HEAD-UP DISPLAY DEVICE

A head-up display device includes: an indicator dimmed by duty ratio control and configured to emit display light; a mirror member rotatable about a rotation shaft and configured to reflect the display light from the indicator to project a display image; a control unit configured to control the dimming of the indicator and the rotation of the mirror member; and a temperature sensor configured to output a signal corresponding to an ambient temperature around the indicator. The control unit includes: a temperature prediction unit configured to predict a temperature of the indicator, and a failure avoidance unit configured to execute lowering an upper limit of the duty ratio or rotation control of the mirror member for reducing the amount of sunlight that enters the indicator through the mirror member when the predicted temperature of the indicator is greater than or equal to a threshold.

TECHNICAL FIELD

The present invention relates to a head-up display device.

BACKGROUND ART

In the related art, there is known a head-up display device that includes, in an opening formed in an upper face of an instrument panel, an indicator and a mirror that reflects an image displayed on the indicator toward a windshield (for example, see JP6107380B).

SUMMARY OF INVENTION

Here, in the head-up display device described in JP6107380B, the sunlight may enter the indicator through the mirror, and in this case, the indicator may be heated and fail. Therefore, when a temperature of the indicator is high, it is conceivable to perform failure avoidance control such as lowering a duty ratio for controlling energization of a backlight constituting the indicator.

However, since the temperature of the indicator in the head-up display device is unknown, the failure avoidance control cannot be performed at an appropriate timing. Therefore, even if a temperature sensor is provided on the indicator, the temperature sensor can only be installed at a position where the temperature sensor does not interfere with display light from the indicator, that is, outside a path of the display light, and it is difficult to accurately detect the temperature of the indicator. As a result, the failure avoidance control may be performed when the temperature of the indicator does not become high enough, or the failure avoidance control may not be executed even though the temperature of the indicator is extremely high.

Aspect of non-limiting embodiments of the present disclosure relates to provide a head-up display device capable of performing failure avoidance control at a more appropriate timing.

According to an aspect of the present disclosure, there is provided a head-up display device including:an indicator dimmed by duty ratio control and configured to emit display light;a mirror member rotatable about a rotation shaft and configured to reflect the display light from the indicator to project a display image;a control unit configured to control the dimming of the indicator by the duty ratio control and control the rotation of the mirror member; anda temperature sensor provided outside a path of the display light emitted from the indicator and configured to output a signal corresponding to an ambient temperature around the indicator, whereinthe control unit includes:a temperature prediction unit configured to predict, based on a duty ratio of the indicator and the ambient temperature based on the signal from the temperature sensor, a temperature of the indicator, anda failure avoidance unit configured to execute, as failure avoidance control, at least one of lowering control for lowering an upper limit of the duty ratio of the indicator or rotation control of the mirror member for reducing the amount of sunlight that enters the indicator through the mirror member when the temperature of the indicator predicted by the temperature prediction unit is greater than or equal to a threshold, whereinwhen the temperature of the indicator predicted by the temperature prediction unit is greater than or equal to the threshold, the failure avoidance unit lowers the upper limit of the duty ratio of the indicator as the temperature of the indicator increases.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the present invention will be described with reference to preferred embodiments. The present invention is not limited to the following embodiments, and can be appropriately modified without departing from the scope of the present invention. In addition, in the embodiments described below, although there are portions in which illustrations and descriptions of some configurations are omitted, it goes without saying that for details of omitted techniques, publicly known or well-known techniques are appropriately applied within a range that does not cause contradiction with contents described below.

FIG.1is a schematic side view showing a head-up display device according to a first embodiment of the present invention, andFIG.2is a schematic side view showing main parts of the head-up display device according to the first embodiment of the present invention.

As shown inFIG.1, a head-up display device1according to the first embodiment is housed in an opening O formed in an upper face of an instrument panel2of a vehicle. As shown inFIGS.1and2, the head-up display device1includes an indicator10, a reflecting mirror20, a concave mirror (mirror member)30, a housing40, a control board (control unit)50, and a temperature sensor60.

