JP2022120376A - Condensed water amount estimation device - Google Patents

Abstract

To highly accurately estimate the amount of condensed water generated in an intake passage of an engine system.SOLUTION: A control device executes processing including: a step (S100) of calculating a first moisture amount Aw1 included in intake air by using an estimation formula; a step (S102) of calculating a second moisture amount Aw2 included in exhaust gas and generated through fuel combustion by using an estimation formula; a step (S104) of calculating a saturated steam amount Aw3; a step (S106) of calculating a condensed water amount Aw4; a step (S108) of setting a correction coefficient Cs; and a step (S110) of calculating an accumulation amount Vw of condensed water.SELECTED DRAWING: Figure 3

Description

The present invention relates to estimation of the amount of condensed water generated in an intake passage of an engine system.

In the engine system, when the temperature of the intake passage in the early stage of warming up is lower than the dew point, the moisture contained in the gas flowing through the intake passage may condense to form condensed water in the intake passage. This condensed water may cause corrosion of components of the intake passage. Therefore, it is required to accurately estimate the amount of condensed water produced (hereinafter sometimes referred to as the amount of condensed water).

Regarding such estimation of the amount of condensed water, for example, Japanese Patent Application Laid-Open No. 2018-188991 (Patent Document 1) describes saturation from the amount of water in the mixed gas calculated using the sum of the intake air flow rate and the EGR gas flow rate. A technique is disclosed for calculating the amount of condensed water generated in the intercooler by subtracting the amount of water vapor.

JP 2018-188991 A

The estimation of the amount of condensed water as described above may be performed using, for example, a map showing the relationship between the intake air flow rate and the amount of condensed water. However, in order to improve the estimation accuracy of the amount of condensed water, it is required to set maps according to various operating conditions of the engine system. Therefore, it may not be possible to appropriately improve the accuracy of estimating the amount of condensed water due to restrictions such as the storage capacity of maps and the like and the number of man-hours for adapting maps and the like.

SUMMARY OF THE INVENTION An object of the present invention is to provide a condensed water amount estimating apparatus that can accurately estimate the amount of condensed water generated in an intake passage of an engine system. is.

A condensed water amount estimating device according to one aspect of the present invention is a condensed water amount estimating device that estimates the amount of condensed water generated in an intake passage of an engine system. The engine system includes cylinders connected to an intake passage. This condensed water amount estimator uses an estimation formula using the flow rate of the intake air taken into the intake passage, the concentration of water vapor contained in the intake air, the humidity of the intake air, the temperature of the intake air, and the atmospheric pressure. a first calculation unit that calculates a first water content contained in the intake air; a second calculation unit that calculates a saturated water vapor content in the intake passage; and a third calculation unit that calculates as an estimated value of

With this configuration, the first water content contained in the intake air flowing through the intake passage can be estimated with high accuracy by the estimation formula. Therefore, by subtracting the saturated water vapor amount from the first water amount, the estimated value of the amount of condensed water in the intake passage can be estimated with high accuracy.

In one embodiment, the engine system includes an exhaust gas recirculation device that returns a portion of the exhaust gas to the intake passage. The condensed water amount estimating device uses an estimation formula using the amount of fuel supplied to the cylinder and the recirculation rate of the exhaust gas returned to the intake passage to estimate the amount of condensed water contained in the exhaust gas flowing through the intake passage and generated by the combustion of the fuel. 2 It further comprises a fourth calculator that calculates the water content. The first calculator calculates the flow rate of the intake air taken into the intake passage, the concentration of water vapor contained in the intake air, the humidity of the intake air, the temperature of the intake air, the atmospheric pressure, and the amount of air returned to the intake passage. The first water content is calculated by an estimation formula using the recirculation rate of the exhaust gas and the recirculation rate of the exhaust gas. The second calculator calculates a saturated water vapor amount in a portion of the intake passage through which the exhaust gas flows. The third calculator calculates a value obtained by subtracting the saturated water vapor content from the sum of the first water content and the second water content as an estimated value of the amount of condensed water.

With this configuration, the first water content and the second water content contained in the exhaust gas flowing through the intake passage and generated by the combustion of the fuel can be estimated with high accuracy by the respective estimation formulas. Therefore, by subtracting the saturated water vapor content from the sum of the first water content and the second water content, the estimated value of the amount of condensed water in the intake passage can be estimated with high accuracy.

In one embodiment, the second calculator calculates the saturated water vapor amount corresponding to the wall surface temperature of the portion of the intake passage that is in contact with the exhaust gas.

In this way, condensed water is generated on the wall surface of the portion of the intake passage through which the exhaust gas flows. The amount of condensed water to be generated can be estimated with high accuracy.

Further, in another embodiment, the third calculator sets a correction coefficient for the estimated value corresponding to the surface area of the wall surface of the intake passage to which condensed water may adhere. The third calculator corrects the estimated value using the correction coefficient.

The amount of condensed water that adheres to the portion of the intake passage through which the exhaust flows can vary depending on the surface area of the wall surface of that portion. Therefore, by setting a correction coefficient for correcting the estimated value of the amount of condensed water corresponding to the surface area of the wall surface of the relevant part, and correcting the estimated value using the set correction coefficient, the amount of condensed water can be accurately adjusted. can be estimated to be high.

Furthermore, in another embodiment, the third calculator sets the correction coefficient using the wall surface temperature of the portion of the intake passage that is in contact with the exhaust.

The amount of condensed water that adheres to the portion of the intake passage through which the exhaust flows can vary depending on the surface area of the wall surface of the portion as well as the wall surface temperature. Therefore, a correction factor for correcting the estimated value of the amount of condensed water is set using the wall surface temperature in addition to the surface area, and the amount of condensed water is corrected by correcting the estimated value using the set correction factor. It can be estimated with high accuracy.

Further, in one embodiment, the condensed water amount estimator uses the notification device to notify predetermined information regarding the amount of condensed water when the estimated value of the amount of condensed water exceeds a threshold value.

In this way, the predetermined information regarding the amount of condensed water is notified to the user, thereby allowing the user to recognize the information.

Further, in one embodiment, the condensed water amount estimator reduces the flow rate of the exhaust gas returned to the intake passage by the exhaust gas recirculation device and reduces the exhaust gas flow rate when the estimated amount of condensed water exceeds a threshold value. Do any of the following: Stop returning to the intake passage.

In this way, an increase in the amount of condensed water produced can be suppressed, and corrosion of the intake passage can be suppressed.

