JPH07100455B2 - Undercarriage frame for trucks - Google Patents

Description

The present invention relates to a chassis frame for a truck.

(Prior Art) An example of a conventional truck chassis frame will be described with reference to FIGS. 1 and 2 showing an embodiment of the present invention for convenience and with reference to FIG. . In the figure, reference numeral 10 generally indicates a chassis frame. The chassis frame 10 includes a pair of left and right side rails 12 extending in the front-rear direction of the vehicle body, each of which has a groove type (channel type), and a side rail 12 extending in the vehicle width direction. It is provided with a so-called alligator-type cross member 14 which is disposed so as to be present and whose both end portions are fixed to the side rail 12.
The cross member 14 includes an upper member 14u having a hat-shaped cross-sectional shape and a lower member having an arbitrary cross-sectional shape such as a flat plate or a hat-shaped cross-section fixed to at least both ends of the upper member by rivets or bolts 16. The upper member 18u and the lower member 14l are formed with a V-shaped expanded upper flange 18u and a lower flange 18l at both ends in the vehicle width direction. The upper flange 18u and the lower flange 18l respectively extend outward in the vehicle width direction and are bent in the vertical direction to form an upper vertical flange 18uf and a lower vertical flange 18lf, respectively. The upper and lower vertical flanges 18uf and 18lf are each provided with a plurality of rivets or bolts.
It is fastened to the web 12w of the side rail 12 by 20u and 20l.

1 and 2, an alligator type cross member 14 is shown.
However, as is well known in the art,
The cross member has a groove-shaped cross section, and the cross section has an I shape.
A mold cross member or the like is appropriately adopted.

A typical arrangement of rivets or bolts 20u and 20l for fastening the upper vertical flange 18uf and the lower vertical flange 18lf to the web 12w of the side rail 12 is illustrated in FIG. This figure is a front view of the vertical flanges 18uf and 18lf, where XX is a horizontal center line, YY is a vertical center line, and O ₁ -O ₂ is an upper vertical flange 18uf and an upper flange 18u. A joint line or a bending line, O ₃ -O ₄ is a joint line or a bending line between the lower vertical flange 18lf and the lower flange 18l, and ai is the above-mentioned bending line O _1- of the upper and lower vertical flanges 18uf and 18lf. The lengths of O ₂ and O ₃ -O ₄ , and b is the vertical distance between the bending lines O ₁ -O ₂ and O ₃ -O ₄ .

During traveling of the truck, the chassis frame 10 is subjected to vertical bending, torsional and lateral bending loads, and further a combined load thereof, so in order to increase the coupling force between the side rails 12 and the cross members 14, The rivets or bolts 20u and 20l for fastening the upper vertical flange 18uf and the lower vertical flange 18lf to the web 12w of the side rail, respectively, have heretofore been almost customary, symmetrically with respect to the longitudinal centerline Y-Y, and in each case. A plurality of vertical flanges 18uf and 18lf (six in the illustrated case) which are substantially in parallel with the horizontal center line X-X.
It is arranged.

(Problems to be Solved by the Invention) An upper vertical flange 18uf and a lower vertical flange 18lf formed at both end portions of the cross member 14 in the vehicle width direction are provided with rivets or patterns arranged as shown in FIG. With respect to the undercarriage frame fastened to the side rail web 12w with the bolts 20u and 20l, a torsion test was conducted focusing on the most important torsion load of the various loads acting during traveling. The applied four triangular areas Ω _{1 to} Ω ₄ (for these areas Ω _{1 to} Ω ₄ ,
Rivets or bolts contained within) which will be described in detail later)
20u and 20l and the surrounding plate members (plates forming the side rail web 12w and the vertical flanges 18uf and 18lf) have extremely large stresses, and therefore, when running on rough roads repeatedly, rivets or bolts in the above area Breaks,
Alternatively, it has been found that defects such as cracks are likely to occur in the plate member around the rivet or the bolt.

According to the present invention, upper and lower vertical flanges formed by bending both ends of upper and lower flanges of a cross member in a vertical direction are formed on a web of a side rail having a groove-shaped cross section by a plurality of rivets or bolts. In the chassis frame that is fastened, by devising the arrangement of rivets or bolts that fasten the upper vertical flange and the lower vertical flange to the side rail web, the rivet or bolts and peripheral parts are secured while ensuring torsional and bending rigidity. It is an object of the present invention to reduce the stress generated in the plate member and improve the durability strength of the cross member connecting portion with respect to the side rail.

