DE102013000060B3 - Method of operating internal combustion engine, involves dividing high pressure pump associated with suction throttle into units, and controlling each unit by separate control loop - Google Patents

Abstract

The method involves driving a high-pressure pump with which a fuel is pumped into a rail, with a suction throttle such that the pressure in the rail is controlled with a pressure regulator. The pressure values measured in the rail is compared with a target pressure, and a pressure control signal for the suction throttle is determined.The suction throttle is driven with the control signal. The high pressure pump associated with the suction throttle is divided into multiple units, and each unit is controlled by a separate control loop. An independent claim is included for a control device for controlling a pressure in a rail of an internal combustion engine.

Description

The invention relates to a method and a control device for operating an internal combustion engine with a common rail injection, wherein a number of high-pressure pumps is driven.

In a common rail injection, a high-pressure pump delivers fuel from a low-pressure region into an accumulator, the so-called rail. The inlet cross-section is determined via a suction throttle. To the rail are connected injectors with which the fuel is injected into the combustion chambers, the cylinders.

It should be noted that it is necessary to keep the pressure in the rail at a certain level in order to ensure a sufficient quality of the combustion. For this purpose, a pressure control is provided. This includes a pressure regulator, the suction throttle with the high-pressure pump and the rail. The pressure in the rail is thus the controlled variable. The measured pressure values are typically converted via a filter into an actual rail pressure and compared with a desired rail pressure. The resulting deviation is converted via the pressure regulator into a control signal for the suction throttle.

The publication DE 10 2005 029 138 B3 describes a control method for an internal combustion engine with a common rail system. In this case, a rail pressure is regulated in normal operation. A second actual rail pressure is determined via a second filter. A load shedding is detected when the second actual rail pressure exceeds a first limit. Upon detection of load shedding, the rail pressure is controlled by setting the PWM signal above PWM default to a higher PWM value than normal operation.

The publication DE 10 2008 036 299 B3 describes a method for pressure control of a common rail system, in which a rail pressure of the common rail system is controlled independently of each other on two separate rails.

The publication DE 10 2004 061 474 A1 describes a method and a device for regulating the rail pressure. In this, a control of the rail pressure is proposed for a common rail system, in which a rail pressure regulator, a current control loop for controlling the Saugdrosselstrom, which flows through the coil of the suction throttle, is subordinate. The current control loop has a feedforward control for calculating a pilot control value and a filter in the feedback branch.

From the DE 10 2007 006 865 A1 A method for controlling the pressure in a pressure accumulator of a fuel injection system of an internal combustion engine is known as known. The system includes at least two high-pressure pumps that jointly supply fuel to the accumulator. The regulation of the pressure in the pressure accumulator takes place by means of a control device which generates an actuating signal for valves lying in the fuel path to the pressure accumulator on the basis of pressure values measured in the rail and as a function of an operating point of the internal combustion engine. The amount of fuel to be measured is divided by the number of high-pressure pumps and the associated valves are controlled such that each valve supplies a uniform fraction of the total amount of fuel to the pressure accumulator.

For common rail engines, two separate rails can be provided. The fuel is pumped with up to eight high-pressure pumps, ie with up to four high-pressure pumps per rail. This means that the engine electronics must control a maximum of eight suction throttles. The number of intake throttles to be controlled depends on the number of cylinders of the engine. Possible examples are:
12-cylinder engine: four suction throttles / high pressure pumps,
16-cylinder engine: six suction throttles / high-pressure pumps,
20-cylinder engine: eight suction chokes / high pressure pumps.

The invention is based on the problem to use several small instead of newly developed high-pressure pumps, with a simple parameterization by automatically taking into account the number of cylinders of the internal combustion engine.

This problem is solved by the features of claims 1 and 8. Advantageous developments of the invention are the subject of the dependent claims.

It is thus presented a method for operating an internal combustion engine, are controlled in the high-pressure pumps, each associated with a suction throttle and with which fuel is conveyed into a rail, wherein the pressure in the rail is controlled by a pressure regulator, which includes a pressure regulator, and wherein pressure values measured in the rail are compared with a desired pressure and the pressure control determines therefrom a control signal for the intake throttles. When calculating the control signal, the number of suction throttles is taken into account by dividing by this number. Finally, all suction chokes are controlled with this control signal. The high pressure pumps are divided into units, each consisting of at least one high-pressure pump and associated intake throttle, each unit through a separate control loop, such as current control circuit, is controlled.

