Imaging device having a magnetic fluid heat transport system

Abstract

To improve the circulation efficiency of magnetic fluid with a conduit line considering the viscosity of the magnetic fluid and the gravity.SOLUTION: A device 100 has a heat generating unit 126, a cooling unit 101, a conduit line 402 that circulates magnetic fluid between the heat generating unit and a cooling unit, and a magnetic field generating member 316a that applies a magnetic field to the magnetic fluid. The conduit line has a first conduit line area 411 in which the magnetic fluid receives heat from the heat generating unit, a second conduit line area 412 directed to the cooling unit from the first conduit line area, a third conduit line area 413 in which the magnetic fluid is cooled by the cooling unit, and a fourth conduit line area 414 directed to the heat generating unit from the cooling unit. The volume of the magnetic fluid in the conduit line area, of the first to fourth conduit line areas, in which the flow direction of the magnetic fluid matches the gravity direction is larger than the volume of the magnetic fluid in the conduit line area in which the flow direction does not match the gravity direction.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a heat transport system using a magnetic fluid.

Background Art

[0002] As a system for circulating a magnetic fluid by utilizing a temperature gradient and a magnetic field in a circulation pipeline, Patent Document 1 discloses a structure in which the inner diameter of the pipeline in the cooling section is made larger than that in the heating section of the circulation pipeline. With this system structure, it is possible to reduce the influence of the viscosity of the magnetic fluid, which changes with temperature, on the circulation resistance and improve the circulation efficiency of the magnetic fluid. Further, Patent Document 2 discloses a system for transporting heat by driving a magnetic fluid with a rotating magnet.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, Patent Documents 1 and 2 do not mention the influence of gravity on the circulation efficiency of the magnetic fluid. Further, when driving a magnetic fluid with a rotating magnet, there is a risk that the rotation of the magnet stops and the circulation of the magnetic fluid is inhibited.

[0005] The present invention provides an apparatus capable of improving the circulation efficiency (heat transport efficiency) of a magnetic fluid by a pipeline that takes into account not only the viscosity of the magnetic fluid but also gravity, and an apparatus capable of smoothly circulating the magnetic fluid even when the rotation of the magnet stops.

Means for Solving the Problems

[0006] An imaging device according to one aspect of the present invention includes a heat generating part including an imaging element, a cooling part, a pipeline for circulating a magnetic fluid between the heat generating part and the cooling part, and a magnetic field generating member disposed on the subject side from the pipeline to apply a magnetic field to the magnetic fluid. The pipeline has a first pipeline region where the magnetic fluid receives heat from the heat generating part, a second pipeline region extending from the first pipeline region toward the cooling part, a third pipeline region where the magnetic fluid is cooled by the cooling part, and a fourth pipeline region extending from the cooling part toward the heat generating part. When the imaging device is viewed from the back side, the magnetic field generating member is disposed between the first pipeline region and the third pipeline region. In a state where the imaging element faces a direction orthogonal to the gravitational direction, the direction in which the magnetic fluid flows in the first pipe region coincides with the gravitational direction. The pipeline internal volume of the first pipeline region is In any case larger than the at all pipeline internal volumes of the second, third, and fourth pipeline regions.

Advantages of the Invention

[0008] According to the present invention, in the imaging device the magnetic fluid used can improve the heat transport efficiency. 。

Brief Description of the Drawings

[0009]

Figure 1

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Mode for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0011] Figs. 1(a) to 1(c) show an interchangeable-lens digital camera (hereinafter simply referred to as a camera) as an imaging device to which an interchangeable lens 102 can be detachably attached. Fig. 1(a) shows the camera 100 and the interchangeable lens 102 as viewed from the obliquely front side (subject side), Fig. 1(b) shows the camera 100 as viewed from the obliquely rear side (rear side), and Fig. 1(c) shows the camera 100 with the interchangeable lens 102 removed.

[0012] On the front surface of the camera 100, a front grip 101 protruding forward is provided for the user to hold the camera 100. In the center of the front surface of the camera 100, a mount portion 107 for making the interchangeable lens 102 detachable is provided.

[0013] On the outer periphery of the interchangeable lens 102, a rotation operation ring 103 is provided. The rotation operation ring 103 can be rotationally operated by the user around the optical axis of the interchangeable lens 102. The user can assign a function to change imaging conditions such as the focus position and exposure value to the rotation operation ring 103. On the upper surface of the camera 100, a power lever 104, a mode dial 105, and a release button 106 are provided. The power lever 104 is an operation member for switching the on / off of the power of the camera 100 by the operation of the user. The mode dial 105 is an operation member for switching the imaging mode by the rotational operation of the user. The imaging modes include a manual still image imaging mode in which the user can arbitrarily set imaging conditions such as the shutter speed and aperture value, an auto still image imaging mode in which an appropriate exposure amount can be obtained automatically, and a video imaging mode for performing video imaging. The release button 106 is an operation member for instructing imaging by the pressing operation of the user.

[0014] On the back surface of the camera 100, a back operation unit 110 and a display unit 111 are provided. When the power of the camera 100 is turned on, a live view image corresponding to an imaging signal from an imaging element (not shown) that has imaged (photoelectrically converted) the subject image formed by the interchangeable lens 102 is displayed on the display unit 111. Also, imaging parameters such as the shutter speed and aperture value are displayed on the display unit 111. The user can change the set value of the imaging parameters by operating the back operation unit 110 while viewing the display on the display unit 111. Further, the back operation unit 110 includes a playback button for instructing the playback of the recorded imaging image and a menu button for shifting to the detailed setting screen of the camera 100.

[0015] An electrical contact group 108 is provided on the mount portion 107 of the camera 100. The camera 100 communicates with the interchangeable lens 102 mounted on the mount portion 107 or supplies power to the interchangeable lens 102 via the electrical contact group 108.

