Method for determining a position of an armature of an electromagnetic valve

Abstract

The invention relates to a method for determining a position of an armature (10) of an electromagnetic valve (12) having two self-holding end positions, the method having the features of claim 1.

Description

[0001] R.414682

[0002] - 1 -

[0003] Description

[0004] title

[0005] Method for determining the position of an armature of an electromagnetic valve

[0006] State of the art

[0007] The invention relates to a method for determining the position of an armature of an electromagnetic valve with two self-maintaining end positions, comprising the features of claim 1.

[0008] In many applications with electromagnetically actuated switching valves, determining the valve's switching position is of interest. This can be achieved by detecting the position of a valve armature that moves within a solenoid coil. The inherent sensor properties of the solenoid coil of the electromagnetic valve can be used for this purpose.

[0009] DE 102019135209 A1 describes a method in which the magnetic coil is subjected to a pulse-width modulated voltage pulse and the resulting voltage across the magnetic coil is measured. The position of the armature can be deduced from the measured voltage.

[0010] A disadvantage is that generating the pulse-width modulated voltage pulse and measuring the voltage requires a separate measurement and evaluation circuit from the magnet drive. Furthermore, due to the dynamic nature of the signals used, high-quality data acquisition is necessary. Both of these aspects increase costs. R.414682

[0011] - 2 -

[0012] Disclosure of the invention

[0013] According to the invention, a method for determining the position of an armature of an electromagnetic valve with two self-holding end positions is proposed. The method comprises the following steps:

[0014] Conducting a preparation phase followed by a measurement phase. The preparation phase comprises the following steps:

[0015] Applying a probe current at a first point in time.

[0016] Waiting for an initial waiting period with the probe current applied until a second point in time.

[0017] Applying a starting current by reducing the probing current at the second time.

[0018] Waiting for a second waiting period with the starting current applied until a third point in time.

[0019] The measurement phase includes the following steps:

[0020] Applying the probe current at the third time point.

[0021] Evaluating a step response.

[0022] Thus, switching position detection of a switching valve with two self-holding end positions, as used, for example, in the thermal management systems of battery-electric vehicles, can be implemented using simple means. Additional electronic hardware is not required. Furthermore, the measurement process is not based on a pulse-width modulated signal response, which would require high-resolution sampling of the generated electrical response signals, but rather evaluates the slow, average current profile of a target current step response of the solenoid coil. The solenoid coil control, measurement data acquisition, and evaluation can therefore be carried out using a cost-effective, freely programmable R.414682.

[0023] - 3 -

[0024] Standard control modules can be used. Switch position detection can be performed with the power stage, control, and evaluation electronics already required for operating the solenoid coil during pauses in the coil's operation, using low currents, slow signals, and minimal signal acquisition and evaluation requirements. The preparation and / or measurement phase can be carried out within a few hundred milliseconds.

[0025] Electromagnetic valves typically have an inductance that depends on the applied current and the armature stroke (or the working air gap). For high magnetic currents, the inductance of the valve's solenoid coil depends only slightly on the armature stroke. This makes armature stroke detection very difficult at high magnetic currents. For low currents, the inductance depends strongly on the armature stroke. Therefore, the smallest possible currents can be used for position detection, as this provides the greatest useful signal spread. The solenoid coil can thus (only) be driven with low currents. Low currents are sufficient, in particular, to reliably move the unloaded armature from any initial position to a stop position.

[0026] The current response, or step response, of the magnetic coil can contain two spectral components. Firstly, the response dominated by eddy currents, occurring within a few milliseconds, and secondly, a current waveform dominated by the inductance and ohmic resistance of the magnetic coil, exhibiting a dynamic range on the order of several multiples of 10 ms. In particular, only the slow (low-frequency) signal component can be used to determine the armature position.

[0027] With this (slow) signal component, it may be sufficient to capture the current signal at low sampling rates in the range of 800 Hz to 1200 Hz, especially 1000 Hz. This makes the use of cost-effective standard components for control feasible.

[0028] To reduce friction, the valve can be operated with current dithering during control. However, for the preparation and / or measurement phase, operation without superimposed current dithering may be advantageous, as this avoids measurement errors caused by the superimposed current dithering (R.414682).

