GB2131381A

GB2131381A - Traction machine for elevators

Info

Publication number: GB2131381A
Application number: GB08332501A
Authority: GB
Inventors: Hiroshi Kamaike
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 1982-12-06
Filing date: 1983-12-06
Publication date: 1984-06-20
Also published as: KR840006155U; KR860003715Y1; HK22687A; MY8700249A; GB8332501D0; CA1207676A; GB2131381B

Abstract

A traction machine for elevators in which a main rope 3 for suspending a cage is wound round a sheave 13 driven by an electric motor 19, and a braking force is generated by frictionally applying brake shoes 30 to the main rope 3 to brake the cage whereby even when the sheave has a small diameter, a sufficient braking force is generated, and the rotational speed of the sheave is raised, so that the electric motor 19 can be smaller. <IMAGE>

Description

SPECIFICATION Traction machine for elevators This invention relates to traction machines for elevators.

In an elevator wherein a cage is caused to ascend and descend by a main rope, the cage is driven by the frictional force between the sheave and the main rope of a traction machine.

Consequently, both the driving force of an electric motor driving the sheave and the braking force of a brake for restraining the sheave are limited to a range within which there is no slip between the main rope and the sheave. If a large driving and braking force is required, therefore, a sheave having a large outside diameter has been used for increasing the area of contact between the sheave and the main rope so as to produce the required frictional force.

Figures 1 and 2 of the accompanying drawings show a conventional traction machine for elevators, particularly a well-known traction machine for gearless elevators.

A cage 2 ascends and descends in a shaft 1 on a main rope 3, one end of which is connected to the cage 2, and the other end of which has a balance weight 4 connected thereto. A machine room 5 is defined in the top part of the shaft 1. A supporting beam 6 is installed on the floor of the machine room 5, and a machine bed 7 bridges the gap between this supporting beam 6 and the wall of the machine room 5. A rotary shaft 11 is carried by supporting legs 12. A sheave 13 is mounted substantially centrally on the rotary shaft 11, and has the main rope 3 wound round it.

A brake wheel or drum 14 is mounted on the rotary shaft 11 adjacent to the sheave 13. A pair of brake shoes 1 5 grip the brake wheel 14 so as restrain the sheave 13. A pair of brake arms 16 are supported by pins 1 6a and operate the brake shoes 1 5 to grip and release the brake wheel 14.

Brake springs 17 press the brake arms 1 6 to apply the brake shoes 15, and a brake coil or solenoid 1 8 moves the brake arms 16 against the brake springs 1 7 when electrically energised, to release the brake shoes 1 5 from the brake wheel 14. The aforementioned brake wheel 14, brake shoes 15, brake arms 16, brake springs 17 and brake coil 1 8 constitute a brake 1 8A. An electric motor 1 9 is disposed opposite to the brake wheel 14 with the sheave 1 3 therebetween, and drives the shaft 1 A deflector wheel 20 is mounted on the machine bed 7, and it guides the main rope 3, wound round the sheave 13, to a position directly over the balance weight 4.

In the traction machine for the elevator constructed as described above, when both the electric motor 19 and the brake coil 18 are deenergised, the brake shoes 1 5 grip the brake wheel 14 to restrain the sheave 13 and to stop the cage 2. On the other hand, when both the brake coil 18 and the electric motor 19 are energised, the brake wheel 14 is released, and the sheave 1 3 is driven by the electric motor 19, so that the main rope 3 moves to raise or lower the cage 2.

Since, in the elevator traction machine stated above, the brake wheel 14, sheave 13 and motor 19 are mounted on the rotary shaft 11 in tandem, the rotary shaft 11 is long. In addition, since the sheave 1 3 is located substantially in the middle of the rotary shaft 11 to support the weights of the cage 2 and the balance weight 4, a thick rotary shaft 11 is required which increases the cost of the traction machine.

The driving torque of the electric motor 1 9 is limited to values at which the cage 2 can be accelerated and decelerated without spoiling a comfortable ride. In contrast, the braking force is determined from the viewpoint of safety, and it requires a value with which the cage can be stopped suddenly even if a comfortable ride is not maintained. Since the cage 2 is driven by friction between the main rope 3 and the sheave 13, even when the sheave 1 3 is stopped suddenly by strongly pressing the brake shoes 1 5 against the brake wheel 14, the cage 2 cannot be stopped suddenly because the main rope 3 slips on the sheave. In order to prevent the main rope 3 from slipping relative to the sheave 13, therefore, the diameter of the sheave 1 3 has been enlarged to increase the area of contact with the main rope 3.

