IE904185A1

IE904185A1 - Acceleration sensor

Info

Publication number: IE904185A1
Application number: IE418590A
Authority: IE
Inventors: Gernot Hilger; Mechtilde Schmid; Hartmut Schultze
Original assignee: Mannesmann Kienzle Gmbh
Priority date: 1989-11-21
Filing date: 1990-11-20
Publication date: 1991-05-22
Also published as: DE59009091D1; JPH0645897Y2; ATE122792T1; DE3938601A1; JPH0488862U; PT95936B; IE71163B1; EP0428952A1; PT95936A; EP0428952B1

Abstract

Proposed for an accelerometer having a spring-mass system and a measuring transducer and consisting of a strip of amorphous metal and a coil arrangement assigned thereto is a design which has a high transverse stability, allows the overall space to be greatly compressed and, if required, enables machine assembly and rapid adjustment in conjunction with good reproducibility in mass production. In detail, apart from a screen (90, 91) assigned to the accelerometer (50) there are assigned to a seismic mass (81, 82), to which one end of the strip (68) is attached, two diaphragm springs (56, 59) which are supported by a supporting sleeve (51). It is possible to attach, by means of hot upsetting, to the latter at the face at one end a base part (58), and at the other end a carrier (60) for the coil arrangement (62) and the bearing for a winding mandrel (70), which serves for fastening the other end of the strip (68), as well as a cover (61), which exercises a braking function for the winding mandrel (70) and is provided with a socket (75). <IMAGE>

Description

Acceleration Transducer The invention concerns an acceleration transducer having a spring-massassembly, a coil arrangement, and a strip-form measuring member of amorphous, magneto-elastic metal which is electro-magnetically coupled with the coil arrangement and is secured on the one hand to the spring-mass assembly and on the other hand to a component of the acceleration transducer which is stationary relative to the spring-mass assembly.

Acceleration or force transducers of this kind, which operate in accordance with the electro-magnetic principle, are especially suited to employment in a rough environment, for instance in a motor vehicle, because the actual measuring element of amorphous metal, a strip-form measuring member described in the following text as a strip, distinguishes itself by being particularly corrosion-resistant and resistant to load reversal, because the measuring system formed by the strip has high sensitivity, and because an acceleration transducer thus equipped is, in principle, easily adjustable. Another reason why the strip made of amorphous metal is especially suited to acceleration transducers is that the strip can be made extremely thin, 20 to 30 pm, therefore of very low mass, which lends the acceleration transducer a particularly well-defined directionality. This quality is particularly advantageous for use in a motor vehicle, where a high level of mechanical interference prevails.

When acceleration transducers are used in the motor vehicle to gather accident data or to produce information for the driver about driving errors or dangerous driving situations, then several acceleration transducers are required for positive, objective recognition of such driving situations, which report on the accelerations for instance in the longitudinal, transverse and vertical axes of the vehicle, i.e. as elements of a data gathering concept, such acceleration transducers must be producible economically despite high precision, i.e. their production must accord with the conditions of mass production, which la•Ε 904185 means the simplest possible components and, if possible, automated assembly.

It is an object of the present invention to provide an architecture for an acceleration transducer through which the advantages of the strip-form measuring member are optimally usable and the sensitivity in respect of the effect of lateral forces is substantially reduced, and which is capable of being mass produced.

The solution to this problem envisages that the spring-mass-assembly is formed of at least one diaphragm spring and a mass centrally secured to this spring, and that a carrier is provided on which are formed means both for receiving the coil arrangement and for mounting the spring-mass assembly, as well as for securing one end of the strip.

A preferred embodiment is characterised by two diaphragm springs being provided for the formation of the spring-mass-assembly, by the diaphragm springs being secured parallel to one another to a mass, by a supporting sleeve being provided, the length of which corresponds to the spacing between the diaphragm springs and the outer diameter of which substantially corresponds to the diaphragm diameter, further by the mass having a central cutaway region which is larger than the outer contours of the coil arrangement, by the diaphragm springs being annularly shaped, and by the supporting sleeve being associated with the carrier, on which the coil arrangement is self-supportingly disposed, in such a manner that the mass at least partially surrounds the coil arrangement.