In a refinement, the actuating signal is determined with the aid of a pump characteristic curve which, for example, converts a nominal volume flow into a current signal.

In one embodiment, for example, at least two high-pressure pumps are provided in at least one of the units whose associated suction throttles are electrically connected in series.

The control signal can be converted into a PWM signal with which the suction throttles are controlled. Typically, a current signal whose current level represents the information carrying the actuating signal is used as the actuating signal.

In a further embodiment, measured pressure values are converted via a filter into an actual rail pressure, which is compared with the desired rail pressure.

The presented method thus relates to the control of the intake throttles of a common rail system and is a control and regulating method in an internal combustion engine with common rail injection.

By using several small suction throttles or high pressure pumps can be used on existing low-cost components.

The method for operating an internal combustion engine provides that a number of high-pressure pumps are controlled, wherein the high-pressure pumps are divided into units, each unit is controlled by a separate current control loop, wherein in an embodiment the pump characteristic of a single high-pressure pump is used.

All pumps in a rail can be divided into two units. One unit contains either one or two high-pressure pumps. If a unit comprises two high-pressure pumps, the associated intake throttles are, for example, electrically connected in series. These are traversed by the same electric current in this way. The electrical intake throttle flow of each unit is typically controlled by a separate flow regulator. Both current controllers are supplied with the same setpoint current.

In an embodiment, the current controller is adapted when a unit contains more than one high-pressure pump with associated intake throttle.

Furthermore, a control device which is suitable for carrying out the method is presented. This control device is used to regulate a pressure in a rail of an internal combustion engine and has a pressure regulator, wherein the control device is adapted to compare pressure values measured in the rail with a desired pressure and to determine therefrom a control signal for the suction throttles, wherein in the calculation of the control signal the number of suction throttles is taken into account by dividing by this number, and all suction throttles are controlled with this actuating signal. The high-pressure pumps are divided into units, each consisting of at least one high pressure pump and associated intake throttle, each unit by a separate control loop, for example current control circuit, can be controlled.

For example, a PI (DT ₁ ) controller serves as a pressure regulator. Furthermore, the control device can have a pump characteristic.

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

The invention is schematically illustrated by means of embodiments in the drawing and will be described in detail below with reference to the drawings.

1 shows a state diagram.

2 shows the high pressure control.

3 shows another high pressure control.

4 shows another high pressure control.

5 shows a current calculation.

6 shows another current calculation.

7 shows a current calculation.

8th shows still a current calculation.

In V engines, the two cylinder banks are each associated with two pressure accumulators extending along the rows of cylinders, which are referred to as the A-side and B-side pressure accumulators. 1 shows a state transition diagram of the A-side high pressure control. Since two units are controlled in this embodiment, two PWM signals, namely PWM _HD ^{A unit 1} and PWM _HD ^A unit 2 are calculated accordingly.

The illustration shows a first state 400 indicating a normal operation of the high pressure and in which a PWM value is calculated as a result of the current regulation, a second state 402 in which a suction throttle is subjected to a constant PWM signal, and a third state 404 , in which the suction throttle is subjected to a second PWM value. The states are indicated by the state variable CM _HD ^A.

The control mode describes the activation of the suction throttle in the case of engine start. This is in the document DE 101 56 637 C1 shown. If the motor is stationary, this variable has the value 1. In this case, the PWM duty cycle is set to the value 0%. If the high pressure reaches the specifiable release high pressure for the first time after starting the engine, for example 600 bar, then the control mode changes to the value 0 and the PWM duty cycle of 0% to the value calculated by the high pressure regulator, ie the high pressure control is then released.

This ensures a safe high pressure build-up at engine start, as the suction throttle is normally open. If the high pressure falls below the release high pressure again during operation, the control mode remains unchanged and the PWM duty cycle continues to be calculated. The I component of the current controller is thereby initialized at engine start up to the first reaching the release high pressure with a constant value. If the release high pressure is reached for the first time, then the I component of the current controller is calculated by the current controller, i. H. In this case both high pressure and current controllers are enabled.

