JPH0341252B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forging segment members for constructing a sprocket.

[Conventional technology]

FIG. 8 is a front view showing an example of a sprocket.

A large number of ribs (25 in this example) are placed around the annular rib 1z.
The teeth 1a, 1b to 1y are arranged in a row.

If these sprockets are large, 1
Since it is difficult to forge the sprocket into a body, a segment sprocket 2 having a shape in which the sprocket 1 is divided into M pieces and having N=5 teeth is made as shown in FIG.

In this case, for convenience in connecting the segment sprockets 2 to each other, the number of teeth on the sprocket 1 is configured to be an integral multiple of the number M of divisions M.times.N.

FIG. 10 is an explanatory diagram of the forging method for the segment sprocket 2.

Die-forging methods for segment sprockets can be roughly divided into vertical forging and horizontal forging.

Vertical striking applies forging force in the radial direction as shown by arrows P ₁ and P ₂ in the figure, and horizontal striking applies forging force in a direction perpendicular to the plane of the paper. Each has its advantages and disadvantages, but it is better to have a precise tooth profile. Vertical hammering is superior in that it has a forged finish and requires only a small amount of machining after forging.

FIG. 11 is an explanatory diagram of problems in vertically driving segment sprockets. The segment sprocket 2 shown in FIG. 11 is a segment having 25 teeth divided into five parts. Let the center line of the rib 2z be XX, and consider a line xx that is in contact with the tooth 2e located at the end and parallel to the center line XX.

Then, when a tangent line is drawn at each point on the tooth surface of the tooth 2e, for example, the illustrated tangent line t is the tangent line x-x
Compared to , they intersect at a clockwise angle φ in the figure.

The above-mentioned angle φ has a reverse punching pattern for vertical die forging in the X-X direction, and die forging cannot be performed with this type of forging.

Therefore, as shown for tooth 2a, useless meat 2a _-1
There is no choice but to set up a special order with a . This waste material 2a _-1 must be removed by machining after forging.

If you want to eliminate the above-mentioned reverse alignment angle φ, you can increase the number of sprocket divisions M, but
This increase in the number of divisions causes various problems.

In the example shown in Fig. 11, the sprocket is divided into five segment sprockets 2 and bolt holes 2 are inserted into the segment sprocket 2.
Four _H 's are provided, but as the number of divided bolt holes increases, the number of bolt holes provided decreases inversely, making the state of attachment and fixation of the segments unstable.

Furthermore, the segment sprocket 2 in this example (Fig. 11) is obtained by dividing the sprocket 1 with 25 teeth in Fig. 8 into 5 parts, but for example, the number of parts is divided into 6 parts.
If you try to set the number to 1, 7, 8, or 9, the number of teeth (M x N = 25) will not be divisible.

If the number of divisions is to be 10, this segment sprocket 2 will be further divided along the center line XX shown in FIG.
This is extremely undesirable in terms of strength.

In the method of die forging a segment sprocket in which the sprocket is divided into M pieces, the number of divided pieces M can be made relatively small, and furthermore, the sprocket can be vertically forged without adding waste to the teeth located at both ends of the segment. As a measure to significantly reduce the machining required after forging by applying
(2) The semi-finished product is vertically forged in a hot state, and (b) The semi-finished product is formed by a line tangent to each point on the tooth surface of the teeth 2a and 2e at both ends shown in FIG. 11 (for example, All of the tangent lines t-t) are set to have a shape with an appropriate cutout pattern compared to the above-mentioned line x-x, and (c) plastic deformation is applied to the above-mentioned intermediate product. It is conceivable to obtain the final target shape. Next, the above method will be described in more detail.

The solid line 2 in FIG. 1 is the segment sprocket shown in FIG. That is, it is the desired shape to be manufactured.

3 drawn with a chain line is the aforementioned semi-finished product.

Compared to the rib 2z of the target shape, the rib 3z of the semi-finished product 3 is deformed to have a smaller curvature (larger radius of curvature).

Furthermore, the teeth 2a and 2e at both ends are deformed inwardly.

The semi-finished product 3 has been deformed as shown by the chain line in FIG. 1, so that the teeth 3a and 3e at both ends thereof have fallen inward. For this reason, for example, the tangent line t'-t' is the line x-
A draft angle θ is formed compared to x.

The above-mentioned draft angle is a two-dimensional consideration of FIG. 11, but when viewed three-dimensionally, in short, a draft angle is attached to all parts of the tooth surface of the tooth.

