Suspension system for vehicle

Abstract

An embodiment suspension system for a vehicle includes: a rocker arm housing coupled to a first end of a lower arm through which an axis of rotation passes; a rocker arm having a first end surrounded by the rocker arm housing and a second end disposed toward the center of the rocker arm housing, the rocker arm being rotatable together with the lower arm about an axis of rotation; a torsion bar having a first end connected to the second end of the rocker arm, and a second end extending along the rotational axis and then coupled to the vehicle body connecting member; and a contact protrusion provided to one of the rocker arm housing and the rocker arm, the contact protrusion configured to start contact with the other of the rocker arm and the rocker arm housing according to a rotation angle of the rocker arm housing.

Description

Technical Field

[0001] The present invention relates to a suspension system for a vehicle. Background Art

[0002] A suspension system for a vehicle refers to a device that connects an axle and a vehicle body and prevents vibration or impact applied from a road surface from being directly transmitted to the vehicle body when the vehicle is running, thereby preventing damage to the vehicle body or cargo and improving ride quality.

[0003] The suspension system has a structure that absorbs impact by restricting rotation of a lower arm using torsion of a torsion bar when a wheel bumps.

[0004] However, the structure in the related art is such that the torsion bar always exhibits a predetermined rigidity regardless of the rotation angle of the lower arm.

[0005] However, in the related art, the torsion bar is configured to absorb the impact by always showing a torsion force having a predetermined magnitude regardless of the rotation angle of the lower arm. That is, the torsion bar is configured to absorb the impact by showing a single rigidity regardless of the rotation angle of the lower arm, but when the vehicle weight greatly increases due to the increase in the number of passengers and loaded items, it is difficult for the torsion bar to effectively cope with the excessive reduction in the vehicle height.

[0006] In the case of a vehicle such as a multi-purpose vehicle (MPV) in which the weight of passengers and cargo fluctuates greatly, a double-rate spring is sometimes used to compensate for excessive reduction in vehicle height. In this case, there is a problem that the cost increases and the layout for the installation space needs to be separately set.

[0007] The foregoing contents described as background technology are only intended to help understand the background of the embodiments of the present invention, and are not intended to mean that the embodiments of the present invention fall within the scope of the relevant technologies known to those skilled in the art. Summary of the invention

[0008] The present invention relates to a suspension system for a vehicle. A specific embodiment relates to a technology related to a suspension system for a vehicle, which absorbs shock by using a torsion bar that achieves double stiffness when a lower arm rotates.

[0009] Embodiments of the present invention can solve the problems in the prior art and aim to provide a suspension system for a vehicle, wherein the structures of a rocker arm housing and a rocker arm for transmitting the rotation of a lower arm to a torsion bar are improved so that the torsion bar can exhibit torsional forces of different magnitudes according to the rotational stroke of the lower arm, thereby absorbing impact by using a torsion bar that achieves dual stiffness.

[0010] In order to achieve the above-mentioned objectives, an embodiment of the present invention provides a suspension system for a vehicle, comprising: a rocker housing, which is connected to one end of a lower arm through which a rotation axis passes; a rocker arm, which has: one end surrounded by the rocker housing, and the other end arranged toward the center of the rocker housing, the rocker arm being configured to rotate around the rotation axis together with the lower arm; and a torsion bar, which has: one end connected to the other end of the rocker arm, and the other end extending along the rotation axis and then connected to a vehicle body connecting member, the torsion bar being configured to: receive the rotation of the lower arm through the rocker housing and the rocker arm, thereby exhibiting torsional force, wherein a contact protrusion is provided on either the rocker housing and the rocker arm, and is configured to: start to contact with the rocker arm or the rocker housing according to the rotation angle of the rocker housing.

[0011] The spring rate of the torsion bar may be determined based on the length of the rocker arm, the total length of the torsion bar, and the diameter of the torsion bar, and the spring rate of the torsion bar may be inversely proportional to the length of the rocker arm and the total length of the torsion bar, and directly proportional to the diameter of the torsion bar.

