cutoff valve 115 and a remote control valve 114.

[0062] The remote control valves 114 (also called pilot valves) are provided corresponding to the respective devices (for example, the travel motor 22, the boom cylinder 31a, etc.) that constitute the hydraulic actuator 112. That is, a plurality of remote control valves 114 are provided.

[0063] For example, an operating lever included in the plurality of operating members 44b is connected to each remote control valve 114. When an operator operates the operating lever, the remote control valve 114 is operated and pilot oil is supplied to the control valve 113.

[0064] The cutoff valve 115 is provided in the flow path between the pilot pump 111b and the remote control valve 114. The cutoff valve 115 switches between connecting and blocking the flow path through which the pilot oil flows, depending on the rotation position of the cutoff lever 109a output from the cutoff switch 109b. Specifically, when the operator tilts (pushes) the cutoff lever 109a downward, the cutoff switch 109b turns ON, and the cutoff valve 115 connects the flow path. This causes pilot oil to be supplied from the pilot pump 111b to the remote control valve 114. Therefore, in this case, the hydraulic actuator 112 becomes operable, and operation of the hydraulic excavator 1 is permitted.

[0065] On the other hand, when the operator raises (pulls up) the cutoff lever 109a upward, the cutoff switch 109b turns OFF and the cutoff valve 115 blocks the flow path. This blocks the supply of pilot oil from the pilot pump 111b to the remote control valve 114. In this case, the hydraulic actuator 112 becomes inoperable and operation of the hydraulic excavator 1 is prohibited. In other words, the switching device 109 (in this embodiment, the cutoff lever 109a and the cutoff switch 109b) can switch between permitting and prohibiting operation of the hydraulic excavator 1. Note that, hereinafter, the state in which the cutoff lever 109a is raised will sometimes be referred to as the locked state, and the state in which the cutoff lever 109a is lowered will sometimes be referred to as the unlocked state.

[0066] [3. How to start an electric motor] A control method for the hydraulic excavator 1 relating to the start of the electric motor 103 (a method for starting the electric motor 103) will now be described. FIG. 3 is a flowchart showing the flow up to the start of the discharge process. The discharge process described above is a preparation process for starting the electric motor 103. In step S0, it is assumed that all relays included in the first connection circuit C1 (and the second connection circuit C2) are in an interrupted state, the charging voltage of the capacitor 102d is equal to or lower than a specified value (for example, zero), and the starting device 107 is in an off state (see FIG. 2).

[0067] In step S1, the discharge control unit 106c (see FIG. 2) determines whether the starting device 107 is in the ON state. In this embodiment, the ON state of the starting device 107 is realized by the operator inserting the key into the key cylinder and turning the key to the ON position of the key cylinder, as described above. When the starting device 107 is in the ON state, control power is supplied from the lead battery 105 to the battery unit 101, the control device 106, etc. If the starting device 107 is in the ON state (Yes in step S1), the process proceeds to the next step S2. If the starting device 107 is not in the ON state (No in step S1), the discharge control unit 106c continues to determine whether the starting device 107 is in the ON state.

[0068] In step S2, the discharge control unit 106c executes the discharge process. That is, the control method for the hydraulic excavator 1 of this embodiment includes executing the discharge process when the starting device 107 is in the on state. Furthermore, the discharge control unit 106c executes the discharge process when the starting device 107 is in the on state.

[0069] As described above, the discharge control unit 106c (and the rotation control unit 106d) is realized by having the arithmetic device 106a of the control device 106 execute arithmetic processing in accordance with the control program 106b1. Therefore, the method for starting the electric motor 103 executed by the discharge control unit 106c (and the rotation control unit 106d) is also realized by having the arithmetic device 106a execute arithmetic processing in accordance with the control program 106b1. In this embodiment, as described above, one arithmetic device 106a executes the above arithmetic processing. However, if there are two or more arithmetic devices 106a, the arithmetic processing may be performed by two or more arithmetic devices 106a. In other words, the control program 106b1 for the hydraulic excavator 1 in this embodiment is a program that causes at least one arithmetic device 106a to execute the control method for the hydraulic excavator 1 (in this embodiment, the method for starting the electric motor 103).

