DESCRIPTION

SENSOR DEVICE

FIELD OF THE INVENTION

The invention relates to a sensor device to measure the speed and to determine acceleration of a linear moving element or of a rotating element as claimed in claim 1 and to a method according to claim 13.

BACKGROUND OF THE INVENTION

Rotating elements or linear moving elements are known in the prior art such as a crank shaft of a combustion engine of a vehicle. Therefore sensor device exist which measure the rotation of the element or the speed of a linear moving element. An example for the use of a sensor for measuring the speed of the rotating element is the measurement of speed of a crankshaft of a combustion engine for the control of ignition and fuel injection of Diesel engines. Another example for the use of such sensors is the switch- off of air and fuel supply to combustion engines in special vehicle or engine work situations. Another example for such an use is the measurement of the rotation of the wheels of a vehicle.

For the control of such rotating or linear moving elements it is moreover necessary not only to measure the speed but additionally the acceleration of the moving element.

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.

In order to better control rotating elements or linear moving elements it is desirable to measure not only the speed but additionally the acceleration of such a linear or rotating movement. This leads to a more precise control and mitigates conditions of less performance or wear.

SUMMARY OF THE INVENTION

Therefore it is an object of the invention to create an inventive sensor device which measures the speed of a moving element and determines the acceleration of the element too.

The above mentioned problems will be solved by using a sensor device for measuring the linear or rotational speed and for determining the linear or rotational acceleration of a linear moving or rotating element, especially of a crank shaft of a combustion engine, comprising an encoder and a sensor element for detecting the movement or 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 linear or rotational acceleration and generates a linear or rotational acceleration signal from the linear or rotational speed signal and comprising an interface driver and an interface allowing to output the signal of the linear or rotational speed and linear or rotational acceleration. Such a sensor device creates a speed signal and determines an acceleration signal based on the speed signal data which then are transferred to a control unit e.g. of the vehicle. This leads to a creation of the speed and acceleration signals within the sensor device and allows to make signal evaluation within the control unit more easy and additionally this makes data transmission between the sensor device and the control unit more easy. According to the invention it is advantageous that the encoder comprises an encoder disk comprising a modulated circumferential area. It is of advantage that the circumferential area comprises teeth and/or a magnetic modulation. Furthermore it is appreciated that the speed signal and the acceleration signal are generated as separate signals. According to another embodiment of the invention it is of advantage that the speed signal and the acceleration signal are generated as one single combined signal. Accordingly the acceleration signal may be added to the speed signal or the acceleration signal and the speed signal can be processed to generate an acceleration modulated speed signal or to generate a speed modulated acceleration signal.

Accordingly it is another object of the invention to create a method of generating an acceleration signal and a speed signal using an above mentioned sensor 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; and

Fig. 2 shows a diagram.

DETAILED DESCRIPTION OF THE DRAWINGS

Figure 1 shows a schematic view of the inventive sensor device 1. The sensor device consists of an encoder 2 which is 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 well known, the combustion engine is not further described in detail here. The sensor device 1 furthermore comprises a sensor element 3 which measures or detects the rotation and/or the position 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 and the signal evaluator evaluates the digital signal from the output of the converter and calculates the acceleration signal on the basis of the digital speed signal. The driver 6 and the interface are responsible to allow other electronic devices to receive the signal information. The encoder 2 is or comprises preferably an encoder disk with or without a reference mark. The encoder may have teeth such that the time of the teeth or the time between the teeth can be measured to obtain a signal representing the rotational speed of the encoder. Since the measured signal will be an analogue signal the analogue-to-digital converter (ADC) converts the analogue signal to a digital signal. Preferably the digital signal will be a binary frequency signal. Through comparison between the binary frequency signal with a time signal e.g. from an oscillator a

change of the frequency signal may be derivable and as such identified as an acceleration signal of the rotating element.

In order to enhance the quality of the acceleration signal the evaluation of the acceleration signal may be performed based on a plurality of periods of the speed signal. Accordingly it may be advantageous to use a full turning cycle of the encoder to evaluate 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 an easy use of the speed signals and of the acceleration signals 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 acceleration signal only and to add this information to the speed signal. Another inventive solution uses the speed and the acceleration signal to create a modulated or encoded signal comprising both types of signal information. This combined signal might be a digital signal. 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 with a modulated magnetic 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 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 an almost the shape of a sine-function which is however modulated with regard to the frequency. The arrows 12 shown at the middle part of the diagram 10 are displaying the time at which the sine-function is zero. Therefore the distance between the arrows 12 is a measure for the frequency or time period of the function 11. At the lower part of the diagram it is shown the general behaviour of the function. In the time window 13 an increasing speed is detected, while in the time window 14 the speed is almost constant, whereas the speed is decreasing in the time window 15.

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 on an integrated circuit.

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 time window

14 time window 15 time window