JP2013099816A - Spindle device and machine tool having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spindle device in which a pressure change of a balance cylinder generated by the vertical movement of a spindle head can be highly accurately stabilized at high speed, and a machine tool having the same.SOLUTION: The spindle device includes the balance cylinder 44 generating an energizing force to support the weight of the spindle head 43, and a pressure regulator 70 regulating the balance cylinder. The pressure regulator regulates an inflow rate of air from an air supply source into an isothermal pressure container, and keeps pressure in the container constant. A pressure control means operating a servo valve includes a pressure control system performing feed-back control to pressure detected by a pressure gauge as a main loop, and an inflow rate control system in the main loop performing feed-back control to an inflow rate measured by a flow meter. Based on the inflow rate and a pressure differential value in the isothermal pressure container measured by a pressure differentiator, the pressure control means estimates an outflow rate of air flowing out of the isothermal pressure container and feeds back the estimated outflow rate to the inflow rate control system.

Description

  The present invention relates to a spindle device and a machine tool including the spindle device. Specifically, the present invention relates to a spindle device having a balance cylinder that generates an urging force that supports at least a part of the weight of a spindle head having a spindle, and a machine tool including the spindle device.

In machine tools, the spindle head is supported so as to be able to move up and down along the guide surface of the column, and a biasing force corresponding to the weight of the spindle head is generated by the balance cylinder so that the spindle head can be raised and lowered smoothly with a light force. A machine tool is known (for example, see Patent Document 1).
Conventionally, a balance device that balances the weight of the spindle head with a balance cylinder is used to reduce the air from the air supply source to a predetermined pressure with a pressure reducing valve and then supply the balance cylinder with the weight of the spindle head, When the pressure in the control circuit increases, the relief valve is activated to keep the pressure in the control circuit at a predetermined pressure.

Japanese Patent Laid-Open No. 5-138419

  However, the balance device having the above-described structure has a problem that the accuracy of the pressure reducing valve is not sufficient and the response speed is slow.

  An object of the present invention is to provide a spindle device capable of stabilizing a pressure change of a balance cylinder generated with respect to vertical movement of a spindle head at high speed and with high accuracy in response to such a conventional problem. To provide a machine tool.

  A spindle apparatus according to the present invention includes a spindle head support member, a spindle head provided on the spindle head support member so as to be movable up and down, a lifting mechanism for raising and lowering the spindle head, and at least a part of the weight of the spindle head. In a spindle device comprising a balance cylinder that generates an urging force that supports the pressure and a pressure regulator that controls the pressure of the balance cylinder, the pressure regulator is a servo valve that regulates an inflow flow rate of air supplied from an air supply source And an isothermal pressure vessel that keeps the air flowing in through the servovalve in an isothermal state and that supplies the balance cylinder, and a flow meter that measures the inflow flow rate of the air flowing into the isothermal pressure vessel, A pressure gauge for detecting the pressure of air in the isothermal pressure vessel, and a pressure for detecting a differential pressure value of air in the isothermal pressure vessel A differential meter and pressure control means for controlling the air in the isothermal pressure vessel to a predetermined pressure by operating the servo valve, the pressure control means feedback-controlling the pressure detected by the pressure gauge Based on the pressure control system, the inflow flow rate control system that feedback-controls the inflow flow rate measured by the flow meter, the differential pressure value measured by the pressure differential meter, and the inflow flow rate measured by the flow meter. An outflow rate estimating means for estimating an outflow rate of air flowing out of the isothermal pressure vessel, and the inflow rate control system is configured in a control loop of the pressure control system, and the outflow rate estimation means A model follow-up control system that feeds back the estimated outflow rate to the inflow rate control system is configured.

According to such a configuration, since the pressure regulator can use the isothermal pressure vessel as a buffer, the inflow process and the outflow process of air into the isothermal pressure container can be regarded as an equal volume and isothermal change. The pressure can be controlled.
In order to control the air in the isothermal pressure vessel to a predetermined pressure, the flow rate of the air supplied from the air supply source to the isothermal pressure vessel is regulated by a servo valve. At this time, the pressure regulator operates the servo valve to regulate the inflow flow rate by pressure control means having a pressure control system that performs feedback control of the pressure of air in the isothermal pressure vessel as a main loop, and the isothermal pressure vessel The air inside is controlled to a predetermined pressure.

