JPH0771720B2 - Single-joint crankcase core - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a crankcase core used for casting a cylinder block, and more particularly to an integrally joined crankcase core formed by a cold box molding material.

(Prior Art) A crankcase core used when forming a cylinder block of an engine includes molding parts such as a crank chamber, a cylinder cavity, and a cylinder side end cavity, and a crank bearing forming portion for crankshaft pivot support. Equipped with.

Such a crankcase core often has a complicated shape, and in particular, in the case of a V6 cylinder engine, it is necessary to previously prepare a plurality of divided cores.

For example, as shown in FIG. 7, in the case of making a crankcase core using the cold box method, the central part of the crank chamber, the central crank bearing forming part, and the integrally joined central core 1 as a cylinder molding part are prepared in advance. Is created using the cold box method. Then, separately, a pair of front and rear end joining cores 2 as both molding parts of both end portions of the crank chamber and end projecting cavities projecting from this to the cylinder projecting side,
3 is formed. Both the joining surfaces of the integrally joined central core 1 and the front and rear end joined cores 2 and 3 are manually joined and used.

In this case, in order to ensure the relative positional accuracy, the mating baseboard portions 6 and 7 may be formed on the front and rear joint surfaces 4 and 5 of the integrally jointed central core 1.

(Problems to be Solved by the Invention) However, an error in dimensional accuracy is apt to occur in the core-integrated assembling by the manual work, and it takes time to transport the plurality of cores.

An object of the present invention is to provide an integrally joined crankcase core in which all members constituting the crankcase core are integrally joined by a cold box method.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention provides a pair of longitudinal end portions of the crank chamber and end protruding cavities protruding from the both end portions toward the cylinder protruding side. An end-bonded core,
A joining core for forming a crank bearing disposed between the pair of end joining cores, and the pair of end joining cores and the joining core that form the crank chamber and the cylinder cavity. A crank chamber molding part integrally joined by a cold box molding material, and a concave portion which is respectively formed on the outer wall surfaces of both ends in the longitudinal direction of the pair of end joining cores and which is integrally filled with the cold box molding material. It is characterized by having.

According to a second aspect of the present invention, in the integrally joined crankcase core according to the first aspect of the present invention, at least one outer wall surface of the pair of end joint cores is a plane perpendicular to the center line of the crank chamber. The feature is that a gradient is provided.

(Operation) In the present invention, the crankcase core integrally joins all the hollow molding parts on the crankcase side simultaneously by the cold box method, and in particular, a pair of end joint cores that are a part of the hollow molding part. Since the cold box molding material is filled into the outer wall surface including each of the concave portions, the one-piece joining of the pair of end joining cores and the other constituent members is firmly and surely performed.

In particular, if at least one outer wall surface of the pair of end joining cores is provided with a gradient with respect to a surface orthogonal to the center line of the crank chamber, the pair of end joining cores are automatically positioned in the longitudinal direction during mold assembly. Can be done accurately.

(Embodiment) FIG. 1 shows an integrally joined crankcase core (hereinafter simply referred to as a crankcase core) as an embodiment of the present invention. This crankcase core is a cylinder molding unit 1 for molding a cylinder cavity of a V-type 6-cylinder engine (not shown).
0, bearing molding parts 11, 12, 13, 14 for molding a crank bearing that pivotally supports the crankshaft at the lower part of the cylinder block, both ends in the longitudinal direction A of the crank chamber, and the cylinder protruding side from these both ends (in FIG. 1, End protruding cavity molding part (hereinafter simply referred to as end cavity molding part) that molds the end protruding cavity (air bleed or oil flow down passage, etc. used as other) protruding to the upper side 15,16 A crank chamber molding unit 17 that covers the entire crank chamber is provided. It should be noted that the term "end cavity" as used herein refers to a cavity located further outside the cylinder molding cavity located at both ends of the crankcase core in the longitudinal direction A, and the cavity is an end cavity. Molding part 15,16
Have a relationship of molding.

The two bearing molding parts 12 and 13 in the center are formed by a cold box method or a shell molding method before forming the crankcase core, and each pair of joining cores c, d, e, f
Is formed by.

As shown in FIG. 2, the jointing core for the bearing is each two plate-like bodies extending in a direction (plane direction of the paper surface) orthogonal to the longitudinal direction A, and these are as shown in FIG. Bearing space
It is used by bringing the mating surfaces 19, 19 with 18 removed into close contact. In this case, the mating surfaces 19, 19 secure the adhesive force by the tabs 9, and are normally kept within a gap of 0.3 [mm].

The front and rear end bearing molding parts 11 and 14 and the front and rear end cavity molding parts 15 and 16 are each manufactured by a cold box method or a shell molding method prior to the molding of the crankcase core. It is formed by a pair of front and rear end joining cores a, b, g, h. Each of these end joining cores is also a plate-shaped body of two sheets each extending in the direction orthogonal to the longitudinal direction A, and the tabs (same as in FIG. 3) hold the close contact of each mating surface, and the bearing cavity is formed. The gap between the removed mating surfaces is kept within 0.3 mm.

