JP2011062753A - Machine tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a damage prevention function against collision in a machine tool for machining a workpiece by relatively moving a spindle device and the workpiece. <P>SOLUTION: A bearing 4 for carrying a spindle 2 is held by an outer ring case 5. The outer ring case 5 moves backward together with the roller bearing 4 and the spindle 2 when axial load of collision exceeds a predetermined value. When a collision detecting sensor 3 detects the collision, a spindle feed motor is stopped within a predetermined time. A retreat stroke of the outer ring case 5 is specified so that retreat time of the outer ring case 5 in collision is longer than time required for the spindle feed motor to stop from start of the collision. Since the force of a predetermined value or larger is thus not loaded to the roller bearing 4 in the collision of the spindle 2 and the workpiece 11, the machine tool is stopped without damaging the roller bearing 4. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a machine tool, and more particularly to a technique for preventing damage to a spindle device due to a collision between a spindle and a workpiece.

In a machine tool that processes a workpiece by moving the spindle that rotates while holding the tool relative to the workpiece, the workpiece or workpiece holder is being moved while the spindle device is moving forward due to a data setting error, workpiece installation error, etc. And the main shaft collided, and the main shaft bearing holding the main shaft could be damaged.
In order to avoid the above damage, an impact absorbing member is installed at the projecting portion of the spindle of the machine tool, and the load on the spindle feed shaft at the time of collision is estimated from the torque command to the servo motor and the rotation speed of the servo motor (for example, Patent Document 1), when the value of the impact absorbing member exceeds a predetermined drag of the impact absorbing member at the time of collision, there is a conventional technique for stopping the feed shaft within the impact absorbing time of the impact absorbing member and preventing damage to the machine tool. (For example, see Patent Document 2).

JP-A-6-289917 JP 11-138380 A

Most of the damage at the time of the collision of the machine tool is that the spindle and the workpiece collide, and the spindle bearing is damaged due to an excessive load received by the spindle bearing of the spindle device at the time of the collision.
There is a conventional technique as shown in the above-mentioned Patent Document 2 in which an impact absorbing member is installed on the projecting portion of the main shaft and the impact at the time of collision is reduced to prevent damage to the main shaft device. An extra space for installation is required, and the area of interference between the spindle and the workpiece increases and the machining range decreases.

Also, the load received by the spindle bearing at the time of collision is the sum of the spindle feed shaft load and the inertial force of the device moved by this spindle feed shaft minus the inertial force of the spindle. The subtracted load.
In the collision damage prevention apparatus of Patent Document 2, collision detection is detected by estimating an increase in the load on the spindle feed shaft. For this estimation, as described in Patent Document 1, the mass of the spindle feed system, the frictional force of the spindle feed shaft, and the estimated value of the torque constant of the motor are used.

  The mass of the spindle feed system varies depending on the mass of the tool used, and the frictional force varies depending on the temperature and aging of the spindle feed shaft, resulting in an error in the estimated increase in the load on the spindle feed shaft and preventing collision damage. May not work properly and the bearings may be damaged.

  The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a machine tool capable of preventing damage to a spindle bearing due to a collision between a spindle and a workpiece.

  In order to solve the above-described problems, the invention according to claim 1 is characterized in that a main shaft that holds and rotates a tool, a rolling bearing that rotatably supports the main shaft, and an outer ring case that holds an outer ring of the rolling bearing. And a housing for holding the outer ring case, and an impact buffering means is provided between the outer ring case and the housing.

  A feature of the invention according to claim 2 is the machine tool according to claim 1, further comprising detection means for detecting the collision of the main shaft by a change in the state of the main shaft, and detecting that the main shaft has collided by the detection means. In this case, the spindle device damage prevention operation is performed to prevent the spindle device from being damaged.

  According to a third aspect of the present invention, in the machine tool according to the second aspect, the state change is that a relative displacement between the main shaft or the outer ring case and the housing fluctuates, and the detecting means is configured to change the relative displacement. The collision detection is performed when the amount exceeds a predetermined amount.

  According to a fourth aspect of the present invention, in the machine tool according to the second aspect, the state change is a change in a force received by the outer ring case, and the detecting means receives the force greater than a predetermined value by the outer ring case. It is to detect when it happens.