[0029] - 4 - can. Performing the preparation phase and / or the measurement phase without current dithering also does not result in any disadvantage, since the armature does not move, especially during the measurement phase, and therefore no friction effects need to be minimized.

[0030] The procedure, and in particular the preparation phase and / or the measurement phase, can be carried out at freely selectable times during the rest phases (or operating breaks) of the valve.

[0031] According to a further development of the procedure, the following step can be performed when evaluating the step response:

[0032] Measuring the time until a predetermined current setpoint of the step response is reached.

[0033] This allows the evaluation of the step response to be implemented using simple means.

[0034] According to a further development of the procedure, the following step can be performed when evaluating the step response:

[0035] Evaluating (calculating or determining) an integral of the step response between the third time point and a fourth time point.

[0036] This allows the evaluation of the step response to be implemented using simple means.

[0037] According to a further development of the procedure, the process can include the following steps:

[0038] Repeated execution of the preparation phase and / or repeated execution of the measurement phase.

[0039] In particular, an average value can be calculated over several measurements. This can increase measurement reliability. R.414682

[0040] - 5 -

[0041] According to a further development of the procedure, the process can include the following steps:

[0042] Storing a voltage applied to the magnetic coil, in particular battery voltage, a current applied to the magnetic coil and / or a duty cycle at the second time.

[0043] Calculating the coil temperature of an electromagnetic valve based on the stored voltage (especially battery voltage), the stored current, and / or the stored duty cycle. The coil temperature refers specifically to the temperature of the solenoid coil.

[0044] This allows the coil temperature to be determined or calculated using simple means.

[0045] According to a further development of the procedure, the preparation phase can be carried out using current control. This can be implemented using a current controller.

[0046] This ensures that the touch current and / or the starting current can be achieved regardless of environmental conditions such as temperature and battery voltage.

[0047] According to a further development of the procedure, the measurement phase can be carried out in a current-controlled manner.

[0048] This allows, in particular, a controlled current jump to be applied to the magnetic coil.

[0049] According to a further development of the method, a duty cycle, a current applied to the magnetic coil 13, and / or a voltage applied to the magnetic coil 13 can be stored at the second time point and used to apply, in particular to start, the duty cycle current at the third time point. R.414682

[0050] - 6 -

[0051] This allows the probe current to be reliably controlled or started.

[0052] According to a further development of the procedure, the preparation phase and / or the measurement phase can be carried out dither-free. In other words, the preparation phase and / or the measurement phase can be carried out without dithering.

[0053] According to a further development of the method, the probing current can be selected such that the magnetic force acting on the armature due to the probing current is large enough to move the armature to a stop position and is smaller than a counterforce, e.g., the spring force of a spring, of the electromagnetic valve. The probing current can, for example, be 300 mA (milliamperes).

[0054] This allows a switching point measurement to be carried out without affecting the switching position of the valve.

[0055] Embodiments of the invention are explained below with reference to the accompanying drawings. These show:

[0056] Figure 1 shows two schematic sectional views of an electromagnetic valve.

[0057] Figure 2 shows a flow diagram during a preparation phase and a measurement phase according to a first embodiment.

[0058] Figure 3 shows a graph of time versus coil temperature and

[0059] Figure 4 shows a flow diagram during the preparation phase and the measurement phase according to a second embodiment.

[0060] Figure 1 shows two schematic sectional views of an electromagnetic valve 12. The valve 12 has a solenoid coil 13 and an armature 10 movable within the solenoid coil 13. The valve 12 has two R.414682

[0061] - 7 - self-maintaining end positions. In this case, valve 12 is designed as a cooling oil valve and is arranged in a receiving bore.

[0062] In Figure 1 (top), the valve 12 is shown in a first self-maintaining end position. This is the closed position. In other words, the valve 12 is closed, and flow through the valve 12 is blocked by a valve disc 15. The valve disc 15 is held in the closed position against a preload force or spring force of a spring 17 of the valve 12 (indicated by an arrow) by means of the hydrostatic pressure acting on the valve disc 15. The solenoid coil 13 is de-energized, and the armature 10 assumes a random position within its possible range of motion. The range of motion of the armature 10 is limited to the left in Figure 1 by a structural stop and to the right in Figure 1 by an actuating pin 19 of the valve disc 15.

