WO2021029282A1 - Transporting roller and method for manufacturing same - Google Patents

Abstract

The present invention addresses the problem of providing: a transporting roller, which has a resin-made shaft part, and in which sink marks are hardly caused during molding, and which has a low price, high accuracy, and excellent wear resistance of a shaft part; and a method for manufacturing the same.　The transporting roller according to the present invention is for transporting an object to be transported, the transporting roller being characterized by comprising at least a resin-made shaft part and an elastic body part for transporting the object to be transported, wherein the shaft part has a porous structure having pores therein.

Description

Transport roller and its manufacturing method

The present invention relates to a transport roller and a method for manufacturing the same. More specifically, in a transport roller having a resin shaft portion, sink marks are less likely to occur during molding, and the shaft portion is inexpensive, highly accurate, and wear resistant to the shaft portion. Regarding transport rollers and the like having excellent properties.

The paper transport roller used in laser beam printers and multifunction devices is a combination of an elastic body for gripping the paper, a roller for kicking the paper, a gear for transmitting rotational drive, and a shaft. As a result, the number of parts is large and the assembly man-hours are high, which is a factor in increasing the cost.

FIG. 1 is a schematic view of a conventional transport roller having a metal shaft portion.

The metal transport roller 1 is composed of a metal shaft portion (also referred to as a shaft) 2, a kick-out roller portion 3, a tubular elastic body portion 4, and a gear portion 5. In the paper feed roller parts of OA equipment and the like, for example, an elastic body such as rubber is used in order to stably convey the paper in contact with the paper to be conveyed.

In recent years, in order to reduce the cost of the transport roller, a method has been considered in which the shaft, the kicking roller portion, and the gear portion are formed of the same sliding resin material instead of the metal shaft, and the elastic body portion is assembled later. ..

FIG. 2 is a schematic view of a transport roller having a resin shaft portion.

The resin transport roller 11 is composed of a resin shaft portion 12, a resin kick-out roller portion 13, a tubular elastic body portion 14, and a resin gear portion 15. However, in this method, if a thick resin is molded by the resin kick-out roller portion 13 or the like, it will sink, so a meat stealing shape is added to take measures. The shape of the meat steal makes it harder to sink, but when the resin is transferred to the uneven part of the meat steal, it sticks to the mold and cannot be released from the mold well, resulting in new dimensional accuracy and deformation. Problems will occur. Further, in this method, since the bearing is supported by the resin, it is important to select the resin to suppress the shaft wear.

On the other hand, as a method of reducing the assembly of the resin shaft portion and the elastic body portion, a method of molding the elastic body portion in two colors by using a thermoplastic elastomer capable of injection molding on the elastic body portion is known ( For example, see Patent Documents 1 to 3). Here, it refers to a technique of molding two types of resins different from two-color molding into one part.

However, in the above method, equipment for two-color molding is required, productivity is poor due to complicated mold mechanism for molding twice, and the resin forming the shaft portion is made of an elastic body. There are many problems such as difficulty in mold processing and molding because the uneven shape is given in order to have adhesiveness, and even if the assembly process is eliminated, the cost cannot be reduced.

Japanese Unexamined Patent Publication No. 9-202486 Japanese Unexamined Patent Publication No. 2001-31265 Japanese Unexamined Patent Publication No. 2006-31293

The present invention has been made in view of the above problems and situations, and the problem to be solved is that in a transport roller having a resin shaft portion, sink marks are less likely to occur during molding, and the cost is low, high accuracy, and the like. It is an object of the present invention to provide a transport roller having excellent wear resistance of a shaft portion and a method for manufacturing the same.

In order to solve the above problems, the present inventor is a transport roller for transporting an object to be transported in a process of examining the cause of the problem, and the transport roller is at least a resin shaft and the above. It is composed of an elastic body part that conveys the object to be transported, and because the resin shaft part has a specific structure, sink marks are less likely to occur during molding, and it is inexpensive, highly accurate, and has abrasion resistance of the shaft part. It has been found that an excellent transport roller can be obtained.

That is, the above problem according to the present invention is solved by the following means.

1. 1. A transport roller that transports the object to be transported.
The transport roller is composed of at least a resin shaft portion and an elastic body portion that transports the object to be transported.
A transport roller characterized in that the shaft portion has a porous structure having holes inside.

2. The transport roller according to item 1, wherein the shaft portion contains a thermoplastic resin and a chemical foaming agent.

3. The transport roller according to item 1 or 2, wherein the transport roller has a structure in which the elastic body portion is insert-molded and integrated with the shaft portion.

4. The transport roller according to any one of items 1 to 3, wherein the thermoplastic resin is any one of polyacetal, polypropylene or rubber-modified polystyrene.

5. The transport roller according to any one of items 2 to 4, wherein the chemical foaming agent is a baking soda-based foaming agent.

6. The transport roller according to any one of items 1 to 5, wherein the porosity represented by the following formula (1) is in the range of 4 to 15% in the shaft portion. ..
Equation (1)
Porosity (%) = (mass of shaft part when resin of shaft part is not made into porous structure-mass of shaft part of porous structure) / (shaft when resin of shaft part is not made into porous structure) Part mass) x 100

7. A method for manufacturing a transport roller for transporting an object to be transported, which is composed of at least a resin shaft portion and an elastic body portion for transporting the object to be transported.
A method for manufacturing a transport roller, which comprises a step of injecting and foaming a molten resin containing the thermoplastic resin to form a shaft portion made of the resin.

8. An insert that integrates the shaft portion and the elastic body portion by setting the elastic body portion in a mold, then filling the mold with the molten resin for the shaft portion, foaming the mold, and then solidifying the mold portion. The method for manufacturing a transport roller according to item 7, wherein the method includes a molding step.

9. The method for producing a transport roller according to item 7 or 8, further comprising a step of mixing the thermoplastic resin and a chemical foaming agent to prepare a composition for the molten resin.

According to the above means of the present invention, in a transport roller having a resin shaft portion, sink marks are less likely to occur during molding, the transport roller is inexpensive, highly accurate, and has excellent wear resistance of the shaft portion, and a method for manufacturing the same. Can be provided.

The effect of the present invention is explained as follows.

In injection molding, the melted resin is injected into the mold while being pressed into the mold to mold the product. Although the degree of injection molding varies depending on the type of resin, the product taken out after cooling is more often compared to the state of the melted resin. It contracts more or less. Therefore, the finished product does not have the same shape as the inner surface of the mold, and may be dented or, in extreme cases, deep holes may be opened. The defect due to this shrinkage is called "sink".

This shrinkage is naturally proportional to the amount of injected material, so the thicker the product, the more likely it is to sink. In order to prevent the occurrence of sink marks, design the product as evenly as possible, and intentionally form recesses in the thick block-shaped part of the same product so as not to affect the quality of the product (so-called "lightening"). Consideration such as "stealing meat") is required. On the contrary, there is also a method of calculating the sink mark in advance and giving the portion a thickness to obtain the desired shape in the sink mark, but this requires extremely advanced mold manufacturing technology.

Further, in order to make the transport roller made of resin, rigidity must be ensured, and in addition to the above-mentioned sink marks at the center of the wall thickness, warpage is likely to occur due to internal stress during molding shrinkage. A method of increasing the resin filling density is also effective as a countermeasure against sink marks, and for this purpose, a method of increasing injection pressure and back pressure is also taken. However, when trying to avoid sink marks at high pressure, warpage due to the internal stress is more likely to occur.

