EP2132069A1

EP2132069A1 - Method for the calibration of analogized valves in a pressure control device

Info

Publication number: EP2132069A1
Application number: EP08701657A
Authority: EP
Inventors: Mirco Loos
Original assignee: Continental Teves AG and Co OHG
Current assignee: Continental Teves AG and Co OHG
Priority date: 2007-03-05
Filing date: 2008-01-23
Publication date: 2009-12-16
Also published as: DE102007010514A1; WO2008107219A1; KR20090116799A; US20100090521A1; CN101626927A; JP2010520427A

Abstract

The invention relates to a method in which a calibration is performed of an electromagnetic valve (2,3) in an electronically controlled pressure control device (6), wherein the prevailing differential pressure on the valve (2,3) to be calibrated is periodically modulated and wherein the electric signal present at the valve coil of the valve (2,3) is analyzed on the valve coil or on an additional measurement coil for calibrating purposes. The invention also relates to an electronically controlled motor vehicle braking pressure control device in which the method described above may be performed.

Description

Method for calibrating analogized valves in a pressure regulator

The invention relates to a method according to the preamble of claim 1 and to a motor vehicle brake pressure regulating device according to the preamble of claim 16.

It is known, inter alia, from DE 10 2005 014 097 A1 to use analogously controlling electrically controllable hydraulic valves for regulating the hydraulic pressure in ABS control units for motor vehicle brake systems, but also in so-called vehicle dynamics controllers with additional functions such as ESP. These so-called analog / digital valves (A / D valves) are in principle conventional electromagnetic (solenoid) switching valves, which are controlled by means of a pulse width modulated current (PWM) in such a way that the valve stem assumes a floating position. In this way, a pressure control is possible, provided that the current control is carried out sufficiently accurate and reproducible. This is usually possible without major problems if the einzuregelnde pressure can be adjusted via a pressure sensor in conjunction with a control loop. It is considerably more difficult to carry out a corresponding analog control method without a pressure sensor in the pressure circuit to be regulated.

In this context, quite a number of pressure control methods have become known which deal with the problem of pressure adjustment of an A / D valve without a pressure sensor in the circuit to be controlled. As is well known, the opening flow of the valve, among other parameters, depends on the pressure difference across the valve (differential pressure). Therefore, the regulator, which regulates the opening current via the electric current setting by means of an electronic PWM driver stage, the pre-pressure, the pressure in the regulated circuit (for example in Radbremszy- Linder) and know the opening flow of the valve. In a brake hydraulic device, to which the invention relates, at least the form can be detected by sensors, so that the problem is reduced to the determination of the pressure in the circuit to be controlled.

The opening flow is known to the flow of a normally open valve, which is just sufficient, at a certain pressure differential to keep the valve closed. For the determination of the opening current characteristic (current over differential pressure) or also "calibration" of the regulating A / D valve, it has already been proposed to carry out an electronically controlled calibration process at least once on the belt and / or in the factory and / or in the vehicle. In this case, certain pressure values are specified and pointwise determined flow points, which reflect the opening flow behavior of the valve. A correspondingly obtained curve or support points for this curve can then be stored in the controller of the electronic brake system for later use. However, the above-described calibration process to be performed individually for each individual valve due to minor manufacturing tolerances to be taken into account requires additional time and makes the production process of the valves produced in large quantities in brake systems overall very complicated.

A whole series of methods has already been proposed with which it is possible to carry out a determination of the opening current characteristic even without a pre-calibration of the brake system at the factory of the brake system manufacturer or on the vehicle manufacturer's line. These known methods are selbstätig after installation in the vehicle by the electronic control of the brake system and without an external pressurization (defined measuring pressures etc.). Some of these methods are based on feedback of direct or indirect information about the wheel pressure actually caused by a particular valve current (eg, from a pressure sensor) or the position of the valve plunger (eg, a signal from the magnetic circuit of the solenoid valve obtained with a pick-up coil ) is being used. A disadvantage of the latter method is that additional costs for pressure sensors or measuring coils arise.

