FR2766521A1 - METHOD AND DEVICE FOR CONTROLLING AN INTERNAL COMBUSTION ENGINE - Google Patents

Abstract

Method for controlling an internal combustion engine, in particular an internal combustion engine equipped with a common rail system with at least one pump taking fuel from a low pressure zone to transfer it to an accumulator and according to which the pressure in the accumulator is detected, the pressure of which is regulated by a pressure regulating means which discharges a quantity of regulation from the accumulator to the low pressure zone. The quantity of regulation is adjusted to a set value.

Description

STATE OF THE ART The present invention relates to a method and a

  control device of an internal combustion engine, no-

  as an internal combustion engine equipped with a common rail system with at least one fuel pump

  a low pressure zone to transfer it to an accumulator

  lator and according to which the pressure in the accumulator is detected, the pressure of which is regulated by a pressure regulating means which discharges a quantity of regulation

  from the accumulator to the low pressure zone.

  According to document DE 195 48 278, a method and a device are already known for controlling a combustion engine.

  internal bustion. This document describes a method and a device for regulating the pressure in an accumulator also called a common rail system. To regulate the pressure, a regulating quantity of the accumulator is discharged into the

  low pressure zone. A second regulation is also planned.

  which acts on the low pressure area.

  The pressure regulating valve that regulates

  the pressure of an accumulator has an

  stable for small amounts of regulation. Through

  elsewhere, we do not wish to have large quantities to be

  Gulate because in this case, the high pressure pump unnecessarily passes fuel. This unnecessary transfer of fuel leads to overheating of the fuel and a reduction in engine power, which in turn results in a

  increased fuel consumption.

  For certain operating states, if the pressure must be lowered quickly to a set value

  Weaker, it is desirable to have large amounts of regulation, to have a rapid drop in pressure. Problems of the invention The object of the present invention is to develop a method and a device for controlling an internal combustion engine according to the type defined above, in order to achieve stable and precise regulation of the pressure, while avoiding 1 mima M heating the fuel or reducing consumption

  of energy to generate pressure.

  To this end, the invention relates to a method of

  type defined above, characterized in that the quantity is adjusted

  regulation unit on a setpoint. The invention also relates to a device for

  control characterized in that it includes means which

  set the regulation quantity to a set value.

  The means of the invention make it possible to regulate

  independently of each other the two important quantities

  ie fuel pressure and amount of fuel

  1 regulation. The fuel pressure can be quickly adjusted to any value regardless of the operating state. The quantity to be regulated can be kept at a very low value. For a rapid decrease in pressure, the quantity to be regulated can be fixed, quickly at

a high value.

  According to other advantageous features of the invention: e a first regulator regulates the pressure in the accumulator and a second regulator regulates the quantity of regulation,

  * the first regulator acts on the means of

  pressure regulation from a setpoint and an actual pressure value,

  * the second regulator acts on a reduction element

  glage provided in the low pressure zone and / or which acts on the high pressure pump,

  * the second regulator controls the cooling element

  setting at least from a variation of the current passing through the pressure regulating means and a variation of pressure in the accumulator,

  * the second regulator controls the cooling element

  setting at least from the difference between the actual value and the pressure setpoint, * the adjusting element is controlled at least by a prior command and the second regulator corrects the values for the prior command,

  the pre-order controls the element of re-

  setting according to different operating parameters such as the quantity of fuel to be injected and / or the engine speed. Drawings

  The present invention will be described below in more detail with the aid of the accompanying drawings in the

  which: - Figure 1 shows a block diagram of a fuel metering system, - Figure 2 shows a block diagram of the regulating structure according to the invention, - Figure 3 shows a block diagram of an embodiment of the device of the invention, FIG. 4 represents the quantity to be regulated as a function of the control current,

  - Figure 5 shows a flow chart.

  Description of the exemplary embodiments

  FIG. 1 shows the components of a fuel supply system necessary for understanding the invention for an internal combustion engine with high pressure injection. The system represented is usually called

"common rail system".

