WO2022090191A1

WO2022090191A1 - Method for operating a scroll vacuum pump

Info

Publication number: WO2022090191A1
Application number: PCT/EP2021/079612
Authority: WO
Inventors: Alexander Kaiser
Original assignee: Leybold Gmbh
Priority date: 2020-10-28
Filing date: 2021-10-26
Publication date: 2022-05-05
Also published as: US20230392600A1; EP4237687A1; CN116438378A; JP2023547422A; DE102020128369A1

Abstract

Method for operating and in particular monitoring a scroll pump, with the steps of: producing a vacuum by means of the scroll pump; determining a pressure of the scroll pump; comparing the recorded pressure with a pre-set threshold value; and if the recorded pressure lies above the pre-set threshold value, emitting a warning signal. The invention furthermore concerns a scroll pump for executing the method.

Description

METHOD FOR OPERATING A SCROLL VACUUM PUMP

The present invention concerns a method for operating a scroll pump and in particular for monitoring a scroll pump, as well as such a scroll pump.

Familiar scroll pumps have a housing with an inlet and an outlet. Here, a first scroll element is arranged in the housing and is connected to the housing, so that the first scroll element acts as a stator. Here, the first scroll element has a base and an essentially spiral wall that extends from the base. Furthermore, arranged in the housing is a second scroll element which orbits around the first scroll element, driven by an electric motor. Here, the second scroll element too has a base and an essentially spiral wall that extends from the base. Here, the wall of the first scroll element and the wall of the second scroll element are nested within one another, so that to at least a partial extent, individual pump chambers are created. Through the movement of the second scroll element relative to the first scroll element, a gaseous medium is transported from the inlet to the outlet.

In order to design the pump chamber to be as gas-tight as possible, a seal is arranged between that end of the spiral wall of the first scroll element that lies opposite the base, and the base of the second scroll element. Likewise, a seal is arranged between that end of the spiral wall of the second scroll element that lies opposite the base, and the base of the first scroll element. This seal is subject to wear on account of the relative movement between the first scroll element and the second scroll element.

Thus the gas-tightness of the individual pump chambers is reduced over the service life, and the respective seals have to be replaced in the course of servicing of the scroll pump.

In the case of familiar scroll pumps, such servicing is envisaged after a pre-set running time. Here, the running time is set by the manufacturer and does not depend on the actual operating parameters of the scroll pump. The pre-set running time until the next service is therefore independent of, for example, the operating load, the gas conveyed, or deviations in the manufacturing quality, all of which influence the wear and tear on the seals. The replacement of seals is thus often too late, for example in the case of increased wear, so that full performance by the scroll pump itself can no longer be achieved. However, this has a negative effect on the application for which the scroll pump provides the vacuum. Alternatively, in the case of reduced wear, the seals are replaced too early, which in turn leads to servicing intervals that are too short, and to increased costs.

The task of the present invention is to provide a method as well as a scroll pump, in which optimum performance is ensured along with reduced servicing costs.

The problem is solved by a method for operating a scroll pump according to claim 1 or 2, as well as a scroll pump according to claim 12.

The method according to the invention for operating a scroll pump and in particular for monitoring a scroll pump has the following steps: a) creating a vacuum by means of the scroll pump; b) determining a pressure of the scroll pump; c) comparing the recorded pressure with a pre-set threshold value; and d) if the recorded pressure lies above the pre-set threshold value, emitting a warning signal.

Here, the recorded pressure is, in particular, an end pressure, i.e. the maximum vacuum or the lowest pressure that can be created by the scroll pump. Alternatively, it can also be a pressure that is recorded under the same pumping conditions, so that there is comparability between the pressure determined at a first time point and the pressure determined at a later time point. Determining a pressure of the scroll pump may comprise recording a pressure of the scroll pump, or determining a recorded pressure of the scroll pump.

