JP2001138841A - Shock absorber of vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light and inexpensive shock absorber which is of a type utilizing plastic deformation and has stable energy absorbing characteristic. SOLUTION: This shock absorber for a vehicle which is interposed between a bumper 2 of a vehicle and a car body frame 1 to absorb shock energy received by the bumper 2 by converting into deformation energy, is so constructed that a plastic worked straight pipe body is partially reduced in diameter or enlarged in diameter to form pipe parts 4, 15, 3 different in outside diameter, and the pipe parts 4, 15, 3 are connected to each other through stepped parts 5 which can be formed between the respective edges of the pipe parts 4, 15, 3 to constitute a three-step pipe body 14. The pipe parts 3, 4 positioned at both ends of the three-step pipe body 14 are respectively connected to the bumper 2 and the car body frame 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shock absorbing device interposed between a bumper of a vehicle and a vehicle body frame to convert shock energy received by the bumper into deformation energy and absorb it.

[0002]

2. Description of the Related Art Japanese Patent Publication No. H06-005271, US Pat. No. 4,537,
Cylinder type (type that absorbs impact energy as degenerate energy of cylinder) seen in No. 734 and plastic deformation seen in JP-A-09-086309 and JP-B-59-009775
There is a type that utilizes (for example, buckling) (a type that converts impact energy into deformation energy of a member and absorbs it).
The cylinder type has the advantage of having stable energy absorption characteristics, but has the disadvantage of being precise, having many parts, and being heavy and expensive. The type using plastic deformation has advantages in that it is lightweight and inexpensive, but has a disadvantage in that energy absorption characteristics are inferior to cylinder types.

[0003]

As apparent from the above description, a shock absorbing device of the type utilizing plastic deformation is:
Since it is lightweight and inexpensive, it is suitable for the recent tendency to reduce vehicle manufacturing costs. Therefore, a study was conducted to develop a lightweight and inexpensive shock absorbing device that is a type that utilizes plastic deformation, has stable energy absorption characteristics, and is inexpensive.

[0004]

SUMMARY OF THE INVENTION As a result of studying the above problems, there is provided an impact absorbing device interposed between a vehicle bumper and a vehicle body frame to convert impact energy received by the bumper into deformation energy and absorb it. In order to form a pipe with a different outer diameter by partially reducing or expanding the diameter of a straight pipe that can be plastically processed (a straight pipe before processing), a step that can be formed between the edges of each pipe A multi-stage pipe is formed by connecting the pipes to each other via a pipe, and the pipes located at both ends of the multi-stage pipe are connected to a bumper and a body frame, respectively. The shock absorbing device of the present invention supports a bumper for a vehicle body frame.

[0005] The shock absorbing device of the present invention absorbs impact energy in the process of pushing a small outside diameter tube into a large outside diameter tube. A part of the impact energy compresses each pipe part, but most of the energy is consumed and absorbed by the stepped up (plastic deformation) caused by the pushing of the pipe part.

Here, the multistage pipe body is formed by (a) folding a step which can be formed between the edges of each pipe section for each of the pipe sections, or (b) forming a step outside the one side of the pipe section connected through the step section. What is necessary is just to comprise so that the other inside diameter may be larger than a diameter. (a)
When the configuration is applied, since the step has already begun to be rolled up, the energy required for the initial plastic deformation is small, and the rolling up proceeds smoothly.

In addition, when the configuration shown in (b) is applied, the continuous pipes are pushed into each other so as to easily overlap each other. The relationship that the inner diameter of one of the pipes is larger than the outer diameter of the other means that the width W of the step is larger than the wall thickness t of the pipe having a larger outer diameter. Here, when referring to the size of the pipe portion connected via the step, the following relationship is generally desirable. Assume that the length of the tube having a small outer diameter is H1, the thickness is t1, the length of the tube having a large outer diameter is H2, the thickness is t2, and the width W of the step connecting the two tubes is H. , T1> t2, and W
> T2.

[0008] Specifically, (1) a circular straight pipe body capable of being plastically worked is partially reduced or expanded to form a substantially circular large outer diameter pipe section and a substantially circular outer diameter pipe section. The ends of the pipes are connected by a step so that the axes of the pipes are substantially on the same line to form a two-stage pipe, and the large-diameter pipe is abutted and fixed to the impact-receiving side of the body frame. (2) Partially reducing or expanding the diameter of a plastically processable circular straight pipe to reduce the substantially circular small, medium, and large external diameter pipes Forming a three-stage pipe body in which the ends of the pipe sections are connected by steps so that the axes of the pipe sections are substantially on the same line, and the pipe sections are arranged in order of diameter. An impact absorbing device in which the diameter pipe portion is fixedly abutted on the impact receiving side of the vehicle body frame has a preferable configuration.

