JP2015206307A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine which can make compatible the improvement of exhaust performance and the improvement of fuel economy performance in the transit operation.SOLUTION: An intake temperature thia is calculated from a signal of an intake temperature sensor 60. Throttle pre-intake pressure P3 is calculated from a signal of an intake pressure sensor 62. Turbo pre-exhaust pressure P4 is calculated from a signal of an exhaust pressure sensor 54. A fresh air amount Ga is calculated from a signal of an airflow meter 58. A transition target pumping loss PL is calculated from an engine rotation number and a fuel injection amount Q. Target intake pressure Pimk is calculated from the transition target pumping loss PL. By substituting the fresh air amount Ga, the target intake pressure Pimk, the intake temperature thia, and the throttle pre-intake pressure P3 into a nozzle formula, an opening area characteristic μAis calculated, and a target throttle opening dthbse is calculated on the basis of the opening area characteristic μA. Then, an opening of a throttle 24 is feed-forward controlled according to the target throttle opening dthbse.

Description

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

  Conventionally, for example, Japanese Unexamined Patent Application Publication No. 2010-265801 discloses a technique related to engine throttle control. According to the technique described in this publication, the target EGR amount is calculated based on the required torque, and the target intake pressure is calculated using the target EGR amount. Then, using a predetermined tracking control method and a non-interference control method, the non-interacting compensation value is calculated so that the intake pressure follows the target intake pressure and does not interfere with the intake air amount. By adding this to the basic throttle opening calculated based on the required torque, the target throttle opening is calculated.

JP 2010-265801 A

  By the way, in order to improve the fuel efficiency, it is desirable to control the throttle so that the pumping loss is minimized. However, the technique disclosed in Patent Document 1 calculates the target intake pressure and performs throttle control from the viewpoint of optimizing the EGR amount, and does not consider pumping loss at all. For this reason, the conventional throttle control can be expected to improve the exhaust performance by optimizing the EGR amount at the time of transient operation, but it is insufficient as a control for improving the fuel efficiency, and there is still room for improvement. ing.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an internal combustion engine control device capable of achieving both improvement in exhaust performance and improvement in fuel efficiency during transient operation. To do.

In order to achieve the above object, a first invention provides a control device for an internal combustion engine,
A turbocharger having a compressor provided upstream of the throttle in the intake passage and a turbine provided in the exhaust passage;
A target differential pressure that calculates a target differential pressure that is a target value of a differential pressure between the intake pressure downstream of the compressor and upstream of the throttle and the exhaust pressure upstream of the turbine, based on the operating state of the internal combustion engine A calculation means;
Exhaust pressure acquisition means for acquiring the exhaust pressure upstream of the turbine;
Target intake pressure calculating means for calculating a target intake pressure that is a target value of the intake pressure based on the target differential pressure and the exhaust pressure;
A target opening calculation means for calculating an opening area of the throttle for realizing the target intake pressure using a nozzle type that models the throttle, and calculating a target opening of the throttle based on the opening area When,
Control means for controlling the throttle opening to the target opening;
It is characterized by providing.

  According to the first invention, since the throttle is controlled so as to achieve the target differential pressure during transient operation, it is possible to achieve both improvement in exhaust performance and improvement in fuel efficiency.

It is a figure which shows the structure of the engine system with which the control apparatus of embodiment of this invention is applied. It is a flowchart which shows the routine for the intake pressure control performed by the control apparatus of embodiment of this invention.

  Embodiments of the present invention will be described with reference to the drawings.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration of an engine system to which a control device according to an embodiment of the present invention is applied. The internal combustion engine according to the present embodiment is a diesel engine with a turbocharger (hereinafter simply referred to as an engine). The engine body 2 is provided with four cylinders in series, 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 through which fresh air taken in from the air cleaner 20 flows is connected to the intake manifold 4. A turbocharger compressor 14 is attached to the intake passage 10. A 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 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 is a variable displacement type, and the turbine 16 is provided with a variable nozzle 18. A catalyst device 26 for purifying exhaust gas is provided downstream of the turbine 16 in the exhaust passage 12.

  The engine according to 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 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 bypass passage 36 branched from the EGR passage 30 joins the EGR passage 30 again.

