Patent Grant
8371420
The present invention relates to an elevator system that is equipped with a brake system for braking its car in emergency.
A conventional brake system for braking an elevator car has been disclosed in JP H07-206288A. The elevator system described therein can prevent the car from colliding with a hoistway end by rapidly decelerating the car when approaching near a terminal floor.
Patent Document 1: JP H07-206288A
Although the elevator system is able to prevent the car from colliding with the hoistway ends and ensures passengers' safety as long as a shock at a collision of the car with the buffer is within a specified value, the deceleration of the car may sometimes become larger than it needs to be, which has brought about a problem of causing passengers in the car to feel uncomfortable.
The present invention is aimed at providing a brake system in which a shock at a collision of the car with a buffer installed on the elevator shaft end is absorbed to a level below a specified value.
An elevator system according to the present invention includes a car traveling up and down along a hoistway; a buffer for stopping the car at an end of the hoistway; a brake for braking travel of the car; a car traveling-information acquisition means for acquiring car traveling information; and a brake control means for controlling the brake, based upon the information acquired by the car traveling-information acquisition means, so as to reduce a collision speed at the collision of the car with the buffer to below a predetermined speed so that a shock at the collision of the car with the buffer can be absorbed to a level below a specified value.
According to the present invention, an elevator system includes a car traveling up and down along a hoistway; a buffer for stopping the car at an end of the hoistway; a brake for braking travel of the car; a car traveling-information acquisition means for acquiring car traveling information; and a brake control means for controlling the brake, based upon the information acquired by the car traveling-information acquisition means, so as to reduce a collision speed at a collision of the car with the buffer to below a predetermined speed so that a shock at the collision of the car with the buffer can be absorbed to a level below a specified value. Therefore, slow stopping of the car can be realized.
1: car, 2: counterweight, 3: hoist rope, 4: sheave, 5: elevator control unit, 6: hoist motor, 7: brake pulley, 8: brake lining, 9: brake lining, 11: hoist-motor encoder, 12: brake coil, 13: brake coil, 14: governor, 15: buffers, 16: brake control unit, 18: safety state determination part, 18a: deceleration calculating part, 18b: determination part, 18c: storage unit, 19: control voltage calculating part, 20: relay, 21: relay, 118: safety state determination part, 118a: speed and remaining distance calculating part, 118b: determination part, 119: control voltage calculating part, 22: weighing device
Embodiment 1
An overall configuration of an elevator system in this embodiment will be described with reference to
In the brake system, a brake pulley 7 that is fixed to the sheave 4 and rotated is pressed by brake linings 8 and 9 by biasing of elastic members of brake springs. Friction force is thereby generated between the brake pulley 7 and the brake linings 8 and 9, so that the brake linings 8 and 9 brake the brake pulley 7. With this braking action, the hoist motor 6 and the sheave 4 are also braked; and hence, the car 1 and the counterweight 2 are braked.
During normal traveling, the brake linings 8 and 9 are spaced away from the brake pulley 7 by electromagnetic force, so as to exert no braking force on the brake pulley 7.
On the other hand, in a case of the elevator coming into an emergency stop mode, a brake control unit 16 receives (i) an instruction to brake the brake pulley 7 to stop the car 1, from the elevator control unit 5 that governs operation of the elevator because the elevator is in a state that requires a halt of its operation, and (ii) car traveling information from a car traveling-information acquisition means such as a hoist-motor encoder 11, a governor 14, or a position sensor. The brake control unit then calculates deceleration of the car 1 to adjust the pressing force of the brake linings 8 and 9 exerted on the brake pulley 7 by applying a voltage to brake coils 12 and 13 so as to keep up the deceleration with a target deceleration (described later in detail). Thereby, the deceleration of the car 1 is controlled to keep up with the target deceleration. While here described is a case where the brake control unit 16 directly stops the car 1 slowly, the present invention is not limited to this case but includes a case where slow stopping of the car 1 is made indirectly by slowly stopping the counterweight 2. In this case, the deceleration of the counterweight 2 is calculated based on information from the car traveling-information acquisition means or a counterweight traveling-information acquisition means in place thereof, to keep up with the target deceleration.
