Patent Publication Number: US-7896136-B2

Title: Elevator apparatus with brake control device

Description:
TECHNICAL FIELD 
     The present invention relates to an elevator apparatus having a brake control device for controlling a brake device. 
     BACKGROUND ART 
     In a conventional brake device for an elevator, a braking force of an electromagnetic brake is controlled at the time of emergency braking such that a deceleration of a car becomes equal to a predetermined value, based on a deceleration command value and a speed signal (e.g., see Patent Document 1). 
     Patent Document 1: JP 07-157211 A 
     DISCLOSURE OF THE INVENTION 
     Problem to be Solved by the Invention 
     In recent years, by the way, reduction of the inertia around a rotary shaft has been promoted through the weight saving of a car and adoption of a gearless hoisting machine, and attempts to reduce the capacities of a motor and a control device and realize the energy saving thereof have been made. However, there is a problem in that the deceleration of the car becomes excessively large to the extent of discomforting passengers when the running car is stopped as an emergency measure. 
     The present invention has been made to solve the above-mentioned problem, and it is therefore an object of the present invention to provide, independently of a normal brake device, a brake control device for preventing the deceleration of a car from becoming excessively large at the time of emergency braking. 
     Means for Solving the Problems 
     An elevator apparatus according to the present invention includes: a car; a brake device for stopping the car from running; and a brake control device for controlling the brake device, in which: the brake control device has a first brake control portion for operating the brake device to stop the car as an emergency measure upon detection of an abnormality, and a second brake control portion for reducing a braking force of the brake control portion when a deceleration of the car becomes equal to or larger than a predetermined value during emergency braking operation of the first brake control portion; and the second brake control portion controls the brake device independently of the first brake control portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram showing an elevator apparatus according to Embodiment 1 of the present invention. 
         FIG. 2  is a circuit diagram showing a control circuit for controlling a brake device of  FIG. 1 . 
         FIG. 3  is a circuit diagram showing a circuit for driving second contacts of  FIG. 2 . 
         FIG. 4  is a flowchart showing the operation of a second brake control portion of  FIG. 1 . 
         FIG. 5  is a timing chart showing how the speed of a car, the acceleration of the car, the open/closed states of first contacts, of the second contacts, and of a second semiconductor switch are related to one another when the elevator apparatus of  FIG. 1  is in normal operation. 
         FIG. 6  is a timing chart showing how the speed of the car, the acceleration of the car, the open/closed states of the first contacts, of the second contacts, and of the second semiconductor switch are related to one another when an emergency stop command is issued during operation of the elevator apparatus of  FIG. 1 . 
         FIG. 7  is a circuit diagram showing a control circuit for controlling a brake device of an elevator apparatus according to Embodiment 2 of the present invention. 
         FIG. 8  is a circuit diagram showing a circuit for driving second contacts and third contacts of  FIG. 7 . 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Preferred embodiments of the present invention will be described hereinafter with reference to the drawings. 
     Embodiment 1 
       FIG. 1  is a schematic diagram showing an elevator apparatus according to Embodiment 1 of the present invention. A car  1  and a counterweight  2 , which are suspended within a hoistway by means of a main rope  3 , are raised/lowered within the hoistway with the aid of a driving force of a hoisting machine  4 . The hoisting machine  4  has a drive sheave  5  around which the main rope  3  is looped, a motor  6  for rotating the drive sheave  5 , and braking means  7  for braking rotation of the drive sheave  5 . 
     The braking means  7  has a brake pulley  8  that is rotated integrally with the drive sheave  5 , and a brake device  9  for braking rotation of the brake pulley  8 . The brake device  9  has a brake shoe  10  that is moved into contact with and away from the brake pulley  8 , a brake spring  11  for pressing the brake shoe  10  against the brake pulley  8 , and a brake release coil  12  for opening the brake shoe  10  away from the brake pulley  8  against the brake spring  11 . 
     The motor  6  is provided with a rotation detector  13  for generating a signal corresponding to a rotational speed of a rotary shaft of the motor  6 , namely, a rotational speed of the drive sheave  5 . Employed as the rotation detector  13  is, for example, an encoder or a resolver. 
