JP2021148052A - Fuel supply system, vehicle, and fuel supply method - Google Patents

Abstract

To provide a fuel supply system, a vehicle, and a fuel supply method capable of preventing occurrence of knocking even when an LNG fuel becomes heavier.SOLUTION: A fuel supply system includes: an LNG tank for storing an LNG fuel; a CNG tank for storing a CNG fuel; an LNG injector capable of adjusting an injection amount of the LNG fuel supplied from the LNG tank and injected to an internal combustion engine; a CNG injector capable of adjusting an injection amount of the CNG fuel supplied from the CNG tank and injected to the internal combustion engine; and a control portion for controlling the LNG injector and the CNG injector so as to increase a ratio of the injection amount of the CNG fuel in the total injection amount as the sum of the injection amount of the LNG fuel and the injection amount of the CNG fuel, according to increase of heaviness of the LNG fuel stored in the LNG tank.SELECTED DRAWING: Figure 3

Description

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

As a fuel for an internal combustion engine, for example, a liquid fuel such as liquefied natural gas (LNG) is known. The LNG fuel filled in the 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), a valve, or the like (for example, Patent Document 1). ).

Japanese Unexamined Patent Publication No. 2006-17058

By the way, LNG fuel contains components such as methane, ethane, propane and butane. The boiling points of each component are different from each other. If the on-board LNG tank is not maintained at a low temperature, each component will vaporize from methane, which has a low boiling point. As a result, if the LNG fuel is not consumed, the composition of the LNG fuel changes, and the residual fuel becomes heavy. Moreover, even if new fuel is replenished, it gradually becomes heavier. As a result, the octane number of the LNG fuel decreases.

Further, each component of the LNG fuel has a different octane number in order to be used as a fuel for the Otto cycle, and as methane is released, the octane number is lowered and knocking is likely to occur.

Further, when the ignition timing is set late to avoid knocking, the ignition timing is deviated from the optimum ignition timing, so that the torque decreases and the exhaust temperature rises. Further, if the exhaust temperature rises and exceeds the heat resistant temperature of the exhaust manifold or the turbocharger, there is a problem that the exhaust manifold or the turbocharger may be damaged.

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

To achieve the above objectives, the fuel supply system in this disclosure is
LNG tank for storing LNG (Liquefied Natural Gas) fuel,
A CNG tank that stores CNG (Compressed Natural Gas) fuel,
An LNG injector capable of adjusting the injection amount of the LNG fuel supplied from the LNG tank and injected into the internal combustion engine.
A CNG injector capable of adjusting the injection amount of the CNG fuel supplied from the CNG tank and injected into the internal combustion engine, and
As the LNG fuel stored in the LNG tank becomes heavier, the ratio of the injection amount of the CNG fuel to the total injection amount of the injection amount of the LNG fuel and the injection amount of the CNG fuel increases. In addition, a control unit that controls the LNG injector and the CNG injector,
To be equipped.

The vehicle in this disclosure is
It is equipped with the above fuel supply system.

The fuel supply method in the present disclosure is
CNG in the total injection amount, which is the total of the injection amount of the LNG fuel injected into the internal combustion engine and the injection amount of the CNG fuel injected into the internal combustion engine according to the heaviness of the LNG fuel supplied to the internal combustion engine. Control is performed so that the ratio of the fuel injection amount increases.

According to the fuel supply system of the present disclosure, it is possible to prevent the occurrence of knocking even when the LNG fuel becomes heavy.

It is a figure which shows typically an example of the structure of the fuel supply system in embodiment of this disclosure. It is a figure which shows an example of the map which shows the relationship between the heaviness index of LNG fuel and the target boost, and the injection ratio of an LNG injector. It is a flowchart which shows an example of a fuel supply process.

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

The fuel supply system 1 includes an LNG fuel supply system 2 that supplies LNG fuel to engine E (internal engine) and a CNG fuel supply system 30 that supplies compressed natural gas (CNG) fuel to engine E. ing.

<LNG fuel supply system 2>
First, the LNG fuel supply system 2 will be described. The LNG fuel supply system 2 includes an LNG tank 4, an LNG fuel supply path 5, a vaporizer 6, a shutoff valve 7, a shutoff valve 7A, an LNG regulator 3, a fuel sensor 9, and a fuel thermometer 9A. It has an LNG injector 20A.

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

The LNG fuel supply path 5 connects the LNG tank 4 to the LNG regulator 3 via the vaporizer 6 and the shutoff valve 7. Further, the LNG fuel supply path 5 connects the LNG regulator 3 to the LNG injector 20A via the shutoff valve 7A.

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

The shutoff valve 7 opens and closes the LNG fuel supply path 5 between the vaporizer 6 and the LNG regulator 3.

The shutoff valve 7A opens and closes the LNG fuel supply path 5 between the LNG regulator 3 and the LNG injector 20A.

