JP5832156B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device that controls a fuel injection amount in an intake port injection type internal combustion engine.

Generally, the exhaust passage of an automobile or the like, harmful substances HC contained in the exhaust gas discharged from an internal combustion engine, CO, is a catalyst to harmless by oxidation / reduction of NO _x is mounted. In order to efficiently purify all of HC, CO, and NO _x , it is necessary to make the air-fuel ratio of the exhaust gas converge to a certain range near the stoichiometric air-fuel ratio called a window. For this purpose, an O ₂ sensor is arranged upstream and / or downstream of the catalyst, and a feedback loop using an output signal of the O ₂ sensor is constructed to feedback control the air-fuel ratio (for example, the following patent document). See).

  In an internal combustion engine configured to inject fuel into an intake port, a portion of the injected fuel may adhere to the inner wall of the intake port or other intake system (port wet). The air-fuel ratio of the gas to be filled may be disturbed.

The fuel adhering to the intake port or the like during high load operation with a large amount of fuel injection evaporates when the throttle valve is throttled and the intake pressure is reduced, and flows into the cylinder and thus the exhaust passage. As a result, the air-fuel ratio signal output from the O ₂ sensor becomes rich, and the feedback controller corrects the fuel injection amount to decrease and brings the air-fuel ratio closer to the target air-fuel ratio. The target air / fuel ratio is usually the stoichiometric air / fuel ratio.

FIG. 6 shows an example of correction of the fuel injection amount by the feedback controller. The feedback controller calculates the air-fuel ratio of the gas filled in the cylinder after the time t _on when the driver's foot is released from the accelerator pedal, the throttle valve is substantially fully closed, and the idle switch is turned _on. The fuel injection amount correction amount FAF continues to decrease gradually. That is, the fuel injection amount gradually decreases.

Thereafter, the accelerator pedal is depressed again, the time t _off idle switch is turned OFF and the throttle valve is widened, the purpose of suppressing the emission increase of the NO _x due to a delay or lean air-fuel ratio of the acceleration due to insufficient fuel supply Thus, the correction amount FAF calculated by the feedback controller is reset to a predetermined value. That is, the fuel injection amount reduction correction is stopped.

Conventionally, the correction amount FAF is reset only when the idle switch is turned off again after being turned on. For this reason, when the accelerator pedal is depressed to such an extent that the idle switch is not turned on from the high load operation state, the correction amount FAF is not reset when the accelerator pedal is depressed again thereafter. It is corrected in the direction of increasing gradually. The pattern is indicated by a broken line in FIG. Even though the throttle valve expands and the intake air amount increases, the fuel injection amount reduction correction by the correction amount FAF does not immediately take place, so a delay in re-acceleration due to insufficient fuel supply, or NO due to air-fuel ratio lean The increase in _x emissions was inevitable.

JP 2010-138791 A

The present invention has been made by paying attention to the above-mentioned problem for the first time, and when the accelerator pedal is depressed from a high-load operation state and then the accelerator pedal is depressed again, the delay of re-acceleration or NO _x is reduced. The intended purpose is to suppress the increase in emissions.

According to the present invention, in a control device having a feedback controller that feedback-controls a fuel injection amount in an intake port injection type internal combustion engine with reference to an air-fuel ratio detected via an air-fuel ratio sensor provided in an exhaust passage. The feedback controller that calculates the correction amount for correcting the basic injection amount based on the amount is corrected in a direction to decrease the fuel injection amount when the air-fuel ratio of the gas flowing through the catalyst in the exhaust passage is richer than a predetermined value. While the air-fuel ratio is leaner than the predetermined value, the correction amount is gradually changed in the direction of increasing the fuel injection amount. Until a predetermined time elapses, a low load state in which the engine load falls below the low judgment value is detected, and this low load state is further detected. The amount of fuel injection amount correction calculated by the feedback controller reduces the fuel injection amount by more than a predetermined amount from the basic injection amount when the engine load becomes higher than the high judgment value after the predetermined time elapses In addition, on the condition that the air-fuel ratio detected via the air-fuel ratio sensor is lean, the correction amount is reset to a predetermined value so that the fuel injection amount is not reduced from the basic injection amount by the correction amount. A control device for an internal combustion engine characterized in that is constructed.

