JP2008106731A - Cooling system of hydrate fuel tank for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain the hydrated state of a fuel in one complete system using a separately provided hydrate fuel as energy source to cool the hydrate fuel stored in a fuel tank. <P>SOLUTION: A cooler system to cool the fuel tank 1 is configured mainly with a condenser 10, an expansion valve 11, an evaporator 12, and an electric-driven compressor 13, and the operation of the electric-driven compressor 13 is controlled by an electronic control unit (ECU) 20 using the electric power fed from a fuel cell 4 to generate electricity using the hydrate fuel 2 stored in the fuel tank 1. This allows the cooling system for the fuel tank 1 to be a complete self cooling system able to work with no energy fed externally, and it is possible to maintain in good performance the hydrated state of the fuel in one complete system. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cooling system for a hydrate fuel tank for a vehicle that stores fuel in a hydrate state.

  In recent years, techniques for storing and transporting gas fuels such as natural gas and hydrogen gas in a hydrate state have been developed. Hydrate has a structure in which gases such as methane and hydrogen are taken into a cluster (cage structure) made of water molecules, and it does not require liquefaction by high-pressure compression of gas, so it has advantages in cost and handling. There are many.

Various techniques for applying such hydrate fuel to a vehicle such as an automobile and using it as a fuel for a gas engine or a hydrogen supply source for a fuel cell have been proposed. For example, in Patent Document 1, fuel obtained by decomposing from a hydrate stored in a fuel tank is used as an engine fuel or a hydrogen source of a fuel cell, and cold heat generated by the decomposition of hydrate is used for a freezer or a vehicle interior cooling system. A technology for using a cold heat source is disclosed.
JP 2000-248996 A

  When hydrate fuel is stored in a fuel tank of a vehicle, it is necessary to maintain the hydrate state for a long time in a state independent from the outside. In the conventional technology as disclosed in Patent Document 1, attention is paid only to taking out gas while melting hydrate fuel using engine exhaust heat, or using cold heat when hydrate melts. Therefore, it has not been considered to properly maintain and manage the fuel hydrate state independently without supplying cooling energy from the outside.

  The present invention has been made in view of the above circumstances, and uses the hydrate fuel of its own as an energy source for cooling the hydrate fuel stored in the fuel tank, so that the hydrate state of the fuel can be maintained in a complete system. It aims at providing the cooling system of the hydrate fuel tank for vehicles.

  In order to achieve the above object, a cooling system for a hydrate fuel tank for a vehicle according to the present invention is mounted on a vehicle, stores a fuel in a hydrated state, is connected to the fuel tank, and is provided in the fuel tank. Cooling means for cooling the hydrate fuel, cooling drive energy generating means for generating drive energy for driving the cooling means using the hydrate fuel in the fuel tank, and hydrate fuel in the fuel tank And a control means for controlling the operation of the cooling means by the drive energy generated by the cooling drive energy generating means based on the temperature.

  The cooling system for a hydrate fuel tank for a vehicle according to the present invention can cool the hydrate fuel stored in the fuel tank using its own hydrate fuel as an energy source, and is completed without supplying energy from the outside. It is possible to maintain a good fuel hydrate state in the system.

  Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 relate to an embodiment of the present invention, FIG. 1 is an overall configuration diagram of a fuel system, and FIG. 2 is a flowchart of a fuel cooling control routine.

  The fuel system shown in FIG. 1 is mounted on a vehicle that uses a fuel obtained by hydrating hydrogen gas, natural gas, or the like as an energy source for driving driving or an energy source for generating electric power. It includes a cooling system that can cool and maintain the fuel hydrate properly. In this embodiment, the hydrate fuel 2 stored in the fuel tank 1 is a fuel obtained by hydrating natural gas such as methane (NGH), and the gas separated from the hydrate fuel 2 is used for driving. An example will be mainly described in which the fuel cell 4 is supplied to the gas engine 3 as a power unit (P / U) and supplied to the fuel cell 4 that generates electric power by an electrochemical reaction between hydrogen and oxygen.

  Hydrate fuel 2 replenished and stored in the fuel tank 1 via the filling valve 1 a is maintained and managed at a constant temperature and supplied to the gas engine 3 and the fuel cell 4 via the control valve 5. The control valve 5 is a pressure control valve that adjusts the pressure in the tank rising due to melting of the hydrate, a separator that separates moisture from the molten / decomposed hydrate fuel, and promotes melting of the hydrate when supplying fuel. For example, a heater for discharging water and a discharge pipe 6 for discharging water are connected to a fuel supply pipe 7 for supplying fuel gas. The water separated from the hydrate fuel 2 is discharged to the outside through the discharge pipe 6 or stored in a predetermined container, and the fuel gas separated from the hydrate fuel 2 is supplied to the gas engine 3 through the fuel supply pipe 7. Are supplied to the fuel cell 4 through a reformer 8 that reforms natural gas into hydrogen gas.

