WO2015090846A1

WO2015090846A1 - Sensor arrangement for an absolute position-measuring device

Info

Publication number: WO2015090846A1
Application number: PCT/EP2014/075246
Authority: WO
Inventors: Johannes Muehlfeld
Original assignee: Robert Bosch Gmbh
Priority date: 2013-12-17
Filing date: 2014-11-21
Publication date: 2015-06-25
Also published as: DE102013226202A1

Abstract

The invention relates to a sensor arrangement (20) for a movable scanning head for an absolute position-measuring device having an absolute material measure (50) for scanning the absolute material measure (50) in a measurement direction (11), said sensor arrangement (20) having at least one transmitter coil (30) and at least one receiver coil (40), and the at least one transmitter coil (30) comprising two winding regions (37, 38) having opposite winding directions.

Description

Sensor arrangement for an absolute position measuring device

The present invention relates to a sensor arrangement for an absolute position measuring device and such a position measuring device

PRIOR ART Inductive sensor systems often work according to the transformer principle. An energized exciter structure generates an alternating magnetic field that can be detected by a receiver structure that is galvanically isolated. If external influence is exerted on the distribution of the magnetic field - e.g. by the presence of magnetically or electrically conductive materials - this has an effect on the measurable voltage of the receiver coil according to the law of induction. With this principle, a non-contact inductive measurement is possible.

Initially, the inductive measurement is strongly offset-related in principle. Namely, only the signal component by which the received signal is modulated by the external influences fluctuates as the useful signal. Typically, the proportion of the useful signal is only about 1% o to max. 10% of the total signal. The rest of the signal is offset and i.d.R. undesirable.

For offset relief, a differential structure can be selected. For example, two receiver turns each can form a differential pair. The two windings are connected in series with opposite winding sense, so that as a measurable signal only the difference of the two coil signals is maintained, an offset is eliminated. From US Pat. No. 6,271,661 B1, an inductive absolute position measuring system is known, which has as a material measure markings in a random order, wherein a marking can represent one of more than two information states. Transverse to the measuring direction run there between the markers webs. Individual sensors with differential receiver coils are used to scan the material measure. There are two groups of individual sensors, which are offset by a fraction of the marking distances from each other. There is also a separate transmitter coil per group of individual sensors. EP 2 502 030 B1 discloses an inductive measuring device in which there are two information states for markings on a material measure. However, no webs between two adjacent markings and also not along the measuring direction are disclosed here. Without a support for the material measure, the material measure thus breaks down into two parts. In this case, a sensor comprises pairs of receiver coils which are connected together in a different manner, the individual coils being arranged in each case transversely to one another relative to the measuring direction. Each receiver coil pair is assigned a transmitter coil.

The absolute position measuring systems of the prior art, however, require laborious manufacturing sensors.

It is therefore desirable to provide a sensor arrangement for an absolute position measuring device which is simple and quick to manufacture.

Disclosure of the invention

According to the invention, a sensor arrangement is proposed for an absolute position-measuring device and a position-measuring device with the features of the independent patent claims. Advantageous embodiments are the subject of the dependent claims and the following description.

A sensor arrangement according to the invention is suitable for a movable scanning head for an absolute position measuring device with an absolute measuring standard with markings, wherein the scanning head is provided for scanning the absolute material measure. Advantages of the invention

A sensor arrangement according to the invention has at least one transmitter coil and at least one receiver coil, wherein the at least one transmitter coil comprises two winding regions with opposite winding directions. Instead of the receiver coil, therefore, the transmitter coil is differentially designed to achieve an offset freedom. As a result, the alternating magnetic field already acts differentially on the receiver coil. The received signal of a receiver coil is thus offset-free. The production in particular as a multilayer arrangement is simplified.

In the context of the present application, a coil is to be understood as any winding arrangement which causes a current distribution which has the same effect as one or more annular circulating currents. With a coil, the meander-shaped winding arrangement or parts thereof explained in more detail below is particularly addressed.

