JP4523304B2 - Ball screw surface lapping device - Google Patents

Description

The present invention is a ball screw surface of the ball screw device, in particular threaded surface (outer peripheral screw groove surface) suitable wrapping device using the ball screw shaft about (lapping device).

  In general, the thread surface (thread groove) of a ball screw device is required to have high accuracy, and after being subjected to grinding, lapping is performed as finishing.

  Conventionally, Patent Documents 1 and 2 have been proposed for lapping of thread surfaces. Actually, lapping tools are consumables and preferably have a simple structure. As the lapping tool, a two-part lapping tool for manual work is used. As shown in FIG. 1 (a), the lap tool 1 is generally made of a casting, and lap teeth 2 made of protrusions aligned with the ball screw grooves of the screw shaft are formed on the inner peripheral surface, and One slit 3 is formed in the radial direction.

  As shown in FIG. 1 (b), the lapping tool 1 is attached to a thread 5 having an adjusting screw 4, and the screw shaft 6 is turned into a lathe with the lapping teeth 2 screwed onto the screw shaft 6. Mounted. Then, the screw shaft 6 is rotated in the forward and reverse directions, and the knurl 5 is held by hand to slide the lap tooth 2 and the screw groove surface of the screw shaft, while lapping abrasive grains ( The thread surface is polished (wrapped) by appropriately supplying lapping abrasive grains). At this time, by looking at the rotational resistance acting on the hand from the knurl 5 and tightening the adjusting screw 4 provided on the knurl 5, the lap tool 1 has a lapping pressure (lapping pressure adjusting force) as shown in FIG. Is adjusted.

  The split lap tool 1 has a predetermined lap processing pressure applied to the ball screw groove surface of the screw shaft, and the lap teeth 2 are slid between the screw surface and the screw surface. Improves surface roughness and removes burrs generated in the pre-grinding process.

Patent Publication 2000-198063 Patent Publication 2002-370155

  As shown in FIG. 2B, the split lap tool 1 is tightened by a lap pressure adjusting screw 4 and lap-processed in a state where the cross-sectional shape is distorted to an elliptical diameter. There are two contact processed parts A and B. For this reason, the lapping speed is very slow compared with other removal processing methods such as grinding, and in lapping of the ball screw shaft, for example, 0.1 to 0.5 pieces / hour, Combined with manual work, it is a bottleneck in improving productivity in precision ball screw devices.

  Furthermore, the surface roughness of the thread surface, which is the machined surface, increases to some extent as the machining progresses, and reaches a steady state, but the cross-sectional shape along the chord winding of the machined ball screw shaft has a diameter at an arbitrary angle. Since it becomes an equal-diameter strain circle with a constant value, the shape accuracy of the ball screw shaft will deteriorate as the lapping progresses.

That is, FIG. 3 shows that the cross-sectional shape of the work piece (thread surface) is a triangular shape of a triangular component (roundness component n = 3), and the lap tool is divided into two (the equilateral polygon k of the lap tool shape). = 2) is a schematic diagram showing a lapping shape depending on the rotation angle of the screw shaft, and the size of the lapping tool is constant at each angle of 0 ° to 135 ° (the distance L between the two sides [tooth A, B] is Constant). When the workpiece is 0 °, the lapping tool center G moves to the position of point G ₁ that is separated from the origin by C ₂ on the y axis. Next, when 45 ° rotated to move in the direction of 135 ° from the origin to the position of the C ₂ apart G ₂ points. Furthermore workpiece center G and is rotated by 45 ° it can be seen that moving the circle of radius C _2. Therefore, the workpiece whirling so that the center draws a circle with a radius C _2, since the three sides uniformly lapping is performed, bringing the rice ball shape a perfect circle will be impossible.

An object of the present invention divides the wrap tool into a plurality, and configured to be equal lapping pressure to the divided piece acts, the wrapping apparatus of the ball screw surfaces which solves the above problems have It is in the child provides.

  Another object of the present invention is to improve the lapping speed while maintaining the shape accuracy of the thread surface by giving vibrations to the lapping teeth and actively feeding fresh lapping abrasive grains to the machining area. This is to improve the efficiency of the lapping work.

