Patent Description:
In heavy snowfall areas, such as Hokkaido, Tohoku and Hokuriku areas, countermeasures against snow and freezing in winter have imposed very serious subjects in order to maintain regional activities in winter and to ensure the safety of local residents.

As a common countermeasure against snowfall, shoveling by using shovels has been carried out for snow removal, and industrial snow countermeasures include snow removing or excavating works by using heavy machineries and snow plows. In addition, road heating systems are sometimes used in highways of large vertical inclinations in order to prevent road surface from freezing (refer, for example, to <CIT>).

For example, <CIT> discloses a simple and less expensive anti-freezing and snow-melting road structure. In the antifreezing and snow-melting road structure, a far-infrared electric heating sheet <NUM> is interposed between a base layer <NUM> and a surface layer <NUM> of an asphalt pavement <NUM> of a road <NUM>, a far-infrared element is disposed in the asphalt of the surface layer <NUM> and, further, a far-infrared lamps <NUM> are arranged in the shoulder of the road <NUM>.

By electric current supply to the far infrared heating sheet <NUM>, far infrared rays emitted from the far infrared heating sheet <NUM> are absorbed to the far infrared elements blended in the asphalt of the surface layer <NUM>, so that the structure is simple and inexpensive, to prevent freezing and snow accumulation efficiently.

Further, since a far infrared lamp <NUM> installed at the shoulder of the road <NUM> emits far infrared rays toward the surface of the road <NUM>, it is possible to melt the frozen surface and prevent snow from depositing on the road surface. Further, the far-infrared rays emitted from the far-infrared ray lamp <NUM> are irradiated to the far-infrared elements blended with the asphalt of the surface layer <NUM>, so that the far-infrared rays emitted from the far-infrared sheet <NUM> can prevent road from freezing and snow from depositing on the surface efficiently, easily and inexpensively.

However, in order to bury the anti-freezing and snow-melting preventing structure disclosed in <CIT> in an existent road, it is necessary to first dig out the load at the surface layer <NUM> covered with an asphalt or concrete pavement, and then fill back the far-infrared heating sheet <NUM> horizontally over the exposed base layer <NUM>.

Thus, it is necessary to refill the excavated surface layer <NUM> of asphalt or concrete pavement. Therefore, not only a lot of construction works were required, but also this may hinder smooth road traffic.

Then, a road heating structure that can facilitate the installation of electric heating sheets and improve the melting efficiency for the road surface has been developed when the road heating structure is installed to the road (refer, for example, to <CIT>).

For example, in the road surface heating structure of <CIT>, each of containing grooves 11b is formed first in a direction perpendicular to the surface 11a of a road <NUM> made of concrete C, and a belt-shaped electric heating sheet <NUM> is buried in the containing groove 11b formed in a direction in perpendicular to the surface 11a. Next, by filling a gap between the inner surface of the containing groove 11b and the lateral surface of the electric heating sheet <NUM> with an insulative mortar <NUM>, the electric heating sheet <NUM> is buried and fixed in the containing groove 11b.

This can eliminate the need of extraction work to bury the electric heating sheet in the road over a wide range. Since the containing groove 11b can be formed easily by a road cutter or the like, the belt-shaped electric heating sheet <NUM> can be contained easily and continuously over a long distance.

Further examples of previously known road surface heating devices, construction methods of such road surface heating devices, road surface heating methods, and/or road surface heating systems for elevating the temperature of a road surface are derivable from <CIT>, which forms the basis for the two-part form of independent claims <NUM> and <NUM>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, as well as <CIT>.

However, roads involve places tending to be frozen, easy to be covered with snow, and tend to remain snow. For example, roads on bridges tend to be frozen. Further, snow tends to remain in a place of the road that is always in the shade of buildings. In addition, such shade areas exist spotwise in the road, so that the environment of the road is not always uniform.

Even if roads under such varied environments are heated by burying long belt-shaped electric heating sheets as in <CIT>, effect of thawing a frozen part and melting deposited snow may be attained only for a place where it is easy to freeze or where snow is easy to accumulate. However, in other places, the road is heated only in vain and to waste energy.

For solving the problem, it may be considered to adjust the temperature over the entire length of the road. However, even when the entire electric heating sheet is set to a high temperature in accordance with the state of freezing of road or remaining of snow that may occur depending on places, effects may be expected only in specific portions tending to cause road freezing of snow deposition.

On the contrary, if the temperature is adjusted depending the conditions on a place where freezing or snow remaining does not occur, this is not effective in other places where freezing or snow remaining may occur, and melting and thawing cannot be attained in the places where they are necessary.

In addition, since the road may expand or contract due to vibrations caused by automobiles and seasonal temperature differences, if an electric heating sheet is buried for a longtime in a road where vibrations or expansions and contractions always occur, the electric heating sheet may be damaged due to the vibrations and expansions or contractions of the road.

For example, when a belt-shaped electric heating sheet buried in a road over a long distance is disconnected even partially, this leads to entire failure due to vibrations or expansions and contractions of the road, and brings about a problem that the whole electric heating sheet can no more be heated.

Further, upon such failure, it is necessary to identify and repair a place of the failed place from the buried electric heating sheet, but it is very difficult to identify a failed place from the buried electric heating sheet. In order to recover the road heating, it is necessary to dig up all the electric heating sheets and then identify the point of the broken wire from the electric heating sheet, or to re-fill the new electric heating sheet entirely. Then, this will make maintenability very poor.

Furthermore, in order to dig up the buried electric heating sheet, it is necessary to close the traffic lane on one side during the day time repair work when there is a lot of traffic, which may hinder the traffic. In addition, it was difficult to perform a large-scale construction work because the work had to be carried out in the daytime while closing the track on one side or carried out in a limited time of the midnight with less traffic, making large-scale construction difficult.

The present invention has been achieved in view of the foregoings and intends to provide a road surface heating device, a method of constructing the road surface heating device, a road surface heating method, and a road surface heating system, capable of heating a road at a saved energy to provide excellent maintainability.

