JP2013104361A - Fuel injection device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve uniformity of fuel/air mixture supplied to a combustion chamber in a fuel injection device for an internal combustion engine where gas fuel including a plurality of fuel components is used as fuel.SOLUTION: The fuel injection device for the internal combustion engine includes: a fuel injection valve which injects the gas fuel including the plurality of fuel compositions to an intake port; and a mixing ratio estimation device for estimating a mixing ratio of the fuel components in the gas fuel. The mixing ratio of the gas fuel is estimated, and an injection start timing of the gas fuel from the fuel injection valve is set based on an estimated mixing ratio.

Description

  The present invention relates to a fuel injection device for an internal combustion engine.

  In the prior art, a port injection type internal combustion engine in which fuel is injected into an intake port communicating with a combustion chamber is known. When air flows into the intake port and fuel is injected, an air-fuel mixture is generated and supplied to the combustion chamber.

  As a fuel for an internal combustion engine, it is known that a gaseous fuel in a gaseous state at room temperature and normal pressure can be used in addition to a liquid fuel. The gaseous fuel is supplied to the fuel injection valve in a pressurized state. In a port injection type internal combustion engine, gaseous fuel is injected from the fuel injection valve into the intake port. As the gaseous fuel, in addition to the fuel composed of a single component, a mixed gas fuel composed of a plurality of components can be used. For example, a mixed gas fuel containing hydrogen and natural gas can be used.

  In Japanese Patent Laid-Open No. 2003-090243, the fuel injection start timing and injection period are set so that the fuel gas at the injection peak flows between the injector and the intake port when the piston speed during the intake stroke is the fastest. A fuel injection control method for a gas engine is disclosed. In this fuel injection control method, it is disclosed that air and fuel gas are allowed to flow between the injector and the intake port at the time of the most intense flow, so that air and fuel gas can be uniformly mixed even in a short mixing path.

JP 2003-090243 A

  In an internal combustion engine that uses gaseous fuel, gaseous fuel can be stored in a fuel tank in the same manner as liquid fuel. However, the component of the gaseous fuel that is replenished to the fuel tank may change depending on the area where the gaseous fuel is replenished, social conditions, and the like. For example, when the gaseous fuel contains hydrogen and natural gas, the hydrogen ratio and natural gas ratio of the fuel to be replenished may change. In this case, the mixing ratio of the gaseous fuel stored in the fuel tank changes, and the mixing ratio of the fuel injected from the fuel injection valve changes.

  By the way, in a port injection type internal combustion engine, when gaseous fuel is injected from a fuel injection valve arranged in an intake port, the injected gaseous fuel advances through the intake port. The gaseous fuel is preferably mixed with air and supplied to the combustion chamber at a desired concentration. Further, it is preferable that a desired fuel concentration distribution is formed in the combustion chamber when the air-fuel mixture flows into the combustion chamber.

  When fuel is injected from the fuel injection valve, when the time when the gaseous fuel reaches the vicinity of the intake valve is earlier than the desired time, the concentration near the intake valve is higher than the desired concentration when the intake valve opens. A mixture of concentrations is formed. For this reason, the rich air-fuel mixture is supplied to the combustion chamber. On the other hand, if the time when the gaseous fuel reaches the vicinity of the intake valve is later than the desired time, an air-fuel mixture having a concentration lower than the desired concentration is formed in the vicinity of the intake valve when the intake valve is opened. Yes. For this reason, a lean air-fuel mixture is supplied to the combustion chamber.

By the way, when the mixing ratio of the fuel injected from the fuel injection valve into the intake port changes, the position where the gaseous fuel reaches when the intake valve opens changes, and the mixture flowing into the combustion chamber is uneven. There was a case. In some cases, a lean air-fuel mixture having a desired concentration is supplied to the combustion chamber, or an air-fuel mixture having a concentration higher than the desired concentration is supplied to the combustion chamber. As a result, the combustion fluctuation may increase. Alternatively, in the case of a lean burn engine or the like that performs combustion with a large air-fuel ratio in the combustion chamber, if an air-fuel mixture with a concentration higher than the desired concentration is supplied in the vicinity of the spark plug, it is discharged from the combustion chamber. _the amount of NO _X is in some cases increased that.

