JP7571593B2 - Condensate volume estimation device - Google Patents

Description

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

In an engine system, if the temperature of the intake passage during initial warm-up is lower than the dew point, moisture contained in the gas flowing through the intake passage may condense, producing condensed water in the intake passage. This condensed water may cause corrosion of the components in the intake passage. For this reason, it is necessary to accurately estimate the amount of condensed water produced (hereinafter sometimes referred to as the condensed water amount).

Regarding such estimation of the amount of condensed water, for example, JP 2018-188991 A (Patent Document 1) discloses a technique for calculating the amount of condensed water generated in an intercooler by subtracting the amount of saturated water vapor from the amount of water in the mixed gas, which is calculated using the sum of the intake air flow rate and the EGR gas flow rate.

JP 2018-188991 A

The estimation of the amount of condensed water as described above can be performed, for example, using a map showing the relationship between the intake air flow rate and the amount of condensed water. However, in order to improve the accuracy of estimating the amount of condensed water, it is necessary to set a map according to the various operating conditions of the engine system. Therefore, due to limitations such as the storage capacity of the map, the amount of work required to adapt the map, etc., it may not be possible to appropriately improve the accuracy of estimating the amount of condensed water.

The present invention has been made to solve the above-mentioned problems, and its purpose is to provide a condensate amount estimation device that can accurately estimate the amount of condensate generated in the intake passage of an engine system.

A condensed water amount estimation device according to one aspect of the present invention is a condensed water amount estimation device that estimates the amount of condensed water generated in an intake passage of an engine system. The engine system includes a cylinder connected to the intake passage. This condensed water amount estimation device includes a first calculation unit that calculates a first moisture amount contained in the intake air using an estimation equation that uses the flow rate of intake air drawn 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 second calculation unit that calculates the saturated water vapor amount in the intake passage, and a third calculation unit that calculates a value obtained by subtracting the saturated water vapor amount from the first moisture amount as an estimate of the amount of condensed water.

In this way, the first moisture content contained in the intake air flowing through the intake passage can be estimated with high accuracy using the estimation formula. Therefore, by subtracting the saturated water vapor content from the first moisture content, 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 estimation device further includes a fourth calculation unit that calculates a second amount of moisture contained in the exhaust gas flowing through the intake passage and generated by combustion of the fuel using an estimation formula that uses the amount of fuel supplied to the cylinder and the return rate of the exhaust gas returned to the intake passage. The first calculation unit calculates the first amount of moisture using an estimation formula that uses 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 return rate of the exhaust gas returned to the intake passage. The second calculation unit calculates the amount of saturated water vapor in the portion of the intake passage through which the exhaust gas flows. The third calculation unit calculates a value obtained by subtracting the amount of saturated water vapor from the sum of the first amount of moisture and the second amount of moisture as an estimate of the amount of condensed water.

In this way, the first moisture amount and the second moisture amount contained in the exhaust gas flowing through the intake passage and generated by fuel combustion can be estimated with high accuracy using their respective estimation equations. Therefore, by subtracting the saturated water vapor amount from the sum of the first moisture amount and the second moisture amount, the amount of condensed water in the intake passage can be estimated with high accuracy.

In one embodiment, the second calculation unit calculates the amount of saturated water vapor corresponding to the wall temperature at the portion of the intake passage that comes into contact with the exhaust gas.

In this way, condensed water is generated on the wall surface of the part of the intake passage through which the exhaust gas flows, so by calculating the amount of saturated water vapor corresponding to the wall surface temperature, the amount of condensed water generated in the part of the intake passage through which the exhaust gas flows can be accurately estimated.

In one embodiment, the third calculation unit sets a correction coefficient for the estimated value that corresponds to the surface area of the wall surface of the intake passage on which condensed water may adhere. The third calculation unit corrects the estimated value using the correction coefficient.

The amount of condensed water that forms in the portion of the intake passage through which exhaust gas flows can vary depending on the surface area of the wall of that portion. Therefore, a correction coefficient is set to correct the estimated value of the amount of condensed water that corresponds to the surface area of the wall of that portion, and the amount of condensed water can be estimated with high accuracy by correcting the estimated value using the set correction coefficient.

In one embodiment, the third calculation unit sets the correction coefficient using the wall temperature of the portion of the intake passage that comes into contact with the exhaust gas.

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

In one embodiment, the condensate amount estimation device uses a notification device to notify predetermined information regarding the amount of condensate when the estimated value of the amount of condensate exceeds a threshold value.

In this way, predetermined information regarding the amount of condensed water is notified to the user, allowing the user to be made aware of the information.

