Field of the invention

The invention relates to the structures of electric machines and more particularly to the structures of hoisting machines.

Background of the invention

It is a general aim to utilize built space as efficiently as possible. For example, owing to space requirements, one aim is to make the hoisting machines of elevators as compact as possible. In order to achieve this, hoisting machines are designed to be as flat as possible in their dimensions in the direction of . the axis of rotation, in which case the hoisting machines fit better in connection with, for instance, the wall part of the elevator hoistway or into some other corresponding narrow space .

A flat hoisting machine can be implemented with both an axial flux motor and with a radial flux motor. For many reasons an axial flux motor is an ideal solution for a flat hoisting machine. In an axial flux motor the winding overhangs do not require space in the direction of the axis of rotation in the same way as in a radial flux motor. In an axial flux motor the torque output can also be increased without the same type of increase in length in the direction of the axis of rotation of the motor as in a radial flux motor.

When minimizing the length in the direction of the axis of rotation of a hoisting machine implemented with an axial flux motor, the rigidity of the machine might form a problem. For example, rigidity is required of the hoisting machine of an elevator because the hoisting machine must support the elevator mechanics suspended in the elevator hoistway. Also the noise level of the hoisting machine might increase to be disturbing when the length in the direction of the axis of rotation of the hoisting machine shortens.

Summary of the invention

The aim of the invention is to disclose an improved hoisting machine and also an elevator system in which such an improved hoisting machine is used. An improved hoisting machine can be made flatter than a prior-art one without the rigidity of . the hoisting machine weakening and/or without the noise level increasing significantly.

In relation to the characteristic attributes of the invention, reference is made to the claims. Some inventive embodiments are also presented in the descriptive section and in the drawings of the present application.

The invention relates to a hoisting machine, which comprises a hoisting motor; which hoisting, motor comprises a ring-like stator; which stator is disposed in a stationary structure of the hoisting machine; and which hoisting motor comprises a rotor; which rotor is disposed in a rotating structure of the hoisting machine; and which rotating structure of the hoisting machine comprises a traction sheave; and which stator and rotor are fitted consecutively in the direction of the axis of rotation of the hoisting machine such that an air gap remains between the stator surface and the rotor surface that face each other, which air gap is essentially in the direction of the axis of rotation of the hoisting machine; and which aforementioned stator, rotor and also air gap remaining between the stator and the rotor form the magnetic circuit of the hoisting motor. The ratio of the effective diameter z of the magnetic circuit of the hoisting motor to the diameter D of the traction sheave of the hoisting z

machine is selected such that the ratio — of the

D

effective diameter z of the magnetic circuit and the diameter D of the traction sheave is smaller than 1.05 and larger than 0.95 when the diameter D of the traction sheave is smaller than 420 millimeters; and z

that the ratio — of the effective diameter z of the

D

magnetic circuit and the diameter D of the traction sheave is smaller than 1.085 and larger than 0.93 when the diameter D of the traction sheave is smaller than or equal to 600 millimeters and larger than or equal to 420 millimeters. The stator and the rotor of the hoisting motor are disposed on opposite sides of the air gap essentially face-to-face. A force component in the direction of the air gap is therefore exerted on the rotor of the hoisting motor at the point at which the magnetic field transfers from the air gap to the rotor and from the rotor to the air gap. The magnitude of the force component is proportional to the magnetic field, so that the harmonics of the magnetic field produce force fluctuations that try to excite vibration in the rotating structure of the hoisting machine. The effective diameter z of the magnetic circuit is determined at the point of the magnetic circuit of the hoisting motor, at which point the resultant of the force component in ^~ the direction of the air gap of the magnetic circuit acts on the rotor. The diameter D of the traction sheave, on the other hand, is determined at the point of exertion of the mechanical force on the rim part of the traction sheave, e.g. at the center point of the ropes or belt on the traction sheave. According to the basic concept of the invention, the rim part of the traction sheave is thus disposed in the rotating structure of the hoisting machine in the direction of the axis of rotation of the hoisting machine at a point at which the resultant of the force component in the direction of the air gap of the magnetic circuit acts on the rotor, or the rim part of the traction sheave is disposed in the immediate proximity of said point. This type of solution stiffens the rotating structure of the electric machine, effectively preventing vibration caused by fluctuations of the magnetic field. In this case the hoisting machine can be made flatter than a prior-art one in its dimension in the direction of the axis of rotation of the hoisting machine without the noise level of the hoisting machine increasing significantly.

