Elevator apparatus

In an elevator apparatus, a brake device is controlled by a brake control device. The brake control device is capable of performing braking force reduction control for reducing the braking force of the brake device at a time of emergency braking of a car. The brake control device monitors a running state of the car at the time of emergency braking thereof, and makes a switchover between validity and invalidity of braking force reduction control such that the car is stopped within a preset allowable stopping distance.

TECHNICAL FIELD

The present invention relates to an elevator apparatus having a brake control device capable of controlling a braking force at the time of emergency braking.

BACKGROUND ART

In a conventional elevator apparatus, at the time of emergency stop, the current supplied to a brake coil is controlled to variably control the deceleration of a car. At the time of emergency stop, a speed command based on an emergency stop speed reference pattern having a predetermined deceleration is output from a speed reference generating portion (e.g., see Patent Document 1).

Patent Document 1: JP 07-206288 A

DISCLOSURE OF THE INVENTION

Problem to be Solved by the Invention

In the conventional elevator apparatus structured as described above, changes in stopping distance in controlling the deceleration of the car at the time of emergency stop are not taken into account. Therefore, for example, should the error from the speed reference pattern increase or should the function of control itself fail to be activated properly, there would be an apprehension that the stopping distance may exceed an allowable stopping distance and that the car may plunge into each of terminal portions of a hoistway.

The present invention has been made to solve the above-mentioned problem, and it is therefore an object of the present invention to provide an elevator apparatus capable of more reliably keeping a car from reaching each of terminal portions of a hoistway while preventing the car from undergoing an excessively high deceleration at the time of emergency braking.

Means for Solving the Problem

An elevator apparatus according to the present invention includes: a car; a brake device for braking running of the car; and a brake control device for controlling the brake device, the brake control device being capable of performing braking force reduction control for reducing a braking force of the brake device at a time of emergency braking of the car, in which the brake control device monitors a running state of the car at the time of emergency braking of the car, and makes a switchover between validity and invalidity of the braking force reduction control such that the car is stopped within a preset allowable stopping distance.

BEST MODES FOR CARRYING OUT THE INVENTION

FIG. 1is a schematic diagram showing an elevator apparatus according to Embodiment 1 of the present invention. Referring toFIG. 1, a car1and a counterweight2are suspended within a hoistway by a main rope (suspension means)3to be raised/lowered within the hoistway due to a driving force of a hoisting machine4. The hoisting machine4has a drive sheave5around which the main rope3is looped, a motor6for rotating the drive sheave5, and braking means7for braking rotation of the drive sheave5.

The braking means7has a brake pulley8that is rotated integrally with the drive sheave5, and a brake device9for braking rotation of the brake pulley8. A brake drum, a brake disc, or the like is employed as the brake pulley8. The drive sheave5, the motor6, and the brake pulley8are provided coaxially.

The brake device9has a plurality of brake shoes10that are moved into contact with and away from the brake pulley8, a plurality of brake springs for pressing the brake shoes10against the brake pulley8, and a plurality of electromagnets for opening the brake shoes10away from the brake pulley8against the brake springs. The electromagnets have brake coils (electromagnetic coils)11. Each of the brake coils11is excited by being supplied with a current.

By causing a current to flow through the respective brake coils11, the electromagnets are excited, so an electromagnetic force for canceling a braking force of the brake device9is generated. As a result, the brake shoes10are opened away from the brake pulley8. By shutting off the supply of the current to the respective brake coils11, the electromagnets are stopped from being excited. As a result, the brake shoes10are pressed against the brake pulley8due to spring forces of the brake springs. In addition, the degree of opening of the brake device9can be controlled by controlling the value of the current flowing through the brake coils11.

The motor6is provided with a hoisting machine encoder12as a speed detector for generating a signal corresponding to a rotational speed of a rotary shaft of the motor6, namely, a rotational speed of the drive sheave5.

A speed governor13is installed in an upper portion of the hoistway. The speed governor13has a speed governor sheave14, and a speed governor encoder15for generating a signal corresponding to a rotational speed of the speed governor sheave14. A speed governor rope16is looped around the speed governor sheave14. The speed governor rope16is connected at both ends thereof to an operation mechanism of a safety gear mounted on the car1. The speed governor rope16is looped at the lower end thereof around a tension pulley17disposed in a lower portion of the hoistway.

The driving of the hoisting machine4is controlled by an elevator control device18. In other words, the raising/lowering of the car1is controlled by the elevator control device18. The brake device9is controlled by a brake control device19. Signals from the elevator control device18and the hoisting machine encoder12are input to the brake control device19.