  The reference 100 designates a fuel tank

  rant. This is connected via a first filter 105 and a controlled supply pump 10 to a second filter 115. The fuel leaving the second filter 115

  goes through a pipe to reach a valve 120. The con-

  connecting line between filter 115 and valve 120 is re-

  linked to the tank 100 by a low pressure limiting valve 140. The solenoid valve 120 is connected by a

  dosing ZME 122 at high pressure pump 125. The dosing unit

  sage ZME is mounted on the suction side on the high pressure pump. The dosing unit can consist of

  example by a proportional valve with electromechanical control

genetic.

  The high pressure pump is connected to a rail 130.

  The rail, also called an accumulator, is connected by the fuel line to different injectors 131. Via a pressure regulating valve 135, the rail 130 is

  connected to the fuel supply tank 100. The support

  pressure regulating valve 135 is controlled by a

  bine 136. The pipes between the outlet of the high

  125 pressure and the inlet of the pressure regulating valve

  sion 135 belong to the high pressure zone. In this area, the fuel is at high pressure. The pressure in the high pressure zone, in particular in the accumulator, is detected by a sensor. The lines between the tank 100 I and the high pressure pump 125 correspond to the low pressure zone.

  A control 160 includes a pressure regulator

  and acts on the appropriate actuators such as for example the coil 136 of the pressure regulating valve 135 and / or the metering unit 122 by supplying them with control signals. The command 160 processes the various signals supplied by the sensors 165, 166 and characterizing the state of

  operation of the internal combustion engine and / or vehicle

  cule driven by this engine. Such an operating state is for example the speed (speed of rotation) N of the engine at

  internal combustion or a temperature measurement.

  It is particularly advantageous if the com-

  mande acts on other elements. In order to regulate the pressure P in the high-pressure zone, it is possible as a variant or in addition to use other adjustment elements. These are

  constituted for example by a feed pump 110 with

  flow control, a high pressure pump 125, controlled and / or a pressure regulation valve 140 in the low pressure zone. The installation described above works as follows: Fuel from the tank is supplied by the pump

  supply 110 through filters 105 and 115. Coming out

  tie of the supply pump 110, the fuel is at a pressure of a few bars. When the pressure in the low pressure area of the fuel system exceeds a predetermined pressure, the valve 120 opens and the inlet of the high pressure pump 125 receives fuel under a certain

  pressure. This pressure depends on the realization of the sou-

  pope 120; usually, the valve 120 is produced for or

  screw the connection to the high pressure pump 125 for a

pressure of a few bars.

  If the pressure in the low pressure zone has

  dyes unacceptable levels, the low pressure limiting valve 140 opens and releases communication between the outlet of the supply pump 110 and the tank

  100. The valve 120 and the limiting valve

  low pressure 140 maintain low range

  pressure at values between 1 and 3 bars.

  The creation of the low pressure zone, in particular

  The valves and filters are only given for

  example. The nature, design and / or number of elements

may be variable.

  The high pressure pump 125 passes the fuel

  from the low pressure zone to the high pressure zone. The high pressure pump builds very high pressure in the

  rail 130. Usually in combustion engine systems

  internal ignition, there are pressures ranging

  from 30 to 100 bars and in the case of internal combustion engines

  dull with uncontrolled ignition, pressures included

  between 1000 and 2000 bars. The injectors 131 inject the car-

  burant under high pressure in the different cylinders of the

  internal combustion engine by metering.

  Sensor 145 detects pressure in the rail

  or throughout the high pressure area. The regulating valve

  pressure 135 controlled by a coil 136, allows to regulate the pressure prevailing in the high pressure zone. Depending on the voltage applied across the coil 136

  or current flowing through the coil 136, the regulating valve

  pressure 135 opens at different pressure values

annuities.

