DE19955617B4 - Method for controlling an internal combustion engine with two high-pressure pumps - Google Patents

Abstract

Method for controlling a first (2) and second high-pressure pump (3) of an internal combustion engine (1), in which fuel under high pressure from the two high-pressure pumps (2, 3) into a first (7) and second high-pressure accumulator (8) is conveyed and the pressure (pCR) of the high-pressure accumulator (7, 8) is detected, characterized in that the operating state of the internal combustion engine (1) is read in and a check is carried out to determine whether the operating state permits a test method, whereby in Depending on the operating state, a first test mode (MOD1) and / or a second test mode (MOD2) is set, in each test mode correction variables (K (i), i = 1, 2, 3 ...) of the two high-pressure pumps (2, 3 ) are determined and in normal operation a constant delivery is set by adapting the control of the first (2) and second high pressure pump (3) depending on the correction variables (K (i), i = 1, 2, 3 ...) ,

Description

The invention relates to a method for controlling a first and second high-pressure pump of an internal combustion engine with high-pressure accumulators according to the preamble of claim 1.

From the DE 42 33 273 A1 a common rail system is known. In this case, a first high-pressure pump delivers fuel via a first line to a first high-pressure accumulator and a second high-pressure pump conveys fuel via a second line to a second high-pressure accumulator. The fuel supply to the two high-pressure pumps takes place via a common line, which is fed by a supply pump. General information on the control of high-pressure pumps can be found here. In practice, uneven delivery of the high pressure pumps can occur in a common rail system with two high pressure pumps. This causes different pressure levels in the two high-pressure accumulators.

From the DE 43 35 171 C1 a common rail system with two high-pressure pumps is also known. The two high-pressure pumps are controlled with identical signals. The problem of unequal delivery can also occur with this common rail system, ie the delivered volumes of the high-pressure pumps are of different sizes. This inequality promotion is caused by tolerances in the signal chain for controlling the high pressure pumps and hydraulic tolerances in the high pressure pumps. This unequal promotion causes different pressure levels in the high pressure accumulators. As a solution to this problem, the DE 43 35 171 C1 a compensation line between the high pressure accumulators. However, this solution does not do justice to the problem of avoiding inequalities.

From the DE 196 33 066 A1 a method for controlling an internal combustion engine with a PLD system (pump-line-nozzle) is known. To minimize the effect of component differences, the method provides that the cylinder-selective mean pressures are determined from the speed of the internal combustion engine. The medium pressures are then assimilated by changing the start of injection and the amount of fuel. The method shown requires a separate, independent fuel supply for each cylinder. It is therefore not transferable to a common rail system with two high pressure pumps.

The invention is based on the object an identical one for a common rail system with two high-pressure pumps output of the two high pressure pumps.

The object is achieved according to the invention solved, that the operating state of the internal combustion engine is read in, and checked whether the operating status permits a test procedure, whereby dependent on a first and / or second test mode of the operating state becomes. In both test modes become correction quantities for the two High pressure pumps determined. about this correction quantities will equal funding in normal operation adjusted by adapting the control of the two high pressure pumps becomes. Under operating condition of the internal combustion engine are in the sense to understand the invention idle, partial and full load.

In an embodiment of this, it is proposed that both in the first test mode as well as the second test mode the two high-pressure pumps are subjected to a test signal. In the first test mode are the test signals identical in amplitude and in opposite phase. Are in the second test mode the test signals executed in the form that the first high pressure pump for maximum delivery while maintaining the second high-pressure pump is set to minimum delivery or vice versa.

The solution according to the invention has the advantage that the direct promotion achieved an identical lifespan for the two high-pressure pumps becomes. As is known, the service life of such a high pressure pump is a function of the funded Volume. For in practice this means that when the engine is serviced it is not always necessary to replace both pumps. In Consequence leads this to longer, customer-friendly maintenance intervals because the life of the High pressure pumps fully used can be.

