JP2011163505A - Feed screw with linear motion bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a feed screw with linear motion bearing, which includes a shaft body capable of being smoothly linearly moved through a small driving force, and is easy to manufacture. <P>SOLUTION: The feed screw with linear motion bearing includes a feed screw 54 in which the shaft body 51 having a thread groove 51a on the outer periphery and a nut 52 having a thread groove 52a on the inner periphery arranged around the shaft body 51, are mutually fitted so as to be rotatable. A plurality of linear grooves 51b each having a depth smaller than that of the thread groove 51a of the shaft body 51, are formed on the periphery of the shaft body 51 so as to extend in the axial direction across the thread groove 51a. The feed screw further includes a linear motion bearing 57 having an outer cylinder 56 which receives the shaft body 51 so as to be non-rotatable but slidable through an engagement means. The engagement means is a columnar body 55 received in each linear groove 51b of the shaft body 51 and extending in the axial direction. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a feed screw with a linear motion bearing that can be used particularly advantageously as a component of an electronic component mounting apparatus that mounts an electronic component on the surface of a printed wiring board.

  Conventionally, a shaft body having a nozzle with an electronic component adsorbed on the lower end is arranged above the printed wiring board, and the shaft body is rotated and moved in the circumferential direction so that the electronic component is disposed at a predetermined angle. Then, an electronic component mounting apparatus is known in which the electronic component is mounted at a predetermined position on the surface of the printed wiring board at a predetermined angle by linearly moving downward (to the printed wiring board side). In order to mount a large number of electronic components on the surface of the printed wiring board in a short time, the shaft body for moving the electronic components is repeatedly rotated and linearly moved at a high speed.

  In order to realize the rotational movement and linear movement (sliding) of the shaft body, a feed screw with a linear motion bearing having a combination of a linear motion bearing and a feed screw is used.

  Patent Document 1 discloses a feed screw 10 with a linear motion bearing shown in FIGS. 1 and 2. In the feed screw 10 with a linear bearing, a shaft body 11 having a thread groove 11a on the outer peripheral surface and a nut 12 having a thread groove 12a on the inner peripheral surface arranged around the shaft body 11 are both thread grooves 11a. , 12a on the outer peripheral surface of the shaft body 11 of a feed screw (ball screw) 14 which is rotatably fitted to each other via a plurality of balls 13 accommodated in the shafts 11, respectively. A plurality of linear grooves 11b having a depth smaller than that and extending in the axial direction intersecting the screw grooves 11a are formed, and the shaft body 11 is slidably accommodated through the engaging means in a non-rotating manner. It has the structure provided with the linear motion bearing 17 with the outer cylinder 16 which is.

  A plurality of linear grooves 16 b are provided on the inner peripheral surface of the outer cylinder 16 of the linear motion bearing 17. As the engaging means, a plurality of spheres 15 accommodated in the respective linear grooves 11b of the shaft body 11 and the respective linear grooves 16b of the outer cylinder 16 are used. Inside the outer cylinder 16, a cylindrical sphere holder 18 including a sphere circulation path 18c constituted by a through groove 18a and a non-through groove 18b connected to each other at both ends is provided. The plurality of spheres 15 are accommodated in the sphere circulation path 18 c of the cylindrical sphere holder 18.

  The outer cylinder 16 and the shaft body 11 are engaged with each other via a plurality of spheres 15. As a result, rotational movement of the shaft body 11 accommodated in the outer cylinder 16 of the linear motion bearing 17 in the circumferential direction (relative rotational movement of the shaft body 11 with respect to the outer cylinder 16) is prevented, and a straight line in the length direction. Movement is allowed.

  Therefore, the shaft body 11 can be rotated together with the outer cylinder 16 in the circumferential direction by rotating the outer cylinder 16 of the linear motion bearing 17 in the circumferential direction. On the other hand, the shaft body 11 can be linearly moved in the length direction (axial direction) by rotating the nut 12 of the feed screw 14 in the circumferential direction.

