KR102413178B1 - Tire and control method the same - Google Patents

Abstract

A tire according to an embodiment of the present invention includes: a tread extending along a circumferential direction of the tire and having a groove; a liquid chamber disposed on the inner surface of the tread and accommodating the fluid; a valve connected to the liquid chamber and configured to open and close the liquid chamber; and a control unit closing the valve when the absolute value of the acceleration of the vehicle exceeds a set value (a) when the vehicle is running.

Description

TIRE AND CONTROL METHOD THE SAME

Embodiments of the present invention relate to a tire and a method for controlling the same.

A vehicle driven by users consists of many parts, and among them, a tire substantially affects the driving of the vehicle, and in particular, it can be said to be one of the key parts for securing the safety of the user.

In particular, due to the development of the industry, the movement of logistics increases, the amount of movement due to an increase in the amount of personal work, etc., and the amount of automobile operation due to the increase in family life are increasing.

On the other hand, the tire can maintain driving safety through friction with the road surface, and driving safety can be secured through the tire having a certain tread rigidity. However, if the tread has a relatively high rigidity, it may not absorb the shock from the road surface and thus driving convenience may decrease.

SUMMARY OF THE INVENTION The present invention is to solve the above problems, and to provide a tire and a method for controlling the same, which can secure not only driving safety but also driving convenience by varying the stiffness of a tread according to driving.

However, these problems are exemplary, and the problems to be solved by the present invention are not limited thereto.

A tire according to an embodiment of the present invention includes: a tread extending along a circumferential direction of the tire and having a groove; a liquid chamber disposed on the inner surface of the tread and accommodating the fluid; a valve connected to the liquid chamber and configured to open and close the liquid chamber; and a control unit closing the valve when the absolute value of the acceleration of the vehicle exceeds a set value (a) when the vehicle is running.

In the tire according to an embodiment of the present invention, the controller may open the valve when the absolute value of the acceleration of the vehicle is equal to or less than a set value (a).

In a tire according to an embodiment of the present invention, a body ply disposed on the inner surface of the tread and forming a skeleton of the tire; and an inner liner disposed on an inner surface of the body ply, wherein the liquid chamber may be disposed on an inner surface of the inner liner.

In the tire according to an embodiment of the present invention, the liquid chamber may be formed of a rubber tube in which the fluid is accommodated.

In the tire according to an embodiment of the present invention, the tire may further include a sensor unit sensing an acceleration of the vehicle, wherein the sensor unit may transmit the sensed acceleration value of the vehicle to the controller.

A method of controlling a tire according to an embodiment of the present invention includes: measuring an acceleration of the vehicle while the vehicle is running; and sealing the inside of the liquid chamber by closing a valve connected to the liquid chamber mounted on the tire when the measured absolute value of the acceleration of the vehicle exceeds the set value (a).

In the method for controlling a tire according to an embodiment of the present invention, when the measured absolute value of the acceleration of the vehicle is equal to or less than the set value (a), the step of opening the valve to circulate air inside and outside the liquid chamber is further performed. may include

In a method for controlling a tire according to an embodiment of the present invention, periodically re-measuring the acceleration of the vehicle; and determining whether to open or close the valve based on the re-measured acceleration of the vehicle.

Other aspects, features and advantages other than those described above will become apparent from the following detailed description, claims and drawings for carrying out the invention.

A tire and a method for controlling the same according to an embodiment of the present invention improve driving convenience by providing high elasticity during general driving through a fluid in a liquid chamber disposed inside a tread, and close the liquid chamber during high-speed driving or rapid rotation to close the tread By increasing the rigidity of the vehicle, driving safety can be improved.

Effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

1 is a view showing a state in which a vehicle equipped with a tire according to an embodiment of the present invention is driven.
2 is a schematic front view of a tire according to an embodiment of the present invention.
FIG. 3 is a partial perspective view viewed from the direction A of FIG. 2 .
FIG. 4 is a cross-sectional view taken along line III-III of FIG. 2 .
FIG. 5 is an enlarged view of part B of FIG. 4 .
6 is a view showing the opening and closing of a valve according to an embodiment of the present invention.
7 is a control block diagram according to an embodiment of the present invention.
8 is a flowchart illustrating a method for controlling a tire according to an exemplary embodiment of the present invention.