For solving the above subjects, the present invention provides a road surface heating device for elevating the temperature of a road surface according to independent claim <NUM>, a construction method of the road surface heating device according to independent claim <NUM>, a road surface heating method according to independent claim <NUM>, and/or a road surface heating system for elevating the temperature of a road surface according to independent claim <NUM>.

Distinct embodiments are derivable from the dependent claims.

According to the road surface heating device, the construction method of the road surface heating device, the road surface heating method, and the road surface heating system of the present invention, since a plurality of belt-shaped electric heating sheets are buried in each of the divisional sections where the construction section is divided into a plurality of sections, along the traveling direction of a road requiring heating, with the sheet plane being in perpendicular to the road surface, and the connection structure links the plurality of electric heating sheets and connecting them to a power supply, the controller controls the heating amount of the electric heating sheets connected to the connection structure in each of the divisional sections, the temperature for each of divisional sections can be controlled in which the construction section is divided into a plurality of sections. Further, since a plurality of electric heating sheets are buried in each of the divisional sections, it is sufficient to replace only the failed portion of the electric heating sheet, thereby improving maintainability.

Preferred embodiments of the present invention will now be described in details with reference to the drawings.

<FIG> is a block diagram showing the concept of a road heating system according to the first embodiment.

A road heating system <NUM> shown in <FIG> is for melting snowfall on the ground of a road, a sidewalk, a parking lot or the like, and preventing the ground surface from freezing. Hereinafter, the road heating system <NUM> will be described by way of an example in a case where the road heating system <NUM> is installed on an existing road <NUM>, in particular, an exclusively used for automobile road such as a highway.

As shown in <FIG>, the road heating system <NUM> includes electric heating sheets <NUM>, a ground temperature sensor <NUM>, a snowfall sensor <NUM>, a controller <NUM>, a power line <NUM>, and a communication cable <NUM>.

The electric heating sheet <NUM> is a belt-shaped heating element at a length of <NUM>,<NUM> and a height of <NUM>, and buried in a containing groove at a depth of <NUM> and a width of <NUM> formed vertically from the surface of the road <NUM>, along the traveling direction of automobiles running on the road <NUM>, so that the short side of the electric heating sheet <NUM> direct the vertical direction.

The electric heating sheet <NUM> generates heat from both sides of the electric heating sheet <NUM> by electric power supplied via the electric power line <NUM>, and can melt snow falling on the road <NUM> and prevent freezing of the ground by heating at the periphery of the road <NUM> in contact with the electric heating sheet <NUM>.

A plurality of the electric heating sheets <NUM> are installed in each of divisional sections formed by dividing a predetermined sections in a road <NUM> into a plurality of sections for constructing the road heating system <NUM>.

As a specific example, in a case where a road heating system <NUM> is installed in a <NUM> construction section, the electric heating sheets <NUM> are installed by an arbitrary number at a predetermined interval in a <NUM> divisional section obtained by dividing the construction section into a number of <NUM>. The electric heating sheets <NUM> are connected in parallel by the power lines <NUM>. The distance and the number of divisions of the divisional sections and the number of electric heating sheets <NUM> buried in the divisional sections may be changed depending on the state of construction.

The ground temperature sensor <NUM> is a temperature sensor for measuring the temperature of the road <NUM> in which the electric heating sheets <NUM> are buried. The sensor is buried together with the electric heating sheet <NUM> in a containing groove that contains the electric heating sheet <NUM>, and may detect to notify the temperature of the road <NUM> where the electric heating sheet is buried.

The ground temperature sensor <NUM> is installed at least by one in the divisional section, and detects and notifies the measured temperature of the road <NUM> to the controller <NUM> connected via a communication cable <NUM>.

A ground temperature sensors <NUM> may be disposed in the vicinity of each of electric heating sheets <NUM> buried in plurality or at a predetermined interval in the divisional section, and may detect and notify the temperature in the vicinity of the buried ground temperature sensor <NUM>.

The snowfall sensor <NUM> is a sensor for detecting snowfall and installed, for example, above the ground near the road <NUM> in which the electric heating sheets <NUM> are buried. Specifically, it may be fixed to a sound proof wall or a guardrail disposed near the road <NUM>.

Examples of the snowfall sensor <NUM> include a moisture detection type sensor having an external atmospheric temperature measuring means and a moisture detection means for determining snowfall based on the acquired external atmospheric temperature and moisture, an infrared detection type sensor for detecting snow as an obstacle by irradiating infrared rays, etc..

The snowfall sensor <NUM> is installed at least by one in the divisional section and notifies the presence or absence of snowfall or the amount of snowfall to the controller <NUM> connected via a communication cable <NUM>. Further, the snowfall sensor <NUM> may be installed at least by one each at a predetermined interval in the divisional section, and may detect the presence or absence of snowfall or the amount of snowfall each in the vicinity of the installed snowfall sensor <NUM>.

In the controller <NUM>, a plurality of electric heating sheets <NUM> are connected via a power line <NUM>, and a ground temperature sensor <NUM> and a snowfall sensor <NUM> are connected via respective communication cables <NUM>, and the controller <NUM> is operated by receiving electric power supplied from a power supply such as a commercial power supply not shown.

Specifically, the controller <NUM> acquires the temperature of the road <NUM> from the ground temperature sensor <NUM> connected via the communication cable <NUM>, detects the presence or absence of snowfall and the amount of snowfall from a snowfall sensor <NUM> connected via the communication cable <NUM>, and controls the amount of power supplied to the electric heating sheet <NUM>.

For example, when the ground temperature sensor <NUM> detects a temperature below a predetermined level, for example, <NUM>, the electric power supply to the electric heating sheet <NUM> is started, whereby the electric heating sheet <NUM> generates heat, to heat the road <NUM> that surrounds the electric heating sheet <NUM>.