1 can the blocks 42 . 142 and 242 of the 2 to 4 and describes the calculation of the PWM signals of the two units.

The states of the state transition diagram are defined by the variable CM _HD ^A. After initialization, state 1 becomes active, ie CM _HD ^A assumes the value 1. For each unit, a PWM signal must be calculated. The corresponding function calls are designated HD control unit1 () and HD control unit 2 (). The two functions have the task from the current controller (blocks 40 . 140 and 240 in 2 to 4 ) calculated voltage to calculate a corresponding PWM signal.

If the unfiltered high pressure p _unfil ^A _{exceeds the specifiable} value p _Max ^HD , z. B. 2200 bar, and is the predetermined time t1 _Temp ^HD greater than 0, z. B. 10 ms, a state change takes place in the state 2. In this state, the two PWM signals by the constant value PWM _Temp ¹ , z. B. 100%, given. If the time t1 _Temp ^{HD has} expired and the time t2 _Temp ^{HD is} parameterized with a value less than or equal to 0, then a state change takes place back to state 1, ie then the PWM signals are calculated again. If the time t1 _Temp ^{HD has} expired and the time t2 _Temp ^HD is parameterized with a value greater than 0, then a change to state 3 takes place. In this state, the PWM signals are preset by a second constant value PWM _Temp ² . If both times have elapsed in total, a state change takes place again into the state 1. If the time t1 _Temp ^{HD is} parameterized with a value less than or equal to 0 and the time t2 _Temp ^HD with a value greater than 0, and reaches or exceeds the unfiltered high pressure the specifiable high pressure value p _Max ^HD , a state change takes place directly from state 1 to state 3.

The illustrated functionality makes it possible to prevent opening of the pressure relief valve in the case of high-pressure overshoots by the suction throttle for a short time, z. For example, for 10 ms, one or two large PWM constant values are applied. In the case of a single suction throttle, the method is in the document DE 10 2005 029 138 B3 described.

Not shown in 1 the calculation of the PWM signal in the case of engine start. The PWM signal is set to the value 0% at engine start, until the high pressure reaches a presettable value of z. B. 600 bar, the release high pressure reached. If this is the case, the PWM signal is calculated as a function of the intake throttle, even if the high pressure then falls below the release high pressure while the engine is running. This procedure allows a safe high-pressure build-up when starting the engine with a normally open suction throttle. In the case of the software implementation of the motor start, the state variable CM _HD ^A is not used in this case, but a variable CM ^A called the control mode is used. If the engine is at standstill, the control mode is 1, if the release high pressure is reached, the control mode changes to 0. This value is maintained until the engine stops. In the case of a single suction throttle this method is in the document DE 101 56 637 C1 described.

2 shows a pressure control 10 namely a high pressure control circuit for a 12 cylinder engine. This includes a first unit 12 and a second unit 14 , The first unit 12 includes a first high-pressure pump 16 and an associated first suction throttle 18 , The second unit 14 includes a second high pressure pump 20 and a second suction throttle 22 , The units 12 and 14 control the pressure in a rail 24 ,

The illustration also shows a pressure regulator 30 whose output coincides with a Value of a disturbance variable, which consists of a calculation unit 32 is received, in a limitation unit 34 is entered. Its output is multiplied by a factor of ½, since this version has two high-pressure pumps. This means that it is divided by the number of high-pressure pumps. The result, which represents a set volume flow, becomes a pump curve 36 entered, which outputs a current value as a manipulated variable. This current value becomes the first unit 12 and the second unit 14 made available. Here is the first suction throttle 18 along with a first regulator 40 , a first institution 42 which calculates a PWM signal and a first current filter 44 in a first current loop 46 contain. Accordingly, the second suction throttle 22 together with a second regulator 50 , a second facility 52 which calculates a PWM signal and a second current filter 54 in a second current loop 56 contain. Both current control circuits 46 and 56 are subjected to the same nominal current.

A pressure on the rail 24 is detected again via a pressure filter 58 as the actual pressure for a nominal-actual pressure comparison for input to the pressure regulator 30 returned.

