JP7660941B2 - Control method for hot air joint heater - Google Patents

Description

The present invention relates to a hot air joint heater used in spreading asphalt mixtures on road surfaces, and in particular to a control method for the same.

The surface and base layers of asphalt pavement are formed using asphalt mixtures manufactured under appropriate temperature and quality control. The method for heating and leveling this asphalt mixture can be done manually or mechanically, depending on the scale and type of work, but currently most work is done mechanically, using a specialized machine called an asphalt finisher.

In general, asphalt layers are constructed by supplying the asphalt mixture transported by dump truck to an asphalt finisher, which spreads and levels it to obtain the specified finished width and thickness. The temperature of the asphalt mixture during spreading and leveling must be kept above 110°C, and the asphalt finisher must be operated as continuously as possible at a constant speed to ensure smoothness.

In addition, when applying a surface layer of asphalt mixture over a base layer of asphalt mixture, an emulsion called a tack coat is sprayed to improve adhesion between the layers.

An asphalt finisher is a self-propelled machine that consists of a hopper that stores the asphalt mixture, a tractor unit with a prime mover and running gear, and a screed that spreads the asphalt mixture. The asphalt mixture is stored in the hopper, and then sent to the front of the screed at the rear by a bar feeder at the bottom of the hopper, where it is spread to the left and right by a screw, and then spread evenly by the screed. During this process, the angle of the screed is changed to adjust the thickness of the asphalt mixture to be spread evenly, and the width of the screed is expanded or contracted left and right to adjust the spreading width (width). To repair an asphalt road surface, the road surface is heated in advance by a road surface heater to soften it, the road surface is scraped apart, and compaction work is performed.

For example, Patent Document 1 proposes a method in which the edges of the existing asphalt pavement for the first lane are heated while the asphalt mixture that will become the asphalt pavement for the second lane is laid out evenly, in which a joint heating device equipped with a magnetron irradiates microwaves onto the edges of the asphalt to heat the edges to an appropriate temperature, and the asphalt mixture is then laid out evenly.

A device for spreading asphalt mixture on an underlying road surface such as an unpaved roadbed, an asphalt pavement or its cut surface, or a concrete pavement surface is known that is equipped with a hopper for storing the asphalt mixture, an asphalt mixture delivery device, an emulsion spray nozzle, and a screed on a traveling vehicle, and the asphalt mixture is delivered from the hopper while the emulsion is sprayed on the underlying road surface with the spray nozzle, and spreads and is leveled with the screed (see Patent Document 2). A road heater for melting a frozen roadbed or roadbed is a paving work road heater that is composed of a rolling roller that is supported on a movable work machine and is supported by a shaft, holes drilled around the roller to blow hot air from the internal space to the outside, a heating device disposed toward the internal space of the roller, and an insulating cover that is wrapped around the roller except for the lower part of the rolling surface with a required gap (see Patent Document 3).

The leveling machine disclosed in Patent Document 1 makes it possible to lay asphalt pavements at low cost overall without using an asphalt distributor, which is a vehicle dedicated to spreading emulsion.

However, the conventional asphalt mixture spreading machines described above are only equipped with an emulsion spray nozzle and auxiliary equipment such as a pump that pressure-transfers the emulsion to the nozzle and an emulsion tank, and so there is a problem in that the decomposition speed of the sprayed emulsion is affected by the outside temperature and wind, which ultimately affects the adhesive strength of the emulsion.

JP 2004-143826 A Japanese Patent Application Publication No. 4-203006 JP 2016-75043 A Utility Model Registration No. 3212830

In addition, the above-mentioned conventional heating devices had the drawback that they did not heat the road surface deep enough, and the scraped asphalt immediately cooled, resulting in an insufficient temperature for the subsequent compaction process. To solve this drawback, it was necessary to heat the road surface sufficiently, but this created another problem of delays to repair work due to the heating process.