Thus, the road <NUM> can be prevented from freezing. Alternatively, electric power supply to the electric heating sheet <NUM> may be controlled depending on the temperature of the road <NUM> detected by the ground temperature sensor <NUM> to keep the temperature of the road <NUM> constant.

When the snowfall sensor <NUM> detects snowfall or judges that the amount of snowfall tends to increase, power supply to the electric heating sheet <NUM> is started, to generate heat from the electric heating sheet <NUM>, and heat the peripheral road <NUM> where the electric heating sheet <NUM> is buried to prevent snowfall on the road <NUM> from remaining.

The controller <NUM> may also be connected to other controllers <NUM> installed in other divisional sections (not shown) by way of the communication cable <NUM>, and a plurality of controllers <NUM> connected by the communication cable <NUM> may be connected to a network such as an internet (not shown) by way of a wiring or in a wireless manner, to control each of controllers <NUM> from the outside by a terminal device such as a computer connected to the network such as the internet.

The power line <NUM> serves to connect the electric heating sheet <NUM> and the controller <NUM>, and transmit the electric power supplied from the controller <NUM> to the electric heating sheet <NUM>, and comprises, for example, a heat resistant, water resistant and flexible cab tire cable.

The communication cable <NUM> serves to transmit information by a wiring mode such as an optical fiber cable or a LAN (local area network) cable. In this embodiment, the ground temperature sensor <NUM> and the snowfall sensor <NUM> are connected to the controller <NUM> via the communication cables <NUM>. In addition, the ground temperature sensor <NUM> and the snowfall sensor <NUM> may be connected in a wireless manner to the controller <NUM> by using a short-range wireless communication technology.

As described above, in the road heating system <NUM> of this embodiment, a plurality of electric heating sheets <NUM> are buried in divisional sections formed by dividing a predetermined section of constructing the road heating system <NUM> in the road <NUM> into a plurality of sections, and the controller <NUM> can control the operation of the electric heating sheets <NUM> on each of the divisional sections. Accordingly, the temperature can be controlled on each of the divisional sections. Thus, the electric heating sheet <NUM> no more generates heat in a part where heating of the road <NUM> is unnecessary, so that the energy efficiency is improved.

Further, since the electric heating sheets <NUM> are connected in parallel between the power lines <NUM>, if one of the electric heating sheets <NUM> installed in plurality should happen be disconnected partially by vibrations or expansions and contractions of the road <NUM> due to earthquake or automobile traffic, and heat can be generated from other heating sheets <NUM>.

In addition, since the electric heating sheet <NUM> no more generates heat due to disconnection or the like, causing no temperature elevation, location of the disconnected electric heating sheet <NUM> can be easily identified from the outside, and by replating the electric heating sheet <NUM>, it is necessary to excavate only the failed portion and replace the disconnected electric heating sheets <NUM> (for about <NUM>,<NUM> or more), so that the maintainability can be improved.

Further, when the controller <NUM> having the electric heating sheets <NUM> connected in parallel is provided with a power supply detection means or a leakage detection means, and the location of the disconnected electric heating sheets <NUM> can be specified without confirming the temperature from the outside. In addition, when the electric heating sheet <NUM> is no longer energized, the power supply detecting means may notify warning to an administrator or the like.

<FIG> is a front elevational view showing details of the electric heating sheet according to the first embodiment.

As shown in <FIG>, the electric heating sheet <NUM> is a belt-shaped rectangular heating element at a length of <NUM>,<NUM>, a height of <NUM>, and a thickness of <NUM>, and includes a heating part <NUM>, electrode parts <NUM>, and a protective sheet part <NUM>.

The heating part <NUM> is a rectangular sheet-like heating strip that generates heat upon voltage supply. The heating part <NUM> is made of Japanese paper mixed with carbon fibers, which generates heat not by gathering electric wires like an existent metal wire heater, but generates heat uniformly from a sheet-like heating part <NUM> under voltage supply, so that the whole of the heating part <NUM> generates heat not from the wires but from the surface.

Since the road <NUM> in contact with the heating part <NUM> is warmed for a wider planar shape, the amount of heat generated by the heating part <NUM> can be transmitted efficiently to the road <NUM>. Ice and snow deposited on the surface of the road <NUM> can be melted by warming the road <NUM>. It is also possible to prevent snow from accumulating to the surface of the road <NUM> thereby preventing the surface of the road <NUM> from freezing.

The electrode parts <NUM> are terminals provided on both longitudinal ends of the heating part <NUM>, and include an anode and a cathode for passing a current to the heating part <NUM>. The electrode parts <NUM> are connected in parallel to the controller <NUM> by a power line <NUM> (not shown). By connecting the electric heating sheets <NUM> in parallel with the controller <NUM> in this manner, even if the electric heating sheets <NUM> are partially disconnected, the road <NUM> can be heated without stopping heat generation from other electric heating sheets <NUM>.

Since the damaged electric heating sheets <NUM> can be replaced sheet by sheet, it may suffice to excavate the road <NUM> only at a portion where the damaged electric heating sheet <NUM> is buried, only the damaged electric heating sheet <NUM> needs to be replaced, so that the amount of repair work and maintenance work can be decreased to improve the maintainability.

The protective sheet part <NUM> comprises a film material for protecting the electric heating sheet <NUM> and a connection part between the electric heating sheet <NUM> and the electrode part <NUM>, which is a water resistant, heat resistant and impact resistant strong film material comprising, for example, polyethylene terephthalate, and is crimped between both sides by the protective sheet parts <NUM> so as to sandwich the electric heating sheet <NUM> and the connection part between the electric heating sheet <NUM> and the electrode parts <NUM>.

Also, butyl rubber of excellent heat resistance, cold resistance, weather resistance, water resistance or the like can be used for the protective sheet part <NUM>.

<FIG> is a cross sectional view of a road in the traveling direction that shows steps of installing an electric heating sheet in the road.

<FIG> shows a state of forming a electric heating sheet containing groove <NUM> for electric heating sheets <NUM> and a cable containing groove <NUM> burying for a power line <NUM> and a communication cable <NUM> in a road <NUM>.

