Description:A VEHICLE SIDE BODY STRUCTURE

TECHNICAL FIELD
[0001] The present disclosure relates generally to body structure of a vehicle and in particular relates to a side body structure of a vehicle.

BACKGROUND
[0002] In the competitive automobile industries, stylish appearance is considered to be a key aspect while launching any new model of a vehicle. The buyers prefer a vehicle with stylish appearance. To meet the expectations of the buyers, many vehicles with different designs are launched in the market each year. However, change in appearance of the vehicle body structure affect the overall manufacturing and assembling of the vehicle. For example, performance experiments are performed on the newly designed body structure parts to monitor the strength of these parts in various conditions.
[0003] While changing the outer appearance of the vehicle side body structure, it is not intended to change design of each and every part of the vehicle side body structure. Since, the intended purpose is to improve the appearance of the vehicle from outside, the only requirement for this purpose is to change the design of the parts which are provided on the outer side of the vehicle side body structure. These parts on which the design modification is intended may be referred as primary body parts. Other parts on which the design modification is not intended may be referred as secondary body parts. However, design of the primary body parts may not fit with the design of the secondary body parts of the vehicle body structure during assembly process. There may arise a condition where no common mounting surface is available for joining primary body parts with the secondary body parts. To overcome the problem, the secondary body parts are also designed freshly (from scratch) in accordance with the new design of the primary body parts. This fresh designing of the secondary body parts increases the cost of the overall manufacturing process due to requirement of new mold as per the new design. Further, it is also time consuming process because new experiments has to be performed on the freshly designed secondary body parts.
[0004] Figures 1a and 1b illustrate a wheel housing outer panel and a wheel housing inner panel, respectively, according to the existing art. The wheel housing outer panel 100A is provided on the outer side, in a vehicle width direction, covering over a rear wheel. A fuel box 101 is provided on the top portion of the wheel housing outer panel 100A for accommodating fuel. A quarter panel 102 is provided affixed on the upper portion of the wheel housing outer panel 100A.
[0005] Similarly, a wheel housing inner panel 100B is provided on the inner side, in a vehicle width direction, corresponding to the wheel housing outer panel 100A. A suspension strut mounting structure 103 is provided on the inner face of the wheel housing inner panel 100B to accommodate suspension strut. A flange 104 is also provided originating from the upper end of the suspension strut mounting structure 103. The suspension strut mounting structure 103 is considered as a critical zone since a huge amount of force is applied in this region. A suspension tower is provided around the suspension strut mounting structure 103 in the wheel housing inner panel 100B for distribution of forces acting on the suspension strut mounting structure 103. Together the suspension tower, the suspension strut mounting structure 103 and the quarter panel 102 are joined to form a box section. This box section is required to be rigid as it comes under high loading condition and forms a critical zone. This box section is capable of distributing the load in the surrounding. The upper portion of the wheel housing outer panel 100A and the flange 104 of the wheel housing inner panel 100B run parallel and are at same height. During assembly of the vehicle side body structure, the upper portion of the wheel housing outer panel 100A and the flange 104 of the wheel housing inner panel 100B are welded together. Further, the wheel housing outer panel 100A is welded with the quarter panel 102 and wheel housing inner panel 100B is welded with the suspension tower. Together, the wheel housing outer panel 100A, the wheel housing inner panel 100B, the quarter panel 102 and the suspension tower provide a rigid assembly to form the vehicle side body structure.
[0006] Design changes are normally performed on outer panels of the vehicle side body structure for example on wheel housing outer panel 100A. For instance, the new design of the vehicle side body structure has fuel box provided slightly above than the existing design for ergonomics or styling purposes. In this new design the structure of the wheel housing outer panel 100A (primary body part) is changed by extending the upper portion of the wheel housing outer panel 100A upwards. With change in the design of the wheel housing outer panel 100A the height of the wheel housing outer panel 100A is not equal to the wheel housing inner panel 100B (secondary body part). Hence, there is no common mounting surface available to join the wheel housing outer panel 100A with the wheel housing inner panel 100B. Since to make the vehicle side body structure the wheel housing outer panel 100A (primary body part) has to be joined with the wheel housing inner panel 100B (secondary body part), a fresh design for wheel housing inner panel 100B becomes a necessity.
