CN117161299A - Multi-degree-of-freedom enveloping forming method for spiral bevel gear with inverted cone tooth shape - Google Patents
Multi-degree-of-freedom enveloping forming method for spiral bevel gear with inverted cone tooth shape Download PDFInfo
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Abstract
The invention relates to a multi-degree-of-freedom enveloping forming method for a spiral bevel gear with a back taper tooth shape, which comprises the following steps: s1, placing and positioning a preform: the enveloping die comprises an enveloping upper die and an enveloping lower die, wherein the enveloping upper die forms the tooth shape and the web upper surface shape above the parting surface of the forging, and the enveloping lower die forms the shaft rod and the web lower surface shape below the parting surface of the forging; s2, enveloping and forming a spiral bevel gear forging: the toothed enveloping upper die performs multi-degree enveloping movement around the enveloping center, and simultaneously performs feeding movement vertically downwards, and the preform performs continuous local plastic deformation under the cooperative loading of the enveloping upper die and the enveloping lower die; s3, envelope finishing; s4, demoulding the forge piece; and S5, ejecting the forging. According to the invention, the spiral bevel gear with full tooth form filling is obtained through multi-degree-of-freedom enveloping loading of the die, and the non-interference demolding of the die and the spiral bevel gear is realized through multi-degree-of-freedom unloading of the die, so that the high-performance multi-degree-of-freedom enveloping forming manufacturing of the spiral bevel gear is realized.
Description
Technical Field
The invention relates to the technical field of plastic forming and manufacturing of spiral bevel gears, in particular to a multi-degree-of-freedom enveloping forming method of a spiral bevel gear with a back taper tooth shape.
Background
Spiral bevel gears are key fundamental components of mechanical equipment, the manufacturing quality of the spiral bevel gears directly determines the service performance and service life of the equipment, and how to manufacture high-performance spiral bevel gears has become the front edge of international gear manufacturing technology research. At present, the spiral bevel gear is commonly manufactured by milling, the milling is low in efficiency and material utilization rate, metal streamline is cut off, grains cannot be refined, and the strength, bearing capacity and fatigue life of the spiral bevel gear are seriously weakened. The metal plastic forming has the advantages of high efficiency, high material utilization rate, continuous metal streamline, fine grain structure and the like, and is an important development direction of the international high-performance gear manufacturing technology. However, the spiral bevel gear tooth form is complicated spiral and takes the back taper structure, if adopt traditional single degree of freedom whole die forging to take shape, not only shaping power is big, and metal flow resistance is big, and the tooth form is difficult to fill fully, and the mould is the unavoidable emergence interference with taking back taper tooth form spiral bevel gear in the vertical upward drawing of patterns of mould single degree of freedom moreover to greatly reduce spiral bevel gear tooth form precision, lead to even spiral bevel gear to scrap.
Disclosure of Invention
The invention aims to solve the technical problem of providing the multi-degree-of-freedom enveloping forming method for the spiral bevel gear with the inverted cone tooth shape, which not only obtains the spiral bevel gear with full tooth shape filling through multi-degree-of-freedom enveloping loading of the die, but also realizes non-interference demolding of the die and the spiral bevel gear through multi-degree-of-freedom unloading of the die, thereby realizing high-performance multi-degree-of-freedom enveloping forming manufacturing of the spiral bevel gear.