FIG. 2is a block diagram showing the brake control device19ofFIG. 1. The brake control device19has a command generating portion21, a safety determining portion22, a first safety relay23, and a second safety relay24.

The command generating portion21determines whether or not the brake device9is in an emergency braking state, based on a signal S1from the elevator control device18. Also, the command generating portion21detects (calculates) a speed of the car1and a deceleration of the car1based on a signal S2from the hoisting machine encoder12. In addition, when the brake device9is in the emergency braking state, the command generating portion21generates a command to be given to the brake device9in accordance with the deceleration of the car1(or speed of car1). That is, the brake control device19can perform braking force reduction control for reducing the braking force of the brake device9to prevent the car1from undergoing an excessively high deceleration at the time of emergency braking.

The safety determining portion22determines whether or not the brake device9is in the emergency braking state, based on the signal S1from the elevator control device18. Also, the safety determining portion22monitors a running state of the car1based on the signal S2from the hoisting machine encoder12at the time of emergency braking, and makes a switchover between validity and invalidity of braking force reduction control such that the car1is stopped within a preset allowable stopping distance. In Embodiment 1 of the present invention, the safety determining portion22detects and monitors the deceleration of the car1as the running state of the car1.

The opening/closing of the first safety relay23and the second safety relay24is controlled by the safety determining portion22. The first safety relay23and the second safety relay24are opened/closed in synchronization with each other. Braking force reduction control performed by the command generating portion21is validated through the closure of the first safety relay23and the second safety relay24. When braking force reduction control is valid, a brake command or a brake release command is selectively output to the brake coils11in accordance with the deceleration of the car1(or speed of car1). The first safety relay23and the second safety relay24correspond to the two brake coils11ofFIG. 1, respectively.

The brake release command during braking force reduction control at the time of emergency braking is not intended to release the brake device9completely but to reduce the braking force exerted by the brake device9to some extent. More specifically, the braking force for decelerating the brake pulley8is controlled by turning a switch for applying a voltage to the brake coils11ON/OFF with a predetermined switching duty.

Braking force reduction control performed by the command generating portion21is invalidated through the opening of the first safety relay23and the second safety relay24. When braking force reduction control is invalid, the supply of a current to the respective brake coils11is shut off regardless of a calculation result in the command generating portion21, so a total braking force is applied to the brake pulley8.

When it is determined that the brake device9is in the emergency braking state and that the car1can be stopped within the allowable stopping distance, the safety determining portion22closes the first safety relay23and the second safety relay24to validate braking force reduction control. Otherwise, the safety determining portion22opens the first safety relay23and the second safety relay24to invalidate braking force reduction control. When it is determined that the car1can be stopped within the allowable stopping distance, the safety relays23and24may be closed again even after having been opened temporarily in the course of braking force reduction control.

The functions of the command generating portion21and the safety determining portion22are realized by a single microcomputer or a plurality of micro computers. That is, programs for realizing the functions of the command generating portion21and the safety determining portion22are stored in the single micro computer of the brake control device19or in the plurality of the micro computers of the brake control device19.

FIG. 3is composed of graphs showing changes over time in braking force, deceleration, speed, and car position in a case where the brake control device19ofFIG. 2performs deceleration control at the time of emergency braking. Referring toFIG. 3, broken lines L1in each of the graphs represent a case where the car1carries a light load while traveling downward or a case where the car1carries a heavy load while traveling upward. In contradiction to the broken lines L1, alternate long and short dash lines L3in each of the graphs represent a case where the car1carries a heavy load while traveling downward or a case where the car1carries a light load while traveling upward. In addition, each of solid lines L2in the graphs represent a case where the car1carries a load somewhere between those of L1and L3regardless of the traveling direction thereof while the weight on the car1side is balanced with the weight on the counterweight2side.

When an emergency stop command is generated at a time instant T1, a braking force is generated at a time instant T2. That is, the supply of a current to the motor6is also shut off at the time of emergency braking, so the car1is either accelerated (as indicated by alternate long and short dash lines L3) or decelerated (as indicated by broken lines L1) due to an imbalance between the weight on the car1side and the weight on the counterweight2side until the braking force is actually generated (until brake shoes10come into abutment on brake pulley8) after generation of the emergency stop command.

