JP7255471B2 - Fuel supply system, vehicle and fuel supply method - Google Patents

Description

The present disclosure relates to fuel supply systems, vehicles, and fuel supply methods.

Liquid fuels such as liquefied natural gas (LNG) are known as fuels for internal combustion engines. LNG fuel filled in a tank (LNG tank) is injected from an injector provided in an intake manifold of an internal combustion engine via a fuel supply system having a vaporizer (evaporator) and valves (for example, Patent Document 1 ).

Japanese Unexamined Patent Application Publication No. 2006-17058

By the way, LNG fuel contains components such as methane, ethane, propane and butane. The boiling point of each component is different from each other. If the LNG tank on board is not kept cold, the components will vaporize from the low boiling point methane. As a result, if the LNG fuel is not consumed, the composition of the LNG fuel will change, and the residual fuel will become heavy. Even if new fuel is replenished, it will gradually become heavier. As a result, the octane number of the LNG fuel decreases.

Further, each component of the LNG fuel has a different octane number for use as a fuel for the Otto cycle, and when methane escapes, the octane number decreases and knocking is likely to occur.

Further, if the ignition timing is set later to avoid knocking, the ignition timing is deviated from the optimum timing, resulting in a decrease in torque and an increase in exhaust temperature. Furthermore, if the temperature of the exhaust gas rises and exceeds the heat-resistant temperatures of the exhaust manifold and the turbocharger, there is a risk of damage.

An object of the present disclosure is to provide a fuel supply system, a vehicle, and a fuel supply method capable of preventing knocking even when LNG fuel becomes heavy.

In order to achieve the above objects, the fuel supply system in the present disclosure is
A LNG tank storing LNG fuel and a CNG tank storing CNG fuel, which are fuel supply sources that supply fuel to the internal combustion engine;
a switching unit for switching the fuel supply source;
a control unit that controls a switching unit to switch the fuel supply source from the LNG tank to the CNG tank when the LNG fuel supplied to the internal combustion engine becomes heavy;
Prepare.

A vehicle in the present disclosure is
The above fuel supply system is provided.

The fuel supply method in the present disclosure includes:
Acquiring properties of LNG fuel supplied to the internal combustion engine,
Based on the obtained properties of the LNG fuel, control is executed to switch a fuel supply source that supplies fuel to the internal combustion engine from the LNG tank storing the LNG fuel to the CNG tank storing the CNG fuel.

According to the fuel supply system of the present disclosure, knocking can be prevented even when the LNG fuel becomes heavy.

It is a figure showing roughly an example of composition of a fuel supply system in an embodiment of this indication. FIG. 4 is a diagram showing an example of a fuel tank switching map; FIG. 4 is a flowchart showing an example of fuel supply processing;

Embodiments of the present disclosure will be described below with reference to the drawings.
FIG. 1 is a diagram schematically showing an example configuration of a fuel supply system 1 according to an embodiment of the present disclosure. Here, the fuel supply system 1 is mounted on a vehicle.

The fuel supply system 1 includes LNG fuel supply systems 2A and 2B for supplying LNG fuel to an engine E (internal combustion engine), an LNG fuel filling system 20 for filling LNG tanks 4A and 4B with LNG fuel, and compressed natural gas. A CNG fuel supply system 30 for supplying (Compressed Natural Gas: CNG) fuel to the engine E is provided.

<LNG fuel supply system 2A>
First, the LNG fuel supply system 2A will be explained. The LNG fuel supply system 2A has an LNG tank 4A, an LNG fuel supply line 5, a vaporizer 6A, a shutoff valve 7A, a shutoff valve 7C, an LNG regulator 3, and a fuel sensor 9.

The LNG tank 4A is one of fuel supply sources that supply fuel to the engine E, and stores LNG fuel. The LNG tank 4A is provided with a remaining amount detection sensor 8A for detecting the remaining amount of LNG fuel. For the remaining amount detection sensor 8A, a known sensor capable of detecting the remaining amount of LNG fuel, for example, a level sensor for detecting the liquid surface level of the LNG fuel in the LNG tank 4A is used.

