DE102016213016A1 - Pre-feed pump with energy-efficient control - Google Patents

Abstract

Prefetching pump (3) for a fuel injection system (2) of a motor vehicle (1), wherein the fuel injection system (2) next to the prefeed pump (3) comprises a high pressure pump (21) for feeding a busbar (22), wherein the distributor rail (22) in turn a A plurality of injectors (23a-23d) feeds and wherein lines (24, 25) for returning fuel (12) from the high-pressure pump (21) and / or from the injectors (23a-23d) in the fuel tank (11) of the motor vehicle ( 1) are provided, wherein the prefeed pump (3) is a piston pump having at least one magnetic reluctance actuator (4, 5) as a drive source for at least one piston (31, 32), wherein the drive (6, 7) of the at least one reluctance (4, 5) includes a regulator (64) adapted to control a fuel pressure p prevailing between the prefeed pump (3) and the high-pressure pump (21) to a desired value psoll.

Description

The present invention relates to feed pumps for fuel injection systems in motor vehicles.

State of the art

In diesel-powered vehicles with common rail injection system, the fuel is compressed with a high-pressure pump to pressures around 2500 bar and fed to a rail, which in turn feeds several injectors. The injectors require a line due to leakage and tax due to the return of fuel in the fuel tank. This fuel has been heated primarily by the losses in the relaxation from high pressure to low pressure, as well as subordinate by the engine. The dissipated heat energy is typically 1% of the rated power of the engine, which are at rated power over 1000 W heating power, which heats the fuel supply. Due to the very high fuel inlet temperature to be covered, the high-pressure pump for cooling must also have a return path to the tank. Due to the high inlet temperature, the efficiency of all components involved is significantly reduced. Due to these return paths and the high temperatures to be covered, the pre-feed pump must be dimensioned well above the injected quantity.

In order to reduce the heating of the fuel supply, therefore, an increasing attempt is made to adapt the delivery rate of the prefeed pump to the actual requirements of the injectors, so that as little fuel unnecessarily revolves over the engine back to the fuel tank and thereby absorbs heat. For this purpose, the speed of the prefeed pump is typically varied in dependence on the speed and the load of the engine. The fuel pressure in the low-pressure circuit is controlled by a spring-loaded overflow valve, which is usually arranged in the high-pressure pump.

The new brushless drives for fuel pumps reduce the resulting power losses, especially in partial load operation. However, rotating drives can only be optimized to a very limited extent for a large speed range. The speed is too high for cost-effective solutions. With additional effort, the number of poles can be increased or a gearbox can be flanged. However, this increases the costs, increases the space requirement and worsens the efficiency.

Therefore, in the DE 10 2013 218 064 A1 proposed to design fuel pumps as piston pumps, which have electromagnetic reluctance actuators as the drive source.

Disclosure of the invention

In the context of the invention, a prefeed pump for a fuel injection system of a motor vehicle has been developed. The fuel injection system has, in addition to the feed pump, a high-pressure pump for feeding a bus bar, and the bus bar feeds a plurality of injectors. There are lines for returning fuel from the high-pressure pump, and / or from the injectors, provided in the fuel tank of the motor vehicle.

According to the invention, the prefeed pump is a piston pump which has at least one magnetic reluctance actuator as the drive source for at least one piston, wherein the actuation of the at least one reluctance actuator includes a regulator which is designed to control a fuel pressure p prevailing between the prefeed pump and the high-pressure pump to a desired value p _should settle.

A reluctance actuator as a drive source for the feed pump has more degrees of freedom for the control than a rotating drive, in which only the speed can be controlled. As a result, the performance of the feed pump is in a wider range and at the same time faster variable. It has been recognized that in this way the prefeed pump is enabled to act as an actuator in an active closed loop, controlled by the controller, which regulates, for example, the fuel pressure p to a desired value p _soll .

With such an active control, the recirculated fuel amount .DELTA.Q into the fuel tank can be more lowered than with a mere control which calculates the discharge capacity of the prefeed pump from the rotational speed and the load of the engine. The actual fuel demand of the injection system to be covered by the priming pump is correlated with the speed and load of the engine. However, only an estimate of the required delivery rate of the prefeed pump can be obtained via this simple relationship, since various influences on the fuel requirement are neglected. For example, the fuel requirement depends on the injection pressure, the number of injections and the operating temperature of the engine. Furthermore, the fuel quantity actually received by the injection system depends on the exact behavior of the high-pressure pump, mediated, for example, by an overflow valve arranged between the pre-feed pump and the high-pressure pump.