  When the hydrate fuel 2 stored in the fuel tank 1 is hydrogen gas hydrate, the reformer 8 is unnecessary. Further, in the case of an electric vehicle using an electric motor as a P / U instead of the gas engine 3, the fuel supply pipe 7 is directly connected (in the case of hydrogen gas) or reformed without being connected to the P / U. It is connected to the fuel cell 4 via the vessel 8 (in the case of natural gas).

  The fuel cell 4 is used as a power source for the gas engine 3 and various devices and a power source for the cooling system of the fuel tank 1. The cooling system for the fuel tank 1 includes a cooling system as cooling means for cooling the fuel tank 1 (hydrate fuel 2), and cooling driving energy for generating driving energy for driving the cooling system using hydrate fuel. The fuel cell 4 as a generation unit and an electronic control unit (ECU) 20 as a control unit are mainly configured.

  In this embodiment, the cooler system is connected to the condenser 10 that liquefies the refrigerant of high-pressure steam, the expansion valve 11 that decompresses the high-pressure refrigerant, and the fuel tank 1, and the evaporator that evaporates the refrigerant and exchanges heat. 12 and an electric compressor (CP) 13 that compresses the evaporated refrigerant to a high pressure and pumps it to the condenser 10. The electric compressor 13 uses hydrate fuel. It is driven by power from the fuel cell 4 that generates power. That is, the cooling system of the fuel tank 1 is configured as a complete self-cooling system that can be operated without supplying energy from the outside.

  Note that the refrigerant cycle system electric compressor 13 may be a compressor mechanically driven by the gas engine 3. In that case, a part of the motive power of the gas engine 3 operated by the hydrate fuel 2 in the fuel tank 1 becomes drive energy for driving the refrigerant cycle system. Furthermore, you may comprise a cooler system by electronic cooling using a Peltier device etc., without using a refrigerant cycle system as a cooler system.

  The operation of the refrigerant cycle system is controlled by an electronic control unit (ECU) 20 comprising a microcomputer or the like. The ECU 20 operates from a power source supplied from the fuel cell 4 to control power generation of the fuel cell 4 and from a temperature sensor 21 that is attached to the fuel tank 1 and detects the temperature in the tank (the temperature of hydrate fuel). Based on the signal, ON / OFF of the electric compressor 13 and relays RY1 and RY2 interposed in the power supply line of the electric compressor 13 are controlled.

  The relay RY1 is a one-circuit open / close type relay interposed between the electric compressor 13 and the relay RY2. The relay RY2 is connected in series to the relay RY1, and is a connector for external power supply as a connection means that can connect the relay RY1 and the fuel cell 4 to the relay RY1, and the external power supply 30 outside the vehicle. 2 is a two-circuit switching type relay that switches between the circuit and the circuit connected to the circuit 22.

  That is, when the contact of the relay RY1 is switched to the fuel cell 4 side with the contact of the relay RY1 closed, the electric compressor 13 can be driven by the electric power from the fuel cell 4. On the other hand, when the contact of the relay RY2 is switched to the external power supply connector 22 side, the electric compressor 13 can be connected to the external power supply 30 via the external power supply connector 22 without consuming the hydrate fuel 2 held by itself. The electric compressor 13 can be driven by a power source outside the vehicle.

  The connection state of the external power supply connector 22 is monitored by the ECU 20. When the vehicle is parked in a place where the external power supply 30 such as a home power supply can be secured and the external power supply connector 22 is connected to the external power supply 30. The connection state is detected by the ECU 20. The ECU 20 that detects the connection of the external power supply connector 22 to the external power supply 30 controls the relays RY1 and RY2, and automatically switches the drive power supply of the electric compressor 13 from its own fuel cell 4 to the external power supply 30. As a result, a power source other than the own fuel cell 4 can be selectively used as a drive power source for the electric compressor 13, and fuel can be saved.

  Next, the operation of the above self-cooling system of the fuel tank 1 will be described. The self-cooling system of the fuel tank 1 is controlled by a fuel cooling control routine of FIG.

  The fuel cooling control routine of FIG. 2 is a routine that is executed every predetermined period or every predetermined time. First, in the first step S1, a signal from the temperature sensor 21 is read to determine the temperature in the fuel tank 1 (hydrate fuel). Temperature) T is checked to determine whether the ON requirement of the electric compressor 13 for cooling the fuel is satisfied. Specifically, the ON requirement of the electric compressor 13 is a condition in which the temperature (the temperature of the hydrate fuel) T in the fuel tank 1 exceeds a preset temperature threshold Tset.

