EP2889481B2 - Method for calibrating a membrane vacuum pump and membrane vacuum pump - Google Patents

Description

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

Diaphragm vacuum pumps are dry displacement pumps. It is known from practice that a connecting rod driven by a crankshaft moves a diaphragm clamped between a head cover and a housing of the diaphragm vacuum pump, which diaphragm 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 reed valves made of elastomeric materials. Since the suction chamber is hermetically sealed by the diaphragm from the drive, the required medium is neither contaminated by oil nor can aggressive media attack the technology. The dead volume between the outlet valve and the suction chamber leads to a limited compression ratio, so that a final pressure of around 70 hectopascals can usually be achieved with one pump stage.

Due to their carbon-free suction chamber, diaphragm vacuum pumps are particularly well suited as dry backing pumps for turbomolecular pumps with a Holweck stage. Even two-stage diaphragm vacuum pumps that achieve a final pressure of around 5 hectopascals can be used as backing pumps for Holweck turbopumps.

On the state of the art ( DE 1 960 371 ) includes a membrane pump that works according to a voice coil principle. In general, these pumps work in such a way that, in known piston pumps, the piston is replaced by a diaphragm which is periodically deformed. Diaphragm pumps based on the voice coil principle are driven by a piston coupled to a voice coil.

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

On the state of the art ( DE 10 2006 044 248 B3 ) also includes a diaphragm pump. This diaphragm pump, which belongs to the state of the art, tries to enable an exact dosing of a fluid to be pumped. 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 that is not dependent on further tolerances.

This diaphragm pump, which is part of the prior art, has the disadvantage that this diaphragm pump has to be manufactured with a very high level of manufacturing accuracy. If the membrane wears out, the dead center cannot be adjusted, so that a dead volume can gradually arise in the suction chamber during operation, which cannot be compensated for.

On the state of the art ( DE 859 477 C ) includes a piston compressor for refrigeration machines. According to this prior art, the piston compressor has a single-acting piston for refrigerating machines. The compressor belonging to the prior art operates in such a way that the piston is actuated on its discharge stroke by means of a one-way device which is unable to have any effect on the piston's descent, while the descent (equal to the suction stroke of the piston) is caused by the differential pressure of the Refrigerant is effected in the evaporator of the refrigerator to the atmosphere. According to this prior art, the piston is designed as a membrane clamped all around. The diaphragm is pressure actuated in both directions by the actuator acting on the diaphragm during the compression stroke, while on the retraction stroke the diaphragm is moved back by the differential pressure of the refrigerant from the evaporator versus atmosphere. This diaphragm pump, which is part of the prior art, also has the disadvantage that this diaphragm pump has to be manufactured with a very high level of manufacturing accuracy. If the membrane wears out, the dead center cannot be adjusted.

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

The technical problem on which the invention is based consists in specifying a method for calibrating a diaphragm vacuum pump and a diaphragm vacuum pump with which the disadvantages of the prior art can be avoided.

This technical problem is solved by a method having the features of claim 1 and by a diaphragm vacuum pump having the features of claim 7 .

The method according to the invention for the self-calibration of a diaphragm vacuum pump for conveying a gas and metering a medium with a conveying chamber that can be filled with the gas with a piston that can be driven linearly with a voice coil drive in a drive chamber with a membrane that separates the conveying chamber and the drive chamber and oscillates between the conveying chamber and the drive chamber is arranged, with a membrane head which forms the pumping chamber with the membrane, the piston being designed as a piston which sets the membrane in motion and can be moved 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 adjusts the dead center depending on the detected signal of the device, and that before the pump is put into operation, i.e. before a pumping process, an automatic calibration run is carried out, the piston with opposite to the Pump operation with reduced force moves the membrane into the membrane head or against a mechanical end point of the membrane.

The method according to the invention has the advantage that the diaphragm 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, the dead center can be calibrated before each start or once after production. The membrane vacuum pump, which is self-calibrating with the method according to the invention, thereby achieves an optimal final pressure. Furthermore, manufacturing tolerances can be compensated for and/or increased by the method according to the invention. The associated cost savings of the mechanical calibration and the faster and cheaper production 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 from at least one knock sensor. In this version, the pump regulates itself using a control loop. If the membrane hits the at least one knock sensor, the piston with the membrane receives the command for the next stroke to gradually minimize the stroke by a certain value in order to finally find the optimum dead center .

The control device advantageously adjusts the dead center only during a calibration run. This self-calibration is carried out before the pump is started up. The dead center is not adjusted during pump operation.

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

The method according to the invention saves the time required for manual calibration and improves the ultimate pressure of the diaphragm vacuum pump.

