JPH08132320A - Outer surface screw grinding method - Google Patents

Abstract

PURPOSE: To provide an extremely effective outer surface screw grinding method in which one screw shaft is ground simultaneously by two grinding wheels. CONSTITUTION: A pair of two grinding wheels 17, 17 are disposed to face each other having a screw shaft W as a work between them. Both grinding wheels 17, 17 are inclined in mirror-image directions by rotating a surface P passing the center of a grinding surface for a lead angle θ of the screw to be worked to the vertical surface. The grinding wheels 17, 17 are operated to cut simultaneously for grinding work in perpendicular directions to the vertical surface passing an axial center of a screw shaft to be worked.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for grinding an outer surface of a screw shaft, and more particularly to a method for grinding an outer surface of a threaded shaft which can greatly reduce the grinding time.

[0002]

2. Description of the Related Art Usually, for example, the external thread grinding of a screw shaft of a ball screw is carried out by using one rotary grinding wheel (hereinafter, simply referred to as a grinding wheel) installed on a grinding machine. The workpiece screw shaft, which is the workpiece, has been hardened by turning the lower screw in advance in anticipation of the grinding allowance.The workpiece is supported horizontally while it is rotated and the grindstone is applied to the workpiece in the radial direction at the specified depth of cut. Grind the single-thread screw by moving it relative to the screw axis while cutting.

By the way, recently, the speed of machines using ball screws has been increased, and along with this, large leads and double threads of ball screws have been remarkable. Conventionally, this double thread is also ground by one grindstone. In that case, a method of first grinding the first row, then rotating the main shaft of the grinder 180 ° and half to shift the phase, and grinding the second row is performed.

[0004]

However, a screw shaft having a significantly large length with respect to the diameter, such as a screw shaft of a ball screw, does not have rigidity, so that it is not possible to take a large amount of grindstone cutting at one time. Therefore, there is a problem that processing time is extremely long. Moreover, when the double thread is ground, the 180 ° index of the main shaft is used to grind each thread, so not only does it take longer processing time, but the following problems are required to ensure accuracy between the two threads. Has occurred.

There is a time difference between the thread grinding of the first thread and the thread grinding of the second thread due to the sequential grinding for each thread, and this time difference causes a slight temperature difference to cause a cumulative lead error, resulting in the adjacent pitch. There will be an error. Further, if the internal stress change occurring during grinding occurs between the first and second threads, it causes expansion and contraction of the work piece, which causes an adjacent pitch error.

In order to suppress this error and perform precision grinding, it is necessary to perform fine grinding so as to suppress heat generation and stress at the time of grinding while controlling the temperature at a high level. This leads to high costs for multi-start screws. For the purpose of improving the efficiency of such conventional screw grinding, particularly grinding of the above single-thread screw, a grinder that grinds a single-thread screw by using two grindstones opposed to each other with a work sandwiched between them is disclosed in Japanese Patent Laid-Open No. H11-242242. 5-162015 and JP-A-6-4
It is proposed in each publication of No. 7621.

[0007] This is equipped with a headstock for mounting a work on a machine base, a tailstock facing the workstock, and a saddle which is arranged at an intermediate position between the two bases and can reciprocate along the work. Is provided with a slide supported via a turning position adjusting device having a vertical axis as a turning center. Then, on this slide, two grindstone bases facing each other so as to move back and forth toward the work are provided on both sides of the work supported by the headstock and the tailstock at substantially the same position in the axial direction. And each driving means for making the ratio of the relative movement in the axial direction between the grinding wheel and the work constant.

In the grinding process, first, the screw pitch to be cut is set, the corresponding lead angle is calculated, and the slide is tilted in the horizontal plane via the turning position adjusting device by operating the lead angle adjusting handle. Tilt the grindstone by the required lead angle with respect to the axis of the workpiece. Both grindstones in this state are used at the same time to perform thread grinding of a work with a predetermined cutting amount set for each.

In the conventional examples disclosed in these publications, the turning position adjusting device tilts (turns) the two grindstones together with the slide along a horizontal plane including the axis of the work with the vertical axis as the turning center. 1 / to both opposing grindstones
The offset for 2 leads is given. However,
Since the slide is also swiveling at the same time, the cutting amount of each grindstone changes, and as a result, an accurate 1/2 lead offset cannot be secured.

Further, since the grindstone is cut into the horizontally supported work from the direction along the horizontal plane including the work axis, it corresponds to the size of the lead angle inclination of the thread groove at the grinding point of the grindstone. Therefore, it is necessary to incline (turn) the surface including the grinding edge of the grindstone with respect to the vertical surface by the lead angle. Nonetheless, no description was found regarding that point, and screw grinding is practically impossible.

