Gas filling method

Abstract

To provide a method for filling a gas which enables a tank to be accurately filled up to a fully-filled tank pressure in a short time.SOLUTION: A method for filling a gas for supplying a gas into a tank (50) through a flow rate regulating valve (28) and piping (100) from a pressure accumulator (20) to fill the tank with the gas includes the steps of: setting a target pressure rise rate (Rptar) that is a temporal change of a target tank pressure (Pt_tar) when filling the tank with the gas; and controlling the flow rate regulating valve (28) during filling the tank with the gas so that a dispenser pressure (Pd) that is a gas pressure of the pressure accumulator becomes larger than the target tank pressure and becomes a pressure capable of maintaining the target pressure rise rate that is a temporal change of a tank pressure.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This invention relates to a gas filling method for filling a fuel gas (gas) from a gas accumulator to a tank via a pipe.

Background Art

[0002] In recent years, in order to enable more people to access affordable, reliable, sustainable, and advanced energy, research and development have been conducted on fuel cells (FCs) that contribute to energy efficiency.

[0003] For example, a fuel cell vehicle is equipped with the fuel cell, a tank for storing fuel gas, and a motor. The fuel cell generates electricity through an electrochemical reaction between the fuel gas supplied from the tank and an oxidant gas (air). The fuel cell vehicle runs by driving the motor using the electricity generated by the fuel cell.

[0004] The tank mounted on a fuel cell vehicle is filled with gas (fuel gas) via a pipe (including a hose) at a filling station (hydrogen station). The hydrogen station includes a high-pressure gas accumulator.

[0005] "Compressed hydrogen filling technology standards" such as JPEC-S 0003 (Non-Patent Document 1) or SAEJ2601 are applied to the filling control of fuel gas (compressed hydrogen) to the fuel cell vehicle, etc. at the hydrogen station.

[0006] In the "compressed hydrogen filling technology standards", considering that the pressure loss due to the pipe connecting the accumulator and the tank changes depending on conditions such as temperature, filling control is implemented based on the detection value of the pressure sensor provided at the hydrogen station.

[0007] In the "compressed hydrogen filling technology standards", filling control is implemented so that the time change (pressure increase rate) of the gas pressure at the hydrogen station detected by the pressure sensor becomes constant (see FIG. 2 on page 12 of Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0008] [Non-Patent Document 1] Refer to "Target Pressure Increase Rate" in Appendix 1 of JPEC-S 0003 (2016), Technical Standards for Compressed Hydrogen Filling, draft by the Japan Petroleum Energy Technology Center. [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] By the way, if there is a large pressure loss in the piping connecting the gas accumulator and the tank, there is a problem in that the pressure inside the tank does not rise easily, and it takes a long time for the tank to be filled to capacity.

[0010] This invention aims to solve the problems described above. [Means for solving the problem]

[0011] A gas filling method according to one aspect of this invention is a gas filling method that connects a tank and a gas accumulator with piping, supplies gas from the accumulator to the tank via the piping, and fills the tank with gas, comprising: a target pressure increase rate setting step of setting a target pressure increase rate which is the time change of a target tank pressure when filling the tank with gas; and a flow rate control step of adjusting the flow rate of gas supplied from the accumulator to the tank during the filling of the tank with gas so that the dispenser pressure, which is the gas pressure of the accumulator, is greater than the target tank pressure and is a pressure that can maintain the target pressure increase rate. [Effects of the Invention]

[0012] This invention allows for rapid and accurate filling of a tank to its full capacity, thereby contributing to improved energy efficiency. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a configuration diagram of a hydrogen filling system according to an embodiment to which the gas filling method according to the embodiment is applied. [Figure 2] Figure 2 is a block diagram showing the configuration of a flow rate adjustment signal generation unit achieved by the arithmetic function of the dispenser ECU and the like. [Figure 3] Figure 3 is a target boost rate map. [Figure 4] Figure 4 is a timing chart showing the temporal changes in the tank pressure and the dispenser pressure. [Figure 5] Figure 5 is a flowchart for explaining the operation of a hydrogen filling system according to an embodiment to which the gas filling method according to the embodiment is applied. [Figure 6] Figure 6 is a flowchart of a gas refill subroutine. [Figure 7] Figure 7 is a flowchart of a leak check subroutine. [Figure 8] Figure 8 is a timing chart showing the temporal changes in the dispenser pressure and the flow rate detected during the leak check. [Figure 9] Figure 9 is a timing chart for comparative explanation of the gas filling method according to the embodiment and the gas filling method according to the comparative example.

Embodiments for Carrying Out the Invention

[0014] [Configuration of Hydrogen Filling System] Figure 1 shows the configuration of a hydrogen filling system 10 according to an embodiment to which the gas filling method according to the embodiment is applied.