[0012] The total length of the torsion bar and the diameter of the torsion bar may be fixed factors whose values ​​remain unchanged, the length of the rocker arm may be a variable factor that changes depending on whether the contact protrusion contacts the rocker arm, and when the contact protrusion contacts the rocker arm, the length of the rocker arm that affects the spring stiffness of the torsion bar may decrease, and the spring stiffness of the torsion bar may increase as the length of the rocker arm decreases.

[0013] When the contact protrusion is not in contact with the rocker arm, the length of the rocker arm affecting the spring rate of the torsion bar may be a total length from one end surrounded by the rocker arm housing to the other end coupled to the torsion bar.

[0014] When the contact protrusion contacts the rocker arm, the length of the rocker arm affecting the spring rate of the torsion bar may be a shortened length from a position where the contact protrusion contacts the rocker arm to the other end coupled to the torsion bar.

[0015] The rocker arm insertion groove may be radially disposed on the rocker arm housing, and one end of the rocker arm may be inserted into the rocker arm insertion groove such that the one end of the rocker arm is installed to be surrounded by the rocker arm insertion groove.

[0016] The contact protrusion may be formed to protrude from an inlet side of the rocker arm insertion groove toward the rocker arm.

[0017] The contact protrusion may be formed to protrude toward the rocker arm only from either side of an inlet side of the rocker arm insertion groove so that when the rocker arm housing is rotated by a bumping operation of the wheel, the contact protrusion comes into contact with the rocker arm.

[0018] The time point when the contact protrusion starts to contact the rocker arm can be defined as a reference time point, the line connecting the centers of the two opposite ends of the rocker arm at the reference time point can be defined as a center line, the line connected to the end of the contact protrusion in a direction perpendicular to the center line can be defined as a reference line, and when the end of the contact protrusion is positioned closer to the other end connected to the torsion bar by exceeding the reference line, the time point of contact between the contact protrusion and the rocker arm can be advanced from the reference time point, and the time point of change in the stiffness of the torsion bar can be advanced from the reference time point.

[0019] The time point at which the contact protrusion starts to contact the rocker arm can be defined as a reference time point, the line connecting the centers of the two opposite ends of the rocker arm at the reference time point can be defined as a center line, and the line connected to the end of the contact protrusion in a direction perpendicular to the center line can be defined as a reference line, and when the end of the contact protrusion is positioned closer to the end connected to the rocker arm housing without exceeding the reference line, the time point of contact between the contact protrusion and the rocker arm can be delayed from the reference time point, and the time point of change in the stiffness of the torsion bar can be delayed from the reference time point.

[0020] The suspension system may further include: a connector connected to the other end of the lower arm through which the rotation axis passes, the connector being configured to rotate around the rotation axis together with the lower arm. The vehicle body connection member includes: a first fixing plate connected to the rocker housing through a first bearing and assembled with the other end of the rocker; a second fixing plate connected to the connector through a second bearing; and a central shaft configured to connect the first fixing plate and the second fixing plate, and configured so that a connection bracket connected to the vehicle body is connected to the central shaft.

[0021] The suspension system according to the embodiment of the present invention is configured such that: a contact protrusion is provided on a rocker housing, the rocker housing is configured to transmit the rotation of the lower arm to the torsion bar, and when the wheel bumps, according to the rotation stroke of the lower arm and the rocker housing, the contact protrusion starts to contact the rocker arm, so that the length of the rocker arm that affects the spring stiffness of the torsion bar can be changed. Therefore, when the wheel bumps completely, the torsion bar shows a torsion of different magnitudes, which makes it possible to achieve dual stiffness of the torsion bar.

[0022] In addition, the suspension system according to the embodiment of the present invention can realize the dual rigidity of the torsion bar, thereby being applied to vehicles in which the weight of passengers and cargo fluctuates greatly. Therefore, it is possible to prevent the vehicle height from being excessively lowered, thereby further improving the durability of the suspension system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 FIG. 4 is an exploded view of a suspension system for a vehicle according to an embodiment of the present invention.

