JP2006125544A - Ball screw device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ball screw device capable of improving durability, realizing high speed and large ball diameter, and further reducing vibration and improving operability. provide.
A ball circulation path 21 in a circulating component 17 that lifts a ball 15 rolling on a spiral track in a substantially tangential direction of the spiral track is lifted from the spiral track by a tongue portion 19a of a leg portion 19. Is provided to the outside of the nut 14, and the radius of curvature r 1 of the ball center locus 42 of the first curved path R 1 is 1.5 times or more the diameter of the ball 15.
[Selection] Figure 1

Description

  The present invention relates to a ball screw device used in various machine devices such as machine tools and injection molding machines.

FIG. 6 shows an example of a conventional circulation tube type ball screw device. This ball screw device 1 includes a screw shaft 3 having a helical thread groove 2 on the outer peripheral surface and a screw groove 2 on the inner peripheral surface. A nut 6 having a helical thread groove 4 corresponding to is screwed together.
The screw groove 4 of the nut 6 and the screw groove 2 of the screw shaft 3 face each other to form a spiral track, and a large number of balls 5 as rolling elements can roll on the spiral track. It is loaded. The nut 6 (or the screw shaft 3) is moved in the axial direction through the rolling of the ball 5 by the rotation of the screw shaft 3 (or the nut 6).

  Further, a part of the outer peripheral surface of the nut 6 is a flat surface, and a pair of circulation holes 7 communicating with both screw grooves 2 and 4 are formed on the flat surface so as to straddle the screw shaft 3, and this pair of circulations By fitting both ends of a tube-shaped circulation component 8 having a substantially U-shape into the hole 7, the ball 5 revolving along the spiral orbit between the screw grooves 2 and 4 is introduced from the middle of the spiral orbit into the circulation component 8. The ball 5 is rolled up and returned to the original load trajectory, whereby the ball 5 is infinitely circulated.

  By the way, in such a tube-type circulation part, since the ball 5 is completely separated from the screw groove 4 of the nut 6 from the side surface direction of the nut 6 and is an external circulation system that can be multi-rowed, especially for a small lead product. It is suitable for high load capacity. However, with the recent increase in the rotation of the ball screw device, the speed at which the ball collides with the circulating component increases and the collision energy increases. As shown in FIG. 7 and FIG. 8, the ball screw in which the direction of scooping up the balls by the circulating parts is inclined substantially in the tangential direction of the spiral track is damaged. The present applicant has previously proposed a device (Japanese Patent Application No. 2003-318123). In addition, in FIG. 8, the nut cross section of less than 1 volume is drawn for convenience of explanation.

As shown in FIGS. 7 and 8, the ball screw device 10 has a screw shaft 12 having a spiral thread groove 11 on the outer peripheral surface and a spiral screw groove 13 corresponding to the screw groove 11 on the inner peripheral surface. A nut 14 having a nut 14 is fitted, and the screw groove 13 of the nut 14 and the screw groove 11 of the screw shaft 12 face each other to form a spiral track that receives a load therebetween.
A large number of balls 15 as rolling elements are slidably loaded in the spiral track, and the nut 14 (or screw shaft 12) rolls the ball 15 by the rotation of the screw shaft 12 (or nut 14). It moves in the axial direction.

A flat surface 14 a is formed on a part of the circumferential side surface of the nut 14, and a pair of circulation holes 20 are drilled in the flat surface 14 a in a direction substantially orthogonal to the axis of the nut 14. The circulation component 17 is fixed to the circulation hole 20 by a set screw or the like via a presser (cap or the like) (not shown).
The circulation component 17 includes a pair of legs 19 fitted in the pair of circulation holes 20 and a main body 17 a connecting the pair of legs 19, and the inside is a circulation path 21 of the ball 15. The divided body 22 (see FIG. 9) divided into two in a point-symmetric manner along the substantially circular direction of the ball circulation path 21 is assembled by joining together at a divided surface. A circulation groove 21 a constituting the circulation path 21 is formed.

