Method of forming a multi-wave narrow-pitch bellows

Abstract

The present application relates to a kind of multi-wave narrow wave distance bellows forming method, comprising the following steps: S1, installing sealing fixture at the both ends of pipe blank;S2, the pipe blank of installing sealing fixture is placed in left mould and right mould, and reserve bulge distance between left mould and right mould;S3, inject hydraulic oil from the liquid hole of sealing fixture, so that pipe blank is bulged out bulge;S4, left mould and right mould are closed, and the pressing of wave is completed;S5, unloading, left mould and right mould open to appropriate distance;S6, insert block is installed on left mould or right mould, and insert block and left mould or right mould wrap the wave that has been formed;S7, repeat step S3-step S6, sequentially complete the forming of all wave shapes of bellows.The forming process condition of each wave shape formed by the method of the present application is consistent, whether the wave shape at the both ends of bellows and the wave shape at the middle position, the feeding amount and the boundary condition of forming remain consistent, and the wave height after forming and the wave shape thickness thinning amount are high in consistency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tube hydroforming, in particular to a method for forming a multi-wave narrow-pitch corrugated tube. BACKGROUND

[0002] The metal corrugated tube used as an elastic element for an accumulator has very small wall thickness and pitch (for example, the tube thickness is 0.15 mm and the pitch is 2 mm). In the forming process, due to the small pitch, it is difficult for a tool using a mechanical forming method to enter the narrow gap, and hydraulic forming is a more suitable method.

[0003] The tube hydraulic forming process is to force the material to yield and flow by using high-pressure liquid acting on the inner wall of the tube, and to control the liquid pressure to make the outer wall of the tube adhere to the die to form. The traditional tube hydraulic forming mainly controls the liquid pressure and the axial load of the push head to realize multi-wave one-time forming.

[0004] For a multi-wave narrow-pitch part, the axial load of the push head is difficult to transmit into the deformation zone of the intermediate part of the corrugation, resulting in extremely difficult material supplement for the intermediate corrugation, and the wave height size of the intermediate corrugation is inconsistent with that of the two end corrugations, and the material thickness changes seriously. The intermediate corrugation part is often broken due to serious material thinning. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a method for forming a multi-wave narrow-pitch corrugated tube, which can solve the problems of inconsistent wave height size and serious material thickness change in the traditional multi-wave one-time forming.

[0006] The technical solution adopted by the present application to solve the technical problem is that a method for forming a multi-wave narrow-pitch corrugated tube is constructed, comprising the following steps:

[0007] S1, installing sealing clamps at both ends of a tube blank;

[0008] S2, placing the tube blank with the installed sealing clamps inside left and right dies, and reserving a bulge distance between the left and right dies;

[0009] S3, injecting hydraulic oil from the liquid injection hole of the sealing clamp to make the tube blank bulge out;

[0010] S4, closing the left and right dies to complete the pressing of the corrugation;

[0011] S5, unloading pressure and opening the left and right dies to a proper distance;

[0012] S6, installing an insert block on the left die or the right die, and the insert block and the left die or the right die wrap around the formed corrugation;

[0013] S7, repeating steps S3-S6 to sequentially form all corrugations of the bellows.

[0014] According to the above scheme, the step S5 further comprises: continuously increasing the liquid pressure to make the pipe blank further fit the left and right molds, and shape the corrugations.

[0015] According to the above scheme, the left and right molds each comprise a split upper mold and a lower mold, and the upper mold and the lower mold are connected by bolts.

[0016] According to the above scheme, the insert block is fixed on the left mold or the right mold by a positioning pin and a bolt.

[0017] According to the above scheme, the sealing clamp comprises a left end clamp and a right end clamp, and the left end clamp and the right end clamp are provided with outer jaws and inner jaws.

[0018] According to the above scheme, the outer jaws and the inner jaws have tapered surfaces with consistent slopes, and the inner jaws are inserted into the inside of the pipe blank before sealing, the pipe blank is provided with a process necking portion, the slope of the process necking portion is consistent with the slope of the tapered surfaces of the outer jaws and the inner jaws, and the length of the process necking portion is less than the length of the tapered surfaces of the inner jaws.

[0019] According to the above scheme, the inner jaws and the outer jaws of the right end clamp are provided with liquid through holes.

[0020] According to the above scheme, the relative position control method of the left end clamp and the right end clamp during the forming process is as follows:

[0021] During the bulging stage, the sealing clamp is at the maximum distance between the left and right ends of the pipe blank, during the clamping stage, the distance is gradually reduced following the clamping action, during the shaping stage, the distance is kept at the position after clamping, and during the unclamping stage, the distance is kept at the position after clamping.

[0022] According to the above scheme, the relative position control method of the left mold and the right mold during the forming process is as follows:

[0023] The distance between the left mold and the right mold is kept at S1 during the bulging stage, is reduced from S1 to 0 during the clamping stage, is kept at 0 during the shaping stage, and is kept at S2 during the unclamping stage, wherein S2=2S1.

[0024] According to the above scheme, a sealing ring is arranged between the sealing clamp and the left and right molds.

