Patent Description:
In a vehicle in which a driving assist control is performed by preventive safety systems, a driving support control sensor, such as a pre-crash safety sensor (abbreviated as "PCS sensor") has been installed at the top center of an inner surface of a windshield (a windscreen). The driving support control sensor includes an on-board camera such as a CCD camera and the on-board camera is configured to photograph the front of the vehicle through the windshield.

When an outside air temperature (e.g., in winter) is low and a temperature difference between the inside and outside of a vehicle increases, condensation occurs on an inner surface of a windshield, which fogs the windshield. When the windshield is fogged, it becomes impossible to properly photograph the front of the vehicle by an on-board camera. As described in <CIT>, for example, it is known to remove a fog of a windshield by heating the windshield in front of the camera by a windshield heating device. <CIT> describes a humidity detection device and frost protection device. <CIT> describes a heating element and method for manufacturing same. <CIT> describes a micro-current sensing eye-shield heater system. <NUM>
<CIT> discloses a windshield heating device for a camera mounted on a vehicle.

A windshield heating device includes a sheet-like electric heating element, such as a PTC heater, and the electric heating element is fixed by adhering to an inner surface of a windshield close to a camera. The electric heating element shall be of a size sufficient to heat the windshield effectively, but it is not allowed to interfere with an imaging range of the camera. Therefore, it is known to form an electric heating element to have a main heating region (a first heating region) that exerts a major heating function at a position close to the camera, and an auxiliary heating region (a second heating region) that exerts an auxiliary heating function. The auxiliary heating region is spaced transversely of the vehicle with respect to an optical axis of the camera, for example. Although an area of the main heating region is greater than an area of the auxiliary heating region, as the main heating region and the auxiliary heating region are formed with the same PTC heater, calorific values per unit area of both heating regions are the same.

In a conventional windshield heating device in which an electrical heating element has a main heating region and an auxiliary heating region as described above, it has been found that by heating of a windshield by the heating device, high tensile stresses are generated in the region around the auxiliary heating region. As described in detail later, when a windshield is heated by the heating device, since a heating area of the main heating area is large, a temperature of the region surrounding the main heating region also becomes higher. Accordingly, the main heating region and the surrounding region can relatively easily expand in the direction of the plane of the windshield.

In contrast, as a heating area of the auxiliary heating region is small, the temperature of the region surrounding the auxiliary heating region does not become higher as the surrounding region of the main heating region. Therefore, since a restraint for expansion of the auxiliary heating area by the surrounding region is strong, high tensile stress in the direction along the outer periphery of the auxiliary heating region is generated in the region around the auxiliary heating region by expansion forces due to the expansion of the auxiliary heating region. The auxiliary heating region cannot easily expand in the planar direction of the windshield and expands to deform in the direction perpendicular to the plane of the windshield, resulting in inclined regions with respect to an original plane of the windshield are generated around the auxiliary heating region.

Incidentally, if a calorific value per unit area of the electric heating element is set low so as to prevent the above-mentioned problems from occurring, not only a calorific value of the auxiliary heating region but also a calorific value of the main heating region are reduced. Therefore, it becomes impossible to effectively heat the windshield to effectively remove a fog of the windshield.

The present invention provides a windshield heating device having a main heating region and an auxiliary heating region that is improved to reduce a risk that high tensile stresses are generated in the region around the auxiliary heating region without reducing a defogging effect on a windshield.

According to the present invention, there is provided a vehicle according to claim <NUM>.

According to the configuration of claim <NUM>, a heating area of the second heating region is smaller than a heating area of the first heating region; and a calorific value per unit area of the second heating region is smaller than a calorific value per unit area of the first heating region. Consequently, as compared with a conventional heating device in which the first and second heating regions are formed by the same heating element, temperature of the second heating region can be lowered and temperature gradients in the periphery of the second heating region can be made gentle. Therefore, it is possible to reduce tensile stresses that are generated in the periphery of the second heating region by expansion force due to an expansion of the second heating region, and to reduce a degree that the second heating region is deformed to expand in the direction perpendicular to the plane of the windshield.

Notably, a heating area of the first heating region is greater than a heating area of the second heating region; and a calorific value per unit area of the first heating region is greater than a calorific value per unit area of the second heating region. Accordingly, as the heated region can effectively be heated by the first heating region, reduction in defogging effect at the windshield can be avoided.

