JPH10264210A - Resin injection mold, and molding method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin injection mold simple in structure and control, not taking labor even in finish processing after molding, good in moldability and capable of forming a resin molded object high in the content of reinforcing fibers having no voids therein and excellent in strength, appearance quality and dimensional accuracy. SOLUTION: A mold consisting of a pair of split molds formed by splitting a cavity 2 formed along the outer shape of a product containing reinforcing fibers has a resin injection gate 3 injecting a resin into the cavity 2, the thin groove 4 provided along the outer periphery of the split line of the cavity 2 and capable of holding the end parts of the reinforcing fibers and the air vent 5 directly connected to the thin groove 4 to guide air to the outside.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a molding die for resin injection (RTM, RI). More specifically, the present invention relates to a molding die for molding a fiber-reinforced thermosetting resin by a resin injection method, and in particular, by using a woven fabric or a sheet-like laminated structure for a reinforcing fiber body, to determine the content thereof, The present invention relates to a molding die for resin injection that can be enhanced without impairing moldability and appearance quality.

[0002]

2. Description of the Related Art Generally, a reinforcing fiber used for a fiber-reinforced thermosetting resin molded article is a sheet-like material such as a nonwoven fabric (random mat) made of glass fiber or carbon fiber or a woven fabric. When molding this molded body, the sheet-like reinforcing fiber body is directly or preformed and placed in a cavity of a pair of upper and lower molds. When a hollow molded body is formed, a reinforcing fiber body is wound around a core serving as a core to form a preform body, which is set in a cavity. After that, the upper and lower molds are closed, and a liquid resin material is injected into the cavity and cured to obtain a molded body. The molded body taken out of the mold is cut off the outer part (burr) of the product and subjected to a finishing treatment to become a product.

An advantage of the resin injection method of injecting and curing a liquid resin material is that a low-viscosity liquid resin material can be injected at a high speed and can be cured in a short time. However, when the reinforcing fiber body is disposed in the cavity, the flow of the injected resin is hindered, and air in the cavity is easily trapped, particularly in the vicinity of the fiber overlapping portion (crimp portion) and the fiber-bonding portion. Air bubbles (voids) remain on the surface and inside of the molded product, and the quality of the product, such as appearance and strength, is significantly reduced. Usually, the voids tend to occur more easily as the resin viscosity is higher, the gelling time of the resin is shorter, and the injection speed of the resin is higher, and this tendency is more remarkable when the filling rate of the reinforcing fiber body is higher. .

[0004] Therefore, optimizing the mold structure so as not to leave voids is an important issue in increasing the content of the reinforcing fiber. This seemingly can be easily solved by providing a large number of air vents for guiding air to the outside. However, providing a large number of air vents is not preferable because a complicated mold structure is required for that purpose. In other words, it is easy to expect that the amount of resin overflowing from these many air vents will increase, which will lead to a decrease in the yield, and the mold will become covered with the resin for each molding operation, and the resin that has been blown out will be worked. A device must be provided at each vent outlet so that no one is injured. In addition, many vent marks remain on the product, which may impair the aesthetic appearance. Furthermore, since the injected resin flows preferentially in the direction of the air vent, it is necessary to design a mold that ensures the flow of the resin so as not to cause stagnation of bubbles in the portion without the air vent. Therefore, providing a large number of air vents is not a good solution because it increases other problems.

That is, voids can be reduced without sacrificing molding workability (a property that the structure of a mold is simple, molding conditions are easily controlled, and a finishing process such as a burr treatment does not require much work). There is a demand for a mold having a structure capable of increasing the filling rate of the reinforcing fiber body.

