JPH10205605A - Seal for ball screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep the seal ridge and the seal internal surface of a wiper type seal evenly adhering to a screw shaft, and maintain a proper sealing function via the display of a sufficient scraping action, regardless of the size of a lead. SOLUTION: Regarding a ball screw seal 6B formed to have a seal ridge 13 for engagement with the thread groove 1a of a screw shaft 1, and fitted to the end of a ball nut 2, the seal 6B is formed to be cylindrical and a seal barrel part 11 as part of the seal 6B is externally projected from the edge of the ball nut 2. At the same time, a plurality of slots 15 are formed, so as to extend from a seal edge to a cylindrical shaft. Also, the inclination angle θ1 of the slots 15 with an axial line X and the lead angle θ of the screw shaft 1 are set to have a relationship of 0<=θ1 <=θ. Foreign materials deposited on the screw shaft 1 and raked with the slots 15 are discharged to the external surface of the seal barrel part 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a seal for a ball screw, and more particularly to an improvement in a wiper seal for both dust prevention of a ball screw and scraping of adhered foreign matter.

[0002]

2. Description of the Related Art As a conventional ball screw seal of this type, for example, the seal shown in FIGS. 12 and 13 is known. The seal S is formed of a plastic ring and has a seal ridge y protruding from the inner peripheral surface thereof so as to fit into a screw groove of a screw shaft, and has a portion extending from the outer end face t of the seal S to an intermediate portion in the axial direction. Is divided into five parts in the circumferential direction by a notch (slit) k, and one part in the circumferential direction is cut off by a slit o crossing the width of the ring, and the end face t
A garter spring g is attached to a groove m provided on the outer periphery of the side ring. This seal S is attached to the end of the ball screw nut, and the divided part is
The inner surface of the seal S is brought into close contact with the screw shaft by elastically pressing the seal S toward the inner diameter side of the seal. This seals the nut against external dust, foreign matter, and the like, and at the same time, exerts a scraper function of scraping foreign matter attached to the screw shaft at the edge of the slit k with the rotation of the screw shaft.

[0003]

However, in the conventional ball screw seal S described above, the width (axial length) L of the seal is at most one to two times the thickness of the seal, and at the same time, The axial length 1 of the split k is also only about half the width L of the seal. Therefore, the part divided by the slit is thick, short, small and hard, and is not easily adapted to the outer surface of the screw shaft despite being tightened by the tension of the garter spring g. In order to make such a hard object adhere simultaneously to both the screw groove portion of the screw shaft and the portion of the screw shaft outer diameter surface which is the land portion, the height of the seal ridge y of the seal inner diameter and the screw groove of the screw shaft are required. It is necessary to fabricate the seal S so that the depth of the seal S is the same, but it is actually very difficult, and dimensional mismatch is inevitable.

The conventional ball screw seal S has the following problems due to such a structure. Originally, the seal ridge and the inner peripheral surface of the seal S should be in close contact with the screw groove of the screw shaft and its land (the outer surface of the screw shaft) with equal strength. Are strongly adhered (a so-called one-sided contact state), so that the adhesion of the other is weakened, and the sealing performance of the entire seal cannot be secured.

Since the seal width (axial length) L is short (necessarily, the axial length l of the slit k is also short), in the case of a large lead specification, the edge portion of the seal slit k is used. However, the number of slits exerting a scraper action of scraping foreign matter on the inner surface of the groove by engaging with the screw groove of the screw shaft is reduced, so that the sealing performance of the screw groove portion is inferior.

[0006] If the sealing performance is inferior in this way, foreign matter that has entered the ball screw will cause early wear and shorten the life. Therefore, the present invention has been made in view of such problems of the conventional ball screw seal. By improving the size and structure of the seal, the seal as a whole is always good without any contact. An object of the present invention is to provide a ball screw seal capable of ensuring performance.

Another object of the present invention is to provide a ball screw seal capable of exhibiting a sufficient scraper function and ensuring good sealing performance even in the case of a large lead specification.

[0008]

In order to achieve the above object, a seal for a ball screw according to claim 1 of the present invention is provided.
In a ball screw seal which has a seal ridge on the inner periphery and engages with a thread groove of a screw shaft of a ball screw and is attached to an end of a ball nut, the seal is formed in a cylindrical shape, and a part of the seal is formed into a ball A plurality of slits extending outward from the nut end face and extending in the cylindrical body axis direction from the seal end face are provided, and the relationship between the inclination angle θ _{1 of the} slit with respect to the screw axis and the lead angle θ of the screw axis is It is characterized in that 0 ≦ θ ₁ ≦ θ is set.

