Patent Application
20190383247
The present disclosure relates to an ultrasonic fuel supplying apparatus and an internal combustion engine and a combustion apparatus employing the same.
The crude oil extracted from the underground mainly includes hydrocarbon, which is a mixture of various impurities including sulfur. The fractional distillation of the crude oil sequentially evaporates substances depending on the evaporation point, providing gasoline, kerosene, diesel oil, and fuel oil in order.
In general, the diesel oil has thermal efficiency higher than the gasoline by about 10%, which is mainly used for a diesel engine vehicle. However, as the diesel oil contains sulfur component, combustion of the diesel oil emits sulfur oxides, generating sulfuric acid by reacting with water vapor, which may affect human bodies.
A fuel line of a typical internal combustion engine includes a fuel pump for supplying a fuel from a fuel tank and a mixing device for mixing the fuel supplied by the fuel pump and air (oxygen) at a constant ratio. The fuel is supplied to a fuel filter from the fuel tank by the fuel pump, and after filtering impurities at the fuel filter, supplied to an injection pump. The injection pump applies a pressure to the fuel and injects the fuel into a cylinder via an injection valve.
The fuel injected into a cylinder of a diesel engine has better properties of evaporation and mixing with the air as a size of a fuel particle decreases, and therefore, the fuel needs to be atomized to a small particle.
KR Utility Model No. 20-1999-0041915, KR Pat. Appl. Laid-Open No. 10-2001-0025533, KR Pat. NO. 10-0840410, and KR Pat. Appl. Laid-Open No. 10-2012-0051462 describe An apparatus for supplying a fuel to an injector using an ultrasonic transducer to reduce an incomplete combustion of the fuel.
However, the descriptions of the above patent documents employ the fuel supplied from the fuel pump as a main fuel supply line and the fuel supplied through the ultrasonic transducer as an auxiliary fuel supply line, to achieve about 30% of increase in the fuel efficiency at maximum.
According to some embodiments of the present invention, an ultrasonic fuel supplying apparatus includes an ultrasonic fuel tank including a fuel storing space for accommodating a fuel and a fuel atomizing space for accommodating an atomized fuel, an input pipe for supplying the fuel from an external main fuel tank to the ultrasonic fuel tank, at least one ultrasonic transducer arranged at a lower portion of the ultrasonic fuel tank and configured to atomize the fuel accommodated in the fuel storing space, an ultrasonic transducer controller configured to drive the at least one ultrasonic transducer, an output pipe for supplying atomized fuel from the ultrasonic fuel tank to an external fuel injection unit, and an output pipe extending unit extended from the output pipe into the fuel atomizing space and including an opening at a distal end.
According to some embodiments of the present invention, an internal combustion engine includes a main fuel tank for storing a fuel, a fuel pump coupled to the main fuel tank, an ultrasonic fuel supplying apparatus according to some embodiments of the present invention, a fuel injection unit configured to supply the fuel from the fuel pump and the atomized fuel from the ultrasonic fuel supplying apparatus to a cylinder chamber, and a drive unit configured to drive using the fuel supplied by the fuel injection unit.
According to some embodiments of the present invention, a combustion apparatus includes a main fuel tank for storing a fuel, an ultrasonic fuel supplying apparatus according to some embodiments of the present invention, a fuel injection unit configured to supply the fuel from the main fuel tank and the atomized fuel from the ultrasonic fuel supplying apparatus into a combustion chamber, and a combusting unit configured to combust the fuel and the atomized fuel supplied by the fuel injection unit in the combustion chamber.
Although the respective embodiments are described herein independently, the embodiments can be mutually combined, and the combined embodiments are also included in the scope of the present invention.
The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings.
Exemplary embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.
In the case of a diesel engine, in order to increase the fuel efficiency by about 30% or more, it is necessary to drive an engine using the atomized fuel by way of the ultrasonic transducer as a main fuel supply line or using the atomized fuel only in a normal RPM region used in everyday life (for example, equal to or lower than about 3000 rpm).
In addition, in order to efficiently reduce the fuel consumption and to efficiently suppress a generation of the harmful exhaust gas in a combustion apparatus such as boiler, heater, electric generator using kerosene, diesel oil, heavy oil, and the like, it is necessary to operate the combustion apparatus using the atomized fuel as a main fuel supply line or using the atomized fuel only.
