GB2557006A - Protection of bearings in an SMA actuator assembly - Google Patents

Protection of bearings in an SMA actuator assembly Download PDF

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Publication number
GB2557006A
GB2557006A GB1716312.2A GB201716312A GB2557006A GB 2557006 A GB2557006 A GB 2557006A GB 201716312 A GB201716312 A GB 201716312A GB 2557006 A GB2557006 A GB 2557006A
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United Kingdom
Prior art keywords
base plate
bearings
actuator assembly
sma actuator
moving plate
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Granted
Application number
GB1716312.2A
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GB201716312D0 (en
GB2557006B (en
Inventor
Eddington Robin
Howarth James
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Cambridge Mechatronics Ltd
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Cambridge Mechatronics Ltd
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Publication of GB201716312D0 publication Critical patent/GB201716312D0/en
Publication of GB2557006A publication Critical patent/GB2557006A/en
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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B7/00—Mountings, adjusting means, or light-tight connections, for optical elements
    • G02B7/02—Mountings, adjusting means, or light-tight connections, for optical elements for lenses
    • G02B7/04—Mountings, adjusting means, or light-tight connections, for optical elements for lenses with mechanism for focusing or varying magnification
    • G02B7/08—Mountings, adjusting means, or light-tight connections, for optical elements for lenses with mechanism for focusing or varying magnification adapted to co-operate with a remote control mechanism
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03G—SPRING, WEIGHT, INERTIA OR LIKE MOTORS; MECHANICAL-POWER PRODUCING DEVICES OR MECHANISMS, NOT OTHERWISE PROVIDED FOR OR USING ENERGY SOURCES NOT OTHERWISE PROVIDED FOR
    • F03G7/00—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for
    • F03G7/06—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for using expansion or contraction of bodies due to heating, cooling, moistening, drying or the like
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03G—SPRING, WEIGHT, INERTIA OR LIKE MOTORS; MECHANICAL-POWER PRODUCING DEVICES OR MECHANISMS, NOT OTHERWISE PROVIDED FOR OR USING ENERGY SOURCES NOT OTHERWISE PROVIDED FOR
    • F03G7/00—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for
    • F03G7/06—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for using expansion or contraction of bodies due to heating, cooling, moistening, drying or the like
    • F03G7/065—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for using expansion or contraction of bodies due to heating, cooling, moistening, drying or the like using a shape memory element
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/64—Imaging systems using optical elements for stabilisation of the lateral and angular position of the image
    • G02B27/646—Imaging systems using optical elements for stabilisation of the lateral and angular position of the image compensating for small deviations, e.g. due to vibration or shake
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B7/00—Mountings, adjusting means, or light-tight connections, for optical elements
    • G02B7/02—Mountings, adjusting means, or light-tight connections, for optical elements for lenses
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B5/00—Adjustment of optical system relative to image or object surface other than for focusing
    • G03B5/02—Lateral adjustment of lens
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B2205/00—Adjustment of optical system relative to image or object surface other than for focusing
    • G03B2205/0007—Movement of one or more optical elements for control of motion blur
    • G03B2205/0015—Movement of one or more optical elements for control of motion blur by displacing one or more optical elements normal to the optical axis
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B2205/00—Adjustment of optical system relative to image or object surface other than for focusing
    • G03B2205/0053—Driving means for the movement of one or more optical element
    • G03B2205/0076—Driving means for the movement of one or more optical element using shape memory alloys

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Optics & Photonics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Rolling Contact Bearings (AREA)
  • Support Of The Bearing (AREA)

Abstract

An SMA actuator assembly, suitable for Optical Image Stabilization (OIS) in cameras, has a bearing shock protection structure. The assembly comprises a base plate 2, a moving plate (3, figure 1) and one or more bearings 4 suspending the moving plate on the base plate to allow the moving plate to move laterally with respect to the base plate. The assembly also comprises at least one SMA wire (20) connected between the moving plate and the base plate and arranged to move the moving plate laterally with respect to the base plate 2 when driven and a bearing shock protection structure comprising cantilever structures 1 formed by one or more cuts in the base plate, the one or more bearings 4 resting on the free ends of the cantilever structures 1. The bearings may comprise either balls or sliding bearing pads, and there may be three or four of them. The assembly may further comprise at least one end stop to limit vertical movement of the moving plate. A camera comprising the assembly, and portable electronic device comprising the camera are also claimed.

