DE102014220214B4 - Optical position detection device, rotary encoder with an optical position detection device and method for position detection with increased operational reliability - Google Patents

Abstract

Optical position detection device (1), in particular a revolution counter for a rotary encoder (3), with a control unit (21), at least one controllable light source (15), at least one optical data carrier (13, 17) with at least one data track (17.1 to 17.n. ), with at least one light sensor unit (19) for generating a light quantity signal (L) when a light quantity reference value (M) is exceeded by a light quantity (Y) received by at least one reference photo receiver (19.r), the light sensor unit (19) at least one photo receiver ( 19.1 to 19.n) for the at least one data track (17.1 to 17.n) of the data carrier (13, 17) and the at least one reference photo receiver (19.r), with a measuring device (36) for determining an operating parameter (B) the light source (15) upon receipt of the light quantity signal (L), with a memory for storing the operating parameter (B) and with a light quantity control unit (38) for controlling the light source (15 ) as a function of the operating parameter (B), the measuring device (36) being a time measuring device, and the operating parameter (B) being the time period (t) which elapses after the light source (15) is switched on until the light quantity signal (L) is generated the measuring device (36) has passed, the light source (19) being able to be operated in a pulsed manner and the pulse duration corresponding at least to the time span (t).

Description

The invention relates to an optical position detection device, in particular a revolution counter for a rotary encoder. The invention also relates to a rotary encoder with a single revolution unit, a multiple revolution unit and a central control unit, the multiple revolution unit being designed both for a mains-operated operation from an external voltage source and for a mains-independent operation from a separate energy store. The invention also relates to a method for position detection with the aid of an optical position detection device, in particular a revolution counter of a rotary encoder.

Optical position detection devices, such as revolution counters, as independent components and as components of rotary encoders are known. In order to be able to operate them in the vicinity of magnetic fields, such as those generated by electric motors, optical revolution counters and optical rotary encoders are increasingly being used. It is often desirable to be able to reliably detect and count revolutions, for example of a machine part, even if the machine and with it an external voltage supply for the revolution counter or the rotary encoder or even just the external voltage supply for the revolution counter or the rotary encoder, for example due to a power failure or an emergency shutdown. For example, when a machine is running after a shutdown, it may be necessary to record the number of revolutions of a machine part that will continue until the machine comes to a standstill, for example, in order to be able to determine the position of a component driven by the rotating machine part when the machine is switched on again. It may also be necessary to generate an emergency signal if at least part of a machine is turned even though the machine is switched off. The emergency signal can, for example, either give a warning to operating people or trigger an automatic braking device on the machine. For these safety-related functions mentioned, revolution counters can have their own energy stores which are separated from the network and which, even if an external power supply is lost, supplies the energy for detecting and counting revolutions. When a revolution counter is operated by a separate energy store, which can be implemented, for example, by a battery, an accumulator, a fuel cell or other suitable storage technologies, it is desirable to operate the revolution counter as energy-saving as possible. As a result, the lifespan of the energy store can be maintained as long as possible.

The desired lifespan for the separate energy storage devices is on the order of approximately 100,000 hours.

The DE 10 2009 017 820 B3 shows an optical rotary encoder with a single-turn unit and a multiturn unit (revolution counter), which is designed for energy-saving operation in the event of the external voltage source being removed. The encoder has a common light source for the single-turn and multi-turn units. If the external voltage is lost, the multiturn unit is operated by a separate energy store and the light source and other parts of the multiturn unit are operated in a clocked manner. The energy consumption of the multiturn unit can already be significantly reduced through the clocked operation. Such a solution is also in the EP 0 158 781 B1 described. Another in the DE 10 2009 017 820 B3 Technique described for energy saving still consists in not waiting for the complete execution of a cycle in order to switch off the elements of the multiturn unit, but rather to end the switched-on state within a cycle when a valid signal has been detected by the multiturn unit. Although this method lowers energy consumption compared to evenly clocked operation, it also has some disadvantages. On the one hand, algorithms that check the validity of the signal and control the shutdown of the multiturn unit on the basis of this information must be carried out in network-independent operation. With each cycle, this leads to a slight increase in energy consumption, which has an overall impact on the service life of the energy store. Another disadvantage is that the multiturn unit also uses photo sensors of the singleturn unit. If the single-turn unit is damaged, the revolution counter can no longer be used. However, since the revolution counter can be used for safety-relevant functions as described above, such an embodiment is disadvantageous in certain areas of application. The publication US 5,569,913 A. relates to an optical displacement sensor supplemented by a system for generating a signal related to information other than the relative displacement of a measured object, such as detection of a change in the amount of light emitted or detection of the origin. It is described that an operating parameter of a light source of an optical position detection device is adapted as a function of a quantity of light detected by means of a light sensor unit.

It is therefore the object of the invention to provide an optical position detection device, a rotary encoder and a method for position detection which enable energy-saving operation, especially in a network-independent state, and also offer high operational reliability.

