GB2588786A

GB2588786A - Static brake assembly

Info

Publication number: GB2588786A
Application number: GB1916152.0A
Authority: GB
Inventors: Turner Jim
Original assignee: Safran Electrical and Power SAS
Current assignee: Safran Electrical and Power SAS
Priority date: 2019-11-06
Filing date: 2019-11-06
Publication date: 2021-05-12
Also published as: GB201916152D0

Abstract

An integrated brake for a motor has frictional contact areas 210, 310 made of an elastomeric material (e.g. a synthetic polymer, such as neoprene, fluorocarbon). The brake has a rotor disc 100 fixedly attached to a motor shaft 20, a static braking member 200 in fixed relation to a frame 10, and moveable braking member 300 worked by actuation means 40 (e.g. a solenoid). Contact members 220,320 may have an annular torus shape surrounding the motor shaft 20 (e.g. an O-ring), and be mechanical attached to braking members 200,300 by an opening 230,330. The motor can be used in aircraft landing gear or brake system.

Description

Static Brake Assembly The invention relates to a brake assembly for a motor of an aircraft, in particular a static brake assembly for a motor of an aircraft.

Background

Motors can be used in aircraft for various functions. Motors can act as primary actuators to activate a part of the aeroplane, or may act as a secondary interlocking device to lock a primary actuator in a chosen position. Specific uses of motors as primary actuators are described in W02019097137, which describes the use of a motor arrangement to drive one or more wheels of an aircraft landing gear. Another application of a motor in an aircraft is in a brake system of an aeroplane. The motor itself may have a brake assembly to prevent rotation of a rotor of the motor.

There is a need for improvements in aircraft brake assemblies for motors of aircraft.

Summary of the Invention

In a typical braking system for a motor, there is a braking contact surface, typically attached to a braking member, which contacts an otherwise moveable component (e.g. a rotor), to prevent it from rotating. In a motor, braking by contacting a moveable component of the motor with the braking contact surface of the rotor would prevent the motor from being operated.

In braking systems for existing motors, it has been typical to design a braking contact surface which has specific material and mechanical properties. These properties include durability, strength, a low degree of compressibility, and easy attachment to a braking component. An example of a material which has been used as a contact surface is carbon fibre, bonded or mechanically attached to rotating or static discs to provide a surface, which is durable over multiple brake applications.

The inventors of the present invention have identified that, contrary to the commonly held perception, in certain applications, a softer and less durable material can be beneficial.

The inventors have identified that use of an elastomeric material as a contact material in a brake assembly provides an improved brake assembly. Use of an elastomeric contact material has numerous advantages. One advantage is that easier manufacture and assembly of the brake assembly is achieved, as will be explained in more detail in the detailed description. A further advantage is that a significant cost saving can be achieved, by using a material and component which would not typically be considered in a braking application for an aircraft.

The inventors have further identified that it is possible to use this material without chemically or thermally bonding the elastomeric material to the body of the braking component, by using a mechanical attachment which can grip the elastomeric material, or about which the elastomeric material can be stretched.

According to the invention, there is provided a motor having an integrated brake assembly, the motor comprising: a motor frame; a motor shaft which is rotatably mounted relative to the frame; a rotor disc which is fixedly attached to the motor shaft; a static braking member which is mounted in fixed relation to the frame, and a moveable braking member which is mounted in moveable relation to the static braking member; wherein each of the static braking member and the moveable braking member comprises a contact region configured to contact the rotor disc when in a braking condition, so as to fix the position of the motor shaft relative to the frame; and wherein at least one of the contact regions comprises an elastomeric material.

At least one of the contact regions may have a static coefficient of friction of at least 0.5 using ISO standard 8295:1995, preferably at least 0.6 using ISO standard 8295:1995, and further preferably at least 0.7 using ISO standard 8295:1995. This has the advantage of providing a particularly effective brake assembly, in which the contact region can effectively prevent rotation of the rotor disc.

