JP2010064201A - Main spindle device of machine tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a main spindle device of a machine tool improving processing accuracy. <P>SOLUTION: A main spindle 1 of the main spindle device is supported in the radial direction by a rotary bearing 2, and journaled in the rotary shaft C direction by a thrust bearing pad 3. A fluid pipe 31 extending upward and downward is formed on the thrust bearing pad 3, and air pressure supplied from an introduction pipeline 62 of an introduction part 61 is injected to a bottom face of the main spindle 1 via the fluid pipe 31. An injection path 37 branched from the fluid pipe 31 is opened at an upper end of a piezoelectric actuator 5 mounted to a bottom end of the thrust bearing pad 3, and a relief valve 4 is provided between the fluid pipe 31 and the injection path 37. The relief valve 4 is closed when the air pressure in the fluid pipe 31 is not more than a predetermined value, and opened when the air pressure in the fluid pipeline 31 exceeds a predetermined value. Then, the air pressure is directly injected to the piezoelectric actuator 5 via the injection path 37, to cool the piezoelectric actuator 5. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a spindle device of a machine tool that supports a spindle by fluid pressure.

  In a machine tool, there has been a related art related to a main shaft device including a journal bearing that rotatably supports a main shaft and a thrust bearing that supports the main shaft in an axial direction (see, for example, Patent Document 1). This is because the thrust bearing is axially opposed to the lower end of the main shaft that rotates about the vertical axis, and the pump air pressure is ejected from the air supply hole formed in the upper end surface of the thrust bearing, causing the main shaft to float upward. Let me support you.

In addition, this spindle device detects the position of the end of the spindle by a position detector, and based on the detected position of the spindle, the control device operates an actuator formed by a piezoelectric element, and between the spindle and the thrust bearing. The distance is feedback controlled.
In general, the main shaft being processed is subject to various vibrations from a workpiece or a cutting tool, and its axial position is likely to fluctuate. The fluctuation of the position of the main shaft lowers the dimensional accuracy of the workpiece. Therefore, in the above-described spindle device according to the prior art, in order to maintain the dimensional accuracy of the workpiece, the actuator is operated to change the position of the thrust bearing based on the detected spindle position, and the thrust bearing is moved from the thrust bearing to the spindle by air pressure. The position of the spindle is corrected by changing the urging force applied to.
JP-A-8-4767

  Therefore, the actuator frequently operates to correct the main shaft position, and the piezoelectric elements constituting the actuator repeatedly expand and contract. The piezoelectric element generates heat by operation, and the generated heat is transmitted from the piezoelectric element to another member, and the heat transmitted to the thrust bearing extends the thrust bearing. When the thrust bearing is extended, the urging force applied to the main shaft is changed by the air pressure supplied to the main shaft, so that the position of the cutting tool or work attached to the tip of the main shaft may be changed. In particular, high-speed rotation of the main shaft has been demanded recently, the vibration frequency of the main shaft has increased with high rotation, and the piezoelectric element of the actuator has repeatedly expanded and contracted, and the problem of heat generation by the piezoelectric element has become more serious. .

As a countermeasure, it is conceivable to cool the piezoelectric element that has generated heat, but it is necessary to newly provide a cooling medium generation source and supply path for cooling, and an increase in the size and cost of the entire spindle device can be avoided. There wasn't.
The present invention has been made in view of the above circumstances, and an object thereof is to provide a spindle device of a machine tool that can improve machining accuracy.

Hereinafter, each means suitable for solving the above-described problems will be described with additional effects and the like as necessary.
(Means 1) A spindle device of a machine tool according to means 1 is
The spindle,
A rotary bearing for rotatably supporting the main shaft;
A fluid conduit that opposes the main shaft in the direction of the rotation axis and opens on a surface facing the main shaft, and by supplying fluid pressure from a fluid pressure source to the fluid conduit, the fluid pressure is A thrust bearing pad that is injected toward the main shaft and that is separated from the main shaft and supports the main shaft in the rotation axis direction;
A piezoelectric element attached to the base and connected to the thrust bearing pad, which expands and contracts when electric power is applied to move the thrust bearing pad relative to the base, and the main shaft of the thrust bearing pad A piezoelectric element that changes the axial position of the main shaft by increasing or decreasing the biasing force due to the fluid pressure injected to the main shaft by changing the distance to
In the spindle device of a machine tool equipped with
By causing the fluid pressure from the fluid pressure source to flow also around the piezoelectric element, heat generated by the operation of the piezoelectric element is taken away, and the temperature of the piezoelectric element is lowered.

  Therefore, according to the spindle device of the machine tool according to the means 1, the fluid pressure from the fluid pressure source is used to support the spindle in the direction of the rotation axis and also flows around the piezoelectric element. The element is cooled to prevent the thrust bearing pad from being stretched by heating, and the machining accuracy can be improved by reducing the squeezing of the spindle. Further, it is not necessary to newly provide a cooling medium generation source, and the spindle device can be reduced in size and cost.

  Here, the fluid pressure is caused to flow around the piezoelectric element when the fluid pressure is caused to flow in a state of direct contact with the piezoelectric element and when a part of the thrust bearing pad is interposed between the fluid pressure and the piezoelectric element. And the like, in which the fluid pressure is caused to flow in the vicinity of the piezoelectric element. In other words, in the present invention, the flow of fluid pressure around the piezoelectric element means a state in which heat is removed from the piezoelectric element regardless of whether the flowing fluid pressure is direct or indirect.

(Means 2) In the spindle device of the machine tool according to the means 1,
The thrust bearing pad is
A cooling pipe that branches off from the fluid pipe and opens toward the periphery of the piezoelectric element;
Provided on the fluid conduit or the cooling conduit, and shuts off the supply of fluid pressure to the periphery of the piezoelectric element by closing when the fluid pressure in the fluid conduit is a predetermined value or less, When the fluid pressure in the fluid line exceeds the predetermined value, the valve is opened, and the fluid pressure from the fluid pressure source is passed around the piezoelectric element via the fluid line and the cooling line. A branch valve to flow,
It has.