The aim of the invention is to provide a calibration method for determining calibration values, in particular for an opening flow curve, which can be automatically and automatically initiated by the electronic control unit after installation in a motor vehicle, without the use of a pressure sensor or a pressure sensor magnetic / electrical Messeselements takes place.

This object is achieved by the method according to claim 1.

According to the inventive method, a calibration of an electromagnetic valve (for example, normally open or normally closed valve) is carried out in an electronically controlled pressure control device in which the prevailing at the valve to be calibrated differential pressure periodically modulates and applied to the corresponding valve coil electrical signal to the valve spool or evaluated on an additional measuring coil for calibration. The electrical signal is, in particular, the electrical induction signal and / or the coil current profile and / or the voltage profile at the valve coil or at an additional measuring coil.

During calibration, the valve coil is preferably supplied with an offset current. The offset current is a current from a current source that flows through the valve during the calibration measurement so that it can be opened or closed more easily, for example by hydraulic pressure pulses acting on it. This does not mean, however, that this current must necessarily always remain constant. Rather, it is according to an embodiment of the calibration so that the current is lowered in accordance with a ramp. During a calibration measurement (recording of a measuring point), the current is still sufficiently constant even with a continuous lowering, so that one can speak of a measurement or calibration at constant current. In principle, however, it is also conceivable to carry out a calibration measurement without an offset current as long as the pressure pulsations are sufficient to produce a measurable valve reaction. The latter will rarely be the case.

Therefore, the valve coil current is preferably applied to a (relative to a certain time) by means of a current regulator. point) predetermined setpoint adjusted. Since in general a controller does not show ideal behavior, the coil current adjusted by the regulator is changed by a hydraulically provoked ram motion. For example, if a periodic excitation of the plunger made, then results in a periodic current waveform whose amplitude depends inter alia on the quality of the regulator and the strength of the excitation. In this case, the instantaneous desired value can also be continuously changed according to a curve, which is preferred according to the method. The curve is particularly easy a particularly preferred straight line or ramp.

For this purpose, the setpoint value modulated by the valve movement (for example the coil voltage) and / or the actual value of the current controller are preferably evaluated for calibration. In particular, the actual value of the controller is evaluated, which is according to the embodiment of the valve coil current. But it is also possible that the magnetic flux is measured in the region of the magnetic circuit of the valve coil with known magnetic sensor means. Thus, for example, a pick-up coil can be arranged in the magnetic field of the coil.

A calibration of the valve is preferably carried out by measuring the opening or closing current. The opening or closing current is in particular the current which flows during a valve movement. This is measured at a differential pressure in the vicinity of 0 bar, in particular at less than 0.5 bar. A measurement at a differential pressure of exactly 0 bar is in principle not possible according to the method according to the invention, since a certain small differential pressure is required to open the valve to be calibrated.

As already mentioned, during calibration of the valve Tils preferably the valve coil current for detecting the switching point of the valve, for example, linear, increased or decreased. The switching point of the valve is determined by a change in the electrical signal measured at the valve.

It may be necessary, according to a preferred improvement of the method, to correct the opening or closing current value obtained with the calibration method described above (for example by an offset) such that this value is accurate within the scope of the measuring accuracy for a pressure difference of 0 bar reproduces. This correction increases the accuracy of the measured value, since, as already mentioned above, a measurement at exactly 0 bar due to the principle is not possible or only with pressure pulsation with high amplitude.

Preferably, the above-mentioned periodic differential pressure is caused by an acting on the valve, conveying hydraulic pump, which is in particular part of the pressure control device.

In this case, in particular the discharge on the delivery side of the hydraulic pump conveying means, which acts on the valve, at least partially escape from the circle in which the pressure pulses. This measure causes the pressure on the side of the valve, which faces the pump outlet, to not increase continuously.

The escape of the conveying means from the region between the pump and the calibration valve can preferably be made possible by a further open electromagnetic valve connected to this circuit.

Preferably, the valve to be calibrated is concerned around an isolation valve or an intake valve of an electric brake control unit.

Surprisingly, it is possible to increase the amplitude of the differential pressure change via additional measures. For this purpose, a component already present in the device (for example, valve, check valve, orifice, pressure accumulator, etc.) is preferably used. If the amplitude of the differential pressure is increased by this measure, there is advantageously also an increase in the amplitude or amplitude change of the electrical measuring signal evaluated for the calibration.