In one aspect of the present invention, the electric heating element is a PTC heater which includes a PTC element in which conductive particles are dispersed in a nonconductive matrix and a pair of electrodes spaced apart by the PTC element, and an upper limit temperature of the PTC heater in the second heating region is lower than an upper limit temperature of the PTC heater in the first heating region and is higher than a target heating temperature at a preset reference point in the heated region.

According to the above aspect, as the electric heating element is a PTC heater, there is no need, for example, to detect a temperature of the electric heating element or the heated region and to control an energization of the electric heating element on the basis of the detected temperature. The upper limit temperature of the PTC heater in the second heating region is lower than the upper limit temperature of the PTC heater in the first heating region and is higher than a target heating temperature at a preset reference point in the heated region. Therefore, according to this aspect, the temperature of the second heating region can be lowered than the temperature in a conventional heating device, and it is possible to ensure a situation in which the second heating region contributes to raise the temperature of the reference point in the heated region to not less than the target heating temperature.

In another aspect of the present invention, a spacing between the electrodes of the PTC heater in the second heating area is greater than a spacing between the electrodes of the PTC heater in the first heating region.

According to the above aspect, by using, for example, the same PTC elements in the first and second heating regions and varying the spacing between the electrodes in one heating region from that in the other heating region, the above-mentioned spacing relationship between the electrodes can easily be achieved. Therefore, according to this aspect, it is possible to easily and inexpensively achieve the above-described relationship of the calorific value per unit area and the upper limit temperature.

In another aspect of the present invention, a thickness of the PTC heater in the second heating region is less than a thickness of the PTC heater in the first heating region.

According to the above aspect, by increasing, for example, the number of sheet-like PTC elements stacked in the first heating region than that in the second heating region, the above-mentioned thickness relationship of the PTC heater can be relatively easily attained. Therefore, according to this aspect, a PTC heater having the first and second heating regions can be formed by using the same sheet-like PTC elements.

In another aspect of the present invention, a dispersion density of the conductive particles in the PTC element in the second heating area is lower than a dispersion density of the conductive particles in the PTC element in the first heating region.

According to the above aspect, by making, for example, the number of conductive particles per unit volume of the PTC element in the first heating region and/or the size of the conductive particles larger than that in the second heating region, the above-mentioned relationship of the dispersion density of the conductive particles can be relatively easily achieved. Therefore, according to this aspect, a PTC heater having the first and second heating regions can be formed by using two kinds of sheet-like PTC elements having different dispersion density of conductive particles due to the difference in the number of conductive particles per unit volume and/or the size of the conductive particles.

The first heating region includes a portion located between the on-board camera and the windshield, and the second heating region is spaced apart in a lateral direction of the vehicle with respect to an optical axis of the on-board camera as viewed in a direction perpendicular to the windshield.

According to the above aspect, the heated region is mainly heated by the heat conduction and radiation from the side of the camera by the first heating region, and is supplementally heated by the heat conduction and radiation in the lateral direction of the vehicle by the second heating region. Thus, while avoiding that the second heating region from interfering with an imaging range of the camera, it is possible to make the second heating region contribute to heat the heated region.

In the present application, "upper limit temperature" of the PTC heater means a temperature at which the temperature rise rate of the PTC heater decreases with the lapse of time and the temperature of the PTC heater becomes constant due to a PTC characteristic of the PTC element.

Other objects, other features and attendant advantages of the present invention will be readily understood from the description of the embodiments of the present invention described with reference to the following drawings.

An embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

A windshield heating device <NUM> for an on-board camera according to an embodiment of the present invention (abbreviated as "heating device ") is applied to a PCS sensor <NUM>. The PCS sensor <NUM> includes a support base member <NUM> made from resin which is fixed to the inner surface of a windshield <NUM> by means such as an adhesive, a sensor body <NUM> which is removably attached to the base member, a cover, not shown, covering the sensor body. The sensor body <NUM> includes a CCD camera <NUM> and a radar sensor device <NUM> adjacent to each other in the lateral direction of the vehicle <NUM> (see <FIG>). The configuration of the PCS sensor <NUM> is not critical to the present invention and the PCS sensor <NUM> may have any configuration as long as it has a camera for photographing the front of the vehicle through the windshield <NUM>. If necessary, for more information about the PCS sensor <NUM>, see <CIT> filed by the applicant of the present application, for example.