This interplay of various influences makes it very difficult to quantitatively fathom the ultimately resulting fuel demand and to predict the delivery rate of the prefeed pump. It was recognized that an active control can remedy this situation precisely: For the design of an active control general statements are required to the qualitative behavior of the controlled system, but not as accurate mathematical model, as required for a precalculation of the flow rate without feedback of the fuel pressure p would.

In an advantageous embodiment of the invention, the controller additionally receives at least one fuel quantity ΔQ returned to the fuel tank of the motor vehicle as feedback. This feedback quantity of fuel ΔQ is determined, inter alia, by the engine map and the behavior of the injectors and is therefore subject to a large number of boundary conditions, so that the possibilities of minimizing this fuel quantity ΔQ in a decided manner are limited. However, the amount of fuel returned, ΔQ, is an important indicator of the heat input into the fuel tank, because this heat input is proportional to the product of fuel quantity ΔQ and the temperature of the recirculated fuel.

The recirculated amount of fuel ΔQ can be measured directly, for example with a flow meter. However, it can also be determined indirectly, for example from the difference between the amount of fuel delivered minus the amount of fuel injected.

The active control improves the achievement of the goal of reducing the heat input to the fuel supply by injecting an increased proportion of the hot fuel into the cylinders. At the same time, energy efficiency can be further improved in an organic way. The delivery rate of a prefeed pump, which is driven by a reluctance actuator, is an interaction of a plurality of actuation parameters, corresponding to the degrees of freedom which are extended in relation to a rotating drive. Accordingly, one and the same delivery rate can be represented by a plurality of combinations of activation parameters, wherein the energy efficiency η of the prefeed pump can be different for each of these combinations. In a further particularly advantageous embodiment of the invention, therefore, the activation of the at least one reluctance actuator contains at least one characteristic map which assigns combinations of at least two independent activation parameters of the at least one reluctance actuator to an energy efficiency η of the prefeed pump. The active control can then be designed, for example, to carry out a change in the delivery rate, preferably with changes in the activation parameters, which at the same time lead to a good efficiency η. However, the active control can also be designed, for example, to continually optimize the control parameters in such a way that a constant delivery rate is always provided in the most energy-efficient manner.

For example, a frequency with which the at least one reluctance actuator is subjected to current pulses, as well as a time portion during which each pulse has a rising edge, may be provided in the control as drive parameters. Such a control is particularly easy to implement circuitry especially in a motor vehicle by the vehicle electrical system voltage is applied to the solenoid for the time portion during which the current in the solenoid coil of the reluctance is to increase. The time course of the applied voltage can then be, for example, a square wave signal. The inductance of the magnetic coil then leads to the fact that the current does not increase instantaneously and decreases, but in the form of an exponential curve.

A pulsed drive may involve oscillating the piston driven by the reluctance actuator. To smooth such oscillations, a spring is advantageously provided. For example, this spring may engage a piston rod which is driven by the reluctance actuator and impart the driving force to the piston.

In a further particularly advantageous embodiment of the invention, the activation of the at least one reluctance actuator contains a plurality of characteristic diagrams which are used for different values or value ranges of the pressure p generated by the prefeed pump and / or the fuel quantity Q delivered by the prefeed pump. Thus, for example, based on the combination of pressure p and fuel quantity Q, it is first possible to select that characteristic map which most accurately reproduces the dependence of the efficiency η on the drive parameters. Alternatively or in combination with this, the desired value p _soll can be adapted via mathematical equations to specific boundary conditions which place a particularly high load on the prefeed pump, eg highest engine speed, high injection pressure, unfavorable ambient boundary conditions or lowest operating frequency (permissible bearing load).

In a further particularly advantageous embodiment of the invention, a two-phase reluctance is provided, wherein the first phase of the reluctance actuator drives at least one piston of the prefeed pump when energized in a first rest position and wherein the second phase of the reluctance the at least one piston of the prefeed pump when energized in one of the first resting position drives different rest position. Then the linear Movement be controlled separately in both possible directions of movement.

For example, the reluctance actuator can drive a piston rod, at whose opposite ends in each case a piston is provided. If one of the pistons then picks up fuel, the other piston simultaneously delivers fuel from the pre-feed pump and vice versa. In this way, the delivery is doubled on the one hand and on the other hand also equalized in time.

