EP2889481B1 - Method for calibrating a membrane vacuum pump and membrane vacuum pump - Google Patents

Description

The invention relates to a method for calibrating a membrane vacuum pump and a membrane vacuum pump.

Diaphragm vacuum pumps are dry positive displacement pumps. It is known in practice that a connecting rod driven by a crankshaft moves a diaphragm clamped between a head cover and a housing of the membrane vacuum pump, which forms a suction chamber with the space in the head cover. Diaphragm vacuum pumps require inlet and outlet valves to achieve directional gas delivery. As valves, it is known from practice to use pressure-controlled flutter valves made of elastomer materials. There the pumping chamber is hermetically sealed by the diaphragm towards the drive, the required medium is neither contaminated by oil, nor can aggressive media attack the technique. The dead volume between the outlet valve and the suction chamber leads to a limited compression ratio, so that with a pumping stage usually a final pressure of about 70 hectopascals can be achieved.

Due to their carbon-free pump chamber, membrane vacuum pumps are particularly well suited as dry backing pumps for turbomolecular pumps with Holweck stage. Already two-stage diaphragm vacuum pumps, which reach about 5 hectopascal final pressure, can be used as backing pumps for Holweckturbopumpen.

The prior art ( DE 1 960 371 ) includes a diaphragm pump that works on a voice coil principle. In general, these pumps operate in such a way that in known piston pumps the piston is replaced by a diaphragm which is periodically deformed. In diaphragm pumps according to the voice coil principle, the drive is effected by a piston coupled to a voice coil.

This belonging to the prior art diaphragm pump has the disadvantage that the dead center of the piston, that is, the maximum stroke, must be set manually, so that the membrane is optimally applied to the diaphragm head. If it is not optimal, a dead volume remains in the delivery chamber, resulting in a limited compression ratio. On the other hand, the membrane must not be pressed too firmly on the membrane head to prevent premature wear.

The prior art ( DE 10 2006 044 248 B3 ) also includes a diaphragm pump. This to the state of the art belonging diaphragm pump tries to allow an exact dosage of a fluid to be delivered. For this purpose, the piston is brought into contact with a bottom surface of the piston working chamber and this defines an exact, bottom dead center, which is not dependent on further tolerances.

This belonging to the prior art diaphragm pump has the disadvantage that must be used in this diaphragm pump with a very high manufacturing accuracy. If the diaphragm is worn, the dead center can not be adjusted, so that a dead volume in the pump chamber can gradually develop during operation, which can not be compensated.

The prior art ( DE 859 477 C ) includes a piston compressor for chillers. According to this prior art, the piston compressor on a one-sided piston for chillers. The compressor belonging to the prior art operates such that the piston is actuated on its pressure stroke by means of a one-way device which is unable to exert any effect on it when the piston is falling, while the decrease (equal to the suction stroke of the piston) is due to the differential pressure of the piston Refrigerant is effected in the evaporator of the refrigerator relative to the atmosphere. According to this prior art, the piston is designed as a membrane clamped around it. The membrane is actuated in both directions by pressure, during the compression stroke, the actuator acts on the membrane, while in the decline, the membrane is moved back by the differential pressure of the refrigerant from the evaporator to the atmosphere. This belonging to the prior art diaphragm pump also has the disadvantage that in this diaphragm pump with a very high manufacturing accuracy has to be worked. If the diaphragm is worn, the dead center is not adjustable.

Furthermore belongs to the state of the art
( US 2005/047923 A1 ) a diaphragm pump with a voice coil drive. This belonging to the prior art linear diaphragm pump has a voice coil drive with a coil and a coil associated with the magnet, wherein the coil is designed as a stator and the magnet as a rotor. This prior art membrane vacuum pump can be further improved.

The technical problem underlying the invention is to provide a method for calibrating a membrane vacuum pump and a membrane vacuum pump, with which the disadvantages of the prior art can be avoided.

This technical problem is solved by a method having the features according to claim 1 and by a membrane vacuum pump having the features according to claim 7.

The method according to the invention for calibrating a diaphragm vacuum pump for conveying a gas and metering a medium with a pumping chamber which can be filled with the medium in a drive chamber having a diaphragm which separates the pumping chamber and the drive chamber and oscillates between the pumping chamber and the drive chamber is arranged, with a membrane head, which forms the delivery space with the membrane, wherein characterized in that a device for detecting a dead center and / or a position of the piston is provided and that a control device the dead center in dependence on the detected signal of the device adjusted.

The inventive method has the advantage that the membrane vacuum pump is designed as a self-calibrating diaphragm vacuum pump. The method according to the invention is carried out by the control device. With the control device and the voice coil drive of the diaphragm vacuum pump, a calibration of the dead center before each start or once after production is possible. The self-calibrating membrane vacuum pump according to the invention thus achieves an optimum final pressure. Furthermore, manufacturing tolerances can be compensated and / or increased by the method according to the invention. The associated cost savings of mechanical calibration and faster and cheaper manufacturing provides an optimal diaphragm vacuum pump.