  Therefore, according to the spindle device of the machine tool according to the means 2, when the fluid pressure in the fluid pipe line is equal to or lower than the predetermined value, the branch valve is closed to ensure the fluid pressure for biasing the spindle. Can do. In addition, when the fluid pressure in the fluid pipe line exceeds a predetermined value, the branch valve opens to energize the main shaft with the predetermined fluid pressure, and use the excess fluid pressure to make the piezoelectric element efficient. Can be cooled.

(Means 3) In the spindle device of the machine tool of means 2,
The thrust bearing pad has a cooling space surrounding the outer peripheral surface of the piezoelectric element, and the cooling pipe line is connected to the cooling space.
Therefore, according to the spindle device of the machine tool according to the means 3, the fluid entering the cooling space through the cooling pipe surrounds the outer peripheral surface of the piezoelectric element, so that the cooling performance can be further improved.

(Means 4) In the spindle device of the machine tool of means 3,
The substrate is
In the case where the rotation axis of the main shaft is the center, an introduction portion that covers the radially outer side of the thrust bearing pad;
A bridge portion extending in a tubular shape from the introduction portion in a direction away from the main shaft;
A discharge portion extending in a flat plate shape radially inward from the bridge portion;
The piezoelectric element is attached so as to extend in the rotational axis direction of the main shaft by connecting an end portion of the thrust bearing pad on the side away from the main shaft and a radially inner end of the discharge portion. When the outer peripheral surface and the inner peripheral surface of the bridge portion face each other in the radial direction, the end surface of the thrust bearing pad, the inner peripheral surface of the bridge portion, the discharge portion, and the outer peripheral surface of the piezoelectric element cause a cylindrical flow. A space is formed,
At least one of the introduction part, the bridge part, and the discharge part has a discharge path for discharging the fluid in the flow space from the flow space to the outside of the flow space,
The cooling space is connected to the cooling pipe at the end of the piezoelectric element on the main shaft side, and extends along the outer peripheral surface of the piezoelectric element and communicates with the flow space.

  Therefore, according to the spindle device of the machine tool according to the means 4, since the outer peripheral surface of the piezoelectric element is covered with the cooling space and the flow space, the entire outer peripheral surface can be exposed to the fluid, and the cooling performance is further improved. . Further, since the fluid is directly applied to the piezoelectric element from the cooling conduit, the cooling performance is further improved.

(Means 5) In the spindle device of the machine tool according to the means 1 or 2,
The substrate is
In the case where the rotation axis of the main shaft is the center, an introduction portion that covers the radially outer side of the thrust bearing pad;
A bridge portion extending in a tubular shape from the introduction portion in a direction away from the main shaft;
A discharge portion extending in a flat plate shape radially inward from the bridge portion;
The piezoelectric element is attached so as to extend in the rotational axis direction of the main shaft by connecting an end portion of the thrust bearing pad on the side away from the main shaft and a radially inner end of the discharge portion. When the outer peripheral surface and the inner peripheral surface of the bridge portion face each other in the radial direction, the end surface of the thrust bearing pad, the inner peripheral surface of the bridge portion, the discharge portion, and the outer peripheral surface of the piezoelectric element cause a cylindrical flow. A space is formed,
The introduction portion includes a fluid introduction conduit that opens to an inner peripheral surface thereof and supplies the fluid pressure from the fluid pressure source to the fluid conduit that opens to the outer peripheral surface of the thrust bearing pad;
The discharge portion has a discharge path that opens to a portion located radially inward from the outer peripheral surface of the thrust bearing pad,
A part of the fluid pressure supplied to the fluid introduction conduit passes between the inner peripheral surface of the introduction portion and the outer peripheral surface of the thrust bearing pad and enters the flow space, and then the discharge passage. It is discharged to the outside through.

  Therefore, according to the spindle device of the machine tool according to the means 5, the fluid pressure that passes between the inner peripheral surface of the introduction portion and the outer peripheral surface of the thrust bearing pad and enters the flow space passes through the discharge path. Further, it proceeds from the outer peripheral surface of the thrust bearing pad inward in the radial direction, so that the outer peripheral surface of the piezoelectric element exposed in the flow space can be easily touched, and the cooling performance can be further improved.

(Means 6) In the spindle device of the machine tool of means 5,
Between the inner peripheral surface of the introduction portion and the outer peripheral surface of the thrust bearing pad, fluid pressure flows out between the introduction portion and the thrust bearing pad closer to the main shaft than the fluid introduction conduit. A seal member is provided to prevent this.

  Therefore, according to the spindle device of the machine tool according to the means 6, the fluid supplied to the fluid introduction conduit is caused to flow between the fluid conduit and the flow space between the introduction portion and the thrust bearing pad by the action of the seal member. Therefore, the fluid supplied to the fluid introduction conduit can be effectively used for the purpose of supporting the main shaft and cooling the piezoelectric element.

(Means 7) The spindle device of the machine tool according to means 7 is:
The spindle,
A rotary bearing for rotatably supporting the main shaft;
A fluid conduit that opposes the main shaft in the direction of the rotation axis and opens on a surface facing the main shaft, and by supplying fluid pressure from a fluid pressure source to the fluid conduit, the fluid pressure is A thrust bearing pad that is injected toward the main shaft and that is separated from the main shaft and supports the main shaft in the rotation axis direction;
A piezoelectric element attached to the base and connected to the thrust bearing pad, which expands and contracts when electric power is applied to move the thrust bearing pad relative to the base, and the main shaft of the thrust bearing pad A piezoelectric element that changes the axial position of the main shaft by increasing or decreasing the biasing force due to the fluid pressure injected to the main shaft by changing the distance to
In the spindle device of a machine tool equipped with
The thrust bearing pad is
By branching from the fluid pipe line and extending toward the periphery of the piezoelectric element, and by causing the fluid pressure supplied to the fluid pipe line to flow around the piezoelectric element, the piezoelectric element is activated. A cooling line that takes away heat and lowers the temperature of the piezoelectric element;
A flow rate adjusting mechanism that is provided on the fluid conduit and that maintains a constant amount of fluid that passes through the fluid conduit and is ejected toward the main shaft;
Equipped with.

