METHOD FOR DETECTING THE POSITION OF AN ELEVATOR CABIN DOOR

Description

Technical field

[0001] The present invention relates to a method for detecting the position of a car door of an elevator.

[0002] Present day elevator door systems have doors mounted on the elevator car - referred to as "car doors", and doors mounted at each hall landing of the elevator hoistway - referred to as "landing doors".

[0003] The elevator car carries an electric motor and door operator for operating the car door.

[0004] The landing doors are typically opened by coupling them with the car doors so that opening of the car doors will open the landing doors in unison therewith.Background art

[0005] Various types of door couplers are already known in the art for establishing this coupling connection.

[0006] Coupling between the car door and the landing doors occurs when the doors are opening and closing, whereas no coupling occurs when the car is moving through the hoistway.

[0007] The same electric motor is configured to activate both the door coupler and opening / closing of the door leaves.

[0008] Control of opening / closing speed of the door is usually entrusted to an incremental encoder. This also serves for obtaining a relative position of the car door. Nevertheless, incremental encoder does not provide an absolute position of the door.

[0009] In a known solution the absolute position may be obtained by a mechanical switch, that is an easy equipment but noisy.

[0010] Another solution consists in placing a permanent magnet on the door and a reed switch above the door, usually integral with the electronic box mounted above the door.

[0011] As it is known, a reed switch consists of a pair of ferromagnetic flexible metal contacts arranged in a hermetically sealed glass case. The contacts are normally open, whereas they close when a magnetic field is detected, or vice versa. The reed switch is operated by the movement of the door leaves; indeed, it is actuated by the permanent magnet integrally mounted on the door.

[0012] The glass case of the reed switch is prone to mechanical damage.

[0013] In addition, switching position depends on magnet strength, relative position of the reed switch and magnet and mechanical set-up.

[0014] As the reed switch is a digital magnetic sensor, reliability requires that it acts before the door is fully closed, that is when the door leaves are still distanced of some millimetres.

[0015] Due to mechanical tolerances and switch tolerances, an uncertainty is introduced in the absolute position, leading to non-optimal operation of both door and door coupler movement. Even a compensation provided by software is not sufficient to fully overcome the issue.

[0016] EP 3 348 508 A1 discloses a method for calculating the position of a car door of an elevator.Disclosure of the invention

[0017] In this context, the technical task underlying the present invention is to propose a method for detecting the position of a car door of an elevator, which overcomes the drawbacks in the prior art as described above.

[0018] In particular, an object of the present invention is to provide a method for detecting the position of a car door of an elevator, which is able to increase accuracy in determining the position of the door (or of the coupler) with respect to prior art solutions.

[0019] Another object of the present invention is to make available a method for detecting the position of a car door of an elevator, which is more reliable and less sensitive to mechanical tolerances than prior art solutions.

[0020] The stated technical task and specified objects are substantially achieved by a method for calculating the position of a car door of an elevator according to independent claim 1.

[0021] Further aspects of the invention are defined in the dependent claims.Brief description of drawings

[0022] Additional features and advantages of the present invention will become more apparent from the non-limiting, description of a preferred, but non-exclusive embodiment of a method for detecting the position of a car door of an elevator, as illustrated in the appended drawings, in which: figure 1 schematically illustrates a non-claimed system for detecting the position of a car door of an elevator; figure 2 is a characteristic curve of a signal detected from the system of figure 1, as a function of the movement of the belt; figure 3 schematically illustrates another embodiment of the non-claimed system of figure 1. Detailed description of preferred embodiments of the invention

[0023] With reference to the figures, number 1 indicates a car door for an elevator.

[0024] According to one embodiment, the car door 1 has two leaves.

[0025] According to another embodiment, the car door 1 has one leaf.

[0026] In any case, the number of leaves and the type of car door are not relevance for the invention.

[0027] The system comprises a door coupler 2 for coupling the car door 1 with a landing door (not illustrated).