The indicator10is a liquid crystal display including a liquid crystal panel11and a backlight12behind the liquid crystal panel11, and is dimmed by controlling the brightness of the backlight12by duty ratio control. The indicator10emits information to be provided to a driver as display light. The display light from the indicator10is emitted toward the reflecting mirror20shown inFIGS.1and2, and is reflected by the reflecting mirror20toward the concave mirror30.

The concave mirror30reflects the display light and projects a display image onto a windshield W of the vehicle via a cover member41of the housing40. The display image projected onto the windshield W is recognized by the driver as a virtual image I. The concave mirror30is rotatable about a rotation shaft. The concave mirror30controls a height of the virtual image I that is visually recognized by the driver by rotating about the rotation shaft.

The control board50controls the entire head-up display device1, and in particular, in the present embodiment, the control board50has a function of performing dimming control of the indicator10by the duty ratio control and controlling the rotation of the concave mirror30. The temperature sensor60is provided outside a path of the display light emitted from the indicator10, and outputs a signal corresponding to an ambient temperature around the indicator10. The temperature sensor60includes a thermistor and transmits the signal corresponding to the ambient temperature to the control board50.

The control board50further includes a temperature prediction unit51, a failure avoidance unit52, and a storage unit53. The temperature prediction unit51predicts a temperature of the indicator10. The temperature prediction unit51predicts the temperature of the indicator10based on a duty ratio of the indicator10and the ambient temperature around the indicator10based on the signal from the temperature sensor60.

Here, the storage unit53stores a temperature rise value for each duty ratio of the indicator10. Therefore, the temperature prediction unit51predicts the temperature of the indicator10by adding the temperature rise value corresponding to the current duty ratio to the ambient temperature detected by the temperature sensor60.

When the temperature of the indicator10predicted by the temperature prediction unit51is greater than or equal to a threshold, the failure avoidance unit52executes failure avoidance control to prevent a failure of the indicator10. The failure avoidance control is at least one of lowering control for lowering an upper limit of the duty ratio of the indicator10or rotation control of the concave mirror30for reducing the amount of sunlight that enters the indicator10through the concave mirror30.

More specifically, when the temperature of the indicator10predicted by the temperature prediction unit51is greater than or equal to the threshold, the failure avoidance unit52lowers the upper limit of the duty ratio of the indicator10as the temperature of the indicator10increases.

FIG.3is a correlation diagram showing a correlation between the temperature and the upper limit of the duty ratio of the indicator10. As shown inFIG.3, the failure avoidance unit52according to the first embodiment sets the upper limit of the duty ratio to A % when the temperature of the indicator10is less than A degree Celsius (threshold). A % is an initial value, and is, for example, 100%. When the temperature of the indicator10is greater than or equal to A degree Celsius (threshold) and less than B degree Celsius, the failure avoidance unit52lowers the upper limit of the duty ratio to B % A %). When the temperature of the indicator10is greater than or equal to B degree Celsius and less than C degree Celsius (specified value), the failure avoidance unit52lowers the upper limit of the duty ratio to C % (<B %).

Further, when the temperature of the indicator10is greater than or equal to C degree Celsius (specified value), the failure avoidance unit52lowers the upper limit of the duty ratio to 0%. That is, the failure avoidance unit52turns off the indicator10.

