U.S. patent application number 09/917546 was filed with the patent office on 2001-12-06 for control valve.
This patent application is currently assigned to Mannesmann VDO AG. Invention is credited to Bachnak, Nouhad.
Application Number | 20010048093 09/917546 |
Document ID | / |
Family ID | 7917126 |
Filed Date | 2001-12-06 |
United States Patent
Application |
20010048093 |
Kind Code |
A1 |
Bachnak, Nouhad |
December 6, 2001 |
Control valve
Abstract
A pressure compensating element (8) for a control valve (3) for
controlling an overflow of a medium from a first pressure space (1)
into a second pressure space (2) has a diaphragm (9) separating the
pressure spaces (1, 2) from one another. The pressure compensating
element (8) compensates forces acting on a valve body (5) of the
control valve (3) and generated by pressure differences in the
pressure spaces (1, 2). However, an overflow of a medium from one
pressure space (1) into the other pressure space (2) takes place
solely in the region of the control valve (3).
Inventors: |
Bachnak, Nouhad; (Frankfurt,
DE) |
Correspondence
Address: |
Martin A. Farber
Suite 473
866 United Nations Plaza
New York
NY
10017
US
|
Assignee: |
Mannesmann VDO AG
|
Family ID: |
7917126 |
Appl. No.: |
09/917546 |
Filed: |
July 27, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09917546 |
Jul 27, 2001 |
|
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09629340 |
Aug 1, 2000 |
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Current U.S.
Class: |
251/282 ;
251/281 |
Current CPC
Class: |
F16K 17/087 20130101;
F02M 26/21 20160201; F02M 26/67 20160201; F02M 26/58 20160201; F02M
26/69 20160201 |
Class at
Publication: |
251/282 ;
251/281 |
International
Class: |
F16K 039/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 4, 1999 |
DE |
199 36 657.8 |
Claims
1. A control valve for controlling an overflow of a medium from a
first pressure space into a second pressure space having a pressure
differing from a pressure in the first pressure space, with a valve
body prestressed against a valve seat, with a control device for
moving the valve body and with a movable pressure compensating
element which is subjected to the pressure difference between the
pressure spaces and is connected to the valve body and which is
intended for compensating the pressure forces acting on the valve
body, wherein the pressure spaces (1, 2) are sealed off relative to
one another in the region of the pressure compensating element (8,
17, 26).
2. The control valve as claimed in claim 1, wherein the pressure
compensating element (8, 17, 26) has a diaphragm (9, 20, 30) for
separating the pressure spaces (1, 2).
3. The control valve as claimed in claim 1 or 2, wherein a valve
shaft (7, 18, 23) designed for adjusting the valve body (5, 16, 24)
is connected to a disk (10, 19, 29) holding the diaphragm (9, 20,
30).
4. The control valve as claimed in at least one of the preceding
claims, wherein the pressure compensating element (8) is designed
to subdivide a container (12) into two chambers (13, 14), and the
first chamber (13) is connected to the first pressure space (1) and
the second chamber (14) to the second pressure space (2).
5. The control valve as claimed in at least one of the preceding
claims, wherein the container (12) is arranged on that side of the
first pressure space (1)
Description
[0001] The invention relates to a control valve for controlling an
overflow of a medium from a first pressure space into a second
pressure space having a pressure different from a pressure in the
first pressure space, with a valve body prestressed against a valve
seat, with a control device for moving the valve body and with a
movable pressure compensating element which is subjected to the
pressure difference between the pressure spaces and is connected to
the valve body and which is intended for compensating the pressure
forces acting on the valve body.
[0002] Such electromagnetic control valves are used, for example,
in devices for exhaust-gas recirculation in internal combustion
engines of present-day motor vehicles. In this case, the pressure
spaces take the forms of the intake duct and the exhaust duct of
the internal combustion engine. In such devices for exhaust-gas
recirculation, a part stream of exhaust gas is branched off from
the exhaust duct and is supplied to the intake duct. The nitrogen
fraction in the exhaust gas can thereby be reduced. The ratio of
the exhaust-gas quantity to be supplied to the fresh-air quantity
depends on, for example, the load state, the temperatures or the
rotational speed of the internal combustion engine and is
determined by the control of the valve body. For this control, the
control device has, for example, a pneumatic, electromagnetic or
electromotive actuating drive.
