Liquefied hydrogen pump system and method for controlling liquefied hydrogen pump system

Abstract

This liquefied hydrogen pump system comprises a liquefied hydrogen pump, and a control device. The liquefied hydrogen pump includes a cylinder, a piston, a rod, a drive part, and a seal part. The seal part includes: a first seal member; a second seal member provided spaced apart from the first seal member in a direction away from the piston in an axial direction; a flow passage part having one end communicating with a gap between the rod and the cylinder, and the other end opening to the outside of the cylinder; and an information acquisition part that acquires information on hydrogen concentration in fluid flowing out of the cylinder through the flow passage part. The control device stops an operation of the liquefied hydrogen pump when it is determined, on the basis of the acquired information on hydrogen concentration, that the hydrogen concentration in the fluid exceeds a preset reference value.

Description

Liquefied hydrogen pump system and control method for liquefied hydrogen pump system

[0001] This application claims priority to Japanese Patent Application No. 2023-198546, filed on November 22, 2023, the contents of which are incorporated herein by reference.

[0002] Reciprocating pumps have been used as liquefied hydrogen pumps for compressing liquefied hydrogen. This type of pump is capable of pressurizing liquefied hydrogen up to approximately 90 MPa, for example. Specifically, a reciprocating pump mainly comprises a piston that reciprocates in the axial direction and a cylinder that covers the piston from the outside. The liquefied hydrogen is compressed as the piston reciprocates within the cylinder and discharged to the outside. The piston is driven by a drive unit. The piston provided within the cylinder and the drive unit provided outside the cylinder are connected via a rod. The rod extends through the interior and exterior of the cylinder.

[0003] For example, Patent Document 1 discloses a configuration of this type of liquefied hydrogen pump in which a plurality of seal members are provided between a rod and a cylinder at intervals in the axial direction of the rod. Patent Document 1 also discloses a configuration for monitoring the pressure of a fluid flow path communicating between the plurality of seal members. In such a configuration, leakage of liquefied hydrogen through gaps between the seal members and the rod due to wear of the seal members is monitored by detecting an increase in pressure in the fluid flow path.

[0004] Patent No. 6982034

[0005] In the above-described liquefied hydrogen pump, even if hydrogen leaks from the liquefied hydrogen pump into the atmosphere, it is required to suppress the hydrogen concentration in the surrounding atmosphere to a predetermined standard value or less. However, while the configuration described in Patent Document 1 can monitor whether or not liquefied hydrogen has leaked, it cannot detect the hydrogen concentration in the surrounding atmosphere if liquefied hydrogen leaks from the liquefied hydrogen pump into the atmosphere.

[0006] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a liquefied hydrogen pump system and a control method for a liquefied hydrogen pump system that can suppress the hydrogen concentration in the surrounding atmosphere to below a specified standard value by detecting changes in hydrogen concentration in the event of a liquefied hydrogen leak.

[0007] In order to solve the above problems, the liquefied hydrogen pump system according to the present disclosure is a liquefied hydrogen pump system comprising a liquefied hydrogen pump that compresses liquefied hydrogen and a control device that controls the operation of the liquefied hydrogen pump, wherein the liquefied hydrogen pump comprises: a cylindrical cylinder extending in an axial direction; a piston that is provided within the cylinder so as to be able to reciprocate in the axial direction and compresses the liquefied hydrogen introduced into the cylinder from the outside and discharges it to the outside of the cylinder; a rod that has one end connected to the piston within the cylinder and the other end protruding to the outside of the cylinder; a drive unit that is connected to the other end of the rod and reciprocates the piston in the axial direction within the cylinder via the rod; and a seal unit. The sealing unit comprises: a first sealing member that seals the gap between the rod and the cylinder; a second sealing member that is spaced apart from the first sealing member in the axial direction away from the piston and that seals between the rod and the cylinder; a flow path that is formed in the cylinder and has one end that communicates with the gap between the rod and the cylinder between the first sealing member and the second sealing member and the other end that opens to the outside of the cylinder; and an information acquisition unit that acquires information about the hydrogen concentration in the fluid that flows out to the outside of the cylinder through the flow path.The control device stops operation of the liquefied hydrogen pump when it is determined that the hydrogen concentration in the fluid has exceeded a predetermined reference value based on the information about the hydrogen concentration acquired by the information acquisition unit.

[0008] The control method for a liquefied hydrogen pump system according to the present disclosure is a control method for a liquefied hydrogen pump system as described above, and includes the steps of acquiring information relating to the hydrogen concentration in the fluid flowing out of the cylinder through the flow path portion, determining whether the hydrogen concentration in the fluid has exceeded a predetermined reference value based on the acquired information about the hydrogen concentration, and stopping operation of the liquefied hydrogen pump when it is determined that the hydrogen concentration in the fluid has exceeded the predetermined reference value.

[0009] According to the liquefied hydrogen pump system and the control method for the liquefied hydrogen pump system disclosed herein, in the event of a liquefied hydrogen leak, the hydrogen concentration in the surrounding atmosphere can be kept below a specified standard value by detecting changes in the hydrogen concentration.

[0010] 1 is a cross-sectional view showing a schematic configuration of a liquefied hydrogen pump system according to an embodiment of the present disclosure. FIG. 2 is a cross-sectional view showing the configuration of a seal unit provided in the liquid hydrogen pump of the liquefied hydrogen pump system according to the first embodiment of the present disclosure. FIG. 3 is a cross-sectional view taken along the arrows III-III of FIG. 2. FIG. 4 is a diagram showing the hardware configuration of a control device according to an embodiment of the present disclosure. FIG. 5 is a functional block diagram showing the functional configuration of the control device of FIG. 4. FIG. 5 is a flowchart showing the procedure of a control method for the liquefied hydrogen pump system according to the first embodiment of the present disclosure. FIG. 6 is a cross-sectional view showing the configuration of a seal unit provided in the liquid hydrogen pump of the liquefied hydrogen pump system according to the second embodiment of the present disclosure. FIG. 7 is a diagram showing an example of the correlation between the temperature of a fluid and the flow rate of a fluid. FIG. 7 is a flowchart showing the procedure of a control method for the liquefied hydrogen pump system according to the second embodiment of the present disclosure. FIG. 8 is a cross-sectional view showing the configuration of a seal unit provided in the liquid hydrogen pump of the liquefied hydrogen pump system according to the third embodiment of the present disclosure. FIG. 9 is a flowchart showing the procedure of a control method for the liquefied hydrogen pump system according to the third embodiment of the present disclosure.

[0011] Hereinafter, embodiments for carrying out a liquefied hydrogen pump system and a control method for a liquefied hydrogen pump system according to the present disclosure will be described with reference to the accompanying drawings. However, the present disclosure is not limited to these embodiments. (First embodiment) (Configuration of liquefied hydrogen pump system) As shown in Figure 1, a liquefied hydrogen pump system 100 includes a liquefied hydrogen pump 101 and a control device 60.

[0012] (Configuration of the liquefied hydrogen pump) The liquefied hydrogen pump 101 is a reciprocating pump for pressurizing liquefied hydrogen to a high pressure (for example, about 90 MPa). The liquefied hydrogen pump 101 mainly includes a piston 1, a cylinder 2, a rod 8, a drive unit 3, a casing 4, and a seal unit 9A.

[0013] (Piston Configuration) The piston 1 has a cylindrical piston body 10 centered on an axis O extending in the vertical direction, and a wear ring 11 and a piston ring 12 attached to the piston body 10. The radial dimension of the piston body 10 is constant throughout the entire area in the direction of the axis O. The wear ring 11 is provided at the tip of the piston body 10. The wear ring 11 has an annular shape centered on the axis O and is made of a resin material.

[0014] One wear ring 11 is provided at the lower end of the piston body 10, and another wear ring 11 is provided at a distance from the wear ring 11 in the axial direction O. A plurality of (for example, six) piston rings 12 are provided between the pair of wear rings 11 and arranged at intervals in the axial direction O. The wear rings 11 are provided to guide the piston body 10 along the inner circumferential surface of the cylinder body 20, which will be described later. On the other hand, the piston rings 12 are provided to maintain liquid-tightness and air-tightness between the piston body 10 and the inner circumferential surface of the cylinder body 20.

[0015] (Configuration of the Cylinder) The cylinder 2 has a cylinder body 20 and a seal portion body 90 (see FIG. 2 ), which will be described later. The cylinder body 20 has a cylindrical shape extending in the direction of the axis O along the axis O. The cylinder body 20 has a bottomed cylindrical shape that covers the piston 1 from the outer periphery. The piston 1 is inserted into the cylinder body 20 from an opening at the top of the cylinder body 20. The space below the piston 1 inside the cylinder body 20 forms a compression chamber 21. A check valve 5 is provided at the bottom of the cylinder body 20 to guide liquefied hydrogen into the compression chamber 21. This check valve 5 is capable of allowing liquefied hydrogen to flow only in a direction from the outside of the cylinder body 20 toward the inside of the compression chamber 21. In other words, even if the pressure in the compression chamber 21 increases, the liquefied hydrogen will not flow out of the cylinder body 20 through the check valve 5.

