DE102016200118A1 - Method for determining the opening flow of an analog controlled valve and pressure control device - Google Patents

Abstract

A method of determining an opening or closing current of an electromagnetic analog controlled valve having a valve spool and a tappet in an electronically controlled pressure regulator, wherein a family of curves of current waveforms (1,2) are sensed, with no differential pressure prevailing on the valve, and wherein each Current profile (1, 2) from a data set of the current flowing through the valve coil current (I _V ) as a function of time (t) and that the opening or closing current is determined by evaluating the family of curves of measured current waveforms.

Description

The invention relates to a method for determining an opening or closing current of an electromagnetic, analog-controlled valve with a valve spool and a valve tappet in an electronically controlled pressure control device, and a pressure control device, in particular a brake pressure control device of a motor vehicle, comprising a hydraulic control unit, which at least one analog controlled Valve comprises, as well as an electronic control device, by means of which a valve associated with the valve coil is driven and which includes means for measuring a current flowing through the valve coil current.

To compensate for production-related tolerances must be made to maintain the control quality, for example, in the printing position in brake control systems, a calibration of the analog valves to produce a control chain economically.

From the DE 10 2006 055 767 A1 For example, a method of valve calibration in a brake pressure control system is known which relies on pressure build-up by the driver and measurements by means of a pressure sensor.

From the EP 1 876 078 A2 a method (so-called Tappet Position Monitoring, TPM) is known in which the opening current is determined by the inductance or the magnetic resistance of the circuit is determined by means of a built-in addition to the drive coil measuring coil and thereby conclusions about the position of the plunger are drawn ,

From the DE 10 2007 010 514 A1 For example, a method for calibrating an electromagnetic valve is known in which a differential pressure prevailing at the valve is periodically modulated and the signal applied to the valve coil during the modulation is evaluated for calibration.

Such methods have the disadvantage that additional components (for example measuring coils) are needed and / or that an external operation must be performed (for example actuation of a brake pedal), so that they can not be performed automatically. In addition, the known methods for certain valve designs, for example heavily damped valves, do not yield any usable results.

Object of the present invention is to provide a method and a pressure control device which / which allows a determination of an opening or closing current precise and largely automated, without the use of additional components or complex external control.

This object is achieved by a method according to claim 1, and a pressure control device according to claim 16.

Advantageous embodiments of the invention are the subject of the dependent claims.

The invention is based on the idea that on the basis of a family of curves of measured current waveforms in a valve coil of an electromagnetic, analog controlled valve, where no differential pressure prevails, conclusions are drawn in an electronically controlled pressure control device on the opening or closing current of the valve spool and this opening or closing current is thus determined.

Advantageously, the determination of the opening or closing current without applying a hydraulic pressure.

According to the invention, the pressure control device includes a hydraulic control unit, which comprises at least the valve for which the determination of the opening or closing current is to be performed, and an electronic control device, by means of which a valve spool belonging to the valve is actuated. The electronic control device includes means for measuring a current flowing through the valve spool.

Preferably, the pressure control device is a brake pressure control device in a motor vehicle.

It is well known that when a first voltage is applied to a coil, whereby a first current flows through the coil and then the voltage is increased to a second, higher value, the current through the inductance of the coil continuously with time to one second current value increases. The course is characteristic of the inductance of the coil. A corresponding decay is observed at a lower second voltage level.

If the coil is a valve coil whose magnetic field moves a valve stem, the position of the stem has an influence on the inductance of the coil. As has now been recognized, this effect can be used to determine from current waveforms on the coil caused by a transition from a first applied voltage to a second applied voltage, the current values at which the plunger is open or closed ,

Preferably, the procedure is such that different current initial values are set for each of the plurality of current profiles. Advantageously, a plurality of current initial values are predetermined and a temporal current profile is measured for each current initial value.

Preferably, at the beginning of the measurement of each current waveform, a first voltage is applied to the valve coil and waited until an approximately constant first current value has been set as the current initial value.

After the first current value has stabilized as the current starting value, a current profile is preferably measured by applying a second voltage and measuring the current flowing through the coil at fixed times after application of the second voltage.

Preferably, the current is measured until a second approximately constant current value has been established.

The current measured values result in a data set which represents the temporal current profile. The procedure is repeated for each predetermined current starting value, so that a family of curves of current profiles with different initial current values results.

Advantageously, the same value for the second voltage is used for each current profile.

As has now been recognized, the shape of the current waveform depends largely on the position in which the plunger is at the beginning of the current flow and whether the plunger moves during the measurement of the current profile. In particular, the movement of the plunger and optionally observed Nachschwingeffekte and / or impact effects lead to a characteristic course.