Currently, the mainstream method of construction for asphalt joints is to use direct-fire joint heaters and handle burners attached to the side of the asphalt finisher. This causes the mix to harden while waiting for the mix dump truck and while pulling the mix by hand, reducing work efficiency, especially in winter. In addition, because the road surface joints are not well bonded, defects such as cracks appear immediately after paving work is completed.

Direct-fire joint heaters are attached to the side of the asphalt finisher, but the heaters are heavy, and attaching and removing them takes time and effort, requiring a great deal of effort from the worker. In addition, hand burners cause discoloration of the asphalt pavement surface as the flame hits the surface directly. Furthermore, depending on where they are attached to the finisher, the hand burner may move due to vibrations, etc., posing safety issues such as the spread of fire to the worker's clothing. In addition, the weak flame makes it difficult to join the joints.

Conventionally, there has been a method of installing a heating device immediately after the road surface scraping device, but this has problems such as high equipment costs and insufficient heating temperature, so the inventor previously proposed a hot air joint heater in Patent Document 4. This hot air joint heater is equipped with a hot air generator including a gas burner and an air blower, and is composed of a front heater with multiple hot air outlets directed toward the road surface, and a pipe-shaped side heater connected to a hot air duct that blows hot air from the hot air generator and with multiple hot air outlets directed toward the road surface. It is mounted on a self-propelled asphalt finisher, and the amount of heat required for scraping is applied to the scraping position and to the asphalt immediately after scraping, so that road surface repair can be performed quickly by applying the amount of heat required for subsequent processes such as compaction.

The present invention relates to an improvement to this hot air joint heater, and aims to provide a control method for a hot air joint heater that can easily control the hot air temperature, hot air volume, and air pressure, thereby increasing the joining productivity of asphalt joints.

For this reason, the present invention provides a control system for a hot air joint heater comprising a front heater (1) equipped with an air blower (4) including a gas burner (2) and an air blower (19) and provided with a plurality of hot air outlets (9) and hot air outlets (10) directed toward the road surface, and a pipe-shaped side heater (11) connected to a combustion tube (3) that delivers hot air from the air blower (4) and provided with a plurality of hot air outlets (17) directed toward the road surface, the control system being mounted on a self-propelled asphalt finisher (AF) and blowing out hot air with the amount of heat required for subsequent processes such as compaction to the asphalt mixture at the scraping position and to the asphalt mixture immediately after scraping, the control system supplying propane gas as fuel from an LP gas cylinder (35) mounted on the asphalt finisher (AF) via a fixed stand (37),
The hot air ejection pipe (14) of the side heater (11) is branched into a front duct pipe (14a) and a rear duct pipe (14b) so that hot air is ejected from the hot air ejection holes (17) of each of the front duct pipe (14a) and the rear duct pipe (14b).
The hot air control circuit (30) controls the supply and stop of gas to the front heater (1) and the side heater (11), the ignition of the spark plug (6), and the supply of electricity to the blower fan (19) by only turning on and off at least one torque switch (18), and automatically controls the opening and closing operation of a gas valve (27) by an electromagnetic valve (28) based on a detection signal from a temperature controller (26), thereby controlling the temperature, volume, and pressure of the hot air to be within certain ranges.
The hot air control circuit (30) is composed of at least an on/off relay circuit (20) for an ignition plug igniter (16) and an open/close relay circuit (21, 22) for a gas valve, and is connected to a start/stop switch line of an asphalt finisher (AF) so that ignition occurs when the asphalt finisher (AF) starts and gas supply is stopped when the AF is stopped.
The first feature is that the temperature of the hot air is detected by a thermocouple (32) and the amount of gas supplied to the gas burner (2) is adjusted to control the amount of combustion, and the temperature controller (26) automatically controls the front heater hot air outlet temperature and the side heater hot air outlet temperature to 150° C. to 300° C. The second feature is that a bifurcated coupler (38) is connected to the regulator (36) of the LP gas cylinder (35) to send gas to combustion tubes (strainers) (3) provided on the left and right sides of the asphalt finisher (AF).

