1. A cylinder cover is applied to a gas engine which is formed by transformation on the basis of a diesel engine and is characterized by comprising a cylinder cover bodyThe air cylinder cover comprises a first air inlet throat (1) and a second air inlet throat (2) of the air cylinder cover, wherein a first air inlet valve seat ring (3) is arranged in the first air inlet throat (1), a second air inlet valve seat ring (4) is arranged in the second air inlet throat (2), and the first air inlet valve seat ring (3) is away from the bottom surface of the air cylinder cover by the height H₁Is greater than the height H of the second intake valve seat ring (4) from the bottom surface of the cylinder head₂。

2. A cylinder head according to claim 1, characterized in that the first inlet valve seat insert (3) has a height H from the bottom surface of the cylinder head₁A height H from the second intake valve seat ring (4) to the bottom surface of the cylinder head₂Height difference H of₃Satisfies the relationship: h is more than 0₃Less than or equal to 0.2D, wherein D is the valve disc diameter of a first inlet valve arranged at the first inlet valve seat ring (3), or the valve disc diameter of a second inlet valve arranged at the second inlet valve seat ring (4).

3. The cylinder head of claim 1, wherein H is₃The following relations are satisfied: h is more than 0₃≤6mm。

4. The cylinder head according to claim 1, characterized in that the distance between the first intake throat (1) and the cylinder head intake port is smaller than the distance between the second intake throat (2) and the cylinder head intake port, a first intake chamfer (5) is formed below the first intake seat ring (3) corresponding to the first intake throat (1), and a second intake chamfer (6) is formed below the second intake seat ring (4) corresponding to the second intake throat (2).

5. A cylinder head according to claim 4, characterized in that the center of the first inlet chamfer (5) is offset by a first preset distance in the direction of the first exhaust throat (7) corresponding to the first inlet throat (1) with respect to the center of the first inlet throat (1); the center of the second air inlet chamfer (6) is offset by a second preset distance relative to the center of the second air inlet throat (2) towards the direction of a second exhaust throat (8) corresponding to the second air inlet throat (2).

6. The cylinder head according to claim 5, characterized in that said first preset distance is equal or unequal to said second preset distance.

7. A cylinder head according to claim 6, characterized in that the first inlet chamfer (5) and the second inlet chamfer (6) are rounded chamfers.

8. The cylinder head of claim 7, wherein the longitudinal section of the leading wall surface of the revolving chamfer is a straight line or a curved line.

9. The cylinder head according to claim 7, wherein a longitudinal section of the guide wall surface of the revolving chamfer is a curve convex toward the cylinder interior.

10. A cylinder head according to claim 7, characterized in that the centre line of revolution of the first inlet chamfer (5) is parallel with respect to the axis of the first inlet throat (1); the revolution center line of the second air inlet chamfer (6) is parallel to the axis of the second air inlet throat (2).

11. A cylinder head according to claim 7, characterized in that the centre line of revolution of the first inlet chamfer (5) is arranged obliquely to the axis of the first inlet throat (1) and with the lower end opening of the first inlet chamfer (5) arranged towards its corresponding first exhaust throat (7).

12. A cylinder head according to claim 11, characterized in that the centre line of revolution of the first inlet chamfer (5) is inclined by 30 ° or less with respect to the axis of the first inlet throat (1).

13. A cylinder head according to claim 7, characterized in that the centre line of revolution of the second inlet chamfer (6) is arranged obliquely to the axis of the second inlet throat (2) and with the lower end opening of the second inlet chamfer (6) arranged towards its corresponding second exhaust throat (8).

14. A cylinder head according to claim 13, characterized in that the centre line of revolution of the second inlet chamfer (6) is inclined by 30 ° or less with respect to the axis of the second inlet throat (2).

15. A cylinder head according to claim 4, characterized in that the first inlet chamfer (5) is identical to the second inlet chamfer (6).

16. A cylinder head according to claim 4, characterized in that the length of the guide wall surface of the first intake chamfer (5) is greater than the length of the guide wall surface of the second intake chamfer (6).

17. The cylinder head of claim 4, wherein the head intake port is disposed in a side or top or bottom surface of the cylinder head.

18. A gas engine comprising a cylinder head, characterized in that the cylinder head is a cylinder head according to any one of claims 1-17.

