U.S. patent application number 12/718361 was filed with the patent office on 2010-09-02 for compact dry-running piston compressor.
This patent application is currently assigned to KNORR-BREMSE Systeme fuer Nutzfahrzeuge GmbH. Invention is credited to Michael Hartl, Joerg MELLAR.
Application Number | 20100221128 12/718361 |
Document ID | / |
Family ID | 40039675 |
Filed Date | 2010-09-02 |
United States Patent
Application |
20100221128 |
Kind Code |
A1 |
MELLAR; Joerg ; et
al. |
September 2, 2010 |
Compact Dry-Running Piston Compressor
Abstract
A compact dry-running piston compressor includes at least one
cylinder for the compression of air by a corresponding piston,
which may be driven by an electric motor with a crank drive made up
of a crankshaft and connecting rod. The crank drive is rotatably
mounted in an oil-bath-free compressor housing on pre-lubricated
roller bearings and generates an internal cooling air flow inside
the housing due to its movement cycle. The compressor housing
includes two housing sections separated by a partition wall, in
order to accommodate the crank drive within the first housing half
and the electric motor in the second housing half. A roller bearing
common to the crank drive and the electric motor is arranged in the
partition wall lying in the cooling air flow passing through the
first housing half.
Inventors: |
MELLAR; Joerg; (Pliening,
DE) ; Hartl; Michael; (Unterhaching, DE) |
Correspondence
Address: |
CROWELL & MORING LLP;INTELLECTUAL PROPERTY GROUP
P.O. BOX 14300
WASHINGTON
DC
20044-4300
US
|
Assignee: |
KNORR-BREMSE Systeme fuer
Nutzfahrzeuge GmbH
Muenchen
DE
KNORR-BREMSE Systeme fuer Schienenfahrzeuge GmbH
Muenchen
DE
|
Family ID: |
40039675 |
Appl. No.: |
12/718361 |
Filed: |
March 5, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP2008/006916 |
Aug 22, 2008 |
|
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12718361 |
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Current U.S.
Class: |
417/410.1 |
Current CPC
Class: |
F04B 39/06 20130101;
F04B 39/121 20130101; F04B 39/128 20130101 |
Class at
Publication: |
417/410.1 |
International
Class: |
F04B 35/04 20060101
F04B035/04 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 6, 2007 |
DE |
10 2007 042 318.9 |
Claims
1. A compact dry-running piston compressor having at least one
cylinder for compressing air via an associated piston, the
compressor comprising: a crank drive including a crankshaft and
connecting rod, the connecting rod being connectable with the
piston; an electric motor operatively configured to drive the
associated piston via the crank drive; an oil-bath-free housing
comprising first and second housing sections separated by a
partition, the crank drive being accommodated within the first
housing section and the electric motor being accommodated within
the second housing section; and pre-lubricated roller bearings
arranged in the housing for rotatably mounting the crank drive, one
of said roller bearings being common to the crank drive and the
electric motor and arranged in the partition, the one roller
bearing being located in a cooling air flow generated by a movement
cycle of the crank drive, which cooling air flow passes through the
first housing section.
2. The compact dry-running piston compressor according to claim 1,
further comprising at least one opening provided in the partition,
the at least one opening allowing at least a portion of the cooling
air flow to be branched from the first housing half into the second
housing half.
3. The compact dry-running piston compressor according to claim 1,
wherein the electric motor comprises a driven-side end winding, the
driven-end side winding being concomitantly cooled via the one
roller bearing located in the cooling air flow and via heat
conduction of the partition.
4. The compact dry-running piston compressor according to claim 2,
wherein the electric motor comprises a driven-side end winding, the
driven-end side winding being concomitantly cooled via the one
roller bearing located in the cooling air flow and via heat
conduction of the partition.
5. The compact dry-running piston compressor according to claim 1,
wherein a further roller bearing rotatably mounts the crankshaft,
the further roller bearing arranged at another side of the
crankshaft.
6. The compact dry-running piston compressor according to claim 5,
further comprising: a relatively flat cover operatively configured
for closing the first housing section; and wherein the further
roller bearing is arranged in the cover so as to be encapsulated
with respect to the area outside of the cover.
7. The compact dry-running piston compressor according to claim 5,
wherein the further roller bearing is also located in the cooling
air flow passing through the first Musing section.