According to a fifth aspect of the present invention, in the machine tool according to any one of the first to fourth aspects, the impact buffering means includes a holding means for slidably holding the outer ring case in an axial direction, and the housing. A hydraulic pressure holding means provided between the axial end face of the outer ring case and the axial end face of the outer ring case, a pressing fixing means provided on the housing for pressing the outer ring case and fixing it at a predetermined position, and the hydraulic pressure Pressure oil is supplied to the holding means, and pressure oil supply means for holding the pressure in the hydraulic pressure holding means at a predetermined pressure, and
During normal use, the outer ring case is pressed against the end surface of the pressing and fixing means by a forward force that is the tool side direction generated by the hydraulic pressure holding means.
When the main shaft receives a predetermined force or more from the tool side at the time of a collision, the main shaft, the bearing, and the outer ring case move in the axial direction in the rear direction opposite to the tool side. .

  A feature of the invention according to claim 6 is that, in the machine tool according to claim 5, the holding means has a static pressure bearing structure.

According to a seventh aspect of the present invention, in the machine tool according to any one of the first to fourth aspects, the outer peripheral portion of the outer ring case is tapered, and a tapered hydrostatic bearing is provided on the inner peripheral portion of the housing. Pressure oil that supplies pressure oil to the pressing portion provided in the housing for pressing the shock absorbing means against the outer ring case and the taper hydrostatic bearing and maintains the pressure of the taper hydrostatic bearing at a predetermined pressure And supply means,
During normal use, the outer ring case is pressed against the end surface of the pressing fixing means by a component force in the front direction that is the tool side direction where the tapered hydrostatic bearing is generated,
When the main shaft receives a predetermined force or more from the tool mounting side at the time of a collision, the main shaft, the bearing, and the outer ring case move in the axial direction in the rear direction opposite to the tool side. .

  According to the first aspect of the present invention, since the shock absorbing means is provided between the outer ring case and the housing, there is no need for an extra space for adding the shock absorbing means to the front surface of the spindle as in the prior art. The interference area between the spindle and the workpiece can be minimized, and the machining range is widened.

  According to the second aspect of the invention, since the detecting means detects that the main shaft has collided due to a change in the state of the main shaft itself, it affects the mass change of the main shaft feeding system and the friction force change of the feeding device as in the prior art. It is possible to accurately detect the load received by the bearing at the time of collision. Therefore, accurate collision detection is possible, detection errors can be prevented, and rolling bearing damage and useless machine stoppage due to malfunction can be prevented.

  According to the invention of claim 3, since the collision of the main shaft is detected when the relative displacement between the main shaft and the housing exceeds a predetermined amount, the degree of collision to be detected can be freely controlled by the magnitude of the relative displacement. It can be set to, and detection that is optimal for the usage conditions can be made.

  According to the invention of claim 4, the force received by the outer ring case is the product of the axial projection area of the hydraulic chamber and the hydraulic chamber hydraulic pressure, and can be detected by measuring the hydraulic chamber pressure. A collision can be detected by measuring the pressure in the hydraulic chamber with a sensor, and an inexpensive detection means can be configured.

According to the fifth aspect of the present invention, the load at the time of collision is transmitted to the housing portion via the pressure oil in the hydraulic chamber, and when a load exceeding the predetermined pressure is applied, the oil in the hydraulic chamber is It absorbs collision energy while discharging and moves backward in the axial direction. The drag generated by the shock absorbing means at the time of collision is the product of the hydraulic chamber pressure and the projected area perpendicular to the axial direction of the hydraulic chamber, and the absorbed energy in this case is the product of the drag and the rearward moving distance. Become.
The conventional plastic deformation type shock absorbing means is damaged once it is operated and requires parts replacement, and the elastic deformation type interference means has a problem that the elastic deformation part is large and the installation space is excessive to increase the absorbed energy. was there.
According to the present invention, the setting of the predetermined drag can be freely determined by the setting of the discharge pressure, and the range of application is wide, and it is not damaged after the operation, and the installation space can be reduced.

