JP3221395U - External circulation ball screw - Google Patents

Abstract

An external circulating ball screw is provided which can realize shortening of the length of a nut, reduction of cost and increase of a displacement stroke. SOLUTION: A screw shaft having an outer spiral groove, a nut 30 having an inner spiral groove, and a return member, the nut externally inserts the screw shaft along the direction of the axis 21 and is disposed between two nut end faces 31. It has a nut outer end face 33 provided and two tube holes 34 disposed on the nut outer end face and in communication with the inner spiral groove, and the inner spiral groove accommodates a plurality of balls. Each tube hole includes a first arc 341, a first straight line 342, a second arc 343, a third arc 345, a second straight line 346, and a fourth arc 347 arranged in order, and the second straight line is a first straight line. Closer to the end face of the nut, the first included angle between the second straight line and the axis is between 88 degrees and 92 degrees. The reflux member is fixed to the nut outer end face 33 and connects the two tube holes to form a ball reflux passage. [Selected figure] Figure 4

Description

  The present invention relates to a ball screw, and more particularly to an external circulating ball screw.

Generally, ball screw types are mainly classified into external circulation type and internal circulation type. Among them, the external circulation ball screw smooth the ball reflux, and the working quality of the general lead and large diameter ball screw is better, while the internal circulation ball screw has a small outer diameter and light weight, so the internal space Is suitable for small devices.

FIG. 1 shows an example of an external circulation screw ball disclosed in Patent Document 1. The external circulation screw ball mainly comprises a screw shaft (not shown) and a nut 11 externally inserted in the screw. A ball (not shown) disposed between the screw shaft and the nut 11, and a reflux member (not shown) disposed on the nut for circulating the reflux of the ball.
The smoothness of this circulation is enhanced by the relationship between the length of the guide portion of the reflux member and the diameter of the ball, but the shape of the tube hole 111 disposed on the nut 11 shortens the length of the nut 11 It has the disadvantages that it can not be done, the cost is high, and the displacement stroke is insufficient. Further, the tube hole 111 has a straight portion 112 near the nut end surface 113, and the angle θ between the extension of the straight portion 112 and the nut end surface 113 is excessive, ie, when the tube hole 111 is excessively inclined, In the design of the length of the nut 11, in order to avoid the occurrence of cracking and insufficient strength of the tube bore, the amount of inclination of the tube bore 111 and the connection between the tube bore 111 and the internal load path must be taken into consideration. It does not.

  In addition, external circulating ball screws currently manufactured in the industry can not meet the nut outer diameter specified by the European Industry Standard (DIN). That is, in addition to the above-mentioned drawbacks and limitations, this main cause is that according to the design of the distance between the tube hole and the locking hole on the nut, the outer diameter of the nut is too large There was a problem that it could not meet the requirements of DIN).

Japanese Patent Application Laid-Open No. 2005-083519

Therefore, an object of the present invention is to provide an external circulating ball screw which can realize shortening of the length of the nut, reduction of cost and increase of displacement stroke.
Another object of the present invention is to provide an external circulating ball screw which can meet the prescribed outer diameter of a nut according to the European Industrial Standard (DIN).

  The external circulation ball screw according to the present invention for solving the above problems comprises a screw shaft, a nut and a return member, the screw shaft being an axis and an outer spiral disposed helically around the axis. A groove, the nut externally fitting the screw shaft along the direction of the axis, and including two nut end faces, and an inner spiral groove helically disposed around the axis; It has a nut outer end face disposed between the two nut end faces, and two tube holes disposed on the nut outer end face and in communication with the inner spiral groove, the inner spiral groove and the outer spiral groove Form a load path for receiving a plurality of balls, and each of the tube holes is arranged in order of a first arc, a first straight line, a second arc, a third arc, a second straight line, and a fourth straight line. And the first straight line is connected to the second arc. While extending through the first arc, the second straight line is connected between the third arc and the fourth arc, and is closer to the end face of the nut than the first straight line, and the second The depression angle between the straight line and the axis is a first depression angle, and the first depression angle is between 88 degrees and 92 degrees, the reflux member is fixed to the nut outer end face, and connects both ends of the load path It has the characteristic that it has the reflux passage which

  According to the above configuration, the tube hole of the nut includes the first arc, the first straight line, the second arc, the third arc, the second straight line, and the fourth arc arranged in order, and the first straight line is The second arc is connected to the second arc and extends through the first arc, the second straight line is connected between the third arc and the fourth arc, and the second straight line is connected to the second straight line more than the first straight line. The end face of the nut is approached, and the depression angle between the second straight line and the axis is a first depression angle, and the first depression angle is between 88 degrees and 92 degrees. Therefore, the second straight line becomes parallel to the end face of the nut, and the problems of shortening the length of the nut, reducing the cost and increasing the displacement stroke can be achieved.

