TW201508193A - Ball screw - Google Patents

Abstract

This ball screw, in a state in which the axial-direction end surfaces of two adjacent nuts (1a, 1b) are in contact with each other and one of the two nuts (1a, 1b) is rotated relative to the other to apply precompression thereto, has a sleeve (4) secured to the outer peripheral surfaces of the axial-direction ends (small-diameter parts 13a, 13b) of the two nuts (1a, 1b) on the sides in contact with each other.

Description

Ball screw

This invention relates to a double nut preloaded ball screw.

The ball screw is used as a device for carrying out transportation or precision positioning in a working machine, a measuring machine, an injection molding machine, and the like. The preloading of the ball screw is performed by a double nut preloading type in which a preloading mechanism is provided between the two nuts.

That is, the double-nut preloading ball screw has two nuts having a spiral groove formed on the inner peripheral surface, a spiral groove formed on the outer peripheral surface, and a screw shaft inserted through the two nuts; a ball between the track formed by the spiral groove of the nut and the spiral groove of the screw shaft; a ball return path for returning the ball from the end of the track to the starting point; and disposed between the two nuts, The preload applying mechanism that applies the force in the axial direction to the respective nuts in the opposite direction is configured to transmit the balls that are rolled in the rails so that the two nuts integrally move relative to the screw shaft.

A conventional example of the double nut preloading ball screw is, for example, the technique described in Patent Document 1. In this example, the preload application mechanism is composed of a spacer and parallel keys. Specifically, the separator according to the thickness of the pre-pressed application amount is sandwiched After the two nuts, in order to maintain the preload, parallel keys are attached to the recesses provided in the spacer and the two nuts, thereby fixing the spacer and the two nuts.

Screw insertion holes are formed at both ends of the parallel key, and the corresponding internal thread holes are formed in the recesses of the two nuts. Further, the front end of the mounting screw through the screw insertion hole is screwed into the internal thread of the recess, whereby the parallel key is fixed to the two nuts.

Another conventional example of the double nut preloading ball screw is, for example, the technique described in Patent Document 2. In this example, the preload applying mechanism includes one or three pre-pressing balls disposed at substantially three equal divisions in the circumferential direction between the two nuts, and the plate thickness is larger than the diameter of the pre-pressing balls. Large disc-shaped ball retaining member. The ball holding member has a center hole for inserting the screw shaft and a holding hole for the ball for pre-compression. In the preload applying mechanism of this example, the diameter of the preloading ball used according to the magnitude of the preload to be applied is changed, thereby adjusting the amount of preload.

Further, in the conventional example shown in Fig. 13 described in Patent Document 3, the preload applying mechanism of the double nut preloading ball screw is an annular shape formed between the two nuts 100a and 100b. Member 110. The preloading mechanism of this example is formed at three positions in the circumferential direction of the annular member 110, and has a through hole 111 extending in the axial direction on the inner circumference side and extending in the radial direction from the outer peripheral surface to the through hole. In the adjustment screw hole (internal thread hole) 112, two pre-pressing balls 120 are disposed in the through hole 111 along the axial direction.

The preload applying mechanism further has an adjusting member 130 and a small screw 140 to which the hemispherical body 132 is fixed at the front end of the coil spring 131. Coil spring The outer diameter of 131 is smaller than the inner diameter of the adjusting screw hole 112 of the annular member 110. The small screw 140 has an external thread portion 141 to be screwed into the internal thread of the adjustment screw hole 112. Further, the axial direction dimension of the through hole 111 is larger than the total diameter of the two balls 120, but is smaller than the total diameter of the two balls 120 and the hemisphere 132.

The preload application method of the preload applying mechanism is as follows. The annular member 110 is disposed between the adjacent nuts 100a and 100b, the hemispherical body 132 side faces the through hole, and the adjustment member 130 is inserted into the adjustment screw hole 112, and the external thread portion 141 is screwed by the adjustment screw hole 112. To turn the small screw 140. As a result, the male screw portion 141 pushes the adjustment member 130 toward the inner side in the radial direction of the annular member 110, and the transmission of the coil spring 131 causes the hemispherical body 132 to widen the interval between the two balls 210 in the through hole 111.

That is, when the small screw 140 is further rotated from the state of Fig. 13, as shown by the two-dotted line in Fig. 13, the hemisphere 132 moves toward the inner side in the radial direction of the annular member 110, and is pressed by the hemisphere 132. The two balls 120 are moved in opposite directions in the axial direction (the center 121 of each ball 120 moves in the direction of the arrow symbol), and the end faces 101a, 101b of the nuts 100a, 100b are respectively pressed to apply the preload to the ball screw. .

