ARRANGEMENT AND METHOD IN AN ELEVATOR WITHOUT COUNTERWEIGHT

The object of this invention is an arrangement for braking an elevator car as defined in the preamble of claim 1, a power supply circuit of a brake as defined in the preamble of claim 8, and a method for braking an elevator car as defined in the preamble of claim 10.

It is very general to use a machinery brake that mechanically connects with a rotating part of the elevator machine as the braking apparatus of an elevator car. When the elevator car is braked, e.g. with the machinery brake in an" emergency stop, the power supply circuit of the brake control coil is disconnected e.g. with a relay or contactor. After the power supply of the brake has been disconnected the brake releases, in which case the brake shoe connects mechanically with a rotating part of the machine and starts to brake the elevator machine and, at the same time, the movement of the elevator car. The release of the brake occurs with a releasing delay, which is determined from the electrical parameters of the brake and of a possible attenuation circuit, such as from the inductance and resistance of the brake, as well as from the impedance of the possible attenuation circuit. When the brake has released, the movement of the elevator car starts to slow down with the deceleration determined by the mechanical connection of the brake shoe.

Conventionally, it is endeavored to minimize the releasing delay of the brake in an emergency stop, to achieve the shortest possible operating delay.

Publication JP 2003081543 presents a control of the brake of an elevator, in which the brake is controlled in an emergency stop of the elevator with a shorter releasing delay than in a normal stop.

In order to overcome the problems presented above and to improve the braking function of an elevator without counterweight, a new type of control of the brake of an elevator without counterweight is presented as an invention. A power supply circuit of the brake according to the control is

also presented in the invention.

The control of the brake according to the invention is intended to achieve a safer and more pleasant user experience from the viewpoint of an elevator passenger, particularly in an emergency stop of the elevator. The purpose of the control of the brake is also to reduce the noise produced by the operation of the brake.

The arrangement according to the invention for braking an elevator car is characterized by what is disclosed in the characterization part of claim 1. The power supply circuit of a brake according to the invention is characterized by what is disclosed in the characterization part of claim 8. The method according to the invention for braking an elevator car is characterized by what is disclosed in the characterization part of claim 10. Other embodiments of the invention are characterized by what is disclosed in the other claims. Some inventive embodiments are also discussed in the descriptive section of the present application. The inventive content of the application can also be defined differently than in the claims presented below. The inventive content may also consist of several separate inventions, especially if the invention is considered in the light of expressions or implicit sub-tasks or from the point of view of advantages or categories of advantages achieved. In this case, some of the attributes contained in the claims below may be superfluous from the point of view of separate inventive concepts . For example, a safety switch according to Fig. 2 and/or a power supply circuit of the brake according to Fig. 3 can be fitted to the elevator system without counterweight presented in Fig. 1.

An elevator system without counterweight refers in the invention to an elevator system that does not comprise the type of counterweight with which the equilibrium of the loading of the elevator is conventionally adjusted. In one such elevator system without counterweight according to the invention the elevator car is moved with a linear motor, in

which case e.g. the rotor can be fixed in the elevator car. On the other hand, in the elevator system without counterweight according to the invention the elevator car can also be moved via elevator ropes connected to the rotating traction sheave of the elevator machine. In this case the elevator system without counterweight can be a positive drive type of elevator, and the elevator system without counterweight can also be e.g. of the type presented in the publication WO 2005/049470 A2. The elevator machine according to the invention can be disposed e.g. in the elevator hoistway, in the machine room, and, for instance, in connection with the elevator car.

One controllable brake according to the invention is a machinery brake.

One controllable brake according to the invention is a guide rail brake connectable between the elevator car and the guide rail of the elevator car.

In one embodiment of the invention two controllable machinery brakes that brake the elevator machine are fitted to the elevator machine.

The brake according to the invention can be e.g. a drum brake or a disc brake.

In one embodiment of the invention a solid-state control unit is fitted to the elevator system, which control unit is fitted to read the safety sensors of the elevator system and to control the brake on the basis of the information read from the safety sensors. The aforementioned safety sensors of the elevator system are e.g. the safety switches of the landing doors, the end limit switches of the elevator hoistway, and also the safety switch of the overspeed governor. The solid-state control unit can in this case be arranged to be redundant, in which case the control is duplicated e.g. with two microcontrollers that monitor the

operating status of each other.

In one embodiment of the invention the controllable switches of the power supply circuit of the brake are fitted in connection with the safety circuit of the elevator.

The controllable switches according to the invention can be mechanical switches, e.g. relays and contactors, and they can also be solid-state switches, e.g. IGBT transistors, MOSFET transistors, thyristors and bipolar transistors.

In the invention control pole refers to the input of the control signal of a controllable switch. This type of control pole is e.g. the coil of a relay or of a contactor, or e.g. the gate of a thyristor, IGBT transistor or MOSFET transistor, or the base of a bipolar transistor.

In the invention elevator machine refers to the combination of the elevator motor and the machine mechanics fitted in connection with it . The aforementioned machine mechanics comprises e.g. a traction sheave. The machine mechanics can also comprise e.g. a machinery brake. If the elevator machine has gears, the machine mechanics can also comprise a gear.