  Furthermore, if the air-fuel mixture blows back from the combustion chamber to the intake port, or the air-fuel mixture remaining without being sucked into the combustion chamber remains in the vicinity of the intake valve in a high concentration state, it will be excessive in the next combustion cycle. In some cases, a rich mixture was sucked into the combustion chamber.

  The present invention is a fuel injection device for an internal combustion engine that uses gaseous fuel containing a plurality of fuel components as fuel, and an object thereof is to improve the uniformity of the air-fuel mixture supplied to the combustion chamber.

  A fuel injection device for an internal combustion engine according to the present invention includes a fuel injection valve that injects gaseous fuel containing a plurality of fuel components into an engine intake passage, and a mixing ratio acquisition unit that acquires a mixing ratio of the fuel components of the gaseous fuel. Gaseous fuel has the characteristic that the momentum of gaseous fuel changes when it injects from a fuel injection valve, when a mixing ratio changes. The mixing ratio of the gaseous fuel is acquired, and at least one of the injection start timing and the injection pressure of the gaseous fuel of the fuel injection valve is set based on the acquired mixing ratio.

  In the above invention, the gaseous fuel contains hydrogen and hydrocarbons, and the injection start timing can be set to the advance side as the hydrogen ratio of the gaseous fuel increases.

  In the said invention, gaseous fuel contains hydrogen and a hydrocarbon, and it can set injection pressure so high that the hydrogen ratio of gaseous fuel becomes high.

  In the above invention, the pressure detector for detecting the pressure of the gaseous fuel supplied to the fuel injection valve is provided, the pressure of the gaseous fuel supplied to the fuel injection valve is detected, and the injection start timing is set later as the detected pressure increases. can do.

  ADVANTAGE OF THE INVENTION According to this invention, it is a fuel-injection apparatus of the internal combustion engine which uses gaseous fuel containing a several fuel component as fuel, Comprising: The uniformity of the air-fuel | gaseous mixture supplied to a combustion chamber can be improved.

1 is a schematic view of an internal combustion engine in an embodiment. It is a graph explaining the relationship between the hydrogen ratio of gaseous fuel and the injection start time of gaseous fuel in embodiment. It is a flowchart of the 1st control of the fuel-injection apparatus in embodiment. It is a flowchart which sets the correction value of the injection start time of the gaseous fuel in the 1st control of the fuel injection apparatus in embodiment. It is a graph explaining the relationship between the hydrogen ratio of gaseous fuel and the injection pressure of gaseous fuel in embodiment. It is a flowchart of the 2nd control of the fuel-injection apparatus in embodiment.

  A fuel injection device for an internal combustion engine according to an embodiment will be described with reference to FIGS. The internal combustion engine of the present embodiment uses gaseous fuel.

  FIG. 1 shows a schematic diagram of an internal combustion engine in the present embodiment. The internal combustion engine includes an engine body 1. The engine body 1 includes a combustion chamber 2 for each cylinder. In the present embodiment, a spark plug 7 is disposed in each cylinder. The engine body 1 includes an engine intake passage communicating with the combustion chamber 2, and the engine intake passage has an intake port 11. The engine body 1 includes an engine exhaust passage communicating with the combustion chamber 2, and the engine exhaust passage has an exhaust port 12. The engine body 1 includes a fuel injection valve 3 that injects fuel into the engine intake passage. The fuel injection valve 3 in the present embodiment injects gaseous fuel into the intake port 11 of each cylinder.

  The engine body 1 includes an intake manifold 4 connected to the intake port 11 and an exhaust manifold 5 connected to the exhaust port 11. The intake manifold 4 is connected to an intake air amount detector 8 via an intake duct 6. The intake air amount detector 8 is connected to an air cleaner 9. A throttle valve 10 driven by a step motor is disposed in the intake duct 6. On the other hand, the exhaust manifold 5 is connected to an exhaust purification catalyst 55 as an exhaust treatment device via an exhaust pipe 51.

