WO1994011741A1 - Detecteur d'acceleration - Google Patents

Detecteur d'acceleration Download PDF

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Publication number
WO1994011741A1
WO1994011741A1 PCT/DE1992/000959 DE9200959W WO9411741A1 WO 1994011741 A1 WO1994011741 A1 WO 1994011741A1 DE 9200959 W DE9200959 W DE 9200959W WO 9411741 A1 WO9411741 A1 WO 9411741A1
Authority
WO
WIPO (PCT)
Prior art keywords
magnet
acceleration sensor
sensor according
switch
acceleration
Prior art date
Application number
PCT/DE1992/000959
Other languages
German (de)
English (en)
Inventor
Dietmar Schwegler
Manfred Sondergeld
Original Assignee
Schmidt Feintechnik Gmbh
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Schmidt Feintechnik Gmbh filed Critical Schmidt Feintechnik Gmbh
Priority to PCT/DE1992/000959 priority Critical patent/WO1994011741A1/fr
Publication of WO1994011741A1 publication Critical patent/WO1994011741A1/fr

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H35/00—Switches operated by change of a physical condition
    • H01H35/14—Switches operated by change of acceleration, e.g. by shock or vibration, inertia switch
    • H01H35/147—Switches operated by change of acceleration, e.g. by shock or vibration, inertia switch the switch being of the reed switch type
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
    • G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
    • G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
    • G01P15/135—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values by making use of contacts which are actuated by a movable inertial mass

