Procedure for adjusting air gaps between rotors and stators...

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

Reexamination Certificate

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Details

C187S289000, C310S114000, C318S540000

Reexamination Certificate

active

06202794

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to elevator drive machines, and more particularly, to a procedure for adjusting air gaps between rotors and stators of an elevator drive machine.
2. Description of Related Art
The drive machine of a traction sheave elevator has a traction sheave with grooves for the hoisting ropes of the elevator and an electric motor driving the traction sheave either directly or via a transmission. Traditionally the electric motor used to drive an elevator has been a d.c. motor, but increasingly a.c. motors, such as squirrel-cage motors with electronic control are being used. One of the problems encountered in gearless elevator machines of conventional construction has been their large size and weight. Such motors take up a considerable space and are difficult to transport to the site and to install. In elevator groups consisting of large elevators, it has sometimes even been necessary to install the hoisting machines of adjacent elevators on different floors to provide enough room for them above the elevator shafts placed side by side. In large elevator machines, transmitting the torque from the drive motor to the traction sheave can be a problem. For example, large gearless elevators with a conventional drive shaft between the electric motor and the traction sheave are particularly susceptible to develop significant torsional vibrations due to torsion of the shaft.
Recently solutions have been presented in which the elevator motor is a synchronous motor, especially a synchronous motor with permanent magnets. For example the specification WO 95/00432 presents a synchronous motor with permanent magnets which has an axial air gap and in which the traction sheave is directly connected to a disc forming the rotor. Such a solution is advantageous in elevator drives with a relatively low torque requirement, e.g. a hoisting load of about 1000 kg, and in which the elevator speed is of the order of 1 m/s. Such a machine provides a special advantage in applications designed to minimize the space required for the elevator drive machine, e.g. in elevator solutions with no machine room.
The specification of 93340 presents a solution in which the traction sheave is divided into two parts placed on opposite sides of the rotor in the direction of its axis of rotation. Placed on both sides of the rotor are also stator parts shaped in the form of a ring-like sector, separated from the rotor by air gaps.
In the machine presented in the specification of 95687, the rotor and the stator parts on either side of it with an air gap in between are located inside the traction sheave. In this way, the traction sheave is integrated with the rotor, which is provided with magnetizing elements corresponding to each rotor part.
The specification of DE 2115490 A presents a solution designed to drive a cable or rope drum or the like. This solution uses separate linear motor units acting on the rim of the drum flanges.
For elevators designed for loads of several thousand kg and speeds of several meters per second, none of the solutions presented in the above-mentioned specifications is capable of developing a sufficient torque and speed of rotation. Further problems might be encountered in the control of axial forces. In motors with multiple air gaps, further difficulties result from the divergent electrical and functional properties of the air gaps. This imposes special requirements on the electric drive of the motor to allow full-scale utilization of the motor. Special requirements generally result in a complicated system or a high price, or both.
The specification of GB 2116512 A presents a geared elevator machine which has several relatively small electric motors driving a single traction sheave. In this way a machine is achieved that needs only a relatively small floor area. The machine presented in GB 2116512 A can be accommodated in a machine room space not larger than the cross-sectional area of the elevator shaft below it. Such an advantageous machine room solution has not been usable in the case of large gearless elevators because these typically have a machine with one large motor that extends a long way sideways from the traction sheave. The specification of EP 565 893 A2 presents a gearless elevator machine comprising more than one modular motor unit, which are connected together to drive traction sheaves also connected together. In such a solution, the length of the machine increases as its capacity is increased by adding a motor module. The problem in this case is that the length of the machine is increased on one side of the traction sheave, which is why the machine extends beyond the width of the elevator shaft below. Supporting and stiffening such a long machine so that its own weight and the rope suspension will not produce harmful deformations is likely to result in expensive and difficult solutions. For instance, the bending of a long machine requires a special and expensive bearing solution. If bending or other forms of load produce even the slightest flattening of the traction sheave to an elliptical shape, this will probably lead to vibrations that reduce the travelling comfort provided by the elevator.
SUMMARY OF THE INVENTION
It is an object of the present invention to achieve a procedure for matching the mutual positions of the functional parts of a gearless elevator drive machine comprising two axial air gaps. More specifically, the invention is directed to a method of adjusting at least one mechanical property of an elevator drive machine, the elevator drive machine including a traction sheave and an electromechanical apparatus that drives the traction sheave, the method including measuring an electrical characteristic of the electromechanical apparatus, the electromechanical apparatus including two motors for driving rotation of the traction sheave, each motor having a stator, a rotor, and an axial air gap between the stator and the rotor, the traction sheave being positioned between and attached to the rotors of the two electric motors along an axis of rotation of the traction sheave; and adjusting the air gap of at least one of the two motors as a function of the measured electrical characteristic.
The procedure of the present invention adjusts the magnitude of the axial air gaps or the mutual positions of the rotors and stators defining the axial air gaps, or both, in a gearless elevator drive machine including a traction sheave and an electromechanical apparatus driving the traction sheave, the electromechanical apparatus having two axial air gaps.
It is possible to apply several different criteria in adjusting or setting the mutual positions of both the air gaps and the rotors and stators to the intended operating position. For instance, it may sometimes be more desirable to optimize the load capacity, and in other cases energy consumption may be a more desirable optimization criterion. According to the principles of the invention, sufficient optimization of an existing drive machine can be achieved by adapting the mechanical properties of the drive machine to produce an electrical property descriptive of the objectives of optimization, a property that can be electrically measured from the stator winding. The descriptive property preferably contains the optimization criterion, preferably e.g. as a maximum or minimum.
The procedure of the present invention is applied in a drive machine in which the torque is developed by two motors or motor blocks, the torque being thus doubled as compared with a corresponding single motor. The axial forces generated by the motor blocks compensate each other, so the strain on the bearings and motor shaft will be minimized.
Due to the good torque characteristics of such a drive machine, a large traction sheave size in relation to the size, weight and performance of the drive machine is achieved. For instance, an axle load of 40000 kg can be handled by a machine weighing below 5000 kg, even if the elevator speed is as high as 9 m/s or considerably higher.
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