The camera <NUM> is an on-board camera configured to photograph the front of the vehicle <NUM> along an optical axis <NUM>. In <FIG> and <FIG>, a dashed line <NUM> indicates a position of lens, not shown, of the camera <NUM> and a two-dot chain line <NUM> indicates a range of an angle of view of the camera <NUM>. A point P indicates an intersection of the optical axis <NUM> and the inner surface of the windshield <NUM> and is a preset reference point in a heated region <NUM> of the windshield <NUM> to be heated by the heating device <NUM>. Incidentally, the preset reference point in the heated region <NUM> may be set to a position other than the intersection point P of the optical axis <NUM> and the inner surface of the windshield <NUM>.

The heating device <NUM> is configured to heat the windshield <NUM> in the heated region <NUM> in front of the camera <NUM>, and includes a sheet-like electric heating element <NUM>. The electric heating element <NUM> extends along the windshield <NUM> in proximity to the camera <NUM>, and is fixed to the inner surface of the windshield <NUM> by means such as an adhesive. As shown in <FIG>, the electric heating element <NUM> includes a PTC element <NUM> in which conductive particles <NUM> such as carbon particles are dispersed in a nonconductive matrix <NUM> made of semiconductor particles or the like, and electrodes <NUM> and <NUM> spaced by the PTC element.

Notably, in <FIG>, reference numerals <NUM> and <NUM> indicate protective sheets that cover the PTC element <NUM> and the electrodes <NUM> and <NUM>, and the protective sheets <NUM> and <NUM> may be made of a non-conductive resin such as polyethylene terephthalate (PET). Further, although it is preferable that, as shown in <FIG>, the conductive particles <NUM> are uniformly dispersed in the matrix <NUM>, the dispersion of the conductive particles may not be uniform. Furthermore, although not shown in <FIG>, the electrodes <NUM> and <NUM> are preferably comb electrodes having a plurality of comb teeth that are alternately arranged along the plane of the electric heating element <NUM>.

The electric heating element <NUM>, i.e. PTC heater includes a first heating region 34A and a second heating region 34B adjacent to each other, and a heating area (S2) of the second heating region is smaller than a heating area (S1) of the first heating region 34A. In the illustrated embodiment, the first heating region 34A is substantially rectangular extending in the lateral direction of the vehicle <NUM>, and the main part thereof is arranged between the camera <NUM> and the radar sensor device <NUM> and the windshield <NUM>.

As shown in <FIG> and <FIG>, the second heating region 34B is substantially forms a triangular projecting forwardly and downwardly from the first heating region 34A, and, as viewed in the direction perpendicular to the windshield <NUM>, is spaced apart in the lateral direction of the vehicle with respect to the optical axis <NUM> of the camera <NUM>. Therefore, the first heating region 34A is located closer to the camera <NUM> than the second heating region 34B, and the second heating region 34B also does not interfere with an imaging range of the camera <NUM>. Although the longitudinal directions of the first heating region 34A and the second heating region 34B substantially intersect perpendicularly, the longitudinal directions of the two heating regions may intersect at an angle other than perpendicular.

As shown in <FIG> to be described later, a calorific value Q2 per unit area of the second heating region 34B is smaller than a calorific value Q1 per unit area of the first heating region 34A. The upper limit temperature T2max of the PTC heater <NUM> in the second heating region 34B is lower than the upper limit temperature T1max of the PTC heater <NUM> in the first heating region 34A. Therefore, the first heating region 34A functions as a main heating region and the second heating region 34B functions as an auxiliary heating region. The differences in the calorific value and the upper limit temperature may be achieved by one or any combination of the following configurations (A) to (C).

Further, the upper limit temperature T2max of the PTC heater <NUM> in the second heating region 34B is higher than a target heating temperature (Tht) of the reference point P in the heated region <NUM>. This relationship between the temperatures may be achieved by appropriately setting the spacing between the electrode <NUM> and <NUM> and/or the dispersion density of the conductive particles <NUM> in the PTC heater <NUM> in the second heating region 34B. Incidentally, the target heating temperature (Tht) of the reference point P in the heated region <NUM> is preset as a temperature that can remove fog in the heated region <NUM> of the windshield <NUM> in a situation where an outside air temperature is low.

