JP2020197179A - Control device for engine - Google Patents

Abstract

To accurately estimate a temperature of exhaust gas at an inlet of a purification device.SOLUTION: A control section (ECU 10) calculates wind speed 78 around an exhaust pipe (exhaust manifold 20) from an opening 77 of an adjustment section (grille shutter 65) and vehicle speed 76, calculates an atmospheric temperature Td around the exhaust pipe on the basis of the wind speed, a temperature 79 of air introduced into an engine room 90 and an outer surface temperature 710 of the exhaust pipe, calculates first heat radiation amount Q1 caused by heat transfer from the exhaust pipe to outside on the basis of the wind speed, the atmospheric temperature and an outer surface temperature Tc of the exhaust pipe, estimates a temperature (main body temperature Tb) of the exhaust pipe at least on the basis of the first heat radiation amount, and estimates a temperature 70 of exhaust gas at an inlet of a purification device 22 on the basis of the estimated temperature of the exhaust pipe and a temperature 71 and flow rate 72 of exhaust gas.SELECTED DRAWING: Figure 7

Description

The techniques disclosed herein relate to engine controls.

Patent Document 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 dissipation coefficient of the exhaust pipe based on the predicted temperature of the exhaust gas and the vehicle speed and the rotation speed of the cooling fan of the radiator. And, based on, the temperature of the exhaust pipe is predicted. Further, when the heat quantity of the exhaust pipe 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 near the exhaust pipe from being exposed to high temperatures.

JP-A-2015-190329

By the way, the exhaust pipe is equipped with a purification device that reduces harmful substances in the exhaust gas discharged from the engine. Purification equipment includes catalyst equipment and / or filter equipment. When the temperature of the catalyst device is lower than the active temperature, the purification rate of the exhaust gas becomes low. Therefore, it is preferable to maintain the temperature of the catalyst device at the active temperature or higher.

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

For example, by applying the technique described in Patent Document 1, it is conceivable that the control device estimates the temperature of the exhaust gas at the inlet of the purification device based on the operating state of the engine, heat dissipation of the exhaust pipe, and the like.

Here, the applicant of the present application proposes 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 that is significantly more lean than the stoichiometric air-fuel ratio when the engine is in a partial operating state. By burning a lean fuel mixture, the engine becomes more thermally efficient. As the thermal efficiency of the engine increases, the fuel efficiency of the vehicle improves.

In order for the engine to burn the lean mixture stably, it is advantageous that the temperature in the engine room is relatively high. Therefore, it is conceivable to provide an adjusting unit for changing the opening degree of the running wind introduction port at the running wind introduction port for introducing the running wind into the engine room. When the engine burns the lean air-fuel mixture, if the adjusting unit closes the running wind introduction port, the introduction of air into the engine room can be suppressed.

The temperature and wind speed in the engine room change depending on the opening and closing of the running wind inlet. Since the technique described in Patent Document 1 does not consider the influence of opening and closing of the traveling wind introduction port, it is not possible to accurately estimate the temperature of the exhaust gas at the inlet of the purification device.

The technique disclosed herein estimates the temperature of the exhaust gas at the inlet of the purification device with high accuracy.

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

The controller of this engine
The engine placed in the engine room and
An adjusting unit that changes the opening degree 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 the introduction of air is suppressed.
A purification device that reduces harmful substances in the exhaust gas of the engine,
An exhaust pipe arranged in the engine room while connecting the engine and the purification device
It includes a control unit that estimates the temperature of the exhaust gas at the inlet of the purification device and controls the engine according to the estimated temperature.

And the control unit
The wind speed of the air around the exhaust pipe is calculated from the opening degree of the traveling wind introduction port and the vehicle speed.
The ambient temperature around the exhaust pipe is calculated based on the wind speed, the temperature of the air introduced into the engine room, and the outer surface temperature of the exhaust pipe.
Based on the wind speed, the atmospheric temperature, and the outer surface temperature of the exhaust pipe, the first heat dissipation amount due to heat transfer from the exhaust pipe to the outside is calculated.
The purification device estimates the temperature of the exhaust pipe based on at least the first heat dissipation amount, and also based on the estimated temperature of the exhaust pipe and the temperature and flow rate of the exhaust gas introduced from the engine into the exhaust pipe. Estimate the temperature of the exhaust gas at the inlet of.

