METHOD AND SYSTEM FOR TRANSMITTING A SENSOR SIGNAL

Abstract

A method and a system for transmitting a sensor signal, transmits the sensor signal in such a way that the analog electrical sensor signal is converted with the aid of a system for signal conversion into a converted signal and that this converted signal is transmitted to a control unit. As a result, the sensor signal is able to be transmitted to the control unit in a reliable manner and be evaluated thereby.

Claims

1-11. (canceled)

12. A method for transmitting a sensor signal, the method comprising: generating, via a sensor element for ascertaining the combustion-chamber pressure, an analog electrical sensor signal in at least one cylinder of an internal combustion engine, the sensor signal corresponding to the pressure and being transmitted to a control unit for controlling the internal combustion engine; converting the analog electrical sensor signal into a converted signal with a system for signal conversion; and transmitting the converted signal to the control unit.

13. The method of claim 12, wherein the converted signal is generated based on the sensor signal, to which a signal is added that represents at least one item of information computable from the sensor signal.

14. The method of claim 13, wherein the added signal is an amplitude-modulated or a frequency-modulated signal.

15. The method of claim 12, wherein the converted signal is generated based on the sensor signal, which is temporally shifted in such a way that in at least one time range, allocated to a low-pressure loop, the signal is replaced with a signal that is allocated to a time range of a preceding high-pressure loop.

16. The method of claim 15, wherein the signal that is allocated to the time range of the preceding high-pressure loop is encoded, in particular amplified, and/or has an offset-shift.

17. The method of claim 15, wherein the temporally shifted signal is generated so that the sensor signal is detected by the system for signal conversion in a time range of a high-pressure loop and the transmission of the converted signal to the control unit takes place in a time range of a low-pressure loop.

18. The method of claim 17, wherein a detection of the top-dead center position of a cylinder of the internal combustion engine takes place to detect the time ranges for the high-pressure loop and the low-pressure loop.

19. The method of claim 12, wherein preprocessing of the sensor signal from the sensor element takes place in the system for signal conversion and the preprocessed signal is transmitted as converted signal.

20. A system for transmitting a sensor signal, comprising: a sensor element in at least one cylinder of an internal combustion engine, which is connected by a transmission line to a control unit; and a system for signal conversion situated between the sensor element and the control unit, which has an input-side analog-to-digital converter and an output-side digital-to-analog converter, the input-side analog-to-digital converter being connected to the sensor element and the output-side digital-to-analog converter being connected to the control unit.

21. The system of claim 20, wherein the system for signal conversion includes an ASIC.

22. A computer readable medium having a computer program, which is executable by a processor, comprising: a program code arrangement having program code for transmitting a sensor signal, by performing the following: generating, via a sensor element for ascertaining the combustion-chamber pressure, an analog electrical sensor signal in at least one cylinder of an internal combustion engine, the sensor signal corresponding to the pressure and being transmitted to a control unit for controlling the internal combustion engine; converting the analog electrical sensor signal into a converted signal with a system for signal conversion; and transmitting the converted signal to the control unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG. 1 shows a system for transmitting a sensor signal according to the present invention including a system for signal conversion.

[0040] FIG. 2 shows a flow diagram for elucidating the method of the present invention.

DETAILED DESCRIPTION

[0041] FIG. 1 shows a system for signal conversion according to the present invention, in which a sensor element 2 such as a combustion-chamber pressure sensor is depicted in a sensor assembly 1. This sensor element senses the pressure in a cylinder of the internal combustion engine.

[0042] Sensor element 2 is advantageously connected directly to the system for signal conversion 3 so that no long connection lines that can be affected by parasitic signals are situated between the two assemblies. The system for signal conversion 3 has an input-side analog to digital converter 4, which converts the analog voltage signal of sensor element 2 into a digital value that is able to be processed by the system for signal conversion 3.

[0043] The system for signal conversion 3 carries out the steps for signal conversion according to the present invention and generates a converted sensor signal.

[0044] The system for signal conversion 3 has an output-side digital to analog converter 5, which converts the signal converted by the system for signal conversion 3 back into an analog signal prior to its transmission to control unit 7.

[0045] This signal is transmitted by way of transmission line 6 to control unit 7. During this transmission the signal to be transmitted may be subject to the usual interference. Since the transmitted signal is a converted signal in which the information is not transmitted in a very small voltage swing of a few mV but in a frequency of the signal or an amplitude of a signal with a carrier frequency, for instance, the interference has virtually no effect on the transmission of the converted signal.

[0046] Control unit 7 is equipped with a signal-processing unit 8 by which the transmitted signal is processed and a value is output such as for the combustion-chamber pressure in a cylinder of the internal combustion engine. Since a digital operation of signal processing unit 8 is provided, the transmitted analog signal is subjected to an analog to digital conversion by signal processing unit 8 prior to the processing.

[0047] Such a system may also be used for the transmission of signals from any other sensors 2.

[0048] The present invention allows for the advantageous use of low-frequency signal ranges of a sensor 2 and for superposing information in the unused higher-frequency ranges, for example. This idea may be applied in an especially advantageous manner to the combustion-chamber pressure signal which, on account of the physical principles that underlie the combustion, regularly includes segments featuring high and low frequencies in the temporal signal curve.

