JP7484611B2 - Casting Equipment - Google Patents

Description

The present invention relates to a casting device that forms a casting passage in a cast product.

To form a linear passage in a product, it is known to use a core pin provided in each of a pair of opposing dies, as disclosed in Patent Document 1, for example.

In this case, molten metal is poured into the mold with one core pin butted against the other core pin, and a cavity is formed at the position of the core pin that was removed when the mold is opened, forming a straight passage in the product.

To form a straight passage with precision, the core pins must be biased against each other with a certain amount of force before pouring. For this reason, a spring is provided on the base end of at least one of the core pins.

Japanese Utility Model Application Publication No. 6-048949

If the spring constant of the spring that biases the core pins together is low, the spring must be significantly deformed to obtain sufficient butting force when the mold is closed, which results in an increased amount of backward displacement of the core pins, leading to an increase in the size of the mold that houses the core pins. The spring constant must be set to an appropriate value.

On the other hand, after the mold is closed, the force acting on the core pins due to their thermal expansion during pouring is added to the butting force between the core pins. If the spring constant of the spring is set to obtain sufficient butting force when the mold is closed, there is a risk that the compressive force acting on the core pins will be too high. In particular, when forming a long passage in the product, the overall length of the core pins will be long, and the core pins will stretch significantly due to thermal expansion. As a result, the compressive force acting on the core pins will exceed the buckling load, and there is a risk that the core pins will buckle when pouring.

Furthermore, if the core pin buckles, the passage formed in the product will bend, and the core pin may not be able to be removed when the mold is opened. This may also cause problems with machining after casting.

Therefore, there is room for improvement in setting the spring constant of the spring that biases the core pin described in Patent Document 1.

In other words, a mechanism is required that ensures the relatively large butt force required when clamping the mold, while preventing the butt force from becoming too large when pouring molten metal.

The inventors of the present invention conducted extensive research to solve the above problem, and as a result, came up with a mechanism that changes the spring constant when the mold is closed and the spring constant after the mold is closed. More specifically, the inventors of the present invention came up with a mechanism that can realize the relatively large spring force required when the mold is closed and suppress the increase in the spring force required when pouring molten metal by making the spring constant when the mold is closed larger than the spring constant after the mold is closed.

That is, the present invention provides a first die having a first core pin for forming at least a part of a core passage in a cast product;
a second die having a second core pin that is abutted against the first core pin; and
a biasing portion that is provided in the first mold and biases the first core pin toward the second core pin when the first mold and the second mold are in a mold clamped state,
The first mold is
a first cylinder portion that opens to an end surface of the first die and extends in a direction of an axis of the first core pin and the second core pin;
a second cylinder portion that is continuous with the first cylinder portion and that houses the biasing portion,
the first core pin has a base end portion accommodated in the second cylinder portion and a main body portion continuous with the base end portion, penetrating the first cylinder portion and protruding from the end face of the first die toward the second core pin, the first core pin being held by the first cylinder portion and the second cylinder portion so as to be reciprocatable in the direction of the butt axis,
the biasing portion includes a first elastic body and a second elastic body that are disposed adjacent to a base end portion of the first core pin in series in the direction of the butt axis and that impart an elastic restoring force to the first core pin when the first elastic body and the second elastic body are compressed and deformed in the direction of the butt axis,
The biasing portion also includes:
A first holding member in contact with one end of the first elastic body; and
a second holding member having a holding portion that contacts the other end of the first elastic body and holds the first elastic body between itself and the first holding member, and a support portion that extends from the holding portion to hold the first elastic body and support the first holding member so as to be reciprocatable in the direction of the butt shaft;
The support portion of the second holding member is formed with a long hole portion extending in the direction of the butt shaft,
a stopper pin is fixed to the first retaining member, the stopper pin extending in a direction perpendicular to the butt axis, and configured to be inserted into the elongated hole portion and reciprocate along the elongated hole portion in the direction of the butt axis, and the first retaining member reciprocates in the direction of the butt axis between a first position and a second position in which a length of the first elastic body is shorter than when the first retaining member is in the first position, within a range in which the stopper pin engages with the elongated hole portion;
The position of the elongated hole is set so that the length of the first elastic body when the first holding member is in the first position is shorter than its natural length.

According to this configuration, the long hole portion is formed so that the length of the first elastic body when the first holding member is in the first position is shorter than its natural length, and the first elastic body is compressed and held by the first holding member and the second holding member at a predetermined load. In other words, if a load equal to or greater than a predetermined load is applied to the first elastic body held between the first holding member and the second holding member, the first elastic body is compressed, but if the load is less than the predetermined load, the first elastic body is not compressed. If the load applied to the first elastic body from the first cast pin is less than the predetermined load, the first elastic body moves in the direction of the butt axis together with the first holding member and the second holding member without being compressed.

When the first and second dies are clamped together, the first core pin butts against the second core pin, and the first core pin is displaced backward and applies a load of less than a predetermined load to the biasing portion. As described above, the first elastic body moves integrally with the first and second holding members. As a result, only the second elastic body arranged in series with the first elastic body undergoes compressive deformation, and only the second elastic body applies an elastic restoring force to the first core pin. If the spring constant of the second elastic body is set to an appropriate value so that a large elastic restoring force is generated in response to the displacement of the first core pin, the first core pin can be biased with a sufficient magnitude, and a large butting force between the first and second core pins can be ensured when the dies are clamped.

When the clamping of the first and second dies progresses and the load applied to the biasing portion from the first core pin reaches or exceeds a predetermined load due to the first core pin being further displaced backward, the second elastic body undergoes compressive deformation and the first elastic body also undergoes compressive deformation. As both the first and second elastic bodies arranged in series undergo compressive deformation, the spring constant of the biasing portion including the first and second elastic bodies changes.

