JP5772586B2 - Ball screw nut - Google Patents

Description

The present invention relates to a method for manufacturing a nut for a ball screw.

The ball screw has a nut having a spiral groove (ball rolling groove) formed on the inner peripheral surface, a screw shaft having a spiral groove (ball rolling groove) formed on the outer peripheral surface, and a spiral groove (ball rolling) of the nut. And a ball return path for returning the ball from the end point of the track to the start point, and the ball rolls in the track. The nut moves relative to the screw shaft.
Such a ball screw is used not only for a general industrial machine positioning device but also for an electric actuator mounted on a vehicle such as an automobile, a two-wheeled vehicle or a ship.

  The ball return path of the ball screw includes a circulation tube system, a top system, and the like. In the case of the top system, a top formed with a recess that forms the ball return path is fitted in the through hole of the nut. On the other hand, if the recess (ball circulation groove) forming the ball return path is directly formed on the inner peripheral surface of the nut, it is possible to reduce the time and cost of assembly and to improve the reliability of the ball circulation.

For example, in Patent Document 1, a single cutting tool whose tip shape is a gothic arc shape is used, and the cutting shaft is disposed on the inner diameter portion of the nut so that the rotation axis of the cutting tool extends in the radial direction with respect to the inner peripheral surface of the nut. To do. Then, by applying a rotary cutting main motion to the cutting tool, the ball rolling groove and the ball circulation groove are continuously processed by cutting in the inner peripheral surface of the nut.
According to the technique of Patent Document 1, since the ball rolling groove and the ball circulation groove are continuously processed with a single cutting tool, the ball rolling groove and the ball circulation groove are displaced in the axial direction, the circumferential direction, and the radial direction. It is possible to prevent the film from being formed.

International Publication No. WO2007 / 046321

However, the technique of Patent Document 1 can only process a nut that has a size that allows the cutting tool and a spindle unit that rotatably supports the cutting tool to extend in the radial direction of the inner diameter portion of the nut. There are restrictions on the size of the nut.
Therefore, the present invention has been made paying attention to the above-mentioned unsolved problems of the conventional example, and there is no restriction on the size of the nut, and the ball rolling groove and the ball circulation for all size nuts. It is an object of the present invention to provide a ball screw nut manufacturing method capable of preventing the grooves from being formed in a state shifted in the axial direction, the circumferential direction, and the radial direction.

In order to achieve the above object, a ball screw nut manufacturing method according to claim 1 of the present invention includes a ball rolling groove that forms a raceway for rolling a ball together with a spiral groove of a screw shaft, a ball circulation groove for returning the ball to the starting point from the end point, a manufacturing method of a cylindrical inner peripheral surface you continuously formed ball screw nut blank is nut material, provided around the helical cutter was rotary blade along Migihitsuji in said circumferential surface of said blank and said helical cutter and a relatively predetermined the blank so that the central axis and the central axis of the blank of the helical cutter is skewed The ball is moved by the rotary blade by moving the helical cutter relative to the inner peripheral surface of the blank while rotating the helical cutter around the central axis. When forming the moving groove and forming the ball circulation groove continuously to the ball rolling groove, an angle formed by the central axis of the helical cutter and the central axis of the blank is set to the ball rolling angle. When the ball circulation groove is formed continuously with the ball circulation groove, the ball circulation groove is formed continuously with the rotary blade by changing the angle different from that when forming the movement groove. It is a manufacturing method of the nut for ball screws which returns the above-mentioned helical cutter and the blank to the original relative slanting arrangement so that it may become the predetermined angle, and forms the ball rolling groove with the rotary blade .
According to a second aspect of the present invention, in the ball screw nut manufacturing method according to the first aspect, the helical cutter is orthogonal to the Z-axis direction along the central axis of the helical cutter and the Z-axis direction. It is possible to move in the X-axis and Y-axis directions orthogonal to each other, and the blank is disposed so as to be rotatable around an orthogonal axis orthogonal to the central axis of the blank, and is continuous with the ball rolling groove. When the ball circulation groove is formed and when the ball rolling groove is formed continuously to the ball circulation groove, the central axis of the helical cutter is rotated by rotating only the blank around the orthogonal axis. And a method for manufacturing a ball screw nut that changes an angle formed by the central axis of the blank.
According to a third aspect of the present invention, in the ball screw nut manufacturing method according to the first or second aspect, the tip of the rotary blade of the helical cutter has a Gothic arch-shaped tip. It is a manufacturing method.

