Device and method for braking and vehicle using same

The present invention relates to a device and a method for braking, and a vehicle comprising the same. The present invention has an effect of easily releasing a braking force of a parking brake by switching between a first state, in which first and second lines of a service brake are connected and first and second lines of the parking brake are connected, and a second state, in which the first line of the service brake and the second line of the parking brake are connected.

CROSS REFERENCE TO RELATED APPLICATION AND CLAIM OF PRIORITY

This application claims benefit under 35 U.S.C. 119(e), 120, 121, or 365(c), and is a National Stage entry from International Application No. PCT/KR2014/007997, filed Aug. 28, 2014, which claims priority to and the benefit of Korean Patent Application Nos. 10-2013-0102383 filed in the Korean Intellectual Property Office on Aug. 28, 2013, and 10-2014-0112985 filed in the Korean Intellectual Property Office on Aug. 28, 2014, the entire contents of which are incorporated herein by reference.

BACKGROUND

Technical Field

The present invention relates to a vehicle braking technology, and more particularly, to a device and method for braking.

Background Art

A brake device is a mechanical device that uses a force generated by an operating force of a driver or an auxiliary power, e.g. a friction force, to convert kinetic energy of vehicles including a car, heavy equipment, etc. to thermal energy in order to perform braking. Brake devices used in the vehicles, etc. include a service brake that operates by a driver's operation during driving and a parking brake that operates by a driver's operation for stopping or parking a vehicle.

The brake devices are classified as friction type and non-friction type depending on whether a friction force is used or not. The friction type includes a vacuum brakes air hydraulic brake, etc. and the non-friction type includes an electronic brake, a fluid type brake, etc. The hydraulic type among the friction type brakes is used in most cars, and a driver's force of stepping on a pedal is transferred via hydraulic pressure to be converted to a braking force on wheels. Also, the air brake is used much in large vehicles including a bus, a truck, etc.

Meanwhile, the brake devices may be classified as a positive brake system and a negative brake system. The positive brake system refers to a brake system that is operated so that a pressure is supplied to brake disks that are basically not in contact so that the brake disks comes in contact for stopping a vehicle or lowering a speed of the vehicle. Conversely, the negative brake system refers to a brake system that is operated so that a pressure is supplied to brake disks that are basically in contact so that the brake disks are detached for moving a vehicle.

Here, in the negative brake system, although a brake in a normal state operates by a release of a pressure under a driver's control, in a situation where a vehicle stalls while driving, a situation where an engine has stopped abnormally, a situation where an abnormality has occurred in an electric system, and a situation where an abnormality has occurred in a hydraulic or pneumatic system, a pressure supplied to a parking brake is automatically released to be in a state where a braking force of the parking brake is applied.

In such an emergency situation, in order to repair the vehicle, the braking force caused by the parking brake has to be released or the vehicle itself has to be lifted and carried.

Here, the braking force caused by the parking brake must be released when moving the vehicle itself is impossible or difficult, and for this, a method of releasing the braking force has been used conventionally where a brake system itself is disassembled or hole is made that communicates with a brake chamber to supply a pressure to a brake by a separate pressure supplying means.

However, since the work required for disassembling the brake system itself in the vehicle or artificially making a hole at the brake system to supply the pressure, the work has to be done by an expert using specific equipment for a long time.

Meanwhile, when a pressure supplied to a parking brake is automatically released due to an abnormality such as a failure of a service brake that occurs during driving a vehicle, the vehicle suddenly stops due to a braking force being applied to the parking brake. In this manner, when the vehicle suddenly stops by the parking brake, a dangerous situation may occur in which a driver or an occupant collides with an inner structure of the vehicle by severely leaning to one side, the vehicle spins out of control due to losing balance, etc.

SUMMARY

The present invention is directed to providing a device and method capable of easily releasing a state in which a braking force of a parking brake has been applied in an emergency state in a vehicle, etc. with a negative brake system applied.

In addition, the present invention is directed to providing a device and method in which a worker may easily release the state in which a braking force of a parking brake is applied by using only a simple operation of a parking releasing valve to apply a service brake.

The present invention is directed to providing a device and method capable of preventing a dangerous situation caused by a sudden braking of a parking brake.

In accordance with an embodiment of the present invention, a brake device is a brake device being used in a negative brake system, and includes a first line of a service brake capable of supplying or withdrawing a pressure to apply or release a braking force of the service brake, a first line of a parking brake capable of supplying or withdrawing a pressure to apply or release a braking force of the parking brake, a second line of the service brake connected to a first chamber at one side of brake disks to supply a pressure to the first chamber, a second line of the parking brake connected to a second chamber at the other side of the brake disks to supply a pressure to the second chamber, and a parking releasing valve capable of switching between a first state in which the first and the second lines of the service brake communicate with each other and the first and the second lines of the parking brake communicates with each other and a second state in which the first line of the service brake and the second line of the parking brake communicate with each other.

The second state may be a state in which the first line of the parking brake and the second line of the service brake are disconnected therebetween.

In the second state switched by the parking releasing valve, a parking brake may be released by a pressure being supplied via the first line of the service brake and the second line of the parking brake.

The parking releasing valve includes a spool inserted into a valve hole communicating with each of the first line of the service brake, the first line of the parking brake, the second line of the service brake, and the second line of the parking brake, wherein the spool may move between a first position causing the first state and a second position causing the second state.

A position at which the first and the second lines of the service brake communicate with the valve hole may be located more inward in the valve hole than a position at which the first and the second lines of the parking brake communicate with the valve hole.

The valve hole may include a first hole part forming a cylindrical hole and a second hole part connected to an inner end portion of the first hole part and forming a cylindrical hole having a smaller diameter than a diameter of the first hole part, and the spool may include a first cylindrical main body part having an outer surface formed in a shape corresponding to the first hole part and a second cylindrical main body part connected to an end portion of the first cylindrical main body part and having an outer surface formed in a shape corresponding to the second hole part.

When the spool is at the first position, the first and the second lines of the service brake may communicate with the valve hole at the second hole part, and the first and the second lines of the parking brake may communicate with the valve hole at the first hole part.

The first position may be a position where an inner end portion of the spool is located more outward in the valve hole than the position at which the first and second lines of the service brake communicate with the valve hole.

The second position may be a position where the inner end portion of the spool is located more inward in the valve hole than the position at which the first line of the service brake communicates with the valve hole.

