JP2014159756A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine having an auxiliary air supply passage and an auxiliary air adjusting valve, and capable of cooperatively controlling a throttle valve and the auxiliary air adjusting valve in an internal combustion engine having an EGR device for taking EGR gas from the downstream side of a turbine and supplying it from the upstream side of a compressor and an electronic control type throttle valve.SOLUTION: An engine 10 comprises: an electronic control type throttle valve 40 provided in an intake passage 11; an EGR device 31; an auxiliary air supply passage 46 bypassing the throttle valve 40 and capable of supplying auxiliary air to a combustion chamber 14; and an auxiliary air adjusting valve 48. A target auxiliary air flow rate is calculated, and an opening of the auxiliary air adjusting valve 48 is operated on the basis of the target auxiliary air flow rate. Further, a target throttle flow rate is calculated, and an opening of the throttle valve 40 is operated on the basis of the difference between the target throttle flow rate and the target auxiliary air flow rate.

Description

  The present invention relates to a control device for an internal combustion engine.

  2. Description of the Related Art Conventionally, as disclosed in, for example, Japanese Patent Application Laid-Open No. 9-209798, an internal combustion engine provided with an exhaust gas recirculation (hereinafter referred to as EGR) device is known. This EGR device includes an EGR passage for sending EGR gas to an intake pipe, and an EGR valve for adjusting the amount of the EGR gas. In this internal combustion engine, the opening degree of the EGR valve is controlled in order to supply the optimum amount of EGR according to the operating state. Specifically, the EGR amount is calculated based on various parameters such as the intake air amount and the throttle opening, and the opening of the EGR valve is set according to the EGR amount. As a result, the EGR rate, which is the ratio between the EGR amount and the intake air amount including the EGR amount, is optimally set according to changes in the operating state.

  Further, the internal combustion engine is provided with an auxiliary air supply passage. The auxiliary air supply passage is provided so as to bypass the throttle valve. Further, an auxiliary air adjustment valve for adjusting the amount of auxiliary air is provided in the auxiliary air supply passage. This auxiliary air control valve is controlled in order to prevent misfire in the internal combustion engine. For example, when the engine is suddenly decelerated from an operating state with a high load and a high EGR rate and the engine shifts to a low load, the EGR valve itself is delayed and the EGR gas before the transition remaining in the intake passage affects the combustion chamber. The intake air with the correct EGR rate is supplied. As a result, the oxygen concentration in the combustion chamber decreases, which may cause misfire. Therefore, in the internal combustion engine described above, a sudden deceleration state is first detected based on the amount of change in the throttle opening. Thereafter, the auxiliary air control valve is quickly opened and fresh air is supplied to suppress an excessive increase in the EGR rate.

JP-A-9-209798

  Incidentally, there are electronically controlled throttle valves for internal combustion engines. In an internal combustion engine provided with an electronically controlled throttle valve, a throttle valve is generally used when supplying auxiliary air to the combustion chamber. For this reason, the auxiliary air supply passage and the auxiliary air control valve are usually not provided. Some internal combustion engines equipped with a supercharger include an EGR device that takes EGR gas from the downstream of the turbine and supplies it from the upstream of the compressor. Here, in an internal combustion engine equipped with an electronically controlled throttle valve and the EGR device, control for supplying auxiliary air is performed by the throttle valve. However, when EGR gas is supplied in such an internal combustion engine, the intake air upstream of the throttle valve contains EGR gas, so that only fresh air cannot be supplied. As a result, there is a concern that when the vehicle decelerates rapidly and the EGR rate becomes excessive, fresh air cannot be supplied and combustion becomes unstable.