  FIG. 7 of Patent Document 2 shows a shaft body (spline shaft) and an outer cylinder (sleeve) that accommodates the shaft body in a non-rotatable manner through a plurality of columnar bodies (rollers). A spline comprising a linear motion bearing provided is disclosed. A plurality of straight grooves (wide grooves) are formed on the outer peripheral surface of the shaft body. Round grooves are respectively formed at corners of both side surfaces of each linear groove and the outer peripheral surface of the shaft body. And the said columnar body is accommodated in each round groove of each linear groove. In order to adjust the clearance between the round groove and the columnar body of the shaft body, a pressing plate for moving the columnar body to the round groove side is provided between the outer cylinder and the columnar body. The outer cylinder is divided into two, and a taper gib used for driving the holding plate is installed between them.

  This document describes that the columnar body rotates little by little in the direction of load, change in size, and vibration, so that the entire surface of the columnar body is evenly worn and has a long life.

JP 2009-103228 A (FIGS. 1 and 2) Japanese Utility Model Publication No. 53-108677 (FIG. 7)

  According to the study of the present inventor, it has been found that the linear motion feed screw 10 of Patent Document 1 may prevent smooth linear movement of the shaft body 11 in the length direction. For example, if the movement of the shaft body 11 in the length direction is continued, the driving force necessary for the movement of the shaft body 11 (the torque necessary for the rotation of the nut 12) may increase intermittently. The cause can be understood as follows.

  FIG. 3 is an enlarged view of the shaft 11 and the sphere 15 shown in FIG. As shown in FIG. 3, the linear groove 11 b of the shaft body 11 is set in an arc shape having the same diameter as the radius of the sphere 15 in a cross section perpendicular to the length direction of the shaft body 11. The spherical body 15 is sandwiched between the outer cylinder (FIG. 2: 16) and the linear groove 11b, and pressure (preload) is uniformly applied to the entire surface area that contacts the inner surface of the linear groove 11b.

  FIG. 4 is a plan view of the shaft 11 and the sphere 15 shown in FIG. When the shaft body 11 moves to the upper side of the figure, the sphere 15 moves (rolls) to the upper side of the figure at a movement distance that is half the movement distance of the shaft body 11 along the linear groove 11b. Therefore, the sphere 15 moves downward relative to the shaft 11 (in the direction indicated by the arrow 19a in the drawing).

  When the spherical body 15 reaches the screw groove 11a of the shaft body 11, since the thread groove 11a and the linear groove 11b cross each other obliquely, the spherical body 15 changes from the right part of the drawing to the screw groove 11a. Start entering. Accordingly, the pressure (preload) applied to the right portion of the sphere 15 is released first. For this reason, the sphere 15 is finely moved in the circumferential direction (rightward in the drawing) while falling into the screw groove 11a of the shaft 11, and is arranged at a position indicated by a broken line in the drawing.

  This sphere is pushed by a subsequent sphere (not shown) and further moves in the direction indicated by the arrow 19b from the position indicated by the broken line in the drawing. For this reason, when the sphere 15 rides on the straight groove 11b from the screw groove 11a (when moving from the position indicated by the broken line to the position indicated by the alternate long and short dash line in the drawing), the sphere 15 is moved to the side surface of the screw groove 11a, for example, the screw groove. It is understood that contact (collision) with the surface region 21 close to the linear groove 11b on the side surface of 11a prevents smooth linear movement of the shaft body 11 in the length direction. For this reason, the driving force required for the movement of the shaft body 11 increases intermittently. As a result, the shaft body 11 and the sphere 15 are worn when the linear movement of the shaft body 11 (particularly, linear movement at a high speed) is repeated. May cause problems with durability.

  The feed screw 10 with the linear motion bearing also requires a complicated process for manufacturing the cylindrical sphere holder 18 including the sphere circulation path 18 c that accommodates the sphere 15.

  In the spline of Patent Document 2, round grooves are formed at the corners of both sides of each linear groove of the shaft body and the outer peripheral surface of the shaft body, and a pressing plate for adjusting the clearance between each round groove and the columnar body is installed. In addition, since the taper gib used for driving the holding plate has a complicated configuration installed between the two outer cylinders, complicated steps are required for its manufacture and assembly.