  Here, the pressure control means performs feedback control of the inflow flow rate of the air flowing into the isothermal pressure vessel by the inflow flow rate control system, which is a minor loop configured inside the pressure control system, and the isothermal flow estimation means by the isothermal flow rate estimation means. Estimate the outflow rate of air flowing out of the isothermal pressure vessel based on the differential pressure value of the air in the pressure vessel and the inflow rate of air flowing into the isothermal pressure vessel, and control the estimated outflow rate for inflow rate control Compensation is performed by a model following system that feeds back to the system.

Therefore, in such a control system, the pressure control is performed in response to a slight change in the downstream flow rate, that is, a slight change in the balance cylinder, so that the control system is resistant to disturbance and has a high response. Can be configured. Further, since the outflow rate is estimated based on the pressure differential value, the influence of the flow rate on the measurement can be reduced and pressure control can be performed with high accuracy compared to the case where the outflow rate is directly measured.
As a result, the pressure change of the balance cylinder that occurs with respect to the vertical movement of the spindle head can be stabilized at high speed and with high accuracy.

In the spindle device according to the present invention, the spindle head includes a spindle head main body that can be moved up and down on the spindle head support member, a spindle that is rotatably supported by the spindle head main body, and a rotation that drives the spindle to rotate. It is preferable that the spindle head main body is composed of pitch-based CFRP.
Here, pitch-based CFRP (carbon fiber reinforced plastic) is obtained by carbonizing a pitch precursor (pitch fiber obtained using coal tar or heavy petroleum as a raw material), and has high strength and high elastic modulus. Has properties.
According to such a configuration, the spindle head is configured to include a spindle head body, a spindle that is rotatably supported by the spindle head, and a rotational drive source that rotationally drives the spindle, and the spindle head body is a pitch system. Therefore, the weight can be reduced while maintaining high strength and high elastic modulus. Therefore, since the raising / lowering speed of the spindle head can be increased, an improvement in productivity can be expected.

In the spindle device according to the present invention, the elevating mechanism includes a magnet provided on one of the spindle head support member and the spindle head main body along the elevating direction of the spindle head, the spindle head support member, and the spindle. It is preferable that the head body includes a linear motor including a coil disposed opposite to the magnet on the other side.
According to such a configuration, since the elevating mechanism for elevating and lowering the spindle head is constituted by the linear motor, the spindle head can be moved up and down smoothly and with high accuracy.

In the spindle apparatus of the present invention, it is preferable that the coil is covered with a heat shield member.
According to such a configuration, when the coil of the linear motor is energized when the spindle head is raised and lowered, the coil generates heat. In the present invention, since the periphery of the coil is covered with the heat shielding member, it is possible to prevent the spindle head body and the like from being thermally deformed by heat generated from the coil. Therefore, high accuracy can be maintained.

The machine tool of the present invention relatively moves at least one axial direction orthogonal to the ascending / descending direction of the spindle head with any of the spindle devices described above, a table on which a workpiece is placed, and the spindle device and the table. And a moving mechanism.
According to such a configuration, a machine tool having the effects described above can be provided.

The perspective view which shows the machine tool which concerns on embodiment of this invention. The figure which shows a main shaft apparatus and its peripheral part in the said embodiment. The block diagram which shows the structure of a pressure regulator in the said embodiment. The figure which shows the verification result of the feed rate of 1000 mm / min in the conventional machine tool. The figure which shows the verification result of the feed rate of 1000 mm / min in the said embodiment. The figure which shows the verification result of feed speed 2000mm / min in the conventional machine tool. The figure which shows the verification result of feed speed 2000mm / min in the said embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. This embodiment is an example applied to a machine tool provided with a spindle device having a balance device.
(Description of machine tool as a whole: see Fig. 1)
As shown in FIG. 1, the machine tool is provided with a base 1, and is movable on the base 1 in the X-axis direction via an X-axis guide mechanism 11 and an X-axis linear motor mechanism 12. The table 13 to be placed, the portal column 20 provided across the table 13, and the horizontal beam 20A of the portal column 20 in the Y-axis direction via the Y-axis guide mechanism 21 and the Y-axis linear motor mechanism 22 The main shaft device 30 is movably provided.