  Further, the amount of fuel adhering to the intake port and the like, and the amount of adhering fuel evaporated and mixed into the intake air greatly depend on the engine speed. Therefore, it is preferable that the threshold value, the low level determination value, and the high level determination value are set according to the engine speed. For example, the threshold value is increased as the engine speed is higher.

According to the present invention, loosened depression of the accelerator pedal from the high-load operating state, it is possible to suppress the emissions increase in re-acceleration delay and NO _x when the subsequent is depressed again the accelerator pedal.

The figure which shows the hardware resource structure of the internal combustion engine and control apparatus in one Embodiment of this invention. Timing diagram illustrating the pattern of the air-fuel ratio feedback control with reference to the output of the front O ₂ sensor. The graph which illustrates the relationship between control center correction amount FACF and delay time TDR, TDL. Timing diagram illustrating the pattern of the air-fuel ratio feedback control with reference to the output of the rear O ₂ sensor. The timing diagram which shows the pattern of the control which the control apparatus of this embodiment performs. The timing diagram which shows the pattern of the control which a known control apparatus performs.

  An embodiment of the present invention will be described with reference to the drawings. In FIG. 1, the outline | summary of the internal combustion engine 0 for vehicles in this embodiment is shown. The internal combustion engine 0 of the present embodiment includes a plurality of cylinders 1 (one of which is shown in FIG. 1), an intake passage 3 for supplying intake air to each cylinder 1, and exhaust from each cylinder 1. An exhaust passage 4 for exhausting the exhaust gas, an exhaust turbocharger 5 for supercharging intake air flowing through the intake passage 3, and an external EGR passage 2 for recirculating EGR gas from the exhaust passage 4 toward the intake passage 3 I have.

  The intake passage 3 takes in air from the outside and guides it to the intake port of the cylinder 1. On the intake passage 3, an air cleaner 31, a compressor 51 of the supercharger 5, an intercooler 32, an electronic throttle valve 33, a surge tank 34, and an intake manifold 35 are arranged in this order from the upstream side.

  The internal combustion engine 0 in this embodiment is of an intake port injection type, and an injector 36 that injects fuel is disposed in the vicinity of the intake port, specifically, in the intake manifold 35.

  The exhaust passage 4 guides exhaust generated as a result of burning fuel in the cylinder 1 from the exhaust port of the cylinder 1 to the outside. An exhaust manifold 42, a drive turbine 52 for the supercharger 5, and a three-way catalyst 41 are disposed on the exhaust passage 4. The exhaust turbocharger 5 is configured such that the drive turbine 52 and the compressor 51 are connected and linked in a coaxial manner. Then, the driving turbine 52 is rotationally driven by using the energy of the exhaust gas, and the compressor 51 is pumped by using the rotational force, whereby the intake air is pressurized and compressed (supercharged) and sent to the cylinder 1.

An air-fuel ratio sensor (not shown) for detecting the air-fuel ratio of the exhaust gas is provided upstream and downstream of the catalyst 41, respectively. The air-fuel ratio sensor may be a linear A / F sensor having a linear output characteristic proportional to the air-fuel ratio of the gas, and outputs a voltage signal corresponding to the oxygen concentration in the exhaust gas. It may be an O ₂ sensor having a non-linear output characteristic. In the present embodiment, an O ₂ sensor is assumed for each of the air-fuel ratio sensors upstream and downstream of the catalyst 41. As is well known, the output characteristics of the O ₂ sensor show a large and steep slope with respect to the air-fuel ratio in the window range, and gradually approach the low saturation value in the lean region where the air-fuel ratio is larger than that. A so-called Z characteristic curve that draws asymptotic to a high-order saturation value is drawn in a rich region where is small.

  The external EGR (Exhaust Gas Recirculation) passage 2 realizes a so-called high-pressure loop EGR. The inlet of the external EGR passage 2 is connected to a predetermined location upstream of the turbine 52 in the exhaust passage 4. The outlet of the external EGR passage 2 is connected to a predetermined location downstream of the throttle valve 33 in the intake passage 3, specifically to a surge tank 34. An EGR cooler 21 and an EGR valve 22 are also provided on the external EGR passage 2.

  The ECU 6 that controls the operation of the internal combustion engine 0 is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like.

