THCHNICAL FIELD
[0001] The invention relates to control of a brake of an elevator, wherein, when an elevator
start signal is issued, an energization circuit is closed, to thereby energize a brake
coil, attract an armature against the force of a spring, disengage from a brake wheel
a brake shoe remaining in pressed contact with the brake wheel, by means of the attracting
action, and release braking force, thereby enabling activation of an elevator; and,
when an elevator stop signal is issued, the energization circuit is interrupted so
as to release the armature and cause the spring to press the brake shoe against the
brake wheel, thereby producing braking force.
BACKGROUND ART
[0002] Fig. 10 shows the schematic configuration of a brake that is commonly used in a cable-type
elevator. A car 1 of an elevator is suspended by a counterweight 4 in the manner of
a windlass by means of a main cable 3 passed around a sheave 2 of a hoisting machine
and driven by a hoisting motor 5. A brake wheel 6 is attached to a shaft 5a for coupling
the hoisting motor 5 to the sheave 2. When the car 1 remains stationary, a brake shoe
9 is pressed against an outer peripheral surface of the brake wheel 6 via a brake
lever 8 by means of a spring 7. Brake force is generated by frictional force.
[0003] When the car 1 is activated, a motor control circuit 10 energizes the hoisting motor
5, and a start signal is sent to a brake controller 11, thereby activating a brake
control circuit 12. A PWM signal generation circuit 14 of a brake drive circuit 13
activates a chopper circuit 15, thereby energizing a brake coil 16 with a variable
d.c. voltage. When the brake coil 16 is energized, an armature 17 is attracted against
the force of the spring 7. Pressure applied to press the brake shoe 9 against the
brake wheel 6 is released by way of the brake lever 8, thereby canceling the brake.
When the armature 17 is attracted, a brake switch 18 is closed, whereby completion
of release of the brake is detected.
[0004] When a stop signal is issued, the motor control circuit 10 de-energizes the hoisting
motor 5 and also de-energizes the brake coil 16 by way of the brake control circuit
12 and the brake drive circuit 13, thereby disengaging the armature 17 from the attracted
state and causing the spring 7 to press the brake shoe 9 against the brake wheel 6.
[0005] Specifically, when the brake coil 16 is de-energized by the chopper circuit 15 provided
in the brake control circuit shown in Fig. 10, a circulating current flows into the
brake coil 16 by way of a diode 20. The circulating current is reduced in accordance
with a time constant Tc determined by the resistance R and reactance L of the brake
coil 16. As a brake coil current is reduced, attracting force also decreases. When
the attracting force has become smaller than the force of the spring 7, the armature
17 is disengaged from the brake coil 16. As a result, the brake shoe 9 is pressed
against the brake wheel 6 by the spring 7, thus generating braking force.
[0006] The outline of operation of the brake controller will now be described by reference
to Fig. 11. A voltage E designated by broken lines is output from the brake controller
11. Specifically, when an attraction voltage Ef to be used for attracting the armature
17 is applied to the brake coil at time t40, a brake coil current Ib increases gradually.
[0007] During the course of the armature 17 being attracted, the brake coil current Ib is
temporarily diminished. The reason for this is that the inductance L is changed by
an air gap "g" and that electromotive force (hereinafter called "speed electromotive
force") is produced at the rate of change in the inductance L; that is, the travel
speed of the armature 17. After attraction of the armature 17 is completed at time
t41, the brake coil current Ib gradually increases at the inductance L yielded in
that status.
[0008] At time t42, which is achieved after lapse of a predetermined period of time after
closing of the brake switch 18 as a result of attraction of the armature 17, the brake
controller 11 decreases the voltage E applied to the armature 17 to a holding voltage
Eh required to hold the armature in the attracted state. In association with a decrease
in the applied voltage, the brake coil current Ib is decreased to a holding current
Ih.
[0009] When an elevator stop signal is issued at time t43, the applied voltage E falls to
zero. As a result of interruption of an energization circuit, the brake coil current
Ib is decreased while circulating through the diode 20 connected in parallel with
the brake coil 16. In association with a decrease in the brake coil current, the armature
17 is disengaged from an attracted state, and the brake shoe 9 is pressed by the spring
7, thus generating braking force.
[0010] During the course of de-energization of the brake coil 16, the brake coil current
Ib is temporarily increased. The reason for this is that an air gap is increased in
association with the armature 17 being disengaged from the attracted state in the
manner set forth, thereby decreasing the inductance L of the brake coil 16. The temporary
increase in brake coil current is also attributable to the speed electromotive force.
