JP2018071383A - Control device for internal combustion engine - Google Patents

Abstract

The boost pressure of super intake air to be supplied to a cylinder in an operating region of low rotation and high load is further increased. An exhaust turbocharger that drives a compressor disposed on an intake passage by a turbine disposed on the exhaust passage, and an upstream side of the turbine in the exhaust passage and a downstream side of the compressor in the intake passage by an EGR passage. An internal combustion engine connected with an exhaust gas recirculation device connected to recirculate EGR gas through the EGR passage and mixed with intake air is controlled, and the engine speed is not more than a predetermined value and the accelerator opening is not less than a predetermined value. At a certain time, the fuel injection amount is increased so that the air-fuel ratio of the air-fuel mixture supplied to the cylinder becomes richer than the stoichiometric air-fuel ratio, and the EGR valve that opens and closes the EGR passage is opened and the EGR passage is opened. A control device for an internal combustion engine that sends fresh air from the intake passage to the exhaust passage is constructed. [Selection] Figure 2

Description

  The present invention relates to a control device for controlling an internal combustion engine associated with an exhaust turbocharger and an exhaust gas recirculation device.

  The energy of the exhaust gas discharged from the cylinder is used to rotate the exhaust turbine (turbine wheel), the rotation is transmitted to the compressor impeller (compressor wheel), and the intake air is pressurized and compressed (supercharged). An exhaust turbocharger that feeds into a cylinder is well known.

  An internal combustion engine equipped with an exhaust turbocharger is usually provided with a waste gate. The waste gate valve opens and closes a bypass connecting the upstream side and the downstream side of the turbine in the exhaust passage, and plays a role of suppressing the pressure of the intake air flowing through the intake passage from becoming excessively large. The waste gate valve is normally opened in a full load or high load operation region where the throttle valve is fully open or close to full open.

  A general wastegate valve is driven by an actuator having a mode in which the pressure of supercharged air is introduced into a diaphragm chamber and the diaphragm and the wastegate valve connected thereto are driven using the supercharging pressure. This diaphragm actuator is accompanied by an adjustment valve (Vacuum Switching Valve) that can open the diaphragm chamber to the atmosphere, and the opening degree of the waste gate valve is adjusted by duty-controlling the opening degree of the VSV. Control of the supercharging pressure can be realized (see, for example, the following patent document).

  In a low-rotation and high-load operating region where the accelerator opening, that is, the required load on the internal combustion engine is large but the engine speed is low, the wastegate valve will not operate even if the VSV is fully closed and the entire boost pressure is applied to the diaphragm chamber. It does not open and all the exhaust gas flows into the exhaust turbine. Nevertheless, the pressure of the intake air to be supplied to the cylinder does not increase sufficiently to meet the required load, and the engine torque is insufficient and the acceleration performance may remain unsatisfactory.

JP2015-140697A

  An object of the present invention is to further increase the pressure of supercharged air to be supplied to a cylinder in an operation region of low rotation and high load.

  In order to solve the above-described problems, in the present invention, an exhaust turbocharger that drives a compressor disposed on an intake passage by a turbine disposed on an exhaust passage, and a compressor in an upstream side of the turbine in the exhaust passage and an intake passage. Is connected to the downstream side of the engine by an EGR passage, and controls the internal combustion engine attached to the EGR device that recirculates the EGR gas through the EGR passage and mixes it with the intake air. When the degree of fuel is greater than a predetermined value, the fuel injection amount is increased so that the air-fuel ratio of the air-fuel mixture supplied to the cylinder is richer than the stoichiometric air-fuel ratio, and the EGR valve that opens and closes the EGR passage is opened. A control device for an internal combustion engine that sends fresh air from the intake passage to the exhaust passage via the EGR passage is configured.

  According to the present invention, it is possible to further increase the pressure of excessive intake air to be supplied to the cylinder in the operation region of low rotation and high load.

The figure which shows the whole structure of the internal combustion engine for vehicles in one Embodiment of this invention. The flowchart which shows the example of a procedure of the process which the control apparatus of the embodiment performs according to a program.