[0070] The discharge process will be described with reference to Fig. 4. Fig. 4 is a flowchart showing the flow of the discharge process. In Fig. 4, the process performed by the discharge control unit 106c (control device 106) is indicated by a solid line, the process performed by the BMU 101c (battery unit 101) is indicated by a dashed line, and the process performed by the relay control unit 102c (inverter unit 102) is indicated by a dashed line.

[0071] In step S11, the discharge control unit 106c determines whether the battery 101a is in a standby state. In this embodiment, this determination is made based on information about the state of the battery 101a transmitted between the battery unit 101 and the control device 106 via CAN communication. In this embodiment, the battery 101a enters a standby state when control power (low-voltage power) is supplied from the lead battery 105 (i.e., the activation device 107 is turned on) and it is confirmed that the battery 101a itself is normal. If the battery 101a is in a standby state (Yes in step S11), the process proceeds to the next step S12. If the battery 101a is not in a standby state (No in step S11), the discharge control unit 106c continues to determine whether the battery 101a is in a standby state.

[0072] In step S12, the discharge control unit 106c transmits an operation instruction for the battery 101a to the battery unit 101 (particularly the BMU 101c) via CAN communication. When the operation instruction is transmitted, the process proceeds to the next step S13.

[0073] In step S13, the BMU 101c switches the first inrush current prevention relay R2a to the connected state based on the operation command. Here, it is assumed that the hydraulic excavator 1 includes an electric device (not shown) connected in series to the battery unit 101 via the first connection circuit C1. It is also assumed that the electric device is connected in parallel to the inverter unit 102.

[0074] Under this assumption, when the first inrush current prevention relay R2a is switched to the connected state, an inrush current may flow between the electrical device and the battery 101a. In this case, the inrush current flows through the second path R2 included in the first inrush current prevention circuit 101b of the first connection circuit C1. As described above, the first inrush current prevention resistor R2b is provided in series with the first inrush current prevention relay R2a on the second path R2, so the inrush current flows through the first inrush current prevention resistor R2b. This reduces the magnitude of the inrush current and prevents damage to the battery 101a and / or the electrical device. Therefore, from the perspective of protecting the devices connected to the first connection circuit C1 (the battery 101a in this embodiment, the electrical device), it is desirable for the first connection circuit C1 to include the first inrush current prevention circuit 101b, as in this embodiment. Note that the magnitude of the inrush current also decreases over time. When the first inrush current prevention relay R2a is switched to the connected state, the process proceeds to the next step S14.

[0075] In step S14, the BMU 101c determines whether the inrush current flowing through the second path R2 has become equal to or less than a specified value. If the inrush current flowing through the second path R2 has become equal to or less than the specified value (Yes in step S14), the process proceeds to the next step S15. If the inrush current flowing through the second path R2 is not equal to or less than the specified value (greater than the specified value) (No in step S14), the BMU 101c continues to determine the inrush current.

[0076] In step S15, the BMU 101c switches the first inrush current prevention relay R2a to an interrupted state and switches both of the two first relays RL1 (one first relay RL1 and the other first relay RL1) of the battery unit 101 to a connected state. This causes the battery 101a to enter a dischargeable state in which it can quickly (at any time) output high-voltage power. That is, the discharge process of this embodiment places the battery 101a in a dischargeable state. The discharge process also includes placing the first relay RL1 in a connected state. The fact that the battery 101a has entered a dischargeable state is included in the information about the state of the battery 101a and is transmitted to the control device 106.

