DE3321480A1 - Linear measuring scale - Google Patents

Abstract

A linear measuring scale has a scale body which is produced from magnetic material, and a plate element having a U-shaped cross-section. The scale body supports wall sections which are parallel to one another. Slots or openings of sinusoidal type or a similar shape are provided in one of the wall sections of the scale body, the slots being at a predetermined distance from one another. A guide element serves to guide a retaining part for a detector head which is mounted displaceably opposite the mutually distanced slots. The detector head with the retaining part is displaceably mounted on the opposite wall section of the scale body. In another embodiment, the plate element consists of two wall sections which are preferably arranged perpendicular to one another and of which one wall section has a guide slot for the retaining part of the detector head and the other wall section has a plurality of slots distanced from one another, the detector head being mounted displaceably with respect to the slots by the retaining part.

Description

Linear measuring scale

The invention relates to a linear measuring scale according to the preamble of claim 1 or claim 2.

A known linear measuring scale has several magnetic elements that have different polarity and are arranged alternately in a linear direction on a non-magnetic material around the scale body to build. A detector head for detecting a large number of gaps has a large number of individual magnetic heads, which differ from each other in the winding direction and essentially in the same distance relationship as the magnetic elements are arranged. This detector

The head is moved along a series of magnetic elements on the scale body to determine the amount or amount of movement. Movement path of the detector head to. measure, i.e. the divisions or gradations of the scale body.

Another linear measuring scale has a conductive circle (coil) in the manner of a square wave, which by machining, such as etching, is formed from a copper plate in a linear direction of the scale body. An alternating voltage is attached to the detector head with a conductive circle, like the mentioned square wave-like conductive circle, applied and the amount of movement or displacement, i.e. the path of the detector head, is determined by changing the induced Voltage measured, which results from a change in the degree of electromagnetic coupling between the head and the conductive circle of the scale body.

In the first-mentioned linear measuring scale, the magnetic elements are arranged on the scale body and therefore that is Working with this measuring scale is complicated, while with the last-mentioned measuring scale the square wave-like conductive one Circle is provided on the scale body and thus a chemical treatment is required. In addition, are the known measuring scales are comparably expensive. If there is a faulty section especially with the last-mentioned measuring scale is present in the rectangular wave-shaped conductive circle, it can no longer work as a linear measuring scale.

The invention is therefore based on the object of a linear To create a measuring scale that can be produced inexpensively by simple mechanical processing.

This object is achieved according to the invention by the subject matter of claim 1 or claim 2 or 4.

Further refinements of the invention emerge from the subclaims.

The invention thus provides a linear measuring scale or a linear measuring stick for determining or measuring linear Dimensions, in particular for use in machine tools or the like with numerical control.

The invention creates a linear measuring scale with a scale body, in which a plurality of slots or sinusoidal wave-like hollow-raised sections in a metal plate are provided, which is produced by simple mechanical processing from a magnetic material. The length measurement is performed due to a change in magnetic reluctance when the detector head along the Slits or hollow-raised sections is moved.

The invention also provides a linear measuring scale with a circuit for compensating for irregularities or irregularities the properties of the magnetic resistance of magnetic resistance elements in the detector head integrated together with magnetic resistance elements is provided, whereby the circuit constant does not increase change is in case the detector head is replaced.

The linear measuring scale can advantageously Carry out exact measurements based on the movement of the magnetic sensors, fine measurements can also be made between the spacing of the slots or hollow-raised sections of the scale body without changing the level of the output voltages of the magnetic sensors.

The linear measuring scale has a scale body made of a magnetic material and in the form of a plate element

with a U-shaped cross-section, the wall sections of which are parallel to each other. In this embodiment, the Slots are in the shape of a sine wave or a similar shape and are in one of the two wall sections of the scale body intended. A guide element is used to guide a holding part or a holding base for the detector head in the slots in opposed relationship on or opposite the wall portion having the slots.

