Sliding nut and sliding screw device

Abstract

Provided are a sliding nut of a sliding screw device and a sliding screw device that have excellent sliding characteristics such as seizure resistance and abrasion resistance even under a high load condition while enabling cost reduction. In a sliding screw device, along with rotation of a screw shaft, a sliding nut 3 relatively moves while sliding on the shaft of the screw shaft. The sliding nut 3 comprises a metal outer ring 4 made of metal, and a resin inner ring 5 that is integrally provided on an inner peripheral part of the metal outer ring 4. An interface of the metal outer ring 4 with the resin inner ring 5 is a cylindrical surface. The resin inner ring 5 is formed with a female thread that is screwed with the screw shaft. The thickness from a threading groove bottom 5b of the female thread to the cylindrical surface of the metal outer ring 4 is greater than or equal to 0.1 mm and less than 1.0 mm. At least the cylindrical surface of the metal outer ring 4 is an etched surface, and a resin of the resin inner ring 5 is impregnated into fine irregularities on the surface.

Description

Sliding nuts and sliding screw devices

[0001] The present invention relates to a sliding nut for a sliding screw device and a sliding screw device using the sliding nut.

[0002] Sliding screw devices, which convert rotary motion into linear motion or linear motion into rotary motion, have the advantage of being able to be designed more compactly than ball screw devices, and are widely used in industrial machinery feeders and positioning devices. Sliding screw devices using metal nuts, such as copper alloys, require regular maintenance due to concerns about torque increase and seizure caused by running out of applied oil or grease. They also cannot be used in environments where oil or grease cannot be applied, such as in a vacuum or underwater. Therefore, sliding screw devices using plastic nuts have been developed for the purpose of lubrication-free operation and maintenance-free operation.

[0003] As an example of a nut in which the entire nut or the thread groove portion that serves as the sliding portion is made of resin, for example, a resin nut has been proposed in which the thread groove portion (or the entire nut) that screws onto the screw shaft is formed from a PPS resin composition obtained by blending polyphenylene sulfide (hereinafter referred to as PPS) resin with at least polytetrafluoroethylene (hereinafter referred to as PTFE) resin and an organic resin powder that does not melt at 280 ° C. (See Patent Document 1.) Also proposed is a sliding screw device that includes a screw shaft and a nut that moves relatively while sliding on the axis of the screw shaft as the screw shaft rotates, and in which a powder coating film of aromatic polyimide resin is formed on at least the internal thread portion of the nut (See Patent Document 2.)

[0004] Furthermore, as an example of a nut made up of a metal portion and a resin portion, there has been proposed a flanged nut that is screwed onto a screw shaft and moves axially relative to the screw shaft, in which the outer periphery including the flange is formed from metal and the inner periphery that is screwed onto the screw shaft is formed from a lubricating resin, and a means for preventing rotation and slippage between the outer periphery and the inner periphery has been provided (see Patent Document 3).

[0005] 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 and its vicinity, a movable mold having a cavity that molds the remaining outer surface of the resin nut and that can move axially relative to the fixed mold, and a core pin that is provided on the movable mold and has a spiral groove for forming a thread groove on its outer diameter surface. A manufacturing method has been proposed in which molten resin is filled into this mold to mold a resin nut, and the mold is then opened and the core pin is rotated to remove the resin nut (see Patent Document 4).

[0006] However, although the resin nut of Patent Document 1 can be used without lubrication, there are concerns about the strength of the attachment portion such as the flange or the tooth base of the female thread portion under high load, making it difficult to use.

[0007] On the other hand, the sliding screw device of Patent Document 2 has a metal or ceramic body, so the nut does not deform even under high loads. However, when forming the aromatic polyimide resin powder coating film, the resin does not completely melt or melt-flow, and it is difficult to apply high pressure at high temperatures, so a dense resin film does not form. Therefore, when used under high loads, the resin film wears significantly, and the adhesion (shear bond strength) to the nut body may be insufficient. Furthermore, it is not easy to form a resin powder coating film accurately and uniformly on the female thread portion of the nut.

[0008] Furthermore, in the flanged nut of Patent Document 3, the outer periphery of the nut is made of metal, but the inner periphery including the female thread portion is made of synthetic resin. Therefore, the mechanical strength of the tooth base of the female thread portion is equivalent to that of the resin nut of Patent Document 1, and there is a risk that the female thread portion or the joint between the metal and resin may be deformed when used under high load.

[0009] As a sliding screw that solves such problems, a sliding nut is known, characterized in that the nut body is made of molten metal, and a resin layer of a resin composition having a synthetic resin as a base resin is formed by injection molding on the surface of the female thread portion of the nut body that threads onto the screw shaft as a thread groove (see Patent Document 5). The sliding nut described in Patent Document 5 has a nut body made of molten metal, and a resin layer of a resin composition having a synthetic resin as a base resin is formed by injection molding on the surface of the female thread portion of the nut body that threads onto the screw shaft as a thread groove. Therefore, the mechanical strength of the attachment portion such as the flange of the nut and the tooth base of the female thread portion is high and they do not deform even under high loads. In addition, because it has excellent heat dissipation properties, softening of the synthetic resin portion can be suppressed, which reduces the actual contact area on the friction surface of the resin, reducing frictional force and frictional heat, and has the advantages of reducing wear and suppressing an increase in the friction surface temperature.

