JP7310322B2 - 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. In some cases, a sensor that outputs a signal regarding the properties of the exhaust gas (for example, a sensor that outputs a signal regarding the NOx concentration in the exhaust gas) is attached to the exhaust pipe downstream of the purification device. The sensor is mounted in the exhaust pipe, for example, in a tunnel behind the dash panel at the rear of the engine compartment.

The temperature of the exhaust gas flowing through the exhaust pipe gradually drops. When the temperature of the exhaust gas drops, water in the exhaust gas may be condensed to generate condensed water. If the sensor is energized with condensed water adhering to it, the sensor may malfunction. Therefore, there is a demand for the control device to estimate the presence or absence of condensed water by accurately grasping the temperature of the exhaust gas near the mounting position of the sensor 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 near the mounting position of the sensor 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.

When the engine performs SPCCI combustion of a stoichiometric air-fuel mixture or SI combustion of a stoichiometric air-fuel ratio mixture, it is not necessary to keep the temperature in the engine room high. In these cases, in order to prevent the temperature in the engine room from rising excessively, air can be introduced into the engine room by opening the travel-air introduction port. In addition, when the temperature of the engine is high and the temperature in the engine room is high, air can be positively introduced into the engine room by opening the running air intake and operating the fan of the radiator. can.

However, the temperature and wind speed in the tunnel leading to the engine room change by opening and closing the running air inlet, and the temperature and wind speed in the tunnel also change by turning the fan on and off. The technique described in Patent Literature 1 does not take into account the effects of opening and closing of the wind inlet and turning on and off of the fan, so the temperature of the exhaust gas at the mounting position of the sensor cannot be estimated with high accuracy.

The technology disclosed herein accurately estimates the temperature of the exhaust gas at the mounting position of the sensor.

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 fan that operates to promote the introduction of air into the engine room from the airflow introduction port;
an exhaust pipe disposed in a tunnel behind the dash panel and leading out exhaust gas from the engine;
a sensor attached to the exhaust pipe in the tunnel and outputting a signal regarding the properties of the exhaust gas;
a control unit to which the sensor is connected and which controls the engine based on the signal of the sensor ;
The control unit also estimates the temperature of the exhaust gas in the vicinity of the mounting position of the sensor in chronological order by repeating the calculation at predetermined time intervals.

The control unit
calculating the wind speed of the air around the exhaust pipe from the opening of the running wind introduction port, the operating state of the fan, and the vehicle speed;
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 Tc around the exhaust pipe, and the temperature Tb of the exhaust pipe;
The temperature Tb of the exhaust pipe is estimated based on the previous temperature Tb of the exhaust pipe and at least the first heat release amount Q1 , and the estimated temperature Tb of the exhaust pipe and the exhaust gas introduced into the exhaust pipe The temperature of the exhaust gas near the mounting position of the sensor is estimated based on the temperature Ta and the flow rate of the sensor.

Exhaust gases discharged from the engine are introduced into the exhaust pipe. The exhaust gas introduced into the exhaust pipe flows through the exhaust pipe while radiating heat, and reaches the vicinity of the mounting position of the sensor. The control unit estimates the temperature of the exhaust gas near the mounting position of the sensor based on the temperature and flow rate of the exhaust gas introduced into the exhaust pipe and the temperature of the exhaust pipe.

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.

Further, the fan accelerates the introduction of air into the engine room from the running air inlet when operating. The fan may be, for example, a radiator cooling fan.

The control unit calculates the wind speed of the air around the exhaust pipe in the tunnel from the opening of the running wind introduction port, the operating state of the fan, and the vehicle speed. For example, the wind speed around the exhaust pipe may be measured while changing the opening of the running wind inlet, the operating state of the fan, 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.

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 temperature of the exhaust pipe. As for the ambient temperature around the exhaust pipe, for example, if the tunnel has a structure in which at least a part of the interior is open to the outside, the ambient temperature can be regarded as the ambient temperature. In addition, if the tunnel is a structure that is shut off from the outside, the ambient temperature around the exhaust pipe is calculated based on the wind speed calculated above, the temperature of the air introduced into the tunnel, and the temperature of the exhaust pipe. can be calculated. 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. When calculating the first heat release amount from the exhaust pipe to the outside, the opening degree of the running wind introduction port and the operating state of the fan are taken into consideration, so the control unit 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, the control unit accurately estimates the temperature of the exhaust gas near the installation position of the sensor in the tunnel. can do.