<FIG> shows an electric circuit of the heating device <NUM>. The first heating region 34A and the second heating region 34B of the PTC heaters <NUM> are connected in parallel to each other, and the electrodes <NUM> and <NUM> of the PTC heater <NUM> are connected to a connector <NUM> by a lead wire <NUM>. A connector <NUM> connected to the connector <NUM> is connected by a lead wire <NUM> to a DC power supply <NUM> of the vehicle. Therefore, the first heating region 34A and the second heating region 34B of the PTC heater <NUM> are connected in parallel to the DC power source <NUM>, and the lead wire <NUM> common to the two heating regions has a switch <NUM> that is opened and closed by an electronic control unit <NUM>.

A signal supplied from an outside air temperature sensor <NUM> and indicating an outside air temperature Tout is input to the electronic control unit <NUM>. Further, the electronic control unit <NUM> is supplied with a signal indicating whether or not the camera <NUM> cannot normally photograph the front of the vehicle <NUM> due to fogging in the heated region <NUM> from an electronic control unit <NUM> that controls the traveling of the vehicle <NUM> based on the detection result of the PCS sensor <NUM>. The electronic control unit <NUM> closes the switch <NUM> when a predetermined operation starting condition of the heating device <NUM> is satisfied such as "an external temperature Tout is equal to or less than a start reference value" or when a predetermined operation continuing condition of the heating device <NUM> is satisfied such as "the camera <NUM> cannot successfully photograph the front of the vehicle <NUM>". In contrast, the electronic control unit <NUM> opens the switch <NUM> when a predetermined operation ending condition of the heating device <NUM> is satisfied, such as "an outside air temperature Tout is equal to or greater than a termination reference value".

The first heating region 34A and the second heating region 34B of the PTC heater <NUM>, when energized by the switch <NUM> being closed, rises in temperature in a known manner. That is, the heater generates heat by electrical resistance when DC current flows from one electrode <NUM> through the conductive particles <NUM> of the PTC element <NUM> to the other electrode <NUM>. When the temperature of the PTC element <NUM> rises due to heat generation, the nonconductive matrix <NUM> expands and the distances between the conductive particles <NUM> increase, so that the electrical resistance of the PTC element <NUM> gradually increases, whereby the electric current passing through the PTC element <NUM> gradually decreases and eventually becomes constant.

Therefore, when first heating region 34A and the second heating region 34B of the PTC heater <NUM> reach a steady state, as shown in <FIG>, they maintain the maximum temperature T1max and T2max, respectively. The two heating regions of the PTC heater <NUM> heat the heated region <NUM> and the surrounding thereof in cooperation with each other so that the heating temperature (Th) of the reference point P of the heated region <NUM> of the windshield <NUM> becomes equal to or higher than the target heating temperature (Tht), whereby fogging of the windshield <NUM> is removed.

In the first heating region 34A and the second heating region 34B, one or any combination of the above configuration (A) to (C) is employed. Consequently, an electrical resistance of the PTC heater <NUM> in the second heating region 34B is higher than an electrical resistance of the PTC heater <NUM> in the first heating region 34A, and, accordingly, an electric current flowing through the second heating region 34B is lower than an electric current flowing through the first heated region 34A. Therefore, as described above, the calorific value Q2 per unit area of the second heating region 34B is smaller than the calorific value Q1 per unit area of the first heating region 34A. In addition, as shown in <FIG>, the upper limit temperature T2max of the second heating region 34B is lower than the upper limit temperature T1max of the first heating region 34A. Furthermore, a contribution degree of the first heating region 34A in heating the heated region <NUM> and the surrounding thereof is higher than a contribution degree of the second heating region 34B.

In a conventional windshield heating device for an on-board camera, both of the first heating region 34A and the second heating region 34B are constituted by PTC heaters of the same configuration. In other words, the above-mentioned configurations (A) to (C) are not adopted.

Therefore, as shown in the upper part of <FIG>, the calorific value Q1 per unit area of the first heating region 34A and the calorific value Q2 per unit area of the second heating region 34B are identical Q12. In addition, as shown in the middle part of <FIG>, the upper limit temperature T1max of the first heating region 34A and the upper limit temperature T2max of the second heating region 34B are also the same T12max. Furthermore, as an area (S1) of the first heating region 34A is greater than an area (S2) of the second heating region 34B, as shown in the lower part of <FIG>, while a temperature gradient around the first heating region 34A is relatively gentle, a temperature gradient around the second heating region 34B is steep.

