EP0415943A1 - Sensor for measuring a motional parameter, in particular crash sensor for a motor vehicle - Google Patents

Abstract

A detector for measuring a movement parameter of an object in the event of an accident comprises a support (H), which serves to fix the detector to the object, a detection element (M / K / C), which emits a electric detection signal in the event of a corresponding movement to be measured, and a seismic mass (M), which, in the event of a movement to be measured and in the event of a test, is projected into another position and which thereby changing position touches or mechanically moves the electrical contact (C) of an electrical current switch (C), which activates the latter. Said detector further comprises a body (F, K), which contains a ferromagnetic material, and an electromagnet (E) with an air gap. When excited by current pulses (I) of a predetermined intensity and path, said electromagnet attracts the body beyond the air gap. The dimensions of the electromagnet (E) and of the body are such that by attracting the body (K), the test current pulse simulates the movement parameter to be measured, even if the support remains stationary because it does not undergo an external mechanical influence which could move it. Indeed, the magnetic field created in the air gap of the electromagnet under the effect of the test current pulse displaces the seismic mass up to or even beyond a position where it actuates the switch current which emits the detector test signal. The seismic mass according to the present invention consists of a cylinder (M) which is held in its rest position by means of a ribbon spring (F) when the detector is in the rest state. The body is either the cylinder itself and / or a part (F) attached to said cylinder. The latter can be attracted by means of a test current pulse directly into the air gap of the electromagnet.

Description

 Sensor for detecting a movement parameter, e.g. B. crash sensor of a motor vehicle

The invention relates to a special type of sensors, namely deceleration or acceleration sensors which can be tested in a certain way and which contain an electromagnet and a body which has ferromagnetic material for test purposes. With the electromagnet you can test the functionality of the testable sensor at any time, even later, e.g. even after years of testing. The principle of this testable sensor type has been known for decades, and another such testable sensor has also become known recently, compare US Pat. Nos. 3,120,622, 3,295,355, 3,664,175 and 3,877,314, furthermore EP-A-251 048 and the recently published DE-Cl-37 26 145 (November 24, 1988).

These known sensors of this testable type differ from one another primarily by the spatial dimensioning and by the kinetic principles for the electromagnet and the body, for the seismic mass and for the mode of operation of the switch which, controlled by the body or by the seismic mass, finally delivers the sensor signal at the sensor output.

All sensors of this type, as well as the invention, solve the general task of checking the reliability of the sensor as often as desired and thus of being able to detect defects in the sensor early, generally in good time, even if the sensor is to be detected during operation

Movement parameters

- e.g. B. the extremely high deceleration in the event of a crash - should never or only rarely occur seriously, º even if the sensor does

- For example, if he is a crash sensor of a motor vehicle - should never or only sporadically operate. Sensors that cannot be tested according to this principle, which detect decelerations or accelerations, but therefore have no electromagnet and no body for any later tests, have been in large numbers for a long time, and such sensors are still available on the market today.

In principle, it is almost always possible to additionally redesign these last-mentioned known non-testable sensors based on the above-mentioned documents using an electromagnet and a body in such a way that they form a testable sensor, which can therefore be subsequently tested as often as desired at any time. The problem here, however, is to make a skilful choice among the many known non-testable sensors, and to skillfully dimension the electromagnet and body, combined with a skilful choice for the seismic mass, for the switch and especially for the general kinetic and that electrical principle, according to which a sensor signal is finally obtained.

Among other things, a non-testable sensor from Technar is already commercially available, which is suitable as a crash sensor for a motor vehicle and essentially corresponds to the FIG. 5 and 6 corresponds to this document. This known sensor, which is accommodated in a housing with a cover D and with a base plate G, contains two components as the actual sensor element, namely a seismic mass M and a switch with a contact C. The seismic mass M is there by a movable roller M is formed, which on a holder H by a band spring F, which tries to stretch, in its rest position, cf. the stop Q is held; one end of this band spring F is fixed to the holder H by means of a support T. In the event of a crash, the roller M is thrown in the direction X into a more or less predetermined second, different position up to the stop P, the roller M actuating the electrical contact C by this spinning, which in turn then emits the sensor signal S. In addition, strain gauges are known that contain a piezoresistive conductor.

It is also known to store any data in a PROM that is not deleted when the power supply is switched off.

The special object of the invention is to provide in a particularly clever, simple manner a low-effort, long-term stable, particularly reliable, and yet very compact, robust sensor, which can also be reliably used later, if possible (even as long as possible, throughout the life of the sensor Object, for example during the entire life of the vehicle) can be tested as often as required for its functionality, especially for its responsiveness.

In this case, the closest possible technical relationship with such a known non-testable sensor should be sought, which is already known to be highly reliable in itself and has proven to be reliable in mass production in order to be able to guarantee maximum reliability of the testable sensor according to the invention.

It was found that there are two solutions according to the invention which are very similar to one another, depending on whether one wants to use a mechanical contact of a current switch to generate the sensor signal or a piezo sensor element instead.