[0016] A discharge pipe 6 is connected to a side surface of the cylinder body 20 facing the compression chamber 21. The discharge pipe 6 is provided to extract the liquefied hydrogen compressed in the compression chamber 21 to the outside of the cylinder body 20. A discharge valve 7 is provided midway along this discharge pipe 6. The discharge valve 7 is capable of circulating the liquefied hydrogen only in the direction from the compression chamber 21 to the outside when the pressure inside the compression chamber 21 reaches or exceeds a predetermined value.

[0017] (Configuration of the rod) The rod 8 connects the piston 1 and the drive unit 3. The rod 8 is formed in a cylindrical shape extending in the direction of the axis O. One end of the rod 8 is connected to a piston body 10 of the piston 1 inside the cylinder 2. The other end of the rod 8 protrudes upward from the upper end of the cylinder 2. The other end of the rod 8 is connected to a swing shaft portion 35 of the drive unit 3 inside a housing 37 of the drive unit 3. The piston 1 and the rod 8 are movable along the direction of the axis O inside the cylinder 2.

[0018] (Configuration of the drive unit) The drive unit 3 reciprocates the piston 1 and the rod 8 in the direction of the axis O within the cylinder body 20. The drive unit 3 has an eccentric shaft portion 31, a rotating body 32, a link portion 33, a crosshead 36, and a housing 37.

[0019] The eccentric shaft portion 31 is driven to rotate around a rotation axis X (central axis) extending in a horizontal direction perpendicular to the axis O by an electric motor (not shown). The eccentric shaft portion 31 is cylindrical and has a center on the rotation axis X. The rotating body 32 is provided integrally with the eccentric shaft portion 31 and has a disk shape and has a center on an axis different from the rotation axis X. In other words, the rotation axis X of the eccentric shaft portion 31 is provided at an eccentric position with respect to the center of the rotating body 32. When the eccentric shaft portion 31 is driven to rotate, the rotating body 32 revolves around the rotation axis X.

[0020] The link portion 33 is a member that converts the orbital motion of the rotor 32 into reciprocating motion in the direction of the axis O and transmits the motion to the piston 1. The link portion 33 has an upper annular portion 33a having an annular shape that covers the rotor 32 from the outer periphery, a connecting portion 33b, and a lower annular portion 33c. A bearing device (not shown) is provided between the inner periphery of the upper annular portion 33a and the outer periphery of the rotor 32. The upper annular portion 33a revolves around the rotation axis X together with the rotor 32. The lower annular portion 33c, like the upper annular portion 33a, is annular and is integrally connected to the upper annular portion 33a by the connecting portion 33b. The lower annular portion 33c is housed within a crosshead 36. The crosshead 36 is cylindrical and has a bottom that covers the lower annular portion 33c from the outside. The crosshead 36 is provided within a housing 37 (described below) so as to be movable in the direction of the axis O. The lower annular portion 33c rotates within a crosshead 36 (described later) as the upper annular portion 33a revolves around the rotation axis X, and reciprocates together with the crosshead 36 in the direction of the axis O within the housing 37. A swing shaft 35 is attached to the lower end of the lower annular portion 33c. The lower end of the swing shaft 35 is connected to the other end of the rod 8. The swing shaft 35 is capable of swinging around a swing axis that extends horizontally and is perpendicular to the axis O relative to the lower annular portion 33c.

[0021] The housing 37 is formed to cover the eccentric shaft portion 31, the rotating body 32, the link portion 33, and the crosshead 36. The housing 37 is cylindrical and extends in the direction of the axis O, and both ends in the direction of the axis O are closed by a top plate 37a and a bottom plate 37b. A wear band 38 is provided between the outer peripheral surface of the crosshead 36 and the inner peripheral surface of the housing 37. The wear band 38 is a member having the same function and material as the wear ring 11 described above.

[0022] An air vent 39 is formed in the lower part of the housing 37. The air vent 39 is formed to penetrate the housing 37 in a direction intersecting the axial line O. The air vent 39 has an air inlet 39a and an air outlet 39b. The air inlet 39a is formed on one radial side of the housing 37 intersecting the axial line O, penetrating from the inside to the outside of the housing 37. The air outlet 39b is formed on the other radial side of the housing 37 intersecting the axial line O, penetrating from the inside to the outside of the housing 37. The air vent 39 introduces air into the space below the crosshead 36 in the housing 37 through the air inlet 39a by a fan, blower, or the like (not shown). The air introduced into the housing 37 is exhausted to the outside of the housing 37 through the air outlet 39b. This ventilates the lower part of the housing 37.

[0023] (Casing Configuration) The casing 4 covers the cylinder body 20 from the outside. The casing 4 has a cylindrical casing body 41 with a bottom, a supply pipe 42, and a gas discharge pipe 43. The supply pipe 42 is a pipe for guiding liquefied hydrogen from an external supply source into the casing body 41. The liquefied hydrogen introduced into the casing body 41 through the supply pipe 42 is stored in a liquid storage chamber 44 at the bottom of the casing body 41. The supply pipe 42 is provided near the bottom of the casing body 41. The gas discharge pipe 43 is provided for discharging vaporized components (gas components) in the liquid storage chamber 44 to the outside. The gas discharge pipe 43 is provided at a position spaced above the supply pipe 42. The liquid level of the liquefied hydrogen in the liquid storage chamber 44 is adjusted to be located below the gas discharge pipe 43. The discharge pipe 6 described above extends to the outside of the casing 4.

[0024] A cylindrical portion 45 is formed at the upper end of the casing 4. The cylindrical portion 45 protrudes upward from the upper surface 4t of the casing 4 along the axis O. The upper end of the cylindrical portion 45 is connected to the bottom plate 37b of the housing 37. The upper end of the cylinder body 20 is housed inside the cylindrical portion 45. The rod 8 extends upward from the upper end of the cylinder body 20 within the housing 37.

[0025] To operate this liquefied hydrogen pump 101, first, liquefied hydrogen is supplied from outside the casing 4 into the casing 4 via the supply pipe 42, and then the piston 1 is reciprocated within the cylinder body 20 by the drive unit 3. As a result, the liquefied hydrogen in the liquid storage chamber 44 is sucked into the cylinder body 20 through the check valve 5. The piston 1 compresses the liquefied hydrogen introduced into the cylinder body 20 from outside, bringing it to a high-pressure state. The operation of the piston 1 causes the high-pressure liquefied hydrogen to be discharged to the outside via the discharge pipe 6 through the discharge valve 7.

[0026] 2 , the seal portion 9A is for sealing the gap between the cylinder 2 and the rod 8. The seal portion 9A includes a seal portion main body 90, a first seal member 91, a second seal member 92, a flow path portion 95, and an inert gas supply flow path portion 96.

[0027] The seal portion main body 90 is fitted into the opening at the upper end of the cylinder main body 20. The seal portion main body 90 integrally includes an insertion tube portion 90a and an expanded diameter portion 90b. The insertion tube portion 90a is inserted into the cylinder main body 20 from the opening at the upper end of the cylinder main body 20. The insertion tube portion 90a is formed in a cylindrical shape extending in the direction of the axis O. The inner circumferential surface of the insertion tube portion 90a is formed so as to be spaced radially outward from the outer circumferential surface of the rod 8. As a result, a cylindrical gap S is formed between the insertion tube portion 90a, which forms part of the cylinder main body 20, and the rod 8. The expanded diameter portion 90b expands radially outward from the upper end of the insertion tube portion 90a, centered on the axis O. The expanded diameter portion 90b is provided so as to close the opening at the upper end of the cylinder main body 20 from above. In the embodiment of the present disclosure, the seal portion main body 90 is attached to the upper end of the cylinder main body 20, but a configuration similar to the seal portion main body 90 may be formed integrally with the upper end of the cylinder main body 20.

[0028] The first seal member 91 and the second seal member 92 are provided on the inner circumferential surface of the insertion cylindrical portion 90a. The first seal member 91 is housed in a groove 90m formed on the inner circumferential surface of the lower end of the insertion cylindrical portion 90a. The first seal member 91 is formed in an annular shape that is continuous in the circumferential direction about the axis O. The first seal member 91 protrudes radially inward from the inner circumferential surface of the insertion cylindrical portion 90a and is in sliding contact with the outer circumferential surface of the rod 8. The first seal member 91 seals between the rod 8 and the seal portion main body 90, which constitutes part of the cylinder 2.

[0029] The second seal member 92 is provided with a gap relative to the first seal member 91 in the direction of the axis O away from the piston 1 (upward). The second seal member 92 is housed in a groove 90n formed on the inner circumferential surface of the upper end of the insertion cylindrical portion 90a. The second seal member 92 is formed in an annular shape that is continuous in the circumferential direction about the axis O. The second seal member 92 protrudes radially inward from the inner circumferential surface of the insertion cylindrical portion 90a and is in sliding contact with the outer circumferential surface of the rod 8. The second seal member 92 provides a seal between the rod 8 and the seal portion main body 90 provided in the cylinder body 20.

[0030] The distance D between the first seal member 91 and the second seal member 92 in the direction of the axis O is larger than the movement stroke in the direction of the axis O of the rod 8 driven together with the piston 1 by the drive unit 3 .