For the above-described amplification, in the case of calibration of the inlet valve, the isolation valve is preferably opened only partially. In this case, "partially open" does not mean that the valve is actually open at each pressure. Rather, it is meant that the valve current is selected so that the valve opens at a certain current-dependent differential pressure. The partial opening of the separating valve used for amplification thus takes place, for example, with a valve current, in which the valve opens even at a fairly low differential pressure. Alternatively, if a calibration of the separating valve is preferably carried out, the inlet valve can be partially opened in order to increase the differential pressure amplitude. The electric current, which is passed through the coil of the respective reinforcing valve for this purpose, has a thickness which corresponds to an opening pressure of preferably about 0.5 to about 8 bar. Particularly preferably, this range is between about 2 to about 4 bar.

Preferably, the calibration is only after installation of the pressure control device in a Nutzanwendung, in particular in a Vehicle, without external pressurization automatically made by the device. This possibility makes it possible to dispense with expensive calibration processes during the production of the pressure control device or when installing the pressure control device in a Nutzanwendung (for example, in a motor vehicle).

Preferably, the control device comprises a per se known current control circuit, which in particular allows multi-channel current control. Particularly preferably, the current control circuit is equipped with a measuring circuit known per se for determining the coil current. Depending on the design and complexity of the current measuring circuit, the coil current can be measured continuously or averaged and, if necessary, precisely regulated.

According to the method of the invention, the current controller used to drive the A / D valve is used quasi "as a sensor". At the same time a hydrodynamic, in particular via the hydraulic system of the brake system, for example via the pump of the brake system, a pressure modulation is performed in such a way that the A / D valve performs a plunger movement. For this purpose, the differential pressure at the valve is preferably modulated periodically or pulsed with an amplitude which opens the A / D valve. The result of the periodic opening of the valve resulting plunger movement of the controlled valve leads to a reaction to the coil current through the voltage induced in the valve coil. The current regulator then tries to readjust the actual current, which has been changed by the periodic ram movement, to the preset desired current. The resulting vibrations of the valve current can then be evaluated on the basis of the valve current itself or the manipulated variable (for example the pulse width, etc.). For the calibration, the valve opening or closing point is preferably determined by evaluating the oscillation signal of the coil current curve. For this purpose, in particular the amplitude of the current curve is considered. If, for example, the valve stem begins to move when the offset current is lowered at a certain time, this can be recognized by a higher amplitude of the valve current. This increase in amplitude normally extends to a certain limited offset current range in which the valve is sensitive to pressure pulsations. In principle, however, the curve can also be evaluated with regard to the frequency or other parameters, provided that a valve movement can still be detected with sufficient accuracy. The offset current flowing at the time of the thus detected valve reaction then corresponds quite accurately to the sought calibration value, which should indicate the opening or closing current at a differential pressure near 0 bar.

The method described above describes one way in which the opening or closing flow of a valve can be measured at a differential pressure of close to 0 bar. According to a further preferred embodiment of the method, a corresponding opening or closing current measurement is carried out, which, however, is representative of a differential pressure greater than 0 bar. This is possible, in particular in which the previously described pressure reduction at another valve, which is not calibrated, is withdrawn, so that the pressure in the area between the pump outlet and the calibration valve increases significantly. This differential pressure increase results in the calibration of an inlet valve, for example, when the isolation valve is closed slightly further than in the above-described 0 bar measurement. The invention also relates to an electronically controlled motor vehicle brake pressure control device having at least one ABS control program according to claim 16. This is in particular a control device for a hydraulic pressure.

Further preferred embodiments will become apparent from the subclaims and the following description of an embodiment with reference to the figures.

Show it

Fig. 1 is a schematic representation of a braking device for ABS and ESP control operations and

Fig. 2 is a diagram of the time course of the coil current of a valve to be calibrated.