The transport roller of the present invention is composed of at least a resin shaft portion and an elastic body portion that transports the object to be transported, and the resin shaft portion has a porous structure having holes inside. It is a feature. In order to form the shaft portion into a porous structure having pores inside, for example, a step of injection-foaming a molten resin containing the thermoplastic resin and molding the resin shaft portion can be performed. it can.

The resin shaft portion is injection-foam molded to form a porous structure having pores inside, thereby suppressing molding shrinkage due to gas pressure due to foaming to prevent sink marks, and the said. Since the gas pressure of foaming is low, the generation of internal stress is reduced, so that the generation of warpage can also be suppressed.
Further, since the gas pressure of the foam is low, there is an advantage that PL marks described later on the elastic body portion can be suppressed.

Schematic diagram of a transport roller with a conventional metal shaft Schematic diagram of a transport roller having a resin shaft Schematic diagram showing a paper feed device in which a paper transport roller is arranged Graph showing change in foaming state (porosity) depending on resin filling rate Graph evaluating the effect of reducing warpage by foam molding Graph evaluating bending strength by foam molding Graph evaluating flexural modulus due to foam molding Schematic diagram illustrating the outline of the wear test Schematic diagram illustrating the wear depth of the wear test Graph evaluating wear resistance due to foam molding Schematic diagram illustrating the generation of PL scars Graph showing the relationship between resin filling pressure and PL marks by mold temperature Schematic diagram showing the outline of integral molding by insert molding of elastic body part and shaft part Schematic diagram of closing the mold and injecting molten thermoplastic resin from the injection molding means to mold the shaft Schematic diagram of a transport roller in which the elastic body and shaft are integrally molded When the absolute value of the difference between the solubility parameter values of the resin material used for the shaft portion and the resin material used for the elastic body portion exceeds 1.0 and is melt-bonded, and when it is melt-bonded within 1.0. Schematic diagram showing a transport roller in the case of Schematic diagram showing a specific flow of integral molding by insert molding of an elastic body part, a sliding member, and a shaft part. Schematic diagram showing a specific flow of integral molding by insert molding of an elastic body part, a sliding member, and a shaft part. Schematic diagram showing a specific flow of integral molding by insert molding of an elastic body part, a sliding member, and a shaft part. Schematic diagram showing a specific flow of integral molding by insert molding of an elastic body part, a sliding member, and a shaft part. A schematic diagram showing a method of providing a resin portion on the side surface of the elastic body portion and physically holding the elastic body portion by a force of molding shrinkage, and holding and holding the elastic body portion by molding shrinkage on the side surface resin portion of the elastic body portion. Graph showing the relationship of deformation of Schematic diagram illustrating a transport roller having a sliding member Schematic diagram showing a transport roller having a sliding member Enlarged view of the sliding member

The transport roller of the present invention is a transport roller that transports an object to be transported, and the transport roller is composed of at least a resin shaft portion and an elastic body portion that transports the object to be transported. It is characterized by having a porous structure having pores inside the portion. This feature is a technical feature common to or corresponding to the following embodiments.

As an embodiment of the present invention, it is preferable that the shaft portion contains a thermoplastic resin and a chemical foaming agent from the viewpoint of exhibiting the effect of the present invention. Chemical foaming agents have a cost advantage because they do not require special equipment and the materials are inexpensive.

Further, since the transport roller has a structure in which the elastic body portion is insert-molded and integrated with the shaft portion, man-hours can be reduced and costs can be reduced by a simple structure in manufacturing the transport roller. From the point of view, it is preferable.

Further, the fact that the thermoplastic resin is any one of polyacetal, polypropylene or rubber-modified polystyrene means that the sliding performance and cost of the thermoplastic resin, and that the elastic body portion is insert-molded and integrated with the shaft portion. It is a preferable material from the viewpoint of having a modified structure.

It is preferable that the foaming agent is a baking soda-based foaming agent from the viewpoint of ease of handling and cost.

It is preferable that the porosity represented by the formula (1) in the shaft portion is within the range of 4 to 15% from the viewpoint of suppressing sink marks and warpage while maintaining rigidity.

The method for manufacturing a transport roller of the present invention is a method for manufacturing a transport roller for transporting an object to be transported, which comprises at least a resin shaft portion and an elastic body portion for transporting the object to be transported. It is characterized by having a step of forming a shaft portion made of the resin by injection foam molding of a molten resin containing a thermoplastic resin.

Further, the elastic body portion is set in a mold, and then the molten resin is filled in the mold for the shaft portion, foamed, and then solidified to integrate the shaft portion and the elastic body portion. It is a preferred embodiment to have an insert molding step to allow.

In addition, it is a preferable embodiment to have a step of mixing the thermoplastic resin and the chemical foaming agent to prepare a composition for the molten resin.

Hereinafter, the present invention, its constituent elements, and modes and modes for carrying out the present invention will be described in detail. In the present application, "-" is used to mean that the numerical values described before and after the value are included as the lower limit value and the upper limit value.

<< Outline of the transport roller of the present invention >>
The transport roller of the present invention is a transport roller that transports an object to be transported, and the transport roller is composed of at least a resin shaft portion and an elastic body portion that transports the object to be transported. It is characterized by having a porous structure having pores inside the portion.

The "porous structure" as used in the present invention means a structure having a large number of pores or voids inside the molded product, and defines the pores or voids by the porosity represented by the formula (1) described later. Therefore, the size of the holes and the state of connection between the holes are not particularly limited.

The "elastic body" referred to in the present invention is a material having rubber elastic properties, has a high elastic limit, and has a low elastic modulus (generally, Young's modulus is 50 MPa or less).

Here, the general form of the "transport roller for transporting the object to be transported" will be described.

The "object to be transported" generally refers to a recording medium, and various media such as paper, resin plate, metal, cloth, and rubber can be used as the recording medium. Examples of the paper include plain paper, paperboard, coated paper, resin-coated paper, and synthetic paper. The “object to be transported” is not limited to the recording medium.

The basic paper feeding mechanism in devices such as laser beam printers and copiers is as introduced in Patent Document 1, for example. That is, as shown in the schematic view showing the paper feed device in which the paper transport roller is arranged in FIG. 3, the paper 52 is stacked and set in the paper feed cassette 50, and is taken out by the hopping roller 51. Further, after the hopping roller 51, a stacking prevention roller 53, 54, a transport roller 55, 56, etc. are arranged. In FIG. 3, the stacking prevention roller 54 is operated by a drive shaft 57, and a friction rubber 58 is wound around the roller main body 61.

The transport roller of the present invention is used for the hopping roller 51, the stacking prevention rollers 53, 54, the transport roller 55, 56, etc., but is used in many laser beam printers, copiers, and the like. Transport rollers are used and are not limited to these.

First, "injection foam molding", which is a feature of the present invention, will be described.

