Engine device

Abstract

To suppress failure of feedback control of an air-fuel ratio.SOLUTION: A control device that performs feedback control of a fuel injection amount of an engine turns off a feedback flag, when, out of a plurality of conditions for executing the feedback control, a first condition indicating that the fuel injection amount of the engine is a minimum injection amount or greater from a fuel injection valve is not satisfied, or a second condition indicating that lower limit guard of a correction amount of the feedback control is not performed so as to prevent the fuel injection amount of the engine from becoming smaller than the minimum injection amount from the fuel injection valve is not satisfied.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an engine device, and more particularly to an engine device that feedback controls the amount of fuel injection into the engine. [Background technology]

[0002] Conventionally, as an engine device of this type, a device has been proposed in which, when the fuel injection amount injected from the direct injection valve or the fuel injection amount injected from the port injection valve is smaller than the minimum injection amount of the direct injection valve, updating by accumulating the integral term in feedback control of the fuel injection amount is prohibited and the integral term is held (see, for example, Patent Document 1). In this device, even when the fuel injection amount of the direct injection valve or the port injection valve is guarded at the minimum injection amount, feedback control is continued simply by holding the integral term, thereby realizing air-fuel ratio feedback control with good controllability. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-032328 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-described engine device, when the fuel injection amount of the fuel injection valve becomes smaller than the minimum injection amount, the feedback control is continued with the integral term in the feedback control held, so that the fuel injection amount of the fuel injection valve may fall below the minimum injection amount depending on the proportional term in the feedback control. Since the fuel is injected, the air-fuel ratio becomes rich, and feedback control fails.

[0005] The engine device of the present disclosure has a primary object to prevent the feedback control of the air-fuel ratio from failing. [Means for solving the problem]

[0006] The engine device of the present disclosure employs the following measures to achieve the above-mentioned main object.

[0007] The engine device of the present disclosure comprises: An engine device comprising an engine and a control device that feedback controls a fuel injection amount of the engine, the control device turns off a feedback flag when a first condition, among the plurality of conditions for executing the feedback control, that the fuel injection amount of the engine is equal to or greater than a minimum injection amount from a fuel injection valve is not satisfied, or when a second condition, that the correction amount of the feedback control is not limited to a lower limit so that the fuel injection amount of the engine does not become less than the minimum injection amount from a fuel injection valve, is not satisfied. It is characterized by:

[0008] In the engine device of the present disclosure, when a first condition, among a plurality of conditions for executing feedback control, that the engine's fuel injection amount is equal to or greater than the minimum injection amount from the fuel injection valve, is not satisfied (when the condition that the engine's fuel injection amount is less than the minimum injection amount from the fuel injection valve is satisfied), or when a second condition, that the feedback control correction amount is not limited to a lower limit so that the engine's fuel injection amount does not become less than the minimum injection amount from the fuel injection valve, is not satisfied (when the second condition that limits the feedback control correction amount is satisfied), the feedback flag is turned off. In other words, when stoichiometric control is not being performed, the feedback flag is turned off. This prevents normal feedback control from being continued when stoichiometric control is not being performed, and prevents normal feedback control from failing.

[0009] In the engine device of the present disclosure, when the feedback flag is off because only the first condition or the second condition among the plurality of conditions for executing the feedback control is not satisfied, the control device may perform feedback control using the correction amount when the correction amount for the feedback control is at the lower limit. Note that when any condition other than the first condition and the second condition among the plurality of conditions for executing the feedback control is not satisfied, not only the feedback flag is turned off but also normal feedback control and the correction amount when the lower limit is satisfied are used to stop the feedback control. This makes it possible to suppress hunting between execution and non-execution of normal feedback control. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a configuration diagram showing an outline of the configuration of an engine device 10 according to an embodiment of the present disclosure. [Figure 2] 4 is a flowchart showing an example of an air-fuel ratio feedback control execution process executed by an electronic control unit 70. DETAILED DESCRIPTION OF THE INVENTION

[0011] Next, a mode (embodiment) for carrying out the present disclosure will be described. Fig. 1 is a configuration diagram showing an outline of the configuration of an engine system 10 according to one embodiment of the present disclosure. As shown in the figure, the engine system 10 of the embodiment includes an engine 12, a fuel supply system 50, and an electronic control unit 70. The engine system 10 is mounted on a general vehicle that runs using power from the engine 12, various hybrid vehicles that include a motor in addition to the engine 12, and stationary equipment (such as construction equipment) that operates using power from the engine 12.