In Fig. 1, tandem master cylinder 5 is connected to hydraulic unit 6 (HCU) of an electronic vehicle brake system. Electronic unit 7 (ECU) comprises a microprocessor / controllerystem with which the actuators and sensors contained in the valve block can be electronically controlled or measured. Hydraulic unit 6 comprises two brake circuits I and II. Furthermore, each of the brake circuits comprises two wheel pressure circuits (A, B or C, D), each with one inlet 3 or 3 'and one outlet valve 4 or 4'. The electronics of the ECU 7 comprise a multi-channel current regulator, which allows independent regulation of the currents through the coils of the valves 2, 2 '(isolation valves) and the inlet valves 3, 3'. Reference numerals 8 and 8 'denote normally closed electronic switching valves. In leading to the master cylinder 5 hydraulic line 8 is a Input pressure sensor 9. The illustrated brake system does not include any other pressure sensors in the wheel pressure circuits themselves. Pump 1 or 1 'can be used for independent pressure build-up, for example in ASR or ESP cases. When pump 1 is switched on, this pressure volume promotes in the direction of line 13. Due to the construction of the pump, the pressure at the outlet of the pump pulsates in a dependent on the structure of the hydraulic components pressure range.

When carrying out the calibration procedure, pump 1 is switched on to generate pressure pulsations on the valve to be calibrated. The calibration will be described below using the inlet valve 3 as an example. Calibration of other A / D valves, such as the isolation valve 2, can be done analogously. As a result of the pressure pulsations occurring during the delivery of pressure medium by means of the hydraulic pump, a periodic differential pressure is produced at inlet valve 3, which in the case of a completely closed inlet valve does not necessarily lead to an opening of the inlet valve. Only when the current through the coil of the isolation valve, for example, ramped lowered, resulting in a suitable current range periodic plunger movements. The plunger movements occur especially in the area of the balance of forces between the spring force of the return spring and the magnetic force of the valve spool. The calibration measurement to be carried out here for a differential pressure of 0 bar is conveniently carried out in a state of the hydraulic system in which the pressure in line 12 is also in the range of the atmospheric pressure.

The curves in FIG. 2 represent the time profile of the valve coil current of the inlet valve 3. The number of recorded measured values is plotted on the x-axis of the diagram. The x-axis can also be understood as a time axis since the measuring points were recorded at regular, constant intervals. The y-axis represents the current which is measured in the current regulator at the flow channel associated with the inlet valve 3.

During calibration, first pump 1 is switched on and separating valve 2 is acted upon by a current which corresponds to an opening pressure of about 3 bar. The pressure pulsations of pump 1 pass via line 13 to the separating valve 2 and are reflected there. A portion of the pumped by pump 1 hydraulic fluid can equally escape through valve 2, so that the average pressure in line 13 does not increase much above 0 bar (about 0 to 3 bar). The amplified pressure pulsations then reach the side of intake valve 3 facing the pump.

At the beginning of the calibration routine, valve 3 is first energized with almost the full current and thus substantially completely closed. Since no pressure prevails on the side facing the wheel cylinder, a pulsating pressure difference builds up on valve 3. Now, according to a ramp, the setpoint value for the coil current of valve 3 is reduced. The pressure pulsations are still insufficient to cause the plunger of valve 3 to move. Meanwhile, the current curve of valve 3 within the electronics unit is regularly measured and stored at short, equidistant intervals (n measuring points). The measured current values are plotted in FIG. 2 as curve 15. Since the PWM current regulator oscillates slightly, current pulsations with a comparatively small amplitude of approximately 10 measuring units can be recognized. While further measuring points are being recorded, the offset current (setpoint current) in valve coil 3 is slowly reduced in a ramp. In a certain current range where the valve stem of valve 3 is pressurized by the pressure Pulsations is movable, changes the recorded current curve. Curve 16 shows the course of the coil current in the steady state and know an amplitude of over 80 units of measurement. For purposes of illustration, the curve is in the same range of points as curve 15. However, these are current values measured at a later time. The current range of the offset current, in which the current curve with increased amplitude can be seen, is used as opening current of the valve at a pressure difference of about 0 bar. The calibration process for valve 3 is completed.