In a further embodiment, the condensate amount estimation device either reduces the flow rate of exhaust gas returned to the intake passage by the exhaust gas recirculation system or stops returning exhaust gas to the intake passage when the estimated value of the amount of condensate exceeds a threshold value.

This can prevent an increase in the amount of condensed water produced, thereby preventing corrosion of the intake passage.

This invention provides a condensate amount estimation device that can accurately estimate the amount of condensate generated in the intake passage of an engine system.

1 is a diagram showing an example of a schematic configuration of an engine system according to an embodiment of the present invention; 4 is a diagram for explaining the relationship between a first moisture amount contained in intake air, a second moisture amount contained in EGR gas, a saturated water vapor amount, and a condensed water amount. FIG. 10 is a flowchart illustrating an example of a process for estimating an amount of condensed water. 10 is a diagram for explaining an example of a change in an estimated value of an accumulation amount of condensed water under certain driving conditions in an environment with a low outside air temperature. FIG. 10 is a diagram for explaining an example of a change in an estimated value of an accumulation amount of condensed water under certain driving conditions in an environment with a high outside air temperature. FIG. 13 shows an example of a change in the estimated value of the amount of accumulated condensed water when the engine system 1 continues to operate after the warm-up is started and completed. 13 shows an example of a change in the estimated value of the accumulated amount of condensed water when an operating state in which the operation of the engine system 1 is stopped before the warm-up is completed is repeated.

The present embodiment will be described below with reference to the drawings. In the following description, identical parts are given the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated.

Figure 1 is a diagram showing an example of the schematic configuration of an engine system 1 according to this embodiment. As shown in Figure 1, the 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, an exhaust pipe 52, and a turbocharger 60. This engine system 1 is mounted on a moving body such as a vehicle.

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

An intake port and an exhaust port (neither shown) are connected to the top of the cylinders 4 of the engine body 2, and an intake manifold 10 is connected to the intake port. For example, the engine body 2 is provided with multiple cylinders 4, and the intake manifold 10 is connected to the intake ports connected to each of the cylinders 4.

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. Note that 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. The other end of the intake pipe 12 is connected to an air cleaner (not shown). When the engine system 1 is operating, air (intake air) sucked in from the air cleaner flows through the intake pipe 12 into the intake manifold 10. The intake manifold 10 and the intake pipe 12 form the "intake passage" of the engine system 1.

An exhaust manifold 50 is connected to the exhaust ports of the engine body 2. More specifically, the exhaust manifold 50 is connected to the exhaust ports of each of the multiple cylinders of the engine body 2.

One end of an exhaust pipe 52 is connected to the exhaust manifold 50. A muffler or other noise absorbing device is provided at the other end of the exhaust pipe 52. Various catalysts for purifying the exhaust are provided midway along the exhaust pipe 52. The exhaust manifold 50 and the exhaust pipe 52 form an "exhaust passage."

The turbocharger 60 includes a compressor 62 provided in the intake pipe 12 and a turbine 64 provided in the exhaust pipe 52. The compressor 62 is provided with rotatably supported compressor blades (not shown). The turbine 64 is provided with rotatably supported turbine blades connected to the compressor blades via a shaft 66. Therefore, when the turbine blades are rotated by exhaust energy supplied from the engine body 2 to the turbine 64, the compressor blades rotate via the shaft 66, and the intake air is compressed in the compressor 62. The intake air compressed (supercharged) in this manner 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 to the cylinder 4 from the fuel injection device 6 is burned in the cylinder 4. The combustion of the mixture in the cylinder 4 generates combustion pressure, which moves the piston housed in the cylinder 4 and rotates the output shaft (neither shown) via a crank mechanism or the like. The exhaust gas generated by the combustion of the mixture in the cylinder 4 is discharged to the outside via the exhaust manifold 50 and the exhaust pipe 52.

The EGR device 20 is configured to return a portion of the exhaust gas flowing through the exhaust manifold 50 to the intake manifold 10. The portion of the exhaust gas returned to the intake manifold 10 flows from the intake manifold 10 to the cylinders 4 together with the intake air. By introducing the exhaust gas into the cylinders 4, the combustion temperature is lowered, which reduces NOx emissions, and fuel efficiency is improved by reducing intake losses and cooling losses. In the following description, the portion of the exhaust gas returned to the intake passage may be referred to as EGR gas.

