JP2007211827A - Backlash removing feed screw device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlash removing feed screw device capable of removing a backlash in both the axial direction and the radial direction. <P>SOLUTION: This backlash removing feed screw device has a screw shaft 1 and a nut 2 threadedly engaging with this screw shaft 1. The nut 2 is divided into two nut divided bodied 2B and 2B by dividing surfaces 2Ba and 2Ba including the axis 2Ao of a screw shaft 2A. These two nut divided bodies 2B and 2B have pin insertion holes 3 extending to both nut divided bodies 2B and 2B in both side parts of mutually sandwiching the screw shaft 1, and both nut divided bodies 2B and 2B are mutually joined by pins 4 inserted over both nut divided bodies 2B and 2B into these pin insertion holes 3. A preload spring 5 for energizing both nut divided bodies 2B and 2B in the mutually approaching direction, is arranged on the outer periphery of the respective pins 4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sliding screw type feed screw device used in a mechanism for converting a rotational motion into a linear reciprocating motion, and more particularly to a backlash removal feed screw device which is designed to remove the backlash.

Conventionally, as a sliding screw type feed screw device, a stainless steel screw shaft (rolled screw) such as SUS304 and a synthetic resin nut in which a special filler is blended with PPS (polyphenylene sulfide) or the like has been used. ing. There is a gap in the radial direction and the axial direction between the screw shaft and the nut, and backlash occurs during driving. This backlash may cause a problem from the viewpoint of smoothness of driving depending on a mechanism portion in which the feed screw device is incorporated, and the backlash may be removed. 2. Description of the Related Art Conventionally, as a feed screw device for removing backlash, a device in which preload is applied by a compression spring, such as the feed screw device of Patent Document 1 or Patent Document 2, has been proposed.
Japanese Patent Laid-Open No. 10-47451 Japanese National Patent Publication No. 10-511757

  In the feed screw devices disclosed in Patent Documents 1 and 2, a compression spring is arranged in the axial direction, and backlash is removed by utilizing the elastic force. However, in the case of such a backlash removal mechanism, the backlash in the axial direction can be removed, but the backlash in the radial direction cannot be removed. Therefore, there is still room for improvement in order to achieve smooth driving as the feed screw device.

  An object of the present invention is to provide a backlash removing feed screw device capable of removing backlash both in the axial direction and in the radial direction.

  The backlash removal feed screw device of the present invention includes a screw shaft and a nut that is screwed to the screw shaft, and the nut is divided into two nut divided bodies at a dividing surface including the shaft center of the screw hole. The nut divided body has pin insertion holes extending over both nut divided bodies on both sides sandwiching the screw shafts, and both nut divided bodies are connected to the pin inserted holes by the pins inserted across the nut divided bodies. A spring that is coupled to each other and biases the nut divided bodies toward each other is provided on the outer periphery of each pin.

According to this configuration, the two nut divided bodies divided by the dividing surface including the axis of the screw hole are coupled to each other by the pin to form the nut, and the nut and the screw shaft are screwed together. The relative rotation with is possible. Since a spring is provided on the outer periphery of the pin that joins both nut divided bodies in a direction that pushes the two nut divided bodies toward each other, the biasing action of this spring causes a gap between the screw hole of the nut and the screw shaft. The radial gap is killed. Further, the biasing action also acts in the axial direction due to the component force based on the screw angle at the threaded portion of the female threaded portion of the nut and the male threaded portion of the screw shaft, so that the gap in the axial direction is also killed. Therefore, both the backlash in the axial direction and the radial direction are removed.

