DE102005025879A1 - Hydraulic valve control`s pressure flow indicating method, for use in hydraulic system, involves calculating volume difference value from two volume values and evaluating pressure value from value based on clock pulse in real time - Google Patents

Abstract

The method involves computing a volume value of hydraulic fluid in a hydraulic system at a time of a clock pulse in real time and another volume value of the fluid in the hydraulic system at another time of the clock pulse in real time. A volume difference value is calculated from the two volume values and a pressure value is evaluated from the difference value under consideration of the clock pulse in real time. Independent claims are also included for: (1) a computer unit with an evaluation unit for indicating pressure flow in a hydraulic system; (2) a computer and/or microprocessor program with a program code unit for execution of a method of indicating pressure flow in a hydraulic system; and (3) a computer and/or microprocessor program product with a program code unit for execution of a method of indicating pressure flow in a hydraulic system.

Description

The The present invention relates to a method for indicating a pressure profile as a function of a pressure in a hydraulic system over the Time with a predetermined time clock in real time, a device to perform this procedure, a computer program and a computer program product.

following is mainly applied to valve controls in motor vehicles (motor vehicles) Without the method being limited to this application.

With camshaft-free engines in internal combustion engines to a higher Efficiency of the engine and a lower exhaust pollution can be achieved. A possibility the control of the gas exchange valves is the electro-hydraulic Valve control. In this case, a hydraulic actuator is electrically controlled.

For complete control need to burn a motor the three main variables: charge change, Mixture preparation and ignition for each Cylinder, cycle for Cycle can be completely controlled or controlled flexibly. through Electronic injection and ignition has been around for a long time Time partially realized, but the charge is still changing always mechanically coupled with the crankshaft.

First concepts for the realization of a fully variable electrohydraulic system for controlling the charge exchange valves are known. One of these systems, the "Electrohydraulic Valve Control - EHVS", consists of a hydraulic actuator for each gas exchange valve of the engine, a hydraulic circuit including a high pressure pump as part of the engine oil circuit and a control unit DE 103 24 782 A1 described in detail.

Around check the gas exchange inside the cylinder in each phase and being able to control is it is necessary to change the pressure in the high pressure circuit during the to know the entire charge phase. The knowledge is consuming and costly about Gained measurements on real systems.

In The development phase in the automotive industry has long been called Laboratory vehicles used as an alternative to real vehicles use Find. The laboratory vehicles are essentially as computing device formed with connected control, regulation and measuring systems. through of these laboratory vehicles it is possible physical processes to reproduce and thus fast, easy and inexpensive to use and comparable results. The already existing ones and planned controllers of a new vehicle be tested even if this vehicle is still in the Concept phase is located. These laboratory vehicles can usually physical processes play only in steps of a given time clock.

Around Realistic by means of simulation, modeling and calculation of physical processes To obtain results, it is necessary to understand the underlying physical connections to faithfully reproduce and integrate in a given time cycle.

task the present invention is therefore to provide a method using the pressure waveform in a hydraulic system using a time clock as possible realistically and can be specified in real time.

Advantages of invention

These Task is solved by a method having the features of patent claim 1, a computer unit with the features of claim 7, a computer program and a computer program product with the features of the claim 8 and 9, respectively. Advantageous embodiments result from the respective ones Subclaims and the following description.

The inventive method, in which the first time preferably directly to the second Timing within the time clock follows offers the advantageous Possibility, to simulate the pressure curve in a hydraulic system realistically and in real time. This makes it possible with the example of the EHVS, fast, inexpensive and without danger of damage real engines, for example, to check the effect of changes in parameters and to optimize the control or to predict malfunctions and thus in the real system to prevent. Likewise, AMESIM (Adaptive Modeling Environment for Simulation) simulations in comparison be checked to the real system.

In preferred embodiment of the method becomes the pressure course in a hydraulic system of Motor vehicle specified. In addition to the already mentioned EHVS systems offer while other hydraulic systems within a motor vehicle.

Likewise preferred is the inventive Method applicable when the hydraulic system comprises a hydraulic supply line, a hydraulic cylinder assembly and a first control valve which is arranged between the hydraulic supply line and the hydraulic cylinder arrangement. The control valve may in particular be designed as an electric and / or magnetic valve.

In a particularly preferred embodiment of inventive method the hydraulic cylinder assembly has a piston inside a Hydraulic cylinder on which at least one plunger is arranged, wherein the Piston an upper and a lower pressure chamber within the hydraulic cylinder Are defined. This hydraulic cylinder assembly can be particularly robust and more reliable Way serve as a valve control.