With an advantageous development of the invention, the control device adjusts the dead center on the basis of a signal of at least one knock sensor. In this embodiment, the pump is controlled by a control loop itself. If the diaphragm strikes against the at least one knock sensor, the piston with the diaphragm is commanded at the next stroke to gradually reduce the stroke by a certain amount to finally find the optimal dead center ,

The control device adjusts the dead point advantageously only during a calibration drive. This self-calibration is carried out before commissioning the pump. During pumping, the dead center is not adjusted.

According to an advantageous embodiment of the invention, it is provided that, at the beginning of the calibration run, the piston drives the membrane into the membrane head or against a mechanical end point of the membrane with a force reduced compared to the pumping operation.

The inventive method saves the time required for a manual calibration and improves the final pressure of the diaphragm vacuum pump.

Before each start of the membrane vacuum pump, an automatic calibration travel is advantageously carried out.

During this calibration travel, the movement limit of the piston in the positive direction is determined by the piston driving the diaphragm into the membrane head or against a mechanical end point of the diaphragm with a force reduced compared to the pumping operation.

Advantageously, the control device continuously detects an actual position of the piston and compares this with a desired position. From the actual position and the desired position, the control device determines the end point of the movement of the diaphragm.

The benefit of this self-calibration results from the cost savings resulting from the lower manufacturing cost. At the same time, the components of such a pump can have lower manufacturing tolerances because the calibration compensates for them, resulting in a more efficient and less expensive one Manufacturing leads. The final pressure and the pumping speed of the membrane vacuum pump can be varied by the method according to the invention.

The determined end point of the membrane is advantageously stored and the end point is used during the pumping operation as the maximum stroke.

According to an advantageous embodiment of the invention, a calibration drive is performed before each startup of the membrane vacuum pump or once after production. This makes it possible to optimize the suction capacity and the final pressure of the diaphragm vacuum pump.

The dead center of the piston can be advantageously adjusted so that the membrane rests against the diaphragm head. This ensures that no dead space is created in the delivery chamber, which is particularly advantageous and optimizes the pumping speed of the membrane vacuum pump.

According to a further advantageous embodiment of the invention, the dead point is adjusted so that the membrane is pressed into the membrane head. This means that the membrane is moved "into the membrane head", or is pressed with a certain pressure, whereby the dead volume is reduced to a minimum, which in turn has a positive effect on the final pressure and pumping speed of the membrane vacuum pump. The pressure used should not lead to a plastic strain or destruction of the diaphragm material.

In principle, there is also the possibility that the dead center is set such that a distance of less than 0.5 millimeters, particularly advantageously less than 0.3 millimeters remains between the membrane and membrane head. Although this embodiment has a small dead volume in the membrane head. As a result, however, wear of the membrane is avoided.

According to a particularly preferred embodiment, the calibration is performed fully automatically. This gives a considerable time savings, since a manual calibration is very time consuming.

A calibration travel preferably comprises at least one stroke of the piston. During the calibration travel, the piston generally advantageously performs several strokes in order to achieve the best possible calibration.

According to a further advantageous embodiment of the invention, it is provided that when using a knock sensor, the stroke of the piston is reduced when the control device receives a signal from the knock sensor. If the knock sensor receives a signal, the diaphragm has moved against the knock sensor. In this case, the control device detects that the stroke is too high or that the dead center has been exceeded for an optimal calibration. In this case, advantageously, the stroke of the piston is either reduced by a predefined value or the stroke is gradually reduced, and after each step, a stroke is executed again to check whether the knock sensor is still providing a signal at a reduced stroke.

The predefined value is set in advance. For example, when the knock sensor gives a signal, the stroke may be reduced in the tenths of a millimeter range. It is also possible to specify from the outset that the stroke of the piston will be reduced by 0.3 millimeters or 0.5 millimeters.

According to a further advantageous embodiment of the invention it is provided that a holding force is adjusted, with which the membrane is pressed against the membrane head, and that this actual position of the piston is detected and stored. This holding force is needed to hold the membrane there for a short time after it has advantageously been pressed slowly into the mechanical end point, with the result that it is possible to detect and store the end point.

According to a further advantageous embodiment of the invention, it is provided that the maximum stroke of the piston during the calibration exceeds the determined actual position. It is possible to deliberately set the maximum stroke at the beginning of the calibration run higher than intended. In this case, the piston pushes the membrane in the end point and it is determined so the maximum stroke of the controller.

If the membrane is driven against the membrane head, the controller determines this movement as faulty. To continue the movement, the piston is prevented from stopping.

The resulting from the contact of the membrane with the membrane head or the constant comparison of the desired and actual position of the piston movement errors are advantageously counted. When the counter reaches a defined value, the control device ends the movement since the end point of the movement has been reached. This means that according to an advantageous embodiment of the invention, before the pumping operation of the membrane vacuum pump is started, the membrane is moved against the membrane head, that the control device detects this movement as faulty and that after at least two faulty movements, the control device detects and reduces the actual position of the dead center of the piston. This measure serves to minimize the wear of the membrane.