In the LNG fuel supply system 2, when the shutoff valve 7 is opened and the shutoff valve 7A is opened, LNG fuel is supplied from the LNG tank 4 to the LNG injector 20A via the vaporizer 6 and the LNG regulator 3. .. When the shutoff valve 7 is closed, the supply of LNG fuel from the LNG tank 4 to the LNG injector 20A is stopped regardless of whether the shutoff valve 7A is open or not.

The LNG regulator 3 decompresses the LNG fuel vaporized by the vaporizer 6.

The LNG injector 20A injects LNG fuel during intake air flowing into the fuel chamber E2 through the intake port E1. The injection amount of the LNG fuel injected from the LNG injector 20A is controlled by the injection time. Hereinafter, the amount of intake air flowing into the fuel chamber E2 through the intake port E1 is referred to as "intake amount".

The fuel sensor 9 is arranged in the LNG fuel supply path 5 between the LNG regulator 3 and the LNG injector 20A. The fuel sensor 9 detects the properties of the LNG fuel passing through the LNG fuel supply path 5. As a result, the fuel sensor 9 can detect the properties of the LNG fuel stored in the LNG tank 4. The fuel sensor 9 may be arranged in the LNG tank 4. Here, the "property of the LNG fuel" includes the components contained in the LNG fuel and the proportions of the components.

The fuel thermometer 9A detects the temperature of the fuel flowing through the LNG fuel supply path 5 between the vaporizer 6 and the LNG regulator 3. The fuel supply control device 10 (described later) executes the control for adjusting the flow rate of the cooling water based on the detection result of the fuel thermometer 9A.

<CNG fuel supply system 30>
Next, the CNG fuel supply system 30 will be described. The CNG fuel supply system 30 includes a CNG fuel supply path 31, a CNG tank 32, a shutoff valve 34, a pressure sensor 35, a shutoff valve 36, a CNG regulator 33, and a CNG injector 20B.

The CNG fuel supply path 31 connects the CNG tank 32 to the CNG regulator 33 via the shutoff valve 34. Further, the CNG fuel supply path 31 connects the CNG regulator 33 to the CNG injector 20B via the shutoff valve 36.

The CNG tank 32 is one of the fuel supply sources for supplying fuel to the engine E, and stores the CNG fuel. Here, it is assumed that the "CNG fuel" is a fuel equivalent to an LNG fuel containing a large amount of methane and not becoming heavy.

The shutoff valve 34 opens and closes the CNG fuel supply path 31 between the CNG tank 32 and the CNG regulator 33.

The shutoff valve 36 opens and closes the CNG fuel supply path 31 between the CNG regulator 33 and the CNG injector 20B.

In the CNG fuel supply system 30, when the shutoff valve 34 is opened and the shutoff valve 36 is opened, CNG fuel is supplied from the CNG tank 32 to the CNG injector 20B via the CNG regulator 33. When the shutoff valve 34 is closed, the supply of CNG fuel from the CNG tank 32 to the CNG injector 20B is stopped regardless of whether the shutoff valve 36 is open or not.

The CNG regulator 33 depressurizes the CNG fuel supplied from the CNG tank 32. The CNG fuel supply path 31 extending downstream from the CNG regulator 33 is connected to the CNG injector 20B.

The CNG injector 20B injects CNG fuel into the intake air flowing into the combustion chamber E2 through the intake port E1. The injection amount of CNG fuel injected from the CNG injector 20B is controlled by the injection time.

The fuel sensor 9 is arranged in the CNG fuel supply path 31 between the CNG regulator 33 and the CNG injector 20B. The fuel sensor 9 detects the properties of CNG fuel passing through the CNG fuel supply path 31.

The pressure sensor 35 detects the internal pressure of the CNG fuel supply path 31 between the shutoff valve 34 and the CNG regulator 33. 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 it is determined 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 under the injection of LNG fuel (torque limit).

<Fuel supply control device 10>
The fuel supply system 1 includes a fuel supply control device 10 (corresponding to the “control unit” of the present disclosure). The fuel supply control device 10 is composed of, for example, an electronic control unit 100 (ECU). The ECU 100 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a 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 described later. The fuel supply control device 10 has functions as an acquisition unit 11, a determination unit 12, and a control unit 13.

For example, when the LNG fuel in the LNG tank 4 becomes heavy (decrease in octane number) and the LNG fuel having a reduced octane number is used as, for example, fuel for the Otto cycle, knocking occurs. When the ignition timing is set late to avoid knocking, the ignition timing is deviated from the optimum ignition timing, so that the torque decreases and the exhaust temperature rises. Further, if the exhaust temperature rises and exceeds the heat resistant temperature of the exhaust manifold or the turbocharger, there is a problem that the exhaust manifold or the turbocharger may be damaged.

