DE19954519A1 - Device to measure load on element, e.g. machine part, subject to varying loads; has dowel body elastically connected to second support point and path sensor to detect spacing variation - Google Patents

Abstract

The device has a dowel body (2), which is inserted in a blind bore (10) in the element to detect deformations of the element. The dowel body has at least one first support point, which is rigidly connected to the dowel body and at least one second support point, which is elastically connected to the dowel body. A path sensor detects the spacing variation of the dowel body with respect to the second support point. The first support point of the dowel body is supported at a first contact area on a first inner side of the bore and the second support point of the dowel body is supported at a second contact area on an opposite second inner side of the bore, so that a deformation of the element varies the spacing between the second contact area and the dowel body. A path detector is provided to detect the variation of the spacing, by measuring the variation in distance between a reference point on the dowel body and a measurement point assigned on the second side of the inner wall of the bore.

Description

The present invention relates to a device for Bela performance measurement of an alternating mechanically loaded element, esp special of a machine part, according to the preamble of the main claim.

Due to the elasticity of solid bodies, solid elements react under which in the following in particular machine parts, tools or work pieces should be understood, with a deformation on the outer tere tensile or compressive stresses. A change of such an external Be load therefore generally goes with a changing deformation of the Elements. Measuring the deformation of a mechanically loaded Elements therefore allows conclusions to be drawn about the mechanical load on the Elements.

From DE 43 30 808 it is known that the measurement of the deformation of a machine element involved in a tool or workpiece drive can be used, the machining power of this Ma to detect machine element driven tool. In particular, can in this way tool wear and possible tool breakage be recognized.

Use generic devices to measure longitudinal expansion Element or contraction of an element often piezoelectric transducers.  

These are inserted into a hole in the element, so that a Deformation of the bore under mechanical stress on the element also a deformation of the piezoelectric contained in the sensor Sensor results. The bore is preferably in such an area of the Elements executed, which in the mechanical Bela undergoes a high, maximum possible deformation, so that gives a maximum signal at the piezoelectric sensor.

Problematic with the known generic devices for Load measurement, which is based on the use of piezoelectric sensors are based on the one hand that when installing such a device best possible application of force resulting from mechanical stress deforming element must be realized in the device so that the greatest possible deformation of the integrated in the device piezoelectric sensor results. This is realized by the device is clamped in the bore with a high preload. Here occurs often the problem is that the piezoelectric sensors in the Monta can be easily damaged by too high a preload. Furthermore, a strong deformation of the mechanically loaded element lead to such a large deformation of the piezoelectric sensor that this is damaged or even destroyed due to the mechanical load becomes.

On the other hand, in the case of generic devices which are based on piezoelectric sensors, low voltages with the lowest measuring currents must be registered, which requires the use of highly insulated supply lines. Maintaining this high insulation, which is expressed in a contact resistance of more than 10 ¹⁴ ohms between the supply lines, represents a major problem in practical use under the aggressive conditions which prevail on material processing machines. In particular, the cooling used in material processing / Lubricant has the ability to penetrate into the smallest gaps and through the smallest openings and thus negatively influence the electrical insulation ability, for example of measuring cables.

The object of the present invention is therefore a device for Bela performance measurement on an alternating mechanically loaded element give, which is easy to insert in a hole in the element, in this Hole must not be clamped with a high preload and whose measuring system has a reduced sensitivity to the aggressive Influences in the environment of material processing machines.

This task is solved by a device for load measurement with the features of the main claim.

Such a device, which is used to measure the load of an alternating mechanically loaded element, especially a machine part, pre can be seen, has a dowel body, which is provided in a Boh tion, in particular to be inserted into a blind hole in the element. It he then summarizes the changing deformation of the element with changing me chanic burden.