In this state, the balls 120 protrude from the through holes 111, so that a gap is formed between the end faces 110a, 110b of the annular member 110 and the end faces 101a, 101b of the nut. According to the insertion length of the small screw 140 inserted into the adjustment screw hole 112, the amount of protrusion of each of the balls 120 protruding from the through hole 111 can be changed, so that the preload can be adjusted by the degree of screwing of the small screw 140. the amount.

[first technology offer] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2004-69013

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2012-145178

[Patent Document 3] Taiwan Patent No. 262994

In the preload application method using the spacer described in Patent Document 1, the separator corresponding to the thickness of the preload set value is sandwiched between the nuts to perform assembly of the ball screw, thereby measuring the actual preload to confirm the preload. The pressure measurement is the same as the preload setting. As a result of the measurement, when the pre-pressure measurement value does not become the pre-pressure set value, it is necessary to repeatedly perform the loading and unloading of the spacers having different thicknesses until the measured value becomes the pre-pressure set value. Therefore, the work given by the preload is cumbersome.

In addition, since the spacers and the parallel screws and the mounting screws for fixing the keys are required, the number of parts is large. In addition, the use of a spacer causes the overall length of the nut to be lengthened.

A first object of the present invention is to provide a double nut preload type ball screw which is configured to have a smaller number of parts than a conventional product and which can shorten the entire length of the nut and can be easily executed by a preloading operation.

The double nut preloading ball screw described in Patent Document 2 is preloaded In the preload application state of the applying mechanism, there are three or nine pre-pressing balls between the ball holding member or the annular member and the facing nuts, but the other portions are gaps. . Although the gap can be made small by the increase in the number of balls for pre-compression, the increase in the balls for pre-compression is limited. When impurities such as dust enter the inside of the ball screw from the gap, the entered impurities may cause abrasion or damage or even peeling of the spiral groove of the screw shaft and the spiral groove and the rolling element of the nut, so the service life of the ball screw may be It will become shorter.

In the preload applying mechanism described in Patent Document 3, since the coil spring is provided in the adjusting member for the two balls for pre-pressing in the through hole, the rigidity of the adjusting member is insufficient. That is, the axial force of the small screw is transmitted to the pre-pressing ball via the coil spring, so it is feared that the axial force of the small screw becomes weak when it is converted into the pressing force against the nut. Based on this, the preload applying mechanism of Patent Document 3 has room for improvement from the viewpoint of surely applying a preload to the ball screw and not reducing the rigidity of the ball screw.

A second object of the present invention is to provide a double nut preload type ball screw capable of causing a preload application mechanism to reliably perform preload application, and it is difficult for impurities such as dust to enter the inside from a gap.

In order to solve the above problems, a first aspect of the present invention provides a double nut preload type ball screw having the following constituent elements (1) and (2).

(1) having: a plurality of nuts having spiral grooves formed on the inner circumference; a spiral groove formed on the outer peripheral surface and inserted into the screw shaft of the plurality of nuts; and a plurality of balls disposed between the spiral groove of the nut and the spiral groove of the screw shaft And a ball return path that allows the ball to return to the starting point from the end of the track. The plurality of nuts are integrally moved relative to the screw shaft by rolling the balls in the track.

(2) the two adjacent nuts are in contact with each other in the axial direction end face, and one of the two nuts is relatively rotated and applied with a preload in the opposite direction, and the two nuts are in contact with each other. A sleeve is fixed to the outer peripheral surface of the end portion in the axial direction.

That is, the ball screw according to the first aspect of the present invention is the double nut preload type ball screw having the above-described constituent element (1), and is characterized by having the above-described constituent element (2).

The ball screw of the first form does not use the spacer to apply the preload, but maintains the preload by fixing the sleeve, so that the preloaded double nut preloading ball screw can be applied than the prior art using the spacer. It also has a small number of parts and can make the overall length of the nut shorter. In addition, since the amount of preload can be adjusted by the degree of rotation, it is necessary to repeatedly perform the loading and unloading of the spacer having a different thickness from the prior art until the actual preload measurement becomes the preload setting. Compared with the screw, the pre-pressure application operation can be performed relatively simply.

The ball screw of the first aspect is preferably one of the following constituent elements (3) and (4).

(3) The above two nuts are at the axial end of the mutually contacting side The small diameter portion is provided, and the sleeve is externally fitted to the two small diameter portions.

(4) The two nuts have recesses on the outer peripheral surface of the end portion in the axial direction on the mutually contacting side, and the sleeve is fixed to the recess.

When the ball screw of the first embodiment is in the form of the above-described constituent element (4), the following constituent element (5) can be provided.

(5) The sleeve has claw portions at both ends in the axial direction, and the claw portions are press-fitted into the concave portions of the two nuts, respectively.

