JP2014178209A - Crack detection structure for axle cases - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to determine in advance the replacement timing for an axle case before the concentration of stresses occurring repeatedly on the axle case breaks it down by cracking.SOLUTION: A crack detection structure for axle cases comprises a first fragile part 1 formed in the edge of the central aperture of an axle case by cracking, penetration or thickness reduction to constitute the first start point of a crack in the axle case; a second fragile part 2 formed in a vicinity position away from the first fragile part 1 by penetration or thickness reduction of the edge to cause the greatest stress on the route linking to the first fragile part 1 to constitute the first crack thereon; and detecting means 3, disposed between the first fragile part 1 and second fragile part 2 to detect any crack occurring between the first fragile part 1 and second fragile part 2.

Description

  The present invention relates to a crack detection structure capable of discriminating the replacement time in advance before the axle case is broken by a crack due to repeated stress concentration on the axle case.

As shown in FIGS. 6 and 7, the axle case 10 has a groove-shaped cross section, and a pair of upper and lower side plates 11, 12 whose longitudinal center part swells to the respective web surface side is butted and welded, A ring-shaped reinforcing member 14 for attaching a gear case is welded to the front of the central opening 13 opened to the central bulge, and a hemispherical shell-shaped cover 15 for sealing the lubricating oil of the gear is provided behind. Welding.
In such an axle case 10, a vertical load that is a main load is input via a spring or the like (not shown), and when the reaction force is received from the ground contact point of the tire 16, the axle case 10 has a central opening 13. A bending moment is applied so as to bend the housing portion 17 surrounding the housing 17 downward.
At this time, the entire axle case is deformed as indicated by the dotted line in FIG. 8, and stress is partially generated in the cover-side inner diameter portion of the housing portion 17.
Then, by repeatedly receiving an excessive load in the vertical direction, the axle case receives the load, for example, at the front side of the axle case 10, as shown in FIG. When welding the inner diameter notch of the opening and the triangular plate, a large load is applied to the back of the triangular plate, the cover back, the bracket weld, etc., and the rear side of the axle case 10 is illustrated in FIG. 9B. As described above, since a large load is applied to the triangular plate welded part, the cover welded part, the brake flange welded part, the tube part welded part, etc., a crack occurs from one or more of these parts, and the progress of the crack As a result, the axle case may break, leading to a serious failure that prevents the vehicle from running.
Although the present applicant has proposed the inventions of Japanese Patent Application Laid-Open Nos. 2005-132249 and 2009-1252, the occurrence of cracks in the axle case could not be predicted.

In general, in order to suppress damage due to cracks, as a first countermeasure, a method of setting a strong specification that does not cause cracks can be considered.
In this case, the thickness of the member constituting the axle case is set to be thick, or the stress change is reduced by making the shape change moderate, but as a result, the component member of the axle case becomes thicker and larger. Increase in material costs is inevitable. Moreover, since the vehicle mass of a vehicle also increases, fuel cost will deteriorate.
Next, as a second countermeasure, there can be considered a method of designing so that a cracked portion caused by severe use can be easily found from the appearance of the vehicle.
In this case, there is a problem in how the failure appears.
Failures are identified by the leakage of lubricating oil inside the axle case and can be easily identified by anyone.
However, the user may lose the reliability of the axle case, and the reliability of the vehicle using the product may be impaired due to reputation. In addition, there is a problem that the lubricant is scattered while the vehicle is running or stopped, and the road surface is contaminated.
Furthermore, if the user leaves the crack and continues to use it, the crack may develop, leading to a serious failure that breaks the axle case and makes the vehicle unable to run.

JP 2005-132249 A JP 2009-1252 A

  The present invention has been made in view of the above circumstances, and its main problem is to prevent the occurrence of a failure by detecting in advance the occurrence of a crack leading to a failure of the axle case.

