PROCESS FOR SENSORLESS DETECTION OF STROKE EXECUTION IN A MAGNETIC PUMP

Abstract

A process for operating a pump, the pump having a conveying chamber for conveying a fluid, the pump having a displacement element, the displacement element delimiting the conveying chamber at least in sections, so that a change in the position or location of the displacement element causes a change in the volume of the conveying chamber, the pump having a drive, the drive having a coil through which an electric current is conductible, the coil having an ohmic resistance value R.sub.DC and an inductance L.sub.coil, the drive includes a pressure element and a coupling device, the pressure element and the coil being configured and arranged such that a magnetic field, generated by an electric current flowing in the coil causes a stroke movement of the pressure element along a longitudinal axis from an initial position P1 to an end position P2.

Claims

1-13. (canceled)

14. A process for operating a pump, wherein the pump has a conveying chamber for conveying a fluid, wherein the pump comprises a displacement element, wherein the displacement element delimits the conveying chamber at least in sections, so that a change in the position or location of the displacement element causes a change in the volume of the conveying chamber, wherein the pump comprises a drive, wherein the drive comprises a coil through which an electric current can be conducted, the coil having an ohmic resistance R.sub.DC and an inductance L.sub.coil, wherein the drive comprises a pressure element and a coupling device, wherein the pressure element and the coil are configured and arranged such that a magnetic field generated by an electric current flowing in the coil causes a stroke movement of the pressure element along a longitudinal axis from an initial position P1 to an end position P2, wherein the coupling device couples the pressure element to the displacement element such that an effected stroke movement of the pressure element causes a change of the position or the position of the displacement element, wherein the displacement element, the coupling device and the pressure element are configured and arranged such that the conveying chamber comprises a first volume when the pressure element is in the initial position P1 and the conveying chamber comprises a second volume when the pressure element is in the final position P2, the first volume being larger than the second volume, the process comprising a first cycle, the first cycle comprising the following steps according to a first alternative: A) Setting a desired current value I.sub.SOLL for the current flowing in the coil, B) applying a voltage U.sub.IN to the coil, C) determining a current value I.sub.IST of the current flowing in the coil, D) comparing the measured current value I.sub.IST with the desired current value I.sub.SOLL, wherein, following step D), a case discrimination is performed with the following steps: E) Maintaining the applied voltage U.sub.IN and repeating steps C) and D) if the comparison made in step D) shows that I.sub.IST is less than I.sub.SOLL, F) regulating the voltage U.sub.IN applied to the coil so that the current value I.sub.IST of the current flowing in the coil does not substantially increase further if the comparison made in step D) shows that I.sub.IST is greater than or equal to I.sub.SOLL, and/or wherein the first cycle comprises the following steps according to a second alternative: A) Setting a target time t.sub.SOLL, B) applying a voltage U.sub.IN to the coil, C) determining the time tis T that has elapsed since the application of the voltage U.sub.IN, D) comparing the measured time t.sub.IST with the target time t.sub.SOLL, wherein, following step D), a case discrimination is performed with the following steps: E) Maintaining the applied voltage U.sub.IN and repeating steps C) and D) if the comparison made in step D) shows that t.sub.IST is less than t.sub.SOLL, F) regulating the voltage U.sub.IN applied to the coil so that the current value I.sub.IST of the current flowing in the coil does not substantially increase further if the comparison made in step D) shows that t.sub.IST is greater than or equal to t.sub.SOLL.

15. The process according to claim 14, wherein the pump comprises a current measuring resistor with ohmic resistance value R.sub.S connected in series with the coil, wherein the first cycle is configured according to the first alternative or according to the second alternative, the first cycle of the process comprising the following further steps: G) determining the current value I.sub.IST of the current flowing in the coil as a function of time t, H) determining a voltage U.sub.S dropping across the current measuring resistor as a function of time t, I) determining a voltage U.sub.C dropping across the coil as a function of time t, J) calculating the differential inductance LD as a function of time t on the basis of the current value I.sub.IST(t) determined in step G), the voltage U.sub.S(t) determined in step H) and the voltage U.sub.C(t) determined in step I), preferably according to the following analytical formula: $L_D\left(t\right)=\frac{{?}_0^t\left(U_C-\frac{U_S}{R_S}.Math.R_{DC}\right)dt}{di},$ where dt is an infinitesimal time interval and where di represents an infinitesimal current value step which is preferably calculated for a point in time to as follows:
di(t.sub.0)=t.sub.IST(t.sub.0+dt)?I.sub.IST(t.sub.0).

