Centrifugal Casting Device and Centrifugal Casting Method

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2024-044395 filed on Mar. 21, 2024, the contents of which are incorporated herein by reference.

The present disclosure relates to a centrifugal casting device and a centrifugal casting method.

JP H07-276022 A discloses a centrifugal casting method.

In recent years, research and development that contributes to energy efficiency has been conducted in order to ensure that more people have access to affordable, reliable, sustainable and modern energy. In this technology, there has been a demand for a more satisfactory centrifugal casting device and a more satisfactory centrifugal casting method.

The present invention has the object of solving the aforementioned problem.

A first aspect of the present disclosure is a centrifugal casting device that casts a cast product by pouring molten metal into a mold while rotating the mold, the centrifugal casting device comprising: a control unit configured to control a rotational speed of the mold; and a determination unit configured to determine whether or not a head position of the molten metal flowing in a direction of a rotation axis of the mold has reached a predetermined position, wherein the control unit rotates the mold at a first rotational speed, and rotates the mold at a second rotational speed in a case where the determination unit determines that the head position has reached the predetermined position.

A second aspect of the present disclosure is a centrifugal casting method for casting a cast product by pouring molten metal into a mold while rotating the mold, the centrifugal casting method comprising: a first rotation step of starting pouring of the molten metal into the mold in a state where the mold is rotated at a first rotational speed; a determination step of determining whether or not a head position of the molten metal flowing in a direction of a rotation axis of the mold has reached a predetermined position; and a second rotation step of rotating the mold at a second rotational speed in a case where it is determined in the determination step that the head position has reached the predetermined position.

According to the present disclosure, a more satisfactory centrifugal casting device and a more satisfactory centrifugal casting method can be provided.

The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings, in which a preferred embodiment of the present invention is shown by way of illustrative example.

is a cross-sectional view of a centrifugal casting deviceaccording to an embodiment of the present disclosure. The centrifugal casting deviceof the embodiment casts, for example, a cylindrical memberas a cast product.

is a partial cross-sectional view of the cylindrical member. The cylindrical memberis cut to a suitable length, and the cut cylindrical memberis used as a cylinder sleeve of an internal combustion engine. The cylinder sleeve is disposed in the bore of a cylinder block. A reciprocating piston is in sliding contact with the inner peripheral wall of the cylinder sleeve. For example, flake graphite cast iron is used as the material of the cylindrical member. The flake graphite cast iron is a material excellent in vibration absorbing performance, thermal shock resistance, and lubricating performance.

A number of spires (protrusions)are formed on an outer circumferential surfaceof the cylindrical member. The height of each spirefrom the outer circumferential surfaceis set according to the outer diameter of the cylindrical member. For example, in a case where the outer diameter of the cylindrical memberis 60 to 100 mm, the height of each spireis set within a range of 0.5 to 1.2 mm.

The spirescan improve the adhesion between the cylinder sleeve and the cylinder block. Further, since the surface area of the cylinder sleeve is increased by providing the spires, heat generated in the cylinder sleeve by sliding of the piston or the like can be efficiently transmitted to the cylinder block. This improves the heat dissipation performance of the cylinder sleeve.

Returning to, the centrifugal casting deviceincludes a cylindrical mold. An annular grooveand an annular grooveare provided in an outer circumferential surfaceof the moldso as to cut out the outer circumferential surfacealong the circumferential direction. A rolleris in contact with the annular groove, and a rolleris in contact with the annular groove. A motoris connected to the roller, and the moldis rotated about a rotation axis A by the driving force of the roller. A rotational speed sensoris connected to the roller, and the rotational speed of the moldis measured by the rotational speed sensor. The motoris controlled by a control device.

An annular closing memberis attached to the distal end of the mold. The closing memberis provided with a window. Images of the inside of the moldare captured through the windowby a cameraprovided outside the mold. An annular frameis attached to the proximal end of the mold. The frameis provided with an opening. A pouring pipeof a troughis inserted into the moldthrough the opening. Molten material (molten metal L) is supplied from a ladleto the trough, and is poured into the moldfrom the trough.

is a partial cross-sectional view of the mold. When the cylindrical memberis manufactured, a mold washis applied to an inner circumferential surfaceof the heated mold. The mold washcontains a heat insulating material, a binder, a mold release agent, a surfactant, and water.

