HEAD UP DISPLAY DEVICE

Abstract

The problem addressed by the present invention is to provide a head up display device capable of counteracting sunlight without using a shutter or a reflection type polarizing film. A first concave mirror has a curvature to cause the reflected display light to intersect vertically before reaching a second mirror, and a second concave mirror serves to reflect the received display light. A case is provided with a first shield and a second shield extending near an intersecting point to sandwich a light path between the first and second concave mirrors. The first and second shields can block external light entering into the case from outside the case and proceeding toward the first concave mirror after being reflected from the second concave mirror.

Claims

1. A head up display device, comprising a display unit for emitting display light; a first mirror for reflecting the display light emitted from the display unit ; a second mirror for reflecting display light reflected by the first mirror; and a case for housing the display unit and the first and second mirrors, wherein: the first mirror is a first concave mirror having a curvature that causes the reflected display light to cross up and down before reaching the second mirror, the second mirror is a second concave mirror that reflects the received display light, the case includes a first shielding portion and a second shielding portion extending to the vicinity of a cross point to sandwich an optical path between the first and second concave mirrors, and the first and second shielding portions shield external light entering to inside the case from the outside of the case and proceeding toward the first concave mirror after being reflected by the second concave mirror.

2. The head up display device according to claim 1, wherein the first and second shielding portions are made of a material having a thermal conductivity higher than that of a general portion of the case.

3. The head up display device according to claim 1, wherein the first and second shielding portions are made of a material having a heat resistance temperature higher than that of a general portion of the case.

4. The head up display device according to claim 1, wherein anti-reflection treatment for weakening or preventing reflection of the external light is applied to the first and second shielding portions at least at a portion to which the external light hits.

5. The head up display device according to claim 1, wherein the case comprises a center frame supporting the first and second concave mirrors and including the second shielding portion; an upper cover attached to an upper side of the center frame and provided with the first shielding portion; and a lower cover attached to a lower side of the center frame.

6. The head up display device according to claim 5, wherein the center frame is a metal molded product, the lower cover is a resin molded product, and the upper cover is a resin molded product or a metal molded product.

7. The head up display device according to claim 6, wherein the metal molded product is an aluminum die-cast product.

8. The head up display device according to claim 1, wherein: the case comprises a center frame supporting the first and second concave mirrors and including the second shielding portion; and an upper cover attached to an upper side of the center frame and provided with the first shielding portion, the upper cover is a resin molded product, a metal plate is disposed at least on the upper surface of the first shielding portion, the density of the resin used for the material of the resin molded product is smaller than the density of the metal plate, and the heat resistant temperature of the metal plate is higher than the heat resistant temperature of the resin.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0049] FIG. 1 is a principle diagram of a first modified device.

[0050] FIG. 2 is a basic configuration diagram of a second modified product, that is, a head up display device according to the present invention.

[0051] FIG. 3 is an exploded view of a head up display device according to a first embodiment of the present invention.

[0052] FIG. 4 is a cross-sectional view of a head up display device according to a first embodiment of the present invention.

[0053] FIG. 5 is a view for explaining a shielding action of first and second shielding portions.

[0054] FIG. 6 is a diagram illustrating the flow of heat in the first and second shielding portions.

[0055] FIG. 7 is a view for explaining a modification example of a center frame.

[0056] FIG. 8 is a cross-sectional view of a head up display device according to a second embodiment of the present invention.

[0057] FIG. 9 is an exploded perspective view of an upper cover and a metal plate.

[0058] FIG. 10 is a view for explaining a modified example of a metal plate.

MODE FOR CARRYING OUT THE INVENTION

[0059] Embodiments of the present invention will be described below with reference to the accompanying drawings.

EXAMPLE 1

[0060] As shown in FIG. 3, in the head up display device 10, the case 20 includes a center frame 30 supporting the first and second concave mirrors 14, 16 and having a second shielding portion 24, an upper cover 50 attached to the upper side of the center frame 30 and having a first shielding portion 23, and a lower cover 55 attached to the lower side of the center frame 30.

[0061] The center frame 30 is an aluminum die-cast product having the mounting flanges 31, 31 on its outer periphery and the second shielding portion 24 extending obliquely upward in the interior.

[0062] For example, a stay 32 is welded to the center frame 30, and the first concave mirror 14 is fixed to the stay 32 with the adhesive layer 33. The second concave mirror 16 is fixed to the stays 34 to 36 welded to the inner surface of the center frame 30 with adhesive layers 37 to 39.

[0063] The stay 41 extends from the lower part of the center frame 30. Meanwhile, the light source 11 and the display unit 13 are fitted to the tubular bracket 42, and the bracket piece 43 extended from the tubular bracket 42 is fixed to the stay 41 with the screws 44, 44.