16. The process according to claim 14, wherein, according to a further first alternative, a new desired current value I.sub.SOLL,neu is set for a second cycle of the process following the first cycle as a function of the differential inductance determined in step J), or according to a further second alternative, a new target time is set for a second cycle of the process following the first cycle, as a function of the differential inductance determined in step J).

17. The process according to claim 15, wherein the process comprises the following further steps: K) setting a limit value L.sub.D.sup.LIMIT for the differential inductance, L) comparing the differential inductance LD calculated in step I) with the limit value L.sub.D.sup.LIMIT, M) If the comparison made in step L) shows that the differential inductance LD exceeded the limit value L.sub.D.sup.LIMIT for the first time during the first cycle at a time t.sup.LIMIT that has elapsed since the voltage U.sub.IN was applied: setting a new desired current value I.sub.SOLL,neu for a second cycle of the process following the first cycle, the new desired current value I.sub.SOLL,neu being set as a function of the current value I.sub.IST(t.sup.LIMIT), which was measured at time t.sup.LIMIT during the first cycle, wherein the new desired current value I.sub.SOLL,neu preferably corresponds to the current value I.sub.IST(t.sup.LIMIT) measured at time t.sup.LIMIT during the first cycle; or setting a new target time t.sub.SOLL,neu for a second cycle of the process following the first cycle, wherein the new target time t.sub.SOLL,neu is set in dependence on time value t.sup.LIMIT, wherein the new target time t.sub.SOLL,neu preferably corresponds to the time t.sup.LIMIT.

18. The process according to claim 15, wherein the process comprises the following further steps: N) determining whether the time variation of the differential inductance during the first cycle has a global peak at a point in time t.sup.PEAK, wherein the global peak is preferably determined such that its value is greater than any of the time varying values of the time variation of the differential inductance, O) if step N) results in the differential inductance having a global peak at point in time t.sup.PEAK: setting a new desired current value I.sub.SOLL,neu for a second cycle of the process following the first cycle, the new desired current value I.sub.SOLL,neu being set as a function of the current value I.sub.IST(t.sup.PEAK), which was measured in the first cycle at point in time t.sup.PEAK, the new desired current value I.sub.SOLL,neu preferably corresponding to the current value I.sub.IST(t.sup.PEAK); or setting a new target time t.sub.SOLL,neu for a second cycle of the process following the first cycle, the new target time t.sub.SOLL,neu being set as a function of time value t.sup.PEAK, wherein the new target time t.sub.SOLL,neu preferably corresponds to the time t.sup.PEAK.

19. The process according to claim 16, wherein the process comprises a second cycle immediately following in time the first cycle, wherein the second cycle comprises at least steps A) to F) according to the first alternative and/or steps A) to F) according to the second alternative, wherein in step A) of the second cycle the new desired current value I.sub.SOLL,neu determined by the first cycle is set as the desired current value for the second cycle and/or the new desired time t.sub.SOLL,neu determined by the first cycle is set as the desired time for the second cycle.

20. The process according to claim 17, wherein the first cycle of the process comprises the following step, insofar as the present claim refers back to claim 3: P) If step L) shows that the differential inductance L D has not exceeded the limit value during the complete first cycle: a) issuing a warning signal and/or issuing a warning message stating that no stroke movement of the pressure element has taken place during the first cycle and/or b) maintaining the desired current value I.sub.SOLL of the first cycle for the second cycle immediately following in time the first cycle, if the first cycle is configured according to the first alternative, or setting the desired current value of the second cycle to a stored initial value I.sub.SOLL.sup.experience, so that during the second cycle: I.sub.SOLL=I.sub.SOLL.sup.experience, or maintaining the target time t.sub.SOLL of the first cycle for the second cycle immediately following in time the first cycle, if the first cycle is configured according to the second alternative, or setting the target time of the second cycle to a stored initial value t.sub.SOLL.sup.experience, so that during the second cycle: t.sub.SOLL=t.sub.SOLL.sup.experience.

