DISPLAY DEVICE FOR VEHICLE

A display device for a vehicle includes a housing, a liquid crystal display device, a transparent plate-shaped first heat conductive member that is arranged in contact with any of a display surface and a back surface of the liquid crystal display device, and a second heat conductive member that conducts heat between the first heat conductive member and the housing. The second heat conductive member is, for example, a Peltier element including a first surface and a second surface, and arranged to bring a first surface into contact with the first heat conductive member and bring a second surface into contact with the housing.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a display device for a vehicle.

2. Description of the Related Art

In the related art, there is known a technique of preventing a display from being damaged for a display device for a vehicle. Japanese Patent Application Laid-open No. 2005-313733 discloses a display device for a vehicle including a heat transmission member that transmits a display image and is in contact with a polarizing member on an emitting side, and a holding member that is made of metallic material and holds the heat transmission member on an optical path for the display image between a liquid crystal cell to a display member.

There is room for improvement in controlling a temperature of a display to be an appropriate temperature. There is a demand to appropriately control a temperature of a liquid crystal display device.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a display device for a vehicle in which a temperature of a liquid crystal display device can be appropriately controlled.

In order to achieve the above mentioned object, a display device for a vehicle according to one aspect of the present invention includes: a first housing fixed to a vehicle body; a liquid crystal display device housed in the first housing; a backlight unit that is housed in the first housing, and irradiates a back surface of the liquid crystal display device with light; a transparent plate-shaped first heat conductive member that is arranged in contact with any of a display surface and the back surface of the liquid crystal display device; a second heat conductive member that conducts heat between the first heat conductive member and the first housing; and the backlight unit includes a second housing, a light source housed in the second housing, and a heat sink that radiates heat of the second housing and the light source, and the second heat conductive member is a Peltier element that is sandwiched between the first housing and the first heat conductive member.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following describes a display device for a vehicle according to an embodiment of the present invention in detail with reference to the drawings. The present invention is not limited to the embodiment. Constituent elements in the following embodiment encompass a constituent element that is easily conceivable by those skilled in the art, or substantially the same constituent element.

EMBODIMENT

The following describes the embodiment with reference toFIG.1toFIG.7. The present embodiment relates to a display device for a vehicle.FIG.1is an arrangement diagram of the display device for a vehicle according to the embodiment,FIG.2is a schematic configuration diagram of the display device for a vehicle according to the embodiment,FIG.3is a cross-sectional view of an image display device according to the embodiment,FIG.4is a plan view of the image display device according to the embodiment,FIG.5is a flowchart for explaining an operation of a control unit according to the embodiment,FIG.6is a cross-sectional view for explaining cooling control according to the embodiment, andFIG.7is a cross-sectional view for explaining heating control according to the embodiment.

As illustrated inFIG.1, a display device1for a vehicle according to the present embodiment is a head-up display device mounted on a vehicle100such as an automobile. The display device1for a vehicle projects display light Lt of an image on a windshield110. The windshield110is positioned on a front side of the vehicle with respect to an eye-point EP of the vehicle100, and opposed to the eye-point EP in a front and rear direction X of the vehicle. The display light Lt is reflected by a reflection surface110aof the windshield110toward the eye-point EP. A driver of the vehicle100can visually recognize a virtual image Vi by the display light Lt.

As illustrated inFIG.1andFIG.2, the display device1for a vehicle includes a housing2, an image display device10, a control unit7, a first mirror11, a second mirror12, and a cover8. The housing2is arranged on the front side of the vehicle with respect to the eye-point EP, and housed in an instrument panel120, for example. The housing2is an outer shell member of the display device1for a vehicle, and fixed to a vehicle body of the vehicle100. The housing2is formed of light-shielding material, for example, formed of metal. The housing2has an opening21opposed to the windshield110in an upper and lower direction Z of the vehicle. The exemplified opening21is arranged on an upper surface of the housing2, and positioned at a front end part of the housing2.

The image display device10, the control unit7, the first mirror11, and the second mirror12are arranged inside the housing2. The image display device10is a device that outputs the display light Lt of an image. As illustrated inFIG.2andFIG.3, the image display device10includes a liquid crystal display device3, a backlight unit4, a first heat conductive member5, and a Peltier element6(second heat conductive member).