In one embodiment of the invention the releasing delay of the brake is selected from a plurality of at least two different releasing delays on the basis of the direction of movement of the elevator car only in a situation when the absolute value of the speed of the elevator car deviates from zero by more than a predetermined limit value, and the releasing delay of the brake is at lower speeds of the elevator car than the aforementioned otherwise determined to be constant irrespective of the direction of movement of the elevator car.

With the invention at least one of the following advantages, among others, is achieved:

Changing the releasing delay of the brake occurs usually

by influencing directly or indirectly the voltage between the poles of the control coil of the brake. To shorten the releasing delay the voltage between the poles of the control coil is in this case increased. Then also the releasing movement is faster in the magnetic circuit of the brake, which may increase the noise produced by releasing the brake. When the releasing delay of the brake is selected according to the invention to be longer in the determined control situation, the release of the brake can in this case occur with a smaller control voltage, and the disturbing noise produced by the release of the brake decreases . This reduces the noise effectively especially in modern elevator systems without machine rooms, in which the elevator machine, as also the brakes and control of the brake of the elevator machine, are disposed in the elevator hoistway.

When an emergency stop is performed as the elevator car is moving upwards, the power supply to the elevator machine is also disconnected in conjunction with the control of the brake. After disconnection of the power supply the speed of the elevator car starts to slow down owing to the imbalance of the loading of the elevator car. In this case the increase in the releasing delay of the brake results in the speed of the elevator at the moment the brake is engaged having had time to decrease, and also the duration of the braking after the brake has engaged shortens . In this case the danger caused to a passenger in an emergency stop from an upward movement of the elevator car is smaller. Neither is the emergency stop experience as unpleasant when using a shorter releasing delay for the control of the brake. Especially with express elevators, the speed of the elevator car when an emergency stop begins is considerable, and with the solution according to the invention it is possible to improve the safety and drive comfort in connection with the emergency stop of an express elevator.

When using the longer releasing delay in the brake control, the voltage of the control coil of the brake can be decreased. Then also the voltage stress in the power supply circuit of the brake and in the attenuation circuit possibly connected in connection with the brake coil also decreases. Components with a service life that is relatively high for the duration of the voltage stress are often used in the attenuation circuit. These types of components are e.g. various resistors, varistors and Zener diodes.

- When the speed of the elevator car has had time to decrease at the moment the brake engages, the braking distance after the brake has engaged also shortens. In this case the heating of the brake caused by the friction of the brake decreases. In addition the wear of the brake pads also decreases.

In the following, the invention will be described in more detail by the aid of some examples of its embodiments, which in themselves do not limit the scope of application of the invention, with reference to the attached drawings, wherein

Fig. 1 presents an elevator system without counterweight according to the invention, Fig. 2 presents a safety circuit of an elevator system according to the invention Fig. 3 presents a power supply circuit of a brake according to the invention,

Fig. 4 presents the electrical parameters of a control winding of the brake in one brake control situation according to the invention, Fig. 5 presents the upward movement of the elevator car in one brake control situation according to the invention,

Fig. 1 presents an elevator system without counterweight, into which is fitted an arrangement according to the invention for braking the elevator car. The elevator car 1 is moved in the

elevator hoistway 22 via ropes connected to the traction sheave of the elevator motor 8. The power supply to the elevator motor 8 occurs from the electricity network 10 with a frequency converter 9. The safety of the elevator system is monitored with a safety circuit. The safety circuit comprises safety sensors 20 that are disposed in the points that are important from the standpoint of the safety of the elevator system. The sensors are disposed e.g. in connection with the landing doors, in the proximity of the ends of the elevator hoistway and also in connection with the overspeed governor. A solid-state safety device 3 is fitted as a part of the safety circuit of the elevator system, which safety device reads the measuring information from the safety sensors 20 during a run of the elevator, and on the basis of the information read from the safety sensors controls the duplicated brake 2, 2' mechanically connected to a rotating part of the elevator machine. The brake engages in this case with the brake disc integrated into the traction sheave of the elevator motor.

The solid-state safety device 3 reads the measuring information from the safety sensors 20 during a run of the elevator. On the basis of the information read, the solid- state safety device determines the operating status of the elevator system, and performs if necessary an emergency stop. In this case the solid-state safety device controls the switch arrangement 6 to disconnect the power supply of the elevator motor. The solid-state safety device then also controls the brake 2 , 2 ' of the elevator machine by sending a control signal 21 according to the control request to at least one controllable switch of the power supply circuit 12 of the brake for disconnecting the power supply of the brake control circuit 12.

The solid-state safety device 3 controls the brake 2, 2' with a releasing delay. The releasing delay comprises in this case, in addition to the delay caused by the power supply circuit of the brake and by the mechanics of the brake, a separate additional delay determined by the solid-state safety device,

the length of which can vary, and the additional delay can also be reduced to zero. The solid-state safety device 3 selects a releasing delay with an additional delay of the control of the brake from a plurality 4,5 of at least two releasing delays of different lengths.