For the optical position detection device mentioned at the outset, the object according to the invention is achieved by an optical position detection device, in particular a revolution counter for a rotary encoder, with at least one controllable light source, at least one optical data carrier with at least one data track, with at least one light sensor unit for generating a light quantity signal when a light quantity reference value is exceeded by a quantity of light received by at least one reference photo receiver, the light sensor unit having at least one photo receiver for the at least one data track of the data carrier and the at least one reference photo receiver, and with a measuring device for determining an updated operating parameter of the light source upon receipt of the light quantity signal and a light quantity control unit for controlling the Light source depending on the operating parameter.

According to the invention, the operating parameter is the period of time that has passed after the light source was switched on. The light quantity signal is then used to determine the time after switching on the light source that it takes until a light quantity reference value is exceeded by the light quantity received by the reference photo receiver. The operating parameter does not necessarily have to be the time span. For example, it can also represent the energy consumed by the light source. The invention is described below by way of example with the time period as the operating parameter. The light quantity reference value is preferably programmed into the light sensor unit. However, it can also be stored in the control unit. If the light quantity reference value is stored in the light sensor unit, the light quantity signal can forward the information to the control unit as to whether the light quantity reference value has been exceeded or fallen short of. If, on the other hand, the light quantity reference value is stored in the control unit, the light quantity signal can contain the information about the light quantity detected by the light sensor unit, which is then compared in the control unit with the light quantity reference value stored therein. The light duration of the light source determined in this way can be used as the minimum light duration for the light source in pulsed operation. The light quantity control unit controls the light source depending on the determined time period. For example, the light quantity control unit can only switch on the light source for a lighting period that corresponds to the previously determined time period, since the receipt of the light quantity signal after the time period indicates that this time period is sufficient as a lighting period for safe operation. The light source is preferably formed by a light emitting diode (LED). The light sensor unit is preferably formed as an integrated circuit on which the at least one photo receiver is applied directly. The at least one photo receiver can, in particular, sit as a photodiode on a housing of the integrated circuit. The light sensor unit can have suitable circuits, for example integrators, in order to determine the amount of light detected and, for example, have at least one comparator which compares the photocurrent generated by the at least one photodiode or a voltage determined therefrom with the light quantity reference value. The control line is preferably designed as a separate line which is physically separated from other lines between the light sensor unit and the control unit. Alternatively, the line can also be designed as a channel of a multiplex transmission or another transmission technology.

For the rotary encoder mentioned at the outset, the object according to the invention is achieved in that the multiple revolution unit is formed by an optical position detection device according to the invention. The position detection device according to the invention represents a revolution counter in a rotary encoder. With such an optical revolution counter, a rotary encoder can be realized, which can count the revolutions reliably even if the external voltage source is no longer present.

For the method for position detection mentioned at the outset, the object of the invention is achieved by a method for position detection with the aid of an optical position detection device, in particular a revolution counter of a rotary encoder, a light quantity signal being generated as soon as a sufficient quantity of light has been detected after switching on a light source of the position detection device, wherein the operating parameter required to achieve the light quantity signal is stored in the control unit of the revolution counter and wherein the light source is controlled as a function of the stored operating parameter. This has the advantage that, in network-independent operation, the light source can be operated with the required lighting duration, which is just sufficient to reliably detect the signal detected by the optical data carrier. Whether the light quantity signal is generated can preferably depend on whether a light quantity reference value is exceeded by the light quantity. The light quantity reference value can be stored in a light sensor unit or in the control unit. The light quantity reference value is preferably stored in the light sensor unit, which also includes photo receivers. This lighting duration can be used to operate the light source in network-independent operation, so that it is ensured that the light source does not last longer than remains switched on, which can save energy.

The solution according to the invention can be further improved by various configurations which are advantageous in each case and can be combined with one another as desired. These embodiments and the advantages associated with them are discussed below.

According to a first advantageous embodiment, the measuring device and / or the light quantity control unit can be integrated in the control unit. This enables a particularly compact construction. In particular, the control unit can be formed as an integrated circuit or microcontroller.

The measuring device is a time measuring device and the operating parameter is the period of time that has passed from switching on the light source until the light quantity signal is received in the measuring device. This can provide a particularly good basis for controlling the light source. In particular, the light source can then be operated at least as long as the period of time thus determined. This enables energy to be saved in off-grid operation.

According to the invention, the light sensor unit has at least one reference photo receiver, which is used exclusively for the detection of the light used for determining the light quantity signal. This reference photo receiver is preferably formed by a photodiode and is also referred to below as a reference diode. It is therefore particularly advantageous if the light sensor unit has a plurality of photodiodes, at least one of which is used as a reference diode. The remaining photodiodes are used to record the data tracks on the data carrier.

The optical position detection device according to the invention is not limited to a revolution counter. With the arrangement according to the invention, linear movements or curved movements can also be detected. In the case of straight-line or curved movements, the optical data carriers can be formed, for example, as strips which contain data tracks which run parallel to the strips. However, the optical position detection device is preferably a revolution counter, in particular for a rotary encoder.