[0015] The hydrogen filling system 10 is composed of a hydrogen station 14, which is a filling station (filling stand) shown on the left side of the two-dot chain line, and a fuel cell vehicle (vehicle) 16 shown on the right side of the two-dot chain line.

[0016] The hydrogen station 14 has an accumulator 20, which is a supply source of hydrogen gas (gas), which is a fuel gas.

[0017] The vehicle 16 is equipped with a hydrogen tank (tank) 50 that fills with the gas supplied from the accumulator 20.

[0018] In addition to the tank 50 that stores the filled gas, the vehicle 16 includes a fuel cell (not shown) and a motor for running (not shown).

[0019] The fuel cell generates electricity through an electrochemical reaction between the fuel gas supplied from the tank 50 and the oxidant gas (air) supplied from a compressor (not shown).

[0020] The vehicle 16 is a fuel cell vehicle that runs by driving the motor using the electricity generated by the fuel cell.

[0021] Fuel cell vehicles include relatively small passenger cars and large vehicles such as buses and trucks.

[0022] A fuel cell vehicle is a moving body that has a tank 50 for storing gas and the fuel cell and travels on the ground.

[0023] The moving body to which this invention is applied is not limited to the moving body traveling on the ground, and includes airplanes, ships, submarines, etc.

[0024] As shown in FIG. 1, the hydrogen station 14 has a dispenser ECU (Electronic Control Unit) 22, and the vehicle 16 has a communication ECU 52.

[0025] In FIG. 1, the communication ECU 52 drawn with a dashed line and the components related to the communication ECU 52 are not necessary for implementing (using) the gas filling method according to the embodiment.

[0026] The dispenser ECU 22 and the communication ECU 52 are control devices, and are constituted by a computer having one or more processors (CPUs), a memory (storage device), a timer (timer), a counter (counter), an input / output interface, and an electronic circuit.

[0027] One or more of the aforementioned processors (CPUs) execute the program stored in the memory. In addition to the program, the memory also stores data such as acquired physical quantities and various control maps referenced by said data.

[0028] The processor (CPU) performs calculations (various functions) according to the program, referring to the control map as needed based on the acquired physical quantities, etc.

[0029] In Figure 1, the vehicle 16 includes vehicle piping (piping) 56 extending from the tank 50 to the receptacle 54, and a communication device 58 that transmits and receives data signals Dt to and from the hydrogen station 14 using infrared or the like.

[0030] The vehicle piping 56 connecting the tank 50 and the receptacle 54 is equipped with a dust filter 60 and a check valve 62 located near the receptacle 54 to prevent gas from flowing back from the tank 50 to the receptacle 54.

[0031] A tank temperature sensor 64 is installed inside the tank 50, and a pressure sensor 66 is installed in the vehicle piping 56 near the tank 50.

[0032] The communication ECU 52 acquires the tank temperature Tt detected by the tank temperature sensor 64 and the tank pressure Pt detected by the pressure sensor 66, and generates a data signal Dt.

[0033] The generated data signal Dt is sent to the dispenser ECU 22 via the communication device 58 and then through the communication device 38 installed at the hydrogen station 14.

[0034] The communication device 38 installed at the hydrogen station 14 is integrally attached to the nozzle 48.

[0035] When the nozzle 48 of the hydrogen station 14 is connected to the receptacle 54 of the vehicle 16, the communication device 38 faces the communication device 58 installed on the vehicle 16. This enables the transmission and reception of data signals Dt and the like via wireless means such as infrared between the communication devices 38 and 58.

[0036] The accumulator 20 of the hydrogen station 14 stores high-pressure hydrogen gas for supply to the tank 50 of the vehicle 16.

[0037] The accumulator 20 is equipped with a shut-off valve 24. Station piping 46, which extends from the shut-off valve 24 to the nozzle 48, is connected between the shut-off valve 24 and the nozzle 48.

[0038] The accumulator 20 and the tank 50 are connected (in communication) by a piping 100 consisting of station piping 46 and vehicle piping 56.

[0039] The station piping (pipe) 46 is equipped with a mass flow meter (MFM) 26, a flow control valve 28, a pre-cooler (Pcool) 30, and a breakaway (BA) 32, extending from the shut-off valve 24 towards the nozzle 48. Within the piping 46, the section between the breakaway 32 and the nozzle 48 is configured as a flexible hose.

[0040] A pressure sensor 34 and a temperature sensor 36 are provided in the piping 46 between the precooler 30 and the breakaway 32.

[0041] The pressure sensor 34 detects the gas pressure in the accumulator 20 (hydrogen station 14) when the shut-off valve 24 is open as the dispenser pressure (gas pressure) Pd. The temperature sensor 36 detects the temperature of the gas supplied from the accumulator 20 as the dispenser temperature (dispenser gas temperature) Td.

