DE102005003488B4 - Capacitive sensor and monitoring method - Google Patents

Abstract

Capacitive sensor having a monitoring device (11) which has at least one first capacitor electrode (13) and an evaluation and control circuit (15), wherein the monitoring device comprises a capacitive proximity switch for securing a motor-driven door - in particular an elevator door (85, 87). forms, by means of the evaluation and control circuit, the capacitance of the first capacitor electrode can be determined, which is determined by the surrounding medium of the first capacitor electrode or an object in the vicinity of the first capacitor electrode, and wherein by means of the evaluation and control circuit in dependence on the determined capacitance the first capacitor electrode, a switching or warning signal is generated, wherein
The monitoring device (11) is designed in addition to the access control,
A coded access authorization signal can be read in by means of the evaluation and control circuit (15) and capacitively coupled to the first (13) or a second capacitor electrode (23) of the monitoring device,
- By means of the evaluation and control circuit, the read access authorization signal is comparable to a given coding and in ...

Description

The The invention relates to a capacitive sensor with a monitoring device, the at least one first capacitor electrode and an evaluation and control circuit, wherein the monitoring device a Capacitive proximity switch for securing a motor-driven door - in particular an elevator door - forms, wherein by means of the evaluation and control circuit, the capacity of the first Capacitor electrode is determined by the surrounding medium the first capacitor electrode or an object near the first one Capacitor electrode is determined, and wherein by means of the evaluation and control circuit in dependence from the determined capacity of the first capacitor electrode, a switching or warning signal generated is.

such Sensors acting as capacitive proximity switches are configured to protect a hazardous area, For example, to secure a motor-driven sliding door of a Elevator. To a possible Obstacle in the door gap or in the path of movement of the door to recognize, the capacity becomes a capacitor electrode continuously determined and changes evaluated. Once an object - for example, a person or a dolly - in nearby the capacitor electrode is located, the capacitance of the capacitor electrode by the dielectric properties or the electrical conductivity of the object. By identifying changes the capacity the capacitor electrode can thus be for the presence of a Object nearby the door be closed, if necessary, a switching or warning signal to generate, for example, to break the door closing movement and the Door in the opening position cut back.

Out EP 1 164 240 a sensor for use with motor vehicle doors is known. A capacitive-sensitive sensor forms a resistor with an RC circuit whose frequency varies with the capacitance. If the frequency determined by a control unit falls below a predetermined threshold value, a request signal is sent, with which an authorization is initiated. The request signal is received by an electronic key that sends a key code to the control unit by means of a transponder.

Out EP 1 134 134 A2 For example, a control unit is known in which an interrogation signal is transmitted and an identification code which is sent by a transponder is verified.

DE 601 02 331 T2 and DE 600 04 980 T2 describe access authorization control systems that include a transmitter worn by a person on the body or on the garments. When the person touches a touch electrode, a circuit is grounded through a receiving electrode, lead wires, the transmitting device, a grounding electrode, and intervening body regions of the person. Signals of the transmitting device received by the receiving electrode from a receiving device are evaluated by means of a demodulator and may include an identification code for the user.

US 4,591,854 describes a similar access control system, wherein the transmitting device is designed in the form of a wristwatch. An identification code is read out as a modulated electrical alternating signal via a touch element.

The capacitive coupling by a human body for the transmission of data is the subject of US 6,211,799 B1 ,

The use of field sensors for monitoring, which are evaluated by means of resonant circuits, is in DE 27 19 955 C2 described.

The comparison of the signals of capacitive proximity sensors with a threshold which depends on the position of a door is in GB 2,243,217 A specified.

It It is an object of the invention to provide a capacitive sensor of the kind explained To create kind, which is universally applicable. Furthermore, a appropriate monitoring procedure be specified.

These Task is performed by a capacitive sensor with the characteristics of Claim 1 or a monitoring method solved with the features of claim 13. Subclaims are directed to preferred embodiments.