21. The process according to claim 17, wherein the first cycle of the process comprises the following step, insofar as the present claim refers back to claim 4: Q) If step N) results in the differential inductance L D not having a global peak during the complete first cycle: a) emitting a warning signal and/or preferably emitting a warning message stating that no stroke movement of the pressure element has occurred during the first cycle and/or b) maintaining the desired current value I.sub.SOLL of the first cycle for the second cycle immediately following in time the first cycle, if the first cycle is configured according to the first alternative, or setting the desired current value of the second cycle to a stored initial value I.sub.SOLL=I.sub.SOLL.sup.experience, or maintaining the target time t.sub.SOLL of the first cycle for the second cycle immediately following in time the first cycle, if the first cycle is configured according to the second alternative, or setting the target time of the second cycle to a stored initial value t.sub.SOLL.sup.experience, so that during the second cycle: t.sub.SOLL=t.sub.SOLL.sup.experience.

22. The process according to claim 15, wherein the process comprises the following steps, R) setting a time interval T, S) regulating the applied voltage U.sub.IN in such a way that the current value I.sub.IST is substantially at the value I.sub.SOLL immediately after reaching or exceeding the desired current value I.sub.SOLL for the duration of the time interval T, T) switching off the voltage U.sub.IN applied to the coil when the time interval T ends.

23. The process according to claim 15, wherein the process is a computer-implemented process.

24. The process according to claim 15, wherein the pump is a diaphragm pump, wherein the displacement element is a diaphragm, wherein the coupling device is preferably a push rod.

25. A pump, wherein the pump comprises a conveying chamber for conveying a fluid, wherein the pump comprises a displacement element, wherein the displacement element delimits the conveying chamber at least in sections, so that a change in the position of the displacement element causes a change in the volume of the conveying chamber, wherein the pump comprises a drive, wherein the drive comprises a coil through which an electric current can be conducted, the coil having an ohmic resistance R.sub.DC and an inductance L.sub.coil, wherein the drive comprises a pressure element and a coupling device, wherein the pressure element and the coil are configured and arranged such that a magnetic field generated by an electric current flowing in the coil can cause a stroke movement of the pressure element along a longitudinal axis from an initial position P1 to an end position P2, wherein the coupling device couples the pressure element to the displacement element such that an effected stroke movement of the pressure element causes a change in the position of the displacement element, wherein the conveying chamber, the coupling device and the pressure element are configured and arranged such that the conveying chamber comprises a first volume value when the pressure element is in the initial position P1 and the conveying chamber comprises a second volume value when the pressure element is in the final position P2, wherein the first volume value is greater than the second volume value, wherein the pump comprises a measuring device and a control device, wherein the measuring device and the control device are arranged to perform a process according to any one of the preceding claims when the pump is in operation.

26. The pump according to claim 23, wherein the pump comprises a spring element, wherein the spring element is configured and arranged to exert a restoring force on the displacement element directed towards the initial position P1 if the displacement element is deflected from the initial position P1.

Description

[0081] Further features, advantages and embodiments of the present invention are apparent from the figures described below. They show:

[0082] FIG. 1: a schematic cross-sectional view of an embodiment of a diaphragm pump with magnetic drive according to the invention,

[0083] FIG. 2: an electronic circuit diagram of the magnetic drive of the diaphragm pump shown in FIG. 1,

[0084] FIG. 3: a time-current diagram showing the time variation of the current flowing through the coil of the diaphragm pump shown in FIG. 1 when carrying out one embodiment of the process according to the invention,

[0085] FIG. 4: an embodiment of the process according to the invention in the form of a diagram.

[0086] In FIG. 1, a magnetically driven diaphragm dosing pump 1 according to one embodiment is shown in a cross-sectional view. This diaphragm dosing pump 1 has a coil 2 which is composed of a plurality of windings of an electrical conductor. Via the electrical connection conductors 10 and 11, the coil is connected to a voltage source 12 via an electric circuit.

[0087] If a voltage UN is applied to the coil 2 during operation of the diaphragm dosing pump 1, there is an approximately linear increase in current within the wound electrical conductors of the coil 2 due to self-induction in the coil 2.

