U.S. patent application number 12/001910 was filed with the patent office on 2008-06-19 for vacuum pump with a fan.
This patent application is currently assigned to Pfeiffer Vacuum GmbH. Invention is credited to Juergen Metzger, Stefan Saenger, Juergen Wagner.
Application Number | 20080145258 12/001910 |
Document ID | / |
Family ID | 39217913 |
Filed Date | 2008-06-19 |
United States Patent
Application |
20080145258 |
Kind Code |
A1 |
Metzger; Juergen ; et
al. |
June 19, 2008 |
Vacuum pump with a fan
Abstract
A vacuum pump for producing low or high vacuum includes a
housing (1') having an inlet (9) and an outlet (9), a pumping
system (30) for compressing gas, a motor (25, 26) for driving the
pumping system (30), and a fan (6) for cooling the pump and having
its own motor (6a) for driving the fan (6).
Inventors: |
Metzger; Juergen; (Giessen,
DE) ; Wagner; Juergen; (Mueschenbach, DE) ;
Saenger; Stefan; (Herborn, DE) |
Correspondence
Address: |
ABELMAN, FRAYNE & SCHWAB
666 THIRD AVENUE, 10TH FLOOR
NEW YORK
NY
10017
US
|
Assignee: |
Pfeiffer Vacuum GmbH
|
Family ID: |
39217913 |
Appl. No.: |
12/001910 |
Filed: |
December 12, 2007 |
Current U.S.
Class: |
418/88 |
Current CPC
Class: |
F04C 2220/10 20130101;
F04C 29/04 20130101 |
Class at
Publication: |
418/88 |
International
Class: |
F04C 29/04 20060101
F04C029/04 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 13, 2006 |
DE |
10 2006 058 842.8 |
Claims
1. A vacuum pump for producing low or high vacuum, comprising a
housing (1') having an inlet (9) and an outlet (9); a pumping
system (30) for compressing gas; a motor (25, 26) for driving the
pumping system (30); a fan (6) for cooling the pump; and a motor
(6a) for driving the fan (6).
2. A vacuum pump according to claim 1, wherein the housing (1') has
cooling ribs (8), and the fan (6) is arranged for feeding cooling
air in space between the cooling ribs (8).
3. A vacuum pump according to claim 2, further comprising a hood
(1) that at least partially surrounds the housing (1'), wherein the
hood (1) is so formed in a region of the cooling ribs (8) that the
cooling air from the fan (6) is deflected in the space between the
cooling ribs (8).
4. A vacuum pump according to claim 1, wherein the housing (1') has
at least one section (3) in which the fan (6) is located.
5. A vacuum pump according to claim 1, wherein the housing has at
least one pumping section (5) in which the pumping system (30) is
located, and a control section (2) in which control electronics
(12) is located.
6. A vacuum pump according to claim 5, wherein the fan (6) is so
arranged that the cooling air from the fan (6) flows to the at
least one pumping section (5).
7. A vacuum pump according to claim 5, wherein the fan (6) is so
arranged that the control section (2), together with the control
electronics is cooled as a result of free convection.
8. A vacuum pump according to claim 1, wherein the pumping system
(30) has a shaft (24) eccentrically arranged in a housing of the
pumping housing section (5), extending through a bore formed in the
pumping housing section (5), and a vane (33) supported on the shaft
(24) for producing a pumping action, and wherein the pumping system
(5) contains oil for sealing and lubricating the vane (33).
9. A method of operating a vacuum pump for producing low or high
vacuum and including a housing (1') having an inlet (9) and an
outlet (9), a pumping system (30) for compressing gas, a motor (25,
26) for driving the pumping system (30), a fan (6) for cooling the
pump, and a motor for driving the fan, the method comprising the
step of operating the pump motor (25, 26) with a first rotational
speed and operating the fan motor (6a) with a second rotational
speed, wherein the first and second rotational speeds are different
at least temporarily.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a vacuum pump for producing
low or high vacuum and including a housing having an inlet and an
outlet, a pumping system for compressing gas, a motor for driving
the pumping system, and a fan for cooling the pump. The present
invention also relates to a method of operating such a vacuum
pump.
