Resin molding method

The present invention relates to a resin molding method.

In general, a flow channel configuration of a liquid ejection head having a winding hollow structure is often molded from resin in view of the ease of manufacturing, lightness, and resistance to corrosion. Japanese Patent Laid-Open No. 2002-178538 discloses a method of performing primary molding by injecting resin into different cavities in the same mold and mold the resin into parts for implementing a complicated internal structure, and then performing secondary molding by engaging the parts in the same mold and further injecting resin into the engaged portions. The above manufacturing method is hereinafter referred to as die slide injection molding. The adoption of the die slide injection molding makes it possible to manufacture molded articles having a complicated internal structure such as the above flow channel configuration with high accuracy and efficiency.

In the die slide injection molding, in secondary molding for engaging and joining hollow structural parts that are separately formed in primary molding, a resin injection pressure for joining may act on the primarily molded parts and deform them. In particular, if the primarily molded parts have a complicated hollow structure like flow channels of an inkjet head, the deformation affects the volume and shape of each liquid chamber, with the result that an ink ejection state becomes unstable. Further, if the primarily molded parts are deformed in the secondary molding, resin does not flow into necessary portions and the molded parts are not completely joined, which leads to a decrease in yields.

The present invention has been accomplished in order to solve the above problem. Accordingly, the present invention aims to provide a resin molding method with high quality and productivity by reliably injecting resin into target portions while preventing primarily molded parts from being deformed along with resin injection in secondary molding in die slide injection molding.

A resin molding method comprising: a first molding step of molding a first molded part and a second molded part in different positions in a mold by injecting resin into the mold; and a second molding step of joining the first molded part and the second molded part to form a resin molded article by engaging the first molded part and the second molded part in a first direction inside the mold and injecting resin into engaged portions, wherein in the first molding step, the second molded part is formed by injecting resin into an area where a first core movable in the first direction and a second core movable in a second direction intersecting with the first direction are engaged, in the second molding step, the second molded part is joined to the first molded part by injecting the resin while the first core is in contact with the second molded part and the second core is removed from the second molded part, areas where the first core and the second core are located in the first molding step become hollow areas connected to each other by removing the first core and the second core from the second molded part, and in the engagement in the first molding step, part of ends of the first core in the first direction is not in contact with the second core.

Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.

FIG. 1 is a perspective view of an inkjet head;

FIG. 2 is an exploded perspective view of the inkjet head;

FIG. 3 is an illustration of a state where primarily molded parts are engaged;

FIG. 4 is an illustration of a state where the primarily molded parts are joined;

FIG. 5 is an illustration of primary molding in a main mold;

FIGS. 6A to 6D are cross-sectional views of the main mold in the primary molding;

FIGS. 7A to 7D are illustrations of steps after the primary molding is finished;

FIGS. 8A to 8C are cross-sectional views of the mold in secondary molding;

FIGS. 9A to 9C are illustrations of a joining state in the secondary molding;

FIG. 10 is an illustration of channels through which liquefied resin flows in the secondary molding;

FIGS. 11A and 11B are illustrations of cores used for molding a second molded part;

FIG. 12 is a cross-sectional view showing the action of an injection pressure; and

FIG. 13 is an illustration of the action of an injection pressure in the present embodiment.

FIG. 1 is a perspective view of an inkjet head H 001 (hereinafter referred to as an IJ head H 001 ), which can be used as a liquid ejection head of the present invention. The IJ head H 001 mainly includes an ejection element section H 002 , an ink storage member H 004 , which is a resin molded article of the present invention, and an ink introduction member H 015 .

It is assumed that the IJ head H 001 of the present embodiment is a color inkjet head for ejecting ink of six colors to print an image. Accordingly, the ink introduction member H 015 is equipped with ink supply ports H 003 for six colors to guide ink supplied through tubes (not shown) to the ink storage member H 004 .