Definitions

  • the invention relates to an acceleration sensor, in particular for safety systems in motor vehicles, with a magnetically actuable electrical switch and a magnet provided for this purpose which is arranged to be variable against the force of a restoring element and which moves as a seismic mass when an acceleration threshold value is exceeded in such a way that it actuates the switch.
  • Acceleration sensors of this type are known, for example, from the publications DE-OS 2 644 606, DE-PS 3 338287, DE-PS 3 216 321 or DE-OS 3 727 351.
  • the magnet is a ring-shaped single magnet, which with its Center opening is pushed onto a support or guide tube and is displaceable in the direction of the support tube.
  • a reed switch Inside the support tube is a reed switch, which is arranged so that it is normally outside the effective range of the permanent magnet and its contact tongues are therefore normally open. If acceleration or deceleration acts on the arrangement, the magnet is displaced against the force of a spring so that it reaches the area of the reed switch. The magnetic field magnetizes the reeds of the reed switch and closes them. After acceleration or deceleration has ended, the spring pushes the permanent magnet back into its original position, and the reed switch opens again.
  • the switch is also a reed switch.
  • there are two permanent magnets which are arranged one behind the other in the direction of their longitudinal axis.
  • the surfaces of the permanent magnets which are remote from each other are supported on the common housing, while the sides facing one another are magnetized by the same name, so that the two permanent magnets repel one another.
  • one of the two ring-shaped permanent magnets will move along the support tube and thereby reach and close the area of the reed switch arranged in the support tube. This magnet moves towards the other magnet and is repelled with increasing distance due to the magnetized facing surfaces of the same name.
  • a bar magnet is provided which is mounted in a tubular housing.
  • a reed switch which is normally outside the operating range. realm of the magnet. If acceleration or deceleration acts on the arrangement, the rod-shaped magnet shifts, its field coming close to the reed switch and switching it. If the acceleration or deceleration is large enough, the permanent magnet finally hits a spring which is compressed by the force exerted on it.
  • the moving magnets are returned to their starting position by the restoring element, which can be a spring or another magnet. Since in both cases - magnet or restoring spring - the restoring force increases progressively the further the magnet is deflected from its rest position, the switching time of the known acceleration sensors depends heavily on the time course of the acceleration or deceleration curve, which is also called the collision curve. from.
  • This type of sensor is used, among other things. in fully passive occupant restraint systems for motor vehicles, such as used in belt tensioners and airbag systems.
  • sensors also referred to as safety switches or safing sensors
  • a gas generator which is required to inflate an airbag or to tighten seat belts.
  • This arrangement ensures that the restraint system can only be triggered when a dangerous situation for the occupants actually occurs. In this case, the sensor must remain in the closed state until the safety device has fully developed its protective effect for the endangered occupants.
  • the reed switch opens briefly and the ignition circuit is temporarily interrupted as a result. This effect is undesirable since it can lead to an uncontrollable impairment of the security system.
  • an acceleration sensor with a degressive characteristic is known from DE-OS 3727351.
  • the known acceleration sensor comprises a switching magnet held in its basic position by a pull-away magnet, which is deflected from its basic position only after an acceleration limit value has been exceeded and can close the contacts of a reed switch.
  • This means that the known acceleration sensor has a degressive characteristic curve in that the magnetic force of the detaching magnet on the switching magnet and thus the restoring force becomes smaller the further the switching magnet moves away from the detaching magnet.
  • the holding force decreases with increasing distance, so that the magnet is less and less braked, so to speak.
  • Only one The adjustment measure is the idle distance between the two magnets, by means of which the switching threshold is set.
  • the switching time itself results from the overall length or the resulting "flight time" of the magnet with corresponding acceleration, as well as from the level of the acceleration value and the course of the collision curve.
  • this known acceleration sensor provides a sufficiently long switching time with very high delays with a correspondingly large overall length, the switching time can be undesirably short, especially in the case of flat collision curves which just exceed the threshold values, so that the disadvantages mentioned above are not sufficient here either long switching time occur.
  • this object is achieved according to the invention in that at least one delay measure is provided which delays the movement of the magnet at least after the switch has been actuated.
  • the object underlying the invention is completely achieved in this way. Because the movement of the magnet is delayed by the delay measure at least after the switch is actuated, a degressive effect is exerted on the movement of the magnet, which leads to longer closing times. Times. Retarding the magnet after the switch has been actuated results in a closing time that is largely independent of the course of the collision curve.
  • a rotational movement is superimposed on the magnet at least during a portion of its movement caused by acceleration of the acceleration sensor.
  • This measure is structurally advantageous because the rotational movement superimposed on the flight movement of the magnet increases the effective mass of the magnet, so to speak, the system becomes "sluggish" after the switch has been actuated.
  • the inertial mass influences the restoring time for the magnet via the restoring force of the restoring element, so that when the inertial mass is increased, the restoring time is also increased compared to a magnet not superimposed by a rotary movement.
  • a guide for the movement of the magnet is provided as a delay measure, which is designed in such a way that the magnet travels an entire distance from its rest position to its end position assumed with corresponding acceleration, which is shorter than its return path from the end position to the Rest position.
  • This measure has a purely constructive advantage, because in this way the rotational movement or the extended return path are always observed. Regardless of whether the acceleration hits the sensor axially or transversely, the magnet executes its intended movement. This measure thus increases in particular the intrinsic safety of the acceleration sensor according to the invention.