     A control panel  14  is provided with a power conversion device  15  such as an inverter for supplying power to the motor  6 , and an elevator control device  16 . The elevator control device  16  has a running control portion  17  and a first brake control portion (main control portion)  18 . The running control portion  17  controls the power conversion device  15  and the first brake control portion  18  in accordance with a signal from the rotation detector  13 . The first brake control portion  18  controls the brake device  9  in accordance with a command from the running control portion  17  and a signal from the rotation detector  13 . 
     More specifically, when the car  1  is stopped at a stop floor during normal operation, the first brake control portion  18  causes the brake device  9  to perform braking operation to maintain a stationary state of the car  1 . Also, when a command to stop the car  1  as an emergency measure is issued, the first brake control portion  18  causes the brake device  9  to perform braking operation. Thus, rotation of the brake pulley  8  and rotation of the drive sheave  5  are braked, so the car  1  is braked as an emergency measure. 
     The brake device  9  is controlled by a second brake control portion (deceleration restraining portion)  19  as well. When the deceleration (the absolute value of a negative acceleration) of the car  1  becomes equal to or larger than a predetermined value during emergency braking operation of the first brake control portion  18 , the second brake control portion  19  reduces the braking force of the brake device  9  and controls the brake device  9  such that the deceleration of the car  1  is held smaller than the predetermined value. The second brake control portion  19 , which is connected in parallel with the elevator control device  16  to the brake device  9 , can reduce the braking force of the brake device  9  independently of the first brake control portion  18 . 
     A signal from a car speed detector  20  for generating a signal corresponding to a speed of the car  1 , a signal from an upper terminal detection switch  21  installed in the vicinity of an upper terminal floor within the hoistway, and a signal from a lower terminal detection switch  22  installed in the vicinity of a lower terminal floor within the hoistway are input to the second brake control portion  19 . The car speed detector  20  is provided on a speed governor  23 . 
     The second brake control portion  19  calculates a deceleration of the car  1  based on the signal from the car speed detector  20 . The second brake control portion  19  detects the arrival of the car  1  in the vicinity of each of the terminal floors based on the signal from a corresponding one of the terminal detection switches  21  and  22 . 
     The elevator control device  16  is constituted by a first computer having a calculation processing unit (CPU), a storage portion (ROM, RAM, hard disk, and the like), and signal input/output portions. That is, the functions of the running control portion  17  and the first brake control portion  18  are realized by the first computer. Programs for realizing the functions of the running control portion  17  and the first brake control portion  18  are stored in the storage portion of the first computer. 
     The second brake control portion  19  is constituted by a second computer. That is, the function of the second brake control portion  19  is realized by the second computer. A program for realizing the function of the second brake control portion  19  is stored in a storage portion of the second computer. A brake control device has the first brake control portion  18  and the second brake control portion  19 . 
       FIG. 2  is a circuit diagram showing a control circuit for controlling the brake device  9  of  FIG. 1 . The first brake control portion  18  and the second brake control portion  19  are connected in parallel to the brake release coil  12 . That is, when power is supplied to the brake release coil  12  from at least one of the first brake control portion  18  and the second brake control portion  19 , the braking force of the brake device  9  is canceled. 
     The first brake control portion  18  closes a pair of first contacts  24   a  and  24   b  to supply power from a first power supply  25  to the brake release coil  12 . A first semiconductor switch  26  such as a MOS-FET is connected between the first power supply  25  and the first contact  24   b . The first semiconductor switch  26  generates an average voltage corresponding to the ratio between an ON time and an OFF time through high-speed switching (step-down chopper). 
     A first circulating current diode  27  is connected in parallel with the brake release coil  12  to the first power supply  25 . The first circulating current diode  27  protects the circuit from a back electromotive force generated by the brake release coil  12 . 
     The second brake control portion  19  closes a pair of second contacts  28   a  and  28   b  to supply power from a second power supply  29  to the brake release coil  12 . A second semiconductor switch  30  such as a MOS-FET and a resistor  31  as a current limiting resistor are connected in series between the second power supply  29  and the second contact  28   b.    
