JP5418787B2 - Intake control device for internal combustion engine - Google Patents

Description

  The present invention relates to an intake air control apparatus for an internal combustion engine, and relates to a technique for calculating an intake air flow rate by estimating a deposit state in an intake passage.

  As means for measuring the intake flow rate of an engine (internal combustion engine), a method of directly detecting with an air flow sensor or a method of estimating from an engine rotational speed and intake pressure as in a speed density method is known. In particular, in the speed density method, for example, by detecting the intake pressure with the intake manifold, it is possible to estimate the intake flow rate immediately before flowing into the combustion chamber and to suppress the intake resistance.

  However, there is a possibility that deposits such as dust adhere to the intake pipe of the engine. If deposits adhere to the intake pipe in this way, the intake pressure changes, and there is a possibility that the intake flow rate cannot be accurately detected by the speed density method as described above. Therefore, a technology for detecting whether the intake flow rate estimated by the speed density method is accurate by newly providing a detection device for intake flow rate other than the speed density method and comparing the detected value of the intake flow rate has been developed. (Patent Document 1).

  Further, in an engine equipped with an exhaust gas recirculation (hereinafter referred to as EGR) device, the intake air amount is detected by an air flow sensor, and immediately before flowing into the combustion chamber of the engine by a speed density method, that is, including EGR gas. A technique for estimating the intake flow rate has been developed. In such an engine, it is possible to detect the intake air amount and the EGR amount, respectively, and it is possible to accurately control both the throttle valve and the EGR valve based on these detected values.

JP 2006-242067 A

In an engine equipped with an EGR device, exhaust gas recirculates to the intake pipe, so that the soot in the exhaust gas easily accumulates in the intake pipe as a deposit. Therefore, when detecting the intake air flow rate by the speed density method, it is necessary to further suppress the influence of the deposit.
However, in an engine equipped with an EGR device, even if an air flow sensor is provided in addition to the speed density method as described above, it is for detecting the flow rate of intake air that does not contain EGR gas. It cannot be simply compared with the intake flow rate detected by the density method. Therefore, in order to accurately detect the intake flow rate including the EGR gas, it is necessary to further provide an intake flow rate detection device as described in Patent Document 1, resulting in an increase in cost.

  An object of the present invention is an internal combustion engine equipped with an EGR device, in which an intake air flow rate can be easily estimated and an intake air flow rate can be accurately detected without providing a new intake flow rate detection device. It is to provide a control device.

In order to achieve the above object, an intake control apparatus for an internal combustion engine according to claim 1 introduces a part of exhaust gas from an exhaust passage of the internal combustion engine and recirculates the exhaust gas to the intake passage, and exhaust gas recirculation that opens and closes the exhaust recirculation passage A fresh air flow rate detection means for detecting a fresh air flow rate that is provided upstream of the connection position between the valve and the exhaust gas recirculation passage and detects the fresh air flow rate that passes through the intake passage, and is located downstream of the connection position of the exhaust gas recirculation passage. An intake pressure detecting means provided in the intake passage for detecting the intake pressure and passing through the intake passage downstream from the connection position with the exhaust gas recirculation passage based on at least the intake pressure and the volumetric efficiency detected by the intake pressure detecting means. Based on the intake air flow rate calculating means for calculating the intake air flow rate, the fresh air flow rate detected by the fresh air flow rate detecting means and the intake air flow rate calculated by the intake flow rate calculating means with the exhaust gas recirculation valve closed. Te, correction for correcting a closing state estimating means for estimating the closed state of the intake passage, based on the closed state of the intake passage estimated by closed state detection means, the volumetric efficiency for calculating the intake air flow rate by the intake air flow rate calculating means And the intake air flow rate calculated by the intake air flow rate calculation means using the volumetric efficiency corrected by the correction means and the fresh air flow rate detected by the fresh air flow rate detection means when the exhaust gas recirculation valve is opened. And an exhaust gas recirculation amount calculating means for calculating the flow rate of the exhaust gas that passes through the exhaust gas recirculation passage and is recirculated to the intake passage.

