JP2001115884A - Method for reducing rail pressure in common rail system of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method to regulate a rail pressure in a common rail system for an internal combustion engine through a pressure reduction valve controlled by an electronic type control device and perform further rapid and proper reduction of a pressure through the pressure reducing valve at individual given operation point of time of the internal combustion engine, in a type to perform control by the pressure reducing valve in relation with a regulation error. SOLUTION: Hysteresis limits ΔPauf and ΔPzu for an opening closing process of a pressure reducing valve are variably set.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adjusting a rail pressure in a common rail system for an internal combustion engine via a pressure reducing valve controlled by an electronic control unit, wherein the pressure reducing valve has an adjustment error. Of a type that can be controlled in relation to

[0002]

2. Description of the Related Art A pressure reducing valve in an internal combustion engine having a common rail system performs pressure reduction at a predetermined operation time of the internal combustion engine in the concept of two regulators of a pressure regulating circuit having a high-pressure pump whose suction side is restricted. It has the role of doing. The function of the pressure reducing valve is advantageously active during engine braking and at other times when no fuel is supplied.

In recent common rail systems, the pressure reducing valve has a pressure reducing function as an adjusting member in the pressure adjusting circuit.

[0004] Published German Patent Application No. 1954
No. 8278 describes a method and a device for regulating the pressure in the accumulator of a common rail system. To control the pressure, a regulating quantity is delivered from the accumulator to the low-pressure area. Furthermore, a second regulator is provided to operate in the low pressure region.

[0005] Published German Patent Application No. 1973
From 1994, a method and a device for controlling an internal combustion engine with a common rail system is known, in which the rail is connected to a fuel storage container via a pressure regulator or a pressure reducing valve. The pressure regulating valve or the pressure reducing valve can be controlled via a coil.

In a wide operating range of an internal combustion engine,
The pressure reducing valve is closed. In this case, the high pressure adjustment is 0
Via a metering device that meteres in amounts from 100 to 100% into a high-pressure pump. In this case, the injection amount, the control amount, and the leakage amount in the injector are sufficient for reducing the pressure.

However, at individual operating points of the internal combustion engine, for example during engine braking or other operating points when no fuel is supplied, the pressure reduction due to injection, control and leakage in the injector is too slow, This can lead to unacceptable noise of the internal combustion engine when receiving the load again.

Thus, the pressure is reduced by the pressure reducing valve.

[0009]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for more quickly and appropriately reducing the pressure at predetermined individual operating points of an internal combustion engine via a pressure reducing valve.

[0010]

According to the method of the present invention, a hysteresis limit for the process of opening and closing the pressure reducing valve can be set variably.

[0011]

According to the method of the present invention, the pressure is reduced with high adjustment accuracy based on the target pressure setting. by this,
A reduction in the controlled variable via the pressure reducing valve is obtained. The use of the pressure reducing valve structure is freely selectable in the engine drive characteristic field. The valve seat wear of the pressure reducing valve is reduced by adapting the switching limits (reduction in the number of switching steps).

Further advantageous embodiments of the invention are evident from the dependent claims.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described in detail with reference to the illustrated embodiments.

FIG. 6 shows components of a fuel supply system of an internal combustion engine which injects fuel at a high pressure, which is necessary for understanding the present invention. The illustrated fuel supply system is generally called a common rail system.

A fuel storage container is designated by the reference numeral 100. This fuel storage container 100 is advantageously connected to a second filter 115 via a first filter 105 of a controllable primary transfer pump 110. From this second filter 115, fuel reaches the valve 120 via a line.
The connecting line between the filter means 115 and the valve 120 is connected to the fuel storage container 100 via a low-pressure limiting valve 140. The valve 120 is a metering unit ZME, which is connected to a high-pressure pump 125. The metering unit ZME is arranged on the suction side of the high-pressure pump.
As a metering unit, for example, a magnetically controlled proportional valve can be used, which can be controlled via a coil 122.

The high pressure pump is connected to rail 130. The rail 130 is also called an accumulator and is connected to various injectors 131 via a fuel line. The rail 130 can be connected to the fuel storage container 100 via a pressure regulating or reducing valve 135. The pressure regulating valve or the pressure reducing valve 135 can be controlled by a coil 136.

The line between the outlet of the high pressure pump 125 and the inlet of the pressure regulating or reducing valve 135 is called the high pressure region. In this high pressure region, the fuel is under high pressure. The high pressure region, in particular the pressure P in the accumulator, is detected by a sensor 145. The line between the tank 100 and the high-pressure pump 125 is called a low-pressure area.

