JP6628520B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine provided with an exhaust gas recirculation device.

An internal combustion engine mounted on a vehicle is often accompanied by an EGR device that lowers the combustion temperature in a cylinder to reduce the amount of NO _x emissions and also reduces the pumping loss. The EGR device connects an exhaust passage and an intake passage of an internal combustion engine via an EGR passage, and recirculates a part of combustion gas generated in a cylinder to the intake passage via the EGR passage to mix with intake air. An EGR valve that opens and closes the EGR passage is provided on the EGR passage, and the amount of recirculation of the EGR gas can be adjusted through the opening operation of the EGR valve.

  When a failure occurs in the EGR valve, proper EGR control is hindered, leading to instability of combustion, deterioration of emission, or occurrence of knocking. Therefore, the vehicle has a diagnosis (self-diagnosis) mechanism for diagnosing the presence or absence of a failure of the EGR valve online, notifying the driver of the fact when the failure is detected, or recording a record in a storage device. Is implemented.

  The diagnosis of the EGR valve is usually performed during a fuel cut in which the fuel supply to the cylinder is temporarily stopped. In the diagnosis, the EGR valve is deliberately opened / closed during the fuel cut, and the pressure in the intake passage at the time of valve closing and at the time of valve opening is respectively measured. Based on the measured values, it is determined whether or not the EGR valve has a failure (for example, And the following patent documents).

JP 2011-252399 A

  The actual fuel cut period is short, and in order to complete the diagnosis within the short period, it can be said that it is desirable to start the diagnosis immediately after the start of the fuel cut.

  However, immediately after the start of the fuel cut, exhaust gas containing a large amount of combustion gas and unburned fuel components flows through the exhaust passage. When the EGR valve is opened, the exhaust gas returns to the intake passage side. Therefore, if the driver cuts the fuel early by depressing the accelerator pedal or the like, the amount of oxygen taken into the cylinder immediately thereafter becomes insufficient, and the engine rotation cannot be performed due to insufficient engine torque. There are concerns about stability.

  An object of the present invention is to prevent engine rotation from becoming unstable due to diagnosis of an EGR valve performed during a fuel cut.

According to the present invention, there is provided a control device for controlling an internal combustion engine provided with an exhaust gas recirculation device provided with an EGR valve in an EGR passage communicating the exhaust passage and the intake passage, and supplies fuel to a cylinder of the internal combustion engine. During the fuel cut that is temporarily interrupted, the EGR valve is opened and closed to perform diagnosis to determine whether or not the EGR valve has failed. After the fuel cut is started, the air-fuel ratio of the gas flowing through the exhaust passage is equal to or more than a predetermined value. becomes lean state is, and on condition that the delay time set has elapsed depending from the start of the fuel cut engine speed at that time, and to start the diagnosis of the EGR valve, the die from the start of fuel cut The control device for an internal combustion engine is configured such that the delay time until the start of the gnosis is longer as the engine speed is lower .

In addition to the above, the EGR rate of the intake air flowing through the intake passage after the start of the diagnosis of the EGR valve can be estimated based on the engine speed at that time and the elapsed time from the start of the fuel cut. At the time, the opening degree of the throttle valve is greatly increased as the EGR rate of the intake air flowing through the intake passage increases after the start of the estimated EGR valve diagnosis, and / or after the start of the estimated EGR valve diagnosis. It is also preferable that the ignition timing be advanced as the EGR rate of the intake air flowing through the intake passage increases .

Further, according to the present invention, there is provided a control device for controlling an internal combustion engine provided with an exhaust gas recirculation device in which an EGR valve is provided in an EGR passage communicating the exhaust passage and the intake passage, wherein fuel is supplied to a cylinder of the internal combustion engine. During a fuel cut in which the supply is temporarily interrupted, the EGR valve is opened and closed to perform a diagnosis for determining whether or not the EGR valve has failed. The EGR of the intake air flowing through the intake passage after the start of the diagnosis of the EGR valve is performed. The rate can be estimated based on the engine speed at that time and the elapsed time from the start of the fuel cut, and at the time immediately after the end of the fuel cut, the estimated intake air flowing through the intake passage after the start of the EGR valve diagnosis is estimated. as the EGR rate is high the degree of opening of the throttle valve greatly expanded, and / or, of the EGR valve is estimated in the diagnosis EGR rate of the intake air flowing through the intake passage Hajimego constituted the control apparatus for an internal combustion engine to advance the higher ignition timing.

  According to the present invention, it is possible to prevent the engine rotation from becoming unstable due to the diagnosis of the EGR valve performed during the fuel cut.

