Earthwork machine

Abstract

This earthwork machine includes a car body, a fuel cell, a housing, and a coolant pipe. The housing stores the fuel cell and is electrically connected to the car body. The coolant pipe passes through the housing and flows a coolant from the outside of the housing to the fuel cell. The coolant pipe is electrically isolated from the housing and configured such that the coolant and car body are electrically connected outside the housing.

Description

Technical Field

[0001] The present disclosure relates to an earthwork machine. 5          Priority is claimed on Japanese Patent Application No. 2022-049821, filed March 25, 2022, the content of which is incorporated herein by reference. Background Art

[0002] In recent years, in order to use clean energy as a power source for an earthwork 10 machine instead of fossil fuels, mounting a fuel cell on the earthwork machine has been studied. Japanese Unexamined Patent Application, First Publication No. 2017-109691 discloses a technology for grounding means of a vehicle equipped with the fuel cell.

[0003] The fuel cell has a low insulation resistance, whereas a high insulation resistance 15 is required for earthwork machines such as dump trucks. For example, in ISO 14990-1, ISO 14990-2, and ISO 14990-3, an insulation resistance of 1 MO or more is required between an electric power circuit provided in the earthwork machine and an equipotential bonding circuit. Some embodiments of the present disclosure aim to provide an earthwork 20 machine capable of achieving a high insulation resistance while mounting a fuel cell thereon.

[0004] Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any 25 or all of these matters form part of the prior art base or were common general knowledge 2023237342   10 Sep 2026 in the field relevant to the present disclosure as it existed before the priority date of each of the appended claims. Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated 5 element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. Summary

[0005] According to one aspect of the present disclosure, an earthwork machine 10   includes: a vehicle body; a fuel cell; a housing storing the fuel cell and electrically connected to the vehicle body; and a refrigerant pipe penetrating the housing, allowing a refrigerant to flow from the outside of the housing to the fuel cell, and electrically insulated from the housing, wherein a length of the refrigerant pipe from the fuel cell to a frame-grounded point at which the refrigerant is electrically connected to the vehicle 15 body is equal to or greater than a length at which a resistance of the refrigerant passing through the refrigerant pipe reaches a predetermined insulation resistance, wherein the refrigerant pipe is connected to a refrigerant pump or a radiator on the outside of the housing, the refrigerant pump configured to be driven by a pump motor electrically connected to the vehicle body, and configured to pressure-feed the refrigerant, and the 20 radiator electrically connected to the vehicle body, and configured to cool the refrigerant.

[0006] According to some embodiments of the present disclosure, it is possible to achieve a high insulation resistance while mounting the fuel cell. 2023237342   10 Sep 2026 Brief Description of Drawings

[0007] [FIG. 1] A perspective view schematically showing a transport vehicle according to a first embodiment. 5          [FIG. 2] A schematic diagram showing the configuration of a fuel cell unit according to the first embodiment. [FIG. 3] A schematic block diagram showing the configuration of the electric system of the transport vehicle according to the first embodiment. Description of Embodiments 10

[0008] <First Embodiment> <<Configuration of Transport Vehicle 10>> Hereinafter, embodiments will be described in detail with reference to the drawings. 15          A transport vehicle 10 according to a first embodiment is a rigid frame-type dump truck that transports a crushed stone material or the like mined in a mine or the like. The transport vehicle 10 is driven by a fuel cell that uses a hydrogen gas as a fuel. The transport vehicle 10 is an example of an earthwork machine. FIG. 1 is a perspective view schematically showing the transport vehicle 10 20 according to the first embodiment. The transport vehicle 10 includes a dump body 11, a vehicle body 12, and a travel device 13.

[0009] The dump body 11 is a member into which a cargo is loaded. At least a part of the dump body 11 is disposed above the vehicle body 12. The dump body 11 performs 25 a dumping operation and a lowering operation. Through the dumping operation and the 2023237342   10 Sep 2026 lowering operation, the dump body 11 is adjusted to have a dumping posture and a loading posture. The dumping posture refers to a posture in which the dump body 11 is raised. The loading posture refers to a posture in which the dump body 11 is lowered.

[0010] 5          The dumping operation refers to an operation of separating the dump body 11 from the vehicle body 12 and inclining the dump body 11 in a dumping direction. The dumping direction is a rearward direction of the vehicle body 12. In the embodiment, the dumping operation includes raising a front end part of the dump body 11 and inclining the dump body 11 rearward. Through the dumping operation, a loading 10 surface of the dump body 11 is inclined rearward and downward.