According to a fourth aspect of the present invention, in the method for manufacturing a ball screw nut according to any one of the first to third aspects, the blade width of the rotary blade gradually increases from the distal end portion toward the proximal end side. This is a method of manufacturing a nut for a ball screw that is increasing.
According to a fifth aspect of the present invention, in the ball screw nut manufacturing method according to any one of the first to fourth aspects, the groove widths at both ends of the ball circulation groove connected from the end point of the track to the start point This is a method for manufacturing a ball screw nut in which the ball circulation groove is formed so that the groove width ta at the center in the length direction of the ball circulation groove is set smaller than tb.
Furthermore, the invention according to claim 6 is the ball screw nut manufacturing method according to any one of claims 1 to 5, wherein the cutting depth of the helical cutter is gradually increased over a plurality of times. The ball rolling groove and the ball rolling groove are continuously formed while continuing, and the cutting depth of the ball circulation groove is made deeper than the cutting depth of the ball rolling groove.

According to the ball screw nut manufacturing method of the present invention, a helical cutter in which a rotary blade can be inserted into the inner diameter of a cylindrical blank is used, and the rotary blade of this helical cutter is connected to the inner peripheral surface from one opening of the blank. The rotating helical cutter and the blank are relatively inclined, and the ball rolling groove and the ball circulation groove are continuously formed by cutting the rotating blade. On the other hand, it is possible to prevent the ball rolling groove and the ball circulation groove from being formed in a state shifted in the axial direction, the circumferential direction, and the radial direction.

It is sectional drawing which shows the ball screw which concerns on this invention. It is a figure which shows the cylindrical blank used when forming the nut for ball screws concerning this invention. It is a figure which shows the helical cutter which forms the nut for ball screws which concerns on this invention. It is a figure which shows the structure of a helical cutter. It is a figure which shows the machining center which manufactures the nut for ball screws concerning this invention. It is a figure which shows the state which forms the ball rolling groove and the ball circulation groove in the blank. It is a figure which shows the shape of the cross section orthogonal to the direction where the ball | bowl of the ball | bowl circulation groove | channel formed in the nut advances. It is the figure which showed the ball | bowl circulation groove | channel formed in the nut from the inner diameter side.

DESCRIPTION OF EMBODIMENTS Hereinafter, modes for carrying out the present invention (hereinafter referred to as embodiments) will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view of a ball screw 1 according to the present invention.
This ball screw 1 has a screw shaft 3 having a spiral ball rolling groove 3a on its outer peripheral surface and a spiral ball rolling groove 5a facing the ball rolling groove 3a of the screw shaft 3 on its inner peripheral surface. A plurality of balls 9 movably loaded in a spiral ball rolling path 7 formed by the nut 5 and both ball rolling grooves 3a, 5a, and the balls 9 from the end of the ball rolling path 7 And a ball circulation groove 11 for circulating back to the starting point.

The ball circulation groove 11 is formed in an S shape on the inner peripheral surface of the nut 5, and spiral ball rolling grooves 5 a are formed at both ends of the ball circulation groove 11.
The ball 9 moves around the screw shaft 3 while moving in the ball rolling path 7 to reach the end point of the ball rolling path 7, where it is scooped up from one end portion of the ball circulation groove 11 to be ball circulation groove. 11, and is returned to the starting point of the ball rolling path 7 from the other end of the ball circulation groove 11.

  In the ball screw 1 having the above-described configuration, when the nut 5 and the screw shaft 3 screwed to the screw shaft 3 through the ball 9 are relatively rotated, the screw shaft 3 and the nut 5 are moved through the rolling of the ball 9. And move relative to each other in the axial direction. An endless ball path is formed by the ball rolling path 7 and the ball circulation groove 11 so that the ball 9 rolling in the ball rolling path 7 circulates infinitely in the endless ball path. Therefore, the screw shaft 3 and the nut 5 can continuously move relative to each other.

As shown in FIG. 2, the nut 5 of the present embodiment is formed from a steel blank 15 in which a flange 13 is provided at one axial end of a cylindrical member.
That is, as shown in FIG. 3, by using a helical cutter 17 of a size that can be inserted into the inner diameter of the blank 15 (nut 5), by cutting the inner peripheral surface 15a of the blank 15 with this helical cutter 17, An S-shaped ball circulation groove 11 and a spiral ball rolling groove 5 a connected to both ends of the ball circulation groove 11 are formed.

