Elevator guidance device

Details Elevator guidance device Elevator guidance device

2001-03-15

2002-06-25

Salata, Jonathan (Department: 2837)

Elevator, industrial lift truck, or stationary lift for vehicle

Having specific load support drive-means or its control

Includes control for power source of drive-means

C187S393000, C187S409000

Reexamination Certificate

active

06408987

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an elevator guidance device that actively guides a moving body such as an elevator cage.
2. Description of the Related Art
An elevator comprises a guide rail arranged in an elevator shaft, an elevator cage that is suspended by a wire, and raising/lowering means (unit) that raise/lower the cage by applying tension to the wire. Since the cage is suspended by the wire, it swings due to imbalances of the load weight or movement of the passengers; however, such swinging is suppressed by its being guided on the guide rails and it therefore ascends/descends along the guide rails. For guidance of the cage, conventionally, a guidance device comprising vehicle wheels in contact with the guide rails and a suspension was employed, however, vibration and noise caused by distortions or joints of the guide rail was transmitted through the vehicle wheels to the passengers and so was a factor impairing the comfort of the elevator. In order to solve this problem, various systems (for example, Laid-open Japanese Patent Publication number Sho. 51-116548, and Laid-open Japanese Patent Publication number H. 06-336383 and the like) have been proposed involving mounting an electromagnet on the elevator cage and guiding the cage in non-contacting manner by having the attractive force of the electromagnet act on an iron guide rail. Of these, Japanese Patent application H. 11-192224 discloses an elevator guide device wherein, in magnetic units comprising an electromagnet constituted by arranging the poles of an electromagnet opposite each other with guide rails in between and facing the guide rails through a gap and a permanent magnet arranged so as to share its magnetic path with the electromagnet in the aforesaid space, guidance control is exercised whereby the attractive forces of these magnetic units that act on the guide rails are stabilized while making the exciting current of the electromagnets converge to zero. By means of this technique, an elevator of low cost can be realized in which a comfortable ride can be provided and installation costs such as those of mounting the guide rails are controlled. However, even in such a case, the following problems arise.
Specifically, when elevator cage guidance control is performed whilst making the electromagnet exciting current of the magnetic units converge to zero, the gap lengths between the magnetic units and the guide rails such that external forces acting on the elevator cage and external disturbance torque due to these are as well as the permanent magnet attractive force of the magnetic units are exactly in balance change. That is, when external force acts on the elevator cage, the gap lengths change such as to oppose the application of the external force. Accordingly, if for some reason excessive external force acts on the elevator cage, the cage moves in the opposite direction to the direction of action of the external force, ultimately causing the magnetic units to contact the guide rails. When the magnetic units contact the guide rails, further external force is applied due to reaction from the guide rails, causing further change of the attractive force of the magnetic units in the guidance control device in the opposite direction to this external force, with the result that further change of the gap length is promoted. Thus, once the magnetic unit contacts the guide rail, guidance control acts such that those gap lengths which had become shorter on contact become even shorter and those gap lengths that had become wider become even wider, with the result that ultimately the elevator cage is completely in contact with the guide rail without any possibility of returning once more to a non-contacting condition.
Even in such a case, for example as disclosed in published Japanese Patent Number H. 06-24405, the phenomenon of adhesion of the elevator cage to the guide rail due to external force can be avoided if the guidance control means (unit) is provided with the function of actuating power control means (unit) having the function of making the electromagnet exciting current converge to zero when the gap length is in a prescribed range. Specifically, the zero power function whereby the electromagnet exciting current is made converge to zero by the guidance control device can be disabled by setting the output of the zero power control means (unit) as in the embodiment of this publication such that it is changed over to zero by setting the operating range of the zero power control means (unit) to be just before contact of the electromagnetic units with the guide rails. Since the attractive force of the magnetic units is controlled so as to return to the set gap length in respect of the external force when operation of the zero power control means (unit) is disabled, it becomes possible for the elevator cage to be again restored to the non-contacting condition by change of the gap length, which had changed so as to oppose the external force, in the direction of application of the external force. However, even in this case, action of the guidance control device of the elevator cage is unsatisfactory. In Published Japanese Patent Number H. 06-24405, magnetic levitation control as described above is applied to a levitation type carrier device. With the chief purpose of completely avoiding contact of the magnetic units and the guide rail in order to prevent generation of dust, in a running carrier vehicle, the gap length is rapidly increased by disabling the zero power control means (unit) in order to avoid contact with the guide rail produced by transient external force applied to the carrier vehicle on for example passage of a step in the guide rail. Consequently, if the gap length is increased by disabling of the zero power control, operation of the zero power control means (unit) is recovered in cases where the external force is not transient, for example cases where the rated carrying weight is exceeded. If this happens, the phenomenon of recovery occurs, in which the zero power control is again disabled by decrease of the gap length. However, even in this case, contact of the carrier vehicle with the guide rail is avoided and the objective of preventing generation of dust is achieved. However, in the case of an elevator, priority is given to a comfortable ride rather than to prevention of generation of dust. Thus, if enabling/disabling of the zero power control means (unit) is determined on the basis of the range of the gap length, if an excessive but steady external force is applied to the elevator cage, continuous fluctuation of the gap length occurs as described above, severely impairing comfort.
In order to solve these problems, it is necessary to make the dimensions of the magnetic units large and to set the gap lengths to a small value beforehand at the design stage, so as to maintain balance with external force by means (unit) of a large change of attractive force for even slight variations of gap length in response to external force, by making the variation of attractive force of the permanent magnet with respect to variation of the gap length large. However, with such measures for solution of the problem, the magnetic units become large in size and high precision is required in the installation of the guide rails, leading, as a result, to the problem of increased costs.
Thus, with the conventional elevator guidance device, there was the problem that since enabling/disabling of the zero power control means (unit) was determined by the gap length between the magnetic units and the guide rails, if an external force of a certain level of magnitude was applied to the elevator cage, the comfort of the ride was severely impaired. Furthermore, if, in order to avoid such problems, the magnetic units were increased in size, the device became of large size; on the other hand, if the designed gap length was set to a small value, installation of the guide rails had to be carried out with great precision, in either case, this made the elevator system complicated and/

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