JP2020122461A - Blow-by gas humidity estimation device and blow-by gas humidity estimation method - Google Patents

Abstract

To estimate blow-by gas humidity.SOLUTION: A blow-by gas humidity estimation device 100 of an internal combustion engine 1 is configured to execute a first step of calculating a moisture content of a blow-by gas based upon a moisture concentration of an exhaust recirculated gas, a moisture concentration of intake air, and a fuel combustion moisture concentration obtained by dividing a moisture content produced in combustion of fuel by an exhaust flow rate; and a second step of estimating humidity of the blow-by gas based upon the moisture content of the blow-by gas.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to an apparatus and method for estimating the humidity of blow-by gas in an internal combustion engine.

2. Description of the Related Art In internal combustion engines, a blow-by gas processing device is known in which blow-by gas that has leaked into a crankcase from a gap between a piston and a cylinder is returned to an intake passage through a blow-by gas passage.

JP-A-58-124064

Blow-by gas contains water. That is, the blow-by gas has a blow-by gas humidity which is a ratio of the amount of water in the blow-by gas. This blow-by gas humidity can be directly detected by a humidity sensor. However, there is no device or method that can estimate the blow-by gas humidity without using a humidity sensor.

Therefore, the present disclosure has been devised in view of such circumstances, and an object thereof is to provide an apparatus and a method capable of estimating blow-by gas humidity.

According to one aspect of the present disclosure,
A device for estimating the humidity of blow-by gas in an internal combustion engine,
Calculating the water content of the blow-by gas based on the water content of the exhaust gas recirculation gas, the water content of the intake air, and the fuel combustion water content obtained by dividing the water content produced by the combustion of fuel by the exhaust flow rate. 1 step,
A second step of estimating the humidity of the blow-by gas based on the water content of the blow-by gas;
A blow-by gas humidity estimation device is provided, which is configured to perform.

Preferably, in the first step, the blow-by gas humidity estimation device calculates the water content of the blow-by gas based on a value obtained by multiplying the fuel combustion water content by a predetermined water mixing rate.

Preferably, the internal combustion engine includes an oil separator that separates oil from blow-by gas using boost gas generated by a compressor of a turbocharger,
In the second step, the blow-by gas humidity estimating apparatus estimates the humidity of the blow-by gas after the boost gas is mixed in the oil separator, based on the water content of the blow-by gas and the water content of the boost gas. ..

According to another aspect of the present disclosure,
A method for estimating the humidity of blow-by gas in an internal combustion engine, comprising:
Calculating the water content of the blow-by gas based on the water content of the exhaust gas recirculation gas, the water content of the intake air, and the fuel combustion water content obtained by dividing the water content produced by the combustion of fuel by the exhaust flow rate. 1 step,
A second step of estimating the humidity of the blow-by gas based on the water content of the blow-by gas;
There is provided a blow-by gas humidity estimation method comprising:

According to the present disclosure, the blow-by gas humidity can be estimated.

FIG. 1 is an overall configuration diagram of an internal combustion engine including a blowby gas processing device. It is a schematic longitudinal cross-sectional view of an oil separator. It is a schematic diagram which shows the flow of gas etc. around a cylinder. It is a flow chart which shows a PCV gas humidity calculation routine.

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be noted that the present disclosure is not limited to the embodiments below.

FIG. 1 is an overall configuration diagram of an internal combustion engine (engine) 1 including a blowby gas processing device 90. In the figure, white arrows indicate the flow of intake air A and boost gas BST (described later), hatched arrows indicate the flow of blow-by gas BBY, and black arrows indicate the flow of exhaust EXH.

As shown in FIG. 1, the internal combustion engine 1 is a multi-cylinder compression ignition internal combustion engine, that is, a diesel engine mounted on a vehicle (not shown). The vehicle is a large vehicle such as a truck. However, there are no particular limitations on the types, types, applications, etc. of the vehicle and the internal combustion engine 1. For example, the vehicle may be a small vehicle such as a passenger car, and the internal combustion engine 1 is a spark ignition internal combustion engine, that is, a gasoline engine. Is also good.