Although the shock absorbing device of the present invention preferably has a multi-stage structure, the number of stages is practically limited due to the installation space. The three-stage pipe is realistic in terms of processing man-hours. For example, if a constant length is reduced and expanded from both ends of a standard metal round pipe (circular straight pipe), the impact of the three-stage pipe An absorption device can be easily realized. Further, in the shock absorbing device including the three-stage pipe body, the tilting of the small outer diameter pipe section is suppressed by the middle outer diameter pipe section, and the small middle diameter outer pipe section can be integrally pushed into the large outer diameter pipe section. .

Here, regarding the shock absorbing device composed of the three-stage pipe, the length of the small outer diameter pipe is H1, the thickness is t1, the length of the middle outer diameter is H2, the thickness is t2, and the thickness is t2. The length of the outer tube is H
3. Assuming that the wall thickness is t3, the width W1 of the step connecting the small and medium outer diameter pipes, and the width W2 of the step connecting the middle and large outer diameter pipes, t1>t2> t3,
Then, W1> t2 and W2> t3. As described above, when a standard metal round pipe is reduced in diameter and expanded to form a three-stage pipe, t1 of the small outer diameter pipe obtained by reducing the diameter is inevitably equal to that of the middle outer diameter pipe. It becomes larger than t2. Further, t3 of the large outer diameter pipe obtained by expanding the diameter is necessarily smaller than t2 of the middle outer diameter pipe. As described above, by performing two types of plastic working, that is, diameter reduction and diameter expansion, on a single metal pipe, there is an advantage that it is possible to manufacture a shock absorber including a suitable three-stage pipe body.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below.
This will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view of a shock absorbing device composed of a two-stage tube 9, FIG. 2 is a sectional view taken along line AA in FIG.
FIG. 3 is a sectional view taken along the line BB in FIG. 1, and FIG. 4 shows the relationship between the degree of shock absorption and the degree of deformation of the two-stage tube body 9 when a shock is applied to the shock absorbing device from the state of FIG. 1 is a longitudinal sectional view corresponding to FIG. 1 and shows a state in which impact energy is almost completely absorbed. 1 and 4, a thin line outside the two-stage tube 9 in which the magnitude of the impact energy is indicated by a bold-line outline arrow in the two-stage tube 9 and the deformation energy is indicated by the amount of plastic deformation (indentation). Each is indicated by a white arrow. Actually, FIG.
Although the impact energy has almost completely been absorbed at the stage of reaching the state, the solid white arrow is left for convenience of explanation.

In the shock absorbing device of this embodiment, the impact energy is converted into deformation energy and absorbed by a two-stage pipe 9 interposed between the bumper 2 and the body frame 1. Two-stage pipe 9
Is composed of a large outer diameter tube portion 3 and a small outer diameter tube portion 4 having a substantially circular cross section, and the edges of both the tube portions 3, 4 are stepped so that the axes of the respective tube portions 3, 4 are substantially on the same line. And the large outer diameter pipe portion 3 is fixedly abutted on the side of the vehicle body frame 1 which receives the impact. In the step 5, the ends of the large outer diameter tube portion 3 and the small outer diameter tube portion 4 overlap in the extending direction of the two-stage tube, and are folded back to the respective tube portions 3, 4. In such a two-stage pipe body 9, the large outer diameter pipe part 3 is a straight pipe body, the small outer diameter pipe part 4 is formed by reducing the diameter (swinging process), and the folded step 5 is formed. By performing press working for compressing in the direction in which the body 9 extends, it can be easily manufactured.

In order to abut and fix the two-stage pipe body of this embodiment on the side of the body frame 1 which receives an impact, a mounting flange 6 having a plurality of bolt holes 10 is welded to the large outer diameter pipe section 3. Also, the diameter of the pipe passage hole 12 provided in the pipe mounting seat 11 on the body frame 1 side is formed smaller than the outer diameter of the large outer diameter pipe section 3,
A step 5 that receives or rolls in the large-diameter tube portion 3 to be pushed in
At the same time, the small outer diameter tube portion 4 can be pushed. As shown in FIGS. 1 and 3, the two-stage pipe 9 and the bumper 2 are attached to each other by an assembling pipe 7 orthogonal to the end of the small outer diameter pipe 4.
And bolt holes 13 of the assembled pipe 7 and bumper 2 are welded.
And a screw 8 is inserted and screwed and fixed.