  • the magnet is an annular magnet which is arranged displaceably on a sliding tube surrounding the switch.
  • the ring magnet is in fact guided on the sliding tube without jamming, while on the other hand the switch itself is arranged in a protected manner in the sliding tube. It is further preferred if the sliding tube has a guide groove in which a guide pin connected to the magnet engages.
  • the guide groove has a section which runs in the longitudinal direction of the sliding tube in a spiral in its surface.
  • This measure is also structurally advantageous, because during a section of the guide groove, a rotary movement is superimposed on the magnet.
  • the spiral-shaped section of the guide groove will be aligned with the switch such that the magnet has already actuated the switch when it reaches this section with its guide pin.
  • the guide groove has a section which runs in a straight line in the longitudinal direction of the sliding tube and parallel to the longitudinal direction.
  • the advantage here is that the magnet can initially "fly" very quickly in a straight line to the switching position before it changes into a curved section in which the deceleration measures take effect.
  • the magnet is the switch actuated before the guide pin leaves the straight section.
  • This measure has the advantage that, depending on the amount of acceleration or deceleration, the magnet moves more or less far along the rectilinear section which, depending on the force of the restoring element, is designed such that the guide pin reaches the end of the rectilinear section then reached when the predetermined acceleration threshold value is reached. If this threshold value is exceeded, the switch is actuated and either a rotary movement and / or the extended feedback takes effect on the magnet via the guide pin and the guide groove.
  • the restoring element is a compression spring.
  • the compression spring is connected at one end in a rotationally fixed manner to the magnet and at the other end in a rotationally fixed manner to a housing part of the acceleration sensor.
  • the compression spring also acts as a torsion spring and thus exerts a rotational force on the magnet during its longitudinal movement.
  • This torque can either be by itself or that of the guide groove and guide pin support the rotational movement exercised.
  • the guide groove describes a kind of heart curve on the unwound sliding tube.
  • This measure advantageously combines the advantages of the superimposed rotary movement on the one hand and the extended return path on the other. While the guide pin is guided in a straight line on the way to the end position, on the way back it runs through the two oppositely curved regions of the heart curve, which additionally causes a reversal of the direction of rotation.
  • the switch is a reed switch.
  • This measure is advantageous in that reed switches, which have a protective gas contact in a known manner, are very low-maintenance, which also increases the intrinsic safety of the new acceleration sensor.
  • FIG. 1 shows a schematic side view of the acceleration sensor according to the invention with a cut ring magnet
  • FIG. 2 in a greatly simplified schematic representation different operating states of the acceleration sensor according to Fig. 1, in a side view;
  • Fig. 3 in a schematic representation of the time
  • FIG. 4 shows the trajectory of the guide pin of the acceleration sensor from FIG. 1 in cylindrical coordinates
  • FIG. 5 shows in diagram form the course of the restoring force acting on the magnet of the acceleration sensor from FIG. 1 as a function of the deflection
  • FIG. 6 in a representation like Fig. 4 a heart-shaped
  • an acceleration sensor denotes how it is used to detect when a predetermined acceleration threshold value has been exceeded.
  • a preferred example of application of the acceleration sensors is occupant safety systems of motor vehicles, for example airbag systems or belt tensioner systems. In these systems, it is important to recognize the state of a rear-end collision with the shortest possible dead time, in which the motor vehicle is suddenly subjected to a very high deceleration, and the exceeding of a (negative) acceleration threshold value is to be detected in order to activate occupant safety systems . In these cases, propellant charges are usually ignited, which either inflate an airbag (airbag) or fasten the seat belts so that the passengers are held in their seats.
  • airbag airbag
  • the acceleration sensor 10 comprises a housing part 11 on which a sliding tube 12 with a cylindrical surface 13 is arranged.
  • the sliding tube 12 extends from a holding plate 14 of the housing part 11 approximately centrally in its longitudinal direction.
  • annular magnet 15 Arranged on the sliding tube 12 is an annular magnet 15, shown in section, with an inner ring 16, which is also shown in section and pressed into the magnet 15.
  • the magnet 15 is displaceably arranged on the sliding tube 12 by means of the inner ring 16 via a sliding fit.
  • a guide pin 17 Provided on the inner ring 16 is a guide pin 17, likewise shown in section, which faces the sliding tube 12 and engages in a guide groove 18 which is introduced into the cylindrical surface 13 of the sliding tube 12.
  • the guide groove 18 runs spirally on the surface 13 of the sliding tube 12 and together with the guide pin 17 is a positive guide for the magnet 15.
  • a restoring element 20 in the form of a compression spring 21 is also pushed over the sliding tube 12, which is supported at one end on the holding plate 14 and at the other end on the ring magnet 15 or the inner ring 16. Due to the action of the compression spring 21, the magnet 15 is thus pressed against stops 22, which are also connected to the housing part 11.
  • the arrangement is such that the magnet 15 executes a movement along the sliding tube, which is predetermined by the path curve of the guide groove, when the mass is accelerated as an inert mass.
  • the ring-shaped magnet 15 serves to actuate a magnetically actuable electrical switch 23 which is arranged in the sliding tube 12 and can therefore only be seen in broken lines in FIG. 1.
  • the protective gas contacts there would also be other magnetically controllable contacts, e.g. contact springs or magnetically influenceable resistors are possible in an air atmosphere.
  • FIG. 1 a protective cover that can possibly be slid over the housing part 11 is not shown in FIG. 1.
  • the longitudinal direction of the switch 23 is indicated in FIG. 1 at 26, which coincides with the longitudinal direction of the magnet 15 and the sliding tube 12; at least sliding tube 12 and Magnet 15 are also arranged coaxially to one another.
  • the magnet 15 While the magnet 15 is in its resting position Z 0 indicated at 30, for example when the acceleration sensor 10 is at rest, when the acceleration is present it moves in the direction of the arrow 27 initially to a switching point Z. indicated at 31, at which it switches over the contacts in this way of the reed switch 24 has come to switch them. Finally, the magnet 15 moves along the guide groove 18 until it reaches its end position Z e indicated at 32.