Conveniently, the hydraulic cylinder assembly is a hydraulic valve control for operation a gas exchange valve of a cylinder of an internal combustion engine, in particular Otto engine, whereby the hydraulic valve control an upper pressure chamber and a lower pressure chamber, wherein the lower pressure chamber through a piston from the upper pressure chamber is separated, and the lower pressure chamber over parts of a high-pressure rail distributor connected to a high-pressure rail, and the lower pressure chamber via a first control valve with the upper pressure chamber is connectable, wherein the upper pressure chamber over a second control valve with a return rail is connectable. In this advantageous embodiment, the pressure curve in a conventional one Valve control device of an internal combustion engine are specified, which especially for the development and optimization of internal combustion engines can be used advantageously.

• – der Volumenfluss V₁ der Hydraulikflüssigkeit in den oberen Druckraum, wobei der Kolben nicht bewegt wird, wobei das zweite Steuerventil geschlossen ist, so dass der obere Druckraum nicht mit dem Rücklaufrail verbunden ist, und wobei das erste Steuerventil geöffnet ist, so dass der untere Druckraum mit dem oberen Druckraum verbunden ist.
• – der Volumenfluss V₂ in den oberen Druckraum, wobei der Kolben bewegt wird, wobei das erste Steuerventil geöffnet ist und das zweite Steuerventil geschlossen ist,
• – der Volumenfluss V₃ in den unteren Druckraum, wobei der Kolben bewegt wird, wobei das erste Steuerventil geschlossen ist und das zweite Steuerventil geöffnet ist,
• – der Volumenfluss V₄, der durch eine im wesentlichen gleichzeitige Betätigung von Gaswechselventilen von unterschiedlichen Zylindern eines Verbrennungsmotors hervorgerufen wird,
• – der Volumenfluss V₅, der durch die Unabhängigkeit des Öffnungszeitpunktes und des Schließzeitpunktes des ersten und/oder zweiten Steuerventils vom Zeittakt verursacht wird.

In an equally preferred embodiment of the inventive method, at least one volume flow is taken into account in the calculation of a volume value as a function of the time of the time clock from the group consisting of:

• - The volume flow V _{1 of} the hydraulic fluid in the upper pressure chamber, wherein the piston is not moved, wherein the second control valve is closed, so that the upper pressure chamber is not connected to the return rail, and wherein the first control valve is open, so that the lower Pressure chamber is connected to the upper pressure chamber.
• The volumetric flow V ₂ in the upper pressure chamber, wherein the piston is moved, wherein the first control valve is opened and the second control valve is closed,
• The volume flow V ₃ into the lower pressure chamber, wherein the piston is moved, wherein the first control valve is closed and the second control valve is open,
• The volume flow V ₄ , which is caused by a substantially simultaneous actuation of gas exchange valves of different cylinders of an internal combustion engine,
• - The volume flow V ₅ , which is caused by the independence of the opening time and the closing time of the first and / or second control valve from the timing.

This allows in a simple way, the real reproduction of the pressure curve in particular in the described valve control: the calculation of the volume and / or pressure values occur at successive times the given time clock. The volume flow is from this time clock independently and will be through the opening hours of the control valve influenced. The opening and / or closing time the control valve will not work regularly coincide with times of the time clock. A consideration the mutual relationship of the timing and the opening and / or closing time leads the specified pressure curve closer to the reality. For example, it is also possible that intake valves of a cylinder substantially simultaneously be actuated to exhaust valves of another cylinder. Through this simultaneous activity lie changed Starting conditions in the high-pressure rail before, whose consideration in turn the goodness and quality significantly increased the specified pressure curve.

According to the invention is a Calculator unit with calculation means specified to all steps of a Method according to one of the preceding claims perform. An example is the system LABCAR, which is a modern one Development and test environment for ECUs represents, and in the computer unit according to the invention with advantage can be integrated.

One Computer computer according to the invention or microprocessor program contains Program code means for carrying out the method according to the invention, when the program on a computer, a microprocessor or a corresponding computer unit, in particular the computer unit according to the invention, accomplished becomes.

An inventive computer or microprocessor program product includes program code means which are stored on a machine or computer readable medium to perform a method according to the invention, when the program product on a computer, a microprocessor or on a corresponding computer unit, in particular the computer unit according to the invention is executed , Suitable data carriers are in particular floppy disks, hard disks, flash memories, EEPROMs, CD-ROMs, etc. Also a download of a program via computer networks (Internet, intranet, etc.) is possible.