[0011] The lowering operation refers to an operation of bringing the dump body 11 closer to the vehicle body 12. In the embodiment, the lowering operation includes lowering the front end part of the dump body 11. 15

[0012] When carrying out dumping work, the dump body 11 performs the dumping operation to change from the loading posture to the dumping posture. In a case where the cargo is loaded into the dump body 11, the cargo is discharged rearward from a rear end part of the dump body 11 through the dumping operation. When carrying out 20 loading work, the dump body 11 is adjusted to have the loading posture.

[0013] The vehicle body 12 includes a vehicle body frame (not shown). The vehicle body frame constitutes a protective equipotential bonding circuit of the transport vehicle 10. The vehicle body 12 rotatably supports the dump body 11 through a hinge pin 25 provided on the vehicle body frame. The vehicle body 12 is supported by the travel 2023237342   10 Sep 2026 device 13. A platform 121 is provided at the vehicle body frame above front wheels of the travel device 13. The platform 121 is a flat plate constituting an upper surface of the vehicle body frame. A cab 122, a control cabinet 123, and a retarder grid 69 are provided on the platform 121. In addition, a fuel cell system 40 is provided on the 5 vehicle body frame. An opening in which a grille 124 is fitted is provided on the front surface of the vehicle body 12.

[0014] The control cabinet 123 converts electric power. Specifically, the control cabinet 123 performs electric power control between the fuel cell system 40, various 10 electric devices (i.e., a battery 62, a traveling motor 65, a hydraulic pump motor 67, or the like), and the retarder grid 69. The retarder grid 69 is a resistor for absorbing regenerative electric power generated by braking of the travel device 13. The retarder grid 69 converts the regenerative electric power into heat energy. 15

[0015] The travel device 13 supports the vehicle body 12. The travel device 13 causes the transport vehicle 10 to travel. The travel device 13 causes the transport vehicle 10 to advance or retreat. At least a part of the travel device 13 is disposed below the vehicle body 12. The travel device 13 includes a pair of front wheels and a pair of rear 20 wheels. The front wheels are steering wheels, and the rear wheels are driving wheels.

[0016] FIG. 2 is a schematic diagram showing the configuration of a fuel cell unit 41 according to the first embodiment. The fuel cell system 40 includes a plurality of fuel cell units 41. As shown in 25 FIG. 2, each fuel cell unit 41 includes a housing 411 and a fuel cell 412. The fuel cell 2023237342   10 Sep 2026 412 is stored in the housing 411. The fuel cell 412 generates electricity by performing an electrochemical reaction between hydrogen supplied from a hydrogen tank (not shown) and oxygen contained in the outside air. The fuel cell 412 is provided with a cooling water channel 413 that is a flow channel through which cooling water flows, and 5 the cooling water channel 413 is configured to enable temperature management of the fuel cell 412. The housing 411 is made of metal. The housing 411 and the fuel cell 412 are electrically insulated from each other. For example, a spacer made of an insulator may be provided between the housing 411 and the fuel cell 412. The housing 411 is electrically connected to the vehicle body frame. That is, the housing 411 is 10 frame-grounded.

[0017] The fuel cell system 40 includes a plurality of radiators 42 corresponding to the fuel cell units 41. The radiators 42 are arranged side by side behind the grille 124. The radiator 42 cools the cooling water with outside air flowing in through the grille and 15 supplies the cooling water to the corresponding fuel cell unit 41. The radiator 42 is electrically connected to the vehicle body frame. That is, the radiator 42 is frame-grounded. A cooling water pipe 43 (i.e., a first cooling water pipe 43A and a second cooling water pipe 43B) is connected to the radiator 42. One end of the first cooling water pipe 43A is connected to the discharge port of the radiator 42, and the other end 20 thereof is connected to the inflow port of the cooling water channel 413 in the fuel cell 412. One end of the second cooling water pipe 43B is connected to the discharge port of the cooling water channel 413 of the fuel cell 412, and the other end thereof is connected to the inflow port of the radiator 42. A wall surface of the cooling water channel 413 in the fuel cell 412 is made of metal. Therefore, the cooling water passing 25 through the cooling water channel 413 is electrically connected to the output voltage of 2023237342   10 Sep 2026 the fuel cell 412. The cooling water is an example of a refrigerant, and the cooling water pipe 43 is an example of a refrigerant pipe.

