JP7310321B2 - engine controller - Google Patents

Description

The technology disclosed herein relates to an engine control device.

Patent Literature 1 describes a technique for predicting the temperature of an exhaust pipe in an engine room. Specifically, the engine control device predicts the temperature of the exhaust gas based on the operating state of the engine, and the heat radiation coefficient of the exhaust pipe based on the predicted temperature of the exhaust gas, the vehicle speed, and the rotation speed of the cooling fan of the radiator. and the temperature of the exhaust pipe is predicted. Further, when the exhaust pipe heat quantity related to the predicted temperature of the exhaust pipe is larger than the predetermined heat quantity, the control device increases the rotation speed of the cooling fan. This prevents the brake hose in the vicinity of the exhaust pipe from being exposed to high temperatures.

JP 2015-190329 A

By the way, the exhaust pipe is equipped with a purifying device for reducing harmful substances in the exhaust gas discharged from the engine. Purification devices include catalytic devices and/or filter devices. If the temperature of the catalytic device is lower than the activation temperature, the purification rate of the exhaust gas becomes low. Therefore, the temperature of the catalytic device is preferably maintained at the activation temperature or higher.

While the automobile is running, for example, the temperature of the exhaust gas increases as the load on the engine increases. If the temperature of the exhaust gas rises, the temperature of the catalytic device may become excessively high. If the temperature of the catalytic converter becomes excessively high, the reliability of the catalytic converter is lowered. The control device needs to accurately grasp the temperature of the exhaust gas introduced into the purification device while the engine is running.

For example, applying the technology described in Patent Document 1, the control device may estimate the temperature of the exhaust gas at the inlet of the purifying device based on the operating state of the engine, the heat radiation of the exhaust pipe, and the like.

Here, the applicant of the present application has proposed SPCCI (SPark Controlled Compression Ignition) combustion, which is a combination of SI (Spark Ignition) combustion and CI (Compression Ignition) combustion. SPCCI combustion can stably burn an air-fuel mixture whose fuel is significantly leaner than the stoichiometric air-fuel ratio when the engine is in a partial operating state. By burning a fuel-lean mixture, the engine becomes more thermally efficient. If the thermal efficiency of the engine increases, the fuel efficiency of the automobile will improve.

In order for the engine to stably burn the lean air-fuel mixture, it is advantageous for the temperature in the engine room to be relatively high. Therefore, it is conceivable to provide an adjustment section for changing the opening degree of the running wind introduction port in the running wind introduction port for introducing the running wind into the engine room. When the engine burns a lean air-fuel mixture, the introduction of air into the engine room can be suppressed by closing the airflow introduction port.

The temperature and wind speed in the engine room change by opening and closing the running wind introduction port. The technique described in Patent Literature 1 does not take into account the influence of opening and closing of the running wind introduction port, and therefore cannot accurately estimate the temperature of the exhaust gas at the inlet of the purifying device.

The technology disclosed herein accurately estimates the temperature of the exhaust gas at the inlet of the purifier.

Specifically, the technology disclosed herein relates to an engine control device.

The controller of this engine is
an engine arranged in an engine room;
an adjustment unit that changes the degree of opening of the running wind introduction port between an open state in which air is introduced into the engine room from the running wind introduction port and a closed state in which introduction of the air is suppressed;
a purification device for reducing harmful substances in exhaust gas of the engine;
an exhaust pipe arranged in the engine room and connecting the engine and the purification device;
a control unit for estimating the temperature of the exhaust gas at the inlet of the purification device in chronological order by repeating calculations at predetermined time intervals , and for controlling the engine according to the estimated temperature ;
The exhaust pipe has an inner surface in contact with the exhaust gas and an outer surface exposed in the engine room .

Then, the control unit
calculating the wind speed of the air around the exhaust pipe from the opening of the running wind introduction port and the vehicle speed;
calculating an ambient temperature Td around the exhaust pipe based on the wind speed, the temperature of the air introduced into the engine room, and the outer surface temperature Tc of the exhaust pipe;
calculating a first heat release amount Q1 by heat transfer from the exhaust pipe to the outside based on the wind speed, the ambient temperature Td , and the outer surface temperature Tc of the exhaust pipe;
estimating the inner surface temperature Tb of the exhaust pipe based on the previous inner surface temperature Tb of the exhaust pipe and at least the first heat release amount Q1 ; Based on the temperature Ta and the flow rate of the exhaust gas introduced into the exhaust pipe, the temperature of the exhaust gas at the inlet of the purification device is estimated.

Exhaust gas introduced from the engine into the exhaust pipe flows through the exhaust pipe while radiating heat, and reaches the inlet of the catalyst device. The control unit calculates the heat release amount of the exhaust gas based on the temperature and flow rate of the exhaust gas introduced from the engine into the exhaust pipe and the temperature of the exhaust pipe, and calculates the exhaust gas at the inlet of the purification device based on the heat release amount. Estimate the temperature of the gas.

An adjustment unit is provided at a running wind introduction port that introduces running wind into the engine room. When the adjustment unit opens the running wind introduction port, air is introduced into the engine room through the running wind introduction port. When the adjustment unit closes the running wind introduction port, introduction of air into the engine room through the running wind introduction port is suppressed. The flow rate of the air introduced into the engine room changes according to the opening degree of the running wind introduction port. Incidentally, the control unit may be configured to switch the running wind introduction port between fully open and fully closed. The adjustment unit may be configured to be able to adjust the opening of the wind introduction port to an intermediate opening degree between fully open and fully closed.

The control unit calculates the wind speed of the air around the exhaust pipe arranged in the engine room from the opening degree of the running wind introduction port and the vehicle speed. For example, the wind speed may be measured around the exhaust pipe while changing the opening of the running wind inlet and the vehicle speed, and a wind speed map may be created based on the statistical data. The controller can calculate the wind speed based on the created wind speed map.

Further, the control unit calculates the ambient temperature around the exhaust pipe based on the wind speed, the temperature of the air introduced into the engine room, and the outer surface temperature of the exhaust pipe. Similarly to the above, the ambient temperature around the exhaust pipe may be measured while changing each parameter, and a temperature map may be created based on the statistical data. The controller can calculate the ambient temperature based on the created temperature map.