The amount of backward displacement of the first core pin can be distributed between the first elastic body and the second elastic body, so that even if the amount of displacement increases, the increase in the load applied to the first core pin can be reduced.

After the first and second dies are clamped and molten metal pouring has begun, the first core pin and/or the second core pin are further displaced backward due to thermal expansion of the first core pin. Even at this time, the biasing portion receives the amount of backward displacement of the first core pin in a distributed manner between the first elastic body and the second elastic body, so that the increase in biasing force can be kept small even if the amount of displacement increases. The load applied to the first core pin and/or the second core pin can be kept below the buckling load.

Therefore, in the casting device of the above configuration, when the first core pin and the second core pin are butted together, the two core pins are butted together with sufficient butting force, and by reducing the increase in the biasing force on the first core pin relative to the amount of elongation of the first core pin and the second core pin due to thermal expansion when forming the cast product after pouring, the biasing force applied to the core pin can be suppressed to a range below the buckling load, thereby suppressing buckling of the core pin.

Here, the increase rate of the load relative to the amount of displacement of the second elastic body is defined as the first load characteristic, and the increase rate of the load relative to the amount of simultaneous displacement of the first elastic body and the second elastic body is defined as the second load characteristic, and the details will be explained.

The first load characteristic is greater than the second load characteristic. By arranging two elastic bodies in series to exert the first and second load characteristics, the core pin is supported with an appropriate butting force when butting together, even if the core pin is long, and buckling caused by a sudden increase in butting force due to an increase in the amount of thermal expansion in the extension direction of the core pin can be suppressed during molding after pouring.

In addition, it can absorb not only the thermal expansion of the core pin, but also variations in the gap between the dies, the expansion of the dies during molding, and the amount of displacement caused by opening the dies during molding. In addition, the first load characteristic acts to return the first core pin to its initial position when the molded casting is removed from the die, and even if molten metal enters the first cylinder portion of the first die, it has the effect of pushing out the molded product.

the first elastic body is disposed at a position close to a base end of the first core pin, and the second elastic body is disposed at a position away from the base end of the first core pin,
the second cylinder portion has a contact surface that expands in a direction intersecting the butt axis and contacts the other end of the second elastic body,
The length of the second cylindrical portion may be set so that, when the biasing portion is housed inside the second cylindrical portion, the length of the second elastic body is shorter than its natural length.

According to this configuration, when the biasing portion is incorporated into the second cylinder portion of the first mold, the second elastic body is compressed between the second holding member and the abutment surface of the second cylinder portion. Before the first mold is closed, the elastic restoring force of the second elastic body is imparted to the first core pin, and the first mold can hold the first core pin without tilting it. When the first mold and the second mold are closed, the first core pin and the second core pin can be butted with high precision on the butt axis, and the core passage can be formed with high precision.

In addition, by setting the length of the second cylinder so that the biasing force of the second elastic body before the first mold is closed is less than the specified load that compresses and holds the first elastic body, when the first core pin and the second core pin are initially butted together, only the second elastic body is compressed by the backward displacement of the first core pin, increasing the biasing force on the first core pin with a small amount of displacement and ensuring the butting force.

The compressive load applied to the first elastic body by the first holding member and the second holding member before the first mold and the second mold are closed may be greater than the load applied to the biasing portion through the first core pin at the start of mold closing, and less than the load applied to the biasing portion through the first core pin at the end of mold closing.

By doing this, when the mold closing starts, only the second elastic body undergoes compressive deformation, and only the second elastic body can apply a biasing force to the first core pin. Thereafter, as the mold closing progresses and ends, both the second elastic body and the first elastic body undergo compressive deformation, and both the second elastic body and the first elastic body can apply a biasing force to the first core pin.

Therefore, when the first core pin and the second core pin are butted together, the biasing force of the biasing part against the backward displacement of the first core pin can be increased, and after the first core pin and the second core pin are butted together, until the mold is opened, the biasing force of the biasing part against the backward displacement of the first core pin can be decreased.

Furthermore, in the casting device of the present invention, the first elastic body and the second elastic body are coil springs.

With this configuration, two coil springs are arranged in series to provide two load characteristics. By changing only the combination of the two load characteristics without changing the storage space for the coil springs housed in the first mold, it becomes easy to set the butt load and the amount of displacement due to thermal expansion to match the length of the core pin.

By optimizing the load characteristics by combining coil springs, it is no longer necessary to change the storage space for the coil springs according to the length of the core pin in the first mold that forms the core passage by combining coil springs according to the length of the core pin. In addition, by taking advantage of the fact that the axial center of the coil spring is hollow, it becomes easy to supply piping for cooling water to the cooling passage at the axial center of the core pin, as described below.

Furthermore, in the casting device of the present invention, the second core pin is fixed to the second mold, and the length of the first core pin is shorter than the length of the second core pin fixed to the second mold.

According to this configuration, the first core pin is supported so as to be capable of reciprocating relative to the first die, and therefore the first core pin is prone to tilt relative to the first die. In other words, the first cylinder section provided in the first die needs to have an appropriate clearance, taking into account the thermal expansion of the first core pin in the radial direction and the thermal contraction of the first cylinder section, and further, in order to reduce sliding resistance, it is preferable to set the support width of the first cylinder section to be short. At this time, the first core pin has a larger amount of positional deviation of the tip due to inclination than the second core pin fixed to the second die, so by making the length of the first core pin shorter than that of the second core pin, the amount of positional deviation of the tip of the first core pin from the first straight line due to inclination can be reduced. Therefore, it is possible to butt the core pins while minimizing the deviation of the butt positions of the first core pin and the second core pin.