At least one of the contact regions may comprise a material having a compression modulus in the range of 0.7 to 2 MPa when measured using method A of ISO standard 7743. At least one of the contact regions may comprise a material having a shear modulus in the range of 0.5 to 1.25 MPa when measured using method A of ISO standard 1827:2016. The compression modulus of one or more of the contact regions may be approximately a third of the shear modulus of that contact region. This has the advantage of providing a particularly effective brake assembly, in which the contact region is suitable for its intended use under repeated applications of the brake.

At least one of the contact regions may comprise a neoprene and/or a fluorocarbon material. At least one of the contact regions may not comprise a silicone material. These materials are, surprisingly, particularly suitable for use as a contact region of the integrated brake assembly.

At least one of the contact regions may comprise a semicrystalline polymeric material. At least one of the contact regions may have a Poisson's ratio of approximately 0.5. The contact regions may have substantially equal properties to one another in respect of one or more of: macroscopic shape; size; chemical composition; topography; friction coefficient; mechanical and/or materials properties. This has the advantage of ease of manufacture and allows the performance of the braking assembly to be predicted reliably.

The contact region on at least one of the static braking member and the moveable braking member may be comprised in a contact member. The or each contact member may be fixedly attached to its respective braking member. The or each contact member may be attached to its respective braking member by means of chemical and/or thermal bonding. Equally, the or each contact member may be attached to its respective braking member by means of a mechanical attachment. Use of a mechanical attachment benefits from an improved ease of manufacture, as it does not require complex chemical or thermal bonding steps, and allows for a more reliable and consistent assembly process.

The mechanical attachment may be provided by an opening in the or each braking member, the opening being configured to partially receive the contact member such that a part of the contact member extends from the opening. This has the advantage of providing an extension from the braking member which is compressible upon contact with the rotor disc. This provides improved performance of the brake assembly.

The opening may have a surface dimension and an inner dimension, the inner dimension being larger than the surface dimension, and the surface dimension being smaller than a maximum dimension of the contact member when in an un-stressed state. This provides a configuration which is particularly easy to assemble, thus saving assembly time and cost.

The or each contact member may have a uniform cross-sectional shape in a circumferential direction of the rotor disc. The or each contact member may have a substantially annular shape which surrounds the motor shaft. The or each contact member may have a rotationally symmetrical shape about a longitudinal axis of the motor shaft. The or each contact member may have a torus shape. Such a shape is advantageous as when used in combination with a circular, planar, rotor disc, the or each contact member can apply a uniform force across the rotor disc.

The rotor disc may have an inner region at which the rotor disc is attached to the motor shaft, and an outer region further away from the motor shaft than the inner region, and the or each contact region may be disposed proximate the outer region. This has the advantage of maximising the effect of the contact region on the rotor disc. When disposed proximate the outer region, the contact region is more effective at preventing rotation of the rotor disc than if it were disposed proximate an inner region.

Brakes can be divided broadly into two main categories: dynamic brakes and static brakes. The function of the dynamic brake is to slow to a stationary position a rotating component of the motor. The function of a static brake is to maintain any or all rotating components of the motor in a stationary position, once stopped. The present integrated brake assembly of the present invention may be a static brake. As such, the integrated brake assembly of the present invention may be configured or adapted to be used as a static brake. The integrated brake assembly of the present invention may have a static torque capacity of up to approximately 1 Nm.

Brief Description of the Drawings

By way of example only, the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a cross-section through a motor with an integrated brake assembly; Figure 2 is an enlarged partial view of the static braking member 200 of figure 1; Figure 3 is an enlarged partial view of the moveable braking member 300 of figure 1.

Detailed Description of Preferred Embodiments

A typical static brake includes a solenoid assembly, which attracts an armature to disengage the brake when energised. This is referred to as a "power off" brake, as it is engaged when power is not provided, and when there is no current passed through the solenoid. When the solenoid is not energised, springs in the assembly push an armature into contact with a rotating disc, which keeps the disc stationary.

With reference to the figures, there is provided a motor 1 having an integrated brake assembly 2. The motor 1 comprises: a motor frame 10; a motor shaft 20; a rotor disc 100; a static braking member 200; and a moveable braking member 300.

Since a skilled person will appreciate how a motor functions, only the components of the motor which help to explain the invention are elaborated on herein.

