Fuel control device of internal combustion engine

Abstract

To provide a fuel control device of an internal combustion engine which can suppress wrong learning of a supply amount of fuel resulting from vaporization of liquefied fuel remaining in a liquid state in a pressure adjustment device after warming up of the internal combustion engine.SOLUTION: A fuel control device 100 of an internal combustion engine includes: a regulator 30 which vaporizes liquefied fuel by heating during an operation of an engine 2; a relief passage 10 which discharges gas fuel from a furl passage 9 into an air suction passage 3 without through an injector 11 according to an increase in pressure of the gas fuel in the fuel passage 9 from the regulator 30 to the injector 11; and an ECU 20 which performs learning control for calculating a leaning correction value for correcting the supply amount of the fuel by using a result of feedback correction of the supply amount of the fuel based on an oxygen concentration of exhaust gas. When the fuel pressure in the fuel passage 9 detected by a fuel pressure sensor 13 is a predefined pressure threshold value or more, the ECU 20 temporarily stops the calculation of the learning correction value.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a fuel control device for an internal combustion engine. [Background technology]

[0002] Conventionally, there is known an engine that uses liquefied petroleum gas and is equipped with an LPG regulator that supplies idle slow fuel from a primary pressure reduction chamber to a venturi and supplies main fuel from a secondary pressure reduction chamber to the venturi (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 02-218853 Summary of the Invention [Problem to be solved by the invention]

[0004] In general, an internal combustion engine that burns gas fuel obtained by vaporizing liquefied fuel is provided with a regulator (pressure regulator) that vaporizes the high-pressure liquefied fuel from a tank and converts it into reduced-pressure gas fuel. During the vaporization process, the fuel expands and loses heat from the surroundings, so a heating device that uses the heat of the cooling water of the internal combustion engine, for example, is provided to heat the regulator when the internal combustion engine is operating.

[0005] In such a regulator, fuel may not be sufficiently vaporized if the regulator is not heated sufficiently, for example, when the internal combustion engine is cold. If the liquefied fuel remaining in liquid form inside the regulator suddenly vaporizes after the internal combustion engine is warmed up, the pressure inside the regulator may become excessively high. Therefore, a configuration may be considered in which gas fuel is allowed to flow from the pressure regulator or the fuel supply passage into the intake passage of the internal combustion engine to prevent the pressure from becoming excessively high. However, if gas fuel is allowed to flow from the pressure regulator or the fuel supply passage into the intake passage, the supply of gas fuel to the internal combustion engine may temporarily become excessive, and the learning correction value of the fuel supply amount may be erroneously calculated to be excessively reduced.

[0006] The present invention aims to provide a fuel control device for an internal combustion engine that can suppress erroneous learning of the fuel supply amount caused by liquefied fuel remaining in liquid form in a pressure regulator vaporizing after the internal combustion engine is warmed up. [Means for solving the problem]

[0007] One aspect of the present invention is a fuel control device for an internal combustion engine capable of supplying gas fuel produced by vaporizing liquefied fuel, the fuel control device comprising: a pressure regulator that is heated during operation of the internal combustion engine to vaporize the liquefied fuel; a fuel supply passage that supplies the gas fuel from the pressure regulator to an injector; an outflow passage that causes the gas fuel to flow from the pressure regulator or the fuel supply passage to an intake passage of the internal combustion engine without passing through an injector in response to an increase in pressure of the gas fuel in the pressure regulator or the fuel supply passage; a pressure detection unit that detects the fuel pressure of the gas fuel in the pressure regulator or the fuel supply passage; and a control unit that performs learning control to calculate a learning correction value for correcting the amount of fuel supply using the result of feedback correction of the amount of fuel supply based on the oxygen concentration of the exhaust gas of the internal combustion engine, and the control unit temporarily stops calculation of the learning correction value when the fuel pressure of the gas fuel is equal to or greater than a predetermined pressure threshold.

[0008] In a fuel control device for an internal combustion engine according to one aspect of the present invention, for example, when the liquefied fuel remaining in a liquid state in the pressure regulator vaporizes after the internal combustion engine is warmed up, the pressure of the gas fuel in the pressure regulator or the fuel supply passage increases. In response to the increase in the pressure of the gas fuel in the pressure regulator or the fuel supply passage, the gas fuel may flow out from the pressure regulator or the fuel supply passage to the intake passage of the internal combustion engine through the outflow passage. Here, when the fuel pressure of the gas fuel in the pressure regulator or the fuel supply passage is equal to or higher than a predetermined pressure threshold, the calculation of the learning correction value is temporarily stopped. Therefore, the calculation of the learning correction value including the influence of the gas fuel that has flowed out excessively to the intake passage through the outflow passage is suppressed. This makes it possible to suppress erroneous learning of the supply amount of fuel caused by the liquefied fuel remaining in a liquid state in the pressure regulator vaporizing after the internal combustion engine is warmed up.