The solution found offers, particularly for the use of a strip-shaped measuring member, optimized formation and mounting which avoids the effect of tilting moments and has a high transverse stability.

It is further advantageous that the essential components of the acceleration transducer can be assembled in one direction so to speak, resulting in a self-effecting centering and aligning of the strip in relation to the attachment points and to the relatively small slit provided in the coil arrangement, in which the strip must be positioned without touching anything. The constructional form of the acceleration - 2 IE 904185 transducer according to the invention also offers good reproducibility and the possibility of mechanizing the assembly, i.e. no securing elements assigned exclusively to the coil arrangement and/or to the spring-mass-assembly are employed, the number of components is greatly reduced, and components of complex construction are avoided. Further, the components are formed in such a manner that they can be connected where possible in a plug-like fashion and their cumulative tolerances, for instance arising from use of a carrier with which are associated the spring-mass assembly, the coil arrangement and means for securing the one end of the strip, are avoided.

An especially advantageous constructional form, which facilitates the greatest possible degree of spatial compactness and thus a smaller overall height, is represented by a coaxial assembly of the coil arrangement and the spring-mass-assembly. In this constructional form, the supporting sleeve forms both a load-bearing component as well as an enclosing part to which the remaining assemblies and components are secured independently of each other, and, in this manner, the assembly tolerances are kept as low as possible.

In this constructional form, it is further of advantage to use only one connection technique, namely hot-upsetting or welding, for the mutual connection of the individual components and assemblies, as well as for securing the winding spindle which can be turned initially after assembly.

A further advantage offered by the solution found is that even after securing the base portion, a mechanical adjustment of the acceleration transducer can be effected, in the form of a displacement measurement, by the winding spindle being still freely accessible in this assembly state and by the position of the spring-mass-assembly being ascertainable on the opposite side by means of a suitable feeler through a bore located in the base portion.

The invention will now be explained in more detail with reference to the accompanying drawings.

FIGURE 1 is a longitudinal section of a first embodiment of an - 3 IE 904185 acceleration transducer, FIGURE 2 is a longitudinal section of a second embodiment of an acceleration transducer, FIGURE 3 is a a partially sectioned front view of the second embodiment of the acceleration transducer, according to the direction of the arrow in FIGURE 2, FIGURE 4 is a view of a diaphragm spring of the spring-mass-assembly, FIGURE 5 shows views of individual components and assemblies of the acceleration transducer according to FIGURES 2 and 3, arranged adjacent to one another and ready for assembly.

As shown in FIGURE 1, the first embodiment of an acceleration transducer 10 according to the invention has a carrier 11 which at the same time functions as a housing and is preferably made of a magnetically highly conductive metal, for instance mu-metal. The carrier 11 is provided with a stepped opening 12 which has an opening section 13 of larger diameter and an opening section 14 of smaller diameter, as well as an annular shoulder 15 which connects the two opening sections 13 and 14.

In the opening section 14, a coil assembly 16 is accommodated, which consists of a centering disc 17, a supporting flange 18 and a flat coil 20 formed with a relatively narrow airgap 19 and glued between the centering disc 17 and the supporting flange 18. A pin 21, secured to the carrier 11 engages in a slot 22 formed in the supporting flange 18 and serves to prevent rotation of the coil assembly 16. One of several contact pins associated with the flat coil 20 and secured in the centering disc 17 is designated by 23.