Of these, the front and rear end joint cores b and g have almost the same shape as the joint cores c, d, e, and f for the bearing, and other than this, that is, the front,
As shown in FIG. 2, the rear end joining cores a and h have a relatively large thick plate shape (only a is shown). In particular, the outer wall surface 20 has a vice-type joining line 11 that intersects the center line 1 of the crankcase core in the up-down direction as a ridge line, and has a gradient α (the first angle) that reduces the thickness of the core toward the left and right. 6 (see FIG. 6A). Moreover, the outer wall surface 20 is formed with a fixed groove 21 as a concave portion centered on the vise-type joining line 11 to a predetermined height position (in FIG. 2) from the lower end. The fixing groove 21 is filled with molding sand described later.

The crank chamber molding part 17 is formed by cold box molding sand (hereinafter simply referred to as molding sand) by the cold box method, which doubles as an integral joint of the cylinder molding part 10 and other members. This part is used for molding the inner space of the crankcase and surrounds and fixes the outer peripheral wall surfaces of the front and rear end joint cores a, b, g, h and the joint cores c, d, e, f. That is, it causes a hugging effect, and in particular, by filling the fixing groove 21,
The front and rear end joint cores a, b, g and h are strengthened in the joint strength. Moreover, the upper ends (in FIG. 1) of the joining cores b, c, d, e, f, g are integrally formed continuously on the cylinder molding part 10 side, and the cylinder molding part side and the crank chamber Molding department
The connection strength with the 17 side is sufficiently secured.

The mold used for the cold box method is shown in FIGS. 5 (a) and 5 (b). This mold includes an upper mold 22, a pair of vice molds 23 as a lower mold, a fixed mold 24, and a mandrel 25.
Consists of. The fixed mold 24 is fixed on a lower mold mounting frame 26, and is housed in a mold 27 having an upper opening on the lower mold mounting frame.
A drive cylinder 28 is attached to the lower part of the lower mold mounting frame 26, and the mandrel 25 is supported by the cylinder so that the mandrel 25 tilts and slides in the vertical direction.

The pair of vise dies 23 are supported by a pair of drive cylinders 29 mounted on the outer wall surface of the mold 27 so that they can come into contact with and separate from each other, and are slidably arranged in the mold 27.

The upper die 22 has a plate-like shape, is disposed in close contact with the upper edge of the mold 27, and a plurality of fixed mandrels 30 are attached to the lower surface thereof. Moreover, the upper mold 22 is formed with the molding sand and the hardening gas blowing hole 31. This fixed mandrel consists of a pair of splicing cores b, c, d, e and f,
Positioning can be performed so that the intervals between g are proper values.

Here, a method of molding the crankcase core will be described along with each step.

First, each joining is performed manually or automatically (an example of which is disclosed in Japanese Patent Laid-Open No. 59-147744) on the lower mold side in the mold open state (the state where the vise mold 23 is released). Core a,
Perform core installation work to mount b, c, d, e, f, g, h.

The joining cores used here are individually molded in advance by molding sand based on the cold box method, and the front end joining cores a and b, the rear end joining cores g and h, and the two bearings Bonded core
The c, d and e, f are placed on the fixed mold 24 in a state of being integrally joined by the action of the tabs 9. Reference numeral 32 in FIG. 6 indicates a pin that can be inserted into the positioning hole on the joining core side, and this pin is provided on the fixed mold 24.

Next, the lower die setting step is started, in which the driving cylinders 28 and 29 are actuated to join the pair of vise dies 23 to each other, and the mandrels 25 are thrust into the vice dies 23.

In this case, the end joint surface 231 of the pair of vise molds 23 is the outer wall surface 2
It is formed so as to maintain the same gradient α as that of 0, and when the vise die 23 is butted, this end joint surface 231 has front and rear end joint cores.
Functions to position a and h in the longitudinal direction A. At the same time, as shown in FIG. 6 (a), a portion S for mutually fitting with the vise mold 23 on both ends of the front and rear end joining cores in the width direction B.
By this, at the end, the position is automatically determined with respect to the case die, and the positional accuracy in the A and B directions is improved and reliability is secured.

Next, in the upper and lower mold setting process, the upper and lower molds on the cold box core molding machine (not shown) are joined and the inside of the mold 27 is sealed. At this time, fixed mandrel 30
Rush into the pair of vise dies 23. Moreover, in the fixed mandrel 30, a plurality of positioning surfaces 301 on the lower end surface of the fixed mandrel 30 are brought into contact with the upper end positioning surfaces of the respective joining cores b, c, d, e, f, g, and the intervals between these joining cores are set. It works to secure a predetermined value.