The exhaust purification catalyst 55 in the present embodiment is constituted by a three-way catalyst. When the ratio of the exhaust air and fuel (hydrocarbon) supplied into the engine intake passage, the combustion chamber or the exhaust passage upstream of the exhaust purification catalyst 55 is called the exhaust air-fuel ratio, the three-way catalyst By making the fuel ratio substantially the stoichiometric air-fuel ratio, it has a function of simultaneously purifying hydrocarbon HC, carbon monoxide CO and nitrogen oxide NO _X contained in the exhaust gas. In the exhaust purification device of the present embodiment, an air-fuel ratio sensor 56 for detecting the air-fuel ratio (A / F) of the exhaust gas flowing into the exhaust purification catalyst 55 is disposed in the engine exhaust passage upstream of the exhaust purification catalyst 55. Has been placed. As the exhaust treatment device, any device that purifies exhaust gas in addition to the three-way catalyst can be adopted. For example, an oxidation catalyst or a NO _x reduction catalyst can be employed.

  An EGR passage 52 is disposed between the exhaust manifold 5 and the intake manifold 4 to perform exhaust gas recirculation (EGR). An electronically controlled EGR control valve 53 is disposed in the middle of the EGR passage 52. Further, an EGR cooling device 54 for cooling the EGR gas flowing in the EGR passage 52 is disposed in the middle of the EGR passage 52.

  The fuel injection device for an internal combustion engine in the present embodiment includes a fuel injection valve 3 and a fuel supply device that supplies pressurized fuel to the fuel injection valve 3. The fuel supply device in the present embodiment includes a fuel tank 61 and a pressure adjustment valve 62. Each fuel injection valve 3 is connected to a fuel tank 61 via a fuel supply pipe 63.

  The fuel supply device is configured to supply pressurized fuel. In the present embodiment, gaseous fuel is pressurized and stored in the fuel tank 61. The fuel stored in the fuel tank 61 is depressurized by the pressure adjustment valve 62. The fuel decompressed by the pressure regulating valve 62 is supplied to each fuel injection valve 3 through the fuel supply pipe 63. A pressure sensor 64 that detects the pressure of the fuel supplied to the fuel injection valve 3 is disposed in the flow path for supplying fuel from the pressure adjustment valve 62 to the fuel injection valve 3. Temperature sensors 65 and 66 are arranged on the upstream side and the downstream side of the pressure regulating valve 62. The temperature sensors 65 and 66 function as a mixing ratio acquisition unit that acquires the mixing ratio of the fuel components of the gaseous fuel supplied from the fuel tank 61 as will be described later. The fuel tank 61 is provided with a pressure sensor 67 for detecting the internal pressure.

  The internal combustion engine in the present embodiment includes an electronic control unit 30. The electronic control unit 30 in the present embodiment is configured by a digital computer. The electronic control unit 30 includes a ROM (Read Only Memory) 32, a RAM (Random Access Memory) 33, a CPU (Microprocessor) 34, an input port 35, and an output port 36 connected to each other by a bidirectional bus 31. In the ROM 32, information such as a map necessary for performing control is stored in advance. The CPU 34 can perform arbitrary calculations and determinations. The RAM 33 is a readable / writable storage device.

  The output signal of the intake air amount detector 8 is input to the input port 35 via the corresponding AD converter 37. Output signals from sensors such as the temperature sensors 65 and 66, the pressure sensors 64 and 67, and the air-fuel ratio sensor 56 are input to the input port 35 via the corresponding AD converter 37.

  A load sensor 41 that generates an output voltage proportional to the amount of depression of the accelerator pedal 40 is connected to the accelerator pedal 40. The required torque can be detected from the output of the load sensor 41. The output signal of the load sensor 41 is input to the input port 35 via the corresponding AD converter 37. Further, the input port 35 is connected to a crank angle sensor 42 that generates an output pulse every time the crankshaft rotates, for example, 15 °. The engine speed and crank angle can be detected from the output of the crank angle sensor 42.

  On the other hand, the output port 36 is connected to the spark plug 7, the step motor for driving the throttle valve 10, and the EGR control valve 53 via a corresponding drive circuit 38. The output port 36 is connected to the pressure regulating valve 62 via a corresponding drive circuit 38.

  As the gaseous fuel in the present embodiment, a mixed gas fuel containing hydrogen and hydrocarbons is used. Examples of the hydrocarbon include natural gas and biomass gas.