When the spool is at the first position, the first and the second lines of the service brake may communicate with each other more inward in the valve hole than the inner end portion of the spool, and the first and the second lines of the parking brake may communicate with each other more outward in the valve hole than the inner end portion of the spool.

The spool may include a spool main body forming an exterior of the spool, a spool groove formed at the spool main body up to a predetermined position in the longitudinal direction, a spool first pipe channel formed from an inside of the spool groove to a radial outer surface of the spool main body to communicate with the first line of the service brake when the spool is at the second position, and a spool second pipe channel formed from an inside of the spool groove to the radial outer surface of the spool main body to communicate with the second line of the parking brake when the spool is at the second position.

The spool first pipe channel may be formed from an inner end portion of the spool groove to the radial outer surface of the spool main body, and the spool may include a spool ball located inside the spool groove, an elastic member having one end elastically supporting the spool ball such that the spool ball is located at the inner end portion of the spool groove, and a support part to support the other end of the elastic member.

The spool may include a first cylindrical main body part forming an exterior of the spool, a second cylindrical main body part having one end connected to one end portion of the first cylindrical main body part and having a smaller diameter than the first cylindrical main body part, and an insertion end portion connected to one end portion of the second cylindrical main body part.

The brake device may further include a control unit to control supply and withdrawal of a pressure in a parking brake line such that a braking force releasing interval of the parking brake exists in addition to a braking force applying interval of the parking brake when a vehicle is stopped by the parking brake when an emergency state of the vehicle occurs.

The brake device may further include a valve provided on the first line of the parking brake, and the control unit may control braking force application of the parking brake and braking force release of the parking brake by controlling the valve to be turned on and off.

The valve may be a proportional valve.

The control unit may control such that the braking force application of the parking brake and the braking force release of the parking brake are repeated.

The control unit may adjust a frequency with which the braking force application and the braking force release of the parking brake are repeated depending on a speed of the vehicle.

The control unit may increase the frequency with which the braking force application and the braking force release of the parking brake are repeated with increasing speed of the vehicle.

In accordance with an embodiment of the present invention, a braking method is a braking method of a negative brake system, and includes a first step of being switched from a first state in which a first line of a service brake capable of supplying or withdrawing a pressure to apply or release a braking force of the service brake is connected to a first chamber at one side of brake disks to communicate with a second line of the service brake capable of supplying a pressure to the first chamber and a first line of a parking brake capable of supplying or withdrawing a pressure to apply or release a braking force of the parking brake is connected to a second chamber at the other side of the brake disks to communicate with a second line of the parking brake capable of supplying a pressure to the second chamber to a second state in which the first line of the service brake and the second line of the parking brake communicate with each other, and a second step in which a pressure is supplied via the first line of the service brake and the second line of the parking brake to release the braking force of the parking brake.

The second state may be a state in which the first line of the parking brake and the second line of the service brake are disconnected therebetween.

In the first step, the switching from the first state to the second state may be performed by a parking releasing valve connected to the first and second lines of the service brake and the first and second lines of the parking brake, the parking releasing valve may include a spool inserted into a valve hole that communicates with each of the first line of the service brake, the first line of the parking brake, the second line of the service brake, and the second line of the parking brake, and the spool may move between a first position causing the first state and a second position causing the second state.

The first position may be a position where an inner end portion of the spool is located more outward in the valve hole than the position at which the first and the second lines of the service brake communicate with the valve hole.

The second position may be a position where the inner end portion of the spool is located more inward in the valve hole than the position at which the first line of the service brake communicates with the valve hole.

When the spool is at the first position, the first and the second lines of the service brake may communicate with each other more inward in the valve hole than the inner end portion of the spool, and the first and the second lines of the parking brake may communicate with each other more outward in the valve hole than the inner end portion of the spool.

Before the first step, the braking method may further include detecting an occurrence of an emergency state of a vehicle in a negative brake system, and stopping the vehicle using a parking brake when the occurrence of an emergency state of the vehicle is detected, and, in the stopping of the vehicle, a braking force releasing interval of the parking brake in addition to a braking force applying interval of the parking brake may exist while the vehicle is stopping.

In the stopping of the vehicle, the braking force application by the parking brake and the braking force release by the parking brake may be repeated.

In the stopping of the vehicle, a frequency with which the braking force application and the braking force release of the parking brake are repeated may be adjusted depending on a speed of the vehicle.

In the stopping of the vehicle, the frequency with which the braking force application and the braking force release of the parking brake are repeated may increase with increasing speed of the vehicle.

The present invention has an effect of easily releasing a state in which a braking force caused by a parking brake has been applied due to an emergency in a vehicle, etc. with a negative brake system applied.

In addition, the present invention has an effect of enabling a worker to easily release the state in which a braking force of a parking brake has been applied by using only a simple operation of a parking releasing valve to apply a service brake.

In accordance with an embodiment of the present invention, a vehicle may be gradually stopped while preventing a sudden stop caused by a parking brake when an emergency state of the vehicle occurs. Thus, the present invention has an effect of protecting an occupant and a vehicle from a dangerous situation caused by a sudden stopping of the vehicle when an emergency state of the vehicle occurs.

DETAILED DESCRIPTION

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, when detailed description of a known art related to the present invention is deemed to make the gist of the present invention unnecessarily vague, the detailed description thereof will be omitted. Also, terms used below are terms defined by considering functions in the present invention and may be different depending on intention or practice of a user and an operator. Thus, the terms should be defined based on content throughout this specification.

Meanwhile, the technical spirit of the present invention is determined by the claims, and the embodiments below are only a means for efficiently describing the technical spirit of the present invention to those of ordinary skill in the art to which the present invention pertains.

Hereinafter, referring toFIGS. 1 to 6, details of a brake device in accordance with a first embodiment of the present invention and compositions and actions, etc. of brake devices in accordance with the first embodiment of the present invention in a state where a parking brake is released when a vehicle is stalled or being parked or stopped, being driven, and in an emergency will be described.

Hereinafter, supplying a pressure for applying and releasing a braking force may be performed using a pressure of a fluid, and here, the pressure of the fluid may be hydraulic or pneumatic. Hereinafter, in describing the embodiments of the present invention, “supplying a pressure” represents supplying a pressure using a hydraulic pressure or a pneumatic pressure.

