JPH0482649A - Control unit for posture of machine tool - Google Patents

Abstract

PURPOSE:To fundamentally correct a microdisplacement and to enable a precise position control, by telescopically controlling a column part wall face with its heating or cooling with the control signal of a thermal actuator for the column part being output from a control part in accordance with the displacement value of the column part wall face detected by the displacement sensor. CONSTITUTION:Displacement sensors S1-S4 with a temperature compensation are fitted to the ends of both side faces of a column part 14 and the displacement quantity by the telescopic motion of the column part 14 is detected. The detected displacement quantity individually controls the current directions fed to 16 thermal actuators 21-28, 31-38 arranged at the upper and lower steps according to the displacement quantities thereof, after being input to a control part. When the wall face where the thermal actuators of the column part 14 are arranged is heated or cooled, the telescopic quantity is adequately adjusted according to the temperature thereof, the positional displacement generated on a tool 11 is corrected with the elastic deformation due to the heating of a motor 13, etc., and the work reaction force of the tool 11 being composed and the original position of the tool 11 is precisely held.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is based on a tool displacement M caused by a temperature rise in a tool drive part of a machine tool such as a machining center or a machining reaction force of the tool. The present invention relates to a posture control device for a machine tool that can prevent deterioration of machining accuracy and realize even more precise machining.

(Prior Art) Conventionally, in machine tools such as machining centers, heat generated by the tool's drive motor and its speed reduction mechanism is transmitted to the head and the column that supports the head while machining a workpiece.
Each part to which heat is transferred thermally expands in accordance with the increased temperature. Further, during machining of a workpiece, a machining reaction force is generated in the tool, and a minute elastic deformation occurs in the head portion and column portion that support the tool in response to the reaction force. When these thermal expansions and elastic deformations occur, the position of the tool changes minutely, reducing machining accuracy. FIG. 8 is an explanatory diagram schematically showing the ladder. In FIG. A temperature gradient is generated in the part 4, and the right side expands more thermally, causing the entire tool to warp to the left. As a result, the tool 1 shifts from the normal level L0 to the level L, which adversely affects machining accuracy. become.

Conventionally, as a countermeasure against these problems, cooling oil or cooling water is circulated within the head section 2 where the tool 1 is attached to cool down the drive motor 3 and its speed reduction mechanism, etc., which are the cause of heat generation, to reduce the effects of thermal expansion. I'm trying to resolve this.

Furthermore, as another solution, the coordinates of the head section 2 may be corrected by NC control depending on the degree of heat generation. Furthermore, attempts have been made to counteract the warpage by installing a counter heater 5 on a part of the left rear surface of the column part 4 and heating it according to the heat transfer to the column part 4 to eliminate the temperature gradient.

(Am to be solved by the invention) However, with these solutions, it is difficult to accurately detect the displacement caused in the tool due to heat generation during operation, and the detected displacement value also changes constantly depending on the operating conditions. Since it fluctuates, the response is poor, and it is impossible to always perform optimal correction.

The present invention has been made to solve the above problems,
The purpose of this is to fundamentally correct minute displacements caused by thermal expansion and elastic changes, which are problems in position control in various industrial machines such as machine tools, as well as to provide more precise control. An object of the present invention is to provide a posture control device for a machine tool that enables position control.

(Means for Solving the Problems) In order to achieve the above object, the first invention provides a structure in which head parts for gripping and driving tools are attached to and supported by a fixed base, and the hollow column parts face each other in the circumferential direction. one or more pairs of thermal actuators for the column section that generate thermal displacement by heating or cooling the wall surface of the column section;
A displacement sensor detects the displacement of the column wall surface caused by temperature changes, tool machining reaction forces, etc., and the column is moved to maintain a preset tool position based on the detected value of the displacement sensor. The present invention is characterized by comprising a control section that outputs a control signal for the thermal actuator to expand and contract.

In the second invention, a head portion for gripping and driving a tool is attached to a fixed pedestal, and one or more pairs are arranged facing each other in the circumferential direction of a hollow column portion that supports the head portion, and the column portion wall surface is heated or cooled to generate heat. A thermal actuator for the column section that generates displacement, a displacement sensor installed on the wall surface of the head section to detect displacement of the wall surface of the head section caused by temperature changes, tool machining reaction forces, etc., and a thermal actuator for the column section are attached. A displacement sensor is installed on the column wall to detect displacement of the column wall caused by temperature changes, tool machining reaction forces, etc., and based on the detected values of each displacement sensor,
The present invention is characterized by comprising a control section that outputs a thermal actuator control signal for expanding and contracting the column section so as to maintain a preset tool position.