  An object of the present invention is to provide a feed screw with a linear motion bearing that can smoothly move a shaft body linearly in its length direction and is easy to manufacture.

  The inventor has a linear motion bearing in which an outer cylinder and a shaft body are engaged via a columnar body, and a linear motion bearing having a shaft body in which a thread groove and a linear groove intersect each other on the outer peripheral surface. As a result of conducting research based on the new knowledge that this columnar body not only supports the shaft body but also realizes a smooth linear movement of the shaft body by adopting it as an attached feed screw, the present invention Reached.

  The present invention provides the above-described shaft body of a feed screw in which a shaft body having a thread groove on the outer peripheral surface and a nut having a thread groove on an inner peripheral surface disposed around the shaft body are rotatably fitted to each other. A plurality of linear grooves each having a depth smaller than the depth of the thread groove of the shaft body and extending in the axial direction across the thread groove, and the shaft body engaging means. A feed screw with a linear motion bearing including a linear motion bearing having an outer cylinder that is slidably accommodated in a non-rotatable manner, wherein the engagement means is accommodated in each linear groove of the shaft body. A feed screw with a linear motion bearing is characterized by being a columnar body extending in the axial direction.

The preferable aspect of the feed screw with a linear motion bearing of this invention is as follows.
(1) Each columnar body has a length exceeding twice the pitch of the thread groove.
(2) Each of the shaft body and each columnar body cut along a direction perpendicular to the central axis of the shaft body has a circular cross section, and the shape of each linear groove of the shaft body in the cross section is the radius of the columnar body. The center of the arc, the center of the columnar body, and the center of the shaft body are set in a straight line. More preferably, the radius of the arc of the straight groove is in the range of 1.01 to 1.4 times the radius of the columnar body.
(3) In the aspect of the above (2), a plurality of linear grooves for accommodating the respective columnar bodies are provided on the inner peripheral surface of the outer cylinder. More preferably, a pair of circumferential grooves are formed on the inner circumferential surface of the outer cylinder with a space between each other, and an annular stopper is provided in a state where the outer circumferential portion is fitted to each circumferential groove, and Each said columnar body is arrange | positioned between the inner peripheral parts of both annular stoppers.
(4) The number of linear grooves of the shaft body is three or more.
(5) A fluororesin thin film or a diamond-like carbon thin film is formed on the outer peripheral surface of the shaft body, the inner peripheral surface of the nut, the inner peripheral surface of the outer cylinder, or the outer peripheral surface of each columnar body.
(6) The shaft body and the nut are fitted together via a plurality of balls disposed between the screw grooves.

  In the feed screw with a linear motion bearing of the present invention, a shaft body in which thread grooves and linear grooves intersect with each other is formed on the outer peripheral surface by linear motion bearings via columnar bodies accommodated in the linear grooves. Since this columnar body does not collide with the side surface of the screw groove when moving along the linear groove of the shaft body, the shaft body can be smoothly linearly moved in the length direction.

  In addition, the feed screw with a linear motion bearing according to the present invention uses a linear motion bearing having a simple structure including a columnar body as an engaging means between the outer cylinder and the shaft body, and further rounds each linear groove of the shaft body. It is not necessary to form a groove, and it is very easy to manufacture because it does not have a complicated structure cage, presser plate, and tapered gib that form a spherical circulation path, and therefore it is not necessary to divide the outer cylinder in two. It is.

It is sectional drawing which shows the structure of the conventional feed screw with a linear motion bearing. It is sectional drawing of the feed screw 10 with a linear motion bearing cut | disconnected along the cutting line II-II line entered in FIG. FIG. 3 is an enlarged view of a shaft body 11 and a sphere 15 shown in FIG. 2. FIG. 4 is a plan view of a shaft body 11 and a sphere 15 shown in FIG. 3. It is sectional drawing which shows the structural example of the feed screw with a linear motion bearing of this invention. It is sectional drawing of the feed screw 50 with a linear motion bearing cut | disconnected along the cutting line VI-VI line entered in FIG. It is sectional drawing which shows another structural example of the feed screw with a linear motion bearing of this invention. It is sectional drawing of the feed screw 70 with a linear motion bearing cut | disconnected along the cutting line VIII-VIII line entered in FIG.

