1. An elevator comprising: a car; 5 a drive unit for moving the car by rotating a rotary body connected to the car; a brake for applying a braking force to the rotary body; an elevator control unit for controlling an 10 operation of the car; a brake control unit for changing a brake torque of the brake stepwise for releasing upon reception of a start signal of the elevator from the elevator control unit; and a torque control unit for controlling a torque of 15 the drive unit to approximate the car speed to zero upon reception of the start signal of the elevator from the elevator control unit.

2. The elevator according to claim 1, further comprising 20 a brake check switch for detecting a contact state between the brake and the rotary body, wherein in the case that the brake check switch detects separation of the brake from the rotary body, the brake control unit fully releases the brake from the rotary body. 25 18

3. The elevator according to claim 1, further comprising a brake check switch for detecting a contact state between the brake and the rotary body, wherein the brake check switch detects separation of the brake from the rotary 5 body, and the torque control unit controls a torque of the drive unit to approximate the car speed to zero until reception of an operation command from the elevator control unit. 10 4. The elevator according to claim 3, wherein the brake control unit determines a brake control process of gradually releasing the brake from the rotary body based on information stored in a type information DB of the brake control unit.

[0001]
5 The present invention relates to an elevator.
[0002]
The elevator car is normally driven under control to
allow the motor to output compensation torque
corresponding to the difference between the car and the
10 counterweight so as to maintain static state of the car
while preventing its fall even in the transition from the
stop state under the braking force to the state where the
braking force is released. In order to determine the
compensation torque upon activation, it is necessary to
15 detect inside weight of the car by means of the weighing
sensor attached to the bottom of the car or the thimble
rod. Possible error of the weighing sensor may fail to
accurately output the required compensation torque, which
shakes the car upon starting at a magnitude corresponding
20 to the error. Japanese Patent Application Laid-Open No.
2015-00796 discloses the method of calibrating the
weighing sensor for the purpose of solving the abovedescribed
problem.
25 SUMMARY
3
[0004]
There may be the case that the car is shaken when
starting the elevator if the weighing sensor fails, or
high detection accuracy cannot be expected. As a result,
5 the appropriate compensation torque cannot be output, thus
shaking the car upon starting of the elevator.
[0005]
The present invention provides the elevator
including a car, a drive unit for moving the car by
10 rotating a rotary body connected to the car, a brake for
applying a braking force to the rotary body, an elevator
control unit for controlling an operation of the car, a
brake control unit for changing a brake torque of the
brake stepwise for releasing upon reception of a start
15 signal of the elevator from the elevator control unit, and
a torque control unit for controlling a torque of the
drive unit to approximate the car speed to zero upon
reception of the start signal of the elevator from the
elevator control unit.
20 [0006]
It is an object of the present invention to lessen
shaking of the car upon starting of the elevator.
BRIEF DESCRIPTION OF THE DRAWINGS
25 [0007]
4
Fig. 1 is a block diagram showing an overall
structure of an embodiment according to the present
invention;
Fig. 2 is a block diagram showing the process flow
5 executed by an elevator controller according to the
embodiment;
Fig. 3 is a view schematically showing the operation
of the embodiment; and
Fig. 4 is a flowchart representing process steps of
10 generating the drive torque according to the embodiment.
DETAILED DESCRIPTION
[0008]
An embodiment according to the present invention
15 will be described referring to the drawings.
[0009]
Fig. 1 is an overall view of an elevator system
structure according to the present invention. An elevator
controller 100 controls movement of a car 104 of the
20 elevator. The elevator controller 100 includes a brake
control unit 20 and a torque control unit 23 in addition
to an elevator control unit 2 for operation control of the
elevator.
[0010]
25 The car 104 operated to move between floors of the
5
building through the hoistway is connected to a weight or
counterweight with a rope for balancing with the car 104.
The car 104 includes a car door that is opened and closed
in engagement with the door at the landing floor side.
