JP2794568B2 - Screw shaft seal and manufacturing method thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a screw shaft seal for sealing between a screw shaft and a female screw bearing of a ball screw device and a method of manufacturing the same.

[Conventional technology]

In a ball screw device used for the purpose of reducing the torque for rotation, between a screw shaft with a thread groove on the peripheral surface and a bearing with a female thread groove on the shaft hole inner surface, Since a ball that engages with the thread grooves of both members is interposed and a large gap is formed between the screw shaft and the female screw bearing, in order to prevent intrusion of dust and the like into the gap,
Special sealing means are required.

FIG. 5 and FIG. 6 show an example of this type of seal conventionally known. That is, the seal (a)
A thread-shaped seal piece (b) having substantially the same cross-sectional shape and lead as the screw groove of the screw shaft is provided on the inner diameter side of the main body portion having a substantially rectangular cross section attached to the end of the female screw bearing for approximately one lead. The seal piece (b) is slidably fitted into the screw groove to prevent intrusion of dust and the like. The seal (a) is formed of a synthetic resin in order to reduce the sliding resistance, and the unevenness of the inner diameter portion provided with the seal piece (b) is cut using a cutting tool or the like.

However, the following problem is pointed out with respect to the screw shaft seal (a).

Since the whole is formed of a synthetic resin and has high rigidity, it is difficult to adapt to a screw shaft as a sliding partner in use, and a large interference with the screw shaft cannot be set. For these reasons, the sealing properties may be insufficient.

Since the complicated unevenness of the inner diameter portion provided with the seal piece (b) is formed by cutting, a high processing technique is required to increase the product accuracy. Products with poor processing accuracy cannot make the contact state with the counterpart material uniform, which adversely affects the sealing performance.

In order to improve the sealing performance with respect to the above problem, as disclosed in Japanese Patent Application Laid-Open No. 55-47045, a sealing member having a thread-shaped sealing piece is molded by felt and resin is applied thereto. It is conceivable that the seal member is impregnated or coated and is brought into close contact with the peripheral surface of the screw shaft while compressing the seal member by utilizing the low rigidity provided in the seal member. However, in this case, although the sealing performance is certainly improved, the sliding resistance is inevitably increased due to the structure in which the low-rigidity sealing member is compressed and pressed against the peripheral surface of the screw shaft. There is a problem of poor abrasion.

[Means for solving the problem]

In view of the above, the present invention has been devised to achieve two contradictory characteristics of sealing and wear resistance, in order to achieve this purpose, for the seal,
As described in claim 1, in the one provided with a thread-shaped seal piece slidably fitted into a thread groove formed on the peripheral surface of the screw shaft, a portion on the inner diameter side that comes into contact with the screw shaft is combined. A sliding ring formed of a resin, wherein the sliding ring has a shape obtained by deforming a synthetic resin cylindrical body along a peripheral surface of the screw shaft having the screw groove; A backup ring formed of synthetic rubber is bonded to the outer peripheral side of the ring, and the manufacturing method is the same as that of the screw shaft as a sliding partner in the cavity of the molding die as described in claim 2. Is placed, a cylindrical body made of a synthetic resin forming a sliding ring is put on the outer periphery of the core, and a synthetic rubber forming a backup ring is injected into the outer periphery of the cylindrical body under pressure to press the cylindrical body. Shape of the core Along deformed, it was decided 突切Ru after molding, it requires demolded moldings width.

(Operation)

In the screw shaft seal according to the first aspect of the present invention having the above-described configuration, the synthetic resin sliding ring provided on the inner diameter side portion that comes into contact with the screw shaft is configured such that the synthetic resin cylindrical body is fixed to the screw. Since it has a shape deformed along the peripheral surface of the screw shaft with a groove, it is relatively thin and has sufficient flexibility, and is therefore pushed by a synthetic rubber backup ring. And the backup ring can set a large interference allowance, while the sliding ring is made of synthetic resin, and the resin is applied to the felt as in the prior art. Since it is not impregnated or coated, the sliding resistance is small even when pressed against the screw shaft by the backup ring.

In the method for manufacturing a screw shaft seal according to the second aspect of the present invention including the above-described steps, since the core having the same shape as the screw shaft is used to mold the inner surface of the seal, irregularities are easily formed. A high-precision product can be formed quickly and reliably.

〔Example〕

 Next, examples of the present invention will be described.

1 and 2 show a screw shaft seal (1) according to an embodiment of the present invention. That is, this seal (1) has a thread-shaped seal piece (2) provided on the inner diameter side of a main body part having a substantially rectangular cross section attached to the end of the female screw bearing and having a lead having substantially the same cross-sectional shape and lead as the screw groove of the screw shaft. And a thin sliding ring (3) formed of a synthetic resin having excellent lubricity at a portion on the inner diameter side that comes into contact with the screw shaft.
The sliding ring (3) has a shape obtained by deforming a cylindrical body (3 ') made of a synthetic resin along a peripheral surface of a screw shaft having a thread groove as described later. ) Is characterized in that a backup ring (4) formed of synthetic rubber having a small spring constant is adhered to the outer peripheral side.

