DE102006023307A1 - Accelerometer device for passenger protection system of motor vehicle, has two acceleration sensors with respective output channels connected with multiplexer, where output of multiplexer is connected with digital-to-analog converter - Google Patents

Abstract

The device (1) has two acceleration sensors (1.1.1, 1.1.2) with respective output channels, and a digital-to-analog (D/A) converter (1.2), where the output channels are connected with a multiplexer (1.6.1). The multiplexer has an output, which is connected with the converter. The converter has an output and is connected with an input of a demultiplexer (1.6.2) by the output of the multiplexer. The multiplexer is connected with the demultiplexer by a synchronization line. Another output of the multiplexer is connected with an offset generator.

Description

The The invention relates to a sensor device having at least two sensors according to claim 1, in particular for an application in a vehicle such as for use as an assistance sensor in a vehicle occupant protection system.

Frequently, so-called assistance sensors, for example side or up-front sensors, are used in safety systems, in particular in occupant protection systems, in order to detect a specific crash situation as early as possible and precisely. Increasingly, so-called multi-dimensional acceleration sensors (hereinafter also referred to as acceleration pickup devices) are used as assistance sensors, which enable direction-dependent acceleration detection and thus more accurate crash-type determination. An example of a sensor arrangement for a motor vehicle with multi-dimensional acceleration pickup devices with differently oriented sensitivity axes in order to enable a direction-dependent impact detection is shown in FIG EP 0 866 971 B1 specified. In each of the two longitudinal halves of a motor vehicle is a Beschleunigungsaufnehmervorrichtung with two sensors whose sensitivity axes are aligned differently from each other to be able to reliably detect collisions of the motor vehicle from different directions.

A conventional Sensor device contains usually next to a sensor element that has a physical size such as detects the acceleration and has a digital sensor output, a signal processing electronics, the sensor output signal digitized for a subsequent analog signal processing, such as filtering and reinforcement for the transmission for further processing in a central control unit of a Occupant protection system. The circuit complexity for the processing that of several sensor elements used in a sensor device generated signals is much higher than a simple, i.e. one-dimensional sensor device, because for each channel, i. each sensor element output signal own signal processing electronics is needed. As the signal processing electronics usually integrated on a semiconductor device, this leads altogether also increased space requirements the sensor device.

task The present invention is therefore a sensor device specify with at least two sensors, which less circuitry complex circuit elements with a much smaller space requirement as an input conventional sensor device required.

These Task is by a sensor device with the features after Claim 1 solved. preferred Embodiments of the invention will become apparent from the dependent claims.

One The essential idea of the invention is the internal signal processing a sensor device, for example an acceleration pickup device, with at least two sensors, for example acceleration sensors, surface optimized to realize or manufacture by individual circuit components the internal signal processing at least partially shared by all sensors can be used. As a result, not all circuit components in the number of Sensors needed. This allows a Implementation of a sensor device, the one possible small area needed and therefore cheaper can be implemented.

Of the Expression "at least two sensors "is in the context of the present invention to be understood that he also may comprise two or more sensors, which in a common casing are integrated. In this case, each of the sensors corresponds to one Output channel of the sensor device.

According to one embodiment According to the invention, the sensor device comprises at least two sensors with respective output channels and a D / A (digital / analog) converter. The output channels of at least two sensors are connected to a multiplexer device, wherein the multiplexer device has an output connected to the D / A converter connected is. The use of a multiplexer makes it possible the number of needed D / A converter to reduce to one. As is the case with a D / A converter an elaborate one Component with relatively large Expansion in particular in an integration on a semiconductor device the sensor device can be compared to those of the prior art the technology with a smaller footprint getting produced. This is especially for use in a motor vehicle advantageous because the components installed there usually mass components are that correspondingly inexpensive have to be. Every space savings therefore directly affects the cost of such a sensor device out.

According to one embodiment, the D / A converter has an output via which it is connected to an input of a demultiplexer device. As a result, the output signals of the two or more sensors are demultiplexed after being converted into analog signals, and may be supplied in a conventional manner to downstream signal processing elements such as low-pass filters and amplifiers in a conventional manner. This off Guidance form has the advantage that the downstream signal processing elements with respect to their arrangement and circuit over the prior art need not be changed, so that an easy adaptation of existing devices is possible.

