JP2021042720A - Controller of internal combustion engine - Google Patents

Abstract

To make an execution frequency of increase correction of a fuel injection amount for protecting members of an exhaust system appropriate or optimal, in control of an internal combustion engine equipped with a water-cooling type exhaust turbocharger.SOLUTION: A controller of an internal combustion engine is configured to: on condition that a delay time has elapsed since an operating region of the internal combustion engine transitioned to a predetermined region that may cause an excessive temperature rise of members of an exhaust system, perform correction control to increase a fuel injection amount so that an air-fuel ratio of an air-fuel mixture supplied to a cylinder becomes richer than a normal target air-fuel ratio; and adjust the delay time according to a flow rate or temperature of cooling water for cooling an exhaust turbocharger.SELECTED DRAWING: Figure 2

Description

The present invention relates to a control device for controlling an internal combustion engine equipped with a water-cooled exhaust turbocharger.

The exhaust gas (turbine wheel) is rotated by using the energy of the exhaust gas discharged from the cylinder of the internal combustion engine, and the rotation is transmitted to the compressor impeller (compressor wheel) to pressurize and compress (supercharge) the intake air. ), And an exhaust turbocharger that feeds into the cylinder is known.

Exhaust turbochargers, especially turbine housings containing turbines, are exposed to hot exhaust gases. As a result, the exhaust system members including the components of the turbocharger may be damaged by heat. Therefore, conventionally, in a situation where there is a concern that an excessive temperature rise of the exhaust system members may occur, the fuel injection amount is increased and corrected, and the heat of vaporization (latent heat) of the fuel is used to lower the exhaust temperature. Therefore, we are trying to protect the members of the exhaust system.

In addition, recently, it has been studied to attach a cooling water jacket to the turbine housing to distribute cooling water to cool the turbocharger with water (see, for example, the following patent documents).

JP-A-2019-044683 JP-A-2019-148224

Compared to the air-cooled type, the water-cooled exhaust turbocharger suppresses the rate of temperature rise. It is not always preferable to directly apply the control of the conventional internal combustion engine equipped with the air-cooled supercharger to the control of the internal combustion engine adopting the water-cooled exhaust turbocharger. If the fuel injection amount is increased and corrected at the same frequency as before, fuel will be injected unnecessarily even though the temperature of the exhaust system members is within the appropriate range, resulting in a decrease in fuel efficiency. In addition, the demerit of worsening emissions (increased HC emissions) due to the rich air-fuel ratio becomes greater.

The present invention is intended to optimize or optimize the execution frequency of the fuel injection amount increase correction for protecting the exhaust system members in the control of the internal combustion engine attached to the water-cooled exhaust turbocharger. Is the purpose of.

In order to solve the above-mentioned problems, the present invention is a control device for controlling an internal combustion engine equipped with a water-cooled exhaust turbocharger, in which the operating region of the internal combustion engine causes an excessive temperature rise of the exhaust system members. The fuel injection amount is adjusted so that the air-fuel ratio of the air-fuel mixture supplied to the cylinder becomes richer than the normal target air-fuel ratio, provided that the delay time has elapsed since the transition to the predetermined region that may be caused. An internal combustion engine control device is configured which adjusts the delay time according to the flow rate and / or temperature of the cooling water for cooling the exhaust turbocharger.

According to the present invention, in the control of an internal combustion engine accompanied by a water-cooled exhaust turbocharger, it is possible to optimize or optimize the execution frequency of the fuel injection amount increase correction for protecting the members of the exhaust system.

The figure which shows the schematic structure of the internal combustion engine for a vehicle and the control device 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. The figure which shows the experimentally measured result of the temperature of the gas flowing into the turbine housing of the exhaust turbocharger, and the temperature rise of the cooling water flowing out from the turbine housing.

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 an induction 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. On the intake passage 3, an air cleaner 31, a compressor 51 of an exhaust turbocharger 5, an intercooler 35, an electronic throttle valve 32, a surge tank 33, and an intake manifold 34 are arranged in this order from the upstream.