One is preferred in the drawings embodiment shown. Show it:

1 System diagram of a common rail system

2 Characteristic curves of the high pressure pumps

3A . 3B . 3C Time diagram, first test mode

4A . 4B . 4C Time diagram, second test mode

5 Program flow chart, first test mode

6 Program flow chart, second test mode

In 1 a system diagram of an internal combustion engine with a storage injection system (common rail) is shown in simplified form. This shows: the internal combustion engine 1 , an electronic engine control unit 11 , two high pressure pumps 2 and 3 , two high-pressure accumulators 7 and 8th and injectors 9 , In a storage injection system, a low-pressure pump or two low-pressure pumps deliver the fuel to the high-pressure pumps from a tank 2 and 3 , The tank and the low pressure pumps are in 1 not shown. The pressure level provided by the low pressure pumps is in 1 referred to as an example with p. In the 1 High-pressure pumps shown are suction-throttled pumps, consisting of a variable throttling point and the actual pump. The throttling point and the pump are combined into one structural unit.

The first high pressure pump 2 supports via a line 5 the fuel under high pressure in the first high-pressure accumulator 7 , At the same time, the second high-pressure pump delivers 3 via a line 6 the fuel into the second high pressure accumulator 8th , Between the two lines 5 and 6 is a compensation line 4 arranged so that there are different pressure levels in the lines 5 and 6 compensate. The pressure level of a high-pressure accumulator is controlled by a pressure sensor 10 , Signal pCR, detected. Lines with injectors connected to each branch from each high-pressure accumulator 9 from. About the injectors 9 the fuel from the high-pressure accumulators into the cylinders of the internal combustion engine 1 injected.

The electronic engine control unit 11 controls and regulates the state of the internal combustion engine 1 , This contains the usual components of a microcomputer system, for example a microprocessor, I / O modules, buffers and memory modules (EEPROM, RAM). Programs and operating data are stored in the memory modules. The data are usually applied in characteristic maps and characteristic curves. In 1 are the input variables of the electronic engine control unit 11 shown: the pressure pCR and with reference symbol E the others for the operation of the internal combustion engine 1 relevant input variables, e.g. engine speed and cooler water temperature. The output variables of the electronic engine control unit 11 are: the control signals for the injectors 9 , corresponding to the start of injection SB and the injection duration SD, and the control signals U1 and U2 for the first 2 and second high pressure pump 3 , The further output variables are summarized with reference symbol A.

In 2 the transmission characteristics of the first and second high-pressure pumps are shown by way of example. The control signals U1 and U2 are plotted on the abscissa. The volume flow Q1 and Q2 are plotted on the ordinate. The volume flow Q1 corresponds to that of the first high-pressure pump 2 conveyed volume flow. The volume flow Q2 corresponds to that of the second high-pressure pump 3 conveyed volume flow. The transfer functions of the first and second high-pressure pumps are designated by the reference symbols KL1 and KL2. An exemplary operating point is shown with the reference symbol B (i). For this operating point B (i), a volume flow Q1 (i) and Q2 (i) result due to the different characteristic curves. This unequal promotion causes, among other things, different wear of the high-pressure pumps.

The 3 consists of the 3A to 3C , according to the first test mode. The following are shown over time: the test signals for the two high-pressure pumps ( 3A ), the volume flow promoted ( 3B ) and the pressure level pCR ( 3C ). The 3A and 3B each contain three curves: the solid line corresponds to that of the first high-pressure pump 2 belonging course; the dash-dotted line corresponds to that of the second high-pressure pump 3 belonging course; the dotted line corresponds to the resulting mean. The volume flow Q shown is inverse to the control signal U. This means that, for example at a voltage value of 0 volts, there is a maximum delivery rate. Of course, implementation with positive logic is also possible without changing the essence of the invention.

The procedure in the first test mode is as follows: The first high pressure pump 2 is controlled with a test signal U1 (PR). The following relationship applies to this signal: U1 (PR) = B (i) + f1 (t) f1 (t) = U1 (AMP) sin ωt here mean:

U1 (PR) test signal, first high pressure pump Bi) Initial value, operating point U1 (AMP) amplitude ω angular frequency t time

The second high pressure pump 3 is controlled with a test signal U2 (PR). The following relationship applies to this signal: U2 (PR) = B (i) - f2 (t) f2 (t) = U2 (AMP) sin ωt here mean:

U2 (PR) test signal, second high pressure pump Bi) Initial value, operating point U2 (AMP) amplitude ω angular frequency t time

