JP5093145B2 - Manufacturing method of seal - Google Patents

Description

  The present invention relates to a ball screw (a nut having a spiral groove formed on the inner peripheral surface, a screw shaft having a spiral groove formed on the outer peripheral surface, and a raceway groove formed by the spiral groove of the nut and the spiral groove of the screw shaft. The present invention relates to a method for manufacturing a seal for a device comprising a ball disposed between them.

A ball screw used in an electric injection molding machine or the like includes a nut having a spiral groove formed on the inner peripheral surface, a screw shaft having a spiral groove formed on the outer peripheral surface, a spiral groove of the nut, and a spiral groove of the screw shaft. And a ball disposed between the formed track grooves.
Since the ball of such a ball screw rolls in the groove along with the rotational movement of the screw shaft, if foreign matter such as dust or abrasion powder adhering to the screw shaft enters the nut, the foreign matter that has entered the nut Can hinder the rolling motion of the ball and cause damage such as seizure. In order to prevent foreign matter from entering the nut, ring-shaped seals are arranged at both axial ends of the nut.

  FIG. 5 is a cross-sectional view showing an example of a conventional ball screw. In the figure, reference numeral 40 denotes a screw shaft, 50 denotes a nut, and a screw groove (spiral groove) 41 is formed on the outer peripheral surface of the screw shaft 40. The thread groove 41 faces a thread groove (spiral groove) 42 formed on the inner peripheral surface of the nut 50, and a large number of balls 60 are provided between the thread groove 41 and the thread groove 42. . These balls 60 roll along a ball load rolling path (rolling groove) between the screw groove 41 and the screw groove 42 as the screw shaft 40 or the nut 50 rotates.

  The ball 60 that has rolled on the ball-loaded rolling path is returned to its original position via a “koma” embedded in the nut 50. A contact-type seal 1 that seals a gap between the screw shaft 40 and the nut 50 is attached to both ends of the nut 50. The seal 1 includes a lip portion 11 that contacts the outer peripheral surface of the screw shaft 40 and the screw groove 41, and a mandrel 20 fixed to the nut.

  Patent Document 1 listed below includes, as a ball screw seal, an annular mandrel having an edge fixed to a nut, and a lip portion that contacts the outer peripheral surface of the screw shaft and the spiral groove in an elastically deformed state. An elastomer molded body (annular seal piece), and the lip portion abuts obliquely with respect to the outer peripheral surface of the screw shaft and bends in a predetermined direction with respect to the outer peripheral surface of the contacting screw shaft. It is listed.

  Such a seal is conventionally manufactured by integrally molding an elastomer molded body including a lip portion by injection molding of a thermoplastic elastomer to a metal annular mandrel. For example, as shown in FIG. 6, an annular mandrel 20 is disposed in the cavity 3 b of the mold 3, and the thermoplastic elastomer is introduced into the mold 3. The mold 3 used in this method includes a movable side mold plate 31 on the elastomer introduction side and a fixed side mold plate 32, and a gate 3a, a runner 3c, and a sprue 3d are formed on the movable side mold plate 31. .

FIG. 7 is a front view showing the movable side mold plate 31 of the mold 3 shown in FIG. 6 (a view showing the surface facing the fixed side mold plate 32). As shown in this figure, a plurality of gates 3 a are formed along a circle E concentric with the annular ring forming the mandrel 20.
The thermoplastic elastomer introduced into the mold 3 from the sprue 3d passes through the runner 3c and enters the cavity 3b from the gate 3a. An anchor hole 20 a corresponding to the position of the gate 3 a of the mold 3 is formed in the annular core metal 20. As a result, as shown in FIGS. 8 and 9 (sectional view taken along the line IX-IX in FIG. 8), the seal 1 is obtained in which the elastomer molded body 10 including the lip portion 11 is integrally formed with the annular mandrel 20.