5 The car 104 is operated by a motor 103 which drives the
sheave. A power converter 101 supplies drive power to the
motor 103. The power converter 101 outputs power for
controlling the motor in accordance with a car position
control command from the elevator controller 100. A
10 rotation sensor as the pulse generator such as an encoder
is attached to the motor 103. The elevator controller 100
counts the pulse generated by rotation of the motor 103 so
as to calculate speed of the motor 103, and moving
direction, position, movement distance of the car 104 in
15 the hoistway. The rotation sensor attached to the motor
will be referred to as a machine encoder. The elevator
controller outputs a brake power source stop command and a
power supply stop command (not shown) for braking the car.
In response to those stop commands, the brake power source
20 actuates a brake 102, and the power supply interrupts
power supply to the power converter 101 so as to brake the
car 104. The brake power source and the power supply are
circuits each constituted by an electromagnetic contactor
called contactor.
25 [0011]
6
The brake 102 includes a brake pad for braking the
sheave through friction sliding operation, a solenoid coil
for lifting the brake pad so as to generate the gap
between the sheave and the brake pad, and a core.
5 Generally, upon power supply to the solenoid coil, the
brake pad is lifted under electromagnetic force so that
the sheave released from restraint of the brake pad
becomes freely rotatable. Power is supplied to the
solenoid coil through relay from the brake power source.
10 The brake 102 is connected to a brake current control
circuit 21 as the circuit configured to control the
current (brake current 22) applied to the solenoid coil
and configured to make the braking force of the brake
variable. The brake 102 is provided with a brake check
15 switch 8 configured to mechanically detect whether the
brake pad and the sheave are separated (uncontact state).
The information detected by the brake check switch 8
indicating as to whether the brake and the sheave are
separated (uncontact state) is output to the elevator
20 control unit 2.
[0012]
The brake current control circuit 21 is constituted
by a converter for controlling current or voltage, for
example, inverter circuit, chopper circuit or the like, a
25 hall CT for detecting the brake current, and a control
7
unit for controlling the brake current. In response to
the current command value (brake current command) applied
from the elevator controller 100 to the solenoid coil, the
brake current 22 is controlled into the command value.
5 This embodiment has been described by taking the brake
mechanism for varying the braking force in accordance with
the current using the solenoid coil as an example of
varying the braking force. It is also possible to employ
the brake configured to vary the braking force in
10 accordance with the distance by utilizing the actuator of
direct drive type, or the brake (shoe brake) configured to
vary the braking force in accordance with the rotation
angle by utilizing the rotation mechanism. Arbitrary type
of brake may be employed so long as the braking force of
15 the brake is variable in accordance with the specific
command.
[0013]
A position sensor 5 is a door zone sensor configured
to detect a detection plate 6 so as to determine if the
20 elevator is at the position where the door can be opened.
A car speed sensor 7 for detecting the car speed may be
formed as a rotation sensor attached to the governor, for
example. The rotation sensor attached to the governor
will be referred to as a governor encoder. It is also
25 possible to directly attach the acceleration sensor to the
8
car.
[0014]
Fig. 2 is a block diagram representing correlation
between the brake control unit 20 and the torque control
5 unit 23 with respect to processing executed by those units.
Upon reception of an operation start command input from
the elevator control unit 2, a speed command output
processing unit 30 issues a zero speed command. The
difference between the zero speed command and a car speed
10 feedback input from a car speed detection processing unit
31 is calculated for execution of target value follow-up
control, for example, proportional integral control.
Finally, the torque command is output. In other words,
the torque command is output so that the car speed becomes
15 zero. The car speed detection processing unit 31 detects
a car speed feedback signal derived from the machine
encoder so that the signal is output for speed command
output processing.
[0015]
20 A torque control processing unit 32 obtains the
difference between the torque command input from the speed
command output processing unit 30 and a torque feedback
signal calculated from a motor current feedback signal,
executes such process as proportional integral control,
25 and outputs the torque output command. The torque output
9
command is input to the power converter 101 so that
voltage is applied to a synchronous motor for generating
the desired torque.