The X-axis guide mechanism 11 includes a guide rail 11A disposed on the upper surface of the base 1 in parallel along the X-axis direction, and a slide member 11B provided on the lower surface of the table 13 so as to be slidable along the guide rail 11A. It is comprised including.
The X-axis linear motor mechanism 12 includes a magnet 12A arranged in parallel with the guide rail 11A on the upper surface of the base 1, and a coil 12B attached to the lower surface of the table 13 with a gap between the magnet 12A. It is comprised by the linear motor containing.

As shown in FIG. 2, the Y-axis guide mechanism 21 includes guide rails 21 </ b> A arranged parallel to each other along the Y-axis direction on the upper surface of the horizontal beam 20 </ b> A of the portal column 20, and guides on the lower surface of the spindle device 30. And a slide member 21B provided so as to be slidable along the rail 21A.
The Y-axis linear motor mechanism 22 includes a magnet 22A arranged in parallel with the guide rail 21A on the upper surface of the horizontal beam 20A of the portal column 20, and a lower surface of the spindle device 30 with a gap between the magnet 22A. It is comprised by the linear motor containing the attached coil 22B.

(Description of spindle device: see FIG. 2)
As shown in FIG. 2, the spindle device 30 is also provided with a spindle head support that is provided on the horizontal beam 20 </ b> A of the portal column 20 so as to be movable in the Y axis direction via the Y axis guide mechanism 21 and the Y axis linear motor mechanism 22. A saddle 33 as a member, a spindle head 43 provided on the saddle 33 through a Z-axis guide mechanism 41 and a Z-axis linear motor mechanism 42 as an elevating mechanism, and at least one of the weights of the spindle head 43 A balance cylinder 44 that generates an urging force to support the unit, an air supply source 60, a pressure regulator 70 that supplies air from the air supply source 60 to the balance cylinder 44 and controls the pressure of the balance cylinder 44, and a saddle 33 The balance head 45 is attached to the opposite side of the main spindle head 43.

The Z-axis guide mechanism 41 includes a guide rail 41A arranged parallel to each other along the Z direction on the back surface of the spindle head 43, and a slide member 41B fixed to the front surface of the saddle 33 and slidably guiding the guide rail 41A. It is configured to include.
The Z-axis linear motor mechanism 42 includes a magnet 42A arranged in parallel with the guide rail 41A on the back surface of the spindle head 43, and a coil 42B attached to the front surface of the saddle 33 with a gap between the magnet 42A. It is comprised by the linear motor containing.
Here, the periphery of the coil 42B is covered with a heat shield member 42C. The heat shield member 42C is formed in a box shape from a material such as aluminum or plastics.

The spindle head 43 includes a spindle head body 51, a spindle 52 that is rotatably supported by the spindle head body 51, and a rotational drive source 53 that rotationally drives the spindle 52.
The spindle head body 51 is composed of pitch-based CFRP. Pitch-based CFRP (carbon fiber reinforced plastic) is obtained by carbonizing a pitch precursor (pitch fiber obtained from coal tar or heavy petroleum oil as a raw material) and has properties of high strength and high elastic modulus. . A tool 54 is detachably attached to the main shaft 52. The rotation drive source 53 is configured by a motor.

