JPH0549235U - Machine Tools - Google Patents

Abstract

(57) [Abstract] [Purpose] The present invention is based on the change over time by devising the axial fixing position of the screw member so that the elongation on the main shaft side and the elongation of the screw member due to heat are offset. An object of the present invention is to provide a machine tool with high processing accuracy that does not require correction work. [Structure] A main shaft part 14 for holding a rotary tool 19, a ball nut 21 connected to the main shaft part side moving bases 12, 13, a ball screw 22 connected to the ball nut 21, and bearing parts 23, 24 for axially supporting the ball screw 22. Feed mechanism 20 that moves the nut 21 in the axial direction of the screw 22
In the machine tool having the feed mechanism 20 for moving the tool 19 in the axial direction of the screw 22 to increase or decrease the working depth of the workpiece 1, the bearing portion 23 regulates the axial displacement of the screw 22. It has the first bearings 41 and 42 and the second bearing 46 that axially supports the screw 22 so as to be axially displaceable. The second bearing 46 is rotatably supported, and the second bearing 46 is rotatably supported on the side where the working depth decreases.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to improvement of a machine tool that performs cutting with a rotary tool.

[0002]

[Prior Art]

 Generally, in a working machine such as a milling machine that cuts a work (workpiece) with a rotary tool, the spindle is attached with the rotary tool and the workpiece is relatively displaced to cut a predetermined portion of the work at a predetermined depth. In recent automatic machine tools, for example, the main shaft part is moved back and forth according to a predetermined control program and is moved in the direction perpendicular to the axis. In addition, a ball screw mechanism is often used as the feed mechanism in order to secure the tool position and its feed accuracy. In addition, in order to eliminate rattling in the axial direction of the main shaft, a pair of angular contact ball bearings, for example, are used for the main shaft bearings. The preload is adjusted by energizing.

[0003]

[Problems to be solved by the device]

 However, in such a conventional machine tool, when machining is performed by continuous operation, heat is generated and each part is stretched, causing the tool tip to displace over time, and at the start of operation the desired range However, there was a problem that the machining accuracy that was present in the machine would deteriorate over time. For this reason, when processing a product that requires high accuracy, it is necessary for the operator to correct the tool position after a predetermined time has passed.

Explaining in a concrete example, first, in FIG. 5, a work 1 constitutes a constant velocity ball joint that transmits rotation in an axially intersecting state, and has a hemispherical concave portion 1a at one axial end thereof. A plurality of curved ball grooves 1b are formed on the inner circumference of the ball groove 1b at equal intervals. The ball groove 1b is adapted to engage with a plurality of balls 5 arranged at equal pitches on a predetermined pitch circle, and the positional accuracy and the shape accuracy of the ball groove 1b are highly required. In order to machine this work 1, the axis of the work 1 and the axis of the rotary tool intersect at a predetermined intersection angle on the XZ plane at the predetermined position (height) in the Y-axis direction, and in that state the position of the tool tip. Is moved in the X and Z directions (axial direction of the main shaft) to form one groove, and the work 1 is rotated by a predetermined angle to form the next groove 1b. In the case of the machine tool used for this machining, the elongation due to heat was almost saturated 2 hours after the start of machining, so the measurement at this point showed that the tool tip position P ₀ at the start of machining The tip position P ₁ was displaced in the direction in which the cutting depth (processing depth) increased by 160 μm at the core height A and 118 μm at the pitch circle diameter B.

The change in the depth of cut due to this heat is caused by the elongation of the ball screw in the Z direction (e _{1 in the} figure) and the elongation of the main shaft (e _{2 in the} figure) in which the temperature rise due to heat generation is significant, It was found that the elongation of the screw (e _{3 in the} figure) had an influence, and in particular, a large thermal displacement occurred due to the polymerization of the elongations (e ₁ , e ₂ ) in the Z direction. Therefore, in the present invention, by devising the axially fixed position of the screw member, the elongation on the main shaft side due to heat and the elongation of the screw member are offset, and the correction work is performed even during continuous operation. It is an object of the present invention to provide a machine tool that does not require high processing accuracy.