The data carrier is preferably formed by a partially permeable code disk. The code disk can have circular data tracks, of which one data track is available for a photo receiver. The data tracks can alternately have light or dark areas, which forms a code.

The optical data carrier can have at least one uncoded reference data track in addition to the data tracks, which can be evaluated by the at least one reference photo receiver. The reference data tracks, which are recorded by the at least one reference photo receiver, are preferably designed to be completely translucent. In this way, a particularly reliable detection of the required amount of light can be made possible.

The determination of the light duration via the operating parameters such. B. the time span not only allows the operation to be adapted to the properties of the light source and photo receiver, but can also provide information about the quality or condition of the optical data carrier during operation. An increase in the duration of light required during operation or a light quantity signal that starts later may indicate increasing contamination or damage to the optical data carrier.

The light sensor unit can be connected to the control unit via data lines for transmitting the signals of the photo receivers, and in addition to the data lines, a control line can be provided between a light quantity signal output of the light sensor unit and an input of the measuring device for transmitting the light quantity signal. This configuration allows the light quantity signal to be transmitted separately from the data signals which are transmitted from the light sensor unit and its photo receivers to the control unit. This independent transmission allows a particularly safe operation, since the light quantity signal does not have to be modulated onto the data signals which are transmitted via the data lines.

The light quantity signal output can in particular be a separate output of the light sensor unit. The light quantity signal can therefore be transmitted to the control unit separately from signals from the position detection.

It is particularly advantageous if a light control output of the control unit is additionally connected to a control input of the light source. The light control output can in particular be controlled by the light quantity control unit or be part of it. The light control unit can, for example, switch the light source on or off depending on the operating parameter.

The lighting duration can be determined in mains operation. One possibility for this is, for example, that the position detection device always is operated pulsed. The duration of the light can then be determined for each pulse or for selected pulses. Alternatively, the position detection device or the light source and the light sensor unit can be operated continuously. However, without endangering the function, the light source and the light sensor unit can be switched off briefly and a single test pulse can be generated. Continuous operation can be resumed after the lighting duration has been recorded. However, it should be noted here that the interruption or the fault, the lighting duration determined in this way can then be stored in the control unit and used to operate the light source and the light sensor unit if the position detection device is supplied by a separate energy store independently of the mains. The advantage now lies in the fact that the lighting duration can be determined without having to consume energy from the separate energy store. In a network-independent operation, the revolution counter can then be operated with the previously determined lighting duration.

A particularly safe operation can be achieved in that a separate energy store and a switchover unit are also provided, the switchover unit being designed for switching between an external voltage supply and the separate energy store. This ensures a smooth changeover between network operation, that is, the external power supply and network-independent operation via the separate energy store.

The separate energy storage device can be an energy source that supplies the position detection device with energy independently of a power network. It is preferably designed as a battery or accumulator, but the use of other energy stores, for example fuel cells or supercapacitors, is also possible. The separate energy store can be accommodated in a common housing with further components of the position detection device. In this way, a particularly compact position detection device or a rotary encoder can be implemented with a position detection device according to the invention.

As an alternative to this, the separate energy store can also be formed as a housing part of the position detection device or a rotary encoder. It is particularly advantageous if the separate energy store is integrated in a plug connection of the position detection device or in a connection cable belonging to the position detection device. The separate energy store can also be arranged at a distance from the position detection device and connected to it by means of an electrical connection. In the aforementioned cases, it is then possible to change, maintain or check the separate energy store without having to open a housing of the position detection device.

Switching from one power supply to another can be communicated to the control unit by the switchover unit. For this purpose, a data line can exist between the two components. As soon as the position detection device is supplied with voltage from the separate energy store, at least the light source and the light sensor unit are operated in pulsed fashion in order to save energy. The pulse duration is preferably at least as long as the previously determined and stored in the control unit lighting duration, since it is known that this lighting duration is at least necessary to enable reliable detection of the data on the data tracks.

If the position detection device according to the invention is a revolution counter, the at least one optical data carrier can be formed by at least part of a rotatable code disk, at least one data track alternately having coded octants. The code disk is preferably mounted on an encoder shaft. The encoder shaft can be part of the machine to be monitored or connected to it. The division into octants is particularly advantageous, since it can be used to determine whether the code disk is rotating even with a slight rotation of the code disk. In principle, it is also possible to use code disks whose code tracks are divided into quadrants. However, it may be possible that the code disk first has to be rotated through 90 ° until this rotation is detected. In addition, the detection of a rotation of the code disk with a division into octants is possible even at high accelerations if the revolution counter is operated in a pulsed manner.

The code disk preferably has several data tracks. The code disk can, for example, have adjacent pairs of data tracks, the coded areas of which are each offset from one another. For a data track that is subdivided into octants, this means, for example, that one data track of a pair in one octant has a light area and the second data track of the pair in the same octant has a dark area. Differential coding is possible in this way. In addition to the at least one data track with octant division, the code disk preferably has further data tracks with quadrant division and / or at least one further data track with a semicircular division. The code disk particularly preferably has exactly one associated data track for each data track subdivided into octants, which is divided into quadrants and exactly one associated one Data track that is divided into semicircles. With such a code disk, the revolution counter can also perform a single revolution evaluation (single-turn evaluation), the resolution of which is 45 °. The revolution counter then represents a particularly compact encoder.