In the shock absorbing device of the present embodiment, as shown in FIG. 4, when a collision is applied to the bumper 2, the step 5 rolls up toward the large outer diameter tube portion 3. If the small outer diameter pipe 4 is formed by reducing the diameter of the metal round pipe while the large outer diameter pipe 3 remains a straight pipe, the small outer diameter pipe 4 becomes thicker, which is convenient. In this case, both the large outer diameter tube portion 3 and the small outer diameter tube portion 4 are substantially circular in cross section, and both axes are substantially collinear, so that the energy absorption efficiency is good and the energy absorption characteristics are stable (with respect to the amount of bumper movement). (The winding load has a rectangular waveform characteristic.)
The shock absorbing device has the following. The small outer diameter tube portion 4 may be a solid body.

FIG. 5 is a longitudinal sectional view of the shock absorbing device comprising the three-stage tube 14 of the present invention. FIG. 5 shows a shock absorbing device of this example.
As can be seen from the figure, a small outer diameter pipe portion 4 whose diameter is reduced from one end of a metal round pipe having a substantially circular cross section to H1 (see FIG. 10; the same applies hereinafter), and a length of H3 from the other end. The structure is such that the large outer diameter pipe portion 3 whose diameter is expanded in the range and the middle outer diameter pipe portion 15 as it is (the straight pipe body) of the metal round pipe of the remaining length H2 are connected via the step 5. The axial centers of the pipe portions 3, 4, 15 are aligned on substantially the same line so that the plastic deformation at the step 5 is equal in the circumferential direction. In addition, the step 5 in this example is a surface that is orthogonal to the extending direction of the three-stage tube. The method of attaching to the vehicle is the same as in the above-described example (FIG. 1 et seq.), And a description thereof will not be repeated. In the present embodiment, the pipe passage holes are not provided in the body frame 1 so that the small and medium outer diameter pipe sections 4 and 15 are not pushed into the inside. For example, the pipe passage holes through which only the small outer diameter pipe section 4 can pass. May be provided.

FIGS. 6 to 8 are longitudinal sectional views corresponding to FIG. 5 showing the relationship between the degree of shock absorption and the degree of deformation of the three-stage tube 14 when a shock is applied to the shock absorbing device from the state of FIG. , FIG.
5 shows a state in which the middle and outer diameter tube portions 15 have been pushed into the large and outer diameter tube portions 3 from the state of FIG. 5, and FIG. 7 shows a state in which the small and outer diameter tube portions 4 have begun to be pushed into the middle and outer diameter tube portions 15 from the state of FIG. 8 shows a state in which almost all impact energy has been absorbed. In each figure, the magnitude of the impact energy is indicated by a bold-line outline arrow in the three-stage tube 14, and the deformation energy is indicated by the magnitude of the amount of plastic deformation (indentation amount) of the thin-line outline outside the three-stage tube 14. Are indicated by. In addition, although the impact energy is almost not completely absorbed until the state shown in FIG. 8 is reached, a bold white outline arrow is left for convenience of explanation.

When a collision is applied to the bumper 2 from the state shown in FIG. 5, the impact is transmitted not only to the small outer diameter pipe portion 4 but also to the middle and large outer diameter pipe portions 3 and 15 through the step 5, and the small Outer diameter tube part 4
Starts to be displaced so as to be pushed into the medium / outside diameter tube portion 15 and the medium / outside diameter tube portion 15 into the large outside diameter tube portion 3. Rolling-in of the step 5 due to plastic deformation is realized not by the pipe section to be pushed in (for example, the middle outer diameter pipe section 15) itself, but by the tube section to be pushed in (for example, the large outer diameter pipe section 3) being rolled inward together with the step 5. . Here, in the three-stage pipe body of the present example, the thickness t1 of the reduced outer diameter pipe section 4 is the thickest, and conversely, the enlarged diameter t2 of the small outer diameter pipe section 4 is based on the thickness t2 of the middle outer diameter pipe section 15 of the straight pipe body. The thickness t3 of the outer diameter tube portion 3 is the thinnest. Also, the width W1 of the step 5 between the small and medium outer diameter pipe sections 4 and 15
Is larger than t2, and the width W2 of the step 5 between the large and middle outer diameter pipe portions 3, 15 is larger than t3. For this reason, the plastic deformation due to the rolling-in of the step 5 occurs in such a manner that the middle outer diameter tube portion 15 is first pushed into the large outer diameter tube portion 3 as shown in FIG.

In this way, the impact energy is first absorbed as the deformation energy of pushing the small and medium-diameter tube sections 4 and 15 together, that is, the stepping-up of the step 5 between the medium and large-diameter tube sections 3 and 15. At the same time, since the impact energy is also used as the deformation energy for pushing the small outer diameter tube portion 4 into the middle outer diameter tube portion 15, as shown in FIG. There is also a slight crowding.