When the wind speed and ambient temperature around the exhaust pipe are determined, the control unit can calculate the first heat release amount due to heat transfer from the exhaust pipe to the outside based on the outer surface temperature of the exhaust pipe. Once the first heat release amount from the exhaust pipe to the outside is determined, the controller can calculate the temperature of the exhaust pipe. Since the degree of opening of the running wind introduction port is taken into consideration when calculating the first heat release amount from the exhaust pipe to the outside, the controller can accurately calculate the temperature of the exhaust pipe.

Then, based on the calculated temperature of the exhaust pipe and the temperature and flow rate of the exhaust gas introduced into the exhaust pipe from the engine, the control unit accurately adjusts the temperature of the exhaust gas at the inlet of the purification device in the engine room. can be estimated.

The control unit controls a radiation model predetermined from the configuration of the engine room, an outer surface temperature Tc of the exhaust pipe, and a temperature related to the radiation model, which is the temperature of parts existing around the exhaust pipe. Based on Te , a second heat release amount Q2 due to radiation from the exhaust pipe to the outside is calculated,
The control unit estimates the inner surface temperature Tb of the exhaust pipe based on the previous inner surface temperature Tb of the exhaust pipe and at least the first heat release amount Q1 and the second heat release amount Q2 . good.

An exhaust pipe arranged in an engine room is surrounded by various parts and the like. Heat dissipation from the exhaust pipe to the outside includes heat dissipation by radiation in addition to heat dissipation by heat transfer. The control unit calculates a second heat release amount due to radiation from the exhaust pipe to the outside based on the outer surface temperature of the exhaust pipe and the temperature of the wall surrounding the exhaust pipe. The wall around the exhaust pipe means the outer surface of engine-related parts around the exhaust pipe and parts constituting the engine room. The temperature of the wall around the exhaust pipe may, for example, be equal to the ambient temperature around the exhaust pipe calculated above. When calculating the ambient temperature around the exhaust pipe, the degree of opening of the running air inlet is taken into consideration, so the control section can accurately calculate the second heat release amount due to radiation.

By estimating the temperature of the exhaust pipe based on at least the first heat release amount and the second heat release amount, the control unit can more accurately estimate the temperature of the exhaust pipe. As a result, the control unit can more accurately estimate the temperature of the exhaust gas at the inlet of the purification device in the engine room.

Based on the temperature Ta of the exhaust gas in the exhaust pipe, the flow rate of the exhaust gas, and the previous inner surface temperature Tb of the exhaust pipe, the control unit controls heat transfer from the exhaust gas to the exhaust pipe. Calculate the third heat release amount Q3 ,
The control unit estimates the inner surface temperature Tb of the exhaust pipe based on the previous inner surface temperature Tb of the exhaust pipe and at least the first heat release amount Q1 and the third heat release amount Q3 . good.

In addition to radiating heat to the outside, the exhaust pipe also receives heat from the exhaust gas inside the exhaust pipe. Based on the temperature of the exhaust gas in the exhaust pipe, the flow rate of the exhaust gas, and the previous temperature of the exhaust pipe, the control unit calculates a third heat release amount due to heat transfer from the exhaust gas to the exhaust pipe, that is, the exhaust pipe. Calculate the amount of heat received. By estimating the temperature of the exhaust pipe based on at least the first heat release amount and the third heat release amount, the control unit can more accurately estimate the temperature of the exhaust pipe. As a result, the control unit can more accurately estimate the temperature of the exhaust gas at the inlet of the purification device in the engine room.

The exhaust pipe has a main body that forms the inner surface , a heat insulating material that covers the main body, and a skin that surrounds the heat insulating material and forms the outer surface ,
The control unit calculates a fourth heat release amount Q4 by heat conduction of the exhaust pipe based on the previous temperature Tb of the main body as the inner surface temperature and the outer skin temperature Tc as the outer surface temperature. death,
The control unit may estimate the temperature Tb of the main body based on the previous temperature Tb of the main body and at least the first heat radiation amount Q1 and the fourth heat radiation amount Q4 .

If the exhaust pipe has a heat insulating material, it is necessary to consider the heat dissipation due to the heat conduction of the heat insulating material when the control unit calculates the temperature of the exhaust pipe. The control unit calculates a fourth heat release amount due to heat conduction of the exhaust pipe based on the previous temperature of the main body and the temperature of the outer skin.

Based on at least the first heat release amount and the fourth heat release amount, the control unit can more accurately estimate the temperature of the exhaust pipe, more precisely, the temperature of the main body in contact with the exhaust gas. As a result, the control unit can more accurately estimate the temperature of the exhaust gas at the inlet of the purification device in the engine room.

The control unit may calculate the wind velocity higher when the opening of the running wind introduction port is larger than when the opening is small.

When the opening degree of the running wind introduction port is large, the flow rate of the air introduced into the engine room from the running wind introduction port increases, so the wind speed around the exhaust pipe increases. The control unit can accurately calculate the wind speed according to the opening of the running wind introduction port.

The increase rate of the wind speed with respect to the increase of the vehicle speed may be higher when the opening degree of the running wind introduction port is larger than when the opening degree is small.

As described above, when the opening degree of the airflow introduction port is large, the flow rate of the air introduced into the engine room from the airflow introduction port increases, so the wind speed greatly increases when the vehicle speed increases. The controller can accurately calculate the wind speed according to the opening of the running wind introduction port and the vehicle speed.

When the estimated temperature of the exhaust gas is higher than a predetermined value, the control unit may control the engine so that the temperature of the exhaust gas introduced from the engine into the exhaust pipe becomes lower.

If the estimated temperature of the exhaust gas is higher than a predetermined value, the controller may increase the amount of fuel supplied to the engine, for example. As the amount of fuel increases, the latent heat of vaporization of the fuel lowers the temperature of the exhaust gas discharged from the engine. When the temperature of the exhaust gas is lowered, the temperature of the purification device is suppressed from becoming too high. The purifier can remain reliable.