The reduction of the actual position of the dead center of the piston is preferably carried out by a predefined value. As already stated, the value can be set beforehand, for example in tenths of a millimeter increments (depending on the resolution of the installed measuring system).

The size of the predefined value advantageously determines whether the membrane is arranged at the dead center of the piston at a distance from the membrane head, adjacent to the diaphragm head or pressed against the membrane head.

Depending on which operation is desired with the diaphragm vacuum pump, the defined value is set in advance.

If the membrane is pressed into the membrane head, the dead volume is reduced as much as possible.

If the membrane is located only at the membrane head or if there is a minimal gap between the membrane and the membrane head, the wear of the membrane is lower.

Before switching on the pump, it is possible according to an advantageous embodiment of the invention that the piston with the diaphragm (actuator) intentionally moves against the diaphragm head. As a result, the control device measures a faulty movement in the form of "moving errors". After a certain number of erroneous movements over a certain period of time, the control device takes the actual value of the incremental sensor and subtracts a certain distance from the actual value.

The defined distance can be specified in millimeters. It is also possible to use another counting unit, for example "counts", which is proportional to the units of length.

The set distance or the set amount of "counts" depends among other things on the manufacturing tolerances.

According to a further advantageous embodiment of the invention, it is provided that an overshoot of the dead center of the piston occurring during a high-frequency operation is taken into account when setting the dead center of the piston.

In high-frequency operation, a so-called "over-shot", ie an overshoot of the actual approaching end point is generated. This is also to be considered in the calculation of the dead center and thus in the distance to be subtracted or the "counts". The maximum value thus determined is stored by the control device for continuous operation as a dead center.

According to a further advantageous embodiment of the invention, a lower movement limit of the piston is determined and stored. A lower movement limit, that is, when the piston moves away from the membrane head, is advantageously calculated and stored as the upper limit. In order to generate the most symmetrical sequence of movement of the membrane, the aim in the calculation is that the membrane travels as far as possible the same path in the positive as in the negative direction.

According to a further advantageous embodiment of the invention, a reduction in the reduction of the actuator unit, consisting of voice coil drive, piston and diaphragm, contributing differential pressure minimization is achieved by sealing the drive space against the atmospheric pressure. If the differential pressure is lowered by independently pumping out the back space of the diaphragm, a smaller voice coil drive or a lower current intensity can be used.

The differential pressure minimization is achieved particularly well with a two-headed diaphragm pump in which the forces of both heads cancel each other out.

For further optimization or reduction of the force, at least one spring can be integrated in the membrane head or in the linear drive. As a result, the actuator is supported in the recovery of the membrane.

The diaphragm vacuum pump according to the invention for conveying a gas with a pumpable with the gas delivery chamber with a linearly driven with a voice coil piston in a drive space with a membrane that separates the delivery chamber and the drive space and is arranged oscillating between the delivery chamber and the drive chamber, with a membrane head, the with the membrane forming the delivery chamber, wherein the piston is designed as a piston moving the membrane in motion and movable by a predetermined distance, is characterized in that a device for detecting a dead center and / or a position of the piston is provided and that a control device is provided, which is designed as a dead center as a function of the detected signal of the device adjustable control device.

The membrane vacuum pump according to the invention has the advantage that it can be carried out with its self-calibration method, as described in claims 1 to 16.

With the membrane vacuum pump according to the invention, the optimum dead center can be detected and adjusted via a self-calibration so that the membrane vacuum pump achieves an optimum final pressure and an optimal compression ratio.

According to a particularly preferred embodiment of the invention, at least one knock sensor is provided. The arranged in the diaphragm vacuum pump control device advantageously adjusted due to a signal of the knock sensor the dead center of the piston. This means that the knock sensor emits a signal when the diaphragm is moving against the knock sensor. In this case, the pressure point is not set correctly and the maximum stroke of the piston is reduced. The reduction can be made incrementally by predetermined path lengths or "counts". It is also possible to provide a predefined value by which the maximum stroke is reduced.

According to a further advantageous embodiment of the invention, the control device is designed as a dead center of the piston only during a calibration travel adjusting control device.

During the calibration, which may consist of at least one stroke, advantageously from several strokes of the piston, the pressure point of the piston can be adjusted by the control device. If the dead center is optimally set, it is stored and no longer changed during operation of the pump, that is to say in pump mode.

Only when a new calibration drive is performed, for example, after a service life of the pump, the dead center is adjusted by the controller if necessary again.

According to a further advantageous embodiment of the invention, the device for detecting a dead center and / or a position of the piston is designed as a Hall sensor.

Advantageously, the device for detecting a dead center and / or a position of the piston is designed as an incremental Hall sensor.

Hall sensors are very suitable as displacement sensors to detect the position of the piston.