[0077] In this case, since the first relay RL1 is in a connected state, if the inverter unit 102 electrically connects the battery 101a and the electric motor 103, at least the standby power is supplied from the battery 101a to the electric motor 103. Therefore, a current flows through the first connection circuit C1, and the first connection circuit C1 is in a conducting state. In other words, the discharging process includes bringing the first connection circuit C1 into a conducting state. In addition, in this embodiment, the conducting state of the first connection circuit C1 may be any state in which a current is able to flow through the first connection circuit C1, even if the current is not (actually) flowing through the first connection circuit C1. In other words, a state in which a current is able to flow through the first connection circuit C1 is included in the conducting state of the first connection circuit C1. After the above switching is performed, the process proceeds to the next step S16.

[0078] In step S16, the battery unit 101 outputs a precharge instruction to the inverter unit 102. In this embodiment, the precharge instruction is realized by control power supplied from the battery unit 101 to the inverter unit 102. At this time, the control power used as a control power source for the inverter unit 102 is supplied from the battery unit 101 to the inverter unit 102 in addition to the control power as the precharge instruction. When the precharge instruction is output, the process proceeds to the next step S17.

[0079] In step S17, the relay control unit 102c switches the second inrush current prevention relay R4a to the connected state based on the precharge instruction. At this time, as described above, because the charging voltage of the capacitor 102d is equal to or lower than the specified value, an inrush current flows through the second connection circuit C2 (the first electric circuit E1 and the second electric circuit E2). Specifically, the inrush current flows through the fourth path R4 included in the second inrush current prevention circuit 102b of the second connection circuit C2. As described above, the second inrush current prevention resistor R4b is provided in series with the second inrush current prevention relay R4a on the fourth path R4, so the inrush current flows through the second inrush current prevention resistor R4b. This reduces the magnitude of the inrush current, preventing damage to at least one of the devices (e.g., the battery 101a, the inverter 102a, etc.) connected to the second connection circuit C2. Therefore, from the viewpoint of protecting devices connected to the second connection circuit C2 (in this embodiment, the battery 101a, the inverter 102a, etc.), it is desirable that the second connection circuit C2 include the second inrush current prevention circuit 102b, as in this embodiment. Once the second inrush current prevention relay R4a is switched to the connected state, the process proceeds to the next step S18.

[0080] In step S18, the discharge control unit 106c determines whether the charging voltage of the capacitor 102d has reached or exceeded a specified value. In this embodiment, this determination is made based on information about the charging voltage of the capacitor 102d transmitted via CAN communication between the inverter unit 102 and the control device 106. If the charging voltage of the capacitor 102d has reached or exceeded the specified value (pre-charging of the capacitor 102d has been completed) (Yes in step S18), the process proceeds to the next step, S19. If the charging voltage of the capacitor 102d is not reached or exceeded the specified value (No in step S18), the discharge control unit 106c continues to determine the charging voltage of the capacitor 102d.

[0081] In step S19, the discharge control unit 106c outputs a connection instruction for the second relay RL2 to the inverter unit 102. In this embodiment, the connection instruction is realized by control power supplied from the control device 106 to the inverter unit 102. At this time, the control device 106 (particularly the rotation control unit 106d) transmits an instruction to start rotation control of the electric motor 103 to the inverter unit 102 via CAN communication. When the connection instruction is output, the process proceeds to the next step S20.

[0082] In step S20, the relay control unit 102c switches the second inrush current prevention relay R4a to an interrupted state and switches the second relay RL2 to a connected state based on the connection instruction. This connects the inverter 102a to the battery 101a, and high-voltage power is supplied from the battery 101a to the inverter 102a. In other words, the discharge process of this embodiment includes supplying power from the battery 101a to the inverter 102a. The discharge process also includes switching the second relay RL2 to a connected state. In this case, because power is being supplied from the battery 101a to the inverter 102a, current flows through the second connection circuit C2. Therefore, the second connection circuit C2 is in a conducting state. In other words, the discharge process includes switching the second connection circuit C2 to a conducting state. After the above switching is performed, the process proceeds to the next step, step S21.