[0006]

[Means for Solving the Problems]

 To achieve the above object, the present invention provides a main shaft part for holding and rotating a rotary tool in a predetermined direction, a moving member connected to the main shaft part and a member on the main shaft part side, and a screw member screwed to the moving part material. And a feed mechanism that has a bearing portion that axially supports the screw member, and that moves the moving member in the axial direction of the screw member. The feed mechanism moves the rotary tool in the axial direction of the screw member and In a machine tool configured to increase or decrease the depth of processing, the bearing portion axially displaces the screw member and a first bearing that axially supports the screw member and restricts axial displacement of the screw member. A second bearing that axially supports the first bearing, and the first bearing axially supports one end of the screw member on the side where the working depth increases due to the movement of the rotary tool, The second bearing is the screw member. Of both axial ends, and is characterized in that the depth of machining by the movement of the rotary tool is journalled the end of the decreasing side.

[0007]

[Action]

 According to the present invention, the end of the axial end of the screw member on the side where the working depth of the rotary tool increases increases is controlled by the first bearing to reduce the working depth. Is rotatably supported by the second bearing so as to be axially displaceable. Therefore, the displacement of the tool tip due to the elongation of the spindle in the spindle direction and the displacement of the tool tip due to the elongation of the screw member are offset, and the displacement of the tool tip is reduced. Kept inside.

[0008]

【Example】

 Hereinafter, the present invention will be described with reference to the drawings. 1 to 4 are views showing an embodiment of a machine tool according to the present invention. Since the work to be processed according to the present embodiment is the same as the work 1 described above, the same reference numerals are used for the construction of the work, and duplicate description will be omitted.

In FIGS. 1 to 3, 11 is a base, 12 and 13 are movable bases, and a main shaft portion 14 is provided on the movable base 13. The main spindle portion 14 is composed of a main spindle 15 and a tool holding portion 16 in which a chuck mechanism (not shown) for holding a tool is installed, and a drive motor portion 18 that drives the main spindle 15 via a belt 17. The rotary tool 19 is held in the Z direction and is rotated. Further, between the base 11 and the moving base 12, there is provided a feed mechanism 20 for moving the moving base 12 in the left-right direction (Z direction) in FIG. 2 on the guide rail 11a of the base 11. A feed mechanism 30 for moving the moving table 13 in the vertical direction (X direction) of FIG. 2 is provided between the moving table 13 and the moving table 13 on the guide rail 12a of the moving table 12. Then, the work 1 is supported by a supporting means (not shown) so that the axis of the work 1 and the axis of the rotary tool 19 intersect at a predetermined intersection angle (for example, 20 degrees) on the XZ plane at a predetermined Y direction position. It is supported. Further, the work 1 is rotated by the supporting means in a predetermined angle unit corresponding to the pitch angle of the groove 1b, and the groove is sequentially processed. That is, the machine tool of this embodiment rotates the rotary tool 19 held on the main spindle portion 14 and, at the same time, on the XZ plane of a predetermined height by the feed mechanisms 20 and 30 in the X and Z directions (screw member By moving in the axial direction), one groove 1b is machined while increasing or decreasing the depth of cut of the rotary tool 19 with respect to the work 1 (the machining depth of the ball groove 1b). It is possible to process a plurality of grooves 1b into the same shape by rotating at a predetermined pitch angle unit.

Here, the feed mechanism 20 includes a ball nut 21 (moving member) fixedly connected to a moving base 12 that is a member on the main shaft portion 14 side, and a ball screw 22 (a screw member that is screwed to the ball nut 21). ), Bearings 23 and 24 that pivotally support the ball screw 22, and a servomotor 26 that rotationally drives the ball screw 22 via a flexible coupling 25. It is designed to move in the 22 axis direction (Z direction).