[0064] The center frame 30 has a much higher strength and rigidity than the resin molded product if it is an aluminum die-cast product. Since the first and second concave mirrors 14 and 16 and the display unit 13 are collectively attached to the center frame 30 rich in rigidity, these optical axis adjustments become difficult to deviate. Further, the center frame 30 rich in rigidity is attached to the vehicle by the mounting flanges 31, 31. When the cover is made of resin as a whole, the rigidity becomes insufficient and readjustment of the optical axis may be necessary. On the other hand, since the head up display device 10 of the embodiment is rich in rigidity, there is little concern.

[0065] The upper cover 50 is, for example, a polycarbonate molded product, and has a cover glass 51 on its upper surface, and integrally includes a first shielding portion 23 extending obliquely downward.

[0066] The lower cover 55 is a bottomed cylindrical body that opens upward, and is, for example, an ABS resin molded product, and incorporates a printed board 56 therein.

[0067] The lower cover 55 is attached to the center frame 30 from the bottom with screws 57, 57, and the upper cover 50 is attached with screws 52 from the top.

[0068] The head up display device 10 shown in FIG. 4 is completed. The display light 12 emitted from the display unit 13 is reflected by the first concave mirror 14, and the display light 15 reflected by the first concave mirror 14 passes between the first and second shielding portions 23 and 24, and reaches the second concave mirror 16. The display light 17 reflected by the second concave mirror 16 rises and reaches the windshield 66 of the vehicle (the projection part 66 on which the reflected display light 17 is projected).

[0069] As shown in FIG. 5(a), when the altitude of the sun 58 is low, the external light 25 typified by sunlight passes through the cover glass 51, is reflected by the second concave mirror 16, and is shielded by the first shielding portion 23. Since the first shielding portion 23 is polycarbonate excellent in heat resistance, it has high strength against heat.

[0070] When the altitude of the sun 58 is high, as shown in FIG. 5(b), the external light 25 passes through the cover glass 51, is reflected by the second concave mirror 16, and is shielded by the second shielding portion 24. Since the second shielding portion 24 is aluminum excellent in heat resistance, the second shielding portion 24 has higher strength against heat.

[0071] Next, thermal conductivity will be discussed.

TABLE-US-00002 TABLE 2 Heat resistant temperature Thermal conductivity PC resin (150° C.) Approx. 0.2 W/m .Math. k ADC 12 (580° C.) Approx. 100 W/m .Math. k ( ) Heat resistance temperature (reference value)

[0072] Polycarbonate (PC) resin has thermal conductivity of about 0.2 W/m/K. On the other hand, the aluminum die-cast product (ADC 12) has a thermal conductivity of about 100 W/m/K.

[0073] FIG. 6(a) is a diagram for explaining a very simple heat transfer model. It is assumed that one end of a rod 59 made of polycarbonate (PC) resin has a high temperature t1p, a temperature lower than tip at the other end (t2p is higher than the atmospheric temperature t3), and in a thermally steady state. Assuming that the outer periphery of the rod 59 is thermally insulated, the heat Q1p flowing inside the rod 59 and the heat Q2p discharged from the other end of the rod 59 to the atmosphere are equal. Here, if the cross-sectional area of the rod is the unit cross-sectional area (1.0), Q1p is calculated by the thermal conductivity λp×the length of the bar×(t1p×t2p). Further, Q2p is calculated by the heat transfer coefficient cp×(t2p−t3).

[0074] It is assumed that one end of a rod 59 of an aluminum die-cast product (ADC 12) is assumed to be thermally steady at a high temperature t1a, a temperature lower than t2a at the other end (t2a is higher than the atmospheric temperature t3), and in a thermally steady state. Assuming that the outer periphery of the rod 59 is thermally insulated, the heat Q1a flowing inside the rod 59 and the heat Q2a discharged from the other end of the rod 59 to the atmosphere are equal. Here, if the cross-sectional area of the rod is the unit cross-sectional area (1.0), Q1a is calculated by the thermal conductivity λa×the length of the bar×(t1a−t2a). Q2a is calculated by the heat transfer coefficient ca×(t2a−t3).

[0075] In the case of Q1p=λp×the length of the bar×(t1p−t2p) and Q1a=λa×the length of the bar×(t1a−t2a), πp is about 1/500 of λa, much smaller than λa. Although Q1p<Q1a, the ratio is expected to be much smaller than 1:500. Since λp is extremely small, (t1p−t2p) becomes significantly larger as a tendency. On the other hand, since λa becomes extremely large, (t1a−t2a) becomes much smaller as a tendency.

[0076] Further, Q1p=Q2p and Q1a=Q2a, and Q1p<Q1a to Q2p<Q2a. In the case of Q2p=cp×(t2p−t3) and Q2a=ca×(t2a−t3), t3 is common. Then, assuming that cp is approximately equal to ca, t2p<t2a.

[0077] From the above, the temperature curve shown in FIG. 6(b) is obtained, and tip becomes significantly larger than t1a. As the thermal conductivity increases, the temperature of the first and second shielding portions 23, 24 can be quickly reduced. The lower the temperature, the less the thermal degradation.

[0078] From this finding, it is preferable that the first shielding portion 23 is also made of aluminum die-cast or light metal, which is the same as the second shielding portion 24.