The pair of leg portions 19 are spaced apart from each other in the axial direction of the screw shaft 12 and spaced apart from each other substantially in the path direction of the screw shaft 12, and are provided with tongue portions 19 a ( As shown in FIG. 9, the ball 15 rolling on the spiral track between the screw grooves 11 and 13 is scooped up in a substantially tangential direction of the spiral track.
Further, in this example, when the angle seen from the axial center of the screw shaft 12 at the scooping point where the ball 15 is separated from the spiral trajectory is the apparent scooping angle γ, the apparent scooping angle γ is increased to some extent. Thus, the number of balls 15 to be loaded is increased, thereby increasing the load capacity of the ball screw device. The apparent scooping angle γ is in the range of 0 <θ ≦ 90 ° (substantially about 20 to 45 °).

Then, by this circulating component 17, the ball 15 that rolls on the spiral track between the screw grooves 11 and 13 is scooped up from one leg 19 and guided into the body 17 a outside the nut 14, and the other leg 19 An infinite circulation trajectory of the ball returning to the spiral trajectory is formed.
In this way, the ball 15 is scooped up at the scooping point in a direction substantially tangential to the spiral trajectory, so that the ball 15 smoothly enters and exits between the circulating component 17 and the spiral trajectory. 12, the impact force of the ball 15 against the tongue 19a or the like of the circulating component 17 is reduced, and thereby, the speed can be increased as compared with the conventional tube circulating ball screw device or the like.

  However, as described above, when the ball 15 is scooped up in the substantially tangential direction of the spiral trajectory (in the lead angle direction at the apparent scooping angle γ position), the change in angle at the scooping point is small, so that the inside of the circulating component 17 When the ball circulation path 21 of the circulation part 17 is complicated and the protrusion dimension of the circulation part 17 from the nut 14 of the main body 17a is to be reduced, the bending R in the ball circulation path 21 must be reduced or the bending angle must be increased. Therefore, the reaction force at the time of changing the direction of the ball 15 in which the circulating component 17 moves is likely to increase, and wear in the ball circulation path 21 or clogging of the ball 15 may occur.

For this reason, the durability in the ball circulation path 21 is lowered, and there is a limit to the increase in speed and the diameter of the ball due to the occurrence of vibration. There is concern about deterioration of characteristics.
The present invention has been made in order to eliminate such inconveniences, and it is possible to easily achieve the scooping of the ball in the substantially tangential direction of the spiral trajectory as well as to improve the durability. An object of the present invention is to provide a ball screw device that can achieve high speed and a large ball diameter, and that can reduce vibration and improve operability.

In order to achieve the above object, the invention according to claim 1 is directed to a screw shaft having a spiral thread groove on the outer peripheral surface, and a spiral thread groove corresponding to the screw groove of the screw shaft on the inner peripheral surface. A nut that is screwed onto the screw shaft, a plurality of balls that are slidably loaded on the spiral track between the screw grooves, and the ball that rolls on the spiral track. Ball circulation that leads to the outside of the nut from one circulation hole of a pair of circulation holes drilled in a direction substantially perpendicular to the axis of the nut on the side surface in the direction, and returns to the spiral track from the other circulation hole In a ball screw device including a circulating component having both ends fitted to each circulation hole to form a path therein,
The circulation component is fitted to the circulation hole of the nut at both ends, and has a pair of tongue portions that roll up the ball that rolls the spiral track at each end in a substantially tangential direction of the spiral track. A leg, and a main body connecting the pair of legs,
The ball circulation path in the circulation part includes a first curved path that guides the ball scooped up from the spiral track by the tongue portion of the leg portion to the outside of the nut, and the first curved path. The radius of curvature of the ball center trajectory of the path is 1.5 times or more the diameter of the ball.

The invention according to claim 2 is characterized in that, in claim 1, the ball center trajectory of each curved path in the ball circulation path including the first curved path and the ball center trajectory of the straight path are connected by a tangent line. And
According to a third aspect of the present invention, in the first or second aspect, the ball center trajectory of the first curved path is changed to the next curved path or straight line before the ball center trajectory becomes parallel to the outer diameter of the leg portion. It is characterized by being connected by a tangent to the ball center locus of the route.
According to a fourth aspect of the present invention, in any one of the first to third aspects, the circulating component is divided into two or more along a substantially path direction of the ball circulation path.