The electric heating sheet containing groove <NUM> is formed of a groove at <NUM> depth × <NUM> width in a road <NUM> along a traveling direction of the road <NUM> by using a road cutter or the like in a section where the road heating system <NUM> is constructed.

As a place to form the electric heating sheet containing groove <NUM>, two electric heating sheet containing grooves <NUM> are preferably formed by two tracks (ruts) for one lane in the road <NUM> where automobiles run frequently. Thus, since the road <NUM> is warmed along the tracks (ruts) where the automobiles run frequently, snowfall and freezing of the road <NUM> can be prevented mainly around the tracks, to improve the safety of the automobiles running along the road <NUM>.

Even if the white lines drawn on the road <NUM> become invisible due to snowfall, since the electric heating sheets <NUM> are buried along the tracks (ruts) on which the automobiles run frequently, so that snow deposition and freezing of the road <NUM> around the tracks (ruts) can be prevented on the road <NUM> by the heat generation of the electric heating sheets <NUM>, so that the tracks can be clearly shown to automobile drivers, to improve the safety of the automobiles running on the road <NUM>.

The cable containing grooves <NUM> are formed each at <NUM> depth × <NUM> width in a road <NUM> by a road cutter or the like in a direction traversing the road <NUM> along each of divisional sections formed by dividing a construction section.

For example, when the road heating system <NUM> is provided for a <NUM> construction section and the construction section is divided into <NUM> sections with the divisional section be formed <NUM>, a cable containing groove <NUM> is formed on every <NUM> divisional section.

<FIG> shows a state of containing electric heating sheets <NUM>, a power line <NUM>, and a communication cable <NUM> in an electric heating sheet containing groove <NUM> and a cable containing groove <NUM> formed in the road <NUM>.

First, a heat insulating material <NUM> is filled to the bottom of an electric heating sheet containing groove <NUM> formed in a road <NUM> along a longitudinal direction of the electric heating sheet containing groove <NUM>. The heat insulating material <NUM> serves to prevent heat generated by the electric heating sheet <NUM> from escaping downward below the road <NUM>, that is, downward, from the bottom of the electric heating sheet containing groove <NUM>.

The heat insulating material <NUM> is formed, for example, of a material excellent in heat insulation and water resistance such as polystyrene foam or cellulose fiber. By installing the heat insulating material <NUM> having such heat insulative and water resistant nature by <NUM> to <NUM> from the bottom of the electric heating sheet containing groove <NUM>, it is possible to prevent downward heat conduction to a road foundation of a steel floor slab, a concrete floor slab or a road foundation structural part of a bridge structure showing high heat loss, thereby improving the horizontal heat conduction of the road <NUM>.

Next, the electric heating sheet <NUM> is inserted in the electric heating sheet containing groove <NUM> so that the short side direction of the electric heating sheet <NUM> is in the vertical direction. The electric heating sheet <NUM> is installed such that the upper end is not exposed from the surface of the road <NUM>. In addition, a ground temperature sensor <NUM> (not shown in the drawing) is also disposed at an arbitrary location in the same manner as the electric heating sheet <NUM> in the electric heating sheet containing groove <NUM>.

Since the height of the electric heating sheet <NUM> is <NUM> relative to the <NUM> depth of the electric heating sheet containing groove <NUM>, the lower end of the electric heating sheet <NUM> may also be buried in the heat insulating material <NUM> disposed at the bottom of the electric heating sheet containing groove <NUM>.

When the electric heating sheet <NUM> is located in the electric heating sheet containing groove <NUM>, a support <NUM> may be inserted preferably into the gap between the electric heating sheet <NUM> and the electric heating sheet containing groove <NUM>, so that the electric heating sheet <NUM> is fixed at the center of the electric heating sheet containing groove <NUM>.

The support <NUM> is formed by hardening a material identical with the joint material <NUM> to be filled in a gap between the electric heating sheet <NUM> and the electric heating sheet containing groove <NUM> subsequently, and is formed in such a shape as not hinder the filling of the joint material <NUM> in a gap between the electric heating sheet <NUM> and the electric heating sheet containing groove <NUM>.

The support <NUM> is, for example, a solid rod or a plate member having a sufficient width to fill the gap between the electric heating sheet <NUM> and the electric heating sheet containing groove <NUM>, and is installed in a gap between the electric heating sheet <NUM> and the electric heating sheet containing groove <NUM> at a predetermined interval. Since the support <NUM> is formed of the same material as the joint material <NUM>, it is subsequently integrated with the joint material <NUM>.

Also the power line <NUM> connected to the electric heating sheet <NUM> and the communication cable <NUM> connected to the ground temperature sensor <NUM> may be wired along the electric heating sheet containing groove <NUM>, and then gathered in the cable containing grooves <NUM>, and then provided on both ends of the divisional section.

Preferably, the power line <NUM> and the communication cable <NUM> may be inserted through a flexible conduit made of a synthetic resin such as a CD (Combined Duct) pipe in advance and then installed in the electric heating sheet containing groove <NUM> and the cable containing groove <NUM>.

<FIG> shows a state of filling a joint material <NUM> in a gap between the electric heating sheet <NUM> and the electric heating sheet containing groove <NUM>.

The joint material <NUM> comprises an elastic, insulative, and water proof material, for example, a urethane rubber of hydroxy terminated polybutadiene, which is, preferably, liquid at the time of filling and cured later to show strength and flexibility, and is filled in the gap between the electric heating sheet <NUM> and the electric heating sheet storage groove <NUM> and the cable containing groove <NUM>.

The joint material <NUM> that is a urethane rubber comprising hydroxy terminated polybutadiene shows high workability in a liquid state upon filling the gap between the electric heating sheet <NUM> and can provide the electric heating sheet containing groove <NUM>, and high flexibility and strength after curing.

