Engine variable cross-section integrated intake port and near-equal wall thickness forming method thereof

Abstract

An engine variable cross-section integral intake port and a near-equal wall thickness forming method thereof, the intake port is a variable cross-section long annular thin wall structure integrally formed by a metal plate, a theoretical model of the intake port is connected as a whole by an upper small horn annular part and a lower large horn annular part, and near-equal wall thickness forming steps thereof are as follows: a process interface is designed according to the theoretical model to construct a process model, a first semi-product is formed by deep drawing, a circumference of the upper part of the process interface is greater than a circumference of the smallest cross-section of the theoretical model, and a circumference of the lower part of the process interface is not greater than a circumference of the corresponding position of the large horn annular part of the theoretical model; an expanding die is manufactured according to the theoretical model and the first semi-product, the lower part of the process interface of the first semi-product is subjected to pressure expansion forming to obtain a second semi-product containing the large horn annular part; after the upper part of the process interface of the second semi-product is turned outward to form the small horn annular part of the theoretical model, local thickening is performed to obtain the near-equal wall thickness integral intake port.

Description

TECHNICAL FIELD

[0001] The application relates to a sheet metal plastic forming technology in the field of aircraft manufacturing, in particular to a whole forming method for an engine variable cross-section air inlet channel, and particularly suitable for whole forming of a deep ring cavity air inlet channel with double-horn structure and close wall thickness. BACKGROUND

[0002] The air inlet channel is a key aerodynamic component for providing air for the engine and ensuring full combustion of fuel to generate thrust, and its working environment is subjected to high-speed airflow impact for a long time. Sheet metal parts have outstanding advantages such as light weight, low cost and toughness, and have been widely used for thousands of years from the cold weapon era to modern aviation, aerospace and automobile fields, and the sheet metal air inlet channel is still internationally recognized as the most reliable technical means. However, due to the limitations of the internal structure space of the engine and the forming of the material, the deep ring cavity air inlet channel with horn profile at both ends has to be formed in two parts and then combined by riveting; not only the fatigue resistance of the product itself is reduced, but also the deformation caused by riveting seriously reduces the precision of the combined parts, and significantly increases the subsequent assembly difficulty and cost. In order to meet the service life requirements of the air inlet channel in extreme environments such as cold and hot alternation and high-frequency vibration, it is very important to use sheet metal material whole air inlet channel to improve the manufacturing precision and service life.

[0003] It is known that deep drawing is one of the main plastic processing methods for forming thin-walled deep cavity parts, and is widely used in open thin-walled metal products with cylindrical, spherical, large-radius square box and other structures. The limit depth that can be achieved by forming is most obviously affected by the ratio of the radius of the corner to the depth of the product. Especially for long circular deep cavity parts, the stress on both sides of the length direction corner area is extremely complex, the material in the flange area is easily thickened by tangential compression, which leads to concentrated pressure boundary load; and the corner area of the two side punches is at high risk of thinning and cracking under deep drawing load. With the increase of depth, the risk of wrinkling and cracking of both sides of the corner during deep drawing increases sharply, and for products that bear harsh loads in service environments, in addition to meeting the basic shape requirements, high anti-fatigue mechanical properties are also required. Especially for double-horn deep ring cavity whole air inlet channel, in order to overcome the problem of outward turning of the obtuse angle affecting deep drawing, generally only one end with open structure is first deep drawn, and then the other end is further expanded after pure thinning. The wall thickness difference is further increased, which cannot meet the service life requirements in extreme environments with high-frequency vibration. SUMMARY

[0004] In order to overcome the problems of the small depth-diameter ratio, the existence of the unloading closed angle, the difficulty in unloading, the deformation damage, the large wall thickness difference and the like in the corner area of the long ring variable cross-section air inlet, and the difficulty in improving the service life, the application aims to provide a near-equal wall thickness forming method for an engine variable cross-section integral air inlet.

[0005] In order to achieve the above-mentioned application purposes, the technical solutions adopted by the application are as follows:

[0006] An engine variable cross-section integral air inlet, characterized in that: the air inlet is a variable cross-section long ring thin-walled structure formed by an integral forming of a metal plate, and a theoretical model of the air inlet is connected as a whole by a small horn annular part at the upper part and a large horn annular part at the lower part, the lower part of the front side wall is a vertical flat side wall, the upper part of the front side wall is an outwardly turned side wall, the rear side wall is an arc-shaped inclined side wall, and the left and right side walls are symmetrical saddle outwardly turned side walls.