As such a ball screw device, a ball screw device described in Patent Document 1 is disclosed.
Further, as a sealing technique, a rolling bearing seal described in Patent Document 2 is disclosed. According to Patent Document 2, a seal is disclosed in which a mandrel is made of a metal material and its peripheral part is made of a thermoplastic elastomer material, and both materials are integrally joined.

Japanese Patent Laid-Open No. 10-252856 Japanese Patent Application Laid-Open No. 09-242864

In such a ball screw seal, the sealing performance is improved by devising the shape of the opening of the seal and the shape of the lip. Regarding the shape of the lip portion, the thickness and the radial dimension are changed in the circumferential direction.
However, conventional ball screw seals have room for improvement in the oil resistance and water resistance of elastomers used as seal materials.

For example, in order to reduce changes in the shape of the shrinkage and expansion of elastomers in solvents such as coolants used in machine tools and greases containing extreme pressure additives, it is necessary to increase the bond between molecules. is there.
However, in conventional thermoplastic elastomers, the rubber hardness increases at the same time when the bonding is increased. As a result, there have been problems such as an increase in tightening force due to seal allowance necessary for design, an increase in torque of the ball screw, and an increase in heat generation due to the seal.

Also, as the rubber hardness increases, the recovery rate of compression set also decreases, so indentation scratches occur during adjustment of the seal phase during assembly, and it can be recovered even after thinning to the normal seal assembly phase. In addition, there is a problem that the sealing performance is lowered.
Furthermore, in the prior art, there is no measure for improving the accuracy in molding the seal, and there are problems as described in (1) to (3) below.

(1) The strain of the mandrel generated by drawing or hole-up processing is deformed following the molding die when the molding die is closed, and is spring-backed when the die is opened after injection molding. As a result, the shape of the lip portion is broken and the sealing performance is lowered.
(2) When the deformation of the mandrel generated at the time of injection of the elastomer springs back, the shape of the lip portion is broken and the sealing performance is lowered.
(3) Due to variations in the thickness of the mandrel (for example, when the plate thickness is large), the upper die and the lower die of the molding die are not properly closed, the burr becomes large, and the sealing performance is deteriorated.

  Accordingly, the present invention has been made paying attention to the above-mentioned problems, and an object thereof is to provide a method for producing a seal that is excellent in oil resistance and water resistance and that can provide good adhesion.

The invention according to claim 1 of the present invention is formed of a nut having a spiral groove formed on the inner peripheral surface, a screw shaft having a spiral groove formed on the outer peripheral surface, a spiral groove of the nut, and a spiral groove of the screw shaft. A ball screw disposed between the raceway grooves, disposed at both ends of the nut in the axial direction, covered with an annular mandrel and an inner peripheral side of the mandrel; A manufacturing method of a ring-shaped seal having an outer peripheral surface and a lip portion that contacts the spiral groove in an elastically deformed state,
Holding the outer peripheral side of the mandrel and using a mold provided with a gate at a position facing the surface of the mandrel, supporting the surface opposite to the surface of the mandrel facing the gate Produced by injection molding of elastic material that can mold the lip,
The allowable value of the variation in the thickness of the outer peripheral region of the lip portion of the mandrel is reduced to a value obtained by adding 30 μm from the lower limit of the general tolerance of the cold rolled steel sheet defined in JIS G 3141.

  The invention according to claim 2 of the present invention is characterized in that, in the seal manufacturing method according to claim 1, the lip portion is manufactured by injection molding of a dynamically cross-linked elastomer.

  According to the method for manufacturing a seal according to the present invention, it is possible to provide a method for manufacturing a seal excellent in oil resistance and water resistance by manufacturing the lip portion by injection molding of a material having elasticity. . Further, when the lip portion is manufactured by injection molding, by performing injection molding while supporting the surface opposite to the surface of the mandrel facing the gate, the mandrel is bent by the injection pressure, and the mandrel becomes On the other hand, it is possible to prevent the shape of the lip portion from being broken. In addition, by making the thickness of the outer peripheral region of the lip portion of the mandrel smaller than the thickness defined in JIS G 3141, the mandrel springs back when the lip portion is manufactured by injection molding. Can be prevented. By these, the manufacturing method of the seal | sticker which prevents a sealing performance fall can be provided.