Description

(54) Title of the Invention: Protection of bearings in an SMA actuator assembly
Abstract Title: SMA Actuator Assembly With Cantilever Shock Protection for Bearings (57) An SMA actuator assembly, suitable for Optical Image Stabilization (OIS) in cameras, has a bearing shock protection structure. The assembly comprises a base plate 2, a moving plate (3, figure 1) and one or more bearings 4 suspending the moving plate on the base plate to allow the moving plate to move laterally with respect to the base plate. The assembly also comprises at least one SMA wire (20) connected between the moving plate and the base plate and arranged to move the moving plate laterally with respect to the base plate 2 when driven and a bearing shock protection structure comprising cantilever structures 1 formed by one or more cuts in the base plate, the one or more bearings 4 resting on the free ends of the cantilever structures 1. The bearings may comprise either balls or sliding bearing pads, and there may be three or four of them. The assembly may further comprise at least one end stop to limit vertical movement of the moving plate. A camera comprising the assembly, and portable electronic device comprising the camera are also claimed.
Fb iq. 2
Figure GB2557006A_D0001
At least one drawing originally filed was informal and the print reproduced here is taken from a later filed formal copy.
1/3
Figure GB2557006A_D0002
Figure GB2557006A_D0003
12 17
Figure GB2557006A_D0004
12 17
Figure GB2557006A_D0005
12 17
Figure GB2557006A_D0006
Figure GB2557006A_D0007
Figure GB2557006A_D0008
Protection of Bearings in an SMA Actuator Assembly
This patent concerns the bearings in an SMA actuator assembly. It particularly concerns the protection of the bearings from mechanical shock. Such an SMA actuator assembly may be used for Optical Image Stabilization (OIS) in miniature cameras in portable devices such as mobile phones.
SMA actuator assemblies are known for various applications, for example effecting OIS in miniature cameras. OIS mechanisms may include a static plate (also described as a static support plate, a support plate or a base plate) mounting the image sensor and a moving plate mounting the lens assembly, and an actuator which moves the moving plate laterally to compensate for vibration. Vibration may be caused by user handshake, and is detected by a sensor such as a gyro. SMA actuators for OIS comprising four SMA wires are described, for example, in WO-2013/175197 and WO-2014/083318.
The moving plate is suspended on the static support plate in such a manner as to allow lateral movement. One means of achieving this is to use ball bearings, as described in the aforementioned WO 2014/083318. An alternative means is to use plain bearings, as described in the co-owned British patent application GB1517202.6 and WO-2017/055788.
The bearings of the suspension rest on the support plate which is generally a smooth hard surface, typically metal, which allows the balls or bearings to freely move laterally in normal operation. However, in conditions of mechanical shock, such as when the portable device is accidentally dropped by the user, the bearings may experience high forces in contact with the hard surface of the metal plate. This leads to a risk of fracture of the bearing, and a risk of deformation of the metal plate. Any of these events would hinder further normal operation.
The need to protect the bearings has been recognised in the abovementioned WO2014/083318, which describes the provision of elongate resilient members attached to a relatively thick support plate, the bearing balls being located in holes provided in the thick support plate and resting on the free (non-attached) ends of the resilient members. Under shock conditions, the resilient members cushion the shock by deflecting to take up the load.
A drawback with attached resilient members is the difficulty of assembling them into the support plate in mass manufacture. There need to be as many resilient members as bearings plus attachment features such as heat stakes, and all need to be accurately placed and aligned to recesses provided in the support plate. This increases manufacturing times and decreases yields.
It would be desirable to alleviate these problems.
According to the present invention there is provided an SMA actuator assembly having a bearing shock protection structure, wherein the SMA actuator assembly comprises: a base plate; a moving plate; one or more bearings suspending the moving plate on the base plate to allow the moving plate to move laterally with respect to the base plate; and one or more SMA wires connected between the moving plate and the base plate and arranged to move the moving plate laterally with respect to the base plate when driven, a bearing shock protection structure comprising cantilever structures formed by one or more cuts in the base plate, the one or more bearings resting on the free ends of the cantilever structures.
Thus, the present invention provides improved shock protection for bearings, for example ball bearings, which is integrated into a single plate and provides greater ease of manufacture.
Further features and advantages of the present invention will be described below by way of non-limiting examples and by reference to the accompanying drawings in which:
Fig.l is a schematic view of an SMA actuator assembly;
Fig. 2 is a perspective view of a base plate including a bearing shock protection structure;
