JP2010190384A - Ball screw device - Google Patents

Abstract

Provided is a means for smoothly guiding a holding belt for holding a ball circulating in a circulation path and improving the life of a ball screw device.
A ball screw device (1) is provided with a holding belt (13) having pocket holes (15) for holding balls (2) circulating in the circulation path and spacers (16) disposed between the balls (2), and a continuous belt (15). Two guide grooves 18 for guiding the side edge portions 14 a on both sides of the holding belt 13 are provided in the passage 10, and the openings of the two guide grooves 18 in the connection portion of the communication passage 10 are switched on the load path. The outer peripheral surface of the screw shaft 3 and the nut around the connection point S on both sides of the spiral rolling path center line Cf of the moving ball 2 and the moving path center line Ci of the ball moving in the bent communication path 10 5 is arranged in parallel with the gap between the inner peripheral surface of each of the holding belts 13 and the guide grooves 18 are symmetrical with respect to the center point P on the movement path center line Ci between the connection points S on both sides. The belt center line Cb is changed to the movement path center line C. In a state of being matched to the form in point symmetry.
[Selection] Figure 1

Description

  The present invention relates to a ball screw device used for driving or power transmission of a linear movement mechanism for positioning a moving table or for conveying a machine device such as a machine tool, an industrial machine, or an electric injection molding machine.

In a conventional ball screw device having a total ball specification that does not have a cage, the balls that roll on the load path compete with each other, and when used for high loads, their operating characteristics and life are affected.
This is because when the ball screw device has a communication member such as a return tube, the filling gap between the balls in the circulation path is shifted to one place, the filling gap between the balls disappears, and the balls compete with each other. The roundness error of the raceway groove and the nut raceway groove causes the balls to interfere with each other as a result of the different revolution speeds of the balls.

In other words, in a ball screw device, each ball can be independently contacted with other balls and cages, and if it rolls with a slight gap, the best operating characteristics and long life can be obtained. Become.
For this reason, the holding piece is inserted between the balls. However, when the holding piece is inserted, the metal contact between the balls can be eliminated to prevent the occurrence of scratches. Although it is effective for extending the life of the device, the holding piece must be held using a ball so that it does not fall down in the circulation path, particularly in the communication path of the communication member where the filling gap tends to be shifted to one place. The ball must be filled in the circulation path with almost no filling gap, and the ball and the holding piece may partially push each other, which may affect the operating characteristics.

In addition, since the filling gap changes due to swelling due to moisture or the like, or expansion or contraction of the ball or holding piece due to heat, etc., there is a concern about the falling of the holding piece. It is necessary to pay sufficient attention to.
In order to maintain the filling gap between the ball and the holding piece, the holding piece needs to maintain its own posture, and the holding piece is connected by a belt.

  A conventional ball screw device having a chain type cage in which such holding pieces are connected by a belt includes a shaft raceway groove formed in a spiral shape on the outer peripheral surface of the screw shaft and a shaft formed on the inner peripheral surface of the nut. A nut raceway groove facing the raceway groove is screwed through a plurality of balls, and both ends of a spiral load path formed by the axial raceway groove and the nut raceway groove arranged to face each other are provided on the end cap. A circulation path is formed by communicating with a communication path formed by a direction change path and a return path provided with a nut, and a ball is lifted from one of the connection paths between the communication path and the load path, and the other is loaded. The ball in the circulation path is circulated while returning to the path, and the spherical surface of the ball is held in four equal parts by four belt members made of a flexible material. A ball chain with a seat is provided. The side edge of each belt member along the longitudinal direction of the chain is provided in the load path at the gap between the outer peripheral surface of the screw shaft and the inner peripheral surface of the nut, and at the groove bottom of the shaft raceway groove and the nut raceway groove. It is accommodated in the escape groove, and in the communication path, it is guided by four guide grooves provided in the communication path, and the ball in the circulation path is held by the ball chain and circulated (for example, patent document) 1).