[0042] The flow sensor 26 detects the mass flow rate (flow rate) m [kg / s] of the gas flowing through the pipe 100.

[0043] The dispenser pressure Pd, dispenser gas temperature Td, and flow rate m, detected by the pressure sensor 34, temperature sensor 36, and flow rate sensor 26, respectively, are acquired as physical quantities by the dispenser ECU 22.

[0044] The shut-off valve 24 opens and closes in response to an on / off signal Soc output from the dispenser ECU 22. The shut-off valve 24 transitions from the open state to the closed state in response to a closed on / off signal Soc and maintains the closed state. The shut-off valve 24 transitions from the closed state to the open state in response to an open on / off signal Soc and maintains the open state.

[0045] The flow control valve 28 can have its opening degree continuously adjusted by the flow control signal Sas output from the dispenser ECU 22. In other words, the flow control valve 28, whose opening degree is adjusted by the flow control signal Sas, can continuously adjust the gas flow rate in the piping 100. By adjusting the gas flow rate in the piping 100, the dispenser pressure Pd is controlled (adjusted).

[0046] The precooler 30 cools the gas supplied from the accumulator 20 to the vehicle piping 56 before it is filled into the tank 50, thereby suppressing the temperature rise of the gas in the tank 50 and enabling rapid filling.

[0047] The breakaway 32 is a safety device connected between the accumulator 20 and the nozzle 48. If the nozzle 48 is dragged by a strong external force, the breakaway 32 automatically closes its valve to seal the flow path and shut off the gas flow.

[0048] The hydrogen station 14 is equipped with an atmospheric temperature sensor (temperature sensor) 42 that detects the air temperature Ta. The air temperature Ta detected by the temperature sensor 42 is acquired by the dispenser ECU 22.

[0049] [Summary of the gas filling method according to the embodiment] The hydrogen refueling system 10 to which the gas refueling method according to the embodiment is applied is basically configured as described above. Now, the outline of the gas refueling method according to the embodiment will be explained.

[0050] (i) The dispenser ECU22 sets the target pressure increase rate Rptar, which is the rate of change of the tank pressure Pt over time. The target pressure increase rate Rptar can be set to a constant pressure increase rate (linear) or a nonlinear pressure increase rate.

[0051] As will be described later with reference to Figure 3, the target pressure increase rate Rptar is expressed as the target increase in tank pressure Pt over a small predetermined time step Δt [sec], known as the target pressure increase amount ΔPt_next {Rptar=(ΔPt_next) / Δt}.

[0052] (ii) The dispenser ECU 22 adjusts the gas flow rate so that the tank pressure Pt increases by the target pressure increase rate Rptar. That is, the dispenser ECU 22 fills the tank 50 with gas so that the tank pressure Pt increases by the target pressure increase rate Rptar.

[0053] (iii) However, the dispenser ECU22 detects the dispenser pressure Pd but does not detect the tank pressure Pt. The actual tank pressure Pt is lower than the dispenser pressure Pd due to the pressure loss dPloss in the piping 100. Therefore, during gas filling, the dispenser ECU22 predicts the pressure loss dPloss in the piping 100, which changes depending on the state of the gas.

[0054] (iv) The dispenser ECU 22 adjusts the valve opening of the flow control valve 28 so that the dispenser pressure Pd (target pressure) detected by the pressure sensor 34 satisfies the following equation (1). Pd = dPloss + Pt …(1) However, Pd: dispenser pressure (target pressure), dPloss: Pressure loss (predicted value) Pt: Tank pressure (predicted value of tank pressure that rises (changes over time in the positive direction) along the target pressure increase rate Rptar)

[0055] In other words, the dispenser ECU 22 adjusts the valve opening of the flow control valve 28 so that the dispenser pressure Pd becomes the value obtained by adding the pressure loss dPloss (a predicted value, shown as dPloss_estimated in Figure 4) to the tank pressure Pt (undetected), which is calculated moment by moment at each time step Δt.

[0056] [Configuration and operation of the flow rate adjustment signal generation unit] In order to carry out the gas filling method according to the embodiment, it is necessary to calculate the dispenser target pressure Pd_next, which is the increase in dispenser pressure Pd for each minute predetermined time step Δt [sec].

[0057] Figure 2 is a block diagram showing the configuration of the flow rate adjustment signal generation unit 70, which is achieved by the calculation functions of the dispenser ECU 22.

[0058] The flow rate adjustment signal generation unit 70 consists of a dispenser target pressure calculation unit 71 and a target pressure feedback control unit 81.