The hot air joint heater of the present invention is configured as described above and has the following excellent effects:
(1) Cold asphalt and warm asphalt do not mix, making them difficult to bond together. However, by heating the asphalt, the cold asphalt and warm asphalt can be mixed together, making them easier to bond, and preventing cracks at the joints in the asphalt pavement.
(2) The material does not solidify because it is kept at a constant temperature by hot air even while the material is waiting for the transport dump and while it is being manually pulled. This also leads to a reduction in the time required for raking and other operations.
(3) Hot air is blown evenly using a blower instead of a direct flame, so discoloration of the asphalt surface does not occur.
(4) Since it is not an open flame, it is highly safe as it will not catch fire on the worker's clothes, etc. Because it is lightweight and compact, disassembly and installation can be done by one person in about five minutes.
(5) Even when the outside temperature is low or the wind is strong, paving can be done well without being adversely affected by these conditions.
(6) Not only can the underlying road surface be heated before the emulsion is applied, but even if the surface is wet with rain or other moisture, the moisture can be removed by heating, resulting in a better pavement.
(7) Both the front heater and the side heater can be controlled automatically as well as manually. In particular, if the gas does not ignite when the asphalt finisher starts moving, the temperature controller does not detect the flame and stops the gas supply, making it safe.
(8) The gas ignition switch and the starter switch are linked, making it easier to use.
(9) The hot air temperature, air volume, air pressure, etc. can be accurately controlled within a certain range based on the detection signal from the hot air sensor. Furthermore, since manual adjustment operations are not required, the drying productivity of asphalt joints can be significantly improved.
(10) Both the front heater and the side heater can be easily attached and detached from the asphalt finisher body with a single bolt.

FIG. 1 is a front perspective view showing a state in which a hot air joint heater according to the present invention is attached to an asphalt finisher. FIG. 1 is a side perspective view showing a state in which a hot air joint heater according to the present invention is attached to an asphalt finisher. 1A and 1B are a front view and a side view, respectively, showing a hot air heating device (front heater) of a hot air type joint heater according to the present invention. FIG. 2( b ) is a bottom view of FIG. FIG. 2 is a schematic diagram showing a configuration of a side heater. 1A is a front view, and FIG. 1B is a plan view, each showing the exterior of a control box. FIG. 2 is a circuit diagram of a hot air joint heater control system according to the present invention. FIG. 2 is an external plan view of the control box. FIG. 11 is a side view showing another embodiment of the side heater. FIG. 11 is a perspective view showing a schematic diagram of another embodiment of a hot air type joint heater according to the present invention. FIG. 11 is a front view showing a schematic installation state of the hot air type joint heater shown in FIG.

Below, the embodiment of this invention is explained based on the example shown in the drawings.

1 to 4 show an embodiment of the hot air joint heater according to the present invention.
The device of the present invention is used by being attached to a self-propelled vehicle such as an asphalt finisher AF. An asphalt finisher is, for example, a self-propelled vehicle equipped with a hopper for storing an asphalt mixture, an asphalt mixture delivery device, an emulsion (asphalt) spray nozzle, and a screed, and while the emulsion is sprayed onto the unpaved roadbed with the spray nozzle, the asphalt mixture is delivered from the hopper by the delivery device onto the sprayed emulsion on the roadbed and spread evenly with the screed.

1 and 2 are perspective views showing the appearance of the hot air joint heater according to the present invention, which is generally composed of a front heater 1, which is a hot air generating device including a gas burner 2 , and a pipe- shaped side heater 11. That is, the hot air joint heater according to the present invention draws in outside air from the open surface of the air blower box 4 , heats the drawn-in outside air in the combustion tube 3 by the gas burner 2, and blows it out as hot air to the joint (seam) part of the asphalt road surface. In addition, the amount of heat required for scraping can be imparted to the scraping position and to the asphalt immediately after scraping for the subsequent process during rolling. Both the front heater 1 and the side heater 11 can be easily attached and detached to the asphalt finisher main body AF with a single bolt.