The running wind introduction port is a grill provided in the front part of the engine room,
The adjustment unit may be a grill shutter provided on the grill.

As described above, the engine control device can accurately estimate the temperature of the exhaust gas at the inlet of the purification device in the engine room.

FIG. 1 is a cross-sectional view of the front of an automobile illustrating the placement of the engine, purifier and sensors. FIG. 2 is a plan view of the front of the automobile illustrating the arrangement of the engine and purifier. 3 is an end view taken along line III--III of FIG. 2. FIG. FIG. 4 is a block diagram illustrating an engine control device. FIG. 5 is a diagram for explaining switching between opening and closing of the grille shutter and on/off of the cooling fan. FIG. 6 is a diagram for explaining the logic for estimating the purifier inlet gas temperature. FIG. 7 is a diagram illustrating the estimation logic of the purifier inlet gas temperature. FIG. 8 is a diagram exemplifying a wind speed map showing the relationship between the vehicle speed, the opening and closing of the grille shutter, and the wind speed. FIG. 9 is a flow chart relating to the logic for estimating the purifier inlet gas temperature.

Hereinafter, embodiments of an engine control device will be described with reference to the drawings. The engine control system described here is an example.

(Engine configuration)
FIG. 1 is a cross-sectional view of the front of the vehicle illustrating the arrangement of the engine, purifier and sensors, and FIG. 2 is a plan view of the front of the vehicle illustrating the arrangement of the engine and purifier.

An engine 1 and a transmission 93 connected to the engine 1 are arranged in an engine room 90 in the front part of the automobile. The illustrated engine 1 is an in-line engine in which a plurality of cylinders 18 (four cylinders 18 in the illustrated example) are arranged in a line. The engine 1 is arranged so that the direction of its cylinder row coincides with the vehicle width direction of the automobile. The engine 1 is placed horizontally.

The engine 1 is a four-stroke engine that operates by repeating an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke in a cylinder 18 . The fuel of the engine 1 is gasoline in this configuration example. The fuel may be liquid fuel containing at least gasoline. Engine 1 is also a spark ignition engine in which a spark plug 82 (see FIG. 4) ignites the air-fuel mixture in cylinder 18 .

The engine 1 has a cylinder head 11 , a cylinder block 12 and an oil pan 13 . The cylinder head 11 is connected above the cylinder block 12 and the oil pan 13 is attached below the cylinder block 12 .

As shown in FIG. 1, the cylinder head 11 is formed with an intake port 111 for introducing intake air into the cylinder 18 and an exhaust port 112 for leading out exhaust gas from the cylinder 18. ing. Although not shown, the intake port 111 is provided with an intake valve that opens and closes in synchronization with the rotation of the crankshaft. The exhaust port 112 is provided with an exhaust valve that opens and closes in synchronization with rotation of the crankshaft.

An intake manifold 14 is attached to the front side of the engine 1 . The intake manifold 14 communicates with each intake port 111 . The intake manifold 14 introduces intake air into each cylinder 18 . An intake pipe 15 is connected to the intake manifold 14 . An intake port 16 is formed at the upstream end of the intake pipe 15 and opens toward the front of the automobile. An air cleaner 17 is provided in the middle of the intake pipe 15 .

An exhaust manifold (that is, an independent exhaust pipe) 20 is attached to the rear side of the engine 1 . The exhaust manifold 20 communicates with each exhaust port 112 . An exhaust manifold 20 directs exhaust gases from each cylinder 18 . A purification device 22 is connected to the exhaust manifold 20 . Purifier 22 reduces harmful substances in the exhaust gas. The purification device 22 has a three-way catalyst and a GPF (Gasoline Particulate Filter), although detailed illustration is omitted.

An exhaust pipe 21 is connected to the purification device 22 . The exhaust pipe 21 extends rearward from the purification device 22 . The exhaust pipe 21 is arranged inside the tunnel 91 . Tunnel 91 is connected to dash panel 92 . A dash panel 92 forms the rear part of the engine compartment 90 . A space within the tunnel 91 is connected to an engine room 90 . A lower portion of the tunnel 91 is open.

A sensor case 26 is interposed in the exhaust pipe 21 in the tunnel 91 . The sensor case 26 has a NOx sensor SW10, which will be described later. The NOx sensor SW10 is located downstream of the purifying device 22 .

The engine 1 is provided with an EGR device. The EGR device recirculates part of the exhaust gas to the intake as EGR gas. The EGR device has an EGR passage 23 , an EGR cooler 24 and an EGR valve 25 . The EGR passage 23 connects the exhaust pipe 21 (more specifically, the downstream end of the purification device 22 ) and the intake pipe 15 . The EGR cooler 24 is provided in the middle of the EGR passage 23 and cools the EGR gas. The EGR valve 25 adjusts the amount of EGR gas recirculated to the intake air.

A front portion of the engine room 90 is formed with a grill 60 as a running wind introduction port. A radiator 40 and a cooling fan 42 are arranged behind the grill 60 . A radiator 40 is positioned in front of the engine 1 and a cooling fan 42 is positioned between the radiator 40 and the engine 1 . A radiator 40 cools the coolant of the engine 1 . When the cooling fan 42 operates, the introduction of air from the grille 60 into the engine room 90 is facilitated.

Here, the engine 1 performs SPCCI combustion, which is a combination of SI combustion and CI combustion, in some operating regions. In other operating regions, the engine 1 performs SI combustion. SPCCI combustion utilizes the heat generation and pressure increase due to SI combustion to control CI combustion. SPCCI combustion, including CI combustion, is advantageous for improving fuel efficiency and improving exhaust gas performance. When the engine 1 performs SPCCI combustion, the air-fuel ratio of the air-fuel mixture is set to the stoichiometric air-fuel ratio (that is, stoichiometric SPCCI) or is made leaner than the stoichiometric air-fuel ratio (that is, lean SPCCI). be. When performing SI combustion, the engine 1 sets the air-fuel ratio of the air-fuel mixture to the stoichiometric air-fuel ratio.