  • the trajectory runs in a straight line and parallel to the main axis (longitudinal direction 26) of the sliding tube 12, as shown in FIG. 2b by a straight trajectory segment 33.
  • the path curve is curved or curvilinear, that is to say it is composed of path elements which run at a certain angle to the longitudinal direction 26 of the sliding tube 12. This is indicated in FIG. 2c by a curved line segment 34.
  • the magnet 15 When the magnet 15 has reached its end position 32 (Z e ), it remains in this position until the acceleration exerted on the acceleration sensor 10 has fallen below the acceleration threshold value again. Then the magnet 15 is first pushed back to the switching point 31 (Z) by the compression spring 21, which is not shown in FIG. 2 for the sake of clarity, in the direction of the arrow 28 ', whereby it carries out a rotating movement 36 opposite the rotating movement 35.
  • the magnet 15 has the switching point 31 (ZJ reached again, the reed switch opens again, while the magnet 15 moves along the straight trajectory segment 33 into its rest position Z 0 .
  • FIG. 3 shows the relationship between a typical collision curve 37 and the closing behavior 38 of the reed switch 24.
  • a (t) describes the time course of the acceleration or deceleration acting on the acceleration sensor 10 from the outside. If a (t) is greater than a dynamic switching threshold a p , the reed switch closes, since the magnet 15 has then moved to the switching point Z t .
  • the collision curve 37 has reached the acceleration threshold a p and the reed switch 24 closes and remains in this state during a closing period t B , as shown in FIG. 3 below.
  • the closing time t s is additively composed of the proportions t c and t r .
  • t c is the so-called collision time in which the magnet moves to its end position 32 (Z e ) with a sufficiently large acceleration amplitude, as shown in FIG. 2c.
  • the return movement of the magnet 15 begins when a (t) falls below a p .
  • the magnet 15 is returned by the resetting force of the spring 21 from the end position 32 via the curvilinear curve segment 34 to the switching point 31.
  • the reset time t r is largely independent of the collision curve 37 and is primarily determined by the retardation, ie by the deceleration measures acting on the magnet 15.
  • the total closing time t s is mainly determined by the reset time t r .
  • the reed is therefore independent of the time course of the collision curve 37.
  • Switch 24 is always closed for a sufficient length of time - namely at least during the reset time t r - so that the occupant safety systems can start safely.
  • the second term is the potential energy of the spring-mass system with the spring constant K at a deflection z.
  • FIG. 4 shows the path curve of the guide pin 17 developed in the (z, r - f) plane on the surface 13 of the sliding tube 12.
  • the path curve 39 is composed of the straight path curve segment 33 and the spiral path curve segment 34, which also represents a straight line due to the development in FIG. 4.
  • the path curve 39 is composed of the straight path curve segment 33 and the spiral path curve segment 34, which also represents a straight line due to the development in FIG. 4.
  • r B the radius of curvature
  • FIG. 5 shows the course of the restoring force F R acting on the magnet 15 as a function of the deflection z.
  • the restoring force F R is determined by the spring characteristic of the compression spring 21 shown at 43.
  • the progression of the spring characteristic 43 is weakened by a declining contribution of the positively guided rotary movement, indicated at 44, by the factor:
  • the closing time t s can thus be set to desired values according to the collision curves a (t) by means of the path curve parameters r and a mentioned.
  • the friction forces occurring in the spring-mass system must also be taken into account.
  • ⁇ , and ⁇ 2 are material-specific coefficients of friction, ⁇ i determines the sliding friction between the inner ring and the sliding tube and ⁇ 2 the rotational friction at the spring end.
  • the spring radius r F is also included in the calculation of the limit value ⁇ 0 .
  • the compression spring 21 also acts as a torsion spring, which also acts as a deceleration measure.
  • the spring ends are namely fastened in such a way that the Three-phase voltage counteracts the compressive stress.
  • This is achieved in that the prestressing angle is opposite to the rotational angle direction forced by the path curve.
  • this means that the magnet 15 is rotated by the rotary action of the compression spring 21 in the direction of the arrow 35 shown in Fig.2b.
  • the maximum deflection of the magnet 15 up to the end position 32 (Z e ) is reached even at relatively low acceleration values a (t), so that the retardation becomes fully effective.
  • the compression spring 21, which additionally acts as a torsion spring is inevitably "pulled up” again during the return movement of the magnet 15 (see FIG. 2c), namely in the direction of the arrow 36 from FIG.
  • the trajectory 39 is designed such that the rotary movement of the ring magnet is only forced beyond the switching point Z a .
  • the slope angle of the trajectory 39 is thus 90 ° in the interval (Z 0 , Z A ) - see trajectory segment 33 in FIG. 4 -, while in the curve interval (Z a , Z ⁇ ) it is greater than ⁇ 0 and less than 90 ° .
  • Fig. 6 is a representation of a guide 50 in cylindrical coordinates, i.e. the sliding tube 12 is shown unwound.
  • the guide 50 has the shape of a heart curve 51, the direction of movement of the guide pin 17 in the guide 50 is indicated by arrows at 52.
  • the magnet 15 moves in a straight line during the outward movement from the rest position Z 0 via the switching point Z a to the end position Z e .
  • the guide pin 17 and thus the magnet 15 follow the two oppositely curved path curve sections of the heart curve 51, so that a change in direction of rotation is additionally forced.
  • These two path curve sections, designated 55 and 56 in FIG. 6a) are designed as spiral curves.
  • a simplified parameter representation of the heart curve 51 is indicated in FIG. 6b) by the sections 55 'and 56'.
  • the transition from section 55 'to section 56' is again realized by a curvature with the radius of curvature r b in order to prevent the guide pin 17 from jamming. prevent.
  • this delay measure increases the reset time t r , since the return path 54 is longer than the outward path 53.
  • the sequence of movements is such that the guide pin 17 initially runs in a straight line over the switching point Z a with sufficient acceleration and stops at a stop point labeled 58.
  • the compression spring 21 presses the guide pin 17 in Fig. 6a) down so that it abuts a triangle labeled 59, which is a kind of switch, so that the pin 17 the extended return path 54 over the curve sections 55, 56 takes.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Switches Operated By Changes In Physical Conditions (AREA)