The longitudinal section in FIGURE 1 further illustrates that a spring-mass-assembly 24, consisting of two diaphragm springs 25 and 26, a supporting sleeve 27 and a mass 28, is centered in the opening section 13. Teeth, which grip the diaphragm spring 26, or at least one spigot and socket connection, neither of which are illustrated, are provided between the mass 28 and the diaphragm spring 26, which is non-rotatably received on a non-circular extension or spigot 29, formed at the front end of the mass 28, as well as between the supporting sleeve 27 and the supporting flange 18 of the coil assembly 16. An - 4 IE 904185 exact positional alignment between the coil assembly 16 and the mass 28 is thus achieved, which is essential for a friction free arrangement of the strip 30 in the coil 20.

The second diaphragm spring 25, which is subject to tensile stress when the acceleration transducer 10 is operating, i.e. when the strip 30 is subjected to tensile stress, must be securely connected to the mass 28. To this end, a threaded connection 31 is illustrated in FIGURE 1, as being representative of various other connecting arrangements.

The attachment of the spring-mass-assembly 24 to the carrier 11 is effected indirectly by means of a base portion 32 in which a recess 33 is formed, which serves for centering the base portion 32 on the supporting ring 27 accommodated in the carrier 11. A threaded extension 34, formed likewise on the base portion 32, is provided for attaching the acceleration transducer 10 to a chassis portion of a vehicle, for instance. When attaching the base portion 32 to the carrier 11 several screws are provided for this purpose, of which two, 35 and 36, are illustrated in FIGURE 1 - the shoulder 15 serves as a stop for both the coil assembly 16 and the spring-mass-assembly 24. An opening 37, provided in the base portion 32, facilitates insertion of a feeler to ascertain the position of the spring-mass-assembly 24 and facilitates mechanical adjustment based on displacement measurement.

The mounting of the strip 30 is effected by multi-layer winding of the ends of the strip around respective winding spindles, one - 38 - of which is journalled in the mass 28 and the other - 39 - in the carrier 11. The bearing mountings of the winding spindles 38 and 39, not dealt with here in greater detail, each have a slit 40 or 41 and a screw-type clamping arrangement 42 or 43, which serve to hold the winding spindles 38 and 39 in a locked condition. The inwardly-located end of each band winding merely requires an attachment arrangement indicated by the illustrated slit-screw-connections 44 and 45.

A magnetically protective hood, designated by 46, covers both the opening 12 and an access opening provided for the operation of the winding spindle 39. Upon insertion of an insulating part 47, only the - 5 IE 904185 plug pins 23 extend from the hood 46. A plug, which projects into the opening 12, can suitably be formed on the hood 46.

The second embodiment of an acceleration transducer 50, which is optimal in terms of operating and manufacture, has, according to the sectional representation of FIGURE 2, a housing 51, with several spigots 52, 53, 54, 55 formed directly on its end faces. A first series of spigots, of which two, 52 and 53, are illustrated in FIGURE 2, serves on the one hand to hold the first diaphragm spring 56 of the spring-mass-assembly 57 and on the other hand to secure a base portion by rivet heads being formed by means of hot-upsetting on the spigots 52 and 53 gripping the base portion 58.

A second series of spigots with unequal spacing, one of which is designated by 54, and a third series of spigots, one of which is representatively designated by 55, formed on the same end face of the housing 51 serve on the one hand to retain the other diaphragm spring and on the other hand for an arrangement which is free from play for securing the spring-mass-assembly 57 to a carrier 60 and for securing a cover 61 associated with carrier 60 to the carrier 60, also by means of hot-upsetting in the manner previously described.

In this embodiment, the carrier 60 is formed in such a manner that a coaxial arrangement of spring-mass-assembly 57 and coil assembly 62 can be achieved with an especially small overall height. I.e., on the flange-shaped carrier 60, an extension 63 with a receiving spigot 64 is formed, onto which a flat coil 65 is directly floatingly formed, which, depending on the intended measurement process, can consist of one or more windings.