[0012] The engine 12 is configured as an internal combustion engine that uses fuel such as gasoline or a mixture of gasoline and alcohol, and outputs power through four strokes: intake, compression, expansion, and exhaust. The engine 12 is equipped with a port injection valve 25 that injects fuel into the intake port, and an in-cylinder injection valve 26 that injects fuel into the cylinder. By being equipped with the port injection valve 25 and the in-cylinder injection valve 26, the engine 12 can be operated in any of a port injection mode, an in-cylinder injection mode, and a common injection mode.

[0013] In the port injection mode, air purified by the air cleaner 22 is drawn into the intake pipe 23 and passes through the throttle valve 24, while fuel is injected from the port injection valve 25 to mix the air and fuel. This mixture is then drawn into the combustion chamber 29 via the intake valve 28, where it is explosively combusted by an electric spark from the spark plug 30. The reciprocating motion of the piston 32, which is pushed down by the energy from the explosive combustion, is then converted into rotational motion of the crankshaft 14. In the direct injection mode, as in the port injection mode, air is drawn into the combustion chamber 29, and fuel is injected from the direct injection valve 26 midway through the intake stroke and / or during the compression stroke, where it is explosively combusted by an electric spark from the spark plug 30, thereby generating rotational motion of the crankshaft 14. In the shared injection mode, fuel is injected from the port injection valve 25 when air is drawn into the combustion chamber 29, and fuel is injected from the in-cylinder injection valve 26 during the intake stroke and the compression stroke, and the fuel is explosively burned by an electric spark from the spark plug 30, generating rotational motion of the crankshaft 14. These injection modes are switched depending on the operating state of the engine 12. Exhaust gas discharged from the combustion chamber 29 into the exhaust pipe 33 via the exhaust valve 31 is discharged into the outside air via a purification device 34 having a purification catalyst (three-way catalyst) 34a that purifies harmful components such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx).

[0014] The fuel supply device 50 is configured as a device that supplies fuel in a fuel tank 51 to the port injection valves 25 and the in-cylinder injection valves 26 of the engine 12. The fuel supply device 50 includes the fuel tank 51, a feed pump (first pump) 52, a low-pressure supply pipe (first supply pipe) 53, a check valve 54, a relief flow path 55, a relief valve 56, a high-pressure pump (second pump) 57, and a high-pressure supply pipe (second supply pipe) 58.

[0015] Feed pump 52 is configured as an electric pump that operates by receiving power from a battery (not shown), and is disposed inside fuel tank 51. Feed pump 52 supplies fuel from inside fuel tank 51 to low-pressure supply pipe 53. Low-pressure supply pipe 53 is connected to port injection valve 25. Check valve 54 is provided in low-pressure supply pipe 53 and allows fuel to flow in the direction from feed pump 52 to port injection valve 25, while restricting fuel flow in the opposite direction.

[0016] The relief flow passage 55 is connected to the low-pressure supply pipe 53 and the fuel tank 51. The relief valve 56 is provided in the relief flow passage 55, and closes when the fuel pressure in the low-pressure supply pipe 53 is below a threshold value Pflolim, and opens when the fuel pressure in the low-pressure supply pipe 53 is equal to or higher than the threshold value Pflolim. When the relief valve 56 opens, a portion of the fuel in the low-pressure supply pipe 53 is returned to the fuel tank 51 via the relief flow passage 55. In this way, the fuel pressure in the low-pressure supply pipe 53 is prevented from becoming excessive.

[0017] The high-pressure pump 57 is driven by power from the engine 12 (in this embodiment, rotation of the intake camshaft that opens and closes the intake valve 28), and is configured as a pump that pressurizes fuel in the low-pressure supply pipe 53 and supplies it to the high-pressure supply pipe 58. The high-pressure pump 57 has an electromagnetic valve 57a connected to its intake port that opens and closes when pressurizing the fuel, a check valve 57b connected to its discharge port that regulates backflow of fuel and maintains the fuel pressure in the high-pressure supply pipe 58, and a plunger 57c that is actuated (moves vertically in FIG. 1 ) by the rotation of the engine 12 (rotation of the intake camshaft). During operation of the engine 12, when the electromagnetic valve 57a is open, the high-pressure pump 57 sucks fuel from the low-pressure supply pipe 53, and when the electromagnetic valve 57a is closed, the high-pressure pump 57 pressurizes the fuel to be supplied to the high-pressure supply pipe 58 by intermittently sending fuel compressed by the plunger 57c into the high-pressure supply pipe 58 via the check valve 57b. When the high-pressure pump 57 is driven, the fuel pressure in the low-pressure supply pipe 53 and the fuel pressure (fuel pressure) in the high-pressure supply pipe 58 pulsate in accordance with the rotation of the engine 12 (the rotation of the intake camshaft). The high-pressure supply pipe 58 is connected to the in-cylinder injection valve 26.