The input interface includes a vehicle speed signal a output from the vehicle speed sensor that detects the vehicle speed, a rotation speed signal b output from the rotation speed sensor that detects the engine rotation speed, the depression amount of the accelerator pedal, or the opening of the throttle valve 33. An opening signal c output from the accelerator opening sensor to detect, an intake pressure signal d output from a pressure sensor to detect intake pressure (supercharging pressure) in the intake passage 3 (particularly, the surge tank 34), an intake passage 3, an intake air temperature signal e output from a temperature sensor for detecting the intake air temperature, a crank angle signal output from a timing sensor at the end of the intake camshaft, a cylinder discrimination signal f, and an end of the exhaust camshaft. An exhaust cam signal g output every rotation of a predetermined crank angle from a certain timing sensor, and a front for detecting the air-fuel ratio of the exhaust gas upstream of the catalyst 41 Switch signal output from the _second sensor h, the signal is output from the rear O ₂ sensor for detecting the air-fuel ratio of the exhaust gas downstream of the catalytic 41 i, the ON / OFF of the electric load of an air conditioner or lighting, etc. A switch signal j or the like is input. The amount of depression of the accelerator pedal or the opening degree c of the throttle valve 33 can be regarded as a required load (engine output) commanded by the driver.

  From the output interface, the fuel injection signal k for the injector 36, the ignition signal l for the ignition plug (ignition coil thereof), the opening operation signal m for the EGR valve 22, and the opening operation for the throttle valve 33. Signal n etc. are output.

  The processor of the ECU 6 interprets and executes a program stored in the memory in advance, and controls the operation of the internal combustion engine 0. The ECU 6 obtains various information a, b, c, d, e, f, g, h, i, j necessary for operation control of the internal combustion engine 0 via the input interface, and based on them, the intake air amount and the request The fuel injection amount, ignition timing, required EGR amount, etc. are calculated. Then, various control signals k, l, m, and n corresponding to the calculation result are applied through the output interface.

  The air-fuel ratio control will be described in detail. In this embodiment, ECU6 which is a control apparatus functions as a feedback controller, and controls the air fuel ratio of the air-fuel mixture with which a cylinder is filled. Specifically, first, the basic injection amount TP is determined by calculating the intake air amount from the intake pressure signal d, intake temperature signal e, engine speed signal b, and the like. Next, the basic injection amount TP is corrected with a feedback correction coefficient FAF determined according to the upstream air-fuel ratio signal j, and various correction coefficients K determined according to the state of the internal combustion engine 0 and the invalid injection time TAUV of the injector 36. , The final fuel injection time (energization time for the injector 36) T is calculated. The fuel injection time T is T = TP × FAF × K + TAUV. Then, the signal k is input to the injector 36 for the fuel injection time T, and the injector 36 is opened to inject fuel.

In the feedback control with reference to the upstream air-fuel ratio signal j, for example, the cooling water temperature of the internal combustion engine 0 is equal to or higher than a predetermined temperature, the fuel is not being cut, the power is not increasing, and a predetermined time has elapsed since the start of the internal combustion engine 0. This is performed when all the conditions such as the front O ₂ sensor is active and the intake pressure is normal are satisfied. The same applies to the idling operation.

As shown in FIG. 2, the ECU 6 compares the output voltage h of the front O ₂ sensor, which is a sensor for detecting the air-fuel ratio of the gas flowing through the catalyst 41, with a predetermined voltage value. If it is lower than that value, it is determined to be lean. When the sensor output h is switched from lean to rich, the feedback correction coefficient FAF is decreased by the skip value RSM after the rich determination delay time TDR has elapsed. Thereafter, the correction coefficient FAF is decreased by a lean integral value KIM per predetermined time. As the correction coefficient FAF decreases, the fuel injection amount is reduced, and the air-fuel ratio of the air-fuel mixture moves toward lean.

  Alternatively, when the sensor output h is switched from rich to lean, the feedback correction coefficient FAF is increased by the skip value RSP after the lean determination delay time TDL has elapsed. Thereafter, the correction coefficient FAF is increased by the rich integral value KIP per predetermined time. As the correction coefficient FAF increases, the fuel injection amount is increased and the air-fuel ratio of the air-fuel mixture becomes richer.

