FR2767358A1 - METHOD AND DEVICE FOR CONTROLLING AN INTERNAL COMBUSTION ENGINE - Google Patents

Abstract

Method and installation for controlling an internal combustion engine comprising a control (150) controlling the injection by the injectors (131) of fuel supplied from a tank (100) by a low supply pump (110) pressure supplied by a high pressure pump (125) a high pressure accumulator (130). The control (150) receives the pressure signals (P) to compare them and establish the control signals (A) of the injectors (131). The pressure is entered only at predetermined time intervals and outside of the injection phases.

Description

STATE OF THE ART: The present invention relates to a method for

  control an internal combustion engine, in particular an engine equipped with a common rail system, according to which at least one pump supplies fuel from a low pressure zone to a pressure accumulator and according to which, the pressure values are entered characterizing the fuel pressure in the pressure accumulator using a pressure sensor

  and therefore the pressure values thus entered and a value

  their setpoint, a control signal is predetermined for

  pressure regulating means.

  The invention also relates to a device for

  control an internal combustion engine.

  Such a method and such a device for controlling an internal combustion engine are known according to document DE 195 48 278. This document describes a method and a device for regulating the pressure in a pressure accumulator of a common rail system . Usually in such systems

  with common rail, the duration of control of the in-

  jets according to the quantity of fuel to be injected and the pressure prevailing in the accumulator. To do this, the accumulator pressure is detected synchronously with the

  rotation speed. The pressure regulation is done

  lon a fixed time frame. For this, we detect in syn-

  chronism in time the pressure of the common rail already detected in synchronism with the speed of rotation. Under unfavorable operating conditions, this can result in considerable downtime for regulating

  pressure. This leads to very slowly applying the regulation.

  pressure but is a limiting condition not

  desired if we want to quickly eliminate the per-

turbine by regulation.

  Aim of the present invention: The aim of the present invention is to develop a method and a device for controlling an internal combustion engine corresponding to the type defined above and the

  pressure control circuit is minimized.

  To this end, the invention relates to a method of

  type defined above, characterized in that one seizes the

  their pressure at predetermined time intervals and

  during a fuel injection, no value is entered

their pressure.

  This problem is also resolved by a provision

  control device of the type defined above, characterized in that means which enter pressure values in

  the predetermined time intervals and during an injection

  fuel, no pressure value is entered.

  Advantages of the invention: The means of the invention make it possible to considerably reduce the dead time in the regulation circuit

pressure.

  According to other advantageous characteristics of the invention: * an input is also made in angular synchronism for the pressure values, * the input in angular synchronism with the pressure values is made directly before the start and / or the end of injection,

  * the pressure values obtained for the synchro-

  angular nism are used to control the injection, * we form a current average value using at least

two pressure values entered.

  Drawings: The present invention will be described below from

  in more detail using embodiments re-

  shown schematically in the drawings in which: - Figure 1 shows a block diagram of the device of the invention, - Figure 2 is a diagram representing the pressure as a function of time (t),

  - Figure 3 is a detailed view of the pressure detection

  sion, - Figure 4 shows a flow chart of the method of the invention, - Figure 5 shows another flow chart of the method of the invention.

  Description of the exemplary embodiments:

  Figure 1 shows the main elements of an embodiment of a fuel supply system

  an internal combustion engine with high pressure injection

  sion, for the understanding of the invention. The system shown is usually called a common rail system, which however is given only by way of example.

  The reference 100 designates a fuel tank

  rant. This tank is connected via a filter, an adjustable supply pump 110 and a second filter 115. The fuel leaving the second filter 115 passes through a line connected to a valve 120. The line of connection between the filter 115 and the valve 120 is connected to the tank 100 by means of a low pressure limiting valve 145. The valve 120 is connected to the rail 130 by

  a high pressure pump 125. The rail also called accumulator-

  fuel is connected by fuel lines to the various injectors 131. A pressure adjustment means in particular a

  pressure adjustment valve 135 connects the rail 130 to the

  servoir 110. The pressure regulating valve 135 is

  controlled using an electromagnetic coil 136.

  The pipes between the outlet of the high pump

  125 pressure and the inlet of the pressure regulating valve

  sion 135 correspond to the high pressure section. In this section, the fuel is at high pressure. The pressure prevailing in the high pressure zone is detected by a sensor 140. The pipes between the tank 100 and the high pressure pump 125 correspond to the low pressure zone Reference 150 designates a command. This control acts on the injectors 131 by the control signals A; it also controls the coil 136 of the pressure regulation valve 135. To do this, use is made of the output signal P of the pressure sensor 140 and various output signals of other sensors 160 such as for example those of a

speed sensor.