Recently, in order to smoothly discharge the air in the mold cavity, the end of the reinforcing fiber is cut or shaped into a size larger than that of the molded product to be obtained, and the end portion is intentionally deliberately cut. Out of the mold cavity, sandwiching the end between the seal rubbers of the mold pinch-off portion, and discharging air from the gap between the fibers at the sandwiching portion (see Reinforced Plastics 38 (10) (1993)). A method in which the distance between the mating surfaces of the upper and lower dies is set to a contact structure close to zero without sandwiching the reinforcing fiber body between the pinch-off portions, and air is discharged while sealing the contact surface with a thin rubber elastic body (Japanese Patent Application Laid-Open No. 6-47675). Use a vacuum line to remove air in the system before resin impregnation, optimize the control of molding conditions such as reducing resin viscosity, and use the resin injection gate as a fan gate. In other words, a method has been proposed in which the air in the cavity is extracted by promoting the resin flow to guide the resin.

[0007]

However, in the above method, the reinforcing fiber body is intentionally sandwiched between the fitting surfaces of the upper and lower molds, so that the upper and lower molds do not completely fit, and the molded body is not formed. There is a problem that dimensions (thickness) become uneven.

In the above-mentioned method, the amount of burrs is reduced and the number of finishing steps is reduced because the space between the mating surfaces is close to a closed state (per zero). However, there is a problem that the removal of voids is incomplete. is there. In addition, there has been a problem that the content of the reinforcing fiber must be reduced so that the reinforcing fiber is not sandwiched between the fitting surfaces.

Further, in the above-mentioned methods, there are problems that the apparatus and the control of the apparatus are complicated, that there are many restrictions such as resin viscosity and resin injection conditions, and that the moldability is poor.
Further, the effect of reducing voids is not perfect.

In particular, when forming a hollow pipe-shaped molded body such as a deformed pipe, it is difficult to uniformly inject resin into a cylindrical space in a cavity formed by a core and a mold. At the same time, bubbles remained during flow and gelation of the resin. In addition, the fibers of the reinforcing material are likely to be caught between the mating surfaces of the mold, and the dimensions of the molded body are likely to be unstable, and unintentionally protruding or fraying of the fibers may cause unsightly parts. Sometimes. Therefore, the amount of the fiber to be filled in the cylindrical space must be reduced to such an extent that the fiber is not pinched, and it is inevitably difficult to obtain a molded body having a high fiber content.

In view of the above-mentioned problems, the present invention provides a mold having a good moldability, in which the structure and the molding conditions can be easily controlled, and the finishing process after molding is not troublesome. Provided is a resin injection molding die capable of forming a resin molded product having a high rate, having no voids in a product, and having excellent strength, appearance quality, and dimensional accuracy.

[0012]

The invention according to claim 1 comprises a pair of split molds having a cavity formed by dividing a cavity formed along the outer shape of a product containing a reinforcing fiber body,
A resin injection gate for injecting resin into the cavity, a thin groove provided along the outer circumference of the dividing line of the cavity and capable of sandwiching the reinforcing fiber body, and an air vent directly connected to the thin groove to guide air. It is characterized by becoming. The resin injection gate, the thin groove, and the air vent may be provided in either of the split molds, or may be provided in both. By intentionally inserting the end of the reinforcing fiber body into a thin groove continuous along the outer circumference of the cavity, the product appearance is improved and the product dimensions are stabilized, and the gap between the inserted fibers is further reduced. Utilization makes it easier for air to escape. An air vent communicating with the outside of the mold is directly connected to the thin groove, and the air in the cavity is collected by the air vent through the thin groove from the gap between the fibers and escapes to the outside. The void remaining in the thin groove may be cut as an outer part (burr) of the product, and no void remains in a formed body (product part) formed in the cavity. Although there may be two or more air vents, the air vent communicates with the thin groove serving as an air vent with the sandwiched fibers, and the void can be sufficiently removed by providing only one air vent. Therefore, control of the mold structure and molding conditions is simple. It is preferable that the resin injection gate is not directly connected to the thin groove from the viewpoint that there is no possibility of causing a defective filling in the cavity. Therefore, it is preferable that the thin groove be provided continuously from the entire periphery of the cavity dividing line except for the vicinity of the resin injection gate. Further, since the burrs formed by the thin grooves are thin, they can be easily removed after the molded product is released from the mold, and the processing steps can be simplified. Also, the appearance of the finished product is beautiful. Further, while the thin groove intentionally causes the reinforcing fiber body to protrude from the cavity, it also serves to prevent the protruding portion from being brought between the mating surfaces. Therefore, the space between the mating surfaces becomes zero (closed state), and the dimension of the molded product is stabilized, and at the same time, it is not necessary to reduce the charge amount of the reinforcing fibrous body into the cavity for the purpose of eliminating the protrusion between the mating surfaces. ,
The proportion of the reinforcing fiber contained in the product can be increased. It is not necessary to form a thin groove in both of the split molds, and only one of them may be used.

