JPH06246439A - High performance automobile driving shaft excellent in torsional fatigue characteristics - Google Patents

Abstract

PURPOSE:To provide the technology for weight reduction of a propeller shaft where the tube of HAZ softening resistant high tensile steel is used. CONSTITUTION:A balance weight of a driving shaft of an automobile is mounted by the arc welding, and a high performance driving shaft for automobile which is excellent in the torsional fatigue characteristics even after the lightweight design is made by setting the length 9 (mm) in the direction 10 of the driving shaft of the deposited metal 8 which is defined as the interval between the outermost parts 12 in the direction of the driving shaft of the arc welded metal to be >=1 time to <=6 times of the wall thickness T (mm) of the steel tube part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive shaft for transmitting an engine propulsion force of a vehicle belonging to a so-called broadly defined vehicle such as a passenger car, a truck or a tractor to each wheel, for example, a propeller shaft or a drive shaft. The present invention relates to a vehicle drive shaft that has improved fatigue characteristics compared to conventional products, can be made lighter by reducing size, and can cope with current serious environmental problems.

[0002]

2. Description of the Related Art As described in the Automotive Engineering Handbook (4th volume, Production / Quality / Maintenance P233 Automotive Industry Association 1991), it is important for a vehicle drive shaft to have little vibration during high-speed rotation. As a countermeasure against this, a balance weight 2 is attached to the steel pipe 1 as shown in the external view of the drive shaft component of FIG. 3 to adjust the weight balance in the circumferential direction.

There are roughly two ways of attaching the balance weight, that is, (a) spot welding and (b) projection welding shown in FIG. 4, and there are two methods. The driving force is similarly repeated in either method. When a torsional fatigue test corresponding to transmission is performed, fatigue cracks 6 near the balance weight may be recognized as shown in FIG. 5 (a). In particular, in the case of a fatigue test of a low-strength material with TS <500 MPa, the characteristic was the fatigue crack 7 from the joint portion 3 as shown in FIG.
As shown in FIG. 5 (a), fatigue cracks 6 near the balance weight dominate fatigue fatigue when the material strength is increased and the drive shaft cross-sectional area is reduced and weight reduction is promoted as described in Japanese Patent Publication No. 97525. This is a major obstacle to weight reduction because it becomes a target and the torsional fatigue characteristics deteriorate.

[0004]

DISCLOSURE OF THE INVENTION The present invention is as described above.
High-performance automobiles with improved torsional fatigue properties as a whole by increasing the torsional fatigue properties of spot welding or projection welding of balance weights, which is a particular problem when trying to reduce the weight of vehicle drive shafts. The idea is to get a drive shaft.

[0005]

DISCLOSURE OF THE INVENTION The gist of the present invention is to provide one balance weight in a drive shaft for transmitting an engine propulsion force of an automobile to a wheel, in which a balance weight for reducing whirling is attached by arc welding. Characterized in that the length L (mm) in the direction of the drive shaft of the one-point or multi-point arc-welded molten metal that fixes the shaft is 1 to 6 times the steel pipe partial plate thickness T (mm) of the drive shaft. It is a high performance automobile drive shaft with excellent torsional fatigue characteristics.

[0006]

[Function] The part to which the balance weight is attached by spot welding or projection welding has a metallic microstructure different from that of the base metal due to rapid heating and rapid cooling, resulting in residual stress and stress at the edge of the geometric shape. When a concentrated portion was generated and a torsional fatigue test was performed on a drive shaft component, fatigue fracture from the vicinity of the balance weight attachment portion was sometimes observed. In particular, in the present invention, a drive shaft in which the material strength is increased and the plate thickness of the drive shaft steel pipe portion is reduced was prototyped, and the fatigue characteristics in the case of further weight reduction that is currently used in an actual vehicle were studied in detail. However, it was confirmed that the fatigue fractures were concentrated in the balance weight attachment area. Therefore, as a result of conducting a search for other industrial joining methods in order to avoid the occurrence of fatigue fracture from the balance weight part, it was found that various arc welding with a specific weld metal length is effective.

