The present invention relates to an elevator braking apparatus that applies braking to a car driving electric motor.

Conventional elevator braking apparatuses includes: an elevator controlling apparatus that controls speed of a car driving electric motor; an electromagnetic brake that applies braking to the car driving electric motor to decelerate and stop the car driving electric motor; and a braking controlling apparatus that controls braking force from the electromagnetic brake during a car urgent stopping command such that deceleration of the car is at a predetermined value.
The electromagnetic brake has: a brake shoe that presses due to a spring force a brake wheel that is coupled coaxially to a driving sheave onto which a main rope is wound; and a brake coil that generates an electromagnetic force that separates the brake shoe from the brake wheel when an electric current is passed therethrough. During urgent stopping commands, braking controlling apparatuses have performed control such that deceleration of the car is at a predetermined value by adjusting the electric current to the brake coil to control the braking force from the electromagnetic brake based on a speed command value and a car speed signal that are output from the elevator controlling apparatus (see Patent Literature 1, for example).
Thus, in conventional elevators, braking apparatuses have avoided imparting discomfort and irritation to users during urgent stopping commands by stopping movement of the car swiftly at a predetermined rate of deceleration without stopping abruptly.

Patent Literature 1:Japanese Patent Laid-Open No. HEI 7-157211 (Gazette)

However, in conventional techniques, there are problems such as the following:

• As the force of the spring that presses the brake shoe onto the brake wheel changes due to deterioration with age, the braking force from the electromagnetic brake when an electric current of predetermined magnitude is passed through the brake coil also changes.

The present invention aims to solve the above problems and an object of the present invention is to provide an elevator braking apparatus that can prevent deterioration in control of deceleration of a car during emergency stopping of the car even if braking forces from an electromagnetic brake fluctuate as a result of deterioration in force from a spring with age.

In order to achieve the above object, according to one aspect of the present invention, there is provided an elevator braking apparatus including: an electromagnetic brake that has: a brake shoe that is disposed so as to be able to contact with and separate from a brake drum that is coupled coaxially to a car driving electric motor that raises and lowers a car; a spring that presses the brake shoe against the brake drum to apply braking to the car driving electric motor; and a brake coil that constitutes an electromagnet that generates an electromagnetic force that separates the brake shoe from the brake drum in opposition to force from the spring; a braking controlling apparatus that separates the brake shoe from the brake drum by supplying a braking releasing electric current that has a value I0 so as to flow to the brake coil when releasing a braking force on the car driving electric motor during normal operation of the car, and that controls the braking force that acts on the car driving electric motor by adjusting the electric current to the brake coil such that deceleration of the car is at a predetermined value during emergency stopping of the car, the elevator braking apparatus being characterized in including: a braking information acquiring apparatus that detects a braking release time during release of the braking force that acts on the car driving electric motor from when supply of the braking releasing electric current to the brake coil is started until the braking force that acts on the car driving electric motor is released, the braking controlling apparatus controlling the braking force that acts on the car driving electric motor during emergency stopping of the car by adjusting the electric current to the brake coil such that deceleration of the car during emergency stopping of the car is at a predetermined value based on the braking release time that is detected during normal operation of the car.

According to an elevator braking apparatus according to the present invention, a braking information acquiring means detects an amount of fluctuation in braking release time, which fluctuates interdependently with fluctuations in braking force that result from changes in force from a spring of an electromagnetic brake, during normal operation of a car, and a braking controlling apparatus controls a braking force that acts on a car driving electric motor by adjusting electric current to a brake coil based on the braking release time such that deceleration of the car is at a predetermined value. Consequently, control of the deceleration of the car during emergency stopping of the car can be prevented from deteriorating even if the force from the spring fluctuates due to aging.

• Figure 1 is an overall block diagram of an elevator that has a braking apparatus according to Embodiment 1 of the present invention;
• Figure 2 is a block diagram of the elevator braking apparatus according to Embodiment 1 of the present invention;
• Figure 3 is a graph that explains an operation in which the elevator braking apparatus according to Embodiment 1 of the present invention detects build-up time and braking release time;
• Figure 4 is an overall block diagram of an elevator that has a braking apparatus according to Embodiment 2 of the present invention;
• Figure 5 is a block diagram of the elevator braking apparatus according to Embodiment 2 of the present invention;
• Figure 6 is a graph that explains an operation in which the elevator braking apparatus according to Embodiment 2 of the present invention detects braking release time, and corresponds to Figure 3; and
• Figure 7 is a graph that explains another method by which the elevator braking apparatus according to Embodiment 2 of the present invention detects build-up time.