According to a second aspect of the present invention, in addition to the first aspect, the product has a hollow pipe shape and is provided at both ends in a longitudinal direction of a cylindrical space in a cavity corresponding to the product portion. The resin injection gate and the air vent are provided. Since the liquid resin raw material is efficiently injected from one end to the other end in the lengthwise direction in the cylindrical space, there is no insufficient filling of the resin and no void remains. This is an efficient configuration that requires the least number of resin injection gates and air vents.

According to a third aspect of the present invention, there is provided the first or second aspect.
The volume of the united thin groove formed by combining the pair of split molds is 1% or more and 10% or less with respect to the volume of the product part of the cavity, and at least one of the split molds Has a depth of 0.
It is not less than 1 mm and not more than 1.0 mm. The product part of the cavity refers to a part into which the resin is injected, and in the case of a hollow molded body, refers to a cylindrical space excluding a core placed in the cavity to form the hollow part. The combined thin groove refers to a thin groove formed by combining a pair of split molds and surrounded on three sides. The fiber is sandwiched in this part. This part is removed as a part outside the product (burr) after molding. The volume ratio of the united thin groove is based on the volume of the product portion of the cavity formed by combining a pair of split dies, and the depth of the thin groove indicates the depth of one thin groove, not the combined thin groove.

According to a fourth aspect of the present invention, in addition to the first, second or third aspect, the volume content of the reinforcing fiber is 40% or more and 70% or less. The configuration in which the end portion of the reinforcing fiber body is sandwiched between the thin grooves has an advantage that the gap between the fibers can be used as a pseudo air vent hole, but the fibers can be zeroed without being interposed between the fitting surfaces. Further, since the bulk of the fiber suddenly protruding outside the cavity can be stored in the thin groove, the fiber filling amount can be increased. Therefore, it is possible to obtain a product having a high content of the reinforcing fiber while ensuring the reduction of voids and the dimensional accuracy of the molded body. Specifically, even in the case of a reinforcing fiber volume content of 50% or more, which was conventionally difficult to commercialize due to the generation of voids, it is possible to perform molding in which the generation of voids is suppressed to a level that can withstand practical use. Was.

According to a fifth aspect of the present invention, there is provided a molding method using the molding die, wherein a pair of split molds are closely attached to each other with a pair of split dies sandwiching an end of a reinforcing fiber body in a thin groove. Closing step, the step of injecting a liquid resin material into the cavity from the resin injection gate, the air in the cavity is drawn out between the fibers sandwiched between the thin grooves in the direction of the outline of the thin groove, and further, The method is characterized by comprising a step of extracting the thin groove to the outside from the air vent along the outline, and a step of curing the resin material.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a resin injection molding die according to the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of one embodiment of a mold of the present invention, FIG. 2 is an explanatory view showing a method of forming a preform when a hollow pipe-shaped formed body is produced, and FIGS. 3 and 4 are reinforcing fibers. It is a figure which shows the relationship between the content rate of a body, the generation rate of a void, and the dimensional deviation of a molded object.