[0031] As shown in FIGS. 2 and 3 , the flow path portion 95 is formed in the seal portion main body 90. The flow path portion 95 is formed on one radial side with respect to the axis O. One end 95a of the flow path portion 95 is provided between the first seal member 91 and the second seal member 92 so as to communicate with the gap S between the rod 8 and the cylinder 2. In the embodiment of the present disclosure, the one end 95a of the flow path portion 95 is formed above the first seal member 91 at the lower end of the insertion tube portion 90a. In other words, the one end 95a is formed so as to face the lower end of the gap S. The flow path portion 95 extends radially outward from the one end 95a. The other end 95b of the flow path portion 95 opens to the outside of the cylinder 2. In the embodiment of the present disclosure, the other end 95b of the flow path portion 95 opens, for example, to the upper surface of the expanded diameter portion 90b. One end of a pipe 95p is connected to the other end 95b of the flow path portion 95. An on-off valve 95v is provided midway along the pipe 95p. The other end of this pipe 95p is connected to a hydrogen recovery unit 95r. When hydrogen leaks from the cylinder body 20 side through between the first seal member 91 and the rod 8 and flows into the gap S, this flow path unit 95 allows the inflowing hydrogen to flow out of the cylinder 2. The hydrogen that flows out of the cylinder 2 from the other end 95b of the flow path unit 95 passes through the pipe 95p and is sent to the hydrogen recovery unit 95r.

[0032] The inert gas supply passage portion 96 is formed in the seal portion main body 90. The inert gas supply passage portion 96 is formed on the other radial side with respect to the axis O. In other words, the inert gas supply passage portion 96 is formed on the opposite side of the passage portion 95 across the axis O. The inert gas supply passage portion 96 is provided such that one end 96a thereof communicates with the gap S between the rod 8 and the cylinder 2 between the first seal member 91 and the second seal member 92. In the embodiment of the present disclosure, the one end 96a of the inert gas supply passage portion 96 is formed below the second seal member 92 at the upper end of the insertion tube portion 90a. In other words, the one end 96a is formed to face the upper end of the gap S. The inert gas supply passage portion 96 extends radially outward from the one end 96a. The other end 96b of the inert gas supply passage portion 96 opens to the outside of the cylinder 2. In an embodiment of the present disclosure, the other end 96b of the inert gas supply channel portion 96 opens, for example, to the upper surface of the expanded diameter portion 90b. One end of a pipe 96p is connected to the other end 96b of the inert gas supply channel portion 96. An on-off valve 96v is provided on this pipe 96p. The other end of the pipe 96p is connectable to an inert gas supply source (not shown), such as a tank filled with inert gas. Inert gas supplied through the pipe 96p from an inert gas supply source provided outside the cylinder 2 flows through the inert gas supply channel portion 96. In an embodiment of the present disclosure, for example, helium (He), which has a specific gravity smaller than that of air, is used as the inert gas.

[0033] In an embodiment of the present disclosure, prior to operating the liquefied hydrogen pump 101, gaseous helium is filled as an inert gas into the seal portion 9A through the inert gas supply passage portion 96. Specifically, filling with inert gas is performed after installation of the liquefied hydrogen pump 101, when the liquefied hydrogen pump 101 is in an initial state prior to operation, that is, prior to operating the liquefied hydrogen pump 101 for the first time. To do this, an inert gas supply source is connected to the pipe 96p, and the on-off valves 95v and 96v are opened. Helium is then sent from the inert gas supply source through the pipe 96p to the inert gas supply passage portion 96. When inert gas is supplied to the inert gas supply passage portion 96 from outside the cylinder 2, the gap S between the rod 8 and the cylinder 2, between the first seal member 91 and the second seal member 92, and the passage portion 95 communicating with this gap S, are filled with inert gas.

[0034] In this manner, when inert gas is supplied from outside the cylinder 2 through the inert gas supply channel 96, the inert gas flows into the gap S from one end 96 a that opens at the upper end of the gap S. At that time, the air present in the inert gas supply channel 96 and the gap S between the rod 8 and the cylinder 2 is pushed downward as the inert gas is supplied. By using helium, which has a lower specific gravity than air, in the gap S, the air present in the gap S sinks below the helium. As a result, the air pushed downward flows into the channel 95 from one end 95 a that opens at the lower end of the gap S, and is pushed out through the channel 95 to the outside of the liquefied hydrogen pump 101. This allows the air inside the seal portion 9A to be efficiently replaced with the inert gas.

[0035] In this way, by filling the liquefied hydrogen pump 101 in its initial state before operation with inert gas, even if hydrogen flows into the gap S between the rod 8 and the cylinder 2 after the liquefied hydrogen pump 101 starts operating, there will be no oxygen-containing atmosphere in the gap S, the flow path 95, or the inert gas supply flow path 96. The hydrogen will flow into the oxygen-free inert gas. As a result, the hydrogen concentration in the atmosphere will not reach the lower explosion limit, and the liquefied hydrogen pump system 100 can be operated safely.

[0036] As shown in FIG. 2 , the seal unit 9A further includes an information acquisition unit 200. The information acquisition unit 200 acquires information related to the hydrogen concentration in the fluid flowing out of the cylinder 2 through the flow path unit 95. In an embodiment of the present disclosure, the information acquisition unit 200 includes, for example, a flow meter 201. The flow meter 201 detects the flow rate of the fluid flowing through the flow path unit 95, i.e., the flow rate of hydrogen leaking from the cylinder main body 20 side through the gap between the first seal member 91 and the rod 8 into the gap S. The greater the fluid flow rate detected by the flow meter 201, the greater the amount of hydrogen flowing from the cylinder main body 20 side through the gap between the first seal member 91 and the rod 8 into the gap S. The flow meter 201 serving as the information acquisition unit 200 outputs a detected value of the flow rate of the fluid flowing through the flow path unit 95 to the control device 60.

[0037] The seal portion 9A also includes a hydrogen concentration detection portion 202 and an atmospheric temperature detection portion 203. The hydrogen concentration detection portion 202 detects the hydrogen concentration in the atmosphere outside the cylinder 2. In an embodiment of the present disclosure, the hydrogen concentration detection portion 202 is, for example, a water concentration sensor that detects the hydrogen concentration in the atmosphere inside the atmosphere circulation portion 39. The atmospheric temperature detection portion 203 detects the atmospheric temperature outside the cylinder 2. In an embodiment of the present disclosure, the atmospheric temperature detection portion 203 is, for example, a thermocouple that detects the atmospheric temperature inside the atmosphere circulation portion 39. The hydrogen concentration detection portion 202 and the atmospheric temperature detection portion 203 output the detected values ​​of the hydrogen concentration and the atmospheric temperature to the control device 60.

[0038] (Hardware Configuration Diagram) As shown in FIG. 4, the control device 60 is a computer including various pieces of hardware such as a CPU 61, a ROM 62, a RAM 63, a storage 64 such as a hard disk drive (HDD), a communication module 65, and the like.

[0039] (Functional Block Diagram) The control device 60 is functionally equipped with an input unit 71, a pump control unit 72, and a command signal output unit 73, as shown in Fig. 5, by the CPU 61 executing a program stored in the control device 60 in advance. The input unit 71 receives signal inputs of each detection value output from the information acquisition unit 200, the hydrogen concentration detection unit 202, the atmospheric temperature detection unit 203, etc. The pump control unit 72 generates a command for the electric motor that rotates the eccentric shaft unit 31 to control the operation of the liquefied hydrogen pump 101 based on the detection values ​​from the information acquisition unit 200, the hydrogen concentration detection unit 202, and the atmospheric temperature detection unit 203. The command signal output unit 73 outputs a signal for controlling the operation of the liquefied hydrogen pump 101 based on the command generated by the pump control unit 72.

[0040] The control device 60 stops the operation of the liquefied hydrogen pump 101 when it is determined that the hydrogen concentration in the fluid has exceeded a preset reference value based on the information on the hydrogen concentration acquired by the information acquisition unit 200. In an embodiment of the present disclosure, the flow meter 201 serving as the information acquisition unit 200 acquires the flow rate of the fluid flowing through the flow path unit 95 as information on the hydrogen concentration. When the flow rate of the fluid is equal to or greater than a preset flow rate threshold, the control device 60 determines that the hydrogen concentration in the fluid has exceeded the preset reference value and stops the operation of the liquefied hydrogen pump 101.

[0041] Furthermore, the control device 60 stops the operation of the liquefied hydrogen pump 101 when the hydrogen concentration in the atmosphere detected by the hydrogen concentration detection unit 202 is equal to or greater than a preset hydrogen concentration threshold. In an embodiment of the present disclosure, the hydrogen concentration detection unit 202 detects the hydrogen concentration in the atmosphere in the atmosphere vent portion 39. If hydrogen leaks from between the second seal member 92 and the rod 8, the hydrogen concentration in the atmosphere in the atmosphere vent portion 39 increases. If the hydrogen concentration in the atmosphere detected by the hydrogen concentration detection unit 202 is equal to or greater than a preset hydrogen concentration threshold, the control device 60 determines that hydrogen is leaking from between the second seal member 92 and the rod 8 and stops the operation of the liquefied hydrogen pump 101. Here, the hydrogen concentration threshold is preferably set to, for example, 1 vol%, which is the lower explosive limit of hydrogen.