The third invention provides one or more pairs of head section thermal actuators that are disposed facing each other in the circumferential direction of the head section that grips and drives the tool, and that heat or cool the Rad section wall surface to generate thermal displacement. , one or more pairs of column part thermal actuators are disposed facing each other in the circumferential direction of a hollow column part which supports and attaches the head part to a fixed pedestal, and heats or cools a wall surface of the column part to generate thermal displacement; A displacement sensor is installed on the head wall surface to which the head thermal actuator is attached, and detects displacement of the head wall surface caused by temperature changes, tool machining reaction forces, etc., and a column to which the column thermal actuator is attached. A displacement sensor is installed on the column wall surface to detect displacement of the column wall surface caused by temperature changes, tool machining reaction force, etc., and a preset tool position is maintained based on the detected values of each displacement sensor. The present invention is characterized by comprising a control section that outputs a thermal actuator control signal that causes the column section and the head section to expand and contract, respectively.

(Function) In the first invention, when a displacement occurs on the column wall surface due to a temperature change, a processing reaction force of a tool, etc., the displacement is detected by a displacement sensor installed on the column wall surface. Next, a control signal for the column thermal actuator is output from the control section in accordance with the detected displacement value, and the column wall surface is heated or cooled by the column thermal actuator. As a result, the wall surface of the column portion is controlled to expand and contract, and the tool is held in a predetermined position.

In the second aspect of the invention, when displacement occurs on the wall surfaces of the head and column parts due to temperature changes, processing reaction forces of tools, etc., the displacement is detected by displacement sensors installed on the wall surfaces of the head and column parts. Next, a control signal for the column thermal actuator is output from the control section in accordance with the detected displacement value, and the column wall surface is heated or cooled by the column thermal actuator. As a result, the wall surface of the column portion is controlled to expand and contract, and the tool is held in a predetermined position.

In the third aspect of the invention, when displacement occurs on the wall surfaces of the head portion and column portion due to temperature change, processing reaction force of a tool, etc., the displacement is detected by displacement sensors installed on the wall surfaces of the head portion and column portion. Next, a control signal for each thermal actuator is outputted from the control section according to the detected displacement value, and the head section and column section wall surfaces are heated or cooled by the respective thermal actuators. As a result, the walls of the head and column are controlled to expand and contract.
The tool is held in place.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a cross-sectional view of an embodiment in which the first and second inventions are applied to a machining center, and FIG.
■It is a cross-sectional view along the line.

In the figure, the column part 14 fixed on the base 6 is formed hollow, and has a balance weight 7 of the head part 12 inside.
is suspended. The head section 12 is supported so as to be able to move up and down by a guide section formed on the front surface of the column section 14, and its position in the vertical direction is controlled by a servo motor 15 attached to the top of the column section 14 and a pole screw 16. It will be done. Further, a tool attachment part 17 is provided at the lower light end of the head part 12, and a tool 11 corresponding to a machining operation is detachably held therein.

The tool 11 is driven by a motor 13 installed above the hand portion 12 via a speed reduction mechanism (not shown).

The workpiece W is fixed on a table 18, and is processed by the tool 11 while the table 18 is moved in the X and Y directions by the drive mechanism section 8.

The column part 14 is formed in a hollow prismatic shape, and ribs are formed at regular intervals in the internal circumferential direction. Thermal actuators 21 to 28.
31 to 3B are installed. 20 The thermal actuator is composed of a thermal semiconductor element capable of electronic cooling and heating, and by changing the direction of current, the contact surface with the wall surface can be changed to either heating or cooling. Furthermore, the thermal actuators 21~
A flow path 19.29.39 is formed in the circumferential direction of the member of the column part 14 at the boundary of the compartment where 28.31 to 38 are installed and the ribs above and below the boundary, and the flow path 19.29. Oil at a predetermined temperature is circulated for thermal insulation. Furthermore, temperature-compensated displacement sensors S1 to S4 each consisting of a strain gauge or the like are attached to the ends of both side surfaces of the column part 14 corresponding to both the upper and lower sides of FIG.
The amount of displacement due to expansion and contraction of the column portion 14 is detected. The detected amount of displacement is input to a control unit (not shown), and then the direction of current supplied to the 16 thermal actuators 21 to 28 and 31 to 38 arranged in the upper and lower stages is individually determined according to the amount of displacement. control. In addition, in the case of the second invention, the third invention described later
The displacement amount detected by the displacement sensors S5 to S10 in the head section 12 in the embodiment of the invention is also input to the control section, and the thermal actuator 21 is
~28. Controls the operations of 31 to 38. In this way, when the wall surface on which the thermal actuator of the column part 14 is installed is heated or cooled, the amount of expansion and contraction is adjusted appropriately according to the temperature, and the heat generation of the motor 13 and the like and the tool 11
The elastic deformations caused by the processing reaction forces are combined, and the positional displacement occurring in the tool 11 is corrected. As a result, tool 11
The original position will be held precisely, and processing can be performed with greater precision than before.