According to the present invention, the ball circulation path in the circulation component has the first curved path for guiding the ball scooped up from the spiral track by the tongue portion of the leg part to the outside of the nut, and the first curved line. Since the radius of curvature of the ball center trajectory of the path is 1.5 times or more of the diameter of the ball, the reaction force when changing the direction of the ball acting on the inner wall of the ball circulation path can be reduced. Wear in the path can be suppressed, and the clogging of the ball can be prevented, and a smooth movement of the ball can be ensured.
As a result, it is possible to improve durability and operability, and since vibration is reduced, it is possible to realize high speed, a large ball diameter and low noise, and the circulating parts are made of resin or the like. Even the material can cope with a large ball diameter.

  Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic perspective view for explaining a circulating component (divided body) of a ball screw device which is an example of an embodiment of the present invention. FIG. 2 is a curvature radius and a DN value of a ball circulating path (ball center locus). FIG. 3 is a graph showing a comparison of the ball circulation path (ball center locus) seen from the axial direction of the screw shaft, and FIG. 4 is a ball circulation path (ball) seen from the lead angle direction of the screw shaft. FIG. 5 is an explanatory diagram for explaining a connection example between the first curved path R1 and the second curved path R2. In this embodiment, only differences from the ball screw device already described with reference to FIGS. 7 to 9 will be described, and reference numerals of overlapping or corresponding members will be described with reference to FIGS.

  As shown in FIG. 1, the ball screw device which is an example of the embodiment of the present invention is configured such that the ball circulation path 21 in the circulation component 17 is spirally formed between the screw grooves 11 and 13 by the tongue 19 a of the leg 19. A first curved path R1 for guiding the ball 15 scooped up from the track to the outside of the nut 14 is provided, and the radius of curvature r1 of the ball center path 42 of the ball circulation path 21 in the first curved path R1 is set to the diameter of the ball. 1.5 times or more.

Details will be described below.
FIG. 1 schematically shows a divided body 22 in which the circulation component 17 is divided into two in a point-symmetric manner along the substantially circular direction of the ball circulation path 21.
Here, reference numeral 40 in the figure denotes a ball center trajectory of a spiral trajectory (loading zone), 41 denotes a tangent to the spiral trajectory (crawling up direction), 42 denotes a ball center trajectory of the ball circulation path 21, and 43 denotes scooping up in design. An apparent scooping position on the BCD at a point, 44 is a scooping completion point, and a tip position of the tongue portion 19a (= position where the ball 15 is considered to have entered the ball circulation path 21), 45 is a first curving path R1 The bending start point of the ball center locus 42, 46 is the straight line starting point of the ball center locus 42 in the straight path S1 between the first bending path R1 and the second bending path R2, and 47 is the second bending path R2. The bending start point 48 of the ball center trajectory 42 is the starting point of the straight path S2 from the bending completion point of the second curved path R2 to the return symmetry point 50.

Here, the return symmetry point 50 is an intermediate point of the ball circulation path 21 and is a symmetry point when the circulation component 17 is divided into two parts in a point-symmetrical direction along the ball circulation path 21. In the figure, Z is the axial direction of the screw shaft 12, Y is the direction perpendicular to the flat surface 14a of the nut 14, and X is the direction along the width direction of the flat surface 14a of the nut 14.
As can be seen from FIG. 1, since the ball 15 is scooped up in the tangential direction of the spiral trajectory, a straight path S3 from the scooping-up point 43 in the vicinity of the tongue 19a to the scooping-up completion point 44 is defined as a straight path S3. The power applied to is relaxed. In the conventional tube-type circulation component, since the direction is forcibly changed in the Y-axis direction of FIG. 1 at the portion of the straight path S3, the repeated load on the tongue portion is large.

