JP2003239932A - Resin nut and sliding screw device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive resin nut with low torque and superior wear resistance in a wide temperature range, and also to provide a sliding screw device. <P>SOLUTION: The resin nut moving while sliding on a shaft of a screw shaft is a molded body of a polyphenylene sulfide resin composition formed by mixing infusible and insoluble organic resin powder and tetrafluoroethylene resin in a polyphenylene sulfide resin molding temperature. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin nut and a slide screw device using the resin nut.

[0002]

2. Description of the Related Art A slide screw device for converting a rotary motion into a linear motion is widely used as a feed device or a positioning device of an industrial machine. Among them, slide screw devices using resin nuts have recently expanded their applications such as optical measurement equipment, semiconductor manufacturing equipment, and medical equipment, and specifications and characteristics according to each equipment have been required. There is.

Conventionally, a resin nut for a slide screw device is formed by dispersing powder of tetrafluoroethylene resin (hereinafter abbreviated as PTFE) in polyacetal resin (Japanese Patent Publication No. 54-33347). , An example formed of glass fiber reinforced plastic (Japanese Patent Laid-Open No. 64-26059),
Example of thermosetting resin with excellent lubricity such as polyimide resin and condensed polycyclic aromatic resin (Japanese Patent Laid-Open No. 4-203650), formed of resin composition in which graphite is added to thermoplastic polyimide resin (JP-A-6-193701), a polyphenylene sulfide resin (hereinafter abbreviated as PPS) formed with a resin composition containing a whisker (JP-A-2001-116102), and the like are known. ing.

[0004]

However, as the use of resin nuts expands, conventional resin nuts have the following problems with respect to specifications, required characteristics, and prices according to each device. (1) When PTFE powder and lubricating oil are mixed with polyacetal resin, the price is satisfactory, but creep deformation occurs and wear becomes significantly large when the ambient temperature or the temperature of the sliding part exceeds 100 ° C. , It may not be used. (2) Aromatic polyimide resin with excellent heat resistance, graphite, P
The resin composition containing TFE or the like has a problem that the price of the resin nut increases because the resin is expensive. Further, since graphite is transferred to and accumulated on the screw shaft of the sliding partner, vibration and sliding noise may be generated when used for a long period of time. (3) Even if a thermosetting resin having excellent lubricity such as an aromatic polyimide resin or a condensed polycyclic aromatic resin is used as a main component, the lubricity is insufficient, and the low friction required for the slide screw device, There are cases where low wear and low noise cannot be satisfied. (4) When a fiber-reinforced resin mixed with glass fiber, carbon fiber, etc. is used as the nut material to improve wear resistance, friction shear force concentrates on the fiber, so that it is large not only on the resin surface but also inside. Power is added. Therefore, the reciprocating motion causes fatigue wear in a large unit starting from the fibrous material. Especially, it occurs early in a slide screw device in which a nut reciprocates on a screw shaft. Moreover, when a fiber material is mixed, the other screw shaft may be damaged. (5) Since the whiskers of the nut made of the resin composition in which the whisker is mixed with the relatively inexpensive PPS are the fibers, the fatigue wear is caused by the reciprocating motion. In addition, lubricity is poor, and there is a case where a slide screw device with low wear and low noise cannot be obtained.

In addition to the above problems, in the slide screw device which has been conventionally required to have a high speed, it is necessary to avoid the increase of the capacity of the motor and increase the lead in view of energy saving and low cost. Since the sliding material has speed dependence,
Sliding at high speed increases the coefficient of friction. Therefore, if a lead having a diameter equal to or more than twice the nominal diameter of the screw shaft is used to increase the speed, the sliding speed increases and the torque increases, so that there is a problem that the conventional motor capacity cannot cope. Further, since the specifications are strict, there is a problem that the amount of wear of the nut material increases.

The present invention has been made to solve the above problems, and provides a resin nut and a slide screw device which are excellent in wear resistance in a wide temperature range, have a low torque, and are inexpensive. With the goal. It is another object of the present invention to provide a slide screw device that has a low torque and has sufficient wear resistance even in the case of a high speed type such as a lead having a diameter twice or more the nominal diameter of the screw shaft.

[0007]

A resin nut according to the present invention is a resin nut that relatively moves while sliding on the axis of a screw shaft, wherein a thread groove portion screwed onto the screw shaft is made of polyphenylene. It is characterized in that it is formed from a polyphenylene sulfide resin composition obtained by mixing at least a tetrafluoroethylene resin and a non-melting organic resin powder at 280 ° C. into a sulfide resin.

