U.S. patent application number 10/591881 was filed with the patent office on 2007-10-18 for device for detecting the combustion-chamber pressure in an internal combustion engine.
Invention is credited to Christoph Kern, Thomas Ludwig.
Application Number | 20070240661 10/591881 |
Document ID | / |
Family ID | 34877507 |
Filed Date | 2007-10-18 |
United States Patent
Application |
20070240661 |
Kind Code |
A1 |
Ludwig; Thomas ; et
al. |
October 18, 2007 |
Device for Detecting the Combustion-Chamber Pressure in an Internal
Combustion Engine
Abstract
A device for detecting the pressure in a combustion chamber of
an engine is designed in such a way that the combustion-chamber
pressure can be detected reliably and reproducibly. For this
purpose, a glow element in a glow plug, exposed to the
combustion-chamber pressure, is fixedly mounted in a housing of the
glow plug via a fastening element. A sensor is fixedly mounted in
the housing of the glow plug using this fastener located at a
distance from the fastening element. This sensor detects the
elastic deformation of the glow element caused by the
combustion-chamber pressure. This device is preferably used in the
automobile industry.
Inventors: |
Ludwig; Thomas; (Gerlinger,
DE) ; Kern; Christoph; (Aspach, DE) |
Correspondence
Address: |
KENYON & KENYON LLP
ONE BROADWAY
NEW YORK
NY
10004
US
|
Family ID: |
34877507 |
Appl. No.: |
10/591881 |
Filed: |
January 13, 2005 |
PCT Filed: |
January 13, 2005 |
PCT NO: |
PCT/EP05/50125 |
371 Date: |
June 26, 2007 |
Current U.S.
Class: |
123/145R |
Current CPC
Class: |
G01L 23/22 20130101 |
Class at
Publication: |
123/145.00R |
International
Class: |
F23Q 7/22 20060101
F23Q007/22 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 6, 2004 |
DE |
10 2004 011 097.2 |
Claims
1-12. (canceled)
13. A device for detecting a cylinder pressure in an internal
combustion engine, comprising: a glow plug having a housing adapted
to be mounted in a cylinder head of the engine, the glow plug
having a first end and a second end; a glow element situated at the
first end of the glow plug, which, when the glow plug is installed,
at least partially protrudes into a combustion chamber of the
engine; a fastening element attaching the glow element to the glow
plug; and a sensor situated between the fastening element and the
second end of the glow plug.
14. The device according to claim 13, wherein the engine is a
diesel engine.
15. The device according to claim 13, wherein the sensor is
separated from the fastening element of the glow element and is
secured in the glow plug at least indirectly via a fastener.
16. The device according to claim 15, wherein the sensor is
connected to the glow element at least indirectly by friction
lock.
17. The device according to claim 16, wherein the at least indirect
friction lock between the sensor and the glow element is
implemented with pre-stress.
18. The device according to claim 15, wherein the sensor is
connected to the fastener at least indirectly by friction lock.
19. The device according to claim 18, wherein the at least indirect
friction lock between the sensor and the fastener is implemented
with pre-stress.
20. The device according to claim 13, wherein the sensor is
separated from the glow element by at least one spacer.
21. The device according to claim 18, wherein the sensor is
separated from the fastening element by at least one spacer
element.
22. The device according to claim 20, wherein the spacer is an
intermediate sleeve.
23. The device according to claim 21, wherein the spacer element is
an intermediate sleeve.
24. The device according to claim 22, wherein the intermediate
sleeve is made of graphite.
25. The device according to claim 23, wherein the intermediate
sleeve is made of graphite.
26. The device according to claim 15, wherein the fastener is a
sleeve caulked to the housing.
27. The device according to claim 13, wherein the sensor is a force
sensor designed as a piezoelectric ring.
Description
BACKGROUND INFORMATION
[0001] A device for detecting a combustion-chamber pressure in a
diesel engine, having a pressure sensor and a heating section of a
glow plug, is described in German Patent No. DE 196 80 912. This
heating section faces an internal space of a cylinder of the diesel
engine and may be exposed to the combustion-chamber pressure. The
heating section is secured within a housing of the glow plug by a
fastening element. The pressure sensor is situated between this
fastening element and the heating section.
[0002] In this system, the glow plug and the pressure sensor are
supported by the same fastening element against the glow plug
housing in such a way that the pressure sensor is affected by at
least approximately the entire force acting upon the glow plug. In
a disadvantageous manner, for certain sensor materials this results
in the pressure sensor being also operated in its non-linear range,
which results in a non-reproducible measuring signal and unreliable
pressure detection in the combustion chamber of the engine.
[0003] Furthermore, the above-described arrangement of the pressure
sensor being situated in the proximity of the internal space of the
cylinder and being directly coupled to the glow plug during
operation of the diesel engine is associated with a substantial
heat load on the pressure sensor, thus jeopardizing its operational
reliability. This may result in malfunction of the device for
detecting the pressure in the combustion chamber of the engine and
thus also in unreliable detection of the pressure in the combustion
chamber of the engine, in particular when the signal output of the
pressure sensor becomes unsteady due to fluctuations between high
and low operating temperatures.
SUMMARY OF THE INVENTION
[0004] The device according to the present invention has the
advantage over the related art that the above-mentioned
shortcomings are avoided to a satisfactory degree.