The technical scheme adopted for solving the technical problems is as follows: the multi-degree-of-freedom enveloping forming method for constructing the spiral bevel gear with the back taper profile comprises an upper part and a lower part: the upper part is a conical tooth shape and a web plate, the tooth shape is provided with a reverse taper structure, the lower part is a gear shaft lever, and the multi-degree-of-freedom enveloping forming method comprises the following steps:
s1, placing and positioning a preform: the enveloping die comprises an enveloping upper die and an enveloping lower die, wherein the enveloping upper die forms the tooth shape and the web upper surface shape above the parting surface of the forging, and the enveloping lower die forms the shaft rod and the web lower surface shape below the parting surface of the forging; placing the preform in an envelope lower die, wherein the conical surface of the lower part of the preform coincides with the conical surface cavity of the envelope lower die, and the lower end surface of the preform disc contacts with a boss in the envelope lower die cavity to realize accurate positioning of the preform in the envelope lower die;
s2, enveloping and forming a spiral bevel gear forging: the method comprises the steps that a toothed enveloping upper die performs multi-degree-of-freedom enveloping movement around an enveloping center, and simultaneously performs feeding movement vertically downwards, a preform continuously performs local plastic deformation under the cooperative loading of the enveloping upper die and a enveloping lower die, metal flows into a enveloping upper die cavity until the tooth form of a spiral bevel gear forging and the shape of the upper surface of a web are enveloped and formed by the toothed enveloping upper die in a multi-degree-of-freedom way, and meanwhile, the shapes of the shaft lever of the spiral bevel gear forging and the shape of the lower surface of the web are enveloped and formed by the enveloping lower die;
s3, envelope finishing: stopping feeding downwards after the enveloping upper die reaches a preset feeding amount, and continuing to perform multi-degree-of-freedom enveloping movement to finish the spiral bevel gear forging;
s4, demoulding of the forge piece: after finishing the envelope, firstly stopping the multi-degree-of-freedom envelope motion of the envelope upper die, then correcting the envelope upper die, ensuring that the axis of the envelope upper die coincides with the vertical axis of envelope forming equipment, and finally driving the envelope upper die to perform rotary motion and axial withdrawal motion according to the designed rotary demoulding motion until the envelope upper die is completely separated from the tooth form of the spiral bevel gear forging; in the demolding process, the profile of the enveloping upper die and the profile of the spiral bevel gear forging are ensured not to interfere, and the spiral bevel gear forging is ensured not to rotate;
s5, ejection of a forging: after demoulding of the spiral bevel gear forging is completed, the enveloping upper die is retracted upwards to the initial position, and under the ejection action of the ejector rod, the spiral bevel gear forging is ejected out in the enveloping lower die cavity.
According to the above scheme, in the step S2, the spiral bevel gear forging design method includes: all tooth surfaces are offset outwards along the normal direction by a distance s and used as machining allowance of subsequent grinding teeth; the outer circle of the gear shaft lever is provided with a draft angle, and the upper end of the gear shaft lever is provided with a section of cylindrical section without the draft angle, so that the forging is ensured to be left in the lower die during demoulding and used as a reference for the subsequent machining of the forging; the lower surface of the forging web is provided with a limit boss for ensuring that the forging does not rotate during demolding; taking the maximum diameter of the spiral bevel gear as a parting surface and designing a horizontal flash; and rounding the tooth-shaped edge.
According to the above scheme, in the step S1, the preform design method is as follows: the prefabricated blank is designed into a revolving body with a T-shaped axial section, and a single side of a shaft lever at the lower part of the prefabricated blank is reduced by a on the basis of the size of the shaft lever of the spiral bevel gear forging piece, so that the prefabricated blank can be smoothly placed into an envelope lower die; the diameter of the upper part of the disc of the preform is smaller than the maximum diameter of the forging piece, so that metal is prevented from flowing out of the cavity of the enveloping die in the initial enveloping forming stage, and the height of the upper part of the disc of the preform is determined according to the principle of equal volume to the spiral bevel gear forging piece.
According to the scheme, the design method of the envelope upper die comprises the following steps: the design principle of the envelope upper die is that the envelope upper die is reversely enveloped by the spiral bevel gear forging, so that interference between the envelope upper die and the spiral bevel gear forging in the envelope forming process is avoided; discretizing the molded surface above the parting surface of the spiral bevel gear forging designed in the step S2, and then carrying out coordinate transformation on the discretized points according to formulas (1) and (2):
[X Y Z 1] T ＝M[x″′ y″′ z″′1] T (1)
wherein: (X ', Y ', Z ') is any discrete point coordinate on the surface above the parting surface of the spiral bevel gear forging, [ X, Y, Z ] is the motion trail equation of the corresponding point of the envelope upper model, gamma is the angle of inclination of the upper envelope mode, theta is the angle of rotation of the upper envelope mode, theta is discretized in one motion period, namely [0,2 pi ], obtaining a motion track of each discrete point of the forging in a reverse enveloping process, dispersing the motion track to obtain coordinates of a group of points, dispersing the motion track of all the discrete points of the forging in the reverse enveloping process to obtain a point cloud, extracting surface layer points of the point cloud, fitting the surface layer points to a curved surface, and obtaining an enveloping upper die surface; the lower enveloping die is matched with the molded surface below the flash lower surface of the spiral bevel gear forging.
