EP1091120B1 - Method for determining and controlling a pump parameter - Google Patents

Description

The invention relates to a method for operating a Fuel injection system and a pump according to the preamble of claims 1 and 4.

In common-rail injection systems, fuel is from a Pre-feed pump taken from a tank and a high-pressure pump fed. The high pressure pump supplies a fuel storage, the so-called common rail, with fuel. At fuel injectors are connected to the fuel reservoir, which are controlled by a controller and accordingly the controller inject fuel into an internal combustion engine. In a volume flow controlled high pressure pump is the Amount of fuel that enters the high-pressure accumulator from the High-pressure pump is pumped through a flow control valve set in the intake of the high pressure pump. Unnecessary Fuel is from the fuel tank via a Pressure control valve returned to the tank. Heated while relaxing the fuel, so that the temperature of the Fuel in the fuel tank increases. In addition, for the Compression of the fuel by the high-pressure pump relative much energy is needed, so that superfluous fuel, the is discharged via the pressure control valve, a power loss represents.

For low power loss and low heating the fuel in the fuel tank is a precise control and an exact determination of the operating parameters of the High pressure pump necessary.

From WO 97/32128 and US 4,964,985 are methods for Determining and controlling a pump depending on the time Course of the angular position of the pressure extremum in the delivery volume the pump known.

The object of the invention is a method for operating a Fuel injection system with a pump to provide the simplified control and monitoring of the Fuel injection system allows.

This object is achieved by the features of claim 1 and solved by the features of claim 4.

An advantage of the invention lies in the fact that the location of Druckextra during a compression process of the pump in the Volume is determined, in which the pump pumps medium and that based on the temporal position and / or angular position of Pressure extrema determines an operating parameter of the pump and / or the pump is controlled.

Further advantageous embodiments of the invention are in the specified dependent claims.

Fig. 1 einen Aufbau einer Einspritzanlage,

Fig. 2 eine Radialkolbenpumpe,

Fig. 3A und Fi. 3 Meßdiagramme bei Voll- bzw. Teilförderung,

Fig. 4 ein Diagramm, das die Position eines Druckminima bezogen auf einen Pumpenwinkel und einen Fördergrad einer Dreikolben-Hochdruckpumpe zeigt,

Fig. 5 ein Verfahren zum Steuern einer Pumpe,

Fig. 6 ein Verfahren zum Steuern eines Volumenstromregelventils, und

Fig. 7 ein Verfahren zum Steuern des Volumenstromes zur Pumpe.

The invention will be explained in more detail below with reference to the figures; it shows

1 shows a structure of an injection system,

2 a radial piston pump,

Fig. 3A and Fi. 3 measuring diagrams for full or partial conveying,

4 shows a diagram which shows the position of a pressure minimum relative to a pump angle and a delivery rate of a three-piston high-pressure pump,

5 shows a method for controlling a pump,

6 shows a method for controlling a volume flow control valve, and

Fig. 7 shows a method for controlling the flow rate to the pump.

Fig. 1 shows a fuel tank 1, from which a prefeed pump 2 takes fuel and a flow control valve 3 and a supply line 19 of a high-pressure pump 4 feeds. The high-pressure pump 4 compresses the supplied fuel and gives the compressed fuel via a drain 20 to a fuel tank 5 on. To the fuel storage 5 injection valves 6 are connected, the controlled by a control unit 8 via a third control line 16 become. According to the control by the control unit 8, the injectors 6 deliver fuel from the fuel accumulator 5 in the engine 17 from.

To the fuel tank 5 and to the high-pressure pump 4 is a pressure control valve 7 connected via an output line is in communication with the fuel tank 1. The Pressure control valve 7 is connected via a second control line 12th with the control unit 8 in connection. Furthermore, a pressure sensor 14 arranged on the fuel reservoir 5, which has a second data line 13 to the controller 8 in conjunction stands. The internal combustion engine 17 are associated with sensors 15, which is connected via a fourth data line 18 to the control unit 8 are. The control unit 8 also has a first one Data line 10 with a data memory 9 in conjunction. Furthermore, the control unit 8 via a first control line 11 connected to the flow control valve 3.