  Therefore, according to the spindle device of the machine tool according to the means 7, since the flow rate adjusting mechanism that keeps a constant amount of fluid that passes through the fluid conduit and is injected toward the spindle is provided, the spindle is axially moved. The amount of fluid required for supporting can be ensured. In addition, the excess amount that does not pass through the flow rate adjusting mechanism out of the amount of fluid supplied to the fluid pipe is caused to flow around the piezoelectric element, thereby energizing the main shaft with a predetermined amount of fluid and using the excess fluid. The piezoelectric element can be cooled. Thereby, without providing a plurality of fluid pressure sources, the axial bearing operation of the main shaft by the thrust bearing pad and the cooling operation of the piezoelectric element can sufficiently function, and both can be achieved.

<Embodiment 1>
Based on FIG. 1 thru | or FIG. 3, the spindle apparatus of the machine tool by Embodiment 1 of this invention is demonstrated. In FIG. 1, fluid pressure lines are indicated by solid arrows, and electrical connections are indicated by broken arrows. In the description, the upper part in FIG. 1 will be described as the upper part of the spindle device.

  As shown in FIG. 1, the spindle device of the machine tool according to the present embodiment includes a spindle 1 (corresponding to the spindle of the present invention) that is connected to an electric motor (not shown) and that can rotate around a rotation axis C. . A pair of rotary bearings 2 (corresponding to the rotary bearing of the present invention) facing each other so as to sandwich the main shaft 1 are provided on the outer side in the radial direction of the main shaft 1. Each rotary bearing 2 includes an air supply path 21 extending radially inward from the outer peripheral surface, and a support chamber 22 that is formed by slightly shaving the inner peripheral surface and communicates with the air supply path 21. . As a result, air pressure supplied from an air pump (not shown) is introduced into the support chamber 22 via the air supply passage 21 and is ejected to the main shaft 1, whereby the main shaft 1 is separated from the rotary bearing 2 in the radial direction. Is supported rotatably.

  The thrust bearing pad 3 (corresponding to the thrust bearing pad of the present invention) is formed in a substantially donut shape around the rotation axis C of the main shaft 1. The thrust bearing pad 3 is opposed to the main shaft 1 in the direction of the rotation axis C, is separated by a predetermined distance, and is provided so as to be movable in the vertical direction.

  2 and 3, a fluid conduit 31 (corresponding to the fluid conduit of the present invention) to which air pressure is supplied is provided in the thrust bearing pad 3 in the same manner as the rotary bearing 2. A plurality are formed at equal intervals on the circumference. Each fluid pipe 31 extends in the vertical direction in the thrust bearing pad 3 and opens to the surface 3a facing the main shaft 1 at the upper end, and is supplied with synthetic rubber or the like so that the supplied air pressure does not flow out at the lower end. The formed lid 32 is mounted in an airtight manner. A small-diameter portion 31 a is formed at the upper end of the fluid conduit 31 so that the supplied air is throttled and ejected at a high pressure. Each fluid conduit 31 branches to have an inlet portion 31 b extending outward in the radial direction of the thrust bearing pad 3, and the inlet portion 31 b opens to the outer peripheral surface 3 b of the thrust bearing pad 3.

  Further, the branch flow path 33 branches from the at least one fluid conduit 31 radially inward. A valve chamber 34, which is a space penetrating the inner peripheral surface 3c of the thrust bearing pad 3, communicates with the branch flow path 33, and the relief valve 4 (corresponding to the branch valve of the present invention) is provided in the valve chamber 34. Is formed.

  The valve chamber 34 has a tapered portion 34a connected to the branch flow path 33 and a cylindrical valve accommodating portion 34b connected to the taber portion 34a. A steel ball 41 that forms the relief valve 4 is built in the tapered portion 34a, and one end of a valve spring 42 that also forms the relief valve 4 is connected to the steel ball 41. A valve plug 43 is connected to the other end of the valve spring 42, and the valve spring 42 is compressed between the steel ball 41 and the valve plug 43 to press the steel ball 41 with a predetermined load. The valve plug 43 is formed of synthetic rubber or the like, and is attached to the opening of the valve housing portion 34b, thereby closing the valve chamber 34 in an airtight manner.

  An element storage portion 35 that is a space having a predetermined volume is formed inside the lower end portion (end portion on the side away from the main shaft 1) of the thrust bearing pad 3. An upper side of a piezoelectric actuator 5 (corresponding to the piezoelectric element of the present invention) formed of a piezoelectric element such as crystal, Rochelle salt, or piezoelectric ceramic is mounted on the element storage unit 35. The piezoelectric actuator 5 has a substantially cylindrical shape extending in the direction of the rotation axis C, and approximately the lower half protrudes from the lower end surface 3 d of the thrust bearing pad 3.

  Further, in the thrust bearing pad 3, an annular cooling space 36 (corresponding to the cooling space of the present invention) is formed around the element storage portion 35. The cooling space 36 is formed on the entire outer peripheral surface of the element storage unit 35 so as to surround the upper half of the outer peripheral surface 5 a of the piezoelectric actuator 5. The cooling space 36 extends along the outer peripheral surface 5 a of the piezoelectric actuator 5 when the piezoelectric actuator 5 is attached to the element storage portion 35, and communicates with a flow space 69 described later.

  Further, the valve chamber 34 and the cooling space 36 are connected by an ejection passage 37 (the branch passage 33 and the ejection passage 37 are included and correspond to the cooling conduit of the present invention). The ejection path 37 extends obliquely downward from the valve chamber 34, communicates with the upper end portion (end portion on the main shaft 1 side) of the cooling space 36, and faces the upper end portion of the piezoelectric actuator 5 attached to the element storage portion 35. Open.