  A feed screw with a linear motion bearing of the present invention will be described with reference to the accompanying drawings. FIG. 5 is a cross-sectional view showing a configuration example of a feed screw with a linear motion bearing of the present invention. 6 is a cross-sectional view of the feed screw 50 with a linear motion bearing cut along the cutting line VI-VI entered in FIG.

  In the feed screw 50 with a linear motion bearing according to the present invention, a shaft body 51 having a thread groove 51a on the outer peripheral surface and a nut 52 having a thread groove 52a on the inner peripheral surface disposed around the shaft body 51 rotate with each other. A plurality of shafts 51 each having a depth smaller than the depth of the thread groove 51a of the shaft body 51 and extending in the axial direction across the thread groove 51a on the outer peripheral surface of the shaft body 51 of the feed screw 54 that can be fitted together. A linear groove 51b is formed, and a linear motion bearing 57 having an outer cylinder 56 that slidably accommodates the shaft body 51 through an engagement means without rotation is provided. The feed screw 50 with linear motion bearing of the present invention is mainly characterized in that a columnar body 55 that is accommodated in each linear groove 51b of the shaft body 51 and extends in the axial direction is used as the engaging means.

  There are various methods for driving the feed screw with the linear motion bearing depending on the configuration of the mechanical device to be attached. For example, the shaft body 51 can be rotated in the circumferential direction together with the outer cylinder 56 by rotating the outer cylinder 56 of the linear motion bearing 57 in the circumferential direction. Further, for example, the shaft body 51 can be linearly moved in the length direction (axial direction) by rotating and moving the nut 52 of the feed screw 54 in the circumferential direction. The movement of the nut 52 in the length direction of the shaft body 51 caused by the rotational movement of the shaft body 51 can be prevented, for example, by rotating the nut 52 in the same direction as the shaft body 51.

  The shaft body 51 of the feed screw 50 with linear motion bearing moves linearly (slids) while being supported by the columnar body 55 accommodated in each linear groove 51b. At this time, each columnar body 55 moves along the linear groove 51b while being guided by the linear groove 51b (moves relatively to the shaft body 51), and therefore collides with the side surface of the screw groove 51a of the shaft body 51. It is hard to do. For this reason, the shaft body 51 can be smoothly linearly moved in the length direction.

  The feed screw 50 with a linear motion bearing intermittently increases the driving force when the shaft body 51 is moved linearly (particularly at a high speed), and wear of the shaft body 51 and the columnar body 55 based on the increase in the driving force. Therefore, it can be used particularly advantageously as a component that constitutes an electronic component mounting apparatus in which linear movement at high speed is repeated.

  Further, the feed screw 50 with a linear motion bearing uses a linear motion bearing 57 having a simple structure including a columnar body 55 as an engagement means between the outer cylinder 56 and the shaft body 51, and is provided in each linear groove of the shaft body. Further, it is not necessary to form a round groove, and it is not provided with a complicated structure cage, presser plate, and taper gib that form a spherical circulation path, and therefore it is not necessary to divide the outer cylinder into two parts. Very easy.

  Each columnar body 55 preferably has a length exceeding twice the pitch of the thread grooves 51 a of the shaft body 51. Thereby, when the shaft body 51 moves in the length direction, the respective columnar bodies 55 are always supported by the linear groove portions formed on the adjacent thread of the shaft body 51 and stably disposed. Accordingly, since the tilt movement of each columnar body 55 with respect to the central axis of the shaft body 51 is suppressed, the shaft bodies 51 supported by these columnar bodies 55 linearly move with high accuracy. Usually, the length of each columnar body 55 is set to a value smaller than the length of the outer cylinder 56.

As shown in FIG. 6, each of the shaft body 51 and each columnar body 55 cut along a direction perpendicular to the central axis of the shaft body 51 has a circular cross section, and each linear groove of the shaft body 51 in the cross section. shape 51b is being shaped arc a having a large radius R ₂ than the radius R ₁ of the columnar body 55, the center O ₁ of the arc a, the center O ₂ of the columnar body 55, the shaft body 51 The center O ₃ is preferably set so as to be aligned on a straight line (above the straight line L).