[0016]
5 The brake control unit 20 includes a brake current
command generation unit 33 and a type information database
(DB) 34. Upon reception of an operation start command
input from the elevator control unit 2, the brake current
command generation unit 33 outputs the brake current
10 command in reference to the type information DB 34 to be
described later. The brake current command is input to
the brake current control circuit 21, based on which the
brake current control circuit 21 controls the brake
current 22 to be applied to the brake solenoid coil.
15 [0017]
Fig. 3 graphically represents the time-series
correlation among waveforms generated upon start of the
brake control unit 20 and the torque control unit 23. For
convenience of explanation, the time axis is divided into
20 four sections from (a) to (d). The basic operation
process will be described with respect to the sections
sequentially from the section (a).
[0018]
In the section (a), the operation start command has
25 not been input to the respective control units, and
10
therefore, the brake current command is in the zero state.
In other words, the car is kept under braking force by the
brake, and accordingly, the car speed is also zero.
Because of the braking force applied by the brake, the
5 torque output command is also in the zero state.
[0019]
In the section (b), the operation start command is
input. Then the brake control unit 20 gradually increases
the brake current command value so that the brake current
10 output from the brake current control circuit 21 is
applied to the solenoid for lifting the brake 102. Upon
increase in the brake current command value, the brake 102
is lifted slowly so as to decrease the brake torque T. In
the case that the unbalance torque between the car and the
15 counterweight is made larger under the decreasing brake
torque, the car is likely to move. At this time, the
speed command output processing unit 30 has already output
the zero speed command. Then the torque control
processing unit 32 outputs the torque output command to
20 the power converter 101 so that the car speed becomes zero.
Then power is output to the motor 103 to output the torque
in accordance with the torque output command to the power
converter 101. Since the speed command output processing
unit 30 has already output the zero speed command, the
25 brake is lifted. As the unbalance torque is made
11
relatively larger than the brake torque, the motor torque
for maintaining the zero speed is increased as well as the
output of the torque command. By releasing the brake
slowly, the brake torque insufficient to bring the car
5 into static state may be compensated in response to the
torque output command. This may maintain the static state
of the car. The gradient of the brake current command in
the section (b) is determined in reference to the type
information DB 34 in order to cope with the response which
10 differs depending on the brake type. For example, in the
case of brake torque response delay to change in the brake
current command, the gradient may be reduced or shaped
into step-like form so as to facilitate the response
following up to the command.
15 [0020]
The section (c) represents the transitional change
into the state that brings the brake torque into zero
state as a result of separation of the brake pad from the
sheave resulting from increasing brake current. At this
20 time, the torque required for making the car into static
state has been already output in the section (b).
Therefore, shaking of the car owing to torque change
rarely occurs even in the state that the brake is released.
[0021]
25 The section (d) represents the state that the brake
12
has been separated. The torque sufficient to bring the
car into static state has been output in the section (c)
so that the car is kept in the static state. At this time,
the torque control processing unit 32 has output the
5 torque output command to set the car speed to zero.
Subsequently, the speed command is applied to start
operation of the car.
[0022]
Fig. 4 is a flowchart according to the present
10 invention. In step S101, the elevator control unit 2
detects whether the operation start command has been input.
If the operation start command is OFF, the process ends.