The rotary encoder mentioned at the outset can be further improved in that the single rotation unit has a single rotation light source and a single rotation light sensor unit, and in that the optical data carrier of the rotation counter has single rotation data tracks for evaluation by the single rotation unit. The single revolution unit and the revolution counter then use a common code disk. This enables a particularly compact construction.

As already mentioned at the beginning, the position detection device according to the invention represents a revolution counter when used in a rotary encoder. Therefore, the optical position detection device according to the invention is referred to below as a revolution counter.

According to the invention, the single revolution unit (single-turn unit) and the revolution counter each have at least one separate light source. This is particularly advantageous since, in the case of mains-independent operation, the light source for the single revolution unit can be switched off. The light source of the revolution counter must therefore only illuminate the data tracks that are necessary for the revolution counter. This is particularly advantageous compared to a rotary encoder in which a single light source has to illuminate all data tracks, since either a particularly strong light source or a complex expansion optics must be used here.

The revolution counter according to the invention can use a light source which is adapted for illuminating the data tracks of the revolution counter. This can mean, for example, that a light source with a lower luminosity can be used than is the case with a rotary encoder with a single light source for all data tracks. Since the light source can be aligned in such a way that it only illuminates the data tracks of the revolution counter, a sufficiently large amount of light can always fall on these data tracks. This enables particularly energy-saving operation. Alternatively, a similarly strong or equally strong light source can be used as for the single revolution unit. Since a particularly high light intensity is then used for the data tracks of the revolution counter, a particularly safe operation of the revolution counter can be made possible.

As an alternative to the previously described rotary encoder with an optical single revolution unit, the revolution counter according to the invention can also be used with a rotary encoder whose single revolution unit is operated by another method such as, for example, magnetically, capacitively, via sliding contacts or inductively. For example, an optical data carrier for the revolution counter can then be attached to the encoder shaft of the single revolution unit, or it can be implemented as an extension of a rotating disk of the single revolution unit.

The above-mentioned method for position detection can be improved by initially determining the time span only in network operation and storing it in the control unit.

In order to save energy in the network-independent state, the light source of the position detection device can be operated in a pulsed manner at least in the network-independent state, the pulse duration corresponding at least to the time period stored in the control unit. It is particularly advantageous if, in addition to the light source, the light sensor unit is also operated in a pulsed manner with the photo receivers.

In order to increase operational reliability, the pulse duration can correspond to the sum of the stored time period and a temporal buffer value. The buffer value can be, for example, 20% to 30% of the stored time period, preferably 25%.

In order to further reduce the energy consumption in the network-independent mode, an economy mode with a first pulse frequency can be provided in the pulsed mode if no movement is detected and a counting mode with a second pulse frequency if a movement is detected, the second pulse frequency being higher than that first pulse rate. With a revolution counter, the movement is a rotation of the code disk.

The first pulse frequency is preferably in the order of 100 Hz, preferably 125 Hz. The second pulse frequency is preferably approximately 1 kHz. The first pulse frequency enables particularly energy-saving operation. According to the invention, the switch to the second pulse frequency and thus to the counting mode only takes place when a movement is detected.

In order to be able to switch from the economy mode to the counting mode particularly quickly in the case of a revolution counter according to the invention, and to ensure safe operation, in particular when the optical data carrier is accelerated rapidly, the revolution counter can be used Detect rotation in economy mode by scanning octants of at least one data track on the optical data carrier and changing to the counting mode when rotation is detected. By scanning octants of the data track, an onset rotation of the data carrier can be detected particularly quickly. In particular in comparison to those optical data carriers which only have a semicircular resolution or a quadrant resolution.

The lighting duration can be redetermined during mains-independent operation and can replace a previously determined lighting duration in the control unit. As a result, the lighting duration can be further optimized or adapted even in off-grid operation. In order to enable safe operation, the lighting duration can be redetermined after a number of pulses specified by the control unit. Since the redefinition of the lighting duration makes it necessary to start algorithms in the control unit, which can increase the power consumption for a short time, the redetermination can only take place every 100,000 pulses, for example. As a result, the total energy consumption increases only slightly, but the reliability of the operation is maintained.

At the same time or in addition to determining the light duration, pulsed operation or individual pulses can also be used to assess the quality of the optical data carrier used, for example the code disk. For this purpose, a single pulse can be generated by the light source in the mains-operated mode and the lighting duration until the light quantity signal is generated can be stored in the control unit. This lighting duration is preferably made available to an external evaluation unit or evaluated directly in a control unit of the position detection device or a rotary encoder. An increase in the light duration until the generation of the light quantity signal can indicate contamination of the data carrier. Further causes for an increase in the lighting duration can be a decrease in the luminosity of the light source or the sensitivity of the light sensor unit. To determine the quality of the data carrier, as described, individual pulses can be generated both in the mains-supplied operation but also in the mains-independent operation and the lighting duration until the light quantity signal is generated can be stored in the control unit.