Background

With the development of gas engine technology, more and more gas engines are transformed on the basis of diesel engines at present. In the case of a diesel engine, the combustion mode is diffusion combustion, and a certain degree of swirl helps the oil bundles to mix with air, thereby improving the combustion process, so that an air inlet passage in the cylinder head of the engine is required to organize the air flow to generate a sufficient swirl ratio during the intake process. Wherein, the vortex refers to the gas rotational flow movement organized around the cylinder axial direction.

However, the combustion mode of the gas engine is premixed combustion, the requirement on the strength of vortex is not high, and small-scale turbulent motion is needed to form a flame wrinkle surface, so that the flame propagation speed is increased, and the heat efficiency is improved, wherein the turbulent motion refers to small rotational flow which is generated in a flow field when the air flow speed is high and has unfixed directions, and is different from laminar motion. For a gas engine, the strength of the vortex does not need to be increased, and the increase of the tumble strength in the cylinder can be beneficial to forming turbulence at the end of compression and generating enough turbulent kinetic energy when the piston moves up to the top dead center, so that the aim of optimizing combustion is fulfilled. Wherein, the tumble refers to the gas rotational flow motion of which the rotation central axis is vertical to the axial direction of the cylinder sleeve.

Therefore, for the existing gas engine cylinder cover which is designed by integrally modifying the diesel engine cylinder cover, tumble flow required by the gas engine is difficult to generate in the cylinder.

In summary, how to improve tumble effect in a combustion chamber of a developed gas engine on the basis of improving a diesel engine has become a technical problem to be solved by those skilled in the art.

Disclosure of Invention

The invention aims to provide a cylinder cover and a gas engine, which are used for improving the tumble effect in a combustion chamber of a developed gas engine on the basis of improving a diesel engine.

In order to achieve the purpose, the invention provides a cylinder cover, which is applied to a gas engine reformed on the basis of a diesel engine and comprises a first air inlet throat opening and a second air inlet throat opening which are formed on the cylinder cover, wherein a first air inlet valve seat ring is arranged in the first air inlet throat opening, a second air inlet valve seat ring is arranged in the second air inlet throat opening, and the height H from the first air inlet valve seat ring to the bottom surface of the cylinder cover₁Is greater than theHeight H of second intake valve seat ring from bottom surface of cylinder cover₂。

Preferably, the height H of the first intake valve seat from the bottom surface of the cylinder head₁The height H from the second air inlet valve seat ring to the bottom surface of the cylinder cover₂Height difference H of₃Satisfies the relationship: h is more than 0₃Less than or equal to 0.2D, wherein D is the valve disc diameter of the first intake valve installed at the first intake valve seat ring, or the valve disc diameter of the second intake valve installed at the second intake valve seat ring.

Preferably, H₃The following relations are satisfied: h is more than 0₃≤6mm。

Preferably, the distance between the first air inlet throat and the cylinder cover air inlet is smaller than the distance between the second air inlet throat and the cylinder cover air inlet, a first air inlet chamfer is formed below the first air inlet throat corresponding to the first air inlet seat ring, and a second air inlet chamfer is formed below the second air inlet throat corresponding to the second air inlet seat ring.

Preferably, the center of the first air inlet chamfer is offset by a first preset distance relative to the center of the first air inlet throat towards the direction of a first exhaust throat corresponding to the first air inlet throat; and the center of the second air inlet chamfer is offset by a second preset distance relative to the center of the second air inlet throat towards the direction of a second exhaust throat corresponding to the second air inlet throat.

Preferably, the first preset distance and the second preset distance are equal or different.

Preferably, the first and second air intake chamfers are rounded chamfers.

Preferably, the longitudinal section of the guide wall surface of the revolving chamfer is a straight line or a curved line.

Preferably, a longitudinal section of the guide wall surface of the rotation chamfer is a curve protruding toward the cylinder inner direction.

Preferably, the revolution center line of the first air inlet chamfer is parallel to the axis of the first air inlet throat; the revolution center line of the second air inlet chamfer is parallel to the axis of the second air inlet throat.

Preferably, the center line of gyration of the first intake chamfer is arranged obliquely with respect to the axis of the first intake throat and the lower end opening of the first intake chamfer is arranged toward the direction of the corresponding first exhaust throat thereof.