Furthermore, in the casting device of the present invention, the tip of the first core pin is convex or concave, and the tip of the second core pin is concave or convex to engage with the tip of the first core pin, and when the first core pin and the second core pin are butted together, a gap is formed between the top of the convex shape and the valley of the concave shape.

With this configuration, when the first core pin and the second core pin are butted together, the tip of the first core pin and the tip of the second core pin are engaged with each other and aligned in a straight line, preventing the tips of the first core pin and the second core pin from misaligning. In addition, a gap is formed between the convex and concave portions after the first core pin and the second core pin are butted together. By providing this gap, the thermal expansion of the concave and convex portions is absorbed so that the butt surfaces of the first core pin and the second core pin do not open, and molten metal can be prevented from entering the butt portion of the first core pin and the second core pin.

Furthermore, in the casting device of the present invention, the cast product is a cylinder block of a multi-cylinder engine, the core passage is formed near the arrangement position of the cylinder bores and parallel to the arrangement direction, the first core pin is provided with a first cooling passage through which cooling water flows, the second core pin is provided with a second cooling passage through which cooling water flows, and the butt position of the tip of the first core pin and the tip of the second core pin is set in the thin-walled portion around the cylinder bore, away from the thick-walled portion between the adjacent cylinder bores.

With this configuration, in order to prevent the occurrence of voids around the core passage when the molten metal solidifies, the butt surfaces of the two core pins are moved away from the center between the first and second dies in the core passage of the molded product, so that the butt surfaces of the tips of the core pins can avoid being on the center line, which is the thick part between the centers of the bores between the cylinders. In addition, since the cooling of the molten metal is promoted by circulating cooling water through the core pins, the cooling is promoted by aligning the thick part with the flow area of the cooling water. In addition, the cooling effect can suppress the expansion of the first core pin in particular, and reduce friction and wear in the sliding parts.

As described above, according to the present invention, the tips of opposing core pins can be butted together reliably with an appropriate butting force during die casting, suppressing bending deformation caused by buckling due to thermal expansion of the core pins.

1 is a schematic diagram showing a cylinder block of a multi-cylinder engine in which a cast-out passage is formed by the casting device according to the present embodiment; FIG. 2 is an enlarged schematic diagram showing the area surrounded by dashed line A in FIG. 1 . FIG. 1 is a front view showing a die-casting apparatus according to an embodiment of the present invention. FIG. 4 is an enlarged schematic diagram showing the area surrounded by dashed line B in FIG. 3 . 5A and 5B are a side view and a cross-sectional view taken along line AA, illustrating the configuration of the urging portion; 6 is a graph showing load characteristics with respect to the amount of displacement of the biasing portion according to the embodiment. FIG. 4 is a schematic diagram showing the state of the urging part from the time when the urging part is attached to the first die to the time when the first core pin and the second core pin are butted together and molten metal is poured. 8 is an enlarged cross-sectional view taken along the line BB in FIG. 7 .

The following describes in detail the embodiments of the present invention with reference to the drawings. The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the present invention, its applications, or its uses.

Using Figure 1, we will explain the cylinder block 100 of a multi-cylinder engine, which is a cast product formed by the casting device of this embodiment. Figure 1 is a cross-sectional view of the cylinder block 100 in which a cast-in passage 1f is formed. Cylinder liners 1c are cast in series to form multiple cylinders. The cast-in passage 1f is an oil passage (main gallery) formed near the arrangement position of the cylinder bores 1a, 2a, 3a, 4a... and parallel to the center line 1d in the arrangement direction of the cylinder bores 1a, 2a, 3a, 4a....

Although details will be described later, the core passage 1f is formed by a first core pin 23 protruding from a first die 21 that forms one end face of the cylinder block 100, and a second core pin 24 protruding from a second die 22 that forms the other end face of the cylinder block 100. The protruding length of the first core pin 23 from the first die 21 is 1g, and the protruding length of the second core pin 24 from the second die 22 is 1h, and the first core pin 23 and the second core pin 24 are butted together to form the core passage 1f.

The multi-cylinder engine is an in-line six-cylinder engine with the first through sixth cylinders arranged in line. The cylinder block 100 is relatively long in the direction of the cylinder row. Accordingly, the length of the core passage 1f is also relatively long. To form the long core passage 1f, the first core pin 23 and the second core pin 24 are also long. The casting device 200 described here has a characteristic configuration described below, which makes it possible to omit machining to form a long oil passage.

Using FIG. 2, the butt position 1i between the tip of the first core pin 23 and the tip of the second core pin 24 will be described. As described above, since the cylinder block 100 constitutes an in-line 6-cylinder engine, the butt position 1i between the first core pin 23 and the second core pin 24 is in the vicinity of the cylinder bores 3a and 4a of the third and fourth cylinders. More specifically, the butt position 1i is set at a position shifted by a distance 1n to one side of the cylinder row direction with respect to the center line 1e between the cylinder bores 3a and 4a (i.e., the center line 1e perpendicular to the cylinder row direction). This is to promote cooling of the thick portion 1j on the center line 1e between the cylinder bores 3a and 4a. In the configuration example of FIG. 2, the butt position 1i is shifted to the first mold 21 side, that is, to the left side of the paper in FIG. 2.

In other words, because the cylinder has a circular cross section, the thickness of the casting is thick on the center line 1e between the cylinder bores 3a and 4a, and the thickness of the casting becomes gradually thinner as the position shifts from the center line 1e in the direction of the cylinder row.

