JP2013072293A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the control accuracy of an internal combustion engine by additionally applying a delay in a response to EGR gas recirculating in an EGR passage.SOLUTION: A control device for controlling the internal combustion engine to which an EGR device is attached having an EGR valve on the EGR passage making an intake passage communicate with an exhaust passage presumes the delay in the response to the EGR gas mixed into intake air to be filled in a cylinder on the basis of the rotating angle of a crankshaft of the internal combustion engine, an engine speed and the operation timing of the EGR valve, and corrects ignition timing.

Description

  The present invention relates to a control device for an internal combustion engine mounted on a vehicle or the like.

The recent internal combustion engine for a vehicle, contemplates the reduction of emissions reduction and NO _x in the pumping loss, EGR (Exhaust Gas Recirculation) is often the device is associated. The EGR device includes an EGR valve that is a flow rate control valve on an EGR passage that communicates an exhaust passage and an intake passage. A part of the combustion gas discharged from the cylinder to the exhaust passage through the operation of the EGR valve is returned to the intake passage, and mixed with the intake air filling the cylinder.

  The amount of EGR gas flowing through the EGR passage when the EGR valve is opened depends on the magnitude of the differential pressure between the exhaust pressure at the exhaust passage side inlet and the intake pressure at the intake passage side outlet.

  In an engine with a small number of cylinders (particularly, two cylinders), both exhaust pulsation and intake pulsation tend to increase. Therefore, a time when the intake pressure exceeds the exhaust pressure instantaneously may occur. At this time, even if the EGR valve is opened, the EGR gas does not recirculate toward the intake passage. Therefore, there is a response delay between the time when the EGR valve is opened and the time when EGR gas required for intake air filling the cylinder is mixed.

  Conventionally, in the operation control of an internal combustion engine, the ignition timing is determined by estimating the EGR amount (or EGR rate) of intake air from the EGR valve opening and the average pressure in the surge tank. However, due to the presence of a response delay between the opening of the EGR valve and the fluctuation of the EGR amount, the estimated EGR amount cannot deviate from the actual EGR amount, and as a result, the ignition timing is excessively advanced. There has been a risk of causing knocking or, on the contrary, excessively retarding the ignition timing to cause misfire.

JP 2004-245107 A

  The present invention has been made by paying attention to the above-mentioned problem for the first time, and an object of the present invention is to improve the control accuracy of the internal combustion engine in consideration of the response delay of the EGR gas recirculating through the EGR passage.

  The present invention controls an internal combustion engine attached to an EGR device having an EGR valve provided on an EGR passage communicating with an intake passage and an exhaust passage, and is based on the rotation angle of a crankshaft of the internal combustion engine. A control apparatus for an internal combustion engine is provided, which estimates a response delay from when the engine is operated until the amount of EGR gas mixed in the intake air charged into the cylinder fluctuates.

  According to the present invention, the control accuracy of the internal combustion engine can be improved by taking into account the response delay of the EGR gas recirculating through the EGR passage.

The figure which shows the whole structure of the internal combustion engine in one Embodiment of this invention. The figure which shows transition of the intake pressure and exhaust pressure of the internal combustion engine in the embodiment. The figure which shows the control response delay time of the EGR gas amount of the internal combustion engine in the embodiment.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an internal combustion engine for a vehicle in the present embodiment. This internal combustion engine is of a direct injection type, and includes a plurality of cylinders 1 (one of which is shown in FIG. 1), an injector 11 for injecting fuel into each cylinder 1, An intake passage 3 for supplying intake air to the cylinder 1, an exhaust passage 4 for discharging exhaust from each cylinder 1, an exhaust turbocharger 5 for supercharging intake air flowing through the intake passage 3, and an exhaust passage And an external EGR device 2 that recirculates EGR gas from 4 toward the intake passage 3.

  The internal combustion engine in the present embodiment is a two-cylinder four-stroke engine, and there is a phase difference of 360 ° CA (crank angle) between the stroke of the first cylinder 1 and the stroke of the second cylinder 1. That is, the piston 12 of the first cylinder 1 and the piston 12 of the second cylinder 1 are simultaneously raised and simultaneously lowered.

