HK1138242B - An elevator brake assembly, an elevator system and a method of controlling an elevator braking system - Google Patents

Description

Elevator brake assembly, elevator system and control method thereof

Technical Field

The present invention relates generally to elevator systems, and more particularly to an elevator braking system.

Background

The elevator system comprises a braking system for braking and holding the elevator in a certain desired position. Typically, the braking system includes a spring that urges an axially movable disc against a brake rotor having brake lining material. The resulting friction between the movable disc and the lining material brakes and holds the elevator in place. The engagement of the movable disc when lowering the brake is considered well known in the art and is typically the default condition. The movable disc is disengaged from the brake lining by a magnetic field generated by an electromagnet. The attractive force generated by the magnetic field overcomes the spring force and pulls the movable disk away from the brake rotor. This is well known in the art when raising the brake.

The electromagnet itself for generating the magnetic field is unstable because the attractive force generated by the electromagnet increases as the movable disk moves away from the engaged position toward the housing. Typically, the disk moves in an air gap of about 0.3mm between the engaged and disengaged positions. The movement of the disc in the air gap and the resulting contact with the brake rotor or the housing can produce an objectionable noise that can be heard by persons in the elevator car. The electromagnetic field increases as the electromagnet members approach each other, tending to provide an acceleration to the moving plate being raised, thereby producing an objectionable noise.

When lowering the brake, if the magnetic field disappears too quickly, the movable disc is accelerated by the spring to abut the brake rotor and the brake housing, again producing noise. This braking noise is reduced to some extent by using a diode circuit to delay the collapse of the magnetic field when the brake is lowered. However, such devices also cause an unexpected delay in the engagement of the brake without sufficiently reducing the noise.

Other devices that attempt to reduce the noise generated by contact between the disk and the electromagnet housing include the use of elastomeric damping elements, such as O-rings. The O-ring dampens movement to reduce impact and reduce noise. Unfortunately, the O-ring is subject to creep, stress relaxation, and aging. Over time, these factors degrade the O-ring resulting in a significant increase in noise, while reducing the force to engage the brake. The increase in noise and reduction in engagement force ultimately requires readjustment of the brake torque, as well as replacement of the O-ring to maintain the desired noise damping characteristics. Other known devices include the use of elastomeric bumpers or gaskets, which, like O-rings, suffer from limited service life.

Accordingly, there is a need for an improved braking system that provides the desired holding and braking forces in a stable controlled manner to prevent unwanted impacts and reduce objectionable noise, improve durability and extend operating life.

Disclosure of Invention

In general, the present invention is a brake assembly for an elevator system that utilizes permanent magnets and electromagnets to stabilize brake application.

One example system designed based on this invention includes a permanent magnet that generates a first magnetic field in a direction that acts on a brake disc to generate a clamping force. Springs are provided between the stationary electromagnet housing and the disk to provide an additional biasing force and to adjust the force on the disk. In one example brake assembly, the attractive force of the permanent magnet and the biasing force of the spring coil sandwich the brake disc between the stationary housing and the axially movable disc when the brake is in a lowered or applied position.

The electromagnet comprises a coil powered by a current of appropriate polarity to generate a second magnetic field in opposition to the first magnetic field. Wherein the frequency and phase of the current applied to the coil generates a controllable and variable second magnetic field. The second magnetic field provides a repulsive force with respect to the first magnetic field to drive the permanent magnet housing away from the electromagnet housing. As the distance between the permanent magnet housing and the electromagnet housing increases, the difference in magnetic field strength between the two magnetic fields decreases until an equilibrium position is reached.

By ramping down the level of the electromagnet current, the brake is lowered in a controlled manner to regulate movement of the permanent magnet housing as it approaches the electromagnet housing. As the equilibrium position becomes closer to the fixed electromagnet housing and the lowered position, the controller reduces the current in the coil.

Thus, one example brake provides controlled movement and application of the brake reduces noise without the use of damping bodies that wear easily and require replacement. Still further, the example brake assembly provides a stable and durable brake assembly.

The various features and advantages of this invention will become more readily apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows.

Drawings

Fig. 1 is a schematic view of an example elevator system of the present invention.

Fig. 2 is a schematic diagram of an example elevator braking system designed by this invention.

