JP2003025372A - Method for manufacturing toothed belt made of thermoplastic elastomer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To mold the back surface of a belt by injecting a thermoplastic elastomer lowered in its melt viscosity in a cavity and to eliminate the disturbance in the arrangement of core wires by preventing the stretching of the elastomer layer of a preformed layer. SOLUTION: The method for manufacturing the toothed belt made of the thermoplastic elastomer includes an initial injection process wherein an inner mold 3 is arranged in an outer mold to form the cavity, and the thermoplastic elastomer is injection-molded to fill the cavity 9 to form the preformed layer 15; a spinning process for winding the core wires 16 around the peripheral surface of the preformed layer 15 of the inner mold 3 demolded from the outer mold; a final injection process again arranging the inner mold 3 after the winding the core wires 16 in the outer mold, and subsequently injection-molding the thermoplastic elastomer lowered in its melt viscosity in the cavity to fully fill the cavity to form the back surface part 17 of the belt; and a process for finishing the belt sleeve released from the inner mold to form the toothed belt.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a toothed belt made of a thermoplastic elastomer, and more specifically, to reduce the melt viscosity of a thermoplastic elastomer layer on the back side of the belt to inject it into a cavity to fill the back side of the belt. The present invention relates to a method for producing a toothed belt made of a thermoplastic elastomer, which is molded into a portion to prevent the elastomer layer of the preformed layer from being stretched to eliminate the disorder of the arrangement of the cords.

[0002]

2. Description of the Related Art Polyurethane toothed belts are widely used as power transmission belts for general industries, precision instruments, etc. because they are synchronous transmission systems for transmitting rotation without slips. This polyurethane toothed belt is usually manufactured by a casting method.Specifically, a cylindrical inner mold in which a core wire is wound around a nose of a ridge is put in an outer mold to form a cavity formed by the inner mold and the outer mold. After the liquid polyurethane is cast and cured, the wide belt sleeve removed from the inner mold is cut into a predetermined width. This nose maintains an appropriate PLD value, which is the distance between the center of the core wire and the bottom surface of the belt groove, and optimizes the meshing with the pulley.

In another injection molding method, which is another manufacturing method, a mold apparatus having a cylindrical inner mold, in which a core wire is wound around a nose of a ridge, is placed in an outer mold, is mounted on an injection molding machine, and a molten resin is injection molded. After filling the cavity while bleeding air from the nose of the machine through the sprue, radial runner, and gate, the belt sleeve is removed from the inner mold, and the belt sleeve is cut to a specified width to make a toothed belt. Was there.

As another method, a reinforcing sheet in which a core wire such as a cord is fixed and integrated with a molten resin in advance is formed, and the sheet is cut into the width of a belt to be formed, and the belt is inserted into an inner die. After assembling the mold with the outer mold, thermoplastic resin is injected into the mold to fill it, and by using a reinforcing sheet in which the core wire is fixed and integrated with molten resin, it is possible to prevent turbulence of the core wire. , JP-A-63-237934.

[0005]

However, in the manufacturing method in which the core wire is wound around the nose, since the resin is molded and solidified in the cavity under pressure, shrinkage stress remains as an internal residual stress, and the belt travels for a long time. However, cracks were likely to occur from the root portion of the belt. Further, when a belt having a nose is run, the belt is folded into a polygonal shape on the pulley, and stress concentrates at the nose position, giving fatigue to the core wire. By repeating this, the core wire at the nose position may reach the limit of bending fatigue and be cut. Moreover, the resin leaked from the parting line of the mold, and it was necessary to perform post-deburring processing.

In particular, the core wire exposed at the nose position such as a glass fiber cord is damaged by rubbing against the inner mold when the belt sleeve is released from the mold, and is easily subject to dynamic fatigue due to the polygonal effect. It has also been proposed to soak the adhesive glue with the inner mold on the core wire before winding, or apply the adhesive glue after winding the core wire. But,
These methods impair the releasability of the belt sleeve, and may cause adverse effects such as short-circuiting of the injection resin filling due to contamination of the inner mold and increase in surface roughness.