It is particularly advantageous if an optical position detection device according to one of the configurations described above is used for the method. It is also advantageous if a rotary encoder with the above-mentioned features is used for the method.

The invention is explained in more detail below by way of example using an advantageous embodiment of an optical position detection device as a revolution counter with reference to the drawing. The combination of features shown by way of example in the embodiment can be supplemented by further features in accordance with the above statements in accordance with the properties of the revolution counter according to the invention and the rotary encoder according to the invention necessary for a specific application. Also, also in accordance with the above, individual features can be omitted from the described embodiment if the effect of this feature is not important in a specific application.

• 1 ein schematisches Blockschaltbild eines erfindungsgemäßen Umdrehungszählers als Teil eines erfindungsgemäßen Drehgebers;
• 2 eine schematische Skizze zur Erläuterung des Lichtmengensignals.

Show it:

• 1 a schematic block diagram of a revolution counter according to the invention as part of an encoder according to the invention;
• 2nd is a schematic sketch for explaining the light quantity signal.

In 1 is a block diagram of a revolution counter according to the invention 1 as part of an encoder according to the invention 3rd shown. For the sake of clarity, only the components necessary to describe the features according to the invention are shown. Next to the revolution counter 1 encompasses the encoder 3rd the single revolution unit 5 , the central control unit 7 and the encoder shaft 9 on which the code disc 11 is arranged. The code disc 11 serves as a common optical data carrier 13 for the single revolution unit 5 and the revolution counter 1 .

First is the structure and function of the revolution counter 1 described. The revolution counter 1 , whose components are summarized with a dashed line, has a light source 15 , which is preferably formed by a light-emitting diode (LED), an optical data carrier 17th , which as the ring section of the common code disc 11 is formed, a light sensor unit 19th with the photo receivers 19.1 to 19.n , a control unit 21st , a switching unit 23 as well as a separate energy storage 25th . The separate energy storage 25th is only an example within the revolution counter 1 shown. It may just as well be part of a housing (not shown), a connector or a connecting cable (both not shown) or outside the revolution counter 1 arranged and via a suitable connection to the switching unit 23 be connected.

The control unit 21st has a light control output 27 on. At this light control output 27 is a control input 29 the light source 15 connected. About this connection is the light source 15 by the control unit 21st controllable. Is the light source 15 switched on, it illuminates the optical data carrier 17th of the revolution counter 1 . The optical data carrier is only an example 17th as part of an optical disc 13 represented by a common code disc 11 is formed. The optical disk 17th can, for example, also be formed by a separate code disk or by a circulating belt or other suitable data carrier. The optical disk 17th can have a variety of data tracks 17.1 to 17.n exhibit. The optical data carrier preferably has 17th at least one data track, which as a reference data track 17.r is formed and is designed to be translucent throughout. This at least one reference data track 17.r is used to determine the required lighting duration.

The one from the light source 15 illuminated data tracks 17.1 to 17.n are used by the photo receivers 19.1 to 19.n the light sensor unit 19th scanned. Every data track is there 17.1 to 17.n at least one photo receiver 19.1 to 19.n assigned. The photo receiver, which is the reference data track 17.r is assigned as a reference photo recipient 19.r designated. At least one of the data tracks 17.1 to 17.n is divided into octants (not shown) and can be used to quickly detect the onset of rotation of the code disk 11 serve. Furthermore, a signal which is assigned to the at least one data track subdivided into octants can be used to roughly determine the position of the code disk 11 serve.

The light sensor unit 19th and the control unit 21st are over the data lines 30.1 to 30.n connected. The light sensor unit 19th captures that from the photo receivers 19.1 to 19.n generated photo streams and directs the resulting code of the data tracks 17.1 to 17.n over the data lines 30.1 to 30.n to the control unit 21st continue. In addition, the light sensor unit 19th a light quantity signal output 31 on which a light quantity signal L is issued as soon as at the reference photo receiver 19.r a sufficient amount of light Y was detected. This can be the amount of light received Y with one in the light sensor unit 19th stored light quantity reference value M be compared. For example, the light quantity signal L then be output when the light quantity reference value M is reached or exceeded. Alternatively, the light quantity reference value could be M also in the measuring system 36 or in the control unit 21st be filed. Then the light quantity signal L Information about those at the reference photo receiver 19.r measured amount of light Y include, which then in the measuring device 36 or in the control unit 21st with the light quantity reference value M is compared. However, the preferred embodiment described here has one in the light sensor unit 19th stored light quantity reference value M on.

