JP2012000646A - Sizing apparatus and sizing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a production yield of a sintered component by stabilizing sizing performance by devising a sizing apparatus and reducing variations in correction.SOLUTION: The sizing apparatus includes a step part 6b and a sizing projection 6c on a side surface 6a of a sizing hole 6 of a sizing die 2 of a sizing mold 1. The dimension of a protruding part of a component is corrected by the sizing projection 6c when a sintered component as a sizing target is pushed in the sizing hole 6 and is pushed out. At a position where a bottom surface of the protruding part is pressed against the step part 6b, the sintered component is compressed by an upper punch 3 and a lower punch 4.

Description

  The present invention relates to a sizing device for correcting the dimensions of a sintered part having a convex portion at a corner where the first surface and the second surface intersect, for example, a bearing cap having a convex portion at a corner where the bottom surface and the side surface intersect. And a sizing method using the same.

  Sintered parts are usually a compacting process in which raw material powder is molded in a mold, a sintering process in which a compact obtained through the process is baked and hardened in a sintering furnace, and the dimensions of the part (sintered body) after completion. Manufactured through a sizing process that corrects using a sizing mold.

  The bearing cap is a member that holds a bearing that rotatably supports the crankshaft with respect to the engine block, and is manufactured in cast iron, an iron-based sintered alloy, an aluminum alloy, or the like. In the following description, the sizing of a sintered bearing cap is taken as an example.

  A general sizing device and sizing mold used for sizing the sintered bearing cap (hereinafter simply referred to as a bearing cap) are disclosed in, for example, Patent Document 1 below.

  FIG. 11 shows a sizing mold described in Patent Document 1. In the figure, 2 is a sizing die, 3 is an upper punch, 4 is a lower punch, 5 is a core rod, and 20 is a sintered part (it is a bearing cap in the figure).

  As shown in FIGS. 12 and 13, the bearing cap is formed from above the second surface 22 at a corner where the first surface (bottom surface) 21 and a second surface (side surface) 22 perpendicular to the first surface (bottom surface) 22 intersect. It has the convex part 23 which protrudes to the side (width direction) axisymmetrically.

  The sizing die 2 has a sizing hole 6, and dimensional correction of the convex portion installation portion of the bearing cap is performed by the sizing surface (side surface 6 a) of the sizing hole 6.

JP-A-2005-254252

In order to position the mating product to be combined in the bearing cap, a high dimensional accuracy is required for the convex width W of FIG. However, in the sizing apparatus as disclosed in Patent Document 1, there is a large variation in correction due to the spring back after sizing, and the dimension after correction at the dimension W of the sintered part is not stable.

  An object of the present invention is to devise a sizing device to stabilize the dimension of a convex portion after sizing, thereby reducing defective products having nonstandard dimensions and improving the yield of production of sintered parts. .

  In order to solve the above-described problems, in the present invention, the first surface has a counterbore portion, and the first surface and a second surface perpendicular to the first surface intersect at an angle. Provided are a sizing device for correcting the size of a sintered part having a convex portion protruding in the width direction from the first surface, and a sizing method using the sizing device.

A sizing device provided by the present invention includes a sizing die including a sizing hole, an upper punch, and a lower punch,
The sizing die has, on the side surface corresponding to the second surface of the sizing hole, a stepped portion corresponding to the bottom surface of the convex portion, and a sizing projection protruding inward.
The sizing protrusion is disposed on the entrance side of the sizing hole with respect to the stepped portion and at a position farther from the stepped portion than the dimension in the mold axial direction of the convex portion.

  The amount of protrusion of the sizing protrusion from the side of the sizing hole is preferably about 0.03 mm to 0.05 mm in the sizing of the sintered bearing cap formed of iron-based powder, but is not limited to that value. Absent. An appropriate value may be set in consideration of the material of the sintered part and the sizing conditions.

The sizing method provided by the present invention is implemented using the above sizing apparatus. In this method, the sintered part set on the sizing die with the first surface facing down is pressed with an upper punch into the sizing hole of the sizing die,
In the pushing process, the convex portion is pressed in the component width direction with the sizing projection,
Next, the sintered part is pressed at the position where the convex portion is pressed against the stepped portion, and the upper punch and the lower punch are pressed so that the convex portion is in close contact with the side surface of the sizing hole,
Thereafter, the sintered part is pushed up by the lower punch, and the convex part is again pressed in the part width direction by the sizing projection.