In <FIG> and <FIG> to be described later, the "Lateral Position" on the horizontal axis means a position located in a direction that is along the plane of the first heating region 34A or the second heating region 34B and is perpendicular to the longitudinal direction of the heating region. Further, W1 is a width of the first heating region 34A, and W2 is a width of the second heating region 34B at the center in its longitudinal direction. The widths W1 and W2 are less than the longitudinal lengths of the first heating region 34A and the second heating region 34B, respectively.

As a temperature around the first heating region 34A is relatively high, restraint against expansion of the first heating region 34A by the region around thereof is weak. Consequently, as shown in <FIG>, the windshield <NUM> around the first heating region 34A is relatively easily expandable along its plane. Accordingly, since the windshield <NUM> in the first heating region 34A is also relatively easily expandable along its plane, thermal stresses in the first heating region 34A and the surrounding thereof are relatively low. In <FIG> and <FIG> to be described below, the bold arrows and bold double-headed arrows indicate the directions of expansion, and the thin arrows and thin double-headed arrows indicate the directions of restraining force and tensile stress, respectively. Further, the lengths of the bold arrows and the bold double-headed arrows indicate the degree of expansion, and the lengths of the thin arrows and the thin double-headed arrows represent the magnitudes of the restraining force and tensile stress, respectively.

On the other hand, as the temperature around the second heating region 34B is low, as shown in <FIG>, restraint against expansion of the second region 34B by the region around thereof is strong. Consequently, high tensile stresses are generated in the region around the second heating region 34B by the expansive force due to the expansion of the second heating region 34B. As the windshield <NUM> in the second heating region 34B cannot easily expand along its plane, as shown in <FIG>, the windshield <NUM> in the second heating region 34B expands and deforms outwardly in a direction perpendicular to the plane thereof.

In contrast, in the embodiment, at least one of the above-mentioned configurations (A) to (C) is adopted. Therefore, as shown in the upper part of <FIG>, the calorific value Q2 per unit area of the second heating region 34B is smaller than the calorific value Q1 per unit area of the first heating region 34A. In addition, as shown in the middle part of <FIG>, the upper limit temperature T2max of the second heating region 34B is lower than the upper limit temperature T1max of the first heating region 34A. Furthermore, as shown in the lower part of <FIG>, the temperature gradient around the first heating region 34A is relatively gentle as in a conventional heating device, and the temperature gradient around the second heating region 34B is steeper than the temperature gradient around the first heating region 34A but is milder than that in the conventional heating device.

The temperature around the first heating regions 34A is higher than that in the conventional heating device, and, accordingly, as in the conventional heating device, restraint against the expansion of the first heating region 34A by the region around thereof is weak. Consequently, as shown in <FIG>, windshield <NUM> around the first heating region 34A can relatively easily expand along its plane. Therefore, as the windshield <NUM> in the first heating region 34A can also relatively easily expand along its plane, the thermal stresses in the first heating region 34A and the surrounding thereof is relatively low.

On the other hand, as the temperature in the second heating region 34B may be low as compared with the conventional heating device, it is possible to reduce a difference between the temperature of the second heating region 34B and the temperature in the region around thereof as compared to that in the conventional heating device. Therefore, as shown in <FIG>, restraint against expansion of the second region 34B by the region around thereof is weak, and, accordingly, tensile stresses that are generated in the region around the second heating region 34B by the expansive force due to the expansion of the second heating region is lower as compared with those in the conventional heating device. Also, an amount that the windshield <NUM> in the second heating region 34B expands to deform in the direction perpendicular to the plane thereof is also smaller as compared with that in the conventional heating device.

Incidentally, a heating area (S1) of the first heating region 34A is greater than a heating area (S2) of the second heating region 34B; and a calorific value Q1 per unit area of the first heating region is greater than a calorific value Q2 per unit area of the second heating region. Accordingly, as the heated region <NUM> can effectively be heated by the first heating region 34A, reduction in defogging effect of the windshield <NUM> can be avoided.