The sensor thus also serves for access control, ie it additionally fulfills the function of identifying persons who are in the vicinity of the sensor, in particular to check and evaluate access authorizations. For this purpose, encoded conditional access signals are fed from an identifier, which is carried by the person concerned, for example in the form of bit patterns in said capacitor electrode or an additional capacitor electrode of the sensor according to the principle of capacitive near-field coupling. The coupled conditional access signals can thus as additional displacement currents in the Kondensatorelekt be recorded and evaluated.

at the capacitive coupling forms the capacitor electrode of the sensor together with a capacitor electrode of said identifier a Capacitor, over the electrical signals can be transmitted as displacement currents. there can the body the person carrying the identifier as a dielectric between the both capacitor electrodes (the encoder and the monitoring device) serve. The signal transmission thus takes place by temporal change the field electrical environment of a capacitor electrode, the by capacitive coupling to the electrical potential of the affects each other capacitor electrode. The capacitive coupling between the capacitor electrodes is therefore not based - as in the transponder technology working in the radio frequency range - on the Radiation and the reception of electromagnetic free space waves. The explained Capacitive coupling is made either by touch, for example when the person carrying the identifier carries an operating key. A However, capacitive coupling is also contactless up to a distance of For example, 15 cm (in air) possible.

Around an access authorization signal on a capacitor electrode of the Coupling sensor is called identifier to an active Influenced his field-electric environment formed. there can be provided that the encoder only then an access authorization signal settles when it comes from the evaluation and control circuit of the sensor receives a corresponding identification request command, the also by capacitive coupling between the mutual Transfer capacitor electrodes can be. Alternatively, the encoder can be constantly or at short intervals settle a predetermined conditional access signal so that at contact with the capacitor electrode of the monitoring device directly an identification is initiated.

The Thus capacitively coupled access authorization signal is in the monitoring device compared with a given coding, depending on generates an access control signal from the result of this comparison can be. The access control signal is used in particular for controlling the driving course of an elevator car. For example, can be provided be that in case of agreement the coupled access authorization signal with the predetermined coding certain building floors be released and thus controlled by the elevator car can, for the without receiving the associated conditional access signal the Access would be denied.

One Advantage of the sensor is that at least one common Evaluation and control circuit or a single corresponding electronic unit as well as the explained Fuse function (proximity switch for detection of obstacles), as well as for the access control function (Identification of an identifier) can be used. Especially in the case of use in or on elevators, this results in the Advantage that for These two features only install a single system must become. A synergy effect can also be seen in terms of Capacitor electrode yield, as this optional also for detection obstacles in the path of movement of the door and capacitive recording a coded conditional access signal can be used.

Compared to the usual used for securing motor-driven doors optical Sensors (light grids, light barriers) have the capacitive sensor the advantage that the door while still the closing movement can be passed through without necessarily generating a switching signal and the door scaled back becomes. Namely, the capacitive sensor can be adjusted in such a way that it only the immediate environment of the capacitor electrode considered, not, however, the entire open Door gap. This results from the use of the capacitive sensor for the illustrated fuse function an increase in effectiveness.

One Another advantage of the capacitive sensor is that after the successful closing the door the at the door arranged capacitor electrode in the immediate vicinity or is in contact with a predetermined environment (eg door frame or another capacitor electrode). The target final value of the capacity of the considered Capacitor electrode is therefore with a comparatively high accuracy For example, it can also be known by a so-called teach process be taught with high accuracy. This can be by means of the evaluation and control circuit are checked particularly reliably, whether the door in question is actually completely closed is, or if there is still a thin one Obstacle (for example, a finger) is located in the remaining door gap.

With regard to the safety function of the sensor, it is preferred if it is checked by means of the evaluation and control circuit whether the ascertained capacitance of the first capacitor electrode differs from a reference value by a predetermined threshold value. Such a reference value can be determined, for example, beforehand in a learning mode with an object-free trajectory of the relevant door and stored in a memory device of the evaluation and control circuit. In a subsequent monitoring operation of the Thus, the reference value is available for comparison with the current capacitance value.

According to one advantageous embodiment is for the explained Backup function the capacity the capacitor electrode by considering the resonance frequency a resonant circuit determined. For this purpose, the evaluation and control circuit of the monitoring device at least one resonant circuit connected to the respective capacitor electrode is connected so that the resonant frequency of the resonant circuit of the capacity of Capacitor electrode depends. A change in the capacity the capacitor electrode is detected by a possible change the oscillation frequency of the resonant circuit is detected. hereby are particularly simple and accurate measurements of capacity changes possible. In the explained Oscillation circuit can be in particular an LC or an RC resonant circuit act.

According to one further advantageous embodiment will that for the explained Access control or identification function used access authorization signal on the Capacitor electrode as frequency modulation in said resonant circuit or an additional one Oscillating circuit coupled. The evaluation and control circuit has preferably a demodulator through which the frequency modulated Access authorization signal from the oscillation of the resonant circuit is demodulated. By this configuration is the common realization the backup function and the access control function especially just possible. Alternatively you can However, the encoded conditional access signals also via a separate capacitor electrode or via a separate resonant circuit be received.