[0007] Further, the ratio of the maximum length of the left and right side walls to the maximum width of the front and rear side walls is between 2.1 and 2.6, and the ratio of the radius of the smallest fillet at the saddle outwardly turned side wall to the depth of the air inlet is less than 0.6.

[0008] The near-equal wall thickness forming method for the above-mentioned engine variable cross-section integral air inlet is realized, and the theoretical model of the engine variable cross-section integral air inlet is known, characterized by comprising the following steps:

[0009] Step 1) constructing a process interface of the theoretical model, the process interface divides the theoretical model into a large horn annular part and a small horn annular part, the position height of the process interface is lower than the position height of the smallest cross-section of the air inlet, and the ratio of the circumference at the process interface to the circumference at the smallest cross-section of the air inlet is not greater than 1.02.

[0010] Step 2) Constructing a process model for drawing, the process model is a variable cross-section basin structure, the top end of the basin structure is a supplementary surface, the bottom end of the annular sidewall of the basin structure is connected with a flange edge, the length-width ratio of the annular sidewall of the process model is less than that of the theoretical model, and the height of the annular sidewall of the process model is greater than that of the theoretical model. In the process model, the front side of the annular sidewall is a vertical sidewall, the back side of the annular sidewall is divided by a process boundary surface, the upper part is a vertical sidewall, and the lower part is outwardly inclined, and the radius of the fillet area on both sides of the annular sidewall is greater than the corresponding fillet radius of the theoretical model. The circumference of the upper vertical sidewall of the annular sidewall of the process model is consistent with the circumference of the process boundary surface, and the circumference of the lower part of the annular sidewall is not greater than the corresponding cross-sectional circumference of the large-horn annular part of the theoretical model.

[0011] Step 3) Drawing the blank according to the process model, cutting the supplementary surface and the adjacent area of the fillet at the top end of the drawn blank to obtain a first semi-finished product matching the flange edge and the annular sidewall of the process model. The height of the annular sidewall of the first semi-finished product is greater than that of the theoretical model, the maximum thinning rate of the top edge of the annular sidewall is less than 8%, and the maximum thickening rate of the bottom edge of the annular sidewall is less than 8%.

[0012] Step 4) Manufacturing an air inlet large-horn annular part flaring die according to the theoretical model and the first semi-finished product, the flaring die comprises a lower die, an upper die and a blank holder, the working surface of the lower die is divided into upper and lower parts by a process boundary surface, the lower part of the working surface matches the inner surface of the large-horn annular part of the theoretical model, and the upper part of the working surface is a variable cross-section; the working surface of the upper die matches the outer surface of the edge area at the bottom end of the large-horn annular part of the theoretical model; and the working surface of the blank holder matches the lower surface of the flange edge of the first semi-finished product.

[0013] Step 5) After the upper part of the first semi-finished product is intervened and deformed, the lower part of the first semi-finished product is flared through the air inlet large-horn annular part flaring die, so that the lower part of the process boundary surface of the first semi-finished product is subjected to circumferential bulging deformation of length increase, width reduction and circumference increase, and a second semi-finished product is formed, in which the lower part of the process boundary surface matches the large-horn annular part of the theoretical model.

[0014] Step 6) Flanging the air inlet small-horn annular part according to the theoretical model, first, the large-horn annular part and the flange edge of the second semi-finished product are clamped by a combined clamp, and the vertical sidewall of the upper part of the process boundary surface of the second semi-finished product is flanged to form a small-horn annular part; and then the flanged small-horn annular part is subjected to local thickening deformation, and the excess amount and the flange edge are cut to obtain an overall air inlet close to equal wall thickness.

[0015] Further, the width of the annular side wall of the process model in step 2) at the upper end of the lower part of the process interface is close to the width of the corresponding position of the lower end of the theoretical model, and the width of the annular side wall of the process model at the bottom end of the lower part of the process interface is greater than the width of the corresponding position of the lower end of the theoretical model. From bottom to top in the lower part of the process interface, the ratio of the circumference of the annular side wall to the circumference of the large-bell annular part of the theoretical model is between 0.95 and 1.0, and the ratio of the left and right side corner radius to the depth of the inlet channel is not less than 0.8.