According to the present invention, it is possible to provide a condensed water amount estimating device that accurately estimates the amount of condensed water generated in an intake passage of an engine system.

It is a figure showing an example of the schematic structure of the engine system concerning this embodiment. FIG. 3 is a diagram for explaining the relationship between a first water content contained in intake air, a second water content contained in EGR gas, a saturated water vapor content, and a condensed water content; It is a flowchart which shows an example of the process which estimates the amount of condensed water. FIG. 4 is a diagram for explaining an example of changes in the estimated value of the accumulated amount of condensed water under constant running conditions in an environment where the outside air temperature is low; FIG. 5 is a diagram for explaining an example of changes in the estimated value of the accumulated amount of condensed water under constant running conditions in an environment with a high outside air temperature; An example of a change in the estimated value of the accumulated amount of condensed water when the engine system 1 operates from the start of warm-up to the completion of warm-up is shown. 4 shows an example of changes in the estimated value of the accumulated amount of condensed water when the operating state in which the operation of the engine system 1 stops before completion of warming up is repeated.

Hereinafter, this embodiment will be described with reference to the drawings. In the following description, identical parts are provided with identical reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

FIG. 1 is a diagram showing an example of a schematic configuration of an engine system 1 according to this embodiment. As shown in FIG. 1, an engine system 1 includes an engine body 2, an intake manifold 10, an intake pipe 12, an exhaust gas recirculation device (hereinafter referred to as an EGR device) 20, an exhaust manifold 50, and an exhaust pipe. 52 and a turbocharger 60 . This engine system 1 is mounted, for example, on a moving object such as a vehicle.

The engine body 2 is an internal combustion engine such as a diesel engine or a gasoline engine including cylinders 4 and a fuel injection device 6 . In this embodiment, it is assumed that the engine body 2 is, for example, a four-stroke engine in which the output shaft rotates twice in one cycle.

An intake port and an exhaust port (both not shown) are connected to the top of the cylinder 4 of the engine body 2, and an intake manifold 10 is connected to the intake port. The engine body 2 is provided with, for example, a plurality of cylinders 4, and an intake manifold 10 is connected to intake ports connected to each cylinder.

The fuel injection device 6 supplies fuel into the cylinder 4 in response to a control signal C1 from the control device 100 . The fuel injection device 6 is provided, for example, at the top of the cylinder 4 and injects fuel directly into the cylinder. If the engine body 2 is a spark ignition gasoline engine, the fuel injection device 6 may be configured to supply fuel to an intake port, for example.

One end of an intake pipe 12 is connected to the intake manifold 10 . An air cleaner (not shown) is connected to the other end of the intake pipe 12 . During operation of the engine system 1 , air (intake air) sucked from the air cleaner flows through the intake pipe 12 to the intake manifold 10 . An “intake passage” of the engine system 1 is configured by the intake manifold 10 and the intake pipe 12 .

An exhaust manifold 50 is connected to the exhaust port of the engine body 2 . More specifically, an exhaust manifold 50 is connected to each exhaust port of a plurality of cylinders of the engine body 2 .

One end of an exhaust pipe 52 is connected to the exhaust manifold 50 . A silencer such as a muffler is provided at the other end of the exhaust pipe 52 . Various catalysts for purifying exhaust gas are provided in the middle of the exhaust pipe 52 . An “exhaust passage” is configured by the exhaust manifold 50 and the exhaust pipe 52 .

Turbocharger 60 includes a compressor 62 provided in intake pipe 12 and a turbine 64 provided in exhaust pipe 52 . The compressor 62 is provided with compressor blades (not shown) that are rotatably supported. The turbine 64 is provided with turbine blades that are rotatably supported and connected to compressor blades via a shaft 66 . Therefore, when the turbine blades are rotated by the exhaust energy supplied from the engine body 2 to the turbine 64 , the compressor blades are rotated via the shaft 66 and the intake air is compressed in the compressor 62 . The intake air thus compressed (supercharged) is cooled in an intercooler (not shown) provided in the intake pipe 12 and supplied to the engine body 2 via the intake manifold 10 .

In the engine body 2 , a mixture of intake air drawn from the intake manifold 10 via the intake pipe 12 and fuel supplied from the fuel injection device 6 into the cylinder 4 is combusted in the cylinder 4 . Combustion pressure is generated by combustion of the air-fuel mixture in the cylinder 4, the piston accommodated in the cylinder 4 operates, and an output shaft (none of which is shown) rotates via a crank mechanism or the like. Exhaust gas generated by the combustion of the air-fuel mixture in the cylinder 4 is discharged to the outside via the exhaust manifold 50 and the exhaust pipe 52 .

EGR device 20 is configured to return a portion of exhaust gas flowing through exhaust manifold 50 to intake manifold 10 . A part of the exhaust gas returned to the intake manifold 10 flows from the intake manifold 10 to the cylinder 4 together with the intake air. The introduction of the exhaust gas into the cylinder 4 lowers the combustion temperature, thereby reducing NOx emissions, and improving fuel efficiency by reducing intake loss and cooling loss. In the following description, part of the exhaust gas returned to the intake passage may be referred to as EGR gas.

EGR device 20 includes a first circulation passage 22 , a second circulation passage 24 and an EGR cooler 30 .

One end of first circulation passage 22 is connected to intake manifold 10 . The other end of first circulation passage 22 is connected to EGR cooler 30 .

The EGR cooler 30 includes an internally housed heat exchanger (not shown). The heat exchanger is configured, for example, so that cooling water that flows inside the engine body 2 flows. Therefore, in the heat exchanger, heat is exchanged between the EGR gas flowing through the EGR cooler 30 and the cooling water. As a result, the temperature of the EGR gas flowing through the EGR cooler 30 is lowered. By cooling the EGR gas in the EGR cooler 30, the volume of the EGR gas flowing through the first circulation passage 22 can be reduced, and much of the EGR gas can be returned to the intake passage.

The EGR device 20 is provided with an EGR valve (not shown). The EGR valve is a control valve that adjusts the flow rate of EGR gas flowing through the EGR device 20 by adjusting the degree of opening according to a control signal from the control device 100 .

One end of the second circulation passage 24 is connected to the EGR cooler 30 . The other end of the second circulation passage 24 is connected to the exhaust manifold 50 .

In the EGR device 20 configured as described above, part of the exhaust gas flowing through the exhaust manifold 50 is flowed as EGR gas, the flowed EGR gas is cooled in the EGR cooler 30, and the flow rate is adjusted by the EGR valve. It is returned to the intake manifold 10.