[0003] 2. Description of the Prior Art
[0004] In vacuum pump, there exist several heat sources one of
which is the pumping system in which the gas is compressed. The
heat, which is generated in the pump, should not cause any
operational disturbances resulting from overheating of pump
components. Therefore, the important components need to be
adequately cooled in order to offset their heating. A contemporary
state of the art of cooling vacuum pump components is disclosed in
a European Publication EP-A 1 242 744. The European Publication
discloses an electromotor that drives a shaft that drives pump
active components of the pumping system. A fan wheel having several
blades is arranged on at least one end of the shaft. The fan wheel
produces, upon rotation of the shaft, a gas flow directed to the
pump components.
[0005] The amount of the produced cooling gas and, thereby, the
cooling effect depends, among others, on the rotational speed of
the shaft. Therefore, the heat balance of the vacuum pump strongly
depends on the operation of the motor. This is often undesirable
and requires a compromise, among others, with respect to selection
of the rotational speed, which can be necessary from the point of
view of the vacuum technology, e.g., to insure an adequate control
a vacuum process.
[0006] Accordingly, an object of the present invention is to
provide a vacuum pump with cooling that overcomes the drawbacks of
the state of the art.
SUMMARY OF THE INVENTION
[0007] This and other objects of the present invention which will
become apparent hereinafter, are achieved by providing a vacuum
pump in which the fan has its own motor.
[0008] Because the fan has its own motor, it is possible to produce
a cooling gas flow independent on the speed of the vacuum pump
motor. With the fan having its own motor, it is possible to place
the fan at a location most favorable for the pump heat balance.
Thus, the cooling can be designed completely based on the needs and
does not require any compromise between the vacuum and cooling
requirements.
[0009] According to the inventive method, the pump motor is
operated with a first rotational speed, and the fan motor is
operated with a second rotational speed, with the first and second
rotational speeds being at least temporarily different. This
permits, e.g., to reduce the rotational speed of the vacuum pump
and, simultaneously, increase the flow of the cooling air produced
by the fan. This can prove advantageous during turning of the pump
off.
[0010] The cooling of the vacuum pump is improved when the housing
has cooling ribs, and the fan is arranged for feeding cooling air
in space between the cooling ribs. This can be achieved when the
fan is so arranged that the cooling gas flow, which is produced by
the fan, is blown into the space between the cooling ribs. The
cooling can further be improved when the vacuum pump includes a
hood that at least partially surrounds the housing and the hood is
so formed in a region of the cooling ribs that the cooling air from
the fan is deflected in the space between the cooling ribs.
[0011] Further advantages in cooling the vacuum pump are achieved
when the fan is located in a separate section of the pump housing.
This permits to arrange the fan or fans in the regions of the
housing where cooling is needed.
[0012] For an adequate heat balance of the vacuum pump and, thus,
for the necessary cooling, it is advantageous when the control
electronics that contains electronic components that require
cooling, and the pump system in which a lot of heat is generated
due to compression of the gases, are arranged in respective
separate housing sections. This permits to thermally separate the
respective cooling regions.
[0013] A vacuum pump can be so formed that the cooling air, which
is generated by the fan, flows to the housing section in which the
pumping system is located. This permits to use the cooling air
entirely for cooling.
[0014] A vacuum pump with a sectional construction of the housing
can be so formed that the housing section, which contains control
electronics, is cooled by free convection. Thus, the cooling air
flow, which is generated by the fan, can be used for cooling the
hot sections of the vacuum pump.
[0015] Cooling, which is independent of the pump drive, is
particularly advantageous in vane rotary vacuum pumps in which the
pumping system contains lubricant for sealing and lubricating the
vane. Inadequate cooling of the pumping system can lead to
destruction of the lubricant.