[0016] Further, the upper working surface of the lower die of the flaring die in step 4) is inclined inward on the left and right sides, the front side matches the inner surface of the vertical side wall of the upper part of the process interface of the first semi-finished product, and the back side matches the inner surface of the arc-shaped inclined side wall of the upper part of the theoretical model.

[0017] Further, the height of the second semi-finished product in step 5) is greater than the height of the first semi-finished product, the wall thickness of the large-bell annular part is less than the wall thickness of the corresponding position of the lower part of the process interface of the first semi-finished product, and the wall thickness of the edge area near the bottom end of the large-bell annular part is equal to the wall thickness of the theoretical model; the circumference of the vertical side wall of the upper part of the process interface is greater than the circumference at the minimum cross section of the theoretical model.

[0018] Further, in step 5), when the lower part of the first semi-finished product is flared by the flaring die of the large-bell annular part of the inlet channel, the upper part of the first semi-finished product needs to be deformed by intervention first, and the implementation is as follows: the corresponding edge area of the upper part of the process interface of the first semi-finished product and the upper end of the arc-shaped inclined side wall of the theoretical model are extruded inward, so that the first semi-finished product is smoothly embedded in the bell mouth at the lower end of the upper die of the flaring die after the width of the upper part of the process interface of the first semi-finished product is reduced.

[0019] Further, after the small-bell annular part of the inlet channel is formed by flanging according to the theoretical model in step 6), the formed small-bell annular part needs to be locally thickened, and the implementation includes the following measures: measure one: knocking the thinned transferred material in the excess area to the effective profile of the small-bell annular part; measure two: cutting the tangential top edge along the edge of the excess area of the small-bell annular part to make it produce a micro-bulge and flatten it.

[0020] Beneficial effects

[0021] The present application firstly constructs a process model similar to the theoretical model shape, and then draws the blank to form a deep drawing, uses the shape more regular, the obvious increase of the fillet, and the uniform deformation advantage to overcome the mutual contradiction problem of forming depth requirement and excessive thinning, and obtains the first semi-finished product with low thinning at the upper end. The present application uses the thickening effect of the drawing edge to expand the large trumpet ring part at the thicker end of the first semi-finished product, and obtains the second semi-finished product with obviously reduced relative wall thickness difference. The present application uses the upper die and lower die working surface and the theoretical model partial matching structure to expand the die, appropriately increases the upper circumference of the first semi-finished product to facilitate reducing the flanging thinning of the small trumpet ring part, and locally thickens the deformation after the final forming of the small trumpet ring part, so that the wall thickness is more uniform and the overall profile is close to the theoretical thickness. Therefore, the variable cross-section overall inlet passage manufactured by the present application has the advantages of uniform wall thickness, high matching degree with the theoretical part profile, and the like.

[0022] The present application will be described in further detail below in combination with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a structural schematic diagram of the theoretical model of the inlet passage of the present application

[0024] Figure 2 is a structural schematic diagram of the process model of the inlet passage of the present application

[0025] Figure 3 is a schematic diagram of the relationship between the longitudinal section of the theoretical model and the process model of the inlet passage of the present application

[0026] Figure 4 is a schematic diagram of the shape of the first semi-finished product of the inlet passage of the present application

[0027] Figure 5 is a schematic diagram of the wide section of the large trumpet ring part of the inlet passage of the present application

[0028] Figure 6 is a schematic diagram of the lower die working surface of the expanding die of the inlet passage of the present application

[0029] Figure 7 is a schematic diagram of the shape of the second semi-finished product of the inlet passage of the present application

[0030] Figure 8 is a schematic diagram of the principle of forming the small trumpet ring part of the inlet passage of the present application

[0031] Explanation of figure numbers: 1. Theoretical model, 2. Small horn annular part, 3. Large horn annular part, 4. Vertical flat side wall, 5. Everted side wall, 6. Arc-shaped inclined side wall, 7. Saddle everted side wall, 8. Fillet, 9. Process interface, 10. Minimum cross section, 11. Process model, 12. Supplementary surface, 13. Flange, 14. Vertical side wall, 15. First half-finished product, 16. Lower die, 17. Upper die, 18. Blank holder, 19. Lower working surface, 20. Upper working surface, 21. Second half-finished product, 22. Assembly fixture. DETAILED DESCRIPTION

[0032] First, the structure of the variable cross-section engine intake duct and the defects in the prior art are introduced.