Preferred embodiments of the present invention will now be explained using drawings.

Figure 1 is an overall block diagram of an elevator that has a braking apparatus according to Embodiment 1 of the present invention, and Figure 2 is a block diagram of the elevator braking apparatus according to Embodiment 1 of the present invention.

In Figures 1 and 2, an elevator 1 includes: a car driving electric motor 10; a driving apparatus 20 that drives the car driving electric motor 10; a driving sheave 11 and a brake drum 12; a main rope 13; a car 15; a counterweight 16; an elevator controlling apparatus 30; and a braking apparatus 50A.

The driving sheave 11 and the brake drum 12 are disposed coaxially on an output shaft 10a of the car driving electric motor 10 so as to rotate together with rotation of the output shaft 10a.
A main rope 13 is wound around the driving sheave 11. The car 15 is coupled to a first end of the main rope 13, and a counterweight 16 is coupled to a second end of the main rope 13.

The elevator controlling apparatus 30 includes: a random-access memory (RAM) (not shown) that functions as a storage means; a read-only memory (ROM) (not shown) in which various kinds of control programs are stored; and an arithmetic controlling means 30a that includes a central processing unit (CPU) (not shown) that performs computation and control that are based on the control programs.
Because the driving apparatus 20 is described in Japanese Patent Laid-Open No. HEI 7-157211 (Gazette), etc., details thereof will not be described here, but the driving apparatus 20 has an inverter apparatus that drives the car driving electric motor 10, etc.

The car 15 ascends and descends inside a hoistway (not shown) by the driving sheave 11 being rotated together with the driving of the car driving electric motor 10. The elevator controlling apparatus 30 is connected so as to be able to control the driving apparatus 20. During normal operation of the car 15, the elevator controlling apparatus 30 can control torque of the car driving electric motor 10 by controlling the driving apparatus 20 such that car speed is at a desired speed.
Moreover, "normal operation" of the car 15 means operation in which the car 15 ascends and descends in response to calls.
The driving apparatus 20 and the car driving electric motor 10 are driven by a commercial power supply 19.

The braking apparatus 50A includes: an encoder 51; an onboard weight detector 52; an electromagnetic brake 60; a braking controlling apparatus 70; a braking information acquiring apparatus 80; and an electric power supplying apparatus 90. The elevator controlling apparatus 30 also serves some of the functions of the braking apparatus 50A.

The electric power supplying apparatus 90 has a voltage converting portion 91 and a battery 92. The voltage converting portion 91 converts alternating-current voltage that is supplied from the commercial power supply 19 into a voltage that is used by the braking apparatus 50A. The converted voltage is supplied to the braking apparatus 50A.
If a power outage occurs, a voltage from the battery 92 is supplied to the voltage converting portion 91 instead of the voltage from the commercial power supply 10. The voltage converting portion 91 converts the voltage from the battery 92 into the voltage that is used by the braking apparatus 50A. The converted voltage is supplied to the braking apparatus 50A.

The encoder 51 and the onboard weight detector 52 are connected to the elevator controlling apparatus 30. The encoder 51 outputs a pulse signal that corresponds to a rotational speed of the car driving electric motor 10. The elevator controlling apparatus 30 computes the car speed from the pulse signal that is output from the encoder 51. in addition, the elevator controlling apparatus 30 is able to ascertain the weight inside the car 15 using a detection signal for the weight inside the car 15 that the onboard weight detector 52 outputs.

