Construction machine

Abstract

To provide a construction machine capable of drying an air discharge path while preventing deterioration of a fuel battery.SOLUTION: A shovel includes: an air supply path 42 for supplying air compressed by a compressor 40 and cooled by a cooler 41 to a fuel battery 28; an air discharge path 43 for discharging air used in the fuel battery 28 to the outside; a bypass path 44 branched from the air supply path 42, bypassing the fuel battery 28, and merging with the air discharge path 43; an air supply valve 45 that is provided to each of the air supply path 42, the air discharge path 43, and the bypass path 44, respectively; an air discharge valve 46; a bypass valve 47; and a fuel battery controller 30. When performing a drying operation for drying the air discharge path 43, the fuel battery controller 30 closes the air supply valve 45 and the air discharge valve 46, opens the bypass valve 47, and limits the amount of cooling water supplied to the cooler 41 to be smaller than that when the fuel battery 28 generates power.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a construction machine equipped with a fuel cell.

Background Art

[0002] A fuel cell generates electricity by chemically reacting, for example, hydrogen and oxygen in the air, and is provided with an air discharge path for discharging the air used in the fuel cell. Water generated by the chemical reaction may remain in the air discharge path, and further, when exposed to a low-temperature environment such as below freezing, the remaining water may freeze. Therefore, there is a possibility that the air discharge path may be blocked, causing a decrease in the power generation efficiency of the fuel cell and malfunctions.

[0003] Patent Document 1 discloses an automobile equipped with a fuel cell. In Patent Document 1, before the operation of the fuel cell stops, if a predetermined condition regarding the outside air temperature is satisfied, a residual water scavenging process for flowing air through the fuel cell and the air discharge path is executed. Thereby, the water remaining in the air discharge path and the like is removed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Construction machinery, for reasons such as operating not only on flat ground but also on sloping ground, in a construction machine equipped with a fuel cell, water tends to remain in the air discharge path, and the remaining amount also tends to increase. Therefore, even if the residual water scavenging process described in Patent Document 1 is executed, there is a possibility that the air discharge path may not be sufficiently dried. More specifically, in the residual water scavenging process described in Patent Document 1, air is passed through the fuel cell and the air discharge path to dry both the fuel cell and the air discharge path. Therefore, it is necessary to limit the residual water scavenging process so that the fuel cell does not dry out excessively and deteriorate. When a large amount of water remains in the air discharge path, there is a possibility that the air discharge path may not be sufficiently dried.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a construction machine capable of drying the air discharge path while preventing deterioration of the fuel cell.

Means for Solving the Problems

[0007] In order to achieve the above object, the present invention provides a construction machine including a fuel cell, a compressor for compressing air, a cooler for cooling the air compressed by the compressor, a cooling water pump for supplying cooling water to the cooler, an air supply path for supplying the air cooled by the cooler to the fuel cell, and an air discharge path for discharging the air used in the fuel cell to the outside. The construction machine further includes a bypass path branched from the air supply path to bypass the fuel cell and merged into the air discharge path, an air supply valve provided downstream of the branch point of the bypass path in the air supply path, an air discharge valve provided upstream of the merge point of the bypass path in the air discharge path, a bypass valve provided in the bypass path, and a control device for controlling the air supply valve, the air discharge valve, the bypass valve, and the cooling water pump. When the fuel cell generates power, the control device opens the air supply valve and the air discharge valve, closes the bypass valve, and drives the cooling water pump to supply the cooling water to the cooler. When performing a drying operation for drying the air discharge path, the control device closes the air supply valve and the air discharge valve, opens the bypass valve, and restricts the amount of the cooling water supplied to the cooler to be less than that when the fuel cell generates power.

Advantages of the Invention

[0008] According to the present invention, it is possible to dry the air discharge path while preventing deterioration of the fuel cell.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0010] The first embodiment of the present invention will be described with reference to the drawings.

[0011] FIG. 1 is a side view showing the structure of the excavator in the present embodiment. FIG. 2 is a top view showing the equipment mounted on the revolving body of the excavator in the present embodiment (however, for convenience, it is a view showing the state where the exterior cover and the cab of the revolving body are removed). FIG. 3 is a cross-sectional view taken along the arrow III-III in FIG. 2.