The invention also provides a linear measuring scale for measuring scale graduations on the scale body Changes in the magnetic gap that result from a movement of the detector head in relation to the scale body. Several Slits or sinusoidal hollow-raised sections are provided in a linear manner in the plate, which is made of magnetic material. In this embodiment, the detector head has a pair of magnetic sensors at a distance of 1/4 the distance between the slots or hollow-raised portions in a direction of movement of the detector head are provided, each magnetic sensor having a bridge circuit. The bridge circuit contains a pair of magnetic resistance elements, which are slotted or hollow-raised on permanent magnets Sections opposite in spaced relation and are arranged in the direction of movement of the detector head; the bridge circuit further includes a pair of Resistances.

The invention finally creates a linear measuring scale with correction resistors to compensate for irregularities the property of the magnetic resistance elements, so that a fixed detector or measurement voltage level is obtained will. The correction resistors are each connected in parallel to the pair of resistors that form the bridge circuit forms.

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According to a further embodiment, the linear measuring scale has slots in the scale body which are at equal intervals are provided. Here, the detector head is moved over a series of slots in the scale body, wherein the output of the detector head is counted to thereby measure the movement of the detector head. A pair of the detector sensors is provided in fixedly spaced relation in the detector head. The linear measuring scale also has a Voltage section for dividing the output voltage of the sensors and a combination circuit for combining the output voltages the voltage divider so that a combined output voltage is obtained; the output pulses of the combination circuit are counted and serve as a measurement for the displacement path of the detector head.

In the following, preferred embodiments of the invention are explained in more detail with reference to drawings. Show it:

Fig. 1 is a perspective view of a linear measuring scale,

Fig. 2 is a front sectional view of a modified measuring scale,

Fig. 3 is a perspective view of the detector head of the measuring scale, Fig. 4 is a sectional view of the detector head,

Fig. 5 is a circuit diagram of the magnetic sensors that make up the detector head;

Fig. 6 is a diagram for explaining the relationship between the displacement of the detector head and the output voltages the magnetic sensors,

7 shows a diagram to explain the principle when differentiating the direction of movement of the detector head,

8 is a diagram for explaining the generation of combined output signals from the output signals the magnetic sensors for the purpose of measuring the displacement of the detector head,

9 is a block diagram of a measuring section of the linear measuring scale;

Fig. 10 shows a combination circuit of the linear measuring scale, and

Fig. 11 shows a discriminator circuit for discrimination the direction of movement of the detector head.

Preferred embodiments of a linear measuring scale or measuring scale are described below. The linear measuring scale, also referred to as a linear scale, has a scale body and a detector head 2, which are shown in FIG. The scale body 10 has a plate member formed from a magnetic material having an L-shaped cross section and has wall sections 6a, 6b which are perpendicular to one another. The wall section 6b is with a slot 4 as Provided in the longitudinal direction extending guide member, while the wall section 6a a plurality of rectangular slots contains, which are each at right angles to the longitudinal direction and at fixed distances from one another. Of the Detector head 2 is attached to a holding part 3 so that it is opposite the slots 7, the holding part 3 is slidably mounted with respect to the longitudinal slot 4.

According to the embodiment according to FIG. 2, the wall sections 6a and 6b are formed by bending a plate member made of a magnetic material and is bent into a substantially U-shaped shape, in which case the two wall sections 6a and 6b connected to each other by a connecting portion 6c

are. One edge of the wall portion 6a is sinusoidal hollow-raised, as indicated by the reference numeral 8 in Fig. 2, i.e. that the edge at 8 is shaped by a hollow-raised course in the manner of a sine wave; a longitudinal slot 5 is in the wall section 6b provided to form the scale body, so that a holding part or a holding base 3 movable relative to the Longitudinal slot 5 is mounted, while a detector head 2 lying opposite the hollow, raised edge 8 is on the holding part 3 is arranged or attached.

3 and 4 show that the detector head 2 is constructed so that an electrically insulating plate 20 within a sample or an outer frame 31, the sample or the frame 31 made of non-magnetic material consists, for example, of synthetic resin; plate-shaped permanent magnets 43 are on the electrically insulating plate attached or preferably glued, while magnetic resistance elements 22 and 23 (Fig. 5) to the permanent magnets 43 adhere by electrically insulating films or layers. A pair of magnetic sensors 32 are shown in FIG fixed spaced relationship to each other provided. Conductors or connections 24 to 27 are from the magnetic sensors 32 led out.

