Head-up display device

Abstract

The present invention increases ease of assembly for a lighting device. A lighting device 23 of a head-up display device 20 includes a plurality of light sources 31 used for transmissive illumination of a display device 21 that displays information, a circuit board 33 on which the plurality of light sources 31 are mounted, and a heatsink 35 overlaid onto a back surface 33b of the circuit board 33. The heatsink 35 includes a sink surface 41c joined to the back surface 33b of the circuit board 33 via a thermal paste 34. The sink surface 41c has a recess 71 that is recessed in the direction going away from the back surface 33b at a location where an edge 33c of the circuit board 33 is positioned.

Description

[Technical Field]

[0001] The present invention relates to a head-up display device having an illumination device used for transmitting illumination of a display device. [Background technology]

[0002] As a conventional technique related to an illumination device used for transmitting illumination of a display device in a head-up display device, for example, there is a technique disclosed in Patent Document 1. The illumination device known from Patent Document 1 is used for transmitting illumination of a liquid crystal display device of the head-up display device. This illumination device has a circuit board on which multiple light sources are mounted and a heat sink that dissipates heat from the circuit board. With a thermally conductive sheet sandwiched between the circuit board and the heat sink, the circuit board is fixed to the heat sink with screw members.

[0003] In recent years, there has been a demand for cost reduction in lighting devices. To achieve this, it is considered to replace the thermal conductive sheet with thermal paste. However, when using thermal paste, there is room for improvement in the assembly of the lighting device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-137089 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a technique for improving the ease of assembly of a lighting device built into a head-up display device. [Means for solving the problem]

[0006] According to the present invention, there is provided a head-up display device comprising an illumination device including a plurality of light sources used for transmitting light to a display device that displays information, a circuit board on which the plurality of light sources are mounted, and a heat sink superimposed on the back surface of the circuit board, wherein the heat sink has a sink surface that is bonded to the back surface of the circuit board via thermal paste, and the sink surface has a recess in the area where the edge of the circuit board is located, recessed in a direction away from the back surface, and on the back surface of which a finger or a tool can be hooked. [Effects of the Invention]

[0007] The present invention improves the ease of assembly of the lighting device built into the head-up display device. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is an explanatory diagram of a vehicle equipped with a head-up display device according to an embodiment of the present invention; [Figure 2] FIG. 2 is a cross-sectional view of the head-up display device shown in FIG. [Figure 3] FIG. 3 is an exploded view of the lighting device shown in FIG. 2. [Figure 4] FIG. 4 is a perspective view of a heat sink incorporating the circuit board shown in FIG. 3. [Figure 5] FIG. 5 is a cross-sectional view taken along line 5-5 in FIG. [Figure 6] FIG. 6 is an enlarged view of part 6 in FIG. 5. [Figure 7] 5 is an exploded view of the circuit board and heat sink shown in FIG. 4. FIG. [Figure 8] FIG. 6 is a perspective view of the heat sink shown in FIG. 5, seen from the rear surface side. [Figure 9] FIG. 6 is a cross-sectional view of a molding die for molding the heat sink shown in FIG. 5. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present invention will be described below with reference to the accompanying drawings. In this embodiment, an illumination device used for transmitting illumination of a display device is described as being adopted in an in-vehicle head-up display device. In the drawings, "Up" indicates the top and "Dn" indicates the bottom.

[0010] As shown in FIG. 1, a vehicle 10 such as a passenger car has a dashboard 12 at the front of a passenger compartment 11. A head-up display device 20 is built into the upper part of the dashboard 12. Display light Ld projected from the head-up display device 20 is displayed as an image on a windshield 13 of the vehicle 10. The driver can view a virtual image Vi together with the background ahead of the vehicle 10.

[0011] 2, the head-up display device 20 includes a display device 21 (projector 21) that projects display light Ld, a reflector 22 that reflects the projected display light Ld, and an illumination device 23 that is used for transmitting illumination of the display device 21. The display device 21, the reflector 22, and the illumination device 23 are stored in a storage box 24. The storage box 24 includes a transmission section 25 that can transmit the display light Ld projected from the display device 21 to the outside.