The coil assembly 62 is formed with a relatively narrow airgap 66, which is aligned with a slit 67 in the carrier 60 and serves for the frictionless passage of the strip 68 functioning as a measuring member, the width of the slit 67, in the embodiment to be described, being formed to be of the order of 5mm, and the particularly sensitive dimension, namely the height of the gap, being in the lower tenth-of-a-millimeter region. - 6 IE 904185 Further, a dish-shaped bearing 69 is formed on the carrier 60 for a winding spindle 70 which receives one end of the strip. Several contact elements, one of which is designated by 71, associated with the flat coil 65, are also embedded in the carrier 60. Tongues 72 formed on the contact elements 71 serve for attaching the ends of the winding wires 73, while pins 74, also formed on the contact elements 71, are associated with a plug which is to be attached to the acceleration transducer 50 from the outside and not illustrated. The plug recess is formed in the cover 61 and is designated by 75. The guiding and holding role of the plug recess 75 is strengthened by tongues 76 and 77 (FIGURE 3), also formed directly on the cover 61, and by a spring latch 78. Further, a dish-shaped bearing 79 associated with the bearing 69 is formed in the cover 61. The measurements between the winding spindle 70 and the bearing 69 are chosen in such a manner that upon connecting the cover 61 to the housing 51 and the carrier 60, for which a spigot 80 formed on the carrier 60 is used, tightening of the winding spindle 70 is effected, and thus, by turning the winding spindle 70, a friction effect is created for tensioning the strip 68.

As previously described, the diaphragm springs 56 and 59 are secured on their outer edges and in parallel alignment by spigots 52, 53, and also 54, 55, which are formed on the end faces of the housing 51. A holder 81 which is connected to both diaphragm springs 56 and 59 is used on the one hand to receive the seismic mass 82 and on the other hand for the winding member 83 associated with the other end of the strip. This winding member 83 has a cylindrical section 84 and end cheeks, one of which is designated by 85 in FIGURE 2. To secure the winding member 83, a suitable link 86 is formed in the holder 81, in which the winding member 83 is secured while under the effect of the tensile stress of the strip 68. A resilient clamping member, designated by 87, acts on the strip winding, which is wrapped in multi-layer manner around the cylindrical section 84 of the winding member 83 after insertion of the winding member 83 into the holder 81, thus preventing the strip winding from jumping out.

As can also be seen from FIGURE 2, the holder 81 is provided with a central cutaway portion 88, which facilitates a coaxial arrangement of spring-mass-assembly 51 and coil assembly 62. - 7 IE 904185 It may also be mentioned that the cylindrical section 84 of the winding member 83 and the cylindrical section 89 of the winding spindle 70 are formed in two parts. The two parts are connected to one another by means of film hinges, and serrations, not shown individually, are formed on the surfaces facing towards one another to ensure that the ends of the strips are securely attached. A hood-shaped case designated by 90 made of magnetically highly-conductive material, for instance of mu-metal, is used for magnetic shielding. The hood-shaped case 90 is flanged to the base portion 58 and a plate 91 which is also made of magnetically highly-conductive material is placed between them, while the case 90 also has an opening 92 through which the plug holder 75 is accessible.

The layered section of the acceleration transducer 50 according to FIGURE 3 illustrates frontal partial views of the hood-shaped case 90, the cover 61, the carrier 60 with the winding spindle 70 positioned in the dished bearing 69, and the diaphragm spring 59.

As can be seen from FIGURE 3, the winding spindle 70 is provided with transverse slots 93 in its end faces, so that it can be used to tighten the strip 68. The transverse slots 93 are accessible through an opening - in FIGURE 3 half of the opening formed in the carrier 60 is designated by 94 - the diameter of the openings being smaller than the diameter of the winding spindle 70. In this way, the winding spindle 70 journalled in the dished bearings 69 and 79 is also secured in an axial direction.

A view of the diaphragm spring 56 is shown in FIGURE 4. In its outer circumferential region, it has apertures 95 which are associated with the spigots 52, 53 of the housing 51. Further, slit-shaped openings 96, 97 are provided, which are staggered in the circumferential direction.