[0007] Although the new design of the wheel housing inner panel 100B (secondary body part) does not provide any advantage to styling purposes, it becomes a necessity to produce the vehicle side body structure. With the change in design of the wheel housing inner panel 100B, manufacturing process and assembling process also get affected. Further, freshly designing the wheel housing inner panel 100B increases the cost of the overall manufacturing process. Also, performance experiments are performed on the newly designed wheel housing inner panel 100B to monitor the strength of these parts in various conditions which are time consuming.
[0008] Hence to produce a vehicle side body structure with change in design of the primary body part, design of the secondary body parts also has to be changed.
[0009] Accordingly, there is a need for a vehicle side body structure to avoid changing the design of the secondary body parts when design changes are performed on the primary body parts.
SUMMARY
[0010] This summary is provided to introduce concepts related to a vehicle side body structure to avoid changing the design of the secondary body parts when design changes are performed on the primary body parts. The concepts are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
[0011] The present disclosure relates to a vehicle side body structure. The vehicle side body structure includes a quarter panel, a wheel housing outer panel, a wheel housing inner panel and a suspension tower. The wheel housing outer panel is provided below the quarter panel. The wheel housing inner panel is provided on the inner side of the wheel housing outer panel. Further, the wheel housing inner panel has a suspension strut mounting structure and a flange originating from the upper end of the suspension strut mounting structure. The suspension tower is provided on inner face of the wheel housing inner panel over the suspension strut mounting structure forming a box section. A bracket is secured on the top of the flange, along the length of the vehicle side body structure, to provide a common annex surface to the quarter panel, the wheel housing outer panel, the wheel housing inner panel and the suspension tower for joining.
[0012] In an aspect, the bracket is welded on the flange of the wheel housing inner panel.
[0013] In an aspect, at least one two-ply joining point is present on bottom part of the bracket to affix the wheel house inner panel on the bracket.
[0014] In an aspect, at least one three-ply joining point is present on the common annex surface of the bracket to affix the wheel housing outer panel and the quarter panel together with the bracket.
[0015] In an aspect, at least one three-ply joining point is present on the common annex surface of the bracket to affix the wheel house outer panel and the suspension tower together with the bracket.
[0016] In an aspect, at least one two-ply joining point is present on the common annex surface of the bracket to affix the wheel housing outer panel on the bracket.
[0017] In an aspect, profile of the common annex surface of the bracket replicates the profile of the corresponding parts of the vehicle side body structure affixed at said joining point.
[0018] In an aspect, the thickness of the bracket could be varied based on the vehicle performance requirements.
[0019] In an aspect, the material of the bracket could be varied based on the vehicle performance requirements.
[0020] In an aspect, the dimensions of the bracket could be varied based on the vehicle performance requirements.
[0021] In an aspect, the wheel housing outer panel, the wheel housing inner panel, the quarter panel and the suspension tower are joined on the corresponding joining points over the common annex surface of the bracket through spot welding.
[0022] To further understand the characteristics and technical contents of the present subject matter, a description relating thereto will be made with reference to the accompanying drawings. However, the drawings are illustrative only but not used to limit the scope of the present subject matter.
[0023] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF FIGURES
[0024] The illustrated embodiments of the present disclosure will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of the vehicle side body structure that are consistent with the subject matter as claimed herein, wherein:
[0025] FIG. 1a illustrates a wheel housing outer panel according to the existing art;
[0026] FIG. 1b illustrates a wheel housing inner panel according to the existing art;
[0027] FIG. 2 illustrates an exemplary vehicle side body structure that can be utilized to implement one or more exemplary embodiments of the present disclosure;
[0028] FIG. 3 illustrates joining points of the exemplary vehicle side body structure that can be utilized to implement one or more exemplary embodiments of the present disclosure;
[0029] FIG. 4 illustrates sectional views of the exemplary vehicle side body structure that can be utilized to implement one or more exemplary embodiments of the present disclosure.