Alternatively or in combination, in a further advantageous embodiment of the invention, the two phases of the reluctance actuator have different transmission ratios between the current intensity of the respective magnet coil and the respective reluctance force exerted. If, for example, only one piston is driven, it can be operated in the intake phase by the one phase of the reluctance actuator with a first force characteristic and in the delivery phase by the second phase of the reluctance factor with a second force characteristic. For example, the magnetic coils of the two phases of the reluctance can be different sizes, and / or differently wound.

In a further particularly advantageous embodiment of the invention, the control is designed to heat by supplying current to at least one magnetic coil of the at least one reluctance actuator, the prefeed pump to prevent Verulatung. In particular, such heating can take place without the pump at the same time promoting, for example, by the solenoid is subjected to a static current. This ensures that during a cold start at low outside temperatures, the first fuel leaving the pre-feed pump is already warm enough. To avoid damage to the high pressure pump by foreign bodies is often arranged between the prefeed pump and the high pressure pump, a fuel filter. This filter is prone to volatilization when the priming pump promotes cold fuel that has formed paraffin crystals. By contrast, a conventional rotating drive for a prefeed pump can not be heated by energizing without starting the prefeed pump at the same time.

Advantageously, the piston is guided into a working space with an inlet valve and an outlet valve, wherein the inlet valve and the outlet valve are each designed as a check valve. The check valve may for example be a ball valve in which a ball is pressed in the closed state by a spring on a valve seat. But it can also be used, for example, a diaphragm valve.

In general, the combination of a piston pump with a linear actuator has the advantage that hydraulic losses are largely avoided compared to a rotating pump. The actuator itself may be dry, i. he does not have to be in contact with the fuel. If the actuator is not in contact with the fuel, the prefeed pump is more robust against particles, water and chemical influences due to admixtures in the fuel. However, the basic operating principle of the feed pump does not rule out that the actuator is in contact with the fuel.

The piston principle can be realized in comparison to a rotating pump with a smaller number of relatively moving parts, and overall with cheaper parts. For example, this eliminates an electric motor and a clutch. As a piston, for example, a high-precision and yet inexpensive roller bearing ball can be used. The reluctance actuator does not require rare-earth permanent magnets. The pre-feed pump works independently of position and therefore does not require a position sensor. Finally, the piston principle with inlet and outlet valve also leads to a good pressure holding capacity, which is particularly advantageous in vehicles with start-stop automatic.

The control electronics is simple and inexpensive. It can be integrated on the housing of the prefeed pump, or directly in its control unit, for example as an application-specific integrated circuit (ASIC). Under favorable low flow conditions, the reluctance factor requires currents of less than 1.5 A on average and currents of less than 4 A in the peak. These currents may be provided by a power output stage located on the ASIC.

The prefeed pump is robust, since it has only a few mutually moving wear points, which are also predominantly charged specifically low. The occurring axial and radial forces are relatively low, especially in the pressure range up to about 2 bar. As a result, the friction losses are comparatively very low. To avoid wear and noise excitation, the piston should be guided and the at least one Reluktanzaktor be designed so that the piston does not abut stops. Furthermore, there are only a few moving seals. The assembly and testing costs are low; In particular, only a few finishes and fits are needed. The piston principle has very small leaks compared to other pumping principles.

Due to the ability to lower the stroke and the frequency independently, the electrical efficiency of the feed pump, in particular in the CO ₂ -relevant part load be improved. In particular, the overall efficiency, which is the product of hydraulic, mechanical and electrical efficiency, advantageously increased even at very low flow rates. The flow rate can be changed very quickly, from one piston stroke to the next, from the minimum to the maximum.

Further measures improving the invention will be described in more detail below together with the description of the preferred embodiments of the invention with reference to figures.

embodiments

It shows:

1 Embodiment of the feed pump 3 and integration into the fuel injection system 2 of the motor vehicle 1 ;

2 Detail view of the piston pump with a reluctance actuator with two phases 4 and 5 ,

3 Electronic control of the phases 4 and 5 the reluctance actuator with two degrees of freedom 61 and 62 ,

To 1 contains the motor vehicle 1 a fuel tank 11 for fuel 12 , The fuel 12 is about the injection system 2 the in 1 not shown combustion chambers of the engine cylinder supplied.