Therefore, when compared with a case of filing the gap between the electric heat sheet <NUM> and the electric heating sheet containing groove <NUM> with mortar, since the joint material <NUM> of high flexibility can correspond to the expansion and contraction of the road <NUM> due to vibration and the temperature difference flexibly, so that the damages of the electric heating sheet <NUM> caused by expansion and contraction of the road <NUM> due to the vibration and the temperature difference can be reduced.

Furthermore, if the electric heating sheet <NUM> is buried in the traffic track (ruts) in the road on which the automobiles runs, since the joint material <NUM> absorbs the vibrations of the automobiles, the damage of the electric heating sheet <NUM> can be reduced even for a road at large traffic amounts, and the electric heating sheet <NUM> can be used for a long time.

The support <NUM> is formed by curing a urethane rubber comprising hydroxy terminated polybutadiene as a joint material <NUM>, and the joint material <NUM> is cured to integrate the joint material <NUM> and the support <NUM>.

Since the joint material <NUM> is resistant to calcium chlorides used as an antifreezing agent or a snow melting agent, it is possible to prevent the joint material <NUM> from deterioration by the snow melting agent, the antifreezing agent or the like scattered on the road <NUM> and invading into the electric heating sheet containing groove <NUM>.

In addition, by incorporating high latent heat melting material such as sodium acetate trihydrate or sodium sulfate <NUM>-hydrate in the joint material <NUM> to improve the heat storability of the joint material <NUM>. When the joint material has high heat storability, temperature keeping performance is improved, and the road <NUM> can be heated at a saved energy.

In addition to incorporation of a material having a high latent heat of melting in the joint material <NUM>, a highly heat storing material may be provided between the electric heating sheet <NUM> and the road <NUM>, or between the electric heating sheet <NUM> and the joint material <NUM>, so that the heat generated from the electric heating sheet <NUM> may be stored in the highly heat storing material.

<FIG> shows a state of laying a surface material <NUM> to the upper end of the joint material <NUM> filled in the electric heating sheet containing groove <NUM>.

The uppermost surface of the joint material <NUM> filled in the electric heating sheet containing groove <NUM> is filled to be lower than the surface of the road <NUM>, and the surface material <NUM> is laid so as to be in flash with the surface of the road <NUM> by filling the step difference.

The surface material <NUM> comprises, for example, silica sand, and a material harder than the joint material <NUM> is laid over the upper end of the joint material <NUM> filled in the electric heating sheet containing groove <NUM>. The surface material <NUM> can adsorb to the joint material <NUM> by scattering to the upper end of the joint material before the hardening of the material.

The surface material <NUM> harder than the joint material <NUM> is laid on the upper end of the elastic joint material <NUM>, peeling and abrasion of the joint material <NUM> caused by running of automobiles can be prevented, to protect the electric heating sheet <NUM>.

In this embodiment, the electric heating sheets <NUM> has been explained as having a length of <NUM>,<NUM> and a height of <NUM>. However, it can be explained, for example, such that the electric heating sheet <NUM> has <NUM>,<NUM> length x <NUM> height and the electric heating sheet containing groove <NUM> has <NUM> depth x <NUM> height and <NUM> height. However, they can be constructed by optionally adjusting the size, for example, such that the electric heating sheet <NUM> has <NUM> to <NUM>,<NUM> of length, <NUM> to <NUM> of height and <NUM> to <NUM> of width, and the electric heating sheet containing groove <NUM> has <NUM> to <NUM> of depth.

Specifically, by reducing the height of the electric heating sheet <NUM>, or increasing the depth of the electric heating sheet containing groove <NUM>, thereby burying the electric heating sheet <NUM> below the surface layer <NUM> by <NUM> to <NUM> in the road <NUM>, so that the asphalt can be peeled in repair work with no effect on the road heating system <NUM>.

Further, by coloring the joint material <NUM> filled in a gap between the electric heating sheet <NUM> and the electric heating sheet containing groove <NUM> and the joint material <NUM> to be filled in the cable containing groove <NUM> with a color, such as white or yellow which is visually distinguishable from the road <NUM>, it is possible to clarify a portion where the electric heating sheet <NUM> is buried upon excavating the road <NUM>, for example, during asphalt repair working.

<FIG> is a block diagram showing details of the controller.

As shown in <FIG>, the controller <NUM> has a power supply unit <NUM>, a ground temperature monitoring unit <NUM>, a snowfall monitoring unit <NUM>, and a power supply unit <NUM>.

The power supply unit <NUM> is connected to a ground temperature monitoring unit <NUM>, a snowfall monitoring unit <NUM>, the power supply unit <NUM>, an electric heating sheet <NUM>, a network <NUM>, and is in connection with other controller <NUM> and serves to adjust the amount of power supplied to the electric heating sheet <NUM> connected therewith.

The ground temperature monitoring unit <NUM> is connected to the ground temperature sensor <NUM>, detects the temperature of the road <NUM> in which the electric heating sheet <NUM> is buried, to monitor the temperature thereof.

The ground temperature monitoring unit <NUM> monitors the temperature of the road <NUM> and, when the temperature of the road <NUM> is lower than a predetermined temperature, the ground temperature monitoring unit <NUM> transmits a signal for increasing the temperature of the road <NUM> to a power supply unit <NUM>, and the power supply unit <NUM> increases the amount of electric power supplied to the electric heating sheet <NUM>.

Further, the ground temperature monitoring unit <NUM> monitors the temperature of the road <NUM> and when it reaches a predetermined temperature, the ground temperature monitoring unit <NUM> transmits a signal to the power supply unit <NUM> for maintaining the temperature of the road <NUM>, and the power supply unit <NUM> reduces the amount of electric power supplied to the electric heating sheet <NUM>.

The snowfall monitoring unit <NUM> is connected to a snowfall sensor <NUM>, and the snowfall sensor <NUM> detects a state of snowfall on a place where the snowfall sensor unit is installed for monitoring the state of snowfall.