The membrane vacuum pump can be designed as a single-headed, double-headed or multi-headed membrane vacuum pump.

For example, it is possible to provide a two-headed membrane vacuum pump, wherein the piston moves a membrane on each side in the axial direction in motion.

It is also possible to provide two membrane heads on one side and a membrane head on the other side of the piston.

According to an advantageous embodiment of the invention, the drive space is formed sealed against atmospheric pressure. The differential pressure minimization contributing to the reduction of the actuator unit is achieved by sealing the drive space against the atmospheric pressure.

Advantageously, the drive space is designed as a pumped drive space. If the differential pressure is lowered by independently pumping out the back space of the diaphragm, a smaller voice coil drive or a lower current intensity can be used.

According to a further advantageous embodiment of the membrane vacuum pump, at least one spring is provided in the membrane head and / or in the linear drive for returning the piston and the membrane. The spring achieves optimization and reduction of force. The actuator is supported by the spring when the diaphragm is returned.

According to a further advantageous embodiment of the invention, the membrane vacuum pump has at least one inlet valve and at least one outlet valve, which communicate with the delivery chamber. The valves are advantageously designed as reed valves and / or ball valves and / or disk valves. Other types of valves are also possible.

According to a further advantageous embodiment of the invention, a diaphragm vacuum pump is provided, wherein a voice coil drive has at least one coil and at least one magnet associated with the coil, in which the coil is designed as a stator and the magnet as a rotor. In this case, the coil of the drive changes from the position of the rotor to the position of the stator. At the same time the magnetic stator becomes the new rotor of the drive. The particular advantage of this embodiment is that the heat that arises primarily through the coil, can be significantly better dissipated. For this purpose, according to a further advantageous embodiment of the invention, it is provided that the stator conducts temperature with a housing is connected, and that are arranged on the housing cooling fins. This makes it possible to derive the temperature of the system very well. It can also be provided, for example, to provide a flow-blowing of the housing in order to keep the temperature of the system at a constant level.

The rotor can advantageously be mounted on at least two plain bearings or at least two ball sleeves.

This makes it possible to effectively reduce the gap between the coil and the magnet, whereby the efficiency of the drive increases.

A further embodiment of the membrane vacuum pump for conveying a gas with a filling chamber which can be filled with the gas, with a piston which can be driven linearly with a voice coil drive in a drive space, with a diaphragm which separates the delivery space and the drive space and is arranged oscillating between the delivery space and the drive space a membrane head which forms the delivery chamber with the membrane, the piston being designed as a piston which moves the membrane in motion and is movable by a predetermined distance, the voice coil drive having at least one coil and at least one magnet associated with the coil, characterized that the coil is designed as a stator and the magnet as a rotor.

In known from practice voice coil drives, the coil is designed as a rotor and the magnet as a stator. In these voice coil drives very high temperatures occur in the voice coil drive, since the coil can be poorly cooled as a runner.

According to the invention, the coil of the drive changes from the position of the rotor to the position of the stator. At the same time the magnetic stator becomes the new rotor of the drive. The particular advantage of the invention is that the heat generated primarily by the coil, can be dissipated significantly better. The coil is connected in accordance with an advantageous embodiment of the invention with a temperature-conducting housing, wherein on the housing advantageously cooling fins are arranged. This makes it possible to derive the temperature of the system very well. It can also be provided, for example, to provide a flow-blowing of the housing in order to keep the temperature of the system at a constant level.

The rotor can advantageously be mounted on at least two plain bearings or at least two ball sleeves.

This makes it possible to effectively reduce the gap between the coil and the magnet, whereby the efficiency of the drive increases.

According to a particularly advantageous embodiment of the diaphragm vacuum pump with the coil as the stator and the permanent magnet as a rotor, a device for detecting a dead center and / or a position of the piston and a control device is provided, which is adjustable as a dead center in response to the detected signal of the device Control device is formed.

This membrane vacuum pump according to the invention has the advantage that it can be carried out with its self-calibration method, as described in claims 1 to 6.

With the membrane vacuum pump according to the invention, the optimal dead center can be detected and adjusted via a self-calibration, so that the membrane vacuum pump reaches an optimal end pressure, at the same time effective cooling of the coils is possible.

According to a particularly preferred embodiment of the invention, at least one knock sensor is provided and the control device is designed as a control device based on a signal of the knock sensor which adjusts the dead center. This means that the knock sensor emits a signal when the diaphragm is moving against the knock sensor. In this case, the pressure point is not set correctly and the maximum stroke of the piston is reduced. The reduction can be made incrementally by predetermined path lengths or "counts". It is also possible to provide a predefined value by which the maximum stroke is reduced.

According to a further advantageous embodiment of the invention, the control device is designed as a dead center of the piston only during a calibration travel adjusting control device.

During the calibration, which may consist of at least one stroke, advantageously from several strokes of the piston, the pressure point of the piston can be adjusted by the control device. If the dead center is optimally set, it is stored and no longer changed during operation of the pump, that is to say in pump mode.