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 exhaust purification 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 so that the exhaust turbine 52 and the compressor impeller 51 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 exhaust turbocharger 5 in this embodiment is a water-cooled type. That is, the supercharger 5 is cooled by attaching a cooling water jacket to at least the turbine housing accommodating the turbine 52 and circulating the cooling water through the cooling water jacket. The cooling water pump that sucks in, discharges, and circulates the cooling water is an electric pump driven by a motor. However, it may be a mechanical pump that operates by receiving torque from the crankshaft, which is the output shaft of the internal combustion engine. The rotation speed of the mechanical pump is proportional to the engine speed, and the flow rate of the cooling water discharged by the pump depends on the engine speed, whereas the rotation speed of the electric pump does not depend on the engine speed. The flow rate of the cooling water discharged by the electric pump can be increased or decreased regardless of the engine speed.

The wastegate valve 44 opens a bypass 43 connecting the upstream side and the downstream side of the turbine 52 in the exhaust passage 4 to prevent the supercharging pressure of the intake air flowing through the intake passage 3 from becoming excessively large. Take a role. Further, it is possible to execute feedback control for making the boost pressure follow the target boost pressure through the opening / closing operation of the wastegate valve 44. The wastegate valve 44 is driven by, for example, 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 supercharging 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. For that purpose, a boost pressure introduction flow path 71 that communicates the diaphragm chamber 61 with the relevant portion of the intake passage 3, a pressure relief flow path 72 that opens the boost pressure introduction flow path 71 and the diaphragm chamber 61 to the atmosphere, and pressure. An adjustment valve (Vacuum 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 flow path 71 from the intake passage 3 is released to the atmosphere via the pressure relief flow path 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 exhaust gas recirculation device 2 realizes a so-called high-pressure loop EGR, and is 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 intake passage. An external EGR passage 21 for communicating the intercooler 35 and a predetermined location (which may be a surge tank 33) on the downstream side of the throttle valve 32 in No. 3, an EGR cooler 22 provided on the EGR passage 21, and an EGR passage 21. The element is an EGR valve 23 that opens and closes and controls the flow rate of EGR gas flowing through the EGR passage 21.

The variable valve timing mechanism 8 that variably controls the opening / closing timing of the intake valve of each cylinder 1 of the internal combustion engine determines the rotation phase of the camshaft that opens / closes the intake valve with respect to the crankshaft by hydraulic pressure (lubricating hydraulic pressure). It is a vane type that can be changed, or an electric type (motor drive VVT) that can be changed by an electric motor. The VVT mechanism 8 changes the rotation phase of the camshaft with respect to the crankshaft by rotating the camshaft relative to the cam sprocket around which the timing chain is wound, thereby changing the opening / closing timing of the intake valve.

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 ECU 0 may be a plurality of ECUs or controllers connected to each other so as to be able to communicate with each other via a telecommunication line such as CAN (Control Area Network).

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 factor for the internal combustion engine, and the brake output from the sensor that detects the amount of depression of the brake pedal. Stepping amount signal d, intake air temperature / intake pressure signal e output from the intake air temperature / intake pressure sensor that detects the intake air temperature and intake pressure (supercharging pressure) in the intake passage 3 (particularly, surge tank 33), cooling water. Cooling water temperature signal f output from the water temperature sensor that detects the temperature of, cam angle signal g that is output from the cam angle sensor at multiple cam angles of the intake camshaft, and output from the outside temperature sensor that detects the outside temperature. The outside temperature signal h and the like are input.

From the output interface of ECU 0, the ignition signal i for the spark plug 12 igniter, 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 is controlled for the signals l and VSV73, the control signal n for the opening / closing timing of the intake valve and / or the exhaust valve is controlled for the VVT mechanism 8, and the rotation speed and thus the discharge flow rate of the cooling water are controlled for the cooling water pump. Outputs the control signal o and the like.

The processor of ECU 0 interprets and executes a program stored in the memory in advance, calculates an operation parameter, 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, the required fuel injection amount (necessary to achieve the target air-fuel ratio), fuel injection timing (including the number of fuel injections per combustion), fuel injection pressure, and ignition timing (once) corresponding to the intake air amount. Various operating parameters such as the required number of ignitions for combustion), the required EGR rate (or the amount of EGR gas), the opening / closing timing of the intake valve, the flow rate of cooling water, and the like are determined. The ECU 0 applies various control signals i, j, k, l, m, n, and o corresponding to the operation parameters via the output interface.