Further, the arrangement of the core wires wound around the inner mold may be disturbed depending on the magnitude of the injection pressure, and the reinforcing function may not be exhibited. The method disclosed in Japanese Patent Laid-Open No. 63-237934 improves this. However, this method is a method in which a reinforcing sheet in which core wires such as cords are fixed and integrated with a molten resin is prepared in advance, and the reinforcing sheet is cut into a predetermined width of a belt and fitted into an inner mold. In addition, it takes too many man-hours to reduce productivity, and the product cost may increase.

Further, in order to solve such a problem,
The applicant molded a nose-free nose-free resin layer by shot molding, spirally winding a core wire around the circumferential surface of the resin layer, and then injecting a second-layer molten resin into the cavity to fill the cavity. We have proposed a method of forming on the back side of the belt. The core wire has an anchoring effect that sinks somewhat into the first resin layer due to the winding tension, and the core wire is unlikely to be disturbed even when subjected to a strong resin pressure or viscous resistance at the time of injection. But 1
The resin layer (sleeve) of the second layer may be stretched in the resin flow direction, and in this case, there is a problem that the arrangement of the core wires is disturbed.

In the present invention, as a result of intensive studies focused on such a problem, as a result of lowering the melt viscosity of the elastomer, the cavity is injection-filled to mold the back surface of the belt to prevent stretching of the elastomer layer of the preforming layer. It is an object of the present invention to provide a method for manufacturing a toothed belt made of a thermoplastic elastomer in which the disorder of the arrangement of the cords is eliminated.

[0010]

In order to achieve the above-mentioned object, the invention according to claim 1 of the present invention is such that the core wire is embedded in the back surface of the belt so as to extend in the longitudinal direction, and at least one of the back surface of the belt is provided. In a method for manufacturing a toothed belt made of a thermoplastic elastomer having teeth at predetermined intervals, a thermoplastic elastomer is used after an inner mold having concave and convex parts alternately provided therein is formed in an outer mold to form a cavity. Injection molding to fill the cavity and form the preforming layer that completely surrounds the surface of the convex portion, and the center of the peripheral surface of the preforming layer of the inner mold removed from the outer mold. After spinning the wire in a spiral and placing the inner mold around which the core wire was wound in the outer mold again, injection molding a thermoplastic elastomer with mixed melt gas to reduce the melt viscosity and complete the cavity. Full belt And final injection step of molding the surface, from releasing the belt sleeve from the inner mold process to finish the toothed belt, the method for producing a thermoplastic elastomer toothed belt comprising a.

In the above manufacturing method, in order to spirally wind the core wire on the surface of the preformed layer formed first,
The core wire sinks to some extent in the resin layer due to tension, and is fixed without moving due to the anchoring effect even if it receives injection pressure or viscous resistance, and especially the thermoplastic elastomer with a low melt viscosity of the raw material forming the back surface of the belt is cavity. Since the back surface of the belt is formed by injection-filling, the stretching of the preforming layer can be prevented and the disorder of the arrangement of the cords can be eliminated.

The invention according to claim 2 of the present application is a tooth made of a thermoplastic elastomer in which the core wire is embedded in the back surface of the belt so as to extend in the longitudinal direction, and tooth portions are provided at a predetermined interval on at least one of the back surface of the belt. In the method for producing a belt with a belt, a molding portion composed of a concave portion and a convex portion extending in the longitudinal direction is alternately provided along the circumferential direction, and a runner ring connected to the molding portion is arranged at one end portion. The inner mold is arranged in at least one space provided in the outer mold composed of the fixed outer mold and the movable outer mold facing each other at the parting line, and the sprue, runner, and gate provided in the fixed outer mold. And the inner runner ring are communicated with each other, and the thermoplastic elastomer is filled into the runner ring having a gradually increasing volume from the gate side of the entrance toward the diagonal side half the circumference, and then along the longitudinal direction of the molding part. Let it flow The initial injection step of forming the preforming layer on the forming part, the spinning step of spirally winding the core wire around the peripheral surface of the preforming layer of the inner mold removed from the outer mold, and the inner mold winding the core wire After again installing in the outer mold, injection molding a thermoplastic elastomer whose melt viscosity has been lowered by mixing gas to completely fill the cavity and mold the back surface of the belt, and the final injection step, from the inner mold A process for producing a toothed belt made of a thermoplastic elastomer, which comprises a step of finishing a toothed belt from a released belt sleeve.