It is a figure which shows the seal | sticker manufactured by embodiment of this invention, (a) is a front view, (b) is sectional drawing which follows the AO-A 'line | wire of (a). It is a figure which shows the metal mold | die used by this embodiment, (a) is a front view which shows the movable side template 31, (b) is a front view which shows the stationary side template 32. It is a front view which shows the annular | circular shaped metal core which comprises the seal | sticker of FIG. It is a figure which shows the holding | maintenance state of the mandrel at the time of integrally forming with the annular mandrel by the injection molding of the raw material which can be shape | molded, (a) is the AO line of Fig.1 (a) FIG. 6B is a diagram corresponding to the cross-sectional view taken along line OA ′ of FIG. It is sectional drawing which shows an example of the conventional ball screw. It is sectional drawing which shows the metal mold | die used when the elastomer molded object containing a lip | rip part is integrally molded by injection molding of the raw material which can be shape | molded with respect to an annular | circular shaped mandrel. It is a front view which shows the movable side template of the metal mold | die used when manufacturing the conventional seal | sticker. It is a front view which shows the conventional seal | sticker. It is sectional drawing which follows the IX-IX line of FIG.

Hereinafter, an embodiment of a manufacturing method of a seal concerning the present invention is described with reference to drawings.
1A and 1B are diagrams showing a seal manufactured in an embodiment of the present invention, in which FIG. 1A is a front view, and FIG. 1B is a cross-sectional view taken along the line AOA ′ of FIG.
In the present embodiment, the seal shown in FIGS. 1A and 1B is manufactured by the following method.
As shown in FIG. 1, the seal 1 is obtained by integrally molding an elastomer molded body 10 including a lip portion 11 on a metal annular mandrel 20. A plurality of positioning pin holes 12, gate traces 13, and seal meat stealing portions 14 are formed in the seal 1 along a circle E concentric with the ring forming the mandrel 20. A pair of positioning pin holes 12 are provided at opposing positions in a concentric circle E. The seal meat stealing portion 14 is provided along the circle E at a predetermined interval on both sides of the gate mark 13. Two combinations of the gate trace 13 and the pair of seal meat stealing portions 14 are formed between the positioning pin holes 12 and 12 along the circle E, for example.

An annular thickness control region 21 having a predetermined width is formed on the outer peripheral side of the elastomer molded body 10 in the mandrel 20.
2A and 2B are views showing the mold 3 used in this embodiment, wherein FIG. 2A is a front view showing the movable side mold plate 31, and FIG. 2B is a front view showing the fixed side mold plate 32. FIG. As shown in FIG. 2A, a gate 3a is formed on the movable side template 31 at a position corresponding to the gate mark 13 shown in FIG. Further, as shown in FIG. 2B, a plurality of positioning pins 3e and a mandrel support pin 3f are formed along a circle E concentric with the ring forming the mandrel 20. The positioning pin 3e and the mandrel support pin 3f are formed at positions corresponding to the positioning pin hole 12 and the seal meat stealing portion 14 in the seal 1, respectively.

  FIG. 3 is a front view showing an annular mandrel constituting the seal of FIG. As shown in FIG. 3, the annular mandrel 20 is formed with an anchor hole 20a corresponding to the position of the gate 3a of the mold 3 in FIG. The mandrel 20 is placed in the cavity 3b of the mold 3 shown in FIGS. 6 and 7, and a material having elasticity that can be molded into the mold 3 is introduced from the sprue 3d to perform injection molding.

  Here, examples of the elastic material that can be molded include rubbers such as fluororubber and nitrile rubber, and thermoplastic elastomers. Examples of the thermoplastic elastomer include thermoplastic elastomers having a durometer A hardness of 75 ± 10, polyester-based elastomers, and polyamide-based elastomers, and olefin-based dynamically cross-linked thermoplastic elastomers are preferable.

