CN102192813A - Method and apparatus for determining analogue value of pressure in engine system with internal combustion engine - Google Patents

Abstract

The invention relates to a method and a device for determining an analog value of pressure in an engine system having an internal combustion engine. In the air intake section (4) there is an intake tract area between the throttle valve (8) and the internal combustion engine (2), wherein the following steps are carried out: The engine system (1) is operated so that the air mass in the intake duct area The flow corresponds to the air mass flow through the throttle valve (8); determine (S3) the actual physical quantity of the air mass flow flowing into the air inlet section, the actual physical quantity of the air temperature before the throttle valve (8), entering the internal combustion engine The actual physical quantity of the volume flow in (2) and the actual physical quantity of the position of the throttle valve (8); form a difference equation, which is discretized by a differential equation, which uses the ideal gas equation and the throttling valve used to simulate the throttle valve (8) The flow equations are generated; and the simulated value of the pressure is determined ( S4 ) by solving the difference equation with the aid of the determined actual physical quantities.

Description

Method and device for determining an analog value of pressure in an engine system with an internal combustion engine

technical field

The present invention generally relates to an internal combustion engine. In particular, the invention relates to determining an analog value for the pressure in the area of the air supply system by means of a suitable model.

Background technique

Modern internal combustion engines are usually operated with the aid of electronic engine controls. Engine systems with such an internal combustion engine have at least one pressure sensor upstream or downstream of a throttle valve in the air supply system in order to optimally control and regulate the air mass flow of intake air and inert gas. This pressure sensor is necessary in order to calculate other corresponding, unmeasured pressures after or before the throttle valve. The pressure values obtained in this way are also necessary for filling calculations and calculations of the gas mass flow through the throttle valve, which in turn are necessary for charge pressure regulation and air mass regulation.

In the event of a pressure sensor failure, the engine control is usually preset with a constant substitute value which corresponds to the ambient pressure and which can additionally be loaded with an applicable offset. But for some functions, the quality of this substitute value for pressure is not enough. As a result, inter alia, boost pressure control and exhaust gas recirculation control must be switched off. If a diesel particulate filter is provided, the consequence is that the possible diesel particulate filter can no longer be restored.

Contents of the invention

It is therefore the object of the present invention to provide a method and a device with which an analog value of the pressure can be provided in the air inlet section of an internal combustion engine, which can be used as a substitute value and has sufficient quality for Subsequent, related functions.

This object is achieved by a method according to claim 1 for determining an analog value of the pressure in an air supply system of an internal combustion engine, and by a device and an engine system according to the accompanying claims.

Further advantageous embodiments are specified in the dependent claims.

According to a first aspect, a method is provided for determining an analog value of the pressure in an air supply section of an engine system having an internal combustion engine. In the air supply section, an intake manifold region is provided between the throttle valve and the internal combustion engine. This method consists of the following steps:

- operate the engine system so that the air mass flow in the area of the intake duct corresponds to the air mass flow through the throttle valve;

- determination of the actual physical quantities of the air mass flow into the air inlet section, the actual physical quantities of the air temperature before the throttle valve, the actual physical quantities of the volume flow into the internal combustion engine and the actual physical quantities of the position of the throttle valve;

- form the difference equation, discretized by the differential equation, which is generated by means of the throttle equation and the ideal gas equation used to simulate the throttle valve; and

- Determine the simulated value of the pressure by solving the difference equation with the help of the determined real physical quantity.

The central idea of the invention is to determine an analog value of the pressure during dynamic operation of the internal combustion engine with the aid of simulation equations. Once the fault has been determined, it is ensured that the mass flow through the throttle valve and into the internal combustion engine are the same. This is the case, for example, during steady-state operation of the internal combustion engine. Based on physical quantities such as charge air-temperature before the throttle valve, mass flow before the compressor, throttle valve position and volume flow into the internal combustion engine (they are respectively either detected sensor quantities or analog quantities), With the help of the ideal gas equation, the throttle equation (which describe the behavior in an air system), and on the basis of mass conservation, an analog value for the pressure before or after the throttle valve can be calculated.

By means of the analog values determined in this way, a charge pressure regulation and an air mass regulation of the internal combustion engine can be carried out. In particular when operating with a diesel particulate filter, the internal combustion engine can only be operated further by means of the restriction of the closed waste gas recirculation valve. Furthermore, it is also possible to use analog values for monitoring the function of the pressure sensor taking into account boundary conditions.