Abstract

Un détecteur d'accéleration (10), notamment pour systèmes de sécurité de véhicules à moteur, comprend un commutateur électrique (23) à commande magnétique et un aimant (15) d'actionnement du commutateur qui se déplace contre la force d'un élément de rappel (20). L'aimant (15) se déplace à la manière d'une masse sismique lorsqu'une valeur limite d'accélération est dépassée, actionnant ainsi le commutateur (23). Dans ce détecteur d'accélération (10), au moins une mesure est prise pour retarder le déplacement de l'aimant (15) au moins après l'actionnement du commutateur (23).
PCT/DE1992/000959 1992-11-17 1992-11-17 Detecteur d'acceleration WO1994011741A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/DE1992/000959 WO1994011741A1 (fr) 1992-11-17 1992-11-17 Detecteur d'acceleration

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/DE1992/000959 WO1994011741A1 (fr) 1992-11-17 1992-11-17 Detecteur d'acceleration

Publications (1)

Publication Number Publication Date
WO1994011741A1 true WO1994011741A1 (fr) 1994-05-26

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ID=6875444

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/DE1992/000959 WO1994011741A1 (fr) 1992-11-17 1992-11-17 Detecteur d'acceleration

Country Status (1)

Country Link
WO (1) WO1994011741A1 (fr)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2746985A1 (de) * 1976-10-20 1978-04-27 Hitachi Ltd Aufprall-fuehler
FR2366683A1 (fr) * 1976-10-02 1978-04-28 Daimler Benz Ag Capteur electrique a commande magnetique
DE3830782C1 (fr) * 1988-09-09 1990-06-07 Audi Ag, 8070 Ingolstadt, De

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2366683A1 (fr) * 1976-10-02 1978-04-28 Daimler Benz Ag Capteur electrique a commande magnetique
DE2746985A1 (de) * 1976-10-20 1978-04-27 Hitachi Ltd Aufprall-fuehler
DE3830782C1 (fr) * 1988-09-09 1990-06-07 Audi Ag, 8070 Ingolstadt, De

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