  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. The internal combustion engine of the present embodiment is a spark ignition type four-stroke gasoline engine, and includes a plurality of cylinders 1 (one of which is shown in FIG. 1). In the vicinity of the intake port of each cylinder 1, an injector 11 for injecting fuel is provided. A spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The spark plug 12 receives spark voltage generated by the ignition coil and causes a spark discharge between the center electrode and the ground electrode. The ignition coil is integrally incorporated in a coil case together with an igniter that is a semiconductor switching element.

  The 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, a compressor 51 of the exhaust turbocharger 5, an intercooler 35, an electronic throttle valve 32 that is an intake throttle valve, a surge tank 33, and an intake manifold 34 are arranged in this order from the upstream side. doing.

  The exhaust passage 4 for discharging the exhaust guides the exhaust generated as a result of burning the fuel in the cylinder 1 from the exhaust port of each cylinder 1 to the outside. An exhaust manifold 42, an exhaust turbine 52 of the exhaust turbocharger 5, and an exhaust purification three-way catalyst 41 are arranged 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 exhaust turbocharger 5 is configured such that an exhaust turbine 52 and an impeller 51 of a compressor are coaxially connected via a shaft 53 and interlocked. Then, the turbine 52 and the impeller 51 are rotationally driven by using the energy of the exhaust gas, and the compressor is pumped with the rotational force, whereby the intake air is pressurized and compressed (supercharged) and sent to the cylinder 1.

  The waste gate valve 44 is opened and closed by a diaphragm actuator 6. The actuator 6 has a diaphragm chamber 61 and a constant pressure chamber 62 separated by a diaphragm 60, and displaces the diaphragm 60 using a differential pressure between the diaphragm chamber 61 and the constant pressure chamber 62. The diaphragm 60 and the waste gate valve 44 are connected via a valve rod 63. When the differential pressure between the diaphragm chamber 61 and the constant pressure chamber 62 exceeds a predetermined set pressure, the diaphragm 60 and the valve rod 63 move from the diaphragm chamber 61 side toward the constant pressure chamber 62 side against the elastic biasing force of the spring 64. To displace. As a result, the waste gate valve 44 that has closed the bypass passage 43 is driven, and the bypass passage 43 is opened. On the other hand, when the differential pressure between the diaphragm chamber 61 and the constant pressure chamber 62 is equal to or lower than the set pressure, the diaphragm 60 and the valve rod 63 are returned to their original positions by the elastic biasing force of the spring 64, and the waste gate valve 44 is completely And the bypass passage 43 is closed.

  Into the diaphragm chamber 61 of the actuator 6, intake pressure, that is, supercharging pressure, is introduced into a portion of the intake passage 3 downstream of the compressor 51 and upstream of the throttle valve 32. For this purpose, a supercharging pressure introduction flow path 71 for communicating the diaphragm chamber 61 and the relevant part of the intake passage 3, a supercharging pressure introduction flow path 71, a depressurization flow path 72 for opening the diaphragm chamber 61 to the atmosphere, An adjustment valve (vacuum switching valve) 73 for opening and closing the drainage channel 72 is provided.

  The VSV 73 is a known flow rate control valve such as a solenoid valve that receives the control signal l and changes its opening degree. If the opening degree of the VSV 73 is manipulated, a part of the supercharged air flowing from the intake passage 3 into the supercharging pressure introduction passage 71 is released to the atmosphere via the decompression passage 72, and the pressure in the diaphragm chamber 61 is increased. Can be controlled. Normally, atmospheric pressure is introduced into the constant pressure chamber 62 of the actuator 6.

  The EGR device 2 realizes a so-called high-pressure loop EGR. The exhaust passage 4 is upstream of the exhaust turbine 52 in the exhaust passage 52 (which may be the exhaust manifold 42), the intercooler 35 and the throttle valve 32 in the intake passage 3. An external EGR passage 21 that communicates with a predetermined location on the downstream side (which may be the surge tank 33), an EGR cooler 22 provided on the EGR passage 21, and an EGR passage 21 that opens and closes and flows through the EGR passage 21 The EGR valve 23 that controls the flow rate of EGR gas is used as an element.