Fig. 3 is a perspective view of a sub-assembly including the base plate of Fig. 1;
Fig. 4 is a cross section taken along line A-A in Fig. 2;
Fig. 5 is a perspective view of an alternative base plate including a bearing shock protection structure;
Fig. 6 is a perspective view of the base plate of Fig. 4 with bearings in place on the cantilevers;
Fig. 7a is a cross section taken along line A-A of Fig. 5; and
Fig. 7b is a cross section taken along line B-B of Fig. 5.
Fig. 1 shows an SMA actuator assembly 100 comprising the base plate 2, a moving plate 3, one or more bearings (for example, the balls 4) which suspend the moving plate 3 on the base plate 2 to allow the moving plate 3 to move laterally with respect to the base plate 2, one or more SMA wires 20 connecting the base plate 2 and the moving plate 3, arranged to move the moving plate 3 laterally with respect to the base plate 2 when driven, and the bearing shock protection structure 10. The SMA actuator 100 may, for example, include three or four bearings. The SMA actuator may include four SMA wires 20.
Fig. 1 is schematic, but the SMA actuator assembly 100 may take the form described in detail in WO-2014/083318 or WO-2017/055788, which illustrate in particular arrangements of four SMA wires 20, apart from the modifications described below.
Fig. 2 shows a first arrangement of the base plate 2 including a bearing shock protection structure 10. Shock protection is provided by cantilevers 1 cut into a base plate 2 (static or support plate). The base plate 2 is typically formed of metal sheet, and one or more shaped cuts 3 form cantilevers 1 in portions of the plate 2. Fig. 2 shows three such cantilevers 1, but there could be more, for example four, cantilevers. Each cantilever supports a ball 4 at its free end 5. The one or more balls 4 in Fig. 2 are shown in exploded view for clarity, the dotted lines indicating where they locate. In normal operation, the ball 4 is free to move laterally over the area at the free end 5 of the cantilever, while in shock conditions, any vertical forces are taken up by bending of the free end 5 of the cantilever 1 (downwards in Fig. 2). The bearing shock protection structure 10 is formed as a single part of cut metal, which is easy to manufacture and assemble to other components.
Fig. 3 shows a sub-assembly including the base plate 2 of Fig. 2. In Fig. 3, a ball retaining structure 6 is shown assembled on top of the base plate 2 which incorporates the cantilevers 1. The ball retaining structure 6 is shown as a relatively thick plate with holes 7 for locating the balls 4.
Also shown in Fig. 3 is a further shock protection structure in the form of end stops 8. Four end stops 8 are shown, but there may be more or fewer. For example, three end stops 8 may be used. Each end stop 8 is a pad of material raised above the main body but lower in height than the balls 4. In normal operation, the end stops 8 play no role, but in shock conditions they prevent the moving plate (which is not shown, but which normally resides at the level of the top of the balls 4) from moving further down than the top of the end stops. Thus under a vertical shock force, the cantilevers 1 take up the first part of the downward movement by deflecting and the end stops 8 limit further movement. The end stops 8 may be arranged to limit vertical movement of the moving plate 3 with respect to the base plate 2. The end stops 8 are simple pads of material and are easily assembled or mounted on to the top of the ball retaining structure.
Fig. 4 shows a cross section taken along line A-A in Fig. 3. It shows the base plate 2 and its integrated cantilever 1, the ball retaining structure 6 with ball 4 located in hole 7.
A second base plate 2 including a bearing shock protection structure 11 is shown in Fig. 5. In this case, the bearings are plain bearings rather than balls. As in the first base plate 2 of Fig. 2, cantilevers 1 are cut into a metal sheet base plate 2 to provide protection for the sliding bearing pads 9. The sliding bearing pads 9 are pads of material (shown in exploded view) which are attached to the free end 5 of the cantilevers 1. The upper surface of the sliding bearing pad 9 engages with the moving plate (not shown), providing a sliding bearing.
As in the case of balls, sliding bearings are vulnerable to fracture or deformation under shock conditions, and the integrated cantilevers 1 provide protection by deflecting to take up the load.
Fig. 6 shows the bearing shock protection structure 11 with the bearings 9 in place on the cantilevers 1. Also shown are further end stops 18, formed as raised bumps in the plate 2. Raised bumps are easy to manufacture by metal forming.
Fig. 7a is a cross section taken along line A-A of Fig. 6, showing the base plate 2, cantilever 1 and plain bearing 9 attached to the free end 5 of the cantilever. Fig. 7b is a cross section taken along line B-B of Fig. 6, showing the raised endstop 18 formed in the plate 2.
The SMA actuator assembly 100 may be incorporated into a camera. The SMA actuator assembly 100 may function as an OIS mechanism when incorporated in a camera. When incorporated in a camera, an image sensor may be mounted on the base plate 2 and a lens assembly may be mounted on the moving plate 3. The SMA wires 20 may drive the moving plate 3 laterally with respect to the base plate 2. The camera may be incorporated into a portable electronic device, such as a mobile phone.