[0083] In step S21, the discharge control unit 106c determines whether the inverter 102a is in an operating state. In this embodiment, this determination is made based on information about the state of the inverter 102a transmitted between the inverter unit 102 and the control device 106 via CAN communication. In this embodiment, the inverter 102a enters an operating state when high-voltage power is supplied from the battery 101a and it is confirmed that the inverter 102a itself is normal (no abnormality). If the inverter 102a is in an operating state (Yes in step S21), the discharge process is completed (step S22). If the inverter 102a is not in an operating state (No in step S22), the discharge control unit 106c continues to determine the operating state of the inverter 102a.

[0084] The flow after the discharge process has been executed (completed) will be described with reference to Fig. 5. Fig. 5 is a flowchart showing the flow after the discharge process has been executed. In step S30, it is assumed that the battery 101a is in a dischargeable state, the inverter 102a is in an operating state, and the cut-off lever 109a (see Fig. 2) is in a locked state.

[0085] In step S31, the rotation control unit 106d (see FIG. 2) determines whether or not a predetermined operation has been performed. In this embodiment, the predetermined operation is an operation of first placing the activation device 107 in the start state when the cutoff lever 109a is in the locked state, and then placing the cutoff lever 109a in the unlocked state. Specifically, the operation of placing the activation device 107 in the start state is, as described above, an operation in which the operator inserts the key into the key cylinder and rotates the key to the start position of the key cylinder. Furthermore, the operation of placing the cutoff lever 109a in the unlocked state is, as described above, an operation of tilting the cutoff lever 109a downward. Furthermore, as described above, when the cutoff lever 109a is in the locked state, operation of the hydraulic excavator 1 is prohibited, and when the cutoff lever 109a is in the unlocked state, operation of the hydraulic excavator 1 is permitted.

[0086] Therefore, the predetermined operation in this embodiment includes an operation of setting the starting device 107 to the start state when the operation of the hydraulic excavator 1 is prohibited by the switching device 109 (in this embodiment, the cutoff lever 109a and the cutoff switch 109b). The predetermined operation also includes an operation of switching the switching device 109 from a state in which the operation of the hydraulic excavator 1 is prohibited (in this embodiment, the locked state) to a state in which the operation of the hydraulic excavator 1 is permitted (in this embodiment, the unlocked state).

[0087] If the predetermined operation has been performed (Yes in step S31), the process proceeds to the next step S32. If the predetermined operation has not been performed (No in step S31), the rotation control unit 106d continues to determine whether the predetermined operation has been performed. Note that while the rotation control unit 106d continues to determine whether the predetermined operation has been performed, the rotation control unit 106d transmits a stop command for the electric motor 103 to the inverter 102a via CAN communication. As a result, the electric motor 103 is stopped during the above period.

[0088] In step S32, the rotation control unit 106d transmits a rotation command for the electric motor 103 to the inverter 102a via CAN communication. The rotation command includes information related to the rotation speed (target rotation speed) of the electric motor 103 set by the rotation speed setting device 108 (see FIG. 2). The inverter 102a supplies an AC voltage to the electric motor 103 based on the rotation command. This causes the electric motor 103 to rotate at the rotation speed of the electric motor 103 set by the rotation speed setting device 108 (step S33). In other words, the electric motor 103 is started. Therefore, the control method for the hydraulic excavator 1 of this embodiment includes rotating the electric motor 103 when a predetermined operation is performed after the discharge process is executed. Furthermore, the rotation control unit 106d rotates the electric motor 103 when a predetermined operation is performed after the discharge process is executed.