[0018] The electronic control unit 70 includes a microcomputer having a CPU 71, ROM 72, RAM 73, flash memory 74, and input / output ports. Signals from various sensors are input to the electronic control unit 70 via the input ports. Examples of signals input to the electronic control unit 70 include a crank angle θcr from a crank position sensor 14a that detects the rotational position of the crankshaft 14 of the engine 12, a coolant temperature Tw from a water temperature sensor 40 that detects the temperature of the coolant for the engine 12, and an oil temperature Toil from an oil temperature sensor 42 that detects the temperature of the lubricating oil for the engine 12. Other examples of signals input to the electronic control unit 70 include cam angles θci and θco from a cam position sensor 44 that detects the rotational position of an intake camshaft that opens and closes the intake valve 28 and the rotational position of an exhaust camshaft that opens and closes the exhaust valve 31. Other examples include the throttle opening TH from a throttle position sensor 24a that detects the position of the throttle valve 24, the intake air amount Qa from an air flow meter 23a attached upstream of the throttle valve 24 in the intake pipe 23, and the intake air temperature Ta from a temperature sensor 23t attached upstream of the throttle valve 24 in the intake pipe 23. Other examples include the air-fuel ratio AF from an air-fuel ratio sensor 35 attached upstream of the purification device 34 in the exhaust pipe 33, and an oxygen signal O2 from an oxygen sensor 36 attached downstream of the purification device 34 in the exhaust pipe 33. Other examples include the fuel temperature Tftnk from a fuel temperature sensor 51t attached to the fuel tank 51, the rotation speed Nlp of the feed pump 52 from a rotation speed sensor 52a attached to the feed pump 52, the low-pressure fuel pressure (the pressure of the fuel supplied to the port injection valve 25) Pflo from a fuel pressure sensor 53p attached to the low-pressure supply pipe 53 near the port injection valve 25 (e.g., the low-pressure delivery pipe), and the high-pressure fuel pressure (the pressure of the fuel supplied to the in-cylinder injection valve 26) Pfhi from a fuel pressure sensor 58p attached to the high-pressure supply pipe 58 near the in-cylinder injection valve 26 (e.g., the high-pressure delivery pipe).

[0019] Various control signals are output from the electronic control unit 70 via the output port. Examples of signals output from the electronic control unit 70 include a control signal to the throttle valve 24 of the engine 12, a control signal to the port injection valve 25, a control signal to the in-cylinder injection valve 26, and a control signal to the spark plug 30. Other examples include a control signal to the feed pump 52 of the fuel supply device 50 and a control signal to the electromagnetic valve 57a of the high-pressure pump 57.

[0020] The electronic control unit 70 calculates the rotation speed Ne of the engine 12 based on the crank angle θcr from the crank position sensor 14a. The electronic control unit 70 also calculates a load factor KL (the ratio of the volume of air actually taken in per cycle to the stroke volume per cycle of the engine 12) based on the intake air amount Qa from the air flow meter 23a and the rotation speed Ne of the engine 12. The electronic control unit 70 also estimates the temperature Tc of the catalyst 34a of the purification device 34 based on the coolant temperature Tw from the water temperature sensor 40, the rotation speed Ne of the engine 12, and the load factor KL. In addition, the electronic control unit 70 estimates the fuel temperature Tfhp in the high-pressure pump 57 based on the coolant temperature Tw, the oil temperature Toil from the oil temperature sensor 42, and the intake air temperature Ta from the temperature sensor 23t.

[0021] In the engine system 10 of the embodiment configured as described above, the CPU 71 of the electronic control unit 70 controls the intake air amount, fuel injection, and ignition of the engine 12 as operation control of the engine 12, and also controls the feed pump 52 and high-pressure pump 57 (electromagnetic valve 57a) of the fuel supply device 50. Note that the fuel injection control will be described below when fuel is injected by the in-cylinder injection valve 26.