In this example, the presence of the body frame 1 limits the winding of the step 5 between the middle and large outer diameter pipe portions 3 and 15 (see FIG. 6). As described above, the impact energy starts to be absorbed as deformation energy, which is the winding of the step 5 between the small and medium outer diameter pipe portions 4 and 15.
If the impact energy still remains, the step-up 5 between the small and medium-diameter outer tube portions 4 and 15 further proceeds until the impact energy is limited as shown in FIG.
In this manner, the impact energy is largely absorbed by the conversion of the two steps 5 into the deformation energy of being rolled up, and the impact energy transmitted to the vehicle body frame 1 can be almost eliminated.

The shock absorbing device of the present invention is more preferably a three-stage tube body 14 in which three or more tube portions having different outer diameters are arranged, and this is proved particularly when an impact is applied to the bumper 2 from an oblique direction. You. FIG. 9 is a longitudinal sectional view corresponding to FIG. 5 showing the relationship between the degree of shock absorption and the degree of deformation of the three-stage pipe body 14 when a shock is applied to the shock absorbing device from an oblique direction from the state of FIG. As described above, each of the small, medium and large outer diameter pipe portions 3, 4, and 15 has a relationship of t1>t2> t3, and has a relationship of W1> t2 and W2> t3 with respect to each step 5. In addition, the relative length of each tube portion is related to the difficulty of tilting. In this example, the length H1 of the small outer diameter tube portion 4 is longer than the length H2 of the middle outer diameter tube portion 15, and The length H2 of the diameter tube portion 15 and the length H3 of the large outer diameter tube portion 3 are substantially equal. For this reason, when an impact is applied to the bumper 2 from an oblique direction, as shown in FIG. 9, the small outer diameter tube portion 4 tilts while slightly rolling the step 5, and the middle outer diameter tube portion 15 The tube portion 4 is supported, and the middle and outer diameter tube portions 15 are plastically deformed so as to be pushed into the large outer diameter tube portion 3 as in FIG. 2, so that impact energy can be absorbed.

As described above, in the shock absorbing device of the present invention composed of a three-stage tube and a multi-stage tube, each of the continuous tube portions suppresses the inclination of each other, and the plastic deformation direction is finally the same.
(In the above example, the middle and outer diameter tube portions 15 are pushed into the large outer diameter tube portion 3), so that the impact energy can be equally absorbed regardless of the direction in which the impact is applied. In addition, the amount of impact energy that can be absorbed is proportional to the total amount of entanglement generated at each step. The roll-in amount of each step follows the shorter length in relation to the pipe section to be pushed in and the pipe section to be pushed in. Therefore, it is preferable that the lengths of the respective pipe sections are equal. In the above example, H
2 = H3, and H1 is equal to the length of the other pipes except for the mounting allowance with the bumper.
= H3.

[0022]

EXAMPLE An energy absorption measurement test was performed on an impact absorbing device comprising a three-stage tube. Fig. 10 shows the test specimen (shock absorber).
With the outer shape shown in the figure, from a steel circular straight pipe φ50.8mm, the small outer diameter pipe part has an outer diameter φ1 = 34.8mm, H1 = 45.0mm and t1 = 2.95mm,
Medium and outer diameter tube section has outer diameter φ2 = 50.8mm, H2 = 50.0mm and t2 =
The large-diameter tube section has a diameter of 2.30 mm, an outer diameter of φ3 = 66.0 mm, and constitutes a three-stage pipe body of H3 = 50.0 mm and t3 = 2.00 mm. From the above,
W1 = 8.0 mm and W2 = 7.6 mm. In addition, each step is 5.0mm
The length is folded back to each of the pipes. In the test, a load was applied to the small outer diameter pipe section and each pipe section was pushed in, and the amount of energy absorbed with respect to the pushing amount (= bumper displacement amount, mm) was measured as the pushing load (kN). FIG. 11 shows a graph of the test results. The specimen has a step formed separately, and this step is the amount of indentation at which the structural deformation occurs first.
Up to 13mm requires a large indentation load once. The indentation (plastic deformation) of the step according to the present invention is observed once at an indentation of 13 mm or more after having once dropped beyond the indentation load, and its energy absorption characteristics are substantially rectangular waveform characteristics. From this, it was confirmed that the shock absorbing device of the present invention had an energy absorbing characteristic according to a rectangular waveform characteristic if the step was processed so as to be plastically deformed from the beginning.

