JP6630644B2 - Axle case crack detection system - Google Patents

Description

  The present invention relates to a system for detecting a crack in an axle case of a vehicle.

  An axle case of a vehicle such as a truck receives an axle load corresponding to the load capacity and repeatedly inputs a road surface reaction force during traveling. Therefore, a fatigue strength corresponding to a service life of the vehicle is required. However, if overloading or running on a rough road is repeated, the degree of deterioration increases, and cracks may occur.

  An axle case crack detection structure described in Patent Document 1 is known. In this 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 is disclosed a crack detection structure that informs a driver that a crack has occurred along a line and prompts the driver to replace the axle case before the end of its life.

JP 2014-178209 A JP 2003-206961 A

  However, since the axle case is purposely formed with the weakest part and the next weakest part, before the crack occurs at the site where the crack originally occurs (the essential weakest part of the axle case), If a crack occurs in the formed part (the weakest part, then the weakest part), the service life of the axle case is shortened.

  On the other hand, the welding of the axle case and the brake flange is set at a critical security site, and cracks must be avoided. Cracking around the brake flange occurs at the weld end of the weld bead and propagates to the overall crack.Therefore, the crack occurrence at the weld end must be predicted in advance or detected immediately after it has occurred. Is desired.

  Then, an object of the present invention is to solve the above problems and to provide a crack detection system for an axle case with a brake flange.

To accomplish the above object, the lower is welded a ring-shaped brake flange so that the unwelded axle casing, attach the strain sensor to the position of the end of the welding bead of the axle case, the In the axle case crack detection system, the strain value detected by the strain sensor is integrated for each unit travel time or unit travel distance, and the occurrence of the axle case crack is predicted from the sum of the integrated strain amounts. is there.

  Preferably, the welding beads are provided on both sides of the brake flange, and the strain sensors are respectively attached to ends of the welding beads.

It is preferable to calculate the loaded weight of the vehicle based on the value detected by the strain sensor .

Preferably, the loading ratio of the vehicle is obtained from the detected value of the distortion sensor, and a warning is issued when the loading ratio exceeds 120% or 150% .

  The present invention exerts an excellent effect that a strain sensor is attached to an axle case located at an end of a weld bead of a brake flange and the strain is detected, whereby the occurrence of a crack can be predicted.

It is a figure showing one embodiment of a crack detection system of an axle case of the present invention. In the present invention, it is a figure explaining compression and tensile stress distribution at the time of axle load being applied to an axle case. It is a perspective view of an axle case in the present invention. FIG. 4 is a sectional view taken along line AA of FIG. 3. FIG. 4 is a diagram illustrating a relationship between a distance from an axle center and a displacement amount in the present invention.

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

  Referring to FIG. 3, an axle case 10 applied to the present invention will be described.

  The axle case 10 is formed to have a banjo section 11 for accommodating a differential gear unit (not shown), a tubular angular section 12 extending left and right from the banjo section 11, and a square section 12 on the center side. The transition portion 13 has a circular cross section on the outside and a cylindrical portion 14 connected to the transition portion 13.

  The banjo part 11 has an opening for inserting a differential gear unit on the front and rear sides, and a ring is welded to a front part of the opening. It is stopped and the cover 15 is welded to the rear.

  A ring-shaped brake flange 16 is welded to the transition portion 13.

  As shown in FIG. 2, the axle case 10 receives a reaction force from the road surface by applying a downward axial load to the angular cross-sectional portion 12 of the axle case 10. And the displacement of the central banjo portion 11 decreases to the maximum, and the displacement amount decreases from the center to the fulcrum SP. Here, with respect to the neutral axis L of the axle case 10, a compressive stress is generated on the upper side and a tensile stress is generated on the lower side, and a higher stress is generated toward the upper and lower surfaces.

  Therefore, as shown in FIG. 4, when welding the ring-shaped brake flange 16 to the transition portion 13 of the axle case 10, the welding bead 18 does not apply to the entire circumference of the brake flange 16, but generates a high tensile stress. The strength is reduced by welding so that the lower part becomes an unwelded portion 19 (Patent Document 2).

  The weld bead 18 is provided on both sides of the brake flange 16, and the unwelded portion 19 has a range of 90 ° to 120 ° around the lowermost ends of the brake flange 16 and the transition portion 13.

  However, even in the weld bead 18 in which the unwelded portion 19 is formed, as shown in the enlarged view of the circle D portion in FIG. 3, stress concentration occurs at the end 18e of the weld bead 18, so that the end of the weld bead 18 The portion 18e becomes the weakest portion, and this portion becomes the crack initiation point Cs, and a crack may be generated from the crack initiation point Cs along the expected crack growth line Cl as indicated by a dotted line.

  Therefore, as shown in the enlarged view of the circle D portion in FIG. 3, by attaching the strain sensor 20 close to the end portion 18e of the weld bead 18, the weak portion is formed on the axle case 10 without being formed. The occurrence of cracks can be predicted, and when a crack occurs, it can be detected immediately.

  That is, in the present invention, since the weakest part and the next weakest part do not need to be formed on the axle case as in Patent Document 1, the life 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 an axle case can be predicted without reducing the service life of the axle case, and the occurrence of the crack can be detected immediately.

  The four strain sensors 20 are attached to each end 18e of the weld bead 18 provided on both sides of the brake flange 16 and a total of eight strain sensors 20 are attached to the left and right brake flanges 16. Is input to an ECU (engine control unit) 30 as shown in FIG.