In a preferred embodiment of the invention the rotor is disposed on a first side of the rotating structure of the hoisting machine, and the traction sheave is disposed on the opposite side of the rotating structure of the hoisting machine.

In a preferred embodiment of the invention the traction sheave is integrated into the same piece as the rotor.

The aforementioned piece comprising the traction sheave and the rotor, as well as the stationary structure of the hoisting machine are preferably discoidal in shape. When the aforementioned discoidal structures are in this case fitted consecutively in the direction of the axis of rotation of the hoisting machine, the hoisting machine can be made essentially flat in the direction of the axis of rotation of the hoisting machine.

The hoisting motor according to the invention is preferably a permanent-magnet motor, the rotor of which is formed in the rotating structure of the hoisting machine such that permanent magnets are fixed into a ring-like rim onto the surface of the rotating structure of the hoisting machine. In some preferred embodiments of the invention the magnetic axes of the permanent magnets are essentially in the direction of the air gap.

The rotating structure of the hoisting machine is preferably made from a magnetic material, at least in the immediate proximity of the permanent magnets, and the aforementioned part of the rotating structure of the hoisting machine, said part being disposed in the immediate proximity of the permanent . magnets and being made of magnetic material, forms together with the permanent magnets the magnetic circuit of the rotor of the hoisting motor. In a preferred embodiment of the invention the width of the permanent magnets in the direction of the air gap is essentially constant; the aforementioned width of the permanent magnets in the direction of the air gap can, however, also vary such that with the variation in width it is endeavored to achieve a density distribution of magnetic flux that is as sinusoidal as possible in the air gap of the magnetic circuit. The aforementioned permanent magnets of the rotor are preferably fitted into a fixing matrix, which in order to reduce eddy currents is made from a material that does not conduct electricity, or conducts electricity poorly, such as from glass fiber composite, stainless steel or corresponding. The permanent magnets can, however, also be fixed e.g. by embedding them into the rotating structure of the hoisting machine into recesses to be machined for this purpose.

In a preferred embodiment of the invention, the traction sheave is hollow. In this case the rim part of the hollow traction sheave is disposed in the rotating structure of the hoisting machine at the point at which the resultant of the force component in the direction of the air gap of the magnetic circuit of the hoisting motor acts on the rotor, or the rim part is disposed in the immediate proximity of said point. The rotating structure of the hoisting machine can therefore be made to be extremely rigid, but the structure is simultaneously light and fits into a small space. In some preferred embodiments of the invention, the machinery brake is disposed inside the hollow traction sheave. In some preferred embodiments of the invention, the sensor that measures the movement of the rotating part of the hoisting machine is disposed inside the hollow traction sheave. The braking surface of the machinery brake can also be formed on the inner surface of the rim part of the hollow traction sheave.

In some preferred embodiments of the invention, the rotating structure of the hoisting machine is supported on the stationary shaft of the hoisting machine via bearings. The shaft can also be made hollow, in which case the hoisting machine lightens without essentially weakening the rigidity of the hoisting machine. The hollow structure of the shaft and/or of the traction sheave also means that the amount of raw material needed for manufacturing the hoisting machine decreases. The sensor that measures the movement of a rotating structure of the hoisting machine can also be disposed inside the hollow shaft.

A drum brake or a disc brake, for example, can be used as machinery brakes of the hoisting machine according to the invention. The braking surface is preferably formed into a ring-like rim as an extension of the outermost rim of the rotating structure of the hoisting machine, e.g. into the brake disc of a disc brake or into the brake rim of a drum brake .

The aforementioned rim-like stator of the hoisting motor comprises teeth as well as slots between them. The stator winding is fitted into the slots. In preferred embodiments of the invention, the stator winding is implemented as a concentrated winding, preferably as a concentrated fractional slot winding. When using a concentrated winding, preferably a concentrated fractional slot winding, the stator winding becomes more compact owing to, inter alia, the shorter winding overhangs. By means of the solution according to the invention, the effect on vibration/noise of the harmonics produced in the circulating magnetic field in the air gap of the motor by a concentrated winding / concentrated fractional slot winding can also be reduced.

With regard to the second aspect, the invention relates to an elevator system, which comprises any hoisting machine described above, for moving the elevator car in the elevator hoistway. The aforementioned hoisting machine is preferably disposed in the elevator hoistway, e.g. in a narrow space between the elevator car and the wall of the elevator hoistway, into which space an essentially flat hoisting machine according to the invention will fit very well.

