JPS632644A - Thermal expansion compensator for boring main shaft device of machine tool - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a spindle device of a machine tool that grips a tool at the tip of the tool spindle and performs relative movement with a workpiece while rotating to perform machining. Regarding a boring spindle device in which the tool spindle is configured to be able to reciprocate in the axial direction, the tool spindle expands and extends in the axial direction due to heat generated in the vaginal boring spindle device during machining of a workpiece. The present invention relates to a thermal expansion correction device for a boring spindle device of a machine tool, which prevents deterioration of machining accuracy.

[Prior art and its problems]

Boring spindle devices are used in the spindle heads of boring machines, milling machines, machining centers, etc. In these machine tools, the tool spindle is formed into an elongated shape to be suitable for deep drilling in narrow places. It is inserted in the axial direction into the hollow part of the boring spindle rotatably supported within the clamp of the spindle head, and is configured to reciprocate with a predetermined stroke. In order to obtain this reciprocating motion, a tool spindle reciprocating means is provided inside the I-clamp and connected to the rear end of the tool spindle. In such a boring spindle device, it is inevitable that the tool spindle expands due to the heat generated from each bearing part during operation, but the extension of the tool spindle in the axial direction due to this thermal expansion causes the tool spindle reciprocating means to expand. It is concentrated exclusively towards the front as a base point. This is because the reciprocating means is configured to be reliably moved by a predetermined amount and stopped by a drive source such as a servo motor driven by an NC command.
This is because rearward extension is prevented by this reciprocating means. Therefore, the tool attached to the tip of the tool spindle is
It will protrude forward by the amount of this thermal expansion, and as a result, excessive cutting will be performed and machining accuracy will decrease. for example,
In the case of mold machining in which the same tool is used to cut the bottom surface for a long period of time, there are drawbacks such as a difference in level occurring due to changes in elongation of the tool spindle over time.

[Means for solving problems]

The purpose of the present invention is to solve the above-mentioned drawbacks of the prior art. That is, even if the tool spindle expands due to thermal expansion during machining, this expansion is prevented as much as possible from moving toward the tip of the spindle. This prevents deterioration in processing accuracy.

The second purpose is to provide a signal regarding the thermal expansion of the tool spindle to the NC device that controls the tool spindle reciprocating means when machining the workpiece.
This corrects the C command signal and prevents a decrease in machining accuracy.

The above-mentioned purpose is to provide a spindle device for machining a machine tool that holds a processing tool at its tip and moves in the axial direction while rotating to process a workpiece. a boring main shaft which is rotatably supported in the radial direction; In the thermal expansion correction device for a boring spindle device of a machine tool, the tool spindle is configured to be capable of reciprocating movement relative to the tool spindle and has a processing tool attached to its tip, and the thermal expansion correction device for a boring spindle device of a machine tool corrects elongation in the axial direction due to thermal expansion of the tool spindle. A feed screw mechanism is provided in the clamp in parallel with the tool spindle, and a tool spindle reciprocating means for driving the feed screw mechanism to reciprocate the tool spindle in the axial direction; A clamp member, which has a thin cylindrical shape and elastically contracts in the inner radial direction when pressure is applied to the outer peripheral portion and tightens the tool spindle, is provided between the boring spindle and the tool spindle, and a pressurized fluid that pressurizes the clamp member. a pressurized fluid supply means for supplying the pressurized fluid to the outer peripheral portion of the clamp member; and a switching control device that releases the tool spindle reciprocating means to a free state when the pressurized fluid is being supplied to the clamp member. This is achieved by a thermal expansion correction device for a boring spindle device of a machine tool.

