JPH0727160A - Suspension device component for vehicle and its production - Google Patents

Abstract

PURPOSE: To provide a leaf spring capable of notifying the final destruction before it occurs by providing a metallurgically changed discontinuous part extending in the axial direction on the leaf spring of a suspension for vehicle to change the direction of propagation of a generated crack in the axial direction. CONSTITUTION: A suspension member for vehicle is like a leaf spring 50 having at least one plate 3. The plate 3 is approximately parallel to the axis 'L/A' in the longitudinal direction extending between both ends of the plate, and generated by projecting one metallurgical discontinuous part extending along the plate between both ends of the plate, i.e., an area R which is a metallurgical discontinuous part effective to convert the direction of propagation of cracks in the direction approximately parallel to the axis 'L/A' parallel to the axis 'L/A' with the radial line 12 toward the center of an end face of the leaf spring 50.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a suspension member for a vehicle and a method for manufacturing the suspension member, and a leaf spring which is a typical suspension member is one metallographically modified part. A plate or spring plate having therein a metallographically altered portion extending along the plate or plate spring between its two ends. Approximately parallel to the longitudinal axis, in which at least one discontinuity, i.e.,
It is a leaf spring that acts to create discontinuities that are effective in diverting crack propagation in a direction generally parallel to the longitudinal axis.

[0002]

BACKGROUND OF THE INVENTION Recently, coil springs have been preferred for passenger car suspension systems, but leaf springs are still, and will continue to be, preferred for truck suspension systems in particular. This is due to the load capacity of the leaf springs, the fit and the advantages in axle position. Although primarily described herein as a leaf spring, the present invention includes any vehicle suspension member that has a longitudinal axis extending between its two ends and is subjected to torsional or bending loads. , Such suspension members include torque rods (also called trailing arms for axle control), traction bars (to prevent the axles from twisting during braking), track rods (axles in the lateral direction). Do not shift).

Leaf springs generally include one or more leaves or plates of constant or tapered thickness, the leaves or plates being most commonly made of steel, Fixed together, they serve to support the vehicle on the axle. As can be envisioned, the number of leaves or leafs used in the leaf spring is determined based on the allowable design stress in order to achieve the desired load capacity and deflection range.

Each leaf in a leaf spring is subjected to a bending force, which causes a (positive) tensile stress at the generally concave surface above the leaf where the vehicle load or force is applied. Occurs. The result is a balancing (negative) compressive stress at the generally convex surface of the underside of the leaf. This tensile stress is maximum at the surface of the leaf and decreases to zero at or near the center of the plate thickness, which is also called the neutral axis. This neutral axis extends between both ends of the leaf or plate and is henceforth referred to as the longitudinal axis.
Similarly, the compressive stress for balancing is maximum at the lower surface and decreases to zero at the longitudinal axis. Virtually all cracks occur at the point of maximum tensile stress at or near the upper surface of the leaf spring leaf.

The leaf spring must have high hardness because high strength is required. Higher hardness means that once a relatively shallow crack is created on the tensile side surface, the crack propagates at high speed. The onset and progression of cracks are generally a function of usage conditions such as elapsed time of use and history of applied load and corrosion. Regardless of how the crack propagates, that is, whether it is fatigue and / or corrosion, it generally progresses rapidly after exceeding a critical depth of less than half the cross-sectional thickness, leading to complete failure or separation. Reach

[0006]

SUMMARY OF THE INVENTION The present invention is directed to the development of cracks that occur on the upper or pull side surface and propagate through the thickness of the leaf or plate in a direction substantially perpendicular to the longitudinal axis of the leaf. Means are provided to retard or redirect the propagation by diverting its direction of travel to a direction generally parallel to the longitudinal axis.
Parallel cracks or delaminations in the cross section of a flat (or tapered) plate effectively reduce the stiffness of the cross section so that the leaf spring will flex appropriately before the final fracture, and thus It will provide the user with some early indication of the imminent failure of the leaf spring before its complete separation, and possibly even vehicle damage.

[0007]

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a vehicle suspension member along which the suspension member extends between both ends thereof. Of the metallurgical discontinuity that is effective in diverting the propagation direction of the crack into a metallurgical discontinuity, i.e., a direction generally parallel thereto. A suspension member having a continuous portion.