[0012] The excavator of the present embodiment includes a traveling body 1 and a revolving body 2 rotatably provided above the traveling body 1. The traveling body 1 travels by the drive of a traveling motor (not shown). The revolving body 2 revolves by the drive of a revolving motor (not shown).

[0013] The working device 3 is connected to the front side (the right side in FIG. 1) of the revolving body 2. The working device 3 includes a boom 4 rotatably connected to the revolving body 2, an arm 5 rotatably connected to the tip of the boom 4, and a bucket 6 rotatably connected to the tip of the arm 5. The boom 4 rotates by the drive of the boom cylinder 7, the arm 5 rotates by the drive of the arm cylinder 8, and the bucket 6 rotates by the drive of the bucket cylinder 9.

[0014] The revolving body 2 includes a revolving frame 10 forming a basic structure, a driver's cab 11 provided on the front side (the right side in FIG. 1) of the revolving frame 10 for the driver to board, a counterweight 12 provided on the rear side (the left side in FIG. 1) of the revolving frame 10, and a machine room 14 provided between the driver's cab 11 and the counterweight 12 for housing the motor 13 and other devices (specifically, a hydraulic pump, a fuel cell, a secondary battery, a hydrogen tank, etc., which will be described in detail later).

[0015] The driver's cab 11 is provided with a traveling operation device (not shown) for instructing the traveling of the traveling body 1, a working operation device (not shown) for instructing the rotation of the boom 4 and the rotation of the bucket 6, a working operation device 15 (see FIG. 4 described later) for instructing the rotation of the revolving body 2 and the rotation of the arm 5, a lock lever device 16 (see FIG. 4 described later) for instructing the switching between a locked state for prohibiting the operation of the excavator and an unlocked state for permitting the operation of the excavator, and a rotation speed dial 17 (see FIG. 4 described later) for setting the rotation speed of the motor 13.

[0016] Next, a drive system for driving a plurality of hydraulic actuators (specifically, the traveling motor, the slewing motor, the boom cylinder 7, the arm cylinder 8, and the bucket cylinder 9 described above) will be described with reference to FIG. 4. FIG. 4 is a schematic diagram showing the configuration of the drive system in the present embodiment. In FIG. 4, for the sake of convenience, only the configuration related to the drive of the arm cylinder 8 among the plurality of hydraulic actuators is shown.

[0017] The drive system of this embodiment includes an electric motor 13, an inverter 18 that controls the rotational speed of the electric motor 13, a variable displacement hydraulic pump 19 driven by the electric motor 13, a regulator 20 that adjusts the displacement of the hydraulic pump 19 (for example, the tilt angle of the swash plate), and a control valve 21 that controls the flow of pressurized oil from the hydraulic pump 19 to the arm cylinder 8 (specifically, the direction and flow rate).

[0018] The drive system of this embodiment includes a pilot pump 22 driven by the electric motor 13, a pilot relief valve 23 that defines the discharge pressure of the pilot pump 22, electromagnetic proportional valves 24A, 24B that generate a pilot pressure using the discharge pressure of the pilot pump 22 as the source pressure and output the generated pilot pressure to the pressure receiving part of the control valve 21, a lock valve 25 (locking device) provided between the pilot pump 22 and the electromagnetic proportional valves 24A, 24B, etc., and a vehicle body controller 26.

[0019] The vehicle body controller 26 has a processor that executes processing according to a program, a memory that stores programs and data, and an interface that can communicate with other controllers.

[0020] The work operation device 15 includes an operation lever (operation member) operable by the driver, a first potentiometer that generates and outputs a first operation signal according to the operation amount on one side of the operation lever, and a second potentiometer that generates and outputs a second operation signal according to the operation amount on the other side of the operation lever.

[0021] The vehicle body controller 26 generates a drive signal according to the first operation signal from the work operation device 15 and outputs it to the electromagnetic proportional valve 24A. The electromagnetic proportional valve 24A generates a pilot pressure corresponding to the drive signal and outputs it to the pressure receiving part on one side of the control valve 21. As a result, the control valve 21 is switched to the switching position on the right side in the figure, and the pressurized oil from the hydraulic pump 19 is supplied through the control valve 21 to the upper rod chamber of the arm cylinder 8 in the figure, causing the arm cylinder 8 to contract.