Refer toFIG.2again. Further, when the temperature of the indicator10is greater than or equal to C degree Celsius (specified value), the failure avoidance unit52according to the present embodiment rotates the concave mirror30to a parking position (hereinafter, referred to as a PP position) where the amount of sunlight that enters the indicator10through the concave mirror30is less than or equal to a predetermined amount of light. The PP position is an example of a first rotation angle. Here, the predetermined amount of light refers to the amount of light that can maintain the indicator10at a temperature less than a failure temperature in a case where a temperature of the upper face of the instrument panel2rises to about 80 degrees in summer or the like. In the above case, the predetermined amount of light is preferably the amount of light that can maintain the indicator10at a temperature less than a guaranteed temperature. Further, the predetermined amount of light is more preferably zero amount of light. In the present embodiment, the PP position is assumed to be an angle at which the amount of light is zero. Here, the amount of sunlight refers to the amount of direct light from the sun that passes through the windshield W, is reflected by the concave mirror30and the reflecting mirror20, and enters the indicator10. Therefore, the amount of sunlight does not include the amount of diffusely reflected light that is reflected by, for example, a building outside the vehicle or an inner surface of the housing40of the head-up display device1and enters the indicator10.

In a case where the temperature of the indicator10is greater than or equal to C degree Celsius, the indicator10is turned off, and the concave mirror30is controlled to rotate to the PP position, when the temperature of the indicator10predicted by the temperature prediction unit51is less than C degree Celsius, the failure avoidance unit52executes restriction release control. The restriction release control is control for turning on the indicator10and returning the concave mirror30to a rotation position (second rotation angle) before the concave mirror is set to the PP position.

In particular, when the temperature of the indicator10predicted by the temperature prediction unit51is less than C degree Celsius and the restriction release control is executed, the failure avoidance unit52increases the upper limit of the duty ratio of the indicator10as the temperature of the indicator10predicted by the temperature prediction unit51is lower.

Refer toFIG.3. When the temperature of the indicator10is greater than or equal to C degree Celsius (specified value), the failure avoidance unit52according to the present embodiment lowers the upper limit of the duty ratio to 0%. In this state, when the temperature of the indicator10is greater than or equal to B degree Celsius and less than C degree Celsius, the failure avoidance unit52increases the upper limit of the duty ratio to C %. When the temperature of the indicator10is greater than or equal to A degree Celsius and less than B degree Celsius, the failure avoidance unit52increases the upper limit of the duty ratio to B %.

Further, when the temperature of the indicator10is less than A degree Celsius (threshold), the failure avoidance unit52increases the upper limit of the duty ratio to A %. That is, the failure avoidance unit52returns the upper limit of the duty ratio to the state before the failure avoidance control is executed.

Next, an operation of the head-up display device1according to the first embodiment will be described.FIG.4is a flowchart showing the operation of the head-up display device1according to the first embodiment, and shows processing related to the failure avoidance control.

As shown inFIG.4, first, the temperature prediction unit51detects the ambient temperature around the indicator10based on the signal from the temperature sensor60(S1). Next, the temperature prediction unit51reads the current duty ratio of the indicator10(S2). Next, the temperature prediction unit51obtains the temperature rise value from the duty ratio read in step S2, and adds the temperature rise value to the ambient temperature detected in step S1to predict the temperature of the indicator10(S3).

Next, the failure avoidance unit52determines whether the temperature of the indicator10is greater than or equal to A degree Celsius (S4). When the temperature of the indicator10is not greater than or equal to A degree Celsius (S4: NO), the failure avoidance unit52sets the upper limit of the duty ratio to A % (S5). Thereafter, the process proceeds to step S1.

On the other hand, when the temperature of the indicator10is greater than or equal to A degree Celsius (S4: YES), the failure avoidance unit52determines whether the temperature of the indicator10is greater than or equal to B degree Celsius (S6). When the temperature of the indicator10is not greater than or equal to B degree Celsius (S6: NO), the failure avoidance unit52sets the upper limit of the duty ratio to B % (S7). Thereafter, the process proceeds to step S1.

When the temperature of the indicator10is greater than or equal to B degree Celsius (S6: YES), the failure avoidance unit52determines whether the temperature of the indicator is greater than or equal to C degree Celsius (S8). When the temperature of the indicator10is not greater than or equal to C degree Celsius (S8: NO), the failure avoidance unit52sets the upper limit of the duty ratio to C % (S9). Thereafter, the process proceeds to step S1.