When release of the armature 17 is finished at time t44, the brake coil current Ib
is gradually decreased with the inductance L yielded in this state and reaches zero
at time t45.
[0011] Accordingly, when a current sensor 19 detects the brake coil current Ib and releases
braking force, the instant when the braking force is released can be detected by means
of detecting a point at which a decrease has arisen in the braking current Ib. When
braking force is produced, the instant when the braking force is generated can be
detected by means of detecting a point at which an increase has arisen in the braking
current Ib.
[0012] The brake of the conventional elevator is constructed in the manner set forth. The
voltage applied to the brake coil 16 at the time of stoppage of the car 1 becomes
0. The brake coil current Ib is a time constant defined by the resistance and inductance
of the brake coil 16 and is gradually decreased. The attracting force of the brake
coil 16 required to attract the armature 17 is proportional to the square of the brake
coil current Ib and substantially inversely proportional to the air gap between the
armature 17 and the brake coil 16. Accordingly, when the attracting force is decreased
as a result of a decrease in the brake coil current Ib, the brake shoe 9 is pressed
by the tensile force of the spring 7, to thereby impinge on the brake wheel 7. The
impinging action induces noise.
[0013] These days, a hoisting machine of an elevator is made compact, and a brake is also
forced to be downsized. Hence, the brake shoe 9 or other elements must be made compact.
In order to ensure required braking force while satisfying such requirements on the
outer shape of the brake, the tensile force of the spring 7 used for pressing the
brake shoe 9 must be increased. This in turn raises a problem of an increase in noise
generated by impingement.
[0014] Especially, the elevator having a hoisting machine installed within a hoistway entails
a problem of ride comfort of the car 1 being deteriorated as a result of propagation
of operating sound of the brake.
[0015] To address this problem, JP-B-7-64493 (JP-A-63-158681) and USP 4,974,703 based thereon
describe the following invention, which utilizes the characteristic of the brake of
the elevator. Specifically, when an elevator start instruction signal is issued, a
decrease in a brake coil current is detected during the course of the brake coil current
being increased as a result of energization of a brake coil, and then a start instruction
is sent to a hoisting motor, thereby energizing the motor. When an elevator stop instruction
signal is issued, an increase in the brake coil current is detected during the course
of the brake coil current being decreased as aresult of de-energization of the brake
coil, and then a stop instruction is sent to the hoisting motor, thereby de-energizing
the hoisting motor. In this way, switching between the brake and the hoisting motor
5 is performed smoothly, thereby attempting an improvement in ride comfort.
[0016] However, detection of a change in the brake coil current which arises at the time
of energization and de-energization of the brake coil described in the patent publication
is intended for improving ride comfort, and the aforementioned patent publication
fails to refer to a reduction in operating sound of the brake. Hence, the invention
does not contribute to solution of the problem.
[0017] JP-B-7-68016 describes the following invention. Specifically, at the time of start
of an elevator, a brake coil current is immediately boosted within a range in which
unbalance torque can be maintained. Then, the brake coil current is gradually increased,
thereby reducing brake torque of the brake. In this state, a hoisting motor is driven,
and from then on a small current which can retain an released state of the brake is
caused to flow to the brake coil, thereby improving ride comfort and suppressing generation
of heat in the brake coil.
[0018] This patent publication also fails to refer to a reduction in operating sound of
the brake and hence does not contribute to solution of the problem.
[0019] Moreover, JP-A-7-2441 describes a braking device which produces braking force by
means of grasping a rail. In order to reduce operating sound, a position immediately
before a movable piece comes into collision with an electromagnet is detected. Further,
a position immediately before a brake shoe grasps the rail is detected. A brake coil
current is controlled so as to reduce operating sound.
[0020] This braking device is aimed at reducing operating sound of the brake. However, the
position of the movable piece and that of the brake shoe cannot be detected easily.
Even when the positions can be detected, there also arises a problem of the positions
being susceptible to changes, for reasons of abrasion of brake linings and adjustment
of the brake.
[0021] Moreover, JP-B-7-80650 describes the following invention. Specifically, a current
pattern used for controlling a brake current is compared with a detected brake current.
On the basis of a result of comparison, activation or deactivation of the brake current
is controlled, thus inhibiting generation of operating sound, which would otherwise
be caused by opening or closing the brake.
[0022] However, in relation to the brake, resistance of the brake coil is changed by temperature,
and abrasion of a brake lining differs from one brake to another. Even in the case
of brakes of the same type, braking torque settings of the brake differ from one brake
to another. For these reasons, operating sound cannot be readily suppressed by uniform
control of a brake current through use of the current pattern.
