Elevator system including monitoring arrangement to activate multiple emergency braking procedures associated with different decelerations and method of operating the same

Abstract

The invention relates to an elevator system and also to a method for monitoring the movement an elevator car. In the method a first emergency braking procedure is activated for braking the elevator car at a first deceleration if the speed of the elevator car exceeds the first limit value for permitted speed, and also a second emergency braking procedure is further activated for braking the elevator car at a second deceleration that is greater than the first, if the speed of the elevator car exceeds the second limit value for permitted speed that is greater than the first limit value for permitted speed.

Claims

1. A method for monitoring movement of an elevator car of an elevator, the method comprising: calculating a first limit value for permitted speed and a second limit value for permitted speed, at least one of (i) the first limit value calculated based on a first deceleration and (ii) the second limit value calculated based on a second deceleration; activating a first emergency braking procedure to brake the elevator car at the first deceleration if the speed of the elevator car exceeds the first limit value for permitted speed; and activating a second emergency braking procedure to brake the elevator car at the second deceleration if the speed of the elevator car exceeds the second limit value for permitted speed, wherein the second deceleration is greater than the first deceleration, the second limit value is greater than the first limit value, the second limit value is a speed limit value enabling the elevator car to slow from the speed of the elevator car at the time of activation of the second emergency braking procedure to a permitted buffer collision speed at the second deceleration.

2. The method according to claim 1, wherein the first deceleration is greater than a reference deceleration of the elevator car.

3. A method for monitoring movement of an elevator car of an elevator, the method comprising: activating a first emergency braking procedure to brake the elevator car at a first deceleration if the speed of the elevator car exceeds a first limit value for permitted speed; activating a second emergency braking procedure to brake the elevator car at a second deceleration if the speed of the elevator car exceeds a second limit value for permitted speed, wherein the second deceleration is greater than the first deceleration, the second limit value is greater than the first limit value, the second limit value is a speed limit value enabling the elevator car to slow from the speed of the elevator car at the time of activation of the second emergency braking procedure to a permitted buffer collision speed at the second deceleration; and activating a third emergency braking procedure to brake the elevator car at a third deceleration if the speed of the elevator car exceeds a third limit value for permitted speed, the third deceleration being greater than the second deceleration, and the third limit value being greater than the second limit value.

4. The method according to claim 3, wherein each of the first, second and third limit values are based on a position of the elevator car on a path of movement within an elevator hoistway such that the first, second and third limit values decrease as the elevator car approaches an end of the elevator hoistway.

5. The method according to claim 4, wherein the first limit value decreases by a gradient, the gradient being dependent on the first deceleration of the elevator car.

6. The method according to claim 4, wherein the second limit value decreases by a gradient, the gradient being dependent on the second deceleration of the elevator car.

7. The method according to claim 4, wherein the third limit value decreases by a gradient, the gradient being dependent on the third deceleration of the elevator car.

8. The method according to claim 1, wherein the activating the first emergency braking procedure comprises: adjusting the speed of the elevator car towards a target value for speed during an emergency stop by controlling an electric drive of the elevator.

9. The method according to claim 1, wherein the activating of the second emergency braking procedure comprises: activating one or more machinery brakes of a hoisting machine of the elevator.

10. The method according to claim 3, wherein the activating of the third emergency braking procedure comprises: activating a safety gear of the elevator car.

11. An elevator system comprising: an electric drive to move an elevator car in an elevator hoistway; a machinery brake; and a monitoring arrangement including a first controller that controls the electric drive and the machinery brake, the monitoring arrangement activating a first emergency braking procedure to brake the elevator car at a first deceleration if the speed of the elevator car exceeds a first limit value for permitted speed, and activating a second emergency braking procedure to brake the elevator car at a second deceleration if the speed of the elevator car exceeds a second limit value for permitted speed, wherein the second deceleration is greater than the first deceleration, the second limit value is greater than the first limit value, and the second limit value is a speed limit value enabling the elevator car to slow from the speed of the elevator car at the time of activation of the second emergency braking procedure to a permitted buffer collision speed at the second deceleration, and wherein at least one of (i) the first limit value for permitted speed is based on the first deceleration, and (ii) the second limit value for permitted speed is based on the second deceleration.

