JP2000179393A - Control method and control unit of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the error in the fuel injection volume and thereby improve the discharge characteristics of pollutants of an internal combustion engine, by obtaining through calculation the pressure value used for fuel injection control from two fuel pressure measurements taken within the reservoir. SOLUTION: The present pressure value P(m) within the reservoir is detected (S300) and checked to confirm whether it has reached a calculation starting point t0 of a control signal beginning from the generation of an increment pulse (S310). If it has reached it, control starting point AB with respect to further injection is calculated (S320). Point tE, which is an estimate of when injection will start, is obtained from point tOT, where point tE reaches top dead center, and the control starting point AB (S330). Then, the pressure value PA of the point when injection begins is obtained as the function of a plurality of pressure values P(m), P(m-1), P(m-n+1) and the calculated starting point t0 and the control starting point tE (S340). This pressure value PA is used to calculate the control continuing time AD. This control continuing time AD is set based on the calculated pressure value PA and another parameter K.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for an internal combustion engine, for example, an internal combustion engine having a common rail system, and a control device for implementing the control method.

[0002]

2. Description of the Related Art An internal combustion engine control method and control device are disclosed in DE.
Known from 19548278. It describes a method and a device for controlling the pressure in a pressure reservoir of a common rail system (CR system). In such a CR system, the control duration of the injector is typically set depending on the amount of fuel to be injected and the pressure in the reservoir. For this reason, the pressure in the reservoir is detected in synchronization with the rotation speed. Pressure control is performed in a fixed time pattern. For this purpose, scanning is performed in synchronization with the rail pressure, which is already detected in synchronization with the rotation speed.

It is furthermore known from DE 197 35 561 to scan pressure values at fixed time intervals. When controlling the amount of injected fuel, an accurate amount can be obtained only when the fuel pressure at the start of injection is known. Inaccurate pressure measurements can lead to volume errors and, consequently, to poor pollutant emission characteristics of the internal combustion engine.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a control method and a control device for an internal combustion engine of the type mentioned at the outset, which reduce the quantity error and thus improve the pollutant emission characteristics of the internal combustion engine. It is.

[0005]

SUMMARY OF THE INVENTION The present invention is directed to a method for controlling an internal combustion engine, for example, an internal combustion engine having a common rail system, wherein the fuel is conveyed to a reservoir by at least one pump and the fuel pressure in the reservoir is reduced. An internal combustion engine control method of detecting an indicated pressure value and using the pressure value for fuel injection control, wherein a pressure value used for fuel injection control is calculated from at least two measured pressure values. This problem can be solved by configuring an internal combustion engine control method described above and a control device that implements the control method.

[0006]

According to the present invention, a pressure value very close to the actual pressure value at the start of injection can be obtained. Advantageous implementations and developments of the invention are set out in the dependent claims.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments shown in the drawings.

FIG. 1 shows, among the embodiments of a fuel supply device for performing high-pressure injection of an internal combustion engine, members necessary for understanding the present invention. The system shown is commonly referred to as a common rail system and is shown by way of example only.

Reference numeral 100 denotes a fuel storage container.
This fuel storage container 100 is connected to a pre-conveyance pump 110. From this pre-conveying pump, the fuel reaches the metering valve 120 via a pipeline. The connection line between the preconveying pump and the metering valve 120 is connected via a low-pressure limiting valve 145 to the storage vessel 1
00 is connected. The metering valve 120 is a high-pressure pump 12
5 is connected to the rail 130. The rail 130 is also called a reservoir, and is connected to a plurality of injectors 131 via a fuel pipe. Pressure limiting valve 1
The rail 130 can be connected to the fuel storage container 110 via 35. The metering valve 120 is controllable using a coil 136.

The outlet of the high-pressure pump 125 and the pressure limiting valve 13
The line between the 5 inlets is called the high pressure zone. In this region, the fuel is under high pressure. The pressure in the high pressure region is detected by the sensor 140. The line between the tank 100 and the high pressure pump 125 is called a low pressure region.

Reference numeral 150 denotes a control unit. This control unit supplies a control signal A to the injector 131 and further controls the coil 136 of the metering valve 120. For this purpose, the output signal P of the pressure sensor 140 and another sensor 16
0 Various output signals, for example a speed sensor, are evaluated.

The control section 150 includes a filter 151 to which the output signal PE of the pressure sensor 140 is supplied. This filter 151 supplies a signal to the quantity calculator 152 and the junction 154. The output signal PS of the target value preset section 153 is supplied to a second input side of the connection point 154. The target value preset unit outputs the output signal N of the rotation speed sensor 160 and the output signal Q of the amount calculation unit 152.
Process K.

The quantity calculation section supplies a control signal A to the injector and a signal QK indicating the injection quantity to be metered to the target preset section 153. The output signal at node 154 is provided to a pressure controller 155, which controls a coil 136 of metering valve 120.