In this invention, each nut divided body includes a nut divided body body made of synthetic resin having a screw hole and a divided surface of each other, and a metal plate stacked on a surface opposite to the divided surface of the nut divided body body. The pins may have a stepped shaft shape having small diameter portions at both ends, and the small diameter portions on both sides may be crimped and fixed to the holes of the metal plate serving as both ends of the pin insertion holes.
According to this configuration, since the screw hole is made of the synthetic resin nut divided body, a smooth feeding operation can be obtained due to its self-lubricating property. It is difficult to directly connect the synthetic resin nut divided body with a pin in terms of securing strength, but because the metal plates are stacked on both nut divided body bodies and the metal plates are connected with pins. Can bind firmly. The pin can be easily coupled to the metal plate by caulking both ends. In addition, since the nut split body is composed of the nut split body main body and the metal plate, the nut split that constitutes the inner surface of the screw hole can be achieved even if a compression coil spring or the like is used as the preload spring by interposing a preload spring between them. A configuration is obtained in which the body main body is biased in a direction in which the nut divided bodies on both sides are brought close to each other. Therefore, the preload spring can be installed with a simple configuration.

In this invention, the portion of the nut divided body in the pin insertion hole has a stepped hole shape with a small diameter hole portion with a hole diameter that allows the pin to be inserted, and a large diameter hole portion into which the preload spring is inserted, The clearance between the inner diameter of the small-diameter hole and the pin may be 0.1 mm or less.
According to this configuration, since the pin insertion hole has a stepped hole shape, the preload spring can be arranged with a simple configuration. In addition, since the gap between the inner diameter of the small diameter hole portion of the pin insertion hole and the pin is 0.1 mm or less, the relative position shift along the split surfaces of both nut divided body hardly occurs. Incidentally, if this gap exceeds 0.1 mm, a relative position shift along the split surfaces of both nut split bodies tends to occur, which tends to impair the smoothness of relative rotation between the screw shaft and the nut. Become.

  In the present invention, the dividing surface may be inclined with respect to the pin insertion hole. According to this configuration, the interval between both nut divided bodies along the axis of the pin insertion hole corresponding to the preload range by the substantial preload spring is slightly larger than the initial setting gap between the divided surfaces of both nut divided bodies. Since it becomes large, a wide preload range in design can be secured. This increases the degree of freedom in design.

  The backlash removal feed screw device of the present invention includes a screw shaft and a nut that is screwed to the screw shaft, and the nut is divided into two nut divided bodies at a dividing surface including the shaft center of the screw hole. The nut divided body has pin insertion holes extending over both nut divided bodies on both sides sandwiching the screw shafts, and both nut divided bodies are connected to the pin inserted holes by the pins inserted across the nut divided bodies. Since the preload springs that are coupled to each other and urge the nut divided bodies toward each other are provided on the outer periphery of each pin, both the backlash in the axial direction and the radial direction are removed, and the feed screw device Driving smoothness is improved. In particular, the suitability for machine parts where backlash is a problem is increased.

  An embodiment of the present invention will be described with reference to FIGS. The backlash removal feed screw device includes a screw shaft 1 and a nut 2 screwed onto the screw shaft 1. The nut 2 is divided into two nut divided bodies 2B and 2B at divided surfaces 2Ba and 2Ba including the axis 2Ao of the screw hole 2A. These two nut division bodies 2B and 2B have pin insertion holes 3 that extend over both nut division bodies 2B and 2B at both sides sandwiching the screw shaft 1 with each other. The nut divided bodies 2B and 2B are coupled to each other by the pins 4 inserted through the pin inserting holes 3 over the nut divided bodies 2B and 2B. A preload spring 5 is provided on the outer periphery of each pin 4 to urge the nut divided bodies 2B, 2B in a direction in which they are brought close to each other. The preload spring 5 is composed of a compression coil spring.

  Each nut divided body 2B is superimposed on a synthetic resin nut divided body 6 having a half screw hole 2A and a divided surface 2Ba, and a surface of the nut divided body 6 opposite to the divided surface 2Ba. It shall have a metal plate 7. Each pin 4 has a stepped shaft shape having a small-diameter portion 4 a at both ends, and the small-diameter portions 4 a on both sides are fastened and fixed to the holes 7 a of the metal plate 7 that are both ends of the pin insertion hole 3. The half screw hole 2A for each nut divided body 2B is formed by simultaneously threading the two nut divided bodies 2B and 2B. Further, the portion of the nut divided body 6 in the pin insertion hole 3 is a stepped hole of a small diameter hole portion 3a having a hole diameter enough to allow the pin 4 to be inserted and a large diameter hole portion 3b into which the preload spring 5 is inserted. Shape. The clearance a between the inner diameter of the small diameter hole 3a and the pin 4 is 0.1 mm or less.