[0028] The door coupler 2 is mounted on top of the car door 1.

[0029] An electric motor 3 is configured to drive the car door 1 between an open position and a closed position, and vice versa.

[0030] According to one aspect, the electric motor 3 is operatively active on a belt 4 to which the door coupler 2 is mechanically connected.

[0031] Thus, the electric motor 3 is configured to move the car door 1 by means of the connection comprising the belt 4 and the door coupler 2.

[0032] Each landing door is moved accordingly, thanks to the coupling with the car door 1.

[0033] Magnetic means 5 are integrally mounted on the car door 1.

[0034] In particular, the magnetic means 5 are mounted on one of the hanger plates 7 (see figure 1). The door leaves are mounted on the hanger plates 7 which have rollers to guide the vertical movement.

[0035] According to one embodiment, the magnetic means 5 are mounted on an external vertical edge of the hanger plate 7.

[0036] According to another embodiment, the magnetic means 5 may be mounted on a lever, e.g. on the top of the hanger plate 7. According to one embodiment, the magnetic means 5 comprises at least one permanent magnet configured to generate a magnetic field.

[0037] The system comprises an analog magnetic sensor 6 configured to detect the magnetic field generated by the magnetic means 5 so as to detect a signal that is representative of the position of the car door 1.

[0038] According to an embodiment, the analog magnetic sensor 6 is integrally mounted on a door operator.

[0039] Preferably, the analog magnetic sensor 6 and the magnetic means 5 are mutually arranged so that their distance is increased or decreased monotonously as the car door 1 is respectively open or close.

[0040] Preferably, the analog magnetic sensor 6 is arranged substantially at the same height of the magnetic means 5 so as to face it. This is shown for example in figure 1.

[0041] This results in a more reliable detection of the magnetic field generated by the magnetic means 5.

[0042] In fact, there is no "dead area" in which the door movement is undetected, but the movement is continuously detected.

[0043] According to another embodiment the analog magnetic sensor 6 is arranged at a higher level than the magnetic means 5.

[0044] In particular, the analog magnetic sensor 6 is arranged above the car door 1.

[0045] This embodiment is still working, even if there is a "dead area" where the door movement is no more detected. Thus, this embodiment provides a less accurate position for the door that the embodiment of figure 1.

[0046] The electric motor 3 is controlled by a control unit (not illustrated).

[0047] The analog magnetic sensor 6 may be integrally mounted on same box of the electronic control unit.

[0048] The analog magnetic sensor 6 used in the current invention may be any type according to the prior art.

[0049] The functioning of the system for detecting the absolute position of a car door of an elevator, according to the claimed invention, is described hereafter.

[0050] When the car door 1 is operated in opening / closing, the electric motor 3 drives the belt 4, so the door coupler 2 starts to move and then the door 1 moves accordingly. This will be better explained below.

[0051] Since the magnetic means 5 are integral to the car door 1, the magnetic means 5 also moves accordingly.

[0052] In particular, when the car door 1 is closed, the magnetic means 5 are brought closer to the analog magnetic sensor 6, so that a higher value of field forces is detected.

[0053] In particular, the closer the magnetic means 5 are to the analog magnetic sensor 6, the higher is the value of magnetic flux density that is detected.

[0054] In particular, the value of magnetic flux density detected by the analog magnetic sensor 6 increases with the gradual closing of the door 1.

[0055] Vice versa, when the door 1 gradually opens the magnetic means 5 are accordingly moved farther from the analog magnetic sensor 6.

[0056] In particular, the farther the magnetic means 5 are from the analog magnetic sensor 6, the lower is the value of magnetic flux density that is detected.

[0057] Thus, the value of magnetic flux density decreases with the gradual opening of the door 1.

[0058] Indeed, the analog magnetic sensor 6 is able to detect a signal - i.e. the magnetic flux density - that changes continuously.