The control device 100 includes an air flow meter 102, an intake air temperature sensor 104, an engine speed sensor 106, a water temperature sensor 108, an atmospheric pressure sensor 110, an intake manifold temperature sensor 112, a boost pressure sensor 114, and an exhaust temperature sensor. 116 and notification device 130 are connected.

The air flow meter 102 is provided in the intake pipe 12 and detects a flow rate (hereinafter referred to as an intake air amount) Q of intake air flowing through the intake pipe 12 . The airflow meter 102 transmits a signal indicating the detected intake air amount Q to the control device 100 .

The intake air temperature sensor 104 is provided in the intake pipe 12 and detects the temperature of intake air flowing through the intake pipe 12 (hereinafter referred to as intake air temperature) Tin. The intake air temperature sensor 104 transmits a signal indicating the detected intake air temperature Tin to the control device 100 .

The engine rotation speed sensor 106 is provided in the engine body 2 and detects the rotation speed Ne of the output shaft of the engine body 2 (hereinafter referred to as engine rotation speed). The engine speed sensor 106 transmits a signal indicating the detected engine speed Ne to the control device 100 .

The water temperature sensor 108 is provided in the engine body 2 and detects the temperature (hereinafter referred to as water temperature) Tw of cooling water flowing through a cooling water passage (not shown) provided in the engine body 2 . Water temperature sensor 108 transmits a signal indicating detected water temperature Tw to control device 100 .

The atmospheric pressure sensor 110 detects the atmospheric pressure Pa. The atmospheric pressure sensor 110 transmits a signal indicating the detected atmospheric pressure Pa to the control device 100 .

Intake manifold temperature sensor 112 is provided in intake manifold 10 and detects a temperature (hereinafter referred to as intake manifold temperature) Tim in the intake manifold. Intake manifold temperature sensor 112 transmits a signal indicating detected intake manifold temperature Tim to control device 100 .

The supercharging pressure sensor 114 is provided in the intake manifold 10 and detects the pressure (hereinafter referred to as supercharging pressure) Pim in the intake manifold. The supercharging pressure sensor 114 transmits a signal indicating the detected supercharging pressure Pim to the control device 100 .

The exhaust temperature sensor 116 is provided in the exhaust pipe 52 and detects the temperature (hereinafter referred to as exhaust temperature) Tex of the exhaust gas flowing through the exhaust pipe 52 . Exhaust temperature sensor 116 transmits a signal indicating the detected exhaust temperature Tex to control device 100 .

The notification device 130 notifies the user of predetermined information. The notification method may be, for example, a method of notifying the predetermined information by displaying character information on the screen, a method of notifying the predetermined information by displaying a warning light, or Alternatively, the predetermined information may be notified by generating a predetermined voice or a predetermined warning sound.

Control device 100 includes a CPU (Central Processing Unit) that performs various processes, a ROM (Read Only Memory) that stores programs and data, and a RAM (Random Access Memory) that stores CPU processing results and the like. include.

The control device 100 includes various sensors (for example, the airflow meter 102, the intake air temperature sensor 104, the engine speed sensor 106, the water temperature sensor 108, the atmospheric pressure sensor 110, the intake manifold temperature sensor 112, the supercharging pressure sensor 114, and the exhaust temperature sensor. 116), and maps and programs stored in memory, various devices (for example, fuel injection device 6, notification device 130, EGR valve, etc.) are controlled so that engine system 1 is in a desired operating state. to control. Various types of processing executed by the control device 100 are not limited to processing by software, and can be processed by dedicated hardware (electronic circuit).

In the engine system 1 as described above, when warm-up is started by starting operation when the water temperature Tw is lower than the threshold value, the longer the operating time of the engine system 1 is, the more The temperature of each part rises.

However, when the temperature of intake manifold 10 is low, such as during warm-up of engine system 1 , condensed water may be generated in intake manifold 10 due to the operation of EGR device 20 . When the EGR device 20 operates, the EGR gas flows through the intake manifold 10, and the EGR gas flowing through the intake manifold 10 contacts the wall surface of the intake manifold 10 whose temperature is lower than the dew point of FIG. Water in the intake air indicated by the arrow in (A) and in the EGR gas indicated by the arrow in (B) in FIG. It is for In addition, if a certain amount of condensed water is generated before the warm-up is completed, the condensed water is acidified by a chemical reaction with the exhaust components of the EGR gas, which may cause corrosion in the intake manifold 10. . Therefore, it is required to estimate the amount of condensed water produced (hereinafter referred to as the amount of condensed water), and to limit the operation of the EGR device 20 or notify the user as necessary.

The amount of condensed water in intake manifold 10 may be estimated using, for example, a map showing the relationship between the amount of condensed water and the sum of the intake air amount and the flow rate of EGR gas. However, in order to improve the estimation accuracy of the amount of condensed water, it is required to set maps according to various operating states of the engine system 1 . Therefore, it may not be possible to appropriately improve the accuracy of estimating the amount of condensed water due to restrictions such as the storage capacity of maps and the like and the number of man-hours for adapting maps and the like.

Therefore, in the present embodiment, control device 100 includes the following configuration.

That is, the control device 100 uses an estimation formula using the intake air amount, the concentration of water vapor contained in the intake air, the humidity of the intake air, and the recirculation rate of the exhaust gas returned to the intake manifold 10 to control the inside of the intake manifold 10. A calculator (1) 120 for calculating a water content (hereinafter referred to as a first water content) Aw1 contained in the circulating intake air is included.

Furthermore, the control device 100 determines the amount of water contained in the EGR gas and generated by the combustion of the fuel (hereinafter referred to as the second water amount) by an estimation formula using the amount of fuel supplied to the cylinder 4 and the recirculation rate of the exhaust gas. A calculation unit (2) 122 for calculating Aw2 is further included.

Furthermore, the control device 100 further includes a calculation section (3) 124 that calculates the saturated water vapor amount Aw3 in the portion of the intake manifold 10 through which the EGR gas flows.

Further, the control device 100 further includes a calculation unit (4) 126 that calculates a value obtained by subtracting the saturated water vapor content Aw3 from the sum of the first water content Aw1 and the second water content Aw2 as the estimated value Aw4 of the condensed water content. . A condensed water amount estimation device according to the present embodiment is implemented by control device 100 .

