WO2010124668A1

WO2010124668A1 - Method for operating a metering pump

Info

Publication number: WO2010124668A1
Application number: PCT/DE2010/000326
Authority: WO
Inventors: Heiko Neuner
Original assignee: Webasto Ag
Priority date: 2009-04-29
Filing date: 2010-03-23
Publication date: 2010-11-04
Also published as: DE102009019450A1

Abstract

The invention relates to a method for operating a metering pump (12), particularly for delivering fuel for a vehicle heater, wherein the metering pump comprises a piston (14) which can be moved back and forth between a starting position and an end position for delivery purposes and a drive unit (18) which can be electrically excited by applying a voltage, wherein the following action is performed and repeated multiple times: controlling/regulating the voltage in order to generate an effective voltage curve having at least two different effective voltage values in order to set the piston in motion starting from the starting position and transfer it to the end position. The voltage is controlled/regulated independently of the movement of the piston. The invention further relates to an apparatus (10) comprising a metering pump (12) and a control/regulating unit (20), which is designed to control/regulate a voltage that is applied to a drive unit (18) of the metering pump.

Description

Method for operating a metering pump

The invention relates to a method for operating a metering pump, in particular for conveying fuel for a vehicle heater, wherein the metering pump comprises a piston for reciprocating between an initial position and an end position and reciprocable piston and an electrically energizable by applying a voltage drive unit, wherein the following measure is carried out and repeated several times: controlling the voltage for generating an effective voltage curve with at least two different effective voltage values, in order to set the piston in motion starting from the initial position and to bring it into the end position.

The invention further relates to an apparatus for carrying out the method.

Such a method is known from DE 10 2005 024 858 A1. The amplitude of the voltage applied to the drive unit determines the magnitude of a driving force acting on the reciprocating piston and thus the speed of the piston. The voltage can be pulse width modulated. In this case, the instantaneous amplitude of the applied voltage does not directly affect the speed of the piston, but a time average of the voltage determines an effective voltage, which in turn determines the force acting on the piston. The RMS voltage results from the instantaneous voltage by averaging over a time interval that is long compared to modulation-related voltage variations, but short in comparison to a period of piston movement. A pulse width modulation of the voltage for driving a metering pump is described in particular in the already mentioned DE 10 2005 024 858 A1 and in DE 101 52 782 B4.

In order to set the piston in motion in an improved manner starting from the initial position and to transfer it into the end position, DE 10 2005 024 858 A1 provides that the effective voltage is not constant during an energization time interval but varies, ie assumes at least two different effective voltage values , In this way, on the one hand, it can be achieved that the piston begins to move as quickly as possible at the beginning of the energization time interval. On the other hand, it can be achieved that the piston reaches its end position with not too high a speed. As a result, an audible and possibly disturbing impact noise can be avoided or at least reduced. A disadvantage of the method known from DE 10 2005 024 858 A1, however, is that the voltage profile or the rms voltage waveform is determined in a relatively complex manner. Specifically, to perform the method, it must be determined whether the piston has reached a position at or near an end position during the energization time interval, and the time during the energization time interval when the piston has reached the position at or near the end position must be determined.

It is the object of the invention to specify a method which can be carried out easily and a corresponding device for operating a metering pump.

This object is solved by the features of the independent claims.

Advantageous embodiments will be apparent from the dependent claims.

The inventive method is based on the generic state of the art in that the voltage is controlled independently of the movement of the piston / regulated. This can be achieved, for example, by setting or setting the rms voltage profile before the action is carried out and repeated. A once determined rms voltage waveform can thus be used for several cycles of the pumping operation. A determination of the intended RMS voltage during normal pumping operation may be omitted. In particular, there is no need to determine the position of the piston or to evaluate information about the current position of the piston to control the tension during the control.