Therefore, the present invention has been made in view of such a conventional problem, and by simultaneously grinding the outer surface screw of one screw shaft by using two facing grindstones, It is an object of the present invention to provide a grinding method for an outer surface screw that enables extremely efficient grinding.

[0012]

SUMMARY OF THE INVENTION To achieve the above object, an external thread grinding method of the present invention is to grind an external thread by rotating a screw shaft to be processed and relatively moving a grinding wheel parallel to the screw axis. In the method of grinding external threads to be processed, two pairs of grinding wheels are arranged opposite to each other with the screw shaft sandwiched therebetween, and the surface passing through the center of the grinding surface in each wheel is perpendicular to the vertical surface of the screw to be ground. Rotate for a considerable amount to incline both grindstones in the opposite direction, and perform grinding by simultaneously cutting these two grindstones from the direction orthogonal to the vertical plane passing through the axis of the screw shaft to be processed. It is characterized by.

[0013]

[Operation] This is a grinding method applicable to both single and double thread screws. In the case of a single thread screw, the two grindstones are offset by ½ lead and one is preceded. The trailing grindstone is set to a depth of cut that is deeper than the depth of cut of the preceding grindstone, and grinding is performed simultaneously. In the case of a double thread screw, two grindstones are not offset but are cut in a state where they face each other in the direction orthogonal to the screw shaft to be processed, and grinding is performed at the same time.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.
1 to 4 show an outline of a first embodiment of the present invention. FIG. 1 is a front view of a grinder for carrying out the method of the present invention, and FIG. 2 is a view taken along the line II-II thereof. 2 is a partially enlarged view of FIG. 2 for explaining one mode of simultaneous grinding of a work by two grindstones, and FIG. 4 is a plan view of FIG.

A screw shaft (work) W to be processed is a headstock 3 mounted on a bed 1 of a grinder via a table 2.
It is horizontally supported by a main shaft 4 which is rotatably provided and a tailstock 5 which faces the main shaft 4. The table 2 is slidably guided in the axial direction on the upper surface of the bed 1 through a linear guide device 7, and can be reciprocated by a table feed drive device 8 having a feed screw device 8a.

On both sides of the table 2, two grindstone mounts 10 are symmetrically arranged on the upper surface of the grindstone mount 11. Each grinding wheel base 10 is provided with a grinding wheel head grinding feed driving device 13 having a linear guide device 13a and a feed screw 13b. While being guided slidably through the linear guide device 13a, forward and reverse rotations of the feed screw 13b are performed. It is possible to reciprocate in the direction orthogonal to the table 2. Further, a slide mechanism 14 is provided on one of the grindstone bases 10 so as to be able to move on the grindstone bed 11 in a direction along the work W by a small amount, whereby the position of the one grindstone base 10 is set to the work W. Can be fine-tuned along.

A lead angle turning mechanism 15 having a cylindrical frame 16, for example, is provided on the base of each grindstone base 10, and a grindstone (car) 17 and its rotation drive device (in the frame 16). For example, a belt type) 18 and a grindstone shaping device (for example, a diamond dresser) 19 arranged so as to be able to move forward and backward immediately after the grindstone are provided. In this case, it is desirable that the grindstone shaping device 19 be provided with a fine adjustment mechanism for the advance / retreat distance. Lead angle turning mechanism 15, there are provided located on the horizontal plane the axis O ₁₆ of the cylindrical frame 16 passing through the axis of the workpiece W which is set in the processing state so as to be perpendicular to the axis of the workpiece W In addition, the cylindrical frame 16 can be turned by a predetermined angle with the frame axis O ₁₆ as the turning center.

The method of grinding the double thread on the outer surface of the work W with the above grinding machine is as follows. Both ends of the work W on which the lower thread of the double thread is formed in advance in consideration of the grinding allowance are supported by the spindle 4 and the tailstock 5, and if necessary, supported by the steady rest 20 from below at the intermediate position. Attach the work W to the grinder.

According to the lead angle θ of the external thread of the work W, the cylindrical frame 16 of the lead angle turning mechanism 15 on one of the grindstones 10 is moved toward the spindle 4 side by the angle θ as shown in FIG. Rotate to and fix. As a result, the grindstone 17 on one of the grindstones 10 is fixed in a posture in which the surface P passing through the center of the grinding surface is inclined by the lead angle θ with respect to the vertical surface passing through the frame axis O ₁₆ . Further, the cylindrical frame 1 of the lead angle turning mechanism 15 on the other grindstone base 10
6 is swung by the angle θ toward the tailstock 5 side and fixed. As a result, the grindstone 17 on the other grindstone base 10 has the surface P passing through the center of the grinding surface thereof on the side opposite to the grindstone 17 corresponding to the lead angle θ with respect to the vertical plane passing through the frame axis O _16. Fixed in a tilted position.