Preferably, the revolution center line of the first air inlet chamfer is inclined by 30 degrees or less relative to the axis of the first air inlet throat.

Preferably, the revolution center line of the second air intake chamfer is arranged obliquely relative to the axis of the second air intake throat and the lower end opening of the second air intake chamfer is arranged toward the direction of the corresponding second exhaust throat.

Preferably, the revolution center line of the second air inlet chamfer is inclined by 30 degrees or less relative to the axis of the second air inlet throat.

Preferably, the first air intake chamfer is the same as the second air intake chamfer.

Preferably, the guide wall surface of the first air intake chamfer has a length greater than that of the second air intake chamfer.

Preferably, the head inlet is arranged in a side or top or bottom face of the cylinder head.

Compared with the introduction content of the background technology, the cylinder cover is applied to the gas engine which is formed by transformation on the basis of the diesel engine, and comprises a first air inlet throat opening and a second air inlet throat opening which are formed in the cylinder cover, wherein a first air inlet valve seat ring is arranged in the first air inlet throat opening, a second air inlet valve seat ring is arranged in the second air inlet throat opening, and the height H of the first air inlet valve seat ring from the bottom surface of the cylinder cover₁Is greater than the height H of the second air inlet valve seat ring from the bottom surface of the cylinder cover₂. In the actual working process of the cylinder cover, when an engine cylinder inhales air, the first/second air inlet valve is opened, air flow enters the cylinder from the first air inlet valve seat ring and the second air inlet valve seat ring of the cylinder cover, and the height H of the first air inlet valve seat ring from the bottom surface of the cylinder cover₁Is greater than the height H of the second air inlet valve seat ring from the bottom surface of the cylinder cover₂Therefore, the opposite air flows in the direction of the central connecting line of the two inlet valves are not opposite to each otherThe symmetrical structure is compared in two traditional intake valve seat insert symmetrical arrangement's mode, can effectively reduce two ascending air current offset interference of intake valve central line side, then reduces the loss of air current kinetic energy, is favorable to promoting the tumble flow effect in the combustion chamber more.

In addition, the invention also provides a gas engine, which comprises a cylinder cover, wherein the cylinder cover is the cylinder cover described in any scheme, and the cylinder cover has the technical effects, so that the gas engine with the cylinder cover also has the corresponding technical effects, and the details are not repeated.

Drawings

FIG. 1 is a schematic structural view of two intake valve races provided in an embodiment of the present invention disposed at different heights;

FIG. 2 is a schematic diagram illustrating arrangement of two intake throat openings and a cylinder head intake port at different intervals according to an embodiment of the present invention;

FIG. 3 is a schematic structural view of an exemplary eccentric chamfer for a first air intake chamfer provided in an embodiment of the present invention;

FIG. 4 is a schematic view of an inlet flow from an inlet throat to an exhaust throat provided in an embodiment of the present invention;

FIG. 5 is a schematic structural diagram of two intake valve races at different heights respectively provided with intake valves in the embodiment of the invention;

FIG. 6 is a schematic view of simulation of the movement of air flow in a combustion chamber of a conventional two intake valve seat ring symmetrical arrangement;

FIG. 7 is a schematic representation of a simulation of airflow movement within a combustion chamber for an arrangement of two intake valve seats one high and one low as provided in an embodiment of the present invention;

fig. 8 is a graph comparing the tumble ratio of the present invention solution with the prior art solution.

In the context of figures 1-7,

the air inlet valve seat ring comprises a first air inlet throat 1, a second air inlet throat 2, a first air inlet seat ring 3, a second air inlet seat ring 4, a first air inlet chamfer 5, a second air inlet chamfer 6, a first exhaust throat 7, a second exhaust throat 8, a first air inlet throat axis 9 and a first air inlet chamfer gyration central line 10.

Detailed Description

The core of the invention is to provide the cylinder cover and the gas engine, so as to improve the tumble effect in the combustion chamber of the developed gas engine on the basis of improving the diesel engine.

