JP3286092B2 - Straightening device for powder sintered bearing cap - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for straightening a bearing cap formed by a powder sintering method.

[0002]

2. Description of the Related Art Parts used for automobile engines, transmissions, chassis, and the like include powder mixing, molding, and sintering in order to reduce the cost without chips.
Some are formed by a powder sintering method comprising a process.
For example, a bearing cap (hereinafter, referred to as a “cap”) is used.

The cap is mounted on a cylinder block via a crank journal. FIG.
As shown in the figure, the lower surface of the cap (21) is formed so as to penetrate a journal groove (22) having a semicircular cross section which fits tightly with a half circumferential portion of the crank journal. The journal groove (2
On both sides of 2), bolt holes (23) are drilled in a direction perpendicular to the journal groove (22), and on the back surface of the journal groove (22), a thin portion is formed along the direction in which the journal groove (22) extends. A reinforcing overlay (26) is provided protruding. The cap (21) is fastened and fixed to the cylinder block by a bolt inserted into the bolt hole (23) with the mating surfaces (25) on both sides of the journal groove (22) in close contact with the mating surface.

[0004] The powder sintering method has a problem in that a deviation in shape and size (sintering distortion) occurs between the powder compact before sintering and the sintered compact after sintering. For example, in the case of a sintered component having a bridge shape such as a bearing cap, the mating surface (25), which had been on the same plane before sintering, was formed as shown in FIG.
After the sintering, as shown in FIG. This is due to the fact that the powder density near the die wall surface during mixing increases, causing a difference in expansion and contraction depending on the density difference during heating, and the fact that the height dimension of the bearing cap is larger than its bottom area. It is considered based.

The amount of distortion t at this time is about 100 μm, although it slightly varies depending on the size and material of the cap.

If such a sintering strain is left unattended, problems such as poor joining at the mating surface (25) with the cylinder block will be caused. Requires a sizing process. Conventionally, as shown in FIG. 12, after sintering is completed, the cap (21) is sandwiched between the upper punch (30) and the lower punch (31) and pressed, or as shown in FIG. While the side surface of (21) is constrained by a die (32), the upper and lower punches (30) and (31) are pressurized to correct both mating surfaces (25) into a flat shape.

[0007]

The straightening device shown in FIG. 12 has an advantage that the structure can be simplified because no die is required, but since the side surface of the cap (21) is not restrained, There is a problem that the cap (21) is deformed in a random direction by a compressive load (see the left side of FIGS. 14A to 14C). When the cap (21) is deformed in this way, even if both the mating surfaces (25) are flattened by pressing, the cap (21) springs back when unloading, and the mating surface (25) is deformed again. To form an inclined surface (see the right side of FIGS. 14A to 14C).

On the other hand, the straightening device shown in FIG. 13 is not deformed because the outer surface of the cap (21) is restrained by the die (32), but has a complicated structure.
There is a drawback that the mold cost is increased and the manufacturing cost is increased.

Accordingly, an object of the present invention is to provide a straightening device capable of stably and reliably correcting sintering distortion with a simple structure.

[0010]

In order to achieve the above object,
The device of the present invention is a journal that fits tightly with a crank journal.
Formed on both sides of the journal groove and the journal groove.
Bridge-shaped bear with mating surface that is in close contact with the lock
The shape of the ring cap that has been changed to a C shape by sintering
It is intended to correct the sloping surface.
It is arranged a pair of punches movable in the spacing direction, base
In an apparatus for performing dimensional correction by sandwiching the aligning cap between the pressing surfaces of both punches, one of the pressing surfaces of both punches is spaced from the pressing surface of the both punches in a direction approaching the opposing punch. Is provided with a pair of tapered surfaces gradually widened, and a pair of flat surfaces
Is a pair of tapered surfaces is gradually widened the gap in a direction approaching the other side punch, the bearing cap case
Contact the outer corner of the contact surface with the flat or tapered surface
Allowed is characterized in was Rukoto.