As described above, when the shape of each linear groove 51 b of the shaft body 51 is the shape of the arc A having the radius R ₂ larger than the radius R _{1 of the} columnar body 55, each columnar body 55 is a straight line of the shaft body 51. Line contact is made with the inner surface of the groove 51b. The shaft body 51 is in a state in which a load is applied in a direction from each columnar body 55 sandwiched between the outer cylinder 56 and the shaft body 51 toward the center O _{3 of the} shaft body 51, while the shaft 51 The body 51 is closely supported by the plurality of columnar bodies 55 in a state where almost no load is applied in the circumferential direction.

Therefore, when a load is applied to the shaft body 51 in the circumferential direction, the radius R ₂ of the arc A of each linear groove 51b of the shaft body 51 is larger than the radius R ₁ of the columnar body 55, Since a slight gap is formed between the two, the shaft body 51 can be slightly rotated (slightly rotated) in the circumferential direction. However, when the rotational movement of the shaft body 51 proceeds (when the angle of the rotational movement of the shaft body 51 increases), the engagement of the linear grooves 51b of the shaft body 51 and the respective columnar bodies 55 causes the shaft body 51 to further move. The rotational movement is prevented. When the application of the load to the shaft body 51 is stopped, the shaft body 51 is the direction of the fine rotation so that each columnar body 55 is arranged at the position where the depth of each linear groove 51b is the largest. A slight rotation in the reverse direction returns to the initial position shown in FIG.

  A large load may be momentarily applied to the shaft body of the feed screw with a linear motion bearing in the circumferential direction. For example, a shaft body of a feed screw with a linear motion bearing incorporated in an electronic component mounting apparatus has a structure in which an outer cylinder is rotated and moved together with the shaft body at a high speed (with a large acceleration) in order to rotate the electronic component. A large load may be momentarily applied in the circumferential direction. In addition, for example, when external vibration (eg, vibration generated by a driving device that linearly moves or rotationally moves the shaft body at high speed in the electronic component device apparatus) is applied to the shaft body, A load may be momentarily applied in the circumferential direction.

  In order to prevent rotational movement of the shaft body in the circumferential direction of the spline of Patent Document 2, the columnar body accommodated in each round groove of each linear groove is formed by a pressing plate provided inside the outer cylinder. Each is pressed against each circular groove so as to rotate and move the shafts in opposite directions. Thus, the shaft body is tightly supported by the plurality of columnar bodies pressed against the respective round grooves of the linear groove so as not to rotate and move in the circumferential direction. For this reason, when a large load is momentarily applied in the circumferential direction of the shaft body as described above, the friction between the shaft body and the columnar body increases, and the wear tends to occur in each. For this reason, the spline of the same literature may not exhibit sufficient durability as a component of an electronic component mounting apparatus in which the rotational movement and linear movement of the shaft body are repeated at high speed.

  In the feed screw with linear motion bearing 50 of the present invention, for example, when a large load is momentarily applied to the shaft body 51 that moves linearly in the circumferential direction, the shaft body 51 is slightly rotated. The increase in friction between the shaft body 51 and the columnar body 55 based on the application of the above is suppressed, and therefore, the occurrence of wear of the shaft body 51 and the columnar body 55 is suppressed. For this reason, the feed screw 50 with a linear motion bearing of the present invention exhibits excellent durability, and therefore is particularly advantageously used as a component constituting an electronic component mounting apparatus in which the shaft body is repeatedly rotated and linearly moved at a high speed. be able to.

The radius R ₂ of the arc A of the linear groove 51b of the shaft body 51 is in the range of 1.01 to 1.4 times (particularly 1.02 to 1.2 times) the radius R ₁ of the columnar body 55. preferable. Thereby, the shaft body 51 can be finely rotated, and the accuracy of the linear movement of the shaft body 51 can be improved. In FIG. 6, the arc A of the linear groove 51 b is written with a radius larger than the actual radius so that the shape of the linear groove 51 b of the shaft body 51 can be easily understood. 5 and 6, the radius R ₂ of the arc A of the linear groove 51 b of the shaft body 51 is actually set to 1.04 times the radius R ₁ of the columnar body 55. ing.