The ball screw of the first aspect can have the following constituent elements (6).

(6) The main body portion of the sleeve has a C-shaped cross section perpendicular to the axial direction.

In order to solve the above problems, a second aspect of the present invention provides a double nut preload type ball screw having the following constituent elements (a) and (b).

(a) having: a plurality of nuts having spiral grooves formed on the inner peripheral surface; a spiral groove formed on the outer peripheral surface; and a screw shaft inserted through all of the plurality of nuts; and a spiral disposed by the nut a plurality of balls between the groove and a track formed by the spiral groove of the screw shaft; and a ball return path for returning the ball from the end point of the track to the starting point. The plurality of nuts are integrally moved relative to the screw shaft by rolling the balls in the track. In addition, the annular member is disposed between the adjacent nuts and inserted into the screw shaft, and is disposed on the annular member, and is configured to move the axial direction toward A preload applying mechanism applied to the above nut in reverse.

(b) Having a gasket capable of closing a gap formed between the annular member and the nut in a circumferential direction in a state in which the preloading mechanism is preloaded. The spacer is disposed on the annular member and is disposed to be pushed out toward the nut side as the preload is applied.

That is, the ball screw according to the second aspect of the present invention is the double nut preload type ball screw having the above-described constituent element (a), and is characterized by having the above-described constituent element (b).

Since the ball screw of the second aspect has the above-described constituent element (b), even if the gap between the annular member and the nut is closed in the preload application state, the entire circumferential direction is closed, so dust It is difficult to enter the interior when impurities are present.

In the ball screw of the second aspect, by having the following constituent elements (c) to (f), it is possible to surely perform the preload application more than the ball screw described in Patent Document 2.

(c) The annular member has a through hole formed in the inner circumferential side and extending in the axial direction, and a female screw hole extending in the radial direction from the outer peripheral surface and communicating with the through hole.

(d) The through hole is formed at a plurality of positions in the circumferential direction of the annular member. Two rolling elements are arranged in the through hole in the axial direction. An externally threaded member is screwed into the internally threaded hole.

(e) a steering member capable of changing the axial force of the male screw member to a force for moving the two rolling elements toward the respective end portions of the through hole in the axial direction, and is disposed on the externally threaded member and the two rolling Between the bodies. The steering member is a rolling body or a wedge structure having a smaller diameter than the rolling element Pieces. The spacer is disposed at an end portion of the through hole in the axial direction.

(f) The preloading mechanism is constituted by the female screw hole, the through hole, the male screw member, the steering member, the two rolling elements, and the spacer.

That is, the ball screw having the above-described constituent elements (a) to (f) has a steering member which is a rolling element or a wedge member having a smaller diameter than the rolling element, and the externally threaded member comes into contact when the preload is applied. In the steering member, the steering member directly presses the two rolling elements in the through hole, and therefore the axial force of the externally threaded member is surely converted into a force for pressing the nut via the spacer. In other words, it is possible to prevent the axis of the small screw when the coil spring is provided in the adjustment member (steering member) of the two pre-balls to be pressed in the through hole in the configuration shown in the third aspect of the invention. The force is weakened when converted into a force to push the nut.

The ball screw of the second aspect preferably has the following constituent elements (g) or (h).

(g) the annular member has a peripheral groove formed on an inner circumferential side of both end faces in the axial direction, and the through hole penetrates through the two surrounding grooves, and the gasket is disposed on both sides of the peripheral groove .

(h) The through holes are formed at equal positions in the circumferential direction of the annular member at equal intervals.

When the constituting element (g) is provided, the externally threaded member is moved inward in the radial direction of the annular member, so that the steering member that the externally threaded member contacts can directly press the two rolling elements. Moving the rolling elements in the opposite directions in the axial direction, and the above-mentioned gaskets are subject to The front end of the nut is pressed by pushing the respective rolling elements to apply a preload.

In the ball screw according to the first aspect of the present invention, compared with the prior art double-nut preloading ball screw, the number of parts used for applying the preload is small, and the total length of the nut can be made short, which can be easily performed. Preloading the application.

A ball screw according to a second aspect of the present invention is a double-nut preload type ball screw configured to prevent impurities such as dust from entering the inside under a preload application state. Further, since the ball screw of the second aspect has the above-described constituent elements (c) to (f), it can be applied more reliably than the ball screw described in Patent Document 3.