The fuel 12 is from the pre-feed pump 3 over a filter 26 a high pressure pump 21 fed. 1 shows two ways in which the fuel quantity can be controlled: The first possibility is that a spring-loaded overflow valve 27a the high pressure pump 21 upstream and excess fuel 12 in a back in the fuel tank 11 leading return 24 feeds. The second option is that excess fuel 12 from the high pressure pump 21 via a spring-loaded overflow valve 27b which also in the high pressure pump 21 can be integrated into the return line 24 is diverted.

The high pressure pump 21 compresses the fuel 12 and lead him to the distribution rail 22 to, from where he passes through the injectors 23a - 23d injected into the combustion chambers. In this case, part of the amount Q of fuel 12 that of the pre-feed pump 3 is encouraged to cool the high-pressure pump 21 used and over the line 24 back to the fuel tank 11 be guided. This and the removal of excess fuel 12 through the spring-loaded overflow valve 27a . 27b have the effect of that of the busbar 22 an amount Q * of fuel is supplied, which is lower than that of the pre-feed pump 3 delivered quantity Q. The return flow to fuel 12 from the injectors 23a - 23d will be in another line 25 collected, with the line 24 is merged. Thus, the return flow is ultimately back into the fuel tank 11 guided. The amount ΔQ of the total through the pipe 24 recycled fuel 12 is optional with the flow meter 24a detected. In return-free systems, this flow meter is eliminated 24a always.

The pre-feed pump 3 includes a piston 31 in a workroom 35 is guided. Will the piston 31 from the workroom 35 moved out, so is via the inlet valve 36 fuel 12 sucked. Will the piston 31 in the workroom 35 moved in, so is via the exhaust valve 37 fuel 12 to the filter 26 promoted. A piston rod 33 , which is a two-phase electromagnetic reluctance actuator 4 and 5 is driven, flows into the piston 31 , Will the phase 4 the Reluktanzaktors energized, this drives the piston 31 in the workroom 35 into it. Will the phase 5 energized by the reluctance, this pulls the piston 31 from the workroom 35 out. The phases 4 and 5 of the reluctance actuator are controlled by a drive 6 are applied to current pulses which recur at a frequency f and have a rising edge in a time component α. The frequency f is the first drive parameter 61 , and the time component α is the second drive parameter 62 , The pulses are powered by power electronics 7 to the currents I ₄ and I ₅ , with which the phases 4 and 5 the reluctance actuator is ultimately applied, amplified.

Centerpiece of control 6 is the regulator 64 that before the high pressure pump 21 prevailing, with the pressure sensor 28 measured pressure p of the fuel 12 as feedback of the actual value p _ist . This is the regulator 64 able to control the pressure p of the fuel 12 to a setpoint p _should be regulated. The controller optionally also receives that from the flowmeter 24a measured, through the line 24 recirculated amount of fuel .DELTA.Q as further feedback, which is a measure of the quantity and temperature entry in the fuel tank 11 is.

The regulator 64 is designed by acting on the control parameters 61 and 62 that of the pre-feed pump 3 delivered quantity Q of fuel 12 track so that the pressure p of the fuel 12 in the best possible agreement with its setpoint p _soll .

To further improve energy efficiency, the controller uses 64 on maps 63a - 63c back, in which for each combination of frequency f (first drive parameter 61 ) and time component α (second activation parameter 62 ) the overall efficiency η of the feed pump 3 including her control 6 and associated power electronics 7 is deposited. This ensures that the current delivery rate of the pre-supply pump 3 always with the combination of the control parameters 61 and 62 is provided for the efficiency η is maximum. The maps 63a - 63c are valid for different ranges of the pressure p and the delivered fuel quantity Q. The regulator 64 So first selects that map on the basis of the pressure p and the amount of fuel Q. 63a - 63c which most appropriately reflects the dependence of the efficiency η on the frequency f and the time component α. The value for the pressure p, either the target value or the actual value p _to p _is in. In the in 1 example shown is the map 63a selected. Within the map, the efficiency η is then optimized under the boundary condition of the required delivery rate.