First, as illustrated inFIGS. 1, 3, and 5, a brake device in accordance with the first embodiment of the present invention is a device used in a negative brake system and includes a first line10of a service brake capable of supplying or recovering a pressure to apply or release a braking force of the service brake and a first line30of a parking brake capable of supplying or recovering a pressure to apply or release a braking force of the parking brake. Also, the brake device includes a second line20of the service brake connected to a first chamber120at one side of brake disks110located in a brake assembly100to supply a pressure to the first chamber120and a second line40of the parking brake connected to a second chamber130at the other side of the brake disks110to supply a pressure to the second chamber130. Here, chamber blocks122and132and elastic mechanism124and134elastically supporting the chamber blocks122and132, respectively, may be disposed at the first chamber120and the second chamber130, respectively. In the first chamber120, the chamber block122overcomes a support force of the elastic mechanism124and apply a braking force to a brake by a supply of pressure, and the brake may be released by a restoring force of the elastic mechanism124when the pressure is recovered. In the second chamber130, a state in which the chamber block132is applying a braking force to a brake by being elastically supported may become a state in which the chamber block132may overcome a support force of the elastic mechanism134and release the brake by a supply of pressure.

Furthermore, the brake device in accordance with the embodiment of the present invention includes a parking releasing valve200. The parking releasing valve200may switch between a first state (FIGS. 1 and 3) in which the first line10of the service brake and the second line20of the service brake communicate and the first line30of the parking brake and the second line40of the parking brake communicates and a second state (FIG. 5) in which the first line10of the service brake and the second line40of the parking brake communicate. Meanwhile, an additional check valve34may be disposed on the first line30of the parking brake to regulate a supply of pressure to the first line30of the parking brake.

Here, referring toFIGS. 2, 4, and 6, a detailed description on the parking releasing valve200in accordance with the first embodiment of the present invention is as follows.

First, the parking releasing valve200may include a spool220inserted into a valve hole210communicating with each of the first line10of the service brake, the first line30of the parking brake, the second line20of the service brake, and the second line40of the parking brake. Here, a guide protruding part250may be formed at an outer surface of the spool220such that the spool220may be guided inside the valve hole210, and a guide groove260may also be formed at an inner surface of the valve hole210to guide the guide protruding part250to a position corresponding to the guide protruding part250. Also, although not illustrated by a drawing, a guide protruding part protruding in the radial direction and extending in the longitudinal direction may be formed at the outer surface of the spool220, and a guide groove corresponding to the guide protruding part may also be formed at an inner surface of the valve hole210, conversely.

Meanwhile, with respect to the valve hole210, a direction in which the valve hole210is shallow, that is, the left direction inFIGS. 2, 4, and 6, is referred to as an outside of the valve hole210, and a direction in which the valve hole210is deep, i.e. the right direction inFIGS. 2, 4, and 6, is referred to as an inside of the valve hole210, and this is the same also in the description below.

Here, the valve hole210may be, for example, formed at a flow pipe body300disposed in a brake system. The flow pipe body300refers to a structure in which a pipe channel is formed to enable each line included in the brake device in accordance with the embodiment of the present invention, that is, the first line10of the service brake, the first line30of the parking brake, the second line20of the service brake, and the second line40of the parking brake for easy communication between each other.

The valve hole210communicates with each of the first line10of the service brake, the first line30of the parking brake, the second line20of the service brake, and the second line40of the parking brake, and the spool220is inserted into the valve hole210, wherein the spool220is inserted into the valve hole210to be able to move by a predetermined distance inside the valve hole210. By the spool220moving by the predetermined distance, the first line10of the service brake, the first line30of the parking brake, the second line20of the service brake, and the second line40of the parking brake communicating with the valve hole210may selectively communicate with each other.

Here, the predetermined distance refers to a distance by which the spool220is moved to switch between the first state (FIGS. 1 and 3) in which the first line10of the service brake and the second line20of the service brake communicate and the first line30of the parking brake and the second line40of the parking brake communicate and the second state (FIG. 5) in which the first line10of the service brake and the second line40of the parking brake communicate. Specifically, the distance refers to a distance between a first position (FIGS. 1 and 3) of the spool220forming the first state and a second position (FIG. 5) of the spool220forming the second state. Meanwhile, in the first state, as illustrated inFIGS. 2 and 4, a locking piece410may be inserted into a locking part400formed at an outer end portion of the spool220for the spool220to be fixed to the first position.

Meanwhile, as illustrated inFIGS. 2, 4, and 6, the first line10of the service brake and the second line20of the service brake may be located even deeper (right side inFIGS. 2, 4, and 6) than the first line30of the parking brake and the second line40of the parking brake in the valve hole210. By this, the movement of the spool220, specifically, the movement between the first position forming the first state and the second position forming the second state, may be more easily set.

Specifically, when the spool220is at the first position where the spool220is moved toward a left side of the valve hole210as illustrated inFIGS. 2 and 4, to form the first state, in other words, when an inner end portion of the spool220is located more leftward (outward) of the valve hole210than a position at which the first line10of the service brake and the second line20of the service brake communicate with the valve hole210, the spool220is deviated from a position at which each of the first line10of the service brake and the second line20of the service brake communicate in the valve hole210. Consequently, the first line10of the service brake and the second line20of the service brake may easily communicate, and therefore, a supply or release of pressure via the first line10of the service brake may be easily applied to the first chamber120via the second line20of the service brake.

In addition, when the spool220is at the second position where the spool220is moved deeply toward a right side of the valve hole210as illustrated inFIG. 6, in other words, when the inner end portion of the spool220is located more rightward (inward) of the valve hole210than a position at which the first line10of the service brake communicates with the valve hole210, the communication between the first line10of the service brake and the second line20of the service brake is disconnected. Furthermore, a spool first pipe channel222formed at the spool220communicates with the first line10of the service brake, and a spool second pipe channel224communicates with the second line40of the parking brake, thereby enabling the first line10of the service brake and the second line40of the parking brake to communicate with each other.

In more detail, as illustrated inFIGS. 2, 4, and 6, the valve hole includes a first hole part210aforming a cylindrical hole and a second hole part210bconnected to an inner end portion of the first hole part210aand forming a cylindrical hole having a smaller diameter than a diameter of the first hole part210a. Also, the spool220includes a first cylindrical main body part220ahaving an outer surface formed in a shape corresponding to the first hole part210aand a second cylindrical main body part220bconnected to an end portion of the first cylindrical main body part220aand having an outer surface formed in a shape corresponding to the second hole part210b.

