DE19824684C2 - Non-contact position and / or path detection - Google Patents

Description

The invention relates to a device for touch loose detection of the position and / or the distance traveled path along a path moving element.

There are numerous in automatic manufacturing processes oscillating movements of various parts of the system and ge devices for gripping, positioning, holding, tensioning etc. available. For controlling the automatic process is the information of the respective position at any time indispensable. With simple Plants and processes can be recorded and informa tion of the end positions should be sufficient. For this end position reports is at the current technical A variety of limit switches stood different known way of working. For large complex ferti highways with many nested individual knowledge of only the end positions will not move reaching. The additional, infinitely variable information  mation of any intermediate positions can the entire optimize the automatic process considerably.

An extensive field of application for way and post The sensor system on system components consists of entire chemical industry, petrochemicals, air conditioning technology, where especially the reporting of any intermediate positions of valves, flaps etc. of fundamental importance for which has process machines. If the frequency of use is less, so there is contact and touch loose system in these areas.

A sensor system that can be used without restriction in the listed areas of application must fulfill a number of basic properties:

• - total insensitivity to strong mag net fields (welding currents)
• - Lifespan always much longer than machines lifespan
• - Small dimensions and easy adaptation to each component mechanics
• - insensitive to jerky movement and He vibration
• - Linearity and resolution if possible ≦ ± 1.5% of Measuring path
• - high temperature stability
• - standardized output signal 0-20 mA and
• - small pieces appropriate for the application costs.

Previously known sensors can have the desired properties achievements only partially.

• 1. Electrical resistance sensors, potentiometers are a technically clear and widely used sensor system  for converting a mechanical path information into an electrical measured variable. Systemic weakness The place of all resistance givers is constantly moved away and subject to wear Resistance track - grinder, what the operating safety when used with a large number of Be questioning away games.
• 2. Inductive encoder systems have that Contact wear problem is not, but are sensitive to external magnetic fields due to the system which and therefore only to a limited extent in systems with sweat operations can be used. For the simple user In general, the costs are too high.
• 3. Systems based on capacity change or ultra sound are of effort and cost not for the massaged use z. B. ge in production lines is suitable.

From US-PS 3,976,963 is an inductive way known encoder system, in which several reed contact switch with a first common voltage potential tial are connected, between the other An conclude two adjacent reed contacts switch a resistor of a resistance Series connection is connected between the ge common voltage potential and a second span potential are switched. The movable element has a switching magnet that ent when moving as long as the reed contact switch switches it on or off tet. With the reed switch contacts each can only switch the "ON" and "OFF" states. The out is the characteristic curve of this inductive displacement sensor system to a large extent not linear. In particular let  no information based on this output characteristic tion about the position of the switching magnet in the area between two reed contact switches.

DE 25 38 275 B2 is a light barrier with several light-emitting elements and face them the light receiving switches known in parallel are switched to a resistance-free circuit.

The invention has for its object a touch to create a seamlessly working sign system the electro despite being spaced apart African switching elements make a statement about the movable Element is possible even if this element in the area between two neighboring electronics switch.

To solve this problem with the invention Device for contactless detection of the position and / or the path covered a path-moving element is proposed, wherein the device is provided with

• - A series connection of several resistors (R), the series connection being connected between a first voltage potential (V _SS ) and a second voltage potential (GND), and
• - Several non-contact electronics switches between the connection points of neighboring resistors (R) and a common if necessary via a stream limiting resistance with the second voltage potential (GND) connected connecting line ge are switched, whereby  
• - the switches along the path in succession are arranged
• One arranged on the movable element, Radiation-releasing trigger element for contact smooth switching of the electronic switches, in which  
• - The radiation area in which the trigger element Emits radiation, and the distance between neighboring Switches are selected so that Relative movement of the switch assembly and the trigger elements up to at least two switches of the Radiation of the trigger element are exposed, and
• - between the connecting line and the second Voltage potential (GND) an output voltage is tapped, the level of which or the schal the switch corresponds and thus the eyes visible position of the movable element ent represented along the movement path.

In the device according to the invention are therefore as non-contact switches electronic, d. H. Semiconductor switches used when suspended electromagnetic radiation, in particular from IR radiation from the conductive to the blocking state pass over. The movable element is with an electro tripping element emitting magnetic radiation ver see whose radiation is in a radiation area (Ab beam angle) is emitted. The arrangement of the elec tronic switch and the trigger element is such hit that when moving the movable Elements along the sequence of electroni at least two electronic switches each The switch is located in the radiation area of the release element the. Because the intensity of the radiation of the trigger elements, which is in particular an IR diode acts, but is constant but not uniform, because the intensity of the radiation to the edges of the Ab beam range falls, so the electronic Switch the moment they are along the edge of the Radiation area exposed to radiation, too next an intermediate state between the blocking  and transferred to the conductive state. The switch-on The state of the electronic switches does not occur abruptly, but gradually, resulting in a "smoothness tion "of the output characteristic of the invention direction leads. In other words, it turns out an output characteristic that is essentially steady and is differentiable, so that the position of the A triggering element can then also be used to make a statement can, if the trigger element is just between two electronic switches.