FIG. 2 shows a result of testing how much high speed rotation can be realized in the curved path in the ball circulation path 21 of the circulation component 17. The test was performed by changing the radius of curvature of the ball center trajectory in the curved path of the ball circulation path 21 and judging whether or not abnormal wear occurred in the wall portion in the ball circulation path 21 when traveling for 1000 km.
The test conditions are as follows.
Screw shaft diameter: 63mm
Lead: 16mm
Circulating parts material: POM
Nut outer diameter temperature: 80 ° C

As shown in FIG. 2, when the radius of curvature of the curved path of the ball circulation path 21 is about 1.5 times the ball diameter, the DN value required for the current high-speed ball screw device can be about 200,000. It can be seen that the tendency to increase DN becomes larger at double or more.
Thus, in this embodiment, the radius of curvature r1 of the ball center locus 42 of the first curved path R1 close to the scooping point 43 of the ball 15 in the curved path of the ball circulation path 21 is the circulating component 17. Therefore, the radius of curvature r1 is set to be 1.5 times the ball diameter or more.
Note that if the radius of curvature r1 of the first curved path R1 is simply increased, the ball circulation path 21 may turn outward, and the projecting dimension of the circulation part 17 from the nut 14 of the body 17a may increase.

3 and 4 show examples of arrangement of the ball center trajectory of the ball circulation path 21 that can reduce the projecting dimension of the main body 17a of the circulation component 17 from the nut 14 and make the nut 14 compact.
3A and 3B are views showing a ball circulation path 21 (ball center locus) viewed from the axial direction of the screw shaft 12, wherein FIG. 3A is an example of the present invention, FIG. 4B is a comparative example, and FIG. FIGS. 12A and 12B are views of a ball circulation path 21 (ball center locus) viewed from the lead angle direction of FIG. 12, in which FIG. Further, the parts a to d in FIG. 4 correspond to the parts a to d in FIG. 3.

In the comparative example of FIG. 3B and FIG. 4B, the ball center locus of the first curved path R1 and the ball center locus of the second curved path R2 are connected in the Y-axis direction in the figure. . The reason for adopting such a connection is to simplify the design including the presser and the like in the same manner as the tube-type circulation part after the second curved path R2.
On the other hand, in the example of the present invention shown in FIGS. 3A and 4A, in order to smoothly connect the tangential scooping position 43 of the ball 15 to the return symmetry point 50, the first curved path R1. Are connected in a plane inclined by α ° with respect to the Y axis. That is, the ball center locus of the first curved path R1 is connected to the ball center locus of the second curved path R2 before the ball center locus becomes parallel to the outer diameter of the leg portion 19. The value of α is preferably about 5 to 15 ° from the shape of the normal circulating component 17.

  Originally, connecting the tangential scooping position 43 and the return symmetry point 50 with one large R is ideal for ensuring smooth movement of the ball 15 in the ball circulation path 21, but the circulation component 17 Are arranged on the flat surface 14a of the nut 14 to form a multi-circuit, and from the viewpoint of simplifying the processing of the circulation hole 20, the path connecting the first curved path R1 and the second curved path R2 It is said.

  The ball center trajectory of the first curved path R1 and the ball center trajectory of the second curved path R2 may be directly connected at the angle α described above, but as shown in FIG. 5, via the extremely short straight path S1. May be connected. Since the length of the straight path S1 is not very meaningful, it is desirable to make it as short as possible. Further, as shown in FIG. 5, it is important that all the ball center trajectories such as the curved paths R1, R2 and the straight paths S1, S3, S3 are smoothly connected by tangent lines. Note that reference symbols A and B in FIG. 5 indicate points where the respective tangents intersect.

The curvature radius r2 of the ball center trajectory of the second curved path R2 is desirably large as in the case of the curvature radius r1, but is less affected by wear than the first curved path R1, and the curvature is small. In order to increase the radius r2, the processing on the nut 14 side becomes complicated, so it is desirable to increase it as much as possible by r1 ≧ r2.
As described above, in this embodiment, the first curved path R1 for guiding the ball 15 scooped up from the spiral track by the tongue portion 19a of the leg portion 19 to the ball circulation path 21 in the circulation component 17 to the outside of the nut 14. And the radius of curvature r1 of the ball center locus of the first curved path R1 is 1.5 times or more the diameter of the ball 15, so that the direction of the ball 15 acting on the inner wall of the ball circulation path 21 is changed. The reaction force of the ball 15 can be reduced, whereby it is possible to suppress wear in the ball circulation path 21 and to prevent the ball 15 from clogging and to ensure a smooth movement of the ball 15. Can do.