According to the above scheme, in the step S2, the envelope motion design method is as follows: the axis of the enveloping upper die always keeps a gamma included angle with the vertical axis of the equipment, and the intersection point of the two axes is the rotation center; the upper enveloping die revolves around the vertical axis of the equipment while rotating around the axis of the upper enveloping die, the two rotating speeds are equal and constant, and the rotating directions are opposite; the envelope lower die is fixed.
According to the scheme, in the step S4, the design method for the interference-free demoulding motion of the spiral bevel gear forging comprises the following steps:
the envelope upper die is required to do circumferential rotation movement along the spiral tooth-shaped rotation direction when being retracted vertically upwards, and the angular speed w and v of the envelope upper die rotating circumferentially along the tooth-shaped rotation direction satisfy the relation: w=kv, and k 1 <k<k 2 The method comprises the steps of carrying out a first treatment on the surface of the Where k is a coefficient of relationship between w and v, k 1 K is critical coefficient when the envelope upper die is tangent to the tooth convex surface of the forging piece in the demolding process 2 The critical coefficient is the critical coefficient when the upper die is enveloped and tangent with the tooth-shaped concave surface of the forging piece in the demolding process;
k 1 and k is equal to 2 The determining method of (1) comprises the following steps: knowing the envelope upper-modulo arbitrary point (x 0 ,y 0 ,z 0 ) The trajectory equation H for the vertical upward return of its rotation is:
k starts from 0, a fixed value delta k is added each time, and for each k value, whether an intersection exists between a motion trail equation H of any point of an envelope upper die and a tooth surface equation F of the spiral bevel gear forging piece or not is judged; when k increases to k 1 When in demolding, the enveloping upper die is tangent to the tooth-shaped convex surface of the forging piece, k is 1 The minimum value for realizing interference-free demoulding of the spiral bevel gear forging; after k is continuously increased, the equation H and the equation F have no intersection; k continues to increase to k 2 When in demolding, the enveloping upper die is tangent to the concave surface of the forging tooth profile, k 2 To realize spiral coneMaximum value of non-interference demoulding of the gear forging; after k is continuously increased, the intersection of the equation H and the equation F exists, and at the moment, the upper envelope die interferes with the profile of the forging tooth.
The implementation of the multi-degree-of-freedom enveloping forming method for the spiral bevel gear with the inverted cone tooth shape has the following beneficial effects:
(1) The method for enveloping and forming the tooth form of the spiral bevel gear forging by the multi-degree-of-freedom upper die enveloping and forming the tooth form of the belt tooth form can reduce metal flow resistance, improve metal fluidity and further obtain the spiral bevel gear forging with full tooth form filling;
(2) The method for obtaining the envelope upper die by the reverse envelope of the spiral bevel gear forging can avoid interference between the envelope upper die and the spiral bevel gear forging in the multi-degree-of-freedom envelope forming process, thereby improving the multi-degree-of-freedom envelope forming precision of the spiral bevel gear forging;
(3) The multi-degree-of-freedom demoulding method for the enveloping upper die can avoid interference between the enveloping upper die and the spiral bevel gear forging with the inverted cone tooth form in the demoulding process, thereby ensuring the multi-degree-of-freedom enveloping forming precision of the spiral bevel gear forging;
(4) The multi-degree-of-freedom enveloping forming method for the spiral bevel gear with the inverted cone tooth shape provided by the invention has the advantages of high manufacturing efficiency, high material utilization rate, continuous metal streamline and fine grain structure, and can greatly improve the strength, the bearing capacity and the fatigue life of the spiral bevel gear.
Drawings
The invention will be further described with reference to the accompanying drawings and examples, in which:
FIG. 1 is a cross-sectional view of a spiral bevel gear shaft;
FIG. 2 is a top view of a spiral bevel gear;
FIG. 3 is a schematic diagram of a spiral bevel gear forging design;
FIG. 4 is a schematic view of a preform shaft cross-section;
FIG. 5 is a schematic diagram of an envelope upper die;
FIG. 6 is a flow chart of a multiple degree of freedom demolding path design;
FIG. 7 is a schematic diagram of a multi-degree of freedom envelope forming principle of a spiral bevel gear;
FIG. 8 is a schematic diagram of a simulation of a multi-degree of freedom envelope forming process of a spiral bevel gear;
FIG. 9 is a schematic view of a tooth form filling process of a spiral bevel gear;
FIG. 10 is a multiple degree of freedom demolding schematic diagram of a spiral bevel gear forging;
FIG. 11 is a schematic illustration of the demolding process without interference when k is within the design range;
FIG. 12 is a schematic diagram showing interference during demolding at a time k-th excess;
FIG. 13 is a schematic diagram showing the interference of the demolding process when k is too large.