On the other hand, the first core pin 23 and the second core pin 24 are formed with a first cooling passage 28 and a second cooling passage 29, through which cooling water flows, along the central axis of the pin. However, the first cooling passage 28 and the second cooling passage 29 do not reach the tip of the first core pin 23 and the second core pin 24, respectively. Therefore, the first cooling passage 28 and the second cooling passage 29 are not present at the butting position 1i of the first core pin 23 and the second core pin 24, and the butting position 1i is difficult to cool during casting. If the butting position 1i were to coincide with the center line 1e between the cylinder bores, there is a risk that the thick portion 1j of the casting, which has a large thickness, cannot be sufficiently cooled.

In response to this, by shifting the butt position 1i from the center line 1e between the cylinder bores 3a, 4a, as in the configuration example of FIG. 2, the butt position 1i is set to the thin-walled portion 1k of the casting, where the thickness is thin. By doing so, the position of the second cooling passage 29 of the second core pin 24 corresponds to the thick-walled portion 1j of the casting, and the thick-walled portion 1j can be sufficiently cooled.

In other words, by butting the first core pin 23 and the second core pin 24 at the thin-walled portion 1k, which is a distance 1n from the center line 1e between the cylinder bores 3a and 4a, the second cooling passage 29 of the second core pin 24 overlaps with the thick-walled portion 1j, promoting cooling of the thick-walled portion 1j.

The butt position 1i between the first core pin 23 and the second core pin 24 is offset from the center line 1e between the cylinder bores 3a and 4a, so the length 1g of the first core pin 23 is shorter than the length 1h of the second core pin 24.

Although not shown, the butting position 1i may be shifted toward the second die 22 with respect to the center line 1e between the cylinder bores 3a, 4a, in the opposite direction to that shown in FIG. 2. However, as described below, since the first core pin 23 is attached displaceably with respect to the first die 21, it is preferable to make the length 1g of the first core pin 23 shorter than the length 1h of the second core pin 24 in order to suppress the inclination of the first core pin 23.

The configuration of the core pin support structure of the casting device according to this embodiment will be described with reference to Figure 3. The casting device 200 has a mold used in casting molding. In the state where the core pins are butted together in the mold clamping position, the casting device 200 forms a cavity 25 using a first mold 21 on the left side, a second mold 22 on the right side, and six molds in the up-down and front-rear directions, and is configured to be slidable so as to move closer to or farther away from each other in each direction. Cast molding is a casting method in which molten metal (aluminum alloy in this embodiment) is injected into the cavity 25 to obtain a cast product, and in this embodiment, the cast product is a cylinder block for an automobile engine.

The first die 21 is a die that is arranged on one side in the left-right direction. As shown in FIG. 4, the first die 21 is equipped with a first core pin 23, a first cylinder portion 26, a biasing portion 27, a first cooling passage 28, and a second cylinder portion 30. The first core pin 23 is configured to be movable forward and backward relative to the first die 21 by the biasing portion 27, as will be described in detail later.

The second die 22 is a die that is arranged on the other side in the left-right direction relative to the first die 21. The second die 22 faces the first die 21. The second die 22 is equipped with a second core pin 24 and a second cooling passage 29. The second core pin 24 is assembled so as to protrude from the second die 22 toward the first die 21. The second core pin 24 is fixed directly to the second die 22 without using a biasing portion. The second core pin 24 does not advance or retreat relative to the second die 22.

The first cylinder portion 26 of the first mold 21 opens to an end face 211 of the first mold 21 (the face at the right end in FIG. 4). The first cylinder portion 26 extends from the end face 211 toward the inside of the first mold 21 along the butt axis of the first core pin 23 and the second core pin 24. The butt axis is an axis that extends in the left-right direction on the paper in FIG. 3 and FIG. 4. The first cylinder portion 26 has a relatively small diameter.

As shown in FIG. 4, the first core pin 23 has a base end 231 and a main body 232. The base end 231 is housed in the second cylinder section 30 described later. The main body 232 is continuous with the base end 231. The main body 232 has a smaller diameter than the base end 231. The main body 232 is inserted into the first cylinder section 26 with a clearance maintained. The main body 232 can slide in the left-right direction with respect to the first cylinder section 26. The first core pin 23 is assembled to the first mold 21 by receiving a biasing force from the biasing section 27, and the main body 232 penetrates the first cylinder section 26 and protrudes from the end surface 211 of the first mold 21 toward the second mold 22 side. The main body 232 of the first core pin 23 is butted against the second core pin 24 described later during molding, and after molding, a cast-out passage (main gallery) penetrating the cylinder block in the left-right direction is formed.

The first cooling passage 28 is formed inside the first core pin 23. More specifically, the first cooling passage 28 extends from the base end of the first core pin 23 to the tip, turns around near the tip of the first core pin 23, and returns to the base end. The first cooling passage 28 is connected to a passage provided in the first mold 21, although detailed illustration is omitted. Cooling water circulates inside the first core pin 23, promoting cooling of the casting around the first core pin 23 during casting.

In addition, the second core pin 24 also has a second cooling passage 29 for cooling water, similar to the first core pin 23.

As described above, a certain clearance is provided between the first core pin 23 and the first cylinder portion 26. This makes it possible to suppress sliding resistance even when the first core pin 23 thermally expands in the radial direction. However, due to the clearance, the amount of positional deviation of the butt end of the first core pin 23 due to inclination is greater than that of the second core pin 24 at the fixed end. In addition, in order to minimize sliding resistance, the length of the first cylinder portion 26 is shortened. For this reason, the angle at which the first core pin 23 inclines is likely to become large. Therefore, as described above, the length of the first core pin 23 is shortened. This suppresses the deviation of the butt position between the first core pin 23 and the second core pin 24 when the mold is closed.