The motor shaft 20 is rotatably mounted relative to the frame 10. The motor shaft 20 may have a central axis 22 about which it is configured to rotate. The motor shaft 20 may be configured to transmit rotational motion to one or more driven components.

The rotor disc 100 is fixedly attached to the motor shaft 20. The rotor disc 100 may comprise a braking surface which is configured to be engaged by a braking means, which in turn brakes the motor shaft 20. The rotor disc 100 may have an inner region 150 at which the rotor disc 100 is attached to the motor shaft 20, and an outer region 160 further away from the motor shaft 20 than the inner region 150. The rotor disc 100 may be provided as an extension of the motor shaft 20, so that the motor shaft 20 and the rotor disc 100 are an integral piece, or may be provided as a separate piece of material which is attachable to the motor shaft 20. The rotor disc 100 may be one or more of: disc shaped; planar; circular; symmetrical about the central axis 22 of the motor shaft 20.

The static braking member 200 is mounted in fixed relation to the frame 10. The static braking member 200 comprises a contact region 210 configured to contact the rotor disc 100 when in a braking condition.

The moveable braking member 300 is mounted in moveable relation to the static braking member 200. The moveable braking member 300 comprises a contact region 310 configured to contact the rotor disc 100 when in a braking condition. The moveable braking member 300 may have a main part and the contact region 310 may extend from the main part. The moveable braking member 300 may be configured to be moveable in a direction substantially or wholly parallel to a longitudinal axis 22 of the motor shaft 20.

There are differences between the performance requirements of static brake assemblies and dynamic brake assemblies and the inventor has identified how to use this to advantageously create more weight-and cost-efficient braking arrangements for static brake assemblies. Firstly, the materials used in static brake assemblies need not be as wear resistant as those used in dynamic brake assemblies. In particular, the static braking member 200 and/or the moveable braking member 300 need not be as wear resistant as corresponding components in a conventional dynamic brake. Secondly, in a static brake, less heat is generated through friction than in a dynamic brake, so it is possible to use less heat-resistant materials, and materials having a lower melting point. The static braking member 200 and/or the moveable braking member 300 may therefore comprise materials having less heat resistant materials, such as materials having a lower melting-point than corresponding components in a conventional dynamic brake arrangement.

The frame 10 may be configured to act as a housing for at least some of the components of the integrated brake assembly 2. The frame 10 may comprise a durable and rigid material such as a suitable metal or alloy.

The motor 1 may also comprise: a rotatable attachment means 30, an actuation means 40, a biasing means 50, and/or a rotor disc attachment means 60.

The rotatable attachment means 30 may be configured to enable rotational movement of the motor shaft 20 relative to the frame 10. The rotatable attachment means 30 may be provided around the motor shaft 20. The rotatable attachment means 30 may be a bearing, such as a rolling element bearing.

The rotor disc attachment means 60 may be configured to fixedly attach the rotor disc 100 to the motor shaft 20. The rotor disc attachment means 60 may provide a mechanical attachment between the rotor disc 100 and the motor shaft 20. The rotor disc attachment means 60 may comprise a first piece 61 and a second piece 62. The first piece 61 may be configured for attachment to the motor shaft 20, for example by being fixed or fixable to the motor shaft 20 by means of an interference fit, and/or any other suitable attachment.

The first and/or second piece may be cylindrically shaped, and/or define a central aperture in which the motor shaft 20 is disposed. The first piece 61 may have a substantially L-shaped cross-section in a radial direction of the motor shaft 20, and/or the second piece 62 may have a substantially square or rectangular shaped cross-section. The second piece 62 and/or the inner region 150 of the rotor disc 100 may be configured to fit into the first piece 61. The second piece 62 may be configured for attachment to the first piece 62, to clamp an inner region 150 of the rotor disc 100 between the first and second pieces 61, 62. A skilled person will appreciate that although one possible attachment means is described here and shown in figure 1, various possible attachment means could be used with the present invention.

The biasing means 50 may be a biasing member, and may be configured to bias the moveable braking member 300 away from and/or out of contact with the rotor disc 100.