Farther It is preferred if the sensor - in addition to - as already explained the actual monitoring device with capacitor electrode and evaluation and control circuit one Having this separately trained identifier. This identifier has a control circuit for generating a coded conditional access signal as well another capacitor electrode. If the Identgeber in sufficient spatial Proximity to the monitoring device of the sensor forms the capacitor electrode of the encoder with the respective capacitor electrode of the monitoring device a Capacitor, over the access authorization signal from the encoder to the monitoring device capacitively transmitted can be.

at this embodiment it is preferred if at the monitoring device an identification request command can be generated, which is transmitted via the there capacitive electrode capacitively transmitted to the encoder when the identifier is in close proximity to the respective capacitor electrode the monitoring device located. This identification query command is then used by the the encoder issuing the coded conditional access signal triggered. In this development, the encoder does not have to be permanent his specific conditional access signal, but he does so only upon receipt of the corresponding identification query command.

The The invention further relates to the use of a capacitive Sensors of the kind explained, the at least one first capacitor electrode, for securing a motor-driven door - in particular a sliding door a lift - through Determination and evaluation of the capacitance of the first capacitor electrode, and at the same time for access control by reading in and evaluating a encoded conditional access signal that is at the first or a Capacitive coupled second capacitor electrode of the sensor becomes.

Further embodiments are in the subclaims called.

The The invention will now be described by way of example only explained on the drawings.

1a and 1b show various embodiments of a monitoring device.

2a to 2d show various embodiments of a monitoring device with different evaluation and control circuits.

3 shows an identifier.

4a to 4d show various possibilities of arranging a monitoring device on an elevator car and a building floor.

1a shows a particularly simple embodiment of a monitoring device 11 , This has a single (first) capacitor electrode 13 and an evaluation and control circuit connected thereto 15 , The evaluation and control circuit 15 has a signal output 17 for outputting a switching or warning signal and / or an access control signal, as will be explained below. The capacitor electrode 13 is formed from an electrically conductive metal, for example as a wire, as a strip, as a surface (eg copper sheet), as a grid or as a parallel arrangement of a plurality of wires or strips. The capacitor select rode 13 For example, it can be arranged on a front edge of a sliding door of an elevator, as in connection with FIGS 4a to 4d will be explained.

The monitoring device shown 11 forms together with an Identgeber, which in connection with 3 is explained, a capacitive sensor. The monitoring device 11 On the one hand, it is configured as a capacitive proximity switch to secure a motor-driven door. For this purpose, by means of the evaluation and control circuit 15 the capacitance of the capacitor electrode 13 determined and evaluated. The capacitor electrode 13 namely forms with ground or a capacitor with a certain capacity, as in 1a is illustrated by the dashed line equivalent circuit diagram. If a person or an object (such as a trolley) is near the capacitor electrode 13 moved, so affects the changed environment of the capacitor electrode 13 (Dielectric or conductive medium) on the capacity of the illustrated capacitor. By determining the change in capacitance that has occurred, it is thus possible to detect the presence of an object in the vicinity of the capacitor electrode 13 getting closed.

As soon as the evaluation and control circuit 15 in this way, a capacitance or a change in the capacitance of the capacitor electrode 13 de tektiert that exceeds or falls below a predetermined threshold, so is at the signal output 17 generates a switching or warning signal, for example, to stop a closing movement of said door and to move the door back to an open position. The mentioned threshold value can be selected as a function of time or depending on the position (closed position) of the door. Furthermore, the said reference value or threshold value can also be taken into account only indirectly, for example as a frequency change, as will be described below in connection with FIG 2a is explained.

For another, the in 1a shown monitoring device 11 configured as access control device. For this purpose, by means of the evaluation and control circuit 15 a coded access authorization signal is read in and evaluated at the capacitor electrode 13 is capacitively coupled from the aforementioned encoder. The evaluation and control circuit 15 is able to compare the read access authorization signal with a stored predetermined coding. Depending on the result of this comparison is at the signal output 17 generates a positive or negative access control signal. On the basis of this access control signal, it is possible, for example, to prevent the elevator from approaching a building floor for which the carrier of the relevant identifier is not authorized.

The explained access authorization signal is at the capacitor electrode 13 coupled by electrostatic coupling in the form of displacement currents (principle of the capacitive Nachfeld coupling). These displacement currents are from the evaluation and control circuit 15 detected.