The dowel body has at least one first contact point that is rigid is connected to the dowel body. Furthermore, the dowel body has min at least a second contact point, which is elastic with the dowel body connected is. The first and second contact points are arranged that the dowel body inserted into the hole with the first app dotted at a first contact area and with the second contact point at a second contact area on the inner wall of the bore supports. The first contact area lies on a first side of the inside wall of the bore and the second contact area on one of which he most side facing away from the second side of the inner wall. The dowel body is supported with the first and the second contact point from the From the inner wall of the hole, which is when the Ele  elements, which result from a change in the mechanical load on the ele results in the distance between the second contact area and the dowel body changed elastically. The position of the dowel body remains pers relatively un relative to the first side of the inner wall of the bore changed. Furthermore, one is preferably non-contact Provided transducer, which is set up to vary the Ab status of the dowel body, in particular one arranged on the dowel body neten reference point, to one of the second side of the inner wall orderly measuring spot. In particular, this measurement spot can un arranged indirectly on the second side of the inner wall of the bore his. As contactless displacement transducers, there are displacement transducers that work according to the inductive principle or the eddy current principle. Next However, there is also the use of touch-sensitive displacement transducers possible, for example a displacement sensor can be used here works on the linear differential transformer principle. Generally displacement sensors can be used that are not between dowel bodies and measuring spot must be clamped with a high preload.

To assemble the device according to the invention in a bore in alternately mechanically loaded element inserted, the bore is dimensioned so that the dowel body essentially by the elasticity the second contact point is held in the hole. Another ver clamping the dowel body in the hole is i. a. not mandatory. Out for this reason, particularly simple assembly is possible, damage supply of the inventive device during assembly can be practical be excluded. By adjusting the elasticity of the second attachment point to the requirements of the measurement task can also large ver Formations of the alternately mechanically loaded element are recorded the, without mechanical damage to the inventive Device, especially the displacement sensor is to be feared. Here you can high safety reserves can be easily realized.  

When using displacement transducers based on the measurement of In ductivities or based on the eddy current principle are not increased To make demands on the supply lines to be used. For this Basically, the reliability of the device according to the invention increases when used under aggressive environmental conditions, especially on material processing machines, considerably. In addition, clear Cost advantages over the previously known devices which piezo use electrical sensors can be realized, since both the one at which he device used according to the invention as well as the downstream evaluation electronics to create significantly cheaper are.

There can be a further improvement of the device according to the invention can be achieved by providing a lever arm that is movable with the dowel body is connected. The second contact point and the Measuring spot arranged on the lever arm. In particular, the second type Position point to be connected elastically to the dowel body by the lever arm itself has a corresponding elasticity.

It is particularly advantageous if the He is so designed and the second contact point and the measurement spot so are arranged on the lever arm that there is a lever ratio. This leverage ratio is advantageously chosen so that the way up the distance between the anchor body and the measuring spot in one Change in the mechanical load on the element varies more than that Inner diameter of the hole at the location of the second contact point. By Such a leverage can increase the sensitivity of the detection of the inside diameter at the location of the second contact point when changing sel the mechanical load of the element compared to the pure Em sensitivity of the displacement sensor used can be increased. With ent speaking execution of the geometry of the lever arm can the sensation in this way can easily be increased by a factor of 10. By  appropriate adjustment of the geometry of the lever arm can this Emp sensitivity increase can be adapted to the respective requirements.

Special advantages arise when the lever arm consists of a permanently elastic rule metal, is made in particular of a spring steel sheet. To this The elastic connection of the second contact point to the Dowel bodies can be realized particularly easily.

There are advantages for the assembly if the device is designed in this way is that they are inserted into the hole without the use of tools can be.

This can be realized, for example, by the device is guided with a preload of less than 30 Newtons, preferably braced less than 15 Newtons in the bore got to. Such pretensioning forces can easily be achieved by using a Device according to the invention with a lever arm made of a permanent arm realize metallic metal.

It is particularly advantageous if the inventive device with such a biasing force is clamped in the hole that it is under Application of one directed in the direction of the longitudinal axis of the bore Force of more than 15 Newtons, preferably more than 5 Newtons from the Hole can be pulled out, but preferably always min at least the weight force acting on the device according to the invention corresponds.

In practice, devices according to the invention can be used without problems gene can be realized using a force of about 11 Newtons pulled out of a hole made in a steel element that can. Such devices can be used without additional Tools are inserted into a hole and remain reliable under normal operating conditions in the bore.  

For practical use in harsh environmental conditions for example on material processing machines, it has proven to be advantageous highlighted when the displacement sensor hermetically captures in the dowel body rare. This can be done, for example, by casting with a plastic be lized. In particular, the encapsulation can also be the supply lines of the displacement sensor. Finally, the dowel body can finally, the displacement sensor integrated in it is completely waterproof be carried out.