In addition, said pressure corresponds to the intake manifold pressure which exists between the throttle valve and the inlet of the internal combustion engine or the charge air pressure which exists between the compressor in the air supply section and the throttle valve between.

An exhaust gas return pipe can be arranged between the exhaust gas discharge section and the air input section. In order to ensure that the air mass flow in the region of the intake tract corresponds to the air mass flow through the throttle valve, the exhaust gas return line can be blocked when a fault in the pressure sensor in the air supply section is determined.

Furthermore, difference equations can be formed according to an implicit method or by discretization of the solution of the differential equation.

Furthermore, an analog value for the pressure can be determined when a failure of the pressure sensor in the air supply section has been determined.

Alternatively, an analog value of the pressure can be determined for checking the plausibility of the pressure measurement determined by the pressure sensor.

According to another aspect, a device is provided for determining an analog value of a pressure in an air supply section of an engine system having an internal combustion engine, wherein an intake manifold region is provided in the air supply section between a throttle valve and the internal combustion engine. This device is constructed

- to determine if there is a pressure sensor failure in the air input section; and

- When a pressure sensor failure has been determined, perform the following steps:

- operate the engine system so that the air mass flow in the area of the intake duct corresponds to the air mass flow through the throttle valve;

- Determination of the actual physical quantities of the air mass flow into the air inlet section, the actual physical quantities of the air temperature before the throttle valve, the actual physical quantities of the volume flow into the internal combustion engine and the actual physical quantities of the position of the throttle valve ;

- form the difference equation, discretized by the differential equation, which is generated by means of the throttle equation and the ideal gas equation used to simulate the throttle valve; and

- Determination of the simulated value of the pressure by solving the difference equation with the help of the determined actual physical quantity.

According to another aspect, an engine system is provided with an internal combustion engine and the above arrangement, into which air is conveyed via an air inlet section and in which combustion exhaust gases are discharged via an exhaust gas discharge section.

According to another aspect, a computer program product is specified which contains program code which implements the above method when it is executed in a data processing device.

Description of drawings

A preferred exemplary embodiment is explained in more detail below with reference to the drawings. in:

Figure 1 shows the engine system in a schematic diagram; and

Fig. 2 shows a flowchart explaining the method for determining an analog value of pressure in the air input system of the engine system of Fig. 1.

Detailed ways

FIG. 1 shows an engine system 1 with an internal combustion engine 2 , which can be designed, for example, as a diesel engine. In the exemplary embodiment shown, internal combustion engine 2 has four cylinders 3 . However, the number of cylinders 3 is not important for the applicability of the method described below.

Engine system 1 also has an air supply section 4 for feeding air into cylinders 3 of internal combustion engine 2 . This air enters the combustion chamber of cylinder 3 via the corresponding intake valve 25 . In the air inlet section 4 of the engine system 1 there are arranged the compressor 5 of the exhaust gas turbocharger 6 , the charge air cooler 7 downstream of the compressor 5 and the throttle valve 8 downstream of the charge air cooler 7 .

Downstream of the throttle valve 8 , the exhaust gas return line 9 opens into the intake tract, ie the so-called section between the throttle valve 8 and the intake valve 25 of the cylinder 3 of the internal combustion engine 2 .

Exhaust gas discharge section 10 is provided to discharge combustion exhaust gas which is ejected from cylinder 3 through exhaust valve 26 . The turbine 11 of the exhaust gas turbocharger 6 is arranged in the exhaust gas discharge section 10 , this turbine 11 is operated by using the exhaust gas enthalpy of the combustion exhaust gas. The turbine 11 operates the compressor 5 of the exhaust gas turbocharger 6 , thus sucking in air from the surroundings and providing it downstream of the compressor 5 at a boost pressure P ₂₁ .

An exhaust gas return line 9 branches off from the exhaust gas discharge section 10 between the exhaust valve 26 and the turbine 1 . The exhaust gas return line 9 has an exhaust gas cooler 12 and a bypass line 13 which short-circuits the exhaust gas cooler 12 . A bypass valve 14 is arranged in the bypass line 13 , by means of which the efficiency of the exhaust gas cooler 12 can be adjusted.

Furthermore, an exhaust gas return valve 15 is arranged in the intake line of the air inlet section 4 between the exhaust gas cooler 12 and the inlet of the exhaust gas return line 9 . By adjusting the exhaust gas return valve 15 , it is possible to adjust the exhaust gas discharge rate, which defines the proportion of the combustion exhaust gas in the gas mixture delivered to the cylinders 3 .