The elevator apparatus is designed such that the car1can be stopped without reaching each of terminal portions of the hoistway even when the distance (stopping distance) to be covered before the stoppage of the car1after the start of emergency braking operation is the longest (as indicated by alternate long and short dash lines L3), unless braking force reduction control is performed. Accordingly, even when braking force reduction control is performed in the vicinity of each of terminal floors, the car1is prevented from reaching a corresponding one of the terminal portions of the hoistway if the car1is stopped at a distance shorter than the longest stopping distance. In this example, the safety determining portion22monitors the deceleration of the car1, determines whether or not the car1can be stopped within the allowable stopping distance, and opens/closes the safety relays23and24.

In the case where a determination on the opening/closing of the safety relays23and24is made on the basis of the deceleration of the car1, the safety relays23and24are closed to validate braking force reduction control only when the deceleration of the car1is higher than a reference deceleration α1ofFIG. 3. Thus, the deceleration of the car1is always held higher than the reference deceleration α1, so the car1can be stopped safely.

The reference deceleration α1needs to be set at least higher than a maximum deceleration in the case where the car1is stopped at the longest stopping distance. If the reference deceleration α1is set lower than the maximum deceleration, a braking force is reduced even when the car1is to be stopped at the longest stopping distance, so an event that the car1cannot be stopped at the envisaged longest stopping distance may occur. As a matter of course, the reference deceleration α1is set lower than a target deceleration α0during braking force reduction control.

More specifically, given that a total reduced inertial mass of the elevator apparatus with respect to the car1is denoted by m, that a maximum value of the braking force exerted by the brake device9is denoted by F1, and that a maximum acceleration force in the case where the difference in weight between the car1side and the counterweight2side is the largest is denoted by F2, the reference deceleration α1is calculated from the following equation.
α1=(F1−F2)/m

In the elevator apparatus structured as described above, at the time of emergency braking of the car1, the brake control device19monitors the running state of the car1and makes a switchover between the validity and invalidity of braking force reduction control such that the car1is stopped within the allowable stopping distance. Therefore, the car1can be kept more reliably from reaching each of the terminal portions of the hoistway while being prevented from undergoing an excessively high deceleration at the time of emergency braking.

The brake control device19monitors the deceleration of the car1as the running state of the car1, and validates braking force reduction control when the deceleration of the car1is higher than the reference deceleration α1. Therefore, the car1can be kept more reliably from reaching each of the terminal portions of the hoistway through relatively simple control.

Reference will be made next toFIG. 4.FIG. 4is composed of graphs showing changes over time in braking force, speed, and car position in a case where the brake control device19of an elevator apparatus according to Embodiment 2 of the present invention performs deceleration control at the time of emergency braking. In Embodiment 2 of the present invention, the brake control device19monitors the speed of the car1and the time elapsed after generation of an emergency stop command as a running state of the car1. The brake control device19then closes the safety relays23and24to validate braking force reduction control only when the brake device9is in an emergency braking state and the speed of the car1shown inFIG. 4is within an allowable range indicated by a hatched region. Embodiment 2 of the present invention is identical to Embodiment 1 of the present invention in other constructional details and other operational details.

Each of solid lines L1shown inFIG. 4indicates changes in a corresponding one of state quantities in the case where the car1is stopped at the longest stopping distance. Accordingly, the car1can be stopped before reaching each of the terminal portions of the hoistway by being stopped at a distance shorter than the stopping distance corresponding to the solid lines L1.

A borderline of the allowable range for validating braking force reduction control (a reference speed change curve) L2is a speed change curve in the case where the car1is stopped as an emergency measure in a certain load-carrying state without performing braking force reduction control. When the speed of the car1exceeds the borderline L2, the safety determining portion22opens the safety relays23and24. The speed of the car1cannot enter the allowable range indicated by the hatched region, which is lower than the borderline L2, unless the car1can be stopped more easily than in that load-carrying state. Accordingly, when the speed of the car1exceeds the borderline L2during the performance of braking force reduction control within the allowable range, a speed curve extending from a point on the borderline L2according to which the car1is stopped at a maximum stopping distance can be calculated on the assumption that the car1carries the load by which the borderline L2is defined.

If the speed of the car1reaches the borderline L2at a point A, the safety relays23and24are opened at a time instant T3to invalidate braking force reduction control (a forcible stop command). A braking force is then generated at a time instant T4. In this case, a speed curve is indicated by a solid line L3.

