ENGINE CONTROL DEVICE, AND VEHICLE

This control device for an engine provided with a fuel supply system capable of supplying liquefied natural gas to the engine as fuel comprises: a control unit for calculating a feedback adjustment value on the basis of a deviation between an actual fuel supply quantity and a target fuel supply quantity, and performing feedback control of the fuel supply system on the basis of the calculated feedback adjustment value; an acquiring unit for acquiring a methane number of the liquefied natural gas; a correcting unit for correcting the feedback adjustment value on the basis of the acquired methane number; and a failure diagnosis unit for performing failure diagnosis of the fuel supply system on the basis of the corrected feedback adjustment value. The engine control device can allow the failure diagnosis of the fuel supply system to operate normally.

TECHNICAL FIELD

The present disclosure relates to an engine control device and a vehicle.

BACKGROUND ART

In the related art, LNG (liquefied natural gas) vehicles that use LNG as a fuel are known. A tank for storing LNG is mounted in an LNG vehicle. The LNG fuel stored in the tank is supplied by the supply system to the engine, and burned and consumed by the engine.

PTL 1 discloses an engine including a control part that calculates a feedback correction value on the basis of the deviation between the target fuel supplying amount and the actual fuel supplying amount, and performs feedback control of the fuel supply system on the basis of the calculated feedback correction value.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

Incidentally, the LNG fuel (hereinafter referred to as fuel) contains components such as methane, ethane, propane and butane. In the case where the fuel in the LNG tank in the vehicle is not maintained at a low temperature, methane with a low boiling point is vaporized first and emitted to the atmosphere because the components of the fuel have different boiling points. In this manner, the fuel supplied to the engine become heavier.

In the engine disclosed in PTL 1, in the case where the defect diagnosis of the fuel supply system is performed on the basis of the difference between the feedback correction value and a reference value, the actual fuel supplying amount varies due to the fuel that has become heavier, and the difference between the feedback correction value and the reference value varies, and as a result, the defect diagnosis of the fuel supply system may not be normally performed.

An object of the present disclosure is to provide an engine control device and a vehicle that can normally perform the defect diagnosis of the fuel supply system.

Solution to Problem

To achieve the above-mentioned object, a control device of an engine including a fuel supply system configured to supply liquefied natural gas as a fuel to an engine according to the present disclosure, includes: a control part configured to calculate a feedback correction value based on a deviation between an actual fuel supplying amount and a target fuel supplying amount, and feedback-control the fuel supply system based on the feedback correction value calculated; an acquiring part configured to acquire a methane value of the liquefied natural gas; a modification part configured to modify the feedback correction value based on the methane value acquired; and a defect diagnosis part configured to perform a defect diagnosis of the fuel supply system based on the feedback correction value modified.

A vehicle of the present disclosure includes the above-described control device of the engine.

Advantageous Effects of Invention

According to the present disclosure, the defect diagnosis of the fuel supply system can be normally performed.

DESCRIPTION OF EMBODIMENTS

An embodiment of the present disclosure is described below with reference to the drawings.FIG.1is a block diagram schematically illustrating a configuration of internal combustion system100according to the embodiment of the present disclosure.

As illustrated inFIG.1, internal combustion system100includes LNG engine10(hereinafter referred to as engine). Cylinder block11of engine10is provided with piston12for each cylinder11c.Piston12is coupled to crankshaft13through connecting rod14. Piston12vertically moves in accordance with the rotation of crankshaft13. Cylinder head15above cylinder block11is provided with ignition plug16for each cylinder11c.

In addition, internal combustion system100includes turbocharger60(supercharger) that supercharges intake gas, and exhaust recirculation device70called EGR (Exhaust Gas Recirculation) that takes out a part of the exhaust gas from the exhaust side and returns it to the intake side. Note that the exhaust gas returned to the intake side is referred to as EGR gas.

