JP2014152802A - Slide nut and slide screw device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a slide nut of a slide screw device, which is excellent in slide characteristics such as seizure resistance and abrasion resistance even in a high load condition, and provide the slide screw device.SOLUTION: A slide nut relatively moves with rotation of a screw shaft in a slide screw device while sliding on the screw shaft. A nut body 3a comprises a sintered metal, and a resin layer 3b of a resin composition having a synthetic resin as a base resin is formed as a screw groove part on the surface of a female screw part screwed into the screw shaft in the nut body. The nut body 3a is subjected to predetermined chemical surface processing on a connection surface with the resin layer 3b.

Description

  The present invention relates to a sliding nut for a sliding screw device and a sliding screw device using the sliding nut.

  A slide screw device that converts a rotational motion into a linear motion has an advantage that it can be designed more compactly than a ball screw device, and is often used for a feed device or a positioning device of an industrial machine. In a sliding screw device using a metal nut such as a copper alloy, there is a concern about torque increase and seizure due to the application of oil or grease being applied, so regular maintenance is required. Also, it cannot be used in an environment where oil or grease such as water cannot be applied in vacuum. Therefore, a sliding screw device using a resin nut has been developed for the purpose of being usable without lubrication and maintenance-free.

  For example, a screw groove portion (or the entire nut) that is screwed onto a screw shaft is made of a polyphenylene sulfide (hereinafter referred to as PPS) resin at least polytetrafluoro. There has been proposed a resin nut formed from a PPS resin composition obtained by blending an ethylene (hereinafter referred to as PTFE) resin and a non-melted organic resin powder at 280 ° C. (see Patent Document 1). The screw shaft and a nut that moves relatively while sliding on the shaft of the screw shaft as the screw shaft rotates, and at least the female screw portion of the nut has an aromatic polyimide resin powder. A sliding screw device in which a body coating film is formed has been proposed (see Patent Document 2).

  Moreover, as a thing which consists of a metal part and a resin part, for example, it is a nut with a flange that is screwed to a screw shaft and moves relative to the screw shaft in the axial direction. The outer periphery including the flange is made of metal, and the screw shaft A flanged nut has been proposed in which an inner peripheral portion to be screwed to the inner peripheral portion is formed of a lubricating resin, and a means for preventing rotation and retaining between the outer peripheral portion and the inner peripheral portion is provided (patent) Reference 3).

  In addition, as a method for manufacturing a resin nut, a fixed mold having a mold surface that molds one end surface of the resin nut, or one end surface thereof and the vicinity thereof, and a cavity that molds the remaining outer surface of the resin nut are used. In contrast, an injection mold having a movable mold movable in the axial direction and a core pin provided on the movable mold and formed with a spiral groove for forming a thread groove on the outer diameter surface is used. There has been proposed a manufacturing method in which a resin nut is formed by filling a molten resin and then opening a mold and rotating a core pin (see Patent Document 4).

JP 2003-239932 A JP 2004-204989 A JP 2006-138405 A JP 2004-025527 A

  However, although the resin nut of Patent Document 1 can be used without lubrication, it is difficult to use at a high load of 1 kPa or more because an attachment portion such as a flange or a tooth base of a female screw portion is broken.

  On the other hand, in the sliding screw device of Patent Document 2, since the main body is made of metal or ceramics, the nut does not break even at a high load of 1 kPa or more. However, it is not easy to accurately and uniformly form the powder coating film of the aromatic polyimide resin on the female screw portion of the nut, and in the formation of the powder coating film of the aromatic polyimide resin, the resin is structurally It is difficult to completely melt or melt flow, and it is difficult to apply a high pressure at a high temperature, so that a dense resin film cannot be obtained. Therefore, when used under a high load, the resin film is greatly worn, and there is a possibility that the adhesiveness (shear adhesive strength) with the nut body is not sufficient. Further, it is not easy to form a resin powder coating film on the female screw portion of the nut with high accuracy and uniformity.

  Further, in the nut with flange of Patent Document 3, the outer peripheral part of the nut is made of metal, but the inner peripheral part including the female screw part is made of a synthetic resin. This is equivalent to the resin nut of No. 1, and there is a possibility that the female screw portion or the joint portion of the metal and the resin may be broken when used under a high load.