[0033] Referring to the accompanying drawings Figure 1 In order to meet the aerodynamic function requirements of an aircraft engine, a variable cross-section engine intake duct with a length significantly greater than the width needs to be integrally formed. The intake duct is a variable cross-section long annular thin-walled structure integrally formed from sheet metal. The theoretical model 1 of the intake duct is connected as a whole by the small horn annular part 2 at the upper part and the large horn annular part 3 at the lower part. The lower part of the front side wall is a vertical flat side wall 4, the upper part of the front side wall is an everted side wall 5, the rear side wall is an arc-shaped inclined side wall 6, and the left and right side walls are symmetrical saddle everted side walls 7. In addition, the ratio of the maximum length of the left and right sides to the maximum width of the front and rear sides of the theoretical model 1 of the intake duct is between 2.1 and 2.6, and the ratio of the radius of the smallest fillet 8 at the saddle everted side wall 7 to the depth of the intake duct is less than 0.6. The intake duct not only has assembly docking matching requirements at both ends, but also has high requirements for overall forming deformation damage and uniform wall thickness to meet the extreme service life requirements of high-frequency vibration. In order to ensure uniform wall thickness and solve the problem of variable cross-section disassembly, there are mainly two schemes in the prior art: one is to divide the part into two horn annular parts along the ring direction and form them respectively before welding and combining, which has the disadvantage that the ring weld cannot meet the aerodynamic force requirement; the other is to divide the part into two saddle-shaped parts along the depth direction and form them respectively before welding and combining, which has the disadvantage that the welding deformation length changes affect the matching accuracy of the two ends with other parts. Both of the above two schemes have the common problems of welding deformation, low strength and toughness of the weld structure, and the like, especially the strength and plasticity product index of the weld area of aluminum alloy material is only about 40% of the base material.

[0034] The most ideal measure to solve the problems of assembly incoordination, service life and so on caused by welding deformation is overall forming, and the deep cavity plastic forming is the first choice of processing method. However, the deep drawing must meet the two conditions of diameter-depth ratio relationship and structural opening. The deep drawing of the deep cavity product with small fillet, complex shape and variable cross section faces the problem of mutual contradiction between the forming depth requirement and the wall thickness difference. Especially, it is more difficult to draw the deep cavity product with large length-width ratio and small fillet 8 with low deformation damage. The overall deep drawing forming of the existing product with approximate straight wall can reach the limit height of 70% of the required depth of the theoretical model 1, the thinning of the upper end area of the fillet 8 is more than 20%, and the thickening of the lower end area of the fillet is more than 10%. In addition, the upper end area of the fillet 8 needs to be manually assisted to expand and thin again after deep drawing. Even if the product with basic shape is formed by repeated annealing, the maximum wall thickness difference is more than 40%, which seriously affects the shape accuracy and service life.

[0035] Secondly, the technical scheme of the near-equal wall thickness forming method of the overall inlet channel is introduced.

[0036] In order to solve the above problems existing in the variable cross section deep cavity inlet channel, referring to the drawings Figure 1 to Figure 8 The main steps of the near-equal wall thickness forming of the overall inlet channel are as follows:

[0037] Step 1) constructing the process interface 9 of the theoretical model 1, referring to the drawings Figure 1 to Figure 3 The process interface 9 divides the theoretical model 1 into two parts of the large horn annular part 3 and the small horn annular part 2, the height position of the process interface 9 is lower than that of the minimum cross section 10 of the inlet channel, and the ratio of the circumference at the process interface 9 to the circumference at the minimum cross section 10 is not greater than 1.02. Since the theoretical model 1 of the inlet channel is a variable cross section, if it is divided along the minimum cross section 2, there will be stamping closed angle on the left and right sides of the upper end of the large horn annular part 3, which is strictly prohibited in production.

[0038] The purpose of constructing the process interface 9 is as follows: one of the purposes is to avoid stamping negative angle; the second purpose is to avoid large deviation of the ratio of the circumference at the process interface 9 to the corresponding circumference at the minimum cross section 10; the third purpose is to simplify the matching relationship between the process model 11 and the theoretical model 1 in the deep direction of multiple variable cross sections in step 2).

