Fuel supply device of internal combustion engine

Abstract

To provide a fuel supply device of an internal combustion engine capable of avoiding closing a solenoid valve due to a load applied from a vehicle body during traveling of a vehicle while suppressing excessive rise of a temperature of the solenoid valve provided in a fuel supply system.SOLUTION: Provided that a vehicle speed is equal to or larger than a predetermined value, a current value passing through an electromagnetic coil of a cutoff valve (solenoid valve) is controlled to be increased (step ST5). Therefore, it is possible to avoid closing the solenoid valve due to a load applied from a vehicle body during traveling of a vehicle while suppressing excessive rise of a temperature of the cutoff valve provided in a fuel supply system.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a fuel supply device provided in an internal combustion engine. [Background technology]

[0002] Conventionally, as disclosed in Patent Document 1, in a gas engine that uses a gas such as hydrogen as fuel, a solenoid valve that can be opened and closed is provided in a fuel supply pipe extending from a fuel tank to an injector in a fuel supply system. When the gas engine is operating, the solenoid valve is opened to enable the supply of fuel to the injector, whereas when the gas engine is stopped, the solenoid valve is closed to disable the supply of fuel to the injector and prevent fuel leakage. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-56380 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, when a normally closed type solenoid valve that closes when not energized is adopted as the solenoid valve, the solenoid coil of the solenoid valve is energized to maintain the open state while the gas engine is in operation. The value of the current that energizes the solenoid coil is set uniformly so that the temperature of the solenoid coil does not exceed a criterion even in a situation where the temperature of the solenoid coil is likely to rise (for example, a situation where the outside air temperature is high and the vehicle speed is low, making it impossible to expect cooling by the traveling wind).

[0005] However, if the current value is set uniformly in this manner, if the load acting from the vehicle body while the vehicle is traveling (the load acting on the solenoid valve from the vehicle body during sudden braking or turning) exceeds the electromagnetic force obtained by the current value, the solenoid valve may close, and in this case, there is a risk that the supply of fuel to the injector may stop.

[0006] The present invention has been made in consideration of the above-mentioned points, and an object of the present invention is to provide a fuel supply device for an internal combustion engine that can prevent the temperature of a solenoid valve provided in a fuel supply system from rising excessively, while avoiding the solenoid valve from closing due to the load acting from the vehicle body while the vehicle is traveling. [Means for solving the problem]

[0007] The solution of the present invention for achieving the above object is based on a fuel supply device for an internal combustion engine, which is mounted on a vehicle and has a fuel supply pipe provided with a solenoid valve that closes when a current is not applied to a solenoid coil and opens when a current is applied. The fuel supply device for an internal combustion engine is characterized by having a current control unit that controls the value of the current applied to the solenoid coil to increase when the vehicle speed is equal to or higher than a predetermined value.

[0008] When the vehicle speed is equal to or higher than a predetermined value, there is a concern that the load acting from the vehicle body may close the solenoid valve. However, in this solution, only in such a situation, the current value passing through the electromagnetic coil is controlled to the increasing side, thereby increasing the electromagnetic force and preventing the solenoid valve from closing. By controlling the current value passing through the electromagnetic coil to the increasing side only when a specific condition is satisfied, the amount of heat generated by the electromagnetic coil can be suppressed. In addition, in this case, since the vehicle speed is high, it is expected that the solenoid valve will be cooled by the wind while the vehicle is traveling. Therefore, while suppressing an excessive rise in the temperature of the solenoid valve provided in the fuel supply system, it is possible to avoid the solenoid valve from closing due to the load acting from the vehicle body while the vehicle is traveling. Effect of the Invention

[0009] In the present invention, the value of the current flowing through the electromagnetic coil of the solenoid valve is controlled to be increased on the condition that the vehicle speed is equal to or greater than a predetermined value, so that it is possible to prevent the solenoid valve in the fuel supply system from closing due to the load acting from the vehicle body while the vehicle is traveling while suppressing an excessive increase in temperature. [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram showing a schematic configuration of a hydrogen engine system. [Diagram 2] FIG. 4 is a flowchart showing a procedure for controlling a current value of a shutoff valve. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this embodiment, the present invention will be described as being applied to a system equipped with a four-cylinder hydrogen engine (an internal combustion engine fueled by hydrogen gas) mounted on a vehicle.

[0012] -Overview of hydrogen engine system- Fig. 1 is a diagram showing a schematic configuration of a hydrogen engine system 1 according to this embodiment. As shown in Fig. 1, the hydrogen engine system 1 according to this embodiment includes an intake system 3, an exhaust system 4, and a fuel supply system 5, which are connected to an engine body (internal combustion engine) 2. Each of these will be briefly described below.