[0016] The novel features of the present invention which are
considered as characteristic for the invention, are set forth in
the appended claims. The invention itself, however, both as to its
construction and its mode of operation, together with additional
advantages and objects thereof, will be best understood from the
following detailed description of preferred embodiment, when read
with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The drawings show:
[0018] FIG. 1a a side view of a vacuum pump equipped with a hood
according to the present invention in a disassembled condition;
[0019] FIG. 1b a side view of the vacuum pump with a hood shown in
FIG. 1a in an assembled condition;
[0020] FIG. 2 a cross-sectional view through the intermediate
section and the control section of the inventive vacuum pump;
[0021] FIG. 3 a horizontal cross-sectional view along III-III in
FIG. 2;
[0022] FIG. 4 a vertical cross-sectional view of through the
pump-section and the peripheral section; and
[0023] FIG. 5 a cross-sectional view along line V-V in FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] FIG. 1 shows a vacuum pump that is formed of four sections
and is surrounded by a hood 1. The hood 1 is shown in FIG. 1a in a
disassembled or dismounted condition. In FIG. 1b, the hood 1 is
shown in a mounted condition on the vacuum pump and surrounds a
portion of the vacuum pump housing 1'. The vacuum pump itself rests
on a stand 10.
[0025] The sections of the vacuum pump include different functional
units. The control section 2 includes the control electronics that
controls feeding of current from a network to the coils of the pump
drive. In the intermediate section 3, a fan 6 is arranged. The fan
6 aspirates air and delivers it in the space between cooling ribs 8
provided on the housing, whereby cooling of the pump takes place.
The suction and the delivery of air by the fan 6 is shown with the
arrows. The peripheral section 4 includes gas connections, i.e.,
gas inlet 9 and gas outlet. The stand 10 also is arranged at the
peripheral section 10. The stand 10 includes means, e.g., an
elastomeric body which reduces transmission of vibrations between
the vacuum pump and the floor. In the pumping section 5, those
components of the pump are located with which the gas is compressed
to such an extent that it can be discharged against the atmosphere.
These four sections are arranged axially one after another, with
the intermediate section being located between the peripheral and
control sections. The pumping section 5 is provided on a side of
the peripheral section 4 remote from the intermediate section
3.
[0026] The sections of the vacuum pump are at least partially
surrounded by the hood 1. In the embodiment shown in the drawings,
the hood 1 is so formed that it covers the lower portion of the
vacuum pump. Lower portion means a portion of the vacuum pump
adjacent to the stand 10, i.e., in the direction of the floor. The
shape of the hood 1 is such that the control and intermediate
sections 2 and 3 are completely covered by the hood 1. The hood is
somewhat short in the region of the pumping section, covering only
the lower part of the pumping section. The cooling ribs 8 are
provided in the lower part of the pumping section 5. However, the
cooling ribs can also be formed in the upper part of the pumping
section 5. The hood 1 covers at least a portion of the cooling ribs
8, forming channels that are limited by the hood 1, the pump
housing, and the cooling ribs 8. For the purpose of protection, it
can be sufficient to cover only the lower portion of the pump
because it is in the lower portions of the pumping and peripheral
sections 4 and 5 that the heat-carrying elements such as lubricant
and coils are provided. When shaping a hood, design consideration
can naturally play a certain role. The hood 1 also covers the fan
6.
[0027] In order for the fan to be able to aspirate the air and to
deliver it into the channels, the hood has an opening. In the shown
embodiment, the opening is formed as a plurality of aeration slots
7. The number and the shape of the slots 7 can vary for different
pumps and are dependent on the requirements to the cooling gas
flow.
[0028] FIG. 2 shows the design of the control and intermediate
sections 2 and 3. The control section 2 has a closed housing with
cooling ribs 11. The cooling ribs 11 insure cooling by a free
convection. Within the control section 2, there are located
electronic components which form control electronics and are
mounted on a printed circuit board. The electronic components
convert a supply voltage in such a way that feeding of voltage and
current in a suitable form to the drive coils to provide for
rotation of the drive shaft is insured. The supply voltage source
can be a conventional network voltage of 220 V and 50 Hz or any
contemporary industrial voltage such as 48V. Those components of
the control electronics, which generate a certain amount of heat,
can be so arranged that they would contact the inner wall of the
housing of the control electronics. Advantageously, the contact
takes place in the region of the cooling ribs 11. Likewise, it is
possible to embed the control electronics in a filling compound
partially or completely. This would also insure a high mechanical
stability.