[0018] The cooling water pipe 43 includes an inner pipe 431 made of an insulator and a 5 shielding part 432 made of metal that covers the inner pipe 431. Therefore, the cooling water passing through the cooling water pipe 43 is electrically insulated from the housing 411. On the other hand, the shielding part 432 of the cooling water pipe 43 is electrically connected to the housing 411. A circulation pump 44 that circulates the cooling water is provided in the first cooling water pipe 43A. The circulation pump 44 10 is driven by a circulation pump motor 64. The circulation pump motor 64 is electrically connected to the vehicle body frame. That is, the circulation pump motor 64 is frame-grounded. The circulation pump 44 is provided on the outside of the housing 411 and is an example of a refrigerant pump that pressure-feeds the cooling water of the cooling water pipe 43. The length of the first cooling water pipe 43A from the fuel cell 412 to 15 the pump 44 is equal to or greater than a length at which the resistance of the cooling water in the cooling pipe reaches a predetermined insulation resistance (for example, 1 MQ), and the length from the second cooling water pipe 43B to the radiator 42 is equal to or greater than a length at which the resistance of the cooling water in the cooling pipe reaches a predetermined insulation resistance (for example, 1 MQ).  Here, in a case 20 where a length of the pipe is denoted by L, a resistivity of the cooling water is denoted by p, and a cross-sectional area of the pipe is denoted by S, the resistance of the cooling water can be represented by R = p^L / S.

[0019] With the above configuration, the fuel cell 412 is connected to the frame- 25 grounded circulation pump motor 64 and the frame-grounded radiator 42 through the 2023237342   10 Sep 2026 cooling water flowing through the cooling water pipe 43. Since the inner pipe 431 of the cooling water pipe 43 is made of an insulator and is configured to have a length such that the resistance of the cooling water is equal to or greater than the insulation resistance, the fuel cell 412 can secure the insulation resistance required for the 5 earthwork machine. Since the cooling water is installed to the frame ground through the insulation resistance, the cooling water has a potential between the output voltage of the fuel cell and the frame ground. However, by providing the metal shielding part 432 on the outside of the cooling water pipe 43, even if water leakage occurs in the cooling water pipe 43, the leaked cooling water comes into contact with the shielding part 432, 10 and thus the cooling water is frame-grounded through the circulation pump motor 64 or the radiator 42.

[0020] <<Configuration of Electric System 60>> FIG. 3 is a schematic block diagram showing the configuration of an electric 15 system 60 of the transport vehicle 10 according to the first embodiment. The electric system 60 includes the fuel cell unit 41, a first DC / DC converter 61, the battery 62, a second DC / DC converter 63, the circulation pump motor 64, the traveling motor 65, a first inverter 66, the hydraulic pump motor 67, a second inverter 68, the retarder grid 69, and a control device 80. The first DC / DC converter 61, the second DC / DC converter 20   63, the first inverter 66, the second inverter 68, and the control device 80 are provided inside the control cabinet 123.

[0021] The electric system 60 includes the same number of first DC / DC converters 61 as the number of the fuel cell units 41. The first DC / DC converter 61 is connected to the 25 corresponding fuel cell unit 41. The first DC / DC converter 61 supplies the DC power 2023237342   10 Sep 2026 generated by the fuel cell system 40 to a bus B. The first DC / DC converter 61 is an isolated DC / DC converter. That is, the first DC / DC converter 61 includes a transformer, and the primary side (the fuel cell unit 41 side) and the secondary side (the bus B side) thereof are insulated. As a result, even if a plurality of fuel cell units 41 are 5 provided in parallel, the required insulation resistance of the entire electric system 60 can be secured as long as each fuel cell unit 41 secures a required insulation resistance therefor.

[0022] The battery 62 stores the electric power generated by the fuel cell system 40. 10 The battery 62 may store the regenerative electric power generated by the traveling motor 65. The battery 62 outputs the stored electric power. The second DC / DC converter 63 supplies electric power charged in the battery 62 to the bus B. In addition, the second DC / DC converter 63 charges the battery 62 by adjusting a voltage of DC power flowing in the bus B and supplying the adjusted voltage to the battery 62. That is, the second 15 DC / DC converter 63 is an example of a DC / DC converter that can perform bidirectional electric power conversion. The battery 62 includes a battery management system (BMS) (not shown) that monitors the state of the battery 62. The BMS measures the charging rate of the battery 62 and outputs the measurement data to the control device 80.

[0023] 20          The circulation pump motor 64 drives the circulation pump 44 shown in FIG. 2 using the DC power flowing in the bus B. The traveling motor 65 is a three-phase AC electric motor that drives the travel device 13. The first inverter 66 converts the DC power flowing in the bus B into three-phase AC power and supplies the three-phase AC power to the traveling motor 65. In 25 addition, the first inverter 66 converts the regenerative electric power generated by the 2023237342   10 Sep 2026 traveling motor 65 into DC current and causes the retarder grid 69 to consume it.