  The gaseous fuel injected from the fuel injection valve advances through the intake port while being mixed with air. It is preferable that an air-fuel mixture having a desired concentration is supplied to the combustion chamber. That is, it is preferable to burn the fuel at the desired air-fuel ratio at the time of combustion. For this reason, it is preferable to perform control so that the gaseous fuel injected from the fuel injection valve reaches the vicinity of the intake valve at a desired time. For example, it is preferable that the gaseous fuel reaches the vicinity of the intake valve immediately before the intake valve is opened. The arrival time of the gaseous fuel also affects the concentration distribution of the gaseous fuel formed in the combustion chamber. A desired fuel concentration distribution is preferably formed in the combustion chamber.

  By the way, when the gas fuel stored in the fuel tank is reduced and replenishment is performed, the mixing ratio of hydrogen and hydrocarbons contained in the gas fuel to be replenished may differ depending on the region where the replenishment is performed. In some cases, a gaseous fuel having a different mixing ratio from the gaseous fuel remaining in the fuel tank is supplied. As a result, the mixing ratio of the gaseous fuel in the fuel tank may change, and the mixing ratio of the gaseous fuel supplied to the fuel injection valve may change. Here, when the mixing ratio of the fuel component of the gaseous fuel changes, the penetration force of the gaseous fuel when the gaseous fuel is injected from the fuel injection valve changes. For this reason, the time when gaseous fuel reaches the vicinity of an intake valve changes.

  The fuel injection device for the internal combustion engine in the present embodiment sets at least one of the fuel injection timing and the fuel injection pressure based on the momentum of the gaseous fuel when the gaseous fuel is injected from the fuel injection valve. The momentum of the gaseous fuel in the present embodiment can be determined as the product of the density of the gaseous fuel and the speed when the gaseous fuel is injected. As the momentum of the gaseous fuel injected from the fuel injection valve increases, the penetration force increases, and the time until the injected gaseous fuel reaches the vicinity of the intake valve is shortened.

  For example, when the density of the gaseous fuel increases (the mass per unit volume increases), the penetration force of the injected gaseous fuel, that is, the penetration increases, and the time when the injected gaseous fuel reaches the vicinity of the intake valve Becomes faster. In addition, when the speed of the gaseous fuel injected from the fuel injection valve increases, the time at which the injected gaseous fuel reaches the vicinity of the intake valve is advanced. The time from the injection of the gaseous fuel to the vicinity of the intake valve affects the concentration of the air-fuel mixture supplied to the combustion chamber and the concentration distribution of the gaseous fuel in the combustion chamber.

  By the way, the density of the gaseous fuel depends on the mixing ratio of the fuel components contained in the gaseous fuel. The smaller the average molecular weight of the components of the plurality of gaseous fuels, the lower the density at the same pressure and the same temperature. In this Embodiment, the density of gaseous fuel becomes small, so that the hydrogen ratio of gaseous fuel becomes high. Further, the speed of the gaseous fuel when injected from the fuel injection valve depends on the mixing ratio of the fuel components contained in the gaseous fuel. In the gaseous fuel containing hydrogen and hydrocarbons of the present embodiment, when the pressure of the gaseous fuel supplied to the fuel injection valve is constant, the larger the hydrogen ratio of the gaseous fuel, the larger the gas when injected. Increases fuel speed.

  Here, when the hydrogen ratio of the gaseous fuel increases, the momentum of the gaseous fuel when injected increases the effect of decreasing the density than the effect of increasing the injected speed. For this reason, the higher the hydrogen ratio of the gaseous fuel, the smaller the momentum of the gaseous fuel when the fuel is injected. That is, as the hydrogen ratio of the gaseous fuel increases, the penetration of the gaseous fuel decreases, and it takes a longer time for the gaseous fuel injected from the fuel injection valve to reach the vicinity of the intake valve. As described above, the mixing ratio of the gaseous fuel has a characteristic that affects the momentum of the gaseous fuel when the gaseous fuel is injected from the fuel injection valve.

  In the first control of the fuel injection device according to the present embodiment, control is performed to acquire the gaseous fuel mixing ratio and set the gaseous fuel injection start timing based on the gaseous fuel mixing ratio. In the gaseous fuel in the present embodiment, since the penetration force of the gaseous fuel decreases as the hydrogen ratio of the gaseous fuel increases, control is performed to set the injection start timing to the advance side. That is, control is performed to advance the injection start timing.