[0059] As shown in Figure 2, the dispenser target pressure calculation unit 71 consists of a gas density calculation unit 72, a pressure loss coefficient calculation unit 74, a pressure loss calculation unit 76, a target (tank pressure / pressure increase amount) calculation unit 78, a dispenser target pressure calculation unit 80, and a leak check switch 84.

[0060] The target pressure feedback control unit 81 includes a differential amplifier (differential amplifier, output amplifier) ​​82 that functions as a comparator amplifier. The output amplifier 82 amplifies the difference (Pd_next-Pd(current)) so that the current dispenser pressure Pd(current) matches the dispenser target pressure Pd_next, and generates a flow rate adjustment signal Sas.

[0061] The gas density calculation unit 72, which constitutes the dispenser target pressure calculation unit 71, calculates the gas density ρ[kg / m³] of the gas flowing through the piping 100. 3 [As described in ].

[0062] The gas density ρ is calculated based on the ideal gas law by referring to the current dispenser pressure Pd (current) detected by the pressure sensor 34 and the current dispenser gas temperature Td (current) detected by the temperature sensor 36 (see equation (2)). ρ=ρ(Pd(current),Td(current)) …(2)

[0063] The gas density ρ calculated by the gas density calculation unit 72 is output from the gas density calculation unit 72 to the pressure loss coefficient calculation unit 74, and also to the pressure loss calculation unit 76 through the fixed contact Xb and common contact (movable contact) Xa of the leak check switch 84.

[0064] The pressure loss coefficient calculation unit 74 calculates the pressure loss coefficient k0 using equation (3) with respect to the gas density ρ, the current mass flow rate m [kg / s] detected by the flow sensor 26, and the pressure loss dPloss [Mpa] due to the piping 100 calculated by the pressure loss calculation unit 76. k0 = dPloss × ρ / (m(current)) 2 ) …(3)

[0065] Before the pressure loss dPloss is initially calculated, in other words, at the start of filling, a typical value or a provisional value such as the historical average is used for the pressure loss coefficient k0.

[0066] The pressure loss coefficient calculation unit 74 outputs the calculated pressure loss coefficient k0 to the pressure loss calculation unit 76.

[0067] [Calculation of pressure loss dPloss] The pressure loss calculation unit 76 calculates the pressure loss dPloss during the leak check and outputs it to the pressure loss coefficient calculation unit 74.

[0068] The pressure loss dPloss, based on the change in dispenser pressure Pd during a leak check performed while filling tank 50 with gas, is calculated, for example, by the following equation (4). dPloss = Pd(i) - Pd(i+tc) …(4)

[0069] Here, Pd(i) is the dispenser pressure Pd immediately before the leak check, and Pd(i+tc) is the dispenser pressure Pd at the end of the leak check time tc. The leak check time tc is a few seconds, and in this embodiment, tc is set to 3 [s] as an example.

[0070] A leak check is performed periodically to detect gas leaks in the piping 100. During the leak check, the movable contact Xa of the leak check switch 84 is switched from the normally closed fixed contact Xb to the fixed contact (momentary contact) Xc for, for example, a few seconds. During this leak check time (time) tc of a few seconds, the movable contact Xa is connected to the fixed contact Xc.

[0071] Synchronized with this connection (contact switching), the shut-off valve 24 is closed for a period of time tc by the on / off signal Soc supplied from the dispenser ECU 22. During the period when the shut-off valve 24 is closed and the gas supply is shut off, the dispenser ECU 22 monitors whether the dispenser pressure Pd changes to check for gas leaks. If the dispenser pressure Pd changes during the shut-off period, the dispenser ECU 22 determines that there is a gas leak, and if it does not change, it determines that there is no gas leak. If a gas leak is determined, the dispenser ECU 22 generates an abort signal and stops the gas filling process.

[0072] [Calculation of predicted pressure loss dPloss_estimated] The pressure loss calculation unit 76 calculates the predicted pressure loss dPloss_estimated, which is a predicted value of the pressure loss dPloss, at each minute time step Δt when no leak check is performed and gas is being supplied from the accumulator 20 to the tank 50, and outputs it to the dispenser target pressure calculation unit 80.

[0073] The pressure loss calculation unit 76 calculates the predicted pressure loss dPloss_estimated based on the pressure loss coefficient k0, the current gas density ρ, and the current flow rate m (current) using the following equation (5). dPloss_estimated =k0(m(current) 2 / ρ(Pd(current),Td(current))) …(5)

[0074] [Calculation of target tank pressure Pt_tar and target pressure increase ΔPt_next] The target (tank pressure / pressure increase amount) calculation unit 78 calculates (predicts) the target tank pressure Pt_tar and the target pressure increase amount ΔPt_next at each time step Δt.

[0075] Figure 3 shows an example of a target pressure boost rate map 90 pre-recorded in the memory of the dispenser ECU 22, and the time evolution of the target tank pressure Pt_tar as it is boosted according to the target pressure boost rate map 90.