Here, with respect to the valve hole210, since the second hole part210bis located more inward in the valve hole210than the first hole part210a, the first line10of the service brake and the second line20of the service brake may communicate with the valve hole210at the second hole part210b, and the first line30of the parking brake and the second line40of the parking brake may communicate with the valve hole210at the first hole part210a. By this, the first line10of the service brake and the second line20of the service brake may be located deeper (right side inFIGS. 2, 4, and 6) than the first line30of the parking brake and the second line40of the parking brake.

Here, “cylindrical shape” and “shape corresponding to the cylindrical shape” used to describe the first hole part210a, the second hole part210b, the first cylindrical main body part220a, and the second cylindrical main body part220brepresent not only a mathematical cylindrical shape but all shapes that may be viewed as a cylindrical shape. For example, as illustrated inFIGS. 2, 4, and 6, with respect to the valve hole210, even when an inclined part along which a diameter of an inner end portion of the first hole part210agradually decreases exists at a portion where the second hole part210bis connected to the inner end portion of the first hole part210a, the inclined part may be viewed as a part of the first hole part210a. Also, with respect to the spool220, even when an inclined part along which a diameter of an inner end portion of the first cylindrical main body part220aslightly decreases exists at a portion where the second cylindrical main body part220bis connected to the inner end portion of the first cylindrical main body part220a, the inclined part may be viewed as a part of the first cylindrical main body part220a.

In addition, when the shape of the spool220is described in more detail, the spool220may include spool main bodies220aand220bincluding the first cylindrical main body part220aand the second cylindrical main body part220bas well as a spool groove220cformed from the spool main bodies220aand220bup to a predetermined position in the longitudinal direction. Also, the spool220may include the spool first pipe channel222formed at an inside of the spool groove220cup to radial outer surfaces of the spool main bodies220aand220bto communicate with the first line10of the service brake when the spool220is at the second position as well as the spool second pipe channel224formed at the inside of the spool groove220cup to the radial outer surfaces of the spool main bodies220aand220bto communicate with the second line40of the parking brake when the spool220is at the second position.

That is, the first pipe channel222and the second pipe channel224formed from the inside of the spool groove220cup to the radial outer surfaces are formed from the inside of the spool groove220c, thus coming into fluidic communication with the spool groove220c. Also, since the first pipe channel222may communicate with the first line10of the service brake and the second pipe channel224may communicate with the second line40of the parking brake when the spool220is at the second position, as a result, the first line10of the service brake and the second line40of the parking brake may come into fluidic communication via the first pipe channel222, the spool groove220c, and the second pipe channel224when the spool220is at the second position.

Besides, a spool ball220d, an elastic member220e, and a support part220fmay be disposed in the spool groove220c. Here, the elastic member220emay have one side supporting the spool ball220dand the other side supported by the support part220fto press the spool ball220dto be located at the inner end portion of the spool groove220c. Here, a diameter of the spool ball220dis formed not to be larger than a diameter of the spool groove220cthus is formed to be movable in the spool groove220c.

This configuration is for enabling the spool ball220dto block the first pipe channel222when the spool220is at the second position.

Specifically, when one end of the first pipe channel222is formed at the inner end portion of the spool groove220cand the other end thereof is formed at the radial outer surfaces of the spool main bodies220aand220b, in other words, when the first pipe channel222is formed beginning from the inner end portion of the spool groove220c, bent, and formed up to the radial outer surfaces of the spool main bodies220aand220b, the first pipe channel222is blocked by the spool ball220dwhen the spool ball220dis located at the inner end portion while being pressed by the elastic member220e.

Here, since the spool220is at the second position, that is, a position causing the second state in which the first line10of the service brake and the second line40of the parking brake may communicate, a pressure is supplied via the first line10of the service brake, wherein, when a pressure greater than a pressing force of the elastic member220eis supplied, the spool ball220dmay overcome the pressing force of the elastic member220eand be moved leftward ofFIG. 6, thereby completing a fluidic communication passage of the first line10of the service brake and the second line40of the parking brake.

By the above configuration, in the second state in which the first line10of the service brake and the second line40of the parking brake may communicate, the fluidic communication passage of the first line10of the service brake and the second line40of the parking brake may be completed only when a pressure is supplied via the first line10of the service brake, specifically, when a driver presses a brake pedal connected to the first line10of the service brake.

Meanwhile, in the above description, the elastic member220emay be a spring, and various elastic members other than the above may be used. Also, the support part220fmay be a member inserted into the spool groove220cfrom an outside of the spool groove220cand may be formed to secure an airtightness to prevent the spool groove220cfrom communicating with the outside of the spool groove220c. Also, a separate oil ring220hmay be disposed at an outside of the first cylindrical main body part220ato definitely secure an airtightness. Here, the oil ring220hmay be an O-ring.

In addition, when the spool220is at the second position, an oil ring220gfor securing airtightness may be provided between the inner end portion of the spool220and the first pipe channel222and between the first pipe channel222and the second pipe channel224such that a fluid for supplying a pressure from the first line10of the service brake may be introduced only to the first pipe channel222.

Next, to describe the brake device in accordance with the embodiment of the present invention in more detail with reference toFIGS. 1, 3, and 5, the present invention will be described with respect to states in which a vehicle is stalled, stopped, or parked, and being driven. Arrows inFIGS. 1, 3, and 5represent a direction in which a pressure may move, and more specifically, a direction in which a fluid for supplying the pressure may move. However, this will be expressed as a movement of pressure, hereinafter.

First, as illustrated inFIGS. 1 and 3, the brake device in accordance with the present invention includes the first line10of the service brake capable of supplying or recovering a pressure to apply or release a braking force of the service brake, the first line30of the parking brake capable of supplying or recovering a pressure to apply or release a braking force of the parking brake, the second line20of the service brake connected to the first chamber120at one side of the brake disks110to supply a pressure to the first chamber120, and the second line40of the parking brake connected to the second chamber130at the other side of the brake disks110to supply a pressure to the second chamber130.

FIG. 1is a view illustrating a state when a vehicle is stalled, stopped, or parked.

As illustrated inFIG. 1, when a vehicle is stalled, stopped, or parked, a valve32provided on the first line30of the parking brake is turned off. In this case, due to the nature of a negative brake system, since a fluid in the second chamber130of the brake assembly100is discharged via the second line40of the parking brake and the first line30of the parking brake, the brake disks110come in contact with each other, causing a state in which a braking force of the parking brake is applied.