[0089] According to the above configuration, by turning on the starting device 107, a discharging process is executed, and the battery 101a can be put into a dischargeable state. As described above, if the battery 101a is in a dischargeable state, power can be supplied from the battery 101a to the electric motor 103 promptly (at any time). That is, power supply from the battery 101a to the electric motor 103 is reliably realized. Therefore, if a predetermined operation is performed after the discharging process is executed, the electric motor 103 is rotated to start the electric motor 103. This eliminates the need to determine whether or not power is being supplied from the battery 101a to the electric motor 103 after the predetermined operation. This allows the determination process to be omitted compared to a configuration in which, for example, whether or not power is being supplied to the electric motor 103 is determined after the predetermined operation is performed, and the electric motor 103 is rotated based on the result of the determination. Therefore, the time from when the predetermined operation is performed until the electric motor 103 starts to rotate can be shortened by the time required for the determination process. As a result, when the starting device 107 is in the ON state, it is possible to reduce the time from when a predetermined operation is performed until the electric motor 103 starts to rotate.

[0090] In a configuration in which the hydraulic excavator 1 is equipped with a switching device 109 that switches between permission and prohibition of operation of the hydraulic excavator 1, the operator operates the switching device 109, thereby switching between permission and prohibition of operation of the hydraulic excavator 1 according to the operator's intention. For example, if a co-worker working together with the hydraulic excavator 1 is located near the hydraulic excavator 1, the operator can operate the switching device 109 to prevent contact between the hydraulic excavator 1 and the co-worker, and the operation of the hydraulic excavator 1 will be prohibited.

[0091] Furthermore, the co-worker is more likely to approach the hydraulic excavator 1 when the hydraulic excavator 1 is stopped (the electric motor 103 is stopped) than when the hydraulic excavator 1 is operating (the electric motor 103 is driving). For this reason, when the electric motor 103 is started (when the hydraulic excavator 1 is stopped), the co-worker may be located near the hydraulic excavator 1, making contact between the hydraulic excavator 1 and the co-worker more likely to occur. At this time, if the operator operates the switching device 109 to a state in which operation of the hydraulic excavator 1 is prohibited (a locked state in this embodiment), the above-mentioned contact can be avoided. However, there is a risk that operation of the hydraulic excavator 1 will be permitted due to an erroneous operation of the switching device 109 by the operator. Therefore, from the viewpoint of reliably avoiding contact between the hydraulic excavator 1 and the co-worker and improving the safety of the hydraulic excavator 1 when the electric motor 103 is started, the following configuration is desirable. That is, as in this embodiment, it is desirable that the predetermined operation include an operation of setting the starting device 107 to a start state when operation of the hydraulic excavator 1 is prohibited by the switching device 109.

[0092] If the electric motor 103 is not rotated when the operation of the hydraulic excavator 1 is prohibited, but is rotated when the operation of the hydraulic excavator 1 is permitted, power consumption due to unnecessary rotation (driving) of the electric motor 103 can be reduced. Furthermore, when the operator operates the switching device 109 to prohibit the operation of the hydraulic excavator 1, the hydraulic excavator 1 is reliably prevented from operating, further improving the safety of the hydraulic excavator 1. From this perspective, it is desirable that the predetermined operation include an operation of switching the switching device 109 from a state in which the operation of the hydraulic excavator 1 is prohibited to a state in which the operation of the hydraulic excavator 1 is permitted, as in this embodiment.

[0093] From the viewpoint of ensuring that the battery 101a is in a dischargeable state in which high-voltage power can be quickly output (to the electric motor 103), the following configuration is desirable: That is, in a configuration in which the hydraulic excavator 1 is provided with a first connection circuit C1 that electrically connects the battery 101a and the electric motor 103, as in this embodiment, the discharge process desirably includes bringing the first connection circuit C1 into an energized state.

[0094] From the viewpoint of realizing, with a simple configuration, putting the battery 101a into a dischargeable state by putting the first connection circuit C1 into a conducting state, the following configuration is desirable: That is, in a configuration like this embodiment, in which the first connection circuit C1 has a first relay RL1 that can switch between electrically connecting and disconnecting the battery 101a and the electric motor 103, the discharging process desirably includes putting the first relay RL1 into a connected state.

