JP2015137613A - Internal combustion engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine control device capable of realizing both exhaust performance and fuel economy not only in a stationary operating state but also in a transient operating state.SOLUTION: An internal combustion engine control device comprises: a turbocharger that includes a compressor provided in an intake passage of an internal combustion engine and a turbine provided in an exhaust passage thereof; a variable nozzle controlling a boost pressure of the turbocharger; an EGR device connecting the exhaust passage upstream of the turbine to the intake passage downstream of the compressor; target differential pressure determination means determining a target differential pressure between an intake pressure downstream of the compressor and an exhaust pressure upstream of the turbine on the basis of an operating state of the internal combustion engine; target exhaust pressure setting means setting a target exhaust pressure from the target differential pressure and the boost pressure; and exhaust pressure control means calculating an opening area of the variable nozzle for realizing the target exhaust pressure on the basis of an exhaust temperature and an exhaust pressure downstream of the variable nozzle using a nozzle formula modeling the variable nozzle, and controlling the opening of the variable nozzle depending on the opening area.

Description

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

  2. Description of the Related Art Conventionally, in an internal combustion engine equipped with a supercharger, an internal combustion engine in which the exhaust pressure of the supercharger is controlled by the opening of a variable nozzle (VN (Variable Nozzle)) is known. For example, Patent Document 1 discloses an internal combustion engine that controls the opening of a variable nozzle so that a differential pressure between an intake pressure downstream of a compressor and an exhaust pressure upstream of a turbine becomes a predetermined value. This predetermined value is a value that can reduce the amount of NOx generated. By controlling the opening of the variable nozzle in this way, exhaust performance can be improved, and at the same time, fuel consumption can be minimized.

JP 2007-192155 A

  However, since the control of the variable nozzle in the internal combustion engine described above is controlled by an intermediate value between the control value of the variable nozzle and the required value of the supercharging pressure in the transient operation state, the control for achieving the maximum compatibility between the exhaust performance and the fuel consumption. That wasn't true.

  The present invention has been made to solve the above-described problems, and provides an internal combustion engine control apparatus capable of achieving both exhaust performance and fuel efficiency not only in a steady operation state but also in a transient operation state. With the goal.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
A supercharging device having a compressor provided in an intake passage of an internal combustion engine and a turbine provided in an exhaust passage;
A variable nozzle for controlling the supercharging pressure of the supercharging device;
An EGR device connecting an exhaust passage upstream of the turbine and an intake passage downstream of the compressor;
Target differential pressure determining means for determining a target differential pressure between an intake pressure downstream of the compressor and an exhaust pressure upstream of the turbine based on an operating state of the internal combustion engine;
Target exhaust pressure setting means for setting a target exhaust pressure from the target differential pressure and the boost pressure;
Using the nozzle formula that models the variable nozzle, calculate the opening area of the variable nozzle for realizing the target exhaust pressure based on the exhaust temperature and the exhaust pressure downstream of the variable nozzle, and calculate the opening area. And an exhaust pressure control means for controlling the opening of the variable nozzle in response,
It is characterized by providing.

  According to the first aspect, even in a transient operation state, the differential pressure between the intake pressure downstream of the compressor and the exhaust pressure upstream of the turbine can be approximated to the target differential pressure. As a result, both exhaust performance and fuel efficiency can be achieved.

It is a figure which shows the structure of the engine system as Embodiment 1 of this invention. 4 is a flowchart of a variable nozzle opening control routine that is executed by an ECU in the present embodiment.

Embodiment 1 FIG.
[Entire configuration of system of this embodiment]
FIG. 1 is a diagram showing a configuration of an engine system as Embodiment 1 of the present invention. The engine of the present embodiment is a diesel engine with a turbocharger (hereinafter simply referred to as an engine). The engine body 2 is provided with a plurality of cylinders, and an injector 8 is provided for each cylinder. An intake manifold 4 and an exhaust manifold 6 are attached to the engine body 2. An intake passage 10 is connected to the intake manifold 4. Fresh air taken from the air cleaner 20 flows through the intake passage 10. A turbocharger compressor 14 is attached to the intake passage 10. A diesel throttle 24 is provided downstream of the compressor 14 in the intake passage 10. An intercooler 22 is provided between the compressor 14 and the diesel throttle 24 in the intake passage 10. The exhaust manifold 6 is connected to an exhaust passage 12 for releasing the exhaust gas emitted from the engine body 2 into the atmosphere. A turbocharger turbine 16 is attached to the exhaust passage 12. The turbocharger of the present embodiment is a variable displacement type, and the turbine 16 is provided with a variable nozzle (VN) 18. A catalyst 26 for purifying exhaust gas is provided downstream of the turbine 16 in the exhaust passage 12.