The liquid crystal display device3is, for example, a Thin Film Transistor-Liquid Crystal Display (TFT-LCD). The liquid crystal display device3includes a display surface31and a back surface32. The display surface31is a surface that displays an image and outputs the display light Lt. The back surface32is a surface opposite to the display surface31. The shape of the liquid crystal display device3in a plan view is rectangular, for example.

The backlight unit4is a device that irradiates the back surface32of the liquid crystal display device3with light. The image display device10generates the display light Lt by the light of the backlight unit4. The backlight unit4includes a housing41, a light source42, and a heat sink43. The light source42includes a plurality of light emitting elements arranged in an image vertical direction GV and an image horizontal direction GH, for example. The backlight unit4may include a lens that condenses light of the light emitting elements, and a diffusion member that diffuses the condensed light. The light source42is arranged to be opposed to the back surface32of the liquid crystal display device3. The shape of the light source42in a plan view is rectangular, for example.

The housing41is arranged on the back surface32side with respect to the liquid crystal display device3, and houses the light source42. The housing41is formed of material having thermal conductivity such as metal. The housing41includes a side wall41athat surrounds the light source42. The side wall41aaccording to the present embodiment has a square cylindrical shape. That is, the shape of the side wall41aon a cross section orthogonal to the display light Lt is rectangular. The side wall41aincludes a first end face41band a second end face41c. The first end face41bis an end face on the liquid crystal display device3side of the side wall41a. The second end face41cis an end face on the opposite side of the first end face41bof the side wall41a.

The heat sink43is a heat radiation member, and radiates heat of the housing41and the light source42to surroundings. The exemplified heat sink43is arranged on the back surface side with respect to the side wall41a. For example, the heat sink43is arranged in contact with the second end face41cof the side wall41a. In a case in which the housing41has a bottom wall, the heat sink43may be arranged in contact with the bottom wall. That is, the heat sink43is arranged to be able to conduct heat between itself and the side wall41a. The heat sink43includes a plurality of fins43fprojecting toward the back surface side.

The first heat conductive member5is a transparent plate-shaped member having thermal conductivity. The first heat conductive member5is preferably colorless and transparent. The first heat conductive member5is formed of glass such as sapphire glass, for example. The first heat conductive member5is arranged between the liquid crystal display device3and the backlight unit4. The first heat conductive member5according to the present embodiment is formed in a flat-plate shape. The shape of the first heat conductive member5in a plan view is rectangular, for example. The first heat conductive member5includes a front surface51and a back surface52. The first heat conductive member5is arranged to bring the front surface51into contact with the back surface32of the liquid crystal display device3. The front surface51is preferably in intimate contact with the entire back surface32. The first heat conductive member5may be bonded to the back surface32of the liquid crystal display device3.

The Peltier element6is a second heat conductive member that conducts heat between the first heat conductive member5and the housing41. The Peltier element6is a thermoelectric element, and includes a first surface61and a second surface62. The Peltier element6transfers heat between the first surface61and the second surface62in accordance with a direction of a current. The Peltier element6can transfer heat from the first surface61toward the second surface62, and can transfer heat from the second surface62toward the first surface61.

The Peltier element6is arranged to bring the first surface61into contact with the first heat conductive member5, and bring the second surface62into contact with the housing41. That is, the Peltier element6is sandwiched between the first heat conductive member5and the housing41, and interposed between the first heat conductive member5and the housing41. The first surface61is in contact with the back surface52of the first heat conductive member5. The first surface61is preferably in intimate contact with the back surface52. The second surface62is in contact with the first end face41bof the side wall41a. The second surface62is preferably in intimate contact with the first end face41b. The Peltier element6according to the present embodiment can transfer heat from the first heat conductive member5to the housing41, and can transfer heat from the housing41to the first heat conductive member5.

As illustrated inFIG.3andFIG.4, the Peltier element6is arranged on an outer peripheral part of the first heat conductive member5. The Peltier element6is also arranged to surround the liquid crystal display device3when viewed in a plan view. The Peltier element6exemplified inFIG.4is arranged in a rectangular frame shape. More specifically, the Peltier element6includes a pair of first extending parts63,63and a pair of second extending parts64,64.