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

An adjustment unit is provided at the running wind introduction port for introducing running wind into the engine room. When the adjusting unit opens the running wind introduction port, air is introduced into the engine room from the running wind introduction port. When the adjusting unit closes the running wind introduction port, the introduction of air from the running wind introduction port into the engine room 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. The adjusting unit may be configured to switch the traveling wind introduction port between fully open and fully closed. The adjusting unit may be configured so that the traveling wind introduction port can be adjusted 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 traveling wind introduction port and the vehicle speed. For example, the wind speed may be measured around the exhaust pipe while changing the opening degree of the traveling wind introduction port and the vehicle speed, and a wind speed map may be created based on the statistical data. The control unit 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. In the same manner as described above, the ambient temperature may be measured around the exhaust pipe while changing each parameter, and a temperature map may be created based on the statistical data. The control unit can calculate the ambient temperature based on the created temperature map.

Once the wind speed and ambient temperature around the exhaust pipe are determined, the control unit can calculate the first heat dissipation 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 dissipation amount from the exhaust pipe to the outside is determined, the control unit can calculate the temperature of the exhaust pipe. Since the opening degree of the traveling wind introduction port is taken into consideration when calculating the first heat radiation amount from the exhaust pipe to the outside, the control unit can accurately calculate the temperature of the exhaust pipe.

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

The control unit calculates the second heat radiation 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 around the exhaust pipe.
The control unit may estimate the temperature of the exhaust pipe based on at least the first heat dissipation amount and the second heat dissipation amount.

The exhaust pipe arranged in the engine room is surrounded by various parts and the like. In addition to heat dissipation by heat transfer, heat dissipation from the exhaust pipe to the outside includes heat dissipation by radiation. The control unit calculates the second heat radiation 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 around the exhaust pipe. The wall around the exhaust pipe means the outer surface of the engine-related parts existing around the exhaust pipe and the parts constituting the engine room. The temperature of the wall around the exhaust pipe may be, for example, equal to the ambient temperature around the exhaust pipe calculated above. Since the opening degree of the traveling wind introduction port is taken into consideration when calculating the ambient temperature around the exhaust pipe, the control unit can accurately calculate the second heat radiation amount due to radiation.

The control unit can estimate the temperature of the exhaust pipe more accurately by estimating the temperature of the exhaust pipe based on at least the first heat radiation amount and the second heat radiation amount. 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 calculates a third heat dissipation amount by heat transfer from the exhaust gas to the exhaust pipe based on the temperature of the exhaust gas in the exhaust pipe, the flow rate of the exhaust gas, and the temperature of the exhaust pipe. And
The control unit may estimate the temperature of the exhaust pipe based on at least the first heat radiation amount and the third heat radiation amount.

In addition to dissipating heat to the outside, the exhaust pipe receives heat from the exhaust gas inside the exhaust pipe. The control unit is based on the temperature of the exhaust gas in the exhaust pipe, the flow rate of the exhaust gas, and the temperature of the exhaust pipe, and the third heat dissipation amount by heat transfer from the exhaust gas to the exhaust pipe, that is, the amount of heat received by the exhaust pipe. Is calculated. The control unit can estimate the temperature of the exhaust pipe more accurately by estimating the temperature of the exhaust pipe based on at least the first heat radiation amount and the third heat radiation amount. 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, a heat insulating material covering the main body, and an exodermis surrounding the heat insulating material.
The control unit calculates the fourth heat dissipation amount due to heat conduction of the exhaust pipe based on the temperature of the main body and the temperature of the exodermis.
The control unit may estimate the temperature of the exhaust pipe based on at least the first heat radiation amount and the fourth heat radiation amount.

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

The control unit can more accurately estimate the temperature of the exhaust pipe, more accurately, the temperature of the main body in contact with the exhaust gas, based on at least the first heat radiation amount and the fourth heat radiation amount. 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 speed higher when the opening degree of the traveling wind introduction port is larger than when it is smaller.