12. The elevator system according to claim 11, wherein the first deceleration is greater than a reference deceleration of the elevator car.

13. The elevator system according to claim 11, wherein the monitoring arrangement further comprises: a second controller for an emergency stop; wherein the second controller adjusts the speed of the elevator car towards a target value for speed during the emergency stop.

14. The elevator system according to claim 11, wherein the monitoring arrangement activates the machinery brake to brake the elevator car at the second deceleration.

15. An elevator system comprising: an electric drive to move an elevator car in an elevator hoistway; a machinery brake; a monitoring arrangement including a first controller that controls the electric drive and the machinery brake, the monitoring arrangement activating a first emergency braking procedure to brake the elevator car at a first deceleration if the speed of the elevator car exceeds a first limit value for permitted speed, and activating a second emergency braking procedure to brake the elevator car at a second deceleration if the speed of the elevator car exceeds a second limit value for permitted speed, wherein the second deceleration is greater than the first deceleration, the second limit value is greater than the first limit value, and the second limit value is a speed limit value enabling the elevator car to slow from the speed of the elevator car at the time of activation of the second emergency braking procedure to a permitted buffer collision speed at the second deceleration; and a safety gear, wherein the monitoring arrangement further includes a second controller for controlling the safety gear, and the monitoring arrangement, as a third emergency braking procedure, activates the safety gear for braking the elevator car at a third deceleration if the speed of the elevator car exceeds a third limit value for permitted speed, the third deceleration being greater than the second deceleration, and the third limit value being greater than the second limit value.

16. The elevator system according to claim 15, wherein each of the first, second and third limit values are dependent on a position of the elevator car on a path of movement within the elevator hoistway such that the first, second and third limit values decrease as the elevator car approaches an end of the elevator hoistway.

17. The elevator system according to claim 16, wherein the first limit value is reduced by a gradient, the gradient being dependent on the first deceleration of the elevator car.

18. The elevator system according to claim 16, wherein the second limit value is reduced by a gradient, the gradient being dependent on the second deceleration of the elevator car.

19. The elevator system according to claim 16, wherein the third limit value is reduced by a gradient, the gradient depending on the third deceleration of the elevator car.

Description

BRIEF EXPLANATION OF THE FIGURES

(1) FIG. 1 presents as a block diagram an elevator system according to a first embodiment of the invention

(2) FIG. 2 presents as a block diagram an elevator system according to a second embodiment of the invention

(3) FIG. 3 illustrates some limit values for permitted speed according to the invention, described in relation to the position of the elevator car

(4) FIG. 4 illustrates the speed reference of an elevator, the limit values for permitted speed of an elevator car, and also the measured speed of an elevator car during the deceleration phase of a run of the elevator car

MORE DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Embodiment 1

(5) FIG. 1 presents as a block diagram an elevator system according to a first embodiment of the invention, wherein the elevator car 1 is moved in the elevator hoistway 24 with an electric drive 6, which comprises the hoisting machine 16 of the elevator and also a frequency converter 7. The elevator car 1 and the counterweight 18 are suspended in the elevator hoistway 24 with hoisting ropes, a belt or corresponding (not shown in the figure) passing via the traction sheave of the hoisting machine 16 of the elevator. The power supply to the electric motor of the hoisting machine 16 of the elevator occurs with a frequency converter 7 from an electricity network 17. The control unit 10 of the elevator calculates the target value for speed, i.e. the speed reference, of the elevator car 1 to be moved in the elevator hoistway 24 and the frequency converter 7 adjusts the speed of the hoisting machine 16, and thereby indirectly also the speed of the elevator car 1, towards the aforementioned speed reference communicated to the frequency converter 7. For adjusting the speed the frequency converter measures the speed of rotation of the hoisting machine 16 of the elevator with a speed sensor, such as with a pulse encoder 20, a tachometer or corresponding, fitted to the shaft of the hoisting machine 16.

