Engine equipment

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 fuel injection amount of an engine.

Background Art

[0002] Conventionally, as this type of engine device, when the fuel injection amount injected from the in-cylinder injection valve is smaller than the minimum injection amount of the in-cylinder injection valve or when the fuel injection amount injected from the port injection valve is smaller than the minimum injection amount of the port injection valve, an update by integration of the integral term in the 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 amounts of the in-cylinder injection valve and the port injection valve are guarded by the minimum injection amount, feedback control is continued only by holding the integral term, thereby realizing good controllability of air-fuel ratio feedback control. <00000*10*>

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems 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, feedback control is continued while holding the integral term in the feedback control. Therefore, depending on the proportional term of the feedback control, the fuel injection amount of the fuel injection valve may fall below the minimum injection amount. In this case, since the minimum injection amount of fuel is injected from the fuel injection valve, the air-fuel ratio becomes rich and the feedback control fails. Since the fuel is injected, the air-fuel ratio becomes rich and the feedback control fails.

[0005] The primary purpose of the engine device described herein is to suppress failure of the air-fuel ratio feedback control. [Means for solving the problem]

[0006] The engine device of this disclosure employs the following means to achieve the main objective described above.

[0007] The engine device of this disclosure, An engine system comprising an engine and a control device that provides feedback control for the amount of fuel injected by the engine, The control device turns off the feedback flag when the first condition, which is among the multiple conditions for executing the feedback control, is not met, or when the second condition, which is not met, is not met, and the correction amount of the feedback control is not lowered to prevent the fuel injection amount of the engine from falling below the minimum injection amount from the fuel injector. It is characterized by the following:

[0008] In the engine device of this disclosure, the feedback flag is turned off when the first condition, which is that the engine's fuel injection amount is equal to or greater than the minimum injection amount from the fuel injector, is not met (when the condition that the engine's fuel injection amount is less than the minimum injection amount from the fuel injector is met), or when the second condition, which is that the correction amount of the feedback control is not lowered to prevent the engine's fuel injection amount from falling below the minimum injection amount from the fuel injector, is not met (when the second condition that the correction amount of the feedback control is lowered to be met), is not met. In other words, the feedback flag is turned off when stoichiometric control is not being performed. This prevents the normal feedback control from continuing when stoichiometric control is not being performed, and prevents the normal feedback control from failing.

[0009] In the engine device of this disclosure, the control device may perform feedback control using the correction amount when the correction amount for the feedback control is lowered, if the feedback flag is turned off because only the first or second condition among the multiple conditions for performing the feedback control is not met. Furthermore, if any of the conditions other than the first and second conditions among the multiple conditions for performing the feedback control is not met, the feedback flag is not only turned off, but the feedback control is stopped using the normal feedback control and the correction amount when the lower limit is guarded. This makes it possible to suppress hunting between the execution and non-execution of normal feedback control. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram showing the configuration of an engine device 10 as one embodiment of the present disclosure. [Figure 2] This flowchart shows an example of the air-fuel ratio feedback control execution process performed by the electronic control unit 70. [Modes for carrying out the invention]

[0011] Next, embodiments for implementing this disclosure will be described. Figure 1 is a schematic diagram showing the configuration of an engine device 10 as one embodiment of this disclosure. As shown in the figure, the engine device 10 of the embodiment comprises an engine 12, a fuel supply device 50, and an electronic control unit 70. This engine device 10 is installed in general vehicles that run using power from the engine 12, various hybrid vehicles that have a motor in addition to the engine 12, and stationary equipment that operates using power from the engine 12 (for example, construction equipment).

[0012] Engine 12 is configured as an internal combustion engine that outputs power through four strokes: intake, compression, expansion, and exhaust, using fuel such as gasoline or a mixture of gasoline and alcohol. This 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 a port injection valve 25 and an in-cylinder injection valve 26, engine 12 can be operated in any of the following modes: port injection mode, in-cylinder injection mode, or shared injection mode.

