JP2014001847A - Slide nut and slide screw device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a slide nut of a slide screw device, and the slide screw device superior in sliding properties such as seizure resistance and abrasion resistance even under a high load condition.SOLUTION: The slide nut relatively moves while sliding on a shaft of a screw shaft in accompany with rotation of the screw shaft in the slide screw device, a nut body 3a is composed of ingot metal, and a resin layer 3b of a resin composition applying a synthetic resin as a base resin, is superposed and formed as a groove portion, on a surface of a female screw portion engaged with the screw shaft of the nut body by injection molding. A prescribed chemical surface treatment is executed on a joint face with the resin layer 3b, of the nut body 3a.

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 2004-25527 A

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

  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 under a high load. However, in the formation of a powder coating film of an aromatic polyimide resin, the resin is not completely melted or melt-flowed, and it is difficult to apply a high pressure at a high temperature, so that it does not become a dense resin film. 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 No. 1, and there is a possibility that the female screw part or the joint part 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 molten metal, and a resin layer of a resin composition having a synthetic resin as a base resin as a thread groove is formed on the surface of the female thread portion screwed into the screw shaft of the nut body by injection molding. It is characterized by that.

  The nut body is characterized in that a chemical surface treatment is applied to a joint surface with the resin layer. Further, 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 mm. Further, the resin layer is characterized in that the layer thickness of the bottom portion of the thread groove is thicker than the layer thickness of the thread groove portion.

  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 Moreover, the said resin composition is characterized by including 10-30 volume% of PTFE resin and 2-10 volume% of graphite with respect to the whole resin composition, without including a fibrous filler.

  The heat conductivity of the molten metal of the nut body is 50 W / (m · K) or more. The molten metal of the nut body is aluminum, an aluminum alloy, copper, or a copper alloy.

  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. Further, the minimum inner diameter of the nut body is smaller than the maximum outer diameter of the screw shaft.

  In the sliding nut of the present invention, the nut body is made of molten metal, and a resin layer of a resin composition having a synthetic resin as a base resin as a thread groove is formed on the surface of the female thread portion that is screwed to the screw shaft in the nut body. Since they are formed by injection molding, 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 high loads. In addition, since the heat dissipation characteristics are excellent, there is an advantage that the real contact area on the friction surface is reduced, the frictional force and the frictional heat generation are reduced, the wear is reduced, and the increase in the friction surface temperature is suppressed.

  In particular, since the resin layer that is the thread groove is a resin layer formed by applying pressure to the resin melted and flown by injection molding and overlapping the nut body, it can be formed as a dense resin film with high load. Less wear even when used. Further, the resin layer bites into the roughness of the molten metal surface, the bonding area is increased, and the adhesion strength between the resin layer and the nut body is also improved. Moreover, there is no gap in the joint surface between the resin layer and the internal thread portion (melted metal), and the heat of the resin layer is easily transmitted to the nut body.

  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. The adhesion strength between the resin layer and the nut body is improved, the heat of the resin layer is easily transmitted to the molten metal 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.

  Since the resin layer is thin with a layer thickness of 0.1 to 1 mm, heat from frictional heat easily escapes from the friction surface to the nut body, is difficult to store heat, has high load resistance, and has a small deformation amount even under high surface pressure. Become. Further, in the above resin layer, since the layer thickness at the bottom of the thread groove is thicker than the layer thickness at the thread groove portion, the joint area between the resin layer and the nut body is increased compared with the case where the layer thickness is uniform, Since the force (load) increases, the safety factor against peeling of the resin layer increases and it can be used even under higher load conditions.

  Since the base resin of the resin composition forming the resin layer is at least one synthetic resin selected from PEK-based resin, thermoplastic PI resin, and PPS resin, load resistance, heat resistance, low friction characteristics, and Excellent wear resistance.