[0030] FIG. 5 illustrates an exploded view of another exemplary vehicle side body structure that can be utilized to implement one or more exemplary embodiments of the present disclosure;
[0031] FIG. 6 illustrates sectional views of the other exemplary vehicle side body structure that can be utilized to implement one or more exemplary embodiments of the present disclosure;
[0032] FIG. 7a and 7b illustrate bracket and its mounting with outer panel and inner panel in accordance with an the exemplary vehicle side body structures that can be utilized to implement one or more exemplary embodiments of the present disclosure; and
[0033] FIG. 7c illustrates another bracket in accordance with another exemplary vehicle side body structures that can be utilized to implement one or more exemplary embodiments of the present disclosure.
[0034] The figures depict embodiments of the present subject matter for the purposes of illustration only. A person skilled in the art will easily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

DETAILED DESCRIPTION
[0035] A few aspects of the present disclosure are explained in detail below with reference to the various figures. Example implementations are described to illustrate the disclosed subject matter, not to limit its scope, which is defined by the claims. Those of ordinary skill in the art will recognize a number of equivalent variations of the various features provided in the description that follows.
Definitions
[0036] In the disclosure hereinafter, one or more terms are used to describe various aspects of the present disclosure. For a better understanding of the present disclosure, a few definitions are provided herein for better understanding of the present disclosure.
[0037] “Annex Surface” may be defined as additional surface. In the present disclosure, the term “Annex Surface” is often used as “Common Annex Surface” to indicate that a common additional surface is provided by the bracket to the quarter panel, the wheel housing inner panel, the wheel housing outer panel and the suspension tower for joining.
[0038] “Primary Body Parts” may be defined, in the context of the disclosure, as body parts of the vehicle side body structure on which the design modification is intended for stylish appearance or for ergonomic purposes.
[0039] “Secondary Body Parts” may be defined, in the context of the disclosure, as body parts of the vehicle side body structure on which the design modification is not-intended but has become a necessity due to design modification in primary body parts.
[0040] “Critical Zone” may be defined as zones which are prone to get damaged due to excessive forces application in certain area of a vehicle.
[0041] “Two-ply joining point” may be defined as a point on the common annex surface of the bracket where any one of the quarter panel, the wheel housing inner panel, the wheel housing outer panel and the suspension tower is directly affixed.
[0042] “Three-ply joining point” may be defined as a point on the common annex surface of the bracket where any two of the quarter panel, the wheel housing inner panel, the wheel housing outer panel and the suspension tower, in any combination, is directly affixed.

EXEMPLARY EMBODIMENTS
[0043] While the present disclosure may be embodied in various forms, there are shown in the drawings, and will hereinafter be described, some exemplary and non-limiting embodiments, with the understanding that the present disclosure is to be considered an exemplification of the invention and is not intended to limit the invention to the specific embodiments illustrated. Not all of the depicted components described in this disclosure may be required, however, and some implementations may include additional, different, or fewer components from those expressly described in this disclosure. Variations in the arrangement and type of the components may be made without departing from the scope of the claims as set forth herein.
[0044] A vehicle side body structure generally comprises outer side body parts and inner side body parts. These outer side body parts are affixed to the inner side body parts to produce the vehicle side body structure. To give a stylish look to a vehicle, design modifications are usually performed on the outer side body parts/primary body parts of a vehicle. Since the outer side body parts are affixed to the inner side body parts, sometimes it becomes a necessity to modify the design of inner side body part/ secondary body parts due to the absence of any common mounting surface over which the primary body parts and the secondary body parts could be affixed.
[0045] This fresh designing of the secondary body parts increases the cost of the overall manufacturing process due to requirement of new mold as per the new design. Further, it is also time consuming process because new experiments have to be performed on secondary body parts.
[0046] To solve the problem, a vehicle side body structure is required which can avoide changing the design of the secondary body parts when design changes are performed on the primary body parts.
[0047] In order to achieve this goal of avoiding changing design of secondary body parts, a vehicle side body structure may be utilized. The features of the vehicle side body structure are described in more detail below.