[0022] The vehicle body controller 26 generates a drive signal according to a second operation signal from the work operation device 15 and outputs it to the electromagnetic proportional valve 24B. The electromagnetic proportional valve 24B generates a pilot pressure corresponding to the drive signal and outputs it to the pressure receiving part on the other side of the control valve 21. As a result, the control valve 21 is switched to the switching position on the left side in the figure, and the pressure oil from the hydraulic pump 19 is supplied to the bottom chamber on the lower side in the figure of the arm cylinder 8 through the control valve 21, and the arm cylinder 8 extends.

[0023] Note that the configuration related to the drive of other hydraulic actuators (specifically, the travel motor, swing motor, boom cylinder 7, or bucket cylinder 9) is also substantially the same as the configuration related to the drive of the arm cylinder 8. That is, the vehicle body controller 26 generates a drive signal according to an operation signal from the potentiometer of the corresponding operation device and outputs it to the corresponding electromagnetic proportional valve. The corresponding control valve is switched by the pilot pressure generated by the electromagnetic proportional valve, and the pressure oil discharged from the hydraulic pump is supplied to other hydraulic actuators, and the other hydraulic actuators are driven. The lock valve 25 is provided between all the electromagnetic proportional valves including the electromagnetic proportional valves 24A and 24B and the pilot pump 22.

[0024] The lock lever device 16 includes a lock lever that can be operated to a lock position (raised position) and a lock release position (lowered position), and a lock switch that does not output a signal when the lock lever is operated to the lock position and outputs a signal when the lock lever is operated to the lock release position.

[0025] When no signal is input from the lock lever device 16, the vehicle body controller 26 does not output a drive signal to the lock valve 25. As a result, the lock valve 25 is in the cutoff position on the right side in the figure, and the discharge pressure of the pilot pump 22 is not introduced into all the electromagnetic proportional valves. Therefore, the drive of all the hydraulic actuators, that is, the operation of the excavator is prohibited, and it is in a locked state.

[0026] When a signal from the lock lever device 16 is input, the vehicle body controller 26 outputs a drive signal to the lock valve 25. As a result, the lock valve 25 assumes the communication position on the left side in the drawing, and the discharge pressure of the pilot pump 22 is introduced to all the electromagnetic proportional valves. Accordingly, all the hydraulic actuators are driven, that is, the lock release state that permits the operation of the excavator is achieved.

[0027] The vehicle body controller 26 controls the inverter 18 so that the rotational speed of the electric motor 13 is the rotational speed set by the rotational speed dial 17. The vehicle body controller 26 controls the regulator 20 to adjust the capacity of the hydraulic pump 19 based on the rotational speed of the electric motor 13 set by the rotational speed dial 17 and the maximum value among the operation amounts of the travel operation device, the work operation device, and the work operation device 15.

[0028] The drive system of the present embodiment includes a high-voltage circuit 27 that supplies power to the electric motor 13 via the inverter 18, a fuel cell 28 capable of generating electricity, a boost converter 29 that connects the fuel cell 28 to the high-voltage circuit 27, a fuel cell controller 30 that controls the fuel cell 28, a secondary battery 31 capable of charging and discharging, and a bidirectional converter 32 that connects the secondary battery 31 to the high-voltage circuit 27.

[0029] The boost converter 29 boosts the power generated by the fuel cell 28 and supplies it to the high-voltage circuit 27. When the power of the high-voltage circuit 27 is excessive with respect to the power consumed by the electric motor 13 (in other words, when the power of the fuel cell 28 is excessive), the bidirectional converter 32 steps down the power of the high-voltage circuit 27 and supplies it to the secondary battery 31 to charge the secondary battery 31. When the power of the high-voltage circuit 27 is insufficient with respect to the power consumed by the electric motor 13 (in other words, when the power of the fuel cell 28 is insufficient), the bidirectional converter 32 steps up the power discharged from the secondary battery 31 and supplies it to the high-voltage circuit 27.

[0030] Next, a fuel cell system that controls the fuel cell 28 will be described with reference to FIGS. 5 and 6. FIGS. 5 and 6 are schematic diagrams showing the configuration of the fuel cell system according to the present embodiment. FIG. 5 shows the state of power generation operation, and FIG. 6 shows the state of drying operation. In FIGS. 5 and 6, the open state of the valve is shown in white, and the closed state of the valve is shown in black.

