JP6630643B2 - Dead axle case crack detection system - Google Patents

Description

  The present invention relates to a dead axle case crack detection system.

  In a two-axle vehicle behind a truck, a drive axle case accommodating a differential gear is used as a front drive axle depending on the application, and a dead axle case 10 shown in FIG. 4 is used as a rear driven axle.

  The central portion of the dead axle case 10 is a square section 11. Both ends of the dead axle case 10 are cylindrical portions 12. The angular section 11 and the cylindrical section 12 are connected by a transition section 13 having a rectangular section to a circular section.

  One of the main external forces applied to the dead axle case 10 is a load in the vertical direction of the vehicle. The vertical load is the mass of the vehicle or the load, and is input to the spring receiving portion 14 of the dead accelerator case 10. Dead accelerator case 10 is supported by tread portion 15 of the tire.

  At this time, the entire dead axle case 10 bends as shown in FIG. 5, and a tensile stress is generated on the LWR side of the dead axle case 10. A brake flange 16 is attached to the cylindrical portion 12 of the dead axle case 10 by welding, and stress tends to concentrate on this welded portion.

  FIG. 3A shows a case where one side of the brake flange 16 is attached to the dead axle case 10 with a weld bead 18i around the entire circumference, and the other is attached with a welding beat 18o with the lower part thereof unwelded. And the stress generated in the welding beats 18i and 18o. When a unit load is applied in the vertical direction, compressive stress of index 62 and index 57 is generated in the welding beats 18i and 18o on the UPR side. Further, in this case, a high tensile stress having an index of 97 is generated at the lowermost portion (the portion receiving the maximum tensile stress) on the LWR side of the weld bead 18i that has been welded all around.

  When the dead axle case is repeatedly subjected to an excessive vertical load, a crack C is generated from the lowermost welding route portion 19 on the LWR side of the welding bead 18i as shown in FIG. 3B.

  In the initial stage of crack propagation, the crack C proceeds in the thickness direction of the cylindrical portion 12 and penetrates the thickness as shown in FIG. Further, in the middle stage, the penetrating portion of the cylindrical portion 12 expands in the circumferential direction. Then, in the last stage, the penetrating portion expands to approximately 180 ° or more at the lower portion, and finally, the crack is largely opened and deformed without enduring the vertical load. At the time of deformation, the axle case bends at the position of the through crack, that is, the brake mounting portion, and the vehicle cannot run.

  Regarding the generation of cracks, lubricating oil for a power transmission gear is contained inside the main body of the drive axle case. When a crack occurs, the lubricating oil leaks to the outside of the main body at an initial stage when the main body plate thickness penetrates, and the existence of the crack can be found by the phenomenon of oil bleeding. This allows the user to take measures such as repairing or replacing the axle case.

  However, in the dead axle case 10, no lubricating oil is contained in the inside of the main body, and it is not possible to detect the presence of a crack by initial oil bleeding. That is, in the dead axle case 10, it is difficult to detect an initial crack in the welded portion of the brake flange 16.

Conventionally, various measures have been taken to prevent cracks in the welded portion of the brake flange (the following countermeasure examples 1 to 3).
Countermeasure example 1: Stress reduction by increasing the thickness and cross-sectional dimension of axle case Countermeasure example 2: Elimination of the lower part of brake flange welding Countermeasure example 3: Adding peening treatment to the brake flange welding toe

  However, most of the measures are minimized due to economic reasons such as increase in cost and mass, and restrictions on layout. Further, since the occurrence of cracks depends on the user's use conditions such as overloading and severe running, a method of completely suppressing the occurrence of cracks cannot be taken.

  An axle case crack detection structure described in Patent Document 1 is known. In Patent Document 1, the weakest part and the next weakest part are formed in the opening of the axle case, a strain gauge is mounted on a line connecting them, and when it is detected that the strain gauge is disconnected, There has been proposed a crack detection structure that informs a driver that a crack has occurred on a line and prompts the driver to replace the axle case before the end of its life.

JP 2014-178209 A JP 2009-202848 A

  However, since the weakest part and the next weakest part are both formed in the axle case, a reduction in the strength of that part is inevitable. For this reason, there is a possibility that cracks may occur at the site where cracks originally occur (the weakest part, then the weakest part) due to aging due to use, and the useful life of the axle case will be shortened.