FIG. 1 is a diagram showing a configuration of a vehicle internal combustion engine and a control device according to an embodiment of the present invention. FIG. 4 is an exemplary flowchart illustrating an example of a procedure of processing executed by the control device of the embodiment. The figure which shows the relationship between the engine speed during fuel cut and the delay time until the start of the diagnosis of an EGR valve.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of a vehicle internal combustion engine according to the present embodiment. The internal combustion engine according to the present embodiment is a spark ignition type four-stroke engine, and includes a plurality of cylinders 1 (one of which is shown in FIG. 1). An injector 11 for injecting fuel is provided near an intake port of each cylinder 1. An ignition plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The ignition plug 12 generates a spark discharge between the center electrode and the ground electrode in response to the application of the induced voltage generated by the ignition coil. The ignition coil is built in the coil case together with the igniter which is a semiconductor switching element.

  An intake passage 3 for supplying intake air takes in air from the outside and guides it to the intake port of each cylinder 1. On the intake passage 3, an air cleaner 31, an electronic throttle valve 32, a surge tank 33, and an intake manifold 34 are arranged in this order from upstream.

An exhaust passage 4 for discharging exhaust gas guides exhaust gas generated as a result of burning fuel in the cylinder 1 from the exhaust port of each cylinder 1 to the outside. On the exhaust passage 4, an exhaust manifold 42 and a three-way catalyst 41 for purifying exhaust gas are arranged. Air-fuel ratio sensors 43 and 44 for detecting the air-fuel ratio of the gas flowing through the exhaust passage 4 are provided upstream and downstream of the catalyst 41 in the exhaust passage 4. Each of the air-fuel ratio sensors 43 and 44 may be an O ₂ sensor having a non-linear output characteristic with respect to the air-fuel ratio of the exhaust gas, or a linear A / F sensor having an output characteristic proportional to the air-fuel ratio of the exhaust gas. There may be. In the present embodiment, it is assumed that the air-fuel ratio sensor 43 on the upstream side of the catalyst 41 is a linear A / F sensor and the air-fuel ratio sensor 44 on the downstream side is an O ₂ sensor.

  The external EGR device 2 implements a so-called high-pressure loop EGR. The EGR device 2 includes an external EGR passage 21 that connects the upstream side of the catalyst 41 in the exhaust passage 4 and the downstream side of the throttle valve 32 in the intake passage 3, an EGR cooler 22 provided on the EGR passage 21, and an EGR passage 21. And an EGR valve 23 for controlling the flow rate of EGR gas flowing through the EGR passage 21 by opening and closing the EGR valve. The inlet of the EGR passage 21 is connected to a predetermined portion of the exhaust passage 4 downstream of the catalyst 41. The outlet of the EGR passage 21 is connected to a predetermined portion of the intake passage 3 downstream of the throttle valve 32, specifically, to a surge tank 33.

  An ECU (Electronic Control Unit) 0 as a control device of the internal combustion engine of the present embodiment is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like.

  The input interface of the ECU 0 includes a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed of the vehicle, a crank angle signal b output from an engine rotation sensor that detects the rotation angle of the crankshaft and the engine speed, and an accelerator pedal. The accelerator opening signal c output from a sensor that detects the amount of depression of the throttle valve or the opening of the throttle valve 32 as an accelerator opening (in other words, a required output and a required load for the internal combustion engine), the downstream of the throttle valve 32 in the intake passage 3 ( In particular, an intake air temperature / intake pressure signal d output from an intake air temperature / intake pressure sensor for detecting the intake air temperature and intake pressure of the surge tank 33) and an output from a water temperature sensor for detecting a cooling water temperature indicating the temperature of the internal combustion engine. The detected cooling water temperature signal e, the air-fuel ratio sensor 43 for detecting the air-fuel ratio of the gas upstream of the catalyst 41, The output air-fuel ratio signal f, the air-fuel ratio signal g output from the air-fuel ratio sensor 44 that detects the air-fuel ratio of the gas on the downstream side of the catalyst 41, the detection that the brake pedal is depressed or the amount of depression of the brake pedal is detected. A brake signal h output from a sensor (a brake switch, a master cylinder pressure sensor, or the like) is input.

  From the output interface of the ECU 0, an ignition signal i for the igniter of the ignition plug 12, a fuel injection signal j for the injector 11, an opening control signal k for the throttle valve 32, and an opening control for the EGR valve 23. It outputs the signal l and the like.

  The processor of the ECU 0 interprets and executes a program stored in the memory in advance, calculates operation parameters, and controls the operation of the internal combustion engine. The ECU 0 obtains various information a, b, c, d, e, f, g, and h necessary for operation control of the internal combustion engine through an input interface, obtains the engine speed, and charges the cylinder 1. Estimate intake (fresh air) volume. The required fuel injection amount, fuel injection timing (including the number of times of fuel injection for one combustion), fuel injection pressure, ignition timing, required EGR rate (or EGR) Various operating parameters such as amount) are determined. The ECU 0 applies various control signals i, j, k, and l corresponding to the operation parameters via an output interface.

