WO2009087503A1

WO2009087503A1 - Sensor device

Info

Publication number: WO2009087503A1
Application number: PCT/IB2008/054540
Authority: WO
Inventors: Bernd Baranski; Torsten Philipp
Original assignee: Nxp B.V.
Priority date: 2008-01-04
Filing date: 2008-10-31
Publication date: 2009-07-16

Abstract

The invention relates to a sensor device (1) for measuring the rotational speed and for determining the rotational speed deviation or the rotational acceleration of a rotating element, especially of a crank shaft of a combustion engine, comprising an encoder (2) and a sensor element (3) for detecting the rotation of the encoder (2) and furthermore comprising a converter (4) to convert the signal of the sensor element to a digital signal, wherein a signal evaluator (5) determines the rotational speed deviation or the rotational acceleration and generates tooth time signal representing the rotational speed signal and the rotational speed deviation or the rotational acceleration.

Description

DESCRIPTION

Sensor Device

FIELD OF THE INVENTION

The invention relates to a sensor device to measure the rotational speed and to determine deviations of the rotational speed or the rotational acceleration of a rotating element as claimed in claim 1 and relates to a respective method according to claim 17.

BACKGROUND OF THE INVENTION

Sensor devices are known which generate binary signals relating to the detected physical quantity. Usually they create a signal which deviates from the detected physical quantity in time e.g. of a moving incremental encoder.

In order to use such data for an analysis with high resolution e.g. to detect a frequency of speed signal with short term variations of frequency or speed it is necessary to use a highly resolved sampling within the device. This makes it necessary to use a very high computation performance.

Additionally the means to transmit data between the place of signal detection and signal processing are in the scope of limitations e.g. of bandwidth and therefore the ability to interpolate such data or signals is limited. Therefore the analysis of the signals or data is complicated Alternating sensor devices have an increasing number of increments but this does not change the need of higher bandwidth.

An internal combustion engine usually comprises a crank shaft as a rotating element of the combustion engine. In case the combustion engine comprises more than one cylinder, e.g. four cylinders short term deviations of the rotation may occur. Therefore the rotation of the engine is not very constant and time dependent variations of the rotational speed of the crank shaft are appearing. Therefore a control of the combustion engine is necessary and the quality of the control may lead to a better behaviour of the engine and reduces fuel consumption and production of exhaust gas. EP 0 128 582 Bl discloses an anti-locking regulation system for vehicles having wheel speed sensors, wherein a wheel speed sensor is used to measure the wheel speed to control the brake of the vehicle. EP 1 010 984 A2 discloses an acceleration detection method and apparatus using a gear wheel.

SUMMARY OF THE INVENTION

It is an object of the invention to create a sensor device that reduces or mitigates the drawbacks of the prior art and allows the detection of signals and analysis of the signals within the sensor device in order to overcome the above mentioned drawbacks. According to the invention this will be achieved by a sensor device for measuring the rotational speed and for determining the rotational speed deviation or the rotational acceleration of a rotating element, especially of a crank shaft of a combustion engine, comprising an encoder and a sensor element for detecting the rotation of the encoder and furthermore comprising a converter to convert the signal of the sensor element to a digital signal, wherein a signal evaluator determines the rotational speed deviation or the rotational acceleration and generates a tooth time signal representing the rotational speed signal and the rotational speed deviation or the rotational acceleration. According to the invention it is of advantage that the speed signal is tagged with a signal information of the respective tooth time. The tooth time represents the time of a modulated area of the encoder passing the sensor element. According to the invention the tooth time may be a signal of a flank of a modulation, such as a tooth or a magnetic or magnetoresistive modulation of the encoder. It is of advantage that the tooth time signal is a digital or an analogue signal.

Furthermore it is of advantage that the encoder is or comprises an encoder disk comprising a modulated circumferential area. The modulation may be a mechanical modulation using teeth or a magnetic or magnetoresistive modulation. Accordingly it is of advantage that the circumferential area comprises teeth and/or a magnetic and/or a magnetoresistive modulation. Furthermore it is of advantage that the speed signal and the deviation signal or the acceleration signal are generated as separate signals.

According to the invention it is of advantage that the speed signal and the deviation signal or the acceleration signal are generated as a combined signal. Accordingly the speed signal may be tagged with signal information of the deviation signal or the acceleration signal.

Accordingly the deviation signal or the acceleration signal can be added to the speed signal. According to another inventive embodiment the deviation signal or the acceleration signal and the speed signal are processed to generate a deviation signal or acceleration signal modulated speed signal or to generate a speed modulated the deviation signal or acceleration signal.

Furthermore according to another inventive object a method is created to generate a deviation signal or an acceleration signal and a speed signal using the above mentioned device.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the invention will be apparent from the following description of an exemplary embodiment of the invention with reference to the accompanying drawings, in which:

Fig. 1 shows a schematic view of the inventive sensor device; Fig. 2 shows a diagram;

Fig. 3 shows a diagram;

Fig. 4 shows a diagram; and

Fig. 5 shows a diagram.