As a result, durability and operability can be improved, and vibrations can be reduced, so that high speed, a large diameter of the ball 15 and low noise can be realized, and the circulating component 17 is made of resin. Even a material such as this can cope with a large ball diameter.
In addition, this invention is not limited to the said embodiment, In the range which does not deviate from the summary of this invention, it can change suitably.

For example, in the above-described embodiment, the case where the circulating component 17 is fixed to the flat surface 14a of the nut 14 via the presser is illustrated, but the circulating component 17 is directly fixed to the flat surface 14a of the nut 14 with a set screw or the like. May be.
In addition, in the above embodiment, the thread groove, the screw shaft, the nut, the ball, the circulation hole, the circulation part, the tongue part, the leg part, the main body, the first curved path, the second curved path, the straight path, the divided body, etc. The material, shape, dimensions, form, number, location, etc. are arbitrary as long as the present invention can be achieved, and are not limited.

It is a typical perspective view for demonstrating the circulation components (partition body) of the ball screw apparatus which is an example of embodiment of this invention. It is a graph which shows the relationship between the curvature radius of a ball circulation path (ball center locus | trajectory), and DN value. It is a figure which shows the comparison of the ball circulation path | route (ball center locus | trajectory) seen from the axial direction of the screw shaft, (a) is an example of this invention, (b) is a comparative example. It is a figure which shows the comparison of the ball circulation path | route (ball center locus | trajectory) seen from the lead angle direction of the screw shaft, (a) is an example of the present invention, and (b) is a comparative example. It is explanatory drawing for demonstrating the connection example of 1st curved path | route R1 and 2nd curved path | route R2. It is sectional drawing which shows an example of the conventional tube circulation type ball screw apparatus. It is explanatory drawing for demonstrating an example of the ball screw apparatus which inclined the scooping up direction of the ball | bowl to the substantially tangential direction of the spiral track. It is sectional drawing which follows the approximate path | route direction of FIG. It is a perspective view which shows an example of a division body.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Screw groove 12 Screw shaft 13 Screw groove 14 Nut 15 Ball 17 Circulation component 17a Main body 19 Leg part 19a Tongue part 20 Circulation hole 21 Ball circulation path 22 Divided body R1 1st curved path R2 2nd curved path S1, S2, S3 Straight path

Claims (4)

A screw shaft having a spiral thread groove on the outer peripheral surface, a nut having a spiral thread groove corresponding to the screw groove of the screw shaft on the inner peripheral surface and screwed onto the screw shaft; A large number of balls loaded so as to be able to roll on the spiral track between the thread grooves and the balls rolling on the spiral track in a direction substantially perpendicular to the axis of the nut on the circumferential side surface of the nut. One end of each of the pair of perforated holes is guided to the outside of the nut, and both ends are fitted to the respective circulating holes so as to form a ball circulation path that returns to the spiral track from the other circulation hole. In a ball screw device with combined circulating parts,
The circulation component is fitted to the circulation hole of the nut at both ends, and has a pair of tongue portions that roll up the ball that rolls the spiral track at each end in a substantially tangential direction of the spiral track. A leg, and a main body connecting the pair of legs,
The ball circulation path in the circulation component includes a first curved path that guides the ball scooped up from the spiral track by the tongue portion of the leg to the outside of the nut, and the first curved path A ball screw device characterized in that a radius of curvature of a ball center locus of a path is 1.5 times or more of a diameter of the ball.   2. The ball screw device according to claim 1, wherein a ball center locus of each curved path in the ball circulation path including the first curved path and a ball center locus of the linear path are connected by a tangent line.   The ball center locus of the first curved path is connected to the ball center locus of the next curved path or straight path by a tangent line before the ball center locus becomes parallel to the outer diameter of the leg portion. The ball screw device according to claim 1 or 2.   The ball screw device according to any one of claims 1 to 3, wherein the circulating component is divided into two or more along a substantially path direction of the ball circulation path.

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