If the speed of the car1reaches the borderline L2at a point B, the safety relays23and24are opened at a time instant T5to invalidate braking force reduction control (a forcible stop command). A braking force is then generated at a time instant T6. In this case, a speed curve is indicated by broken lines L4.

In calculating a speed curve as described above according to which the car1is stopped at the longest stopping distance, an idle running time before generation of a braking force needs to be taken into account as well. The borderline L2is set such that a speed curve extending from any point on the borderline L2remains below the speed curve L1according to which the car1is stopped at the longest stopping distance. By validating braking force reduction control only when the relationship between the speed of the car1and time is within the allowable range indicated by the hatched region, the car1can be stopped within the allowable stopping distance.

In the elevator apparatus structured as described above, the speed of the car1and the time elapsed after generation of an emergency stop command are monitored as the running state of the car1, and braking force reduction control is validated when the relationship between the speed of the car1and the time is within the allowable range. Therefore, the car1can be kept more reliably from reaching each of the terminal portions of the hoistway while being prevented from undergoing an excessively high deceleration at the time of emergency braking.

Next, Embodiment 3 of the present invention will be described.

In Embodiment 2 of the present invention, the load-carrying state of the car1is assumed to be unknown, so the safety relays23and24are controlled so as to stop the car1within the allowable stopping distance even when the relationship between the load-carrying state of the car1and the running direction of the car1constitutes a condition under which the car1is stopped at the longest stopping distance. Thus, when the car1can be decelerated easily, the speed curves extending from the points A and B ofFIG. 4are indicated by, for example, a solid line L5and broken lines L6, respectively, so there is a sufficient margin between each of these speed curves and the solid line L1. Accordingly, the allowable range can be enlarged toward the solid line L1side if the easiness with which the car1is decelerated can be understood.

FIG. 5is composed of graphs showing changes over time in braking force, speed, and car position in a case where the brake control device19of an elevator apparatus according to Embodiment 3 of the present invention performs deceleration control at the time of emergency braking. The safety determining portion22determines whether or not the car1can be decelerated easily, based on information from a weighing device and a running direction of the car1. When the car1can be decelerated easily, for example, when the car1carries a light load while traveling downward or when the car1carries a heavy load while traveling upward, the reference speed change curve is changed from the borderline L2to a borderline L7to enlarge the allowable range.

If the speed of the car1reaches the borderline L7at a point C, the safety relays23and24are opened at a time instant T7to invalidate braking force reduction control (a forcible stop command). A braking force is then generated at a time instant T8. In this case, a speed curve is indicated by a solid line L8.

If the speed of the car1reaches the borderline L7at a point D, the safety relays23and24are opened at a time instant T9to invalidate braking force reduction control (a forcible stop command). A braking force is then generated at a time instant T10. In this case, a speed curve is indicated by broken lines L9.

The brake control device19closes the safety relays23and24to validate braking force reduction control only when the brake device9is in an emergency braking state and the relationship between the speed of the car1and time shown inFIG. 5is within a range indicated by a hatched region. However, in the case where it is determined that the car1can be decelerated easily, the safety relays23and24are closed to validate braking force reduction control even when the relationship between the speed of the car1and time is in a meshed region. Thus, the car1can be stopped within the allowable stopping distance. That is, the allowable range is constituted by the meshed region as well as the hatched region.

The borderline L7is set such that a speed curve extending from any point on the borderline L7remains below the speed curve L1according to which the car1is stopped at the longest stopping distance in a running state to which the borderline L7is applied. In other words, when speed change curves are drawn after having determined reference points such as the points C and D at each of the time instants, the borderline L7can be set as an aggregate of points each corresponding to a maximum speed which are on those speed change curves which always remain below the solid line L1.

In the elevator apparatus structured as described above, the degree of easiness with which the car1is decelerated is monitored in addition to the speed of the car1and the time elapsed after generation of an emergency stop command, and the allowable range is changed in accordance with the degree of easiness with which the car1is decelerated. Therefore, when the car1can be decelerated easily, the allowable range of speed and time in which braking force reduction control can be performed can be enlarged.

The aforementioned change in the allowable range may be made either in stages through staged determinations on the degree of easiness with which the car1is decelerated or continuously.

Reference will be made next toFIG. 6.FIG. 6is composed of graphs showing changes over time in braking force, speed, and car position in a case where the brake control device19of an elevator apparatus according to Embodiment 4 of the present invention performs deceleration control at the time of emergency braking. The safety determining portion22monitors whether or not the car1is being decelerated, and closes the safety relays23and24to validate braking force reduction control only when a logical conjunction of a condition that the car1is being decelerated and a condition that the relationship between the speed of the car1and time is within an allowable range indicated by a hatched region ofFIG. 6is true.