Since the present invention can apply various transformations and can have various embodiments, specific embodiments are illustrated in the drawings and described in detail in the description of the invention. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention. In the description of the present invention, even though shown in other embodiments, the same identification numbers are used for the same components.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, and when described with reference to the drawings, the same or corresponding components are given the same reference numerals, and the overlapping description thereof will be omitted. .

In the following embodiments, terms such as first, second, etc. are used for the purpose of distinguishing one component from another, not in a limiting sense.

In the following examples, the singular expression includes the plural expression unless the context clearly dictates otherwise.

In the following embodiments, terms such as include or have means that the features or components described in the specification are present, and the possibility that one or more other features or components will be added is not excluded in advance.

In the drawings, the size of the components may be exaggerated or reduced for convenience of description. For example, since the size and thickness of each component shown in the drawings are arbitrarily indicated for convenience of description, the present invention is not necessarily limited to the illustrated bar.

In the following embodiments, the x-axis, the y-axis, and the z-axis are not limited to three axes on a Cartesian coordinate system, and may be interpreted in a broad sense including them. For example, the x-axis, y-axis, and z-axis may be orthogonal to each other, but may refer to different directions that are not orthogonal to each other.

In cases where certain embodiments may be implemented otherwise, a specific process sequence may be performed different from the described sequence. For example, two processes described in succession may be performed substantially simultaneously, or may be performed in an order opposite to the order described.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. In the present application, terms such as "comprise" or "have" are intended to designate that a feature, number, step, operation, component, part, or a combination thereof described in the specification exists, but one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof.

For reference, unless specifically limited herein, the traveling direction may correspond to the X-axis direction, the width direction to the Y-axis direction, and the height direction to the Z-axis direction, respectively.

Hereinafter, a tire according to an embodiment of the present invention will be described with reference to FIGS. 1 to 3 .

1 is a view showing a state in which a vehicle equipped with a tire according to an embodiment of the present invention is driven. 2 is a schematic front view of a tire according to an embodiment of the present invention. FIG. 3 is a partial perspective view viewed from the direction A of FIG. 2 . For a description of a configuration not shown in FIGS. 1 to 3 , reference may be made to the content shown in FIG. 4 . The in-direction shown in FIGS. 1 and 4 and 5, which will be described later, refers to the direction of the inner surface of the tire 100 , and the out-direction refers to the direction of the outer surface of the tire 100 .

Referring to FIG. 1 , a tire according to an embodiment of the present invention may be mounted on a vehicle C. Referring to FIG. According to the present invention, the stiffness of the tire may vary according to acceleration or deceleration of the vehicle while the vehicle C is driving.

The tire 100 is a pneumatic tire and may include a tread 110 , a sidewall 120 extending from both sides of the tread 110 , and a bead 130 disposed at an end of the sidewall 120 . have.

In addition, the tire 100 may include a body ply 140 and a belt layer 170 positioned under the tread 110 , and a cap ply 160 may be further included on the belt layer 170 . have. Also, the tire 100 may include the inner liner 150 positioned inside the tread 110 and the pair of sidewalls 120 to maintain the internal air pressure of the tire 100 .

Referring to FIG. 2 , the tire 100 may have a shape extending in the circumferential direction RT about the central axis AX. In addition, a wheel (not shown) may be coupled to the inner side of the tire 100 in the radial direction r from the central axis AX.

The tread 110 may include a region facing the road surface when the tire 100 is mounted on the vehicle C and then driven. For example, the tread 110 may include a region in contact with the road surface when the vehicle is driving. The tread 110 is made of a thick rubber layer and transmits the driving lock and braking force of the vehicle to the ground.

The tread 110 may have one or more patterns, and a plurality of grooves 115 may be formed adjacent to these patterns. The groove 115 may have a shape that is elongated in at least the first direction. In addition, the groove 115 may also include a region having a form that is elongated in a direction crossing the first direction.

The number and shape of the grooves 115 may be variously determined according to the driving characteristics and use of the tire 100 .

The groove 115 may be formed adjacent to the pattern of the tread 110 . For example, the groove 115 may form a boundary of one area of the tread 110 in a form in which one area of the tread 110 is removed.