[0031] The fuel cell system of the present embodiment includes a hydrogen tank 33 for storing hydrogen, a hydrogen supply path 34 for supplying the hydrogen stored in the hydrogen tank 33 to the anode side of the fuel cell 28, a hydrogen discharge path 35 for discharging the hydrogen used in the fuel cell 28, a hydrogen circulation path 36 branched from the hydrogen discharge path 35 and merged into the hydrogen supply path 34 for reusing the hydrogen used in the fuel cell 28, a hydrogen supply valve 37A provided upstream of the merging point of the hydrogen circulation path 36 in the hydrogen supply path 34, a hydrogen supply valve 37B provided downstream of the merging point of the hydrogen circulation path 36 in the hydrogen supply path 34, a hydrogen discharge valve 38A and a hydrogen pump 39 provided upstream of the branching point of the hydrogen circulation path 36 in the hydrogen discharge path 35, and a hydrogen discharge valve 38B provided downstream of the branching point of the hydrogen circulation path 36 in the hydrogen discharge path 35.

[0032] The fuel cell system of the present embodiment includes a compressor 40 for compressing air, a cooler 41 for cooling the air compressed by the compressor 40, an air supply path 42 for supplying the air cooled by the cooler 41 to the cathode side of the fuel cell 28, an air discharge path 43 for discharging the air used in the fuel cell 28 to the outside, a bypass path 44 branched from the air supply path 42, bypassing the fuel cell 28, and merged into the air discharge path 43, an air supply valve 45 provided downstream of the branching point of the bypass path 44 in the air supply path 42, an air discharge valve 46 provided upstream of the merging point of the bypass path 44 in the air discharge path 43, and a bypass valve 47 provided in the bypass path 44.

[0033] The cooler 41 circulates cooling water with the heat exchanger 49 via a cooling water pump 48 or the like. The cooler 41 cools the air compressed by the compressor 40 with the cooling water supplied from the heat exchanger 49. The heat exchanger 49 cools the cooling water used by the cooler 41 with, for example, the cooling air generated by a cooling fan, and supplies the cooled cooling water to the cooler 41.

[0034] As shown in FIG. 3 described above, the air discharge path 43 extends upward from the fuel cell 28. That is, the outlet 43a of the air discharge path 43 is disposed above the inlet 43b of the air discharge path 43 (in other words, the connection portion between the fuel cell 28 and the air discharge path 43).

[0035] A water discharge path 50 branches off downstream of the confluence point of the bypass path 44 in the air discharge path 43, and a water tank 51 and a water discharge valve 52 are provided in the water discharge path 50. The water discharge path 50 extends downward from the air discharge path 43. The water tank 51 stores the water separated from the air by its own weight.

[0036] The fuel cell controller 30 includes a processor that executes processing according to a program, a memory that stores programs and data, and an interface capable of communicating with the vehicle body controller 26.

[0037] The fuel cell controller 30 executes a power generation operation in response to a power generation command from the vehicle body controller 26 (see FIG. 5). In this power generation operation, the fuel cell controller 30 opens the hydrogen supply valves 37A and 37B and the hydrogen discharge valve 38A, closes the hydrogen discharge valve 38B, and drives the hydrogen pump 39. Thereby, hydrogen is supplied to the anode side of the fuel cell 28. Further, the fuel cell controller 30 opens the air supply valve 45 and the air discharge valve 46, closes the bypass valve 47 and the water discharge valve 52, drives the compressor 40, and drives the cooling water pump 48 to supply cooling water to the cooler 41. At this time, the amount of cooling water (the amount of water per unit time) supplied from the cooling water pump 48 to the cooler 41 is set to a predetermined amount. Note that the amount of cooling water may be directly set by setting the capacity of the cooling water pump 48 (for example, the inclination angle of the inclined plate) to a predetermined value, or alternatively, for example, the rotation speed of the cooling water pump 48 may be set to a predetermined rotation speed, the discharge pressure of the cooling water pump 48 may be set to a predetermined pressure, or the opening of a valve provided between the cooling water pump 48 and the cooler 41 may be set to a predetermined value to indirectly set the amount of cooling water. Thereby, the air compressed by the compressor 40 and cooled by the cooler 41 is supplied to the cathode side of the fuel cell 28. Therefore, hydrogen and oxygen in the air are chemically reacted in the fuel cell 28 to generate power. During the power generation operation, in order to adjust the amount of air supplied to the fuel cell 28, the fuel cell controller 30 may close the air supply valve 45 and the air discharge valve 46 and open the bypass valve 47.