[0013] In port injection mode, air cleaned by the air cleaner 22 is drawn into the intake manifold 23, passes through the throttle valve 24, and 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 and ignited by an electric spark from the spark plug 30, causing explosive combustion. The reciprocating motion of the piston 32, pushed down by the energy from the explosive combustion, is then converted into rotational motion of the crankshaft 14. In in-cylinder injection mode, air is drawn into the combustion chamber 29 in the same way as in port injection mode, and fuel is injected from the in-cylinder injection valve 26 during the intake stroke and / or after reaching the compression stroke, and ignited by an electric spark from the spark plug 30, causing explosive combustion and generating rotational motion of the crankshaft 14. In shared injection mode, fuel is injected from the port injection valve 25 when air is drawn into the combustion chamber 29, and also from the in-cylinder injection valve 26 during the intake stroke and compression stroke. This fuel is then combusted by an electric spark from the spark plug 30 to generate rotational motion of the crankshaft 14. These injection modes can be switched according to the operating state of the engine 12. The exhaust gas discharged from the combustion chamber 29 to the exhaust pipe 33 via the exhaust valve 31 is discharged into the outside air via a purification device 34 which has 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 system 50 is configured to supply fuel from the fuel tank 51 to the port injection valves 25 and in-cylinder injection valves 26 of the engine 12. The fuel supply system 50 comprises a fuel tank 51, a feed pump (first pump) 52, a low-pressure supply pipe (first supply pipe) 53, a check valve 54, a relief passage 55, a relief valve 56, a high-pressure pump (second pump) 57, and a high-pressure supply pipe (second supply pipe) 58.

[0015] The feed pump 52 is configured as an electric pump that operates on power supplied from a battery (not shown) and is located inside the fuel tank 51. This feed pump 52 supplies fuel from the fuel tank 51 to the low-pressure supply pipe 53. The low-pressure supply pipe 53 is connected to the port injection valve 25. A check valve 54 is provided in the low-pressure supply pipe 53 and allows fuel to flow from the feed pump 52 side to the port injection valve 25 side, while restricting fuel flow in the reverse direction.

[0016] The relief passage 55 is connected to the low-pressure supply pipe 53 and the fuel tank 51. A relief valve 56 is provided in the relief passage 55 and closes when the fuel pressure in the low-pressure supply pipe 53 is below the threshold Pflolim, and opens when the fuel pressure in the low-pressure supply pipe 53 is equal to or greater than the threshold 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 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, by the rotation of the intake camshaft that opens and closes the intake valve 28) and is configured as a pump that pressurizes the 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 restricts the backflow of fuel and maintains the fuel pressure in the high-pressure supply pipe 58, and a plunger 57c that is operated by the rotation of the engine 12 (rotation of the intake camshaft) (moves in the vertical direction in Figure 1). When the engine 12 is running, the high-pressure pump 57 draws in fuel from the low-pressure supply pipe 53 when the electromagnetic valve 57a is open, and when the electromagnetic valve 57a is closed, it intermittently sends the fuel compressed by the plunger 57c to the high-pressure supply pipe 58 via the check valve 57b, thereby pressurizing the fuel supplied to the high-pressure supply pipe 58. When the high-pressure pump 57 is driven, the fuel pressure in the low-pressure supply pipe 53 and the fuel pressure in the high-pressure supply pipe 58 pulsate in accordance with the rotation of the engine 12 (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 with 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 the crank angle θcr from the crank position sensor 14a, which detects the rotational position of the crankshaft 14 of the engine 12; the coolant temperature Tw from the water temperature sensor 40, which detects the temperature of the coolant in the engine 12; and the oil temperature Toil from the oil temperature sensor 42, which detects the temperature of the lubricating oil in the engine 12. Other examples include the cam angles θci and θco from the cam position sensor 44, which detects the rotational position of the intake camshaft that opens and closes the intake valve 28 and the rotational position of the exhaust camshaft that opens and closes the exhaust valve 31. Other examples include the throttle opening TH from the throttle position sensor 24a which detects the position of the throttle valve 24, the intake air volume Qa from the airflow meter 23a which is installed upstream of the throttle valve 24 in the intake manifold 23, and the intake air temperature Ta from the temperature sensor 23t which is installed upstream of the throttle valve 24 in the intake manifold 23. Other examples include the air-fuel ratio AF from the air-fuel ratio sensor 35 which is installed upstream of the purification device 34 in the exhaust manifold 33, and the oxygen signal O2 from the oxygen sensor 36 which is installed downstream of the purification device 34 in the exhaust manifold 33. Other examples include the fuel temperature Tftnk from the fuel temperature sensor 51t attached to the fuel tank 51, the rotational speed Nlp of the feed pump 52 from the rotational speed sensor 52a attached to the feed pump 52, the low-pressure fuel pressure (pressure of fuel supplied to the port injection valve 25) Pflo from the fuel pressure sensor 53p attached near the port injection valve 25 of the low-pressure supply pipe 53 (for example, the low-pressure delivery pipe), and the high-pressure fuel pressure (pressure of fuel supplied to the in-cylinder injection valve 26) Pfhi from the fuel pressure sensor 58p attached near the in-cylinder injection valve 26 of the high-pressure supply pipe 58 (for example, the high-pressure delivery pipe).