[0009] In one embodiment, the pressure threshold value may be a value smaller than an outflow pressure, which is a fuel pressure at which the gas fuel flows out to the intake passage through the outflow passage, and larger than a warm pressure, which is a fuel pressure in a warm state of the internal combustion engine. In this case, since the calculation of the learning correction value is temporarily stopped earlier than the gas fuel flows out to the intake passage through the outflow passage, erroneous learning of the fuel supply amount can be more reliably suppressed.

[0010] In one embodiment, the fuel control device for the internal combustion engine may further include a relief passage that connects the fuel supply passage and the intake passage and has a relief valve that flows the gas fuel at a predetermined relief pressure, the pressure regulator supplies the gas fuel to the injector at a warm pressure that is the fuel pressure in the warm state when the internal combustion engine is in a warm state, and the outflow passage may cause the gas fuel to flow from the fuel supply passage to the intake passage via the relief passage without passing through the injector in response to a pressure increase of the gas fuel in the pressure regulator and the fuel supply passage. In this case, it is possible to suppress calculation of the learning correction value including the influence of the gas fuel excessively flowing out to the intake passage via the relief passage.

[0011] In one embodiment, the fuel control device for the internal combustion engine further includes a mixer provided in an intake passage of the internal combustion engine, the pressure regulator has a primary chamber that supplies gas fuel to the injector at a warm pressure that is a fuel pressure in the warm state when the internal combustion engine is in a warm state, and a secondary chamber into which the gas fuel from the primary chamber flows and supplies the gas fuel to the mixer at a pressure lower than the warm pressure in the warm state, and the outflow passage may cause the gas fuel to flow out to the intake passage via the mixer without passing through the injector in response to a pressure increase of the gas fuel in the primary chamber and the fuel supply passage of the pressure regulator. In this case, it is possible to suppress calculation of a learning correction value including the influence of the gas fuel excessively flowing out to the intake passage via the secondary chamber and the mixer. Effect of the Invention

[0012] According to the present invention, it is possible to suppress erroneous learning of the fuel supply amount caused by the liquefied fuel remaining in liquid form in the pressure regulator vaporizing after the internal combustion engine is warmed up. [Brief description of the drawings]

[0013] [Figure 1] 1 is a schematic configuration diagram showing an internal combustion engine system including a fuel control device for an internal combustion engine according to an embodiment; [Diagram 2] 2 is a schematic block diagram illustrating a functional configuration of an ECU in FIG. 1; [Diagram 3] 4 is a flowchart showing an example of a calculation process of a learning correction value by an ECU. [Figure 4] FIG. 11 is a schematic configuration diagram showing an internal combustion engine system including a fuel control device for an internal combustion engine according to a modified example. [Diagram 5] FIG. 13 is a schematic configuration diagram showing an internal combustion engine system including a fuel control device for an internal combustion engine according to another modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0015] Fig. 1 is a schematic diagram showing an internal combustion engine system including a fuel control device for an internal combustion engine according to one embodiment. In Fig. 1, an internal combustion engine system 1 is mounted on, for example, a vehicle. The vehicle may be a passenger car or the like, or an industrial vehicle such as a forklift.

[0016] The internal combustion engine system 1 is a system for operating an engine 2 (internal combustion engine) capable of supplying gas fuel obtained by vaporizing liquefied fuel, and includes a fuel control device 100 for the internal combustion engine. For example, LPG [Liquefied Petroleum Gas] is used as the liquefied fuel. LPG is a liquefied petroleum gas whose main components are propane and butane.

[0017] The internal combustion engine system 1 includes an engine 2, an intake passage 3, an air cleaner 4, a throttle valve 5, an LPG cylinder 6, a fuel passage 7, an solenoid valve 8, a regulator (pressure adjuster) 30, a fuel passage (fuel supply passage) 9, a relief passage (outlet passage) 10, an injector 11, and an exhaust passage 12.

[0018] The engine 2 is, for example, a four-cylinder reciprocating engine having a cylinder head and a cylinder block. The engine 2 has a spark plug (not shown) that ignites a mixture of fuel and air to ignite the fuel.

[0019] The intake passage 3 is connected to the cylinder head of the engine 2. The intake passage 3 is a passage through which air (intake air) supplied to the engine 2 flows. The air cleaner 4 is disposed in the intake passage 3. The air cleaner 4 removes foreign matter such as dust and dirt contained in the intake air. The throttle valve 5 is disposed in the intake passage 3 between the air cleaner 4 and the cylinder head of the engine 2. The throttle valve 5 is, for example, an electromagnetic flow control valve that controls the flow rate of the intake air.