[0038] The fuel cell controller 30 opens the hydrogen discharge valve 38B, for example, at a predetermined time interval. Thereby, the hydrogen used in the fuel cell 28 is discharged to the outside through the hydrogen discharge path 35.

[0039] The air used in the fuel cell 28 is discharged to the outside through the air discharge path 43. The air in the air discharge path 43 contains the water generated by the above-described chemical reaction, and most of the water is discharged to the outside together with the air or flows into the water discharge path 50 and the water tank 51. The fuel cell controller 30 opens the water discharge valve 52, for example, when the excavator is in a drainable location. Thereby, the water stored in the water tank 51 is discharged to the outside.

[0040] However, since the excavator operates not only on flat ground but also on sloping ground, and the outlet 43a of the air discharge path 43 is arranged above the connection portion between the fuel cell 28 and the air discharge path 43, etc., the water contained in the air in the air discharge path 43 tends to remain, and the remaining amount also tends to increase. Therefore, as a feature of the present embodiment, the fuel cell controller 30 executes a drying operation for drying the air discharge path 43 (see FIG. 6). In this drying operation, the fuel cell controller 30 closes the hydrogen supply valves 37A, 37B and the hydrogen discharge valves 38A, 38B, and stops the hydrogen pump 39. Thereby, hydrogen is not supplied to the anode side of the fuel cell 28. Further, the fuel cell controller 30 closes the air supply valve 45 and the air discharge valve 46. Thereby, air is not supplied to the cathode side of the fuel cell 28. Further, the fuel cell controller 30 opens the bypass valve 47, closes the water discharge valve 52, and drives the compressor 40. Further, the fuel cell controller 30 stops the cooling water pump 48 or reduces any one of the capacity, rotation speed, discharge pressure, and valve opening of the cooling water pump 48, thereby restricting the amount of cooling water supplied from the cooling water pump 48 to the cooler 41 to be less than that when the fuel cell 28 generates power (i.e., a predetermined amount). Thereby, the high-temperature air compressed by the compressor 40 is made to flow through the bypass path 44 and the air discharge path 43 to dry the air discharge path 43.

[0041] The fuel cell system of the present embodiment further includes a temperature sensor 53 for detecting the temperature of the outside air. The fuel cell controller 30 determines whether to execute the drying operation based on the detection result of the temperature sensor 53 and the switching of the lock valve 25. The control procedure of this drying operation will be described with reference to FIG. 7.

[0042] Figure 7 is a flowchart showing the control procedure of the drying operation in the present embodiment.

[0043] In step S61, the fuel cell controller 30 determines whether the temperature detected by the temperature sensor 53 is equal to or lower than a predetermined temperature threshold (for example, 0°C). If the temperature detected by the temperature sensor 53 exceeds the temperature threshold, the drying operation is not executed. On the other hand, if the temperature detected by the temperature sensor 53 is equal to or lower than the temperature threshold, the process proceeds to step S62.

[0044] In step S62, the fuel cell controller 30 uses a first table representing the relationship between the outside air temperature and a first time threshold with respect to the power generation time of the fuel cell 28 (in other words, the amount of water generated) to set a first time threshold corresponding to the temperature detected by the temperature sensor 53. Specifically, the first time threshold is set so as to decrease in response to the decrease in the temperature detected by the temperature sensor 53.

[0045] Further, the fuel cell controller 30 uses a second table representing the relationship between the outside air temperature and a second time threshold with respect to the power generation time of the fuel cell 28 to set a second time threshold corresponding to the temperature detected by the temperature sensor 53. Specifically, the second time threshold is set to be smaller than the first time threshold and to decrease in response to the decrease in the temperature detected by the temperature sensor 53.

[0046] Thereafter, the process proceeds to step S63, where the fuel cell controller 30 acquires the power generation time of the fuel cell 28 using a timer and determines whether the power generation time of the fuel cell 28 is equal to or longer than the first time threshold. If the power generation time of the fuel cell 28 is equal to or longer than the first time threshold, the process proceeds to step S64.