Furthermore, a controller 20 is provided which operates the internal combustion engine 2 . This controller 20 carries out, for example, charge pressure regulation, air mass regulation and exhaust gas recirculation regulation in order to operate internal combustion engine 2 in an optimal manner. Regulations carried out for operating the internal combustion engine 2 are sufficiently known from the prior art.

。Sensors are provided in order to obtain the physical quantities of the engine system required for carrying out the regulation. Furthermore, position indicators or actuators are provided in order to influence the operation of internal combustion engine 2 . For example, a temperature sensor 21 is provided between the charge air cooler 7 and the throttle valve 8 for determining the charge air temperature T ₂₁ of the charge air upstream of the throttle valve 8 . Furthermore, an air mass sensor 22 is arranged upstream of the compressor 5 , which can be designed, for example, as a hot-film air mass sensor (abbreviation: HFN) in order to determine the fresh air mass flow drawn in by the engine system 1

.

Furthermore, means (not shown) are provided to detect the rotational speed of internal combustion engine 2 . The volume flow in the internal combustion engine 2 can be determined from the rotational speed, the number of cylinders, the air consumption (ratio between the actual gas mass in the internal combustion engine and the theoretically possible gas mass) and the intake manifold pressure P ₂₂ in the intake manifold . Alternatively or additionally, a pressure sensor 23 for determining the charge air pressure P ₂₁ can be provided in the region between the charge air cooler 7 and the throttle valve 8 . Alternatively, a pressure sensor can also be arranged in the intake manifold, ie between the throttle valve 8 and the intake valve 25 of the cylinder 3 , in order to directly determine the intake manifold pressure P ₂₂ .

In addition, a throttle valve 8 is provided as a position indicator, the position of which can be adjusted (for example, by adjusting the tilting angle) by the control unit 20; an exhaust gas recirculation valve 15; for regulating the exhaust gas, for example by means of an adjustable turbine geometry Means of efficiency of the turbocharger 6 ; intake valve 25 and exhaust valve 26 .

With the help of a suitable position sensor on the throttle valve 8, the throttle valve position POS _RKL can be determined and thus the throttling effect of the throttle valve 8 can be determined, so that the charge air pressure P ₂₁ can be converted into the intake pipe pressure P ₂₂ , or vice versa. For this, for example, the following system of equations can be used:

Where f and h represent functions of the ideal gas equation, g corresponds to a function describing the efficiency of the throttle valve 8 in the air input system 4 . This latter function represents the law of conservation of mass by which the above equations can be combined.

The above system constitutes a differential equation, which is discretized in a suitable manner for application in the controller 20 .

FIG. 2 shows a flow chart explaining the method for determining analog values of the pressures P ₂₁ , P ₂₂ in the air supply section 4 of the engine system 1 as substitute values. Firstly, in step S1 it is queried whether the pressure sensor 23 located in the air supply section 4 is faulty. A faulty pressure sensor 32 can be detected by known methods, which will not be explained in detail.

与进入内燃机2中的质量流

相同。Once it has been determined that the pressure sensor 23 is faulty (alternative: Yes), the exhaust gas recirculation valve 15 is completely closed in step S2, so that the mass flow through the throttle valve 8 is assumed in principle

with the mass flow into the internal combustion engine 2

same.

（其由气缸3的冲程容积得出），并检测压缩机5之前从周围环境中吸入的质量流

，并检测在发动机控制器20中的节流阀位置POS_RKL。所述检测在顺序的离散时间点t_k上进行。Then in step S3, at a defined discrete point in time t, the charge air temperature T 21 of the charge air between charge air cooler 7 and throttle valve 8 is detected by means of temperature sensor ₂₁ and is detected Volume flow in combustion engine 2

(which is derived from the stroke volume of cylinder 3) and detects the mass flow drawn in from the surrounding environment before compressor 5

, and detect the throttle valve position POS _RKL in the engine controller 20 . The detection takes place at sequential discrete time points _tk .

The above functions f(), g(), h() are equivalent to analog functions, and are used to describe the relationship between quantities. Here, the functions f and h correspond to the known ideal gas equations, and the function g corresponds to the known throttle equation, which describes the relationship between the states of the gas volume upstream and downstream of the throttle valve 8 . Through the above equations, the pressures P ₂₁ , P ₂₂ in the air input system 4 can be determined in step S4. From the above system of equations a differential equation can be derived which can be solved by suitable discretization.

Discretization of differential equations can be performed by means of implicit and/or explicit methods. When applying the explicit methods commonly used in the prior art, there are sometimes problems with band stability, which are usually balanced by reducing the cycle time. However, this results in a higher necessary computing performance, which generally necessitates the use of more expensive controllers.