1a, 1b‧‧‧ nuts

11‧‧‧Spiral groove of the nut

12‧‧‧Flange

13a‧‧‧The small diameter of the nut

13b‧‧‧The small diameter of the nut

14‧‧‧ Flat Department

15‧‧‧ surrounding trench

16a, 16b‧‧‧ recess

2‧‧‧ screw shaft

21‧‧‧Spiral groove of the screw shaft

3‧‧‧ balls

4‧‧‧ sleeve

5‧‧‧Circulating hose (ball return path)

51‧‧‧The foot of the circulation hose

52‧‧‧ main body of the circulation hose

6‧‧‧Installation hardware accessories

7‧‧‧Sleeve

71‧‧‧ body part of the sleeve

72‧‧‧The claws of the sleeve

7A‧‧‧Sleeve

71A‧‧‧ body part of the sleeve

17a, 17b‧‧‧through holes for connecting the ends of the nut (ball return path)

40‧‧‧Ring members

400‧‧‧Preloading mechanism

41‧‧‧ surrounding trench

41a‧‧‧The bottom surface of the surrounding groove

42‧‧‧through holes

43‧‧‧Threaded hole

50‧‧‧End plug (ball return path)

61‧‧‧ balls (rolling elements)

60‧‧‧ Roller (rolling body)

63‧‧‧ Small diameter ball (steering member)

65‧‧‧Wedge members (steering members)

8‧‧‧With hexagonal hole fixing screws (external threaded members)

9‧‧‧shims

9A‧‧‧shims

9B‧‧‧shims

91‧‧‧Circular groove (ball bearing part)

92‧‧‧Spherical groove (ball bearing)

Fig. 1 is a partial cross-sectional front view showing the ball screw of the first embodiment.

Fig. 2 is a partially enlarged perspective view showing the engagement state of the end portions of the two nuts in the axial direction.

Fig. 3 is a front elevational view showing a sleeve having a claw portion.

Fig. 4 is a side view showing a sleeve having a claw portion.

Fig. 5 is a side view showing a sleeve having a C-shaped cross section and having a claw portion.

Fig. 6 is a view showing the ball screw of the second embodiment, and is a cross-sectional view of the screw shaft and the balls.

Fig. 7 is a view for explaining the preload applying mechanism of the ball screw of the second embodiment.

Fig. 8(a) is a plan view showing an annular member for forming a preload applying mechanism according to a second embodiment, and Fig. 8(b) is a side view thereof.

Fig. 9(a) is a plan view showing a configuration of a preload applying mechanism according to a second embodiment, and Fig. 9(b) is a cross-sectional view taken along line A-A.

Fig. 10(a) is a plan view showing a spacer example different from Fig. 9, and Fig. 10(b) is a cross-sectional view taken along line A-A.

Fig. 11 is a plan view showing an example of a spacer different from Fig. 9.

Fig. 12 is a perspective view showing an example of a rolling element and a steering member which are different from Fig. 7.

Fig. 13 is a cross-sectional view showing the preload applying mechanism described in Patent Document 3.

[Embodiment of the Invention]

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the embodiments.

[First Embodiment]

As shown in Fig. 1, the double nut preloading ball screw of this embodiment includes two nuts 1a and 1b, a screw shaft 2, a ball 3, a sleeve 4, and a circulation hose (ball return path) 5.

A spiral groove 11 is formed in the inner circumferential surface of the two nuts 1a, 1b. A spiral groove 21 is formed on the outer peripheral surface of the screw shaft 2. Between the spiral groove 11 of the two nuts 1a, 1b and the track formed by the spiral groove 21 of the screw shaft 2, a plurality of balls 3 are disposed.

One of the nuts 1a has a flange 12 at one end in the axial direction and a small diameter portion 13a at the other end in the axial direction. The other nut 1b has a small diameter portion 13b that is in contact with the end surface of the small diameter portion 13a of the one nut 1a. That is, the two nuts 1a, 1b are formed such that the end faces in the axial direction are in contact with each other.

As shown in FIGS. 1 and 2, a flat portion 14 for arranging the circulation hose 5 is formed in a peripheral portion other than the small diameter portions 13a and 13b of the two nuts 1a and 1b. Further, peripheral grooves 15 formed by the small diameter portions 13a and 13b are formed in portions other than the flat portions 14 of the two nuts 1a and 1b.

The two nuts 1a and 1b have recesses 16a and 16b extending perpendicularly to the peripheral groove 15 and having arc-shaped ends at the portions other than the flat portion 14 at the axial end portions of the mutually contacting side. As shown in FIG. 2, the recesses 16a, 16b are formed deeper than the bottom surface of the surrounding groove 15.

The sleeve 4 is a metal endless annular body, and is obtained by, for example, machining using a cold-rolled steel sheet defined by "JIS G3141" or a carbon steel for construction machinery specified in "JIS G4051".

