WO2009004473A2

WO2009004473A2 - Suspension structure

Info

Publication number: WO2009004473A2
Application number: PCT/IB2008/001760
Authority: WO
Inventors: Shinpei Matsumoto; Toru Uchiyama
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 2007-07-05
Filing date: 2008-07-04
Publication date: 2009-01-08
Also published as: WO2009004473A3; JP4289424B2; JP2009012626A

Abstract

A suspension structure (100) includes: a chassis frame including a pair of side frames (12); leaf springs (20); and brackets (22, 24). One end of the leaf spring (20) is attached to an outer side surface (12f) of the side frame (12) through the bracket (22). The other end is attached to a lower surface of the side frame (12) through the bracket (24). The bracket (22) is fixed to a first position (P1) located in the side frame (12), and the bracket (24) is fixed to a second position (P2) at which a distance between the side frames (12) in the width direction of the vehicle is larger than the distance between the side frames (12) at the first position (P1).

Description

SUSPENSION STRUCTURE

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The invention relates to a suspension structure including a leaf spring.

2. Description of the Related Art

[0002] In a vehicle that is relatively heavy and carries a large load, such as a pickup truck, a vehicle body structure in which an upper body, including a cabin, is supported on a chassis frame is available (for example, see Japanese Patent Application Publication No. 7-267137 (JP-A-7-267137)). Further, a pickup truck, in which a suspension is provided with a leaf spring, is available. Japanese Utility Model Application Publication No. 61-134412 (JP-U-61-134412) describes a frame structure in which the leaf spring is attached on the lower side of the side frame through a link and a bracket.

[0003] The leaf spring that supports an end of an axle shaft is deformed in a vertical direction of the vehicle to reduce a shock and vibration when a vertical force is applied from a road surface to the leaf spring through the axle shaft. Therefore, when the leaf spring is attached to a frame with the position of the leaf spring being offset in a width direction of the vehicle, each end of the leaf spring is supported by a bracket that is fixed to an outer side surface of the frame and projects from the side surface of the frame. With this configuration, a torsional moment is applied to the frame through the bracket due to the vertical force applied to the leaf spring.

[0004] If the brackets that support the ends of the leaf spring are fixed to the lower surface of the frame, the torsional moment as described above does not occur. However, if the leaf spring is largely deformed, the leaf spring is brought into contact with the lower surface of the frame, which results in restricting the size and characteristics of the leaf spring used.

SUMMARY OF THE INVENTION

[0005] The invention provides a suspension structure with which it is possible to suppress occurrence of a moment that adversely affects a frame, and reduce restriction on the amount of deformation of a leaf spring attached to the frame.

[0006] A first aspect of the invention relates to a vehicle suspension structure that includes: a chassis frame that includes a pair of side frames, each extending in a longitudinal direction of a vehicle; a leaf spring that absorbs a force applied from the road surface to the chassis frame through an axle shaft; a first attachment member by which one end of the leaf spring is attached to an outer side surface of at least one of the pair of side frames; and a second attachment member by which the other end of the leaf spring is attached to a lower surface of the at least one of the pair of side frames. In the vehicle suspension structure, the at least one of the pair of side frames includes a bent portion that is bent in a crank shape in a width direction of the vehicle. Further, the first attachment member is fixed to a first position on the at least one of the pair of side frames, the first position being located in, of first and second portions of the at least one of the pair of side frames that are adjacent to the bent portion on both sides of the bent portion, the first portion, wherein a distance between the first portions of the pair of side frames in the width direction of the vehicle is smaller than a distance between the second portions of the pair of side frames in the width direction of the vehicle, and the second attachment member is fixed to a second position on the at least one of the pair of side frames, the second position being located in one of the bent portion and the second portion of the at least one of the pair of side frames.

[0007] According to the aforementioned configuration, the other end of the leaf spring is attached to the lower surface of the side frame. Therefore, it is possible to suppress a torsional moment from occurring in the side frame even when a vertical force is transmitted from the road surface to the second attachment member by which the other end of the leaf spring is attached to the lower surface of the side frame. Further, because the one end of the leaf spring is attached to the outer side surface of the side frame, the leaf spring does not coincide with the side frame when viewed from above, and therefore it is possible to prevent the leaf spring from being brought into contact with the side frame when the leaf spring is deformed in the vertical direction of the vehicle. This configuration makes it possible to employ the type of leaf spring with large deformation, making it easier to design a suspension with suitable spring characteristics.