  The present invention has been made in order to solve the above-described problems. In an internal combustion engine including an EGR device that takes EGR gas from the downstream of a turbine and supplies the EGR gas from the upstream of a compressor, and an electronically controlled throttle valve. Another object of the present invention is to provide a control device for an internal combustion engine that includes an auxiliary air supply passage and an auxiliary air adjustment valve, and that can control the throttle valve and the auxiliary air adjustment valve in a coordinated manner.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
A turbocharger having a turbine provided in an exhaust passage of an internal combustion engine and a compressor provided in an intake passage;
An electronically controlled throttle valve provided in an intake passage downstream of the compressor;
An EGR device that returns part of the exhaust gas to the combustion chamber of the internal combustion engine via an EGR passage that connects an exhaust passage downstream from the turbine and an intake passage upstream from the compressor;
An auxiliary air supply passage that bypasses the throttle valve and can supply auxiliary air to the combustion chamber of the internal combustion engine;
An internal combustion engine control device comprising: an auxiliary air control valve provided in the auxiliary air supply passage;
Target auxiliary air flow rate calculating means for calculating the target auxiliary air flow rate;
An auxiliary air control valve operating means for operating the opening of the auxiliary air control valve based on the target auxiliary air flow rate;
Target throttle flow rate calculating means for calculating the target throttle flow rate;
Throttle valve operating means for operating the throttle valve opening based on the difference between the target throttle flow rate and the target auxiliary air flow rate;
It is characterized by providing.

The second invention is the first invention, wherein
The target auxiliary air flow rate calculation means is
Throttle valve upstream EGR rate calculation means for calculating a throttle valve upstream EGR rate, which is an EGR rate upstream of the throttle valve, from an intake air amount supplied from the intake passage and an EGR amount sent from the EGR device;
When the throttle valve upstream EGR rate is larger than the upper limit EGR rate set on the basis of the maximum EGR rate that does not misfire, the target auxiliary air is set so that the EGR rate of the air supplied into the combustion chamber is equal to or lower than the upper limit EGR rate. Setting means for setting the flow rate;
It is characterized by including.

  According to the first invention, the throttle valve and the auxiliary air adjustment valve can be controlled in a coordinated manner, so that the controllability of the intake air supplied into the cylinder is improved.

  According to the second invention, it is possible to prevent the EGR rate in the combustion chamber from becoming excessively high, so that misfire can be prevented in advance.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram for demonstrating the structure of the system of Embodiment 1 of this invention. The block diagram of the control system structure in this embodiment is shown.

Embodiment 1 FIG.
[System Configuration of Embodiment 1]
FIG. 1 is a schematic configuration diagram for explaining the configuration of the system according to the first embodiment of the present invention. The system shown in FIG. 1 includes an engine 10. The engine 10 is a spark ignition type four-cycle engine, and is a supercharged engine with an EGR device. Normally, the engine 10 is composed of a plurality of cylinders, but only one cylinder is depicted in FIG. In the present invention, the number of cylinders and the cylinder arrangement are not limited thereto.

  The turbocharger 23 in the present embodiment employs a turbocharger that compresses intake air using exhaust gas. The supercharger 23 has a structure in which a compressor 24 provided in the intake passage 11 and a turbine 22 provided in the exhaust passage 13 are connected via a shaft.

  An intake passage 11 is connected to the combustion chamber 14 of the engine 10. An intake valve 16 is provided at a connection portion between the combustion chamber 14 and the intake passage 11. The intake passage 11 includes an air cleaner 26 at the inlet thereof. A compressor 24 is provided downstream of the air cleaner 26. An intercooler 38 is provided downstream of the compressor 24. A throttle valve 40 is provided downstream of the intercooler 38 to adjust the amount of intake air supplied. Here, the intake air flowing through the intake passage 11 will be described. The intake air drawn from the air cleaner 26 is compressed by the compressor 24 and then cooled by the intercooler 38. The intake air cooled by the intercooler 38 passes through the throttle valve 40 and then flows into the intake manifold 42 that is a part of the intake passage 11. The intake air flowing into the intake manifold 42 is taken into the combustion chamber 14 from the intake manifold 42 when the intake valve 16 is opened.