According to a second aspect of the present invention, there is provided an intake control apparatus for an internal combustion engine according to the first aspect, wherein the blockage state estimating means calculates the blockage index of the intake passage from the ratio of the fresh air flow rate to the intake flow rate and the rotational speed of the internal combustion engine. Features .

According to a third aspect of the present invention, the intake air control apparatus for an internal combustion engine according to the first or second aspect is characterized in that the fresh air flow rate detecting means is an air flow sensor.
According to a fourth aspect of the present invention, there is provided the intake control device for an internal combustion engine according to any one of the first to third aspects, wherein the blockage state estimating means forcibly closes the exhaust gas recirculation valve for a predetermined time during operation of the internal combustion engine. Thus, the blockage state of the intake passage is estimated.

  According to the intake control apparatus for an internal combustion engine of claim 1 of the present invention, in the state where the exhaust gas recirculation valve is closed, the larger the blockage state of the intake passage, the greater the difference between the exhaust gas recirculation passage detected by the fresh air flow rate detecting means. Since the difference between the fresh air flow rate that passes through the intake passage upstream from the connection position and the intake flow rate that passes through the intake passage downstream from the connection position of the exhaust gas recirculation passage calculated by the intake flow rate calculation means increases, Based on the fresh air flow rate and the intake air flow rate, it is possible to easily estimate the closed state of the intake passage without providing a new intake flow rate detection device.

Then, the correction means corrects the volumetric efficiency for calculating the intake flow rate based on the blockage state of the intake passage, and corrects the intake flow rate using the corrected volumetric efficiency. Regardless, the intake air flow rate can be accurately obtained based on the intake pressure and the intake air temperature.
Further, in a state where the exhaust gas recirculation valve is opened, the exhaust gas recirculation amount calculating means is based on the difference between the fresh air flow rate detected by the fresh air flow rate detecting means and the corrected intake air flow rate calculated by the intake air flow rate calculating means. Since the flow rate of exhaust gas recirculated to the intake passage is calculated, the flow rate of exhaust gas recirculated to the intake passage can be accurately obtained regardless of the closed state of the intake passage.
According to the exhaust gas purification apparatus for an internal combustion engine of claim 2 of the present invention, the blockage index of the intake passage is calculated from the ratio of the fresh air flow rate to the intake flow rate and the rotational speed of the internal combustion engine. It is possible to estimate the occlusion state more accurately without being affected somewhat.

According to the exhaust gas purification apparatus for an internal combustion engine of the third aspect of the present invention, it is possible to easily detect the flow rate of fresh air passing through the intake passage upstream from the connection position with the exhaust gas recirculation passage.
According to the exhaust gas purification apparatus for an internal combustion engine of claim 4 of the present invention, the blockage state estimating means forcibly closes the exhaust gas recirculation valve for a predetermined time during operation of the internal combustion engine to estimate the blockage state of the intake passage. Therefore, the opportunity to estimate the occlusion state can be increased. Therefore, the opportunity for correcting the intake air flow rate by the correcting means increases, and the calculation accuracy of the intake air flow rate in the intake flow rate calculating means can be further improved.

1 is a schematic configuration diagram of an intake / exhaust system of an engine to which an intake control device of the present invention is applied. It is a flowchart which shows the correction | amendment point of volumetric efficiency. It is an example of the map which calculates | requires an obstruction | occlusion coefficient. It is an example of the map which calculates | requires the correction coefficient of volumetric efficiency.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an intake / exhaust system of an engine 1 (internal combustion engine) to which an intake control device of the present invention is applied.
The engine 1 of the present embodiment is a diesel engine provided with a turbocharger 2 and an EGR device 3.