3 shows a pressure control 100 namely, an A-side high pressure control circuit, for a 16-cylinder engine. This includes a first unit 112 and a second unit 114 , The first unit 112 includes a first high-pressure pump 116 and an associated first suction throttle 118 , The second unit 114 includes a second and third high pressure pump 120 and a second suction throttle 122 and a third suction throttle 123 , The units 112 and 114 control the pressure in a rail 124 ,

The first unit 112 This engine consists of a suction throttle 118 and a high pressure pump 116 , The second unit 114 consists of two suction throttles connected in series 122 and 123 and two associated high pressure pumps 120 ,

The illustration also shows a pressure regulator 130 , whose output together with a value of a disturbance variable, which consists of a calculation unit 132 is received, in a limitation unit 134 is entered. Their output is multiplied by a factor of 1/3, since this version has three high-pressure pumps. The result, which represents a set volume flow, becomes a pump curve 136 entered, which outputs a current value as a manipulated variable. This current value becomes the first unit 112 and the second unit 114 made available. Here is the first suction throttle 118 along with a first regulator 140 , a first institution 142 which calculates a PWM signal and a first current filter 144 in a first current loop 146 contain. Accordingly, the second suction throttle 122 and the third suction throttle 123 together with a second regulator 150 , a second facility 152 which calculates a PWM signal and a second current filter 154 in a second current loop 156 contain. Both current control circuits 146 and 156 are subjected to the same nominal current. The two Saugdrosselströme are thus in turn by two separate current control loops 146 and 156 controlled with identical suction throttle setpoint.

A pressure on the rail 124 is detected again via a pressure filter 158 as the actual pressure for a nominal-actual pressure comparison for entry into the pressure regulator 130 returned.

4 shows a pressure control 200 namely, an A-side high-pressure control circuit, for a 20-cylinder engine. This includes a first unit 212 and a second unit 214 , The first unit 212 includes a first and second high-pressure pump 216 and an associated first suction throttle 218 and second suction throttle 219 , The second unit 214 includes a third and fourth high pressure pump 220 and a third suction throttle 222 and a fourth suction throttle 223 , The units 212 and 214 control the pressure in a rail 224 ,

The first unit 212 This engine consists of a first suction throttle 218 and a second suction throttle 219 , which are connected in series, and two high-pressure pumps 216 , The second unit 214 consists of two suction throttles connected in series 222 and 223 and two associated high pressure pumps 220 ,

Furthermore, the illustration shows a controller 230 , whose output together with a value of a disturbance variable, which consists of a calculation unit 232 is received, in a limitation unit 234 is entered. Their output is multiplied by a factor of 1/4, since four high-pressure pumps are provided in this version. The result, which represents a set volume flow, becomes a pump curve 236 entered, which outputs a current value as a manipulated variable. This current value becomes the first unit 212 and the second unit 214 made available. Here is the first suction throttle 218 and the second suction throttle 219 along with a first regulator 240 , a first institution 242 which calculates a PWM signal and a first current filter 244 in a first current loop 246 contain. Accordingly, the third suction throttle 222 and the fourth suction throttle 223 together with a second regulator 250 , a second facility 252 which calculates a PWM signal and a second current filter 254 in a second current loop 256 contain. Both current control circuits 246 and 256 are subjected to the same nominal current. The two Saugdrosselströme thus again by two separate current control circuits 246 and 256 controlled with identical suction throttle setpoint.

A pressure on the rail 224 is detected again via a pressure filter 258 as actual pressure for a nominal-actual pressure comparison for input to the controller 230 returned.

The two units 212 and 214 Thus, each consist of two high-pressure pumps with associated suction throttles connected in series. Both current control circuits 246 and 256 again have the same rated current.

The calculation of the setpoint current I _setpoint ^A takes place in accordance with 2 to 4 as follows:
The limited nominal volume flow is divided by the number of high-pressure pumps, which is the reference to a high pressure pump reference flow V. ^A _nominal yields as an input variable of the pump curve. As a result, the pump characteristic of a single high-pressure pump can be used to determine the _nominal electrical current I _setpoint ^A.