(Means for Solving the Problems) A chassis frame of a truck according to the present invention comprises the following two inventions that have been devised in order to achieve the above object. First, the first invention extends in the vehicle body front-rear direction. The pair of left and right side rails each having a groove-shaped cross section and the vertical flanges are formed by bending the extension parts at both ends of the upper and lower flanges extending in the vehicle width direction to form vertical flanges. A plurality of rivets for fastening the upper vertical flange and the lower vertical flange to the side rail web, respectively, in which the flange comprises an alligator type cross member fastened to the side rail web by a plurality of rivets or bolts. Area where the bolt meets the following formula for each vertical flange Ω
_i (i = 1 to 4; i = 1 and 2 are upper vertical flanges, i = 3
And 4 are lower vertical flanges), ie However, ξ _i : Coordinates in the direction along the bending line in the local coordinate system whose origins are both ends O _{i of the} bending lines of the upper and lower vertical flanges η _i : Bending in the local coordinate system whose origin is O _i Coordinates in the direction perpendicular to the line a _i : Length of bend line of upper and lower vertical flanges b: Distance between bend lines of upper and lower vertical flanges At least one region defined by the formula It is characterized in that it is not disposed in the. According to a second aspect of the present invention, a pair of left and right side rails extending in the front-rear direction of the vehicle body each having a groove-shaped cross section, and a pair of left and right extending portions of the upper and lower flanges extending in the vehicle width direction are formed in the vertical direction. And a cross member having a groove-shaped or I-shaped cross-section, which are each bent to form a vertical flange, and the vertical flange is fastened to the web of the side rail by a plurality of rivets or bolts. A region in which a plurality of rivets or bolts for fastening the vertical flange and the lower vertical flange to the side rail web respectively satisfy the following formula of each vertical flange Ω _i (i = 1 to 4; i = 1 and 2 are upward vertical Flange, i = 3 and 4 are lower longitudinal flanges), ie However, ξ _i : Coordinates in the direction along the bending line in the local coordinate system whose origins are both ends O _{i of the} bending lines of the upper and lower vertical flanges η _i : Bending in the local coordinate system whose origin is O _i Coordinates in the direction perpendicular to the line a _i : Length of bend line of upper and lower vertical flanges b: Distance between bend lines of upper and lower vertical flanges At least one region defined by the formula The undercarriage frame of the truck is characterized in that it is not disposed in the vehicle.

(Operation) According to the present invention, by disposing a plurality of rivets or bolts in the flange surfaces of the upper and lower vertical flanges of the cross member excluding the above-mentioned region Ω _i , the torsional rigidity of the both end joints of the cross member with respect to the side rails. It is possible to reduce the stress generated in the rivet or bolt and its peripheral plate member while ensuring the above, and to improve the durability strength of the joint portion.

EXAMPLES Examples of the present invention will be specifically described below with reference to the accompanying drawings. (Note that re-statement of the matters already described in relation to the above-mentioned conventional configuration is omitted.) First, in the first embodiment of the present invention shown in FIGS. 1 to 3, the cross member 14 is used. FIG. 3 clearly shows an arrangement pattern of rivets or bolts 20u and 20l for fastening the upper and lower vertical flanges 18uf and 18lf formed at both ends in the vehicle width direction to the web 12w of the side rail 12, respectively. As shown,
The six rivets or bolts 20u arranged on the vertical flange 18uf of the upper flange 18u are all arranged in the flange surface except the elongated triangular region Ω ₁ or Ω ₂ shown by hatching in the drawing. Similarly 6 rivets or bolts 20l arranged on the vertical flange 18lf of the lower flange 18l
Is a slender triangular area Ω ₃ or Ω ₄
All are arranged in the flange surface except for.

The region Ω ₁ is a bending line in the local Cartesian coordinate system with the origin at the joining line between the upper flange 18u and the vertical flange 18uf, that is, one end of the bending line O ₁ -O ₂ of the vertical flange, for example, the front end O _1. Let ξ ₁ be the coordinate along the line O ₁ -O ₂ and bend line O ₁
When the coordinate in the direction orthogonal to -O ₂ is η ₁ , Becomes a region of the elongated triangle of the formula, as well as regions Omega ₂ is in a local rectangular coordinate system to the other end for example the rear end O ₂ of the fold line O ₁ -O ₂ as the origin, folding Line O ₁
When the coordinate in the direction along -O ₂ is ξ ₂ and the coordinate in the direction orthogonal to the bending line O ₁ -O ₂ is η ₂ , Is a slender triangular region that satisfies As shown,
The same applies to the lower vertical flange 18lf with respect to the bending lines O ₃ -O ₄ . And expression The slender triangular regions satisfying the above are set respectively.