[0023] JP-A-7-2452 also describes the following invention. Specifically, a brake shoe is
gently pressed against a guide rail, thereby reducing operating sound. Further, in
order to shorten an operation time, a brake coil current is diminished to essentially
the same level as that of the holding current.
[0024] However, there may arise a problem of the brake being erroneously activated by fluctuations
in voltage as a result of a decrease in the brake coil current.
[0025] The invention aims at solving the problem of the brake of the conventional elevator
and providing an elevator brake whose operating sound is reduced.
DISCLOSURE OF THE INVENTION
[0026] The invention is arranged in the following manner. In a case where braking force
is caused to develop in a brake of an elevator in which braking force is released
when an armature is attracted by energization of a brake coil and when pressure exerted
to press a brake shoe against a brake wheel is released by attraction, thereby releasing
braking force, first brake coil control means decreases energization of the brake
coil such that the armature is released from an attracted state. When the rate of
decrease in the brake coil current has become slow or the brake coil current has turned
into an increase during the course of the armature being released from an attracted
state by the first brake coil control means, there is effected switching to second
brake coil control means which energizes the brake coil with a current that produces
power greater than that applied by the first brake coil control means within a range
in which the armature is not attracted again, and the brake coil is then energized.
[0027] As a result, the pressing force of the spring becomes weaker as a result of the attracting
force of the armature being increased again by the brake coil during the course of
release of the armature from an attracted state. Therefore, the pressure stemming
from the force of the spring is lessened, which in turn enables a reduction in operating
sound caused when the brake shoe collides with the brake wheel. Switching to the second
brake coil control means is performed when the rate of decrease in the brake coil
current has become slowed to a level lower than a predetermined value or when the
brake coil current has turned into an increase. Hence, the armature is released from
the attracted state, and energization of the brake coil is increased immediately after
the armature has started moving. Moreover, a limitation is imposed on an energization
value to be increased. Even when the brake coil is energized by the second brake coil
control means, a delay in release of the armature from an attracted state is limited.
Further, the energization value is increased after actual movement of the armature
has been detected. Hence, even when a resistance value is varied for reasons of a
temperature change, switching to the second brake coil control means can be effected
at an appropriate time.
[0028] Further, according to the invention, the first brake coil control means is arranged
such that the armature is released from the attracted state by means of a gradual
decrease in the brake coil current circulating through a branch circuit connected
in parallel with the brake coil, by means of interruption of an energization circuit.
[0029] Since the brake coil current circulating through the branch circuit is attenuated
within a short period of time, a delay in release of the armature from the attracted
state is limited, and hence the availability factor of an elevator can be improved.
[0030] Moreover, according to the invention, the first brake coil control means controls
the brake coil such that the brake coil is energized with a voltage which gradually
lowers with lapse of time and such that the armature is released from an attracted
state in association with a reduction in the voltage. Hence, the first brake coil
control means can be smoothly switched to the second brake coil means.
[0031] Further, according to the invention, the first brake coil control means is switched
to the second brake coil control means when the rate of decrease in brake coil current
assumes a value of zero orwhen the brake coil current has turned into an increase.
Hence, even when fluctuations have arisen in the force of the spring required to press
the brake shoe against the brake wheel or when the resistance of the brake coil has
been changed by temperature, switching can be effected at an appropriate time.
[0032] Further, according to the invention, the second brake coil control means energizes
the brake coil with a voltage obtained by multiplication of the brake coil current
value with the resistance of the brake coil, the current and resistance being obtained
when the rate of decrease in the brake coil current assumes a value of zero.
[0033] Therefore, the brake coil can be energizedwith an electric current close to the maximum
current obtained within a range in which the armature is not attracted again, thereby
reducing operating sound of the armature.
[0034] Further, according to the invention, the brake coil resistance value is determined
from a ratio of a voltage of the brake coil to the brake coil current, the ratio being
obtained when the brake coil current has assumed a constant value while the braking
force is released in response to an elevator start signal.
[0035] Therefore, even when the resistance has been changed by a temperature change, the
brake coil can be energized with a current value close to the maximum current obtained
within an allowable range of the thus-changed resistance value. Hence, the effectiveness
of the invention can be achieved.
[0036] Moreover, according to the invention, the rate of change in the brake coil current
is computed, and a limitation is imposed on the rate of change such that the armature
is not attracted again. The brake coil is energized with a voltage proportional to
a value obtained through computation.