  As the supply pump 110, the usual

  also mechanical feed pumps. We can also

  Use electric pumps driven by a DC motor or alternatively DC electric motors. For the high flow rates required, particularly in utility vehicles, several supply pumps connected in parallel can be used. In this case, it is preferable to use DC motors, switched, because of their greater reliability and

their greater availability.

  In order to regulate the pressure P in the high pressure zone, it is possible, as a variant and / or in addition, to use other adjustment elements. It is for example an electric supply pump 110, with adjustable flow rate or a pump

  high pressure controlled 125. In addition to the regulating valve

  pressure lation 135, it is also possible to provide a pressure limiting valve which releases the communication between the high pressure zone and the low pressure zone for a

given pressure.

  The flow rate QP is transferred by the high pressure pump 125 into the rail 130. The regulated quantity QDRV is discharged into the low pressure zone through the pressure regulation valve 135. The quantity for establishing the pressure QR is available to establish pressure. By the injectors 131, the quantity QI metered arrives at the injectors 131. The quantity QI consists of the quantity of fuel to be injected QK, the quantity of leakage and a quantity of control necessary for the injectors. The amount of leakage and

  the quantity of orders returns in the low area near-

  if we. The quantity of fuel to be injected arrives in the

  combustion chambers of the internal combustion engine. The re-

  reference A designates the respective quantity variations

  for a certain time interval.

  FIG. 2 shows the regulation according to the invention using a block diagram. A command 200 provides a set value PS for the pressure in the accumulator as well as a set value QDRVS for the adjustment quantity. The pressure setpoint PS is applied with a positive algebraic signal at the combination point 205 whose second input receives the value

  real pressure P with a negative sign.

  The output of the combination point 205 is applied to a pressure regulator 210 also called the first regulator. The output signal ID of the pressure regulator 210 arrives at a first regulating element 135. The first regulating element 135 is preferably the pressure regulating valve 135. This pressure regulating valve defines the quantity of regulation QDRV discharged from

  the accumulator 130 in the low pressure zone.

  The QDRVS setpoint of the quantity of re-

  glage is combined at a combination point 230 at the quan-

  tity of effective adjustment QDRV this being affected by a negative algebraic sign on its entry at the point of combination 230. The result of this combination is applied to the second

  regulator 220 also called quantity regulator. The regu-

  quantity reader 220 supplies a control signal IN to a second adjustment element 122. This second adjustment element

influences the flow rate of the QP pump.

  Reference 240 designates the regulation path.

  Combination point 246 indicates that the pump flow

  QP is reduced by the quantity IQ supplied to the injectors 131.

  Combination point 244 means that this quantity is

  further reduced by the amount of QDRV regulation. The quan-

  residual quantity QR, also called quantity of establishment

  pressure, used to establish the pressure in the rail 130.

  If we consider the quantity of QR pressure establishment, the rail 130 functions as an integrator whose output

provides pressure P in the rail.

  The first regulator regulates the

  pressure in the accumulator below a set value.

  Starting from the regulation deviation between the value of con-

  sign and the actual value of the pressure, the first regula-

  tor defines a control signal applied by means of

  pressure regulation. This releases a quantity of re-

  regulation of the accumulator towards the low pressure zone according to the control signal. This amount of regulation

  is regulated by a second regulator under a con-

sign.

  This installation works as follows:

  Vante: The command provides a setpoint for the desired pressure PS. This value is compared at the combination point 205 with the effective pressure P measured for example

  by sensor 145. On the basis of this comparison, the regulation

  pressure tor 210 defines the control signal ID for

  order the first adjustment element 135. This first element

  The regulating element is preferably a pressure regulating valve which makes it possible to control the quantity discharged in a controlled manner from the high pressure zone into the low pressure zone. Due to the pressure reaction, the valve

  pressure regulation in itself constitutes a pressure loop

  gulation. In the stationary state, there is a current ID cross-

  the coil of the pressure regulating valve; this

  current is proportional to pressure. We thus have the rela-

tion:

AQDRV = AQP - AQI

  In this formula, AQP represents the flow of the

  pump per unit of time and the quantity AQI the quantity in-

  thrown per unit of time. The metered quantity AQI thus contains the quantity of fuel to be injected QK as well as the

  quantity of leak and order quantity for injections

  teurs. The amount of AQDRV regulation is the amount of re-

  gulation evacuated by the pressure regulating valve

  during a unit of time in the low pressure zone.

