ELEVATOR CONTROL SYSTEM

Abstract

 In an elevator including: an electric motor for rotating a sheave wounded with a main rope suspending an elevator car and a counterweight to move the electric car; a controller for driving the electric motor; an electromagnetic brake for stopping the elevator car to hold the elevator car in a stationary state; and an encoder for detecting rotation of the electric motor, when in a state in which after the elevator car is stopped at a certain hall, a door of the elevator car is opened to permit passengers to get on and off the elevator car, while the electromagnetic brake is in operation, a standstill holding force of the electromagnetic brake is insufficient to permit the elevator car to start a little movement, and thus an rotational angle of the electric motor is detected by the encoder, the controller controls the driving of the electric motor so as to generate a torque used to prevent the rotation of the electric motor.

Description

TECHNICAL FIELD

[0001] The present invention relates to an elevator control system for, when malfunction occurs in an electromagnetic brake to cause an elevator car to move while passengers get on and off the elevator car after the elevator car of an elevator is stopped at a certain floor, carrying out control so as to cause an electric motor to generate a torque used to prevent the movement of the elevator car to stop the movement of the elevator car of the elevator, thereby further enhancing safety for passengers.

BACKGROUND ART

[0002] A conventional elevator control system, when malfunction occurs in an electromagnetic brake, restarts control for driving an electric motor, and operates an elevator car or counterweight at a safe speedup to a buffer to stop the elevator car or counterweight. In this case, for detection of the movement of the elevator car due to occurrence of malfunction in the electromagnetic brake, a tachometer generator for measuring a rotational speed of the electric motor is used, but a detector for measuring a rotational angle as well like an encoder is not used (refer to JP 61-86380 A (page 2 and page 3, and FIG. 1), for example).

[0003] The conventional elevator control system aims at merelymoving the elevator car including passengers to a safe position when malfunction occurs in the electromagnetic brake. Thus, it is not taken into consideration at all that the elevator car is prevented from being moved for the purpose of ensuring safety of passengers getting on and off the elevator car. In addition, for preventing the elevator car from being moved in such a situation, it becomes necessary to measure and control not only a rotational speed of the electric motor but also a rotational position of the electric motor. However, no consideration is taken with this respect.

[0004] In the conventional elevator control system, there is encountered a problem that when malfunction such as insufficiency in braking force should occur in the electromagnetic brake in a door open state where the elevator car is stopped at a certain floor, the elevator car is moved with the door of the elevator car being opened, and hence passengers getting on and off the elevator car are exposed to danger.

DISCLOSURE OF THE INVENTION

[0005] The present invention has been made in order to solve the above-mentioned problems, and it is, therefore, an object of the present invention to obtain an elevator control system in which even when malfunction such as insufficiency in braking force occurs in an electromagnetic brake during activation of the electromagnetic brake, the braking force is increased by an electric motor to prevent passengers from being exposed to danger.

[0006] The present invention aims at ensuring a necessary standstill holding force while an elevator car is stopped to further enhance safety even when malfunction should occur in an electromagnetic brake by using control for a driving torque of an electric motor.

[0007] An elevator control system according to the present invention, includes: a main rope for suspending an elevator car and a counterweight; a sheave wound with the main rope; an electric motor for rotating the sheave to move the elevator car; a controller for driving the electric motor; an electromagnetic brake for stopping the elevator car to hold the elevator car in a stationary state; and an encoder for detecting rotation of the electric motor. In the system, in a state in which after the elevator car is stopped at a certain hall, a door of the elevator car is opened to permit passengers to get on and off the elevator car, and a standstill holding force of the electromagnetic brake is insufficient due to occurrence of malfunction of some sort though the electromagnetic brake is in operation to cause the elevator car to start a little movement, a rotational angle of the electric motor is detected by the encoder. Then, the controller controls driving of the electric motor so as to generate a torque used to prevent the rotation of the electric motor to thereby bring the elevator car to a stationary state at a landing position of the hall.