In order to at least partially solve the above problems, it is an object of the present invention to provide an ultrasonic fuel supplying apparatus capable of atomizing the fuel using an ultrasonic transducer and driving or operating an internal combustion engine or a combustion apparatus using the atomized fuel as a main fuel supply line or using the atomized fuel only.
It is another object of the present invention to provide an internal combustion engine or a combustion apparatus employing the ultrasonic fuel supplying apparatus.
Although a diesel engine for a vehicle using the diesel oil is exemplified as an internal combustion engine, the present invention is not limited to this, but can be applied to any internal combustion engine using a fuel having the evaporation point of 150 degrees Celsius (for example, kerosene, diesel oil, heavy oil, and the like) and any combustion apparatus using such fuel, such as boiler, heater, electric generator, and the like.
Further, the present invention can be applied regardless of a type of the combustion chamber of the internal combustion engine (for example, direct injection and indirect injection), a type of the fuel injection pump (for example, inline injection pump, distributor injection pump), unit injector, and the like), and a type of the fuel injection (for example, mechanical type, electronic control type, and the like).
As shown in
In
In some embodiments of the present invention, the fuel accommodated in the main fuel tank 10 is supplied to the fuel injection unit 40 via a first fuel supply line in which the fuel is pumped by the fuel pump 20 and directly supplied to the cylinder chamber 30 in a liquid state and a second fuel supply line in which the fuel is atomized by the ultrasonic fuel supplying apparatus 50 and supplied to the cylinder chamber 30 in a gas state.
In some embodiments of the present invention, the fuel supply via the second fuel supply line is always in an open stage (100% ON), while the fuel supply via the first fuel supply line is in an open state (100% ON), a close state (0% ON), or a partially open state (between 0% and 100%) depending on an operation status of the internal combustion engine, which is a sort of hybrid mode.
The fuel injection unit 40 includes an injection pump 41 and an injection nozzle 42. The fuel supplied to the fuel injection unit 40 via the first fuel supply line, the second fuel supply line, or both is injected into the cylinder chamber 30 through the injection nozzle 42 by the injection pump 41. As typical devices and structures can be used for a fuel filter for removing impurities from the fuel and a mixing device for mixing the air taken from an air cleaner with the injected fuel, these devices are omitted from drawing and detailed descriptions thereof are also omitted.
As shown in
An oscillating plate 58 is arranged on the bottom of the ultrasonic fuel tank 51, and the ultrasonic transducer 54 is attached to the back of the oscillating plate 58. Typical piezoelectric ceramics can be used for the ultrasonic transducer 54. When a current is applied to the ultrasonic transducer 54, the oscillating plate 58 makes an oscillation, which generates ultrasonic waves to cause an oscillation in the fuel.
That is, when the electric power is supplied to the ultrasonic transducer 54 by the ultrasonic transducer controller 55, the ultrasonic transducer 54 causes the oscillation from the bottom of the fuel. Such oscillation causes molecules of the fuel to collide each other to transfer the oscillation among the molecules, and when the oscillation reaches the surface of the fuel, fuel particles on the surface of the fuel are emitted from the surface in a fine particle state. Therefore, when the depth of the fuel is too deep or too shallow, the fuel cannot be efficiently atomized. In addition, in order to secure the atomized fuel, the fuel atomizing space 514 needs to be a few times or more of the fuel storing space 513 in volume.
In this manner, as the atomization amount by the ultrasonic transducer 54 depends on the fuel level (that is, the height OL1 from the bottom to the surface of the fuel), it is required to maintain a proper level of the fuel accommodated in the fuel storing space 513. In the case of an ultrasonic transducer used in a typical humidifier, a proper height from the bottom to the surface of the water is about 20 mm to 50 mm, and the atomization amount in this case is about 200 ml to 500 ml per hour.
As shown in
As described above, in order to achieve an enough atomization of the fuel using the ultrasonic transducer 54, a proper height OL1 from the bottom to the surface of the fuel needs to be maintained. In some embodiments of the present invention, the opening amount of the valve 531 is controlled by the valve controller 532 such that the fuel is supplied from the fuel pump 20 by the amount atomized and consumed in the cylinder chamber 30. In some embodiments of the present invention, the valve 531 is always opened by a few millimeters using a manual valve switch (not shown) instead of using the valve controller 532 such that the fuel is supplied from the fuel pump 20 into the ultrasonic fuel tank 51 by the amount of the atomized fuel supplied to the cylinder chamber 30.
