CN115318928A

CN115318928A - Rear axle housing forming method

Info

Publication number: CN115318928A
Application number: CN202211139987.6A
Authority: CN
Inventors: 范佳祥; 张涛焘
Original assignee: Individual
Current assignee: Individual
Priority date: 2022-09-19
Filing date: 2022-09-19
Publication date: 2022-11-11

Abstract

The invention relates to a rear axle housing forming method, which comprises the steps of injecting high-pressure gas into a tube blank and extruding the tube blank along the axial direction from two ends of the tube blank so as to enable the middle area of the tube blank to be subjected to bulging, and therefore a rear axle housing is obtained. Because the tube blank is expanded by adopting high-pressure gas, the middle area of the tube blank can be heated before expansion so as to reduce the yield strength of the tube blank. The tube blank is axially extruded from both ends of the tube blank while high-pressure gas is injected, so that material can be supplemented to the middle area of the tube blank in the bulging process, and uneven thickness caused by insufficient material in the bulging of the middle area can be prevented. Moreover, the axial pressure applied to the two ends of the tube blank can make the tube blank have the tendency to expand in the radial direction, so that the resistance to bulging of the tube blank is smaller. Therefore, the rear axle housing forming method can realize one-time forming of the rear axle housing, and therefore production efficiency can be remarkably improved.

Description

Rear axle housing forming method

Technical Field

The invention relates to the technical field of machining, in particular to a rear axle housing forming method.

Background

The rear axle housing of the automobile plays roles in bearing the automobile body, protecting a main reducer and the like, and is an important automobile part. The traditional process generally adopts a stamping welding or casting mode to manufacture the rear axle housing, but welding defects are easily generated on welding parts, and the casting process wastes materials and is not environment-friendly. In recent years, a new hydraulic bulging process is proposed in the industry for processing a rear axle housing. The hydroforming is a process in which high-pressure oil is introduced into a tube blank and the tube blank is expanded in a cavity to obtain a desired shape.

The hydraulic bulging process has the advantages of high material utilization rate, easiness in realization of automatic production, and high strength and light weight of the obtained rear axle housing. However, since the seamless tube used for processing the rear axle housing has high yield strength, the hydroforming method cannot realize one-step forming, and the bulging operation is often repeated for many times to obtain the required shape. Thus, the production efficiency is not high.

Disclosure of Invention

In view of the above, it is necessary to provide a rear axle housing molding method with high production efficiency.

A rear axle housing molding method includes the steps of:

lifting the tube blank formed by the previous procedure;

heating the middle area of the tube blank;

putting the heated tube blank into a cavity of a rough expansion die, and pressing the rough expansion die tightly;

and injecting high-pressure gas into the tube blank and extruding the tube blank from the two ends of the tube blank along the axial direction so that the middle area of the tube blank expands along the contour of the inner wall of the cavity to form the rear axle housing.

In one embodiment, before heating the middle area of the tube blank, the method further comprises the steps of: and preprocessing the tube blank to form a square tube area in the middle area of the tube blank and form round tube areas on two sides of the square tube area.

In one embodiment, the step of pretreating the tube blank comprises the following steps: reducing the diameters of two ends of the tube blank to obtain the circular tube area; and performing roller square operation between the two circular tube areas to obtain the square tube area.

In one embodiment, the step of heating the middle area of the tube blank is: and simultaneously heating the middle area of the tube blank to a preset temperature from the outside and the inside of the tube blank.

In one embodiment, the predetermined temperature is greater than or equal to 900 degrees celsius.

In one embodiment, the step of injecting high-pressure gas into the tube blank comprises the following steps: injecting high-pressure gas into the tube blank for multiple times, and presetting time at intervals each time so as to gradually increase the pressure in the tube blank until the rear axle housing is molded.

In one embodiment, the high pressure gas injected into the tube blank is compressed nitrogen.

In one embodiment, the pressure of the high-pressure gas injected into the tube blank is 30 mpa to 100 mpa.

In one embodiment, the axial pressure applied to both ends of the tube blank is between 125 tons and 500 tons.

In one embodiment, after the step of injecting high-pressure gas into the tube blank and axially pressing the tube blank from the two ends of the tube blank to expand the middle area of the tube blank along the contour of the inner wall of the cavity to form the rear axle housing, the method further comprises the following steps: and extracting high-pressure gas remained in the rear axle housing.