8. The compact dry-running piston compressor according to claim 5,
wherein a rotor of the electric motor is mounted in the housing via
two roller bearings of the crankshaft.
9. The compact dry-running piston compressor according to claim 1,
wherein a rotor of the electric motor is attached directly to an
end of the crankshaft, said end of the crankshaft projecting into
the second housing section.
10. The compact dry-running piston compressor according to claim 1,
wherein the electric motor is a brushless direct-current motor
having a stator composed of coil windings with an iron core and a
rotor equipped with permanent magnets.
11. The compact dry-running piston compressor according to claim 1,
further comprising commutating electronics for controlling the
electric motor, the commutating electronics being arranged on a
printed circuit board accommodated in or on the second housing
section.
12. The compact dry-running piston compressor according to claim 1,
further comprising a relatively flat cover for closing-off an end
side of the second housing section.
13. The compact dry-running piston compressor according to claim 1,
wherein the first housing section includes an opening in which the
cylinder, formed as a separate component, is releasably
attached.
14. The compact dry-running piston compressor according to claim 1,
further comprising inflow ducts arranged in the compressor, the
inflow ducts having varying cross-sections to provide different
cooling air flows through individual assemblies of the compressor.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of PCT International
Application No. PCT/EP2008/006916, filed Aug. 22, 2008, which
claims priority under 35 U.S.C. .sctn.119 from German Patent
Application No. DE 10 2007 042 318.9, filed Sep. 6, 2007, the
entire disclosures of which are herein expressly incorporated by
reference.
BACKGROUND AND SUMMARY OF THE INVENTION
[0002] The present invention relates to a compact dry-running
piston compressor, particularly for commercial vehicles, having at
least one cylinder for compressing air by way of an associated
piston. The piston can be moved by electric motor via a crank drive
composed of a crankshaft and a connecting rod, which crank drive is
rotatably mounted by way of permanently lubricated roller bearings
in a compressor housing which has no oil bath. The crank drive
generates a cooling air flow within the housing as a result of the
movement cycle.
[0003] The field of application of the present invention extends
primarily to rail vehicle and commercial vehicle construction.
Here, as auxiliary compressors, use is made of small
electromotively driven units which produce compressed air for
consumers or loads within the vehicle. In the past, use was made
predominantly of oil-lubricated piston compressors for this
purpose. Modern compressor concepts based on piston compressors
also permit oil-free operation. Instead of the crankcase being
filled with oil, the bearing points of the crank drive are in this
case mounted using roller bearings, and the roller bearing
arrangements are provided with local permanent lubrication. The
oil-free piston compressor has been developed in particular for
servicing and environmental reasons.
[0004] DE 10 2004 042 944 A1 discloses a generic dry-running piston
compressor. The piston compressor is composed substantially of a
compressor unit for producing compressed air, which compressor unit
is driven by a drive unit for producing a rotational movement.
Here, the drive unit is usually in the form of an electric motor. A
crankshaft is rotatably mounted within the crankcase of the
compressor unit. Two connecting rods are attached to the
crankshaft, which connecting rods are connected to associated
pistons in order to convert the drive-side rotational movement into
a linear movement of the pistons which, in order to compress air,
are accommodated within associated cylinders. Here, the cylinders
are attached to the crankcase in a 180.degree. position. To improve
the cooling of the cylinders, an inlet-side valve is provided which
moves into its open position in the event of a vacuum being
produced in the crankcase by the movement of the piston. In this
way, cooling air is sucked in from the outside, and at least one
outlet-side valve, which is arranged spaced apart from the
inlet-side valve on the crankcase, moves into its open position in
the event of an excess pressure being produced in the crankcase by
the movement of the piston. In this way, consumed cooling air is
discharged such that an internal cooling air flow flows through the
crankcase as a result of the movement cycle of the pistons.
[0005] Although the above technical solution utilizes a cooling air
flow for the internal cooling of a dry-running piston compressor,
the flange-mounted electric motor must be cooled separately, which
usually takes place by means of a fan impeller on the electric
motor. This again permits the infiltration of moisture and dirt
from the environment. To prevent this, additional encapsulation of
the piston compressor together with the electric motor has hitherto
been provided, but this considerably increases the space
requirements of the unit.
