CN220739360U - Cold forging die for half shaft gear of differential mechanism - Google Patents

Abstract

The utility model discloses a cold forging die for a half shaft gear of a differential mechanism, which relates to the technical field of gear processing, and comprises an upper die, a lower die, an upper die cavity, a lower die cavity and a diversion hole, wherein the upper die cavity is arranged in the upper die, the lower die cavity is arranged in the lower die, the diversion hole is arranged in the middle of the bottom of the lower die cavity, and all small end tooth surfaces in the lower die cavity are provided with diversion branch holes for axially diverting metal in the cold forging forming process of the gear; all the branch flow holes are communicated with the branch flow holes; when the die is assembled, the tooth hole height in the lower die cavity is 0.1mm smaller than the tooth height of the cold forging blank, and the tooth thickness profile in the lower die cavity is attached to the tooth thickness of the cold forging blank. Through the technical scheme, the problem of incomplete metal filling is well solved, and the forming quality of the side gear is guaranteed.

Description

Cold forging die for half shaft gear of differential mechanism

Technical Field

The utility model relates to the technical field of gear machining, in particular to a cold forging die for a half shaft gear of a differential mechanism.

Background

In an automobile differential, precision control of a side gear is one of research hot spots, and because forging is the last procedure of forming a side gear tooth surface, the processing quality of the side gear directly influences the meshing effect of the side gear and a planetary gear. The machining precision of the half shaft gear is not high, and the failure of the differential gear in the running process of the automobile can be possibly caused, so that safety accidents are caused.

At present, the half-shaft gear is processed by direct hot forging and cold forging. Taking cold forging as an example, a die extrusion scheme is generally adopted, as shown in fig. 1, the cold forging die mainly comprises an upper die 1 and a lower die 3, an upper die cavity 2 and a lower die cavity 4 are respectively arranged in the upper die 1 and the lower die 3, a softened and annealed blank material is placed into the lower die cavity, and then the upper die and the lower die are subjected to die clamping and forging, so that metal is forced to fill the upper die cavity and the lower die cavity, and a gear is formed. Because of the law of minimum resistance, when metal is subjected to plastic deformation under the action of external force, all internal quality points flow along the direction with minimum resistance, and in order to reduce the forming resistance of metal materials in the forming process, the filling property of a cavity can be improved, the forming force is reduced, and the service life of a die is prolonged by arranging the diversion holes 5 at the bottom of the lower cavity 4.

The problem that exists in above-mentioned current cold forging mould is, because the semi-axis gear structure is comparatively complicated, and frictional force between mould and the blank material is big for the resistance that the metal flows receives is also comparatively big, and the compound die forging and pressing begins the time, and blank material center metal's velocity of flow is greater than outside, and along with the progress of shaping, inside and outside two partial velocity difference increase gradually, at this moment, because center metal flows too fast, and the metal very easily piles up at the tooth hole inward flange of lower die cavity, leads to near the tip tooth face to appear the not full defect of metal filling. In this way, not only is the forming quality of the side gear susceptible to influence, but also the secondary processing is frequent, and the waste of metal materials is also caused.

Disclosure of Invention

The utility model aims to provide a cold forging die for a half shaft gear of a differential mechanism, which aims to ensure the forming quality of the half shaft gear, reduce the secondary processing times and avoid the waste of metal materials.

In order to achieve the above purpose, the technical scheme adopted by the utility model is as follows:

the cold forging die for the half shaft gear of the differential mechanism comprises an upper die, a lower die, an upper die cavity arranged in the upper die, a lower die cavity arranged in the lower die and a diversion hole arranged in the middle of the bottom of the lower die cavity, wherein diversion branch holes are formed in all small end tooth surfaces in the lower die cavity and used for axially diverting metal in the cold forging forming process of the gear; all the branch flow holes are communicated with the branch flow holes; when the die is assembled, the tooth hole height in the lower die cavity is 0.1mm smaller than the tooth height of the cold forging blank, and the tooth thickness profile in the lower die cavity is attached to the tooth thickness of the cold forging blank.

Further, the width of the branch flow hole is 0.6mm.

Still further, the utility model also comprises a mandril arranged below the diversion hole.