The internal combustion engine 1 includes an engine body 2 and an intake passage 10 and an exhaust passage 11 connected to the engine body 2. The engine body 2 includes structural parts such as a cylinder head, a cylinder block, and a crankcase, and movable parts such as a piston, a crankshaft, and a valve that are housed inside. Reference numeral 3 represents a head cover attached to the upper part of the cylinder head.

The intake passage 10 is mainly defined by an intake manifold 12 connected to the engine body 2 (in particular, a cylinder head) and an intake pipe 13 connected to an upstream end of the intake manifold 12. The intake pipe 13 is provided with an air cleaner 14, a compressor 20C of the turbocharger 20, and an intercooler 21 in order from the upstream side.

Here, the air introduced from the air cleaner 14 into the intake pipe 13 and before being supercharged by the compressor 20C is referred to as intake air A, and the air after being supercharged by the compressor 20C is referred to as boost gas BST.

The exhaust passage 11 is mainly defined by an exhaust manifold 15 connected to the engine body 2 (in particular, a cylinder head) and an exhaust pipe 16 arranged on the downstream side of the exhaust manifold 15. A turbine 20T of the turbocharger 20 is provided between the exhaust manifold 15 and the exhaust pipe 16.

The engine 1 includes an exhaust gas recirculation (EGR) device 4. The EGR device 4 includes an EGR passage 5 for recirculating a part of exhaust gas (referred to as EGR gas) in the exhaust passage 11 (in particular, the exhaust manifold 15) into the intake passage 10 (in particular, the intake manifold 12), and an EGR passage. An EGR cooler 6 that cools the EGR gas flowing in 5 and an EGR valve 7 that adjusts the flow rate of the EGR gas are provided.

The blow-by gas processing device 90 includes a blow-by gas passage 30 for returning the blow-by gas to the intake passage 10 on the upstream side of the compressor 20C. As is well known, blow-by gas is gas that has leaked into the crankcase from the gap between the cylinder and the piston in the engine body 2. The blow-by gas passage 30 is provided with an oil separator 40 for separating oil from the blow-by gas. In particular, the oil separator 40 of the present embodiment is configured to separate the oil from the blow-by gas by utilizing the compressed air generated by the compressor 20C, that is, the boost gas, as described later.

The blow-by gas passage 30 is arranged on the gas passage 31 in the engine main body 2 extending from the inside of the crank case through the cylinder block and the cylinder head into the head cover 3, and on the downstream side of the gas passage 31, and is exposed to the outside. It is formed by the blow-by gas pipe 32. The oil separator 40 is exposed to the outside and arranged on the head cover 3. The downstream end of the gas passage 31 and the upstream end of the blow-by gas pipe 32 are connected to the oil separator 40. That is, the oil separator 40 is provided between the gas passage 31 and the blow-by gas pipe 32. The downstream end of the blow-by gas pipe 32 is connected to the intake pipe 13 on the upstream side of the compressor 20C.

The blow-by gas processing device 90 includes a boost gas passage 50 that takes out the boost gas BST from the intake passage 10 on the downstream side of the compressor 20C and supplies the boost gas BST to the oil separator 40. The boost gas passage 50 is defined by a boost gas pipe 51. In the case of the present embodiment, the upstream end of the boost gas passage 50 is connected to the intake pipe 13 on the upstream side of the intercooler 21, and the boost gas BST before being cooled by the intercooler 21 is taken out. The downstream end of the boost gas passage 50 is connected to the oil separator 40.

FIG. 2 is a schematic vertical sectional view of the oil separator 40. As illustrated, the oil separator 40 is installed on the upper surface portion of the head cover 3. A gas outlet 31a of a gas passage 31 on the engine body side is formed on the upper surface of the head cover 3.