JP-A-10-169653 (3rd page, paragraphs 0013-0017, 4th page, paragraphs 0027-0034, FIG. 1, FIG. 2, FIG. 7)

  However, in the above-described conventional technology, the spacer is connected by four belt members, so that the spacer does not fall down and the space between each ball and the belt member holding the ball is filled. Since the gap is formed, it is effective to improve the operating characteristics. However, since the belt members are equally arranged on the four sides of the ball, the two pairs of bells and members arranged in a cross shape are used. Pass through the clearance groove provided in the bottom of the shaft raceway groove and the nut raceway groove in the load path, and in the direction change path of the communication path, the inner R side and the outer R of the bent portion In the load path, the path lengths of the escape grooves provided at the bottom of the shaft raceway groove and the nut raceway groove are different, and the direction of the communication path is changed. In the road, it was formed on the inner R side and the outer R side of the bent part. Each guide groove has a different path length, and due to the difference in the path length of the belt members guided in the respective grooves, an excessive tensile stress is applied to the outer belt member and an inner belt member is not allowed. There is a problem in that a large compressive stress is generated and an unreasonable repetitive stress acts on the belt member to reduce its operating life as well as its life.

  Also, normally, a connecting portion on both sides of the communication path and the load path is provided with a tongue portion having a thin tip loosely fitted in the shaft raceway groove in order to smoothly lift the ball from the load path to the communication path. However, in the conventional ball chain, since the belt member is arranged in a cross shape, in the communication path, the guide groove that guides the side edge of at least one of the four belt members is divided into two halves. Alternatively, the tongue portion must be formed so as to cross the oblique eye, and there is a problem that the strength of the tongue portion is lowered and the life of the ball screw device is shortened.

This is particularly noticeable in the case of a ball screw device operated at high speed.
The present invention has been made to solve the above-described problems, and provides a means for smoothly guiding a holding belt that holds a ball circulating in a circulation path and improving the life of a ball screw device. Objective.

  In order to solve the above problems, the present invention provides a screw shaft in which a spiral shaft raceway groove is formed on an outer peripheral surface, a nut in which a nut raceway groove facing the shaft raceway groove is formed on an inner peripheral surface, and the shaft A spiral load path formed by the raceway groove and the nut raceway groove, a bent communication path communicating at both ends of the load path, and a plurality of circulation paths formed by the load path and the communication path. A ball screw device comprising: a ball, and a tongue portion formed at a connection portion between both the communication path and the load path, and passing the ball between the load path and the communication path. A holding belt having a pocket hole for holding each ball circulating in the circulation path and a spacer disposed between adjacent balls held in the pocket hole is provided. Plan side edges on both sides along the longitudinal direction Two guide grooves are provided, and the two guide grooves are provided on the spiral rolling path center line of the ball that rolls on the load path and the movement path center line of the ball that moves on the bent communication path. The center point on the moving path center line between the connection points on both sides of the holding belt is set as a symmetrical point, and the belt center line along the longitudinal direction of the holding belt is made coincident with the moving path center line so as to be point symmetric. It is characterized by that.

  Accordingly, the present invention can form the two guide grooves to the same length, and the holding belt when the side edge of the holding belt is guided by the guide groove and passes through the communication path. It is possible to prevent the holding belt from being damaged by preventing excessive tensile stress or compressive stress from acting on the holding belt, and to prevent the holding belt from being damaged. The effect that the lifetime can be improved is improved.

Explanatory drawing which shows the cross section of the ball screw apparatus of an Example The perspective view which shows the division | segmentation piece of the return tube of an Example The perspective view which shows the holding belt of an Example Explanatory drawing which shows the upper surface of the belt part in the communicating path of the holding belt of an Example. Explanatory drawing which shows the arrow view seen from the arrow A direction of FIG. The perspective view which shows the shape of the belt part in the communicating path of the holding belt of an Example. The perspective view which shows the other form of the shape of the belt part in the communicating path of the holding belt of an Example.

  Embodiments of a ball screw device according to the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory view showing a cross section of the ball screw device of the embodiment, FIG. 2 is a perspective view showing a split piece of the return tube of the embodiment, and FIG. 3 is a perspective view showing a holding belt of the embodiment.
In FIG. 1, 1 is a ball screw device.
Reference numeral 2 denotes a ball as a rolling element of the ball screw device 1, which is a sphere made of a steel material such as alloy steel.