The balance cylinders 44 are provided on both sides of the spindle head 43, respectively.
Each balance cylinder 44 has a cylinder main body 44 </ b> A whose upper end is supported by the saddle 33 via a bracket 55, and a piston which is slidably housed in the cylinder main body 44 </ b> A at its upper end, and its lower end is at the lower end of the spindle head 43. The piston rod 44B is connected to the piston rod 44B.
Air from the air supply source 60 is supplied to the lower chamber of the cylinder main body 44 </ b> A partitioned by the piston via the pressure regulator 70. As a result, an urging force that balances the weight of the spindle head 43 is applied upward to the spindle head 43 by the balance cylinder 44.

(Description of pressure regulator: see Fig. 3)
The pressure regulator 70 holds the pressure at a target pressure with high speed and precision. For example, a pressure regulator disclosed in Japanese Patent Application Laid-Open No. 2009-110033 can be used.
As shown in FIG. 3, there are a servo valve 71 that regulates the flow rate of air supplied from the air supply source 60, and an isothermal pressure vessel that holds the air that has passed through the servo valve 71 in an isothermal state. 72, a flow meter 73 for measuring the inflow flow rate of air flowing into the isothermal pressure vessel 72, a pressure meter 74 for detecting the pressure of air in the isothermal pressure vessel 72, and the isothermal pressure vessel 72 A pressure differential meter 75 for detecting a differential pressure value of air, an A / D converter 76 for A / D converting signals detected by the flow meter 73, the pressure gauge 74 and the pressure differential meter 75, and this A / D conversion Pressure control means 77 that calculates a control voltage of the servo valve 71 based on a signal supplied through the controller 76 and applies the control voltage to the servo valve 71 via the D / A converter 78.

Here, the control system of the pressure regulator 70 of the present embodiment feeds back the pressure P of the air in the isothermal pressure vessel 72 to the target set pressure (target value) Pref and performs PI (proportional operation, integral operation) control. The pressure control system is configured as a main loop.
Inside the main loop, an inflow flow rate control system that feedback-controls the inflow flow rate Gin of air flowing into the isothermal pressure vessel 72 via the servo valve 71 is configured as one minor loop, and is made isothermal with the inflow flow rate Gin. An observer (inflow rate estimating means) for estimating the outflow rate Gout flowing out of the isothermal pressure vessel 72 based on the pressure differential value dP / dt of the air in the pressure vessel 72 is configured, and the outflow rate Gout (estimated by the observer) The model follow-up control system that compensates by feeding back the hat) to the inflow flow rate control system is configured as another minor loop.

Accordingly, it is assumed that the pressure regulator 70 is activated and the pressure P of the air in the isothermal pressure vessel 72 is set to a predetermined target value. At this time, the servo valve 71 is adjusted to an opening degree that balances the outflow rate flowing out from the outlet of the isothermal pressure vessel 72 and the inflow rate flowing in from the inlet.
Here, when the pressure Ps of the air from the air supply source 60 or the outflow flow rate Gout of the air flowing out from the isothermal pressure vessel 72 is changed, the pressure P in the isothermal pressure vessel 72 changes from the target value Pref. The pressure regulator 70 measures the inflow flow rate Gin measured by the flow meter 73, the pressure P measured by the pressure meter 74, and the pressure differential meter 75 by the pressure control means 77 in order to compensate for fluctuations in air pressure. The pressure differential value dP / dt is received via the A / D converter 76, the control voltage Ei for the servo valve 71 is calculated based on the received measurement data, and the calculated control voltage Ei is calculated as D / A. This is supplied to the servo valve 71 via the converter 78.
Then, the servo valve 71 controls the servo valve 71 to an opening corresponding to the control voltage Ei calculated by the pressure control means 77, and air flows into the isothermal pressure vessel 72 with an inflow flow rate Gin corresponding to the opening. To do. Thus, control is performed so that the pressure P of the air in the isothermal pressure vessel 72 is set to the target value Pref.