[0042] Furthermore, the control device 60 stops the operation of the liquefied hydrogen pump 101 when the atmospheric temperature detected by the atmospheric temperature detection unit 203 is below a preset atmospheric temperature threshold. If the atmospheric temperature is low enough that moisture in the air freezes, there is a risk that the frozen moisture (ice) will damage the second seal member 92. In contrast, the control device 60 stops the operation of the liquefied hydrogen pump 101 when the atmospheric temperature is below the preset atmospheric temperature threshold. The atmospheric temperature in the atmospheric circulation unit 39 also drops when hydrogen leaks from between the second seal member 92 and the rod 8. Here, the atmospheric temperature threshold is preferably set to, for example, a temperature above 0°C, which is the freezing point (freezing point) of water.

[0043] 6, the control method for the liquefied hydrogen pump system according to the embodiment of the present disclosure includes a hydrogen concentration detection step S10, a hydrogen concentration determination step S11, a flow rate detection step S12, a flow rate determination step S13, an ambient temperature detection step S14, an ambient temperature determination step S15, automatic shutdown steps S16 to S18, and a restart step S 19. These steps S10 to S19 are repeatedly executed at preset time intervals while the liquefied hydrogen pump 101 is in operation.

[0044] In the hydrogen concentration detection step S10, the hydrogen concentration detection unit 202 detects the hydrogen concentration in the atmosphere within the atmosphere circulation unit 39. The detected value of the hydrogen concentration in the atmosphere detected by the hydrogen concentration detection unit 202 is output to the control device 60.

[0045] In hydrogen concentration determination step S11, the pump control unit 72 determines whether the hydrogen concentration in the atmosphere detected by the hydrogen concentration detection unit 202 is less than a preset hydrogen concentration threshold value. If the result of the determination is that the hydrogen concentration in the atmosphere detected by the hydrogen concentration detection unit 202 is less than the preset hydrogen concentration threshold value (Yes in step S11), the process proceeds to step S12.

[0046] On the other hand, if the hydrogen concentration in the atmosphere detected by the hydrogen concentration detection unit 202 is equal to or higher than the predetermined hydrogen concentration threshold value (No in step S11), it is determined that hydrogen is leaking from between the second seal member 92 and the rod 8, and the system proceeds to the automatic stop step S16.

[0047] In the automatic stop step S16, the pump control unit 72 stops the operation of the liquefied hydrogen pump 101. At this time, in addition to stopping the operation of the liquefied hydrogen pump 101, information indicating that the hydrogen concentration is equal to or higher than the hydrogen concentration threshold may be output to the operator by, for example, lighting a warning lamp, sounding a warning buzzer, or outputting a message. If the operation of the liquefied hydrogen pump 101 stops in the automatic stop step S16, the operator or worker takes measures to reduce the hydrogen concentration in the atmosphere, for example, by increasing the rotation speed of the fan or blower that circulates air through the air circulation unit 39 or by ventilating the location where the liquefied hydrogen pump 101 is installed. After completing the measures, the operator or worker performs a predetermined operation to restart the liquefied hydrogen pump 101. When a predetermined operation input to restart the liquefied hydrogen pump 101 is made, the control device 60 restarts the liquefied hydrogen pump 101 (step S19).

[0048] In a flow rate detection step S12, the flow rate of the fluid (hydrogen) flowing through the flow path portion 95 is detected by the flow meter 201 serving as the information acquisition unit 200. The detected value of the fluid flow rate detected by the information acquisition unit 200 is output to the control device 60. In a flow rate determination step S13, the pump control unit 72 determines whether the flow rate of the fluid detected by the flow meter 201 is less than a preset flow rate threshold. As a result, if the flow rate of the fluid flowing through the flow path portion 95 detected by the flow meter 201 is less than the preset flow rate threshold (Yes in step S13), the process proceeds to step S14.

[0049] On the other hand, if the flow rate through the flow path section 95 detected by the flow meter 201 is equal to or greater than the preset flow rate threshold (No in step S13), it is determined that hydrogen is leaking from between the first seal member 91 and the rod 8, and the process proceeds to the automatic stop step S17.

[0050] In the automatic stop step S17, the pump control unit 72 stops the operation of the liquefied hydrogen pump 101. At this time, as in the automatic stop step S16, the operation of the liquefied hydrogen pump 101 is stopped, and information indicating that the flow rate in the flow path unit 95 is equal to or greater than the flow rate threshold may be output. If the operation of the liquefied hydrogen pump 101 has stopped in the automatic stop step S17, the operator or worker takes corrective action to reduce the flow rate of the fluid in the flow path unit 95, for example, by replacing the first seal member 91. After completing the corrective action, the operator or worker performs a predetermined operation to restart the liquefied hydrogen pump 101. When a predetermined operation input to restart the liquefied hydrogen pump 101 is made, the control device 60 restarts the liquefied hydrogen pump 101 (step S19).

[0051] In an atmospheric temperature detection step S14, the atmospheric temperature detection unit 203 detects the temperature of the atmosphere in the atmospheric circulation unit 39. The detected value of the atmospheric temperature detected by the atmospheric temperature detection unit 203 is output to the control device 60. In an atmospheric temperature determination step S15, the pump control unit 72 determines whether the atmospheric temperature detected by the atmospheric temperature detection unit 203 is equal to or higher than a preset atmospheric temperature threshold. As a result, if the atmospheric temperature detected by the atmospheric temperature detection unit 203 is equal to or higher than the preset atmospheric temperature threshold (Yes in step S15), the series of processes ends.

[0052] On the other hand, if the atmospheric temperature detected by the atmospheric temperature detection unit 203 is lower than the preset atmospheric temperature threshold (No in step S15), it is determined that there is a risk of moisture in the air freezing within the atmospheric circulation unit 39, and the process proceeds to automatic stop step S18.

[0053] In automatic stop step S18, the pump control unit 72 stops the operation of the liquefied hydrogen pump 101. At this time, as in automatic stop steps S16 and S17, the operation of the liquefied hydrogen pump 101 is stopped and information indicating that the atmospheric temperature is below the atmospheric temperature threshold may be output. If the operation of the liquefied hydrogen pump 101 has stopped in automatic stop step S18, the operator or worker will take corrective action, such as heating the periphery of the second seal member 92, to raise the atmospheric temperature to or above the atmospheric temperature threshold. After completing the corrective action, the operator or worker will perform a predetermined operation to restart the liquefied hydrogen pump 101. When a predetermined operational input for restarting the liquefied hydrogen pump 101 is made, the control device 60 restarts the liquefied hydrogen pump 101 (step S19).

[0054] (Operation and Effect) In the liquefied hydrogen pump system 100 configured as described above, the drive unit 3 reciprocates the piston 1 in the axial direction O within the cylinder 2 via the rod 8, thereby compressing liquefied hydrogen introduced into the cylinder 2 from the outside and discharging it out of the cylinder 2. If a portion of the liquefied hydrogen in the cylinder 2 passes through the gap S between the first seal member 91 and the outer peripheral surface of the rod 8, the liquefied hydrogen or low-temperature hydrogen gas generated by vaporization of the liquefied hydrogen flows into the gap S between the rod 8 and the cylinder 2 between the first seal member 91 and the second seal member 92. The hydrogen (liquefied hydrogen or hydrogen gas) that flows into the gap S between the rod 8 and the cylinder 2 flows as a fluid through the flow path unit 95 and is discharged to the outside of the cylinder 2. The information acquisition unit 200 acquires information regarding the hydrogen concentration in the fluid flowing to the outside of the cylinder 2 through the flow path unit 95. When hydrogen flows through the flow path unit 95, the information regarding the hydrogen concentration acquired by the information acquisition unit 200 changes. The control device 60 stops the operation of the liquefied hydrogen pump 101 when it determines that the hydrogen concentration in the fluid exceeds a preset reference value based on the information on the hydrogen concentration acquired by the information acquisition unit 200. In this way, in the event of a liquefied hydrogen leak, the operation of the liquefied hydrogen pump 101 can be stopped by detecting a change in the hydrogen concentration, thereby keeping the hydrogen concentration in the surrounding atmosphere below the set reference value.

[0055] The information acquisition unit 200 also acquires the flow rate of the fluid as information related to the hydrogen concentration. When a portion of the liquefied hydrogen in the cylinder 2 passes through the gap S between the first seal member 91 and the outer peripheral surface of the rod 8, the hydrogen that has flowed into the gap S between the rod 8 and the cylinder 2 flows as a fluid through the flow path portion 95. Therefore, the greater the flow rate of the fluid flowing through the flow path portion 95, the greater the amount of hydrogen leakage. In this way, the flow rate of the fluid in the flow path portion 95 is acquired as information related to the hydrogen concentration. If the flow rate of the fluid is equal to or greater than a predetermined flow rate threshold, the control device 60 determines that the hydrogen concentration in the fluid has exceeded a predetermined reference value and can stop the operation of the liquefied hydrogen pump 101. As a result, the hydrogen concentration in the surrounding atmosphere can be kept below the specified reference value.

[0056] Furthermore, in the liquefied hydrogen pump system 100, when the atmospheric temperature is below a preset atmospheric temperature threshold, the operation of the liquefied hydrogen pump 101 is stopped. This prevents the liquefied hydrogen pump 101 from operating in a temperature environment where moisture in the air freezes, thereby preventing damage to the second seal member 92. As a result, hydrogen leakage from between a damaged second seal member 92 and the rod 8 can be prevented.