When the engine 1 performs lean SPCCI combustion, maintaining a relatively high temperature in the engine 1 and the engine room 90 is advantageous for stable combustion. Therefore, this automobile has a grille shutter 65 for adjusting the amount of air introduced into the engine room 90 . The grille shutter 65 is an example of an adjustment section.

A grill shutter 65 is provided on the grill 60 . The grille shutter 65 has a plurality of fins 66 arranged vertically. Each fin 66 is configured to be rotatable. The grille shutter 65 is minimally opened (that is, closed) when the fins 66 are oriented perpendicular to the direction of vehicle travel, and is open when the fins 66 are oriented parallel to the direction of vehicle travel. maximum (that is, fully open). FIG. 1 exemplifies a state in which the opening degree of the grille shutter 65 is maximum. The opening of the grille shutter 65 can also be set to an intermediate opening between the minimum and maximum. The larger the opening of the grille shutter 65, the larger the opening of the grille 60, so the flow rate of the air introduced into the engine room 90 increases. When the grille shutter 65 is closed, the opening degree of the grille 60 is reduced and the introduction of air into the engine room 90 is restricted. Restricting the introduction of air into the engine room 90 increases the temperature inside the engine room 90 . When the grille shutter 65 is opened to introduce air into the engine room 90, the temperature inside the engine room 90 is lowered. The radiator 40 cools the coolant of the engine 1 by the air introduced into the engine room 90 . When the grille shutter 65 is opened and the cooling fan 42 is operated, the flow rate of the air introduced into the engine room 90 is increased, so the temperature inside the engine room 90 is further lowered. The radiator 40 further lowers the temperature of the coolant of the engine 1 .

This automobile also has a heat insulating cover 50 in the engine room 90 . 2 shows the engine room 90 with the heat insulating cover 50 removed. The heat insulating cover 50 covers the entire upper surface, left and right side surfaces, and rear surface of the cylinder head 11 of the engine 1 . By covering the engine 1 with the heat insulating cover 50, the engine 1 is kept warm and the diffusion of the sound of the engine 1 is suppressed.

When the engine 1 performs lean SPCCI combustion, the temperature of the exhaust gas discharged from the engine 1 is low because the combustion temperature is low. If the temperature of the exhaust gas is low, the temperature of the purification device 22 will fall below the activation temperature of the three-way catalyst. Therefore, in this engine 1, the exhaust manifold 20 is covered with a heat insulating material in order to keep the temperature of the exhaust gas introduced into the purification device 22 high. FIG. 3 shows an end view taken along line III--III of FIG. The exhaust manifold 20 is composed of four main bodies 201 forming independent exhaust pipes, heat insulating materials 202 surrounding the four main bodies 201 , and a pair of outer skins 203 surrounding the heat insulating materials 202 . A pair of outer skins 203 sandwich the heat insulating material 202 and hold the heat insulating material 202 . The heat insulating structure of the exhaust manifold 20 contributes not only to maintaining exhaust gas temperature but also to reducing engine noise.

(Engine control device)
FIG. 4 is a block diagram illustrating the configuration of the control device for the engine 1. As shown in FIG. The engine control device includes an ECU (Engine Control Unit) 10 . The ECU 10 is a well-known microcomputer-based controller, and includes a central processing unit (CPU) 101 that executes programs, and a RAM (random access memory) or ROM (read only memory), for example. It has a memory 102 for storing programs and data, and an input/output bus 103 for inputting/outputting electric signals. The ECU 10 is an example of a control section.

Various sensors SW1 to SW11 are connected to the ECU 10 . The sensors SW1 to SW11 output signals to the ECU 10. FIG. The sensors include the following sensors.

Airflow sensor SW1: arranged downstream of the air cleaner 17 in the intake pipe 15 to measure the flow rate of air flowing through the intake pipe 15. Intake air temperature sensor SW2: arranged downstream of the air cleaner 17 in the intake pipe 15 and arranged in the intake pipe. 15 Cylinder pressure sensor SW3: Attached to the cylinder head 11 corresponding to each cylinder 18 and measures the pressure in the cylinder 18 EGR differential pressure sensor SW4: Installed in the EGR passage 23 Also measures the pressure difference between the upstream and downstream sides of the EGR valve 25. Vehicle speed sensor SW5: measures vehicle speed. Fluid temperature sensor SW6: detects the fluid temperature of the cooling fluid of the engine 1. and measures the rotation angle of the crankshaft Accelerator opening sensor SW8: Attached to an accelerator pedal mechanism (not shown) and measures the accelerator opening corresponding to the amount of operation of the accelerator pedal Fuel pressure sensor SW9: Fuel supply system 85 and measures the pressure of the fuel supplied to the injector 81 NOx sensor SW10: attached to the exhaust pipe 21 downstream of the purification device 22 and measures the NOx concentration in the exhaust gas Outside air temperature sensor SW11: Measures the outside air temperature under the environment in which the automobile is running.

The ECU 10 determines the operating state of the engine 1 based on the signals from these sensors SW1 to SW11, and determines control amounts of devices 81 to 86, 25, 65, and 42, which will be described later, in accordance with predetermined control logic. to calculate The control logic is stored in memory 102 . The control logic includes using the operational map stored in memory 102 to compute target and/or control variables.

The ECU 10 transmits electric signals related to the calculated control amount to the injector 81, the spark plug 82, the electric intake S-VT 83, the electric exhaust S-VT 84, the fuel supply system 85, the throttle valve 86, the EGR valve 25, the grill shutter 65, Then, it is output to the cooling fan 42 .

The injector 81 is attached to the cylinder head 11 and directly injects fuel into the cylinder 18 . The spark plug 82 is attached to the cylinder head 11 and forcibly ignites the air-fuel mixture in the cylinder 18 . The electric intake S-VT 83 is attached to the cylinder head 11 and continuously changes the rotation phase of an intake camshaft (not shown) within a predetermined angle range. The intake camshaft opens and closes an intake valve (not shown). The electric exhaust S-VT 84 is attached to the cylinder head 11 and continuously changes the rotation phase of an exhaust camshaft (not shown) within a predetermined angle range. The exhaust camshaft opens and closes an exhaust valve (not shown). A fuel supply system 85 supplies fuel to the injector 81 . The throttle valve 86 is attached to the intake pipe 15 downstream of the air cleaner 17 and adjusts the amount of air introduced into the cylinder 18 .