[0063] In Figure 1 below, the valve 12 is shown in a second self-holding end position. This is the open position. In other words, the valve 12 is open and flow through the valve 12 is possible. The valve disc 15 is held in the open position shown by the spring force or the preload force of the spring 17 (indicated by an arrow). The solenoid coil

[0064] 13 is de-energized and the armature 10 is positively engaged against the right stop formed by the actuating pin 19.

[0065] The process includes the following steps:

[0066] Conducting a preparation phase 14 and one linked to the preparation phase

[0067] 14 subsequent measurement phase 16.

[0068] Figure 2 shows a current diagram during the preparation phase 14 and the measurement phase 16 according to a first embodiment. The current intensity is plotted against time.

[0069] Preparation phase 14 includes the following steps:

[0070] Applying a probe current 18 at a first time point 20. R.414682

[0071] - 8 -

[0072] Waiting for an initial waiting period 22 with applied probe current 18 until a second time point 24.

[0073] Applying a starting current 26 by reducing the probe current 18 at the second time 24.

[0074] Waiting for a second waiting period 28 with applied starting current 26 until a third time 30.

[0075] Measurement phase 16 includes the following steps:

[0076] Applying the probe current 18 at the third time point 30,

[0077] Evaluating a step response 32 of the magnetic coil 13.

[0078] When evaluating the step response 32, the following step can be performed:

[0079] Measuring a time 34 until a predetermined current setpoint 36 of the step response 32 is reached.

[0080] Preparation phase 14 and / or measurement phase 16 can be performed multiple times.

[0081] The preparation phase 14 can be current-controlled (e.g. by means of a current controller) and / or the measurement phase 16 can be carried out in a current-controlled manner.

[0082] Preparation phase 14 and / or measurement phase 16 can be performed without dither.

[0083] At the first time point 20, the valve 12 can be in the open or closed position (see Figure 1). The solenoid coil 13 can be de-energized. It is also conceivable that a (small) current can flow before the first time point 20. The armature 10 is in a random position within its range of motion. At the first time point 20, an R.414682

[0084] - 9 -

[0085] The current setpoint step is applied to the probing current 18 on the magnetic coil 13.

[0086] An electric current can flow through the solenoid 13, generating a magnetic force that moves the armature 10 towards the actuating pin 19 or the valve disc 15. The armature 10 will perform a substantially undamped movement until it encounters the actuating pin 19 in its current position. Due to the unknown starting position of the armature 10 and the unknown position of the right-hand stop in Figure 1, determined by the current end position of the actuating pin 19, the current flow through the solenoid 13 is unpredictable. A possible current flow is sketched in Figure 2. Because of the described uncertainties and the influence of the current regulator, this current flow over time is unsuitable for position detection of the armature 10.

[0087] At the second point in time 24, the armature 10 is positively engaged with the actuating pin 19 in its respective position. Depending on the switching position of the valve 12 (open position or closed position), the armature 10 is therefore now in a position as shown in Figure 1 above or Figure 1 below.

[0088] The probing current 18, applied until the second time point 24, can be selected such that the magnetic force acting on the armature 10 due to the probing current 18 is large enough to move the armature 10 into a stop position and is less than the preload force (or spring force) of the spring 17 of the electromagnetic valve 12. The probing current 18 can, for example, be 300 mA. This ensures that the switching position of the valve 12 is not changed or influenced during the position detection of the armature 10.

[0089] During the first waiting period 22, the valve 12 can be in a stationary state and the solenoid coil 13 can be energized via the current regulator with the probe current 18.

[0090] In particular, due to the use of the current regulator in preparation phase 14, in accordance with the prevailing R.414682

[0091] - 10 -

[0092] Boundary conditions, such as ambient temperature and applied battery voltage, require a duty cycle to be selected that reliably sets the probe current. The duty cycle, a current applied to the solenoid 13, and / or a voltage applied to the solenoid 13 can be stored upon reaching the second time point 24 and (subsequently) used to reliably apply or restart the probe current 18 at the third time point 30 for the subsequent position measurement of the armature 10. This ensures that, for all ambient conditions, the desired probe current 18 for the following measurement phase 16 can be reliably set even without a current controller by switching to the duty cycle.