The control device 160 has a pressure regulating device and loads corresponding regulating elements with control signals, such as, for example, the coil 136 of the pressure regulating or reducing valve 135 and / or the coil 122 of the metering unit. The controller 160 processes the various signals of the different sensors 165 and 166. These sensors 165 and 166 characterize the operating state of the internal combustion engine and / or the motor vehicle (driven by the internal combustion engine). Such an operating state is, for example, the rotational speed N or the temperature value of the internal combustion engine.

It is particularly advantageous for the control device to control another regulating element. Another regulating element can be used selectively and / or additionally to regulate the pressure P in the high-pressure area. The adjusting element is, for example, an electric primary transfer pump 110 adjustable in the amount of transfer and / or a controllable high pressure pump 125 and / or an electrically controllable pressure limiting valve 140 in the low pressure range.

The device of the present invention operates as follows. The fuel in the fuel storage container is transported by the primary transport pump 110 through the filter elements 105 and 115. At the outlet side of the primary transport pump 110, fuel is loaded at a pressure of several bar.

When the pressure in the low pressure region of the fuel system reaches a settable pressure, the low pressure limiting valve 140 is opened, and the connection between the outlet of the primary transfer pump 110 and the fuel storage container 100 is opened. By means of the low-pressure limiting valve 140, the pressure in the low-pressure area is maintained at a value of about 5 bar.

The configuration of the low-pressure area, in particular the arrangement of the valves and the filters, is only shown by way of example. The type and / or arrangement and / or number of components may differ from the embodiment shown.

The high-pressure pump 125 transfers fuel from a low-pressure area to a high-pressure area. High pressure pump 125 creates a significantly higher pressure in rail 130. In general, a pressure value of about 30 to 100 bar is obtained in a fuel supply system for an external ignition type internal combustion engine, and about 1 to 100 bar in a self ignition type internal combustion engine.
Pressure values of 2,000 to 2,000 bar are obtained. Fuel under high pressure via the injector 131 is metered into individual cylinders of the internal combustion engine.

The sensor 145 detects the pressure P on the rail or the entire high-pressure area. This pressure P is adjusted via the valve 120 of the metering unit ZME. This valve 1
20 can be controlled by a coil 122, and can adjust the amount of conveyance of the high-pressure pump 125. Coil 1
The pressure in the high pressure region can be rapidly reduced through the pressure reducing valve 135 which can be controlled by the control unit 36.

Generally, the primary transfer pump 110 is as follows:
A mechanical primary transfer pump is used. However, it is also possible to use an electric fuel pump with a DC motor (DC motor) or an electrically commutated DC motor (EC motor). Due to the high transport volumes required especially in the case of industrial vehicles, it is also possible to use a plurality of primary transport devices connected in parallel. In this case, an EC motor is advantageously used because it has a long service life and is more easily available.

The transport amount QP is transported from the high-pressure pump 125 to the rail 130. Via the pressure reducing valve 135 the quantity QDAV
Is sent to the low pressure region. The transport amount QR is provided for increasing the pressure. The metering amount QI reaches the injector 131 via the rail 130. The quantity QI is composed of the total quantity of the injected fuel QK, the leakage quantity, and the control quantity of the injector. The amount of leakage and the amount of control return to the low pressure region. The amount of fuel injected reaches the internal combustion engine.

FIG. 1 shows a typical temporal operation for the process of opening and closing the pressure reducing valve. Δtein / aus (Δt on / off) indicates the minimum time indicating the progress from the opening process to the instantaneous closing process. Δtraster (Δt raster)
Is the time belonging to the inquiry about the opening and closing process. In this case, the following conditions apply: Δtein / aus <Δtraster + Δtaus and Δtaus <Δtraster.

FIG. 2 shows the flow rate with respect to the pressure difference ΔP. FIG. 3 again clearly shows how the time and the pressure difference are related. The following two equations: Q (ΔP) _DAV = Δt _i × A × (2 / ρ) ^1/2 ΔP ^1/2 _DAV ΔP = Q (ΔP) _DAV / E _pRail × V _{Rail In} this case, Q (ΔP) = Control quantity through DAV (pressure reducing valve) Δt _i = Opening time of DAV ( _{tein / aus} for ΔP _auf ) A = Throttle cross section of DAV for ΔP _zu Δt _aus ρ = fuel density ΔP = at DAV Pressure differential Eo = fuel modulus (a function of rail pressure) V _Rail = rail volume P = depressurization in the rail via which the parameter characteristic fields for ΔP _auf and ΔP _zu are obtained as shown in FIG. . As shown in FIG. 5, the rail pressure in the common rail system is controlled by a coil and an electronic controller to reduce pressure 135
Is controlled via The pressure reducing valve 135 has an adjustment error P _Rail −
It is opened or closed in the hysteresis characteristic curve in relation to P _soll (P target value). According to the invention, the hysteresis limit for the opening and closing process of the pressure reducing valve 135 is made variable via a calculation scheme stored in the electronic control unit. The hysteresis limit for opening and closing the pressure reducing valve 135 is parameterized as a characteristic field value. The upper hysteresis limit for the opening of the pressure reducing valve 135 is related to the first characteristic field, where the output value ΔP _auf is a function of the pressure P _Rail , and the lower hysteresis limit for the closing of the pressure reducing valve 135 is , The output value ΔP _zu is related to a second characteristic field which is a function of the rail pressure P _Rail .