[0003] In order to avoid particularly high actuating forces during
the movement of the valve body when there are high pressure
differences between the pressure spaces, a control valve has become
known from practice, in which a second valve body is designed as a
pressure compensating element. The valve bodies are fastened on a
common valve shaft and, in the basic position, in each case bear on
a valve seat. One of the pressure spaces is connected to the region
between the valve bodies, whilst the regions on those sides of the
valve bodies which face away from one another are connected to the
other pressure space. As a result, forces generated due to pressure
differences in the pressure spaces act in each case on the valve
shaft, but in opposite directions of force.
[0004] A disadvantage of the known control valve is that the
respective distances between the valve bodies and the valve seats
must have particularly low tolerances. Moreover, for example, in
the event of thermal expansion of the valve shaft or wear of the
valve bodies and of the valve seats, the control valve does not
reliably seal off the pressure spaces from one another. Different
expansions of the valve bodies and the valve seats likewise result
in leaks.
[0005] The problem on which the invention is based is to design a
control valve of the type initially mentioned, in such a way that
it does not need low tolerances and reliably seals off the pressure
spaces relative to one another.
[0006] This problem is solved, according to the invention, in that
the pressure spaces are sealed off relative to one another in the
region of the pressure compensating element.
[0007] By virtue of this design, the control valve according to the
invention has a single valve body. The valve body and the pressure
compensating element are separated from one another as result of
the invention. The control valve according to the invention
therefore does not need to have particularly low tolerances. A leak
in the control valve according to the invention can consequently be
avoided in a simple way. The control valve according to the
invention is therefore suitable, in particular, for use in a device
for exhaust-gas recirculation in an internal combustion engine of a
motor vehicle.
[0008] The pressure compensating element could, for example, be a
piston displaceable in a cylinder arranged between the pressure
spaces. According to another advantageous development of the
invention, the pressure compensating element reliably seals off the
two pressure spaces relative to one another if the pressure
compensating element has a diaphragm for separating the pressure
spaces.
[0009] According to another advantageous development of the
invention, the pressure compensating element has a particularly
simple construction if a valve shaft designed for adjusting the
valve body is connected to a disk holding the diaphragm.
[0010] According to another advantageous development of the
invention, disturbances of the pressure compensating element which
are generated by flows within the pressure spaces can reliably be
avoided if the pressure compensating element is designed to
subdivide a container into two chambers, and if the first chamber
is connected to the first pressure space and the second chamber to
the second pressure space.
[0011] The control valve according to the invention has a
particularly compact design if the container is arranged on that
side of the first pressure space which is located opposite the
second pressure space, and if a pressure compensating duct is
designed to connect the second pressure space to the second
chamber.
[0012] When the control valve according to the invention is in the
basic position, particularly reliable sealing off of the pressure
spaces can be ensured in a simple way if the valve body is capable
of being returned into the closing position by means of a spring
element. The spring element may be manufactured, for example, from
spring steel. Since the spring element has to transmit only very
low return forces, it may also consist of a metal memory alloy.
[0013] According to another advantageous development of the
invention, an equilibrium of the forces acting on the valve body
and on the pressure compensating element can be established in a
simple way if a lever is arranged between the valve body and the
pressure compensating element.
[0014] The invention permits numerous embodiments. In order to make
its basic principle even clearer, three of these are illustrated in
the drawing and are described below. In the drawing:
[0015] FIG. 1 shows a sectional illustration through a first
embodiment of a control valve according to the invention in
longitudinal section,
[0016] FIG. 2 shows a further embodiment of the control valve
according to the invention in longitudinal section,
[0017] FIG. 3 shows a diagrammatic illustration of a further
embodiment of the control valve according to the invention.