[0020] The LPG cylinder 6 is a fuel cylinder that stores LPG in a liquid state. The fuel passage 7 connects the LPG cylinder 6 and the regulator 30. The fuel passage 7 is a passage through which liquefied fuel flows from the LPG cylinder 6 to the regulator 30. A filter (not shown) may be disposed at the connection between the LPG cylinder 6 and the fuel passage 7. The solenoid valve 8 is an opening / closing valve that opens and closes the inlet of the fuel passage 7.

[0021] The fuel passage 9 is a fuel passage that connects the regulator 30 and the injector 11. The fuel passage 9 is a fuel supply passage that supplies fuel vaporized by the regulator 30 (gas fuel) from the regulator 30 to the injector 11.

[0022] The regulator 30 is a pressure regulator that vaporizes the high-pressure liquefied fuel from the LPG cylinder 6 to convert it into a depressurized gas fuel, and is also called an evaporator. In the example of FIG. 1, the regulator 30 is configured to perform one-stage depressurization for supplying to the injector 11. The regulator 30 has, for example, a depressurization chamber including a valve portion 30a and a diaphragm portion 30b. The valve portion 30a is attached to the diaphragm portion 30b, and the valve portion 30a is opened and closed in response to the elastic deformation of the diaphragm portion 30b so that the pressure in the depressurization chamber approaches a predetermined set pressure. The liquefied fuel from the LPG cylinder 6 flows into the depressurization chamber in response to the opening and closing of the valve portion 30a.

[0023] In this way, the valve portion 30a and the diaphragm portion 30b operate to balance the fuel pressure in the pressure reduction chamber and the fuel passage 9 of the regulator 30, and the fuel pressure is adjusted to a predetermined set pressure for supplying the fuel to the engine 2. The predetermined set pressure is, for example, a warm pressure that is set in advance as the fuel pressure when the engine 2 is in a warm state. That is, when the engine 2 is in a warm state, the regulator 30 supplies gas fuel to the injector 11 at the warm pressure, which is the fuel pressure in the warm state.

[0024] The warm state here means a state in which the engine 2 is warmed up to a certain extent so that the fuel pressure in the pressure reduction chamber of the regulator 30 and in the fuel passage 9 is roughly constant, and does not include a cold state in which poor vaporization of the liquefied fuel occurs inside the regulator 30, etc.

[0025] In the regulator 30, the LPG becomes cold due to the latent heat of vaporization during the vaporization process. Therefore, in order to stably vaporize the LPG, it is necessary to heat it from the outside, and the regulator 30 is provided with a heating device (not shown) that uses the heat of the cooling water of the engine 2, for example. For example, LPG is a mixture of propane and butane, and the boiling points differ depending on the components. The boiling point of propane is -42°C, and the boiling point of butane is -0.5°C, so the boiling point of LPG is a temperature that depends on the components and falls within the range of -42°C to -0.5°C.

[0026] Due to this boiling point, the regulator 30 is heated when the engine 2 is operating. However, if the regulator 30 is not heated sufficiently, for example, when the engine 2 is cold, the LPG may not vaporize sufficiently and the LPG may remain in liquid form. If the LPG remaining in liquid form suddenly vaporizes after the engine 2 is warmed up, the pressure inside the regulator 30 may become excessively high. Therefore, in the example of FIG. 1, a relief passage (outflow passage) 10 is provided to flow gas fuel from the fuel passage 9 to the intake passage 3 of the engine 2 to prevent the pressure from becoming excessively high.

[0027] The relief passage 10 connects the fuel passage 9 and the intake passage 3, and has a relief valve 10a that allows gas fuel to flow at a predetermined relief pressure (outflow pressure). The relief pressure is preset to a pressure higher than the warm pressure, which is the fuel pressure when the engine 2 is in a warm state, so as to prevent the fuel pressure in the fuel passage 9 from becoming excessively high. The warm pressure corresponds to the fuel pressure in a state where the effect of vaporization of the liquefied fuel remaining in liquid form inside the regulator 30 or the like has been sufficiently eliminated. The relief pressure refers to the pressure (outflow pressure) at which the pressure increases due to subsequent vaporization of poorly vaporized liquefied fuel, causing the vaporized fuel to flow out to the intake passage 3.