The simulated value of the charge air-pressure P ₂₁ in the air inlet section 4 can then be used in step S5 in order to determine and/or adjust the above air system quantities with the aid of other models, such as charge pressure regulation, air mass regulation and exhaust gas recirculation regulation.

By alternatively using the above method, the charge air pressure P ₂₁ detected by the relevant pressure sensor 23 can be additionally The plausibility is checked by the calculated simulated values. A fault in the pressure sensor 23 is detected here if the charge air pressure P ₂₁ detected by the pressure sensor 23 deviates from the charge air pressure simulated value simulated as above by more than a predetermined amount.

In an alternative exemplary embodiment, in addition to pressure sensor 23 or instead of pressure sensor 23 , a further pressure sensor is provided in the intake tract section between throttle valve 8 and internal combustion engine 2 . At the operating moment when the exhaust gas recirculation valve 15 is closed and the other pressure sensors in the air supply section 4 are active, the intake manifold pressure P ₂₂ detected by the associated pressure sensor can additionally be checked by means of calculated analog values. trustworthiness. In this case, a fault in the other pressure sensor can be detected if the intake manifold pressure P ₂₂ detected by the other pressure sensor deviates from the intake manifold pressure simulated value simulated as above by more than a predetermined amount.

Claims (10)

1. A method for determining an analog value of a pressure in an air supply section (4) of an engine system (1) with an internal combustion engine (2), wherein in the air supply section (4) a throttle valve (8) Between the engine (2) and the combustion engine (2) there is an area of the intake duct, in which the following steps are carried out: - operate the engine system (1) so that the air mass flow in the area of the intake manifold corresponds to the air mass flow through the throttle valve (8); - determination (S3) of the actual physical quantities of the air mass flow into the air inlet section, the actual physical quantities of the air temperature before the throttle valve (8), the actual physical quantities of the volume flow into the internal combustion engine (2) and the throttle valve (8) The actual physical quantity of the position; - form the difference equation, discretized by the differential equation, which is generated by means of the ideal gas equation and the throttle equation used to simulate the throttle valve (8); and - Determining (S4) the simulated value of the pressure by solving the difference equation with the aid of the determined actual physical quantities. 2. The method as claimed in claim 1, wherein the pressure corresponds to the intake manifold pressure which exists between the throttle valve (8) and the inlet of the internal combustion engine (2). 3. The method as claimed in claim 1, wherein the pressure corresponds to the charge air pressure which is present in the air supply section between the compressor (5) and the throttle valve (8). 4. The method according to any one of claims 1 to 3, wherein an exhaust gas return line (9) is arranged between the exhaust gas discharge section (10) and the air input section (4), wherein after determining the air input section ( 4) When the pressure sensor (23) fails, the exhaust gas return pipe (9) is cut off. 5. The method as claimed in claim 1, wherein the difference equation is formed according to an implicit method or by discretization of the solution of the differential equation. 6 . The method as claimed in claim 1 , wherein an analog value of the pressure is determined when a failure of the pressure sensor ( 23 ) in the air supply section ( 4 ) is detected. 7 . 7. The method as claimed in claim 1, wherein an analog value of the pressure is determined for checking the plausibility of the measured pressure value determined by the pressure sensor (23). 8. A device for determining an analog value of pressure in an air inlet section of an engine system (1) with an internal combustion engine (2), wherein in the air inlet section (4) between a throttle valve (8) and an internal combustion engine ( 2) There is an air intake duct area in between, wherein the device is constructed to perform the following steps: - operate the engine system so that the air mass flow in the area of the intake manifold corresponds to the air mass flow through the throttle valve (8); - determination of the actual physical quantities of the air mass flow into the air inlet section, the actual physical quantities of the air temperature before the throttle valve (8), the actual physical quantities of the volume flow into the internal combustion engine and the position of the throttle valve (8) actual physical quantity; - form the difference equation, discretized by the differential equation, which is generated by means of the ideal gas equation and the throttle equation used to simulate the throttle valve (8); and - Determination of the simulated value of the pressure by solving the difference equation with the help of the determined actual physical quantity. 9. An engine system (1) having an internal combustion engine (2) and a device according to claim 8, into which the air is conveyed via an air supply section (4) and in which the internal combustion engine (2) The combustion exhaust gas is discharged through the exhaust gas discharge section (10). 10. A computer program product containing program code which implements the method as claimed in one of claims 1 to 7 when it is executed in a data processing device.

Images