  Further, since the resin composition does not include 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 The problem that the part becomes an edge and wears and damages the mating screw shaft does not occur and the friction coefficient is low and stable. Further, during the reciprocating movement of the sliding nut, the problem that the end of the fiber is subjected to repeated stress and fatigue wear of the resin does not occur, and the wear resistance is excellent even under a high load.

  Further, by including PTFE resin in the resin composition, a low friction coefficient is obtained, frictional heat generation is reduced, and a sliding nut having excellent frictional wear characteristics even at high loads is obtained. Also, it can be used without lubrication. In particular, with respect to the resin composition described above, without including a fibrous filler, 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 allows high load. In addition, deformation and wear of the resin layer and damage to the mating material are small, and the resin layer can be used without lubrication, and also has high resistance to oil, grease and the like. Moreover, since graphite has high thermal conductivity, it is easy to dissipate frictional heat.

  Since the heat conductivity of the molten metal of the nut body is 50 W / (m · K) or more, the heat of the resin layer is easily transmitted from the molten metal nut body to the outside, and the real contact area on the friction surface is further increased. It becomes smaller and can reduce frictional force, wear, and increase in friction surface temperature. Furthermore, since the material of the molten metal of the nut main body is aluminum, an aluminum alloy, copper, or a copper alloy, required mechanical strength, thermal conductivity, and load resistance can be ensured.

  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 the above-mentioned sliding screw device, the minimum inner diameter of the nut body (projection to the nut inner diameter) is smaller than the maximum outer diameter of the screw shaft (convex to the shaft outer diameter). Even when the load is higher than expected, the tooth base of the female screw portion of the nut is not broken and detached from the screw shaft, so that the safety during use can be increased.

It is a perspective view of the slide screw device of the present invention. It is an axial sectional view of a sliding nut. It is a figure which shows nut test pieces, such as an Example. 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 such as stainless steel and aluminum alloys are preferable because they are high in strength and can be used at high loads, and do not generate rust. 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, the sliding nut has a nut body 3a made of a molten metal, and a synthetic resin, which will be described later, is used as a thread groove on the surface of a female thread portion that is screwed onto a screw shaft in 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 and the nut body 3a are brought into close contact with each other by the injection of the resin layer 3b into the surface roughness of the molten metal of the nut body 3a. 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 female screw portion (melted 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, trapezoidal screw such as 30 degree trapezoidal screw, metric trapezoidal screw, round screw, gothic An arc shape may be used, and any screw shape can 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 molten metal, and the resin layer 3b is formed thinly along this surface, so that the above shape can be realized. With this shape, the molten 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 internal thread can be destroyed. Etc. can be prevented.

  The material of the molten metal constituting the nut body is preferably iron, aluminum, aluminum alloy, copper, or copper alloy. By adopting these materials, it is possible to ensure the required thermal conductivity and load resistance in the molten metal nut body, and heat radiation from the resin layer to the molten metal nut body and from the molten metal nut body to the outside. It can be used easily even at high loads.

  As iron, general structural carbon steel (SS400, etc.), mechanical structural carbon steel (S45C, etc.), stainless steel (SUS303, SUS316, etc.) can be used. Further, these irons may be plated with zinc, nickel, copper or the like.

  A1050, A1100, etc. can be used as aluminum, and A2017, A2024, A5056, A6061, etc. can be used as aluminum alloys. Since it is excellent in cutting workability, A2017 and A2024 are preferable. Moreover, aluminum alloy die casting (ADC12 etc.) and aluminum alloy casting (AC4B etc.) can also be used. Moreover, it is good also as an anodized article for the improvement of the corrosion resistance of aluminum, and abrasion resistance.

  C1100 or the like can be used as copper, and C3604 or the like can be used as a copper alloy. From the viewpoints of cutting workability and environmental properties, C6801 and C6802 containing 0.1% or less of lead and 0.0075% or less of cadmium are preferable. A copper alloy casting (such as CAC406) can also be used.

