Circuit and method for the operation of a position sensor using Hall elements

The invention relates to a method of operating a position transducer, preferably a rotary encoder of the Hall elements, according to the preamble of claim 1 and a position sensor according to the preamble of claim 10 for implementing the method.

From the prior art have been known for a long time encoder that have a magnetic graduation with a code structure. According to DE 44 42 371 A1 by the applicant to such divisions are characterized by a multilane alternating magnetization of a rotationally symmetrical Body from which proportionally of the encoder supplied Rotational movement rotates. This alternating magnetization is at a Rotational movement detected by static Hall elements for any trace of the division and output an absolute position signal.

From EP 0331828 A1 a multi-turn encoder is known which in itself principle composed of two measurement systems. It is an incremental optical measuring system the exact position in the range of a 360 ° rotation determines the optical division and in addition the number of revolutions the optical splitting determined with the aid of a magnetic detector. It may then have a control unit, the absolute position even when identify several revolutions of the encoder. If the multi-turn encoder connected to the supply voltage, the stored number Revolutions and the stored incremental output. To the to reduce consumption of electric power, are magnetoresistive Elements with a few hundred kilohms internal resistance used and additional Resistors connected in series. Furthermore, digital modules, which were manufactured in CMOS technology used.

It is disadvantageous that the electrical power requirement of CMOS-assemblies increases proportionally with frequency so that high at a Processing speed, the demand for electrical power large is. Furthermore, specific magnetoresistive elements with a high Internal resistance required the costly processing of their make output required, leading to an increased susceptibility leads.

From EP 0158781 A1 an incremental encoder is known in which determined with an optical measuring system, the position or the angle of rotation becomes. The optical measuring system in this case has a light source, a static and a rotating pitch and photosensitive boards with associated Evaluation electronics. For energy savings, the light source and the transmitter only as long connected to the supply voltage, how to determine the position within the smallest graduation period is required. In the remaining time, these assemblies of are Power supply disconnected.

It is disadvantageous in that when using a magnetic detector system owing to the need for much larger currents throughout the circuit with only a temporary connection the light source and the evaluation unit with the power supply voltage Disturbances.

The invention is therefore based on the object, a position transmitter with embody magnetic measuring system in such a way and a method for its specify operation that the electric power demand significantly is reduced, whereby it must be ensured that no interference by caused.

This object is achieved by the features of independent claims 1 and 10 dissolved.

The dependent claims are further advantageous refinements to remove.

The inventive method for operating a position detector comprises the advantage that the provided for detecting a position of Hall elements not simultaneously but one after the other in a specific sequence are turned on and off again queried. Since the maximum power requirement of the entire circuit arrangement essentially is determined by the power requirements of the Hall elements, can be prepared by the sequential interrogation of the individual Hall elements of the maximum power demand be substantially reduced.

Furthermore, only a small number of Hall elements are switched simultaneously, whereby the induced by the switching operation disturbances in electrical mains practically no longer occur. Furthermore, by Advantage is delayed storing the output of each Hall element, thereby disturbances which the in a stabilization phase, Hall elements occur are suppressed. The position sensor according to the invention has the advantage that individual Hall elements on an individual Control line are activated and deactivated by a control unit can. Further, each memory module may be formed separately from the control unit are driven.

The inventive method and the inventive position transducer will now be described in detail based on the drawings and explained in will. Show it:<dl tsize="9" compact="compact"><dt>Fig. 1:</dt><dd>a possible circuit implementation of the invention Position transmitter,</dd><dt>Fig. 2:</dt><dd>a possible implementation of a magnetic division with Code structure</dd><dt>Fig. 3a:</dt><dd>a possible course of control signals for the Hall elements,</dd><dt>Fig. 3b:</dt><dd>Another possible course of control signals for Hall elements and</dd><dt>Fig. 4:</dt><dd>a possible course of speed-related control signals the shutdown of individual Hall element.</dd></dl>

The inventive method and the inventive position transducer to be exemplified in a multi-turn encoder, the directly outputs a parallel code and in addition at least one magnetic Division with code structure and at least one optical division comprises both a code structure and an incremental structure may have. However, it is apparent to those skilled in the art that the inventive A method as in position encoders for linear encoders, for single-turn encoders or measuring systems, the incremental one output value, can be used.

The measured rotational motion is in a first step to an optical transmitted Encoder pitch which several graduation tracks which are formed according to a code. Thereby, the significant generated bits of the output of the encoder. By optical division is thus a single-turn encoder with example six bit resolution implemented.