[0093] At the second time point 24, the battery voltage can also be stored. This can serve as a basis for calculating the coil temperature of the electromagnetic valve 12.

[0094] At the second time point 24, a current-controlled jump to the starting current 26 can occur, and the attainment of a steady state can be awaited (in this case, until the third time point 30). Since the valve 12 has self-holding end positions as shown in Figure 1 (top) and Figure 1 (bottom), it can be ensured that even with the starting current 26 being reduced compared to the probing current 18, the armature 10 is securely held against the actuating pin 19 by the magnetic force. The measurement can thus be prepared, and the measurement phase 16 can be started.

[0095] At the third time point 30, the current controller can be switched off and the current duty cycle can be switched to the stored duty cycle. Since the armature 10 is firmly supported against the actuating pin 19 and the current controller is switched off, the resulting current step is determined only by the time constant T of the solenoid 13 with T = L / R, where L is the inductance and R is the ohmic resistance of the solenoid 13. As explained above, the inductance L provides a unique characteristic for the armature stroke or armature position. This current step is therefore very well suited to determining the current armature position based on the time course of the step response 32, which is determined by the time constant T. Reaching or exceeding the current setpoint 36 represents the measurement time point 31. The time 34 until the R.414682

[0096] - 11 - When the predefined current setpoint 36 of the step response 32 is reached, this represents the desired measured value and contains the information about the armature position. This allows the measurement phase 16 to be ended and the magnetic coil 13 to be de-energized.

[0097] The measured time 34 depends on the stroke-dependent inductance L via T, as described above. However, it also depends on the current coil temperature via the temperature-dependent coil resistance R.

[0098] Figure 3 shows a diagram of the measured time 34 versus the coil temperature. A first characteristic curve 33 and a second characteristic curve 35 are depicted. The first characteristic curve 33 represents the measured time 34 as a function of the coil temperature for the closed position of the valve 12. The second characteristic curve 35 represents the measured time 34 as a function of the coil temperature for the open position of the valve 12. The first characteristic curve 33 lies above a time limit 37, and the second characteristic curve 35 lies below the time limit 37. The two extreme positions of the armature stroke, or the position of the armature 10, can now be determined by simply checking whether the measured time 34 is greater or less than the time limit 37. This allows a decision to be made as to whether the valve 12 is in the closed position (first characteristic curve 33) or in the open position (second characteristic curve 35).

[0099] The first and / or second characteristic curves 33, 35 can be easily determined by measurement. The time limit value 37 can thus be determined and, for example, stored in a control unit.

[0100] Alternatively or additionally, a bilinear function can be described based on the first and / or the second characteristic curve 33, 35. The approximately linear relationship between the measured time 34 and the coil temperature (see Figure 3) can then be described by a linear equation: t = a + b*^, R.414682

[0101] - 12 - where t is the measured time, 34 and 3 is the coil temperature. The parameters a and b of the linear equation are assumed to be linearly dependent on the armature stroke h (or the armature position):

[0102] Therefore, for t (the measured time 34) the equation is: t = (a11 + a12 * h) + (b11 + b12 * h) * -9.

[0103] The coefficients a11, a12, b11 and b12 are determined based on the first and / or the second characteristic curve 33, 35. The armature stroke h is then calculated as: h = (t - (a11 + b11 * S)) / (a12 + b12 * S)

[0104] The coefficients a11, a12, b11, and b12 can be stored in the control unit. The coil temperature can be roughly approximated as equal to the valve temperature (system temperature) or, for higher positional accuracy requirements and / or unfavorable characteristic curves 33, 35, calculated using the voltage (e.g., battery voltage), current, and / or duty cycle measured at the second time point 24 and the known touch current 18 via the relationship between the coil resistance and temperature: d = 9ref + 1 / a * (R& - R2O) / R2O R» =(Uon * dc + Uoff * (1-dc) ) / leff where 3 is the desired coil temperature, a is a temperature coefficient of the ohmic resistance of copper, 9 ref Reference temperature for the magnet coil resistance (typically 20°C), R20 Ohmic magnet coil resistance at the reference temperature, U on Magnet supply voltage at the second time point 24, U O ff Zener voltage of the PWM, dc duty cycle at the second time point 24 and l e ff the probing current is 18. R.414682

[0105] - 13 -

[0106] Figure 4 shows a flow diagram during the preparation phase 14 and the measurement phase 16 according to a second embodiment. The second embodiment differs from the first embodiment in the following ways:

[0107] When evaluating the step response 32, the following step can be performed:

[0108] Evaluating (calculating or determining) an integral of the step response 32 between the third time 30 and a fourth time 38.