The number and shape of the grooves 115 may be variously determined according to the driving characteristics and use of the tire 100 . The groove 115 may include a plurality of grooves.

The tread 110 may have a tread block partitioned by a plurality of grooves 115 . The tread block is a portion in contact with the road surface during driving of the vehicle, and may be divided by a first groove circumferentially extending in a radial direction of the tire 100 and a second groove formed in a transverse direction of the tire 100 .

On the surface of the tread block, tread patterns for steering stability, traction, and braking performance, and blocks partitioned by the tread patterns may be located. The tread patterns may include a plurality of grooves for Chinese cabbage when driving on a road surface, and sipes for improving traction and braking force. The sipe is formed in the tread block, and may be a groove having a size smaller than that of the groove. The sipe serves to break the water film by absorbing moisture when driving on a wet road surface, thereby increasing the driving force and braking force of the tire 100 .

The sidewall 120 extends from both sides of the tread 110 to form a side surface of the tire 100 . The sidewall 120 is made of the same or different material from the tread 110 and protects the bead 130 and the body ply 140 to be described later. In an embodiment, one end of the sidewall 120 may extend from one side of the tread 110 and the other end may contact the tire rim.

The bead 130 is disposed at the lower end of the sidewall 120, and is formed in the form of a wire bundle of a square or hexagonal shape coated with rubber on a steel wire, and the tire 100 and the tire rim. can help the bonding of In an embodiment, the bead 130 may be disposed to be surrounded by the body ply 140 to seat and fix the tire 100 to the tire rim.

The bead 130 may include a bead core and a bead filler. The bead core is disposed under the bead filler, and may be formed by twisting a plurality of rubber-coated steel bead cords (wires). The bead filler may be disposed extending from the bead core in the sidewall direction. The bead filler is a rubber filler attached to one side of the bead core, and serves to reinforce the bead core. In another embodiment, a plurality of bead fillers may have different physical properties. The bead 130 may have a plurality of insertion grooves (not shown). The insertion groove is inserted into the mounting protrusion of the rim, so that the tire can be mounted on the rim.

The body ply 140 is configured to form the skeleton of the tire 100 and increase durability of the tire 100 , and may be formed by topping the fiber cord with a rubber material. The body ply 140 absorbs a load and an impact received by the tire 100 , and may maintain the air pressure of the tire 100 at a predetermined level. In an embodiment, the body ply 140 may be turned up from the inner surface In to the outer side of the tire 100 to surround at least a portion of the bead 130 .

The body ply 140 may be formed by overlapping a plurality of cord papers made of a high-strength fiber organic material such as steel, polyester, rayon, or the like, and then coating it with rubber and rolling it. Specifically, the body ply 140 includes one or more rubber components selected from the group consisting of synthetic rubber and natural rubber, and may include at least one or more tire cords. Various natural fibers or rayon, nylon, polyester, and Kevlar may be used as the tire cord, and a steel cord formed by twisting a plurality of thin wires may also be used.

The inner liner 150 may be disposed on the inner surface In of the body ply 140 . The inner liner 150 may prevent air leakage of the tire 100 and may maintain an air pressure in the tire 100 . The inner liner 150 may be formed of a rubber layer having excellent sealing properties. For example, the inner liner 150 may be made of butyl rubber having a high density.

The inner liner 150 may be disposed inside the body ply 140 and extend to the bead 130 . The inner liner 150 may contact one surface of the body ply 140 , and both ends may contact the bead 130 .

The belt layer 170 may be disposed between the tread 110 and the body ply 140 . The belt layer 170 relieves the shock received by the tire 100 from the road surface when the vehicle C equipped with the tire 100 is driven and expands the tread surface of the tread 110 to improve the grounding characteristics and driving stability. have. The belt layer 170 may be formed by rolling by coating a plurality of belt cords made of steel or organic fiber with rubber. The belt layer 170 may be provided in a plurality of layers. For example, the plurality of belt layers may be disposed on the upper surface of the inner liner 150 .

A cap ply 160 may be disposed between the belt layer 170 and the tread 110 . The cap ply 160 may be formed of a special cord paper to minimize the movement of the belt layer 170 during driving of the vehicle C, and may prevent separation of the belt layer 170 during high-speed driving. The cap ply 160 may include a polyester synthetic fiber. The cap ply 160 is supported by the belt layer 170 and the body ply 140 , thereby minimizing movement of the belt layer 170 during driving.