  An exhaust passage 13 is connected to the combustion chamber 14. An exhaust valve 18 is provided at the connection between the combustion chamber 14 and the exhaust passage 13. When the exhaust valve 18 is opened, the exhaust gas generated in the combustion chamber 14 is discharged to the exhaust passage 13. Then, the turbine 22 is rotated by the discharged exhaust gas. When the turbine 22 rotates, the compressor 24 rotates through the shaft, and supercharging is performed.

  The EGR device 31 in the present embodiment includes an EGR passage 29, an EGR cooler 30, and an EGR valve 32. The EGR passage 29 is provided with the exhaust passage 13 downstream of the turbine 22 as an inlet and the intake passage 11 upstream of the compressor 24 as an outlet. An EGR cooler 30 for cooling the exhaust gas is provided in the EGR passage 29. Further, the EGR passage 29 is provided with an EGR valve 32 for adjusting the amount of gas supplied when the cooled exhaust gas is supplied to the intake passage 11 as EGR gas. The EGR gas is compressed by the compressor 24 together with the intake air from the air cleaner 26 because the outlet of the EGR passage 29 is upstream of the compressor 24.

  An auxiliary air supply passage 46 is provided in the engine 10. The auxiliary air supply passage 46 has a structure in which the intake passage 11 between the air cleaner 26 and the compressor 24 is an inlet and the intake passage 11 between the intake manifold 42 and the intake valve 16 is an outlet. Further, the inlet of the auxiliary air supply passage 46 is provided upstream of the outlet of the EGR passage 29. For this reason, only fresh air drawn from the air cleaner 26 passes through the auxiliary air supply passage 46. An auxiliary air adjustment valve 48 for adjusting the amount of fresh air supplied is provided in the auxiliary air supply passage 46.

  According to the configuration of the system of FIG. 1, the intake air supplied to the combustion chamber 14 after passing through the throttle valve 40 contains EGR gas. On the other hand, the auxiliary air supplied from the auxiliary air supply passage 46 to the combustion chamber 14 does not contain EGR gas, that is, only fresh air can be supplied from the auxiliary air supply passage 46. Then, the intake air from the intake passage 11 and the auxiliary air from the auxiliary air supply passage 46 are mixed in the intake passage 11 between the intake manifold 42 and the intake valve 16. The air thus mixed is finally supplied into the combustion chamber 14.

  Various sensors for grasping the operating state of the engine 10 are attached to the intake passage 11. An air flow sensor 28 is attached to the downstream side of the air cleaner 26 in order to grasp the flow rate of fresh air sucked into the intake passage 11. A boost pressure sensor 36 is attached between the compressor 24 and the intercooler 38. In the vicinity of the throttle valve 40, a throttle position sensor (not shown) is attached to grasp the opening of the throttle valve 40. An intake manifold temperature sensor 44 is attached in the intake manifold 42.

上記（１）式のB_egrはスロットル開口面積に、p_scはスタコン前圧力に、p_acはエアクリ後圧力に、p_０は標準大気圧に、th_egrはＥＧＲガス温度に、th_０は標準温度にそれぞれ相当する。 The system configuration of the first embodiment includes an ECU 100 (Engine Control Unit) that controls the operating state of the engine 10. Various sensors such as an air flow sensor 28, a supercharging pressure sensor 36, an intake manifold temperature sensor 44, a throttle position sensor, and a crank angle sensor (not shown) are connected to the input side of the ECU 100. The ECU 100 detects the operating state of the engine 10 based on signals output from the various sensors. Specifically, ECU 100 detects engine speed NE from a constant pulse signal output from the crank angle sensor. Further, the ECU 100 detects the intake air amount KL from the signals output from the air flow sensor 28 and the crank angle sensor. Further, the ECU 100 calculates the current EGR amount from signals output from the supercharging pressure sensor 36, the intake manifold temperature sensor 44, the throttle position sensor, and the like. Here, the current EGR amount is the amount of EGR gas supplied from the EGR passage 29 to the intake passage 11. The current EGR amount can be obtained by the following equation (1).