[0095] When the hydraulic excavator 1 is configured to include an inverter 102a that supplies power from the battery 101a to the electric motor 103, the following configuration is desirable from the viewpoint of reliably realizing power supply from the battery 101a to the electric motor 103. That is, as in this embodiment, the discharge process desirably includes supplying power from the battery 101a to the inverter 102a.

[0096] When the hydraulic excavator 1 is configured to include a second connection circuit C2 that electrically connects the battery 101a and the inverter 102a, the following configuration is desirable from the viewpoint of reliably putting the battery 101a into a state in which it can be discharged (to the electric motor 103). That is, as in this embodiment, the discharge process desirably includes putting the second connection circuit C2 into a conducting state.

[0097] From the viewpoint of realizing, with a simple configuration, putting the battery 101a into a dischargeable state by putting the second connection circuit C2 into a conducting state, the following configuration is desirable: That is, in a configuration like this embodiment, in which the second connection circuit C2 has a second relay RL2 that can switch between electrically connecting and disconnecting the battery 101a and the inverter 102a, the discharging process desirably includes putting the second relay RL2 into a connected state.

[0098] [4. Supplementary Information] In the present embodiment, a configuration has been described in which multiple instructions (e.g., an instruction to activate the battery 101a, an instruction to precharge, etc.) in the method of starting the electric motor 103 are given via CAN communication or control power, but this is not limiting. For example, in the present embodiment, an instruction given via CAN communication (e.g., an instruction to activate the battery 101a) may be given via control power, and in the present embodiment, an instruction given via control power (e.g., a precharge instruction) may be given via CAN communication. Furthermore, all of the multiple instructions may be given via either CAN communication or control power.

[0099] In this embodiment, a hydraulic excavator 1, which is a construction machine, has been described as an example of a work machine, but the work machine is not limited to the hydraulic excavator 1 and may be a construction machine such as a wheel loader or a mobile crane. The work machine may also be an agricultural machine such as a combine harvester or a tractor.

[0100] [5. Notes] The control method, control program 106b1, control system 100, and hydraulic excavator 1 described in this embodiment can also be expressed as a control method, control program, control system, and work machine shown in the following appendix.

[0101] The control method for the work machine in Appendix (1) is as follows: A battery for storing power; an electric motor that is driven by receiving power from the battery; a starter that starts the electric motor, When the starting device is in an on state, executing a discharge process to set the battery in a dischargeable state; When a predetermined operation is performed after the discharge process is performed, the electric motor is rotated.

[0102] A control method for a work machine according to supplementary note (2) is the control method according to supplementary note (1), The work machine is equipped with a switching device that switches between permitting and prohibiting operation of the work machine, The predetermined operation includes an operation of placing the starting device in a start state when the operation of the work machine is prohibited by the switching device.

[0103] A control method for a work machine according to supplementary note (3) is the control method according to supplementary note (2), The predetermined operation includes an operation of switching the switching device from a state in which operation of the work machine is prohibited to a state in which operation of the work machine is permitted.

[0104] A control method for a work machine according to supplementary note (4) is a control method according to any one of supplementary notes (1) to (3), the work machine includes a first connection circuit that electrically connects the battery and the electric motor; The discharging process includes bringing the first connection circuit into a conducting state.

[0105] A control method for a work machine according to supplementary note (5) is the control method according to supplementary note (4), the first connection circuit has a first relay that can switch between electrical connection and disconnection between the battery and the electric motor, The discharge process includes bringing the first relay into a connected state.

[0106] The control method for a work machine according to supplementary note (6) is the control method according to supplementary note (4) or (5), The first connection circuit includes a first inrush current prevention circuit.

[0107] A control method for a work machine according to supplementary note (7) is a control method according to any one of supplementary notes (1) to (6), the work machine includes an inverter that supplies power supplied from the battery to the electric motor; The discharging process includes supplying power from the battery to the inverter.

[0108] A control method for a work machine according to supplementary note (8) is the control method according to supplementary note (7), the work machine includes a second connection circuit that electrically connects the battery and the inverter, The discharging process includes energizing the second connection circuit.