  The ECU 30 includes a vehicle total load amount calculating unit 31, a load amount calculating unit 32 for each axis, a strain amount integrating unit 33 for each strain sensor, and a crack occurrence predicting unit 34 based on the detection value of each strain sensor 20. And outputs the results calculated by these means 31 to 34 to the driver's seat multiplex monitor 35.

The vehicle total load amount calculating means 31 calculates an axle load (load amount) based on the following equation from a distortion value which is a detection value detected when the vehicle stops.
Total vehicle load = Front shaft load + Rear shaft load

  The total vehicle load calculated by the total vehicle load calculating means 31 is displayed in analog or digital form with the load indicator 36 of the driver's multiplex monitor 35, and when the load ratio exceeds 150%, the driver's multiplex monitor 35 is displayed. The warning is given by the red lamp 37R, the warning is given by the yellow lamp 37Y when it is less than 150% and more than 120%, and the blue lamp 37B is turned on when it is less than 120%.

  FIG. 5 shows the displacement distribution with respect to the distance from the axle case center when the axle case 10 is subjected to the axial load as described in FIG.

  When an axle load is applied to the axle case 10, the displacement of the central banjo portion 11 is large, and the distribution of the displacement is small from the center to the support point.

  Here, at the position of the distortion sensor 20, the distortion values of the loading amounts of 120% and 150% can be obtained in advance, and the yellow lamp 37Y is turned on at the loading amount of 120% based on the detection value of the distortion sensor 20, and the loading is performed. When the amount is 150%, the red lamp 37R is turned on to give a warning.

  That is, in a truck with a total weight of 25 tons (in the case of 6 × 4: a front wheel side axle of 5 tons, and two rear wheel side axle cases each having an axle load of 10 tons), with a loading capacity of 110%, The axle case has an axle load of 10 tons, but at a loading rate of 120%, an axle load of 11 tons and at a loading rate of 150%, an axle load of 13 tons.

Therefore, the loading amount calculation means 32 for each axis calculates the axle load (loading amount) from the distortion value detected when the vehicle stops, based on the following equation.
Load capacity for each axis = (measured value / deflection at fixed load) x load capacity at fixed load * Load capacity at fixed load is calculated from the specification table for each vehicle.

  The load amount for each axis calculated by the load amount calculation means 32 for each axis is displayed on the display 38.

  The distortion amount integrating means 33 of each distortion sensor integrates the distortion value detected by each distortion sensor during traveling of the vehicle for every unit time or every unit distance. Thus, the total sum of the strain amounts applied to the end portions 18e of the weld beads 18 described with reference to FIG. 3 is obtained.

  The crack occurrence predicting means 34 is based on a fatigue limit diagram (generally an SN diagram) obtained by a separate experiment from the sum of the strain amounts integrated by the strain amount integrating means 33 in each strain sensor 20. The occurrence of a crack at the end 18e is predicted.

  In ordinary trucks, the strength of the axle case 10 is secured so that cracks do not occur in the axle case 10 up to the target life distance or the service life set by the vehicle manufacturer, but overloading and frequent rough roads are repeated. When the vehicle runs, the axle case has a large axle load, which may cause cracks. When this crack actually occurs, the detected value of the strain sensor at the crack occurrence location is such that the detected strain amount before the crack occurrence is the maximum and the detected strain after the crack occurrence is reduced to almost zero.

  Therefore, the crack occurrence predicting means 34 calculates the degree of fatigue of the axle case at the position of the strain sensor from the sum of the strain amounts integrated by the strain amount integrating means 33 in each strain sensor. By calculating the degree of fatigue, it is possible to predict the aged deterioration of the axle case from the detected strain amount based on the currently detected load amount and the initial strain amount change based on the load amount without fatigue. It is possible to estimate the time until the crack is generated in the case or the travelable distance, and by displaying this on the display 38, it is possible to prevent the crack from occurring.

  As described above, the present invention has the following effects by monitoring distortion data in real time.

  Since it is possible to know the signs of failure around the welded portion of the brake flange of the axle case, parts can be prepared in advance, and the vehicle stop time due to the failure can be minimized.

  Since the operation can be stopped before the breakdown around the brake flange welding of the axle case, an accident due to the failure can be avoided.

  Displaying the loaded weight in the vehicle based on the distortion value when the vehicle is stopped has the following effects.

  The operation of the vehicle in overloading can be prevented.

  Traffic accidents and breakdowns caused by overloading can be avoided.

DESCRIPTION OF SYMBOLS 10 Axle case 16 Brake flange 18 Weld bead 18e End 19 Unwelded part 20 Strain sensor 30 ECU

Claims (4)

Downward welding the annular brake flange so that the unwelded axle casing, attach the strain sensor to the position of the end of the welding bead of the axle case, the strain value detected by the strain sensor, unit travel A crack detection system for an axle case, wherein a system is integrated for each time or unit traveling distance, and the occurrence of the crack in the axle case is predicted from the sum of the integrated strain amounts .   The axle case crack detection system according to claim 1, wherein the weld bead is provided on both sides of the brake flange, and the strain sensors are respectively attached to ends of the weld bead.   The crack detection system for an axle case according to claim 1, wherein a load weight of the vehicle is calculated based on a detection value of the strain sensor.   The axle case crack detection system according to claim 3, wherein a loading ratio of the vehicle is obtained from a value detected by the strain sensor, and a warning is issued when the loading ratio exceeds 120% or 150%.

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