  The depth of the linear groove 51b of the shaft body 51 is 5 to 40% of the diameter of the columnar body 55 (preferably, in order to ensure the prevention of the rotational movement of the shaft body 51 (a large rotational movement exceeding the fine rotation)). Is preferably in the range of 10 to 40%).

  The number of linear grooves of the shaft body 51 (that is, the number corresponding to the number of columnar bodies 55) is preferably 3 or more. The number of linear grooves is more preferably in the range of 3 to 10, and particularly preferably in the range of 3 to 8. When the number of linear grooves is three or more, the shaft body is stably supported by a plurality of columnar bodies accommodated in each linear groove. Further, when the number of linear grooves is 10 or less, the shaft body can be easily manufactured. The plurality of linear grooves of the shaft body are preferably formed at equal intervals on the outer peripheral surface of the shaft body. In addition, a plurality of (for example, 2 to 10) columnar bodies can be accommodated in each linear groove of the shaft body side by side in the length direction of the linear groove.

  A through hole may be formed on the central axis of the shaft body 51. By exhausting the gas inside the through hole from one end of the shaft body, the electronic component is sucked into the opening at the other end of the shaft body (or the suction nozzle of the electronic component connected to the opening). Can be made.

  The “arc shape” used in this specification does not mean only a strict arc shape. When the straight groove is not in the shape of a strict arc, the “arc shape having a radius larger than the radius of the columnar body” used in the present specification means “a radius of curvature larger than the radius of the columnar body”. Or “a shape formed from two or more curves”. And, “the setting that the center of the arc, the center of the columnar body, and the center of the shaft are aligned in a straight line” is “the position where the depth of the linear groove is greatest in the width direction of the linear groove” , “A setting in which the center of the columnar body and the center of the shaft body are aligned in a straight line”. Thus, even when the linear groove is not in the shape of a strict arc, the same fine rotation of the shaft body as described above can be realized.

  As shown in FIGS. 5 and 6, the inner peripheral surface of the outer cylinder 56 of the linear motion bearing 57 is provided with a plurality of linear grooves 56 b that accommodate the respective columnar bodies 55. A pair of circumferential grooves 56a are formed on the inner circumferential surface of the inner circumferential surface of each of the circumferential grooves 56a, and an annular stopper (eg, a known snap ring) 59 in a state where the outer circumferential portion is fitted in each of the circumferential grooves 56a. It is more preferable that each of the columnar bodies 55 is disposed between the inner peripheral portions of the annular stoppers 59.

  By adopting such a configuration, each columnar body 55 disposed between the outer cylinder 56 and the shaft body 51 cannot move relative to the outer cylinder 56. For this reason, jumping out from the end of the outer cylinder 56 of each columnar body 55 is prevented.

  However, each columnar body 55 can be rotationally moved in the circumferential direction. For this reason, each columnar body 55 is slightly rotated in the circumferential direction under the influence of a change in the direction and magnitude of the load applied to the columnar body 55 when the feed screw 50 with a linear motion bearing is used or external vibration. To do. In particular, in the feed screw 50 with a linear motion bearing according to the present invention, the fine rotation generated in the shaft body 51 greatly promotes the fine rotation of each columnar body 55. Thereby, since the extremely uniform wear of the outer peripheral surface of each columnar body 55 is realized, the durability of the feed screw 50 with a linear motion bearing becomes particularly good.

  Each linear groove 56b of the outer cylinder 56 is also in the shape of an arc having a radius larger than the radius of the columnar body 55, like each linear groove 51b of the shaft body 51, and the center of the arc is on the straight line (see FIG. 6 is preferably on the straight line L shown in FIG. A preferable aspect regarding the depth, number, or arrangement of the linear grooves 56b of the outer cylinder 56 is the same as that of the linear grooves 51b of the shaft body 51.