With regard to the third aspect, the invention relates to a method for manufacturing a hoisting machine. In the method a rotor and a traction sheave are fitted into a rotating structure of the hoisting machine, a ring-like stator is fitted into a stationary structure of the hoisting machine, the stator and the rotor are fitted consecutively in the direction of the axis of rotation of the hoisting machine, the stator and the rotor are fitted into the magnetic circuit of the motor such that an air gap remains between the stator surface and the rotor surface that face each other, which air gap is essentially in the direction of the axis of rotation of the hoisting machine, and the rim part of the traction sheave is disposed in a rotating structure of the hoisting machine in the direction of the axis of rotation of the hoisting machine at a point, at which the resultant of the force component in the direction of the air gap of the magnetic circuit acts on the rotor.

In one preferred embodiment of the invention slots are made in the stator and a concentrated winding is fitted into the stator slots. In one preferred embodiment of ^' the invention a concentrated fractional slot winding is fitted into the stator slots.

In some preferred embodiments of the invention the band-like rim part of the traction sheave is fitted to continue outwards from the rotor in the direction of the axis of rotation of the hoisting machine.

The aforementioned summary, as well as the additional features and advantages of the invention presented below, will be better understood by the aid of the following description of some embodiments, said description not limiting the scope of application of the invention.

Brief explanation of the figures

Fig. 1 presents a part of one hoisting machine according to the invention, sectioned open upwards from the axis of rotation of the hoisting machine in the direction of the radius Fig. 2 illustrates a stator according to the invention as viewed from the direction of the axis of rotation

Fig. 3 illustrates a rotor according to the invention as viewed from the direction of the axis of rotation

Fig. 4 presents as a block diagram an elevator system according to the invention

More detailed description of preferred embodiments of the invention

In Fig. 1 only that part of the hoisting machine 1 that goes upwards from the axis of rotation 8 of the hoisting machine in the direction of the radius is shown. In Fig. 1, for the sake of clarity, the machinery brakes and parts of the frame part 5, inter alia, have been omitted from the drawing of the hoisting machine 1. The hoisting machine 1 of Fig. 1 is, however, rotationally symmetrical in relation to the axis of rotation 8, so that e.g. the diameter D of the traction sheave 7 is double with respect to the radius 23 of the traction sheave measured from the axis of rotation 8 of the hoisting machine. The diameter D of the traction sheave, as also the radius 23, is determined at the center point of the hoisting ropes disposed in the rope grooves 14 of the traction sheave .

The hoisting machine 1 of Fig. 1 comprises a hoisting motor, which comprises a ring-like stator 2, which is disposed in the stationary frame part 5 of the hoisting machine. The hoisting motor also comprises a rotor 3, which is disposed in a rotating piece 6 of the hoisting machine, on the opposite side to the traction sheave 7, which is integrated into the rotating piece 6, of the hoisting machine. The traction sheave 7 is hollow. The rotating piece 6 is supported on the stationary hollow shaft 12 by means of bearings 11. The rotor 3 is situated consecutively to the stator 2 in the direction of the axis of rotation 8, such that an air gap 4 remains between the stator surface and the rotor surface that are parallel and face each other. The magnetic field passes over the air gap 4 between the stator 2 and the rotor 3 and circulates in the parts of the rotor and of the stator that conduct magnetic flux. The part that conducts magnetic flux is made from a material with a relative permittivity that is greater than one. Usually a ferromagnetic material, such as iron or crystal-aligned dynamo plate, is used. In the hoisting motor of Fig. 1, the rotor 3, the stator 2 as well as the air gap 4 between them, in which the magnetic flux flows, form the magnetic circuit of the hoisting motor. The stator 2 of Fig. 1 is illustrated in more detail in Fig. 2 as viewed from the direction of the axis of rotation 8 of the hoisting machine 1. A three-phase stator winding 18 is fitted into the slots 17 between the stator teeth 16, which stator winding is here implemented as a concentrated fractional slot winding. Fig. 2 presents only one of the three phases of the winding. The alternating current to be supplied to the phases of the stator winding 18 produces magnetic flux circulating in the magnetic circuit 2, 3, 4 of the hoisting motor. The density distribution of magnetic flux produced in the air gap 4 of the magnetic circuit of the motor by the current flowing in a concentrated fractional slot winding 18 deviates from sinusoidal.