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

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

The control device advantageously continuously detects an actual position of the piston and compares it with a target position. The control device determines the end point of the movement of the membrane from the actual position and the target position.

The advantage that arises from this self-calibration results from the cost savings that come about as a result of the lower production costs. At the same time, the components of such a pump can have lower manufacturing tolerances, since the calibration compensates for them, which leads to more efficient and cheaper manufacturing. The ultimate pressure and the pumping speed of the diaphragm vacuum pump can be varied using the method according to the invention.

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

According to an advantageous embodiment of the invention, a calibration run is carried out before each start-up of the membrane vacuum pump or once after manufacture. This makes it possible to optimize the pumping speed and the ultimate pressure of the diaphragm vacuum pump.

The dead center of the piston can advantageously be set in such a way that the membrane is in contact with the membrane head. This ensures that there is no dead space in the pumping chamber, which is particularly advantageous and optimizes the pumping speed of the diaphragm vacuum pump.

According to a further advantageous embodiment of the invention, the dead center is set in such a way that the membrane is pressed into the membrane head. This means that the membrane is moved "into the membrane head" or is pressed on with a certain pressure, which reduces the dead volume to a minimum, which in turn has a positive effect on the ultimate pressure and pumping speed of the membrane vacuum pump. The pressure used should not lead to plastic expansion or destruction of the diaphragm material.

In principle, there is also the possibility that the dead center is set in such a way that a distance of less than 0.5 millimeters, particularly advantageously less than 0.3 millimeters, remains between the membrane and the membrane head. According to this embodiment, there is a small dead volume in the membrane head. However, this avoids wear on the membrane.

According to a particularly preferred embodiment, the calibration is carried out fully automatically. This saves a considerable amount of time, since manual calibration is very time-consuming.

A calibration run preferably includes at least one stroke of the piston. During the calibration run, 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 membrane has moved against the knock sensor. Here, the control device detects that the hub is too large, or that the dead center has been exceeded for optimal calibration. In this case, the stroke of the piston is advantageously either reduced by a predefined value or the stroke is reduced in steps and after each step another stroke is carried out in order to check whether the knock sensor is still delivering a signal when the stroke is reduced.

The predefined value is set in advance. For example, when the knock sensor gives a signal, the stroke can be reduced by a tenth of a millimeter. It is also possible to specify from the outset that the stroke of the piston is 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 set, with which the membrane is pressed against the membrane head, and that this actual position of the piston is recorded and stored. This holding force is required in order to briefly hold the membrane there after it has advantageously been pressed slowly into the mechanical end point, which means that there is the possibility of detecting and storing the end point.

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

If the membrane is moved against the membrane head, the control device determines that this movement is faulty. In order to be able to continue the movement, the piston is prevented from stopping.

The movement errors resulting from the contact of the membrane with the membrane head or the constant comparison of the target and actual position of the piston are advantageously counted. If 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 pumping operation of the diaphragm vacuum pump is started, the diaphragm is moved against the diaphragm head, that the control device detects this movement as incorrect and that after at least two incorrect movements the control device detects the actual position of the dead center of the piston and decreased. This measure serves to minimize wear on the membrane.

The actual position of the dead center of the piston is preferably reduced by a predefined value. As already explained, the value can be specified 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, lying against the membrane 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 only in contact with the membrane head or if there is a minimal gap between the membrane and the membrane head, the wear on the membrane is lower.

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

The defined distance can be given in millimeters. It is also possible to use a different counting unit, such as "counts", which is proportional to the units of length.

The specified distance or the specified 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 as a result of high-frequency operation is taken into account when setting the dead center of the piston.

In high-frequency operation, a so-called "overshot" is generated, i.e. an overshoot of the actual end point to be approached. This must also be taken into account when calculating the dead center and thus the distance to be deducted or the "counts". The control device stores the maximum value determined in this way as a dead center for continuous operation.

According to a further advantageous embodiment of the invention, a lower movement limit of the piston is determined and stored. A lower movement limit, ie when the piston moves away from the membrane head, is advantageously calculated and stored like the upper limit. In order to generate the most symmetrical possible movement sequence of the membrane, the calculation strives for the membrane to cover the same distance in the positive as in the negative direction.

According to a further advantageous embodiment of the invention, a reduction in the size of the actuator unit, consisting of the voice coil drive, piston and membrane, contributes to minimizing the differential pressure by sealing the drive chamber against the reached atmospheric pressure. If the differential pressure is lowered by self-pumping of the rear chamber of the membrane, a smaller voice coil drive or a lower amperage can be used.