[0028] The relief valve 10a allows the gas fuel to flow when the fuel pressure in the fuel passage 9 reaches or exceeds a predetermined relief pressure. Therefore, when the fuel pressure reaches or exceeds the relief pressure, the gas fuel flows out through the relief valve 10a into the intake passage 3 of the engine 2 even if the injector 11 is not injecting the gas fuel. In other words, the relief passage 10 is an outflow passage that allows the gas fuel to flow from the fuel passage 9 to the intake passage 3 of the engine 2 without passing through the injector 11 in response to a pressure increase of the gas fuel in the pressure reduction chamber of the regulator 30 or in the fuel passage 9.

[0029] The injector 11 is an electromagnetic fuel injection valve that supplies gas fuel from the LPG cylinder 6 to the engine 2. The injector 11 injects the gas fuel between the throttle valve 5 and the engine 2 in the intake passage 3. The injector 11 may also directly inject the gas fuel into a cylinder of the engine 2.

[0030] The exhaust passage 12 is connected to a cylinder head of the engine 2. The exhaust passage 12 is a passage through which combustion gas generated when a mixture of intake air and gas fuel is burned in a combustion chamber of the engine 2 flows.

[0031] The fuel control device 100 for an internal combustion engine includes a fuel pressure sensor (pressure detection unit) 13, an intake pressure sensor 14, a rotation speed sensor 15, and 2 The system includes a sensor 16 and an ECU (Electronic Control Unit) 20 electrically connected to the sensors 13-16.

[0032] The fuel pressure sensor 13 is a pressure detection unit that detects the fuel pressure of the gas fuel in the regulator 30 or the fuel passage 9. As an example, the fuel pressure sensor 13 detects the fuel pressure of the gas fuel in a fuel supply rail to which a plurality of injectors 11 are attached.

[0033] The intake pressure sensor 14 is a pressure sensor that detects the pressure of the intake air inside the intake passage 3. The rotation speed sensor 15 is a sensor that detects the rotation speed of the engine 2.

[0034] O 2 The sensor 16 is an exhaust sensor that detects the oxygen concentration in the exhaust gas of the engine 2. 2 The sensor 16 detects the oxygen concentration of the exhaust gas flowing through the exhaust passage 12 .

[0035] The ECU 20 is an electronic control unit that controls the engine 2. The ECU 20 has a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), a controller area network (CAN) communication circuit, and the like. For example, the ECU 20 loads a program stored in the ROM into the RAM and executes the program loaded into the RAM by the CPU, thereby achieving various functions. The ECU 20 may be composed of multiple electronic control units.

[0036] The ECU 20 is connected to a fuel pressure sensor 13, an intake pressure sensor 14, a rotation speed sensor 15, and an O 2 Based on the detection values ​​of the sensors 16, the ECU 20 executes predetermined processing to control the throttle valve 5, the solenoid valve 8, and the injector 11. The ECU 20 performs learning control to calculate a learning correction value for the amount of fuel supply using the result of feedback correction of the amount of fuel supply based on the oxygen concentration of the exhaust gas of the engine 2. Here, the ECU 20 corrects the amount of gas fuel supply to the engine 2 using the learning correction value.

[0037] Fig. 2 is a schematic block diagram illustrating the functional configuration of the ECU in Fig. 1. As shown in Fig. 2, the ECU 20 has, as its functional configuration, an engine state quantity acquisition unit 21, a fuel feedback correction unit 22, a fuel learning correction unit 23, a fuel injection control unit 24, and a throttle control unit 25.

[0038] The engine state quantity acquisition unit 21 is a fuel pressure sensor 13, an intake pressure sensor 14, a rotation speed sensor 15, and an O 2Based on the detection values ​​of the sensors 16, the fuel pressure, the pressure of the intake air, the rotation speed of the engine 2, and the oxygen concentration of the exhaust gas of the engine 2 are obtained.

[0039] The fuel feedback correction unit 22 2 Based on the detection result of the sensor 16, a fuel feedback control is executed to correct (feedback correct) the amount of fuel supply so that the air-fuel ratio of the exhaust gas becomes a predetermined target air-fuel ratio. The fuel feedback correction unit 22 calculates, for example, a fuel feedback correction amount for correcting a basic supply amount of gas fuel calculated based on the rotation speed of the engine 2 and the pressure of the intake air in the fuel feedback control. Here, the "fuel" that is the target of the feedback correction and learning control is the gas fuel supplied from the injector 11.

[0040] The fuel learning correction unit 23 performs learning control to calculate a learning correction value of the fuel supply amount using the result of the feedback correction. For example, when a predetermined learning execution condition is satisfied, the fuel learning correction unit 23 updates the learning correction value at regular intervals based on the fuel feedback correction amount. The predetermined learning execution condition may be, for example, a condition that the coolant temperature of the engine 2 is equal to or higher than a predetermined value. This predetermined value is a coolant temperature threshold value for determining whether the engine 2 is in a warmed-up state.