Hereinafter, a liquid chamber according to an embodiment of the present invention will be described with reference to FIGS. 4 and 5 .

FIG. 4 is a cross-sectional view taken along line III-III of FIG. 2 . FIG. 5 is an enlarged view of part B of FIG. 4 . For a description of a configuration not shown in FIGS. 4 and 5 , reference may be made to the contents shown in FIGS. 1 to 3 .

According to one embodiment of the present invention, the tire 100 is disposed on the inner surface of the tread 110 and includes a liquid chamber 200 in which the fluid is accommodated. As an embodiment, the liquid chamber 200 may be disposed on the inner surface (in direction) of the inner liner 150 disposed on the inner surface of the body ply 140 as shown in FIG. 5 .

However, the arrangement position of the liquid chamber is not limited thereto, and may be located on any one of the inner surface portions of the tread 110 . In another embodiment, the liquid chamber may be disposed between the body ply 140 and the inner liner 150 .

The liquid chamber 200 may be formed of a rubber tube in which a fluid is accommodated. The rubber tube is a material having basic elasticity, and elasticity and rigidity may vary depending on the pressure inside the rubber tube.

The fluid accommodated in the liquid chamber 200 may help the liquid chamber 200 to acquire elasticity. The liquid chamber 200 may have elasticity due to the flow of the fluid. The fluid may be formed into a liquid. The fluid may be formed of oil with strong flame resistance.

Hereinafter, the opening and closing of the valve according to an embodiment of the present invention will be described with reference to FIG. 6 .

6 is a view showing the opening and closing of a valve according to an embodiment of the present invention. For a description of a configuration not shown in FIG. 6 , reference may be made to the contents shown in FIGS. 1 to 5 .

According to an embodiment of the present invention, as shown in FIGS. 4 and 6 , the valve 300 is connected to the liquid chamber 200 and opens and closes the liquid chamber 200 . The valve 300 is an air valve, and may block or flow air flowing into and out of the liquid chamber 200 through opening and closing of the valve.

The valve 300 may be formed of a valve according to various embodiments. According to one embodiment, the valve 300 may include a solenoid valve. The solenoid valve may open or close the solenoid valve by an electrical signal from the control unit, which will be described later, to open or block the flow of air flowing through the liquid chamber 200 .

When the valve 300 is opened, the air inside the liquid chamber 200 may circulate with the outside. Accordingly, the liquid chamber 200 may be elastically deformed as the air inside the liquid chamber 200 circulates with the outside according to the pressure applied to the tire 100 when the vehicle C is driven. Accordingly, the elasticity of the tread 110 portion of the tire 100 is increased, and the tire 100 absorbs an impact from the road surface when the vehicle C is driven, thereby improving driving convenience.

When the valve 300 is closed, the air inside the liquid chamber 200 may be blocked from the outside. At this time, as the inside of the liquid chamber 200 is sealed from the outside, deformation is difficult to occur, and at the same time, the liquid chamber 200 may have a rigidity of a certain level or more. Accordingly, as the rigidity of the tread 110 portion of the tire 100 is increased, stability with respect to the adjustment of the vehicle C when the vehicle C is driven can be secured.

According to an embodiment of the present invention, when the absolute value of the acceleration of the vehicle C exceeds a preset absolute value of acceleration (hereinafter defined as a set value) (a) when the vehicle C is driving, the valve 300 Includes a control unit to close the. Also, the controller may open the valve 300 when the absolute value of the acceleration of the vehicle C is equal to or less than the set value a.

When driving the vehicle (C), it is necessary to improve the convenience of driving in a general driving state, and it is necessary to improve the stability of adjustment for more precise control of the vehicle (C) during rapid acceleration, rapid deceleration and sharp rotation.

Accordingly, according to an embodiment of the present invention, the rigidity of the tread 110 portion can be varied according to the acceleration of the vehicle C during driving, thereby variably securing the necessary driving convenience and adjustment stability according to the driving state. can

More specifically, when the absolute value of the acceleration of the vehicle C exceeds the set value (a), it is determined that the vehicle is performing relatively sharp deceleration, rapid acceleration, or sharp rotation, and the valve 300 is closed to close the liquid chamber ( 200) By sealing the inside, the rigidity of the liquid chamber 200 and the rigidity of the tread are strengthened at the same time, so that precise control of the vehicle C can be achieved.