BRIEF DESCRIPTION OF THYE DRAWINGS

[0008] 

FIG. 1 is a view showing a schematic construction of an elevator control system according to Embodiment 1 of the present invention;

FIG. 2 is a view showing a schematic construction of an elevator control system according to Embodiment 1 of the present invention;

FIG. 3 is a diagram showing a detailed configuration of the elevator control system according to Embodiment 1 of the present invention;

FIG. 4 is a diagram showing a braking force of an electromagnetic brake required for an elevator in the elevator control system according to Embodiment 1 of the present invention;

FIG. 5 is a diagram showing a torque which is generated by an electric motor in order to prevent rotation of the electric motor in the elevator control system according to Embodiment 1 of the present invention; and

FIG. 6 is a diagram showing a torque which is generated by an electric motor in order to prevent rotation of the electric motor (when measures to cope with an overload of the electric motor are taken) in the elevator control system according to Embodiment 1 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0009] Embodiment of the present invention will hereinafter be described on the basis of the accompanying drawings.

Embodiment 1.

[0010] An elevator control system according to Embodiment 1 of the present invention will now be described with reference to the accompanying drawings. FIGS. 1 and 2 are views each showing a schematic construction of the elevator control system according to Embodiment 1 of the present invention. Note that, in these figures, the same reference numerals designate the same or corresponding constituent elements.

[0011] FIG. 1 shows an embodiment in roping at a ratio of 1 : 1, and FIG. 2 shows an embodiment in roping at a ratio of 2 : 1. There is no large difference between both the cases except that there is a difference in position of a loadweighing device 10. In addition, the load weighing device 10 is not necessarilymounted to the positions shown in the figures, and hence may be mounted to a position where a total weight of passengers and their loads within an elevator car 1 can be directly or indirectlymeasured. FIG. 1 will hereinafter be described.

[0012] In FIG. 1, in an elevator, the elevator car 1 and a counterweight 2 are suspended through a sheave 4 by a main rope 3. Then, a weight obtained by adding a weight about half the passenger capacity to a weight of the elevator car 1 balanced with a weight of the counterweight 2. However, in a normal operation state, since the number of passengers on the elevator car 1 changes from zero to the passenger capacity, the two weights are not balanced. For this reason, when the elevator car 1 is stopped at a certain floor, an unbalanced weight, i.e., a torque corresponding to an unbalanced load is given to the sheave 4 by an electric motor 5, and an electromagnetic brake 6 is then operated to hold the elevator car 1 in a stationary state without being self-propelled.

[0013] While an encoder (rotation detector) 7 is directly connected to a shaft of the electric motor 5, it may be mounted to any position of a hoisting machine 8 as long as such a position allows the rotation of the electric motor 5 or the sheave 4 to be detected. In addition, finally, a detector for detecting movement of the elevator car 1 may also be mounted to the elevator car 1 in order to detect movement of the elevator car 1. Moreover, for the encoder 7, any other measuring instrument such as a resolver may also be adopted as long as it can detect a rotational angle of the electric motor 5 or the sheave 4.

[0014] A controller 9 drives the electric motor 5 to control an ascending/descending operation of the elevator car 1. In addition, as an object of this application, the controller 9 controls the driving of the electric motor 5 so as to generate a torque used to prevent rotation of the electric motor 5 to thereby stop the elevator car 1 at a landing position of a certain hall 12 in a stationary state. This is performed such that when in a state in which after the elevator car 1 is stopped at the certain hall 12, a door 13 of the elevator car 1 and a door 14 of the hall 12 are opened in order to permit passengers to get on and off the elevator car 1, and a standstill holding force of the electromagnetic brake 5 is insufficient due to malfunction of some sort though the electromagnetic brake 9 is in operation to cause the elevator car 1 to start a little movement, a rotational angle of the electric motor 5 is detected by the encoder 7. Note that, elevator car position sensors (position detectors) 11 are mounted to lower portions of the hall 12 and the elevator car 1, respectively.

[0015] FIG. 3 is a diagram showing a detailed configuration of the elevator control system according to Embodiment 1 of the present invention. Note that, a basic construction of FIG. 3 is the same as that of FIGS. 1 and 2 except that the mounting positions of the load weighing device 10 and the elevator car position sensors 11 are different from those shown in FIGS. 1 and 2.

[0016] In FIG. 3, the encoder 7 used as an example of a rotation detector generates a pulse signal (rotation signal) in accordance with the rotation of the electric motor 5. Consequently, by counting those pulses, it is possible to obtain a conversion value of a rotation amount of the electric motor 5 or the sheave 4, i.e., a movement amount of the elevator car 1, and it is also possible to obtain a moving speed from generation intervals of the pulses.