The pair of first extending parts63,63are arranged to sandwich the liquid crystal display device3in the image vertical direction GV when viewed in a plan view. The first extending part63is positioned at an end part in the image vertical direction GV of the first heat conductive member5, and extends along the image horizontal direction GH. The pair of second extending parts64,64are arranged to sandwich the liquid crystal display device3in the image horizontal direction GH when viewed in a plan view. The second extending part64is positioned at an end part in the image horizontal direction GH of the first heat conductive member5, and extends along the image vertical direction GV. The end part of the first extending part63may be connected to the end part of the second extending part64, or positioned in the vicinity of the second extending part64.

The Peltier element6may be one element formed in a frame shape, or may be configured in a frame shape by combining a plurality of elements. For example, elements of the first extending part63may be different from elements of the second extending part64. The first extending part63may be configured by arranging a plurality of elements. The second extending part64may be configured by arranging a plurality of elements.

As illustrated inFIG.4, the Peltier element6is arranged not to overlap with the liquid crystal display device3in a plan view. That is, the Peltier element6is arranged not to block light from the light source42toward the liquid crystal display device3. A slight gap may be disposed between the Peltier element6and the liquid crystal display device3when viewed in a plan view. In the image display device10according to the present embodiment, the first heat conductive member5is a size larger than the liquid crystal display device3. The first heat conductive member5includes a rectangular frame-shaped part53surrounding the liquid crystal display device3. The Peltier element6is arranged on the frame-shaped part53, and in contact with the frame-shaped part53. A width of the frame-shaped part53is determined to secure a sufficient contact area between the Peltier element6and the first heat conductive member5.

The control unit7illustrated inFIG.2is configured to control the image display device10. The control unit7is, for example, a computer including an arithmetic unit, a memory, a communication interface, and the like. The control unit7performs cooling control and heating control (described later) in accordance with a computer program stored in the memory, for example. In the image display device10, a temperature sensor9is disposed to detect a temperature of the liquid crystal display device3. The control unit7acquires information about the temperature of the liquid crystal display device3from the temperature sensor9.

The following describes an operation of the control unit7with reference toFIG.5toFIG.7. A flowchart illustrated inFIG.5is repeatedly performed when a power source of the image display device10is turned on, for example. At Step S10, the control unit7acquires temperature information. The control unit7acquires the information about the temperature of the liquid crystal display device3from the temperature sensor9. After Step S10is performed, the process proceeds to Step S20.

At Step S20, the control unit7determines whether control is required. At Step S20, necessity for temperature control using the Peltier element6is determined. In a case in which the temperature of the liquid crystal display device3is equal to or larger than a lower limit value and equal to or smaller than an upper limit value, the control unit7determines that temperature control is not required. On the other hand, in a case in which the temperature of the liquid crystal display device3is smaller than the lower limit value or exceeds the upper limit value, the control unit7determines that temperature control is required. As a result of the determination at Step S20, the process proceeds to Step S30in a case in which affirmative determination is made such that control is required, and the flowchart is once ended in a case in which negative determination is made.

At Step S30, the control unit7determines whether the temperature of the liquid crystal display device3is high. In a case in which the temperature of the liquid crystal display device3exceeds the upper limit value, the control unit7determines that the temperature is high. As a result of the determination at Step S30, the process proceeds to Step S40in a case in which affirmative determination is made, and the process proceeds to Step S50in a case in which negative determination is made.

At Step S40, the control unit7performs cooling control. The cooling control is control for cooling the liquid crystal display device3with the Peltier element6. As illustrated inFIG.6, in a case in which external light L1such as sunlight is condensed to the liquid crystal display device3, the temperature of the liquid crystal display device3rises. In a high-temperature environment, the temperature of the liquid crystal display device3may exceed the upper limit value. In this case, the control unit7cools the liquid crystal display device3by cooling control.

The control unit7transfers heat from the first surface61to the second surface62by controlling a direction of a current caused to flow to the Peltier element6. That is, the control unit7can cause the Peltier element6to absorb heat through the first surface61and to radiate heat through the second surface62. Through the cooling control, as indicated by an arrow AR1inFIG.6, heat is conducted from the first heat conductive member5to the housing41of the backlight unit4via the Peltier element6. The heat of the housing41is radiated mainly from the heat sink43. When the first heat conductive member5is cooled, as indicated by an arrow AR2, the heat of the liquid crystal display device3is released to the first heat conductive member5.