  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 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. In addition, an exhaust bypass passage 43 that bypasses the turbine 52 and a waste gate valve 44 that is a bypass valve that opens and closes the inlet of the bypass passage 43 are provided. The waste gate valve 44 is an electric waste gate valve that can be opened and closed by inputting a control signal l to the actuator, and a DC servo motor is used as the actuator.

  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.

  The external EGR device 2 realizes a so-called high-pressure loop EGR. The inlet of the external EGR passage is connected to a predetermined location upstream of the turbine 52 in the exhaust passage 4. The outlet of the external EGR passage 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.

  An ECU (Electronic Control Unit) 0 that is a control device for an internal combustion engine 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 a vehicle speed sensor for detecting the vehicle speed, an engine rotation signal b output from an engine rotation sensor for detecting the rotation angle and engine speed of the crankshaft, an accelerator pedal depression amount or a throttle. An accelerator opening signal c output from an accelerator opening sensor that detects the opening of the valve 33 as an accelerator opening (so-called required load), and a temperature for detecting the intake air temperature in the intake passage 3 (particularly, the surge tank 34). An intake air temperature signal d output from the sensor, an intake air pressure signal e output from a pressure sensor that detects the intake pressure (or supercharging pressure) in the intake passage 3 (particularly, the surge tank 34), and the cooling water temperature of the internal combustion engine The cooling water temperature signal f output from the water temperature sensor for detecting the air temperature is output from the cam angle sensor at a plurality of cam angles of the intake camshaft. Exhaust cam signal g and the like are input. The engine rotation sensor generates a pulse signal b every 10 ° CA. The cam angle sensor generates a pulse signal g every 360 ° CA in an angle obtained by dividing 720 ° CA by the number of cylinders or a two-cylinder engine.

  From the output interface, the fuel injection signal h for the injector 11, the ignition signal i for the ignition plug (ignition coil thereof), the opening operation signal j for the EGR valve 22, and the opening operation for the throttle valve 33. An opening operation signal l and the like are output to the signal k and the waste gate valve 44.

  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 acquires various information a, b, c, d, e, f, and g necessary for operation control of the internal combustion engine via the input interface, knows the engine speed, and fills the cylinder 1 with the intake air amount. Is estimated. Based on the engine speed and intake air amount, the required fuel injection amount, fuel injection timing (including the number of times of fuel injection for one combustion), fuel injection pressure, ignition timing, EGR amount (or EGR rate) And various operating parameters such as the opening degree of the EGR valve 22 are determined. As the operation parameter determination method itself, a known method can be adopted, and the description thereof will be omitted. Accordingly, various control signals h, i, j, k, and l corresponding to the operation parameters are applied through the output interface.

  In the present embodiment, the ECU 0 calculates a differential pressure between the exhaust passage 4 side inlet and the intake passage 3 side outlet of the EGR passage in the EGR device 2 based on the rotation angle of the crankshaft detected via the engine rotation sensor. Infer. The transition of the exhaust pressure with exhaust pulsation and the transition of the intake pressure with intake pulsation can be obtained experimentally (by adaptation) at the design stage of the internal combustion engine.

  FIG. 2 shows a time series of fluctuations in exhaust pressure near the exhaust manifold 42 of the internal combustion engine and a time series of fluctuations in intake pressure near the intake manifold 35. In FIG. 2, the solid line is the exhaust pressure, and the broken line is the intake pressure. When the intake pressure exceeds the exhaust pressure, it becomes difficult for the EGR gas to flow from the EGR passage toward the intake passage 3 from the exhaust passage 4 side, resulting in a response delay in the EGR control.

  Based on the rotation angle of the crankshaft, the ECU 0 opens or closes the EGR valve 22 so as to achieve the required EGR gas amount, and then the amount of EGR gas mixed with the intake air filling the cylinder 1 is actually Estimate the response delay until the vicinity of the required amount is reached. FIG. 3 shows the control response delay time (time constant) of the stroke and crank angle in the first cylinder (or second cylinder) 1 and the amount of EGR gas to be charged in the first cylinder (or second cylinder) 1. ). This response delay can also be determined experimentally (by adaptation) during the design phase of the internal combustion engine.