[0017] The load weighing device 10 is a device for measuring a payload such as passengers and the like within the elevator car 1. In case of this example, there is shown the device which is provided between a car frame and the elevator car 1 suspended by the main rope 3. That is to say, there is adopted the construction that the load weight within the elevator car 1 is transmitted to the car frame through the load weighing device 10 (it should be noted that the function of the load weighing device 10 is the same as that of the load weighing device 10 provided between the main rope 3 and the elevator car 1 as shown in FIG. 1).

[0018] The elevator car position sensor 11 used as an example of a position detector is a sensor for detecting a position of the elevator car 1 in a hoistway of the elevator, and serves to detect a positional deviation amount or the like when the stop position of the elevator car 1 is deviated in an ascending or descending direction within the hoistway with a position of the elevator car 1 when properly stopped (this state is called landing) as a reference.

[0019] A door open sensor 15 is a sensor provided in the elevator car 1 for detecting that the door 13 of the elevator car 1 is opened.

[0020] An indicator 16 designates an indicator provided in the elevator car 1 in this example. As for the indicator, there are various kinds of notifying means for passengers including visually notifying information in the form of a pattern such as characters or a picture using a display device, notifying information in the form of an alarm sound using a buzzer, and telling information using a broadcasting device.

[0021] Moreover, in FIG. 3, the controller 901 includes: an operation control unit 901; a driving control unit 902; a car position operation unit 903; a car speed operation unit 904; an auxiliary torque quantity operation unit 905; limitation means 906; a brake auxiliary torque control unit 907; a brake auxiliary torque command unit 908; a battery 909; and a notification control unit 910.

[0022] The operation control unit 901 carries out control for a normal operation of the elevator. The operation control unit 901 issues a release command to release the electromagnetic brake 6 in accordance with an instruction for a operation, and issues a torque command for a torque to be generated by the electric motor 5 in accordance with a speed command arithmetically operated from a traveling speed pattern as a reference and a rotation signal from the encoder 7. Inaddition, when the elevator is intended to be stopped, the operation control unit 901 issues a command for a restraint torque used to make the speed of the elevator zero and issues a command to operate the electromagnetic brake 6, and after stop of the elevator, outputs a stop signal.

[0023] The driving control unit 902 outputs a motor driving current in accordance with the torque command issued from the operation control unit 901 in order to cause the electric motor 5 to generate a specified torque.

[0024] The car position operation unit 903 serves to detect a movement amount (degree) from the reference value, e.g., a movement amount from a position where the elevator car 1 is to be stopped on the basis of the rotation signal from the encoder 7.

[0025] The car speed operation unit 904 detects a moving speed of the elevator car 1 on the basis of the rotation signal of the encoder 7.

[0026] The auxiliary torque quantity operation unit 905 arithmetically operates a quantity of torque to be generated in the form of an auxiliary torque in the electric motor 5 in accordance with a balance signal from the load weighing device 10, or a movement amount representing positional deviation of the elevator car 1 expressed by a signal from the car position operation unit 903, or a moving speed of the elevator car 1 expressed by a signal from the car speed operation unit 904 (refer to FIGS. 5 and 6) . In addition, the auxiliary torque quantity operation unit 905 includes limitation means 906 for limiting the torque so as not to generate the torque larger than is needed, or for limiting a motor driving current, i.e., limiting the torque for the purpose of preventing burning of the electric motor 5 in order to prevent a main brake auxiliary torque from permitting a current to be continuously caused to flow through the electric motor 5 without releasing the electromagnetic brake 6.

[0027] The brake auxiliary torque control unit 907, while continuing to receive a door open signal which has been sent from the door open sensor 15 and which exhibits that the door 13 of the elevator car 1 is opened with an input of the stop signal from the operation control unit 901 exhibiting that the elevator has been stopped as a start, judges on the basis of an output from the car position operation unit 903 or the elevator car position sensor 11 that a position of the elevator car 1 is being deviated from the position where the elevator is to be stopped to issue a command to generate a brake auxiliary torque in the electric motor 5 for the brake auxiliary torque command unit 908. The brake auxiliary torque control unit 907, even when the movement of the elevator car 1 is stopped, may continue to issue that command until the elevator car 1 starts to travel next time, or may continue to issue that command until the door 13 of the elevator car 1 is closed. In other words, that command is a command for preventing the elevator car 1 from continuing to be deviated from the stop position at least while a stop mode is valid.