[0047] In step S64, the fuel cell controller 30 executes the drying operation for a predetermined time. Thereafter, the process proceeds to step S65, where the fuel cell controller 30 resets the power generation time of the fuel cell 28.

[0048] If the power generation time of the fuel cell 28 is less than the first time threshold in step S63, the process proceeds to step S66. In step S66, the fuel cell controller 30 determines whether the power generation time of the fuel cell 28 is equal to or greater than the second time threshold. If the power generation time of the fuel cell 28 is less than the second time threshold, the drying operation is not executed. On the other hand, if the power generation time of the fuel cell 28 is less than the first time threshold and equal to or greater than the second time threshold, the process proceeds to step S67.

[0049] In step S67, the fuel cell controller 30 determines, based on the information acquired from the vehicle body controller 26, whether the lock valve 25 is in the blocked state (in other words, whether the locking device is in the locked state). If the lock valve 25 is in the communicating state (in other words, the locking device is in the unlocked state), the drying operation is not executed. On the other hand, if the lock valve 25 is in the blocked state (in other words, the locking device is in the locked state), the process proceeds to step S64.

[0050] In step S64, the fuel cell controller 30 executes the drying operation for a predetermined time. Then, the process proceeds to step S65, and the fuel cell controller 30 resets the power generation time of the fuel cell 28.

[0051] Next, the operation and effects of the present embodiment will be described using a comparative example. FIG. 8 is a schematic diagram showing the configuration of a fuel cell system in the comparative example and shows the state of the drying operation.

[0052] In the drying operation of the comparative example, the fuel cell controller 30 closes the hydrogen supply valves 37A and 37B and the hydrogen discharge valves 38A and 38B, and stops the hydrogen pump 39. Thereby, hydrogen is not supplied to the anode side of the fuel cell 28. Further, the fuel cell controller 30 opens the air supply valve 45 and the air discharge valve 46, closes the bypass valve 47, closes the water discharge valve 52, and drives the compressor 40. Further, the fuel cell controller 30 restricts the amount of cooling water supplied from the cooling water pump 48 to the cooler 41 to be less than that when the fuel cell 28 generates power. Thereby, the high-temperature air compressed by the compressor 40 is caused to flow through the fuel cell 28 and the air discharge path 43 to dry both the fuel cell 28 and the air discharge path 43. Therefore, it is necessary to limit the drying operation so that the fuel cell 28 does not dry out excessively and deteriorate, and there is a possibility that the air discharge path 43 may not be sufficiently dried.

[0053] On the other hand, in the drying operation of the present embodiment, as described above, the high-temperature air compressed by the compressor 40 is caused to flow through the bypass path 44 and the air discharge path 43 to dry the air discharge path 43. Therefore, the fuel cell 28 can be prevented from drying out excessively and deterioration of the fuel cell 28 can be prevented. Further, there is no need to limit the drying operation, and the air discharge path 43 can be sufficiently dried.

[0054] A second embodiment of the present invention will be described with reference to the drawings. In this embodiment, parts equivalent to those of the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

[0055] FIG. 9 is a schematic diagram showing the configuration of the fuel cell system in this embodiment and shows the state of the drying operation.

[0056] The fuel cell system of the present embodiment includes, in addition to the configuration of the first embodiment, a pressure sensor 54 that detects the pressure in the air discharge path 43. The fuel cell controller 30 determines whether to execute the drying operation based on the detection results of the temperature sensor 53 and the pressure sensor 54 and the switching of the lock valve 25. This control procedure for the drying operation will be described with reference to FIG. 10.

[0057] FIG. 10 is a flowchart showing the control procedure of the drying operation in the present embodiment.

[0058] In step S61, the fuel cell controller 30 determines whether the temperature detected by the temperature sensor 53 is equal to or lower than a predetermined temperature threshold (for example, 0°C). If the temperature detected by the temperature sensor 53 exceeds the temperature threshold, the drying operation is not executed. On the other hand, if the temperature detected by the temperature sensor 53 is equal to or lower than the temperature threshold, the process proceeds to step S68.

[0059] In step S68, the fuel cell controller 30 determines whether the pressure detected by the pressure sensor 54 is equal to or higher than a preset first pressure threshold (that is, whether the amount of water remaining in the air discharge path 43 is large). If the pressure detected by the pressure sensor 54 is equal to or higher than the first pressure threshold, the process proceeds to step S64.