[0076] The target boost rate map 90 records the target boost rate Rptar for each time step Δt along the time axis on the horizontal axis.

[0077] By setting a target pressure boost map 90 with a constant pressure boost rate, where Rptar = (ΔPt_next / Δt) is shown as a solid straight line, filling control becomes simpler, and the continuity of filling control can be easily maintained even when it is paused and restarted midway.

[0078] As shown by the dashed line in Figure 3, for example, the overall boost rate may be nonlinear, with the target boost rate Rptar increasing in the latter half of the process. Note that the boost rate may rise in a straight line (a linear function) or in a gradual upward curve.

[0079] However, the upper limit of the target tank pressure Pt_tar is set to prevent the value of the target tank pressure Pt_tar from exceeding the upper limit of the allowable supply pressure range (which increases linearly) of the dispenser target pressure Pd_next.

[0080] The vertical axis scale in Figure 3, labeled "Targe Tank Pressure Pt_tar," includes both the initial tank pressure P0 and the target tank pressure (full tank pressure) Pt_tarfull.

[0081] The target (tank pressure / pressure increase) calculation unit 78 calculates the target pressure increase ΔPt_next for each time step Δt using equation (6). ΔPt_next = Rptar × Δt …(6)

[0082] The current target tank pressure Pt_tar(current), calculated (predicted) by the target (tank pressure / pressure increase amount) calculation unit 78, increases over time according to equation (7). Pt_tar(current)=Rptar×t(current)+P0…(7) However, t (current) is the cumulative value of the time step Δt from time 0.

[0083] The target pressure increase amount ΔPt_next and the current target tank pressure Pt_tar(current), calculated by the target (tank pressure / pressure increase amount) calculation unit 78, are output from the target (tank pressure / pressure increase amount) calculation unit 78 to the dispenser target pressure calculation unit 80.

[0084] [Calculation of dispenser target pressure Pd_next] The dispenser target pressure calculation unit 80 calculates the dispenser target pressure Pd_next shown in equation (8) based on the predicted (calculated) current target tank pressure Pt_tar(current), the target pressure increase amount ΔPt_next, and the predicted pressure loss dPloss_estimated (see Figure 4). Pd_next =Pt_tar(current)+ΔPt_next+dPloss_estimated …(8)

[0085] According to equation (8), the dispenser target pressure Pd_next is calculated as the sum of the current target tank pressure Pt_tar(current), the target pressure increase ΔPt_next, and the predicted pressure loss dPloss_estimated.

[0086] Equation (9) shows the dispenser target pressure Pd_next obtained by substituting equation (6) for ΔPt_next in equation (8) and equation (5) for dPloss_estimated in equation (8). Pd_next =(Pt_tar(current)+Rptar×Δt) +k0(m(current) 2 / ρ(Pd(current),Td(current))) …(9)

[0087] [Flow rate control by the flow rate adjustment signal generation unit 70 of the dispenser ECU22] The dispenser target pressure calculation unit 71 outputs the dispenser target pressure Pd_next, calculated according to equation (9), to the non-inverting input terminal of the output amplifier 82.

[0088] The current dispenser pressure Pd (current), detected by the pressure sensor 34, is input to the inverting input terminal of the output amplifier 82.

[0089] At each time step Δt, the dispenser ECU 22 adjusts the opening of the flow control valve 28 by changing the flow control signal Sas of the output amplifier 82 so that the current dispenser pressure Pd (current) input to the inverting input terminal of the output amplifier 82 becomes the dispenser target pressure Pd_next (see Figure 4).

[0090] The gas flow rate is adjusted by the flow control valve 28 until the dispenser target pressure Pd_next reaches the full tank pressure Pt_tarfull (see Figure 4).

[0091] As can be seen from equation (8) or (9), detection of tank pressure Pt and tank temperature Tt is unnecessary for calculating the dispenser target pressure Pd_next. In other words, the data signal Dt is not necessary for calculating the dispenser target pressure Pd_next.

[0092] Figure 4 shows an example of the time evolution of the controlled dispenser pressure Pd when the tank pressure Pt is increased by a linear target pressure increase rate Rptar.

[0093] The dispenser ECU 22 calculates the dispenser target pressure Pd_next after time step Δt at the current time t (current) and sets it in the output amplifier 82. The output amplifier 82 generates a flow rate adjustment signal Sas that adjusts the opening of the flow control valve 28 (adjusts the gas flow rate) so that the current dispenser pressure Pd (current) detected by the pressure sensor 34 becomes the set dispenser target pressure Pd_next.