The LNG fuel supply line 5 connects the LNG tank 4A to the LNG regulator 3 via the vaporizer 6A, the shutoff valve 7A and the shutoff valve 7C. Further, the LNG fuel supply path 5 connects the LNG regulator 3 and the engine E.

The vaporizer 6A vaporizes the LNG fuel from the LNG tank 4A with cooling water of the engine E, for example. A cooling water passage (not shown) extends from the engine E to the carburetor 6A.

The shutoff valve 7A opens and closes the LNG fuel supply line 5 between the vaporizer 6A and the shutoff valve 7C.

The shutoff valve 7C opens and closes the LNG fuel supply path 5 between the shutoff valve 7A and the LNG regulator 3 .

In the LNG fuel supply system 2A, when the shutoff valve 7A and the shutoff valve 7C are opened, the LNG fuel is supplied from the LNG tank 4A to the engine E via the vaporizer 6A and the LNG regulator 3. . When the cutoff valve 7A is closed, the supply of LNG fuel from the LNG tank 4A to the engine E is stopped regardless of whether the cutoff valve 7C is open.

The LNG regulator 3 reduces the pressure of the LNG fuel vaporized by the vaporizer 6A.

The fuel sensor 9 is arranged in the LNG fuel supply path 5 between the LNG regulator 3 and the engine E (eg, intake manifold). The fuel sensor 9 detects properties of LNG fuel passing through the LNG fuel supply path 5 . Here, the "property of LNG fuel" includes the components contained in the LNG fuel and the proportions of the components.

<LNG fuel supply system 2B>
Next, the LNG fuel supply system 2B will be explained. The LNG fuel supply system 2B includes an LNG tank 4B, an LNG fuel supply line 5, a vaporizer 6B, a shutoff valve 7B, a shutoff valve 7C (shared with the shutoff valve 7C of the LNG fuel supply system 2A), and an LNG regulator. 3 (shared with the LNG regulator 3 of the LNG fuel supply system 2A). The LNG tank 4B is one of fuel supply sources that supply fuel to the engine E, and stores LNG fuel. The configurations of the LNG tank 4B, the vaporizer 6B, the shutoff valve 7B, and the residual amount detection sensor 8B are the same as the configurations of the LNG tank 4A, the vaporizer 6A, the shutoff valve 7A, and the residual amount detection sensor 8A. Therefore, their description is omitted.

The LNG fuel supply path 5 extending downstream from the shutoff valve 7A toward the shutoff valve 7C and the LNG fuel supply path 5 extending downstream from the shutoff valve 7B toward the shutoff valve 7C are connected to the shutoff valve 7C. merges at the upstream position of

In the LNG fuel supply system 2B, when the shutoff valve 7B and the shutoff valve 7C are opened, the LNG fuel is supplied from the LNG tank 4B to the engine E via the vaporizer 6B and the LNG regulator 3. . When the cutoff valve 7B is closed, the supply of LNG fuel from the LNG tank 4B to the engine E is stopped regardless of whether the cutoff valve 7C is open.

<LNG fuel filling system 20>
Next, the LNG fuel filling system 20 will be explained. The LNG fuel filling system 20 has an LNG fuel filling passage 21 and a filling valve 22 .

A filling port is arranged at one end of the LNG fuel filling path 21 . The LNG fuel filling path 21 connects the filling port side and the LNG tank 4A. Also, the LNG fuel filling path 21 connects the filling port side and the LNG tank 4B. The LNG fuel filling passage 21 is provided with check valves 23A and 23B in the LNG tanks 4A and 4B, respectively, so that the fuel entering the LNG tanks 4A and 4B does not flow back.

The filling valve 22 is opened when filling the LNG tanks 4A and 4B with LNG fuel. The fill valve 22 is closed when the filling of LNG fuel is finished.