The cylinder head 4 of the engine 1 is provided with a fuel injection valve 5 for each cylinder. The fuel injection valve 5 has a function of injecting high-pressure fuel supplied from a common rail (not shown) into the cylinder.
An air cleaner 12 is interposed in the intake pipe 10 (intake passage) of the engine 1 upstream of the compressor 11 of the turbocharger 2. A throttle valve 13 is interposed in the intake pipe 10 on the downstream side of the compressor 11. The air cleaner 12 has a function of capturing dust in the intake air. The throttle valve 13 has a function of controlling the fresh air flow rate by adjusting the flow passage area of the intake pipe 10.

The intake pipe 10 between the air cleaner 12 and the compressor 11 is provided with an air flow sensor 20 (new air flow rate detecting means) for detecting the new air flow rate Ga. The intake manifold 21 of the engine 1 is provided with an intake pressure sensor 22 (intake pressure detection means) for detecting the intake pressure Pim and a temperature sensor 23 for detecting the intake air temperature.
The exhaust pipe 30 of the engine 1 is provided with a turbine 31 of the turbocharger 2 and an exhaust purification device such as an oxidation catalyst and a DPF (not shown) on the downstream side thereof.

  The EGR device 3 includes an EGR passage 32 and an EGR valve 33 that opens and closes the EGR passage 32. The EGR passage 32 connects the exhaust manifold 34 of the engine 1 and the intake pipe 10 downstream of the throttle valve 13. The EGR device 3 has a function of opening part of the EGR valve 33 to recirculate part of the exhaust gas into the intake pipe 10 and lowering the combustion temperature of the engine 1 to suppress NOx emission.

The ECU 40 is a control device for performing comprehensive control including operation control of the engine 1, and includes an input / output device, a storage device (ROM, RAM, nonvolatile RAM, etc.), a central processing unit (CPU), and the like. It consists of
Various sensors such as an air flow sensor 20, an intake pressure sensor 22, a temperature sensor 23, a crank angle sensor 24 for detecting the crank angle of the engine 1 and an accelerator position sensor (not shown) are connected to the input side of the ECU 40. Detection information from a class is input.

  Various output devices such as the throttle valve 13, the EGR valve 33, and the fuel injection valve 5 are connected to the output side of the ECU 40. The ECU 40 calculates a fresh air flow rate, an EGR amount, a fuel injection amount, a fuel injection timing, and the like based on detection information from various sensors, and outputs them to various output devices, so that the throttle valve 13, The EGR valve 33, the fuel injection valve 5 and the like are controlled.

  In the present embodiment, the fresh air flow rate Ga introduced into the intake pipe 10 is detected by the air flow sensor 20, and the ECU 40 is based on the intake pressure Pim detected by the intake pressure sensor 22 and the intake air temperature Tim detected by the intake air temperature sensor. Then, the gas flow rate (intake flow rate) Gt in the intake pipe flowing into the combustion chamber of the engine 1 is estimated by the speed density method. The intake pipe gas flow rate Gt is a total flow rate including the EGR gas recirculated by the EGR device 3 and the fresh air that has passed through the throttle valve 13. The ECU 40 calculates the EGR amount Ge by subtracting the fresh air flow rate Ga detected by the air flow sensor 20 from the gas flow rate Gt in the intake pipe by the speed density method (exhaust recirculation amount calculation means). The ECU 40 uses the fresh air flow rate Ga and the EGR amount Ge obtained in this way, so that the throttle valve 13 and the EGR valve 33 are set so as to obtain a desired intake air flow rate and EGR amount set based on an accelerator operation or the like. Control.

  Further, in the present embodiment, the ECU 40 has a function of estimating the blockage state due to the deposit of the intake pipe 10 and improving the calculation accuracy of the intake pipe gas flow rate Gt by the speed density method. Specifically, when deposits are accumulated in the intake pipe 10 due to soot contained in the exhaust gas recirculated by the EGR device 3, the actual flow rate is reduced even if the intake pressure Pim detected by the intake pressure sensor 22 is the same. Therefore, an error may occur in the calculation of the intake pipe gas flow rate Gt based on the intake pressure Pim. Therefore, the gas flow rate Gt in the intake pipe is corrected so that the error due to deposit accumulation is eliminated.