The outer diameter of the sleeve 4 is the same as the outer diameter of the nut 1b, and the inner diameter (diameter) of the sleeve 4 is substantially the same (slightly larger) than the small diameter portions 13a, 13b. The width of the sleeve 4 is substantially the same (slightly smaller) than the total width of the small diameter portions 13a and 13b. As shown in Fig. 1, the sleeve 4 is externally fitted to the two small diameter portions 13a, 13b, and the portion 45 disposed in the recess portions 16a, 16b is Fixed with inlays.

The pair of through holes provided in the flat portions 14 of the two nuts 1a, 1b are the leg portions 51 into which the circulation hose 5 is inserted, and the main body portion 52 of the circulation hose 5 is fixed to the flat portion by the mounting hardware 6. 13.

According to the double nut preloading ball screw of this embodiment, when the two nuts 1a, 1b integrally move relative to the screw shaft 2, the balls 3 roll on the spiral groove 11 and the screw shaft of the two nuts 1a, 1b. In the track formed by the spiral groove 21 of 2, the circulation hose 5 is then returned to the starting point from the end point in the track.

The double nut preloading ball screw of this embodiment can be assembled, for example, by the following method.

First, after the circulation hose 5 is attached to each of the nuts 1a and 1b, the sleeve 4 is externally fitted to the small-diameter portion 13a of the nut 1a, and the small-diameter portion 13b of the nut 1b is fitted into the sleeve 4, thereby The sleeve 4 is coupled to the two nuts 1a, 1b.

Next, after the balls 3 and the screw shaft 2 are assembled to the combined nuts 1a and 1b, one of the nuts 1a is relatively rotated with respect to the other nut 1b, thereby applying a preload to the ball screw. Next, the portion of the sleeve 4 disposed in the recesses 16a, 16b is inlaid, whereby the sleeve 4 is fixed to the two nuts 1a, 1b to prevent relative rotation of the two nuts 1a, 1b. In this way, the applied preload can be maintained.

According to the ball screw of this embodiment, the preload can be applied without using the spacer, and the sleeve 4 can be fixed to the recesses 16a, 16b to maintain the preload, so that it is possible to use the prior art double nut pre-preparation using the spacer. The compression ball screw also has a small number of parts and can make the overall length of the nut short. In addition, The degree of rotation can adjust the amount of preload, so it is comparable to the prior art double nut preloaded ball screw that requires repeated loading and unloading of the spacers of different thickness until the measured value becomes the preload setting. Simply perform a preload application.

Further, by fitting the sleeve 4 to the small-diameter portions 13a and 13b of the nuts 1a and 1b and fitting the sleeve 4 to the recesses 16a and 16b, it is possible to be externally fitted to the nuts 1a and 1b. The inner circumference of the casing is a simple circumferential surface.

Further, in this embodiment, the sleeve 4 is fixed to the recesses 16a and 16b of the nuts 1a and 1b, but may be provided with internal threaded holes in the nuts 1a and 1b instead of the recesses 16a and 16b, for example. A screw insertion hole is provided in the sleeve 4, and the sleeve 4 is fixed to the nuts 1a, 1b by screwing. In addition, the material of the sleeve 4 has engineering plastics other than metal, such as PA (polyamide) or POM (polyoxymethylene).

Further, the fixed position of the sleeve 4 is a peripheral surface of the end portion in the axial direction on the side where the nuts 1a, 1b contact each other, and any position other than the flat portion 14 can be used as a fixed position of the sleeve 4. .

Further, when the ball return path is not the circulation hose 5 but is formed by the through hole of the nut and the end turn-off plug in the axial direction, the flat portion 14 is not provided in the nut, so that only the second A small diameter portion is provided at an end portion of the nut in contact with each other in the axial direction, and the sleeve is externally fitted to the surrounding groove formed by the two small diameter portions.

Further, when the sleeve 4 of Fig. 1 is replaced, as shown in Figs. 3 and 4, it is used at both ends in the axial direction of the endless annular body, i.e., the main body portion 71. In the case of the sleeve 7 of the claw portion 72, the sleeve 7 can be fixed to the two nuts 1a and 1b by pressing the claw portion 72 into the recessed portions 16a and 16b of the nuts 1a and 1b.

The fixed sleeve 7 can be detached from the main body portion 71 without being deformed by releasing the pressing of the claw portions 72 into the recess portions 16a and 16b. Based on this, when the sleeve 7 having the claw portion 72 is used, it is easier to attach and detach than the inlaid fixed sleeve 4 and can be used plural times.

Further, in place of the sleeve 4 of Fig. 1, as shown in Fig. 5, when the sleeve 7A having the main body portion 71A and the main body portion 71A having a C-shaped cross section perpendicular to the axial direction is used, the two nuts 1a are When the small diameter portions 13a and 13b of the 1b are in contact with each other, the balls 3 and the screw shaft 2 are assembled to the two nuts 1a and 1b, and the tube 7A can be nested outside the small diameter portions 13a and 13b.