The first characteristic field ΔP _auf (P _Rail )
Is the minimum allowable pressure difference Δ for the opening and closing process of the pressure reducing valve
P _auf and a second characteristic field ΔP _zu (P _Rail )
So they indicate the pressure difference [Delta] P _zu acceptable minimized, the first characteristic field ΔP _auf (P _{R ail)} and a second characteristic field [Delta] P _zu the (P _Rail) is set from a mathematical-physical relationship, which This ensures that the pressure reducing valve can be closed without any actual pressure drop.

[Brief description of the drawings]

FIG. 1 is a time diagram for an opening and closing process of a pressure reducing valve.

FIG. 2 is a diagram showing the flow rate as a function of the pressure difference.

FIG. 3 is a diagram showing the pressure course of the rail during the opening and closing process.

4 is a diagram showing a parameterized characteristic field [Delta] P _auf and [Delta] P _{z u} as a function of rail pressure.

FIG. 5 is a structural diagram.

FIG. 6 is a block circuit diagram.

[Explanation of symbols]

100 fuel storage container, 105 first filter,
110 primary transfer pump, 115 second filter,
120 valve, 122 metering unit, 125 high pressure pump, 130 rail, 131 injector, 135 pressure regulating or reducing valve, 136 coil, 140 low pressure limiting valve, 145 sensor, 16
0 control device, 165,166 sensor

Continued on the front page (72) Inventor Jürgen Hammer Germany Fellbach-Kappe Lubergstrasse 28/1

Claims (6)

[Claims] 1. A method for adjusting a rail pressure in a common rail system for an internal combustion engine via a pressure reducing valve controlled by an electronic control device, wherein the pressure reducing valve has an adjustment error (P _Rail −P _soll). ), The hysteresis limit (ΔP) for opening and closing the pressure reducing valve.
_auf , ΔP _zu ) can be set variably. A method for reducing rail pressure in a common rail system for an internal combustion engine. 2. Hysteresis limit (ΔP _auf , ΔP _zu )
The method according to claim 1, wherein at least one of the following is configurable in relation to the rail pressure (P _Rail ). 3. A first hiss for closing said pressure reducing valve.
The lysis limit (ΔP _zu) In the first property field
And the rail pressure (P_Rail) As a function of
The method according to claim 1. 4. A second hiss for opening said pressure reducing valve.
The lysis limit (ΔP _auf) In the second property field
The rail pressure (P_Rail) As a function
4. The method according to any one of the preceding claims. 5. The second characteristic field (ΔP
_auf (P _Rail )) and the first characteristic field (Δ
P _zu (P _Rail )) is expressed by the following mathematical and physical relational expression: Q (ΔP) _DAV = Δt _i × A × (2 / ρ) ^1/2 × (ΔP)
^{1/2 ΔP = Q (ΔP) /} E Rail × V Rail formula: Q (ΔP) = DAV opening time for the control quantity Δt _i = ΔP _auf through the DAV Δt _{ein / aus} A = for [Delta] P _zu The throttle cross section _ΔTAus ρ = fuel density _ΔPDAV = pressure difference at DAV of the _DAV E _Rail = fuel elastic modulus as a function of rail pressure and temperature V _Rail = rail volume The controller stores the following equation: Or the method of 2. 6. The first characteristic field (ΔP
_auf (P _Rail )) indicates the minimum allowable pressure difference (ΔP _auf) for the opening and closing process of the pressure reducing valve, and the second characteristic field (ΔP _zu (P _Rail )) indicates the minimum allowable pressure difference. Setting the first characteristic field (ΔP _auf (P _Rail )) and the second characteristic field (ΔP _zu (P _Rail ) ₎ to indicate (ΔP _zu) , and 6. The method according to claim 1, which ensures that the closure is possible without shaking.