[0037] Therefore, the brake coil is energized on the basis of the rate of change in the
brake coil current. Hence, the brake can be caused to sensitively respond to actuation
of the armature.
[0038] Further, according to the invention, the second brake coil control means has a circuit
model of a brake coil. A model current is obtained by application, to the circuit
model, of a voltage to be applied to the brake coil. The model current is subtracted
from the brake coil current, and the brake coil is energized with a voltage proportional
to the rate of change in a result of subtraction.
[0039] Since the inductance of the circuit model is a constant value, the brake coil is
energized on the basis of the speed of movement of the armature; that is, an increment
in the brake current stemming from speed electromotive force. Hence, movement of the
armature can be controlled smoothly.
[0040] Moreover, according to the invention, a time constant of the brake coil is determined
from an increment ΔI of the brake coil current obtained when a voltage Ei is applied
to the brake coil in a stepped manner. The inductance L of the circuit model of the
brake coil is determined by multiplying the resistance R of the brake coil by the
time constant.
[0041] Therefore, the circuit model of the brake coil can be constituted in accordance with
the status of each brake.
BRIEF DESCRIPTION OF THE DRAWINGS
[0042]
Fig. 1 is a block diagram showing a control circuit of a brake controller of an elevator
according to a first embodiment of the invention, and Fig. 2 is a view for describing
operation of the control circuit;
Fig. 3 is a block diagram showing a control circuit of a brake controller of an elevator
according to a second embodiment of the invention, and Figs. 4 and 5 are views for
describing operation of the control circuit;
Fig. 6 is a block diagram showing a control circuit of a brake controller of an elevator
according to a third embodiment of the invention, and Fig. 7 is a view for describing
operation of the control circuit;
Fig. 8 is a flowchart showing procedures for measuring inductance of a brake coil,
and Fig. 9 is a descriptive view; and
Fig. 10 is a block diagram showing a control circuit of a brake controller of a related-art
elevator, and Fig. 11 is a view for describing operation of the control circuit.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0043] In order to describe the invention in more detail, the invention will be described
by reference to the accompanying drawings.
[0044] Figs. 1 and 2 show a first embodiment of a brake controller of an elevator according
to the invention. Fig. 1 is a block diagram showing a control circuit of a brake.
In the illustration, reference numeral 1 designates a car; 2 designates a sheave of
a hoisting machine; 3 designates a main cable passed around the sheave 2; 4 designates
a counterweight suspended by the main cable 3 with the car 1 in the manner of a windlass;
5 designates a hoisting motor which rotatively drives the sheave 2 via a shaft 5a;
and 6 designates a brake wheel coupled directly to the shaft 5a.
[0045] Reference numeral 7 designates a spring which presses and brings a brake shoe 9 against
and into pressing contact with an outer peripheral surface of the brake wheel 6 via
a brake lever 8 at all times, thereby producing braking force from frictional force.
Reference numeral 10 designates a motor control circuit for controlling the hoisting
motor 5. Reference numeral 16 designates a brake coil; and 17 designates an armature
which opposes the brake coil 16 with an air gap "g" interposed between the armature
and the brake coil and which is attracted by the brake coil 16 against the force of
the spring 7 by means of energization of the brake coil 16. By means of attracting
action, pressure exerted to press the brake shoe 9 against the brake wheel 6 is released.
When the brake coil 16 is de-energized, the spring 7 releases the armature 17 from
the attracted state. Reference numeral 18 designates a brake switch which is closed
when the armature 17 is attracted, thereby sensing completion of release of the braking
force; and 19 designates a current sensor for sensing the brake coil current Ib.
[0046] Reference numeral 30 designates a brake control circuit which controls energization
and de-energization of the brake coil and is constituted in the following manner.
Reference numeral 31 designates a mode controller for controlling energization of
the brake coil 16; and If*, Ih*, and I0* designate target values of the brake coil
current Ib. If* takes an attracting current as a target value; Ih* takes a holding
current as a target value; and I0* takes a value of zero as a target value. Reference
numeral 32 designates a changeover switch for selecting any one from the target values
If*, Ih*, and I0* of the brake coil current Ib. Reference numeral 33 designates a
subtracter for computing a difference between the target value If* and the brake current
Ib, a difference between the target value Ih* and the brake current Ib, and a difference
between the target value I0* and the brake current Ib. Reference numeral 34 designates
a current controller for performing control operation such that the brake current
Ib assumes any one of the target values If*, Ih* and I0* on the basis of the difference.