Particularly, in order to mold the back surface of the belt by injecting and filling the cavity with a thermoplastic elastomer having a lower melt viscosity of the raw material for forming the back surface of the belt, the extension of the preforming layer is prevented and the cords are aligned. Disturbance of can be eliminated. Further, since the elastomer is made to flow from the inner mold runner ring along the lengthwise direction of the molding portion composed of the concave portion and the convex portion, the cavity is sufficiently filled, and no defective portion such as a weld line occurs. There is no leakage of raw materials from the external parting line, and post-processing such as deburring is unnecessary. Also, since the peripheral surface of the runner ring is gradually abraded from the gate side of the entrance where the raw material enters to the diagonal side half way around this, the raw material is used as the initial flow path to face the runner ring from the gate side. After filling toward the corner side, as a next flow path, it flows in the longitudinal direction of the molding part all at once to form a pre-molded layer that uniformly fills up to the end of the molding part. .

The invention according to claim 3 of the present application is the method for producing a toothed belt made of a thermoplastic elastomer, which comprises injection-molding a thermoplastic elastomer having a melt viscosity reduced by mixing a gas in an initial injection step. The initial injection step of forming the preforming layer with one outer mold having two different cavities and the final injection step of forming the belt back surface portion can be performed at the same time.

The invention according to claim 4 of the present application is the method for producing a toothed belt made of a thermoplastic elastomer, wherein the gas is carbon dioxide.

According to the fifth aspect of the present invention, the thermoplastic elastomer is made of at least one selected from the group consisting of polyester thermoplastic elastomer, olefin thermoplastic elastomer, and dynamically crosslinked thermoplastic elastomer. There is a method for manufacturing a toothed belt.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method for manufacturing a toothed belt made of a thermoplastic elastomer according to the present invention will be described in detail with reference to the drawings. FIG. 1 is an assembly view of a mold device for forming a toothed belt according to the present invention, FIG. 2 is a schematic view of an injection molding machine equipped with the mold device of the AA cross section of FIG. 1, and FIG. Partial cutaway front view, FIG. 4 is a partially enlarged view of FIG. 3, FIG. 5 is a view of FIG. 4 seen from the BB direction, and FIG. 6 is a view showing the thermoplastic resin from the gate after the inner mold is installed in the outer mold. The figure which shows the resin flow path at the time of injecting to a runner ring, and FIGS. 7-10 shows the manufacturing process of the thermoplastic elastomer toothed belt which concerns on this invention.

In the mold apparatus 1 used in the present invention, the fixed outer mold 2a installed in the vertical (vertical) injection molding machine 30 and the movable outer mold 2b which moves in the vertical direction are arranged in the parting line 4. The inner mold 3 is housed in two cavities 5 a and 5 b facing each other and provided in parallel on the parting line 4. That is,
One space 5a provided in the outer mold 2 is used in the initial injection step in which the inner mold 3 is installed and the cavity is filled with the thermoplastic elastomer to form the first preform layer 15. The other cavity 5b having a volume larger than that of the cavity 5a is provided with the inner mold 3 having the core wire 16 wound around the surface of the preforming layer 15 obtained in the initial injection step, and the cavity is filled with the thermoplastic elastomer. It is used in the final injection process for molding the belt back surface portion 17 of the second layer.

In the injection molding machine 30, as shown in FIG. 2, carbon dioxide 33 is pressed into an elastomer melt 32 in a cylinder 31 and a screw 34 is used to melt the melt 3.
It is equipped with a gas supply device 35 which is melted in 2 to reduce the viscosity and greatly improve the fluidity.