[0010] JP 2003-239932 A JP 2004-204989 A JP 2006-138405 A JP 2004-25527 A JP 2014-1847 A

[0011] The manufacturing method of the sliding nut described in Patent Document 5 requires, for example, the manufacturing method described in Patent Document 4, or a manufacturing method in which a resin layer is injection-molded onto the nut body and then machined to form a predetermined female thread shape, due to the shape of the inner diameter portion of the nut body.

[0012] However, the manufacturing method described in Patent Document 4 requires a complex and expensive injection molding die, which results in expensive sliding nuts and sliding screw devices. Furthermore, the manufacturing method of forming a predetermined female thread shape by machining after injection molding a resin layer onto the nut body requires synchronizing the female thread shape of the nut body with the lathe feed, which makes it difficult to machine the female thread.

[0013] The present invention has been made in consideration of these circumstances, and is capable of reducing costs while providing a sliding nut for a sliding screw device that has excellent sliding characteristics such as seizure resistance and wear resistance even under high load conditions. An object of the present invention is to provide a sliding screw device.

[0014] The sliding nut of the present invention is a sliding screw device. It is a sliding nut that moves relatively while sliding on the axis of the screw shaft as the screw shaft rotates, or a sliding nut that rotates the screw shaft by moving relatively while sliding on the axis of the screw shaft. The sliding nut comprises a metal outer ring formed of metal and a resin inner ring integrally formed on the inner peripheral portion of the metal outer ring, and the interface between the metal outer ring and the resin inner ring is a cylindrical surface. A female thread that screws onto the screw shaft is formed in the resin inner ring, and the thickness to the cylindrical surface of the metal outer ring at the bottom of the thread groove of the female thread is 0.1 mm or more and less than 1.0 mm. At least the cylindrical surface of the metal outer ring is an etched surface, and the fine irregularities on the surface are impregnated with the resin of the resin inner ring.

[0015] The metal outer ring is characterized in that a structure for preventing the resin inner ring from coming off is provided on at least one inner diameter side end in the axial direction of the metal outer ring.

[0016] The anti-slip structure is characterized in that the metal outer ring has an inclined surface that expands in diameter as it extends axially outward, and the resin inner ring has an expanded diameter portion that expands radially along the inclined surface.

[0017] The etching amount of the etched surface is greater than 5 μm as calculated by the following formula (1): Etching amount (μm) = Weight reduction (g) / (Surface area (cm ２ ) x specific gravity (g / cm ３ )) x 10000... (1)

[0018] The resin inner ring is characterized in that the thickness at the bottom of the thread groove is greater than 0.5 mm and less than 1.0 mm.

[0019] The sliding nut of the present invention is characterized in that it can be suitably provided for a sliding screw device.

[0020] The sliding nut of the present invention comprises a metal outer ring, which is the nut body, and a resin inner ring integrally formed on the inner periphery of the metal outer ring, and is therefore stronger than a resin sliding nut and can be used under high loads. Furthermore, the resin inner ring has an internal thread that threads onto the screw shaft, allowing for excellent sliding properties and smooth movement. Furthermore, the thickness of the metal outer ring from the bottom of the female thread groove to the cylindrical surface is 0.1 mm or more and less than 1.0 mm, allowing for effective dissipation of sliding heat, minimizing wear on the sliding surface of the female thread and improving durability. As a result, high-speed operation is also possible.

[0021] Furthermore, at least the cylindrical surface of the metal outer ring is an etched surface, and the resin of the resin inner ring is impregnated into the fine irregularities on that surface, improving the adhesion strength between the metal outer ring and the resin inner ring.Furthermore, the contact area between the resin inner ring with the internal thread formed thereon and the metal outer ring is increased, making heat transfer easier and further improving the heat dissipation of sliding heat.Furthermore, because the interface between the metal outer ring and the resin inner ring is a cylindrical surface, the internal thread can be formed by tapping, making it easier to manufacture the sliding nut.Furthermore, this leads to a reduction in manufacturing time and cost, making it possible to reduce costs.

[0022] A retaining structure for the resin inner ring is provided on at least one inner diameter end of the metal outer ring in the axial direction, preventing separation of the resin inner ring from the metal outer ring even during long-term use under harsh conditions. Separation of the resin inner ring can also be prevented even when extreme axial loads are applied to the sliding nut. Furthermore, as a retaining structure, the metal outer ring has an inclined surface that expands in diameter outward in the axial direction, and the resin inner ring has an expanded diameter portion that expands radially along the inclined surface. Therefore, compared to a case where the retaining structure has a non-inclined surface, the heat dissipation effect of sliding is not reduced, and the wear resistance of the sliding surface of the female thread can be maintained. Furthermore, when extreme axial loads are applied to the sliding nut, the load transferred from the metal outer ring to the resin inner ring is easily distributed, maintaining the wear resistance of the sliding surface of the female thread.