The Peltier element6can efficiently cool the first heat conductive member5by causing the temperature of the first surface61to be lower than a temperature of a peripheral environment. Thus, the image display device10according to the present embodiment can lower the temperature of the liquid crystal display device3to be equal to or smaller than the upper limit value by cooling control.

When the temperature of the liquid crystal display device3is lowered to an appropriate temperature, the control unit7ends the cooling control. A threshold of the temperature at the time of ending the cooling control is, for example, a value on a lower temperature side than the upper limit value described above. When Step S40is performed, this control procedure ends.

At Step S50, the control unit7performs heating control. The heating control is control for heating the liquid crystal display device3with the Peltier element6. The heating control is performed in a case in which the temperature of the liquid crystal display device3is low such as when it is cold.

The control unit7transfers heat from the second surface62to the first surface61by controlling the direction of the current caused to flow to the Peltier element6. That is, the control unit7can cause the Peltier element6to absorb heat through the second surface62and to heat the first heat conductive member5with the first surface61. Through the heating control, as indicated by an arrow AR3inFIG.7, heat is conducted from the housing41to the first heat conductive member5via the Peltier element6. The heat conducted to the first heat conductive member5heats the liquid crystal display device3as indicated by an arrow AR4.

The control unit7turns on the light source42in the heating control. The light source42irradiates the liquid crystal display device3with light L2. Heat of the light source42heats the first heat conductive member5and the liquid crystal display device3from the back surface side as indicated by an arrow AR5. Furthermore, the heat of the light source42is conducted from the housing41to the first heat conductive member5via the Peltier element6.

In the heating control according to the present embodiment, the liquid crystal display device3is heated by the Peltier element6and the light source42. The Peltier element6arranged in a frame shape with respect to the liquid crystal display device3can heat edge parts of the liquid crystal display device3. Accordingly, the entire liquid crystal display device3can be quickly heated by the heating control according to the present embodiment.

When the temperature of the liquid crystal display device3rises to an appropriate temperature, the control unit7ends the heating control. A threshold of the temperature at the time of ending the heating control is, for example, a value on a higher temperature side than the lower limit value described above. When Step S50is performed, this control procedure ends.

As described above, the display device1for a vehicle according to the present embodiment can selectively perform the cooling control and the heating control based on the temperature of the liquid crystal display device3. Thus, the display device1for a vehicle according to the present embodiment can appropriately control the temperature of the liquid crystal display device3.

As described above, the display device1for a vehicle according to the present embodiment includes the housing41, the liquid crystal display device3, the transparent plate-shaped first heat conductive member5, and the Peltier element6. The exemplified first heat conductive member5is arranged in contact with the back surface32of the liquid crystal display device3. The Peltier element6is a second heat conductive member that conducts heat between the first heat conductive member5and the housing41. The display device1for a vehicle according to the present embodiment can conduct heat between the first heat conductive member5and the housing41by the second heat conductive member. Accordingly, the temperature of the liquid crystal display device3can be appropriately controlled.

The display device1for a vehicle according to the present embodiment includes the control unit7, which controls the Peltier element6. The Peltier element6as the second heat conductive member includes the first surface61and the second surface62, and is arranged to bring the first surface61into contact with the first heat conductive member5and bring the second surface62into contact with the housing41. The control unit7selectively performs cooling control for cooling the liquid crystal display device3with the Peltier element6and heating control for heating the liquid crystal display device3with the Peltier element6based on the temperature of the liquid crystal display device3. Thus, the display device1for a vehicle can appropriately control the temperature of the liquid crystal display device3.

The display device1for a vehicle according to the present embodiment includes the backlight unit4, which irradiates the back surface32of the liquid crystal display device3with light. The backlight unit4includes the housing41and the light source42housed in the housing41. The first heat conductive member5is arranged in contact with the back surface32of the liquid crystal display device3. The Peltier element6is arranged in a frame shape surrounding the liquid crystal display device3and is sandwiched between the first heat conductive member5and the housing41. Thus, the Peltier element6according to the present embodiment can efficiently cool or heat the liquid crystal display device3.