FIG. 2 is a diagram for explaining the relationship between the first water content Aw1 contained in the intake air, the second water content Aw2 contained in the EGR gas, the saturated water vapor content Aw3, and the condensed water content Aw4.

The sum of the first water content Aw1 contained in the intake air shown in (a) of FIG. 2 and the second water content Aw2 contained in the EGR gas shown in (b) of FIG. It is the total amount of water that is absorbed. Of these, only the saturated water vapor amount Aw3 shown in (c) of FIG. 2 can exist as water vapor. Therefore, a value obtained by subtracting the saturated water vapor amount Aw3 from the sum of the first water amount Aw1 and the second water amount Aw2 corresponds to the condensed water amount Aw4 shown in (d) of FIG.

Therefore, the first water content Aw1 contained in the intake air flowing through the intake manifold 10 and the second water content Aw2 contained in the EGR gas flowing through the intake manifold 10 can be estimated with high accuracy by respective estimation formulas. Therefore, the estimated value Aw4 of the amount of condensed water in the intake manifold 10 can be estimated with high accuracy by subtracting the saturated water vapor amount Aw3 from the sum of the first water amount Aw1 and the second water amount Aw2.

Hereinafter, an example of processing executed by the control device 100 will be described with reference to FIG. 3 . FIG. 3 is a flowchart showing an example of processing for estimating the amount of condensed water.

At step (hereinafter referred to as S) 100, control device 100 (that is, calculation unit (1) 120) calculates first water content Aw1. The estimation formula for estimating the first water content Aw1 [g/s] is the following formula (1 ) can be represented by

Aw1=Qa×Cw1×H/100 [%]/(1−R) (1)
Here, the control device 100 acquires the intake air amount Qa using the detection result of the airflow meter 102 . The water vapor concentration Cw1 indicates the ratio of water vapor in the intake air. An estimation formula for the water vapor concentration Cw1 can be expressed by the following formula (2) using the saturated water vapor pressure Pw1 [kPa] of the intake air and the atmospheric pressure (pressure of the intake air) Pa [kPa].

Cw1=Pw1/Pa (2)
Furthermore, the estimation formula for the saturated water vapor pressure Pw1 [kPa] of the intake air can be expressed by the following formula (3) ((Formula of Tetens (1930))) using the atmospheric temperature t [°C].

Pw1==0.61078×10 ^{(7.5t/(t+237.3))} (3)
The control device 100 acquires the atmospheric temperature t using the detection result of the intake air temperature sensor 104 . Control device 100 calculates atmospheric temperature t using, for example, a map showing the relationship between intake air temperature Ti and atmospheric temperature t and intake air temperature Tin detected by intake air temperature sensor 104 . The map showing the relationship between the intake air temperature Tin and the atmospheric temperature t is, for example, a one-dimensional map, adapted experimentally or by design, determined in advance, and stored in the memory of the control device 100 .

The control device 100 calculates the saturated water vapor pressure Pw1 of the intake air using the acquired temperature t of the atmosphere and the estimation formula shown in the formula (3). Control device 100 acquires atmospheric pressure Pa using the detection result of atmospheric pressure sensor 110 . The control device 100 calculates the water vapor concentration Cw1 using the acquired atmospheric pressure Pa, the calculated Pw1, and the estimation formula shown in Equation (2).

Humidity H in formula (1) is, for example, a predetermined humidity. In this embodiment, it is assumed that the predetermined humidity is 100%, for example.

The recirculation rate R in the formula (1) is a value (EGR rate) indicating the ratio of the EGR gas to the gas taken into the cylinder 4 . The control device 100 estimates the EGR gas flow rate Qegr based on, for example, a value indicating the operating state of the engine system 1 such as the opening of the EGR valve, and combines the estimated EGR gas flow rate with the estimated EGR gas flow rate Qegr. The reflux rate R is calculated by dividing by the sum of the intake air amount Qa and the fuel amount. Note that the estimation of the EGR rate may be performed using a well-known technique, and is not limited to the calculation method described above.

The first water content Aw1 is the water content derived from the intake air, and includes the water content derived from the intake air contained in the recirculated EGR gas in addition to the water content contained in the air taken in from the air cleaner. Therefore, the relationship between the first water content Aw1, the water content A contained in the intake air, and the reflux rate R is expressed by the formula Aw1=A+(Aw1×R), where Aw1=A/(1 -R) is established. Therefore, in the formula (1), 1/(1−R) is multiplied in order to include the water content derived from the intake air contained in the EGR gas recirculated from the EGR device 20 in the first water content Aw1.

The control device 100 calculates the first water content Aw1 using the acquired intake air amount Qa and humidity H, the calculated water vapor concentration Cw1, humidity H and reflux rate R, and equation (1).

In S102, control device 100 (that is, calculation unit (2) 122) calculates second water content Aw2. The estimation formula for estimating the second water content Aw2 [g/s] can be expressed by the following formula (4) using the fuel amount Af [g/s], the constant Co, and the reflux rate R. can.

Aw2=Af×Co×R/(1−R) (4)
The fuel amount Af indicates the fuel amount (fuel mass) injected in the cylinder 4 per unit time. The estimation formula for the fuel amount Af is the volume of fuel injected per stroke Vf [mm ³ /st], the engine speed Ne [rpm], the number of cylinders N, and the fuel density ρf [g/mm ³ ]. It can be represented by the following formula (5) using and.

Af=Vf×Ne/60 [s]/2/N×ρf (5)
Control device 100 acquires volume Vf of fuel injected per stroke using, for example, a control command value for fuel injection device 6 . Control device 100 acquires engine speed Ne using the detection result of engine speed sensor 106 . The number of cylinders N and fuel density ρf in equation (5) are predetermined values and stored in the memory of control device 100 in advance. Therefore, the control device 100 acquires the number of cylinders N and the fuel density ρf from the memory.

The control device 100 calculates the fuel amount Af using the acquired volume Vf, the engine speed Ne, the number of cylinders N, the fuel density ρf, and the estimation formula shown in Equation (5).

The constant Co in equation (4) indicates the amount of water that can be produced from a given amount (eg, 1 g) of fuel, and is determined by the properties of the fuel (eg, the weight ratio of carbon and hydrogen (C/H ratio)). value. The constant Co is set to, for example, half the C/H ratio.