In addition, the first line10of the service brake is connected to a brake pedal12, and a service brake pressure supply device14is provide on a path of the brake pedal12.

In this manner, when the vehicle is stalled, stopped, or parked, the vehicle becomes standstill due to the state in which the braking force of the parking brake is applied.

Next,FIG. 3is a view illustrating a state in which a vehicle is being driven.

As illustrated inFIG. 3, when a vehicle is being driven, the valve32provided on the first line30of the parking brake is turned on. In this case, a pressure may be supplied to the second chamber130of the brake assembly100via the second line40of the parking brake from the first line30of the parking brake, and due to the supply of pressure, the brake disks110are spaced apart from each other, causing a state in which the braking force of the parking brake is released.

In addition, the first line10of the service brake is connected to the brake pedal12, and the service brake pressure supply device14is provided on the path of the brake pedal12. Here, when a pressure is supplied to the first chamber120of the brake assembly100from the service brake pressure supply device14due to a driver pressing the brake pedal12, the brake disks110may come in contact such that a braking force may be applied by a service brake. Conversely, since a fluid in the first chamber120of the brake assembly100is discharged via the second line20of the service brake and the first line10of the service brake when pressing of the brake pedal12by the driver is released, the brake disks110are spaced apart such that the braking force caused by the service brake is released. That is, the brake disks110may come in contact or be apart depending on whether the brake pedal12is pressed by the driver.

In this manner, the braking force of the parking brake is released while the vehicle is being driven, and the braking force of the service brake may be applied or released depending on whether the brake pedal12is pressed.

As described above, a vehicle is in a normal state when the vehicle is stopped, or parked, and being driven, and the parking releasing valve200in accordance with the embodiment of the present invention is in the first state, that is, a state in which the first line10of the service brake and the second line20of the service brake communicate and the first line30of the parking brake and the second line40of the parking brake communicate.

When the first state is examined in detail related to the first embodiment of the present invention, as illustrated inFIG. 2, the spool220is at the first position of being moved a predetermined distance outward from the valve hole210, in other word, the spool220is at a state in which the inner end portion of the spool220is placed more outward than the first line10of the service brake and the second line20of the service brake. Here, the first line10of the service brake and the second line20of the service brake communicate with each other at a right side of the inner end portion of the spool220.

Meanwhile, in the first state as above, as illustrated inFIGS. 2 and 4, the locking piece410may be inserted into the locking part400formed at an outer end portion of the spool220such that the spool220may be fixed to the first position.

Here, since a diameter of the first hole part210aof the valve hole210is larger than a diameter of the second cylindrical main body part220bof the spool220having a portion thereof located at the first hole part210a, the first line30of the parking brake and the second line40of the parking brake communicating with the first hole part210amay communicate with each other via a space between the second cylindrical main body part220band the first hole part210a.

By this, when described with respect to the inner end portion of the spool220, the first line10of the service brake and the second line20of the service brake communicate at a more inward side of the valve hole210than the inner end portion of the spool220, and the first line30of the parking brake and the second line40of the parking brake communicate at a more outward side of the valve hole210than the inner end portion of the spool220.

Next,FIG. 5is a view illustrating an emergency state such as a situation where a vehicle is stalled, a situation where an engine is stopped abnormally, a situation where an abnormality has occurred in an electric system, and a situation where an abnormality has occurred in a hydraulic or pneumatic system.

As illustrated inFIG. 5, when a vehicle is in an emergency state, a supply of pressure to the first line30of the parking brake of the vehicle stops, causing the fluid in the second chamber130of the brake assembly100to be discharged via the second line40of the parking brake and the first line30of the parking brake. Consequently, the brake disks110come in contact with each other, causing a state in which the braking force of the parking brake is applied. Meanwhile, to easily describe the state here, the valve32provided on the first line30of the parking brake is illustrated as being turned off.

In addition, likewise, the first line10of the service brake is connected to the brake pedal12, and the service brake pressure supply device14is provided on the path of the brake pedal12.

In this manner, since the braking force of the parking brake is applied when the vehicle is in an emergency state, the vehicle becomes standstill.

In this state, when the parking releasing valve200that has been in the first state is switched to the second state in which the first line10of the service brake and the second line40of the parking brake communicate as illustrated inFIG. 6, in other words, when the spool220moves (displayed by a solid line inFIG. 5) to the second position causing the second state, the state in which the braking force of the parking brake is applied may be released.

When the second state is examined in detail related to the first embodiment of the present invention, in the second state, as illustrated inFIG. 6, the spool220is at the second position of being deeply inserted into the valve hole210, that is, a state in which the inner end portion of the spool220is placed more inward than the first line10of the service brake. In this state, the first line10of the service brake communicates with the first pipe channel222of the spool220, and the second line40of the parking brake communicates with the second pipe channel224of the spool220.

Consequently, the first line10of the service brake may communicate with the second line40of the parking brake via the first pipe channel222, the spool groove220c, and the second pipe channel224. Here, when the brake pedal12is pressed, a pressure is supplied to the first line10of the service brake via the service brake pressure supply device14, and accordingly, the spool ball220dthat has been supported by the elastic member220eto block the first pipe channel222is moved to the left side inFIG. 6, and the pressure supplied to the first line10of the service brake is supplied to the second line40of the parking brake.

As a result, a pressure is supplied to the second chamber130at the other side of the brake disks110connected to the second line40of the parking brake, thereby releasing the braking force of the parking brake.

In such an emergency state, the first line30of the parking brake and the second line20of the service brake may be in a disconnected state. However, in the brake device in accordance with the embodiment of the present invention, the first line30of the parking brake and the second line20of the service brake being connected is immaterial since the pressure that has passed through the first line10of the service brake is passed through the second line40of the parking brake to release the braking force of the parking brake in an emergency state and a pressure is not supplied via the first line30of the parking brake.

Next, referring toFIGS. 7 to 10, a brake device in accordance with a second embodiment of the present invention will be described in detail. In describing the second embodiment of the present invention, description of parts overlapping with the above-mentioned first embodiment will be omitted, and since an element having the same reference numeral represents an element performing the same function, the detailed description thereof will also be omitted. Also, when a structure described related to the first embodiment can also be employed to the second embodiment from the point of view of those of ordinary skill in the art, the second embodiment includes the structure, but will not describe them in detail below.