The oil separator 40 includes an oil separation portion 41 that introduces the blow-by gas BBY from the gas outlet 31a and separates the oil O from the blow-by gas BBY. Further, the oil separator 40 generates a negative pressure by the boost gas BST supplied thereto, and the negative pressure sucks the blow-by gas BBY after the oil O is separated by the oil separation unit 41, by the negative pressure. Equipped with. The oil separator 40 also includes a gas discharge part 43 that discharges the blow-by gas BBY sucked by the gas suction part 42 together with the boost gas BST.

The oil separating unit 41 includes a lower casing 44 connected to the upper surface of the head cover 3, an upper casing 45 connected to the upper surface of the lower casing 44, a gas injection member 46, and an outlet casing 47.

The lower casing 44 covers the gas outlet 31a and has a communication port 44a, and a bottomed cylindrical gas injection member 46 is mounted coaxially with the communication port 44a. Thereby, the lower casing 44 connects the gas outlet 31a to the gas injection member 46. The lower casing 44 is provided with an oil outlet 48 for discharging the oil O accumulated at the bottom of the outlet casing 47. A drain valve 49 described later is attached to the oil outlet 48.

The upper casing 45 covers and accommodates the gas injection member 46 from above. At the lower end position of the upper casing 45, a discharge port 45 a for discharging the blow-by gas BBY and the oil O after oil separation into the outlet casing 47 is formed.

The gas injection member 46 is formed in a bottomed cylindrical shape that extends in the vertical direction and has an open lower end, and has a lid 46a at the upper end. Further, a plurality of through holes 46b extending in the radial direction are formed on the peripheral surface portion of the gas injection member 46.

The outlet casing 47 is formed in a gutter shape that extends in the vertical direction, covers the discharge port 45 a, and is connected to the side surface of the upper casing 45. A gas outlet 41 a is formed at the upper end of the outlet casing 47. The gas outlet 41a serves as an outlet for the blow-by gas BBY in the oil separation section 41.

The discharge valve 49 is always closed by the urging force of a spring (not shown). When the oil O is accumulated in the outlet casing 47 in a certain amount or more, the load of the accumulated oil O opens the valve against the spring biasing force. At this time, the oil O discharged from the oil outlet 48 is finally returned into the engine body 2 through an oil return pipe (not shown).

The gas suction portion 42 is formed in a tubular shape extending in the horizontal direction, and is supported on the upper casing 45 and the outlet casing 47. The downstream end of the boost gas pipe 51 is connected to the upstream end of the gas suction unit 42.

A small-diameter orifice 42a serving as a throttle is formed at the upstream end of the gas suction portion 42. On the other hand, a taper portion 42b whose diameter gradually increases toward the downstream side is formed at the downstream end portion of the gas suction portion 42, and the gas discharge portion 43 is integrally formed at the downstream end thereof. The upstream end of the blow-by gas pipe 32 is connected to the gas discharge part 43.

The above-mentioned gas outlet 41a is provided so as to face the position of the outlet of the orifice 42a or be orthogonal thereto. As a result, a negative pressure is generated by the flow of the high-speed boost gas BST ejected from the orifice 42a, and the blow-by gas BBY after oil separation is sucked by this negative pressure and discharged from the gas outlet 41a. The blow-by gas BBY discharged from the gas outlet 41a flows in the gas suction part 42 together with the boost gas BST, and is discharged from the gas discharge part 43 into the blow-by gas pipe 32. As described above, the oil separator 40 of the present embodiment uses the negative pressure generated by the boost gas BST to separate the oil O from the blow-by gas BBY.

The suction of the blow-by gas BBY causes a flow of the blow-by gas BBY as shown in FIG. 2 in the oil separator 40.