Detailed Description
For a clearer understanding of technical features, objects and effects of the present invention, a detailed description of embodiments of the present invention will be made with reference to the accompanying drawings.
As shown in fig. 1, the spiral bevel gear is composed of an upper part and a lower part: the upper part is a conical tooth shape and a web plate, the height is 28.5mm, the maximum diameter is 140.7mm, and the tooth shape is provided with an inverted cone structure, as shown in figure 2; the lower part is a gear shaft rod with the diameter of 57mm and the height of 99mm. The invention relates to a multi-degree-of-freedom enveloping forming method for a spiral bevel gear with a back taper tooth shape, which comprises the following steps:
(1) And (3) forging design: the design schematic diagram of the spiral bevel gear forging is shown in fig. 3, and tooth surfaces of all tooth shapes are outwards deviated by 1mm along the normal direction and used as machining allowance of subsequent gear grinding; setting a 1-degree draft angle on the outer circle of a gear shaft lever, and reserving a cylindrical section with the height of 15mm at the upper end of the shaft lever, wherein the cylindrical section is used for ensuring that a forging piece is reserved in a lower die during demolding and is used as a reference for subsequent machining of the forging piece; a limiting boss with the height of 2mm is reserved on the lower surface of the forging web and is used for ensuring that the forging does not rotate during demolding; a horizontal flash with the thickness of 2mm is downwards arranged at the maximum diameter of the gear; rounded corners with the radius of 1mm are arranged on each side line of the tooth shape.
(2) Preform design: the axial section of the preform is shown in fig. 4, the axial section of the preform is a revolving body with a T-shaped axial section, and the axial rod of the lower part of the preform is unilaterally reduced by 0.5mm on the basis of the axial rod size of the spiral bevel gear forging, namely the diameter of the lower end face of the axial rod of the preform is 56mm; the diameter of the upper part of the disc of the preform is smaller than the maximum diameter of the forging piece, 124mm is taken, metal is prevented from flowing out of a cavity of the enveloping die in the initial stage of enveloping forming, the height of the upper part of the disc of the preform is determined according to the principle of equal volume, and 27.1mm is taken.
(3) Envelope mold design: the enveloping die comprises an enveloping upper die and an enveloping lower die, wherein the enveloping upper die forms the tooth shape and the web upper surface shape above the parting surface of the forging, and the enveloping lower die forms the shaft rod and the web lower surface shape below the parting surface of the forging.
The design method of the envelope upper die comprises the following steps: discretizing the molded surface above the parting surface of the spiral bevel gear forging, and then carrying out coordinate transformation on the discretized points according to formulas (1) and (2):
wherein: (X ', Y ', Z ' ") is any discrete point coordinate on the surface above the parting surface of the spiral bevel gear forging designed in the step S2, [ X, Y, Z ] is a motion trail equation of a corresponding point of an envelope upper model, gamma is an inclination angle of the envelope upper model, and 1.5 degrees is taken; θ is the rotation angle of the envelope upper die, θ is discretized in a motion period, namely [0,2 pi ], a motion track of each discrete point of the forging in a reverse envelope process is obtained, the motion track is discretized to obtain a group of coordinates of points, accordingly, the motion track of all the discrete points of the forging in the reverse envelope process is discretized to obtain a point cloud, the surface layer points of the point cloud are extracted and fitted into a curved surface, and the envelope upper die surface can be obtained;
the lower enveloping die is matched with the molded surface below the flash lower surface of the spiral bevel gear forging;
(4) An included angle of 1.5 degrees is always kept between the axis of the enveloping upper die and the vertical axis of the equipment, and the intersection point of the two axes is the rotation center; the upper enveloping die revolves around the vertical axis of the equipment while rotating around the axis of the upper enveloping die, the two rotating speeds are 1rad/s, and the rotating directions are opposite; meanwhile, the enveloping upper die is vertically fed downwards at a constant speed of 1 mm/s; the lower enveloping die is fixed;