Only when a new calibration drive is performed, for example, after a service life of the pump, the dead center is adjusted by the controller if necessary again.

According to a further advantageous embodiment of the invention, the device for detecting a dead center or a position of the piston is designed as a Hall sensor. Advantageously, the device for detecting a dead center or a position of the piston is designed as an incremental Hall sensor.

Hall sensors are very suitable as displacement sensors to detect the position of the piston.

The membrane vacuum pump can be designed as a single-headed, double-headed or multi-headed membrane vacuum pump.

For example, it is possible to provide a two-headed membrane vacuum pump, wherein the piston moves a membrane on each side in the axial direction in motion.

It is also possible to provide two membrane heads on one side and a membrane head on the other side of the piston.

According to an advantageous embodiment of the invention, the drive space is formed sealed against atmospheric pressure. The differential pressure minimization contributing to the reduction of the actuator unit is achieved by sealing the drive space against the atmospheric pressure. According to a further advantageous embodiment of the invention, the drive space is designed as an evacuated drive space. If the differential pressure is lowered by independently pumping out the back space of the diaphragm, a smaller voice coil drive or a lower current intensity can be used.

According to a further advantageous embodiment of the membrane vacuum pump, at least one spring is provided in the membrane head and / or in the linear drive for returning the piston and the membrane. The spring achieves optimization and reduction of force. The actuator is supported by the spring when the diaphragm is returned.

According to a further advantageous embodiment of the invention, the membrane vacuum pump has at least one inlet valve and at least one outlet valve. The valves are advantageously in communication with the delivery chamber. The valves are advantageously designed as reed valves and / or ball valves and / or disk valves. Other types of valves are also possible.

The method according to the invention can be used with all the features in the membrane vacuum pumps described in the application. The membrane vacuum pumps described can also be combined with their features disclosed in the application.

The membrane vacuum pump can advantageously be designed as a two-headed membrane vacuum pump with a voice coil drive.

Two-headed diaphragm vacuum pump means that on both sides of the piston a diaphragm is driven by the reciprocating piston.

It can be provided here by an energy recovery by springs on both sides of the piston. Instead of the springs and capacitors may be provided.

In this case, a differential pressure minimization is not necessary because two membranes lie in one axis. As a result, the forces arising from the differential pressure cancel each other out.

With the membrane vacuum pumps according to the invention, lower ultimate pressures can be achieved since the dead volume is significantly reduced compared with the prior art.

The connection of the at least one coil of the voice coil drive or the coil pairs of the voice coil drive directly to the housing allow effective cooling, for example by blowing a Gehäusiverrippung.

1. 1. Kipp- beziehungsweise Pendelbewegungen der Membran von konventionellen, zum Stand der Technik gehörenden Membranpumpen mit Kurbelwelle werden durch eine rein lineare Bewegung verhindert. Ein Verschleiß der Membran im Membrankopf durch Schleifen oder Reiben am Membrankopf wird dadurch eliminiert.
2. 2. Die erfindungsgemäße Membranpumpe weist einen optimal angepassten Membrankopf an eine reine Linearbewegung der Membran auf, wodurch effektiv das Totvolumen verringert wird.
3. 3. Die Verringerung oder Verkleinerung der Ventilkanäle verringert das Totvolumen und verbessert damit den Enddruck beziehungsweise das Kompressionsverhältnis.

The diaphragm pump with voice coil drive according to the invention has the following advantages:

1. 1. Tilting or pendulum movements of the diaphragm of conventional, belonging to the prior art diaphragm pumps with crankshaft are prevented by a purely linear movement. A wear of the membrane in the membrane head by grinding or rubbing on the membrane head is thereby eliminated.
2. 2. The membrane pump according to the invention has an optimally adapted membrane head to a pure linear movement of the membrane, which effectively reduces the dead volume.
3. 3. The reduction or reduction of the valve channels reduces the dead volume and thus improves the final pressure or the compression ratio.

Fig. 1

einen Längsschnitt durch eine zweiköpfige Membranvakuumpumpe;

Fig. 2

eine perspektivische Ansicht mit Längsschnitt durch eine Membranvakuumpumpe gemäß Fig. 1;

Fig. 3

eine Seitenansicht in Längsrichtung der Membranvakuumpumpe der Fig. 1;

Fig. 4

eine perspektivische Ansicht einer Membranvakuumpumpe;

Fig. 5

einen Längsschnitt durch eine dreiköpfige Membranvakuumpumpe;

Fig. 6

ein Schnittbild durch eine Membranvakuumpumpe in vier Phasen in Funktion.