FIG. 3 is a schematic view of one face of an exemplary permanent magnet of the present invention.

Fig. 4 is a schematic view of the interface between the permanent magnet and the electromagnet in the lowered position.

FIG. 5 is a schematic of a face of an exemplary electromagnet of the present invention.

Fig. 6 is a schematic view of an example elevator braking system of the present invention in a raised position.

Fig. 7 is a schematic view of the interface between the permanent magnet and the electromagnet in the raised position.

Detailed Description

Fig. 1 schematically illustrates an elevator system 10 that includes an elevator car 12 that moves within a hoistway 14, with an electric motor 16 moving the elevator 12 in a known manner. The brake assembly 18 utilizes permanent magnets in combination with electromagnets for stable operation. The braking assembly 18 is mounted adjacent the motor 16 to brake and maintain the elevator car 12 in a desired position within the hoistway 14.

FIG. 2 schematically illustrates the example brake assembly 18 in a braking or lowering position. The motor 16 drives a shaft 28 about an axis 30, the shaft 28 extending from the motor 16 and into the motion assembly 18. The brake assembly 18 includes a stationary housing 20, an axially movable disk 22 and an axially movable plate 26. The disc 22 has a friction material 24 that engages both the housing 20 and the plate 26 in the lowered position. Further, the disc 22 is keyed to the shaft 28 in a known manner so as to be axially movable, but not rotationally movable relative to the shaft 28. The keyed feature of the disc 22 is known, such as by a key in a keyway or by mating splines on the disc 22 and shaft 28.

The plate 26 is connected to the permanent magnet housing 34 by pins 46. The latch 46 passes through an aperture 48 in the fixed electromagnet housing 32. The permanent magnet 36 within the permanent magnet housing 34 generates a first magnetic field 52 that provides an attractive force directed toward the electromagnet housing 32 in the direction indicated by the arrow. The permanent magnet 36 includes a face 35 that is perpendicular to the direction of the first magnetic field 52.

With respect to fig. 3 as well as fig. 2, the face 35 includes a north pole 61 and a south pole 62. The permanent magnet 36 is configured to generate a first magnetic field 52. The north and south poles 61, 62 are arranged symmetrically about the axis 28. The north and south poles 61, 62 are annularly arranged about the shaft 28 and are oval in shape. This elliptical shape maximizes the area of the north and south poles 61, 62 on the permanent magnet face 35. The north and south poles 61, 62 protrude a length 39 from the face 35 to direct the repulsive magnetic force and prevent leakage that could degrade the strength of the magnetic field.

The first magnetic field 52 provides an attractive force to drive the permanent magnet housing 34 in a direction indicated by arrow 52 toward the electromagnet housing 32. The movement of the permanent magnet housing 34 is transmitted to the plate 26 by the pins 46. The disc 22 is then sandwiched between the housing 20 and the plate 26 to generate a braking force that resists rotation of the shaft 28.

With respect to fig. 4, the permanent magnet 36 continues to generate the first magnetic field 52 to generate an attractive force to drive the plate 26 in a direction indicated by arrow 60 toward the down or braking position. The strength of the magnetic field 52 is such as to produce the desired force to clamp the disc 22 and the braking force required for the particular situation.

The electromagnet 38 remains in a non-energized state at all times when the brake assembly 18 is in the lowered position. The electromagnet housing 32 is configured to cooperate with the permanent magnet 36 to provide the necessary coupling configuration to produce the desired first magnetic field 52 magnitude.

With reference to fig. 5, the electromagnet 38 includes a face 19 having a series of coils 40 wound on a core 41 and arranged annularly about the axis 28. The core 41 protrudes from the face 19 by a distance 45 (fig. 2) to create the desired counteracting magnetic force. Most of the magnetic field generated by the electromagnet 38 passes through the core 41. The core 41 is arranged in parallel and aligned with the poles 61, 62 on the face 35 of the permanent magnet 36. The electromagnet face 19 is arranged so as to reduce the magnetic flux passing through the air gap. These magnetic fluxes across the air gap limit the ability to provide a repulsive force.

Although a particular configuration is described, workers will appreciate, based on this disclosure, that other configurations that include features that optimize attraction by the permanent magnets 36 fall within the scope of the present invention. For example, these features may include a desired air gap, as well as connection features to improve and optimize the flux path for specific needs.