In order to achieve the above object, according to the present invention,
A pair of upper and lower cross-sectional groove-shaped side plates whose center in the longitudinal direction swells to the web surface side are butted and welded, and a hemispherical cover that covers one of the center openings opened at the center is welded In the crack detection structure of the axle case,
A first fragile portion that cuts or penetrates at the mouth edge of the central opening or thins the wall thickness and becomes the first crack in the axle case;
A second portion that first cracks by generating the highest stress in the path connecting the first fragile portion by penetrating the mouth edge portion or by reducing the wall thickness in the vicinity of the first fragile portion. Vulnerable areas,
A detecting means provided between the first fragile portion and the second fragile portion for detecting a crack generated between the first fragile portion and the second fragile portion is provided.
In the invention of claim 2,
The 1st weak part and the 2nd weak part are arrange | positioned inside the welding location of a cover in the edge part of a center opening part, It is characterized by the above-mentioned.
In the invention of claim 3,
The detection means is composed of a strain gauge, and is provided with a strain detection device for determining the presence or absence of a crack and measuring the load applied to the axle case.

Before the axle case cracks in the product life due to fatigue, a small crack is first formed between the first fragile portion and the second fragile portion, and this is detected by the detection means, so that the product life of the axle case is The axle case can be repaired or replaced before it runs out.
Thereby, the following effects can be produced.
(1) Avoid serious failure of the axle case.
(2) Since the axle case can be replaced without failure, the reliability of the user's product is not impaired.
(3) Since the vehicle can be replaced before the failure, the replacement axle case can be prepared in advance, and the travel stop time of the vehicle can be minimized.
Further, by using a strain gauge as the detection means, data can be processed in real time, and the following effects are obtained.
(4) The input to the axle can be known, the presence or absence of an excessive input in use can be known, and the optimum product design can be made according to the size of the input.
(5) A strain gauge can be used as an axle weight meter.
(6) The user can know whether there is an incorrect usage such as overloading or severe driving.

It is the partial explanatory view which provided the 1st weak part and the 2nd weak part. (A) is explanatory drawing at the time of setting it as the filament which penetrated the 1st weak part and the 2nd weak part, (b) is explanatory drawing at the time of making the 1st weak part into the thin part. (A) is explanatory drawing at the time of arrange | positioning the 1st weak part in the position slightly spaced apart from the opening edge of an opening part, (b) is explanatory drawing at the time of making a 1st weak part into a substantially spindle shape. . It is a partial explanatory view provided with detection means. It is explanatory drawing which illustrated the preferable arrangement | positioning area of an 11th weak part and a 2nd weak part. It is a disassembled perspective view which shows the assembly state of an axle case. It is a rear view of an axle case. It is a front view which shows a deformation | transformation at the time of receiving the load of an up-down direction to an axle case with a dotted line. (A) is an explanatory view showing a part where the crack of the axle case is likely to occur when viewed from the front, and (b) is an explanatory diagram showing a part where the crack of the axle case is likely to occur when viewed from the back.

  According to the present invention, a first fragile portion that triggers a crack and a second fragile portion that causes the crack to progress are provided, and a detection unit that detects the presence or absence of a crack is provided between the two, so that a small portion is previously set in advance. By detecting and detecting cracks, it was possible to avoid serious failure of the axle case.

Below, the crack detection structure of an axle case is demonstrated, referring drawings.
As shown in FIG. 7, the axle case 10 of the present embodiment has a groove-shaped cross section, and a pair of upper and lower side plates 11 and 12 whose center portions in the longitudinal direction swell to the respective web surface sides are butted and welded. A ring-shaped reinforcing member 14 for attaching a gear case (not shown) is welded to the front of the central opening 13 opened to the central bulging portion, and a hemispherical shell shape for sealing gear lubricating oil or the like on the rear. The cover 15 is welded to a known structure.
In the present invention, the structure of the axle case 10 is not limited to the illustrated example, and may be a structure in which a pair of triangular plates are welded to the left and right of the central opening 13 or other structures.

In the housing 17 of the axle case 10 shown in the figure, a high stress is generated in the inner diameter portion of the cover 15 due to the vertical load in the portion directly below or obliquely above in the figure, and conventionally, a location where a crack occurs in the inner diameter portion of the housing. Was the above site.
Therefore, as shown in FIG. 1, before the crack is generated, the first fragile portion 1 and the second fragile portion 2 are provided to generate a small crack.