[0029] The intermediate section 3 contains several components in
its housing. A switch 15 serves for turning the vacuum pump on and
off. Further switches can be also arranged in the intermediate
section housing. The further switches can include, e.g., a standby
switch or a speed selection switch. Here, likewise, a socket 16, to
which the power supply is connected, is arranged. This power is
transmitted to the control electronics, on one hand, and on the
other hand, it is transmitted to a small panel that is connected by
suitable conductors with an auxiliary electronics 18, supplying it
with power. The auxiliary electronics serves for converting the
switching condition of the switch 15 in a control signal that is
transmitted over suitable conductors to the control electronics.
The auxiliary electronics has also means that insures feeding
voltage to the fan motor 6a and that controls switching the fan
motor 6a on and off. According to further development of the
present invention, further communication means can be arranged in
the intermediate section 3, including the necessary switches,
plugs, and bushings which are arranged on the housing wall similar
to switch 15. These components are connected by electrical
conductors or the like with the expanded auxiliary electronics that
includes, e.g., means for controlling a field bus or serial
interfaces and the like. These interfaces can be used for obtaining
information from external control means and related to the
operational state of the pump such as, e.g., "pump is operated,"
actual rotational speed of the pump, or active standby.
[0030] A seal 14 provided between the housings of the intermediate
section 3 and the control section 2. The seal 14 serves, on one
hand, for sealing the inner space against the moisture and dust. On
the other hand, the seal 14 functions as a thermal barrier, making
the transmission of heat from the intermediate section to the
control section more difficult. A similar seal is also provided
between the intermediate section 3 and the peripheral section 4,
making the transmission of heat therebetween also more difficult.
In a portion of the intermediate section 3, a support 19 supports
the fan 6 that includes the motor 6a and a fan blade 6b. The dash
arrows show the cooling gas flow that is aspirated by the fan 6.
The air is aspirated and flows between the cooling ribs 8.
[0031] FIG. 3 shows a cross-sectional view of the control and
intermediate sections 2 and 3 and a portion of the peripheral
sections 4. In this view, cooling ribs 11, which are provided on a
control section-side, end side of the vacuum pump, are shown in
cross-section. The longitudinal axis of the ribs 11 is oriented in
direction of the gravity force in order to optimize the free
convection. Advantageously, the cooling ribs of the control section
are not covered by the hood 1 in order not to obstruct the air flow
of the free convection. The feeding electrical conductors from the
control section 2 pass to the peripheral section 4 through a cable
channel provided in the intermediate section 3. Two channel seals
21 and 22 protect the cable channel from moisture and dust. In
particular, on a side of the motor control, a cable leadthrough 27
is provided. Inside the peripheral section 4, there are provided
coils 26 of the pump drive.
[0032] The control electronics 12 provides for feeding power to the
coils 26. A rotationally symmetrical separation member 23 is
arranged between the coils 26 hermetically separating them from the
inner space of the separation member 23. An end of a shaft 24, on
which permanent magnets 25 are secured, projects into the inner
space of the separation member 23. The cooling gas flow, which is
generated by the fan 6, is again shown with dash arrows. The
suction is effected through the aeration slots 7, and the air is
delivered in the direction of the peripheral section 4. According
to a further modification of the vacuum pump, such aeration slots
are formed in the pump bottom. The stand then needs to be
sufficiently spaced from the pump bottom in order to provide a
clearance through which the air can be aspirated.
[0033] From FIG. 3, it should be clear that the present invention
is not limited to the provision of a single fan. There can be
provided a plurality of fans. In the discussed embodiment, two fans
are provided in the lower portion of the intermediate section each
of which feeds cooling air in the channel. The two fans are
arranged on opposite sides of the vacuum pump, in particular, of
the peripheral and pumping sections. Further fans can be provided
for feeding cooling air to heat sources of the vacuum pump.
[0034] FIG. 4 shows a cross-sectional view of the peripheral and
pumping section 4 and 5. The embodiment of the vacuum pump shown in
the drawings represents a one-stage, lubricant-tight vane rotary
vacuum pump. The vacuum pump shown in FIG. 4 has a pumping system
30 located in the pumping section 5. The pumping system 30 has its
end side connected with the peripheral section 4 along a large
surface, whereby a good heat transmission is insured.
[0035] The housing of the pumping section 5 has good
heat-conducting characteristics, so that the heat of the peripheral
section 4 is transmitted to a large-surface body. The shaft 24
eccentrically extends through a cylindrical bore formed in the
pumping section 5. The shaft 24 can be formed of one or several
pieces and is supported by first and second slide bearings 31 and
32 which are lubricated by a lubricant. The lubricant is supplied
from a lubricant reservoir 35 that surrounds the pumping system 30.