In order to It does not lead to a misallocation of the individual output channels of the respective Sensors comes, should be a synchronization between the multiplexer device and the demultiplexer device. To ensure this is according to a another embodiment the invention proposed that the multiplexer with the demultiplexer device directly via a synchronization line connected is.

According to one alternative embodiment of the Invention is provided that another output of the multiplexer device is connected to an offset generator, wherein an output of the offset generator to a first input of an adder and the second input the adder connected to an output of the D / A converter is. By means of the offset generator and the adder, the Signals of the various sensors are processed so that they be moved into different voltage or current ranges. In this way, a simple distinction or assignment the respective signals possible. This embodiment has the particular advantage that the downstream components for signal processing merely be present within the sensor device and connected in series to the output of the adder circuit have to.

According to one another embodiment The invention is an output of the multiplexer device to a Signal information line out. This means that the output signals which are an output channel the sensor device according to the invention present, synchronized can be tapped. The assignment of the individual Signals to the respective sensors must therefore no longer of the evaluating Unit made on the basis of the above-mentioned different voltage ranges become.

at an embodiment The invention may provide an output of the multiplexer device for a signal information line guided be without the above-mentioned combination of offset generator and adder is present. The reason is in that, due to the unique assignability of the signals the respective sensors on the output channel of the sensor device no Shifting the signals into different voltage or current ranges more necessary is. In addition to the special cost savings through component reduction This solution stands out also by an improved channel resolution, since the entire band range of the channel now for each of the signals available stands.

Instead of connecting a signal information line to an output the multiplexer may according to another embodiment According to the invention, the multiplexer device also has a control input which is connected to a synchronization line. In this embodiment the control of the multiplexer takes place by means of external control information, which over transmit the synchronization line becomes. This offers the particular advantage that a targeted access to a channel of a particular sensor from the outside for an externally definable time is possible.

alternative or in addition to the features described above can according to a embodiment the invention between the respective output channels of at least two sensors and the multiplexer each a buffer memory be set. This can be guaranteed be that the information of at least two sensors at the same time captured and forwarded sequentially. This is special then advantageous if, for example, in the case of acceleration sensors on the basis of the directed acceleration information Direction determination of the applied force or impact, for example by vector calculation, to be made. Especially with modern ones Occupant protection systems for Motor vehicles passing over several protective agents, e.g. Front, side, head and window airbags, feature, is such a determination of direction for the targeted use of Protective means advantageous.

at everyone mentioned Embodiments may the output of the D / A converter directly or indirectly with at least one low-pass filter and at least an amplifier be connected in series to the usual signal processing too guarantee. The low-pass filter is used to the upper limit frequency of a sensor to determine while through the amplifier a signal impedance adjustment and optionally a signal amplification is possible.

Next the mentioned components can further be present, such as High-pass filter to compensate for offset errors, programmable devices for compensation of manufacturing tolerances the electronic components etc.

The sensor device according to the invention can be accommodated in its entirety in a suitable housing whose outputs on or meh Rere signal outputs and optionally have an output for said signal information line. The inputs of the housing accordingly have the sensor input lines and optionally the aforementioned signal information line.

Further Advantages and applications The present invention will become apparent from the following description in conjunction with the embodiments illustrated in the drawings.

In the description, in the claims, in the abstract and in the drawings are those in the listed below List of reference symbols used terms and associated reference numerals used.

The Drawings show in:

1 an example of a prior art acceleration pickup device;

2 a first embodiment of an acceleration pickup device according to the invention;

3a a second embodiment of an acceleration pickup device according to the invention;

3b a representation of the output signals of the acceleration pickup device of 3a ;

4 a third embodiment of an acceleration pickup device according to the invention;

5 a fourth embodiment of an acceleration pickup device according to the invention;

6 A fifth embodiment of an acceleration pickup device according to the invention;

7a a sixth embodiment of an acceleration pickup device according to the invention; and

7b a functional scheme for explaining the sixth embodiment of the invention.

in the Following can identical and / or functionally identical elements with the same reference numerals be provided. Absolute size information are exemplary only and do not limit the invention. The invention will now be described below with reference to an acceleration pickup device described as a sensor device, although not limited thereto, but basically for any Sensor device with multiple sensor elements is suitable.