Each magnetic sensor 32 has a pair of magnetic resistance elements 22, 23 and resistors as shown in FIG 33, 35, which form a bridge circuit. A fixed DC voltage is applied to connection terminals Va and Vb, the terminal Va being connected to the magnetic resistance element 22 and the resistor 33, while the terminal Vb is connected to the magnetic resistance element 23 and the resistor 35, so that the resistances of the magnetic resistance elements 22, 23 depending on the magnetic (air) gap between

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the detector head 2 and the scale body 10 vary so that an output voltage is output between a terminal Vo and Vr with the terminal Vo connected to the connection between the magnetic resistance elements 22 and 23 while the terminal Vr is led out from the junction between the resistors 33 and 35. When this output voltage between the terminals Vo and Vr is converted into a digital signal by an analog / digital converter to convert a To deliver counting display, it is possible to digitally display the path or amount over which the detector head 2 was moved.

To compensate for irregularities in the characteristics of the magnetic resistance elements 22, 23 is a correction resistor stood 34 in parallel with resistor 33 and a correction resistor 36 connected in parallel with resistor 35. at the adjustment of irregularities in the characteristic or characteristic curve, the resistors 33, 35 together with the Magnetic resistance elements 22, 23 preset and it is a suitable direct voltage or alternating voltage is applied to the terminals Va and Vb, whereupon the output at the terminal Vo is observed by an oscilloscope or the like will. The values of the correction resistors 34, 36 are then selected so that an output value at the connection Vo coincides with the voltage at the terminal Vr as shown in FIG. . ,

Fig. 7 is an illustration for discrimination the direction of movement of the detector head 2. In Fig. 7, at (a), wave-shaped output voltages A and B of the magnetic sensor pair 32, which are housed in the detector head 2, where L denotes the movement path of the Detector head 2 is designated. The output signals of the sensors 32 are essentially sinusoidal and the distance between the sensors 32 corresponds to 1/4 of the distance A.

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Slots 7; therefore, the phase difference between the output voltages A and B of the sensors 32 is about 90 °.

In Fig. 7 at (b) pulse signals A _n and B are shown, into which the output voltages A and B are converted after an analog / digital conversion. When these pulses A and B are displayed as a count or number, the movement path of the detector head 2 can be in a 1/4 unit of the distance Λ. of the slot 7 can be represented digitally.

However, if such pulses of a quarter-turn distance are only adidated it is not possible to distinguish whether the detector head 2 has been moved to the left or to the right and thus, the amount of movement from a starting point cannot be obtained with accuracy. To the amount of movement to obtain accurate, it is necessary to count the display in such a way that the pulses im In the case of a movement from left to right, the pulses are added in the case of a movement from right to left be subtracted.

Under these circumstances, the following processing is carried out in the linear measuring scale of the present invention. If a pulse B is differentiated as for the case in which the detector head 2 is moved from left to right, as indicated by an arrow at (c) in FIG. 7, an output pulse C_ results as shown in FIG. 7 ( c). If the logical product A_ · C _{n of} the pulses C _n and A_ is determined,

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gives the pulse shape as shown in Fig. 7 at (d). When these pulses are counted by an adder, can be the amount of movement of the detector head 2 of get left to right.

When the detector head 2 is moved from right to left, a pulse C- is _{generated based on the pulse B n} , like this

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in Fig. 7 at (e); this then results in a pulse train of opposite polarity to the correspondingly differentiated pulses C ₁ -, when the head moves from left to right. If the logical product of the pulses C _T and A_ is formed, there is no output pulse because the pulse A has a different polarity than the pulse C. If the pulse A is inverted in order to form the logical product A - C from the pulses A _n and C, the pulse sequence is obtained which is shown in FIG. 7 at (f). If this pulse of an added value

the pulses A_ · C_ of the previous case is subtracted, D K

in which the detector head 2 is moved from left to right, the absolute value of the movement in the case in which the detector head 2 is moved from left to right and back from right to left, are counted and displayed. The differentiation of the direction of the linear measuring scale according to the invention has already been described above.