Further Advantages and embodiments of the invention will become apparent from the Description and attached drawing.

It it is understood that the above and the following yet to be explained features not only in the specified combination, but also in other combinations or alone, without to leave the scope of the present invention.

The Invention is based on an embodiment schematically shown in the drawing and is below under Referring to the drawings described in detail.

figure description

1 shows a schematic diagram of a hydraulic valve control;

2 shows a Flußdigramm a preferred embodiment of the method according to the invention; and

3 shows a pressure curve in a hydraulic valve control, which is indicated by means of a preferred embodiment of the method according to the invention.

Based on 1 the principle of a hydraulic valve control will first be shown, the pressure curve in the high-pressure rail can be simulated by the inventive method. It is understood that other implementations of a hydraulic valve control can be used. The valve control is part of an internal combustion engine with a reciprocating piston, wherein the gas exchange via known intake and exhaust valves, the so-called. Gas exchange valves, takes place. The opening and closing of the intake and exhaust valves instead of, for example, a camshaft and rocker arm or plunger for transmitting the movement on the basis of the 1 illustrated hydraulic valve control. The engine itself and the intake and exhaust valves are not shown here, as they are known per se.

The illustrated in the form of a schematic diagram hydraulic valve control 1 essentially comprises a double piston 2 that with a lower pressure chamber 3 as well as an upper pressure chamber 4 interacts. The double piston 2 is with a solid pestle 5 connected. The pestle 5 in turn is divided into a lower plunger 6 as well as an upper ram 7 , The lower plunger 6 is with an exhaust valve, not shown 8th mechanically connected. Depending on the direction of actuation of the exhaust valve 8th This can also be done with the upper pestle 7 be connected. In a further embodiment, the plunger, which is not connected to the outlet valve, can not be provided.

The hydraulic system for the exhaust valve shown here 8th is in principle identical to the hydraulic system of an intake valve. The lower pressure chamber 3 forms together with the double piston 2 and the lower plunger 6 a lower piston 11 , Accordingly, the upper pressure chamber forms 4 together with the double piston 2 and the upper plunger 7 an upper piston 12 ,

The double piston 2 forms together with the lower pressure chamber 3 and the upper pressure chamber 4 an acting in two directions or usable piston / cylinder assembly. The hydraulic shading and the mode of operation and at least approaches for integration into the engine management of the piston engine are described below. A high pressure rail 9 is via a first check valve RV1 with the lower pressure chamber 3 hydraulically connected. The high pressure rail 9 is a hydraulic control line connecting all the valve controls of the engine, which is held at a certain pressure level depending on the operating condition of the engine, this affects in particular the speed and load, but also parameters such as injection pressure and the like. In operation, the pressure prevails in the high-pressure rail in the order of 50 · 10 ⁵ - 200 · 10 ⁵ Pa.

The first check valve RV1 causes a flow of the hydraulic fluid only from the high-pressure rail 9 in the lower pressure chamber 3 can be done. A backflow even at a higher pressure in the lower pressure chamber 3 opposite the high pressure rail 9 is thus prevented. The lower pressure chamber 3 is with the upper pressure chamber 4 connected via a first solenoid valve MV1. This solenoid valve MV1 is the first control valve.

The first solenoid valve MV1 has a closed and an open position, the representation of 1 shows the open position. Instead of a solenoid valve, other externally controllable valves can be used here. In the open position of the first solenoid valve MV1, a pressure equalization between the lower pressure chamber 3 and the upper pressure chamber 4 respectively. The upper pressure chamber 4 is also a second check valve RV2 with the high pressure rail 9 connected. Should the pressure in the upper pressure chamber 4 be larger than in the high pressure rail 9 , so here can be a pressure equalization. The pressurizable in operation with the pressure of the high pressure rail lines and valves of the hydraulic system are conceptually as a high-pressure rail distributor 22 summarized, this is in the sketch of 1 represented by a dashed line representing the high-pressure rail distributor 22 from the double piston 2 with the associated pressure chambers 3 . 4 and the return trail 10 diagrammatically delimited as a subsystem.