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

The rate of increase in the wind speed with respect to the increase in the vehicle speed may be higher when the opening degree of the traveling wind introduction port is large than when it is small.

As described above, when the opening degree of the traveling wind introduction port is large, the flow rate of the air introduced into the engine room from the traveling wind introduction port increases, so that the wind speed increases significantly when the vehicle speed increases. The control unit can accurately calculate the wind speed according to the opening degree of the traveling wind introduction port and the vehicle speed.

When the estimated exhaust gas temperature 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 low.

When the estimated exhaust gas temperature is higher than a predetermined value, the control unit may increase the amount of fuel supplied to the engine, for example. As the amount of fuel increases, the temperature of the exhaust gas emitted from the engine decreases due to the latent heat of vaporization of the fuel. When the temperature of the exhaust gas is lowered, it is suppressed that the temperature of the purification device becomes too high. The purification device can maintain reliability.

The running wind inlet is a grill provided at the front of the engine room.
The adjusting portion 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 part of an automobile exemplifying the arrangement of an engine, a purification device, and a sensor. FIG. 2 is a plan view of the front part of the automobile illustrating the arrangement of the engine and the purification device. FIG. 3 is an end view of the line III-III of FIG. FIG. 4 is a block diagram illustrating an engine control device. FIG. 5 is a diagram illustrating switching between opening and closing the grill shutter and turning on / off the cooling fan. FIG. 6 is a diagram for explaining a logic for estimating the gas temperature at the inlet of the purification device. FIG. 7 is a diagram illustrating an estimation logic of the gas temperature at the inlet of the purification device. FIG. 8 is a diagram illustrating a wind speed map showing the relationship between the vehicle speed, the opening / closing of the grill shutter, and the wind speed. FIG. 9 is a flowchart relating to the estimation logic of the gas temperature at the inlet of the purification device.

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

(Engine configuration)
FIG. 1 is a cross-sectional view of an automobile front portion exemplifying the arrangement of an engine, a purification device and a sensor, and FIG. 2 is a plan view of an automobile front portion exemplifying the arrangement of an engine and a purification device.

An engine 1 and a transmission 93 connected to the engine 1 are arranged in an engine room 90 at the front of the automobile. The engine 1 in the example is an in-line engine in which a plurality of cylinders 18 (four cylinders 18 in the example) are arranged in a row. 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 so-called transversely installed.

The engine 1 is a 4-stroke engine in which the cylinder 18 is operated by repeating an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. The fuel of the engine 1 is gasoline in this configuration example. The fuel may be at least a liquid fuel containing gasoline. The engine 1 is also a spark-ignition engine in which the spark plug 82 (see FIG. 4) ignites the air-fuel mixture in the 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 mounted 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 drawing out exhaust gas from the inside of 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 the 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 intake port 16 that opens toward the front of the automobile is formed at the upstream end of the intake pipe 15. 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. The exhaust manifold 20 derives exhaust gas from each cylinder 18. A purification device 22 is connected to the exhaust manifold 20. The purification device 22 reduces harmful substances in the exhaust gas. Although detailed illustration is omitted, the purification device 22 has a three-way catalyst and a GPF (Gasoline Particulate Filter).

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 in the tunnel 91. The tunnel 91 is connected to the dash panel 92. The dash panel 92 forms the rear part of the engine compartment 90. The space in the tunnel 91 is connected to the engine room 90. The lower part 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 purification device 22.

The engine 1 is provided with an EGR device. The EGR device returns a part of the exhaust gas to the intake air 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 regulates the amount of EGR gas recirculated to the intake air.

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

Here, the engine 1 performs SPCCI combustion, which is a combination of SI combustion and CI combustion, in a part of the operating region. In other operating regions, the engine 1 performs SI combustion. SPCCI combustion controls CI combustion by utilizing heat generation and pressure increase due to SI combustion. SPCCI combustion, including CI combustion, is advantageous in improving fuel efficiency and exhaust gas performance. When the engine 1 performs SPCCI combustion, there are cases where the air-fuel ratio of the air-fuel mixture is set to the stoichiometric air-fuel ratio (that is, stoichiometric SPCCI) and cases where the air-fuel ratio is leaner than the stoichiometric air-fuel ratio (that is, lean SPCCI). is there. When SI combustion is performed in the engine 1, the air-fuel ratio of the air-fuel mixture is set to the stoichiometric air-fuel ratio.