[0012] The display device 21 displays various types of information such as driving information, and is configured, for example, by a liquid crystal display device. This liquid crystal display device employs, for example, a TFT-type liquid crystal panel as a display medium (display element). In addition to the liquid crystal panel, this liquid crystal display device is configured to include, although not shown in detail here, a circuit board on which a control unit for controlling the display of the liquid crystal panel is mounted, a flexible wiring board for electrically connecting the liquid crystal panel to the circuit board, and the like.

[0013] The reflector 22 is made of a concave mirror that magnifies the display light Ld projected from the display device 21 and reflects it toward the windshield 13 (see FIG. 1).

[0014] 2 and 3, the illumination device 23 includes a plurality of light sources 31 used for transmitted illumination of the display device 21, a lens array 32 that uniforms the illuminance distribution of the light emitted by the plurality of light sources 31, a circuit board 33 having the plurality of light sources 31 mounted on a mounting surface 33a, and a heat sink 35 that is bonded to a back surface 33b of the circuit board 33 (the surface 33b opposite to the mounting surface 33a) via thermal paste 34. The plurality of light sources 31, the lens array 32, and the circuit board 33 are housed in a case 36.

[0015] The plurality of light sources 31 are configured by, for example, light emitting diodes, and are arranged at a predetermined pitch on the mounting surface 33a of the circuit board 33. One example of these light emitting diodes is a surface-mounted light emitting diode.

[0016] The circuit board 33 is formed in a roughly rectangular shape and is made of a plate material with excellent thermal conductivity, such as an aluminum alloy.

[0017] The thermal paste 34 is made of a material that efficiently transfers heat from the circuit board 33 to the heat sink 35 (enhancing heat transfer). It is also known as thermal grease, thermal compound, heat-dissipating grease, or thermally conductive grease. The thermal paste 34 may be, for example, a room-temperature-curing, two-component silicone grease. It can be applied by mixing two liquid materials. The grease is liquid immediately after mixing the two liquids, but hardens (solidifies) over time. The thermal paste 34 forms a thermal paste layer upon hardening, providing a relatively firm bond between the surfaces of the circuit board 33 and the heat sink 35. For example, the thermal paste 34 may be the "CGW Series Two-Component Room-Temperature-Curing Thermal Grease" (registered trademark) manufactured by Sekisui Polymatech Co., Ltd.

[0018] The heat sink 35 is an injection-molded product made of a thermally conductive resin (also known as a high thermal conductivity resin) in which an electrically insulating and highly thermally conductive ceramic filler is blended into the resin material, or a lightweight alloy with excellent thermal conductivity such as an aluminum alloy.

[0019] As shown in Figures 4 to 7, the heat sink 35 has a generally rectangular dish-like configuration and is integrally formed from a flat heat sink substrate 41 (cooling plate 41), a peripheral wall 51 that stands up from the periphery 41a of the heat sink substrate 41 and surrounds the periphery of the heat sink substrate 41, and at least one vertical plate-shaped heat dissipation fin 61 that stands up from the back surface 41b of the heat sink substrate 41 on the side opposite to the peripheral wall 51.

[0020] The peripheral wall 51 has a substantially rectangular shape when viewed from the open end side (the side of the edge 51a at the tip of the peripheral wall 51), that is, when viewed from the side of the circuit board 33. A part 51b of the edge 51a at the tip of the peripheral wall 51 is supplied with the molten material during injection molding, and therefore is referred to as the "edge 51b on the supply side."

[0021] The heat sink substrate 41 has a flat sink surface 41c (thermal conduction surface 41c). That is, the heat sink 35 has the sink surface 41c that is joined to the rear surface 33b of the circuit board 33 via the thermal paste 34.