How out 3A can be seen, the two test signals U1 (PR) and U2 (PR) are identical in amplitude and frequency. Due to the different sign, the two test signals add up to the mean value MW, corresponding to the level of the operating point B (i). The two test signals cause a volume flow Q1 or Q2 according to the two high-pressure pumps 3B , In this example, the characteristics of the 2 on the basis, ie the delivery rate of the first high-pressure pump 2 is lower than that of the second high pressure pump at point B (i) 3 , This results in a resulting pressure curve, corresponding to the mean value Q (MW). This causes the in 3C pressure curve shown pCR. The pressure curve pCR has the same frequency as the mean value of the volume flow Q (MW), but is offset by an angle Phi with respect to this. The reason for this phase shift is that the high-pressure accumulator acts as an integrator, ie the phase shift is 90 degrees. This corresponds to the distance between point A ( 3B ) to point B ( 3C ). The in 3C The sinusoidal pressure curve shown moves between the two extreme values of points B and C. This distance results from the amplification error of the entire signal chain and is a measure of the correction of the control signals U1 and U2 of the two high-pressure pumps. The distance corresponds to the correction variable K (i).

The two signal chains are identical when the correction variable K (i) is zero or lies within a tolerance band TB. The control signals U1 and U2 for the two high-pressure pumps are then via the correction variable K (i) 2 and 3 adapted. Of course, it is also possible that a control signal is selected as a reference, for example U1, and only the second signal, here U2, is adapted. Different correction variables are successively determined by changing the operating point B (i), so that equal delivery can be set in the entire operating range of the two high-pressure pumps.

The 4 consists of the 4A to 4C , according to the second test mode. The following are shown over time: the test signals for the two high-pressure pumps ( 4A ), the volume flow of the two high pressure pumps ( 4B ) and the resulting pressure curve pCR ( 4C ). In the 4A and 4B are as a solid line to the first high-pressure pump 2 belonging course or as a dash-dotted line of the second high-pressure pump 3 belonging course drawn.

The procedure is as follows: During the period t1 / t2, the test signal U1 (PR) is set to a minimum value, here: zero. At the same time, the test signal U2 (PR) of the second high-pressure pump 3 set to a maximum value. In response to the two test signals, the in 4B The course of the volume flows shown, ie the volume flow Q1 (MAX) corresponds to the maximum delivery capacity of the first high-pressure pump 2 or the volume flow Q2 (MIN) corresponds to a minimum delivery rate of the second high-pressure pump 3 , Due to the maximum delivery rate Q1 (MAX) of the first high pressure pump 2 there is a pressure curve pCR according to the 4C , In the period t1 / t2 this increases according to the line AB. The curve results from the integrator effect of the high pressure accumulator. At time t2, the two test signals U1 (PR) and U2 (PR) are controlled to the level of the operating point B (i). For the pressure level in the high-pressure accumulators, there is a pressure curve pCR along the line with points B and C. The pressure difference between the two points B and C is in 4C as the first printer elevation dp1 (k) is shown. At a time t3, the test signal U1 (PR) of the first high-pressure pump 2 set to a maximum value corresponding to a minimum delivery rate Q1 (MIN). This value is maintained during the period t3 / t4. At the same time, the test signal U2 (PR) of the second high-pressure pump 3 set to a minimum value corresponding to a maximum delivery rate Q2 (MAX). In this example, the two characteristics were also according to the 2 based on. This means that the maximum delivery rate of the second high pressure pump 3 is lower than the maximum delivery rate of the first high-pressure pump 2 , For the period t3 / t4 there is a pressure curve pCR corresponding to the line with the points D and E. This pressure difference, corresponding to the distance between the two points D and E, is in the 4C referred to as the second pressure increase dp2 (k). At time t4, the two test signals are controlled again to the original value of the operating point B (i). Due to the switch-off edge of the second test signal, there is a pressure curve corresponding to the line EF.

According to the invention it is now provided that the signal pattern of the two test signals during the period t1 to t4 for a predeterminable number is repeated. The resulting ones first and second pressure increases dp1 (k) and dp2 (k) are each counted in a sum memory. at The presence of a predeterminable number of pressure increase values is then carried out the final status of the first sum memory SUM1 and the final status of the a second mean value F1 or a second mean value F2 calculated. The two mean values F1 and F2 can be arithmetically averaged be calculated. These mean values F1 and F2 determine significantly the correction quantities K (i). The correction sizes are a measure of the offset the transfer function.