Fig. 6 and 7 show the brake assembly 18 in a released or raised position. In the raised position, plate 26 is no longer in clamping contact with disk 22. Release of the clamping contact rotates the disc 22 with the shaft 28. The raised position is entered by activating the electromagnet 38 to generate a second magnetic field 54 opposite the first magnetic field 52 generated by the permanent magnet 36. A supply current is delivered from a controller 50 (fig. 6) to the coil 40 of the electromagnet 38 to generate a second magnetic field 54. In one example, the magnitude of the current supplied to the coil 40 determines the magnitude of the second magnetic field strength 54. One example includes controlling the polarity of the current to direct the desired magnetic field.

The second magnetic field 54 has a strength greater than the first magnetic field 52 generated by the permanent magnet 36. The first magnetic field 52 cooperates with the second magnetic field 54 to generate a total repulsive force to drive the permanent magnet housing 34 axially away from the electromagnet housing 32. Movement of the permanent magnet housing 34 results in corresponding movement of the pin 46 and the plate 26. Axial movement of the plate 26 releases the disc 22 so that no braking force is applied.

The electromagnet 38 generates a second magnetic field 54 whose strength is proportional to the supply current from the controller 50. Therefore, the control of the permanent magnet case 34 is realized by controlling the magnitude and frequency of the supply current. The current is suitably controlled so that the distance between the electromagnet housing 32 and the permanent magnet housing 34 is varied and the force can be adjusted accordingly to prevent unwanted impacts that can produce objectionable noise.

In the depicted example, the coil spring 42 is located between the plate 26 and the axially fixed electromagnet housing 32. The coil spring 42 biases the plate 26 toward the lowered position. Although the illustrated coil spring 42 is other spring components, components such as Belleville washers are also within the contemplation of this invention.

The coil spring 42 provides a biasing force in the same direction as the permanent magnet 36. The coil spring 42 also provides an adjustment function to balance the force generated by the permanent magnet 36 and the force generated by the electromagnet 38. The example coil spring 42 is partially disposed in a spring pocket 43 in the plate 26. An adjuster 44 provided for each coil spring 42 can adjust the biasing force generated by the spring 42. The adjuster 44 is a known arrangement such as a threaded pin for varying the depth and corresponding spring force of the spring housing 43. The depicted example includes four coil springs 42, however, any number of coil springs 42 can be used to generate the counterbalancing force and move the plate 26 in certain desired situations.

The coil spring 42 is disposed in a spring housing 43 within the plate 26. However, the coil spring 42 may be installed in the electromagnet housing 32. The adjuster 44 is a known arrangement such as a threaded pin for varying the depth and corresponding spring force of the spring housing 43. In this example, the strength of the magnetic field 54 is sufficient to overcome the bias of the spring 42 and the magnetic field 52 for raising the brake.

As the distance between the permanent magnet housing 34 and the electromagnet housing 32 increases, the difference in the two magnetic field forces gradually decreases until an equilibrium position is reached. In the equilibrium position, the permanent magnet 36 is held in a desired position relative to the stationary electromagnet housing 32. The equilibrium position can be adjusted by adjusting the current in the coil 40.

The brake can then be lowered in a controlled manner by ramping down the current level to regulate movement of the permanent magnet housing 32 as the permanent magnet housing 34 approaches the electromagnet housing 32. The controller 50 reduces the current in the coil 40 to bring the permanent magnet 36 closer and closer to the stationary electromagnet housing 32 moving it from the equilibrium position to the lowered position.

Thus, the example brake assembly may be controllably moved to minimize noise without the use of damping components that are easily worn and require replacement. Further, the example brake assembly provides a stable and durable brake assembly.

The preceding description is exemplary rather than limiting in nature. Modifications and variations to the described embodiments will be apparent to those skilled in the art without departing from the spirit of the invention. The scope of legal protection given to this invention can only be determined by studying the following claims.

Claims (20)

1. An elevator brake assembly (18), comprising:

a brake member (26) movable between an engaged position and a disengaged position;

a permanent magnet (36) that generates a first magnetic field (52) to bias the brake component (26) toward the engaged position; and

an electromagnet (38) actuatable to generate a second magnetic field (54) opposite the first magnetic field (52) to repel the permanent magnet (36) and maintain the brake member (26) in the disengaged position, wherein one of the permanent magnet (36) and the electromagnet (38) is movable with the brake member (26) between the engaged and disengaged positions.