[0008] In the aforementioned configuration, the second portion may be located more outward in the width direction of the vehicle than the first portion is located. This configuration also brings about the advantageous effects similar to those achieved by the above aspect of the invention.

[0009] In the aforementioned configuration, the suspension structure may further include: an auxiliary leaf spring; a third attachment member by which one end of the auxiliary leaf spring is attached to the side surface of the at least one of the pair of side frames; and a fourth attachment member by which the other end of the auxiliary leaf spring is attached to the side surface of the at least one of the pair of side frames. In the suspension structure, the third attachment member and the fourth attachment member may be fixed to the at least one of the pair of side frames at positions between the first position and the second position so that the auxiliary leaf spring is disposed immediately above the leaf spring. Further, the auxiliary leaf spring may be designed so as to make spring characteristics of a suspension nonlinear by being deformed along with the leaf spring when a force equal to or greater than a predetermined force is applied to the leaf spring.

[0010] According to the aforementioned configuration, the auxiliary leaf spring is disposed immediately above the leaf spring so as to prevent the auxiliary leaf spring from being brought into contact with the side frame, whereby it is possible to realize a compact suspension that exhibits nonlinear spring characteristics.

[0011] The leaf spring may be attached to the at least one of the pair of side frames through the first attachment member and the second attachment member in a manner such that a longitudinal direction of the leaf spring is arranged in parallel to a longitudinal direction of the at least one of the pair of side frames. With this configuration, the moment applied to the first attachment member through the leaf spring due to the force applied in the vertical direction of the vehicle acts in a direction such that rotation about an axis extending in the longitudinal direction of the side frame is caused.

[0012] The bent portion may be bent, for example, in a crank shape in a vertical direction of the vehicle so that the second position is positioned lower than the first position. With this configuration, the other end of the leaf spring is disposed further below, so that the space laterally beside the side frame and above the leaf spring is enlarged, thereby increasing the design freedom relating to the selection and layout of the auxiliary leaf spring.

[0013] The bent portion may be formed so that a distance in the width direction of the vehicle between the pair of side frames on a side closer to a center of the vehicle in the longitudinal direction of the vehicle is larger than a distance between the pair of side frames on a side farther from the center of the vehicle. With this configuration, it is possible to increase the design freedom with respect to the layout for arranging the plurality of components, such as a fuel tank and an exhaust muffler, in a central area of the vehicle.

[0014] A second aspect of the invention relates to a vehicle suspension structure that includes: a chassis frame that includes a side frame, extending in a longitudinal direction of a vehicle; a leaf spring that absorbs a force applied from a road surface to the chassis frame through an axle shaft; a first attachment member by which one end of the leaf spring is attached to an outer side surface of the side frame; and a second attachment member by which the other end of the leaf spring is attached to a lower surface of the side frame. In the vehicle suspension structure, the side frame includes a bent portion that is bent in a crank shape in a width direction of the vehicle. Further, the first attachment member is fixed to a first position on the side frame, the first position being located in one portion of portions that are adjacent to the bent portion on both sides of the bent portion. The one portion is narrower than other portion in the width direction of the vehicle, the second attachment member is fixed to a second position on the side frame, and the side frame in the second position spreads more in the width direction of the vehicle than the side frame in the first position.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The foregoing and further objects, features and advantages of the invention will become apparent from the following description of an embodiment with reference to the accompanying drawings, wherein like numerals are used to represent like elements and wherein:

FIG. 1 is a top view schematically showing a configuration of a chassis frame according to an embodiment;

FIG. 2 is an enlarged top view of a portion of a suspension structure in a region II, which is indicated by a dotted line in FIG. 1 ; and

FIG. 3 is a side view of the side frame shown in FIG. 2 when viewed from the direction indicated by the arrow III.

DETAILED DESCRIPTION OF THE EMBODIMENT

[0016] Hereinafter, an embodiment of the invention will be described in detail with reference to the attached drawings. It should be noted that the same elements in the description of the drawings will be denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

[0017] FIG. 1 is a top view schematically showing a configuration of a chassis frame according to an embodiment of the invention. A suspension structure described using this embodiment is one in which leaf springs are attached to a chassis frame of a vehicle, such as a pickup truck, which is heavy and carries a large load. It should be noted that the left side in FIG. 1 corresponds to the front side (Fr) of the vehicle.