  The ECU 0 executes a fuel cut for interrupting the fuel supply to the cylinder 1 according to the driving situation. The ECU 0 stops fuel cut, that is, fuel injection from the injector 11 (and ignition by the spark plug 12) when a predetermined fuel cut condition is satisfied. The ECU 0 determines that the fuel cut condition has been satisfied, at least when the depression amount of the accelerator pedal is equal to or less than 0 or a threshold value close to 0 and the engine speed is equal to or more than the fuel cut permission speed. During the fuel cut, the throttle valve 32 is opened to a predetermined opening that does not depend on the accelerator pedal depression amount (0 or close to 0), or the throttle valve 32 is fully closed.

  When a predetermined fuel cut end condition is satisfied after the start of the fuel cut, the ECU 0 ends the fuel cut, that is, restarts the fuel injection (and ignition). The ECU 0 determines that the fuel cut end condition has been satisfied by any of the cases where the depression amount of the accelerator pedal exceeds the threshold value, the engine speed decreases to the fuel cut return speed, and the like. After the fuel cut end condition is satisfied, it goes without saying that the opening of the throttle valve 32 follows the opening corresponding to the amount of depression of the accelerator pedal.

  The ECU 0 of the present embodiment performs the diagnosis of the EGR valve 23 during the fuel cut. In this diagnosis, the EGR valve 23 is intentionally opened and closed during the fuel cut, and the intake pressure in the surge tank 33 when the EGR valve 23 is fully closed and when the EGR valve 23 is opened to a predetermined opening degree. The intake pressure in the surge tank 33 is measured. Then, it is determined whether or not the EGR valve 23 has failed based on the measured intake pressure. For example, if the difference between the two intake pressures is equal to or greater than the determination threshold, the EGR valve 23 is normally operating. If the difference is less than the determination threshold, it is determined that the EGR valve 23 is not operating normally due to sticking or the like. I do.

  FIG. 2 shows a procedure example of a process executed by the ECU 0 regarding the diagnosis of the EGR valve 23. As described above, when the fuel cut condition is satisfied (step S1), the ECU 0 starts executing the fuel cut (step S2). Then, the air-fuel ratio of the gas flowing upstream of the catalyst 41 in the exhaust passage 4 is lean, that is, the air-fuel ratio becomes equal to or more than a predetermined value (step S3), and after a required delay time has elapsed since the start of the fuel cut (step S3). S4) Diagnosis with the operation of opening the EGR valve 23 is started (step S5).

  The length of the delay time in step S4 is set according to the engine speed during fuel cut. Specifically, as shown in FIG. 3, the lower the engine speed, the longer the delay time until the start of diagnosis. By the steps S3 and S4, it is possible to suppress the exhaust gas containing a large amount of the combustion gas and the unburned combustion components from flowing back to the intake passage 3 side during the diagnosis, and the cylinder 1 is charged immediately after the fuel cut is completed. It becomes possible to secure a sufficient amount of oxygen.

  When the fuel cut end condition is satisfied (step S6), the ECU 0 ends the fuel cut and restarts the fuel supply (step S9). Thus, immediately after the end of the fuel cut, the EGR rate of the intake air flowing through the intake passage 3 is estimated (step S7), and the opening of the throttle valve 32 and / or the ignition timing are corrected according to the estimated EGR rate. (Step S8).

  In step S7, the EGR rate of the intake air immediately after the end of the fuel cut is determined based on the engine speed during the fuel cut, the elapsed time from the start of the fuel cut, the opening degree of the EGR valve 23 during the fuel cut and / or at the end of the fuel cut, and the like. Is estimated. The EGR rate, which is the proportion of the EGR gas in the intake air, increases as the engine speed decreases, increases as the time elapsed from the start of the fuel cut decreases, and increases as the opening of the EGR valve 23 increases.

  The memory of the ECU 0 stores in advance map data or a function formula that defines the relationship between the engine speed, the elapsed time from the start of fuel cut, the opening of the EGR valve 23, and the EGR rate of intake air. In step S7, the ECU 0 uses the engine speed during the fuel cut, the elapsed time from the start to the end of the fuel cut, the opening of the EGR valve 23 during the fuel cut and / or at the end of the fuel cut, and the like as keys. The EGR rate of the intake air immediately after the end of the fuel cut is estimated by retrieving maps or substituting them into the function formulas for calculation.

  Then, as the estimated EGR rate of the intake air becomes higher, the opening degree of the throttle valve 32 at the time immediately after the end of the fuel cut is greatly increased (from the basic amount corresponding to the depression amount of the accelerator pedal) in step S8, and By stabilizing combustion of the air-fuel mixture in the cylinder 1 by advancing the ignition timing.