[0025] The multi-wave narrow-pitch corrugated pipe forming method has the following beneficial effects:

[0026] The forming process conditions of each wave shape formed by the method are consistent, the material supplement amount and the forming boundary conditions are consistent, the wave height and the wave shape thickness reduction amount after forming are high in consistency, and the forming quality is greatly improved. BRIEF DESCRIPTION OF DRAWINGS

[0027] The application will be further described below in combination with the drawings and examples, wherein:

[0028] Figure 1 is a schematic view of the device used in the forming method of the multi-wave narrow wave pitch corrugated pipe of the application;

[0029] Figure 2 is a schematic view of the mold opening state;

[0030] Figure 3 is a schematic view of the mold closing state;

[0031] Figure 4 is a schematic view of the hydraulic oil pressure control strategy of the application;

[0032] Figure 5 is a schematic view of the mold and push head load control strategy of the application. DETAILED DESCRIPTION

[0033] In order to have a clearer understanding of the technical features, objects and effects of the application, the specific embodiments of the application will be described in detail with reference to the drawings.

[0034] As shown in Figures 1-3 the forming method of the multi-wave narrow wave pitch corrugated pipe of the application comprises the following steps:

[0035] S1, installing sealing clamps at both ends of the pipe blank 4;

[0036] S2, placing the pipe blank 4 with the installed sealing clamps inside the left mold 1 and the right mold 2, reserving a bulge distance S1 between the left mold 1 and the right mold 2, and the distance is determined according to the material amount required for corrugated forming;

[0037] S3, injecting hydraulic oil from the liquid hole of the sealing clamp, controlling the liquid pressure P1, and making the pipe blank 4 bulge out to form a bulge with a height of D1; the hydraulic oil pressure P1 determines the height of the bulge;

[0038] S4, closing the left mold 1 and the right mold 2, and increasing the hydraulic oil pressure to P2 at the same time, when the left mold 1 and the right mold 2 are completely closed, the pipe blank 4 is attached to the mold cavity under the joint action of the mold and the hydraulic oil, and is better filled into the wave crest and the wave trough of the corrugated pipe, and the wave shape pressing is completed;

[0039] S5, continue to increase the hydraulic oil pressure to P3, make the pipe blank 4 further adhere to the mold cavity, shape the corrugation, and further ensure the corrugation height and the corrugation shape of the corrugated pipe;

[0040] S6, after the pressure is maintained for a period of time, the hydraulic oil is released, and the left mold 1 and the right mold 2 are opened to a proper distance S2, preparing for the next corrugation shaping;

[0041] S7, the insert 3 is installed on the right mold 2, the insert 3 and the right mold 2 wrap the shaped corrugation, and the shaped corrugation does not deform in the subsequent operation; at this time, the left mold 1 and the insert 3 form a next corrugation shaping working area, and the distance between the left mold 1 and the insert 3 is S1;

[0042] S8, repeat steps S3-S7 to sequentially complete the shaping of all corrugation shapes of the corrugated pipe.

[0043] Preferably, the left mold 1 and the right mold 2 are designed as half molds, including split upper molds and lower molds, and the upper molds and the lower molds are connected by bolts.

[0044] Preferably, the insert 3 adopts a half mold structure and is fixed on the right mold 2 by positioning pins and bolts.

[0045] Preferably, the sealing clamp includes a left end clamp and a right end clamp, and the left end clamp and the right end clamp are provided with outer jaws 5 and inner jaws 6. Before sealing, the sealing clamp needs to be subjected to a hole shrinking process to ensure that the slope of the hole shrinking is consistent with the clamp. After the sealing clamp is installed, the sealing clamp and the pipe blank 4 form an integral whole, and even during the shaping process, the two maintain an integral state.

[0046] Preferably, the outer jaws 5 and the inner jaws 6 have taper surfaces with consistent slopes, the inner jaws 6 are deeply inserted into the pipe blank 4 before sealing, the end of the pipe blank 4 is provided with a process hole, the slope of the process hole is consistent with the slope of the taper surfaces of the outer jaws 5 and the inner jaws 6, and the length of the process hole is less than the length of the taper surface of the inner jaws 6.

[0047] Preferably, the inner jaws 6 and the outer jaws 5 of the right end clamp are provided with liquid holes 7 for injecting hydraulic oil. The inner jaws 6 and the outer jaws 5 of the left end clamp are connected by bolts 9.

[0048] Preferably, a sealing ring 8 is arranged between the sealing clamp and the left mold 1 and the right mold 2.

[0049] The process route disclosed by the application mainly includes the following steps: bulging, clamping, shaping, and opening, and the above four processes form a working cycle, one cycle completes one corrugation, and the above cycle is repeated to complete the shaping of multiple corrugations.

