JP2012241574A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent engine speed from being reduced when an external load on an internal combustion engine increases in an idle or low-load/low-speed operation region.SOLUTION: When an external load on an internal combustion engine increases, a control device increases the opening degree of an ISC (idle speed control) valve and increases a fuel injection amount. In this operation, when the air-fuel ratio of the gas circulating in catalyst is lean, the control device sets larger expansion DSKIP of the opening degree of the ISC valve than when an air-fuel ratio is rich.

Description

  The present invention relates to air-fuel ratio control performed for the purpose of maintaining exhaust gas purification efficiency by a catalyst.

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 converge the air-fuel ratio of the exhaust gas to a certain range near the stoichiometric air-fuel ratio called a window. For this purpose, an air-fuel ratio sensor is arranged upstream and downstream of the catalyst, and a double feedback loop using the output signals of both the front and rear sensors is constructed to feedback control the air-fuel ratio (for example, , See the following patent document).

  Such feedback control is continued even during idle operation. The air-fuel ratio of the controlled gas oscillates so as to repeat rich / lean slowly with the target air-fuel ratio (theoretical air-fuel ratio or the vicinity thereof) as the center in order to maintain the exhaust gas purification efficiency of the catalyst.

  When an electric load such as an air conditioner or a headlamp is turned on during idle operation, the load applied to the internal combustion engine increases and the engine speed drops. Therefore, when the switch of the electrical load is switched from OFF to ON, the intake air amount and the fuel injection amount are increased by a predetermined amount, the engine output is increased to prevent the engine speed from falling and the engine stall resistance is improved. It has been broken.

  However, there is a difference in the original output of the internal combustion engine between the period in which the air-fuel ratio of the gas charged in the cylinder is rich and the period in which it is lean, and the degree of decrease in the engine speed due to the electric load being ON differs. . When the electric load is turned on during the air-fuel ratio lean period, there is a possibility that the engine speed drop cannot be suppressed.

JP 2010-138791 A

  The present invention has been made by paying attention to the above-mentioned problem for the first time, and avoids the problem that the engine speed drops when the external load on the internal combustion engine increases in an idling or low load / low speed operation region. The intended purpose.

In the present invention, when the external load on the internal combustion engine increases in an idling or low load / low speed operation region, an operation of increasing the opening of an ISC (Idle Speed Control) valve or a throttle valve is performed and the fuel injection amount is increased. In the above-described operation, the ISC valve or the throttle valve is compared with the rich control when the air-fuel ratio on the upstream side of the catalyst detected through the front O ₂ sensor is lean. When the air-fuel ratio on the downstream side of the catalyst detected through the rear O ₂ sensor is lean, the ISC valve or the throttle valve is set as compared with the rich case. The control device is characterized in that the amount of increase in the degree of opening is corrected to be larger.

  That is, when the external load represented by the electric load increases during the air-fuel ratio lean period, the intake air amount and the fuel injection amount are increased more than the air-fuel ratio rich period, and the engine speed is increased. The depression was suppressed.

  According to the present invention, it is possible to effectively avoid the problem that the engine speed drops when the external load on the internal combustion engine increases in an idling or low load / low speed operation region.

The figure which shows the hardware resource structure of the air fuel ratio control apparatus of 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 correction | amendment of the ISC valve opening degree when an electrical load turns ON during idle driving | operation. The graph which shows the relationship between the air fuel ratio of the gas which distribute | circulates a catalyst, and ISC correction amount DSKIP.

  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 injector 11 that injects fuel into each cylinder 1, and supplies intake air to each cylinder 1. An intake passage 3 for exhausting the exhaust gas, an exhaust passage 4 for discharging exhaust gas from each cylinder 1, an exhaust turbocharger 5 for supercharging intake air flowing through the intake passage 3, and an exhaust passage 4 to the intake passage 3. And an external EGR passage 2 for refluxing the EGR gas.

  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, a throttle valve 33, a surge tank 34, and an intake manifold 35 are arranged in this order from the upstream side.

  In the intake system, an ISC valve 36 is provided on a bypass path that bypasses the throttle valve 33. While the throttle valve 33 opens and closes according to the amount of depression of the accelerator pedal, the ISC valve opens and closes upon receiving a control signal n from the ECU (electronic control unit) 6 during idle operation when the accelerator pedal is not depressed.

  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. Each air-fuel ratio sensor is an O ₂ sensor having a non-linear output characteristic with respect to the air-fuel ratio of the exhaust gas that outputs a voltage signal corresponding to the oxygen concentration of the gas by contacting and reacting with the exhaust gas. . 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, and a throttle position sensor that detects the opening of the throttle valve 33. The opening degree signal c that is output, the intake pressure signal d that is output from the pressure sensor that detects the intake pressure (supercharging pressure) in the intake passage 3 (particularly, the surge tank 34), and the intake air temperature in the intake passage 3 are detected. The intake air temperature signal e output from the temperature sensor, the crank angle signal and cylinder discrimination signal f output from the timing sensor at the end of the intake camshaft, and the predetermined crank angle from the timing sensor at the end of the exhaust camshaft. of the output of the exhaust cam signal g which is output every rotation, from the front O ₂ sensor for detecting the air-fuel ratio of the exhaust gas upstream of the catalytic 41 That signal 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, an air conditioner and switches the ON / OFF of the electric load of the illumination lamp such as the signal j of the switch or the like Is entered. From the output interface, the fuel injection signal k for the injector 11, the ignition signal 1 for the ignition plug (ignition coil), the opening operation signal m for the EGR valve 22, and the opening operation for the ISC valve 36. 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 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 by 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 11. , The final fuel injection time (energization time for the injector 11) T is calculated. The fuel injection time T is T = TP × FAF × K + TAUV. Then, the signal k is input to the injector 11 for the fuel injection time T, and the injector 11 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 determination value. If it is lower than the determination value, it is determined as 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 determination value, and determines that it is rich if it is higher than the determination value and lean if it is lower than the determination 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, in the present embodiment, during the idling operation, when the external load on the internal combustion engine 0 increases, for example, when the electric load is switched from OFF to ON, an operation for increasing the opening of the ISC valve 36 is performed. Control to increase the fuel injection amount.