When the engine 1 performs lean SPCCI combustion, it is advantageous to keep the temperatures in the engine 1 and the engine room 90 relatively high for the stability of combustion. Therefore, this automobile is provided with a grill shutter 65 for adjusting the amount of air introduced into the engine room 90. The grill shutter 65 is an example of an adjustment unit.

The grill shutter 65 is provided on the grill 60. The grill shutter 65 has a plurality of fins 66 arranged in the vertical direction. Each fin 66 is configured to be rotatable. The grill shutter 65 has a minimum opening (that is, closed) when the direction of the fins 66 is perpendicular to the traveling direction of the automobile, and is opened when the orientation of the fins 66 is parallel to the traveling direction of the automobile. The degree is maximum (that is, fully open). FIG. 1 illustrates a state in which the opening degree of the grill shutter 65 is maximum. The opening degree of the grill shutter 65 can be set to an intermediate opening degree between the minimum and the maximum. The larger the opening degree of the grill shutter 65, the larger the opening degree of the grill 60, so that the flow rate of air introduced into the engine room 90 increases. When the grill shutter 65 is closed, the opening degree of the grill 60 becomes small and the introduction of air into the engine room 90 is restricted. When the introduction of air into the engine room 90 is restricted, the temperature in the engine room 90 becomes high. When the grill shutter 65 is opened and air is introduced into the engine room 90, the temperature in the engine room 90 drops. The radiator 40 cools the coolant of the engine 1 by the air introduced into the engine room 90. When the grill shutter 65 is opened and the cooling fan 42 is operated, the flow rate of the air introduced into the engine room 90 increases, so that the temperature in the engine room 90 further decreases. 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. Note that FIG. 2 illustrates the engine room 90 from which the heat insulating cover 50 has been removed. The heat insulating cover 50 covers the entire upper surface of the cylinder head 11 of the engine 1, the left and right side surfaces, and the rear surface. By covering the engine 1 with the heat insulating cover 50, the engine 1 is kept warm and the diffusion of the engine 1 sound 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 be lower than the active 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 maintain a high temperature of the exhaust gas introduced into the purification device 22. FIG. 3 shows an end view of the line III-III of FIG. The exhaust manifold 20 is composed of four main bodies 201 forming an independent exhaust pipe, a heat insulating material 202 that covers the periphery of the four main bodies 201, and a pair of outer skins 203 that surround the heat insulating material 202. The 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 the 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 of the engine 1. The engine control device includes an ECU (Engine Control Unit) 10. The ECU 10 is a controller based on a well-known microcomputer, and is composed of a central processing unit (CPU) 101 that executes a program, and for example, a RAM (Random Access Memory) or a ROM (Read Only Memory). It is provided with 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 unit.

Various sensors SW1 to SW11 are connected to the ECU 10. The sensors SW1 to SW11 output a signal to the ECU 10. The sensors include the following sensors.

Air flow sensor SW1: Arranged downstream of the air cleaner 17 in the intake pipe 15 and measure the flow rate of air flowing through the intake pipe 15 Intake temperature sensor SW2: Arranged downstream of the air cleaner 17 in the intake pipe 15 and the intake pipe In-cylinder pressure sensor SW3 that measures the temperature of the air flowing through the 15: EGR differential pressure sensor SW4 that is attached to the cylinder head 11 corresponding to each cylinder 18 and measures the pressure in the cylinder 18: is arranged in the EGR passage 23. In addition, the vehicle speed sensor SW5 that measures the pressure difference between the upstream and downstream of the EGR valve 25: the liquid temperature sensor SW6 that measures the vehicle speed of the automobile: the crank angle sensor SW7 that detects the liquid temperature of the coolant of the engine 1 is attached to the engine 1. Accelerator opening sensor SW8: which is attached to the accelerator pedal mechanism (not shown) and measures the accelerator opening corresponding to the operation amount of the accelerator pedal Fuel pressure sensor SW9: Fuel supply system which measures the rotation angle of the crank shaft. NOx sensor SW10 attached to 85 and measuring the pressure of fuel supplied to the injector 81: Outside temperature sensor SW11: attached to the exhaust pipe 21 downstream of the purification device 22 and measuring the NOx concentration in the exhaust gas. Measure the outside temperature in the environment where the car is running.