Further features and advantages of the invention will become apparent from the accompanying drawings, in which several embodiments of a membrane vacuum pump according to the invention are shown only by way of example. In the drawing show:

Fig. 1

a longitudinal section through a two-headed diaphragm vacuum pump;

Fig. 2

a perspective view with a longitudinal section through a diaphragm vacuum pump according to Fig. 1 ;

Fig. 3

a side view in the longitudinal direction of the diaphragm vacuum pump of Fig. 1 ;

Fig. 4

a perspective view of a membrane vacuum pump;

Fig. 5

a longitudinal section through a three-headed diaphragm vacuum pump;

Fig. 6

a sectional view through a diaphragm vacuum pump in four phases in operation.

Fig. 1 shows a membrane vacuum pump 1 with two non-positively connected to a piston 2 in connection membranes 3, 4. The membranes 3, 4 is associated with a respective membrane head 5, 6, against which the membranes 3, 4 go at maximum deflection of the piston 2.

In order to produce a continuous oscillation or oscillating movement of the piston 2, coils 7, that is current-carrying conductors, are operated in a magnetic field of permanent magnets 8 with a constantly changing current direction. Between the coil 7 and the permanent magnet 8, an air gap is present. This should be as low as possible be to increase the efficiency of the actuator consisting of piston 2 and membranes 3, 4.

The piston 2 is non-magnetic and is mounted on plain bearings 9. It is also a bearing without plain bearings possible with optimized positive (stabilizing) radial stiffness of the membrane assemblies (perpendicular to the stroke direction) and negative (destabilizing) radial stiffness of the coil assembly (perpendicular to the stroke direction).

In order to permanently determine the position of the piston 2, there is an incremental Hall sensor 10, which in the Fig. 1 is shown only schematically, for detecting the path in the region of the piston 2. The Hall sensor 10 is also used for current reversal, depending on the position of the piston 2, the current direction is reversed early. For energy recovery springs 11 are provided. The springs 11 are arranged on both sides of the piston 2. It may also be provided capacitors (not shown) for energy recovery.

The membranes 3, 4 are clamped between a housing 12 and the membrane heads 5, 6, so that a delivery chamber 13, 14 is gas-tightly separated from a drive space 15.

Compared to a conventional voice coil drive, the in Fig. 1 Drive shown on the coil 7, which is designed as a stator. The permanent magnets 8 are formed as a rotor. As a result, a very good heat dissipation from the coil 7 by direct contact with the housing 12 is possible. The housing 12 has cooling ribs 16, in particular in the region of the coil 7. These cooling fins, for example, with room air, which has a lower temperature compared to the housing temperature, flows around be, whereby the coil 7 can be kept at a constant temperature.

In the Fig. 1 shown coil 7 advantageously consists of a plurality of coil pairs, which can be energized differently in order to move the permanent magnet rotor can.

In Fig. 2 the vacuum pump 1 is shown in cutaway form. The same parts are provided with the same reference numbers. To avoid repetition, refer to the description of the figure Fig. 1 directed.

In Fig. 2 the cooling fins 16 can be seen, which serve to cool the coil 7.

Fig. 3 shows a side view of the vacuum pump 1 with the cooling fins 16.

Fig. 4 shows a perspective view of the diaphragm pump 1. Also clearly the cooling fins 16 can be seen.

The vacuum pump 1, which in Fig. 1 is shown, has the Hall sensor 10, which serves to detect the position of the piston 2. An only schematically indicated control device 17, to which the signals of the Hall sensor 10 are transmitted, detects the dead center of the piston 2. The control device 17 detected in dependence on the position of the piston 2, the dead center of the piston. Before the pump is put into operation, ie before a pumping operation, a calibration run is carried out. Here, the piston 2 moves with respect to the pumping operation reduced force the membrane 3 in the diaphragm head 5 or against a mechanical end point of the diaphragm 3. In this case, the control device 17 detects the actual position of the piston 2 continuously and compares this with a target position. From a comparison of the actual position with the desired position, the control device 17 determines the end point of the movement of the diaphragm. This end point is continuously used during the pumping operation of the membrane vacuum pump 1 as the maximum stroke.

The dead center of the piston 2 can be adjusted such that the membrane 3 is arranged adjacent to the membrane head 5. The dead center can also be adjusted so that a distance of less than 0.3 mm remains between the membrane and membrane head. The dead center can also be adjusted so that the membrane 3 is pressed against the membrane head 5 with a certain force.

Advantageously, the dead center is set such that the membrane 3 rests completely on the membrane head 5, so that the delivery chamber 13 has no dead volume, so that the pump power of the pump is optimized.

According to the in Fig. 1 illustrated two-head diaphragm pump, the calibration described also for the membrane 4 and the diaphragm head 6 is carried out accordingly.

The drive space 15 is sealed against atmospheric pressure. Advantageously, the drive chamber 15 is additionally pumped out. The membrane vacuum pump 1 according to Fig. 1 has an inlet valve and an outlet valve for each delivery chamber 13, 14.

Fig. 5 shows a modified embodiment of a membrane vacuum pump 20. The membrane vacuum pump 20 has a housing 21 in which the piston 22 is linearly mounted.