[0048] FIG. 2 illustrates an exploded view of exemplary vehicle side body structure that can be utilized to implement one or more exemplary embodiments of the present disclosure. The vehicle side body structure 200 includes a quarter panel 201, a wheel housing outer panel 202, a wheel housing inner panel 203 and a suspension tower 204. The quarter panel 201 is generally provided between the door and the trunk of the vehicle on the outer side. Just below the quarter panel 201 the wheel housing outer panel 202 is provided. On the wheel housing outer panel 202 a fuel box is mounted to accommodate fuel filling system. Both the quarter panel 201 and the wheel housing outer panel 202 are provided on the outer side of the vehicle side body structure 200.
[0049] The wheel housing inner panel 203 is provided towards the inner side of the wheel housing outer panel 202. The wheel housing inner panel 202 primarily comprises a suspension strut mounting structure 203a and a flange 203b originating from the upper end of the suspension strut mounting structure 203a. Both the suspension strut mounting structure 203a and the flange 203b are provided on the inner surface of the wheel housing inner panel 203. The suspension tower 204 is provided over the suspension strut mounting structure 203a on the inner surface of the wheel housing inner panel 203. Together, the flange 203b, the quarter panel 201 and the suspension tower 204 form a box section in joined condition. This box section is required to be rigid as it comes under the critical zone.
[0050] To avoid any design modification on secondary body parts, a bracket 205 is provided on the secondary body part in a way that it can provide a common mounting surface for joining purposes. In an aspect, the bracket 205 is provided on the wheel housing inner panel 203 and more particularly on the top of the flange 203b of the wheel housing inner panel 203 along the length of the vehicle side body structure 200. Since the bracket 205 is provided on the top of the wheel housing inner panel 203, it provides a common annex surface for joining to the quarter panel 201, the wheel housing inner panel 203, the wheel housing outer panel 202 and the suspension tower 204. Thus the bracket could be divided into two parts, i.e. a top part providing the common annex surface and a bottom part.
[0051] In an aspect, the bottom part of the bracket 205 is welded on the top of the flange 203b of the wheel housing inner panel 203 through at least one two-ply joining point.
[0052] FIG. 3 illustrates joining points of the exemplary vehicle side body structure 200 that can be utilized to implement one or more exemplary embodiments of the present disclosure. The diagram clearly illustrates the joining points of the quarter panel 201, the wheel housing inner panel 203, the wheel housing outer panel 202 and the suspension tower 204 with the bracket 205. For easy illustration on joining points, the joining points are referenced in the exemplary embodiment. It is to be appreciated that location of the joining points on the common annex surface as well as on the parts of the vehicle side body structure 200 are illustrated for understanding purpose only. Other locations of such joining points on the common annex surface as well as on the parts of the vehicle side body structure 200 are equally possible.
[0053] A three-ply joining point is created on the common annex surface of the bracket 205 resulting from the joining of point a1 of the wheel housing outer panel 202, point a2 of the quarter panel 201 and point a3 on the common annex surface of the bracket 205. In an aspect, there could be more than one joining points provided among same parts of the vehicle side body structure 200 on different locations in case there is need for more stability in that area. Accordingly, a three-ply joining point is created on the common annex surface of the bracket 205 resulting from the joining of point b1 of the wheel housing outer panel 202, point b2 on the quarter panel 201 and point b3 on the common annex surface of the bracket 205.
[0054] A three-ply joining point is created on the common annex surface of the bracket 205 resulting from the joining of point c1 of the wheel housing outer panel 202, point c2 on the common annex surface of the bracket 205 and point c3 on the suspension tower 204. Together these three three-ply joining points are utilized to create a vehicle side body structure 200 which can withstand forces in side body area of the vehicle. All the three ply joining points are present on the top part of the bracket 205 acting as a common annex surface.