FIG. 3 is an external view of main parts of an embodiment in which the third invention is applied to a machining center, FIG. 4 is a cross-sectional view of FIG. 3, and FIG. 5 is a cross-sectional view of FIG. It is a sectional view on the V line.

The difference between the embodiment of the third invention and the embodiment of the first invention is that a thermal actuator and a heat insulating section are also installed in the head section 12, and the thermal actuators installed in the column section 14 and the head section 12 are replaced with an electric heater. It is constructed by a combination of an oil jacket and an oil jacket. in particular,
Similar to the embodiment shown in FIG. 1, a thermal actuator 41a for cooling is installed on the outer circumferential surface of the lower division from the lower base 6, which is divided by ribs formed at regular intervals in the column part 14.
~48a is also a cooling thermal actuator 5 on the upper stage.
1a to 58a are installed respectively.

Thermal actuators 41a to 48a51a in each of these stages
Reference numeral 58a is formed by an oil jacket, through which low-temperature oil supplied from a separate oil cooler (not shown) is circulated to connect the thermal actuators 41a to 48a, 51a.
~58a becomes low temperature, and the column part 1 in contact with these
Cool the wall of 4. Moreover, the column part 1 is located opposite to these thermal actuators 41a to 48a and 51a to 58a.
Thermal actuators 41b to 48 for heating are provided on the inner peripheral surface of 4.
b, 51b to 58b are installed in the lower and upper stages, respectively. These thermal actuators 41b to 48b, 51b to
58b is formed by a planar electric heater, and by supplying current, thermal actuators 41b to 48b
, 51b to 58b generate heat and reach a high temperature, heating the wall surface of the column portion 14 with which they come into contact.

When these pairs of heating or cooling thermal actuators 41a, 41b to 58a, 58b are operated, one of the inner and outer surfaces operates to cool or heat the block to which they are attached.

Furthermore, as shown in FIG. 4, displacement sensors S1 to S4 are attached to the ends of both side surfaces of the column section 14 to detect the amount of displacement of the column section 14 in the axial direction.

Further, the head portion 12 is formed by a hollow frame,
Cooling thermal actuators 62a to 57a and 72a to 77a are respectively installed on the upper and lower outer peripheries of the frame.
At the same time, thermal actuators 61b to 68b and 71b to 78b for heating are installed in upper and lower two stages on the inner periphery of the frame, respectively. Further, inside the frame member from the column part 14, passages 69 for cooling oil circulation are formed at equal intervals in the horizontal direction in order to thermally insulate the head part 12 and the column part 14.

These cooling thermal actuators 62a to 67a, 72
a to 77a are also formed of an oil jacket like the column part 14, and are also provided with a heating thermal actuator 61.
b to 68b and 71b to 78b are similarly formed by planar electric heaters, and are supplied with low temperature oil or electric current to cool or heat each block of the head portion 12 that comes into contact with them. Furthermore, a thermal actuator 66a disposed on the side surface of the head section 12 shown in FIG.
Temperature-compensated displacement sensors S5 to S7, which are horizontally arranged strain gauges, are installed at the center positions of 67a, 76a, and 77a, and at the upper and lower ends, respectively.
Similarly, displacement sensors S8 to S are placed at the same position on the rear surface (not shown).
The IO is attached to detect the amount of displacement that occurs in the head section 12.

The displacement amounts detected by the displacement sensors S5 to S10 are input to a control section (not shown), and then the thermal actuators 62a to 67a, 72a to 77a, and 61b are activated according to the displacement amounts.
~68b, 71b~78b are heated or cooled block by block to heat or cool each surface of the head section 12 where the thermal actuator is installed, thereby adjusting the amount of expansion and contraction as appropriate to the tip of the tool 11. The generated displacement can be corrected and the original position of the tool 11 can be maintained during processing.

FIG. 6 shows a typical example of a control mode in which the operations of the respective thermal actuators of the column section 14 are combined in the embodiment of the first or second invention described above.
Actuators labeled "C" indicate that they are being cooled, and actuators labeled 'H' indicate that they are being heated.

Figure a shows a mode in which the right side of the head side of both the upper and lower rows is cooled as indicated by "C", and the left side is heated as indicated by "H", and the column section 14 is tilted to the right at an angle θI. shows.

The figure shows a mode in which the right side on the head side is heated and the left side is cooled in both the upper and lower stages, and the column part 14 is tilted to the left at an angle θ2.

Figure C shows a mode in which the right side of the upper stage is heated and the left side is cooled, and the right side of the lower stage is cooled and the left side is heated, and the column section 14 moves approximately parallel to the right side a distance lI.