The blow-by gas BBY before oil separation introduced into the gas injection member 46 from the gas outlet 31 a through the lower casing 44 is injected radially outward through the through hole 46 b of the gas injection member 46 and collides with the inner wall of the upper casing 45. .. At this time, the oil O contained in the blow-by gas BBY adheres to the inner wall of the upper casing 45, and the oil O is separated from the blow-by gas BBY.

The blow-by gas BBY after the oil separation then passes through the outlet 45a and the outlet casing 47, and is sucked into the gas suction portion 42 from the gas outlet 41a as described above. On the other hand, the separated oil O enters the outlet casing 47 through the discharge port 45a and is stored there. When the amount of the accumulated oil O reaches a certain amount, the discharge valve 49 opens and the oil O is discharged from the oil outlet 48.

Next, the blow-by gas humidity estimation device and the blow-by gas humidity estimation method of this embodiment will be described.

As shown in FIG. 1, the blow-by gas humidity estimation apparatus of the present embodiment is mainly configured by an electronic control unit (ECU) 100 mounted on a vehicle. The ECU 100 forms a control unit, a circuit element or a controller. The ECU 100 includes a CPU (Central Processing Unit) having an arithmetic function, a ROM (Read Only Memory) and a RAM (Random Access Memory) that are storage media, an input/output port, and a storage device other than the ROM and the RAM. The ECU 100 is configured to control the EGR valve 7 according to the engine operating state.

Further, as sensors constituting the blow-by gas humidity estimating device, a rotation speed sensor 61 for detecting the rotation speed of the engine (specifically, the engine speed (rpm) per minute), and an accelerator opening degree are detected. An accelerator opening sensor 62 is provided for the operation. Further, a pressure sensor 63 for detecting the internal pressure of the intake manifold 12 (referred to as intake manifold pressure), a flow rate sensor 64 for detecting the flow rate of the intake air A sucked from the air cleaner 14, and a humidity sensor for detecting atmospheric humidity. A humidity sensor 65 is provided.

The quantities used in the following calculations and the corresponding symbols and units are shown in the table below.

In this embodiment, the humidity of the blow-by gas BBY after the boost gas BST is mixed in the oil separator 40 is estimated. Therefore, in this embodiment, the humidity of the mixed gas of the boost gas BST and the blow-by gas BBY is estimated. This mixed gas is called "PCV gas" for convenience. The PCV gas means, for example, a gas flowing in the blow-by gas pipe 32.

Further, in the above table and the following description, “boost gas BST” means the boost gas BST taken out from the intake passage 10 and supplied to the oil separator 40, unless otherwise specified. The boost gas BST is, for example, the boost gas BST flowing in the boost gas pipe 51. It should be noted that this does not mean the boost gas BST in the intake passage 10 downstream of the branch point of the boost gas pipe 51.

The “blow-by gas BBY” means purely the blow-by gas BBY generated in the engine body 2 and supplied to the oil separator 40. The blow-by gas BBY means, for example, the blow-by gas BBY before being discharged from the gas outlet 41a of the oil separator 40.

Now, the humidity Hpcv of the PCV gas estimated in the present embodiment is a value obtained by dividing the water content of the PCV gas (the water content of the PCV gas. The same applies hereinafter) Wpcv by the flow rate Qpcv of the PCV gas. is there. The PCV gas moisture content Wpcv is the sum of the blowby gas moisture content Wbby and the boost gas moisture content Wbst, and the PCV gas flow rate Qpcv is the sum of the blowby gas flow rate Qbby and the boost gas flow rate Qbst. Therefore, the following expression (1) is established.

Here, the blow-by gas flow rate Qbby is a value that changes according to the engine operating state. Therefore, in the present embodiment, the relationship between the parameter indicating the engine operating state (specifically, the engine speed and load) and the blow-by gas flow rate Qbby is determined in advance through an experiment or the like, and the blow-by gas flow rate Qbby is determined according to this relationship. calculate.