[0039] Step 2) constructing the deep drawing process model 11, referring to the drawings Figure 1 to Figure 3, the process model 11 is a variable cross-section basin structure, the top end of the basin structure is a supplementary surface 12, the bottom end of the annular sidewall of the basin structure is connected with a flange edge 13, the length-width ratio of the annular sidewall of the process model 11 is less than the length-width ratio of the annular sidewall of the theoretical model 1, and the height of the annular sidewall of the process model 11 is greater than the height of the annular sidewall of the theoretical model 1. In the process model 11, the front side of the annular sidewall is a vertical sidewall 14, the rear side of the annular sidewall is divided by the process boundary surface 9, the upper part is a vertical sidewall, and the lower part of the sidewall is outwardly inclined, and the radius of the round corner 8 area on both sides of the annular sidewall is greater than the round corner radius at the corresponding position of the theoretical model 1. The circumference of the upper vertical sidewall 14 of the annular sidewall of the process model 11 is consistent with the circumference of the process boundary surface 9, and the circumference of the lower part of the annular sidewall is not greater than the cross-sectional circumference at the corresponding position of the large horn annular part 3 of the theoretical model 1.

[0040] The following points need to be emphasized for the design of the process model: the design points of the process model 11 are to compensate for the increase in length caused by the increase in the width of the round corner 8 to reduce the excessive reduction in the circumference, to ensure that the corresponding height circumferences of the annular sidewall of the theoretical model 1 and the process model 11 are as close as possible, and to minimize the risk of interference between the second semi-finished product 21 and the lower end of the upper die 18 of the flaring die during forming. Therefore, the width of the annular sidewall of the process model 11 at the upper end of the lower part of the process boundary surface 9 is close to the width at the corresponding position of the lower end of the theoretical model 1, and the width of the annular sidewall of the process model 11 at the bottom end of the lower part of the process boundary surface 9 is greater than the width at the corresponding position of the lower end of the theoretical model 1. From bottom to top in the lower part of the process boundary surface 9, the ratio of the circumference of the annular sidewall to the circumference of the large horn annular part 3 of the theoretical model is between 0.95 and 1.0, and the ratio of the radius of the round corner 8 on both sides to the depth of the inlet passage is not less than 0.8. The above design purpose is to reduce the thinning rate of the upper part of the first semi-finished product 15, while avoiding large deviations in the circumference at the corresponding height position between the process model 11 and the theoretical model 1 caused by the variable cross-section.

[0041] Step 3) refer to the drawings Figure 2 to the drawings Figure 4 , the blank is deep drawn according to the process model 11, and the supplementary surface 12 and the adjacent area of the round corner at the top end of the deep drawn blank are cut to obtain the first semi-finished product 15 matched with the flange edge 13 and the annular sidewall of the process model 11. The height of the annular sidewall of the first semi-finished product 15 is greater than the height of the annular sidewall of the theoretical model 1, the maximum thinning rate of the edge at the top end of the annular sidewall is less than 8%, and the maximum thickening rate of the edge at the bottom end of the annular sidewall is less than 8%.

[0042] The following needs to be explained for the drawing forming of the first semi-finished product 15: first, the wall thickness of the drawing part gradually increases from the inside to the edge, which is a common feature of all drawing parts. Second, the wall thickness distribution of the first semi-finished product 15 is mainly determined by the radius-to-depth ratio of the fillet 8 of the process model 11, and can also be optimized by matching the drawing die gap and the drawing process parameters to reduce the maximum thinning rate. Third, the purpose of controlling the maximum thinning rate and the large thickening rate is to reduce the wall thickness difference by subsequent targeted deformation thinning in different degrees. Fourth, the purpose of the supplementary surface 12 cut at the top end of the first semi-finished product 15 is to reduce the rigidity of the upper vertical side wall 14, facilitating the intervention deformation flaring positioning in step 5).

