JPH0645088Y2 - Precision lead screw device nut - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) This invention is for moving a movable member such as a precision machine tool, a semiconductor manufacturing apparatus, a disk master manufacturing apparatus, such as a table, a precision tool post, a laser cutter, or the like. Related to the nut that constitutes the precision feed screw device.

(Prior art) Making a printing original plate used when manufacturing LSI etc.,
Alternatively, when manufacturing a master disc for various discs (CD, LVD, etc.) for AV and the like, it is necessary to move a tool such as a laser cutter for processing holes and grooves with ultra-precision of μm or less. .

As a mechanism for moving such a tool, a screw shaft having a first spiral groove formed on the outer peripheral surface is screwed with a nut having a second spiral groove portion formed on the inner peripheral surface to form a screw shaft and a nut. Using the relative spiral motion of the above, the rotation of the screw shaft in the twisting direction is converted into the axial motion of the nut to move the tool,
The so-called feed screw mechanism is widely used.

However, in the conventional feed screw mechanism, a screw shaft is usually screwed into a nut having an integral structure. Therefore, when the first spiral groove formed on the outer peripheral surface of the screw shaft and the second spiral groove portion formed on the inner peripheral surface of the nut make a spiral motion due to sliding contact, there is a slight gap between both members. There is a gap, and backlash is inevitable.
Therefore, it is difficult to obtain a positioning accuracy of μm or less as it is.

Conventionally, as a means to eliminate such backlash,
The structures shown in Figures 16-18 are known.

The structure of the first example shown in FIG. 16 is a pair of nuts 2 screwed with a screw shaft 1 provided with a slit 3 orthogonal to the screw shaft 1 and connected to each other through a slight connecting portion. Half of 2a, 2b
Is formed. Then, the bolt 4 is screwed into the screw hole provided in the one half portion 2a. Then, by screwing the bolt 4 into the screw hole, the tip of the bolt 4 is brought into contact with the other half portion 2b, and the other half portion 2b is pressed to make the half portion 2a of the nut 2 The slot 3 between the 2b's is widened in the axial direction of the screw shaft 1 (left-right direction in FIG. 16).
Therefore, one half portion 2a of the nut 2 presses the right flank surface of the thread of the screw shaft 1, and the other half portion 2b presses the left flank surface. In this way, by pressing the flank surfaces on the opposite sides of the respective half portions 2a and 2b, backlash between the screw shaft 1 and the nut 2 is prevented.

In addition, in the structure of the second example shown in FIG. 17, the nut 5 is provided with a slit in the axial direction (the left-right direction in FIG. 17) so that the nut 5 has a C shape and the slit portion is narrowed. Similarly, it is tightened with bolts 6. That is, the tightening of the bolt 6 reduces the diameter of the nut 5, and the thread of the nut 5 is pressed against the thread of the screw shaft 1 to prevent backlash.

Further, Japanese Utility Model Publication No. 60-30512 discloses a nut body 26 having a plurality of slits 25 in the axial direction (left and right direction in FIG. 18) like the structure of the third example shown in FIG. There is described a structure in which the inner diameter is contracted by a coil spring wire 27 attached to the outer peripheral surface of the nut body 26. In the case of the structure of the third example, the threads formed on the inner peripheral surface of the nut body 26 are pressed against the threads of the screw shaft 1 so that these nut bodies 26
Backlash between the screw shaft and the screw shaft 1 is excluded.

(Problems to be Solved by the Invention) However, in the case of the conventional feed screw device configured as described above, the following inconvenience occurs.

That is, in any of the structures shown in FIGS. 16 to 17, when the bolts are firmly tightened to surely eliminate the backlash between the screw shaft 1 and the nuts 2 and 5, the operation becomes heavy and the operation is smooth. If set to, backlash tends to occur. Therefore, it is very difficult to adjust the tightening of the bolts 4 and 6.

Further, with these conventional structures, it is difficult to obtain desired performance when the dimensions of each part are slightly deviated due to the deformation of the screw threads or the influence of thermal expansion. Therefore, it is necessary to move the nuts 2 and 5 with a stable torque over a long period of time and
It is difficult to move the robot accurately.

Further, in the case of the structure shown in FIG. 16, between the female screw (second spiral groove portion) formed on the inner peripheral surface of the nut 2 and the male screw (first spiral groove) formed on the outer peripheral surface of the screw shaft 1. In addition, a non-uniform thrust load is applied in the circumferential direction, and uneven wear is likely to occur on the female screw and the male screw.