It is advantageous that in the monitoring device 11 a common evaluation and control circuit 15 is used both for the illustrated security function and for the access control function, so that both functions can be realized with a uniform system. It is particularly advantageous that, in addition, for both functions, a common capacitor electrode 13 is used, that is, the detection of capacitance changes and the reading of conditional access signals carried on the same capacitor electrode 13 ,

Additionally, at the monitoring device 11 according to 1a be provided that the evaluation and control circuit 15 generates at certain times an identification request command, for example, as a bit pattern in the capacitor electrode 13 is fed and is capacitively transmitted from this to the aforementioned identifier, if the encoder is in spatial proximity to the capacitor electrode 13 located. In this case, the evaluation and control circuit are used 15 and the capacitor electrode 13 ie in addition to issuing such an identification request command. The identification request command initiates the issuing of the explained coded access authorization signal at the identifier.

1b shows an embodiment of the monitoring device 11 in which, in addition to the (first) capacitor electrode 13 a second capacitor electrode 23 with the evaluation and control circuit 15 connected is. In this case, the first capacitor electrode serves 13 again for the explained fuse function, ie for detecting an object in the immediate vicinity of the capacitor electrode 13 , The explained access control function - ie the detection of a coupled access authorization signal and / or the discontinuation of an identification request inquiry command from or to an identifier - is in contrast to the second capacitor electrode 23 executed. As in the embodiment according to 1a is a common evaluation and control circuit for both functions 15 intended.

2a to 2d show possible embodiments of the monitoring device 11 and ins special the evaluation and control circuit 15 , For simplicity of illustration, it is assumed that a single (first) capacitor electrode 13 is intended for both the illustrated backup function and for the access control function. However, there may be two separate capacitor electrodes for this purpose 13 . 23 be provided as related to 1b has been explained.

According to 2a is the capacitor electrode 13 a resonant circuit 31 connected in parallel. This has a capacitor 33 and an inductance 35 connected to the respective one terminal with the capacitor electrode 13 and the evaluation and control circuit 15 are connected and connected at the respective other connection to ground or ground. The resonant circuit 31 resonates at a resonant frequency, basically by the capacitance of the capacitor 33 and by the inductance 35 is predetermined and is typically between 100 and 1000 kHz.

The resonant frequency, however, also depends on the capacitance of the capacitor electrode 13 or the capacitor formed thereby, the capacitor 33 is connected in parallel. Because the capacitance of the capacitor electrode 13 in turn - as already explained - depends on the surrounding medium, can by determining the resonant frequency of the resonant circuit 31 on the capacitance of the capacitor electrode 13 and thus the presence of an object near the capacitor electrode 13 getting closed. The capacity of the capacitor 33 and the inductance 35 are known and can therefore from the evaluation and control circuit 15 be taken into account.

2 B shows a possible embodiment of the evaluation and control circuit 15 according to 2a , Here is a reference resonant circuit 41 with a capacitor 43 and an inductance 45 provided, which generates a reference signal, that is, a predetermined constant oscillation frequency. This reference signal is located at a first input of a comparison device 47 at. At a second input of the comparator 47 the vibration signal of the resonant circuit 31 - That of the environment of the capacitor electrode 13 dependent resonant frequency of the resonant circuit 31 - supplied. In the comparison device 47 these two frequencies are compared.

For example, the two oscillations can be combined into a common oscillator signal whose amplitude depends on the difference between the oscillation frequencies of the resonant circuits 31 . 41 varied. A switch or warning signal is sent to the signal output 17 the comparison device 47 For example, then output when the oscillation frequency of the resonant circuit 31 by a predetermined threshold of the oscillation frequency of the reference resonant circuit 41 deviates or if the amplitude of the oscillator signal in the comparator 47 differs from a reference value by a predetermined threshold. The thereby taken into account threshold and / or reference value can be selected in dependence on the closed position in which the door is located at the capacitor electrode 13 is appropriate. As a result, different sensitivities can be set for different closed positions.

Furthermore, the evaluation and control circuit has 15 according to 2 B a demodulator 49 with an associated signal output 17 ' , The demodulator 49 is used to demodulate a coded conditional access signal that is in the oscillation of the resonant circuit 31 additionally included as frequency modulation. The access authorization signal may be from the aforementioned identifier on the capacitor electrode 13 namely coupled as frequency modulation, the vibration frequency of the resonant circuit 31 is superimposed. This overlay can be done, for example, in the form of a bit pattern. In particular, the carrier frequency, ie the oscillation frequency of the resonant circuit 31 , are modulated according to the principle of "pseudo random noise", whereby an increased bandwidth is available (spread spectrum).