On the bottom of the elevator shaft, a car buffer 15a is provided for downward traveling of the car 1 (a counterweight buffer 15b for upward traveling). Even if the car 1 cannot be stopped after passing either terminal floor, the car 1 can avoid colliding with the hoistway ends because the car comes into contact with the car buffer 15a (or the counterweight buffer 15b in a case of upward traveling) and a shock that would be generated at the collision is thereby absorbed. While the description will be made below for a case where the car 1 travels downwardly and then stops by colliding with the car buffer 15a, the present invention is not limited to this case. The invention also includes a case where the car 1 travels upwardly and then stops by collision of the counterweight 2 with the counterweight buffer 15b.
The buffers 15 here are devices that serve to stop the car 1, when the car 1 rushes through either terminal floor, without posing a severe shock by being brought into contact with the car 1 before reaching a hoistway end. However, if the car 1 collides with the buffer 15a with an unexpected high speed, the car 1 will be subject to a large shock for ensuring safety that the car must be stopped within the limited distance from a contact point with the buffer 15a to the hoistway end. The buffers 15 have respective predetermined speeds (hereinafter, “specified speed(s)) depending on their capabilities, below which speeds a shock at a collision can be absorbed to a level below a specified value. Hence, a speed at a collision of the car 1 with the buffer 15a (hereinafter, “collision speed”) must be lower than the specified speed. While this embodiment is described taking the specified speed as a base, the present invention is not limited to this speed. Another predetermined speed lower than the specified speed may be employed as a base in order to pursue a slower stopping. Note that a specified speed for the buffer 15b is calculated taking into account a shock to which the car 1 is subjected when the counterweight 2 collides with the buffer 15b.
A configuration of the brake control unit 16 will be described in detail with reference to
Next, operation of the elevator system in this embodiment will be briefly described. If the elevator is in an emergency mode, both signals from the hoist-motor encoder 11 (or the governor 14) and the elevator control unit 5 are transferred to the safety state determination part 18 and the control voltage calculating part 19 of the brake control unit 16. The brake control unit 16 controls the brake, based upon the information acquired by the car traveling-information acquisition means, to reduce a collision speed to below the specified speed so that a shock at a collision of the car 1 with the buffer 15a can be absorbed to a level below the specified value.
To be specific, the deceleration calculating part 18a firstly calculates a deceleration of the car 1, based upon both the signals. Then, in a case of the safety relays 20 and 21 being open, the determination part 18b compares the deceleration calculated by the deceleration calculating part 18a with the reference deceleration stored in the storage part 18c. If the deceleration of the car 1 is larger than the reference deceleration, the safety relays 20 and 21 are closed to put the brake into a state ready to weaken the braking force exerted on the brake pulley 7 by the brake linings 8 and 9.
In a case of the safety relays 20 and 21 being closed, if a deceleration of the car 1 is smaller than the reference deceleration by comparing, in the determination part 18b, the deceleration of the car 1 with the reference deceleration, the safety relays are opened to put the brake into a state unable to weaken the braking force exerted on the brake pulley 7 by the brake linings 8 and 9.
The control voltage calculating part 19 calculates and outputs, based upon (i) the signal from the hoist-motor encoder 11 (or the governor 14) and (ii) the signal from the elevator control unit 5, a voltage to be applied to the brake coils 12 and 13, in order to decelerate the car 1 with the target deceleration. While described in this embodiment is the case where the voltage is calculated and outputted with respect to the target deceleration by the control voltage calculating part 19, the present invention is not limited to this case. The voltage may be calculated with respect to the reference deceleration or a speed variation ideal for the car 1 when decelerating.