The mold of the present invention comprises a pair of split molds having a cavity formed along the outer shape of the product. In FIG. 1, a split mold 1 shows one of a pair of split molds, and has a divided cavity 2, a resin injection gate 3, a thin groove 4, and an air vent 5. Resin injection gate 3, thin groove 4, and air vent 5
May not be in the other split type not shown.
In the following description, a molded article of a fiber-reinforced thermosetting resin formed into a hollow pipe (for example, a prosthesis frame or the like)
Is used as an example. However, the present invention is not limited to this, and is generally used for a solid or hollow resin molded article containing a reinforcing fibrous body. As the reinforcing fiber body, in addition to a sheet-like nonwoven fabric (random mat) or woven fabric made of glass fiber, carbon fiber, or the like, a preformed body, a braid, or a braided body in which short fibers are fixed with a binder can also be used. . Also,
Thermosetting resins such as epoxy resins, polyester resins, vinyl ester resins, urethane resins, and acrylic resins are preferably used as the resin raw material from the viewpoints of viscosity, reactivity, and the like. It may be a body.

In FIG. 1, the cavity 2 forms the outer shape of the product together with the other divided mold (not shown). Dividing line 8 for cavity 2
Faces the other dividing line (not shown) with the thin groove 4 interposed therebetween, and the inside of the dividing line 8 (inside the cavity 2).
The part is the product part, and the outer part (thin groove 4) is the outer part (burr). Burrs are later removed. The mating surface 7
Is a surface which comes into contact when the split mold 1 is joined to another split mold, and is sealed by a sealing material 6 formed in a closed loop surrounding the cavity 2, the thin groove 4, the injection gate 3, and the air vent 5. You. In addition, the mold clamping after closing the pair of split molds can be performed by providing simple clamps at several places, but is not limited as long as an appropriate mold fastening force can be obtained.

The thin groove 4 is provided continuously on the outer periphery of the cavity 2, sandwiches the end of the reinforcing fiber body filled in the cavity 2, and uses a space between the fibers as an air vent hole. To make it possible. Thus, the air in the cavity can be uniformly discharged toward the outer peripheral direction without providing a large number of air vents. In addition,
Even if the air that cannot be removed by the air vent remains in the thin groove 4, it is cut and removed as a void outside the product, and therefore does not remain in the product.

In FIG. 1, the outline 9 of the thin groove 4 has a width W substantially equal to the dividing line 8 over substantially the entire periphery except for the vicinity of the resin injection gate 3. If the resin injection gate 3 is directly connected to the thin groove 4, the injected resin may flow preferentially through the thin groove 4 rather than the product portion (cavity 2). It is preferable that the entire circumference except for the above is continuous. However, the present invention is not limited to this, as long as the cavity 2 is reliably filled with the resin and there is no possibility of causing a defective filling. The size of the depth D of the thin groove 4 is determined in accordance with the depth D '(not shown) of the other divided thin groove (not shown). That is, the depth of the thin groove (merged thin groove) that is united by closing the split mold is D + D ′,
From the viewpoint that burrs formed during this time can be easily removed, it is preferable that D + D ′ be as thin as possible.
From the viewpoint of making it easy for air to move toward the air vent between the fibers sandwiched between + D ′,
Requires some size. On the other hand, together with the width W of the thin groove, the volume of the united thin groove (W
If × (D + D ′) × L (L: peripheral length of the thin groove)) is too large, the liquid resin raw material will be thinner than the inside of the cavity 2 in the thin groove 4.
, Causing poor filling of the resin. There is also a problem of burr cutability. In consideration of these, the size (width W, depth D, D ', and circumferential length L) of the thin groove and the combined thin groove is determined. That is, the volume of the united thin groove (W ×
(D + D ′) × L) is preferably 1% or more and 10% or less with respect to the volume of the product part of the cavity,
Further, within this range, the depth D of the thin groove formed in the split mold is set.
(Or D ') is 0.1 to 1.0 mm, desirably
It is preferably in the range of 0.2 to 0.6 mm. The thickness of one fiber of the reinforcing fiber is about 5 to 50 μm.

In order to utilize the effect of the thin groove 4 more effectively, the outline 9 of the thin groove 4 may have a shape slightly different from the dividing line 8 of the cavity 2.
It is also useful to cut the depth of the thin groove 4 partially or deeply. Furthermore, if the depth of the united thin groove is reduced within the range that does not hinder the effect of the thin groove, the burr can be cut by hand without using a cutting machine such as a water jet for cutting the burr. Can contribute to shortening of working time and saving of energy and capital investment by simplifying the work with grinder and paper finishing.