The pre-set threshold value here can be the specification of the possible pressure of the scroll pump that can be achieved, and in particular the end pressure, or can be determined for example by the user's requirements. Here, the threshold value can be the same for a plurality of scroll pumps, or it is set by the type or construction of the scroll pump. If the scroll pump reaches an end pressure that lies above the pre-set threshold value, i.e. is greater than the pre-set threshold value, so that no adequate vacuum is created by the scroll pump, a warning signal is emitted. On the basis of the warning signal, it is apparent to the user that servicing is required, and in particular, the seals in the scroll pump must be replaced. The replacement or servicing of the scroll pump is thus guided by the actual scroll pump end pressure which has been reached, which is essentially influenced by the wear on the seals, so that the servicing intervals are independent of a pre-set running time, and in particular the operating load, the gas that has been conveyed and/or deviations in the manufacturing quality of the scroll pump are taken into account. Thus for example the servicing intervals can be notably longer than the currently specified running time if there is less wear. Through this, the servicing intervals can be lengthened and costs can be saved. If, however, operation of the scroll pump results in greater wear, so that the required end pressure is reached by the scroll pump even before the previously set running time, and thus there is an associated drop in performance of the scroll pump, servicing of the scroll pump is triggered earlier, in order to ensure the optimum performance of the scroll pump at all times.

For preference, the end pressure is determined at the inlet. Flow characteristics within the scroll mechanism are irrelevant here, and the end pressure can be recorded directly. Alternatively or additionally, the pressure is not recorded directly at the inlet; rather, the pressure is recorded by means of a pressure sensor within the scroll mechanism, and an end pressure or the wear on the seals is inferred on the basis of the recorded pressure.

For preference, a first warning signal is generated when a first pre-set threshold value is exceeded, and a second warning signal is generated when a second preset threshold value is exceeded. Here, in particular, the first threshold value is below the second threshold value. The condition of the seals can thus be indicated to the user. In particular, the first threshold value and/or the second threshold value can be associated with a seal quality. Thus if for example the first limit value is exceeded and a first warning signal is triggered, the seal quality has been reduced, but further operation is possible. Corresponding servicing can be instigated. If the second threshold value is exceeded, the seal quality has been reduced to such an extent as to result in performance deficits and reliable operation may no longer be possible; servicing is required. In particular, additional threshold values can be envisaged, and preferably there can be continuous comparison of the achieved end pressure with a pre-set end pressure, and for example a continuous percentage display of the seal quality.

For preference, a remaining running time is predicted from the end pressure that has been achieved, and is displayed. Here, the remaining running time can be calculated on the basis of the loading of the vacuum pump in a previous time period, the wear of the seal in a previous time period, the required operating pressure, operating temperature or the like. Servicing can thus be planned early, and outages of the vacuum pump can be prevented.

For preference, before the end pressure is created, an intake valve arranged at the inlet of the scroll pump is closed. Here, the end pressure is measured or recorded before the intake valve, starting out from the scroll pump. In particular, in operation it is not immediately apparent whether the pressure that has been reached is an end pressure, i.e. the maximum vacuum that can be created or the lowest pressure that can be achieved, or whether the pressure that has been reached is an operating pressure with a gas load. By closing the intake valve, the scroll pump is specifically separated from the gas load, so that the pressure that is now created and recorded corresponds in any case to the end pressure of the scroll pump. It is thus ensured that the correct end pressure is always recorded, regardless of a possible gas load.

The warning signal is preferably an optical signal and/or an acoustic signal and/or a data signal that can be transmitted by means of a communication device. Here, the optical or acoustic warning signal can be generated directly by the scroll pump or by means of a warning device on the scroll pump. Alternatively, the optical signal and/or acoustic signal is generated at a further device, such as for example an external control device. In particular, the data signal is forwarded by means of the communication device to a user interface, for control of the scroll pump by the user. Alternatively or additionally, to this end the data signal is forwarded to the manufacturer, for automatic triggering of servicing of the scroll pump. For preference, the method described above is implemented at pre-set time intervals. In particular, the pre-set time intervals can be shorter, the closer the end pressure comes to the pre-set threshold value without overstepping it. Alternatively, the above method is triggered on the basis of a user input or input signal by the user, so that the monitoring of the scroll pump can be triggered by the user.