Fig. 8 is an illustration for explaining the principle of measuring a moving distance smaller than the distance

Λ- / 4 of a pair of magnetic sensors 32 of the detector head 2 is. In Fig. 8, letters A and B at (a) denote an output voltage of the pair of magnetic sensors 3 2 of the detector head 2, while the pulse signals A, B _n in Fig. 8 are shown at (b) and (e) which follow an analog / digital conversion from the aforementioned output voltages. Even if the pulses A, B are only counted, the movement which is smaller than the distance between the two sensors 32 of the detector head 2 cannot be measured.

The output voltages A and B of the sensors 32, which are different in phase, are vector-combined by a method, thereby obtaining a combined output X ₁ , X ₂ , X ₃ ...; which result from it

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The resulting analog / digital converted output signals are accordingly X ₁₀ / ^X OD ' ^X 3D' ^X 4D "** ^unc ^ ^{sin (} ^ ^{in Fi} <J- 8 (c), (d), (f), (g), ... If these output _signals X 1n / etc. are differentiated, the result is a pulse sequence X _R , X according to Fig. 8 (h), (i) corresponding to the movement of the detector head 2 from left to right or from right to left If these pulses are added or subtracted, the movement path of the detector head 2 can be measured and the more combined output signals X ₁ , X ~, X ^, X ₄ , the finer the measuring unit works without going through the distance between the sensors 32 of the detector head 2 to be impaired.

_{If the logic products of the pulses X 0} and A ^ are added and the logic products of the pulses X _T and A ^ are subtracted according to the same principle described with reference to FIG. 7, the result obtained is that the direction of movement in the measurement is differentiated or is taken into account. The operating principle has been described above in which the measuring unit of the linear measuring scale is smaller than the distance between the magnetic sensors 32.

Figure 9 is a block diagram of a linear measuring scale in accordance with the invention. In Fig. 9, 2 denotes the detector head, in which the two magnetic sensors 32 are arranged at a distance of 1/4 / I of a slot 7, while with 30 denotes a DC voltage source. According to Fig. 9, an amplifier 37 is also provided, which the output signals of sensors 3 2 amplified. A combination circuit 39 receives the output voltages A, B from the two Sensors 32 and provides a vector combination, so that a combined output voltage corresponding to that shown in Fig. shown principle results. An analog / digital converter circuit supplies transformed pulses, as in Fig. 8 at (b) to (g) is shown from the output voltages A and B of each sensor

332 H80

and the combined output voltages X., X-, X ₃ , X ..

A circuit 41 serves to distinguish between directions and thus recognizes the movement of the detector head 2 from left to right on the basis of a logical pulse product of the pulse series X_ according to FIG. 8 (h) and the pulse series A _n . 8 (b) and the movement of the detector head 2 from right to left from a logical pulse product of the pulse series X according to FIG. 8 (i) and the negation A of the pulse series A _n according to FIG. 8 (b), so that a added pulse or subtracted pulse is fed to counter 4 2. The counter 42 adds and subtracts the pulses from the discriminator 41 to count and display the absolute amount of movement of the detector head.

FIG. 10 shows an example of a combination circuit 30 which supplies a combined output signal from the output voltages A and B of each sensor 32. An amplifier is designated by 44, which amplifies the output voltages A and B of the sensors 32. An inverted amplifier receives the output signal 44 of the amplifier 44 and provides an output voltage λ. With Rl, R-, R ₃ resistors are referred to, which are used to divide jier output voltages A, B, A of the amplifier 44 and the inverted amplifier (push-pull amplifier in grid base circuit) 45.

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An operational amplifier 46 is divided by the resistors R _1, R_, R-, the output voltages ^A! , B, A of amplifiers 44, 45, after which these voltages are appropriately combined to provide the combined output signals X ₁ , X-, X ₃ , X ₄ . The operational amplifier 46 also has the function of a so-called A / D conversion, an input signal being inverted every time it passes through the zero point; the operational amplifier 46 supplies shaped pulses, for example square-wave pulses A, X _1n / B, X, _D , ^X 4n '. With 47 a buffer circuit is designated.