[0005] For this purpose, the sensor is situated between the
fastening element of the glow element of the glow plug and a second
end of the glow plug. This offers the possibility of uncoupling the
sensor from the total force acting upon the glow element and of
operating it in its linear and low-hysteresis range. The separation
between the attachment of the glow element and the attachment of
the sensor in the glow plug allows the stressed area of the sensor
to be delimited in a controlled manner in such a way that the
optimum area of the sensor with respect to signal generation may be
used for reliable and reproducible detection of the pressure in the
combustion chamber of the engine.
[0006] Furthermore, the distance between the sensor and the glow
element, as well as the thermal connection of the glow element via
its attachment to the housing, causes a reduction in the heat load
on the sensor, in such a way that its operational reliability is
less affected, making the detection of the pressure in the
combustion chamber of the engine more reliable.
[0007] According to an advantageous embodiment, there is an at
least indirect frictional connection with pre-stress between the
sensor and the glow element, which counteracts a hysteresis effect
in detecting measured values.
[0008] It is furthermore advantageous that the sensor is separated
from the glow element and the fastening element by at least one
spacer. This design and stiffness may allow the maximum force
acting upon the sensor to be adjusted.
[0009] It is also advantageous if the at least one spacer is
designed as an intermediate sleeve, the sensor is designed as a
piezoelectric ring, and the fastening element is designed as a
sleeve. This allows heating and signal lines for the sheathed
element glow plug and the sensor to be run through in a simplified
manner.
BRIEF DESCRIPTION OF THE DRAWING
[0010] FIG. 1 shows a simplified longitudinal section of the device
for detecting the pressure in a combustion chamber of an
engine.
DETAILED DESCRIPTION
[0011] A device for detecting the pressure in a combustion chamber
of an engine according to FIG. 1 has a glow plug 11, which is
installed in a cylinder head 14 of the engine depicted only
schematically, in particular of a diesel engine, via an external
thread 12 of a tubular metal housing 13.
[0012] A first end 16 of glow plug 11 has a glow element 17, which
partially protrudes from housing 13 and a free end 18 of the glow
plug protrudes into an internal space 19 of the engine, forming a
combustion chamber. Glow element 17 is secured in glow plug 11 by a
fastening element 22. This fastening element 22 is designed as a
support tube which surrounds and fastens glow element 17 over its
circumference in an end area 23 of its other end. Fastening element
22, in turn, is pressed into housing 13.
[0013] Alternatively, fastening element 22 may also be implemented
as a graphite sleeve or in the form of a permanent bond, for
example, a weld.
[0014] Sensor 26 is situated between fastening element 22 and thus
between end area 23 of glow element 17 and second end 24 of glow
plug 11. Sensor 26 is separated from glow element 17 by a spacer 27
in this embodiment. Alternatively, sensor 26 may also directly rest
against glow element 17.
[0015] Sensor 26 is also supported by a fastener 29 for sensor 24
fixedly situated in housing 13 with spacer element 28 in between,
thus establishing the position of sensor 26 in housing 13. Fastener
29 is designed, for example, as a sleeve caulked in housing 13 and
may also alternatively rest directly against sensor 26.
[0016] Spacer 27 and spacer element 28 are designed as an
intermediate sleeve 31, which is preferably made of ceramic or
steel.
[0017] Contacting elements in the form of electric lines, used for
supplying glow element 17 with power and for conducting the signals
output by sensor 26, lead away from second end 24 of glow plug
11.
[0018] The above-described geometric arrangement of the important
individual elements of the device for detecting the pressure in a
combustion chamber of an engine is based on the following functions
and effects.
[0019] During operation of the engine, combustion gases are
generated in combustion chamber 19 and exert a pressure force on
glow element 17 due to their limited expansion in combustion
chamber 19. The axial components of the pressure force, directed in
the longitudinal direction of glow plug 11 tend to displace glow
element 17 toward second end 24 of glow plug 11. However, glow
element 17 is largely prevented from being displaced by fastening
element 22, which absorbs most of these pressure forces and
transmits them to housing 13 and to cylinder head 14.
[0020] The pressure force on glow element 17 results, however, in
elastic deformation of glow element 17, which is then absorbed by
sensor 26, which is implemented, for example, as a pressure or
distance sensor designed as a piezoelectric ring. The signal output
by sensor 26 may be correlated with the pressure in combustion
chamber 19 via characteristic curves. Ideally, the signal output by
sensor 26 is a quantity proportional to the pressure in combustion
chamber 19.
[0021] To detect the pressure in combustion chamber 19, sensor 26
may also be operated in a pre-stressed manner to reduce hysteresis
effects, for example. For this purpose, after glow element 17 is
fastened to housing 13 via fastening element 22, a predefined force
is applied to sensor 26, to press it against glow element 17 even
when the engine is stopped, alternatively even indirectly via
intermediate spacer 27. This pre-stress is maintained by fastener
29 fixedly mounted in housing 13 or a spacer element 28 fastened to
housing 13.
[0022] The maximum force on sensor 26 may then be adjusted via the
stiffness of housing 13, fastening element 22, or fastener 29.
[0023] The separation between fastening element 22 for glow element
17 and fastener 29 for sensor 26 allows the optimum area of sensor
26 with respect to signal generation to be used for reliable and
reproducible detection of the pressure in the combustion chamber of
the engine.
* * * * *