JPH0414246Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a cast iron torque rod used in a tandem suspension system of a vehicle.

[Prior Art] As shown in FIG. 10, a tandem suspension system includes a trunnion shaft 10 supported on a vehicle frame 3, and a rotatable seat plate (seat bracket) 9. The center portions of the plurality of leaf springs 8 stacked on top of each other are supported on the seat plate 9 by a pair of front and rear U bolts 12. Both ends of the leaf spring 8 are slidably supported by an axle 7 that supports the wheel 2 via pads.
Knuckles 5 that engage with upper brackets 6 fixed to each axle 7, and brackets 4 fixed to the vehicle frame 3.
The centerpiece 32 of the torque rod 30 is connected between the two and the other through a known elastic bushing. The center portions 32 of the torque rods 30 are connected between the lower end portions of the seat plate 9 and the lower brackets 7a of the front and rear axles 7, respectively.

Each torque rod 30 supports the torque reaction force against the rotation of the wheel 2, and also serves to suppress the load transfer between the axles during braking and acceleration. At the same time, the beam section 31 hits a stone thrown up from the road surface, and sometimes the torque rod 31 hits a stone thrown up from the road surface.
0 is subjected to a large impact, such as when it hits a bump directly on the road surface. Therefore, the eye portion 32 is required to have strength to withstand torque load, and the beam portion is required to have strength to withstand impact load (particularly bending load).

Conventionally, as disclosed in Japanese Utility Model Application Publication No. 56-33706, the torque rod used in the above-mentioned suspension system uses a steel tube that easily bends under bending load for the beam portion 31, while the center portion 32 are manufactured by forging and are connected to both ends of the beam portion 31 by welding. Although the steel pipe torque rod 30 described above is relatively lightweight, it takes time and effort to manufacture the centerpiece 32 and weld it to the beam part 31, making it difficult to reduce costs.

In recent years, high-strength ductile cast iron (spheroidal graphite cast iron), which has excellent castability and machinability, has been widely used for automotive casting parts. Ductile cast iron is hard and has high strength against compressive loads, but has little elongation and is therefore somewhat brittle against tensile loads.

The present applicant has proposed a cast iron torque rod in Utility Model Application No. 59-44271, in which ductile cast iron is partially made into a pearlite structure to improve mechanical strength in necessary parts. However, compared to steel pipe torque rods, cast iron torque rods cannot be said to have a sufficient effect in mitigating the impact by appropriately bending the beam portion against bending loads.

[Problems to be solved by the invention] In view of the above-mentioned problems, the purpose of the invention is to provide a beam part that is integrally cast from ductile cast iron, so that the beam part properly bends under bending loads and does not suffer from excessive tensile stress. The object of the present invention is to provide a cast iron torque rod that can avoid the above problems.

[Means for Solving the Problems] In order to achieve the above object, the configuration of the present invention has a cross-sectional structure in which each side edge of a wide flat upper wall portion and a lower wall portion are connected by a thin vertical wall portion. A substantially C-shaped beam portion and eye portions connected to both ends of the beam portion are integrally cast from ductile cast iron, with the beam portion having a ferrite structure and the eye portion having a pearlite structure.

[Function] Since the beam portion has a ferrite structure that is relatively soft and has impact resistance, it can sufficiently withstand impact loads.

The beam part has a flat upper wall part and a lower wall part that are integrated with a thin vertical wall part, so in response to the bending load acting on the beam part, the vertical wall part bends and the upper wall part and the lower wall part curve as they approach each other, and at this time, the section modulus decreases, making it easier to bend, and the tensile stress is alleviated.

[Embodiment of the invention] As shown in FIG. 1, the present invention is for casting a torque rod from ductile cast iron (for example, XFCD50). The cast iron torque rod 30 has a cross-sectional shape in which a wide horizontal upper wall portion 21 and a lower wall portion 23 are integrally connected by a thin vertical wall portion 22 at one side edge. As shown in FIG. 2, the cross section of the beam portion 31 of the cast iron torque rod 30 is approximately C-shaped, and as shown in FIG. is formed. The wall thickness of the beam part 31 is relatively thick, and the eyeball part 3
2 has a cylindrical shape that is thicker at the center in the axial direction than the beam section 31.