[0024] Figure 2 for Figure 1 The connection status view of

[0025] Figure 3 It is a view showing an initial state where the wheel has not bumped and rebounded.

[0026] Figure 4 A view for explaining elements for determining the spring rate of a torsion bar.

[0027] Figure 5 This is a view showing a state where the wheel has fully rebounded.

[0028] Figure 6 A view showing the point in time when the wheel bumps and the contact protrusion starts to contact the rocker arm.

[0029] Figure 7 for Figure 6 A magnified view of .

[0030] Figure 8 This is a view showing a state where the wheel is completely bumped.

[0031] Fig. 9 Graph for explaining the spring stiffness of a torsion bar according to an embodiment of the present invention. DETAILED DESCRIPTION

[0032] Hereinafter, the embodiments disclosed in the present specification will be described in detail with reference to the accompanying drawings. Regardless of the figure numbers, the same or similar constituent elements are given the same reference numerals, and repeated descriptions thereof are omitted.

[0033] For convenience of description, the suffixes “module,” “unit,” “part,” and “portion” used to describe constituent elements are used together or interchangeably in the following description, but the suffixes themselves do not have distinguishable meanings or functions.

[0034] In the description of the embodiments disclosed in this specification, when it is determined that the specific description may obscure the subject matter of the embodiments disclosed in this specification, the specific description of the well-known related art will be omitted.

[0035] In addition, it should be understood that the drawings are provided only to make it easy for those skilled in the art to understand the embodiments disclosed in this specification, and that the technical spirit disclosed in this specification is not limited to the drawings, and includes all changes, equivalents and substitutions included in the spirit and technical scope of the embodiments of the present invention.

[0036] Terms including ordinal numbers such as "first", "second", etc. may be used to describe various constituent elements, but the constituent elements are not limited by the terms. These terms are only used to distinguish one constituent element from another constituent element.

[0037] When a constituent element is described as being “coupled” or “connected” to another constituent element, it should be understood that the one constituent element may be directly coupled or connected to the other constituent element and an intervening constituent element may also be present between the constituent elements.

[0038] When a constituent element is described as being “directly coupled to” or “directly connected to” another constituent element, it should be understood that there is no intervening constituent element between the constituent elements.

[0039] A singular expression includes a plural expression unless it is clearly described as having a different meaning in the context.

[0040] In the present specification, it should be understood that the terms "comprises", "comprising", "includes", "including", "containing", "has", "having" or other variations thereof are inclusive, and thus specify the presence of stated features, integers, steps, operations, elements, components or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components or combinations thereof.

[0041] In addition, the term "control unit" or "unit" included in the name of "Motor Control Unit (MCU)" or "Hybrid Control Unit (HCU)" is merely a term widely used to name a control device (controller or control unit) used to control specific vehicle functions, but does not mean a general functional unit.

[0042] The controller may include: a communication device configured to communicate with another control unit or sensor to control a corresponding function; a memory configured to store an operating system, logic instructions, and input / output information; and one or more processors configured to perform measurements, calculations, decisions, etc. required to control the corresponding function.

[0043] Hereinafter, a suspension system for a vehicle according to an exemplary embodiment of the present invention will be described with reference to the accompanying drawings.

[0044] like Figures 1 to 9As shown, the suspension system for a vehicle according to an embodiment of the present invention includes: a rocker housing 200, which is coupled to one end of a lower arm 100 through which a rotation axis L1 passes, and the rocker housing 200 is configured to rotate around the rotation axis L1 together with the lower arm 100; rocker arms 300, each having one end surrounded by the rocker housing 200 and the other end disposed toward the center of the rocker housing 200; and a torsion bar 500, each having one end connected to the other end of each rocker arm 300 and the other end extending along the rotation axis L1 and then coupled to the vehicle body connection member 400, and the torsion bar 500 is configured to receive the rotation of the lower arm 100 through the rocker housing 200 and the rocker arm 300, thereby exhibiting a torsion force. The contact protrusion 600 is provided in either the rocker housing 200 or the rocker arm 300, and is configured to start contacting with the rocker arm 300 or the rocker housing 200 according to the rotation angle of the rocker housing 200.