As shown in
In some embodiments of the present invention, the fuel gauge 533 detects the height OL1 of the surface of the fuel (i.e., the fuel level) indicating the amount of the fuel in the ultrasonic fuel tank 51, and outputs a detection result to the valve controller 532. Upon receiving the detection result from the fuel gauge 533, the valve controller 532 compares the height OL1 of the surface of the fuel detected by the fuel gauge 533 with a predetermined value and controls the opening amount of the valve 531 based on a result of the comparison. That is, when the result of the comparison says that the detected height OL1 of the surface of the fuel is larger than the predetermined value, the valve controller 532 closes the valve 531 to reduce or cut the fuel supplied to the ultrasonic fuel tank 51. On the contrary, when the result of the comparison says that the detected height OL1 of the surface of the fuel is smaller than the predetermined value, the valve controller 532 opens the valve 531 to start or increase the fuel supplied to the ultrasonic fuel tank 51.
When detecting the height OL1 of the surface of the fuel in the ultrasonic fuel tank 51 by the fuel gauge 533 while the internal combustion engine is being driven, the height OL1 of the surface of the fuel may randomly fluctuate due to the oscillation of the ultrasonic transducer 54 and the vibration caused by the driving of the internal combustion engine (for example, running of a vehicle driven by the internal combustion engine (diesel engine) according to some embodiments of the present invention).
For this reason, in some embodiments of the present invention, the fuel gauge 533 divides time sectors, obtains an average value of the height OL1 in each time sector, and outputs the average value of the height OL1 to the valve controller 532. In some embodiments of the present invention, the valve controller 532 divides time sectors and obtains an average value of the height OL1 inputted from the fuel gauge 533 in each time sector, to reduce an error caused by the random fluctuation of the height OL1.
As shown in
As described above, while the internal combustion engine is being driven, the height OL1 of the surface of the fuel randomly fluctuates due to eruptions of the surface of the fuel caused by the oscillation of the ultrasonic transducer 54 and vibrations caused by the driving of the internal combustion engine. In some embodiments of the present invention, the fuel level in the ultrasonic fuel tank 51 is more efficiently controlled using the level control fuel tank 534 that is separately provided.
As shown in
As the eruptions of the surface of the fuel due to the oscillation of the ultrasonic transducer 54 may affect the detection of the height OL1 more than the fluctuation due to the running of the vehicle, the fuel level in the ultrasonic fuel tank 51 can be controlled more efficiently by using the level control fuel tank 534 that is separately provided and receives less influence by the oscillation of the ultrasonic transducer 54.
The fuel gauge 535 detects the height OL2 of the surface of the fuel in the level control fuel tank 534 and outputs a result of the detection to the valve controller 532. Upon receiving the detection result from the fuel gauge 535, the valve controller 532 compares the height OL2 detected by the fuel gauge 535 with a predetermined value and controls the opening amount of the valve 531 based on a result of the comparison. That is, when the result of the comparison says that the detected height OL2 of the surface of the fuel is larger than the predetermined value, the valve controller 532 closes the valve 531 to reduce or cut the fuel supplied to the ultrasonic fuel tank 51. On the contrary, when the result of the comparison says that the detected height OL2 of the surface of the fuel is smaller than the predetermined value, the valve controller 532 opens the valve 531 to start or increase the fuel supplied to the ultrasonic fuel tank 51.
In order to improve the accuracy also in this case, the fuel gauge 535 divides time sectors, obtains an average value of the height OL1 in each time sector, and outputs the average value of the height OL2 to the valve controller 532, or the valve controller 532 divides time sectors and obtains an average value of the height OL2 inputted from the fuel gauge 535 in each time sector, to reduce an error caused by the random fluctuation of the height OL2.
An oil gauge, a float switch, or the like can be used for the fuel gauges 533 and 535.
When the ultrasonic transducer 54 is operated in a state in which the fuel in the ultrasonic fuel tank 51 runs out so that the bottom of the ultrasonic transducer 54 is exposed, a bonding portion is peeled off leading to a malfunction. In order to avoid this kind of situation, in some embodiments of the present invention, the amount of the fuel in the ultrasonic fuel tank 51 is constantly monitored using the fuel gauge 533 or 535. When it is determined that the fuel in the ultrasonic fuel tank 51 runs out, the ultrasonic transducer controller 55 stops the operation of the ultrasonic transducer 54.