When the form of the sleeve 4 is used, as described above, it is necessary to join the two nuts 1a, 1b with the sleeve 4 before assembling the balls 3 and the screw shaft 2 to the two nuts 1a, 1b, but if the sleeve 7A is used, Since the combination of the two nuts 1a and 1b is not required, the assembly workability of the ball screw can be improved.

Further, since the sleeve 7A has the claw portions 72 at both ends in the axial direction of the main body portion 71A, the front surface shape thereof is the same as that of Fig. 3. Based on this, since the sleeve 7A has the claw portion 72 similarly to the sleeve 7, it has the same effect of being easily detachable and can be used plural times.

Further, even when a sleeve having no claw portion 72 is formed by the main body portion 71A having a C-shaped cross section perpendicular to the axial direction, the small diameter portions 13a, 13b of the two nuts 1a, 1b are in contact with each other. In the state in which the balls 3 and the screw shafts 2 are assembled to the two nuts 1a and 1b, the sleeve can be fitted to the small diameter portions 13a and 13b. Based on this, only the main body portion 71A is formed. The sleeve also has an effect of improving the assembly workability of the ball screw.

[Second embodiment]

As shown in Fig. 6, the double nut preloading ball screw of this embodiment includes a screw shaft 2, a ball 3, and two nuts 1a and 1b, and includes a ring shape disposed between the nuts 1a and 1b. a preload applying mechanism 400 of the member 40; and an end plug 50. A spiral groove 21 is formed on a peripheral surface of the screw shaft 2, and a spiral groove 31 is formed in an inner circumferential surface of the two nuts 1a and 1b.

Between the spiral groove 31 of the two nuts 1a, 1b and the track formed by the spiral groove 21 of the screw shaft 2, a plurality of balls 3 are disposed. The end plug 50 forms a ball return path together with the through holes 17a and 17b that connect the both end faces of the two nuts 1a and 1b. A flange 12 is formed at one end of the one nut 1a in the axial direction.

As shown in FIGS. 7 and 8, the annular member 40 has a peripheral groove 41 formed on the inner circumferential side of the both end faces in the axial direction, and extends in the axial direction and penetrates between the bottom faces 41a of the surrounding grooves 41. The through hole 42 and the female screw hole 43 extending from the outer peripheral surface in the radial direction and communicating with the through hole 42. The through holes 42 are formed at four positions in the circumferential direction of the annular member 40 at equal intervals. The annular member 40 is made of a steel material such as a carbon steel SG material for construction machinery specified in "JIS G4051" or a SPC material such as a cold-rolled steel sheet specified in "JIS G3141".

Two balls (rolling elements) 61 are arranged in the through holes 42 along the axial direction. A small-diameter ball (steering member) 63 having a smaller diameter than the ball 61 is disposed at a boundary portion between the female screw hole 43 and the through hole 42. Through hole The axial direction dimension of 42 is larger than the total diameter of the two balls 61, but is smaller than the total diameter of the two balls 61 and the small diameter balls 63. The two balls 61 and the small diameter balls 63 are made of bearing steel specified by "JIS G4805".

A hexagonal hole fixing screw (external screw member) 8 is screwed into the female screw hole 43 of the annular member 40. A spacer 9 is disposed in the surrounding groove 41 of the annular member 40. The shape of the spacer 9, as shown in Fig. 9, is a disk shape having an opening to be embedded in the size of the surrounding groove 41.

The preload applying mechanism 400 of the embodiment is formed by a female screw hole 43 formed in the annular member 40, a through hole 42 and a hexagonal hole fixing screw (external screw member) 8 and a small diameter ball (steering member) 63. The ball (rolling element) 61 and the spacer 9 are formed. When the preloading mechanism is to be attached to the ball screw, first, two balls 61 are placed in the through holes 42 of the annular member 40, and the spacers 9 are disposed in the respective peripheral grooves 41, and the internal threads are provided. After the hole 43 is placed in the small diameter ball 63, the hexagonal hole fixing screw 8 is screwed to the female screw hole 43. Next, the annular member 40 in this state is disposed between both end faces of the nuts 1a and 1b, thereby assembling the ball screw.

The preload application method of the preload applying mechanism 400 is as follows. In the assembled state of the ball screw, the preloading mechanism 400, as shown in Fig. 7(a), contacts the small diameter ball 63 with the hexagonal hole fixing screw 8, and the small diameter ball 63 contacts the two balls 61.