[0045] The lower arm 100 has an A-shaped outer shape with three ends. One end is coupled to a wheel 10 of a vehicle through a ball joint, and the remaining two ends are connected to a vehicle body 20 .

[0046] The wheel 10 bumps and rebounds based on the initial state. When the wheel 10 bumps and rebounds, the lower arm 100 rotates clockwise or counterclockwise around the rotation axis L1 passing through the center of the remaining two ends.

[0047] The rocker arm housing 200 is coupled to one end of the lower arm 100 , which is one of the remaining two ends through which the rotation axis L1 passes, and when the lower arm 100 rotates, the rocker arm housing 200 rotates together with the lower arm 100 .

[0048] According to an embodiment of the present invention, the rocker arm insertion groove 210 is radially provided in the rocker arm housing 200, and one end of the rocker arm 300 is inserted into the rocker arm insertion groove 210. Therefore, one end of the rocker arm 300 is installed in a state surrounded by the rocker arm insertion groove 210.

[0049] The other end of the rocker arm 300 disposed toward the center of the rocker arm housing 200 is coupled to one end of a torsion bar 500 extending along the rotation axis L1 , and the other end of the torsion bar 500 is fixedly coupled to the vehicle body connection member 400 .

[0050] Therefore, by the bump and rebound operation of the wheel 10, the lower arm 100 rotates about the rotation axis L1, and the rocker housing 200 rotates together with the lower arm 100. When one end of the rocker arm 300 inserted into the rocker arm insertion groove 210 rotates, the torsion bar 500 having two opposite ends connecting the rocker arm 300 and the vehicle body connection member 400 performs a twisting operation by the rotation of the rocker arm 300, thereby exhibiting a torsion force, and the torsion force of the torsion bar 500 can be used to absorb the impact.

[0051] The contact protrusion 600 may be formed at any one of the rocker housing 200 and the rocker arm 300. In the embodiment according to the present invention, a structure in which the contact protrusion 600 is formed at the rocker housing 200 and comes into contact with the rocker arm 300 when the rocker housing 200 rotates will be basically described.

[0052] In the case where the contact protrusion 600 is formed on the rocker arm 300 , when the rocker arm housing 200 rotates, the contact protrusion 600 comes into contact with the rocker arm housing 200 .

[0053] In the embodiment according to the present invention, the length of the rocker arm 300 affecting the spring stiffness of the torsion bar 500 may vary according to the contact between the contact protrusion 600 and the rocker arm 300 based on the rotation stroke of the lower arm 100. Therefore, the torsion bar 500 may realize spring stiffness K (torsion) with different sizes.

[0054] That is, the spring stiffness K (torsion) of the torsion bar 500 is determined based on the length of the rocker arm 300, the total length L2 of the torsion bar 500, and the diameter D1 of the torsion bar 500. The spring stiffness of the torsion bar 500 is inversely proportional to the length of the rocker arm 300 and the total length L2 of the torsion bar 500 and is proportional to the diameter D1 of the torsion bar 500.

[0055] In this case, the total length L2 of the torsion bar 500 and the diameter D1 of the torsion bar 500 are fixed factors whose values ​​do not change.

[0056] The total length L2 of the torsion bar 500 is the length from one end coupled to the other end of the swing arm 300 to the other end coupled to the vehicle body connection member 400 .

[0057] In addition, the length of the swing arm 300 is a variable factor that changes depending on whether the contact protrusion 600 contacts the swing arm 300 .

[0058] That is, when the contact protrusion 600 is not in contact with the rocker arm 300 , the length of the rocker arm 300 affecting the spring rate K of the torsion bar 500 is a total length L3 from one end surrounded by the rocker arm housing 200 to the other end coupled to the torsion bar 500 .

[0059] In this case, factors affecting the spring stiffness K of the torsion bar 500 are the total length L3 of the rocker arm 300 , the total length L2 of the torsion bar 500 , and the diameter D1 of the torsion bar 500 .