If an emergency stopping command is input for the car 15, the elevator controlling apparatus 30 decelerates the car 15 at a predetermined rate of deceleration based on car speed and the weight inside the car 15, and sets a speed pattern for which the car speed is zero.
Moreover, the emergency stopping command is issued from respective apparatuses if a power outage detecting apparatus of the commercial power supply 19 detects a power outage for any reason during operation of the elevator 1, or if a safety apparatus such as a governor (not shown) is activated, or if an earthquake detecting apparatus is activated, for example.
The elevator 1 is configured such that the supply of electric power that acts on the car driving electric motor 10 is interrupted if the emergency stopping command is issued.

The electromagnetic brake 60 includes: a brake shoe 65; a spring 63; and an electromagnet 61 that has a brake coil 62.
The spring 63 is a helical spring, for example, and the brake shoe 65 is disposed on one end of the spring 63. The spring 63 is supported at a position at which the brake shoe 65 is pressed onto the brake drum 12, and braking force on the car driving electric motor 10 is generated by friction between the brake shoe 65 and the brake drum 12.

The electromagnet 61 generates an electromagnetic force in a direction in which the brake shoe 65 separates from the brake drum 12 in opposition to the force of the spring 63 when electric power is being supplied to the brake coil 62.
Here, the electromagnetic force that is generated in the electromagnet 61 changes in response to the electric current value that flows to the brake coil 62.

The braking information acquiring apparatus 80 includes an electric current detecting means 81, a braking release detecting switch 82, and a braking information computing apparatus 83.
The electric current detecting means 81 is connected to the brake coil 62 and detects the electric current that flows to the brake coil 62. The braking release detecting switch 82 switches output when the brake shoe 65 is separated from the brake drum 12. In other words, the braking release detecting switch 82 detects a state in which the braking force that acts on the car driving electric motor 10 is released.

The braking information computing apparatus 83 is connected to the elevator controlling apparatus 30, and the electric current detecting means 81 and the braking release detecting switch 82 are connected to the braking information computing apparatus 83. Details will be described below, but the braking information computing apparatus 83 computes build-up time and braking release time based on signals that are output from the electric current detecting means 81, the braking release detecting switch 82, and the elevator controlling apparatus 30 whenever the car 15 starts moving during normal operation of the car 15, in other words, when the braking force that acts on the car driving electric motor 10 is released.

The braking controlling apparatus 70 includes an adder 71, a coil current setting portion 72, and a coil current controlling portion 73.
The adder 71 computes the difference between the car speed that is output from the elevator controlling apparatus 30 and the speed command value that is based on the speed pattern.

The coil current setting portion 72 has an arithmetic controlling means 72a that has a similar configuration to the arithmetic controlling means 30a. An electric current command value that defines the magnitude of the electric current that is passed to the brake coil 62 is set based on the output from the adder 71 and the build-up time and the braking release time that are output from the braking information computing apparatus 83.

The coil current controlling portion 73 includes: an arithmetic controlling means 73a that has a configuration that is similar to that of the arithmetic controlling means 30a; and a coil current controlling circuit 73b that is configured so as to be able to vary the electric current to the brake coil 62.

During normal operation of the car 15, the coil current controlling portion 73 applies braking to the car driving electric motor 10, or releases the braking, by controlling the electric current that flows to the brake coil 62 based on the coil electric current command value that is output from the elevator controlling apparatus 30.
If an emergency stopping command is issued for the car 15, the coil current controlling portion 73 controls the braking force from the electromagnetic brake 60 that acts on the car driving electric motor 10 by controlling the electric current that flows to the brake coil 62 based on the coil electric current command value that is output from the coil current setting portion 72.

Next, operation of a braking apparatus 50A that is configured as described above will be explained.
Figure 3 is a graph that explains an operation in which the elevator braking apparatus according to Embodiment 1 of the present invention detects build-up time and braking release time.
Figure 3 shows time variation in the coil electric current command value that the elevator controlling apparatus 30 outputs when movement of the car 15 starts during normal operation of the car 15, time variation in the electric current value of the brake coil 62 that is controlled by the coil current controlling portion 73 based on the coil electric current command value, and time variation in the output from the braking release detecting switch 82.

First, operation of the braking apparatus 50A during normal operation will be explained.
As the car 15 is brought to a scheduled floor, the elevator controlling apparatus 30 interrupts the supply of electric power that acts on the car driving electric motor 10, and also outputs a coil electric current command value for interrupting the electric current to the brake coil 62 to the coil current controlling portion 73 and the braking information computing apparatus 83. The coil current controlling portion 73 applies braking to the car driving electric motor 10 by interrupting the electric current to the brake coil 62 to reliably restrict movement of the car 15.

