EP3954641A1

EP3954641A1 - A method for testing machinery brakes in an elevator

Info

Publication number: EP3954641A1
Application number: EP20190818.3A
Authority: EP
Inventors: Juha-Matti Aitamurto; Ari Kattainen
Original assignee: Kone Corp
Current assignee: Kone Corp
Priority date: 2020-08-13
Filing date: 2020-08-13
Publication date: 2022-02-16
Anticipated expiration: 2040-08-13
Also published as: CN114074870A; EP3954641B1

Abstract

The elevator comprises a car (10), an electric motor (32), a drive unit (31), and a machinery brake (100). The method comprises moving the car in accordance with a drive profile by adjusting a drive torque of the electric motor, generating a brake dropping command, monitoring the drive torque, and if the drive torque does not follow a desired drive torque change pattern during a predefined time period, indicating that the machinery brake does not work properly, else indicating that the machinery brake works properly.

Description

FIELD

The invention relates to a method for testing machinery brakes in an elevator.

BACKGROUND

An elevator may comprise a car, a shaft, hoisting machinery, hoisting ropes, and a counterweight. A separate or an integrated car frame may surround the car.
The hoisting machinery may be positioned in the shaft. The hoisting machinery may comprise an electric drive, a traction sheave, and a machinery brake. The electric drive may comprise an electric motor and a drive unit controlling the electric motor. The car frame may be connected by the hoisting ropes via the traction sheave to the counterweight. The electric motor may rotate the traction sheave for moving the car upwards and downwards in the shaft. The machinery brake may stop the rotation of the traction sheave and thereby the movement of the elevator car.
The car frame may be supported with guide means at guide rails extending in the vertical direction in the shaft. The guide rails may be attached with fastening brackets to the side wall structures in the shaft. The guide means keep the car in position in the horizontal plane when the car moves upwards and downwards in the shaft. The counterweight may be supported in a corresponding way on guide rails that are attached to the wall structure of the shaft.
The car may transport people and/or goods between the landings in the building. The shaft may be formed so that the wall structure is formed of solid walls or so that the wall structure is formed of an open steel structure.
The machinery brake may be formed of at least one electromechanical brake. The machinery brake forms a safety device of the elevator. The machinery brake applies braking force to the traction sheave or to a rotating axis of the hoisting machinery in order to stop the movement of the hoisting machinery and thereby also the movement of the elevator car. A machinery brake may comprise at least two brakes, e.g. two, three or four brakes. The machinery brake should according to EN 81-20:2014 be dimensioned so that it is able to stop the elevator machinery when the car is travelling downwards at rated speed and with the rated load plus an overload of 25% i.e. with a load of 125%. If one brake fails, then the other brake should still be able to decelerate, stop and hold an elevator car standstill with the rated load i.e. with a load of 100% The machinery brake forms a safety device in the elevator and should therefore be tested periodically to ensure that it is working properly.
The electromagnetic brake may comprise a frame part and an armature part being movably attached to the frame part. Spring means may be arranged to operate between the frame part and the armature part for pushing the armature part away from the frame part when the machinery brake is activated. A brake shoe acting on a rotating brake surface may be attached to the armature part. The rotating brake surface may be connected to the traction sheave. The brake shoe is pushed against the rotating brake surface when the machinery brake is activated. Electromagnet means may further be arranged in the frame part. The magnetic field of the electromagnet means pulls the armature part against the force of the spring means towards the frame part. The machinery brake is deactivated i.e. the brake shoe is drawn away from the brake surface when the electromagnet is activated. The machinery brake is on the other hand activated i.e. the brake shoe is pushed towards the brake surface when the electromagnet is deactivated. The machinery brake may be a shoe brake, a drum brake, a disk brake, or any corresponding machinery brake.
Prior art brake tests are based on the principle of opening one of the brakes in the machinery brake when the car stands at a landing. The remaining brakes in the machinery brake will thus be subject to a force originating from either the gravity (the unbalance between the car and the counterweight) or from the gravity and an additional force produced by the motor in the hoisting machinery. The monitoring is based on detecting a movement of the hoisting machinery in said state. The test may be carried out for each brake at a time in the machinery brake.