[0016] Figure 2 shows the electrical and optical configurations of the camera 100 and the interchangeable lens 102. The camera 100 has a power supply unit 113 that supplies power to each part within the camera 100, and also has an operation unit 114 that includes the aforementioned power lever 104, mode dial 105, release button 106, and rear operation unit 110. The control unit 115 controls the entire camera system composed of the camera 100 and the interchangeable lens 102. The interchangeable lens 102 communicates with the control unit 115 via the aforementioned electrical contact group 108. The control unit 115 controls the entire camera system by reading and executing a control program stored in a memory (not shown).

[0017] The interchangeable lens 102 has a zoom unit 116 that includes a zoom lens that moves in the optical axis direction to perform zooming, and a lens vibration prevention unit 118 that includes a shift lens. The shift lens moves (shifts) in two directions orthogonal to the optical axis (the X direction and the Y direction in FIGS. 1(a) and 1(b)) to reduce (correct) image blur. Further, the interchangeable lens 102 has a diaphragm unit 122 that has a light amount adjustment function, and a focus unit 124 that includes a focus lens that moves in the optical axis direction to perform focus adjustment.

[0018] Furthermore, the interchangeable lens 102 has a rotation detection unit 133 that detects the rotation of the rotation operation ring 103. When the rotation operation ring 103 is operated and a zoom instruction is input via the rotation detection unit 133, the control unit 115 controls the driving of the zoom unit 116 via a zoom driving unit 117 provided in the interchangeable lens 102 to perform zooming.

[0019] Also, the control unit 115 controls the driving of the diaphragm unit 122 via a diaphragm driving unit 123 provided in the interchangeable lens 102 according to the set value of the diaphragm value received from the operation unit 114 or the luminance signal acquired from the image processing unit 131. Further, the control unit 115 performs autofocus by controlling the driving of the focus unit 124 via a focus driving unit 125 provided in the interchangeable lens 102 according to the focus signal acquired from the image processing unit 131.

[0020] The camera 100 is provided with a pitch anti-shake arithmetic unit 121a and a yaw anti-shake arithmetic unit 121b. The pitch anti-shake arithmetic unit 121a calculates the shift positions in the Y direction of the lens anti-shake unit 118 (shift lens) and the sensor anti-shake unit 130 (imaging element 126) using the shake signal from the pitch shake detection unit 120a. The yaw anti-shake arithmetic unit 121b calculates the shift positions in the X direction of the lens anti-shake unit 118 and the sensor anti-shake unit 130 using the shake signal from the yaw shake detection unit 120b. The camera 100 is provided with a sensor drive unit 127 for driving the sensor anti-shake unit 130. The interchangeable lens 102 is provided with an anti-shake drive unit 119 for driving the lens anti-shake unit 118. The control unit 115 controls the shift positions of the lens anti-shake unit 118 and the sensor anti-shake unit 130 via the anti-shake drive unit 119 and the sensor drive unit 127 according to the shift positions in the pitch / yaw directions calculated by the pitch and yaw anti-shake arithmetic units 121a and 121b. Thereby, an anti-shake operation for correcting image blur is performed.

[0021] The camera 100 includes a focal plane shutter unit (hereinafter simply referred to as the shutter unit) 300 and a shutter drive unit 301 for driving the same. The control unit 115 controls the driving of the shutter unit 300 via the shutter drive unit 301 in response to an imaging instruction operation on the release button 106. Thereby, the subject image formed by the interchangeable lens 102 is formed on the imaging element 126, and the imaging element 126 generates and outputs an imaging signal by its photoelectric conversion function. The image processing unit 131 performs various image processes on the imaging signal to generate image data. The data of the imaging image for recording among the image data is stored in a storage unit 132 constituted by a semiconductor memory or the like. Also, the display unit 111 displays a live view image corresponding to the image signal or reproduces and displays the imaging image recorded as data in the storage unit 132.

[0022] Figs. 3(a) to 3(c) show the configuration of the sensor anti-vibration unit 130. Fig. 3(a) shows the sensor anti-vibration unit 130 as viewed from the front side. The sensor anti-vibration unit 130 has a fixed part 200 and a movable part 250. Fig. 3(b) shows the fixed part 200 of the sensor anti-vibration unit 130 disassembled. Fig. 3(c) shows the movable part 250 of the sensor anti-vibration unit 130 disassembled.

[0023] The fixed part 200 has a base plate 201, and magnets 202a, 202b, and 202c are fixed to the base plate 201. Between the base plate 201 and a holding frame 251 of the movable part 250 described later, balls 203a, 203b, and 203c held between them are arranged. The fixed part 200 is fixed to a base unit 140 (see Fig. 4) described later.

[0024] The base plate 201 is provided with attachment hole portions for attaching spacers 204a, 204b, and 204c. The spacers 204a, 204b, and 204c have a front yoke 205 fixed to one end thereof and a rear yoke 206 fixed to the other end thereof. The movable part 250 is held movably (shiftable) within the XY plane in the drawing in the space formed between the base plate 201 and the front yoke 205.

[0025] The magnets 202a, 202b, and 202c are each magnetized so as to generate a magnetic flux density in the optical axis direction (Z direction), and are arranged at positions facing each other between the front yoke 205 and the rear yoke 206. Therefore, the front yoke 205, the magnets 202a, 202b, 202c, and the rear yoke 206 form a magnetic circuit (closed magnetic circuit). The front yoke 205 and the rear yoke 206 are attracted by the magnetic force of the magnets 202a, 202b, and 202c.

[0026] The movable part 250 has a holding frame 251. The holding frame 251 holds the imaging element 126, coils 252a, 252b, 252c, and the optical filter 253. The coils 252a, 252b, 252c are respectively arranged at positions facing the magnets 202a, 202b, 202c of the fixed part 200. A coil substrate 254 is electrically connected to the coils 252a, 252b, 252c.