In the rear axle housing forming method, the tube blank is expanded by adopting high-pressure gas, so that the middle area of the tube blank can be heated before expansion to reduce the yield strength of the tube blank. The tube blank is axially extruded from both ends of the tube blank while injecting high-pressure gas, so that the material can be supplemented to the middle area of the tube blank in the bulging process, and uneven thickness caused by insufficient material in the bulging of the middle area can be prevented. Moreover, the axial pressure applied to the two ends of the tube blank can make the tube blank have the tendency to expand in the radial direction, so that the resistance to bulging of the tube blank is smaller. Therefore, the rear axle housing forming method can realize one-time forming of the rear axle housing, and therefore production efficiency can be remarkably improved.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic flow chart illustrating a method for forming a rear axle housing in accordance with a preferred embodiment of the present invention;

FIG. 2 is a schematic view of a situation in which a tube blank is placed into a cavity of a rough expansion die;

FIG. 3 is a schematic view of a scenario of a tube blank pre-processing;

FIG. 4 is a schematic structural view of a rear axle housing made by the method of forming the rear axle housing of FIG. 1.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention more comprehensible, embodiments accompanying figures are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein, as those skilled in the art will recognize without departing from the spirit and scope of the present invention.

In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are not to be considered limiting of the invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or to implicitly indicate the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood according to specific situations by those of ordinary skill in the art.

In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "above," and "over" a second feature may be directly on or obliquely above the second feature, or simply mean that the first feature is at a higher level than the second feature. A first feature "under," "beneath," and "under" a second feature may be directly under or obliquely under the second feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. As used herein, the terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like are for purposes of illustration only and do not denote a single embodiment.

The present invention provides a method of forming a rear axle housing for use in forming a rear axle housing 200 as shown in figure 4. Wherein, rear-axle housing 200 includes bridge package 210, rear cover 220 and connecting portion 230, and rear cover 220 is located bridge package 210 both sides, and connecting portion 230 distributes in the both ends of rear-axle housing 200 lengthwise direction.

Referring to fig. 1 and 2, a method for forming a rear axle housing according to an embodiment of the present invention includes steps S110 to S140. Wherein:

step S110, providing the tube blank 300 formed in the previous process. The previous process may be cutting, rounding, etc., and the tube blank 300 in the initial state is as shown in fig. 3 (a), and the tube blank 300 has a cylindrical shape and a length within a predetermined range. The tube blank 300 is generally a seamless tube made of stainless steel, aluminum alloy, or the like, and has a high yield strength under normal operating conditions.

Step S120, a middle region of the tube blank 300 is heated.

The middle area of the tube blank 300 is the area that needs to be expanded and thickened to form the bridge package 210 and the rear cover 220, and the purpose of heating is to reduce the yield strength of the tube blank 300, so that the bulging is facilitated.

Specifically, in the present embodiment, when the middle region of the hollow shell 300 is heated, the middle region of the hollow shell 300 is heated to a predetermined temperature from the outside and the inside of the hollow shell 300 at the same time. The outer portion of the pipe blank 300 may be heated by electromagnetic heating, infrared heating, gas combustion, or the like, and the outer portion of the pipe blank 300 may be heated by inserting a heating wire. By heating from the inner and outer sides of the tube blank 300 simultaneously, the tube blank 300 can be heated more uniformly, so that the temperature consistency of the material in the middle area is better.

Further, specifically in the embodiment, the preset temperature is greater than or equal to 900 ℃. When the temperature of the tube blank 300 reaches 900 ℃, the yield strength is obviously reduced, and the requirement of subsequent bulging is met.

Step S130, placing the heated tube blank 300 into the cavity of the rough expansion die 400, and pressing the rough expansion die 400.

As shown in fig. 2, the expanding die 400 generally includes an upper die (not shown) and a lower die (not shown), and is typically placed on a table on a closed press. The upper die and the lower die are provided with grooves at corresponding positions so as to form a cavity in a matched manner, and the inner wall profile of the cavity is approximately the same as the outer profile of the rear axle housing 200. After the tube blank 300 is placed into the cavity of the rough expansion die 400, the upper die and the lower die of the rough expansion die 400 can be pressed tightly by closing the press machine. Specifically, the pressure of the closed press is usually about 1600 tons, so that the structure of the cavity can be effectively prevented from fluctuating in the subsequent bulging process.

Further, since the heating of the tube blank 300 is completed before the tube blank is put into the expansion die 400, the heating in the cavity is not necessary. Thus, the thermal expansion deformation of the rough expansion die 400 caused by heating in the cavity can be avoided, and the machining precision is finally influenced.