The control unit is configured based on a radiation model predetermined from the configuration of the tunnel, a temperature Tb of the exhaust pipe, and a temperature Td of a wall surrounding the exhaust pipe , which is a temperature related to the radiation model. to calculate a second heat release amount Q2 due to radiation from the exhaust pipe to the outside,
The control unit may estimate the temperature Tb of the exhaust pipe based on the previous temperature Tb of the exhaust pipe and at least the first heat release amount Q1 and the second heat release amount Q2 .

An exhaust pipe installed in a tunnel is surrounded by the walls and road surface that constitute the tunnel. 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 temperature of the exhaust pipe and the temperature of the wall surrounding the exhaust pipe. The wall around the exhaust pipe means the wall of the tunnel and the road surface around the exhaust pipe. The temperature of the surrounding wall of the exhaust pipe may be equal to the ambient temperature, for example.

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 near the installation position of the sensor in the tunnel.

Based on the temperature Ta of the exhaust gas in the exhaust pipe, the flow rate of the exhaust gas, and the previous temperature Tb of the exhaust pipe, the control unit performs a third heat transfer by heat transfer from the exhaust gas to the exhaust pipe. Calculate the amount of heat release Q3 ,
The control unit may estimate the temperature Tb of the exhaust pipe based on the previous temperature Tb of the exhaust pipe and at least the first heat release amount Q1 and the third heat release amount Q3 .

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 controller can more accurately estimate the temperature of the exhaust gas in the vicinity of the sensor installation position in the tunnel.

When the fan is off, the control unit may calculate the wind speed higher when the opening of the running wind introduction port is larger than when the opening is small.

If the opening 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 around the exhaust pipe in the tunnel increases. The control unit can accurately calculate the wind speed according to the opening of the running wind introduction port.

The control unit may calculate the wind velocity higher when the running wind inlet is open and when the fan is on than when the fan is off.

When the fan is on, the introduction of air into the engine room through the running air inlet is facilitated, so the wind speed around the exhaust pipe in the tunnel also increases. The controller can accurately calculate the wind speed according to the operating state of the fan.

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

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

The rate of increase in the wind speed with respect to the increase in vehicle speed may be equal or substantially equal when the running wind inlet is open and when the fan is on and off.

If the opening degree of the running wind introduction port is the same, the rate of increase in wind speed with respect to the increase in vehicle speed is equal or substantially equal whether the fan is on or off. The control unit can accurately calculate the wind speed according to the opening of the running wind introduction port, the operating state of the fan, and the vehicle speed.

The control unit may prohibit energization of the sensor when the temperature of the exhaust gas estimated by the temperature estimation unit is lower than a predetermined value.

If the temperature of the exhaust gas is lower than the predetermined value, there is a high possibility that condensed water is generated by condensing moisture in the exhaust gas. By prohibiting the energization of the sensor by the controller, failure of the sensor can be suppressed.

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 near the installation position of the sensor in the tunnel.

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. FIG. 3 is a block diagram illustrating an engine control device. FIG. 4 is a diagram for explaining switching between opening and closing of the grille shutter and on/off of the cooling fan. FIG. 5 is a diagram for explaining the logic for estimating the gas temperature inside the sensor case. FIG. 6 is a diagram illustrating logic for estimating the gas temperature in the sensor case. FIG. 7 is a diagram exemplifying a wind speed map showing the relationship between the vehicle speed, the opening/closing of the grille shutter, the ON/OFF of the cooling fan, and the wind speed. FIG. 8 is a flowchart relating to the logic for estimating the gas temperature in the sensor case.

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. 3) 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 vehicle. 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 . Cooling fan 42 is an example of a fan. 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.

(Engine control device)
FIG. 3 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 electrical 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. 4 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)
The temperature of the exhaust gas flowing through the exhaust pipe 21 gradually drops. When the temperature of the exhaust gas drops, water in the exhaust gas may be condensed to generate condensed water. If the NOx sensor SW10 is energized while the condensed water is attached to the NOx sensor SW10, the NOx sensor SW10 may malfunction. Therefore, it is preferable that the ECU 10 accurately grasps the temperature of the exhaust gas in the sensor case 26 having the NOx sensor SW10 while the engine 1 is running.