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

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

The EGR cooler 30 includes a heat exchanger (not shown) housed therein. The heat exchanger is configured, for example, so that the cooling water flowing through the engine body 2 flows through it. Therefore, in the heat exchanger, heat is exchanged between the EGR gas flowing through the EGR cooler 30 and the cooling water. This reduces the temperature of the EGR gas flowing through the EGR cooler 30. By cooling the EGR gas in the EGR cooler 30, the gas volume of the EGR gas flowing through the first circulation passage 22 can be reduced, making it possible to return a large amount of EGR gas to the intake passage.

The EGR device 20 is provided with an EGR valve (not shown). The EGR valve is an adjustment valve that adjusts the flow rate of EGR gas flowing through the EGR device 20 by adjusting the opening in response 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 in this manner, a portion of the exhaust gas flowing through the exhaust manifold 50 is introduced as EGR gas, which is cooled in the EGR cooler 30 and returned to the intake manifold 10 with its flow rate adjusted by the EGR valve.

The control device 100 is connected to 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, an exhaust temperature sensor 116, and a notification device 130.

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

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

The engine speed sensor 106 is provided in the engine body 2 and detects the rotation speed (hereinafter referred to as engine speed) Ne of the output shaft of the engine body 2. 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 Tw of the cooling water (hereinafter referred to as the water temperature) flowing through a cooling water passage (not shown) provided in the engine body 2. The water temperature sensor 108 transmits a signal indicating the detected water temperature Tw to the 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.

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

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

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

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

The control device 100 includes a CPU (Central Processing Unit) that performs various processes, and memory including a ROM (Read Only Memory) that stores programs and data, and a RAM (Random Access Memory) that stores the results of CPU processing, etc.

The control device 100 controls various devices (such as the fuel injection device 6, the notification device 130, or the EGR valve) so that the engine system 1 is in a desired operating state based on signals from various sensors (such as the air flow 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 boost pressure sensor 114, and the exhaust temperature sensor 116, as described above), as well as maps and programs stored in memory. Note that the various processes executed by the control device 100 are not limited to software processes, and can also be processed by dedicated hardware (electronic circuits).

In the engine system 1 described above, when warm-up is initiated, for example by starting operation during a cold state when the water temperature Tw is lower than the threshold value, the temperature of each component of the engine system 1 increases the longer the engine system 1 is operated.

However, when the temperature of the intake manifold 10 is low, such as during warm-up of the engine system 1, the EGR device 20 may operate, causing condensed water to be generated in the intake manifold 10. This is because when the EGR device 20 operates, EGR gas flows through the intake manifold 10, and the EGR gas flowing through the intake manifold 10 comes into contact with the wall surface of the intake manifold 10 whose temperature is below the dew point, causing the moisture in the intake air shown by the arrow in FIG. 1A and the EGR gas shown by the arrow in FIG. 1B to condense and adhere to the wall surface of the intake manifold 10 as condensed water, as shown in FIG. 1C. In addition, if a certain amount of condensed water is generated before the warm-up is completed, the condensed water becomes acidic due to a chemical reaction with the exhaust components of the EGR gas, which may cause corrosion in the intake manifold 10. Therefore, it is necessary to estimate the amount of condensed water produced (hereinafter referred to as the condensed water amount) and, if necessary, to limit the operation of the EGR device 20 or notify the user.

The amount of condensed water in the intake manifold 10 can be estimated, for example, using a map showing the relationship between the amount of condensed water and the sum of the flow rate of intake air and EGR gas. However, in order to improve the accuracy of estimating the amount of condensed water, it is necessary to set a map according to various operating conditions 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 limitations such as the storage capacity of the map, the amount of work required to adapt the map, etc.

Therefore, in this embodiment, the control device 100 has the following configuration:

That is, the control device 100 includes a calculation unit (1) 120 that calculates the amount of moisture (hereinafter referred to as the first moisture amount) Aw1 contained in the intake air flowing through the intake manifold 10 using an estimation equation that uses the intake air volume, the concentration of water vapor contained in the intake air, the humidity of the intake air, and the reflux rate of the exhaust gas returned to the intake manifold 10.

The control device 100 further includes a calculation unit (2) 122 that calculates the amount of moisture Aw2 (hereinafter referred to as the second moisture amount) contained in the EGR gas and generated by the combustion of the fuel using an estimation equation that uses the amount of fuel supplied to cylinder 4 and the exhaust gas recirculation rate.

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

The control device 100 further includes a calculation unit (4) 126 that calculates an estimated value Aw4 of the condensed water amount by subtracting the saturated water vapor amount Aw3 from the sum of the first moisture amount Aw1 and the second moisture amount Aw2. The condensed water amount estimation device according to this embodiment is realized by the control device 100.