[0006] It is therefore an object of the present invention to
provide a compact dry-running piston compressor suitable for use in
contaminated environments and distinguished by a long service
life.
[0007] This and other objects are achieved by a compact dry-running
piston compressor having at least one cylinder for compressing air
via an associated piston which can be moved by electric motor via a
crank drive composed of a crankshaft and a connecting rod. The
crank drive is rotatably mounted by way of permanently lubricated
(pre-lubricated) roller bearings in a compressor housing which has
no oil bath. The crank drive generates a cooling air flow within
the housing as a result of the movement cycle. The compressor
housing comprises two housing sections separated by a partition
such that the crank drive is accommodated within the first housing
section and the electric motor is accommodated within the second
housing section. A roller bearing, which is common to the crank
drive and to the electric motor, is inserted into the partition.
The roller bearing is situated in the cooling air flow passing
through the first housing section.
[0008] An advantage according to the invention is, in particular,
that a common housing is provided for the compressor unit and for
the drive, which housing ensures complete encapsulation with
respect to contaminated environments. At the same time, the thermal
problems arising with such encapsulation are solved overall for the
compressor unit and for the drive unit by way of a common cooling
air flow. The solution according to the invention can be
accomplished because of the realization that the driven-side end of
the motor windings is the decisive heat source, which can be
efficiently cooled by way of local cooling measures in conjunction
with a common housing. The solution according to the invention is
optimized with regard to the required number of roller bearings. It
is thus possible to use a single roller bearing jointly for the
electric motor and the crankshaft mounting. If the single roller
bearing is cooled in a targeted fashion, then an adequate cooling
action is also obtained for the electric motor, which is made
possible by way of the heat conduction in the region of the
partition.
[0009] According to a preferred embodiment of the invention, at
least one opening for branching or diverting parts of the cooling
air flow of the first housing section into the second housing
section is provided in the partition. In this way, the cooling air
flow can be conducted in a targeted fashion also into the region of
the second housing section, such that the cooling action can be
improved using this measure.
[0010] The crankshaft is preferably rotatably mounted not only by
way of the roller bearing arranged in the partition but also, at
its other side, by way of a further roller bearing. A total of two
roller bearings for the crankshaft is therefore adequate for
rotatably mounting the crank drive together with the electric
motor. Here, the further roller bearing can be inserted, so as to
be encapsulated with respect to the outside, in a cover, which is
flat in terms of its basic shape, of the first housing section. As
a result of the flat cover, the external geometric dimensions of
the piston compressor are not increased considerably. At the same
time, the flat cover provides an easily dismountable facility for
accessing the interior of the crankcase. The second roller bearing
should likewise be situated in the cooling air flow passing through
the first housing section.
[0011] To maximize compactness, it is proposed that the rotor of
the electric motor be attached directly to an end, which projects
into the second housing section, of the crankshaft. This attachment
may take place by way of a conical flange with an end-side screw
connection. However, it is also contemplated for the crankshaft and
rotor to be formed in one piece. This is expedient in particular if
the electric motor is in the form of a brushless electric motor
whose rotor need merely be equipped with permanent magnets. In
contrast, the stator is provided with electric coil windings.
[0012] The commutating electronics required for such a brushless
electric motor which is preferably to be used here can likewise be
integrated in a simple manner into the second housing section. The
commutating electronics should preferably be arranged on a flat
printed circuit board which is arranged in the region of the
housing wall. For better accessibility to the commutating
electronics, the latter may be closed off by a cover which can be
screwed on. The second housing section is closed off at the end
side by a cover which is likewise flat in terms of basic shape.
After the cover has been mounted, the inner region of the electric
motor is accessible for servicing and repair purposes.
[0013] The integrated compressor housing designed according to the
invention also has, in the region of the first housing section, an
opening for the releasable attachment of a cylinder, which is
preferably formed as a separate component. As a result of the
cylinder being formed separately, it is possible for the integrated
compressor housing with the two housing sections or halves to be
formed in a simple manner in terms of casting, preferably by means
of light metal casting.