  In addition, when the columnar body 55 is fixed to the outer cylinder 56 directly or indirectly through another part (for example, an annular stopper 59), the straight line is formed on the inner peripheral surface of the outer cylinder 56. The groove 56b may not be provided.

  In the feed screw 50 with the linear motion bearing shown in FIGS. 5 and 6, a plurality of spheres that support the shaft body are circulated as the outer cylinder 56 of the linear motion bearing 57 between the outer cylinder and the shaft body. By using an outer cylinder of a known linear motion bearing as it is, further simplification of the manufacturing is realized. The plurality of linear grooves 56c provided in the outer cylinder 56 are used to form the trajectory of the sphere, and are not used in the present invention.

  The materials forming the shaft body 51, the nut 52, the ball 53, the columnar body 55, the outer cylinder 56, and the annular stopper 59 constituting the feed screw 50 with the linear motion bearing of the present invention are known linear motion bearings. This is the same as the case of the feed screw, and examples thereof include metal materials typified by steel, resin materials, and ceramic materials. If all of these parts are made of a metal material, the rigidity of the feed screw 50 with a linear motion bearing is increased, and the heat resistance is also improved.

  Next, the configuration of the feed screw 54 provided in the feed screw 50 with a linear motion bearing will be described.

  The feed screw 54 has a configuration in which a shaft body 51 having a screw groove 51a on the outer peripheral surface and a nut 52 having a screw groove 52a on an inner peripheral surface arranged around the shaft body 51 are fitted to each other so as to be rotatable relative to each other. Have. As the feed screw 54, a feed screw (ball screw) in which the shaft body 51 and the nut 52 are fitted through a plurality of balls 53 arranged between the screw grooves 51a and 52a is used. ing. The configuration of the feed screw 54 is the same as that of the feed screw 14 shown in FIG. 1 except that the number of linear grooves 51b formed in the shaft body 51 is different.

  In the conventional feed screw with linear motion bearing 10 shown in FIG. 1 and FIG. 2, a sphere 15 is provided between the outer cylinder 16 of the linear motion bearing 17 and the shaft body 11, and the nut 12 and the shaft body 11 of the feed screw 14. A ball 13 is arranged between the two. In the feed screw 10 with a linear motion bearing, since the load is concentrated and applied to the contact position of the shaft body 11 with the sphere 15 or the ball 13, the shaft body 11 is usually subjected to heat treatment to harden the surface thereof. The

  Since the feed screw with a linear motion bearing of the present invention uses a feed screw having a configuration in which a shaft body and a nut are fitted together without a ball as the feed screw, a sphere or a ball is not used. The body can also be manufactured at low cost without heat treatment. Further, since it is not necessary to provide a ball circulation path in the nut of the feed screw, the shape of the nut can be set freely, and it becomes easy to set the nut to a shape suitable for its rotational drive. Since the structure of such a feed screw is well known, no further explanation will be given.

  It is also preferable to form a fluororesin thin film or a diamond-like carbon thin film on the outer peripheral surface of the shaft body, the inner peripheral surface of the nut, the inner peripheral surface of the outer cylinder, or the outer peripheral surface of each columnar body. For example, if a fluororesin thin film or diamond-like carbon thin film is formed on the shaft body, the sliding friction between the shaft body and each columnar body, and the shaft body and the nut is reduced. Especially when a diamond-like carbon thin film is used, the shaft body wear resistance is reduced. Improves. A fluororesin thin film or a diamond-like carbon thin film can be formed on two or more of the outer peripheral surface of the shaft body, the inner peripheral surface of the nut, the inner peripheral surface of the outer cylinder, and the outer peripheral surface of each columnar body. .

  FIG. 7 is a cross-sectional view showing another configuration example of the feed screw with a linear motion bearing of the present invention. 8 is a cross-sectional view of the feed screw 70 with a linear motion bearing cut along the cutting line VIII-VIII written in FIG.

  The configuration of the feed screw 70 with the linear motion bearing shown in FIGS. 7 and 8 is the same as that of the feed screw 50 with the linear motion bearing shown in FIGS. 5 and 6 except that the shape of the outer cylinder 76 provided in the linear motion bearing 77 is different. It is the same.