[0055] FIG. 4 illustrates sectional views of the exemplary vehicle side body structure that can be utilized to implement one or more exemplary embodiments of the present disclosure. The diagram illustrates three sectional views of the vehicle side body structure 200 in assembled condition along A-A, B-B and C-C axes. The A-A section illustrates the three-ply joining point created on the common annex surface of the bracket 205 resulting from the joining of the point a1 of the wheel housing outer panel 202, the point a2 of the quarter panel 201 and the point a3 on the common annex surface of the bracket 205. The B-B section illustrates the three-ply joining point created on the common annex surface of the bracket 205 resulting from the joining of the point b1 of the wheel housing outer panel 202, the point b2 on the quarter panel 201 and the point b3 on the common annex surface of the bracket 205. The C-C section illustrates the three-ply joining point created on the common annex surface of the bracket 205 resulting from the joining of the point c1 of the wheel housing outer panel 202, the point c2 on the common annex surface of the bracket 205 and the point c3 on the suspension tower 204.
[0056] Profile of the common annex surface of the bracket 205 depends on the surface of the corresponding part of the vehicle side body structure 200 which is to be joined at that point. In an aspect, the profile of the common annex surface of the bracket 205 replicates the profile of the corresponding parts of the vehicle side body structure 200 affixed at said joining point. Accordingly, there is possibility of brackets with different profiles of the common annex surface.
[0057] FIG. 5 illustrates an exploded view of another exemplary vehicle side body structure that can be utilized to implement one or more exemplary embodiments of the present disclosure. In this exemplary embodiment, the profile of the common annex surface of this bracket 501 is different from the profile of the common annex surface of the bracket 205 of previous embodiment. In this exemplary embodiment, the wheel housing outer panel 502 is directly joined on the common annex surface of the bracket 501 attached to the wheel housing inner panel 503. Accordingly, the profile of the common annex surface is planer and matches the profile of the wheel housing outer panel 502, which is to be affixed on the common annex surface. Further, a reinforcing bead 504 is provided on the bracket 501 to strengthen the flat area of the bracket 501.
[0058] FIG. 6 illustrates sectional view of the other exemplary vehicle side body structure that can be utilized to implement one or more exemplary embodiments of the present disclosure. The A-A section illustrates the two-ply joining point created on the common annex surface of the bracket 501 resulting from the joining of the wheel housing outer panel 502 and the common annex surface of the bracket 501.
[0059] FIG. 7a and 7b illustrate brackets in accordance with both the exemplary vehicle side body structures that can be utilized to implement one or more exemplary embodiments of the present disclosure. The profile of the common annex surface of the bracket 205 of the exemplary embodiment is different from the profile of the common annex surface of the bracket 501 of other exemplary embodiment. As already discussed, the profile of the common annex surface of the brackets 205, 501 depends on the profile of the corresponding parts of the vehicle side body structure 200, 500 affixed at said joining point.
[0060] Referring to fig. 7a, illustrating profile and structure of the bracket 205. The bracket 205 may define a step 205c that extended in vehicle longitudinal direction along L1-L2 along with the profile of the bracket 205 and divide the bracket 205 in an upper portion 205a and a lower portion 205b in vehicle height direction along H1-H2. The upper portion 205a may define as three-ply joining point and the lower portion 205b may define as two-ply joining point. When viewing from rear side of the vehicle, the step 205c increases horizontal distance in widthwise direction W1-W2 in between straight the upper portion 205a and the lower portion 205b. By increasing the horizontal distance in widthwise direction W1-W2 in between straight the upper portion 205a and the lower portion 205b, a required distance in widthwise direction W1-W2 can be achieved.
[0061] The upper portion 205a of the bracket 205, the wheel housing outer panel 202 and the quarter panel 201 joined to form a three-ply joining point. Accordingly, the profile 701 of the said common annex portion of the bracket 205 around this three-ply joining point is identical to the corresponding profile of the quarter panel 201 in said three-ply joining point. As illustrated in the diagram, the profile of the bracket 205 in this three-ply joining point is not planar. The lower portion 205b affixes with the wheel house inner panel (203) to define a two-ply joining point.
[0062] As shown in fig. 7c, similarly, in case of bracket 501, the wheel housing outer panel 502 is directly affixed to the common annex surface of the bracket 501 forming a two-ply joining point. Accordingly, the profile 702 of the said common annex portion of the bracket 501 around this two-ply joining point is identical to the corresponding profile of the wheel housing outer panel 502. As illustrated in the diagram, the profile of the bracket 501 in this two-ply joining point is planar which is similar to the planar profile of the wheel housing outer panel 502.