  Referring to FIG. 1, the fuel injection device includes a mixture ratio estimation device as a mixture ratio acquisition unit that acquires a mixture ratio of fuel components of gaseous fuel. The mixing ratio estimation apparatus in the present embodiment includes a pressure adjustment valve 62 and temperature sensors 65 and 66. The temperature difference between the upstream side and the downstream side of the pressure regulating valve 62 can be detected by the outputs of the temperature sensors 65 and 66. A pressurized gaseous fuel is supplied from the fuel tank 61 and is depressurized by the pressure regulating valve 62. When the gaseous fuel is depressurized, the temperature decreases because the gaseous fuel expands. The amount of temperature drop at this time depends on the specific heat of the gaseous fuel. For this reason, the amount of temperature drop when flowing through the pressure regulating valve 62 depends on the mixing ratio of the fuel components.

  In the gaseous fuel of the present embodiment, the endothermic amount during decompression expansion is smaller for hydrogen than for hydrocarbon. The higher the hydrogen ratio, the smaller the temperature drop when the pressure regulating valve 62 is circulated. The mixing ratio estimation apparatus according to the present embodiment detects a temperature decrease amount when flowing through the pressure regulating valve 62 in a predetermined internal combustion engine operation state, and estimates a hydrogen ratio based on the detected temperature decrease amount. Yes. Furthermore, the mixing ratio estimation apparatus in the present embodiment detects the pressure of the gaseous fuel flowing into the pressure regulating valve 62 by the pressure sensor 67. The pressure of the gaseous fuel flowing out from the pressure regulating valve 62 is detected by the pressure sensor 64. Based on the outputs of the pressure sensors 64 and 67, the pressure difference between the upstream side and the downstream side of the pressure regulating valve 62 is calculated.

  Next, the hydrogen ratio of the gaseous fuel is estimated based on the pressure difference between the upstream side and the downstream side of the pressure regulating valve 62 and the temperature difference between the upstream side and the downstream side of the pressure regulating valve 62. In the present embodiment, a map of the hydrogen ratio of the gaseous fuel that is a function of the pressure difference between the upstream side and the downstream side of the pressure regulating valve 62 and the temperature difference between the upstream side and the downstream side of the pressure regulating valve 62 is shown. It is stored in the electronic control unit 30. By detecting the pressure difference and the temperature difference between the upstream side and the downstream side of the pressure regulating valve 62, the hydrogen ratio of the gaseous fuel can be estimated.

  FIG. 2 is a graph illustrating the relationship between the hydrogen ratio of the gaseous fuel and the injection start timing of the fuel injection valve in the first control in the present embodiment. The injection start timing on the vertical axis is indicated by the crank angle. In the example shown in FIG. 2, the intake valve is open at the crank angle θIBO. As the hydrogen ratio of the gaseous fuel increases, the momentum of the fuel when being injected from the fuel injection valve decreases. Therefore, in the first control, the injection start timing is set to the advance side as the hydrogen ratio of the gaseous fuel increases. To do.

  FIG. 3 shows a flowchart of the first control of the fuel injection device in the present embodiment. In the present embodiment, the reference injection start timing is set, the mixing ratio of the gaseous fuel stored in the fuel tank is acquired, the correction value for the injection starting timing is set based on the mixing ratio of the gaseous fuel, and the reference injection start is started. Control is performed to correct the timing with a correction value and set the final injection start timing. The first control shown in FIG. 3 can be performed repeatedly, for example, at predetermined time intervals or every predetermined number of combustion cycles.

  First, in step 101, the fuel injection amount to be supplied to each cylinder is set. The fuel injection amount can be set, for example, based on the required load of the internal combustion engine and the engine speed. With reference to FIG. 1, a map of the fuel injection amount having the required load and the engine speed as a function can be stored in the electronic control unit 30 in advance. The required load can be detected from the output of the load sensor 41, and the engine speed can be detected from the output of the crank angle sensor 42. The fuel injection amount can be set based on the detected required load and the engine speed.

  In step 102, a fuel injection period is set. The fuel injection valve 3 in the present embodiment is formed so that the fuel injection flow rate is substantially constant when the valve is opened at a constant gas fuel pressure. The period (time length) during which the fuel injection valve is opened is calculated from the fuel injection amount set in step 101.

  In step 103, a reference injection start timing θFSB serving as a reference is set. The reference injection start timing can be set based on the predetermined opening timing of the intake valve and the fuel injection period calculated in step 102.