[0022] The intake air amount of the engine 12 is controlled, for example, by setting a required air amount Qa* based on the accelerator opening and the engine speed Ne of the engine 12, setting a target opening TH* of the throttle valve 24 so that the intake air amount Qa becomes the required air amount Qa*, and controlling the throttle valve 24 using the target opening TH*.The fuel injection of the engine 12 is controlled by setting a basic fuel injection amount Qfbase based on the air amount Qa and the target air-fuel ratio AF*, calculating a feedback correction amount kfb so that the air-fuel ratio AF becomes the target air-fuel ratio AF*, setting the fuel injection amount Qf by adding the feedback correction amount kfb to the basic fuel injection amount Qfbase, setting a fuel injection time Tf based on the fuel injection amount Qf and the high-pressure fuel pressure Pfhi, and controlling the direct injection valve 26 so that fuel is injected at a predetermined timing for the fuel injection time Tf. Ignition control of the engine 12 is performed by setting a target ignition timing Ti* of the spark plug 30 based on the engine speed Ne, required air volume Qa*, etc., and controlling the spark plug 30 using the set target ignition timing Ti*.

[0023] Next, the operation of the engine system 10 of this embodiment configured as described above, particularly the operation when turning on and off feedback control for setting the air-fuel ratio AF to the target air-fuel ratio AF*, will be described. Figure 2 is a flowchart showing an example of an air-fuel ratio feedback control execution process executed by the electronic control unit 70. This process is repeatedly executed at predetermined time intervals.

[0024] When the air-fuel ratio feedback control execution process is executed, the electronic control unit 70 first inputs the set fuel injection amount Qf (step S100). The fuel injection amount Qf is set for each cylinder at a predetermined timing by adding the feedback correction amount kfb to the basic fuel injection amount Qfbase as described above.

[0025] Next, it is determined whether predetermined conditions for executing feedback control of the air-fuel ratio are satisfied (step S110). The conditions for executing feedback control of the air-fuel ratio include a condition (first condition) in which the fuel injection amount Qf is equal to or greater than the minimum injection amount Qfmin, a condition (second condition) in which the feedback correction amount kfb is greater than a lower limit guard value so that the fuel injection amount Qf does not become less than the minimum injection amount Qfmin, a condition (second condition) in which the feedback correction amount kfb is not lower-limit guarded, a condition in which the cooling water temperature Tw of the engine 12 is equal to or greater than a predetermined temperature, and a condition in which the catalyst temperature is equal to or greater than a predetermined temperature. The predetermined conditions are the conditions for executing feedback control of the air-fuel ratio excluding the first and second conditions (the condition (i.e., the condition (i.e., the condition (i.e., the condition (i.e., the condition (i.e., the condition (i.e., the condition (i.e., the condition (i.e., the condition (i.e., the condition (i.e., the If any of the predetermined conditions for executing the feedback control of the air-fuel ratio is not satisfied, the feedback flag Ffb is turned off and the normal feedback control of the air-fuel ratio is stopped (step S160), and this process is terminated.

[0026] If it is determined in step S100 that the predetermined conditions for executing feedback control of the air-fuel ratio are met, it is determined whether the fuel injection amount Qf is equal to or greater than the minimum injection amount Qfmin (step S120). The minimum injection amount Qfmin can be calculated by multiplying the minimum fuel injection time Tfmin, during which the direct injection valve 26 can be opened, by the high-pressure fuel pressure Pfhi. If it is determined that the fuel injection amount Qf is equal to or greater than the minimum injection amount Qfmin, it is determined whether or not the feedback correction value kfb is greater than a lower limit guard value that prevents the fuel injection amount Qf from falling below the minimum injection amount Qfmin (step S130). In this embodiment, a lower limit guard is applied to the feedback correction amount kfb to prevent the fuel injection amount Qf from falling below the minimum injection amount Qfmin as much as possible, so in step S130 it is determined whether or not the feedback correction amount kfb is not lower-limit guarded. If it is determined that the feedback correction amount kfb is greater than the lower limit guard value (not within the lower limit guard value), the feedback flag Ffb is set to ON and normal air-fuel ratio feedback control is performed (step S140), and this process ends.

[0027] When it is determined in step S120 that the fuel injection amount Qf is less than the minimum injection amount Qfmin, or when it is determined in step S130 that the feedback correction value kfb is the lower limit guard value (lower limit guarded), the feedback flag Ffb is turned off, and feedback control is performed using the feedback correction amount kfb that is the lower limit guard value (step S150), and this process ends. By performing feedback control using the feedback correction amount kfb of the lower limit guard value in this way, it is possible to suppress hunting, which is the frequent switching between performing and not performing normal air-fuel ratio feedback control.