For each current profile, a conclusion about the position of the plunger at the beginning of the current profile is preferably drawn from the data set of the current profile and from this it is determined whether the current initial value corresponds to an open or closed position of the plunger. Each current initial value is assigned the determined position of the plunger at the beginning of the associated current profile.

It is preferred to identify that current value at which the valve tappet changes position, the so-called opening current or closing current. The opening current is defined for normally open valves as the current value which is just enough to keep the valve closed. A corresponding definition applies to the closing current for normally closed valves.

Preferably, the smallest current initial value whose assigned position does not correspond to the de-energized position of the valve tappet is selected from the current starting values of the measured current profiles. From this selected current starting value, the opening or closing current of the valve is determined. Preferably, the determined opening or closing current corresponds to the selected current starting value.

In a preferred embodiment of the invention, the position of the plunger is determined at the beginning of the current profile by means of a comparison of the current profile with a predetermined reference curve.

Preferably, a characteristic value is determined from each measured current profile by means of suitable calculation methods. The characteristic values of the current curves for different current initial values result in a value curve, by means of which it is possible to determine the opening or closing current of the valve. Two variants for determining characteristic values from the current curves are explained below.

In a preferred embodiment of the invention, the characteristic value of each current profile at the beginning of the current profile is determined by means of a comparison of the current profile with a predetermined reference curve.

Particularly preferably, the reference curve is determined by measuring a first current profile with a first current starting value and from this a reference curve is generated. Advantageously, the first current starting value of the first current profile is chosen so that, starting from the construction of the valve, it can be assumed with great certainty that the valve is in a state which does not correspond to the de-energized state, i. closed in the case of a normally open valve, or open in the case of a normally closed valve. Alternatively, the reference curve is fixed and read from a memory.

Most preferably, the reference curve is generated by approximating the first current waveform with an analytic equation. The reference curve then corresponds to the curve described by the equation and is described by the parameters of the equation.

Preferably, a deviation measure between the reference curve and calculated the current profile and used as a characteristic value for the current waveform. For example, the least square error between the reference curve and the current waveform is used as a measure of the deviation. The deviation measures of the different current profiles yield a value curve as a function of the initial values of the current characteristics.

Preferably, the opening or closing current is determined on the basis of the value curve of the deviation measures.

Most preferably, the opening or closing current is the smallest current initial value, for the course of the current of which the calculated deviation measure lies below a predetermined limit value.

In another preferred embodiment of the invention, the position of the plunger at the beginning of the current profile by means of the evaluation of a current value at a specified time after the start of the current waveform is determined (characteristic current value). Particularly preferably, the characteristic current value is compared with a reference value, and the characteristic value of the current characteristic is determined from the difference between the two values.

Preferably, a characteristic curve of the characteristic current values is generated as a function of the current initial values, and the opening or closing current is determined from the course of the values.

Particularly preferably, the time at which the characteristic current value is determined, of the order of a millisecond.

Preferably, the opening or closing current value determined by this method is suitably used for calculating the characteristic of the valve.

Preferably, the valve is a normally open valve and the current waveform is a current increase curve.

Particularly preferably, the valve is an isolation valve or an intake valve of an electronically controlled brake circuit, which is arranged in a hydraulic connection between a master cylinder and a wheel brake.

Advantageously, the process is carried out at the end of the production chain of the pressure control device. Likewise, the method can be carried out when a pressure control device in its place of use, in particular as a brake pressure control device in a motor vehicle, is replaced.

The method is preferably triggered by a control by a connected to the pressure control device diagnostic device. Subsequently, the method is preferably carried out without further external control by the control device of the pressure control device.

The determined value of the opening or closing current is advantageously stored.

In a preferred embodiment of the invention, an expected range of values for the opening or closing current is specified. The range of values is determined by the design characteristics of the valve and valve requirements. If a determined opening or closing current is outside this expectation range, the method is repeated if the faulty measurement is suspected and / or the valve is rejected as unsuitable for use.

Furthermore, the invention relates to a pressure control device, in particular a brake pressure control device of a motor vehicle, comprising a hydraulic control unit, which comprises at least one analog controlled valve, and an electronic control device, by means of which a valve spool associated with the valve is driven and which means for measuring a flowing through the valve spool Contains stream, wherein in this a method according to one of the preceding claims for determining the opening or closing current of the valve is performed.

An embodiment of the invention will be explained in more detail with reference to three drawings. In it show in a highly schematic representation:

1 two exemplary temporal current courses,

2 : an exemplary value curve of evaluated current rise curves,

3 : an exemplary temporal current curve, suitable for evaluation at predetermined times.