  According to the sixth aspect of the present invention, since there is no direct contact between the outer periphery of the outer ring case of the holding portion and the inner periphery of the housing during operation, friction and wear do not occur and the reliability of the shock absorbing means is high.

  According to the seventh aspect of the invention, the outer ring case is pressed against the front cover fixed to the spindle housing by the axial component force acting on the tapered surface of the static pressure pocket. The shock absorbing means can be realized, and a small and inexpensive shock absorbing means can be provided.

It is the schematic which shows the structure of the main axis | shaft apparatus of 1st Embodiment. It is a schematic diagram showing the whole machine tool composition of a 1st embodiment. It is a block diagram of damage prevention operation of a 1st embodiment. It is the schematic which shows the structure of the main axis | shaft apparatus of 2nd Embodiment.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of a machine tool according to the invention will be described with reference to the drawings.
<First Embodiment>
The machine tool of 1st Embodiment is demonstrated based on FIGS. 1-3. 1 and 2, the left-right direction is the axial direction or the spindle feed direction, and the left side is the front. As shown in FIG. 2, the machine tool 1 according to the present embodiment holds a workpiece 11 and a tool 10 on a bed 12 so as to be relatively movable, and processes the workpiece 11.
The tool 10 is mounted on a spindle device 25 via a tool holder 14, and the spindle device 25 is fed back and forth by a feed motor 9 driven by an NC control device 26 via a feed screw 7 held by a screw holder 8. It is done. Further, the workpiece 11 is fed by a feed shaft that is orthogonal to the axial direction (not shown) and moves relative to the tool 10. The NC control device 26 includes a collision determination unit 21, an NC control unit 22, and a servo amplifier 23, and the spindle device damage prevention means 30 of the present invention includes the NC control device 26 and the feed motor 9.

As shown in FIG. 1, in the spindle device 25, the spindle 2 is an angular contact type rolling bearing 4 that is held in both the axial and radial directions, and is supported in the radial direction (not shown) and slidable in the axial direction. It is rotatably supported by a rear roller bearing held by a linear guide, and is rotated by a drive motor (not shown). The angular contact bearing 4 is held by an outer ring case 5, and the outer ring case 5 is slidable in the axial direction and fixedly supported in the radial direction by the main shaft housing 6 via an impact buffering means 20. The impact buffering means 20 includes a hydraulic chamber 13, an oil supply / discharge port 16, a relief valve 17, and a slide guide 18. The outer ring case 5 is pressed against a front cover 15 fixed to the main shaft housing 6 by supplying pressure oil to a hydraulic chamber 13 formed between the main shaft housing 6 and the outer ring case 5. The internal pressure of the hydraulic chamber 13 is maintained below a certain pressure by a relief valve 17 provided at the supply / discharge oil port 16.
A non-contact type displacement sensor 3 is disposed on the front surface of the spindle housing 6 to detect the axial position of the spindle 2.

  A case where the workpiece 11 or a workpiece holder (not shown) and the spindle 2 collide during the spindle device advance due to a data setting error, a workpiece mounting error, or the like will be described below.

  In FIG. 1, the impact force due to the collision of the main shaft 2 is transmitted to the outer ring case 5 via the rolling bearing 4. When this impact force exceeds a drag determined by the product of the upper limit internal pressure set by the relief valve 17 provided in the supply / discharge oil port 16 of the hydraulic chamber 13 and the axial projection area of the hydraulic chamber 13, The outer ring case 5 is a hydraulic shock absorbing means that moves rearward together with the rolling bearing 4 and the main shaft 2. Thus, the force acting on the rolling bearing 4 during the backward movement does not exceed a predetermined drag determined by the relief valve 17, and the rolling bearing is set by setting this drag to be equal to or less than the damage load of the rolling bearing 4. 4 damage does not occur.

  The relative displacement amount d between the spindle housing 6 and the spindle 2 accompanying this movement is measured by the displacement sensor 3 and sent to the collision determination unit 21 in the NC controller 26 as shown in FIG. The collision determination unit 21 determines a collision when the relative displacement d exceeds a predetermined amount S, and transmits a damage prevention command to the NC control unit 22. The NC control unit 22 transmits a motor stop command to the servo amplifier 23 based on the damage prevention command. The servo amplifier 23 stops the feed motor 9 based on the motor stop command.