Compared with the prior art, the utility model has the following beneficial effects:

according to the utility model, the split branch holes are formed in the small end tooth surface in the lower cavity and are communicated with the middle split branch holes, so that metal is axially split along the small end split branch holes in the tooth form in the gear forging forming process, the downward flowing trend of the metal in the middle is slowed down, the accumulation of the metal at the inner edge of the tooth hole of the lower cavity can be avoided, meanwhile, the tooth groove and the tooth height are fully pressed through adjusting the height and the width of the tooth hole in the lower cavity (the height of the tooth hole in the cavity is 0.1mm smaller than the tooth height of a cold forging blank and the tooth thickness profile is attached to the tooth thickness of the cold forging blank), and in the cold forging forming process, the tooth top of the blank is contacted with the tooth hole of the lower cavity firstly, and when the metal fills the tooth side, the tooth groove and the tooth height are fully pressed after cold forging forming. Therefore, the problem of incomplete metal filling can be well solved, and the waste of materials is avoided.

Moreover, by adopting the scheme, the pressure required by the initial upsetting is small, and the space required by finally extruding in the material is relatively small, so that the final forging pressure is effectively reduced, and the requirement on forging equipment is reduced.

Meanwhile, the ejector rod is arranged below the split hole, the upper die is removed after cold forging is finished, and then the finished product is ejected out of the lower die cavity by the ejector rod, so that the demolding efficiency of the product is effectively improved.

Drawings

Fig. 1 is a schematic diagram of a conventional side gear cold forging die.

FIG. 2 is a schematic diagram of the structure of an embodiment of the present utility model.

Fig. 3 is a schematic view of the velocity profile during axial flow splitting in an embodiment of the present utility model.

Fig. 4 is a schematic diagram showing the closing of the teeth holes in eight lower cavities and the teeth of the cold forging blank according to the embodiment of the present utility model.

FIG. 5 is a schematic view showing the position of the 1# scheme at the start of cold forging in the present embodiment.

Fig. 6 is a schematic diagram of blank filling of scheme 1# at different upper die strokes in an embodiment of the present utility model.

FIG. 7 is a schematic illustration of the material flow at the final fill location for scheme 1 in the present utility model-example.

Fig. 8 is a schematic diagram of the material flow at the final filling position of the 5# scheme in the present utility model-example.

Fig. 9 is a schematic view of the flow direction of tooth top material of the 8# scheme in the present utility model-example.

Wherein, the spare part names that the reference numerals correspond are:

1-upper die, 2-upper die cavity, 3-lower die, 4-lower die cavity, 5-branch hole, 6-branch hole and 7-ejector rod.

Detailed Description

The utility model will be further illustrated by the following description and examples, which include but are not limited to the following examples.

Examples

The present embodiment provides a cold forging die for forming a side gear applied to an automobile differential, which has the same general structure as the prior art, as shown in fig. 2, and mainly includes an upper die 1, a lower die 3, an upper cavity 2, a lower cavity 4, and a split hole 5 provided in the middle of the bottom of the lower cavity 4. The main innovation points of the cold forging die of the embodiment are as follows:

1. and all the small end tooth surfaces in the lower cavity 4 are provided with a diversion branch hole 6 for axially diverting metal in the cold forging forming process of the gear. In this embodiment, the width of the branch holes 6 is 0.6mm, and all branch holes are communicated with the branch holes 5. Fig. 3 shows the distribution of the metal flow velocity obtained by the split branch hole scheme of the present embodiment, and it can be seen that the metal in the middle of the blank is not in direct contact with the upper cavity 2 at the beginning of forging forming, so that the downward flow trend of the metal in the middle can be effectively slowed down.

2. When the die is assembled, the height of the tooth holes in the lower die cavity 4 is 0.1mm smaller than the tooth height of the cold forging blank, and the tooth thickness profile in the lower die cavity 4 is attached to the tooth thickness of the cold forging blank. In this embodiment, the mold closing conditions of the tooth holes in the eight lower cavities and the teeth of the cold forging blank are given, as shown in fig. 4, wherein the dotted line is the cross-sectional profile of the large end gear of the cold forging blank, the solid line is the profile of the large end gear of the lower cavity, and the 8# is the scheme adopted in this embodiment.

To verify the effectiveness of the 8# scheme, on the basis of the provision of the split branch holes, the following simulation analysis was performed on the mold using the eight mold closing conditions in fig. 4:

(1) First, the results of the simulation analysis of the final forging pressure are shown in table 1:

sample number	1#	2#	3#	4#	5#	6#	7#	8#
									Final forging pressure (ton)	616	618	620	607	624	657	622	604

(2) For the scheme 1, when the upper die is pressed down, the tooth side surface of the cold forging blank is contacted with the cavity first, and as the resistance of the material flowing to the lower cavity is larger than the resistance of the material flowing to other positions of the lower die, the material fills the position with smaller resistance in fig. 5 first, namely the tooth slot is formed first. As shown in fig. 6, after the tooth space position of the blank is filled (the blank and the mold are in contact and show dark color, and the mold is not in contact and show bright color), the upper mold is continuously pressed down to press the tooth crest material of the blank into the cavity, and at the moment, the material is filled first due to the large-end tooth surface size and small resistance. As shown in fig. 7, the final filling position has two directions of material flowing in at the same time, and there is a possibility that the folding problem occurs at the position.