  In the present embodiment, a control device 0 for controlling an internal combustion engine provided with an EGR device 2 in which an EGR valve 23 is provided in an EGR passage 21 communicating the exhaust passage 4 and the intake passage 3, and the cylinder 1 of the internal combustion engine During the fuel cut in which the supply of fuel to the fuel supply is temporarily stopped, the EGR valve 23 is opened and closed to perform a diagnosis for determining whether or not the EGR valve 23 has a failure. After the fuel cut is started, the exhaust passage 4 is closed. A control device for an internal combustion engine that starts diagnosis of the EGR valve 23 on condition that the air-fuel ratio of the flowing gas is in a lean state that is equal to or higher than a predetermined value and that a delay time set according to the engine speed at that time has elapsed. 0 was configured.

  According to the present embodiment, it is possible to reduce the amount of the combustion gas and the unburned fuel component flowing back from the exhaust passage 4 to the intake passage 3 during the fuel cut due to the diagnosis of the EGR valve 23. As a result, at the time immediately after the end of the fuel cut, a necessary and sufficient amount of oxygen can be caused to flow into the cylinder 1, and the combustion of the air-fuel mixture can be stabilized to obtain a sufficient engine torque, and the engine rotation becomes unstable. Problems can be avoided.

  In addition, the control device 0 of the present embodiment calculates the EGR rate of the intake air flowing through the intake passage 3 after the start of the diagnosis of the EGR valve 23 based on the engine speed at that time and the elapsed time from the start of the fuel cut. At the time immediately after the end of the fuel cut, the opening degree of the throttle valve 32 is expanded and corrected in accordance with the estimated intake EGR rate to reduce the EGR rate of the intake air charged into the cylinder 1. In addition, the ignition timing can be advanced and the stability of the ignition combustion of the air-fuel mixture in the cylinder 1 can be improved.

  Note that the present invention is not limited to the embodiment described in detail above. In particular, steps S3 and S4 shown in FIG. 2 are omitted, and the diagnosis of the EGR valve 23 is started as soon as possible after the start of the fuel cut. To stabilize the combustion of the air-fuel mixture immediately after the end of the fuel cut, thereby preventing the engine rotation from becoming unstable.

  In addition, the specific configuration of each unit and the specific processing procedure 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.

0 ... Control device (ECU)
DESCRIPTION OF SYMBOLS 1 ... Cylinder 2 ... EGR apparatus 21 ... EGR passage 23 ... EGR valve 3 ... Intake passage 32 ... Throttle valve 4 ... Exhaust passage

Claims (2)

A control device for controlling an internal combustion engine provided with an exhaust gas recirculation device provided with an EGR valve in an EGR passage communicating the exhaust passage and the intake passage,
During a fuel cut in which the supply of fuel to the cylinder of the internal combustion engine is temporarily interrupted, an EGR valve is opened and closed to perform diagnosis to determine whether or not the EGR valve has failed,
After the start of the fuel cut, the air-fuel ratio of the gas flowing upstream of the catalyst in the exhaust passage is in a lean state where it is equal to or higher than a predetermined value, and a delay time set according to the engine speed at that time has elapsed since the start of the fuel cut. Under the condition that the diagnosis of the EGR valve is started,
The delay time from the start of the fuel cut and the start of the diagnosis, the lower the engine speed long DOO is,
The EGR rate of the intake air flowing through the intake passage after the start of the diagnosis of the EGR valve can be estimated based on the engine speed at that time and the elapsed time from the start of the fuel cut,
Immediately after the end of the fuel cut, as the EGR rate of the intake air flowing through the intake passage becomes higher after the start of the estimated EGR valve diagnosis, the opening of the throttle valve is greatly increased, or the estimated EGR valve diagnosis is started. A control device for an internal combustion engine that advances the ignition timing as the EGR rate of the intake air flowing through the intake passage after the start of gnosis is higher . A control device for controlling an internal combustion engine provided with an exhaust gas recirculation device provided with an EGR valve in an EGR passage communicating the exhaust passage and the intake passage,
During a fuel cut in which the supply of fuel to the cylinder of the internal combustion engine is temporarily interrupted, an EGR valve is opened and closed to perform diagnosis to determine whether or not the EGR valve has failed,
The EGR rate of the intake air flowing through the intake passage after the start of the diagnosis of the EGR valve can be estimated based on the engine speed at that time and the elapsed time from the start of the fuel cut,
Immediately after the end of the fuel cut, as the EGR rate of the intake air flowing through the intake passage increases after the start of the estimated EGR valve diagnosis, the opening degree of the throttle valve is greatly increased, or the estimated EGR valve diagnosis is started. A control device for an internal combustion engine that advances the ignition timing as the EGR rate of intake air flowing through an intake passage increases after the start of gnosis.

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