[1] Injection foam molding "Injection foam molding" in the present invention has a bubble structure (also referred to as vacancies) by injection-filling a mold with a molten resin having foamability in the injection molding process. This is a molding technique for obtaining a molded product. In injection foam molding, if an attempt is made to increase the porosity, filling will be insufficient and voids and unfilling are likely to occur. When the porosity is lowered, there is no foaming effect and sink marks, and the effects expected of the foamed molded product (prevention of sink marks, low warpage, etc.) do not appear.

Injection foam molding methods include chemical foaming, physical foaming, and thermal expansion microcapsules, all of which are effective, but in terms of cost, no special equipment is required and the materials are inexpensive. The chemical foaming method is the most effective.

In the chemical foaming method, an organic foaming agent such as ADCA (azodicarbonamide) and an inorganic foaming agent such as baking soda are decomposed and reacted by resin heat to generate gas and foam.

Among them, baking soda is suitable for resin molding because the foaming residue is sodium carbonate, which is harmless and has little effect on mold stains.

In the physical foaming method, a supercritical fluid of nitrogen or carbon dioxide is supplied to the molten resin for foaming. Trexal's "MuCell®" is known.

The method using heat-expandable microcapsules foams when the heat-expandable microcapsules expand due to heat. Kureha Microsphere of Kureha is known.

The chemical foaming method will be explained in more detail.

As the effervescent agent used, as the organic chemical effervescent agent, a polycarboxylic acid, an azo compound, a nitroso compound, a hydrazine derivative, a semicarbazide compound and the like can be used.

Specific examples of polycarboxylic acids in organic chemical foaming agents include citric acid, oxalic acid, fumaric acid, and phthalic acid.

Specific examples of the azo compound include azodicarboxylic amide (ADCA), 1,1'-azobis (1-acetoxy-1-phenylethane), dimethyl-2,2'-azobisbutyrate, and dimethyl-2,2'. -Azobisisobutyrate, 2,2'-azobis (2,4,4-trimethylpentane), 1,1'-azobis (cyclohexane-1-carbonitrile), 2,2'-azobis [N- (2) -Carboxyethyl) -2-methyl-propionamidine] and the like.

Specific examples of the nitroso compound include N, N'-dinitrosopentamethylenetetramine (DPT).

Specific examples of the hydrazine derivative include 4,4'-oxybis (benzenesulfonyl hydrazide), diphenylsulfone-3,3'-disulfonylhydrazide and the like.

Specific examples of the semicarbazide compound include p-toluenesulfonyl semicarbazide.

Specific examples of other organic chemical foaming agents include trihydrazinotriazine and the like.

Specific examples of bicarbonate in the inorganic chemical foaming agent include sodium hydrogen carbonate, ammonium hydrogen carbonate and the like.

Specific examples of carbonates include sodium carbonate, ammonium carbonate and the like.

Specific examples of organic acid metal salts include sodium citrate.

A specific example of nitrite is ammonium nitrite.

Among these foaming agents, it is preferable to use a foaming agent that does not decompose below the melting temperature of the resin constituting the foamed molded product but decomposes below the decomposition temperature. As such a foaming agent, azodicarbonamide (ADCA), sodium hydrogen carbonate, citric acid, sodium citrate and the like can be preferably used. In particular, it is preferable to use sodium hydrogen carbonate (baking soda) from the viewpoint of preventing odor and color unevenness from being generated in the obtained foamed molded product.

As the foaming agent, it is preferable to use a nonflammable gas as the main component of the generated gas. Specific examples of such a foaming agent include azodicarbonamide and the like as a foaming agent that generates nitrogen gas and carbon dioxide gas, and sodium hydrogencarbonate as a foaming agent that generates carbon dioxide gas. Examples of the foaming agent that generates nitrogen gas include dinitrosopentamethylenetetramine, p, p'-oxybisbenzenesulfonylhydrazide and the like.

The amount of the foaming agent added to the resin material for the foamed molded product is determined in consideration of the type of the foaming agent, the weight reduction rate of the obtained foamed molded product, etc., but is usually the resin material for the foamed molded product. It is 0.2 to 10 parts by mass with respect to 100 parts by mass.

The injection foam molding method will be explained in detail. A known method can be applied to the injection foam molding method itself, and the molding conditions may be appropriately adjusted according to the melt flow rate (MFR) of the thermoplastic resin, the type of foaming agent, the type of molding machine, or the shape of the mold. Usually, in the case of polypropylene resin as the thermoplastic resin, the resin temperature is 170 to 250 ° C., the mold temperature is 10 to 100 ° C., the molding cycle is 1 to 60 minutes, the injection speed is 10 to 300 mm / sec, the injection pressure is 10 to 200 MPa, and the mold is used. The filling pressure of the resin inward is set under conditions such as 1 to 20 MPa.

In addition, there are various methods for foaming in the mold, but among them, a mold composed of a fixed mold and a movable mold that can move forward and backward at an arbitrary position is used, and after the injection is completed, the movable mold is used. In the so-called core back method of retracting and foaming, a non-foamed layer is formed on the surface, the foamed layer inside tends to become uniform fine bubbles, and a foamed molded product having excellent lightness and good impact resistance can be obtained. It is preferable because it is easy. As a method of retreating the movable type, it may be performed in one step, it may be performed in multiple steps of two or more steps, and the speed of retreating may be appropriately adjusted.

In addition, by using the so-called counter pressure method in which polypropylene-based resin is introduced into the mold while applying pressure in the mold with an inert gas or the like in advance, it is possible to reduce surface appearance defects called swirl marks. preferable.

Further, a short shot method may be adopted in which the filling amount of the molten resin in the mold is adjusted to be small and foam molding is performed in the cavity portion.

Since the obtained injection foam molded product is excellent in balance between lightness and rigidity and prevention of sink marks and warpage, the porosity defined by the following formula (1) is in the range of 4 to 15% in the shaft portion. Is preferable.

Equation (1)
Porosity (%) = (mass of shaft part when resin of shaft part is not made into porous structure-mass of shaft part of porous structure) / (shaft when resin of shaft part is not made into porous structure) Part mass) x 100

The porosity is calculated by measuring the masses of the non-foamed molded product (shaft portion when not made into a porous structure) and the foamed molded product (shaft portion having a porous structure) having the same volume, and the mass difference is that of the foamed molded product. Since the mass is reduced due to the pores, the difference in mass is divided by the mass of the non-foamed molded product to express the porosity (%). The mass refers to the average mass of the molded product. The "porosity" referred to in the present application is synonymous with the "forosity" generally referred to in the injection foam molding method.

The porosity can be controlled by the filling rate of the molten resin in the mold. When the filling rate is low, the porosity is large, and when the filling rate is high, the porosity is small.

FIG. 4 is a graph showing changes in the foaming state (porosity) depending on the resin filling rate.

Filling of molten resin when polycarbonate (PC) and polyacetal (POM) are used as the resin, and 3% by mass of a baking soda-based foaming agent (Polyslen ES405 manufactured by Eiwa Kasei Co., Ltd.) is added to the resin for injection foam molding into a mold. The relationship between the rate (horizontal axis) and the porosity is shown. At the same time, a region where voids are generated (void region) and a region where sink marks are generated (sink region) as a molded product are shown.