When the diameter of the sheave 13 becomes large, the rotational frequency thereof for operating the cage 2 lowers. This has led to the drawback that the electric motor 1 9 inevitably becomes large in size and high in cost.

This invention has for its object to provide a traction machine for elevators in which a main rope fotr suspending a cage is wound round a sheave, the cage is raised and lowered by driving the sheave with an electric motor, a braking force is generated by frictionally applying brake shoes to the main rope, and the cage is restrained by the braking force, whereby, even when the sheave has a small diameter, a required braking force is generated, and the rotational speed of the sheave is raised, to render the size of the electric motor smaller.

Another object of this invention is to provide a traction machine for elevators in which a rotor core is held in magnetic engagement with a stator core outside the stator core, the resulting structure is supported by a frame, this frame is formed with grooves so as to construct a sheave, and a main rope is wound round the sheave by three or more turns, whereby a frictional force is increased without enlarging the external shape of the traction machine, to generate a required braking force.

Brief description of the drawings Figures 1 and 2 show a conventional elevator, in which Figure 1 is a vertical sectional view of a shaft while Figure 2 is a side view of a traction machine; Figures 3 to 5 show an embodiment of this invention in which Figure 3 is a front view of a traction machine, Figure 4 is a side view thereof, and Figure 5 is a detailed view of essential portions; Figures 6 to 8 show another embodiment of this invention, in which Figure 6 is a front view of a traction machine, Figure 7 is a sectional view taken along line VIl-VIl in Figure 6, and Figure 8 is a diagram of a control circuit; Figure 9 is a side view showing a sheave round which a main rope is wound by two turns; Figure 10 is a view showing still another embodiment of this invention; and Figure 11 is a side view showing a sheave round which a main rope is wound by three turns.

Figures 3 to 6 show an embodiment of this invention. First, in Figures 3 and 4, the same symbols as in Figures 1 and 2 denote the same or corresponding parts, and these parts will not be described again. A first deflector wheel 20a guides the main rope 3 so as to be wound round the sheave 13, while a second deflector wheel 20b guides the main rope 3 from the first deflector wheel 20a to the balance weight 4. A pair of brake shoes 30 grip the outer peripheral surface of the sheave 1 3 so as to restrain the rotation thereof, and they also touch the main rope 3 in its part wound in the sheave 13, so as to directly restrain the main rope. A pair of brake arms 31 are pivoted through pins 31 a to a base 32 to which the supporting legs 12 are fixed, so as to turn about the pins, and they cause the brake shoes 30 to grip and release the sheave 13.

The brake shoe 30 is shown in Figure 5 in more detail. Number 40 designates a metallic holder which is arcuately curved in conformity with the sheave 13, while numeral 41 designates a brake lining which is stuck on the concave surface of the holder 40 and which comes into contact with the outer peripheral surface of the sheave 1 3.

Grooves 41 a are formed in the concave surface of the brake lining 41, and come into frictional contact with the main rope 3.

The traction machine for the elevator constructed as stated above operates similarly to the prior-art example shown in Figures 1 and 2, but to restrain the cage 2, the brake shoes 30 grip the sheave 13 and the main rope 3; when the brake shoes 30 release the sheave 13 and the main rope 3, the cage 2 is allowed to ascend and descend.

Since the brake shoes 30 grip the sheave 13, the brake wheel can be dispensed with, and the rotary shaft 11 is correspondingly shorter.

Moreover, the brake shoes 30 directly restrain the main rope 3, so that even when the frictional force between the sheave 1 3 and the main rope 3 is not sufficient value, a great braking force can be exerted to stop the cage 2 quickly.

Figures 6 to 8 show another embodiment of this invention.

In a traction machine of the type wherein a shaft rotates, the shaft is thick because the load is concentrated near the middle of the shaft.

Therefore, a traction machine of the so-called external rotor type, with a fixed shaft, a stator core mounted thereon, and a rotor core disposed around the outer periphery of the stator core so as to drive a sheave, has been disclosed in Japanese Utility Model Application Laid-Open No. 52- 32870. Figures 6 and 7 show a traction machine of the external rotor type. In Figures 6 and 7, the same symbols as in Figures 3 and 4 denote the same or corresponding parts. Numeral 51 designates a base, and numeral 52 a pair of supporting legs which are erected on and fixed to the base 51. A stationary shaft 53 is supported with both its ends fixed to the supporting legs 52.