A particular insensitivity of the device according to the invention against shocks, vibrations and vibrations of all kinds can be achieved if the displacement sensor, which is the distance between the nozzle body, in particular a reference point located thereon, and the Measuring spot recorded, is set up this distance over a time interval T averaged. The time interval T is preferably ge chooses that it has a plurality of oscillation periods more characteristic Vibrations of the element, the associated machine, in particular Machine tool, as well as the dowel body including any existing lever arm includes. In this way, disruptive influences of vibrations, which are often not with the Bela to be detected Element correlation are eliminated with high efficiency.

The same effect is achieved if one follows the displacement sensor switched evaluation electronics performs the function described.

Interfering influences of the displacement transducer leads can be eliminated be by a wireless transmitter in the inventive direction is integrated, which the data recorded by the displacement sensor the required time resolution, preferably digitized to a nearby one gene receiving station in which the received data processed and further processing. Especially comes here  the use of optically working wireless communication links in Question.

Other features and advantages of the device according to the invention ben from the following examples, which are not are to be understood as restrictive and explained on the basis of the drawings the. In this show:

Fig. 1 is a schematic view of a multi-spindle automatic lathes with egg ner inserted in a rocker arm according to the invention before direction,

Fig. 2 is a plan view of a first embodiment of an inventive device inserted into a bore in the rocker arm,

Fig. 3 is a side view along the cut line AA of Fig. 2 inserted into the bore in the rocker arm first embodiment,

Fig. 4 is a plan view of a second embodiment of an inventive device inserted into a bore in the rocker arm,

Fig. 5 is a side view along the cut line AA of Fig. 4 of the second embodiment inserted into the bore in the rocker arm similar to FIG. 3,

Fig. 6 is a side view of a third embodiment of an inventive device analogous to Fig. 3 and

Fig. 7 is a side view of a fourth embodiment of a device according to the Invention comprising a lever arm, also analogous to FIG. 3.

Fig. 1 shows a device according to the invention, which is used in a multi-spin automatic lathe for measuring the tool feed forces. The link lever 1 of such a multi-spindle automatic lathe is moved by a control cam 4 and drives a feed rod 5 to which a tool 6 is attached. This tool 6 processes a workpiece 7 . When machining the workpiece 7 , forces occur on the link lever 1 , which deform it. In particular, when changing from "no material processing" to "material processing", an alternating deformation of the link lever 1 occurs. This changing deformation is particularly influenced by the machining forces that occur, which in turn depend on the degree of wear of the tool used. A load measurement on the link lever is therefore a possibility to infer the degree of wear of the tool 6 . For this purpose, a device according to the invention is inserted into a bore 10 in the link lever 1 . The link lever 1 thus represents the element 1 on which the load measurement is to be carried out. From the device according to the invention, the dowel body 2 can be seen from FIG. 1.

Fig. 2 shows the bore 10 in the link lever 1 in supervision. In this Boh tion 10 , an inventive device is inserted. This has egg nen plug body 2 , with which a first contact point 21 is rigidly connected. Furthermore, the device according to the invention has a second contact point 22 which is elastically connected to the dowel body 2 of the device according to the invention via an elastic metal tongue 222 . From the supervision it can be seen that the dowel body 2 is supported with the bearing points 21 and 22 on sides of the inner wall of the bore 10 facing away from one another. In FIG. 2, the first side 11 and second side 12 and the first contact region 111 and the second contact region 121 on are interpreted. Furthermore, the feed lines 31 of the displacement sensor 3 can be seen from the supervision shown.