[First vulnerable part]
The first fragile portion 1 is the earliest occurrence of cracking (starting point of cracking) earlier than other parts of the axle case 10. In this embodiment, the first fragile portion 1 is formed at the periphery of the mouth edge portion 13 a of the central opening portion 13. It consists of a notch connected to the opening 13 and a series.
The first fragile portion 1 is likely to cause a crack at a place where a crack is likely to occur and a high stress is applied, and it is difficult to generate a crack first at a place where the stress is hardly applied.

Therefore, the arrangement of the first fragile portions 1 is not particularly limited as long as it is in a range where stress is appropriately applied while avoiding both the above-mentioned portions.
In this embodiment, the peripheral edge of the upper half mouth edge 13a of the central opening 13 is used, but as shown in FIG. It is more preferable that the first fragile portion 1 and / or the second fragile portion 2 be disposed within a range of ° to 80 °.

In the illustrated example, the first fragile portion 1 has a rectangular notch, but the shape is not particularly limited.
However, since it is necessary to surely cause a crack between the second fragile portion 2 described later, for example, in the case of a shape having a plurality of corner portions on the outside, in order to specify the corner portion to be broken first The shape must always be broken before the other corners.

In this embodiment, since the rectangular cutout is formed, the outer upper corner portion 1a is formed in a small arc shape, and the crack is developed toward the second fragile portion 2 starting from the corner portion 1a. Has been.
The first fragile portion 1 is not limited to the case where it is newly formed in the product, but is formed because of a gap with a part such as a gear case formed in the mouth portion 13a of the central opening 13 and incorporated therein. You may also use the existing notch.

As described above, the first fragile portion 1 is the one that induces cracks at the beginning, and may be any shape that can cause the crack to progress toward the second fragile portion 2, and is not limited to a rectangle. The shape is not particularly limited, such as an arbitrary geometric shape.
Further, in the present embodiment, the first fragile portion 1 has a notch shape that is continuous with the central opening 13, but as shown in FIG. 2 (a), the notch is formed in a line like a perforation. Alternatively, as shown in FIG. 2 (b), it may be a thin portion having a thinner thickness than others.

Further, the first fragile portion 1 is not limited to the opening of the central opening 13, but may be able to induce a crack first, and is slightly separated from the mouth edge 13 a of the central opening 13 as shown in FIG. 3. You may arrange in a position.
FIG. 3A shows a slight gap provided between the central opening 13 and the mouth edge 13a, and the corner 1a is sharpened as one, and FIG. An example of a substantially spindle shape in which the edge portion 13a side is also sharpened is illustrated.

[Second vulnerable section]
The 2nd weak part 2 is the most weak part in the vicinity periphery of the 1st weak part 1, and a crack progresses in the vicinity periphery of the corner | angular part 1a used as the starting point of the crack of the 1st weak part 1 in a present Example. A second fragile portion 2 is provided on the planned route R.

The 2nd weak part 2 should just be the most weak structure in the area | region of the 1st weak part 1 at equal intervals so that a crack can be reliably induced | guided | derived from the origin of the said crack of the 1st weak part 1. FIG.
As a result, the highest stress is generated in the path connecting the first fragile part 1 and the second fragile part 2, and first along the path R between the first fragile part 1 and the second fragile part 2. Cracks can be generated.

The second fragile portion 2 is a through hole in this embodiment, and this through hole is a circular hole in the illustrated example, but the shape of the hole is not limited to a circle, and the length of the diameter is not particularly limited.
Further, the second weakened portion 2 is not a hole, but may be a penetrated filament or a thin-walled portion having a reduced thickness, similar to the first weakened portion 1.

In the present embodiment, the second weakened portion 2 is set within the range of the circular welded portion L2 of the cover 15 along with the first weakened portion 1 at the peripheral edge of the mouth edge portion 13a of the central opening portion 13.
If it arrange | positions in the said position, even if a crack generate | occur | produces, since it is the inside covered with the cover 15, lubricating oil does not leak outside.