  This method can be suitably used for sizing a bearing cap having a hemispherical counterbore, but the sizing object is not limited to the bearing cap.

  When the sizing target is, for example, a bearing cap, before the sizing, a flat chamfered portion is provided at the corner of the bottom surface of the convex portion due to the shape restriction of the powder molding die.

  Such a bearing cap is required to be rounded in advance because the corner of the convex portion is easily caught by the entrance of the seat when assembled to the engine block.

  According to the sizing method of the present invention, when the sintered part is compressed and deformed by the upper punch and the lower punch, the bottom surface of the convex portion pressed against the step portion is rounded to the corner of the bottom surface by the step portion. By adopting this method, it is possible to eliminate the need for machining for rounding the corners of the bottom surface of the convex portion after sizing.

  According to the sizing mold and the sizing method of the present invention, when the sintered part is pushed into and out of the sizing hole, the projections are respectively pressed by the sizing projections, and correction is performed twice in one cycle. Is done. Of these, the second correction is performed under stable conditions, which stabilizes the post-correction dimensions.

  Sintered parts before sizing have large dimensional variations. Therefore, in the conventional sizing apparatus and sizing method, the sizing conditions (sizing allowance and springback amount after sizing) fluctuate, which causes the post-correction dimensions to vary greatly.

  The present invention solves this problem. This is due to the following mechanism. That is, in the present invention, the sintered part is pressed and deformed with the upper punch and the lower punch at the position where the sintered part is pressed against the stepped part of the sizing hole, and the convex part of the part is brought into close contact with the side surface of the sizing hole. Let

  As a result, the sizing conditions (sizing allowance and springback amount after sizing) in the second correction (secondary correction) in which the part is pushed out from the sizing hole are substantially constant, and the post-correction dimensions are stabilized.

Sectional drawing which shows an example of the sizing apparatus of this invention Sectional view of the sizing die used in the device of FIG. Plan view of the sizing die in FIG. FIG. 2 is an enlarged sectional view of a sizing protrusion provided on the sizing die of FIG. FIG. 2 is a perspective view showing the sizing die of FIG. 2 cut vertically. The figure which shows the state which set sintered parts to the sizing device The figure which shows the state which pushed the sintered part halfway into the sizing hole of the sizing die The figure which shows the state which pressed the sintered part against the level difference part of the sizing hole and compressed it in the mold axial direction with the punch The figure which shows the state which extruded the sintered part after compression from the sizing hole with the lower punch Chart showing the evaluation results of the effectiveness of axial compression after primary correction Sectional view showing an example of a conventional sizing mold Sectional view showing an example of sizing object (bearing cap) 12 is a perspective view of the bearing cap of FIG.

  Hereinafter, embodiments of the sizing apparatus and the sizing method of the present invention will be described. An example of a sizing mold used in the sizing apparatus of the present invention is shown in FIGS. This sizing die 1 performs sizing of the sintered part 20 shown in FIGS. 6 to 9, and includes a sizing die 2, an upper punch 3, and a lower punch 4 opposed to the upper punch 3. The core rod 5 is combined.

  The illustrated sintered component 20 is the bearing cap shown in FIGS. The bearing cap (sintered part 20) has a first surface (bottom surface) 21 and a second surface 22 (side surface) perpendicular to the first surface at a corner intersecting from the second surface 22 at an angle. It has the convex part 23 which protrudes to the side (width direction) symmetrically. The first surface 21 has a semi-circular counterbore 24 in the width direction, and further has a side hole 25 through which a fastening bolt is passed between the first surface 21 and the convex portion 23. Yes. Furthermore, a flat chamfered portion 26 is provided at the corner of the bottom surface of the convex portion 23.

  The sizing die 2 is provided with a sizing hole 6 penetrating in the mold axial direction. The sizing hole 6 has a side surface 6a corresponding to the second surface 22, a step portion 6b corresponding to the bottom surface of the convex portion 23, and a sizing projection 6c characterizing the present invention. The sizing projection 6c provided on 6a pressurizes the convex portion 23 of the sintered part 20 and the projection amount p of the convex portion 23 from the second surface 22 (width direction dimension W of the convex portion installing portion in FIG. 12). Adjust. The side surface 6a is not a sizing surface.