Since the reflux rate R in formula (4) is as described above, detailed description thereof will not be repeated. The second water content Aw2 is a combustion-derived water content, and includes the combustion-derived water content contained in the recirculated portion of the EGR gas in addition to the water content generated by the combustion of the fuel. Therefore, the relationship between the second water content Aw2, the water content B generated by the combustion of the injected fuel, and the reflux rate R is expressed by the formula Aw2=(Aw2+B)×R, where Aw2=B A relational expression of ×R/(1-R) holds. Therefore, in formula (4), R/( 1-R) are multiplied.

The control device 100 calculates the second water content Aw2 using the calculated fuel amount Af and the reflux rate R, the obtained constant Co, and equation (4).

At S104, control device 100 (that is, calculation unit (3) 124) calculates saturated water vapor amount Aw3. The estimation formula for estimating the saturated water vapor amount Aw3 [g/s] is the number of moles M [mol/s] of the gas in the intake manifold 10, the water vapor concentration Cw2 in the intake manifold 10, and the water per mole can be represented by the following formula (6) using the molecular weight L1 [g/mol] of

Aw3=M×Cw2×L1 (6)
The molecular weight L1 of water per mole in formula (6) is 18 [g/mol]. The calculation formula for calculating the number of moles M [mol/s] of the gas in the intake manifold 10 is based on the amount of air drawn into the intake manifold 10 Qb [g/s], the average gas molecular weight L2 [g/mol ] and the following formula (7).

M=Qb×L2 (7)
The control device 100 acquires the air amount Qb taken into the intake manifold 10 from, for example, the intake air amount Qa and the supercharging pressure. The supercharging pressure may be detected using a supercharging pressure sensor (not shown), or may be estimated from the operating state of the engine system 1, for example.

The average gas molecular weight L2 in equation (7) is, for example, a predetermined value experimentally set and stored in advance in the memory of control device 100 . Therefore, the control device 100 acquires the average gas molecular weight L2 from the memory.

The control device 100 calculates the number of moles M of gas in the intake manifold 10 using the acquired air amount Qb, average gas molecular weight L2, and equation (7).

The water vapor concentration Cw2 indicates the ratio of water vapor in the gas inside the intake manifold 10 . The estimation formula for the water vapor concentration Cw2 is expressed by the following formula (8) using the saturated water vapor pressure Pw2 [kPa] of the gas within the intake manifold 10 and the pressure (supercharging pressure) Pim [kPa] within the intake manifold 10. can be done.

Cw2=Pw2/Pim (8)
Furthermore, the equation for estimating the saturated water vapor pressure Pw2 [kPa] of the gas in the intake manifold is expressed by the following equation (9) (equation of Tetense (1930)) using the temperature T [° C.] in the intake manifold 10. can be done.

Pw2=0.61078×10 ^{(7.5T/(T+237.2))} (9)
Control device 100 estimates wall surface temperature Twl [° C.] of a predetermined portion in intake manifold 10 where condensed water is generated. Control device 100 calculates temperature T in intake manifold 10 using, for example, a map showing the relationship between wall surface temperature Twl and temperature T in intake manifold 10 and estimated wall surface temperature Twl. The map showing the relationship between the wall surface temperature Twl and the temperature T in the intake manifold 10 is, for example, a one-dimensional map, adapted experimentally or by design, determined in advance, and stored in the memory of the control device 100. be done. The predetermined portion where condensed water is generated in intake manifold 19 includes, for example, a portion of the pipes forming intake manifold 10 whose temperature is the least likely to rise during warm-up.

Further, the wall surface temperature Twl is estimated by the control device 100 using a flow rate Qb [g/s] of the gas in the intake manifold 10, a temperature Tim [°C] of the intake manifold 10, and a temperature Tegr [°C] of the EGR gas. and the flow rate Qegr [g/s] of the EGR gas.

Twl=a×(Qb×Tim+Tegr×Qegr)+b (10)
The control device 100 sets a using the water temperature Tw and the intake air temperature Tin. For example, the control device 100 sets a value obtained by multiplying the base value Ba by a correction coefficient Ca1 set using the water temperature Tw and a correction coefficient Ca2 set using the intake air temperature Tin.

Control device 100 sets correction coefficient Ca1 using, for example, a map showing the relationship between water temperature Tw and correction coefficient Ca1, and water temperature Tw, and uses a map showing the relationship between intake air temperature Tin and correction coefficient Ca2 and a map showing the relationship between intake air temperature Tin and correction coefficient Ca2. A correction coefficient Ca2 is set using the temperature Tin. A map indicating the relationship between the water temperature Tw and the correction coefficient Ca1 and a map indicating the relationship between the intake air temperature Tin and the correction coefficient Ca2 are each adapted experimentally or by design, and stored in the memory of the control device 100. stored in

Furthermore, the control device 100 sets b using the water temperature Tw and the intake air temperature Tin. For example, the control device 100 sets a value obtained by multiplying the base value Bb by a correction coefficient Cb1 set using the water temperature Tw and a correction coefficient Cb2 set using the intake air temperature Tin as b.

Control device 100 sets correction coefficient Cb1 using, for example, a map showing the relationship between water temperature Tw and correction coefficient Cb1 and water temperature Tw, and uses a map showing the relationship between intake air temperature Tin and correction coefficient Cb2, and a map showing the relationship between intake air temperature Tin and correction coefficient Cb2. A correction coefficient Cb2 is set using the temperature Tin. The map indicating the relationship between the water temperature Tw and the correction coefficient Cb1 and the map indicating the relationship between the intake air temperature Tin and the correction coefficient Cb2 are each adapted experimentally or by design, and stored in the memory of the control device 100. stored in

Also, since the method of obtaining the flow rate Qb and the flow rate Qegr is as described above, detailed description thereof will not be repeated. Control device 100 acquires temperature Tim of intake manifold 10 using the detection result of intake manifold temperature sensor 112, for example. Control device 100 may estimate temperature Tim of intake manifold 10 using water temperature Tw, for example.

The control device 100 calculates the temperature Tegr of the EGR gas using an estimation formula. An estimation formula for the temperature Tegr of the EGR gas can be expressed by the following formula (11) using the exhaust temperature Tex, the water temperature Tw, and the temperature Texm of the exhaust gas flowing through the exhaust manifold 50 .

Tegr=Tex−Texm×(Tex−Tw) (11)
Control device 100 acquires water temperature Tw and exhaust temperature Tex using the detection results of water temperature sensor 108 and exhaust temperature sensor 116, respectively. Control device 100 acquires temperature Texm, for example, using water temperature Tw and exhaust temperature Tex. Control device 100 may acquire temperature Texm by a temperature sensor (not shown) provided in exhaust manifold 50, for example. The control device 100 calculates the EGR gas temperature Tegr using the obtained temperatures Tex, Texm and Tw and the equation (11).