[0028] The brake auxiliary torque command unit 908, in response to the command to generate the brake auxiliary torque, outputs a motor driving current used to generate an auxiliary torque required for the driving control unit 902.

[0029] The battery 909 is a unit for storage of electricity which is provided for the purpose of allowing the main function to be maintained even in a power failure. Thus, a secondary battery, a fuel cell or the like as well as a so-called lead storage battery may also be adopted as the battery 909. The battery 909 is adapted to be connected to the driving control unit 902 in accordance with a battery connection signal from the brake auxiliary torque control unit 907 to supply a power supply.

[0030] The notification control unit 910 is a unit for operating the indicator 16 provided in the elevator car 1. A period of time when the main function of the brake auxiliary torque becomes valid corresponds to a period of time when the elevator car 1 is moved in spite of a door open state. Then, the notification control unit 910 carries out the control for the indicator 16 for informing passengers getting on the elevator car 1 of occurrence of a gap between a car floor and a hall floor, or informing passengers of that the main function of the brake auxiliary torque is intended to be utilized. In addition, since such a state may be caused in a case or the like where passengers over the designed capacity of the elevator car 1 get on the elevator car 1, the notification control unit 910 is also effective for information for urging some passengers to get off the elevator car 1.

[0031] Next, an operation of the elevator control system according to Embodiment 1 will hereinafter be described with reference to the drawings.

[0032] In the following description, a case where the weight of the counterweight 2 is balanced with a load which is 50% of the designed capacity of the elevator car 1 is given as an example.

[0033] FIG. 4 is a diagram showing a relationship between a load and an unbalanced load (compensation for 50% of the counterweight), and a braking force required for the electromagnetic brake.

[0034] In FIG. 4, a %load is a value exhibiting a percentage of the load with which the elevator car 1 is loaded compared with a weight when passengers reaching the passenger capacity (for example, 10 persons in the figure) of the elevator car 1 get on the elevator car as a reference (100% load). Hence, the %load becomes a reference exhibiting the braking force of the electromagnetic brake 6. In Japanese Standard, for a load up to 125%, an ability to safely decelerate the elevator car 1 to hold the elevator car 1 in a stationary state is required for the electromagnetic brake 6. On the other hand, in European Standard, two sets of mechanical brakes are necessary as the electromagnetic brake 6. As for the ability, in case of double braking, there is required an ability to stop a hoisting machine 8 when a 125% load is descended at a rated speed, while in case of single braking when one set of mechanical brakes has lost its abilities, there is required an ability to stop the hoisting machine 8 when a 100% load is descended at a rated speed.

[0035] As described above, the electromagnetic brake 6 is a unit which is very important for safety of the elevator. Thus, a highly reliable method is adopted for the electromagnetic brake 6 in order to prevent any of failures or mal functions fromoccurring, and hence the periodic maintenance becomes essential to the electromagnetic brake 6. However, a case where though being very unusual, a failure or malfunction occurs in the electromagnetic brake 6 resulting in insufficient braking force should be considered.

[0036] The present invention aims at providing the controller 9 for, when in a state in which after the elevator car 1 is stopped at a certain hall 12, the door 13 of the elevator car 1 is opened in order to permit passengers to get on and off the elevator car 1, and the standstill holding force of the electromagnetic brake 6 is insufficient due to malfunction of some sort in the electromagnetic brake 6 though the electromagnetic brake 6 is in operation to cause the elevator 1 to start a little movement, and thus the rotational angle of the electric motor 5 is detected by the encoder 7, carrying out control for driving of the electric motor 5 so as to generate a torque used to prevent the rotation of the electric motor 5 to thereby stop the elevator car 1 at a landing position of the hall 12 in a stationary state.

[0037] In addition, the present invention aims at providing the controller 9 for, when in a state in which after the elevator car 1 is stopped at a certain hall 12, the door 13 of the elevator car 1 is opened in order to permit passengers to get on and off the elevator car 1, the standstill holding force of the electromagnetic brake 6 is insufficient due to malfunction of some sort in the electromagnetic brake 6 though the electromagnetic brake 6 is in operation to permit the elevator 1 to start a little movement, and thus the rotational angle of the electric motor 5 is detected by the encoder 7, firstly carrying out the motor driving control for returning and moving the elevator car 1 to the position before the elevator car 1 starts the little movement, and next carrying out the motor driving control for causing the electric motor 5 to generate a torque used to prevent the movement of the elevator car 5 in order to maintain the stationary state of the elevator car 1.