An emergency releasing device in accordance with the second embodiment of the present invention uses two spools, and by a first spool being inserted into a second spool, the first state is changed to the second state.

Same as the case of the first embodiment, a supply of pressure for applying and releasing a braking force may be performed by a pressure of a fluid, and here, the pressure of the fluid may be a hydraulic pressure or pneumatic pressure. Hereinafter, in describing the embodiment of the present invention, “supply of pressure” represents a supply of pressure by the hydraulic pressure or the pneumatic pressure.

First, as illustrated inFIGS. 7 and 9, a brake device in accordance with the present invention is a device used in a negative brake system and includes the first line10of the service brake capable of supplying or recovering a pressure to apply or release a braking force of the service brake and the first line30of the parking brake capable of supplying or recovering a pressure to apply or release a braking force of the parking brake. Also, the brake device includes the second line20of the service brake connected to the first chamber120at one side of the brake disks110located in the brake assembly100to supply a pressure to the first chamber120and the second line40of the parking brake connected to the second chamber130at the other side of the brake disks110to supply a pressure to the second chamber130. Here, the chamber blocks122and132and the elastic mechanism124and134elastically supporting the chamber blocks122and132, respectively, may be disposed at the first chamber120and the second chamber130, respectively. In the first chamber120, the chamber block122may overcome a support force of the elastic mechanism124and apply a braking force to a brake by a supply of pressure, and the brake may be released by a restoring force of the elastic mechanism124when the pressure is recovered. In the second chamber130, a state in which the chamber block132is applying a braking force to a brake by being elastically supported may become a state in which the chamber block132may overcome a support force of the elastic mechanism134and release the brake by a supply of pressure.

The brake device in accordance with the second embodiment of the present invention includes a parking releasing valve500. The parking releasing valve500may switch between a first state (FIGS. 7 and 8) in which the first line10of the service brake and the second line20of the service brake communicate and the first line30of the parking brake and the second line40of the parking brake communicate and a second state (FIGS. 9 and 10) in which the first line10of the service brake and the second line40of the parking brake communicate.

In addition, a bypass line18bypassing the parking releasing valve500to connect the first line10of the service brake and the second line20of the service brake may be provide, and check valves16aand16blimiting a supply of pressure to one direction may be provided at the first line10of the service brake and the bypass line18, respectively.

Here, referring toFIGS. 8 and 10, detailed description on the parking releasing valve500in accordance with the second embodiment of the present invention is as follows.

First, the parking releasing valve500may include a first spool520aand a second spool520binserted into valve holes510communicating with each of the first line10of the service brake, the first line30of the parking brake, the second line20of the service brake, and the second line40of the parking brake. Here, guide protruding parts550aand550bprotruding from outer surfaces of the first and second spools520aand520bmay be formed such that the first and second spools520aand520bmay be guided inside the valve holes510, and guide grooves560aand560bmay be formed at an inner surface of the valve holes510to guide the guide protruding parts550aand550bto a position corresponding to the guide protruding parts550aand550b. Also, although not illustrated by a drawing, guide protruding parts protruding in the radial direction and extending in the longitudinal direction may be formed at the outer surfaces of the spools520aand520b, and guide grooves corresponding to the guide protruding parts may be formed at an inner surface of the valve holes510, conversely.

Here, the valve holes510may be, for example, formed at the flow pipe body300disposed in a brake system. The flow pipe body300refers to a structure in which a pipe channel is formed to enable each line included in the brake device in accordance with the present invention, that is, the first line10of the service brake, the first line30of the parking brake, the second line20of the service brake, and the second line40of the parking brake, to easily communicate with each other.

The valve holes510communicates with each of the first line10of the service brake, the first line30of the parking brake, the second line20of the service brake, and the second line40of the parking brake, and the first spool520ais inserted into the valve holes510, wherein the first spool520ais inserted into the valve holes510to be able to move a predetermined distance inside the valve holes510. By the first spool520amoving the predetermined distance, the first line10of the service brake, the first line30of the parking brake, the second line20of the service brake, and the second line40of the parking brake communicating with the valve holes510may selectively communicate with each other. Here, a state in which an insertion end portion610of the first spool520ais not inserted into a spool insertion groove600of the second spool520bis a first state, and conversely, a state in which an insertion end portion610of the first spool520ais inserted into the spool insertion groove600of the second spool520bis a second state.

Here, the predetermined distance is a distance in which the insertion end portion610of the first spool520amoves to be inserted into the spool insertion groove600formed at an inner end portion of the second spool520band refers to an interval in which the first spool520ais moved to switch between the first state (FIG. 8) in which the first line10of the service brake and the second line20of the service brake communicate and the first line30of the parking brake and the second line40of the parking brake communicate and the second state (FIG. 10) in which the first line10of the service brake and the second line40of the parking brake communicate.

Meanwhile, in the first state, as illustrated inFIG. 8, the locking piece410may be inserted into the locking part400formed at an outer end portion of the first spool520afor the first spool520ato be fixed at the first position.

Meanwhile, as illustrated inFIG. 8, in the first state, the first line10of the service brake and the second line20of the service brake communicate via the second spool520b, and the first line30of the parking brake and the second line40of the parking brake communicate via the first spool520a.

Specifically, the valve holes510include a first valve hole510ainto which the first spool520ais inserted and a second valve hole510binto which the second spool520bis inserted, wherein the first valve hole510aand the second valve hole510bmay communicate via a third valve hole510cformed relatively narrowly between the two.

In the first state, the first spool520ais inserted into the first valve hole510a, wherein the end portion610is inserted into the third valve hole510cand an oil ring620is disposed around the inner end portion610to block a portion between the first valve hole510aand the second valve hole510b.

Here, the first spool520ahas a first cylindrical main body part520aaand a second cylindrical main body part520abcoupled to the inner end portion610at both sides and having a relatively smaller diameter than the first cylindrical main body part520aa. In the first state, the first line30of the parking brake and the second line40of the parking brake communicate by an outer circumferential portion of the second cylindrical main body part520abhaving the small diameter.

In addition, since a through-hole630formed at the second spool520band communicating with the second line20of the service brake communicates with the spool insertion groove600, a pressure from the first line10of the service brake may communicate with the second line20of the service brake via the spool insertion groove600and the through-hole630. Here, of course, the opposite side in which the through-hole630is connected to the spool insertion groove600is sealed.

Here, a notion that “cylindrical shape” may include all shapes that may be viewed as a cylindrical shape is the same as in the above description related to the first embodiment.