[0024] The hydraulic pump motor 67 is a three-phase AC electric motor that drives a hydraulic pump (not shown) for driving the dump body 11. The second inverter 68 5 converts the DC power flowing in the bus B into three-phase AC power and supplies the three-phase AC power to the hydraulic pump motor 67.

[0025] The control device 80 controls the first DC / DC converter 61, the second DC / DC converter 63, the first inverter 66, and the second inverter 68. 10

[0026] <<Action and Effect>> As described above, the transport vehicle 10 according to the first embodiment includes the following configurations. The transport vehicle 10 includes the housing 411 electrically connected to the vehicle body 12 and storing the fuel cell 412, and the 15 cooling water pipe 43 penetrating the housing 411 and allowing a refrigerant to flow from the outside of the housing 411 to the fuel cell 412. The cooling water pipe 43 according to the first embodiment is electrically insulated from the housing 411, and the cooling water passing through the cooling water pipe 43 is electrically connected to the vehicle body 12 on the outside of the housing 411. The fuel cell 412 according to the 20 first embodiment is electrically insulated from the housing 411, and thus can be prevented from being electrically connected to the vehicle body 12 through the housing 411 with low resistance. In addition, although electricity flows through the cooling water passing through the cooling water pipe 43, since the cooling water is insulated from the housing 411 and is electrically connected to the vehicle body 12 on the outside 25 of the housing 411, a resistance corresponding to the distance from the fuel cell 412 to 2023237342   10 Sep 2026 the frame-grounded point can be obtained. As a result, the transport vehicle 10 can achieve a high insulation resistance while mounting the fuel cell 412 thereon.

[0027] In addition, the circulation pump motor 64 according to the first embodiment is 5 frame-grounded, and thus the electricity flowing through the cooling water passing through the cooling water pipe 43 is frame-grounded through the circulation pump motor 64. It should be noted that, in the transport vehicle 10 according to another embodiment, the electricity may not be frame-grounded through the circulation pump motor 64, and may be frame-grounded through, for example, the circulation pump 44, or 10 may be frame-grounded by another configuration, such as bringing a frame-grounded brush (not shown) into contact with the shaft of the motor 64. Further, since the radiator 42 according to the first embodiment is frame-grounded, the electricity flowing through the cooling water is not only frame-grounded through the circulation pump motor 64 but is also frame-grounded through the radiator 42. On the other hand, the radiator 42 can 15 also be set to a floating potential without being frame-grounded. In this case, since the radiator 42 has a potential, the radiator 42 is covered with the grille 124 and a housing such that a person cannot easily access the radiator 42. In addition, the circulation pump motor 64 or the circulation pump 44 can also be set to a floating potential. In this case, since the circulation pump motor 64 or the circulation pump 44 has a potential, the 20 circulation pump motor 64 or the circulation pump 44 is covered with a housing (not shown) such that a person cannot easily access the circulation pump motor 64 or the circulation pump 44.

[0028] In addition, in the transport vehicle 10 according to the first embodiment, the 25 length of the first cooling water pipe 43A of the cooling water pipe 43 from the fuel cell 2023237342   10 Sep 2026 412 to the pump 44 and the length from the second cooling water pipe 43B of the cooling water pipe 43 to the radiator 42 are each equal to or greater than the length at which the resistance of the cooling water passing through the cooling water pipe 43 reaches a predetermined insulation resistance. As a result, the transport vehicle 10 can achieve 5 the desired insulation resistance. It should be noted that, by ensuring the insulation resistance with the length of the portion that is exposed to the outside of the housing 411, the length of the pipe inside the housing 411 can be shortened, and the size of the housing 411 itself can be reduced. In addition, although the distances between the plurality of fuel cell units 41 and the corresponding radiators 42, which are provided in the transport 10 vehicle 10 according to the first embodiment, are different from each other, the insulation resistances of the fuel cell units 41 can be made to be equivalent by making the lengths of the portions of the cooling water pipes 43 that are exposed to the outsides of the housings 411 be equivalent.