The rotor 3 of Fig. 1 is illustrated in more detail in Fig. 3 as viewed from the direction of the axis of rotation 8 of the hoisting machine 1. The rotor 3 is formed in the rotating piece 6 of the hoisting machine such that permanent magnets 9 are fixed consecutively into a ring-like rim onto the surface of the rotating piece 6 of the hoisting machine. The permanent magnet 9 is shaped like a parallelogram, being formed from two parallelograms that are disposed side by side in the direction of the rim and are mirror images of each other. The aim of the shaping of the permanent magnet 9 is to bring about an essentially sinusoidal density distribution of magnetic flux in the air gap 4 of the magnetic circuit of the hoisting motor. A sinusoidal density distribution of magnetic flux can also be achieved by using many different shapes of the permanent magnets 9 that deviate from a parallelogram. The magnetic poles of two consecutive permanent magnets 9 are always opposite to each other. The permanent magnets are fitted into a fixing matrix 10, which is in turn fixed to the surface of a rotating piece 6 of the hoisting machine. The thickness of the permanent magnets in the direction of the air gap 4 is essentially constant. The rotating piece 6 is made from ferromagnetic material in the proximity of the permanent magnets 9, in which material the magnetic flux flowing in the magnetic circuit circulates. The effective diameter z of the magnetic circuit is also marked in Fig. 3.

The magnetic flux circulating in the magnetic circuit 2, 3, 4 of the hoisting motor produces a force effect between the rotor and the stator. The tangential force component causes rotation of the rotor, whereas the force component in the direction of the air gap 4 produces an attractive force between the rotor and the stator. The effective diameter z of the magnetic circuit is determined at the point 21 of the magnetic circuit of the hoisting motor at which point the resultant of the force component in the direction of the air gap 4 of the magnetic circuit acts on the rotor 3. The force component in the direction of the air gap 4 of the magnetic circuit varies owing to, inter alia, the harmonics in the circulating magnetic flux. The variation of the aforementioned force component in the direction of the air gap 4 of the magnetic circuit tries to produce vibration in the rotating piece 6, which vibration might further cause e.g. noise problems, vibration of the hoisting machine

1 and/or wearing of the bearings 11. To damp vibration and thereby to stiffen the rotating piece 6, the z

ratio— of the effective diameter z of the magnetic D

circuit 2, 3, 4 of the hoisting motor to the diameter D, of the traction sheave 7 of the hoisting machine is selected according to table 1:

Table 1.

In table 1 the rim part 13 of the hollow traction

z sheave 7 at the given ranges of the ratio — is disposed in the moving piece of the hoisting machine at the point 21, at which the resultant of the force component in the direction of the air gap 4 of the magnetic circuit of the hoisting motor acts on the rotor 3, or the rim part 13 of the traction sheave is disposed in the immediate proximity of said point 21. This type of structure stiffens the rotating piece 6 of the hoisting machine. In this case the rotating piece 6 can also be made flatter than a prior-art one in the direction of the axis of rotation 8 of the hoisting machine without the vibration of the hoisting machine increasing significantly. The vibration can be forced oscillation or vibration that occurs at the resonance frequencies (in vibrational modes) of the rotating piece. Fig. 4 presents as a block diagram an elevator system, in which the elevator car 19 and the counterweight 22 are suspended in the elevator hoistway 20 with elevator ropes passing via the traction sheave of the hoisting machine 1 of the elevator. The elevator car is moved by exerting a force effect on the elevator car via the hoisting ropes by operating the hoisting machine 1 of the elevator. The power supply to the hoisting machine 1 of the elevator occurs with a frequency converter (not shown in figure) connected between the electricity network and the hoisting machine 1 of . the elevator. The frequency converter and the hoisting machine 1 of the elevator are disposed in the elevator hoistway, in connection with the wall of the elevator hoistway 20 outside the path of movement of the elevator car 19. The hoisting machine 1 of the elevator is of the type presented in the embodiment of Fig. 1. The hoisting machine 1 of the elevator is therefore made flatter in its dimension in the direction of the axis of rotation 8 than a prior-art one. As can be observed from Fig. 4, a flatter hoisting machine 1 of an elevator enables increasing the width of the elevator car 19 in the direction of the axis of rotation 8 of the hoisting machine 1 of the elevator, in which case a more spacious elevator car 19 than before can be fitted into the same elevator hoistway. Increasing the volume of the elevator car 19 also increases the transport capacity of the elevator.

The hoisting machine 1 according to the invention is suited for use in different lifting systems; in addition to a passenger elevator and freight elevator system, the hoisting machine can be used e.g. in mine elevators, drum drive elevators, and also in cranes.

The invention is not only limited to be applied to the embodiments described above, but instead many variations are possible within the scope of the inventive concept defined by the claims below.