In addition, when the absolute value of the acceleration of the vehicle C is less than or equal to the set value (a), it is determined that the vehicle is traveling at a relatively normal constant speed, and the valve 300 is opened to circulate the inside and the outside of the liquid chamber 200, so that the liquid chamber ( 200), it is possible to secure the convenience of driving the vehicle (C) according to the elastic deformation of the tread.

In an embodiment, a pump may be connected to the valve 300 . As described above, the liquid chamber 200 maintains a state in which a significant amount of internal air is discharged to the outside by the repeated opening and closing operations of the valve, so that the rigidity or elasticity of the liquid chamber 200 may gradually weaken. In this case, the pump forcibly injects a certain amount of air into the liquid chamber 200 through the valve 300 at regular intervals to maintain the rigidity or elasticity of the liquid chamber 200 above a certain level.

Hereinafter, control of the valve according to an embodiment of the present invention will be described with reference to FIGS. 7 and 8 .

7 is a control block diagram according to an embodiment of the present invention. 8 is a flowchart illustrating a method for controlling a tire according to an embodiment of the present invention. For a description of a configuration not shown in FIGS. 7 and 8 , reference may be made to the contents shown in FIGS. 1 to 6 .

Referring to FIG. 7 , the sensor unit 400 may measure the acceleration or speed of the vehicle C. As shown in FIG. In one embodiment, the sensor unit 400 may include an acceleration sensor for measuring the acceleration of the vehicle (C). The sensor unit 400 may be disposed inside the tire 100 to detect acceleration during rotation through a gravitational field. The sensor unit 400 may transmit the detected acceleration value of the vehicle to the control unit 500 .

In another embodiment, the sensor unit 400 may include a speed sensor for measuring the speed of the vehicle (C). When the speed is measured by the speed sensor, an acceleration value according to a change amount of the speed may be calculated. The sensor unit 400 may transmit the calculated acceleration value of the vehicle to the control unit 500 .

The control unit 500 may control the opening and closing of the valve 300 based on the vehicle acceleration information received from the sensor unit 400 . The controller 500 may close the valve 300 when the absolute value of the acceleration of the vehicle exceeds the set value (a). Also, when the absolute value of the acceleration of the vehicle C is equal to or less than the set value a, the valve 300 may be opened. After determining whether to open or close the valve, the control unit 500 transmits a signal for whether to open or close the valve to the valve driving unit 510 , and the valve driving unit 510 drives the valve 300 based on the opening/closing signal of the control unit 500 . to open and close the valve 300 .

For example, when the valve 300 is formed of a solenoid valve according to an embodiment, the valve driving unit 510 transmits an electrical signal to the solenoid valve to drive the solenoid valve, thereby opening and closing the valve.

In another embodiment, the controller 500 may control the pump connected to the valve 300 . The controller 500 may control the pump connected to the valve 300 at regular intervals to inject air into the liquid chamber 200 . The control unit 500 may control the amount of air introduced into the liquid chamber 200 at regular intervals by controlling the driving time of the pump and the like.

Referring to FIG. 8 , in the method for controlling a tire according to an embodiment of the present invention, the step ( S100 ) of measuring the acceleration of the vehicle while the vehicle (C) is driving and the measured absolute value of the acceleration of the vehicle are set as a set value (a) In the case of exceeding the value, the step of sealing the inside of the liquid chamber 200 by closing the valve 300 connected to the liquid chamber 200 mounted on the tire ( S300 ) is included.

In addition, when the measured absolute value of the acceleration of the vehicle is equal to or less than the set value (a) (S400), the method may further include opening the valve 300 to circulate air inside and outside the liquid chamber 200 (S500). have.

Measure the acceleration of the driving vehicle (C), and adjust the elasticity and stiffness of the axle based on the measured acceleration to vary the stiffness of the tread, thereby changing the stiffness and elasticity of the tire according to the changing driving conditions. Driving convenience and adjustment stability can be variably reflected.