As already mentioned, in the previous configuration shown in Figure 12,
On the upper vertical flange 18uf and the lower vertical flange 18lf, the third
If you set the same area Ω _{1 to} Ω ₄ as in the figure, the center line
Of the upper and lower three rivets or bolts 20u and 20l arranged on the left side of YY, each two rivets or bolts on the side farther from the center line have at least a part of their cross-sectional area within these regions. Included in.

Now, in the upper part of FIG. 4, a perspective view of the end part of the cross member 14 fastened to the web of the side rail is drawn, and on the upper and lower vertical flanges 18uf and 18lf thereof, the fold line O _1- Row A close to and parallel to O ₂ and O ₃ -O ₄ ,
And B rows far from and parallel to the fold lines O ₁ -O ₂ and O ₃ -O ₄ , and the first closest to the center line YY in the direction parallel to the center line YY (up and down direction). A rivet or bolt placement pattern consisting of a row, an intermediate second row, and a furthest third row is shown. Also, in the middle of the figure, the stress sensitivity (kgf / mm ² / kgf ・ m) and torsional rigidity (kgf) to the torsional moment of the vertical flange joint when the positions of the rivets or bolts 20u and 20l are variously changed.
m ² ) data is shown, in which the symbol ○ (white circle) indicates the stress sensitivity of the above-mentioned joint and the symbol Δ (white triangle).
Indicates torsional rigidity. Finally, in the lower part of the figure, the types of four kinds of arrangement patterns Pa # 1 to Pa # 4 of the rivets or bolts 20u and 20l, and a schematic diagram showing the specific rivet or bolt positions are described. .

The arrangement pattern of the conventional rivets or bolts 20u, 20l shown in FIG. 12 corresponds to the pattern Pa # 1 in FIG. _4, and is of the row A close to the bending lines O ₁ -O ₂ and O ₃ -O _4. Rivets or bolts are placed on all of the first, second and third rows, ie A ₁ , A ₂ , A ₃ . The pattern Pa # 2 in FIG. 4 corresponds to the first embodiment of the present invention shown in FIGS. _{1 to 3} and is close to the bending lines O ₁ -O ₂ and O ₃ -O _4. In the column, rivets or bolts are placed only in the first row (hence A ₁ ) closest to the center line YY, and the fold lines O ₁ -O ₂ and Rivets or bolts are arranged in rows B far from O ₃ -O ₄ , that is, B ₂ and B ₃ , respectively. Pattern Pa #
Comparing No. 1 and Pa # 2, the torsional rigidity of the upper and lower vertical flanges is not so different between the two,
It is shown that the stress sensitivity of the pattern Pa # 1 is much higher than that of the pattern Pa # 2. Therefore, when running on a rough road is performed repeatedly, in the conventional upper and lower vertical flange coupling portion, maximum stress occurs at the farthest A ₃ position of the rivets or bolts from the center line YY, Ya rupture of the rivets or bolts , Side rail web around the same rivet or bolt 12
w or (and) cracks are likely to occur in the upper and lower vertical flanges 18uf, 18lf, but in the configuration of the pattern Pa # 2 according to the present invention, since the stress sensitivity is remarkably small, the durability strength of the upper and lower vertical flange joints is high. Is significantly improved, and the risk of breakage of the rivets or bolts and the surrounding side rail webs and / or the cross member vertical flanges is extremely small, which is a reliable advantage.

Next, in the pattern Pa # 3 in FIG. 4, six rivets or bolts 20u and 20l for the upper and lower vertical flanges are placed in the regions Ω ₁ and Ω ₂ , Ω ₃ and Ω ₄ , respectively. It shows a modified example in which each row is arranged in each row of column B, that is, B ₁ , B ₂ , and B ₃ far from the joining lines O ₁ -O ₂ , O ₃ -O ₄ so as not to belong.
It is clear from the test results that this modified example can also reduce the stress sensitivity while securing a sufficient torsional rigidity of the cross member coupling portion, as in the case of the pattern Pa # 2. Further, the pattern Pa # 4 in FIG. 4 has four rivets or bolts for fastening the upper and lower vertical flanges to the side rail web, respectively, in the first row of column A and the second row of column B.
Another variant is shown arranged in rows, A ₁ and B ₂ , all of these rivets or bolts are not included in any of the regions Ω _{1 to} Ω ₄ . Also in this modification, the stress sensitivity is remarkably reduced as compared with the conventional configuration, that is, Pa # 1, while ensuring the torsional rigidity of the upper and lower cross member coupling portions that are substantially the same as those of the patterns Pa # 2 and Pa # 3. Therefore, there is an advantage that the durability and reliability of the joint can be effectively improved.