[0023] Since the etching amount calculated by the above formula (1) on the etched surface is greater than 5 μm, the adhesive strength of the resin inner ring can be improved and it can withstand high loads, as will be shown in the examples below.

[0024] In the resin inner ring, the resin thickness at the bottom of the thread groove is more than 0.5 mm and less than 1.0 mm, so that the dissipation of sliding heat is ensured while variations in wear resistance can be suppressed.

[0025] Since the sliding screw device of the present invention is equipped with the sliding nut of the present invention, it has excellent sliding characteristics such as seizure resistance and wear resistance even under high load conditions, and can be made cost-effective.

[0026] FIG. 1 is a perspective view of a sliding screw device of the present invention. FIG. 2 is an axial cross-sectional view of an example of a sliding nut of the present invention. FIG. 3 is a cross-sectional perspective view of another example of a sliding nut of the present invention. FIG. 4 is a partial enlarged view of another example of a sliding nut of the present invention. FIG. 5 is a diagram showing the outer shapes of sliding screw test pieces of Example 1 and Comparative Examples 1 and 2. FIG. 6 is a graph showing the results of Test 1. FIG. 7 is a graph showing the results of Test 2. FIG. 8 is a diagram showing an outline of the test method for Test 3. FIG. 9 is a graph showing the results of Test 3.

[0027] An embodiment of the sliding screw device of the present invention will be described with reference to Figures 1 and 2. Figure 1 is a perspective view of the sliding screw device, and Figure 2 is an axial cross-sectional view of an example of a sliding nut. The sliding screw device 1 of the present invention is composed of a screw shaft 2 and a sliding nut 3 of the present invention that is threaded into the thread groove of the screw shaft 2 and moves relatively while sliding on the screw shaft. The rotational motion of the screw shaft 2 is converted into linear motion of the sliding nut 3. Alternatively, linear motion can be imparted to the screw shaft 2 by rotating the sliding nut 3 at the same position.

[0028] The screw shaft 2 can be made of stainless steel, carbon steel, or other iron-based metals plated with zinc, nickel, or steel chrome, or an aluminum alloy, or a resin shaft such as polyimide (PI) resin or phenolic resin. Corrosion-resistant metals or resins, such as stainless steel or aluminum alloys, are preferred because they do not rust and are also suitable because rust prevention treatment can be omitted. In the present invention, corrosion-resistant metals, which can ensure dimensional accuracy and have excellent durability, are most preferred.

[0029] The screw shaft 2 can be processed by rolling, cutting, grinding, or any other method. Considering sliding characteristics such as wear resistance under high load conditions, it is preferable for the surface roughness of the contact surface of the screw shaft with the sliding nut to be small. If the surface roughness of the screw shaft is 0.1 μm Ra or less, there is very little digging wear of the sliding nut due to the convexity of the screw shaft surface. In particular, a surface roughness of 0.05 μm Ra or less is optimal.

[0030] The screw shaft 2 can be used without lubrication. Furthermore, if low friction is more important than maintenance-free operation, a lubricant such as oil or grease may be used in the sliding portion between the screw shaft 2 and the sliding nut 3. In this case, a linear groove may be formed in the axial direction on the sliding surface of the sliding nut with the screw shaft, so that wear debris is retained therein, thereby suppressing abrasive wear.

[0031] The sliding nut 3 may have a flange at one end as shown in FIG. 1 . Alternatively, the flange may be provided at the axial center of the sliding nut, or between one end and the axial center. The flange is not necessarily required. As shown in FIG. 2 , the sliding nut 3 comprises a metal outer ring 4 and a resin inner ring 5 integrally formed on the inner periphery of the metal outer ring 4. An internal thread that threadably engages with the screw shaft is formed on the resin inner ring 5. The surface of the internal thread is in direct sliding contact with the screw shaft 2 (see FIG. 1 ). The sliding nut 3 has a nut body formed from the metal outer ring 4. The inner periphery 4 a of the metal outer ring 4 is a cylindrical surface. In other words, the interface between the metal outer ring 4 and the resin inner ring 5 is a cylindrical surface. The cylindrical surface is a concept that encompasses not only a straight cylindrical surface, but also a structure in which a cylindrical surface is provided with protrusions or recesses for preventing slippage or rotation.