The control device 100 calculates the wall surface temperature Twl using the acquired flow rates Qb, Qegr, and Tim, the calculated Tegr, the set a and b, and equation (10). Control device 100 obtains pressure Pim in intake manifold 10 using the detection result of supercharging pressure sensor 114 .

The control device 100 calculates the temperature T inside the intake manifold 10 using the calculated wall surface temperature Twl, and calculates the saturated water vapor pressure Pw2 using the calculated temperature T and equation (9). Control device 100 calculates water vapor concentration Cw2 using calculated Pw2, pressure (supercharging pressure) Pim in intake manifold 10, and equation (8). The control device 100 calculates the saturated water vapor amount Aw3 using the calculated number of moles M of the gas in the intake manifold 10, the water vapor concentration Cw2, the molecular weight L1 of water per mole, and equation (6). .

At S106, control device 100 (that is, calculation unit (4) 126) calculates condensed water amount Aw4. A formula for calculating the amount of condensed water Aw4 can be represented by the following formula (12) using the first water content Aw1, the second water content Aw2, and the saturated water vapor content Aw3.

Aw4=Aw1+Aw2-Aw3 (12)
The control device 100 uses the first water content Aw1 calculated in S100, the second water content Aw2 calculated in S102, the saturated water vapor content Aw3 calculated in S104, and equation (12). to calculate the amount of condensed water Aw4.

In S108, control device 100 (for example, calculation unit (4) 126) sets correction coefficient Cs. The amount of condensed water adhering inside the intake manifold 10 correlates with the surface area of the wall portion inside the intake manifold 10 to which the condensed water can adhere. Therefore, for example, a one-dimensional map showing the relationship between the surface area of the plane portion and the correction coefficient is set experimentally or by design, and the reference value of the correction coefficient is set in advance using the surface area of the plane portion of the intake manifold 10. and stored in the memory of the control device 100 . Furthermore, the amount of condensed water adhering inside the intake manifold 10 correlates with the wall surface temperature inside the intake manifold 10 . Therefore, the control device 100 sets the correction coefficient Cs by, for example, multiplying the reference value described above by a coefficient corresponding to the wall surface temperature. Control device 100 sets a coefficient corresponding to the wall surface temperature, for example, using a map or the like indicating the relationship between the wall surface temperature and the coefficient. A map or the like showing the relationship between the wall surface temperature and the coefficient is, for example, adapted experimentally or by design so as to be corrected to the actual amount of condensed water, and stored in the memory of the control device 100 in advance.

At S110, control device 100 (for example, calculation unit (4) 126) calculates accumulated amount Vw of condensed water (an integrated value of the amount of condensed water). The formula for calculating the accumulated amount of condensed water Vw includes the current value Vw (n) of the accumulated amount of condensed water, the amount of condensed water Aw4, the correction coefficient Cs, and the amount of scavenging air (the amount of water sucked into the cylinder during the intake stroke). ) and the previous value Vw(n−1) of the accumulated amount of condensed water are expressed by the following equation (13).

Vw(n)=Aw4×Cs+Vw(n−1)−Aw5(n) (13)
The control device 100 controls the amount of condensed water Aw4 calculated in S106, the correction coefficient Cs set in S108, and the previous value Vw (n−1) of the accumulated amount of condensed water stored in the memory of the control device 100. , and the current value Vw(n) of the accumulated amount of condensed water is calculated as the accumulated amount Vw of the condensed water using equation (13). Control device 100 estimates scavenging air amount Aw5 using wall surface temperature Twl, flow rate Qb in intake manifold 10, and water temperature Tw. As for the method of estimating the scavenging amount Aw5, a well-known technique may be used, and detailed description thereof will not be given.

The operation of the control device 100 based on the above structure and flow chart will be described with reference to FIGS. 4 and 5. FIG.

For example, when the engine body 2 is warmed up, the temperatures of the intake pipe 12 and the intake manifold 10 are low. water is produced.

At this time, the first water content Aw1 is calculated by the estimation formula (1) using the intake air amount Qa, the humidity H, the water vapor concentration Cw1, the humidity H, and the reflux rate R (S100). Further, the second water content Aw2 is calculated by the estimation formula shown in formula (4) using the fuel amount Af, the reflux rate R, and the constant Co (S102). Then, the saturated water vapor amount is calculated by the estimation formula (6) using the number of moles M of the gas in the intake manifold 10, the water vapor concentration Cw2, and the molecular weight L1 of water per mole (S104). .

A condensed water amount Aw4 is calculated by subtracting the saturated water vapor amount Aw3 from the sum of the calculated first water amount Aw1 and second water amount Aw2 (S106). When the correction coefficient Cs is set based on the wall surface temperature Twl (S108), the condensed water amount Aw4 is corrected using the correction coefficient Cs, and the scavenging air amount Aw5 is subtracted from the corrected value (Aw4×Cs). The amount of condensed water generated in the intake manifold is calculated, and the calculated value is added to the previous value of accumulated amount Vw of condensed water to calculate the current value of accumulated amount Vw of condensed water (S110).

In this way, the first water content Aw1 and the second water content Aw2 are calculated individually by the respective estimation formulas, and the saturated water vapor content Aw3 is calculated using the wall surface temperature Twl. It becomes possible to estimate the quantity Vw with high accuracy.

Therefore, for example, when the EGR device 20 is controlled using the accumulated amount Vw of condensed water, the control accuracy of the EGR device 20 can be improved. Alternatively, an appropriate notification is performed when performing a notification process of notifying the user of information about condensed water (hereinafter also referred to as condensed water information) using the notification device 130 using the accumulated amount Vw of condensed water. It becomes possible to

FIG. 4 is a diagram for explaining an example of changes in the estimated value of the accumulated amount of condensed water under constant driving conditions in an environment with a low outside air temperature. The horizontal axis of FIG. 4 indicates time. The vertical axis in FIG. 4 indicates the accumulated amount of condensed water.

LN1 in FIG. 4 shows an example of a change in the accumulated amount of condensed water when the amount of condensed water is estimated using, for example, the intake air amount Qa and the engine speed Ne. LN2 in FIG. 4 shows an example of a change in the accumulated amount of condensed water when the process of estimating the above-described amount of condensed water is executed.