  The present invention has been made to cope with such problems, and provides a sliding nut and a sliding screw device of a sliding screw device which are excellent in sliding characteristics such as seizure resistance and wear resistance even under high load conditions. Objective.

  The sliding nut of the present invention is a sliding nut that moves relatively while sliding on the shaft of the screw shaft as the screw shaft rotates in the sliding screw device, and the sliding nut is a nut The main body is made of a sintered metal, and a resin layer of a resin composition having a synthetic resin as a base resin is formed as a screw groove portion on the surface of the female screw portion that is screwed to the screw shaft in the nut main body. A chemical surface treatment is performed on the joint surface with the resin layer. In particular, the resin layer is a resin layer that is injection-molded over the nut body.

  The chemical surface treatment is characterized in that a fine uneven shape is formed on the bonding surface, or a bonding film that chemically reacts with the resin layer is formed on the bonding surface.

  The resin layer has a layer thickness of 0.1 to 1.5 mm.

  The synthetic resin is at least one synthetic resin selected from an aromatic polyether ketone (hereinafter referred to as PEK) resin, a thermoplastic polyimide (hereinafter referred to as thermoplastic PI) resin, and a PPS resin. And

  The sliding screw device of the present invention is a sliding screw device comprising a screw shaft and a sliding nut that moves relatively while sliding on the shaft of the screw shaft as the screw shaft rotates. The sliding nut is the sliding nut of the present invention.

  In the sliding nut of the present invention, the nut body is made of a sintered metal, and a resin layer of a resin composition having a synthetic resin as a base resin is formed as a thread groove on the surface of the female thread that is screwed onto the screw shaft of the nut body. Therefore, the mechanical strength of the base of the mounting portion such as the flange of the nut and the female screw portion is high, and it is not broken even under a high load. Because the nut body is made of sintered metal, it has excellent heat dissipation characteristics, and the resin layer bites into the pores (surface irregularities) of the sintered metal, making the resin layer The nut body can be firmly attached.

  Further, the nut body is subjected to a chemical surface treatment on the joint surface with the resin layer, more specifically, a treatment to form a fine uneven shape or a treatment to form a joining film that chemically reacts with the resin layer. Therefore, the adhesion strength between the resin layer and the nut body is further improved, the heat of the resin layer is easily transmitted to the nut body, the resin layer is not peeled off due to the frictional force with the screw shaft, and the load resistance is high. A sliding nut with excellent friction and wear characteristics even under load. As a result, the true contact area on the friction surface is reduced, and the frictional force and the heat generated by friction are reduced. This has the advantage of reducing wear and suppressing the increase in the friction surface temperature.

  Since the resin layer that is the thread groove portion is a resin layer that is injection molded over the nut body, the resin layer that is the thread groove portion is formed by applying pressure to the melted and flowed resin and overlapping the nut body. It can be formed as a resin film and can be easily and accurately formed on the surface of the female screw portion. In addition, the resin layer deeply penetrates the pores on the surface of the sintered metal at the time of injection molding, the true bonding area is increased, and the adhesion strength between the resin layer and the nut body is further improved. In addition, there is no gap in the joint surface between the resin layer and the female thread portion (sintered metal), and the heat of the resin layer is easily transmitted by the nut body, and wear is small even when used under high loads.

  Since the resin layer is thin with a layer thickness of 0.1 to 1.5 mm, heat generated by frictional heat easily escapes from the friction surface to the nut body, is difficult to store heat, has high load resistance, and can be deformed even under high surface pressure. Becomes smaller.

  Since the synthetic resin is at least one synthetic resin selected from an aromatic PEK-based resin, a thermoplastic PI resin, and a PPS resin, the load resistance, heat resistance, low friction characteristics, and wear resistance characteristics are excellent.

  The sliding screw device of the present invention comprises the screw shaft and the sliding nut of the present invention that moves relatively while sliding on the shaft of the screw shaft as the screw shaft rotates. Excellent sliding characteristics such as seizure resistance and wear resistance even under load conditions. In particular, by forming the resin layer by injection molding, manufacturing is easy and inexpensive.