The differential design of the transmitter coil also allows a simple configuration of the receiver coils. The receiver coils can in particular be designed with only one winding sense and are thus easier to implement and require fewer vias (layer vias) than the differential receiver coil pairs in the prior art. The number and position of vias plays an important role in the choice of manufacturing technology, since vias occupy a relatively large area. The receiver coils may be formed in only one layer of the multilayer assembly.

If a sensor arrangement comprises a plurality of individual sensors, advantageously the individual sensors each have one transmitter coil and one receiver coil each. This represents a very simple, yet powerful form of a single sensor. Sensor arrangements comprising more than one individual sensor can also be produced very simply within the scope of the invention. In particular, each transmitter sensor may be associated with a transmitter coil, which nevertheless are all connected in series. To provide the two winding regions with opposite winding sense, therefore, only a few layers of a multilayer arrangement are required for a plurality of individual sensors. This reduces the number of required vias. The differential transmitter coil structure requires only a few vias (in series connection only 1). These are only at the extreme ends, where enough space is available. For the realization of the differential transmitter coil structure therefore no particularly fine feature sizes are required.

Preferably, the at least one transmitter coil comprises the two winding areas with opposite winding sense transverse to the measuring direction. The respective information states representing markings on the material measure can thus be arranged transversely to the measuring direction, which increases the resolution.

Between the winding regions with opposite winding sense, in particular, a crossing point can be defined at which the winding sense changes.

Advantageously, adjacent winding areas in the measuring direction also have opposite winding directions if they belong to different individual sensors. As a result, an influence of adjacent markers in the measuring direction when reading a single sensor is reduced.

Advantageously, the transmitter coils are formed as meander turns, in particular galvanically separated in at least two layers one above the other. A meandering turn is a turn that alternately has one or more right turns and one or more left turns. The curves may be curved or angular, with straight areas between the curves. By such a course of a conductor track windings of different coils can be formed with a conductor track in a layer or layer. Windings with opposite sense of winding or windings for closing open meandering sides can be formed by a further conductor track in a further layer without the conductor tracks of the different layers intersecting in an electrically conductive manner. This allows an execution in only two layers and thus a simple and thin design.

It is also advantageous if the transmitter and / or receiver coils project beyond the markings in a direction transverse to the measuring direction at both ends. In other words, the width of a single sensor across the measuring direction is greater than the width of the markers. A possible displacement of the scanning head transversely to the measuring direction thus has a less impact on the generated signals. Alternatively, the markers can survive slightly, whereby the same effect is achieved. The sensor would then be a little narrower than the markings. An absolute position measuring device according to the invention with an absolute measuring standard and a scanning head with a sensor arrangement according to the invention comprises an absolute measuring graduation on which markings are formed in the measuring direction, wherein a marking represents one of at least two, in particular also at least four, different information states. Such a material measure can be easily read with the sensor arrangement according to the invention and is easy to manufacture. In a preferred measuring standard, marking segments are formed next to one another in the measuring direction. At least two marking areas are formed next to one another in each marking segment transversely to the measuring direction. Each marking area may carry a mark or no mark. A marking segment thus represents one of at least two different information states. In the case of an absolute measuring standard, the information states are arranged such that a pattern of n information states does not repeat, x "then corresponds to the number of detectable positions, where x is the number of possible positions Information states per marking segment is Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

The invention is illustrated schematically by means of exemplary embodiments in the drawing and will be described in detail below with reference to the drawing.

figure description

FIG. 1 shows schematically a sensor arrangement for an absolute position measuring device in a first preferred embodiment. FIG. 2 schematically shows a sensor arrangement for an absolute position-measuring device in a second preferred embodiment. FIG. 3 schematically shows an absolute measuring standard for an absolute position measuring device in a preferred embodiment.

DETAILED DESCRIPTION OF THE DRAWING FIG. 1 schematically shows a sensor arrangement 20 of, for example, three individual sensors a, b, c above a measuring graduation 50 with markings (see 51 in FIG. 3). The sensor arrangement 20 is in particular part of a scanning head movably mounted along a measuring direction 1 1. A typical sensor arrangement usually comprises more than three individual sensors, usually 10-25, depending on the accuracy or length of the position measuring device.