As shown in FIG. 4, the helical cutter 17 rotates about the axis P, and the blank 15 is cut with a plurality of rotary blades 19 provided at predetermined intervals in the circumferential direction. The plurality of rotary blades 19 of the helical cutter 17 have a distal end portion 19a formed in a Gothic arch shape and a shape in which the blade width H gradually increases from the distal end portion 19a toward the proximal end side 19b.
FIG. 5 shows a machining center 21 with a two-axis table according to this embodiment.
The machining center 21 includes a rotational drive mechanism (not shown) that rotates the helical cutter 17 about its axis, and the helical cutter 17 in the X-axis direction (horizontal direction), the Y-direction (horizontal direction orthogonal to the X-axis direction), and the Z-axis. A helical cutter feed drive mechanism (not shown) that moves in the direction (vertical direction) and a table 23 that holds the blank 15 are provided.

  The table 23 is provided with a chuck 25 for holding the blank 15, a θ-direction feed drive mechanism (not shown) that rotates the chuck 25 in the θ direction so that the blank 15 rotates about the axis, and a chuck 25. A Φ direction feed drive mechanism (not shown) that rotates in the Φ direction is provided. The helical cutter feed drive mechanism, the θ direction feed drive mechanism, and the Φ direction feed drive mechanism are devices that use a motor or the like as a drive source. The Φ direction is the rotation direction around the X axis extending in the horizontal direction, and the θ direction is the rotation direction around the axis of the blank 15 extending in the vertical direction (intersect with the Φ center axis and the Φ center axis). Direction of rotation about an axis perpendicular to the axis.

  The machining center 21 having the above-described configuration arranges the rotary blade 19 of the helical cutter 17 along the inner peripheral surface 15a from one opening of the blank 15, and makes θ based on NC data input from a computer (not shown). By driving the direction feed drive mechanism and the Φ direction feed drive mechanism, the movement of the blank 15 is controlled, and by driving the helical cutter feed drive mechanism, the helical cutter 17 rotating around the axis is moved to the X and Y axes. Send a predetermined amount in the axis and Z direction.

  Thereby, the nut 5 is manufactured by continuously forming the ball circulation groove 11 and the ball rolling groove 5 a on the inner peripheral surface 15 a of the blank 15. That is, in FIGS. 6A to 6C, the ball circulation groove 11 and the ball rolling groove 5a are continuously formed while gradually increasing the cutting depth of the helical cutter 17 over several times. Indicates the state. Here, the ball circulation groove 11 and the ball rolling groove 5a are formed with different depths of cut.

  Here, the plurality of rotary blades 19 of the helical cutter 17 have a tip portion 19a formed in a Gothic arch shape and a shape in which the blade width H gradually increases from the tip portion 19a toward the base end side 19b. Therefore, the shape of the cross-section perpendicular to the direction in which the ball 9 of the manufactured ball circulation groove 11 and ball rolling groove 5a of the nut 5 travels forms a Gothic arch shape in which the ball 9 contacts two points. The taper shape opens from the groove bottom toward the radially inner side of the blank 15 (nut 5). That is, FIG. 7 shows the ball circulation groove 11, but a Gothic arch-shaped groove bottom 11 a is formed and an opening 11 b opening in a tapered shape is formed.

  As shown in FIG. 8, the ball circulation groove 11 has both ends connected to the ball rolling groove 5a in a straight line, and the central part located between the both ends is curved in an approximately S shape. It has a curved shape. The groove width ta at the center of the ball circulation groove 11 and the groove width tb at both ends are formed so as to satisfy ta <tb. Note that a gradually decreasing portion in which the groove width gradually decreases from the end portion toward the central portion is formed between the end portion and the central portion.

  Therefore, the nut 5 having the above-described configuration uses the helical cutter 17 having a size that can be inserted into the inner diameter of the blank 15, and the rotary blade 19 of the helical cutter 17 extends from one opening of the blank 15 along the inner peripheral surface 15 a. The blank 15 is moved and controlled in the θ direction and the Φ direction, and the helical cutter 17 rotated around the axis is fed in a predetermined amount in the X, Y, and Z directions to cut the inner peripheral surface 15a of the blank 15. Accordingly, the S-shaped ball circulation groove 11 and the spiral ball rolling groove 5a connected to both ends of the ball circulation groove 11 are continuously formed. Thus, it is possible to prevent the ball rolling groove 5a and the ball circulation groove 11 from being formed in a state shifted in the axial direction, the circumferential direction, and the radial direction.

Further, the ball screw 1 provided with the nut 5 has a cross-sectional shape perpendicular to the direction in which the ball 9 of the ball circulation groove 11 and the ball rolling groove 5a of the nut 5 travels, and the ball 9 contacts two points. Since the Gothic arch shape is formed, meandering of the ball 9 passing through the ball circulation groove 11 and the ball rolling groove 5a can be prevented.
In addition, the ball circulation groove 11 and the ball rolling groove 5a are formed so as to be tapered from the bottom of the ball circulation groove 11 and the ball rolling groove 5a of the nut 5 toward the inside in the radial direction of the nut 5. And the ball 9 can be set small to suppress abnormal noise and vibration.