[0047] Reference numeral 35 designates a differentiating circuit for computing a differential
value of the brake current Ib; and 36 designates a reference voltage circuit which
outputs a threshold value and is usually set to zero. Reference numeral 37 designates
a comparator for outputting a positive saturation voltage when the differential value
is greater than a threshold value.
[0048] Reference numerals 38 and 39 designate control voltage circuits for outputting voltage
values V1 and V2 used for energizing the brake coil 16 after a stop signal has been
issued from the motor control circuit 10. V1 is set to a value of zero; and V2 designates
a pulse-like voltage which is increased in response to a stop signal and reduced after
lapse of a predetermined period of time since the brake switch 18 was released. V1
is set to a high constant voltage within a range in which the armature 17 is not attracted
again. Here, the control voltage circuit 38 corresponds to first brake coil control
means, and the control voltage circuit 39 corresponds to second brake coil control
means.
[0049] Reference numeral 40 designates a changeover switch which is connected to the control
voltage circuit 38 at all times and switched to the control voltage circuit 39 by
means of a positive saturation voltage output from the comparator 37; and 41 designates
a changeover switch which is switched by the mode controller 34 and connected selectively
to the current controller 34 or an output terminal c0 of the changeover switch 40,
thereby outputting a coil control signal E*.
[0050] Reference numeral 50 designates a brake drive circuit which energizes the brake coil
16 and is constituted in the following manner. Reference numeral 51 designates a d.c.
power supply for energizing the brake coil 16; and 52 designates a chopper circuit
which outputs a variable d.c. voltage and constitutes the circuit for energizing the
brake coil 16. Reference numeral 53 designates a branch circuit connected in parallel
with the brake coil 16. Here, the branch circuit 53 is constituted of a diode. When
the chopper circuit 52 interrupts energization of the brake coil 16, the brake coil
current Ib is circulated. Reference numeral 54 designates a PWM signal generator which
is connected to the changeover switch 41 and produces a PWM signal corresponding to
the coil control signal E*; and 55 designates a base driver which controls activation
and deactivation of the chopper circuit 52 by means of the PWM signal.
[0051] Operation of the brake controller will now be described by reference to Fig. 2.
1. Mode 0 (a3, b1, c1)
[0052] When the car 1 remains stationary, the changeover switch 32 is switched to a terminal
a3, and the changeover switch 41 is switched to a terminal b1. For this reason, a
coil control signal E* assumes a value of 0, and the brake coil 16 is de-energized.
2. Mode 1 (a1, b1, c1)
[0053] When the motor control circuit 10 issues a start signal, the changeover switch 41
is switched to a terminal a1 by a mode controller 31, thereby selecting the target
value If*. The coil control signal E* corresponding to the target value If* is output,
whereby the brake coil current Ib rises from time t11. Attracting force fc is also
increased gradually. At time t12, the attracting force fc becomes equal to force fs
of the spring 7. The armature 17 is attracted as a result of further energization
of the brake coil, and the brake coil current Ib is temporarily decreased. The reason
for this is that the inductance L of the brake coil 16 is increased as a result of
a decrease having arisen in the air gap "g" in association with attraction of the
armature 17. Another reason is responsible for speed electromotive force. When attraction
of the armature 17 is completed, the brake coil current Ib is increased gradually
with the inductance L yielded in that state.
[0054] When the brake coil current Ib has reached the attraction current If at time t13,
the coil control signal E* is decreased, whereby the brake coil current Ib is maintained
at the attraction current If.
3. Mode 2 (a2, b1, c1)
[0055] At time t14, which is achieved after lapse of a predetermined period of time since
the brake switch 18 was closed as a result of attraction of the armature 17, the changeover
switch 32 selects the target value Ih*. By means of such a selection operation, the
brake coil current Ib drops to the holding current Ih required to hold the armature
17 in an attracted state.
4. Mode 3 (a3, b2, c1)
[0056] When the motor control circuit 10 issues the stop signal at time t15, the changeover
switch 32 selects the target value I0*, and the changeover switch 41 is connected
to a terminal b2. Since the changeover switch 40 is connected to a terminal c1 at
this time, the coil control signal E* assumes a value of 0. The brake coil current
Ib circulates through a diode 53 and is gradually decreased at a predetermined time
constant Tc, and the attracting force fc is also decreased. At time t16 the attracting
force becomes equal to the force fs of the spring 7. The brake coil current Ib is
further decreased to a level below the force fs of the spring, whereupon the armature
17 starts being disengaged from the brake coil 16. In association with movement of
the armature 17, speed electromotive force develops. The rate of decrease in the brake
coil current Ib is slowed and turns into a gradual increase.