The releasing delay 4,5 to be used is selected on the basis of the direction of movement of the elevator car. The solid-state safety device 3 determines the direction of movement of the elevator car from the signal that expresses the movement of the elevator machine, such as from the signal of a tachometer or encoder connected to the elevator machine, or from the source voltage of the elevator motor. The solid-state safety device 3 controls the brake 2,2' with a first shorter releasing delay 4 when the direction of movement of the elevator car 1 is downwards, and with a second longer releasing delay 5 when the direction of movement of the elevator car 1 is upwards.

The magnitude of the aforementioned releasing delay 4,5 can vary. The releasing delay can in this case be determined e.g. on the basis of the speed of the elevator car and/or the nominal speed of the elevator, in which case the aforementioned second releasing delay 5 can be reduced as the speed of the elevator car and/or the nominal speed increases.

Fig. 5 presents the speed v of the elevator car 1 when driving upwards in one emergency stop situation according to the invention. At the time t ₀ the contactors 6 of the power supply circuit of the elevator motor are controlled to disconnect the power supply of the elevator motor. After an opening delay 7 the contactors open, in which case the power supply of the motor ceases. The speed of the elevator car starts to slow down owing to the imbalance of the loading of an elevator system without counterweight, in which case gravity brakes the elevator car. After the determined releasing delay 5 of the brake control , the brake 2 , 2 ' engages to brake the movement of the elevator car, in which case the deceleration of the

elevator car increases. Since the speed v of the elevator car has had time to decrease during the releasing delay 5 of the brake control, the braking distance of braking performed at great deceleration shortens compared to the situation in which engagement of the brake 2 , 2 ' would have occurred at the speed of the initial moment of the emergency stop.

Fig. 2 presents a safety circuit 19 of an elevator system according to the invention, which safety circuit comprises a serial circuit of the safety switches 20 of the elevator that function as safety sensors. The serial circuit of safety switches is connected to the coil of the main contactor 6 of the motor and also to the coil of the relay 25 fitted in connection with the power supply circuit of the brake. A hazardous situation is detected as an opening of at least one safety switch 20, in which case the current supply to the coil of the main contactor 6 and of the relay 25 ceases. In this case the main contactor 6 opens, and at the same time the relay 25 opens preventing power supply via the power supply circuit 12 to the coil 11 of the brake, in which case the brake releases on the basis of the status of the safety switches 20.

Fig. 3 presents the power supply circuit 12 of the brake according to the invention. The power supply circuit comprises an alternating electricity circuit 13 and a direct electricity circuit 14, which are connected to each other with a rectifying bridge 15. An attenuation circuit 16 is fitted into the direct electricity circuit 14 in parallel with the control coil 11 of the brake, which attenuation circuit here comprises a diode and a varistor connected in series . The direct electricity circuit comprises at least a first controllable switch 17 for controlling the brake with a first shorter releasing delay 4. The alternating electricity circuit comprises a second controllable switch 18 for controlling the brake with a second longer releasing delay 5. Here the aforementioned first (17) and second (18) controllable switches are relays . The control logic 24 of the relays is

fitted as a part of the control electronics of the elevator. The control logic can be implemented e.g. with discrete IC circuits or with programmed software, for instance with a microcontroller .

The control of the brake 2,2' occurs by controlling the first 17 and the second 18 controllable switch of Fig. 3 as follows: when the elevator car is moving downwards the brake is controlled with the first shorter releasing delay 4. In this case the switch 17 opens, in which case the current of the coil of the brake starts to pass through the attenuation circuit 16. The voltage over the attenuation circuit forms a control voltage for the coil 11, under the influence of which the current of the coil decreases rapidly. The topmost graph in Fig. 4 presents the control voltage of the coil 11 of the brake and the next to topmost graph presents the current of the coil 11 of the brake in a situation when the brake is controlled with the first shorter releasing delay 4. The change 23 of the current marked in Fig. 4 causes opening of the air gap of the magnetic circuit of the brake. When the magnetic circuit opens the reluctance of the magnetic circuit changes, and the change in reluctance induces a voltage in the coil 11 of the brake, which causes the aforementioned change 23 in the current of the coil 11.

When the elevator car is moving upwards the brake is controlled with a second longer releasing delay 5. In this case the first controllable switch 17 is kept closed and the second controllable switch 18 is opened, in which case the current of the coil 11 of the brake starts to pass through the series-connected diodes of the rectifying bridge 15. In this case the control voltage of the coil 11 of the brake remains low, because it is formed only from the voltage of the conductive state of the diodes of the rectifying bridge. Then the current of the coil 11 of the brake also decreases more slowly, and the releasing delay of the brake increases. The next to bottommost graph in Fig. 4 presents the control voltage of the coil 11 of the brake and the bottommost graph

presents the current of the coil 11 of the brake in a situation when the brake is controlled with the second longer releasing delay 5 as described above.

The control of the brake described in the embodiment of Fig. 3 can be fitted to start e.g. after some safety switch 20 of the elevator described in the embodiment of Fig. 2 has opened.

It is obvious to the person skilled in the art that the invention is not limited solely to the examples described above, but that it may be varied within the scope of the claims presented below.