It is a perspective view of the slide screw device of the present invention. It is an axial sectional view of a sliding nut.

  An embodiment of the sliding screw device of the present invention will be described with reference to FIGS. FIG. 1 is a perspective view of a sliding screw device, and FIG. 2 is an axial sectional view of a sliding nut. A sliding screw device 1 according to the present invention comprises a screw shaft 2 and a sliding nut 3 according to the present invention which is screwed into a screw groove of the screw shaft 2 and moves relatively while sliding on the screw shaft. Is done. The rotational movement of the screw shaft 2 is converted into the linear movement of the sliding nut 3. In addition, by rotating the sliding nut 3 at the same position, it is possible to apply a linear motion to the screw shaft 2.

  The screw shaft 2 includes stainless steel, carbon steel, etc., or a metal shaft made of galvanized, nickel plated, steel chrome plated, etc., a metal shaft such as an aluminum alloy, or a resin shaft such as a polyimide resin or a phenol resin. Can be used. Corrosion resistant metals or resins such as alloys such as stainless steel and aluminum alloys are preferred because they do not generate rust, and are also suitable from the point that rust prevention treatment can be omitted. In the present invention, corrosion-resistant metals that can ensure dimensional accuracy and have excellent durability are most preferable.

  The processing method of the screw shaft 2 includes rolling, cutting, grinding and the like, and any processing method may be used. In consideration of sliding characteristics such as wear resistance under high load conditions, it is preferable that the surface roughness of the contact surface of the screw shaft with the sliding nut is smaller. When the surface roughness of the screw shaft is 0.1 μmRa or less, the wear of the sliding nut due to the convexity of the screw shaft surface is very small. In particular, a surface roughness of 0.05 μmRa or less is optimal.

  The screw shaft 2 can be used without lubrication. Further, when importance is attached to low friction rather than maintenance-free, a lubricant such as oil or grease may be used for the sliding portion between the screw shaft 2 and the sliding nut 3. In this case, it is preferable to take a countermeasure so as to suppress the abrasive wear by forming a linear groove in the axial direction of the female thread portion of the sliding nut so as to hold the wear powder there. By lubricating with oil or grease, it is possible to withstand a higher load than with no lubrication and to ensure high-precision rotational stability.

  As shown in FIG. 2, in the sliding nut, the nut body 3a is made of a sintered metal, and a synthetic resin, which will be described later, is used as a thread groove on the surface of the female thread portion that is screwed to the screw shaft of the nut body 3a. A resin layer 3b of the resin composition is formed. The female thread portion is a part of the nut main body 3a and is formed in the inner diameter portion of the nut main body 3a, and the resin layer 3b which is a thread groove portion is formed so as to cover the surface of the female thread portion. The resin layer 3b, which is a screw groove, is in direct sliding contact with the screw shaft 2 (see FIG. 1). In addition, the resin layer 3b should just be formed in the surface of the internal thread part at least, and may be formed in the surface other than that of the nut main body 3a.

  The resin layer 3b bites into the sintered metal holes of the nut body 3a, so that the resin layer 3b and the nut body 3a are firmly adhered. In particular, when injection molding is performed by insert molding, the resin layer 3b deeply bites into the irregularities on the surface of the nut body (sintered metal) during injection molding, and the true bonding area increases, so the resin layer 3b and the nut body 3a The adhesion strength with is improved. Further, the true bonding area between the resin layer 3b and the nut body 3a is increased, and there is no gap in the bonding surface between the resin layer and the internal thread portion (sintered metal), so that the heat of the resin layer 3b is easily transmitted to the nut body 3a. .

  The thread shape is, for example, a triangular screw such as a miniature screw, metric coarse screw, metric fine screw, unified coarse screw, or unified fine screw, a trapezoidal screw such as a 29 degree trapezoidal screw or a metric trapezoidal screw, or a round screw. Any screw shape may be applied. Further, it may be a single thread, a double thread, or a multiple thread.