(5) And (3) designing demoulding movement of the forging: the envelope upper die is required to do circumferential rotation movement along the spiral tooth-shaped rotation direction while retracting vertically upwards. Assuming that the speed of the vertical upward withdrawal of the envelope upper die is v, the angular speeds w and v of the circumferential rotation of the envelope upper die along the tooth-shaped rotation direction satisfy the relation: w=kv, and k 1 <k<k 2 The method comprises the steps of carrying out a first treatment on the surface of the Where k is a coefficient of relationship between w and v, k 1 K is critical coefficient when the envelope upper die is tangent to the tooth convex surface of the forging piece in the demolding process 2 The critical coefficient is the critical coefficient when the upper die is enveloped and tangent with the tooth-shaped concave surface of the forging piece in the demolding process;
a multi-degree-of-freedom demolding path design flow chart is shown in FIG. 6, k 1 And k is equal to 2 The determining method of (1) comprises the following steps: knowing the envelope upper-modulo arbitrary point (x 0 ,y 0 ,z 0 ) The trajectory equation H for the vertical upward return of its rotation is:
k starts from 0, a fixed value of 0.01 is added each time, and for each k value, whether an intersection exists between a motion trail equation H of any point of an envelope upper die and a tooth surface equation F of the spiral bevel gear forging or not is judged; when k increases to k 1 When=0.20, the upper envelope die is tangent to the convex surface of the forging tooth form in the demolding process, k is 1 =0.20 is the minimum to achieve interference free demoulding of spiral bevel gear forgings; after k is continuously increased, the equation H and the equation F have no intersection; k continues to increase to k 2 When the value is=0.98, the upper envelope die is tangent to the concave surface of the forging tooth form in the demolding process, and k is 2 =0.98 is the maximum value to achieve interference-free demolding of spiral bevel gear forgings; after k is continuously increased, the intersection of the equation H and the equation F exists, and at the moment, the upper envelope die interferes with the profile of the forging tooth.
(6) The multi-degree-of-freedom enveloping and forming process of the spiral bevel gear with the inverted cone tooth shape comprises the following steps:
s1, placing and positioning a preform: placing the preform 1 in an envelope lower die 2, wherein the conical surface of the lower part of the preform coincides with the conical surface cavity of the envelope lower die, and the lower end surface of the preform disc contacts with a boss in the envelope lower die cavity to realize accurate positioning of the preform in the envelope lower die;
s2, enveloping and forming a spiral bevel gear forging: the toothed enveloping upper die 3 performs multi-degree-of-freedom enveloping movement around the enveloping center, and performs feeding movement vertically downwards, the preform performs continuous local plastic deformation under the cooperative loading of the enveloping upper die and the enveloping lower die, and metal flows into the enveloping upper die cavity until the shape of the toothed shape of the spiral bevel gear forging and the shape of the upper surface of the web are formed by the multi-degree-of-freedom enveloping of the toothed enveloping upper die, and simultaneously the shape of the shaft lever of the spiral bevel gear forging and the shape of the lower surface of the web are formed by the enveloping lower die. A schematic diagram of the multi-degree-of-freedom envelope forming principle of the spiral bevel gear is shown in fig. 7.
S3, envelope finishing: and stopping feeding downwards when the envelope upper die reaches a preset feeding amount, namely the flash thickness is 2mm, and continuously performing multi-degree-of-freedom envelope motion on the envelope upper die for 8 circles to finish the spiral bevel gear forging 4. A simulation schematic diagram of the multi-degree-of-freedom enveloping forming process of the spiral bevel gear is shown in fig. 8, and a tooth form filling process is shown in fig. 9;
s4, demoulding of the forge piece: after finishing the envelope, firstly stopping the multi-degree-of-freedom envelope motion of the envelope upper die, then correcting the envelope upper die, ensuring that the axis of the envelope upper die coincides with the vertical axis of envelope forming equipment, and finally driving the envelope upper die to perform rotary motion and axial withdrawal motion according to the designed rotary demoulding motion until the envelope upper die is completely separated from the tooth form of the spiral bevel gear forging; in the demolding process, the envelope upper die and the tooth form of the spiral bevel gear forging are prevented from interfering, and the spiral bevel gear forging is prevented from rotating. A multi-degree-of-freedom demoulding schematic diagram of the spiral bevel gear forging is shown in FIG. 10.