[0029] 15          In addition, the cooling water pipe 43 according to the first embodiment includes the inner pipe 431 made of an insulator and the shielding part 432 made of metal that covers the inner pipe 431. As a result, even if water leakage occurs in the cooling water pipe 43, the cooling water can be frame-grounded by coming into contact with the shielding part 432. 20

[0030] In addition, the transport vehicle 10 according to the first embodiment is connected to the first DC / DC converter 61, which is an isolated DC / DC converter, corresponding to each of the plurality of fuel cell units 41. As a result, as long as the required insulation resistance can be secured in each of the fuel cell units 41, the required 25 insulation resistance can be secured in the entire electric system 60. For example, as a 2023237342   10 Sep 2026 comparative example, in a case where the first DC / DC converter 61 is a non-isolated DC / DC converter, since the fuel cell units 41 are connected in parallel, the insulation resistance that needs to be ensured by each of the fuel cell units 41 is required to be parallel number times the insulation resistance required by the earthwork machine. 5 Therefore, in the transport vehicle 10 according to the first embodiment, the insulation resistance that needs to be ensured for each of the fuel cell units 41 can be reduced. It should be noted that, in a case where the non-isolated DC / DC converter is adopted as the first DC / DC converter 61, the length of the cooling water pipe 43 may be set to a length at which a resistance value that is parallel number times the insulation resistance required 10 for one fuel cell unit 41 can be obtained, and thus the required insulation resistance may be secured in the entire electric system 60.

[0031] <Another Embodiment> Although the embodiments have been described in detail with reference to the 15 drawings, a specific configuration is not limited to the above-described configuration, and various design changes and the like can be made. The fuel cell system 40 according to the above-described embodiment includes the plurality of radiators 42 corresponding to the plurality of fuel cell units 41, but the present disclosure is not limited to this. For example, the fuel cell system 40 may 20 include a single radiator 42. In this case, the cooling water cooled by the radiator 42 may be branched to the fuel cell units 41, for example, through a manifold. A circulation pump 44 is provided for each fuel cell unit 41 at the latter stage of the manifold. In addition, according to another embodiment, the cooling water cooled by the radiator 42 may be supplied to a plurality of fuel cell units 41 by a single circulation 25 pump 44. In this case, the cooling water pipe 43 branches at the latter stage of the 2023237342   10 Sep 2026 circulation pump 44 and is connected in parallel to the fuel cell units 41. Industrial Applicability

[0032] According to the above-described aspect, it is possible to achieve a high 5 insulation resistance while mounting the fuel cell. Reference Signs List

[0033] 10: Transport vehicle 11: Dump body 10          12: Vehicle body 121: Platform 122: Cab 123: Control cabinet 124: Grille 15           13: Travel device 40: Fuel cell system 41: Fuel cell unit 411: Housing 412: Fuel cell 20          413: Cooling water channel 42: Radiator 43: Cooling water pipe 431: Inner pipe 432: Shielding part 2023237342   10 Sep 2026 10 43B: Second cooling water pipe 44: Circulation pump 60: Electric system 61: First DC / DC converter 62: Battery 63: Second DC / DC converter 64: Circulation pump motor 65: Traveling motor 66: First inverter 67: Hydraulic pump motor 68: Second inverter 69: Retarder grid 80: Control device B: Bus

Claims

1. An earthwork machine, comprising:a vehicle body;5            a fuel cell;a housing storing the fuel cell and electrically connected to the vehicle body; anda refrigerant pipe penetrating the housing, allowing a refrigerant to flow from an outside of the housing to the fuel cell, and electrically insulated from the housing,wherein a length of the refrigerant pipe from the fuel cell to a frame-grounded10 point at which the refrigerant is electrically connected to the vehicle body is equal to or greater than a length at which a resistance of the refrigerant passing through the refrigerant pipe reaches a predetermined insulation resistance,wherein the refrigerant pipe is connected to a refrigerant pump or a radiator onthe outside of the housing,15          the refrigerant pump configured to be driven by a pump motor electricallyconnected to the vehicle body, and configured to pressure-feed the refrigerant, andthe radiator electrically connected to the vehicle body, and configured to cool the refrigerant.20

2. The earthwork machine according to claim 1,wherein a length of the refrigerant pipe from the fuel cell to the refrigerant pump is equal to or greater than a length at which a resistance of the refrigerant passing through the refrigerant pipe reaches a predetermined insulation resistance.2023237342   10 Sep 2026

3. The earthwork machine according to claim 1,wherein a length of the refrigerant pipe from the fuel cell to the radiator is equal to or greater than a length at which a resistance of the refrigerant passing through the5 refrigerant pipe reaches a predetermined insulation resistance.

4. The earthwork machine according to any one of claims 1 to 3,wherein the refrigerant pipe includes an inner pipe made of an insulator and a 10 shielding part made of metal covering the inner pipe.

5. The earthwork machine according to claim 4,wherein the shielding part is electrically connected to the housing,15           the inner pipe is connected to the fuel cell, andthe shielding part is unconnected to the fuel cell.

6. The earthwork machine according to any one of claims 1 to 5, further comprising:20           a plurality of fuel cells including the fuel cell; anda plurality of isolated DC / DC converters having primary sides connected to the plurality of fuel cells and secondary sides connected in parallel to each other.

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