  In the process of inserting the molten metal nut body into the mold and injection molding the resin, a clearance is required between the mold and the nut body. For example, when a nut body is inserted into a mold and resin is injection molded into the inner diameter, the nut body is stretched to the outer diameter side by the clearance due to the injection molding pressure, so the elongation of the molten metal in the nut body is small. And may break. Therefore, the elongation of the molten metal is preferably 5% or more, and other than aluminum alloy die casting, aluminum alloy casting, and copper alloy casting is preferable.

  The molten metal of the nut body preferably has a thermal conductivity of 50 W / (m · K) or more. By adopting a material having a thermal conductivity of 50 W / (m · K) or more, heat is easily radiated from the resin layer to the molten metal nut main body and from the molten metal nut main body to the outside, and it can be used at a higher load. Examples of the material having a thermal conductivity of 50 W / (m · K) or more include the above-described aluminum, aluminum alloy, copper, and copper alloy. The higher the thermal conductivity of the molten metal nut, the easier it is to dissipate frictional heat, so 100 W / (m · K) or more is more preferable.

  In order to improve the adhesiveness with the resin layer at the time of injection molding, it is preferable to roughen the joint surface with the resin layer in the molten metal nut main body to an uneven shape by shot blasting, tumbler, machining or the like. The surface roughness at that time is preferably Ra 4 μm or more. Moreover, surface treatments, such as metal plating, can also be given to the surface of a molten metal nut main body.

  In order to improve the adhesion between the molten 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 molten 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.

  By making the joining surface into a fine concavo-convex shape, the true joining area is increased, the adhesion strength between the resin layer and the molten metal nut body is improved, and the heat of the resin layer is easily transmitted to the molten metal nut body. Become. Also, 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 molten metal nut body is improved, and a micro gap is formed between the resin layer and the molten metal nut body. The heat of the resin layer is easily transferred to the molten 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) The method of melting the surface of the melted metal nut main body by mixing). 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.

  When the resin layer is formed by injection molding, since the resin material is poured at a high speed, the resin material can penetrate deeply into the fine concavo-convex shape having a concave pitch of several nanometers to several tens of micrometers by a shearing force. it can. Thereby, the adhesive strength of a molten 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 molten metal nut main body is put into a mold and injection molded, and the adhesion between the resin layer and the molten metal nut main 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 manufactured by Mec, NMT treatment manufactured by Taisei Plus, and TRI treatment manufactured by Toa Denka are suitable for aluminum and copper. For this reason, when performing these processes, it is preferable that the surface of a molten metal nut main body is aluminum or copper at least.

  The shear bond strength between the molten metal nut body and the resin layer is preferably 2 MPa or more. If it is this range, sufficient adhesive 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 molten metal nut main body. In order to further increase the safety factor, 4 MPa or more is preferable. 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 will be described with reference to FIG. FIG. 4 is an axial sectional view of a sliding nut similar to FIG. A resin layer 3b is formed as a thread groove on the surface of the female thread in the nut body 3a made of molten metal. The layer thickness of the resin layer is the distance from the nut body surface to the resin layer surface at the same position in the screw axis direction. Figure 4 (a), the layer thickness of the screw Mizoyama portion 3c _{(t 1),} a thickness of the thread groove bottom 3d _{(t 2)} and the same _(t 1 = t _2), substantially over the entire resin layer The layer thickness is uniform. On the other hand, in FIG. 4B, the screw groove bottom of the nut body is deep, and the layer thickness (t ₃ ) of the screw groove bottom 3d is thicker than the layer thickness (t ₁ ) of the screw groove crest 3c. (T ₃ > t ₁ ). The layer thickness at the bottom of the thread groove varies in the screw axis direction as shown in the figure, but the layer thickness (t ₃ ) here varies from the resin layer surface at the bottom of the thread groove to the thread groove bottom surface of the nut body. It is the distance to the deepest position. By adopting the structure of FIG. 4B, as compared with the structure of FIG. 4A, the joining area between the resin layer and the nut body is increased at the bottom of the thread groove, and the joining force is increased. For this reason, the safety factor against peeling of the resin layer is increased, and the resin layer can be used even under higher load conditions. In addition, the shape of the groove bottom is not particularly limited, and any shape such as a V shape or a U shape may be employed as long as t ₃ > t ₁ .