Reference numeral 3 denotes a screw shaft of the ball screw device 1, which is a rod-shaped member made of a steel material such as alloy steel, and an axial raceway groove 4 having an arc-shaped cross-section is spirally formed with a predetermined lead on the outer peripheral surface thereof. Is formed.
Reference numeral 5 denotes a nut of the ball screw device 1, which is a cylindrical member made of a steel material such as alloy steel, and the inner peripheral surface thereof has a nut raceway groove 6 having an arcuate cross-sectional shape facing the shaft raceway groove 4. Is formed with the same lead as the shaft raceway groove 4, and a flange portion 7 for fixing the nut 5 to a moving table of a mechanical device (not shown) with a bolt or the like is provided at one end portion of the outer peripheral portion thereof. Yes.

A spiral load path is formed by the shaft raceway groove 4 and the nut raceway groove 6 which are arranged to face each other.
Reference numeral 9 denotes a return tube as a communication member of the ball screw device 1, which is made of a steel material or a resin material, has a communication passage 10 formed as an inner diameter through which the ball 2 can pass, and has bent portions at two locations. A straight pipe portion at both ends of a fitting hole reaching a nut raceway groove 6 provided in a flat surface 5a which is a pipe bent in a substantially U shape and which is notched in parallel with the axial direction. The nut is engaged and communicated with the nut raceway groove 6 and fastened to the flat surface 5a of the nut 5 with a small screw or the like.

  As shown in FIG. 2, the return tube 9 of the present embodiment was halved on the plane including the U-shaped moving path center line Ci (see FIG. 1) of the ball 2 moving through the bent communication path 10. The two split pieces 9a of the same shape made of resin material are combined to form a part of the end surface of the return tube 9 connected to the load path at both ends of the communication path 10 and rolls on the load path respectively. A tongue 11 is formed that extends to the vicinity of the bottom of the shaft raceway groove 4 so as to block the downstream side and the upstream side in the moving direction of the ball 2 to be loosely fitted with the shaft raceway groove 4. .

  The tongue portion 11 formed at the end of the return tube 9 smoothly transfers the ball 2 between the load path and the communication path 10, that is, returns the ball 2 rolling on the load path on one side of the tongue portion 11. The ball 2 that smoothly crawls up to the communication path 10 of the tube 9 and smoothly passes through the communication path 10 to the load path, and both ends of the load path are smoothly communicated with the communication path 10 of the return tube 9. A circulation path through which the balls 2 circulate is formed.

  Reference numeral 13 denotes a holding belt, which is a long belt member having a length equivalent to the path length of the circulation path, which is made of a flat plate made of an elastomer that is a highly deformable and flexible resin material. As shown in FIG. 3, the ball 2 circulates in the circulation path through the belt portion 14 having a thickness smaller than the gap between the outer peripheral surface of the screw shaft 3 and the inner peripheral surface of the nut 5 in the thickness direction. Each of which is loosely fitted and held, and a disc-shaped spacer 16 disposed between adjacent balls 2 held in the pocket hole 15.

The spacer portion 16 is formed with a bottomed spherical concave surface 16a formed at a radius larger than the radius of the ball 2 on both end faces thereof, and is disposed between the adjacent balls 2 so that the balls 2 It has a function to prevent contact.
The side edge portions 14a on both sides along the longitudinal direction of the belt portion 14 of the holding belt 13 of the present embodiment pass through a gap between the outer peripheral surface of the screw shaft 3 and the inner peripheral surface of the nut 5 in the load path. As shown, the spiral rolling path center line Cf (see FIG. 1) of the ball 2 rolling on the load path and the belt center line Cb along the longitudinal direction of the belt portion 14 of the holding belt 13 (see FIG. 3). And are arranged in a state of being wound into a planar coil as shown in FIG.

Moreover, in the communicating path 10, it arrange | positions in the state loosely fitted in the two guide grooves 18 which combined the guide groove 18 formed in each division | segmentation piece 9a shown in FIG.
Such a guide groove 18 is formed along the side edge portion 14a of the belt portion 14 of the holding belt 13 shown in FIGS.
That is, assuming a strip-shaped belt portion 14 having the same length as the movement path center line Ci of the bent communication path 10, that is, the length of the side edge portions 14a on both sides is the same length as the movement path center line Ci, As shown in FIG. 4, at a connection point S (see FIG. 5) between the rolling path center line Cf of the load path and the movement path center line Ci of the communication path 10 at the connection portions on both sides of the road and the communication path 10. In addition, the plane of the one end is centered on one connection point S, parallel to the gap between the outer peripheral surface of the screw shaft 3 and the inner peripheral surface of the nut 5, and the end surface of the end is screwed. The other is located parallel to the axial direction of the shaft 3 and the plane of the other end is shifted in the axial direction by the pitch of the axial raceway groove 4 constituting the load path (2 pitches and a half in the example of FIG. 4). The belt portion 14 is assumed to be arranged in the same manner as described above with the connection point S as the center. Are shown in Figure 6.).