[0019] From the electronic control unit 70, various control signals are output via the output ports. Examples of the 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 ignition plug 30. Control signals to the feed pump 52 of the fuel supply device 50 and the electromagnetic valve 57a of the high-pressure pump 57 can also be mentioned.

[0020] The electronic control unit 70 calculates the engine speed Ne of the engine 12 based on the crank angle θcr from the crank position sensor 14a. Further, the electronic control unit 70 calculates the load factor KL (the ratio of the volume of air actually inhaled in one 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 engine speed Ne of the engine 12. Furthermore, the electronic control unit 70 estimates the temperature Tc of the catalyst 34a of the purification device 34 based on the cooling water temperature Tw from the water temperature sensor 40, the engine 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 cooling water 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 device 10 of the embodiment thus configured, the CPU 71 of the electronic control unit 70 performs intake air amount control, fuel injection control, and ignition control of the engine 12 as the operation control of the engine 12, and also controls the feed pump 52 and the high-pressure pump 57 (electromagnetic valve 57a) of the fuel supply device 50. Regarding the fuel injection control, the case of fuel injection by the in-cylinder injection valve 26 will be described below.

[0022] As for the intake air amount control of the engine 12, for example, a required air amount Qa* is set based on the accelerator opening degree and the rotational speed Ne of the engine 12, a target opening degree TH* of the throttle valve 24 is set so that the intake air amount Qa becomes the required air amount Qa*, and the throttle valve 24 is controlled using the target opening degree TH* to perform the control. As for the fuel injection control of the engine 12, a basic fuel injection amount Qfbase is set based on the air amount Qa and the target air-fuel ratio AF*, a feedback correction amount kfb is obtained so that the air-fuel ratio AF becomes the target air-fuel ratio AF*, the fuel injection amount Qf is set by adding the feedback correction amount kfb to the basic fuel injection amount Qfbase, a fuel injection time Tf is set based on the fuel injection amount Qf and the high-pressure fuel pressure Pfhi, and the in-cylinder injection valve 26 is controlled so as to inject fuel for the fuel injection time Tf at a predetermined timing. As for the ignition control of the engine 12, a target ignition timing Ti* of the spark plug 30 is set based on the rotational speed Ne of the engine 12, the required air amount Qa*, etc., and the spark plug 30 is controlled using the set target ignition timing Ti*.

[0023] Next, the operation of the engine device 10 of the embodiment configured in this way, particularly the operation when turning on and off the feedback control for making the air-fuel ratio AF the target air-fuel ratio AF* will be described. FIG. 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 every predetermined time.

[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 by adding the feedback correction amount kfb to the basic fuel injection amount Qfbase as described above at a predetermined timing for each cylinder.

[0025] Next, it is determined whether predetermined conditions for performing air-fuel ratio feedback control are met (step S110). Conditions for performing air-fuel ratio feedback control include the condition that the fuel injection amount Qf is greater than or equal to the minimum injection amount Qfmin (first condition), the condition that the feedback correction amount kfb is greater than the lower limit guard value so that the fuel injection amount Qf does not fall below the minimum injection amount Qfmin (condition where the feedback correction amount kfb is not lower limit guarded: second condition), the condition that the coolant temperature Tw of the engine 12 is above a predetermined temperature, and the condition that the catalyst temperature is above a predetermined temperature. The predetermined conditions are those conditions for performing air-fuel ratio feedback control, excluding the first and second conditions (the condition that the fuel injection amount Qf is greater than or equal to the minimum injection amount Qfmin and the condition that the feedback correction amount kfb is greater than or equal to the lower limit guard value so that the fuel injection amount Qf does not fall below the minimum injection amount Qfmin). If any of the predetermined conditions for performing air-fuel ratio feedback control are not met, the feedback flag Ffb is turned off and normal air-fuel ratio feedback control is stopped (step S160), and this process is terminated.