[0060] However, when the contact protrusion 600 contacts the rocker arm 300 , the length of the rocker arm 300 affecting the spring rate K of the torsion bar 500 is a shortened length L4 from the position where the contact protrusion 600 contacts the rocker arm 300 to the other end coupled to the torsion bar 500 .

[0061] In this case, factors affecting the spring rate K of the torsion bar 500 are the shortened length L4 of the rocker arm 300 , the total length L2 of the torsion bar 500 , and the diameter D1 of the torsion bar 500 .

[0062] When the lower arm 100 and the rocker arm housing 200 rotate by the bumping operation of the wheel 10, when the contact protrusion 600 comes into contact with the rocker arm 300, the length of the rocker arm 300, which affects the spring stiffness K of the torsion bar 500, is reduced to a shortened length L4. The spring stiffness K of the torsion bar 500 increases as the length of the rocker arm 300 is reduced. A higher spring stiffness K of the torsion bar 500 can prevent an excessive decrease in the height of the vehicle, thereby further improving the durability of the suspension system.

[0063] The contact protrusion 600 according to the embodiment of the present invention is configured to protrude from the inlet side of the rocker arm insertion groove 210 toward the rocker arm 300 .

[0064] That is, the contact protrusion 600 is configured to protrude toward the rocker arm 300 only from either side of the inlet side of the rocker arm insertion groove 210, so that the contact protrusion 600 can come into contact with the rocker arm 300 only when the rocker arm housing 200 rotates by the bumping operation of the wheel 10. In the drawings according to the embodiment of the present invention, the contact protrusion 600 is formed only on the inlet side of the rocker arm insertion groove 210 based on the upper side of the rocker arm 300.

[0065] Figure 3 shows the initial state of the wheel 10 without bumping and rebounding, and Figure 5 FIG. 1 is a view showing a state where the wheel 10 is fully rebounded. Figure 3 The initial state and Figure 5 In the fully rebounded state in , the contact protrusion 600 is not in contact with the rocker arm 300. In this case, the length of the rocker arm 300 that affects the spring stiffness K of the torsion bar 500 is the total length L3 from one end to the other end.

[0066] Reference Fig. 9 As shown in the graph in FIG. 1 , when the wheel 10 changes from the initial state to the fully rebounded state, the spring stiffness K11 of the torsion bar 500 can be represented as a graph of a linearly increasing single stiffness.

[0067] Figure 6 A view showing a point in time when the wheel 10 bumps and the contact protrusion 600 contacts the rocker arm 300 by the rotation of the rocker arm housing 200, Figure 7 for Figure 6 A magnified view of Figure 8 This is a diagram showing a state where the wheel fully bumps.

[0068] refer to Fig. 9, when the wheel 10 changes from the initial state to the full bump state, the spring stiffness K21 of the torsion bar 500 is represented as a double stiffness curve diagram, in which the spring stiffness increases linearly and then increases rapidly after the inflection point P1 at a certain time point.

[0069] That is, when the wheel 10 bumps in the initial state, the contact protrusion 600 does not contact the rocker arm 300 until the lower arm 100 and the rocker arm housing 200 rotate a predetermined angle. In this case, the length of the rocker arm 300 that affects the spring stiffness K1 of the torsion bar 500 is the total length L3 from one end to the other end.

[0070] When the contact protrusion 600 comes into contact with the rocker arm 300 as the bumping operation continues and the rocker arm housing 200 continues to rotate, the length of the rocker arm 300 that affects the spring rate K2 of the torsion bar 500 is a shortened length L4 from the position where the contact protrusion 600 comes into contact with the rocker arm 300 to the other end coupled to the torsion bar 500. The spring rate K2 of the torsion bar 500 increases from this point.

[0071] That is, when the wheel 10 bumps, the torsion bar 500 exhibits a single spring rate K1 until the contact protrusion 600 starts to contact the rocker arm 300. The torsion bar 500 exhibits an increased spring rate K2 from the inflection point P1 where the contact protrusion 600 contacts the rocker arm 300 to the fully bumped state. Therefore, even in the case where the weight of passengers and cargo fluctuates greatly, an excessive decrease in the height of the vehicle can be prevented, thereby further improving the durability of the suspension system.