As described in Embodiment 2 of the present invention, the borderline L2of the allowable range needs to be set such that the car1can be stopped within an allowable stopping distance if the safety relays23and24are opened when the borderline L2is exceeded during the performance of braking force reduction control within the allowable range. In Embodiment 4 of the present invention, in the case where the relationship between the speed of the car1and time is within the allowable range, a braking force is applied to the car1even when the safety relays23and24are closed if the car1is decelerated such that the laden weight of the car1and the running direction of the car1are related to each other so as to accelerate the car1. Thus, the idle running time of the car1resulting from a brake gap does not need to be taken into account in calculating the longest stopping distance.

On the contrary, when the laden weight of the car1and the running direction of the car1are related to each other so as to decelerate the car1, the car1may be decelerated with no braking force applied thereto in the idle running time resulting from the brake gap. Therefore, the idle running time of the car1needs to be taken into account in calculating the longest stopping distance.

Accordingly, when the safety relays23and24are opened during deceleration of the car1to forcibly stop the car1, the car1may be stopped at the longest stopping distance in the case where the car1is stopped without taking an idle running time into account while a force resulting from an imbalance between the weight on the car1side and the weight on the counterweight2side acts to the utmost in such a direction as to accelerate the car1, or in the case where the car1is stopped without taking the idle running time into account while there is no force resulting from the imbalance.

Referring toFIG. 6, broken lines L4extending from a point E and broken lines L6extending from a point F represent speed curves in the case where the car1is forcibly stopped without taking the idle running time into account while the force resulting from the imbalance acts to the utmost in such a direction as to accelerate the car1. According to the broken lines L4, the safety relays23and24are opened at a time instant T11, and a braking force is generated at a time instant T12. According to the broken lines L6, the safety relays23and24are opened at a time instant T13, and a braking force is generated at a time instant T14.

In the case where speed curves as mentioned above, according to which the car1may be stopped at the longest stopping distance, are drawn while making changes in reference time instant, the borderline L2is an aggregate of points each corresponding to a maximum reference speed which are on those speed curves which always remain below the solid line L1at each of the time instants. Accordingly, the car1is stopped within the allowable stopping distance by opening the safety relays23and24to forcibly stop the car1when the borderline L2is exceeded.

In the elevator apparatus structured as described above, the speed of the car1, the time elapsed after generation of an emergency stop command, and the presence/absence of the state of deceleration of the car1are monitored, and braking force reduction control is validated when the logical conjunction of the condition that the car1is being decelerated and the condition that the relationship between the speed of the car1and time is within the allowable range (indicated by the hatched region ofFIG. 6) is true. Therefore, the allowable range of the relationship between speed and time in which braking force reduction control can be performed can be enlarged in comparison with that of Embodiment 2 of the present invention.

By combining the method of control according to Embodiment 3 of the present invention with the method of control according to Embodiment 4 of the present invention, the allowable range of speed and time in which braking force reduction control can be performed can be further enlarged in comparison with that of Embodiment 4 of the present invention. In this case, the degree of easiness with which the car1is decelerated is monitored in addition to the items monitored in Embodiment 4 of the present invention. When it is determined that the car1can be decelerated easily, the reference speed change curve is shifted toward the solid line L1side to enlarge the allowable range. Even when the speed of the car1is in a meshed region ofFIG. 6, the safety relays23and24are closed to validate braking force reduction control.

Next, Embodiment 5 of the present invention will be described. In Embodiment 5 of the present invention, the speed of the car1and the position (remaining distance) of the car1are monitored as the running state of the car1.

FIG. 7is a graph showing an example of a condition for validating braking force reduction control in the brake control device19of an elevator apparatus according to Embodiment 5 of the present invention. Referring toFIG. 7, the axis of ordinate represents the speed of the car1, and the axis of abscissa represents the remaining distance to an allowable stopping position. The safety determining portion22closes the safety relays23and24to validate braking force reduction control only when the relationship between the remaining distance and the speed of the car1is within an allowable range indicated by a hatched region ofFIG. 7.