In the state shown in Fig. 7(a), the hexagonal hole fixing screw 8 is rotated to facilitate the screwing with the female screw hole 43, whereby the small diameter ball 63 directly presses the two balls 61 to make the balls 61. Inward through the through hole 42 Move in the opposite direction. In other words, the axial force of the hexagonal hole fixing screw 8 is converted into a force by which the small balls 63 are moved to the respective end portions of the through holes 42 in the axial direction. As the two balls 61 move, the spacers 9 disposed in the peripheral grooves 41 of the annular member 40 are pressed by the respective balls 61 to generate a force for pressing the end faces of the nuts 1a and 1b. With this force it is possible to apply a preload to the rolling thread. Figure 7(b) shows this state.

In the state of Fig. 7(b), at the positions on the outer peripheral side and the inner peripheral side of the groove 41 around the annular member 40, gaps 34, 35 are generated in the annular member 40 and the respective nuts. Between 1a and 1b. However, each of the spacers 9 is separated from the end surface 41a of the peripheral groove 41, protrudes from the end surface of the annular member 40, and contacts the end faces of the respective nuts 1a, 1b. That is, the gap 34 is closed by the spacer 9 in the entire circumferential direction. Based on this, the ball screw of this embodiment is difficult to enter into the inside of the ball screw due to impurities such as dust inside the ball screw. Further, the insertion depth (the degree of latching) of the hexagonal hole fixing screw 8 can be adjusted by the amount of preload.

Further, the axial force of the hexagonal hole fixing screw 8 is surely changed to the force for pressing the nuts 1a and 1b via the spacer 9. In the preload applying mechanism shown in FIG. 13, the adjusting member (steering member) 130 that presses the two pre-pressing balls 120 disposed in the through hole 111 of the annular member 110 has the coil spring 131. On the other hand, in the preload applying mechanism of the embodiment, since the steering member is formed only of the small diameter balls 63, it is possible to prevent the axial force of the hexagonal hole fixing screw 8 which is the male screw member from being converted into the ball 61. The force of the nuts 1a, 1b becomes weak.

Further, instead of the spacer 9 shown in Fig. 9, the spacer 9A shown in Fig. 10 or the spacer 9B shown in Fig. 10 may be used.

In the spacer 9A shown in Fig. 10, a circumferential groove 91 for receiving the balls 61 is formed on one end surface of the spacer 9 in the axial direction of Fig. 9. The cross-sectional shape of the circumferential groove 91 is an arc shape corresponding to the spherical surface of the ball 61. The spacer 9B shown in Fig. 10 is formed at an equidistant position in the circumferential direction in which four spherical grooves 92 for receiving the balls 61 are formed on one end surface in the axial direction of the spacer 9 of Fig. 9. When the spacer 9B is used, when the spacer 9B is to be fitted into the peripheral groove 41 of the annular member 40, it is necessary to align the spherical groove 92 with the through hole 42 of the annular member 40.

When the spacers 9A and 9B having the ball 61 receiving portions such as the circumferential groove 91 or the spherical groove 92 are used, it is possible to obtain the ball 61 stable pressing pad than the case of using the spacer 9 having no receiving portion. The effect of 9A, 9B.

In the preload applying mechanism of this embodiment, although the rolling elements are the balls 61 and the steering members are the small diameter balls 63, the rolling elements and the steering members are not limited to the balls. As shown in Fig. 12, the steering member may be a roller 64 or a wedge member 65, and the rolling body may be a roller 62.

Fig. 12(a) shows an example in which the roller 62 is used for the rolling elements and the roller 64 is used for the steering member. Fig. 12(b) shows an example in which the roller 62 is used for the rolling elements and the small diameter balls 63 are used for the steering member. The 12th (c) is an example in which the rolling element 62 is used for the rolling element and the wedge member 65 is used for the steering member.

Further, in the preload applying mechanism of the embodiment, the spacer 9 is disposed at both ends of the through hole 42 in the axial direction, but may be disposed only on the shaft of the through hole 42. One end of the direction.

Further, in the preload applying mechanism of the embodiment, the spacer 9 is disposed at the end portion of the through hole 42 in the axial direction, and is pressed by the two balls 61 to press the end faces of the respective nuts 1a and 1b, but the pad The sheet may be disposed at a position on the outer side or the inner side of the through hole 42 of the annular member 40. In this form, the balls 61 directly press the end faces of the nuts 1a and 1b, and the spacers are not pressed by the balls 61. Therefore, it is necessary to separately provide the annular member 40 with a pre-compression mechanism. A mechanism in which the gasket is pushed out toward the respective nuts 1a, 1b as the preload is applied.

Further, in the preload applying mechanism of the embodiment, the through holes 42 are formed at equal intervals at four positions in the circumferential direction of the annular member 40, but the through holes 42 need not be arranged at plural positions. In the interval configuration, the through hole 42 may be disposed at three or more positions.