[0072] refer to Figure 7 , the time point when the contact protrusion 600 contacts the rocker arm 300 is defined as a reference time point, a line connecting the centers of the two opposite ends of the rocker arm 300 at the reference time point is defined as a center line L5, and a line connected to the end of the contact protrusion 600 in a direction perpendicular to the center line L5 is defined as a reference line L6. When the end of the contact protrusion 600 is positioned closer to the other end connected to the torsion bar 500 by exceeding the reference line L6 Figure 7 When the position in the middle direction M1 is reached, the time point of contact between the contact protrusion 600 and the rocker arm 300 is advanced from the reference time point. Therefore, the time point of change in the stiffness of the torsion bar 500 can be adjusted to be advanced from the reference time point.

[0073] On the contrary, when the end of the contact protrusion 600 is positioned closer to the end connected to the rocker arm housing 200 without exceeding the reference line L6 ( Figure 7 When the position in the middle direction M2 is reached, the time point of contact between the contact protrusion 600 and the rocker arm 300 is delayed from the reference time point. Therefore, the time point of change in the stiffness of the torsion bar 500 can be adjusted to be delayed from the reference time point.

[0074] The embodiment according to the present invention further includes a connector 700 coupled to the other end of the lower arm 100 through which the rotation axis L1 passes, and the connector 700 is configured to rotate around the rotation axis L1 together with the lower arm 100 .

[0075] In addition, the vehicle body connecting member 400 may include: a first fixing plate 410, which is connected to the rocker housing 200 through a first bearing 800 and assembled with the other end of the rocker 300; a second fixing plate 420, which is connected to the connector 700 through a second bearing 900; and a central shaft 440, which is configured to connect the first fixing plate 410 and the second fixing plate 420, and is configured so that the connecting bracket 430 connected to the vehicle body 20 is connected to the central shaft 440.

[0076] An inner ring of the first bearing 800 is coupled to the rocker housing 200 by press-fitting, and an outer ring of the first bearing 800 is coupled to the vehicle body 20 by press-fitting.

[0077] An inner ring of the second bearing 900 is coupled to the connector 700 by press-fitting, and an outer ring of the second bearing 900 is coupled to the vehicle body 20 by press-fitting.

[0078] Both opposite ends of the center shaft 440 may be spline-coupled to central portions of the first and second fixing plates 410 and 420 , and a connecting bracket 430 may be coupled to connect the vehicle body 20 and the center shaft 440 .

[0079] As described above, the suspension system according to the embodiment of the present invention is configured such that the contact protrusion 600 is provided on the rocker housing 200, which is configured to transmit the rotation of the lower arm 100 to the torsion bar 500, and when the wheel 10 bumps, the contact protrusion 600 starts to contact the rocker arm 300 according to the rotation stroke of the lower arm 100 and the rocker housing 200, so that the length of the rocker arm 300 that affects the spring stiffness of the torsion bar 500 can be varied. Therefore, when the wheel 10 bumps completely, the torsion bar 500 shows a torsion of different magnitudes, which makes it possible to achieve dual stiffness of the torsion bar 500.

[0080] In addition, the suspension system according to the embodiment of the present invention can realize the dual rigidity of the torsion bar 500, thereby being applied to a vehicle in which the weight of passengers and cargo fluctuates greatly. Therefore, excessive reduction in vehicle height can be prevented, thereby further improving the durability of the suspension system.

[0081] While specific embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that various modifications and changes may be made to the embodiments of the present invention without departing from the technical spirit of the embodiments of the present invention as defined in the appended claims.