(6) The elevator system also comprises a monitoring arrangement, which is usually made to be at least partly separate from the rest of the control system of the elevator. The task of the monitoring arrangement is to take care of the safety of the elevator system. The monitoring arrangement comprises, in addition to the safety circuit 11 of the elevator, inter alia, monitoring units 8, 14, sensors 20, and braking devices 9, 12. The braking devices, such as a machinery brake 9 and a safety gear 12, are connected to the safety circuit such that the machinery brake 9 and the safety gear 12 can be activated via the safety circuit. The monitoring arrangement measures the operating state of the elevator system and when it detects a hazardous situation performs one or more procedures for bringing the elevator system to a safe state. These procedures are e.g. activation of emergency braking and also prevention of the starting of a run of the elevator car 1.

(7) The sensors incorporated in the safety circuit 11 of the elevator system are e.g. the safety switches (not shown in the figure) monitoring the locking/state of entrances to the elevator hoistway 24, and also the limit switches (not shown in the figure) monitoring the limits of the areas of permitted movement of the elevator car 1 in the elevator hoistway 24. The speed of the elevator car is measured with sensors 20 that measure the speed of rotation of the hoisting machine 16.

(8) In this embodiment of the invention the monitoring arrangement comprises speed monitoring units 14, which are disposed in the bottom end zone of the elevator hoistway 24. Each of the speed monitoring units 14 comprises an input for the speed measurement signal 21 of the elevator car, which signal is formed here with the encoder 20 of the hoisting machine of the elevator; the speed measurement signal 21 of the elevator car could, however, also be formed with e.g. a sensor that measures the speed of rotation of a rope pulley 13 fitted in connection with the rope pulley 13 of the overspeed governor. The speed monitoring units 14 are disposed at different points beside the path of movement of the elevator car 1. The speed monitoring units 14 are connected to the safety circuit 11 of the elevator such that each of the speed monitoring units is able, if necessary, to activate the machinery brake 9.

(9) The monitoring arrangement measures the speed of the elevator car 1 and compares the measured speed to the limit values for permitted speed. When the speed of the elevator car 1 exceeds the limit value for permitted speed, the monitoring arrangement activates consecutive emergency braking procedures such that the deceleration of the elevator car increases progressively. FIG. 3 illustrates in more detail some limit values v.sub.lim1, v.sub.lim2 for permitted speed according to the embodiment of FIG. 1, described in relation to the position 15 of the elevator car in the end zone of the elevator hoistway. Each of the limit values v.sub.lim1, v.sub.lim2 for permitted speed of the elevator car depends upon the position 15 of the elevator car on its path of movement such that the limit value v.sub.lim1, v.sub.lim2 for permitted speed, to which the speed v of the elevator car 1 is compared, decreases when the position 15 of the elevator car 1 towards the end 2 of the elevator hoistway changes. The control unit 8 of an emergency stop fitted in connection with the frequency converter 7 compares the speed v of the elevator car 1 measured with the encoder 20 of the hoisting machine of the elevator to the first limit value v.sub.lim1 for permitted speed. If the speed v of the elevator car 1 exceeds the first limit value v.sub.lim1 for permitted speed, the control unit 8 of an emergency stop activates a first emergency braking procedure. As a first emergency braking procedure the control unit 8 of an emergency stop controls the electric drive 6, adjusting the speed v of the elevator car towards the target value 5 for speed during an emergency stop. The control unit 8 of an emergency stop also calculates the aforementioned target value 5 for speed during an emergency stop such that the target value for speed during an emergency stop is formed independently from the speed reference during normal operation of the elevator calculated by the control unit 10 of the elevator.

(10) The aforementioned first limit value v.sub.lim1 for permitted speed of an elevator car is determined such that the elevator car can be stopped at a first deceleration a.sub.1 at the terminal floor 4, or in the immediate proximity of the terminal floor 4, from the speed v that the elevator car has at the moment of activating the first emergency braking procedure. The first limit value v.sub.lim1 for permitted speed is determined by means of the first deceleration a.sub.1 of the elevator car and also the distance of the elevator car from the terminal floor s from the equation:
v.sub.lim1=√{square root over (2a.sub.1(s+Δs))}.

(11) In addition, the first limit value v.sub.lim1 for permitted speed in the equation above is increased by adding the term Δs to the distance of the elevator car from the terminal floor s. This ensures that the first emergency braking procedure is not activated in the proximity of the stopping floor of the elevator owing to a fluctuation in the instantaneous speed of the elevator car.