[0057] Furthermore, in the liquefied hydrogen pump system 100, when the hydrogen concentration in the atmosphere detected by the hydrogen concentration detection unit 202 is equal to or higher than a preset hydrogen concentration threshold, the operation of the liquefied hydrogen pump 101 is stopped. This makes it possible to prevent hydrogen leaking from the liquefied hydrogen pump 101 from further increasing the hydrogen concentration in the atmosphere.

[0058] Furthermore, in the liquefied hydrogen pump system 100, inert gas is supplied from outside the cylinder 2 through the inert gas supply flow path 96. This allows the gap S between the rod 8 and the cylinder 2, between the first seal member 91 and the second seal member 92, and the flow path 95 communicating with this gap S, to be filled with inert gas. By filling the liquefied hydrogen pump 101 in its initial state before the first operation with inert gas, even if hydrogen flows into the gap S between the rod 8 and the cylinder 2 after the liquefied hydrogen pump 101 starts operating, the hydrogen will flow into the oxygen-free inert gas. This prevents the hydrogen concentration in the atmosphere from reaching the lower explosion limit, allowing the liquefied hydrogen pump system to be operated safely.

[0059] Furthermore, in the liquefied hydrogen pump system 100, one end 96a of the inert gas supply channel portion 96 is in communication with the gap S between the rod 8 and the cylinder 2 at a position above one end 95a of the channel portion 95. As a result, when helium, an inert gas with a specific gravity lower than that of air, is supplied from outside the cylinder 2 through the inert gas supply channel portion 96, the air present in the inert gas supply channel portion 96 and the gap S between the rod 8 and the cylinder 2 at that time is pushed downward as the inert gas is supplied. As a result, the pushed air is pushed out from the gap S between the rod 8 and the cylinder 2 through the channel portion 95 to the outside of the liquefied hydrogen pump 101. This allows the air inside the liquefied hydrogen pump 101 to be efficiently replaced with inert gas.

[0060] Furthermore, in the liquefied hydrogen pump system 100, the distance D between the first seal member 91 and the second seal member 92 in the direction of the axis O is larger than the movement stroke of the rod 8 in the direction of the axis O. As a result, when the rod 8 moves in the direction of the axis O, foreign matter, etc. generated by the sliding between the second seal member 92 and the rod 8 can be prevented from reaching the sliding portion between the first seal member 91 and the rod 8. As a result, damage to the first seal member 91 due to foreign matter, etc. generated by the sliding between the second seal member 92 and the rod 8 can be prevented. Furthermore, foreign matter, etc. generated by the sliding between the first seal member 91 and the rod 8 can be prevented from reaching the sliding portion between the second seal member 92 and the rod 8. As a result, damage to the second seal member 92 due to foreign matter, etc. generated by the sliding between the first seal member 91 and the rod 8 can be prevented.

[0061] In the control method for the liquefied hydrogen pump system 100 configured as described above, information regarding the hydrogen concentration in the fluid flowing out of the cylinder 2 is acquired, and if it is determined based on the acquired information regarding the hydrogen concentration that the hydrogen concentration in the fluid has exceeded a preset reference value, the operation of the liquefied hydrogen pump 101 is stopped. In this way, if liquefied hydrogen leaks, the change in hydrogen concentration is detected, thereby stopping the operation of the liquefied hydrogen pump 101 and suppressing the hydrogen concentration in the surrounding atmosphere to below the set reference value.

[0062] Second Embodiment Next, a second embodiment of the liquefied hydrogen pump system and the control method for the liquefied hydrogen pump system according to the present disclosure will be described. In the second embodiment described below, components common to the first embodiment will be denoted by the same reference numerals in the drawings, and their description will be omitted. The second embodiment differs from the first embodiment in that a fluid thermometer 205 is provided instead of the flow meter 201.

[0063] As shown in FIG. 7 , in the liquefied hydrogen pump 101 of the liquefied hydrogen pump system 100 of this embodiment, the seal unit 9B is equipped with, for example, a thermometer 205 as the information acquisition unit 200. The thermometer 205 is, for example, a thermocouple that detects the temperature of the fluid flowing through the flow path 95, i.e., the temperature of hydrogen that has leaked from the cylinder body 20 side through the gap between the first seal member 91 and the rod 8 and into the gap S. The thermometer 205 as the information acquisition unit 200 outputs the detected value of the temperature of the fluid flowing through the flow path 95 to the control device 60. As shown in FIG. 8 , the lower the fluid temperature detected by the thermometer 205 after a certain period of time, the greater the estimated flow rate of hydrogen (fluid) leaking from the cylinder body 20 side through the gap between the first seal member 91 and the rod 8 and flowing into the gap S. The thermocouple that is the thermometer 205 is preferably located as close to the lower first seal member 91 as possible in the flow path 95. This allows a temperature drop caused by the influence of hydrogen passing between the first seal member 91 and the rod 8 to be detected with better response.

[0064] (Processing Procedure) As shown in FIG. 9, the control method for a liquefied hydrogen pump system according to an embodiment of the present disclosure includes a hydrogen concentration detection step S10, a hydrogen concentration determination step S11, a temperature detection step S22, a temperature determination step S23, an atmospheric temperature detection step S14, an atmospheric temperature determination step S15, automatic shutdown steps S16 to S18, and a restart step S19.

[0065] In the hydrogen concentration detection step S10, the hydrogen concentration detection unit 202 detects the hydrogen concentration in the atmosphere in the atmosphere circulation unit 39.

[0066] In hydrogen concentration determination step S11, the pump control unit 72 determines whether the hydrogen concentration in the atmosphere detected by the hydrogen concentration detection unit 202 is less than a preset hydrogen concentration threshold value. If the result of the determination is that the hydrogen concentration in the atmosphere detected by the hydrogen concentration detection unit 202 is less than the preset hydrogen concentration threshold value (Yes in step S11), the process proceeds to step S22.

[0067] On the other hand, if the hydrogen concentration in the atmosphere detected by the hydrogen concentration detection unit 202 is equal to or higher than the predetermined hydrogen concentration threshold value (No in step S11), it is determined that hydrogen is leaking from between the second sealing member 92 and the rod 8, and as in the first embodiment described above, the system proceeds sequentially to automatic stop step S16 and restart step S19.

[0068] In a temperature detection step S22, the thermometer 205 serving as the information acquisition unit 200 detects the temperature of the fluid (hydrogen) flowing through the flow path unit 95. The detected value of the fluid temperature detected by the information acquisition unit 200 is output to the control device 60. In a temperature determination step S23, the pump control unit 72 determines whether the temperature of the fluid detected by the thermometer 205 is equal to or higher than a preset temperature threshold. As a result, if the temperature of the fluid flowing through the flow path unit 95 detected by the thermometer 205 is equal to or higher than the preset temperature threshold (Yes in step S23), the process proceeds to step S14.

[0069] On the other hand, if the temperature of the fluid flowing through the flow path portion 95 detected by the thermometer 205 is below a predetermined temperature threshold (No in step S23), it is determined that hydrogen is leaking from between the first seal member 91 and the rod 8, and the process proceeds to automatic stop step S17. In automatic stop step S17, the operation of the liquefied hydrogen pump 101 is stopped. At this time, in addition to stopping the operation of the liquefied hydrogen pump 101, information indicating that the temperature of the flow path portion 95 is equal to or higher than the temperature threshold may be output. If the operation of the liquefied hydrogen pump 101 is stopped in automatic stop step S17, the operator or worker takes countermeasures to suppress a drop in the temperature of the fluid in the flow path portion 95, such as by replacing the first seal member 91. After completing the countermeasures, the operator or worker performs a predetermined operation to restart the liquefied hydrogen pump 101. When a predetermined operation input for restarting the liquefied hydrogen pump 101 is made, the control device 60 restarts the liquefied hydrogen pump 101 (step S19).

[0070] In an atmospheric temperature detection step S14, the atmospheric temperature detection unit 203 detects the temperature of the atmosphere in the atmospheric circulation unit 39. In an atmospheric temperature determination step S15, the pump control unit 72 determines whether the atmospheric temperature detected by the atmospheric temperature detection unit 203 is equal to or higher than a preset atmospheric temperature threshold. As a result, if the atmospheric temperature detected by the atmospheric temperature detection unit 203 is equal to or higher than the preset atmospheric temperature threshold (Yes in step S15), the series of processes ends.

[0071] On the other hand, if the atmospheric temperature detected by the atmospheric temperature detection unit 203 is lower than the preset atmospheric temperature threshold (No in step S15), it is determined that there is a risk of moisture in the air freezing within the atmospheric circulation unit 39, and the process proceeds sequentially to automatic stop step S18 and restart step S19.

[0072] (Effects) In the liquefied hydrogen pump system 100 configured as described above, the temperature of the fluid in the flow path 95 is acquired as information related to the hydrogen concentration. If the acquired fluid temperature is below a preset temperature threshold, the control device 60 determines that the hydrogen concentration in the fluid has exceeded a preset reference value, and can stop the operation of the liquefied hydrogen pump 101. As a result, the hydrogen concentration in the surrounding atmosphere can be kept below the set reference value.

[0073] (Third Embodiment) Next, a third embodiment of the liquefied hydrogen pump system and the control method for the liquefied hydrogen pump system according to the present disclosure will be described. In the third embodiment described below, components common to the first embodiment will be denoted by the same reference numerals in the drawings, and description thereof will be omitted. The third embodiment differs from the first embodiment in that it includes a heater 98. In addition to the components shown in the first embodiment, the third embodiment includes a heater 98.