The thermoplastic elastomer is the sprue 6 provided in the fixed outer mold 2a from the nozzle 36 of the injection molding machine.
Outer mold 2 and inner mold 3 via runner 7 and gate 8
The cavities 9 between them are filled, but it is also possible to open both runners 7 and simultaneously flow into both cavities 9.
Also, only one runner 7 is open and one cavity 9
It can also be flushed to. Two cavities 5a having different volumes,
When using the mold apparatus 1 having 5b, a means for opening only one runner 7 and flowing it to one cavity 9 is preferable.

As shown in FIG. 3, the inner mold 3 has support portions 10 at both ends and a molding portion 11 for molding a belt sleeve at the center.
And the molding portion 11 has a concave portion 12 extending in the longitudinal direction.
And the convex portions 13 are alternately arranged along the circumferential direction to form the molding portion 11
A runner ring 14 communicating with the gate 8 is provided at the boundary of the one support portion 10.

The runner ring 14 has a peripheral surface 40.
Is gradually removed from the gate 8 side of the entrance into which the thermoplastic elastomer penetrates toward the diagonal side 41 half-circled. In other words, the outer surface 40 of the runner ring
Is gradually reduced in radius of curvature from the gate side 8 to the diagonal side 41, and the depth of the runner ring 14 is D on the gate side 8 and D ′ on the diagonal side 41. Four
It gradually becomes larger toward 1, and also the runner ring 14
As shown in FIG. 5, the increase amount of the volume V is gradually increased from the gate side 8 to the diagonal side 41.

The difference between the depths D'and D is 0.5 to 3.0.
mm, and more preferably 1.0 to 2.0 mm. Within this range, the melt will be as shown in FIG.
After filling the runner ring 14 from the gate 8 side to the diagonal side 41 as the initial flow passage 42, the concave portion 12 and the convex portion 13 in which the peripheral surface of the molding portion 11 is longitudinally arranged as the next flow passage 43 are formed. Along the same time, the flow forming section 11 is evenly filled up to the end.

Further, since the thermoplastic elastomer flows in the longitudinal direction from the runner ring 14 along the concave portions 12 and the convex portions 13, the cavity 9 is completely filled, and no problems such as weld lines occur. Moreover, no leakage occurs from the parting line 4 of the outer molds 2a and 2b, and post-processing such as deburring becomes unnecessary.

In the embodiment described below, an outer mold 2 having two cavities 5a and 5b having different volumes is used, one runner 7 is opened, and only one cavity 9 is filled with the thermoplastic elastomer. The following shows the case of making.

When a toothed belt is manufactured by using the above-mentioned mold device, the inner mold 3 is installed in the space 5a provided in the outer mold 2,
An initial injection step of filling the cavity 9 formed between the void 5a and the inner mold 3 with the thermoplastic elastomer to form the preforming layer 15 is performed.

In this initial injection step, as shown in FIG. 7, after the inner mold 3 is installed in the space 5a of the fixed side outer mold 2a,
The thermoplastic elastomer melted from the nozzle of the injection molding machine 30 is filled with the runner ring 14 from the gate 8 side toward the diagonal side 41 via the sprue 6, runner 7, and gate 8 and then molded as the next-stage flow path 43. The preform layer 15 is formed by pouring the peripheral surface of the part 11 along the concave part 12 and the convex part 13 arranged in the longitudinal direction all at once, and uniformly filling up to the end part of the forming part 11. Therefore, the defective rate of the preforming layer 15 is reduced.

Further, since the thermoplastic elastomer flows from the runner ring 14 through the concave portions 12 and the convex portions 13 along the longitudinal direction, the cavity 9 is completely filled without the generation of weld lines, and the outer mold is also used. It does not leak from the parting line 4 of 2a, 2b.

In this case, the mold temperature of the inner mold 3 and the outer molds 2a, 2b is preferably 30 to 90 ° C. Convex portion 13 and outer mold 2
The distance d between a and 2b is a thick portion that secures the PLD of the core wire, and is designed according to the size of the belt.