A stator core 54 is fixed to the middle part of the stationary shaft 53. Shown at numeral 55 is a primary winding which is wound around the stator core 54 and to which a three-phase A.C.

voltage is applied. A pair of end disks or spiders 56 are rotatably mounted on the end parts of the stationary shaft 53 through bearings 56a. A sheave 57 is constructed of a cylindrical frame which has both its end held in engagement with the end members 56 and which is formed with a plurality of grooves 57a in its outer peripheral surface, the main rope 3 being wound in each groove 57a over substantially half of the circumference of the sheave. A brake wheel 58 projects radially at one end of the sheave 57 over the whole circumference thereof. Numeral 59 indicates a cylindrical rotor core which is fixedly disposed on the inner surface of the sheave 57 and in which the stator core 54 is loosely inserted. The rotor core 59 constitutes a threephase induction motor 100 in magnetic engagement with the stator core 54.A pair of brake shoes 60 grip to release the brake wheel 58 as well as the part of the main rope 3 wound round the sheave 57. A pair of metallic holders 61 constitute the brake shoes 60, and have their arcuately-curved concave surfaces facing the sheave 57. First and second brake linings 61 a and 61 b are stuck on the concave surfaces of the holders 61. The linings 61 a grip or release the main rope 3 wound round the sheave 57, and the linings 61 b grip or release the brake wheel 58. A pair of brake arms 62 are pivoted to the base 51 through pins 62a. Numeral 63 indicates brake springs, and numeral 64 a brake coil which is mounted on the supporting legs 52 through arms 64a. The brake wheel 58, brake shoes 60, metallic holders 61, first brake linings 61 a, second brake linings 61 b, brake arms 62, brake springs 63 and brake coil 64 constitute a brake 64A, which functions in the same manner as in the embodiment of Figures 3 to 5. A deflector wheel 65 mounted on the machine bed 7 guides the main rope 3 to the balance weight 4, the main rope 3 making several turns between it and the sheave 57.

Figure 8 is a diagram of a control circuit for the traction machine shown in Figures 6 and 7. In Figure 8, the same symbols as in Figures 6 and 7 denote the same or corresponding parts. Numeral 71 designates a three-phase A.C. power source. A converter 72 for power running is constructed of thyristors and is connected to the three-phase A.C. power source 71 so as to convert alternating current into direct current by full-wave rectification, while a converter 73 for regenerating braking is similarly constructed of thyristors and is connected in inverse parallel relationship to the power running converter 72 so as to convert direct current into alternating current. A capacitor 74 is connected across the positive pole and negative pole of the power running converter 72.Numeral 75 indicates an inverter of the well-known PWM type which is formed of a parallel circuit consisting of a transistor and a diode, and which is connected across both the terminals of the capacitor 74. The inverter 75 changes direct current into alternating current of variable voltage and variable frequency and supplies the latter to the primary winding 55 of the stator core 54, and it also changes alternating current into direct current when the primary winding 55 has produced regenerative electric power. A tachometer 76 senses the velocity of the cage 2 from the rotational frequency of the sheave 57. A velocity pattern generator 77 generates a velocity curve for operating the cage 2.

Comparison means 78 compares the actual velocity signal of the tachometer 76 with the velocity pattern signal of the velocity pattern generator 77. Control means 79 alternatively controls the power running converter 72 and the regenerative braking converter 73 on the basis of the result of the comparison of the comparison means 78, and it also controls the inverter 75.

Running means 80 issues a start command signal and a stop command signal so as to energise the brake coil 64 and the velocity pattern generator 77.