As described above, the ball screw seal of the present invention is formed in a long cylindrical shape, a part of which protrudes outward from the end face of the ball nut, and the protruding portion is divided by a plurality of slits. Since the length of the seal itself and the length of the slit are longer than before, and the portion divided by the slit is long and thin and has a soft elasticity, the seal can be easily brought into close contact with the screw shaft. therefore,
If the height of the seal ridge on the inner periphery of the seal is set slightly larger than the depth of the screw groove on the screw shaft, the screw groove is positively sealed and easily adheres to the outer surface of the screw shaft (land). As a result, the overall sealing performance can be ensured.

Further, in the ball screw seal of the present invention, the inclination angle θ ₁ of the slot with respect to the screw axis is set at 0 ° or more and θ or less with respect to the ball screw lead angle θ. Foreign matter adhering to the surface of the shaft is scraped off at the slit edge, then scraped along the slit slope toward the top of the seal or toward the nut, and discharged to the outer surface of the seal. It does not get on the surface. Therefore, dust protection in the nut is performed very effectively.

Here, in the ball screw seal of the present invention, the length of the slot can be at least 0.7 times the length of the ball screw lead, and the number of slots can be evenly distributed to at least six. In this way, as described later, it is possible to exert the scraper function at four or more slits without fail during one rotation of the screw shaft. In this case, if the number of slits is less than 6, the number of locations where the scraper acts is reduced and the performance is reduced, and the divided portions are difficult to uniformly fit into the outer surface of the screw shaft. Performance decreases.

Further, in the ball screw seal of the present invention, a garter spring can be mounted on the outer periphery of the seal, and it can be mounted at a plurality of axial positions of the seal. . Thereby, even if the axial length of the seal is long, the divided portions can be elastically pressed from a plurality of locations toward the inner diameter side, and the sealing performance is improved.

Further, the slits may be separately formed from both end faces of the ring body toward the center in the seal axial direction. Thereby, it is possible to provide a double seal function.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show a first embodiment of the present invention.
FIG. 1 is a front view of a ball screw showing a seal mounting portion in a half section, FIG. 2A is an end view of a seal, FIG. 2B is an enlarged perspective view of a slit slope, FIG. 3 is a cross-sectional view at right angles to the axis of the seal.

First, the configuration of the ball screw will be described. The ball screw has a screw shaft 1 having a spiral screw groove 1a on the outer peripheral surface, and a screw groove (not shown) corresponding to the screw groove 1a of the screw shaft 1 on the inner peripheral surface. The ball screw nut 2 is screwed via a number of balls (not shown). When the screw shaft 1 rotates, the ball passes through a ball circulation path (illustrated by a dashed line) 3 provided in the body of the ball screw nut 2 while rolling in a spiral space formed by the two screw grooves. Circulate.
Thereby, the ball screw nut 2 reciprocates linearly along the screw shaft 1 according to the rotation direction of the screw shaft 1.

An annular concave portion 5 is formed on both end surfaces of the ball screw nut 2, and a cylindrical seal 6 made of, for example, a high molecular weight polyethylene resin is attached to the concave portion 5. The seal 6 is fixed by fitting a flange-shaped mounting portion 7 formed at one end thereof into the concave portion 5 and tightening a set screw 8.

A flange 9 is formed at the other end of the seal 6, and a seal body 11 between the root of the flange 9 and the mounting portion 7 has a smaller outer diameter than the flange 9. And the thickness is thin. 6 g of outer peripheral surface of the seal body 11
Has an annular garter spring groove 12 at the base of the collar portion 9.
Are formed. On the other hand, on the inner peripheral surface 6n of the seal 6, a convex portion (seal peak) that fits into the thread groove 1a of the screw shaft 1 is provided.
13 is formed in a spiral shape. As shown in FIG. 3, the height H of the seal ridge 13 is set slightly larger than the depth h of the thread groove 1a of the screw shaft. As a result, the garter spring 14 mounted in the garter spring groove 12 is
The sealing groove 13 pressed by the tension of
a.

A slot 15 extending in the axial direction of the cylinder from one end face having the flange 9 is provided on the cylinder of the seal 6.
However, there are six locations around the circumference. Each of the six slits 15 obliquely crosses the seal thickness and extends parallel to the seal center axis X. In other words, the lead angle of the screw groove 1a of the screw shaft 1 is θ
And then, also Supposing the seal central axis X and the angle between the slit 15 and theta _1, the lead theta in this case, between the angle theta ₁ can be said to be in the following relationship.