Next, FIG. 5 shows an alligator type cross member similar to the above.
Upper and lower vertical flanges 18uf and 18lf, which are formed by extending the ends of the upper and lower flanges 18u and 18l of 14 toward the outside in the vehicle width direction and bending them in the vertical direction, are formed so as to point away from each other, and rivets are formed, respectively. Alternatively, the second embodiment of the present invention fastened to the side rail web 12w by bolts 20u and 20l is shown, and FIG. 6 is the same as FIG. 3 showing the arrangement pattern of the rivets or bolts 20u and 20l in the same embodiment. FIG. FIG. 6 corresponds to the pattern Pa # 2 of FIG. 4 (only the relative positions of the bending lines O ₁ -O ₂ , O ₃ -O ₄ differ) and all the rivets or bolts 20u and 20l are It is arranged on the flange surface other than the regions Ω _{1 to} Ω ₄ .

Also in this second embodiment, similar to the first embodiment, the stress sensitivity of the conventional example is maintained while ensuring sufficient torsional rigidity at the joint between the upper and lower vertical flanges 18uf and 18lf and the side rail web 12w. It was confirmed that it can be significantly reduced compared to the configuration, and thus the durability and reliability of the joint can be improved. Also. Rivet or bolt 20 above
Even when u and 20l are arranged in the same relational positions as the patterns Pa # 3 and Pa # 4 in FIG. _{4 with} respect to the bending lines O ₁ -O ₂ , O ₃ -O ₄ , they are omitted from the first embodiment. Similar effects were obtained.

Further, although not shown, the cross member is reverse to the one shown in FIG.
Vertical flange 18 formed by bending up and down at the end of 14
If uf and 18lf extend in the direction of being close to each other, that is, the fold line O ₁ -O ₂ is arranged at the upper end edge of the upper vertical flange 18uf, and the fold line O _{3 at} the lower end edge of the lower vertical flange 18lf. ‐O ₄
Also in the modified example in which is arranged, the stress sensitivity is remarkably reduced as compared with the conventional configuration while ensuring the torsional rigidity at the joint between the end of the cross member 14 and the side rail web 12w as in the above-described embodiments. It was confirmed to get. The plurality of rivets or bolts in the first and second embodiments and the modifications thereof are Although the case where the regions represented by the formula are arranged in the plane excluding the regions satisfying both of them has been described, the present invention is not limited to this, and the region excluding at least one of the four regions can be arranged in the plane. , Rivets or bolts may be provided.

Next, the second invention will be described. The second invention is structurally different from the first invention in that the first invention includes an alligator type cross member, whereas the second invention has a cross-section groove-shaped or I-shaped cross section. A point including members, and in the first invention, an expression representing a region is However, in the second invention, The other configurations are the same in both cases.

The first embodiment of the second invention will be described below with reference to FIGS. 7 and 8. In this embodiment, the cross member 14 is composed of a groove-shaped member composed of upper and lower flanges 14u and 14l and a web 14w, and the upper flange 14u and the lower flange 14l.
The upper and lower vertical flanges 14uf and 14lf are formed by bending the outer extensions of the vehicle width direction in the vertical direction, respectively, and these vertical flanges 14uf and 14lf are formed by the side rails 12u and 20l, respectively. Web 12w
Has been concluded.

Also in this first embodiment, the upper vertical flanges 14uf and 14
The rivets or bolts 20u and 20l for fastening lf to the side rail web 12w are bent along the bending lines O ₁ -O ₂ , O ₃ -O ₄ of each vertical flange as in the first embodiment and the modified example. The cross member 14 and the side rail web 12w are arranged on the vertical flange surface other than the areas Ω _{1 to} Ω ₄ in the local coordinate system as the axis, as in the first embodiment of the first invention.
While sufficiently securing the torsional rigidity of the joint portion with and, the durability strength of the joint portion can be improved and the reliability can be improved.
Here, the region Ω ₁ is And the area Ω ₂ is And the area Ω ₃ is And the area Ω ₄ is The area represented by the formula It should be noted that the upper vertical flange 14uf and the lower vertical flange 14lf in this embodiment may be provided so as to be directed away from each other, as in FIG. 5, or may be provided so as to be opposed to each other. You may be asked.