(12) The speed monitoring units 14 presented above that are fitted beside the path of movement of the elevator car 1 monitor the speed v of the elevator car 1 arriving at the point of a speed monitoring unit 14. The speed monitoring unit 14 compares the speed data of the speed measurement signal 21 of the elevator car to the second limit value v.sub.lim2 for permitted speed of the elevator car, which limit value is determined for each speed monitoring unit 14 separately such that the limit values for permitted speed of the different monitoring units 14 are located on the limit value curve for permitted speed of the second limit value v.sub.lim2, which curve is illustrated in FIG. 3. If the speed v of the elevator car 1 still increases, exceeding the second limit value v.sub.lim2 for permitted speed that is larger than the aforementioned first limit value v.sub.lim1 for permitted speed, the speed monitoring unit 14 activates, as a second emergency braking procedure, the machinery brake 9.

(13) The aforementioned second limit value v.sub.lim2 for permitted speed of the elevator car is determined such that the speed of the elevator car can be slowed down before collision with the end buffer 3 at a second deceleration a.sub.2 determined by the machinery brake 9 to the permitted buffer collision speed v.sub.coll from the speed v that the elevator car has at the moment of activating the second emergency braking procedure. The second limit value v.sub.lim2 for speed is determined by means of the second deceleration a.sub.2 of the elevator car, the distance of the elevator car from the end buffer d and also the permitted buffer collision speed v.sub.coll, from the equation:
v.sub.lim2=√{square root over (2a.sub.2d+v.sub.coll.sup.2)}−Δv.sub.safety.

(14) In addition, the second limit value v.sub.lim2 for speed in the equation above is reduced for safety reasons with the term Δv.sub.safety. This ensures an adequate braking distance irrespective of a possible instantaneous fluctuation in the deceleration of the elevator car and also irrespective of e.g. an activation delay of the machinery brake.

(15) The accuracy of the monitoring of the movement of the elevator car can be improved by increasing the number of consecutively disposed speed monitoring units 14 such that the intermediate distance between the speed monitoring units 14 decreases.

Embodiment 2

(16) FIG. 2 presents as a block diagram an elevator system according to a second embodiment of the invention, wherein the elevator car 1 is moved in the elevator hoistway 24 with an electric drive 6, which comprises the hoisting machine 16 of the elevator and also a frequency converter 7. The elevator car 1 and the counterweight 18 are suspended in the elevator hoistway 24 with hoisting ropes, a belt or corresponding (not shown in the figure) passing via the traction sheave of the hoisting machine 16 of the elevator. The power supply to the electric motor of the hoisting machine 16 of the elevator occurs with a frequency converter 7 from an electricity network 17. The control unit 10 of the elevator calculates the target value for speed, i.e. the speed reference, of the elevator car 1 to be moved in the elevator hoistway 24 and the frequency converter 7 adjusts the speed of the hoisting machine 16, and thereby indirectly also the speed of the elevator car 1, towards the aforementioned speed reference communicated to the frequency converter 7. For adjusting the speed the frequency converter measures the speed of rotation of the hoisting machine 16 of the elevator with a speed sensor, such as with a pulse encoder 20, a tachometer or corresponding, fitted to the shaft of the hoisting machine 16.

(17) The elevator system also comprises a monitoring arrangement, which is usually made to be at least partly separate from the rest of the control system of the elevator. The task of the monitoring arrangement is to take care of the safety of the elevator system. The monitoring arrangement comprises, in addition to the safety circuit 11 of the elevator, inter alia, monitoring units 8, sensors 20, 22, and braking devices 9, 12. The braking devices, such as a machinery brake 9 and a safety gear 12, are connected to the safety circuit such that the machinery brake 9 and the safety gear 12 can be activated via the safety circuit. The monitoring arrangement measures the operating state of the elevator system and when it detects a hazardous situation performs one or more procedures for bringing the elevator system to a safe state. Such procedures are, inter alia, activation of emergency braking and also prevention of the starting of a run of the elevator car 1.