[0018] FIG. 1 shows in longitudinal section a device for
exhaust-gas recirculation in an internal combustion engine of a
motor vehicle, with a first pressure space 1 taking the form of the
exhaust duct and with a second pressure space 2 taking the form of
the intake duct. A control valve 3 allows an overflow of exhaust
gas from the first pressure space 1 into the second pressure space
2. The control valve 3 has a valve body 5 bearing on a valve seat 4
and a control device 6 for moving the valve body 5 perpendicularly
to the valve seat 4. The valve body 5 is connected to the control
device 6 via a valve shaft 7. The control device 6 can adjust the
valve shaft 7, for example by means of an electromagnet which is
not illustrated. Consequently, for example depending on the
rotational speed of the internal combustion engine, on the load
state or on the temperatures, a connection of the pressure space 1
taking the form of the exhaust duct to the pressure space 2 taking
the form of the intake duct can be made and exhaust gas can be
mixed with fresh air.
[0019] A pressure compensating element 8 with a disk 10 holding a
diaphragm 9 is fastened to the valve shaft 7. The disk 10 is
prestressed downward by a spring element 11 designed as a helical
spring. The diaphragm 9 is arranged in a container 12 and
subdivides the latter into two chambers 13, 14. The diaphragm 9
allows movement of the disk 10 and consequently of the valve shaft
7 and separates the media flowing in the pressure spaces 1, 2. The
first chamber 13 is connected to the first pressure space 1 and the
second chamber 14 is connected, via a pressure compensating duct
15, to the second pressure space 2. The pressure compensating
element 8 has essentially the same cross-sectional area as the
valve body 5, so that a pressure difference between the chambers
13, 14 and consequently between the pressure spaces 1, 2
introduces, via the pressure compensating element 8, the same
forces into the valve shaft 7 as the valve body 5. In this case,
the forces point in opposite directions and therefore cancel one
another out. For the sake of clarity, the forces acting on the
valve body 5 and on the disk 10 are identified by arrows in the
drawing for the situation where a lower pressure prevails in the
first pressure space 1 than in the second pressure space 2. The
spring element 11 serves as a return element for holding the valve
body 5 on the valve seat 4 when the control device 6 is under no
force. Since the forces acting on the valve body 5 due to the
pressure difference between the pressure spaces are compensated by
the pressure compensating element 8, the spring element 11 can have
a low spring force and a particularly flat spring
characteristic.
[0020] FIG. 2 shows a further embodiment of the control valve.
Here, a part region of the first pressure space 1 is surrounded by
a second pressure space 2 having a C-shaped cross section. A valve
body 16 and a pressure compensating element 17 are arranged in the
legs of the second pressure space 2. The pressure compensating
element 17 has a disk 19 fastened to a valve shaft 18 and a
diaphragm 20 fastened to the disk 19. The valve body 16 is likewise
fastened to the valve shaft 18 and, in the position depicted, bears
on a valve seat 21. When the valve body 16 is in this position, the
media flowing in the pressure spaces 1, 2 are separated from one
another. As in the case of the control valve from FIG. 1, forces
acting on the valve shaft 18 and generated due to a pressure
difference in the pressure spaces 1, 2 cancel one another out.
[0021] FIG. 3 shows diagrammatically a further embodiment of the
control valve. Here, the pressure spaces 1, 2 take the form of
ducts arranged parallel to one another. The control valve has a
valve shaft 23 displaceable by a control device 22 and a valve body
24 fastened on the valve shaft 23. In the position depicted, the
valve body 24 is prestressed against a valve seat 25. A lever 28
engages on the valve shaft 23. The lever 28 is mounted pivotably
about a fixed bearing 27 and connects the valve shaft 23 to a
pressure compensating element 26. The pressure compensating element
26 has a disk 29 which is articulated on the lever 28 and which is
held in an orifice 31 by means of a diaphragm 30. The diaphragm 30
seals off the orifice 31 relative to the disk 29.
* * * * *