  In the memory of the ECU 0, map data that defines the relationship between the crank angle and the engine speed at that time and the response delay time of EGR control is stored in advance. The ECU 0 searches the map using the crank angle and the engine speed as keys to know the response delay time of the EGR control.

  In the operation control of the internal combustion engine, the ECU 0 estimates the amount of fresh air and the amount of EGR gas contained in the intake air charged in the cylinder 1, and calculates the fuel injection amount and the ignition timing corresponding to them. The amount of EGR gas mixed into the intake air, in other words, the EGR rate of the intake air, is determined according to the operating region (engine speed and required load), and varies depending on the opening of the EGR valve 22, As described, even if the ECU 0 operates the EGR valve 22, the required EGR amount is not immediately realized.

  Therefore, the ECU 0 determines the fuel injection amount and the correction amount of the ignition timing corresponding to the required EGR amount corresponding to the operation region, but immediately injects the fuel with this fuel injection amount and ignites at this ignition timing. Do not do. The ECU 0 waits for the elapse of the response delay time obtained from the EGR map data, and then reflects the determined fuel injection amount and ignition timing correction amount in the operation control of the internal combustion engine.

  In the present embodiment, an internal combustion engine attached with an EGR device 2 having an EGR valve 22 provided on an EGR passage communicating the intake passage 3 and the exhaust passage 4 is controlled, and the rotation angle of the crankshaft of the internal combustion engine is controlled. The internal combustion engine control device 0 is characterized in that a response delay is estimated from the time when the EGR valve 22 is operated until the amount of EGR gas mixed in the intake air charged into the cylinder 1 fluctuates. did.

  According to the present embodiment, taking into account the response delay of the EGR gas that recirculates in the EGR passage 2, the intake EGR amount that is actually charged into the cylinder 1 reaches the vicinity of the required EGR amount only until the required EGR amount is met. The engine is burned at the fuel injection amount and ignition timing. Therefore, the actual EGR amount is less than the assumed EGR amount, the fuel injection amount becomes insufficient, combustion becomes unstable, and the possibility of causing knocking due to excessive advance of the ignition timing is reduced. On the contrary, the actual EGR amount is larger than the assumed EGR amount, the fuel injection amount becomes excessive, fuel consumption and emission are deteriorated, and the possibility of misfire due to excessive retardation of the ignition timing is reduced. .

  Not only the accuracy of air-fuel ratio control is improved, but also the risk of troubles associated with EGR control is reduced, so that it is allowed to raise the EGR limit and return a larger amount of EGR gas to the intake passage 3. . For this reason, it is effective also in the further improvement of a fuel consumption.

  The present invention is not limited to the embodiment described in detail above. In the above-described embodiment, a two-cylinder engine is assumed as the internal combustion engine, but the present invention can naturally be applied to control of a small-cylinder engine such as a single cylinder or three cylinders.

  The EGR device is not limited to a high pressure loop EGR device. The present invention is applied to the control of an internal combustion engine with a low-pressure loop EGR device that connects the upstream side of the compressor 51 and the downstream side of the turbine 52 (and further the catalyst 41) via an EGR passage to recirculate low-temperature and low-pressure EGR gas. May be applied.

  Other specific configurations of each part can be variously modified without departing from the spirit of the present invention.

  The present invention can be used for controlling an internal combustion engine mounted on a vehicle or the like.

0 ... Control unit (ECU)
DESCRIPTION OF SYMBOLS 1 ... Cylinder 2 ... EGR apparatus 22 ... EGR valve 3 ... Intake passage 4 ... Exhaust passage

Claims (1)

An internal combustion engine that is attached to an EGR device having an EGR valve on an EGR passage communicating the intake passage and the exhaust passage;
An internal combustion engine characterized by estimating a response delay from the time when an EGR valve is operated until the amount of EGR gas mixed in intake air charged into a cylinder fluctuates based on a rotation angle of a crankshaft of the internal combustion engine Control device.

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