(18) The sensors incorporated in the safety circuit 11 of the elevator system are e.g. the safety switches (not shown in the figure) monitoring the locking/state of entrances to the elevator hoistway 13, and also the limit switches (not shown in the figure) monitoring the limits of the areas of permitted movement of the elevator car 1 in the elevator hoistway 24. The speed of the elevator car is measured with sensors 20 that measure the speed of rotation of the hoisting machine 16. Additionally, in this embodiment of the invention the speed of the elevator car is measured directly with a sensor 22, which is arranged in connection with the rope pulley 13 of the overspeed governor, for measuring the speed of rotation of the rope pulley 13.

(19) The monitoring arrangement also comprises a speed monitoring unit 23, which is connected to a sensor 22 arranged in connection with the rope pulley 13. The speed monitoring unit 23 is connected to the safety circuit of the elevator.

(20) The monitoring arrangement measures the speed of the elevator car 1 and compares the measured speed to the limit values for permitted maximum speed. When the speed of the elevator car 1 exceeds the limit value for permitted speed, the monitoring arrangement activates consecutive emergency braking procedures such that the deceleration of the elevator car increases progressively. FIG. 3 illustrates in more detail some limit values v.sub.lim1, v.sub.lim2, v.sub.lim3 for permitted speed according to the embodiment of FIG. 2, described in relation to the position 15 of the elevator car. Each of the limit values v.sub.lim1, v.sub.lim2, v.sub.lim3 for permitted speed of the elevator car depends upon the position 15 of the elevator car on its path of movement such that the limit value v.sub.lim1, v.sub.lim2 for permitted speed, to which the speed v of the elevator car 1 is compared, decreases when the position 15 of the elevator car 1 towards the end 2 of the elevator hoistway changes. The control unit 8 of an emergency stop fitted in connection with the frequency converter 7 compares the speed v of the elevator car 1 measured with the encoder 20 of the hoisting machine of the elevator to the first limit value v.sub.lim1 for permitted speed. If the speed v of the elevator car 1 exceeds the first limit value v.sub.lim1 for permitted speed, the control unit 8 of an emergency stop activates a first emergency braking procedure. As a first emergency stop procedure the control unit 8 of an emergency stop controls the electric drive 6, adjusting the speed v of the elevator car towards the target value 5 for speed during an emergency stop. The control unit 8 of an emergency stop also calculates the aforementioned target value 5 for speed during an emergency stop such that the target value 5 for speed during an emergency stop is formed independently from the speed reference during normal operation of the elevator calculated by the control unit 10 of the elevator.

(21) The aforementioned first limit value v.sub.lim1 for permitted speed of an elevator car is determined such that the elevator car can be stopped at a first deceleration a.sub.1 at the terminal floor 4, or in the immediate proximity of the terminal floor 4, from the speed v that the elevator car has at the moment of activating the first emergency stop procedure. The first limit value v.sub.lim1 for permitted speed is determined by means of the first deceleration a.sub.1 of the elevator car and also the distance of the elevator car from the terminal floor s from the equation:
v.sub.lim1=√{square root over (2a.sub.1(s+Δs))}.

(22) In addition, the first limit value v.sub.lim1 for permitted speed in the equation above is increased by adding the term Δs to the distance of the elevator car from the terminal floor s. This ensures that the first emergency braking procedure is not activated in the proximity of the stopping floor of the elevator owing to a fluctuation in the instantaneous speed of the elevator car.

(23) The sensor 22 presented above that is arranged in connection with the rope pulley 13 of the overspeed governor measures the speed v of the elevator car 1. The speed monitoring unit 23 connected in connection with the sensor 22 compares the speed data measured by the sensor 22 also to the second limit value v.sub.lim2 for permitted speed of the elevator car. If the speed v of the elevator car 1 still increases, exceeding the second limit value v.sub.lim2 for permitted speed that is larger than the aforementioned first limit value v.sub.lim1 for permitted speed, the speed monitoring unit 23 activates, as a second emergency braking procedure, the machinery brake 9.