Accordingly, claim 1, compare its preamble, is based on US 3,295,355, FIG. 1. However, the invention is more compact, robust, reliable in the long term, and can also be produced from particularly small components, the seismic mass being able to be stabilized reliably in a particularly simple manner in its rest position in the long term. The same object of the invention is achieved by the subject matter of patent claim 5, which, compared to the preamble thereof, is based on US Pat. No. 3,120,622, in particular FIG. 4. However, this variant of the invention avoids a piezo-ceramic or a piezo-crystal that tends to break, both of which are also insulators instead of conductors and therefore have too high a voltage / current ratio (high output-side internal resistance) and are therefore very susceptible to interference from inductive and capacitive interference Are interference voltages from external sources of interference. Instead, the invention uses a piezoresistive sensor element with low internal resistance, which is more reliable with regard to interference voltages and mechanical robustness.

All sensors of the testable type, especially the two named variants according to the invention, can be observed in a particularly simple manner precisely with regard to their long-term behavior if the measures defined in claim 14 are used.

The sensor according to the invention was initially developed as a crash sensor of a motor vehicle. It turned out, however, that the invention is also of importance for all other sensors which are intended to detect with high reliability a movement parameter of any objects occurring in an accident.

The invention is therefore also for testing automotive sensors, and also for testing sensors for linear and rotating movements of other objects such as rail vehicles, airplanes, machine tools and. Robots, doors, locks and many other objects are suitable.

The additional claims in the remaining claims allow additional advantages to be achieved. Among other things, allow the measures according to the claim

2, the behavior of the particularly simply constructed sensor under extreme accelerations or. To simulate delays For example, to simulate its behavior in a crash case and still achieve a particularly high reliability of the sensor as long as the sensor is in operation.

3, to be able to apply the electrical potential required for operating the switch to the switches in a particularly simple manner,

4, to be able to produce the ferromagnetic body necessary for the invention in a particularly simple manner and to be able to mount it in the sensor, 6, 7, 8 and 9, each to enable a particularly compact structure of the sensor,

10 to increase the ratio of the amplitude of the sensor signals - including the test sensor signals - to the respective strength of the motion parameter to be measured and thus to improve the sensitivity of the sensor,

11, to be able to make the distance between the poles of the electromagnet on the one hand and the ferromagnetic body on the other hand very small even when the seismic mass is at rest, 12, continuously testing the sensor from time to time during the entire connection to the object - thus in generally also during the entire life of the object - to enable 13 to be able to continuously measure the degree of aging of the sensor in a particularly simple manner,

15, to be able to observe the long-term behavior very precisely in a particularly simple manner,

16, the sensitivity of the sensor for different types of movement, e.g. to test for different linear directions of movement and / or for revolutions around different axes of rotation of the objects, and

17 to enable a particularly simple construction of the sensor, although different types of movement are simulated, ie the sensor is tested for different movement parameters. The invention and its developments are further explained on the basis of the examples shown schematically in the FIGURES. It shows

1 shows an example of an acceleration sensor / deceleration sensor with a bending beam,

2 shows an example of an acceleration sensor / deceleration sensor with a semiconductor membrane, the holder and the power lines for forwarding the generated electrical sensor signal not being shown here for reasons of clarity,

3 shows an object, namely a motor vehicle, in which the sensor is mounted, FIG. 4 shows an example of a sensor according to the invention which contains a switch or contact actuated by a roller-shaped seismic mass,

5 shows an oblique view of the opened example shown in FIG. 4, but omitting the electromagnet to be attached according to the invention, FIG. 6 shows a detail of the examples shown in FIGS. 4 and 5, in which a band spring comprises the roller-shaped seismic

7 holds an example of the band spring shown in FIG. 6 in the extended state, FIG. 8 schematically shows the principle according to which the seismic mass shown in FIGS. 4 and 6 is generated by the magnetic field of the

Electromagnet is moved from the rest position into another position lying between the poles of the electromagnet, and, FIG. 9 is an oblique view to explain an example of the position of the electromagnet in the example shown in FIGS. 4 and 5.

All FIGURES therefore show an example of the sensor H / E / K / W in FIG. 1 to 3 or H / E / (K / W = M / K / C) in FIG. 4 to 9 or parts of these examples. The sensor is used in each case to record a movement parameter, that is to say, for example, to record the acceleration, deflection and / or rotation of an object tes 0, for example a vehicle 0, cf. 3. It is therefore, for example, a crash sensor for detecting a strong jerky acceleration and / or deceleration of a motor vehicle 0, parts of the sensor, for example its seismic mass M or K, being thrown in the direction X in FIG. 3 in the event of a crash become - cf. thus also the direction X and the direction X 'of the movement of a seismic mass M or K in FIG. 1, 2, 4 to 6 and 8, 9, which can also often be used in such a crash trap.