(3) For the cases # 2 and # 3, the cold forging stock was positioned at the same location as that of the case # 1 at the beginning of forging, but the tooth tip-to-cavity clearance was 0.1mm and 0.2mm greater than that of the case # 1, and the required forging force was increased at the end of forging, as shown in table 1. Finally, the filling position is unchanged, and materials in two directions (with larger included angles) flow into the filling position, so that the folding problem is easy to occur.

(4) For the scheme 4#, when the upper die descends, tooth grooves and tooth flanks of the cold forging blank are contacted, material flows from the tooth root of the blank to the tooth top direction, the gap between tooth tops to be filled is small, and the required final forging pressure is small (specific numerical values are shown in table 1).

(5) For the scheme 5#, the tooth groove position of the cold forging blank is in contact with the cavity, the tooth top and the tooth side are not in contact (the gap is 0.1 mm), along with the descending of the die, the blank and the cavity are not in contact with the tooth surface of the big end and the small end at the moment, the material inflow resistance is zero, the material inflow speeds of the tooth surface of the big end and the tooth surface of the small end are basically consistent, as shown in fig. 8, the material flow directions of the tooth top at the position close to the small end are basically consistent, folding defects are not easy to form, but unfilled areas are also arranged at the tooth side, and finally the gap of the tooth side formed needs to be filled with extruded material in a transverse flow mode, and the pressure is high during final forging.

(6) For the scheme 6, the tooth top and the tooth groove of the cold forging blank are directly contacted with the lower die cavity, the whole gap of the tooth side needs to be filled by the transverse flow of the material, and the required final forging pressure is larger.

(7) For the 7# and 8# schemes, the material filling process is basically consistent, the tooth tops of the blanks are contacted with the die cavity firstly (as shown in the circled part in fig. 9, only one direction of material flow exists, folding defects are not easy to form at the small end), the blank is filled into the tooth side die cavity, the required pressure for upsetting is small firstly and then extruding is carried out, the space for finally extruding the material to fill is relatively small, and the final forging pressure is small.

In order to reduce the probability of incomplete filling, simultaneously ensure that the folding of the gear small end tooth top is not generated as much as possible (when the blank tooth top and the cavity are contacted firstly, the folding is not easy to generate), and according to the analysis result, the 8# scheme is selected for actual production verification, so that small-batch production is performed, the rejection rate is about 0.16%, and the production expectation is met.

Therefore, on the basis of setting the branch holes, the problem of incomplete metal filling is well solved by combining the design of the 8# scheme (namely, the tooth hole height in the lower cavity is 0.1mm smaller than the tooth height of the cold forging blank, and the tooth thickness profile in the lower cavity is attached to the tooth thickness of the cold forging blank), the waste of materials is avoided, and the final forging pressure is effectively reduced.

In addition, after the cold forging is finished, in order to facilitate pushing the finished product out of the die, a push rod 7 is further arranged below the split hole 5 in the embodiment. After the cold forging is finished, the upper die 1 is removed, and then the finished product is ejected out of the lower die cavity by the ejector rod 7.

The present utility model can be preferably implemented according to the above embodiments.

Claims (3)

1. The cold forging die for the half shaft gear of the differential mechanism comprises an upper die (1), a lower die (3), an upper die cavity (2) arranged in the upper die (1), a lower die cavity (4) arranged in the lower die (3) and a split hole (5) arranged in the middle of the bottom of the lower die cavity (4), and is characterized in that split branch holes (6) are formed in all small-end tooth surfaces in the lower die cavity (4) and used for axially splitting metal in the cold forging forming process of the gear; all the branch flow holes are communicated with the branch flow holes (5); when the die is assembled, the height of the tooth hole in the lower die cavity (4) is 0.1mm smaller than the tooth height of the cold forging blank, and the tooth thickness profile in the lower die cavity (4) is attached to the tooth thickness of the cold forging blank.

2. A differential side gear cold forging die according to claim 1, wherein the width of the split branch hole (6) is 0.6mm.

3. A differential side gear cold forging die according to claim 1 or 2, further comprising a carrier rod (7) provided below the split hole (5).