[0022] The sink surface 41c has a predetermined application area Ap for applying the thermal paste 34, and a groove 41d surrounding the application area Ap. The application area Ap is generally rectangular when viewed from the open end of the peripheral wall 51 (the edge 51a at the tip of the peripheral wall 51), i.e., when viewed from the circuit board 33 side, and is narrower than the edge 33c of the circuit board 33. The groove 41d is a frame-shaped relief groove that is generally rectangular when viewed from the open end of the peripheral wall 51. It is recessed from the sink surface 41c to prevent the thermal paste 34 from spilling out of the application area Ap to the surrounding area, and is configured, for example, as a V-shaped or U-shaped cross-section as shown in FIG. 6. However, the cross-sectional shape of the groove 41d is arbitrary. The depth and width of the groove 41d are set taking into account the amount of thermal paste 34 spilling out of the application area Ap.

[0023] The liquid thermal paste 34 is applied within the application range Ap of the sink surface 41c. Excess liquid thermal paste 34 goes beyond the application range Ap and enters the groove 41d. Therefore, there is no need to worry about the excess liquid thermal paste 34 spreading over the entire sink surface 41c. Since there is no need to wipe off the excess liquid thermal paste 34, the assembly of the lighting device 23 can be improved.

[0024] In addition, since excess liquid thermal paste 34 that has been applied finds its way into groove 41d, there is no need to strictly control the amount of thermal paste 34 applied. This makes it easy to set the desired range and thickness of thermal paste 34 to be applied between rear surface 33b of circuit board 33 and sink surface 41c of heat sink 35. This further improves the ease of assembly of the lighting device 23.

[0025] As shown in Figures 4, 5 and 7, the sink surface 41c of the heat sink 35 has a recess 71 at the location where the edge 33c of the circuit board 33 is located, which is recessed in a direction away from the back surface 33b of the circuit board 33 and allows a finger or a tool To (see Figure 5) to be hooked onto this back surface 33b.

[0026] As shown in FIG. 5, the bottom surface 71a of the recess 71 that overlaps the back surface 33b of the circuit board 33 is referred to as the "overlap bottom surface 71a." The depth from the edge 33c of the circuit board 33 to the inner wall surface 71b of the recess 71, i.e., the overlap between the back surface 33b of the circuit board 33 and the overlap bottom surface 71a of the recess 71, is Wd. The depth from the back surface 33b of the circuit board 33 to the overlap bottom surface 71a of the recess 71 (the depth of the recess 71) is Dp. The size of the overlap Wd and the depth Dp is determined by the amount of the overlap that occurs when a finger or a tool To is hooked on the back surface 33b of the circuit board 33 and solidifies on the sink surface 41c. The size of the circuit board 33, which is connected via the thermal paste 34, is set so that it can be peeled off.

[0027] Furthermore, recess 71 extends to edge 51b on the supply side within the inner circumferential surface of peripheral wall 51. Length Ln from wall surface 71b at the back of recess 71 to the back surface of edge 51b on the supply side (length Ln of recess 71) is set in consideration of ease of use when hooking a finger or a tool To on back surface 33b of circuit board 33. For this reason, distance L1 from edge 33c of circuit board 33 to edge 51b on the supply side of peripheral wall 51 is longer than distance L2 from edge 33c of circuit board 33 to edge 51a of another portion of peripheral wall 51.

[0028] Generally, as shown in FIG. 5, thermal paste 34 hardens (solidifies) to firmly bond circuit board 33 and heat sink 35. This makes it difficult to remove circuit board 33 from heat sink 35. For example, if light source 31 mounted on circuit board 33 breaks down, disassembly of circuit board 33 is difficult when replacing it. Because it takes time to disassemble and reassemble circuit board 33 to heat sink 35, there is room for improvement in the ease of assembly of lighting device 23.

