IE902903A1

IE902903A1 - Transducer for measuring mechanical forces

Info

Publication number: IE902903A1
Application number: IE290390A
Authority: IE
Original assignee: Mannesmann Kienzle Gmbh
Priority date: 1989-08-11
Filing date: 1990-08-10
Publication date: 1991-02-27
Also published as: EP0412304B1; DD297242A5; PT8413U; EP0412304A3; DE8909652U1; DE59004990D1; JPH0336937U; ATE103067T1; PT8413T; EP0412304A2

Abstract

For a transducer for measuring mechanical forces by means of a preferably strip-shaped measuring body made of amorphous, magneto-elastic metal, an absolutely creep-proof and high-duty attachment of the ends of the measuring body is proposed. In particular, provision is made for fixing (screw 30) at least one end of the measuring body (17) to a winding mandrel (21), for winding several layers on the winding mandrel (21) rotatably mounted in the transducer (1), and then for locking the winding mandrel (21) against rotation. <IMAGE>

Description

The invention concerns a transducer for measuring mechanical forces comprising a measuring body of amorphous magnetically elastic metal, having a very small cross-section to length ratio which is electromagnetical ly coupled with a coil arrangement and is disposed under pre-stressing between mounting points of the transducer which are displaceable relative to one another.

It is know to use magnetic-elastic effects for measuring mechanical forces, preferably because sensors of this kind are on the one hand comparatively sensitive and provide correspondingly large measuring signals, and on the other hand are easy to manufacture and in particular are usable where adverse operational conditions prevail.

However, substantial disadvantages, such as susceptability to magnetic influences and therefore costs in shielding, and also non-linearity, must also be taken into account.

Amorphous metal alloys have proved to be the most suitable material for the measuring bodies in question. Metals of this type have extraordinarily weak magnetic properties, i.e. extremely low magnetic hysteresis losses and high permeability values. In addition, the mechanical characteristics, such as tensile strength and elastic region, are many times higher than for polycrystalline, weakly magnetic metals, so that the measuring body may be formed as an extremely thin strip of an order of size of 20 to 30>im or as a relatively thin portion of wire, the measuring body being therefore of extremely low mass.

As a result of the high capacity of the amorphous material for mechanical loads, the pre-stressing desired for setting the zero point of the transducer is only limited by magnetic values, in this case by the saturation magnetostriction, i.e. that a good adjustability is provided. Since amorphous metal is distinguished by especially good resistance to corrosion and stability under load reversal, there is also provided suitability in particular for use in motor vehicles.

In spite of the amorphous structure, these metals can be bent, stamped and spot welded. It has, however, been shown that it is not hitherto -2IE 902903 been possible to satisfactorily solve the mounting of the measuring body on the force transmitting components of the transducer, which are displaceable relative to one another, in particular in regard to the preservation of pre-stressing over a long period as well as impact loads. Even by use of special laser welding methods, it has not been possible to avoid changes in the material, in particular recrystallisation. Force fitting, adhesive connections and clamping arrangements using suitable clamping members are not sufficiently creep-resistant, not least on account of the extremely limited roughness of the material, while on the other hand point and line-type clamping connections, which make use of a notch effect, are not sufficiently resistant to impact loading.

It was therefore an object of the present invention to provide a completely creep-resistant mounting of the ends of a strip or wire-form measuring body of amorphous metal, and also a mounting of high load capacity, for a transducer for measuring mechanical forces of the kind mentioned in the generic description.

This object is met by a winding mandrel being provided for securing at least one end of a preferably strip-form measuring body and a mounting arrangement being formed at the relevant mounting point of the transducer, the mounting arrangement providing for rotational movement and securing of the winding mandrel.

A preferred embodiment is characterised in that a winding mandrel is provided for securing at least one end of a preferably strip-form measuring body and that a mounting arrangement is formed at the relevant mounting point of the transducer, the mounting arrangement providing for rotational displacement and securing of the winding mandrel.

An advantageous embodiment of the transducer is further characterised in that the components of the transducer which are displaceable relative to one another include a housing which carries the coil arrangement and is formed for mounting the transducer and a mass which is resiliently arranged in the axial direction of the coil arrangement, and in that a mounting arrangement associated with a winding mandrel -3IE 902903 and at least one clamping catch are formed directly both on the housing and also on the displaceable mass.