[0059] In figure 2 it is reported a curve of the signal detected by the analog magnetic sensor 6, which is in the y axis, as a function of the movement of the belt 4, which is in the x axis.

[0060] It is assumed that the car door 1 is initially in the closed position. When the belt 4 starts to move for opening the door 1, the door coupler 2 moves but the car door 1 does not move for a first part of the belt 4 movement - that is referred here as "coupler movement".

[0061] As the belt 4 moves further the first part, the car door 1 also starts moving. Thus, the magnetic means 5 are moved relative to the analog magnetic sensor 6 only when door 1 is moving.

[0062] As it is shown in figure 2, the characteristic curve consists of a substantially constant part followed by a non-constant part.

[0063] The constant part, which is numbered as 10, refers to the door coupler 2 being operated, whereas the door 1 is still closed (not moving). This is the "coupler movement" part.

[0064] The non-constant part, which is numbered as 11, is relative to the actual movement of the door 1, together with the door coupler 2.

[0065] In this context, with the expression "constant part" it is considered a part of the curve that is approximately constant, at least compared with the non-constant part 11, whereas the door 1 is moving.

[0066] An intersection point A between the constant part 10 and the non-constant part 11 can be determined by calculating the second derivative of the curve and searching for the maximum of it.

[0067] An offset / correction value may be applied (depending on filter time constant applied together with calculation of derivative).

[0068] Other algorithms might be used as well, for example curve fittings (for example constant function on the "constant part" 10, exponential function on the "non-constant" part 11).

[0069] The characteristics of a method for detecting the position of a car door of an elevator, according to the present invention, emerge clearly from the above description, as do the advantages.

[0070] In particular, the accuracy in determining the absolute position of the door is higher than in prior art solutions thanks to use of an analog magnetic sensor for detecting the field generated by the magnetic means integral to the door.

[0071] In addition, arranging the analog magnetic sensor at the same height of the magnetic means so as to face it results in optimization of the accuracy and thus in optimization of the travel speed curve of the door.

Claims

1. A method for calculating the position of a car door (1) of an elevator using a system comprising: - a door coupler (2) for coupling the car door (1) with a landing door, said door coupler (2) being mounted on the car door (1); - an electric motor (3) configured to drive the car door (1) between an open position and a closed position, and vice versa; - a belt (4) to which the door coupler (2) is mechanically connected, the electric motor (3) being operatively active on said belt (4) so as to move the car door (1); - magnetic means (5) integrally mounted on the car door (1), said magnetic means (5) being configured to generate a magnetic field; - an analog magnetic sensor (6) configured to detect the magnetic field generated by the magnetic means (5) so as to detect a signal that is representative of the position of the car door (1), the method comprising: - detecting a signal that is representative of the position of the car door (1) by means of the analog magnetic sensor (6), so obtaining a characteristic curve of the detected signal (y) as a function of a position (x) of the belt (4); - estimating a point (A) in the characteristic curve that represents the position of the belt (4) corresponding to the car door (1) passing from the open position to the close position, wherein the step of estimating said point (A) comprises calculating a second derivative of the characteristic curve and determining its maximum.

2. The method according to claim 1, further comprising a step of applying a correction value to said point (A).

3. The method according to claim 1 or 2, wherein the analog magnetic sensor (6) and the magnetic means (5) are mutually arranged so that their distance is increased or decreased monotonously as the car door (1) is respectively brought in the open position or closed position.

4. The method according to any one of the preceding claims, wherein the system further comprises a hanger plate (7), said analog magnetic sensor (6) being mounted on a door operator.

5. The method according to claim 4, wherein the analog magnetic sensor (6) is arranged substantially at the same height of the magnetic means (5).

6. The method according to claim 1, wherein the analog magnetic sensor (6) is arranged at a higher level than the magnetic means (5).

7. The method according to claim 6, wherein the system further comprises an electronic control unit configured to control said electric motor (3).

8. The method according to any one of the preceding claims, wherein the magnetic means (5) comprise at least one permanent magnet.