2 to 4, the hot air generator (front heater) 1 contains a gas burner 2 in a combustion tube 3, and is connected to an air blower box 4 having an air fan 19. The hot air generator (front heater) 1 includes a hot air control circuit (control box) 30 that detects the temperature of the hot air with a thermocouple 32 and adjusts the amount of gas supplied to the gas burner 2 to control the amount of combustion, and also controls the hot air temperature to a maximum of about 350° C. with a temperature controller 15 described later.

3 and 4, the combustion tube 3 blows hot air from a hot air blowing skirt box 7 provided below it . A plurality of hot air blowing holes 9 and hot air blowing outlets 10 are formed in the bottom plate 8 of the hot air blowing skirt box 7, and the blown hot air heats the asphalt road surface immediately after it has been scraped apart.

As shown in Fig. 5, the side heater 11 is constructed by inserting a side gas burner 12 connected to the gas pipe 5 from above a burner mounting bracket (including a T-shaped socket) 13, fixing it at a desired position with a burner position fixing bolt 12a, and connecting a hot air blowing pipe 14 with multiple hot air blowing holes 17 drilled therein and directed toward the road surface in the left and right directions at its lower end , so that hot air is blown out directly. The diameter of the hot air blowing holes 17 is preferably 0.5 mm to 10 mm, particularly 0.7 mm to 0.8 mm, and can be adjusted appropriately depending on the work situation.

The hot air joint heater of this embodiment configured as described above (fuel is propane gas: propane pressure 0.05 MPa, front hot air outlet temperature: 230°C, side heater hot air outlet temperature: 160°C-180°C. The emulsion is dried by hot air outlet (230°C) from the front heater. The propane gas fuel is supplied from the main gas tank in the asphalt fisher body, but as the pressure is 0.05 MPa, there is no need to adjust the amount and it can be supplied without stress at the same gas pressure, while the gas combustion efficiency is improved, resulting in energy savings.

In this way, the hot air (160°C to 180°C) blown from the side heater 11 softens the mix, increasing the efficiency of the rake work and improving the finished surface of the paving joints. The mix does not cool down during paving work, while waiting for the mix, or when the finisher is stopped, and the mix can remain soft even when restarting. Since there is no direct flame, the mix does not discolor.

In order to prevent deterioration of the asphalt, the appropriate hot air temperature is approximately 250°C to 300°C. Depending on the outside temperature and the condition of the asphalt, it is also possible to use only one of the front heater 1 and the side heater 11, rather than using both.

Figure 6 shows the control box 30 equipped with the hot air control circuit for the side heater 11, Figure 7 shows the control system circuit, and Figure 8 shows the external plan view. In the hot air control circuit, two torque switches 18 are connected to the power on/off circuit, the ignition on/off relay circuit 20 which is the first relay circuit, the open/close relay circuits 21 and 22 of the gas valve 27 which are the second and third relay circuits, and the power relay circuit of the air blower 4's air blower fan 19, and are also connected to the start/stop switch line of the asphalt finisher (vehicle). A fluid control solenoid valve (Multilex Valve: CKD GAB312-3-0-03A-DCV: product name: manufactured by CKD Corporation) is used for the gas valve 27. In the figure, 32 is a thermocouple (measuring temperature difference), and the ignition plug 6 is connected to the igniter 16.

That is, in the first relay circuit 20, a timer relay 24 is connected to the on/off circuit of an ignition 23 for a spark plug, and is also connected to a temperature controller 15 equipped with a digital display panel 26 via opening/closing relay circuits 21 and 22 for a gas valve 27. The gas supply, stop, and ignition to the side heater 11 can be controlled simply by turning on/off at least one torque switch 18. The opening and closing operation of the gas valve 27 can be automatically controlled by a signal from the temperature controller 15. In the figure, 33 is a metal connector for power supply, 33a is its cover, 34 is a gas supply coupler, and 34a is its cap.