Further, in FIGS. 9 to 11, the cross member 14 is composed of upper and lower flanges 14u and 14l and a vertical web 14w.
The second embodiment of the second invention is substantially the same as the first embodiment except that it is formed as a member having a mold cross-sectional shape. In this embodiment, the ends of the upper and lower flanges 14u and 14l of the cross member 14 in the vehicle width direction are extended outward, and the respective extension portions are bent vertically to form an upper vertical flange 14uf and a lower vertical flange. Flange 14
lf is formed. The upper vertical flange 14uf and the lower vertical flange 14lf are fastened and fixed to the web 12w of the side rail 12 by rivets or bolts 20u and 20l, respectively.

Also in this embodiment, the upper and lower vertical flanges 14uf
, 14lf and the rivets or bolts 20u and 20l for fastening the web 12w of the side rail 12 to the fold line O ₁ of the upper and lower vertical flanges as in the first embodiment of the first invention and its modification. -O ₂ , O ₃ -O ₄ is arranged on the vertical flange surface other than the region Ω _i in the local Cartesian coordinate system with the horizontal axis as the horizontal axis, so that the webs of the cross member 14 and the side rail are arranged in the same manner as in the first embodiment. It is possible to significantly reduce the stress sensitivity as compared with the conventional configuration while sufficiently ensuring the torsional rigidity of the joint with 12w, and to improve the durability and reliability of the joint. The upper and lower vertical flanges in this embodiment
The arrangement of 14uf and 14lf may be provided so as to be directed away from each other as in the case of FIG. 5, or both may be provided in a downward direction as in FIG. 8 or may be provided in an upward direction on the contrary. Good.

The surface on which the rivets or bolts are arranged in each of the above-described embodiments and their modifications is not limited to a surface other than the area in which the above-mentioned formulas representing the respective areas Ω _{1 to} Ω ₄ are both satisfied. The rivets or bolts may be arranged in the plane excluding the region satisfying at least one formula.

It should be noted that, in all the embodiments of the first and second inventions described above and their modifications, the upper and lower vertical flanges 18u
The number of rivets or bolts 20u and 20l that fasten f, 14uf and 18lf, 14lf to the web 12w of the side rail can be increased or decreased as appropriate, and the front shape of each vertical flange is not limited to the illustrated rectangle but a trapezoid. You can also do it.

(Advantages of the Invention) As described above, the truck chassis frame according to the first invention has a pair of left and right side rails extending in the vehicle front-rear direction and each having a groove-shaped side rail, and extending in the vehicle width direction. And an alligator-type cross member in which extension parts of the upper and lower flanges are bent vertically to form vertical flanges, and the vertical flanges are fastened to the side rail web by a plurality of rivets or bolts. A plurality of rivets or bolts for respectively fastening the upper vertical flange and the lower vertical flange to the web of the side rail satisfying the following formula of each vertical flange Ω _i (i =
1-4; i = 1 and 2 are upper vertical flanges, i = 3 and 4 are lower vertical flanges), that is, However, ξ _i : Coordinates in the direction along the bending line in the local coordinate system whose origins are both ends O _{i of the} bending lines of the upper and lower vertical flanges η _i : Bending curve in the local coordinate system whose origin is O _i Coordinates in the direction perpendicular to a _i : Length of bending lines of upper and lower vertical flanges b: Distance between bending lines of upper and lower vertical flanges At least one of the regions defined by the formula Is not provided, and the second invention is
A pair of left and right side rails extending in the front-rear direction of the vehicle body each having a groove-shaped cross section, and side flanges extending in the vehicle width direction and extending at both ends of the upper and lower flanges are bent vertically to form vertical flanges. And a cross member having a groove-shaped or I-shaped cross-section, which is formed by forming the same vertical flange on the web of the side rail with a plurality of rivets or bolts, wherein the upper vertical flange and the lower vertical flange are Area where multiple rivets or bolts that are fastened to the side rail web satisfy the following formula for each vertical flange Ω
_i (i = 1 to 4; i = 1 and 2 are upper vertical flanges, i = 3
And 4 are lower vertical flanges), ie However, ξ _i : Coordinates in the direction along the bending line in the local coordinate system whose origins are both ends O _{i of the} bending lines of the upper and lower vertical flanges η _i : Bending in the local coordinate system whose origin is O _i Coordinates in the direction perpendicular to the line a _i : Length of bend line of upper and lower vertical flanges b: Distance between bend lines of upper and lower vertical flanges At least one region defined by the formula Both of the inventions are devised in the arrangement pattern of rivets or bolts for fastening the upper and lower vertical flanges formed at both end portions of the side rail in the vehicle width direction to the web of the side rail in both inventions. By adding the above, it is possible to effectively reduce the stress generated in the rivet or bolt and the plate member around the same while securing the torsional and bending rigidity of the fastening portion, and to improve durability and reliability. Yes, the industry is extremely beneficial.