DETAILED DESCRIPTION OF THE DRAWINGS

Figure 1 shows a schematic view of the inventive sensor device 1. The sensor device 1 consists of an encoder 2 which is mounted or can be mounted on a rotating or rotatable element e.g. of a combustion engine of e.g. a motor vehicle. Since combustions engines especially of motor vehicles are commonly known, the combustion engine is not further described in detail. Instead of a combustion engine another rotatable element may use - A -

the inventive sensor device too. The sensor device 1 furthermore comprises a sensor element 3 which measures the rotation of the encoder 2. The sensor element 3 comprises a converter 4, a signal evaluator 5, an interface driver 6 and an interface 7. The converter 4 converts the analogue signal to a digital signal (ADC) and the signal evaluator 5 evaluates the digital signal from the output of the converter 4 and determines the speed signal and the deviation of the speed signal as a function of time or the acceleration signal on the basis of the incoming signal especially like a digital speed signal. The driver 6 and the interface 7 are responsible to allow other electronic devices to receive the signal information from the sensor device e.g. to control an engine. The encoder 2 is preferably an encoder disk with or without a reference mark.

The encoder 2 may have teeth along the circumference of the encoder and respective gaps between adjacent teeth such that the measured time of the teeth, when the teeth are turning in front of the sensor element 3, or the measured time of a gap between the teeth can be used to obtain a signal representing the rotational speed of the encoder 2. Since the measured signal will be an analogue signal the analogue-to-digital converter (ADC) converts the analogue signal to a digital signal. The sensor element 3 observes the incremental teeth modulations or magnetic and/or magnetoresistive modulations of the encoder and creates a binary signal especially a binary switching signal from each of the increments of the encoder 2. Preferably the digital signal will be a binary speed signal. Through comparison between the binary speed signal or between a difference of a tooth time of one tooth and the tooth time of an other preferably adjacent tooth with a time signal e.g. from an oscillator a change or deviation of the speed signal is derivable and as such can be identified as an acceleration signal of a rotating element. Preferably a change of sign of the deviation of the speed signal can be selected as a separate signal. Therefore the speed signal and the sign (plus or minus) of a change of the speed signal can be used to control the speed of the rotating element. Additionally the tooth time of a tooth may be combined with a signal of the sign of deviation of the tooth time. This sign of the deviation may be positive if the tooth time increases or negative if the tooth time decreases. Furthermore the tooth time may be issued and/or used separately and independent of the tooth time itself. According to another inventive idea the tooth time may be encoded or modulated as an analogue signal as a voltage or current signal.

In order to enhance the quality of the acceleration signal the evaluation of the deviation signal or acceleration signal may be performed based on a plurality of periods of the tooth time signal. Accordingly it may be advantageous to use at least some teeth or a full turning cycle of the encoder to evaluate the deviation signal or the acceleration signal.

According to the invention it is possible to change or configure the number of periods of the speed signal to generate the acceleration signal.

For a better evaluation of the speed signal and/or the deviation signal or the acceleration signal the two signals may be combined to a single signal comprising the signal information of the speed signal and of the acceleration signal. Accordingly it is advantageous to use the sign of the deviation or acceleration signal only and to add this information to the speed signal. Accordingly the two signals may be coded or modulated together as binary signals. Another inventive solution uses the speed and the deviation or acceleration signal to create a modulated or encoded signal comprising both types of signal information. This combined signal might be a digital signal.

In order to reach better signal performance it is possible to calculate a mean tooth time calculated over a number of tooth times to receive a mean signal without the influence of the single tooth deviations due to e.g. tolerances. In case of a use of a reference mark on the encoder it is possible to include the signal information of the identified reference mark too. Therefore the signal might include an acceleration signal, a speed signal and possibly the signal of the identification of the reference mark.

According to the invention the encoder may be a gear wheel or a magnetic encoder disk or a magnetoresistive encoder disk with a modulated magnetic or magnetoresistive behaviour along the circumference of the disk. Accordingly the sensing device of the analogue-to-digital converter (ADC) is able to measure the time of the teeth or the space between the teeth or the space of the magnetic or magnetoresistive modulation when the encoder disk is turning. Figure 2 shows a diagram 10 to explain the function of the inventive sensor device. The signal curve 11 is displayed in the upper part of the diagram 10. The curve shows almost the shape of a sine-function which is however modulated with regard to the amplitude and frequency. The function represents the behaviour of the time incidents (tooth flanks). The arrows 12 shown at the middle part of the diagram 10 are displaying the time at which the function 11 is zero. Therefore the distance between the arrows 12 is a measure for the frequency or time period of the function 11. The lower part of the diagram shows encoding marks to be used as encoding signals of a line coding representing the time at which the signal 11 is zero. Figure 3 shows a diagram 20 to explain the function of the inventive sensor device. The signal curve 21 is displayed in the upper part of the diagram 20. The curve 21 shows almost the shape of a sine-function which is however modulated with regard to the amplitude and frequency. The function 21 represents the behaviour of the time incidents 22 (tooth flanks). The arrows 22 shown at the middle part of the diagram 20 are displaying the time at which the function 21 is zero that means tooth incidents happens. Therefore the distance between the arrows 22 is a measure for the frequency or time period of the function 21. Accordingly the encoding marks 23 may be used as encoding signals of a line coding representing the time at which the signal 21 is zero or incidents happens. At the lower part of Figure 3 data content is shown. Figure 3 shows a binary output signal which includes a mean signal which consists of an average of different tooth signals which is distributed over different tooth time slots.