In one embodiment, the method may further include periodically re-measuring the acceleration of the vehicle C ( S600 ) and determining whether to open or close the valve 300 based on the re-measured acceleration of the vehicle. Acceleration values such as acceleration, deceleration, and sudden turn during driving of the vehicle (C) may vary continuously depending on the situation. Therefore, the acceleration of the vehicle (C) is re-measured, and the absolute value of the re-measured acceleration is compared with the set value (a). By periodically performing the comparison process, the opening/closing of the valve 300 and the rigidity and elasticity of the tread may be periodically varied according to driving conditions.

As described above, the present invention has been described with reference to the embodiment shown in the drawings, but this is only an example. Those of ordinary skill in the art can fully understand that various modifications and equivalent other embodiments are possible from the embodiments. Therefore, the true technical protection scope of the present invention should be determined based on the appended claims.

Specific technical content described in the embodiment is an embodiment and does not limit the technical scope of the embodiment. In order to concisely and clearly describe the description of the invention, descriptions of conventional general techniques and configurations may be omitted. In addition, the connection or connection member of the lines between the components shown in the drawings exemplarily shows functional connections and/or physical or circuit connections, and in an actual device, various functional connections, physical connections that are replaceable or additional It may be expressed as a connection, or circuit connections. In addition, unless there is a specific reference such as "essential", "importantly", etc., it may not be a necessary component for the application of the present invention.

In the description and claims, "above" or similar referents may refer to both the singular and the plural unless otherwise specified. In addition, when a range is described in the embodiment, it includes the invention to which individual values belonging to the range are applied (unless there is a description to the contrary), and each individual value constituting the range is described in the description of the invention. same. In addition, the steps constituting the method according to the embodiment may be performed in an appropriate order unless the order is clearly stated or there is no description to the contrary. The embodiments are not necessarily limited according to the order of description of the above steps. The use of all examples or exemplary terminology (eg, etc.) in the embodiment is merely for describing the embodiment in detail, and unless it is limited by the claims, the scope of the embodiment is limited by the examples or exemplary terminology. it is not In addition, those skilled in the art will appreciate that various modifications, combinations, and changes can be made in accordance with design conditions and factors within the scope of the appended claims or their equivalents.

100: tire
110: tread
120: side wall
130: bead
140: body fly
150: inner liner
160: cap ply
170: belt layer
200: axil
300: valve
400: sensor unit
500: control
510: valve driving unit

Claims (8)

In a tire mounted on a vehicle,
a tread extending along a circumferential direction of the tire and having a groove;
a liquid chamber disposed on the inner surface of the tread and accommodating the fluid;
a valve connected to the liquid chamber and configured to open and close the liquid chamber; and
A control unit for closing the valve when the absolute value of the acceleration of the vehicle exceeds a set value (a) when the vehicle is running;
The tire has one liquid chamber, and when the valve is opened, the air inside the liquid chamber is circulated to the outside, and when the valve is closed, the air inside the liquid chamber is blocked from the outside. According to claim 1,
The controller is configured to open the valve when the absolute value of the acceleration of the vehicle is equal to or less than a set value (a). According to claim 1,
a body ply disposed on the inner surface of the tread and forming a skeleton of the tire; and
Further comprising an inner liner disposed on the inner surface of the body ply,
The liquid chamber is disposed on an inner surface of the inner liner. According to claim 1,
wherein the liquid chamber is formed of a rubber tube in which the fluid is accommodated. According to claim 1,
Further comprising a sensor unit for sensing the acceleration of the vehicle,
The sensor unit transmits the detected acceleration value of the vehicle to the control unit. measuring an acceleration of the vehicle while the vehicle is running; and
When the measured absolute value of the acceleration of the vehicle exceeds the set value (a), closing a valve connected to the liquid chamber mounted on the tire to seal the inside of the liquid chamber;
The method of controlling a tire, wherein the liquid chamber is formed in one piece, the air inside the liquid chamber circulates with the outside when the valve is opened, and the air inside the liquid chamber is blocked from the outside when the valve is closed. 7. The method of claim 6,
When the measured absolute value of the acceleration of the vehicle is equal to or less than a set value (a), the method further comprising the step of opening the valve to circulate air inside and outside the liquid chamber. 8. The method of claim 7,
periodically re-measuring the acceleration of the vehicle; and
and determining whether to open or close the valve based on the re-measured acceleration of the vehicle.

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