In the above equation (1), B _egr is the throttle opening area, p _sc is the pre-stacon pressure, p _ac is the air post-pressure, p ₀ is the standard atmospheric pressure, th _egr is the EGR gas temperature, and th ₀ is the standard. It corresponds to each temperature.

  On the other hand, actuators such as an intake valve 16, an exhaust valve 18, an EGR valve 32, a throttle valve 40, and an auxiliary air adjustment valve 48 are connected to the output side of the ECU 100. The ECU 100 outputs signals for operating various actuators according to the operating state. For example, the ECU 100 adjusts the opening degree of the EGR valve 32 in order to supply the target EGR amount to the intake passage 11 upstream of the compressor 24. In addition, the ECU 100 adjusts the throttle flow rate by operating the opening of the throttle valve 40. Further, when supplying fresh air from the auxiliary air supply passage 46 to the combustion chamber 14, the ECU 100 operates the opening of the auxiliary air adjustment valve 48 to adjust the auxiliary air flow rate.

  According to the above system configuration, in order to supply a target intake air amount KL (hereinafter referred to as target KL) to the combustion chamber 14, the throttle flow rate and the auxiliary air flow rate must be controlled simultaneously. The air finally supplied to the combustion chamber 14 is a mixture of intake air containing EGR gas and fresh air. Therefore, it is necessary to prevent the intake air containing the EGR gas from being excessively increased and the EGR rate of the air supplied into the combustion chamber 14 to a value that may cause a misfire. In the present embodiment, the target valve KL can be supplied to the combustion chamber 14, and the throttle valve 40 and the auxiliary air adjustment valve 48 can be controlled to prevent the EGR rate of the combustion chamber 14 from becoming excessively high. We decided to perform cooperative control. Below, the specific method of the coordinated control of the valve | bulb in this embodiment was described.

[Coordinated control of valves]
The coordinated control of the valve in this embodiment will be described with reference to FIG. FIG. 2 shows a block diagram of the control system configuration in the present embodiment. FIG. 2 shows each unit of the control system in the ECU 100. The ECU 100 is provided with a KL → Pm conversion unit 50. In the KL → Pm conversion unit 50, a limit EGR amount calculation unit 52, a Min selection unit 54, and an intake valve inverse model 56 are provided. Further, the ECU 100 is provided with a throttle control unit 60. In the throttle control unit 60, a differential processing unit 62, an intake manifold inverse model 64, a target auxiliary air flow rate calculation unit 66, a difference calculation unit 67, a throttle inverse model 68, and an auxiliary air control valve inverse model 70 are provided.

  In this embodiment, the flow of the coordinated control of the valve performed by the ECU 100 will be described. First, in the limit EGR amount calculation unit 52 in the KL → Pm conversion unit 50, parameters such as the engine speed NE and the intake air amount KL are acquired. Next, the limit EGR amount calculation unit 52 calculates the limit EGR amount based on these parameters. Thereby, the limit EGR amount that can be supplied into the combustion chamber 14, that is, the limit EGR amount that is the maximum EGR amount that does not misfire can be calculated according to the operating state.

  Next, the Min selector 54 compares the limit EGR amount with the current EGR amount, and selects a smaller value. Therefore, if the limit EGR amount is equal to or less than the current EGR amount, the limit EGR amount calculated by the limit EGR amount calculation unit 52 is output from the Min selection unit 54 as it is. On the other hand, when the limit EGR amount exceeds the current EGR amount, the current EGR amount is output from the Min selection unit 54.

  Next, the limit EGR amount or the current EGR amount selected by the Min selector 54 is added to the target KL, and then input to the intake valve inverse model 56. The intake valve inverse model 56 calculates a target intake pipe pressure Pm from the input value.