Specifically, the ECU 100, in accordance with a predetermined injection amount map (may be a function; the same applies hereinafter) based on the engine speed Ne and the accelerator opening Ac detected by the rotation speed sensor 61 and the accelerator opening sensor 62, respectively. A target fuel injection amount Q, which is an instruction injection amount to the in-cylinder injector (indicated by reference numeral 28 in FIG. 3), is calculated. Then, based on the engine speed Ne and the target fuel injection amount Q, the blow-by gas flow rate Qbby is calculated according to a predetermined blow-by gas flow rate map representing the above relationship.

In this case, the target fuel injection amount Q is used as the parameter representing the engine load, but the present invention is not limited to this, and other parameters such as the accelerator opening may be used.

Next, the boost gas flow rate Qbst is a value that is determined according to the specifications of the oil separator 40 and that changes according to the pressure of the boost gas. The boost gas flow rate Qbst tends to increase as the pressure of the boost gas increases. The pressure of the boost gas is equal to the intake manifold pressure Pim detected by the pressure sensor 63. Therefore, the boost gas flow rate Qbst is calculated by the ECU 100 according to the following equations (2) and (3) based on the intake manifold pressure Pim (absolute pressure) detected by the pressure sensor 63.

It can be said that Pimr is a value obtained by converting the intake manifold pressure Pim (kPa) into a unit of atmospheric pressure. The first constant A and the second constant B in the equation (2) are determined according to the specifications of the oil separator 40. The values of the first constant A, the second constant B, and the atmospheric density ρ are stored in the ECU 100 in advance.

Next, the boost gas moisture content Wbst is calculated by the ECU 100 from the following equation (4).

The boost gas flow rate Qbst is calculated from the above equation (2). The atmospheric humidity Hamb is a value detected by the humidity sensor 65.

Next, a method for calculating the blow-by gas moisture content Wbby will be described. Of course, this calculation is also performed by the ECU 100.

In calculating the blow-by gas moisture content Wbby, first, the intake moisture content Wa, the fuel combustion moisture content Wcomb, and the exhaust moisture content Wexh are calculated. The fuel combustion moisture content Wcomb is the amount of moisture generated by combustion of the fuel in the cylinder.

The intake moisture amount Wa is calculated by the following equation (5). The intake air flow rate Ga is a value detected by the flow rate sensor 64.

The fuel combustion water content Wcomb is calculated from the following equation (6).

Here, in the calculation of the fuel combustion moisture content Wcomb, the high heating value = 10857 (kcal/kJ) and the low heating value = 10188 (kcal/kJ) of light oil, which is a fuel specified by JIS K2279, are considered. .. In the case of complete combustion, 1.24 g of water is produced for 1 g of light oil, so the fuel flow rate Gf is multiplied by 1.24 in the equation (6). The fuel flow rate Gf is a value converted from the target fuel injection amount Q described above.

The exhaust water content Wexh is calculated from the following expression (7) using the intake water content Wa and the fuel combustion water content Wcomb calculated from the previous expressions (5) and (6).

As is known, the EGR rate γ is a value that changes according to the engine operating state. In this embodiment, the EGR rate γ is calculated according to the EGR rate map based on the engine speed Ne and the target fuel injection amount Q, as in the blow-by gas flow rate Qbby.

In general, exhaust contains more water than intake. The higher the EGR rate γ, the larger the amount of exhaust gas that is recirculated to the intake side, so the exhaust water content Wexh tends to increase.

FIG. 3 is a schematic diagram showing the flow of gas and the like around the cylinder. 22 is a piston, 23 is a cylinder, 24 is an intake port, 25 is an intake valve, 26 is an exhaust port, 27 is an exhaust valve, and 28 is an in-cylinder injector.

The water contained in the intake air A (more specifically, the intake air component in the boost gas BST) is introduced into the cylinder 23. In the cylinder 23, the fuel injected from the injector 28 burns to generate water. On the other hand, a part of the exhaust EXH discharged from the cylinder 23 becomes EGR gas and is introduced into the cylinder 23 again. The water contained in the EGR gas is introduced into the cylinder 23. The water concentration of EGR gas can be regarded as equal to the water concentration of exhaust gas.