Next, when starting movement of the car 15 toward a destination floor, the elevator controlling apparatus 30 outputs to the coil current controlling portion 73 a coil electric current command value that changes according to the pattern that is shown in Figure 3. The pattern of the coil electric current command value is constituted by a checking pattern and a braking releasing pattern that continues from the checking pattern.

The checking pattern has the purpose of controlling the coil current controlling portion 73 such that a checking current at a predetermined peak value I1 is passed to the brake coil 62, and then the supply of electric power to the brake coil 62 is interrupted. The peak value I1 of the checking pattern is set such that the brake shoe 65 will not separate from the brake drum 12 even if the electric current to the brake coil 62 that flows in response to the checking pattern is at the peak value I1.

The braking releasing pattern that is transmitted after the checking pattern has the purpose of controlling the coil current controlling portion 73 such that a braking releasing electric current that has a magnitude 10 sufficient to release the braking that acts on the car driving electric motor 10 is passed to the brake coil 62 until the car 15 arrives at the destination floor. Moreover, when a predetermined voltage is applied to the brake coil 62 in order to pass the braking releasing electric current that is based on the braking releasing pattern to the brake coil 62, reverse electromotive force is generated in the brake coil 62 in response to the brake shoe 65 being separated from the brake drum 12. Because of this, the braking releasing electric current falls off once before reaching the magnitude I0, then builds up again to reach the magnitude I0.

When the coil current controlling portion 73 passes the checking current to the brake coil 62, as shown in Figure 3, the electric current that actually flows to the brake coil 62 requires time from the start of supply of electric power for the checking current until a peak value level is reached. Here, the time until the electric current that flows to the brake coil 62 reaches the peak value 11 becomes more delayed as ambient temperature of the electromagnetic brake 60 increases and resistance in the brake coil 62 is increased.

The coil current command value that the elevator controlling apparatus 30 outputs and the output from the electric current detecting means 81 are input into the braking information computing apparatus 83. Here, the time at which the checking pattern of the coil current command value is input into the braking information computing apparatus 83, in other words, the time at which supply of the checking current to the brake coil 62 is started is t1. The time from when supply of the checking current to the brake coil 62 is started until a first threshold value αI1 (where α < 1) that functions as a preset build-up detection threshold value is reached is t2. The braking information computing apparatus 83 computes Ta = t2 - t1 as the build-up time.

The time at which supply of the braking releasing electric current to the brake coil 62 is started is t3. Output from the braking release detecting switch 82 is switched over at time t4. In other words, at time t4, the braking release detecting switch 82 detects a state in which the braking force that acts on the car driving electric motor 10 is released.
The braking information computing apparatus 83 computes Tb = t4 - t3 as the braking release time.

The braking information computing apparatus 83 outputs the build-up time Ta and the braking release time Tb to the braking controlling apparatus 70.
In the coil current setting portion 72 of the braking controlling apparatus 70, the build-up time Ta and the braking release time Tb are updated and stored each time the build-up time Ta and the braking release time Tb are input.

Next, operation of the braking apparatus 50A when any kind of abnormality arises in the elevator 1 that should make the car 15 perform emergency stopping will be explained.

When an emergency stopping command is issued due to any kind of abnormality, power supply to the car driving electric motor 10 is interrupted automatically. Then, the elevator controlling apparatus 30 sets the speed pattern to decelerate the car 15 at a predetermined speed based on the car speed when the abnormality occurs and the weight inside the car 15. The elevator controlling apparatus 30 transmits a speed command value that is based on the present car speed and the speed pattern to the adder 71 of the braking controlling apparatus 70.