  The control 150 comprises a pressure calculation means 151 which receives the output signal from the pressure sensor 140. The pressure calculation means 151 supplies a quantity calculation means 152 and a combination point 154 with signals. The second input of the combination point 154 receives the output signal PS from a means generating a setpoint 153. The setpoint generator processes the output signal N of a speed sensor 160 as well as the signal the quantity calculation means 152. The latter acts on the injectors by control signals A; the pressure calculating means receives a signal QK which indicates that an injection is taking place. The output signal from the combination point 154 acts on a pressure regulator 155 which in turn controls the coil 136 of the pressure relief valve.

pressure regulation.

  The installation described above operates as follows: The fuel from the tank is transferred by the supply pump 10 through the filters 105, 115. In

  output of the feed pump 110, the fuel is at a pressure between 1 and about 3 bars. When the pres-

  In the low pressure zone of the fuel system reaches a predetermined pressure, the valve 120 opens and releases the inlet to the high pressure pump 125 with a determined pressure. This pressure depends on the construction of the valve 120. Usually, the valve 120 is designed

  to release communication with the high pressure pump 125 at a pressure of approximately 1 bar.

  If the pressure in the low pressure zone has

  if high levels are not allowed, the low pressure limiting valve 145 opens and frees communication

  between the outlet of the feed pump 110 and the tank 100. The valve 120 and the low pressure limiting valve 145 maintain the pressure of the low pressure zone at values of between approximately 1 and 3 bars.

  The high pressure pump 125 passes the fuel

  from the low pressure zone to the high pressure zone. The high pressure pump 125 establishes a very high pressure in the rail 130. Usually in systems fitted with

  internal combustion engines with positive ignition, the

  sions are between 30 and 100 bars; in the case of internal combustion engines with uncontrolled ignition, the pressures are between 1000 and 2000 bars. The injectors 131 make it possible to inject metered fuel under high pressure into the various cylinders of the engine

internal combustion.

  Sensor 140 detects pressure in the rail

  or throughout the high pressure area. The regulating valve

  pressure 135 controlled by a coil 136 allows the pressure in the high pressure area to be regulated. The valve

  pressure regulator 135 opens at different pressures

  annuities depending on the voltage applied to the coil 136 or

  of current flowing through this coil 136.

  To regulate the pressure P in the upper zone

  pressure, other pressure relief devices can also be used

  glage or actuation. It is a power supply pump 10 with adjustable flow rate or a high pressure pump

  125 ordered. In addition to the pressure regulating valve

  sion 135, we can also provide a pressure limiting valve which frees communication between the upper zone

  pressure and the low pressure zone for a given pressure.

  The pressure detection means 151 processes the signal supplied by the pressure sensor 140 and applies it to the

  quantity calculation means 152 as well as at the point of comparison

  reason 154 to regulate the pressure. The quantity calculation means 152 calculates the control signals A of the injectors

  131 depending on the pressure P and the amount of fuel

that you want to inject.

  The setpoint generator 153 calculates a setpoint PS of the fuel pressure value

  rant in the accumulator 130 from different operating parameters such as the speed N of the internal combustion engine and the quantity of fuel to be injected.

  This setpoint PS is compared with the point of combi-

  naison 154 to the actual value PI provided by the means of

  pressure sensing 151. Based on this comparison, the

  pressure regulator 155 calculates the control signal

  to the pressure control valve.

  Calculation of control signals as a function of

  the pressure P is done before each injection. This calculation

  thus hangs from the rotational speed with intervals of

  variable times. The interval between calculations depends strongly-

  speed of rotation. This computation of the com-

  pressure regulator valve in the

  pressure regulator 155 is done at a fixed rate. This ca

  dence is chosen so that the regulator can react without delay to variable PS setpoints and allows the new setpoint to be established as quickly as possible. According to the invention, the pressure is detected for the

  real projection, synchronously in time with a

  very small dence, preferably around 10 ms. The va-

  their pressure are entered at predetermined, in particular fixed, time intervals. In parallel, the pressure is used in angular synchronism or speed synchronism

  of rotation to calculate the control signal A. The diffi-

  cultured is that as shown in figure 2, the pressure P will

  laughs very loudly during the injection.

  Figure 2 shows the pressure P as a function of time (t). At times t1, t2, t3 each time begins an injection. This leads to a rapid drop in pressure, then a return to the initial value. The injection ends each time at times tl ', t2', t3 'The pressure oscillations during the injection cannot be compensated simply by the pressure regulation. When these oscillations are taken into account when entering the actual value, this means that the pressure regulator output signal is subjected to very strong

  annoying variations. For this, the invention provides that during

  during the injection, that is to say between the intervals tl and tl 'or t2 and t2' or t3 and t3 ', no pressure is entered

for pressure regulation.