  It is preferable that the minimum inner diameter of the nut body 3a (projection toward the nut inner diameter) be smaller than the maximum outer diameter (projection toward the shaft outer diameter) of the screw shaft. In the sliding nut of the present invention, the female thread portion of the nut body 3a itself is made of sintered metal, and the resin layer 3b is formed thinly along this surface, so that the above shape can be realized. With this shape, the sintered metal nut body can receive the load from the screw shaft, and even if the impact load becomes higher than expected, the tooth base of the nut's female thread will break down and screw It is possible to increase safety in use without being off-axis.

  Examples of the material of the sintered metal constituting the nut body include iron, copper iron, copper, and stainless steel. By adopting these materials, it is possible to ensure the required thermal conductivity and load resistance in the sintered metal nut body, and heat radiation from the resin layer to the sintered metal nut body and from the sintered metal nut body to the outside. It can be used easily even at high loads.

  Since adhesion between the resin layer and the nut body can be enhanced, it is preferable to use a sintered metal containing iron as a main component, and further an iron-based sintered metal having a copper content of 10% by weight or less. In addition, since copper is inferior to adhesiveness (adhesiveness) with resin rather than iron, 10 weight% or less of copper content is preferable. More preferably, the copper content is 5% by weight or less.

  If the sintered metal that makes up the nut body contains oil or other oil, oil residue that decomposes and gasifies during injection molding of the resin layer is present at the interface. May deteriorate. Therefore, it is preferable to use a sintered metal not impregnated with oil for the nut body. Moreover, when using oil in the process of shaping | molding or re-pressing (sizing) of a sintered metal, it is preferable to set it as the non-oil-containing sintered metal which removed oil by solvent washing etc.

  In the nut body, the density of the sintered metal (sintered body) is preferably a theoretical density ratio of materials of 0.7 to 0.9. The theoretical density ratio of the material is the ratio of the density of the nut body when the theoretical density of the material (density when the porosity is 0%) is 1. If the theoretical density ratio is less than 0.7, the mechanical strength of the sintered metal is lowered, and the sintered metal may be broken by the injection molding pressure at the time of insert molding. When the theoretical density ratio exceeds 0.9, the unevenness is reduced, so that the surface area and the anchor effect are lowered, and the adhesion with the resin layer is lowered. More preferably, the theoretical density ratio of the materials is 0.72 to 0.84.

  Sintered metal with iron as its main component is an effect that removes oil and deposits adhering to the sintered surface or penetrating into the sintered body unintentionally during the molding or re-pressing (sizing) process by applying steam treatment Therefore, variation in adhesion with the resin layer is small and stable. Moreover, rust prevention can also be provided to the nut body. The conditions for the steam treatment are not particularly limited, but a method of spraying steam heated to about 500 ° C. is common.

  Examples of the method for forming the resin layer include coating by dipping and injection molding. Considering screw dimensional accuracy, adhesion between the resin layer and the nut body, ease of manufacturing, etc., there is a method of injection molding over the nut body, that is, injection molding in which the resin layer is insert-molded to the nut body. preferable.

  In order to increase the adhesion between the sintered metal nut body and the resin layer, it is preferable to perform a chemical surface treatment on the joint surface of the resin layer in the sintered metal nut body. As the chemical surface treatment, it is preferable to perform (1) a process in which a fine uneven shape is formed on the bonding surface, or (2) a process in which a bonding film that chemically reacts with the resin layer is formed on the bonding surface. Note that, here, the bonding surface includes an uneven surface constituting pores of the sintered metal microscopically.

  By making the joining surface into a fine uneven shape, the true joining area increases, the adhesion strength between the resin layer and the sintered metal nut body improves, and the heat of the resin layer is easily transmitted to the sintered metal nut body Become. Further, by interposing a bonding film that chemically reacts with the resin layer on the bonding surface, the adhesion strength between the resin layer and the sintered metal nut body is improved, and a micro gap is formed between the resin layer and the sintered metal nut body. The heat of the resin layer is easily transmitted to the sintered metal nut body.