The air vent 5 is directly connected to the thin groove 4,
It is provided at a position facing the resin injection gate 3 with the cavity 2 interposed therebetween. The air vent guides air from the thin groove 4 to the outside of the split mold 1. Although two or more air vents may be provided, the air vents serve as the air vent with the fiber sandwiched between the thin grooves 4, so that the void can be sufficiently removed by providing only one air vent as in the illustrated example. If a large number is provided, molding workability is not good, so there is no particular limitation, but one is preferred, and such a position and size are taken into consideration.

The split mold 1 shown in FIG. 1 forms a hollow pipe-shaped molded body with a line connecting the resin injection gate 3 and the air vent 5 in a longitudinal direction (a direction from one opening end to the other end). is there. As shown in FIG. 2, the hollow pipe-shaped molded body is formed by winding a sheet-like reinforcing fiber body around the core 10 and arranging the core 10 together with the core 10 in the cavity 2. Therefore, the reinforcing fiber body is the core 1
It is disposed in a cylindrical space formed by a mold including the mold 0 and the split mold 1, and this cylindrical space is a product part. The resin injection gate 3 and the air vent 5 are provided at both ends in the longitudinal direction of the cylindrical space. Thereby, the number of the resin injection gates 3 and the number of the air vents 5 can be reduced (for example, one), and the resin can be efficiently filled in the cylindrical space so that insufficient filling does not occur and voids do not occur. .

Next, a method of manufacturing a hollow pipe-shaped molded body using the split mold 1 will be described with reference to FIG. FIG.
In the figure, reference numeral 10 denotes an aluminum split core, which is formed by wrapping the core 10 with a predetermined number of thin cloth (sheet) -like carbon fiber cloths 12 to form a preform body 11. I do. The outermost carbon fiber cloth 13 is arranged along the cavity 2 so that the end 13a is sandwiched between the thin grooves 4, and the preform body 11 is placed thereon. Then, the split mold 1 and the other split mold (not shown) are closed so that the fitting surface 7 comes into contact with zero, and the mold is clamped by simple clamps arranged at several places. Next,
A mold (a pair of split molds) is maintained at a constant temperature by an external temperature control device, and a liquid resin material (epoxy resin mixture or the like) heated to a predetermined temperature at a predetermined pressure from a resin discharger is
It is injected from the resin injection gate 3 and cured. At this time,
The air in the cavity 2 flows out of the air vent 5 through the thin groove 4. After a certain period of time, the mold is opened, the molded body is taken out, the split core 10 is pulled out from the inside of the molded body, and the burr formed by the thin groove 4 is cut by a water jet machine, and the cut surface is polished by a polishing machine. Finish to get the final product.

[0026]

Next, the content of the reinforcing fiber was kept constant (60%).
To change the size of the thin groove, resin impregnation, appearance quality,
Table 1 shows a comparison of dimensional variation, void generation rate, and secondary workability. In addition, the measurement of the void generation rate is based on JI
The measurement was performed according to the method of measuring the porosity specified in S-K5400.

[0027]

[Table 1]

As shown in FIG. 2, when forming Examples 1 and 2 and Comparative Examples 1 to 3, a split core made of aluminum and a molding die made of aluminum were used to form a core 10. Sheet-shaped carbon fiber cloths were laminated so that the volume content after molding was 60% to form a preform body 11, which was set in a mold. The mold is clamped in several places by a simple clamp, held at 80 ° C., and 0.02-0.5 MPa
The epoxy resin mixed liquid heated at the discharge pressure of 1 was injected.
Fifteen minutes after the injection, the mold was opened and the molded body was taken out.
The core 10 is taken out from the molded body while dividing, and the burr formed in the thin groove 4 is cut by a water jet machine.
The cut surface was finished with a grinder.