In the adder 71, the difference between the speed command value and the car speed value is found, and the value of the difference between the speed command value and the car speed value is input into the coil current setting portion 72. In the coil current setting portion 72, the coil current command value is set based on the value of the difference between the speed command value and the car speed value, the build-up time Ta, and the braking release time Tb as follows:

Here, an initial state of the electromagnetic brake 60 is designated as a state in which the spring 63 presses the brake shoe 65 with a predetermined force F when the ambient temperature of the electromagnetic brake 60 is at a reference temperature Tm, and the electric current to the brake coil 62 is interrupted. When emergency stopping of the car 15 is performed, the braking controlling apparatus 70 passes a cyclic pulsed current, for example, to the brake coil 62 to control the braking force from the electromagnetic brake 60. If the electromagnetic brake 60 is in the initial state, when the electric current to the brake coil 62 is controlled based on the coil current command that is set to the reference current command value la, braking force from the electromagnetic brake 60 is exerted that decelerates the car 15 at a predetermined rate of deceleration.
Hereinafter, the electric current to the brake coil 62 that is controlled based on the reference current command value Ia when the electromagnetic brake 60 is in the initial state is designated as a reference current Ib.

If the electromagnetic brake 60 is in the initial state, and the electric current to the brake coil 62 is interrupted, and the brake shoe 65 presses the brake drum 12 with a predetermined force F, the braking release time when the braking releasing electric current of magnitude I0 is passed to the brake coil 62 is a reference braking release time T2. In addition, the build-up time for the brake coil 62 when the electromagnetic brake 60 is in the initial state is a reference build-up time T1.

The coil current setting portion 72 compares the build-up time Ta and the reference build-up time T1.
If the build-up time Ta is greater than the reference build-up time T1, the magnitude (the average value) of the electric current when the electric current to the brake coil 62 is controlled based on the reference current command value Ia is reduced below the magnitude of the reference current Ib.

If the build-up time Ta is less than the reference build-up time T1, the magnitude of the electric current when the electric current to the brake coil 62 is controlled based on the reference current command value Ia is increased to greater than the magnitude of the reference current Ib.
Moreover, the ambient temperature of the electromagnetic brake 60 is changed, and for each ambient temperature that is changed, the data of the brake coil 62 and the build-up time when the checking current is passed to the brake coil 62 are measured in advance. Data of electric current characteristics of the brake coil 62 that correspond to the build-up time are stored in the coil current setting portion 72. The coil current setting portion 72 estimates the magnitude of the electric current Ic that actually flows to the brake coil 62 in the present state from the electric current characteristics of the brake coil 62 for the build-up time from the build-up time Ta even if the build-up time Ta is greater than the reference build-up time T1 and the build-up time Ta is less than the reference build-up time T1. In addition, the coil current setting portion 72 stores a value that is obtained by subtracting the magnitude of the electric current lc from the magnitude of the reference current Ib as a correcting amount Ie1.
If the build-up time Ta equals the reference build-up time T1, the coil current setting portion 72 sets the correcting amount Ie1 to 0.

Here, the braking release time Tb fluctuates interdependently with fluctuations in the force of the spring 63, and also fluctuates interdependently with ambient temperature fluctuations of the electromagnetic brake 60.
The amount of fluctuation td in the braking release time Tb that results from the ambient temperature fluctuations of the electromagnetic brake 60 in such cases is approximately proportional to (Ta - T1)*I0/I1/α.
The coil current setting portion 72 computes Tc = Tb - td as an estimated braking release time.
The estimated braking release time Tc is a value that is estimated with the ambient temperature of the electromagnetic brake 60 in the present state set as the reference temperature Tm when the braking release time Tb is measured.

Next, the coil current setting portion 72 compares the estimated braking release time Tc and the reference braking release time T2.
If the estimated braking release time Tc is greater than the reference braking release time T2, the brake shoe 65 presses the brake drum 12 with a force that is greater than the spring force F during interruption of the electric current to the brake coil 62.

The characteristics of the braking release time when the force of the spring 63 is changed are measured in advance when the ambient temperature of the electromagnetic brake 60 is at the reference temperature Tm, and the characteristics of the braking release time for the force of the spring 63 are stored in the coil current setting portion 72.
In the characteristics of the braking release time for the force of the spring 63 that are stored, the coil current setting portion 72 stores the force of the spring 63 when the estimated braking release time Tc is applied to the braking release time. The stored force of the spring 63 corresponds to the present force F1 of the spring 63.