[0018] A chassis frame 10 is a component formed by pressing or bending a steel plate, and includes a pair of side frames 12 that extends in a longitudinal direction of the vehicle. Each of the side frames 12 may have a sectional shape similar to that of a rail. The chassis frame 10 includes a front frame 14 that connects the right and left side frames 12 at front ends of the side frames 12, and a rear frame 16 that connects the right and left side frames 12 at rear ends of the side frames 12. Further, the chassis frame 10 includes cross member frames 18 that are disposed between the front frame 14 and the rear frame 16 at intervals. The number of the cross member frames 18 is suitably selected in accordance with the strength required of the chassis frame 10.

[0019] Each of the side frames 12 includes a linear-shaped front and rear portion 12a and 12b. The side frame 12 also includes a center portion 12c between the front portion 12a and the rear portion 12b. The rear portion 12b may serve as a first portion of the side frame 12, and the center portion 12c may serve as a second portion of the side frame 12. The distance between the center portions 12c of the side frames 12 in a width direction of the vehicle is larger than the distance between the front portions 12a of the side frames 12 and the distance between the rear end portions 12b of the side frames 12 in the width direction of the vehicle.

[0020] Further, each of the side frames 12 includes a bent portion 12d between the front portion 12a and the center portion 12c, the bent portion 12d being bent in a crank shape in the width direction of the vehicle. Further, the side frame 12 includes a bent portion 12e between the center portion 12c and the rear portion 12b, the bent portion 12e being bent in a crank shape in the width direction of the vehicle. Here, the shape that is "bent in a crank shape in the width direction of the vehicle" may be considered to be the shape that is bent outward and then bent inward in the width direction of the vehicle, or the shape that is bent inward and then bent outward in the width direction of the vehicle. In other words, the bent portions 12d, 12e may be considered to be the portions of the side frame 12 that do not include portions parallel to the longitudinal direction of the vehicle. In the chassis frame 10 according to the embodiment, the bent portions 12d, 12e are formed as described above in a manner such that the front portion 12a, the rear portion 12b, and the center portion 12c of one of the side frames 12 are disposed in parallel to the front portion 12a, the rear portion 12b, and the center portion 12c of the other side frame 12, respectively.

[0021] Next, a configuration of a portion around the bent portion 12e, which is in a region II indicated by the dotted line in FIG 1, will be described with reference to FIGS. 2 and 3. FIG. 2 is an enlarged top view showing a portion of a suspension structure in the region II indicated by the dotted line in FIG. 1. FIG. 3 is a side view of the side frame 12 shown in FIG. 2 when viewed from the direction indicated by the arrow III. It should be noted that, the pair of the side frames 12 are the same as each other in the main configuration thereof, except that the pair of the side frames 12 are disposed so as to have a mirror-image relationship. Therefore, only one of the side frames 12 disposed on the left side with respect to the vehicle, which is the lower side in FIG. 1, will be described below, and the description of the other side frame 12 disposed on the right side with respect to the vehicle, which is the upper side in FIG. 1, will be omitted.

[0022] A suspension structure 100 includes: the chassis frame 10 including the side frame 12; a leaf spring 20 that absorbs a force applied from the road surface to the chassis frame 10 through an axle shaft; a bracket 22 by which one end 20a of the leaf spring 20 is attached to an outer side surface 12f of the side frame 12; and a bracket 24 by which the other end 20b of the leaf spring 20 is attached to a lower surface 12g of the side frame 12.

[0023] The side frame 12 includes, as described above, the bent portion 12e that is bent in the crank shape in the width direction of the vehicle. The bracket 22 is fixed to a first position Pl, and the bracket 24 is fixed to a second position P2. The first position Pl is located in one of portions of the side frame 12 that are adjacent to the bent portion 12e on both sides of the bent portion 12e, the one of the portions being disposed farther inward in the width direction of the vehicle than the other. The second position P2 is located in the bent portion 12e and is disposed farther outward in the width direction of the vehicle than the first position Pl .

[0024] The leaf spring 20 is formed by, for example, layering a plurality of elastic steel plates, and both ends of one of the layered steel plates are rolled and wound around cores provided for the brackets 22, 24, respectively. Further, the axle shaft (not shown) is attached to a center portion of the leaf spring 20, and wheels (not shown) are attached to both ends of the axle shaft, respectively. With this configuration, the leaf spring 20 is elastically deformed in reaction to the force applied from the road surface so that the shock caused by uneven road surface, etc. is absorbed by the leaf spring 20.