The sensor in each case has a holder H, via which it can be fastened to the object 0, cf. 1 and 4 to 6 and 9 (in FIGS. 2, 7 and 8, the holder H is not shown for the sake of clarity), the holder H holding the actual sensor element W or M / K / C, which in turn holds one corresponding movement X or X 'an electrical

Outputs sensor signal S via at least one of its connections A, cf. 1 and 4 to 6 and 9. (In FIGS. 2, 7 and 8, the tapping of this sensor signal S was not shown for the sake of clarity).

The actual sensor element W or M / K / C, which emits an electrical sensor signal S with a corresponding movement X or X ', can in the invention itself - within the scope of the scope defined by claims 1, 5 and 14 - in Principle can be constructed arbitrarily, so also largely known sensors, - but according to the invention at least one electromagnet E and at least one ferromagnetic body K is additionally attached. Advantageous variants of the invention are defined in the subclaims.

In FIG. 1 it is assumed by way of example that it is a piezoresistive meander line which can be produced using layer technology or else as a compact line or by means of strain gauges.

In FIG 2 - in which to improve clarity, the bracket H, with which the other sensor components ge hold or which carries the other sensor components directly or indirectly, has been omitted - it is assumed by way of example that it is a silicon frame Z / a silicon holder Z with a thin piezoresistive silicon membrane W, with a seismic oscillating mass M in the middle of the membrane - For example made of silicon - to increase the vibration amplitude of the membrane W when it moves accordingly, for example in the direction X or 'X', that is to increase the sensitivity of this sensor.

In the further sensor example shown in FIGS. 4 to 9, the actual sensor element, like the Technar sensor, consists of an electrical switch with a contact C, which is activated by a seismic mass M with a corresponding movement X - i.e. in the event of a crash - is actuated and then emits the sensor signal S.

In all cases, however, at least one electromagnet, cf. E in FIGS. 1, 2, 4, 8, 9, and at least one ferromagnetic body, cf. K in Figures 1, 2, 4 to 6, 8, 9, attached so that this body K under the influence of a test current pulse I flowing through the electromagnet E, cf. 1, 2, 8, 9, a corresponding movement of the sensor is simulated or a corresponding movement of the associated object 0 is simulated, as a result of which a test sensor signal S is generated as long as the sensor is in order, as long as the sensor is not defective.

The sensor element W or M / K / C held by the holder H is therefore, according to the invention, directly or indirectly - for example mechanically rigid, or via a spring and / or a lever - connected to a ferromagnetic body K, which in turn, depending on Need, a compact seismic mass M = K, cf. 1, 4 to 6 and 8, 9, or a sufficiently thick magnetic layer K, for example according to FIG. 2. In addition, the sensor therefore contains at least one single electromagnet E, which can be mechanically attached, for example, directly to the holder H, cf. in particular FIG 1, 2, 4, 8, 9 and which is stronger and defined with test current pulses I and can be excited by means of a correspondingly generated voltage U. These test current pulses I generate in the electromagnet E in each case certain magnetic fields, which can be defined with regard to strength and time, and which act on the ferromagnetic body K in such a way that the test current pulse I simulates a corresponding movement of the object 0, even when the holder H or an object attached to it 0 remains motionless. The test current pulse I namely causes the body K to move in the magnetic field and thus triggers a corresponding movement and / or deformation of the sensor element W or M / K / C and thus the emission of a test sensor signal S. In this way, the invention makes it possible to generate a sensor signal S by means of the test current pulse I of defined strength and defined course for test purposes, that is, to simulate a specific movement of the object 0, even when the sensor H / E / K / W or H / E / M / K / C itself has not yet been attached to object 0, but if this sensor is still being tested, for example in the course of its manufacture, during the final inspection.

But even if the sensor is already attached to object 0, this sensor can be tested at any time, even several times in succession from time to time, e.g. to monitor whether it still works properly with sufficient sensitivity by checking whether the sensor emits the sensor signal S, more precisely: test sensor signal S, or not.

The time course and the maximum amplitude of the relevant movement of the body K in the magnetic field do not only depend on the time course and on the strength of the test current pulse I and thus on the time course and the strength of the associated voltage U at the inputs of the electromagnet E. . The course and the maximum amplitude of the relevant movement supply of the body K also depends on other constructive measures, for example on the shape and size and open magnetic properties of the body K, on the shape and the intensity of the magnetic field generated and thus also on the structure of the electromagnet E and on the distance of the electromagnet E. to the body K, but also from the spring constant of resilient parts of the sensor, such as from the spring constant of the bending beam B in FIG. 1, on which the sensor element W is fastened, or from the spring constant of the semiconductor membrane W, on which, according to FIG. 2, the seismic mass M and above the body K is fastened, or also from the spring constant shown in FIGS. 4 to 7 and 9, spring F. In addition, the course and the maximum amplitude of the relevant movement of the body K also depend on the preloads of such springs. The invention thus allows the sensitivity of the respective sensor type to be adjusted or selected according to the respective requirement by appropriate dimensioning of the spring constant and / or the spring preload.