The demodulator 49 can be formed in a known per se, for example, as a PLL circuit (phase-locked loop). The demodulator 49 performs a comparison of the demodulated conditional access signal with a predetermined encoding, wherein at the signal output 17 ' of the demodulator 49 a positive or negative access control signal is generated, depending on whether a sufficient or an insufficient match of the conditional access signal is determined with the predetermined coding.

The embodiment according to 2c corresponds to that according to 2 B , where instead of the reference resonant circuit 41 a clock 51 is provided.

2d shows an embodiment in which compared to the embodiment according to 2c in addition a signal modulator 53 is provided, which is a microcontroller 55 and an amplifier 57 and also with the capacitor electrode 13 connected is. By means of the signal modulator 53 an identification request command is generated via the capacitor electrode 13 decoupled and in particular capacitively transmitted to the aforementioned identifier, to this at the Abset trigger an access authorization signal. For this purpose, it is again necessary for the identifier to be in spatial proximity to the capacitor electrode 13 located. The identification request command is from the signal modulator 53 as frequency modulation of the frequency of the resonant circuit 31 into the capacitor electrode 13 fed. The same resonant circuit 31 So serves both for the backup function as well as for the access control function; however, this is not mandatory.

3 shows the already mentioned identifier 71 , This has its own capacitor electrode 73 , The capacitor electrode 73 of the identifier 71 forms with the first capacitor electrode 13 ( 1a ) or the second capacitor electrode 23 the monitoring device 11 ( 1b ) a capacitor if the respective capacitor electrodes 73 and 13 respectively. 23 are in close proximity to each other. On the one hand, the previously formed coded access authorization signal of the identifier can be transmitted via the condenser thus formed 71 and on the other hand, the identification request command of the monitoring device 11 be transmitted capacitively.

The Identifier 71 also has a receive and control circuit 75 and a battery 77 or an electric accumulator for supplying power to the receiving and control circuit 75 , The receiving and control circuit 75 serves to receive an identification request command of the monitoring device 11 at the capacitor electrode 73 of the identifier 71 capacitively coupled. In response to receipt of such an identification request command, the receive and control circuit causes 75 generating and issuing one for the particular identifier 71 characteristic coded conditional access signal via the capacitor electrode 73 to the monitoring device 11 ,

4a to 4d each show in a schematic plan view parts of an elevator system with an inside of a hoistway 81 vertically movable elevator car 83 holding a cabin sliding door 85 having. The elevator system further has a plurality of hoistway sliding doors 87 which are assigned to different building floors, wherein in the 4a to 4d only a building floor is shown. In addition, the elevator system has a capacitive sensor of the type described, with a monitoring device 11 according to 1 and 2 and with multiple identifiers 71 according to 3 , The cabin sliding door 85 and the elevator shaft sliding doors 87 are by a respective associated drive means (in 4a to 4d not shown) movable by motor.

According to the various embodiments according to 4a to 4d serves the monitoring device 11 as a capacitive proximity switch for detecting obstacles in the path of movement of the car sliding door 85 and / or the elevator shaft sliding door 87 , At the same time, the monitoring device 11 together with the assigned identifiers 71 used for access control, ie for identification with the identifiers 71 equipped people holding the elevator car 83 enter or leave. For this purpose, in the manner already described encoded conditional access signals from the identifiers 71 deposed and from the monitoring device 11 read. Depending on the compliance of a read access authorization signal with one or more in the monitoring device 11 stored codings enable or prevent the approach of certain building floors.

If several people with a respective Identgeber 71 within the detection range of the monitoring device 11 stop, by an anti-collision protocol a separation, ie a distinction of the various identifiers 71 be achieved.

It proves to be particularly advantageous that the monitoring device 11 It can also be recognized when a first person becomes an Identgeber 71 with a relatively high degree of authorization, the elevator car 83 leaves again. This may make for a possibly still in the elevator car 83 remaining second person who is an Identgeber 71 with a lower degree of entitlement, in turn, be denied the approach of building floors that would have been released for the first person.

4a shows an embodiment in which a single (first) capacitor electrode 13 along the front edge of the cabin sliding door 85 is arranged. This capacitor electrode 13 is with an evaluation and control circuit 15 connected to the elevator car 83 assigned and with an operating device 89 the elevator car 83 connected is.