  The sizing protrusion 6c is provided in the middle of the side surface 6a in the mold axial direction, specifically, on the inlet side of the sizing hole 6 with respect to the step portion 6b.

  The sizing projection 6c is provided at a position farther from the step portion 6b than the dimension h of the convex portion 23 in the mold axial direction. Therefore, the sizing protrusion 6c rises gently so that an unreasonable pressure is applied.

  It should be noted that the protrusion amount p1 of the sizing projection 6c from the side surface 6a has a problem that the side hole 25 may be inclined if the value is excessive in the sizing of the bearing cap in FIG. Choose a value that does not cause any problems. In the illustrated mold, the protrusion amount p1 is set to 0.03 mm, but is not limited to this value.

  The dimension L in the mold axial direction (see FIG. 4) of the effective portion (the portion excluding the rising portion from the side surface 6a) of the sizing projection 6c is appropriately about 5 mm.

  The upper punch 3 has a molding surface 3 a for molding the third surface (upper surface) of the sintered component 20. The lower punch 4 has a molding surface 4 a for molding the first surface (bottom surface) 21 of the sintered part 20 and a convex semicircular molding surface 4 b corresponding to the spot facing portion 24.

  The sintered part 20 is provided with a side hole 25 through which a fastening bolt is passed. For this purpose, the exemplary sizing mold 1 includes the core rod 5 that corrects the side hole 25. However, depending on the shape to be sized, the sizing mold 1 does not include the core rod 5.

  The lower punch 4 is supported by a fixed base plate (not shown). The upper punch 3 is an upper punch plate (not shown) driven by an upper ram (not shown) of the press machine, and the sizing die 2 is a yoke plate (these are also driven by a lower ram of the press machine). (Not shown).

Sizing using this sizing device is performed according to the following procedure.
First, as shown in FIG. 6, the lower punch 4 is raised until the molding surface 4 a is substantially aligned with the upper surface of the sizing die 2, and the upper punch 3 is lowered under this condition to contact the lower punch 4. The sintered component 20 is sandwiched therebetween.

  Next, the sintered product 20 is pushed into the sizing hole 6 by the upper punch 3 while maintaining the above-described situation by synchronizing the upper punch 3 and the lower punch 4 and lowering them relative to the sizing die 2 (FIG. 7).

  During the pushing process, the convex portion 23 is pressed in the component width direction by the sizing projection 6c, and primary correction is performed. However, at this stage, the size of the component is not yet stable due to the influence of the variation in the size of the component before sizing.

  Therefore, the relative position of the lower punch 4 and the sizing die 2 is fixed at the position of FIG. 8 where the sintered part 20 is pressed against the step portion 6b of the sizing hole, and the upper punch 3 is further lowered under this condition. The sintered part 20 is compressed in the mold axial direction by the upper punch 3 and the lower punch 4.

  By this compression, a part of the material is deformed to widen the width of the convex portion installation part of the part. And the convex part 23 which is displaced toward the width direction outer side is restrained by the side surface 6a of the sizing hole, and the convex part 23 is brought into close contact with the side surface 6a.

  Thereafter, as shown in FIG. 9, the upper punch 3 and the lower punch 4 are raised relative to the sizing die 2, and the sintered part 20 is pushed out from the sizing hole 6 by the lower punch 4. 23 is pressed again in the component width direction by the sizing projection 6c.

  Since this second pressurization (secondary correction) is performed on the convex portion installation portion whose width is adjusted to be constant by the forming action by the side surface 6a, the sizing allowance in the secondary correction, the springback amount after sizing, etc. The sizing conditions are almost constant, the variation in correction is reduced, and the dimensions of the finished part are stabilized.

  When the sintered part 20 is the illustrated bearing cap, a flat chamfered portion 26 is formed at the corner of the bottom surface of the convex portion 23. According to the method of the present invention, the corner of the stepped portion 6b provided in the sizing hole 6 is formed. It is possible to form a circular arc and press the corners of the bottom surface of the convex portion 23 so that the corners are rounded, and the rounding of the corners of the bottom surface of the convex portion can be realized in the sizing process.

  The sizing die 2 of FIGS. 2 to 5 and the sizing die 2 of FIG. 11 were used for sizing the sintered component (bearing cap) 20 of FIGS.