[0014] In one refinement of the invention, inflow ducts are
provided in the piston compressor, the cross sections of which
inflow ducts vary such that different cooling air flows flow
through the individual assemblies. Here, the individual assemblies
are the crankcase, the winding space of the electric motor and the
commutating electronics. It is advantageous for the corresponding
regions to be supplied optimally with a sufficient quantity of
cooling air.
[0015] Other objects, advantages and novel features of the present
invention will become apparent from the following detailed
description of one or more preferred embodiments when considered in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a longitudinal section view through a compact
dry-running piston compressor; and
[0017] FIG. 2 is a longitudinal section view through a compact
dry-running piston compressor with inflow ducts.
DETAILED DESCRIPTION OF THE DRAWINGS
[0018] In FIG. 1, the compressor has a single cylinder 1 in which
is arranged a piston 2 for compressing air sucked in from the
environment via a cylinder head 3. The linear reciprocating working
movement of the piston 2 is generated by a crank drive. The crank
drive is composed essentially of a crankshaft 4 and a connecting
rod 5. The crankshaft 4 is mounted so as to be rotatable with
respect to the compressor housing 7 by way of two roller bearings
6a and 6b.
[0019] The compressor housing 7 is composed of a first housing
section 8, such as a first housing half, which forms the crankcase,
and a second housing section 9, such as a second housing half,
which houses an electric motor 10. As used herein, the term housing
"half" is not limited to an evenly divided housing.
[0020] In this exemplary embodiment, the electric motor 10 is in
the form of a brushless electric motor and includes a stator 11
composed of coil windings with an iron core. The stator 11
interacts with a rotor 12, which is equipped with permanent
magnets. The rotor 12 of the electric motor 10 is screwed onto a
conical end of the crankshaft 4, which conical end projects into
the second housing half 9. Commutating electronics 13 of the
electric motor 10 are integrated in the wall of the second housing
half 9. For a space-saving arrangement, the commutating electronics
13 are accommodated on one printed circuit board. The second
housing half 9 is closed off by a flat cover 14 at the end side by
use of individual screws. The first housing half 8 also has a cover
15, which is flat in terms of its basic shape and which closes off
the housing half 8 at the end side also by use of screw
connections.
[0021] The cover 15 of the first housing half 8 includes a seat for
the roller bearing 6a of the crankshaft 4. The other roller bearing
6b of the crankshaft 4 is located in a partition 16 of the
compressor housing 8. The roller bearing 6b is provided both for
mounting the crankshaft 4 at one side and also for mounting the
rotor 12 of the electric motor 10.
[0022] The two roller bearings 6a and 6b are situated in a cooling
air flow which passes through the first housing half 8. On account
of the movement cycle of the crank drive, the cooling air flow
passes, in a manner controlled by a valve, via a cylinder-side duct
17 into the interior of the first housing half 8 and leaves the
latter through a valve-switched opening 18. Here, the cooling air
flow is conducted through the first housing half 8 in such a way
that the two roller bearings 6a and 6b are cooled. To deflect parts
of the cooling air flow of the first housing half 8 into the second
housing half 9, the partition 16 has a ring of openings 19.
[0023] FIG. 2 shows another embodiment in which inflow ducts 20 are
provided. The inflow ducts 20 are supplied with air via the duct
17. These inflow ducts convey cooling air to the individual
components, with the quantity of cooling air being defined by the
respective cross sections. The flow of air is shown by the block
arrows in FIG. 2.
[0024] The invention is not restricted to the preferred exemplary
embodiments described above. For example, it is also possible for
the electric motor to be of some other type. In principle, any type
is suitable which can be accommodated, so as to be encapsulated,
within the housing half 9.
TABLE-US-00001 Table of Reference Numerals 1 Cylinder 2 Piston 3
Cylinder head 4 Crankshaft 5 Connecting rod 6 Roller bearing 7
Compressor housing 8 First housing half 9 Second housing half 10
Electric motor 11 Stator 12 Rotor 13 Commutating electronics 14
Cover 15 Cover 16 Partition 17 Duct 18 Opening 19 Opening 20 Inflow
ducts
[0025] The foregoing disclosure has been set forth merely to
illustrate the invention and is not intended to be limiting. Since
modifications of the disclosed embodiments incorporating the spirit
and substance of the invention may occur to persons skilled in the
art, the invention should be construed to include everything within
the scope of the appended claims and equivalents thereof.
* * * * *