JP6824572B2 - Internal combustion engine control device - Google Patents

Description

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

The exhaust gas (turbine wheel) is rotated by using the energy of the exhaust gas discharged from the cylinder, and the rotation is transmitted to the compressor impeller (compressor wheel) to pressurize and compress (supercharge) the intake air. Exhaust turbochargers that feed into cylinders are well known.

It is customary to attach a wastegate to an internal combustion engine equipped with an exhaust turbocharger. The wastegate 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 wastegate valve usually opens in the full load or high load operating range where the throttle valve is fully open or close to fully open.

A general wastegate valve is driven by an actuator in which the pressure of supercharged air is introduced into a diaphragm chamber and the boost pressure is used to drive a diaphragm and a wastegate valve connected to the diaphragm. This diaphragm type actuator is accompanied by an adjustment valve (Vacum Switching Valve) that can open the diaphragm chamber to the atmosphere, and adjusts the opening of the wastegate valve by duty-controlling the opening of the VSV. It is possible to control the boost pressure (see, for example, the following patent documents).

In the low-speed, high-load operating region where the accelerator opening, that is, the load required for the internal combustion engine is large, but the engine speed is low, even if the VSV is fully closed and the entire boost pressure is applied to the diaphragm chamber, the wastegate valve will be It does not open and all the exhaust gas flows into the exhaust turbine. Nevertheless, the intake pressure to be supplied to the cylinder was not high enough to meet the required load, and the engine torque was insufficient, which sometimes left dissatisfaction with the acceleration performance.

JP-A-2015-1040697

The present invention is directed to the intended purpose of Rukoto increase further enhanced engine torque pressure of the supercharged air to be supplied to the cylinder in the operation region of low rotation and high load.

In order to solve the above-mentioned problems, in the present invention, an exhaust turbo supercharger that drives a compressor arranged on the intake passage by a turbine arranged on the exhaust passage, and a compressor on the upstream side of the turbine in the exhaust passage and in the intake passage. An exhaust gas recirculation device that connects the downstream side of the cylinder with an EGR passage and recirculates the EGR gas through the EGR passage to mix with the intake air is attached, and an injector for injecting fuel is provided near the intake port of each cylinder. It controls the internal combustion engine in which the air-fuel mixture is supplied to the cylinder, and is supplied to the cylinder when the engine rotation speed is equal to or less than the rotation speed of the intercept point and the accelerator opening is at least the threshold of fully open or close to fully open. The fuel injection amount is increased so that the air-fuel ratio of the air-fuel mixture to be mixed is richer than the theoretical air-fuel ratio, and the EGR valve that opens and closes the EGR passage is opened to change from the intake passage to the exhaust passage via the EGR passage. A control device for an internal combustion engine is configured which sends air but does not enrich the air-fuel ratio and open the EGR valve when the temperature of the exhaust passage is below a predetermined level.

According to the present invention increases more enhanced engine torque pressure over the intake to be supplied to the cylinder in the operation region of low rotation and high load can Rukoto.

The figure which shows the whole structure of the internal combustion engine for a vehicle in one Embodiment of this invention. The flow chart which shows the procedure example of the process which the control device of the same embodiment executes 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 according to the present embodiment. The internal combustion engine of the present embodiment is a spark-ignition type 4-stroke gasoline engine, and includes a plurality of cylinders 1 (one of which is illustrated in FIG. 1). An injector 11 for injecting fuel is provided in the vicinity of the intake port of each cylinder 1. Further, a spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The spark plug 12 receives the application of the induced voltage generated by the ignition coil and causes a spark discharge between the center electrode and the ground electrode. The ignition coil is integrally built in the coil case together with the igniter which 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. An air cleaner 31, a compressor 51 of an exhaust turbocharger 5, an intercooler 35, an electronic throttle valve 32 which is a valve for an intake throttle, a surge tank 33, and an intake manifold 34 are arranged in this order from the upstream on the intake passage 3. doing.

The exhaust passage 4 for discharging the exhaust guides the exhaust generated as a result of burning the fuel in the cylinder 1 to the outside from the exhaust port of each cylinder 1. An exhaust manifold 42, an exhaust turbine 52 of an exhaust turbocharger 5, and a three-way catalyst 41 for purifying exhaust are arranged on the exhaust passage 4. In addition, an exhaust bypass passage 43 that bypasses the turbine 52 and a wastegate 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 the exhaust turbine 52 and the impeller 51 of the compressor are coaxially connected via a shaft 53 and interlocked with each other. Then, the turbine 52 and the impeller 51 are rotationally driven by using the energy of the exhaust gas, and the compressor is made to perform a pumping action by the rotational force, so that the intake air is pressurized and compressed (supercharged) and sent to the cylinder 1.