[0049] For example, items of combustion-chamber pressure information, detected with the aid of a combustion-chamber pressure sensor 2, which are small in comparison with a base pressure or peak pressure and thus are difficult or impossible to detect in control unit 7, can thereby be shifted from the high-pressure loop to the low-pressure loop in ASIC 3 of sensor assembly 1. They can then be detected in control unit 7 at a very satisfactory quality.

[0050] Because of the analog transmission of the combustion-chamber pressure information from sensor 2 to control unit 7, small signal components are subject to heavy interference over transmission line 6 and are therefore unable or difficult to be evaluated (schematically shown in FIG. 1 by arrow S). By using the present invention, combustion-chamber pressure information pertaining to the combustion process caused by pre-injections in the case of a diesel engine or by the high-frequency small pressure vibrations caused by knocking in the case of a gasoline engine, is able to be evaluated in control unit 7 at a very satisfactory quality.

[0051] The impressing of the information as converted signal in the low-pressure loop may be carried out in different manners, e.g., as a signal curve or a calculated feature.

[0052] In this way the real information density of the analog transmission can be considerably improved because a “multi-channel” transmission is basically possible on one line from the aspect of information technology.

[0053] The shift to the low-pressure loop may be accomplished in such a way that the real low-pressure loop is able or unable to be reconstructed in control unit 7.

[0054] FIG. 2 schematically shows steps of the method according to the present invention for an exemplary embodiment. In a first step 210, the sensor signal output by sensor element 2 is made available. It is processed in a step 220, in which a signal is generated that represents at least one item of information able to be calculated from the combustion-chamber pressure or which includes another item of information that is able to impressed onto a signal. This signal is signal 210 output by the sensor. It is possible to add the signal processed in step 220 to this signal in step 230 and to generate a converted signal in this manner.

[0055] As an alternative, in step 230 the supplied signal from step 210 is able to be replaced with the signal processed in step 220 for a specified time segment, such as a time range allocated to the low-pressure loop.

[0056] In step 240, the converted signal generated in step 230 is then output, and it is this signal that is transmitted to control unit 7 after passing through digital to analog converter 5.

[0057] In an advantageous manner, the present invention assumes that, for instance, an approximate determination of the instant of the top-dead center (TDC) of the indicated cylinder is possible through an evaluation of the pressure information of sensor element 2 in ASIC 3, thereby enabling a differentiation between low-pressure loop and high-pressure loop.

[0058] This may be done with the aid of different methods, for instance by evaluating the compression, the peak pressure, and the charge exchange, which is able to be detected on the basis of the opening of the discharge or intake valves.

[0059] As an alternative, an item of angle information may also be transmitted from the control unit via a separate line, from which a TDC reference and an item of information regarding the low-pressure and high-pressure loop is then able to be obtained.

[0060] This ascertaining of the top-dead center position forms the basis for the shift of the converted signal into the low-pressure loop. Such a shift is able to take place in different ways: [0061] 1. By calculating features in the high-pressure loop and subsequent coding/modulation onto the low-pressure loop or by subsequent coding/modulation independently of the high-pressure or the low-pressure loop. [0062] 2. By extracting a time curve in the high-pressure loop, which is amplified and/or offset-compensated and is transmitted in place of the signal allocated to the time range of the low-pressure loop.

[0063] The coding/modulation may be carried out according to a generally known ASIC 3 of sensor assembly 1, which is connected to sensor element 2 (combustion-chamber pressure sensor).

[0064] For point 1, a coding is advantageous in which a so-called feature occurs into the amplitude strength of a signal with a constant frequency. In this case, the carrier frequency is selected in such a way that it is at least greater than the highest frequency that may occur in the low-pressure loop, and optionally, also greater than the highest frequency that occurs in the high-pressure loop.

[0065] In an advantageous manner, such carrier frequencies lie at 6 kHz, 8 kHz or 10 kHz. The amplitude of this converted signal is then calculated via a linear correlation from the feature selected for the transmission, for instance. In control unit 7, the information may be realized by estimating the amplitude of the converted signal having a known frequency according to the related art.

[0066] The term feature, for example, is to be understood as a sensor signal of sensor element 2 that has been preprocessed by the system for signal conversion 3.

[0067] In a gasoline engine, for instance, such a feature is the energy of the cylinder-pressure signal in a frequency band of 5-20 kHz, in a relevant range of the high-pressure loop, which is then transmitted in the low-pressure loop as converted signal.

[0068] As an alternative, it is also possible to transmit energies of different frequency bands.

[0069] The peak value in terms of its amount, which can be used as a reference for knocking, may also be transmitted in the above frequency band.

[0070] A further feature may be the maximum pressure or the maximum pressure gradient in the high-pressure loop.

[0071] As an alternative, the modulation in point 1 may also be accomplished in such a way that the item of information is coded into the frequency, while the amplitude retains a constant value.

[0072] In a special embodiment, it is provided that a first feature defines the frequency of the signal and a second feature defines the amplitude of the frequency defined by the first feature.

[0073] In an advantageous manner, the duration of the impressing of the converted signal onto the low-pressure loop, for example, may be a function of a rotational frequency of the internal combustion engine calculated in the ASIC, or in other words, it may be dependent on the rotational frequency.

[0074] In another specific embodiment, it is provided to calculate, i.e. preprocess, also features from the low-pressure loop, and to modulate them as converted signals onto the signal of the remaining low-pressure loop or upcoming high-pressure loop.