[0027] The coil substrate 254 is provided with a position detection element (not shown). As the position detection element, a Hall element that detects the position of the movable part 250 using the magnetic circuit described above is used. The coil substrate 254 is also connected to a main substrate (not shown).

[0028] The coils 252a, 252b, 252c, the coil substrate 254, and the position detection element (Hall element) are included in the sensor drive unit 127 described above, and chips such as a CPU that constitutes the control unit 115 described above are mounted on the main substrate. When the sensor drive unit 127 receives a control signal from the control unit 115 and energizes the coils 252a, 252b, 252c, a force according to Fleming's left-hand rule is generated, and the movable part 250 is shift-driven in the XY plane to perform an anti-vibration operation.

[0029] The imaging element 126 is connected to the main substrate via a flexible printed circuit board (FPC) (not shown).

[0030] The optical filter 253 is held by a filter holding frame 255. The optical filter 253 has a rectangular shape that covers a range wider than the effective pixel region of the imaging element 126. The filter holding frame 255 is fixed to the holding frame 251.

[0031] FIG. 4 shows the base unit 140, the sensor anti-vibration unit 130, and the shutter unit 300 that constitute the camera 100. The fixed part 200 of the sensor anti-vibration unit 130 is fixed to the base unit 140.

[0032] The shutter unit 300 is arranged to overlap in the Z direction between the base unit 140 and the sensor anti-vibration unit 130. The base unit 140 includes a base member for fixing an exterior cover (not shown). From the front portion to the side portion of the base member, a front grip 101 having elasticity on the surface layer and for the user to grip is fixed with double-sided tape or the like.

[0033] Next, the shutter unit 300 will be described. The shutter unit 300 has a blade portion, a blade driving portion, and a shutter control portion.

[0034] First, the blade portion will be described. FIG. 5(a) shows the shutter unit 300 disassembled as viewed from the front side. 302 is the shutter bottom plate, 303 is the partition plate, 304 is the cover plate, and 307a to 307c are spacers. Apertures 302a, 303a, and 304a through which the light beam from the interchangeable lens 102 passes are formed in the shutter bottom plate 302, the partition plate 303, and the cover plate 304.

[0035] 305 is the front blade group and 306 is the rear blade group, each of which is composed of a plurality of light-shielding blades and two rotating arms or the like that rotatably support these light-shielding blades. Between the shutter bottom plate 302 and the cover plate 304, two blade chambers are formed by the partition plate 303 and the spacers 307a to 307c. The front blade group 305 is arranged in one blade chamber, and the rear blade group 306 is arranged in the other blade chamber. At the time of exposure of the imaging element 126, the front blade group 305 travels from the position where the aperture is closed in the opening direction, and the rear blade group 306 travels from the position where the aperture is open in the closing direction.

[0036] The blade drive unit will be described. Fig. 5(b) shows the shutter unit 300 disassembled as viewed from the imaging element side. 308 is the upper floor plate, 309 is the shutter control unit, 310 is the front blade drive lever unit, and 311 is the rear blade drive lever unit. During exposure, current flows from a capacitor (not shown) to the coil of the shutter control unit 309. As a result, the front blade drive lever unit 310 and the rear blade drive lever unit 311 are driven, and the front blade group 305 and the rear blade group 306 are driven to travel.

[0037] The shutter control unit 309 will be described. Fig. 5(c) shows the shutter control unit 309 disassembled as viewed from the front side. 312 is the MG floor plate.

[0038] 313 is the front MG cam unit, which is composed of a front magnet 313a, a front collar 313b, a front MG return spring 313c, and a front MG cam 313d. The front magnet 313a is a circular permanent magnet. The front MG return spring 313c is assembled to the outer periphery of the front MG cam 313d. Thereafter, in order to prevent the front MG return spring 313c from contacting the front magnet 313a, the front collar 313b provided with a flange portion is assembled to the front MG cam 313d. Further, the front magnet 313a is press-fitted and adhered to the outer periphery of the front MG cam 313d. The front MG cam unit 313 assembled in this way is rotatably attached to the first shaft portion of the MG floor plate 312.

[0039] 314 is the front yoke, which has a hole portion 314a with an inner diameter larger than the diameter of the front magnet 313a. 315 is the front coil, which is attached to the front yoke 314. When assembled to the MG floor plate 312, the front magnet 313a is disposed within the hole portion 314a of the front yoke 314.

[0040] The front MG cam unit 313 is biased in the clockwise direction as viewed from the front side by the front MG return spring 313c. When the front MG cam 313d abuts against the first stopper portion of the upper floor plate 308, the front MG cam unit 313 stops at the set position.

[0041] 316 is the rear MG cam unit, which is composed of a rear magnet 316a, a rear collar 316b, a rear MG return spring 316c, and a rear MG cam 316d. The rear magnet 316a is a circular permanent magnet. The rear MG return spring 316c is assembled on the outer periphery of the rear MG cam 316d. Then, in order to prevent the rear MG return spring 316c from contacting the rear magnet 316a, the rear collar 316b with a flange portion is assembled on the rear MG cam 316d. Further, the rear magnet 316a is press-fitted and adhered to the outer periphery of the rear MG cam 316d. The rear MG cam unit 316 assembled in this way is rotatably attached to the second shaft portion of the MG floor 312.

[0042] 317 is the rear yoke, which has a hole portion 317a with an inner diameter larger than the diameter of the rear magnet 316a. 318 is the rear coil, which is attached to the rear yoke 317. When assembled to the MG floor 312, the rear magnet 316a is disposed within the hole portion 317a of the rear yoke 317.

[0043] The rear MG cam unit 316 is biased in the clockwise direction when viewed from the front side by the rear MG return spring 316c. When the rear MG cam 316d abuts against the second stopper portion of the upper floor 308, the rear MG cam unit 316 stops at the set position.