Further, in the case of the structure shown in FIG. 18, if the nut body 26 is worn, it is necessary to readjust it, and the adjustment can be made only in stages, so it is not suitable for a precise feed screw device.

The purpose of the nut for a precision feed screw device of the present invention is to solve the above-mentioned inconvenience and to provide an extremely precise feed screw device.

(Means for Solving the Problem) A nut for a precision feed screw device according to the present invention has a second spiral groove portion, which is screwed with a first spiral groove provided on the outer peripheral surface of the screw shaft, on the inner peripheral surface. , Is relatively displaced in the axial direction of the screw shaft based on the relative rotation with the screw shaft.

In particular, the nut for the precision feed screw device of the present invention includes an annular nut body surrounding the screw shaft, at least one displacement portion provided on the inner peripheral side of the nut body, and an inner peripheral surface of the displacement portion. It is provided with a female screw thread portion that is provided on the side and that constitutes the second spiral groove portion, and a leaf spring portion that elastically connects and supports the displacement portion to the nut body.

The leaf spring portion is orthogonal to a straight line that bisects a displacement portion that passes through the center of the nut body and is coupled and supported by the leaf spring portion to the nut body, and that is perpendicular to the screw shaft. It is a thin plate shape provided on parallel planes. The diameter of the pitch circle of the second spiral groove portion including the female screw thread portion in the free state of the leaf spring portion is slightly smaller than the diameter of the pitch circle of the first spiral groove portion.

(Operation) In the nut for the precision feed screw device of the present invention, the female screw (second spiral groove portion) of the nut screwed to the screw shaft is divided into a plurality of portions, and at least one of the plurality of divided portions is displaced. The displacement portion is integrally connected to the nut main body through the leaf spring portion, so that the structural accuracy is unlikely to be incorrect.

Further, due to the elastic deformation of the leaf spring portion, the displacement portion can be finely displaced in the radial direction of the second spiral groove portion, and a predetermined preload is applied to the screw surface by the leaf spring portion. Can be designed to be small. Therefore, it has sufficient allowance for thermal expansion and a slight error in processing dimension, and the function is not impaired even if there is some wear.

Further, since the leaf spring portion is provided on a plane parallel to the axis of the screw shaft, the rigidity against the axial force is large.
Therefore, the axial force and torque applied to the nut can be effectively received by the displacement portion.

Further, in the case where the female screw thread portion is provided in the plurality of displacement portions arranged at equal intervals in the circumferential direction, in addition to the above-mentioned action, the screw shaft and the nut are not aligned due to the aligning property. There is no sharpness and the operation is not hindered. That is, when assembled as a feed screw device, even if the screw shaft may shake due to the accuracy of the bearing that rotatably supports the screw shaft or the eccentricity of the screw shaft, each displacement part Can be slightly bent in the radial direction, and the slight bending can be allowed even with respect to the moment displacement, so that the above-described action can be obtained.

(Embodiment) FIGS. 1 to 6 show a first embodiment of the present invention. The nut body 19 is integrally formed by cutting an elastic metal material such as stainless steel by wire cut electric discharge machining or the like. As shown in FIGS. 3 to 4, the nut main body 19 is provided with displacement supporting portions 8 and 8 each formed in an arc shape at three positions inside the outer cylindrical portion 7 formed in a short cylindrical shape. There is. Both ends of each of the displacement supporting portions 8 and 8 are connected to the inner peripheral surface of the outer tubular portion 7 via the leaf spring portions 9 and 9.

In addition, each of these leaf spring portions 9 and 9 is a thin plate shape provided on a plane that satisfies the following.

It passes through the center of the nut body 19 and the leaf spring portions 9, 9
Thus, the displacement support portions 8, 8 coupled and supported by the nut body 19 are orthogonal to a straight line bisecting in the circumferential direction.

It is parallel to the screw shaft 1 with which the nut is screwed.

That is, the pair of leaf springs 9 and 9 provided at both ends in the circumferential direction of one displacement support portion 8 and supporting the displacement support portion 8 in the radial direction so as to be capable of minute displacement are located on the same plane with each other. is doing. Moreover, the plane in which both leaf springs 9, 9 are present (see the chain line a in FIGS. 2 and 4) is parallel to the central axis of the screw shaft 1. Further, in the illustrated embodiment, a part of this plane is made as close as possible to a screw hole 18 described later.