[0041] Here, if gas fuel is caused to flow from the fuel passage 9 to the intake passage 3 of the engine 2 without passing through the injector 11 in response to an increase in the pressure of the gas fuel in the pressure reduction chamber of the regulator 30 or in the fuel passage 9, there is a risk that the supply of gas fuel to the engine 2 will temporarily be excessive, and the learning correction value for the amount of fuel supplied will be erroneously calculated to be excessively low.

[0042] Therefore, when the fuel pressure of the gas fuel is equal to or higher than a predetermined pressure threshold, the ECU 20 temporarily stops the calculation of the learning correction value. Specifically, when the fuel pressure is equal to or higher than the predetermined pressure threshold, the fuel learning correction unit 23 temporarily does not update the learning correction value. When the fuel pressure is equal to or higher than the predetermined pressure threshold, the fuel learning correction unit 23 may temporarily not execute the learning control itself.

[0043] The pressure threshold is a predetermined threshold of the fuel pressure for temporarily stopping the calculation of the learning correction value. The pressure threshold can be set, for example, as a value larger than the warm pressure to an extent that is not usually reached in the warm state. The pressure threshold may be, for example, a value smaller than the relief pressure (outflow pressure) and larger than the warm pressure. The pressure threshold may be, for example, a pressure value obtained by subtracting a predetermined margin based on the relief pressure, taking into account individual variations of parts, etc.

[0044] When the fuel pressure is equal to or higher than the pressure threshold, even if a predetermined learning execution condition is satisfied, the ECU 20 temporarily stops the calculation of the learning correction value, thereby suppressing the influence of the temporary excess supply of gas fuel to the engine 2 on the learning correction value, which in turn leads to a deterioration in the controllability of the air-fuel ratio. During the period when the calculation of the learning correction value is temporarily stopped, the influence of the temporary excess supply of gas fuel to the engine 2 is compensated for by the fuel feedback correction amount calculated by the fuel feedback correction unit 22, and the amount of fuel supplied is corrected so that the air-fuel ratio of the exhaust gas becomes the target air-fuel ratio. The ECU 20 may resume the calculation of the learning correction value when the fuel pressure of the gas fuel becomes equal to or higher than the predetermined pressure threshold and then drops to less than the pressure threshold.

[0045] The fuel injection control unit 24 uses the result of the feedback correction of the fuel supply amount and the learning correction value to supply gas fuel to the injector 11. For example, the fuel injection control unit 24 calculates an injection time equivalent to an injection amount for supplying gas fuel to the injector 11 by correcting a basic supply amount with the fuel feedback correction amount calculated by the fuel feedback correction unit 22 and the learning correction value calculated by the fuel learning correction unit 23. The fuel injection control unit 24 controls the opening of the injector 11 based on the calculated injection time to supply gas fuel to the injector 11.

[0046] The throttle control unit 25 controls the opening degree of the throttle valve 5 based on the detection result of an accelerator sensor (not shown) that detects the amount of operation of an accelerator pedal, for example.

[0047] 3 is a flowchart showing an example of a calculation process of the learning correction value of the ECU. The process of the flowchart shown in FIG 3 is repeatedly executed at predetermined calculation intervals when a predetermined learning execution condition is satisfied while the engine 2 is in operation.

[0048] In S01, the ECU 20 of the fuel control device 100 for an internal combustion engine detects the fuel pressure by the engine state quantity acquisition unit 21. The engine state quantity acquisition unit 21 detects the fuel pressure while the engine 2 is operating from the detection signal of the fuel pressure sensor 13, for example.

[0049] In S02, the ECU 20 determines whether or not the fuel pressure is equal to or greater than the pressure threshold value using the fuel learning correction unit 23. If it is determined that the fuel pressure is equal to or greater than the pressure threshold value (S02: YES), the ECU 20 proceeds to processing in S04. If it is determined that the fuel pressure is less than the pressure threshold value (S02: NO), the ECU 20 proceeds to processing in S03.

[0050] In S03, the ECU 20 continues to calculate the learning correction value by the fuel feedback correction unit 22 and the fuel learning correction unit 23 without stopping the calculation of the learning correction value. 2 Fuel feedback control is executed based on the oxygen concentration of the exhaust gas detected by the sensor 16. The fuel learning correction unit 23 calculates a learning correction value based on the correction value of the fuel feedback control. After that, the ECU 20 ends the process of FIG.

[0051] In S04, the ECU 20 causes the fuel feedback correction unit 22 and the fuel learning correction unit 23 to temporarily stop the calculation of the learning correction value, and does not calculate the learning correction value. 2Fuel feedback control is executed based on the oxygen concentration of the exhaust gas detected by the sensor 16. Thereafter, the ECU 20 ends the process of FIG.