The engine control device disclosed herein estimates the temperature of the exhaust gas in the sensor case 26 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. 5 is a diagram for explaining the logic for estimating the exhaust gas temperature inside the sensor case 26. As shown in FIG. The sensor case 26 is connected to the purification device 22 via the exhaust pipe 21 . Exhaust gas that has passed through the purification device 22 radiates heat while passing through the exhaust pipe 21 (see arrows in FIG. 5). Within the sensor case 26 the temperature of the exhaust gas is lower than the temperature of the exhaust gas at the outlet of the purification device 22 .

The amount of heat released by the exhaust gas passing through the exhaust pipe 21 is determined according to the temperature difference between the temperature of the exhaust gas and the temperature of the exhaust pipe 21 . The temperature of the exhaust pipe 21 is determined according to the amount of heat released from the exhaust gas, in other words, the amount of heat received by the exhaust pipe 21 from the exhaust gas and the amount of heat released from the exhaust pipe 21 to the outside. The amount of heat released from the exhaust pipe 21 to the outside depends on the wind speed of the air around the exhaust pipe 21, the ambient temperature around the exhaust pipe 21, and the wall existing around the exhaust pipe 21 (that is, the floor constituting the tunnel 91). It is determined according to the temperature of the surface and the road surface).

FIG. 6 shows logic for estimating the exhaust gas temperature within the sensor case 26, which is executed by the ECU 10. As shown in FIG. The ECU 10 performs calculation with the gas temperature 71 at the outlet of the purification device 22 and the flow rate 72 of the exhaust gas introduced into the exhaust pipe 21 as inputs and the gas temperature 70 in the sensor case 26 as output. The ECU 10 observes the time-series gas temperature 70 by repeating the calculation at predetermined time intervals.

If a temperature sensor is attached near the outlet of the purification device 22, the ECU 10 can obtain the exhaust gas temperature 71 at the outlet of the purification device 22 based on the output signal of the temperature sensor.

Further, even if a temperature sensor is not attached near the outlet of the purification device 22, the ECU 10 can calculate the gas temperature 71 at the outlet of the purification device 22 based on the temperature and flow rate of the exhaust gas discharged from the engine 1. can be done. As shown in FIG. 5 , the purification device 22 is connected to the engine 1 via the 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 releases heat while passing through the exhaust manifold 20 . 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 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 engine 1 , exhaust manifold 20 and purification device 22 are arranged in an engine room 90 . 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

The thermal system between the engine 1 and the purification device 22 and the thermal system between the purification device 22 and the sensor case 26 are similar. The ECU 10 can estimate the temperature 71 of the exhaust gas at the outlet of the purification device 22 according to logic (see FIG. 6) for estimating the temperature of the exhaust gas inside the sensor case 26, which will be described later. That is, the ECU 10 uses the gas temperature at the exhaust port and the exhaust gas flow rate as inputs and the gas temperature at the inlet of the purifier as an output to calculate the gas temperature at the inlet of the purifier 22 and can estimate the gas temperature at the outlet of

Here, the ECU 10 may calculate the gas temperature of the exhaust port. 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 using a model or map representing the relationship between the degree of combustion progress and the exhaust port gas temperature.

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

Returning to FIG. 6, the ECU 10 outputs the output signal of the airflow sensor SW1 (that is, the amount of air in the engine 1), the amount of fuel supply determined by the ECU 10, and the output signal of the EGR differential pressure sensor SW15 (that is, the amount of external EGR gas). , the exhaust gas flow rate 72 discharged from the engine 1 and introduced into the exhaust pipe 21 can be calculated.

The ECU 10 also calculates an exhaust gas thermal energy 73 and an exhaust gas flow rate 74 from the exhaust gas temperature 71 and the exhaust gas flow rate 72 at the outlet of the purification device 22 .