Claims (10)

1. An SMA actuator assembly having a bearing shock protection structure, wherein the SMA actuator assembly comprises:
a base plate; a moving plate;
one or more bearings suspending the moving plate on the base plate to allow the moving plate to move laterally with respect to the base plate; and one or more SMA wires connected between the moving plate and the base plate and arranged to move the moving plate laterally with respect to the base plate when driven, a bearing shock protection structure comprising cantilever structures formed by one or more cuts in the base plate, the one or more bearings resting on the free ends of the cantilever structures.
2. The SMA actuator assembly of claim 1, wherein the one or more bearings comprise either balls or sliding bearing pads.
3. The SMA actuator assembly of any one of the preceding claims, wherein the number of bearings is three or four.
4. The SMA actuator assembly of any one of the preceding claims, further comprising one or more end stops arranged to limit vertical movement of the moving plate with respect to the base plate.
5. The SMA actuator assembly of claim 4, wherein the one or more end stops comprise pads of material mounted on the base plate.
6. The of claim 4, wherein the one or more end stops comprise raised bumps in the base plate.
7. The SMA actuator assembly of claim 4, wherein the number of end stops is three or four.
8. The SMA actuator assembly of any one of the preceding claims, wherein the number of SMA wires is four.
5
9. A camera comprising the SMA actuator assembly of any one of the previous claims.
10. A portable electronic device comprising the camera of claim 9.
Intellectual
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Application No: GB1716312.2
GB1716312.2A 2016-10-05 2017-10-05 Protection of bearings in an SMA actuator assembly Active GB2557006B (en)

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GBGB1616939.3A GB201616939D0 (en) 2016-10-05 2016-10-05 Protection of bearing in an SMA actuator

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GB2557006A true GB2557006A (en) 2018-06-13
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2023135431A1 (en) 2022-01-13 2023-07-20 Cambridge Mechatronics Limited Actuator assembly

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017055788A1 (en) * 2015-09-29 2017-04-06 Cambridge Mechatronics Limited Shape memory alloy actuator arrangement
WO2017072525A1 (en) * 2015-10-28 2017-05-04 Cambridge Mechatronics Limited Camera assembly providing optical image stabilisation
WO2018029458A1 (en) * 2016-08-08 2018-02-15 Cambridge Mechatronics Limited Dual camera apparatus

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017055788A1 (en) * 2015-09-29 2017-04-06 Cambridge Mechatronics Limited Shape memory alloy actuator arrangement
WO2017072525A1 (en) * 2015-10-28 2017-05-04 Cambridge Mechatronics Limited Camera assembly providing optical image stabilisation
WO2018029458A1 (en) * 2016-08-08 2018-02-15 Cambridge Mechatronics Limited Dual camera apparatus

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2023135431A1 (en) 2022-01-13 2023-07-20 Cambridge Mechatronics Limited Actuator assembly

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GB201716312D0 (en) 2017-11-22
GB2557006B (en) 2019-04-17

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