The dashed line, which is denoted by AA, represents a section line. From FIG. 3, a section through the link lever 1 can be seen along this section line AA. One recognizes the dowel body 2 of the device according to the invention inserted into the bore 10 . In the implementation shown, the dowel body 2 has two first contact points 21 which are rigidly connected to the dowel body 2 . Furthermore, the second contact point 22 can be seen, which is connected to the dowel body via the U-shaped bent elastic metal tongue 222 . The dowel body 2 is supported with the two first contact points 21 and the second contact point on opposite sides of the inner wall of the bore 10 . A slight pretension is built up by the elastic metal tongue 222 , so that the dowel body 2 is fixed in the bore 10 by a low pretensioning force. When the link lever 1 is deformed in the direction of the double arrow in FIG. 2, as occurs, for example, due to machining forces, the bore 10 is deformed. This changes the inner diameter of the bore 10 . With such a change in the inner diameter, the first contact points 21 are fixed by the pre-tensioning force of the elastic metal tongue 222 on the first side of the inner wall of the bore 10 . Furthermore, the second contact point 22 remains essentially fixed on the second contact area 121 on the second side 12 of the inner wall of the bore 10 . As a result, the distance of the dowel body 2 from the second side 12 of the inner wall of the bore changes when the link lever 1 is deformed. In particular, the distance between the second contact region 121 and the dowel body 2 changes . A displacement transducer 3 is integrated in the dowel body, this detects the distance D of the dowel body 2 , in particular the reference point 23 arranged on the dowel body, from the measuring spot 13 assigned to the second side 12 of the inner wall of the bore 10 . In the exemplary embodiment shown, the measurement spot 13 is arranged directly on the second side 12 of the inner wall of the bore 10 . In the exemplary embodiment shown, a non-contact displacement transducer is used which, for example, can work inductively or can be based on an eddy current measurement. Via the feed line 31 , the distance D detected by the displacement sensor 3 is passed to a downstream electronics system for further processing.

From Fig. 4, a slightly modified embodiment of a OF INVENTION dung device according to supervision can be seen that only differs from the embodiment in Fig. 2 that, instead of two first bearing points 21, which are arranged on a line parallel to the longitudinal axis of the dowel body, four first contact points 21 are provided. These four first contact points 21 are realized by a protruding nose at the upper end and at the lower end of the dowel body 2 . Inserted into the bore 10 , these thus form a total of four first contact points 21 , as can be seen from FIG. 4. However, the embodiment shown continues to use only a second contact point 22 .

From Fig. 5 a section along the line AA through the Kulis senhebel 1 can be seen again, wherein the inventive device shown corresponds to the embodiment shown in Fig. 4. The two noses mentioned are clearly recognizable in side view, which form a total of four first contact points 21 .

From Fig. 6, another embodiment of an inventive device is shown which essentially corresponds to the embodiment of FIG. 5, with the main difference that the second Appendices is gepunkt 22 is not connected via a resilient metal tongue 222 with the plug body 2, but by the probe tip 32 of a touching the transducer 3 is formed. Such a displacement sensor 3 can be based on the linear differential transformer principle or the capacitive principle, for example. This displacement sensor 3 is sensitive to changes in length in the direction of arrow 8 . The probe tip 32 can be displaced in the direction of the arrow 8 and is furthermore set up to apply a slight pretensioning force in the direction of the arrow 8 . That is to say, in the embodiment shown, the touch-working displacement sensor 3 builds the clamping force required to fix the dowel body 2 in the bore 10 itself. In particular, the second contact point 22 is formed by the probe tip 32 of the displacement transducer 3 working in contact.

From Fig. 7, another embodiment of the erfindungsge MAESSEN apparatus finally is visible, which has an additional lever arm 24th This lever arm 24 is realized by an elastic metal tongue. The anchor body itself corresponds to the realization shown in FIG. 5. The second contact point 22 is arranged on the lever arm 24 . Furthermore, as can be seen, the measuring spot 13 is also arranged on the lever arm 24 . If the inside diameter of the bore 10 changes at the location of the second contact point 22 , this variation of the inside diameter is increased by the lever ratio L2 / L1 to the location of the measuring spot 13 . This means that the distance D between the transducer 3 and the measuring spot 13 varies more than the inner diameter of the bore 10 at the location of the second contact point 22 by the amplification factor L2 / L1. This means in particular that the sensitivity of the displacement sensor 3 can be increased again by the said amplification factor. With a suitable choice of leverage ratios, the increase in resolution thus achieved can be adapted to the given requirements.

One possibility for further processing the distance D measured by the displacement sensor 3 is shown in FIG. 1. The recorded signal is transferred via the feed line 31 to a first electronic processing unit 8 , for example a preamplifier with a downstream A / D converter. It is particularly advantageous if the first processing unit 8 comprises a device for external or internal zero adjustment, indicated here by the arrow 81 . This device for external or internal zero adjustment uses the distance D 1 detected by the displacement sensor 3 at a low load on the link lever 1 as a reference value ("zero value") with which the distance D2 detected by the displacement sensor 3 under high load on the link lever 1 is compared , so that influences of a possible thermal drift ete. be minimized the inventive device. The resulting difference value D2-D1 is then further processed by a further electronic, preferably digital processing unit 9 .