The invention offers the crucial advantage that a very great frictional surface is provided, in particular when a strip-type measuring body is used and this is wound up in a multi-layer manner, and the individual turns are drawn firmly against one another by virtue of the pre-stressing. In this way, the inwardly disposed end of the strip, which is bent over into the slot, is completely relieved of any load by virtue of the resulting reduction in the force acting in the strip, while the outwardly disposed entry point of the strip is curved around onto the strip roll in a kink-free manner with a relatively large radius. In this manner, the invention affords not only a creep-free mounting of the ends of the measuring body, but also one which is secure against breakage.

A further advantage is to be seen is that the pre-stressing of the measuring body is sensitively adjustable and in the last analysis also measurable, i.e. that the operating point is adjustable at will in simple manner, and thus suitability for large scale series production is also provided, while the tolerances required for this are also adjustable in simple manner in contrast to other mounting methods.

The direct mounting of the strip according to the invention also enables use of a non-releasable connecting method, i.e. to secure the winding mandrel in its mounting arrangement after tensioning and adjustment of the strip, for example, by use of an adhesive or by welding.

The invention will be described in more detail in the following text with reference to the accompanying drawings.

Figure 1 shows a partially-sectioned representation of an acceleration transducer, Figure 2 is a plan view of an end face of the acceleration transducer according to Figure 1, -4902903 Figure 3 is a plan view of a force transducer having a ring-form force transmitting member.

The acceleration transducer 1 according to Figure 1, which records acceleration-dependent mechanical forces by means of a seismic mass and converts them into an electrical measurement quantity, consists of two sleeves 2 and 3, which are engaged in one another and are formed to be displaceable relative to one another in an axial direction. A threaded extension 4 is formed on one of the sleeves 2, by means of which the acceleration transducer 1 may be mounted for example on a chassis member of a vehicle, possibly using a suitable bracket, which optionally serves for alignment of the acceleration transducer. A bobbin 5 is mounted in the interior of the sleeve 2, which carries a coil arrangement for the transforming conversion of the measured value selected in this case, the coil arrangement consisting of two primary coils 6 and 7 and a secondary coil 8. A cable associated with the coils is designated by reference 9, the cable being brought out of the transducer 1 through a suitable opening in a flange 10 formed on the sleeve 2.

The other sleeve 3 serves as a seismic mass. It is guided on the sleeve 2, two rows of balls 11 and 12 being interposed as rolling bodies for minimising the friction. A roller 14 serves to guard against twisting of the two sleeves 2 and 3 relative to one another, the roller 14 being mounted on a pin 15 secured in the sleeve 3 and engaging in a slot 13 formed in the sleeve 2. A wavy spring acting between the two sleeves 2 and 3 is designated by reference 16 and provides the pre-stressing force for the measuring body itself, this being a thin strip 17 of amorphous metal, which on the one hand is secured in the sleeve 2 and on the other hand in the sleeve 3 in such a manner that it is disposed in a slot 18 of the bobbin 5 without touching the slot, the slot 18 being as narrow as possible.

The mounting of the strip 17 in the sleeve 2 is achieved by means of a clamping portion 19, on which there acts a screw 20 located in the flange 10. For the mounting of the strip 17 in the sleeve 3, a winding mandrel 21 is provided, which is rotatably mounted in an opening 22 extending transversely to the geometrical axis of the sleeve 3 in the 5IE 902903 base of the sleeve 3, which is not shown in more detail. The opening 22 is at least in part cut away by a bore 23 extending in the axial direction of the sleeve 3, so that in advantageous manner, two bearing points are formed for the winding mandrel 21 and a slot 24 provided in the centre of the winding mandrel 21, which serves for hooking in one end of the strip, is readily accessible from the exterior.

For securing the winding mandrel 21 in its bearing, the opening 22, a clamping catch is provided. For this purpose the base of the sleeve 3 is slotted (slot 25) in the axial plane of the opening 22. The winding mandrel 21 may be firmly gripped by means of screws 26 and 27 by the spring-like portion 28 of the base of the sleeve 3 separated from the remainder of the sleeve by the slot 25.

A screw 30 engaged in the winding mandrel 21, which screw has an actuating slot 29, represents an additional security feature and serves for arresting the end of the strip hooked into the slot 24, before several windings of the end of the strip are taken up over one another by rotation of the winding mandrel and finally, the two sleeves 2 and 3 are finally drawn towards one another against the action of the spring 16 to achieve the required pre-stressing in the strip 17. For actuation of the winding mandrel 21 and adjustment of the strip 17, it is advantageous for a stop in the axial direction to be associated with the winding mandrel 21. According to Fig 2, the opening 22 is for this purpose provided with a cylindrical recess 31 and the winding mandrel 21 is provided with a collar 32.