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3321481

10 (b) shows a vector representation of the output voltages A, B of the sensors 32. The output voltages A, B are phase-shifted by approximately 90 °; the combined output signals X., X ~ cannot be obtained by simple vector combination of signals A and B, but are rather obtained by dividing signals A, B by resistors R, R ', R_ before their vector combination. When a phase difference cO of A, X ₁ , X_, B is 30 °, the ratio of the resistances R ₁ , R ₃ , R _{3 is} 0.14: 0.36: 0.5. provided that a resistor as a combination of a series circuit of R ₁ , R ₃ , R ₃ is R _Q , then the values of the resistors R ₁ , R ₃ , R ₃ in the combination circuit of Fig. 10 (a) are respectively 0.14 R _Q , 0.36 R _Q , 0.5 R _Q.

Fig. 11 is a view of one embodiment of the discriminator circuit 41 used in a linear measuring scale according to the invention to discriminate direction to produce added or subtracted pulses. In Fig. 11 (a), there is shown a direction discriminating circuit for discriminating the direction in the case where the detector head 2 is moved from left to right. Fig. 11 (b) shows a direction discriminating circuit in the case where the detector head 2 is moved from right to left. In Fig. 11 (b), denoted at 50 is an inverting buffer circuit. When the detector head 2 moves from left to right and output _{signals A, D 1n} / X ₂ , B, X ₃₀ / D ₄ from the combination circuit 39 are applied to an input terminal, a pulse train as shown in FIG. 8 (h) is generated , in which the signals A, ^X 1D ' ^X 2D' ^B D ' ^X 3D' ^X 4D ^^ ^ are erented to sequentially output pulses from AND circuits 48 to apply added pulses to the counter 42. When the detector head 2 moves from right to left, output _{signals A D} , X- _D , X ₂ D ' ^B D' ^X 3D ' ^X 4D ^{from the combination circuit} 9 ³⁹ are inverted by the inverting buffer circuit 50 and

a differentiated pulse train thereof provides an inverted pulse train as shown in Fig. 8 (i), to output a pulse train from AND circuit 48 to apply subtracted pulses to counter 42.

It should be noted that in the embodiment described above, the distance between the sensors 32 of the Detector head 2 not to 1/4 of the distance λ. of the slots is limited as shown in Fig. 8 (a), however For example, the distance can be set at 5/4.

While in the embodiment described above, the phase difference of the output voltages of the sensors is divided into three, it should be noted that with an increase in the number of divider resistors R ₁ , R- / R- ^ of the combination circuit 39 and with a corresponding selection of their values, the measuring unit is theoretically designed more finely.

Since, according to the invention, the scale body made of a metal plate is produced by pressing, it can be produced very cheaply compared to conventional products and the precision is uniform. In addition, a small and fixed linear scale can be obtained.

The detector head 2 advantageously has a simple structure and two magnetic sensors, i.e. it uses only four magnetic resistance elements as main parts and it is therefore possible to create an extremely cheap linear scale or measuring scale, which has a measurement accuracy which in the is essentially the same as compared to conventional devices.

The resistors 34 and 36 for correcting irregularities in the characteristic curve or property of the magnetic resistance elements 22 and 23 are included in the detector head 2; therefore, if the detector head 2 due to wear or

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the like is replaced, the mean value of the detection voltage between the terminals V and V is reduced to a predetermined one Pre-adjusted value. Hence the special one Effect that the linear measuring scale can be used without modification, as well as without changing the circuit constant of the amplifier to the detector or measurement voltage to convert it into a digital signal.

In the case of the linear measuring scale according to the invention, the magnetic Sensors of the D ± ector head 2 provided in a suitable spaced relationship to each other; the output voltages the sensors, which differ in their phase, are simply divided by resistances; the output signals divided in this way are appropriately combined and provide a plurality of combined output voltages. These combined output voltages are subjected to an analog / digital conversion and counted. With this arrangement, the measuring unit can easily be selected so that fine measurements are possible without being limited by the spacing of the slots. As the output voltages of the two Magnetic sensors have phase differences and are analyzed to determine the direction of movement of the detector head 2, it is possible to determine the absolute movement of the detector head 2 with extremely high precision measure up.