In 1 two exemplary temporal current curves are shown, selected from the plurality of current curves, from which, for example, the opening current of a valve can be determined. The example shows rising current curves 1 . 2 for a normally open analog controlled valve. In this case, the time t is plotted on the x-axis, while on the y-axis the measured, through the valve coil flowing current I _{V is} applied. The illustrated curves represent current waveforms with different current initial values, but are shifted for presentation and comparison purposes compared to the measured raw data so that the current initial values are exactly on top of each other.

course 2 shows a typical example current flow in the event that the valve was closed at the beginning of the current flow. Therefore, the increase in the current does not produce movement of the valve stem, so that the course is determined solely by the inductance of the valve spool with closed plunger. This causes the relatively smooth, monotonically increasing course.

course 1 on the other hand, shows a typical example of a course of current in the event that the valve was initially open and closes during the measurement of the current profile. The current course 1 has one of course 2 clearly different characteristic shape, which is not monotonically increasing in the example shown. The course at the beginning is steeper and there are several oscillations visible in the course. This is partly due to the different inductance of the valve spool depending on the position of the valve stem, on the other hand by vibration phenomena that occur during a movement of the valve stem.

For example, a reference curve is generated by measuring a first current waveform with a first current seed. The first current starting value is selected so that, based on the design characteristics of the valve, it can be assumed that the valve is closed by applying the first current initial value.

For example, the plot is approximated with an analytic equation, for example, with a second or third order polynomial. By such a polynomial the course can be approximated sufficiently accurately. The specific parameters of the analytic equation are stored. Using an analytic equation has the advantage of saving storage space and speeding up the calculation.

Subsequently, a plurality of further current waveforms is measured. In this case, a different initial current value I _{A is} set at the beginning of each current waveform. The current initial values used are specified. After setting the respective current initial value, a higher voltage is applied so that the current flowing through the valve coil changes. At predetermined times, measured values of the current flowing through the valve coil are measured. The measured values yield a data record of a temporal current profile. The current is then lowered to the next current starting value, so that a further course can be measured. The measured current waveforms represent a family of curves of current curves with different initial current values.

The measured current profiles are now compared in a preferred embodiment in each case with the reference curve.

In a particularly preferred embodiment, this is carried out by determining in each case a deviation measure χ between the reference curve and each measured current profile. As the deviation measure χ, for example, the least square error can be used.

In 2 is the result of the calculation of the deviation measure χ (in this embodiment, the smallest quadratic error) between the reference curve and current waveforms with different current initial values I _A shown.

In this case, the respective current initial value I _{A is} plotted on the x-axis, and the calculated deviation amount χ between the reference curve and the current profile which corresponds to the current initial value is plotted on the y-axis. An exemplary corresponding value curve is graphically through the course 7 shown.

The values are filtered by means of filtering methods known per se in order to eliminate the influence of measurement errors. An exemplary filtered course of the deviation measure χ is as a course 8th shown.

It can be seen that for current initial values below the opening current 9 having a current characteristic characteristic of an opening movement of the valve stem, the deviation amount χ is relatively high. The opening current can thus be recognized by the fact that the deviation measure χ is low.

In a preferred embodiment, a threshold for the deviation measure is set. The smallest current initial value I _A applies as the opening current whose calculated deviation measure χ is below the limit value.

In 3 an exemplary series of measurements with several measured current curves is shown. The time t is plotted on the x-axis, while the current measured values I _{V are} plotted on the y-axis. The line 12 represents the course of the measured current I _V over time t.

It is first a first current starting value 14 set. Thereafter, the voltage is increased, so that an increasing current flow 101 results until the current trend 101 a current end value 13 reached. Subsequently, the current I _V is lowered again and the procedure with the other current initial values 15 . 16 . 17 and 18 repeated. By way of example, thus, there are five current courses 101 - 105 with different current starting values 14 - 18 measured.

reference numeral 20 and 22 each time points, to each of which a current curve begins. timings 21 . 23 are each set after a fixed time interval after the start of a current waveform. At these times, a characteristic current value is in each case 24 . 25 measured.

From the characteristic current values of all current curves 101 - 105 becomes a course 26 generated. The history 26 represents the characteristic current values as a function of the corresponding current initial values I _A , 14 - 18 the current courses 101 - 105 , From this course, the opening current can be determined. If the current initial values I _A , 14 - 18 timed in ascending order, so can the course 26 also represent as a function of the time t and from the temporal representation to the dependence of the characteristic current values on the current initial values I _A , 14 - 18 draw conclusions. For example, the history is 26 then everywhere monotonously rising to one place. The last set current value 16 before the non-monotonically rising point, for example, is recognized as the opening current.