It can be provided that the voltage is at least temporarily pulse-width modulated. This can be done by controlling a duty cycle. As an alternative to pulse width modulation, the voltage could, for example, also be controlled in such a way that it is as identical as possible to the intended effective voltage at all times.

It may be provided that the rms voltage waveform is monotone and monotonically decreasing in magnitude. This can be achieved that the piston is decelerated before reaching the end position, or that it is braked more than it would be the case, if the effective voltage from the time when the piston leaves the initial position to the time in which the piston reaches the end position, remains constant. Will the voltage Controlled pulse width modulated / regulated, so a monotonically decreasing effective effective voltage can be achieved by a duty cycle of the voltage is reduced.

It can further be provided that the rms voltage curve corresponds to a staircase function. This means that the intended effective voltage changes its value only at discrete times. For each time block between two successive times, an effective voltage value, for example the arithmetic mean value of the instantaneous voltage, can be determined in advance.

It can further be provided that the rms voltage waveform has a final phase during which the rms voltage is zero. Thus, the rms voltage is regulated / controlled to zero before the piston reaches the end position. During the final phase, no further energy is supplied to the piston. This can result in an improved energy balance.

It may be provided that the effective voltage curve is chosen such that the speed of the piston when reaching the end position is at least 10% (or at most 3% or at most 1%) of a maximum speed of the piston. The maximum speed of the piston is understood to be the maximum speed which the piston achieves when carrying out the method on its way from the initial position to the end position. The speed of the piston is thus considerably reduced before reaching the end position. In this way, a quiet and / or energy-efficient operation of the metering pump can be achieved.

It can be provided that a control unit accesses stored information defining the rms voltage waveform and controls the voltage based on this information. The information can be stored, for example, in the form of a digital list or table, for example on an electronic, optical or magnetic memory or data carrier. The list or table may associate a corresponding set of intended values of effective voltage with a set of times. Alternatively, the list or table can assign voltage values to a set of times such that the corresponding voltage curve yields the intended effective voltage curve. Alternatively, the list or table may associate a corresponding set of duty cycles with a set of times. - A -

In this context, it may be provided that the control unit does not use information that allows conclusions about an actual position or speed of the piston. As a result, a particularly inexpensive and robust method is created.

It can be provided that a restoring force causes a return of the piston to the initial position. The restoring force is understood to mean a force which acts in the direction of a rest position of the piston when the piston is deflected out of the rest position. The rest position can be identical to the initial position of the piston. The restoring force can be generated, for example, by a spring which is arranged so that it is elastically deformed during a movement of the piston from the initial position to the end position.

It may be provided that the measure further comprises: further controlling the voltage according to an intended further rms voltage waveform having at least two different rms voltage values to set the piston in motion from the end position and to transfer to the initial position. In particular, in the case of a metering pump in which there is no purely mechanical automatic return of the piston from the end position to the initial position, so the piston can be transferred in a controlled manner from the end position to the initial position. All of the features disclosed in this application in connection with the movement of the piston from the initial position to the final position and the associated rms voltage waveform can be readily transferred to the rms voltage waveform provided for transferring the piston from the end position to the initial position ,

The measure may also include controlling the voltage to zero during a time out. In this context, it can be provided that the length of the time-out is controlled during the execution of the method in order to control the delivery rate of the metering pump.

The device according to the invention comprises a metering pump of the type described in the introduction and a control / regulating unit which defines an intended effective voltage curve with at least two different effective voltage values, and which is suitable or designed to carry out the following measure and to repeat it several times: controlling the voltage in accordance with Effective voltage curve to set the piston starting from the initial position in motion and to transfer to the end position, wherein the control unit is configured to control the tension independent of the movement of the piston. The advantages explained in connection with the method according to the invention are analogous to the device according to the invention.

It can be provided that the control unit comprises a memory and a processor and the rms voltage waveform is at least partially defined by processor-readable information present in the memory. The information may include, for example, a digital list / table that explicitly or implicitly assigns a respective rms voltage value to at least two points in time. The memory can be, for example, an electronic, optical or magnetic memory or data carrier, for example a read-only memory (ROM).