In the present invention (see, for example, FIG. 4, FIG. 5 and FIG. 13), a lap tooth (20) of a lap tool (11) is provided on a ball screw surface (21a) which is a screw groove formed on the outer periphery of a screw shaft (21). In a lapping device (10, 10 ′) that contacts by lapping pressure and lapping by sliding the lapping teeth through lapping abrasive grains on the thread surface,
The lapping tool (11) is formed of a nut-like member having the lapping teeth (20) formed on the inner peripheral surface, and a plurality of slits (17) are alternately formed from both ends in the axial direction, and the like in the circumferential direction. It consists of a large number of divided pieces (11a ...) divided at an angle and connected by thin-walled connecting portions (19) ,
The displacement of the operating portion (14a) is transmitted to each of the divided pieces (11a) as a substantially uniform radial deformation over the entire axial length thereof, and the lap teeth (20 ) Is provided with working pressure adjusting means (13, 14) (14, 11b, 16b) for applying the substantially equal lapping pressure.
The lap teeth of the split pieces (11 a) (20) becomes in contact with each substantially s uniform lapping pressure polygonal shape on the threaded surface (21a) over its axial length,
A ball screw surface lapping device is characterized by the above.

For example with reference to FIG. 4, the processing pressure adjusting means, housed elastic body in a closed space (K) and (13), the axial end face displaced freely adjusted in the axial direction within the space And obtaining said operation part (14),
The fixed part of the outer axial end surface and the radial direction of the space together with a (15,16), arranged the respective segments radially inward (11a ...) over its entire axial length, the operating unit based on the axial displacement (14) by the elastic body (13), substantially equal wrap throughout its axial length to the each divided pieces (11a ...) is deformed the elastic body (13) in the radial direction A processing pressure is applied .

For example, referring to FIG. 13, the lapping tool (11) has a tapered surface (11b) over the entire axial length of the outer peripheral surface of each of the divided pieces (11a...)
The working pressure adjusting means includes a housing (16) having a tapered surface (16b) and a female screw (16a) on an inner peripheral surface, and the operating unit (14) having a male screw portion (14b) that can be screwed to the female screw. Have
Based on the axial displacement of the operating portion (14) due to the screwing of the female screw (16a) and the male screw portion (14b), the divided pieces (11a...) Are engaged by the engagement of the tapered surfaces (11b, 16b). A substantially uniform lapping pressure is applied over the entire length in the axial direction.

Before Symbol divided pieces (11a ...) is five or more obtained by dividing the cylindrical conformal,
The polygon formed by the wrap teeth (20) of each of the divided pieces in contact with the thread surface (21a) is a pentagon or more .

For example, referring to FIG. 11 and FIG. 12, an exciter (12a, 12b, 12c) for applying vibration to the divided pieces (11a...) Is provided, and vibration is applied to the divided pieces to provide the lap teeth (20). And while supplying a fresh lapping abrasive grain (T) to the process part which consists of a thread surface (21a), the lapping abrasive grain crushed by the lapping process is discharged | emitted from the said process part.
For example, referring to FIG. 11, the exciter includes a vibration exciter (12a) and a vibration absorber (12b), and generates a bending traveling wave from one axial end to the other end of each divided piece (11a...). Do it.
For example, referring to FIG. 12, the exciter includes a piezoelectric element (12c) and vibrates each of the divided pieces (11a...) In the radial direction.

  In addition, although the code | symbol in the said parenthesis is for contrast with drawing, this does not have any influence on the structure of a claim.

  According to the first aspect of the present invention, the lapping tool is composed of a large number of divided pieces, and each of the lap teeth of the divided pieces is substantially uniformly added to the polygonal shape with respect to the thread surface that is the machining surface. Since contact is made with pressure, a large number of lapping teeth can simultaneously act to increase the machining speed, and the shape accuracy of the thread surface is improved, so that highly accurate lapping can be performed with high work efficiency.

According to the first aspect of the present invention, since the thread groove of the ball screw shaft is used as a processed screw surface, in the ball screw device, the screw shaft is long and has a great influence on the feeding accuracy. Such lapping can improve the accuracy of the ball screw shaft.

According to the second aspect of the present invention, since the working pressure adjusting means has an elastic member, the lap tool which is a consumable item is sufficient in a simple shape, and the lap tool can be made inexpensive to reduce the cost of the lap work. It becomes possible.