[0011]

A pair of tapered surfaces whose intervals are gradually widened toward the direction approaching the opponent punch are provided on one of the pressing surfaces of both punches, and the other is flat or the other is opposing. When a pair of tapered surfaces whose widths are gradually widened toward the direction approaching is provided, a part of the pressing force applied to the sintered component through this tapered surface is parallel to the tapered surface and directed toward the inner diameter side. It is converted to the constraint force P _t (see FIG. 3). Since the deformation of the sintered component is prevented by the restraining force, the sintering distortion can be reliably corrected without disposing the die on the outer diameter side.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a first embodiment of a straightening device according to the present invention. The straightening device comprises a lower punch (1) fixed to a stationary member (not shown) and an upper punch (3) mounted on a ram plate (2) that moves up and down.

At the center of the pressing surface (5) of the upper punch (3), a concave groove (6) for accommodating the build-up portion (26) of the cap (21) is formed in a direction in which the journal groove (22) extends. That is, the axial direction of the crank journal (hereinafter, this direction is simply referred to as the "axial direction").
). The pressing surfaces (5) located on both sides of the concave groove (6) are located on the same plane so as to be able to adhere to the upper surface of the cap (21).

A pair of tapered surfaces (9) are provided along the axial direction on the pressing surface (7) of the lower punch (1) (FIG. 2).
(See the plan view of (a)). The two tapered surfaces (9) are formed such that the width increases as the distance between them increases, that is, in the direction approaching the upper punch (3). The shape of the tapered surface (9) is arbitrary as long as the outer corners (25a) of both mating surfaces (25) come into contact with the tapered surface (9), and as shown in FIG. ) May have a structure in which the center of the upper surface is depressed and an annular tapered surface (9 ′) is provided around the center.

In the apparatus according to the present invention, a correcting operation is performed in the following procedure.

First, an upper punch (3) and a lower punch (1)
Between the two pressing surfaces (5) and (7), the mating surface (25) is brought into contact with the tapered surface (9) of the lower punch (1), and the sintered cap (21) is sandwiched. Next, the ram plate (2)
And lower the upper and lower punches (3) and (1) with caps (2
1) is pressed to correct the mating surface (25: indicated by a two-dot chain line) deformed into a U shape as shown in FIG. 3 (shown by a solid line). At this time, as shown in FIG. 3, the cap (21) acting tapered surfaces (9) parallel to the direction of the component force (P _t) is inwardly, the cap (21 This component force (P _t) ) Since the whole is constrained inside, the cap (21) under pressure is smoothly corrected without being deformed.

FIGS. 4A and 4B show another embodiment of the present invention. 1A, the pressing surface (7) of the lower punch (1) is a flat surface and the upper punch (3) is opposite to FIG.
Is provided with a tapered surface (9) on the pressing surface (5).
In this case, the tapered surface (9) is formed so that the width thereof increases in the direction (downward) approaching the lower punch (1). On the other hand, FIG. 4 (b) is a combination of the structures of FIGS. 1 and 4 (a), wherein both the pressing surfaces (5) and (7) of the upper punch (3) and the lower punch (1) have tapered surfaces (5). 9) is provided. In any structure, a capping force (P _t ) acts on the cap (21) inward with pressurization, so that the cap (21) is surely prevented from being deformed similarly to the device shown in FIG. be able to.

Hereinafter, an experiment for confirming the effect of the present invention was conducted, and the results are shown in FIGS. 5 and 6.

In this experiment, the taper angles of the upper punch (3) and the lower punch (1) (tan α = a [mm] / b [mm], tan β = c [ mm] /
d [mm]: see FIG. 7) and pressurized at a predetermined pressure, and the flatness (tan γ) on the mating surface (25) after pressurization.
= E [mm] / f [mm]: see FIG. 8) and its distribution was examined. In this experiment, not only the flatness (tan γ) of the mating surface (25) but also the parallelism (ta
n δ = g [mm] / h [mm]: See FIG. 9) (the experimental results are shown on the right side of the flatness distribution diagram). The parallelism (tan δ) was added to the measurement object because the flatness (tan δ)
Even if γ) is within the specified value, unless the bolt bearing surface is parallel, the bolt head is in one end and a predetermined tightening torque cannot be obtained.