[0032] In Figure 2, the inner peripheral surface 4a of the metal outer ring 4 is an etched surface. The etched surface has fine irregularities of micron size or less, which are impregnated with the resin of the resin inner ring 5. Specifically, the resin that forms the resin inner ring 5 is injection molded onto the inner peripheral surface 4a of the metal outer ring 4, so that the molten resin penetrates the fine irregularities and solidifies, firmly bonding the metal outer ring 4 and the resin inner ring 5. Furthermore, the actual bonding area between the resin inner ring 5 and the metal outer ring 4 is increased, and they are in close contact, so that sliding heat generated on the surface of the resin female thread is more easily transferred to the metal outer ring 4.

[0033] Examples of etching treatments include chemical etching treatments and plasma etching treatments. Among these etching treatments, chemical etching treatments, which form intricately intricate fine irregularities, are preferred. By allowing etching to proceed in the horizontal direction as well as the vertical direction of the treated surface, three-dimensionally intricate fine irregularities can be formed, which makes it easier to exert a strong anchor effect.

[0034] Examples of chemical etching treatments that can be applied include acidic solution treatment (sulfuric acid, nitric acid, hydrochloric acid, etc., or a mixture with other solutions), alkaline solution treatment (sodium hydroxide, potassium hydroxide, etc., or a mixture with other solutions), Amalfa treatment by MEC, and NMT treatment by Taisei Plus. The fine irregular shape varies depending on the concentration, treatment time, post-treatment, etc., but in order to enhance the binding strength due to the anchor effect, it is preferable to have fine irregularities with a concave pitch of several nm to several tens of μm. When Amalfa treatment by MEC is applied, it is preferable that at least the surface of the metal outer ring that forms the interface with the resin inner ring is aluminum-based or copper-based. If it is copper-based, the metal outer ring may be iron-based and the surface that forms the interface with the resin inner ring may be copper-plated, or the metal outer ring may be aluminum-based or copper-based molten metal.

[0035] In order to improve the bonding strength of the resin inner ring 5 to the metal outer ring 4, the etching amount (1 cm of the surface to be etched) on the etching treatment surface is ２ The etching amount per unit area is preferably greater than 5 μm. The etching amount can be calculated using the following formula (1): Etching amount (μm) = Weight reduction (g) / (Surface area (cm ２ ) x specific gravity (g / cm ３ )) x 10000... (1)

[0036] In the above formula (1), "weight loss" is the value obtained by subtracting the weight of the metal outer ring after etching from the weight of the metal outer ring before etching. "Surface area" is the area of ​​the surface to be etched, and for example, in the case of Figure 2, if no masking is performed, it is the total surface area (including the areas of the inner peripheral surface, outer peripheral surface, and flange surface) of the metal outer ring before etching. "Specific gravity" is the specific gravity of the metal outer ring.

[0037] The etching amount calculated by the above formula (1) is preferably 7 μm or more, more preferably 8 μm or more, and may be 10 μm or more. Note that, since an increase in the etching amount to a certain extent makes it difficult to achieve an improvement in adhesion strength, the etching amount is, for example, 20 μm or less, and may be 15 μm or less.

[0038] In the chemical etching process, a combination of multiple solutions (chemicals) may be used, or the process may be carried out in stages.

[0039] As shown in Figure 2, in the sliding nut 3, the internal thread that screws onto the screw shaft is formed of resin. In Figure 2, the internal thread is composed of a thread 5a that protrudes toward the inner diameter side and a thread groove bottom 5b, and the thread 5a and the thread groove bottom 5b are arranged alternately along the axial direction. The shape of the thread 5a is not particularly limited, and in addition to the trapezoidal shape shown in Figure 2, it may be a triangular, rectangular, or gothic arc shape. Furthermore, although the thread groove bottom 5b is formed with a flat surface in Figure 2, its shape is not particularly limited, and it may be a V-shape, a U-shape, or the like.

[0040] In FIG. 2, in the resin inner ring 5, the resin thickness t ａ is constant, and the resin thickness t ｂ is constant. Also, the resin thickness t ａ is the resin thickness t at the bottom 5b of the thread groove ｂ It is thicker than (t ａ >t ｂ ). Here, the resin thickness t ａ is the vertical distance from the apex of the thread 5a to the thread groove bottom 5b. ｂ is the vertical distance from the bottom 5b of the thread groove to the inner peripheral surface 4a of the metal outer ring 4.

[0041] As shown in FIG. 2, the resin thickness t ｂ Specifically, the resin thickness t ｂ The resin thickness t is 0.1 mm or more and less than 1.0 mm. ｂ If the resin thickness t is less than 0.1 mm, the durability of the thread groove bottom 5b may be reduced. ｂ If the resin thickness t is 1.0 mm or more, the heat dissipation performance of the sliding surface cannot be sufficiently ensured, and the amount of wear on the sliding surface may increase. ｂIn order to suppress variations in wear resistance, the thickness is preferably 0.2 mm or more and less than 0.9 mm, and more preferably 0.3 mm or more and less than 0.8 mm.

[0042] Resin thickness t ａ , t ｂ The required thickness may be obtained by injection molding, or the resin may be finished to the required thickness by machining after injection molding.