The frame axis O of both of these whetstones 10
₁₆ finely adjusts the position of one of the grindstones 10 in the direction along the work W by the slide mechanism 14 so as to completely align it on a straight line with the axis of the work W interposed therebetween. The work W is rotated by the drive of the spindle 4, and the grinding head grinding feed drive device 13
The grinding wheels 17 on both sides are brought closer to the work W by the driving of the above, and cut by a predetermined cut amount as shown in FIGS. 3 and 4. At this time, the grinding points K ₁ and K _{2 of} both grindstones 17 and 17
Is completely aligned with the line connecting the frame axes O ₁₆ and O ₁₆ and is orthogonal to the axis of the work W. One grinding point K ₁ is cut into one thread groove W _a of the double thread, and the other grinding point K ₂ is cut into a position opposite to the thread groove W _b of the other thread.

In this state, the table feed driving device 8 is driven to feed the table 2 and then the work W in the axial direction while accurately synchronizing with the rotation of the spindle 4, and simultaneously grinds two threads. Next, using the above grinder, the work W
A method of grinding a single thread screw on the outer surface of the will be described.

In this case, one of the grindstone bases 10 is moved in parallel along the work W by the slide mechanism 14, and as shown in FIG.
/ 2 The lead is shifted and placed. Then, one of the grinding wheel 17 preceding the the depth of the sum (t ₁ + t ₂₎ of the further depth of cut t ₂ therefrom depth of cut t ₁ and the rear row of the other grinding wheel 17 in two of the grinding wheel 17 Cut continuously. In this way, it takes about half the time as compared with the case where the conventional grindstone first grinds with the cutting depth of t ₁ and then grinds again with the cutting depth t _2. It becomes possible to grind.

Needless to say, the present invention is not limited to the structure of the grinding machine illustrated in the above embodiment.

[0024]

As described above, according to the method for grinding an outer surface screw of the present invention, the outer surface screw is ground by relatively moving the grinding wheel parallel to the screw shaft while rotating the screw shaft to be processed. In this case, two pairs of grinding wheels are arranged opposite to each other with the screw shaft in between, and the surface passing through the center of the grinding surface in each wheel is turned by the lead angle of the screw to be ground with respect to the vertical surface to make both grinding wheels. The two grinding wheels were tilted in the opposite directions, and the two grinding wheels were cut at the same time from a direction perpendicular to the vertical plane passing through the axis of the screw shaft to be processed. Therefore, the single-thread screw or the double-thread screw can be ground very efficiently in a short time.

Further, with respect to the accuracy of the grinding screw, the following effects can be obtained. When grinding a single thread, two grindstones offset along the work screw axis by 1/2 lead are used to cut simultaneously from the right angle direction. Therefore, two conventional opposed grindstones are cut diagonally to the screw axis. Just like the one, the cutting amount of each grindstone changes and accurate 1/2
According to the present invention, extremely accurate grinding of the single thread can be performed without the offset for the lead being not secured.

In the case of grinding a double thread, since there is simultaneous double thread grinding, there is no time difference and no cumulative read error due to temperature difference occurs. As a result, adjacent pitch error is prevented. Therefore, it is not necessary to perform fine grinding to suppress heat generation and stress generation during grinding while maintaining a high degree of temperature control, ensuring high precision, low cost, and high productivity even with long multi-thread screws. To be done.

[Brief description of drawings]

FIG. 1 is a front view of a grinding machine for carrying out the method of the present invention.

FIG. 2 is an arrangement relational diagram of main parts shown by an arrow II-II in FIG.

FIG. 3 is a partially enlarged view of FIG. 2 for explaining a mode of simultaneous grinding of a double thread screw by two grindstones of the present invention.

FIG. 4 is a plan view of FIG. 3;

FIG. 5 is a plan view for explaining a mode of simultaneous grinding of single thread screws by two grindstones of the present invention.

[Explanation of symbols]

 W Worked screw shaft (workpiece) 15 Lead angle turning mechanism 17 (Grinding) Wheel

Claims (1)

[Claims] 1. A method of grinding an external thread, wherein a grinding wheel is relatively moved in parallel to the threaded shaft while rotating the threaded shaft to be machined to grind an external thread. While facing each other across the grinding wheel, the surface passing through the center of the grinding surface in each grindstone is turned by the angle equivalent to the lead angle of the screw to be ground with respect to the vertical surface, and both grindstones are tilted in the opposite direction. A method for grinding an external thread, which comprises simultaneously cutting a grinding wheel from a direction perpendicular to a vertical plane passing through the axis of a screw shaft to be processed to perform grinding.