When k is 0.2< 0.98, the spiral bevel gear forging piece does not interfere with the envelope upper die in the demolding process, as shown in FIG. 11; when k is less than 0.2, the spiral bevel gear forging interferes with the envelope upper die on the tooth-shaped convex surface of the forging in the demolding process, as shown in fig. 12; when k is more than 0.98, the spiral bevel gear forging interferes with the envelope upper die on the concave surface of the forging tooth profile in the demolding process, as shown in fig. 13.
S5, ejection of a forging: after demoulding of the spiral bevel gear forging is completed, the enveloping upper die is retracted upwards to the initial position, and under the ejection action of the ejector rod, the spiral bevel gear forging is ejected out in the enveloping lower die cavity.
The embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to the above-described embodiments, which are merely illustrative and not restrictive, and many forms may be made by those having ordinary skill in the art without departing from the spirit of the present invention and the scope of the claims, which are to be protected by the present invention.
Claims (6)
1. A multi-degree-of-freedom enveloping forming method for a spiral bevel gear with a back taper profile comprises an upper part and a lower part: the upper part is a conical tooth shape and a web plate, the tooth shape is provided with a reverse conical structure, and the lower part is a gear shaft rod, and the multi-degree-of-freedom enveloping forming method is characterized by comprising the following steps:
s1, placing and positioning a preform: the enveloping die comprises an enveloping upper die and an enveloping lower die, wherein the enveloping upper die forms the tooth shape and the web upper surface shape above the parting surface of the forging, and the enveloping lower die forms the shaft rod and the web lower surface shape below the parting surface of the forging; placing the preform in an envelope lower die, wherein the conical surface of the lower part of the preform coincides with the conical surface cavity of the envelope lower die, and the lower end surface of the preform disc contacts with a boss in the envelope lower die cavity to realize accurate positioning of the preform in the envelope lower die;
s2, enveloping and forming a spiral bevel gear forging: the method comprises the steps that a toothed enveloping upper die performs multi-degree-of-freedom enveloping movement around an enveloping center, and simultaneously performs feeding movement vertically downwards, a preform continuously performs local plastic deformation under the cooperative loading of the enveloping upper die and a enveloping lower die, metal flows into a enveloping upper die cavity until the tooth form of a spiral bevel gear forging and the shape of the upper surface of a web are enveloped and formed by the toothed enveloping upper die in a multi-degree-of-freedom way, and meanwhile, the shapes of the shaft lever of the spiral bevel gear forging and the shape of the lower surface of the web are enveloped and formed by the enveloping lower die;
s3, envelope finishing: stopping feeding downwards after the enveloping upper die reaches a preset feeding amount, and continuing to perform multi-degree-of-freedom enveloping movement to finish the spiral bevel gear forging;
s4, demoulding of the forge piece: after finishing the envelope, firstly stopping the multi-degree-of-freedom envelope motion of the envelope upper die, then correcting the envelope upper die, ensuring that the axis of the envelope upper die coincides with the vertical axis of envelope forming equipment, and finally driving the envelope upper die to perform rotary motion and axial withdrawal motion according to the designed rotary demoulding motion until the envelope upper die is completely separated from the tooth form of the spiral bevel gear forging; in the demolding process, the profile of the enveloping upper die and the profile of the spiral bevel gear forging are ensured not to interfere, and the spiral bevel gear forging is ensured not to rotate;
s5, ejection of a forging: after demoulding of the spiral bevel gear forging is completed, the enveloping upper die is retracted upwards to the initial position, and under the ejection action of the ejector rod, the spiral bevel gear forging is ejected out in the enveloping lower die cavity.
2. The multi-degree-of-freedom enveloping forming method for spiral bevel gears with inverted tooth profiles according to claim 1, wherein in the step S2, the spiral bevel gear forging design method is as follows: all tooth surfaces are offset outwards along the normal direction by a distance s and used as machining allowance of subsequent grinding teeth; the outer circle of the gear shaft lever is provided with a draft angle, and the upper end of the gear shaft lever is provided with a section of cylindrical section without the draft angle, so that the forging is ensured to be left in the lower die during demoulding and used as a reference for the subsequent machining of the forging; the lower surface of the forging web is provided with a limit boss for ensuring that the forging does not rotate during demolding; taking the maximum diameter of the spiral bevel gear as a parting surface and designing a horizontal flash; and rounding the tooth-shaped edge.