The calibration method described above allows a valve calibration in the motor vehicle. A calibration of the valves in the factory or at the motor vehicle manufacturer can be advantageously eliminated. It is particularly expedient if the calibration method described above is carried out in the wake of the brake system after switching off the ignition or while driving in suitable situations. A particularly suitable situation is given in particular when the vehicle is currently executing an acceleration process. Particularly preferably, the method is configured such that a termination or interruption of the calibration process takes place in the event of an inappropriate driving situation. In these non-suitable driving situations, proper functioning of the brake system has the highest priority. The calibration value, which was determined for a pressure difference of 0 bar, can preferably be used to correct an already stored opening flow characteristic for the valve.

Claims

claims

A method of calibrating an electromagnetic valve in an electronically controlled pressure regulating device, characterized in that the differential pressure prevailing at the valve to be calibrated is periodically modulated and that the electrical signal applied to the valve spool of the valve, in particular the electrical induction signal and / or or the coil current profile and / or the voltage curve is evaluated at the valve coil or at an additional measuring coil for calibration.

2. The method according to claim 1, characterized in that the valve coil is acted upon during the calibration with an offset current.

3. The method according to claim 2, characterized in that the valve coil current is adjusted by means of a current regulator to a predetermined desired value.

4. The method according to claim 3, characterized in that is evaluated for calibration of the modulated by the valve movement control value and / or the actual value of the current controller.

5. The method according to at least one of claims 1 to 4, characterized in that a calibration of the valve by measuring the opening or closing current at a differential pressure in the vicinity of 0 bar is measured.

6. The method according to claim 5, characterized in that during the calibration of the valve coil current for Er- increase or decrease of the switching point of the valve is detected and the switching point of the valve is determined by a change in the measured electrical signal to the valve.

7. The method according to claim 5 or 6, characterized in that the opening or closing current value obtained with the calibration method is corrected in such a way that it reproduces the exact value for a pressure difference of 0 bar within the scope of the measuring accuracy.

8. The method according to at least one of claims 1 to 7, characterized in that the periodic differential pressure is caused by acting on the valve, promotional hydraulic pump.

9. The method according to claim 8, characterized in that the exiting on the delivery side of the hydraulic pump conveying means, which acts on the valve, at least partially from the circle in which the pressure pulses, can escape.

10. The method according to claim 9, characterized in that the escape of the conveying means is made possible by a partially opened further electromagnetic valve.

11. The method according to at least one of claims 1 to 10, characterized in that an isolation valve or an intake valve of an electric brake control unit is calibrated.

12. The method according to at least one of claims 1 to 11, characterized in that to amplify the Ampli Tude the differential pressure change in the device already existing components are used.

13. The method according to claim 12, characterized in that for the gain in the case of calibration of the inlet valve, the separating valve is partially opened or in the case of calibration of the separating valve, the inlet valve is partially opened.

14. The method according to at least one of claims 1 to 13, characterized in that the calibration is performed automatically by the device after installation of the pressure control device in a Nutzanwendung without external pressurization.

15. The method according to at least one of claims 1 to 14, characterized in that the valve opening or - closing point for the calibration by evaluation of the oscillation signal of the coil current curve is determined.

16. Electronically controlled motor vehicle brake pressure control device with at least one ABS control program, in particular also an ESP control program, comprising a pressure generating means (5) with which the driver request dependent pressure means via pressure lines in a hydraulic unit (6) can be controlled, with isolation valves (2, 2 ' ) for separating the wheel pressure circuits (A .... D) from the pressure generating means (5) and inlet valves (3,3 ') which are hydraulically connected to the isolation valves and the wheel pressure circuits, further comprising means for an active pressure build-up (8, 8'). , 1, 1 '), characterized in that the electronic control of the device is arranged so that this if necessary, a method according to at least one of claims 1 to 14 can perform.

17. The apparatus according to claim 15, characterized in that the modulation of the differential pressure by pressure modulation with the pressure building means (8, 8 ', 1, 1') takes place.

18. Device according to claim 15 or 16, characterized in that the valve to be calibrated according to the method is an inlet valve of a wheel brake cylinder or an isolation valve which decouples the admission pressure applied by the driver from the area of the active pressure buildup.

19. The device according to at least one of claims 15 to 17, characterized in that the current control of at least a portion of the valves by means of a PWM controller takes place.