Therefore, the acquisition unit 11 acquires the properties of the LNG fuel from the fuel sensor 9. Here, the "property of the LNG fuel" means, for example, the ratio of methane contained in the LNG fuel. The proportion of methane is referred to as a weighting index, which indicates the degree of weighting of LNG fuel.

Further, 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 required torque sensor is an accelerator opening sensor that uses the required torque as a sensor output. The required torque corresponds to the "load applied to the internal combustion engine" of the present disclosure. In the following description, the required torque may be referred to as "target boost".

FIG. 2 is a diagram showing an example of a map showing the relationship between the heaviness index of LNG fuel and the target boost and the injection ratio of the LNG injector 20A. In the map shown in FIG. 2, the height of the heaviness index (ratio of methane) of the LNG fuel is shown in the horizontal direction, and the height of the target boost is shown in the vertical direction. In the map shown in FIG. 2, the injection ratio (MAP reading value) of the corresponding LNG injector 20A is set at the position where the heaviness index of the LNG fuel and the target boost intersect. The injection ratio of the CNG injector 20B is obtained as a value obtained by subtracting the MAP reading value from "10". For example, when the MAP reading value is "10", the injection ratio of the LNG injector 20A is "10" and the injection ratio of the CNG injector 20B is "0". Further, for example, when the MAP reading value is "0", the injection ratio of the LNG injector 20A is "0", and the injection ratio of the CNG injector 20B is "10".

The map shown in FIG. 2 is stored in the storage unit of the ECU 100. As shown in FIG. 2, the injection ratio of the LNG injector 20A is set to decrease according to the height of the heaviness index and the height of the target boost. In other words, the injection ratio of the CNG injector 20B is set to increase according to the height of the heaviness index and the height of the target boost. Maps can be obtained by experiments and simulations. The injection ratio of the LNG injector 20A may be calculated by referring to a predetermined calculation formula based on the heaviness index of the LNG fuel and the target boost.

The determination unit 12 determines the injection ratio (MAP reading value) of the LNG injector 20A with reference to the map shown in FIG. 2 based on the acquired target boost and the heaviness index of the LNG fuel. The injection ratio of the CNG injector 20B is determined by subtracting the injection ratio (MAP reading value) of the LNG injector 20A from "10".

The control unit 13 controls the LNG injector 20A and the CNG injector 20B based on the injection ratio of the LNG injector 20A determined by the determination unit 12 (hereinafter, simply referred to as “injection ratio”). Specifically, the control unit 13 calculates the injection time of the LNG fuel injected from the LNG injector 20A based on the intake amount and the determined injection ratio, and based on the calculated injection time of the LNG fuel. , Controls the LNG injector 20A. Further, the control unit 13 calculates the injection time of the CNG fuel injected from the CNG injector 20B based on the intake amount and the determined injection ratio, and based on the calculated injection time of the CNG fuel, the CNG injector. 20B is controlled.

Next, an example of the fuel supply process will be described with reference to FIG. FIG. 3 is a flowchart showing an example of fuel supply processing. Hereinafter, the ECU 100 having the functions of the acquisition unit 11, the determination unit 12, and the control unit 13 will be described as performing the fuel supply process. This flow is started, for example, when the ECU 100 receives a request to start this flow.

First, in step S100, the ECU 100 acquires the LNG fuel weighting index from the fuel sensor 9.

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

In step S120, the ECU 100 determines the injection ratio of the LNG injector 20A (injection ratio of the CNG injector 20B) with reference to the map shown in FIG. 2 based on the heaviness index of the LNG fuel and the target boost.

Next, in step S130, the ECU 100 determines whether or not the determined injection ratio of the LNG injector 20A is less than "10", in other words, whether or not the injection ratio of the CNG injector 20B is greater than "0". judge. When the injection ratio of the CNG injector 20B is larger than "0" (step S130: YES), the process proceeds to step S140. When the injection ratio of the CNG injector 20B is “0” or less (step S130: NO), the process proceeds to step S150.

In step S140, the ECU 100 determines whether the CNG tank 32 has sufficient fuel, and if the CNG tank 32 has sufficient fuel (remaining amount) (step S140: YES), the process proceeds to step S150. If there is not enough fuel in the CNG tank 32 (step S140: NO), the process transitions to step S160.

In step S150, the ECU 100 controls the LNG injector 20A based on the injection ratio of the LNG injector 20A, and controls the CNG injector 20B based on the injection ratio of the CNG injector 20B. After that, the flow shown in FIG. 3 ends.

In step S160, the ECU 100 executes control to reduce the torque to a torque at which knocking does not occur under the injection of LNG fuel (torque limit). After that, the flow shown in FIG. 3 ends.