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

At least one spring can be integrated in the diaphragm head or in the linear drive to further optimize or reduce the force. This supports the actuator in restoring the membrane.

The diaphragm vacuum pump according to the invention, which is designed as a self-calibrating diaphragm vacuum pump, for delivering a gas with a delivery chamber that can be filled with the gas, with a piston that can be driven linearly with a voice coil drive in a drive chamber with a membrane that separates the delivery chamber and the drive chamber and between the delivery chamber and the drive chamber is arranged to oscillate, with a membrane head which forms the pumping chamber with the membrane, the piston being designed as a piston which sets the membrane in motion and can be moved by a predetermined distance, is characterized in that a device for detecting a dead center and/or 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, and that the diaphragm vacuum pump before the pump is put into operation, i.e. before a pump The piston is designed as a piston that drives the diaphragm into the diaphragm head or against a mechanical end point of the diaphragm with a reduced force compared to pump operation.

The diaphragm pump according to the invention has the advantage that it can be used to carry out self-calibration methods as described in claims 1 to 15.

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

According to a particularly preferred embodiment of the invention, at least one knock sensor is provided. The control device arranged in the diaphragm vacuum pump advantageously adjusts the dead center of the piston on the basis of a signal from the knock sensor. This means that the knock sensor emits a signal when the membrane moves 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 may be incremental 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 control device that adjusts the dead center of the piston only during a calibration run.

During the calibration run, which can consist of at least one stroke, advantageously 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 saved and no longer changed during operation of the pump, i.e. during pumping operation.

Only when a new calibration run is carried out, for example after the pump has been idle, is the dead center adjusted again by the control device if necessary.

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.

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

Hall sensors are very well suited as displacement sensors to record the position of the piston.

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

It is possible, for example, to provide a two-head diaphragm vacuum pump, with the piston moving a diaphragm on each side, viewed in the axial direction.

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

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

The drive space is advantageously designed as a pumped-out drive space. If the differential pressure is lowered by self-pumping of the rear chamber of the membrane, a smaller voice coil drive or a lower amperage can be used.

According to a further advantageous embodiment of the diaphragm vacuum pump, at least one spring is provided in the diaphragm head and/or in the linear drive to reset the piston and the diaphragm. The spring optimizes and reduces the force. The actuator is supported by the spring when the membrane returns.

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

According to a further advantageous embodiment of the invention, a membrane vacuum pump is provided, with a voice coil drive at least has a coil and at least one magnet associated with the coil, in which the coil is designed as a stator and the magnet is designed as a rotor. 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 runner of the drive. The particular advantage of this embodiment lies in the fact that the heat that is primarily generated by the coil can be dissipated much better. For this purpose, according to a further advantageous embodiment of the invention, it is provided that the stator is connected to a housing in a temperature-conducting manner, and that cooling fins are arranged on the housing. This makes it possible to derive the temperature of the system very well. It can also be provided, for example, that the housing be blown on in a streamlined manner in order to keep the temperature of the system at a constant level.

The runner 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 magnet, which increases the efficiency of the drive.

A further embodiment of the membrane vacuum pump for conveying a gas with a conveying chamber that can be filled with the gas, with a piston that can be driven linearly with a voice coil drive in a drive chamber, with a membrane that separates the conveying chamber and the drive chamber and is arranged to vibrate between the conveying chamber and the drive chamber, with a membrane head which forms the pumping chamber with the membrane, the piston being designed as a piston which sets the membrane in motion and can be moved by a predetermined distance, the voice coil drive having at least one coil and at least one magnet assigned to the coil, is characterized that the coil is designed as a stator and the magnet as a rotor.

In the case of voice coil drives known from practice, the coil is designed as a rotor and the magnet as a stator. In the case of these voice coil drives, very high temperatures occur in the voice coil drive, since the coil, being the runner, is difficult to cool.

According to the invention, the coil of the drive changes from the rotor position to the stator position. At the same time, the magnetic stator becomes the new runner of the drive. The particular advantage of the invention lies in the fact that the heat that is primarily generated by the coil can be dissipated much better. According to an advantageous embodiment of the invention, the coil is connected to a housing in a temperature-conducting manner, with cooling ribs advantageously being arranged on the housing. This makes it possible to derive the temperature of the system very well. It can also be provided, for example, that the housing be blown on in a streamlined manner in order to keep the temperature of the system at a constant level.

The runner 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 magnet, which increases the efficiency of the drive.

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

This diaphragm vacuum pump according to the invention has the advantage that it can be used to carry out self-calibration methods 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 self-calibration, so that the membrane vacuum pump achieves an optimal final pressure, with effective cooling of the coils being possible at the same time.