  Accordingly, the geometric center point P on the movement path center line Ci between the connection points S on both sides is symmetrical with the belt center line Cb of the holding belt 13 and the movement path center line Ci aligned. As a point, a point-symmetric belt portion 14 twisted in accordance with the number of pitches constituting the load path around the belt center line Cb is assumed, and along the side edge portions 14a of the same length on both sides of the belt portion 14. The two guides in which the respective openings in the connecting portion between the load path and the communication path 10 are arranged in parallel with the gap between the outer peripheral surface of the screw shaft 3 and the inner peripheral surface of the nut 5 with the connection point S as the center. A groove 18 is formed.

Further, chamfers are provided at the corners of the opening of the guide groove 18 and at the front and rear ends of the holding belt 13, respectively, so that these parts are not caught by the seam during movement.
The circulation path configured in this manner is filled with a plurality of balls 2 that are held in the pocket holes 15 of the holding belt 13 while being spaced apart by the spacers 16 and a predetermined amount of lubricant, for example, grease. By rotating the shaft 3, the side edge portion 14 a is held by the holding belt 13 guided in the gap between the guide groove 18 of the communication path 10 and the outer peripheral surface of the screw shaft 3 and the inner peripheral surface of the nut 5. The ball 2 circulates in the circulation path, and the ball 2 rolling on the load path moves the nut 5 in the axial direction while reciprocally supporting the load applied to the nut 5, and the rotational movement of the screw shaft 3 Is converted to a linear motion of 5.

  At this time, since the two guide grooves 18 formed in the communication path 10 of the present embodiment are formed to have the same length by the above-described configuration, the side edge portion 14a of the belt portion 14 of the holding belt 13 is guided by When the belt 18 is guided by a gap between the groove 18 or the screw shaft 3 and the nut 5 and passes through the communication path 10 or the load path, an excessive tensile stress or a compressive stress is not applied to the belt portion. The portion 14 can be prevented from being broken and its life can be improved, and the side edge portion 14a of the holding belt 13 guided by the guide groove 18 can be smoothly passed to improve the operation characteristics of the ball screw device 1. Can be made.

  Further, since the holding belt 13 of the present embodiment is formed of an elastomer having high elasticity, even if the holding belt 13 is twisted in the communication path 10 and bent in a coil shape in the load path, the holding belt 13 is flexible in its twisting and bending. It is possible to reduce the stress accompanying them, improve the life of the holding belt 13, and make the passage of the side edge portion 14a of the holding belt 13 guided by the guide groove 18 smoother. In addition to improving the operating characteristics of the ball screw device 1, the ball 2 can be easily inserted into the pocket hole 15.

In this case, if the thickness of the belt portion 14 is 0.3 times or less the diameter of the ball 2, the movement of the belt portion 15 can be made smooth.
Further, the guide groove 18 of the present embodiment has an opening at the connection portion between the communication passage 10 and the load path, and a clearance between the outer peripheral surface of the screw shaft 3 and the inner peripheral surface of the nut 5 with the connection point S as the center. Since the guide grooves 18 are arranged in parallel, the guide grooves 18 can be arranged in parallel with the scooping surfaces of the tongue portions 11 formed in the connecting portions, and the guide grooves 18 are formed on the scooping surfaces of the tongue portions 11. In addition, the strength of the tongue portion 11 can be prevented from being lowered and its breakage can be prevented.

  As described above, in this embodiment, in the ball screw device, the pocket holes that respectively hold the balls that circulate in the circulation path, and the spacers that are disposed between the adjacent balls held in the pocket holes, And two guide grooves for guiding side edges on both sides along the longitudinal direction of the holding belt are provided in the communication path, and each of the two guide grooves in the connection part of the communication path is provided. The screw shaft is centered on a connection point S on both sides of the spiral rolling path center line Cf of the ball rolling on the load path and the moving path center line Ci of the ball moving on the bent communication path. Are arranged in parallel with the gap between the outer peripheral surface of the nut and the inner peripheral surface of the nut, and each guide groove is held with the center point P on the movement path center line Ci between the connection points S on both sides as a symmetry point. Belt center line C along the length of the belt Are made symmetrical with respect to the movement path center line Cf, so that the length of the two guide grooves can be the same length, and the side edge of the holding belt is guided by the guide belt. The holding belt can be smoothly passed through the communication path guided by the groove, and the holding belt can be prevented from being subjected to repeated stress due to excessive tensile stress or compressive stress. Breakage can be prevented, and the life of the ball screw device can be improved while improving the operating characteristics of the ball screw device.

