JPH02159537A - Detection for generation of fatigue cracking in radial load endurance test for wheel of automobile - Google Patents

Abstract

PURPOSE:To enable the detecting of a generation timing of a fatigue cracking by measuring a change in a distance between a wheel and a rotary drum during a endurance test. CONSTITUTION:When a wheel 18 having a tire 17 mounted thereon is pressed by a load of 500-2,000kgf on a rotary drum 13 rotating at a speed of 60-100km per hour with the driving of a hydraulic cylinder 15, an air pressure of the tire rises remarkably with thermal expansion of air within the tire so that a distance between the wheel and the drum expands to be stabilized. Here, wheel position detectors 19 and 20 are set to measure a distance between the wheel 18 and the drum 13 and a change in the distance is measured with a cracking generation detector 21. Then, the detector 21 detects the timing of generation of even a fine fatigue cracking precisely based on a change from a reference state at which the distance between the wheel and the drum with the thermal expansion of the air within the tire. Then, a radial load endurance can be evaluated depending on a total of revolutions or a total of running distance until a fatigue cracking occurs.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for detecting the occurrence of fatigue cracks in a radial load durability test of automobile wheels.

[Prior Art] As specified in JIS-D4103, the durability strength of automobile wheels is determined by rotational bending durability and radial load i.
It will be evaluated for a long time. Of these, the radial load durability is when the wheels with tires are operated at speeds of 60 to 1100 km/h.
A load of 500 kgf to 2000 kgf is pressed onto a drum rotating at a speed of 500 kgf, and the total number of rotations or total travel distance is evaluated until fatigue cracks occur in the wheel rim or wheel disc.

Conventional radial load durability testers focus on the case where fatigue cracks occur in the wheel rim.In other words, when a crack penetrates the thickness of the wheel rim, air leakage occurs in the tire. The timing of crack occurrence was detected by capturing the following phenomena: (2) the wheel moves toward the drum. Specifically, (1
) is a limit switch for load fluctuation, (2
), the method used was to set limits using microswitches.

[Problem to be solved by the invention] However, with regard to (1) above, recent advances in hydraulic control systems have made it difficult to detect the timing of crack occurrence, as changes in load such as tire air leakage are immediately corrected. This is the actual situation. In addition, regarding (2) above, even if the setting position of the limit switch is set with an accuracy of degrees OIi 1lIfW, as a result, the timing at which the rack occurs will not be detected.

Therefore, for example, cracks with a length of 3 to 5 m + n may occur in 3 to 4 of the 8 welds from the subhole that joins the rim to the disc. However, there is a problem that there is no such thing.

For safe driving of automobiles, even minute fatigue cracks are
This is not desirable as it will cause air leakage if it penetrates the wheel rim, and the point at which the first one of the cracks that occur at multiple locations on the wheel rim penetrates should be taken as the evaluation point for durability strength. .

The present invention aims to (1) precisely detect the timing of fatigue crack occurrence and improve the accuracy of evaluating durability strength.

[L stage for solving 5a] The present invention is a fatigue test in a radial load durability test of an automobile wheel, in which a wheel with a tire mounted thereon is pressed against a rotating drum and the timing at which fatigue cracks occur in the constituent members of the wheel is detected. In the crack generation detection method, the change in the distance between the wheel and the rotating drum during the durability test is measured, and the change in the distance due to thermal expansion of the air inside the tire or the saturated state is set as a reference state, and the change from this reference state is determined. The timing of occurrence of a C fatigue crack is detected based on the change in the distance.

[Function] As a result of determining the distance between the wheel and the rotating drum in detail during the radial direction 11 durability test, the following new findings were not obtained. That is, (1) After the start of the test, the air pressure of the tire increases significantly due to thermal expansion of the air inside the tire, and the distance between the wheel and the rotating drum increases by about 3 to 71fi11.

In addition, holes were intentionally drilled in the wheel rim, and the holes were filled and drilled to 0.1
A gap of less than mm2 was created, and the change in distance between the wheel and the rotating drum was measured when a load was applied in that state.

As a result, it was found that (2) even if there is an air leak of about 1n+m'/sec, the distance between the wheel and the rotating drum changes.

In other words, according to the present invention, which measures the distance between the wheel and the rotating drum after the thermal expansion of the air inside the tire has reached a stable state, subsequent changes in distance are measured, thereby preventing the occurrence of minute fatigue cracks. However, this can be detected in detail and the accuracy of evaluating durability strength can be improved.

[Example] Fig. 1 is a front view showing a durability testing machine used for carrying out the present invention, Fig. 2 is a detection diagram of fatigue crack occurrence according to the present invention, Fig. 3 is a sectional view showing a wheel, Fig. 4 The figure is a schematic diagram showing the state of crack occurrence.

The durability testing machine 10 supports a rotary ram 13 on a drum support bracket 1-12 provided on a pedestal 11, supports a hydraulic cylinder 15 on a cylinder support bracket 14 provided on the pedestal 11, and attaches a wheel to the hydraulic cylinder 15. A support arm 16 is connected thereto. A wheel 18 equipped with a tire 17 is attached to the wheel support arm 16.