The calorific value Q1 per unit area of the first heating region 34A and the calorific value Q2 per unit area of the second heating region 34B may be set appropriately, as far as the two heating regions of the PTC heater <NUM> can cooperate to perform heating so that a heating temperature (Th) at the reference point P becomes equal to or higher than a target heating temperature (Tht). Further, the upper limit temperature T1max of the first heating region 34A and the upper limit temperature T2max of the second heating region 34B may be set appropriately, as far as the upper limit temperature T1max is higher than the upper limit temperature T2max and the upper limit temperature T2max is higher than the target heating temperature (Tht) of the reference point P in the heated region <NUM>.

For example, assuming that an increase amount of the calorific value Q1 per unit area of the first heating region 34A in comparison to a conventional heating device is represented by ΔQ1 (=Q1 - Q12), and a decrease amount of the calorific value Q2 per unit area of the second heating region 34B is represented by ΔQ2 (=Q12 - Q2). A total calorific value Qp in a conventional heating devise and a total calorific value Qe in the embodiment are represented by the following equations (<NUM>) and (<NUM>), respectively. <MAT> <MAT> <MAT>.

Therefore, If the calorific values Q1, Q2 and the areas S1, S2 are set so that ΔQ1·S1 and ΔQ2·S2 become equal to each other, the total calorific value Qe in the embodiment becomes equal to the total calorific value Qp in the conventional heating device, the power consumption amount in the embodiment can be made equal to the power consumption amount in the conventional heating device.

In particular, in the embodiment, the electric heating element <NUM> having the first and second heating regions is a PTC heater which includes a PTC element <NUM> in which conductive particles <NUM> are dispersed in a nonconductive matrix <NUM>, and electrode <NUM> and <NUM> spaced by the PTC element. Therefore, when electric current is supplied to the PTC heater, temperatures of the first heating region 34A and the second heating region 34B are automatically controlled to be the maximum temperature T1max and T2max by a PTC characteristic. Therefore, according to the embodiment, for example, it is unnecessary to control the energization when a resistive wire heater, for example, is used as the electric heating element. That is, it is unnecessary to control the energization to the heater based on the heating temperature of the heater.

The upper limit temperature T2max of the PTC heater in the second heating region 34B is lower than the upper limit temperature T1max of the PTC heater in the first heating region 34A and higher than the target heating temperature (Tht) of the reference point P in the heated region <NUM>. Therefore, while decreasing the tensile stress around the second heating region 34B than that in the conventional heating device, it is possible to increase the degree of contribution of the PTC heater in the heating region 34B as compared to where the upper limit temperature T2max is equal to or lower than the target heating temperature (Tht).

In the embodiment, at least one of the configurations (A) to (C) is adopted as described above in order to achieve the relationships of the calorific values per unit area and the upper limit temperatures for the first and second heating regions.

The configuration (A) can easily be achieved by, for example, using the same PTC element <NUM> in the first heating region <NUM> A and the second heating region <NUM> B and varying the spacing between the electrodes <NUM> and <NUM> in the two heating regions. Therefore, according to this configuration, the above relationships of the calorific values per unit area and the upper limit temperatures can easily and inexpensively be achieved.

The configuration (B) can relatively easily be achieved by, for example, by increasing the stack number of the sheet-like PTC element <NUM> in the first heating region 34A than in the second heating region 34B. Therefore, according to this configuration, a PTC heater having the first and second heating regions 34A and 34B can be formed using the same sheet-like PTC element <NUM>.

Furthermore, the configuration (C) can relatively easily be achieved by, for example, making the number of the conductive particles <NUM> per unit volume and/or the size of the conductive particles <NUM> of the PTC element <NUM> in the first heating region 34A larger than that in the second heating region 34B. Therefore, according to this configuration, the PTC heaters having the first and second heating regions <NUM> A and <NUM> B can be formed by using two kinds of sheet-like PTC elements <NUM> having different conductive particles <NUM> and different number of conductive particles <NUM> and/or different sizes of conductive particles <NUM>.

Further, in the embodiment, the first heating region 34A includes a portion located between the camera <NUM> and the windshield <NUM>, and the second heating region 34B is spaced in the lateral direction of the vehicles <NUM> with respect to the optical axis <NUM> of the camera <NUM> as viewed in the direction perpendicular to the windshield <NUM>. Thus, according to the embodiment, the heated region <NUM> can mainly be heated by the heat conduction and radiation from the side of the camera <NUM> by the first heating region 34A and supplementarily heated by the heat conduction and radiation in the lateral direction of the vehicle <NUM> by the second heating region 34B. Therefore, it is possible to reliably make the second heating region 34B contribute to heat the heated region <NUM> while avoiding the second heating region 34B from interfering with the photographing range of the camera <NUM>.