Next, as illustrated inFIG. 10, in the second state, the end portion610of the first spool520ais inserted into the spool insertion groove600of the second spool520b. By this, the first line10of the service brake and the second line20of the service brake that pass through the spool insertion groove600are made not to communicate with each other, and the first line30of the parking brake and the second line40of the parking brake are made not to communicate with each other as the first cylindrical main body part520aacovers the first line30of the parking brake. Furthermore, an oil ring520his disposed at an outer circumferential surface of the first cylindrical main body part520aa, and the oil ring520his located between the first line30of the parking brake and the second line40of the parking brake in the second state, thereby effectively blocking (to not communicate) the first line30of the parking brake and the second line40of the parking brake. When the oil ring520his formed, since the communication between the first line30of the parking brake and the second line40of the parking brake is blocked, it is immaterial for the first cylindrical main body part520aato be formed such that the diameter thereof slightly decreases at a portion facing the first line30of the parking brake.

In the second state, the first line10of the service brake and the second line40of the parking brake communicate with each other. That is, the diameter of the second cylindrical main body part520abis formed smaller than an inner diameter of the third valve hole510c, and a flow passage is formed between an outer surface of the second cylindrical main body part520aband an inner surface of the third valve hole510csuch that a pressure from the first line10of the service brake may be supplied to the second line40of the parking brake.

By the configuration of the parking releasing valve500, the brake device in accordance with the second embodiment of the present invention may be switched between the first state in which the first line10of the service brake and the second line20of the service brake communicate and the first line30of the parking brake and the second line40of the parking brake communicate and the second state in which the first line10of the service brake and the second line40of the parking brake communicate.

In addition, the switching may be performed by the movement of the first spool520a, and this may be performed by removing the locking piece410. Of course, by fitting the locking piece410again, the first spool520amay be moved back from the second position to the first position inside the first valve hole510a, and thereby may be switched back to the first state corresponding to the normal state of the vehicle.

Next, referring toFIG. 11, a braking method in accordance with the present invention will be described in detail.

The braking method in accordance with the present invention is a braking method of releasing a state in which a parking brake is automatically applied in an emergency situation in a negative brake system.

First, in a normal state that is not an emergency state in the negative brake system, the first line10of the service brake capable of supplying or recovering a pressure to apply or release a braking force of the service brake and the second line20of the service brake connected to the first chamber120at one side of the brake disks110to supply a pressure to the first chamber120communicate, and the first line30of the parking brake capable of supplying or recovering a pressure to apply or release a braking force of the parking brake and the second line40of the parking brake connected to the second chamber130at the other side of the brake disks110to supply a pressure to the second chamber130communicate, thus entering a first state.

Here, when a vehicle is in an emergency state, that is, a situation where a vehicle has stalled, a situation where an engine has stopped abnormally, a situation where an abnormality has occurred in an electric system, or a situation where an abnormality has occurred in a hydraulic or pneumatic system (S1), a state in which a braking force of a parking brake is applied occurs as mentioned above. Here, to release the braking force of the parking brake, the first state is switched to a second state in which the first line10of the service brake and the second line40of the parking brake may communicate (S2).

Then, the braking force of the parking brake is released by a pressure being supplied through the second line40of the parking brake via the first line10of the service brake due to a driver pressing the brake pedal12(S3).

Meanwhile, in the second state, the first line30of the parking brake and the second line20of the service brake are not required, thus may be disconnected.

Meanwhile, in the first step described above, the switching from the first state to the second state may be performed by the parking releasing valve200connected to the first line10of the service brake, the second line20of the service brake, the first line30of the parking brake, and the second line40of the parking brake.

When the switching from the first state to the second state is examined in detail related to the first embodiment of the present invention, the parking releasing valve200may include the spool220inserted into the valve hole210communicating with each of the first line10of the service brake, the first line30of the parking brake, the second line20of the service brake, and the second line40of the parking brake, and due to the movement of the spool220, a switching from the first state to the second state occurs.

That is, the switching from the first state to the second state may occur due to the spool220moving from the first position causing the first state to the second position causing the second state while being inserted into the valve hole210. Of course, the spool220may move back to the first position from the second position in the valve hole210, thereby may definitely be switched back to the first state corresponding to the normal state of the vehicle.

Here, the first position of the spool220may be a position where an inner end portion of the spool220is located more outward in the valve hole210than the position at which the first line10of the service brake and the second line20of the service brake communicate with the valve hole210, and the second position may be a position where the inner end portion of the spool220is located more inward in the valve hole210than the position at which the first line10of the service brake communicates with the valve hole210.

When the position of the spool220and communication relation between the lines are described in more detail, when the spool220is at the first position, the first line10of the service brake and the second line20of the service brake communicate at a part more inward in the valve hole210than the inner end portion of the spool220, and the first line30of the parking brake and the second line40of the parking brake communicate at a part more outward in the valve hole210than the inner end portion of the spool220.

In addition, when the spool220is at the second position, the first line10of the service brake and the second line40of the parking brake communicate with each other, and this may be enabled by the spool220.

Specifically, to enable the communication, the spool220may include the spool main bodies220aand220bforming an exterior of the spool220, the spool groove220cformed from the spool main bodies220aand220bup to a predetermined position in the longitudinal direction, the spool first pipe channel222formed at an inside of the spool groove220cup to the radial outer surfaces of the spool main bodies220aand220bto communicate with the first line10of the service brake when the spool220is at the second position, and the spool second pipe channel224formed at the inside of the spool groove220cup to the radial outer surfaces of the spool main bodies220aand220bto communicate with the second line40of the parking brake when the spool220is at the second position.

By this, a communication passage connecting the first line10of the service brake, the spool first pipe channel222, the spool groove220c, the spool second pipe channel224, and the second line40of the parking brake may be formed such that a pressure to the first line10of the service brake may be transferred to the second chamber130at the other side of the brake disks110via the second line40of the parking brake to release the braking force of the parking brake.

When the switching from the first state to the second state is examined in detail in relation to the second embodiment of the present invention, the parking releasing valve500may include the first spool520ainserted into the first valve hole510acommunicating with each of the first line10of the service brake, the first line30of the parking brake, the second line20of the service brake, and the second line40of the parking brake, and due to the movement of the first spool520a, a switching from the first state to the second state occurs.