[0038] Moreover, the present invention aims at providing the controller 9 for, when in a state in which after the elevator car 1 is stopped at a certain hall 12, the door 13 of the elevator car 1 is opened in order to permit passengers to get on and off the elevator car 1, the standstill holding force of the electromagnetic brake 6 is insufficient due to occurrence of malfunction in the electromagnetic brake 6 to permit the elevator car 1 to start a little movement, and thus the rotational angle of the electric motor 5 is detected by the encoder 7, and the movement of the elevator car 1 is prevented in accordance with the control for a torque of the electric motor 5, and the door 13 of the elevator car 1 is then closed, stopping the operation of the elevator after releasing the torque control for the electric motor 5 to move the elevator car 1 to an uppermost portion of a hoistway when a total weight of the elevator car 1 is smaller than that of the counterweight 2 and to move the elevator car 1 to a lowermost portion of hoistway when the total weight of the elevator car 1 is larger than that of the counterweight 2.

[0039] Furthermore, the present invention includes the indicator 16 for, in a stage in which, when the elevator car 1 is stopped at a certain hall 12 and the door 13 of the elevator car 1 is opened, the elevator car 1 starts a little movement due to occurrence of malfunction in the electromagnetic brake 6, and the torque control for the electric motor 5 used to prevent the little movement of the elevator car 1 is activated to stop the elevator car 1, informing passengers within the elevator car 1 of that they are urged to go out into the hall 12 from the elevator car 1 using a display device, a broadcasting device, or a buzzer.

[0040] FIG. 5 is a diagram showing a relationship between the braking force generated by the electromagnetic brake and the payload of the elevator car.

[0041] In FIG. 5, a solid line I represents a relationship between the braking force generated by the electromagnetic brake 6 and the payload (%load) of the elevator car 1 while the elevator car 1 is stopped at the hall 12. Since when the payload of the elevator car 1 is smaller than 50% (indicated by a point M), the weight of the counterweight 2 is heavier than that of the payload of the elevator car 1, a force in an ascending direction acts on the elevator car 1. Thus, this force in the ascending direction is balanced with the braking force of the electromagnetic brake 6 in a descending direction to hold the elevator car 1 in a stationary state. When the elevator car 1 is empty, the braking force of the electromagnetic brake 6 in the descending direction becomes maximum. On the other hand, when the payload of the elevator car 1 is equal to or larger than 50% (indicated by the point M), a force in a descending direction acts on the elevator car 1, and this force in the descending direction will be balanced with the braking force of the electromagnetic brake 6 in the ascending direction.

[0042] An operation of Embodiment 1 will hereinafter be described by giving as an example a case where malfunction should occur in the electromagnetic brake 6 when the number of passengers within the elevator car 1 reaches nearly the passenger capacity.

[0043] At the time when the braking force of the electromagnetic brake 6 becomes equal to or smaller than any value expressed by the solid line I of FIG. 5 due to malfunction of the electromagnetic brake 6, the elevator car 1 starts to be moved in the descending direction. At this time, the sheave 4 (or the electric motor 5) of the hoisting machine 8 is rotated by an angle determined on the basis of a movement amount of the elevator car 1, and a rotation amount of the sheave 4 (or the electric motor 5) is then detected by the encoder 7.

[0044] When the rotation of the sheave 4 is detected by the encoder 7 though the electromagnetic brake 6 is in operation, the controller 1 of Embodiment 1 judges that malfunction has occurred in the electromagnetic brake 6 to start the torque control for the electric motor 5 to generate the braking force (the torque generated by the electric motor 5) as indicated by a straight line (dotted line) II shown in FIG. 5, a polygonal line (broken line) III, or a polygonal line (dashed line) IV in accordance with the payload. If not only the rotation detected by the encoder 7, but also the output of the elevator car position sensor 11 are used at the same time for the judgment concerned with whether or not malfunction has occurred in the electromagnetic brake 6, then it is possible to enhance the accuracy for the judgment.