1 shows the basic structure of an integrated circuit designed as an acceleration pickup device 1 using an example of the prior art. The accelerometer device 1 In the example shown, two acceleration sensors or sensor elements 1.1.1 and 1.1.2 , their respective digital outputs on each digital / analog converter 1.2.1 respectively. 1.2.2 are guided. The outputs of the digital / analog converter 1.2.1 respectively. 1.2.2 are each via a first and a second (analog) low-pass filter 1.4.1 respectively. 1.4.2 and via a downstream first or second (analog) amplifier 1.7.1 respectively. 1.7.2 to a first and second output channel 3.2.1 respectively. 3.2.2 connected in order to provide reliable signal information available there. As already mentioned, additional circuit components for signal processing may be present.

Unlike the in 1 shown accelerometer device 1 comes in the embodiments of the invention, which are also integrated accelerometer devices and in the 2 to 7 are shown, each a multiplexer 1.6.1 which makes it possible to use the two mentioned digital / analogue converters 1.2.1 respectively. 1.2.2 through a single digital / analog converter 1.2 to replace, which leads to both an area and a space savings.

At the in 2 The embodiment shown, the respective outputs of the two acceleration sensors 1.1.1 and 1.1.2 to the inputs of a multiplexer device 1.6.1 whose output via the single digital / analog converter 1.2 with a demultiplexer device 1.6.2 connected is. The two outputs of the demultiplexer are in the usual way with downstream low-pass filters 1.4.1 respectively. 1.4.2 and amplifiers 1.7.1 respectively. 1.7.2 connected. Moreover, the multiplexing means and the demultiplexing means are interconnected via a synchronization line (referred to as select / status in the figures) which ensures the required synchronization between these units. In this way, a misallocation of the respective channels is avoided. By the synchronization line is in principle the setting of the multiplexer and demultiplexer 1.6.1 respectively. 1.6.2 synchronized so that the demultiplexer 1.6.2 to the same channel as the multiplexer device 1.6.1 is switched.

3a shows a further embodiment of the invention and in 3b the voltage range split between the output signals shown on an output channel is shown 3.2 abut the acceleration pickup device according to the invention in operation. In the embodiment of the 3a come instead of the demultiplexer an offset generator 1.8.1 and an adder circuit 1.8.2 used, by means of which the sensor signals from the acceleration sensors via a common low-pass filter 1.4 and a downstream common amplifier 1.7 be routed to a common output channel.

How out 3b can be seen, the two sensor signals are offset by the offset generator and the adder so against each other that the information of the channel 1 in the diagram in the voltage range between 2.5 and 5 volts appears by a suitable offset, for example, plus 1.25 volts superimposed while the information of channel 2 in the diagram occurs in the voltage range between 0 and 2.5 volts by superimposing an appropriate offset, eg, minus 1.25 volts. As a result, the sensor signals, which typically have 2.5 volt rest voltage, shifted so that the output channel 3.2 the acceleration pickup device according to the invention 1 a simple assignment of the sensor signals to the various sensors 1.1.1 respectively. 1.1.2 is possible.

In the 4 embodiment shown in addition to those already in 3 existing components a status information output or a signal information line 4.1 on. This has the advantage that the signal at the signal output 3.2 the acceleration pickup device according to the invention due to the status information on the signal information line 4.1 synchronized can be tapped. For this reason, the channel discrimination need not be made based on the output signal range from the evaluating unit (not shown).

In 5 a further embodiment is shown, which is characterized by a particularly simple structure. In contrast to the example of 4 Here was dispensed with the use of the offset generator and the adder circuit. This is possible because of the signal information line 4.1 a unique assignment of the output channel 3.2 applied signals is ensured to the respective sensors. Thus, no "2-range representation" as in 3a so that an increase in the resolution for the representation of the individual channels is made possible (in the example shown, each channel can be imaged over the entire range from 0 to 5 volts).

In the 6 The embodiment shown differs from that of 5 in that instead of the signal information line 4.1 a channel selection line 4.2 is connected to a control input of the multiplexer device. Thus, the control of the multiplexer device takes place via external control information transmitted via the channel selection line 4.2 is entered. This allows targeted access to a specific channel from outside. The time for this can also be specified externally.