Θ> θ ₁ = 0 ° On the other hand, the opposed surfaces 15a and 15b of the slits 15 obliquely crossing the seal thickness, as shown in FIG. 2, have an inclination angle with respect to a vertical line in the seal thickness direction. It is inclined by θ _2.

The six slits 15 thus set are set.
5 places the slit 15 of, the length l is set as a reference lead L _e of the ball screw, slit length l is set to be at least 0.7 times the lead L _e of the ball screw ing. For example, in the case of the seal 6 of the total length 35mm illustrated, the lead L _e = 32 mm of the ball screw, are the length L = 23 mm and 0.72 times the slit 15.

The other slit extends over the entire length of the seal 6 from one end face of the cylindrical body to the end face of the mounting portion 7 at the opposite end, and is formed as a slit 17 for cutting the cylindrical body.

Next, the operation will be described. This seal 6
After the slit 17 is opened and the cylindrical body is expanded and fitted to the screw shaft 1, the mounting portion 7 at the rear end of the seal is fitted into the recess 5 on the end face of the ball screw nut 2, and the side surface of the ball screw nut 2 is inserted. The tip of the set screw 8 screwed from the above is fixed by engaging the tip of the set screw 8 with the mounting portion 7, and is attached to both ends of the ball screw nut 2.

Subsequently, the garter spring 14 is attached to the garter spring groove 12 provided at the tip end of the seal 6 with the slit 17 expanded and attached, and the seal 6 is elastically moved by the tightening force. Tighten. If the seal 6 of the present invention, the length of the slit 15 for lead L _e of the ball screw is longer than conventionally it is and set thinner. Therefore, as can be seen from one perpendicular cross section in the axial direction shown in FIG. 3, the six divided portions A _{1 to} A _{6 of} the seal body 11 which are equally divided into six by the slit 15 and the slit 17 are formed. It has a soft elasticity and is easily adhered to the outer surface of the screw shaft 1 regardless of the presence or absence of the screw groove 1a of the screw shaft 1. Also, the height H of the seal ridge 13 on the inner periphery of the seal 6 is set slightly larger than the depth h of the thread groove 1a of the screw shaft,
A slight clearance C is provided between the inner peripheral surface 6n of the seal and the outer peripheral surface 1b of the screw shaft at the divided portion (A _{6 in} FIG. 3) having the seal ridge 13.

[0024] Therefore, when tension of the outer periphery of the seal body 11 at the garter spring 14, the divided portion A ₆ having a seal mountain 13 in the screw groove 1a, the other divided portion A ₁ to A ₅
Can easily adhere to the outer diameter surface (land portion) 1b of the screw shaft.

The seal ridge 13 of the seal 6 has a helical shape corresponding to the helical shape of the thread groove 1a of the screw shaft 1.
Divided portion is from A ₆ will be successively shifted to the other divided portions, the divided portions be in any position as the position in the axial direction perpendicular cross section of the seal shown in FIG. 3 is shifted in the axial direction Since the same adhesion as described above is obtained in A _{1 to} A ₆ , good sealing performance of the entire seal 6 is secured.

Seals 6 are provided at both ends of the ball screw nut 2.
Is mounted, and the screw shaft 1 is rotated once, the ball screw nut 2 is linearly moved by one pitch in accordance with the rotation direction. At this time, each of the divided portions A _{1 to} A ₆ of the seal 6 performs a relative sliding motion for one round of the consistency with the rotation of the shaft while being kept in close contact with the outer surface of the screw shaft. As a result, each of the divided parts A _{1 to} A
The edge ₆ (the edge of the slit 15 and the edge of the slit 17) scrapes and wipes off the adhered foreign matter on the outer surface of the screw shaft 1 by the scraper action.

[0027] In this embodiment, the slit 15 of approximately 0.7 times the length of the thread of the lead L _e 6 places (one places the slit 17) by set, the first screw shaft 1 of the ball screw The scraper function works on four or more slits 15 out of the six slits per rotation. Thus, according to the ball screw seal 6 of the present embodiment,
The slot 15 makes it possible to exert the scraper action on four or more slots 15 per rotation, regardless of the size of the screw lead. Foreign matter removal performance and thus excellent sealing performance can be obtained.