[0052] According to the fuel control device 100 for an internal combustion engine configured as described above, for example, when the liquefied fuel remaining in the regulator 30 in a liquid state vaporizes after the engine 2 is warmed up, the pressure of the gas fuel in the regulator 30 or the fuel passage 9 increases. In response to the increase in the pressure of the gas fuel in the regulator 30 or the fuel passage 9, the gas fuel may flow out from the regulator 30 or the fuel passage 9 to the intake passage 3 of the engine 2 through the relief passage 10. Here, when the fuel pressure of the gas fuel in the regulator 30 or the fuel passage 9 is equal to or higher than a predetermined pressure threshold, the calculation of the learning correction value is temporarily stopped. Therefore, the calculation of the learning correction value including the influence of the gas fuel that has flowed out excessively to the intake passage 3 through the relief passage 10 is suppressed. This makes it possible to suppress erroneous learning of the supply amount of fuel caused by the liquefied fuel remaining in the regulator 30 vaporizing after the engine 2 is warmed up.

[0053] In the fuel control device 100 for an internal combustion engine, the pressure threshold value is a value smaller than the outflow pressure, which is the fuel pressure at which the gas fuel flows out to the intake passage 3 through the relief passage 10, and larger than the warm pressure, which is the fuel pressure in the warm state of the engine 2. As a result, the calculation of the learning correction value is temporarily stopped earlier than the gas fuel flows out to the intake passage 3 through the relief passage 10, so that erroneous learning of the fuel supply amount can be more reliably suppressed.

[0054] The fuel control device 100 for an internal combustion engine further includes a relief passage 10 having a relief valve 10a that connects the fuel passage 9 and the intake passage 3 and flows the gas fuel at a predetermined relief pressure. The regulator 30 supplies the gas fuel to the injector 11 at a warm pressure that is the fuel pressure in the warm state when the engine 2 is in a warm state, and the relief passage 10 causes the gas fuel to flow from the fuel passage 9 to the intake passage 3 via the relief valve 10a without passing through the injector 11 in response to a pressure increase of the gas fuel in the regulator 30 and the fuel passage 9. In this configuration, it is possible to suppress calculation of a learning correction value that includes the influence of the gas fuel excessively flowing into the intake passage 3 via the relief valve 10a.

[0055] [Variations] The present invention is not limited to the above-described embodiment. The present invention can be implemented in various forms including the above-described embodiment and various modifications and improvements based on the knowledge of those skilled in the art.

[0056] In the above embodiment, the pressure threshold value is a value smaller than the relief pressure (outflow pressure) and larger than the warm pressure, but is not limited to this example. For example, the pressure threshold value may be equal to the relief pressure, or may be a value slightly larger than the relief pressure as a result of including individual variations of parts or adjustments in control.

[0057] In the above embodiment, the fuel pressure sensor 13 detects the fuel pressure in the fuel supply rail, but it may also detect the fuel pressure in the fuel passage 9 other than the fuel supply rail, or it may detect the fuel pressure in the regulator 30.

[0058] In the above embodiment, the exhaust sensor for detecting the oxygen concentration in the exhaust gas of the engine 2 is an O 2 Although the sensor 16 is used, an air-fuel ratio sensor capable of linearly detecting the air-fuel ratio may be used.

[0059] In the above embodiment, the injector 11 mainly supplies fuel, and the regulator 30 has a single-stage pressure reduction chamber, but the invention is not limited to this example. For example, an internal combustion engine system 1A shown in FIG. 4 may further include a mixer 17 provided in the intake passage 3 of the engine 2.

[0060] 4 is a schematic diagram showing an internal combustion engine system including a fuel control device for an internal combustion engine according to a modified example. A mixer 17 is installed in the intake passage 3 of the engine 2 and performs main fuel supply. The mixer 17 has a venturi that mixes gas fuel supplied from a regulator (pressure regulator) 40 with intake air. An injector 11A in the internal combustion engine system 1A performs auxiliary fuel supply. A fuel passage (fuel supply passage) 9a is a fuel passage that connects the regulator 40 and the injector 11A. A fuel passage (outflow passage) 9b is a fuel passage that connects the regulator 40 and the mixer 17.