For completeness, it should also be mentioned that a capsule may be associated with the acceleration transducer 1, which covers access to the mounting points and at the same time fulfils a magnetic shielding function. It is also possible to form the mounting point described for the strip 17 in a component which is connectible to the sleeve 3.

In the force tranducer 33 shown in Figure 3, a strip 34 serving as measuring member is diametrally clamped in a holder 35 serving as a force transmitter. The force to be measured is applied to the support 35 at right angles to the strip 34, as indicated by arrows, for which suitable transmission means securely connected to the subject of the -6IE 902903 measurement must be provided. Other constructions are obviously also possible for the support 35, for example U-shaped or L-shaped bending bars, which may also be used for acceleration transducers.

Extensions 36 and 37 are provided on the ring-shaped support 35, in which the mounting points for the strip 34 are formed. In other words, a respective winding mandrel 38 and 39 is provided for each end of the strip, each winding mandrel being mounted in an opening, not shown in greater detail, in a respective one of the extensions 36 and 37. In addition, a clamping catch is provided for each winding mandrel 38, 39, formed on the respective extensions 36, 37, i.e. there is formed on each extension 36, 37 a resilient portion 42, 43 by means of a slot 40, 41, each resilient portion being provided with at least one screw 44, 45. A slot 46, 47 respectively formed in each extension 36, 37 serves to receive a coil arrangement 48, while tangs formed on the bobbin 49 and not shown in more detail engage in the slots 46 and 47 and are additionally secured, for example by gluing, which however is not strictly necessary, in the case of the spigot and socket connection shown between the support 35 and the bobbin 49. Apertures 50, 51 facilitate access to the insertion slots in the winding mandrels 38 and 39 associated with the ends of the strip. Cutaway portions formed in the extensions 36 and 37 for contact-free passage of the strip 34 are indicated by references 52 and 53.

Claims

1. A transducer for measuring mechanical forces, comprising a measuring body having a very small cross-section to length ratio, the measuring body being formed from amorphous, magnetically elastic metal, the measuring body being electro-mechanically coupled with a coil arrangement and located under pre-stressing between mounting points of the transducer which are moveable relative to one another, wherein a winding mandrel is provided for securing at least one end of a preferably strip-form measuring body, and a mounting arrangement is formed at the relevant mounting point of the transducer, the mounting arrangement providing for rotational displacement and securing of the winding mandrel.

2. A transducer according to claim 1, wherein a clamping catch is provided for securing the winding mandrel in the mounting arrangement.

3. A transducer according to claim 1 and 2, wherein at least one mounting point for the strip is provided in a component which is connectible to the transducer, in which component a mounting arrangement for a winding mandrel and a clamping catch are formed.

4. A transducer according to claim 1, wherein a non-releasable connection is provided for securing the winding mandrel in the mounting arrangement.

5. A transducer according to claim 1, wherein a slot is formed on an end face of the winding mandrel serving for rotation of the winding mandrel, and a slit is formed on the side face of the winding mandrel, serving for hooking-in the strip.

6. A transducer according to claim 1, wherein a winding mandrel is provided for each end of the strip. -8IE 902903

7. A transducer according to claim 1, wherein the mounting arrangement for the winding mandrel is formed as a two-point mounting 5 arrangement.

8. A transducer according to claim 1, wherein the mounting arrangements associated with the winding mandrels and at least one clamping catch are formed directly on components of the transducer which 10 are displaceable relative to one another.

9. A transducer according to claim 1, wherein the components of the transducer which are displaceable relative to one another include a housing carrying the coil arrangement and formed for mounting the 15 transducer and a mass arranged resiliently in the axial direction of the coil arrangement, and a mounting arrangement associated with a winding mandrel and at least one clamping catch are formed directly both on the housing and also on the displaceable mass. 20

10. A transducer according to claim 6, wherein the components of the transducer which are displaceable relative to one another are formed by a first sleeve carrying the coil arrangement and a second sleeve displaceably mounted on the first sleeve and serving as a displaceable mass.

11. A transducer according to claim 1, wherein the mounting points for the strip are provided on a unitary, resiliently deformable support member of the transducer. 30

12. A transducer substantially as described herein with reference to and as shown in Figures 1 and 2 or Figure 3 of the accompanying drawings.