The exhaust turbocharger 5, particularly the turbine housing containing the turbine 52, is exposed to high temperature exhaust gas. As a result, the members of the exhaust system 4 including the components of the turbocharger 5 may be damaged by heat. The ECU 0 of the present embodiment performs correction control to increase the fuel injection amount from the normal level in a situation where there is a concern that the temperature of the members of the exhaust system 4 may be excessively raised, and utilizes the heat of vaporization of the fuel. By lowering the temperature of the exhaust, the members of the exhaust system 4 are protected.

As shown in FIG. 2, the ECU 0 describes the operating region of the internal combustion engine [engine speed, engine load factor (or engine torque, intake pressure (supercharging pressure) in surge tank 33, intake air amount or fuel injection amount)]. After transitioning to a predetermined region (step S1), after setting a delay time (step S2), counting of the elapsed time thereafter is started (step S3). The predetermined region referred to in step S1 is an operation in which the temperature of the exhaust gas rises or the flow rate of the exhaust gas increases, which causes an excessive temperature rise of the members of the exhaust system 4 and may cause heat damage to the members. This is a region where the engine speed is relatively high and the engine load factor is relatively large.

The delay time referred to in step S2 is a waiting time between the transition of the internal combustion engine to the predetermined region and the actual start of the fuel injection amount increase correction. If the engine speed or the engine load factor decreases before the delay time elapses and the engine speed deviates from the above-mentioned predetermined region, the fuel injection amount is not increased and corrected. The delay time is adjusted according to the current operating range of the internal combustion engine and the flow rate and / or temperature of the cooling water for cooling the exhaust turbocharger 5.

FIG. 3 shows the results of conducting an experiment in which a high-temperature gas flows into the turbine housing of the exhaust turbocharger 5 and measuring the transition of the temperature rise of the cooling water flowing out from the turbine housing. In FIG. 3, the solid line represents the case where the flow rate of the cooling water is relatively small, and the broken line represents the case where the flow rate of the cooling water is relatively large. The temperature rise of the cooling water is faster as the flow rate of the circulating cooling water is smaller, and slower as the flow rate of the cooling water is larger. The same applies to the temperature rise of the turbine housing. The larger the circulation flow rate of the cooling water, the higher the cooling effect, and there is a time allowance until the temperature of the turbine housing and other members of the exhaust system 4 becomes high.

As a general rule, the delay time is longer as the engine speed is lower (higher is shorter), longer as the engine load factor is smaller (shorter as it is larger), longer as the flow rate of cooling water is higher (shorter as it is lower), and cooling water. Set longer as the temperature is lower (shorter as the temperature is higher). In the memory of the ECU 0, map data that defines the relationship between the engine speed, the engine load factor, the flow rate and temperature of the cooling water, and the delay time is stored in advance. In step S2, the ECU 0 searches the map using the current engine speed, engine load factor, cooling water flow rate, temperature, and the like as keys, and knows the delay time to be set. If an electric pump is used as the cooling water pump, the control signal o, the applied current, the applied voltage, or the rotation speed of the pump given to the pump suggests the current discharge flow rate of the cooling water. .. If a mechanical pump is used, the engine speed, in other words the engine speed, suggests the current discharge flow rate of the cooling water.

The delay time set in step S2 may be increased or decreased depending on factors other than the flow rate and temperature of the cooling water, for example, the current outside air temperature and vehicle speed. The outside air temperature and vehicle speed are related to the temperature and flow rate of the running wind blown into the engine room (engine compartment). The lower the outside air temperature and the higher the vehicle speed, the easier it is for each part of the internal combustion engine to be cooled, and the delay time can be extended accordingly.

The history of driving so far can also be taken into account. The longer the time that the internal combustion engine is operated by continuously burning fuel, the time that has passed since the fuel cut that was executed in the latest past, or the time that has passed since the idle stop that was executed in the latest past, the more the internal combustion engine Since it is considered that the temperature of the members of the exhaust system 4 has risen, it is an idea to shorten the delay time by that amount.