The magnitude characteristics of the electromagnetic force of the electromagnet 61 that is generated when the magnitude of the electric current that flows to the brake coil 62 of the electromagnetic brake 60 that is in the initial state is changed are measured in advance, and the electric current that flows to the brake coil 62 and the magnitude characteristics of the electromagnetic forces of the electromagnet 61 are stored in the coil current setting portion 72. The electromagnetic force that is generated in the electromagnet 61 when the reference current Ib is supplied to the brake coil 62 of the electromagnetic brake 60 in the initial state is D1. The coil current setting portion 72 estimates an electric current value Id1 for the brake coil 62 that is required to generate an electromagnetic force in the electromagnet 61 that is greater than the electromagnetic force D1 by force F1 minus force F from the electric current that flows to the brake coil 62 and the magnitude characteristics of the electromagnetic force of the electromagnet 61. In addition, the coil current setting portion 72 stores a value that is obtained by subtracting the magnitude of the reference current Ib from the electric current value Id1 as a correcting amount le2 (> 0).

If the estimated braking release time Tc is less than the reference braking release time T2, the brake shoe 65 presses the brake drum 12 with a force that is less than the predetermined force F of the spring 63 during interruption of the electric current to the brake coil 62.
In the force of the spring 63 and the characteristics of the braking release time that are stored in advance, the coil current setting portion 72 stores the force of the spring 63 when the estimated braking release time Tc is applied to the braking release time. The stored force of the spring 63 corresponds to the present force F1 of the spring 63.

The coil current setting portion 72 estimates an electric current value ld2 for the brake coil 62 that is required to generate an electromagnetic force in the electromagnet 61 that is less than the electromagnetic force D1 by force F minus force F1. In addition, the coil current setting portion 72 stores a value that is obtained by subtracting the magnitude of the reference current Ib from the electric current value ld2 as the correcting amount le2 (< 0).
If the estimated braking release time Tc is equal to the reference braking release time T2, the coil current setting portion 72 stores 0 as the correcting amount le2.

Next, the coil current setting portion 72 outputs a coil current command value for passing to the coil current controlling portion 73 an electric current that has a magnitude that is obtained by adding the correcting amounts Ie1 and le2 to the magnitude of the reference current Ib, and the coil current controlling portion 73 controls the amount of electric current to the brake coil 62 in response to the input coil current command value.

The build-up time Ta fluctuates interdependently with changes in the ambient temperature of the electromagnetic brake 60, and the braking release time Tb fluctuates interdependently with deterioration in force from the spring 63 with age and changes in the ambient temperature of the electromagnetic brake 60. By setting the coil current command value such that an electric current flows that is obtained by adding correcting amounts Ie1 and Ie2 to the reference current Ib that are based on the changes in build-up time Ta and the braking release time Tb from the initial state, fluctuations in the braking force from the electromagnetic brake 60 that result from deterioration in the force from the spring 63 with age and changes in the ambient temperature of the electromagnetic brake 60 can be suppressed.
In other words, the car 15 decelerates and stops according to a predetermined rate of deceleration that is set by the elevator controlling apparatus 30. Moreover, it is necessary for the deceleration of the car 15 to be set to a value that stops the car 15 promptly without causing discomfort to users, i.e., approximately 1 m/sec².

According to the braking apparatus 50A according to Embodiment 1, during normal operation of the car 15, the braking controlling apparatus 70 passes to the brake coil 62 a braking releasing electric current for releasing the braking force that acts on the car driving electric motor 10. In addition, before passing the braking releasing electric current to the brake coil 62, the braking controlling apparatus 70 passes to the brake coil 62 a checking current that has a predetermined magnitude that is less than the magnitude I0 of the braking releasing electric current, and by which the electromagnetic force that is generated in the electromagnetic brake 60 does not release the braking force that acts on the car driving electric motor 10, and then interrupts the power supply to the brake coil 62.
The braking information acquiring apparatus 80 detects the build-up time from when the power supply for the checking current to the brake coil 62 is started until the magnitude of the electric current that flows to the brake coil 62 reaches a first threshold value. In addition, the braking information acquiring apparatus 80 detects the braking release time from when the checking current is supplied to the brake coil 62 until the braking force that acts on the car driving electric motor 10 is released.
During emergency stopping of the car 15, the braking controlling apparatus 70 controls the braking force that acts on the car driving electric motor 10 by adjusting the electric current to the brake coil 62 such that the deceleration of the car 15 during emergency stopping of the car 15 is at a predetermined value based on the build-up time and the braking release time detected during normal operation of the car 15.