The biasing means 50 may be configured to maintain the moveable braking member 300 out of contact with the rotor disc 100 upon actuation. The biasing means 50 may be a spring.

The actuation means 40 may be configured to move the moveable braking member 300 into contact with the rotor disc 100 upon actuation. The actuation means 40 may be configured to move the moveable braking member 300 by overcoming the biasing force exerted by the biasing means 50. The actuation means 40 may be a solenoid, although a skilled person will appreciate that any suitable actuation means may be used.

With reference to figure 1, when the motor 1 is in operation, the motor shaft 20 rotates about the motor shaft axis 22. Given that the rotor disc 100 is fixedly attached to the motor shaft 20, the rotor disc 100 rotates along with the motor shaft 20 about the motor shaft axis 22. The motor shaft 20 may be brought to a stop either by removing any actuating force causing it to rotate, and/or applying a dynamic braking means (not shown).

The dynamic braking means may be friction-based, or may be implemented by electronic motor control to slow the rotation of the motor.

When the motor shaft 20 and rotor disc 100 are in a stationary position relative to the frame 10, the integrated brake assembly 2 may be applied. The integrated brake assembly 2 may be applied by actuating the actuation means 40. Actuation of the actuation means 40 may cause the moveable braking member 300 to move towards the rotor disc 100, specifically in a substantially or wholly axial direction, which may be parallel to the central axis 22 of the motor shaft 20, towards an outer region 160 of the rotor disc 100, and towards the static braking member 200. The actuation means 40 may continue to move the moveable braking member 300 towards the rotor disc 100 until an outermost part of the contact region 310 is in contact with the rotor disc 100. The actuation means 40 may then continue to move the moveable braking member 300 towards the rotor disc 100 until at least part of the contact region 310 of the moveable braking member 300 is elastically deformed, or squashed between the rotor disc 100 and the moveable braking member 300. The actuation means 40 may then continue to move the moveable braking member 300 in the same direction, and may start to move the rotor disc 100 towards the static braking member 200, until a side of the rotor disc 100 closest to the static braking member 200 contacts an outermost part of the contact region 210 of the static braking member 200. The actuation means 40 may then continue to move the moveable braking member 300 and the rotor disc 100 towards the static braking member 200 until at least part of the contact region 210 of the static braking member is elastically deformed, or squashed, between the rotor disc 100 and the static braking member 200. In this position, referred to as the static braking position, the rotor disc 100, and as a result the motor shaft 20, are held in place between the braking members 200, 300, through the elastically deformed contact regions 210, 310 of the braking members 200, 300.

At least one of the contact regions 210, 310, comprises an elastomeric material. The braking position of the integrated brake assembly is facilitated by the elasticity of the elastomeric material of the contact region(s).

A person skilled ion the art of materials will readily identify an elastomeric material and those which are not elastomeric. As a skilled person will appreciate, an elastomeric material is a high molar mass material which when deformed at room temperature reverts quickly to nearly original size and form when the load causing the deformation has been removed. An elastomeric material may be a macromolecular material. An elastomeric material can be defined according to ISO 1382:1996. As a skilled person will appreciate, elastomeric material may be flexible, resilient, and/or elastically deformable. An elastomeric material will typically comprise a high molecular weight polymeric material, which may be a synthetic polymer, such as a neoprene and/or a fluorocarbon material. In embodiments according to the present disclosure, elastomeric material is used in place of the typical materials used in brake friction elements, such as ceramics, metals, alloys etc. Both of the contact regions 210, 310, may comprise or be composed of an elastomeric material. At least one of the contact regions may have a static coefficient of friction of at least 0.5 using ISO standard 8295:1995, preferably at least 0.6 using ISO standard 8295:1995, and further preferably at least 0.7 using ISO standard 8295:1995. At least one or both of the contact regions 210, 310, may comprise a material having a compression modulus in the range of 0.7 to 2 MPa when measured using method A of ISO standard 7743. At least one or both of the contact regions 210, 310 may comprise a material having a shear modulus in the range of 0.5 to 1.25 MPa when measured using method A of ISO standard 1827:2016. The compression modulus of one or more of the contact regions 210, 310 is approximately a third of the shear modulus of that contact region 210, 310. At least one of the contact regions 210, 310 may comprise a neoprene and/or a fluorocarbon material. At least one of the contact regions 210, 310 may comprise a fluorocarbon material supplied under the name Viton (RTM), which may be an 0-ring material under the trade mark Viton (RTM). At least one of the contact regions 210, 310 may not comprise silicone. The contact regions 210, 310 may have substantially equal properties to one another in respect of one or more of: macroscopic shape; size; chemical composition; topography; friction coefficient; mechanical and/or materials properties.