The bearing portion 23 of the feed mechanism 20 is located on the front end portion of the ball screw 22, that is, on the side of the axial end portions of the ball screw 22 where the cutting depth (machining depth) increases due to the movement of the rotary tool 19. The end portion is axially supported, and the bearing portion 24 is the rear end portion of the ball screw 22, that is, the end portion on the side where the cutting amount is reduced by the movement of the rotary tool 19 among the axial end portions of the ball screw 22. Is pivotally supported. Further, the bearing portion 23 has a pair of angular ball bearings 41 and 42 (first bearing) symmetrically arranged in the bearing housing portion 11h of the base 11, and one end of the ball screw 22 is formed by the both bearings 41 and 42. The part is axially supported and its axial displacement is regulated. Specifically, bearings 41 and 42 are attached to the stepped front end of the ball screw 22 with the thickened portion of the outer ring being opposite to the front and rear sides. A nut 43 is attached to the tip of the ball screw 22 so as to clamp the inner rings of the bearings 41 and 42. Further, the outer rings of both bearings 41 and 42 are designed to be pinched between the bearing retainer 45 fixed to the base 11 by a plurality of bolts 44 and the annular protrusion 11a of the base 11, and the nuts With the inner ring of both bearings 41, 42 firmly clamped and fixed by 43, the bearing retainer 45 clamps the outer rings of both bearings 41, 42 appropriately in the axial direction, so that the bearing part 23 Axial displacement will be regulated. The bearing portion 24 has a deep groove ball bearing 46 (second bearing) inserted in the bearing housing portion 11d of the base 11.

Further, similar to the feed mechanism 20, the feed mechanism 30 includes a ball nut 31 (moving member) fixedly connected to a moving base 13 which is a member on the main shaft portion 14 side, and a screw nut that is screwed to the moving member 31. A ball screw 32 (screw member), bearings 33 and 34 that axially support the ball screw 32, and a servomotor 36 that rotationally drives the ball screw 32 via a flexible coupling 35. Is moved in the axial direction (X direction) of the ball screw 32. The bearing portion 33 of the feed mechanism 30 pivotally supports the end portion (the right end portion in FIG. 3) of the axial ends of the ball screw 32 on the side where the cutting depth increases due to the movement of the rotary tool 19. The portion 34 pivotally supports one end portion (the left end portion in FIG. 3) of the axial ends of the ball screw 32 on the side where the cutting depth is reduced by the movement of the rotary tool 19. The bearing portion 33 has angular ball bearings 51 and 52 (first bearing) symmetrically arranged in the bearing housing portion 12h of the movable table 12, and the inner ring of both bearings 51 and 52 is sandwiched by the nut 53. The bearing retainer 55 is tightened with a plurality of bolts 54 while being pressed and fixed, so that the outer rings of both bearings 51 and 52 are appropriately clamped in the axial direction, and the axial displacement of the ball screw 32 is restricted. The bearing 54 has a deep groove ball bearing 56 (second bearing) housed in the bearing housing 12d of the movable table 12.

The drive motor unit 18 and the servomotors 36 and 46 are connected to a control circuit (not shown) and controlled according to a predetermined control program. The supporting means for the work 1 is also controlled by this control circuit. In the machine tool of the present embodiment configured as described above, the drive motor unit 18 and the servomotors 36 and 46 are controlled by the control circuit, and the rotary tool 19 moves on a predetermined curved orbit while rotating. The groove 1b is processed. Further, the supporting means for the work 1 is also controlled by this control circuit, and the work 1 is rotated by a predetermined pitch angle while the rotary tool 19 is retracted from the work 1 to move the next groove machining position to the XZ plane. Position it on top. Then, when a plurality of grooves 1b are cut at a predetermined pitch angle for one work 1 and the groove processing of the work 1 is completed, the processed work 1 supported by the supporting means is the unprocessed work 1 Will be replaced and a series of processing will be performed continuously.