As a result, when a load in the vertical direction is repeatedly received, a high stress is generated on the path connecting the first fragile portion 1 and the second fragile portion 2, and a small crack is first generated in a limited range in the axle case. Can be generated.
In this invention, although not shown in figure, by making the plan course of crack progress assumed between the 1st weak part 1 and the 2nd weak part 2 into a thin part, or making a perforation or a half-cut ruled line, etc., You may guide the propagation direction of a crack.

[Detection means]
By detecting a crack that occurs between the first fragile part 1 and the second fragile part 2, it is possible to determine in advance when to replace the axle case, and prevent troubles such as lubricating oil leakage due to the crack. can do.
In the present embodiment, since the first fragile portion 1 and the second fragile portion 2 are set within the range covered by the cover, the crack cannot be visually observed, and the first fragile portion 1 and the second fragile portion 2 is provided with a strain gauge 3 as a detection sensor to detect the occurrence of cracks.

That is, it is preferable that the strain gauge 3 is pasted so as to intersect with the planned path R where the crack propagates.
The strain gauge 3 is connected to a strain detection device 5 provided outside the axle case 10 via a lead wire 4.
When the crack progresses and reaches the strain gauge 3, the strain gauge 3 is disconnected along with the crack.

Therefore, even if the strain gauge 3 is energized from the strain detector 5, the strain amount is not output, so that it is possible to detect the occurrence of a crack without disassembling the axle case 10.
Therefore, the presence or absence of the crack is determined by connecting the strain detection device 5 to the lead wire 4 of the strain gauge 3 periodically, for example, during periodic inspection or vehicle inspection, and checking the output by energizing the strain gauge 3. Can do.

If the strain detector 5 is always connected to the lead wire 4 of the strain gauge 3, the above detection can be performed continuously.
In this case, if the output from the strain gauge 3 is continuously input to the strain detection device 5, the strain data detected by the strain gauge 3 can be recorded in the memory 6 of the strain detection device 5 in time series, or External display can be performed on an external display device.
As a result, it is possible to know the load applied to the axle case 10 and to know whether there is an excessive input in use.

Further, the strain gauge 3 can also be used as an axial weight meter.
Further, by processing the record in the memory 6, it is possible to know the magnitude of the input to the axle case 10 at the time of use, so that there is information on the presence or absence of incorrect usage such as overloading and severe driving by the user. It is also possible to obtain reference information for optimal product design according to the input size.

In this invention, although the case where the strain gauge was used as a crack detection sensor was illustrated, the presence or absence of a crack may be determined using the sensor which emits a signal by a crack, and other well-known sensors.
Of course, various design changes can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 1st weak part 1a Corner | angular part 2 2nd weak part 3 Strain gauge 5 Strain detector 10 Axle case 11, 12 Side plate 13 Central opening part 13a Mouth part 14 Reinforcement material 15 Cover 16 Tire 17 Housing part L1 Central opening part Center line L2 Welded part of cover R Planned path of crack growth

Claims (3)

A pair of upper and lower cross-sectional groove-shaped side plates whose center in the longitudinal direction swells to the web surface side are butted and welded, and a hemispherical cover that covers one of the center openings opened at the center is welded In the crack detection structure of the axle case,
A first fragile portion that first cuts or penetrates at the periphery of the mouth edge of the central opening, or has a reduced wall thickness and is the first crack origin in the axle case;
A second portion that first cracks by generating the highest stress in the path connecting the first fragile portion by penetrating the mouth edge portion or by reducing the wall thickness in the vicinity of the first fragile portion. Vulnerable areas,
An axle case comprising: a detecting means provided between the first fragile portion and the second fragile portion to detect a crack generated between the first fragile portion and the second fragile portion. Crack detection structure.   The crack detection structure for an axle case according to claim 1, wherein the first fragile portion and the second fragile portion are disposed inside a welded portion of the cover at a mouth edge portion of the central opening.   3. The axle case according to claim 1, wherein the detection means is made of a strain gauge, and includes a strain detection device that determines whether or not there is a crack and / or measures a load applied to the axle case. Crack detection structure.

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