The thermoplastic elastomer used here is, for example, an ester-based thermoplastic elastomer (for example,
Toyobo Co., Ltd .: trade name Perprene, DuPont Co .: trade name Hytrel), olefin-based thermoplastic elastomer (for example, AES Japan Co .: trade name Santoprene), dynamically cross-linked thermoplastic elastomer (For example, Riken Vinyl Industry Co., Ltd .: Actimer), styrene-based thermoplastic elastomer, urethane-based thermoplastic elastomer, polyamide-based thermoplastic elastomer, vinyl chloride-based thermoplastic elastomer, fluorine-based thermoplastic elastomer, etc., and transmission belts. In consideration of the use, the polyester-based thermoplastic elastomer, the olefin-based thermoplastic elastomer, and the dynamically cross-linked thermoplastic elastomer are preferable.

In the spinning process, the inner mold 3 on which the preforming layer 15 is formed in the initial injection process is taken out from the fixed side outer mold 2a and mounted on the rotary shaft of the spinning device (not shown) for the core wire, A core wire 16 made of a glass fiber, an aramid fiber, a polyester fiber, a steel cord, which has a low elongation and a high strength, through a tension roll.
Is spirally wound at a predetermined spinning pitch. The spinning tension is 30 to 70 N, and the core wire 16 cuts into the preforming layer 15.

In this spinning step, the method of fixing the end of the core wire 15 when the core wire 16 is started to be wound on the surface of the preforming layer 15 is, for example, a groove formed on the surface of the thick end formed from the runner ring 14. 16 and the core wire 16
Can be fixed by inserting the end of. The core wire 16 is wound on the flat pre-molding layer 15 having a large friction coefficient, and is further depressed by the tension by about 0.05 to 0.1 mm to be securely fixed on the pre-molding layer 15 by the anchoring effect.

Subsequently, as shown in FIG. 6, the inner mold 3 around which the core wire 16 is wound is again mounted on the fixed side outer mold 2a in the other space 5b.
After transferring to (as shown in FIG. 1), the movable outer die 2b is moved to be joined with the fixed outer die 2a on the parting line 4. As shown in FIG. 2, carbon dioxide 33 is press-fitted into the cylinder 31 from the gas supply device 35, and the screw 34
By mixing with a thermoplastic elastomer to plasticize the elastomer and reduce the melt viscosity. The plasticized solution type thermoplastic elastomer flows from the runner ring 14 along the longitudinal direction by injection molding to completely fill the cavity 8 and mold the belt back surface portion 17. The plasticized thermoplastic elastomer can prevent the preforming layer 15 from being stretched and eliminate the disorder of the arrangement of the cords. Further, since carbon dioxide is released from the back surface portion 17 of the belt over time, its physical properties are not changed as compared with the case where carbon dioxide is not mixed. In this case, as described above, the thermoplastic elastomer is opened only in one runner 7 and does not flow into the other cavity 9.

After the movable outer die 2b is separated from the fixed outer die 2a, the inner die 3 is taken out from the fixed outer die 2a, and the belt sleeve 18 is removed from the inner die 3. In the case of the present invention, since the core wire 16 is not directly wound around the inner mold 3, the mold release agent can be positively applied to the inner mold 3 in advance, so that there is no problem in the mold release property of the belt sleeve 18. Becomes

Thereafter, the belt sleeve 18 is suspended and rotated by two rolls of a cutting machine (not shown) and cut into a predetermined width by a cutter to form the toothed belt 20 shown in FIG. .

In this toothed belt 20, the core wire 16 is embedded in the belt back surface portion 17 so as to extend in the longitudinal direction, and tooth portions 19 are provided below the belt back surface portion 17 at predetermined intervals.
Since the core wire 16 has no disorder in the arrangement and has no nose, it is not damaged by rubbing against the inner mold at the time of demolding. Also, since the core wire 16 is buried, it is less likely to receive dynamic fatigue,
The life of the belt can be extended.