  In step 104, the injection start timing correction value θα is read. In the present embodiment, the injection start timing correction value θα is set so that the injection start timing is earlier as the hydrogen ratio of the gaseous fuel is higher. Here, control for setting the correction value θα of the injection start timing will be described.

  FIG. 4 shows a flowchart for setting the correction value of the injection start timing in the first control of the present embodiment. In this embodiment, every time fuel gas is supplied to the fuel tank, a correction value for the injection start timing is set. The control shown in FIG. 4 can be repeatedly performed at predetermined time intervals, for example.

  In step 111, it is determined whether or not gaseous fuel has been supplied to the fuel tank. Referring to FIG. 1, in the present embodiment, it is detected that gaseous fuel has been replenished by the output of pressure sensor 67 attached to fuel tank 61. In the present embodiment, it is determined that the gaseous fuel has been replenished when the internal pressure of the current fuel tank 61 has risen more than a predetermined determination value compared to the previous pressure. The determination of the presence / absence of replenishment of gaseous fuel is not limited to this mode, and can be performed by an arbitrary device and control.

  In step 111, when gaseous fuel is supplied to the fuel tank, the routine proceeds to step 112. In step 111, if the fuel tank is not replenished with gaseous fuel, this control is terminated.

  In step 112, the hydrogen ratio of the gaseous fuel is acquired. The hydrogen ratio contained in the fuel can be estimated by the above-described mixing ratio estimation device. The acquisition of the mixing ratio of the gaseous fuel is not limited to the above-described mixing ratio estimation device, and may be acquired by, for example, a mixing ratio acquisition sensor that directly detects the mixing ratio. Alternatively, the driver or the like may input the mixing ratio to the electronic control unit when fuel is supplied.

  Next, in step 113, a correction value θα for the injection start timing is set. Referring to FIG. 2, the correction value θα of the injection start timing is set so that the injection start timing becomes earlier (advanced side) as the hydrogen ratio increases. For example, the correction value θα of the injection start timing as a function of the hydrogen ratio can be stored in advance in the electronic control unit 30. Thus, the correction value of the injection start timing can be set every time the gaseous fuel is replenished. The correction value θα of the set injection start timing can be stored in the electronic control unit 30.

  Referring to FIG. 3, after reading correction value θα of the injection start timing in step 104, corrected injection start timing θFS is set in step 105. In the present embodiment, the corrected injection start timing θFS is set by adding the correction value θα to the reference injection start timing θFSB. The correction method is not limited to this mode, and any correction method such as setting a correction coefficient for the injection start timing and multiplying by the correction coefficient can be employed.

  Next, in step 106, gaseous fuel is injected based on the set injection start timing θFS.

The fuel injection device for an internal combustion engine in the present embodiment sets the injection start timing based on the mixing ratio of the gaseous fuel, so that the time required to reach the vicinity of the intake valve from the fuel injection valve due to the penetration force of the gaseous fuel Fluctuations can be corrected. The gaseous fuel can be injected so that the gaseous fuel reaches the vicinity of the intake valve at a desired time. The uniformity of the concentration of the gaseous fuel supplied to the combustion chamber can be improved. Further, a desired concentration distribution of the gaseous fuel can be formed in the combustion chamber. For this, it suppresses combustion variation which the concentration of the gaseous fuel supplied to the combustion chamber for each combustion cycle due to different, when the internal combustion engine is lean-burn engine or suppress an increase of the NO _X be able to.

  Next, the second control in the present embodiment will be described. In the second control of the present embodiment, the injection pressure of the gaseous fuel in the fuel injection valve is set based on the mixing ratio of the gaseous fuel. The higher the injection pressure at the fuel injection valve, the higher the speed of the gaseous fuel injected from the fuel injection valve. That is, the momentum of the gaseous fuel injected from the fuel injection valve increases.

  FIG. 5 shows a graph for explaining the relationship between the hydrogen ratio of the gaseous fuel and the injection pressure of the gaseous fuel in the fuel injection valve in the second control of the present embodiment. When the injection pressure from the fuel injection valve is constant, the momentum of the fuel when injected from the fuel injection valve decreases as the hydrogen ratio of the gaseous fuel increases. For this reason, in 2nd control, control which raises the injection pressure at the time of injecting gaseous fuel from a fuel injection valve is performed, so that the hydrogen ratio of gaseous fuel becomes high. In the present embodiment, control is performed to increase the pressure of the gaseous fuel supplied to the fuel injection valve as the hydrogen ratio of the gaseous fuel increases. Referring to FIG. 1, in the fuel injection device of the present embodiment, the pressure of the gaseous fuel supplied to fuel injection valve 3 can be changed by pressure adjustment valve 62.