  With the above-described configuration, when the air pressure in the fluid line 31 is equal to or less than a predetermined value that is the valve opening pressure of the relief valve 4 (determined by the load by which the valve spring 42 presses the steel ball 41), the relief valve 4 is closed, and communication between the fluid conduit 31 and the ejection passage 37 is blocked. Further, when the air pressure in the fluid pipe line 31 exceeds a predetermined value, the relief valve 4 is opened to connect the ejection path 37 to the fluid pipe line 31.

  On the other hand, the spindle housing 6 (corresponding to the base body of the present invention), which is a fixed object, is an introduction portion 61 (introduction portion of the present invention) that covers the outer side in the radial direction of the thrust bearing pad 3 when the rotation axis C is the center. ), A bridge portion 67 (corresponding to a bridge portion of the present invention) extending downward from the introduction portion 61 in a cylindrical shape, and a bottom portion 68 (book) extending radially inward from the bridge portion 67 Corresponding to the discharge part of the invention).

  As shown in FIGS. 2 and 3, the introduction portion 61 is formed in a ring shape so as to surround the entire periphery of the thrust bearing pad 3 with a predetermined distance from the outer peripheral surface 3 b. The introduction portion 61 is formed with an introduction conduit 62 (corresponding to the fluid introduction conduit of the present invention) so as to connect the outer peripheral surface 61a and the inner peripheral surface 61b, and the introduction conduit 62 is a thrust bearing pad. 3 and an inlet portion 31 b formed in the thrust bearing pad 3 through a gap between the inlet 3 and the introduction portion 61. A counterbore 63 is formed in the opening of the introduction pipe 62 on the inner peripheral surface 61 b of the introduction 61. The seat facing portion 63 is formed in a ring shape over the entire inner peripheral surface 61b of the introduction portion 61, and this seat facing portion 63 causes a small amount of the thrust bearing pad 3 in the direction of the rotation axis C to the introduction portion 61. Regardless of the movement, the communication between the inlet portion 31b and the introduction pipe line 62 is maintained.

In addition, a seal groove 64 is formed on the inner peripheral surface 61 b of the introduction portion 61 facing the outer peripheral surface 3 b of the thrust bearing pad 3 so as to be positioned above the introduction pipe line 62. The seal groove 64 is formed in a ring shape over the entire circumference of the inner peripheral surface 61b, and its cross section has a rectangular shape.
An O-ring 65 made of synthetic rubber or the like is provided in the seal groove 64 so as to be in airtight contact with the bottom surface. Further, between the O-ring 65 and the outer peripheral surface 3b of the thrust bearing pad 3, a corner seal ring 66 (an O-ring 65 and a corner seal ring 66 are formed of a synthetic resin material having elasticity such as Teflon). The corner seal ring 66 receives a biasing force radially inward from the O-ring 65. The O-ring 65 and the square seal ring 66 pass air through the gap between the inner peripheral surface 61 b of the introduction portion 61 and the outer peripheral surface 3 b of the thrust bearing pad 3, thereby causing the air pressure upward from the introduction pipe line 62. Prevents outflow. Since the angular seal ring 66 has a low frictional resistance with respect to the outer peripheral surface 3b of the thrust bearing pad 3, the sealing performance between the two can be ensured regardless of the relative movement of the thrust bearing pad 3 with respect to the introduction portion 61.

As described above, the bridge portion 67 forming the main shaft housing 6 extends downward from the introduction portion 61 in a cylindrical shape, and the bottom portion 68 extends from the bridge portion 67 radially inward in a flat plate shape. The lower end of the piezoelectric actuator 5 is attached to the inner end in the radial direction of the bottom 68. As a result, the outer peripheral surface 5a of the piezoelectric actuator 5 and the inner peripheral surface 67a of the bridge portion 67 are opposed to each other in the radial direction, so that the lower end surface 3d of the thrust bearing pad 3, the lower end surface of the introduction portion 61, A cylindrical flow space 69 (corresponding to the flow space of the present invention) is formed by the peripheral surface 67a, the upper end surface 68a of the bottom 68, and the outer peripheral surface 5a of the piezoelectric actuator 5. In this case, the inner peripheral surface 67a of the bridge portion 67 is made smaller in diameter, and only by the lower end surface 3d of the thrust bearing pad 3, the inner peripheral surface 67a of the bridge portion 67, the upper end surface 68a of the bottom portion 68, and the outer peripheral surface 5a of the piezoelectric actuator 5. A flow space 69 may be formed.
Further, the bottom 68 is disposed in a portion located radially inward of the outer peripheral surface 3b of the thrust bearing pad 3 in a vertical direction (in the direction of the rotation axis C of the main shaft 1), and a discharge path 70 (in the discharge path of the present invention). Applicable)

  Returning to FIG. 1, an air pump unit PU (corresponding to the fluid pressure source of the present invention) is connected to the opening of the introduction pipe line 62 in the outer peripheral surface 61 a of the introduction part 61, and the air pump is provided in the introduction pipe line 62. The air pressure generated by the unit PU can be supplied. The air pump unit PU includes a drive circuit, is electrically connected to the controller EC, and is rotationally controlled by a drive signal transmitted by the controller EC.

Further, a non-contact type position detector DS is provided inside the thrust bearing pad 3 in the radial direction. The position detector DS is for detecting the position of the main shaft 1 with respect to the main shaft housing 6 and is fixed to the main shaft housing 6. As the position detector DS, an eddy current type position sensor, a capacitance type position sensor, a laser type position sensor, or the like is used, and the position of the main shaft 1 can be detected without touching the main shaft 1. The position detector DS is electrically connected to the controller EC, and a detection signal from the position detector DS is input to the controller EC.
Further, the piezoelectric actuator 5 is also electrically connected to the controller EC, and the piezoelectric actuator 5 is operated by an operation signal transmitted from the controller EC.