Inside the ink storage member H 004 , ink chambers and flow channels are formed for six colors, respectively, to guide ink supplied from the ink supply ports H 003 to the ejection element section H 002 . In the ejection element section H 002 , a plurality of ejection elements are arranged for each ink color. Each ejection element ejects ink as droplets in a −z direction in response to an ejection signal.

FIG. 2 is an exploded perspective view showing primarily molded parts in die slide injection molding of the present embodiment. In primary molding, a first molded part H 011 , a second molded part H 012 , and a flow channel lid member H 013 are formed. These three parts are molded in different positions in a main mold. Next, the first molded part H 011 and the second molded part H 012 are engaged in a z direction with a filter H 014 sandwiched therebetween. Further, the flow channel lid member H 013 is brought into contact with the second molded part H 012 from a −y side. After that, the three parts are joined together by using resin for joining while they are engaged with each other, thereby forming the ink storage member H 004 . The IJ head H 001 of the present embodiment is obtained by further attaching, to the ink storage member H 004 , the ink introduction member H 015 from a +y side and the ejection element section H 002 from the −z side.

Inside the second molded part H 012 , liquid chambers and flow channels for guiding ink to the ejection element section H 002 are formed independently for six ink colors. The liquid chambers and the flow channels have a complicated hollow structure for miniaturization. The hollow structure is formed by injecting resin while a first core and a second core are inserted from the −z side and the −y side, respectively, in the primary molding. The present invention is characterized by the shapes of the cores, which will be described later in detail.

FIG. 3 shows a state where the first molded part H 011 , the second molded part H 012 , and the flow channel lid member H 013 molded in the primary molding are engaged. The first molded part H 011 and the second molded part H 012 are stacked in the z direction with the filter H 014 sandwiched therebetween, and opposing walls of the first molded part H 011 and second molded part H 012 are thereby engaged with each other. As a result, a box shape is formed by the four walls.

FIG. 4 shows a state where liquid resin is further injected into the parts shown in FIG. 3 to join them. Gate runners H 031 for guiding the liquid resin are formed in the engaged portions between the first molded part H 011 and the second molded part H 012 and the engaged portions between the second molded part H 012 and the flow channel lid member H 013 (not shown). If the liquid resin is injected, the resin flows along the gate runners H 031 and joins the first molded part H 011 , the second molded part H 012 , and the flow channel lid member H 013 . A sealing member can be quickly guided to all the engaged portions by providing the gate runners H 031 .

The die slide injection molding process of the present embodiment will be hereinafter described in detail with reference to FIGS. 5 to 8C . It should be noted that the x, y, and z axes shown in FIGS. 1 to 4 and those in FIGS. 5 to 8C are common directional axes which are fixed with respect to the ink storage member H 004 and are irrelevant to the direction of gravity. In the actual use of the finished IJ head, the −z direction in FIGS. 1 to 4 corresponds to the direction of gravity. However, in the die slide injection molding process shown in FIGS. 5 to 8C , the −y direction corresponds to the direction of gravity.

FIG. 5 is an illustration of primary molding in a main mold K 001 of the present embodiment. The main mold K 001 used in the present embodiment includes a fixed mold K 010 and a movable mold K 020 removable from the fixed mold K 010 in the −z direction. Further, first to fourth valve gates K 041 to K 044 are connected to a surface of the fixed mold K 010 on the +z side. Each valve gate can inject liquefied resin into the mold at a predetermined timing.

In the primary molding, liquid resin is injected from the first to third valve gates K 041 , K 042 , and K 043 while the fixed mold K 010 and the movable mold K 020 are clamped as shown in FIG. 5 to form the first molded part H 011 , the second molded part H 012 , and the flow channel lid member H 013 . On the −x side of the main mold, the first molded part H 011 is molded by using the first valve gate K 041 . In a position spaced apart from the first molded part H 011 in the −y direction, the flow channel lid member H 013 is molded by using the third valve gate K 043 . In a position spaced apart from the first molded part H 011 in the +x direction, the second molded part H 012 is molded by using the second valve gate K 042 .