[0061] The regulator 40 has a primary chamber 41 and a secondary chamber 42 as pressure reduction chambers that perform two-stage pressure reduction. The primary chamber 41 supplies gas fuel to the injector 11A at a warm pressure, which is the fuel pressure in the warm state, when the engine 2 is in a warm state. The primary chamber 41 is basically configured in the same manner as the regulator 30, and includes a valve portion 41a and a diaphragm portion 41b that operate so that the fuel pressure in the primary chamber 41 and the fuel passage 9a of the regulator 40 is balanced at the warm pressure in the warm state. The secondary chamber 42 includes a valve portion 42a and a diaphragm portion 42b that operate so that the gas fuel flows in from the primary chamber 41 and supplies the gas fuel to the mixer 17 at a pressure lower than the warm pressure of the primary chamber 41 in the warm state.

[0062] For example, when the pressure in the primary chamber 41 becomes excessively high due to the liquefied fuel remaining in the regulator 40 vaporizing after the engine 2 is warmed up, the gas fuel flows from the primary chamber 41 to the secondary chamber 42 through the valve portion 42a. As a result, the gas fuel flows excessively from the regulator 40 to the mixer 17 through the fuel passage 9b. That is, the fuel passage 9b causes the gas fuel to flow to the intake passage 3 through the mixer 17 without passing through the injector 11A in response to a pressure increase of the gas fuel in the primary chamber 41 or the fuel passage 9a of the regulator 40. The outflow pressure in this case is the pressure of the gas fuel in the primary chamber 41 of the regulator 40 when the gas fuel flows from the primary chamber 41 to the secondary chamber 42 through the valve portion 42a.

[0063] In the fuel control device 100A for an internal combustion engine as shown in FIG. 4, a fuel pressure sensor (pressure detection unit) 13A is provided in the fuel passage 9a. The fuel pressure sensor 13A detects the fuel pressure of the gas fuel in the primary chamber 41 of the regulator 40 or the fuel passage 9a. The ECU 20 of the fuel control device 100A for an internal combustion engine performs feedback correction of the supply amount of the gas fuel (fuel) supplied from the injector 11A based on the oxygen concentration of the exhaust gas of the engine 2 as a learning control, and calculates a learning correction value for correcting the supply amount of the gas fuel supplied from the injector 11A using the result of the feedback correction. When the fuel pressure of the gas fuel in the regulator 40 or the fuel passage 9a is equal to or higher than a predetermined pressure threshold, the ECU 20 of the fuel control device 100A for an internal combustion engine temporarily stops the calculation of the learning correction value of the supply amount of the gas fuel supplied from the injector 11A. Therefore, the calculation of the learning correction value including the influence of the gas fuel that has flowed out excessively into the intake passage 3 via the fuel passage 9b is suppressed. This makes it possible to suppress erroneous learning of the supply amount of gas fuel supplied from the injector 11A, which is caused when the liquefied fuel remaining in liquid form in the regulator 40 vaporizes after the engine 2 is warmed up. In other words, in the configuration of Fig. 4, it is possible to suppress calculation of the learning correction value including the influence of the gas fuel that has excessively flowed out into the intake passage 3 via the secondary chamber 42 and the mixer 17.

[0064] In the fuel control device 100A for an internal combustion engine in FIG. 4, a motor for air-fuel ratio control may be built in the mixer 17. The motor for air-fuel ratio control is an actuator that moves a needle valve inside the mixer 17 in response to a signal from the ECU 20 related to the control amount of the motor to change the passage area of ​​the fuel connected to the venturi, thereby controlling the fuel flow rate of the mixer 17. In this case, the ECU 20 may perform feedback correction of the supply amount of gas fuel (fuel) supplied from the mixer 17 based on the oxygen concentration of the exhaust gas of the engine 2 as a learning control, and calculate a learning correction value for correcting the supply amount of gas fuel supplied from the mixer 17 using the result of the feedback correction. The "learning correction value for correcting the supply amount of fuel" here corresponds to a learning correction value of the control amount of the motor for air-fuel ratio control. When the fuel pressure of the gas fuel in the regulator 40 or the fuel passage 9a is equal to or higher than a predetermined pressure threshold, the ECU 20 temporarily stops calculation of the learning correction value of the control amount of the motor for air-fuel ratio control. Therefore, it is possible to suppress the calculation of the learning correction value of the control amount of the motor for air-fuel ratio control, which includes the influence of the gas fuel that has flowed out in excess into the intake passage 3 via the fuel passage 9b.