Next, an operation method of the spindle device according to the present embodiment will be described. The air pressure applied to the air supply path 21 of the rotary bearing 2 is ejected to the outer peripheral surface of the main shaft 1 through the support chamber 22 and supports the main shaft 1 rotated by the electric motor.
At the same time, the air pressure generated by the air pump unit PU is supplied from the opening of the introduction pipe line 62 formed on the outer peripheral surface 61 a of the introduction part 61. The controller EC controls the operation of the air pump unit PU so that the air pressure discharged from the air pump unit PU becomes a constant value. Most of the air pressure introduced into the introduction pipe line 62 is supplied from the introduction pipe line 62 into the fluid pipe line 31 through the inlet portion 31 b of the thrust bearing pad 3.

  As described above, since the relief valve 4 is closed when the air pressure in the fluid line 31 is equal to or lower than the predetermined value, the supply of air pressure to the cooling space 36 is interrupted. The air pressure applied into the fluid conduit 31 is ejected from the small diameter portion 31 a to the lower surface of the main shaft 1 to press the main shaft 1, and the thrust bearing pad 3 is separated from the main shaft 1 so that the main shaft 1 moves in the direction of the rotation axis C. To support.

  At the same time, the controller EC controls the position of the spindle 1 based on the detection signal from the position detector DS. For example, when the controller EC recognizes that the main shaft 1 has been displaced due to vibration received during processing or the like based on a detection signal from the position detector DS, power is applied to the piezoelectric actuator 5 to expand and contract, and the thrust bearing pad 3 Is moved with respect to the main shaft housing 6 and the distance of the thrust bearing pad 3 to the main shaft 1 is changed to increase or decrease the urging force caused by the air pressure injected to the main shaft 1 to change the position of the main shaft 1 in the direction of the rotation axis C. Change.

  A part of the air pressure introduced into the introduction pipe 62 passes through the gap between the inner peripheral surface 61b of the introduction portion 61 and the outer peripheral surface 3b of the thrust bearing pad 3, and proceeds downward to flow space. Flows into 69. The air pressure that has entered the flow space 69 is then discharged to the outside via a discharge path 70 formed in the bottom 68. At this time, since the discharge passage 70 is opened radially inward from the outer peripheral surface 3 b of the thrust bearing pad 3, the air pressure flowing into the flow space 69 moves inward in the radial direction, and the piezoelectric actuator 5 The heat generated by the operation of the piezoelectric actuator 5 through the periphery of the outer peripheral surface 5a is taken, and the temperature of the piezoelectric actuator 5 is lowered.

  Further, when the air pressure in the fluid pipe line 31 exceeds a predetermined value, the relief valve 4 is opened to cause the ejection path 37 to communicate with the fluid pipe line 31. As a result, excess air pressure supplied to the fluid conduit 31 flows from the fluid conduit 31 into the cooling space 36 via the branch passage 33, the relief valve 4, and the ejection passage 37. The air pressure that has entered the cooling space 36 passes through the periphery of the outer peripheral surface 5 a of the piezoelectric actuator 5 and enters the flow space 69, and is then discharged from the discharge path 70 to the outside. The air pressure that has flowed into the cooling space 36 removes heat generated by the operation of the piezoelectric actuator 5 as in the case described above, and lowers the temperature of the piezoelectric actuator 5.

  According to the present embodiment, the main shaft 1, the rotary bearing 2 that rotatably supports the main shaft 1, and the fluid pipe that faces the main shaft 1 in the direction of the rotation axis C and opens to the facing surface 3 a with the main shaft 1. By supplying the air pressure from the air pump unit PU to the fluid conduit 31, the air pressure is injected toward the main shaft 1, and the main shaft 1 is moved away from the main shaft 1 in the direction of the rotation axis C. A thrust bearing pad 3 to be supported is provided.

  The thrust bearing pad 3 is attached to the thrust bearing pad 3 and connected to the thrust bearing pad 3 to expand and contract when electric power is applied to move the thrust bearing pad 3 with respect to the spindle housing 6. A piezoelectric actuator 5 that changes the axial position of the main shaft 1 by increasing or decreasing the biasing force due to the air pressure injected to the main shaft 1 by changing the distance is provided, and the air pressure from the air pump unit PU is changed around the piezoelectric actuator 5. Also, the heat generated by the operation of the piezoelectric actuator 5 is taken away, and the temperature of the piezoelectric actuator 5 is lowered.

  Therefore, since the air pressure from the air pump unit PU is used to support the main shaft 1 in the direction of the rotation axis C and is also caused to flow around the piezoelectric actuator 5, the piezoelectric actuator 5 is cooled and the thrust bearing pad 3 is cooled. The elongation due to heating is prevented, and the precision of the position of the main shaft 1 is reduced, so that the machining accuracy can be improved. Further, it is not necessary to newly provide a cooling medium generation source, and the spindle device can be reduced in size and cost.

  Further, according to the present embodiment, the thrust bearing pad 3 is provided on the branch flow path 33, the branch flow path 33 that branches off from the fluid conduit 31, the ejection path 37 that opens toward the periphery of the piezoelectric actuator 5, and the branch flow path 33. When the air pressure in the fluid conduit 31 is below a predetermined value, the valve is closed to cut off the supply of air pressure to the periphery of the piezoelectric actuator 5 and the air pressure in the fluid conduit 31 is reduced. The relief valve 4 is opened when the predetermined value is exceeded, and causes the air pressure from the air pump unit PU to flow around the piezoelectric actuator 5 via the fluid conduit 31, the branch passage 33 and the ejection passage 37. I have.

  Therefore, when the air pressure in the fluid conduit 31 is equal to or lower than a predetermined value, the relief valve 4 is closed, so that the air pressure that urges the main shaft 1 can be secured. Further, when the air pressure in the fluid pipe line 31 exceeds a predetermined value, the relief valve 4 is opened so that the main shaft 1 is urged by the predetermined air pressure and the excess air pressure is used for piezoelectricity. The actuator 5 can be efficiently cooled.

Further, according to the present embodiment, the thrust bearing pad 3 includes the cooling space 36 that surrounds the outer peripheral surface 5 a of the piezoelectric actuator 5, and the ejection path 37 is connected to the cooling space 36.
Therefore, the air that has entered the cooling space 36 via the ejection path 37 surrounds the outer peripheral surface 5a of the piezoelectric actuator 5, so that the cooling performance can be further improved.