[0060] In step S64, the fuel cell controller 30 executes the drying operation for a predetermined time. Thereafter, the process proceeds to step S65, and the fuel cell controller 30 resets the power generation time of the fuel cell 28.

[0061] If the pressure detected by the pressure sensor 54 in step S68 is less than the first pressure threshold, the process proceeds to step S69. In step S69, the fuel cell controller 30 determines whether the pressure detected by the pressure sensor 54 is equal to or higher than a preset second pressure threshold that is smaller than the first pressure threshold (that is, whether the amount of water remaining in the air discharge path 43 is slightly large). If the pressure detected by the pressure sensor 54 is less than the second pressure threshold, the drying operation is not executed. On the other hand, if the pressure detected by the pressure sensor 54 is less than the first pressure threshold and equal to or higher than the second pressure threshold, the process proceeds to step S67.

[0062] In step S67, the fuel cell controller 30 determines whether the lock valve 25 is in a blocked state (in other words, whether the locking device is in a locked state) based on the information obtained from the vehicle body controller 26. If the lock valve 25 is in a communicating state (in other words, the locking device is in an unlocked state), the dry operation is not executed. On the other hand, if the lock valve 25 is in a blocked state (in other words, the locking device is in a locked state), the process proceeds to step S64.

[0063] In step S64, the fuel cell controller 30 executes the dry operation for a predetermined time. Then, the process proceeds to step S65, and the fuel cell controller 30 resets the power generation time of the fuel cell 28.

[0064] Also in the present embodiment configured as described above, similar to the first embodiment, it is possible to dry the air discharge path 43 while preventing deterioration of the fuel cell 28.

[0065] In the first or second embodiment, the case where only the dry operation of flowing air through the bypass path 44 and the air discharge path 43 is performed has been described as an example, but it is not limited thereto. For example, a dry operation of flowing air through the fuel cell 28 and the air discharge path 43 (see FIG. 8 described above) may be performed, and then a dry operation of flowing air through the bypass path 44 and the air discharge path 43 may be performed. That is, the former dry operation may be restricted so that the fuel cell 28 is not excessively dried and deteriorated, and the latter dry operation may be supplemented so that the air discharge path 43 is sufficiently dried.

[0066] Also, in the first embodiment, the fuel cell controller 30 determines whether to execute the drying operation based on the detection result of the temperature sensor 53 and the switching of the lock valve 25. In the second embodiment, the case where the fuel cell controller 30 determines whether to execute the drying operation based on the detection results of the temperature sensor 53 and the pressure sensor 54 and the switching of the lock valve 25 has been described as an example, but it is not limited thereto. The fuel cell controller 30 may determine whether to execute the drying operation based on the detection result of the temperature sensor 53. That is, when the temperature detected by the temperature sensor 53 exceeds a predetermined temperature threshold (for example, 0°C), the drying operation may not be executed. When the temperature detected by the temperature sensor 53 is equal to or lower than the temperature threshold, the drying operation may be executed every predetermined time. Alternatively, the fuel cell controller 30 may determine whether to execute the drying operation based on the switching of the lock valve 25. That is, when the lock valve 25 is in the communicating state (in other words, the locking device is in the unlocked state), the drying operation may not be executed. When the lock valve 25 is in the blocking state (in other words, the locking device is in the locked state), the drying operation may be executed for a predetermined time.

[0067] Also, in the first or second embodiment, the case where the fuel cell controller 30 determines whether to execute the drying operation based on the detection result of the temperature sensor 53 or the like (in other words, the case where the fuel cell controller 30 constitutes the control device described in the claims) has been described as an example, but it is not limited thereto. For example, the vehicle body controller 26 may determine whether to execute the drying operation based on the detection result of the temperature sensor 53 or the like, and when it is determined to execute the drying operation, output a command thereto to the fuel cell controller 30. In other words, the vehicle body controller 26 and the fuel cell controller 30 may constitute the control device described in the claims.

[0068] Also, in the first or second embodiment, the locking device that switches between the locked state that prohibits the operation of the excavator and the unlocked state that permits the operation of the excavator has been described by taking the example of the lock valve 25 that switches between the cutoff position and the communication position, but it is not limited to this. The locking device may be, for example, the function of the vehicle body controller 26 that switches between invalidation and validation of the operation signal of the operating device.