[0088] FIG. 3 shows a corresponding time-current diagram 200 for the time variation of the current 203 for the time after the voltage is switched on at the voltage source 12. The vertical axis 202 of the diagram indicates the current intensity, the horizontal axis 201 indicates the time t elapsed since the voltage was switched on. The time variation of the current is symbolised by line 203.

[0089] The approximately linear increase of the current intensity in the coilcaused by self-inductiondescribed above can be seen very clearly in FIG. 3, namely within the time interval that extends from the point in time when the voltage is applied, i.e. from the beginning of the time axis 201, to time 204. In the embodiment shown here, time 204 corresponds to time t.sup.LIMIT. As the current strength within the coil 2 increases, so does the field strength of the magnetic field, which is generated in the interior of the coil 2 and is approximately homogeneously configured there.

[0090] As can be seen in FIG. 1, a magnetic pressure element 13 is arranged in the interior space enclosed by the coil 2 and is mechanically coupled to the diaphragm 4, 4 of the diaphragm dosing pump 1 via a push rod 3. The coil 2 and the magnetic pressure element 13 are configured in such a way that the magnetic field building up inside the coil 2 causes a force which acts on the magnetic pressure element 13 and is directed towards the dosing chamber 5. This magnetic force is counteracted by a restoring and position-dependent spring force which is transmitted to the pressure element 13 via the spring 8. Acceleration of the pressure element 13 in the direction of the dosing chamber 5 therefore only occurs when the field strength of the magnetic field within the coil 2 has increased to such an extent that, despite the restoring force of the spring 8, a sufficient net force acts on the magnetic pressure element 13 in the direction of the dosing chamber 5.

[0091] In practice, a very sudden acceleration of the magnetic pressure element 13 occurs as soon as a sufficiently strong magnetic field has built up within the coil 2. Due to the mechanical coupling of the pressure element 13 with the diaphragm 4, 4 via the push rod 9, the resulting movement of the pressure element 13 moves the diaphragm 4, 4 from an initial position P1 (symbolised here by the diaphragm 4 shown solid) to an end position P2 (symbolised here by the dashed diaphragm 4).

[0092] The movement of the diaphragm 4, 4 from the starting position P1 to the end position P2 is the pre-stroke movement of a stroke cycle. The return stroke movement is a subsequent movement of the diaphragm from the end position P2 to the starting position P1. This is caused by the spring 8 after the voltage abutting the coil has been regulated in such a way that the magnetic force acting on the pressure element no longer compensates for the restoring force of the spring.

[0093] As can be seen in FIG. 3, the voltage is regulated from point in time 204 in such a way that the current flowing in the coil is approximately constant for a time interval T which extends between times 204 and 205, so that a magnetic field with approximately constant field strength is generated within the coil during this time. This means that the diaphragm does not perform a return stroke immediately after the pre-stroke movement. Rather, the diaphragm 4 is essentially held in the end position P2 for the time interval T. When the voltage is switched off at point in time 205, the magnetic field within the coil and thus the magnetic force acting on the pressure element is also set to zero. Consequently, the return stroke movement begins at point in time 205, since a net force now acts on the pressure element in the direction opposite to that of the pre-stroke movement due to the spring force. When the diaphragm returns to the starting position P1, a stroke cycle of the diaphragm dosing pump is completed.

[0094] In FIG. 4, an embodiment of the process described here is shown again as a diagram. First, the pump is put into operation with step 301 and the process for operating a pump is started. Either an initial desired current value in the sense of the first alternative or an initial target time in the sense of the second alternative has already been determined before the process is started or the determination takes place at the same time or following the start of commissioning in step 302. In the following, the description of the process shown in FIG. 4 refers exclusively to the first alternative for a cycle in which the voltage control is coupled to a desired current value. Analogously, however, the voltage control can also be coupled to a target time in the same way.

