CHRISTMANN RALF DR (DE)
JP2003113795A | 2003-04-18 | |||
JP2002544443A | 2002-12-24 | |||
JP2005248952A | 2005-09-15 | |||
JPS6421226U | 1989-02-02 |
Claims 1. Α method for preventing the rapture of a compressor wheel and/or turbine rftieel of an exhaust-gas turborharger of a motor vehicle, having the following method steps: establishing loading limit values (n (G) } for the compressor wheel and/or bhe turbine w^eel in oench tests; - determining loading vaπaoles (n) for the compressor wheel and/or turbine wheel during the operation of the exhaust-gas turbocharger m the motor vehicle; processing the determineo loading variεtoles (n) in order to establish a loading characteristic ^τalue (n{i)) which represents real exhaust-gas tuiDocharger operation; comparing the loading lirr_t value (n{&)) with the loading characteristic alue (nu) ) ; and - outputtmg a warning (W) if the comparison of the loading limit value (n (G) ) with the loading characteristic v^alue (n(i)) yields an exceedance of a predefmaole safety margin. 2. The metnod as clamed in claim 1, wherein t^e rotational speed of the exhaust-gas turbocharger, the time pericds of the occurrence of certain rotational speeds and the rotational speed gradients are determined as loading variables. 3. The method as claimed m claim 2, wherein the change m altitude covered by the vehicle and tne number of kilometers trave_led are determined as aαditional loading variables. 4. The method as claimed in claim 1 or 2 or 3, wherein the determineo loading variables are processed oy means of a mεtthematical algorithm. The method as claimed in claim 4, wherein the processing takes place online. |
Description
The invention relates to a method for preventing the rupture of a compressor wheel and/or turbine wheel of an exhaust-gas turbocharger which is used in motor vehicles, according to claim 1.
The ezpression "rupture" is to be understood to mean an explosive disintegration of a compressor wheel and/or turbine wheel on account of excessive loading. Under sufficiently high loading, such a rupture may even occur in turbine and compressor wheels which have been produced to a correct specification, that is to say which do not have any production defects.
One possible cause of a rupture of said type is an excessively high rotational speed of the turbocharger, which may for example occur if the turbocharger and/or the motor vehicle in which the turbocharger is installed have/has been manipulated.
Such loading is generally a one-off loading which leads to the rupture of the wheel .
Of more importance in practice, however, are loadings which are within the normally permitted limits but which may add up on account of a high number of cyclic repetitions, for example constant changes in rotational speed.
It is therefore an object of the present invention to create a method for preventing the rupture of a compressor wheel and/or of a turbine wheel of an exhaust -gas turbocharger which is used in motor vehicles . Said object is achieved by neans of the features of clam 1.
According to the invention, loading limit values for the compressor wheel and/or " " " he turbi n e wheel are firstly established, said loading unit values beirg determined during the course of oenc^ tests. One option for such a bench test is the frequent repetition of a start/sτop process for the respective whee_, wnich represents the most severe load_ng test since t^e wheel constantly fluctuates between standstill and maximum rotational speed.
It is however alternatively corceivable for a multiplicity of different loading cycles to be run through in the bench test, with the aim oeing to reproduce a multiplicity of real driving conditions.
The result m every situation is t^e establishment of a loading limit value whic 1 " represents t^e time at w^ich, statistically, a rupture of the compressor and/or turome wheel would occur.
The method according to the invention also comprises the method step of determining ±oadmg variables for the compressor wheel and/or turbi n e w^eel dur_ng the operation of the exhaust-gas turbocharger m the motor vehicle. For this purpose, consideration s^o ^ ld be given in particular to the engine rotational speed and/or the rotational speed of t κ e exhaust-gas turbccharger and/or the time periods of the occurrence of certdi" rotational speeds and/or the exhaust-gas tuiDocharger rotational speed gradients and/or the change in altitude and/or kilometers covered by the motor vehicle.
Said determi n ed loading variables, a^d if appropriate also further suitεtole variables, are used to establish a loading characteristic value which represents real exhaust-gas turbocharger operation.
Said loading characteristic value is compared with the loading limit value in order to establish whether, statistically, there is a threat of a rupture of a compressor wheel and/or turbine wheel.
If said comparison yields that a safety margin which can be defined on the basis of the previously established loading limit value is exceeded, a warning is output such that it is possible for the operator of a motor vehicle which uses a turbocharger to reduce the loεtding before the occurrence of a rupture and to have suitable repairs carried out.
The subclaims relate to advantageous refinements of the invention .
The invention will be explained in more detail below on the basis of a schematically highly simplified block circuit diagram.
The block circuit diagram depicts one possibility for carrying out a method according to the invention, with the example being a so-called LCF method, with the abbreviation "LCF" standing for the expression "Low Cycle Fatigue", which means fatigue on account of low loading.
In the illustrated example, a rotational speed n of the exhaust-gas turbocharger and/or of the internal combustion engine is determined and filtered in a filter F. The filtered rotational speed values are buffered in a buffer P, for example for 60 seconds, and are subsequently processed in a calculation block C in order to be able to determine a loading chεtracteristic value n(i) . - A -
Said loading characteristic value n(i) is compared with a loading limit value n{G) in a comparator V in order to be able to output a warning W if appropriate in the event of an exceedance of a safety margin value.
List of reference symbols
F Filter
P Buffer C Calculation unit
V Comparator
W Warning n Rotational speed riFiii-er Filtered rotational speed n(i) Loading characteristic value n(G) Loading limit value