[Brief description of drawings]

FIG. 1 is a plan view of an essential part showing a first embodiment of the first invention, FIG.
The figure is a front view seen from the direction of arrow II in FIG. 1, and FIG.
FIG. 4 is a front view showing the arrangement pattern of rivets or bolts on the upper and lower vertical flanges shown in FIGS. 2 and 3, and FIG. 4 is a connecting portion between the upper and lower vertical flanges and the side rail web in the first embodiment. A diagram showing stress sensitivity and torsional rigidity in comparison with the conventional configuration, FIG. 5 is a front view similar to FIG. 2 showing a second embodiment of the first invention, and FIG. 6 is shown in FIG. FIG. 7 is a front view showing a rivet or bolt arrangement pattern of the upper and lower vertical flanges in the second embodiment, FIG. 7 is a plan view of a main portion of the first embodiment of the second invention, and FIG. FIG. 9 is a front view seen from the direction of arrow VIII, FIG. 9 is a plan view of an essential part showing a second embodiment of the second invention, FIG. 10 is a front view seen from the direction of arrow X in FIG. 9, and FIG. FIG. 9 is a side view seen from the direction of arrow XI in FIG. 9, and FIG. 12 is a vehicle similar to the first embodiment of the first invention. It is a front view showing a conventional rivet or bolt arrangement pattern in the upper and lower vertical flange of the frame. 10 ... Chassis frame, 12 ... Side rail, 12w ... Side rail web, 14 ... Cross member, 14uf and 18uf ... Upper vertical flange, 14lf and 18lf ... Lower vertical flange, 20u and 20l
… Rivets or bolts.

Claims (2)

[Claims] 1. A pair of left and right side rails extending in the front-rear direction of the vehicle body, each of which has a groove-shaped cross-section, and an upper and lower flange extending at both ends of the side rails extending vertically. A vertical rail formed by bending each vertical flange, and the vertical flange having an alligator type cross member fastened to the web of the side rail by a plurality of rivets or bolts, wherein the upper vertical flange and the lower vertical flange are side rails. a plurality of rivets or bolts to respective fastening of the web, the area Omega _i that satisfies the following equation for each vertical flange
(I = 1 to 4; i = 1 and 2 are upper vertical flanges, i = 3 and 4 are lower vertical flanges), that is, However, ξ _i : Coordinates in the direction along the bending line in the local coordinate system whose origins are both ends O _{i of the} bending lines of the upper and lower vertical flanges η _i : Bending in the local coordinate system whose origin is O _i Coordinates in the direction perpendicular to the line a _i : Length of bend line of upper and lower vertical flanges b: Distance between bend lines of upper and lower vertical flanges At least one region defined by the formula Chassis frame for trucks, characterized in that it is not installed in 2. A pair of left and right side rails extending in the front-rear direction of the vehicle body, each having a groove-shaped cross-section, and extended end portions of upper and lower flanges of the side rails extending in the vehicle width direction. An upper vertical flange, wherein each of the vertical flanges is bent to form a vertical flange, and the vertical flange is cross-shaped with a groove or I-shaped cross section fastened to the web of the side rail by a plurality of rivets or bolts. And a plurality of rivets or bolts for fastening the lower vertical flanges to the side rail webs respectively satisfy the following formula of each vertical flange: Ω _i (i = 1 to 4; i = 1 and 2 are upper vertical flanges, i = 3 and 4 are lower vertical flanges), ie However, ξ _i : Coordinates in the direction along the bending line in the local coordinate system whose origins are both ends O _{i of the} bending lines of the upper and lower vertical flanges η _i : Bending in the local coordinate system whose origin is O _i Coordinates in the direction perpendicular to the line a _i : Length of bend line of upper and lower vertical flanges b: Distance between bend lines of upper and lower vertical flanges At least one region defined by the formula Chassis frame for trucks, characterized in that it is not installed in