When the temperature of the indicator10is greater than or equal to C degree Celsius (S8: YES), the failure avoidance unit52sets the upper limit of the duty ratio to zero and rotates the concave mirror30to the PP position so that the sunlight does not enter the indicator10(S10). Thereafter, the process shown inFIG.4ends.

FIG.5is a flowchart showing an operation of the head-up display device1according to the first embodiment, and shows processing related to the restriction release control. First, in the processing of steps S11to S13shown inFIG.5, the same processing as steps S1to S3shown inFIG.4is performed.

Thereafter, the failure avoidance unit52determines whether the predicted temperature of the indicator10is less than C degree Celsius (S14). When the temperature of the indicator10is not less than C degree Celsius (S14: NO), the failure avoidance unit52sets the concave mirror30to the PP position (S15). Thereafter, the process proceeds to step S11.

On the other hand, when the temperature of the indicator10is less than C degree Celsius (S14: YES), the failure avoidance unit52returns the angle of the concave mirror30to the original angle position (S16). Next, the failure avoidance unit52determines whether the temperature of the indicator10is less than B degree Celsius (S17). When the temperature of the indicator10is not less than B degree Celsius (S17: NO), the failure avoidance unit52sets the upper limit of the duty ratio to C % (S18). Thereafter, the process proceeds to step S11.

When the temperature of the indicator10is less than B degree Celsius (S17: YES), the failure avoidance unit52determines whether the temperature of the indicator10is less than A degree Celsius (S19). When the temperature of the indicator10is not less than A degree Celsius (S19: NO), the failure avoidance unit52sets the upper limit of the duty ratio to B % (S20). Thereafter, the process proceeds to step S11.

When the temperature of the indicator10is less than A degree Celsius (S19: YES), the failure avoidance unit52sets the upper limit of the duty ratio to A % (S21). Thereafter, the processing shown inFIG.5ends.

In this way, according to the head-up display device1according to the present embodiment, the temperature of the indicator10is predicted based on the duty ratio of the indicator10and the ambient temperature based on the signal from the temperature sensor60. Here, in the head-up display device1, although the temperature sensor60can only be provided outside the path of the display light, making it difficult to accurately measure the temperature of the indicator10, by considering the duty ratio that contributes to heat generation of the indicator10, the temperature of the indicator10can be predicted more accurately. Then, by executing the failure avoidance control when the predicted temperature of the indicator10is greater than or equal to A degree Celsius, it is possible to provide the head-up display device1capable of performing the failure avoidance control more appropriately.

When the temperature of the indicator10is greater than or equal to A degree Celsius, the upper limit of the duty ratio of the indicator10is lowered as the temperature of the indicator increases. Therefore, when the temperature is greater than or equal to A degree Celsius but not extremely high, the degree of restriction of the duty ratio is small, and it is possible to prevent the display light from becoming too dark.

When the predicted temperature of the indicator10is greater than or equal to C degree Celsius, the indicator10is turned off, and the concave mirror30is rotated to the PP position to make the amount of sunlight that reaches the indicator10through the concave mirror less than or equal to the predetermined amount of light, for example, to make the amount of direct light zero. Therefore, when the temperature of the indicator10is extremely high, the indicator10is turned off and the entering sunlight is restricted to less than or equal to the predetermined amount of light from the viewpoint of emergency failure avoidance, making it even easier to avoid a failure.

In addition, in a case where the indicator10is turned off and the entering sunlight is restricted to less than or equal to the predetermined amount of light, when the temperature of the indicator10is less than C degree Celsius, the restriction release control is executed to turn on the indicator10and return the concave mirror30to the rotation angle before the concave mirror30is set to the PP position. Therefore, when the temperature of the indicator10decreases to less than C degree Celsius, the restriction is released, and for example, the virtual image display is restarted at an early stage without waiting for the temperature to decrease to less than A degree Celsius, and the usability of the head-up display device1can be improved.