The or each contact region 210, 310 may be disposed at or proximate the outer region 160 of the rotor disc 100. A skilled person will appreciate that the or each contact region 210, 310 may be disposed at or proximate the inner region 150 of the rotor disc 100. Locating the or each contact region 210, 310 at or proximate the outer region 160 of the rotor disc 100 has the advantage of providing a contact region 210, 310 at a location where movement of the rotor disc 100 is relatively high, and as such, torque exerted on the rotor disc 100 by the or each contact region 210, 310 may be maximised. The or each contact region 210, 310 may be disposed proximate an outer half, preferably an outer third, preferably an outer quarter of the radius of the rotor disc 100.

The contact region 210, 310 on at least one of the static braking member 200 and the moveable braking member 300 may be comprised in a contact member 220, 320. The or each contact member 220, 320 may have one or more of: a uniform cross-sectional shape; a substantially annular shape which may surround the motor shaft 20; a rotationally symmetrical shape about a longitudinal axis 22 of the motor shaft 20; a torus shape. The or each contact member 220, 320 may be an 0-ring.

The or each contact member 220, 320 may be fixedly attached to its respective braking member 200, 300. Such attachment may be by means of a mechanical attachment, which may be provided by an opening 230, 330 in the or each braking member 200, 300. The opening 230, 330 may be configured to at least partially receive the contact member 220, 320 such that a part of the contact member 220, 320 extends from the opening 230, 330.

The contact member 220, 320 may be attached to its respective braking member 200, 300 such that the elastomeric material of the contact member 220, 320 is in a substantially or wholly mechanically relaxed (i.e. un-stressed) state. As shown in figure 2, the opening 230, 330 may have a surface dimension 270 and an inner dimension 271. The inner dimension 271 may be larger than the surface dimension 270. The surface dimension 270 may be smaller than a maximum dimension 272 of the contact member 220, 320 when in an un-stressed state. There may be provided an inner lip 202 and/or an outer lip 204 on the braking member 200, 300, between which a surface dimension 270 is defined.

Alternatively or in addition, the contact member 220, 320 may be attached to its respective braking member 200, 300 such that the elastomeric material of the contact member 220, 320 is in a substantially or wholly mechanically stressed state. The contact member 220, 320 may be attached to its respective braking member 200, 300 in a tensioned state. Mechanical attachment may be provided by means of an inner lip 202, 302 on one or more of the braking members 200, 300. The inner lip 202, 302 and the contact member 220, 320 may be configured such that the or each contact member 220, 320 may be stretched over the lip 202, 302. The lip 202, 203 of the braking member may prevent the stretched contact member 220, 230 from moving into a relaxed position, i.e. position in which it is not stretched. The lip 202, 302, may be configured to extend from the braking member 200, 300. The lip 202, 302 may be configured to at least partially extend away from the motor shaft 20 and/or an inner region 150 of the rotor disc 100. The lip 202, 302 may at least partially define a groove 203, 303. The groove 203, 303 may be annular, and/or at least partially face away from the motor shaft 20. The groove 203, 303 may be configured to at least partially receive a corresponding contact member 220, 320. The groove 203, 303 may be dimensioned such that a corresponding contact member 220, 320 may be at least partially received in the groove 203, 303. The contact member 220, 320, may be held in place by means of tension in the contact member 220, 320, acting inwardly on its respective braking member 200, 300 within the groove 203, 303.