Further, in the embodiment, the first heating region 34A and the second heating region 34B are connected in parallel to the DC power source <NUM>. Therefore, the first heating region 34A and the second heating region 34B can be applied to the same voltage.

Further, in the embodiment, the first heating region 34A and the second heating region 34B are connected in parallel to the DC power source <NUM>, and the switch <NUM> is provided in the lead wire common to the first and second heating regions, namely in the lead wire <NUM> between the connector <NUM> and the DC power source <NUM>. Therefore, the number of parts can be reduced as compared to where the switches are provided on the lead wires peculiar to the first and second heating regions, and the two heating regions can concurrently conducted and interrupted by opening and closing one switch <NUM> by means of the electronic control unit <NUM>.

Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that the present invention is not limited to the above-described embodiments, and various other embodiments are possible within the scope of the present invention.

For example, while in the above-described embodiment, the first heating region 34A and the second heating region 34B of the PTC heater <NUM> are connected in parallel to the DC power source <NUM>, they may be independently connected to the DC power source <NUM>. In the latter case, a switch may be provided on the lead wire between the first heating region 34A and the DC power supply <NUM> and the lead wire between the second heating region 34B and the DC power supply <NUM>.

Further, while in the above-described embodiment, the electric heating element <NUM> is a PTC heater, it may be a resistance wire heater. In the latter case, the resistance wire heater of the first heating region 34A and the second heating region 34B may be connected in parallel to the DC power supply <NUM> or may be connected in series to the DC power source <NUM>. Incidentally, when the connection to the DC power source <NUM> is in series, the electric resistance of the resistance wire heater of the second heating region 34B is set to a smaller value than the electrical resistance of the resistance wire heater of the first heating region 34A.

Further, while in the above-described embodiment, the PTC element <NUM> is an element in which conductive particles <NUM> are dispersed in a nonconductive matrix <NUM>, PTC element may be made of semiconductor such barium titanate or the like that changes electric resistance by phase transformation.

Further, in the above-described embodiment, the first heating region 34A and the second heating region 34B are rectangular and triangular, respectively. However, as long as the heating area of the second heating region is smaller than the heating area of the first heating area and the calorific value per unit area of the second heating region is smaller than the calorific value per unit area of the first heating region, at least one of the heating regions may form other shapes.

Further, while in the above-described embodiment, the heating device <NUM> is applied to the PCS sensor <NUM> provided with one CCD camera <NUM>, the heating device <NUM> may be applied to a driving support control sensor provided with a stereo camera. In that case, two heating devices <NUM> having the first heating region 34A and the second heating region 34B may be used, and each heating device may be disposed in proximity to the corresponding camera.

Claim 1:
A vehicle comprising a windshield (<NUM>), a sensor (<NUM>) that is fixed to an inner surface of the windshield and includes an on-board camera (<NUM>) that is configured to photograph the front of the vehicle, and a windshield heating device (<NUM>) for the on-board camera (<NUM>) that comprises a sheet-like electric heating element (<NUM>) that extends along the inner surface of the windshield (<NUM>) adjacent to the on-board camera (<NUM>) and is configured to heat the windshield in a heated region (<NUM>) in front of the on-board camera (<NUM>), characterized in that
the electric heating element (<NUM>) comprises a first and a second heating region (34A, 34B) that are adjacent to each other between the windshield (<NUM>) and the sensor (<NUM>);
the first heating region (34A) includes a portion located between the on-board camera (<NUM>) and the windshield (<NUM>), and the first heating region (34A) and the second heating region (34B) are spaced apart in vertical and lateral directions, respectively, of the vehicle (<NUM>), with respect to an optical axis (<NUM>) of the on-board camera (<NUM>) as viewed in a direction perpendicular to the windshield (<NUM>); and a heating area (S2) of the second heating region (34B) is smaller than a heating area (S1) of the first heating region (34A); and a heat quantity per unit area (Q2) of the second heating region (34B) is smaller than a heat quantity per unit area (Q1) of the first heating region (34A).