[0013] The engine body 2 includes four cylinders #1 to #4, the first to fourth cylinders #1 to #4, and obtains a rotational driving force by the reciprocating movement of pistons (not shown) that accompany the combustion of a mixture (a mixture of hydrogen gas and air) in the combustion chambers (inside the cylinders) of these cylinders #1 to #4. A cylinder head (not shown) is attached to the upper end of a cylinder block 21 in the engine body 2, and spark plugs 22 are arranged in the cylinder head so as to face the combustion chambers of each of the cylinders #1 to #4. Also, an injector (direct injection injector: fuel injection valve) 54 that injects hydrogen gas (fuel) supplied from a fuel supply system 5 into the combustion chamber is arranged in each of the cylinders #1 to #4. A water temperature sensor 23 that detects the temperature of engine cooling water, a crank angle sensor 24 that detects the crank angle, and the like are arranged in the cylinder block 21. The configuration of the engine body 2 is not limited to this.

[0014] The intake system 3 includes an intake passage 31, a surge tank 32, and an intake manifold 33 for supplying intake air (air) toward the combustion chambers of each of the cylinders #1 to #4. An air cleaner 34, an air flow meter 35, an intake air temperature sensor 36 (built into the air flow meter 35), and an electronically controlled throttle valve 37 are arranged on the upstream side of the intake passage 31 (upstream side of the flow of intake air). The throttle valve 37 is driven by a throttle motor 38. An intake valve (not shown) is arranged at the downstream end of an intake port formed in the cylinder head, and intake air is supplied into the combustion chamber by opening this intake valve. The configuration of the intake system 3 is not limited to this. For example, the configuration may be such that the surge tank 32 is not included.

[0015] The exhaust system 4 includes an exhaust manifold 41 and an exhaust passage 42. A catalytic converter 43 for purifying exhaust (mainly NOx in the exhaust) is disposed in the exhaust passage 42. An exhaust valve (not shown) is disposed at the upstream end of an exhaust port formed in the cylinder head, and exhaust gas is discharged from the combustion chamber when this exhaust valve is opened. The configuration of the exhaust system 4 is not limited to this.

[0016] The fuel supply system 5 includes a hydrogen storage tank (high-pressure tank) 51, a fuel supply pipe 52, a delivery pipe 53, and an injector 54 for each cylinder. The hydrogen storage tank 51 is a tank that stores hydrogen under high pressure. The fuel supply pipe 52 is provided with a pressure reducing valve 55 for reducing the pressure of the hydrogen gas supplied to the delivery pipe 53, a relief valve 56 that opens when the fuel pressure inside the fuel supply pipe 52 exceeds a predetermined value, and a shutoff valve (electromagnetic valve) 6 that can be switched between an open state and a closed state. The shutoff valve 6 includes a valve body and an electromagnetic solenoid (not shown) therein, and is of a normally closed type that closes when the electromagnetic coil of the electromagnetic solenoid is not energized and opens when it is energized. That is, when the engine body 2 is operating, the electromagnetic coil is energized to open the shutoff valve 6, enabling the supply of hydrogen gas toward the delivery pipe 53 and the injector 54, whereas when the engine body 2 is stopped, the electromagnetic coil is deenergized to close the shutoff valve 6, preventing the supply of hydrogen gas toward the delivery pipe 53 and the injector 54 and preventing fuel leakage. Note that the shutoff valve 6 is not limited to being switchable between the open state and the closed state, but may be configured to be switchable between a plurality of open states having different flow passage areas for hydrogen gas as the open state, and to have different supply fuel pressures in each state.

[0017] Further, a pressure sensor 57 for detecting the pressure of the hydrogen gas in the delivery pipe 53 and a temperature sensor 58 for detecting the temperature of the hydrogen gas in the delivery pipe 53 are disposed in the delivery pipe 53 .

[0018] Each injector 54 injects hydrogen gas supplied via a delivery pipe 53 into the combustion chamber at a predetermined timing. The hydrogen gas injected from the injector 54 into the combustion chamber mixes with air supplied from the intake system 3 to form an air-fuel mixture in the combustion chamber. This mixture is ignited by the spark plug 22 and combusted. The high-temperature, high-pressure combustion gas generated thereby pushes the pistons down from top dead center during the expansion stroke of each of the cylinders #1 to #4, rotating the crankshaft and generating a rotational driving force (output torque).

[0019] The ECU (Electronic Control Unit) 100 is a known device that includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and a backup RAM. The CPU executes various arithmetic processing based on various control programs and maps stored in the ROM. The RAM temporarily stores the results of calculations performed by the CPU and data input from each sensor, and the backup RAM stores data that should be saved when the engine is stopped, for example.