  The engine of the present embodiment includes an EGR device that recirculates exhaust gas from the exhaust system to the intake system. In the EGR device, a position downstream of the diesel throttle 24 in the intake passage 10 and the exhaust manifold 6 are connected by an EGR passage 30. An EGR valve 32 is provided in the EGR passage 30. An EGR cooler 34 is provided on the exhaust side of the EGR valve 32 in the EGR passage 30. The EGR passage 30 is provided with a bypass passage 36 that bypasses the EGR cooler 34. A bypass valve 38 that switches the direction in which the exhaust gas flows is provided at a location where the EGR passage 30 and the bypass passage 36 merge.

  The engine system of the present embodiment includes an ECU (Electronic Control Unit) 50. The ECU 50 is a control device that comprehensively controls the entire engine system. The ECU 50 takes in signals from sensors provided in the engine system and executes various processes. Sensors are installed in various parts of the engine system. For example, an air flow meter 58 is attached to the intake passage 10 downstream of the air cleaner 20, an intake air temperature sensor 60 is attached near the outlet of the intercooler 22, and a supercharging pressure sensor 54 is attached downstream of the diesel throttle. ing. A pre-turbo exhaust pressure sensor 56 and an exhaust manifold temperature sensor 66 are attached to the exhaust manifold 6. A turbo post-exhaust pressure sensor 64 is attached between the variable nozzle 18 and the catalyst 26. Furthermore, a rotation speed sensor 52 that detects rotation of the crankshaft, an accelerator opening sensor 62 that outputs a signal corresponding to the opening of the accelerator pedal, and the like are also attached. The ECU 50 processes the signals of the acquired sensors and operates the actuators according to a predetermined control program. The actuator operated by the ECU 50 includes the variable nozzle 18, the injector 8, the EGR valve 32, the diesel throttle 24, and the like. There are many actuators and sensors connected to the ECU 50 other than those shown in the figure, but the description thereof is omitted in this specification.

[Nozzle type modeling variable nozzle 18]
In this embodiment, in order to approximate the differential pressure between the intake pressure downstream of the compressor 14 and the exhaust pressure upstream of the turbine 16 to the target differential pressure PL, the opening of the variable nozzle 18 provided in the turbine 16 is set. A control method is adopted. Here, the target differential pressure PL is determined based on engine operating conditions, and specifically, is determined from the fuel injection amount from the injector 8, the engine speed, and the like. Further, in the present embodiment, in the steady state, the differential pressure that can improve the fuel efficiency most in a range where the exhaust performance is not deteriorated is measured for each driving condition by a test or simulation, and the result is a target difference. It is recorded on a map that associates the pressure PL with the operating conditions.

In order to determine the opening degree of the variable nozzle 18 that achieves this target differential pressure, the ECU 50 is set with a nozzle type that models the variable nozzle 18. By solving this nozzle equation, the opening area characteristic μAvn of the variable nozzle 18 is obtained. This nozzle type is expressed by the following formula (1). Where μ is the flow coefficient, Avn is the opening area (m ² ), Mvn is the VN passage gas flow rate, R is the gas constant, κ is the specific heat ratio, T4 is the exhaust gas temperature, P4k is the target exhaust pressure, and P6 is after the turbo Exhaust pressure. The target exhaust pressure P4k is derived by adding the target differential pressure PL and the supercharging pressure pim.

  Based on the opening area characteristic μAvn of the variable nozzle 18 calculated by the above equation (1), the opening target value vnbse of the variable nozzle 18 is calculated by the following equation (2). Here, a is a coefficient (adapted value), and b is a constant (adapted value).

  The opening degree of the variable nozzle 18 is controlled based on the opening degree target value vnbse calculated by the above equation (2). By controlling the opening degree of the variable nozzle 18 based on the nozzle type in this way, the variable nozzle is reflected by reflecting values that change during transient operation, such as the exhaust gas temperature T4, the exhaust pressure P6 after turbo, and the supercharging pressure pim. The opening degree of 18 can be controlled. For this reason, even in the transient operation state, the differential pressure between the intake pressure downstream of the compressor 14 and the exhaust pressure upstream of the turbine 16 can be approximated to the target differential pressure. As a result, both exhaust performance and fuel efficiency can be achieved.