[0029] In contrast, in this embodiment, as shown in FIG. 5 , the heat sink substrate 41 has a recess 71 on the sink surface 41c (thermal conduction surface 41c). This recess 71 is located in the portion of the sink surface 41c where the edge 33c of the circuit board 33 overlaps, and is recessed in a direction away from the back surface 33b (the surface 33b opposite the mounting surface 33a) of the circuit board 33. To disassemble the circuit board 33 from the heat sink 35, simply insert a finger or a tool To into the recess 71, hook the back surface 33b of the circuit board 33, and pull it off. This pulling force allows the circuit board 33 to be easily disassembled from the heat sink 35. After that, new liquid thermal paste 34 is applied to the sink surface 41c, and the circuit board 33 is bonded to the sink surface 41c, allowing the circuit board 33 to be reassembled to the heat sink 35. In this way, the circuit board 33 can be easily disassembled and reassembled to the heat sink 35 in a short time. As a result, the ease of assembly of the lighting device 23 can be improved.

[0030] 4, 5, and 8, a recess-forming portion 81 that forms the recess 71 is integrally formed with the heat sink 35. This recess-forming portion 81 extends at an angle from the supply-side edge 51b of the peripheral wall 51 to the back surface 41b of the heat sink substrate 41. The portion 81a of the recess-forming portion 81 that forms the overlap bottom surface 71a of the recess 71 is referred to as the "overlap bottom plate 81a."

[0031] More specifically, the edge 51a at the tip of the peripheral wall 51, including the edge 51b on the supply side, is located closer to the light source 31 than the heatsink substrate 41. Meanwhile, the overlap bottom surface 71a of the recess 71 is located in a direction away from the back surface 33b of the circuit board 33, so the overlap bottom plate 81a in the recess forming portion 81 bulges out toward the opposite side of the circuit board 33 from the heatsink substrate 41. This overlap bottom plate 81a is parallel to the heatsink substrate 41. The height from the edge 51b on the supply side of the peripheral wall 51 to the overlap bottom plate 81a is H1.

[0032] The recess-forming portion 81 extends while sloping from the edge 51b on the supply side of the peripheral wall 51 toward the back surface 41b of the heat sink substrate 41 (toward the overlap bottom surface 71a). It is preferable that the slope of this recess-forming portion 81 be gentle from the edge 51b on the supply side of the peripheral wall 51 toward the overlap bottom surface 71a.

[0033] 5 and 8, all of the heat dissipation fins 61 extend in the direction along the inclination of the recess-forming portion 81, spanning between both ends 41e, 41e of the rear surface 41b of the heat sink substrate 41. It is preferable that the tip surface 61a of each of the heat dissipation fins 61, which faces the edge 51b on the supply-side, forms an obtuse angle with respect to the inclined surface of the recess-forming portion 81. The height of the tip surface 61a is H2.

[0034] A base portion 61b (base end portion 61b where the tip surface 61a of the heat dissipating fin 61 intersects with the recessed portion 81) does not have a recess, and is curved at least to the center in the height direction of the heat dissipating fin 61 (preferably in the range of 1 / 3 to 1 / 2 of the height H2 of the tip surface 61a). It is preferable that the radius rf of the curve of the base end portion 61b is as large as possible.

[0035] 5 and 9, a molding die 90 for molding the heat sink 35 has a first space 91 for molding the peripheral wall 51 and the recess forming portion 81, a second space 92 for molding the heat sink substrate 41, and a third space 93 for molding the heat dissipation fins 61. These spaces 91 to 93 are also called cavities because they are filled with molten material Mo. The first space 91 has a gate 95 of the molding die 90 at a portion 94 for molding the edge 51b on the supply side.

[0036] 5, recess-forming portion 81 extends at an angle from supply-side edge 51b toward overlap bottom surface 71a. Correspondingly, first space 91 shown in FIG. 9 extends at an angle from gate 95 toward second space 92 and third space 93, and the portion where it joins third space 93 is curved with a radius rf.

[0037] When molding the heat sink 35, the molten material Mo supplied from the gate 95 flows from the portion 94 that molds the edge 51b on the receiving side to the first space 91, and then flows from the first space 91 to the second space 92 and the third space 93.