Figure 2 is a diagram illustrating the relationship between the first moisture amount Aw1 contained in the intake air, the second moisture amount Aw2 contained in the EGR gas, the saturated water vapor amount Aw3, and the condensed water amount Aw4.

The sum of the first moisture amount Aw1 contained in the intake air shown in FIG. 2(a) and the second moisture amount Aw2 contained in the EGR gas shown in FIG. 2(b) is the total amount of moisture contained in the gas in the intake manifold 10. Of that, only the saturated water vapor amount Aw3 shown in FIG. 2(c) can exist as water vapor. Therefore, the value obtained by subtracting the saturated water vapor amount Aw3 from the sum of the first moisture amount Aw1 and the second moisture amount Aw2 corresponds to the condensed water amount Aw4 shown in FIG. 2(d).

Therefore, the first moisture amount Aw1 contained in the intake air flowing through the intake manifold 10 and the second moisture amount Aw2 contained in the EGR gas flowing through the intake manifold 10 can be estimated with high accuracy using their respective estimation equations, and 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 moisture amount Aw1 and the second moisture amount Aw2.

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

In step (hereinafter, step will be abbreviated as S) 100, the control device 100 (i.e., calculation unit (1) 120) calculates the first moisture amount Aw1. The estimation formula for estimating the first moisture amount Aw1 [g/s] can be expressed by the following formula (1) using the intake air amount Qa [g/s], the water vapor concentration Cw1, the humidity H [%], and the reflux rate R.

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

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

Pw1==0.61078×10 ^{(7.5t/(t+237.3))} ...(3)
The control device 100 obtains the temperature t of the atmosphere using the detection result by the intake air temperature sensor 104. For example, the control device 100 uses a map showing the relationship between the intake air temperature Ti and the temperature t of the atmosphere and the 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, which is determined experimentally or by design. It is adapted, predetermined 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 atmospheric temperature t and the estimation formula shown in equation (3). The control device 100 acquires the atmospheric pressure Pa using the detection result of the 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).

The humidity H in formula (1) is, for example, a predetermined humidity. In this embodiment, the predetermined humidity is described as, for example, 100%.

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

The first moisture amount Aw1 is the amount of moisture derived from the intake air, and includes the amount of moisture derived from the intake air contained in the recirculated EGR gas in addition to the amount of moisture contained in the air taken in from the air cleaner. Therefore, the relationship between the first moisture amount Aw1, the amount of moisture A contained in the taken in air, and the recirculation rate R is expressed by the formula Aw1 = A + (Aw1 x R), and the relational formula Aw1 = A/(1-R) is established. Therefore, in formula (1), 1/(1-R) is multiplied to include the amount of moisture derived from the intake air contained in the EGR gas recirculated from the EGR device 20 in the first moisture amount Aw1.

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

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

Aw2=Af x Co x R/(1-R)...(4)
The fuel amount Af indicates the amount of fuel (fuel mass) injected per unit time in the cylinder 4. The estimation formula for the fuel amount Af is ^given by: It can be expressed by the following equation (5) using the engine speed Ne [rpm], the number of cylinders N, and the fuel density ρf [g/mm ³ ].

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

The control device 100 calculates the fuel amount Af using the acquired volume Vf, engine speed Ne, number of cylinders N, 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 of fuel (e.g., 1 g), and is a value determined by the properties of the fuel (e.g., the weight ratio of carbon to hydrogen (C/H ratio)). The constant Co is set to, for example, half the C/H ratio.

The reflux rate R in formula (4) is as described above, and will not be described in detail again. The second moisture amount Aw2 is the amount of moisture derived from combustion, and includes the amount of moisture derived from combustion contained in the refluxed EGR gas in addition to the amount of moisture generated by the combustion of the fuel. Therefore, the relationship between the second moisture amount Aw2, the amount of moisture B generated by the combustion of the injected fuel, and the reflux rate R is shown by the formula Aw2 = (Aw2 + B) x R, and the relational formula Aw2 = B x R / (1 - R) is established. Therefore, in formula (4), R / (1 - R) is multiplied in order to include the amount of moisture derived from combustion among the amount of moisture generated by the combustion of the fuel contained in the EGR gas refluxed from the EGR device 20 in the second moisture amount Aw2.