That is, the switching from the first state to the second state may occur due the first spool520amoving from the first position causing the first state to the second position causing the second state while being inserted into the first valve hole510a. Of course, the first spool520amay move back to the first position from the second position in the first valve hole510a, thereby definitely may be switched back to the first state corresponding to the normal state of the vehicle.

Here, the first position of the first spool520amay be a position where the inner end portion of the first spool520ais located at the third valve hole510c, and the second position may be a position where the inner end portion610of the first spool520ais located to be inserted into the spool insertion groove600of the second spool520b.

When the position of the first spool520aand communication relation between the lines are described in more detail, when the first spool520ais at the first position, the first line30of the parking brake and the second line40of the parking brake communicate by a portion around the outer circumferential portion of the first spool520a, and the first line10of the service brake and the second line20of the service brake communicate by passing through the spool hole600of the second spool520band the through-hole630.

In addition, when the first spool520ais at the second position, the first line10of the service brake and the second line40of the parking brake communicate with each other, and the communication may occur via a flow passage formed between the inner surface of the third valve hole510cand the outer surface of the second cylindrical main body part520ab.

By this, the pressure to the first line10of the service brake may be transferred to the second chamber130at the other side of the brake disks110via the second line40of the parking brake, thus releasing the braking force of the parking brake.

The device and method for braking described above may be applied to a vehicle to which a negative brake system is applied to release a braking force applied by a parking brake in an emergency state such as a situation where a vehicle has stalled, a situation where an engine has stopped abnormally, a situation where an abnormality has occurred in an electric system, and a situation where an abnormality has occurred in a hydraulic or pneumatic system.

Here, the vehicle to which the device and method for braking are applied may not only be a car, etc. but also a heavy equipment vehicle such as a tractor, an excavator, etc. and may also be any vehicle to which the negative brake system may be applied.

Hereinafter, ways to prevent a dangerous situation caused by a sudden stopping of a vehicle due to a braking force automatically applied to a parking brake (for example, when an abnormality such as a failure of a service brake occurs while driving a vehicle) will be examined.

FIG. 12is a view schematically illustrating a brake device in accordance with still another embodiment of the present invention. Here, differences from the embodiment illustrated inFIG. 1will be mainly described.

Referring toFIG. 12, a brake device may further include a control unit60and a speed sensor62. The control unit60may control applying and releasing of a braking force by a parking brake. The control unit60controls the valve32provided on the first line30of the parking brake to be turned on and off to control the applying and releasing of the braking force by the parking brake. Specifically, when an abnormality such as a failure of a service brake occurs while driving a vehicle, the control unit60turns the valve32provided on the first line30of the parking brake off (applies the braking force caused by the parking brake) and makes an interval in which the valve32is turned on (the braking force caused by the parking brake being released) to be included until the vehicle is stopped to prevent the vehicle from being suddenly stopped. Here, the control unit60may be a transmission electronic control unit (TECU).

For example, when an abnormality such as a failure of a service brake occurs while driving a vehicle, the control unit60may repeat turning on and off the valve32provided on the first line30of the parking brake to repeat operations of applying and releasing the braking force to and from the parking brake. Then, even when the service brake is out of order, the vehicle may be stopped by gradually decreasing the speed of the vehicle using the parking brake. That is, when turning on and off of the valve32is repeated, a high friction force is repeatedly generated by a repeated contact and separation between the chamber block132and the brake disks110, thus gradually decreasing the speed of the vehicle. Here, a proportional valve may be used as the valve32provided on the first line30of the parking brake, for example. In this case, the valve32may be electronically controlled and may also be complexly controlled.

The speed sensor62serves to measure a speed of a vehicle and transmit the speed to the control unit60. When an abnormality such as a failure of a service brake occurs while driving a vehicle, the control unit60may control a repetition frequency (or a repetition cycle) of the valve32being turned on and off in accordance with the speed of the vehicle received from the speed sensor62. Here, it has been described that the separate speed sensor62is disposed for measuring the speed of the vehicle, but embodiments are not limited thereto, and the control unit60may also receive vehicle speed information from another electronic device in the vehicle. For example, the control unit60may receive the vehicle speed information from a navigation of the vehicle. Also, the control unit60may directly calculate the speed of the vehicle and control the valve32in accordance with the speed. For example, the control unit60may receive the vehicle speed information in real time from a global positioning system (GPS) mounted on the vehicle and calculate the speed of the vehicle.

The control unit60may increase the repetition frequency of the valve32being turned on and off correspondingly for a higher vehicle speed. That is, the control unit60may shorten the repetition cycle of the valve32being turned on and off correspondingly for a higher vehicle speed. In this case, a frequency of the high friction force generated due to the repetitive contact and separation between the chamber block132and the brake disks110may be increased to gradually decrease the speed of the vehicle effectively.

FIG. 13is a view illustrating graphs comparing a parking brake control operation of the prior art and a parking brake control operation of the present invention when an emergency state of a vehicle occurs.

Referring to (a) ofFIG. 13, in the prior art, when an emergency state of a vehicle occurs while a braking force of a parking brake is released, the braking force of the parking brake is applied until the vehicle stops ((a-1) ofFIG. 13). In this case, the vehicle suddenly stops as the speed of the vehicle suddenly decreases ((a-2) ofFIG. 13).

Referring to (b) ofFIG. 13, in an embodiment of the present invention, when an emergency state of a vehicle occurs while a braking force of a parking brake is released, states in which the braking force of the parking brake is applied and released are repeated until the vehicle stops ((b-1) ofFIG. 13). In this case, the speed of the vehicle slightly decreases every time the braking force of the parking brake is applied, thus enabling the vehicle to gradually stop ((b-2) ofFIG. 13). The control unit60may control applying and releasing of the braking force of the parking brake by turning the valve32on and off. Here, the control unit60may control the valve32to be turned on and off using pulse width modulation (PWM).

Here, states in which the braking force of the parking brake is applied and released may be repeated in a predetermined cycle until the vehicle stops, but embodiments are not limited thereto. Also, although it has been described here that the states in which the braking force of the parking brake is applied and released are repeated, embodiments are not limited thereto, and an interval in which the braking force of the parking brake is applied and an interval in which the braking force is released (braking force release interval) need only co-exist until the vehicle stops.

The embodiments described in the specification and elements illustrated in the drawings are merely embodiments of the present invention and do not show all technical spirits of the present invention. Thus, it should be understood that various equivalents and modified embodiments that may substitute the embodiments may be present at the time of applying this application.