5. Mode 4 (a3, b2, c2)
[0057] When the rate of decrease in the brake coil current Ib assumes a value of zero or
turns into an increase, the comparator 37 switches the changeover switch 40 to a terminal
c2 at time t17, and a voltage value V2 is output from the voltage circuit 39 as the
coil control signal E*. The brake coil 16 is again energized, whereupon the coil current
Ib is increased gradually. The attracting force fc is shifted substantially constant
as a result of a gradual increase in the coil current Ib. The armature 17 keeps moving
under the attracting force fc and is released at time t18. The changeover switch 40
is reset at time t19, which is achieved after lapse of a predetermined period of time
since the brake switch 18 was released, and is then connected to the terminal c1,
thereby outputting a value of 0.
6. Mode 5 (a3, b1, c1)
[0058] Mode 0 is set at time t19, and the coil current Ib is gradually decreased and assumes
a value of 0.
[0059] According to the first embodiment, when the armature 17 starts moving, the brake
coil 16 is energized at the high voltage V2 within a range in which the armature is
not again attracted, thereby producing the attracting force fc slightly smaller than
the force of the spring 7. Hence, noise generated by the force of spring 7 when the
armature is released from an attracted state can be reduced.
[0060] Figs. 3 to 5 show a second embodiment of the brake controller of the elevator according
to the invention.
[0061] In Fig. 3, those reference numerals which are the same as those shown in Fig. 1 designate
the same elements, and their explanations are omitted.
[0062] Reference numeral 60 designates a brake control circuit which controls energization
and de-energization of the brake coil and is constituted in the following manner.
Reference numeral 61 designates a pattern signal generator for outputting a ramp signal
which decreases linearly. Reference numeral 62 designates a latch circuit for holding
an output from the pattern signal generator 61 at a point in time when the comparator
37 has output a positive saturation voltage; 63 designates a differentiating circuit
for computing a differential value of the brake coil current Ib; 64 designates a proportionality
element of gain Kd; 65 designates a limiter for suppressing the armature 17 within
a range in which the armature 17 is not attracted again; and 66 designates a changeover
switch which is switched to the limiter 65 by an output from the comparator 37 and
returns to the terminal c1 after lapse of a predetermined period of time since the
brake switch 18 was released. Reference numeral 67 designates an adder for adding
an output Vp from the latch circuit 62 to an output Vd from the limiter 65, to thereby
output the coil control signal E*.
[0063] Here, the pattern signal generator 61 corresponds to first brake coil control means;
and the pattern signal generator 61, the latch circuit 62, the differentiating circuit
63, the proportionality element 64, and the limiter 65 correspond to second brake
coil control means.
[0064] Operation of the brake controller will now be described by reference to Fig. 4.
1. Operations pertaining to Mode 0, Mode 1, Mode 2, and Mode 5 are the same as those
shown in Fig. 2, and hence their explanations are omitted.
2. Mode 3 (a3, b2, c1)
When the motor control circuit 10 has issued a stop signal at time t15, the changeover
switch 32 selects the target value I0*, and the changeover switch 41 is connected
to the terminal b2, thereby outputting the ramp signal Vp of the pattern signal generator
61 as the coil control signal E*. The brake coil 16 is controlled by the ramp signal
Vp, whereby the brake coil current Ib is gradually decreased, thereby decreasing the
attracting force fc. The attracting force becomes equal to the force fs of the spring
7 at time t16, and the brake coil current Ib is further decreased. As a result, the
attracting force becomes lower than the force fs of the spring, and the armature 17
starts being disengaged from the brake coil 16. In association with movement of the
armature 17, the air gap "g" is increased, thereby producing speed electromotive force.
The rate of decrease in the brake coil current Ib is slowed and eventually turns into
a gradual increase.
3. Mode 4 (a3, b2, c2)
When the rate of decrease in the brake coil current Ib assumes a value of 0 or turns
into an increase, the comparator 37 switches the changeover switch 66 to the terminal
c2 at time t17. The latch circuit 62 holds an output Vp produced by the pattern signal
generator 61 when the comparator 37 has issued a saturation signal. Further, a differential
value of the brake coil current Ib output from the differentiating circuit 63 is limited
by the limiter 65, whereby a value Vd is output. The outputs Vp and Vd are added together,
to thereby produce the coil control signal E*. The coil control signal E* further
increases the brake coil current Ib that has turned into an increase. However, re-attraction
of the armature 17 is not intended, and hence an increase in the brake coil current
Ib has become slow and turned into an increase. By means of such a variation in the
brake coil current Ib, an output from the differentiating circuit 63 is also changed
and pulsated in the manner shown in Fig. 4.