  The dividing surface 2Ba is inclined with respect to the pin insertion hole 3, and a design gap b is secured between the dividing surfaces 2Ba and 2Ba. Since both the dividing surfaces 2Ba and 2Ba are inclined at the same angle, the gap (interval) c along the axis of the pin insertion hole 3 is slightly larger than the gap b. Both nut division bodies 2B and 2B are connected to each other by a pin 4. In the example shown in the figure, the pin 4 and the pin insertion hole 3 are provided at a total of four locations, two locations with the screw hole 2A interposed therebetween. . As described above, the pin 4 is connected to the nut divided bodies 2B and 2B by inserting the pin 4 over the nut divided bodies 2B and 2B into the pin insertion hole 3, and the small diameter portions 4a on both sides of each pin 4 are connected to each other. This is done by caulking and fixing in the hole 7a of the metal plate 7. At this time, the preload spring 5 is arranged in a compressed state and externally fitted to the pin 4 in the large-diameter hole portion 3 b of the pin insertion hole 3. The hole 7a of the metal plate 7 has a tapered shape that expands outwardly as shown in the drawing, whereby the caulking and fixing are firmly and reliably performed.

  According to the backlash removal feed screw device having the above-described configuration, the nut divided body bodies 6 and 6 of both nut divided bodies 2B and 2B are urged toward each other by the restoring elasticity of the preload spring 5, and the gaps b and c Is narrowed. This acts to constantly reduce the substantial inner diameter of the screw hole 2A, so that the gap with the male screw portion of the screw shaft 1 screwed into the female screw portion of the screw hole 2A is killed. The urging action for constantly reducing the inner diameter is not only the radial direction of the screw shaft 1 but also the component force due to the screw angle acts in the axial direction, so that the gap in the axial direction is also killed, and backlash in both the radial and axial directions. Is removed.

  Since both the divided surfaces 2Ba and 2Ba are inclined at the same angle, the gap c along the axis of the pin insertion hole 3 is slightly larger than the designed gap b of both the divided surfaces 2Ba and 2Ba. Therefore, a wide preload range in design by the preload spring 5 can be secured, and a range for killing and absorbing gaps based on machining tolerances of the female screw portion of the screw hole 2A and the male screw portion of the screw shaft 1 is widened. The degree of freedom is improved. Further, since the gap a between the inner diameter of the small diameter hole portion 3a of the pin insertion hole 3 and the pin 4 is 0.1 mm or less, the coupling of the nut divided bodies 2B and 2B by the pin 4 causes backlash. It is made stable.

  In the feed screw device having the above configuration, the screw shaft 1 is made of metal, and the nut divided body 6 is made of synthetic resin. When the nut divided body 6 is made of synthetic resin, it is preferable to use a material that can be injection-molded, has self-lubricating properties, and is excellent in mechanical strength. Examples of such resins include polyimide resins, polyphenylene sulfide resins, fused fluororesins such as ethylene tetrafluoride / ethylene copolymer resin (ETFE), epoxy resins, polyethylene resins, polyacetal resins, polyamide resins. There are resins. When selecting a material having mechanical strength and dimensional stability and good wear resistance as the material of the nut divided body 6, for example, polyimide resin, polyamideimide resin, polyetherimide resin Polyphenylene sulfide resin, epoxy resin, polyether ketone resin, polyether sulfone resin and the like can be used. Further, when the resin of the nut divided body 6 is a thermoplastic resin, it has an appropriate rigidity, excellent mechanical strength, injection moldability, complicated shape, and excellent dimensional moldability. A polyphenylene sulfide resin having excellent performance on average in terms of performance, efficient mass productivity by injection molding, and price is preferable.