In addition, since the holding belt is made of an elastomer, the high elasticity can be used to reduce the stress caused by twisting and bending applied to the holding belt, thereby improving the life of the holding belt. In addition, the operation of the ball screw device can be improved by smoothly passing the side edge of the holding belt guided by the guide groove.
In the above-described embodiment, the belt portion of the holding belt in the communication path is twisted according to the number of pitches constituting the load path around the belt center line Cb with the center point P on the movement path center line Ci as a symmetry point. However, as shown in FIG. 7, the belt may be formed by twisting once on one side and twice on both sides as shown in FIG. In short, as long as the belt portion is twisted around the belt center line Cb, the number of twists is not limited.

Moreover, in the said Example, although demonstrated that the holding belt was one, you may make it divide | segment into 2 or more according to the path | route length of a circulation path. Even in this case, since the guide groove of the present invention smoothly connects the load path and the communication path, there is no risk that the tip of the holding belt is detached from the guide groove.
Further, in the above-described embodiment, the guide groove is described as being provided over the entire length of the side edge of the holding belt that passes through the communication path. However, the guide groove is provided partially to guide the path of the side edge of the holding belt. You may do it. In this case, the length of the guide groove is equal to the length including the space where the actual guide groove is not formed, that is, the length of the side edge of the holding belt passing through the communication path.

Furthermore, in the above embodiment, the case where the present invention is applied to a ball screw device using a tube-type circulation system in which a ball is circulated using a return tube as a communication path has been described as an example. Even if the present invention is applied to a circulation type ball screw device such as a cap type or a deflector type, the same effect can be obtained.
Further, in each of the above embodiments, the screw shaft of the ball screw device is rotated and the nut is moved in the axial direction. However, in the ball screw device of the type in which the nut is rotated and the screw shaft is moved in the axial direction. The same effect can be obtained even when the present invention is applied.

DESCRIPTION OF SYMBOLS 1 Ball screw apparatus 2 Ball 3 Screw shaft 4 Shaft raceway groove 5 Nut 5a Plane 6 Nut raceway groove 7 Flange part 9 Return tube 9a Divided piece 10 Communication path 11 Tongue part 13 Holding belt 14 Belt part 14a Side edge part 15 Pocket hole 16 Spacer 16a Spherical concave surface

Claims (4)

A screw shaft having a spiral shaft raceway groove formed on the outer peripheral surface;
A nut having a nut raceway groove facing the shaft raceway groove on the inner peripheral surface;
A spiral load path formed by the shaft raceway groove and the nut raceway groove;
A bent communication path communicating with both ends of the load path;
A plurality of balls circulating in a circulation path formed by the load path and the communication path;
In a ball screw device comprising: a tongue portion that is formed at both connection portions of the communication path and the load path and delivers the ball between the load path and the communication path.
A holding belt having a pocket hole for holding each ball circulating in the circulation path and a spacer disposed between adjacent balls held in the pocket hole is provided, and the holding belt is provided in the communication path. Two guide grooves for guiding the side edges on both sides along the longitudinal direction of
The two guide grooves are formed between the connection points on both sides of the spiral rolling path center line of the ball rolling on the load path and the moving path center line of the ball moving on the bent communication path. The ball screw device is characterized in that the center point on the moving path center line is a symmetric point and the belt center line along the longitudinal direction of the holding belt is coincident with the moving path center line so as to be point symmetric. . In claim 1,
The openings of the two guide grooves in the connecting portion of the communication path are arranged in parallel with the gap between the outer peripheral surface of the screw shaft and the inner peripheral surface of the nut with the connection point as the center. A ball screw device characterized by that. In claim 1 or claim 2,
The ball screw device is characterized in that the difference between the lengths of the two guide grooves is equal to or less than the diameter of the ball. In any one of Claims 1 to 3,
The ball screw device, wherein the holding belt is made of an elastomer.

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