[0094] By controlling the flow control valve 28 in accordance with the flow control signal Sas, the tank pressure Pt can be linearly increased (linearly increased) from the initial tank pressure P0 to the full tank pressure Pt_tar, according to the target tank pressure Pt_tar.

[0095] In this case, the gas filling method according to the embodiment allows for large gas flow rates during the initial stages of filling (first half of filling) because the pressure difference between the dispenser pressure Pd and the tank pressure Pt is large. Therefore, the filling time to reach the full tank pressure Pt_tarfull can be shortened. Furthermore, the filling time does not vary. In other words, the tank pressure Pt can be filled to the full tank pressure Pt_tarfull quickly and accurately.

[0096] Even if the filling process is interrupted and then resumed, the dispenser ECU22 can easily maintain the continuity of the target tank pressure Pt_tar and continue filling.

[0097] [Flowchart illustrating the gas filling method according to the embodiment] Next, the operation of the hydrogen refueling system 10 according to the embodiment to which the gas refueling method according to the embodiment is applied will be described in detail based on the flowchart shown in Figure 5. Unless otherwise specified, the program related to the flowchart is executed by the CPU of the dispenser ECU 22, but since it would be cumbersome to describe this each time, it will simply be referred to as the CPU.

[0098] Before gas refueling begins, with the shut-off valve 24 of the accumulator 20 of the hydrogen station 14 closed, the nozzle 48 of the hydrogen station 14 is fitted onto the receptacle 54 of the vehicle 16 by an operator or other person.

[0099] When the fill start button (not shown) of the hydrogen station 14 is operated by an operator, the CPU obtains the dispenser pressure Pd from the pressure sensor 34 which is indicating (detecting) the tank pressure Pt, and sets it to the initial tank pressure P0 (Pd=Pt=P0).

[0100] In step S1, the CPU refers to the target pressure boost rate map 90 shown in Figure 3, sets the target pressure boost rate Rptar in the target (tank pressure / pressure boost amount) calculation unit 78, sets a provisional pressure loss coefficient k0 in the pressure loss coefficient calculation unit 74, and proceeds to the gas refilling subroutine in step S2.

[0101] Figure 6 shows the flowchart of the gas refilling subroutine in step S2.

[0102] In step S2a, the CPU opens the shut-off valve 24 (or leaves it open if it is already open), causes the pressure loss calculation unit 76 to calculate the predicted pressure loss dPloss_estimated shown in equation (5), and proceeds to step S2b.

[0103] In step S2b, the CPU instructs the target (tank pressure / pressure increase amount) calculation unit 78 to calculate (predict) the target pressure increase amount ΔPt_next for the next time step Δt of the tank 50 according to equation (6), and then proceeds to step S2c.

[0104] In step S2c, the CPU instructs the dispenser target pressure calculation unit 80 to calculate the dispenser target pressure Pd_next shown in equation (8), and proceeds to step S2d.

[0105] In step S2d, the CPU adjusts the opening of the flow control valve 28 via the output amplifier 82 so that the current dispenser pressure Pd(current) becomes the dispenser target pressure Pd_next after time step Δt, then exits the subroutine in step S2 and proceeds to step S3.

[0106] In step S3, the CPU checks whether it is time to perform a leak check (gas leak confirmation). If the answer is positive (step S3: YES), the process proceeds to the leak check subroutine in step S4.

[0107] Figure 7 shows the flowchart of the leak check subroutine in step S4.

[0108] Figure 8 shows the time variation of dispenser pressure Pd and flow rate m detected during leak check. The tank pressure Pt is the target tank pressure Pt_tar (predicted value) based on equation (7).

[0109] In step S4a, the CPU detects (measures) the dispenser pressure Pd(i), dispenser gas temperature Td(i), and flow rate m(i) immediately before the leak check, which is just before closing the open shut-off valve 24, using the pressure sensor 34, temperature sensor 36, and flow rate sensor 26, respectively, and proceeds to step S4b.

[0110] In step S4b, the CPU closes the shut-off valve 24, interrupting the supply of gas from the accumulator 20 to the tank 50. At this time, the gas flow rate m detected by the flow sensor 26 becomes m=0, which is zero.

[0111] In step S4c, the CPU uses a preset downtime timer / counter (not shown) to perform a leak check for a few seconds, for example, 3 seconds, during which time tc is used for the leak check.

[0112] If the dispenser pressure Pd detected by the pressure sensor 34 changes during a leak check with the shut-off valve 24 closed, the CPU estimates that a gas leak has occurred in the hydrogen filling system 10 and immediately stops the gas filling process.

[0113] If, in step S4c, no gas leak is detected and the timer / counter (not shown) finishes measuring the leak check time tc, the CPU proceeds to step S4d.