The sensor arrangement 20 comprises three planar layers (A), (B), (C) of electrical conductor tracks, which are arranged opposite to one another, wherein they are electrically insulated from one another. The layer (B) comprises three receiver coils 40, which are each a pitch λ in the measuring direction 1 1 long. Contrary to what is shown, a receiver coil 40 preferably has a plurality of winding turns. The reference symbols a, b, c denote the positions of the three receiver coils 40 within the sensor arrangement 22. The receiver coils can each be designed as a single turn in a layer or layer of a multilayer or multilayer arrangement.

Two meander turns 31 and 32 together form the transmitter coils 30, with the two meander turns formed in the two different layers (A) and (B) of the multilayer assembly. For the sake of clarity, the two meander turns 31, 32 are shown next to one another, but in a practical embodiment they lie one above the other. The exact position is indicated by the reference symbols a, b, c. Likewise, the two meandering windings 31, 32 and thus the transmitter coils 30 in a practical embodiment above or below the receiver coils 40. The exact location is again indicated by the reference numerals a, b, c. Each of the meander turns 31, 32 has alternately three right-hander curves and three left-hander curves, of which two angular 90 curves and one angular one are about 45 -curve. Between the curves lie straight areas. Contrary to the illustration, the transmitter coils 30 preferably have a plurality of winding turns.

The reference numeral 33 denotes a through-hole, with which the two turns 31 and 32 are connected to one another. Through the via 33 it is also achieved that the meandering windings are connected in series and thus the same current flows in both.

With l (t) is a transmitter current referred to, the transmitter coils 30 and the two meander turns 31, 32 flows through. It can be seen from the arrows to l (t) that the two meander windings 31, 32 are flowed through by the transmitter current such that two windings which are assigned to a receiver coil 40 are flowed through in opposite directions. In the receiver coils 40 at the bottom in the middle, this is indicated by way of example with the first effective circular current 42 and the second effective circular current 43.

A single sensor is thus formed according to the example shown from a receiver coil 40 and two windings of a transmitter coil 30, which are stacked in layers, i. For example, above the area designated a, are arranged. Further, an intersecting portion 36 of the transmitter coils 30 is shown, which is an area in which the winding sense of a meandering turn changes and the meandering turns 31 and 32 intersect, but in different layers, i. there is no electrical contact.

Transverse to the measuring direction there are two winding regions 37, 38 (which are formed by the same meandering winding, eg 37a, 38a), in which the winding sense of the transmitter coil of a single sensor differs. According to the embodiment shown, adjacent winding regions of the transmitter coils of different individual sensors (which are formed by different meandering windings, eg 37a, 37b) also have different winding directions in the measuring direction. In the transmitter coils 30 during operation of the position measuring device in each case a transmitter alternating current (eg 100 kHz) is fed, which causes a plurality of effective circular currents, with immediately adjacent circular currents have an opposite direction. A receiver coil 40 are each assigned two effective circular currents with opposite direction. These each induce an alternating voltage in the receiver coil 40. If a scale 50 without markers were present, these AC voltages would be equal in magnitude, but with the opposite sign, so that they cancel each other exactly. This effect is called compensation. If this were to be dispensed with, the voltage at the receiver coil 40 would fluctuate depending on an information state by a signal offset, which may be greater in magnitude than the fluctuations in the signal caused by the different information states. This considerably complicates the signal evaluation.

At the top and bottom of the receiver coils 40 is indicated that these, as well as the transmitter coils 30, in each case by a distance 35 over the maximum width (across the measuring direction 1 1) of the markers 51 survive. This ensures that a possible slight displacement of a sensor arrangement 20 of individual coils (virtually always only together with the entire absolute sensor arrangement) in a direction transverse to the measuring direction 1 1 has no influence on a change in the voltage induced in a receiver coil 40 voltage signal since the mark is still covered by the receiver coil 40. The reference numeral 41 denotes connections of the receiver coils to an evaluation unit, the reference numeral 34 designates connections of the transmitter windings 30 to this or another evaluation unit from which they are supplied with voltage.