The light quantity signal output 31 the light sensor unit 19th is with the entrance 33 the measuring device 36 through the control line 34 connected. The measuring device 36 is in the control unit 21st integrated. The control line 34 is in addition to the data lines 30.1 to 30.n available. Via the control line 34 are no signals of the encoded data tracks 17.1 to 17.n transfer. The control line 34 only serves to transmit the light quantity signal L . The light quantity signal output 31 is a separate output of the light sensor unit 19th . The timespan t by switching on the light source 15 up to the entrance of the light quantity signal at the entrance 33 the measuring device 36 passes by the measuring device 36 measured. The timespan t is in memory 35 the control unit. The light quantity control unit 38 then controls the light source based on this value 15 . The lighting duration of the light source 15 the saved period of time t correspond. However, the lighting duration or the pulse duration can also be the sum of the time span t and correspond to a temporal buffer value. The control line 34 is shown as an example as a separate line. Alternatively, the light quantity signal can be multiplexed together with other signals from the light sensor unit, for example 19th to the control unit 21st be transmitted.

The voltage supply of the revolution counter 1 can optionally by the separate energy storage 25th or by an external voltage source (not shown). This is the switchover unit 23 with the separate energy storage 25th connected and also has a connection 37 For connecting an external power supply such as a rotary encoder power supply 3rd on. In the event of a failure or a shutdown of the external power supply, the switchover unit switches 23 to the separate energy storage 25th around. The revolution counter 1 is then in network-independent operation.

• Im Netzbetrieb erfolgt die Spannungsversorgung des Umdrehungszählers 1 über eine externe Spannungsquelle (nicht gezeigt), welche am Anschluss 37 der Umschalteinheit 23 angeschlossen ist. Der interne Energiespeicher 25 kann ein Akkumulator sein, welcher über die externe Spannungsquelle geladen wird. Um die Produktionskosten niedrig zu halten und um die bei Akkumulatoren bekannte Selbstentladung zu vermeiden, ist der Energiespeicher jedoch bevorzugt durch eine Batterie gebildet.

The following are the function of the revolution counter 1 and the inventive method for controlling the optical revolution counter 1 described:

• The voltage supply of the revolution counter takes place in mains operation 1 via an external voltage source (not shown), which at the connection 37 the switchover unit 23 connected. The internal energy storage 25th can be an accumulator that is charged via the external voltage source. To the To keep production costs low and to avoid the self-discharge known with accumulators, the energy store is preferably formed by a battery.

The light source becomes in mains-independent operation 15 operated either constant or pulsed. As already described above, the revolutions are recorded by evaluating at least the data tracks, which are divided into octants.

Mains operation of the revolution counter 1 can be used to determine the minimum required lighting duration of the light source 15 to determine which one should be used in the event of a loss of external power supply. Becomes the light source 15 continuously operated, the continuous operation can be briefly interrupted to send a test pulse. Ie the light source 15 is switched on again and by the measuring device 36 the timespan t measured which passes until the reference photo receiver 19.r enough light has been detected until at the light quantity signal output 31 the light quantity signal L spent and at the entrance 33 the control unit 21st or measuring device 36 has been received. After the acquisition and storage of the time period t In the storage room 35 the control unit 21st can the continuous operation of the light source 15 to be resumed.

Becomes the light source 15 if, on the other hand, it is also operated in pulsed mode during mains operation, the required time period can in principle be determined for each pulse t respectively. In pulsed operation, not only the light source is preferred, even when generating a test pulse 15 , but also the light sensor unit 19th operated pulsed.

If the external voltage source ceases to exist, the switchover unit switches 23 to the separate energy storage 25th around. The control unit 21st detects the switchover and switches to pulsed operation of the light source 15 and preferably also the light sensor unit 19th around. The length of a pulse then corresponds at least to the determined time period t which are in store 35 is stored and by the light quantity control unit 38 the control unit 21st to operate the light source 15 and the light sensor unit 19th is read out. The determined and stored time period is preferred t an additional time buffer was added. This is preferably 25% of the determined lighting duration.

As long as no rotation of the code disk 11 the control unit can be detected 21st activate an economy mode in which the light source 15 and the light sensor unit 19th operated with a first frequency pulsed. The first frequency is chosen so that even when the encoder shaft starts up quickly 9 and thus a quick rotation of the code disk 11 another movement of the code disc 11 is detected. For this purpose, at least one of the data tracks is also 17.1 to 17.n divided into octants.

As soon as the code disc rotates 11 or the encoder shaft 9 is detected, the control unit switches 21st in a counting mode so that the light source 15 and the light sensor unit 19th operated with a second frequency. The second frequency is higher than the first frequency.

As long as the code disc 11 the revolution counter remains 1 in counting mode and the revolutions of the code disk 11 are counted and added or subtracted depending on the direction in which the code disk rotates. The turns are in a turn memory 39 the control unit 21st filed. As soon as no more rotation is detected, the control unit can 21st the revolution counter 1 switch back to economy mode so that the light source 15 and the light sensor unit 19th again operated with the first frequency pulsed.