In order to make those skilled in the art better understand the technical solutions provided by the present invention, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

As shown in figures 1-5, the embodiment of the invention provides a cylinder cover, which is applied to a gas engine reformed on the basis of a diesel engine, and comprises a first air inlet throat 1 and a second air inlet throat 2 which are formed on the cylinder cover, wherein a first air inlet valve seat ring 3 is arranged in the first air inlet throat 1, a second air inlet valve seat ring 4 is arranged in the second air inlet throat 2, and the height H of the first air inlet valve seat ring 3 from the bottom surface of the cylinder cover₁Is larger than the height H of the second air inlet valve seat ring 4 from the bottom surface of the cylinder cover₂。

In the actual working process of the cylinder cover, when an engine cylinder inhales air, the first/second air inlet valve is opened, air flow enters the cylinder from the first air inlet valve seat ring and the second air inlet valve seat ring of the cylinder cover, and the height H of the first air inlet valve seat ring from the bottom surface of the cylinder cover₁Is greater than the height H of the second air inlet valve seat ring from the bottom surface of the cylinder cover₂Therefore, two ascending offset airflows of (air) intake valve central line direction are the asymmetric structure of one on the other, compare in two traditional (air) intake valve seat insert symmetrical arrangement's mode, can effectively reduce two ascending air flow offset interferences of (air) intake valve central line direction, reduce the air current kinetic energy loss then, are favorable to promoting the tumble flow effect in the combustion chamber more.

Referring to fig. 8, compared with the prior art (i.e. the prior art does not have a cylinder head scheme in which the intake valve seat is designed in a high-low manner), in the process that the valve lift gradually increases, because the present scheme uses two intake valve seats with different heights to avoid the collision of the air flow in the middle area of the two intake valves, higher intake energy can be maintained, so that the tumble motion is more stable and the intensity is higher, particularly in the stage of the large valve lift, the higher first intake valve seat 3 can organize the air flow by using a longer guide distance below the higher first intake valve seat, so that the tumble ratio formed in the cylinder is larger.

In order to better understand the technical effect achieved by the technical scheme of the invention, the air flow motion in the combustion chamber of the traditional symmetrical arrangement structure of two intake valve seat rings is simulated as shown in fig. 6, the air flow motion in the combustion chamber of the arrangement structure of two intake valve seat rings with one higher and one lower as shown in fig. 7 is simulated, and the obvious large-scale tumble effect of the air flow entering the cylinder cover from the valve can be observed through simulation calculation after the intake valve seat rings are arranged in different heights.

In some specific embodiments, the height H of the first intake valve seat insert 3 from the bottom surface of the cylinder head₁Height H from the second intake valve seat ring 4 to the bottom surface of the cylinder head₂Height difference H of₃Specifically, the relationship: h is more than 0₃And D is not more than 0.2D, wherein D is the valve disc diameter of the first inlet valve arranged at the first inlet valve seat ring 3 or the valve disc diameter of the second inlet valve arranged at the second inlet valve seat ring 4. H is found by simulation test₃The above relationship is set, so that a good tumble effect can be generated in most engine models.

It is understood that the above relation is only the preferred value taking mode given by the invention after the simulation of the mainstream engine model, and in the practical application process, other corresponding value taking ranges, such as H, can be selected according to the specific engine model₃The selection and meeting relationship can also be selected according to the configuration requirements of different machine types as follows: h is more than 0₃Less than or equal to 1 mm; or 0 < H₃Less than or equal to 2 mm; or 0 < H₃Less than or equal to 3 mm; or 0 < H₃Less than or equal to 4 mm; or 0 <H₃Less than or equal to 5 mm; or 0 < H₃Less than or equal to 6mm, and the like. In the practical application process, the selection can be performed according to the practical requirements, and is not specifically limited herein.

It should be noted that, as will be understood by those skilled in the art, the first intake throat 1 communicates with an intake port outside the cylinder head through a first intake passage in the cylinder head, and the second intake throat 2 communicates with an intake port outside the cylinder head through a second intake passage in the cylinder head, wherein the first intake passage and the second intake passage are mainly used for guiding airflow. A first air inlet valve seat ring 3 is arranged in the first air inlet throat 1 and is used for being matched with a first air inlet valve to open and close so as to realize the on-off control of air inlet; and a second air inlet valve seat ring 4 is arranged in the second air inlet throat 2 and is used for being matched with a second air inlet valve to open and close so as to realize the on-off control of air inlet.