Figure 4 shows an enlarged schematic diagram of the dashed line portion B in Figure 3. The biasing portion 27 is housed in the second cylinder portion 30. More specifically, the biasing portion 27 is disposed adjacent to the base end of the first core pin 23 on the base end side.

The second cylinder section 30 is continuous with the base end of the first cylinder section 26. The second cylinder section 30 and the first cylinder section 26 are in communication with each other. The second cylinder section 30 has a larger diameter than the first cylinder section 26. The base end of the second cylinder section 30, i.e., the left end of the paper in FIG. 4, is provided with an abutment surface 301 against which the fourth retaining member 35, which will be described later, abuts. The abutment surface 301 extends in the axial direction of the biasing section 27, i.e., in a direction perpendicular to the direction of the butt shaft.

Here, the first mold 21 is configured to be divided into a first portion 21a and a second portion 21b at a position corresponding to the second cylinder portion 30 (see also FIG. 7). The biasing portion 27 is inserted into the second cylinder portion 30 in the divided first portion 21a and second portion 21b, and is accommodated in the second cylinder portion 30 by assembling the first portion 21a and the second portion 21b to form the first mold 21.

The biasing section 27 has a second spring 31 and a first spring 32, which are made up of coil springs arranged in series. The first spring 32 and the second spring 31 may have the same spring constant, or the spring constant of the first spring 32 and the spring constant of the second spring 31 may be different.

The first spring 32 is sandwiched between a second holding member 36, whose cylindrical end is shaped like a flange, and a first holding member 34, which contacts one end of the first spring 32. The first spring 32 is sandwiched between the second holding member 36 and the first holding member 34 in a state where it is compressed in advance at a predetermined load, as will be described in detail later. In other words, the first spring 32 is compressed in advance before the first mold 21 and the second mold 22 are clamped. The first spring 32 can be further compressed at a load equal to or greater than the predetermined load.

Using Figure 5, we will explain the method of clamping the first spring 32 between the second holding member 36 and the first holding member 34 in a state where it is compressed in advance with a predetermined load. Figure 5 shows the A-A cross section, which corresponds to the longitudinal cross section of the biasing portion 27. The second holding member 36 has a cylindrical support portion 361 that passes through the axial center of the first spring 32, and a flange-shaped clamping portion 362 at the base end of the support portion 361 that abuts against the third holding member 33.

The support portion 361 is inserted into the first spring 32 and holds the first spring 32 in an expandable and contractible manner. The holding portion 362 has a larger diameter than the support portion 361 and abuts against the base end of the first spring 32.

The first holding member 34 has a through hole into which the support portion 361 of the second holding member 36 can be inserted. The first holding member 34 is fitted onto the support portion 361. The support portion 361 supports the first holding member 34 so that it can move back and forth in the axial direction. The first spring 32 is disposed between the first holding member 34 and the clamping portion 362 of the second holding member 36. The first holding member 34 abuts against the tip surface of the first spring 32.

A first long hole portion 39 is formed in the tip side portion of the support portion 361. The first long hole portion 39 penetrates the support portion 361 in the radial direction and extends in the axial direction of the second holding member 36, i.e., in the direction of the butt axis.

A first stopper pin 40 is inserted into the first long hole portion 39. The first stopper pin 40 is fixed to the first holding member 34 by press-fitting or screwing. The first stopper pin 40 protrudes radially inward from the inner peripheral surface of the first holding member 34.

The first retaining member 34 can reciprocate in the direction of the butt axis between a first position (position shown in FIG. 5) where the length of the first spring 32 is long and a second position where the length of the first spring 32 is short, within the range where the first stopper pin 40 engages with the first long hole portion 39.

The first long hole portion 39 is provided in the second holding member 36 so that the length from the clamping portion 362 of the second holding member 36 to the first holding member 34 is shorter than the natural length of the first spring 32 when the first holding member 34 is in the first position. As a result, the first holding member 34 and the second holding member 36 regulate the extension direction of the first spring 32 and hold the first spring 32 in a compressed state with a predetermined load. The elastic restoring force of the first spring 32 acts on the first holding member 34, and the first stopper pin 40 is pushed toward the tip side within the first long hole portion 39.

As described later, when the first holding member 34 is pushed toward the base end by the first core pin 23 during mold closing, etc., the first stopper pin 40 can be displaced toward the base end within the first long hole portion 39, so that the first spring 32 abutting against the first holding member 34 is further compressed between the first holding member 34 and the clamping portion 362 of the second holding member 36. Then, when the load on the first holding member 34 is released during mold opening, etc., the first stopper pin 40 returns to its original position within the first long hole portion 39, and the first spring 32 is compressed under a predetermined load.

In the configuration example of FIG. 5, the fourth holding member 35 and the third holding member 33 sandwich the second spring 31. The fourth holding member 35 has a support portion 351 and a clamping portion 352, and the second spring 31 is clamped between the clamping portion 352 of the fourth holding member 35 and the third holding member 33. However, in this configuration example, the second spring 31 clamped between the third holding member 33 and the fourth holding member 35 is not held in a pre-compressed state, unlike the first spring 32.

The fourth retaining member 35 has the same shape as the second retaining member 36, and the support portion 351 is formed with a second long hole portion 37 extending in the direction of the butt shaft. A second stopper pin 38 is inserted into the second long hole portion 37.