The reference deceleration and the target deceleration are explained here. The reference deceleration is defined to be always larger than a deceleration necessary for reducing a collision speed to below the specified speed, even under a worst condition for the car 1 to decelerate (a condition where the car 1 is descending with a maximum load or ascending with a minimum load) in an emergency stop mode. The target deceleration is defined to be larger than the reference deceleration (see
Three typical decelerating cases c1, c2, and c3 are explained with reference to
In each graph of
After that, in the case c1, a large braking force is temporarily exerted by the brake, whereby the deceleration exceeds the target deceleration. For this reason, the braking force of the brake is weakened. As a result, since the collision speed does not exceed the specified speed, no excessive decelerating is needed, thereby allowing the car 1 to be slowly stopped without being subjected to an excessive deceleration shock.
In the case c2, a large braking force is temporarily exerted by the brake, and then, if the deceleration exceeds the target deceleration, the braking force is weakened by adjusting down the brake. If the deceleration falls again below the target deceleration by the weakening of the braking force, a large braking force acts again by the brake. Thus, by controlling the deceleration to keep up with the target deceleration larger than the reference deceleration, the collision speed can be reduced to below the specified speed. Therefore, the car 1 can be stopped without being subjected to an excessive deceleration shock.
In the case c3, the force due to the weight difference between the car and the counterweight acts maximally in the traveling direction. For that reason, the deceleration is minimal and the collision speed becomes larger. However, since the reference deceleration is, as described above, set larger than a maximum deceleration that will be generated under such conditions, a larger braking force is exerted to approximate the deceleration to the target deceleration (in
It is noted here that deceleration is expressed by the following relation:
where m is total inertia mass of the elevator (including mass of the car 1 and mass of passengers); F1 is braking force to be exerted on the car 1 for it to reach the target deceleration, and F2 is accelerating force due to the weight difference between the car and the counterweight.
As described above, in Embodiment 1, collision speeds of the car 1 can be reduced to below the specified speed as well as slow stopping can be realized.
While the three typical cases are explained here, the behavior of the car 1 is not limited to that shown in
Embodiment 2
A brake control unit 16 in this embodiment determines whether a collision speed of the car 1 can be reduced to below the specified speed, based upon a current speed of the car 1 and a current remaining distance from the car 1 to the buffers 15 (hereinafter, “remaining distance”) that are acquired from the car traveling-information acquisition means such as the hoist-motor encoder 11, governor 14, or a position sensor, thereby to instruct to open or close the safety relays 20 and 21.
A configuration of the brake control unit 16 of this embodiment will be described with reference to
The brake control unit 16 is configured with a safety state determination part 118, a control voltage calculating part 119, and the safety relays 20 and 21. The safety state determination part 118 determines whether to open or close the safety relays 20 and 21 and is composed of a speed and remaining distance calculating part 118a, a determination part 118b, and a storage part 118c that stores relations of speeds of the car 1 versus remaining distances at opening the safety relays 20 and 21 (hereinafter, “speed versus remaining distance relations” at opening the relays), which relations enable collision speeds of the car 1 to be reduced to below the specified speed.
The boundary line BL1 of the shaded region shows plots of maximum speeds for respective remaining distances, below which speeds collision speeds of the car 1 can be reduced to below the specified speed in cases of the car 1 being stopped in emergency. In these cases, defining a time t0 as an interval until the car 1 comes into contact with the buffer, a remaining distance x0 on the line for an initial speed can be calculated from the following integral equations:
The boundary line BL1 can thereby be plotted in the graph of
Each variable and constant is defined with respect to the car 1, and α(t) denotes acceleration of the car 1, F(t) braking force by the brake, F2′ a maximum accelerating force in a case of a maximum weight difference between the car 1 and the counterweight 2, m total inertia mass of the elevator in a loaded state at the weight difference, v0 a speed of the car 1 at the start of an emergency stop, and V a speed at the time of contact with the buffer.
The dotted lines L1 to L3 in the figure indicate trajectories of speeds and remaining distances when the car is forcibly decelerated from states S1, S2, and S3 on the boundary of the shaded region to stopped states, under loaded conditions where respective collision speeds become maximal. Thus, the collision speeds are ensured that they are always reduced to below the specified speed. On the other hand, the solid lines L4 to L6 in the figure indicate trajectories of speeds and remaining distances in cases of the car being forcibly decelerated from the states S1, S2, and S3 on the boundary of the shaded region to stopped state, under loaded conditions where respective collision speeds become minimal. In these cases, of course, collision speeds are reduced to below the specified speed.