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

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

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

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

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

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

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

Pw2=0.61078×10 ^{(7.5T/(T+237.2))} ...(9)
The control device 100 estimates a wall surface temperature Twl [° C.] of a predetermined portion where condensed water is generated in the intake manifold 10. The control device 100 estimates, for example, a relationship between the wall surface temperature Twl and the temperature T in the intake manifold 10. The temperature T in the intake manifold 10 is calculated using a map showing the relationship between the wall surface temperature Twl and the temperature T in the intake manifold 10. 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 The predetermined portion where the condensed water is generated in the intake manifold 19 is, for example, the intake manifold 19a. Among the piping that constitutes the manifold 10, this portion includes the portion whose temperature is least likely to increase during warm-up.

Furthermore, the control device 100 can estimate the wall temperature Twl using the following equation (10) using the gas flow rate Qb [g/s] in the intake manifold 10, the temperature Tim [°C] of the intake manifold 10, the EGR gas temperature Tegr [°C], and the EGR gas flow rate Qegr [g/s].

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 the base value Ba using a correction coefficient Ca1 set using the water temperature Tw and a correction coefficient Ca2 set using the intake air temperature Tin. The value obtained by multiplying this by a correction coefficient Ca2 set by the above formula is set as a.

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

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 b to 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.

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

The method of acquiring the flow rate Qb and the flow rate Qegr has been described above, and therefore will not be described in detail again. The control device 100 acquires the temperature Tim of the intake manifold 10, for example, using the detection result of the intake manifold temperature sensor 112. Note that the control device 100 may estimate the temperature Tim of the intake manifold 10, for example, using the water temperature Tw.

The control device 100 calculates the EGR gas temperature Tegr using an estimation formula. The estimation formula for the EGR gas temperature Tegr can be expressed by the following formula (11) using the exhaust gas 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)
The control device 100 obtains the water temperature Tw and the exhaust temperature Tex using the detection results of the water temperature sensor 108 and the exhaust temperature sensor 116. For example, the control device 100 obtains the temperature Texm using the water temperature Tw and the exhaust temperature Tex. The control device 100 may acquire the temperature Texm by, for example, a temperature sensor (not shown) provided in the exhaust manifold 50. The control device 100 calculates the temperature Tex, Texm, and Tw acquired by the following equation (11): The EGR gas temperature Tegr is calculated using the above.

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

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

In S106, the control device 100 (i.e., the calculation unit (4) 126) calculates the amount of condensed water Aw4. The calculation formula for the amount of condensed water Aw4 can be expressed by the following formula (12) using the first moisture amount Aw1, the second moisture amount Aw2, and the saturated water vapor amount Aw3.

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

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

At S110, the control device 100 (for example, the calculation unit (4) 126) calculates the amount of accumulated condensed water Vw (the cumulative amount of condensed water). The calculation formula for the amount of accumulated condensed water Vw can be expressed as the following formula (13) using the current value Vw(n) of the amount of accumulated condensed water, the amount of condensed water Aw4, the correction coefficient Cs, the current value Aw5(n) of the scavenging amount (the amount of water sucked into the cylinder during the intake stroke), and the previous value Vw(n-1) of the amount of accumulated condensed water.

Vw(n)=Aw4×Cs+Vw(n-1)-Aw5(n)...(13)
The control device 100 calculates the condensed water amount 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. The control device 100 calculates the current value Vw(n) of the amount of accumulated condensed water as the amount of accumulated condensed water Vw by using the formula (13). The scavenging amount Aw5 is estimated using the flow rate Qb and the water temperature Tw. A well-known technique may be used to estimate the scavenging amount Aw5, and detailed description thereof will not be provided.

The operation of the control device 100 based on the above-described structure and flowchart will be described with reference to Figures 4 and 5.

For example, when the engine body 2 is warming up, the temperature of the intake pipe 12 and the intake manifold 10 is low, so when the EGR valve of the EGR device 20 opens and exhaust gas flows through the intake manifold 10, condensed water is generated inside the intake manifold 10.

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

The saturated water vapor amount Aw3 is subtracted from the sum of the calculated first moisture amount Aw1 and second moisture amount Aw2 to calculate the condensed water amount Aw4 (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 amount Aw5 is subtracted from the corrected value (Aw4 x Cs) to calculate the amount of condensed water generated in the intake manifold. The calculated value is added to the previous value of the accumulated amount Vw of condensed water to calculate the current value of the accumulated amount Vw of condensed water (S110).

In this way, the first moisture amount Aw1 and the second moisture amount Aw2 are calculated individually using their respective estimation formulas, and the saturated water vapor amount Aw3 is calculated using the wall temperature Twl, making it possible to estimate the accumulated amount Vw of condensed water 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, when a notification process is performed in which the accumulated amount Vw of condensed water is used to notify the user of information related to condensed water (hereinafter also referred to as condensed water information) using the notification device 130, it becomes possible to provide an appropriate notification.