The reverse stroke of the outer ring case 5 is set so that the reverse time of the outer ring case 5 at the time of collision is longer than the time required from the start of the collision until the feed motor 9 stops.
Thus, the machine tool 1 can be stopped without damaging the rolling bearing 4 when the main shaft 2 and the workpiece 11 collide.
As described above, according to the present invention, since the shock buffering means 20 is provided in the main shaft, compared with the conventional shock buffering device installed on the front surface of the main shaft, there is no extra protrusion on the front surface of the main shaft and the workpiece. The interference area can be minimized and the machining range can be increased.
In the present invention, when the relative displacement d between the main shaft 2 and the main shaft housing 6 exceeds a predetermined amount S, it is determined as a collision and the collision is detected, so that the main shaft is compared with the load detection method in the conventional motor unit. Accurate collision detection that is not affected by changes in the mass of the feed system or frictional force of the spindle feed device is possible, preventing detection errors and preventing unnecessary machine stoppage due to bearing damage or malfunction.
The conventional plastic deformation type shock absorbing means is damaged once and needs to be replaced. However, according to the present invention, the shock absorbing means 20 can be prevented from being damaged without being damaged. Can return to normal operation.
In the elastic deformation type shock absorbing means, the elastic deformation part becomes large and the installation space becomes excessive in order to increase the absorbed energy. However, since the present invention is a hydraulic type, the shock absorbing means can be configured compactly.
Furthermore, in the present invention, the setting of the drag force for detecting the collision can be freely determined by the setting of the discharge pressure, and the condition for preventing damage at the time of the collision that is optimal for the use environment can be set.

Second Embodiment
The machine tool of 2nd Embodiment is demonstrated based on FIG.
In the present embodiment, the hydraulic pressure chamber 13 in the first embodiment is omitted, and the outer ring case 5 and the inner diameter portion of the housing 6 are changed from a cylindrical shape to a taper shape, and the shock absorbing means 40 is a housing. The hydrostatic pocket 37 of the hydrostatic bearing configured between the outer ring case 36 and the outer ring case 35, the oil outlet 39 of the hydrostatic pocket, and the upper limit pressure connected to the oil outlet 39 is equal to or higher than the supply pressure to the hydrostatic pocket 37. It is comprised from the relief valve 17 set to (1), and a more compact structure than the first embodiment is possible.

  The outer ring case 35 is supported in the radial direction by oil supplied to the static pressure pocket 37 and is pressed against the front cover 15 fixed to the spindle housing 36 by an axial component force acting on the tapered surface. The pressing force to the front cover 15 is the product of the axial projection area of the taper bearing and the hydraulic pressure in the pocket.

The case where the workpiece 11 or the workpiece holder (not shown) collides with the main shaft 2 will be described below.
In FIG. 4, the impact force due to the collision of the main shaft 2 is transmitted to the outer ring case 35 via the rolling bearing 4. When this impact force exceeds the drag determined by the product of the upper limit internal pressure set by the relief valve 17 provided at the oil discharge port 39 of the static pressure pocket 37 and the axial projected area of the static pressure pocket 37, the outer ring The case 35 moves backward together with the rolling bearing 4 and the main shaft 2. Thus, the force acting on the rolling bearing 4 during the backward movement does not exceed a predetermined drag determined by the relief valve 17, and the rolling bearing is set by setting this drag to be equal to or less than the damage load of the rolling bearing 4. 4 damage does not occur.
The reverse stroke L of the outer ring case 35 is expressed as L = h / sin θ, where θ is the half angle of the taper angle of the outer ring case 35 and h is the clearance of the land portion of the hydrostatic bearing. This L is set so that the retreat time of the outer ring case 35 at the time of collision is longer than the time required from the start of collision until the feed motor 9 stops.
Thus, the machine tool 1 can be stopped without damaging the rolling bearing 4 when the main shaft 2 and the workpiece 11 collide.