<CNG fuel supply system 30>
Next, the CNG fuel supply system 30 will be explained. The CNG fuel supply system 30 has a CNG fuel supply path 31 , a CNG tank 32 , a shutoff valve 34 , a pressure sensor 35 , a shutoff valve 36 and a CNG regulator 33 .

The CNG fuel supply path 31 connects the CNG tank 32 to the CNG regulator 33 via the shutoff valves 34 and 36 . Further, the CNG fuel supply path 31 connects the CNG regulator 33 and the engine E.

The CNG tank 32 is one of fuel supply sources that supply fuel to the engine E, and stores CNG fuel. Here, "CNG fuel" is assumed to be a fuel equivalent to LNG fuel, which contains a large amount of methane and is not heavy.

The shutoff valve 34 opens and closes the CNG fuel supply path 31 between the CNG tank 32 and the shutoff valve 36 .

The shutoff valve 36 opens and closes the CNG fuel supply path 31 between the shutoff valve 34 and the CNG regulator 33 .

The CNG regulator 33 reduces the pressure of the CNG fuel supplied from the CNG tank 32 . A CNG fuel supply path 31 extending downstream from the CNG regulator 33 is connected to the LNG fuel supply path 5 between the LNG regulator 3 and the engine E.

A pressure sensor 35 detects the internal pressure of the CNG fuel supply line 31 between the shutoff valves 34 and 36 . The fuel supply control device 10 (described later) determines whether or not there is a remaining amount of CNG fuel in the CNG tank 32 based on the detection result of the pressure sensor 35 . When determining that there is no remaining amount of CNG fuel, the fuel supply control device 10 executes control to reduce the torque to a torque at which knocking does not occur without switching the fuel supply source from the LNG tanks 4A and 4B to the CNG tank 32. do.

<Other configurations>
Other configurations will be described below. Other configurations include a gas discharge path 41 and tank vent valves 45A and 45B.

The gas discharge path 41 is connected to the LNG tank 4A. Also, the gas discharge path 41 is connected to the LNG tank 4B.

The tank vent valve 45A is connected to the gas discharge path 41. As shown in FIG. The tank vent valve 45A discharges the gas in the LNG tank 4A to the outside. The tank vent valve 45B is connected to the gas discharge path 41 . The tank vent valve 45B discharges the gas in the LNG tank 4B to the outside.

<Fuel supply control device 10>
The fuel supply system 1 includes a fuel supply control device 10 (corresponding to the "control section" of the present disclosure). The fuel supply control device 10 is configured by, for example, an electronic control unit 100 (Electronic Control Unit: ECU). The ECU 100 has a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), an input device and an output device. The CPU expands the program stored in the ROM into the RAM and executes each function to be described later. The fuel supply control device 10 has respective functions as an acquisition section 11 , a determination section 12 and a valve control section 13 .

For example, when the LNG fuel in the LNG tanks 4A and 4B becomes heavy (decrease in octane number) and the LNG fuel with the lowered octane number is used as fuel for the Otto cycle, for example, knocking occurs. If the ignition timing is set later to avoid knocking, the ignition timing will deviate from the optimal timing, resulting in a decrease in torque and an increase in exhaust temperature. Furthermore, if the temperature of the exhaust gas rises and exceeds the heat-resistant temperatures of the exhaust manifold and the turbocharger, there is a risk of damage.

Therefore, the acquisition unit 11 acquires properties of the LNG fuel from the fuel sensor 9 . Here, "property of LNG fuel" means, for example, the ratio of methane contained in the LNG fuel.

In addition, the acquisition unit 11 acquires the torque (required torque) required for the engine E from the engine required torque sensor (see FIG. 1). For example, the engine demand torque sensor is an accelerator opening sensor whose sensor output is the demand torque. In the following description, the required torque may be referred to as "target boost".