[0043] Another example of the sliding nut of the present invention will be described with reference to Figures 3 and 4. Figure 3 is a cross-sectional perspective view of the sliding nut, and Figure 4 is an enlarged view of the area around the retaining structure. These figures mainly describe configurations that differ from the sliding nut in Figure 2. Note that Figure 3 shows the sliding nut 6 in a state where the screw shaft is threadedly engaged. Also, for convenience, Figure 4 shows parts of the metal outer ring 7 and the resin inner ring 8 with hatching.

[0044] As shown in FIG. 3 , the sliding nut 6 includes a metal outer ring 7 and a resin inner ring 8 integrally formed on the inner periphery of the metal outer ring 7. The resin inner ring 8 has an internal thread that threads onto a screw shaft. In the sliding nut 6, a retaining structure for the resin inner ring 8 is provided on both axially inner diameter end portions of the metal outer ring 7. Specifically, as the retaining structure, the metal outer ring 7 has an inclined surface 7b that expands in diameter toward the outside in the axial direction, and the resin inner ring 8 has an expanded diameter portion 8c that expands in the radial direction along the inclined surface 7b. In the sliding nut 6, the expanded diameter portion 8c of the resin inner ring 8 catches on the metal outer ring 7 in the axial direction, thereby preventing the resin inner ring 8 from coming off. While the retaining structure may be provided on only one axial side, it is preferable to provide it on both sides.

[0045] Furthermore, the inclined surface 7b is etched, and the resin of the enlarged diameter portion 8c is impregnated into the minute irregularities of the inclined surface 7b, so that the resin inner ring 8 can be more effectively prevented from coming off.

[0046] As shown in Figure 3, the inclined surface 7b is formed around the entire circumference of the metal outer ring 7. The expanded diameter portion 8c of the resin inner ring 8 is also formed around the entire circumference. By forming the inclined surface 7b around the entire circumference, when a load is applied in the axial direction of the sliding nut 6, the load transmitted from the metal outer ring 7 to the resin inner ring 8 is easily dispersed, which ultimately leads to improved wear resistance of the sliding surfaces. Although the sliding nut 6 does not have a rotation prevention structure between the metal outer ring 7 and the resin inner ring 8, this is not necessary because the cylindrical surface of the metal outer ring 7 (including the inclined surface 7b) is an etched surface and is firmly bonded to the resin of the resin inner ring 8.

[0047] As shown in FIG. 4, the radial depth t ｃ The radial depth t (in FIG. 4, the radial depth of the inclined surface 7b) is preferably 0.3 mm to 2.0 mm. ｃ If the radial depth t is smaller than 0.3 mm, it is difficult to exert the retaining effect. ｃ If the distance is greater than 2.0 mm, the ability to dissipate sliding heat may decrease, which may lead to early wear of the sliding surface.

[0048] The inner peripheral surface of the expanded diameter portion 8c of the resin inner ring 8 is a tapered surface that expands in diameter outward in the axial direction, which makes assembly easier when threading the screw shaft into the threaded hole of the sliding nut 6.

[0049] The retaining structure for the metal outer ring may be any structure that allows the resin inner ring to be hooked onto the metal outer ring in the axial direction, and may be a rectangular recess, a trapezoidal recess, or the like, in addition to the inclined portions shown in Figures 3 and 4. The retaining structures may also be provided spaced apart (e.g., at equal intervals) in the circumferential direction, in which case they will also have a rotation prevention function.

[0050] The materials used for each part of the sliding nut are explained below.

[0051] The metal constituting the metal outer ring is preferably a melt-cast metal because of its high thermal conductivity. Specific metal materials are preferably iron, aluminum, aluminum alloys, copper, or copper alloys. By using these materials, the metal outer ring can ensure the required thermal conductivity and load-bearing capacity, and the sliding heat generated on the sliding surface can be easily dissipated from the metal outer ring to the outside, making it usable even under high loads.

[0052] As the iron, general structural carbon steel (SS400, etc.), mechanical structural carbon steel (S45C, etc.), stainless steel (SUS303, SUS316, etc.), etc. can be used. These irons may also be plated with zinc, nickel, copper, etc. However, when applying corrosion-resistant plating such as zinc plating or nickel plating, the surface that forms the interface with the resin inner ring is masked.

[0053] Examples of aluminum that can be used include A1050 and A1100, and examples of aluminum alloys that can be used include A2017, A2024, A5056, and A6061. A2017 and A2024 are preferred due to their excellent machinability. Aluminum alloy die-casts (such as ADC12) and aluminum alloy castings (such as AC4B) can also be used. Anodizing may be applied to improve the corrosion resistance of aluminum. However, if anodizing is applied, the surface that interfaces with the resin inner ring must be masked.

[0054] Copper alloys such as C1100 and C3604 can be used. From the viewpoint of machinability and environmental friendliness, C6801 and C6802 containing 0.1% or less of lead and 0.0075% or less of cadmium are preferred. Copper alloy castings (such as CAC406) can also be used.