A vane 33 is rotatably supported in the cylindrical bore of the
pumping section 5, with a compression chamber 34 being formed
between the wall of the cylindrical bore and the vane 33. The
permanent magnets 25 are secured, as it has already been discussed
above, on the end of the shaft 24 that projects into the peripheral
section 4 in which the coils 26 are located. Cooperation of the
magnets 25 with coils 26 provides for ration of the shaft 24, with
the coils 26 and permanent magnets 26 forming an electric motor.
Here, there is provided a brushless D.C. motor. Though the
advantages of the present invention are particularly apparent with
this type of an electric motor, the invention is not limited to
this type of a drive motor. The lubricant, primarily oil, serves,
in addition to lubrication of the bearings, also for lubrication
and sealing of the vane 33.
[0036] FIG. 5 shows a vertical cross-sectional view of the pumping
section 5. FIG. 5 illustrates in particular the eccentric position
of the shaft 24 and the position of vane 33. Between the vane 33
and the shaft 24, there is provided a spring, not shown. The
pumping section housing has the cooling ribs 8. The hood 1 covers
the cooling ribs 8, forming flow channels 42. The cooling gas flow,
which is generated by the fan 6, flows through the flow channels
42, which can be connected with each other, absorbs the heat of the
housing and carries the heat away from the housing. The heat is
produced in the pumping system 30 and is transmitted to the housing
by the lubricant reservoir 36.
[0037] Preferably, the hood 1 is so shaped that the channels are
open at their ends. This can be managed very easily as the hood 1
does not cover the pumping section-side, end side of the inventive
vacuum pump. Between the hood 1 and the housing, there is provided
an intermediate element 40 that, e.g., has highly elastomeric
components. The intermediate element 40 serves as a thermal barrier
and also for reduction of transmission of vibrations from the pump
housing to the hood 1. The hood 1 is fixed with attachment means,
e.g., with screws 41.
[0038] The embodiment of the vacuum pump shown in the drawings has
a favorable heat balance. A first source of an extensive heat is
the heat of compression in the pumping section 5. A further source
of an extensive heat is the peripheral section 4 because it is
there that the drive coils, in which the power dissipation is
converted into heat, are located. In addition, the heat to the
peripheral section 4 is transmitted by the end side of the pumping
system 30 which contact the peripheral section 4 along a large
surface. These heat sources are isolated from the control section
by the intermediate section. In view of the serial connection of
the pump sections, this distance is maximized. Also, the thermal
resistance of the seals, which are provided between the
intermediate section and the adjacent sections, contributes to
isolation of the heat sources from the control section 2. These
passive measures provide for a very favorable heat balance. The
active cooling with a fan also contributes to the favorable heat
balance. By locating the fan in the intermediate section, the
sections, which generate most of the heat, are subjected to the
action of the cooling air. The hood serves, on one hand, as a
convection protector and, on the other hand, guides the cooling air
flow, which is generated by the fan, in optimal manner to the heat
sources of the pumping and peripheral sections. In those regions,
where no air movement takes place, under the hood, the air acts as
an air cushion and isolates the environmental heat from the bottom
parts, e.g., of the control section. In sum, the cooling of the
inventive vacuum pump is noticeably improved in comparison with the
state of the art.
[0039] The embodiment shown in the drawings represents an oil-tight
vane rotary vacuum pump. However, the present invention can be
adapted to other vacuum pumps for producing low and high vacuum by
replacing the pumping section. In the replaced pumping section
other pumping principles can be used. Examples of the applicable
principles can be found in, e.g., dry piston compressor, dry van
rotary or rotary piston pump.
[0040] Though the present invention was shown and described with
references to the preferred embodiment, such is merely illustrative
of the present invention and is not to be construed as a limitation
thereof and various modifications of the present invention will be
apparent to those skilled in the art. It is therefore not intended
that the present invention be limited to the disclosed embodiment
or details thereof, and the present invention includes all
variations and/or alternative embodiments within the spirit and
scope of the present invention as defined by the appended
claims.
* * * * *