  The same remark applies to the dependent command.

  in operating parameters for the con-

  QDRVS sign of the regulation quantity. This is

  defined in combination point 230 for the quantity of regulation

  effective QDRV connection to be applied to the

  quantity 220. Based on this regulatory deviation, this-

  this defines a control signal IN of the second adjustment element. The second metering element is preferably a flow solenoid valve 122. This flow solenoid valve is designed to adjust a quantity supplied by the pump QP which is proportional to the current IN. In place of the element

  metering 122, it is also possible to order appropriately

  the supply pump 110 or the high pressure pump 125 are required. The regulation carried out uses two quantities.

  The pressure P in the accumulator 130 is regulated by the sou-

  pressure regulation valve 135 and the quantity delivered QP,

  with an adjustment element in the low pressure range.

  The PS setpoint value of the

  pressure according to the different operating parameters

  is lying. These include the quantity to be injected QK and the speed of rotation N of the internal combustion engine. The QDRVS setpoint for the control quantity is kept as low as possible taking into account the

  driving power and fuel heating.

  If you want a rapid drop in pressure, you set the

  setpoint to a high value.

  The actual value QDRV can be measured by a flow sensor which is provided between the pressure regulator 135 and the tank 100. Such a flow sensor can be

  produced in the form of a differential pressure sensor.

  It is particularly advantageous to use an observer structure to determine the actual QDRV value for the

quantity to be regulated.

  The quantity to be regulated QDRV is regulated to a setpoint which is just large enough for the pressure regulating valve to operate

  stable. The regulation is done through an

  adjustment in the low pressure range, for example the metering unit 122 or a controlled high pressure pump 125.

  The pressure regulating valve 135 operates

  operates unstably when the amounts of regulation

  tion are weak. For small amounts of regulation, the force generated by the pressure is very small. This results in the injector needle abutting on the seat

  from the injector and immediately lifts. Such bones-

  cillations should be avoided as much as possible. According to

  the invention, oscillations are avoided by increasing the quantity

regulatory entity.

  Figure 3 shows an observer structure

  shown in detail. The elements already represented

  tees described in Figure 2 have the same references.

  The observer proper bears the reference 300.

  The observer 300 receives the actual value P of the pressure as well as the signal ID which characterizes the current flowing through

  the pressure regulating valve 135.

  The output signal of the observer 300 and the regulation deviation which corresponds to the output signal of the

  combination point 205 are supplied to a fault regulator

  bit 310. The output signal K of the flow regulator passes through a combination point 315 to be applied to a point

  combination 330 of the second metering element 122.

  The second entry of combination point 315 re-

  receives the output signal Vi of a first prior command 320 processing various operating parameters such as

  temperature T and speed N (speed of rotation).

  The combination point 333 receives the output signal V2 of a second prior command 335 which processes various operating parameters such as the quantity of fuel injected QK and the speed N. According to the invention, the objective has two purposes. Rail pressure is regulated at high dynamic pressure

  and a high regulation quality at a set value

  PS sign depending on the operating state. That means

  that the setpoint is reached with a regulation time

  lation small and a deviation of regulation and a duration of

  extremely weak end of oscillation.

  The quantity of QDRV regulation is regulated on a minimum flow. This is done in particular for quantities

  injection and control, important in operating mode-

  stationary engine. This regulatory objective is

  reached by an adjustment element fitted to the low pressure side. For this, preferably, the unit of do-

wise 122.