[0055] The metal of the metal outer ring preferably has a thermal conductivity of 50 W / (m K) or more, such as the above-mentioned aluminum, aluminum alloy, copper, and copper alloy. The higher the thermal conductivity of the metal, the easier it is to dissipate sliding heat, so a thermal conductivity of 100 W / (m K) or more is more preferable.

[0056] The synthetic resin forming the resin inner ring is preferably an injection-moldable synthetic resin as the base resin, and is preferably a synthetic resin with excellent lubrication properties. Furthermore, a highly heat-resistant synthetic resin is preferred so that the sliding nut can be used in locations with high ambient temperatures. Examples of such synthetic resins include aromatic polyetherketone resins such as polyetheretherketone (PEEK) resin, polyetherketone (PEK) resin, and polyetherketoneetherketoneketone (PEKEKK) resin, polyacetal (POM) resin, PPS resin, injection-moldable thermoplastic PI resin, polyamideimide (PAI) resin, polyamide (PA) resin, and injection-moldable fluororesin. These synthetic resins may be used alone or as a polymer alloy containing two or more types. Among these synthetic resins, PEEK resin, thermoplastic PI resin, PPS resin, and PA resin are particularly preferred.

[0057] The synthetic resin forming the resin inner ring preferably does not contain fibrous inorganic compounding materials such as glass fiber, carbon fiber, whiskers, etc. If the resin inner ring contains a fibrous inorganic compounding material, when the sliding nut moves back and forth relative to the screw shaft while sliding on the axis of the screw shaft as the screw shaft rotates, the ends of the fibers may become edges and cause wear and damage to the mating screw shaft, or the ends of the fibers may be subjected to repeated stress during the reciprocating movement of the sliding nut, causing fatigue wear of the resin.

[0058] The synthetic resin forming the resin inner ring preferably contains PTFE resin. The inclusion of PTFE resin reduces friction, reduces sliding heat, and provides excellent friction and wear characteristics even under high loads. The PTFE resin may be a molding powder produced by suspension polymerization, a fine powder produced by emulsion polymerization, or recycled PTFE.

[0059] The synthetic resin forming the resin inner ring preferably contains graphite. The inclusion of graphite improves friction and wear characteristics. Furthermore, its high thermal conductivity facilitates dissipation of sliding heat to the metal outer ring. Graphite is broadly classified into natural graphite and artificial graphite, and further includes flake, granular, and spherical graphite, and any of these can be used. Flake-shaped graphite is preferred to increase the elastic modulus of the synthetic resin, improve wear resistance and creep resistance, and obtain stable low friction.

[0060] The synthetic resin forming the resin inner ring preferably contains an organic resin powder such as a thermosetting PI resin, a phenolic resin, or a wholly aromatic polyester resin. The inclusion of the organic resin powder improves friction and wear characteristics. Furthermore, the elastic modulus of the synthetic resin is increased, improving wear resistance and creep resistance, and achieving stable low friction.

[0061] The synthetic resin forming the resin inner ring preferably contains 10 to 40 volume % of PTFE resin relative to the total synthetic resin without containing any fibrous inorganic compounding material, and more preferably contains 3 to 30 volume % of graphite or organic resin powder. This results in a low coefficient of friction even under high loads, less deformation and wear of the resin inner ring, less damage to the mating screw shaft, and higher resistance to oils, etc.

[0062] Well-known resin compounding agents may be added to the synthetic resin to the extent that the effects of the present invention are not impaired. Examples of such compounding agents include friction property improvers such as boron nitride, molybdenum disulfide, and tungsten disulfide; thermal conductivity improvers such as carbon powder and metal oxide powder; colorants such as carbon powder, iron oxide, and titanium oxide; granular inorganic fillers such as calcium carbonate, calcium sulfate, mica, and talc; and aramid fibers.

[0063] The means for mixing and kneading the above raw materials is not particularly limited. For example, only the powder raw materials can be dry-mixed in a Henschel mixer, ball mixer, ribbon blender, Loedige mixer, Ultra Henschel mixer, or the like, and then melt-kneaded in a melt extruder such as a twin-screw extruder to obtain pellets for molding. Furthermore, when melt-kneading in a twin-screw extruder, side feed may be used to add compounding materials. Furthermore, heat treatment such as annealing may be performed to improve physical properties.

[0064] The sliding nut of the present invention can be obtained, for example, by setting a metal outer ring (nut body) with an etched surface in an injection molding die, injection molding a synthetic resin onto the metal outer ring, and then machining (tapping, etc.) to form a predetermined female thread shape. By insert molding in this way, the resin inner ring can be firmly attached to the inner peripheral surface of the metal outer ring without using an adhesive.