(24) The speed monitoring unit 23 connected in connection with the sensor 22 determines the aforementioned second limit value v.sub.lim2 for permitted speed of the elevator car such that the speed of the elevator car can be slowed down before collision with the end buffer 3 at a second deceleration a.sub.2 determined by the machinery brake 9 to the permitted buffer collision speed v.sub.coll from the speed v that the elevator car has at the moment of activating the second emergency braking procedure. The second limit value v.sub.lim2 for permitted speed is determined by means of the second deceleration a.sub.2 of the elevator car, the distance of the elevator car from the end buffer d and also the permitted buffer collision speed v.sub.coll, from the equation:
v.sub.lim2=√{square root over (2a.sub.2d+v.sub.coll.sup.2)}−Δv.sub.safety.

(25) In addition, the second limit value v.sub.lim2 for speed in the equation above is reduced for safety reasons with the term Δv.sub.safety. This ensures an adequate braking distance irrespective of a possible instantaneous fluctuation in the deceleration of the elevator car and also irrespective of e.g. an activation delay of the machinery brake.

(26) The speed monitoring unit 23 connected in connection with the sensor 22 compares the speed data measured by the sensor 22 also to the third limit value v.sub.lim3 for permitted speed of the elevator car. If the speed v of the elevator car 1 still increases, exceeding the third limit value v.sub.lim3 for permitted speed that is larger than the aforementioned second limit value v.sub.lim2 for permitted speed, the speed monitoring unit 23 activates, as a third emergency braking procedure, the safety gear 12 of the elevator car by stopping the rotation of the rope pulley 13 of the overspeed governor, and thus the movement of the rope of the overspeed governor, by controlling a solenoid into the path of movement of the rope pulley 13 of the overspeed governor.

(27) The speed monitoring unit 23 connected in connection with the sensor 22 determines the aforementioned third limit value v.sub.lim3 for permitted speed of the elevator car such that the speed of the elevator car 1 can be slowed down before collision with the end buffer 3 at a third deceleration a.sub.3 determined by the safety gear 12 of the elevator car to the permitted buffer collision speed v.sub.coll from the speed v that the elevator car has at the moment of activating the third emergency braking procedure. The third limit value v.sub.lim3 for permitted speed is determined by means of the third deceleration a.sub.3 of the elevator car, the distance of the elevator car from the end buffer d and also the permitted buffer collision speed v.sub.coll, from the equation:
v.sub.lim3=√{square root over (2a.sub.3d+v.sub.coll.sup.2)}+Δv.sub.safety.

(28) In addition, the third limit value v.sub.lim3 for speed in the equation above is further reduced for safety reasons with the term Δv.sub.safety. This ensures an adequate braking distance irrespective of a possible instantaneous fluctuation in the deceleration of the elevator car and also irrespective of e.g. an activation delay of the safety gear of the elevator car.

(29) The magnitude of the progressive increase in deceleration in connection with the first and the second emergency braking procedure is in the first and second embodiment of the invention set at ten percent of the normal deceleration of the elevator, in which case e.g. when the normal deceleration determined by the speed reference of the elevator is 1 m/s^2 the first deceleration according to the first emergency braking procedure is approx. 1.1 m/s^2 and the second deceleration according to the second emergency braking procedure is approx. 1.2 m/s^2.

(30) For illustrative purposes and relating to the embodiments of the invention that are described above, FIG. 4 further presents the speed reference v.sub.ref of an elevator, the starting moment 19 of the deceleration phase of an elevator car, the target value 5 for speed during an emergency stop, the limit values v.sub.lim1, v.sub.lim2, v.sub.lim3 for permitted speed of an elevator car, and also the measured speed v of an elevator car as a function of time in the deceleration phase of a run of an elevator car.

(31) In the preceding embodiments of the invention, the monitoring of the movement of an elevator car in the bottom part of an elevator hoistway is described. The invention can, however, be used for monitoring the movement of an elevator car also in the top part of an elevator hoistway in a corresponding manner, taking into account the effect on the second and third deceleration of the elevator car possibly caused by a change in the direction of movement of the masses of the elevator. Likewise the invention can be applied to monitoring the movement of a counterweight, instead of or in addition to the movement of an elevator car.

(32) The elevator system according to the invention can be provided with a counterweight or can be one without a counterweight.

(33) The invention is described above by the aid of a few examples of its embodiment. It is obvious to the person skilled in the art that the invention is not limited only to the embodiments described above, but that many other applications are possible within the scope of the inventive concept defined by the claims.