[0025] As described above, in the suspension structure 100 according to the embodiment, the other end 20b of the leaf spring 20 is attached to the lower surface 12g of the side frame 12. Therefore, it is possible to suppress the occurrence of a torsional moment in the side frame 12 even when a vertical force from the road surface is transmitted to the bracket 24 by which the other end 20b of the leaf spring 20 is attached to the lower surface 12g of the side frame 12. In other words, the bracket 24 is less likely to be affected by a vertical moment, as compared to a suspension structure in which the other end 20b of the leaf spring 20 is attached to the outer side surface 12f. As a result, it is possible to reduce the strength required of the bracket 24, thereby reducing the costs and weight of the suspension structure 100.

[0026] Further, because the one end 20a of the leaf spring 20 is attached to the outer side surface 12f of the side frame 12, the leaf spring 20 does not coincide with the side frame 12 when viewed from above (see FIG. 2), and therefore it is possible to prevent the leaf spring 20 from being brought into contact with the side frame 12 when the leaf spring 20 is deformed in the vertical direction of the vehicle. This configuration makes it possible to employ the type of leaf spring 20 with large deformation, making it easier to design a suspension with suitable spring characteristics.

[0027] The suspension structure 100 further includes: an auxiliary leaf spring 26 that is designed so as to make the spring characteristics of the suspension nonlinear by being deformed along with the leaf spring 20 when a force equal to or greater than a predetermined force is applied to the leaf spring 20; a bracket 28 by which one end 26a of the auxiliary leaf spring 26 is attached to the outer side surface 12f of the side frame 12, and a bracket 30 by which the other end 26b of the auxiliary leaf spring 26 is attached to the outer side surface 12f of the side frame 12. The brackets 28, 30 are fixed to the side frame 12 at positions between the first position Pl and the second position P2 so that the auxiliary leaf spring 26 is disposed immediately above the leaf spring 20.

[0028] The auxiliary leaf spring 26 has basically the same configuration as that of the leaf spring 20, and the leaf spring 20 and the auxiliary leaf spring 26 together function as two-stage leaf springs. With this spring configuration, it is possible to achieve the nonlinear spring characteristics, which cannot be achieved by the leaf spring 20 only, by appropriately setting the spring characteristics for each of the leaf spring 20 and the auxiliary leaf spring 26.

[0029] Therefore, in the suspension structure 100 according to the embodiment, the auxiliary leaf spring 26 is disposed immediately above the leaf spring 20 so that the leaf spring 20 is not brought into contact with the side frame 12, whereby it is made possible to realize a compact suspension that exhibits the nonlinear spring characteristics.

[0030] The leaf spring 20 is attached to the side frame 12 through the brackets 22, 24 so that the longitudinal direction of the leaf spring 20 (the longitudinal direction of the vehicle) and the longitudinal direction of the side frame 12 (the longitudinal direction of the vehicle) are arranged in parallel to each other.

[0031] As shown in FIG. 3, the bent portion 12e of the side frame 12 in the suspension structure 100 is bent in the crank shape in the vertical direction of the vehicle so that the second position P2 is positioned lower than the first position Pl. Here, the shape that is "bent in the crank shape in the vertical direction of the vehicle" may be considered to be the shape that is bent upward in the vertical direction of the vehicle and then bent downward in the vertical direction of the vehicle, or the shape that is bent downward in the vertical direction of the vehicle and then bent upward in the vertical direction of the vehicle. Therefore, in the suspension structure 100, the other end 20b of the leaf spring 20 is disposed farther below, so that the space laterally beside the side frame 12 and above the leaf spring 20 is enlarged, thereby increasing the design freedom relating to the selection and layout of the auxiliary leaf spring 26.

[0032] Further, the bent portions 12e of the suspension structure 100 are such that the distance between the bent portions 12e on the center portion 12c side, which is closer to the center of the vehicle, in the width direction of the vehicle is larger than the distance between the bent portions 12e on the rear portion 12b side, which is located farther from the center of the vehicle. Therefore, in the chassis frame 10 of the suspension structure 100, the distance between the pair of the side frames 12 is large on the center portion 12c side, which is closer to the center of the vehicle than the bent portions 12e, so that the design freedom relating to the layout for arranging a plurality of components, such as a fuel tank and an exhaust muffler, in this area is increased.