The ECU 10 calculates the wind speed of the air around the exhaust pipe 21 in order to calculate the amount of heat released from the exhaust pipe 21 to the outside. According to studies by the inventors of the present application, the wind speed of the air around the exhaust pipe 21 arranged in the tunnel 91 correlates with the vehicle speed of the automobile, the opening degree of the grille shutter 65, and the operating state of the cooling fan 42. found to have. Therefore, the wind speed map 75 is prepared in advance based on the statistical data of the wind speed measured around the exhaust pipe 21 while changing the vehicle speed, the opening degree of the grille shutter 65 and the operating state of the cooling fan 42 . The ECU 10 controls the exhaust pipe 21 based on the wind speed map 75, the vehicle speed 76 obtained from the signal of the vehicle speed sensor SW5, the opening degree 77 of the grille shutter 65 determined by the ECU 10, and the on/off state 78 of the cooling fan determined by the ECU 10. Calculate the wind speed 79 around the .

Here, FIG. 7 exemplifies the wind speed map 75 . The wind speed map 75 defines the relationship between the vehicle speed, the degree of opening of the grille shutter 65, the ON/OFF state of the cooling fan 42, and the wind speed of the air around the exhaust pipe 21, as described above. When the vehicle speed is high, the amount of air flowing into the engine room 90 and the tunnel 91 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 pipe 21 .

When the grille shutter 65 is open (that is, fully open) while the cooling fan 42 is off, the engine room 90 and the engine room 90 through the grille 60 are more likely to be cooled than when the grille shutter 65 is closed (that is, fully closed). The flow rate of the air flowing into the tunnel 91 increases. Therefore, when the grille shutter 65 is open, the air velocity around the exhaust pipe 21 is higher than when it is closed.

When the cooling fan 42 is off, the rate of increase in wind speed (that is, the slope of the straight line in FIG. 7) is higher when the opening of the grille shutter 65 is larger than when the opening is small. When 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 and the tunnel 91 increases, so that the wind speed greatly increases when the vehicle speed increases.

When the grille shutter 65 is open, the air velocity around the exhaust pipe 21 is higher when the cooling fan 42 is on than when it is off.

Also, when the grille shutter is open, the rate of increase in wind speed with respect to the increase in vehicle speed (that is, the slope in FIG. 7) is equal or substantially equal between when the cooling fan 42 is on and when it is off.

The wind speed map 75 of FIG. 7 includes 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 pipe 21 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 pipe 21 from the opening degree of the grille shutter 65, the operating state of the cooling fan 42, and the vehicle speed.

The ECU 10 also sets the ambient temperature Tc around the exhaust pipe 21 . According to studies by the inventors of the present application, the temperature around the exhaust pipe 21 in the tunnel 91 is substantially equal to the outside air temperature 710 because the lower portion of the tunnel 91 is open. Therefore, the ECU 10 sets the signal of the outside air temperature sensor SW11 to the ambient temperature Tc.

If the tunnel 91 has a closed structure, the ambient temperature around the exhaust pipe 21 may not match the outside air temperature. The ambient temperature in this case has a correlation with the wind speed 79 calculated above, the temperature of the air flowing into the tunnel 91, and the outer surface temperature of the exhaust pipe 21, for example. A temperature map may be created in advance based on statistical data of ambient temperature measured around the exhaust pipe 21, and the ECU 10 may calculate the ambient temperature around the exhaust pipe 21 based on the temperature map. good. The ECU 10 may calculate the ambient temperature around the exhaust pipe 21 using a model instead of the temperature map.

The ECU 10 calculates the first heat release amount Q1 by heat transfer from the exhaust pipe 21 to the outside based on the wind speed 79 and the ambient temperature Tc described above, and the temperature Tb of the exhaust pipe 21 . 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 32 as a functional block. The first heat radiation amount calculator 32 calculates a first heat radiation amount Q1 due to heat transfer from the exhaust pipe 21 to the outside.