  The engine system according to the present embodiment includes an ECU (Electronic Control Unit) 50. The ECU 50 is a control device that comprehensively controls the entire engine system, and the control device according to the present invention is embodied as one function of the ECU 50.

  The ECU 50 captures and processes a sensor signal provided in the engine system. Sensors are installed in various parts of the engine system. An air flow meter 58 for detecting a fresh air amount Ga is attached to the intake passage 10 downstream of the air cleaner 20. An intake air temperature sensor 60 for detecting a pre-throttle intake pressure P3, which is a pressure upstream of the throttle 24, and an intake air upstream of the throttle 24 are positioned downstream of the compressor 14 and upstream of the throttle 24 in the intake passage 10. An intake pressure sensor 62 for detecting the temperature thia is attached, and a boost pressure sensor 64 for detecting the boost pressure Pim is attached downstream of the throttle 24. Further, an exhaust pressure sensor 54 for detecting a pre-turbo exhaust pressure P4 that is a pressure upstream of the turbine 16 is attached to the exhaust manifold 6. Further, the engine system is also provided with a rotation speed sensor 52 that detects rotation of the crankshaft, an accelerator opening sensor 56 that outputs a signal corresponding to the opening of the accelerator pedal, and the like. 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 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.

  The engine control executed by the ECU 50 includes intake pressure control. In the intake air pressure control of the present embodiment, a target throttle opening for realizing the target intake air pressure calculated based on the operating state of the engine is calculated, and feedforward control is performed so as to obtain the calculated target intake air pressure. The throttle 24 is operated. In carrying out the present invention, there is no limitation regarding a specific method of feedforward control in intake pressure control.

  The intake pressure control executed in the present embodiment is characterized by a method for determining a target intake pressure. That is, the intake pressure control executed in the present embodiment is a differential pressure between the pre-throttle intake pressure P3 downstream of the compressor 14 and upstream of the throttle 24 and the pre-turbo exhaust pressure P4 upstream of the turbine 16 during transient operation. In order to approximate the pumping loss at the time of transition expressed by the formula (1) to the transient target pumping loss PL that is the target value, a method of controlling the throttle opening of the throttle 24 is employed. Here, the transient target pumping loss PL is determined based on the operating condition of the engine, and specifically, is determined from the fuel injection amount Q from the injector 8 and the engine speed. . 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 the transient target. It is recorded in a map that associates the pumping loss PL with the operating conditions.

In order to determine the throttle opening degree that achieves this transient target pumping loss PL, a nozzle type that models the throttle 24 is set in the ECU 50. By solving this nozzle equation, the opening area characteristic μA _th of the throttle 24 is obtained. This nozzle type is expressed by the following formula (1). In the following equation (1), μ is a flow coefficient, A _th is an opening area (m ² ), R is a gas constant (J / K · Kg), Pimk is a target intake pressure, and κ is a specific heat ratio. Yes.

The target throttle opening dthbse of the throttle 24 is calculated by substituting the opening area characteristic μA _th of the throttle 24 calculated by the above equation (1) into the following equation (2). Here, a is a coefficient (adapted value), and b is a constant (adapted value).

  The opening degree of the throttle 24 is controlled based on the target throttle opening degree dthbse calculated by the above equation (2). Thus, by controlling the opening degree of the throttle 24 based on the nozzle type, the intake air temperature thia, the pre-throttle intake pressure P3, and the pre-turbo exhaust pressure P4 that change during transient operation can be reflected in the opening degree of the throttle 24. it can. As a result, the pumping loss can be approximated to the transient target pumping loss even in the transient operation state, so that both improvement in exhaust performance and improvement in fuel efficiency can be achieved.

  Hereinafter, the intake pressure control using the nozzle type executed by the ECU 50 will be described with reference to FIG. FIG. 2 is a flowchart showing a routine executed by ECU 50 in the present embodiment.