Next, the shapes of the thin grooves formed in the split mold used in the molding of Examples 1 and 2 and Comparative Examples 1 to 3 will be described. Example 1 Both split molds had a depth D = 0.3 mm (depth 2 of the united thin groove).
D = 0.6 mm) and a thin groove having a width W = 20 mm is provided over almost the entire circumference of the cavity. The volume of the united thin groove with respect to the volume of the product part of the cavity (hereinafter referred to as volume ratio) is 4%. Example 2 A thin groove was formed not in both split molds but in only one split mold. The formed thin groove has a depth D = 0.6 mm (the depth D of the united thin groove = 0.6 mm) and a width W = 20 mm.
The volume ratio of the thin groove is 4% as in the first embodiment. Comparative Example 1 No thin groove was provided (depth D = 0 of united thin groove). Comparative Example 2 The depth D = 0.2 mm (depth 2 of the united thin groove)
D = 0.4 mm) and a thin groove having a width W = 20 mm is provided. The volume ratio is 25%. Comparative Example 3 A depth D = 0.1 mm (depth 2 of the united thin groove)
D = 0.2 mm) and a thin groove having a width W = 20 mm is provided. The volume ratio is 1%.

When the fiber-reinforced thermosetting resin is manufactured by the conventional resin injection method, the void generation rate is 3 to
5%. As shown in Table 1, the rate of occurrence of voids in a product molded by the molding die of the present invention is 1% or less.

Further, as shown in Table 1, in Examples 1 and 2, excellent molded articles having excellent resin impregnating properties and appearance quality, small dimensional variations and a small void generation rate were obtained. On the other hand, in Comparative Example 1, since there were no thin grooves, the appearance quality and dimensional accuracy were poor, and many voids were observed on the surface of the molded body. Further, a resin-unimpregnated portion also occurred at the upper end of the molded body. Comparative Example 2 and Comparative Example 3 have thin groove dimensions (volume ratio).
Shows the results when the value is out of the proper range. In Comparative Example 2, if the width of the groove is too large, the injected resin selectively passes (not the cavity but the thin groove).
This resulted in poor filling of the resin into the preform body. In Comparative Example 3, the width of the groove was small and the depth was not sufficient, so that a molded article having many voids was obtained.

In order to determine such an appropriate range of the dimension of the thin groove, the size of the thin groove was variously changed, and an experiment was conducted under the same conditions. As a result, the volume of the thin groove is approximately 1 to 1 with respect to the cavity volume of the mold (volume of only the product portion).
It is preferably in the range of 0 percent, within which the depth of the thin groove is preferably in the range of 0.1-1.0 mm, most preferably in the range of 0.2-0.6 mm. Good results were obtained. Note that the width of the thin groove is calculated from the relationship between the volume and the depth.

Next, FIG. 3 shows the relationship between the fiber content and the void generation rate. The effect of thin grooves on void removal becomes more pronounced as the fiber volume content of the product increases. As shown in FIG. 3, a molded article having a relatively low fiber content of up to about 30% (which is rather common due to the generation of voids in the past) has no thin grooves. Although there is not much difference, the void reduction effect is clearly recognized from 40% in the mold structure according to the present invention. For example, when a product was formed using a mold having no thin grooves, a product having a fiber content of 50% or more due to generation of voids had no value as a product. However, by using a mold having a thin groove formed therein, the generation of voids can be suppressed to a level that can be practically used as a product even if the fiber content is 50% or more. In FIG. 3, a molded product having a fiber content exceeding 70% is not investigated, but a product having a fiber content higher than 70% is not practical and is excluded from the investigation.