FIGS. 6A to 6D are cross-sectional views of the main mold K 001 in the primary molding shown in FIG. 5 . FIGS. 6A and 6B are perspective views of the main mold K 001 of FIG. 5 when viewed from the +y side and the +z side. FIG. 6C is a cross-sectional view along VIC-VIC in FIG. 6A . FIG. 6D is a cross-sectional view along VID-VID in FIG. 6A . A die slide mold K 050 movable in the +x and −x directions inside the movable mold K 020 is located in a position shown in FIG. 6A in the primary molding.

As shown in FIG. 6A , the most part of the first molded part H 011 is molded in the fixed mold K 010 . In the primary molding, in the fixed mold K 010 , slide cores (not shown) are put from the +y and −y sides, and in this state, liquefied resin is injected from the first valve gate K 041 . The flow channel lid member H 013 is mainly molded in the movable mold K 020 as shown in FIG. 6C . In the primary molding, in the movable mold K 020 , a first slide core K 051 movable in the +y and −y directions is put to a position of the third valve gate K 043 from the −y side, and in this state, liquefied resin is injected from the third valve gate K 043 . In the primary molding, the first molded part H 011 and the flow channel lid member H 013 are molded in the positions that are about the same in the x direction and different in the y direction.

The second molded part H 012 is molded in both the die slide mold K 050 inside the movable mold K 020 and the fixed mold K 010 as shown in FIG. 6A . More specifically, a flow channel structure of the second molded part H 012 is mainly molded in the die slide mold K 050 and two walls extending in the +z direction from the flow channel structure are mainly molded in the fixed mold K 010 . Further, in the die slide mold K 050 , a second slide core K 052 movable in the +y and −y directions is put from the −y side as shown in FIGS. 6B and 6D , and in this state, liquefied resin is injected from the second valve gate K 042 . The die slide mold K 050 , the first slide core K 051 , and the second slide core K 052 are actuated by a pneumatic, hydraulic, or electric cylinder.

FIGS. 7A to 7D are cross-sectional views showing steps after the primary molding is finished in the die slide injection molding. FIG. 7A corresponds to FIG. 6A . After the primary molding is finished, the movable mold K 020 moves in the −z direction away from the fixed mold K 010 ( FIG. 7B ). At this time, the first molded part H 011 formed mainly by the fixed mold K 010 is held in the fixed mold K 010 , and the flow channel lid member H 013 formed mainly by the movable mold K 020 is held in the movable mold K 020 . The second molded part H 012 formed by putting the second slide core K 052 inside the die slide mold K 050 is held in the die slide mold K 050 after the second slide core K 052 is removed in the −y direction.

Next, inside the movable mold K 020 , the die slide mold K 050 moves in the −x direction to align the second molded part H 012 with the first molded part H 011 and the flow channel lid member H 013 in the x direction ( FIG. 7C ). Then, a prepared filter H 014 is inserted between the first molded part H 011 and the second molded part H 012 and the movable mold K 020 moves in the +z direction again ( FIG. 7D ). Further, the first slide core K 051 is slid in the +y direction and brought into contact with the second molded part H 012 that has moved there. In the above manner, the first molded part H 011 , the second molded part H 012 , and the flow channel lid member H 013 are engaged with each other, thereby forming the liquid storage container shown in FIG. 3 .

FIGS. 8A to 8C are cross-sectional views of the mold K 001 in the secondary molding in the die slide injection molding. FIG. 8A corresponds to the state shown in FIG. 7D . At this time, as shown in FIGS. 8B and 8C , the first slide core K 051 moves in the +y direction toward the second molded part H 012 that has moved there to bring the flow channel lid member H 013 molded in the primary molding into contact with the second molded part H 012 . The first slide core K 051 supports the molded parts from the −y side, that is, from below in the direction of gravity. In the secondary molding, the fixed mold K 010 and the movable mold K 020 are clamped in this state and liquefied resin is injected from the fourth valve gate K 044 .