[0044] The coil 315 and the coil 318 are connected to the main board via a flexible board (not shown). As described above, when current flows from a capacitor (not shown) to the coil 315 and the coil 318, the front blade drive lever unit 310 and the rear blade drive lever unit 311 are driven, and the front blade group 305 and the rear blade group 306 are driven for running.

[0045] Next, with reference to FIG. 6, the magnetic fluid heat transport system 400 provided in the camera 100 will be described. FIG. 6 schematically shows the configuration of the magnetic fluid heat transport system 400. In FIG. 6, 401 represents magnetic fluid, 402 represents a circulation pipeline through which the magnetic fluid 401 circulates inside, 403 represents a magnetic field generating member such as a magnet, 404 represents a heat generating part, and 405 represents a cooling part. Also, 402a represents a magnetic field acting part to which the magnetic field generated by the magnetic field generating member 403 is applied in the circulation pipeline 402, and 402b represents a heat receiving part that receives heat from the heat generating part 404 within the magnetic field acting part 402a. 402c represents a non-heat receiving part that does not receive heat from the heat generating part 404 within the magnetic field acting part 402a. Further, 407 surrounded by a dotted line represents a power conversion part including the magnetic field generating member 403, the heat generating part 404, and the magnetic field acting part 402a.

[0046] Arrows 408a and 408b indicate the typical directions and magnitudes of the magnetic body forces acting on the magnetic fluid 401 in the heat receiving part 402b and the non-heat receiving part 402c of the circulation pipeline 402. Arrow 408 indicates the driving force as the resultant of those forces. The other arrows indicate the flow direction of the magnetic fluid 401 within the circulation pipeline 402.

[0047] The magnetic fluid heat transport system 400 converts the thermal energy of the heat generating part 404 into the kinetic energy of the magnetic fluid in the power conversion part 407. When using an electronic component to be cooled (for example, the imaging element 126 of the camera 100) as the heat generating part 404, it becomes a self-circulating liquid cooling system that circulates the magnetic fluid by that heat and transports and cools the heat to the cooling part 405. This liquid cooling system is power-saving because it does not require a power source when using a permanent magnet as the magnetic field generating member 403, and has the feature of not generating extra heat.

[0048] The principle of the magnetic fluid heat transport system 400 is as follows. A magnetic field acting part 402a is provided in a part of the circulation pipeline 402 filled with the magnetic fluid 401, and a magnetic field generated by a magnetic field generating member 403 is applied to the magnetic fluid 401 inside. At this time, one of approximately two halves of the magnetic field acting part 402a is used as a heat receiving part 402b, and the other is used as a non-heat receiving part 402c, so that magnetic fields in opposite directions along the pipeline direction are generated in these regions. That is, the direction of the magnetic field in each region is set so as to receive the force (magnetic body force 408a, 408b in the pipeline direction) by which the internal magnetic fluid 401 is attracted to the side of the other region.

[0049] In such a configuration, when heat is applied to the heat receiving part 402b by the heat generating part 404 to increase the temperature of the internal magnetic fluid 401, the magnetism of the magnetic fluid 401 weakens due to its temperature sensitivity, so the magnetic body force 408a received from the magnetic field also weakens. As a result, the balance of the magnetic body forces between the magnetic fluid 401 in the heat receiving part 402b and the magnetic fluid 401 in the non-heat receiving part 402c is disrupted, so a force (driving force 408) for the magnetic fluid 401 to move from the non-heat receiving part 402c toward the heat receiving part 402b is generated. Based on the above principle, the magnetic fluid 401 flows so as to circulate in the circulation pipeline 402, and transports the heat received by the heat receiving part 402b to the cooling part 405.

[0050] As the magnetic fluid 401, a material in which ferromagnetic fine particles such as magnetite and manganese zinc ferrite are dispersed in a mother liquid such as water or oil can be used.

[0051] The tube or pipe constituting the circulation pipeline 402 is preferably formed using a non-magnetic material such as resin, rubber, copper, or aluminum so that a magnetic field acts inside. Also, in order to improve the power conversion efficiency, it is desirable to transfer as much heat as possible to the magnetic fluid 401 in the heat receiving part 402b and transfer as little heat as possible to the magnetic fluid 401 in the non-heat receiving part 402c. For this reason, the circulation pipeline 402 may be configured with a plurality of parts by partially changing the material. For example, the heat receiving part 402b may be made of copper with high thermal conductivity, and the non-heat receiving part 402c may be made of nylon with low thermal conductivity.

[0052] As the magnetic field generating member 403, a permanent magnet is preferable. For example, it is preferable to use a neodymium magnet that generates a high-density magnetic flux. In this case, a yoke formed of iron or the like may be combined so that the magnetic field in the pipe direction (flow direction) becomes stronger, or a plurality of magnetic field generating members 403 may be provided. Further, as the magnetic field generating member 403, an electromagnet that generates a magnetic field by energization and is easy to control the strength and on / off of the magnetic field may be used. Furthermore, as the magnetic field generating member 403, a coil that generates a magnetic field by energization may be used.

[0053] The heat generating part 404 is the cooling target itself such as an electronic component as described above. However, for example, one end of a heat conduction member such as a metal sleeve or a graphite sheet may be connected so as to surround a tube or a pipe, and the other end may be connected to the cooling target so that the heat of the cooling target is indirectly transmitted to the heat receiving part 402c.

[0054] The cooling part 405 is provided to lower the temperature of the magnetic fluid 401 that becomes high due to the heat from the heat generating part 404 and flows from the heat receiving part 402b and return it to the non-heat receiving part 402c. As the cooling part 405, for example, a radiator incorporated in the middle of the circulation pipe 402 or cooling fins attached to a part of the circulation pipe 402 can be used. Further, the circulation pipe 402 itself may be arranged in the cooling air from a fan or other refrigerant to constitute the cooling part 405.