[0069] In addition, in the above, the excavator has been described as an example of the application target of the present invention, but it is not limited to this. That is, the present invention may be applied to other construction machines other than the excavator.

Explanation of Signs

[0070] 25 Lock valve (locking device) 28 Fuel cell 30 Fuel cell controller (control device) 40 Compressor 41 Cooler 42 Air supply path 43 Air discharge path 44 Bypass path 45 Air supply valve 46 Air discharge valve 47 Bypass valve 48 Cooling water pump 50 Water discharge path 52 Water discharge valve 53 Temperature sensor 54 Pressure sensor

Claims

1. A fuel cell, a compressor for compressing air, a cooler for cooling the air compressed by the compressor, a cooling water pump for supplying cooling water to the cooler, an air supply path for supplying the air cooled by the cooler to the fuel cell, a construction machine comprising an air discharge path for discharging the air used in the fuel cell to the outside, a bypass path branched from the air supply path, bypassing the fuel cell, and merging into the air discharge path, an air supply valve provided downstream of the branch point of the bypass path in the air supply path, an air discharge valve provided upstream of the merging point of the bypass path in the air discharge path, a bypass valve provided in the bypass path, and a control device for controlling the air supply valve, the air discharge valve, the bypass valve, and the cooling water pump, wherein the control device when the fuel cell generates electricity, opens the air supply valve and the air discharge valve, closes the bypass valve, and drives the cooling water pump to supply the cooling water to the cooler, when performing a drying operation for drying the air discharge path, closes the air supply valve and the air discharge valve, opens the bypass valve, and restricts the amount of the cooling water supplied to the cooler to be less than that when the fuel cell generates electricity. The construction machine is characterized by this.

2. In the construction machine according to Claim 1, a water discharge path branched downstream of the merging point of the bypass path in the air discharge path and discharging water separated from the air, and a water discharge valve provided in the water discharge path, wherein the control device closes the water discharge valve when performing the drying operation. The construction machine is characterized by this.

3. In the construction machine according to Claim 1, the outlet of the air discharge path is arranged above the connection part between the fuel cell and the air discharge path. The construction machine is characterized by this.

4. In the construction machine according to Claim 1, comprising a temperature sensor for detecting the temperature of the outside air, wherein the control device performs the drying operation when the temperature detected by the temperature sensor is equal to or lower than a predetermined temperature threshold. The construction machine is characterized by this.

5. In the construction machine according to Claim 4, comprising a lock device for switching between a locked state for prohibiting the operation of the construction machine and an unlocked state for permitting the operation of the construction machine, wherein the control device When the temperature detected by the temperature sensor is equal to or lower than the temperature threshold value and the power generation time of the fuel cell is equal to or longer than a predetermined first time threshold value, the drying operation is executed. A construction machine, characterized in that when the temperature detected by the temperature sensor is equal to or lower than the temperature threshold value, the power generation time of the fuel cell is less than the first time threshold value, is equal to or longer than a second time threshold value smaller than the first time threshold value, and the locking device is in the locked state, the drying operation is executed.

6. In the construction machine according to claim 5, the construction machine is characterized in that the first time threshold value and the second time threshold value are set so as to decrease in accordance with a decrease in the temperature detected by the temperature sensor.

7. In the construction machine according to claim 4, a locking device that switches between a locked state that prohibits the operation of the construction machine and an unlocked state that permits the operation of the construction machine, and a pressure sensor that detects the pressure in the air discharge path are provided, and the control device executes the drying operation when the temperature detected by the temperature sensor is equal to or lower than the temperature threshold value and the pressure detected by the pressure sensor is equal to or higher than a preset first pressure threshold value, a construction machine, characterized in that when the temperature detected by the temperature sensor is equal to or lower than the temperature threshold value, the pressure detected by the pressure sensor is less than the first pressure threshold value, is equal to or higher than a second pressure threshold value smaller than the first pressure threshold value, and the locking device is in the locked state, the drying operation is executed.

8. In the construction machine according to claim 1, a locking device that switches between a locked state that prohibits the operation of the construction machine and an unlocked state that permits the operation of the construction machine is provided, and the construction machine is characterized in that the control device executes the drying operation when the locking device is in the locked state.

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