The exhaust pipe 21 arranged in the tunnel 91 is surrounded by walls (that is, the floor surface) and the road surface that constitute the tunnel 91 . Heat dissipation from the exhaust pipe 21 to the outside includes heat dissipation due to heat transfer as well as heat dissipation due to radiation. The ECU 10 calculates a second heat release amount Q2 by radiation from the exhaust pipe 21 to the outside based on the temperature Tb of the exhaust pipe 21 and the road surface and/or floor surface temperature Td. The inventors of the present application have confirmed that the road surface and/or floor surface temperature Td substantially matches the ambient temperature Tc in the configuration example in which the tunnel 91 is open. The road surface and/or floor surface temperature Td can be equal to the outside air temperature 710 measured by the outside air temperature sensor SW11. If the vehicle has a configuration in which the road surface and/or floor surface temperature Td does not match the ambient temperature Tc, the ECU 10 may calculate the road surface and/or floor surface temperature Td separately from the ambient temperature Tc. .

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 33 as a functional block. The second heat release amount calculator 33 calculates a second heat release amount Q2 due to radiation from the exhaust pipe 21 to the outside.

The exhaust pipe 21 not only radiates heat to the outside, but also receives heat from the exhaust gas inside the exhaust pipe 21 . The ECU 10 calculates a third heat release amount Q3 due to heat transfer from the exhaust gas to the exhaust pipe 21 based on the temperature Ta of the exhaust gas in the exhaust pipe 21, the flow rate of the exhaust gas, and the temperature Tb of the exhaust pipe 21. . The third heat release amount Q3 is the amount of heat received by the exhaust pipe 21 . 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 34 as a functional block. The third heat release amount calculation unit 34 calculates a third heat release amount Q3 due to heat transfer from the exhaust gas to the exhaust pipe 21 based on the exhaust gas temperature Ta, the exhaust gas flow rate 72, and the temperature Tb of the exhaust pipe 21. calculate.

The ECU 10 calculates the temperature Tb of the exhaust pipe 21 based on the calculated heat release amounts Q1, Q2 and Q3. More specifically, the ECU 10 determines the temperature of the exhaust pipe 21 based on the difference between the heat quantities Q1 and Q2 radiated from the exhaust pipe 21 and the heat quantity Q3 received by the exhaust pipe 21 from the previous temperature of the exhaust pipe 21. Estimate Tb.

After estimating the temperature Tb of the exhaust pipe 21, the ECU 10 determines the temperature from the inlet to the outlet of the exhaust pipe 21 based on the temperature Tb of the exhaust pipe 21 and the thermal energy 73 of the exhaust gas introduced into the exhaust pipe 21. The amount of heat radiated from the exhaust gas to the exhaust pipe 21 is calculated until , and the temperature 70 of the exhaust gas in the sensor case 26 is estimated based on the amount of heat radiated. The ECU 10 has a temperature estimator 35 as a functional block.

The ECU 10 accurately measures the temperature of the exhaust gas in the sensor case 26 in the tunnel 91 based on the temperature of the exhaust pipe 21 calculated in consideration of the vehicle speed, the opening of the grille shutter 65, and the operating state of the cooling fan 42. can be estimated well.

FIG. 8 is a flowchart illustrating an exhaust gas temperature estimation procedure executed by the ECU 10 . It should be noted that the order of steps S1 to S11 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 4).

In step S<b>3 , the ECU 10 calculates the wind speed 79 around the exhaust pipe 21 based on the grille shutter opening 77 , the cooling fan 42 on/off 78 , the vehicle speed 76 , and the wind speed map 75 .

In step S4, the ECU 10 calculates a first heat release amount Q1 by heat transfer from the exhaust pipe temperature Tb, the wind speed 79, and the ambient temperature Tc (that is, the outside air temperature 710). Further, in step S5, the ECU 10 calculates a second heat release amount Q2 by radiation from the exhaust pipe temperature Tb and the road surface/floor surface temperature Td (=Tc, that is, the outside air temperature 710).

In step S6, the ECU 10 calculates a third heat release amount Q3 by heat transfer from the exhaust gas temperature Ta and the exhaust pipe temperature Tb.

Then, in step S7, the ECU 10 calculates the current exhaust pipe temperature Tb based on the previous exhaust pipe temperature and the heat release amounts Q1 to Q3 calculated in steps S4 to S6. , the amount of heat released from the exhaust gas to the exhaust pipe 21 is calculated from the exhaust gas thermal energy 73 calculated from the exhaust gas temperature 71 and the exhaust gas flow rate 72 at the outlet of the purification device 22, and the exhaust pipe temperature Tb. Calculate (ie, estimate) the temperature 70 of the exhaust gas within.