Turbocharger60includes turbine61that is driven by exhaust gas, and compressor62that is driven by the driving force of turbine61to compress intake gas. Inter cooler63that cools intake gas is provided at intake pipe23between compressor62and intake manifold25. Intake gas regulation throttle valve23bthat regulates the amount of intake gas of bypass passage23ais provided at bypass passage23a.

Exhaust recirculation device70includes exhaust recirculation passage71that connects the exhaust side and the intake side of engine10, exhaust recirculation cooler72that is provided at exhaust recirculation passage71to cool EGR gas, and exhaust recirculation valve73that is provided at exhaust recirculation passage71to regulate the exhaust recirculation amount.

The intake gas to engine10passes from cleaner22to intake pipe23or bypass passage23a.The intake gas past intake pipe23is compressed by compressor62and cooled by inter cooler63. The intake gas past intake pipe23or bypass passage23aflows into intake manifold25together with the EGR gas from exhaust recirculation passage71so as to be mixed with the fuel obtained by vaporizing at LNG vaporizer33the liquefied natural gas (LNG) from fuel injector36provided for each cylinder11cand introduced into cylinder11c,and, ignited and burned by ignition plug16.

On the intake side of engine10, throttle opening sensor41that detects the opening of intake throttle valve24, intake gas pressure sensors42and43that detect the pressure of the intake gas, and intake gas temperature sensors44and45that detect the temperature of the intake gas are provided. The detection values of sensors41,42,43,44and45are input to control device50(engine control unit). In addition, airflow sensor47that detects the amount of the intake gas taken from air cleaner22is provided. The detection value of airflow sensor47is input to control device50.

The exhaust gas from cylinder11cis exhausted to exhaust manifold27through exhaust valve18such that a part of the gas flows into exhaust recirculation passage71and that another part of the gas is supplied to exhaust pipe28through turbine61. The exhaust gas is supplied from exhaust pipe28to three-way catalyst29such that CO, non-methane hydrocarbon (NMHC), and NOx are removed by three-way catalyst29and that it is exhausted to the atmosphere through silencer29a.

Air-fuel ratio sensor46(random sensor) that detects the air-fuel ratio on the basis of the oxygen concentration of the exhaust gas exhausted from exhaust manifold27is disposed at exhaust pipe28. The detection value of air-fuel ratio sensor46is input to control device50.

The LNG is supplied by fuel supply system20to engine10and used as the fuel of the engine10. Fuel supply system20includes LNG tank31, LNG pressure regulator32, LNG vaporizer33, LNG regulator34, LNG supply path35, fuel injector36and the like.

LNG tank31is mounted in the vehicle, and stores at a low temperature the LNG to maintain it in the liquid state. LNG pressure regulator32, LNG vaporizer33, and LNG regulator34are disposed at LNG supply path35. The LNG guided from LNG tank31and gas fuel regulated by LNG pressure regulator32are mixed, and vaporized by LNG vaporizer33. The vaporized fuel is depressurized to a given pressure by LNG regulator34, and supplied by fuel injector36to intake manifold25of engine10. The supplied fuel is mixed with the intake gas flown into intake manifold25so as to be introduced to each cylinder11c, and ignited and burned by ignition plug16. In the following description, the “fuel” means vaporized LNG, not LNG before vaporization.

Methane value sensor48that detects the methane value of the fuel supplied from LNG tank31to cylinder11cis disposed at LNG supply path35. The detection value of methane value sensor48is input to control device50.

Control device50includes a CPU (Central Processing Unit), a ROM (Read Only Memory), an EEPROM (Electrically Erasable Programmable Read Only Memory), a RAM (Random Access Memory), an input port, an output port and the like. The CPU of control device50executes various functions by loading in the RAM a predetermined program stored in the ROM.

FIG.2is a block diagram illustrating a configuration of control device50of engine10. Control device50includes, as the various functions, acquiring part51, modification part52, control part53, and defect diagnosis part54.

Acquiring part51acquires the detection value of air-fuel ratio sensor46. In addition, acquiring part51acquires the detection value (intake gas amount) of airflow sensor47. In addition, acquiring part51acquires the methane value of the fuel from methane value sensor48.