The third retaining member 33 has the same shape as the first retaining member 34, and the second stopper pin 38 is fixed to the third retaining member 33.

As described later, when the third holding member 33 is pressed by the first core pin 23 via the first spring 32 and the second holding member 36 during mold closing, the third holding member 33 is pressed toward the base end, and the second spring 31 is compressed between the third holding member 33 and the clamping portion 352 of the fourth holding member 35. When the load on the third holding member 33 is released during mold opening, the second stopper pin 38 returns to its original position within the second long hole portion 37.

The second spring 31 may also be compressed and held by a holding member, similar to the first spring 32. In that case, however, it is preferable that the compression load of the second spring 31 is smaller than the compression load of the first spring 32.

As shown in FIG. 5, the cylindrical second retaining member 36 and fourth retaining member 35 form a cooling passage in the biasing portion 27 that is connected to the first cooling passage 28 of the first core pin 23.

The biasing portion 27 supports the load caused by the backward displacement of the first core pin 23 when the first core pin 23 and the second core pin 24 are butted against each other when the first mold 21 and the second mold 22 are clamped, by the second spring 31 and the first spring 32. At the base end 231, the first core pin 23 presses the first holding member 34, the holding portion 362 of the second holding member 36 holding the first spring 32 presses the third holding member 33, and the holding portion 352 of the fourth holding member 35 holding the second spring 31 abuts against the abutment surface 301 of the second cylinder portion 30, so that the load caused by the displacement of the first core pin is supported by the second spring 31 and the first spring 32.

The load characteristics of the biasing portion 27 will be explained using the graph in Figure 6. The vertical axis shows the load acting on the biasing portion 27, and the horizontal axis shows the amount of displacement of the biasing portion 27. The horizontal axis shows the change in the amount of displacement of the biasing portion 27 from the state before the biasing portion 27 is assembled to the first mold 21 until it is assembled, until the tip sides of the first core pin 23 and the second core pin 24 are butted together and the mold is closed, and from after the mold is closed until molding is completed.

The first load characteristic 51 in the graph of FIG. 6 is the characteristic with a spring constant due to the second spring 31 only, and the second load characteristic 52 from the point of change in slope 53 onwards is the characteristic with a spring constant due to the combination of the first spring 32 and the second spring 31.

The slope of the second load characteristic 52 is set to be smaller than the slope of the first load characteristic 51. In other words, the load 56 at the slope change point 53 corresponds to a predetermined load that compresses and holds the first spring 32, and if the load applied to the biasing portion 27 is less than the load 56, only the second spring 31 contracts, and if the load applied to the biasing portion 27 is equal to or greater than the load 56, both the second spring 31 and the first spring 32 contract.

The compression behavior of the first spring 32 and the second spring 31 will be described in more detail with reference to Figures 6 and 7.

Step P1 in FIG. 7 illustrates the process of assembling the biasing portion 27 to the first mold 21. When the first spring 32 and the second spring 31 are assembled into the first mold 21 so as to be sandwiched between the first portion 21a and the second portion 21b, the base end portion 231 of the first core pin 23 engages with the surface on the tip side of the second cylinder portion 30, and the clamping portion 352 of the fourth holding member 35 abuts against the abutment surface 301 of the second cylinder portion 30. Since the first spring 32 is compressed by a predetermined load, only the second spring 31 is compressed, as shown by the arrow in step P1 in FIG. 7. In other words, when the first portion 21a and the second portion 21b are assembled, the length of the second cylinder portion 30 is set to a length such that the second spring 31 is shorter than its natural length.

When the biasing portion 27 is housed in the second cylinder portion 30, the biasing portion 27 is in a state of displacement amount 54 shown in FIG. 6. In a state in which the biasing portion 27 is assembled to the first mold 21, a compressive load is also applied to the second spring 31. However, the compressive load applied to the second spring 31 is smaller than the load applied to the first spring 32 by the first holding member 34 and the second holding member 36. In other words, the length of the second cylinder portion 30 is adjusted so as not to compress the second spring 31 too much.

Process P2 in FIG. 7 illustrates a process of clamping the first mold 21 and the second mold 22 after the assembly of the first mold 21 is completed. This process corresponds to the process from the displacement amount 54 to the displacement amount 55 shown in FIG. 6.

When the first die 21 and the second die 22 start to be closed, the first core pin 23 and the second core pin 24 are butted together. The load applied to the biasing portion 27 by the butted first core pin 23 is initially equal to or less than load 56. As illustrated in FIG. 6, at the beginning of the closing, only the second spring 31 is compressed. At this time, the second spring 31 generates a large load with a small amount of displacement, and biases the first core pin 23. The first core pin 23 and the second core pin 24 are butted together with a large force.

Now, with reference to Figure 8, the structure of the tip portions of the first core pin 23 and the second core pin 24 when they are butted together will be described. Figure 8 is a cross-sectional view showing an enlarged view of the tip portions of the first core pin 23 and the second core pin 24. Reference numeral 60 denotes the butt portion 60 where the tip sides of the first core pin 23 and the second core pin 24 are butted together.

The tips of the first core pin 23 and the second core pin 24 have a tapered convex shape for the first core pin 23 and a tapered concave shape for the second core pin 24 in order to align their axes when they are butted together. When they are butted together, the tips of the first core pin 23 and the second core pin 24 engage with each other in a concave-convex manner, so that the axes of the first core pin 23 and the second core pin 24 coincide with each other.

The first core pin butt portion 61 of the first core pin 23 is composed of a first core pin convex portion 63, a first core pin flat portion 65, and a first core pin conical surface portion 67. The second core pin butt portion 62 of the second core pin 24 is composed of a second core pin concave portion 64, a second core pin flat portion 66, and a second core pin conical surface portion 68.