The prefeed pump 2 and the high pressure pump 4 are mechanical driven by the internal combustion engine 17. The speed the prefeed pump 2 and the speed of the high pressure pump. 4 are proportional to the speed of the engine 17. Die High-pressure pump 4 is for example a radial piston pump with three pistons 22, as shown in Fig. 2.

Fig. 2 shows schematically the piston assembly of a radial piston pump with three pistons. Each piston 22 is above a first one Check valve 23 in the inlet and a second check valve 25 in the process with the supply line 19 or with the Derivative 20 connected. The pistons 22 of the radial piston pump are star-shaped around a rotary shaft 21 of the high pressure pump. 4 arranged, driven by the internal combustion engine 17 becomes. The rotary shaft 21 is surrounded by an eccentric ring 26, the eccentric rotational movement of the rotary shaft 21 in a radial lifting movement of the piston 22 is implemented.

The piston 22 is 360 ° during one complete revolution Rotary shaft 21 from its bottom dead center to top dead center moved and then from top dead center back to moved bottom dead center.

During a suction, the piston 22 from the top Dead center moves to bottom dead center and over a first Check valve 23 fuel from the supply line 19 in the Cylinder chamber 24 sucked. The piston 22 is forced, so that it is independent of the amount of fuel that exceeds the first check valve 23 is sucked, always from the bottom Dead center to top dead center and then to the bottom Dead center during one revolution of the rotary shaft 21 moves. The first check valve 23 is biased by a spring 27. The spring 27 ensures that a negative pressure always in the cylinder chamber 24 and not in the supply line 19 is formed. For example, negative pressure can occur when the volume flow control valve 3 less fuel supplied to the piston 22 is, as due to the size of the cylinder chamber 24 at a suction between the top dead center and the bottom Dead center could be sucked by the piston 22.

The degree of filling of the cylinder chamber 24 after a suction process, in which the piston 22 is at the bottom dead center is in the illustrated embodiment by the opening cross-section of the flow control valve 3 is set.

In a compression process, the piston 22 from the lower Dead center shifted to top dead center. It is the Fuel, which is located in a cylinder chamber 24, from Piston 22 via the second check valve 25 for discharge 20 and pumped into the fuel tank 5.

The degree of filling of the cylinder chamber 24 defines that of the piston 22nd during a compression process funded amount of fuel firmly. The piston 22 pushes in a compression process each amount of fuel in the derivative 20, during of the suction process was sucked into the cylinder chamber 24. In each compression operation of the three pistons 22 of the High pressure pump 4 is activated by pushing fuel in the fuel reservoir 5, a pressure wave in the fuel tank 5 generated.

The pressure waves generated by the three pistons 22 are due the phase shift of the movements of the three pistons 22 at the same flow rate of the three pistons by 120 ° added.

The timing and thus the angular position to which the pressure wave a piston 22 is generated in the fuel reservoir 5, depends on the degree of filling of the cylinder chamber 24. Fig. 3A and Fig. 3B show the delivery volume flow V of the piston 22 in dependence from the rotational angle α of the rotary shaft 21 for different Filling levels. The piston 22 moves from the bottom Dead center UT to top dead center OT. Furthermore, in Fig. 3A and FIG. 3B that measured by the control unit 8 via the pressure sensor 14 Pressure signal p for the piston 22 shown. in principle holds that, if more fuel from the fuel tank 5 drains as from the high pressure pump 4 in the Fuel storage is promoted, the pressure in the fuel tank falls, because the mass balance is negative. in the In contrast, the pressure in the fuel accumulator 5 increases a positive mass balance, i. if more fuel in the fuel storage is conveyed as it drains off, at. In FIGS. 3A and 3B, the delivery volume flow is in each case V of the piston 22 shown in dashed lines, in which the middle Inflow into the fuel tank 5 whose average outflow equivalent. Compared to the real flow then with N the areas of a negative mass balance and thus a pressure drop in the fuel tank or with the P Areas of a positive pressure balance and thus an increase in pressure characterized in fuel storage 5.