The water contained in the blow-by gas BBY can be generally regarded as a combination of the water derived from the intake air A, the water derived from the fuel, and the water derived from the EGR gas. In consideration of this, in the present embodiment, the blow-by gas moisture content Wbby is calculated from the following equation (8).

The first term (γ×Wexh/Ge) in the parentheses represents the water concentration of the EGR gas introduced into the cylinder 23. The second term in parentheses ((1-γ)×Wa/Ga) represents the water concentration of the intake air A introduced into the cylinder 23. (Wcomb/Ge) in the third term in the parentheses represents the concentration of water in the exhaust gas generated by the combustion of the fuel in the cylinder 23, and is obtained by dividing the fuel combustion water content Wcomb by the exhaust gas flow rate Ge. .. Hereinafter, this concentration is referred to as the fuel combustion moisture concentration.

In Expression (8), generally, the values obtained by multiplying the respective concentrations by the blow-by gas flow rate Qbby are summed to calculate the blow-by gas water content Wbby.

By the way, there is a problem of non-uniformity in fuel combustion moisture concentration. This point will be described below.

For example, with respect to EGR gas, the EGR gas is introduced into the cylinder 23 via a relatively long path including the exhaust port 26, the exhaust manifold 15, the EGR passage 5, the intake manifold 12, and the intake port 24. Therefore, when the water is introduced into the cylinder 23, the water content of the EGR gas and the components other than the water content are sufficiently stirred and mixed, and the water content of the EGR gas is uniform. In other words, the water concentration is the same regardless of which part of the EGR gas introduced into the cylinder 23 is extracted. The same applies to the intake air A.

However, the fuel is injected from the injector 28 at the center of the cylinder 23 and ignites, and then spreads outward in the radial direction. Therefore, the fuel concentration is highest at the center of the cylinder 23, and becomes lower toward the outside in the radial direction. The same applies to the water concentration. As described above, the fact that the water concentration differs depending on the location in the cylinder 23, more specifically, the water concentration decreases toward the radially outer side is a problem of non-uniformity.

The blow-by gas BBY is a gas that leaks from the gap between the piston 22 and the cylinder 23. On the other hand, the gap is located on the outermost side in the radial direction of the cylinder 23. Therefore, it is considered that the portion of the exhaust gas in the cylinder 23 having the lowest water content substantially constitutes the blow-by gas BBY.

Therefore, in the present embodiment, in order to reflect this problem of non-uniformity, the fuel combustion water concentration Wcomb/Ge is multiplied by a predetermined water mixing rate α as shown in the above equation (8), and the value obtained by this is obtained. Based on this, the blow-by gas moisture content Wbby is calculated. The water content rate α is a positive value smaller than 1 (0<α<1).

The fuel combustion moisture concentration obtained by simply dividing the fuel combustion moisture amount Wcomb by the exhaust gas flow rate Ge is the moisture concentration on the assumption that the moisture concentration of the exhaust gas in the cylinder 23 is uniform. On the other hand, the value obtained by multiplying the fuel combustion water concentration by the water mixing rate α (referred to as corrected concentration) is a value estimated to be lower than the uniform concentration, and the value of the exhaust gas that substantially constitutes the blow-by gas BBY. It is a value close to some actual water concentrations. A concrete numerical value of the water content rate α is optimally set or adapted through an actual machine test or the like, and is stored in the ECU 100.

In this way, by correcting the fuel combustion moisture concentration by the moisture mixing ratio α, the nonuniformity of the concentration of the fuel-derived moisture in the cylinder 23 is reflected, and the calculation accuracy of the blow-by gas moisture content Wbby, and eventually the PCV gas humidity. It is possible to improve the calculation accuracy of Hpcv.