Broken lines L2, L3, and L4ofFIG. 7represent speed curves in the case where the car1is forcibly stopped from points G, H, and J, respectively, in a load-carrying state corresponding to the longest stopping distance. A borderline L1of the allowable range is set such that the speed of the car1always becomes 0 before the remaining distance becomes 0 when the car1is forcibly stopped from a state corresponding to the borderline L1. That is, the borderline L1is set as an aggregate of points each corresponding to a maximum speed at which the car1can be stopped within the allowable stopping distance with each remaining distance in the load-carrying state corresponding to the longest stopping distance.

In the case where the car1is caused to run according to a speed command, the command speed generated by the elevator control device18is set such that the speed of the car1becomes 0 at a stop floor. Accordingly, it is also possible to estimate a minimum remaining distance to each of the terminal portions of the hoistway from a relationship between changes in command speed over time and the position of the car1on the assumption that the stop floor is a corresponding one of the terminal floors, and set the estimated remaining distance as a distance to an allowable stop position. In this case, however, the actual speed of the car1is required to follow the command speed appropriately.

On the other hand, a normal elevator apparatus has such a braking performance as can stop the car1prior to the arrival thereof at each of the terminal portions of the hoistway even in a load-carrying state corresponding to the longest stopping distance. Therefore, if the longest stopping distance at a speed at the beginning of emergency braking operation is set as a remaining distance at that time instant, the car1can be stopped without reaching that terminal portion of the hoistway.

In this case, a remaining distance x0can be calculated from the following integral equations, using a time t0required until stoppage of the car1.

The variables and the constants will now be described below. A total reduced inertial mass of the elevator apparatus with respect to the car1is denoted by m. An acceleration of the car1is denoted by α(t). A braking force exerted by the brake device9is denoted by F(t). A maximum acceleration force in the case where there is a maximum difference between the weight on the car1side and the weight on the counterweight2side is denoted by F2. A speed of the car1at the beginning of emergency braking operation is denoted by v0. However, if the brake device9is designed to exert a braking force ensuring a certain margin with respect to an allowable stopping distance, a remaining distance having a certain margin with respect to an allowable stop position is calculated.

In the elevator apparatus structured as described above, the speed of the car1and the remaining distance to each of the terminal portions of the hoistway or to the allowable stop position are monitored as the running state of the car1, and braking force reduction control is validated when the relationship between the speed of the car1and the remaining distance is within a preset allowable range. Therefore, the car1can be kept more reliably from reaching each of the terminal portions of the hoistway while being prevented from undergoing an excessively high deceleration at the time of emergency braking. Further, braking force reduction control can be performed in a larger number of cases.

Reference will be made next toFIG. 8.FIG. 8is a graph showing an example of a condition for validating braking force reduction control in the brake control device19of an elevator apparatus according to Embodiment 6 of the present invention. In this example, as described in Embodiment 3 of the present invention, the degree of easiness with which the car1is decelerated is monitored in addition to the items monitored in Embodiment 5 of the present invention. When it is determined that the car1can be decelerated easily, the allowable range is enlarged to a meshed region ofFIG. 8. Even when the relationship between the speed of the car1and the remaining distance is in the meshed region ofFIG. 8, the safety relays23and24are closed to validate braking force reduction control.

A borderline L11of the allowable range in this case is set as an aggregate of points each corresponding to a maximum speed at which the car1can be stopped within an allowable stopping distance with each remaining distance in an understood load-carrying state. Thus, the allowable range of speed and remaining distance in which braking force reduction control can be performed can be further enlarged in comparison with that of Embodiment 5 of the present invention.

In each of the foregoing examples, it is determined based on a signal from the elevator control device18whether or not the car1is in an emergency braking state. However, the brake control device19may independently determine whether or not the car1is in the emergency braking state, without resort to the signal from the elevator control device18. For example, the determination on the emergency braking state of the car1may be made by detecting approach of the brake shoes10to the brake pulley8or contact of the brake shoes10with the brake pulley8. Alternatively, it is possible to determine that the car1is in the emergency braking state, when the current value of each of the brake coils11is smaller than a predetermined value although the speed of the car1is equal to or higher than a predetermined value.

In each of the foregoing examples, the speed of the car1, the deceleration of the car1, the position of the car1, or the like is calculated using a signal from the hoisting machine encoder12. However, a signal from another sensor such as the speed governor encoder15, an acceleration sensor mounted on the car1, or a position sensor mounted on the car1may be used instead.

Further, although the safety determining portion22is designed to open/close the safety relays23and24in each of the foregoing examples, a command to generate/stop a command may be transmitted to the command generating portion21from the safety determining portion22.

Still further, the safety determining portion22and the command generating portion21may be constructed separately from each other.