[0065] Example 1 A sliding nut having the dimensions shown in Figure 5 was made of a metal outer ring made of A5056 (aluminum alloy). A through hole of φ13.2 mm was provided in the central axis of the metal outer ring, and a 45-degree inclined surface was provided on the inner diameter portion at both axial ends of the metal outer ring as a retaining structure (see Figure 4). The length of the inclined surface was 1 mm in the axial direction. This metal outer ring was subjected to an etching treatment on the entire surface without being masked. For the etching treatment, an Amalfa treatment manufactured by MEC was performed, and the chemicals used were A-10101 (pretreatment) and A-10156 (roughening treatment). The etching amount calculated from the following formula (1) was 6 µm. Etching amount (µm) = weight loss (g) / (surface area (cm ２ ) x specific gravity (g / cm ３ )) × 10000 (1) In the above formula (1), the "weight loss" is 0.0614 g and the "surface area" is 38.803 cm ２ and the "specific gravity" is 2.64 g / cm ３ It was.

[0066] The following raw materials were dry-blended using a Henschel dry mixer and melt-kneaded using a twin-screw extruder to produce pellets of a PPS resin composition. Using these pellets, an etched metal outer ring was placed in a mold, and the PPS resin composition was insert-molded into the inner diameter portion of the metal outer ring. A female thread was formed on the central shaft of the insert-molded nut by tapping, and a nut test piece was produced. In the resin inner ring, the resin thickness at the bottom of the thread groove was 0.55 mm, and the resin thickness at the thread was 1.49 mm. (1) PPS resin: 60% by volume (2) Thermosetting PI resin powder: 15% by volume (3) PTFE resin: 25% by volume

[0067] [Comparative Example 1] Comparative Example 1 is a resin sliding nut (without molten metal). Using the pellets produced in Example 1, a sliding nut having the dimensions shown in FIG. 5 was injection molded, and tapping was performed in the same manner as in Example 1. A nut test piece was produced.

[0068] [Comparative Example 2] A metal outer ring made of A5056 (aluminum alloy) was used as a sliding nut having the dimensions shown in Figure 5. An internal thread was formed on the inner diameter of this metal outer ring, and the inner peripheral surface was subjected to an etching treatment with an etching amount of 6 μm, as in Example 1. Insert molding was performed using the pellets produced in Example 1, and then the resin was machined along the internal thread of the metal outer ring to produce a nut test piece with a resin layer thickness of 0.3 mm (uniform).

[0069] A rolled screw shaft made of SUS304 was assembled to each nut test piece, and the following wear test was carried out.

[0070] Test 1: Wear Test Nut test pieces of Example 1 and Comparative Example 1 were each assembled to a vertically installed screw shaft. Under the following Condition 1, the nut test piece was reciprocated with an axial load applied, and continuous operation was performed until the total travel distance reached 5,000 m. During the test, the amount of axial wear (amount of wear on the thread tooth flank) was measured over time. The results are shown in Figure 6(a). In addition, the surface temperature of the screw shaft was measured after 100 m and 500 m. <Condition 1> Axial load: 300 N Rotation speed: 300 min －１Stroke: 150 mm Nut travel distance: 5000 m Lubrication: Dry Temperature: Room temperature

[0071] 6(a), the amount of axial wear was significantly reduced in Example 1 compared to Comparative Example 1. Furthermore, the surface temperature of the screw shaft after 100 m was 98°C in Example 1 and 175°C in Comparative Example 1, and the surface temperature of the screw shaft after 500 m was 80°C in Example 1 and 210°C in Comparative Example 1.

[0072] <Condition 2> For the sliding screw test pieces of Example 1 and Comparative Example 2, an axial load of 1200 N and a rotation speed of 100 min were applied. －１ The continuous operation was carried out under the same conditions as in Condition 1, except that the temperature was set to . The results are shown in Figure 6(b).

[0073] As shown in Fig. 6(b), the amount of axial wear was equivalent in Example 1 and Comparative Example 2. Furthermore, the surface temperature of the screw shaft after 100 m was 70°C in Example 1 and 62°C in Comparative Example 2, and the surface temperature of the screw shaft after 500 m was 67°C in Example 1 and 48°C in Comparative Example 2. Note that the flange portion of Comparative Example 1 was damaged when an axial load (1200 N) was applied, so the test was not possible.

[0074] The results of the above wear tests under conditions 1 and 2 confirmed that the amount of axial wear was affected by sliding heat. The sliding screw test piece of Example 1 was easier to manufacture and cheaper than the sliding screw test piece of Comparative Example 2, yet exhibited equivalent wear resistance.

[0075] Test 2: Investigation of resin thickness at the bottom of the thread groove By changing the inner diameter of the metal outer ring, three levels of resin thickness at the bottom of the thread groove of the resin inner ring were set (0.3 mm, 0.7 mm, 1.0 mm), and sliding screw test pieces were prepared for Examples 2 and 3 and Comparative Example 3. These were used in continuous operation under Condition 1, and the amount of axial wear after 3000 m was measured. Tests were conducted for each level, with n = 1 or 2. The results are shown in Figure 7.