  This second adjusting element 122 is controlled so that the high pressure pump 125 receives metered fuel only until the pressure regulating valve 135 of the high pressure circuit has only the minimum quantity of regulation necessary. This quantity is chosen to ensure on the one hand the functioning of the valve of

  pressure regulation as an adjusting element in the pressure regulating circuit and on the other hand to guarantee the reliability of the sealing seat at the level of the pressure regulating valve.

  According to the invention, the regulation circuit for

  regulate the quantity is designed so that the regulating valve

  pressure operation works with a minimum flow without having

  to measure the quantity of effective QDRV regulation.

  According to the invention, the relationship between the quantity of regulation QDRV and the electric current ID passing through the pressure regulating valve for a predetermined pressure P is used under these conditions. Figure 4 shows the relationship between the amount of QDRV regulation and the ID current. Two characteristics

  are shown for different pressures. The character

  ristic represented by a solid line is that corresponding

  dant at a low pressure and the dashed line characteristic is that of a high pressure. Minimum flow

  used as setpoint is indicated under ref-

rence QDRVS and a broken line.

  In the regulation range, for a small variation of the electric current ID, there is a large variation

  of the quantity of QDRV regulation which results in a large variation of the pressure P. When the quantity of QDRV regulation reaches the minimum flow rate, the characteristic curve

  tick makes a strong angle. At this angle, the minimum flow QDRVS that the pressure control valve requires to operate without error is reached. For small control quantities, there is a large variation in the electric current ID and a small variation in the control quantity QDRV which in turn results in a small variation in the pressure P.

  The second pre-order 335 provides a

  V2 control channel requesting the second adjustment element

  depending on the quantity IQ that we want to provide to the in-

  jectors. This quantity depends on the quantity of fuel injected QK, the engine speed, the order quantity of the injectors. In addition, this signal V2 is predetermined as a function of the desired variation of the pressure and / or of the variation of the quantity of fuel to be injected. The height

  V2 functions as a pre-command for the control unit

  setting 122 in the low pressure range.

  The first pre-order takes into account the variation of the pump efficiency as a function of the temperature.

  ture of the fuel as well as the drop in pump efficiency over time. 15 This pre-order also takes account of leaks at the injector as a function of time and temperature. These quantities lead over a very wide range of vehicle operation to a greater quantity of regulation at the level of the pressure regulation valve. The first prior order thus gives a

  multiplication coefficient by which we multiply the if-

  general quantity control output 310 at the point of

combination 315.

  The two prior commands 320, 335 give such a control signal so that for all operating states, a quantity of QDRV regulation is established greater than the minimum flow rate. The flow regulator 310 provides such a correction coefficient K for the signal of

  IN command in the dosing element 122, so that the quantity

* regulating head is in the range of minimum flow or slightly above it. To do this, the

  flow uses the output signal from observer 300.

  When the flow regulator recognizes that there is a large regulation deviation, it emits a signal opposing the regulation deviation. As a result, the setpoint is quickly reached. This is true

  especially if you want a rapid decrease in pressure

  if we. In this case, the flow controller emits a signal such

  that the amount of regulation becomes maximum.

  The cooperation according to the invention between the first pre-order 320 and the flow regulator 310 and the observer 300 is shown in FIG. 5 in the form of a flowchart. When in step 500, the installation

  recognizes the existence of a station operating state

  nary, it activates an adaptation. In non-stationary mode, the coefficient V1 of the first preliminary command is equal to 1. It is recognized that one is in a stationary operating state if the load and the speed of rotation of the internal combustion engine are constant and / or if these quantities do not vary beyond a certain limit value. As a load signal, a quantity characterizing the

amount of fuel to inject.