As an alternative to the construction of the Of course, it is also possible to use the device Arrange trigger element to be fixed to relative to this the succession of electronic scarf tern to move. Another alternative is that thought, selectively via a sliding aperture the electronic switches of the electromagnetic To expose radiation. The aperture would be that Take over the function of the trigger element, the Aperture between the sequence of the electro African switch on the one hand and an electromagnetic cal radiation emitting "bar" on the other hand is arranged. The previously described "aperture system" net is particularly useful in rotary encoders, since the This structure does not lead to an "extension" of the Ge velvet arrangement in an end position, as in a linear detector based on the aperture principle would be the case.

In the drawing is an embodiment of the Erfin basically based on an electrical circuit shown.

The main components of the arrangement are a tension part ler who formulated from a larger number n in series teter equal resistances R exists, and a same number of n semiconductor switches (transistors), whose switching position is contactless and potential-free e.g. B. infrared influence can be controlled. Every ver binding point between two resistors R is with the Collector of a transistor T connected. The ranks circuit of the resistors R is between VSS and ground switched while the emitters of the transistors over a current limiting resistor S connected to ground are. If one of the transistors has an IR emission exposed, it changes into the conductive state and switches the respective one to its collector two resistors R applied voltage potential through the common emitter test lead to which the Emitters of all transistors are connected.

If the IR detectors are arranged geometrically in a row as they are electrically connected to the voltage divider in the circuit diagram, then an element E (hereinafter referred to as IR emitter element) emitting IR radiation is passed depending on the direction of movement and is 0 Connect volt to V _SS rising or falling from V _SS to 0 volt depending on the position of the IR emitter element on the test lead.

If the movement of the IR emitter element to a mechanical encoder of the travel to be monitored coupled so that the travel length of the path with the geometric length of the IR detector row is identical, is that of the activated IR detector on the Test line switched voltage level an image of the respective position.  

This voltage level theoretically changes to jumps against the size U: n. The number n of the resistors R and IR detectors should therefore not be below 25-30, by a theoretical grade rule of less than 3.5-4.0% hold.

Since the optical transition of the IR emission to two fol IR detectors do not jump in the direction of movement is carried out with the appropriate design of the optical IR path "soft" switching transitions arise, the grade rule goes back to values below ± 1%. The resulting path-proportional voltage level seems to be "infinitely proportional for further processing tional ".

The innovation described enables with simple opening wall a contactless, contactless and stepless Detection and implementation of mechanical routes and positions into a path-proportional, analog electrical Control signal.

The sensor system described above for contactless and non-contact position and displacement detection is therefore particularly characterized in that an optical transistor with the mechanical movement element to be recognized with a moving IR emitter element switches on IR transistors (detectors), each of which (as shown in Fig. 1) ) is connected with its collector to the connection between two resistors R of the voltage divider with n equal resistors R and switches the applied partial voltage to the common emitter line, with the geometrical arrangement of the IR transistors (detectors) a fixed assignment between the mechanical path and Partial voltage switched through by the respective IR transistor (detector) arises, which represents a clear statement about the path and position and, with a large number of n resistors R and transistors (detectors), enables an almost infinitely variable change of the measuring voltage via the path to be detected. Instead of IR radiation, (visible) light, sound, ultrasound or a magnetic field can be used with the appropriate semiconductor switches.

Claims (6)

1. Device for contactless detection of the position and / or the distance covered by an element moving along a path, with

• 1. a series circuit comprising a plurality of resistors (R), the series circuit being connected between a first voltage potential (V _SS ) and a second voltage potential (GND), and
• 2. a plurality of non-contact electronic switches which are connected between the connection points of adjacent resistors (R) and a common connection line, optionally connected via a current limiting resistor to the second voltage potential (GND), where
• 3. the switches are arranged in succession along the path,
• 4. an arranged on the movable element, emitting radiation trigger element for contactless viewing of the electronic switch, wherein
• 5. the radiation area in which the trigger element emits radiation, and the distance between adjacent switches is selected such that up to at least two switches are exposed to the radiation of the trigger element upon relative movement of the switch arrangement and the trigger element, and
• 6. between the connecting line and the second voltage potential (GND), an output voltage can be tapped, the level of which corresponds to the one or more switched switches and thus represents the current position of the movable element along the movement path.

2. Device according to claim 1, characterized in that the trigger element is an electromagnetic Radiation emitting element is and that the Switch upon exposure to radiation this Switch the trigger element. 3. Device according to claim 2, characterized in that the trigger element emits an IR radiation Element is. 4. The device according to claim 1, characterized in that the trigger element is a sound emitting element and that the switches when the sound is suspended of the trigger element switch. 5. The device according to claim 4, characterized in that the trigger element emits an ultrasound Element is. 6. The device according to claim 1, characterized in that the trigger element generating a magnetic field Element is and that the switches when the Switch the magnetic field of the trigger element.