While the lip 202, 203 may be provided as an integral piece of its respective braking member 200, 300, as shown in figures 2 and 3, the skilled person will appreciate that various manufacturing methods of the lip 202, 302 are possible. One alternative method involves provision of a plate, and/or grip or clipping means such as a circlip, which is attached to the braking member 200, 300 so as to provide a lip 202, 302 on the braking member 200, 300.

A skilled person will appreciate that the material properties, shape and/or configuration of the static braking member 200 and the moveable braking member 300 may be equal to one another, or may differ from one another. As a skilled person will appreciate, a feature described herein in relation to only one of the braking members 200, 300, may apply to the other braking member 200, 300, or to both braking members 200, 300.

Features of the present invention are defined in the appended claims. While particular combinations of features have been presented in the claims, it will be appreciated that other combinations, such as those provided above, may be used.

The above example describe one way of implementing the present invention. It will be appreciated that modifications of the features of the above examples are possible within the scope of the independent claims and that any and all compatible features of any embodiments described separately above, can be combined within a single embodiment of a device in accordance with the invention.

Claims

Claims 1. A motor having an integrated brake assembly, the motor comprising: a motor frame; a motor shaft which is rotatably mounted relative to the frame; a rotor disc which is fixedly attached to the motor shaft; a static braking member which is mounted in fixed relation to the frame, and a moveable braking member which is mounted in moveable relation to the static braking member; wherein each of the static braking member and the moveable braking member comprises a contact region configured to contact the rotor disc when in a braking condition, so as to fix the position of the motor shaft relative to the frame; and wherein at least one of the contact regions comprises an elastomeric material.
2. A motor according to claim 1, wherein at least one of the contact regions has a static coefficient of friction of at least 0.5 using ISO standard 8295:1995, preferably at least 0.6 using ISO standard 8295:1995, and further preferably at least 0.7 using ISO standard 8295:1995.
3. A motor according to claim 1 or claim 2, wherein at least one of the contact regions comprises a material having a compression modulus in the range of 0.7 to 2 MPa when measured using method A of ISO standard 7743.
4. A motor according to any of the preceding claims, wherein at least one of the contact regions comprises a material having a shear modulus in the range of 0.5 to 1.25 MPa when measured using method A of ISO standard 1827:2016.
5. A motor according to any of the preceding claims, wherein the compression modulus of one or more of the contact regions is approximately a third of the shear modulus of that contact region.
6. A motor according to any of the preceding claims, wherein at least one of the contact regions comprises a neoprene and/or a fluorocarbon material.
7. A motor according to any of the preceding claims, wherein the contact regions have substantially equal properties to one another in respect of one or more of: macroscopic shape; size; chemical composition; topography; friction coefficient; mechanical and/or materials properties.
8. A motor according to any of the preceding claims, wherein the contact region on at least one of the static braking member and the moveable braking member is comprised in a contact member.
9. A motor according to claim 8, wherein the or each contact member is fixedly attached to its respective braking member.
10. A motor according to claim 9, wherein the or each contact member is attached to its respective braking member by means of a mechanical attachment.
11. A motor according to claim 10, wherein the mechanical attachment is provided by an opening in the or each braking member, the opening being configured to partially receive the contact member such that a part of the contact member extends from the 15 opening.
12. A motor according to claim 11, wherein the opening has a surface dimension and an inner dimension, the inner dimension being larger than the surface dimension, and the surface dimension being smaller than a maximum dimension of the contact member when in an un-stressed state.
13. A motor according to any of claims 8 to 12, wherein the or each contact member has a uniform cross-sectional shape in a circumferential direction of the rotor disc.
14. A motor according to any of claims 8 to 13, wherein the or each contact member has a substantially annular shape which surrounds the motor shaft.
15. A motor according to any of claims 8 to 14, wherein the or each contact member has a rotationally symmetrical shape about a longitudinal axis of the motor shaft.
16. A motor according to any of claims 8 to 15, wherein the or each contact member has a torus shape.
17. A motor according to any of the preceding claims, wherein the rotor disc has an inner region at which the rotor disc is attached to the motor shaft, and an outer region further away from the motor shaft than the inner region, and wherein the or each contact region is disposed proximate the outer region.