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 that adjusts the dead center on the basis of a signal from the knock sensor. This means that the knock sensor emits a signal when the membrane moves 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 may be incremental 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 control device that adjusts the dead center of the piston only during a calibration run.

During the calibration run, which can consist of at least one stroke, advantageously 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 saved and no longer changed during operation of the pump, i.e. during pumping operation.

Only when a new calibration run is carried out, for example after the pump has been idle, is the dead center adjusted again by the control device if necessary.

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. The device for detecting a dead center or a position of the Piston designed as an incremental Hall sensor.

Hall sensors are very well suited as displacement sensors to record the position of the piston.

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

It is possible, for example, to provide a two-head diaphragm vacuum pump, with the piston moving a diaphragm on each side, viewed in the axial direction.

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

According to an advantageous embodiment of the invention, the drive space is sealed against atmospheric pressure. The differential pressure minimization contributing to the reduction of the actuator unit is achieved by sealing the drive chamber against atmospheric pressure. According to a further advantageous embodiment of the invention, the drive space is designed as a pumped-out drive space. If the differential pressure is lowered by self-pumping of the rear chamber of the membrane, a smaller voice coil drive or a lower amperage can be used.

According to a further advantageous embodiment of the diaphragm vacuum pump, at least one spring is provided in the diaphragm head and/or in the linear drive to reset the piston and the diaphragm. The spring optimizes and reduces the force. The actuator is supported by the spring when the membrane returns.

According to a further advantageous embodiment of the invention, the diaphragm vacuum pump has at least one inlet valve and at least one outlet valve. The valves are advantageously connected to the pumping chamber. The valves are advantageously designed as reed valves and/or ball valves and/or disc valves. Other types of valves are also possible.

The method according to the invention can be used with all of 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 either side of the piston, a diaphragm is driven by the reciprocating piston.

In this case, energy recovery can be provided by springs on both sides of the piston. Capacitors can also be provided instead of the springs.

In this case, minimizing the differential pressure is not necessary, since two membranes are in one axis. This cancels out the forces that arise from the differential pressure.

With the membrane vacuum pumps according to the invention, lower ultimate pressures can be achieved since the dead volume is significantly reduced compared to 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 enables effective cooling, for example by blowing on housing ribbing.

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. This eliminates wear and tear on the membrane in the membrane head caused by grinding or rubbing on the membrane head.
2. 2. The membrane pump according to the invention has a membrane head that is optimally adapted to a purely linear movement of the membrane, as a result of which the dead volume is effectively reduced.
3. 3. Reducing or reducing the size of the valve ports reduces the dead volume and thus improves the end 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 result from the associated drawing, in which several exemplary embodiments of a diaphragm vacuum pump according to the invention are shown only as examples. Show in the drawing:

1

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

2

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

3

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

4

a perspective view of a diaphragm vacuum pump;

figure 5

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

6

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

1 shows a diaphragm vacuum pump 1 with two non-positively connected to a piston 2 stationary membranes 3, 4. The membranes 3, 4 are each assigned a membrane head 5, 6, against which the membranes 3, 4 drive when the piston 2 is at its maximum deflection.

In order to generate a continuous oscillation or oscillating movement of the piston 2, coils 7, ie current-carrying conductors, are operated in a magnetic field by permanent magnets 8 with a constantly changing current direction. There is an air gap between the coils 7 and the permanent magnets 8 . This should be as low as possible in order 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 slide bearings 9 . Storage without plain bearings is also possible with optimized positive (stabilizing) radial rigidity of the membrane arrangements (perpendicular to the stroke direction) and negative (destabilizing) radial rigidity of the coil arrangement (perpendicular to the stroke direction).

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

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

Compared to a conventional voice coil drive, the in 1 shown drive on the coil 7, which is designed as a stator. The permanent magnets 8 are designed as runners. This enables very good heat dissipation from the coil 7 through direct contact with the housing 12 . The housing 12 has cooling ribs 16 in particular in the area of the coil 7 . Room air, for example, which has a lower temperature than the housing temperature, can flow around these cooling fins, as a result of which the coil 7 can be kept at a constant temperature.

In the 1 The coil 7 shown advantageously consists of several pairs of coils which can be energized differently in order to be able to move the permanent magnet rotor.

In 2 the vacuum pump 1 is shown in cutaway form. Identical parts are provided with the same reference numbers. In order to avoid repetition, the description of the figures by 1 referred.