Of course, a difference in hardness between the thermoplastic resins used in the initial injection step and the final injection step can be provided. For example, the tooth portion 19 is a hard resin with little deformation, and the belt back surface portion 17 is provided.
Can also improve the life of the belt by using a flexible resin with good flexibility. Further, teeth can be formed on the belt back surface portion 17.

In another embodiment, an outer mold 2 having two cavities 5a and 5b having different volumes is used, and both runners 7 are opened to allow the thermoplastic elastomer to flow into the two cavities 9 at the same time. Good. In this case, two empty spaces 5
The sizes of the gate and runner are adjusted in advance so that the filling properties of a and b are the same. That is, one empty space 5a
Is an initial injection step in which the inner mold 3 is installed, and the cavity is filled with the thermoplastic elastomer to form the preforming layer 15, and the other cavity 5 having a volume larger than the cavity 5a is formed.
In b, the inner mold 3 in which the core wire 16 is wound around the surface of the pre-molding layer 15 obtained in advance in the initial injection step is accommodated, and the cavity is filled with the thermoplastic elastomer and the belt rear surface portion 1
Used in the final injection step to mold 7.

In order to carry out these moldings at the same time, a thermoplastic elastomer in which carbon dioxide and a thermoplastic elastomer are mixed and plasticized to reduce the melt viscosity is used. Since carbon dioxide is naturally released in the preforming layer 15,
The physical properties of the elastomer layer are the same as those without carbon dioxide.

In yet another embodiment, the outer mold 2 for the initial injection process having at least one cavity 5a and the outer mold 2 for the final injection process having at least one cavity 5b are separately prepared. In this case, the thermoplastic elastomer that has been plasticized to reduce the melt viscosity may be used only in the final injection step.

[0041]

EXAMPLES Next, specific examples of the method for manufacturing a toothed belt according to the present invention will be described below. Example 1 Inner mold shown in FIG. 3 (S3M210, molding part length 100 m
m) was prepared. The radius of curvature of the outer periphery of the runner ring was gradually decreased so that the depth D on the gate side was 1.5 mm and the depth D'on the diagonal side was 3.0 mm.

(Initial Injection Step) After the inner mold is installed in one of the cavities of the fixed outer mold shown in FIG. 1, the movable outer mold is moved to be combined with the fixed outer mold on the parting line. ,
After adjusting the mold temperature to 70 ° C., pellets of an ester-based thermoplastic elastomer (manufactured by Toyobo Co., Ltd .: trade name Perprene P47CHFX, number average molecular weight 30,000) are CO ₂
The molten elastomer was charged into an injection molding machine equipped with an assisting device, and the runner ring was filled with the melted elastomer via a sprue, a runner, and one gate and then flowed in the longitudinal direction to form a preforming layer, thereby completing the initial injection step. The distance d between the convex portion of the inner mold and the outer mold was 0.25 mm. In this case, CO ₂ was not mixed into the molten elastomer.

After moving the movable side outer mold, the inner mold with the preforming layer was taken out from the fixed side outer mold, but the preforming layer was filled up to the end of the molding portion of the outer mold and cut off on the way. Moreover, no leakage was observed from the parting line on the surface of the preformed layer, and post-deburring processing was unnecessary.

(Spinning process) After mounting the inner die on the rotary shaft of the spinning device, the aramid fiber cord (400D
/ 2) is wrapped around the end of the preformed layer and tied,
It was wound with a spinning tension of 50 N / piece, and the winding end was also wound around the end of the preformed layer and fixed.

(Final Injection Process) After the inner die wound with the core wire is installed in the other space of the fixed outer die shown in FIG. 1, the movable outer die is moved in the same manner to move on the parting line. After combining with the fixed side outer mold and adjusting the mold temperature to 70 ° C,
Using the ester-based thermoplastic elastomer of the same material as in the initial injection process, CO ₂ was pressed into the cylinder at a pressure of 12 MPa, the molten elastomer adjusted to a temperature of 220 ° C was finally injected, and the thickness of the back of the belt was 0.6 mm. The part was molded.

Table 1 shows the relationship between the pressure of CO ₂ , the melt viscosity of the above ester-based thermoplastic elastomer, and the molding result of the toothed belt.