  Further, according to the present embodiment, the main shaft housing 6 includes the introduction portion 61 that covers the thrust bearing pad 3 in the radial direction (when the rotation axis C of the main shaft 1 is the center), and the introduction portion 61 downward. And a bridge portion 67 extending in a cylindrical shape, and a bottom portion 68 extending in a flat plate shape radially inward from the bridge portion 67. The piezoelectric actuator 5 is attached so as to extend in the direction of the rotation axis C of the main shaft 1 by connecting the lower end portion of the thrust bearing pad 3 and the radially inner end of the bottom portion 68. Since the inner peripheral surface 67a of the portion 67 faces the radial direction, a cylindrical flow is formed by the lower end surface 3d of the thrust bearing pad 3, the inner peripheral surface 67a of the bridge portion 67, the bottom 68, and the outer peripheral surface 5a of the piezoelectric actuator 5. A space 69 is formed.

The bottom 68 has a discharge path 70 for discharging the fluid in the flow space 69 from the flow space 69 to the outside. The cooling space 36 is connected to the ejection path 37 at the upper end of the piezoelectric actuator 5, and the piezoelectric actuator 5. It extends along the outer peripheral surface 5a of the gas and communicates with the flow space 69.
Therefore, since the outer peripheral surface 5a of the piezoelectric actuator 5 is covered with the cooling space 36 and the flow space 69, the entire outer peripheral surface 5a can be exposed to air pressure, and the cooling performance is further improved. Further, since the air pressure is directly applied to the piezoelectric actuator 5 from the ejection passage 37, the cooling performance is further improved.

  Further, the introduction pipe line 62 of the introduction part 61 opens to the inner peripheral surface 61 b, and supplies the air pressure by the air pump unit PU to the fluid pipe line 31 of the thrust bearing pad 3, and the discharge path 70 has a thrust bearing pad at the bottom 68. 3 is opened at a portion located radially inward from the outer peripheral surface 3b. Thereby, after a part of the air pressure supplied to the introduction pipe 62 passes between the inner peripheral surface 61 b of the introduction portion 61 and the outer peripheral surface 3 b of the thrust bearing pad 3 and enters the flow space 69. Then, it is discharged to the outside through the discharge path 70.

  Therefore, the air pressure that has entered the flow space 69 through the space between the inner peripheral surface 61 b of the introduction portion 61 and the outer peripheral surface 3 b of the thrust bearing pad 3 passes through the discharge path 70 and is thus outer periphery of the thrust bearing pad 3. Proceeding inward in the radial direction from the surface 3b, it becomes easier to touch the outer peripheral surface 5a of the piezoelectric actuator 5 exposed in the flow space 69, and the cooling performance can be further improved.

Further, according to the present embodiment, the introduction portion 61 and the thrust bearing pad are located between the inner peripheral surface 61 b of the introduction portion 61 and the outer peripheral surface 3 b of the thrust bearing pad 3 on the main shaft 1 side with respect to the introduction pipe line 62. 3, an O-ring 65 and a square seal ring 66 are provided as seal members that pass through the gap between them and prevent air pressure from flowing out.
Therefore, due to the action of the O-ring 65 and the square seal ring 66, the air pressure supplied to the introduction pipe line 62 is applied only to the fluid pipe line 31 and the flow space 69 through the space between the introduction part 61 and the thrust bearing pad 3. Therefore, the air pressure supplied to the introduction pipe 62 can be effectively used for the purpose of supporting the main shaft 1 and cooling the piezoelectric actuator 5.

<Embodiment 2>
Next, the spindle device of the machine tool according to the second embodiment will be described with reference to FIG. In the spindle device according to the present embodiment, an air space 38 is formed in the thrust bearing pad 3. Unlike the cooling space 36 in the first embodiment, the air space 38 is not formed so as to directly surround the outer peripheral surface 5 a of the piezoelectric actuator 5, and is a wall portion radially outward of the outer peripheral surface 5 a of the piezoelectric actuator 5. It is formed in an annular shape through 3e. The upper end portion of the air space 38 is connected to the valve chamber 34 by an ejection passage 39 (including the branch passage 33 and the ejection passage 39 and corresponds to the cooling pipe of the present invention), and the lower end portion is connected to the flow space 69. Communicate. Air pressure is supplied to the air space 38 via the ejection path 39, and the piezoelectric actuator 5 is indirectly cooled via the wall portion 3 e and then enters the flow space 69. Since other configurations are the same as those in the first embodiment, description thereof is omitted.

<Embodiment 3>
Next, the spindle device of the machine tool according to the third embodiment will be described with reference to FIGS. As shown in FIG. 5, the fluid conduit 81 capable of supplying air pressure from the outer peripheral surface of the thrust bearing pad 8 extends in the vertical direction as in the first embodiment, and air pressure is ejected toward the main shaft 1 at the upper end. A possible opening is formed, and a closed lid 82 made of synthetic rubber or the like is airtightly attached to the lower end.

Although the branch flow path 83 branches off from the fluid conduit 81, unlike the first embodiment, the relief valve 4 is not formed on the branch flow path 83. The branch flow path 83 penetrates the inner peripheral surface of the thrust bearing pad 8, and the opening on the inner peripheral surface is hermetically closed by a sealing plug 84 formed of synthetic rubber or the like.
On the branch flow path 83, a throttle hole member 83a having a pipe having a smaller diameter than an orifice hole 92a of the constant flow valve 9 described later is provided. The pipe diameter of the throttle hole member 83a may be fixed or variable. The throttle hole member 83a supports the main shaft 1 and prevents all of the air pressure introduced into the fluid pipe 81 from escaping to the branch flow path 83 side.

