U.S. patent application number 10/580128 was filed with the patent office on 2007-03-29 for method for controlling the drive motor of a positive displacement vaccum pump.
Invention is credited to Michael Holzemer, Karl-Heinz Ronthaler, Frank Schonborn.
Application Number | 20070071610 10/580128 |
Document ID | / |
Family ID | 34609147 |
Filed Date | 2007-03-29 |
United States Patent
Application |
20070071610 |
Kind Code |
A1 |
Holzemer; Michael ; et
al. |
March 29, 2007 |
Method for controlling the drive motor of a positive displacement
vaccum pump
Abstract
Method for controlling a drive motor of a positive displacement
vacuum pump A method for controlling a drive motor of a positive
displacement vacuum pump comprises the following method steps:
storing a curve (32) indicating a respective speed value n of the
drive motor for inlet pressure values p, wherein the curve (32)
comprises: an upper range (34) for inlet pressure values p larger
than or equal to an upper limit pressure p.sub.1, with a single
constant upper speed value n.sub.1 being associated with said upper
range (34), and an alteration range (36) for inlet pressure values
p smaller than the upper limit pressure p.sub.1, wherein in the
alteration range different speed values n.sub.v are associated with
the inlet pressure values p; determining the inlet pressure value
p; determining the speed n associated with the inlet pressure value
p in the curve (32); and operating the drive motor (20) at the
determined speed n. By providing an alteration range the vacuum
pump can always be operated at a speed which allows maximum
effective suction capacity of the positive displacement pump.
Inventors: |
Holzemer; Michael;
(Bergheim, DE) ; Schonborn; Frank; (Mainweg,
DE) ; Ronthaler; Karl-Heinz; (Zulpich, DE) |
Correspondence
Address: |
FAY SHARPE LLP
1100 SUPERIOR AVENUE, SEVENTH FLOOR
CLEVELAND
OH
44114
US
|
Family ID: |
34609147 |
Appl. No.: |
10/580128 |
Filed: |
November 5, 2004 |
PCT Filed: |
November 5, 2004 |
PCT NO: |
PCT/EP04/12529 |
371 Date: |
May 19, 2006 |
Current U.S.
Class: |
417/44.1 ;
417/53 |
Current CPC
Class: |
F04B 2205/01 20130101;
F04B 49/065 20130101 |
Class at
Publication: |
417/044.1 ;
417/053 |
International
Class: |
F04B 49/06 20060101
F04B049/06 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 20, 2003 |
DE |
10354205.1 |
Claims
1. A method for controlling a drive motor of a positive
displacement vacuum pump, the method: storing a curve indicating a
respective speed n of the drive motor for inlet pressure values p,
the curve comprising: an upper range for inlet pressure values p
larger than or equal to an upper limit pressure p.sub.1, a single
constant upper speed value n.sub.1 being associated with said upper
range, and an alteration range for inlet pressure values p smaller
than the upper limit pressure p.sub.1, in the alteration range
different speed values n.sub.v being associated with the inlet
pressure values p; determining the inlet pressure value p;
determining the speed n associated with the determined inlet
pressure value p in the curve; and operating the drive motor at the
determined speed n.
2. The method according to claim 1, wherein the curve comprises a
lower range for inlet pressure values p smaller than or equal to a
lower limit pressure p.sub.2, a single constant lower speed value
n.sub.2 being associated with the lower range, and the alteration
range being limited to inlet pressure values p larger than the
lower limit pressure p.sub.2.
3. A method for controlling a drive motor of a positive
displacement vacuum pump, the method comprising: storing a curve
indicating a respective speed n of the drive motor for inlet
pressure values p, the curve comprising: a lower range for inlet
pressure values p smaller than or equal to a lower limit pressure
p.sub.2, a single constant lower speed value n.sub.2 being
associated with said lower range, an alteration range for inlet
pressure values p larger than the lower limit pressure p.sub.2, in
the alteration range different speed values n.sub.v being
associated with the inlet pressure values p; determining the inlet
pressure value p; determining the speed n associated with the
determined inlet pressure value p in the curve; and operating the
drive motor at the determined speed n.
4. The method according to claim 1, wherein in the alteration range
decreasing speeds n.sub.v are associated with decreasing inlet
pressure values p.
5. The method according to claim 2, wherein the upper limit value
p.sub.1 ranges between 20 mbar and 1 mbar, and the lower limit
value p.sub.2 ranges between 1.0 mbar and 0.005 mbar.
6. The method according to claim 2, wherein the upper constant
speed value n.sub.1 ranges between 2,200 and 1,000 rpm, and the
lower constant speed value n.sub.2 ranges between 300 and 1,300
rpm.