Further, in the preload applying mechanism of the embodiment, the annular member 40 is composed of one member, but the annular member for the preloading mechanism may be divided into a plurality of divided bodies in the circumferential direction (for example, A two-part body or a four-part body is formed.

1a, 1b‧‧‧ nuts

11‧‧‧Spiral groove of the nut

12‧‧‧Flange

13a‧‧‧The small diameter of the nut

13b‧‧‧The small diameter of the nut

14‧‧‧ Flat Department

15‧‧‧ surrounding trench

16a, 16b‧‧‧ recess

2‧‧‧ screw shaft

21‧‧‧Spiral groove of the screw shaft

3‧‧‧ balls

4‧‧‧ sleeve

45‧‧‧The sleeve 4 is placed in the recess 16a, 16b

5‧‧‧Circulating hose (ball return path)

51‧‧‧The foot of the circulation hose

52‧‧‧ main body of the circulation hose

6‧‧‧Installation hardware accessories

Claims (10)

A ball screw having: a plurality of nuts having a spiral groove formed on an inner circumferential surface; a spiral groove formed on a peripheral surface; and a screw shaft inserted through all of the plurality of nuts; and being disposed by the nut a plurality of balls between the spiral groove and the track formed by the spiral groove of the screw shaft; and a ball return path for returning the ball from the end point of the track to the starting point, configured to transmit the ball rolling in the track The plurality of nuts are integrally moved relative to the screw shaft, and the two adjacent nuts are in contact with each other in the axial direction, and one of the two nuts is relatively rotated to the other and preloaded. In a state, a sleeve is fixed to a peripheral surface of the axial end portion of the mutual contact side of the two nuts. The ball screw according to the first aspect of the invention, wherein the two nuts have a small diameter portion at an end portion in the axial direction on the side in contact with each other, and the sleeve is externally fitted to the two small diameter portions. The ball screw according to the first aspect of the invention, wherein the two nuts have a concave portion on a peripheral surface of an axial end portion of the mutually contacting side. The sleeve is fixed to the recess. The ball screw according to the third aspect of the invention, wherein the sleeve has a claw portion at both ends in the axial direction, and the claw portion is press-fitted into the concave portion of the two nuts. The ball screw according to any one of claims 1 to 4, wherein the main body portion of the sleeve has a C-shaped cross section perpendicular to the axial direction. A ball screw having: a plurality of nuts having a spiral groove formed on an inner circumferential surface; a spiral groove formed on a peripheral surface; and a screw shaft inserted through all of the plurality of nuts; and being disposed by the nut a plurality of balls between the spiral groove and the track formed by the spiral groove of the screw shaft; and a ball return path for returning the ball from the end point of the track to the starting point, configured to transmit the ball rolling in the track The plurality of nuts are integrally moved relative to the screw shaft, and are characterized in that: the annular member is disposed between the adjacent nuts and inserted into the screw shaft; and the annular member is disposed And a preload applying mechanism that applies a force in the axial direction to the nut in a reverse direction; and a gap between the annular member and the nut in a preload application state of the preload applying mechanism Closed in the circumferential direction The gasket is disposed on the annular member and is disposed to be pushed out toward the nut side as the preload is applied. The ball screw according to claim 6, wherein the annular member has a through hole that is formed on the inner circumference side and extends in the axial direction, and extends from the outer surface in the radial direction and communicates with the through hole. The through hole of the hole is formed at a plurality of positions in the circumferential direction of the annular member, and two rolling elements are disposed in the through hole along the axial direction, and external threads are screwed into the internal thread. The member is configured such that the axial force of the male screw member is changed so that the two rolling elements move toward the respective end portions of the through hole in the axial direction, and the steering member is disposed between the male screw member and the two rolling elements. The steering member is a rolling element or a wedge-shaped member having a smaller diameter than the rolling element, and the spacer is disposed at an axial end portion of the through hole, and the female screw hole, the through hole, and the male screw member The steering member, the two rolling elements, and the spacer constitute the preload applying mechanism. The ball screw according to the seventh aspect of the invention, wherein the annular member has a peripheral groove formed on an inner circumferential side of both end faces in the axial direction, and the through hole is a bottom surface penetrating the two surrounding grooves The spacer is disposed on both sides of the surrounding groove. The ball screw according to claim 8, wherein the externally threaded member is moved inward in the radial direction of the annular member, and the steering member that the externally threaded member contacts is directly pressed against the second The rolling elements move the rolling elements in opposite directions in the axial direction, and the respective spacers are pressed by the rolling elements to press the end faces of the nuts to apply the preload. The ball screw according to any one of claims 7 to 9, wherein the through holes are formed at a plurality of positions in the circumferential direction of the annular member at equal intervals.