[0026] If it is determined in step S100 that predetermined conditions for performing air-fuel ratio feedback control are met, it is determined whether the fuel injection amount Qf is greater than or equal to the minimum injection amount Qfmin (step S120). The minimum injection amount Qfmin can be determined by multiplying the minimum fuel injection time Tfmin, which allows the in-cylinder injection valve 26 to be opened, by the high-pressure fuel pressure Pfhi. If it is determined that the fuel injection amount Qf is greater than or equal to the minimum injection amount Qfmin, it is determined whether the feedback correction value kfb is greater than the 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 so that the fuel injection amount Qf does not fall 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 lowered. When it is determined that the feedback correction amount kfb is greater than the lower limit guard value (i.e., the lower limit guard is not applied), the feedback flag Ffb is turned on and normal air-fuel ratio feedback control is performed (step S140), and this process is terminated.

[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 at the lower limit guard value (lower limit guarded), the feedback flag Ffb is turned off and feedback control is performed using the lower limit guarded feedback correction amount kfb (step S150), and this process is terminated. By performing feedback control using the lower limit guard value feedback correction amount kfb in this way, hunting, which occurs when feedback control for the normal air-fuel ratio is frequently performed and not performed, can be suppressed.

[0028] In the engine device 10 of the embodiment described above, the feedback flag Ffb is turned on and normal air-fuel ratio feedback control is performed when all of the following conditions for performing feedback control are met: the condition that the fuel injection amount Qf is greater than or equal to the minimum injection amount Qfmin (first condition) and the condition that the feedback correction amount kfb is greater than the lower limit guard value (condition where the lower limit guard is not applied: second condition). If any of the conditions for performing feedback control, excluding the first and second conditions, is not met, the feedback flag Ffb is turned off and normal feedback control is stopped. If only one or both of the first and second conditions are not met, the feedback flag Ffb is turned off and feedback control is performed using the feedback correction amount kfb of the lower limit guard value. In other words, the feedback flag Ffb is turned off when stoichiometric control is not being performed. This prevents normal feedback control from continuing when stoichiometric control is not being performed and suppresses the failure of normal feedback control. It also suppresses hunting, in which normal feedback control is frequently performed and not performed.

[0029] In the engine device 10 of this embodiment, fuel injection control was described for when fuel is injected from the in-cylinder injection valve 26. However, it may also be applied when fuel is injected from the port injection valve 25, or when fuel is injected from both the port injection valve 25 and the in-cylinder injection valve 26.

[0030] In the embodiment of the engine device 10, a port injection valve 25 and an in-cylinder injection valve 26 are provided, but the port injection valve 25 may be omitted, or the in-cylinder injection valve 26 may be omitted.

[0031] The correspondence between the main elements of the embodiment and the main elements of the invention described in the section on means for solving the problem will be explained. In the embodiment, the engine 12 corresponds to "engine," and the electronic control unit 70 corresponds to "control device."

[0032] Furthermore, the correspondence between the main elements of the embodiment and the main elements of the invention described in the section on means for solving the problem is merely an example to specifically explain the form in which the embodiment implements the invention described in the section on means for solving the problem, and does not limit the elements of the invention described in the section on means for solving the problem. In other words, the interpretation of the invention described in the section on means for solving the problem should be based on the description in that section, and the embodiment is merely one specific example of the invention described in the section on means for solving the problem.

[0033] The above describes the forms for implementing this disclosure using embodiments, but this disclosure is not limited in any way to these embodiments, and can of course be implemented in various forms without departing from the gist of this disclosure. [Industrial applicability]

[0034] This disclosure can be used in industries such as the manufacturing of engine equipment. [Explanation of symbols]

[0035] 10 Engine assembly, 12 Engine, 14 Crankshaft, 14a Crank position sensor, 15 Crank position sensor, 22 Air cleaner, 23 Intake pipe, 23a Airflow 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 Catalytic converter, 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 Rotational speed sensor, 53 Low-pressure supply pipe, 53p Fuel pressure sensor, 54 Check valve, 55 Relief passage, 56 57 Relief valve, 57a High-pressure pump, 57b Solenoid valve, 57c Check valve, 58 Plunger, 58 High-pressure supply pipe, 58p Fuel pressure sensor, 70 Electronic control unit, 71 CPU, 72 ROM, 73 RAM, 74 Flash memory.

Claims

[Claim 1] An engine system comprising an engine and a control device that provides feedback control for the amount of fuel injected by the engine, The control device turns off the feedback flag when the first condition, which is one of the multiple conditions for executing the feedback control, is not met, or when the second condition, which is not met, is not met, and the correction amount of the feedback control is not lowered to prevent the fuel injection amount of the engine from falling below the minimum injection amount of the fuel injector. When the feedback flag is turned off because only the first or second condition is not met, the control device performs feedback control using the correction amount that would be lowered if the correction amount of the feedback control were lowered. An engine device characterized by the following features.

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