  2 and 3 of each sizing die 2 are as follows: the sizing hole 6 has a hole width w1 = 104.37 mm, the stepped portion 6b has a hole width w2 = 96.4 mm, and the sizing hole 6 has a hole width. The dimension s = 21 mm in the perpendicular direction, the distance d1 from the hole entrance to the stepped portion 6b = 63 mm, the distance d2 from the hole entrance to the effective portion of the sizing projection 6c = 40 mm, the effective portion of the sizing projection 6c shown in FIG. The mold axis direction dimension L = 5 mm, the protrusion amount p1 of the sizing protrusion 6c = 0.03 mm, and the inclination angle θ of the end of the sizing protrusion 6c = 5 °.

  In the evaluation test, the part after the primary correction is compressed in the mold axial direction, and the applied pressure at that time is varied in increments of 200 kN from 600 kN to 1200 kN. ) Standard deviation was investigated. Measurement of the standard deviation 6σ at each applied pressure was performed with the number of samples n = 10.

  The result is shown in FIG. In FIG. 10, the standard deviation decreases as the applied pressure increases. From this data, it can be seen that compressing the sintered parts after primary correction and performing secondary correction can reduce the variation in post-correction dimensions compared to the case of secondary correction without compression.

  In the data of the example, the fluctuation range of the standard deviation with respect to the standard value is 0.03 mm or less at a pressure of 1000 kN or less. This is because the sintered parts are sufficiently compressed and deformed by sufficient pressure. Therefore, the pressurization performed at the position where the sintered part is pressed against the step portion of the sizing hole obtains the lower limit pressure according to the type and size of the part and applies the pressure higher than the lower limit pressure. It is necessary to carry out the plastic deformation until the portion comes into close contact with the side surface of the sizing hole.

DESCRIPTION OF SYMBOLS 1 Sizing metal mold 2 Sizing die 3 Upper punch 3a Molding surface 4 Lower punch 4a, 4b Molding surface 5 Core rod 6 Sizing hole 6a Side surface 6b Step part 6c Sizing protrusion 20 Sintered part 21 First surface 22 Second surface 23 Convex part 24 Counterbore part 25 Side hole 26 Chamfered part p Protruding protrusion amount h Convex axial dimension L Mold axial direction length w1 of sizing projections W1 Sizing hole width w2 Stepped part Width of the sizing hole Dimension of the sizing hole perpendicular direction d1 Distance from the hole entrance to the stepped portion d2 Distance from the hole entrance to the effective portion of the sizing projection p1 Protrusion amount of the sizing projection θ Inclination of the end of the sizing projection Corner

Claims (4)

The first surface (21) has a counterbore (24), and further protrudes in the width direction from the first surface (21) and the second surface (22) perpendicular to the first surface. A sizing device for correcting the dimensions of a sintered part (20) having a convex part (23),
A sizing die (1) including a sizing die (2) having a sizing hole (6), an upper punch (3), and a lower punch (4),
The sizing die (2) includes a step portion (6b) corresponding to the bottom surface of the convex portion (23) on a side surface (6a) corresponding to the second surface (22) of the sizing hole (6). , Having a sizing protrusion (6c) protruding inward,
The sizing projection (6c) is closer to the entrance side of the sizing hole (6) than the stepped portion (6b) and from the stepped portion (6b) to the convex portion (23) in the mold axial direction. A sizing device placed at a large distance. A sintered part (20) set on a sizing die (2) with the first surface (21) facing downward using the sizing device according to claim 1, with an upper punch (3) Press into the sizing hole (6),
In the pushing process, the convex portion (23) is pressed in the component width direction by the sizing projection (6c), and then the convex portion (23) is pressed against the stepped portion (6b). The sintered part (20) is pressed with an upper punch (3) and a lower punch (4),
Thereafter, the sintered part (20) is pushed up by the lower punch (4), and the convex part (23) is pressed again in the part width direction by the sizing projection (6c).   The method according to claim 2, wherein the sintered part (20) is a bearing cap, and the bearing cap is sized by the sizing device.   The sintered part (20) before sizing has a flat chamfered part (26) at the corner of the bottom surface of the convex part (23), and the sintered part (20) is connected to the upper punch (3) and the lower part. When the punch (4) is compressed and deformed, the bottom surface of the convex portion (23) pressed against the step portion (6b) is shaped so that the corner of the bottom surface is rounded by the step portion (6b). A method for sizing a sintered part according to claim 2 or 3.

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