2 shows a detailed view of the piston pump and its drive source, which is a reluctance with two phases 4 and 5 is. The first phase 4 the reluctance actuator comprises a magnetic coil 41 on a stator 42 is wound, as well as one on the piston rod 33 attached first mover 43 , The second phase 5 the reluctance actuator comprises a magnetic coil 51 on a stator 52 is wound, as well as one on the piston rod 33 attach second mover 53 , In addition, between the first mover 43 and the second mover 53 still a spacer arranged. The magnetic coils 41 and 42 are each ring coils with high fill factor and around the axis 33a the piston rod 33 symmetrical. The stators 42 and 52 are also around the axis 33a symmetrical. From the control of the phases 4 and 5 is in the detail view of 2 only the power electronics 7 located.

The power electronics 7 does not necessarily have to be radially spaced from the piston pump. It can be arranged at any point, for example, also axially along the axis 33a spaced from the piston pump. The movers 43 and 53 , as well as optionally the spacer 54 , Optionally, may also be combined into a single, preferably one-piece, part.

Each of the phases 4 . 5 the reluctance actuator pulls when energized their solenoid 41 respectively. 51 the associated movers 43 respectively. 53 so in the gap of the respective stator 42 respectively. 52 in that the magnetic circuit is closed. In another arrangement, the working air gap and the tensile and compressive direction of the phases 4 and 5 of the reluctance actuator are reversed. For example, the arrangement of the phases 4 and 5 be dictated by the ease of assembly, especially when the phases 4 and 5 are not identical.

The phases 4 and 5 the reluctance actuator are in a common cylinder housing 38a framed by flanges 38b and 38e as well as lids 38c and 38d is closed. The lid 38c contains the installation space for the axial spring 34 , The piston rod 33 is in plain bearings 39a and 39b with associated seals 39c and 39d stored. It can be the seal 39c omitted when the case 38a . 38b . 38c is tight. In particular, the seal 39c omitted when the phases 4 and 5 of the reluctance actuator dry, ie without contact with the fuel 12 , operate. The inlet valve 36 and the exhaust valve 37 at the workroom 35 are each designed as check valves. The plain bearing 39b Optionally can also be omitted, to avoid the guidance of the piston 31 and its piston rod 33 is overdetermined overall. This is especially true when the piston rod 33 and the piston 31 manufactured as a one-piece part.

The pump housing 38f that the workroom 35 can, with the flange 38e optionally combined into a single, preferably one-piece, part. The lid 38d can optionally be omitted. The parts 38a . 38b and 38c may optionally be combined into a single, preferably one-piece, part. The spacers between the stator 42 and the flange 38b , or between the stator 52 and the flange 38e , can be omitted with appropriate part quality (manufacturing tolerance).

The required finishes and fits are essentially limited to the guidance of the piston 31 in the workroom 35 , Secondary air column, the axial position of the magnetic circuit parts, valve sealing surfaces and floating bearings.

3 illustrates the electronic control of the phases 4 and 5 the reluctance actuator via the power electronics 7 , 3a shows the schematic structure. The power electronics 7 is via the electrical system 13 of the motor vehicle 1 supplied with a mains voltage U ₀ . Depending on the control 6 transmitted values of the control parameters 61 and 62 charges the power electronics 7 the magnetic coil 41 the first phase 4 with a voltage U ₄ , whereupon in this magnetic coil 41 a current I ₄ flows. Likewise, the power electronics act on 7 the magnetic coil 51 the second phase 5 with a voltage U ₅ , whereupon in this magnetic coil 51 a current I ₅ flows. Schematically, the double piston amplitude 2Δ is also plotted, which of the mains voltage U ₀ , the currents I ₄ and I ₅ and the control parameters 61 and 62 depends. The power electronics 7 Internally uses two asymmetric MOSFET bridges to energize the solenoids 41 and 51 with the currents I ₄ and I ₅ .

3b shows the curves of the voltages U ₄ and U ₅ , and the currents I ₄ and I ₅ , plotted against the time t. Each pulse has a period T. During a time component α of each pulse, the vehicle electrical system voltage U _{0 is connected} through as a voltage U ₄ or U ₅ . For the remaining duration of the pulse, the voltage U ₄ or U _{5 is} zero. The two magnetic coils 41 respectively. 51 are always energized alternately.

The sudden increase of the voltage U ₄ or U ₅ from zero to the vehicle electrical system voltage U ₀ leads in each case to an exponential increase of the associated current I ₄ or I ₅ , whose speed through the inductance of the respective magnetic coil 41 respectively. 51 is predetermined. In the in 3b As shown, this increase is not continued until saturation, but is interrupted by the voltage U ₄ and U _{5 is} skipped back to zero. From this point on, the respective current I ₄ or I ₅ drops again with an exponential function.