The wastegate valve 44 is driven to open and close by a diaphragm type 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 by utilizing the differential pressure between the diaphragm chamber 61 and the constant pressure chamber 62. The diaphragm 60 and the wastegate 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 to the constant pressure chamber 62 side against the elastic urging force of the spring 64. Displace. As a result, the wastegate valve 44 that 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 less than the set pressure, the elastic urging force of the spring 64 returns the diaphragm 60 and the valve rod 63 to their original positions, and the wastegate valve 44 is completely completed. The bypass passage 43 is closed.

The intake pressure, that is, the boost pressure, is introduced into the diaphragm chamber 61 of the actuator 6 at a portion of the intake passage 3 on the downstream side of the compressor 51 and on the upstream side of the throttle valve 32. Therefore, the boost pressure introduction flow path 71 that communicates the diaphragm chamber 61 with the relevant portion of the intake passage 3, the pressurization flow path 72 that opens the boost pressure introduction flow path 71, and thus the diaphragm chamber 61 to the atmosphere, and the pressure. An adjustment valve (Vacum Switching Valve) 73 that opens and closes the drawing flow path 72 is provided.

The VSV73 is a known flow rate control valve such as a solenoid valve that receives a control signal l and changes its opening degree. By manipulating the opening degree of the VSV 73, a part of the supercharged air flowing into the supercharging pressure introduction passage 71 from the intake passage 3 is released to the atmosphere via the pressure relief passage 72, and the magnitude of the pressure in the diaphragm chamber 61 is increased. Can be controlled. Atmospheric pressure is usually introduced into the constant pressure chamber 62 of the actuator 6.

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

The ECU (Electronic Control Unit) 0, which is a control device for an 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 ECU0 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 rotation speed, and an accelerator pedal. Accelerator opening signal c output from a sensor that detects the amount of depression or the opening of the throttle valve 32 as the accelerator opening (so to speak, the required load on the internal combustion engine, the required output), from the sensor that detects the amount of depression of the brake pedal. Brake depression signal d output, intake temperature / intake pressure signal output from the intake temperature / intake pressure sensor that detects the intake temperature and intake pressure (supercharging pressure) in the intake passage 3 (particularly, surge tank 33). e, cooling water temperature signal f output from the water temperature sensor that detects the cooling water temperature suggesting the temperature of the internal combustion engine, cam angle signal g output from the cam angle sensor at a plurality of cam angles of the intake camshaft or the exhaust camshaft. , The battery status signal h or the like output from the sensor that detects the index (battery current and / or battery voltage) suggesting the charge status of the vehicle-mounted battery is input.

From the output interface of ECU 0, the ignition signal i for the igniter of the spark plug 12, the fuel injection signal j for the injector 11, the opening operation signal k for the throttle valve 32, and the opening operation for the EGR valve 23. The opening operation signal m and the like are output to the signals l and VSV73.

The processor of 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, h necessary for the operation control of the internal combustion engine via the input interface, obtains the engine speed, and fills the cylinder 1. Estimate the amount of intake air. Then, based on the engine speed, intake amount, etc., the required fuel injection amount, fuel injection timing (including the number of fuel injections for one combustion), fuel injection pressure, ignition timing, required EGR rate (or EGR). Determine various operating parameters such as gas volume). The ECU 0 applies various control signals i, j, k, l, and m corresponding to the operation parameters via the output interface.

In the low rotation and high load operating region where the accelerator opening, that is, the load required for the internal combustion engine is large but the engine speed is low, even if the VSV 73 is fully closed and the entire boost pressure is applied to the diaphragm chamber 61 of the actuator 6. The diaphragm 60 and the valve rod 63 are not displaced, the wastegate valve 44 is not opened, and all the exhaust gas flows into the exhaust turbine 52. The upper limit of the engine speed at which the wastegate valve 44 does not open even when the VSV73 is fully closed is called an intercept point. When the engine speed exceeds the intercept point, the wastegate valve 44 begins to open.

In the low-load, high-speed operating region, the work of the exhaust turbocharger 5 does not increase even though all the exhaust gas flows into the turbine 52, and the intake boost pressure to be supplied to the cylinder 1 is the required load. It may not be high enough to match. As a result, there is a problem that the engine torque is insufficient for 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 less than the rotation speed of the intercept point (step S1), and the accelerator opening is not more than the threshold value of fully open or close to fully open (step S2). ) At that time, 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. The process of opening the EGR passage 21 (step S5) is executed.