A second aspect of the present invention is a boring spindle device for a machine tool that holds a processing tool at its tip and moves in the axial direction while rotating to machine a workpiece, which includes a housing and a main shaft in the housing that moves in the axial direction. a boring main shaft which is fixed and rotatable in the radial direction; A thermal expansion correction device for a boring spindle device of a machine tool, comprising a tool spindle configured to be able to reciprocate with respect to the spindle and having a machining tool attached to its tip, and correcting elongation in the axial direction due to thermal expansion of the tool spindle. , a feed screw mechanism is provided in the housing parallel to the tool spindle! a tool spindle reciprocating means for reciprocating the tool spindle in the axial direction by driving s with a servo motor, and a thin cylindrical shape between the boring spindle and the tool spindle in a region near the front end of the boring spindle. a clamp member that elastically contracts in the inner radial direction and tightens the tool spindle when the outer peripheral portion is pressurized; and a pressurized fluid supply means for supplying pressurized fluid for pressurizing the clamp member to the outer peripheral portion of the clamp member. a switching control device that releases the tool spindle reciprocating means to a free state when pressurized fluid is being supplied to the clamp member; movement amount detection means for detecting the amount of movement of the feed screw of the tool spindle reciprocating means due to thermal expansion and elongation in the axial direction of and a numerical control device that corrects the amount of movement of the tool spindle reciprocating means based on the value detected by the shearing amount detection means when the supply of pressurized fluid to the clamp member is stopped,
This is achieved by a thermal expansion correction device for a boring spindle device of a machine tool, which is characterized in that it corrects elongation in the axial direction due to thermal expansion of the tool spindle.

〔Example〕

In order to explain the present invention in more detail, its structure and operation will be described based on preferred embodiments shown in the drawings.

FIG. 1 shows a side sectional view of a boring spindle device according to the present invention.

Figure 2 is a sectional view taken along the line ■-■ in Figure 1, and Figure 3 is a cross-sectional view of the
FIG. 3 is a sectional view taken along line 11-1 in the figure.

A boring spindle 2 is inserted into the first half of a hollow housing 1 of a spindle head A of a machine tool, and is rotatably rotated in the radial and It is mounted so that it cannot move in the axial direction.

A tool spindle 4 is inserted coaxially through the hollow portion of this boring spindle 2 and is supported by bushings 30 and 30. A key groove 6 is formed in the axial direction on the outer peripheral surface of the rear half of the tool spindle 4, and a key 5 bolted to the rear end of the boring spindle 2 is engaged therewith. In cooperation with tool spindle reciprocating means, which will be described later, the tool spindle 4 is configured to rotate integrally with the boring spindle 2 in the rotational direction and to be able to reciprocate in the axial direction. A tool holder 7 is removably provided at the front end of the tool spindle 4 and holds various tools.

In the boring spindle device having such a configuration, when the boring spindle 2 is rotationally driven by a drive system (not shown) via the gear 8 fixed to the outer periphery of the boring spindle 2, the tool spindle 4 is rotated accordingly. is also rotationally driven. The above configuration is substantially the same as a conventional boring spindle device.

One of the features of the present invention is that an annular clamp sheath 9 surrounding the outer circumferential surface of the tool spindle 4 is provided on a part of the inner circumferential surface of the boring spindle 2.
This is due to the fact that it has been fixed. An annular recess is provided on the outer circumferential surface of the clamp shoe 9 so that an annular pressurizing chamber 10 is formed between the clamp shoe 9 and the inner circumferential surface of the boring spindle 2, so that the wall surface facing the tool spindle 4 is thin. It has a section 11. Since the clamp shoe 9 is formed in such a shape, it is easily deformed elastically in the radial direction and has high rigidity in the axial direction. In the case of this embodiment, when the Crangunyu 9 is not activated,
A clearance of approximately 20 μm exists between the tool spindle 4 and the tool spindle 4, and during operation, the thin wall portion 11 elastically contracts in the radial direction to tighten the tool spindle, and the tool spindle is attached to the boring spindle 2 at an arbitrary position. It can be clamped against. A pressure oil supply ring 12 is inserted into and surrounded by the outer peripheral surface of the boring spindle 2 corresponding to the pressurizing chamber 10 .