Figure 4 is a diagram illustrating an example of the change in the estimated amount of accumulated condensed water under certain driving conditions in an environment with a low outside air temperature. The horizontal axis of Figure 4 indicates time. The vertical axis of Figure 4 indicates the amount of accumulated condensed water.

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

For example, in an environment with low outside air temperature, by calculating the amount of accumulated condensed water taking into account the wall surface temperature, it is possible to suppress overestimation of the amount of accumulated condensed water, as shown by LN1 and LN2 in FIG. 4. Therefore, when executing notification control to notify the user of condensed water information indicating that the amount of accumulated condensed water exceeds a threshold value using the notification device 130 when the amount of accumulated condensed water exceeds a threshold value, unnecessary notification of the information to the user using the notification device 130 is suppressed. Alternatively, when executing EGR control to reduce the flow rate of EGR gas by controlling the EGR valve of the EGR device 20 to the closing side when the amount of accumulated condensed water exceeds a threshold value, it is suppressed that the operation of the EGR device 20 is unnecessarily restricted, thereby worsening fuel efficiency and reducing the purification performance of NOx.

Figure 5 is a diagram illustrating an example of the change in the estimated amount of accumulated condensed water under certain driving conditions (the same driving conditions as those described above) in an environment with a high outside air temperature. The horizontal axis of Figure 5 indicates time. The vertical axis of Figure 5 indicates the amount of accumulated condensed water.

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

For example, in an environment with high outside air temperature, by calculating the amount of accumulated condensed water taking into account the wall surface temperature, it is possible to suppress underestimation of the amount of accumulated condensed water, as shown by LN3 and LN4 in FIG. 5. Therefore, when notification control is performed according to the amount of accumulated condensed water as described above, it is possible to suppress a situation in which the amount of accumulated condensed water actually exceeds a threshold but the notification device 130 is not used to notify the user of condensed water information. Alternatively, when EGR control is performed according to the amount of accumulated condensed water as described above, it is possible to suppress a situation in which the amount of accumulated condensed water actually exceeds a threshold but the EGR control is not performed. Therefore, the promotion of corrosion in the intake manifold 10 is suppressed.

Figure 6 shows an example of the change in the estimated amount of accumulated condensed water when engine system 1 continues to operate after warm-up has started and is completed. The vertical axis of Figure 6 indicates the amount of accumulated condensed water. The horizontal axis of Figure 6 indicates time. LN5 in Figure 6 shows an example of the change in the amount of accumulated condensed water. For example, assume that engine system 1 starts operating when it is cold.

When the engine system 1 starts operating at time zero, the EGR valve opens and exhaust gas flows through the intake manifold 10 as EGR gas via the EGR device 20. When the wall temperature inside the intake manifold is low, moisture in the intake air and EGR gas condenses, so the estimated value of the accumulated amount of condensed water changes to increase. As the engine system 1 continues to operate, the wall temperature inside the intake manifold increases. Therefore, condensation of moisture 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 changes to decrease. Then, at time t(1), after the water temperature Tw reaches a value indicating the completion of warm-up, the estimated value of the accumulated amount of condensed water becomes zero. In this way, when the engine system 1 operates from the start of warm-up to the completion of warm-up of the engine system 1, the estimated value of the accumulated amount of condensed water is calculated with high accuracy.

Figure 7 shows an example of the change in the estimated amount of accumulated condensed water when an operating state in which engine system 1 stops before warm-up is complete is repeated. The vertical axis of Figure 7 shows the amount of accumulated condensed water. The horizontal axis of Figure 7 shows time. LN6 in Figure 7 shows an example of the change in the estimated amount of accumulated condensed water when an operating state in which engine system 1 stops before warm-up is complete is repeated. LN7 in Figure 7 shows an example of the change in the amount of accumulation when engine system 1 continues to operate until warm-up is complete.

As shown by LN6 in FIG. 7, for example, when the operation of the engine system 1 starts at time zero, the estimated amount of accumulated condensed water changes to increase as described above. When the operation of the engine system 1 is stopped at time t(2) before the warm-up is completed, the amount of accumulated condensed water is maintained at Aw(1) during the stop period of the engine system 1 until time t(3). During this time, the temperature of the engine system 1 decreases and it becomes cold again.