Step S140, injecting high-pressure gas into the tube blank 300 and extruding the tube blank 300 from the two ends of the tube blank 300 along the axial direction, so that the middle area of the tube blank 300 expands along the contour of the inner wall of the cavity to form the rear axle housing 200.

The high pressure gas injected into the tube blank 300 may be air, nitrogen or other inert gas. The injected high-pressure gas raises the pressure inside the tube blank 300, so that the tube blank 300 can expand outward, and the rear axle housing 200 is finally obtained. Specifically, in the present embodiment, the pressure of the high-pressure gas injected into the pipe blank 300 is 30 mpa to 100 mpa.

Moreover, compared with hydraulic oil, high-pressure gas is not easy to burn in a high-temperature environment, so that the safety problem cannot be caused on the premise that the tube blank 300 is preheated. Specifically, in this embodiment, the high-pressure gas injected into the tube blank 300 is compressed nitrogen. The chemical property of the nitrogen is stable, and the nitrogen is not easy to react with the material of the tube blank 300 in a high-temperature environment, so that the tube blank 300 can be effectively prevented from being oxidized, and the quality of the finally obtained rear axle housing 200 is ensured.

Further, in the bulging process of the hollow shell 300, high-pressure gas is injected into the hollow shell 300, and the hollow shell 300 is also axially pressed from both ends of the hollow shell 300. Specifically in the present embodiment, the axial pressure applied to both ends of the tube blank 300 is between 125 tons and 500 tons.

Hydraulic cylinders can be arranged at the two ends of the tube blank 300, and the hydraulic cylinders also apply axial pressure to the two ends of the tube blank 300. Openings at two ends of the tube blank 300 are sealed by using sealing dies 500, and an air inlet channel (not shown) is formed on the sealing die 500 at least one end of the tube blank to facilitate the injection of high-pressure gas into the tube blank 300.

The purpose of axially pressing the tube blank 300 is to supplement the material to the middle region of the tube blank 300 during bulging to prevent thickness unevenness due to insufficient material at the time of bulging of the middle region. On the other hand, the axial pressure applied to both ends of the tube blank 300 gives the tube blank 300 a tendency to expand in the radial direction. That is, the resistance to the outward bulging of the tube blank 300 is smaller under the action of the axial pressure. And the yield strength of the tube blank 300 is reduced by heating the middle area of the tube blank 300 before bulging. Therefore, the rear axle housing 200 can be molded at one time by adopting the rear axle housing molding method, so that the production efficiency can be obviously improved. Furthermore, the one-time forming mode can ensure the thickness consistency of the manufactured rear axle housing 200.

In this embodiment, the step of injecting the high-pressure gas into the raw pipe 300 is: high-pressure gas is injected into the tube blank 300 for multiple times, and the interval of each time is preset for a preset time, so that the pressure in the tube blank 300 is gradually increased until the rear axle housing 200 is molded.

That is, in the bulging process of the tube blank 300, the pressure inside the tube blank 300 is not pressurized to a preset value at one time, but is pressurized in a plurality of stages. The pressure in the latter stage is higher than the pressure in the former stage, and each stage is kept for a certain time (i.e. the preset time). So increase gradually, make the bloated thick process of pipe 300 be progressive to can guarantee the uniformity of rear-axle housing 200 thickness effectively.

For example, the preset value of the internal pressure of the tube blank 300 in the bulging process is 100 MPa, and the tube blank is pressurized to 100 MPa in three times. When high-pressure gas is injected for the first time, the pressure in the tube blank 300 reaches 50 MPa; after keeping for 10 seconds, injecting high-pressure gas into the tube blank 300 again, and enabling the pressure in the tube blank 300 to reach 75 MPa; after keeping for 10 seconds, high-pressure gas is injected once, the pressure in the tube blank 300 reaches 100 MPa, and the pressure is maintained until the rear axle housing 200 is molded.

Obviously, the number of times of pressurization, the pressure intensity corresponding to each stage, and the pressure maintaining time of each stage can be correspondingly adjusted for tube blanks 300 with different sizes and different materials.

Further, in the present embodiment, after step S140, the method further includes the steps of: the high-pressure gas remaining in the rear axle housing is extracted. Therefore, the recycling of the high-pressure gas can be realized, and the cost is saved.