  More preferably, the first depression angle is 90 degrees. This achieves the objectives of shortening the length of the nut, reducing the cost and increasing the displacement stroke.

  More preferably, the first straight line is not parallel to the second straight line. The inner spiral groove of the nut has a lead angle, and an angle between a first straight line of the nut and the axis is a second depression angle, and the second depression angle subtracts the lead angle from 90 degrees. This can improve the smoothness of the ball flow.

  More preferably, the nut further has a locking hole recessed in the nut outer end surface corresponding to the number of the tube holes, and the locking hole is an extension of the first straight line and the second straight line Located within the range of Thereby, if the hole edge of the locking hole is within the above range, shortening of the length of the nut, reduction of cost and increase of the displacement stroke can be achieved. Otherwise, the length of the nut is too long, which increases costs and shortens the displacement stroke.

More preferably, each of the locking holes has a locking hole center, and the nut further has a first connection line connecting the second arc and the third arc, and the first hole is connected from the locking hole center. The vertical distance to the connecting line is 1 to 1.5 times the diameter of the ball. Thereby, when the vertical distance from the center of the locking hole to the first connection line is 1 to 1.5 times the diameter of the ball, the outer diameter of the nut becomes relatively small, and the European Industrial Standard (DIN Can meet the specified outer diameter of the nut.
Conversely, if the vertical distance from the locking hole center to the first connection line is 1.5 times or more the diameter of the ball, the distance between the locking hole and the tube hole becomes too long, and the screw is Is projected from the reflux member. For this reason, it is necessary to increase the diameter of the nut, and furthermore, it is not possible to satisfy the prescribed outer diameter of the nut according to the European Industrial Standard (DIN).
If the vertical distance from the center of the locking hole to the first connection line is less than one time the diameter of the ball, the locking hole is too close to the tube hole, the thickness of the nut becomes too thin, and the engagement of the screw There is not enough stopping power.

  More preferably, the first connection line is 1.1 to 1.4 times the diameter of the ball. This improves the smoothness of the ball flow, and prevents the length of the nut from becoming too long and the tube hole being too small to deform the ball and making the ball flow non-smooth.

The external circulation ball screw of the present invention has at least the following effects.
(1) The second straight line becomes parallel to the end face of the nut, and shortening of the length of the nut, reduction of cost and increase of displacement stroke can be achieved.
(2) When the vertical distance from the center of the locking hole to the first connection line is 1 to 1.5 times the diameter of the ball, the outer diameter of the nut becomes relatively small. Can meet the specified outer diameter of the nut.
(3) The first straight line of the nut tube hole is configured not to be parallel to the second straight line, and at the same time the second wedge angle between the one straight line and the axis line is 90 degrees The lead angle is subtracted. Therefore, the smoothness of the ball flow can be improved.
In addition, when the first connection line of the tube hole is 1.1 to 1.4 times the diameter of the ball, the smoothness of the flow of the ball can be improved as described above. In addition, it is possible to avoid that the tube hole is too large and the length of the nut is too long, and the tube hole is too small to deform the ball and the flow of the ball is not smooth.

FIG. 5 is a cross-sectional view showing an external circulation ball screw according to Patent Document 1; 1 is an exploded perspective view of an embodiment of the present invention. FIG. 1 is an overall perspective view of an embodiment of the present invention. FIG. 1 is a plan view of an embodiment of the present invention showing the state of the nut viewed from above. FIG. 5 is a close-up view of an embodiment of the present invention showing an enlarged view of the tube bore of the nut; FIG. 6 is a cross-sectional view of an embodiment of the present invention showing a cross-sectional view along line 6-6 of FIG. 3;

  The external circulation ball screw according to the present invention will be specifically described below with reference to the drawings.

  The external circulation ball screw according to the present invention comprises a screw shaft 20, a nut 30, two guide members 40, and a return member 50, as shown in FIGS. Each component will be described below.

  The screw shaft 20 has an axis 21 and an outer spiral groove 22 helically disposed around the axis 21.