[0050] The application relates to a loading path, including hydraulic oil pressure control and action control of a sealing clamp and a die. Figure 4 In the four stages of bulging, die closing, shaping and die opening, the hydraulic oil control is as follows: in the bulging stage, the hydraulic oil pressure is raised from 0 to P1; in the die closing stage, the hydraulic oil pressure is continuously raised from P1 to P2; in the shaping stage, the hydraulic oil pressure is raised from P2 to P3; and in the die opening stage, the hydraulic oil pressure is lowered from P3 to 0. Wherein, P1 is the bulging pressure, P1=2hs b / d (h is the wall thickness of the bellows, s b is the tensile strength of the material, and d is the inner diameter of the bellows), P2 is the die closing pressure, the pressure size is suggested to be P2=1.1~1.5 P1, and P3 is the shaping pressure, the pressure size is suggested to be P3=1.5~2 P1.

[0051] The action control strategy of the die is as shown in Figure 5 (a schematic diagram of die clamp action control), the die adopts displacement control strategy, and in the four stages of bulging, die closing, shaping and die opening, the relative position (the distance between the left die and the right die) control of the die is as follows: in the bulging stage, S1 is kept; in the die closing stage, S1 is reduced to 0; in the shaping stage, the die closing state is still kept as 0; and in the die opening stage, the die is opened to S2, wherein S2=2S1.

[0052] The sealing clamp control strategy is as shown in Figure 5 The clamp control adopts displacement control strategy, and in the four stages of bulging, die closing, shaping and die opening, the relative position (distance) control of the two sealing clamps is as follows: in the bulging starting stage, the sealing clamps are kept at the farthest distance around the pipe blank 4; in the die closing stage, the distance is gradually reduced following the die closing action; in the shaping stage, the position after die closing is kept; and in the die opening stage, the position after die closing is kept. In short, the sealing clamps keep the sealing of the two ends of the pipe material, and after the sealing is established in the starting stage, the two sealing clamps follow the two ends of the pipe blank 4, and the distance is only reduced in the die closing stage, and is kept unchanged in the other stages.

[0053] The embodiments of the application are described above in combination with the drawings, but the application is not limited to the above specific embodiments, the above specific embodiments are only illustrative but not restrictive, and those skilled in the art can make many forms under the inspiration of the application without departing from the purpose of the application and the scope protected by the claims, which all belong to the protection of the application.

Claims

1. A method of forming a multi-wave narrow-pitch bellows, characterized by, The method comprises the following steps: S1, installing sealing fixtures on both ends of the pipe blank; S2, placing the pipe blank with the sealing fixtures inside left and right molds, leaving a bulging distance between the left and right molds; S3, injecting hydraulic oil from the liquid passage of the sealing fixtures to make the pipe blank bulge out; S4, closing the left and right molds to complete the pressing of the corrugation; S5, releasing the pressure and opening the left and right molds to a proper distance; S6, installing the inserts on the left or right mold, and the inserts and the left or right mold wrap around the formed corrugation; at this time, the opposite side and the last installed insert form the next corrugation forming working area; S7, repeating steps S3-S6 to complete the forming of all corrugation shapes of the corrugated pipe.

2. The multi-wave narrow-pitch bellows forming method according to claim 1, wherein The step S5 further comprises: continuously increasing the liquid pressure to make the pipe blank further fit the left and right molds, and to reshape the corrugation.

3. The method of forming a multi-wave narrow-pitch bellows of claim 1 wherein, The left and right molds each comprise a split upper mold and a lower mold, and the upper mold and the lower mold are connected by bolts.

4. The method of forming a multi-wave narrow-pitch bellows of claim 1 wherein, The inserts are fixed on the left or right mold by positioning pins and bolts.

5. The method of forming a multi-wave narrow-pitch bellows of claim 1 wherein, The sealing fixtures comprise left and right end fixtures, and the left and right end fixtures are provided with outer and inner jaws.

6. The method of forming a multi-wave narrow-pitch bellows of claim 5, wherein, The outer and inner jaws have consistent taper surfaces, and the inner jaw is inserted into the pipe blank before sealing; the end of the pipe blank is provided with a process necking, and the taper of the process necking is consistent with the taper of the outer and inner jaws; the length of the process necking is less than the length of the taper surface of the inner jaw.

7. The method of forming a multi-wave narrow-pitch bellows of claim 5, wherein, The inner and outer jaws of the right end fixture are provided with liquid passages.

8. The method of forming a multi-wave narrow-pitch bellows of claim 5, wherein, The control method of the relative position of the left and right end fixtures during the forming process is as follows: During the bulging starting stage, the sealing fixtures are kept at the maximum distance between the left and right most ends of the pipe blank, and gradually reduced during the closing stage, and kept at the position after closing during the reshaping stage, and kept at the position after closing during the opening stage.

9. The method of forming a multi-wave narrow-pitch bellows of claim 1 wherein, The control method of the relative position of the left and right molds during the forming process is as follows: The distance between the left and right molds is kept at S1 during the bulging stage, reduced from S1 to 0 during the closing stage, kept at 0 during the reshaping stage, and opened to S2 during the opening stage, wherein S2=2S1.

10. The method of forming a multi-wave narrow-pitch bellows of claim 1 wherein, The sealing fixtures are provided with sealing rings between the left and right molds.

Images