The water contained in the mold washapplied to the moldis evaporated by the heat of the moldto form bubbles, and the surface of the mold washis spherically expanded to form protrusions. A large number of the protrusionsare formed on the surface of the mold wash, and recessesare each formed between the protrusions. The recessesare transferred to the outer circumferential surfaceof the cylindrical memberto form the spires.

After the mold washis applied to the inner circumferential surfaceof the mold, the pouring pipeof the troughis inserted into the moldthrough the openingof the frame. The motorrotates the roller, whereby the moldrotates. Thereafter, the molten metal L is supplied from the ladleto the trough, and is poured into the moldfrom the trough. The molten metal L contained in the moldflows along the direction of the rotation axis A of the mold. Further, the molten metal L is supplied to the entire circumference along the inner circumferential surfaceof the moldby the action of the centrifugal force of the rotating mold.

As the rotational speed of the moldincreases and the centrifugal force increases, the contact pressure of the molten metal L against the inner circumferential surfaceof the moldincreases, and the flow velocity of the molten metal L in the direction of the rotation axis A decreases. Therefore, the molten metal L solidifies before reaching a distal end P1 () of the inner circumferential surfaceof the mold, and there is a concern that the cylindrical memberhaving desired length and thickness cannot be obtained. On the other hand, in a case where the rotational speed of the molddecreases and the centrifugal force decreases, the molten metal L does not enter the tips of the recessesof the inner circumferential surfaceof the mold, and the height of the spiresis reduced. The reduced height of the spiresreduces the adhesion between the cylinder sleeve and the cylinder block. Further, the reduced height of the spiresreduces the heat dissipation performance of the cylinder sleeve.

is a control block diagram of the control device. The control deviceincludes a computation unitand a storage unit. The computation unitis, for example, a processor such as a central processing unit (CPU) or a graphics processing unit (GPU). The computation unitincludes a control unitand a determination unit. The control unitand the determination unitare realized by the computation unitexecuting a program stored in the storage unit. At least part of the control unitand the determination unitmay be realized by an integrated circuit such as an application specific integrated circuit (ASIC) or a field-programmable gate array (FPGA). At least part of the control unitand the determination unitmay be realized by an electronic circuit including a discrete device.

The storage unitis a computer-readable non-transitory tangible storage medium. The storage unitis constituted by a volatile memory (not shown) and a non-volatile memory (not shown). The volatile memory is, for example, a random access memory (RAM) or the like. The non-volatile memory is, for example, a read only memory (ROM), a flash memory, or the like. Data and the like are stored in, for example, the volatile memory. Programs, tables, maps, and the like are stored in, for example, the non-volatile memory. At least part of the storage unitmay be included in the processor, the integrated circuit, or the like described above. At least part of the storage unitmay be mounted on a device connected to the centrifugal casting devicevia a network.

The control unitacquires the rotational speed of the moldmeasured by the rotational speed sensor. The control unitperforms feedback-control of the motorso that the rotational speed of the moldbecomes a predetermined rotational speed.

The determination unitacquires the image of the inside of the moldcaptured by the camera. The determination unitanalyzes the acquired image and determines whether or not the head position of the molten metal L flowing along the direction of the rotation axis A of the moldhas reached a predetermined position. The determination unitmay determine whether or not the head position of the molten metal L has reached the predetermined position, based on the elapsed time from the point in time when the molten metal L starts to be poured into the mold.

is a flowchart showing a rotation control process for the moldexecuted by the control device. The rotation control process is executed when the molten metal L is poured into the mold.

In step S, the control unitcontrols the motorto rotate the moldat a first rotational speed. The first rotational speed is set to a rotational speed at which the relative centrifugal acceleration of the moldis, for example, a value of 90 [G] to 100 [G]. The first rotational speed is set based on the flow velocity (pouring speed) of the molten metal L at which the molten metal L is poured from the troughinto the mold.