  The instants of the synchronous pressure detection at which the pressure is detected for pressure regulation are indicated by circles in the

  graph of figure 2. The instants of pressure detection

  angularly synchronized for which we de-

  tect the pressure to calculate the control signals A for the injectors are marked with crosses. In the embodiment shown, for entering the pressure, the value is used directly before injection both for pressure regulation and for controlling the injectors A. FIG. 3 shows an embodiment of this process. The elements already described in Figure 1 have the same references. The elements 400, 410, 420 correspond to the main elements of the pressure detection means 151 providing the value PI. The output signal P from the pressure sensor 140 arrives by a first switching means 400 to an alternating switching means 420. The output signal from the alternating switching means 420 is applied as a value

  real PI at the combination point 154.

  The switching means 400 is controlled at a predetermined rate by a rate generator (clock) 410. At each rate, the switching means 400 closes and the signal applied to its input is transmitted to the

  exit. The switching means 420 is generally closed. This-

  la means that at predetermined time intervals by the cadence generator 410, the signal P of the sensor 140 is

  transmitted as actual value PI to the combination point 154.

  When the quantity control means 152

  provides a signal A indicating an injection, the means of

  mutation 420 goes into its second position. As a result, the output signal of the switching means 420 remains at its old value. The QK signal is between the instants

ti and tl 'or t2 and t2' or t3, t3 '.

  FIG. 4 shows an illustrated embodiment

  cited by a flow chart. In a first step 500, the time counter (t) is set to the value 0. In the next step

  510, the time counter (t) is increased by a specific value

  mined At. The interrogation 520 checks whether the time counter (t) is greater than a value (St). This value (St)

  determines the interval between entering the metric values

  safe. If the answer is negative, there is a new step

  510. If yes, the interrogation 530 verifies the pre-

  sence of a control signal A for the injectors. If not, step 540 detects the value P2 and uses it as

actual PI value.

  In this flowchart as well as in the ordino-

  following gram, by convention the letter N represents a

  negative answer to a question and the letter J an answer

positive.

  It is particularly advantageous to do each

  that once a current mean value for at least two pressure values detected synchronously in the

  time. This means that next to the current P2 value

  detected in step 540, the old value P1 detected in the previous program passage is also taken into account. The P value used for pressure regulation is calculated

  in step 550 by forming the average of the values P1 and P2.

  Then in step 560, the new value P2 is subscribed in place of the old value Pl. This is shown as

  example in Figure 4 by blocks surrounded by a dashed line

  overwhelmed. It is advantageous that the average value is obtained

  naked with more than two measurement values.

  To detect the pressure intended for the quantity calculation means, proceed as follows:

  In a first step 600, the value an-

  gular W to 0. In the following step 610, the value is increased

  their angular W of the increment (AW). Then the interrogation 620 checks whether the angle W is greater than a threshold SW. The threshold SW is chosen to correspond to the rotation of the crankshaft since the last calculation. If this is not the case, step 610 is repeated. If this is the case, the pressure value P is detected in step 630 and this value is transmitted to the quantity calculation means. The only SW is chosen35 so that this angularly synchronized entry of the pressure value is done directly before the start and / or before

  the end of the injection The threshold is predetermined preferably

  according to the operating conditions.

RE VE N D I C A T I ON S

  1) Method for controlling an internal combustion engine no-

  In particular, an engine fitted with a common rail system, according to which at least one pump supplies the fuel from a low pressure zone to a pressure accumulator, and according to which the pressure values characterizing the pressure of the fuel in the pressure accumulator using a pressure sensor and hence pressure values as well

  entered and a set value, a predetermined

  general control for a pressure regulating means, characterized in that the pressure values are entered at predetermined time intervals and during fuel injection, no

enter no pressure value.

  2) Method according to claim 1, characterized in that an input is also carried out in angular synchronism

for pressure values.

  3) Method according to claim 2, characterized in that the entry in angular synchronism of the pressure values is done directly before the start and / or the end of

injection.

  4) Method according to claim 2, characterized in that

  the pressure values obtained for the synchro-

  angular nism are used to control the injection.

   ) Method according to any one of the preceding claims.

  teeth, characterized in that a current mean value is formed using at least

two pressure values entered.

  6) Device for controlling an internal combustion engine, in particular for a combustion engine equipped with a common rail system according to which at least one pump supplies fuel from a low pressure zone to a pressure accumulator5 and comprising a pressure sensor recording the pressure values characterizing the pressure of the fuel in the pressure accumulator, a pressure regulator which, on the basis of the entered pressure values and a set value, provides a control signal for a means pressure re-regulation, characterized by means which enter pressure values in the predetermined time intervals and during a fuel injection no pressure value is entered.