It is preferable that the pressure oil supply ring 12 has an inner circumferential portion 14 facing the boring main shaft 2 made of a bearing material such as gun metal, and is integrally molded with the outer circumferential steel material. The tip of the pipe 13, which is fixed through the housing 1, is fitted into a through hole 12a drilled in the radial direction of the pressure oil supply ring 12, and the pressure oil supply ring 12 is fixed in the rotational direction and the axial direction. ing.

An annular oil reservoir υ15 is formed on the inner peripheral surface of the pressure oil supply ring 12, and at least one through hole 31 is bored in the radial direction in the boring main shaft 2 facing the core oil reservoir 15. .

When the pressurized oil is completely supplied from the pressurized oil supply device 29 as shown by the arrow 32, it passes through the pipe 13 and the through holes 12m and 31, whether the boring spindle 2 is stationary or rotating. The pressure oil reaches the pressurizing chamber 10 of the clamp shoe 9.

In this embodiment, the clearance between the inner circumferential portion 14 of the pressure oil supply ring 12 and the outer circumferential portion of the boring spindle 2 is approximately 20μ.
There is virtually no leakage of pressure oil from here,
Therefore, there is almost no pressure drop in the pressurizing chamber 10.

Note that the pressure of the pressure oil in this example is 70 kg/cm2. - On the other hand, when the hydraulic pressure is released, the thin-walled portion 11 elastically returns to its original state, and the predetermined clearance is restored between the boring spindle 2 and the tool spindle 4, allowing the tool spindle 4 to move in the axial direction. becomes. As described above, according to the clamp shoe of the present invention, gripping is performed by applying uniform pressure from the outer periphery of the spindle using the annular pressurizing chamber, so eccentricity of the tool spindle is avoided and highly accurate machining is guaranteed.

Next, the structure of the tool spindle reciprocating means for reciprocating the tool spindle 4 in the axial direction with respect to the boring spindle 2 will be described. This tool spindle reciprocating means is provided in the rear half of the housing 1, and includes two feed screw mechanisms 16 arranged symmetrically and parallel to each other with the axis of the tool spindle 4 in between. This feed screw mechanism 16 has bearings 17 at both ends.
A ball screw 18 rotatably supported with respect to the housing 1 by a nut 1 screwed onto the ball screw 18.
9. As shown in FIGS. 1 and 3, each feed screw mechanism 16C nut 19 is attached to both end regions of a common bracket 21 rotatably attached to the rear end of the tool spindle 4 via a bearing 20. Fixed and supported. A timing belt 22 is fixed with a key to each rear end of the ball screw 18 that passes through the bearing 17 and extends further rearward. A timing belt 23 is stretched between these pulleys 22, and this belt 2
3 is configured to be driven by a servo motor 24 attached to the rear wall of the housing 1 via a motor gully 25. As a result, it will be understood that both the sol screws 18 are rotated in synchronization with each other by the servo motor 24 receiving the NC command.

The operation of the above-mentioned tool spindle reciprocating means will be described. When the tool spindle 4 is to be moved relative to the boring spindle 2 by a predetermined distance, a signal is inputted to the servo motor 24 to give the desired rotation while the grip of the clamp shoe 9 is loosened. Correspondingly, this rotation is Gu IJ 25, 22
and is transmitted to the ball screws 18 through the belt 23, and each sol screw 18 rotates in the same direction in synchronization. By this.

The lever 19 moves on the male screw 18 in the forward or backward direction. This movement of the nut 19 is transmitted to the tool spindle 4 via the plug and nut 21, causing it to move forward or backward in the same way. - On the other hand, regarding the axial direction of the main shaft 2,
Since it is fixed relative to the housing 1, the tool spindle 4 can eventually move back and forth relative to the boring spindle 2. In this embodiment, the structure is such that a reciprocating motion of 300 cm is possible. As mentioned above, this reciprocating motion is performed simultaneously and equally by the two feed screw mechanisms arranged symmetrically with respect to the axis of the tool spindle, so it is as if the axis of the tool spindle is being driven. It has the same effect as that, and eliminates the twisting between the boring spindle and the tool spindle, which has been a problem in the past.