Therefore, vertical die forging is possible without adding excess material to the teeth at both ends.

The semi-finished product 3 deformed and configured as described above is
This can be modified into the desired shape by plastic working.

The solid line 2 in FIG. 5 is the target shape for which the segment sprocket is to be forged. Based on this target shape 2, the shape of the semi-finished product 3 drawn with a chain line is set.

Next, a method for setting the semi-finished product 3 will be described.

The rib 3z of the semi-finished product is set to have a larger radius of curvature than the rib 2z of the segment sprocket 2, which is the target shape.

As a result, the five teeth lined up on the rib have their tips brought together. Therefore, the teeth 3a and 3e of the semi-finished products are further set so that the teeth 2a and 2e at both ends are tilted inward (as shown by chain lines).

As a result, the tangent line t'- of the tooth 3e located at the end
t′ is given the draft of angle θ. The same applies to the tooth 3a.

The material is heated to a forging temperature, and the semi-finished product 3 is first formed by vertical die forging.

FIGS. 6 and 7 show an example of modifying the semi-finished product 3 described above into a segment sprocket 2 having a desired shape by plastic working.

FIG. 6 is a schematic diagram showing the state before correction,
For convenience of illustration, the upper mold 4 and the semi-finished product 3 are not cut, but the lower mold 5 is shown cut.

The upper mold 4 is provided with an arcuate groove 4a having a shape corresponding to the rib 2z of the sprocket 2 having the desired shape (not shown in this figure).

The lower mold 5 is formed with four tooth surface-like protrusions 5a to 5c that fit into the valleys between the teeth, corresponding to the five teeth of a sprocket (not shown) having the desired shape. .

Therefore, among the five teeth of the semi-finished product, the three teeth near the center undergo finish forging of the tooth profile while being sandwiched between the tooth surface-like protrusions. Further, the two teeth at both ends are corrected by being subjected to a forging force in one direction (in the direction in which they are caused to fall) in the direction of arrow a' by the tooth surface-like projections 5a and 5d.

FIG. 7 shows a state in which the segment sprocket 2 has been formed through plastic working. As is clear from FIG. 7, the teeth 2a and 2e at both ends are not sandwiched by the tooth surface-like protrusions 5a to 5d of the lower mold 5, but are pressed against them only from one side. Therefore,
No problems related to draft angle.

[Problem to be solved by the invention]

The semi-finished product 3 shown in FIG. 5 is forged and formed into a sixth
Segment sprocket 2 (seventh
The method for obtaining the tooth surface shown in FIG. It only receives the force of arrow a' and arrow a (Fig. 6).

That is, unlike the three central teeth 2b, 2c, and 2d, it is not sandwiched between two tooth surface-like projections.

For this reason, the teeth at both ends are less precise in shape and size than the teeth at the center. However, since the tooth surfaces of the teeth 2a and 2e at both ends have a reverse slope (a slope opposite to the draft slope) as explained with reference to FIG. Correction processing is extremely difficult.

The present invention was made in view of the above circumstances, and
This is a semi-finished product of a segment sprocket, which has ribs with a shape that increases the radius of curvature of the ribs of the segment sprocket, which is the molding object, and teeth at both ends that are tilted toward the center of the segment. However, when the shape of the semi-finished product is modified by plastic working to obtain the desired shape, it is an object of the present invention to provide a method that can easily and accurately modify the semi-finished product.

[Means to solve the problem]

In order to achieve the above object, the forging method according to the present invention, when modifying the semi-finished product into the desired shape by plastic working, uses a forged shape that contacts the inner peripheral surface of the rib and a tooth surface of the tooth. A force in the radial direction of the sprocket is applied by a plurality of abutting split pieces.

[Effect]

When a segment sprocket is constructed by dividing a sprocket into M pieces, it becomes difficult to forge and cut if the number of divided pieces M is small, but various problems may occur even if the number of divided pieces is increased, as shown in Fig. 11. As mentioned above, if the number of parts to be divided is doubled, for example, the teeth of the sprocket may have to be divided.

However, by dividing the mold member for forging the segment members without changing the number M of segment members, the shape of the semi-finished product by forging can be improved without causing any particular problems (particularly problems with draft angles). Modification becomes significantly easier, and plastic working can be performed by sandwiching both sides of the tooth.

〔Example〕

Next, an embodiment of plastic working modification of a semi-finished product according to the present invention will be described with reference to FIGS. 1 to 4.