In Fig. 3A, the flow rate of the piston 22 at a degree of filling F of the cylinder chamber 24 of 100%, that is the volume flow control valve 3 from the control unit 8 so far opened is that during the suction of the piston 22, the Cylinder chamber 24 is completely filled with fuel. As shown in Fig. 3A, the delivery volume flow V of the piston increases 22 from bottom dead center UT to first, then to to drop back to top dead center OT. Because of this History of the flow rate is the mass balance in Fuel storage 5 negative first, then positive and to End negative again. These fluctuations in the mass balance lead over the pump movement of the piston 22 from the bottom Dead center UT to top dead center OT to an approximately sinusoidal Course of the pressure signal p in the fuel reservoir 5, with a pressure minimum and a maximum pressure at the transition from negative to positive or from positive to positive negative mass balance.

The measurement diagram shown in Fig. 3B corresponds to a Filling degree F of the cylinder chamber 24 of 25%. This means that the volume flow control valve 3 from the control unit 8 so far opened is that during the suction of the piston 22, the Cylinder chamber 24 was only 25% filled with fuel. As the course of the delivery volume flow V of the piston 22nd shows that the points of a balanced mass balance are Transition from the negative mass balance N to the positive mass balance P and from the positive mass balance P back to negative mass balance N via the pumping movement of the piston 22 from bottom dead center UT to top dead center OT in the direction moved to top dead center. This results then how the course of the pressure signal p in the fuel tank 5 also shows a shift in the pressure extrema Direction to top dead center OT. From the shift of Printing extreme can thus be on the degree of filling of the cylinder chamber Close 24 in the high pressure pump 4.

With multi-piston pumps, there is a superimposition of the flow rates the individual pistons, but the in Fig. 3A and FIG. 3B show variations in mass balance and FIG thus remain in the pressure of the fuel tank 5. Even with multi-piston pumps shifts the position of Pressure extremes with different degree of filling of the cylinder chambers. In Fig. 4, the shift of the pressure maximum for simulates a three-piston pump, as shown in Fig. 3 is. The graph clearly shows that the situation the maximum pressure with decreasing flow rate and thus decreasing Filling level of the cylinder chambers towards larger pump angles and thus in the direction of the top dead center OT shifts.

Accordingly, the position of the pressure minimum shifts in Direction to top dead center OT.

FIG. 5 shows a method for operating a pump Figures 1 and 2 described. At program point 40 starts the engine 17 by a starter and turns it the prefeed pump 2 and the high-pressure pump 4 with predetermined Initial speeds. In addition, the control unit 8 opens the Volume flow control valve 3 to a cross section for the Boot process is stored in the data memory 9. In general becomes the opening cross section of the flow control valve. 3 selected as large as possible when starting the internal combustion engine 17, so that the high pressure pump 4 as fast as possible for the operation of the internal combustion engine 17 required fuel pressure builds up in the fuel tank 5. After the boot process are the feed pump 2 and the high pressure pump. 4 driven by the internal combustion engine 17.

Subsequently determined at program point 41, the controller 8 the angular position of the pressure peak with respect to the rotational position the rotary shaft 21. The lower and upper dead center UT, OT of the piston 22 are predetermined angular values of the rotary shaft 21 assigned. From the angular position of the pressure peak Program point 42 determines the control unit 8, the angular difference to the top dead center of the piston 22 from which the pressure peak was generated. The angular position of the pressure peak can So also directly from the evaluation of an amplitude and a Phase response of the pressure curve can be obtained. At program point 43 calculates the control unit 8 from the angular position the pressure peak the volume of fuel delivered by the piston 22. For this purpose, a table is stored in the data memory 9, in the for the piston 22 of the high pressure pump 4 values for the delivered fuel volume as a function of the angular position the pressure peak are stored.

These data become experimental in corresponding test series determined. Through appropriate attempts becomes a dependency between the angular position at which the pressure peak occurs in the fuel tank 5, and the degree of filling of Cylinder chamber 24 determined experimentally and in the data memory 9 filed. In addition, the delivery volume of a piston 22 as a function of the angular position of the pressure accumulator 5 generated pressure peak measured experimentally and as Function of the angular position of the pressure peak, d. H. the maximum pressure or the pressure minimum stored in the data memory 9.