  In general, in order to completely stop the decomposition of hydrate fuel, it is necessary to lower the temperature to, for example, about −80 ° C. under atmospheric pressure. However, as a characteristic of hydrate fuel, the temperature is much higher than this stable boundary condition. It is known to have a self-preserving property that can exist in an apparently stable state even under unstable conditions at low pressure. Therefore, the temperature threshold value Tset that determines the ON requirement of the electric compressor 13 is set to a temperature at which the self-preserving property of the hydrate fuel can be most effectively used, for example, −20 ° C.

  As a result, if T ≦ Tset, it is assumed that the hydrate state can be maintained satisfactorily, branching from step S1 to step S7, relay RY1 is turned off (contact open), electric compressor 13 is turned off, and the routine is executed. Exit. The relay RY2 is normally connected to the fuel cell 4 side with the external power supply side open, and only when the external power supply connector 22 is detected to be connected to the external power supply 30 side. Is switched to.

  On the other hand, if T> Tset and the ON requirement of the electric compressor 13 is satisfied, the process proceeds from step S1 to step S2, and the connection state of the external power supply connector 22 is checked to determine whether or not the external power supply 30 is connected. . If the external power supply 30 is not connected, the process proceeds from step S2 to step S3, where the fuel cell 4 is started to generate power and the electric compressor 13 is started.

  Next, the process proceeds from step S3 to step S4, the relay RY1 is turned on (contact closed) with the relay RY2 connected to the fuel cell 4, and the electric compressor 13 is turned on in step S6 to exit the routine. When the electric compressor 13 is turned on, the refrigerant cycle system is operated, and the hydrate fuel 2 in the fuel tank 1 is cooled via the evaporator 12.

  When the hydrate fuel 2 in the fuel tank 1 is cooled by the self-cooling via the fuel cell 4 and the temperature drops and reaches the temperature threshold Tset, the electric compressor 13 is turned on in the process of repeatedly executing this routine. It is determined that the requirement is satisfied (step S1), and the driving of the electric compressor 13 is stopped in step S7. By stopping the driving of the electric compressor 13, the fuel cooling of the fuel tank 1 is also stopped.

  On the other hand, when it is detected in step S2 that the external power supply connector 22 is connected to the external power supply 30, the process proceeds from step S2 to step S5 to turn on the relay RY1 and connect the relay RY2 from the fuel cell 4 side to the external power supply. Switch to 30 side. As a result, power is supplied from the external power supply 30 to the electric compressor 13.

  In step S 6, the electric compressor 13 is turned on to operate the refrigerant cycle system, and the hydrate fuel 2 in the fuel tank 1 is cooled via the evaporator 12. Also in the fuel cooling by the external power source 30, when the fuel temperature reaches the temperature threshold value Tset, the electric compressor 13 is automatically stopped as described above.

  As described above, in the present embodiment, the cooling system for cooling the hydrate fuel 2 in the fuel tank 1 is configured as a complete self-cooling system, and as long as the hydrate fuel 2 remains in the fuel tank 1, The refrigerant cycle system electric compressor 13 can be driven by the electric power generated using the hydrate fuel 2 owned by the self. This makes it possible to maintain the hydrate state of the fuel in the fuel tank 1 satisfactorily over a long period of time even under an energy-independent state from the outside.

  In addition, by providing the external power supply connector 22 in a part of the cooling system, the electric compressor 13 can be connected to the household power supply without consuming the hydrate fuel 2 that it owns during long-term parking or the like. It can be connected to the external power source 30 and driven to improve fuel efficiency.

Overall configuration of fuel system Flow chart of fuel cooling control routine

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel tank 2 Hydrate fuel 4 Fuel cell (cooling drive energy production | generation means)
13 Electric compressor (cooling means)
20 Electronic control device (control means)
22 External power supply connector (connecting means)
30 External power supply

Claims (5)

A fuel tank mounted on the vehicle for storing hydrated fuel;
A cooling means connected to the fuel tank for cooling the hydrate fuel in the fuel tank;
Cooling drive energy generating means for generating drive energy for driving the cooling means using hydrate fuel in the fuel tank;
And a control means for controlling the operation of the cooling means by the drive energy generated by the cooling drive energy generating means based on the temperature of the hydrate fuel in the fuel tank. Tank cooling system. The cooling drive energy generating means is constituted by a fuel cell that generates power using hydrate fuel in the fuel tank,
2. The cooling system for a hydrate fuel tank for a vehicle according to claim 1, wherein the electric power generated by the fuel cell is used as driving energy for the cooling means. The cooling means comprises a refrigerant cycle system including a refrigerant compression process by an electric compressor,
The cooling system for a hydrate fuel tank for a vehicle according to claim 2, wherein the electric compressor is driven by electric power generated by the fuel cell.   4. The cooling system for a hydrate fuel tank for a vehicle according to claim 3, further comprising connecting means capable of connecting a power source outside the vehicle to the electric compressor. The control means includes
5. The cooling system for a hydrate fuel tank for a vehicle according to claim 4, wherein the fuel cell and the external power source are selectively switched through the connection means to drive and control the electric compressor.

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