Subsequently, the rotation of the optical division is a transmission by a factor of 1: 2⁶ stocky and a magnetic graduation T supplied, which is shown in Fig. 2. The reduction ratio corresponds Here, the resolution of the optical division, so that the most significant bit of the optical splitting half the value of the least significant bits of the magnetic Graduation T has. The magnetic graduation T is usually basically identical to the optical division, according to a digital code, eg the Gray code, configured.

Immediately above the individual graduation tracks TS1 to TS4 of magnetic Graduation T are Hall elements arranged statically, which detect, which magnetization has the underlying division track straight. The Hall elements output an output signal corresponding to the magnetization of the division track has two states. Since the graduation periods the graduation tracks TS1 - TS4 always by a factor of 2 differ, also differentiates the value of the output signals the Hall elements corresponding to the pitch period to the factor 2. The Hall elements are such to the individual graduation tracks TS1 - TS4 arranged such that the output signal of the Hall element HE1 the lowest has value because it exceeded the graduation track TS1 with the shortest Graduation period is arranged. The numbering of the Hall elements was chosen so that the value of the output signal of the Hall element by whose number is expressed, so that the output signal is output with the highest value from the Hall element HE18.

As shown in Fig. 1, the output signals of the Hall elements are HE1 - HE18 respectively a switch S1 - S18 supplied by the outputs D1 - D18 either the input of memory modules SP18 will be forwarded directly or as outputs of the encoder - SP1 to be provided. How many switches are provided, depends from the maximum velocity V of the change in position, which is the maximum Speed ​​of the encoder, and the processing speed the modules used.

Each Hall element HE1 - HE18 is a via a control line with Control unit ST connected that characterized every single Hall element HE1 - HE18 on and to turn off. It is obvious that a switched off or disabled Hall element having no power consumption and thus the power consumption is reduced by disabling of Hall elements becomes. Also, the switches S1 - S18 are connected via control lines to the And control unit ST connected to be switched from this. furthermore are the memory modules SP1 - SP18 via a respective control line either directly connected to the control unit ST, or it is the control signal for the memory modules SP1 - SP18 from the control signal of the respective associated Hall element HE1 - HE18 by a time delay .DELTA.t generated.

In the following, the operation of the encoder according to the invention is explained will. After the control unit ST of the encoder to the supply voltage was connected, identified the control unit ST by interrogation of each Hall element HE1 - HE18 in a specific, stored order, the absolute position of the encoder.

For this disables the control unit ST via the respective control lines the Hall elements HE2 - HE18 and activates the Hall element HE1. this happens 3a is shown at the time t1 as shown in Fig., where an example of the Control signals of the control unit ST for the Hall elements HE1 - about HE4 the time is plotted. By disabling power requirements of entire circuitry of the significantly by the current requirement Hall elements HE1 - HE18 is determined drastically reduced. furthermore be by the control unit ST switches S1 - initially switched S18, that the output signals D1 - D18 of Hall elements HE1 - HE18 the memory modules SP1 - SP18 are supplied. This is it assumed that the speed of the positional change does not a threshold value. After a certain time, which is required thus at the input of the storage module a stable output signal SP1 D1 of the Hall element HE1 is present, preferably on the time delay .DELTA.t Or via a separate control line to the control unit ST which the Hall element HE1 associated memory module SP1 is driven to the output D1 of the Hall element HE1 to save. The output D1 is transmitted through the data line DL. After that the Hall element HE1 is deactivated by the control unit ST at the time t2, as is apparent from Fig. 3a, which this module does not requires power more.

Thereafter, the control unit ST repeats this process for the next Hall element HE2. This is at the instant t2 from the control unit ST activated and the associated memory module SP2 with a time delay also activated. Subsequently, the output signal D2 is the Hall element HE2 stored in the storage module and the SP2 Hall element HE2 is deactivated at the time t3 of the control unit ST. This process is repeated until the outputs of all Hall elements HE1 - HE18 in the respective associated memory module SP1 - SP18 were stored. be SP18 - The memory modules SP1 thereby advantageously implemented as flip-flops, which the stored bit until a new activation and do not change as the output of Encoder to deploy in parallel form.

In addition, since an optical pitch is provided which has a significantly higher has resolution, it is also possible that the position determination only takes place with the aid of Hall elements, when the absolute Position must be determined, for example, when the encoder is turned on , or that the Hall-elements only in certain time intervals be used for position determination. In continuous operation can be used for absolute Positioning the rotational speed of the optical division are counted by the control unit ST.