FIG. 1 is a layout diagram schematically showing the state of a semi-finished product 3 before modification by plastic working, but for convenience of reading, the usage of contour lines and hidden lines is not necessarily in accordance with the drafting standard.

As shown in FIG. 4, one semi-finished product 3 is placed between mold A 6 and mold O 7.

Between the above molds A and B are two warikoma 8A and 8.
B is provided. A cross section thereof is shown in FIG.

A slope 8a is formed on the warikoma 8B, and a corresponding slope 6a is formed on the mold shell 6. When a force is applied in the direction of arrow _P3 , the warikoma 8B is moved by the action of the slope. As a result, it receives a force directed to the left in the figure, and is pressed toward the segment/sprocket semi-finished product 3.

9 is a push rod for opening the mold.

3 and 4 show the state in which the segment sprocket 2 of the desired shape has been formed by modification by plastic working.

As shown in Figure 4, the arrow for mold Otsu 7
Due to the pressurizing force _P3 , a forging force as indicated by the arrow _P4 is applied to the split piece 8B. When the segment sprocket 2 is molded, the force of arrow _P5 is applied to the push rod 9 to open the mold.

According to this example (FIGS. 1 to 4), two split pieces 8A and 8B are pressed against one semi-finished product 3, which causes a problem regarding the draft angle of the teeth at both ends. It is possible to modify semi-finished products by plastic working without any problems.

〔Effect of the invention〕

As detailed above, when die-forging a segment sprocket in which the sprocket is divided into M pieces, the number of divided pieces can be made relatively small, and moreover, the teeth located at both ends of the segment can be provided with extra filler. When forming an intermediate product with a shape that is easy to forge, and applying plastic working to the intermediate product to modify it into the desired shape, so that the machining required after forging can be significantly reduced by performing vertical strike forging without any process. When the forging method of the present invention is applied to perform the above correction, the correction can be performed easily and with high precision without the risk of causing problems regarding the draft angle of the sprocket tooth profile.

[Brief explanation of drawings]

FIG. 1 is a schematic layout diagram depicting the state before plastic working in an embodiment of the present invention, FIG. 2 is a cross-sectional view of the above layout diagram, and FIG. Fig. 4 is a schematic layout diagram depicting the state after processing, Fig. 4 is a sectional view thereof, Fig. 5 is an explanatory diagram of a semi-finished product of a segment sprocket, Fig. 6 and Fig. 7 are FIG. 8 is an explanatory diagram of the problem related to the modification of the semi-finished product, FIG. 9 is an explanatory diagram of the sprocket, FIG. 9 is an explanatory diagram of the segment sprocket, and FIG. 10 is an explanatory diagram of forging the segment sprocket. 1
FIG. 1 is an explanatory diagram of problems related to forging a segment sprocket. 1... Sprocket, 2... Segment sprocket, 2a, 2b to 2e... Teeth, 2 _H ... Bolt hole, 2z... Rib, 3... Segment sprocket semi-finished product, 3a, 3b to 3e... teeth, 3
z...Teeth, 4...Upper mold, 4a...Circular groove, 5
... Lower mold, 5a, 5b to 5d ... Tooth surface projection,
6...Mold A, 6a...Slope, 7...Mold B, 8
A, 8B...Warikoma, 8a...Slope, 9...Putshurotsudo.

Claims (1)

[Claims] 1 N×M ribs around the annular rib (however, N
and M are integers of 3 or more) are divided into M pieces in the circumferential direction, and when a segment sprocket having N teeth is forged, the forming target is The ribs have a shape that increases the radius of curvature of the ribs of the segment sprocket, and the teeth at both ends are bent toward the center of the segment and have punched holes on all parts of the tooth surface. In the forging method, the shape of the semi-finished product is modified by plastic working to obtain the desired shape. This is done by using a plurality of splitting pieces that come into contact with the tooth surfaces of the teeth, and the splitting pieces are provided in advance with a sliding surface obliquely intersecting the central axis of the sprocket, and the plastic working mold is A sliding surface corresponding to the above sliding surface is provided, and a force is applied to the split piece in the direction of the center axis of the sprocket, and a force in the radial direction of the sprocket is generated by the action of the sliding surface, A forging method for a segment sprocket, characterized in that the forging force is applied to the semi-finished product in a substantially radial direction by pressing the split piece toward the tooth surface of the segment sprocket with a force of .