Another object of the present invention is to provide a method of manufacturing a vehicle suspension member, the suspension member extending therethrough between its two ends. A longitudinal discontinuity in which there is a metallurgical discontinuity, that is, a metallurgical discontinuity that is effective in diverting the propagation direction of the crack into a direction generally parallel thereto. Is a suspension member having.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The leaf spring 50 of FIG. 1 illustrates a situation in which the propagation of cracks is delayed by the present invention. Leaf spring 50
Is characterized by having at least one substantially rectangular cross-section as shown in FIG. 2 at both ends (not shown).
Including a flat or tapered leaf or plate 3 extending therebetween, both ends of which are spring leaf 5 thereof.
In order to fix the 0 to the frame of the vehicle or another suspension fixed to the vehicle, it has a suitable shape such as forming a bolt through hole. In some cases, it is better not to have bolt through holes. Normally, only one of the stacked leaf spring plates need have bolt through holes at one or both ends thereof. Although the leaf spring 3 tapers towards both ends in FIG. 1 and has a maximum thickness in the center, as is well known to those skilled in the art of leaf springs, the leaf spring has a length It may have a substantially constant thickness throughout.

The spring plate 3 has a longitudinal axis L indicated by the reference numeral 4 extending therealong between its two ends.
/ A. Due to the generally symmetrical cross-section of the leaf or plate 3, the axis "L / A" will generally pass through the center of the plate 3, as shown in FIG.

Generally, the spring plate 3 has a fixed point (shown in FIG. 1).
Repeated bending load "P" ₁"And" P₂"by
If it is repeatedly bent at
Reaction force "F" on the spring seat surface located so as to straddle the center point
Occurs, which is ultimately indicated by reference numeral 8.
As shown in Fig.
There is a crack caused by. But crack
Does not completely penetrate the plate 3, but will be explained later.
As will be seen, the metallurgy intentionally introduced in the plate 3.
Because of the discontinuity, crack propagation is on the axis "L /
The direction is changed over a distance L in a direction substantially parallel to A ”.
Has been.

As used herein, the term "discontinuity" means a discontinuity in mechanical properties, which is a plane, or a direction generally parallel to the longitudinal axis. At, but are not necessarily continuous along. If the suspension member is a bending-loaded leaf or plate, the discontinuity is preferably near the neutral axis of the leaf or plate.

The metallurgical discontinuity originates from a region "R" exposed to radiation, which is a deliberately introduced region, generally parallel to the axis "L / A".

One way to create the metallurgically altered region "R", designated by the reference numeral 10 in FIG. 2, is by exposure to radiation, for which FIG. Will be described later.

In FIG. 3, a plate 50 having a substantially rectangular cross section is made. The axial axis "L / A" extends through the central part because the cross-sectional shape is generally symmetrical.

At least one, and preferably both sides of the plate 50 are exposed to the radiation 12 emitted by the radiation source 14. The radiation source 14 is preferably directed toward the center of the end face of the plate 50 so that the region "R" is created symmetrically to the axis "L / A" and generally parallel thereto.

If the radiation has sufficient energy,
Molecules of metal that have sufficient energy to hit the molecules of the metal and heat up to the annealing temperature at which the crystal of the metal begins to grow, and further to the temperature at which the metal melts (here remelts) and later solidifies during cooling. It is known that can be given to. As such, the energy of the radiation can metallurgically change the metal in the region "R", which is well known to those skilled in the art.
This is because the width and focus of the radiation beam can be controlled with high precision by means of shielding, magnetic fields, optical and other means.

The radiation is preferably high energy electron radiation as described in US Pat. No. 4,644,126. The disclosure of that patent is included herein by reference. The term "radiation" as shown therein and also used in the description of the invention is
Includes electron and laser beam type radiation, as well as proton and helium ion beams from the Duoplasmatron, all of which melt metal when focused to a sufficiently high power density. And then weld.

As an example, an electron beam having a radiance of about 10 ⁸ to 10 ¹¹ watts / cm ² steradian or a laser beam having a radiance of about 10 ⁶ to 10 ⁸ watts / cm ² steradian melts a metal. Have sufficient ability to

The energy of the radiation particles can be focused on a fine target, such as the location of the axis "L / A" extending along the spring leaf of the vehicle suspension.