Both with the pre-feed pump 3 generated pressure p as well as the delivered amount Q (volume flow) of fuel 12 depend solely on the vehicle electrical system voltage U ₀ , the pulse frequency f (or period T) and the time component α.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 102013218064 A1 [0005]

Claims (11)

Pre-feed pump ( 3 ) for a fuel injection system ( 2 ) of a motor vehicle ( 1 ), wherein the fuel injection system ( 2 ) next to the pre-feed pump ( 3 ) a high pressure pump ( 21 ) for feeding a busbar ( 22 ), wherein the busbar ( 22 ) in turn a plurality of injectors ( 23a - 23d ) and where lines ( 24 . 25 ) for the return of fuel ( 12 ) from the high pressure pump ( 21 ) and / or injectors ( 23a - 23d ) in the fuel tank ( 11 ) of the motor vehicle ( 1 ), characterized in that the prefeed pump ( 3 ) is a piston pump having at least one magnetic reluctance actuator ( 4 . 5 ) as a drive source for at least one piston ( 31 . 32 ), wherein the control ( 6 . 7 ) of the at least one reluctance actuator ( 4 . 5 ) a controller ( 64 ), which is adapted to a between the feed pump ( 3 ) and the high pressure pump ( 21 ) to regulate the fuel pressure p to a setpoint p _soll . Pre-feed pump ( 3 ) according to claim 1, characterized in that the controller ( 64 ) additionally at least one in the fuel tank ( 11 ) of the motor vehicle ( 1 ) receives returned amount of fuel ΔQ as feedback. Pre-feed pump ( 3 ) according to one of claims 1 to 2, characterized in that the control ( 6 . 7 ) of the at least one reluctance actuator ( 4 . 5 ) at least one map ( 63 ; 63a - 63c ), the combination of at least two independent control parameters ( 61 . 62 ) of the at least one reluctance actuator ( 4 . 5 ) an energy efficiency η of the feed pump ( 3 ). Pre-feed pump ( 3 ) according to claim 3, characterized in that the control ( 6 . 7 ) of the at least one reluctance actuator ( 4 . 5 ) several maps ( 63a - 63c ) for different values or ranges of values of the pre-feed pump ( 3 ) generated pressure p, and / or funded by the prefeed pump fuel quantity Q, are used. Pre-feed pump ( 3 ) according to one of claims 1 to 4, characterized in that a frequency ( 61 ), with which the at least one reluctance factor ( 4 . 5 ) is applied with current pulses, as well as a time proportion ( 62 ), during which each pulse has a rising edge, in the control ( 6 . 7 ) as a driving parameter ( 61 . 62 ) are provided. Pre-feed pump ( 3 ) according to claim 5, characterized in that a spring ( 34 ) for smoothing oscillations of the at least one piston ( 31 . 32 ) is provided. Pre-feed pump ( 3 ) according to one of claims 1 to 6, characterized in that a two-phase reluctance actuator ( 4 . 5 ), the first phase ( 4 ) of the reluctance actuator at least one piston ( 31 ) of the feed pump ( 3 ) when energized in a first rest position ( 31a ) and the second phase ( 5 ) of the reluctance actuator the at least one piston ( 31 ) of the feed pump ( 3 ) when energized in one of the first rest position ( 31a ) different rest position ( 31b ) drives. Pre-feed pump ( 3 ) according to claim 7, characterized in that two at opposite ends of a piston rod ( 33 ) arranged piston ( 31 . 32 ) are provided. Pre-feed pump ( 3 ) according to one of claims 7 to 8, characterized in that the two phases ( 4 . 5 ) of the reluctance actuator different transmission ratios between the current intensity of the respective magnetic coil ( 41 . 51 ) and the respective reluctance force exerted. Pre-feed pump ( 3 ) according to one of claims 1 to 9, characterized in that the control ( 6 . 7 ) is designed, by energizing at least one magnetic coil ( 41 . 51 ) of the at least one reluctance actuator ( 4 . 5 ) the prefeed pump ( 3 ) to prevent volatilization. Pre-feed pump ( 3 ) according to one of claims 1 to 10, characterized in that the piston ( 31 . 32 ) in a workroom ( 35 ) with an inlet valve ( 36 ) and an outlet valve ( 37 ), wherein the inlet valve ( 36 ) and the exhaust valve ( 37 ) are each designed as a check valve.

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