FIGS. 9A to 9C are illustrations of a joining state in the secondary molding. FIG. 9A is a cross-sectional view of the ink storage member H 004 along an xz-plane. FIGS. 9B and 9C are enlarged cross-sectional views of an area surrounded by a rectangle DT. FIGS. 9B and 9C show states before and after injecting liquefied resin, respectively.

The engagement between the first molded part H 011 and the second molded part H 012 forms six liquid chambers H 022 corresponding to respective ink colors in the ink storage member H 004 . When liquefied resin is injected from the fourth valve gate K 044 , the liquefied resin flows along the gate runners H 031 and fixes the filter H 014 in the positions where the gate runners H 031 are located.

FIG. 10 is an illustration of channels through which the liquefied resin flows along the gate runners H 031 in the secondary molding. FIG. 10 shows a state where the first molded part H 011 is removed for ease of explanation. In FIG. 10 , the −y direction corresponds to the direction of gravity. The resin injected from two injection positions K 044 p of the fourth valve gate K 044 flows along the gate runners H 031 in the directions shown by arrows, and joins the first molded part H 011 and the second molded part H 012 with the filter H 014 sandwiched therebetween. In this manner, the filter H 014 extending along the xy-plane is sealed while being held between the first and second molded parts from the +z and −z sides and the liquid chambers H 022 are separated from each other. Consequently, the filter H 014 can protect each liquid chamber H 022 against foreign matter.

After that, the liquefied resin that has reached the wall on the −y side further moves ahead in the −z direction along the gate runners H 031 to join the flow channel lid member H 013 and the second molded part which are engaged in this area. As a result, ink flow channels for six colors connecting the respective liquid chambers H 022 to the ejection element section H 002 are obtained.

After the aforementioned primary molding and secondary molding are finished, the movable mold K 020 moves in the −z direction again to open the main mold K 001 , which allows the finished ink storage member H 004 to be extracted from the main mold K 001 .

Next, the flow channel structure that characterizes the present invention and the shapes of the cores that implement the structure will be described in detail. In an ejection element section H 002 of a serial inkjet printing apparatus, ejection element arrays that eject different types of ink are arranged in parallel in a scanning direction of the IJ head (i.e., the x direction). However, if a lot of ejection element arrays are arranged in the scanning direction (the x direction), the width of the ejection element section H 002 in the x direction becomes large, which results in a decrease in printing speed. Therefore, the ejection element section H 002 needs to be miniaturized by arranging the ejection element arrays in the x direction at high density.

On the other hand, the liquid chambers H 022 of the IJ head H 001 need to have sufficient capacity to store bubbles that are gradually accumulated along with ejection operations. That is, in the second molded part (i.e., the flow channel member) that guides ink to the miniaturized ejection element section H 002 while ensuring sufficient capacity to store bubbles, flow channels need to be sloped to become narrower in the x direction toward the −z side. However, such flow channels cannot be formed by clamping the fixed mold K 010 and the movable mold K 020 in the z direction. Therefore, the present embodiment is provided with a second slide core K 052 , which is movable in the +y and −y directions and is sloped to become narrower in the x direction toward the −z side, and the primary molding is performed with the second slide core K 052 inserted into an area where the second molded part H 012 will be formed.

FIGS. 11A and 11B are illustrations of cores used for molding the second molded part H 012 . A first core K 201 is formed on a surface of the die slide mold K 050 . An area into which the ejection element section H 002 is fitted and six flow channels for guiding ink to the ejection element arrays of the ejection element section H 002 are formed by locating the first core K 201 on the −z side of the second molded part H 012 .

A second core K 202 is formed on the second slide core K 052 . When the second slide core K 052 is located in the position shown in FIG. 6D , the second core K 202 is located in the area where the second molded part H 012 will be formed. In this state, liquid resin is injected into the area, thereby forming flow channels that gradually become narrower in the x direction toward the −z side inside the second molded part H 012 .