FIG. 5 shows an example of control of the grille shutter 65 and the cooling fan 42 executed by the ECU 10. As shown in FIG. The ECU 10 opens and closes the grille shutter 65 and turns the cooling fan 42 on and off according to the coolant temperature and/or the temperature in the engine room 90 . Specifically, the ECU 10 closes the grill shutter 65 and turns off the cooling fan 42 when the coolant temperature and/or the temperature in the engine room 90 are low. Thereby, the temperature in the engine 1 and the engine room 90 is maintained high. The engine 1 can stably perform lean SPCCI combustion.

When the engine 1 performs stoichiometric SPCCI combustion or SI combustion, the coolant temperature and/or the temperature inside the engine room 90 rise. The ECU 10 opens the grille shutter 65 when the coolant temperature and/or the temperature in the engine room 90 increases. As a result, air is introduced from the grille 60 into the engine room 90, so that the coolant of the engine 1 and the temperature inside the engine room 90 are lowered.

When the coolant temperature and/or the temperature in the engine room 90 further rise, the ECU 10 opens the grille shutter 65 and turns on the cooling fan 42 . As a result, the flow rate of the air introduced from the grill 60 into the engine room 90 increases, so that the coolant of the engine 1 and the temperature in the engine room 90 can be further lowered.

(Estimation of exhaust gas temperature)
When the temperature of the purification device 22 including the three-way catalyst is lower than the activation temperature, the purification rate of the exhaust gas becomes low. On the other hand, while the automobile is running, for example, the temperature of the exhaust gas increases as the load on the engine 1 increases, and the temperature of the purification device 22 may become excessively high. If the temperature of the purification device 22 becomes excessively high, the reliability of the purification device 22 will deteriorate. Therefore, the ECU 10 needs to accurately grasp the temperature of the exhaust gas introduced into the purification device 22 while the engine 1 is running.

The engine control device disclosed herein estimates the temperature of the exhaust gas introduced into the purifying device 22 by computation rather than by detecting it with a temperature sensor. The engine controller can omit the temperature sensor. Omitting the temperature sensor has the advantage of not only reducing costs but also eliminating the need to repair or replace the temperature sensor due to deterioration or failure of the temperature sensor.

FIG. 6 is a diagram for explaining the logic for estimating the exhaust gas temperature at the inlet of the purification device 22. As shown in FIG. The engine 1 and the purification device 22 are arranged in the engine room 90 as described above. The engine 1 and the purification device 22 are connected via an exhaust manifold 20 . Exhaust gas discharged from the cylinders 18 of the engine 1 is introduced into the exhaust manifold 20 through the exhaust port 112 . The exhaust gas radiates heat while passing through the exhaust manifold 20 (see arrows in FIG. 6). At the inlet of the purification device 22 the temperature of the exhaust gas is lower than the temperature of the exhaust gas at the exhaust port 112 of the engine 1 .

The amount of heat released by the exhaust gas passing through the exhaust manifold 20 is determined according to the temperature difference between the temperature of the exhaust gas and the temperature of the exhaust manifold 20 . The temperature of the exhaust manifold 20 is determined according to the amount of heat released from the exhaust gas, in other words, the amount of heat received by the exhaust manifold 20 from the exhaust gas and the amount of heat released from the exhaust manifold 20 to the outside. The amount of heat radiation from the exhaust manifold 20 to the outside depends on the wind speed of the air around the exhaust manifold 20, the ambient temperature around the exhaust manifold 20, and the temperature of the wall existing around the exhaust manifold 20 (that is, the inner wall of the engine room). determined according to

FIG. 7 shows the logic executed by the ECU 10 to estimate the exhaust gas temperature at the inlet of the purification device 22 . The ECU 10 performs calculation using the gas temperature 71 at the exhaust port and the exhaust gas flow rate 72 as inputs and the gas temperature 70 at the inlet of the purifier as output. The ECU 10 observes the time-series gas temperature 70 by repeating the calculation at predetermined time intervals.

The ECU 10 may calculate the exhaust port gas temperature 71 . Although detailed description is omitted, the inventors of the present application have found that there is a linear correlation between the degree of combustion progress and the exhaust port gas temperature in the engine 1 that performs SPCCI combustion and SI combustion. . Combustion progress is the crank angle at which combustion has progressed to a specified degree. The crank angle (mfb50) at which the mass combustion ratio becomes, for example, 50% can be used as the degree of combustion progress. The ECU 10 can calculate mfb50 based on the output signal of the in-cylinder pressure sensor SW3 and the output signal of the crank angle sensor SW7. When the degree of combustion progresses retarded, the exhaust port gas temperature increases, and when the degree of combustion advances, the exhaust port gas temperature decreases. The ECU 10 can calculate the exhaust port gas temperature 71 using a model or map that represents the relationship between the degree of combustion progress and the exhaust port gas temperature.

A temperature sensor for measuring the exhaust port gas temperature 71 may be attached to the engine 1 instead of the ECU 10 calculating the exhaust port gas temperature 71 . The ECU 10 can acquire the gas temperature 71 of the exhaust port based on the output signal of the temperature sensor.

Based on the output signal of the airflow sensor SW1 (that is, the amount of air in the engine 1), the fuel supply amount determined by the ECU 10, and the output signal of the EGR differential pressure sensor SW15 (that is, the amount of external EGR gas), An exhaust gas flow rate 72 discharged from the engine 1 can be calculated.

The ECU 10 also calculates an exhaust gas thermal energy 73 and an exhaust gas flow rate 74 from the exhaust port gas temperature 71 and the exhaust gas flow rate 72 .