A central cutaway region, designated by 98, is used for reception of the diaphragm spring 56 on a shaped portion 99 (FIGURE 2) formed on the holder 81, which corresponds to the cutaway 98. Holes 100 and 101, provided for the connection to the holder 81, facilitate a hot-upsetting connection, together with the spigots formed on the holder 81. The diaphragm spring 59 is connected in a similar manner to the holder 81, but is provided with a differently formed central - 8 IE 904185 cutaway portion, apart from the hole spacing on the outer edge, as a result of the flat cross-section of the coil 65. It is obviously also possible to form the slit-shaped openings 96, 97 in another manner, for instance in an arc-shaped manner.

FIGURE 5 illustrates the components and assemblies of the preferred acceleration transducer 50 laid out for assembly. Proceeding from the situation illustrated in FIGURE 5, the first step in the assembly of the acceleration transducer 50 is, preferably, to connect the pre-assembled spring-mass-assembly 57 to the assembly consisting of the carrier 60 and the coil arrangement 62. The unequal spacing of the spigots 54, which is critical for a positive mutual alignment of the airgap 66 and the winding member 83, allows only one relative disposition of the two assemblies. Following this, the free end of the strip 68 wound around the winding member 83 is threaded through the slit 66, 67, and the winding member 83 is loosely inserted into the portion 86 of the holder 81 for the spring-mass-assembly 57. The next step is that the end of the strip projecting out of the carrier 60 is attached to the winding spindle 70 and wound up, and the winding spindle 70 is inserted into the dished bearing 69 provided in the carrier 60. The placing and securing of the cover 61 follows, thus completing the positioning of the winding spindle 70 and the plug connection. In order to secure the diaphragm spring 56 before tightening the strip 68, the base portion 58 is then flanged onto the spring-mass-assembly 57 and is secured by hot-upsetting the spigots 52, 53. In the following tightening of the strip 68 by rotating the winding spindle 70, the diaphragm springs 56 and 59 are distorted in an axial direction. The adjustment of the requisite tensile stress and therefore of the position of the operating point of the acceleration transducer 50 is effected by measuring the electro-magnetic properties of the coil arrangement 62 and the measuring member (strip 68) and/or by mechanically checking the position of the diaphragm spring 56, this being accessible through a suitable opening in the base portion 58. Following adjustment of the pre-stressing of the strip 68, the winding spindle 70 and the cover 61, which serves as a brake during tensioning, are welded together, the transducer is inserted into the case 90, and the case 90 is flanged to the plate 91 on the base portion 58. - 9 IE 904185 Attachment of the acceleration transducer 50, for instance to the chassis wail of a vehicle - the space requirements of the acceleration transducer 50 amount to 7 cm - can be done, without problems, by gluing, the acceleration transducer being either flanged on at one end or inserted into a suitable opening. It is further possible to eliminate the plug holder 75 by the acceleration transducer 50 being mounted directly on a printed circuit board, which carries the requisite electronics for signal processing.

Claims

Claims :

1. An acceleration transducer having a spring-mass-assembly, a coil arrangement and a strip-form measuring member made of amorphous, magneto-elastic metal, which is electromagnetically coupled with the coil arrangement and is secured, on the one hand, to the spring-massassembly, and on the other hand, to a component of the acceleration transducer which is stationary in relation to the spring-mass-assembly, characterised in that the spring-mass-assembly (24 or 57) is formed of at least one diaphragm spring and a mass (28 or 81, 82) which is centrally mounted on this, and that a carrier (11 or 60) is provided, on which means are formed both for reception of the coil arrangement (16 or 62) and for retention of the spring-mass-assembly (24 or 57) as well as for securing one end of the strip (30 or 68).

2. An acceleration transducer according to claim 1, characterised in that a stepped opening (12) is provided in the carrier (11) and that the opening section (13) of larger diameter and the annular shoulder (15) between the two opening sections (13, 14) form a region for accommodating the spring-mass-assembly (24).