In addition, at both ends in measuring direction 1 1, the meandering turns can extend beyond the receiver coils 40, i. Transmitter coils would be formed which create a field, but this will not affect a receiver coil. These additional transmitter coils, also referred to as compensation coils, serve to homogenize the field generated by the transmitter coils. Over the last receiver coil, the field thus behaves as over a receiver coil within the transmitter. Without the compensation coils, the field at the edge region would change and the voltage signals generated in the receiver coils would be unclear.

FIG. 2 schematically shows a sensor arrangement 20 for an absolute position-measuring device in a second preferred embodiment. For the sake of clarity includes the sensor array 20 five individual sensors in the measuring direction 1 1 side by side, of which three are denoted by the reference numerals a, b, c.

The sensor assembly 20 in turn comprises three planar layers (A), (B), (C) of electrical conductor tracks, which are arranged opposite to each other, wherein they are electrically isolated from each other. The layer (C) comprises five receiver coils 40 which are each a pitch λ in the measuring direction 1 1 long. The receiver coils can each be designed as a single turn in a layer or layer of a multilayer or multilayer arrangement.

Next, transmitter coils 30 are shown. Four meander turns 31 and 32 each form part of the transmitter coils 30, wherein the four meander turns 31, 32 are formed in two different layers (B), (A). In each of the layers (A) and (B), two meander turns (31 in A; 32 in B) are arranged side by side transversely to the measuring direction. For the sake of clarity, the two pairs 31, 32 in the two layers (B), (A) are shown offset one above the other, but in practical implementation these layers lie one above the other. Similarly, the meandering windings 31, 32 and thus the transmitter coils 30 are in a practical embodiment above or below the receiver coils 40. Below in Figure 2 is a superposition of the three layers (A), (B), (C) is shown. The mode of operation of the sensor arrangement in FIG. 2 corresponds to that which has been described for the sensor arrangement in the first preferred embodiment to FIG.

The reference numeral 33 through holes are marked, with the meandering fertilize 31 and 32 are interconnected. The reference numeral 41 designates connections of the receiver coils to an evaluation unit, the reference numeral 34 designates connections of the transmitter coils 30 to the same or another evaluation unit from which they are supplied with voltage. Specifically, the upper meandering turn 31 in the figure is connected to the upper meandering turn 32 at 33 in the figure and connected in series, and the lower meandering turn 31 in the figure is connected to the lower meandering turn 32 at 33 in the figure and connected in series. Due to the series connection, the same current flows in all transmitter windings, whereby the generated fields for all individual sensors and winding areas amount- are moderately equal. Preferably, a series connection is also realized at 33 ', so that all transmitter coils can be energized at only two (in the figure, the two upper) terminals 34. With l (t), a transmitter current is referred to, the transmitter coils 30 and thus the meandering windings 31, 32 flows through. It can be seen from the arrows at l (t) that the meander windings 31, 32 are flowed through by the transmitter current such that two sections which form a transmitter coil 30 and are thus associated with a receiver coil 40 are flowed through in opposite directions. In the case of the receiver coils 40, this is indicated by way of example by the reference numerals 42, 43, which represent two sections with opposite winding sense. Through the plated-through holes 33 it is also achieved that the meandering windings are connected in series and thus the same current flows in all.

Each of the meander turns 31, 32 alternately has two right-hand curves and two left-hand turns, which are approximately 90 angular curves. Between the curves lie straight areas.

A single sensor a, b, c is formed from a receiver coil 40 and two winding regions 37, 38 of the meandering windings 31, 32, which are arranged transversely to the measuring direction 1 1 side by side.

FIG. 3 schematically shows an absolute material measure 50 in a preferred embodiment. In the measuring direction 1 1 marks 51 of length λ are formed. A marker 51 represents one of two different states of information, depending on whether the marker 51 is formed at the top or the bottom (with respect to FIG. 3).