3. The multi-degree of freedom enveloping forming method for spiral bevel gears with back taper profiles according to claim 2, wherein in the step S1, the preform design method is as follows: the prefabricated blank is designed into a revolving body with a T-shaped axial section, and a single side of a shaft lever at the lower part of the prefabricated blank is reduced by a on the basis of the size of the shaft lever of the spiral bevel gear forging piece, so that the prefabricated blank can be smoothly placed into an envelope lower die; the diameter of the upper part of the disc of the preform is smaller than the maximum diameter of the forging piece, so that metal is prevented from flowing out of the cavity of the enveloping die in the initial enveloping forming stage, and the height of the upper part of the disc of the preform is determined according to the principle of equal volume to the spiral bevel gear forging piece.
4. The multi-degree-of-freedom enveloping forming method for spiral bevel gears with inverted tooth profiles according to claim 1, wherein the enveloping upper die design method is as follows: the design principle of the envelope upper die is that the envelope upper die is reversely enveloped by the spiral bevel gear forging, so that interference between the envelope upper die and the spiral bevel gear forging in the envelope forming process is avoided; discretizing the molded surface above the parting surface of the spiral bevel gear forging designed in the step S2, and then carrying out coordinate transformation on the discretized points according to formulas (1) and (2):
[X Y Z 1] T ＝M[x″′ y″′ z″′ 1] T (1)
wherein: (X ', Y ', Z ') is any discrete point coordinate on the surface above the parting surface of the spiral bevel gear forging, [ X, Y, Z ] is the motion trail equation of the corresponding point of the envelope upper model, gamma is the angle of inclination of the upper envelope mode, theta is the angle of rotation of the upper envelope mode, theta is discretized in one motion period, namely [0,2 pi ], obtaining a motion track of each discrete point of the forging in a reverse enveloping process, dispersing the motion track to obtain coordinates of a group of points, dispersing the motion track of all the discrete points of the forging in the reverse enveloping process to obtain a point cloud, extracting surface layer points of the point cloud, fitting the surface layer points to a curved surface, and obtaining an enveloping upper die surface; the lower enveloping die is matched with the molded surface below the flash lower surface of the spiral bevel gear forging.
5. The multi-degree of freedom enveloping forming method for spiral bevel gears with inverted tooth profiles according to claim 4, wherein in the step S2, the enveloping motion designing method is as follows: the axis of the enveloping upper die always keeps a gamma included angle with the vertical axis of the equipment, and the intersection point of the two axes is the rotation center; the upper enveloping die revolves around the vertical axis of the equipment while rotating around the axis of the upper enveloping die, the two rotating speeds are equal and constant, and the rotating directions are opposite; the envelope lower die is fixed.
6. The multi-degree-of-freedom enveloping molding method for spiral bevel gears with inverted tooth profiles according to claim 1, wherein in the step S4, the design method for the non-interference demolding motion of the spiral bevel gear forging is as follows:
the envelope upper die is required to do circumferential rotation movement along the spiral tooth-shaped rotation direction when being retracted vertically upwards, and the angular speed w and v of the envelope upper die rotating circumferentially along the tooth-shaped rotation direction satisfy the relation: w=kv, and k 1 <k<k 2 The method comprises the steps of carrying out a first treatment on the surface of the Where k is a coefficient of relationship between w and v, k 1 K is critical coefficient when the envelope upper die is tangent to the tooth convex surface of the forging piece in the demolding process 2 The critical coefficient is the critical coefficient when the upper die is enveloped and tangent with the tooth-shaped concave surface of the forging piece in the demolding process;
k 1 and k is equal to 2 The determining method of (1) comprises the following steps: knowing the envelope upper-modulo arbitrary point (x 0 ,y 0 ,z 0 ) The trajectory equation H for the vertical upward return of its rotation is:
k starts from 0, a fixed value delta k is added each time, and for each k value, whether an intersection exists between a motion trail equation H of any point of an envelope upper die and a tooth surface equation F of the spiral bevel gear forging piece or not is judged; when k increases to k 1 When in demolding, the enveloping upper die is tangent to the tooth-shaped convex surface of the forging piece, k is 1 The minimum value for realizing interference-free demoulding of the spiral bevel gear forging; after k is continuously increased, the equation H and the equation F have no intersection; k continues to increase to k 2 When in demolding, the enveloping upper die is tangent to the concave surface of the forging tooth profile, k 2 The maximum value of interference-free demoulding of the spiral bevel gear forging is realized; after k is continuously increased, the intersection of the equation H and the equation F exists, and at the moment, the upper envelope die interferes with the profile of the forging tooth.
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