  As described above, the reverse stroke L is set by properly selecting the half angle θ of the taper angle of the outer ring case 35 and the clearance h of the land portion of the static pressure bearing, and by setting the drag with the relief valve 17, The shock absorbing means 40 can be realized by eliminating the chamber, and a small and inexpensive shock absorbing means can be provided.

<Modification of First Embodiment>
Next, the deformation | transformation aspect of 1st Embodiment is demonstrated. You may comprise the slide guide part 18 of said 1st Embodiment by a static pressure guide or a rolling guide.
Further, the outer ring case 5 may be pressed against the front cover 15 with a spring instead of the hydraulic chamber 13.

  The collision detection may be detected when the force applied to the main shaft exceeds a predetermined value. For example, when the pressure in the hydraulic chamber 13 exceeds a predetermined value, or the load on the main shaft rotation drive motor exceeds a predetermined value. Detect a collision in case. In this case, it can be detected with a simple hydraulic pressure measuring device or an existing spindle rotation driving motor current measuring device and can be implemented at low cost.

<Modifications of the first and second embodiments>
Next, modifications of the first embodiment and the second embodiment will be described.
As the damage prevention operation, the feed motor may be reversed and the main shaft may be moved backward.
Further, when the feed axis is provided on the workpiece side and the tool and the workpiece are relatively cut, the damage prevention operation may be performed by the workpiece feed axis.

2: spindle, 3: displacement sensor, 4: rolling bearing, 5, 35: outer ring case, 6, 36: spindle housing, 10: tool, 11: workpiece, 13: hydraulic chamber, 15: front cover, 17: Relief valve, 20, 40: Impact buffering means, 25: Spindle device, 30: Spindle device damage prevention means

Claims (7)

  A main shaft that rotates while holding a tool; a rolling bearing that rotatably supports the main shaft; an outer ring case that holds an outer ring of the rolling bearing; and a housing that holds the outer ring case, the outer ring case, A machine tool characterized in that an impact buffering means is provided between the housing and the housing. A detecting means for detecting that the main shaft has collided by a change in the state of the main shaft;
2. The machine tool according to claim 1, wherein when the detecting unit detects that the main shaft has collided, a main shaft device damage preventing operation for preventing damage to the main shaft device is performed.   The state change is that a relative position of the main shaft or the outer ring case and the housing fluctuates, and the detection means determines a collision when the relative displacement becomes a predetermined amount or more. Item 2. The machine tool according to Item 2.   3. The machine tool according to claim 2, wherein the state change is a change in a force received by the outer ring case, and the detection unit determines that a collision occurs when the outer ring case receives a predetermined force or more. machine. The impact buffering means includes a holding means for slidably holding the outer ring case in an axial direction, a hydraulic pressure holding means provided between an axial end surface of the housing and an axial end surface of the outer ring case, and the outer ring case. Pressing and fixing means provided in the housing for pressing and fixing in a predetermined position, and pressure oil for supplying pressure oil to the hydraulic pressure holding means and holding the pressure in the hydraulic pressure holding means at a predetermined pressure Supply means,
During normal use, the outer ring case is pressed against the end surface of the pressing and fixing means by a forward force that is the tool side direction generated by the hydraulic pressure holding means.
When the main shaft receives a predetermined force or more from the tool side at the time of a collision, the main shaft, the bearing, and the outer ring case move in the axial direction in the rear direction opposite to the tool side. The machine tool according to any one of claims 1 to 4.   The machine tool according to claim 5, wherein the holding means has a static pressure bearing structure. An outer peripheral portion of the outer ring case has a tapered shape, a tapered hydrostatic bearing is provided on an inner peripheral portion of the housing, and a pressing portion provided in the housing for pressing the shock absorbing means against the outer ring case; A pressure oil supplying means for supplying pressure oil to the taper hydrostatic bearing and holding the pressure of the taper hydrostatic bearing at a predetermined pressure;
During normal use, the outer ring case is pressed against the end surface of the pressing fixing means by a component force in the front direction that is the tool side direction where the tapered hydrostatic bearing is generated,
When the main shaft receives a predetermined force or more from the tool mounting side at the time of collision, the main shaft, the bearing, and the outer ring case move in the axial direction in the rear direction opposite to the tool side. The machine tool according to any one of claims 1 to 4.

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