For preference, during operation the operating pressure is measured at the inlet of the scroll pump, and if the measured operating pressure falls below a second threshold value, the rotational speed of the scroll pump is reduced. This can be a continuous adjustment of the rotational speed depending on the operating pressure. Alternatively, the rotational speed of the scroll pump can be reduced in a stepwise manner, until the operating pressure at the inlet of the scroll pump lies above the second threshold value. In particular, since a pressure sensor is envisaged at the inlet of the scroll pump in order to record the end pressure that has been reached, this pressure sensor can be used during the operation of the scroll pump in order to record the operating pressure produced for example with a gas load. During normal operation, the gas load at the inlet of the pump is approximately constant and the recorded operating pressure produced with said gas load should also be constant. The same might be true for cycled operation wherein after a certain and fixed amount of time an almost identical pressure is reached being used as the operating pressure. If the operating pressure falls below the second threshold value, the output of the scroll pump can be reduced by reducing the rotational speed, through which energy can be saved and seal wear can be prevented. Hence, efficient pressure control can be performed, seal life can be extended and thus, service costs can be reduced and optimum performance can be ensured. In particular here, the first threshold value is greater than the second threshold value.

For preference, operating pressure can be used as recorded pressure, wherein comparison of the operating pressure with the first threshold can be used to emit a warning signal. For preference, the intake valve is closed when the scroll pump is switched off. Alternatively or additionally, the intake valve is closed in the event of a malfunction of the scroll pump. The intake valve that is provided is thus intended both for monitoring the scroll pump in the production of the end pressure, and additionally the intake valve can prevent the connected vacuum system from being reventilated when the scroll pump is switched off, or in the event of a malfunction of the scroll pump.

For preference, a gas load is recorded at the inlet. If a gas load is present and the pressure is on a predefined base value, either no measurement of the pressure is carried out, since this would not be an end pressure, or the recorded gas load is taken into account when determining the end pressure.

The present invention furthermore relates to a method for operating a scroll pump and in particular for monitoring a scroll pump, and has the following steps: a) creating a vacuum by means of the scroll pump; b) recording a first pressure of the scroll pump and a second pressure of the scroll pump; c) comparing the difference between the first pressure and the second pressure with a pre-set threshold value; and d) if the pressure difference lies below the pre-set threshold value, emitting a warning signal.

Here, the first pressure and the second pressure are recorded at different positions within the scroll pump. Thus for example the first pressure can be recorded directly at the inlet and the second pressure can be recorded within the scroll mechanism. Alternatively, the first pressure and the second pressure are recorded at different positions along the scroll mechanism. On the basis of the pressure difference, the wear on the seal can be inferred. Since the position of the first pressure recording and the second pressure recording do not change, a change in the pressure difference is caused by wear to the seals. If the sealing effect of the seals is reduced here, the pressure difference between two points along the flow path in the scroll pump changes proportionately. Thus on the basis of the pressure difference, the condition of the seals of the scroll mechanism can be inferred. If the pressure difference falls below a pre-set threshold value, a warning signal is emitted. Here, the threshold value can be the same for a plurality of scroll pumps, or it is set by the type or construction of the scroll pump. On the basis of the warning signal, it is apparent to the user that servicing is required, and in particular, the seals in the scroll pump must be replaced. The replacement or servicing of the scroll pump is thus guided by the actual scroll pump end pressure which has been reached, which is essentially influenced by the wear on the seals, so that the servicing intervals are independent of a pre-set running time, and in particular the operating load, the gas conveyed, and/or deviations in the manufacturing quality of the scroll pump are taken into account. Thus for example the servicing intervals can be notably longer that the currently specified running time if there is wear.

Through this, the servicing intervals can be lengthened and costs can be saved. If, however, operation of the scroll pump results in greater wear, so that the required end pressure is reached by the scroll pump even before the previously set running time, and there is thus an associated drop in performance of the scroll pump, servicing of the scroll pump is triggered earlier, in order to ensure optimum performance of the scroll pump at all times.