Control part53calculates the actual fuel injection amount jetted from fuel injector36on the basis of the detection value of air-fuel ratio sensor46and the detection value (intake gas amount) of airflow sensor47. Control part53calculates a feedback correction value for each block on the basis of the deviation between the actual fuel injection amount and the target fuel injection amount. Note that the block is elaborated later. The fuel injection time (ms) per stroke is used for “fuel injection amount”. The fuel injection time per stroke is determined on the basis of the fuel amount calculated from the amount of intake gas of engine10and the injector coefficient. The amount of intake gas of engine10is determined on the basis of the pressure of the intake gas detected by intake gas pressure sensor43, the temperature of the intake gas detected by intake gas temperature sensor45, the atmospheric pressure detected by the atmospheric pressure sensor (not illustrated), and the engine rotational frequency detected from a crank angle sensor (not illustrated), for example.

FIG.3is a diagram illustrating an example of control map55. Control map55illustrated inFIG.3is stored in the EEPROM of control device50. In control map55, feedback correction values are associated with a plurality of respective blocks sectioned by the engine rotational frequency and the engine load. Control map55is sectioned into m blocks by the engine rotational frequency and into n blocks by the engine load. Specifically, control map55is sectioned into (m×n) blocks by the engine rotational frequency and the engine load. Note that m and n are integers of two or more, and may be the same or different from each other. The engine load is determined on the basis of an intake manifold pressure. The intake manifold pressure is detected by intake gas pressure sensors42and43. Note that the engine load this is not limited to this, and may be determined on the basis of a detection value of a torque sensor that detects the degree of the variation of the rotation of the crankshaft, for example.

Control part53controls fuel supply system20on the basis of the feedback correction value. More specifically, control part53controls fuel injector36.

Incidentally, the feedback correction value and the variation of the actual fuel supplying amount due to the fuel that has become heavier are correlated, and therefore the actual fuel supplying amount varies due to the fuel that has become heavier, and as a result the feedback correction value varies. In addition, since the methane value of the fuel and the variation of the actual fuel supplying amount are correlated, the relational expression representing the relationship between the methane value of the fuel and the feedback correction value can be determined. In addition, the relationship between the methane value of the fuel and the feedback correction value can be determined through experiments and/or simulations, and thus the relationship determined through experiments and/or the like can be stored in the form of table in the EEPROM of control device50.

Modification part52modifies the feedback correction value for each block on the basis of the methane value of the fuel with reference to the relational expression or the table. Thus, the feedback correction value is a numerical value that is not influenced by the fuel that has become heavier. Note that the methane value of the fuel is detected by methane value sensor48as described above.

Defect diagnosis part54calculates the difference between the reference value and the feedback correction value modified by modification part52for each block. Note that the reference value is set with a certain acceptable range on the basis of the results of experiments and/or simulations. When the number of blocks of which the difference exceeds a threshold value is equal to or greater than a predetermined number, defect diagnosis part54determines that there is a defect of fuel supply system20. Here, a defect of fuel supply system20is a defect of one or more of the components (such as LNG tank31, LNG pressure regulator32, LNG vaporizer33, LNG regulator34, LNG supply path35, and fuel injector36) of fuel supply system20, control device50that controls fuel supply system20, and a sensor that outputs the detection value of control device50.

Next, an example of a process of control device50of engine10according to the embodiment of the present disclosure is described with reference toFIG.4.FIG.4is a flowchart illustrating an example of a process of control device50of engine10. This procedure is started in response to the start operation of engine10and repeated at a given time interval after the start. Note that the following description will be made on the assumption that various functions of control device50are executed by the CPU. In addition, the calculation and modification of the feedback correction value are performed for each block, but the description thereof will be omitted here.

As illustrated inFIG.4, at step S100, the CPU acquires the actual fuel injection amount.

Next, at step S110, the CPU calculates the feedback correction value on the basis of the deviation between the actual fuel injection amount and the target fuel injection amount.