This device operates as follows. The fuel in the storage container is transported by the preliminary transport pump 110.

If the pressure in the low-pressure region rises to an unacceptably high value, the low-pressure limiting valve 145 opens and a connection is made between the outlet of the pre-transport pump 110 and the storage container 100.

The high pressure pump 125 transports fuel from a low pressure area to a high pressure area. High pressure pump 125 creates a very high pressure on rail 130. As a rule, in systems for externally ignited internal combustion engines, the pressure value is about 30 to 200 bar
In the self-ignition type internal combustion engine, the pressure value is about 1000 to
Reaches 2000 bar. Via the injector 131, the fuel under high pressure is metered into the individual cylinders of the internal combustion engine.

The sensor 140 detects the pressure in the rail or in the entire high-pressure area. The pressure in the high pressure region can be controlled using the metering valve 120 that can be controlled by the coil 136. Depending on the voltage supplied to the coil 136 or the current flowing through the coil 136, the metering valve 120 makes available a different delivery of the high-pressure pump.

Another control element can be used to control the pressure P in the high pressure range. These actuating members are, instead of the metering valve 120, an electric pre-conveyance pump 110 with an adjustable conveying amount or a pressure limiting valve 135 which can also be controlled by a coil.

The calculation of the control signal A takes place before each injection, depending on the pressure P. This calculation is performed at variable time intervals depending on the rotational speed. The interval of this calculation strongly depends on the rotation speed. The calculation of the control signal for the metering valve in the pressure controller 155 is performed with a fixed clock. This clock is selected so that the controller can respond immediately to the changing setpoint value PS and the new setpoint value is adjusted as quickly as possible.

The filter 151 filters the sensor signal supplied from the pressure sensor 140 so that this signal can be used on the one hand by the quantity calculator 152 and on the other hand by the connection point 154 for pressure control. . The amount calculation unit 152 calculates a control signal A to be supplied to the injector 131 depending on the pressure P and a desired amount of fuel to be injected.

The target value preset unit 153 calculates a target value PS for the fuel pressure in the reservoir 130 from various operation parameters, for example, the rotational speed N of the internal combustion engine and the fuel amount QK to be injected. This target value PS is compared at a connection point 154 with the actual value PI supplied from the filter 151. Depending on the result of this comparison, the pressure controller 155 calculates a control signal to be supplied to the pressure control valve.

The pressure in the reservoir fluctuates very significantly.
This fluctuation is caused by injection and by pressure buildup.
The pressure values required for volume calculation and / or pressure control are scanned at predetermined fixed time intervals. This causes the pressure value used for the quantity calculation to fluctuate greatly. A large change in the pressure value causes a large change in the value of the quantity. Furthermore, the pressure value detected at the time of pressure detection also greatly deviates from the pressure at the time of injection. This results in an incorrect injection.

FIG. 2 plots various signals over time. Vertical marks indicate pulses of an increment wheel (not shown). This pulse occurs at predetermined angular intervals of the crankshaft or camshaft. In the embodiment shown, the interval between two injections is 2
It is divided into one increment, one increment pulse is generated in the area of the ejection and another one increment pulse is generated between the two ejection pulses.

The evolution of the pressure P in the reservoir is shown by a solid line. The signal here is preferably a filtered signal. Injection is started at time tE. As a result, the pressure drops very quickly. Subsequently, the pressure rises again. The pressure immediately after the start of the injection is the value PA.

The measurement of the pressure was made at the points of time tn,
, t0, at which point the pressure values P (mn), P (mn + 1),.
(M) is detected. The pressure detection preferably takes place at fixed time intervals, which are selected in such a way that at least two, preferably three or more pressure values occur between two injections.

At the time of the occurrence of the increment pulse between the two injections, the calculation of the control signal for the injector is initialized and carried on. These points are marked by small vertical arrows. The region where the control signal calculation is performed is indicated by a hatched region.

In this calculation, a signal indicating the injection start time is first calculated. What is important here is the amount giving the interval AB between the injection start time marked by the jagged arrow and the top dead center O occurring at the time tOT. Further, the control duration AD is determined. The control duration AD is also
Time AB is also marked by a double arrow. Furthermore, the distance K between the top dead center tOT and the start of the calculation of the control signal is also marked by a double arrow.

The method according to the invention estimates the pressure value PA at the start of the injection in order to reduce measurement errors. Here, the estimation is based on a plurality of previous measurements P (mn), P (m
−n + 1),..., P (m). The measured value is preferably detected when the pressure rises. That is, the detection of the measured value is started after the top dead center of the preceding injection. This means that the pressure value PA is estimated at the start of the injection to be calculated from at least two measured values occurring between the preceding injection and the current injection, ie the injection to be calculated. It is. That is, the pressure value PA representing the fuel pressure in the reservoir at the start of the injection is obtained by calculation from at least two measured pressure values. The pressure value PA thus obtained is used for fuel injection control.