The build-up time fluctuates interdependently with changes in the ambient temperature of the electromagnetic brake 60, and the braking release time fluctuates interdependently with deterioration in the force from the spring 63 with age. In other words, during emergency stopping of the car 15, the braking controlling apparatus 70 adjusts the electric current to the brake coil 62 such that deceleration during emergency stopping of the car 15 is at a predetermined value by allowing for fluctuations in the braking force from the electromagnetic brake 60 that result from changes in the ambient temperature of the electromagnetic brake 60 and deterioration in the force from the spring 63 with age. Control of the deceleration of the car 15 can thereby be prevented from deteriorating during emergency stopping of the car 15 even if the ambient temperature of the electromagnetic brake 60 changes or the force from the spring 63 deteriorates with age.

Figure 4 is an overall block diagram of an elevator that has a braking apparatus according to Embodiment 2 of the present invention, Figure 5 is a block diagram of the elevator braking apparatus according to Embodiment 2 of the present invention, and Figure 6 is a graph that explains an operation in which the elevator braking apparatus according to Embodiment 2 of the present invention detects braking release time, and corresponds to Figure 3.
Moreover, in Figures 4 through 6, identical numbering will be given to portions identical to those of Embodiment 1 above, and explanation thereof will be omitted.

In Figures 4 and 5, a braking apparatus 50B is configured in a similar manner to that of the braking apparatus 50A except that the braking release detecting switch 82 is omitted.

Next, operation of the braking apparatus 50B during normal operation will be explained.
Figure 6 shows time variation in the coil electric current command value that the elevator controlling apparatus 30 outputs when movement of the car 15 starts during normal operation of the car 15, time variation in the electric current value of the brake coil 62 that is controlled by the coil current controlling portion 73 based on the coil electric current command value, and the time differential value in the electric current to the brake coil 62 that corresponds to the braking releasing pattern.
In Figures 4 through 6, when starting movement of the car 15 toward a destination floor, the elevator controlling apparatus 30 outputs a coil electric current command value that is similar to that of Embodiment 1 above to the coil current controlling portion 73.
As described above, when the coil current controlling portion 73 applies a predetermined voltage to the brake coil 62 in order to pass the braking releasing electric current to the brake coil 62, reverse electromotive force is generated in the brake coil 62 in response to the brake shoe 65 being separated from the brake drum 12. This is because the spring 63 onto which the brake shoe 65 is mounted is compressed at a high speed in an axial direction of the brake coil 62. Because of this, as shown in Figure 6, when the braking force from the electromagnetic brake 60 is released, the electric current that flows to the brake coil 62 follows peculiar changes that include dropping off once and then building up again.

Now, the characteristics of the electric current that flows to the brake coil 62 and the time differential value of the electric current that flows to the brake coil 62 when a voltage that is based on the coil current command value is supplied to the brake coil 62 are measured in advance. A value (< 0) that is slightly larger than the time differential value of the electric current that flows to the brake coil 62 at the time when the electric current drops off maximally is stored in the braking information computing apparatus 83 as a drop detection reference value K.
Here, as mentioned above, the time at which the power supply of the brake coil 62 is started based on the braking releasing pattern is t3. The braking information computing apparatus 83 computes the time differential of the electric current that flows to the brake coil 62 in response to the braking releasing pattern, and detects time t5 at which the computational result reaches the predetermined drop detection reference value K that is less than 0. Moreover, the braking force from the electromagnetic brake 60 can generally be considered to be released at time t5.
The braking information computing apparatus 83 detects Tb = t5 - t3 as the braking release time.
The rest of the operation of the braking apparatus is similar to that of the braking apparatus 50A.