[0020] The ECU 100 is connected to the above-mentioned water temperature sensor 23, crank angle sensor 24, air flow meter 35, intake air temperature sensor 36, pressure sensor 57, temperature sensor 58, etc. Also connected to the ECU 100 is an accelerator opening sensor 101 that outputs a detection signal corresponding to the depression amount of an accelerator pedal (not shown). Furthermore, the ECU 100 is connected to the ignition plug 22 (more specifically, an igniter), throttle motor 38, injector 54, etc.

[0021] Based on signals from the various sensors, the ECU 100 executes various controls including drive control of the injector 54 (control of the amount of fuel injection), control of the ignition timing of the spark plug 22, and drive control of the throttle motor 38 (control of the amount of intake air).

[0022] As described above, since the shutoff valve 6 is of a normally closed type that closes when not energized, the electromagnetic coil of the shutoff valve 6 is energized to maintain an open state during operation of the engine body 2. In this case, if the current value for energizing the electromagnetic coil is set uniformly to a value that does not cause the temperature of the electromagnetic coil to exceed a criterion even under conditions in which the temperature of the electromagnetic coil is likely to rise (for example, under conditions in which cooling by the traveling wind cannot be expected due to high outside air temperature and low vehicle speed), the shutoff valve 6 may close if the load acting from the vehicle body while the vehicle is traveling (the load acting from the vehicle body on the shutoff valve 6 during sudden braking or turning) exceeds the electromagnetic force obtained by the current value, and in this case, there is a risk that the supply of fuel to the delivery pipe 53 may be stopped.

[0023] In view of this, the ECU 100 is provided with a current control unit 110 as a functional unit realized by the control program. The current control unit 110 is a functional unit that controls the current value passed through the electromagnetic coil of the shutoff valve 6. The current control unit 110 has a function of controlling the current value passed through the electromagnetic coil of the shutoff valve 6 to the increasing side on condition that the vehicle speed is equal to or higher than a predetermined value. In other words, only when the vehicle speed is equal to or higher than a predetermined value, the current value passed through the electromagnetic coil of the shutoff valve 6 is controlled to the increasing side to increase the electromagnetic force, thereby suppressing the shutoff valve 6 from being closed due to the load acting from the vehicle body while the vehicle is traveling. In this way, only when a specific condition (the vehicle speed is equal to or higher than a predetermined value) is satisfied, the current value passed through the electromagnetic coil is controlled to the increasing side (the current value is not controlled to the increasing side when the vehicle speed is less than the predetermined value), thereby suppressing the amount of heat generated by the electromagnetic coil. In addition, in this case, since the vehicle speed is high, cooling of the shutoff valve 6 by the traveling wind can be expected. This makes it possible to prevent the temperature of the shutoff valve 6 provided in the fuel supply system 5 from increasing excessively, while also making it possible to prevent the shutoff valve 6 from being closed due to the load acting from the vehicle body while the vehicle is traveling.

[0024] Due to this configuration, the fuel supply system 5 and the ECU 100 (particularly the current control unit 110) constitute a fuel supply device according to the present invention.

[0025] -Shutoff valve current control- Next, a description will be given of the shutoff valve current value control, which is a characteristic control of this embodiment. This shutoff valve current value control is the control of the current value to the electromagnetic coil performed by the current control unit 110, and as described above, controls the current value flowing through the electromagnetic coil of the shutoff valve 6 to the increasing side on the condition that the vehicle speed is equal to or higher than a predetermined value.

[0026] 2 is a flowchart showing a procedure for controlling a current value of a shutoff valve, which is repeatedly executed at predetermined time intervals while the vehicle is running.

[0027] First, in step ST1, it is determined whether the vehicle speed is equal to or higher than a preset threshold value. The vehicle speed is detected by a vehicle speed sensor (not shown). Alternatively, the vehicle speed may be calculated from the engine speed calculated based on a crank angle detection signal from the crank angle sensor 24 and the gear ratio of a transmission (not shown). The threshold value is preset by experiment or simulation as a vehicle speed value at which a load from the vehicle body that closes the shutoff valve 6 may occur. Examples of the load from the vehicle body include G (acceleration) during sudden braking of the vehicle, G during turning, and G input from the road surface.

[0028] If the vehicle speed is below the threshold and the judgment result in step ST1 is NO, the process proceeds to step ST6, where it is determined whether or not shut-off valve current value control is currently being performed (controlling the current value passing through the electromagnetic coil of the shut-off valve 6 to increase the value) and if the judgment result in step ST6 is NO and the process is not currently being performed, the process returns.