The fuel supply system 1 in the above embodiment adjusts the injection amount of the LNG tank 4 for storing the LNG fuel, the CNG tank 32 for storing the CNG fuel, and the LNG fuel supplied from the LNG tank 4 and injected into the engine E. Depending on the possible LNG injector 20A, the CNG injector 20B that can adjust the injection amount of CNG fuel supplied from the CNG tank 32 and supplied to the engine E, and the LNG fuel stored in the LNG tank 4, the weight of the LNG fuel becomes heavier. A control unit 13 for controlling the LNG injector 20A and the CNG injector 20B is provided so that the ratio of the injection amount of the CNG fuel to the total injection amount which is the total injection amount of the LNG fuel and the injection amount of the CNG fuel increases.

With the above configuration, when the LNG fuel becomes heavier, CNG fuel, which is the same fuel as the LNG fuel with a large amount of methane and not heavier, is supplied to the engine E according to the degree of heaviness, so that knocking occurs. Can be prevented from occurring.

Further, in the fuel supply system 1 in the above embodiment, when the LNG fuel becomes heavy, the torque is not limited by avoiding knocking, so that the operation without hindering the running of the vehicle becomes possible.

Further, in a normal vehicle, the LNG tank 4 is equipped with a large one, but the CNG tank 32 is equipped with only a small one. Therefore, when the CNG fuel is used frequently, the CNG fuel decreases rapidly. However, when the LNG fuel becomes heavy and the engine E is in a high load state, the CNG fuel cannot be used, and as a result, the cruising range is reduced. In the fuel supply system 1 of the above embodiment, LNG fuel is used in a low load state in which knocking is unlikely to occur, and CNG fuel is used only in a high load state in which knocking is likely to occur. It can be suppressed and it is possible to prevent a significant decrease in cruising range.

In addition, the above embodiments are merely examples of embodiment of the present disclosure, and the technical scope of the present disclosure should not be construed in a limited manner by these. .. That is, the present disclosure can be implemented in various forms without departing from its gist or its main features.

In the above embodiment, the case where the proportion of methane (property of the LNG fuel) is small is defined as the case where the LNG fuel becomes heavy, but the present disclosure is not limited to this, and for example, the LNG fuel injected into the engine E is used. The case where the output of the engine E with respect to the injection amount of the above is less than the threshold value may be the case where the LNG fuel becomes 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 value.

Further, in the above embodiment, the injection ratio of the LNG injector 20A is determined based on the torque (target boost) required for the engine E, but the present disclosure is not limited to this, and for example, the load applied to the engine E It may be determined based on the size. In this case, the load applied to the engine E may be measured by a torque sensor, for example, a strain gauge adhered to the crankshaft.

The present disclosure is suitably used for a vehicle provided with a fuel supply system that is required to prevent the occurrence of knocking even when the LNG fuel becomes heavy.

1 Fuel supply system 2 LNG fuel supply system 3 LNG regulator 4 LNG tank 5 LNG fuel supply path 6 Vaporizer 7, 7A shutoff valve 8 Remaining amount detection sensor 9 Fuel sensor 10 Fuel supply control device 11 Acquisition unit 12 Decision unit 13 Control unit 20A LNG injector 20B CNG injector 30 CNG fuel supply system 31 CNG fuel supply path 32 CNG tank 33 CNG regulator 34, 36 Shutoff valve 35 Pressure sensor 100 ECU

Claims (5)

LNG tank for storing LNG (Liquefied Natural Gas) fuel,
A CNG tank that stores CNG (Compressed Natural Gas) fuel,
An LNG injector capable of adjusting the injection amount of the LNG fuel supplied from the LNG tank and injected into the internal combustion engine.
A CNG injector capable of adjusting the injection amount of the CNG fuel supplied from the CNG tank and injected into the internal combustion engine, and
As the LNG fuel stored in the LNG tank becomes heavier, the ratio of the injection amount of the CNG fuel to the total injection amount of the injection amount of the LNG fuel and the injection amount of the CNG fuel increases. In addition, a control unit that controls the LNG injector and the CNG injector,
To prepare
Fuel supply system. The control unit controls the LNG injector and the CNG injector so that the ratio of the injection amount of the CNG fuel increases according to the load of the internal combustion engine.
The fuel supply system according to claim 1. The control unit includes the LNG injector and the LNG injector based on a heaviness index indicating the degree of heaviness of the LNG fuel and a map showing the relationship between the load of the internal combustion engine and the ratio of the injection amount of the CNG fuel. Controlling the CNG injector,
The fuel supply system according to claim 2. A vehicle comprising the fuel supply system according to any one of claims 1 to 3. CNG in the total injection amount, which is the total of the injection amount of the LNG fuel injected into the internal combustion engine and the injection amount of the CNG fuel injected into the internal combustion engine according to the heaviness of the LNG fuel supplied to the internal combustion engine. Perform control to increase the proportion of fuel injection,
Fuel supply method.

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