3. An acceleration transducer according to claim 2, characterised in that a base portion (31) which can be connected to the carrier (11) is provided and that means for securing the acceleration transducer (10) are formed on the base portion (32) and that the base portion (32) is formed as a securing element associated with the spring-massassembly (24).

4. An acceleration transducer according to claim 1, characterised in that a substantially flat disc is provided as the diaphragm spring (for example 56), in which slit-shaped openings (96, 97) are formed.

5. An acceleration transducer according to claim 1, characterised in that the diaphragm spring is formed as a point-symmetrical wavy disc.

6. An acceleration transducer according to claim 2, characterised in that the coil arrangement is introduced from one one side into the opening (14) of lesser diameter and has a flange (18) which has a diameter equal to that of the opening section (13) of greater diameter.

7. An acceleration transducer according to claim 1, characterised in that positioning means are provided between the carrier (11) and the coil arrangement (16) and between the coil arrangement (16 ) and the spring-mass-assembly (24).

8. An acceleration transducer according to claim 1, characterised in that a winding spindle (39) is provided on the carrier (11) for securing the one end of the strip and that a hole for placement of the winding spindle (39) is formed in the carrier (11) transverse to the opening section (14) of smaller diameter.

9. An acceleration transducer according to claim 1, characterised in that the coil arrangement (62) is formed by at least one coil (65) wound directly onto a receiving spigot (64) formed on the carrier (60).

10. An acceleration transducer according to claim 1, characterised in that two diaphragm springs (25,26 or 56,59) are provided for the formation of the spring-mass assembly (24 or 57), that the diaphragm springs (15, 26 or 56, 59) are secured parallel to each other to a mass (28 or 81, 82), and that a supporting sleeve (27 or 51) is provided, the length of which corresponds to the spacing of the diaphragm springs (25, 26 or 56, 59) and the outer diameter of which substantially corresponds to the diameter of the diaphragm spring.

11. An acceleration transducer according to claim 10, characterised in that spigots (52,53,54,55) are formed on end faces of the supporting sleeve (51) and that openings associated with the spigots (52,53,54,55) are formed in the diaphragm springs (56,59), in the carrier (60) and in the base portion (58) closing off the acceleration transducer (50) on the other side of the carrier (60).

12. An acceleration transducer according to claim 11, characterised in that the openings in the carrier and in the base portion are formed as through holes and that the mutual connection of the spring-massassembly (57), of the carrier (60) and of the base portion (58) is effected by hot-upsetting of the spigots (52,53,54,55) which engage in - 12 IE 904185 the through holes.

13. An acceleration transducer according to claim 1, characterised in that a winding spindle (70) is provided for securing the end of the strip on the carrier (60), that a first dished bearing (69) associated with the winding spindle (70) is formed on the carrier (60), and that a cover (61) is provided, which has a second dished bearing (79) and has means for securing the acceleration transducer (50) to a static component.

14. An acceleration transducer according to claim 13, characterised in that the carrier (60) and the cover (61) are connected to the supporting sleeve (51) on the same end face of the supporting sleeve (51).

15. An acceleration transducer according to claim 13, characterised in that a plug holder (75) is formed in the cover (61).

16. An acceleration transducer according to claim 10, characterised in that the mass (81,82) has a central cutaway region (88) which is larger than the outer contours of the coil arrangement (62), and that the supporting sleeve (51) is disposed on the carrier (60), on which the coil arrangement (62) is self-supportingly formed, in such a manner that the mass (81,82) suspended on the diaphragm springs (56,59) at least partially embraces the coil arrangement (62).

17. An acceleration transducer according to claim 1, characterised in that a hood-shaped housing (90) combined with an end plate (91), of magnetically highly conductive material, is provided and is secured to a base portion (58) of the acceleration transducer (50).

18. An acceleration transducer substantially as described herein with reference to and as shown in Figure 1 or Figures 2 to 5 of the accompanying drawings.