  FIG. 6 shows a flowchart of the second control in the present embodiment. The control shown in FIG. 6 can be performed repeatedly, for example, at predetermined time intervals or every predetermined number of combustion cycles. In the second control of the present embodiment, every time fuel gas is supplied to the fuel tank, the mixing ratio of the gaseous fuel stored in the fuel tank is acquired and injected from the fuel injection valve based on the mixing ratio of the gaseous fuel. The fuel injection pressure is set, and the pressure of the gaseous fuel supplied to the fuel injection valve is adjusted.

  In step 121, it is determined whether gaseous fuel has been supplied to the fuel tank. If gaseous fuel is replenished to the fuel tank at step 121, the routine proceeds to step 122. In step 121, when gaseous fuel is not replenished to the fuel tank, this control is terminated.

  In step 122, the hydrogen ratio of the gaseous fuel is acquired. The acquisition of the hydrogen ratio can be estimated by the mixing ratio estimation device, similarly to the first control in the present embodiment.

  In step 123, an injection pressure for injecting gaseous fuel is set. The injection pressure is set higher as the hydrogen ratio of the gaseous fuel increases. Referring to FIG. 5, in the present embodiment, the value of the fuel injection pressure that is a function of the hydrogen ratio of the gaseous fuel is stored in advance in the electronic control unit. Based on the estimated hydrogen ratio of the gaseous fuel, the injection pressure when injecting from the fuel injection valve can be set.

  Next, in step 124, the pressure of the gaseous fuel supplied to the fuel injection valve is adjusted based on the set injection pressure of the fuel injection valve. With reference to FIG. 1, in the present embodiment, the pressure of the gaseous fuel supplied to fuel injection valve 3 is adjusted by pressure adjustment valve 62 so that the injection pressure of the gaseous fuel is set.

As described above, in the second control of the present embodiment, the injection pressure of the gaseous fuel in the fuel injection valve is adjusted every time fuel is supplied to the fuel tank. Also in the second control in the present embodiment, it is possible to correct the variation in the operating amount of the gaseous fuel due to the mixing ratio of the gaseous fuel. The uniformity of the air-fuel mixture supplied to the combustion chamber can be improved. Further, when the gaseous fuel flows into the combustion chamber, a desired gaseous fuel concentration distribution can be formed in the combustion chamber. For this reason, the variation in the concentration of the gaseous fuel in the air-fuel mixture among a plurality of combustion cycles can be suppressed, and the combustion fluctuation can be suppressed. Or, for example, in a lean-burn engine, it is possible to suppress the increase in the NO _X amount exhausted.

  Furthermore, the fuel injection device in the present embodiment includes a pressure detector that detects the pressure of the gaseous fuel supplied to the fuel injection valve, detects the pressure of the gaseous fuel supplied to the fuel injection valve 3, and the detected pressure is It is possible to control to set the injection start timing later as the value becomes higher. Referring to FIG. 1, in the present embodiment, a pressure sensor 64 attached to a fuel supply pipe 63 functions as a pressure detector that detects the pressure of gaseous fuel supplied to the fuel injection valve 3. The pressure of the gaseous fuel supplied to the fuel injection valve 3 is equivalent to the injection pressure of the fuel injection valve 3. For example, in the first control described above, the set injection start timing can be further corrected based on the pressure of the gaseous fuel detected by the pressure sensor 64.

  An internal combustion engine that uses gaseous fuel has a greater influence of the injection pressure on the fuel injection amount than an internal combustion engine that uses liquid fuel. For this reason, by setting the injection start timing based on the pressure supplied to the fuel injection valve, the gaseous fuel can be supplied to the vicinity of the intake valve more accurately at a desired timing.

  The mixing ratio acquisition means of the present embodiment estimates the hydrogen ratio of the gaseous fuel based on the temperature difference between the upstream side and the downstream side of the pressure regulating valve. Any means capable of acquiring the ratio can be adopted.