[0028] In the engine system 10 according to the embodiment described above, when all of the conditions for executing feedback control, including the condition that the fuel injection amount Qf is equal to or greater than the minimum injection amount Qfmin (first condition) and the condition that the feedback correction amount kfb is greater than the lower limit guard value (second condition), are met, the feedback flag Ffb is set to ON and normal air-fuel ratio feedback control is performed. When any of the conditions for executing feedback control, except for the first and second conditions, is not met, the feedback flag Ffb is set to OFF and normal feedback control is stopped. When only one or both of the first and second conditions are met, the feedback flag Ffb is set to OFF and feedback control is performed using the feedback correction amount kfb of the lower limit guard value. That is, when stoichiometric control is not being performed, the feedback flag Ffb is set to OFF. This prevents normal feedback control from being continued when stoichiometric control is not being performed, thereby preventing normal feedback control from failing. Furthermore, hunting, which occurs when normal feedback control is frequently switched on and off, can be suppressed.

[0029] In the engine device 10 of the embodiment, the fuel injection control has been described as being performed when fuel is injected from the in-cylinder injection valve 26. However, the fuel injection control may be applied when fuel is injected from the port injection valve 25, or when fuel is injected from the port injection valve 25 and the in-cylinder injection valve 26.

[0030] Although the engine device 10 of the embodiment is provided with the port injection valve 25 and the in-cylinder injection valve 26, the port injection valve 25 may not be provided, or the in-cylinder injection valve 26 may not be provided.

[0031] The correspondence between the main elements of the embodiment and the main elements of the invention described in the "Means for Solving the Problem" section will be explained below. In the embodiment, the engine 12 corresponds to the "engine" and the electronic control unit 70 corresponds to the "controller."

[0032] The correspondence between the main elements of the embodiments and the main elements of the invention described in the "Means for Solving the Problem" section does not limit the elements of the invention described in the "Means for Solving the Problem" section, since the embodiments are examples for specifically explaining the mode for implementing the invention described in the "Means for Solving the Problem" section. In other words, the interpretation of the invention described in the "Means for Solving the Problem" section should be based on the description in that section, and the embodiments are merely specific examples of the invention described in the "Means for Solving the Problem" section.

[0033] The above describes the forms for implementing the present disclosure using embodiments, but the present disclosure is not limited to these embodiments in any way, and it goes without saying that the present disclosure can be implemented in various forms within the scope that does not deviate from the gist of the present disclosure. [Industrial Applicability]

[0034] The present disclosure is applicable to the engine device manufacturing industry and the like. [Explanation of symbols]

[0035] 10 engine device, 12 engine, 14 crankshaft, 14a crank position sensor, 15 crank position sensor, 22 air cleaner, 23 intake pipe, 23a air flow meter, 23t temperature sensor, 24 throttle valve, 24a throttle position sensor, 25 port injection valve, 26 in-cylinder injection valve, 28 intake valve, 29 combustion chamber, 30 spark plug, 31 exhaust valve, 32 piston, 33 exhaust pipe, 34 purification device, 34a catalyst, 35 air-fuel ratio sensor, 36 oxygen sensor, 40 water temperature sensor, 42 oil temperature sensor, 44 cam position sensor, 50 fuel supply device, 51 fuel tank, 51t fuel temperature sensor, 52 feed pump, 52a rotation speed sensor, 53 low-pressure supply pipe, 53p fuel pressure sensor, 54 check valve, 55 relief flow path, 56 Relief valve, 57 high-pressure pump, 57a solenoid valve, 57b check valve, 57c plunger, 58 high-pressure supply pipe, 58p fuel pressure sensor, 70 electronic control unit, 71 CPU, 72 ROM, 73 RAM, 74 flash memory.

Claims

1. An engine device including an engine and a control device that feedback controls a fuel injection amount of the engine, the control device turns off a feedback flag when a first condition, among the multiple conditions for executing the feedback control, that the fuel injection amount of the engine is equal to or greater than a minimum injection amount from a fuel injection valve is not satisfied, or when a second condition, that the correction amount of the feedback control is not limited to a lower limit so that the fuel injection amount of the engine does not become less than the minimum injection amount from the fuel injection valve, is not satisfied. An engine device characterized by:

2. 2. The engine device according to claim 1, When a feedback flag is turned off because only the first condition or the second condition among the plurality of conditions for executing the feedback control is not satisfied, the control device performs the feedback control using a correction amount when the correction amount of the feedback control is guarded against a lower limit. Engine equipment.

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