[0063] Thus, with the implementation of the vehicle side body structure of the present subject matter, it is ensured that there is no need to freshly (from scratch) design the secondary body parts in accordance with the freshly designed primary body parts. With reference to the exemplary embodiments it implies that there is no need to freshly design the wheel housing inner panel in accordance with the newly designed wheel housing outer panel. The elimination of unintended change in design saves cost as well as time during manufacturing and assembling.
[0064] The above description does not provide specific details of the manufacture or design of the various components. Those of skill in the art are familiar with such details, and unless departures from those techniques are set out, techniques, known, related art or later developed designs and materials should be employed. Those in the art are capable of choosing suitable manufacturing and design details.
[0065] Further, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be combined into other systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may subsequently be made by those skilled in the art without departing from the scope of the present disclosure as encompassed by the following claims.
[0066] The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.
[0067] It will be appreciated that variants of the above-disclosed and other features and functions, or alternatives thereof, may be combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.

Claims:

We Claim:
1. A vehicle side body structure (200), comprising:
a quarter panel (201);
a wheel housing outer panel (202) provided below the quarter panel (201);
a wheel housing inner panel (203) provided on inner side of the wheel housing outer panel (202) having a suspension strut mounting structure (203a) and a flange (203b) originating from upper end of the suspension strut mounting structure (203a); and
a suspension tower (204) provided on inner face of the wheel housing inner panel (203) over the suspension strut mounting structure (203a) forming a box section,
characterized in that
a bracket (205) is secured on the top of the flange (203b), along the length of the vehicle side body structure (200), to provide common annex surface to the quarter panel (201), the wheel housing outer panel (202), the wheel housing inner panel (203) and the suspension tower (204) for joining to form the vehicle side body structure (200).
2. The vehicle side body structure (200) as claimed in claim 1, wherein the bracket (205) is welded on the flange (203a) of the wheel housing inner panel (203).
3. The vehicle side body structure (200) as claimed in claim 1, wherein at least one two-ply joining point is present on bottom part of the bracket (205) to affix the wheel housing inner panel (203) on the bracket (205).
4. The vehicle side body structure (200) as claimed in claim 1, wherein at least one three-ply joining point is present on the common annex surface of the bracket (205) to affix the wheel housing outer panel (202) and the quarter panel (201) together with the bracket (205).
5. The vehicle side body structure (200) as claimed in claim 1, wherein at least one three-ply joining point is present on the common annex surface of the bracket (205) to affix the wheel house outer panel (202) and the suspension tower (204) together with the bracket (205).
6. The vehicle side body structure (200) as claimed in claim 1, wherein at least one two-ply joining point is present on the common annex surface of the bracket (205) to affix the wheel housing outer panel (202) on the bracket (205).
7. The vehicle side body structure (200) as claimed in claim 1, wherein the profile of the common annex surface of the bracket (205) replicates the profile of the corresponding parts of the vehicle side body structure (200) affixed at said joining point.
8. The vehicle side body structure (200) as claimed in claim 1, wherein the thickness of the bracket (205) dependes on the vehicle performance requirements.
9. The vehicle side body structure (200) as claimed in claim 1, wherein the material of the bracket (205) depends on the vehicle performance requirements.
10. The vehicle side body structure (200) as claimed in claim 1, wherein the wheel housing outer panel (202), the wheel housing inner panel (203), the quarter panel (201) and the suspension tower (204) are joined on the joining points over the common annex surface of the bracket (205) through spot welding.
11. The vehicle side body structure (200) as claimed in claim 1, wherein the bracket (205) comprises a step (205c) along longitudinal direction (L1-L2) of the bracket (205), the step (205c) defines an upper portion (205a) and a lower portion (205b), where the step (205c) varies horizontal distance between the wheel inner panel (203) and the wheel outer panel (202) in vehicle width direction (W1-W2).