The linear drive, consisting of coils and magnets, is in Fig. 5 not shown, but according to the principle of Fig. 1 ,

According to Fig. 5 the vacuum pump has three membrane heads 22, 23, 24. The membrane heads 22, 23, 24 are associated with membranes 25, 26, 27. The movement of the membrane 27 by the piston 22 is effected directly via a rod 28. The movement of the membranes 25, 26 through the piston 22 via a tee 29. The membrane heads 22, 23 may be connected in parallel or in series.

In Fig. 5 only the membrane heads 22, 23, 24 are shown schematically. Inlets and outlets are not shown.

Fig. 6 shows the sake of completeness, the principle of operation of a diaphragm vacuum pump according to the prior art.

Fig. 6 shows a membrane vacuum pump 1 with a housing 12 having a membrane 30 which is clamped in the edge of the housing 12 and can be offset by a drive connecting rod 31 of a motor drive in a tumbling downward movement.

In the housing 12 is a limited by the membrane 3 of a housing head 32 suction chamber 13, which is limited relative to the membrane 3 of the housing head 5 of the housing 12.

In the housing head 5 is at least one leading into the pumping chamber 13 suction line 18 with an inlet valve assembly 33 and at least one of the suction chamber 13 leading discharge line 19 with an outlet valve assembly 34th

In general, the inlet valve arrangement 33 has an inlet valve opening 35 and an inlet valve opening 36 which closes the inlet valve opening 35 when there is overpressure in the suction chamber 13. In a corresponding manner, the outlet valve arrangement 34 has a closing outlet valve body 37 at negative pressure in the suction chamber 13.

During the downward movement of the membrane 3, a negative pressure is created in the delivery chamber 13, whereby a differential pressure is present at the inlet valve body 36, which presses the valve body 36 in the direction of the delivery chamber 13. Through the open inlet valve, gas flows from the suction line 18 into the suction chamber 13. During the upward movement of the membrane 3, an overpressure is created in the delivery chamber 13, whereby a differential pressure is present at the inlet valve body 36 which presses the valve body 36 in the direction of the valve opening 35. During the downward movement of the diaphragm 3, a negative pressure is created in the delivery chamber 13, whereby a differential pressure arises at the outlet valve body 38, which presses the valve body 38 in the direction of delivery chamber 13 and into the valve opening 39. During the upward movement of the diaphragm 3, an overpressure is created in the delivery chamber 13, whereby a differential pressure is present at the outlet valve body 38 which presses the valve body 38 in the direction of the housing cover 40. This means that upon downward movement of the connecting rod 31, the inlet valve arrangement 33 opens, so that gas flows from the conduit 18 into the delivery chamber 13. Upon upward movement of the connecting rod 31, the inlet valve arrangement 33 and the outlet valve arrangement 34 close, so that the gas located in the delivery space 13 flows into the conduit 19.

reference numerals

1

Diaphragm vacuum pump

2

piston

3

membrane

4

membrane

5

membrane head

6

Kitchen sink

7

Kitchen sink

8th

magnet

9

bearings

10

Hall sensor

11

feathers

12

casing

13

delivery chamber

14

delivery chamber

15

drive space

16

cooling fins

17

control device

18

inlet

19

outlet

20

diaphragm pump

21

casing

22

membrane head

23

membrane head

24

membrane head

25

membrane

26

membrane

27

membrane

28

pole

29

Tee

30

membrane

31

pleuel

32

housing head

33

Inlet valve arrangement

34

The discharge valve

35

Intake valve opening

36

valve body

37

valve body

38

valve body

39

exhaust valve opening

40

housing cover

Claims (16)