7. The method according to claim 1, wherein the positive
displacement vacuum pump is a fore vacuum pump arranged upstream of
a high vacuum pump, and the inlet pressure p is a suction-side
pressure of the high vacuum pump.
8. The method according to claim 1, wherein the curve is saved in a
characteristic diagram storage.
9. The method according to claim 1, wherein the drive motor is an
asynchronous motor.
10. A positive displacement vacuum pump comprising: a drive motor,
an inlet pressure sensor and a drive motor control for controlling
a speed n of the drive motor in dependence on the inlet pressure
value p determined by the inlet pressure sensor, the drive motor
control comprising a storage for storing a curve which indicates a
respective speed n of the drive motor for inlet pressure values p
of the inlet pressure sensor, the curve comprising: at least one of
(a) an upper range for inlet pressure values p larger than or equal
to an upper limit pressure p.sub.1, a single constant upper speed
value n.sub.1 being associated with said upper range and (b) a
lower range for the inlet pressure values p lower than or equal to
a lower pressure limit p.sub.s, a single constant lower speed value
n.sub.2 being associated with the lower range: and an alteration
range for inlet pressure values p smaller than the upper limit
pressure p.sub.1 or larger than the lower limit pressure p.sub.s,
in the alteration range different speed values n.sub.v being
associated with the inlet pressure values p.
11. The positive displacement vacuum pump according to claim 10,
wherein the drive motor control comprises a processor which has
connected therewith the inlet pressure sensor and which evaluates
signals from the inlet pressure sensor.
12. The method according to claim 3, wherein in the alteration
range decreasing speeds n.sub.v are associated with decreasing
inlet pressure values p.
13. The method according to claim 3, wherein the positive
displacement vacuum pump is a fore vacuum pump arranged upstream of
a high vacuum pump, and the inlet pressure p is a suction-side
pressure of the high vacuum pump.
14. The method according to claim 3, wherein the curve is saved in
a characteristic diagram storage.
15. The method according to claim 3, wherein the drive motor is an
asynchronous motor.
Description
BACKGROUND
[0001] The invention relates to a method for controlling a drive
motor of a positive displacement vacuum pump, and to a positive
displacement vacuum pump comprising a drive motor control.
[0002] Positive displacement vacuum pumps are, for example,
membrane pumps, rotary vane pumps, piston pumps or Roots pumps, and
are frequently used as fore vacuum pumps in combination with a high
vacuum pump. A special feature of these positive displacement
vacuum pumps is that the final pressure attainable by said pumps,
i.e. the fore vacuum pressure, is speed-dependent to a high extent,
wherein the speed must be high at high inlet pressures, and must be
low at low inlet pressures for attaining an optimum suction
capacity. This can be explained by the fact that at low inlet
pressures filling of the suction space takes place at a relatively
slow rate due to the small difference between inlet pressure and
suction pressure in the working chamber. This results in a poor
filling level of the positive displacement vacuum pump at low inlet
pressures, which filling level can only be improved by extending
the opening times of the inlet valve, i.e. a speed reduction.
[0003] From DE 198 16 241 C1 a positive displacement vacuum pump is
known which is operated, in dependence on an inlet pressure value,
at two different speeds, namely at a high speed for evacuation
purposes, and at a low speed for reaching the lowest final pressure
possible. Relatively much time is required between the beginning of
the pumping process and reaching of the final pressure.
SUMMARY
[0004] It is an object of the invention to provide a method and a
positive displacement vacuum pump with the aid of which the final
pressure can be more rapidly reached.
[0005] According to one aspect, a method is provided for
controlling a drive motor of a positive displacement vacuum pump
comprises the method steps of storing a pressure-speed curve,
determining the inlet pressure value, determining the speed value
from the curve, and operating the drive motor at the determined
speed value.
[0006] First, a curve is stored in which a single constant upper
speed value n.sub.1 is associated with inlet pressure values p
larger than or equal to an upper limit pressure p.sub.1, and which
comprises an alteration range for inlet pressure values p smaller
than the upper limit pressure p.sub.1, wherein in the alteration
range different speed values n.sub.v are associated with the inlet
pressure values p.
[0007] During operation of the drive motor the inlet pressure value
p is permanently determined, the associated speed n is determined
from the inlet pressure value p of the curve, and the drive motor
is operated at the determined speed n. While at high inlet pressure
values p above the upper limit value p.sub.1 the drive motor is
operated at a maximum constant speed n.sub.1, a corresponding speed
value n.sub.v is approximately continuously associated for speeds
above the upper limit value p.sub.1 in dependence on the inlet
pressure value p. In this manner, the effective suction capacity of
the positive displacement pump can be kept at the highest level
possible for each inlet pressure value. Thus, the time between
beginning of evacuation and reaching of the final pressure is
decreased. By adapting the speed to the inlet pressure value, the
required drive energy and, due to the lower average speed level,
the wear are reduced. Thereby, the maintenance and operating costs
are reduced, and thus the efficiency of the positive displacement
vacuum pump is improved.