The upper pressure chamber 4 is via a second solenoid valve MV2, which is the second control valve, with a return rail 10 connected. In operation, the pressure prevailing in the return rail is on the order of 1 × 10 ⁵ - 2 × 10 ⁵ Pa. The return rail is used to supply the by the hydraulic valve control 1 passed hydraulic oil or the hydraulic fluid to a pump, the high-pressure rail 9 supplied with hydraulic oil of higher pressure. The entire system is closed in this respect. In 1 is only the part of the hydraulic valve control of interest here 1 by means of a double piston 2 for actuating an exhaust valve 8th shown. In an internal combustion engine, one or more exhaust valves 8th , each from the same double piston 2 or from each individually associated double piston 2 be controlled, be present.

In 1 shown is the valve position of each controllable valves, these are the first solenoid valve MV1 and the second solenoid valve MV2, in the closed position of the exhaust valve 8th , In this case, the first solenoid valve MV1 is closed, the second solenoid valve MV2 open. This causes the lower pressure chamber 3 at the pressure level of the high pressure rail 9 is, the upper pressure chamber 4 is at the pressure level of the return rail 10 , The pressure in the lower pressure chamber 3 is thus higher than that in the upper pressure chamber 4 , The double piston 2 is therefore in the direction of the upper pressure chamber 4 pressed. The outlet valve 8th is closed by it.

To open the exhaust valve 8th if first the second solenoid valve MV2 is closed, then the first solenoid valve MV1 is opened. So it can no longer hydraulic fluid from the upper pressure chamber 4 in the return trail 10 flow. But now is an exchange of hydraulic fluid between the lower pressure chamber 3 and the upper pressure chamber 4 possible via the first solenoid valve MV1. Like the sketch of the 1 it can be seen, the lower piston 11 a lower hydraulically effective surface than the upper piston 12 , The hydraulically effective area of the lower piston 11 is smaller than the hydraulically effective area of the upper piston 12 , By hydraulically effective area is meant the area fraction which is pressurized when pressure is applied to the respective pressure chamber in the direction of movement of the piston. The different hydraulically effective surfaces are in the illustration of 1 by different diameters of the lower plunger 6 opposite the upper plunger 7 indicated. The lower plunger 6 has a larger diameter than the upper plunger 7 , therefore, is the hydraulically effective area of the lower piston 11 smaller than that of the upper piston 12 ,

The opening of the first solenoid valve MV1 prevails in static view, ie, without taking into account dynamic effects due to previously existing pressure differences in the lower pressure chamber 3 the same pressure as in the upper pressure chamber 4 , But because the hydraulically effective area of the upper piston 12 larger than that of the lower piston 11 , results from this same pressure one in the direction of the lower pressure chamber 3 directed total force, leaving the exhaust valve 8th is opened.

When opening the first solenoid valve MV1 there is a large pressure difference between the lower pressure chamber 3 and the upper pressure chamber 4 , In the lower pressure chamber 3 There is essentially the pressure of the high pressure rail 9 in the upper pressure room 4 At this moment, the pressure of the return flow prevails 10 , The pressure in the lower pressure chamber 3 is in 1 represented as p_u_Dr, according to the pressure in the upper pressure chamber is shown as p_o_Dr.

To open the gas exchange valve 8th Solenoid valve MV2 are closed and the solenoid valve MV1 opened. The resulting volume flow is referred to as V ₁ . V1 corresponds to the high pressure difference between the upper pressure chamber 4 and the lower pressure chamber 3 essentially the volume of the upper pressure chamber 4 in the closed position of the gas exchange valve 8th , When opening the solenoid valve MV1, the hydraulic fluid expands into the upper pressure chamber 4 , In this expansion finds no movement of the piston 2 instead of. The volume V _{1 of} the upper pressure chamber in the closed position of the gas exchange valve typically has a value between 150 mm ³ and 300 mm ³ . The expansion takes a predetermined period of time, designated t1, which is typically less than 1 ms, typically about 0.5 ms.

After the expansion of the hydraulic fluid in the upper pressure chamber 4 the same pressure prevails in the upper and lower pressure chamber. As explained, it is now due to the different hydraulic effective surfaces of the piston 2 to a displacement of the piston and to a reduction of the lower pressure chamber 3 , The resulting volume flow is referred to as V ₂ . V ₂ corresponds to the difference of the hydraulically effective areas multiplied by the height of the displacement, which is denoted by s. The hydraulically effective surfaces typically range between 15 mm ² and 30 mm ² .

The height of Displacement s is of an opening period of the solenoid valve MV1, the is denoted by tm1, of an opening size of the solenoid valve MV1, of a pressure P and a temperature T of the hydraulic oil, continue from the pressure curve in the cylinder of the internal combustion engine. It comes to an ignition, For example, in the cylinder, there is a higher pressure against which the valve rests must be moved as if it comes to a misfire.