From FIG. 4, when the porosity is less than 4%, the gas pressure is insufficient and the molding shrinkage cannot be completely canceled, and sink marks are likely to occur. When the porosity exceeds 15%, voids (cavities, vacancies) are generated. It can be seen that the size increases and the deformation and rigidity of the molded body tend to decrease. Therefore, in injection foam molding, the foaming agent type and amount used are selected, the resin filling rate in the mold is adjusted, the temperature and pressure related to injection are adjusted so that the porosity is in the range of 4 to 15%. It is preferable to do so.

(Effect of injection foam molding)
(1) Warpage reduction effect by foam molding Using polycarbonate (PC) and polyacetal (POM) as thermoplastic resins, a baking soda-based foaming agent (Polyslen ES405 manufactured by Eiwa Kasei Co., Ltd.) was added to the resin in an amount of 3% by mass, and the porosity was 10 A plate-shaped molded product having a length of 300 mm and a thickness of 4 mm was injection-foam molded and the amount of warpage was evaluated. Injection foam molding is performed using an injection molding machine "J140AD-110H" (manufactured by Japan Steel Works, Ltd.) under molding conditions of a cylinder temperature of 230 ° C, a mold temperature of 50 ° C, an injection speed of 30 mm / sec, and a holding pressure of 5 MPa. Pieces were made.

FIG. 5 is a graph evaluating the warp reduction effect of foam molding.

The amount of warpage was evaluated by placing the above-molded test piece on a flat table and measuring the maximum value of the amount of warp with the end floating from the flat table with a caliper. The measurement was carried out at 25 ° C. and 50% RH, after adjusting the humidity for 24 hours, the rise of the end portion was measured.

As a result, as shown in FIG. 5, the amount of warpage is reduced to 1/5 by foam molding as compared with normal molding (non-foam molding).

(2) Effect on strength and rigidity in foam molding Polycarbonate (PC), polycarbonate containing glass fibers (PC-GF), polyacetal (POM), high-impact (impact-resistant) polystyrene (HIPS), polypropylene as thermoplastic resins Using (PP) and cycloolefin (COP), a baking soda-based foaming agent (polystyrene ES405 manufactured by Eiwa Kasei Co., Ltd.) was added to the resin in an amount of 3% by mass, and a plate-shaped molded product having a void ratio of 10% and a width of 300 mm was injected. Foam molding was performed to evaluate bending strength and bending elasticity.

Bending strength refers to the maximum bending stress that the test piece can withstand during the bending test. Measured with Tencilon under the test conditions of JIS K7171 (2008). For example, a test piece of an injection foam molded product conforms to JIS K7171 under the conditions of a bending speed of 100 mm / min, a jig tip R5 mm, a span interval of 100 mm, and a test piece (width 50 mm × length 150 mm × thickness 4 mm). Measure and obtain. As a measuring device, Tencilon RTC-1225A manufactured by Orientec Co., Ltd. is used, and the measurement is performed at a temperature of 23 ° C. and a humidity of 55% RH. The evaluation is made based on the ratio (%) of the bending strength of the foam-molded test piece to the non-foam-molded test piece.

The flexural modulus is measured according to JIS K7171 (2008) and evaluated according to the following criteria. The test piece is measured and obtained under the conditions of a bending speed of 100 mm / min, a jig tip R5 mm, a span interval of 100 mm, and a test piece (width 50 mm × length 150 mm × thickness 4 mm) in accordance with JIS K7171. As a measuring device, Tencilon RTC-1225A manufactured by Orientec Co., Ltd. is used, and the measurement is performed at a temperature of 23 ° C. and a humidity of 55% RH. The evaluation is made based on the ratio (%) of the flexural modulus of the foam-molded test piece to the test piece not foam-molded.

As a result, as shown in FIG. 6A bending strength and FIG. 6B bending elasticity, in the case of a foam molded product, the decrease in bending elasticity is small as a whole, but the bending strength depends on the type of thermoplastic resin, and polypropylene (POM). ), High-impact (impact resistant) polystyrene (HIPS), polypropylene (PP), and cycloolefin (COP) are excellent, and among them, polyacetal (POM) and polypropylene (PP) have less deterioration and are related to the present invention. It can be seen that the resin used for forming the shaft portion is preferable. In addition, in FIG. 6A and FIG. 6B, the ratio (%) of the bending strength and the bending elastic modulus of each material was shown when the normal molding strength (non-foam molding strength) was set to 100%.

(3) Abrasion resistance test by foam molding Since a gas pattern called a swirl mark is generated during foam molding and there is concern about abrasion resistance due to the effect, an abrasion resistance test was conducted.

Using polyacetal (POM) as the thermoplastic resin, a test piece was prepared by injection foam molding as described above, and the abrasion resistance was evaluated by the abrasion tester shown in FIG. 7A. The porosity was set to 9%.

(Abrasion resistance test)
A steel wire spring 202 is brought into point contact with the cylindrical resin material 201, and the resin material is rotated while applying a pressure (about 140 MPa) equivalent to that of a paper ejection roller. After the test for a certain period of time, the wear depth of the resin (see FIG. 7B) is measured and converted into a wear volume.

As a result, as shown in FIG. 8, in reality, no deterioration in wear resistance was observed as compared with normal molding, and the amount of wear was reduced to 1/4 by foam molding. Under the same conditions, a large amount of abrasion powder is usually attached to the molded product, and there is a problem in durability.

(4) Effect of filling pressure during foam molding The tube-shaped elastic body, which will be described later, is deformed by the pressure during foaming of the molding resin due to the filling pressure of the resin during injection foam molding, and the fixed side mold A failure may occur in which a burr-like protrusion occurs between the mold and the movable mold. This is referred to as a "PL (parting line) mark" in the present invention.

FIG. 9A is a schematic diagram illustrating the generation of PL marks.

A part of the tube protrudes from the parting line (PL) between the fixed side mold and the movable mold due to the filling pressure of the molten resin to form burrs.

FIG. 9B is a graph showing the relationship between the resin filling pressure and the PL mark for each mold temperature.

Two types of polyethylene-based elastomer (TPS) (rubber hardness A40 ° and A80 °) are used for the tubular elastic body, and polypropylene (PP) and baking soda-based foaming agent (Polyslen ES405 manufactured by Eiwa Kasei Co., Ltd.) are used as molding resins. After setting the resin temperature to 210 ° C. and the mold temperature to 57 ° C., the filling pressure of the molten resin into the mold was changed at an injection speed of 20 mm / sec to increase the height of the PL marks generated. It was measured. The porosity was set to 10%.

From FIG. 9B, it can be seen that in order to satisfy the target value of 0.05 mm for PL marks, it is preferable to set the filling pressure to 20 MPa or less regardless of the rubber hardness of the elastic body.

In normal injection molding, sink marks occur at 20 MPa or less and molding accuracy is not obtained, but in injection foam molding, it is preferable to mold without applying filling pressure.

[2] Injection foam molding of a transport roller [2.1] First embodiment The first embodiment of the transport roller of the present invention is a transport roller that transports an object to be transported, and the transport roller is It is characterized in that it is composed of at least a resin shaft portion and an elastic body portion that conveys the object to be transported, and the shaft portion has a porous structure having holes inside.

Further, it is preferable that the transport roller has a structure in which the elastic body portion is insert-molded on the outer periphery of the shaft portion.