  On the other hand, the brake attached to the brake flange is an important security component. For this reason, it is desired to reliably detect a crack generated near the welded portion of the brake flange.

  Therefore, an object of the present invention is to solve the above-mentioned problem and to provide a crack detection system for a dead axle case that can detect a through crack from a weld portion of a brake flange before the dead axle case is deformed.

To achieve the above object, the present invention is circumferential welding one side of the axle direction by inserting a ring-shaped brake flange dead axle case, the dead just above the weld root portion at the bottom of the weld bead below the inner surface of the axle case, fitted with a strain detector for detecting strain generated in an inner surface thereof, with the strain detector, crack detection of dead axle casing, characterized in that predicting the crack of the dead axle casing System.

The strain detector consists strain gauge lead wire connected to the strain gauges, the through holes and vertical neutral position through the formation of dead axle casing, extending to the outside of the dead axle case, the strain detecting It is preferable that the value detected by the detector is input to the strain displacement amount measuring means.

Together with the above strain displacement amount measuring means obtains the strain displacement quantity from the detected value from the distortion detector, from the distortion amount seeking axle load exerted on the dead axle case, it is preferable to determine whether overloading .

The strain displacement amount accumulating means accumulates the strain displacement amount obtained by the strain displacement amount measuring means for each unit time or unit distance, and the crack occurrence predicting means determines the time of crack occurrence from the sum of the accumulated strain displacement amounts. It is preferable to predict.

  The present invention has an excellent effect that a crack generated in a dead axle case can be predicted.

It is a figure showing one embodiment of the present invention. It is sectional drawing to which the distortion detector part shown in FIG. 1 was expanded. (A) is a figure explaining the stress when a load is applied to the dead axle case to which the brake flange is welded, and (b) is a view showing a cross section of the lowermost part of the brake flange of the dead axle case to which the brake flange is welded. . It is a figure showing a dead axle case. It is a figure showing the state where load was applied to the dead axle case and it bent.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 schematically shows a system for detecting a crack in a dead axle case according to the present invention.

  The dead axle case 10 has a square section 11 formed in the center, a transition section 13 connected to the square section 11 to be changed from the square section to a circular section, and further, the circular section is reduced in diameter. And a cylindrical portion 12 for supporting the tread.

  The brake flange 16 includes a flange portion 16f for mounting a brake device, and inner and outer collar portions 16i and 16o for supporting the flange portion 16f. The inner collar portion 16i is formed thicker than the outer collar portion 16o, and the inner collar portion 16i is welded to the dead axle case 10 (cylindrical portion 12) by a welding bead 18i. The outer collar portion 16o is partially welded with a weld bead 18o from the upper portion to the lower portion of the outer collar portion 16o except for the unwelded portion in the range of 90 ° to 180 ° around the lowermost portion where the stress is concentrated.

  When the brake flange 16 is attached to the dead axle case 10 by full circumference welding on one side, as shown in FIG. 2, the lowermost portion of the weld bead 18i that is full circumference welded with a vertical load (a portion that receives the maximum tensile stress). , A high tensile stress is generated in the welding root 19. The starting point of the crack is the welding root 19. The crack starting from the welding root portion 19 extends in the thickness direction of the dead axle case 10 and penetrates.

  Here, the starting point of the crack and the crack propagation direction, that is, the vertical direction of the cross section perpendicular to the minimum cross section of the main body of the dead axle case 10 are known.

  A strain detector (strain gauge) 20 is previously attached to the inner surface 10c of the dead axle case 10 at the penetrating position (FIG. 2), and the lead wire 21 of the strain detector 20 is connected to the dead axle as shown in FIG. It extends outside the dead axle case 10 through a hole 22 formed through the case 10 at a neutral position in the vertical direction, and inputs the value detected by the strain detector 20 to an ECU (engine control unit) 30.

  Considering the vehicle weight applied to the dead axle case 10 and the stress and bending moment generated by the road surface reaction force, the hole 22 is desirably located near the brake flange 16 on the neutral axis in the vertical direction of the dead axle case 10 and outside the vehicle.