In addition, as will be appreciated by those skilled in the art, an engine cylinder head typically has intake and exhaust ports located on opposite sides of the cylinder head in the longitudinal direction, with the intake port responsible for organizing the air flow during intake of the engine. In general, in the case of a diesel engine, a connecting line of centers of two intake valves and a connecting line of centers of a crankshaft of the engine form a certain angle alpha, which inevitably results in that one of the two intake valves is closer to an intake side and the other valve is farther from the intake side. Because the distances from the intake valve to the intake side are different, the intake passage close to the intake side is generally designed to be shorter and thicker, and because the space of the intake passage is limited, the tumble ratio is limited by only changing the shape of the inner wall of the intake passage to increase the tumble ratio.

Therefore, as shown in fig. 1 and 2, when the first intake throat 1 is spaced from the cylinder head intake port by a distance L₁Is less than the distance L between the second air inlet throat 2 and the cylinder cover air inlet₂When the height H of the first air inlet valve seat ring 3 which is closer to the air inlet of the cylinder cover from the bottom surface of the cylinder cover₁Designed to be higher than the height H of the second intake valve seat ring 4 from the bottom surface of the cylinder head₂The circulation capacity of the air passage can be improved to the maximum extent on the premise of ensuring the tumble ratio of the air passage. The basic principle is that the height of the first inlet valve seat ring 3 relative to the bottom surface of the cylinder head is higherIn the process of opening the first air inlet valve, the flow guiding length of the guiding wall below the first air inlet valve seat ring 3 can be further prolonged, so that tumble flow is generated more favorably. Meanwhile, due to the fact that the airflow is guided by the guide wall, and the valve disc corresponding to the first air inlet valve is closer to the bottom surface of the cylinder cover when the first air inlet valve is opened along with the increase of the first air inlet valve seat ring, the airflow is more favorable for moving towards a target direction (towards the direction of the first exhaust throat opening 7), and meanwhile, the airflow interference in the direction of the central connecting line of the two air inlet valves is reduced. The specific form of the flow guiding structure below the air inlet seat ring can be that a first air inlet chamfer 5 is formed below the first air inlet throat 1 corresponding to the first air inlet seat ring 3, and a second air inlet chamfer 6 is formed below the second air inlet throat 2 corresponding to the second air inlet seat ring 4.

In some specific embodiments, the first air inlet chamfer 5 and the second air inlet chamfer 6 may be designed specifically as follows: the center of the first air inlet chamfer 5 is deviated by a first preset distance towards the direction of a first exhaust throat 7 corresponding to the first air inlet throat 1 relative to the center of the first air inlet throat 1; the center of the second air inlet chamfer 6 is offset by a second preset distance relative to the center of the second air inlet throat 2 towards the direction of a second exhaust throat 8 corresponding to the second air inlet throat 2. Because the first/second air inlet chamfers have obvious flow guiding effect, and as shown in fig. 3, the first air inlet chamfers 5 are designed to be deviated towards the first exhaust throat opening 7, so that the width of a gap on one side close to the first exhaust throat opening 7 is larger, most of the air flow enters the air cylinder from the gap on one side close to the first exhaust throat opening 7, the air flow on one side far away from the first exhaust throat opening 7 is reduced, and the air flows on the two sides are easier to form large-scale tumble motion after entering the air cylinder. Similarly, the second air inlet chamfer 6 is designed to be deviated towards the second exhaust throat 8, so that the width of the gap on one side close to the second exhaust throat 8 is larger, most of the air flow enters the cylinder from the gap on one side close to the second exhaust throat 8, the air flow on one side far away from the second exhaust throat 8 is reduced, and the air flows on the two sides are easier to form large-scale tumble motion after entering the cylinder.

Therefore, on the basis of the existing diesel engine, the first/second air inlet chamfers are designed into the eccentric chamfers, so that the effective diversion of the air inlet flow is realized, the tumble strength is favorably enhanced, the turbulent flow is favorably formed at the last stage of compression, and the heat efficiency of the gas engine is improved.

It should be noted that, in the practical application process, the first preset distance and the second preset distance may be designed to be equal or unequal, and may be selected according to the practical requirements.

In addition, the first air intake chamfer 5 and the second air intake chamfer 6 may be both a rotary chamfer or a non-rotary chamfer, and may be selected according to actual requirements in the practical application process.