The elastic body portion is a material having rubber elastic properties, has a high elastic limit, and has a low elastic modulus (generally, Young's modulus is 50 MPa or less). The elastic body does not have to be made with the same mold as the shaft, and it can be made of rubber products as well as thermoplastic elastomers, and the manufacturing method may be cut out of an extruded tube other than injection molding, and is not particularly limited. ..

In particular, the elastic body portion according to the present invention is preferably a molded product obtained by molding a thermoplastic elastomer into a cylindrical shape (tube shape).

Further, the absolute value of the difference between the values of the solubility parameters of the resin material used as the matrix material of the thermoplastic elastomer contained in the elastic body portion and the resin material used for the shaft portion to be injection-molded is within 1.0. Moreover, having a structure in which the elastic body portion and the shaft portion are melt-bonded is a viewpoint of integrally molding the elastic body portion and the shaft portion (hereinafter, also referred to as integral molding). Therefore, it is preferable.

The thermoplastic elastomer used for the elastic body is a styrene elastomer, a chlorinated polyethylene elastomer, a vinyl chloride elastomer, an olefin elastomer, a urethane elastomer, an ester elastomer, an amide elastomer, an ionomer elastomer, or an ethylene / ethylene acrylate. Elastomers selected from the group consisting of copolymerization-based elastomers and ethylene / vinyl acetate copolymer-based elastomers are preferable, and styrene-based elastomers and olefin-based elastomers are more preferable.

Examples of the styrene-based elastomer include SBS (styrene-butadiene-styrene block copolymer), SIS (styrene-isoprene-styrene block copolymer), SEBS (styrene-ethylene-butylene-styrene block copolymer: hydride SBS), and SEEPS ( Styrene-ethylene-ethylene-propylene-styrene block copolymer), SEPS (styrene-ethylene-propylene-styrene block copolymer: hydride SIS), HSBR (hydride styrene-butadiene random copolymer) and the like can be mentioned. Examples of commercially available styrene-based thermoplastic elastomers include "Septon" (trade name, manufactured by Kuraray), "Tough Tech" (trade name, manufactured by Asahi Kasei Chemicals), and "Dynaron" (trade name, manufactured by JSR). be able to.

Olefin-based thermoplastic elastomers (TPOs: Thermoplastic Organic Elastomers) use polypropylene (PP), polyethylene (PE), and other polyolefins as hard segments (matrix materials in the present invention), such as ethylene-propylene rubber (EPM, EPDM). A thermoplastic elastomer having a rubber component as a soft segment. The TPO is broadly divided into three types: a blend type of polyolefin and rubber components, their dynamic cross-linking type (TPV: Themoplastic Vulcanize), and a polymerization type (R-TPO: Reactor-TPO). Can be separated.

Examples of commercially available products include "Thermoran (registered trademark)" and "TREXPRENE (registered trademark)", which are TPOs of Mitsubishi Chemical Corporation.

When the thermoplastic elastomer and the thermoplastic resin as the matrix material are blended, the thermoplastic resin is blended in the range of 25 to 100 parts by mass with respect to 100 parts by mass of the thermoplastic elastomer, and the thermoplastic elastomer is blended. A composition that is dynamically vulcanized by sulfur vulcanization or resin vulcanization and dispersed in the thermoplastic resin is preferably used.

As described above, it is preferable to use the thermoplastic resin as the matrix material for the thermoplastic elastomer from the viewpoint of integrally molding the elastic body portion and the shaft portion by melt joining, and the thermoplastic used for the shaft portion. As the resin, acrylonitrile-butadiene-styrene (ABS), thermoplastic (POM), polypropylene (PP), polyethylene (PE) or polycarbonate (PC) are preferably exemplified.

Here, in order to have a structure in which the elastic body portion and the shaft portion are melt-bonded, the value of the solubility parameter of the resin material used as the matrix material of the thermoplastic elastomer and the resin material used for the shaft portion. The absolute value of the difference is preferably 1.0 or less, and the resins are melted by heating and the resins are easily melt-bonded to each other to achieve integral molding.

"Melting joint" generally means that heat or pressure or both are applied to the joints of two or more types of members, and if necessary, an appropriate filler metal is added to make the joints continuous. It refers to a joining method for forming a member, and in the present invention, it means that the resins are melted by heating or the like and come into contact with each other, so that the resins are mixed at the interface and integrally molded as one mixture.

In addition, "integral molding" refers to a state in which the members to be joined do not separate unless force is applied.

Here, the solubility parameter value (also referred to as SP value) of the resin material is calculated by the Bicerano method based on the regression equation obtained by statistically analyzing the correlation between the molecular structure and the physical property value of the polymer material. Specifically, in the software "Scigress Version 2.6" (manufactured by Fujitsu Limited) installed on a commercially available personal computer, the structure of each compound is substituted and the value calculated by the Bicerano method is adopted.

Table I shows the thermoplastic elastomer species (silicone rubber, fluorine-based rubber, ethylene propylene rubber (EPDM), natural rubber, olefin-type elastomer, styrene-based elastomer (SBR), and matrix grades) used for the elastic body portion according to the present invention. The solubility parameter values of (polypropylene, polyester resin, acrylic resin) and the thermoplastic resin type (polypropylene, polyethylene, polycarbonate, polyacetal) used for the shaft portion, and the elastic body portion when made into a molded part. The results of the degree of peeling of the shaft (evaluation that it cannot be peeled, easily peeled, or not joined) are shown.

From Table I, the absolute value of the difference between the solubility parameter values of the resin material used as the matrix material of the thermoplastic elastomer contained in the elastic body portion and the resin material used for the shaft portion is within 1.0. It can be seen that sometimes the resin materials are melt-bonded to each other to enable integral molding.

Therefore, by optimizing the combination of the resin material used as the matrix material of the thermoplastic elastomer contained in the elastic body portion and the resin material used for the shaft portion, integral molding becomes possible, and the elastic body portion is further formed. By having a structure in which the portion and the shaft portion are insert-molded, the shaft portion does not have to have a special shape for preventing the elastic body portion from being displaced, and in terms of structure and mold design. Will have the advantage of. For example. Advantages include the ability to accurately produce a molded product without the effects of mold release during molding, and the ease of designing the elastic body when obtaining a predetermined nip amount without interfering with the anti-displacement shape. Be done.

In addition, the toner used during printing (styrene acrylic and polyester are used and the melting point is around 100 ° C.) may adhere to the elastic body of the transport roller.

Table II shows the thermoplastic elastomer species (silicone rubber, fluororubber, ethylene propylene rubber (EPDM), natural rubber, olefin-type elastomer, styrene-based elastomer (SBR), and matrix grades) used for the elastic body portion according to the present invention. Degree of toner adhesion to elastic body when the combination of (polypropylene, polyester resin, acrylic resin) is changed as shown in Table II below and the temperature during transportation is changed to 80 to 100 ° C. Was evaluated.

From Table II, when the toner adhesion to the elastic body when the temperature during transportation was changed to 80 to 100 ° C. was visually evaluated, polypropylene (PP) was used as the matrix material with the olefin elastomer or styrene elastomer. Experimental results have been obtained that toner adhesion can be suppressed at each temperature by using the existing thermoplastic elastomer for the elastic body. Therefore, it can be seen that polypropylene (PP) is excellent as the matrix material for the thermoplastic elastomer.