Further, foreign matter attached to the surface of the screw shaft, after being scraped off by the slit edge, climb obliquely toward the seal attachment portion 7 along the inclination angle theta ₂ of the inclined surfaces 15a of the slit 15 (P _A direction) Scraped and sealed body 1
1 and does not rest on the screw shaft surface again, so that foreign matter intrusion into the ball screw nut 2 can be effectively prevented, and the sealing performance can be improved.

FIGS. 4 to 6 show a second embodiment of the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted (the same applies hereinafter).

The ball screw seal 6A of this embodiment
The difference is that the garter spring groove 12 is also formed at an intermediate position of the seal body 11, so that the garter spring 14 is disposed at two positions, that is, at the tip portion and the intermediate portion of the seal. Also in this case, as shown in FIG.
Is set slightly larger than the depth h of the thread groove 1a of the screw shaft 1. Therefore, when viewed in the axial cross section, as shown in FIG. 6, the sealing ridge 13 closely adheres to the thread groove 1 a, and a gap 18 is formed on both the front and rear sides near the root of the sealing ridge 13. Since the portion 11 can be easily deformed, the inner surface of the seal can be in close contact with the outer diameter surface 1b of the screw shaft at a portion slightly away from the screw groove 1a due to the tightening force of the two garter springs 14, 14, so that the entire seal is high. Sealability is ensured. Other configurations, operations, and effects are the same as those of the first embodiment.

FIGS. 7 and 8 show a third embodiment of the present invention. In the ball screw seal 6B of this embodiment, the slit 15 in the seal 6A of the second embodiment is used.
But it extends inclined by the inclination angle theta ₁ with respect to the seal central axis X. That is, in the case of this embodiment, the relationship between the lead angle θ of the screw shaft 1 and the inclination angle θ ₁ formed by the slit 15 and the seal center axis X is 0 <θ ₁ ≦ θ.

Further, the opposing surfaces 15a, 15b of the slits 15 obliquely crossing the seal thickness are also inclined by an inclination angle θ _{2 with} respect to a vertical line in the seal thickness direction. That is, as shown in FIG. 8B, the surface 15a of the slit 15 is inclined in two directions with inclination angles θ ₁ and θ ₂ . Therefore, foreign matter scraped from the screw groove 1a and the outer portion 1b of the screw shaft of the screw shaft 1 along the inclined surface 15a of the slit, towards the seal mounting portion 7 direction (P _B direction) obliquely or directly above ( (when θ ₁ = θ), and is scraped off by the outer surface of the seal body 11. After that, it accumulates to some extent and falls naturally from the outer surface of the seal body 11. Therefore, foreign matter does not get on the screw shaft 1 again, and dust can be effectively prevented.

The other structures, operations and effects are the same as those of the second embodiment. FIG. 9 shows a fourth embodiment of the present invention. Seal 6C of ball screw of this embodiment
Is different from the above embodiments in that a slit 15 exhibiting a scraper action is formed by cutting from both ends of the seal 6C. That is, this seal 6
C has a flange-shaped mounting portion 7 provided at a central portion in the length direction of the seal, and seal body portions 11 on both sides of the mounting portion 7.
a and 11b are provided continuously. And each seal body 11
A slit 15 is cut into each of a and 11b so as to extend obliquely in the axial direction from the end. Although not shown, the slit 17 is continuously cut out from the end face of the seal body 11a to the end face of the seal body 11b.

[0034] As the length of the slit 15 of the case, both the seal body 11a, a length obtained by adding the slit 15, 15 and 11b is at least 0.7 times the length of the lead L _e of the screw Is set.

At the end of the ball screw nut 2 to which the seal 6C is attached, a deep recess 5 into which the attachment portion 7 of the seal 6C and the inner seal body 11b are inserted is formed. Further, a plurality of discharge windows 20 are formed on the cylindrical surface at the end of the nut 2 so as to be arranged in the circumferential direction, and the inner seal body 11b is formed.
The foreign matter that has been scraped and accumulated at the edge of the slit 15 formed in the slit 15 is discharged through the discharge window 20 to the outside.

The seal 6C of this embodiment functions as a double seal by forming the slits 15 on the outer side and the inner side of the nut 2 and on both sides. The foreign matter scraped off by the slit 15 outside the nut is removed from the external seal body 1.
It is scraped by the outer surface of 1a and falls. On the other hand, the foreign matter scraped off by the slot 15 inside the nut is scraped by the outer surface of the inner seal body 11b and then falls out of the nut through the discharge window 20, so that in any case, the foreign matter is screwed again. Axis 1
Don't get on.