The control / regulating unit can be designed, for example, as an integrated circuit.

The invention will now be elucidated by way of exemplary embodiments and with reference to the accompanying drawings. Here, the same reference numerals designate the same or similar components.

Show it:

1 shows a metering pump at a first time of a pumping cycle.

2 shows the metering pump at a second time of the pumping cycle.

Figure 3 shows the course of an effective voltage.

4 shows the course of an effective voltage according to another embodiment.

Figure 5 shows the course of an effective voltage according to another embodiment.

6 shows the course of a voltage with pulse width modulation.

FIG. 7 shows a flow chart of a method according to the invention. Figure 1 shows schematically an example of a device 10 for pumping a liquid, for example a fuel, from an input line 22 by means of a metering pump 12 to an output line 24. The metering pump 12 comprises a housing and a piston 14, which together with the housing a pumping chamber 16 defined. The current position of the piston 14 relative to the housing defines a current volume of the pumping chamber 16. Figure 1 shows the piston 14 in an initial position where the pumping chamber 16 assumes its maximum volume.

Figure 2 shows the piston 14 in an end position in which the volume of the pumping chamber 16 is zero. The piston 14 is connected to an electric drive unit 18 in connection. The drive unit 18 is adapted to apply cyclically or periodically a force F to the piston 14 to reciprocate the piston 14 between its initial position and its end position. The metering pump 12 may include a spring (not shown) which causes return of the piston 14 from the end position to the initial position without requiring the application of force by the drive unit 18. The drive unit 18 has a coil to which an electrical voltage U can be applied to generate a current and thus the force F. The voltage U applied to the coil is controlled by a control unit 20. The voltage U may be amplitude modulated. Alternatively, it can be pulse width modulated.

FIG. 3 illustrates, by way of example, the time profile of an effective voltage (effective voltage) Ueff which corresponds to the voltage U applied to the coil of the drive unit 18. The effective voltage Ueff (effective voltage) is periodic with a period T. At time tθ, the piston 14 is in its initial position. At this time, an effective voltage of the height U1 is applied. By this voltage, the piston 14 is set in the direction of the end position in motion. At a later time t1, the effective voltage is reduced to a value U2 (U2 <U1). At a later time t2, the rms voltage is reduced to zero. The piston 14 then continues to move until it stops due to its inertia, that is to say to its end position, which it reaches at time t3. At time t4, a new pump cycle begins, in which an effective voltage is applied analogously to the effective voltage in the interval [0, t4]. The interval [t3, t4] forms a time-out in which the applied effective voltage is zero, and in which the piston is returned to the initial position by a restoring force and remains there until a positive effective voltage Ueff is applied again at time t4. The length of the timeout [t3, t4] defines the delivery rate of the dosing pump 12. The longer the timeout, the lower the delivery rate. While the length of the time-out is freely selectable, the course of the rms voltage is fixed at the interval [O, t3], for example by a look-up table in electronically stored form or by a specially configured circuit. The course of the effective voltage from the time tθ (end of a time-out) to the time t3 (beginning of the next time-out) is thus not affected by the actual movement of the piston and is repeated identically many times.

FIG. 4 schematically illustrates the course of the effective voltage Ueff according to an alternative embodiment. After the end of a timeout, the effective voltage jumps to the value U1 and then decreases linearly. At time t2, the rms voltage is zero. At time t3, the piston reaches its end position and then moves back to its initial position due to a restoring force.

FIG. 5 schematically illustrates the course of an effective voltage according to a further embodiment. In contrast to the embodiments explained with reference to FIG. 3 and FIG. 4, the return of the piston 14 does not take place by a restoring force, but by the application of an effective voltage of opposite sign (during the time interval [tO ¹ , t ² ']).