[0079] As shown in FIG. 7, an aluminum die-cast product 63 integrally formed with the heat radiation fin 61 is preliminary manufactured in the first shielding portion 23, the aluminum die-cast product 63 is placed in a cavity of a molding die, and the PC resin 64 is injected into the cavity thereby performing so-called insert molding.

[0080] When the first shielding portion 23 is heated by the external light 25, heat propagates through the first shielding portion 23 and reaches the heat radiation fins 61. Since the heat radiation fin 61 has a large heat radiation area, it actively radiates heat towards the atmosphere.

[0081] It is to be noted that the whole of the upper cover 50 may be made of aluminum die-cast or light metal.

EXAMPLE 2

[0082] Refer to FIG. 8. Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 8 shows a sectional configuration of the head up display device of the second embodiment. FIG. 8 corresponds to FIG. 4 above.

[0083] In the head up display device 10A according to the second embodiment, the metal plate 71 is disposed on the upper surface of the first shielding portion 23. The other basic configuration is common to the head up display device 10 (see FIG. 4) according to the first embodiment. For parts common to the first embodiment, reference numerals are used, and detailed description is omitted.

[0084] The upper cover 50A is a resin molded product, and for example, a mixed resin material of polycarbonate and polyethylene terephthalate (PET) can be used.

[0085] As the material of the metal plate 71, aluminum or an aluminum alloy can be used.

[0086] The resin as the material of the resin molded product is smaller than the density of the metal used for the metal plate 71. In addition, the heat resistant temperature of the resin used for the material is lower than the heat resistant temperature of the metal used for the metal plate 71. That is, the heat resistant temperature of the metal plate 71 is higher than the heat resistant temperature of the resin. As long as these conditions are satisfied, any material can be selected for resin or metal.

[0087] Refer to FIG. 9. Three metal plates 71 are attached to the upper cover 50A. The metal plates 71 are respectively attached to the upper surface of the first shielding portion 23, and the inner surfaces of the left and right side surfaces of the upper cover 50A extending forward from and the left and right end portions of the upper surface. These can be said to be design surfaces visible from the outside. That is, the metal plate 71 is arranged on the design surface. By placing the metal plate 71 on the visually recognizable part, it is possible to further improve the design.

[0088] The metal plate 71 can be disposed on the upper cover 50A by an arbitrary method such as sticking with a double-sided tape, adhesion with an adhesive, screwing using a screw, locking using a fixing hook, or the like.

[0089] 30

[0090] The above can be summarized as follows. A metal plate 71 is disposed on the upper surface of the first shielding portion 23 that is a resin molded product. The first shielding portion 23 is a portion for blocking external light traveling into the case 20A. That is, the upper surface of the first shielding portion 23 is exposed to external light. As an example of external light striking the first shielding portion 23, sunlight can be mentioned. High heat resistance is required for the first shielding portion 23 against which sunlight impinges. On the other hand, it is desirable that the head up display device 10A as a whole be lightweight. The density of the resin used for the upper cover 50A is smaller (lower) than that of the metal plate 71. Therefore, by making the upper cover 50A a resin molded product, it is possible to reduce the weight of the head up display device 10A. On the other hand, the metal plate 71 has higher heat resistance temperature (heat resistance) than the resin used for the upper cover 50A. Therefore, by arranging the metal plate 71 on the upper surface of the first shielding portion 23 to which sunlight impinges, the heat resistance can be enhanced. That is, it is possible to increase the heat resistance of the first shielding portion 23 while reducing the weight of the head up display device 10A.

[0091] Refer to FIG. 10. FIG. 10 shows a modified example of the head up display device 10B in which the metal plate 71B is changed. That is, the metal plate 71B can also be constituted by a single plate. Even in this case, the predetermined effect of the present invention can be obtained. In addition, in the case of a single plate, there is no joint between the metal plates compared with the case where it is constituted by a plurality of plates, and the design can be further enhanced.

[0092] Although the head up display device of the present invention is suitable for passenger cars, it may be applied to general vehicles, ships and aircraft. That is, the present invention is not limited to the examples as long as the effects and advantages of the present invention are exhibited.

INDUSTRIAL APPLICABILITY

[0093] The head up display device of the present invention is suitable for a vehicle having a windshield.

DESCRIPTION OF REFERENCE NUMERALS

[0094] 10, 10 A, 10 B Head up display device

[0095] 11 Light source

[0096] 12, 15 Display light

[0097] 13 Display unit

[0098] 14 First mirror (first concave mirror)

[0099] 16 Second mirror (second concave mirror)

[0100] 20, 20A Case

[0101] 22 Cross point

[0102] 23 First shielding portion

[0103] 24 Second shielding portion

[0104] 25 External light

[0105] 26 General section

[0106] 27 Anti-reflection treated film

[0107] 30 Center frame

[0108] 50, 50A Upper cover

[0109] 55 Lower cover

[0110] 71, 71 B Metal plate claims