[0076] As shown in Figure 7, when the resin thickness at the bottom of the thread groove of the resin inner ring was 1.0 mm, the heat dissipation from the sliding heat was insufficient, and the amount of axial wear increased significantly. In contrast, in Examples 2 and 3, where the resin thickness at the bottom of the thread groove was less than 1.0 mm, the amount of axial wear was significantly reduced to 0.08 mm or less, and the variation in Example 3 was particularly small.

[0077] Test 3: Study of Etching Amount Using the same metal outer ring as in Example 1, the entire surface of this metal outer ring was subjected to the same etching treatment as in Example 1 without processing the retaining structure and without masking. The etching amount defined by the above formula (1) was adjusted to three levels (5 μm, 7 μm, and 10 μm). Next, the same PPS resin composition as in Example 1 was injection molded onto the inner surface of the metal outer ring to prepare an adhesion strength test piece consisting of a metal outer ring and a resin inner ring. Note that no internal threads were machined into this adhesion strength test piece.

[0078] As shown in Fig. 8, a load was applied in the axial direction to only the resin inner ring 13 of the adhesion strength test piece 11 using a press-fit jig 14, and the strength at which the metal outer ring 12 and the resin inner ring 13 peeled off was taken as the adhesion strength. The results are shown in Fig. 9.

[0079] 9, when the etching depth on the etched surface was 5 μm, the adhesion strength was significantly low. In contrast, when the etching depth was 7 μm, the adhesion strength was significantly improved to 5 MPa or more, and when the etching depth was 10 μm, the variation was further reduced.

[0080] The sliding screw device equipped with the sliding nut of the present invention can reduce costs and has excellent sliding characteristics such as seizure resistance and wear resistance even under high load conditions. Therefore, it can be suitably used as a sliding screw device used under high load and high temperature conditions in industrial machinery, etc.

[0081] REFERENCE SIGNS LIST 1 sliding screw device 2 screw shaft 3 sliding nut 4 metal outer ring 4a inner peripheral surface 5 resin inner ring 5a thread 5b thread groove bottom 6 sliding nut 7 metal outer ring 7a inner peripheral surface 7b inclined surface 8 resin inner ring 8c enlarged diameter portion 11 adhesion strength test piece 12 metal outer ring 13 resin inner ring 14 press-fit jig

Claims

1. In a sliding screw device, a sliding nut that relatively moves while sliding on the axis of a screw shaft as the screw shaft rotates, or a sliding nut that rotates the screw shaft by relatively moving while sliding on the axis of the screw shaft, wherein the sliding nut is composed of a metal outer ring formed of metal and a resin inner ring integrally provided on the inner peripheral portion of the metal outer ring; the interface between the metal outer ring and the resin inner ring is a cylindrical surface; a female screw that engages with the screw shaft is formed on the resin inner ring; the thickness from the bottom of the screw groove of the female screw to the cylindrical surface of the metal outer ring is 0.1 mm or more and less than 1.0 mm; at least the cylindrical surface of the metal outer ring is an etched surface, and the resin of the resin inner ring has infiltrated into the fine irregularities of the surface. A sliding nut characterized by this.

2. The sliding nut according to claim 1, characterized in that a retaining structure for the resin inner ring is provided at at least one inner diameter side end portion in the axial direction of the metal outer ring.

3. As the retaining structure, the metal outer ring has an inclined surface that expands in diameter as it goes outward in the axial direction, and the resin inner ring has an expanded diameter portion formed to expand in the radial direction along the inclined surface. The sliding nut according to claim 2, characterized by this.

4. The sliding nut according to claim 1, wherein the etching amount calculated by the following formula (1) on the etching treatment surface is greater than 5 μm. Etching amount (μm) = weight reduction amount (g) / (surface area (cm ２ ) × specific gravity (g / cm ３ )) × 10000... (1) 5. In the resin inner ring, the thickness at the bottom of the screw groove is more than 0.5 mm and less than 1.0 mm. The sliding nut according to claim 1, characterized by this.

6. At least one inner diameter side end portion in the axial direction of the metal outer ring is provided with a retaining structure for the resin inner ring. As the retaining structure, the metal outer ring has an inclined surface that expands in diameter toward the outside in the axial direction, and the resin inner ring has an expanded diameter portion formed to expand in the radial direction along the inclined surface. The etching amount calculated by the following formula (1) on the etching treatment surface is greater than 5 μm and 15 μm or less. In the resin inner ring, the thickness at the bottom of the thread groove is more than 0.5 mm and less than 1.0 mm. The sliding nut according to claim 1, characterized in that: Etching amount (μm) = Weight reduction amount (g) / (Surface area (cm ２ )× Specific gravity (g / cm ３ ))× 10000 ··· (1) 7. A sliding screw device characterized by comprising the sliding nut according to claim 1.

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