The capacitor electrode 13 serves on the one hand for detecting objects in the path of movement of the cabin sliding door 85 in that the evaluation and control circuit changes the capacitance of the capacitor electrode 13 detected and evaluated, the evaluation and control circuit 15 where appropriate, the cabin sliding door 85 associated drive means for stopping or retracting the cabin sliding door 85 causes.

On the other hand, by the evaluation and control circuit 15 over the capacitor electrode 13 Access authorization signals are read in and be evaluated by an identifier 71 ( 3 ) are coupled, if one the Identgeber 71 Carrying person the cabin sliding door 85 or the capacitor electrode 13 happens. The evaluation and control circuit 15 at the same time - in particular via a central elevator control device (not shown) -, the driving course of the elevator car 83 to influence, ie the access control signals of the evaluation and control circuit 15 determine which building floors and, if necessary, in which order the building floors of the elevator car 83 be approached. This is the evaluation and control circuit 15 also with the operating device 89 connected. Depending on the read access authorization signals and thus of the access authorization in the elevator car 83 Person can control commands issued by the person on the operating device 89 be entered by the evaluation and control circuit 15 accepted or ignored.

4b shows an embodiment in which additionally a second capacitor electrode 23 at the operating device 89 the elevator car 83 is provided. The two capacitor electrodes 13 . 23 are with a common evaluation and control circuit 15 connected. The first capacitor electrode 13 in turn serves to detect objects that are in the path of movement of the cabin sliding door 85 are located. Optionally, the first capacitor electrode 13 in addition to identification purposes, as already related to 4a explained. The second capacitor electrode 23 is used exclusively for the explained identification function, ie for detecting capacitively coupled conditional access signals. In this case, a particularly reliable detection of the conditional access signals is guaranteed, as the the encoder 71 the person carrying the operating device 89 and thus the second capacitor electrode 23 touched.

4c and 4d show embodiments that are alternative or in addition to the embodiments according to 4a and 4b can be realized.

In the embodiment according to 4c is a first capacitor electrode 13 along the front edge of the elevator shaft sliding door 87 arranged. The capacitor electrode 13 is with an evaluation and control circuit 15 connected, and she serves in the context of 4a explained manner for capacitive proximity protection of the elevator shaft sliding door 87 (Safeguard function) and at the same time for the capacitive detection of conditional access signals of persons using the elevator shaft sliding door 87 happen and an identifier 71 according to 3 carry (access control function). To the driving course of the elevator car 83 - so the approach of the various building floors - to control, the in 4c shown evaluation and control circuit 15 communicate in particular via a central elevator control device with an evaluation and control circuit in the elevator car 83 is arranged ( 4a and 4b ).

Optional are in the embodiment according to 4c also another capacitor electrode 91 in the floor area in front of the elevator shaft sliding door 87 and / or another capacitor electrode 93 on the elevator shaft wall next to the elevator shaft sliding door 87 arranged. Based on these other capacitor electrodes 91 . 93 can the evaluation and control circuit 15 to recognize if there is a person holding the elevator car 83 has requested via a corresponding floor control device, even in the passenger waiting area before the elevator shaft on sliding door 87 or in front of the floor control unit.

This check is made by determining the respective capacitance of the capacitor electrode 91 respectively. 93 and comparison with a reference value, as related to the fuse function of the first capacitor electrode 13 according to 1a has already been explained. In the case of a negative test result, ie if there is no person in the area in front of the elevator shaft sliding door 87 can, the evaluation and control circuit 15 the previously entered request of the elevator car 83 Ignore or generate a corresponding elevator control signal for a central elevator control device. In this case, the elevator car drives 83 the building floor concerned no longer at all. As a result, an unnecessary idling is avoided, and it is achieved a higher efficiency of the elevator system.

4d shows an embodiment in which compared to 4c in addition to the first, at the elevator shaft sliding door 87 arranged capacitor electrode 13 a second capacitor electrode 23 is provided, which is used for the already explained access control function and for this purpose at a stationary operating device 95 the relevant building floor is arranged.