When the set delay time elapses after the internal combustion engine transitions to the above-mentioned predetermined region (step S4), the ECU 0 starts executing the fuel injection amount increase correction (step S6). In the correction control in step S6, the fuel injection amount is such that the air-fuel ratio of the air-fuel mixture supplied to the cylinder 1 becomes richer than the normal target air-fuel ratio (in the spark-ignition internal combustion engine, the stoichiometric air-fuel ratio or its vicinity). To increase the amount.

When the operating region of the internal combustion engine transitions to a region having a lower rotation speed or a lower load than the above-mentioned predetermined region before the delay time elapses (step S5), the fuel injection amount increase correction is not executed (step S7).

In the present embodiment, the control device 0 for controlling the internal combustion engine to which the water-cooled exhaust turbocharger 5 is attached, and the operating region of the internal combustion engine may cause an excessive temperature rise of the members of the exhaust system 4. The air-fuel ratio of the air-fuel mixture supplied to the cylinder 1 becomes richer than the normal target air-fuel ratio on condition that the delay time elapses (step S4) after the transition to a predetermined region (step S1). A correction control for increasing the fuel injection amount is performed (step S6), and the delay time is adjusted to increase or decrease according to the flow rate and / or temperature of the cooling water for cooling the exhaust turbocharger 5 (step S2). ) The control device 0 of the internal combustion engine was configured.

The control device 0 of the present embodiment is an element that actually affects the temperature of the members of the exhaust system 4 including the turbine 52 of the supercharger 5 and the turbine housing, that is, the flow rate of the cooling water for cooling the supercharger 5 and / Alternatively, the delay time until the start of execution of the fuel injection amount increase correction is extended or shortened based on the temperature, the outside temperature, the vehicle speed, the driving history, and the like. According to the present embodiment, the merit of making the supercharger 5 water-cooled is fully utilized, and the frequency of executing the fuel injection amount increase correction for protecting the members of the exhaust system 4 is optimized or optimized. can do. In a situation where the members of the exhaust system 4 are well cooled and the temperature of the members rises slowly, a long delay time is taken to make it easier to satisfy the condition of step S5, and unnecessary increase correction of the fuel injection amount is avoided as much as possible. To do. If the frequency of execution of the increase correction is reduced, the fuel consumption will be reduced. At the same time, it also leads to suppressing the deterioration of emissions due to the enrichment of the air-fuel ratio.

On the contrary, in a situation where the member of the exhaust system 4 is difficult to be cooled and the temperature of the member rises quickly, the delay time is shortened, the condition of step S4 is easily satisfied, and the fuel injection amount is corrected in a timely manner. It can be so. As a result, excessive temperature rise of the member of the exhaust system 4 is suppressed, and the member is appropriately prevented from being damaged by heat.

Further, according to the present embodiment, it is not necessary to install a sensor that directly detects the temperature of the member of the exhaust system 4 and the temperature of the exhaust gas, and it is not necessary to increase the cost due to the addition of hardware. Since the electric cooling water pump can increase or decrease the discharge flow rate of the cooling water regardless of the engine speed, the flow rate of the cooling water is positively increased when it is highly necessary to cool the members of the exhaust system 4. The amount can be increased to protect the members, and the delay time can be extended to reduce the frequency of execution of the fuel injection amount increase correction.

The present invention is not limited to the embodiments described in detail above. 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 11 ... Injector 4 ... Exhaust system 5 ... Exhaust turbocharger 52 ... Turbine a ... Vehicle speed signal b ... Crank angle signal c ... Accelerator opening signal f ... Cooling water temperature signal h ... Outside temperature signal j ... Fuel injection signal o ... Control signal of cooling water pump

Claims (1)

A control device that controls an internal combustion engine with a water-cooled exhaust turbocharger.
The air-fuel ratio of the air-fuel mixture supplied to the cylinder is such that the delay time has elapsed since the operating region of the internal combustion engine transitioned to a predetermined region that may cause excessive temperature rise of the exhaust system members. Correction control shall be implemented to increase the fuel injection amount so that it becomes richer than the normal target air-fuel ratio.
An internal combustion engine control device that adjusts the delay time according to the flow rate or temperature of the cooling water that cools the exhaust turbocharger.

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