In addition, when the predicted temperature of the indicator10is less than C degree Celsius and the indicator10is turned on, the upper limit of the duty ratio of the indicator10is increased as the predicted temperature of the indicator10is lower. Therefore, even in a case where the restriction is released, when the temperature is not extremely high, the degree of restriction of the duty ratio is small, and it is possible to prevent the display light from becoming too dark.

Next, a second embodiment of the present invention will be described. The head-up display device1according to the second embodiment is similar to that according to the first embodiment, but some processes are different. Hereinafter, differences from the first embodiment will be described.

FIG.6is a correlation diagram showing a correlation between a temperature and an upper limit of a duty ratio of the indicator10according to the second embodiment. As shown inFIG.6, in the second embodiment, the failure avoidance unit52does not lower the upper limit of the duty ratio even when the predicted temperature of the indicator10is greater than or equal to A degree Celsius, and when the predicted temperature of the indicator10is greater than or equal to C degree Celsius, which is a threshold in the second embodiment, the failure avoidance unit52lowers the duty ratio of the indicator10to zero to turn off the indicator10. The second embodiment is similar to the first embodiment in that the concave mirror30is set to a PP position when the temperature of the indicator10is greater than or equal to C degree Celsius.

As described above, in the second embodiment, failure avoidance control is not executed even when the predicted temperature of the indicator10is greater than or equal to A degree Celsius, and the failure avoidance control is executed when the temperature is C degree Celsius, which is higher than A degree Celsius. That is, in the second embodiment, no failure avoidance control is performed when the temperature is less than C degree Celsius, and the indicator10is turned off when the temperature reaches C degree Celsius, that is, control of setting the duty ratio to zero and setting the concave mirror30to the PP position is executed at once. Therefore, even when the temperature of the indicator10increases to a certain extent, the failure avoidance control is executed to prevent a failure that may occur while ensuring the visibility without darkening the indicator10, and the failure can be avoided while ensuring the visibility as much as possible.

In the second embodiment, it is assumed that the failure avoidance unit52performs the same restriction release control as in the first embodiment, but the present invention is not limited thereto, and when the predicted temperature of the indicator10changes from greater than or equal to C degree Celsius to less than C degree Celsius, the failure avoidance unit52may increase the upper limit of the duty ratio to A % at once according to the correlation diagram shown inFIG.6.

FIG.7is a flowchart showing an operation of the head-up display device1according to the second embodiment, and shows processing related to the failure avoidance control. First, in steps S31to S33shown inFIG.7, the same processing as steps S1to S3shown inFIG.4is executed.

Next, in step S34shown inFIG.7, the failure avoidance unit52determines whether the temperature of the indicator10is greater than or equal to C degree Celsius (S34). When the temperature of the indicator10is not greater than or equal to C degree Celsius (S34: NO), the failure avoidance unit52sets the upper limit of the duty ratio to A % (S35). Thereafter, the process proceeds to step S31.

When the temperature of the indicator10is greater than or equal to C degree Celsius (S34: YES), the failure avoidance unit52sets the upper limit of the duty ratio to zero and rotates the concave mirror30to the PP position so that sunlight does not enter the indicator10(S36). Thereafter, the processing shown inFIG.7ends.

In this way, according to the head-up display device1of the second embodiment, the same effects as those of the first embodiment can be obtained.

In addition, according to the second embodiment, the failure avoidance control is not executed even when the predicted temperature of the indicator10is greater than or equal to A degree Celsius, and the failure avoidance control is executed when the temperature is greater than or equal to C degree Celsius, which is higher than A degree Celsius. Therefore, even when the temperature of the indicator10increases to a certain extent, the failure avoidance control is executed to prevent a failure that may occur while ensuring the visibility without darkening the indicator10, and the failure can be avoided while ensuring the visibility as much as possible.

Next, a third embodiment of the present invention will be described. The head-up display device1according to the third embodiment is similar to that according to the first embodiment, but some processes are different. Hereinafter, differences from the first embodiment will be described.