  Since this position is a portion covered by the vehicle brake device, the vehicle is not exposed to the sludge water wound up by the tire during traveling, and there is no fear that the sludge water enters the inside of the axle through the hole 22. Also, when the lead wires 21 of the strain detector 20 are routed, the lead wires 21 of various sensors of the brake device which are originally present can be combined with each other, which is convenient.

  The ECU 30 includes a strain displacement amount measuring unit 31, a strain displacement amount integrating unit 32, and a crack occurrence predicting unit 33. The results measured or predicted by these means 31 to 33 can be displayed on the display 34.

  The strain detector 20 is formed of a strain gauge, and is attached to the inner surface 10c of the axle case directly above the welding root portion 19. The resistance value of the strain gauge changes when the portion to which the strain gauge is attached is distorted according to the stress generated in the welding root portion 19. From the change in the resistance value, the strain displacement amount measuring means 31 measures the stress generated in the welding route portion 19.

  Here, when a through crack is generated, the tensile stress is repeatedly generated in the welding root portion 19, so that the fatigue resistance of the welding root portion 19 is reduced, and the crack is finally generated in the welding root portion 19. When the crack propagates to the position where the strain gauge is attached, the strain gauge is disconnected, and at that time, the strain cannot be detected.

  Therefore, a fatigue limit diagram (S-N diagram) before cracking is obtained in advance by an experiment, and the maximum value of the stress detected at a unit time or a unit traveling distance by the strain displacement amount measuring means 31 is determined by the strain displacement. The amount accumulating means 32 accumulates, and based on this, the crack occurrence predicting means 33 predicts the time when the crack occurs in the welding route portion 19 and the distance until the crack occurs.

  Normally, when the strain gauge is broken, that is, when the crack penetrates, the dead axle case 10 is not in a deformed state, and the crack propagates from the crack penetrating portion in the circumferential direction and deforms. For this reason, the crack occurrence predicting means 33 can predict the time until the deformation, and can warn the inspection / replacement of the dead axle case 10 on the display 34.

  The occurrence of cracks tends to occur at an early stage when the vehicle repeats overloading, or repeats running on a rough road, suddenly starting, and suddenly braking.

  Therefore, the distortion displacement amount measuring means 31 can also warn the display 34 that the vehicle is overloaded when the vehicle is overloaded (for example, 150% overloaded) based on the detected distortion amount.

  As described above, in the present invention, since the axle case need not be formed with the weakest portion and the next weakest portion as in Patent Document 1, the strength inherent in the axle case does not decrease. . Therefore, in the present invention, a crack generated in a welded portion of a brake flange of a dead axle case can be accurately detected without reducing the service life of the dead axle case.

  In the dead axle case, the presence of a crack can be found at the time of penetration of the main body plate, which is the initial stage of crack propagation. Thereby, the failure of the vehicle can be avoided and the dead axle case can be replaced before the failure of the dead axle case, so that the non-operation time of the vehicle can be minimized.

10 Dead Axle Case 16 Brake Flange 18i Weld Bead 19 Root 20 Strain Detector

Claims (4)

And circumferential welding one side of the axle direction by inserting a ring-shaped brake flange dead axle case, the lower side of the inner surface of the dead axle casing just above the weld root portion at the bottom of the weld bead, the inner surface the strain detector for detecting strain generated in the mounting, with the strain detector, the crack detection system dead axle casing, characterized in that predicting the crack of the dead axle case. The strain detector consists strain gauge lead wire connected to the strain gauges, the through holes and vertical neutral position through the formation of dead axle casing, extending to the outside of the dead axle case, the strain detecting The dead-axle case crack detection system according to claim 1, wherein a value detected by the detector is input to a strain displacement amount measuring means. Together with the above strain displacement amount measuring means obtains the strain displacement quantity from the detected value from the distortion detector, from the distortion amount seeking axle load exerted on the dead axle case, overloading whether judges claim 2 A crack detection system for the dead axle case described. The strain displacement amount accumulating means accumulates the strain displacement amount obtained by the strain displacement amount measuring means for each unit time or unit distance, and the crack occurrence predicting means determines the time of crack occurrence from the sum of the accumulated strain displacement amounts. The dead axle case crack detection system according to claim 3 for predicting.

Images