Referring to fig. 3, in the present embodiment, before the step S120, the method further includes the steps of: the blank tube 300 is pretreated to form a square tube region 301 in the middle region of the blank tube 300 and round tube regions 302 on both sides of the square tube region 301. The square tube area 301 is heated

Specifically, the square tube region 301 expands during the expansion process to form the bridge pack 210 and the rear cover 220, while the circular tube region 302 does not expand during the expansion process to form the connection portion 230. The bridge package 220 is flat, and the middle area of the tube blank 300 is processed into a square shape in advance, so that materials can be prevented from being accumulated in the bulging process, and the yield can be improved.

Further, in this embodiment, the step of pretreating the tube blank 300 is: firstly, carrying out treatment on two ends of the tube blank 300 to obtain the circular tube area 302; a roll-to-roll operation is then performed between the two circular tube regions 302 to obtain the square tube region 301.

Reducing the diameters of two ends of the tube blank 300 to obtain a structure with thin ends and thick middle as shown in (b) of figure 3; further, the roll-side operation is performed between the round tube regions 302, whereby the hollow shell 300 shown in fig. 3 (c) is obtained. In the process, the material can freely extend in all directions, so that the problem that the thickness of the tube blank 300 is uneven due to accumulation of the material at a certain position is avoided, and the phenomenon that the material is accumulated at the connection position of the bridge package 230 and the connecting part 230 during bulging is avoided.

In the rear axle housing forming method, the tube blank 300 is expanded by adopting high-pressure gas, so the middle area of the tube blank 300 can be heated before the expansion so as to reduce the yield strength of the tube blank 300. The blank tube 300 is axially extruded from both ends of the blank tube 300 while injecting the high-pressure gas, so that the material can be supplemented to the middle region of the blank tube 300 during the bulging process to prevent thickness unevenness due to insufficient material at the time of bulging of the middle region. Moreover, the axial pressure applied to both ends of the tube blank 300 can give the tube blank 300 a tendency to expand in the radial direction, so that the resistance to bulging of the tube blank 300 is smaller. Therefore, the rear axle housing forming method can form the rear axle housing 200 at one time, so that the production efficiency can be obviously improved.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that various changes and modifications can be made by those skilled in the art without departing from the spirit of the invention, and these changes and modifications are all within the scope of the invention. Therefore, the protection scope of the present patent should be subject to the appended claims.

Claims

1. A rear axle housing forming method is characterized by comprising the following steps:

providing a tube blank formed by the previous procedure;

heating the middle area of the tube blank;

placing the heated tube blank into a cavity of a rough expansion die, and pressing the rough expansion die tightly;

2. A method of forming a rear axle housing as set forth in claim 1, further comprising the step of, before heating the middle region of the blank: and preprocessing the tube blank to form a square tube area in the middle area of the tube blank and form round tube areas on two sides of the square tube area.

3. A rear axle housing molding method as claimed in claim 2, characterized in that the step of pretreating the tube blank is: reducing the diameters of two ends of the tube blank to obtain the circular tube area; and performing roller square operation between the two circular tube areas to obtain the square tube area.

4. A rear axle housing forming method as set forth in claim 1, wherein the step of heating the middle area of the tube blank is: and simultaneously heating the middle area of the tube blank to a preset temperature from the outside and the inside of the tube blank.

5. The rear axle housing molding method of claim 4 wherein the predetermined temperature is greater than or equal to 900 degrees celsius.

6. A method of forming a rear axle housing as claimed in claim 1, wherein the step of injecting high-pressure gas into the tube blank is: injecting high-pressure gas into the tube blank for multiple times, and presetting time at intervals each time so as to gradually increase the pressure in the tube blank until the rear axle housing is molded.

7. A method of forming a rear axle housing as claimed in claim 1, wherein the high-pressure gas injected into the tube blank is compressed nitrogen.

8. A method of forming a rear axle housing as claimed in claim 7, wherein the pressure of the high-pressure gas injected into the tube blank is 30 mpa to 100 mpa.

9. A rear axle housing forming method as set forth in claim 1, wherein the axial pressure applied to both ends of said tube blank is between 125 tons and 500 tons.

10. A rear axle housing forming method as claimed in claim 1, further comprising, after the step of injecting high-pressure gas into the blank tube and axially pressing the blank tube from both ends thereof to expand a middle region of the blank tube along an inner wall contour of the cavity to form a rear axle housing, the step of: and extracting the high-pressure gas remained in the rear axle housing.