Between the outer peripheral surface of each displacement supporting portion 8, 8 and the inner peripheral surface of the outer cylindrical portion 7, each of which is supported by the leaf spring portions 9, 9 at both circumferential ends thereof, a circle is formed. Arc-shaped gap 10, 10
Are formed. Therefore, the displacement supporting portions 8 and 8 are
Is elastically displaceable over the radial direction of the nut body 19.

Further, two screw holes 11 and 11 are formed in each of the displacement supporting portions 8 and 8, and female bolt elements (split nut pieces) 13 and 13 for mounting bolts 12 and 12 (first to first) described below are formed. 2) can be screwed freely.

As described above, female screw elements 13 and 13 as shown in FIGS. 5 and 6 are attached to the three displacement supporting portions 8 and 8 elastically supported by the nut body 19 by bolts 12 and 12, respectively. The displacement parts 24 and 24 are fixed by coupling. Then, each female screw element 13, 13
A screw shaft 1 having a first spiral groove (male screw) formed on the outer peripheral surface inside thereof is screwable.

Each of the female screw elements 13 and 13 has a female screw forming wall portion 14 formed in a third arc shape, and the female screw forming wall portion.
And an outward flange portion 15 formed at the end of 14. The three female screw elements 13 and 13 as described above are provided in the outward flange portions 15,
The displacement supporting portions 8 and 8 are coupled and fixed by bolts 12 and 12 inserted into circular holes 16 and 16 formed in the hole 15.

The female screw elements 1 fixed to the displacement supporting portions 8 and 8 respectively.
The inner peripheral surfaces of the female screw forming wall portions 14 and 14 of 3 and 13 have an arc-shaped cross section. Then, female thread portions 17 for forming the second spiral groove portions are formed on the inner peripheral surface.
The internal thread crests 17, 17 are three internal thread forming wall parts 14, 14
Together, one screw hole 18 having a second spiral groove portion on the inner peripheral surface is formed.

In addition, three female screw forming wall portions 14 and 14 are formed respectively,
The curvature of the female thread ridges 17, 17 for forming the screw hole 18 is the same as that of the male screw formed on the outer peripheral surface of the screw shaft 1. This is to prevent a gap from being formed between the inner peripheral surface of the screw hole 18 and the outer peripheral surface of the screw shaft 1 when the screw hole 18 and the screw shaft 1 are screwed together. However, each female screw element 1
When 3 and 13 are coupled and fixed to the nut body 19, the inner diameter of the screw hole 18 (the diameter of the pitch circle of the female screw) in the free state of the leaf springs 9 and 9 is the outer diameter of the screw shaft 1 (of the male screw). The diameter is slightly smaller than the pitch circle diameter).

As described above, the nut 20 which is the nut for the precision feed screw device of the present invention has three displacement support portions 8 and 8 elastically attached to one outer cylinder portion 7 provided in one nut body 19. And the female screw elements 13 and 13 are respectively supported on the displacement supporting portions 8 and 8.
It is made by connecting and fixing. As shown in FIG. 1, this nut 20 is constituted by a screw hole 18 formed by three female screw elements 13, 13 and a first spiral groove formed on the outer peripheral surface of the screw shaft 1. A precision feed screw device is obtained by screwing it together with a male screw. In this way, when the screw hole 18 and the screw shaft 1 are screwed together, the displacement support portions 8 and 8 to which the female screw elements 13 and 13 are coupled and fixed respectively have a radius based on elastic deformation of the leaf spring portions 9 and 9, respectively. Displaces outward in the direction.

In this state, when the screw shaft 1 is rotated in the twisting direction, the nut 20 moves in the length direction (axial direction) of the screw shaft 1 and is supported by a member connected to the nut body 19 of the nut 20. It is possible to accurately move such as.