The layer thickness of the resin layer is preferably 0.1 to 1 mm. If the resin thickness is less than 0.1 mm, durability during long-term use, that is, life may be shortened. On the other hand, if the resin thickness exceeds 1 mm, heat due to friction is difficult to escape from the friction surface to the nut body, and the friction surface temperature increases. 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 the heat generated by friction increase, and the wear may increase. The resin thickness is determined by the nut inner diameter. In the case of the structure shown in FIG. 4 (b), it is preferable that the thickness of the portion other than the thread groove bottom (t ₃₎ is within the above range.

  In consideration of the heat radiation of the frictional heat to the nut body, the resin thickness is more preferably 0.2 to 0.5 mm. The required thickness may be obtained by injection molding, or the required resin thickness may be finished by machining after injection molding (insert molding).

  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 molten metal is high, and there is no worry 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: Victorex: PEEK (90P, 150P, 380P, 450P, 90G, 150G, etc.), Solvay Advanced Polymers: KetaSpire (KT-820P, KT-880P) Etc., manufactured by Daicel Degussa, Inc .: 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 crosslinked type, a semi-crosslinked type, a linear type, and a branched type. In the present invention, the PPS resin can be used without being limited to these molecular structures and molecular weights. Examples of commercially available PPS resins that can be used in the present invention include Tosoh Corp. # 160, B-063, Dainippon Ink Corp. 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 stabilizes the fluidity of the resin composition. It is more preferable because it can be improved.

  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 composition is poor in the effect of imparting abrasion resistance, creep resistance and heat conduction characteristics, 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 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. .

[Examples 1 to 16, Comparative Examples 1 to 3, Reference Examples 1 to 7]
Table 1 summarizes the materials and surface treatments of the molten metal nut bodies used in Examples, Comparative Examples, and Reference Examples. In Table 1, acid treatment (nitric acid) is obtained by immersing a test piece in a 20% nitric acid aqueous solution at room temperature (about 20 to 30 ° C.) for 30 seconds to 1 minute. The acid treatment (sulfuric acid) is obtained by immersing in a 24% aqueous sulfuric acid solution at room temperature (about 20 to 30 ° C.) for 30 seconds to 1 minute. The amalfa treatment was performed at room temperature (about 20 to 30 ° C.) under conditions of immersion for 1 to 5 minutes. The NMT treatment was performed at a temperature of 75 ° C. for 5 minutes. The TRI treatment was performed under conditions of immersion and energization at a temperature of 60 ° C. for 1 to 10 minutes. In addition, degreasing washing was performed before the treatment, and washing and drying were performed after the treatment.

Moreover, the raw material of the resin layer used for an Example, a comparative example, and a reference example is shown collectively below. These raw materials were dry-blended using a Henschel dry mixer at the blending ratio (volume%) shown in Tables 2 and 3, and melt-kneaded using a twin-screw extruder to produce pellets.
(1) Polyetherketone resin [PEK] manufactured by Victrex: PEEK 150P
(2) Thermoplastic polyimide resin [PI] manufactured by Mitsui Chemicals: Aurum PD450
(3) Polyphenylene sulfide resin [PPS] manufactured by Tosoh Corporation: Sustain B063
(4) PTFE resin [PTFE] manufactured by Kitamura Co., Ltd .: KTL610 (regenerated PTFE)
(5) Graphite [GRP] manufactured by Timcal Japan Co., Ltd .: TIMREX KS6 (flakes)
(6) Carbon fiber [CF] Kureha Co., Ltd .: Kureka M-101S (average fiber length 100 μm, average fiber diameter 14.5 μm)
(7) Glass fiber [GF] manufactured by Asahi Fiber Glass Co., Ltd .: MF06JB1-20 (average fiber length 30 to 100 μm, average fiber diameter 10 μm)