A so-called compensation function is preferably used for the estimation. In other words, it is advantageous to determine a compensation line from which the measured values deviate only slightly from different measured values at different times.

This straight line gives the relationship between pressure P and time t. Thereafter, the pressure value PA at the injection time tE can be determined using this straight line. For this purpose, the time point tE must be known. Time point tE is equal to time point t0.
From the start time of the calculation of the control signal at, and the top dead center tOT. Here, known angle values are preferably used. This is because the calculation of the control signal is started by the generation of the increment pulse, and the top dead center also coincides with the increment pulse.

The interval between the two increment pulses corresponds to a known angle value at which the crankshaft or camshaft rotates during the increment pulse. By using the instantaneous rotational speed of the internal combustion engine, this quantity is converted into a time giving the interval between top dead center tOT and the time point t0 at which the control signal is calculated.

If the interval K is reduced by the value AB, that is, if the interval K is decreased by the value AB which is the interval between the injection start time tE and the top dead center tOT, the interval between the calculation start time of the injection data and the injection start time is reduced. You can see the interval of Then the quantity K-AB
The pressure PA is determined from the equation and a linear equation for the pressure.

It is particularly advantageous if, instead of the compensation line, another function approximating the pressure profile is used so that only small deviations occur between the measured value and the function value. It is also particularly advantageous to use a function which approximates the pressure profile during injection.

FIG. 3 shows a flow chart of the method according to the invention. In the first step 300, the current pressure value P
(M) is detected. In the subsequent decision 310, the time t
It is checked whether it has reached zero. The time point t0 is reached when the interval between the time point and the top dead center is smaller than the value K. Alternatively, it is possible to check whether an increment pulse has been generated.

If this condition is not satisfied, step 3
At 60, the pressure value P (m-1) is changed to the pressure value P (m), the pressure value P (m-2) is changed to the pressure value P (m-1), and the pressure value P (m-n) is changed to the pressure value. The value P (mn +
Overwrite by 1).

If it is determined at decision 310 that time t0 has been reached, then at step 320 the control start time AB for the subsequent injection is calculated. Subsequently, at step 330, the time point tE at which the start of injection is expected is determined from the time point tOT at which the top dead center is reached and the control start time AB. Next, in the subsequent step 340, the pressure value PA at the start of the injection is calculated as a plurality of pressure values P (m), P (m-1), P (m-1).
(M−n + 1) and time t0 and time t at which injection is performed
It is obtained as a function of E. This calculated pressure value P
A is used in step 350 to calculate the control duration AD. This control duration AD is set as a function of the calculated pressure value and another parameter K. This means that by using this value PA, a control signal A for controlling the injection of the fuel amount is obtained.
Furthermore, this pressure value PA can be used as the actual value of the pressure controller 155.

[Brief description of the drawings]

FIG. 1 is a block diagram of an apparatus according to the present invention.

FIG. 2 is a diagram plotting various signals with respect to time.

FIG. 3 is a flow chart of a method according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 Fuel storage container 110 Pre-conveyance pump 120 Metering valve 125 High-pressure pump 130 Rail 131 Injector 135 Pressure limiting valve 136 Coil 140 Pressure sensor 145 Low-pressure limiting valve 150 Controller 151 Filter 152 Quantity calculation unit 153 Target value preset unit 154 Connection point 155 Pressure controller

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Andreas Kerner Germany Mecklingen Jägerstrasse 8

Claims (6)

[Claims] 1. A control method for an internal combustion engine, wherein fuel is conveyed to a reservoir by at least one pump, a pressure value representing a fuel pressure in the reservoir is detected, and the pressure value is used for fuel injection control. An internal combustion engine control method according to claim 1, wherein a pressure value used for fuel injection control is calculated from at least two measured pressure values. 2. The internal combustion engine control method according to claim 1, wherein the pressure value obtained by the calculation represents the fuel pressure in the reservoir at the start of the injection. 3. The internal combustion engine control method according to claim 1, wherein a pressure value obtained by the calculation is obtained from the plurality of measured pressure values using a compensation function. 4. The method according to claim 1, wherein the plurality of measured pressure values are detected between a previous injection and a current injection. 5. A pressure value obtained by the calculation, the plurality of measured pressure values, a signal indicating the injection start time,
5. The method according to claim 1, wherein the rotation speed is set based on the rotation speed.
The method described in the section. 6. A control device for an internal combustion engine, comprising means for conveying fuel to a reservoir by at least one pump, detecting a pressure value representing a fuel pressure in the reservoir, and using the detected pressure value for fuel injection control. An internal combustion engine control device according to claim 1, further comprising means for calculating a pressure used for fuel injection control from at least two measured pressure values.