In addition, the invention in principle allows the structure of the sensor to be varied - e.g. a sensor based on the bending beam principle according to FIG. 1 with the piezo line W attached to the bending beam B, e.g. Strain gauges W, or a semiconductor motion sensor according to FIG. 2 with a piezoresistive membrane W as the actual sensor element W, which can emit an electrical sensor signal S when there is a corresponding movement, cf. also the sensor example shown in FIGS. 4 to 9 with seismic mass M and contact C.

A basic concept of the invention is based here on using at least one single electromagnet E and at least one single ferromagnetic body K to simulate corresponding movements of the sensor H / E / K / W or of the object 0, in principle repeatable at any time in order to check the sensitivity and thus the reliability of the sensor and in order to be able to detect defects in the sensor at an early stage, that is to say - generally in good time - if necessary, the sensor repair or exchange.

For the sake of clarity, only a single electromagnet E per sensor was shown in FIGS. 1 and 2 and 4, 8, 9. However, it is often very advantageous not to attach a single electromagnet E to the sensor. Instead, several electromagnets E, which can be excited separately by test current pulses I, can be attached, the test current pulses I, depending on which one of the electromagnets E is energized, different types of movement - e.g. can simulate different linear directions of movement, ie also linear directions perpendicular to one another, and / or different axes of torsional movements - of the sensor or of the object 0. In this way, the sensitivity of the sensor for the different types of movement can be tested individually, one after the other, or also simultaneously superimposed on one another, using the various electromagnets E of the sensor.

If several such electromagnets E are attached per sensor, then one can mechanically equip or connect his sensor element W or M / K / C with a single ferromagnetic body K instead of several ferromagnetic bodies, which in turn is arranged in such a way that that it is moved in different ways by the different electromagnets E, for example by one electromagnet in the X direction and by the other electromagnet perpendicular to it, cf. 1 and 2, if two separate electromagnets E are attached in these two examples, in which one accelerates the body K in the X direction, the other in the other direction. For example, by means of several such testable sensors, which are located at different locations on the object 0, cf. FIG. 3, are attached, rotary movements of the object 0 can also be measured, and the functionality of these sensors for detecting sudden rotations of the object can then also be tested. In this way, the test current pulses I supplied to the electromagnet E simulate different types of movement of the sensor or the object 0 because the body is typical in each case Movements that are only assigned to the relevant electromagnet E triggers. In this way, it is possible, with particularly little effort and with a particularly simple construction of the sensor, to test the sensitivity of the sensor for the associated different types of movement at any time.

If the sensor H / E / K / W or H / E / M / K / C is connected to oem object 0, cf. 3, this sensor can contain the body K and the electromagnet E or the electromagnet E even uninterrupted throughout the entire duration of its connection to the object 0. In this way, the sensitivity of the sensor for the relevant movement parameters of object 0 can in principle be measured during the entire life of object 0, at least continuously from time to time during the entire connection of this sensor to object 0, using test current impulse I are tested - whereby by attaching a single electromagnet E, generally only a single movement parameter is detected, whereby by attaching several electromagnets E per sensor, very different movement parameters are also detected, if necessary separately from one another and / or simultaneously superimposed on top of one another can be.

If the sensor in question is suitable for detecting an abrupt linear movement in a certain direction, for example X or X ', with a certain minimum acceleration / minimum deceleration, for example if it is a crash sensor, the test current pulse I should be a corresponding one Abrupt linear movement X or X 'of the sensor can simulate. This can be, for example, the test of a crash sensor for a motor vehicle 0, cf. 3, or, for example, a sensor for a corresponding other object 0, which represents, for example, an arm of a robot or a handling device, regardless of whether these objects 0 are controlled more or less automatically or by hand. Such a sensor can serve, for example, as a trigger in an ignition device of an airbag and / or a belt tensioner in a motor vehicle 0, with the behavior of the electromagnet E and body K even when the motor vehicle 0 is stationary of the sensor in the case of extreme accelerations or decelerations, which means that the sensor can also be tested for a crash even when the vehicle 0 is stationary.

Of course, it is in a - e.g. serving as a vehicle airbag trigger - crash sensor generally advisable to ensure that the test sensor signal S triggered by the test current pulse I does not really ignite the squib of the airbag and thus inflate the airbag, for which purpose the electrical one during the test of the sensor Transmission of the test sensor signal S to the squib of the airbag can be interrupted by means of one or more switches.

It is already clear from the foregoing that the test current pulse I can be repeated from time to time and that the test sensor signal S generated by the test current pulses I is used for repeated checks of the functionality of the sensor H / E / K / W or H / E / M / K / C can serve. Such a repeated testing of the sensor from time to time makes it possible to guarantee a particularly high reliability of the sensor, because damage to the sensor is recognized in good time, and in principle this reliability of the sensor can be checked continuously during the entire life of the sensor.