The ECU 10 calculates the wind speed of the air around the exhaust manifold 20 in order to calculate the amount of heat released from the exhaust manifold 20 to the outside. According to studies by the inventors of the present application, the wind speed of the air around the exhaust manifold 20 disposed on the rear side of the engine 1 has a correlation with the vehicle speed of the automobile and the opening degree of the grille shutter 65. I found out. Therefore, a wind speed map 75 is created in advance based on statistical data of wind speed measured around the exhaust manifold 20 while changing the vehicle speed and the opening of the grille shutter 65 . The ECU 10 calculates the wind speed 78 around the exhaust manifold 20 based on the wind speed map 75, the vehicle speed 76 obtained from the signal of the vehicle speed sensor SW5, and the opening 77 of the grille shutter 65 determined by the ECU 10.

Here, FIG. 8 exemplifies the wind speed map 75 . The wind speed map 75 defines the relationship between the vehicle speed, the opening of the grille shutter 65, and the wind speed of the air around the exhaust manifold 20, as described above. When the vehicle speed is high, the amount of air flowing into the engine room 90 through the grille 60 and other parts increases. Therefore, the higher the vehicle speed, the higher the wind speed of the air around the exhaust manifold 20 .

Also, when the grille shutter 65 is open (that is, fully open), the flow rate of air flowing into the engine room 90 through the grille 60 is greater than when the grille shutter 65 is closed (that is, fully closed). Therefore, when the grille shutter 65 is open, the air velocity around the exhaust manifold 20 is higher than when it is closed.

When the grille shutter 65 is open, the rate of increase in wind speed with respect to the increase in vehicle speed (that is, the slope of the straight line in FIG. 8) is higher than when the grille shutter 65 is closed. This is because if the opening of the grille shutter 65 is large, the flow rate of the air introduced from the grille 60 into the engine room 90 increases, so that the wind speed greatly increases when the vehicle speed increases.

The wind speed map 75 of FIG. 8 includes only two straight lines, ie, a straight line when the grille shutter 65 is fully open and a straight line when the grille shutter 65 is fully closed. Wind speed map 75 may further include a straight line when grille shutter 65 is at an intermediate opening.

Further, when the grille shutter 65 is at an intermediate opening, the ECU 10 interpolates between the straight line when the grille shutter 65 is fully open and the straight line when the grille shutter 65 is fully closed. The wind velocity of the air around the manifold 20 may be calculated.

The ECU 10 may calculate the wind speed of the air around the exhaust manifold 20 using a model instead of the wind speed map 75 .

The ECU 10 has a wind speed calculator 31 as a functional block. The wind speed calculator 31 calculates the wind speed of the air around the exhaust manifold 20 from the opening degree of the grille shutter 65 and the vehicle speed.

The ECU 10 also calculates the ambient temperature around the exhaust manifold 20 . According to studies by the inventors of the present application, the temperature around the exhaust manifold 20 is determined by the wind speed 78 calculated above, the temperature of the air flowing into the engine room 90 (engine room inlet temperature 79), and the skin temperature of the exhaust manifold 20. 710 and correlation. Therefore, while changing these parameters, a temperature map 711 is created in advance based on the statistical data of the ambient temperature measured around the exhaust manifold 20 . The ECU 10 calculates the ambient temperature Td around the exhaust manifold based on the temperature map 711 , the wind speed 78 , the engine room inlet temperature 79 and the outer skin temperature 710 .

The ECU 10 may use the signal of the intake air temperature sensor SW2 for the engine room inlet temperature 79, for example. As shown in FIG. 2, the intake air temperature sensor SW2 outputs to the ECU 10 a signal corresponding to the temperature of the air taken in from the intake port 16 provided in the front part of the engine room 90. As shown in FIG. Further, the ECU 10 calculates an outer skin temperature Tc as described later. The ECU 10 uses the previous value of the outer skin temperature Tc as the outer skin temperature 710 .

The ECU 10 may calculate the ambient temperature around the exhaust manifold 20 using a model instead of the temperature map 711 .

The ECU 10 has an ambient temperature calculator 32 as a functional block. The ambient temperature calculator 32 calculates the ambient temperature around the exhaust manifold 20 based on the wind speed, the temperature of the air introduced into the engine room 90 , and the skin temperature of the exhaust manifold 20 .

The ECU 10 calculates a first heat release amount Q1 due to heat transfer from the exhaust manifold 20 to the outside based on the wind speed and ambient temperature Td described above and the skin temperature Tc of the exhaust manifold 20 . The ECU 10 may calculate the first heat release amount Q1 based on a predetermined heat transfer model. The ECU 10 has a first heat dissipation calculation section 33 as a functional block. The first heat radiation amount calculator 33 calculates a first heat radiation amount Q1 due to heat transfer from the exhaust manifold 20 to the outside.

The exhaust manifold 20 arranged in the engine room 90 is surrounded by various parts and the like. Heat dissipation from the exhaust manifold 20 to the outside includes heat dissipation by heat transfer as well as heat dissipation by radiation. The ECU 10 calculates a second heat release amount Q2 by radiation from the exhaust manifold 20 to the outside based on the outer skin temperature Tc and the engine room inner wall temperature Te. The inner wall of the engine room means the outer surface of the parts related to the engine existing around the exhaust manifold 20 and the parts constituting the engine room 90 . The inventors of the present application have confirmed that in the configuration example of the engine room 90 shown in FIGS. 1 and 2, the engine room inner wall temperature Te and the ambient temperature Td around the exhaust manifold 20 are substantially the same. The engine inner wall temperature Te can be equal to the ambient temperature Td calculated using the temperature map 711 . If the vehicle has a configuration in which the engine room inner wall temperature Te and the ambient temperature Td around the exhaust manifold 20 do not match, the ECU 10 may calculate the engine inner wall temperature Te separately from the ambient temperature Td.

The ECU 10 may calculate the second heat release amount Q2 based on a predetermined radiation model. The ECU 10 has a second heat dissipation calculation section 34 as a functional block. The second heat radiation amount calculation unit 34 calculates a second heat radiation amount Q2 due to radiation from the exhaust manifold 20 to the outside.