Furthermore, the method is developed further on the basis of the features as described above. In particular, the features of the two methods described above can be combined freely with one another. This for example a first pressure and a second pressure can always be recorded during operation, wherein for example the first pressure is recorded directly at the inlet. From the pressure difference, the condition of the seals can then be inferred. If however a gas load is present, the first pressure can be applied as the end pressure and compared with a threshold value. Alternatively or additionally, the end pressure can be inferred from the pressure difference that has been determined, and then the determined end pressure can be compared with a threshold value. Thus the results of the two methods can be combined with one another and can be used to achieve improved predictive accuracy concerning the wear on the seals. The present invention furthermore concerns a scroll pump with a housing that has an inlet and an outlet. In particular, a first scroll element is arranged in the housing and is connected to the housing, so that the first scroll element acts as a stator. The first scroll element here has a base and an essentially spiral wall that extends from the base. Also arranged in the housing is a second scroll element which orbits around the first scroll element, driven by an electric motor. The second scroll element too has a base and an essentially spiral wall that extends from the base. Here, the wall of the first scroll element and the wall of the second scroll element are nested within one another, so that to at least a partial extent, individual pump chambers are created.

Through the movement of the second scroll element relative to the first scroll element, a gaseous medium is then conveyed from the inlet to the outlet. In order to design the pump chamber to be as gas-tight as possible, a seal is arranged between that end of the spiral wall of the first scroll element lying opposite the base, and the base of the second scroll element. A seal is likewise arranged between that end of the spiral wall of the second scroll element lying opposite the base, and the base of the first scroll element.

According to the invention, a control device is connected to the scroll pump, to control the scroll pump. Furthermore, at least one pressure sensor is envisaged, for recording a pressure of the scroll pump. The pressure sensor is connected to the control device. Here, the control device is designed to implement the method as described above.

For preference, the pressure sensor is arranged at the inlet of the scroll pump, for the direct recording of the pressure at the inlet and, in particular, of the end pressure if no gas load is present. Alternatively, the recorded pressure is an operating pressure in particular with gas load.

For preference, the pressure sensor is arranged within the scroll mechanism that is formed by the first scroll element and the second scroll element. Here, it is not the actual end pressure that is measured, but a pressure that is greater than the end pressure. However, a conclusion can be drawn accordingly about the end pressure, or from the pressure recorded within the scroll mechanism it is likewise possible to infer the wear of the seal. Through this, the design of the pressure sensor can be simpler and thus more economical.

For preference, a first pressure sensor and a second pressure sensor are provided, wherein the first pressure sensor and second pressure sensor are arranged within the scroll mechanism and are connected to the control device. Alternatively, the first pressure sensor is arranged at the inlet of the scroll pump and the second pressure sensor within the scroll mechanism.

Thus two pressures are recorded, wherein in particular the condition of the seals can be inferred from the pressure difference between the first pressure sensor and the second pressure sensor.

For preference, an intake valve is arranged at the inlet of the scroll pump, wherein the intake valve is connected to the control device, wherein the control device is designed to close the intake valve in order to determine the end pressure. Additionally, the intake valve can be closed by the control device when the scroll pump is switched off, and/or in the event of a malfunction of the scroll pump, in order to prevent the connected vacuum system from being re-ventilated.

For preference, the control device and/or the pressure sensor and/or the intake valve are arranged in the housing of the scroll pump. A particularly simple and compact structure of the scroll pump is thereby achieved. At the same time, it is ensured that both the pressure sensor and the intake valve for implementing the method for monitoring the scroll pump are present and do not need to be provided separately by the user.

For preference, the scroll pump has a communication device for transmitting an operating pressure recorded by means of the pressure sensor and/or the recorded end pressure and/or the generated warning signal. Here, the operating pressure, end pressure and/or generated warning signal can be transmitted to a user interface, so that the recorded operating pressure, the recorded end pressure and/or the generated warning signal is apparent to the user. Alternatively or additionally, to this end this information can be transmitted to the manufacturer of the vacuum pump, for monitoring of the scroll pump.

Alternatively or additionally, the scroll pump has a warning device for emitting an optical and/or acoustic warning if the end pressure that has been reached lies above the pre-set threshold value.

In the following, the invention is elucidated further on the basis of preferred embodiments, with reference to the enclosed drawings.

In the drawing,

Figures 1A and IB show a schematic representation of a scroll pump,

Figure 2 shows a detailed view of the scroll pump,

Figure 3 shows a process flow of the method according to the invention,

Figure 4 shows a schematic representation of the scroll pump according to the present invention, and

Figure 5 shows a process flow of a further embodiment of the method according to the invention.