  Next, the target value of the intake pipe pressure Pm output from the intake valve inverse model 56 is input to the differentiation processing unit 62 in the throttle control unit 60. Then, a differential value of the target intake pipe pressure Pm is input to the intake manifold inverse model 64. The intake manifold inverse model 64 calculates the target throttle flow rate from the differential value of the target intake pipe pressure Pm.

  Next, the target auxiliary air flow rate calculation unit 66 will be described. The target auxiliary air flow rate calculation unit 66 determines whether or not to calculate the target auxiliary air flow rate before calculating the target auxiliary air flow rate. This determination is whether or not the throttle upstream EGR rate is larger than the upper limit EGR rate. Hereinafter, the throttle upstream EGR rate and the upper limit EGR rate will be described in detail.

  The throttle upstream EGR rate is an EGR rate during intake upstream of the throttle valve 40, and is a value estimated by an air model or the like. There is a reason to use the throttle upstream EGR rate to calculate the target auxiliary air flow rate. This is because fresh air is supplied to the combustion chamber 14 before misfire occurs. For example, if the EGR rate in the air supplied into the combustion chamber 14 is used for calculation of the target auxiliary air flow rate, misfire may already occur when the EGR rate becomes excessive. This makes it difficult to prevent misfire. Therefore, the throttle upstream EGR rate is used to open the auxiliary air control valve 48 before misfire occurs.

  The upper limit EGR rate is a value set based on the maximum EGR rate that does not cause misfire. The maximum EGR rate that does not cause misfire here is a value determined by the limit EGR amount calculated by the limit EGR amount calculation unit 52, that is, the limit EGR amount that can be supplied into the combustion chamber 14. The upper limit EGR rate is set to a value lower than the maximum EGR rate that does not cause misfire. This is to provide a margin so that if there is a delay in the operation of the auxiliary air adjustment valve 48 and fresh air cannot be supplied by the next intake stroke, misfire will not occur immediately in the next intake stroke. This is the setting.

  The flow in which the target auxiliary air flow rate calculation unit 66 calculates the target auxiliary air flow rate will be described. As described above, first, it is determined whether or not the throttle upstream EGR rate is larger than the upper limit EGR rate. If the throttle upstream EGR rate is larger than the upper limit EGR rate, it is determined that a large amount of EGR gas is present in the intake passage 11 upstream of the throttle valve 40, and the target auxiliary air flow rate is calculated to supply fresh air. Then, after the target auxiliary air flow rate is calculated, the auxiliary air adjustment valve 48 opens quickly so as to satisfy the flow rate, so that misfire can be prevented. When the throttle upstream EGR rate is equal to or lower than the upper limit EGR rate, the target auxiliary air flow rate is not calculated, that is, a value of 0 is output from the target auxiliary air flow rate calculation unit 66, so the auxiliary air adjustment valve 48 does not open. .

  Here, the target auxiliary air flow rate is calculated so that the EGR rate of the air supplied into the combustion chamber 14 becomes the upper limit EGR rate. That is, the auxiliary air regulating valve 48 has an upper limit EGR rate so that the EGR rate of the air mixed with the fresh air supplied from the auxiliary air supply passage 46 and the intake air containing the EGR gas supplied from the intake passage 11 becomes the upper limit EGR rate. The flow rate is adjusted. As a result, fresh air is supplied so that the EGR rate of the air supplied into the combustion chamber 14 is less than or equal to the upper limit EGR rate. Such a target auxiliary air flow rate can be obtained by the following equation (2).

m _st = m _ct × (Rate.EGR × (1−Rate.EGR.limit) −Rate.EGR.limit)
÷ (Rate.EGR × (1−Rate.EGR.limit)) (2)
In the above equation (2), m _st is the target auxiliary air flow rate, m _ct is the target air flow rate passing through the intake valve 16, Rate.EGR is the throttle upstream EGR rate, and Rate.EGR.limit is the upper limit EGR rate. Equivalent to.

  After the target auxiliary air flow rate is calculated, the difference calculation unit 67 calculates the difference between the target throttle flow rate and the target auxiliary air flow rate.