If the operation start command is ON, the process proceeds
to step S102. In step S102, the car speed detection
15 processing unit 31 converts the machine encoder
information or the information output from the car speed
sensor 7, which has been input via the elevator control
unit into the car speed. The speed command output
processing unit 30 judges whether or not the car speed is
20 zero. If the car speed is zero, the process proceeds to
step S103 where the brake current command value is
increased through the brake current command generation
process. In step S104, the brake torque is reduced as the
brake current varies. If it is judged in step S102 that
25 the car speed is not zero, the process proceeds to step
13
S105 where the speed command output processing unit
outputs the torque control command to set the car speed to
zero. In step S106, it is judged whether or not the brake
pad has been separated. Separation of the brake pad may
5 be detected by utilizing the brake check switch 8 for
detecting the brake operation state. If the brake pad has
not been separated, the process proceeds to the step prior
to step S102. That is, when the brake pad is not
separated at the speed other than zero, the control for
10 increasing the brake current is executed while outputting
the torque that approximates the speed to zero. If the
brake pad is separated by decreasing the brake torque
stepwise, the process proceeds to step S107 where the
process is kept stand-by until the operation command is
15 input while allowing the speed control unit to output the
torque to set the car speed to zero. The current command
generation increasing process executed by the brake
current command generation unit 33 ends to terminate the
series of process steps.
20 [0023]
The above-described structure allows the unbalance
torque corresponding to the difference between the car and
the counterweight to be gradually activated under the
decreasing braking force resulting from the brake slowly
25 released by the elevator control unit. The control unit
14
subjects the torque command to the follow-up control,
which allows slow follow-up to the unbalance torque
without causing sharp torque change. This makes it
possible to make the acceleration change owing to torque
5 gentle. In the case of error in the weighing sensor and
the rotation sensor, the resultant shaking may be
suppressed.
[0024]
The present invention is useful for the case that
10 the magnetic pole position of the motor as the drive unit
is estimated for driving operation. In particular, so
called vector control is executed for the general torque
control or speed control of the motor as the permanent
magnet synchronous motor. As the above-described control
15 needs detection of the magnetic pole position of the
synchronous motor, the magnetic pole is detected by the
rotation sensor. The detection error of the rotation
sensor attached to the synchronous motor with respect to
the magnetic pole position may influence the compensation
20 torque. As a result, the large detection error and the
error in estimation with respect to the magnetic pole
position through sensor-less driving operation may cause
shaking of the car.
[0025]
25 The current value kept constant for the magnetic
15
pole position estimation is output immediately after
execution of step S101, and the brake is gradually
released by the control unit to bring the unbalance torque
as the difference between the car and the counterweight
5 into activated state under the weakening braking force.
At this time, the control unit subjects the torque command
to the follow-up control to allow slow follow-up to the
unbalance torque without causing sharp torque change.
This makes it possible to make the acceleration change
10 owing to torque gentle. In spite of torque inversion,
large torque is not required, and shaking may be lessened
without generating high acceleration under the active
braking force. In the case of error in the weighing
sensor and the rotation sensor, it is possible to lessen
15 shaking of the car.
16
List of Reference Signs
[0026]
2 elevator control unit

We claim:
1. An elevator comprising:
a car;
5 a drive unit for moving the car by rotating a rotary
body connected to the car;
a brake for applying a braking force to the rotary
body;
an elevator control unit for controlling an
10 operation of the car;
a brake control unit for changing a brake torque of
the brake stepwise for releasing upon reception of a start
signal of the elevator from the elevator control unit; and
a torque control unit for controlling a torque of
15 the drive unit to approximate the car speed to zero upon
reception of the start signal of the elevator from the
elevator control unit.
2. The elevator according to claim 1, further comprising
20 a brake check switch for detecting a contact state between
the brake and the rotary body, wherein in the case that
the brake check switch detects separation of the brake
from the rotary body, the brake control unit fully
releases the brake from the rotary body.
25
18
3. The elevator according to claim 1, further comprising
a brake check switch for detecting a contact state between
the brake and the rotary body, wherein the brake check
switch detects separation of the brake from the rotary
5 body, and the torque control unit controls a torque of the
drive unit to approximate the car speed to zero until
reception of an operation command from the elevator
control unit.
10 4. The elevator according to claim 3, wherein the brake
control unit determines a brake control process of
gradually releasing the brake from the rotary body based
on information stored in a type information DB of the
brake control unit.