This repeated testing becomes particularly precise and meaningful if the test sensor signal S is fed via an A / D converter to a permanent memory, i.e. to a PROM of some kind - e.g. an EEPROM - in the PROM at least that for a single one, e.g. the first-time / original test test signal S is digitized accordingly. In order to be able to recognize aging of the sensor better, in the test case it is also possible to measure the amplitude given to generate the test sensor signal S and / or the minimum amplitude required for the test current pulse I to excite the electromagnet E more or less precisely and in save this PROM. The relevant minimum amplitude of the test current pulse I shows, for example, whether the spring constant te, spring preloads and / or the size of a seismic

Mass M or even whether the ferromagnetic properties of the body K somehow changed over time due to aging, damage or wear. The long-term behavior of the sensor can even be monitored very precisely, e.g. in routine checks in workshops, if in the PROM - instead of only storing the last test sensor signal S in each case - at least some of the test sensor signals S emitted in previous tests are also stored instead of deleted.

A particularly simple and compact design of the sensor can be achieved above all by selecting one of the many possible non-testable sensor types which has a simple, compact design from the start. It was found that sensor elements which are made of a piezoresistive conductor or which have a contact or switch controlled by the seismic mass, e.g. according to the dimensioning in FIGS. 4 to 9.

The measurement of accelerations and / or decelerations is particularly simple. if its sensor element W, cf. 1, is attached to a bending beam B or if this sensor element W itself represents such a bending beam B, the free end of the bending beam B being directly or indirectly, i.e., for example via at least one spring and / or e.g. at least one lever - is connected to the ferromagnetic body K. Such a sensor can be made particularly sensitive by appropriately selecting the spring constant for bending the bending beam B.

In addition, the sensor element W can also, cf. 2, are formed by a semiconductor membrane W, the resistance of which when the membrane W is knocked out is a measure of the relevant movement of the sensor or the object 0. The type of movement measured by such a semiconductor sensor element W represents normally represents an acceleration or deceleration. With such a sensor element W formed by a semiconductor membrane, the body K can - likewise directly or indirectly - be attached to a particularly oscillatable point of the semiconductor membrane W, that is to say, for example, according to FIG. 2, approximately in the middle of the membrane W. Such a semiconductor membrane sensor element W is particularly compact. In order to make the ratio of the amplitude of the sensor signals to the respective strength of the movement parameter to be measured even greater, and thus to increase the sensitivity of the sensor even further, the seismic mass can be amplified on a well-vibratable element to amplify the deflections of the membrane W. Attach the membrane W, cf. the seismic mass M in the middle of the membrane W in FIG. 2. Such a seismic mass M can, for example, also be attached to a point of the bending beam B in FIG.

Incidentally, the construction of such a sensor with a seismic mass M becomes particularly compact if the seismic mass M itself consists of ferromagnetic material and thus itself represents the ferromagnetic body K, cf. also FIG 1. Then a smaller, lighter electromagnet E can also be used.

FIGURES 4 to 9 relate to an example of the invention, which represents a further development of the previously known sensor from Technar. This example, shown in these FIGURES, also demonstrates that the measures according to the invention can also be applied to a known sensor, the sensor element of which here contains a seismic mass, which is thrown into a more or less predetermined other position during the movement to be detected and through this spinning an electrical contact, cf. C, touches or moves an electrical switch and thus actuates this switch, in which case this switch preferably emits a binary sensor signal S or a signal pulse S. 4 shows a further development according to the invention with electromagnets E, the magnetic field of which is intended to move the seismic mass M from its rest position, ie from the stop Q, to its other position at the stop P, cf. also FIG 5 and 6. During this movement, the mass M touches the contact C and presses this contact into its position C '. This contact between the mass M and the contact C triggers the output of the sensor signal S.

FIG. 4 additionally shows an ohmic resistor R which is inserted into the current profile of the sensor signal S and represents a protective resistor R which limits the current of the sensor signal S. This current of the sensor signal S flows in the exemplary embodiment shown via the resistor R, via the electrically conductive support T and via an electrically conductive band spring F - cf. 6 and in particular around the seismic mass M to the point at which the spring F contacts the contact C, and along the resilient extension of this contact C / C 'to the external connection of the two-pole sensor signal connection, cf. S. How the band spring F is constructed and dimensioned here, so that it not only presses the mass M normally in its rest position with a prestress against the stop Q, but also forms part of the switch F / C, will be explained later particularly with reference to FIG 7 described in more detail. - By the way, for the sake of clarity, FIG. 4 does not show how special rails inside the cover D prevent the mass M from being thrown upwards against the cover D, so that the mass M only runs more or less along the path in FIG an arrow marked path from αer rest position, cf. Q, in the other position, cf. P, is moved.