In a further embodiment, the delivery volume of Pump 4 per revolution of the rotary shaft 21 as a function of the angular positions of the pressure peaks generated in the pressure accumulator 5 measured during one revolution of the rotary shaft 21 and as a function of the angular positions of the pressure peak in the data memory 9 filed. These are the pressure peaks of the three Piston 22 of the pump 4 evaluated, during a revolution the rotary shaft 21 are generated. This will be after a Calculation method averages the angular positions of the pressure peaks, which generates during one revolution of the rotary shaft 21 become. Based on the average angular position is a mean Delivery rate from the table read from the data memory 9, multiplied by the number three of the pistons is and thus the flow rate of the high-pressure pump 4 per revolution the rotation shaft 21 is calculated.

In another calculation method, for each piston 22 measured the angular position of the pressure wave and based on the calculated three angular positions respectively the flow rate of the pistons, the during one revolution of the rotary shaft 21 fuel promote. From the sum of the three flow rates is the Flow rate of the high pressure pump 4 calculated for one revolution.

When determining the table for determining the volume of funding depending on the angular position of the pressure peak is from the control unit 8, the flow control valve. 3 opened according to predetermined values in such a way that specified Delivery volume can be generated. Depending on the Flow volumes are the angle differences that the pressure peaks to the top dead center OT, from the control unit 8 measured. According to the experiments, a table in the data memory 9 stored, which funded by the piston 22 Fuel volume as a function of the angular difference of the Pressure peak to top dead center OT sets.

The determined by the controller value for the by the Piston 22 and the pump 4 funded fuel volume is stored in the data memory 9. Subsequently, after program point 41 branched back.

A further embodiment of the method according to FIG. 5 is based on the fact that the fuel quantity K conveyed by the high-pressure pump 4 is calculated in real time with the aid of an analytically or empirically determined formula: K = n * V * F or K = n * V * f (W), where K is the quantity of fuel delivered per unit time,
with n the rotational speed of the rotary shaft 21 per unit time,
with V the stroke volume of the cylinder chamber,
with F the delivery rate of the high-pressure pump 4 and
f denotes a conveying function which, depending on the angular position W of the pressure peak, indicates the delivery rate of the pump.

In Fig. 6 is a method for detecting a defect in the injection system shown. At program point 50 reads the control unit 8, the angular position of the pressure extrema from the Data storage 9 off, previously according to the procedure were determined according to FIG. 5. From the angular position becomes then in program item 51 corresponding to the data memory in the 9th table stored the funded by the pump 4 amount of fuel certainly.

Subsequently, at program point 52 from the control unit 8, the via the fuel injection valves 6 delivered amount of fuel determined. At program point 52 is that of the high pressure pump 4 amount of fuel delivered over a certain period of time determined and over the same period of the injection valves 6 delivered fuel quantity determined. This is done from the fuel pressure during injection operations prevailed in the fuel storage 5 and the opening times the injection valves 6, the injection valves of the sixth amount of fuel delivered during the specified period calculated.

At program point 53, the controller compares the over the Period from the high pressure pump 4 to the fuel tank. 5 delivered amount of fuel with the via the injectors 6 fuel delivered over the same period and checks whether the pressure in the fuel tank 5 accordingly the difference has increased or decreased. Is that true? Change of the fuel pressure in the fuel storage 5 not with the guided over the high pressure pump 4 and over Injectors 6 discharged fuel amount, so if a defect such as increased leakage in the injection system recognized.

Fig. 7 shows a method for controlling the flow control valve 3 depending on the angular position of the pressure peaks, generated by the piston 22 in the fuel tank 5 become. At program point 60, the controller determines 8 shows the angular position of the pressure extremes of the piston 22. From the Table in the data memory 9, the controller 8 calculates the according to the high-pressure pump 4 in the fuel tank 5 amount of fuel delivered. The amount of fuel delivered compares the controller 8 at program point 61 with a predetermined delivery rate by a control program.

If the delivered quantity differs from the nominal delivery quantity, then changes the controller 8 at program point 62 accordingly the opening cross-section of the volume flow control valve 3, so that the high-pressure pump and thus supplied by the High-pressure pump 4 delivered amount of fuel to the desired delivery is adapted. In this way, the flow control valve 3 depending on the angular position of Pressure peak controlled.