In the heating control according to the present embodiment, the control unit7turns on the light source42and causes the Peltier element6to absorb heat through the second surface62and to heat the first heat conductive member5with the first surface61. The image display device10according to the present embodiment can heat the liquid crystal display device3by conducting heat of the light source42to the liquid crystal display device3via the housing41, the Peltier element6, and the first heat conductive member5.

The following examines a configuration not including the Peltier element6as a comparative example for the present embodiment. In the comparative example, cooling of the liquid crystal display device3is performed by heat absorption by the first heat conductive member5or heat transfer from the first heat conductive member5to the housing41and the like. In the configuration of the comparative example, heat capacity of the first heat conductive member5is set based on the amount of heat received by the liquid crystal display device3. Due to this, the size of the first heat conductive member5needs to be adjusted for each product. Considering the heat capacity required for the first heat conductive member5, there is a limit to downsizing of the first heat conductive member5, and the image display device tends to be upsized.

On the other hand, the display device1for a vehicle according to the present embodiment can cool the first heat conductive member5with the Peltier element6, so that it is possible to reduce the thickness of the first heat conductive member5or downsize the first heat conductive member5.

In the comparative example, in a case in which the temperature of the liquid crystal display device3exceeds the upper limit value in a high-temperature environment, the light source42needs to be attenuated or turned off. On the other hand, the display device1for a vehicle according to the present embodiment can control the temperature of the liquid crystal display device3to be equal to or smaller than the upper limit value by cooling control. The light source42does not need to be attenuated or turned off, so that visibility of the virtual image Vi is improved.

The control unit7may acquire the temperature information of the liquid crystal display device3from a control device and the like of the vehicle100. By way of example, the control unit7may estimate the temperature of the liquid crystal display device3based on information acquired from the temperature sensor or an illuminometer of the vehicle100.

First Modification of Embodiment

The following describes a first modification of the embodiment.FIG.8is a diagram illustrating the image display device according to the first modification of the embodiment. The image display device10according to the first modification is different from the embodiment described above in that a heat transfer part44is included, for example. As illustrated inFIG.8, the heat transfer part44conducts heat between the side wall41aof the backlight unit4and the housing2of the display device1for a vehicle. The heat transfer part44is formed of material having thermal conductivity such as metal. The heat transfer part44may be part of the housing41. The heat transfer part44may be a fixing member for fixing the housing41of the backlight unit4to the housing2.

The heat transfer part44is arranged between the first end face41band the second end face41cof the side wall41a. The heat transfer part44may be arranged at an end part on the first end face41bside of the side wall41a. The heat transfer part44may be arranged in a flange shape surrounding the side wall41a.

In a case in which cooling control is performed by the Peltier element6, as indicated by an arrow AR6inFIG.8, heat is released from the side wall41ato the housing2via the heat transfer part44. The heat transfer part44can improve cooling capacity for the liquid crystal display device3.

Second Modification of Embodiment

The following describes a second modification of the embodiment.FIG.9andFIG.10are diagrams illustrating the display device for a vehicle according to the second modification of the embodiment. The second modification of the embodiment is different from the embodiment described above in that the Peltier element6is interposed between the first heat conductive member5and the housing2, for example.

As illustrated inFIG.9, the first heat conductive member5includes a projecting part54projecting toward a lateral side with respect to the liquid crystal display device3. The projecting part54projects toward a side wall of the housing2. The Peltier element6is arranged to bring the first surface61into contact with the first heat conductive member5, and bring the second surface62into contact with an inner wall surface22of the housing2. The second surface62is in contact with a surface facing upward of the inner wall surface22, for example. The Peltier element6is sandwiched between the back surface52of the first heat conductive member5and the inner wall surface22of the housing2.

The Peltier element6according to the second modification of the embodiment can release the heat of the first heat conductive member5to the housing2. A physique of the housing2is larger than that of the housing41of the backlight unit4. Thus, the display device1for a vehicle according to the second modification of the embodiment can appropriately control the temperature of the liquid crystal display device3. In the configuration according to the second modification, it is possible to easily widen a contact area between the Peltier element6and the first heat conductive member5, and a contact area between the Peltier element6and the housing2. For example, the contact area described above can be expanded without being limited by the size of the housing41.