As shown in FIG. 3, the exhaust manifold 20 is composed of a main body 201, a heat insulating material 202, and an outer skin 203. As shown in FIG. The ECU 10 calculates a fourth heat release amount Q4 due to heat conduction of the exhaust manifold 20 based on the main body temperature Tb and the outer skin temperature Tc. The ECU 10 may calculate the fourth heat release amount Q4 based on a predetermined heat conduction model. The ECU 10 has a fourth heat dissipation calculation section 35 as a functional block. A fourth heat radiation amount calculation unit 35 calculates a fourth heat radiation amount Q4 due to heat conduction of the exhaust manifold 20 based on the temperature Tb of the main body 201 and the temperature Tc of the outer skin 203 .

The exhaust manifold 20 receives heat from the exhaust gas inside the exhaust manifold 20 in addition to dissipating heat to the outside. The ECU 10 calculates a third heat release amount Q3 due to heat transfer from the exhaust gas to the main body 201 based on the exhaust gas temperature Ta in the exhaust manifold 20, the flow rate of the exhaust gas, and the temperature Tb of the main body 201. The third heat release amount Q3 is the amount of heat received by the main body 201 . The ECU 10 may calculate the third heat release amount Q3 based on a predetermined heat transfer model. The ECU 10 has a third heat dissipation calculation section 36 as a functional block. Based on the exhaust gas temperature Ta, the exhaust gas flow rate 72, and the temperature Tb of the main body 201, the third heat dissipation calculation unit 36 calculates a third heat dissipation amount due to heat transfer from the exhaust gas to the main body 201 of the exhaust manifold 20. Calculate Q3.

The ECU 10 calculates the temperature Tb of the main body 201 based on the calculated heat release amounts Q1, Q2, Q3 and Q4. More specifically, the ECU 10 determines the temperature of the main body 201 of the exhaust manifold 20 based on the difference between the amounts of heat Q1, Q2, and Q4 radiated from the main body 201 and the amount of heat Q3 received by the main body 201 from the previous temperature of the main body 201 of the exhaust manifold 20. Estimate the temperature Tb of

After estimating the temperature Tb of the main body 201, the ECU 10 calculates the temperature from the inlet to the outlet of the exhaust manifold 20 based on the temperature Tb of the main body 201 and the thermal energy 73 of the exhaust gas introduced into the exhaust manifold 20. The amount of heat radiated from the exhaust gas to the main body 201 is calculated, and the temperature 70 of the exhaust gas at the inlet of the purification device 22 is estimated based on the amount of heat radiated. The ECU 10 has a temperature estimator 37 as a functional block.

The ECU 10 can accurately estimate the temperature of the exhaust gas at the inlet of the purification device 22 in the engine room 90 based on the temperature of the exhaust manifold 20 calculated in consideration of the vehicle speed and the opening of the grille shutter 65. can.

FIG. 9 is a flowchart illustrating a procedure for estimating the exhaust gas temperature, which is executed by the ECU 10. FIG. It should be noted that the order of steps S1 to S13 in this flow chart can be changed within a possible range.

First, in step S1 after the start, the ECU 10 reads signals from various sensors SW1 to SW11. In subsequent step S2, the ECU 10 sets the opening degree of the grille shutter 65 and the operating state of the cooling fan 42 according to the coolant temperature and/or the temperature in the engine room 90 as described above ( See Figure 5).

In step S<b>3 , the ECU 10 calculates the wind speed 78 around the exhaust manifold 20 from the grille shutter opening 77 , the vehicle speed 76 and the wind speed map 75 . Further, in step S4, the ECU 10 calculates the ambient temperature Td around the exhaust manifold 20 from the wind speed 78, the engine room inlet temperature 79, the skin temperature 710, and the temperature map 711.

In step S5, the ECU 10 calculates a first heat release amount Q1 by heat transfer from the outer skin temperature Tc, the wind speed 78, and the ambient temperature Td. Further, in step S6, the ECU 10 calculates a second heat release amount Q2 by radiation from the outer skin temperature Tc and the engine room inner wall temperature Te (=Td).

In step S7, the ECU 10 calculates a fourth heat release amount Q4 by thermal conduction from the main body temperature Tb and the outer skin temperature Tc. Further, in step S8, the ECU 10 calculates a third heat release amount Q3 by heat transfer from the exhaust gas temperature Ta and the body temperature Tb.

Then, in step S9, the ECU 10 calculates the current body temperature Tb based on the previous body temperature and the heat release amounts Q1 to Q4 calculated in steps S5 to S8. From the exhaust gas thermal energy 73 calculated from the port gas temperature 71 and the exhaust gas flow rate 72, and the main body temperature Tb, the amount of heat released from the exhaust gas to the exhaust manifold 20 is calculated, and the temperature of the exhaust gas at the inlet of the purification device 22 is calculated. 70 is calculated (ie estimated).

After calculating the temperature 70 of the exhaust gas at the inlet of the purifying device, the ECU 10 determines whether or not the calculated temperature 70 of the exhaust gas is less than a predetermined first threshold in step S11. The first threshold may be determined as a temperature at which the temperature of the catalyst does not rise excessively. If the temperature is below the first threshold, the process proceeds from step S11 to step S12. If the temperature is greater than or equal to the first threshold, that is, if the temperature of the exhaust gas at the purifier inlet is high, the process proceeds from step S11 to step S13. In step S<b>13 , the ECU 10 increases the amount of fuel injected into the cylinder 18 . As the amount of fuel increases, the combustion temperature decreases due to the latent heat of vaporization of the fuel. Since the temperature of the exhaust gas discharged from the engine 1 is lowered, the temperature of the exhaust gas at the inlet of the purifier is lowered. The temperature of the purification device 22 is suppressed from becoming too high. A decrease in the reliability of the purification device 22 is suppressed.