Figure 1A shows a cross section of a scroll pump with a housing which defines an inlet 12 and an outlet 14. Connected to the housing is a first scroll element 16 which acts as a stator. Furthermore, arranged in the housing 10 is a second scroll element 18, wherein the second scroll element 18 orbits around the first scroll element 16. Here, the second scroll element 18 is connected to a shaft 20 that is driven by an electric motor 22, so that the second scroll element 18 is rotated around a common axis 34.

The first scroll element 16 has a base 26 and an essentially spiral first wall 28, which extends from the base 26.

RECTIFIED SHEET (RULE 91) ISA/EP Furthermore, the second spiral element 18 has a second base 30 and an essentially spiral second wall 32 which extends from the second base 30 and engages into the first wall 28, or fits into it. The first wall 28 and the second wall 32 define at least a part of a pump chamber 33, so that during the movement of the second scroll element 18, a gaseous medium is conveyed from the inlet 12 to the outlet 14.

Figure 2 shows an example of a detailed view of the first wall 28. Here, the first wall 28 of the first scroll element 16 has a first end 40 which faces the second base 30 of the second scroll element 18, and is arranged opposite the first base 26 of the first scroll element 16. Arranged on the first end 40 of the first wall 28 is a seal element 42 which is in contact with the second base 30 of the second scroll element 18. Here, the seal element extends at least over a part and preferably over the whole length of the essentially spiral first wall 28. In the same way, a seal element is provided at the end of the spiral wall of the second scroll element 18, which is in contact with the base 26.

Due to the contact between the seal element 42 and the surface 44 of the second scroll element 18 lying opposite, because of the relative movement between the first scroll element 16 and the second scroll element 18, wear is sustained by the seal element 42. Through this wear, the sealing action of the seal element 42 is reduced, so that the gas-tightness of the respective pump chambers 33 is reduced and the output of the scroll pump is likewise reduced.

Figure 3 shows a flow diagram according to the method according to the invention, for the operation and/or monitoring of a scroll pump, with the steps of: a) creating an end pressure by means of the scroll pump, SOI; b) recording the end pressure that has been achieved at the inlet of the scroll pump, S02; c) comparing the end pressure that has been achieved with a pre-set threshold value, S03; and d) if the achieved end pressure lies above the pre-set threshold value, emitting a warning signal, S04.

Thus on the basis of the end pressure that has been achieved, a decision can be made as to whether the seal elements 42 need to be replaced or not. Through this, the servicing intervals can be adapted to the actual wear on the seal elements, so that servicing that is too early or too late can be prevented.

Figure 4 shows the schematic structure of the scroll pump. Here, a scroll mechanism 60 is provided, as per Figure IB. The scroll mechanism 60 is connected to a control device 62, to control the operation of the scroll mechanism 60. An intake valve 64 is connected to the inlet 12 of the scroll mechanism 60. A vacuum system or a receiving vessel 66 can be connected to the intake valve 64. Here, the intake valve 64 has a connection to the control device 62. Between the intake valve 64 and the scroll mechanism 60, the pressure at the inlet 12 of the scroll mechanism 60 is measured by means of a pressure sensor 68. Here, according to step SOI, an end pressure is created by the scroll mechanism 60, and this end pressure is recorded by the pressure sensor 68. If this end pressure lies above a pre-set threshold value, a warning signal is emitted by a warning device 70, which indicates to the user that the scroll pump, and in particular the seal elements 42, must be serviced. Alternatively, the control device 62 can output a data signal by means of a communication device (not shown), which can be transmitted by means of a data interface 72 to a user interface of the user or to the manufacturer, for monitoring of the vacuum pump. Here, the scroll mechanism 60, intake valve 64, pressure sensor 68 and control device 62 are arranged within a common housing 74, through which a particularly compact construction is achieved.

According to Figure 5, before the end pressure is produced by the scroll pump, in step Sil the intake valve 64 is closed. A gas load at the scroll mechanism 60 is thus prevented, and by means of the pressure sensor 68 the actual maximum achievable vacuum or the lowest pressure that can be achieved by the scroll mechanism 60 is recorded. On the basis of the end pressure that has been

RECTIFIED SHEET (RULE 91) ISA/EP recorded in this way, a reliable conclusion can be drawn about the wear or condition of the seal elements 42 in the scroll mechanism 60, and servicing can be triggered if necessary.