When the first core pin 23 and the second core pin 24 are butted together, the first core pin cone surface portion 67 and the second core pin cone surface portion 68 are in contact with each other, and the misalignment of the axes of the first core pin 23 and the second core pin 24 is corrected while they are butted together so that the axes of the first core pin 23 and the second core pin 24 are aligned on the same straight line, thereby butting the axes of the first core pin 23 and the second core pin 24 together without any misalignment.

After the first core pin 23 and the second core pin 24 are butted together, a gap 69 is formed between the first core pin 23 and the second core pin 24 near the axial center from the conical surface portion. The gap 69 can absorb the amount of thermal expansion near the axial center when the first core pin convex portion 63 and the second core pin concave portion 64 undergo thermal expansion, and prevents the butt surface between the first core pin flat portion 65 and the second core pin flat portion 66 of the butt portion 60 from opening and allowing molten metal to enter, thereby suppressing the occurrence of burrs.

The tip shapes of the first core pin 23 and the second core pin 24 are not limited to either being concave or convex, but for the sake of explanation, the tip shape of the first core pin 23 is convex and the tip shape of the second core pin 24 is concave.

After the first core pin 23 and the second core pin 24 butt together, as the clamping of the first mold 21 and the second mold 22 progresses, the load applied to the biasing portion 27 increases and exceeds the load 56 shown in FIG. 6. Then, as shown by the arrow in step P2 of FIG. 7, both the second spring 31 and the first spring 32 are compressed. The spring constant of the biasing portion 27 is changed, and the load characteristic of the biasing portion 27 transitions from the first load characteristic 51 to the second load characteristic 52 as shown in FIG. 6. The displacement amount 55 is the displacement amount when the mold clamping is completed. The second load characteristic 52 is adjusted so that the displacement amount 55 becomes the target load 57.

Process P3 in FIG. 7 illustrates the process of pouring molten metal after clamping the first and second dies 21 and 22. The state of the biasing portion 27 when the first core pin 23 and the second core pin 24 are butted together will be described. During pouring and molding, the first core pin 23 and/or the second core pin 24 thermally expand. The first spring 32 and the second spring 31 of the biasing portion 27 are further compressed and deformed from the displacement amount 55 in FIG. 6. Here, the upper broken line position of the vertical axis of the graph in FIG. 6 indicates the buckling limit load 58. The second load characteristic 52 is a load characteristic that does not exceed the buckling limit load 58 with respect to the displacement amount, even if the first core pin 23 is displaced backward due to the thermal expansion of the first core pin 23 and the second core pin 24 during pouring and molding. In other words, the slope of the second load characteristic 52 is determined from the thermal expansion amount of the core pin and the buckling limit load 58. A sufficient amount of space can be provided to absorb thermal expansion.

Next, we will explain the function and effect of the biasing unit 27 of the casting device 200 configured as described above.

The biasing portion 27 ensures that the first core pin 23 and the second core pin 24 are butted together, and also suppresses bending deformation of the core pin due to buckling caused by thermal expansion of the core pin.

In a casting device 200, a method is known in which a core pin is used to inject molten metal and form a casting having a core passage, and the core pin provided on one die is butted against the core pin provided on the other die to form the casting. However, if the butting force of the core pin is weak, the core pin will vibrate due to the impact of the molten metal during casting, causing bending deformation, and there is a concern that burrs will be formed if the molten metal penetrates the butted portion of the core pin, blocking the passage. On the other hand, if the butting force of the core pin is strong, there is a risk that the core pin will bend and deform due to thermal expansion of the core pin during molding.

In this embodiment, when the biasing portion 27 is assembled into the first mold 21, the second spring 31, which is sandwiched between the fourth holding member 35 and the third holding member 33, is assembled into the first mold 21 while being compressed from a state in which no biasing force is applied, and supports the first core pin 23 with the first load characteristic 51. At this time, the first spring 32 is sandwiched between the second holding member 36 and the first holding member 34, and is in a state in which it is compressed and held under a predetermined load.

By supporting the first core pin 23 with the first load characteristic 51, a biasing force acts on the first core pin 23, and the base end 231 of the first core pin 23 is pressed against the step between the first cylinder portion 26 and the second cylinder portion 30. This makes it possible to prevent the first core pin 23 from falling over due to the gap between the first cylinder portion 26 and the first cylinder portion 26. In addition, when the first mold 21 and the second mold 22 are clamped together, the first load characteristic 51 due to the spring constant of the second spring 31 reliably butts the tips of the opposing core pins together, making it possible to prevent axial misalignment.

After the first core pin 23 and the second core pin 24 are butted together, the biasing portion 27 changes to the second load characteristic 52. The second load characteristic 52 absorbs the variation in the gap between the dies when clamping, the expansion of the dies when molding, or the amount of displacement caused by opening the dies. In particular, the second load characteristic 52 is a load characteristic that does not exceed the buckling limit load 58 for the amount of displacement due to the low spring constant, even if the first core pin 23 is displaced backward due to the thermal expansion of the first core pin 23 and the second core pin 24 during molding. The slope of the second load characteristic 52 is determined from the amount of thermal expansion of the core pin and the buckling limit load 58, and the slope of the second load characteristic 52 is set to be smaller than the slope of the first load characteristic 51. Bending deformation due to thermal expansion of the core pin that occurs during molding can be suppressed.