FIG. 4 shows the relationship between the fiber content and the dimensional deviation. As shown in FIG. 4, the dimensional accuracy of the fiber-reinforced thermosetting resin molded article molded by the mold of the present invention is as follows.
Dramatically higher and more accurate than products with molds without thin grooves. In the present invention, since the protrusion or bulkiness of the reinforcing fiber body to the fitting surface at the time of fitting the mold can be sealed in this thin groove, the mold fitting surface is always in contact with zero contact, This is because the size of the molded product always reflects the size of the mold cavity. In particular, a high level (for example, 40% or more) of fiber filling, which has conventionally been difficult to close the mold due to the bulkiness of the fiber reinforcement, causes the fiber to be thinner than the mating surface of the mold. This was made possible by intentional accommodation within the depth of the groove. That is, in the conventional mold structure without a thin groove, as the fiber content (the amount of filled fibers in the cavity) increases, the molded body size shifts from the mold size to the + side. It can be seen that the deviation is kept constant (in FIG. 4, the thickness of a particular part of the molded body is taken as an example). Furthermore, since the turbulence, fraying, cutting marks, etc. of the fiber generated at the end portion or the bulky portion of the fibrous body are housed in a thin structure, if this is removed as a burr after molding, the vicinity of the mold fitting portion can be obtained. The finished product has a very good appearance. Therefore, while the present invention is an effective method for removing voids from a molded article,
The present invention has made it possible to obtain a hollow pipe-shaped molded article having a high fiber content, which is stable in terms of quality such as the appearance and dimensional accuracy of the molded article.

[0035]

The present invention is configured as described above.
By optimizing the mold structure, that is, by providing a groove for a bubble trap of a predetermined shape at the boundary between the fitting portion of the mold and the cavity, and connecting this groove to the air vent port, resin injection is performed. By efficiently discharging the air in the mold, and by inserting the protruding portion of the reinforcing fiber into the groove when the mold is closed, voids can be formed without sacrificing secondary workability and resin impregnation. It has become possible to stably produce a hollow pipe-shaped molded body which can be reduced and has excellent appearance quality and dimensional accuracy.

[Brief description of the drawings]

FIG. 1 is an explanatory perspective view of one embodiment of a mold according to the present invention.

FIG. 2 is a view showing a method for forming a hollow pipe-shaped molded body using the mold of the present invention.

FIG. 3 is a diagram comparing the relationship between the fiber content and the void fraction of a product molded by the mold of the present invention with a conventional mold.

FIG. 4 is a diagram comparing the relationship between the fiber content and the dimensional deviation of a product molded by the mold of the present invention with a conventional mold.

[Explanation of symbols]

 Reference Signs List 1 split mold 2 cavity 3 resin injection gate 4 thin groove 5 air vent 8 cavity split line 9 thin groove outline 12 and 13 carbon fiber cloth (reinforced fiber body)

Claims (5)

[Claims] 1. A mold comprising a pair of split molds formed by dividing a cavity formed along an outer shape of a product containing a reinforcing fiber body, wherein a resin injection gate injects resin into the cavity. And a thin groove provided along the outer periphery of the dividing line of the cavity and capable of sandwiching the end of the reinforcing fiber body, and an air vent directly connected to the thin groove and guiding air to the outside. Characteristic mold for resin injection. 2. The product according to claim 1, wherein the product has a hollow pipe shape, and the resin injection gate and the air vent are disposed at both ends in a longitudinal direction of a cylindrical space in a cavity corresponding to the product portion. The molding die for resin injection according to the above. 3. A volume of a united thin groove formed by combining a pair of the split dies is 1% or more and 10% or less with respect to a volume of a product portion of the cavity, and is formed in at least one of the split dies. 3. The molding die for resin injection according to claim 1, wherein the depth of the thin groove is 0.1 mm or more and 1.0 mm or less. 4. The molding die for resin injection according to claim 1, wherein the ratio of the reinforcing fiber body contained in the product is 40% or more and 70% or less by volume content. 5. A molding method using said mold, comprising: a step of closing a pair of split molds so that fitting surfaces thereof come into close contact with each other by sandwiching an end portion of a reinforcing fiber body in a thin groove; Injecting a more liquid resin material into the cavity, bleeding the air in the cavity in the direction of the outline of the thin groove through the space between the fibers sandwiched between the thin grooves, and further following the outline of the thin groove A step of extracting the resin material from the air vent to the outside, and a step of curing the resin raw material, using a molding die for resin injection.