11

monitoring device

13

first capacitor electrode

15

evaluation and control circuit

17

signal output

17 '

signal output

23

second capacitor electrode

31

resonant circuit

33

capacitor

35

inductance

41

Reference resonant circuit

43

capacitor

45

inductance

47

comparator

49

demodulator

51

clock

53

signal modulator

55

microcontroller

57

amplifier

71

Ident donors

73

capacitor electrode

75

reception and control circuit

77

battery

81

elevator shaft

83

car

85

Cabin door

87

Hoistway door

89

operating device the elevator car

91

capacitor electrode

93

capacitor electrode

95

operating device a building floor

Claims (21)

Capacitive sensor with a monitoring device ( 11 ) comprising at least a first capacitor electrode ( 13 ) and an evaluation and control circuit ( 15 ), wherein the monitoring device has a capacitive proximity switch for securing a motor-driven door - in particular an elevator door ( 85 . 87 ) - forms, by means of the evaluation and control circuit, the capacitance of the first capacitor electrode can be determined, which is determined by the surrounding medium of the first capacitor electrode or an object in the vicinity of the first capacitor electrode, and wherein by means of the evaluation and control circuit in dependence determined capacitance of the first capacitor electrode, a switching or warning signal is generated, wherein - the monitoring device ( 11 ) is designed in addition to the access control, - by means of the evaluation and control circuit ( 15 ) a coded access authorization signal is read, which at the first ( 13 ) or a second capacitor electrode ( 23 ) is capacitively coupled to the monitoring device, - by means of the evaluation and control circuit, the read-in conditional access signal is comparable to a predetermined coding and depending on the result of the comparison, an access control signal can be generated, - another capacitor electrode ( 91 ) of the monitoring device ( 11 ) connected to the evaluation and control circuit ( 15 ) forms a capacitive proximity switch, as a bottom electrode for placement in the bottom area in front of an elevator shaft door ( 87 ) and / or in front of a floor operating device ( 95 ) of an elevator and / or as a wall electrode ( 93 ) for placement in the wall area next to an elevator shaft door ( 87 ), - the evaluation and control circuit ( 15 ) for generating an elevator control signal for controlling the driving course of an elevator car in dependence on the capacity of the wall or bottom electrode ( 91 . 93 ), and - can be prevented by the elevator control signal, that the elevator car approaches the building floor, at which the wall or floor electrode ( 91 . 93 ) is arranged, even if at the relevant building floor by operating a floor control device ( 95 ) a cabin request command has been triggered. Sensor according to claim 1, characterized in that the monitoring device at least one resonant circuit ( 31 ) whose resonant frequency depends on the capacitance of the first capacitor electrode ( 13 ), and that for the function as a capacitive proximity switch, the capacitance of the first capacitor electrode can be determined by means of the evaluation and control circuit ( 15 ) the oscillation frequency of the resonant circuit can be evaluated. Sensor according to claim 2, characterized in that the monitoring device a reference resonant circuit ( 41 ), and that for evaluating the oscillation frequency of said resonant circuit ( 31 ) of the monitoring device, the oscillation frequency of the resonant circuit ( 31 ) with the oscillation frequency of the reference resonant circuit ( 41 ) is comparable. Sensor according to one of claims 2 or 3, characterized in that in the resonant circuit ( 31 ) or another resonant circuit of the monitoring device that at the first ( 13 ) or second capacitor electrode ( 23 ) coupled access authorization signal of the oscillation frequency is superimposed as frequency modulation, and that the evaluation and control circuit ( 15 ) a demodulator ( 49 ), by which the frequency-modulated access authorization signal from the oscillation of the respective resonant circuit is demodulated. Sensor according to one of the preceding claims, characterized in that by means of the evaluation and control circuit ( 15 ) the switching or warning signal can be generated as a function of whether the determined capacitance of the first capacitor electrode ( 13 ) differs from a reference value by a predetermined threshold. Sensor according to one of the preceding claims, characterized in that the Auswer te and control circuit ( 15 ) in such a way with the first capacitor electrode ( 13 ) is connected, that by means of the evaluation and control circuit, the capacitance of the first capacitor electrode can be determined and an access authorization signal is read, which is capacitively coupled to the first capacitor electrode. Sensor according to one of the preceding claims, characterized in that the sensor further comprises at least one of the monitoring device ( 11 ) separately formed identifiers ( 71 ) having a control circuit ( 75 ) for generating the coded conditional access signal and a dedicated capacitor electrode ( 73 ), wherein the capacitor electrode ( 73 ) of the encoder - if the encoder ( 71 ) in close proximity to the monitoring device ( 11 ) of the sensor - with the first ( 13 ) or second capacitor electrode ( 23 ) of the monitoring device forms a capacitor, via which the access authorization signal from the identifier to the monitoring device is capacitively transferable. Sensor according