Further, the polyphenylene sulfide resin composition is characterized by further containing a whisker having a fiber length shorter than the average particle diameter of the organic resin powder.

The organic resin powder used for the resin nut is at least one selected from thermosetting polyimide resin, thermoplastic polyimide resin, wholly aromatic polyester resin, aromatic polyamide resin and polyether ether ketone resin. It is a powder of two organic resins. The PTFE is at least one type of molding powder or fine powder. Further, the convex shape of the thread groove portion is characterized in that the axial cross section is semicircular.

The slide screw device of the present invention is a slide screw device comprising a screw shaft and a resin nut that moves while sliding on the screw shaft as the screw shaft rotates. It is characterized by using a resin nut.
In addition, the lead of the slide screw device is 2 of the nominal diameter of the screw shaft.
It is characterized by having more than double. Here, the lead is
The linear movement distance of the nut per one rotation of the screw shaft.

By using PPS as the main component of the resin composition that forms the resin nut, the resin is inexpensive and has a wide practical temperature range (sliding part temperature is -5 ° C to 150 ° C). A nut and slide screw device is obtained. Also, P
Since PS has excellent chemical resistance, it can be used in environments such as water and chemicals. PTFE in the PPS composition
By blending, stable low friction properties can be obtained,
There is no noise, the starting friction coefficient is low, and the wear resistance is also improved. In addition, by using a molding powder or fine powder that has not been subjected to γ-ray irradiation or firing, it becomes fibrous and has a three-dimensional network structure in the melt kneading of PPS, so that the abrasion resistance is significantly improved. Further, because of the miniaturization, the existence probability on the sliding surface also increases, resulting in extremely stable and low friction. Since PTFE is soft, it does not cause fatigue wear unlike hard fibers such as glass fibers and carbon fibers even if it becomes fibrous. In addition, since the molding powder has a better lubricating effect on the sliding surface than the fine powder, it can be used particularly preferably.

By blending the non-melting organic resin powder at 280 ° C., the powdery form can be maintained in the resin molded body, so that it bears the load on the sliding surface and increases the true contact area in a wide temperature range. No friction and wear. In addition, since the organic resin powder is softer than metal, it does not cause wear damage to the mating material. In particular, the thermosetting polyimido resin powder and wholly aromatic polyester resin powder have less temperature dependence of physical properties than the thermoplastic resin and do not melt at all and have high heat resistance. Even if it becomes higher, the load sharing capacity is high and the torque increase is extremely small. Further, when the sliding surface plays a role of load sharing, local heat is generated, but at that time, neither melting nor softening occurs.

Further, by further blending a whisker having a fiber length shorter than the average particle diameter of the organic resin powder which is not melted at 280 ° C., the load distribution on the sliding surface is carried out by the organic resin powder. Since there is no load sharing, whiskers micro-reinforce between the organic resin powders without fatigue wear. Therefore, the temperature dependence of the resin composition is reduced, and even if the temperature of the sliding surface is increased, the torque increase is extremely small. Further, since the wear unit is extremely small, the wear resistance is remarkably improved. Further, when the nut thread portion is formed by injection molding, dimensional accuracy is improved.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A slide screw device of the present invention will be described with reference to FIG. FIG. 1 is a perspective view of a slide screw device.
The slide screw device 2 includes a screw shaft 1 and a resin nut 3 that is screwed into a screw groove of the screw shaft 1 and moves while sliding on the screw shaft. It is converted into the linear movement of the nut 3 made by the manufacturing method. In addition, the resin nut 3 may be rotated at the same position to impart linear motion to the screw shaft 1. Further, in this resin nut 3, the thread groove portion that is screwed into the screw shaft has the above-mentioned P
It is formed from a PS composition. In this case, after the metal nut body is placed in the injection molding die, the thread groove is
Insert molding may be performed with the PS composition, or a resin nut may be integrally injection-molded with the PPS composition using an injection molding die that does not distinguish between the thread groove portion and the nut body.

The thread shape is, for example, a miniature screw, a metric coarse screw, a metric fine screw, a unified coarse screw, a unified fine screw, a triangular screw, a 29-degree trapezoidal screw, a metric trapezoidal screw, or a trapezoidal screw. It may be a screw, and any screw shape can be applied. Further, a single-start screw, a double-start screw, or a multiple-start screw may be used.
In particular, the slide screw device 2 having a lead having twice or more the nominal diameter of the screw shaft as the characteristic of the screw is preferable because it can correspond to the speeding up of the feed screw.