  For example, the mixture ratio acquisition means may estimate the oxygen concentration contained in the exhaust gas and estimate the gas fuel mixture ratio based on the estimated oxygen concentration. Referring to FIG. 1, the internal combustion engine in the present embodiment is provided with an air-fuel ratio sensor 56 for detecting the air-fuel ratio of the exhaust gas flowing out from combustion chamber 2 in the engine exhaust passage. Based on the output of the air-fuel ratio sensor 56, the oxygen concentration contained in the exhaust gas can be estimated. The exhaust gas has a higher oxygen concentration as the hydrogen ratio of the gaseous fuel is higher. That is, the higher the hydrogen ratio of the gaseous fuel, the leaner the air / fuel ratio of the exhaust gas becomes. For this purpose, for example, in a predetermined operating state of the internal combustion engine, the oxygen concentration of the exhaust gas is estimated based on the output of the air-fuel ratio sensor 56, and the hydrogen ratio of the gaseous fuel is estimated based on the estimated oxygen concentration. it can.

  Alternatively, the exhaust purification catalyst 55 in the present embodiment is composed of a three-way catalyst, and feedback control is performed so that the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst 55 is substantially the stoichiometric air-fuel ratio. In the internal combustion engine in the present embodiment, the air-fuel ratio of the exhaust gas is detected by the air-fuel ratio sensor 56, and at least one of the injection amount of gaseous fuel and the intake air amount is adjusted so that the air-fuel ratio of the exhaust gas becomes substantially the stoichiometric air-fuel ratio. It is adjusted. The amount of adjustment when performing feedback control depends on the hydrogen ratio of the gaseous fuel. For this reason, the mixture ratio acquisition means may estimate the hydrogen ratio of the gaseous fuel based on the adjustment amount when the feedback control is performed.

  In the first control and the second control of the present embodiment, either the injection start timing or the injection pressure is changed. However, the present invention is not limited to this mode, and the injection timing and the injection are based on the momentum of the fuel. Both pressures may be changed.

  In the present embodiment, the gas fuel is described by taking a mixed gas of hydrogen and hydrocarbon as an example. However, the present invention is not limited to this mode, and a fuel injection valve that injects an arbitrary gaseous fuel containing a plurality of fuel components. The present invention can be applied to a fuel injection device including the above.

  The above embodiments can be combined as appropriate. In each of the above-described controls, the order of the steps can be appropriately changed within a range where the function and the action are not changed. In the respective drawings described above, the same or equivalent parts are denoted by the same reference numerals. In addition, said embodiment is an illustration and does not limit invention. In the embodiment, the change shown in a claim is included.

2 Combustion chamber 3 Fuel injection valve 6 Intake duct 11 Intake port 30 Electronic control unit 51 Exhaust pipe 55 Exhaust purification catalyst 56 Air-fuel ratio sensor 61 Fuel tank 62 Pressure adjustment valve 63 Fuel supply pipe 64 Pressure sensor 65, 66 Temperature sensor 67 Pressure sensor

Claims (4)

A fuel injection valve for injecting gaseous fuel containing a plurality of fuel components into the engine intake passage;
A mixing ratio acquisition means for acquiring the mixing ratio of the fuel component of the gaseous fuel,
Gaseous fuel has the characteristic that the momentum of gaseous fuel changes when injected from the fuel injection valve by changing the mixing ratio,
A fuel injection device for an internal combustion engine, which acquires a mixing ratio of gaseous fuel and sets at least one of injection start timing and injection pressure of gaseous fuel of a fuel injection valve based on the acquired mixing ratio. Gaseous fuel contains hydrogen and hydrocarbons,
The fuel injection device for an internal combustion engine according to claim 1, wherein the injection start timing is set to an advance side as the hydrogen ratio of the gaseous fuel increases. Gaseous fuel contains hydrogen and hydrocarbons,
The fuel injection device for an internal combustion engine according to claim 1 or 2, wherein the injection pressure is set higher as the hydrogen ratio of the gaseous fuel becomes higher. A pressure detector for detecting the pressure of the gaseous fuel supplied to the fuel injection valve;
The fuel injection device for an internal combustion engine according to any one of claims 1 to 3, wherein the pressure of gaseous fuel supplied to the fuel injection valve is detected, and the injection start timing is set later as the detected pressure increases.

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