FIG. 2 is a flowchart showing a procedure for correcting the volumetric efficiency ηv used when calculating the gas flow rate Gt in the intake pipe. This routine is repeatedly performed at predetermined intervals when the EGR valve 33 is closed during engine operation.
First, in step S10, the fresh air flow rate Ga detected by the air flow sensor 20 is input. Then, the process proceeds to step S20.

In step S20, the intake pressure Pim detected by the intake pressure sensor 22 is input, and the intake pipe gas flow rate Gt is calculated. The intake pipe gas flow rate Gt is calculated by the following equation (1).
Gt = Vcyl × ηv × ρa × (Pim / Pa) × √ (Ta / Tim) (1)
Where Vcyl is the cylinder volume, ηv is the volumetric efficiency, ρa is the atmospheric density, Pa is the atmospheric pressure, Ta is the reference atmospheric temperature, and Tim is the intake air temperature detected by the temperature sensor 23. The volume efficiency used here is an index of the intake flow rate that can be taken into the combustion chamber in the intake stroke, and is a value obtained by dividing the intake volume in the state of the intake pipe by the exhaust amount. Then, the process proceeds to step S30. The calculation of the intake pipe gas flow rate Gt in this step corresponds to the intake flow rate calculation means of the present invention. In the system configuration, when the EGR valve 33 is closed and there is no change due to deposit accumulation or the like, the fresh air flow rate Ga and the intake pipe gas flow rate Gt are basically equal.

In step S30, the fresh air flow rate Ga input in step S10 is compared with the intake pipe gas flow rate Gt calculated in step S20. Specifically, it is determined whether or not Ga / Gt <1, and if Ga / Gt <1, the process proceeds to step S40.
In step S40, the blockage index is calculated based on Ga / Gt, which is the ratio between the fresh air flow rate Ga and the intake pipe gas flow rate Gt, and the engine speed Ne obtained from the change in the crank angle input from the crank angle sensor 23. Ib is calculated. The block index Ib may be obtained using a map as shown in FIG. 3, for example. As shown in FIG. 3, the blockage coefficient Ib is set to increase as the ratio Ga / Gt between the fresh air flow rate Ga and the intake pipe gas flow rate Gt decreases. The closing index Ib is an index indicating the degree of blocking of the intake pipe 10, and indicates that the blocking degree increases as the closing index Ib increases. Then, the process proceeds to step S50. The calculation of the blockage coefficient Ib in this step corresponds to the blockage state estimation means of the present invention.

  In step S50, the volumetric efficiency ηv used to calculate the intake pipe gas flow rate Gt represented by the above equation (1) is corrected. The volumetric efficiency ηv is corrected by multiplying the correction coefficient Cηv. The correction coefficient Cηv may be obtained using a map as shown in FIG. 4 based on the closing index Ib calculated in step S40 and the engine speed Ne. Note that the correction of the volumetric efficiency ηv in this step corresponds to the correction means of the present invention. Then, this routine ends.

In step S40, if Ga / Gt <1, that is, if the fresh air flow rate Ga and the intake pipe gas flow rate Gt are the same, the process returns to step S10.
By controlling as described above, the volume efficiency ηv used for calculating the gas flow rate Gt in the intake pipe is corrected. The correction coefficient Cηv for correcting the volumetric efficiency ηv is obtained based on the blockage index Ib indicating the blockage degree of the intake pipe 10. In this embodiment, the ECU 40 stores the closing index Ib, and then uses the closing index Ib when calculating the intake pipe gas flow rate Gt when the EGR valve 33 is opened. Then, the correction coefficient Cηv is calculated and the corrected volumetric efficiency ηv is used. Therefore, when the intake pipe gas flow rate Gt is calculated, the degree of blockage of the intake pipe 10 is reflected. For example, it is assumed that the intake pipe 10 is closed by deposit and the intake pressure Pim increases or the actual intake flow rate decreases. In addition, the gas flow rate Gt in the intake pipe can be accurately calculated.