For example, in an environment where the outside air temperature is low, by calculating the accumulated amount of condensed water in consideration of the wall temperature, as shown by LN1 and LN2 in FIG. be able to. Therefore, when the notification control is performed to notify the user of the condensed water information indicating that the accumulated amount of condensed water exceeds the threshold using the notification device 130 when the accumulated amount of condensed water exceeds the threshold. , unnecessary notification of the information to the user using the notification device 130 is suppressed. Alternatively, when the accumulated amount of condensed water exceeds a threshold value, the EGR valve of the EGR device 20 is controlled to the closing side to reduce the flow rate of EGR gas, and EGR control is performed to suppress an increase in the amount of generated condensed water. In the case of execution, unnecessary restriction of the operation of the EGR device 20 to deteriorate the fuel consumption or decrease the NOx purification performance is suppressed.

FIG. 5 is a diagram for explaining an example of changes in the estimated value of the accumulated amount of condensed water under certain driving conditions (the same driving conditions as those described above) in an environment where the outside air temperature is high. The horizontal axis of FIG. 5 indicates time. The vertical axis in FIG. 5 indicates the accumulated amount of condensed water.

LN3 in FIG. 5 shows an example of a change in the accumulated amount of condensed water when the amount of condensed water is estimated using, for example, the intake air amount Qa and the engine speed Ne. LN4 in FIG. 5 shows an example of a change in the accumulated amount of condensed water when the process of estimating the above-described amount of condensed water is executed.

For example, in an environment where the outside air temperature is high, by calculating the accumulated amount of condensed water in consideration of the wall surface temperature, as shown by LN3 and LN4 in FIG. 5, underestimation of the accumulated amount of condensed water is suppressed. be able to. Therefore, when the notification control is executed according to the accumulated amount of condensed water as described above, the user who uses the notification device 130 even though the accumulated amount of condensed water actually exceeds the threshold value is notified to the user. A state in which notification of condensed water information is not performed is suppressed. Alternatively, when EGR control is executed in accordance with the accumulated amount of condensed water as described above, the fact that the EGR control is not executed when the accumulated amount of condensed water exceeds the threshold value is suppressed. be. Therefore, promotion of corrosion in the intake manifold 10 is suppressed.

FIG. 6 shows an example of changes in the estimated value of the accumulated amount of condensed water when the engine system 1 operates from the start of warm-up to the completion of warm-up. The vertical axis in FIG. 6 indicates the accumulated amount of condensed water. The horizontal axis of FIG. 6 indicates time. LN5 in FIG. 6 shows an example of changes in the accumulated amount of condensed water. For example, assume that the operation is started while the engine system 1 is cold.

At time zero, when the engine system 1 starts operating, the EGR valve opens and the exhaust gas flows through the intake manifold 10 via the EGR device 20 as EGR gas. When the wall surface temperature inside the intake manifold is low, water in the intake air and EGR gas is condensed, so the estimated value of the accumulated amount of condensed water increases. As the operation of the engine system 1 continues, the wall surface temperature inside the intake manifold rises. Therefore, condensation of water in the intake air and EGR gas is suppressed, and the scavenging amount increases. As a result, at time t(0), the estimated value of the accumulated amount of condensed water begins to decrease. At time t(1), the estimated value of the accumulated amount of condensed water becomes zero after the water temperature Tw reaches the value indicating the completion of warming up. In this manner, when the engine system 1 continues to operate from the start of warming up of the engine system 1 to the completion thereof, the estimated value of the accumulated amount of condensed water is calculated with high accuracy.

FIG. 7 shows an example of changes in the estimated value of the accumulated amount of condensed water when the operating state in which the operation of the engine system 1 stops before completion of warming up is repeated. The vertical axis in FIG. 7 indicates the accumulated amount of condensed water. The horizontal axis of FIG. 7 indicates time. LN6 in FIG. 7 shows an example of a change in the estimated value of the accumulated amount of condensed water when the operating state in which the operation of the engine system 1 stops before completion of warming up is repeated. LN7 in FIG. 7 shows an example of a change in the accumulated amount when the operation of the engine system 1 continues until the warm-up is completed.

As indicated by LN6 in FIG. 7, for example, at time zero, when the engine system 1 starts operating, the estimated value of the accumulated amount of condensed water increases as described above. When the operation of the engine system 1 is stopped at time t(2) before the warm-up is completed, the accumulated amount of condensed water is Aw (1) is maintained. During this time, the temperature of the engine system 1 decreases and becomes cold again.

Then, after time t(3), when the same operation as the operation from time 0 to time t(3) is repeated, the period from time t(3) to time (4), time t(5) to The period from time zero to time t(4) in the period to time(6), the period from time t(7) to time t(8), and the period from time t(9) to time (10) The amount of condensed water accumulated at the same level as the amount accumulated in the As a result, the accumulated amount of condensed water becomes Aw(2) at time t(4), Aw(3) at time t(6), and Aw(4 ), and becomes Aw(5) at time t(10).

Note that when the operation of the engine system 1 continues after time t(4), condensation of moisture in the intake air and EGR gas is suppressed due to the increase in wall surface temperature, as described with reference to FIG. At the same time, the amount of scavenging air increases, so as shown by LN7 in FIG. 7, after time t(4), the estimated value of the accumulated amount of condensed water changes so as to start decreasing, and the warm-up is completed. At or around the time when the estimated amount of condensed water accumulation becomes zero.

In this way, even if the operation of the engine system 1 stops before the warm-up of the engine system 1 is completed, and even if the engine system 1 operates until the warm-up is completed, the estimated value of the accumulated amount of condensed water is accurate. highly calculated.

Therefore, for example, if there is a possibility that corrosion will be accelerated when the accumulated amount of condensed water increases to Aw (5), when the accumulated amount of condensed water increases to Aw (3), the notification device 130 may be used to notify that condensed water is accumulating or that it is desirable to continue the operation of the engine system 1 to eliminate the accumulation of condensed water. When it increases, the operation of the EGR device 20 is stopped (that is, the EGR valve is closed), or the flow rate of EGR gas is reduced (that is, the opening degree of the EGR valve is reduced). ), the generation of condensed water may be suppressed.

As described above, according to the condensed water amount estimation device according to the present embodiment, the first moisture amount Aw1 contained in the intake air and the second moisture amount Aw2 contained in the exhaust gas and generated by combustion of the fuel are By calculating using each of the estimation formulas, the water content in the intake manifold 10, which is the portion of the intake passage through which the exhaust gas flows, can be calculated with high accuracy. Therefore, the condensed water amount Aw4 in the intake manifold 10 can be calculated with high accuracy by subtracting the saturated water vapor amount Aw3 from the sum of the first water amount Aw1 and the second water amount Aw2. Therefore, it is possible to provide a condensed water amount estimating device that accurately estimates the amount of condensed water generated in the intake passage of the engine system.