The water content rate α is 1 when the water concentration is uniform. It can be said that the water mixing rate α is an index value indicating the degree of nonuniformity of the water concentration of the object.

The PCV gas humidity Hpcv is calculated by substituting the blow-by gas flow rate Qbby, the boost gas flow rate Qbst, the boost gas moisture amount Wbst, and the blow-by gas moisture amount Wbby calculated as described above into the equation (1).

Next, the PCV gas humidity calculation routine will be described with reference to FIG. This routine is repeatedly executed by the ECU 100 at every predetermined calculation cycle τ (for example, 10 msec).

In step S 101, the engine speed Ne detected by the rotation speed sensor 61, the accelerator opening Ac detected by the accelerator opening sensor 62, the intake manifold pressure Pim detected by the pressure sensor 63, and the flow sensor 64 are detected. The values of the intake air flow rate Ga and the atmospheric humidity Hamb detected by the humidity sensor 65 are acquired.

In step S102, the target fuel injection amount Q is calculated based on the engine speed Ne and the accelerator opening Ac.

In step S103, the blow-by gas flow rate Qby and the EGR rate γ are calculated based on the engine speed Ne and the target fuel injection amount Q. Further, the fuel flow rate Gf is calculated based on the target fuel injection amount Q.

In step S104, the boost gas flow rate Qbst is calculated according to the equations (2) and (3).

In step S105, the boost gas moisture content Wbst is calculated according to the equation (4).

In step S106, the intake moisture amount Wa is calculated according to the above equation (5).

In step S107, the fuel combustion water content Wcomb is calculated according to the above equation (6).

In step S108, the exhaust water content Wexh is calculated according to the equation (7).

In step S109, the blow-by gas moisture content Wbby is calculated according to the equation (8).

In step S110, the PCV gas humidity Hpcv is calculated according to the above equation (1).

As described above, the ECU 100 of the present embodiment is configured such that the water concentration of EGR gas (γ×Wexh/Ge), the water concentration of intake air ((1-γ)×Wa/Ga), and the water amount Wcomb generated by the combustion of the fuel. Is calculated by dividing the fuel combustion moisture concentration (Wcomb/Ge) by the exhaust flow rate Ge, and the first step of calculating the moisture content Wbby of the blow-by gas, and the blow-by gas based on the moisture content Wbby of the blow-by gas. The second step of estimating the humidity Hpcv of (the PCV gas that is the blow-by gas after the boost gas is mixed in the present embodiment) is configured to be executed. Therefore, it is possible to appropriately estimate the blow-by gas humidity.

In the first step, the ECU 100 of the present embodiment calculates the moisture amount Wby of the blow-by gas based on a value obtained by multiplying the fuel combustion moisture concentration (Wcomb/Ge) by a predetermined moisture mixing rate α. Therefore, it is possible to improve the calculation accuracy of the blow-by gas moisture content Wbby and hence the blow-by gas humidity Hpcv by reflecting the non-uniformity of the fuel combustion moisture concentration.

Further, in the second step, the ECU 100 of the present embodiment determines the humidity Hpcv of the blow-by gas (that is, the PCV gas) after the boost gas is mixed in the oil separator 40 as the moisture amount Wbby of the blow-by gas and the moisture amount Wbst of the boost gas. And estimate based on. Therefore, even when the boost gas is mixed in the blow-by gas, the humidity Hpcv of the PCV gas, which is the mixture, can be appropriately estimated.

By the way, the estimated value of the PCV gas humidity Hpcv estimated according to the present embodiment can be used for various purposes. For example, as shown by a phantom line in FIG. 1, when the blow-by gas pipe 32 on the downstream side of the oil separator 40 is provided with a humidity sensor 70 for detecting the PCV gas humidity, the PCV gas humidity is used for diagnosis of the humidity sensor 70. An estimate of is available. The present embodiment may include such a diagnostic device and a diagnostic method for the humidity sensor 70.