  Below, the variable nozzle opening degree control using the nozzle type performed by ECU50 is demonstrated with reference to FIG.

[Variable nozzle opening control routine]
FIG. 2 is a flowchart of a variable nozzle opening control routine executed by the ECU 50 in the present embodiment. The ECU 50 has a memory for storing this routine. The ECU 50 has a processor for executing the stored routine.

  First, the ECU 50 detects the engine speed based on the output of the speed sensor 52 (S100).

  Next, the ECU 50 calculates the fuel injection amount Q according to the output of the accelerator opening sensor 62 (S102).

  Next, the ECU 50 detects the supercharging pressure pim based on the current output of the supercharging pressure sensor 54 (S104).

  Next, the ECU 50 detects the pre-turbo exhaust pressure P4 based on the current output of the pre-turbo exhaust pressure sensor 56 (S106).

  Next, the ECU 50 detects the exhaust gas temperature T4 based on the current output of the exhaust manifold temperature sensor 66 (S108).

  Next, the ECU 50 detects the post-turbo exhaust pressure P6 based on the current output of the post-turbo exhaust pressure sensor 64 (S110).

  Next, the ECU 50 calculates the fresh air amount Gst by substituting the engine speed and the fuel injection amount Q into a map stored in advance (S112). In this map, the engine speed, the fuel injection amount Q, and the fresh air amount Gst are associated on the assumption of steady performance.

  Next, the ECU 50 calculates the current VN passage gas flow rate Mvn (S114). The VN passage gas flow rate Mvn is the sum of the fresh air amount Gst and the fuel injection amount Q.

  Next, the ECU 50 calculates a target differential pressure PL according to the engine speed and the fuel injection amount Q (S116).

  Next, the ECU 50 calculates the target exhaust pressure P4k from the target differential pressure PL (S118). The target exhaust pressure P4k is a sum of the target differential pressure PL and the supercharging pressure pim.

  Next, the ECU 50 calculates a VN opening area characteristic μAvn from the VN passage gas flow rate Mvn, the target exhaust pressure P4k, the turbo post-exhaust pressure P6, and the exhaust manifold gas temperature T4 based on the equation (1) (S120).

  Next, the ECU 50 calculates the VN opening target value vnbse from the VN opening area characteristic μAvn based on the equation (2) (S122). As an example of the VN opening target value vnse, there is an effective opening area of a variable nozzle.

  Next, the ECU 50 feedforward-controls the VN opening according to the VN opening target value vnbse (S124). Thereafter, this routine ends.

  When the ECU 50 executes the above-described S116, the “target differential pressure determining means” of the first aspect of the invention causes the “target exhaust pressure setting means” of the first aspect of the invention to execute the above-described S118. By executing S120, S122, and S124, the “exhaust pressure control means” of the first aspect of the present invention is realized.

2 Engine body 4 Intake manifold 6 Exhaust manifold 8 Injector 10 Intake passage 12 Exhaust passage 14 Compressor 16 Turbine 18 Variable nozzle 24 Diesel throttle 30 EGR passage 32 EGR valve 52 Speed sensor 54 Supercharging pressure sensor 56 Pre-turbo exhaust pressure sensor 58 Airflow Meter 60 Intake air temperature sensor 62 Accelerator opening sensor 64 Turbo exhaust pressure sensor 66 Exhaust manifold temperature sensor

Claims (1)

A supercharging device having a compressor provided in an intake passage of an internal combustion engine and a turbine provided in an exhaust passage;
A variable nozzle for controlling the supercharging pressure of the supercharging device;
An EGR device connecting an exhaust passage upstream of the turbine and an intake passage downstream of the compressor;
Target differential pressure determining means for determining a target differential pressure between an intake pressure downstream of the compressor and an exhaust pressure upstream of the turbine based on an operating state of the internal combustion engine;
Target exhaust pressure setting means for setting a target exhaust pressure from the target differential pressure and the boost pressure;
Using the nozzle formula that models the variable nozzle, calculate the opening area of the variable nozzle for realizing the target exhaust pressure based on the exhaust temperature and the exhaust pressure downstream of the variable nozzle, and calculate the opening area. And an exhaust pressure control means for controlling the opening of the variable nozzle in response,
A control device for an internal combustion engine, comprising:

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