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

If the operation of the engine system 1 continues after time t(4), as explained above with reference to FIG. 6, the rise in the wall temperature suppresses the condensation of moisture in the intake air and EGR gas, and the amount of scavenging increases, so that, as shown by LN7 in FIG. 7, the estimated amount of accumulated condensed water starts to decrease after time t(4), and the estimated amount of accumulated condensed water becomes zero at or around the time when the warm-up is completed.

In this way, even if the operation of the engine system 1 stops before the warm-up of the engine system 1 is completed after the start of the warm-up, or even if the engine system 1 operates until the warm-up is completed, the estimated amount of accumulated condensed water can be calculated with high accuracy.

Therefore, for example, if the amount of accumulated condensed water increases to Aw(5) and there is a possibility that corrosion will be accelerated, when the amount of accumulated condensed water increases to Aw(3), the notification device 130 may be used to notify the user that condensed water has accumulated and that continued operation of the engine system 1 is desirable to eliminate the accumulation of condensed water, or when the amount of accumulated condensed water increases to Aw(4), the operation of the EGR device 20 may be stopped (i.e., the EGR valve may be closed) or the flow rate of EGR gas may be reduced (i.e., the opening of the EGR valve may be reduced) to suppress the generation of condensed water.

As described above, the condensed water amount estimation device according to this embodiment calculates the first moisture amount Aw1 contained in the intake air and the second moisture amount Aw2 contained in the exhaust and generated by fuel combustion using the respective estimation equations, thereby enabling the moisture amount in the intake manifold 10, which is the portion of the intake passage through which the exhaust flows, to 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 moisture amount Aw1 and the second moisture amount Aw2. Therefore, it is possible to provide a condensed water amount estimation 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 amount of saturated water vapor corresponding to the wall surface temperature.

Furthermore, the amount of condensed water that is generated can vary depending on the surface area of the intake manifold 10. Therefore, a correction coefficient Cs is set to correct the amount of condensed water Aw4 that corresponds to the surface area of the intake manifold 10, and the amount of condensed water can be estimated with high accuracy by correcting the amount of condensed water Aw4 using the set correction coefficient Cs.

Furthermore, the amount of condensed water that is generated can vary depending on the wall temperature as well as the surface area of the intake manifold 10. Therefore, the correction coefficient Cs for correcting the amount of condensed water Aw4 is set using the wall temperature as well as the surface area of the intake manifold 10, and the amount of condensed water Aw4 is corrected using the set correction coefficient Cs, thereby enabling the amount of condensed water to 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 this is not particularly limited to 100% and may be set to a predetermined value lower than 100%, or the humidity H inside the intake manifold 10 may be detected by a humidity sensor (not shown), and the amount of condensed water Aw4 may be calculated using the detection result.

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

Furthermore, in the above embodiment, the estimation of the accumulated amount of condensed water was described using as an example a case where the engine system 1 is provided with an EGR device 20, but the engine system 1 may be configured without an EGR device 20 or may be configured to stop operation of the EGR device 20 during warm-up.

In this case, the control device 100 can estimate the accumulated amount of condensed water in the same manner as described above, for example, by setting the reflux rate R and the flow rate Qegr of EGR gas to zero. That is, the control device 100 can accurately estimate the amount of condensed water in the intake passage by subtracting the saturated water vapor amount from the first moisture amount calculated by an estimation formula using the flow rate of the intake air drawn 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.

The above-described modified examples may be implemented in whole or in part in combination.
The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

1 engine system, 2 engine body, 4 cylinder, 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 pipe, 60 turbocharger, 62 compressor, 64 turbine, 66 shaft, 100 control device, 102 air flow meter, 104 intake temperature sensor, 106 engine speed sensor, 108 water temperature sensor, 110 atmospheric pressure sensor, 112 intake manifold temperature sensor, 114 boost pressure sensor, 116 exhaust temperature sensor, 120 first calculation unit, 122 second calculation unit, 124 third calculation unit, 126 fourth calculation unit.