  Table 1 shows the results of evaluating the changes in the shape of various elastomers in various solutions selected in consideration of the use environment for the ball screw, based on the following evaluation criteria. In Table 1, “Mecha 68” indicates “Dafney Mechanic Oil 68 manufactured by Idemitsu Kosan Co., Ltd.”, “Anti-last P-2810” indicates “Anti-Last P-2810 manufactured by Nippon Oil Corporation”, and “YS2 Grease” indicates “Lube Co. YS2 grease” is shown. Immersion conditions and sample shapes are as follows. As shown in Table 1, the olefinic dynamically cross-linked elastomer exhibited excellent dimensional stability in any solution.

(conditions)
Immersion condition: 25 ° C., 75 hours Sample shape: 25 mm long, 10 mm wide, 1 mm thick strip (evaluation criteria)
○: No problem (dimensional change rate is 1% or less)
− ×: Shrinkage-side dimensional change rate of more than 1% to 3% or less + ×: Expansion-side dimensional change rate of more than 1% to 3% or less

  As described above, the material of the lip portion 11 is made of an olefin-based dynamically cross-linked elastomer, so that it has high solvent resistance to various coolants and greases falling on the ball screw and is generated at the time of assembly. Scratches against indentation due to misassembly are difficult to enter, and good adhesion between the seal lip portion and the outer peripheral surface of the pole screw shaft can be obtained for a long time even under various usage environments.

The thermoplastic elastomer introduced into the mold 3 from the sprue 3d passes through the runner 3c and enters the cavity 3b from the gate 3a as shown in FIG. Thereby, as shown in FIG. 1, the seal | sticker by which the elastomer molded object 10 containing the lip | rip part 11 was integrally molded by the annular | circular shaped metal core 20 is obtained.
FIG. 4 is a view showing a holding state of the mandrel 20 when the elastomer molded body 10 is integrally formed with the annular mandrel 20 by injection molding of a thermoplastic elastomer using the mold 3. FIG. 2A is a view corresponding to a cross-sectional view taken along the line AO in FIG. 1A, and FIG. 2B is a view corresponding to a cross-sectional view taken along the line OA ′ in FIG.

As shown in FIG. 4 (a), the positioning pin 3e (see FIG. 7) provided in the fixed side mold plate 32 (see FIG. 2) of the mold 3 is placed in the positioning pin hole 12 of the mandrel 20. Is inserted to hold the mandrel 20. In addition, when the elastomer molded body 10 is integrally molded, the elastomer molded body 10 is formed so as to cover the tip portion of the positioning pin 3e (so that the elastomer molded body 10 is not penetrated by the positioning pin 3e).
Further, as shown in FIG. 4B, the support pin contact area 22 of the mandrel 20 is contacted with the mandrel support pin 3f provided on the fixed side mold plate 32 (see FIG. 2) of the die 3. In the state of contact, injection molding of a thermoplastic elastomer is performed. Therefore, the seal meat stealing portion 14 is formed at a position corresponding to the support pin contact region 22 of the elastomer molded body 10.

  Here, among thermoplastic elastomers that are injection-molded, dynamic cross-linkable elastomers are inferior in flowability and increase in injection pressure as compared with general elastomers and resins. Therefore, by placing the mandrel support pin 3f that supports the mandrel 20 from the back side in the vicinity of the gate 3a for injecting the elastomer that constitutes the lip portion 11 at the time of injection molding, the mandrel is bent by the injection pressure at the time of injection, A seal that suppresses deformation and exhibits good adhesion to the ball screw can be obtained.