[0023]

The shock absorbing device for a vehicle according to the present invention has the following effects. (1) The energy absorption characteristic shows a characteristic (rectangular waveform characteristic) in which the amount of energy absorption sharply increases and immediately becomes a constant rate absorption, and the energy absorption efficiency is good. (2) A multistage pipe body in which pipe sections are arranged in the order of the diameters can easily obtain bumper support rigidity and a cross section corresponding to a bending moment distribution. (3) Since the step that undergoes plastic deformation is present at the outer periphery of the end of the pipe, stable plastic deformation is easily obtained. (4) Since the load is transmitted to the bracket to be mounted by compression, the strength is stable. (5) Diameter reduction, diameter expansion or press working using metal pipes,
It is easy to mold and it is easy to obtain products with stable shapes. (6) The reduced-diameter tube portion has a large thickness, and the enlarged-diameter tube portion has a small thickness, so that it is easy to realize a size relationship between the tube portions suitable for efficiently causing plastic deformation. (7) Compared with the conventional double-pipe type shock absorber, there is no need for a structure that ensures the accuracy, lubricity, dustproofness, and fixed support of the pipes, and is superior in weight, cost, and reliability. (8) If the number of stages of the multi-stage tube is increased, the amount of plastic deformation can be increased, and the amount of energy absorption can be easily increased.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a shock absorbing device comprising a two-stage tube of the present invention.

FIG. 2 is a sectional view taken along the line AA in FIG.

FIG. 3 is a sectional view taken along line BB in FIG.

FIG. 4 is a longitudinal sectional view corresponding to FIG. 1 showing a state in which almost all impact energy has been absorbed.

FIG. 5 is a longitudinal sectional view of the shock absorbing device including the three-stage tube of the present invention.

6 is a longitudinal sectional view corresponding to FIG. 5, showing a state in which the middle outer diameter pipe portion is pushed into the large outer diameter pipe portion from the state of FIG. 5;

7 is a longitudinal sectional view corresponding to FIG. 5, showing a state in which the small outer diameter tube portion has begun to be pushed into the middle outer diameter tube portion from the state of FIG. 6;

FIG. 8 is a longitudinal sectional view corresponding to FIG. 5, showing a state in which almost all impact energy has been absorbed.

9 is a longitudinal sectional view corresponding to FIG. 5 and showing a state where a shock is applied to the shock absorbing device from an oblique direction from the state of FIG. 5;

FIG. 10 is a longitudinal sectional view showing the shock absorbing device used for the test specimen.

FIG. 11 is a graph showing the results of an energy absorption measurement test on a test sample.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Body frame 2 Bumper 3 Large outer diameter pipe part 4 Small outer diameter pipe part 5 Step 6 Mounting flange 7 Assembling pipe 8 Bolt 9 Two-stage pipe body 10 Bolt hole 11 Pipe mounting seat 12 Pipe passage hole 13 Bolt hole 14 Three-stage pipe 15 Medium outer diameter pipe

Claims (5)

[Claims] 1. An impact absorbing device interposed between a bumper of a vehicle and a body frame to convert impact energy received by the bumper into deformation energy and absorb the deformation energy. The multi-stage pipe body is formed by gradually reducing or expanding the diameter to form pipe sections having different outer diameters, and connecting the pipe sections to each other through a step that can be formed between the ends of the pipe sections. An impact absorbing device for a vehicle, wherein pipe sections located at both ends of a pipe body are connected to a bumper and a body frame, respectively. 2. The impact absorbing device for a vehicle according to claim 1, wherein a step that can be formed between the edges of each tube portion is turned back to each of the tube portions. 3. The shock absorbing device for a vehicle according to claim 1, wherein the inner diameter of one of the pipe portions connected via the step is larger than the outer diameter of the other. 4. A circular straight pipe body capable of being plastically worked is partially reduced or expanded to form a substantially circular large outer diameter pipe section and a substantially circular outer diameter pipe section, and the axis of each pipe section is substantially 2. The large-diameter pipe section is fixed to an impact-receiving side of the vehicle body frame by forming a two-stage pipe body by connecting the ends of the pipe sections with a step so as to be on the same line. Vehicle shock absorber. 5. A circular straight pipe body capable of being plastically worked is partially reduced or expanded to form a substantially circular small outer diameter pipe section, a middle outer diameter pipe section, and a large outer diameter pipe section. The pipe edges are connected by steps so that the axes of the pipes are substantially on the same line to form a three-stage pipe body in which the pipe parts are arranged in order of diameter. 2. The impact absorbing device for a vehicle according to claim 1, wherein the impact absorbing device is fixedly abutted on a side receiving the impact.