The ECU 10 determines the operating state of the engine 1 based on the signals of the sensors SW1 to SW11, and controls the devices 81 to 86, 25, 65, and 42 described later according to a predetermined control logic. Is calculated. The control logic is stored in the memory 102. The control logic includes calculating a target amount and / or a control amount using the operation map stored in the memory 102.

The ECU 10 outputs an electric signal related to the calculated control amount to the injector 81, the spark plug 82, the intake electric S-VT83, the exhaust electric S-VT84, the fuel supply system 85, the throttle valve 86, the EGR valve 25, the grill shutter 65, and the like. And, it outputs to the cooling fan 42.

The injector 81 is attached to the cylinder head 11 and injects fuel directly 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 intake electric S-VT83 is attached to the cylinder head 11 and continuously changes the rotation phase of the intake camshaft (not shown) within a predetermined angle range. The intake camshaft opens and closes an intake valve (not shown). The exhaust electric S-VT84 is attached to the cylinder head 11 and continuously changes the rotation phase of the exhaust camshaft (not shown) within a predetermined angle range. The exhaust camshaft opens and closes an exhaust valve (not shown). The 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 to adjust the amount of air introduced into the cylinder 18.

FIG. 5 shows a control example of the grill shutter 65 and the cooling fan 42 executed by the ECU 10. The ECU 10 opens and closes the grill 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, when the temperature of the coolant and / or the temperature in the engine room 90 is low, the ECU 10 closes the grill shutter 65 and turns off the cooling fan 42. As a result, the temperatures in the engine 1 and the engine room 90 are maintained high. The engine 1 can stably execute lean SPCCI combustion.

When the engine 1 executes stoichiometric SPCCI combustion or SI combustion, the coolant temperature and / or the temperature in the engine room 90 becomes high. The ECU 10 opens the grill shutter 65 when the coolant temperature and / or the temperature in the engine room 90 rises. As a result, air is introduced from the grill 60 into the engine room 90, so that the coolant of the engine 1 and the temperature in the engine room 90 are lowered.

When the coolant temperature and / or the temperature in the engine room 90 becomes higher, the ECU 10 opens the grill 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)
If the purification device 22 containing the three-way catalyst is below the active temperature, the purification rate of the exhaust gas is low. Therefore, it is preferable to maintain the purification device 22 at a temperature equal to or higher than the active temperature during the operation of the engine 1. On the other hand, while the automobile is running, for example, as the load on the engine 1 increases, the temperature of the exhaust gas may increase, 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 decrease. Therefore, the ECU 10 needs to accurately grasp the temperature of the exhaust gas introduced into the purification device 22 during the operation of the engine 1.

The engine control device disclosed here estimates the temperature of the exhaust gas introduced into the purification device 22 by calculation rather than by detecting it by a temperature sensor. The engine control device can omit the temperature sensor. In addition to reducing costs, omitting the temperature sensor also has the advantage of eliminating the need for repair or replacement of the temperature sensor due to deterioration or failure of the temperature sensor.

FIG. 6 is a diagram for explaining a logic for estimating the exhaust gas temperature at the inlet of the purification device 22. As described above, the engine 1 and the purification device 22 are arranged in the engine room 90. The engine 1 and the purification device 22 are connected to each other via an exhaust manifold 20. The exhaust gas discharged from the cylinder 18 of the engine 1 is introduced into the exhaust manifold 20 via the exhaust port 112. Exhaust gas dissipates heat while passing through the exhaust manifold 20 (see the arrow 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 radiated from 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 radiated from the exhaust manifold 20 to the outside is 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 (that is, the inner wall of the engine room) existing around the exhaust manifold 20. It is decided according to.