FIG. 6 schematically illustrates the course of a pulse width modulated voltage U, which generates the effective voltage Ueff shown in FIG. The mean value of the voltage U on the interval [t0, t1] and the mean value of the voltage U on the interval [t1, t2] correspond to the value U1 or the value U2 of the effective voltage Ueff. On the interval [t1, t2], the duty cycle is about half the duty cycle on the interval [t0, t1], that is, the rms voltage is reduced from U1 to the lower value U2 at time t1.

FIG. 7 shows a flowchart which illustrates by way of example the sequence of a method according to the invention. In a first step S1, a voltage is applied to the drive unit 18 of the metering pump 12 on the basis of fixed information defining an effective voltage profile and controlled / controlled so that the applied voltage results in the predefined effective voltage curve. In a subsequent step S2, the duration of a time-out is determined as a function of a current desired delivery rate. In the following step S3, the voltage is set to zero during the so determined time-out. Subsequently, the process returns to step S1. Reference numerals:

10 device

12 metering pump 14 piston

16 pumping chamber

18 drive unit

20 control unit

22 input line 24 output line

U voltage

Ueff rms voltage t time

Claims

claims

1. A method for operating a metering pump (12), in particular for conveying fuel for a vehicle heater, wherein the metering pump for reciprocating between an initial position and an end position reciprocable piston (14) and an electrically excitable by applying a voltage drive unit ( 18), whereby the following measure is carried out and repeated several times:

Controlling the voltage to generate an effective voltage waveform having at least two different effective voltage values to set the piston in motion from the initial position and to translate it to the final position;

characterized in that the tension is controlled independently of the movement of the piston.

2. The method according to claim 1, characterized in that the voltage is at least temporarily pulse width modulated.

3. The method according to claim 1 or 2, characterized in that the rms voltage waveform is monotone and monotonically decreasing amount.

4. The method according to claim 1, 2 or 3, characterized in that the effective voltage curve corresponds to a staircase function.

5. The method according to claim 1, 2, 3 or 4, characterized in that the effic- tivspannungsverlauf has a final phase during which the effective voltage is zero.

6. The method according to claim 1, 2, 3, 4 or 5, characterized in that the Ef- fektivspannungsverlauf is selected such that the speed of the piston (14) when reaching the end position in terms of magnitude not more than 10% of a maximum speed of the piston.

A method according to claim 1, 2, 3, 4, 5 or 6, characterized in that a control unit (20) accesses stored information defining the rms voltage waveform and controls the voltage based on said information.

8. The method according to claim 7, characterized in that the control unit (20) does not use information that allows conclusions about an actual position or speed of the piston (14).

9. The method according to claim 1, 2, 3, 4, 5, 6, 7 or 8, characterized in that a restoring force causes a return of the piston (14) to the initial position.

10. The method according to claim 1, 2, 3, 4, 5, 6, 7 or 8, characterized in that the measure also comprises:

further controlling the tension in accordance with an intended further effective voltage waveform having at least two different effective voltage values to set the piston (14) in movement from the end position and to transfer it to the initial position.

11. The method according to any one of claims 1 to 10, characterized in that the measure also comprises:

Controlling the tension to zero during a break.

12. Device (10) comprising: a metering pump (12) in particular for conveying fuel for a vehicle heater, wherein the metering pump for reciprocating between an initial position and an end position reciprocable piston (14) and an electrically excitable by applying a voltage Drive unit (18), and - a control unit (20), which is suitable or designed to perform the following action and repeat several times:

Controlling the voltage to produce a rms voltage waveform for starting the piston from the initial position and transferring it to the final position; characterized in that the control unit is configured to control the tension independently of the movement of the piston.

The apparatus (10) according to claim 12, characterized in that the control unit (20) comprises a memory and a processor and the RMS voltage waveform is at least partially defined by processor readable information present in the memory.

14. Device (10) according to claim 12, characterized in that the control / regulating unit (20) is designed as an integrated circuit.