[0065] Also, for example, as in the internal combustion engine system 1B shown in FIG. 5, a gasoline injector 18 may be further provided. FIG. 5 is a schematic diagram showing an internal combustion engine system equipped with a fuel control device for an internal combustion engine according to another modified example. The internal combustion engine system 1B is a bi-fuel engine system using LPG and gasoline in combination. The ECU 20 of the fuel control device 100B for the internal combustion engine performs feedback correction of the supply amount of "fuel" based on the oxygen concentration of the exhaust gas of the engine 2 as learning control, and calculates a learning correction value for correcting the supply amount of "fuel" using the result of the feedback correction. The "fuel" subject to feedback correction and learning control may be gas fuel supplied from the injector 11A, may be gas fuel supplied from the mixer 17 adjusted by a motor for air-fuel ratio control, or may be gasoline fuel supplied from the gasoline injector 18. For example, in a situation where the engine 2 is operated only with gasoline fuel supplied from the gasoline injector 18 and the "fuel" subject to feedback correction and learning control is only gasoline, the ECU 20 of the internal combustion engine fuel control device 100B may temporarily stop calculating the learning correction value for the gasoline fuel supplied from the gasoline injector 18 when the fuel pressure of the gas fuel in the regulator 40 or the fuel passage 9a is equal to or higher than a predetermined pressure threshold.

[0066] In the above embodiment, the regulator 30 incorporates a heating device that uses, for example, the heat of the coolant of the engine 2. However, even if the regulator 30 is heated using a heat source such as an electric heater, the present invention can be applied in cases where a situation occurs in which the regulator 30 is not heated sufficiently.

[0067] In the above embodiment, LPG is used as the liquefied fuel, but the liquefied fuel is not limited to this. The liquefied fuel may be, for example, dimethyl ether (DME). The liquefied fuel may be any fuel that may remain in liquid form inside the pressure regulator during cold operation of the internal combustion engine when a pressure regulator that is heated during operation of the internal combustion engine is used, and may be rapidly vaporized after the internal combustion engine is warmed up. [Explanation of symbols]

[0068] 2...engine (internal combustion engine), 3...intake passage, 9, 9a...fuel passage (fuel supply passage), 9b...fuel passage (outflow passage), 10...relief passage (outflow passage), 10a...relief valve, 11, 11A...injector, 13, 13A...fuel pressure sensor (pressure detection unit), 17...mixer, 20...ECU (control unit), 30, 40...regulator (pressure adjuster), 41...primary chamber, 42...secondary chamber, 100, 100A, 100B...fuel control device for internal combustion engine.

Claims

1. A fuel control device for an internal combustion engine capable of supplying gas fuel obtained by vaporizing liquefied fuel, a pressure regulator that is heated during operation of the internal combustion engine to vaporize the liquefied fuel; a fuel supply passage for supplying the gas fuel from the pressure regulator to an injector; an outflow passage for allowing the gas fuel to flow from the pressure regulator or the fuel supply passage to an intake passage of the internal combustion engine without passing through the injector in response to a pressure increase of the gas fuel in the pressure regulator or the fuel supply passage; a pressure detection unit that detects a fuel pressure of the gas fuel in the pressure regulator or in the fuel supply passage; a control unit that performs learning control to calculate a learning correction value for correcting the amount of fuel supplied using a result of feedback correction of the amount of fuel supplied based on an oxygen concentration of exhaust gas from the internal combustion engine, A fuel control device for an internal combustion engine, wherein the control unit temporarily stops calculation of the learning correction value when the fuel pressure of the gas fuel is equal to or higher than a predetermined pressure threshold.

2. 2. The fuel control device for an internal combustion engine according to claim 1, wherein the pressure threshold value is a value smaller than an outflow pressure, which is the fuel pressure at which the gas fuel flows out to the intake passage through the outflow passage, and larger than a warm pressure, which is the fuel pressure in a warm state of the internal combustion engine.

3. a relief passage that connects the fuel supply passage and the intake passage and has a relief valve that allows the gas fuel to flow at a predetermined relief pressure; The pressure regulator supplies the gas fuel to the injector at a warm pressure, which is the fuel pressure in the warm state, when the internal combustion engine is in a warm state; 3. A fuel control device for an internal combustion engine according to claim 1, wherein the outflow passage causes the gas fuel to flow from the fuel supply passage to the intake passage via the relief passage without passing through the injector in response to a pressure increase of the gas fuel in the pressure regulator and the fuel supply passage.

4. The internal combustion engine further includes a mixer provided in an intake passage of the internal combustion engine, the pressure regulator has a primary chamber that supplies the gas fuel to the injector at a warm pressure that is the fuel pressure in a warm state of the internal combustion engine, and a secondary chamber into which the gas fuel from the primary chamber flows and into which the gas fuel is supplied to the mixer at a pressure lower than the warm pressure in the warm state, 3. The fuel control device for an internal combustion engine according to claim 1, wherein the outflow passage causes the gas fuel to flow into the intake passage via the mixer without passing through the injector in response to a pressure increase of the gas fuel in the primary chamber of the pressure regulator and in the fuel supply passage.

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