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

The ECU 10 may obtain the gas temperature 71 of the exhaust port by calculation. Although detailed description is omitted, the inventors of the present application have found that in the engine 1 that performs SPCCI combustion and SI combustion, there is a linear correlation between the combustion progress and the exhaust port gas temperature. .. Combustion progress is the crank angle when combustion has progressed to a certain degree. The crank angle (mfb50) at which the mass combustion ratio is, for example, 50% can be used as the 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 combustion progress is retarded, the exhaust port gas temperature rises, and when the combustion progress advances, the exhaust port gas temperature decreases. The ECU 10 can calculate the gas temperature 71 of the exhaust port by using a model or a map showing the relationship between the combustion progress and the gas temperature of the exhaust port.

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

The ECU 10 is based on the output signal of the air flow 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). The exhaust gas flow rate 72 discharged from the engine 1 can be calculated.

The ECU 10 also calculates the exhaust gas thermal energy 73 and the exhaust gas flow velocity 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 radiated from the exhaust manifold 20 to the outside. According to the study by the inventors of the present application, the wind speed of the air around the exhaust manifold 20 arranged on the rear side of the engine 1 has a correlation with the vehicle speed of the automobile and the opening degree of the grill shutter 65. I understood. Therefore, the wind speed map 75 is created in advance based on the statistical data of the wind speed measured around the exhaust manifold 20 while changing the vehicle speed and the opening degree of the grill 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 of the automobile obtained from the signal of the vehicle speed sensor SW5, and the opening degree 77 of the grill shutter 65 defined by the ECU 10.

Here, FIG. 8 illustrates the wind speed map 75. As described above, the wind speed map 75 defines the relationship between the vehicle speed, the opening degree of the grill shutter 65, and the wind speed of air around the exhaust manifold 20. When the vehicle speed is high, the flow rate of air flowing into the engine room 90 through the grill 60 and other parts increases. Therefore, the higher the vehicle speed, the higher the wind speed of air around the exhaust manifold 20.

Further, when the grill shutter 65 is open (that is, fully open), the flow rate of air flowing into the engine room 90 through the grill 60 is larger than when the grill shutter 65 is closed (that is, fully closed). Therefore, when the grill shutter 65 is open, the wind speed of air around the exhaust manifold 20 is higher than when it is closed.

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

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

Further, when the grill shutter 65 has an intermediate opening degree, the ECU 10 complements the straight line when the grill shutter 65 is fully open and the straight line when the grill shutter 65 is fully closed to exhaust the air. The wind speed of air around the manifold 20 may be calculated.

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

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

The ECU 10 also calculates the ambient temperature around the exhaust manifold 20. According to the study by the inventors of the present application, the ambient temperature of the exhaust manifold 20 is the wind speed 78 calculated above, the temperature of the air flowing into the engine room 90 (engine room inlet temperature 79), and the outer skin temperature of the exhaust manifold 20. It has a correlation with 710. Therefore, while changing each of 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.

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

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

The ECU 10 has an atmospheric temperature calculation unit 32 as a functional block. The atmosphere temperature calculation unit 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 outer skin temperature of the exhaust manifold 20.

The ECU 10 calculates the first heat dissipation amount Q1 by heat transfer from the exhaust manifold 20 to the outside based on the above-mentioned wind speed and atmospheric temperature Td and the outer skin temperature Tc of the exhaust manifold 20. The ECU 10 may calculate the first heat dissipation amount Q1 based on a predetermined heat transfer model. The ECU 10 has a first heat dissipation amount calculation unit 33 as a functional block. The first heat dissipation amount calculation unit 33 calculates the first heat dissipation amount Q1 by 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 radiation as well as heat dissipation by heat transfer. The ECU 10 calculates the second heat dissipation amount Q2 due to 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 engine-related parts 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 temperature Te of the inner wall of the engine room and the ambient temperature Td around the exhaust manifold 20 are substantially the same. The engine inner wall temperature Te can be set to be equal to the ambient temperature Td calculated using the temperature map 711. If the automobile 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 atmospheric temperature Td.