<Operation and Effect of Embodiment>
In the machine tool having such a configuration, in order to process the workpiece W, after setting the workpiece W on the table 13, the table 13 is set in the X-axis direction, the saddle 33 is set in the Y-axis direction, and the spindle head 43 is set in the Z-axis. The workpiece is machined by the tool 54 while moving in the direction.
Here, when the spindle head 43 is moved in the Z-axis direction, the pressure of the balance cylinder 44 varies. In the present embodiment, the pressure change of the balance cylinder 44 caused by the vertical movement of the spindle head 43 can be stabilized by the pressure regulator 70 at high speed and with high accuracy. Therefore, the moving speed can be increased and the machining time can be shortened, and the load during movement can be stabilized and the controllability can be improved, so that the machining accuracy can be improved.

For example, FIGS. 4 and 5 are verification results when the spindle head 43 is moved at a feed rate of 1000 mm / min in a conventional machine tool and the machine tool of the present embodiment.
FIG. 4 shows a conventional machine tool (in the configuration shown in FIG. 1, the spindle head is made of cast material, the pressure regulator is a fairchild pressure regulator verification result, and the upper diagram shows the position command for the Z-axis linear motor mechanism 42. The figure which shows a value and an electric current command value, and a lower figure are figures which show the balance pressure of the balance cylinder at that time.
FIG. 5 is a verification result of the machine tool of the present embodiment. The upper diagram shows the position command value and the current command value for the Z-axis linear motor mechanism 42, and the lower diagram shows the balance pressure of the balance cylinder at that time. FIG.
As is apparent from the above, according to this embodiment, it can be seen that the balance pressure of the balance cylinder is significantly smaller than that of the conventional machine tool.

6 and 7 show the verification results when the spindle head 43 is moved at a feed rate of 2000 mm / min in the conventional machine tool and the machine tool of the present embodiment.
FIG. 6 is a result of verification of a conventional machine tool (the same configuration as FIG. 4). The upper diagram shows the position command value and the current command value for the Z-axis linear motor mechanism 42, and the lower diagram shows the balance at that time. It is a figure which shows the balance pressure of a cylinder.
FIG. 7 is a result of verification of the machine tool of the present embodiment (the same as the description of FIG. 5). The upper diagram shows the position command value and the current command value for the Z-axis linear motor mechanism 42, and the lower diagram shows the result. It is a figure which shows the balance pressure of the balance cylinder at the time.
As is apparent from the above, according to this embodiment, it can be seen that the balance pressure of the balance cylinder is significantly smaller than that of the conventional machine tool.

  Further, according to the present embodiment, the spindle head 43 includes the spindle head main body 51, the main shaft 52 rotatably supported by the main spindle head main body 51, and the rotation drive source 53 that rotationally drives the main spindle 52. Since the spindle head body 51 is made of pitch-based CFRP, the weight can be reduced while maintaining high strength and high elastic modulus. Therefore, since the raising / lowering speed of the spindle head 43 can be increased, an improvement in productivity can be expected.

Further, according to the present embodiment, the elevating mechanism for elevating the spindle head 43 is disposed on the spindle head 43 along the elevating direction of the spindle head 43 and the saddle 33 is opposed to the magnet 42A. Since the Z-axis linear motor mechanism 42 includes the coil 42B, the spindle head can be moved up and down smoothly and with high accuracy.
Moreover, since the periphery of the coil 42B constituting the Z-axis linear motor mechanism 42 is covered with the heat shield member 42C, it is possible to prevent the spindle head main body 51 and the like from being thermally deformed due to heat generated from the coil. Therefore, high accuracy can be maintained.

<Modification>
It should be noted that the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
In the embodiment, the table 13 is movable in the X-axis direction and the spindle head 43 is movable in the Y-axis direction and the Z-axis direction as a machine tool. However, the present invention is not limited to this. In short, any structure may be used as long as the table 13 and the spindle head 43 can move relative to each other in two dimensions (two-axis direction) or three dimensions (three-axis direction).

Further, in the above-described embodiment, each axis moving mechanism is configured by the linear motor mechanism, that is, the X-axis linear motor mechanism 12, the Y-axis linear motor mechanism 22, and the Z-axis linear motor mechanism 42, but is not necessarily a linear motor mechanism. May be. A feed mechanism using a ball screw may be used.
Moreover, in the said embodiment, although the motor was used as the rotational drive source 53 of the main axis | shaft 52, it is not restricted to this, For example, an air turbine mechanism etc. may be sufficient.