Next, a molding sand blowing step is started, in which molding sand is blown from the molding sand supply device side (not shown) into the molding cavity in the mold through the blowing hole 31. At this time, the crank chamber molding part 17 shown in FIGS. 6 (b) and (c) and the cylinder molding part 10 shown in FIG.
Is filled with molding sand.

This molding sand is used within the pot life not exceeding 120 minutes after mixing two liquids, Part I (phenol resin) and Part II (polyisocyanate), which are commonly used in the cold box method, with sand. .

Next, in the gassing process, a hardening gas is supplied from a hardening gas supply device (not shown) into the molding sand through the blowing hole 31. This curing gas is triethylamine which is commonly used in the cold box method, which causes a chemical reaction by Part I, Part II and triethylamine in the molding sand to form a urethane resin, which acts as a binder and the molding sand Each bonded core a, b, c, d, e, f,
g, h, the cylinder molding part, and the crank chamber molding part 17 are integrally joined.

After this, the mold opening process of the upper and lower molds is performed, in which the reverse operation to the mold clamping is performed, and the hardened crankcase core as shown in FIG. Which is used for casting cylinder blocks.

In addition, in the above-mentioned place, you may perform the manual molding sand filling process instead of the molding sand blowing process.

As described above, in the crankcase core shown in FIG. 1, since the void molding parts on all crankcase sides are integrally joined simultaneously by the cold box method, the relative positional accuracy between the molding parts can be relatively enhanced. it can.

Moreover, it is used as an integral crankcase core during the cylinder block casting process, and is relatively easy to carry because it is a single article.

In particular, when the fixed groove 21 is formed in the end joining core a, h, the hugging effect of the molding sand filled in this portion is enhanced,
The coupling force with the crank chamber molding part side can be further strengthened.

Furthermore, when a gradient α is formed on the outer wall surface 20 of the front and rear end joining cores a and h, the positioning in the longitudinal direction A is automatically performed. The structure on the lower die side can be simplified without the need for an operating sliding block.

(Effect of the invention) The crankcase core is integrally joined at the same time by the cold box method to all the hollow molding parts on the crankcase side,
In particular, since the outer wall surface including the concave portions of the pair of end joining cores that are part of the void molding portion is integrated in the crank chamber molding portion where the cold box molding material is solidified, the pair of end joining members is joined. The core and the other hollow molding portion are integrally and firmly joined together. Therefore, it is possible to enhance the relative positional accuracy between the hollow molding parts, improve the dimensional accuracy of the product formed by casting the cylinder block, and convey the crankcase core and move it into the casting mold. Is easy to install,
There is an advantage that the working process during casting is simplified.

In particular, when a gradient is formed on the outer wall surfaces of both ends in the longitudinal direction of the end joining core, positioning in the longitudinal direction can be automatically performed with high accuracy, and a member for positioning can be omitted, which simplifies the core molding machine. And cost can be reduced.

[Brief description of drawings]

FIG. 1 is a sectional view of a crankcase core as an embodiment of the present invention, FIG. 2 is a side view of the same core, and FIG. 3 is an enlarged sectional view of a tab formed with the same core. FIG. 5 is an enlarged front view of the joining core, FIG. 5 (a) is a schematic side sectional view of a mold for molding the core, and FIG. 5 (b) is a schematic plan view of the mold, FIG. a) is a schematic plan sectional view in the mold of the same core,
FIG. 6 (b) is a schematic front sectional view of the same core, and FIG. 6 (c).
Shows a schematic side sectional view of the core, and FIG. 7 shows a sectional view of a conventional crankcase core. 10 …… Cylinder molding part, 11,12,13,14 …… Bearing molding part, 1
5,16 …… End cavity molding part, 17 …… Crank chamber molding part, 20
…… Outer wall, 21 …… Fixed groove, α …… Slope, a, b, g, h ……
End joining core, c, d, e, f …… Joining core, l …… Center line, l
1 ... Vise type joining line, A ... longitudinal direction, B ... width direction, S ... fitting part.

Claims (2)

[Claims] 1. A pair of end joint cores, which form both end portions in the longitudinal direction of the crank chamber and end protrusion cavities protruding from these end portions toward the cylinder protrusion side, and between the pair of end joint cores. And a crank chamber in which the crank chamber and the cylinder cavity are formed and the pair of end joining cores and the joining core are integrally joined by a cold box molding material. An integrally joined crankcase core having a molding portion and concave portions respectively formed on the outer wall surfaces of both ends in the longitudinal direction of the pair of end joining cores and integrally filled with the cold box molding material. 2. An outer wall surface of at least one of the pair of end joining cores is provided with a slope with respect to a plane orthogonal to the center line of the crank chamber.
The integrally joined crankcase core described in the item.