[0045] As a result, if the electromagnetic brake 6 has only to generate the braking force corresponding to a difference between the straight line I and the line II, III, or IV, then the elevator car 1 can be held in a stationary state. If the reduction in braking force due to malfunction in the electromagnetic brake 6 results in the braking force equal to or smaller than the braking force generated in accordance with the torque control for the electric motor of Embodiment 1, then the movement of the elevator car 1 can be prevented.

[0046] For to what value the torque value generated in accordance with the torque control for the electric motor is set, various kinds of methods are conceivable.

[0047] In a stage in which a little movement of the electric motor 5 is detected by the encoder 7, which of the ascending braking force or the descending braking force is insufficient can be judged on the basis of a direction of the rotation concerned. In addition, if the weight of the counterweight 2 is subtracted from an output value from the load weighing device 10, then a value of the unbalanced load is obtained. Thus, a direction and a magnitude of the braking force required to hold the elevator car 1 in a stationary state can be estimated with higher accuracy.

[0048] It is also possible that an output of the elevator car position sensor 11 for measuring an ascending or descending position of the elevator car 1 within the hoistway is used together with the output of the encoder 7 to enhance accuracy and redundancy.

[0049] For a value of the torque applied to the electric motor 5 in order to prevent the rotation of the electric motor 5, there are a method in which the braking force corresponding to the unbalanced load is generated with the electric motor 5 as indicated by the straight line II of FIG. 5 on the basis of a value of the unbalanced load measured with the load weighing device 10, a method in which as indicated by the polygonal line III, no braking force is generated when the payload falls within a dead zone lying between a point A and a point B, but in any zone other than the dead zone, the braking force is generated with the electric motor 5 in correspondence with the unbalanced load, a method in which in zones other than the dead zone, the braking force (point C) having a positive constant value and the braking force having a negative constant value are generated with the electric motor 5 as indicated by the polygonal line IV, respectively, or the like.

[0050] Even in a case where no load weighing device 10 is provided, it is also possible that an arithmetic operation is carried out on the basis of the direction of a little movement of the elevator car 1 detected by the encoder 7, the degree (movement amount), and the moving speed to generate the braking force as indicated by the polygonal line IV of FIG. 5 with the electric motor 5. Of course, a method of using an output of the load weighing device 10 together with an output of the encoder 7 is desirable.

[0051] FIG.6 is a diagram showing a relationship between the braking force generated by the electromagnetic brake and the payload of the elevator car.

[0052] In a case where the braking force is generated with the electric motor 5, a limitation may be given by the limitation means 906 of the controller 9 so that in order to prevent the electric motor 5 from being overloaded, the braking force generated as shown in FIG. 6 neither becomes equal to or larger than a value indicated by a point P nor equal to or smaller than a value indicated by a point Q.

[0053] In a case where there can be verified a safe state in which after the elevator car 1 is stopped, the door of the elevator car 1 is opened in accordance with the torque control for the electric motor of this embodiment, passengers may be informed of the fact that they are urged to early get out the elevator car 1 using the indicator 16 under the control of the notification control unit 910 of the controller 9.

[0054] If it is verified that after the movement of the elevator car 1 has been prevented in accordance with the torque control for the electric motor 5, the door 13 of the elevator car 1 is closed, then in order to cope with malfunction of the electromagnetic brake 6, it is important that even when the torque control for the electric motor 5 is released, the elevator car 1 is moved up to a position which is safe for the elevator car 1. It is to be understood that thereafter, the operation of the elevator should be stopped.

[0055] This embodiment does not function when a power failure occurs in the power supply of the controller 9 occurs. In order to avoid this situation, the controller 9 is provided with the battery 909 provided for coping with a power failure of the power supply. Thus, measures to cope with a power failure are taken so that this embodiment functions even in when a power failure occurs.

INDUSTRIAL APPLICABILITY

[0056] In the elevator control system according to the present invention, as described above, when in a state in which after the elevator car is stopped at a certain hall, the door of the elevator car is opened to permit passengers to get on and off the elevator car, the standstill holding force of the electromagnetic brake is insufficient due to malfunction of some sort though the electromagnetic brake is in operation to cause the elevator car to start a little movement, and thus a rotational angle of the electric motor is detected by the encoder, the driving control for the electric motor is carried out by the controller so as to generate a torque used to prevent the rotation of the electric motor. Consequently, there is offered an effect that it is possible to obtain the elevator control system in which even when malfunction such as insufficiency in braking force occurs in the electromagnetic brake, the braking force is increased by the electric motor to prevent any of passengers from being exposed to danger.