In the present invention, the convex shape of the thread groove portion of the resin nut preferably has a semicircular cross section in the axial direction because the contact area with the screw shaft is reduced. Further, it is preferable to adopt the Gothic arc type for the thread groove of the screw shaft in combination with the shape of the thread groove portion of the resin nut, because dimensional accuracy can be secured. FIG. 2 shows a partially enlarged cross section of the Gothic arc type in the axial direction. The cross section of the thread trough of the screw shaft 1 is formed by the inclined surfaces of two arcs 1a and 1b having different circle centers, and the cross section of the thread of the resin nut 3 is formed by a semicircle 3a. The screw trough and the screw thread are in line contact with each other at point C.

The screw shaft 1 is made of stainless steel, carbon steel, or the like, a metal shaft made of iron-based metal, aluminum alloy, or the like plated with zinc, nickel, or steel chrome, or a resin such as polyimide or phenol resin. An axis can be used. Corrosion-resistant metals or resins such as alloys such as stainless steel and aluminum alloys are preferable because rust does not occur, and are also preferable from the viewpoint that rust prevention treatment can be omitted. In the present invention, corrosion-resistant metals that can ensure dimensional accuracy and have excellent durability are most preferable.
The screw shaft 1 can be used without lubrication, but a lubricant such as grease or oil may be applied to obtain a longer life and lower torque.

PP for forming the resin nut according to the present invention
S is a well-known polymer composed of the repeating unit represented by Chemical formula 1, and is classified into cross-linking type, semi-cross-linking type, straight-chain type, branched type and the like depending on the state of the molecular chain.

[Chemical 1] As the PPS, any of cross-linking type, semi-cross-linking type, linear type, branched type and the like can be used, and a blend of these may be used. Examples of commercially available PPS include T4, T4AG, LN2 and the like manufactured by DC EP, B063, B042, # 160 manufactured by Tosoh Corporation and the like.

The 280 ° C. non-melting organic resin powder usable in the present invention is a non-melting resin powder at the PPS molding temperature. Since the molding temperature of PPS is 280 to 330 ° C, it can be used unless it melts at a temperature of at least 280 ° C, preferably 330 ° C. Suitable organic resin powders include thermosetting polyimide resins, thermoplastic polyimide resins, wholly aromatic polyester resins, aromatic polyamide resins, and polyether ether ketone resins. Examples of suitable commercially available organic resins include UIP-R, UIP-S manufactured by Ube Industries, P84-HT manufactured by Ranging Co., TI3000 manufactured by Toray Co., Ltd. as thermosetting polyimide resins, and Mitsui Chemicals as thermoplastic polyimide resins. Company Aurum # 400, # 5
00 is mentioned. Sumika Super E101S, E101M manufactured by Sumitomo Chemical Co., Ltd. is used as the wholly aromatic polyester resin, and Nippon Aramid Co., Ltd. 5 is used as the aromatic polyamide resin.
010, 5011 and the like are PEEK-150PF manufactured by Victorex Co., Ltd. as the polyether ether ketone resin.
450PF and the like, respectively. In addition, you may use these organic resin powders in mixture of 2 or more types. Among these, more preferable organic resin powders are thermosetting polyimide resin powders and wholly aromatic polyester resins.

The average particle size of the organic resin powder is 3 to 100 μm, preferably 5 to 50 μm. This is because if it exceeds 100 μm or is less than 3 μm, the load bearing ability is poor, and sufficient wear resistance and low friction characteristics cannot be obtained.

Examples of PTFE which can be used in the present invention include raw PTFE such as molding powder by suspension polymerization method, fine powder by emulsion polymerization method, and regenerated PTFE. Regenerated PTFE includes a heat-treated product to which heat history is added and an irradiated product irradiated with γ-rays or electron beams. Of these, molding powders and fine powders are preferable, and molding powders are most preferable. Next is recycled PTFE of the heat-treated product. The reason is that PT is caused by shearing during PPS melt kneading.
This is because the order in which FE easily becomes fibrous is fine powder, molding powder, heat treated product recycled PTFE, and irradiated product recycled PTFE. Since fine powder is finely fibrillated, the lubricating effect on the sliding surface may be poor. On the other hand, recycled PTFE does not become fibrous.
However, it also has an advantage of having an internal lubrication effect and excellent melt fluidity.