  The delay times TDR and TDL increase or decrease according to the control center correction amount FACF. FIG. 3 illustrates the relationship between the correction amount FACF and the delay times TDR and TDL. As the correction amount FACF increases, the rich determination delay time TDR is extended and the lean determination delay time TDL is shortened. In this case, the time when the feedback correction coefficient FAF starts to decrease is delayed, and the time when the feedback correction coefficient FAF starts to increase increases. As a result, the fuel injection amount increases on average, and the control center of the air-fuel ratio feedback control is displaced to the rich side.

  On the other hand, the smaller the correction amount FACF, the shorter the rich determination delay time TDR and the lean determination delay time TDL. Then, the time when the feedback correction coefficient FAF starts to decrease from the increase is advanced, and the time when the feedback correction coefficient FAF starts to increase is delayed. As a result, the fuel injection amount decreases on average, and the control center of the air-fuel ratio feedback control is displaced to the lean side.

The ECU 6 also calculates the control center correction amount FACF during the feedback control. In the feedback control with reference to the downstream air-fuel ratio signal i, for example, the cooling water temperature is equal to or higher than a predetermined temperature, a predetermined time elapses from the start of the air-fuel ratio feedback control, and a predetermined time elapses after the front O ₂ sensor is activated, All conditions such as the fuel correction amount in the transition period is less than a predetermined value, the vehicle speed is 0 or less than a predetermined threshold value close to 0 in the idle state, or the vehicle is in the predetermined operation region in the non-idle state are satisfied. If you do.

As shown in FIG. 4, the ECU 6 compares the output voltage i of the rear O ₂ sensor with a predetermined voltage value, and determines that it is rich if it is higher than that value and lean if it is lower than that value. Then, while the sensor output i is rich, the control center correction amount FACF is decreased by a lean integrated value FACFKIM per predetermined time. As already described, as the correction amount FACF decreases, the control center of the air-fuel ratio feedback control moves toward lean.

  Conversely, while the sensor output i is lean, the control center correction amount FACF is increased by the rich integral value FACFKIP per predetermined time. As the correction amount FACF increases, the control center of the air-fuel ratio feedback control becomes richer.

Thus, the ECU 6 resets the feedback correction coefficient FAF, which is the correction amount of the fuel injection amount, to a predetermined value when a specific reset condition is satisfied. The reset condition here is
(I) The amount of depression of the accelerator pedal or the opening degree c of the throttle valve 33 is regarded as an engine load, and a high load state in which the engine load c is equal to or greater than a threshold is detected. (Ii) A predetermined value is detected after the high load state is detected. A low load state in which the engine load c is equal to or lower than the low determination value is detected until the time elapses. (Iii) The engine load c is detected until a predetermined time elapses after the low load state is detected. Re-acceleration is detected when is higher than the high judgment value. Further, the high determination value in (iii) is larger than the low determination value in (ii).

  The amount of fuel adhering to the intake port and the like, and the amount of adhering fuel evaporated and mixed into the intake air largely depend on the engine speed b. Therefore, the threshold value in (i), the low determination value in (ii), and the high determination value in (iii) are preferably set according to the engine speed b.

  When the engine speed b is high, the amount of intake air flowing through the intake passage inevitably increases, and the amount of fuel adhering to the inside of the intake port and the like decreases. Therefore, the threshold value in (i) is set to a larger value as the engine speed b is higher. Then, it is not necessary to reset the feedback correction coefficient FAF unnecessarily.

  In addition, the lower determination value in (ii) is set to a smaller value as the engine speed b is higher, and the higher determination value in (iii) is also set to a smaller value as the engine speed b is higher. The difference increases as the engine speed b increases. That is, as the engine speed b increases, the lower determination value decreases more than the higher determination value.

As shown in FIG. 5, the ECU 6 reduces the engine load c to fall below the low determination value within _a predetermined time t _a from the time t ₁ when the high load state in which the engine load c is equal to or greater than the threshold value is detected. at time t ₃ when exceeding the high decision value from the time t ₂ within the predetermined time t _b elevated engine load c again, the front O ₂ output h of the sensor indicates a lean air-fuel ratio, and the feedback correction coefficient FAF When the fuel injection amount (TP × K) is a value less than 1 that reduces the fuel injection amount (TP × K) by a predetermined value or more, the correction coefficient FAF is set to a predetermined value, for example, one or more values that do not decrease the fuel injection amount (TP × K). Reset. The correction coefficient FAF is reset even if the idle switch is not turned on (the accelerator pedal is hardly or not depressed) after time t ₁ . It goes without saying that after the correction coefficient FAF is reset, the FAF is increased or decreased based on the output voltage h of the front O ₂ sensor, starting from the reset value.