A snowfall monitoring unit <NUM> monitors the state of snowfall in the road <NUM> on which the snowfall sensor <NUM> is installed and, when the snowfall sensor <NUM> detects snowfall or when the snowfall monitoring unit <NUM> judges that the snowfall amount tends to increase, the snowfall sensor <NUM> transmits, a signal for increasing the temperature of the road <NUM> to a power supply unit <NUM>, and the power supply unit <NUM> increases the amount of electric power supplied to the electric heating sheet <NUM>.

Thus, the power supply unit <NUM> can supply an accurate amount of electric power to the electric heating sheet <NUM> based on the signals transmitted from the ground temperature sensor <NUM> and the snowfall monitoring unit <NUM>.

The power supply unit <NUM> may be connected to other controllers <NUM> installed in other divisional sections by communication cables <NUM>. A plurality of controllers <NUM> connected by the communication cables <NUM> may be connected to a network such as an internet (not shown), and each of the controllers <NUM> can be controlled from the outside by using a terminal equipment such as a computer connected to the network such as an internet.

The power supply unit <NUM> is connected to the power supply unit <NUM> and a commercial power source P installed near the road <NUM>, and serves to supply electric power obtained from a commercial power source P via the power supply unit <NUM> to each of devices constituting the road heating system <NUM>. The commercial power supply P may be available from electric power obtained by natural energy source such as a solar panel or wind power generation, or electric power generated from a generator using a fuel such as gasoline, in addition to electric power available from existent electric power companies.

<FIG> is a top plan view and a cross-sectional view showing a state of road heating system installed to a road formed on bridge piers.

As shown in the cross-sectional view of <FIG>, a bridge pier <NUM> comprises columns <NUM> disposed each at a predetermined interval, beams <NUM> disposed over columns <NUM>, and a floor plates <NUM> made of concrete or steel, and disposed on two adjacent beams <NUM>. The road <NUM> is formed on a floor board <NUM>.

As shown in the top plan view of <FIG>, the road <NUM> has two lanes on each side of a median strip <NUM>, each lane is demarcated by a roadway centerline <NUM>, and the roadway and shoulder or the roadway and the median <NUM> are demarcated by the roadway outside line <NUM> on the side opposite to the roadway centerline <NUM> of each lane. On the outside of the road <NUM>, there are formed walls <NUM> such as wall balustrades to preventing falling of people, automobiles, and the like from the bridge, and noise preventive sound proof walls.

The electric heating sheets <NUM> are buried in track portion where automobiles run on each lane. Further, since the joint between the floor boards <NUM> tends to undergo the effect of the expansions and contractions of the road <NUM> due to the vibration of the road <NUM> and the temperature difference, the joint material is inserted for joining the floor boards <NUM>, the divisional section for burying the electric heating sheet <NUM> may be provided so as not to cross the joint as shown in the top plan view of <FIG>. The controller <NUM> and the snowfall sensor <NUM> may be provided, for example, on the wall <NUM>.

<FIG> is a cross sectional view showing the state of providing the road heating system in the automobile traveling direction.

As shown in <FIG>, the electric heating sheets <NUM> are buried in two rows, for example, along tire tracks (ruts) where the tire and the road <NUM> are usually in contact each other during running of the automobiles <NUM>, for example, between roadway center line <NUM> and the roadway outside line <NUM>.

Thus, since the road <NUM> is warmed mainly around the track traces (ruts) where the automobiles <NUM> frequently run, snow accumulation and the freezing of the road <NUM> can be prevented to improve the safety of the road <NUM>.

A plurality of the electric heating sheets <NUM> buried in the road <NUM> are connected via power lines <NUM> to the controller <NUM> fixed to the wall <NUM>. The ground temperature sensor <NUM> for measuring the temperature of the road <NUM> where the electric heating sheets <NUM> are buried is also connected to the controller <NUM> fixed to the wall <NUM> via the communication cable <NUM>.

<FIG> is a top plan view showing the state of the road heating system installed in the vicinity of a tollgate.

As shown in <FIG>, in the vicinity of the tollgate, the electric power can be supplied to the road heating system <NUM> by using a mobile power supply vehicle <NUM> having a diesel engine or a gas turbine-driven generator loaded instead of a commercial power source P.

For example, in the tollgate, an optional lane among a plurality of lanes is closed to stop a power supply vehicle <NUM>, the power supply unit <NUM> of the controller <NUM> is connected and the power supply vehicle <NUM>, and the power generated by the power supply vehicle <NUM> is supplied to the road heating system <NUM>.

Thus, by using the mobile power supply vehicle <NUM>, the road heating system <NUM> can be used even in a case of a power failure caused, for example, by a disaster, and the safety of the road <NUM> can be maintained.

<FIG> is a diagram showing an example for the method of controlling a plurality of divisional sections.

As shown in <FIG>, a plurality of electric heating sheets <NUM> are buried in each of the divisional sections of the road <NUM>, and the buried electric heating sheets <NUM> are connected to one controller <NUM> for control. Each of the controllers <NUM> is connected to other controllers <NUM> via a network <NUM> such as an internet, and each of the controllers <NUM> is controlled by a computer <NUM> connected to the network <NUM>.

A plurality of controllers <NUM> installed in a road <NUM> are configured so as to allocate the two groups of the section A and the section B, and the allocated sections A and the sections B are connected alternately.

First as shown in <FIG>, upon starting operation of the road heating system <NUM>, the divisional sections each allocated as the section A are heated first. Specifically, the controllers <NUM> supply electric power to the electric heating sheets <NUM> buried in the divisional sections allocated as the sections A.

Next, as shown in <FIG>, the divisional sections allocated as the section B are heated. Specifically, the controller <NUM> supplies electric power to the electric heating sheets <NUM> buried in each of the divisional sections and allocated as the sections B.

As shown in <FIG>, by alternately heating the sections A and the sections B thereby performing the heating in the sections A and in the sections B at an interval, for example, of about <NUM> or <NUM> minutes, it is possible to reduce the power supply in the initial stage of snowfall to one-half.