[0074] As shown in Figure 10, in the liquefied hydrogen pump 101 of the liquefied hydrogen pump system 100 of this embodiment, the seal portion 9C further includes a heater 98 that heats the second seal member 92. The heater 98 is provided, for example, on the upper surface of the expanded diameter portion 90b of the seal portion main body 90, at a position that overlaps with the second seal member 92 when viewed from above. The heater 98 may be provided over the entire upper surface of the expanded diameter portion 90b. Alternatively, the heater 98 may be embedded in the expanded diameter portion 90b.

[0075] In this embodiment, the control device 60 heats the second sealing member 92 by the heater 98 when the atmospheric temperature detected by the atmospheric temperature detection unit 203 is lower than a preset temperature threshold value.

[0076] (Processing Procedure) As shown in FIG. 11 , the control method for a liquefied hydrogen pump system according to an embodiment of the present disclosure includes a hydrogen concentration detection step S10, a hydrogen concentration determination step S11, a flow rate detection step S12, a flow rate determination step S13, an atmospheric temperature detection step S14, an atmospheric temperature determination step S15, automatic stop steps S16 and S17, a heater activation step S28, and a restart step S19.

[0077] In this embodiment, heater activation step S28 is executed when the atmospheric temperature detected by the atmospheric temperature detection unit 203 in atmospheric temperature determination step S15 is below the atmospheric temperature threshold (No in step S15). In heater activation step S28, the pump control unit 72 stops operation of the liquefied hydrogen pump 101 and activates the heater 98. This increases the temperature of the second seal member 92, the vicinity of the second seal member 92, and the interior of the atmospheric circulation unit 39, thereby preventing moisture in the air from freezing within the atmospheric circulation unit 39. After the atmospheric temperature has risen to or above the atmospheric temperature threshold in heater activation step S28, the operator or worker performs a predetermined operation to restart the liquefied hydrogen pump 101. The control device 60 restarts the liquefied hydrogen pump 101 (step S19).

[0078] (Operation and Effect) In the liquefied hydrogen pump system 100 configured as described above, as in the first embodiment, when the atmospheric temperature is below a preset atmospheric temperature threshold, the operation of the liquefied hydrogen pump 101 is stopped. This prevents the liquefied hydrogen pump 101 from operating in a temperature environment where moisture in the air freezes, thereby preventing damage to the second seal member 92. As a result, hydrogen leakage from between a damaged second seal member 92 and the rod 8 can be prevented.

[0079] Furthermore, the seal unit 9C further includes a heater 98 that heats the second seal member 92, and the control device 60 causes the heater 98 to heat the second seal member 92 and its vicinity when the atmospheric temperature detected by the atmospheric temperature detection unit 203 is below a preset temperature threshold. In this way, when the atmospheric temperature is below the preset atmospheric temperature threshold, heating by the heater 98 prevents moisture in the atmosphere from freezing. As a result, damage to the second seal member 92 due to frozen moisture can be prevented, and hydrogen leakage from between the second seal member 92 and the rod 8 can be prevented.

[0080] Furthermore, similar to the first embodiment, the operation of the liquefied hydrogen pump 101 is stopped when it is determined that the hydrogen concentration in the fluid exceeds a preset reference value based on the information on the hydrogen concentration acquired by the information acquisition unit 200. In this way, in the event of a leak of liquefied hydrogen, the operation of the liquefied hydrogen pump 101 is stopped by detecting a change in the hydrogen concentration, and the hydrogen concentration in the surrounding atmosphere can be kept below the set reference value.

[0081] (First Modification of the Embodiment) Although the embodiment of the present disclosure has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and design modifications and the like are also included within the scope of the gist of the present disclosure. For example, as shown in Figure 12, a dust seal 99 may be provided in the atmosphere vent portion 39 as the seal portion 9D of the liquefied hydrogen pump system 100.

[0082] The dust seal 99 is provided in the expanded diameter portion 90b of the seal portion main body 90. The dust seal 99 integrally includes a fixed portion 99a fixed to the expanded diameter portion 90b and a protruding portion 99b extending radially inward from the upper end of the fixed portion 99a. The protruding portion 99b is formed to overlap with the second seal member 92 when viewed from above. This prevents foreign matter that has entered the air vent portion 39 from reaching the second seal member 92.

[0083] Furthermore, it is preferable that the protruding portion 99b be provided at a distance radially outward from the outer peripheral surface of the rod 8. This makes it possible to prevent hydrogen that has leaked from between the second seal member 92 and the rod 8 from accumulating between the rod 8 and the dust seal 99. To prevent hydrogen from accumulating, the dust seal 99 may be formed from a mesh-like material, a porous material, or the like. In this case, it is preferable to use a mesh-like material or a porous material with an opening size that allows hydrogen to pass through while preventing foreign matter from entering.

[0084] With this configuration, the dust seal 99 provided in the atmospheric circulation section 39 can prevent foreign matter present in the atmosphere flowing through the atmospheric circulation section 39 from entering the gap S between the rod 8 and the second seal member 92.

[0085] Second Modification of the Embodiment As shown in FIG. 13, a seal portion 9E of the liquefied hydrogen pump system 100 may be provided with a recess 300 in a seal portion main body 90E.

[0086] The recess 300 is formed in the insertion tube portion 90a of the seal portion main body 90E. The recess 300 is formed in the insertion tube portion 90a of the seal portion main body 90E, which constitutes the cylinder 2, between the first seal member 91 and the second seal member 92. The recess 300 is formed in the insertion tube portion 90a below an inner wall surface 94, which is formed at a distance from the outer peripheral surface of the rod 8 to the radially outer side of the rod 8. The recess 300 is recessed radially outward from the inner wall surface 94. The recess 300 is formed continuously in the circumferential direction around the axis O. A bottom surface 300b of the recess 300 is inclined obliquely downward from the radially inner side to the outer side. A guide portion 301 is provided on the bottom surface 300b and protrudes radially inward relative to the inner wall surface 94. The guide portion 301 extends obliquely upward from the radially outer side to the radially inner side.

[0087] In this way, by providing the recess 300 at a position below the inner wall surface 94, wear debris and the like from the second seal member 92 generated by sliding between the second seal member 92 and the rod 8 can be collected in the recess 300. In particular, by providing the guide portion 301 in the recess 300, wear debris falling from the second seal member 92 can be efficiently guided into the recess 300 and collected. This makes it possible to prevent foreign matter and the like generated by sliding between the second seal member 92 and the rod 8 from reaching the sliding portion between the first seal member 91 and the rod 8 below when the rod 8 moves in the direction of the axis O. This makes it possible to prevent damage to the first seal member 91 caused by foreign matter and the like generated by sliding between the second seal member 92 and the rod 8.

[0088] Other Embodiments In addition to the above, the configurations shown in the above embodiments and their modifications may be combined as appropriate. Furthermore, the order of the steps in the control method for the liquefied hydrogen pump system shown in the above embodiments and the threshold values ​​used for various determinations may be changed as appropriate.

[0089] <Additional Notes> The liquefied hydrogen pump system 100 and the control method for the liquefied hydrogen pump system 100 described in each embodiment can be understood, for example, as follows.

[0090] (1) A liquefied hydrogen pump system 100 according to a first aspect is a liquefied hydrogen pump system 100 including a liquefied hydrogen pump 101 that compresses liquefied hydrogen and a control device 60 that controls the operation of the liquefied hydrogen pump 101, wherein the liquefied hydrogen pump 101 includes a cylindrical cylinder 2 extending in an axial direction O, a piston 1 that is provided in the cylinder 2 so as to be reciprocable in the axial direction O, compresses the liquefied hydrogen introduced into the cylinder 2 from the outside, and discharges the liquefied hydrogen to the outside of the cylinder 2, a rod 8 that has one end connected to the piston 1 in the cylinder 2 and the other end protruding outside the cylinder 2, a drive unit 3 that is connected to the other end of the rod 8 and reciprocates the piston 1 in the axial direction O within the cylinder 2 via the rod 8, and seal units 9A to 9E that seal a gap S between the rod 8 and the cylinder 2, and the seal units 9A to 9E are a first seal member 91 that seals a gap S between the rod 8 and the cylinder 2; a second seal member 92 that is provided at a distance from the first seal member 91 in a direction away from the piston 1 in the direction of the axis O and that seals between the rod 8 and the cylinder 2; a flow path portion 95 that is formed in the cylinder 2 and has one end that communicates with the gap S between the rod 8 and the cylinder 2 between the first seal member 91 and the second seal member 92 and the other end that opens to the outside of the cylinder 2; and an information acquisition unit 200 that acquires information about the hydrogen concentration in the fluid that flows out to the outside of the cylinder 2 through the flow path portion 95. The control device 60 stops the operation of the liquefied hydrogen pump 101 when it is determined that the hydrogen concentration in the fluid has exceeded a predetermined reference value based on the information about the hydrogen concentration acquired by the information acquisition unit 200.