Now, in the medium p spindle device having the above-mentioned configuration, when machining is performed for a long time by positioning the tool spindle at a certain position in the axial direction, such as mold machining, the pressure is changed by the action of the switching control device 28. Pressure oil is supplied from the oil supply device 29 into the pressurizing chamber 10, the clamp shoe 9 is operated, and the tool spindle 4 and the boring spindle 2 are fixed integrally. At the same time, the switching control device 28 causes the servo to release the drive system of the motor 24 through the NC device 26, so that the servo motor 24
is held in a state where it can move freely by external force. When the tool spindle 4 thermally expands in this state, the resulting expansion in the axial direction is distributed based on the portion gripped by the clamp shoe 9, corresponding to the length of the front and rear regions. That is, since the servo motor 24 is in a free rotation state, the extension of the tool spindle 4 in the rear area is only possible through the bracket 21.
Applying a pushing force toward the rear (to the right in Figure 1),
This causes the ball screw 18 to rotate, and the servo motor 24 is eventually rotated from the output side. In addition, sol screws,
The mechanism is highly efficient, so it is negligible.

The sol screw can be easily rotated due to the direct motion of the shaft.

- The extension in the manly region advances the tip of the tool spindle, but as is clear from the figure, since the clamp shoe is located near the front end of the housing 1, the front region of the tool spindle 4 It is shorter than the rear region, so the absolute value of thermal expansion in this region is smaller than that of the entire region.

If you want to start the next process by releasing the clamp between the tool spindle 4 and the boring spindle 2, you can correct the origin using a known automatic centering device (not shown), and then the clamp shoe 9 can be The desired machining accuracy can be obtained by correcting the amount of forward restoration and extension of the tool spindle 4 that occurs when the tool is released.

If the machine tool is not equipped with this automatic centering device, it may be controlled as follows. In the second method, the tool spindle 4 and the boring spindle 2 are clamped, the servo motor 24 is rotated from the output side due to rearward thermal expansion of the tool spindle 4, and then the clamp shoe 9 is released and the When giving NC commands for machining in a process, if the NC commands are given in an incremental manner starting from the final position where the servo motor 24 is rotated from the output side, the tool spindle 4 can be moved backwards. The amount of thermal elongation is substantially canceled, and high processing accuracy can be obtained.

In the second method, the rotation of the ball screw 18 due to thermal expansion of the tool spindle 4 is transmitted to the servo motor 24 via the pulley 22, belt 23, and motor pulley 25i to rotate it, but the amount of rotation is It is counted by a rotary encoder 27 built into the servo motor 24,
The signal is input to the NC device 26 and stored as a corresponding signal Δθ.

In this state, in order to finish a predetermined machining stage and move on to the next stage of machining, loosen the clamp shoe 9 and press the ambidextrous shaft 2.
, 4 is released, and a predetermined amount of NC command θ is given to the servo motor 24 from the NC device 26 again. When an NC command is given in the absolute system, the position origin remains unchanged as a characteristic of the servo motor, so if this continues, the servo motor will compensate for the length of the tool spindle 4 that has been freely extended backwards, return to the origin, and then return to the origin by an additional Δθ. This causes the tool spindle 4 to rotate so as to move it forward, which adversely affects machining accuracy. In order to solve this problem, in the present invention, when the clamp shoe 9 is released, the NC command signal of the movement amount θ given from the outside in advance corresponds to the backward extension of the tool spindle 4 measured during the previous machining. The configuration is such that the value obtained by subtracting the value Δθ is input to the servo motor 24.