Claims (12)

1. Device for measuring the load of an alternating mechanically loaded element ( 1 ), in particular a machine part, with a Dü belkörper ( 2 ), which is provided in a bore ( 10 ), in particular in a blind hole in the element ( 1 ) and to detect the deformation of the element ( 1 ) under changing mechanical loads, characterized in that:

• a) the anchor body ( 2 ) has at least a first contact point ( 21 ) which is rigidly connected to the anchor body ( 2 ) and has at least a second contact point ( 22 ) which is elastically connected to the anchor body ( 2 ), wherein the first ( 21 ) and the second ( 22 ) contact point are arranged such that the dowel body ( 2 ) inserted into the bore ( 10 ) with the first contact point ( 21 ) is located on a first contact area ( 111 ) which is on a first side ( 11 ) the inner wall of the bore ( 10 ) is supported and with the second contact point ( 21 ) on a second contact area ( 112 ) which is on a second side ( 12 ) of the inner wall facing away from the first side ( 11 ), supports, such that when the element ( 1 ) is deformed, the distance between the second contact area ( 112 ) and the dowel body ( 2 ) with largely unchanged position of the dowel body ( 2 ) relative to the first side ( 11 ) of the inn wall changed elastically, and that
• b) a displacement transducer ( 3 ) is provided, which is set up to vary the distance D of the dowel body ( 2 ), in particular a reference point ( 23 ) arranged on the dowel body ( 2 ), to one of the second side ( 12 ) of the inner wall associated measurement spot ( 13 ).

2. Device according to claim 1, characterized in that the measuring spot ( 13 ) is arranged directly on the second side ( 12 ) of the inner wall. 3. Device according to claim 1, characterized in that a He belarm ( 24 ) is provided, which is movably connected to the dowel body ( 2 ), and that the second contact point ( 22 ) and the measuring spot ( 13 ) on the lever arm ( 24 ) are arranged. 4. The device according to claim 3, characterized in that the lever arm ( 24 ) is designed and the second contact point ( 22 ) and the measuring spot ( 13 ) are arranged on the lever arm ( 24 ) so that there is a lever ratio, so that the distance D between the dowel ( 3 ) between the dowel body ( 2 ) and measuring spot ( 13 ) varies more with a changing mechanical load on the element ( 1 ) than the inside diameter of the bore at the location of the second contact point ( 22 ). 5. The device according to claim 3, characterized in that the lever arm ( 24 ) is made of a permanently elastic metal or a metal alloy, in particular a spring steel sheet. 6. The device according to claim 1, characterized in that the displacement sensor ( 3 ) is a touch-working displacement sensor, in particular according to the principle of the linear differential transformer or the capacitive principle. 7. The device according to claim 1, characterized in that the displacement transducer ( 3 ) is a non-contact displacement transducer, in particular an inductive displacement transducer or one based on eddy current measurements. 8. The device according to claim 1, characterized in that the device is clamped with a biasing force of less than 30 Newton, preferably less than 15 Newton in the bore ( 10 ). 9. The device according to claim 1, characterized in that the device can be pulled out of the bore ( 10 ) by means of a force K acting in the direction of the longitudinal axis of the bore ( 10 ), the force K corresponding at least to the weight force acting on the device and a maximum of 50 newtons, in particular less than 30 newtons and preferably less than 15 newtons. 10. The device according to claim 1, characterized in that the device can be inserted into the bore ( 10 ) without tools. 11. The device according to claim 1, characterized in that the displacement sensor ( 3 ) is hermetically encapsulated in the plug body ( 2 ), in particular encapsulated. 12. The device according to claim 1 or 3, characterized in that the displacement sensor ( 3 ) is provided to detect the distance D of the dowel body ( 2 ) to the measuring spot ( 13 ) averaged over a time interval T, T being selected so that in a time interval T a number of oscillation periods of characteristic oscillations of the element ( 1 ), the associated machines and the dowel body ( 2 ) including any lever arm ( 24 ) that may be present.