The known sensor from the Technar company was thus further developed according to the invention above all by attaching an electromagnet E and a ferromagnetic body K movable by its magnetic field, which is intended to trigger a test sensor signal S under the influence of the magnetic field. For this purpose, for example, the seismic mass M or a section thereof could be made of ferromagnetic material, for example by A ferromagnetic core K was coaxially mounted in this, in the rest of the drum-shaped seismic mass M consisting of, for example, ceramic or plastic, cf. the core K in FIGS. 4 to 6 as well as 8 and 9. In addition, according to the invention, an electromagnet E was attached to the sensor, see FIGS. 4, 5, 8 and 9, that its magnetic field under the influence of the test current pulse I, cf. 8, 9, the ferromagnetic body K together with the associated seismic mass M is moved up to that position or is moved beyond that position at which the seismic mass M switches F / C by touching the contact C, cf. 4 to 6, 9, operated.

Because this contact C is part of an electrical switch, cf. F / C, the test current pulse I generates the test sensor signal S by spinning the seismic mass M in the direction X by means of the contact C, if a test current pulse I is supplied to the electromagnet E and if a test sensor signal S is thereby at the corresponding signal output of the sensor is given, the reliability of the sensor is given. If, on the other hand, the test current pulse I does not trigger a test sensor signal S, a defect in the sensor is detected, at least if the test current pulse I in itself was sufficiently strong to trigger the test sensor signal S in a properly functioning sensor.

Instead of forming the entire mass M or its core K as a ferromagnetic body K, a separate additional ferromagnetic body can also be attached, initially separately from the mass M, this body then then indirectly, for example again via a spring or a lever, according to the invention can act on the relevant seismic mass M. Then the magnetic field of the electromagnet E acts only indirectly on the seismic mass M via this body K in order to generate a test sensor signal S. In this way, a small magnetic field, despite the relatively small spatial expansion of this magnetic field, can still have a strong effect on a seismic mass M if this mass M is far from the small magnetic field in its rest position. The seismic mass M can be held in its rest position, for example by means of the band spring F shown in FIGS. 4, 7 to 9, so that the roller-shaped mass M in question is held in its rest position with a certain spring preload. The minimum deceleration / minimum acceleration at which the sensor in question emits a sensor signal S depends on the size of the spring preload in question - with lower decelerations / accelerations, the mass M in question remains in its rest position and then does not trigger a sensor signal S.

The relevant band spring F itself attached to the seismic mass M can itself form the ferromagnetic body K, the rest of the sensor, apart from the electromagnet E itself, no longer having to contain any further ferromagnetic bodies. Even then, the sensor in question can be tested as often as required according to the invention because the band spring F, which then forms the ferromagnetic body K by itself, is influenced by the magnetic field of the electromagnet E in such a way that it moves, e.g. rolls up, and thus moves the seismic body M into its other position and thus generates the test sensor signal S.

In the example shown in FIGS. 4 to 9, the contact C is fitted in a hole V in the band spring F, cf. 7 with FIG. 4, 5 and 9 in particular. The bandfeer F can then be connected to an electrical potential if it is electrically conductive, for example made of metal; In addition, the band spring F can be given such a shape that when the seismic mass M is moved as intended, the band spring F - more precisely: a section of the band spring F lying on the electrical potential - touches the electrically conductive contact C and thus triggers a current which forms the sensor signal S and flows through the contact C and via the band spring F. 5 to 7, the band spring F can also have a section L which is more or less wound around the roller-shaped seismic mass M, this section L of the band spring F being able to have a special extension as a separate contact surface, which in turn touches contact C in the event of a spin - cf. also the reference to the diameter d of the seismic mass M in FIG. 6 and the reference to the rolling distance shown in FIG. 7, which corresponds to the circumference of the mass.

In general, the seismic mass, cf. M, itself - and / or a component attached to this mass that moves both during the movement to be detected and in the test case, cf. F - an electrically conductive surface as a contact surface, cf. F, which is applied to an electrical potential during operation of the sensor, with both the relevant contact surface, cf. F, as well as that

Contact, cf. C, are in each case components of a switch which can be actuated by the seismic mass and which supplies or triggers the sensor signal S or the test sensor signal S both in the case of the movement to be detected and in the test case. Such utilization of an electrically conductive contact surface, which is moved with the seismic mass M, enables a particularly simple construction of the switch in question, cf. C / F.

FIG. 9 shows, in an oblique view, again schematically how the electromagnet E can be spatially arranged with respect to the seismic mass M, the band spring F, the contact C and the support T. In this example, the mass M is drawn into the air gap of the electromagnet E according to FIG. 8 because of its ferromagnetic core K as soon as a magnetic field arises between the poles of the electromagnet E by means of the test current pulse I, which pulls the ferromagnetic body K into the air gap of the electromagnet. An advantage of the flat band spring F is that, in the example shown in FIG. 9, the roller-shaped mass M according to FIG. 8 is drawn into the air gap largely without tilting, because the flat, and therefore relatively wide band spring F prevents the axis of the roller-shaped mass M additionally rotated instead of moving into the air gap by parallel movement of its roller axis.

otherwise, by omitting the housing D / G and partially omitting the holder H, FIG. 9 shows particularly clearly how the air gap of the electromagnet E can be fitted in order to be able to act in accordance with the invention. With regard to the position of the electromagnet in the sensor, the position of the air is namely gap of this electromagnet E, based on the mass M, more important than the spatial position of the electrical windings and the magnetic core of this electromagnet E. The electromagnet E can therefore fundamentally have a completely different position in the sensor, as long as its air gap is so appropriate next to the mass M is attached so that the mass M moves as intended under the influence of the test current pulse I and then triggers the sensor signal S as a rule.

