DE8307146U1 - Measuring device - Google Patents

Description

mm 1 mm

DR. JOHANNES HEIDENHAIN GMBH · ⁴ · ^{Mar2 1S83}

Measuring device

The invention relates to a measuring device according to the preamble of claim 1.

With such a measuring device, the electrical control pulses generated at the reference marks can can be used in various ways, e.g. to reproduce the zero position in the counter, for moving to a certain position at the beginning of the measurement and for checking interference pulses as well as to act on a downstream control device.

From DE-PS 24 16 212 is an incremental one Length or angle measuring device known, in which on a scale in addition to the incremental division Reference marks are provided on a separate track. The absolute values of these reference marks are determined by the different distances -

between the individual reference marks; these distances between the reference marks are given by Scanning of the incremental division determined. To recognize the absolute position of a reference mark therefore always two reference marks have to be scanned. This procedure is cumbersome and time-consuming if, for example, two such reference marks are far apart. In addition, incorrect counting of the increments between two reference marks can result in incorrect Distances and thus incorrect absolute values for the reference marks are determined.

In DE-PS 29 52 106 an incremental length or angle measuring device is described in the reference marks on a scale next to the division, each with different line group distributions are provided. The individual reference marks are represented by scanning fields in a down |

scanning unit scanned, each scanning field being uniquely assigned to a reference mark by it has the same line group distribution. This arrangement is relatively expensive because the line group distributions of the individual reference marks differ as much as possible from one another must distinguish in order to enable a clear identification of the individual reference marks. The scanning unit must have an identical scanning field for each reference mark.

DE-OS 30 39 483 shows an incremental length or angle measuring device in which on

a scale next to a graduation track parallel to each other a reference mark track and a code mark track are arranged. For scanning the reference

However, reference marks and the associated code marks are separate scanning fields on a scanning plate required in a scanning unit, each code mark being assigned its own scanning field.

The invention is based on the object of specifying a measuring device of the above-mentioned type, in which the scanning of the reference marks and the respectively associated code marks is significantly simplified can be.

According to the invention, this object is achieved by the characterizing features of claim 1.

The advantages achieved by the invention are in particular that for scanning the reference marks and the associated code marks only one scanning field on the scanning plate of the scanning unit is necessary because the reference marks and the code marks are the same, at least in the measuring direction Have structure. This structural correspondence between the code marks and the reference marks the production of the scale and the scanning plate is significantly simplified, so that a cheaper measuring device results.

Advantageous further developments of the invention can be found in the subclaims.

Embodiments of the invention are explained in more detail with reference to the drawing.

f show it

Figure 1 schematically an incremental length measuring device,

! Figure 2 a scale and a scanning

, plate of the length measuring device,

, Figure 3 is a signal diagram of Re-

j reference and code signals and

(10 Figure 4 shows a section of the scale

according to Figure 2.

In Figure 1, a photoelectric incremental length measuring device is shown schematically, the

consists of a scale M and a scanning unit A, each in a manner not shown are connected to objects to be measured on a processing machine. On the M scale there is an I. incremental graduation T in the form of a line grid

(Figure 2) applied, which photoelectrically in incident light is scanned by the scanning unit A without contact. Along the division T is on the

Scale M a series of reference marks R

(n = 1, 2, 3, ...) are provided, each of which has identical groups of lines with a specific line distribution. _{The periodic scanning signals S 1} , S- generated by scanning the graduation T, which are amplified in the scanning unit A and converted into rectangular signals S .. ', S ₃ ¹ , control an electronic counter Z, which displays the measured values in digital form . The around a

; ■ Quarter of the lattice constant (grating period) of the

% Division T mutually phase-shifted rectangular

«■ *« III

Signals S ₁ ¹ , S ₃ ¹ are used to discriminate the scanning direction. The reference signal RS generated at the reference marks R is amplified in the scanning unit A, converted into a square-wave signal RS _n ¹ and also fed to the counter Z.

Various functions can be triggered with the reference signals RS _{n obtained.} By evaluating the reference _{signals RS n} , for example, an incremental measuring device becomes a quasi-absolute measuring device if each reference mark R is assigned a number which represents its absolute position in relation to an invariable zero point. Furthermore, a specific reference mark R can serve to set the counter Z to the value “zero” when the _{reference signal RS fl obtained from the specific reference mark R occurs.} But these functions -are only be used if the selected reference \ brand R can be clearly identified.

For identification, each individual reference mark R is serially at least one code mark C (n, m = 1, 2, 3, ...), where the code mark C at least in measuring direction X strukturnm

moderately coincides with the reference mark R.

According to Figure 2, the code marks C between the individual identical reference marks R are serial ! to the reference marks R on the scale M indicated

arranges. From the series of reference marks R _n is>

only one reference mark R shown, which the

Code marks C ₁ -C _{4 are} assigned. To distinguish the code marks C _nl - C _fl4 from the Re- I _;

ferenzraarke R is the width a of the code waves η

perpendicular to the measuring direction X less than

b
is a = b / 2.

the width b of the reference mark R; according to Figure 2

For scanning the scale M in the scanning unit Α a scanning AP that for scanning the graduation T two to one quarter of the lattice constants of the pitch T staggered scanning fields AT is provided in FIG 2, .., having AT _3, which are identical with the division T are; the scanning fields AT., AT “are assigned photo elements (not shown) for generating the scanning signals S-, S ₂ . For scanning the reference mark R and the code marks C ₁ -C. a scanning field AR is provided on the scanning plate AP, to which a photo element (not shown) for generating the reference signal RS and code signals CS .. - CS. assigned; the scanning field AR coincides with the reference mark R.

match.