Claims

1. An elevator control system, comprising:

an electric motor for rotating a sheave wounded with a main rope suspending an elevator car and a counterweight to move the elevator car;

a rotation detector for detecting rotation of the electric motor to output a rotation signal;

a brake for stopping the elevator car to hold the elevator car in a stationary state; and

a controller for, when the rotation of the electric motor is detected on the basis of the rotation signal from the rotation detector while the brake is in operation, controlling driving of the electric motor so as to generate a torque used to prevent the rotation.

2. An elevator control system, comprising:

an electric motor for rotating a sheave wounded with a main rope suspending an elevator car and a counterweight to move the elevator car;

a position detector for detecting a position of the elevator car to output a position signal;

a brake for stopping the elevator car to hold the elevator car in a stationary state; and

a controller for, when a positional deviation of the elevator car caused due to rotation of the electric motor is detected on the basis of the position signal from the position detector while the brake is in operation, controlling the driving of the electric motor so as to generate a torque used to prevent the rotation.

3. An elevator control system, comprising:

an electric motor for rotating a sheave wounded with a main rope suspending an elevator car and a counterweight to move the elevator car;

a rotation detector for detecting rotation of the electric motor to output a rotation signal;

a position detector for detecting a position of the elevator car to output a position signal;

a brake for stopping the elevator car to hold the elevator car in a stationary state; and

a controller for, when the rotation of the electric motor is detected on the basis of the rotation signal from the rotation detector, or when a positional deviation of the elevator car caused due to the rotation of the electric motor is detected on the basis of the position signal from the position detector while the brake is in operation, controlling driving of the electric motor so as to generate a torque used to prevent the rotation.

4. An elevator control system according to any one of claims 1 to 3, further comprising a door open sensor provided in the elevator car for detecting that a door of the elevator car is opened to output a door open signal,
   wherein when it is judged on the basis of the door open signal from the door open sensor that after the elevator car is stopped at a predetermined hall, the door of the elevator car is opened to permit passengers to get on and off the elevator car, and while the brake is in operation, the elevator car starts a little movement, the controller controls the driving of the electric motor so as to generate the torque used to prevent the rotation.

5. An elevator control system according to any one of claims 1 to 4, wherein the controller obtains at least one value of a movement direction, a movement amount, and a moving speed of the elevator car on the basis of the rotation signal from the rotation detector to arithmetically operate a torque value used to prevent the rotation of the electric motor in accordance with the resultant value.

6. An elevator control system according to any one of claims 1 to 4, further comprising a load weighing device for measuring a total payload of the elevator car to output a balance signal,
   wherein the controller obtains an unbalanced load value on the basis of the balance signal from the load weighing device to arithmetically operate a torque value to prevent the rotation of the electric motor in accordance with the resultant unbalanced load value.

7. An elevator control system according to any one of claims 1 to 6, wherein the controller limits an absolute value of the torque used to prevent the rotation of the electric motor to a value equal to or smaller than a predetermined value so as to prevent the electric motor from being overloaded.

8. An elevator control system according to claim 6 or 7, wherein when in a state in which after the elevator car is stopped at a predetermined hall, the door of the elevator car is opened to permit passengers to get on and off the elevator car, while the brake is in operation, the elevator car starts a little movement, and the movement of the elevator car is prevented in accordance with torque control for the electricmotor, and thereafter the door of the elevator car is closed, the controller releases the torque control for the electric motor, and when a total payload of the elevator car is smaller than a total weight of the counterweight, moves the elevator car to an uppermost portion of a hoistway, and when a total payload of the elevator car is larger than a total weight of the counterweight, moves the elevator car to a lowermost portion of the hoistway, and then stops the operation of the elevator.

9. An elevator control system according to any one of claims 1 to 8, further comprising an indicator provided in the elevator car for, when under the control made by the controller, the torque control for preventing the rotation of the electricmotor is activated to stop the elevator car, outputting predetermined notifying information to passengers within the elevator car.

10. An elevator control system according to any one of claims 1 to 9, wherein the controller has an electricity storing unit which serves to supply power for controlling the driving of the electric motor during a power failure.

Drawing