The durability tester 10 is for evaluating the radial load durability of the wheel 18, and is a rotary tram 13 that rotates the wheel 18 on which the tire 17 is mounted at a speed of 60 to 100 km/h, and a hydraulic cylinder 15. A load of 500 kgf to 2000 kgf is applied by the operation of the wheel rim or wheel disc, and the radial load durability is evaluated based on the total number of rotations or total travel distance before fatigue cracks occur on the wheel rim or wheel disc.

However, in the durability testing machine 10, a wheel position detector 19 is provided between the wheel 18 and the rotating drum 13, or a wheel position detector 20 is provided between the fixed part 15A of the hydraulic cylinder 15 and the movable part 15) 3. . The output of the wheel position detector 19 , 20 is transmitted to a crack occurrence detector 21 . That is, the wheel position detectors 19,20 measure the distance between the wheel 18 and the rotating drum 13 during the durability test by measuring the position of the wheel 18 relative to the rotating drum 13. The crack occurrence detector 21 obtains the detection results of the wheel position detectors 19 and 20, measures the change in the distance between the wheel 18 and the rotating drum 13 during the durability test, and measures the distance due to thermal expansion of the air inside the tire. The state in which the change in is saturated is defined as the reference state, and the timing of fatigue crack occurrence (C) is calculated based on the change in the distance from this reference state.
Detects cracks or timing of penetration through the rim).

At this time, the crack occurrence detector 21 may record changes in the position of the wheel 18 as shown in FIG. A certain limit may be set in advance for the output from the tester 19 or 20, and the tester 10 may be automatically stopped by this limit.

According to the above embodiment, the thermal expansion of the air inside the tire does not affect the change in the distance between the wheel 18 and the rotating tram 13, thereby eliminating its influence. I mean, those wheels 8
Based on the change in the distance between the rotary drum 13 and the rotary drum 13, even the occurrence of minute fatigue cracks can be detected in detail, and the accuracy of evaluation of durability strength can be improved.

Hereinafter, specific implementation results of the present invention will be explained.

100 on a wheel with a rim diameter of 13 inches and a rim width of 5 inches.
Radial load durability strength when subjected to a heavy load of 100O (
Table 1 shows the mileage (mileage without air leakage) and other information.

Method 1 in Table 1 is a conventional method in which a microswitch attached to the testing machine determines that a "crack has occurred" when the wheel approaches the drum side by 10μ from the initial position, and stops the testing machine.

The methods of the present invention using wheel position detectors (19, 20) are shown in Methods 2.3.4 in Table 1, and the distance between the wheel and the drum is determined by the amount of air in the tire as shown in No. 2 and 4. Based on the position where the distance changes due to thermal expansion or reaches a stable state due to saturation, the wheel changes by 10 minutes from the reference state.
μm, 20 μm, 30 μm The test machine was set to stop when it was determined that a crack had occurred at a position close to the drum side.

The crack length in Table 1 is the total length of cracks (a in Figure 4) observed on the rim surface at the end of the test. All of these cracks occurred at the spot welds 3 (there are 8 locations around the entire circumference) between the rim 1 and the disc 2 (
(See Figure 3), Table 1 also shows the number of spot welds where cracks penetrated.

Method 1 (comparative method) and Method 2 (method of the present invention) both have test stop settings of IO μm'C, and there are large differences in the number of cracks, total length, and running distance. This is because Method 1 is based on the position of the wheel before thermal expansion during the test.

From the chart recorded at the same time in Method 2.3.4, the travel distance at the time of fatigue crack penetration was calculated using the method shown in Figure 2. Both travel distances were 2149kIIl and matched with an error of less than 1km, that is, the true durability strength. or obtained. Comparing this with method 1, the error is about 146 km,
The conventional method may have overestimated the durability and strength.

[Effects of the Invention] As described above, according to the present invention, the timing of fatigue crack occurrence can be detected in detail, and as a result, the radial load durability of a wheel, which is an important characteristic for safe driving, can be evaluated with high accuracy. Therefore, it is possible to obtain accurate indicators for designing wheel shapes and materials to improve durability and strength.

[Brief explanation of the drawing]

Fig. 1 is a front view showing a durability testing machine used in carrying out the present invention, Fig. 2 is a detection diagram of fatigue crack occurrence according to the present invention, Fig. 3 is a sectional view showing a wheel, and Fig. 4 is a diagram showing the occurrence of cracks. It is a schematic diagram showing a state. 10... Durability testing machine, 13... Rotating tram, 17... Tire, 8... Wheel, ] 9. 20...Wheel position detector, 1...Crack occurrence detector.

Claims (1)

[Claims] (1) A method for detecting the occurrence of fatigue cracks in a radial load durability test of automobile wheels, in which a wheel with a tire attached is pressed against a rotating drum and the timing at which fatigue cracks occur in the component members of the wheel is detected. The change in the distance between the wheel and the rotating drum is measured, and the state where the change in the distance due to thermal expansion of the air inside the tire is saturated is set as the reference state, and the occurrence of fatigue cracks is determined based on the change in the distance from this reference state. A method for detecting the occurrence of fatigue cracks in a radial load durability test of automobile wheels, which is characterized by detecting timing.