After calculating the temperature 70 of the exhaust gas in the sensor case 26, the ECU 10 determines whether or not the calculated temperature 70 of the exhaust gas exceeds a predetermined threshold in step S9. The threshold may be determined as a temperature at which condensed water is not generated from the exhaust gas. If the temperature exceeds the threshold, the process proceeds from step S9 to step S10. If the temperature is equal to or less than the threshold, that is, if the temperature of the exhaust gas inside the sensor case 26 is low, the process proceeds from step S9 to step S11. In step S10, the ECU 10 permits energization of the NOx sensor SW10 and measures the NOx concentration. In step S11, the ECU 10 prohibits energization of the NOx sensor SW10. It is avoided that the NOx sensor SW10 is energized while condensed water is attached. It is possible to prevent the NOx sensor SW10 from breaking down.

Of the heat release amounts Q1 to Q3 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 and Q3 if possible.

Also, 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)
21 exhaust pipe 26 sensor case 42 cooling fan (fan)
31 Wind speed calculator 32 First heat dissipation calculator 33 Second heat dissipation calculator 34 Third heat dissipation calculator 35 Temperature estimator 60 Grill (running wind inlet)
65 Grille shutter (control part)
90 Engine room 91 Tunnel 92 Dash panel SW10 NOx sensor

Claims (9)

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 fan that operates to promote the introduction of air into the engine room from the airflow introduction port;
an exhaust pipe disposed in a tunnel behind the dash panel and leading out exhaust gas from the engine;
a sensor attached to the exhaust pipe in the tunnel and outputting a signal regarding the properties of the exhaust gas;
a control unit to which the sensor is connected and which controls the engine based on the signal of the sensor;
The control unit also estimates the temperature of the exhaust gas in the vicinity of the mounting position of the sensor in time series by repeating the calculation at predetermined time intervals,
The control unit
calculating the wind speed of the air around the exhaust pipe from the opening of the running wind introduction port, the operating state of the fan, and the vehicle speed;
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 Tc around the exhaust pipe, and the temperature Tb of the exhaust pipe;
The temperature Tb of the exhaust pipe is estimated based on the previous temperature Tb of the exhaust pipe and at least the first heat release amount Q1 , and the estimated temperature Tb of the exhaust pipe and the exhaust gas introduced into the exhaust pipe an engine control device for estimating the temperature of the exhaust gas in the vicinity of the mounting position of the sensor based on the temperature Ta and the flow rate of the sensor. In the engine control device according to claim 1,
The control unit is configured based on a radiation model predetermined from the configuration of the tunnel, a temperature Tb of the exhaust pipe, and a temperature Td of a wall surrounding the exhaust pipe , which is a temperature related to the radiation model. to calculate a second heat release amount Q2 due to radiation from the exhaust pipe to the outside,
The engine control device, wherein the control unit estimates the temperature Tb of the exhaust pipe based on the previous temperature Tb of the exhaust pipe and at least the first heat release amount Q1 and the second heat release amount Q2 . 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 temperature Tb of the exhaust pipe, the control unit performs a third heat transfer by heat transfer from the exhaust gas to the exhaust pipe. Calculate the amount of heat release Q3 ,
The engine control device, wherein the control unit estimates the temperature Tb of the exhaust pipe based on the previous temperature Tb of the exhaust pipe and at least the first heat release amount Q1 and the third heat release amount Q3 . In the engine control device according to any one of claims 1 to 3,
The control unit of the engine, when the fan is off, calculates the wind speed higher when the opening of the running wind introduction port is larger than when the opening is small. 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 velocity higher when the running wind inlet is open and when the fan is on than when the fan is off. 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 fan is off and when the opening of the running wind introduction port is larger than when the opening is small. In the engine control device according to any one of claims 1 to 6,
An engine control device in which a rate of increase in wind speed with respect to an increase in vehicle speed is equal or substantially equal when the running wind inlet is open and when the fan is on and off. In the engine control device according to any one of claims 1 to 7,
The control device for an engine, wherein the control unit prohibits energization of the sensor when the estimated temperature of the exhaust gas is lower than a predetermined value. In the engine control device according to any one of claims 1 to 8,
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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