SUMMARY

An object of the invention is an improved method for testing machinery brakes in an elevator.
The method for testing machinery brakes in an elevator according to the invention is defined in claim 1.
The elevator comprises a car movably arranged in a shaft, an electric motor for moving the car, a drive unit for controlling the electric motor, and a machinery brake for braking and holding the car.
The method for testing the machinery brakes comprises
moving the car with the electric motor in accordance with a drive profile by adjusting a drive torque of the electric motor with the drive unit,
generating a brake dropping command to the machinery brake,
monitoring the drive torque of the electric motor, and
if the drive torque of the electric motor does not follow a desired drive torque change pattern during a predefined time period starting from the generation of the brake dropping command to the machinery brake, indicating that the machinery brake does not work properly, else indicating that the machinery brake works properly.
The drive unit may calculate a drive profile for the car moving between the landings in the building. The drive unit may comprise a speed controller. The speed controller may adjust the drive torque of the electric motor to implement said drive profile of the car.
The machinery brake may comprise at least two brakes, e.g. two, three or four brakes. The machinery brake should be dimensioned so that it is able to stop the elevator machinery when the car is travelling downwards at rated speed and with the rated load plus an overload of 25% i.e. with a load of 125%. If one brake fails, then the other brake should still be able to decelerate, stop and hold an elevator car standstill with the rated load i.e. with a load of 100%. The method, for testing the functionality of the machinery brake, may be stored in a memory in the elevator control.
The brake dropping command may thus be issued to the machinery brake while the elevator car is running. The drive torque of the electric motor may be monitored. The machinery brake will, if the machinery brake works properly, engage against the traction sheave of the hoisting machinery after a certain dropping delay and start a braking of the movement of the hoisting machinery. At the same time the speed controller of the drive unit tries to maintain the prevailing speed condition by increasing the drive torque. The drive torque or the drive torque reference may be monitored. If the drive torque or the drive torque reference forms an increasing pattern congruent with an expected braking torque of the machinery brake, then a conclusion may be made that the machinery brake is working properly. Otherwise, if the drive torque does not increase as expected during a predefined time period, then a conclusion may be made that the machinery brake is not working properly. In the latter case, the elevator may be taken out of use and/or a maintenance request may be generated to a remote service center.
The brake test may be done while the car is driven in a light direction of the elevator car. The light direction means that the car is driven upwards in the shaft so that the car is empty and downwards in the shaft so that there is full load in the car. The speed of the car during the brake test may be the nominal speed of the car or some other lower test speed of the car.
The weight of the ropes of the elevator may not be compensated so that the degree of unbalance of the elevator may vary in different parts of the shaft. The position of the car as well as the torque of the motor just before the dropping of the machinery brake in the brake test may therefore be recorded in the test. This will make it possible to establish the unbalance situation of the elevator during the test. The test may be performed during the start-up of the elevator in a position in the shaft in which the unbalance of the elevator reaches a minimum value and in a position of the shaft in which the unbalance of the elevator reaches a maximum value.
One or more brakes of the machinery brake may be tested during one test drive. When the brake to be tested has passed the test, the control system draws said brake (deactivates the brake) and drops (activates) the next brake. There is no need for stopping the elevator between the tests. In some other embodiments, a subset of brakes, i.e. more than one but less than all the brakes in a set of brakes, may be tested at the same time.
In case the machinery brake comprises two brakes, the two brakes may be tested alternately during one elevator travel so that a brake dropping command is issued to the brake to be tested while the other brake in the machinery brake is kept open.
The results of the measurements and the acceptance limits may be transmitted to a cloud service. The trend may thus be observed by algorithms from the data in the cloud service and a correct time for maintenance measures may be determined.
The motor current or the motor current reference is directly proportional to the drive torque of the motor in modern vector-controlled electric drives, especially in case of permanent magnet motors. The motor current or the motor current refence is thus the parameter that may in practice be monitored.
During the same test it is also possible to measure the activation delay (dropping delay) of the machinery brake. This may be done by measuring the time delay starting at the instant the brake dropping command is issued and ending at the instant the change pattern in the drive torque is detected. The time delay for engaging the machinery brake should not be too long. Thus, if the measured time delay exceeds a given threshold, then indication of an operational anomaly of the machinery brake should be issued.
After the brake test is successfully completed, the elevator run may be continued to the destination landing without interruption.
Alternatively, upon detecting a desired drive torque change pattern, the drive torque may be interrupted so that the machinery brake will stop the car. The stopping distance of the car may be recorded. By verifying that the stopping distance of the car is within desired limits, additional diagnostic data of the machinery brake may be obtained.
A brake dropping command means activation of the machinery brake. The machinery brake may be activated by deactivating the electromagnet in the machinery brake i.e. by cutting the current supply to the electromagnet. The spring means in the machinery brake start to press the brake shoe or shoes against the rotating brake surface causing a braking of the movement of the hoisting machinery. Instead of a shoe brake, a drum brake, a disc brake or any corresponding machinery brake.
Prior art brake tests do not measure the dropping delay of the machinery brake. The novel brake test makes it possible to measure the dropping delay or activation delay of the machinery brake. It is important to monitor the dropping delay of the machinery brake to make sure that the machinery brake functions properly in all situations.
Prior art brake tests measure the brake force in a static situation i.e. the hoisting machinery is at a standstill when the brake test is performed. The torque produced by the brake in a dynamic situation may, however, differ from the toque produced by the brake in a static situation. The novel brake test makes it possible to measure the dynamic torque of the machinery brake.
Contaminants may in time accumulate on the friction surface of the brake shoes in the machinery brake. The contaminants may have an influence on the characteristics of the brake at the beginning of the braking event. The contaminants will have time to wear out from the friction surface of the brake shoes during the novel brake test.
The novel brake test may also eliminate additional wearing of the brakes as it is possible to perform the test at a lower test speed.