In 5 a program flow chart for the first test mode is shown. This begins in step S1 by reading in the operating state of the internal combustion engine. In step S2, the first test mode MOD1 or second test mode MOD2 or the first and the second test mode are then set depending on the operating state. In addition, step S2 checks whether the operating state permits a test procedure. Operating state in the sense of the invention is to be understood as idling, partial load and full load of the internal combustion engine. The invention can be embodied as follows: only the second test mode MOD2 is run through when idling. The first test mode MOD1 and the second test mode MOD2 are run through in a first area of the partial load. In a second area of the partial load, only the first test mode MOD1 is run. There is no test at full load.

The program part with steps S4 to S13 denotes the first test mode MOD1. The reference symbol B denotes the jump to the second test mode. The second test mode MOD2 is used in conjunction with the 6 explained. If it is determined in step S2 that full load is present, for example, no test method is activated and a waiting loop is run through in step S3. If the first test mode is set in step S2, a run variable i is set to the value 1 in step S4. In step S5, the operating point B (i) is set. Then in step S6 the first test signal U1 (PR) for the first high-pressure pump 2 set. The first test signal U1 (PR) corresponds to in 3 the sinusoidal curve with the solid line. In step S7, the second test signal U2 (PR) is set. This second test signal U2 (PR) is identical in amplitude and in phase opposition to the first test signal U1 (PR). In step S8, the correction variable K (i) is determined from the pressure curve pCR. Then, in step S9, the correction variable K (i) is compared with a limit value GW. If the correction variable K (i) is greater than the limit value GW, a diagnostic entry is made in step S10. This program path is always run through when a high-pressure pump is no longer running in a stable range.

If the check in step S9 shows that the correction variable K (i) is smaller than the limit value GW, then in step S11 it is checked whether the value of the correction variable K (i) lies within a tolerance band TB. If this is the case, it is not necessary to correct the two control signals U1 and U2, step S13. If the correction variable K (i) lies outside the tolerance band TB, as is shown, for example, in 3C is shown, the two control signals U1 and U2 are adapted in step S12 as a function of the correction variable K (i). The program flow then branches to point A with the reading in of the operating state again.

In 6 the program sequence for the second test mode MOD2 is shown. This begins in step S1 with the setting of the boundary parameters. In step S2, the test signal U1 (PR) of the first high-pressure pump 2 to a minimum value MIN or the test signal U2 (PR) for the second high-pressure pump 3 set to a maximum value MAX. The first pressure increase dp1 (k) is then measured in step S3. In step S4, this first pressure increase is added to a first sum memory SUM1. In step S5, the first test signal U1 (PR) is set to a maximum value MAX, corresponding to the minimum delivery rate Q1 (MIN), and the second test signal U2 (PR) to a minimum value MIN, corresponding to the maximum delivery rate Q2 (MAX). In step S6, the second pressure increase dp2 (k) which arises is measured and then added in a second summation memory SUM2, step S7. In step S8, it is checked whether the running variable k has reached its final value N. If this is not the case, the run variable k is increased by one in step S9 and the loop is repeated with steps S2 to S7.

If the check shows that the loop has been run through N times, the program branches to step S10. In this step, depending on the value of the run variable i, either the program path run through with steps S11 to S13 or with steps S14 to S16 or the program sequence is ended. In the first run, ie the run variable i is 1, an average value F1 is calculated in step S11 from the end status of the first sum memory SUM1. In step S12, the correction variable K (i) is calculated from this first mean value F1. Then the control signal U1 of the first high-pressure pump is adapted in step S13 2 , In step S17, the characteristic variable K (i) is compared with the limit value GW. If the test result is positive, ie the first high-pressure pump is already defective, a diagnostic entry is made in step S18. The program flow chart is then ended. If the check in step S17 shows that the characteristic variable K (i) is smaller than the limit value GW, the run variable i is increased by 1 in step S19. The program flow then branches to point C, ie to step S10.