The code signals CS> CS generated when the scale M is scanned from left to right according to the figure . result in the binary combination "1010" for unambiguous identification of the associated reference mark R (FIG. 3). Since the width b of the reference mark R is twice as large as the width a of the code marks C ₁ -C ₄ , the code signals CS-CS. be clearly distinguished from the reference signal RS due to the different signal levels; the ratio between the widths a and b can be chosen arbitrarily. The code signals CS ₁ - CS ₄ are fed to an evaluation device in the Z counter.

If the scanning unit A scans the scale M in the positive S measuring direction X from left to right, so

the reference mark R is followed by the next code— ³ η

marks C ₁ and then the associated reference _{mark R +1} etc. (not shown in FIG. 2). To get the first in this scanning direction

Code mark C,., ,, to be able to recognize should η + ι, ι

this code mark C ₊₁ . for example have the binary value "1". In general, the code marks C can have start and end information. With the initial information, the evaluation device in the counter Z can be prepared for code information to be read out following the initial information. The end information serves to ensure that the entire code information has been read out; in this way, a possible reversal of the measuring direction X in the middle of the scanning of the code information can be recognized.

20th

When the scanning unit A moves in the positive measuring direction X from left to right, the code information of the code marks C is scanned before the associated reference mark R _{n is} scanned.

When scanning in the negative measuring direction -X from right to left, the direction-dependent Evaluation of the code information recognized,

that after the code marks C. "^ The reference

n + 1, m

30th

mark R must follow.

The code marks C and the associated reference mark R can or can follow one another without gaps

^ B ^ ft ^

M have a certain distance from one another.

I The gapless arrangement is recommended if between ^J

> see the individual reference marks R only a little

h η

I have space. The code

fc 5 brands C and the reference brands R as whole-number

f liger part and / or as integral multiples of the

Graduation period of the incremental graduation T on the

* ^: Scale M applied so that the scanning dsr

4 code marks C and the reference marks R im

I 10 cycle of the sampling of the incremental graduation T

| - follows.

I according to Figure 4 are on an enlarged scale

cut of the scale M according to FIG. 2 a reference mark R as well as the associated code marks C ' _nl - C' _n4 and the first code mark C ' _{n +} .. not the one following in the positive measuring direction X.

j reference mark R _{n + 1 shown in} series. '

The code marks C _Λ - C ' . and C _Λ . are

ni n4 η + 1, 1

20 completely identical to the reference mark R and are

the scanned by the scanning field AR of the scanning plate AP according to FIG.

To distinguish the reference mark R from the 25 associated code marks C ' _nl - C' _n4

the distance r between the reference mark R

and the nearest code mark C. of the distance c between the individual neighboring code, marks C ' _nl - C' _{n4 <} To differentiate the re-

i 30 reference mark R _R from that in the positive measuring direction X

following, non-associated code mark C _{+ 1}

the mutual distance u is provided. The code signals CS '- CS' generated result in the Binary combination "1101".

ι I

I I

1 I.

I ■

> IMi u ■ · ■■ j

* I t p, ' <I t ι ι t

To distinguish, instead of the distances c,
r, u also the corresponding distances c ¹ , r ' _F u ¹
between the centers of gravity (centers) of the reference mark R and the code marks C are used

will. The reference mark R and the code marks

C and the distances c, r, u, c ¹ , r ¹ , u ¹ in
Measurement direction X can in turn be an integer

Parts and / or as integer multiples of the |

Graduation period of the incrementation T on the i

Scale M be formed. |

The evaluation of the generated code signals CS

as well as the distances c, r, u, c ' , r ¹ , u ¹ takes place |

in the evaluation device of the counter Z. This I

Evaluation device can be a selection device %

I, with the help of which certain reference 1

I mark R from the series of reference marks R 1

can be selected and brought into effect. 4th

Claims (6)

- 10 claims 1. Measuring device, especially incremental Measuring device / provided along the division of a scale in the measuring direction Reference marks that are absolutely assigned to the division and on which they interact reproducible electrical impulses are generated with a scanning unit, which have a Acting on the counter of the measuring device and / or a control device, characterized in that that each of the identical reference marks (R) is serially assigned at least one code mark (C) (n, m = 1, 2, 3, ..,) is and that the code mark (C) at least in the measuring direction X corresponds structurally with the reference mark (R). 2. Measuring device according to claim 1, characterized in that to differentiate the code mark (C) from the reference mark (R) the width a of the code mark (C) perpendicular to the measuring direction X is smaller than the width b of the reference mark (R). 3. Measuring device according to claim 1, characterized in that to distinguish the reference mark (R) of the associated code mark (C) is the distance r between the reference mark (R) and the closest associated code mark (C) at distance c between neighboring associated code marks i - 11 - j, - ^tc - nm ^fu n, id + 1 ^w * ^U nm ' ^u n, m - 1 ^J ^ I -distinguishes. s 4, measuring device according to claim 1, characterized 5 shows that in order to distinguish the re- reference mark (R) from the closest M η ■ 'subordinate code mark (C J and from the next lying non-associated code mark (C ^ ₁ ) I the distance r between the reference mark <R) Jl 10 and the closest associated code mark r (C) from the distance u between the reference nm I mark (R) and <? He closest not subordinate code mark (C ₁ ..) differs. 15th 5. Measuring device according to claim 1, characterized in that that the code marks (C) in addition to the identification features for the associated j Reference mark (R) at least information, 'have functions for completeness detection. 20th 6. Measuring device according to claim 1, characterized in that the code marks (C _nm ) and the ι reference mark (R) and the distances c, r, u in measuring direction X as an integer part and / or 25 as an integer multiple of the graduation period the division (T) of the scale (M) are formed.