When a result of the monitoring received from the fuel gauge 533 or 535 is lower than a predetermined amount, the ultrasonic transducer controller 55 determines that the fuel in the ultrasonic fuel tank 51 is fully consumed. In such a case, the ultrasonic transducer controller 55 outputs an alarm to prompt a driver to remove a cause or to output a signal for causing the valve controller 532 to immediately open the valve 531 to supply the fuel into the ultrasonic fuel tank 51.
Upon driving an internal combustion engine (for example, a diesel engine) employing the ultrasonic fuel supplying apparatus 50 according to some embodiments of the present invention, depending on the stroke of the combustion process, the atomized fuel in the ultrasonic fuel supplying apparatus 50 is drawn into the cylinder chamber 30. This causes the pressure inside the ultrasonic fuel tank 51 to be lower than the atmospheric pressure, generating a phenomenon that a wall of the ultrasonic fuel tank 51 is inwardly shrunken. For this reason, the air from the outside needs to be injected into the ultrasonic fuel tank 51 as appropriate, in order to maintain the normal pressure (atmospheric pressure) inside the ultrasonic fuel tank 51, even when the atomized fuel in the ultrasonic fuel tank 51 is drawn into the cylinder chamber 30.
As shown in
The diameter of the air inlet 512 is set smaller than the diameter of the spring 573 and the diameter of the spring 573 is set smaller than the diameter of the second end of the pin 571. In order for the pin 571 to travel back and forth inside the air inlet 512 and to allow the air flows between the outer circumference of the pin 571 and the inner wall of the air inlet 512, the diameter of the air inlet 512 is set larger than the diameter of the body of the pin 571.
Therefore, in a state in which the pin 571 is inserted through the spring 573, the pin 571 is inserted into the air inlet 512, and then, in a state in which the spring 573 is slightly compressed, the first end of the pin 571 and the caulking member 572 are attached to each other with the caulking member 572 making contact with the wall 511 from the inside. In this state, the tension of the spring 573 causes the caulking member 572 to be pulled towards the wall 511, achieving a tight contact between the caulking member 572 and the wall 511.
As shown in
When the atomized fuel in the ultrasonic fuel supplying apparatus 50 is drawn into the cylinder chamber 30 due to a driving of the internal combustion engine so that the pressure inside the ultrasonic fuel tank 51 decreases, As shown in
When the pressure inside the ultrasonic fuel tank 51 is low enough to cause a force for pulling the caulking member 572 inwards to exceed the tension of the spring 573, As shown in
When the injection of the air is enough to cause the pressure inside the ultrasonic fuel tank 51 to be back to the normal pressure, the tension of the spring 573 pulls the caulking member 572 towards the wall 511 so that the caulking member 572 makes contact with the wall 511 of the ultrasonic fuel tank 51 and the air inlet 512 is sealed with the caulking member 572.
Although the spring 573 is used as an example of the elastic member for providing the tension in the above embodiment, the present invention is not limited to this, but materials such as rubber, silicone, or the like having elasticity or a solenoid can be used as the elastic member.
In an apparatus for atomizing the fuel using the ultrasonic wave, the oscillation frequency of the ultrasonic transducer and the fuel level (depth of the fuel in which the ultrasonic transducer is submerged) greatly affects the amount of the atomization. For example, even when the same frequency is used, the atomization depends on the fuel level. For this reason, in some embodiments of the present invention, the fuel level in the ultrasonic fuel tank 51 is maintained in a predetermined range using the fuel level control unit 53.
In the ultrasonic fuel supplying apparatus 50, a fuel pillar is formed right above the ultrasonic transducer 54 in a direction perpendicular to a plane of the ultrasonic transducer 54, and the emitted particles form a high density area 563 of the atomized fuel right above the fuel pillar (see
As shown in
Further, the air intake port 57 is arranged at the wall 511 of the ultrasonic fuel tank 51 at a position higher than the opening 562 of the output pipe extending unit 561. When the air is injected into the ultrasonic fuel tank 51, the injected air may cause a perturbation inside the ultrasonic fuel tank 51. By setting the position of the air intake port 57 higher than the opening 562 of the output pipe extending unit 561, the area around the opening 562 where the atomized fuel is drawn into the output pipe 56 can experience less influence of the injected air.