First, even when the predicted temperature of the indicator10is greater than or equal to C degree Celsius and then less than C degree Celsius, the head-up display device1according to the third embodiment returns the concave mirror30to a second rotation angle without turning on the indicator10.

FIG.8is a correlation diagram showing a correlation between the temperature and an upper limit of a duty ratio of the indicator10according to the third embodiment. As shown inFIG.8, in the third embodiment, the failure avoidance unit52lowers the upper limit of the duty ratio each time the predicted temperature of the indicator10reaches A degree Celsius (threshold) and B degree Celsius, and lowers the duty ratio of the indicator10to zero to turn off the indicator10when the predicted temperature of the indicator10is greater than or equal to C degree Celsius (specified value).

In the third embodiment, even when the predicted temperature of the indicator10decreases from greater than or equal to C degree Celsius to less than C degree Celsius, the failure avoidance unit52maintains the upper limit of the duty ratio at zero until the predicted temperature of the indicator10reaches D degree Celsius (specific value). That is, even when the predicted temperature of the indicator10decreases from greater than or equal to C degree Celsius to less than C degree Celsius, the failure avoidance unit52according to the third embodiment returns the concave mirror30to the original rotation angle (second rotation angle) without turning on the indicator10.

Thereafter, when the predicted temperature of the indicator10decreases to less than D degree Celsius, the failure avoidance unit52increases the upper limit of the duty ratio to C % to turn on the indicator10, and increases the upper limit of the duty ratio to B % and A % each time the temperature reaches B degree Celsius and A degree Celsius from then on.

As described above, in the third embodiment, the concave mirror30is returned before the indicator10is turned on. Here, when the concave mirror30is returned, sunlight exceeding a predetermined amount of light may enter the indicator10. Therefore, the temperature of the indicator10may be greater than or equal to C degree Celsius again. Therefore, the predicted temperature of the indicator10may change back and forth several times around C degree Celsius. In such a case, in the first embodiment, the indicator10may be repeatedly turned on and off, but in the third embodiment, since the indicator10is turned on when the temperature of the indicator10is less than D degree Celsius, such a situation can be avoided. Therefore, it is possible to prevent the indicator10from being repeatedly turned on and off. In the above description, the indicator10is turned on when the predicted temperature of the indicator10decreases to less than D degree Celsius, but the timing at which the indicator10is turned on is not limited to the timing at which the predicted temperature of the indicator10is less than D degree Celsius, and may be, for example, the timing at which the predicted temperature of the indicator10is less than A degree Celsius.

FIG.9is a flowchart showing an operation of the head-up display device1according to the third embodiment, and shows processing related to restriction release control. First, in steps S41to S46shown inFIG.9, the same processing as steps S11to S16shown inFIG.5is executed.

Next, in step S47shown inFIG.9, the failure avoidance unit52determines whether the temperature of the indicator10is less than D degree Celsius (S47). When the temperature of the indicator10is not less than D degree Celsius (S47: NO), the process proceeds to step S41.

When the temperature of the indicator10is less than D degree Celsius (S47: YES), the failure avoidance unit52determines whether the temperature of the indicator10is less than B degree Celsius (S48). When the temperature of the indicator10is not less than B degree Celsius (S48: NO), the failure avoidance unit52sets the upper limit of the duty ratio to C % (S49). Thereafter, the process proceeds to step S41.

When the temperature of the indicator10is less than B degree Celsius (S48: YES), the failure avoidance unit52determines whether the temperature of the indicator10is less than A degree Celsius (S50). When the temperature of the indicator10is not less than A degree Celsius (S50: NO), the failure avoidance unit52sets the upper limit of the duty ratio to B % (S51). Thereafter, the process proceeds to step S41.

When the temperature of the indicator10is less than A degree Celsius (S50: YES), the failure avoidance unit52sets the upper limit of the duty ratio to A % (S52). Thereafter, the processing shown inFIG.9ends.

In this way, according to the head-up display device1of the third embodiment, the same effects as those of the first embodiment can be obtained.