  Surface roughening treatment that results in fine irregularities includes acidic solution treatment (sulfuric acid, nitric acid, hydrochloric acid, etc., or mixed with other solutions), alkaline solution treatment (sodium hydroxide, potassium hydroxide, etc., or other solutions) In which the surface of the sintered metal nut body is melted. Although the fine uneven shape varies depending on the concentration, processing time, post-treatment, etc., in order to improve the adhesion due to the anchor effect, it is preferable to make the fine unevenness with a concave pitch of several nanometers to several tens of micrometers. Further, in addition to general acidic solution treatment and alkaline solution treatment, a special Amalfa treatment manufactured by Mech, an NMT treatment manufactured by Taisei Plus, etc. can be exemplified. Here, the NMT treatment is performed by sequentially performing a post-treatment such as a degreasing treatment with an alkaline solution, a neutralization treatment with an acidic solution, an immersion treatment with a special solution, washing with water and drying on the base material. It is the process which forms uneven | corrugated shape.

  When the resin layer is formed by injection molding, since the resin material is poured at a high speed, the resin material has the fine pores and the concave pitch of the sintered metal of several nanometers to several tens of micrometers due to the shearing force. It can penetrate deeply into the irregular shape. Thereby, the adhesive strength of a sintered metal nut main body and a resin layer is securable. In addition, the fine irregularities formed by chemical surface treatment have a complex three-dimensional structure such as porous, unlike mechanically roughened shapes. Is possible.

  Examples of the surface treatment for forming a bonding film that chemically reacts with the resin layer include an immersion treatment in a solution of a triazinedidiol derivative, an s-triazine compound, or the like. These surface treatments react with the resin material by heat and pressure when the treated sintered metal nut body is put into a mold and injection molded, and the adhesion between the resin layer and the sintered metal nut body is increased. Examples of such surface treatment include TRI treatment manufactured by Toa Denka Co., Ltd.

  Among the chemical surface treatments, special surface treatments such as Amalfa treatment by MEC and TRI treatment by Toa Denka are suitable for aluminum and copper. For this reason, when performing these processes, it is preferable that the surface of a sintered metal nut main body is aluminum or copper at least.

  The shear bond strength between the sintered metal nut body and the resin layer is preferably 2 MPa or more. If it is this range, sufficient adhesion strength with respect to the friction force in use can be obtained, and even if it uses by high load, a resin layer does not peel from a sintered metal nut main body. In order to further increase the safety factor, 4 MPa or more is preferable. In addition, in order to further increase the shear adhesion strength between the sintered metal of the nut body and the resin layer, the sintered metal surface on which the resin layer is formed may be provided with physical stoppers such as irregularities and grooves, and rotation prevention. Good. The adhesion improving means such as physical fixation, mechanical roughening treatment, and chemical roughening treatment are preferably selected and used in combination so as to ensure the shear bond strength.

  The layer thickness of the resin layer is preferably 0.1 to 1.5 mm. If the resin thickness is less than 0.1 mm, insert molding is difficult. In addition, durability during long-term use, that is, life may be shortened. On the other hand, if the resin thickness exceeds 1.5 mm, sink marks may occur and dimensional accuracy may be reduced. Further, heat due to friction is difficult to escape from the friction surface to the nut body side, and the friction surface temperature becomes high. In addition, the amount of deformation due to the load increases, the true contact area on the friction surface also increases, the frictional force and frictional heat generation increase, and the seizure resistance may decrease. The resin thickness is determined by the nut inner diameter.

  In consideration of heat radiation of the frictional heat to the nut body, the resin thickness is more preferably 0.2 to 0.7 mm. A sliding nut with high dimensional accuracy is made by insert molding the resin layer with a thin wall (0.1 to 1.5 mm) on the surface of the internal thread of the nut body made of sintered metal with high dimensional accuracy. Can do. Alternatively, thick injection molding (insert molding) may be performed, followed by finishing to a required resin thickness by machining.

  The resin composition for forming the resin layer is based on a synthetic resin that can be injection-molded. As the synthetic resin, a synthetic resin excellent in lubricating properties is preferable. Further, a synthetic resin having high heat resistance is preferable so that the sliding nut can be used in a part having a high ambient temperature. Examples of such synthetic resins include PEK-based resins, polyacetal (POM) resins, PPS resins, injection-moldable thermoplastic PI resins, polyamide-imide (PAI) resins, polyamide (PA) resins, and injection-moldable fluorine. Resin etc. are mentioned. Each of these synthetic resins may be used alone or may be a polymer alloy in which two or more kinds are mixed.