     The second semiconductor switch  30  generates an average voltage corresponding to the ratio between an ON time and an OFF time through high-speed switching (step-down chopper). The second semiconductor switch  30  is controlled by a command signal generated by the second computer constituting the second brake control portion  19 . The resistor  31  limits the current flowing through the brake release coil  12  even when there is an ON malfunction in the second semiconductor switch  30 . 
     A second circulating current diode  32  is connected in parallel with the brake release coil  12  to the second power supply  29 . The second circulating current diode  32  protects the circuit from a back electromotive force generated by the brake release coil  12 . 
     A circuit in which a diode  33  and a resistor  34  are connected in series to each other is connected in parallel to the brake release coil  12 . The circuit composed of the diode  33  and the resistor  34  promptly consumes a back electromotive force that is generated by the brake release coil  12  when the first contacts  24   a  and  24   b  or the second contacts  28   a  and  28   b  are opened. 
       FIG. 3  is a circuit diagram showing a circuit for driving the second contacts  28   a  and  28   b  of  FIG. 2 . The second contacts  28   a  and  28   b  are closed by exciting a contact driving coil  35 , and opened by shutting off the supply of current to the contact driving coil  35 . The upper terminal detection switch  21 , the lower terminal detection switch  22 , and a brake control switch  36  are connected in series to the contact driving coil  35 . 
     When the car  1  is located within a predetermined distance from an upper end or a lower end of the hoistway, the terminal detection switch  21  or  22  is opened, respectively, to shut off the supply of current to the contact driving coil  35 . Accordingly, when the car  1  is located within the predetermined distance from the upper end or the lower end of the hoistway, the second contacts  28   a  and  28   b  are opened, so the control of braking force performed by the second brake control portion  19  is invalidated. The brake control switch  36  is closed/opened in accordance with a drive command generated by the second computer constituting the second brake control portion  19 . 
     The second brake control portion  19  monitors the speed of the car  1  based on a signal from the car speed detector  20 . When the speed of the car  1  becomes equal to or higher than a first threshold VH, the second brake control portion  19  closes the second contacts  28   a  and  28   b . When the speed of the car  1  becomes equal to a second threshold VL (VH&gt;VL) while the second contacts  28   a  and  28   b  are in their closed states, the second brake control portion  19  opens the second contacts  28   a  and  28   b.    
     The second brake control portion  19  also monitors the deceleration of the car  1  based on a signal from the car speed detector  20 . When the deceleration of the car  1  becomes equal to or larger than a predetermined value while the second contacts  28   a  and  28   b  are closed, the second brake control portion  19  turns the second semiconductor switch  30  ON to urge the brake release coil  12 . That is, when the acceleration of the car  1  becomes equal to or smaller than a predetermined value αL while the second contacts  28   a  and  28   b  are closed, the second brake control portion  19  turns the second semiconductor switch  30  ON. 
     In addition, when the deceleration of the car  1  becomes equal to or larger than the predetermined value and the second semiconductor switch  30  is turned ON, the second brake control portion  19  starts measuring time by means of a timer circuit. When a predetermined time Tm elapses after the start of the measurement of time by the timer circuit, the second brake control portion  19  opens the second contacts  28   a  and  28   b  to deenergize the brake release coil  12 . 
     Next, an operation will be described.  FIG. 4  is a flowchart showing the operation of the second brake control portion  19  of  FIG. 1 . The second brake control portion  19  repeatedly performs the operation shown in  FIG. 4  on a predetermined cycle. This cycle is sufficiently shorter than a time required for an emergency stop of the car  1 . 
     The second brake control portion  19  determines whether or not the absolute value of the speed of the car  1  is equal to or smaller than the second threshold VL (Step S 1 ). When the absolute value of the speed of the car  1  is equal to or smaller than the second threshold VL, the second brake control portion  19  resets a timer (Step S 2 ), turns the second contacts  28   a  and  28   b  OFF (Step S 3 ), and turns the second semiconductor switch  30  OFF (Step S 4 ), thereby terminating the current processing. 
     When the absolute value of the speed of the car  1  is larger than the second threshold VL, the second brake control portion  19  determines whether or not time is up as a result of the attainment of the predetermined time Tm by the time measured by the timer (Step S 5 ). When time is up, the second brake control portion  19  turns the second contacts  28   a  and  28   b  OFF (Step S 3 ) and turns the second semiconductor switch  30  OFF (Step S 4 ), thereby terminating the current processing. 