In step S12, the ECU 10 determines whether or not the catalyst temperature of the purification device 22 is lower than a predetermined second threshold. The second threshold may be determined as a temperature at which the reliability of the catalyst can be maintained. The ECU 10 may estimate the catalyst temperature based on the temperature of the exhaust gas at the inlet of the purification device. If the determination in step S12 is YES, that is, if the catalyst temperature is not high, the process returns. If the determination in step S12 is NO, that is, if the catalyst temperature is high, the process proceeds to step S13. As described above, the CU 10 increases the injection amount of fuel supplied into the cylinder 18 in step S13. As the temperature of the exhaust gas discharged from the engine 1 drops, the temperature of the catalyst drops. A decrease in the reliability of the purification device 22 is suppressed.

Although the exhaust manifold 20 has the heat insulating material 202 in the above configuration, the heat insulating material 202 and the outer skin 203 can be omitted. When the heat insulating material 202 and the outer skin 203 are omitted, the ECU 10 omits the calculation of the fourth heat release amount Q4 by the heat conduction of the exhaust manifold 20 in the logic of FIG. Further, the ECU 10 matches the outer skin temperature Tc with the exhaust manifold temperature Tb to calculate the heat release amounts Q1 and Q2.

Further, among the heat release amounts Q1 to Q4 related to the calculation of the temperature of the exhaust manifold 20, the ECU 10 may omit the calculation of the heat release amounts Q2, Q3 and Q4 if possible.

Furthermore, the technology disclosed herein is not limited to application to the engine 1 that performs SPCCI combustion. The engine 1 to which the technology disclosed herein can be applied is not particularly limited. The technology disclosed herein may be applied to a so-called spark ignition engine or a gasoline engine that performs only SI combustion. Also, the technique disclosed herein may be applied to a so-called diesel engine that performs CI combustion.

1 engine 10 ECU (control unit)
20 exhaust manifold (exhaust pipe)
201 main body 202 heat insulating material 203 outer skin 22 purification device 31 wind speed calculator 32 ambient temperature calculator 33 first heat dissipation calculator 34 second heat dissipation calculator 35 fourth heat dissipation calculator 36 third heat dissipation calculator 37 temperature estimation Part 60 Grill (running wind inlet)
65 Grille shutter (control part)
90 engine room

Claims (8)

an engine arranged in an engine room;
an adjustment unit that changes the degree of opening of the running wind introduction port between an open state in which air is introduced into the engine room from the running wind introduction port and a closed state in which introduction of the air is suppressed;
a purification device for reducing harmful substances in exhaust gas of the engine;
an exhaust pipe arranged in the engine room and connecting the engine and the purification device;
a control unit for estimating the temperature of the exhaust gas at the inlet of the purification device in chronological order by repeating calculations at predetermined time intervals , and for controlling the engine according to the estimated temperature;
The exhaust pipe has an inner surface in contact with the exhaust gas and an outer surface exposed in the engine room,
The control unit
calculating the wind speed of the air around the exhaust pipe from the opening of the running wind introduction port and the vehicle speed;
calculating an ambient temperature Td around the exhaust pipe based on the wind speed, the temperature of the air introduced into the engine room, and the outer surface temperature Tc of the exhaust pipe;
calculating a first heat release amount Q1 by heat transfer from the exhaust pipe to the outside based on the wind speed, the ambient temperature Td , and the outer surface temperature Tc of the exhaust pipe;
estimating the inner surface temperature Tb of the exhaust pipe based on the previous inner surface temperature Tb of the exhaust pipe and at least the first heat release amount Q1 ; An engine control device for estimating the temperature of the exhaust gas at the inlet of the purification device based on the temperature Ta and the flow rate of the exhaust gas introduced into the exhaust pipe. In the engine control device according to claim 1,
The control unit controls a radiation model predetermined from the configuration of the engine room, an outer surface temperature Tc of the exhaust pipe, and a temperature related to the radiation model, which is the temperature of parts existing around the exhaust pipe. Based on Te , a second heat release amount Q2 due to radiation from the exhaust pipe to the outside is calculated,
The control unit controls the engine to estimate the inner surface temperature Tb of the exhaust pipe based on the previous inner surface temperature Tb of the exhaust pipe and at least the first heat release amount Q1 and the second heat release amount Q2 . Device. In the engine control device according to claim 1 or 2,
Based on the temperature Ta of the exhaust gas in the exhaust pipe, the flow rate of the exhaust gas, and the previous inner surface temperature Tb of the exhaust pipe, the control unit controls heat transfer from the exhaust gas to the exhaust pipe. Calculate the third heat release amount Q3 ,
The control unit controls the engine to estimate the inner surface temperature Tb of the exhaust pipe based on the previous inner surface temperature Tb of the exhaust pipe and at least the first heat radiation amount Q1 and the third heat radiation amount Q3 . Device. In the engine control device according to any one of claims 1 to 3,
The exhaust pipe has a main body that forms the inner surface , a heat insulating material that covers the main body, and a skin that surrounds the heat insulating material and forms the outer surface ,
The control unit calculates a fourth heat release amount Q4 by heat conduction of the exhaust pipe based on the previous temperature Tb of the main body as the inner surface temperature and the outer skin temperature Tc as the outer surface temperature. death,
The engine control device, wherein the control unit estimates the temperature Tb of the main body based on the previous temperature Tb of the main body and at least the first heat radiation amount Q1 and the fourth heat radiation amount Q4 . In the engine control device according to any one of claims 1 to 4,
The control unit for an engine, wherein the control unit calculates the wind speed higher when the opening degree of the running wind introduction port is larger than when the opening degree is small. In the engine control device according to any one of claims 1 to 5,
A control device for an engine, wherein a rate of increase in wind speed with respect to an increase in vehicle speed is higher when the opening degree of the running wind introduction port is larger than when the opening degree is small. In the engine control device according to any one of claims 1 to 6,
The control unit controls the engine so that the temperature of the exhaust gas introduced from the engine into the exhaust pipe becomes lower when the estimated temperature of the exhaust gas is higher than a predetermined value. In the engine control device according to any one of claims 1 to 7,
The running wind introduction port is a grill provided in the front part of the engine room,
The control device of the engine, wherein the adjustment unit is a grill shutter provided on the grill.

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