  In the present embodiment, the thickness variation of the thickness control region on the outer peripheral side of the elastomer molded body 10 in the mandrel 20 is made smaller than the tolerance defined in JIS G 3141. Specifically, in order to reduce the mold-to-die clearance caused by the variation in the thickness of the core 20 when the mold 3 is clamped, an allowable variation of the thickness of the core 20 is set in JIS G 3141. It was made into the value which added 30 micrometers from the minimum of the general tolerance of the defined cold rolled steel plate. For example, a mandrel 20 was obtained by pressing a mandrel into a ring shape and processing a plate having a plate thickness tolerance of ± 0.1 mm so as to have a plate thickness tolerance of −0.07 to −0.1 mm. That is, the plate thickness was set within a range of 0.90 to 0.93 mm. In addition, when there exists a press capacity | capacitance, you may give a plane press to the whole surface of the mandrel 20.

  As described above, according to the method for manufacturing a seal of the present invention, a method for manufacturing a seal excellent in oil resistance and water resistance can be obtained by manufacturing the lip portion by injection molding of a material having elasticity. Can be provided. Further, when the lip portion is manufactured by injection molding, by performing injection molding while supporting the surface opposite to the surface of the mandrel facing the gate, the mandrel is bent by the injection pressure, and the mandrel becomes On the other hand, it is possible to prevent the shape of the lip portion from being broken. In addition, by making the thickness of the outer peripheral region of the lip portion of the mandrel smaller than the thickness defined in JIS G 3141, the mandrel springs back when the lip portion is manufactured by injection molding. Can be prevented. By these, the manufacturing method of the seal | sticker which prevents a sealing performance fall can be provided.

  As mentioned above, although embodiment of this invention has been described, this invention is not limited to this, A various change and improvement can be performed. For example, in the above-described embodiment, the seal provided in the ball screw device has been described. However, the seal relatively moves the track shaft and the slide member via a transfer body such as a linear guide or a bearing, such as a ball or a roller. You may apply to the seal | sticker of the linear or rotary motion apparatus assembled | attached freely. For example, the seal may be applied to a seal of a ball linear guide or a roller linear guide mounted directly via a bearing end of the linear guide or a seal cap. Further, the seal may be applied to a seal of a ball bearing or a roller bearing attached directly through a bearing end or a seal cap.

  Among these, the seal obtained by the present invention is, in particular, a clamping shaft of an electric injection molding machine used for grease lubrication or oil lubrication equipped with an automatic lubricant supply device, a ball screw for an injection shaft, or a vertical screw. The same action and effect are exhibited by being applied to the seal of the ball screw for the drive shaft of the press machine used in the direction.

DESCRIPTION OF SYMBOLS 1 Seal 3 Mold 3a Gate 3b Cavity 3c Runner 3d Sprue 3e Mandrel support pin 10 Elastomer molded body 11 Lip part 12 Alignment pin hole 13 Gate mark 14 Seal meat stealing part 20 Mandrel 20a Anchor hole 21 Thickness control region 22 Mandrel support pin contact area 31 Movable side mold plate 32 Fixed side mold plate 40 Screw shaft 41, 42 Screw groove (spiral groove)
50 nuts 60 balls

Claims (2)

A nut having a spiral groove formed on the inner peripheral surface, a screw shaft having a spiral groove formed on the outer peripheral surface, and a ball disposed between the spiral groove of the nut and the raceway groove formed by the spiral groove of the screw shaft; The ball screw is arranged at both ends in the axial direction of the nut, and is covered with an annular mandrel and an inner peripheral side of the mandrel, and in contact with the outer peripheral surface of the screw shaft and the spiral groove in an elastically deformed state. A method for producing a ring-shaped seal having a lip portion,
Holding the outer peripheral side of the mandrel and using a mold provided with a gate at a position facing the surface of the mandrel, supporting the surface opposite to the surface of the mandrel facing the gate Produced by injection molding of elastic material that can mold the lip,
A manufacturing method of a seal, characterized in that an allowable value of variation in thickness of the outer peripheral region of the lip portion of the mandrel is reduced to a value added by 30 μm from a lower limit of general tolerance of a cold rolled steel sheet defined in JIS G 3141 .   The method for manufacturing a seal according to claim 1, wherein the lip portion is manufactured by injection molding of a dynamic cross-linkable elastomer.

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