In a further embodiment, the chamfer structure with different longitudinal section shapes can be obtained according to different rotary processing surfaces, for example, after the cylinder cover material is removed by adopting a conical rotary processing surface, the longitudinal section of the guide wall surface of the chamfer structure is in a linear structure. In practical application, the longitudinal section of the guide wall surface of the chamfer structure can be a straight line or a curve.

Further, the longitudinal section of the guide wall surface of the chamfer structure is preferably a curve protruding towards the inner direction of the cylinder, as shown in fig. 3, in the scheme, the chamfer surface protruding towards the inner side of the cylinder can prevent airflow from flowing and separating when the airflow passes through the chamfer, and is beneficial to improving the tumble effect of the airflow.

The gyration center line 10 of the first air inlet chamfer 5 can be arranged in parallel or inclined relative to the axis 9 of the first air inlet throat 1; similarly, the rotation center line of the second air inlet chamfer 6 can be arranged in parallel or inclined relative to the axis of the second air inlet throat 2. In the practical application process, the air inlet chamfering device can be configured according to specific requirements, and the first air inlet chamfering and the second air inlet chamfering are preferably arranged in the same arrangement mode.

For example, the gyration central line 10 of the first air inlet chamfer 5 is obliquely arranged relative to the axis 9 of the first air inlet throat 1 and the lower end opening of the first air inlet chamfer 5 is arranged towards the corresponding first exhaust throat 7; likewise, the center line of gyration of the second intake chamfer 6 is arranged obliquely with respect to the axis of the second intake throat 2 and with the lower end opening of the second intake chamfer 6 arranged towards its corresponding second exhaust throat 8. By the arrangement, a wider chamfer surface can be processed at the edge of one side of the air inlet throat close to the exhaust throat, and meanwhile, the transition between the chamfer surface at the side and the bottom surface of the cylinder cover and the wall surface of the air inlet throat is smoother, so that the kinetic energy loss of airflow flowing through the air inlet chamfer is reduced.

The inclination angle of the gyration center line of the first air inlet chamfer relative to the axis of the first air inlet throat and the inclination angle of the gyration center line of the second air inlet chamfer relative to the axis of the second air inlet throat can be designed to be equal or different. In a further embodiment, the setting of the selectable value range of the inclination of the rotation center line of the first air inlet chamfer 5 relative to the axis of the first air inlet throat 1 is different for different engine models, for example, the selectable value range can be 0-30 degrees, 0-20 degrees, 0-10 degrees or 0-5 degrees; similar to the inclination angle of the rotation center line of the first air inlet chamfer, the rotation center line of the second air inlet chamfer 6 is set in an optional value range of 0-30 degrees, 0-20 degrees, 0-10 degrees or 0-5 degrees relative to the inclination angle of the axis of the second air inlet throat 2.

It should be further noted that the first air inlet chamfer 5 and the second air inlet chamfer 6 can be designed to have the same structure and size; the structure and the size of the device can be designed to be different, and the device can be selected according to actual requirements in the actual application process. For example, as shown in fig. 1, the length of the guide wall surface of the first inlet chamfer 5 is greater than the length of the guide wall surface of the second inlet chamfer 6, when the distance L between the first inlet throat 1 and the cylinder head inlet is larger than the distance L between the first inlet throat 1 and the cylinder head inlet₁Is less than the distance L between the second air inlet throat 2 and the cylinder cover air inlet₂When the air conditioner is arranged, the diversion length is favorably increased, so that tumble flow is more favorably generated.

In a further embodiment, the cylinder head air inlet can be specifically arranged on the side face or the top face or the bottom face of the cylinder head, and in the practical application process, the air inlet can be selectively arranged according to the practical requirements, so that the installation and arrangement of engines of different models can be realized.

In addition, the invention also provides a gas engine, which comprises a cylinder cover, wherein the cylinder cover is the cylinder cover described in any scheme, and the cylinder cover has the technical effects, so that the gas engine with the cylinder cover also has the corresponding technical effects, and the details are not repeated.

The cylinder head and the gas engine provided by the invention are described in detail above. It should be noted that, in the present specification, the embodiments are all described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments may be referred to each other.

It is also noted that, in this document, terms such as "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that an article or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such article or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in an article or device that comprises the element.

The principles and embodiments of the present invention are explained herein using specific examples, which are presented only to assist in understanding the core concepts of the present invention. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.