Claims (1)

Claims characterized in that a scale body (10) made of magnetic material and consists of a plate element with a U-shaped cross-section, the wall sections (6a, 6b) lying parallel to one another has that recesses (8) in the manner of a sinusoidal shape uder a similar shape with a predetermined distance ; iinem of the wall sections (6a) are formed, and. that a guide part (4) for guiding a holding part (3) is provided, which holds a detector head (2) against the recesses (7) in the other wall section (6b) of the scale body (10) are formed. 2. Linear measuring scale for measuring gradations or divisions of a scale body through changes in a magnetic one Gap as a result of a displacement of a detector head opposite the scale body, in which a plurality of slits or sinusoidal-shaped mis-raised portions linearly in one plates made of magnetic material are arranged, characterized in that the detector head (2) has a pair of magnetic sensors (32) having at a distance of 1/4 of the distance difference of a distance between the slots or hollow-raised portions are arranged in a direction of movement of the detector head (2), that each sensor (32) has a bridge circuit in which a pair of magnetic resistance elements (22, 23) on one Permanent magnets (20) the slots (7) or hollow-raised portions (8) opposite in a spaced relationship in a Direction of movement of the detector head (2) are arranged, and that the bridge circuit is a pair of resistors (33, 35) having. j Linear measuring scale according to claim 1 or 2, characterized in that that correction resistors (34, 36) to compensate for irregularities in the characteristics of magnetic resistance elements (22, 23) are provided in order to obtain a fixed measurement or detector voltage value, and that the correction resistors (34, 36) are each connected in parallel to the pair of resistors (33, 35) which form the bridge circuit form. 4. Linear measuring scale with a scale body in which slots are formed at equal intervals, with a detector head, which moves on a series of slots in the scale body, counting the output of the detector head is to thereby measure the movement path of the detector head, characterized in, that a pair of detector sensors (32) at a fixed distance 332H80 ratio on the detector head (2) are arranged that a voltage divider (R .., R ₂ / R ^) for dividing the output voltage of the sensors (32) and a combination circuit (37, 39 to 42) for combining output voltages of the voltage divider are provided are to provide a combined output voltage, whereby the output pulses of the combination circuit (37, 39 to 42) are counted, thereby measuring the movement path of the detector head (2). 5. Linear measuring scale according to at least one of the preceding claims, characterized in that a pair of detector sensors (3 2) are arranged in a fixed spaced relationship on the detector head (2), that a voltage divider (R .., R ", R ) for dividing an output voltage of the detector sensors (32) and a combination circuit (39, 40 to 42; 44 to 4 7) are provided for combining the output voltages of the voltage divider, so that a combined output voltage is provided that a discriminator circuit (41 / to differentiate the direction of movement of the = detector ko | "iS (2) is arranged from the output pulses of _{the combination circuit and applies pulses f} depending on the direction to a counter, whereby the output pulses of the combination circuit are counted and thereby a measure for the Movement j away from the detector head is obtained. 6. Linear measuring scale according to at least one of the preceding claims, characterized in that the combination circuit (39; 44 to 47) has amplifier (44) for amplifying the output voltage (A, B) of the sensors (32), the outputs of which via the voltage divider circuit ( R ₁ , R-, R) are applied to operational amplifiers and buffer circuits (4 7) connected to them. COPY ··. "··· 332U80 7. Linear measuring scale according to at least one of the preceding Claims, characterized in that the detector head (2) has an electrically insulating plate (20) which is inside a sample or a housing or frame (31) is arranged, wherein the housing or the frame (31) consists of a non-magnetic material, and that preferably plate-shaped permanent magnets (43) are arranged on the electrically insulating plate (20), which in turn Wear the magnetic resistance elements (22, 23) via electrically insulating layers. 8. Linear measuring scale according to at least one of the preceding claims, characterized in that the hollow-raised Edge section (8) of one wall section (6) is formed by its edge.