U.S. patent application number 09/785683 was filed with the patent office on 2001-09-20 for device for limiting the speed of an exhaust-gas turbocharger.
Invention is credited to Koelle, Ulrich, Lussman, Armin.
Application Number | 20010022084 09/785683 |
Document ID | / |
Family ID | 7631166 |
Filed Date | 2001-09-20 |
United States Patent
Application |
20010022084 |
Kind Code |
A1 |
Koelle, Ulrich ; et
al. |
September 20, 2001 |
Device for limiting the speed of an exhaust-gas turbocharger
Abstract
A device for limiting the supercharger speed which makes do
without a speed sensor or an atmospheric pressure sensor has a
bandpass filter which filters out a spectral component from the
output signal of a boost pressure sensor arranged in the induction
pipe of the engine, the spectral component appearing in the signal
spectrum of the boost pressure sensor when the air column in the
induction pipe is set into a vibration which develops when the
compressor of the turbocharger rotates at the maximum permissible
speed.
Inventors: |
Koelle, Ulrich;
(Schwieberdingen, DE) ; Lussman, Armin;
(Stuttgart, DE) |
Correspondence
Address: |
Richard L. Mayer, Esq.
Kenyon & Kenyon
One Broadway
New York
NY
10004
US
|
Family ID: |
7631166 |
Appl. No.: |
09/785683 |
Filed: |
February 16, 2001 |
Current U.S.
Class: |
60/602 ; 123/564;
60/600; 60/601; 60/603 |
Current CPC
Class: |
Y02T 10/12 20130101;
F02B 2039/168 20130101; F02B 37/18 20130101; Y02T 10/144
20130101 |
Class at
Publication: |
60/602 ; 60/600;
60/601; 60/603; 123/564 |
International
Class: |
F02B 033/00; F02D
023/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 16, 2000 |
DE |
1 00 07 013.2 |
Claims
What is claimed is:
1. A device for limiting a speed of an exhaust-gas turbocharger of
an internal combustion engine, the turbocharger including a
compressor, the device comprising: a boost pressure sensor
measuring a boost pressure on a pressure side of the compressor
situated in an induction pipe of the engine, a spectral component
appearing in an output signal of the boost pressure sensor when an
air column in the induction pipe is set into a vibration which
develops when the compressor rotates at a maximum permissible
speed; and a pressure reducing arrangement for reducing a
preselected setpoint boost pressure when a rotational speed reaches
a maximum permissible value, the pressure reducing arrangement
including a bandpass filter for filtering out the spectral
component from the output signal of the boost pressure sensor.
2. The device according to claim 1, wherein the pressure reducing
arrangement further includes a correcting element, the correcting
element comparing the spectral component delivered by the bandpass
filter to a threshold value and, if the threshold value is
exceeded, the correcting element generating a correction signal
which reduces the preselected setpoint boost pressure.
3. The device according to claim 1, wherein the boost pressure
sensor is a piezoelectric sensor.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a device for limiting the
speed of an exhaust-gas turbocharger of an internal combustion
engine, a pressure sensor measuring the boost pressure
(supercharging pressure) on the pressure side of a compressor of
the turbocharger arranged in the induction pipe of the engine, and
provision being made for means which reduce a preselected setpoint
boost pressure when the speed (rotational speed) reaches a maximum
permissible value.
BACKGROUND INFORMATION
[0002] When designing an exhaust-gas turbocharger and its control,
care must be taken that the supercharger speed does not exceed a
maximum permissible value. As can be gathered from "MTZ
Motortechnische Zeitschrift" [Motor Engineering Journal] 53 (1992),
10, pages 454-462, the boost pressure is controlled in a known
manner by comparing a setpoint boost pressure resulting from the
driver's command to an actual boost pressure measured by a boost
pressure sensor in the induction pipe. For monitoring the
supercharger speed, usually a speed sensor is used which detects
the speed of the compressor in the induction pipe. By comparing the
measured supercharger speed to a threshold value which corresponds
to maximum permissible speed value, it can determine whether the
turbocharger reaches a critical speed range and act upon the boost
pressure control correspondingly. From the mentioned MTZ it follows
that the boost pressure in the induction pipe is always adjusted to
programmed values which were determined in standard atmosphere.
With increasing altitude and, consequently, dropping pressure,
therefore with decreasing air density, the demanded setpoint boost
pressure is only attained by increasing the supercharger speed. To
this end, the wastegate of the turbocharger is closed to a greater
degree and, consequently, the turbine is charged with a larger
quantity of exhaust gas. Using an atmospheric pressure sensor, the
setpoint boost pressure preselected by the boost pressure control
can be lowered in the case of dropping ambient pressure, thereby
also allowing the supercharger speed to be limited below its
maximum permissible value.
[0003] An object of the present invention is to provide a device
for limiting the speed of an exhaust-gas turbocharger, the device
neither requiring a speed sensor for the supercharger speed nor an
atmospheric pressure sensor.