  Thus, since the intake pipe gas flow rate Gt is accurately calculated without being affected by deposits, the EGR amount Ge obtained by the difference between the intake pipe gas flow rate Gt and the fresh air flow rate Ga can be accurately calculated. It becomes possible to operate the EGR valve 33 accurately. Specifically, even if the actual intake flow rate decreases due to the deposit, the EGR amount Ge is not set too small, and an increase in NOx can be suppressed.

  In this embodiment, in the engine 1 provided with the EGR device 3, an intake flow rate calculation means by a speed density method for calculating an intake pipe gas flow rate Gt (intake flow rate) including fresh air and EGR gas based on the intake pressure Pim; When the EGR valve 33 is closed using the fresh air flow rate detecting means for detecting the fresh air flow rate Ga by the air flow sensor 20, the intake pipe gas flow rate Gt is compared with the fresh air flow rate Ga. The degree of blockage of the intake pipe 10 is estimated based on the ratio Ga / Gt. The intake flow rate detection means and the fresh air flow rate detection means are provided in advance for calculating the EGR amount, By using these, it is possible to easily estimate the degree of blockage without increasing the component cost.

  In this embodiment, the volumetric efficiency ηv is corrected when the EGR valve 33 is closed. However, the volumetric efficiency ηv may be corrected by forcibly closing the EGR valve 33 during engine operation. Good. In this way, the opportunity for correcting the volumetric efficiency ηv increases, the deposit blockage situation can always be accurately grasped, and the subsequent operation control when the EGR valve 33 is opened can be performed more accurately.

  Moreover, in this embodiment, although this invention is applied to the diesel engine, this invention is applicable also to a gasoline engine.

1 Engine 10 Intake pipe
13 Throttle valve 20 Air flow sensor
22 Intake pressure sensor
32 EGR passage
33 EGR valve 40 ECU

Claims (4)

An exhaust gas recirculation passage for introducing a part of the exhaust gas from the exhaust passage of the internal combustion engine and returning it to the intake air passage;
An exhaust gas recirculation valve for opening and closing the exhaust gas recirculation passage;
A fresh air flow rate detecting means that is provided in the intake passage upstream of the connection position with the exhaust gas recirculation passage and detects a fresh air flow rate passing through the intake passage;
An intake pressure detecting means that is provided in the intake passage downstream from the connection position with the exhaust gas recirculation passage, and detects intake pressure;
An intake flow rate calculating means for calculating an intake flow rate passing through the intake passage downstream from the connection position with the exhaust gas recirculation passage based on at least the intake pressure and volumetric efficiency detected by the intake pressure detection means;
The closed state of the intake passage is estimated based on the fresh air flow rate detected by the fresh air flow rate detection means and the intake air flow rate calculated by the intake air flow rate calculation means with the exhaust gas recirculation valve closed. Occlusion state estimation means;
Correction means for correcting the volumetric efficiency for calculating the intake flow rate by the intake flow rate calculating means based on the closed state of the intake passage estimated by the closed state detecting means;
In the state where the exhaust gas recirculation valve is opened, the intake air flow rate calculated by the intake air flow rate calculation unit using the fresh air flow rate detected by the fresh air flow rate detection unit and the volume efficiency corrected by the correction unit. And an exhaust gas recirculation amount calculating means for calculating a flow rate of exhaust gas that passes through the exhaust gas recirculation passage and is recirculated to the intake passage,
An intake control device for an internal combustion engine, comprising:   2. The intake control of the internal combustion engine according to claim 1, wherein the blockage state estimation unit calculates a blockage index of the intake passage based on a ratio between the fresh air flow rate and the intake flow rate and a rotation speed of the internal combustion engine. apparatus.   The intake air control apparatus for an internal combustion engine according to claim 1 or 2, wherein the fresh air flow rate detection means is an air flow sensor.   4. The blockage state estimating means estimates the blockage state of the intake passage by forcibly closing the exhaust gas recirculation valve for a predetermined time during operation of the internal combustion engine. The intake control device for an internal combustion engine according to any one of the preceding claims.

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