  The nut 30 externally fits the screw shaft 20 along the direction of the axis 21 and further includes two nut end faces 31, and an inner spiral groove 32 spirally disposed around the axis 21; It has a nut outer end face 33 disposed between the two nut end faces 31 and two tube holes 34 disposed on the nut outer end face 33 and in communication with the inner spiral groove 32. Among them, the inner spiral groove 32 and the outer spiral groove 22 form a load path for accommodating the plurality of balls 91.

  The tube holes 34 have a first arc 341, a first straight line 342, a second arc 343, a first connection line 344, a third arc 345, a second straight line 346, a fourth arc 347, and a second arc 341, which are disposed in order. Connection line 348 is included. The first straight line 342 is connected to the second arc 343 and extends through the first arc 341, and the connection line 344 is connected between the second arc 343 and the third arc 345. The second straight line 346 is connected between the third arc 345 and the fourth arc 347, and the second connection line 348 is connected between the fourth arc 347 and the first arc 341.

  As used herein, the term "connected" means that a straight or connecting line is connected to the end point (or end point) of the corresponding arc.

  Among them, the second straight line 346 is closer to the nut end surface 31 than the first straight line 342, and the depression angle between the second straight line 346 and the axis line 21 is a first depression angle θ1. The first depression angle θ1 is 90 degrees, but is not limited thereto. Said first included angle θ1 lies between 88 ° and 92 °, ie 90 ° is optimal. In practical situations, plus or minus two degree machining tolerances can be tolerated.

  Further, in the present embodiment, the first straight line 342 is not parallel to the second straight line 346. At the same time, the inner spiral groove 32 of the nut 30 has a lead angle θ2. The angle between the first straight line 342 of the nut 30 and the axis line 21 is a second depression angle θ3, and the second depression angle θ3 is obtained by subtracting the lead angle θ2 from 90 degrees.

  Furthermore, in the present embodiment, the nut 30 further has a locking hole 35 recessed in the nut outer end surface 33 in accordance with the number of the tube holes 34, and the locking hole 35 has the first straight line. 342 and an extension of the second straight line 346. At the same time, each locking hole 35 has a center 351 of the locking hole 35, and the nut 30 further has a first connection line 344 connecting the second arc 343 and the third arc 345, the locking The vertical distance L 1 from the hole center 351 to the first connection line 344 is 1 to 1.5 times the diameter of the ball 91. In addition, the first connection line 344 is 1 to 1.4 times the diameter of the ball 91.

  Each of the guide members 40 includes a pair of locking portions 41 corresponding to the locking holes 35, and a guide portion 42 connected to the locking portions 41 and mounted on the tube hole 34 and the load path. Have. Thereby, the entry and exit of the ball 91 to the nut 30 are guided.

  The reflux member 50 has a reflux passage 51 fixed to the nut outer end surface 33 and connecting both ends of the load path. In the present embodiment, the reflux member 50 and the guide are inserted by being inserted into the reflux member 50 via the screws 92 and by locking the locking portions 41 of the respective guide members 40 in the locking holes 35 of the nut 30. The member 40 and the nut 30 are integrally fixed.

The above is the description of the main components of the external circulation ball screw according to the embodiment of the present invention. The actions and effects of the present invention will be described below.

<a> Shortening of nut length, reduction of cost, increase of displacement stroke The tube holes 34 of the nut 30 according to the present invention are a first arc 341, a first straight line 342, a second arc 343, arranged in order. The first straight line 342 is connected to the second circular arc 343 and includes the first connecting line 344, the third circular arc 345, the second straight line 346, the fourth circular arc 347, and the second connecting line 348 342 extends through the first arc 341, the second straight line 346 is connected between the third arc 345 and the fourth arc 347, and the second straight line 346 is from the first straight line 342. Also, the nut approaches the end face 31 of the nut, and at the same time, the depression angle between the second straight line 346 and the axis line 21 is taken as a first depression angle θ1, and the first depression angle θ1 is 90 degrees. As a result, the second straight line 346 becomes parallel to the nut end face 31 and the distance between the nut end face 31 and the second straight line 346 of the tube hole 34 can be controlled to the minimum distance. The objectives of shortening the length, reducing the cost and increasing the displacement stroke can be achieved.
Further, by positioning the locking hole 35 of the nut 30 within the range of the extension lines of the first straight line 342 and the second straight line 346, the locking hole 35 is a nut end face 31 than the second straight line 346. As a result, the length of the nut 30 can be shortened, the cost can be reduced, and the purpose of increasing the displacement stroke can be achieved.