In step S, the determination unitdetermines whether or not the head position of the molten metal L flowing along the direction of the rotation axis A of the moldhas reached a predetermined position. The predetermined position is set, for example, to the distal end P1 () of the inner circumferential surfaceof the mold. The predetermined position is not limited to the distal end P1. In a case where it is determined that the head position of the molten metal L flowing along the direction of the rotation axis A of the moldhas reached the predetermined position (step S: YES), the process proceeds to step S. In a case where it is determined that the head position of the molten metal L has not reached the predetermined position (step S: NO), the process of step Sis repeated.

In step S, the control unitcontrols the motorto rotate the moldat a second rotational speed. The second rotational speed is set to a rotational speed at which the relative centrifugal acceleration of the moldis, for example, a value of 100 [G] to 130 [G]. After the process of step Sis performed for a predetermined period of time, the rotation control process is ended.

In a case where the cylindrical memberis cast by the centrifugal casting device, an unsound layer is formed at the distal end portion of the cylindrical member. Since the portion where the unsound layer is formed cannot be used as a cylinder sleeve, the distal end portion of the cylindrical memberis cut off and discarded. In order to reduce the amount of waste, it is required to reduce the length of the unsound layer in the cylindrical member.

are schematic diagrams explaining a mechanism of formation of the unsound layer in the cylindrical member.

The molten metal L initially poured into the mold(hereinafter, referred to as a first group L1) flows in the direction of the rotation axis A along the inner circumferential surfaceof the mold. At this time, since the moldis rotating, the centrifugal force acts on the first group L1, and the flow velocity of the first group L1 in the direction of the rotation axis A decreases. The molten metal L contains impurities (slag). Since the impurities have a specific weight smaller than that of the flake graphite cast iron, which is the material of the cylindrical member, the impurities float on the inner circumferential side of the first group L1 ().

The molten metal L (hereinafter, referred to as a second group L2) poured into the moldafter the first group L1 flows in the direction of the rotation axis A along the inner circumferential surface of the first group L1. Since the second group L2 is poured after the first group L1, the flow velocity of the second group L2 is higher than that of the first group L1 immediately after the second group L2 is poured. Therefore, the second group L2 overtakes the first group L1, and the second group L2 flows ahead of the first group L1. When the second group L2 overtakes the first group L1, the second group L2 sweeps away the impurities floating on the inner circumferential side of the first group L1 (). Further, the second group L2 positioned at the head sweeps away the inclusions adhering to the inner circumferential surfaceof the mold(). The inclusions are, for example, the peeled mold washor the like.

Since the centrifugal force caused by the rotation of the moldalso acts on the second group L2, the flow velocity of the second group L2 in the direction of the rotation axis A also decreases. The first group L1 and the second group L2 are pushed toward the distal end of the moldby the molten metal L (hereinafter, referred to as a third group L3) poured into the moldafter the second group L2. As a result, the first group L1 and the second group L2 integrally flow in the direction of the rotation axis A (). An oxide film is formed on the entire inner circumference of the molten metal L ().

When the second group L2 reaches the distal end of the mold, a portion (hereinafter, referred to as a head portion LH) of the second group L2 that is located forward of the first group L1 is compressed, and the oxide film of the head portion LH of the second group L2 is folded. In the head portion LH of the second group L2, the proportion of the impurities, the inclusions, and the oxide film is relatively large, and thus an unsound layer is generated ().

As the rotational speed of the moldincreases, the flow velocity of the first group L1 decreases, and therefore, the length of the head portion LH of the second group L2 increases, and the length of the unsound layer also increases. That is, in order to reduce the length of the unsound layer, the rotational speed of the moldmay be decreased to delay the decrease in the flow velocity of the first group L1. On the other hand, when the rotational speed of the moldis decreased, the height of the spiresis decreased as described above. Therefore, in the embodiment, the rotational speed of the moldis set to the first rotational speed at the point in time when the pouring of the molten metal L into the moldis started, and the rotational speed of the moldis set to the second rotational speed when the head position of the molten metal L reaches the predetermined position.