In the second run, ie the run variable i is now 2, a second mean F2 is calculated, step S14. In step S15, the characteristic variable K (i) is calculated from this second mean value F2. The control signal U2 of the second high-pressure pump is then adapted in step S16 3 , Then, as described above, the program part takes place with steps S17 to S19. In the third program run, ie the run variable is now 3, the jump to the end of the program takes place in step S10.

1

Internal combustion engine

2

first High pressure pump

3

second High pressure pump

4

compensation line

5

management

6

management

7

first High-pressure storage

8th

second High-pressure storage

9

injector

10

pressure sensor

11

electronic Engine control unit

Claims (13)

Method for controlling a first ( 2 ) and second high pressure pump ( 3 ) an internal combustion engine ( 1 ) where the fuel is under high pressure from the two high pressure pumps ( 2 . 3 ) in a first ( 7 ) and second high-pressure accumulator ( 8th ) is promoted and the pressure (pCR) of the high pressure accumulator ( 7 . 8th ) is detected, characterized in that the operating state of the internal combustion engine ( 1 ) is read in, and a check is made as to whether the operating state permits a test method, a first test mode (MOD1) and / or a second test mode (MOD2) being set as a function of the operating state, correction variables (K (i), i = 1 in each test mode , 2, 3 ...) of the two high pressure pumps ( 2 . 3 ) are determined and equal funding is set in normal operation by controlling the first ( 2 ) and second high pressure pump ( 3 ) is adapted depending on the correction variables (K (i), i = 1, 2, 3 ...). Method according to claim 1, characterized in that both in the first (MOD1) and the second test mode (MOD2) the two high-pressure pumps ( 2 . 3 ) each with a test signal (U1 (PR), U2 (PR)). A method according to claim 2, characterized in that in the first test mode (MOD1) the test signals (U1 (PR), U2 (PR)) depending an operating point (B (i), i = 1, 2, 3 ...) can be changed. A method according to claim 3, characterized in that the test signal (U1 (PR)) for the first high-pressure pump ( 2 ) and the test signal (U2 (PR)) for the second high pressure pump ( 3 ) are amplitude identical and out of phase. A method according to claim 4, characterized in that the correction quantities (K (i)) can be determined from a modulation of the detected pressure (pCR) (K (i) = f (PCR)). A method according to claim 5, characterized in that no adaptation of the control of the first ( 2 ) and second high pressure pump ( 3 ) occurs when the pressure values (pCR) are within a tolerance band (TB). A method according to claim 2, characterized in that in the second test mode (MOD2) in a first test step (U1 (PR)) of the first high-pressure pump ( 2 ) is set to a minimum value, corresponding to maximum delivery capacity (Q1 (MAX)), and at the same time the test signal (U2 (PR)) of the second high-pressure pump ( 3 ) is set to a maximum value corresponding to the minimum delivery rate (Q2 (MIN)). Method according to Claim 7, characterized in that, in a second step, the test signal (U1 (PR)) of the first high-pressure pump ( 2 ) is set to a maximum value corresponding to the minimum delivery rate (Q1 (MIN)) and at the same time the test signal (U2 (PR)) of the second high-pressure pump ( 3 ) is set to a minimum value corresponding to the maximum delivery rate (Q2 (MAX}). Method according to claims 7 and 8, characterized in that that in the first step a first pressure increase (dp1 (k), k = 1, 2, 3 ...) and in the second step a second pressure increase (dp2 (k), k = 1, 2, 3 ...) is detected becomes. A method according to claim 9, characterized in that both the first (dp1 (k)) and the second pressure increase (dp2 (k)) be summed (SUM1, SUM2) and if there is a specifiable one Number (N) of pressure increase values (dp1 (k), dp2 (k)) a first (F1) mean (F1 = SUM1 / N) and second Average value (F2 = SUM2 / N) can be calculated. A method according to claim 10, characterized in that the correction quantities (K (i)) can be determined from the two mean values (F1, F2). A method according to claim 1, characterized in that the correction quantities (K (i)) be compared with a limit value (GW) and a diagnostic entry occurs when a correction quantity (K (i)) larger than the limit (GW) is (K (i)> GW). A method according to claim 12, characterized in that the correction quantities (K (i)) additionally be filtered (FIL-K (i)) and a diagnosis entry is made if a filtered correction variable (FIL-K (i)) larger than the limit (GW) is (FIL-K (i)> GW).