The other structures, operations and effects are the same as those of the second embodiment. FIG. 10 shows an embodiment relating to a thread groove shape of a screw shaft using the ball screw seal of the present invention.

Generally, a grinding relief 21 as shown in FIG. 11 is formed at the bottom of the thread groove 1a formed on the screw shaft 1 of the ball screw. It is difficult to remove such foreign matter accumulated in the grinding relief 21 and even if the seal of each embodiment of the present invention having an excellent scraper action is applied, the inside of the grinding relief 21 cannot be scraped off.

Therefore, as shown in FIG. 10, the grinding relief 21 at the bottom of the thread groove 1a of the screw shaft 1 is eliminated. If the ball screw seal of the present invention shown in the above embodiments is applied to a ball screw having no grinding relief in the thread groove of the screw shaft,
The sealing performance of the thread groove can be further improved.

Although the seal of each of the above embodiments uses a high molecular weight polyethylene resin as a raw material, the seal of the ball screw of the present invention may be made of other lubricant-containing polymers. It can be a cut product or an injection molded product using a raw material. An example in which a lubricant-containing polymer is used as a raw material will be described. For example, 45% by weight of low-molecular-weight polyethylene (molecular weight 1 × 10 ^{3 to} 5 × 10 ⁵ ) and ultra-high-molecular-weight polyethylene (molecular weight 1 × 10 ^{6 to} 5)
× 10 ⁶ ) A mixture of 5% by weight of polyethylene and 50% by weight of paraffinic mineral oil as a lubricant is used as a raw material. The mixture is heated and melted, and then poured into a predetermined mold and cooled while being pressurized. It is solidified and molded. As a molding method, compression molding or injection molding can be used.

[0041]

As described above, according to the ball screw seal of the present invention, the seal width (length in the seal axial direction) is increased, and a part of the seal is projected outward from the ball nut end face. Since a plurality of slits are arranged parallel to the axis of the screw axis or at an inclination within the screw axis lead angle θ, foreign matter adhering to the screw shaft is scraped off and continuously discharged outside the nut. It can be prevented from accumulating on the surface, ensuring high sealing performance especially without requiring high-precision sealing, as a result, preventing early wear due to foreign matter entering the ball screw and maintaining for a long time This has the effect of providing a ball screw that can be used for free.

[Brief description of the drawings]

FIG. 1 is a front view of a ball screw in which a mounting portion of a seal according to a first embodiment of the present invention is shown in a half section.

FIG. 2 (a) is an end view of the tip of the seal of FIG. 1,
(B) is an enlarged perspective view of a slit slope.

FIG. 3A is a cross-sectional view of the seal of FIG. 1 taken at right angles to the axis, and FIG.
Is an enlarged view of part b.

FIG. 4 is a front view of a ball screw in which a mounting portion of a seal according to a second embodiment of the present invention is shown in a half cross section.

FIG. 5 is an end view of the tip of the seal of FIG. 4;

FIG. 6 is an axial sectional view of the seal of FIG. 4;

FIG. 7 is a front view of a ball screw in which a seal mounting portion according to a third embodiment of the present invention is shown in a half cross section.

8 (a) is an end view of the tip of the seal of FIG. 7,
(B) is an enlarged perspective view of a slit slope.

FIG. 9 is a front view of a ball screw in which a seal mounting portion according to a fourth embodiment of the present invention is shown in a half cross section.

FIG. 10 is a cross-sectional view of a screw shaft according to an embodiment in which grinding relief at the bottom of a screw groove is eliminated to improve sealing performance.

FIG. 11 is a sectional view of a thread groove of a screw shaft in a general ball screw.

FIG. 12 is a front view of a conventional wiper seal of a ball screw.

FIG. 13 is a side view of what is shown in FIG.

[Explanation of symbols]

 1 Screw Shaft 2 Ball Screw Nut 6 Seal 6A Seal 6B Seal 6C Seal 13 Seal Crest 14 Garter Spring 15 Slot 17 Slit

Claims (1)

[Claims] 1. A seal for a ball screw, which has a seal ridge on its inner periphery and engages with a screw groove of a screw shaft of a ball screw and is attached to an end of a ball nut, wherein the seal is formed in a cylindrical shape. A part of the slit protrudes outward from the end face of the ball nut, and a plurality of slits extending in the axial direction of the cylinder from the end face of the seal are provided. The inclination angle θ _{1 of the} slit with respect to the screw axis and the lead angle θ of the screw axis are provided. The ball screw seal is characterized in that the relationship is set to 0 ≦ θ ₁ ≦ θ.