[0091] In this liquefied hydrogen pump system 100, the drive unit 3 reciprocates the piston 1 in the axial direction O within the cylinder 2 via the rod 8, thereby compressing liquefied hydrogen introduced into the cylinder 2 from the outside and discharging it out of the cylinder 2. If some of the liquefied hydrogen in the cylinder 2 leaks through the gap S between the first seal member 91 and the outer peripheral surface of the rod 8, the liquefied hydrogen, or hydrogen gas generated by the evaporation of the liquefied hydrogen, flows into the gap S between the rod 8 and the cylinder 2 between the first seal member 91 and the second seal member 92. The hydrogen that flows into the gap S between the rod 8 and the cylinder 2 flows as a fluid through the flow path unit 95 and is discharged to the outside of the cylinder 2. The information acquisition unit 200 acquires information regarding the hydrogen concentration in the fluid flowing to the outside of the cylinder 2 through the flow path unit 95. As hydrogen flows through the flow path unit 95, the information regarding the hydrogen concentration acquired by the information acquisition unit 200 changes. The control device 60 stops the operation of the liquefied hydrogen pump 101 when it determines that the hydrogen concentration in the fluid has exceeded a preset reference value based on the information on the hydrogen concentration acquired by the information acquisition unit 200. In this way, if liquefied hydrogen leaks, the control device 60 can detect a change in the hydrogen concentration and stop the operation of the liquefied hydrogen pump 101, thereby suppressing the hydrogen concentration in the surrounding atmosphere to below the set reference value.

[0092] (2) The liquefied hydrogen pump system 100 according to the second aspect is the liquefied hydrogen pump system 100 of (1), in which the information acquisition unit 200 acquires the flow rate of the fluid as information relating to the hydrogen concentration, and the control device 60 stops the operation of the liquefied hydrogen pump 101 when the flow rate of the fluid is equal to or greater than a preset flow rate threshold.

[0093] As a result, when a portion of the liquefied hydrogen in the cylinder 2 passes through the gap S between the first seal member 91 and the outer peripheral surface of the rod 8, the hydrogen (liquefied hydrogen or hydrogen gas) that has flowed into the gap S between the rod 8 and the cylinder 2 flows as a fluid through the flow path portion 95. Therefore, the greater the flow rate of the fluid flowing through the flow path portion 95, the greater the amount of hydrogen leakage. In this way, the flow rate of the fluid in the flow path portion 95 is acquired as information regarding the hydrogen concentration, and when the flow rate of the fluid is equal to or greater than a predetermined flow rate threshold, the control device 60 determines that the hydrogen concentration in the fluid has exceeded a predetermined reference value and can stop the operation of the liquefied hydrogen pump 101. As a result, the hydrogen concentration in the surrounding atmosphere can be kept below the specified reference value.

[0094] (3) The liquefied hydrogen pump system 100 according to a third aspect is the liquefied hydrogen pump system 100 according to (1) or (2), wherein the information acquisition unit 200 acquires the temperature of the fluid as information relating to the hydrogen concentration, and the control device 60 stops the operation of the liquefied hydrogen pump 101 when the temperature of the fluid is below a preset temperature threshold value.

[0095] As a result, when a portion of the liquefied hydrogen in the cylinder 2 passes through the gap S between the first seal member 91 and the outer peripheral surface of the rod 8, the hydrogen that has flowed into the gap S between the rod 8 and the cylinder 2 flows as a fluid through the flow path portion 95. The greater the flow rate of hydrogen flowing through the flow path portion 95, the lower the temperature of the fluid. Therefore, the temperature of the fluid in the flow path portion 95 is acquired as information regarding the hydrogen concentration, and if the temperature of the fluid is below a predetermined temperature threshold, the control device 60 can determine that the hydrogen concentration in the fluid has exceeded a predetermined reference value and stop the operation of the liquefied hydrogen pump 101. As a result, the hydrogen concentration in the surrounding atmosphere can be kept below a specified reference value.

[0096] (4) The liquefied hydrogen pump system 100 according to a fourth aspect is the liquefied hydrogen pump system 100 of any one of (1) to (3), wherein the sealing parts 9A to 9E further include an atmospheric temperature detection part 203 that detects the atmospheric temperature outside the cylinder 2, and the control device 60 stops the operation of the liquefied hydrogen pump 101 when the atmospheric temperature detected by the atmospheric temperature detection part 203 is lower than a preset atmospheric temperature threshold value.

[0097] If the atmospheric temperature is low enough to freeze the moisture in the air, there is a risk that the frozen moisture (ice) will damage the second seal member 92. In response to this, the operation of the liquefied hydrogen pump 101 is stopped when the atmospheric temperature is below a preset atmospheric temperature threshold. This prevents the liquefied hydrogen pump 101 from operating in a temperature environment where the moisture in the air would freeze, thereby preventing damage to the second seal member 92. As a result, hydrogen leakage from between a damaged second seal member 92 and the rod 8 can be prevented.

[0098] (5) The liquefied hydrogen pump system 100 according to a fifth aspect is the liquefied hydrogen pump system 100 of (4), wherein the sealing unit 9C further includes a heater 98 that heats the second sealing member 92, and the control device 60 heats the second sealing member 92 with the heater 98 when the atmospheric temperature detected by the atmospheric temperature detection unit 203 is lower than a preset temperature threshold value.

[0099] As a result, when the atmospheric temperature is below a preset atmospheric temperature threshold, the heater 98 heats the second seal member 92, thereby raising the temperature of the second seal member 92 and its vicinity. This prevents moisture in the air from freezing, even in a temperature environment where moisture in the air would freeze. As a result, damage to the second seal member 92 due to frozen moisture can be prevented, and hydrogen leakage from between the second seal member 92 and the rod 8 can be prevented.

[0100] (6) The liquefied hydrogen pump system 100 according to a sixth aspect is the liquefied hydrogen pump system 100 of any one of (1) to (5), wherein the sealing parts 9A to 9E further include a hydrogen concentration detection part 202 that detects the hydrogen concentration in the atmosphere outside the cylinder 2, and the control device 60 stops the operation of the liquefied hydrogen pump 101 when the hydrogen concentration in the atmosphere detected by the hydrogen concentration detection part 202 is equal to or greater than a predetermined hydrogen concentration threshold value.

[0101] This allows the operation of the liquefied hydrogen pump 101 to be stopped when the hydrogen concentration in the atmosphere is above a predetermined hydrogen concentration threshold, thereby preventing the hydrogen concentration in the atmosphere from increasing further due to hydrogen leaking from the liquefied hydrogen pump 101.

[0102] (7) The liquefied hydrogen pump system 100 according to a seventh aspect is the liquefied hydrogen pump system 100 according to any one of (1) to (6), wherein the seal portions 9A to 9E are formed in the cylinder 2, and further includes an inert gas supply passage portion 96 through which an inert gas is supplied from outside the cylinder 2 to a gap S between the rod 8 and the cylinder 2 between the first seal member 91 and the second seal member 92.

[0103] As a result, when inert gas is supplied from outside the cylinder 2 through the inert gas supply flow path 96, the gap S between the rod 8 and the cylinder 2, between the first seal member 91 and the second seal member 92, and the flow path 95 communicating with this gap S, can be filled with inert gas. Therefore, by filling the liquefied hydrogen pump 101 in its initial state before operation with inert gas, even if hydrogen flows into the gap S between the rod 8 and the cylinder 2, the hydrogen will flow into the oxygen-free inert gas. This prevents the hydrogen concentration in the atmosphere from reaching the lower explosion limit, allowing the liquefied hydrogen pump system to be operated safely.

[0104] (8) The liquefied hydrogen pump system 100 according to the eighth aspect is the liquefied hydrogen pump system 100 of (7), wherein the inert gas has a specific gravity lower than that of the atmosphere, and one end of the inert gas supply flow path 96 is in communication with the gap S between the rod 8 and the cylinder 2 at a position above one end of the flow path 95.

[0105] As a result, when inert gas is supplied from outside the cylinder 2 through the inert gas supply flow path 96, the air that is present in the inert gas supply flow path 96 and in the gap S between the rod 8 and the cylinder 2 at that time is pushed downward as the inert gas is supplied. As a result, the pushed air is pushed out from the gap S between the rod 8 and the cylinder 2 through the flow path 95 to the outside of the liquefied hydrogen pump 101. In this way, the air inside the liquefied hydrogen pump 101 can be efficiently replaced with inert gas. An example of an inert gas that has a specific gravity smaller than that of air is helium.

[0106] (9) The liquefied hydrogen pump system 100 according to the ninth aspect is any one of the liquefied hydrogen pump systems 100 of (1) to (8), in which the distance D between the first seal member 91 and the second seal member 92 in the direction of the axis O is greater than the movement stroke of the rod 8 in the direction of the axis O.

[0107] As a result, by making the distance D between the first seal member 91 and the second seal member 92 larger than the movement stroke of the rod 8, foreign matter, etc. generated by the sliding of the second seal member 92 and the rod 8 when the rod 8 moves in the direction of the axis O can be prevented from reaching the sliding portion between the first seal member 91 and the rod 8 below. This makes it possible to prevent damage to the first seal member 91 caused by foreign matter, etc. generated by the sliding of the second seal member 92 and the rod 8. Furthermore, it is possible to prevent foreign matter, etc. generated by the sliding of the first seal member 91 and the rod 8 from reaching the sliding portion between the second seal member 92 and the rod 8. This makes it possible to prevent damage to the second seal member 92 caused by foreign matter, etc. generated by the sliding of the first seal member 91 and the rod 8.