On the other hand, it is also preferable that the shaft portion contains a resin reinforcing agent in order to suppress deformation of the bearing portion and improve durability. For example, a fibrous filler such as polybenzazole fiber, carbon fiber, aramid fiber, metal fiber, glass fiber, ceramic fiber or polyparaphenylene terephthalamide fiber can be mixed in the thermoplastic resin forming the shaft portion. preferable. Above all, the fibrous filler is more preferably at least one of carbon fibers and glass fibers.

The average diameter of the fibrous filler is preferably in the range of 0.2 to 10.0 μm, and the average aspect ratio is preferably in the range of 10 to 100. The smaller the average diameter of the fibrous filler, the less likely it is to affect the surface smoothness of the shaft portion, so the average diameter is preferably 10 μm or less. Further, if it is 0.2 μm or more, sufficient strength can be obtained.

Also, the average length of the fibrous filler is preferably 100 μm or less because the shorter the average length, the less likely it is to affect the surface smoothness of the shaft portion. Further, if the average length of the fibrous filler is 10 μm or more, sufficient strength can be obtained.

Further, it is preferable that the average aspect ratio of the fibrous filler is in the range of 10 to 100. If it is within this range, it is easily compatible with the resin, and it is considered that the reinforcing effect of the shaft portion is good.

Specific examples of the fibrous filler include carbon fiber milled fiber (manufactured by Mitsubishi Chemical Co., Ltd.), glass fiber T-289DE (manufactured by JEOL Ltd.), milled fiber (manufactured by Asahi Glass Fiber Co., Ltd.), and the like. Can be done.

Further, the composition for the elastic body portion and the shaft portion may contain various polymers and additives other than the thermoplastic elastomer and the thermoplastic resin as long as the object of the present invention is not impaired. Specific examples of additives include antioxidants, heat-resistant stabilizers, weather-resistant stabilizers, light-resistant stabilizers, UV absorbers, antistatic agents, anti-aging agents, fatty acid metal salts, softeners, dispersants, nucleating agents, and lubricants. , Flame retardants, pigments, dyes, organic fillers.

Each component and other additives are injection-foamed when a predetermined amount thereof is uniformly mixed using a Henschel mixer, V-blender, ribbon blender, tumbler blender, etc., and then processed into a normal pellet shape using an extruder. It can be used as a resin composition suitable for molding.

The method for manufacturing a transport roller of the present invention is a method for manufacturing a transport roller for transporting an object to be transported, which is composed of at least a resin shaft portion and an elastic body portion for transporting the object to be transported. It is characterized by having a step of forming a shaft portion made of the resin by injection foam molding of a molten resin containing a thermoplastic resin, the elastic body portion is set in a mold, and then the shaft portion is used. It is preferable to have an insert molding step of integrating the shaft portion and the elastic body portion by filling the mold with the molten resin, foaming the mold, and then solidifying the resin.

As described above, the elastic body portion does not need to be made of the same mold as the shaft portion, and can be made of a rubber product as well as a thermoplastic elastomer, and the manufacturing method may be injection molding or cutting out of an extruded tube. For example, it is preferable that the elastic body portion is molded by the following method.

1) Extrude a cylindrical (tube-shaped) molded product using a thermoplastic elastomer and a matrix material.

2) The obtained cylindrical molded product is polished for dimensional adjustment, cut to the desired roller length, and then washed.

3) Set the cut cylindrical molded product in the mold for integral molding by insert molding with the shaft.

Known molding methods for obtaining a molded product include, for example, an injection molding method, an injection compression molding method, an extrusion molding method, a deformed extrusion method, a transfer molding method, a hollow molding method, a gas-assisted hollow molding method, and a blow molding method. Extrusion blow molding, IMC (in-mold coating molding) molding method, rotary molding method, multi-layer molding method, two-color molding method, insert molding method, sandwich molding method, foam molding method, pressure molding method and the like can be mentioned. In the present invention, it is preferable to insert mold the elastic body portion and the shaft portion by using an injection foam molding method.

In the present invention, "insert molding" means that a tube such as an elastic body portion or a sliding member described later, which is inserted and set in a mold, is filled with a molten thermoplastic resin to form an elastic body portion or a sliding member. A molding method that integrates the elastic body portion and the shaft portion that penetrates the sliding member.

FIG. 10 is a schematic view showing an outline of integral molding by insert molding of an elastic body portion and a shaft portion.

In FIG. 10A, the elastic body portion 102 is set at a predetermined position on the open / close mold 101 by the member setting means 106.

The molten resin is prepared in advance by the step of mixing the thermoplastic resin and the chemical foaming agent and preparing a composition for the molten resin.
In FIG. 10B, the mold 101 is closed, and the thermoplastic resin (molten resin 104) melted from the injection molding means 103 is injected into the space forming the shaft portion to mold the shaft portion 105.

In FIG. 10C, the one-sided mold 101 is removed to obtain a transport roller in which the elastic body portion 102 and the shaft portion 105 are integrally molded.

As described above, the transport roller of the present invention preferably has a structure in which the thermoplastic elastomer layer is integrated on the outer periphery of the roller shaft portion by insert molding.

FIG. 11 shows the case where the absolute value of the difference between the solubility parameter values of the resin material used for the shaft portion and the resin material used for the elastic body portion exceeds 1.0 and is melt-bonded within 1.0. It is a schematic diagram which shows the transport roller at the time of melt-joining in.

FIG. 11A is a schematic view showing a case where the absolute value of the difference between the solubility parameter values of the resin material used as the matrix material of the thermoplastic elastomer and the resin material used for the shaft portion exceeds 1.0. is there.

In this case, when the resin is filled, the elastic body portion 102 and the shaft portion 105 are in close contact with each other (see B in FIG. 11), but when the thermoplastic resin of the shaft portion is cooled, the elastic body portion due to molding shrinkage Peeling, poor idling, etc. occur (see C in FIG. 11). The arrow given to the shaft portion 105 during cooling indicates the direction of molding shrinkage.

D of FIG. 11 and E of FIG. 11 are schematic views showing a conventional case in which a shape for preventing displacement to the periphery of an elastic roller is provided in response to such an idling defect.

For example, a convex shape 107 made of resin is given to the shaft portion 105 around the elastic body roller 102 (see D in FIG. 11), or a concave shape in which resin is injected into the elastic body part is given to the elastic body part. (See E in FIG. 11).

On the other hand, F in FIG. 11 shows a case where the absolute value of the difference between the values of the solubility parameters of the resin material used as the matrix material of the thermoplastic elastomer and the resin material used for the shaft portion is within 1.0. There is, the resin materials are integrally molded for melt-bonding, and even if molding shrinkage occurs when the thermoplastic resin of the shaft is cooled, the shaft is melt-bonded, so that the shaft is an elastic part. It is possible to suppress idling failure without peeling from the resin (see G in FIG. 11 and H in FIG. 11).

FIG. 12 is a schematic view showing a specific flow of integral molding by insert molding of an elastic body portion, a sliding member described later, and a shaft portion. Here, a specific example of integrally molding the elastic body portion, the sliding member described later, and the shaft portion will be shown.

FIG. 12A is a step of setting an elastic body portion and a tube which is a sliding member at a necessary position during mold opening.