FIG. 2 is a diagram showing an example of a fuel tank switching map (hereinafter referred to as map). In the map shown in FIG. 2, the vertical direction indicates the target boost height, and the horizontal direction indicates the properties of the LNG fuel (methane ratio). In FIG. 2, when the data intersecting vertically and horizontally is "1", it indicates that the fuel supply source is the CNG tank. If the vertically and horizontally crossed data are "0", it indicates that the fuel supply source is the LNG tank.

The map shown in FIG. 2 defines the relationship between the target boost, the properties of the LNG fuel, and the fuel supply source. By referring to the map, the fuel supply source is determined from the target boost and the properties of the LNG fuel. A map can be obtained by experiments or simulations. The map is stored in the storage section of ECU 100 .

The determining unit 12 refers to the map shown in FIG. 2 and determines the fuel supply source based on the obtained target boost and the properties of the LNG fuel.

When the fuel supply source determined by the determination unit 12 is the CNG tank, the valve control unit 13 controls the switching unit to switch the fuel supply source from the LNG tanks 4A and 4B to the CNG tank 32 . Here, the “switching unit” includes the shutoff valve 7C, the shutoff valve 34 and the shutoff valve 36. FIG. Specifically, when the fuel supply source determined by the determination unit 12 is the CNG tank, the valve control unit 13 controls the shutoff valve 7C to close and opens the shutoff valve 34 and the shutoff valve 36. to control. In addition, when the fuel supply source determined by the determination unit 12 is the LNG tank, the fuel supply source is maintained at the LNG tanks 4A and 4B and is not switched.

Next, an example of fuel supply processing will be described with reference to FIG. FIG. 3 is a flow chart showing an example of fuel supply processing. In the following description, it is assumed that the ECU 100, which functions as the acquisition unit 11, the determination unit 12, and the valve control unit 13, performs the fuel supply process. This flow is started, for example, when the ECU 100 receives a request to start this flow. At the start of this flow, the cutoff valves 7A, 7B, 7C are open and the cutoff valves 34, 36 are closed. That is, the engine E is supplied with LNG fuel and is not supplied with CNG fuel.

First, in step S<b>100 , the ECU 100 acquires properties of the LNG fuel from the fuel sensor 9 .

In step S110, the ECU 100 acquires the target boost from the engine demand torque sensor.

In step S120, the ECU 100 refers to the map shown in FIG. 2 to determine the fuel supply source based on the properties of the LNG fuel and the target boost.

Next, in step S130, the ECU 100 determines whether or not the determined fuel supply source is the CNG tank. If the fuel supply source is the CNG tank (step S130: YES), the process transitions to step S140. If the fuel supply source is not the CNG tank (step S130: NO), the process shown in FIG. 3 ends.

In step S140, the ECU 100 determines whether the CNG tank 32 has enough fuel. The switching unit (the shutoff valve 7C, the shutoff valve 34 and the shutoff valve 36) is controlled so as to switch from the tanks 4A and 4B to the CNG tank 32. After that, the processing shown in FIG. 3 ends. Under the control of the ECU 100, the shutoff valve 7C is closed and the shutoff valves 34 and 36 are opened. As a result, CNG fuel is supplied to the engine E and LNG fuel is not supplied. When it is determined in step S140 that there is no fuel in the CNG tank 32 (step S140: NO), the process proceeds to step S160, LNG fuel remains, and torque is limited to prevent knocking.

The fuel supply system 1 in the above embodiment switches between the LNG tanks 4A and 4B storing LNG fuel and the CNG tank 32 storing CNG fuel, which are fuel supply sources for supplying fuel to the engine E, and the fuel supply source. A switching unit, and a fuel supply control device 10 that controls the switching unit to switch the fuel supply source from the LNG tanks 4A and 4B to the CNG tank 32 when the LNG fuel supplied to the engine E becomes heavy. .