[0008] Preferably, the curve comprises a lower range for inlet
pressure values p smaller than or equal to a lower limit pressure
p.sub.2, wherein a single constant lower speed value n.sub.2 is
associated with the lower range, and the alteration range is
limited to inlet pressure values p larger than the lower limit
pressure range p.sub.2. The curve thus comprises both an upper
pressure range of constant speed and a lower pressure range of
constant speed, as well as an alteration range of non-constant
speed between said two ranges. Such a curve is, for example,
necessary and useful for fore vacuum pumps which need a given
minimum speed for pumping action since below the minimum speed no
pumping capacity can be attained, in particular due to backflow
losses. This applies, for example, to oil-sealed rotary vane pumps.
Thus it is ensured that the positive displacement vacuum pump is
always operated above a speed at which the pumping function is
still guaranteed even at very low inlet pressures.
[0009] According to a further aspect, the curve comprises, instead
of an upper range, a lower range for inlet pressure values p
smaller than or equal to a lower limit pressure p.sub.2, wherein a
single constant lower speed n.sub.2 is associated with the lower
range.
[0010] Preferably, in the alteration range decreasing speeds
n.sub.v are associated with decreasing inlet pressure values p,
i.e. low speed values n.sub.v are associated with low inlet
pressure values p.
[0011] Preferably, the upper limit pressure p.sub.1 ranges between
20 mbar and 1 mbar, and the lower pressure p.sub.2 ranges between
1.0 mbar and 0.005 mbar, wherein the upper limit pressure p.sub.1
is larger than the lower limit pressure p.sub.2.
[0012] According to a preferred aspect, the upper constant speed
value n.sub.1 ranges between 2,200 and 1,000 rpm, and the lower
constant speed value n.sub.2 ranges between 300 and 1,300 rpm,
wherein the upper constant speed value n.sub.1 is larger than the
lower constant speed value n.sub.2.
[0013] Preferably, the positive displacement pump is a fore vacuum
pump arranged upstream of a high vacuum pump, and the inlet
pressure value p is the suction-side pressure of the high vacuum
pump. The inlet pressure value p thus is the pressure in the
recipient evacuated by the high vacuum pump. Alternatively, the
inlet pressure value p may also be the fore vacuum pressure
immediately before the inlet of the fore vacuum pump.
[0014] According to a preferred aspect, the inlet pressure-speed
curve is saved in a characteristic diagram storage. In the
characteristic diagram storage, a corresponding speed n is
associated with each inlet pressure value p.
[0015] Preferably, the drive motor is an asynchronous motor driven
by a correspondingly driven frequency converter. However, the drive
motor may also be configured as a synchronous motor.
[0016] The positive displacement vacuum pump comprises a drive
motor, an inlet pressure sensor and a drive motor control which
controls the speed n of the drive motor in dependence on the inlet
pressure value p determined by the inlet pressure sensor. Further,
the drive motor control comprises a storage for storing a curve
that indicates a respective speed n of the drive motor for the
inlet pressure values p of the inlet pressure sensor, wherein the
curve comprises two ranges: the first range is an upper range for
inlet pressure values p larger than or equal to an upper limit
pressure p.sub.1, with a single constant upper speed value n.sub.1
being associated with said first range. The second range is an
alteration range for inlet pressure values p smaller than the upper
limit pressure p.sub.1, wherein in the alteration range different
speed values n.sub.v are associated with the inlet pressure values
p.
[0017] Preferably, the drive motor control comprises a processor
which has connected therewith the inlet pressure sensor and
evaluates the signals from the inlet pressure sensor. The evaluated
inlet pressure sensor signals can be supplied to a pressure
indicator associated with the positive displacement vacuum pump.
The inlet pressure sensor signals are thus not only evaluated by
the drive motor control with regard to controlling the drive motor,
but also converted into an indication format, and finally supplied
to an indicator associated with the vacuum pump. Thus a separate
evaluating and indicating device for indicating the inlet pressure
is not required.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] An embodiment of the invention will now be described in
greater detail with reference to the figures in which:
[0019] FIG. 1 shows a schematic representation of a pump assembly
comprising a positive displacement vacuum pump according to the
invention configured as a fore vacuum pump, and a high vacuum pump,
and
[0020] FIG. 2 shows an inlet pressure-speed curve according to
which the speed of the drive motor of the positive displacement
vacuum pump is controlled.