The control unit7can perform the cooling control and the heating control similarly to the control unit7in the embodiment described above. The control unit7may turn on the light source42of the backlight unit4at the time of performing the heating control by the Peltier element6.

As illustrated inFIG.10, heat conduction sheets65may be interposed between the first heat conductive member5and the Peltier element6, and between the housing2and the Peltier element6. The heat conduction sheet65is a sheet member having high thermal conductivity. The thermal conductivity of the heat conduction sheet65is preferably larger than the thermal conductivity of the first heat conductive member5. The heat conduction sheet65may be a sheet having flexibility and adhesion. The heat conduction sheet65may be formed of resin such as silicon, for example. Instead of the heat conduction sheet65, a bonding agent having thermal conductivity may be used.

In the second modification of the embodiment, the position of the first heat conductive member5with respect to the liquid crystal display device3is not limited to the back surface32side. The first heat conductive member5may be arranged on the display surface31side of the liquid crystal display device3.

Third Modification of Embodiment

The following describes a third modification of the embodiment.FIG.11toFIG.13are diagrams illustrating the display device for a vehicle according to the third modification of the embodiment. The third modification of the embodiment is different from the embodiment described above in that a metal member having high thermal conductivity is provided as a second heat conductive member, for example.

A second heat conductive member70illustrated in FIG.11has higher thermal conductivity than that of the first heat conductive member5. The second heat conductive member70is formed of metal or alloy such as copper or aluminum, for example. The shape of the second heat conductive member70is a plate shape or a rod shape, for example. The second heat conductive member70exemplified inFIG.11is bent to form a substantially L-shape. The second heat conductive member70includes a first contact part71and a second contact part72. The second heat conductive member70is bent between the first contact part71and the second contact part72. The first contact part71is in contact with the first heat conductive member5, and bonded to the back surface52of the first heat conductive member5, for example. The second contact part72is in contact with the inner wall surface22of the housing2. The second contact part72may be bonded to the housing2, or may be fixed to the housing2by a fastening member and the like.

The housing2illustrated inFIG.12includes a main body23and a cover24. The main body23has a cylindrical shape, and houses the image display device10. The cover24blocks an opening of the main body23. The exemplified main body23is formed of resin, and the cover24is formed of metal. The thermal conductivity of the cover24is larger than the thermal conductivity of the main body23.

The second heat conductive member70illustrated inFIG.12is bent to form a substantially U-shape. More specifically, the second heat conductive member70includes the first contact part71, a second contact part73, and an intermediate part74. The shape of the exemplified intermediate part74is a linear shape along an axial direction of the main body23. The second heat conductive member70is bent so that the first contact part71and the second contact part73are orthogonal to the intermediate part74. The first contact part71is in contact with the first heat conductive member5, and bonded to the back surface52, for example. The second contact part73is in contact with the cover24of the housing2. The second contact part73may be bonded to the cover24, or may be fixed to the cover24by a fastening member and the like.

As illustrated inFIG.13, the heat conduction sheets65may be interposed between the first heat conductive member5and the second heat conductive member70, and between the housing2and the second heat conductive member70. Instead of the heat conduction sheet65, a bonding agent having thermal conductivity may be used.

The shape of the second heat conductive member70is not limited to the shapes exemplified inFIG.11toFIG.13. For example, instead of the shape illustrated inFIG.12, the second heat conductive member70may be bent to form a substantially Z-shape. In other words, the first contact part71and the second contact part73may be bent toward opposite sides with respect to the intermediate part74. The shape of the second heat conductive member70is optional, and designed so that heat can be appropriately conducted between the first heat conductive member5and the housing2.

In the third modification of the embodiment, the position of the first heat conductive member5with respect to the liquid crystal display device3is not limited to the back surface32side. The first heat conductive member5may be arranged on the display surface31side of the liquid crystal display device3.

Pieces of the content disclosed in the embodiment and modifications described above can be appropriately combined to be performed.

The display device for a vehicle according to the present invention includes a second heat conductive member that conducts heat between a first heat conductive member and a housing. Thus, the display device for a vehicle according to the present invention exhibits an effect of appropriately controlling the temperature of the liquid crystal display device.