[0095] Now, in step 303, a cycle is carried out as a function of the determined desired current value as described in the preceding paragraphs in connection with FIGS. 1 and 3. In a further step 304, which may be carried out either at least partially simultaneously with the execution of the stroke cycle in 303 or immediately following it in terms of time, the differential inductance is determined. To determine the differential inductance, the physical quantities shown in the electrical circuit diagram of FIG. 2 and known in advance are used, in particular the ohmic resistance R.sub.DC 101 of the coil 2, the inductance 102 of the coil 2 and the current measuring resistor R.sub.S 103. In addition, to determine the differential inductance, the time variation of the coil voltage is measured, which can be tapped betweenas shown in FIG. 2the two conductors running to the coil 2 and a diode 105 connected in parallel. The diode 105 serves as a free-wheeling diode by which voltage peaks are avoided when inductive loads of the solenoid are switched off. The arrow 107 symbolises the direction of flow of the electric current which flows through the electrical conductors of the coil 2 when a voltage is applied to the coil 2. According to the embodiment shown in FIG. 2, the voltage source 12 may provide a pulse width modulation (PWM) voltage controlled by the current flow defined in FIG. 3 to cause an alternating movement of the pressure element 13 configured as a magnetic armature.

[0096] The determination of the differential inductance now enables the step 305 shown in FIG. 4, in which it is checked whether a stroke movement, also referred to as stroke execution, has taken place at all by checking the determined time variation of the differential inductance to see whether it has a peak characteristic of a stroke execution. This can be done, for example, by checking whether the time variation has a peak whose maximum value is at least twice as large as the mean value of the differential inductance values outside the peak, i.e. for the time before and after the peak. However, other determination methods for determining a peak and thus for determining a stroke execution are also possible and are encompassed by the present disclosure.

[0097] If it has been determined in step 305 that no stroke execution has occurred, step 309 first outputs a warning message and sets a new desired current value, so that step 302 is then performed again. This can be, for example, a desired current value based on experience at which stroke execution can be expected with a probability bordering on certainty. Steps 303, 304 and 305 are then carried out again and this cycle is repeatedwith desired current values that increase further and further, if necessary, until a stroke execution is detected in step 305.

[0098] If it is determined in step 305 that a stroke execution has taken place, the current intensity at the point in time when the stroke movement started is determined. The point in time at which differential inductance reaches the peak maximum also represents the point in time at which the stroke movement starts, or more precisely, the pre-stroke movement. The current value determined in this way is set as the new desired current value in step 307 and implemented as the desired current value for a further cycle following the cycle described in step 308. Then a step 303 starts again and thus the new cycle.

LIST OF REFERENCE SIGNS

[0099] 1 Pump, in particular diaphragm dosing pump [0100] 2 Coil [0101] 3 Push rod [0102] 4 Diaphragm or diaphragm system when pressure element in starting position P1 [0103] 4 Diaphragm or diaphragm assembly when pressure element in end position P2 [0104] 5 Conveying chamber, in particular dosing chamber [0105] 6 Suction channel [0106] 7 Pressure channel [0107] 8 Spring element [0108] 9 Sealing element, in particular O-ring [0109] 10 Electrical connection [0110] 11 Electrical connection [0111] 12 Voltage source [0112] 13 Pressure element [0113] 50 Longitudinal axis [0114] 100 Circuit diagram of the coil circuit [0115] 101 Ohmic resistance of the coil Roc [0116] 102 Inductance of the coil [0117] 103 Current measuring resistor R.sub.S [0118] 104 Measuring range for coil voltage U.sub.C [0119] 105 Diode [0120] 106 Grounding [0121] 107 Direction of electric current [0122] 200 Diagram for the time variation of the electric current value I.sub.IST(t) [0123] 201 Time axis t [0124] 202 Axis for current value I.sub.IST [0125] 203 Linear increase until the value I.sub.SOLL is reached [0126] 204 Point in time t.sup.LIMIT [0127] 205 Point in time t.sup.LIMIT+T [0128] 300 Diagram [0129] 301 Start of the process [0130] 302 Setting the initial desired current value I.sub.SOLL=I.sub.SOLL.sup.experience for the current flowing in the coil [0131] 303 Execution of a cycle with steps B), C), D), E), F), G), H) and I) [0132] 304 Calculate the differential inductance LD according to step J) [0133] 305 Checking whether stroke execution has occurred [0134] 306 Determining when stroke execution has occurred [0135] 307 Set new desired current value [0136] 308 Implement new desired current value for next cycle [0137] 309 Issuing a warning message