  Among these synthetic resins, it is preferable to use PEK-based resins, thermoplastic PI resins, and PPS resins. By using these synthetic resins as the base resin of the resin composition for forming the resin layer, a sliding nut having excellent heat resistance, oil resistance, creep resistance characteristics, load resistance, and friction and wear characteristics is obtained. Moreover, the adhesion strength with the nut body made of sintered metal is high, and there is no fear of peeling from the nut body.

  PEK resin is a crystalline thermoplastic resin with a melting point of 340 ° C, a glass transition point of 143 ° C, and a continuous use temperature of 260 ° C. Excellent heat resistance, oil / chemical resistance, creep resistance, load resistance In addition to durability, wear resistance, sliding characteristics, etc., it has high toughness, mechanical properties at high temperatures, fatigue resistance, impact resistance, and good moldability. Suitable for resin.

  Examples of the PEK resin that can be used in the present invention include polyetheretherketone (PEEK) resin, polyetherketone (PEK) resin, and polyetherketoneetherketoneketone (PEKEKK) resin. Examples of commercially available PEEK resins that can be used in the present invention include: Victrex: VICTREX PEEK (90P, 150P, 380P, 450P, 90G, 150G, etc.), Solvay Specialty Polymers: Keta Spire PEEK (KT-820P, KT) -880P, etc.), manufactured by Daicel Evonik Co., Ltd .: VESTAKEEEP (1000G, 2000G, 3000G, 4000G, etc.). Examples of the PEK resin include Victrex_HT manufactured by Victrex, and examples of the PEKKK resin include Victrex_ST manufactured by Victrex.

  Thermoplastic PI resin is a crystalline thermoplastic resin having a melting point of 388 ° C., a glass transition point of 250 ° C., and a continuous use temperature of 240 ° C., and is excellent in heat resistance, oil resistance, load resistance, friction wear characteristics, etc. Therefore, it is suitable for the base resin of the sliding nut of the sliding screw device. Since the in-mold crystallization speed during injection molding is slow, the molded product is in an amorphous state, but the crystallinity can be increased by heat treatment. Examples of commercially available thermoplastic PI resins that can be used in the present invention include Aurum (PD450, PD6200, etc.) manufactured by Mitsui Chemicals.

  PPS resin is a crystalline thermoplastic resin having a melting point of 280 ° C, a glass transition point of 88 ° C, and a continuous use temperature of 240 ° C. It has extremely high rigidity, excellent heat resistance, dimensional stability, wear resistance, Since it has sliding characteristics, high fluidity, etc., it is suitable as a base resin for sliding nuts in sliding screw devices. Depending on the molecular structure of the PPS resin, there are types such as a cross-linked type, a semi-cross-linked type, a linear type, and a branched type. Examples of commercially available PPS resins that can be used in the present invention include Tosoh's # 160, B-063, DIC's T4AG, LR-2G, and the like.

  It is preferable that the resin composition forming the resin layer does not contain a fibrous inorganic filler such as glass fiber, carbon fiber, or whisker. When the resin layer includes a fibrous filler, when the sliding nut relatively reciprocates while sliding on the axis of the screw shaft as the screw shaft rotates, the end of the fiber becomes an edge. There is a possibility that the mating screw shaft may be worn and damaged, or that the end of the fiber is subjected to repeated stress during the reciprocating movement of the sliding nut, and the fatigue wear of the resin may occur. These concerns can be eliminated by adopting a configuration that does not include a fibrous filler.

  The resin composition forming the resin layer preferably contains a PTFE resin. By including PTFE resin, the friction can be reduced, the frictional heat generation can be reduced, and the friction and wear characteristics are excellent even at high loads. As the PTFE resin, any of molding powder by suspension polymerization, fine powder by emulsion polymerization, and recycled PTFE may be used. Regenerated PTFE is a powder that has been irradiated with a heat-treated powder (heated history added), γ-rays or electron beams. For example, a powder obtained by heat-treating molding powder or fine powder, a powder obtained by further irradiating this powder with γ-rays or an electron beam, a powder obtained by pulverizing a molding powder or a molded product of fine powder, and then a γ-ray or electron beam. There are types such as irradiated powder, molding powder or fine powder irradiated with gamma rays or electron beams.