According to the present invention according to claim 5, 6 or 7 , since the lapping abrasive grains crushed in the processing section are discharged to the outside and fresh lapping abrasives are always supplied, lapping abrasive grains with a sharp cutting edge are provided. Thus, high-precision lapping can be performed with high efficiency.

According to the fourth aspect of the present invention, when the number of divided pieces is five or more and the polygon formed by the wrap teeth is five or more corners, the thread surface can be processed so as to approach a perfect circle. The shape accuracy of the surface can be improved.

  Hereinafter, in order to describe embodiments of the present invention with reference to the drawings, first, a lap device (tool) will be described with reference to FIGS. 4 and 5.

  As shown in FIG. 4, the ball screw shaft lapping apparatus 10 includes a lapping tool 11, an exciter 12, an elastic body 13, an outer cylinder 16, a machining pressure adjusting screw 14, and a housing 15. As shown in FIG. 5, the lapping tool 11 has a large number of slits 17 formed alternately from both ends in the axial direction, which are divided at equal angles in the circumferential direction and connected by thin connection portions 19. 5 or more in the case of FIG. 5 and 8 pieces in the case of FIG. 6), and the inner peripheral surface thereof has a shape that matches the thread groove surface 21a of the ball screw shaft 21 that is a workpiece. A wrap tooth 20 is formed (see FIGS. 7 and 8).

A hollow cylindrical elastic body 13 is fitted on the outer peripheral surface of the lapping tool 11, and the elastic body 13 is a non-compressed material such as a synthetic rubber such as polyurethane, natural rubber, a gel-like material, or a liquid such as oil. It is made of a material that is deformed substantially uniformly with respect to the entire circumference in the circumferential direction by axial displacement. A cylindrical outer cylinder 16 is closely fitted on the outer peripheral surface of the elastic body 13, and a female thread portion 16 a is formed on one inner peripheral surface of the outer cylinder 16. The pressure adjusting screw 14 has an operating portion 14a and the male screw portion 14b of the knurling or the like arranged in the outer periphery, the male screw portion 14b is screwed into the female screw portion 16a of the outer cylindrical member 16. A cylindrical housing 15 with a flange is fixed to the other end side of the outer cylindrical body 16 with a screw.

Accordingly, the elastic body 13 has an outer peripheral surface on the outer cylinder 16, an axial other end on the housing 15, an axial end on the one end surface of the pressure adjusting screw 14 via the washer 22, and an inner surface. The circumferential surface is stored in the closed space K in close contact with each divided piece 11a of the lapping tool over its entire length in the axial direction . Then, when one end surface of the elastic body 13 is compressed and deformed via the washer 22 by tightening the machining adjusting screw 14, the outer peripheral surface and the other end surface of the elastic body 13 are displaced by the outer cylindrical body 16 and the housing 15, respectively. And the divided pieces 11a can be deformed in the radial direction by the slits 17 to 17f and the connecting thin wall portions 19, respectively. Therefore, the elastic body 13 swells in the inner diameter direction. As shown in FIG. 6B, an equal lapping pressure adjusting force acts on the divided pieces 11a... Over the entire length in the axial direction .

  On the other hand, the exciter 12 is fixed to the outer peripheral surface of each of the divided pieces 11a. The exciter 12 is, for example, a piezoelectric element that converts electrical energy by mechanical vibration, and vibrates each of the divided pieces 11a in the radial direction. As an example, as shown in FIG. 7, the exciter includes a vibration exciter 12a connected to a power source 25 and a vibration absorber 12b connected to a resistor 26, and outputs vibration of a predetermined frequency to the exciter 12a. At the same time, when the vibration absorber 12b is activated to absorb a predetermined frequency, each divided piece 11a ... propagates the vibration from the vibrator 12a toward the vibration absorber 12b, and each divided piece, and therefore its circumference. A bending traveling wave is generated in the surface wrap teeth 20. As another example, the exciter includes a toy-type piezoelectric element 12c that is polarized in the radial direction and extends in the axial direction, as shown in FIG. The piezoelectric element 13c generates radial vibrations in the divided pieces 11a.