  The linear motion bearing 77 provided in the feed screw with linear motion bearing 70 has a simple shape in which the outer cylinder 76 has a circular outer peripheral edge and an inner peripheral edge, respectively, and a plurality of linear grooves 76b are formed on the inner peripheral surface. Therefore, its manufacture is easy.

DESCRIPTION OF SYMBOLS 10 Feed screw with a linear motion bearing 11 Shaft 11a Thread groove 11b Linear groove 12 Nut 12a Thread groove 13 Ball 14 Feed screw 15 Sphere 16 Outer cylinder 16b Linear groove 17 Linear motion bearing 18 Cylindrical sphere holder 18a Through groove 18b Non-through Groove 18c Spherical circuit 19a, 19b Arrow indicating the moving direction of the sphere relative to the shaft 21 Surface area near the straight groove on the side surface of the screw groove 50 Feed screw with linear motion bearing 51 Shaft 51a Screw groove 51b Straight groove 52 Nut 52a Thread groove 53 Ball 54 Feed screw 55 Columnar body 56 Outer cylinder 56a Circumferential groove 56b, 56c Linear groove 57 Linear motion bearing 59 Annular stopper 70 Feed screw with linear bearing 76 Outer cylinder 76b Linear groove 77 Linear motion bearing R ₁ Column shape Body radius R ₂ Arc radius of straight groove O ₁ Center of arc of straight groove O ₂ Center of columnar body O ₃ Center of axis A Circle Arc L straight line

Claims (9)

On the outer peripheral surface of the shaft body of the feed screw formed by fitting a shaft body having a thread groove on the outer peripheral surface and a nut having a thread groove on the inner peripheral surface arranged around the shaft body so as to be rotatable relative to each other. A plurality of linear grooves each having a depth smaller than the depth of the thread groove of the shaft body, extending in the axial direction across the thread groove, and the shaft body via the engaging means. A feed screw with a linear motion bearing comprising a linear motion bearing having an outer cylinder slidably accommodated in a non-rotating manner,
A feed screw with a linear motion bearing, wherein the engaging means is a columnar body that is accommodated in each linear groove of the shaft body and extends in the axial direction.   The feed screw with a linear motion bearing according to claim 1, wherein each columnar body has a length exceeding twice the pitch of the thread groove.   Each cross section of the shaft body and each columnar body cut along a direction perpendicular to the central axis of the shaft body is circular, and the shape of each linear groove of the shaft body in the cross section is larger than the radius of the columnar body. The linear motion bearing according to claim 1, wherein the linear bearing has a shape of an arc having a radius, and is set so that the center of the arc, the center of the columnar body, and the center of the shaft body are aligned in a straight line. With feed screw.   The feed screw with a linear motion bearing according to claim 3, wherein the radius of the arc of the straight groove is in the range of 1.01 to 1.4 times the radius of the columnar body.   The feed screw with a linear motion bearing according to claim 3 or 4, wherein a plurality of linear grooves are provided on the inner peripheral surface of the outer cylinder to accommodate the respective columnar bodies.   A pair of circumferential grooves are formed on the inner circumferential surface of the outer cylinder with a space between each other, and an annular stopper is provided in a state in which the outer circumferential portion is fitted to each circumferential groove, and both annular stoppers are provided. The feed screw with a linear motion bearing according to claim 5, wherein each of the columnar bodies is disposed between inner peripheral portions of the tool.   The feed screw with a linear motion bearing according to any one of claims 1 to 6, wherein the number of linear grooves of the shaft body is three or more.   The fluororesin thin film or the diamond-like carbon thin film is formed on the outer peripheral surface of the shaft body, the inner peripheral surface of the nut, the inner peripheral surface of the outer cylinder, or the outer peripheral surface of each columnar body. A feed screw with a linear motion bearing as described in the section.   The feed with a linear motion bearing according to any one of claims 1 to 7, wherein the shaft body and the nut are fitted through a plurality of balls arranged between the thread grooves of the shaft body and the nut. screw.

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