  In order to improve the abrasion resistance of the resin layer, molding powder having a high molecular weight or recycled PTFE of the molding powder (heat treated powder, powder irradiated with γ rays or electron beams) is preferable. Molded powder recycled PTFE irradiated with γ-rays or electron beams does not agglomerate and fiberize at the resin injection molding temperature, has internal lubrication effect, and improves the fluidity of the resin composition stably. It is more preferable because it can be made to occur.

  Examples of commercially available PTFE resins that can be used in the present invention include Kitamura Co., Ltd .: KTL-610, KTL-450, KTL-350, KTL-8N, KTL-400H, Mitsui DuPont Fluorochemical Co., Ltd .: Teflon (registered trademark). 7-J, TLP-10, Asahi Glass Co., Ltd .: Fullon G163, L150J, L169J, L170J, L172J, L173J, Daikin Industries, Ltd .: Polyflon M-15, Lubron L-5, Hoechst: Hostaflon TF9205, TF9207, etc. Can be mentioned. Further, it may be a PTFE resin modified with a perfluoroalkyl ether group, a fluoroalkyl group, or another side chain group having a fluoroalkyl group. The regenerated PTFE resin heat-treated in the above is made by Kitamura KKT-400H, and the regenerated PTFE resin irradiated by γ-ray or electron beam is made by Kitamura KKT-610, KTL-450, KTL. -350, KTL-8N, KTL-8F, manufactured by Asahi Glass Co., Ltd .: Full-on L169J, L170J, L172J, L173J and the like.

  The resin composition forming the resin layer preferably contains graphite. By including graphite, the friction and wear characteristics can be improved. Moreover, since heat conductivity is high, it becomes easy to radiate frictional heat. Graphite is roughly classified into natural graphite and artificial graphite, and further includes flakes, granules and spheres, and any of them can be used. In order to increase the elastic modulus of the resin composition, improve the wear resistance and creep resistance, and obtain stable low friction characteristics, flake graphite is preferred.

  It is particularly preferable that the resin composition forming the resin layer has a composition containing 10 to 30% by volume of PTFE resin and 2 to 10% by volume of graphite with respect to the entire resin composition without including a fibrous filler. . By adopting this blending ratio, even at high loads, with a low coefficient of friction, there is little deformation and wear of the resin layer, damage to the mating screw shaft, and resistance to oil and the like is increased.

  When the blending ratio of the PTFE resin exceeds 30% by volume, the wear resistance and creep resistance are lowered from the required levels, and the adhesion strength with the nut body and the melt fluidity may be significantly lowered. Further, if the blending ratio of PTFE resin is less than 10% by volume, the effect of imparting low friction characteristics and wear characteristics to the composition is poor, and sufficient sliding characteristics may not be obtained.

  When the blending ratio of graphite exceeds 10% by volume, the wear resistance, friction characteristics, and damage to the mating screw shaft are lowered from the required levels, and the melt fluidity is remarkably lowered, which may make molding difficult. Further, if the blending ratio of graphite is less than 2% by volume, the effect of imparting abrasion resistance, creep resistance and heat conduction characteristics to the composition is poor, and sufficient sliding characteristics may not be obtained.

  In addition, you may mix | blend a well-known resin additive with respect to a resin composition to such an extent that the effect of this invention is not inhibited. Examples of the additive include friction property improvers such as boron nitride, molybdenum disulfide, and tungsten disulfide, thermal conductivity improvers such as carbon powder and metal oxide powder, carbon powder, iron oxide, and titanium oxide. Coloring agents are mentioned. In addition, particulate inorganic fillers such as calcium carbonate, calcium sulfate, mica and talc, thermosetting PI resins, wholly aromatic polyester resins, and non-melting organic fillers even at the injection molding temperature of the above resins such as aramid fibers Abrasion resistance improving material is mentioned.

The resin composition has a resin layer thickness of 0 on the surface of the nut body made of sintered metal by adjusting the melt viscosity at a resin temperature of 380 ° C. and a shear rate of 1000 s ^{−1 to} a range of 50 to 200 Pa · s. It is desirable because thin insert molding of 0.1 to 1.5 mm can be performed smoothly.