The proportion of the PPS composition blended is as follows:
3 to 30% by volume of organic resin powder based on the entire composition,
It is preferably 5 to 20% by volume, and PTFE is 10 to 40.
% By volume, preferably 20-30% by volume, the balance being PP
It is S. It is preferable that PPS is contained in an amount of 40% by volume or more. By containing 40% by volume or more of PPS, the moldability and strength of the PPS composition are improved. If the organic resin powder is less than 3% by volume, the required load bearing capacity cannot be obtained, and if it exceeds 30% by volume, the true contact area increases and the friction coefficient increases. Also, PTFE is 10
If it is less than volume%, the required lubricity and wear resistance cannot be obtained.
If the content is more than volume%, the abrasion resistance is lowered and the melt viscosity is so high that injection molding may not be possible in some cases.

The PPS composition may further contain a whisker having a fiber length shorter than the average particle diameter of the organic resin powder. As whiskers, potassium titanate whiskers,
Examples thereof include titanium oxide whiskers, zinc oxide whiskers, aluminum borate whiskers, calcium carbonate whiskers, magnesium sulfate whiskers, wollastonite, zonotolite, magnesium oxide whiskers and the like. Among these whiskers, whiskers having an average fiber length shorter than the average particle diameter of the organic resin powder can be used. When the fiber length of the whiskers is longer than the particle diameter of the organic resin powder, the sliding surface is subjected to shearing, and when added, the abrasion resistance is lowered conversely.

The blending ratio of whiskers is 1 to 10% by volume based on the whole PPS composition. If it is less than 1% by volume, abrasion resistance is not improved. Wear resistance deteriorates because of high shear and shearing.

To the extent that the effects of the present invention are not impaired, coloring agents such as carbon powder, iron oxide and titanium oxide, and thermal conductivity improving agents such as graphite and metal oxide powder are added to the PPS composition. Resin additives can be added.

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, a ball mixer, a ribbon blender, a Loedige mixer, an Ultra Henschel mixer, etc. Further, it can be melt-kneaded with a melt extruder such as a twin-screw extruder to obtain molding pellets (granules). In addition, the filler may be charged by side feed when melt-kneading with a twin-screw extruder or the like. Then, as the molding method, extrusion molding, injection molding, heat compression molding and the like can be adopted, but injection molding is particularly preferable from the viewpoint of production efficiency and the like. Further, although it is preferable that the inner diameter threaded portion is formed by molding in terms of cost, it may be machined if it has high precision. Furthermore, a treatment such as an annealing treatment may be adopted for the molded product in order to improve the physical properties.

[0027]

EXAMPLES The raw materials used in Examples and Comparative Examples are collectively shown below. The serial numbers in parentheses on the raw materials are the same as the raw material numbers in the table. (1) PPS [PPS]: Tosoh Corp .; B-054 (2) Thermosetting polyimide resin powder [PI-1]: Ube Industries Ltd .; UIP-R (average particle size 10 μm) (3) Thermoplastic polyimide Resin powder [PI-2]: Mitsui Chemicals Co., Ltd .; Aurum # 500 (average particle size 30 μm) (4) Wholly aromatic polyester [OBP]: Sumitomo Chemical Co., Ltd .; Sumika Super E101S (average particle size 15 μm) (5) PTFE [PTFE-1]: manufactured by Mitsui DuPont Fluorochemicals; Teflon 7J (molding powder) (6) PTFE [PTFE-2]: manufactured by Kitamura; KT-
400H (heat treated recycled PTFE) (7) PTFE [PTFE-3]: Kitamura Co .: KTL
-610 (γ-ray or electron beam irradiation regenerated PTFE) (8) Titanium oxide whiskers [Titanium oxide whiskers]: manufactured by Ishihara Sangyo Co., Ltd .; FTL-100 (average fiber length 3 to 6 μm, fiber diameter 0.05 to 0.1 mm) ( 9) Potassium titanate whiskers [potassium titanate whiskers]: Otsuka Chemical Co .; Tismo N (average fiber length 10
〜20 μm, fiber diameter 0.3 to 0.6 μm) (10) Calcium carbonate whisker [Calcium carbonate whisker]: Maruo calcium; Calcium carbonate whisker (average fiber length 20 to 30 μm, fiber diameter 0.5 to 1 μm) (11) Glass fiber [GF] : Asahi Fiber Glass Co., Ltd .; MF-KAC