Further, a plurality of controllers <NUM> installed to the road <NUM> may be configured to be assigned to three groups of sections A, sections B, and sections C, and the assigned sections A, sections B, and sections C are sequentially connected to each other, so that the power load of the power supply can be reduced to <NUM>/<NUM> by heating each of groups in rotation.

In this embodiment, the electric heating sheet containing groove <NUM> is formed in the existing road <NUM> and the electric heating sheets <NUM> are buried in the electric heating sheet containing groove <NUM>. Instead, in a case of newly constructing a road, electric heating sheets <NUM> previously surrounded with the joint material <NUM> may also be provided in a road.

Next, a second embodiment of the invention will be described. The road heating system <NUM> of the second embodiment is substantially similar to the configuration of the first embodiment excepting that the method of connecting the electric heating sheets <NUM> is different from the connection method for heating sheets <NUM>. For this reason, components that are substantially identical with those in the first embodiment are denoted by the same reference numerals, for which description will be omitted as a rule.

<FIG> is a block diagram showing the concept of a road heating system according to the second embodiment.

As shown in <FIG>, the road heating system <NUM> includes electric heating sheets <NUM>, a ground temperature sensor <NUM>, a snowfall sensor <NUM>, a controller <NUM>, a power line <NUM>, a communication cable <NUM>, and a current monitoring unit <NUM>.

A plurality of electric heating sheets <NUM> are buried at a predetermined interval in each of the divisional sections, and respective electric heating sheets <NUM> are connected in series by a power line <NUM>. Note that the distance and the number of divisions for the divisional sections and the number of electric heating sheets <NUM> buried in each of the divisional sections may be varied depending on the state of construction.

A power supply monitoring unit <NUM> is provided straddling each of the electric heating sheets <NUM> for monitoring the state of power supply to the electric heating sheet <NUM>, and the power supply monitoring unit <NUM> periodically confirms whether the corresponding electric heating sheet <NUM> is correctly supplied with power or not, and notifies the result of the check to a controller <NUM> connected via a communication cable <NUM> (not shown).

If the power supply monitoring unit <NUM> detects that the electric heating sheet <NUM> is not energized, a signal informing that the electric heating sheet <NUM> corresponding to the controller <NUM> is not energized is immediately reported, and the controller <NUM> informs a manager that the electric heating sheet <NUM> is not energized through the network <NUM>.

If one of the electric heating sheets <NUM> connected in series no more supplies power, the entire divisional section cannot be heated. However, since the energization monitoring unit <NUM> can periodically monitor the power supply state and can identify that the electric heating sheet <NUM> is in failure, only the portion of the not energized heating sheet <NUM> can be found and repaired or replaced, so that the maintainability can be improved greatly as compared with the conventional case.

<FIG> is a front elevational view showing details of the electric heating sheet according to the second embodiment of the invention.

As shown in <FIG>, the electric heating sheet <NUM> is a rectangular belt-shaped heating element at <NUM>,<NUM> length x <NUM> height x <NUM> thickness, and includes a heating part <NUM>, electrode parts <NUM>, and sheet protective parts <NUM>.

The electrode parts <NUM> are terminals formed continuously along the upper and lower ends in the longitudinal direction of the heating part <NUM>, and has an anode and a cathode for passing a current to the heating part <NUM>. The electrode parts <NUM> are connected in series to the controller <NUM> by a power line <NUM> (not shown).

In the following explanatory, the electrode part <NUM> protruding from the left of the upper end of the electric heating sheet <NUM> is referred to as the electrode part 112A, and the electrode part <NUM> protruding from the right of the lower end of the electric heating sheet <NUM> is referred to as the electrode part 112B.

Since the electric heating sheets <NUM> can be replaced sheet by sheet for a failed portion identified by the power supply monitoring unit <NUM>, it is necessary that the road <NUM> may be excavated only for a portion where the failed electric heating sheet <NUM> is buried and that only the failed electric heating sheet <NUM> is replaced or repaired, maintenance work can be reduced to improve the maintainability.

<FIG> is a front elevational view showing a state of connecting electric heating sheets according to the second embodiment.

As shown in <FIG>, respective electric heating sheets <NUM> are connected in series and connected via a power line <NUM> to a (not shown) controller <NUM>. The power supply monitoring unit <NUM> is not illustrated.

As a specific connection example, a power supply unit <NUM> of the controller <NUM> is connected via a power line <NUM> to the electrode part 112A of the electric heating sheet <NUM>. The electrode part 112B of the electric heating sheet <NUM>-<NUM> is connected to the electrode 112B of the electric heating sheet <NUM>-2B in a state of turning the electric heating sheet <NUM> upside down.

Further, the electrode part 112A of the electric heating sheet <NUM>-<NUM> is connected to the electrode part 112A of the electric heating sheet <NUM>-<NUM> such that the upper and the lower surfaces of the electric heating sheet <NUM> are reversed upside downs and connected to the electrode part 112A of the electric heating sheet <NUM>. Thus, the voltage can be divided depending on the resistance.

In this state, in the electric heating sheet <NUM>-<NUM>, a current flows from the electrode part 112A to the electrode part 112B to generate heat in the heating part <NUM> and, in the electric heating sheet <NUM>-<NUM>, a current flows from the electrode part 112B to the electrode part 112A to generate heat in the electric heating sheet <NUM>.

Further, as shown in <FIG>, by connecting the electrode part 112A and the electrode part 112A or connecting the electrode part 112B and the electrode part 112B each at an angle, the electric heating sheets <NUM> can be installed in accordance with the unevenness or inclination of the road.

Specifically, the road is inclined in the vicinity of a tollgate, an entrance, etc., of an expressway, and the electric heating sheet <NUM> can be connected in accordance with the inclination and the unevenness of the road by connecting the connecting part of the electrode part <NUM> at an angle.