[0109] A control method for a work machine according to supplementary note (9) is the control method according to supplementary note (8), the second connection circuit has a second relay that can switch between electrical connection and disconnection between the battery and the inverter, The discharge process includes bringing the second relay into a connected state.

[0110] A control method for a work machine according to supplementary note (10) is the control method according to supplementary note (8) or (9), The second connection circuit includes a second inrush current prevention circuit.

[0111] The control program for a work machine of supplementary note (11) causes at least one arithmetic device to execute the control method described in any one of supplementary notes (1) to (10).

[0112] The control system of the work machine of appendix (12) A battery for storing power; an electric motor that is driven by receiving power from the battery; a starter that starts the electric motor, a discharge control unit that executes a discharge process to set the battery in a dischargeable state when the starting device is in an on state; The electric motor is rotated when a predetermined operation is performed after the discharge process is performed.

[0113] The work machine of appendix (13) is equipped with the control system described in appendix (12).

[0114] Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to these, and the invention can be expanded or modified without departing from the spirit of the invention. [Industrial Applicability]

[0115] The present invention can be used in work machines such as construction machines and agricultural machines. [Explanation of symbols]

[0116] 1 Hydraulic excavator (work machine) 100 Control System 101a Battery 101b 1st inrush current prevention circuit 102a inverter 102b Second inrush current prevention circuit 103 Electric motor 106a Arithmetic unit 106b1 Control Program 106c Discharge control unit 106d Rotation control section 107 Starting device 109 Switching Device C1 First connection circuit C2 Second connection circuit RL1 Relay 1 RL2 Second relay

Claims

1. A battery for storing power; an electric motor that is driven by receiving power from the battery; a starter that starts the electric motor, When the starting device is in an on state, executing a discharge process to set the battery in a dischargeable state; rotating the electric motor when a predetermined operation is performed after the discharge process is performed.

2. The work machine is equipped with a switching device that switches between permitting and prohibiting operation of the work machine, 2. The control method for a work machine according to claim 1, wherein the predetermined operation includes an operation of placing the starting device in a start state when operation of the work machine is prohibited by the switching device.

3. 3. The control method for a work machine according to claim 2, wherein the predetermined operation includes an operation of switching the switching device from a state in which operation of the work machine is prohibited to a state in which operation of the work machine is permitted.

4. the work machine includes a first connection circuit that electrically connects the battery and the electric motor; The control method for a work machine according to claim 1 , wherein the discharge process includes placing the first connection circuit in a conducting state.

5. the first connection circuit has a first relay that can switch between electrical connection and disconnection between the battery and the electric motor, The control method for a work machine according to claim 4 , wherein the discharge process includes bringing the first relay into a connected state.

6. The method for controlling a work machine according to claim 4, wherein the first connection circuit includes a first inrush current prevention circuit.

7. the work machine includes an inverter that supplies power supplied from the battery to the electric motor; The method for controlling a work machine according to claim 1 , wherein the discharging process includes supplying power from the battery to the inverter.

8. the work machine includes a second connection circuit that electrically connects the battery and the inverter, The control method for a work machine according to claim 7, wherein the discharge process includes placing the second connection circuit in an energized state.

9. the second connection circuit has a second relay that can switch between electrical connection and disconnection between the battery and the inverter, The control method for a work machine according to claim 8 , wherein the discharge process includes bringing the second relay into a connected state.

10. The method for controlling a work machine according to claim 8 , wherein the second connection circuit includes a second inrush current prevention circuit.

11. A control program for a work machine, which causes at least one arithmetic unit to execute the control method according to any one of claims 1 to 10.

12. A battery for storing power; an electric motor that is driven by receiving power from the battery; a starter that starts the electric motor, a discharge control unit that executes a discharge process to set the battery in a dischargeable state when the starting device is in an on state; a rotation control unit that rotates the electric motor when a predetermined operation is performed after the discharge process is executed.

13. A work machine comprising the control system of claim 12.

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