In the figure, X and Y represent flatness (tan), respectively.
γ) and the parallelism (tan δ). That is, the flatness and parallelism of the product must be smaller than the standard values (X, Y). In this experiment, as an example, the standard values are set to X = 0.04 and Y = 0.09. N represents the number of samples, and ● represents a simple average of the measured values. FIG. 5 shows an experimental result for a cap having a small width, and FIG. 6 shows an experimental result for a cap having a large width.

From FIGS. 5 and 6, if one of the upper punch (3) and the lower punch (1) is provided with a taper angle, both taper angles are set to 0 (tan α = 0 / 21.75, tan β
= 0 / 21.75), it can be understood that at least the flatness (tan γ) can be improved. Therefore, according to the device of the present invention, the mating surface (25) can be corrected more stably and reliably than the conventional device shown in FIG. In addition, in order to satisfy not only the flatness (tan γ) but also the parallelism (tan δ), in the case of a cap having a small width (see FIG. 5),

The combination of tan α = 0 / 21.75 and tan β = 0.05 / 21.75, and for a cap having a large width (see FIG. 6), tan α = 0 / 21.75, tan β = 0.02 / 21.75 tan α = 0.05 It can be understood that the combination of /21.75, tan β = 0 / 21.75, tan α = 0.1 / 21.75, and tan β = 0 / 21.75 is good.

As described above, the taper angle of the tapered surface (9) must be determined in consideration of not only the material and dimensions of the cap (21) but also the parallelism (tan δ).

[0025]

[0026]

As described above, according to the present invention, when pressurized by the upper and lower punches, a restraining force can be applied inward, so that the sintered component does not deform due to the pressurization. Therefore, the correction work can be performed more stably and accurately than the conventional apparatus shown in FIG. Further, since there is no need to restrain the outer peripheral surface of the sintered part with a die or the like at the time of pressing, the structure can be simplified as compared with the conventional apparatus shown in FIG. 13, and the manufacturing cost can be reduced by reducing the number of molds used. Reduction can be achieved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of the device of the present invention.

FIGS. 2A and 2B are plan views of a lower punch. FIG. 2A shows tapered surfaces arranged in two rows, and FIG. 2B shows a tapered surface provided in an annular shape.

FIG. 3 is a front view of a cap and a lower punch during pressurization.

4A and 4B are front views showing another embodiment, in which FIG. 4A shows a case where a tapered surface is provided only on an upper punch, and FIG. 4B shows a case where a tapered surface is provided on both upper and lower punches. Show.

FIG. 5 is a diagram showing experimental results.

FIG. 6 is a diagram showing experimental results.

FIG. 7 is a front view of an upper punch and a lower punch.

FIG. 8 is an enlarged sectional view of a side of a cap on a journal groove.

FIG. 9 is a cross-sectional view of one side of the cap.

FIG. 10 is a front view of a cap before sintering.

FIG. 11 is a front view of the cap after the completion of sintering.

FIG. 12 is a longitudinal sectional view of a conventional device.

FIG. 13 is a longitudinal sectional view of a conventional device.

FIG. 14 is a front view showing a deformed cap (left side) and a spring-backed cap (right side).

[Explanation of symbols]

 1 Lower Punch 3 Upper Punch 5 Pressing Surface of Upper Punch 7 Pressing Surface of Lower Punch 9 Tapered Surface 21 Bearing Cap (Sintered Parts)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-168225 (JP, A) JP-A-3-155416 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22F 3/24 101

Claims (1)

(57) [Claims] 1. A journal closely fitting with a crank journal.
Formed on both sides of the journal groove and the journal groove.
Bridge-shaped bear with mating surface that is in close contact with the lock
The shape of the ring cap that has been changed to a C shape by sintering
It is intended to correct the sloping surface.
It is arranged a pair of punches movable in the spacing direction, base
A device for correcting the dimensions of the punch by sandwiching the aligning cap between the pressing surfaces of both punches, wherein one of the pressing surfaces of both punches is spaced from the pressing surface of the other punch in a direction approaching the opposing punch. progressively provided with a widened pair of tapered surfaces were provided a pair of tapered surfaces gradually by widening the gap in a direction to approach the pair of flat, or the mating punch to the other, the outer mating surface of the bearing cap Corner
Properly the correction device powder sintering bearing cap, characterized in Rukoto brought into contact with the tapered surface.