The parameters s, P, T are calculated by the computer unit, for example integrated in LABCAR, by other methods or received from external control units and fed to this method. It makes sense, for the solenoid valve MV1, a flow rate V _MV1 per unit time t, ie V _MV1 / t, set in dependence of the mentioned parameters in a map. Of the possible parameters are pressure or pressure difference P and temperature T variable, the opening size of the solenoid valve specified. In the first embodiment, therefore, a flow rate per unit time as a function of temperature and pressure V _MV1 / t (P, T) in a map, z. As a table, set. In a further refinement, further parameters can be added for refinement, for example the pressure difference between the upper and lower pistons.

To close the gas exchange valve, the solenoid valve MV1 are closed and the solenoid valve MV2 opened. As a result, the hydraulic fluid of the upper pressure chamber 4 in the return trail 10 escape. The resulting volume flow is referred to as V ₃ . V ₃ corresponds to the hydraulically effective area of the lower pressure chamber 3 multiplied by the amount of displacement s.

Due to the high pressure differences between the upper pressure chamber and the return rail escapes the contents of the upper pressure chamber very quickly in the return rail, resulting in a rapid return movement of the piston. It makes sense to set for the second solenoid valve MV2 a flow rate V _VM2 per unit time t, ie V _MV2 / t, depending on the already mentioned parameters in a map. Of the possible parameters, pressure or pressure difference P and temperature T are variable, and the opening size of the solenoid valve MV2 is predetermined. In the first embodiment, therefore, a flow rate per unit time as a function of temperature and pressure V _MV2 / t (P, T) in a. Map set. In a further embodiment, additional parameters can be added for refinement, such as the pressure difference between the upper piston 12 and return trail 10 ,

During the simulation of different operating and load conditions of an internal combustion engine, it is possible that substantially simultaneously the gas exchange valves of different cylinders are actuated. If, for example gas exchange valves of two different cylinders are opened, it comes from each of the gas exchange valves caused pressure changes in the high-pressure rail, which take influence on the respective other gas exchange valve. For example, if the pressure at the beginning of the opening phase of a gas exchange valve for these reasons not according to the predetermined pressure, incorrect values are read from maps. Also, in particular, there are volume changes of the volumes V ₂ and V ₃ , since the height of the displacement s is changed. This contribution of the volume flow, which is caused by a substantially simultaneous actuation of gas exchange valves of different cylinders of an internal combustion engine, is referred to as overlap volume V ₄ .

It is possible to calculate V ₄ from empirical values. If one gas exchange valve is opened at the same time and another is closed, V ₄ almost disappears. If gas exchange valves are opened or closed at the same time, the change in the displacement s must be specified as approximately 5%. Therefore, in a simple approximation, V ₄ corresponds to approximately 5% of the displacement s multiplied by the difference of the hydraulically effective areas of the relevant valve controls for each cylinder involved. In an advantageous embodiment, the values of V _{4 are} written into a characteristic field as a function of the parameters number of overlapping valves and overlapping time. The values can be obtained from experiments for more precise modeling. V _{4 should be} subtracted from the volume.

Finally, a volume flow V _{5 is} considered. The calculation of the volume and / or pressure values takes place at successive times of the given time cycle. The real volume flow is independent of this timing and is controlled by the opening time tm1 of the solenoid valve MV1 as a function of the crankshaft angle φ. For opening an inlet valve, for example, the solenoid valve MV1 is opened at φ = 350 ° and closed at φ = 180 °. The opening time is now set in relation to the trigger clock. Typically, MV1 and MV2 are opened and closed between two times of the clock (trigger). The fraction within a time clock before opening, at which no change in volume still takes place, is referred to as the _flow volume V _{5_less} , and is subtracted from the volume value calculated over the entire _cycle . The proportion within a time clock after closing, in which also no more of the above-mentioned volume changes take place, is referred to as the follow-up volume V _{5_more} and is the calculated volume value deduct the entire time.

In 2 is a flowchart of an embodiment of the method according to the invention with respect to the valve control 1 shown in more detail. In the following it will be described how from the given volumes in relation to the timing of the pressure profile is given. The trigger time, ie the time interval between two immediately consecutive times of the clock cycle with which the computer unit can perform the calculation, is denoted by dT. For example, dT is 1.6 ms.