[0065] By reference to Fig. 5, the operation of the brake controller to be performed in
mode 4 will be described in detail.
(1) τ1-τ2: By means of slowing or gradually increasing the rate of decrease in the
brake coil current Ib, the comparator 37 is activated, thereby switching the changeover
switch 66 to the limiter 65. When the brake coil current Ib starts being increased
as a result of the armature 17 being subjected to displacement, the output Vd of the
limiter 65 is also increased. The output Vd and the output Vp are added together,
to thereby produce the coil control signal E*.
(2) τ2-τ3: The limiter 65 causes the coil control signal E* to assume a constant value.
Since the brake coil current Ib is increased, the speed of disengagement of the armature
17 becomes slow.
(3) τ3-τ4: Since the coil control signal E* is limited by the limiter 65, an increase
in the brake coil current Ib is stopped, and a differential value assumes 0. When
the brake coil current Ib is decreased, the differential value becomes negative. Accordingly,
E*<Vp, and the attracting force is reduced, whereby the speed of disengagement of
the armature 17 is increased.
(4) Operation pertaining to τ4-τ5: identical with that pertaining to τ1-τ2.
(5) Operation pertaining to τ5-τ6: identical with that pertaining to τ2-τ3.
(6) Operation pertaining to τ6-τ7: identical with that pertaining to τ3-τ4.
[0066] The armature 17 is disengaged from the brake coil 16 while repeatedly performing
the same fluctuations.
[0067] According to the second embodiment, when the armature 17 starts moving, the brake
coil 16 is energized with a high voltage (Vp+Vd) within a range in which the armature
17 is not again attracted, thereby generating the attracting force fc slightly smaller
than the force fs of the spring 7. Hence, there can be reduced noise generated when
the armature 17 is released from an attracted state.
[0068] In particular, according to the second embodiment, the brake coil 16 is energized
with a differential value of the brake coil current Ib. Hence, noise can be reduced
quickly in accordance with fluctuations in the brake coil current Ib.
[0069] Figs. 6 to 9 show a third embodiment of the brake controller of the elevator according
to the invention.
[0070] In Fig. 6, those reference numerals which are the same as those shown in Fig. 1 or
3 designate the same elements, and their explanations are omitted.
[0071] Reference numeral 71 designates a model circuit which simulates the brake coil 16
through use of the resistance R of the brake coil 16 and the inductance L obtained
at the time of attraction of the armature 17. The model circuit outputs a model current
Ihat on the basis of the output Vd from the differentiating circuit 63 and the proportionality
element 64. Reference numeral 72 designates a subtracter for determining a difference
value between the actual brake coil current Ib and the model current Ihat; and 73
designates a reference voltage circuit for outputting a reference voltage Ei. The
reference voltage circuit is for measuring the inductance L of the brake coil 16.
Reference numeral 74 designates a changeover switch which is selectively connected
to any one of the current controller 34, the adder 67, and the reference voltage circuit
73 and outputs the coil control signal E*.
[0072] Here, the pattern signal generator 61 corresponds to first brake coil control means;
and the pattern signal generator 61, the latch circuit 62, the differentiating circuit
63, the proportionality element 64, and the model circuit 71 correspond to second
brake coil control means.
[0073] Reference numeral 80 designates a CPU; 81 designates ROM in which is stored a program
to be used for computing the inductance L of the brake coil 16; 82 designates RAM
for storing temporary data; and 83 designates an input/output device.
[0074] Operation of the brake controller will now be described by reference to Fig. 7.
1. Operations pertaining to a period of Mode 1 to Mode 3 and that pertaining to a
period of Mode 5 are identical with those shown in Fig. 4, and their explanations
are omitted.
2. Mode 4 (a3, b2, c2)
When the rate of decrease in the brake coil current Ib has assumed a value of 0 or
turned into an increase, the comparator 37 switches the changeover switch 66 to the
terminal c2 at time τ21. The connected status of the changeover switch is maintained,
and the latch circuit 62 holds the output Vp from the pattern signal generator 61
at time τ21. The subtracter 72 computes a difference value (Ib-Ihat) between the brake
coil current Ib and the model current Ihat produced by the model circuit 71. The difference
value (Ib-Ihat) is output as the value Vd by way of the differentiating circuit 63
and the proportionality element 64. The output Vd is added to the output Vp by the
adder 67, to thereby produce the coil control signal E*.
[0075] Operation of the brake controller in Mode 4 will be described in detail by reference
to Fig. 7.