In the traction machine for the elevator contructed as stated above, the main rope 3 and the sheave 57 are normally restrained by the brake shoes 60. When the start command signal is produced from the running means 80, the brake coil 64 is energised. Then, the sheave 57 is released, while at the same time, the velocity pattern generator 77 produces the velocity pattern signal. The control means 79 actuates the power running converter 72 or the regenerative braking converter 73 in accordance with the result of the comparison of the velocity pattern signal with the actual velocity signal of the tachometer 76, and it also actuates the inverter 75 to generate the alternating current of variable voltage and variable frequency and to energise the primary winding 55. Upon the energisation of the primary winding 55, the rotor core 59 rotates to drive the sheave 57.The main rope 3 is driven by its friction with the sheave 57, to raise and lower the cage 2. If the velocity pattern signal of the velocity pattern generator 77 is greater than the actual velocity signal of the tachometer 76 due to the unbalanced load between the cage 2 and the balance weight 3, the control means 79 actuates the power running converter 72 and the inverter 75 to feed the primary winding 55 with A.C. power, and to rotate the rotor core 59 as the three-phase induction motor. Conversely, if the actual velocity signal is greater than the velocity pattern signal, the primary winding 55 generates regenerative power. The control means 79 actuates the inverter 75 so as to invert the regenerative power into direct current, and it also actuates the regenerative braking converter 73 so as to return the regenerative power to the threephase A.C. power source 71.When the cage 2 has reached a predetermined distance before a destination floor, the inverter 75 gradually lowers the voltage and the frequency to decelerate the rotor core 59. When the destination floor has been reached, the brake coil 64 is deenergised, and the brake shoes 60 grip the main rope 3 as well as the brake wheel 58. The main rope 3 is restrained directly by the brake shoes 60 and through the brake wheel 58 as well as the sheave 57, thereby to stop the cage 2.

Also in the embodiment shown in Figures 6 to 8, the main rope 3 is directly restrained by the brake shoes 60, so that a large braking torque can be generated to stop the cage 2 suddenly.

Since the sheave 57 is placed around the outer periphery of the rotor core 59, and the brake shoes 60 act on the main rope 3 wound round the sheave 57, this arrangement is much shorter than that in which the electric motor, the sheave and the brake wheel are arranged in a line, and the machine room 5 can be made smaller.

Moreover, the sheave 57 has an axial length which is required as the frame for supporting the rotor core 59. Usually, the axial length is a length enough to wind the main rope 3 back and forth between the sheave 57 and the deflector wheel 65 in a plurality of turns. Owing to such winding in a plurality of turns, the area of contact is increased, and the frictional force is increased, so that when the brake wheel 58 is strongly pressed by the brake shoes 60, it does not slip, and the cage 2 can be stopped suddenly. In consequence, the diameter of the sheave 57 can be reduced, raising the rate of rotation thereof for a given cage speed, so that the traction machine can be made smaller in size.

Although, in the embodiment of Figures 6 to 8, the stator core 54 and the rotor core 59 have been described as constituting an induction motor, a D.C. motor can be used.

The brake shoes 60 need not slidingly compress the main rope 3 in its part wound round the sheave 57, but may grip the main rope 3 directly instead or in addition, and the place of the compression is not especially limited.

As set forth above, a main rope for suspending a cage is wound round a sheave, the cage is raised and lowered by driving the sheave with an electric motor, a braking force is generated by frictionally applying brake shoes to the sheave and the main rope, and the cage is restrained by the braking force, so that even when the braking force is increased, the main rope and the sheave do not slip. As a result the electric motor can be made small in size by reducing the diameter of the sheave to raise the rate of rotation thereof.

Figure 9 illustrates a concrete example of the relationship between the diameter d of each element of the main rope 3 wound around the sheave 13 and the pitch D of the main rope 3 on the sheave 1 3. In the case where the element of the main rope 3 has a diameter d=1 2 millimeters, the pitch is set at D=1 6 millimeters.

Usually, the elements of the main rope 3 are used in a number of 3 to 6. Assuming now that 6 elements are used, the axial length W2 of the sheave 13 becomes: W2=6(elements) x2(turns) x 6+12 =204 millimeters (1) On the other hand, the axial length of the electric motor 19 is about 1000 millimeters in the case of a gearless elevator Accordingly, the length of the motor 1 9 and the sheave 13 combined is about 1200 millimeters.

If the main rope 3 is wound round the sheave 1 3 in 3 turns, the length of W3 of the sheave 13 becomes: W3=6(elements)x3(turns)xl 16+12 =300 millimeters (2) Thus, W3 is about 100 millimeters more than W2.

Accordingly, when the main rope 3 is wound in 3 turns, the rotary shaft 11 must be thickened from the standpoint of strength, resulting in a high cost. Moreover, in installing the traction machine, interference with the other equipment and the machine room 5 is apt to occur, and many restrictions in layout are involved.