From the computer unit via control units, so-called. ECU (Electronic Control Unit), signals regarding the state of the solenoid valves (MV1 / 2 open, MV1 / 2 closed), the time tm1 and the length of the distance s received. The expansion time t ₁ is predetermined, for example, t ₁ = 0.5 ms.

The Calculation is initiated, as soon as the solenoid valve MV1 is opened becomes (MV1 = 1) after the solenoid valve MV2 is closed (MV2 = 0). The volume change dV / dt, from which finally the pressure change is calculated from v (j · dT) / dT.

In the first process step 201 the parameter j = 1 is set and checks whether the solenoid valve MV1 is still open. Is it still open, with procedural step 202a continued, otherwise with 202b ,

In step 202a the volume change is calculated in the first time clock V (j · dT). It is composed of the static expansion _volume V ₁ , the proportional dynamic expansion _volume V _MV1 / t · dT, which is corrected by the _{flow volume} V _{5_less} , and the overlap _volume V ₄ .

The volume change dV / dt, finally the pressure change is calculated from V (j · dT) / dT.

In the process step 203 the parameter j is incremented and checked again whether the solenoid valve MV1 is still open. Is it still open, with procedural step 204a continued, otherwise with 204b ,

In step 204a the volume change is calculated in a further time interval j, V (j · dT), as a proportional dynamic expansion volume V _MV1 / t · dT.

The volume change dV / dt, from which finally the pressure change is obtained, is calculated from V (j · dT) / dT. Then it becomes step 203a returned.

In step 204b _{For example} , the volume change at the last timing j, V (j * dT), is calculated as the proportional dynamic expansion _volume V _VM1 / t * dT which is corrected by the _{tracking volume} V _{5_more} .

The volume change dV / dt, from which finally the pressure change is obtained, is calculated from V (j · dT) / dT. Subsequently, with step 205 continued.

In step 202b the volume change is calculated in the single time clock V (j · dT). It is composed of the static expansion _volume V ₁ , the proportional dynamic expansion _volume V _MV1 / t · dT, which is corrected by the _{supply volume} V _{5_less} and the follow-up _volume V _{5_more} , and the overlap _volume V ₄ .

The volume change dV / dt, from which finally the pressure change is obtained, is calculated from V (j · dT) / dT. Subsequently, with step 205 continued.

In step 205 the pressure curve is calculated after the first solenoid valve MV1 is closed again (MV1 = 0). Closing the MV1 valve causes a pressure increase, followed by a pressure drop, etc. This pressure builds up through dynamic pressure equalization between the upper pressure space 4 , the lower pressure chamber 3 and the high-pressure rail 9 caused by the check valves RV1 and RV2. This oil flow depends on the configuration of the check valves RV1 and RV2. It makes sense to set a flow rate V _RV1 and V _RV2 per unit time t, ie V _RV1 / t, V _RV2 / t, depending on the parameters mentioned in a map for the check valves RV1 and RV2. Of the possible parameters are pressure or pressure difference P and temperature T variable, the opening size of the valves specified. In the first embodiment, therefore, a flow rate per unit time as a function of temperature and pressure V _RV1 / t (P, T) and V _RV2 / t (P, T) in a map, eg a table set. The time required for pressure equalization is referred to as t _RV . This will be analogous to the above detailed explanations in relation to the timing as in the steps 202a to 204b the pressure curve is calculated, with only map-dependent calculations analog 202a to 204b be used. The number of clock cycles is determined by the ratio of t _RV to dT.

The pressure curve associated with the closing of the exhaust valve 8th goes along, is described below. The calculation is triggered by opening the solenoid valve MV2 (MV2 = 1).

The steps 206 to 210 are analogous to the steps 201 to 205 built up.

In step 206 the parameter j = 1 is set and checks whether the solenoid valve MV2 is still open. Is it still open, with procedural step 207a continued, otherwise with 207b ,

In step 207a the volume change is calculated in the time clock V (j · dT). It corresponds to the proportional dynamic expansion _volume V _MV2 / t · dT, which is corrected by the _{flow volume} V _{5_less} .

The volume change dV / dt, finally the pressure change is calculated from V (j · dT) / dT.

In the process step 208 the parameter j is incremented and checked again whether the solenoid valve MV2 is still open. Is it still open, with procedural step 209a continued, otherwise with 209b ,

In step 209a the volume change is calculated in a further time interval j, V (j · dT), as a proportional dynamic expansion _volume V _MV2 / t · dT.

The volume change dV / dt, from which finally the pressure change is obtained, is calculated from V (j · dT) / dT. Then it becomes step 208a returned.