[0043] Step 4) refer to the attached Figure 5 to the attached Figure 7 , according to the theoretical model 1 and the first semi-finished product 15, a flaring die for the large horn annular part 3 of the air inlet is manufactured, which includes a lower die 16, an upper die 17, and a blank holder 18. The working surface of the lower die 16 is divided into upper and lower parts by the process interface 9, the lower working surface 19 matches the inner surface of the large horn annular part 3 of the theoretical model 1, and the upper working surface 20 is a variable cross-section. The working surface of the upper die 17 matches the outer surface of the edge area at the bottom end of the large horn annular part 3 of the theoretical model 1, and the working surface of the blank holder 18 matches the lower surface of the flange edge 13 of the first semi-finished product.

[0044] The following needs to be emphasized for the manufacture of the flaring die: the left and right sides of the upper working surface 20 of the lower die 16 of the flaring die are inclined inward, the front side matches the inner surface of the upper vertical side wall 14 of the first semi-finished product 15, and the back side matches the upper inner surface of the arc-shaped inclined side wall 6 of the theoretical model 1. One of the design purposes is to reduce the risk of interference between the first semi-finished product 15 and the lower end of the working surface of the upper die 17 due to the increase in width, and to avoid the second semi-finished product 21 from interfering again in the left and right fillet 8 areas due to the lengthening of the upper end after forming. The second purpose is to fully utilize the thickening effect of the lower end of the first semi-finished product 15 to reduce the wall thickness difference of the second semi-finished product 21 by expanding the large horn annular part 3. The third purpose is to increase the shape matching degree of the upper end of the second semi-finished product 21 and the corresponding position of the theoretical model 1 as much as possible, and to reduce the workload of manual assistance in subsequent forming of the small horn annular part 2. The fourth purpose is to produce an extrusion effect at the edge area of the bottom end of the large horn annular part 3 by the working surfaces of the lower die 16 and the upper die 17, which not only ensures the uniformity of the wall thickness of the edge area, but also controls the closing stroke of the lower die 16 and the upper die 17.

[0045] Step 5) refer to the attached Figure 5 to the attached Figure 7After the upper part of the first semi-finished product 15 is subjected to intervention deformation, the lower part of the first semi-finished product 15 is widened by the flaring mold of the large horn ring part 3 of the air intake, so that the lower part of the process interface 9 of the first semi-finished product 15 undergoes circumferential expansion deformation with increased length, decreased width and increased circumference, forming the second semi-finished product 21 that matches the lower part of the process interface 9 with the large horn ring part 3 of the theoretical model 1.

[0046] Regarding the flaring of the large horn-shaped annular portion 3 of the second semi-finished product 21, the following explanations are needed: First, the height of the second semi-finished product 21 is slightly greater than the height of the first semi-finished product 15. The wall thickness of its large horn-shaped annular portion 3 is less than the wall thickness of the corresponding position at the lower part of the process interface 9 of the first semi-finished product 15. The wall thickness of the large horn-shaped annular portion 3 near the bottom edge is equal to the wall thickness of the theoretical model 1. The perimeter of the vertical sidewall 14 at the upper part of its process interface 2 is greater than the perimeter at the minimum cross-section 10 of the theoretical model 1. Second, to meet the thinning requirement of the fillet radius 8 in the forming control of the first semi-finished product 15, the increased width due to the variable cross-section inevitably leads to the risk of interference between the upper end of the first semi-finished product 15 and the lower end of the upper mold 17 of the flaring die. This is also the reason why the working surface of the upper mold 17 only matches the edge area at the bottom of the large horn-shaped annular portion 3. Therefore, when flaring the lower part of the first semi-finished product 15, it is necessary to first intervene and deform the upper part of the first semi-finished product 15. The implementation method is as follows: the upper part of the process interface 9 of the first semi-finished product 15 and the corresponding edge area of ​​the upper end of the arc-shaped inclined sidewall 6 of the theoretical model 1 are squeezed inward, so that the width of the upper part of the process interface 9 of the first semi-finished product 15 is reduced and it is smoothly embedded into the flared mouth at the lower end of the upper mold 18 of the flaring mold.

[0047] Step 6) Refer to Appendix Figure 7 Appendix Figure 8 According to theoretical model 1, the small horn ring part 2 of the air intake is formed by flanging. First, the large horn ring part 3 and the flange edge 13 of the second semi-finished product 21 are clamped by the combination jig 22. The upper vertical side wall 14 of the process interface 9 of the second semi-finished product 21 is flanged to form the small horn ring part 2. Then, the small horn ring 2 is locally thickened and deformed, and the allowance and flange edge are cut to obtain an integral air intake with a near-equal wall thickness.