[0029] On the other hand, if the vehicle speed is equal to or higher than the threshold value and the determination in step ST1 is YES, the process proceeds to step ST2, where various state quantities are acquired. The state quantities acquired here include the engine coolant temperature, hydrogen gas temperature (fuel temperature), engine rotation speed, engine output (engine torque), etc. The engine coolant temperature is acquired from a detection signal from the water temperature sensor 23. The hydrogen gas temperature is acquired from a detection signal from the temperature sensor 58. The engine rotation speed is calculated based on a crank angle detection signal from the crank angle sensor 24. The engine torque is calculated based on a detection signal from a torque sensor (not shown) or information on the fuel injection amount and fuel injection timing from each injector 54.

[0030] In step ST3, the temperature of the shutoff valve 6 is estimated. Methods for estimating the temperature of the shutoff valve 6 include estimating the temperature of the shutoff valve 6 based on the hydrogen gas temperature (fuel temperature), the engine coolant temperature, the engine rotation speed, the engine output (engine torque), and the like. The temperature of the shutoff valve 6 may also be estimated by fitting these state quantities to a map created by a pre-test. Instead of estimating the temperature of the shutoff valve 6, a temperature sensor may be directly attached to the shutoff valve 6 to detect the temperature of the shutoff valve 6.

[0031] In step ST4, a maximum allowable current value that can be passed through the electromagnetic coil of the shutoff valve 6 is calculated. This maximum allowable current value takes into consideration the amount of heat generated by the electromagnetic coil in the current state quantity acquired in step ST2, and is calculated by converting the amount of heat generated from the difference between the heat resistance temperature criteria and the temperature of the shutoff valve 6. In other words, the maximum current value within the range in which the amount of heat generated by the electromagnetic coil does not exceed the criteria is calculated as the maximum allowable current value. As an example, if the predicted temperature at the base current value is X°C and the criteria temperature is Y°C, there is a temperature margin of "YX"°C, so a current value obtained by adding a current value that increases the temperature by "YX"°C calculated in advance evaluation or the like to the base current value is calculated as the maximum allowable current value.

[0032] In step ST5, a shutoff valve current value control is performed. In this shutoff valve current value control, a current is applied to the electromagnetic coil at a current value set in consideration of the maximum allowable current value calculated in step ST4. In other words, the current value applied to the electromagnetic coil of the shutoff valve 6 is controlled to the increasing side, with the maximum allowable current value as the upper limit. Specifically, the electromagnetic coil may be energized with a current value equal to the maximum allowable current value, or with a current value obtained by multiplying the maximum allowable current value by a predetermined safety factor. This shutoff valve current value control is performed continuously for a predetermined period of time.

[0033] During the execution of this shutoff valve current value control, if the vehicle speed falls below the threshold and a NO determination is made in step ST1, a YES determination is made in step ST6, and the process proceeds to step ST7. In this step ST7, the shutoff valve current value control is terminated because the vehicle speed has fallen below the threshold. In other words, the current value passing through the electromagnetic coil of the shutoff valve 6 is returned to the aforementioned base current value. The above operations are repeated at predetermined time intervals while the vehicle is traveling.

[0034] -Effects of the embodiment- As described above, in this embodiment, on condition that the vehicle speed is equal to or higher than a predetermined value, the value of the current passed through the electromagnetic coil of the shutoff valve 6 is controlled to the increasing side. Therefore, while suppressing an excessive increase in temperature of the shutoff valve 6, it is possible to avoid the shutoff valve 6 being closed due to the load acting from the vehicle body while the vehicle is traveling, and a stable supply of fuel can be achieved.

[0035] -Other embodiments- The present invention is not limited to the above-described embodiment, and all modifications and applications within the scope of the claims and equivalents thereto are possible.

[0036] For example, in the above embodiment, the present invention has been described as being applied to a system equipped with a four-cylinder hydrogen engine mounted on a vehicle. The present invention is not limited to this, and can also be applied to gas engines used for purposes other than vehicles. The number of cylinders is not limited to four. The fuel is not limited to hydrogen gas. [Industrial Applicability]

[0037] The present invention is applicable to a fuel supply device that performs current control of a shutoff valve provided in a fuel supply system of a hydrogen engine. [Explanation of symbols]

[0038] 2...Engine body (internal combustion engine) 5...Fuel supply system 52...Fuel supply piping 6...Shut-off valve (solenoid valve) 100...ECU 110...Current control unit

Claims

1. A fuel supply device for an internal combustion engine, the device being mounted on a vehicle and including a fuel supply pipe provided with a solenoid valve that closes when an electromagnetic coil is de-energized and opens when an electromagnetic coil is energized, the device comprising:

1. A fuel supply device for an internal combustion engine, comprising: a current control section that controls a current value supplied to said electromagnetic coil to an increasing side on the condition that the vehicle speed is equal to or higher than a predetermined value.

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