Example

[0055] FIGS. 7 and 8 show Example 1 as an example of mounting the magnetic fluid heat transport system 400 on the camera 100. FIG. 7 shows the camera 100 equipped with the magnetic fluid heat transport system 400 as viewed from the Z direction. FIG. 8(a) shows the same camera 100 as viewed from the obliquely rear side, and FIG. 8(b) shows the same camera 100 disassembled.

[0056] In this embodiment, the heat generating part 404 in FIG. 6 is the imaging element 126, the cooling part 405 is the front grip 101, and the magnetic field generating member 403 is the rear magnet 316a of the shutter unit 300. The circulation pipeline 402 is provided so as to overlap with the magnetic field generating member 403 (rear magnet 316a) in the Z direction.

[0057] Among the circulation pipelines 402, the region thermally connected to the imaging element 126 (receiving heat from the heat generating part 404) is defined as the first pipeline region 411, and the region from the imaging element 126 toward the cooling part 405 is defined as the second pipeline region 412. Also, the region thermally connected to the cooling part 405 (cooled by the cooling part 405) is defined as the third pipeline region 413, and the region from the cooling part 405 toward the imaging element 126 is defined as the fourth pipeline region 414.

[0058] In FIG. 7, when the direction in which gravity acts on the camera 100 (gravity direction) is the -Y direction, as indicated by the arrow, the magnetic fluid in the first pipeline region 411 flows in the -Y direction, and the magnetic fluid in the second pipeline region 412 flows in the -X direction. Also, the magnetic fluid in the third pipeline region 413 flows in the +Y direction, and the magnetic fluid in the fourth pipeline region 414 flows in the +X direction.

[0059] The magnetic fluid flowing in the first pipeline region 411 has its flow direction coinciding with the gravity direction. And the in-pipeline volume of the first pipeline region 411 (that is, the volume of the magnetic fluid in the first pipeline region 411) is larger than the in-pipeline volume of any of the pipeline regions of the second pipeline region 412, the third pipeline region 413, and the fourth pipeline region 414. For this reason, the influence exerted by gravity on the magnetic fluid 401 has a component that assists circulation rather than a component that resists circulation. Thus, in this embodiment, the volume of the magnetic fluid in the first pipeline region 411 where the flow direction of the magnetic fluid coincides with the gravity direction is made larger than the volume of the magnetic fluid in the other pipeline regions 412 to 414 where the gravity direction and the flow direction do not coincide.

[0060] Moreover, the magnetic fluid has the property that its viscosity decreases as the temperature increases and increases as the temperature decreases. Therefore, the viscosity of the magnetic fluid flowing through the fourth pipeline region 414 is greater than that of the magnetic fluid flowing through the second pipeline region 412, and similarly, the flow resistance is large. For this reason, the cross-sectional area perpendicular to the flow direction of the magnetic fluid in the fourth pipeline region 414 is made larger than the cross-sectional area perpendicular to the same flow direction in the second pipeline region 412. As a result, the internal volume of the pipeline in the fourth pipeline region 414 becomes larger than the internal volume of the pipeline in the second pipeline region 412, and the volume of the magnetic fluid flowing through the fourth pipeline region 414 becomes larger than the volume of the magnetic fluid flowing through the second pipeline region 412. For this reason, the flow resistance of the magnetic fluid is offset, and the magnetic fluid can be circulated smoothly.

[0061] Furthermore, in each of the first to fourth pipeline regions 411 to 414, the pipeline cross-sectional area may be changed midway. In this case, by changing the pipeline cross-sectional area, that is, the volume of the flowing magnetic fluid, according to the temperature distribution of the magnetic fluid in each pipeline region, it is possible to favorably adjust the overall flow rate and flow velocity of the circulation pipeline 402. For example, in the second pipeline region 412, since the temperature of the magnetic fluid near the first pipeline region 411 is higher than the temperature of the magnetic fluid near the third pipeline region 413, it is preferable to gradually increase the pipeline cross-sectional area from the first pipeline region 411 toward the third pipeline region 413.

[0062] Also, the pipeline width H of the fourth pipeline region 414 (the width in the direction perpendicular to the flow direction of the magnetic fluid) when viewed from the direction (Z direction) in which the fourth pipeline region 414 and the rear magnet 316a overlap is not less than the width (diameter) D in the same direction of the rear magnet 316a, that is, H≧D is preferable. This is because the volume of the magnetic fluid affected by the magnetic field generated by the rear magnet 316a is larger than in the case of H < D, and the circulation efficiency of the magnetic fluid is increased.

[0063] Furthermore, the first pipeline region 411 and the third pipeline region 413 each have a larger projected area on the XY plane than the projected areas of the second pipeline region 412 and the fourth pipeline region 414 on the XY plane, and are in contact with the heat generating part 404 and the cooling part 405 over a wide range. Therefore, the heat transfer efficiency from the outside of the circulation pipeline 402 to the circulation pipeline 402 is high. That is, the heat transfer efficiency to the magnetic fluid is high. Moreover, since the heat transfer efficiency between the outside of the circulation pipeline 402 and the outside is high, the temperature difference between the first pipeline region 411 and the fourth pipeline region 414 becomes large, and the circulation efficiency of the magnetic fluid becomes high.

[0064] (Modification Example 1) FIG. 9 shows a camera equipped with a magnetic fluid heat transfer system as a modification of Example 1. In this modification, the second pipeline region 412 and the fourth pipeline region 414 are each inclined with respect to the X direction such that the flow direction of the magnetic fluid inside them includes a component in the gravitational direction, that is, is positioned more downstream in the -Y direction. At this time, since the flow of the magnetic fluid flowing in the second pipeline region 412 and the fourth pipeline region 414 is assisted by gravity, the circulation efficiency of the magnetic fluid becomes high.