[0109] Instead of measuring the time 34 until the target current value 36 is reached, an integral Int is calculated as a measure for the current armature stroke position: where the third time point is 30, t2, the fourth time point is 38, I mag the step response 32 and I start The starting current is 26. Here, t2 (the fourth time point 38) can be chosen such that the integration time t2- This corresponds approximately to 1.5 times the maximum expected time constant T=L / R (see above). This is the time constant that results at the lowest temperature and the largest armature stroke (or smallest working air gap).

[0110] Due to the integration, measurement errors can be averaged out, thus achieving higher measurement accuracy.

[0111] Analogous to the first embodiment described above, characteristic curves also result here that depend on the armature stroke or armature position and the coil temperature. Thus, a bilinear function can be represented analogously to the explanations above. The current armature position can be determined from the corresponding equation h = (ln - (a11 + b11 * •&)) / (a12 + b12 * -9), where h is the armature stroke, int is the integral described above, 3 is the coil temperature, and a11, a12, b11, and b12 are coefficients. The coefficients a11, a12, b11, and b12 can be derived from the values ​​of the armature stroke and the coil temperature.

[0112] - 14 -

[0113] The coil temperature-dependent characteristic curves can be determined, whereby the coil temperature can be handled or determined as described above (for the first embodiment).

Claims

R.414682 - 15 - Claims 1. Method for determining a position of an armature (10) of an electromagnetic valve (12) with two self-maintaining end positions comprising the steps: Performing a preparation phase (14) and a measurement phase (16) following the preparation phase (14), wherein the preparation phase (14) comprises the following steps: Applying a probe current (18) at a first time point (20); Waiting for a first waiting period (22) with applied probe current (18) until a second time point (24); Applying a starting current (26) by reducing the probing current (18) at the second time (24); Waiting for a second waiting period (28) with applied starting current (26) until a third time point (30); wherein the measurement phase (16) comprises the steps: Applying the probe current (18) at the third time point (30); evaluating a step response (32).

2. Method according to claim 1, characterized in that the following step is performed when evaluating the step response (32): Measuring a time (34) until a predetermined current setpoint (36) of the step response (32) is reached.

3. Method according to claim 1, characterized in that the following step is performed when evaluating the step response (32): Evaluating an integral of the step response (32) between the third time (30) and a fourth time (38).

4. A method according to any of the preceding claims, characterized by the steps: Repeated execution of the preparation phase (14) and / or R.414682 - 16 - Repeated execution of the measurement phase (16).

5. A method according to any of the preceding claims, characterized by the steps: Storing a voltage applied to the magnetic coil (13), in particular battery voltage, a current applied to the magnetic coil (13) and / or a duty cycle at the second time (24); Calculating the coil temperature of the electromagnetic valve (12) based on the stored voltage, the stored current and / or the stored duty cycle.

6. Method according to one of the preceding claims, characterized in that the preparation phase (14) is carried out under current control.

7. Method according to one of the preceding claims, characterized in that the measurement phase (16) is carried out by current control.

8. Method according to one of the preceding claims, characterized in that a duty cycle, a current applied to the magnetic coil (13) and / or a voltage applied to the magnetic coil (13) are stored when the second time (24) is reached and are used to apply, in particular to start, the duty cycle current (18) at the third time (30).

9. Method according to one of the preceding claims, characterized in that the preparation phase (14) and / or the measurement phase (16) be carried out dither-free.

10. Method according to one of the preceding claims, characterized in that the probing current (18) is selected such that the magnetic force acting on the armature (10) due to the probing current (18) is large enough to move the armature (10) into a stop position and is smaller than a counterforce, in particular a spring force of a spring. (17), of the electromagnetic valve (12).

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