FIG. 1 is an explanatory view showing how to weld metal 8 without causing fatigue fracture from the balance weight portion. The weld metal 8 should not be too long in the drive shaft direction 10. The length (L) 9 of the multi-point arc-welded molten metal in the drive shaft direction is 6 times the plate thickness (T) of the steel pipe portion of the drive shaft, although it may be dispersed in multiple points instead of one point. If it exceeds, fatigue cracking occurs at the outermost portion 12 in the drive axis direction as a result of the torsional fatigue test. It is considered that this is because the shear displacement of the steel pipe constrained by the weld metal becomes large enough to cause fatigue fracture at the outermost portion in the axial direction. When L was not less than 1 time and not more than 6 times T, fatigue fracture from the vicinity of the drive shaft balance weight mounting portion did not occur, and good fatigue characteristics were obtained.
However, if L is less than T, the joint strength of the balance weight itself becomes a problem, and it is recognized that peeling of the balance peak during the torsional fatigue test or fatigue cracking of the weld metal may lead to early fatigue fracture of the drive shaft. It was Therefore,
The length L of the weld metal in the drive axis direction must be T ≦ L ≦ 6 × T. Further, compared with the conventional spot welding nugget diameter, it is considered that the geometrical shape, the residual stress, etc. are complicatedly entangled in that the length of the axial restraint of the welded joint portion is long and the fatigue base point is unlikely to occur. Also, the welding method is MI
The method such as G / TIG / SAW does not matter, but it is desirable to select a weld metal having a strength equivalent to that of the drive shaft steel pipe.

[0008]

EXAMPLES Table 1 shows high-performance automobile drive shafts having excellent torsional fatigue characteristics according to the present invention and comparative examples. The steel pipe part of the drive shaft is a steel pipe with a tensile strength of 780 MPa class, an outer diameter of 60.5 mm, and a plate thickness of 1.6 mm, and the balance weight is the same material as the steel pipe and has a shape of 20 mmL × 20 mmW × 1.6 mmt. .

In Comparative Examples A and B, the center portion of the balance weight is attached to the steel pipe by spot welding and projection welding, which are currently used, respectively. In both cases, the balance weight portion is fractured and the fatigue life is short. Examples C to J are weldings using the L-80 welding rod, and FIG. 2 shows how the welded molten metal is piled up. Comparative Examples C and D in which the length L of the molten metal in the drive axis direction was made larger than 6 × T,
In Comparative Example F in which E and L were made smaller than T, fatigue fracture occurred from the toe portion of the weld metal of the balance weight, the fatigue life was short, and in some cases it was inferior to conventional spot welding.
However, in the case of Examples G, H, I, and J in which the length L of the weld metal in the drive axis direction was 1 time or more and 6 times or less the plate thickness T, fatigue fracture from the balance weight portion did not occur, Good fatigue properties were obtained.

[0010]

[Table 1]

[0011]

EFFECTS OF THE INVENTION In a drive shaft that transmits an engine propulsion force of an automobile to wheels, balance weights for reducing whirling are attached by arc welding, and individual balance weights are fixed. The length L (mm) of the welded molten metal in the drive shaft direction is set to be 1 to 6 times the steel pipe partial plate thickness T (mm) of the drive shaft to reduce the torsional fatigue characteristics from the balance piece mounting portion. It is possible to avoid the occurrence of fatigue fracture and improve the torsional fatigue characteristics as a component. As a result, the stress in actual use can be increased, and the weight of the automobile drive shaft can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a length of a molten metal in a drive axis direction defined in the present invention.

FIG. 2 is a diagram showing how to fill a weld metal and a crack generation position in each sample shown in the examples.

FIG. 3 is a diagram showing a structure of a typical automobile drive shaft.

FIG. 4 is a diagram showing an outline of spot welding and projection welding for attaching a balance weight.

FIG. 5 is a diagram showing a fatigue fracture occurrence position when a torsional fatigue test, which is a main performance evaluation, is performed on the drive shaft.

[Explanation of symbols]

 1 Steel pipe 2 Balance weight 3 Joint part 4 Joint part 5 Electrode tip 6 Fatigue crack near the balance weight 7 Fatigue crack from joint part 8 Weld metal 9 Length of molten metal in driving axis direction (= L) 10 Driving axis direction 11 Drive shaft circumferential direction 12 The outermost part of the arc welding molten metal in the drive shaft direction

Claims (1)

[Claims] 1. A single or multi-point balance weight is fixed to a drive shaft for transmitting the engine propulsion force of an automobile to a wheel, in which a balance weight for reducing whirling is attached by arc welding. A high-performance automobile drive with excellent torsional fatigue characteristics, characterized in that the length L (mm) of the arc-welded molten metal in the drive axis direction is 1 to 6 times the steel pipe partial plate thickness T (mm) of the drive shaft. axis.