[0065] (Modification Example 2) FIG. 10 shows a camera equipped with a magnetic fluid heat transfer system as another modification of Example 1. In this modification, the upstream part of the second pipeline region 412 is inclined with respect to the X direction so as to be positioned more downstream in the -Y direction as in Modification Example 1, and the downstream part extends in the +Y direction. Further, the third pipeline region 413 extends in the -Y direction, and the upstream part of the fourth pipeline region 414 is inclined with respect to the X direction so as to be positioned more downstream in the +Y direction. The downstream part of the fourth pipeline region 414 extends in the +X direction. At this time, the flow direction of the magnetic fluid in the first pipeline region 411, which has the largest internal volume in the circulation pipeline 402, and the third pipeline region 413, which has the second largest internal volume, coincides with the gravitational direction. Therefore, the magnetic fluid can receive high-efficiency circulation assistance by gravity, and the circulation efficiency becomes high.

[0066] Furthermore, when the posture of the camera 100 is changed such that the +X direction becomes the gravity direction, the flow direction in the upstream portion of the fourth pipeline region 414 includes a component in the gravity direction, and the flow direction in the downstream portion coincides with the gravity direction. Since the internal volume of the pipeline in the fourth pipeline region 414 is larger than that in the second pipeline region 412, the sum of the effects of gravity in the circulation pipeline 402 is positive in the circulation direction of the magnetic fluid. As a result, the circulation efficiency of the magnetic fluid can be increased.

[0067] In any of Example 1 and Modifications 1 and 2, the projected area of the first to fourth pipeline regions 411 to 414 on the XY plane is such that the second pipeline region 412 is the smallest, and the fourth pipeline region 414 is larger than the second pipeline region 412. Also, for the above projected area, the third pipeline region 413 is larger than the fourth pipeline region 414, and the first pipeline region 411 is the largest. Also, the internal volume of the pipeline is large in the same order.

[0068] Note that each of the first to fourth pipeline regions 411 to 414 may be composed of a plurality of pipelines, and the flow direction of the magnetic fluid in the circulation pipeline 402 may be opposite to the flow direction described above.

Example

[0069] FIG. 11 shows a camera 600 equipped with a magnetic fluid heat transport system which is Example 2. The camera 600 has a front grip 601 that a user holds, and a side slit portion 600a as an air intake is provided on its side surface. Also, a bottom slit portion as an exhaust port is provided on the bottom surface of the camera 600 (not shown). The air sucked in from the side slit portion 600a reaches the cooling portion through a flow path (not shown) inside the camera 600, and then is discharged from the bottom slit portion.

[0070] FIG. 12(a) shows a magnetic fluid heat transport system 602 disposed inside the camera 600. The magnetic fluid heat transport system 602 includes a circulation pipeline 603 in which a magnetic fluid circulates internally, a first magnet 605 which is a first magnetic field generating member, a second magnet 606 which is a second magnetic field generating member, a heat generating portion 607, and a cooling portion 608.

[0071] The heat generating part 607 is the sensor anti-vibration unit 130 equipped with the imaging element 126, which was described with reference to FIGS. 3(a) to 3(c). The heat source is the imaging element 126, but the heat emitted from the imaging element 126 is transmitted to the entire sensor anti-vibration unit 130, and the base plate 201 of the sensor anti-vibration unit 130 also stores heat. Therefore, the entire sensor anti-vibration unit 130 becomes the heat generating part 607. The circulation pipeline 603 is thermally connected to the base plate 201 via a heat conduction member (not shown), so that the heat of the sensor anti-vibration unit 130 (imaging element 126) can be transmitted to the magnetic fluid. The circulation pipeline 603 is preferably formed of a non-magnetic material with low flow path resistance and high thermal conductivity.

[0072] In this embodiment, as the first magnet 605, the magnet 202a mounted on the sensor anti-vibration unit 130 is used. The portion of the circulation pipeline 603 that is close to (opposite to) the first magnet 605 passes between the first magnet 605 and the recess provided in the rear yoke 206. FIG. 12(b) shows an enlarged view of a part of the first magnet 605 and the circulation pipeline 603. In FIG. 12(b), the illustration of the rear yoke 206 is omitted.

[0073] The second magnet 606 is rotatably held about an axis extending in the Y direction. The cooling part 608 is arranged inside the front grip 601. In FIG. 12(a), the first magnet 605 is arranged so as to face the circulation pipeline 603 between the heat generating part 607 and the cooling part 608, that is, on the upstream side of the heat generating part 607. Due to the magnetic field generated by the first magnet 605, the magnetic fluid in the circulation pipeline 603 flows in the circulation pipeline 603 in the direction of arrow A shown in FIG. 12(a) (from the +X direction to the -X direction). The circulation pipeline 603 is arranged such that the magnetic fluid follows the positions of the first magnet 605, the heat generating part 607, the second magnet 606, the cooling part 608, and the first magnet 605 in this order.

[0074] The magnetic fluid in the circulation pipeline 603 becomes hot due to the heat from the heat generating part 607 on the downstream side, i.e., the side of the heat generating part 607, with reference to the position of the first magnet 605, and thus reaches a high temperature. On the other hand, it is cooled by the cooling part 608 on the upstream side, i.e., the side of the cooling part 608, and thus reaches a low temperature. That is, the temperature gradient of the magnetic fluid in the circulation pipeline 603 near the first magnet 605 is a positive gradient (the temperature increases towards the downstream side) in the flow direction of the magnetic fluid.

[0075] In this embodiment, the first magnet 605 is the magnet 202a mounted on the fixing part 200 of the sensor vibration-proof unit 130. However, other magnets, electromagnets, etc. may be used as the magnetic field generating members.