When the engine speed is in the low speed region below the intercept point and the accelerator opening, in other words, the throttle valve 32 is fully open or close to fully open, the entrance of the EGR passage 21 connected to the exhaust passage 4 The exhaust pressure in the vicinity of 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, the fresh air flowing through the intake passage 3 flows into the upstream side of the exhaust turbine 52 in the exhaust passage 4 via the EGR passage 21. In this state, when the air-fuel ratio rich combustion gas is sent to the exhaust passage 4, the unburned fuel component contained in the combustion gas reacts with the oxygen contained in the fresh air and is oxidized (or burned). As a result, the gas flowing into the exhaust turbine 52 becomes high temperature and high pressure, the work of the exhaust turbocharger 5 increases, and the boost pressure of the intake air flowing through the intake passage 3 toward the cylinder 1 increases. As a result, it becomes possible to obtain sufficient engine torque required for acceleration.

In the present embodiment, the exhaust turbo supercharger 5 that drives the compressor 51 arranged on the intake passage 3 by the turbine 52 arranged on the exhaust passage 4, and the upstream side of the turbine 52 and the intake passage 3 in the exhaust passage 4 The engine controls an internal combustion engine equipped with an exhaust gas recirculation device 2 that connects the downstream side of the compressor 51 with an EGR passage 21 and recirculates the EGR gas through the EGR passage 21 to mix with the intake air. When the number of revolutions is less than a predetermined value and the accelerator opening is more 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 1 becomes richer than the theoretical air fuel ratio, and the EGR passage 21 The EGR valve 23 that opens and closes the EGR valve 23 is opened to form a control device 0 for an internal combustion engine that sends fresh air from the intake passage 3 to the exhaust passage 4 via the EGR passage 21.

According to the present embodiment, it is possible to increase the engine torque by further increasing the over-intake pressure to be supplied to the cylinder 1 in the operation region of low rotation and high load. Further, on the condition that the engine rotation speed is equal to or less than the rotation speed of the intercept point and the accelerator opening is at least the threshold value of fully open or close to fully open, the EGR valve 23 is opened and the fuel injection amount is increased. Therefore, even if a sensor for measuring the back pressure, that is, the exhaust pressure of the exhaust passage 4 is not installed, 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. Can be done.

The present invention is not limited to the embodiments 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 more 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 air-fuel ratio may be enriched and the EGR valve 23 may not be opened (steps S4 and S5). Even if unburned fuel and fresh air are sent to the exhaust passage 4 when the temperature of the exhaust passage 4 is not sufficiently high, there is a possibility that the fuel oxidation reaction does not occur, and the surplus fuel is wasted. This is because there are concerns that the emissions will worsen. The current temperature of the exhaust passage 4 may be measured by installing a temperature sensor in a portion (particularly, the exhaust manifold 42) on the upstream side of the turbine 52 in the exhaust passage 4, but the current cooling water temperature of the internal combustion engine, And / or, it can be estimated based on the integrated amount (time integration) of the intake amount or the fuel injection amount in the latest predetermined period. Needless to say, it is estimated that the higher the cooling water temperature and the larger the integrated amount of the intake air amount or the fuel injection amount in the most recent predetermined period, the higher the temperature of the exhaust passage 4.

In addition, the specific configuration of each part, 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 the control of an internal combustion engine mounted on a vehicle or the like.

0 ... Control device (ECU)
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 ... Wastegate valve 5 ... Exhaust turbo excess Feeder 51 ... Compressor 52 ... Turbine 6 ... Actuator 60 ... Diaphragm 61 ... Diaphragm chamber 62 ... Constant pressure chamber 71 ... Supercharging pressure introduction flow path 72 ... Exhaust gas recirculation flow path 73 ... Adjustment valve (VSV)

Claims (1)

An exhaust turbocharger that drives a compressor placed on the intake passage by a turbine placed on the exhaust passage, and an EGR passage connecting the upstream side of the turbine in the exhaust passage and the downstream side of the compressor in the intake passage. An exhaust gas recirculation device that recirculates EGR gas through the passage and mixes it with the intake air is attached, and an injector that injects fuel is provided near the intake port of each cylinder, and an internal combustion engine that supplies the air-fuel mixture to the cylinders. To control
Fuel injection so that the air-fuel ratio of the air-fuel mixture supplied to the cylinder becomes richer than the stoichiometric air-fuel ratio when the engine speed is less than or equal to the speed of the intercept point and the accelerator opening is greater than or equal to the threshold of fully open or close to fully open. The amount is increased, and the EGR valve that opens and closes the EGR passage is opened to send fresh air from the intake passage to the exhaust passage via the EGR passage, but when the temperature of the exhaust passage is below the specified value, the air-fuel ratio is adjusted. An internal combustion engine control device that does not enrich or open the EGR valve.

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