As a material for the material measure 50 is in particular a photochemically etched metal strip of ferromagnetic material, preferably stainless ferritic steel, in question. The marks 51 are preferably made as rectangular holes in the metal strip. The markers 51 can all have the same shape and size. However, different sizes are also conceivable, in particular with regard to the width across

Measuring direction, depending on the number of different information states that can be displayed. Instead of holes, it is also possible to provide solid, non-ferromagnetic material. This is a possible embodiment of the absolute material measure, but there are also other embodiments, in particular with regard to the number of possible information states that can be displayed with a marker and distances of the markings to each other, possible.

At the points where marks 51 are provided in the material measure 50, the induction effect weakens, so that the two induced voltages no longer cancel each other out. At the receiver coil then there is an induced alternating voltage whose amplitude represents the information state.

It should be noted that eddy currents are also induced in the material measure 50, which counteract the above effect exactly. Since the material measure is preferably made of stainless steel with low electrical conductivity, but these are low. Finally, at the lower and upper edge of the material measure 50, a first longitudinal web 53 and a second longitudinal web 54 are formed, whereby the material measure stability is given.

Claims

claims

1. Sensor arrangement (20) for a movable scanning head for an absolute position measuring device with an absolute material measure (50), for scanning the absolute material measure (50) in a measuring direction (1 1),

wherein the sensor arrangement (20) has at least one transmitter coil (30) and at least one receiver coil (40),

wherein the at least one transmitter coil (30) comprises two winding regions (37, 38) of opposite winding sense.

2. Sensor arrangement according to claim 1, wherein the at least one transmitter coil, the two winding regions (37, 38) with opposite winding sense transverse to the measuring direction (1 1).

3. Sensor arrangement according to claim 1 or 2, wherein lying in the measuring direction (1 1) adjacent Windungsbereiche opposite winding sense.

4. Sensor arrangement according to one of the preceding claims, wherein the at least one transmitter coil (30) by at least one meandering winding is formed (31, 32), which alternately has one or more right-hand curves and one or more left-hand curves.

5. A sensor arrangement according to claim 4, wherein at least one curve of the one or more right-hand curves and the one or more left-hand curves is curved.

6. Sensor arrangement according to claim 4 or 5, wherein at least one curve of the one or more right-hand curves and the one or more left-hand curves is angular.

7. Sensor arrangement according to claim 4, 5 or 6, wherein the at least one meandering turn (31, 32) between two successive curves straight.

8. Sensor arrangement according to one of claims 4 to 7, wherein the at least one transmitter coil (30) formed by at least two meandering turns (31, 32) extending in different layers (A, B, C) of a multilayer arrangement.

9. Sensor arrangement according to one of claims 4 to 8, wherein the at least one transmitter coil (30) by at least two meander turns formed (31, 32) which extend in the same layer (A, B, C) of a multilayer arrangement.

10. A sensor arrangement according to one of claims 4 to 9, wherein the at least one transmitter coil (30) by at least one meandering winding formed (31, 32), which alternately has three right-hander curves and three left-hander curves or which alternately has two right-hander curves and two left-hander curves.

1 1. Sensor arrangement according to one of the preceding claims, wherein the at least one receiver coil (40) has only one winding sense.

12. Sensor arrangement according to one of the preceding claims, comprising a plurality of individual sensors, each of the plurality of individual sensors (a, b, c) each having a transmitter coil and a respective receiver coil.

13. Absolute position measuring device with an absolute measuring graduation (50) and a scanning head with a sensor arrangement (20) according to one of the preceding claims, wherein on the absolute measuring graduation (50) in the measuring direction (1 1) markings (51) are formed and wherein a mark (51) represents one of at least two different information states.

14. An absolute position measuring apparatus according to claim 13, wherein a marker (51) represents one of at least four different information states.

15. Absolute position measuring device according to claim 13 or 14 in reference to at least claim 12, wherein a marking (51) in the measuring direction (1 1) has a length (λ) corresponding to the length (λ) of a single sensor (a, b, c) equivalent.