<B> Reduction of the outer diameter of the nut and fulfillment of the requirements of the European Industrial Standard (DIN) The vertical distance L1 from the locking hole center 351 of the locking hole 35 of the nut 30 to the first connection line 344 is the ball By setting the diameter to 1 to 1.5 times the diameter of 91, the outer diameter of the nut 30 becomes relatively small, so that the defined outer diameter dimension of the nut according to the European Industrial Standard (DIN) can be satisfied.
Conversely, if the vertical distance L1 from the locking hole center 351 to the first connection line 344 is 1.5 times or more the diameter of the ball 91, the distance between the locking hole 35 and the tube hole 34 Become too far, and the screw 92 comes to project from the reflux member 50. For this reason, it is necessary to increase the diameter of the nut 30, and furthermore, it becomes impossible to satisfy the prescribed outer diameter of the nut according to the European Industrial Standard (DIN).
When the vertical distance L1 from the locking hole center 351 to the first connection line 344 is less than one time the diameter of the ball 91, the locking hole 35 is too close to the tube hole 34, and the thickness of the nut 30 is It becomes too thin and the locking force of the screw becomes insufficient.

<Ha> Improving the Smoothness of the Ball Flow The first straight line 342 of the tube hole 34 of the nut 30 is configured not to be parallel to the second straight line 346, and at the same time, the one straight line 342 and the axis 21 And the lead angle .theta.2 of the nut 30 is subtracted from 90.degree. Therefore, the smoothness of the flow of the balls 91 can be improved.
When the first connection line 344 of the tube hole 34 is 1.1 to 1.4 times the diameter of the ball 91, the smoothness of the flow of the ball 91 can be improved as described above. In addition, it can be avoided that the tube hole 34 is too large and the length of the nut 30 is too long, and the tube hole 34 is too small to deform the ball 91 and the flow of the ball 91 is not smooth.

11 nut 111 tube hole 112 straight portion 113 nut end face θ depression angle 20 screw shaft 21 axis 22 outer spiral groove 30 nut 31 nut end face 32 inner spiral groove 33 nut outer end face 34 tube hole 341 first arc 342 first straight 343 second arc 344 1st connection line 345 3rd circular arc 346 2nd straight line 347 4th circular arc 348 2nd connection line 35 locking hole 351 locking hole center 40 guide member 41 locking portion 42 guide portion 50 reflux member 51 reflux passage 91 ball 92 Screw θ1 first wedge angle θ2 lead angle θ3 second wedge angle L1 vertical distance

Claims (5)

External circulation ball screw,
Including a screw shaft, a nut and a return member,
The screw shaft has an axis and an outer spiral groove disposed helically around the axis;
The nut externally fits the screw shaft along the direction of the axis, includes two nut end faces, and an inner spiral groove spirally disposed around the axis, and between the two nut end faces. A nut outer end face disposed, and two tube holes disposed on the nut outer end face and in communication with the inner spiral groove;
The inner spiral groove and the outer spiral groove form a load path for receiving a plurality of balls,
Each of the tube holes includes a first arc, a first straight line, a second arc, a third arc, a second straight line, and a fourth arc arranged in order;
The first straight line is connected to the second arc and extends through the first arc,
The second straight line is connected between the third circular arc and the fourth circular arc and approaches the nut end face more than the first straight line,
A depression angle between the second straight line and the axis line is a first depression angle,
The first depression angle is between 88 degrees and 92 degrees,
The reflux member is fixed to the outer end face of the nut, and has a reflux passage connecting both ends of the load path.
External circulating ball screw.   The external circulation ball screw according to claim 1, wherein the first straight line is not parallel to the second straight line.   The inner spiral groove of the nut has a lead angle, and an angle between a first straight line of the nut and the axis is a second depression angle, and the lead angle is subtracted from the second depression angle of 90 degrees. The external circulating ball screw according to claim 2, characterized in that:   The nut further has a locking hole recessed in the nut outer end surface corresponding to the number of the tube holes, and the locking hole is within the range of the first straight line and the extension line of the second straight line. The external circulating ball screw according to claim 1, characterized in that it is located.   Each of the locking holes has a locking hole center, and the nut further has a first connection line connecting the second arc and the third arc, and the nut from the center of the locking hole to the first connection line 5. The external circulating ball screw according to claim 4, wherein the vertical distance is 1 to 1.5 times the diameter of the ball.

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