[0047]

[Table 1]

As a result, when the CO ₂ pressure was up to 8 MPa, the core wire was disturbed on the back surface of the belt in the final injection step, but when it exceeded 10 MPa, the melt viscosity was reduced and the core wire was not disturbed. .

(Finishing Step for Toothed Belt) After moving the movable outer mold, the inner mold with the belt sleeve was taken out from the fixed outer mold, and the belt sleeve was removed from the inner mold. No leakage was seen from the parting line on the surface of the belt sleeve, and post-deburring processing was unnecessary. The belt sleeve was attached to a cutting machine to obtain a toothed belt having a width of 6 mm. The toothed belt had a tooth pattern (STPD), a belt pitch length of 210 mm, a tooth portion pitch of 3 mm, and a number of teeth of 70, and there was no disorder in the arrangement of the cords, and the pitch was normal.

Comparative Example 1 In the final injection step in Example 1, after the inner die wound with the core wire was installed in the other space of the fixed outer die, the movable outer die was moved in the same manner to perform parting. After joining the fixed side outer mold on the line and adjusting the mold temperature to 70 ° C,
Using an ester-based thermoplastic elastomer of the same material as in the initial injection process, final injection was performed under the same conditions as in the initial injection process without CO ₂ being pressed into the cylinder, and a thickness e of 0.6 m was obtained.
The belt back part of m was molded. As a result, after moving the outer mold on the movable side, taking out the inner mold with the belt sleeve from the outer mold on the fixed side and observing the appearance, the preforming layer was seen to be stretched in the filling direction, and the side opposite the gate. There was a part of the elastomer layer rising in the axial direction, and there was a wavy turbulence in the core wire at this part.

Comparative Example 2 After mounting the inner die on the rotary shaft of the spinning device, the aramid fiber cord (400D / 2) was directly wound around the nose of the ridge with a spinning tension of 50 N / piece, and then the inner die was fixed. After installing in the other space of the outer mold, the mold temperature was adjusted to 70 ° C., the ester-based thermoplastic elastomer of the same material as in the initial injection step was used, and CO ₂ was pressed into the cylinder at a pressure of 12 MPa, The melted elastomer adjusted to a temperature of 220 ° C was injection-molded to form a belt sleeve. As a result, when observing the appearance of the inner-type belt sleeve taken out from the fixed-side outer die, there was a portion where the core wire disorder was large.

[0052]

As described above, in the method for manufacturing a thermoplastic elastomer toothed belt according to the claims of the present application, since the core wire is spirally wound on the surface of the preformed layer formed first, the core wire is tensioned. Due to the anchoring effect, it is fixed to the preforming layer to some extent, and even if it receives injection pressure or viscous resistance, it is fixed without moving.In particular, the thermoplastic elastomer with a low melt viscosity of the raw material that forms the back side of the belt is injected and filled into the cavity. Since the back surface of the belt is molded, the preforming layer can be prevented from being stretched and the arrangement of the cords can be prevented from being disturbed.

Further, since the above-mentioned elastomer is made to flow from the inner runner ring along the longitudinal direction of the molding portion composed of the concave portion and the convex portion, the cavity is sufficiently filled, and a defective portion such as a weld line is generated. Since there is no leakage of raw material from the external parting line, there is no need for post-processing such as deburring, and the peripheral surface of the runner ring is the diagonal side half way around the gate side of the inlet where raw material enters. Since the raw material is gradually scraped away toward the front side, the raw material is filled in the runner ring from the gate side toward the diagonal side as the initial flow path, and then flows all at once in the longitudinal direction of the molding part as the next flow path. Since the pre-molded layer is formed so as to uniformly fill up to the end of the molded part, there is an effect of reducing the occurrence of defective rate.

[Brief description of drawings]

FIG. 1 is an assembly diagram of a toothed belt molding die apparatus according to the present invention.

FIG. 2 is a schematic view of an injection molding machine equipped with a mold device having an AA cross section of FIG.