As shown in
A prototype of the ultrasonic fuel supplying apparatus 50 was actually manufactured and applied to a diesel engine of a vehicle. A result of an experiment confirmed that the diesel engine was driven only with the atomized fuel supplied from the ultrasonic fuel supplying apparatus 50 according to some embodiments of the present invention in an RPM region that is used in the everyday life (equal to or lower than about 3,000 rpm) or when driving the vehicle at a constant speed with the engine RPM lower than 3,000 rpm.
A plastic container having a size of 14 cm×18 cm×9 cm (width×height×depth) was used for the ultrasonic fuel tank 51. As the ultrasonic transducer 54, a TDK ultrasonic transducer with a controller was used, which produces the atomization amount of about 200 ml per hour with the particle size of about 3 μm to 4 μm. Only a valve with the valve controller was used for the fuel level control unit 53 with the opening of the valve about 1 mm to 2 mm fixed. The fuel level from the bottom to the surface of the fuel was set to about 20 mm and constantly maintained. A total of four ultrasonic transducers were installed at the bottom of the plastic container, and the number of which was set ultrasonic transducers was set to be adjusted as appropriate in an actual operation.
The ultrasonic fuel supplying apparatus 50 manufactured in the above manner was applied to a diesel engine of a 1993 Hyundai Galloper to perform an engine driving experiment. The Galloper is a sports utility vehicle equipped with a 2.5 L (2,476 cc) diesel engine, which is a 4×4 vehicle with a manual five-speed transmission. The type of the engine is D4BX using the diesel with the maximum output of 73/4,200 ps/rpm, maximum torque of 14.9/2,500 kg*m/rpm, and the fuel efficiency of 17.3 km/l in the specification.
A fuel supply pipe connecting a fuel pump and an injection pump was cut, the pipe on the fuel pump side was connected to the input pipe 52 of the ultrasonic fuel supplying apparatus 50, and the pipe on the injection pump side was connected to the output pipe 56 of the ultrasonic fuel supplying apparatus 50. The fuel was supplied to the ultrasonic fuel tank 51 to set the fuel level to 25 mm. The fuel was atomized by oscillating the ultrasonic transducer 54 via the ultrasonic transducer controller 55, and then the engine started, and the accelerator was controlled to change the engine RPM.
The result of the experiment confirmed that, by atomizing the fuel of about 400 ml per hour using two ultrasonic transducers, without using the first fuel supply line that directly supplies the fuel from the main fuel tank 10 to the fuel injection unit 40 via the fuel pump 20, the engine was driven for about an hour using the second fuel supply line only in which the atomized fuel was supplied from the ultrasonic fuel supplying apparatus 50 to the fuel injection unit 40 while randomly changing the engine RPM below 3,000 rpm.
When the engine starts or when the engine RPM exceeds 3,000 rpm, the fuel density of the atomized fuel may not be enough. In some embodiments of the present invention, the internal combustion engine employing the ultrasonic fuel supplying apparatus 50 includes the valve 60 arranged between the fuel pump 20 and the fuel injection unit 40 to switch ON and OFF the fuel supply from the fuel pump 20 and the valve controller 70 for controlling the valve 60.
As shown in
As described above, according to some embodiments of the present invention, by driving an engine using the atomized fuel supplied from the ultrasonic fuel supplying apparatus 50 as the main fuel supply line or using the atomized fuel only in the RPM region used in the everyday life (hybrid mode), it is possible to greatly increase the fuel efficiency and to efficiently suppress the harmful exhaust gas.
In some embodiments of the present invention, using the atomized fuel supplied from the ultrasonic fuel supplying apparatus 50 as the main fuel supply line means that a proportion of the fuel supply from the fuel pump 20 (first fuel supply line) is equal to or less than 49% of the total fuel supply and a proportion of the atomized fuel supply from the ultrasonic fuel supplying apparatus 50 (second fuel supply line) is equal to or more than 51% of the total fuel supply.