[0114] In step S4d, the CPU uses the pressure sensor 34 to detect (measure) the dispenser pressure Pd(i+3) at the end of the leak check time tc, which is just before the shut-off valve 24 is opened again, and proceeds to step S4e.

[0115] In step S4e, the CPU instructs the pressure loss calculation unit 76 to calculate the pressure loss dPloss (tc=3) according to equation (4), and the pressure loss coefficient calculation unit 74 to calculate the pressure loss coefficient k0 according to equations (2) and (3).

[0116] At this point, the CPU exits the subroutine in step S4 and returns to the gas refilling subroutine in step S2.

[0117] If, in step S3 described above, the CPU is not yet ready to perform a leak check (step S3: NO), the process proceeds to step S5.

[0118] In step S5, the CPU checks whether the dispenser pressure Pd has reached the full tank pressure Pt_tarfull of tank 50, or whether an abort signal has been generated. If the full tank pressure Pt_tarfull has not been reached and no abort signal has been generated (step S5: NO), the process proceeds to the gas refilling subroutine in step S2.

[0119] In step S2, the CPU continues the gas filling process and adjusts the opening of the flow control valve 28 via the output amplifier 82 so that the current dispenser pressure Pd becomes the dispenser target pressure Pd_next after time step Δt. The CPU then exits the subroutine in step S2 and proceeds to step S3.

[0120] If, in step S3, the CPU is not yet ready to perform a leak check (step S3: NO), the process proceeds to step S5.

[0121] In step S5, the CPU terminates the current filling process when the dispenser pressure Pd reaches the full tank pressure Pt_tarfull of tank 50. Alternatively, in step S5, if the CPU confirms that an abort signal has been generated, it immediately stops the current refilling process even if the full tank pressure Pt_tarfull has not been reached.

[0122] As described above, in the gas filling method, gas is supplied from the accumulator 20 to the tank 50 via the flow control valve 28 and piping 100. When filling the tank 50 with gas, a target pressure increase rate Rptar, which is the time change of the target tank pressure Pt_tar, is set (step S1). During the filling of the tank 50 with gas, the flow control valve 28 is adjusted so that the dispenser pressure Pd, which is the gas pressure in the accumulator 20, is greater than the target tank pressure Pt_tar and maintains the target pressure increase rate Rptar (step S2d).

[0123] [Comparative Example and Embodiment Comparison] Referring to Figure 9, the gas filling method according to the embodiment shown by the solid line and the gas filling method according to the comparative example shown by the dashed line will be explained in comparison.

[0124] In the comparative example gas filling method, the gas is filled such that the dispenser pressure Pd increases at a constant rate, as shown in dispenser pressure Pd_old.

[0125] In a relatively small tank installed in a passenger car, for example, the tank pressure Pt increases along the curve of the tank pressure Pt_small-tank, which is a dashed line with an upward concave shape.

[0126] In this case, as the tank pressure Pt_small-tank approaches the full tank pressure, the pressure difference between the dispenser pressure Pd_old and the tank pressure Pt_small-tank decreases, causing the gas filling flow rate to decrease. As a result, the filling time until the full tank pressure Pt_tarfull is reached gradually increases.

[0127] In large tanks installed in large vehicles such as buses and trucks, the pressure loss is greater compared to smaller tanks, as shown, for example, by the double-dotted line curve of the tank pressure Pt_large-tank which is concave upwards. Therefore, it takes even longer to reach the full tank pressure Pt_tarfull.

[0128] In contrast, in the gas filling method according to this embodiment, the tank pressure Pt is increased (linearly increased) in a straight line (one example) of a constant pressure increase rate of the tank pressure Pt_new shown by the solid line. The gas flow rate is varied by adjusting the valve opening of the flow control valve 28 so that the tank pressure Pt_new increases linearly to the full tank pressure Pt_tarfull. In this way, the dispenser pressure Pd is changed not in a straight line, but along a curve that is slightly concave downwards, as shown in dispenser pressure Pd_new.

[0129] In the gas filling method according to this embodiment, the dispenser pressure Pd_new (pressure at the hydrogen station 14) is considerably higher than the tank pressure Pt_new during the first half of the filling process, allowing for an increase in gas flow rate. As a result, the filling time from the initial tank pressure P0 to the target tank pressure (fully filled tank pressure) Pt_tarfull can be significantly shortened compared to the comparative example.

[0130] Thus, in the gas filling method according to this embodiment, the tank pressure Pt can be increased linearly with the tank pressure Pt_new, so regardless of the size of the tank, the variation in filling time until the tank reaches full capacity Pt_tarfull is reduced. In other words, the tank 50 can be filled to full capacity Pt_tarfull quickly and accurately.

[0131] [An invention that can be understood from the embodiments] The inventions that can be understood from the above embodiments are described below. For the sake of ease of understanding, some of the components are given the same reference numerals as used in the above embodiments, but these components are not limited to those with such reference numerals.