In the figure, the tubular elastic body portion 102 and the tubular sliding member 152 for bearings are set in the mold opening mold 151.
The tube may be inserted into the mold by hand, but it is desirable to use a robot such as a take-out machine during mass production. Further, the tube may be set on either the fixed side or the movable side of the mold. You can judge the better one from the mold mechanism. The mold holding of the tube can be carried out by light press-fitting the diameter of the tube, but it is also possible to incorporate a mechanism such as air suction or adhesion into the mold.

FIG. 12B is a step of molding the mold and injecting the thermoplastic resin for the shaft portion from the gate portion.

In the figure, the mold opening mold 151 in which the tubular elastic body portion 102 and the tubular sliding member 152 for bearings are set is closed, and the molten resin 154 is injected from the injection molding means 153 to form the shaft portion. .. When injecting the resin, the gate portion 155 prevents leakage of the molten resin.

The following conditions can be given as an example of the resin injection conditions, but the conditions are not limited to these.

<Case example with melt bonding: 1st embodiment>
Molding resin for shaft: Polypropylene (PP SP value 8.1)
Baking soda-based foaming agent (Polyslen ES405 manufactured by Eiwa Kasei Co., Ltd.) was added to the resin in an amount of 3% by mass, and the porosity was 10%.
Elastic tube: Polyethylene elastomer (TPS: Polypropylene (PP) matrix SP value 8.1)
・ Resin temperature: 220 ℃
・ Mold temperature: 50 ℃
-Holding condition: 20 MPa-10s cycle In FIG. 12C, after injecting and filling the molten resin, the molten resin is foamed in the mold and then cooled to integrate the elastic body portion, the sliding member and the shaft portion. It is a process.

It is preferable to appropriately adjust the conditions related to foaming from the preferable range of the above-mentioned injection foam molding conditions.

For cooling, a low-temperature medium such as low-temperature water is circulated in the flow path in the mold 151, and the mold 151 is cooled until the temperature of the mold becomes equal to or lower than the glass transition temperature Tg of the thermoplastic resin. At this time, it is preferable to adjust the average cooling rate defined below to 0.4 to 3.0 K / sec.
(Average cooling rate) = (heat absorption amount when cooling the mold 151: J / sec) / (heat capacity of the mold 151: J / cm ³ / K) / (size of the mold 151: cm ³ )
FIG. 12D is a step of opening the mold 151 and taking out the insert molded product. It is preferable to project and take out by an ejector pin or the like as in normal injection molding. After taking it out, the gate is cut to separate the molded part from the runner or the like.

By this step, the transport roller according to the first embodiment of the present invention is obtained in which the elastic body portion 102, the sliding member 152 described later, and the shaft portion 105 which is a foam molded body are integrally molded by insert molding. Be done.

[2] Second embodiment (modification example)
As another embodiment of the present invention (second embodiment: modified example), in the transport roller of the present invention, the resin portion constituting the shaft portion is in contact with both sides of the side surface portion of the elastic body portion. The height of the resin portion is within the range of 30 to 70% of the thickness of the elastic body portion, and the resin portion has a structure in which the elastic body portion is held by shrinkage during molding. ,preferable.

This is because one of the functions required of the transport roller is slidability (low friction, wear resistance), and as a resin for the shaft portion, the slidability is generally good and inexpensive polyacetal (POM: SP value 11). There is also a demand for using nylon (PA6, PA66: around SP value 13), etc., and there is also a demand for using inexpensive silicone rubber, fluororubber, ethylene propylene rubber (EPDM), etc. as the elastic body part. In that case, since it is difficult to integrate by melt joining with the combination of the materials, a method of providing a resin part on the side surface of the elastic body part and physically holding the elastic body part by the force of molding shrinkage is used. It is preferable to do so.

FIG. 13 is a schematic view showing a method of providing a resin portion on the side surface of the elastic body portion and physically holding the elastic body portion by a force of molding shrinkage, and holding the elastic body portion on the side surface resin portion of the elastic body portion by molding shrinkage. It is a graph which shows the relationship between the deformation of an elastic body part.

13A to 13C are schematic views showing a method of providing a resin portion on the side surface of the elastic body portion and physically holding the elastic body portion by a force of molding shrinkage.
In FIGS. 13A to 13C, a convex resin portion is provided on the shaft portion 105 on the side surface of the elastic body portion 105, and is 0% with respect to the thickness of the elastic body portion (see A in FIG. 13). It is a case of physically holding at a height of 70% (see B in FIG. 13) and 100% (see C in FIG. 13).

D in FIG. 13 is a schematic view showing that the elastic body portion 102 is deformed by the resin portion on the side surface of the elastic body portion due to the molding shrinkage of the shaft portion 105. The arrow indicates the direction of molding shrinkage.

FIG. 13E is a graph showing the relationship between the holding of the elastic body portion side resin portion during molding shrinkage and the deformation of the elastic body portion.

The horizontal axis indicates the ratio (%) of the height of the resin for the shaft portion in contact with the elastic body, and the vertical axis indicates the roundness indicating the degree of deformation of the elastic body. Due to the molding shrinkage of the resin for the shaft portion, the elastic body portion is deformed and the roundness is deteriorated. Therefore, it is necessary to adjust the shape within a certain degree of deformation (roundness).

"Roundness" measures the contours of the elastic body surface on the 2 or 3 equatorial planes that form 90 ° with each other using a commercially available roundness measuring device, and measures the contours of the elastic body surfaces in the radial direction from the respective minimum circumscribed circles to the elastic body surface. The maximum value of the distance can be calculated as the roundness.

In the graph of E in FIG. 13, there are four types of results: different hardness of the rubber tube of the elastic body (A40 °, A80 °) × different joining method (melt joining, physical joining).

The degree of deformation of the elastic body can achieve the target roundness change of 0.2 mm or less in the area below the black dotted line.

From this result, it can be seen that the rubber hardness is low and it does not deform as much as A40 °. Further, in order to hold the elastic body portion and keep the roundness change within the target even at A40 °, which has a low rubber hardness, the height of the side resin needs to be 30% of the thickness of the elastic body portion. On the other hand, if the rubber hardness is A80 or higher, the height of the side resin needs to be 80% or more of the thickness of the elastic body part, and a nip (the elastic body part elastically deforms to grip the paper) is obtained. It becomes a problem because it cannot be transformed.

Therefore, from the above results, it is preferable that the rubber hardness of the elastic body portion is A80 ° or less, and in order to keep the change in roundness within the target and to obtain the effect of the nip of the elastic body, the elastic body The height of the resin for the shaft portion in contact with the elastic body portion is preferably in the range of 30 to 70% with respect to the thickness of the elastic body portion.

In the case of the first embodiment of melt joining, it can be seen from the graph of FIG. 7B that the change in roundness is not affected by the rubber hardness.

In the method for manufacturing a transport roller of the present invention in the second embodiment, the resin portion constituting the shaft portion is said to have a height within a range of 30 to 70% of the thickness of the elastic body portion. It is characterized by having a step of molding by injection foam molding so as to be in contact with both sides of a side surface portion of the elastic body portion, and then holding the elastic body portion by shrinkage during molding of the resin portion.