  An ECU (Electronic Control Unit) 0 serving as a control device for an internal combustion engine according to 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 a crank angle sensor that detects the rotation angle of the crankshaft and the engine speed, and an accelerator pedal. From the sensor for detecting the depression amount of the engine or the opening of the throttle valve 32 as the accelerator opening (so-called demand load, demand output for the internal combustion engine), and from the sensor for detecting the depression amount of the brake pedal. Brake pedaling amount signal d output, intake air temperature / intake pressure signal output from intake air temperature / intake pressure sensor for detecting intake air temperature and intake pressure (supercharging pressure) in intake passage 3 (especially surge tank 33) e, a cooling water temperature signal f output from a water temperature sensor for detecting a cooling water temperature indicating the temperature of the internal combustion engine, an intake camshaft Is output from a sensor that detects a cam angle signal g output from the cam angle sensor at a plurality of cam angles of the exhaust camshaft, and an index (battery current and / or battery voltage) that indicates the state of charge of the in-vehicle battery. A battery status signal h or the like is input.

  From the output interface of the ECU 0, an ignition signal i for the igniter of the spark plug 12, a fuel injection signal j for the injector 11, an opening operation signal k for the throttle valve 32, and an opening operation for the EGR valve 23. An opening operation signal m or the like is output for the signals l and VSV 73.

  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, g, and h necessary for operation control of the internal combustion engine via the input interface, knows the engine speed, and is filled in the cylinder 1. Estimate the intake volume. Based on the engine speed, the intake air amount, etc., 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 rate) Various operating parameters such as gas amount) are determined. The ECU 0 applies various control signals i, j, k, l and m corresponding to the operation parameters via the output interface.

  Even in a low-rotation and high-load operating region where the accelerator opening, that is, the required load on the internal combustion engine is large but the engine speed is low, even if the VSV 73 is fully closed and the entire supercharging pressure is applied to the diaphragm chamber 61 of the actuator 6, The waste gate valve 44 is not opened because the diaphragm 60 and the valve rod 63 are not displaced, and all the exhaust gas flows into the exhaust turbine 52. The upper limit of the engine speed at which the waste gate valve 44 does not open even when the VSV 73 is fully closed is called an intercept point. When the engine speed exceeds the intercept point, the waste gate valve 44 starts to open.

  In the low-load high-rotation operation region, the exhaust turbocharger 5 does not increase in work despite the fact that all exhaust gas flows into the turbine 52, and the intake supercharging pressure to be supplied to the cylinder 1 is the required load. May not be high enough to meet. As a result, there is a problem that the engine torque is insufficient with respect to the required load and sufficient acceleration performance cannot be obtained.

  Therefore, as shown in FIG. 2, in the ECU 0 of the present embodiment, the engine speed is equal to or lower than the speed of the intercept point (step S1), and the accelerator opening is equal to or greater than a threshold value that is fully open or close to full open (step S2). ), The amount of fuel injected from the injector 11 is increased so that the air-fuel ratio of the air-fuel mixture supplied to the cylinder 1 becomes richer than the stoichiometric air-fuel ratio (step S4), and the EGR valve 23 is opened. Then, the EGR passage 21 is opened (step S5).

  When the accelerator opening, in other words, the opening of the throttle valve 32 is fully open or close to full open in a low speed region where the engine speed is below the intercept point, the inlet of the EGR passage 21 connected to the exhaust passage 4 Is lower than the intake pressure in the vicinity of the outlet of the EGR passage 21 connected to the intake passage 3. At this time, when the EGR valve 21 is opened, fresh air flowing through the intake passage 3 flows into the exhaust passage 52 upstream of the exhaust passage 4 via the EGR passage 21. In this state, when an air-fuel ratio rich combustion gas is sent into the exhaust passage 4, unburned fuel components contained in the combustion gas react with oxygen contained in fresh air and oxidize (or burn). As a result, the gas flowing into the exhaust turbine 52 becomes high temperature and pressure, the work by the exhaust turbocharger 5 increases, and the boost pressure of the intake air flowing toward the cylinder 1 through the intake passage 3 increases. As a result, sufficient engine torque required for acceleration can be obtained.