The diagnostic device can be configured by the ECU 100. In this case, the ECU 100 compares the detection value of the humidity sensor 70 with the estimated value of the PCV gas humidity Hpcv to determine whether the humidity sensor 70 is normal or abnormal. Specifically, the ECU 100 determines that the humidity sensor 70 is normal when the absolute value of the difference between the detected value and the estimated value is less than or equal to a positive threshold value, and when the absolute value of the difference is greater than the threshold value, the ECU 100 sets the humidity sensor 70 to the normal value. Judge as abnormal. This makes it possible to suitably diagnose whether the humidity sensor 70 is normal or abnormal.

Although the embodiments of the present disclosure have been described above in detail, various other embodiments and modifications of the present disclosure are possible.

(1) For example, the above embodiment can be modified so as to estimate the humidity of the pure blow-by gas, not the blow-by gas after mixing the boost gas, that is, the PCV gas. In this case, the moisture content Wbst of the boost gas and the boost gas flow rate Qbst in the above equation (1) may be set to zero, and thus the blowby gas humidity can be simply calculated from the equation: Wbby/Qbby. In the above embodiment, the blow-by gas in this case corresponds to, for example, the blow-by gas upstream of the gas outlet 41a before the boost gas is mixed in the oil separator 40. In addition, in the case of a general oil separator that does not use boost gas, the present disclosure can be applied to estimate the humidity of blow-by gas on the downstream side of the oil separator.

(2) The boost gas passage 50 may take out the boost gas from the downstream side of the intercooler 21. Alternatively, the boost gas passage 50 may take out the boost gas from both the upstream side and the downstream side of the intercooler 21. In this case, the boost gas passage 50 may be provided with a temperature control valve that controls the temperature of the boost gas by adjusting the mixing ratio of the boost gas extracted from both.

(3) The blow-by gas processing device may be one that releases the blow-by gas to the atmosphere without circulating it into the intake passage.

The embodiments of the present disclosure are not limited to the above-described embodiments, and all modifications, applications, and equivalents included in the concept of the present disclosure defined by the claims are included in the present disclosure. Therefore, the present disclosure should not be limitedly interpreted, and can be applied to any other technique belonging to the scope of the idea of the present disclosure.

1 Internal Combustion Engine 20 Turbocharger 20C Compressor 40 Oil Separator 100 Electronic Control Unit (ECU)

Claims (4)

A device for estimating the humidity of blow-by gas in an internal combustion engine,
Calculating the water content of the blow-by gas based on the water content of the exhaust gas recirculation gas, the water content of the intake air, and the fuel combustion water content obtained by dividing the water content produced by the combustion of fuel by the exhaust flow rate. 1 step,
A second step of estimating the humidity of the blow-by gas based on the water content of the blow-by gas;
A blow-by gas humidity estimation device characterized in that it is configured to perform. The blow-by gas humidity estimation device according to claim 1, wherein in the first step, the moisture content of the blow-by gas is calculated based on a value obtained by multiplying the fuel combustion moisture concentration by a predetermined moisture mixing rate. The internal combustion engine includes an oil separator that separates oil from blow-by gas using boost gas generated by a compressor of a turbocharger,
In the second step, the blow-by gas humidity estimating apparatus estimates the humidity of the blow-by gas after the boost gas is mixed in the oil separator, based on the water content of the blow-by gas and the water content of the boost gas. The blow-by gas humidity estimation device according to claim 1. A method for estimating the humidity of blow-by gas in an internal combustion engine, comprising:
Calculating the water content of the blow-by gas based on the water content of the exhaust gas recirculation gas, the water content of the intake air, and the fuel combustion water content obtained by dividing the water content produced by the combustion of fuel by the exhaust flow rate. 1 step,
A second step of estimating the humidity of the blow-by gas based on the water content of the blow-by gas;
A method for estimating the humidity of blow-by gas, comprising:

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