As described above, the cylinder block 100 is a cylinder block for an in-line six-cylinder engine, and since its length in the cylinder row direction is long, the length of the oil passage formed by the first core pin 23 and the second core pin 24 is also long. In other words, the length of the first core pin 23 and the second core pin 24 is long. For this reason, the length that the first core pin 23 and the second core pin 24 expand due to thermal expansion is relatively long, but the biasing portion 27 prevents the load acting on the core pin from exceeding the buckling limit load.

The casting device 200 can precisely mold long oil passages, eliminating the need for machining to mold the oil passages.

The order of the first spring 32 and the second spring 31 within the second cylinder section 30 may be reversed.

The biasing portion 27 may be configured using a coned disc spring or the like in addition to a coil spring. In addition, in this embodiment, two coil springs are used as the combination of the first spring and the second spring in the elastic body, but it is also possible to use a combination of members that function as an elastic body, such as a combination of a coil spring and a coned disc spring, or a combination of a coil spring and a rubber member.

As described above, the die-casting device according to this embodiment can reliably butt the tips of opposing core pins during die-casting, thereby suppressing bending deformation due to thermal expansion of the core pins.

Reference Signs List 200 Casting device 25 Cavity 21 First die 23 First core pin 231 Base end 232 Body 22 Second die 24 Second core pin 26 First cylinder 27 Pressing portion 28 First cooling passage 29 Second cooling passage 30 Second cylinder 301 Contact surface 31 Second spring (second elastic body)
32 First spring (first elastic body)
33 Third holding member 34 First holding member 35 Fourth holding member 36 Second holding member 361 Support portion 362 Narrowing portion 39 First oblong hole portion 40 First stopper pin 51 First load characteristic 52 Second load characteristic 1g First core pin length 1h Second core pin length 100 Cylinder block (cast product)
1a, 2a, 3a, 4a Cylinder bore 61 First core pin abutment portion 62 Second core pin abutment portion

Claims (7)

a first die having a first core pin for forming at least a portion of a core passage in the cast product;
a second die having a second core pin that is abutted against the first core pin; and
a biasing portion that is provided in the first mold and biases the first core pin toward the second core pin when the first mold and the second mold are in a mold clamped state,
The first mold is
a first cylinder portion that opens to an end surface of the first die and extends in a direction of an axis of the first core pin and the second core pin;
a second cylinder portion that is continuous with the first cylinder portion and that houses the biasing portion,
the first core pin has a base end portion accommodated in the second cylinder portion, and a main body portion continuous with the base end portion, penetrating the first cylinder portion, and protruding from the end face of the first die toward the second core pin, and is held by the first cylinder portion and the second cylinder portion so as to be reciprocatable in the direction of the butt axis,
the biasing portion includes a first elastic body and a second elastic body that are disposed adjacent to a base end portion of the first core pin in series in the direction of the butt axis and that impart an elastic restoring force to the first core pin when the first elastic body and the second elastic body are compressed and deformed in the direction of the butt axis,
The biasing portion further comprises:
A first holding member in contact with one end of the first elastic body; and
a second holding member having a holding portion that contacts the other end of the first elastic body and holds the first elastic body between itself and the first holding member, and a support portion that extends from the holding portion to hold the first elastic body and support the first holding member so as to be reciprocatable in the direction of the butt shaft;
The support portion of the second holding member is formed with a long hole portion extending in the direction of the butt shaft,
a stopper pin is fixed to the first retaining member, the stopper pin extending in a direction perpendicular to the butt axis, and configured to be inserted into the elongated hole portion and reciprocate along the elongated hole portion in the direction of the butt axis, and the first retaining member reciprocates in the direction of the butt axis between a first position and a second position in which a length of the first elastic body is shorter than when the first retaining member is in the first position, within a range in which the stopper pin engages with the elongated hole portion;
A casting device characterized in that the position of the long hole portion is set so that the length of the first elastic body when the first holding member is in the first position is shorter than its natural length. the first elastic body is disposed at a position close to a base end of the first core pin, and the second elastic body is disposed at a position away from the base end of the first core pin,
the second cylinder portion has a contact surface that expands in a direction intersecting the butt axis and contacts the other end of the second elastic body,
The casting device according to claim 1, characterized in that the length of the second cylindrical portion is set so that when the biasing portion is housed inside the second cylindrical portion, the length of the second elastic body is shorter than its natural length. The casting device according to claim 1 or 2, characterized in that the compressive load applied to the first elastic body by the first holding member and the second holding member before the first and second molds are closed is greater than the load applied to the biasing part through the first core pin at the start of mold closing and is smaller than the load applied to the biasing part through the first core pin at the end of mold closing. The casting device according to any one of claims 1 to 3, characterized in that the first elastic body and the second elastic body are coil springs. The second core pin is fixed to the second die;
5. The casting apparatus according to claim 1, wherein the length of the first core pin is shorter than the length of the second core pin. The tip portion of the first core pin has a convex or concave shape,
The tip portion of the second core pin has a concave or convex shape that engages with the tip portion of the first core pin,
The casting device according to any one of claims 1 to 5, characterized in that when the first core pin and the second core pin are butted together, a gap is formed between the top of the convex shape and the valley of the concave shape. the casting product is a cylinder block for a multi-cylinder engine, and the cast-out passage is formed in the vicinity of an arrangement position of the cylinder bores and parallel to the arrangement direction;
The first core pin is provided with a first cooling passage through which cooling water flows,
The second core pin is provided with a second cooling passage through which cooling water flows,
The casting device according to any one of claims 1 to 6, characterized in that the abutting position of the tip of the first core pin and the tip of the second core pin is set in a thin-walled portion around the cylinder bore, away from the thick-walled portion between adjacent cylinder bores.

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