[0033] While the invention has been described with reference to an example embodiment thereof, it is to be understood that the invention is not limited to the example embodiment or construction. To the contrary, the invention is intended to cover those obtained by appropriately combining and/or replacing the components of the embodiment. In addition, it is also possible to make various modifications, such as design change, to the embodiment based on the knowledge of those skilled in the art, and the embodiments to which such modifications are made are also within the scope of the invention. One of such modifications will be described below.

[0034] In the above-described embodiment, the suspension structure 100 is employed as the rear suspension of the vehicle. However, the invention may be applied to the front suspension of the vehicle.

Claims

1. A vehicle suspension structure, characterized by comprising: a chassis frame that includes a pair of side frames, each extending in a longitudinal direction of a vehicle; a leaf spring that absorbs a force applied from a road surface to the chassis frame through an axle shaft; a first attachment member by which one end of the leaf spring is attached to an outer side surface of at least one of the pair of side frames; and a second attachment member by which the other end of the leaf spring is attached to a lower surface of the at least one of the pair of side frames, wherein: the at least one of the pair of side frames includes a bent portion that is bent in a crank shape in a width direction of the vehicle; the first attachment member is fixed to a first position on the at least one of the pair of side frames, the first position being located in, of first and second portions of the at least one of the pair of side frames that are adjacent to the bent portion on both sides of the bent portion, the first portion, wherein a distance between the first portions of the pair of side frames in the width direction of the vehicle is smaller than a distance between the second portions of the pair of side frames in the width direction of the vehicle; and the second attachment member is fixed to a second position on the at least one of the pair of side frames, the second position being located in one of the bent portion and the second portion of the at least one of the pair of side frames.

2. The vehicle suspension structure according to claim 1, wherein the second position is located in the second portion.

3. The vehicle suspension structure according to claim 1, wherein the second position is located in the bent portion.

4. The vehicle suspension structure according to any one of claims 1 to 3, wherein the second portion is located more outward in the width direction of the vehicle than the first portion is located.

5. The vehicle suspension structure according to any one of claims 1 to 4, further comprising: an auxiliary leaf spring; a third attachment member by which one end of the auxiliary leaf spring is attached to the side surface of the at least one of the pair of side frames; and a fourth attachment member by which the other end of the auxiliary leaf spring is attached to the side surface of the at least one of the pair of side frames, wherein the third attachment member and the fourth attachment member are fixed to the at least one of the pair of side frames at positions between the first position and the second position so that the auxiliary leaf spring is disposed immediately above the leaf spring.

6. The vehicle suspension structure according to claim 5, wherein the auxiliary leaf spring is designed so as to make spring characteristics of a suspension nonlinear by being deformed along with the leaf spring when a force equal to or greater than a predetermined force is applied to the leaf spring.

7. The vehicle suspension structure according to claim 5 or 6, wherein the side surface of the at least one of the pair of side frames on which the auxiliary leaf spring is attached is an outer side surface of the at least one of the pair of side frame.

8. The vehicle suspension structure according to any one of claims 1 to 7, wherein the leaf spring is attached to the at least one of the pair of side frames through the first attachment member and the second attachment member in a manner such that a longitudinal direction of the leaf spring is arranged in parallel to a longitudinal direction of the at least one of the pair of side frames.

9. The vehicle suspension structure according to any one of claims 1 to 8, wherein the bent portion is bent in a crank shape in a vertical direction of the vehicle so that the second position is positioned lower than the first position.

10. The vehicle suspension structure according to any one of claims 1 to 9, wherein the bent portion is formed so that a distance in the width direction of the vehicle between the pair of side frames on a side closer to a center of the vehicle in the longitudinal direction of the vehicle is larger than a distance between the pair of side frames on a side farther from the center of the vehicle.

11. A vehicle suspension structure, characterized by comprising: a chassis frame that includes a side frame, extending in a longitudinal direction of a vehicle; a leaf spring that absorbs a force applied from a road surface to the chassis frame through an axle shaft; a first attachment member by which one end of the leaf spring is attached to an outer side surface of the side frame; and a second attachment member by which the other end of the leaf spring is attached to a lower surface of the side frame, wherein: the side frame includes a bent portion that is bent in a crank shape in a width direction of the vehicle; the first attachment member is fixed to a first position on the side frame; the first position is located in one portion of portions that are adjacent to the bent portion on both sides of the bent portion; the one portion is narrower than other portion in the width direction of the vehicle; the second attachment member is fixed to a second position on the side frame; and the side frame in the second position spreads more in the width direction of the vehicle than the side frame in the first position.