When casting the torque rod 30, the beam portion 31 is made of a ferrite structure that is relatively soft and has impact resistance, and the eye portion 32 is made of a pearlite structure that has high hardness and mechanical strength.

In the present invention, due to the above-described configuration, when a bending load (generally an upwardly convex bending load) is applied to the beam part 31, the vertical wall part 22 of the beam part 31 is thin, so that the vertical wall part 22 becomes elastic. When crushed, the upper wall portion 21 and the lower wall portion 23 approach each other, and the beam portion 31 is curved as a whole. At this time, vertical wall part 2
2 maintains an appropriate distance between the upper wall portion 21 and the lower wall portion 23 to maintain strength against buckling.

In each embodiment shown in FIGS. 3 to 5, the vertical wall portion 22
The vertical wall portion 22 is not flat, but is curved in a dogleg shape or a C shape, so that the vertical wall portion 22 is easily bent under bending load. When the center portion of the beam portion 31 is bent by a bending load that pushes up from below, the vertical wall portion 22 is bent and the upper wall portion 21 and the lower wall portion 23 are brought closer together, so that the section modulus decreases.
The beam portion 31 becomes easier to curve. Upper wall part 2
1 and the lower wall portion 23 approach the neutral layer, the bending (elongation) of the upper wall portion 21 at this time is small, and the upper wall portion 2
The tensile stress acting on 1 is relaxed.

In each of the embodiments shown in FIGS. 6 to 9, the upper wall portion 21 and the lower wall portion 23 are integrally connected at one side edge by a thin vertical wall 22, unlike the embodiment shown in FIGS. 2 to 5. Similarly, by providing a projecting edge 24 on the other side edge of the upper wall 21 and the lower wall 23, the upper wall 21 and the lower wall 23 can be easily bent without hindering the flexibility of the vertical wall 22. It has increased rigidity and strength.

[Effects of the invention] As mentioned above, in the present invention, the beam part is made of a ferrite structure that is relatively soft and has impact resistance.
Sufficiently withstand impact loads.

The cross-sectional shape of Torquerod's beam section is such that the wide, flat upper and lower walls are integrally connected by a thin vertical wall, so when the beam section is bent by bending load, the compressive load can be absorbed. As the vertical wall part receives the crushing load, the lower wall part, which receives the compressive load, deforms and approaches the upper wall part, which receives the tensile load. At this time, the section modulus of the beam part is reduced and the beam part becomes more bendable, so that tensile stress in the upper wall part, which is a problem in terms of strength of cast iron, can be suppressed.

Since it is made from a single material, it does not require welding like conventional products, and the process is simple and easy to manufacture, reducing costs.

[Brief explanation of the drawing]

Fig. 1 is a side view of a cast iron torque rod according to a first embodiment of the present invention, Fig. 2 is a front sectional view of the central portion of the cast iron torque rod, and Figs. Embodiment 9 is a front sectional view of the central portion of the cast iron torque rod according to the present invention, and FIG. 10 is a side view showing an outline of a general suspension system in which the cast iron torque rod according to the present invention is used. 21...Top wall part, 22...Vertical wall part, 23...
Lower wall part, 30... Cast iron torque rod, 31...
Beam part, 32...Eyeball part.

Claims (1)

[Scope of utility model registration request] A beam section with a nearly C-shaped cross section, which connects the wide, flat upper and lower side edges of the upper and lower walls by thin vertical walls, and a centerpiece extending to both ends of the beam section are made of ductile cast iron. A cast iron torque rod that is cast in one piece and has a beam part with a ferrite structure and an eyepiece part with a pearlite structure.