In step 209b _{For example} , the volume change at the last timing j, V (j * dT), is calculated as a pro-rata dynamic expansion _volume V _MV2 / t * dT which is corrected by _{tracking volume} V _{5_more} .

The volume change dV / dt, from which finally the pressure change is obtained, is calculated from V (j · dT) / dT. Subsequently, with step 210 continued.

In step 207b is the volume change in the time clock V (j · dT) as a proportionate dynamic expansion _volume V _MV2 / t · dT, which is the _{supply volume} V _{5_less} and corrected by the caster _volume V _{5_more} , calculated.

The volume change dV / dt, finally the pressure change is calculated from V (j · dT) / dT.

In step 210 the pressure profile is calculated after the second solenoid valve MV2 is closed again. Closing valve MV2 causes a pressure increase, followed by a pressure drop, etc. This pressure builds up through dynamic pressure equalization across check valves RV1 and RV2 between the upper pressure chamber 4 and the lower pressure chamber 3 caused. The calculation of the pressure change takes place analogously to step 205 ,

From the given volume changes dV / dt the pressure changes dP / dt can be calculated from the equation dP = -K 1 K dV; calculated in each step, wherein the compression modulus K of the hydraulic fluid depends in particular on the temperature.

In 3 a pressure curve is shown, as it can be indicated by means of an embodiment of the method according to the invention. It is the pressure curve p_u_Dr over the time in the lower pressure chamber 3 shown. In addition to the pressure curve, the opening or closing of the first solenoid valve MV1 as a curve A_AV1_MV1 and the second solenoid valve MV2 as a curve A_AV1_MV2 and the lift curve s_GWV_AV1 of the exhaust valve 8th shown.

The opening state of the two solenoid valves MV1, MV2 is represented by the electrical signal, resulting in the shown rectangular shape. As can be seen, the hydraulic pressure p_u_Dr is in the lower pressure space 3 before opening the first solenoid valve MV1 at an approximately constant initial pressure 300 , The closing of the second solenoid valve MV2 is by the jump 301 recognizable in the curve A_AV1_MV2. The comparable rectangular deflection of the curve A_AV1_MV1 at 302 and 303 corresponds to the opening and closing of the first solenoid valve MV1.

First, the second solenoid valve MV2 is closed, resulting in the jump 301 is represented from a high to a low value of the curve A_AV1_MV2. Subsequently, the first solenoid valve MV1 is opened, resulting in the jump 302 the curve A_AV1_MV1 is shown. After a short time, the first solenoid valve MV1 is closed again, which is the jump 303 in the curve A_AV1_MV1 shows.

As can be seen, the pressure curve p_u_Dr remains in the lower pressure chamber 3 until the opening of the first solenoid valve MV1 is substantially constant. Thereafter, the pressure drops to a first minimum value 304 from. A first increase in pressure now leads to a first local maximum value 305 , which is slightly above the initial pressure 300 lies. Depending on the operating state of the internal combustion engine, the first local maximum may also be below the initial pressure 300 lie.

How farther 3 can be seen, followed by a slight pressure drop, then a strongly fluctuating pressure rise to a high maximum value 306 , In the further course, the pressure settles at weaker pressure fluctuations to a level that is approximately in the order of magnitude of the initial pressure 300 lies.

Subsequently, the solenoid valve MV2 is reopened, which by a jump 307 is shown in the curve A_AV1_MV2. The hydraulic fluid can then from the upper pressure chamber 4 in the return trail 10 escape, with hydraulic fluid from the high pressure rail 9 in the lower pressure chamber 3 nachströmt. This again creates pressure oscillations in the lower pressure chamber 3 , as shown in the further course of the curve p_u_Dr.

The curve s_GWV_AV1 shows the associated course of movement of the exhaust valve 8th , After opening the solenoid valve MV1, which occurs after closing the solenoid valve MV2, the exhaust valve moves 8th up until it's at 308 reached a maximum. It then settles on its opening stroke of about 4.0 mm 309 one. This stroke s is determined by the opening time of the solenoid valve 1 certainly.

By opening the solenoid valve 2 becomes the exhaust valve 8th closed again. This is due to a waste 310 shown in the curve s_GWV_AV1.