[0108] (10) The liquefied hydrogen pump system 100 according to a tenth aspect is the liquefied hydrogen pump system 100 of any one of (1) to (9), further comprising: an air circulating portion 39 formed on the side of the second seal member 92 away from the piston 1 in the direction of the axis O, through which the air circulates; and a dust seal 99 provided within the air circulating portion 39, covering the second seal member 92.

[0109] As a result, the dust seal 99 installed in the atmospheric circulation section 39 can prevent foreign matter present in the atmosphere flowing through the atmospheric circulation section 39 from entering the gap S between the rod 8 and the second seal member 92.

[0110] (11) The liquefied hydrogen pump system 100 according to an eleventh aspect is the liquefied hydrogen pump system 100 of any one of (1) to (10), further comprising: an inner wall surface 94 formed in the cylinder 2 between the first seal member 91 and the second seal member 92, the inner wall surface 94 being spaced apart radially outward from the outer circumferential surface of the rod 8; and a recess 300 formed between the first seal member 91 and the second seal member 92 below the inner wall surface 94, the recess 300 being recessed radially outward from the inner wall surface 94.

[0111] As a result, by providing the recess 300 at a position below the inner wall surface 94, wear powder and the like of the second seal member 92 generated by sliding between the second seal member 92 and the rod 8 can be collected in the recess 300. As a result, when the rod 8 moves in the direction of the axis O, foreign matter and the like generated by sliding between the second seal member 92 and the rod 8 can be prevented from reaching the sliding portion between the first seal member 91 and the rod 8 below. As a result, damage to the first seal member 91 due to foreign matter and the like generated by sliding between the second seal member 92 and the rod 8 can be prevented.

[0112] (12) A control method for a liquefied hydrogen pump system 100 according to a twelfth aspect is a control method for a liquefied hydrogen pump system 100 according to any one of (1) to (11), and includes the steps of acquiring information about the hydrogen concentration in the fluid flowing out of the cylinder 2 through the flow path portion 95, steps S13 and S23 of determining whether the hydrogen concentration in the fluid has exceeded a predetermined reference value based on the acquired information about the hydrogen concentration, and step S17 of stopping the operation of the liquefied hydrogen pump 101 when it is determined that the hydrogen concentration in the fluid has exceeded the predetermined reference value.

[0113] This allows information about the hydrogen concentration in the fluid flowing out of the cylinder 2 to be obtained, and if it is determined based on the obtained information about the hydrogen concentration that the hydrogen concentration in the fluid has exceeded a preset reference value, the operation of the liquefied hydrogen pump 101 is stopped. In this way, if liquefied hydrogen leaks, the change in hydrogen concentration can be detected, and the hydrogen concentration in the surrounding atmosphere can be kept below the set reference value.

[0114] According to the liquefied hydrogen pump system and the control method for the liquefied hydrogen pump system disclosed herein, in the event of a liquefied hydrogen leak, the hydrogen concentration in the surrounding atmosphere can be kept below a specified standard value by detecting changes in the hydrogen concentration.

[0115] DESCRIPTION OF SYMBOLS 1...piston 2...cylinder 3...drive unit 4...casing 4t...upper surface 5...check valve 6...discharge piping 7...discharge valve 8...rod 9A to 9E...seal unit 10...piston body 11...wear ring 12...piston ring 20...cylinder body 21...compression chamber 31...eccentric shaft portion 32...rotating body 33...link portion 33a...upper annular portion 33b...connection portion 33c...lower annular portion 35...oscillating shaft portion 36...crosshead 37...housing 37a...top plate 37b...bottom plate 38...wear band 39...atmospheric circulation portion 39a...atmospheric inlet port 39b...atmospheric outlet port 41...casing body 42...supply pipe 43...gas exhaust pipe 44...liquid storage chamber 45...cylindrical portion 60...control device 61...CPU 62...ROM 63...RAM 64...Storage 65...Communication module 71...Input section 72...Pump control section 73...Command signal output section 90, 90E...Seal section main body 90a...Insertion tube section 90b...Expanded diameter section 90m, 90n...Groove 91...First seal member 92...Second seal member 94...Inner wall surface 95...Flow path section 95a...One end 95b...Other end 95p...Piping 95r...Hydrogen recovery section 95v...Open / close valve 96...Inert gas supply flow path section 96a...One end 96b...Other end 96p...Piping 96v...Open / close valve 98...Heater 99...Dust seal 99a...Fixed section 99b...Protruding section 100...Liquefied hydrogen pump system 101...Liquefied hydrogen pump 200...Information acquisition section 201...Flow meter 202...Hydrogen concentration detection section 203...Atmospheric temperature detection section 205... Thermometer 206... Thermometer 300... Recess 300b... Bottom surface 301... Guide portion O... Axis S... Gap

Claims

1. A liquefied hydrogen pump system comprising: a liquefied hydrogen pump which compresses liquefied hydrogen; and a control device which controls the operation of the liquefied hydrogen pump, wherein the liquefied hydrogen pump comprises: a cylindrical cylinder extending in an axial direction; a piston which is provided within the cylinder so as to be capable of reciprocating in the axial direction, compressing the liquefied hydrogen introduced into the cylinder from the outside and discharging it to the outside of the cylinder; a rod having one end connected to the piston within the cylinder and the other end protruding outside the cylinder; a drive unit which is connected to the other end of the rod and reciprocates the piston in the axial direction within the cylinder via the rod; and a seal unit, wherein the seal unit comprises: a first seal member which seals a gap between the rod and the cylinder; and a second seal member which is provided with a gap from the first seal member in a direction away from the piston in the axial direction, and which seals between the rod and the cylinder. a flow path portion formed in the cylinder, one end of which communicates with the gap between the rod and the cylinder between the first seal member and the second seal member and the other end of which opens to the outside of the cylinder; and an information acquisition unit that acquires information regarding the hydrogen concentration in a fluid flowing out to the outside of the cylinder through the flow path portion, wherein the control device stops operation of the liquefied hydrogen pump when it is determined that the hydrogen concentration in the fluid has exceeded a predetermined reference value based on the information regarding the hydrogen concentration acquired by the information acquisition unit.

2. The liquefied hydrogen pump system according to claim 1, wherein the information acquisition unit acquires the flow rate of the fluid as information relating to the hydrogen concentration, and the control device stops operation of the liquefied hydrogen pump when the flow rate of the fluid is equal to or greater than a preset flow rate threshold.

3. The liquefied hydrogen pump system according to claim 1 or 2, wherein the information acquisition unit acquires the temperature of the fluid as information relating to the hydrogen concentration, and the control device stops operation of the liquefied hydrogen pump when the temperature of the fluid is below a preset temperature threshold value.

4. The liquefied hydrogen pump system according to claim 1 or 2, wherein the sealing portion further comprises an atmospheric temperature detection portion which detects the atmospheric temperature outside the cylinder, and the control device stops operation of the liquefied hydrogen pump when the atmospheric temperature detected by the atmospheric temperature detection portion is lower than a preset atmospheric temperature threshold value.

5. The liquefied hydrogen pump system according to claim 4, wherein the sealing unit further comprises a heater for heating the second sealing member, and the control device heats the second sealing member using the heater when the atmospheric temperature detected by the atmospheric temperature detection unit is lower than a preset atmospheric temperature threshold value.

6. The liquefied hydrogen pump system according to claim 1 or 2, wherein the sealing portion further comprises a hydrogen concentration detection portion which detects the hydrogen concentration in the atmosphere outside the cylinder, and the control device stops operation of the liquefied hydrogen pump when the hydrogen concentration in the atmosphere detected by the hydrogen concentration detection portion is equal to or higher than a predetermined hydrogen concentration threshold value.

7. The liquefied hydrogen pump system according to claim 1 or 2, wherein the sealing portion further comprises an inert gas supply passage portion formed in the cylinder, through which an inert gas is supplied from outside the cylinder to a gap between the rod and the cylinder.

8. The liquefied hydrogen pump system according to claim 7, wherein the inert gas has a specific gravity smaller than that of air, and one end of the inert gas supply passage portion is in communication with the gap between the rod and the cylinder at a position above one end of the passage portion.

9. The liquefied hydrogen pump system according to claim 1 or 2, wherein the distance between the first seal member and the second seal member in the axial direction is greater than the movement stroke of the rod in the axial direction.

10. The liquefied hydrogen pump system according to claim 1 or 2, further comprising: an air circulation section formed on a side of the second seal member away from the piston in the axial direction, through which air flows; and a dust seal provided within the air circulation section, covering a gap between the rod and the second seal member.

11. The liquefied hydrogen pump system according to claim 1 or 2, further comprising: an inner wall surface formed in the cylinder between the first seal member and the second seal member, the inner wall surface being spaced apart radially outward from the outer circumferential surface of the rod; and a recess formed below the inner wall surface between the first seal member and the second seal member, the recess being recessed radially outward from the inner wall surface.

12. A control method for a liquefied hydrogen pump system as described in claim 1 or 2, comprising the steps of: acquiring information relating to the hydrogen concentration in the fluid flowing out of the cylinder through the flow path portion; judging whether or not the hydrogen concentration in the fluid has exceeded a preset reference value based on the acquired information about the hydrogen concentration; and stopping operation of the liquefied hydrogen pump when it is determined that the hydrogen concentration in the fluid has exceeded the preset reference value.

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