  During the idling operation, the ECU 6 refers to the deviation between the actually measured engine speed and the target idle engine speed in order to maintain the engine engine speed at a predetermined target idle engine speed (for example, about 800 rpm), and reduces the deviation. In addition, the ISC valve 36 is operated, that is, the intake air amount (and the fuel injection amount) is controlled. After that, when it is detected that the switch of the electric load is switched from OFF to ON, as shown in FIG. 5, the opening of the ISC valve 36 is determined from a value calculated based on the air-fuel ratio feedback. Enlarge only DSET. In FIG. 5, t1 and t2 are the time points when the electric load is switched to ON, respectively. It is desirable to set DSET, which is the increment of the intake air amount, to an amount corresponding to the increasing amount of electric load. That is, the larger the external load newly applied to the internal combustion engine 0 is, the larger it is.

In addition, in order to suppress a drop in the engine speed at the moment when the electric load is turned on, the opening of the ISC valve 36 is further increased from the above DSET by DSKIP when the electric load is turned on. After the expansion, the operation of gradually narrowing down to DSET is performed. The intake air amount skip increment DSKIP changes according to the air-fuel ratio detected via the O ₂ sensor.

FIG. 6 shows the relationship between the air-fuel ratio of the gas flowing through the catalyst 41 and DSKIP. DSKIP is larger as the air-fuel ratio is leaner and smaller as it is richer. The ECU 6 sets DSKIP larger as the air-fuel ratio upstream of the catalyst 41 indicated by the output h of the front O ₂ sensor is leaner, and sets DSKIP smaller as it is richer. Further, the ECU 6 corrects the DSKIP larger as the air-fuel ratio downstream of the catalyst 41 indicated by the output i of the rear O ₂ sensor is leaner, and corrects the DSKIP smaller as it is richer. As shown in FIG. 5, DSKIP at time point t1 during the period when the output h of the front O ₂ sensor shows lean is larger than DSKIP at time point t2 when the output h shows rich.

  It goes without saying that the fuel injection amount calculated by the ECU 6 (as air-fuel ratio feedback control) increases as the intake air amount increases due to the increase in the opening of the ISC valve 36.

In the present embodiment, the control device 6 of the internal combustion engine 0 performs an operation of expanding the opening of the ISC valve 36 when the external load on the internal combustion engine 0 increases in the idle operation region and increases the fuel injection amount. In the above operation, when the air-fuel ratio upstream of the catalyst 41 detected via the front O ₂ sensor is lean, the increase amount DSKIP of the opening of the ISC valve 36 is made larger than when the air-fuel ratio is rich. When the air-fuel ratio on the downstream side of the catalyst 41 detected through the rear O ₂ sensor is lean, the amount of expansion DSKIP of the opening of the ISC valve 36 is made larger than when it is rich. The control device 6 is characterized by correcting.

According to the present embodiment, when the external load represented by the electric load increases during the air-fuel ratio lean period, the intake air amount and the fuel injection amount are increased more than the air-fuel ratio rich period, and the engine rotation The drop in the number can be suppressed. The idle rotation can be stabilized while using an inexpensive O ₂ sensor having a non-linear output characteristic without using an expensive linear air-fuel ratio sensor having a linear output characteristic, which can contribute to cost reduction.

The present invention is not limited to the embodiment described in detail above. For example, when the present invention is applied to the internal combustion engine 0 in which the electronic throttle valve 33 is mounted without mounting the ISC valve 36, the opening degree of the electronic throttle valve 33 is increased when the external load on the internal combustion engine 0 increases. Operate and increase the fuel injection amount. In the above operation, when the air-fuel ratio upstream of the catalyst 41 detected via the front O ₂ sensor is lean, the increase amount DSKIP of the opening degree of the electronic throttle valve 33 is set as compared with the case where the air-fuel ratio is rich. When the air-fuel ratio on the downstream side of the catalyst 41 detected through the rear O ₂ sensor is lean, the opening amount DSKIP of the electronic throttle valve 33 is increased compared to the rich case. To a larger value.

  In the above embodiment, the operation of expanding the opening of the ISC valve 36 or the electronic throttle valve 33 by the DSKIP during the idle operation is performed. You may perform the same operation in the driving | running | working area | region of the low rotation speed below a predetermined threshold value. In this case, it is possible to prevent the engine speed from dropping and the engine rotation from becoming unstable due to an increase in electric load or the like in the low load and low rotation range.

  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.

DESCRIPTION OF SYMBOLS 0 ... Internal combustion engine 36 ... ISC valve 6 ... Control apparatus (ECU)

Claims (1)

A control device for an internal combustion engine that performs an operation of expanding an opening of an ISC valve or a throttle valve and increases a fuel injection amount when an external load on the internal combustion engine increases in an idling or low load / low speed operation region. ,
In the above operation, when the air-fuel ratio upstream of the catalyst detected via the front O ₂ sensor is lean, the enlargement amount of the opening of the ISC valve or the throttle valve is set larger than when the air-fuel ratio is rich. In addition, when the air-fuel ratio on the downstream side of the catalyst detected via the rear O ₂ sensor is lean, the amount of expansion of the opening of the ISC valve or the throttle valve is corrected more than when it is rich. A control device for an internal combustion engine.

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