In this embodiment, the road heating system <NUM> has been described as having the power supply monitoring unit <NUM> and the communication cable <NUM>. Alternately, the road heating system <NUM> excluding the power supply monitoring unit <NUM> and the communication cable <NUM> connecting the power supply monitoring unit <NUM> and the controller <NUM> may be buried in the road <NUM>.

By saving the power supply monitoring unit <NUM> and the communication cable <NUM>, since the volume of the power supply monitoring unit <NUM> and the communication cable provided in the electric heating sheet containing groove <NUM> and the cable containing groove <NUM> can be reduced, the formed electric heating sheet containing groove <NUM> and the cable containing groove <NUM> can be reduced at least to the volume capable of containing the electric heating sheet <NUM>.

Thus, since the working time for excavating the electric heating sheet containing groove <NUM> and the cable containing groove <NUM> in the road <NUM> can be decreased, it can cope with the short-time construction which is required during a limited midnight work in the construction state.

Next, a third embodiment of the invention will be described. The road heating system <NUM> of this embodiment is substantially similar to the configuration of the second embodiment excepting that the method of forming the electric heating sheet <NUM> is different. Then, components substantially similar to those of the second embodiment are denoted by the same reference numerals, without particularly mentioning them.

<FIG> is a front elevational view showing details of an electric heating sheet according to the third embodiment.

As shown in <FIG>, the electric heating sheet <NUM> is a rectangular belt-shaped heating element having a <NUM> height x a <NUM> ~ <NUM> thickness x an arbitrary length, including a heating part <NUM>, electrode parts <NUM>, and protective sheet parts <NUM>. For example, the electric heating sheet <NUM> is formed to several tens or hundreds meters of length, and can be carried to the working site in a rolled state or the like.

The electrode parts <NUM> are terminals provided on both ends of the heating part <NUM>, and have an anode side and a cathode side for passing a current to the heating part <NUM>. By forming upper and lower recesses to the electrode part <NUM> to form notches in the heating sheet <NUM>, the same state as that where the heating sheet <NUM> according to the second embodiment is connected in series can be formed. Details will be described later.

The protective sheet part <NUM> is made of protective material for protecting the electric heating sheet <NUM> and a connection part between the electric heating sheet <NUM> and the electrode part <NUM>, and is made of a material having a thickness of about <NUM>, excellent in flexibility, heat resistance, cold resistance, weather resistance, water resistance, etc., comprising, for example, butyl rubber, and is bonded from both sides by protective sheet parts <NUM> so as to sandwich the electric heating sheet <NUM> and the connection part between the electric heating sheet <NUM> and the electrode part <NUM>. By protecting another surface of the protective sheet part <NUM> with releasable paper or the like, it is possible to prevent the protective sheet part <NUM> from adhering to other parts.

<FIG> is a front elevational view showing a method of forming an electric heating sheet.

As shown in <FIG>, an electric heating sheet <NUM> formed in an arbitrary length includes notches <NUM>.

The notches <NUM> are formed at arbitrary places depending on the conditions of the road where the road heating system <NUM> is installed, and the notched parts <NUM> are formed in the electric heating sheet <NUM> so as to cut only one electrode part <NUM> from the upper direction or the lower direction of the electrode part <NUM>.

A specific installation method of the electric heating sheets <NUM> will be described below.

First, an electric heating sheet <NUM> formed of an arbitrary length in a rolled state or the like is cut in accordance with the length of an electric heating sheet containing groove <NUM> to be installed.

Then, notches <NUM> are formed to the electric heating sheet <NUM>. The notches <NUM> are formed such that one side of the electrode part <NUM> is exposed on both ends of the cut electric heating sheet <NUM>, and the notches are formed in the electric heating sheet <NUM> so as to cut the electrode part <NUM> from above or below. As a result, the same state as that where the electric heating sheets <NUM> according to the second embodiment of the invention are connected in series, so that the voltage can be divided depending on the resistance of the electric heating sheets <NUM>.

Further, the power from the electric heating sheets <NUM> can be varied also by increasing or decreasing the number of notches <NUM> formed in the electric heating sheet <NUM>. More specifically, by reducing the number of the notches <NUM>, the electric resistance value of the entire electric heating sheet <NUM> is reduced, so that the power of the electric heating sheet <NUM> can be increased. Further, by increasing the number of the notches <NUM>, the electric resistance value of the entire electric heating sheet <NUM> is increased, so that the power for the electric heating sheet <NUM> can be reduced.

As described above, by adjusting the number of the notches <NUM> formed in the electric heating sheet <NUM>, it is possible to construct the system corresponding appropriately to any type of power supply such as DC or AC, and at a voltage, for example, of <NUM> V, <NUM> V, <NUM> V, <NUM> V, <NUM> V, and <NUM> V.

Further, as shown in <FIG>, by forming each of the notches <NUM> to the electric heating sheet <NUM>, the electric heating sheet <NUM> can be curved near the electrode <NUM> connected by the formed notch <NUM>. Thus, the electric heating sheets <NUM> can be installed in accordance with irregularity and inclination of the road.

Further, since the electric heating sheet <NUM> can be cut in accordance with the electric heating sheet containing groove <NUM> formed in the road, and the notches <NUM> are formed to the recessed electric heating sheet <NUM>, the adaptability to the construction site can be improved.

Claim 1:
A road surface heating device for elevating the temperature of a road surface including:
a plurality of belt-shaped electric heating sheets (<NUM>) buried in divisional sections of the road (<NUM>), with a plane of the sheet being in perpendicular to the road surface, and
a connection structure for linking the plurality of electric heating sheets (<NUM>) and connecting them to a power source (P), and
a controller (<NUM>) for controlling the amount of heating of the electric heating sheets (<NUM>) connected to the connection structure in each of divisional sections,
characterized in that
the electric heating sheets (<NUM>) comprise Japanese paper blended with carbon fibers and in that the belt-shaped electric heating sheets (<NUM>) are buried in said divisional sections along the travelling direction of the road (<NUM>).