     When the absolute value of the speed of the car  1  is larger than the second threshold VL and the time measured by the timer is not up, the second brake control portion  19  determines whether or not: the absolute value of the speed of the car  1  is within a range from the first threshold VH to a third threshold Vmax (Step S 6 ). When the absolute value of the speed of the car  1  is outside the above-mentioned range, the second brake control portion  19  turns the second semiconductor switch  30  OFF (Step S 4 ), thereby terminating the current processing. 
     When the absolute value of the speed of the car  1  is larger than the second threshold VL, the time measured by the timer is not up, and the absolute value of the speed of the car  1  is within the range from the first threshold VH to the third threshold Vmax, the second brake control portion  19  turns the second contacts  28   a  and  28   b  ON (Step S 7 ), and determines whether or not the acceleration of the car  1  is equal to or smaller than the predetermined value αL (Step S 8 ). 
     When the acceleration of the car  1  is larger than the predetermined value αL, the second brake control portion  19  turns the second semiconductor switch  30  OFF (Step S 4 ), thereby terminating the current processing. When the acceleration of the car  1  is equal to or smaller than the predetermined value αL, the second brake control portion  19  turns the second semiconductor switch  30  ON (Step S 9 ) and starts the timer (Step S 10 ), thereby terminating the current processing. 
       FIG. 5  is a timing chart showing how the speed of the car  1 , the acceleration of the car  1 , the open/closed states of the first contacts  24   a  and  24   b , of the second contacts  28   a  and  28   b , and of the second semiconductor switch  30  are related to one another when the elevator apparatus of  FIG. 1  is in normal operation. 
     At a time point t 0 , the first contacts  24   a  and  24   b  are turned ON immediately before the car  1  starts running, so the brake release coil  12  is supplied with power. As a result, the braking force of the brake device  9  is canceled. 
     When the speed of the car  1  reaches the first threshold VH at a time point t 1 , the second contacts  28   a  and  28   b  are turned ON, so the second brake control portion  19  is validated. However, the acceleration of the car  1  is larger than the predetermined value αL during normal operation, so the second semiconductor switch  30  remains OFF. As a result, no power is supplied from the second brake control portion  19  to the brake release coil  12 . 
     When the speed of the car  1  drops to the second threshold VL at a time point t 2 , the second contacts  28   a  and  28   b  are turned OFF, so the second brake control portion  19  is invalidated. Then, the first contacts  24   a  and  24   b  are turned OFF at a time point t 3  after a stop of the car  1 , so the braking force of the brake device  9  is applied to the brake pulley  8 . 
       FIG. 6  is a timing chart showing how the speed of the car  1 , the acceleration of the car  1 , the open/closed states of the first contacts  24   a  and  24   b , of the second contacts  28   a  and  28   b , and of the second semiconductor switch  30  are related to one another when an emergency stop command is issued during operation of the elevator apparatus of  FIG. 1 . 
     When the emergency stop command is issued at a time point t 4 , the first contacts  24   a  and  24   b  are turned OFF, so the supply of power to the brake release coil  12  and the supply of power to the motor  6  are shut off. Thus, the car  1  starts decelerating. 
     When the acceleration of the car  1  becomes equal to or smaller than the predetermined value αL at a time point t 5 , the second semiconductor switch  30  is turned ON, so the brake release coil  12  is supplied with power. Thus, the braking force of the brake device  9  is canceled, so the acceleration of the car  1  increases. Then, when the acceleration of the car  1  exceeds the predetermined value αL, the second semiconductor switch  30  is turned OFF, so the braking force of the brake device  9  is applied to the brake pulley  8 . By repeating the switching operation of the second semiconductor switch  30  as described above at high speed, the acceleration of the car  1  is held approximately equal to the predetermined value αL. 
     When the speed of the car  1  becomes equal to or lower than the second threshold VL at a time point t 6 , the second contacts  28   a  and  28   b  are turned OFF, so the second brake control portion  19  is invalidated. Then, the car  1  is stopped at a time point t 7 . 