FIG. 3 is a partially cutaway front view of the inner mold.

FIG. 4 is a partially enlarged view of FIG.

FIG. 5 is a view of FIG. 4 viewed from the BB direction.

FIG. 6 is a view showing a flow path when a thermoplastic elastomer is injected from a gate to a runner ring after the inner mold is installed in the outer mold.

FIG. 7 shows an initial injection step in the manufacturing process of the toothed belt of the present invention.

FIG. 8 is a cross-sectional view showing a process of manufacturing the toothed belt of the present invention, in which a core wire is wound around the surface of the preforming layer.

FIG. 9 shows a final injection step in the manufacturing process of the toothed belt of the present invention.

FIG. 10 is a sectional view of a toothed belt made of a thermoplastic elastomer obtained by the method of the present invention.

[Explanation of symbols]

1 Mold equipment 2a Fixed side outer type 2b Movable side outer type 3 Internal type 4 parting line 5a vacant place 5b empty space 6 sprue 7 runners 8 gates 9 cavities 15 Preformed layer 16 cores 17 Belt back 18 Belt sleeve 30 injection molding machine 31 cylinders 33 carbon dioxide 34 screw 35 gas supply device

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Claims (5)

[Claims] 1. A method for manufacturing a thermoplastic elastomer toothed belt in which a core wire is embedded in a belt rear surface portion so as to extend in a longitudinal direction, and tooth portions are provided on at least one of the belt rear surface portions at predetermined intervals, After placing the inner mold with the concave and convex parts alternately inside the outer mold to form the cavity, injection molding thermoplastic elastomer to fill the cavity and completely surround the surface of the convex part. Such an initial injection step of forming a preformed layer, a spinning step of spirally winding the core wire around the peripheral surface of the preformed layer of the inner mold removed from the outer mold, and the inner mold wound with the core wire again After setting in the mold, injection molding of the thermoplastic elastomer whose melting viscosity is lowered by melting gas to completely fill the cavity and mold the back part of the belt, and the belt released from the inner mold sleeve Method for producing a thermoplastic elastomer toothed belt which comprises the steps of finishing the Luo toothed belt. 2. A method for manufacturing a thermoplastic elastomer toothed belt in which a core wire is embedded in a belt rear surface portion so as to extend in a longitudinal direction, and tooth portions are provided at predetermined intervals on at least one of the belt rear surface portions, A parting line is provided with an inner die having alternately arranged along the circumferential direction molding portions each having a concave portion and a convex portion extending in the longitudinal direction, and having a runner ring connected to the molding portion at one end. The sprue, runner, gate and inner mold runner ring provided in the fixed outer mold are placed in at least one space provided in the outer mold consisting of the fixed outer mold and the movable outer mold. The thermoplastic elastomer from the gate side of the inlet to the diagonal side half around it, and then gradually fills the runner ring with a large volume, and then flows along the longitudinal direction of the molded section. Preformed The initial injection step of forming a core wire, the spinning step of spirally winding the core wire around the peripheral surface of the preforming layer of the inner mold removed from the outer mold, and the inner mold around which the core wire is wound is installed again in the outer mold. After that, the final injection process of injection molding a thermoplastic elastomer whose melt viscosity is reduced by mixing gas to completely fill the cavity and mold the back surface of the belt, and the tooth sleeve from the belt sleeve released from the inner mold. The method for producing a toothed belt made of a thermoplastic elastomer, comprising: 3. The method for producing a toothed belt made of a thermoplastic elastomer according to claim 1, wherein in the initial injection step, a thermoplastic elastomer having a melt viscosity reduced by mixing gas is injection-molded. 4. The method for manufacturing a toothed belt made of a thermoplastic elastomer according to claim 1, wherein the gas is carbon dioxide. 5. The thermoplastic elastomer according to claim 1, wherein the thermoplastic elastomer is at least one selected from a polyester-based thermoplastic elastomer, an olefin-based thermoplastic elastomer, and a dynamically cross-linked thermoplastic elastomer. A method for manufacturing a toothed belt made of a thermoplastic elastomer.