Furthermore, since condensed water is generated on the wall surface of the intake manifold 10, the amount of condensed water in the intake manifold 10 can be calculated with high accuracy by calculating the saturated water vapor amount corresponding to the wall surface temperature.

Furthermore, the amount of adhered condensed water generated may vary depending on the surface area of the intake manifold 10 . Therefore, a correction coefficient Cs for correcting the amount of condensed water Aw4 corresponding to the surface area of the intake manifold 10 is set, and the amount of condensed water is accurately estimated by correcting the amount of condensed water Aw4 using the set correction coefficient Cs. can be done.

Furthermore, the amount of adhered condensed water generated may vary depending on the surface area of the intake manifold 10 as well as the wall surface temperature. Therefore, a correction coefficient Cs for correcting the amount of condensed water Aw4 is set using the wall surface temperature in addition to the surface area of the intake manifold 10, and the amount of condensed water Aw4 is corrected using the set correction coefficient Cs. can be estimated with high accuracy.

Modifications will be described below.
In the above-described embodiment, the amount of condensed water Aw4 is calculated assuming that the humidity H is 100% as an example, but it is not particularly limited to 100%. Alternatively, the humidity H in the intake manifold 10 may be detected by a humidity sensor (not shown) and the condensed water amount Aw4 may be calculated using the detection result.

Furthermore, in the above-described embodiment, control device 100 has been described as calculating the accumulated amount of condensed water by executing the processing shown in the flowchart of FIG. 3 regardless of the operating state of engine system 1. The accumulated amount of condensed water may be calculated while the engine system 1 is warming up. For example, when the water temperature Tw is lower than the threshold value, the control device 100 may perform the processing shown in the flowchart of FIG. 3 to calculate the accumulated amount of condensed water.

Furthermore, in the above-described embodiment, the estimation of the accumulated amount of condensed water has been described by taking as an example the case where the engine system 1 is provided with the EGR device 20. The configuration may be such that the operation of the EGR device 20 is stopped at times.

In this case, the controller 100 can, for example, set the reflux rate R and the EGR gas flow rate Qegr to zero, and estimate the accumulated amount of condensed water in the same manner as described above. That is, the control device 100 uses an estimation formula using the flow rate of the intake air taken into the intake passage, the concentration of water vapor contained in the intake air, the humidity of the intake air, the temperature of the intake air, and the atmospheric pressure. By subtracting the saturated water vapor amount from the calculated first water content, the estimated value of the amount of condensed water in the intake passage can be estimated with high accuracy.

In addition, you may implement the above-described modification combining all or one part.
It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the meaning and range of equivalents of the scope of the claims.

1 engine system, 2 engine body, 4 cylinders, 6 fuel injection device, 10 intake manifold, 12 intake pipe, 20 EGR device, 22 first circulation passage, 24 second circulation passage, 30 EGR cooler, 50 exhaust manifold, 52 exhaust tube, 60 turbocharger, 62 compressor, 64 turbine, 66 shaft, 100 control device, 102 air flow meter, 104 intake air temperature sensor, 106 engine speed sensor, 108 water temperature sensor, 110 atmospheric pressure sensor, 112 intake manifold temperature sensor, 114 over Supply pressure sensor 116 Exhaust temperature sensor 120 First calculator 122 Second calculator 124 Third calculator 126 Fourth calculator.

Claims (7)

A condensed water amount estimation device for estimating the amount of condensed water generated in an intake passage of an engine system, wherein the engine system includes a cylinder connected to the intake passage,
The intake air is obtained by an estimation formula using the flow rate of the intake air taken into the intake passage, the concentration of water vapor contained in the intake air, the humidity of the intake air, the temperature of the intake air, and the atmospheric pressure. A first calculation unit that calculates the first water content contained in the
a second calculator that calculates the saturated water vapor content in the intake passage;
A condensed water amount estimating device comprising: a third calculator that calculates, as an estimated value of the amount of condensed water, a value obtained by subtracting the saturated water vapor amount from the first water amount. The engine system includes an exhaust recirculation device that returns a portion of the exhaust to the intake passage,
The condensed water amount estimating device uses an estimation formula that uses the amount of fuel supplied to the cylinder and the recirculation rate of the exhaust gas returned to the intake passage to estimate the amount of fuel contained in the exhaust gas flowing through the intake passage. Further comprising a fourth calculation unit that calculates the second water content generated by
The first calculator calculates the flow rate of intake air taken into the intake passage, the concentration of water vapor contained in the intake air, the humidity of the intake air, the temperature of the intake air, and the atmospheric pressure. In addition, calculating the first water content by an estimation formula using the recirculation rate of the exhaust gas returned to the intake passage,
The second calculation unit calculates a saturated water vapor amount in a portion of the intake passage through which the exhaust gas flows,
The condensation according to claim 1, wherein the third calculator calculates a value obtained by subtracting the saturated water vapor content from the sum of the first water content and the second water content as an estimated value of the amount of the condensed water. Water quantity estimator. 3. The condensed water amount estimation device according to claim 2, wherein said second calculator calculates said saturated water vapor amount corresponding to a wall surface temperature of a portion of said intake passage in contact with said exhaust gas. The third calculator,
setting a correction coefficient for the estimated value corresponding to the surface area of the wall surface of the intake passage to which the condensed water may adhere;
The condensed water amount estimation device according to claim 2 or 3, wherein the estimated value is corrected using the correction coefficient. 5. The condensed water amount estimation device according to claim 4, wherein said third calculator sets said correction coefficient using a wall surface temperature of a portion of said intake passage with which said exhaust gas contacts. The condensed water amount estimating device according to any one of claims 1 to 5, wherein when the estimated value of the condensed water amount exceeds a threshold value, the apparatus notifies predetermined information regarding the amount of the condensed water using a notification device. The condensed water amount estimating device according to claim 1. When the estimated amount of condensed water exceeds a threshold value, the condensed water amount estimating device reduces the flow rate of the exhaust gas returned to the intake passage by the exhaust gas recirculation device and returns the exhaust gas to the intake passage. The condensed water amount estimating device according to any one of claims 1 to 6, wherein any one of stopping the return is performed.

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