Examples 1 to 10 and Comparative Examples 1 to 4 The raw materials were dry-blended using a Henschel dry mixer at the compounding ratios (volume%) shown in Tables 1 and 2, and melt-kneaded using a twin-screw extruder. Then, pellets were prepared. From this pellet, cylinder temperature 270-310 ℃, nozzle temperature 3
A nut was produced by injection molding under the conditions of 20 ° C and a mold temperature of 140 ° C. The slide screw device has the following specifications. The lead is 3 times the nominal diameter of the screw shaft. (1) Screw shaft specifications-Shaft diameter: φ8 mm, Lead: 24 mm, Number of threads: 6, Pitch: 4, Material: SUS304 (2) Nut specifications-Outer diameter: φ14 mm, Total length: 18 mm

The resulting slide screw device was evaluated by the following functional tests. Functional test Axial load 100N, screw shaft speed 8.3s-1 (500rpm
), Stroke 250 mm, unlubricated, reciprocating with a travel distance of 100 km and increasing axial clearance before and after the test (mm
), And the friction torque (comparison between materials) after the test was measured. The results are shown in Tables 1 and 2.

[0030]

[Table 1]

[0031]

[Table 2]

As is apparent from Table 1, the non-melting organic resin powder at 280 ° C. and PTFE were each used alone for PPS.
In Comparative Examples 1 to 4, which were compounded in No. 1, the torque was high and the increase in the axial clearance was also large. In particular, Comparative Examples 3 and 4 in which fibrous whiskers and glass fibers were blended were significantly fatigue-weared. On the other hand, Examples 1 to 7 in which a predetermined amount of non-melting organic resin powder and PTFE were blended at 280 ° C
Had low torque and excellent wear resistance. Further, in Examples 8 and 9 in which a predetermined amount of whiskers having a fiber length shorter than the particle size of the unmelted organic resin powder was mixed, the increase in the axial clearance was small.

[0033]

The resin nut according to the present invention comprises a PPS composition in which the groove portion to be screwed with the screw shaft is formed by mixing at least PPS with PTFE and an organic resin powder which is not melted at 280 ° C. So low friction in a wide temperature range,
A resin nut with low noise, excellent wear resistance, and low cost can be obtained. Furthermore, since a whisker having a fiber length shorter than the average particle size of the organic resin powder is blended, a resin nut having excellent screw precision in addition to the above characteristics can be obtained.

Since the slide screw device according to the present invention uses the resin nut, and the axial cross section of the thread groove portion is semicircular, even if the lead has a diameter twice or more of the nominal diameter of the screw shaft. It has low torque and sufficient abrasion resistance.
Moreover, since it has excellent environment resistance, it can be used in water, in a chemical solution, or the like.

[Brief description of drawings]

FIG. 1 is a perspective view of a slide screw device.

FIG. 2 is a partially enlarged sectional view in the axial direction of a Gothic arc type.

[Explanation of symbols]

1 screw shaft 2 Sliding screw device 3 resin nuts

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08L 101/00 C08L 101/00 F16B 35/00 F16B 35/00 Z F term (reference) 4F071 AA27 AA48 AA51 AA56 AA60 AA62 AB18 AB20 AB21 AD01 AE11 AF28 BA01 BB05 BC07 BC08 4J002 BD15X CF16Y CH09Y CL06Y CM04Y CN01W DE076 DE106 DE136 DE186 DE236 DG046 DJ006 DK006 FA066 FD016 GM00

Claims (7)

[Claims] 1. A resin nut that relatively moves while sliding on the axis of a screw shaft, wherein a thread groove portion screwed into the screw shaft is made of polyphenylene sulfide resin and at least tetrafluoroethylene resin at 280 ° C. A resin nut formed from a polyphenylene sulfide resin composition prepared by blending a non-melted organic resin powder. 2. The resin nut according to claim 1, wherein the polyphenylene sulfide resin composition further contains a whisker having a fiber length shorter than the average particle diameter of the organic resin powder. 3. The organic resin powder is a powder of at least one organic resin selected from thermosetting polyimide resin, thermoplastic polyimide resin, wholly aromatic polyester resin, aromatic polyamide resin and polyetheretherketone resin. The resin nut according to claim 1, wherein the nut is made of resin. 4. The resin nut according to claim 1 or 2, wherein the tetrafluoroethylene resin is at least one type of molding powder or fine powder. 5. The convex shape of the thread groove portion has a semicircular cross section in the axial direction.
The resin nut according to any one of 1. 6. A sliding screw device comprising a screw shaft and a resin nut that relatively moves while sliding on the shaft of the screw shaft as the screw shaft rotates. Is a resin nut according to any one of claims 1 to 5, and a slide screw device. 7. The lead of the slide screw device has at least twice the nominal diameter of the screw shaft.
The described slide screw device.