According to Embodiment 2, the braking information acquiring apparatus 80 detects as the braking release time Tb the time from when the braking releasing electric current is supplied to the brake coil 62 until a change in the electric current value of the brake coil 62 that corresponds to a reverse electromotive force that arises in the brake coil 62 due to the release of the braking force that acts on the car driving electric motor 10 is detected.

During emergency stopping of the car 15, the braking controlling apparatus 70 of the braking apparatus 50B allows for the detection output from the braking information acquiring apparatus 80 and adjusts the electric current to the brake coil 62 such that deceleration during emergency stopping is at a predetermined value in a similar manner to the braking controlling apparatus 70 of the braking apparatus 50A.
Consequently, similar effects to those in Embodiment 1 above can also be achieved.
In addition, because the braking release time Tb can be detected by detecting the change in the electric current value of the brake coil 62 that corresponds to a reverse electromotive force that arises in the brake coil 62 due to the release of the braking force that acts on the car driving electric motor 10, the braking release detecting switch 82 can be omitted. In other words, parts costs for the braking apparatus SOB can be reduced.

Moreover, in each of the above embodiments, the braking apparatuses 50A and 50B are explained as detecting both the build-up time Ta and the braking release time Tb during normal operation of the car 15, and allowing for the build-up time Ta and the braking release time Tb and controlling the deceleration of the car 15 so as to be at a predetermined value during emergency stopping of the car 15. However, the braking apparatuses 50A and 50B may also detect only the braking release time Tb during normal operation of the car 15, and adjust the electric current to the brake coil 62 based only on the braking release time Tb to control the deceleration so as to be at a predetermined value during emergency stopping of the car 15.

Effects that result from fluctuations in the force from the spring 36 due to aging on the braking performance of the electromagnetic brake 60 are often greater than those that result from the ambient temperature fluctuations of the electromagnetic brake 60. Consequently, even if the braking apparatuses 50A and 50B detect only the braking release time Tb during normal operation of the car 15, and allow only for the braking release time Tb to control the deceleration so as to be at a predetermined value during emergency stopping of the car 15, sufficient effects can be obtained that improve control of the braking force on the car driving electric motor 10 by the braking apparatuses 50A and 50B.

However, if the braking force from the electromagnetic brake 60 is controlled by allowing for the build-up time Ta and the braking release time Tb during emergency stopping of the car 15, as in the braking apparatus 50A, control of the braking force that acts on the car driving electric motor 10 is improved further. In other words, control of the deceleration of the car is improved further.

Braking is explained as being applied to the car driving electric motor 10 by a single electromagnetic brake 60 that has one brake shoe 65, one spring 63, and one electromagnet 61. However, braking may also be applied to the car driving electric motor 10 by two sets of electromagnetic brakes 60 by disposing an electromagnetic brake that has a similar configuration to the electromagnetic brake 60 such that the brake shoes are offset in a circumferential direction of the brake drum 12. Control over the deceleration of the car 15 is improved further by applying braking to the car driving electric motor 10 using the two sets of electromagnetic brake 60.

The braking information acquiring apparatus 80 is explained as detecting the build-up time Ta and the braking release time whenever movement of the car 15 is started during normal operation, but the build-up time Ta and the braking release time Tb may also be detected whenever movement of 15 is performed a predetermined number of times, for example.

In each of the embodiments, the build-up time Ta is explained as being detected as the time from when the checking current is supplied to the brake coil 62 until the magnitude of the checking current reaches the first threshold value αI1, but detection of the build-up time Ta is not limited thereto.
For example, during normal operation of the car 15, as shown in Figure 7, the elevator controlling apparatus 30 may also output a coil current command value that is output when the braking that acts on the car driving electric motor 10 is released from which the checking pattern is excluded. In that case, the build-up time may also be a time from when supply of the braking releasing electric current to the brake coil 62 is started until the value of the electric current that flows to the brake coil 62 reaches a second threshold value βI0 that functions as a build-up detection threshold value. Moreover, because the braking releasing electric current drops off once before reaching I0 as mentioned above, β is set so as not to be affected by this drop off in electric current.
In contrast thereto, if the build-up time is detected by supplying the checking current to the brake coil 62, the first threshold value αI1 can be set without having to consider the drop off in electric current that occurs when the braking releasing electric current is passed.