The energy of the radiation beam applied to the plate 50 of FIG. 3 causes a metallurgically altered region "R" to appear due to the annealing by focusing and also by the melting, of the crystal structure occurring in this region. The difference is that the metallurgical discontinuity, ie the metallurgical discontinuity, is effective in turning the propagation direction of the crack into a direction generally parallel to the axis "L / A", as shown in FIG. It works to create parts.

FIG. 4 shows the principle that heating by radiation is most effective when it is focused on the object as a cone-shaped radiation beam, which in the case of FIG. The beam is directed to opposite edges of the spring leaf 100 and the radiation beam has an included angle alpha. That is why the area of the plate 16 "
The thickness "T ₁ " at the center of the R "is smaller than the thickness" T ₂ "of the region" R "of the plate 16 shown in FIG.
In such cases, the area on the side or edge "
The taper of the cone is controlled so that R "remains substantially parallel to the axis" L / A "and still exists across the gold width of the spring leaf 100.

Still referring to FIG. 4, as shown in FIG. 4, both sides or edges of the plate 16 are advanced beyond the center of the plate 16 so that each beam is focused.
By exposing to radiation such that both radiation beams 18 overlap in the center of the plate 16, the thickness "
It shows the principle that the difference between T ₂ ″ and “T ₁ ” can be minimized.

The average thickness of the region "R" for a spring leaf having a thickness of about 0.250 inches is about 0.050 to about 0.080 inches, or about 1/4 to about 1 of the total thickness of the spring leaf plate. / 3 is desirable.

FIG. 5 shows a modification of the method of FIG.
There, only one edge of the spring leaf is exposed to radiation from only one side. This is most advantageous due to the thick and narrow cross section of the plate and is therefore economically attractive. In such a case, even though the beam has an angle alpha, the thickness of the affected area is acceptable for the required fatigue life, as shown in FIG.
T ₃ "and" T ₄ "is generated.

In order to promote slowing and turning of cracks, it is desirable to control the thickness of the affected area "R" to be as small as possible so as to create an area of rapid metallurgical change. . Therefore, even for thick cross sections of the order of 0.500 inches or more, "T ₃ " and "T ₄ " are approximately
It is recommended to stay at 0.050 to about 0.080 inches. However, as mentioned above, about 1/4 of the total thickness of the spring leaf plate
Greater thicknesses of up to about 1/3 are also acceptable.

The method of FIGS. 3 and 5 requires only a plate of constant thickness if appropriate processing equipment and / or computational controls are used to guide the beam of energy along the longitudinal axis. Instead, it can also be applied to plates or leaves that taper in thickness along their length, which would normally be used for single leaf type suspensions.

[Brief description of drawings]

FIG. 1 is a side view of a leaf spring 50 of a suspension system for a vehicle, showing a pattern of crack propagation.

FIG. 2 is a sectional view of the leaf spring 50 of FIG. 1 taken along the line 2-2.

FIG. 3 is a schematic block diagram of a preferred embodiment of a method of manufacturing the leaf spring 50 of FIGS.

FIG. 4 is a cross-sectional view of one leaf spring 100 made in accordance with the present invention.

5 is a schematic block diagram of a variant of the embodiment of the method shown in FIG.

6 is a cross-sectional view of a leaf spring 100 made by the method of FIG.

[Explanation of symbols]

 3 Spring Leaf (Spring Leaf) 4 Longitudinal Axis 8, 8'Crack 10 Metallurgically Modified Region 12 Radiation 14 Radiation Source 16 Plate 18 Radiation Beam 50 Leaf Spring (Spring Leaf) 100 Spring Leaf (Spring) Plate) P, F force L Crack length L / A Lengthwise axis R Metallurgically changed region T Thickness α Conical angle

Claims (4)

[Claims] 1. A vehicle suspension member including at least one metallic member, the metallic member having a longitudinal axis extending between both ends thereof. Has a region exposed to radiation, the region being substantially parallel to the longitudinal axis and having therein a metallurgical discontinuity, ie, a direction generally parallel thereto. A suspension member for a vehicle, which serves to create a metallurgical discontinuity that is effective in diverting the direction of propagation of a hecrack. 2. The suspension member according to claim 1, wherein the area exposed to radiation is the area exposed to the radiation of the high energy electron beam. 3. The suspension member according to claim 1, wherein the metallurgical discontinuity is a discontinuity solidified after remelting. 4. The suspension member according to claim 3, wherein the discontinuous portion solidified after remelting is a discontinuous portion solidified after being remelted by radiation.