1. Method for calibrating a membrane vacuum pump (1) for delivering a medium, with a delivery chamber (13, 14) that can be filled with the medium, with a piston (2) in a drive chamber (15), which piston can be linearly driven by means of a moving coil drive, with a membrane (3, 4), which separates the delivery chamber (13, 14) and the drive chamber (15) and is arranged in a reciprocating manner between the delivery chamber (13, 14) and drive chamber (15), with a membrane head (5), which together with the membrane (3, 4) forms the delivery chamber (13, 14), wherein the piston (2) is configured as a piston (2) that sets the membrane (3, 4) in motion and that can be moved over a predetermined path length,
   characterised in that a device (10) for detecting a dead centre and/or position of the piston (2) is provided, and in that a control device (17) adjusts the dead centre depending on the detected signal of the device (10).
2. Method according to claim 1, characterised in that the control device (17) adjusts the dead centre on the basis of a signal of at least one knock sensor, and/or in that the control device (17) adjusts the dead centre of the piston (2) solely during a calibration run.
3. Method according to either one of the preceding claims, characterised in that the control device (17) continuously detects a current position of the piston (2) and compares it with a target position, and in that the control device (17) determines the end point of the movement of the membrane (3, 4) from the current position and the target position, in particular in that the determined end point of the membrane (3, 4) is stored, and in that the end point is used as maximum stroke during operation of the pump.
4. Method according to any one of the preceding claims, characterised in that the dead centre is set in such a way that a spacing of less than 0.5 millimetres remains between the membrane (3, 4) and membrane head (5, 6), in particular in that the dead centre is set in such a way that the membrane (3, 4) abuts the membrane head (5, 6), in particular in that the dead centre is set in such a way that the membrane (3, 4) is pressed into the membrane head (5, 6).
5. Method according to any one of the preceding claims, characterised in that the calibration is performed in a fully automated manner, and in that a calibration run comprises at least one stroke of the piston (2), in particular in that, with use of a knock sensor, the stroke of the piston (2) is reduced if the control device (17) receives a signal from the knock sensor.
6. Method according to any one of the preceding claims, characterised in that, before starting pump operation of the membrane vacuum pump (1), the membrane (3, 4) is driven against the membrane head (5, 6), and in that the control device (17) detects this movement as being defective, and in that, after at least two defective movements, the control device (17) detects and reduces the current position of the dead centre of the piston (2), and in that the current position of the dead centre of the piston (2) is reduced by a predefined value, in particular in that the magnitude of the predefined value determines whether the membrane (3, 4) in the dead centre of the piston (2) is arranged at a spacing from the membrane head (5, 6), abutting the membrane head (5, 6), or pressed against the membrane head (5, 6).
7. Membrane vacuum pump (1) for delivering and metering a gas, with a delivery chamber (13, 14) that can be filled with the gas, with a piston (2) in a drive chamber (15), which piston can be linearly driven by means of a moving coil drive, with a membrane (3, 4) which separates the delivery chamber (13, 14) and the drive chamber (15) and is arranged in a reciprocating manner between the delivery chamber (13, 14) and the drive chamber (15), with a membrane head (5), which together with the membrane (3, 4) forms the delivery chamber (13, 14), wherein the piston (2) is configured as a piston (2) that sets the membrane (3, 4) in motion and that can be moved over a predetermined path length,
   characterised in that a device (10) for detecting a dead centre and/or a position of the piston (2) is provided, and in that a control device (17) is provided, which is configured as a control device (17) that can adjust the dead centre depending on the detected signal of the device (10).
8. Membrane vacuum pump according to claim 7, wherein a moving coil drive comprises at least one coil and at least one magnet associated with the coil, characterised in that the coil (7) is formed as a stator and the magnet (8) is formed as a rotor.
9. Membrane vacuum pump according to claim 7 for delivering a gas, with a delivery chamber that can be filled with the gas, with a piston in a drive chamber, which piston can be linearly driven by means of a moving coil drive, with a membrane, which separates the delivery chamber and the drive chamber and is arranged in a reciprocating manner between the delivery chamber and drive chamber, with a membrane head, which together with the membrane forms the delivery chamber, wherein the piston is configured as a piston that sets the membrane in motion and that can be moved over a predetermined path length, wherein the moving coil drive comprises at least one coil and at least one magnet associated with the coil, characterised in that the coil (7) is formed as a stator and the magnet (8) is formed as a rotor.
10. Membrane vacuum pump according to claim 7, 8 or 9, characterised in that the stator is connected in thermally conductive manner to a housing (12), and in that cooling ribs (16) are arranged on the housing (12).
11. Membrane vacuum pump according to any one of claims 7 to 10, characterised in that a device (10) for detecting a dead centre and/or a position of the piston (2) is provided, and in that a control device (17) is provided, which is configured as a control device (17) that can adjust the dead centre depending on the detected signal of the device (10).
12. Membrane vacuum pump according to any one of claims 7 to 11, characterised in that at least one knock sensor is provided, and in that the control device (17) is configured as a control device (17) adjusting the dead centre on the basis of a signal of the knock sensor, and/or in that the control device (17) is configured as a control device (2) adjusting the dead centre of the piston (2) solely during a calibration run, and/or in that the device (10) for detecting a dead centre and/or a position of the piston (2) is configured as a Hall sensor, and/or in that the device (10) for detecting a dead centre and/or a position of the piston (2) is configured as an incremental Hall sensor.
13. Membrane vacuum pump according to any one of claims 7 to 12, characterised in that the membrane vacuum pump (1, 21) is configured as a single-head, twin-head, or multi-head membrane vacuum pump (1, 21), in particular in that the drive chamber (15) is sealed with respect to atmospheric pressure.
14. Membrane vacuum pump according to any one of claims 7 to 13, characterised in that the drive chamber (15) is configured as a drive chamber (15) that is pumped out.
15. Membrane vacuum pump according to any one of claims 7 to 14, characterised in that, in order to restore the piston (2) and the membrane (3, 4), at least one spring (11) is provided in the membrane head (5, 6) and/or in the linear drive.
16. Membrane vacuum pump according to any one of claims 7 to 15, characterised in that the membrane vacuum pump (1, 21) has at least one inlet valve (18) and at least one outlet valve (19), and in that the valves (18, 19) are formed as reed valves and/or ball valves and/or disc valves.

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