(1) Shear bond strength test Resin layer using pellets of resin compositions a to c in Table 2 on the inner diameter portion (straight) of the cylindrical body (φ12 × φ18 × 25 mm) made of the molten metal material of Table 1 Was insert-molded with a thickness of 1 mm to prepare a shear bond strength test piece. The cylindrical body is manufactured by machining a molten metal material, and the entire surface is subjected to the surface treatment shown in Table 1 (other than metals H and I). In the shear bond strength test, the test cylinder was fixed, an axial shear force was applied to the inner diameter resin layer, and the load at which the resin layer peeled from the test cylinder was measured. Table 4 shows the value obtained by dividing this load by the apparent bonding area between the resin layer and the inner diameter portion of the test cylindrical body as the shear bond strength. Further, the surface roughness Ra in Table 4 is the surface roughness after the surface treatment (other than the metals H and I) of the joint surface of the resin layer in the cylindrical body.

  As shown in Table 4, in Examples 1 to 7, the shear bond strength between the cylindrical body and the resin layer was 2 MPa or more, and a sufficient adhesion strength against the frictional force during use could be obtained.

(2) Static fracture test About Examples 8-10, the pellet shown in Table 5 is used for the inner diameter portion (female thread) of the nut body for a nut test piece made of a molten metal material. After insert molding of the resin layer, the nut test piece (see FIG. 3 (a)) with a thickness of 0.3 mm (uniform) is produced by machining the resin along the female screw of the nut body. did. The screw was a gothic arc shape, a lead of 2 mm, and a single thread. The shape and dimensions of the nut test piece other than the resin layer are as shown in FIG. In the static destructive test, the nut test piece was fixed with the screw shaft passed through the inner diameter of the nut test piece, and the destructive load when an axial load was applied to the screw shaft was measured. Indicated.

  The resin nut (without melted metal) of Comparative Example 1 was formed into the shape and dimensions shown in FIG. 3A by injection molding / machining using pellets of the resin composition c shown in Table 2. Further, as shown in FIG. 3 (b), the nut made of the molten metal and the resin of Comparative Example 2 is made of stainless steel (SUS303), the outer periphery 4 of the nut (with a detent and a retainer on the inner diameter), and a female screw. The inner peripheral part 5 including the part was formed by insert molding of the resin composition c. The resin thickness (maximum portion) of the inner diameter portion was 10 mm, the screw was a gothic arc shape, the lead was 2 mm, and the single screw. The other dimensions of the nut test piece are as shown in FIG. The nut test pieces of Comparative Examples 1 and 2 were also subjected to the same static fracture test as in Example 8, and the fracture load was measured. The results are shown in Table 5.

  As shown in Table 5, Examples 8 to 9 had a high static fracture load of 28 kN or higher. The nut of Comparative Example 1 made only of resin had a very low static breaking load, and even the nut of Comparative Example 2 made of molten metal and resin was about 1/4 of the example. Further, in Comparative Example 2, the nut outer diameter becomes very large in order to increase the breaking load, and it is difficult to achieve a compact design with the same dimensions as in the example. If the dimensions are reduced, the breaking load decreases.

(3) Wear test For Examples 8 to 16 and Reference Examples 3 to 7, in the combinations shown in Table 7 and Table 8, the inner diameter portion (female thread) of the nut body for a nut test piece made of a molten metal material, After the resin layer is insert-molded using the pellet of the resin composition, the resin is machined along the female screw of the nut main body, so that the thickness of the resin layer is 0.3 mm (uniform). (See (a)). The screw was a gothic arc shape, a lead of 2 mm, and a single thread. The shape and dimensions of the nut test piece other than the resin layer are as shown in FIG. In addition, the nut test piece of Examples 8-10 has the same structure as the test piece (Examples 8-10) used in the static destructive test. These nut test pieces were subjected to a screw wear test under the test conditions shown in Table 6, and the amount of wear after the test (increase in axial clearance) was measured. The results are shown in Tables 7 and 8.