Alternatively, there is the possibility that not, as described above, always only a Hall element after the other Hall element at the instants t1, t2, t3, etc. activated, whereby only a single Hall element is activated at the same time, but that a number of Hall elements are simultaneously activated will. However, it should be noted that no longer only a single data line DL between Hall elements HE1 - HE18 and Memory Board SP1 - SP18 is required, but for each combination from Hall element and associated memory module a separate data line provide is.

A further alternative is, the next Hall element to already to activate a time t2 before the previous Hall element HE1 was turned off at the time t3, as shown in Fig. 3b. Thereby the Hall elements and associated memory modules are sequentially activated, it does not wait until the previously activated Hall element was disabled, so that a plurality of Hall elements with associated memory module are overlapping in time activated. This can be an arbitrary Compromise between processing speed and low achieve power consumption, depending on how many Hall elements simultaneously are activated. Also in this alternative is for each combination of Hall element and memory module to provide a separate data line.

In a possible advantageous embodiment of the invention the control unit is ST a signal fed to the speed V of the change in position, with a rotary encoder, the angular velocity, quantified. This signal can, for example, the output signal D1 of the first Hall element be HE1.

The control unit ST then compares whether the speed V of the position change greater than a first threshold Vmax1 is. If this is the case is, is determined by the control unit ST to the switch S1 a control signal output, which switches the switch S1, whereby the memory module SP1 is bridged. It is then immediately the output signal D1 of the Hall element HE1 outputted without intermediate storage. It can be connected to the memory module SP1, which is now not required, the Control unit ST a signal to the deactivation are issued. Here, the first threshold value Vmax1 is selected such that when it is Exceeding the velocity V of the change in position is so large that an intermediate storage is no longer necessary because the output signal D1 permanent present.

If the first threshold value Vmax1 has been exceeded, it is checked whether also a second threshold value Vmax2 is exceeded. If this is the case, and the second switch S2 is switched so that the memory module SP2 is bridged. It is then immediately and the output signal D2 of the Hall element HE2 outputted without intermediate storage. It can also be to the memory module SP2, which is now not required, issued by the control unit ST a signal to the deactivation will. Here, the second threshold value Vmax2 is similar to the first Threshold value Vmax1 selected so that when it is exceeded the speed V of the change in position is so large that an intermediate storage is no longer necessary because the output signal D1 permanent present. Usually the second threshold Vmax2 is twice as big be like the first threshold value Vmax1 as the change of the magnetic field the Hall element HE1 twice the frequency as the change in the Magnetic field at the Hall element HE2.

This process of switching the output signals of Hall elements can be carried out HE1 HE18 up for all Hall elements, due to the the provisions for the encoders maximum speed virtually permanent spend an output signal and for which therefore no caching is required. The other required thresholds Vmax3, Vmax4, etc. are in accordance with the above example, twice as size of each previous threshold chosen.

Immediately after falling below one of the thresholds for speed the change in position is of each threshold associated switch knob and the associated memory module reactivated.

Another advantageous feature, a plurality of magnetic provide partitions T, whereby resolution and / or range of values Speed ​​enco bers extended for each additional division track by a factor of 2 can be. In this case, the rotation corresponding to the number stocky existing division tracks via a gear or at a appropriate arrangement of divisions optionally also translated. As with the coupling between the optical and magnetic division T described must, for each graduation track with a digital code that forwarded speed geared down by a factor of 2 on the next pitch T will. So, are on a first pitch T four graduation tracks TS1 - TS4 provided that rotational movement of this first division for a second T must Dividing T by a factor of 2⁴ be stocky.

The frequency with which the individual Hall elements HE1 - HE18 activated be, is chosen depending on the frequency of the output signals. Since the output of the Hall element HE1 has the greatest frequency, It is most commonly activated and therefore occurs in the order of essentially sequentially activated by the control unit ST Hall elements on on frequently. The output signal of the Hall element HE2 has half the frequency of the output signal of the Hall element HE 1 and therefore in the order occurs only half as often as the Hall element HE1. the same applies for the other Hall elements. With the additional condition, that two activations of a single Hall element HE1 - HE18 whenever possible have the same temporal distance from each other should the order is clearly defined, in which the control unit ST the individual Hall elements HE1 - HE18 activated.