  Next, the lapping method according to the present invention will be described using the lapping apparatus 10 described above. The nut-shaped lap device 11 is attached to the ball screw shaft 21, and the ball screw shaft 21 is mounted on a lathe in this state. The ball screw shaft 21 rotates forward and backward so that the lap device 11 moves with a predetermined stroke corresponding to the screw shaft length, and the lap device 11 is held by hand or fixed by a predetermined jig. Thereby, relative sliding occurs between the thread surface 21a of the ball screw shaft and the lap teeth 20 of the lap tool 11, and the lap polishing is performed by supplying the lap abrasive grains.

At this time, since the wrap teeth 20 are formed on each of the divided pieces 11a, the screw surface is formed by a polygon having the number of each divided piece with respect to the screw surface, in the case of this embodiment, a hexagon or an octagon. A lapping process is performed with a large number of teeth (three or more, for example, six or eight). Then, as the lapping process proceeds, the process pressure adjusting screw 14 is tightened, whereby the elastic body 13 is compressed and deformed, so that the radially inflated part can be deformed by the thin part 19. The lapping is continued by a large number of lapping teeth that act as a uniform lapping pressure adjusting force in the inner diameter direction with respect to the entire axial length of the piece 11a and that have a uniform machining pressure in the radial direction.

  Thereby, since it is based on a large number of lap teeth, the processing speed can be improved and lap work can be performed with high efficiency, compared with the conventional lap teeth. Further, the shape accuracy of the ball screw shaft can be improved by processing with polygonal teeth using a large number of divided pieces.

  Hereinafter, improvement of the shape accuracy of the screw shaft will be described.

[Theoretical analysis in cylindrical lapping]
It is assumed that the shape of the lapping tool is an equiangular polygon (k-square), and the workpiece and lapping tool are always circumscribed during lapping. Find out how the center of the lapping tool swings according to the workpiece shape.

  The workpiece radius r (θ) can be displayed in the form of a Fourier series using tangential polar coordinates as follows:

As shown in FIG. 9, the lapping of one side of the lapping tool is taken as l _i , the center O of the workpiece is taken as the origin, and the perpendicular point A _i · l _i and l _{i + 1} crossing from O to l _i is taken as B _i . The center G (x _G + y _G ) of the tool is considered to be at the average position of each vertex B _i .

Here, assuming that the center G (x _G + y _G ) of the lapping tool is at the average position of each vertex B _i ,

  The results are shown in Table 1.

A: When n + 1 = mk

B: When n-1 = mk

C: When sandwiched between two parallel straight lines (k = 2), the lapping tool fluctuates in the same manner as A and B with respect to the odd component of n.

  The blank indicates that the center of the workpiece and the center of the lapping tool are coincident.

  Hereinafter, Table 1 will be considered in two cases.

Case 1: Blank
The blank in Table 1 indicates that x _G = y _G = 0, that is, the center of the workpiece and the lapping tool always coincide during lapping. That is, during machining, the lap tool is not touched, and the convex part of the workpiece is actively cut, so that the shaft shape approaches a perfect circle.

Case 2: Cases A, B, and C In all cases, the physical meaning is the same, and the lapping tool swings by the same amount according to the unevenness of the workpiece. Accordingly, since the lap finish is uniformly applied to the convex portion and the concave portion, no matter how much the lap finish is made, it does not approach a perfect circle.

  For example, in the case of k = 4, it indicates that the even component is decreased, but the odd component is not decreased. Moreover, it turns out that all the components of n <= k-2 become blank, and the effectiveness of a multi-division tool is proved theoretically.

  Therefore, the number of the divided pieces of the tool is preferably 5 or more, and the shape accuracy improves as the number increases.

[Circularity component of cylindrical shaft and staggering component of ball screw shaft]
The description so far has been made on the machining of cylinders. Here, due to the similarity between the “roundness component in the cross-sectional shape of the cylinder” and the “variation component due to one rotation of the ball screw shaft (hereinafter referred to as the staggering component)”, the theoretical analysis in the lapping of the cylindrical shaft is applied to the ball screw shaft. It shows that it can be applied.

  Due to the eccentricity of the cylindrical shaft being machined and the accuracy of the lead screw of the lathe, the cylindrical shaft has a cross-sectional shape in the radial direction as shown by a two-dot chain line with respect to the solid circle of the cross-section AA in FIG. An irregularity has occurred. In order to correct this to a perfect circle, it is necessary to reduce all the polygons included in the cross-sectional shape such as an ellipse or a rice ball shape.