These control operations are performed according to the block diagram shown in FIG. That is, the release of the clamp shoe 9 is commanded by the switching control device 28 to cut off the supply of pressure oil from the hydraulic pressure supply device 29. And at the same time N
A command is also given to the C device 26 to reactivate the servo motor 24, which was held in a free state. At that time, N
Inside the C device 26, an NC command signal of a predetermined amount θ input from the outside using an NC tape or the like is corrected by Δθ corresponding to the previously detected thermal expansion, and a command signal of a smaller value θ is corrected.
-Δθ is input to the servo motor 24. As a result, the tool held at the tip of the tool spindle 4 can be moved to a desired position by subtracting the amount of thermal expansion of the tool spindle 4.

On the other hand, when fixing the ambidextrous shafts 2 and 4 integrally, the hydraulic pressure supply device 29 is activated by a command from the switching control device 2B to feed pressurized oil into the pressurizing chamber lo and actuate the clamp shoe 9. urge At the same time, the NC device 26 also has a servo control function for the servo motor 24. A release command is issued to hold it in the free state. Therefore, as described above, the expansion of the tool spindle 4 due to thermal expansion is mainly borne by the rear region button while the servo motor 24 is rotated from the output side.

〔Effect of the invention〕

As detailed above, according to the present invention, the elongation of the tool spindle due to heat generation during workpiece machining is mainly borne by the rear region of the tool spindle with respect to the position of the clamp shoe.
Since the front region carrying the tool is prevented from elongating as much as possible, machining accuracy in the axial direction is improved. As a specific example, in the case of a mold blade Roe that performs long bottom cutting using the same tool, the servo motor of the tool spindle reciprocating means is released to a free state while the tool spindle and boring spindle are clamped. As a result, the next level difference, which conventionally occurs due to changes in elongation of the tool spindle over time, no longer occurs.

Furthermore, once the grip of the clamp shoe on the tool spindle whose extension has been controlled in this way is released, in the conventional device, the thermal elongation is measured based on the NC command signal at that time with the rear end of the tool spindle as a reference. However, in the present invention, the NC command is given in an incremental manner starting from the position of the servo motor immediately before the clamp is released, or the servo motor is extended forward due to thermal expansion immediately before the clamp is released. The amount of rotation in the reverse direction of the tool is memorized and subtracted from the next NC command signal to correct the origin before being input to the servo motor, so the tip position of the tool spindle is determined by the amount of thermal expansion. It becomes possible to occupy a desired position corrected by the amount, and the machining accuracy in the axial direction is also improved.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view schematically showing the boring spindle device of the present invention, FIG. 2 is a sectional view taken along the line ■-■ in FIG. 1 showing the coupled state of the tool spindle and the boring spindle, FIG. 3 is a sectional view taken along the line ■-■ in FIG. 1, showing the drive of the tool spindle reciprocating means. 1...Housing, 2...Boring spindle, 3...Bearing, 4...Tool spindle, 5...Key, 6...
Keyway, 7... Tool holder, 8... Gear, 9...
Clamp sea, 10... Pressure chamber, 11... Thin wall portion, 12... Pressure oil supply ring, 12a... Through hole, 1
3... Volume, 14... Inner peripheral portion of pressure oil supply ring, 15... Oil reservoir, 16... Feed screw mechanism, 17
...bearing, 18...sol screw, 19...
Nut, 20... Bearing, 21... Bracket, 22... Timing pulley, 23... Timing belt, 24... Servo motor, 25... Motor pulley, 26... NC device, 27... ... rotary encoder, 28 ... switching control device, 29 ... pressure oil supply device, 30 ... bushing, 31 ... through hole, 32 ...
...Arrow, A...Spindle head.