(1) τ21-τ22: The armature 17 starts becoming displaced, and the difference value (Ib-Ihat)
is also increased as a result of slowing of the rate of decrease in the brake coil
current Ib or a gradual increase in the same. The output Vd proportional to a differential
value is added to the output Vp, thereby producing the coil control signal E*. Hence,
the attracting force is increased, whereby the speed of disengagement of the armature
17 is decreased.
(2) τ22-τ23: When the speed of disengagement of the armature 17 is decreased, the
speed electromotive force developing in the brake coil 16 is also decreased. For this
reason, the brake coil current Ib is decreased, and the difference value (Ib-Ihat)
between the brake coil current Ib and the model current Ihat is also decreased. For
this reason, the coil control signal E* is decreased, which in turn results in a decrease
in attracting force. Accordingly, the speed of disengagement of the armature 17 is
increased.
(3) τ23-τ24: When the speed of disengagement of the armature 17 is increased, the
difference value (Ib-Ihat) is increased again, whereby the coil control signal E*
is increased. As a result, the attracting force is increased, whereby the speed of
disengagement of the armature 17 is decreased.
(4) Operation pertaining to τ24-τ25: identical with that pertaining to (τ22-τ23),
and its explanation is omitted.
[0076] The above-described operations are repeated, whereby the armature 17 is released
from an attracted state.
[0077] Measurement of the inductance L of the brake coil 16 will now be described by reference
to Figs. 8 and 9.
[0078] In step S11, a determination is made as to whether or not the brake coil current
Ib has reached the holding current Ih. In step S12, the changeover switch 74 is connected
to the reference voltage circuit 73. The reference voltage Ei is applied in a stepped
manner to the brake coil 16. In step S13, the time "t"; that is, time T31 shown in
Fig. 9, is recorded in the memory T1. The brake coil current Ib is increased gradually,
and an increment ΔI is computed in step S14. In step S15, a determination is made
as to whether or not the increment ΔI has reached a value which is computed from the
target value Ii of the brake coil Ib corresponding to the reference voltage Ei, by
means of an equation of 0.632x(Ii-Ih). If the value has been reached, the time "t";
that is, time T32 shown in Fig. 9, is recorded in the memory T2. In step S17, a difference
between the data stored in the memory T2 and those stored in the memory T1; that is,
the time constant Tc of the brake coil 16, is determined. In step S18, the inductance
L can be determined from a product of the time constant Tc and the resistance R of
the brake coil 16.
[0079] Here, a previously-measured value may be used for the resistance R. However, in consideration
of a change in temperature, in the third embodiment the resistance R is determined
from the coil control signal E* obtained when the brake coil current Ib has reached
the holding current Ih.
[0080] As mentioned above, even in the third embodiment, when the armature 17 starts moving,
the brake coil 16 is energized within a range in which the armature 17 is not attracted
again. Hence, there can be reduced noise generated by the force of the spring 7 required
at the time of disengagement of the armature from an attracted state.
[0081] In particular, the model circuit 71 simulates the brake coil 16 remaining in the
state in which the armature 17 is attracted. Hence, the inductance L is eventually
that achieved in the attracted state. Accordingly, the coil control signal E* can
be computed from an increment (Ib-Ihat) of the brake coil current Ib determined by
the speed of movement of the armature 17. A vibration component of the coil control
signal E* can be suppressed, thereby rendering the speed of movement of the armature
17 smooth.
[0082] In the third embodiment, actually-measured values are adopted as the resistance R
and inductance L of the model circuit 17. Even when changes in temperature have arisen,
effective reduction of noise can be achieved.
INDUSTRIAL APPLICABILITY
[0083] As has been mentioned, an elevator brake controller of the invention can be widely
used with a so-called drum-type elevator brake. In this brake, an armature is attracted
against the force of a spring when a brake coil is energized, and a brake shoe remaining
in pressed contact with a brake wheel is then released from a pressed state by means
of attraction. When energization of the brake coil is interrupted, the armature is
released from an attracted state. The brake shoe is pressed by the force of the spring,
thereby producing braking force. In particular, the brake controller is suitable for
use with a brake which applies strong pressure to a brake shoe by increasing the force
of the spring required to produce required braking force in association with downsizing
of a brake itself.
[0084] The brake controller is also suitable for use with an elevator in which a hoisting
machine is installed in a hoistway and involves a high probability of propagation
of operating sound of a brake to a car.
[0085] The brake controller is further suitable for use with an elevator installed in an
apartment building; particularly, in an environment in which noise presents problems.