     In the elevator apparatus configured as described above, the second brake control portion  19  for controlling the deceleration during emergency braking controls the brake device  9  independently of the first brake control portion  18 . It is therefore possible to start the operation of emergency braking more reliably and promptly while restraining the deceleration during emergency braking. 
     The second brake control portion  19  is invalidated when the car  1  reaches the vicinity of each of the terminal floors. It is therefore possible to stop the car  1  more reliably in the vicinity of each of the terminal floors. 
     In addition, the second brake control portion  19  is invalidated upon the lapse of the predetermined time after the deceleration of the car  1  becomes equal to or larger than the predetermined value. It is therefore possible to limit the time for deceleration control within the predetermined time and hence stop the car  1  more reliably. 
     Embodiment 2 
     Reference will be made next to  FIG. 7 .  FIG. 7  is a circuit diagram showing a control circuit for controlling the brake device  9  for an elevator apparatus according to Embodiment 2 of the present invention. Referring to  FIG. 7 , the second brake control portion  19  closes the pair of the second contacts  28   a  and  28   b  and a pair of third contacts  37   a  and  37   b  to supply power from the second power supply  29  to the brake release coil  12 . 
       FIG. 8  is a circuit diagram showing a circuit for driving the second contacts  28   a  and  28   b  of  FIG. 7  and the third contacts  37   a  and  37   b  of  FIG. 7 . The third contacts  37   a  and  37   b  are closed by exciting a contact driving coil  38 , and opened by shutting off the supply of current to the contact driving coil  38 . The upper terminal detection switch  21 , the lower terminal detection switch  22 , and a brake control switch  39  are connected in series to the contact driving coil  38 . This circuit for driving the third contacts  37   a  and  37   b  is connected in parallel to the circuit for driving the second contacts  28   a  and  28   b.    
     The second computer constituting the second brake control portion  19  has a first calculation processing unit (first CPU)  41  as a first deceleration monitoring portion, and a second calculation processing unit (second CPU)  42  as a second deceleration monitoring portion. The first calculation processing portion  41  and the second calculation processing portion  42  monitor the deceleration of the car  1  independently of each other. The brake control switch  36  for driving the second contacts  28   a  and  28   b  is closed/opened in accordance with a drive command generated by the first calculation processing portion  41 . The brake control switch  39  for driving the third contacts  37   a  and  37   b  is closed/opened in accordance with a drive command generated by the second calculation processing portion  42 . Embodiment 2 of the present invention is identical to Embodiment 1 of the present invention in other configurational details. 
     In the elevator apparatus configured as described above, the second brake control portion  19  is not validated unless the second contacts  28   a  and  28   b  and the third contacts  37   a  and  37   b  are all closed through drive commands from both the first calculation processing portion  41  and the second calculation processing portion  42 . It is therefore possible to prevent the second brake control portion  19  from malfunctioning due to an abnormality in the first calculation processing portion  41  or the second calculation processing portion  42 . As a result, it is possible to achieve an improvement in reliability. 
     In each of the foregoing examples, the acceleration of the car  1  is calculated based on the signal from the car speed detector  20 . However, the acceleration of the car  1  may be calculated based on an output from, for example, a rotation detector provided on the hoisting machine  4 , or an acceleration sensor provided on the car  1 . 
     In each of the foregoing examples, the drive command for driving the second contacts  28   a  and  28   b  is generated by the computer. However, the drive command may be generated by means of an electric circuit for processing analog signals. 
     Further, in each of the foregoing examples, the presence of the car  1  in the vicinity of each of the terminal floors is detected from the signal from a corresponding one of the terminal detection switches  21  and  22 . However, this detection may be carried out using car position information that has been obtained based on a signal from, for example, the car speed detector  20  provided on the speed governor  23 , or the rotation detector  13  provided on the hoisting machine  4 . 
     Still further, in each of the foregoing examples, the brake device  9  is provided on the hoisting machine  4 . However, the brake device  9  may be provided at another position. In other words, the brake device  9  may be designed as, for example, a car brake mounted on the car  1 , or a rope brake for gripping the main rope  3  to brake the car  1 . 
     Further, a brake device having a plurality of brake shoes for performing braking/releasing operations independently of one another may be employed.