In the manufacture of the seal (1), as shown in FIG. 3, a plurality of (seven in the figure) seals (1) are formed into a cylindrical body having a shape that is continuous in the axial direction, and as shown by a two-dot chain line. It is efficient to cut through each seal (1). Next, an example of a manufacturing method will be described with reference to FIG.

That is, a cavity (7) having a substantially columnar shape is formed by the molds (5) and (6) which can be freely separated from each other, and a core (7) having the same shape as a screw shaft as a sliding partner is formed in the cavity (7). 9) is positioned and fixed coaxially with the cavity (7) and detachably with respect to the molds (5) and (6). Before and after this fixation, a thin cylindrical body (3 ') made of synthetic resin forming a sliding ring (3) is put on the outer periphery of the core (9), the mold is clamped, and the cavity (7) is inserted through the injection hole (8). ) Is pressurized and injected with a synthetic rubber material forming a backup ring (4). The rubber material injected into the outer periphery of the cylindrical body (3 ') deforms the cylindrical body (3') according to the shape of the core (9) by the pressure, and waits for hardening, and the cylindrical body (3 ') Adhered to the outer periphery of Then, the mold is opened, the molded body having the shape shown in FIG. 3 is removed from the core (9) along the screw, and the seals (1) are cut through one by one.

〔The invention's effect〕

 The present invention has the following effects.

That is, first, in the screw shaft seal according to the first aspect of the present invention having the above-described structure, the synthetic resin sliding ring provided on the inner diameter side portion that comes into contact with the screw shaft is formed of a synthetic resin cylindrical body. Has a shape deformed along the peripheral surface of the screw shaft provided with a screw groove, so that it is relatively thin and has sufficient flexibility, and thus a backup ring made of synthetic rubber. And a large interference can be set by being pressed by the backup ring while being in good contact with the screw shaft, thereby exhibiting excellent sealing properties. On the other hand, since the sliding ring is made of synthetic resin and is not made by impregnating or coating the felt with resin as in the above prior art, the sliding resistance is small even when pressed against the screw shaft by the backup ring. , Thereby exhibiting excellent wear resistance.
Therefore, it is excellent in both the sealing property and the abrasion resistance, and can provide a high quality sealing product in such a meaning. That is, in the screw shaft seal according to claim 1 of the present application, a sliding ring made of a synthetic resin having relatively high rigidity and relatively low sliding resistance is processed to be thin to have flexibility and to be in close contact with the screw shaft. Thus, the sealing property can be improved while taking advantage of the synthetic resin having excellent wear resistance.

In the method for manufacturing a screw shaft seal according to the second aspect of the present invention including the above-described steps, since the core having the same shape as the screw shaft is used to mold the inner surface of the seal, irregularities are easily formed. Thus, a highly accurate seal product can be formed reliably and uniformly, and the contact state with the screw shaft can be made uniform over the entirety of the seal.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a screw shaft seal according to an embodiment of the present invention, FIG. 2 is a front view of the seal, FIGS. 3 and 4 are cross-sectional views showing manufacturing steps of the seal, FIG. The figure is a cross-sectional view of a conventional screw shaft seal, and FIG. 6 is a front view of the seal. (1) Seal for screw shaft, (2) Seal piece (3) Slide ring, (3 ') Cylindrical body (4) Backup ring, (5) (6) Mold (7) ... cavity, (8) ... injection hole, (9) ...
core

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Claims (2)

(57) [Claims] 1. A seal (1) having a thread-shaped seal piece (2) slidably fitted into a screw groove formed on a peripheral surface of a screw shaft, wherein a portion on an inner diameter side in contact with the screw shaft. And a sliding ring (3) formed of a synthetic resin, wherein the sliding ring (3) is a cylindrical body (3 ') made of a synthetic resin.
Having a shape deformed along the peripheral surface of the screw shaft having the screw groove, and having a backup ring (4) formed of synthetic rubber adhered to an outer peripheral side of the slide ring (3). A seal for a screw shaft. 2. A core (9) having the same shape as a screw shaft as a sliding partner is disposed in a cavity (7) of a mold (5) (6), and a core (9) is slid on the outer periphery of the core (9). A synthetic resin cylindrical body (3 ') forming a ring (3) is covered, and synthetic rubber forming a backup ring (4) is injected around the outer periphery of the cylindrical body (3') by pressure and the cylindrical body (3 ') is formed. 3 ′) is deformed along the shape of the core (9), and after molding, a molded product released from the mold is cut to a required width.