The ECU 10 may calculate the second heat dissipation amount Q2 based on a predetermined radiation model. The ECU 10 has a second heat dissipation amount calculation unit 34 as a functional block. The second heat dissipation amount calculation unit 34 calculates the second heat dissipation 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. The ECU 10 calculates the fourth heat dissipation amount Q4 due to heat conduction of the exhaust manifold 20 based on the temperature Tb of the main body and the outer skin temperature Tc. The ECU 10 may calculate the fourth heat dissipation amount Q4 based on a predetermined heat conduction model. The ECU 10 has a fourth heat dissipation amount calculation unit 35 as a functional block. The fourth heat radiation amount calculation unit 35 calculates the 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.

In addition to dissipating heat to the outside, the exhaust manifold 20 receives heat from the exhaust gas in the exhaust manifold 20. The ECU 10 calculates the third heat dissipation amount Q3 by 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 radiation amount Q3 is the heat reception amount of the main body 201. The ECU 10 may calculate the third heat dissipation amount Q3 based on a predetermined heat transfer model. The ECU 10 has a third heat dissipation amount calculation unit 36 as a functional block. The third heat dissipation amount calculation unit 36 is based on the exhaust gas temperature Ta, the flow rate 72 of the exhaust gas, and the temperature Tb of the main body 201, and the third heat dissipation amount by 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 dissipation amounts Q1, Q2, Q3 and Q4. More specifically, the ECU 10 subtracts the amount of heat Q1, Q2, Q4 radiated from the main body 201 and the amount of heat Q3 received by the main body 201 with respect to the previous temperature of the main body 201 of the exhaust manifold 20. Estimate the temperature Tb of.

Then, if the temperature Tb of the main body 201 is estimated, the ECU 10 determines the temperature Tb of the main body 201 and the heat energy 73 of the exhaust gas introduced into the exhaust manifold 20 from the inlet to the outlet of 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 estimation unit 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 degree of the grill shutter 65. it can.

FIG. 9 is a flowchart illustrating an exhaust gas temperature estimation procedure executed by the ECU 10. The order of steps S1 to S13 in this flowchart can be changed as much as possible.

First, in step S1 after the start, the ECU 10 reads the signals of the various sensors SW1 to SW11. In the following step S2, as described above, the ECU 10 sets the opening degree of the grill 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 ( (See FIG. 5).

In step S3, the ECU 10 calculates the wind speed 78 around the exhaust manifold 20 from the grill shutter opening degree 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 outer skin temperature 710, and the temperature map 711.

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

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

Then, in step S9, the ECU 10 calculates the current main body temperature Tb based on the previous main body temperature and the heat dissipation amounts Q1 to Q4 calculated in steps S5 to S8, and in the subsequent step S10, the ECU 10 exhausts. The amount of heat radiated from the exhaust gas to the exhaust manifold 20 is calculated 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, and the temperature of the exhaust gas at the inlet of the purification device 22. 70 is calculated (that is, estimated).

If the temperature 70 of the exhaust gas at the inlet of the purification device is calculated, the ECU 10 determines in the subsequent step S11 whether or not the calculated exhaust gas temperature 70 is less than a predetermined first threshold value. The first threshold value may be set 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. When the temperature is equal to or higher than the first threshold value, that is, when the temperature of the exhaust gas at the inlet of the purification device is high, the process proceeds from step S11 to step S13. In step S13, the ECU 10 increases the injection amount of fuel supplied 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 purification device is lowered. It is suppressed that the temperature of the purification device 22 becomes too high. It is suppressed that the reliability of the purification device 22 is lowered.

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 value. The second threshold value may be set 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, in step S13, the CU 10 increases the injection amount of the fuel supplied into the cylinder 18. As the temperature of the exhaust gas discharged from the engine 1 decreases, the temperature of the catalyst decreases. It is suppressed that the reliability of the purification device 22 is lowered.