5 to 8th show an adapted current regulation:
5 shows the current regulation for the unit 1 of the A-side rail. The precontrol U _set ^{before A unit 1} results from multiplication 300 of the setpoint current I _setpoint ^A with the resistance R _SR ^{specification of} a suction throttle and the factor f _R. The factor f _R depends on whether a single suction throttle or two intake throttles connected in series are used. In the case of the 12-cylinder or 16-cylinder engine, the Saugdrosselwiderstand is defined solely by the resistance R _SR ^{specification of} a suction throttle, whereby the factor f _{R has} the value 1. In the case of the 20-cylinder engine, two intake throttles connected in series are used, so that the intake throttle resistance is defined by twice the value of the resistance R _SR ^default . Thus the factor f _{R has} the value 2.

5 thus describes the calculation of Saugdrosselsollspannung U _Soll ^{A Einheit1} . According to the switch position of the switch S1 (block 304 ) one of three possible variants can be applied:
If the switch S1 to position 1, so there is a pilot control and no current control, the Saugdrosselsollspannung is calculated in this case according to the Ohm's law by multiplying the Saugdrosselsollstrom I _Soll ^A with the ohmic resistance of the suction throttle (s). With one intake throttle per unit, the intake throttle resistance is identical to the ^preset resistance R _SR (f _R = 1), in the case of two high-pressure pumps with twice the specified resistance 2 · R _SR ^default (f _R = 2). The variant described here is also present if a sensor defect of the suction throttle current sensor is detected.

If the switch S1 assumes the position 2, then there is a current control, ie, the Saugdrosselsoll voltage is calculated from the output of the current controller. The input variable of the current controller is the current control deviation e _I ^A , which _is calculated as the difference between intake throttle _target current I _setpoint ^A and intake throttle current I ^A unit1. The current controller algorithm is in the 7 and 8th described.

If the switch S1 assumes the position 3, the suction throttle setpoint voltage is calculated as the sum of the current controller output variable and pilot control. In this case, the current controller has the task of correcting the Saugdrosselsollspannung defined by the pilot control, ie correct deviations of the ohmic resistance by temperature changes and manufacturing tolerances. This case is in the Scriptures US Pat. No. 7,240,667 B2 described.

The block 306 defines the limitation of the suction throttle set voltage. The upper limit value is identical to the battery voltage U _Batt , the lower limit value is identical to zero.

6 shows the current control in a similar manner for the unit 2 of the A-side rail.

The 7 and 8th show the algorithm of the current controller for units 1 and 2 of the A-side rail. The adaptation is shown as follows:
Since the suction throttle resistance in the 20-cylinder engine is twice as large as in the 12-cylinder and 16-cylinder engine, the proportionality factor kp _I ^SR must be twice as large in this engine as with other cylinder variants: kp _I ^SR = 2 · kp _I ^Dia

The proportionality factor kp _I ^Dia can be specified as a constant by the operator of the motor.

The initialization value of the integrating component U _Soll ^{I Init} depends on the number of cylinders. For the 20-cylinder engine, the initialization value must be doubled compared to the 12- and 16-cylinder engines due to the double intake throttle resistance. This is achieved by doubling the factor f _I.

7 describes the discrete algorithm of the current controller. It is a PI (DT ₁ ) algorithm. The algorithm was obtained from the continuous algorithm by discretization with the trapezoid rule.

The input variable of the algorithm is the current control deviation e _I ^{A unit 1} , the output variable is the coil _target voltage U _target ^{PI (DT} ₁ ^{) A unit} ₁ . The calculation of the algorithm is done internally by a factor of 100 more precisely (internal arithmetic variable: 0.01 Volt). For this reason, the value 100 is divided at the end.

The highest calculation path represents the calculation of the proportional component (P component). This is calculated by multiplying the current controller deviation by the proportional coefficient kp _I ^SR . In the case of a suction throttle per unit, the proportional coefficient is identical to the proportional coefficient kp _I ^{SR Dia} that can be specified by dialogue. With two suction throttles per unit, the proportional coefficient is identical to the corresponding double value 2 · kp _I ^{SR Dia} .

The mean calculation path describes the calculation of the integrating component (I-component) of the current controller. The I component is calculated internally by the further factor 128, ie a total of 12800, since the I component defines the stationary accuracy of the control. The I component is limited upwards to the battery voltage. At the bottom, the I component must be limited so that the voltage 0 V can be displayed. Therefore, the lower limit depends on whether the feedforward control is active or not. If the feedforward control is not active, the I-component is limited downwards to the value 0 Volt. If the pilot control is active, however, the I component is limited downwards to the negative value of the pilot control.