  Comparative Examples 1 and 2 have the same configuration as the test pieces (Comparative Examples 1 and 2) used in the static fracture test. Comparative Example 3 is a powder coating of a resin layer made of a thermosetting polyimide resin (containing 15% graphite) on the inner diameter (female thread) of a nut body for a nut test piece machined from a molten metal material (SUS303). After the formation of the nut test piece, the resin layer is machined along the female screw of the nut main body so that the thickness of the resin layer is 0.3 mm (uniform). For the nut test pieces of these comparative examples, the same wear test as in Example 8 was performed, and the amount of wear after the test (increase in axial clearance) was measured. The results are shown in Table 9.

  As shown in Table 7, Examples 8 to 16 in which the surface treatment was performed on the melted metal nut main body were not broken during the test and the resin layer was not peeled off, and the wear amount was less than 0.1 mm. As for a nut main body, the aluminum alloy (Example 9) and copper alloy (Example 10) whose heat conductivity is higher than stainless steel (Example 8) were excellent in abrasion resistance.

  As shown in Table 9, the nut of Comparative Example 1 containing only a resin could not be subjected to a wear test because the flange was broken during the test. The nut of Comparative Example 2 made of molten metal and resin had a very large amount of wear. Although the resin layer was provided in the molten metal nut main body, the nut of the comparative example 3 which is the thermosetting polyimide resin in which the resin layer was powder-coated was inferior in abrasion resistance.

  The sliding screw device provided with the sliding nut of the present invention has excellent sliding characteristics such as seizure resistance and wear resistance even under high load conditions, and is therefore suitable as a sliding screw device used under high load and high temperature conditions in industrial machinery. Available to:

DESCRIPTION OF SYMBOLS 1 Sliding screw apparatus 2 Screw shaft 3 Sliding nut 3a Nut main body 3b Resin layer 3c Thread groove crest 3d Thread groove bottom part 4 Nut outer periphery (melted metal)
5 Inner circumference of the nut (resin)

Claims (11)

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,
In the sliding nut, the nut body is made of molten metal, and a resin layer of a resin composition having a synthetic resin as a base resin as a thread groove is injection-molded on the surface of the female thread portion that is screwed to the screw shaft in the nut body. A sliding nut characterized by being formed by overlapping.   The sliding nut according to claim 1, wherein the nut body is subjected to a chemical surface treatment on a joint surface with the resin layer.   3. The chemical surface treatment is a process in which a fine uneven shape is formed on the joint surface, or a process in which a joint film that chemically reacts with the resin layer is formed on the joint surface. Sliding nut.   The sliding nut according to claim 1, 2 or 3, wherein the resin layer has a thickness of 0.1 to 1 mm.   5. The sliding nut according to claim 1, wherein in the resin layer, a layer thickness of a bottom portion of the thread groove is thicker than a layer thickness of the thread groove portion.   6. 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.   7. The resin composition contains 10 to 30% by volume of polytetrafluoroethylene resin and 2 to 10% by volume of graphite with respect to the whole resin composition without including a fibrous filler. The sliding nut described.   The sliding nut according to any one of claims 1 to 7, wherein a thermal conductivity of the molten metal of the nut body is 50 W / (m · K) or more.   The sliding nut according to claim 8, wherein the molten metal of the nut body is aluminum, an aluminum alloy, copper, or a copper alloy. 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 9, wherein the sliding nut is the sliding nut.   The sliding screw device according to claim 10, wherein a minimum inner diameter of the nut body is smaller than a maximum outer diameter of the screw shaft.

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