DRAWINGS

The invention will in the following be described in greater detail by means of preferred embodiments with reference to the attached drawings, in which

Figure 1 shows a side view of an elevator,
Figure 2 shows a side view of an elevator machinery brake system,
Figure 3 shows a flow diagram for testing the machinery brake of an elevator.

DETAILED DESCRIPTION

Fig. 1 shows a side view of an elevator.
The elevator may comprise a car 10, an elevator shaft 20, hoisting machinery 30, hoisting ropes 42, and a counterweight 41. A separate or an integrated car frame 11 may surround the car 10.
The hoisting machinery 30 may be positioned in the shaft 20. The hoisting machinery may comprise an electric drive 31, 32, a traction sheave 33, and a machinery brake 100. The electric drive 31, 32 may comprise an electric motor 32 and a drive unit 31 controlling the electric motor 32. The electric motor 32 may be a permanent magnet electric motor and the drive unit 31 may be a frequency converter. The drive unit 31 controls the electric motor 32 and the electric motor 32 rotates the traction sheave 33. The car frame 11 may be connected by the hoisting ropes 42 via the traction sheave 33 to the counterweight 41. Rotation of the traction sheave 33 with the electric motor 32 will move the car 10 in a vertical direction Z upwards and downwards in the vertically extending elevator shaft 20. The machinery brake 100 may stop the rotation of the traction sheave 33 and thereby the movement of the elevator car 10.
The car frame 11 may be supported with guide means 27 at guide rails 25 extending in the vertical direction in the shaft 20. The guide means 27 may comprise rolls rolling on the guide rails 25 or glide shoes gliding on the guide rails 25 when the car 10 is moving upwards and downwards in the elevator shaft 20. The guide rails 25 may be attached with fastening brackets 26 to the side wall structures 21 in the elevator shaft 20. The guide means 27 keep the car 10 in position in the horizontal plane when the car 10 moves upwards and downwards in the elevator shaft 20. The counterweight 41 may be supported in a corresponding way on guide rails that are attached to the wall structure 21 of the shaft 20.
The car 10 may transport people and/or goods between the landings in the building. The elevator shaft 20 may be formed so that the wall structure 21 is formed of solid walls or so that the wall structure 21 is formed of an open steel structure.
The elevator may be controlled with a main controller 300.
Figure 2 shows a side view of an elevator machinery brake system.
The car 10 may hang on a first side of the traction sheave 33 and the counterweight 41 may hang on an opposite second side of the traction sheave 33. The hoisting ropes 42 may pass from the car 10 over the traction sheave 33 to the counterweight 41. The traction sheave 33 may be driven by the electric motor 32. The electric motor 32 may be formed of a synchronous, permanent magnet electric motor. The electric motor 32 may be controlled by a drive unit 31. The drive unit 31 may be formed of a frequency converter.
The machinery brake 100 may comprise two electromagnetic brakes 110, 120 acting on the traction sheave 33. The electromagnetic brakes 110, 120 may be controlled by a machinery brake controller 200.
The elevator, the drive unit 31 and the brake controller 200 may be controlled by a main controller 300. The traction sheave 33 may be provided with a motion measuring device 130. The motion measuring device 130 may be formed of a tachometer.
Figure 3 shows a flow diagram for testing the machinery brake of an elevator.
Step 501 comprises moving the car with an electric motor in accordance with a drive profile by adjusting a drive torque of the electric motor. The electric motor may be controlled with a drive unit. The drive unit may be controlled with a main controller of the elevator.
Step 502 comprises generating a brake dropping command to a machinery brake. The brake dropping command may be generated by the machinery brake controller and/or by the main controller.
Step 503 comprises monitoring a drive torque of the electric motor. This may in practice be done by monitoring the current of the electric motor. The motor current of the electric motor is directly proportional to the drive torque of the electric motor in modern vector-controlled electric drives, especially in case of permanent magnet motors.
Step 504 comprises determining whether the drive torque of the electric motor follows a desired change pattern during a predefined time period starting from the generation of the brake dropping command to the machinery brake.
Step 505 comprises, if the answer in step 504 is yes, indicating that the machinery brake works properly.
Step 506 comprises, if the answer in step 504 is no, indicating that the machinery brake does not work properly.
The use of the invention is not limited to the elevator disclosed in the figures. The invention can be used in any type of elevator e.g. an elevator comprising a machine room or lacking a machine room, an elevator comprising a counterweight or lacking a counterweight. The counterweight could be positioned on either side wall or on both side walls or on the back wall of the elevator shaft. The drive unit, the motor, the traction sheave, and the machinery brake could be positioned in a machine room or somewhere in the elevator shaft. The car guide rails could be positioned on opposite side walls of the shaft or on a back wall of the shaft in a so called ruck-sack elevator.
It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