During continuous operation, the spindle 15 and the ball screws 22 and 32 are subjected to load and heat, so that the ball screw 22 in the Z direction extends, the spindle 15 extends, and the ball screw 32 in the X axis direction extends. Is noticeable. However, in the case of this embodiment, the bearing portions 23 and 33 regulate the axial displacement of the ball screws 22 and 32, and the bearing portions 24 and 34 pivotally support the ball screws 22 and 32 so as to be axially displaceable. Of the axial ends of the ball screws 22 and 32, the end on the side where the working depth increases by the rotary tool 19 is restricted from moving in the axial direction, and the end on the side where the working depth decreases is displaced in the axial direction. It will be possible. Therefore, as shown in FIG. 4, the displacement of the tool tip (e _{2 in the} figure) due to the elongation of the spindle 14 side and the displacement of the tool tip (e _{1 in the} figure) due to the extension of the lead of the ball screw 22 are offset. Due to the influence of this and the elongation e _{3 in the} X direction, the rotary tool 19 is displaced from the machining start position Pb to the tool tip position Pa after thermal displacement, and this displacement amount is shown in FIG. It will be significantly reduced compared to the one shown.

When an experiment was conducted under the same machining conditions as those of the conventional example (the arrangement of the bearing portion is different), the extension e ₁ was about 70 μm, e ₂ was about 100 μm, and e ₃ was about 20 μm. Regarding the displacement, the displacement E _A in the height direction of the core was cut by about 34 μm, and the displacement E _B in the pitch radius direction was displaced by about 12 μm on the relief side (reduction side of the cut). These displacement amounts E _A and E _B are within the range of allowable displacement ± 50 μm.

As described above, in the present embodiment, it is possible to prevent the deterioration of the machining accuracy during the continuous operation, and it is possible to perform the continuous operation without the conventional work of correcting the tool position based on the change over time. .. As a result, it is possible to improve the machine operation rate and reduce the work load on the worker.

[0017]

[Effect of the device]

 According to the present invention, of the axial end portions of the screw member, the end portion on the side where the working depth of the rotary tool is increased is pivotally supported by the first bearing, and its axial movement is restricted, so that the working depth is increased. Since the end part on the side of the decrease of the shaft is axially supported by the second bearing so that it can be displaced in the axial direction, the displacement of the tool tip due to the extension in the spindle direction on the spindle side and the displacement of the tool tip due to the extension of the screw member By offsetting, the displacement of the tool tip can be reduced, and the machining accuracy can be kept within a predetermined range even during continuous operation. As a result, it is possible to eliminate the need for the work of correcting the tool position based on changes over time, and also to improve the operating rate of the machine.

[Brief description of drawings]

FIG. 1 is a front sectional view of an embodiment of a machine tool according to the present invention.

FIG. 2 is a plan view of an embodiment.

FIG. 3 is a sectional view taken along the line KK of FIG.

FIG. 4 is an explanatory view of the operation of the embodiment.

FIG. 5 is an explanatory diagram of a conventional problem.

[Explanation of symbols]

 1 Work 1b Groove 12, 13 Moving base (main shaft side member) 14 Main shaft 19 Rotating tool 20 Feed mechanism 21 Ball nut (moving member) 22, 32 Ball screw (screw member) 23, 24, 33, 34 Bearing 41, 42, 51, 52 Angular contact ball bearings (1st bearing) 46, 56 Deep groove ball bearings (2nd bearing)

Claims (1)

[Scope of utility model registration request] 1. A main shaft part for holding and rotating a rotary tool in a predetermined direction, a moving member connected to the main shaft part or a member on the main shaft part side, a screw member screwed to the moving member, and a shaft for the screw member. And a feed mechanism for moving the moving member in the axial direction of the screw member, which has a supporting bearing portion, and the feed mechanism moves the rotary tool in the axial direction of the screw member to increase or decrease the working depth of the workpiece. In the machine tool configured as described above, the bearing portion axially supports the screw member and restricts axial displacement of the screw member, and a second bearing axially displaces the screw member. And a first bearing rotatably supports one end of the screw member on the side where the working depth increases due to the movement of the rotary tool, and the second bearing has Of the axial ends of the screw member, Machine characterized in that the depth of the machining is journalled the end of the decreasing side by movement of the serial rotary tool.