Claims

1. A suspension system for a vehicle, the suspension system comprising: a rocker housing coupled to a first end of a lower arm through which the axis of rotation passes; a rocker arm having: a first end surrounded by the rocker arm housing, and a second end disposed toward a center of the rocker arm housing, the rocker arm being configured to: rotate about the rotation axis together with the lower arm; a torsion bar having a first end connected to the second end of the rocker arm and a second end extending along the rotation axis and then coupled to a vehicle body connection member, the torsion bar being configured to receive rotation of the lower arm through the rocker arm housing and the rocker arm, thereby exhibiting a torsion force; and A contact protrusion is provided on one of the rocker arm housing and the rocker arm, and is configured to come into contact with the other of the rocker arm and the rocker arm housing according to a rotation angle of the rocker arm housing.

2. The suspension system of claim 1, wherein: The spring rate of the torsion bar is determined based on the length of the rocker arm, the overall length of the torsion bar, and the diameter of the torsion bar; and The spring rate of the torsion bar is inversely proportional to the length of the rocker arm and the overall length of the torsion bar, and is directly proportional to the diameter of the torsion bar.

3. The suspension system of claim 2, wherein: The total length of the torsion bar and the diameter of the torsion bar are fixed factors whose values ​​do not change, and the length of the rocker arm is a variable factor that changes depending on whether the contact protrusion contacts the rocker arm; and In a state in which the contact protrusion is in contact with the rocker arm, the length of the rocker arm that affects the spring stiffness of the torsion bar decreases, and the spring stiffness of the torsion bar increases as the length of the rocker arm decreases.

4. The suspension system according to claim 1, wherein: In a state where the contact protrusion is not in contact with the rocker arm, the length of the rocker arm affecting the spring rate of the torsion bar is a total length from the first end surrounded by the rocker arm housing to the second end coupled to the torsion bar.

5. The suspension system according to claim 1, wherein: In a state where the contact protrusion contacts the rocker arm, the length of the rocker arm that affects the spring rate of the torsion bar is a shortened length from a position where the contact protrusion contacts the rocker arm to the second end coupled to the torsion bar.

6. The suspension system according to claim 1, further comprising: a rocker arm insertion slot radially disposed in the rocker arm housing, wherein: The first end of the rocker arm is inserted into the first rocker arm insertion groove of the rocker arm insertion groove, so that the first end of the rocker arm is surrounded by the first rocker arm insertion groove.

7. The suspension system according to claim 6, wherein: The contact protrusion protrudes from an entrance side of the first rocker arm insertion groove toward the rocker arm.

8. The suspension system according to claim 6, wherein: The contact protrusion protrudes toward the rocker arm only from either side of an entrance side of the first rocker arm insertion groove, so that when the rocker arm housing rotates by a bumping operation of a wheel, the contact protrusion comes into contact with the rocker arm.

9. The suspension system of claim 1, wherein: The time point at which the contact protrusion starts to contact the rocker arm is defined as a reference time point; A first line connecting the centers of the two opposite ends of the rocker arm at the reference time point is defined as a center line; A second line connected to the end of the contact protrusion in a direction perpendicular to the center line is defined as a reference line; and When the end of the contact protrusion is positioned closer to the second end of the rocker arm connected to the torsion bar by exceeding the reference line, a first time point of contact between the contact protrusion and the rocker arm is advanced from the reference time point, and a second time point of change in the stiffness of the torsion bar is advanced from the reference time point.

10. The suspension system of claim 1, wherein: The time point at which the contact protrusion starts to contact the rocker arm is defined as a reference time point; A first line connecting the centers of the first end and the second end of the rocker arm at the reference time point is defined as a center line, the second end being opposite to the first end; A second line connected to the end of the contact protrusion in a direction perpendicular to the center line is defined as a reference line; and Wherein, when the end of the contact protrusion is positioned closer to the first end of the rocker arm connected to the rocker arm housing without exceeding the reference line, a first time point of contact between the contact protrusion and the rocker arm is delayed from the reference time point, and a second time point of change in the stiffness of the torsion bar is delayed from the reference time point.

11. The suspension system of claim 1, further comprising: a connector connected to the second end of the lower arm through which the rotation axis passes, the connector being configured to rotate together with the lower arm about the rotation axis.