[Switching Timing between First Rotational Speed and Second Rotational Speed]

is a graph showing a relationship between the switching timing from the first rotational speed to the second rotational speed, and the length of the unsound layer. The switching timing is indicated such that the point in time when the head position of the molten metal L reaches the distal end P1 () of the inner circumferential surfaceof the moldis set as 0 [s].

As shown in, it is understood that the length of the unsound layer can be reduced by switching from the first rotational speed to the second rotational speed at the timing of −2 [S] to 3 [S].

As shown in, when the switching timing from the first rotational speed to the second rotational speed is too late, the length of the unsound layer increases. This is because the molten metal L that has collided with the closing memberreturns toward the proximal end of the moldtogether with impurities and inclusions.

According to the above-described embodiment, the length of the unsound layer can be reduced while the height of the spiresof the cylindrical memberis ensured. This in turn contributes to energy efficiency.

The following supplementary notes are further disclosed in relation to the above-described embodiment.

The centrifugal casting device () of the present disclosure is a centrifugal casting device that casts a cast product by pouring the molten metal (L) into the mold () while rotating the mold, the centrifugal casting device including: the control unit () configured to control the rotational speed of the mold; and the determination unit () configured to determine whether or not the head position of the molten metal flowing in the direction of the rotation axis (A) of the mold has reached a predetermined position, wherein the control unit rotates the mold at the first rotational speed, and rotates the mold at the second rotational speed in a case where the determination unit determines that the head position has reached the predetermined position. This makes it possible to reduce the length of the unsound layer while ensuring the height of the spires.

In the centrifugal casting device according to Supplementary Note 1, the second rotational speed may be higher than the first rotational speed. This makes it possible to reduce the length of the unsound layer while ensuring the height of the spires.

In the centrifugal casting device according to Supplementary Note 1, the first rotational speed may be set in accordance with the pouring speed that is a flow velocity of the molten metal at which the molten metal is poured into the mold. This can reduce the length of the unsound layer.

In the centrifugal casting device according to any one of Supplementary Notes 1 to 3, a plurality of recesses () may be formed in the inner circumferential surface () of the mold. This makes it possible to form the spires on the outer circumferential surface of the cast product.

The centrifugal casting method of the present disclosure is a centrifugal casting method for casting a cast product by pouring the molten metal into the mold while rotating the mold, the centrifugal casting method including: the first rotation step of starting pouring of the molten metal into the mold in a state where the mold is rotated at the first rotational speed; the determination step of determining whether or not the head position of the molten metal flowing in the direction of the rotation axis of the mold has reached a predetermined position; and the second rotation step of rotating the mold at the second rotational speed in a case where it is determined in the determination step that the head position has reached the predetermined position. This makes it possible to reduce the length of the unsound layer while ensuring the height of the spires.

In the centrifugal casting method according to Supplementary Note 5, the second rotational speed may be higher than the first rotational speed. This makes it possible to reduce the length of the unsound layer while ensuring the height of the spires.

In the centrifugal casting method according to Supplementary Note 5, the first rotational speed may be set in accordance with the pouring speed that is a flow velocity of the molten metal at which the molten metal is poured into the mold. This can reduce the length of the unsound layer.

In the centrifugal casting method according to any one of Supplementary Notes 5 to 7, a plurality of recesses may be formed in the inner circumferential surface of the mold. This makes it possible to form the spires on the outer circumferential surface of the cast product.

Although the present disclosure has been described in detail, the present disclosure is not limited to the above-described individual embodiments. Various additions, replacements, modifications, partial deletions, and the like can be made to these embodiments without departing from the gist of the present disclosure, or without departing from the essence of the present disclosure derived from the claims and equivalents thereof. Further, these embodiments can also be implemented in combination. For example, in the above-described embodiments, the order of operations and the order of processes are shown as examples, and are not limited to these. Furthermore, the same applies to a case where numerical values or mathematical expressions are used in the description of the above-described embodiments.