An embodiment of the method according to FIG. 7 is based on that the flow control valve based on one of a Control program predetermined target angular position for the pressure peak is controlled. The control program is dependent on it of operating parameters of the internal combustion engine, a desired angular position for the pressure peak. The control unit 8 measures via the pressure sensor 14, the position of the pressure peak and compares the measured position with the nominal position of the Pressure peak.

Is the measured angular position of the pressure peak in comparison to the target angular position too close to top dead center of promotional piston, then the opening cross section of Volume flow control valve 3 increased by a predetermined value. Preferably, the predetermined value is proportional to the difference angle between the desired angular position and the measured angular position of the pressure peak.

Is the measured angular position of the pressure peak in comparison to the desired angular position too far away from top dead center, then the opening cross section of the flow control valve reduced by a predetermined value. Preferably the given value is proportional to the difference angle between the desired angular position and the measured Angular position of the pressure peak.

In this way, a direct control of the opening cross-section of the flow control valve in dependence on the Angular position of the pressure peak allows.

A preferred embodiment of the method according to FIG. 7 is based in that the control unit 8, the angular position of the Pressure peaks of at least two consecutively conveying piston 22 determined and the angular position of the pressure peaks to used to the volume flow control valve 3 in the way Control that the angular positions of successive promotional Piston 22 are identical, so that an equal promotion by the piston 22 is reached. This will be an equal size Flow rate through the piston 22 of the high pressure pump 4 thereby achieved that the flow control valve 3 is controlled in the manner is that the angular positions of the pressure peaks of the different pistons 22 are the same. This procedure allows a simple method for controlling the equal promotion a plurality of pistons 22 of a high-pressure pump 4th

The method described is applicable to any type of pump and not limited to the described system.

Claims (6)

1. Method for operating a fuel injection system with a pump (4), whereby the pump (4) is fed pump medium,
   whereby at least one displacement element (22) is driven by a rotary shaft (21) of the pump (4), said displacement element pumping pump medium into a volume (5, 20) during a compression process,
   and
   whereby the position of a pressure extreme in the volume (20, 5) is determined during the pump process,
   characterised in that
   the supply of pump medium to the pump (4) is controlled as a function of the temporal position and/or angular position of the pressure extreme.
2. Method according to Claim 1, characterised in that
   the temporal positions and/or angular positions of the pressure extremes of any two successive displacement elements (22) of the pump (4) are determined, and that the quantity of pump medium fed to the pump (4) is adjusted as a function of the angular position of the two pressure extremes such that the two displacement elements pump virtually the same quantity of medium into the volume (20, 5)
3. Method according to Claim 1 or 2, characterised in that
   the quantity of pump medium delivered by at least one displacement element (22) into the volume (20, 5) is determined as a function of the temporal position and/or angular position of the pressure extreme.
4. Method for operating a fuel injection system with a pump (4) whereby the pump (4) is fed pump medium
   whereby at least one displacement element (22) is driven by a rotary shaft (21) of the pump (4), said displacement element pumping pump medium into a volume (5, 20) during a compression process,
   and
   whereby the position of a pressure extreme in the volume (20,5) is determined during the pressure process,
   characterised in that
   a fuel pump is used as the pump (4), whereby an injection valve (6) is connected to the volume configured as a line (20) and a fuel storage unit (5)
   the quantity of fuel emitted by the injection valve (6) is determined during a comparison period,
   the quantity of fuel emitted is compared with the output volume and as a result of the comparison, a statement is provided regarding the mode of operation of the injection system.
5. Method according to Claim 3 or 4, characterised in that
   a table is used in which the output of the displacement element is stored as a function of the angular position of the pressure extreme, and
   the output of the displacement element (22) is determined with reference to the values in the table.
6. Method according to Claim 3 or 4, characterised in that
   the output of the pump (4) is calculated as a function of the speed of the pump (4), as a function of the piston displacement of the pump (4) per rotation of the rotary shaft (21) and as a function of the angular position of the pressure extreme, whereby a table is used in which the output of the pump (4) is stored as a function of the angular position of the pressure extreme.

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