  The means for mixing and kneading the above raw materials is not particularly limited, and only the powder raw material is dry-mixed with a Henschel mixer, ball mixer, ribbon blender, ladyge mixer, ultra Henschel mixer, etc. Melting and kneading can be performed with a melt extruder such as an extruder to obtain molding pellets (granules). In addition, a side feed may be used for charging the filler when melt kneading with a twin screw extruder or the like. Moreover, you may employ | adopt treatments, such as an annealing process, for physical property improvement. In the sliding nut of the present invention, the resin layer is injection-molded by insert molding on the nut body using the molding pellets. As this specific method, for example, a manufacturing method described in Patent Document 4 or a manufacturing method in which a resin layer is injection-molded on a nut body and then machined into a predetermined female thread shape can be used. .

In the evaluation test, a sintered metal having iron as a main component and a density of 6.2 g / cm ³ (theoretical density ratio of the base material: 0.79) was used as the main body material. The material of the resin layer includes PPS resin (manufactured by Tosoh Corporation: Sastil B063), PTFE resin (manufactured by Kitamura Corporation: KTL610), 25% by weight (20.6% by volume), flake graphite (TIMCAL) The resin composition which mix | blended 5 weight% (3.9 volume%) and Japan, respectively: TIMREX KS6) was used.

  A sintered metal material made of a main body material is machined to form a cylindrical body (φ12 × φ18 × 25 mm), and the entire surface of the cylindrical body is subjected to NMT processing by Taisei Plus Co. (sample for example), An untreated product (sample for comparison) was produced. Next, the resin layer was insert-molded with a thickness of 1 mm using the pellets of the resin composition described above on the inner diameter portion (straight) of the cylindrical body to prepare a shear bond strength test piece.

  In the shear bond strength test, a cylindrical test piece was fixed, an axial shearing force was applied to the inner diameter resin layer, and a load at which the resin layer peeled from the cylindrical test piece was measured. The value obtained by dividing this load by the apparent bonding area of the inner diameter portion of the resin layer and the cylindrical test piece was defined as the shear bond strength.

  As a result of the shear bond strength test, the shear bond strength of the example was 6.7 MPa, the shear bond strength of the comparative example was 3.2 MPa, and a chemical surface treatment was applied to the joint surface with the resin layer. The examples had a shear bond strength more than twice that of the untreated comparative examples.

  The slide screw device provided with the sliding nut of the present invention is easy to manufacture and has excellent sliding characteristics such as seizure resistance and wear resistance even under high load conditions. It can utilize suitably as a sliding screw apparatus to be used.

1 Sliding screw device 2 Screw shaft 3 Sliding nut 3a Nut body 3b Resin layer

Claims (6)

In the sliding screw device, a sliding nut that moves relatively while sliding on the axis of the screw shaft as the screw shaft rotates,
The sliding nut has a nut body made of sintered metal,
A resin layer of a resin composition having a synthetic resin as a base resin is formed as a thread groove portion on the surface of the female screw portion that is screwed to the screw shaft in the nut body,
The nut nut is a sliding nut characterized in that a chemical surface treatment is applied to a joint surface with the resin layer. The sliding nut according to claim 1, wherein the resin layer is a resin layer that is injection-molded over the nut body.   The chemical surface treatment is a treatment for forming a fine uneven shape on the bonding surface or a treatment for forming a bonding film that chemically reacts with the resin layer on the bonding surface. The sliding nut according to claim 2.   The sliding nut according to claim 1, 2, or 3, wherein the resin layer has a thickness of 0.1 to 1.5 mm.   5. The synthetic resin according to claim 1, wherein the synthetic resin is at least one synthetic resin selected from an aromatic polyether ketone resin, a thermoplastic polyimide resin, and a polyphenylene sulfide resin. Sliding nut. A sliding screw device comprising a screw shaft and a sliding nut that moves relatively while sliding on the shaft of the screw shaft as the screw shaft rotates.
The sliding screw device according to any one of claims 1 to 5, wherein the sliding nut is the sliding nut according to any one of claims 1 to 5.

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