In this embodiment, a solid-state timer H3N-2 (product name: manufactured by Omron Corporation) was used as the timer relay circuit 20 for ignition of the spark plug 6 and for interlocking with the start/stop switch. A mini power relay G2R-2-SD (product name: manufactured by Omron Corporation) was used as the gas valve opening/closing relay circuits 21 and 22, which are the second and third relay circuits connected to the temperature controller 15. In addition, a digital PID temperature controller RKC C100KF02-V (product name: manufactured by Rika Kogyo Co., Ltd.) was used as the temperature controller 15 .

In the hot air joint heater of this embodiment, the opening and closing of the gas valve 27 is automatically controlled by the solenoid valve 28 in response to a detection signal from the temperature controller 15 , and the temperature, volume, pressure, etc. of the hot air can be accurately kept within a certain range, and furthermore, since no manual adjustment work is required, the drying productivity of the asphalt joints can be significantly improved. Also, for example, it is possible to control the volume and pressure of the hot air by adjusting the rotation speed of the air blower fan 19 of the air blower 4.

That is, a gas ignition relay 20 and a gas valve 27 that control the flow of electricity to the spark plug ignition 23 , and a switch 18 that is connected to the spark plug ignition 23 and is linked to the start/stop of the asphalt finisher (vehicle), and the first relay circuit 20 for gas ignition, the second relay circuit 21 that controls the front heater, and the third relay circuit 22 that controls the side heater 11 are automatically linked by the operation of at least one switch, and the spark plug ignition 23 , which is the gas ignition switch, is linked to the start/stop switch line of the asphalt finisher (vehicle) AF, making it easy to use.

When the gas burner ignition is automatically controlled, it is ignited when the asphalt finisher AF starts and extinguished when it stops, so there is no risk of forgetting to turn it off even when waiting for the mix to be added, and the gas supply is also cut off when the machine is stopped, providing excellent safety.

9 to 11 show another embodiment of the device of the present invention. For convenience, the same components as those in the first embodiment are given the same reference numerals.
In this embodiment, instead of the front heater 1 of the first embodiment, the hot air ejection pipe 14 of the side heater 11 is branched from the combustion tube 3 into a front duct pipe 14a and a rear duct pipe 14b, and hot air is ejected from each of the hot air ejection holes 17, which contributes to making the entire device more compact.

The propane gas fuel is supplied from an LPG cylinder 35 mounted on the asphalt finisher AF via a fixed stand 37. A bifurcated coupler 38 is connected to the regulator 36 of the LPG cylinder 35, and gas is sent to each of the left and right strainers 3. This configuration makes it easy to install and remove the entire device, and also makes it easy to transfer it to a different vehicle.

With the above configuration, hot air is always blowing on the road surface even when the asphalt finisher is stopped, making the mixture soft and easy to work with. The joint heater and emulsion (adhesive) in the center joint are also heated to the point where bubbles appear, improving adhesion between the mixtures and making it less likely for cracks to occur in the center joint. Although the heat is sufficient, no flames come out of the joint heater, only hot air. Discoloration is prevented because the flame does not directly hit the mixture.

In winter or in cold regions, the hot air joint heater can sufficiently heat the screed side temperature, the mix material at the corners of the side plate and moldboard is soft, and rake work on the left and right sides can be performed smoothly. There is no need to stop the asphalt finisher except when waiting for the mix material to be dumped.

The hot air burner type applies hot air of 150°C to 200°C to the composite material to soften it, and because the flame does not come into direct contact with the composite material, the material does not discolor. It also prevents malfunctions caused by flames.

The joint sides of the asphalt pavement surface, the screed side brake and under the steps are heated with hot air at 150℃ to 200℃, which softens the composite material at the corners of the moldboard, reduces snagging and damages to the pavement surface.

Even with poor quality materials (recycled materials, etc.), flexibility is maintained, and the entire material does not move as a unit during leveling with a rake, allowing for smooth work and reducing the workload of workers.
Previously, the finisher had to be stopped temporarily when touch-up work was required, but with this system, paving work can continue without stopping, improving work efficiency and producing a neater finished pavement.