SUMMARY OF THE INVENTION
[0004] The mentioned objective is achieved by providing a bandpass
filter which filters out a spectral component from the output
signal of a boost pressure sensor existing in the induction pipe,
the spectral component appearing in the signal spectrum of the
boost pressure sensor when the air column in the induction pipe is
set into a vibration which develops when the compressor of the
turbocharger rotates at the maximum permissible speed. Here, a
criterion for limiting the supercharger speed below its maximum
permissible value is derived from the output signal of a boost
pressure sensor which exists anyway. In this context, a speed
sensor and an atmospheric pressure sensor can be dispensed
with.
[0005] Accordingly, a correcting element exists which compares the
spectral component delivered by the bandpass filter to a threshold
value and, in the case that the threshold value is exceeded,
generates a correction signal which reduces the preselected
setpoint boost pressure.
[0006] The boost pressure sensor is expediently a piezoelectric
sensor since a piezoelectric element responds to vibrations of the
air column in the induction pipe in a very sensitive manner.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The FIGURE shows a schematic representation of an internal
combustion engine having an exhaust-gas turbocharger and a control
unit limiting the supercharger speed.
DETAILED DESCRIPTION
[0008] The FIGURE shows an internal combustion engine 1 having an
induction pipe 2 and an exhaust duct 3. In exhaust duct 3, a
turbine 4 of a turbocharger is located which is mechanically
coupled to a compressor 5 arranged in induction pipe 2. To be able
to control the boost pressure in the induction pipe, turbine 4 in
exhaust duct 3 is bridged by a bypass 6 accommodating a
controllable valve 7. Valve 7 is driven by an actuator 8. On the
pressure side of compressor 5 in induction pipe 2, a boost pressure
sensor 9 is located whose output signal Id is fed to a control unit
SE. Boost pressure signal Id is applied to the input of a low pass
filter TPF at whose output a mean actual boost pressure Idi freed
from all disturbances appears. A boost pressure controller LDR
(e.g., a PD or PI or PID controller) derives a controlled variable
wg for actuator 8 of wastegate 7 from the offset did between actual
boost pressure Idi and a setpoint boost pressure Ids which depends
on the driver's command and, possibly, on other performance
quantities of the engine.
[0009] As already explained by way of introduction, care must be
taken that the turbocharger does not exceed a maximum permissible
speed to prevent it from destruction. When operating the vehicle at
higher altitudes, the maximum permissible supercharger speed can
easily be exceeded since, with increasing altitude and,
consequently, dropping ambient pressure, the demanded setpoint
boost pressure is only attained by increasing the supercharger
speed. In the case of an atmospheric pressure heavily dropping with
respect to the standard atmosphere therefore, special care must be
taken that the supercharger speed does not exceed the maximum
permissible value to prevent the turbocharger from destruction. To
this end, a bandpass filter BPF is provided in control unit SE,
output signal Id of boost pressure sensor 9 being fed to the
bandpass filter in parallel to low-pass filter TPF.
[0010] Boost pressure sensor 9 also detects vibrations in the air
column in the induction pipe resulting from the rotational movement
of compressor 5. The frequency of these vibrations depends on the
speed of compressor 5; in particular, if boost pressure sensor 9 is
a piezoelectric sensor it responds in a very sensitive manner to
the vibrations of the air column in the induction pipe which are
generated by the compressor. These vibrations manifest themselves
in the form of high-frequency signal components which are
superimposed upon sensor signal Id. With regard to its frequency
passband, bandpass filter BPF is to be designed such that only
those spectral components snv appear at its output which are due to
vibrations of the air column in induction pipe 2 which develop when
compressor 5 rotates at the maximum permissible speed.
[0011] Output signal snv of bandpass filter BPF is fed to a
correcting element KG. This correcting element KG compares signal
snv to a threshold value which is calculated such that when it is
exceeded by spectral component snv filtered out from boost pressure
signal Id, it can be reliably assumed that filtered out spectral
component snv has been generated by a speed of compressor 5
reaching the maximum permissible value. So if correcting element KG
detects the maximum permissible supercharger speed in this manner,
it emits a correction signal ldk. In logic element V1, this
correction signal ldk is subtracted from setpoint boost pressure
Ids.
[0012] In logic element V2, offset did between corrected, reduced
setpoint boost pressure ldsk and actual boost pressure Idi is
generated, the offset finally being fed to boost pressure
controller LDR. The boost pressure controller then controls
wastegate 7 in such a manner that a smaller quantity of exhaust gas
is led via turbine 4 of the exhaust-gas turbocharger, thus reducing
the speed of the exhaust-gas turbocharger below the maximum
permissible value.
[0013] Using the described device, it is achieved, without using a
supercharger speed sensor or an atmospheric pressure sensor, that
the exhaust-gas turbocharger can indeed be run up to its maximum
permissible speed without exceeding it even when traveling at high
geographical altitudes.
* * * * *