[0076] As described above, the portion of the circulation pipeline 603 facing the first magnet 605 is arranged between the first magnet 605 and the rear yoke 206. In the range where the first magnet 605 and the rear yoke 206 face each other, the magnetic flux density increases because the rear yoke 206 collects the magnetic field of the first magnet 605 more. Therefore, the gravitational force on the magnetic fluid flowing through this range becomes stronger, and the flow efficiency of the magnetic fluid improves.

[0077] Fig. 13(a) shows the XY cross-section of the cooling part 608. The cooling part 608 includes fins 608b and a fan 608a arranged inside the fins 608b. The fan 608a is rotationally driven by a motor 604 fixed to the fins 608b, and allows external air to flow into the fins 608b as shown by the dashed arrow in the figure from the side slit part 600a described above, and flow out from the bottom slit part described above. The fins 608b are thermally connected to the circulation pipeline 603 through a heat conducting member (not shown). Therefore, the heat of the magnetic fluid in the circulation pipeline 603 is absorbed by the air passing through the fins 608b, and the magnetic fluid is cooled. Note that the dashed arrow in Fig. 13(a) shows the path of the air.

[0078] On the portion of the rotating shaft of the motor 604 opposite to the side where the fan 608a is fixed, the second magnet 606 is fixed. The second magnet 606 is arranged such that the direction of the magnetic field generated from the second magnet 606 faces the circulation pipeline 603. The motor 604 may be a brushless motor. In this case, the magnet which is the rotor of the brushless motor may be extended to the outside and used as the second magnet 606.

[0079] FIGS. 13(b) and (c) show an enlarged view of the circulation pipeline 603 and the second magnet 606 in the vicinity thereof. The second magnet 606 rotates from the state where the direction J of the magnetic field generated therefrom faces the upstream side of the circulation pipeline 603 as shown in FIG. 13(b) to the state where it faces the downstream side as shown in FIG. 13(c). At this time, the magnetic fluid attracted to the second magnet 606 side receives a force flowing in the direction of arrow A due to the rotation of the second magnet 606. That is, by setting the rotation direction of the second magnet 606 to the direction that gives the magnetic fluid a force flowing in the direction of arrow A (the direction of circulating in the circulation pipeline), the flow of the magnetic fluid 401 can be assisted.

[0080] Also, in FIGS. 13(b) and (c), a yoke 609 is provided on the side opposite to the second magnet 606 with the circulation pipeline 603 interposed therebetween. By providing the yoke 609, the magnetic field from the second magnet 606 can be collected more efficiently, and the flow assistance effect of the magnetic fluid due to the rotation of the second magnet 606 can be enhanced.

[0081] After the circulation pipeline 603 passes through the section where the flow of the magnetic fluid is assisted by the rotation of the second magnet 606, it is thermally connected to the fins 608b of the cooling unit 608 as described above. That is, the temperature gradient of the magnetic fluid near the second magnet 606 is almost 0 in its flow direction (the direction of arrow A). That is, the absolute value of the temperature gradient is smaller than the above-mentioned positive gradient. Also, the location where the circulation pipeline 603 and the cooling unit 608 are thermally connected is on the downstream side of the range where the yoke 609 faces the circulation pipeline 603. For this reason, in the section where the rotation of the second magnet 606 assists the flow of the magnetic fluid, the magnetic fluid is hardly cooled.

[0082] It is desirable that the density of the magnetic flux generated by the first magnet 605 is higher than that of the second magnet 606. Thereby, even when the rotation of the second magnet 606 stops due to the power supply of the camera 600 being turned off or the like, the flow force applied to the magnetic fluid by the magnetic field generated by the first magnet 605 is stronger than the force that inhibits the flow by the second magnet 606, and the magnetic fluid can be circulated smoothly.

[0083] As described above, by arranging the rotatable second magnet 606 at a position where the temperature gradient of the magnetic fluid in the circulation pipe 603 is almost 0, it is possible to efficiently transport the heat of the heat generating part 607 to the cooling part 608 even when the rotation of the fan 608a and the second magnet 606 stops. Further, by cooling the imaging element 126 with a heat transport system using magnetic fluid, it is possible to relax the limitation of imaging due to the temperature rise of the imaging element 126.

[0084] Note that power generation may be performed by a Peltier element using the temperature difference between the heat generating part 607 and the cooling part 608, and the fan 608a of the cooling part 608 may be rotationally driven with the electric power. Further, even after the power supply of the camera 600 is turned off, cooling by the fan 608a may be continued by power generation by the Peltier element while there is a temperature difference between the heat generating part 607 and the cooling part 608.

Example

[0085] FIG. 14 shows a magnetic fluid heat transport system 700 which is Example 3. The magnetic fluid heat transport system 700 of this example is also mounted on the camera 600 shown in FIG. 6. In this example, the same components as those in Example 2 are denoted by the same reference numerals as those in Example 2.

[0086] The magnetic fluid heat transport system 700 includes a circulation pipeline 701 through which the magnetic fluid circulates internally, a first magnet 605, a second magnet 606, a heat generating part 607, and a cooling part 608. Also in this embodiment, the heat generating part 607 is the sensor vibration-proof unit 130 equipped with the imaging element 126. Further, as the first magnet 605, the magnet 202a mounted on the sensor vibration-proof unit 130 is used. The second magnet 606 is rotatably held around an axis extending in the Y direction. The cooling part 608 is disposed inside the front grip 601 shown in FIG. 6.

[0087] In FIG. 14, the first magnet 605 is disposed between the heat generating part 607 and the cooling part 608. Due to the magnetic field generated by the first magnet 605, the magnetic fluid in the circulation pipeline 701 flows in the circulation pipeline 701 in the direction of arrow A (+X direction to -X direction). The circulation pipeline 701 is arranged such that the magnetic fluid traverses the positions of the first magnet 605, the heat generating part 607, the second magnet 606, the cooling part 608, and the first magnet 605 in this order.