Namely, an actual speed of the car 1 acquired by the car traveling-information acquisition means is compared with a speed of the car 1 for a remaining distance, which are stored in the storage means, corresponding to an acquired actual remaining distance. Moreover, in the case of monitoring speed and remaining distance, if the car 1 is determined to be in a loaded state easy to stop by being further provided with a car load-weight acquisition means that calculates a load weight of the car 1 and with a car traveling-direction detecting means that detects a traveling direction of the car 1, the conditions able to reduce collision speeds to below the specified speed can be extended by closing the safety relays 20 and 21 to put the brake into a state ready to weaken. In a case of taking easiness of stopping the car out of consideration, the speed versus remaining distance relations at opening the relays are calculated by presuming a situation of a maximum weight difference between the car 1 and the counterweight 2 to set values of the acceleration force F2′ and the total inertia mass m in the integral equations (2) for calculating the boundary BL1 in
It is note here that the car load-weight acquisition means in this embodiment is provided with a weighing device 22 that measures a load weight in the car, and calculates a load weight of the car 1 from a signal of the device; and the car traveling-direction detecting means determines a traveling direction from the signal of the hoist-motor encoder 11, the governor 14, or the like.
Specifically, controlling the braking force to weaken is also allowable in the extended shaded region C as illustrated in
Next, operation of the elevator system in this embodiment is briefly described. In a case of the elevator being in an emergency stop mode, both signals from the hoist-motor encoder 11 (or the governor 14) and the elevator control unit 5 are transferred to the safety state determination part 118 and the control voltage calculating part 119. The control voltage calculating part 119 calculates based on both signals a voltage to be applied to the brake coils 12 and 13 and outputs it.
In the safety state determination part 118, the speed and remaining distance calculating part 118a calculates a current speed of the car 1 and a current remaining distance, based on traveling state information of the car 1 obtained from the car traveling-information acquisition means such as the hoist-motor encoder 11, the governor 14, or the position sensor. Then, the determination part 118b compares data in the storage part 118c (the speed of the car 1 versus remaining distance relations shown in
As described above, in this embodiment, since determination whether or not to open the safety relays 20 and 21 is made by monitoring (i) a current speed of the car 1 and (ii) a current remaining distance, an effect is brought about that extends controllable conditions as wide as possible.
Namely, in the case of ensuring the reduction to the specified speed within a predetermined distance while keeping a predetermined deceleration as with Embodiment 1, even though there is a sufficient distance to the buffer for keeping the predetermined deceleration, the car may in some cases come into a state not allowed to weaken the braking force and the decelerating may thereby exhibit a small effect in shock reduction. On the other hand, in this embodiment, stopping of the car can be accomplished with a deceleration lower than that in a case with Embodiment 1 by controlling the braking force according to determinations response to the state varying from time to time, even if the car comes into a state not allowed to weaken the braking force when the remaining distance is determined to be shorter than a distance necessary for reducing the speed to below the specified speed. Therefore, slow stopping of the car 1 can be realized.
The technologies have been described in Embodiments 1 and 2 that realize slow stopping of the car 1, when coming into contact with the buffers 15, by controlling the braking force. A position, a speed, a deceleration, and a traveling direction of the car 1 may be converted from a signal from the hoist-motor encoder 11 or the governor 14, or may be acquired from an acceleration sensor or a position sensor (both not shown) provided with the car 1. Moreover, the car load-weight acquisition means may utilize a method of calculating a traveling load from a hoist-motor coil current during traveling. Furthermore, while the safety state determination part 18 or 118 is configured to send the instruction to the safety relays 20 and 21, the safety state determination parts 18 or 118 may send a stop instruction to the control voltage calculating part 19 or 119. Furthermore, while the safety state determination part 18 or 118 is provided in the brake control unit 16, a controllable state determination part (not shown) may be separately provided in place of the safety state determination part 18 or 118.
Industrial Applicability
The present invention can be applied to a brake system for braking an elevator car in emergency.
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