to claim 7, characterized in that by means of the evaluation and control circuit ( 15 ) an identification request command can be generated for the monitoring device, which is included in the first ( 13 ) or second capacitor electrode ( 23 ) and there to the encoder ( 71 ) is capacitively transferable if the identifier is in spatial proximity to the monitoring device of the sensor. Sensor according to claim 8, characterized in that the evaluation and control circuit ( 15 ) of the monitoring device at least one resonant circuit ( 31 ) associated with the first ( 13 ) or second capacitor electrode ( 23 ), and that the identification request command as frequency modulation of the frequency of the resonant circuit in the first or second capacitor electrode can be fed. Sensor according to one of claims 8 or 9, characterized in that the encoder ( 71 ) a receiving circuit ( 75 ) for receiving the identification interrogation command applied to the capacitor electrode ( 73 ) of the encoder is capacitively coupled. Sensor according to one of claims 7 to 10, characterized in that the evaluation and control circuit ( 15 ) of the monitoring device in such a way with the first capacitor electrode ( 13 ) is connected, that the identification request command can be fed into the first capacitor electrode and there capacitively transferable to the identifier. Sensor according to one of the preceding claims, characterized in that the first capacitor electrode ( 13 ) of the monitoring device ( 11 ) at a front edge of an elevator car door ( 85 ) and / or at a front edge of an elevator shaft door ( 87 ) is arranged, and / or that the second capacitor electrode ( 23 ) of the monitoring device ( 11 ) at an operating device ( 89 ) an elevator car and / or at a floor operating device ( 95 ) is arranged an elevator. Method for monitoring a motor-driven door, in particular a sliding door ( 85 . 87 ) of an elevator, by means of a capacitive sensor, in which: for detecting an object in the path of movement of the door, the capacitance of a first capacitor electrode ( 13 ) is determined and evaluated, which is determined by the surrounding medium of the first capacitor electrode or the proximity of the object to the first capacitor electrode, characterized in that - for the purpose of access control in addition a coded access authorization signal is read and evaluated by an encoder ( 71 ) at the first ( 13 ) or a second capacitor electrode ( 23 ) is coupled capacitively. - That the read access authorization signal is compared with a predetermined coding and depending on the result of the comparison, an access control signal is generated, and - that is prevented depending on the result of the comparison that the elevator anfährt certain building floors. A method according to claim 13, characterized in that a switching or warning signal is generated if the determined capacitance of the first capacitor electrode ( 13 ) differs from a reference value by a predetermined threshold. Method according to one of claims 13 and 14, characterized in that the capacitive sensor at least one resonant circuit ( 31 ) whose resonant frequency depends on the capacitance of the first capacitor electrode ( 13 ), and that for determining the capacitance of the first capacitor electrode, the oscillation frequency of the resonant circuit is evaluated. A method according to claim 15, characterized in that the conditional access signal from the encoder ( 71 ) about the first ( 13 ) or second capacitor electrode ( 23 ) in the resonant circuit ( 31 ) or another resonant circuit as frequency modulation of the oscillation frequency is coupled, and that for reading the access authorization signal, the frequency modulated access authorization signal from the oscillation of the respective resonant circuit is demodulated. Method according to one of Claims 13 to 16, characterized in that the determination of the capacitance and the reading of conditional access signals on the same capacitor electrode ( 13 ) respectively. Method according to one of claims 13 to 17, characterized in that the encoder ( 71 ) a separate capacitor electrode ( 73 ) associated with the first ( 13 ) or second capacitor electrode ( 23 ) of the sensor forms a capacitor when the encoder is in spatial proximity to the first or second capacitor electrode, and that the conditional access signal is capacitively transmitted from the encoder via the capacitor thus formed. A method according to claim 18, characterized in that an identification request command is generated, which over the first ( 13 ) or second capacitor electrode ( 23 ) to the identifier ( 71 ) is capacitively transmitted when the encoder is in spatial proximity to the first or second capacitor electrode. Method according to one of claims 13 to 19, characterized in that the first capacitor electrode ( 13 ) at a front edge of an elevator car door ( 85 ) and / or at a front edge of an elevator shaft door ( 87 ) is arranged, and / or that the second capacitor electrode ( 23 ) at an operating device ( 89 ) an elevator car and / or at a floor operating device ( 95 ) is arranged an elevator. Method according to one of claims 13 to 20, characterized in that a further capacitor electrode ( 91 . 93 ) in the floor area in front of an elevator shaft door ( 87 ), in the floor area in front of a floor operating device ( 95 ) of an elevator and / or in the wall area next to an elevator shaft door ( 87 ) is arranged, and that on the basis of the capacity of the further capacitor electrode ( 91 . 93 ) is checked if a person waiting is in the area of the elevator shaft door.