In some embodiments of the present invention, using the atomized fuel supplied from the ultrasonic fuel supplying apparatus 50 as the main fuel supply line means that a proportion of the fuel supply from the fuel pump 20 (first fuel supply line) is equal to or less than 19% of the total fuel supply and a proportion of the atomized fuel supply from the ultrasonic fuel supplying apparatus 50 (second fuel supply line) is equal to or more than 81% of the total fuel supply.
In some embodiments of the present invention, using the atomized fuel supplied from the ultrasonic fuel supplying apparatus 50 only means that the fuel supply from the fuel pump 20 (first fuel supply line) is cut (0%) so that the atomized fuel supply from the ultrasonic fuel supplying apparatus 50 (second fuel supply line) takes 100% of the total fuel supply.
Although a diesel engine is used as an example of the internal combustion engine employing the ultrasonic fuel supplying apparatus according to some embodiments of the present invention, the present invention is not limited to this, but can be applied to any internal combustion engine using a fuel having the evaporation point of 150 degrees Celsius (for example, kerosene, diesel oil, heavy oil, and the like) and any combustion apparatus using such fuel, such as boiler, heater, electric generator, and the like.
In the case of an internal combustion engine or a combustion apparatus employing a specific start mechanism, it is possible to use the second fuel supply line only without using the first fuel supply line even at the time of starting the internal combustion engine or the combustion apparatus
Although the high RPM region is described to be an RPM region of equal to or higher than 3,000 rpm in the specification, this value can be changed depending on the type and the specification of the engine.
Further, various controllers for controlling various valves and ultrasonic transducers can be separately provided or can be integrated into an electronic control device such as an engine control unit (ECU) or an engine control module (ECM).
As shown in
A pump or a fan for sending the fuel from the main fuel tank 1110 to the combustion chamber 1130 or the atomized fuel from the ultrasonic fuel supplying apparatus 50 to the combustion chamber 1130 can be arranged at a proper position as appropriate.
Similar to the internal combustion engine, in the case of the combustion apparatus, the fuel accommodated in the main fuel tank 1110 is supplied to the combustion chamber 1130 via a first fuel supply line in which the fuel is directly supplied to the fuel injection unit 1140 in a liquid state and a second fuel supply line in which the fuel is atomized by the ultrasonic fuel supplying apparatus 50 and supplied to the fuel injection unit 1140 in an atomized state.
In the case of the combustion apparatus, by using the atomized fuel from the start to the normal operation status as the main fuel supply line or operating the combustion apparatus using the atomized fuel only, it is possible to greatly increase the fuel efficiency and to efficiently suppress the harmful exhaust gas.
As described above, according to some embodiments of the present invention, an ultrasonic fuel supplying apparatus capable of atomizing the fuel using an ultrasonic transducer and driving or operating an internal combustion engine or a combustion apparatus using the atomized fuel as a main fuel supply line or using the atomized fuel only can be provided.
Further, according to some embodiments of the present invention, the fuel consumption can be efficiently reduced and the harmful exhaust gas can be efficiently suppressed an internal combustion engine or a combustion apparatus using kerosene, diesel oil, heavy oil, and the like
The present disclosure should not be limited to these embodiments but various changes and modifications are made by one ordinarily skilled in the art within the subject matter, the spirit and scope of the present disclosure as hereinafter claimed. Specific terms used in this disclosure and drawings are used for illustrative purposes and not to be considered as limitations of the present disclosure. Exemplary embodiments of the present disclosure have been described for the sake of brevity and clarity. Accordingly, one of ordinary skill would understand the scope of the claimed invention is not to be limited by the explicitly described above embodiments but by the claims and equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2017-0026448 | Feb 2017 | KR | national |
| 10-2017-0026502 | Feb 2017 | KR | national |
| 10-2017-0026557 | Feb 2017 | KR | national |
| 10-2018-0023385 | Feb 2018 | KR | national |
This application is a continuation-in-part of International Application No. PCT/KR2018/002393, filed Feb. 27, 2018, which is based upon and claims the benefit of priority from Korean Patent Application No. 10-2017-0026448, filed on Feb. 28, 2017, Korean Patent Application No. 10-2017-0026502, filed on Feb. 28, 2017, Korean Patent Application No. 10-2017-0026557, filed on Feb. 28, 2017, Korean Patent Application No. 10-2018-0023385, filed on Feb. 27, 2018, the contents of which are incorporated herein by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/KR2018/002393 | Feb 2018 | US |
| Child | 16553953 | US |