Next, at step S120, the CPU acquires the methane value from methane value sensor48.

Next, at step S130, the CPU modifies the feedback correction value with the methane value.

Next, at step S140, the CPU calculates the difference between the reference value and the modified feedback correction value.

Next, at step S150, the CPU determines whether the difference exceeds a threshold value. When the difference exceeds a threshold value (step S150: YES), the process is advanced to step S160. When the difference is equal to or smaller than the threshold value (step S150: NO), the procedure illustrated inFIG.4is terminated.

At step S160, the CPU executes a control of a defect notification of fuel supply system20.

Control device50of engine10according to the present embodiment is control device50of engine10including fuel supply system20that can supply liquefied natural gas as a fuel to engine10, and includes control part53that calculates a feedback correction value based on a deviation between an actual fuel supplying amount and a target fuel supplying amount, and feedback-controls fuel supply system20based on the calculated feedback correction value, acquiring part51that acquires a methane value of the liquefied natural gas, modification part52that modifies the feedback correction value based on the acquired methane value, and defect diagnosis part54that calculates the difference between the reference value and the modified feedback correction value and determines that there is a defect of fuel supply system20when the calculated difference exceeds a threshold value.

With the above-mentioned configuration, the difference between the feedback correction value and the reference value is not varied by the fuel that has become heavier because the feedback correction value is modified with the methane value, and thus the defect diagnosis of fuel supply system20that is performed on the basis of the difference can be normally performed.

Control device50of engine10according to the present embodiment further includes control map55in which the feedback correction value is associated with each of a plurality of blocks sectioned by the engine rotational frequency and the engine load, and defect diagnosis part54calculates the difference between the reference value and the modified feedback correction value for each block, and determines that there is a defect of fuel supply system20when the number blocks of which the difference exceeds a threshold value is equal to or greater than a predetermined value. In this manner, the feedback correction value is calculated and modified for each block, and thus the accuracy of the defect diagnosis can be increased.

Note that control part53according to the present embodiment calculates a feedback correction value on the basis of the deviation between the actual fuel supplying amount and the target fuel supplying amount and feedback-controls fuel supply system20on the basis of the calculated feedback correction value, but the present disclosure is not limited to this. For example, control part53may calculate the feedback correction value on the basis of the deviation between the actual air-fuel ratio and the target air-fuel ratio, and feedback-control fuel supply system20on the basis of the calculated feedback correction value.

In addition, in the present embodiment, the CPU executes the control of the defect notification of fuel supply system20when the difference between the reference value and the modified feedback correction value exceeds a threshold value (step S150: YES). For example, when the difference exceeds a threshold value, the CPU executes a control of displaying on the in-vehicle display device defect information indicating that the difference exceeds a threshold value. In addition, the CPU may execute a control of transmitting the defect information from an in-vehicle information communication terminal to a management terminal via the Internet. In this manner, the defect information can be notified from the management terminal to the driver's personal computer and/or mobile terminal.

In addition, in the present embodiment, the configuration of internal combustion system100is applied to engine10that supplies the fuel to cylinder11ctogether with the intake gas and ignites and burns it by ignition plug16, but the configuration of internal combustion system100may be applied to a direct injection engine that directly jets the fuel into cylinder11c.

In addition, control device50of engine10according to the present embodiment may be applied to a dual fuel engine that can use both liquefied natural gas (LNG) and compressed natural gas (CNG) as the fuel in a switching manner.

The above-mentioned embodiments are merely examples of embodiments for implementing the present disclosure, and the technical scope of the present disclosure should not be interpreted as limited by them. In other words, the present disclosure can be implemented in various forms without departing from its gist or its main features.

This application is entitled to and claims the benefit of Japanese Patent Application No. 2021-186450 filed on Nov. 16, 2021, the disclosure each of which including the specification, drawings and abstract is incorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

The present disclosure is suitable for a vehicle equipped with a control device of an engine that needs to normally perform the defect diagnosis of the fuel supply system.

REFERENCE SIGNS LIST