FIG. 11B is an illustration of an engaged state of the first core H 201 and the second core K 202 in the primary molding. As shown in FIG. 11B , resin is injected while the first core H 201 and the second core K 202 are engaged in the intersecting directions, thereby molding walls in areas where the cores do not exist. Areas where the cores exist will become hollow areas, namely, flow channels. Therefore, in the primary molding, it is necessary to connect the second core K 202 , which forms the areas to be liquid chambers, and the first core K 201 , which forms liquid channels to guide ink from the liquid chambers to the ejection element section H 002 , to each other at six positions corresponding to ink colors.

In the secondary molding, after extracting the second core H 202 , the flow channel lid member H 013 is engaged with the second molded part H 012 from the −y side and joined to the second molded part H 012 . At this time, the first molded part H 011 after extracting the second core H 202 includes elongated hollow areas separated by thin walls and arranged in parallel, which is not so strong. For that reason, if resin is injected while clamping, the pressure of the resin may deform the flow channel structure or the resin may flow out of the proper channels.

FIG. 12 is a cross-sectional view showing the action of the injection pressure. FIG. 12 corresponds to the step shown in FIG. 7D . That is, the second core K 202 , which has formed the flow channel structure, is removed along with the slide core K 052 and six hollow liquid chambers H 022 are formed in the areas where the second core K 202 has existed. Although not shown in the drawing, the flow channel lid member H 013 molded in the primary molding is brought into contact with the second molded part H 012 from the −y side (i.e., from the backside of the drawing) along with the movement of the first slide core K 051 . Since the first core K 201 is formed on the moving surface of the die slide mold K 050 , it remains in contact with the second molded part H 012 even in the secondary molding.

In the first core K 201 shown in FIG. 12 , all the six walls, which will form channels, have the same height and shape in the +z direction, and all of their ends are in contact with the second core in the +z direction in the primary molding. Accordingly, in the state shown in FIG. 12 where the second core K 202 is removed, all the ends of the six walls of the first core K 201 are in contact with the hollow areas in the +z direction but are not in contact with wall areas. If liquid resin is injected in this state, the injection pressure of the resin spreads around the gate runners H 031 and the pressure in the −z direction acts on the walls forming the hollow liquid chambers, which may result in deformation of the liquid chambers H 022 . In order to avoid the deformation, the present embodiment is characterized by the shapes of the first core K 201 and the second core K 202 and their engaged state.

FIG. 13 is a cross-sectional view showing the action of the injection pressure in the case of using the first core K 201 and second core K 202 of the present embodiment. In the present embodiment, some of the ends of the first core K 201 are not in contact with the second core K 202 in the +z direction when the first core K 201 and the second core K 202 are engaged. More specifically, as shown in FIG. 11A , six walls of the first core K 201 have different heights and end shapes such that four of the six walls are in contact with the second core not in the +z direction but in the x direction and are exposed in the +z direction. Since the exposed areas are formed, walls can be molded in these areas in the primary molding and the molded walls can be directly supported from the −z side in the secondary molding. Therefore, even if liquid resin is injected in the secondary molding, drag in the +z direction against the injection pressure is produced in the molded walls supported by the first core K 201 and the molded article can be prevented from being deformed. In particular, since the two second walls from the outermost sides in the x direction extend in the +z direction to about the center of the hollow liquid chambers H 022 , the second molded part H 012 can be securely supported in the secondary molding.

In the present embodiment, out of the six liquid chambers, four liquid chambers particularly susceptible to the injection pressure are supported in the secondary molding. However, all the liquid chambers or less liquid chambers may be supported as a matter of course. In either case, the effect of the present invention can be achieved as long as at least part of the ends of the first core in the +z direction is not in contact with the second core in the primary molding where the first core and the second core are engaged.

According to the present invention, the liquid chambers can be prevented from being deformed in the secondary molding and the injected resin can be guided to the proper channel. As a result, a high precision ink storage member H 004 can be manufactured with high productivity.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

This application claims the benefit of Japanese Patent Application No. 2016-130581 filed Jun. 30, 2016, which is hereby incorporated by reference wherein in its entirety.