  Then, in step 510, the value is stored in memory.

  their instantaneous Pl of pressure I and the current Il. Then,

  in step 520, the flow regulator 310 modifies the coefficient

  K to decrease the amount of QDRV regulation of the

  value A. Then, we measure the new values of the

  sion P2 and intensity I2. In step 540, the differences dP / dI between the old values P1, Il and the new values P2, I2 are defined. On the basis of these values, step 550 calculates the ratio dP / dI. The interrogation 560 checks whether this ratio dP / dI is greater than a threshold SW. If so, this means that the amount of regulation has

  lowered enough to reach lower values

  below the minimum QDRVS rate so that in step 580 we

  modifies the coefficient K to increase the amount of QDRV regulation by the value A. When the state of operation is reached

  next stationary operation, the program is run again.

  It is particularly advantageous that the coefficient

  cient K keeps QDRV constant when leaving

  the stationary operating state.

  If the interrogation 560 finds that the threshold SW has not yet been reached, in step 570 the old values P1 and II are replaced by the new values P2 and 11a I2. Then, we run the program again from

step 520.

  According to the invention, in the stationary operating states, the control signal of the control element

  sage 122 is changed to decrease the amount of regulation. The modification of the pressure P is taken independently of the current I. The control signal is modified until

  a significant modification of the current is required for mo-

change the pressure in the rail.

  The invention provides that in stationary mode, the flow regulator 310 predetermines a control signal for the second metering element 122 to just discharge the minimum flow in the low pressure zone by the pressure relief valve.

pressure regulation.

  Starting from the quantities to be regulated, that is to say the pressure P and the adjustment quantity, that is to say the

  current, passing through the first adjusting element 135 of the first

  mier regulation circuit, we form the actual value of the

  cond regulation circuit. The actual value of the second regulation circuit reaches its setpoint if a large variation in the adjustment variable only causes a small variation in the quantity to be regulated. The actual value of the second control circuit reaches its setpoint if the behavior of the first control circuit does not change significantly. This means that if the report

  between the variation of the current dI and the variation of the pressure

  sion dP varies significantly.

  For non-stationary operating states

  res, the flow regulator 310 defines the control signal of the second metering element 122 as a function of the difference between the setpoint PS and the actual value P of the pressure.

Claims (6)

R E V E N D I C A T I O N S   1) Method of controlling an internal combustion engine, no-   In particular, an internal combustion engine equipped with a common rail system with at least one pump taking fuel from a low pressure zone to transfer it to an accumulator and according to which the pressure in the accumulator is detected. the pressure is regulated by a pressure regulating means which discharges a regulating quantity from the accumulator to the low pressure zone, characterized in that   the regulation quantity is adjusted to a set value   gne. 2) Method according to claim 1, characterized in that a first regulator regulates the pressure in the accumulator   and a second regulator regulates the amount of regulation.   ) Method according to any one of claims 1 or 2,   characterized in that the first regulator acts on the pressure regulating means on the basis of a set value and a value real pressure.   4) Method according to any one of the preceding claims.   teeth, characterized in that the second regulator acts on an adjustment element provided in the low pressure zone and / or which acts on the high pump pressure.   ) Method according to any one of the preceding claims.   teeth, characterized in that the second regulator controls the adjusting element at least at   from a variation of the current flowing through the means of   pressure regulation and pressure variation in the accumulator.   6) Process according to any one of the preceding claims.   teeth, characterized in that the second regulator controls the adjusting element at least from the difference between the actual value and the pressure setpoint;   7) Process according to any one of the preceding claims.   teeth, characterized in that the adjusting element is controlled at least by one control   and the second regulator corrects the values of prior request.   8) Process according to any one of the preceding claims. teeth, characterized in that   the pre-order controls the adjustment element in function   tion of different operating parameters such as   quantity of fuel to inject and / or engine speed.   9) Control device for an internal combustion engine   in particular an internal combustion engine fitted with a system   common rail, according to which at least one fuel pump   rant transfers the fuel from a low pressure zone to an accumulator whose pressure is detected, and to adjust the   pressure in the accumulator, a means of pressure regulation   sion discharges a regulating quantity from the accumulator to the low pressure zone, characterized in that it comprises means which regulate the regulating quantity on a setpoint.