Particularly, in the case of the nut for the precision feed screw device of the present invention, as described above, when the leaf spring portions 9, 9 elastically supporting both ends of the displacement supporting portions 8, 8 are in the free state, The diameters of the screw holes 18 formed by the female screw threads 17, 17 on the inner peripheral surfaces of the female screw forming walls 14, 14 of the elements 13, 13 are made slightly smaller than the diameter of the male screw formed on the outer peripheral surface of the screw shaft 1. ing. Therefore, when the nut 20 is screwed onto the screw shaft 1, the displacement supporting portions 8 and 8 to which the female screw elements 13 and 13 are fixed are elastically deformed to the leaf spring portions 9 and 9 and outwardly in the radial direction. It is displaced to allow the screw hole 18 and the screw shaft 1 to be screwed together.

In this state, the screw hole 18 and the male screw on the outer peripheral surface of the screw shaft 1 that have the same diameter due to the screwing tightly abut with each other by the elastic force of the leaf spring portions 9, 9, and Backlash between the peripheral surface and the outer peripheral surface of the male screw is eliminated.

Further, in the case of this embodiment, a plurality of (three) female screw elements 13, 13 for forming the screw holes 18 are elastically supported inside the outer cylindrical portion 7. Therefore, even if the center of the nut 20 and the center of the screw shaft 1 are slightly deviated due to the influence of the mounting accuracy or the bearing accuracy, the female screw elements 13, 13 are elastically displaced, Absorbs the displacement of the nut 20 in the lateral direction, pitching and yawing directions.

Even in this case, since the nut 20 is supported with high rigidity in the rotation direction and the axial direction, no unreasonable force acts on the nut 20 and backlash due to insufficient rigidity does not occur. For this reason, stable performance can be obtained over a long period of time even if the precision of each part constituting the precision feed screw device is not made extremely severe.

Next, a second embodiment of the present invention shown in FIGS. 7 to 11 will be described. In the case of the present embodiment, only one displacement support portion 8 is provided on the nut body 19, and two female screw elements 13 and 13a are coupled and fixed to the nut body 19. In the case of the present embodiment, only the female screw element 13 coupled and fixed to the displacement support portion 8 is elastically displaceable in the outer peripheral direction, and the female screw element 13a directly supported and fixed to the outer cylinder portion 7 of the nut body 19 cannot be displaced. .

For this reason, in the case of this embodiment, when the nut 20 and the screw shaft 1 are screwed together, there is no function of absorbing the deviation between the center of the nut 20 and the center of the screw shaft 1, but the displacement support portion to which the female screw element 13 is fixed is fixed. 8
Due to the elastic displacement, the backlash between the screw hole 18 and the female screw formed on the outer peripheral surface of the screw shaft 1 can be eliminated.

Next, FIGS. 12 to 14 show a third embodiment of the present invention. In the case of the present embodiment, any one of the three displacement supporting portions 8 provided on the nut body 19 so as to be elastically displaceable can be elastically pressed from the outside. ,
The preload acting between the screw shaft 1 and the nut 20 (Figs. 1, 2, 7, 8) can be freely adjusted to absorb machining errors.

That is, a screw hole 21 penetrating from the outer peripheral surface to the inner peripheral surface of the outer cylindrical portion 7 is formed in a part of the outer cylindrical portion 7 facing the outer peripheral surface of the intermediate portion of any one of the displacement supporting portions 8. Is forming. An adjusting screw 22 is screwed into the screw hole 21, and a disc spring 23 is supported between the adjusting screw 22 and the outer peripheral surface of the displacement supporting portion 8. The elastic force of the disc spring 23 in the free state is weaker than the elastic force of the plate spring portions 9 and 9 supporting both ends of the displacement supporting portion 8.

Since the adjustment screw 22 is rotated as described above, if the pressing amount of the disc spring 23 against the displacement support portion 8 by the adjustment screw 22 is adjusted, the displacement support contacting the disc spring 23 is adjusted. The force required when the part 8 moves outward is adjusted.
Then, if this force is adjusted, the preload acting between the screw shaft 1 and the nut 20 can be adjusted.

For example, when increasing the preload, adjust screw 22
13-14, the elastic compression amount of the disc spring 23 is increased by moving the disc spring 23 to the right. On the contrary, when the preload is reduced, the adjusting screw 22 is moved in the opposite direction to reduce the elastic compression amount of the disc spring 23. Such a preload adjusting mechanism has a nut body 19 having three displacement supporting portions 8 as shown in FIG.
Besides, it can be provided on the nut body 19 having only one displacement supporting portion 8 as shown in FIG.