  Next, a lapping method using the exciter 12 will be described. In order to increase the efficiency of the lapping process, it is important to positively feed fresh lapping abrasive grains with a sharp cutting edge to the machined part. In this lapping method, each of the lapping tools 11 by the exciter 12 is used. The divided pieces 11a ... vibrate, and the lapping abrasive grains crushed in the machining area due to the pump effect thereby are discharged to the outside, and the lapping abrasive grains that are fresh and have a sharp cutting edge are fed into the machining area.

  An embodiment using the vibrator 12a and the vibration absorber 12b shown in FIG. 7 is shown in FIG. A bending traveling wave from one end E to the other end F of the lapping tool 11 is generated in each divided piece 11a by the vibrator and the vibration absorber. Thereby, the part where the lap tooth 20 contacts and separates from the screw surface 21a is sequentially moved in the axial direction, and the lap abrasive grain T is forcibly sent from one end E to the other end F like a screw pump. As a result, fresh lapping abrasive grains are always supplied to the machining portion between the lapping teeth 20 and the thread surface 21a, and lapping abrasive grains crushed by machining are sequentially discharged from the machining surface.

  FIG. 12 shows an embodiment using the exciter 12c shown in FIG. 8. Each of the divided pieces 11a of the lapping tool 11 vibrates in the radial direction by the exciter 12c made of a piezoelectric element. 20 and the threaded surface 21a are brought into contact with and separated from each other, and the lap abrasive grains T are repeatedly supplied to and discharged from the processed portion. At the same time, since the lapping apparatus 10 reciprocates in the axial direction based on the screw motion, fresh lapping abrasive grains are always supplied to the processing portion composed of the lapping teeth 20 and the screw surfaces 21a, and the abrasive grains crushed by the machining are supplied. It is discharged from the processed part.

  10 and 12 are drawn with high emphasis so that they can be easily understood as images. Actually, however, the vibration by the exciter 12 is extremely fine, and is due to friction between the lap teeth 10 and the screw surface 21a. It does not affect the polishing finish. In addition, since the exciter 12c shown in FIG. 12 is supported by the elastic body 13, a large synchronous vibration is generated by the resonance of the elastic body 13 together with the fine vibration of the exciter 12c, and the pump to the above-described machining surface is generated. There is also the possibility of increasing the effect.

FIG. 13 shows an embodiment in which an elastic body is not used as the lap pressure adjusting means of the lap tool split piece. The lapping apparatus 10 ′ includes a lapping tool 11, a housing 16, a lapping pressure adjusting screw 14, and an end cap 15, and the lapping tool 11 is similarly formed with a number of divided pieces 11 a. The outer peripheral surface is formed of a tapered surface 11b over the entire length in the axial direction . A taper surface 16b is formed on the inner peripheral surface of the housing 16, and the taper surface 11b is engaged with the taper surface 16b so that the lapping tool 11 is fitted.

  An end cap 15 is fixed to one end face of the housing 16 by a hexagon socket head cap bolt 31 with a spring washer 29 and a plain washer 30 interposed between the end cap 15 and the lapping tool 11. The male screw portion 14 b of the wrap pressure adjusting screw 14 is screwed to the female screw 16 a formed at the other end of the housing 16.

  As a result, by tightening the lap pressure adjusting screw 14 with the operation portion 14a, each of the divided pieces 11a of the lap tool 11 is moved uniformly in the inner diameter direction by the taper surfaces 11b and 16b, and a uniform lap working pressure is applied. Is granted. The lap pressure adjusting means using the taper surface is troublesome to process the taper surface, and the lap tool as a consumable is preferably the elastic body 13 according to the previous embodiment.