In the present embodiment, a control device 6 having a feedback controller that feedback-controls the fuel injection amount in the intake port injection type internal combustion engine 0 with reference to an air-fuel ratio detected via an air-fuel ratio sensor provided in the exhaust passage 4. And detecting _a low load state in which the engine load c is equal to or lower than a low determination value after _a predetermined time ta passes after the high load state in which the engine load c is greater than or equal to a threshold value. when the engine load c between from the detection of the low load state until the predetermined time t _b elapses becomes high determination value or more, the correction amount FAF fuel injection amount feedback controller calculates the fuel injection amount The correction amount FAF is reduced to a predetermined value on the condition that the amount is reduced by a predetermined amount or more and the air-fuel ratio h detected through the air-fuel ratio sensor is lean. The control device 6 for the internal combustion engine 0 is characterized by being set.

According to the present embodiment, when the accelerator pedal is depressed from the high load operation state and then the accelerator pedal is depressed again, the air-fuel ratio can be quickly recovered from lean to near the stoichiometric air-fuel ratio. It is possible to prevent an increase in _x emission. In addition, it is possible to quickly increase the fuel injection amount in response to the re-acceleration request and suppress the delay of re-acceleration. Then, during the period from when the accelerator pedal is depressed to when the accelerator pedal is depressed again, the fuel injection amount can be suppressed to improve fuel efficiency.

  The control device 6 of the present embodiment can be constructed simply by adding a logic of resetting the correction amount FAF when the reset condition is satisfied, and the design man-hour does not increase easily and is simple.

  In addition, the threshold value in (i), the low level determination value in (ii), and the high level determination value in (iii) are each varied according to the engine speed b, so that the fuel in the intake port and the like In the situation where the amount of adhesion is small, the air-fuel ratio can be converged to the target by leaving the original feedback control without unnecessarily resetting the correction amount FAF.

  The present invention is not limited to the embodiment described in detail above. For example, the engine load may be obtained by referring to the intake pipe pressure or the amount of air charged in the cylinder.

  In addition, the specific configuration of each unit, the processing procedure, and the like can be variously modified without departing from the spirit of the present invention.

  The present invention can be applied to control of an internal combustion engine mounted on a vehicle or the like.

0 ... Internal combustion engine 6 ... Control unit (ECU)

Claims (3)

In a control device having a feedback controller that feedback-controls the fuel injection amount in an intake port injection type internal combustion engine with reference to an air-fuel ratio detected via an air-fuel ratio sensor provided in an exhaust passage.
The feedback controller that calculates the correction amount for correcting the basic injection amount based on the intake air amount is directed to decrease the fuel injection amount when the air-fuel ratio of the gas flowing through the catalyst in the exhaust passage is richer than a predetermined value. While the correction amount is gradually changed, the correction amount is gradually changed in the direction of increasing the fuel injection amount when the air-fuel ratio is leaner than a predetermined value.
After detecting a high load state in which the engine load is equal to or higher than the threshold and until a predetermined time elapses, a low load state in which the engine load is equal to or lower than the low determination value is detected, and further, this low load state is detected. If the engine load becomes higher than the high judgment value before the predetermined time elapses,
The correction amount of the fuel injection amount calculated by the feedback controller is to reduce the fuel injection amount from the basic injection amount by a predetermined amount or more, and the air-fuel ratio detected via the air-fuel ratio sensor is lean. A control apparatus for an internal combustion engine , wherein the correction amount is reset to a predetermined value so that the fuel injection amount is not reduced from the basic injection amount by the correction amount . 2. The control device for an internal combustion engine according to claim 1, wherein the threshold value, the low-order determination value, and the high-order determination value each vary according to an engine speed. The control device for an internal combustion engine according to claim 1 or 2, wherein the threshold value increases as the engine speed increases.

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