  In step S <b> 1 of the routine shown in FIG. 2, the engine speed is measured from the signal of the speed sensor 52. In step S2, the fuel injection amount Q is calculated according to the accelerator opening obtained from the signal of the accelerator opening sensor 56. In step S3, the intake air temperature thia of the intake air flowing to the throttle 24 is calculated from the signal of the intake air temperature sensor 60 at the current time. In step S4, the pre-throttle intake pressure P3, which is the pressure upstream of the throttle 24, is calculated from the signal of the intake pressure sensor 62 at the present time. In step S5, the pre-turbo exhaust pressure P4, which is the pressure upstream of the turbine 16, is calculated from the signal of the exhaust pressure sensor 54 at the current time. In step S6, the fresh air amount Ga sucked into the intake passage 10 is calculated from the signal of the air flow meter 58 at the present time. The processing in the above steps is processing for obtaining data necessary for processing in the steps described later. Therefore, the order of each step can be changed as appropriate.

In the next step S7, the transient target pumping loss PL is calculated from the engine speed and the fuel injection amount Q. Here, a map in which the transient target pumping loss PL is associated with the operating conditions is used. In the next step S8, the target intake pressure Pimk is calculated from the transient target pumping loss PL. The target intake pressure Pimk can be expressed by the following function using the transient target pumping loss PL and the pre-turbo exhaust pressure P4.
Pimk = P4−PL (3)

In the next step S9, the opening area characteristic μA _th is calculated by substituting the new air amount Ga, the target intake pressure Pimk, the intake air temperature thia, and the pre-throttle intake pressure P3 into the above equation (1). In the next step, the target throttle opening degree dthbse is calculated by substituting the calculated opening area characteristic μA _th into the above equation (2). In the next step S11, the opening degree of the throttle 24 is feedforward controlled in accordance with the target throttle opening degree dthbse, and this routine is ended.

  By performing intake pressure control according to the routines described above, the pumping loss during transient operation is always controlled to the transient target pumping loss PL, so both improvement in fuel efficiency and exhaust performance during transient operation must be achieved. Can do.

  By the way, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the following modifications may be made.

  In the above-described embodiment, the pre-throttle intake pressure P3 and the turbo pre-exhaust pressure P4 are calculated from the signals of the intake pressure sensor 62 and the exhaust pressure sensor 54, but the pre-throttle intake pressure P3 and the pre-turbo exhaust pressure P4 are calculated. The calculation method is not limited to the method of directly detecting with a sensor, but may be estimated using another known method.

  In the above-described embodiment, the pre-throttle intake pressure P3 is the “intake pressure” of the first invention, the pre-turbo exhaust pressure P4 is the “exhaust pressure” of the first invention, and the transient target pumping loss PL Is the “target differential pressure” of the first invention, the target intake pressure Pimk is the “target intake pressure” of the first invention, and the target throttle opening dthbse is the “target opening” of the first invention. , Respectively. In the above-described embodiment, the ECU 50 executes the steps S1, S2 and S7, so that the “target differential pressure calculating means” of the first aspect of the invention causes the ECU 50 to execute the step S5. The “exhaust pressure acquisition means” according to the first aspect of the invention is executed when the ECU 50 executes step S8, and the “target intake pressure calculation means” according to the first aspect of the invention is executed when the ECU 50 executes steps S9 and S10. The “target opening calculation means” of the first invention is realized by the “control means” of the first invention by the ECU 50 executing step S11.

2 Engine body 4 Intake manifold 6 Exhaust manifold 8 Injector 10 Intake passage 12 Exhaust passage 14 Compressor 16 Turbine 24 Throttle 50 ECU
52 Rotational speed sensor 54 Exhaust pressure sensor 56 Accelerator opening sensor 58 Air flow meter 60 Intake air temperature sensor 62 Intake air pressure sensor 64 Supercharging pressure sensor

Claims (1)

A turbocharger having a compressor provided upstream of the throttle in the intake passage and a turbine provided in the exhaust passage;
A target differential pressure that calculates a target differential pressure that is a target value of a differential pressure between the intake pressure downstream of the compressor and upstream of the throttle and the exhaust pressure upstream of the turbine, based on the operating state of the internal combustion engine A calculation means;
Exhaust pressure acquisition means for acquiring the exhaust pressure upstream of the turbine;
Target intake pressure calculating means for calculating a target intake pressure that is a target value of the intake pressure based on the target differential pressure and the exhaust pressure;
A target opening calculation means for calculating an opening area of the throttle for realizing the target intake pressure using a nozzle type that models the throttle, and calculating a target opening of the throttle based on the opening area When,
Control means for controlling the throttle opening to the target opening;
A control device for an internal combustion engine, comprising:

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