With the above configuration, when the LNG fuel becomes heavy, the fuel supply source is switched from the LNG tanks 4A and 4B to the CNG tank 32, and the CNG fuel, which is a fuel equivalent to the LNG fuel that has a large amount of methane and is not heavy, is supplied to the engine. Since it is supplied to E, it is possible to prevent the occurrence of knocking.

Further, in the fuel supply system 1 in the above embodiment, when the LNG fuel becomes heavy, torque is not limited by avoiding knocking, so that the vehicle can be operated without hindrance.

Also, in a normal vehicle, large-sized LNG tanks 4A and 4B are mounted, but only a small CNG tank 32 is mounted. , the LNG fuel becomes heavy, and when the engine E is in a high load state, the CNG fuel cannot be used, resulting in a reduction in cruising distance. In the fuel supply system 1 of the above embodiment, LNG fuel is used in low load conditions where knocking is unlikely to occur, and CNG fuel is used only in high load conditions where knocking is likely to occur. It is possible to prevent the cruising range from significantly decreasing.

In addition, the above-described embodiments are merely examples of specific implementations of the present disclosure, and the technical scope of the present disclosure should not be construed to be limited by these. . That is, the present disclosure can be embodied in various forms without departing from its spirit or key features.

In the above embodiment, when the proportion of methane (the properties of the LNG fuel) is small, and when the LNG fuel is heavy, the present disclosure is not limited to this. If the output is less than the threshold, it may be assumed that the LNG fuel has become heavy. In this case, the fuel supply control device 10 may determine whether or not the output of the engine E is less than the threshold.

Further, in the above-described embodiment, the determination unit 12 determines the fuel supply source based on the torque (target boost) required for the engine E, but the present disclosure is not limited to this. The fuel supply source may be determined based on the magnitude of . In this case, the load applied to the engine E may be measured by a torque sensor such as a strain gauge adhered to the crankshaft.

INDUSTRIAL APPLICABILITY The present disclosure is suitably used for vehicles equipped with a fuel supply system that requires prevention of knocking even when LNG fuel becomes heavy.

1 fuel supply system 2A, 2B LNG fuel supply system 3 LNG regulator 4A, 4B LNG tank 5 LNG fuel supply path 6A, 6B vaporizer 7A, 7B, 7C cutoff valve 8A, 8B remaining amount detection sensor 9 fuel sensor 10 fuel supply Control device 11 acquisition unit 12 determination unit 13 valve control unit 20 LNG fuel filling system 21 LNG fuel filling path 22 filling valve 23A, 23B check valve 30 CNG fuel supply system 31 CNG fuel supply path 32 CNG tank 33 CNG regulator 34, 36 Shutoff valve 35 Pressure sensor 41 Gas exhaust path 45A, 45B Tank vent valve 100 ECU

Claims (6)

A LNG tank storing LNG fuel and a CNG tank storing CNG fuel, which are fuel supply sources that supply fuel to the internal combustion engine;
a switching unit for switching the fuel supply source;
a control unit that controls a switching unit to switch the fuel supply source from the LNG tank to the CNG tank when the LNG fuel supplied to the internal combustion engine becomes heavy;
comprising
fuel supply system. When the LNG fuel is heavy, including when the output of the internal combustion engine with respect to the supply amount of the LNG fuel is less than a threshold,
The fuel supply system according to claim 1. The control unit further controls the switching unit to switch the fuel supply source when the magnitude of the load required for the internal combustion engine exceeds a threshold.
The fuel supply system according to claim 1 or 2. The control unit further controls the switching unit to switch the fuel supply source when the magnitude of the load applied to the internal combustion engine exceeds a threshold.
The fuel supply system according to any one of claims 1 to 3. A vehicle comprising the fuel supply system according to any one of claims 1 to 4. Acquiring the properties of the LNG fuel supplied to the internal combustion engine,
Based on the acquired properties of the LNG fuel, control is performed to switch a fuel supply source that supplies fuel to the internal combustion engine from the LNG tank that stores the LNG fuel to the CNG tank that stores the CNG fuel.
Fuel supply method.

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