  In the present embodiment, the turbocharger 5 that drives the compressor 51 disposed on the intake passage 3 by the turbine 52 disposed on the exhaust passage 4, and the upstream side of the turbine 52 in the exhaust passage 4 and the intake passage 3 An internal combustion engine connected to an exhaust gas recirculation device 2 connected to the downstream side of the compressor 51 by an EGR passage 21 and recirculating EGR gas through the EGR passage 21 and mixed with intake air is controlled. The fuel injection amount is increased so that the air-fuel ratio of the air-fuel mixture supplied to the cylinder 1 becomes richer than the stoichiometric air-fuel ratio when the rotational speed is less than the predetermined value and the accelerator opening is greater than the predetermined value, and the EGR passage 21 A control device 0 for an internal combustion engine that opens an EGR valve 23 that opens and closes the engine and sends fresh air from the intake passage 3 to the exhaust passage 4 via the EGR passage 21 is configured. .

  According to the present embodiment, the engine torque can be increased by increasing the pressure of the excessive intake air to be supplied to the cylinder 1 in the low rotation and high load operation region. In addition, the opening operation of the EGR valve 23 and the fuel injection amount increase correction are performed on condition that the engine speed is equal to or lower than the rotation speed of the intercept point and the accelerator opening is equal to or greater than a threshold value close to full open. Therefore, the process of sending fresh air from the downstream of the compressor 51 in the intake passage 3 to the upstream of the turbine 52 in the exhaust passage 4 is executed without installing a sensor for measuring the back pressure, that is, the exhaust pressure in the exhaust passage 4. Can do.

  The present invention is not limited to the embodiment described in detail above. For example, as shown in FIG. 2, even if the engine speed is not more than a predetermined value and the accelerator opening is not less than a predetermined value (steps S1 and S2), the temperature of the exhaust passage 4 is not more than a predetermined value (step SS3). In this case, the enrichment of the air-fuel ratio and the opening of the EGR valve 23 (steps S4 and S5) may not be performed. Even if unburned fuel and fresh air are fed into the exhaust passage 4 in a situation where the temperature of the exhaust passage 4 is not sufficiently increased, there is a possibility that the oxidation reaction of the fuel does not occur, and excess fuel is wasted. This is because there are concerns that cause worse emissions. The current temperature of the exhaust passage 4 may be measured by installing a temperature sensor at a portion upstream of the turbine 52 (particularly, the exhaust manifold 42) in the exhaust passage 4, but the current cooling water temperature of the internal combustion engine, It is also possible to estimate based on the integrated amount (time integration) of the intake air amount or the fuel injection amount within the most recent predetermined period. Needless to say, it is estimated that the temperature of the exhaust passage 4 is higher as the cooling water temperature is higher and as the integrated amount of the intake air amount or the fuel injection amount in the most recent past predetermined period is larger.

  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 ... Control unit (ECU)
DESCRIPTION OF SYMBOLS 1 ... Cylinder 2 ... Exhaust gas recirculation (EGR) device 21 ... EGR passage 23 ... EGR valve 3 ... Intake passage 32 ... Throttle valve 35 ... Intercooler 4 ... Exhaust passage 43 ... Bypass passage 44 ... Waste gate valve 5 ... Exhaust turbo valve Feeder 51 ... Compressor 52 ... Turbine 6 ... Actuator 60 ... Diaphragm 61 ... Diaphragm chamber 62 ... Constant pressure chamber 71 ... Supercharging pressure introduction flow path 72 ... Depressurization flow path 73 ... Adjustment valve (VSV)

Claims (1)

An exhaust turbocharger that drives a compressor disposed on the intake passage by a turbine disposed on the exhaust passage, and an upstream side of the turbine in the exhaust passage and a downstream side of the compressor in the intake passage are connected by an EGR passage. Controlling an internal combustion engine accompanied by an exhaust gas recirculation device that recirculates EGR gas through a passage and mixes with intake air,
When the engine speed is below a predetermined value and the accelerator opening is above a predetermined value, the fuel injection amount is increased so that the air-fuel ratio of the air-fuel mixture supplied to the cylinder becomes richer than the stoichiometric air-fuel ratio, and the EGR passage is A control apparatus for an internal combustion engine that opens an EGR valve that opens and closes and sends fresh air from an intake passage to an exhaust passage through an EGR passage.

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