The determined opening current can now be stored and used as characteristic of the installed valve.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102006055767 A1 [0003]
• EP 1876078 A2 [0004]
• DE 102007010514 A1 [0005]

Claims (16)

Method for determining an opening or closing current of an electromagnetic, analog-controlled valve having a valve coil and a valve tappet in an electronically controlled pressure regulating device, characterized in that a family of curves of current profiles ( 1 . 2 . 101 - 105 ), wherein no differential pressure prevails at the valve, and wherein each current course ( 1 . 2 . 101 - 105 ) consists of a data set of the current flowing through the valve coil (I _V ) as a function of time (t) and that the opening or closing current is determined by evaluating the family of curves of measured current waveforms. Method according to claim 1, characterized in that each current course ( 1 . 2 . 101 - 105 ) is measured by applying a first predetermined voltage value to the valve coil, whereby a current initial value (I _A , 14 . 15 . 16 . 17 . 18 ) Sets, then a second voltage value is applied and from the application of the second voltage values measured current values (I _V) at predetermined times are measured and the measured current values (I _V) result in the data set (the current profile 1 . 2 . 101 - 105 ). Method according to claim 1 or 2, characterized in that a different initial current value (I _A , 14 . 15 . 16 . 17 . 18 ) for each current course ( 1 . 2 . 101 - 105 ) is impressed in the family of curves of current curves at the beginning of the respective current waveform on the valve spool. Method according to claim 3, characterized in that for each current course ( 1 . 2 . 101 - 105 ) a conclusion is drawn from the data record of the current flow to the position of the valve tappet at the beginning of the current profile, and that each current initial value (I _A , 14 . 15 . 16 . 17 . 18 ) the determined position of the valve stem at the beginning of the associated current waveform ( 1 . 2 . 101 - 105 ). Method according to claim 4, characterized in that the smallest current initial value ( 14 . 15 . 16 . 17 . 18 ) is determined, the associated position of the valve stem does not correspond to the de-energized position of the valve stem and from the opening current or closing current of the valve is determined. Method according to one of claims 4 or 5, characterized in that the position of the plunger at the beginning of each current waveform ( 1 . 2 . 101 - 105 ) by means of a comparison of the current profile ( 1 . 2 . 101 - 105 ) is determined with a predetermined reference curve. Method according to one of claims 3 to 6, characterized in that from each measured current waveform ( 1 . 2 . 101 - 105 ) in each case a characteristic value is determined, and the characteristic values of the current profiles ( 1 . 2 . 101 - 105 ) for the different current initial values (I _A , 14 . 15 . 16 . 17 . 18 ) a value course ( 7 . 8th . 26 ), by means of which the opening current or closing current of the valve is determined. Method according to Claim 7, characterized in that the characteristic value of each current profile ( 1 . 2 . 101 - 105 ) by means of a comparison of the current profile ( 1 . 2 . 101 - 105 ) is determined with a predetermined reference curve. A method according to claim 8, characterized in that the reference curve is determined by a first current waveform with a first current initial value (I _A ) is measured and from a reference curve is generated. A method according to claim 9, characterized in that the reference curve is generated by approximating the first current waveform with an analytic equation. Method according to one of claims 8 to 10, characterized in that for each current course ( 1 . 2 . 101 - 105 ) a deviation measure (χ) between the reference curve and the current profile ( 1 . 2 . 101 - 105 ), the calculated deviation measure (χ) being used as the characteristic value for the current profile. A method according to claim 11, characterized in that the opening current or closing current is the smallest current initial value, for the current flow ( 1 . 2 . 101 - 105 ) the calculated deviation measure (χ) is below a predetermined limit value. Method according to Claim 7, characterized in that the characteristic value of each current profile ( 101 - 105 ) by means of the evaluation of a current value at a given time ( 21 . 23 ) is determined after the beginning of the current flow. Method according to one of the preceding claims, characterized in that the valve is a normally open valve and the current waveform ( 1 . 2 . 101 - 105 ) is a current increase curve. Method according to one of the preceding claims, characterized in that the valve is an isolation valve or an inlet valve of an electronically controlled brake circuit, which is arranged in a hydraulic connection between a master cylinder and a wheel brake. Pressure control device, in particular a brake pressure control device of a motor vehicle, comprising a hydraulic control unit, which comprises at least one analog controlled valve, and an electronic control device, by means of which a valve spool belonging to the valve is controlled and which means for measuring a current flowing through the valve coil current, characterized in that in this method a method according to one of the preceding claims is carried out for determining the opening or closing flow of the valve.

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