It is a figure which shows the conventional lapping tool, (a) is the front view and side sectional drawing of a lapping tool, (b) is the figure which shows the state which attached the lapping tool to the popping. It is sectional drawing which shows the lapping process by the conventional lapping tool, (a) is the state which has not applied the lapping pressure, (b) shows the state which applied the lapping pressure. The figure which shows the state in each angle of the lapping process by the conventional lapping tool. The cross section and front view which show the lap | wrap apparatus which concerns on this invention. It is a figure which shows the lapping tool which concerns on this invention, (a) is a perspective view, (b) is sectional drawing. It is a figure which shows the lapping process by the lapping tool which concerns on this invention, (a) is the state which has not applied the lapping process pressure, (b) shows the state which applied the lapping process pressure. The schematic diagram which shows an example of the exciter which concerns on this invention. The schematic diagram which shows the other example of the exciter which concerns on this invention. The figure which shows the lapping process with respect to the workpiece of arbitrary cross-sectional shape. The figure which shows the roundness component of a cylindrical shaft, and the stagger component of a ball screw shaft. The schematic diagram which shows the lapping by the lapping apparatus which attached the excitation vibrator of an example. The schematic diagram which shows the lapping by the lapping apparatus which attached the exciter of the other example. Front sectional drawing which shows the lap | wrap apparatus by other embodiment.

Explanation of symbols

10, 10 'Lapping device 11 Lapping tool 11a Dividing piece 12, 12a, 12c Exciter (piezoelectric element)
13 Elastic body 14, 14a Operation part (working force adjusting screw)
15 Outer cylinder part 16 Housing 17 Slit 19 Thin connection part 20 Lap tooth 21 Ball screw shaft 21a Ball screw surface (screw groove)
14b, 16b Tapered surface T Lap abrasive

Claims (7)

Lapping is performed by bringing the lapping teeth of the lapping tool into contact with the ball screw surface, which is a screw groove formed on the outer periphery of the screw shaft, with lapping pressure, and slidingly contacting the lapping teeth with lapping abrasive grains on the thread surface. In the lapping machine to process,
The lapping tool is formed of a nut-like member having the lapping teeth formed on the inner peripheral surface, and a plurality of slits are alternately formed from both ends in the axial direction so as to be divided at equal angles in the circumferential direction and formed into thin connection portions. Consisting of a number of divided pieces connected together
Displacement of the operating portion is transmitted to each of the divided pieces as a substantially uniform radial deformation over the entire axial length thereof, and the lapping process is substantially equivalent to the lap teeth formed on each of the divided pieces. A processing pressure adjusting means for applying pressure is provided,
The wrap teeth of each of the divided pieces are in contact with the thread surface over the entire length in the axial direction in a polygonal shape with a substantially uniform wrap processing pressure.
A ball screw surface lap device characterized by the above. The processing pressure adjusting means includes an elastic member which is accommodated in a closed space, the operation section, which can be displaced freely axially adjustable in the axial direction one end face of the said space,
With a fixed portion of the outer axial end surface and the radial direction of the space, the respective segments radially inwardly disposed over its axial length, based on the axial displacement of the elastic body by the operation unit The elastic body is deformed in the radial direction and a substantially uniform lapping pressure is applied to each of the divided pieces over the entire axial length thereof .
The ball screw surface lapping device according to claim 1 . The lapping tool has a tapered surface over the entire axial length of the outer peripheral surface of each divided piece,
The working pressure adjusting means includes a housing having a tapered surface and an internal thread on an inner peripheral surface, and the operation section having an external thread portion that can be screwed into the internal thread.
Based on the axial displacement of the operating portion due to the screwing of the female screw and the male screw portion, the substantially equal lapping pressure is applied to the divided pieces over the entire axial length by the engagement of the tapered surfaces. Become,
The ball screw surface lapping device according to claim 1 . The divided pieces are five or more obtained by dividing a cylindrical shape into equal angles,
The polygon formed by the wrap teeth of each of the divided pieces that contacts the thread surface is a pentagon or more,
The ball screw surface lapping device according to any one of claims 1 to 3 . An exciter that gives vibration to the divided pieces is provided, and vibration is given to the divided pieces to supply fresh lapping abrasive grains to the processing portion composed of the lapping teeth and the threaded surface, and to be crushed by lapping. Wrapping abrasive particles are discharged from the processed part,
The ball screw surface lapping apparatus according to any one of claims 1 to 4 . The exciter is composed of an exciter and a vibration absorber, and generates a traveling wave that bends from one axial end to the other end of each divided piece.
The ball screw surface lapping device according to claim 5. The exciter is composed of a piezoelectric element, and the divided pieces are vibrated in a radial direction.
Wrap device of the ball screw surfaces according to claim 5, wherein.

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