Control Apparatus for Elevator Doors Using Velocity Limiting Circuits

This invention relates to a control apparatus for elevator doors.

When entering and exiting elevator cars, passengers are frequently required to move hurriedly to avoid being caught between elevator doors and to avoid having the doors close before they are able to exit or enter the elevator car.

Heretofore, a control apparatus for elevator doors, such as the one described in Japanese Publication No. 93194/87, has been proposed which includes a pulse counter for determining door positions, a velocity command circuit for supplying a velocity command based on the output of the pulse counter, and a door operation system for opening and closing the doors based on the velocity command. When the pulse counter malfunctions, this apparatus is susceptible to sudden, undesired accelerations thus causing difficulty in passenger ingress and egress.

It is an object of this invention to provide an apparatus for controlling the operation velocity of elevator doors.

It is a further object of this invention to protect against sudden acceleration of elevator doors.

These and other objects are realized by an apparatus for controlling elevator doors comprising a velocity calculation circuit for calculating the actual operation velocity of elevator doors. A timer check circuit is coupled with the velocity calculation circuit and it detects abnormalities in door opening and closing motion based on the actual operation velocity and a predetermined reference velocity. A velocity limiting circuit is coupled with the timer check circuit and it decelerates the elevator doors when abnormalities are detected by the timer check circuit.

An advantage of this invention is that it prevents elevator doors from closing before the passengers can exit the elevator car.

Further objects and advantages of the invention will become apparent from the following description of the illustrated embodiment when taken in conjunction with the drawings.

FIG. 1 is a block diagram of a control apparatus for elevator doors according to the present invention.

FIG. 2(a) is a graph of the relationship between velocity and time during the normal door closing operation.

FIG. 2(b) is a graph of the relationship between velocity and time during the abnormal door closing operation.

Referring now to FIG. 1, there is shown a control apparatus for elevator doors according to this invention. A motor 4 is provided for driving the doors. A pulse encoder 5 is connected to motor 4 and supplies pulses to velocity calculation circuit 6 which are proportional to the number of motor rotations thus enabling the velocity calculation circuit 6 to calculate actual door operation velocity. For limiting door operation velocity and detecting door abnormalities, a door opening detector 1 and a door closing detector 2 are depicted connected to a timer check circuit 3. Also, the velocity calculation circuit 6 and an abnormality display means 12 are connected to a timer check circuit 3 which determines door abnormalities. A velocity command limit circuit 10 is connected to the timer check circuit 3 to limit door operation velocities based on detected abnormalities. To generate door operation velocity commands, a velocity command generating circuit 8 is connected to a pulse encoder 5 via a position calculation circuit 7. A velocity deviation calculation circuit 9 is connected to the velocity calculation circuit 6 and the velocity command generating circuit 8 for determining any deviation between the actual door operation velocity and the door operation command velocity. For regulating the velocity of the motor 4 such that the doors travel at a safe velocity, a current amplifier 11 is connected to the velocity command limit circuit 10 and velocity deviation calculation circuit 9.

By way of operation, a door opening or closing command is generated at an elevator control board 13. The door opening detector 1 determines when the door is completely opened while the door closing detector 2 determines when the door is completely closed. The timer check circuit 3 measures the time period between when the door opening or closing command is generated and the door opening detector or the door closing detector determines that the door is completely opened or completely closed. The timer check circuit 3 selects a velocity at a fixed time, e.g., during a period of deceleration of the elevator doors, and compares the selected velocity with a predetermined check velocity. An abnormality in the door operation velocity will be registered in the timer check circuit 3 if the measured door operation velocity is greater than the predetermined check velocity. The timer check circuit 3 is reset by the door opening detector 1 or the door closing detector 2.

The pulse encoder 5 supplies output pulses to the velocity calculation circuit 6 which are proportional to the number of rotations of the motor 4. The velocity calculation circuit 6 determines the motor rotational velocity based on the number of pulses supplied by pulse encoder 5. From the motor rotation velocity, the velocity calculation circuit 6 calculates a door operation velocity after a fixed time.

The position calculation counter 7 determines the position of the doors based on the pulses output from the pulse encoder 5. The velocity command generator circuit 8 supplies a velocity command for door operation based on the door position determined by the position calculation counter 7. The velocity deviation calculation circuit 9 calculates the deviation between the actual door operation velocity and the velocity command value. To prevent the door operation velocity from exceeding a safe level, the velocity command limit circuit 10 supplies a certain limit value based on the output of the timer check circuit 3 to limit the door operation velocity. That is, when the timer check circuit 3 determines that the door opening and closing motion is abnormal, the velocity command limit circuit 10 quickly reduces the door operation velocity and opens and closes a door to test for proper operation at low velocity. The current amplifier 11 supplies a signal to activate the motor 4 which in turn causes the door operation velocity to change by an amount equivalent to the deviation value as long as the door operation velocity does not exceed the limit value. Otherwise, the door operation velocity is decreased until it equals the limit value. The abnormality display circuit 12 is connected to the timer check circuit 3 and it displays abnormalities to inform the elevator room supervisor when the rotational velocity of the motor 4 exceeds a predetermined reference velocity.

Referring now to FIG. 2, FIG. 2(a) describes a normal door closing operation, and FIG. 2(b) describes an abnormal door closing operation.

In a conventional apparatus, when a present door operation position is not ascertainable due to trouble with the position calculation counter 7, the door running velocity command V.sub.4 is generated as an abnormal command of the velocity command generator circuit 8. This command is generated based on a count value of the position calculation counter 7. In this case, entry and exit from the elevator car can be very dangerous for a passenger because the motor rotational velocity is greater than the reference velocity during most of the door opening and closing operation. Therefore, the door operation velocity does not begin to decrease until the door is almost completely closed. However, in this apparatus, the motor rotational velocity is compared with a check velocity at check time T.sub.1. Therefore, the timer check circuit 3 can determine whether the door opening and closing motion is abnormal by comparing the motor rotational velocity to the check velocity V.sub.1. In the presence of an abnormality (where the check velocity is less than the motor rotational velocity as in FIG. 2(b)), the velocity command limit circuit 10 reduces the door operation velocity by supplying a rapid deceleration command V.sub.5 to the motor 4 and the abnormality display circuit displays an abnormality. Under normal conditions the timer check circuit 3 determines that the door opening and closing motion is not abnormal because the value of the motor rotational velocity is lower than the value of the check velocity V.sub.1, as in FIG. 2(a).

The illustrated embodiment having been described, it should be noted that numerous variations, modifications and other embodiments will become apparent to a person having ordinary skill in the art.