  Similarly to the first embodiment, the upper side of the piezoelectric actuator 5 is mounted on the element storage portion 85 of the thrust bearing pad 8, and a cooling space 86 is formed around the outer peripheral surface 5 a of the piezoelectric actuator 5. From the middle of the branch flow path 83, an ejection path 87 (including the branch path 83 and the ejection path 87 and corresponding to the cooling pipe of the present invention) branches, and the ejection path 87 is an upper end portion of the cooling space 86. Communicating with

  In the upper part of the fluid pipe 81, a known constant flow valve 9 (corresponding to the flow regulating mechanism of the present invention) that maintains a constant amount of air pressure that is injected toward the main shaft 1 through the fluid pipe 81. ) Is formed. As shown in an enlarged view in FIG. 6, the constant flow valve 9 is formed by a valve sleeve 91 having a cylindrical shape with a flow passage hole 91 a passing therethrough, and a valve plate 92 attached to the valve sleeve 91. . The valve plate 92 is fitted in an annular mounting groove 91b formed on the flow path hole 91a. The valve sleeve 91 is fitted in the fluid pipe 81 in an airtight manner on the outer peripheral surface thereof. The valve plate 92 is formed in a disc shape from synthetic rubber or the like, and an orifice hole 92a having a diameter D passes through the central portion in a natural state. The central portion of the valve plate 92 can be bent in the vertical direction in the figure by air pressure.

  Usually, in the fluid line 81, when the differential pressure between the air pressure P1 on the inlet side (lower side in FIG. 6) and the air pressure P2 on the outlet side (upper side in FIG. 6) of the constant flow valve 9 is small, The deflection of the valve plate 92 is negligible, and the air pressure in the fluid pipe 81 passes through the orifice hole 92a and is ejected from the opening at the upper end surface of the thrust bearing pad 8 toward the main shaft 1 (shown in FIG. 6). ).

  On the other hand, the air pressure P1 on the inlet side of the constant flow valve 9 increases with respect to the air pressure P2 on the outlet side, and the differential pressure between the air pressure P1 on the inlet side and the air pressure P2 on the outlet side increases. In this case, the central portion of the valve plate 92 is biased and bent toward the outlet side by the differential pressure, and the diameter of the orifice hole 92a is reduced to d (d <D) (shown in FIG. 7).

  As a result, the flow resistance when the air pressure passes through the orifice hole 92a is increased. As a result, the flow rate of the air passing through the constant flow valve 9 is substantially constant regardless of the increase or decrease of the air pressure P1 on the inlet side. Kept. The surplus air pressure generated on the inlet side of the constant flow valve 9 is supplied to the cooling space 86 around the piezoelectric actuator 5 through the pipe line of the throttle hole member 83a, the branch flow path 83, and the ejection path 87. Since other configurations are the same as those in the first embodiment, description thereof is omitted.

  According to the present embodiment, since the constant flow valve 9 that maintains a constant flow rate of air pressure that is injected toward the main shaft 1 through the fluid pipe 81 is provided, the main shaft 1 is supported in the axial direction. Therefore, the amount of air pressure necessary for this can be ensured. Further, the main part 1 is urged by the flow rate of a predetermined air pressure by causing the excess of the amount of air pressure supplied to the fluid pipe 81 not to pass through the constant flow valve 9 to flow around the piezoelectric actuator 5. At the same time, the piezoelectric actuator 5 can be cooled using the flow rate of the excess air pressure. Thereby, without providing a plurality of air pump units PU, the bearing operation in the axial direction of the main shaft 1 and the cooling operation of the piezoelectric actuator 5 can sufficiently function and both can be achieved.

<Other embodiments>
The present invention is not limited to the above-described embodiments, and can be modified or expanded as follows.
The fluid ejected to support the main shaft 1 and cool the piezoelectric actuator 5 is not limited to air pressure, and any fluid pressure such as hydraulic pressure or water pressure can be applied.
The seal member between the outer peripheral surface 3b of the thrust bearing pad 3 and the inner peripheral surface 61b of the introduction portion 61 does not necessarily require both the O-ring 65 and the square seal ring 66, but the thrust bearing pad 3 and the introduction. As long as fluid leakage from between the portion 61 and the main shaft 1 can be prevented, only the square seal ring 66 may be used.

The constant flow valve 9 provided in the fluid pipe 81 is not limited to that described above, and any system can be applied.
In the spindle device of the machine tool according to the present invention, the rotation axis C of the spindle 1 does not necessarily have to extend in the vertical direction, and the rotation axis C may extend in the horizontal direction or the oblique direction.
The bridge portion 67 and the bottom portion 68 forming the main shaft housing 6 may be formed integrally or separately.
The air pressure for supporting the main shaft 1 in the radial direction and the air pressure for supporting the main shaft 1 in the direction of the rotation axis C may be supplied from the same air pressure source.

1 is an overall view showing a spindle device of a machine tool according to Embodiment 1 of the present invention. 1 is an enlarged view of the main part of FIG. AA sectional view of FIG. The principal part enlarged view of the spindle apparatus of the machine tool by Embodiment 2 The principal part enlarged view of the spindle apparatus of the machine tool by Embodiment 3 Enlarged sectional view of the constant flow valve shown in FIG. FIG. 6 is an enlarged cross-sectional view of the constant flow valve shown in FIG.

Explanation of symbols

  In the drawings, 1 is a main shaft, 2 is a rotary bearing, 3, 8 is a thrust bearing pad, 3a is a surface facing the main shaft of the thrust bearing pad, 3d is a lower end surface of the thrust bearing pad, 4 is a relief valve (branch valve), 5 is a piezoelectric actuator (piezoelectric element), 5a is an outer peripheral surface of the piezoelectric actuator, 6 is a spindle housing (base), 9 is a constant flow valve (flow rate adjusting mechanism), 31 and 81 are fluid lines, and 33 and 83 are branch flows 36, 86 are cooling spaces, 37 and 87 are ejection paths (cooling pipelines), 61 is an introducing portion, 61a is an outer peripheral surface of the introducing portion, 61b is an inner peripheral surface of the introducing portion, and 62 is Introduction pipe (fluid introduction pipe), 65 is an O-ring (seal member), 66 is a square seal ring (seal member), 67 is a bridge portion, 67a is an inner peripheral surface of the bridge portion, and 68 is a bottom portion (discharge portion). 69 is a flow space, 70 is a discharge path, C is The rotation axis of the shaft, PU indicates the air pump unit (fluid pressure source).