A ferromagnetic body is understood here to mean a body which, at least under certain conditions such as under certain temperatures, has a permeability which is very much higher than the permeability of the vacuum. Some authors differentiate between ferromagnetic and ferrimagnetic bodies by referring to certain conditions under which the high permeability occurs and changes. In the present document only "ferromagnetic" bodies are always given, but the invention also covers those "ferrimagnetic" bodies as long as they have a high permeability compared to the vacuum under the normal operating conditions of the sensor. In the sense of the present document, there is no linguistic distinction between "ferromagnetic" and "ferrimagnetic" bodies, but only the expression "ferromagnetic" body is used for all of these bodies, which have the high permeability required according to the invention under the operating conditions of the sensor.

Claims

Claims

1. Sensor (H, E, M, K, C in FIGS. 4 to 9) for detecting a movement parameter of an object (0) that occurs in an accident,

- e.g. Deceleration, acceleration, deflection and / or rotation of an object (0), i.e. e.g. a crash sensor (H, E, M, K, C) for triggering the ignition of an airbag of a motor vehicle (0) - with a bracket (H), via which (H) it can be attached to the object (0), and one of the Holder (H) held by the actual sensor element (M / K / C), which (M / K / C) emits an electrical sensor signal (S) during a relevant movement to be detected, a seismic mass (M), which (M ) in the movement to be recorded

- For example in a crash case - and in the test case is thrown into a more or less predetermined other position and mechanically touches or moves an electrical contact (C) of the electrical current switch and thus actuates the current switch (C), a body (F , K), which (F, K) consists of ferromagnetic material or at least contains a section (K) consisting of ferromagnetic material and which (F, K) is identical to the seismic mass (M) or to the seismic mass (M) mechanically directly or indirectly connected, _ an electromagnet (E) having an air gap, which is held by the holder (H) and which, when excited with test current pulses (I) of defined strength and defined course, in each case across the air gap onto the body (F, K) has an attractive effect - electromagnet (E) and body (F, K) dimensioned so that the test current pulse (I) by tightening the body (K) the z u simulates the movement parameters of the object (0) connected or not connected to the sensor (H, E, M, K, C), even if the holder (H) is missing external mechanical action

- e.g. of the object (0) - on the sensor (H, E, M, K, C), is unmoved by the magnetic field generated by the electromagnet (E) under the influence of the test current pulse (I) in the air gap of the electromagnet (E) moves the seismic mass (M) up to or above the position at which the

Test sensor signal (S) emitting current switch (C) is actuated, so that the seismic mass (M) is held in its rest position by means of a band spring (F) when the sensor is in the idle state

Roller (M) is (FIG. 4 to 9), the body (K) is identical to the roller (M) and / or is a part (band spring part F) fastened to the roller (M), and the roller (M ) can be drawn directly into the air gap of the electromagnet (E) by means of the test current pulse.

2. Sensor (H, E, K, W) according to claim 1, d a d u r c h g e k e n n z e i c h n e t that the body (K) is attached to the axis of the roller (M) (FIG. 4, 5, 6, 8).

3. Sensor (H, E, K, W) according to claim 1 or 2, characterized in that the seismic mass (M) itself and / or an attached to it in the movement to be detected and in the test case by the seismic mass (M) Moving element (F) has an electrically conductive surface as a contact surface (F), which is connected to an electrical potential during operation of the sensor, and both the relevant contact surface (F) and the contact (C) are components of the seismic mass ( M) are operable current switch.

4. Sensor (H, E, K, W) according to one of the preceding claims, characterized in that - The band spring (F) represents the body (K) or one of several bodies (F, K) which can be attracted by the electromagnet (E).

5. Sensor (H, E, K, W in FIGS. 1 to 3) for detecting a movement parameter of an object (0) that occurs in an accident - for example deceleration, acceleration, deflection and / or rotation of an object (0), that is to say, for example Crash sensor (H, E, M, K, C) for triggering the ignition of an airbag of a motor vehicle (0) with a bracket (H), via which (H) it can be attached to the object (0), one of the bracket ( H) held bent part (B, W / K) with actual piezo sensor element (W), which (W) in turn emits an electrical sensor signal (S) by bending the bent part (B, W / M / K), a seismic mass ( K), which (K) causes the bent part (B, W / M / K) to bend during the movement to be detected - for example in a crash case - and in the test case and triggers the emitting of the sensor signal (S) by this bending , a body (K) which (K) consists of ferromagnetic material or at least contains a section consisting of ferromagnetic material and which (K) is identical to the seismic mass (K) or is directly or indirectly mechanically connected to the seismic mass (K) in such a way that when the body (K) is moved, the bent part (B, W / M / K) is bent and the sensor signal ( S) is drawn, an air gap having an electromagnet (E) which is held by the holder (H) and which, when excited with test current pulses (I) of defined strength and defined course, in each case attracts the body (K) via the air gap so that the body (K) bends the bent part (B, W / M / K) in the DESIRED bending direction, the electromagnet (E) and the body (K) are dimensioned such that the test current pulse (I) by tightening the body (K) Motion parameters to be recorded of the object (0) connected or not connected to the sensor (H, E, K, W) are simulated, even if the holder (H) is lacking external mechanical action