[0088] The circulation pipeline 701 has a first pipeline region 701a thermally connected to the heat generating part 607 (receiving heat from the heat generating part 607) and a second pipeline region 701b extending from the heat generating part 607 toward the cooling part 608. Further, the circulation pipeline 701 has a third pipeline region 701c thermally connected to the cooling part 608 (cooled by the cooling part 608) and a fourth pipeline region 701d extending from the cooling part 608 toward the heat generating part 607.

[0089] The first magnet 605 is arranged to be close to (opposite) the portion of the fourth pipeline region 701d immediately before the first pipeline region 701a. For this reason, the magnetic fluid receives a force to flow in the +X direction within the fourth pipeline region 701d due to the magnetic field generated by the first magnet 605.

[0090] When the camera is in the correct posture, the -Y direction, which is the flow direction of the magnetic fluid in the third pipeline region 701c, coincides with the gravitational direction G. Also, the internal volume of the pipeline in the third pipeline region 701c is larger than the internal volumes of the pipelines in the other pipeline regions 701a, 701b, and 701d. Therefore, the effect of gravity assisting the flow of the magnetic fluid in the third pipeline region 701c is greater than the effect of gravity acting as a resistance to the flow of the magnetic fluid in the other pipeline regions 701a, 701b, and 701d. Also, the internal volume of the pipeline in the fourth pipeline region 701d, through which the magnetic fluid with a high viscosity at low temperatures flows, is larger than the internal volume of the pipeline in the second pipeline region 701b, through which the magnetic fluid with a low viscosity at high temperatures flows. By having a larger internal volume in the fourth pipeline region 701d through which the more viscous magnetic fluid flows, the flow resistance due to the viscosity of the magnetic fluid can be alleviated.

[0091] The second magnet 606 is arranged so as to be close (opposite) to the portion of the second pipeline region 701b immediately before the third pipeline region 701c. As described in Example 2, the second magnet 606 rotates to assist the flow of the magnetic fluid, and when the rotation of the second magnet 606 stops, it becomes a factor that inhibits the flow of the magnetic fluid. The internal volume of the pipeline in the second pipeline region 701b opposite the second magnet 606 is smaller than the internal volume of the pipeline in the fourth pipeline region 701d opposite the first magnet 605. Also, the density of the magnetic flux generated by the second magnet 606 is lower than the density of the magnetic flux generated by the first magnet 605. As a result, the force that causes the magnetic fluid to flow by the magnetic field generated by the first magnet 605 is stronger than the force that inhibits the flow of the magnetic fluid by the second magnet 606 whose rotation has stopped. Therefore, even when the rotation of the second magnet 606 stops due to the camera power being turned off or the like, the magnetic fluid can flow smoothly.

[0092] Furthermore, also in this embodiment, similar to Example 2, the rotatable second magnet 606 is arranged at a position in the circulation pipeline 603 where the temperature gradient of the magnetic fluid is almost 0. As a result, even when the rotation of the second magnet 606 stops, it is possible to efficiently transport the heat of the heat generating portion 607 to the cooling portion 608.

[0093] In each of the above embodiments, the magnetic fluid heat transport system mounted on the camera has been described. However, a magnetic fluid heat transport system having the same configuration as each embodiment may be mounted on electronic devices other than cameras or other devices.

[0094] Each of the embodiments described above is merely a representative example, and various modifications and changes can be made to each embodiment when implementing the present invention.

Description of Reference Numerals

[0095] 100, 600 Camera 126 Image Sensor 130 Sensor Anti-Vibration Unit 202a(605) Magnet (First Magnet) 300 Shutter Unit 316a Rear Magnet 400, 602, 700 Magnetic Fluid Heat Transport System 401 Magnetic Fluid 402, 603, 701 Circulation Pipeline 402b Heat-Receiving Portion 402c Non-Heat-Receiving Portion 403 Magnetic Field Generation Member 404, 607 Heat Generation Portion 405, 608 Cooling Portion 411, 701a First Pipeline Region 412, 701b Second Pipeline Region 413, 701c Third Pipeline Region 414, 701d Fourth Pipeline Region 606 Second Magnet

Claims

1. An imaging device comprising a heat generating part including an imaging element, a cooling part, a pipeline for circulating a magnetic fluid between the heat generating part and the cooling part, and a magnetic field generating member disposed on the subject side of the pipeline for applying a magnetic field to the magnetic fluid, The pipeline has a first pipeline region where the magnetic fluid receives heat from the heat generating part, a second pipeline region extending from the first pipeline region toward the cooling part, a third pipeline region where the magnetic fluid is cooled by the cooling part, and a fourth pipeline region extending from the cooling part toward the heat generating part, When the imaging device is viewed from the back side, the magnetic field generating member is disposed between the first pipeline region and the third pipeline region, In a state where the imaging element faces a direction orthogonal to the gravitational direction, the direction in which the magnetic fluid flows in the first pipeline region coincides with the gravitational direction, An imaging device characterized in that the pipeline inner volume of the first pipeline region is larger than the pipeline inner volume of any of the second, third, and fourth pipeline regions.

2. The imaging device according to claim 1, characterized in that the pipeline inner volume of the fourth pipeline region is larger than the pipeline inner volume of the second pipeline region.

3. The imaging device according to claim 1 or 2, characterized in that the pipeline cross-sectional area orthogonal to the flow direction of the magnetic fluid in the second pipeline region increases from the first pipeline region toward the third pipeline region.

4. The imaging device according to any one of claims 1 to 3, characterized in that when the imaging device is viewed from the back side, the magnetic field generating member overlaps the fourth pipeline region.

5. The imaging device according to any one of claims 1 to 4, characterized in that the projected area of each of the first pipeline region and the third pipeline region on a plane orthogonal to the optical axis is larger than the projected area of either the second pipeline region or the fourth pipeline region on the plane.

Images