Claims (6)

A condensate amount estimation device that estimates an amount of condensate generated in an intake manifold of an engine system, the engine system including a cylinder connected to the intake manifold, the engine system including an exhaust gas recirculation device that returns a portion of exhaust gas to the intake manifold,
a first calculation unit that calculates a first moisture amount contained in the intake air by a first estimation equation using at least a flow rate of the intake air taken into the intake manifold, a concentration of water vapor contained in the intake air, a humidity of the intake air, a temperature of the intake air, and an atmospheric pressure;
A second calculation unit that calculates a saturated water vapor amount in the intake manifold;
a third calculation unit that calculates a value obtained by subtracting the amount of saturated water vapor from the first moisture amount as an estimate of the amount of condensed water;
a fourth calculation unit that calculates a second amount of water contained in the exhaust gas flowing through the intake manifold and generated by combustion of the fuel by a second estimation equation using an amount of fuel supplied to the cylinder and a reflux rate of the exhaust gas returned to the intake manifold ,
the first calculation unit calculates the first moisture amount by the first estimation equation using a flow rate of intake air taken into the intake manifold, a concentration of water vapor contained in the intake air, a humidity of the intake air, a temperature of the intake air, the atmospheric pressure, and a recirculation rate of exhaust gas returned to the intake manifold;
The second calculation unit calculates an amount of saturated water vapor in a portion of the intake manifold through which the exhaust gas flows,
the third calculation unit calculates a value obtained by subtracting the amount of saturated water vapor from the sum of the first water amount and the second water amount as an estimate of the amount of condensed water;
The second calculation unit calculates the amount of saturated water vapor corresponding to a wall surface temperature of a portion of the intake manifold with which the exhaust gas comes into contact. A condensate amount estimation device that estimates an amount of condensate generated in an intake manifold of an engine system, the engine system including a cylinder connected to the intake manifold, the engine system including an exhaust gas recirculation device that returns a portion of exhaust gas to the intake manifold,
a first calculation unit that calculates a first moisture amount contained in the intake air by a first estimation equation using at least a flow rate of the intake air taken into the intake manifold, a concentration of water vapor contained in the intake air, a humidity of the intake air, a temperature of the intake air, and an atmospheric pressure;
A second calculation unit that calculates a saturated water vapor amount in the intake manifold;
a third calculation unit that calculates a value obtained by subtracting the amount of saturated water vapor from the first moisture amount as an estimate of the amount of condensed water;
a fourth calculation unit that calculates a second amount of water contained in the exhaust gas flowing through the intake manifold and generated by combustion of the fuel by a second estimation equation using an amount of fuel supplied to the cylinder and a reflux rate of the exhaust gas returned to the intake manifold ,
the first calculation unit calculates the first moisture amount by the first estimation equation using a flow rate of intake air taken into the intake manifold, a concentration of water vapor contained in the intake air, a humidity of the intake air, a temperature of the intake air, the atmospheric pressure, and a recirculation rate of exhaust gas returned to the intake manifold;
The second calculation unit calculates an amount of saturated water vapor in a portion of the intake manifold through which the exhaust gas flows,
the third calculation unit calculates a value obtained by subtracting the amount of saturated water vapor from the sum of the first water amount and the second water amount as an estimate of the amount of condensed water;
The third calculation unit is
setting a correction coefficient for the estimated value corresponding to a surface area of a wall surface of the intake manifold to which the condensed water may adhere;
The condensed water amount estimating device corrects the estimated value using the correction coefficient. The condensed water amount estimating device according to claim 2 , wherein the third calculation unit sets the correction coefficient using a wall surface temperature of a portion of the intake manifold with which the exhaust gas comes into contact. The condensed water amount estimation device according to any one of claims 1 to 3 , wherein the condensed water amount estimation device notifies predetermined information regarding the amount of condensed water using a notification device when the estimated value of the amount of condensed water exceeds a threshold value. 3. The condensed water amount estimation device according to claim 1, wherein when the estimated value of the amount of condensed water exceeds a threshold value, the condensed water amount estimation device either reduces a flow rate of exhaust gas returned to the intake manifold by the exhaust gas recirculation device, or stops returning exhaust gas to the intake manifold. A condensate amount estimation device that estimates an amount of condensate generated in an intake manifold of an engine system, the engine system including a cylinder connected to the intake manifold,
a first calculation unit that calculates a first moisture amount contained in the intake air by a first estimation equation using at least a flow rate of the intake air taken into the intake manifold, a concentration of water vapor contained in the intake air, a humidity of the intake air, a temperature of the intake air, and an atmospheric pressure;
A second calculation unit that calculates a saturated water vapor amount in the intake manifold;
a third calculation unit that calculates a value obtained by subtracting the amount of saturated water vapor from the first moisture amount as an estimate of the amount of condensed water;
a fourth calculation unit that calculates a change in the amount of accumulated condensed water by subtracting a scavenging amount indicating an amount of water sucked into the cylinder during an intake stroke from a value obtained by multiplying the estimated value by a correction coefficient ,
The scavenging amount is estimated using a wall surface temperature in the intake manifold, a flow rate of the intake air, and a cooling water temperature .
The correction coefficient is set using the wall surface temperature .

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