In any of the above-described embodiments, the female screw thread portions 17, 17 are formed on the female screw elements 13, 13a supported and fixed to the displacement supporting portion 8. However, female screw elements 13, 13
It is also possible to omit “a” and directly form the internal thread portions 17, 17 on the inner peripheral surfaces of the displacement supporting portions 8, 8 to form the displacement portions. In this case, the diameter of the screw hole 18 formed by the female screw threads 17, 17 in the free state (before screwing with the screw shaft 1) is made slightly smaller than the diameter of the screw shaft 1.

(Effect of the Invention) Since the nut for the precision feed screw device of the present invention is configured and operates as described above, it has a relatively simple structure,
It is possible to eliminate backlash in the screwed portion between the screw shaft and the nut. Moreover, since no unnatural force is applied to the screwed portion, the durability and reliability of the precision feed screw device can be improved. Furthermore, since the rigidity of the screw shaft in the axial direction can be sufficiently increased, stable operation can be achieved even when a large torque is applied to the screw shaft.

[Brief description of drawings]

1 to 6 show a first embodiment of the present invention, FIG. 1 is a side view showing a state where an assembled nut is screwed onto a screw shaft, and FIG. 2 is a front view of the assembled nut. FIG. 3 is a side view of a nut body that constitutes a nut, FIG. 4 is a front view of the same, and FIG. 5 is a side view showing three female screw elements used for forming screw holes in an array state, FIG. 6 is a front view, FIGS. 7 to 11 show a second embodiment of the present invention, and FIG. 7 is a side view showing a state in which the assembled nut is screwed onto a screw shaft, and FIG. FIG. 9 is a front view of the assembled nut, FIG. 9 is a front view of a nut body that constitutes the nut, and FIG. 10 is a side view showing two female screw elements used for forming screw holes in an array state. FIG. 11 shows the same front view, and FIGS. 12 to 14 show the third embodiment of the present invention.
FIG. 12 is a side view of the nut body, FIG. 13 is a front view of the same, and FIG.
The figure is an enlarged view of part A of FIG. 13, FIG. 15 is a front view showing another example of the nut body provided with a preload adjusting mechanism, and FIGS.
FIG. 18 is a side view showing first to second examples of a conventional feed screw nut, and FIG. 18 is a sectional view showing a third example of a conventional feed screw nut. 1: Screw shaft, 2: Nut, 2a, 2b: Half part, 3: Slot, 4: Bolt, 5: Nut, 6: Bolt, 7: Outer cylinder part, 8: Displacement support part,
9: Leaf spring part, 10: Gap, 11: Screw hole, 12: Bolt, 13, 13
a: Internal thread element (split nut piece), 14: Internal thread forming wall, 1
5: Outward flange part, 16: Circular hole, 17: Female thread part, 18: Screw hole, 19: Nut body, 20: Nut, 21: Screw hole, 22: Adjusting screw, 23: Disc spring, 24: Displacement part , 25: slot, 26: nut body, 27: wire.

Claims (3)

[Scope of utility model registration request] Claim: What is claimed is: 1. A screw shaft has a second spiral groove portion screwed into a first spiral groove provided on an outer peripheral surface of the screw shaft, and the second spiral groove portion is screwed on the inner peripheral surface based on relative rotation with the screw shaft. In a nut for a precision feed screw device that is relatively displaced in the axial direction, an annular nut body surrounding the screw shaft, at least one displacement portion provided on the inner peripheral side of the nut body, and the displacement portion An internal thread portion that is provided on the inner peripheral surface side and that constitutes the second spiral groove portion, and a leaf spring portion that elastically couples and supports the displacement portion with respect to the nut body are provided. , On a plane that passes through the center of the nut body and is orthogonal to a straight line that bisects the displacement portion that is coupled and supported by the nut body by the leaf spring portion in the circumferential direction and that is parallel to the screw axis. Is a thin plate provided on the Second diameter of the pitch circle of the helical groove, precision feed screw apparatus nut, characterized in that the slightly smaller than the diameter of the pitch circle of the first spiral groove including a threaded portion. 2. A displacement portion is provided by two leaf spring portions provided on the opposite sides in the circumferential direction of the displacement portion and existing on the same plane.
The precision feed screw device nut according to claim 1, which is coupled and supported by the nut body. 3. A nut for a precision feed screw device according to claim 1, wherein the plurality of displacement portions are arranged at equal intervals in the circumferential direction.