[0048] The following explanations are needed regarding the flanging forming of the small horn-shaped annular portion: First, due to the irregular shape of the air intake, uneven wall thickness is inevitable between the first semi-finished product 15 and the second semi-finished product 21 during the forming process. However, except for the larger thinning in the rounded corner 8 areas on both sides, the wall thickness difference in other areas is generally less than 5%. Second, to reduce the increased wall thickness difference caused by further thinning after flanging the small horn-shaped annular portion 2, local thickening deformation of the formed small horn-shaped annular portion 2 is required. There are two main measures: Measure 1: tapping the remaining area to thin and transfer material to the effective surface of the small horn-shaped annular portion 2; Measure 2: tangentially shaping the top edge along the edge of the small horn-shaped annular portion 2 to create a micro-bulge and then flattening it. Usually, to improve the uniformity of wall thickness, these two measures are combined and alternated.

[0049] Finally, in order to ensure that the person skilled in the art correctly understands and implements the technical solutions of the present application, the following is explained for the near-equal wall thickness forming of the variable cross-section overall inlet channel:

[0050] The technical key to the near-equal wall thickness forming of the variable cross-section deep inlet channel with double-horn structure due to the large difference in forming wall thickness caused by the small ratio of two side fillets 8 to depth is as follows: first, by constructing a variable cross-section deep drawing process model 11 containing a large fillet 8 and having an approximately equivalent circumference, the first semi-finished product 15 with a low-thinned top end of the vertical side wall 14 on the process interface 9 is obtained by fully utilizing the large fillet drawing, and the first semi-finished product 15 is thickened at the lower part by fully utilizing the drawing edge thickening. Then, by flaring, the second semi-finished product 21 containing a large horn annular part 3 is formed at the thickened lower part of the first semi-finished product 15, so that the wall thickness difference of the second semi-finished product 21 is further reduced due to the annular thinning. Finally, the small horn annular part 2 of the second semi-finished product 21 with relatively small deformation is flanged, and part of the material in the excess material area is transferred to the effective profile of the small horn annular part 2, further reducing the wall thickness difference at both ends of the overall inlet channel, achieving both the overall forming of the variable cross-section inlet channel and the uniform wall thickness at both ends, and achieving a high matching degree of the inner and outer surfaces with the theoretical model 1.

Claims

1. A method for forming a nearly constant wall thickness of an engine variable cross-section integral intake port, the intake port being a variable cross-section long annular thin wall structure integrally formed from a metal plate, a theoretical model of the intake port being connected as a whole by a flow line of an upper small horn annular portion and a lower large horn annular portion, a lower portion of a front side wall thereof being a vertical flat side wall, an upper portion of the front side wall being an everted side wall, a rear side wall thereof being an arc-shaped inclined side wall, left and right side walls thereof being symmetrical saddle everted side walls, the method for forming the nearly constant wall thickness of the engine variable cross-section integral intake port being characterized by comprising the steps of: Comprising the following steps: ​ Step 1) constructing a process interface of the theoretical model, the process interface divides the theoretical model into two parts of large horn annular part and small horn annular part, the process interface position is lower than the position height of the minimum cross section of the inlet channel perimeter, the ratio of the perimeter at the process interface to the perimeter at the minimum cross section of the inlet channel is not greater than 1.02; Step 2) constructing a process model for drawing, the process model is a variable cross section basin cavity structure, the top end of the basin cavity structure is a supplementary surface, the bottom end of the annular side wall of the basin cavity structure is connected with a flange edge, the length-width ratio of the annular side wall of the process model is smaller than that of the theoretical model, and the height of the annular side wall of the process model is greater than that of the theoretical model; In the process model, the front side of the annular side wall is a vertical side wall, the rear side of the annular side wall is divided into an upper part and a lower part by the process interface, the upper part is a vertical side wall, the lower part is outwardly inclined, and the radius of the fillet area on both sides of the annular side wall is greater than the corresponding fillet radius of the theoretical model; the perimeter of the upper vertical side wall of the annular side wall of the process model is consistent with the perimeter of the process interface, and the perimeter of the lower part of the annular side wall is not greater than the cross section perimeter of the corresponding position of the large horn annular part of the theoretical model; Step 3) drawing the blank according to the process model, cutting the supplementary surface and the adjacent area of the fillet at the top end of the drawn blank to obtain a first semi-finished product matching the flange edge and the annular side wall of the process model, the height of the annular side wall of the first semi-finished product is greater than that of the theoretical model, the maximum thinning rate of the top edge of the annular side wall is less than 8%, and the maximum thickening rate of the bottom edge of the annular side wall is less than 8%; Step 4) manufacturing an expanding die for the large horn annular part of the inlet channel according to the theoretical model and the first semi-finished product, the expanding die comprises a lower die, an upper die and a blank holder; the working surface of the lower die is divided into upper and lower parts by the process interface, the lower part of the working surface matches the inner surface of the large horn annular part of the theoretical model, and the upper part of the working surface is a variable cross section; the working surface of the upper die matches the outer surface of the edge area at the bottom end of the large horn annular part of the theoretical model; and the working surface of the blank holder matches the lower surface of the flange edge of the first semi-finished product; Step 5) after the upper part of the first semi-finished product is intervened and deformed, the lower part of the first semi-finished product is expanded through the expanding die for the large horn annular part of the inlet channel, so that the lower part of the process interface of the first semi-finished product is subjected to circumferential bulging deformation of length increase, width reduction and perimeter increase, and a second semi-finished product is formed, which matches the large horn annular part of the theoretical model at the lower part of the process interface; Step 6) flanging the small horn annular part of the inlet channel according to the theoretical model, first clamping the large horn annular part and the flange edge of the second semi-finished product through a combined clamp, flanging the upper vertical side wall of the process interface of the second semi-finished product to form the small horn annular part, then locally thickening the flanged small horn annular part, and cutting the excess part and the flange edge to obtain an overall inlet channel close to equal wall thickness.