  Next, the difference calculated by the difference calculation unit 67 is input to the throttle inverse model 68. Based on this difference, a target throttle opening degree TA is calculated. Similarly, the target auxiliary air flow rate is input to the auxiliary air control valve inverse model 70, and the target auxiliary air control valve opening is calculated. Further, the throttle inverse model 68 and the auxiliary air control valve inverse model 70 can be expressed by a throttle equation.

  According to the above-described coordinated control of the valve, it is possible to perform coordinated control in which the opening degree of the throttle valve 40 is reduced by the amount by which the auxiliary air adjustment valve 48 is opened. As a result, the target KL can be stably controlled according to the operating state, so that the air supplied into the combustion chamber 14 can be maintained at a constant amount.

  In the target auxiliary air flow rate calculation unit 66, the throttle upstream EGR rate and the upper limit EGR rate are used to calculate the target auxiliary air flow rate. However, instead of these, calculation is performed using the throttle upstream EGR amount and the limit EGR amount. May be.

  Moreover, in this embodiment, although this invention is applied to the gasoline engine with a supercharger, you may apply this to the diesel engine with a supercharger.

  In the present embodiment, the target auxiliary air flow rate calculation unit 66 is used as the “target auxiliary air flow rate calculation means” according to the first invention, and the auxiliary air adjustment valve inverse model 70 is used as the “auxiliary air adjustment method according to the first invention. The intake manifold inverse model 64 corresponds to the “target throttle flow rate calculation means” according to the first invention, and the throttle inverse model 68 corresponds to the “throttle valve operation means” according to the first invention. .

DESCRIPTION OF SYMBOLS 10 Engine 11 Intake passage 13 Exhaust passage 14 Combustion chamber 22 Turbine 23 Supercharger (turbocharger)
24 Compressor 31 EGR device 40 Throttle valve 46 Auxiliary air supply passage 48 Auxiliary air regulating valve 50 KL → Pm conversion unit 52 Limit EGR amount calculation unit 60 Throttle control unit 64 Intake manifold inverse model 66 Target auxiliary air flow rate calculation unit 67 Difference calculation unit 68 Throttle reverse model 70 Auxiliary air control valve reverse model

Claims (2)

A turbocharger having a turbine provided in an exhaust passage of an internal combustion engine and a compressor provided in an intake passage;
An electronically controlled throttle valve provided in an intake passage downstream of the compressor;
An EGR device that returns part of the exhaust gas to the combustion chamber of the internal combustion engine via an EGR passage that connects an exhaust passage downstream from the turbine and an intake passage upstream from the compressor;
An auxiliary air supply passage that bypasses the throttle valve and can supply auxiliary air to the combustion chamber of the internal combustion engine;
An internal combustion engine control device comprising: an auxiliary air control valve provided in the auxiliary air supply passage;
Target auxiliary air flow rate calculating means for calculating the target auxiliary air flow rate;
An auxiliary air control valve operating means for operating the opening of the auxiliary air control valve based on the target auxiliary air flow rate;
Target throttle flow rate calculating means for calculating the target throttle flow rate;
Throttle valve operating means for operating the throttle valve opening based on the difference between the target throttle flow rate and the target auxiliary air flow rate;
A control device for an internal combustion engine, comprising: The target auxiliary air flow rate calculation means is
Throttle valve upstream EGR rate calculation means for calculating a throttle valve upstream EGR rate, which is an EGR rate upstream of the throttle valve, from an intake air amount supplied from the intake passage and an EGR amount sent from the EGR device;
When the throttle valve upstream EGR rate is larger than the upper limit EGR rate set on the basis of the maximum EGR rate that does not misfire, the target auxiliary air is set so that the EGR rate of the air supplied into the combustion chamber is equal to or lower than the upper limit EGR rate. Setting means for setting the flow rate;
The control apparatus for an internal combustion engine according to claim 1, comprising:

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