  Various kinds of fillers, oils, and the like may be mixed in the respective resins. That is, in order to improve the self-lubricating property of the synthetic resin, it may be filled with a solid lubricant such as fluororesin, molybdenum disulfide, graphite, mica, lead, boron nitride, tungsten disulfide, and the like. For reasons, it may contain lubricating oil, for example, various synthetic oils such as fluorine oil and silicone oil, wax, grease and the like. Moreover, in order to adjust the degree of elastic deformation and the sound absorption effect of the synthetic resin, as a modifier of mechanical properties to the above synthetic resin, for example, glass fiber, carbon fiber, potassium titanate fiber, talc, white carbon, metal, Metal oxide, ceramic powder, organic fiber, etc. may be filled. If at least one of these fillers is added, for example, 5 to 30% by weight, preferably 10 to 25% by weight, of a lubricant and a fiber, the slidability and strength can be improved. The material of the synthetic resin can be appropriately selected depending on the use environment conditions. For example, a fluorine resin can be used in a chemical solution, and a polyimide resin can be used in a place where radiation is a problem.

  The screw shaft 1 is formed of a metal material such as steel or an aluminum alloy, but the screw surface may be coated with a resin layer having a small friction coefficient, such as polytetrafluoroethylene. In that case, better sliding performance can be obtained by the self-lubricating property of the resin layer.

  In the above embodiment, the pin 4 and the pin insertion hole 3 are provided at four locations with the screw hole 2A interposed therebetween. However, the pin 4 and the pin insertion hole 3 are provided at two locations with the screw hole 2A interposed therebetween, or in a staggered manner with the screw hole 2A interposed therebetween. The number and position of these are set as appropriate according to the conditions of the application apparatus, such as three places, and more than five places. Further, the nut 2 may be provided with a flange as shown in Patent Document 1. In addition, the shape of the screw shaft 1 such as the pitch is not limited to the shape shown in the drawings as long as it has the function of a feed screw.

It is a partial notch front view of the nut used for the backlash removal feed screw device concerning one embodiment of this invention. It is a partial vertical front view of the backlash removal feed screw device according to the same embodiment. FIG. 3 is an enlarged sectional view taken along line XX in FIG. 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Screw shaft 2 ... Nut 2A ... Screw hole 2Ao ... Screw hole axial center 2B ... Nut division body 2Ba ... Split surface 3 ... Pin insertion hole 3a ... Small diameter hole part 3b ... Large diameter hole part 4 ... Pin 4a ... Small diameter part 5 ... Preload spring 6 ... Nut split body 7 ... Metal plate 7a ... Hole a ... Clearance between pin and pin insertion hole

Claims (4)

  The nut includes a screw shaft and a nut that is screwed to the screw shaft, and the nut is divided into two nut divided bodies by a dividing surface including the shaft center of the screw hole, and the two nut divided bodies sandwich the screw shaft from each other. On both sides, it has pin insertion holes that span both nut divisions, and both nut divisions are connected to each other by pins inserted across these nut divisions into these pin insertion holes. A backlash removal feed screw device provided with a preload spring that urges both nut divided bodies toward each other.   In Claim 1, each nut division body is a nut division body main part made from a synthetic resin which has a screw hole and a mutual division surface, and a metal plate piled up on the surface on the opposite side to the division plane of this nut division body main body, Each pin has a stepped shaft shape having a small diameter portion at both ends, and the small diameter portions on both sides are fastened and fixed to the holes of the metal plate serving as both ends of the pin insertion hole. Removal feed screw device.   In Claim 2, the part of the said nut division body main body in the said pin insertion hole is made into the stepped hole shape of the small diameter hole part of the hole diameter which can insert the said pin, and the large diameter hole part into which the said preload spring enters. A backlash removal feed screw device in which the gap between the inner diameter of the small-diameter hole and the pin is 0.1 mm or less.   The backlash removal feed screw device according to any one of claims 1 to 3, wherein the dividing surface is inclined with respect to the pin insertion hole.

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