  In the embodiment, the urging force that balances the weight of the spindle head 43 is generated by the balance cylinder 44. However, the urging force that balances the weight of the spindle head 43 is not necessarily required. The structure which generate | occur | produces the urging | biasing force which supports at least one part of the weight of may be sufficient.

  Although the machine tool provided with the spindle device 30 having the balance cylinder 44 has been described in the above embodiment, the machine tool is not limited to the machine tool as long as the machine device includes the spindle device 30 having the balance cylinder 44. It can also be applied to ultra-precision machine tools such as

  Since the present invention can control the position of the spindle head at high speed and with high accuracy, it can be applied not only to general machine tools but also to ultraprecision machine tools such as ultraprecision aspherical processing machines.

12 ... X-axis linear motor mechanism (moving mechanism),
22 ... Y-axis linear motor mechanism (moving mechanism),
33. Saddle (main spindle head support member),
42 ... Z-axis linear motor mechanism (elevating mechanism),
42A ... Magnet,
42B ... coil,
42C ... heat shield member,
43 ... spindle head,
44 ... balance cylinder,
51 ... spindle head body,
52 ... Spindle,
53 ... Rotation drive source,
60 ... Air supply source,
70: Pressure regulator,
71 ... Servo valve,
72 ... isothermal pressure vessel,
73 ... Flow meter,
74 ... Pressure gauge,
75 ... Pressure differential meter,
77: Pressure control means.

Claims (5)

A spindle head support member, a spindle head that is provided on the spindle head support member so as to be movable up and down, has a spindle, a lifting mechanism that lifts and lowers the spindle head, and generates a biasing force that supports at least a part of the weight of the spindle head. In a spindle device comprising a balance cylinder and a pressure regulator for controlling the pressure of the balance cylinder,
The pressure regulator includes a servo valve that regulates an inflow flow rate of air supplied from an air supply source, an isothermal pressure vessel that maintains the air flowing in through the servo valve in an isothermal state and supplies the air to the balance cylinder A flow meter for measuring the flow rate of air flowing into the isothermal pressure vessel, a pressure meter for detecting the pressure of the air in the isothermal pressure vessel, and a pressure differential value of the air in the isothermal pressure vessel A pressure differential meter for detecting the pressure and a pressure control means for operating the servo valve to control the air in the isothermal pressure vessel to a predetermined pressure,
The pressure control means is measured by the pressure control system that feedback controls the pressure detected by the pressure gauge, the inflow flow rate control system that feedback controls the inflow flow rate measured by the flow meter, and the pressure differential meter. An outflow rate estimating means for estimating an outflow rate of air flowing out of the isothermal pressure vessel based on a differential pressure value and an inflow rate measured by the flow meter, and the inflow rate control system is configured as the pressure Configuring in the control loop of the control system and configuring a model following control system that feeds back the outflow rate estimated by the outflow rate estimation means to the inflow rate control system;
A spindle device characterized by that. The spindle device according to claim 1,
The spindle head includes a spindle head main body that is provided on the spindle head support member so as to be movable up and down, a main spindle that is rotatably supported by the spindle head main body, and a rotational drive source that rotationally drives the spindle. And
The spindle head body is composed of pitch-based CFRP,
A spindle device characterized by that. The spindle device according to claim 2,
The elevating mechanism includes a magnet provided along one of the main spindle head support member and the main spindle head body along the elevating direction of the main spindle head, and either the main spindle head support member or the main spindle head main body. It is composed of a linear motor including a coil disposed opposite to the magnet.
A spindle device characterized by that. The spindle device according to claim 3, wherein
The periphery of the coil is covered with a heat shield member,
A spindle device characterized by that. The spindle device according to any one of claims 1 to 4,
A table for placing a workpiece;
A moving mechanism that relatively moves the spindle device and the table in at least one axis direction orthogonal to the ascending / descending direction of the spindle head;
A machine tool characterized by that.

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