Specifically, the elastic body portion is set in the mold according to the flow of integral molding by insert molding of the elastic body portion and the sliding member and the shaft portion shown in FIG. 12 (FIGS. 12A to 12D). Create a mold so that the resin portions constituting the shaft portion are in contact with both sides of the side surface portion of the elastic body portion at a predetermined height, inject the thermoplastic resin for the shaft portion, cool it, and then take out the insert molded product. Just do it.

For example, the following conditions can be exemplified, but the conditions are not limited to these.

<Case example without melt bonding: Second embodiment>
Shaft molding resin: Polyacetal (POM SP value 11)
Baking soda-based foaming agent (Polyslen ES405 manufactured by Eiwa Kasei Co., Ltd.) was added to the resin in an amount of 3% by mass, and the porosity was 10%.
Elastic tube: Polyethylene elastomer (TPS: Polypropylene (PP) matrix SP value 8.1)
-Resin temperature: 210 ° C
・ Mold temperature: 70 ℃
-Holding condition: 20 MPa-10s cycle-Height of the resin part in contact with the elastic body part: 30 to 70% of the thickness of the elastic body part

[3] Third Embodiment (Modified example)
In another embodiment of the transport roller of the present invention (third embodiment: modified example), a portion corresponding to the bearing portion of the shaft portion has a tubular sliding member, and the sliding portion is provided. It is preferable that the member and the shaft portion have a structure in which they are insert-molded and integrated.

Problems in plasticizing metal shafts include dimensional accuracy and rigidity. Materials with good slidability are usually crystalline resins such as polyacetal (POM) and nylon (PA6, PA66), but their dimensional accuracy is not very good. However, if an amorphous resin having good dimensional accuracy or a resin to which a resin reinforcing agent such as glass fiber is added to increase the rigidity is used, a problem occurs in slidability. Therefore, a material having good slidability may be used only for the sliding member.

FIG. 14 is a schematic view illustrating a transport roller having a sliding member.

FIG. 14A shows a paper feed unit 160 having four bearing portions. The part surrounded by the alternate long and short dash line is the bearing.

FIG. 14B shows a transport roller in which four sliding members 152 are insert-molded on the shaft portion 105.

FIG. 14C is an enlarged view of the sliding member 152, which is a cylindrical (tube-shaped) member.

In the paper feed unit, pressure is applied to the bearing portion to generate friction, so it is preferable to use a sliding material having good wear resistance. There are friction coefficient and limit PV value (load pressure x speed) as indexes showing sliding characteristics, but it is necessary to select an appropriate material depending on the conditions and environment of use.

Here, the limit PV value is a limit value at which the sliding surface of the material is deformed or melted due to frictional heat generation.

As the sliding member, it is preferable to select a material having better wear resistance than polypropylene (PP), which is preferable as the shaft resin, according to the wear test apparatus and procedure shown in FIGS. 7A and 7B.

Table III shows the results of wear resistance tests for various resins.

The test materials are polymethylmethacrylate (PMMA), tetrafluoroethylene (PTFE), high-impact (impact-resistant) polystyrene (HIPS), tetrafluoroethylene (PFA), polypropylene (PP), and polyphenylene sulfide (shown in Table III). PPS), polyetheretherketone (PEEK), nylon (PA66), ultrahigh molecular weight polyethylene (PE) and polyacetal (POM).

From Table III, as the sliding member according to the present invention, polyacetal (POM), ultrahigh molecular weight polyethylene (PE), nylon (PA66), polyphenylene sulfide (PPS), which have better wear resistance than polypropylene (PP), Alternatively, it is preferable to use polyetheretherketone (PEEK). Among them, it is preferable that the sliding member contains polyacetal (POM) from the viewpoint of wear resistance and cost.

In the method for manufacturing a transport roller according to a third embodiment (modification example) of the present invention, a portion corresponding to a bearing portion of the shaft portion is formed of a tubular sliding member, and the sliding member is used as a mold. It is preferable to have an insert molding step of integrating the shaft portion and the sliding member by injection foam molding in which the molten resin is filled in a mold and then foamed and solidified for the shaft portion.

The details of the process are as shown in the above-mentioned steps of FIGS. 12A to 12D. The molding of the tube-shaped sliding member may be injection molding or cutting out of an extruded tube in the same manner as the molding of the tubular elastic body.

Although the present invention has been described above based on a preferred embodiment, the present invention is not limited to this, and other detailed configurations of each member constituting the transport roller, a mold, and injection molding are performed. The detailed configuration of the device can also be appropriately changed without departing from the spirit of the present invention.

The transport roller of the present invention is a transport roller having a resin shaft portion, which is less likely to cause sink marks during molding, is inexpensive, highly accurate, and has excellent wear resistance of the shaft portion. It is suitably used for paper transporting rollers used in machines and multifunction devices.

1 Metal transfer roller 2 Shaft 3 Kick-out roller part 4 Elastic body part 5 Gear part 11 Resin transfer roller 12 Resin shaft part 13 Resin kick-out roller part 14 Elastic body part 15 Resin gear part 50 Paper cassette 51 Hopping roller 52 Paper 53, 54 Stacking prevention roller 55, 56 Transport roller 57 Drive shaft 58 Friction rubber 61 Roller body 101 Mold 102 Elastic body part 103 Injection molding means 104 Molten resin 105 Shaft part 106 member Setting means 107 Convex shape 108 Concave shape 151 Mold opening mold 152 Sliding member 153 Injection molding means 154 Molten resin 155 Gate 160 Feeding unit 201 Resin material 202 Wire spring

Claims (9)

1. A transport roller that transports the object to be transported.
   The transport roller is composed of at least a resin shaft portion and an elastic body portion that transports the object to be transported.
   A transport roller characterized in that the shaft portion has a porous structure having holes inside.
2. The transport roller according to claim 1, wherein the shaft portion contains a thermoplastic resin and a chemical foaming agent.
3. The transport roller according to claim 1 or 2, wherein the transport roller has a structure in which the elastic body portion is insert-molded and integrated with the shaft portion.
4. The transport roller according to any one of claims 1 to 3, wherein the thermoplastic resin is any one of polyacetal, polypropylene or rubber-modified polystyrene.
5. The transport roller according to any one of claims 2 to 4, wherein the chemical foaming agent is a baking soda-based foaming agent.
6. The transport roller according to any one of claims 1 to 5, wherein the porosity represented by the following formula (1) is in the range of 4 to 15% in the shaft portion. ..
   Equation (1)
   Porosity (%) = (mass of shaft part when resin of shaft part is not made into porous structure-mass of shaft part of porous structure) / (shaft when resin of shaft part is not made into porous structure) Part mass) x 100
7. A method for manufacturing a transport roller for transporting an object to be transported, which is composed of at least a resin shaft portion and an elastic body portion for transporting the object to be transported.
   A method for manufacturing a transport roller, which comprises a step of injecting and foaming a molten resin containing the thermoplastic resin to form a shaft portion made of the resin.
8. An insert that integrates the shaft portion and the elastic body portion by setting the elastic body portion in a mold, then filling the mold with the molten resin for the shaft portion, foaming the mold, and then solidifying the mold portion. The method for manufacturing a transport roller according to claim 7, further comprising a molding step.
9. The method for manufacturing a transport roller according to claim 7, wherein the method includes a step of mixing the thermoplastic resin and a chemical foaming agent to prepare a composition for the molten resin.

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