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

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

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

The vacuum pump 1, which is in 1 is shown, has the Hall sensor 10, which is used to detect the position of the piston 2. A control device 17, indicated only schematically, to which the signals of the Hall sensor 10 are transmitted, detects the dead center of the piston 2. The control device 17 detects the dead center of the piston as a function of the position of the piston 2. A calibration run is carried out before the pump is put into operation, ie before a pumping process. The piston 2 moves the membrane 3 into the membrane head 5 or against a mechanical end point of the membrane 3 with a reduced force compared to pump operation. The control device 17 continuously detects the actual position of the piston 2 and compares it with a target position. The control device 17 determines the end point of the movement of the membrane by comparing the actual position with the target position. This end point is used continuously as the maximum stroke during the pumping operation of the diaphragm vacuum pump 1 .

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

The dead center is advantageously set in such a way that the membrane 3 bears completely against the membrane head 5 so that the pumping space 13 has no dead volume, so that the pump performance of the pump is optimized.

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

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

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

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

According to figure 5 the vacuum pump has three diaphragm heads 22, 23, 24. The membrane heads 22, 23, 24 are associated with membranes 25, 26, 27. The membrane 27 is moved by the piston 22 directly via a rod 28. The movement of the membranes 25, 26 by the piston 22 takes place via a T-piece 29. The membrane heads 22, 23 can be connected in parallel or in series.

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

6 shows the functional principle of a membrane vacuum pump according to the prior art for the sake of completeness.

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

In the housing 12 there is a suction chamber 13 which is delimited by the membrane 3 by a housing head 32 and which is delimited in relation to the membrane 3 by the housing head 5 of the housing 12 .

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

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

During the downward movement of the membrane 3 , a negative pressure is created in the conveying chamber 13 , as a result of which a differential pressure is present at the inlet valve body 36 , which presses the valve body 36 in the direction of the conveying chamber 13 . Gas flows from the intake line 18 into the suction chamber 13 through the open inlet valve. During the upward movement of the diaphragm 3, an overpressure is created in the pumping chamber 13, as a result of which there is a differential pressure 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 membrane 3 , a negative pressure is created in the delivery chamber 13 , as a result of which a differential pressure is created at the outlet valve body 38 , which presses the valve body 38 in the direction of the delivery chamber 13 and into the valve opening 39 . During the upward movement of the membrane 3 , an overpressure occurs in the pumping chamber 13 , as a result of which 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 when the connecting rod 31 moves downwards, the inlet valve arrangement 33 opens, so that gas flows out of the line 18 into the conveying chamber 13 . When the connecting rod 31 moves upwards, the inlet valve arrangement 33 closes and the outlet valve arrangement 34 opens, so that the gas in the delivery chamber 13 flows into the line 19 .

reference numbers

1

diaphragm vacuum pump

2

Pistons

3

membrane

4

membrane

5

membrane head

6

Kitchen sink

7

Kitchen sink

8th

magnet

9

bearings

10

Hall sensor

11

feathers

12

Housing

13

conveyor room

14

conveyor room

15

drive room

16

cooling fins

17

control device

18

inlet

19

outlet

20

diaphragm pump

21

Housing

22

membrane head

23

membrane head

24

membrane head

25

membrane

26

membrane

27

membrane

28

pole

29

tee

30

membrane

31

connecting rod

32

housing head

33

intake valve assembly

34

exhaust valve assembly

35

intake valve opening

36

valve body

37

valve body

38

valve body

39

exhaust valve opening

40

housing cover

Claims (15)

1. Method for self-calibrating a membrane vacuum pump (1) for delivering 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 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), and in that before initial operation of the pump (1), that is before a pumping process there is undertaken an automatic calibration run, wherein, with a reduced force relative to the pumping operation, the piston (2) drives the membrane (3) into the membrane head (5) or against a mechanical end point of the membrane (3).
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), which is configured as a self-calibrating membrane vacuum pump, 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), and in that the membrane vacuum pump, before initial operation of the pump, that is before a pumping process is configured as a membrane vacuum pump undertaking an automatic calibration run, wherein the piston (2) is configured as a piston which, with a reduced force relative to the pumping operation, drives the membrane (3) into the membrane head (5) or against a mechanical end point of the membrane (3).
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 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.
12. Membrane vacuum pump according to any one of claims 7 to 11, characterised in that the membrane vacuum pump (1, 21) is configured as a single-head, twin-head, or multihead membrane vacuum pump (1, 21), in particular in that the drive chamber (15) is sealed with respect to atmospheric pressure.
13. Membrane vacuum pump according to any one of claims 7 to 12, characterised in that the drive chamber (15) is configured as a drive chamber (15) that is pumped out.
14. Membrane vacuum pump according to any one of claims 7 to 13, 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.
15. Membrane vacuum pump according to any one of claims 7 to 14, 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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