[0038] As described above, the recess-forming portion 81 extends at an incline from the edge 51b on the supply side toward the overlap bottom surface 71a, and the base portion 61b between the tip surface 61a of the heat dissipation fin 61 and the recess-forming portion 81 is curved. Therefore, when molding the heat sink 35, the molten material Mo supplied from the gate 95 can flow smoothly and efficiently from the inclined first space 91 to every corner of the third space 93. Therefore, the molten material Mo can be easily and reliably filled throughout the entire third space 93. This improves the molding quality of the heat dissipation fin 61, and as a result, improves the molding quality of the heat sink 35.

[0039] In addition, as shown in FIG. 5, the recess 71 is set so as to satisfy the following three conditions. First, the distance L1 (corresponding to the length Ln of the recess 71) from the edge 33c of the circuit board 33 to the edge 51b of the supply side of the peripheral wall 51 is set to be longer than the distance L2 from the edge 33c of the circuit board 33 to the edge 51a of another part of the peripheral wall 51. Secondly, the recess 71 is set to have a downward slope from the edge 51b on the supply side of the peripheral wall 51 toward the overlap bottom surface 71a. Thirdly, the overlap width Wd and the depth Dp are set in consideration of the ease with which fingers or a tool To are hooked onto the rear surface 33b of the circuit board 33.

[0040] Therefore, when disassembling the circuit board 33 from the heat sink 35, a finger or a tool To can be easily inserted into the recess 71, hooked onto the back surface 33b of the circuit board 33, and pulled off. This makes it even easier to disassemble the circuit board 33 from the heat sink 35.

[0041] Although the head-up display device 20 according to the present invention has been described using the vehicle 10 as an example, it is applicable to other vehicles and is not limited to these types. In other words, the present invention is not limited to the present embodiment as long as the functions and effects of the present invention are achieved. [Industrial Applicability]

[0042] The lighting device 23 of the present invention is suitable for use in lighting a liquid crystal head-up display device. [Explanation of symbols]

[0043] 20 Head-up display device 21 Display device 23 Lighting equipment 31 Light source 33 Circuit Board 33a Mounting surface 33b back 33c Circuit board edge 34 Thermal Paste 35 Heatsink 41 Heatsink board 41a Periphery 41b back side 41c Sink surface 41d Groove surrounding the application area 41e Both ends of the backside of the heat sink board 51 Peripheral wall 51a Edge of the tip of the peripheral wall 51b Edge of the supply side (part of the edge at the tip of the peripheral wall) 61 Heat dissipation fin 61a The tip surface of the heat dissipation fin facing the edge of the supply side 61b Base 71 Recess 81 recessed portion Ap application range

Claims

1. A head-up display device having an illumination device including a plurality of light sources used for transmitting illumination of a display device that displays information, a circuit board on which the plurality of light sources are mounted, and a heat sink superimposed on the back surface of the circuit board, the heat sink has a sink surface coupled to the rear surface of the circuit board via thermal paste; This head-up display device is characterized in that the sink surface is recessed in a direction away from the back surface at the location where the edge of the circuit board is located, and has a recess on the back surface that can be used to hook a finger or a tool.

2. 2. The head-up display device according to claim 1, wherein the sink surface has a groove that can prevent the thermal paste from spilling out from an application area to the surrounding area.

3. The heat sink is an injection-molded product that is integrally formed of a heat sink substrate having the sink surface, a peripheral wall that stands from the periphery of the heat sink substrate and surrounds the periphery of the heat sink substrate, vertical plate-shaped heat dissipation fins that stand from the back surface of the heat sink substrate toward the opposite side to the peripheral wall, and a recess forming portion that forms the recess, a part of the edge of the tip of the peripheral wall is an edge on a supply side to which molten material is supplied during injection molding, the recess-forming portion extends obliquely from the edge of the supply-side portion toward the back surface of the heat sink substrate, the heat dissipation fins extend along the inclination direction of the recessed portion across the rear surface of the heat sink substrate, The head-up display device according to claim 1, characterized in that the tip surface of the heat dissipation fin facing the edge of the supply side and the base portion of the recess forming portion are formed in a curved shape at least to the center of the height direction of the heat dissipation fin without having a depression.

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