Therefore, the number of turns of the main rope 3 round the sheave 13 has heretofore been limited to 2.

However, no such limit is imposed by the external rotor type traction machine as shown in Figures 6 and 7. There will now be described an embodiment in which the main rope is wound in 3 turns.

Referring to Figure 10, a large number of grooves 57a are formed in the outer peripheral surface of a sheave 57 constructed of the frame 57b of an electric motor, and the main rope 3 is wound in the grooves 57a in three turns in such a manner that each groove receives the main rope over substantially half of the circumference thereof.

In the embodiment iliustrated in Figures 10 and 11, the sheave 57 is provided in a part of the frame 57b which has a size necessary for functioning as the electric motor. As stated before, the frame 57b is about 1000 millimeters long in the gearless elevator often used. On the other hand, assuming the diameter d of each of the elements of the main rope 3 to be 12 millimeters, the axial length W3 of the sheave 57 round which the main rope 3 is wound in three turns is given from Equation (2) as 300 millimeters. Accordingly, the length of the frame 57b of the electric motor is greater than the length W3 of the sheave 57, so that the main rope 3 can be changed from a 2-turn winding to a 3-turn winding without increasing the axial length of the whole traction machine.Further, as can be seen from Equations (2) and (3), when the number of turns is increased by one, the length of the sheave 57 increases by about 100 millimeters, whereas in an external-rotor drive, the main rope 3 can be wound up to eight turns or so without increasing the external dimensions of the electric motor. By selecting an appropriate number of turns, the frictional force can be adjusted, and the cage 2 can be stopped by exerting a braking force as needed.

Although, in the above embodiment, the sheave has been described as the frame of the motor directly formed with the grooves, the intended purpose can be achieved by a separate cylindrical or arcuate sheave attached to the outer periphery of the frame.

As set forth above, according to this embodiment, a hollow rotor core is mounted inside a cylindrical frame and is rotatably supported, a stator core is loosely inserted inside the rotor core so as to be in magnetic engagement therewith, thus to form an electric motor for rotating the external frame, grooves are formed in a part of the frame so as to form a sheave, a deflector wheel is disposed in a position opposite the sheave, a main rope for suspending a cage and a balance weight is wound round the sheave and the deflector wheel, and the main rope is tensed so that the number of turns thereof wound round the sheave may become at least three. This brings forth the effects that the frictional force between the main rope and the sheave can be increased without changing the external dimensions of the electric motor and that a high cost can be suppressed.

Claims

1. A traction machine for an elevator comprising: (a) a sheave round which a main rope for suspending the elevator cage is wound, and which frictionally drives the main rope; (b) an electric motor which is connected to rotate said sheave, and (c) a brake which is disposed near the path of the main rope and which is arranged to impart a braking force to the main rope in sliding compression, thereby to stop the cage.

2. A traction machine for an elevator as defined in Claim 1, wherein said brake is arranged to slidingly compress the main rope in a curved part thereof wound round said sheave.

3. Traction machinery for an elevator as defined in Claim 2, wherein said electric motor includes a stationary shaft, a stator core which is fixed to said stationary shaft, and a rotor core which is rotatably supported round said stationary shaft and which rotates about the stator core, and wherein said sheave is disposed outside said rotor core.

4. A traction machine as claimed in Claim 3 in which the main rope makes at least three turns about the sheave.

5. A traction machine for an elevator as defined in Claim 2, 3 or 4 wherein said brake has at least one brake lining which has a curved surface extending along an outer peripheral surface of said sheave, and recesses to come into frictional contact with the main rope are formed in the said curved surface of the brake lining.

6. A traction machine for an elevator, comprising an electric motor which includes a stator core, and a rotor core that is mounted inside a cylindrical frame and is rotatable about the outer periphery of said stator core; a brake for restraining the rotation of said electric motor; a sheave on the outside of the frame and an outer peripheral surface of which is formed with an endless groove; a static deflector wheel whose outer periphery is formed with an endless groove and which is mounted with its rotational axis extended parallel to the rotational axis of said sheave; and a main rope which suspends a cage on one end and a balance weight on the other end thereof and which is wound round both said sheave and said deflector wheel in at least three turns in engagement with said grooves.

7. A traction machine for an elevator, substantially as herein described with reference to Figures 3 to 5, Figures 6 to 8 or Figure 10 of the accompanying drawings.