- e.g. of the object (0) - on the sensor (H, E, K, W), is not moving, so that its sensor element (W / K) represents a piezoresistive conductor (W) (FIG 1 and 2).

6. Sensor (H, E, K, W) according to claim 5, d a d u r c h g e k e n n e e c h n e t that its piezo sensor element (W) contains a strain gauge (W) (FIG. 1).

7. Sensor (H, E, K, W) according to claim 5, d a d u r c h g e k e n n z e i c h n e t that its bending part (B) is a bending beam (B), at the (B) free end of which the body (K) is directly or indirectly attached ..

8. Sensor (H, E, K, W) according to claim 7, d a d u r c h g e k e n n z e i c h n e t that its bending beam (B) itself is piezoresistive.

9.Sensor (H, E, K, W) according to claim 5, so that the sensor element (W / M / K) contains a semiconductor membrane (W), the resistance of which, when the membrane is deflected, is a measure of the movement parameters, e.g. Acceleration / deceleration is, and the body (K) is attached directly or indirectly to an oscillatable point of the semiconductor membrane (W) (FIG 2).

10. Sensor (H, E, K, W) according to claim 9, characterized in that a seismic mass (M) is attached to an oscillatable point of the membrane (W) to amplify the deflections.

11. Sensor (H, E, K, W) according to one of the preceding claims, characterized in that the body (K) - or in the presence of several bodies (K): at least one of these bodies (K) - indirectly, namely via at least a lever and / or via at least one spring (F) acting on the seismic mass (M).

12. Sensor (H, E, K, W) according to one of the preceding claims, characterized in that it (H, E, K, W) the body (K) and the electromagnet (E) during the entire duration of its connection with the Contains object (0).

13. Sensor (H, E, K, W) according to one of the preceding claims, characterized in that in the test case, the minimum amplitude of the test current pulse (I) required for generating the test sensor signal (S) to excite the electromagnet (E ) is measured more or less precisely.

14. Sensor (H, E, K, W in FIG. 1 to 3 or H, E, M, K, C with

W = M / K / C in FIG. 4 to 9) for detecting a movement parameter of an object (0),

- For example deceleration, acceleration, deflection and / or rotation of an object (0), for example a crash sensor (H, E, M, K, C) for triggering the ignition of an airbag of a motor vehicle (0) with a holder (H), via which (H) it can be attached to the object (0), and an actual sensor element (W) held by the holder (H), which (W) emits an electrical sensor signal (S) during a relevant movement to be detected, a seismic mass (K) which occurs during the movement to be recorded - For example, in a crash case - and in the test case triggers the output of the sensor signal (S), a body (K) which consists of ferromagnetic material or at least contains a section made of ferromagnetic material and which is identical to the seismic mass (M) or is directly or indirectly mechanically connected to the seismic mass (M) in such a way that when the body (K) moves, the sensor signal (S) is triggered, an electromagnet (E) having an air gap, which is held by the holder (H) and which, when excited with test current impulses (I) of defined strength and defined course, in each case attracts the body (K) across the air gap, and electromagnets (E) and body (K) dimensioned such that the test current impulse (I) by attraction of the body (K) simulates the movement parameters of the object (0) connected or not connected to the sensor (H, E, K, W), even if the Bracket (H), due to lack of external mechanical action

- e.g. of the object (0) - on the sensor (H, E, K, W), unmoved, e.g. according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that the test current pulse (I) for repeated checking of

Functionality of the sensor (H, E, K, W) from time to time

Repeated time, its test sensor signal (S) via an A / D converter to a PROM

- e.g. an EEPROM - is fed, and in the PROM the test sensor signal (S) given in an original test is digitized.

15. Sensor (H, E, K, W) according to claim 14, characterized in that at least some of the test sensor signals (S) emitted during later tests are also stored in the PROM.

16. Sensor (H, E, K, W) according to one of the preceding claims, characterized in that its holder (H) holds several, separately excitable electromagnets (E), each of which (E) by means of separately feedable test current pulses (I) each a different way of moving

- e.g. Movements around different axes of rotation and / or in different linear directions - simulated.

17. Sensor (H, E, K, W) according to claim 16, characterized in that - its sensor element (W / K) contains only a single body (K), the body (K) of the different electromagnets (E) in different Directions can be tightened, and the body (K) under the influence of one of the different electromagnets (E) each simulates different movements of the sensor (H, E, K, W) or the object (0).