According to the embodiment, which in 7a are the only difference to the previously described embodiment of the 6 respective buffer memory 1.9.1 respectively. 1.9.2 downstream of the acceleration sensors. This buffer ensures that the information of the at least two acceleration sensors can be detected at the same time and forwarded sequentially. As already mentioned, this is particularly advantageous if, on the basis of the directional acceleration information, a direction determination of the acting force or of the impact is to be made, for example by means of vector calculation.

In 7b It can be seen how the advantage of the simultaneous detection and sequential forwarding of the signals is achieved. This is done in the case shown by the fact that at the rising edge of the select information to select the channel 1 or 2, the output signals of the sensors are each retained in the associated buffer memory, wherein at the same time the signals of the buffer memory 1.9.1 to the output of the multiplexer device 1.6.1 is controlled. In contrast, as shown, with the falling edge of the signal on the synchronization line 4.2 the signals of the buffer memory 1.9.2 controlled by the output of the multiplexer. The control shown is given by way of example only, and it will be readily apparent to those skilled in the art that the signal control may be reversed from the example shown.

It It should be noted that, although in the illustrated and described Each embodiment two acceleration sensors are used, their number in the frame of special requirements can be. For example, three, four or more acceleration sensors are used.

With The present invention provides a low cost accelerometer device disposal which, compared to the prior art with reduced area- and space requirements can be realized.

1

Beschleunigungsaufnehmervorrichtung

1.1.1

first Sensor (channel 1)

1.1.2

second Sensor (channel 2)

1.2

THERE converter

1.2.1

first D / A converter

1.2.2

second D / A converter

1.4

Low Pass Filter

1.4.1

first Low pass filter (channel 1)

1.4.2

second Low pass filter (channel 2)

1.6.1

multiplexer (MUX)

1.6.2

demultiplexer (DEMUX)

1.7

amplifier

1.7.1

first amplifier (Channel 1)

1.7.2

second amplifier (Channel 2)

1.8.1

Offset generator

1.8.2

adder

1.9.1

buffer memory (Channel 1)

1.9.2

buffer memory (Channel 2)

3.2

output channel

3.2.1

first output channel

3.2.2

second output channel

4.1

Signal information line

4.2

Channel selection line

Claims (8)

Sensor device which has at least two sensors ( 1.1.1 . 1.1.2 ) with respective output channels and a D / A converter ( 1.2 ), wherein the output channels of the at least two sensors with a multiplexer device ( 1.6.1 ) and the multiplexer device has an output connected to the D / A converter. Sensor device according to claim 1, characterized in that the D / A converter ( 1.2 ) has an output via which it is connected to an input of a demultiplexer device ( 1.6.2 ) connected is. Sensor device according to claim 2, characterized in that in addition the multiplexer device ( 1.6.1 ) with the demultiplexer device ( 1.6.2 ) is connected directly via a synchronization line. Sensor device according to claim 1, characterized in that a further output of the multiplexer device ( 1.6.1 ) with an offset generator ( 1.8.1 ), wherein an output of the offset generator is connected to a first input of an adder circuit ( 1.8.2 ) and the second input of the adder circuit with an output of the D / A converter ( 1.2 ) connected is. Sensor device according to claim 1 or 4, characterized in that an output of the multiplexer device ( 1.6.1 ) on a signal information line ( 4.1 ) is guided. Sensor device according to claim 1, characterized in that the multiplexer device ( 1.6.1 ) has a control input which is connected to a synchronization line ( 4.2 ) connected is. Sensor device according to one of the preceding claims, characterized in that between the respective output channels of the at least two sensors ( 1.1.1 . 1.1.2 ) and the multiplexer device ( 1.6.1 ) one buffer memory each ( 1.9.1 . 1.9.2 ) is set. Sensor device according to one of the preceding claims, characterized in that the output of the D / A converter ( 1.2 ) directly or indirectly with at least one low-pass filter ( 1.4 ; 1.4.1 . 1.4.2 ) and at least one amplifier ( 1.7 ; 1.7.1 . 1.7.2 ) is connected in series.