In contrast to Figure 3 Figure 4 shows a diagram 30 of a function 31 with arrows 32 indicating where the function 30 reaches the value of zero, where a binary output signal includes a tooth time content 33 and every tooth incident is tagged by the respective tooth time. The width of the block 33 represents the respective tooth time such that the tooth time of a single tooth is used to indicate the respective tooth incident.

Figure 5 shows a diagram 40 of a function 41 with arrows 42 indicating where the function 40 reaches the value of zero, while the analogue output signal includes a tooth time content 43 and every tooth incident is tagged by the respective tooth time. The value of the shoulder 44 represents the respective tooth time such that the tooth time of a single tooth is used to indicate the respective tooth incident. Accordingly the line signal serves as a reference for decoding the analogue tooth time code.

The invention is not limited to the use of measuring crank shafts of an engine but may be used to measure the rotation of other rotating mechanical elements like axles, wheel or the like.

In order to create a small integrated solution it is appreciated to integrate the sensor element 3 and/or the converter 4 and/or the signal evaluator 5 and/or the interface driver 6 and/or the interface 7 on an integrated circuit board such that the sensor element can be build as an integrated device.

References

1 sensor device

2 encoder

3 sensor element

4 converter

5 signal evaluator

6 interface driver

7 interface

10 diagram

11 signal curve, signal function

12 arrow

13 encoding marks

20 diagram

21 signal curve, signal function

22 arrow

23 encoding marks

30 diagram

31 signal curve, signal function

32 arrow

33 time content, encoding marks

40 diagram

41 signal curve, signal function

42 arrow

43 time content, encoding marks

44 shoulder

Claims

1. Sensor device (1) for measuring the linear or rotational speed and for determining the linear or rotational speed deviation and the linear or rotational acceleration of a moving or rotating element, especially of a crank shaft of a combustion engine, comprising an encoder (2) and a sensor element (3) for detecting the linear movement or rotation of the encoder (2) and furthermore comprising a converter (4) to convert the signal of the sensor element to a digital binary signal, wherein a signal evaluator (5) determines the linear or rotational speed deviation or the linear or rotational acceleration and generates a tooth time signal representing the linear or rotational speed signal and the linear or rotational speed deviation or the linear or rotational acceleration.

2. Sensor device according to claim 1 , wherein the speed signal is tagged with a signal information of the respective tooth time.

3. Sensor device according to claims 1 or 2, wherein the tooth time signal is a digital or an analogue signal.

4. Sensor device according to one of the claims 1 to 3 wherein the encoder is an encoder disk comprising a modulated circumferential area.

5. Sensor device according to one of the claims 1 to 3, wherein the circumferential area of the encoder comprises teeth and/or a magnetic modulation.

6. Sensor device according to claim 4 or 5, wherein the difference time signal between two incidents of the modulated circumferential area as a frequency signal will be compared with a frequency signal of an internal or external reference signal, e.g. of an oscillator, wherein the difference time signal will be determined with high resolution.

7. Sensor device according to claim 6, wherein the algebraic sign of the difference time signal will be separately evaluated or determined.

8. Sensor device according to claim 6 or 7, wherein the difference time signal will be coded or modulated as analogue signal.

9. Sensor device according to at least one of the preceding claims, wherein the time signal of the modulated area and the deviation of the time signal will be jointly modulated or coded as digital binary signal.

10. Sensor device according to claim 8 or 9, wherein the signal is a current signal or a voltage signal.

11. Sensor device according to claim 9, wherein the digital signal will be outputted over a predetermined period of time or over a predetermined number of time signals.

12. Sensor device according to one of the preceding claims, wherein the detected reference will be coded or integrated in the coded signal.

13. Sensor device according to at least one of the preceding claims, wherein the speed signal and the deviation signal or the acceleration signal are generated as separate signals.

14. Sensor device according to at least one of the preceding claims, wherein the speed signal and the deviation signal or the acceleration signal are generated as a combined signal.

15. Sensor device according to claim 14, wherein the deviation signal or the acceleration signal is added to the speed signal.

16. Sensor device according to one of the preceding claims, wherein the deviation signal or the acceleration signal and the speed signal are processed to generate an acceleration modulated speed signal or to generate a speed modulated deviation signal or acceleration signal.

17. Method of generating an acceleration signal and a speed signal using a device according to at least one of the preceding claims 1 to 16.