In order to increase operational safety in off-grid operation, the time span can be t can also be determined in off-grid operation. To do this, the control unit measures 21st like in mains operation, the time from switching on the light source 15 until the input of the light quantity signal L at the entrance 33 passes. The determined value for the period t is in memory 35 written and can use the previously existing value for the time span t replace. Because that to determine the time span t required algorithms in the control unit 21st consuming additional energy will determine the time span t not performed on every pulse. A good compromise between energy-saving operation and high operational reliability can be achieved, for example, by the time period for every one hundred thousandth pulse t is redetermined.

The control unit 21st can have a separate signal output 41 have, from which signal to the outside of the encoder 3rd can be sent. This signal can be an emergency signal, which can also be sent in network-independent operation and provides information about whether the code disk is rotating 11 takes place. That at the signal output 41 tapped signal can be used for safety-related functions. For example, it can be used to trigger emergency braking of a machine part or to generate a warning signal.

• Zusätzlich zum Umdrehungszähler 1, welcher die Mehrfachumdrehungseinheit 1 (Multiturneinheit) für den Drehgeber 3 darstellt, weist der Drehgeber 3 die Einzelumdrehungseinheit 5 (Singleturneinheit) auf. Die Einheiten 1 und 5 werden zumindest im Netzbetrieb durch die Zentralsteuereinheit 7 gesteuert und durch diese ausgewertet.

The structure of the rotary encoder according to the invention is as follows 3rd described:

• In addition to the revolution counter 1 which is the multi-turn unit 1 (Multiturn unit) for the encoder 3rd represents the encoder 3rd the single revolution unit 5 (Single turn unit). The units 1 and 5 are at least in network operation by the central control unit 7 controlled and evaluated by this.

The single revolution unit 5 has a single revolution light source 43 and the single turn light sensor unit 45 . The single turn light source 43 illuminates the data track area 47 the code disc 11 which tracks the single turn data 47.1 to 47.n having. Just like the data tracks 17.1 to 17.n of the revolution counter 1 can trace the single rotation data 47.1 to 47.n have the required coding depending on the application. Binary coding and gray coding are only mentioned here by way of example. The single turn data tracks 47.1 to 47.n are from the single turn light source 43 illuminated and by the photo receivers 45.1 to 45.n the single turn light sensor unit 45 scanned.

The single revolution unit 5 is only an example on the revolution counter 1 opposite side of the encoder shaft 9 shown. The two units 1 and 5 can, however, also be arranged closer together. Likewise, it is only shown as an example that the data tracks 17.1 to 17.n of the revolution counter 1 on the radially outer area of the code disk 11 are arranged.

The single turn light sensor unit 45 is via a digital interface 49 with the central control unit 7 bidirectionally connected. The control unit is also preferred 21st of the revolution counter 1 to the digital interface 49 connected. The digital interface 49 is used for serial exchange of data between the components. For example, the single turn light sensor unit transmits 45 the code captured by the code tracks via the digital interface 49 to the central control unit 7 .

The single-turn light sensor unit preferably determines 45 the information about the absolute value of the position of the code disk is already obtained from the recorded code 11 and transmits it in binary form via the digital interface 49 to the central control unit 7 . The single turn light sensor unit 45 is also with the control unit 21st connected and can by the light sensor unit 19th recorded data, in particular the code of the data tracks 17.1 to 17.n receive. Are preferred by the control unit 21st the number of detected revolutions and / or the number of detected octants to the single-revolution light sensor unit 45 transmitted. This can be done by the control unit 21st Add the transferred data to your own recorded absolute values and the resulting overall position of the code disk 11 to the central control unit 7 to transfer.

In addition, the information about the detected revolutions and / or detected octants of the data tracks 17.1 to 17.n from the control unit 21st to the central control unit 7 transmitted. The central control unit 7 can then do a comparison of the control unit 21st and from the single turn light sensor unit 45 received data on the detected revolutions or recorded octants. This represents an additional security level in operation. Detects the central control unit 7 a deviation in from the units 21st and 45 transmitted data, an error signal can be output. As an alternative or in addition, an error comparison in the individual connection light sensor unit can also be carried out beforehand 45 be carried out since the data of the octant evaluation by the control unit 21st directly to the single turn light sensor unit 45 be transmitted.

In addition to the digital interface 49 can the single turn light sensor unit 45 over an analog connection 51 with the central control unit 7 be connected. The analog interface 51 can have multiple lines, each line of a particular data track 47.1 to 47.n is assigned. Via the analog interface 51 can in particular direct voltage values to the central control unit 7 are transmitted, which are proportional to the photo streams, which are in the photo receivers belonging to these data tracks of the photo receivers 45.1 to 45.n were generated. This is particularly useful for data tracks that have a very dense code sequence. For example, these data tracks 1,024 or 2,048 Have sectors.

The central control unit 7 itself can be via a suitable interface from outside the encoder 3rd addressed and read out.

In the event of a failure of the external power supply, the central interface 7 as well as the single revolution unit 5 are no longer supplied with voltage and are deactivated. Only the revolution counter 1 will then continue to operate in off-grid operation and continue to count the revolutions. If the external power supply is restored, the number of revolutions that have taken place can again be generated by the central control unit that is active again from the control unit 21st be read out. The position of the code disk 11 can from single revolution unit 5 based on the single revolution data tracks 47.1 to 47.n be determined.