DETAILED DESCRIPTION
[0021] FIG. 1 schematically shows a pump assembly 10 for generating
a high vacuum in a recipient 12. For the purpose of generating the
high vacuum in the recipient 12, two pumps are arranged in series,
namely a high vacuum pump 14, for example a turbomolecular pump,
and a positive displacement vacuum pump 16 configured as a fore
vacuum pump, for example a membrane, piston or rotary vane
pump.
[0022] The positive displacement vacuum pump 16 essentially
comprises a pump device 18 having a displacement body arranged in a
pumping chamber, a drive motor 20 for driving the pump device 18,
and a drive motor control 22 for controlling and supplying energy
to the drive motor 20. The drive motor 20 is configured as a
synchronous motor.
[0023] Further, the pump assembly 10 comprises two inlet pressure
sensors 24,26, wherein one of the inlet pressure sensors 24
determines the fore vacuum pressure immediately at the inlet of the
positive displacement vacuum pump 16, and the other inlet pressure
sensor 26 determines the high vacuum pressure sure in the recipient
12. Both inlet pressure sensors 24,26 are connected with a
processor 28 of the drive motor control 22, said processor 28 being
continuously supplied with inlet pressure values p by the inlet
pressure sensors 24, 26. The drive motor control 22 further
comprises a frequency converter 30 driven by the processor 28, and
is connected with the drive motor 20. Further, the inlet pressure
sensor 24 associated with the positive displacement vacuum pump 16
may be integrated in the positive displacement vacuum pump 16.
[0024] The processor 28 comprises a characteristic diagram storage
for saving a curve 32 in which a respective speed n of the drive
motor 20 is associated with inlet pressure values p.
[0025] The curve 32 comprises an upper range 34 extending from the
atmospheric pressure of 1,013 mbar to an upper limit pressure
p.sub.1 of 10 mbar. A single constant upper speed value n.sub.1 is
associated with the upper range 34 of the curve 32. Between the
upper limit pressure p.sub.1 and a lower limit pressure p.sub.2 of
approximately 0.01 mbar, the curve 32 comprises an alteration range
36 in which various speed values n.sub.v are associated with the
inlet pressure values p. In the alteration range 36 of the curve 32
decreasing speeds n.sub.v are associated with decreasing inlet
pressure values p. In the alteration range 36 a different speed
value n.sub.v is associated with each inlet pressure value p. The
curve 32 further comprises a lower range 38 for inlet pressure
values p smaller than or equal to the lower limit pressure p.sub.2.
In the lower range 38 of the curve 32 a single speed value n.sub.2
is associated with all inlet pressure values p.
[0026] In a pump device 18 configured as a piston pump, the upper
speed value n.sub.1 is approximately 1,800 rpm, and the lower speed
value n.sub.2 is 500 rpm. In a pump device 18 configured as an
oil-sealed rotary vane pump, the upper speed value n.sub.1 is, for
example, 2,100 rpm, and the lower speed value n.sub.2 is 1,000
rpm.
[0027] The high vacuum pressure serves as the inlet pressure value
p which is supplied by the inlet pressure sensor 26 arranged at the
recipient 12 and on the suction side of the high vacuum pump 14.
Alternatively, the fore vacuum pressure of the inlet pressure
sensor 24 may be used for determining the inlet pressure values
p.
[0028] The shape of the curve 32, the limit pressures p.sub.1 and
p.sub.2, and the upper and lower speed values n.sub.1 and n.sub.2
are determined in test series for establishing for each inlet
pressure value p a drive motor 20 speed at which a maximum
effective suction capacity of the positive displacement pump 16 is
attained. The determined curve is subsequently stored in the
characteristic diagram storage of the processor 28. During
operation of the pump assembly 10, the drive motor control 22
determines, from the curve 32 saved in the characteristic diagram
storage, the speed n of the drive motor 20 in dependence on the
high vacuum inlet pressure value p. The determined speed value n is
fed to the frequency converter 30 which generates corresponding
rotating fields in the stator coils of the drive motor 20
configured as asynchronous or synchronous motor, and operates the
motor at the determined speed. In this manner, the positive
displacement pump 16 can always be operated at the maximum
effective suction capacity.
[0029] The processor 28 of the drive motor control 22 further
carries out evaluation and conversion of the signals from the inlet
pressure sensor 24 into an indication format. The inlet pressures
converted into the indication format are supplied to an indicating
device arranged at the positive displacement vacuum pump 16, for
example at the housing of the drive motor control 22. The
indicating device may further be used for speed indication.
[0030] The invention has been described with reference to the
preferred embodiments. Modifications and alterations may occur to
others upon reading and understanding the preceding detailed
description. It is intended that the invention be constructed as
including all such modifications and alterations insofar as they
come within the scope of the appended claims or the equivalents
thereof.
* * * * *