Claims

A method for testing machinery brakes in an elevator comprising a car (10) movably arranged in a shaft (20), an electric motor (32) for moving the car (10), a drive unit (31) for controlling the electric motor (32), and a machinery brake (100) for braking and holding the car (10), the method comprising
moving the car (10) with the electric motor (32) in accordance with a drive profile by adjusting a drive torque of the electric motor (32) with the drive unit (31),
generating a brake dropping command to the machinery brake (100),
monitoring the drive torque of the electric motor (32), and
if the drive torque of the electric motor (32) does not follow a desired drive torque change pattern during a predefined time period starting from the generation of the brake dropping command to the machinery brake (100), indicating that the machinery brake does not work properly, else indicating that the machinery brake (100) works properly.
The method according to claim 1, wherein the elevator car (10) is moved with the electric motor (32) in accordance with the drive profile in a light direction of the elevator car (10).
The method according to claim 1 or 2, wherein the machinery brake (100) comprises at least two brakes (110, 120), the at least two brakes (110, 120) being tested in turns so that a brake dropping command is issued for a brake (110, 120) to be tested while the other brakes are kept open.
The method according to any one of claims 1 to 3, wherein a brake dropping delay is measured, the brake dropping delay starting from the instant the brake dropping command is issued and lasting to the instant the drive torque change pattern is detected, and if the brake dropping delay exceeds a predetermined threshold, then indicating an operational anomaly of the machinery brake (100).
The method according to claim 4, wherein upon detecting a desired drive torque change pattern, interrupting the drive torque, measuring the resulting stopping distance of the car (10) and verifying that the stopping distance of the car (10) is within desired limits.
The method according to any one of claims 1 to 5, wherein the desired drive torque change pattern is based on a desired increase and/or a desired rate of increase of the drive torque.
An elevator comprising a car (10) movably arranged in a shaft (20), an electric motor (32) for moving the car (10), a drive unit (31) for controlling the electric motor (32), a machinery brake (100) for braking and holding the car (10), a machinery brake controller (200) for controlling the machinery brake (100), and a main controller (300), wherein the main controller (300) controls the elevator according to any one of claims 1-6.
A computer program product comprising program instructions, which, when run on a computer, causes the computer to perform a method as claimed in any of claims 1-6.