In addition, according to the third embodiment, the concave mirror30is returned when the predicted temperature of the indicator10is less than C degree Celsius, and the indicator10is turned on when the temperature of the indicator10is less than D degree Celsius. Here, when the concave mirror30is returned, sunlight exceeding a predetermined amount of light may enter the indicator10. Therefore, the temperature of the indicator10may rise to greater than or equal to C degree Celsius again. Therefore, the predicted temperature of the indicator10may change back and forth several times around C degree Celsius. In such a case, in the first embodiment, the indicator10may be repeatedly turned on and off, but in the third embodiment, since the indicator10is turned on when the temperature of the indicator10is less than D degree Celsius, such a situation can be avoided. Therefore, it is possible to prevent the indicator10from being repeatedly turned on and off.

Although the present invention has been described above based on the embodiments, the present invention is not limited to the embodiments described above, and modifications may be made without departing from the gist of the present invention, or publicly known or well-known techniques may be appropriately combined.

For example, in the present embodiment, the temperature prediction unit51predicts the temperature of the indicator10based on an ambient temperature and a temperature rise value obtained from the duty ratio, but the present invention is not limited thereto, and for example, a heat generation amount may be obtained based on the duty ratio and a lighting time, and the temperature rise value based on the heat generation amount may be calculated and added to the ambient temperature. This is because as a result, the temperature prediction is performed in consideration of the heat generation amount, and the temperature prediction can be performed more accurately.

In the above embodiments, the failure avoidance unit52sets the concave mirror30at the PP position when the temperature of the indicator10is greater than or equal to C degree Celsius, but the failure avoidance unit52may set the concave mirror30at another rotation position instead of the PP position to reduce the amount of entering sunlight or limit the amount of entering sunlight to less than or equal to a predetermined amount of light, particularly zero. That is, the first rotation angle is not limited to the PP position.

In addition, the failure avoidance unit52may control the rotation angle of the concave mirror30such that the amount of entering sunlight reaching the indicator10decreases as the temperature of the indicator10increases. At this time, the failure avoidance unit52may control the angle by determining the position of the sun with respect to a host vehicle based on season and time data and an orientation of the host vehicle.

Further, in the present embodiment, the content in which the duty ratio is changed in stages has been described with reference toFIG.3, but the present invention is not limited thereto, and the duty ratio may be changed continuously. In addition, in the failure avoidance control, only one of the duty ratio control and the rotation control of the concave mirror30may be performed.

In the third embodiment, the concave mirror30is returned before the indicator10is turned on, but the present invention is not limited thereto, and the indicator10may be turned on before the concave mirror30is returned. That is, the upper limit of the duty ratio may be set to A % when the temperature of the indicator10decreases to C degree Celsius, and the concave mirror30may be returned when the temperature decreases to D degree Celsius. Here, when the indicator10is turned on, the temperature of the indicator10increases, and the predicted temperature of the indicator10may change back and forth several times around C degree Celsius. In such a case, the indicator10is repeatedly turned on and off, but even if the concave mirror30is not returned and is repeatedly turned on and off, this can be prevented from being noticed by the driver.