As with center joints, side joints come in both manual and automatic control types. If ignition does not occur when the vehicle starts moving, the controller does not detect the flame and the safety device activates, cutting off the gas supply, making it safe. In this way, according to the present invention, the asphalt joints can be constantly heated. Also, the large heating area allows for sufficient softening. This allows for faster repairs, and by installing a front heater at the front, labor savings can be achieved even in winter.

1. Hot air heating device (front heater)
2 Front gas burner 2a Gas ejection nozzle 3 Combustion tube (strainer)
4 Air blower box 5 Gas pipe or gas hose 6 Spark plug 7 Hot air outlet skirt box 8 Bottom plate of skirt box 9 Hot air outlet hole 10 Hot air outlet 11 Side heater 12 Side gas burner 12a Burner position adjustment bolt 13 Burner mounting bracket (T-type socket)
14 Hot air outlet pipe 15 Temperature controller 16 Igniter 17 Hot air outlet hole 18 Torque switch 19 Air supply fan 20 First relay circuit (timer relay circuit)
21 Second relay circuit 22 Third relay circuit 23 Spark plug ignition 24 Timer relay 25 Earth (ground)
26 Digital display panel of temperature controller 27 Gas valve 28 Solenoid valve 29 Shielded housing 30 Control box (hot air control circuit)
31 High voltage wire 32 Thermocouple 33 Metal connector 33a Connector cover 34 Coupler 34a Coupler cap 35 LP gas cylinder 36 Regulator 37 Gas cylinder fixing stand 38 Two-way coupler AF Asphalt finisher (vehicle)

Claims (2)

The control system for a hot air joint heater comprises a front heater (1) equipped with an air blower (4) including a gas burner (2) and an air blower (19), and provided with a plurality of hot air outlets (9) and hot air outlets (10) directed toward the road surface, and a pipe-shaped side heater (11) connected to a combustion tube (3) that blows hot air from the air blower (4) and provided with a plurality of hot air outlets (17) directed toward the road surface, the control system being mounted on a self-propelled asphalt finisher (AF) and blowing out hot air with the amount of heat required for subsequent processes such as compaction to the asphalt mixture at the scraping position and to the asphalt mixture immediately after scraping, and the supply of propane gas as fuel is performed from an LP gas cylinder (35) mounted on the asphalt finisher (AF) via a fixed stand (37),
The hot air ejection pipe (14) of the side heater (11) is branched into a front duct pipe (14a) and a rear duct pipe (14b) so that hot air is ejected from the hot air ejection holes (17) of each of the front duct pipe (14a) and the rear duct pipe (14b).
The hot air control circuit (30) controls the supply and stop of gas to the front heater (1) and the side heater (11), the ignition of the spark plug (6), and the supply of electricity to the blower fan (19) by only turning on and off at least one torque switch (18), and automatically controls the opening and closing operation of a gas valve (27) by an electromagnetic valve (28) based on a detection signal from a temperature controller (26), thereby controlling the temperature, volume, and pressure of the hot air to be within certain ranges.
The hot air control circuit (30) is composed of at least an on/off relay circuit (20) for an ignition plug igniter (16) and an open/close relay circuit (21, 22) for a gas valve, and is connected to a start/stop switch line of an asphalt finisher (AF) so that ignition occurs when the asphalt finisher (AF) starts and gas supply is stopped when the AF is stopped.
The method for controlling a hot air joint heater is characterized in that the temperature of the hot air is detected by a thermocouple (32) and the amount of gas supplied to the gas burner (2) is adjusted to control the amount of combustion, and the front heater hot air outlet temperature and the side heater hot air outlet temperature are automatically controlled to 150°C to 300°C by the temperature controller (26). A method for controlling a hot air joint heater as described in claim 1, characterized in that a bifurcated coupler (38) is connected to the regulator (36) of the LP gas cylinder (35), and gas is sent to combustion tubes (strainers) (3) installed on the left and right sides of the asphalt finisher (AF).

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