12. The suspension system of claim 11, wherein: The vehicle body connecting component comprises: a first fixing plate coupled to the rocker arm housing through a first bearing and assembled with the second end of the rocker arm; a second fixing plate coupled to the connector via a second bearing; as well as A center shaft connects the first fixing plate and the second fixing plate and is configured to be coupled to a connecting bracket connected to a vehicle body.

13. A vehicle comprising: Car body; A lower arm having: an A-shaped profile with three ends, wherein: A first end is connected to the vehicle body, a second end is connected to the vehicle body, and a third end is coupled to a wheel of the vehicle; a rocker housing coupled to the first end of the lower arm through which the axis of rotation passes; a rocker arm having: a first end surrounded by the rocker arm housing, and a second end disposed toward a center of the rocker arm housing, the rocker arm being configured to rotate about the rotation axis together with the lower arm; a torsion bar having a first end connected to the second end of the rocker arm and a second end extending along the rotation axis and then coupled to a vehicle body connection member, the torsion bar being configured to receive rotation of the lower arm through the rocker arm housing and the rocker arm, thereby exhibiting a torsion force; and A contact protrusion is provided on one of the rocker arm housing and the rocker arm, and is configured to come into contact with the other of the rocker arm and the rocker arm housing according to a rotation angle of the rocker arm housing.

14. The vehicle of claim 13, wherein: The spring rate of the torsion bar is determined based on the length of the rocker arm, the overall length of the torsion bar, and the diameter of the torsion bar; and The spring rate of the torsion bar is inversely proportional to the length of the rocker arm and the overall length of the torsion bar, and is directly proportional to the diameter of the torsion bar.

15. The vehicle of claim 14, wherein: The total length of the torsion bar and the diameter of the torsion bar are fixed factors whose values ​​do not change, and the length of the rocker arm is a variable factor that changes depending on whether the contact protrusion contacts the rocker arm; and In a state in which the contact protrusion is in contact with the rocker arm, the length of the rocker arm that affects the spring stiffness of the torsion bar decreases, and the spring stiffness of the torsion bar increases as the length of the rocker arm decreases.

16. The vehicle of claim 13, wherein: In a state where the contact protrusion is not in contact with the rocker arm, the length of the rocker arm affecting the spring rate of the torsion bar is a total length from the first end surrounded by the rocker arm housing to the second end coupled to the torsion bar.

17. The vehicle of claim 13, wherein: In a state where the contact protrusion contacts the rocker arm, the length of the rocker arm that affects the spring rate of the torsion bar is a shortened length from a position where the contact protrusion contacts the rocker arm to the second end coupled to the torsion bar.

18. The vehicle of claim 13, further comprising: a rocker arm insertion slot radially disposed in the rocker arm housing, wherein: The first end of the rocker arm is inserted into a first rocker arm insertion groove of the rocker arm insertion groove, so that the first end of the rocker arm is surrounded by the first rocker arm insertion groove.

19. The vehicle of claim 13, wherein: The time point at which the contact protrusion starts to contact the rocker arm is defined as a reference time point; A first line connecting the centers of the two opposite ends of the rocker arm at the reference time point is defined as a center line; A second line connected to the end of the contact protrusion in a direction perpendicular to the center line is defined as a reference line; and When the end of the contact protrusion is positioned closer to the second end of the rocker arm connected to the torsion bar by exceeding the reference line, a first time point of contact between the contact protrusion and the rocker arm is advanced from the reference time point, and a second time point of change in the stiffness of the torsion bar is advanced from the reference time point.

20. The vehicle of claim 13, wherein: The time point at which the contact protrusion starts to contact the rocker arm is defined as a reference time point; A first line connecting the centers of the first end and the second end of the rocker arm at the reference time point is defined as a center line, the second end being opposite to the first end; A second line connected to the end of the contact protrusion in a direction perpendicular to the center line is defined as a reference line; and Wherein, when the end of the contact protrusion is positioned closer to the first end of the rocker arm connected to the rocker arm housing without exceeding the reference line, a first time point of contact between the contact protrusion and the rocker arm is delayed from the reference time point, and a second time point of change in the stiffness of the torsion bar is delayed from the reference time point.

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