Likewise during operation, via the pressure sensor 68 an operating pressure can be recorded which for example also records a gas load. If this operating pressure falls below a second pre-set threshold value, the rotational speed or output of the scroll mechanism 60 can be reduced by the control device 62, through which the scroll mechanism continues to produce an adequate vacuum according to the second threshold value, but in an energy-saving manner. The pressure sensor thus has two functions: firstly, to record the end pressure to determine the wear on the seal elements 42, and secondly, to record the operating pressure to save energy.

The intake valve 64 likewise has two functions: firstly, the intake valve 64 can be used as described above, in order to separate off a gas load from the receiving vessel 66, so that the end pressure that can be produced by the scroll mechanism 60 can be determined reliably. Furthermore, when the scroll pump is switched off or if there is a malfunction of the scroll mechanism 60, the intake valve 64 can be closed, so that return ventilation of the receiving vessel by the scroll pump is prevented.

Claims

Claims Method for operating and in particular monitoring a scroll pump, with the steps of: a) creating a vacuum by means of the scroll pump; b) determining a pressure of the scroll pump; c) comparing the recorded pressure with a pre-set threshold value; and d) if the recorded pressure lies above the pre-set threshold value, emitting a warning signal. Method for operating and in particular monitoring a scroll pump, with the steps of: e) creating a vacuum by means of the scroll pump; f) recording a first pressure of the scroll pump and a second pressure of the scroll pump; g) comparing the difference between the first pressure and the second pressure with a pre-set threshold value; and h) if the pressure difference lies below the pre-set threshold value, emitting a warning signal. Method according to claim 1 or 2, in which the pressure at the inlet of the scroll pump is recorded and/or within a scroll mechanism of the scroll pump. Method according to one of the claims 1 to 3, in which the recorded pressure is an end pressure. Method according to claim 4, in which before the production of the end pressure, this step is carried out: closing of an intake valve arranged at the inlet of the scroll pump. Method according to one of the claims 1 to 5, in which the warning signal is an optical signal and/or an acoustic signal and/or a data signal that can be transmitted by means of a communication device. Method according to one of the claims 1 to 6, in which the warning signal is a remaining running time predicted from the end pressure that has been reached. Method according to one of the claims 1 to 7, in which the method is implemented at pre-set time intervals or on the basis of an input signal. Method according to one of the claims 1 to 8, in which during operation, the operating pressure is measured at the inlet of the scroll pump, and if the measured operating pressure falls below a second threshold value, the rotational speed of the scroll pump is reduced. Method according to one of the claims 1 to 9, in which the intake valve is closed when the scroll pump is switched off and/or in the event of a malfunction of the scroll pump. Method according to one of the claims 1 to 10, in which a gas load is recorded and the end pressure or pressure difference is not recorded if a gas load is present. Scroll pump with a housing which has an inlet and an outlet, a control device connected to the scroll pump, 16 at least one pressure sensor arranged on the scroll pump to record a pressure of the scroll pump, wherein the pressure sensor is connected to the control device, wherein the control device is designed to implement the method according to one of the claims 1 to 11. Scroll pump according to claim 12, characterised in that the pressure sensor is arranged at the inlet of the scroll pump. Scroll pump according to claim 12 or 13, characterised in that the recorded pressure is an end pressure or an operating pressure. Scroll pump according to one of the claims 12 to 14, characterised in that the pressure sensor is arranged within a scroll mechanism of the scroll pump. Scroll pump according to one of the claims 12 to 15, characterised in that at least two pressure sensors are provided, to record a first pressure and a second pressure, wherein the recorded pressure is determined from the difference between the first pressure and the second pressure. Scroll pumps according to one of the claims 12 to 16, characterised in that an intake valve is arranged at the inlet, wherein the intake valve is connected to the control device, wherein the control device is designed to close the intake valve to determine the end pressure. Scroll pumps according to one of the claims 12 or 17, characterised in that the control device and/or the pressure sensor and/or the intake valve are arranged in the housing of the scroll pump. 17 Scroll pumps according to one of the claims 12 to 18, characterised by a communication device for transmitting an operating pressure that has been recorded by means of the pressure sensor and/or the recorded end pressure and/or the warning signal that has been generated.