[0132] (1) The gas filling method according to the present invention is a gas filling method which connects a tank 50 and a gas accumulator 20 with piping 100, supplies gas from the accumulator to the tank via the piping, and fills the tank with gas, comprising: a target pressure increase rate setting step S1 which sets a target pressure increase rate Rptar which is the time change of a target tank pressure Pt_tar when filling the tank with gas; and a flow rate control step S2d which adjusts the flow rate of gas supplied from the accumulator to the tank during the filling of the tank with gas so that the dispenser pressure Pd, which is the gas pressure of the accumulator, is greater than the target tank pressure and is a pressure that can maintain the target pressure increase rate.

[0133] This configuration adjusts the flow rate of gas supplied from the accumulator to the tank via piping so that the dispenser pressure is greater than the target tank pressure and maintains the target pressure increase rate, which is the time variation of the target tank pressure. This allows the tank to be filled accurately and quickly with gas from the accumulator via piping up to the full tank pressure, ultimately contributing to energy efficiency.

[0134] (2) In the gas filling method, the dispenser pressure that can maintain the target pressure increase rate may be calculated in the flow rate control step so as to be equal to the sum of the pressure loss dPloss in the piping and the tank pressure Pt.

[0135] The pressure loss in the piping can be calculated based on the gas density ρ and the mass flow rate m. Therefore, the tank can be filled with gas from the accumulator through the piping while confirming that the time change of the tank pressure is rising in line with the target pressure increase rate.

[0136] (3) Furthermore, in the gas filling method, the pressure loss may be calculated as the value obtained by multiplying the pressure loss coefficient k0 by the square of the mass flow rate m of the gas and dividing the result by the gas density, and the pressure loss coefficient may be updated based on the detected pressure loss detected when the gas supply is intentionally stopped while the gas is being supplied from the accumulator.

[0137] In this way, by calculating the pressure loss in the piping during gas supply, it is possible to continuously monitor whether the time-dependent change in tank pressure matches the target pressure increase rate.

[0138] (4) Furthermore, in the gas filling method, the target pressure increase rate may be set to a constant pressure increase rate.

[0139] In this way, by setting the target pressure increase rate so that the gas increases linearly, gas filling control becomes simpler, and even if the process is paused midway, the gas filling can be easily maintained when it is resumed.

[0140] Furthermore, this invention is not limited to the disclosures described above, and can take various configurations without departing from the spirit of the invention. [Explanation of Symbols]

[0141] 10…Hydrogen refueling system 14…Hydrogen station 16...Vehicle 20...Accumulator 22…Dispenser ECU 24…Shut-off valve 26…Flow sensor 28…Flow control valve 34...Pressure sensor 36...Temperature sensor 46... Station piping 48... Nozzle 50... Tank 54... Receptacle 56...Vehicle piping 70...Flow rate adjustment signal generation unit 71, 80... Dispenser target pressure calculation unit 72...Gas density calculation unit 74...Pressure loss coefficient calculation unit 76... Pressure loss calculation unit 78...Target (tank pressure / pressure increase amount) calculation unit 81…Target pressure feedback control unit 82…Output amplifier 84... Leak check switch 90... Target boost rate map 100... Piping

Claims

1. A gas filling method comprising connecting a tank and a gas accumulator with piping, supplying the gas from the accumulator to the tank via the piping, and filling the tank with the gas, When filling the tank with the gas, a target pressure increase rate setting step is performed to set a target pressure increase rate, which is the time change of the target tank pressure. During the filling of the tank with the gas, the dispenser pressure, which is the gas pressure of the accumulator, is calculated to match the sum of the pressure loss in the piping and the tank pressure predicted by the target pressure increase rate. Furthermore, the system includes a flow rate control step that adjusts the flow rate of the gas supplied from the accumulator to the tank so that the dispenser pressure is greater than the target tank pressure and can maintain the target pressure increase rate. The gas filling method is characterized by the flow rate control step being performed multiple times.

2. In the gas filling method described in claim 1, The flow rate control process is performed at predetermined intervals. Gas filling method.

3. In the gas filling method described in claim 2, The flow rate control process is repeated until the tank pressure reaches the full tank pressure. Gas filling method.

4. In the gas filling method described in claim 1, The pressure loss is calculated by multiplying the pressure loss coefficient by the square of the mass flow rate of the gas and dividing the result by the gas density. The pressure loss coefficient is updated based on the detected pressure loss detected when the supply of the gas from the accumulator is intentionally stopped during the supply of the gas. Gas filling method.

5. In the gas filling method according to any one of claims 1 to 4, The aforementioned target voltage boost rate is set to a constant voltage boost rate. Gas filling method.

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