2. The assembly as claimed in claim 1 wherein said brake member (26) cooperates with a stationary housing (20) to apply a braking force, said electromagnet (38) being stationary relative to movement of said housing (20) and said permanent magnet (36) such that said brake member (26) moves in conjunction with said permanent magnet (36).

3. The assembly as claimed in claim 1 wherein the electromagnet (38) is disposed within a housing (32) and the permanent magnet (36) is movable relative to the housing (32).

4. An assembly as set forth in claim 3 wherein said electromagnet (38) includes a coil (40) disposed within said housing (32), and further including a controller (50) controlling the current supplied to said coil (40) for generating said second magnetic field (54) in a selectively controllable manner.

5. The assembly as recited in claim 4, wherein the controller (50) varies the current in response to a position of the permanent magnet (36) relative to the housing (32).

6. The assembly as claimed in claim 3, wherein the housing (32) includes at least one opening (48), the permanent magnet (36) and the brake member (26) being connected together by at least one pin (46) that extends at least partially through the at least one opening (48) in the housing (32).

7. The assembly as set forth in claim 3 including a spring (42) to regulate movement of the brake member (26) relative to the housing (32).

8. The assembly as claimed in claim 7, including an adjustment device (44) to adjust a force exerted by the spring (42) between the housing (32) and the brake component (26) to balance a braking force generated by the spring (42) in cooperation with the first magnetic field (52).

9. The assembly as claimed in claim 1 including a rotor (22) having a friction lining (24), the rotor (22) rotating with the motor (16) and selectively engaging the brake member (26).

10. The assembly as claimed in claim 1 wherein said electromagnet (38) comprises a plurality of coil assemblies (40) wound on a corresponding plurality of core pieces (41) protruding from the face (19) of said permanent magnet (36).

11. The assembly as claimed in claim 1 wherein the permanent magnet (36) includes a plurality of north cores (61) and a corresponding plurality of south cores (62) protruding from a face surface (37).

12. An elevator system (10), comprising:

an elevator car (12);

a motor assembly (16) to move the elevator car (12); and

a braking system (18) including a rotor (22) driven by the motor assembly (16), a braking member (26) selectively movable into engagement with the rotor (22), a permanent magnet (36) generating a first magnetic field (52) to bias the braking member (26) into engagement with the rotor (22), an electromagnet (38) for generating a repelling magnetic field (54) opposing the first magnetic field (52) to hold the braking member (26) in a position disengaged from the rotor (22), wherein one of the permanent magnet (36) and the electromagnet (38) is movable with the braking member (26).

13. The system of claim 12, wherein the electromagnet (38) generates the repelling magnetic field (54) in a selective manner to control a relative position between the brake component (26) and the rotor (22).

14. The system of claim 13, wherein the electromagnet (38) is disposed within a housing (32) and is fixed relative to movement of the brake member (26) and the permanent magnet (36), the brake member (26) and the permanent magnet (36) being connected by at least one pin (46) that extends at least partially through an aperture (48) in the housing (32).

15. The system of claim 14, wherein the permanent magnet (36) is disposed on an opposite side of the housing (32) relative to the brake component (26).

16. The system of claim 14, including a spring (42) between the housing (32) and the brake member (26) to balance the force applied by the electromagnet (38).

17. A method of controlling an elevator braking system, the method comprising the steps of:

a) generating a first magnetic field (52) by the permanent magnet (36) to apply a braking force; and

b) a repelling magnetic field (54) is generated by the electromagnet (38) opposite the first magnetic field (52) to release the braking force and hold the braking component (26) in a release position.

18. The method of claim 17, comprising selectively controlling current supplied to the electromagnet (38) to control the strength of the repulsive magnetic field (54).

19. The method of claim 18, including controlling the relative position between movable components in a braking system by selectively controlling the difference between the first magnetic field (52) and the repulsive magnetic field (54).

20. The method of claim 17, wherein one of the permanent magnet (36) and the electromagnet (38) is movable with a brake member (26).