Claims (7)

The spindle,
A rotary bearing for rotatably supporting the main shaft;
A fluid conduit that opposes the main shaft in the direction of the rotation axis and opens on a surface facing the main shaft, and by supplying fluid pressure from a fluid pressure source to the fluid conduit, the fluid pressure is A thrust bearing pad that is injected toward the main shaft and that is separated from the main shaft and supports the main shaft in the rotation axis direction;
A piezoelectric element attached to the base and connected to the thrust bearing pad, which expands and contracts when electric power is applied to move the thrust bearing pad relative to the base, and the main shaft of the thrust bearing pad A piezoelectric element that changes the axial position of the main shaft by increasing or decreasing the biasing force due to the fluid pressure injected to the main shaft by changing the distance to
In the spindle device of a machine tool equipped with
A spindle device for a machine tool, wherein fluid pressure from the fluid pressure source is caused to flow also around the piezoelectric element, thereby removing heat generated by the operation of the piezoelectric element and lowering the temperature of the piezoelectric element. The thrust bearing pad is
A cooling pipe that branches off from the fluid pipe and opens toward the periphery of the piezoelectric element;
Provided on the fluid conduit or the cooling conduit, and shuts off the supply of fluid pressure to the periphery of the piezoelectric element by closing when the fluid pressure in the fluid conduit is a predetermined value or less, When the fluid pressure in the fluid line exceeds the predetermined value, the valve is opened, and the fluid pressure from the fluid pressure source is passed around the piezoelectric element via the fluid line and the cooling line. A branch valve to flow,
The spindle device for a machine tool according to claim 1, comprising:   The spindle device for a machine tool according to claim 2, wherein the thrust bearing pad includes a cooling space surrounding an outer peripheral surface of the piezoelectric element, and the cooling pipe line is connected to the cooling space. The substrate is
In the case where the rotation axis of the main shaft is the center, an introduction portion that covers the radially outer side of the thrust bearing pad;
A bridge portion extending in a tubular shape from the introduction portion in a direction away from the main shaft;
A discharge portion extending in a flat plate shape radially inward from the bridge portion;
The piezoelectric element is attached so as to extend in the rotational axis direction of the main shaft by connecting an end portion of the thrust bearing pad on the side away from the main shaft and a radially inner end of the discharge portion. When the outer peripheral surface and the inner peripheral surface of the bridge portion face each other in the radial direction, the end surface of the thrust bearing pad, the inner peripheral surface of the bridge portion, the discharge portion, and the outer peripheral surface of the piezoelectric element cause a cylindrical flow. A space is formed,
At least one of the introduction part, the bridge part, and the discharge part has a discharge path for discharging the fluid in the flow space from the flow space to the outside of the flow space,
The cooling space is connected to the cooling pipe at an end of the piezoelectric element on the main shaft side, and extends along an outer peripheral surface of the piezoelectric element to communicate with the flow space. Item 4. A spindle device for a machine tool according to item 3. The substrate is
In the case where the rotation axis of the main shaft is the center, an introduction portion that covers the radially outer side of the thrust bearing pad;
A bridge portion extending in a tubular shape from the introduction portion in a direction away from the main shaft;
A discharge portion extending in a flat plate shape radially inward from the bridge portion;
The piezoelectric element is attached so as to extend in the rotational axis direction of the main shaft by connecting an end portion of the thrust bearing pad on the side away from the main shaft and a radially inner end of the discharge portion. When the outer peripheral surface and the inner peripheral surface of the bridge portion face each other in the radial direction, the end surface of the thrust bearing pad, the inner peripheral surface of the bridge portion, the discharge portion, and the outer peripheral surface of the piezoelectric element cause a cylindrical flow. A space is formed,
The introduction portion includes a fluid introduction conduit that opens to an inner peripheral surface thereof and supplies the fluid pressure from the fluid pressure source to the fluid conduit that opens to the outer peripheral surface of the thrust bearing pad;
The discharge portion has a discharge path that opens to a portion located radially inward from the outer peripheral surface of the thrust bearing pad,
A part of the fluid pressure supplied to the fluid introduction conduit passes between the inner peripheral surface of the introduction portion and the outer peripheral surface of the thrust bearing pad and enters the flow space, and then the discharge passage. 3. The spindle device for a machine tool according to claim 1, wherein the spindle device is discharged outside through the machine tool.   Between the inner peripheral surface of the introduction portion and the outer peripheral surface of the thrust bearing pad, fluid pressure flows out between the introduction portion and the thrust bearing pad closer to the main shaft than the fluid introduction conduit. 6. A spindle device for a machine tool according to claim 5, wherein a seal member for preventing the above is provided. The spindle,
A rotary bearing for rotatably supporting the main shaft;
A fluid conduit that opposes the main shaft in the direction of the rotation axis and opens on a surface facing the main shaft, and by supplying fluid pressure from a fluid pressure source to the fluid conduit, the fluid pressure is A thrust bearing pad that is injected toward the main shaft and that is separated from the main shaft and supports the main shaft in the rotation axis direction;
A piezoelectric element attached to the base and connected to the thrust bearing pad, which expands and contracts when electric power is applied to move the thrust bearing pad relative to the base, and the main shaft of the thrust bearing pad A piezoelectric element that changes the axial position of the main shaft by increasing or decreasing the biasing force due to the fluid pressure injected to the main shaft by changing the distance to
In the spindle device of a machine tool equipped with
The thrust bearing pad is
By branching from the fluid pipe line and extending toward the periphery of the piezoelectric element, and by causing the fluid pressure supplied to the fluid pipe line to flow around the piezoelectric element, the piezoelectric element is activated. A cooling line that takes away heat and lowers the temperature of the piezoelectric element;
A flow rate adjusting mechanism that is provided on the fluid conduit and that maintains a constant amount of fluid that passes through the fluid conduit and is ejected toward the main shaft;
A spindle device of a machine tool characterized by comprising:

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