2. The method of near constant wall thickness forming of a variable area engine intake of claim 1 wherein: The width of the annular side wall of the process model in step 2 at the upper end of the lower part of the process interface is close to the width of the corresponding position of the lower end of the theoretical model, and the width of the annular side wall of the process model at the bottom end of the lower part of the process interface is greater than the width of the corresponding position of the lower end of the theoretical model; from the bottom to the top of the lower part of the process interface, the ratio of the annular side wall to the circumference of the large horn annular part of the theoretical model is between 0.95 and 1.0, and the ratio of the left and right side corner radius to the depth of the inlet channel is not less than 0.

8.

3. The method of near constant wall thickness forming of a variable area engine intake of claim 1 wherein: In step 4, the upper working surface of the lower die of the flaring die is inclined inward on the left and right sides, and the front side matches the inner surface of the vertical side wall of the upper part of the process interface of the first semi-finished product, and the back side matches the inner surface of the arc-shaped inclined side wall of the theoretical model.

4. The method of near constant wall thickness forming of a variable area engine intake of claim 1 wherein: In step 5, the height of the second semi-finished product is greater than the height of the first semi-finished product, the wall thickness of the large horn annular part is less than the wall thickness of the corresponding position of the lower part of the process interface of the first semi-finished product, and the wall thickness of the edge area near the bottom end of the large horn annular part is equal to the wall thickness of the theoretical model, and the circumference of the vertical side wall of the upper part of the process interface is greater than the circumference at the minimum cross section of the theoretical model.

5. The method of near constant wall thickness forming of a variable area engine intake of claim 1 wherein: In step 5, when the lower part of the first semi-finished product is flared by the flaring die of the large horn annular part of the inlet channel, the upper part of the first semi-finished product needs to be intervened and deformed first, and the implementation method is as follows: the upper part of the process interface of the first semi-finished product is extruded inward to the corresponding edge area of the upper end of the arc-shaped inclined side wall of the theoretical model, so that the width of the upper part of the process interface of the first semi-finished product is reduced and then smoothly inserted into the horn mouth of the lower end of the upper die of the flaring die.

6. The method of near constant wall thickness forming of a variable area engine intake of claim 1 wherein: After the small horn annular part of the inlet channel is formed according to the theoretical model in step 6, the formed small horn annular part needs to be locally thickened and deformed, and the implementation method includes the following measures: measure one: knock the thinned transferred material in the excess area to the effective profile of the small horn annular part; measure two: cut the tangential top edge along the edge of the excess area of the small horn annular part to make it produce a micro-bulge and flatten it.

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