With the aid of the switch S, the initialization of the I-component is defined. If the control mode CM ^{A has} the value 1 (switch S = 1), then the rail pressure has not yet reached the release high pressure. In this case, the I component is initialized with the constant predefinable value U ^I _Soll ^Init if a suction throttle is used per unit. If two suction throttles are used per unit, the I component is initialized to the value 2 · U ^I _Soll ^Init .

If the high pressure has reached the release high pressure, the control mode changes to the value 0 (switch S = 0). In this case, the I component is calculated as the output of the limiting block.

The lower path describes the DT _{1 part of} the current controller. This is additionally calculated by a factor of 8, in total by a factor of 800.

The presented method is distinguished by the fact that up to four high-pressure pumps are conveyed into each rail fuel with, for example, up to. The high-pressure pumps are divided into two pump units with the associated suction throttles for each of the two rails. Each pump unit consists either of a high-pressure pump with associated suction throttle or of two high-pressure pumps with suction throttles connected in series. The two pump units of a rail are supplied with the same suction throttle target flow. The Saugdrosselsollstrom is the output of a pump curve, which maps the characteristics of a single high-pressure pump. The output variable of the pressure regulator is the limited nominal volume flow. This is divided by the number of high-pressure pumps per rail and used as the input variable of the pump characteristic.

If two intake throttles of a pump unit are connected in series, the intake throttle control must be adjusted as follows: When calculating the feedforward control, the suction throttle resistance must be multiplied by a factor of 2. The proportionality coefficient must be doubled. Furthermore, the I component must be initialized with twice the value.

The presented method has, at least in some of the embodiments, the following advantages: Instead of large, newly developed high-pressure pumps, several small, already available high-pressure pumps can be used to deliver the fuel. The number of high-pressure pumps can be optimally adapted to the required fuel delivery. Furthermore, the method is easy to parameterize, since the number of cylinders is automatically taken into account and in each case the pump characteristic of a single high-pressure pump is used.

Claims (10)

Method for operating an internal combustion engine, are controlled in the high-pressure pump, each associated with a suction throttle and with which fuel is conveyed into a rail, wherein the pressure in the rail is regulated by a pressure regulator comprising a pressure regulator, measured in the rail pressure values are compared with a set pressure and the pressure control determines therefrom a control signal for the suction throttles, the number of suction throttles is taken into account in the calculation of the control signal by dividing by this number, and all suction throttles are controlled with this actuating signal, wherein the high-pressure pumps are divided into units, each consisting of at least one high-pressure pump and associated intake throttle, each unit being controlled by a separate control circuit. Method according to Claim 1, in which the actuating signal is determined by means of a pump characteristic curve. The method of claim 1, wherein for each unit with at least two high-pressure pumps, the associated suction throttles are electrically connected in series. Method according to one of Claims 1 to 3, in which a current signal whose current strength represents the information carrying the actuating signal is used as the actuating signal. Method according to one of claims 1 to 4, wherein the control signal is converted by means of a current regulator into a PWM signal, with which the suction throttles are driven. Method according to one of claims 1 to 5, wherein the current regulator is adapted when a unit contains more than one high pressure pump with associated suction throttle. Method according to one of claims 1 to 6, are converted in the measured pressure values via a filter in an actual rail pressure, which is compared with the target rail pressure. Control device for regulating a pressure in a rail of an internal combustion engine for carrying out a method according to one of claims 1 to 7, having a pressure regulator, wherein the control device is designed to to compare pressure values measured in the rail with a setpoint pressure and to determine therefrom a control signal for the suction throttles, wherein the number of suction throttles is taken into account in the calculation of the control signal by dividing by this number, and all suction throttles are controlled with this actuating signal, wherein the high-pressure pumps are divided into units, each consisting of at least one high-pressure pump and associated intake throttle, each unit being controlled by a separate control circuit. Control device according to claim 8, in which a PIDT ₁ controller serves as pressure regulator. Control device according to claim 8 or 9, which has a pump characteristic.

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