Here, features of the embodiments of the head-up display device according to the present invention described above are briefly summarized and listed below in (1) to (8).(1) A head-up display device (1) including:an indicator (10) dimmed by duty ratio control and configured to emit display light;a mirror member (concave mirror30) rotatable about a rotation shaft and configured to reflect the display light from the indicator to project a display image;a control unit (control board50) configured to control the dimming of the indicator by the duty ratio control and control the rotation of the mirror member; anda temperature sensor (60) provided outside a path of the display light emitted from the indicator and configured to output a signal corresponding to an ambient temperature around the indicator, whereinthe control unit includes:a temperature prediction unit (51) configured to predict, based on a duty ratio of the indicator and the ambient temperature based on the signal from the temperature sensor, a temperature of the indicator, anda failure avoidance unit (52) configured to execute, as failure avoidance control, at least one of lowering control for lowering an upper limit of the duty ratio of the indicator or rotation control of the mirror member for reducing the amount of sunlight that enters the indicator through the mirror member when the temperature of the indicator predicted by the temperature prediction unit is greater than or equal to a threshold.(2) The head-up display device according to the above (1), whereinwhen the temperature of the indicator predicted by the temperature prediction unit is greater than or equal to the threshold, the failure avoidance unit lowers the upper limit of the duty ratio of the indicator as the temperature of the indicator increases.(3) The head-up display device according to the above (1) or (2), whereinwhen the temperature of the indicator predicted by the temperature prediction unit is greater than or equal to a specified value exceeding the threshold, the failure avoidance unit (52) lowers the upper limit of the duty ratio of the indicator to zero to turn off the indicator, and rotates the mirror member to a first rotation angle at which the amount of sunlight that enters the indicator through the mirror member is less than or equal to a predetermined amount of light.(4) The head-up display device according to the above (1), whereinwhen the temperature of the indicator predicted by the temperature prediction unit is greater than or equal to the threshold, the failure avoidance unit (52) executes failure avoidance control in which the upper limit of the duty ratio of the indicator is lowered to zero to turn off the indicator, and the mirror member is rotated to a first rotation angle at which the amount of sunlight that enters the indicator through the mirror member is less than or equal to a predetermined amount of light.(5) The head-up display device according to the above (3), whereinwhen the temperature of the indicator predicted by the temperature prediction unit is less than the specified value from the state in which the temperature of the indicator predicted by the temperature prediction unit is greater than or equal to the specified value, and the indicator is turned off and the mirror member is rotated to the first rotation angle, the failure avoidance unit (52) executes restriction release control, which is at least one of lighting control for lighting the indicator or return control for returning the mirror member to a second rotation angle before the first rotation angle is set.(6) The head-up display device according to the above (5), whereinwhen the lighting control is executed, the failure avoidance unit (52) increases the upper limit of the duty ratio of the indicator as the temperature of the indicator predicted by the temperature prediction unit decreases.(7) The head-up display device according to any one of the above (1) to (6), whereinthe temperature prediction unit (51) predicts the temperature of the indicator based on the ambient temperature detected by the temperature sensor and a heat generation amount obtained based on the duty ratio and a lighting time of the indicator.(8) A head-up display device (1) including:a liquid crystal display (indicator10) including a backlight dimmed by duty ratio control and configured to emit display light;a reflecting mirror (20) configured to reflect the display light from the liquid crystal display;a concave mirror (30) rotatable about a rotation shaft and configured to reflect the display light from the reflecting mirror toward a windshield of a vehicle to project a display image onto the windshield;a control unit (control board50) configured to control the dimming of the liquid crystal display by the duty ratio control and control the rotation of the concave mirror; anda thermistor (temperature sensor60) provided outside a path of the display light emitted from the liquid crystal display and configured to output a signal according to an ambient temperature around the liquid crystal display, whereinthe control unit includes:a temperature prediction unit (51) configured to predict a temperature of the liquid crystal display by adding a temperature rise value obtained based on a duty ratio of the liquid crystal display to the ambient temperature based on the signal from the thermistor, anda failure avoidance unit (52) configured to execute lowering control for lowering an upper limit of a duty ratio of the backlight when the temperature of the liquid crystal display predicted by the temperature prediction unit is greater than or equal to a threshold, and execute rotation control of the concave mirror for reducing the amount of sunlight that enters the liquid crystal display through the reflecting mirror and the concave mirror when the temperature of the liquid crystal display predicted by the temperature prediction unit is greater than or equal to a specified value exceeding the threshold.

Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to these examples. It is apparent that those skilled in the art can come up with various modifications or corrections within the scope of the claims, and it is understood that the modifications or corrections naturally fall within the technical scope of the present invention. In addition, the components described in the above embodiments may be combined freely without departing from the spirit of the invention.