2nd serves to explain the light quantity signal L . The operating parameter B is plotted on the abscissa and one from the reference photo receiver 19.r amount of light detected Y on the ordinate. The amount of light Y is proportional to the number of those from the reference photo receiver 19.r received photons. In the optical position detection device 1 or the revolution counter 1 can the amount of light Y can be represented by a size proportional to the number of photons. This can be, for example, that of the reference photo receiver 19.r generated voltage. The operating parameter B shown is time only by way of example. For example, the light source 15 switched on at time t = 0, the amount of light detected increases Y with time. When the light quantity reference value is exceeded M , which serves as a threshold, becomes the light quantity signal L from the control unit 19th generated and sent to the measuring device 36 headed. The timespan t from switching on the light source 15 until the light quantity signal is received L is saved as updated operating parameter B. In terms of 1 The exemplary embodiment described becomes the operating parameter B, that is to say the time span t In the storage room 35 the control unit 21st filed.

Claims (11)

Optical position detection device (1), in particular a revolution counter for a rotary encoder (3), with a control unit (21), at least one controllable light source (15), at least one optical data carrier (13, 17) with at least one data track (17.1 to 17.n. ), with at least one light sensor unit (19) for generating a light quantity signal (L) when a light quantity reference value (M) is exceeded by a light quantity (Y) received by at least one reference photo receiver (19.r), the light sensor unit (19) at least one photo receiver ( 19.1 to 19.n) for the at least one data track (17.1 to 17.n) of the data carrier (13, 17) and the at least one reference photo receiver (19.r), with a measuring device (36) for determining an operating parameter (B) the light source (15) upon receipt of the light quantity signal (L), with a memory for storing the operating parameter (B) and with a light quantity control unit (38) for controlling the light source (15 ) as a function of the operating parameter (B), the measuring device (36) being a time measuring device, and the operating parameter (B) being the time period (t) which elapses after the light source (15) is switched on until the light quantity signal (L) is generated the measuring device (36) has passed, the light source (19) being able to be operated in a pulsed manner and the pulse duration corresponding at least to the time span (t). Optical position detection device (1) according to Claim 1 , wherein the measuring device (36) and / or the light quantity control unit (38) are integrated in the control unit (21). Optical position detection device (1) according to Claim 1 or 2nd , wherein the light sensor unit (19) is connected to the control unit (21) via data lines (30.1 to 30.n) for transmitting the signals of the photo receivers (19.1 to 19.n), and wherein in addition to the data lines (30.1 to 30.n ) there is a control line (34) between a light quantity signal output (31) of the light sensor unit (19) and an input (33) of the measuring device (36) for transmitting the light quantity signal (L). Optical position detection device (1) according to one of the Claims 1 to 3rd The optical data carrier (13, 17) has at least one reference data track (17.r) in addition to the data tracks (17.1 to 17.n), which can be evaluated by the at least one reference photo receiver (19.r). Method for position detection using an optical position detection device (1), according to one of the Claims 1 to 4th , in particular a revolution counter of a rotary encoder (3), a light quantity signal (L) being generated as soon as a light quantity received by at least one reference photo receiver (19, r) of a light sensor unit (19) after switching on a light source (15) of the position detection device (1) (Y) exceeds a light quantity reference value (M), an operating parameter (B) required to reach the light quantity signal (L) being determined by means of a measuring device (36) and this operating parameter (B) being stored in a control unit (21) of the revolution counter (1) and the light source (15) is controlled as a function of the stored operating parameter (B), the operating parameter (B) being the time period (t) which elapsed after the light source (15) was switched on until the light quantity signal (L) was generated , the measuring device (36) being a time measuring device and the light source (15) of the position detection device (1) at least in the mains-operated state is operated in a pulsed manner, the pulse duration corresponding at least to the time period (t) stored in the control unit (21). Procedure according to Claim 5 , the pulse duration corresponding to the sum of the stored time period (t) and a temporal buffer value. Procedure according to Claim 5 or 6 , wherein in the pulsed mode, an economy mode with a first pulse frequency is activated as long as no movement is detected, and a counting mode with a second pulse frequency when movement is detected, the second pulse frequency being higher than the first pulse frequency. Procedure according to Claim 7 , wherein the position detection device (1) detects the movement in economy mode by scanning octants of at least one data track (17.1 to 17.n) of an optical data carrier (13, 17), and in the case of detected movement it is switched to the counting mode. Procedure according to one of the Claims 5 to 8th , wherein the time period (t) is determined anew in the network-independent and / or network-supplied operation and replaces a previously determined time period (t) in the control unit (21). Procedure according to Claim 9 , the redetermination of the time period (t) taking place after a number of pulses predetermined by the control unit (21). Procedure according to one of the Claims 5 to 10th , wherein a single pulse is generated by the light source (15) in the mains-supplied and / or in the mains-independent operation and the time period (t) until the generation of the light quantity signal (L) is stored in the control unit (21).

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