Claims (1)

[Scope of Claims] 1. A boring spindle device for a machine tool that holds a processing tool at its tip and moves in the axial direction while rotating to process a workpiece, comprising a housing and a main shaft device fixed in the axial direction within the housing. and a boring main shaft that is rotatably mounted in the radial direction,
A tool spindle inserted into the boring spindle coaxially with the boring spindle, rotates integrally with the boring spindle in the rotational direction, and is configured to be able to reciprocate with respect to the boring spindle in the axial direction, and has a machining tool attached to its tip. In the thermal expansion correction device for a boring spindle device of a machine tool, the feed screw mechanism is provided in the housing in parallel with the tool spindle, and the feed screw mechanism is provided in the housing in parallel with the tool spindle. a tool spindle reciprocating means for reciprocating the tool spindle in the axial direction by driving the tool spindle; and a thin-walled cylindrical outer peripheral portion between the boring spindle and the tool spindle in a region near the front end of the boring spindle. a clamp member that elastically contracts in the inner radial direction when pressurized to tighten the tool spindle; a pressurized fluid supply means for supplying pressurized fluid to an outer peripheral portion of the clamp member to pressurize the clamp member; A thermal expansion correction device for a boring spindle device of a machine tool, comprising a switching control device that releases the tool spindle reciprocating means to a free state when pressurized fluid is being supplied to a member. 2. The tool spindle reciprocating means has two nuts each fixed to both ends of a bracket attached to the rear end of the tool spindle via a bearing, and is threadedly engaged with each nut to move the tool spindle toward the tool spindle. and a pulley fixed to the rear end of each ball screw, which is rotatably supported by the housing in parallel and symmetrically about the axis of the tool spindle. The thermal expansion correction device for a boring spindle device of a machine tool according to claim 1, comprising a motor that rotationally drives the ball screw via a belt. 3. The thermal expansion correction device for a boring spindle device of a machine tool according to claim 2, wherein the motor is a servo motor capable of positioning control in accordance with an NC command. 4. A boring spindle device for a machine tool that holds a machining tool at its tip and rotates while moving in the axial direction to machine a workpiece, which includes a housing, and is fixed in the axial direction within the housing and rotates in the radial direction. A freely mounted boring spindle,
A tool spindle inserted into the boring spindle coaxially with the boring spindle, rotates integrally with the boring spindle in the rotational direction, and is configured to be able to reciprocate with respect to the boring spindle in the axial direction, and has a machining tool attached to its tip. In the thermal expansion correction device for a boring spindle device of a machine tool, the feed screw mechanism is provided in the housing in parallel with the tool spindle, and the feed screw mechanism is provided in the housing in parallel with the tool spindle. a tool spindle reciprocating means for reciprocating the tool spindle in the axial direction by driving the tool spindle with a servo motor; and a thin cylindrical shape between the boring spindle and the tool spindle in a region near the front end of the boring spindle. a clamp member that elastically contracts in the inner radial direction when pressure is applied to the outer peripheral portion thereof and tightens the tool spindle; and a pressurized fluid supply means for supplying pressurized fluid for pressurizing the clamp member to the outer peripheral portion of the clamp member. a switching control device that releases the tool spindle reciprocating means to a free state when pressurized fluid is being supplied to the clamp member; a movement amount detection means for detecting the amount of movement of the feed screw of the tool spindle reciprocating means due to thermal expansion and elongation in the axial direction; a servo motor of the tool spindle reciprocating means; a numerical control device that corrects the amount of movement of the tool spindle reciprocating means based on the value detected by the movement amount detection means when the supply of pressurized fluid to the clamp member is stopped; A thermal expansion correction device for a boring spindle device of a machine tool, which is characterized by correcting elongation in the axial direction due to expansion. 5. The tool spindle reciprocating means has two nuts each fixed to both ends of a bracket attached to the rear end of the tool spindle via a bearing, and is threadedly engaged with each nut to move the tool spindle toward the tool spindle. and a pulley fixed to the rear end of each ball screw, which is rotatably supported by the housing in parallel and symmetrically about the axis of the tool spindle. 5. The thermal expansion correction device for a boring spindle device of a machine tool according to claim 4, comprising a servo motor that rotationally drives the ball screw via a belt based on a command from the numerical control device. 6. The thermal expansion correction device for a boring spindle device of a machine tool according to claim 5, wherein the movement amount detection means is a rotary encoder that detects the rotation amount of the servo motor.