Furthermore, since the groove width ta at the center of the ball circulation groove 11 of the nut 5 is set smaller than the groove width tb at both ends, the meandering of the ball 9 when passing through the ball circulation groove 11 is suppressed, and the operation Improves. As a result, the operation noise generated when the ball 9 collides with the inner wall of the ball circulation groove 11 is reduced, and wear of the ball circulation groove 11 and the ball 9 is reduced. Further, since the ball 9 is not easily worn, the ball screw 1 has a long life in addition to the fact that the torque fluctuation is hardly generated in the ball screw 1.
In the above-described embodiment, the processing by cutting using the helical cutter 17 as a tool has been shown. However, the rolling groove and the circulation groove are ground using a grinding wheel having the same cross-sectional shape as the helical cutter 17. The present invention can also be applied when finishing by machining.

  DESCRIPTION OF SYMBOLS 1 ... Ball screw, 3 ... Screw shaft, 3a ... Ball rolling groove, 5 ... Nut, 5a ... Ball rolling groove, 7 ... Ball rolling path, 9 ... Ball, 11 ... Ball circulation groove, 11a ... Gothic arch shape Groove opening, 11b ... opening opening in taper shape, 13 ... flange, 15 ... blank, 15a ... inner peripheral surface of blank, 17 ... helical cutter, 19 ... rotary blade of helical cutter, 19a ... tip, 19b ... Base end side, 21: machining center, 23 ... table, 25 ... chuck, H ... blade width, P ... shaft, ta ... groove width at the center of the ball circulation groove, tb ... groove width at both ends of the ball circulation groove

Claims (6)

A ball rolling groove of the raceway for rolling the balls is formed with helical grooves of the screw shaft and a ball circulation groove for returning the ball to the starting point from the end point of the track, the inner peripheral surface of the cylindrical blank is nut material a method of manufacturing a continuous ball screw nut you formed on,
Along Migihitsuji to the rotary blade provided around the inner peripheral surface of the blank of helical cutter and the helical cutter and the like central axis of the central shaft and the blank of the helical cutter is skewed The blank is inclined at a relatively predetermined angle,
By rotating the helical cutter around the central axis and relatively moving along the inner peripheral surface of the blank, the rotary blade forms the ball rolling groove,
When forming the ball rolling groove, the angle formed by the central axis of the helical cutter and the central axis of the blank when forming the ball circulation groove continuously to the ball rolling groove is The ball circulation groove is formed with the rotary blade by continuously changing to different angles,
When the ball rolling groove is formed continuously with the ball circulation groove, the helical cutter and the blank are returned to the original relative inclined arrangement so that the predetermined angle is obtained, and the ball is moved by the rotary blade. A method for manufacturing a ball screw nut , characterized by forming rolling grooves . The helical cutter is movable in the Z-axis direction along the central axis of the helical cutter and the X-axis and Y-axis directions orthogonal to the Z-axis direction and orthogonal to each other,
The blank is arranged so as to be rotatable around an orthogonal axis orthogonal to the central axis of the blank,
When the ball circulation groove is formed continuously with the ball rolling groove and when the ball rolling groove is formed continuously with the ball circulation groove, only the blank is rotated about the orthogonal axis. The ball screw nut manufacturing method according to claim 1 , wherein an angle formed by the central axis of the helical cutter and the central axis of the blank is changed . The ball screw nut manufacturing method according to claim 1 or 2 , wherein a tip portion of the rotary blade of the helical cutter is formed in a Gothic arch shape . 4. The ball screw nut manufacturing method according to claim 1 , wherein a blade width of the rotary blade gradually increases from the distal end portion toward the proximal end side . 5. The ball circulation so that the groove width ta at the center in the length direction of the ball circulation groove is set smaller than the groove width tb at both ends of the ball circulation groove connected from the end point to the start point of the track. 5. A method for producing a ball screw nut according to claim 1, wherein a groove is formed. The ball rolling groove and the ball rolling groove are continuously formed while gradually increasing the cutting depth of the helical cutter over a plurality of times, and the cutting depth of the ball circulation groove 6. The method for manufacturing a nut for a ball screw according to any one of claims 1 to 5, wherein a depth of the ball rolling groove is made deeper than a cutting depth of the ball rolling groove.

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