1

hydraulic valve control

2

double piston

3

lower pressure chamber

4

Oberer pressure chamber

5

tappet

6

lower tappet

7

Oberer tappet

8th

outlet valve

9

High-pressure rail

10

Return rail

11

lower piston

12

Oberer piston

22

High-pressure rail distributor

RV1

first check valve

RV2

second check valve

MV1

first magnetic valve

MV2

second magnetic valve

201 ... 210

step

300

initial pressure

301

Close MV2

302

Open MV1

303

Close MV1

304

first minimum value

305

local maximum value

306

maximum value

307

Open MV2

308

maximum value s

309

opening stroke

310

Close exhaust valve

Claims (9)

Method for specifying a pressure profile in a hydraulic system ( 1 ) as a function of a pressure (p_u_Dr) over a period of time wherein a hydraulic fluid pressurizes the hydraulic system and the pressure is indicated in real time at predetermined times (dT), comprising the steps of: - calculating a first volume value of the hydraulic fluid in the Hydraulic system at a first time of the time clock in real time, - Calculating a second volume value of the hydraulic fluid in the hydraulic system at a second time of the time clock in real time, - Calculating a volume difference value from the first volume value and the second volume value in real time, - Calculating a pressure value from the Volume difference value taking into account the time clock in real time. A method according to claim 1, characterized in that the pressure curve in a hydraulic system ( 1 ) of a motor vehicle. Method according to one of the preceding claims, characterized in that the hydraulic system ( 1 ) a hydraulic supply line ( 9 ), a hydraulic cylinder assembly ( 2 to 7 . 11 . 12 ) and a first control valve (MV1) connected between the hydraulic supply line ( 9 ) and the hydraulic cylinder assembly ( 2 to 7 . 11 . 12 ) is arranged. Method according to claim 3, characterized in that the hydraulic cylinder arrangement ( 2 to 7 . 11 . 12 ) a piston ( 2 ) inside a hydraulic cylinder ( 11 . 12 ), on which at least one plunger ( 5 ) is arranged, wherein the piston ( 2 ) an upper ( 4 ) and a lower ( 3 ) Pressure space defined within the hydraulic cylinder. Method according to one of claims 3 or 4, characterized in that the hydraulic cylinder arrangement ( 2 to 7 . 11 . 12 ) as a hydraulic valve control for actuating a gas exchange valve ( 8th ) is formed of a cylinder of an internal combustion engine, wherein the hydraulic valve control an upper pressure chamber ( 4 ) and a lower ( 3 ) Has pressure space, the lower ( 3 ) Pressure chamber through a piston ( 2 ) from the upper pressure space ( 4 ) and the lower pressure space ( 3 ) over parts of a high-pressure rail distributor ( 22 ) with a high pressure rail ( 9 ), and the lower pressure space ( 3 ) via a first control valve (MV1) with the upper pressure chamber ( 4 ) is connectable, wherein the upper pressure chamber ( 4 ) via a second control valve (MV2) with a return rail ( 10 ) is connectable. A method according to claim 5, characterized in that in the calculation of a volume value as a function of time of the time clock at least one volume flow is taken into account from the group consisting of: - the volume flow V _{1 of} the hydraulic fluid in the upper pressure chamber ( 4 ), the piston ( 2 ) is not moved, wherein the second control valve (MV2) is closed, so that the upper pressure chamber ( 4 ) not with the return trail ( 10 ), and wherein the first control valve (MV1) is open, so that the lower pressure chamber ( 3 ) with the upper pressure chamber ( 4 ) connected is. - The volume flow V ₂ in the upper pressure chamber ( 4 ), the piston ( 2 ) is moved, wherein the first control valve (MV1) is open and the second control valve (MV2) is closed, - the volume flow V ₃ in the lower pressure chamber ( 3 ), the piston ( 2 ), wherein the first control valve (MV1) is closed and the second control valve (MV2) is open, - the volume flow V ₄ , which by an essentially simultaneous operation of gas exchange valves ( 8th ) is caused by different cylinders of an internal combustion engine, - the volume flow V ₅ , which is caused by the independence of the opening time and the closing time of the first and / or second control valve (MV1, MV2) from the timing. Computer unit with calculation means to all steps a method according to a of the preceding claims perform. Computer or microprocessor program with program code means, to all steps of a method according to one of claims 1 to 6 to perform if the program is on a computer, a microprocessor or a corresponding computer unit, in particular according to claim 7, executed becomes. Computer or microprocessor program product with Program code means based on a machine or computer readable disk are saved to all steps of a procedure according to one of claims 1 to 6, if the program product is on a computer, a microprocessor or on a corresponding computer unit, in particular according to claim 7, executed becomes.