In the above configuration, the exhaust manifold 20 has the heat insulating material 202, but 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, in the logic of FIG. 7, the ECU 10 omits the calculation of the fourth heat dissipation amount Q4 by the heat conduction of the exhaust manifold 20. Further, the ECU 10 calculates the heat dissipation amounts Q1 and Q2 by matching the outer skin temperature Tc with the exhaust manifold temperature Tb.

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

Further, the technique disclosed herein is not limited to application to the engine 1 that performs SPCCI combustion. The engine 1 to which the technique disclosed here can be applied is not particularly limited. The technique disclosed herein may be applied to a so-called spark-ignition engine or a gasoline engine that performs only SI combustion. Further, 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 Insulation material 203 Outer skin 22 Purifying device 31 Wind speed calculation unit 32 Atmosphere temperature calculation unit 33 1st heat dissipation calculation unit 34 2nd heat dissipation calculation unit 35 4th heat dissipation calculation unit 36 3rd heat dissipation calculation unit 37 Temperature estimation Part 60 Grill (running wind inlet)
65 Grill shutter (adjustment part)
90 engine room

Claims (8)

The engine placed in the engine room and
An adjusting unit that changes the opening degree 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 the introduction of air is suppressed.
A purification device that reduces harmful substances in the exhaust gas of the engine,
An exhaust pipe arranged in the engine room while connecting the engine and the purification device
A control unit that estimates the temperature of the exhaust gas at the inlet of the purification device and controls the engine according to the estimated temperature is provided.
The control unit
The wind speed of the air around the exhaust pipe is calculated from the opening degree of the traveling wind introduction port and the vehicle speed.
The ambient temperature around the exhaust pipe is calculated based on the wind speed, the temperature of the air introduced into the engine room, and the outer surface temperature of the exhaust pipe.
Based on the wind speed, the atmospheric temperature, and the outer surface temperature of the exhaust pipe, the first heat dissipation amount due to heat transfer from the exhaust pipe to the outside is calculated.
The purification device estimates the temperature of the exhaust pipe based on at least the first heat dissipation amount, and based on the estimated temperature of the exhaust pipe and the temperature and flow rate of the exhaust gas introduced from the engine into the exhaust pipe. An engine control device that estimates the temperature of the exhaust gas at the inlet of the engine. In the engine control device according to claim 1,
The control unit calculates the second heat radiation 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 around the exhaust pipe.
The control unit is an engine control device that estimates the temperature of the exhaust pipe based on at least the first heat dissipation amount and the second heat dissipation amount. In the engine control device according to claim 1 or 2.
The control unit calculates a third heat dissipation amount by heat transfer from the exhaust gas to the exhaust pipe based on the temperature of the exhaust gas in the exhaust pipe, the flow rate of the exhaust gas, and the temperature of the exhaust pipe. And
The control unit is an engine control device that estimates the temperature of the exhaust pipe based on at least the first heat dissipation amount and the third heat dissipation amount. In the engine control device according to any one of claims 1 to 3.
The exhaust pipe has a main body, a heat insulating material covering the main body, and an exodermis surrounding the heat insulating material.
The control unit calculates the fourth heat dissipation amount due to heat conduction of the exhaust pipe based on the temperature of the main body and the temperature of the exodermis.
The control unit is an engine control device that estimates the temperature of the exhaust pipe based on at least the first heat dissipation amount and the fourth heat dissipation amount. In the engine control device according to any one of claims 1 to 4.
The control unit is an engine control device that calculates the wind speed higher when the opening degree of the traveling wind introduction port is larger than when the opening degree is smaller. In the engine control device according to any one of claims 1 to 5.
The engine control device has a higher rate of increase in wind speed with respect to an increase in vehicle speed when the opening degree of the traveling wind introduction port is large than when it is small. In the engine control device according to any one of claims 1 to 6.
The control unit is an engine control device that controls the engine so that when the estimated exhaust gas temperature is higher than a predetermined value, the temperature of the exhaust gas introduced from the engine into the exhaust pipe is lowered. In the engine control device according to any one of claims 1 to 7.
The running wind inlet is a grill provided at the front of the engine room.
The adjusting unit is an engine control device which is a grill shutter provided on the grill.

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