FIG. d shows a mode in which the right side of the upper stage is cooled and the left side is heated, and the right side of the lower stage is heated and the left side is cooled, and the column part 14 moves a distance it to the left almost in parallel.

Note that the four control modes described above are examples in which the heating and cooling of the corresponding thermal actuators are the same between the front side and the back side of the drawing. In addition to these combination modes, since the number of thermal actuators installed in the column section 14 is 16, there are many combinations of heating and cooling of each thermal actuator, and the detected value of the displacement sensor 5l-34 or the displacement sensor S1 ~Detection value of S4 and displacement sensor S5~
Fine control becomes possible according to the detected value in S10.

FIG. 7 similarly shows a typical example of a control mode that combines the operations of the thermal actuators in the head section 12 attached to the embodiment of the third invention.

Figure a shows a mode in which both the upper thermal actuators of the head section 12 are cooled and both the lower sections are heated;
2 indicates that the angle θ is tilted counterclockwise.

The figure shows a mode in which both the upper thermal actuators are heated and both the lower thermal actuators are cooled, and the head portion 12 is tilted clockwise at an angle θ4.

Figure C shows a mode in which the upper left side and the lower right side are cooled, and the upper right side and lower left side are heated, and the lower end of the tool attachment part 17 is raised upward in a distance of 2. Indicates movement.

FIG. d shows a mode in which the upper left side and the lower right side are heated and the upper right side and the lower left side are cooled, and the tool attachment shows that the lower end of the part 17 moves downward by a distance * i 4 substantially in parallel.

Note that the four control modes described above are examples in which the heating and cooling of the corresponding thermal actuators are the same between the front side and the back side of the drawing. In addition to these combination modes, since the number of thermal actuators installed in the head section 12 is 16, there are many combinations of heating and cooling of each thermal actuator, and fine control is possible according to the detected values of displacement sensors S5 to 310. becomes possible.

In addition, in the machining center shown in the embodiment of the third invention, the head section 12 is thermally deformed due to heat generated by the drive motor 13 and its deceleration mechanism section, and the tool deforms due to the machining of the workpiece W. Sensors S5 to SIO comprehensively detect irregular elastic deformations due to machining reaction forces generated in one machining process, and control heating and cooling of each thermal actuator according to the amount of displacement to measure displacement in real time. It becomes possible to proceed with the machining of the workpiece W while correcting and controlling.

Further, a flow path 69 for circulating cooling oil is installed on the column portion 14 side of the head portion 12, and cooling oil having a temperature slightly lower than the ambient temperature is constantly supplied. As a result, heat generation from the head portion 12 is suppressed from being transmitted to the column portion 14, and thermal expansion and warping of the column portion 14 due to heat transfer from the head portion 12 is prevented.

In addition, displacements that cannot be corrected by controlling only the head section 12,
If displacement occurs in the entire head section 12 or even in the column section 14 itself, the column section 14 itself can also be corrected for displacement according to the detected values of sensors S1 to S4 and furthermore sensors S5 to S10. can be controlled. At this time, the displacement control of the head section 12 and the column section 14 is combined to control the position of the tool, making it possible to realize higher precision machining.

According to the applicant's experience, the machining process shown in Figure 1
In the example of the center, as a result of controlling the operation of each thermal actuator under the conditions of an ambient temperature of 35 degrees, a heating temperature of the thermal actuator of 45 degrees, and a cooling temperature of 25 degrees, the tip position of the tool 11 was adjusted within a range of about 30 μm. It was confirmed that it could be controlled.

In each of the above embodiments, the operation of each thermal actuator is only heating or cooling. In addition, more precise control can be achieved by setting the temperature of the thermal actuator not only at two points, the high temperature of the heating section and the cold temperature of the cooling section, but also at a continuous intermediate temperature.

In addition, in the embodiment, control was explained in which each thermal actuator corrects positional deviation caused mainly by thermal deformation due to heat generation of the tool motor 30 and elastic deformation due to machining reaction force. By actively controlling the operation of each thermal actuator, tool position control can also be performed more precisely, e.g.
When machining molds and the like using a machining center, using this attitude control device makes it possible to achieve ultra-precise machining on the micron order, which was previously impossible.

Furthermore, in each of the above embodiments, four thermal actuators are installed on each surface of the column section 14 and the head section 12, with two thermal actuators in two stages, but it is also possible to install one thermal actuator on each surface and two stages. Furthermore, depending on the position of the surface on which the thermal actuators are installed, the number of installed stages and the number of installed thermal actuators can be arbitrarily combined and controlled.

Furthermore, by installing temperature sensors in each part of the main structural frame that makes up the machine tool, it is also possible to control each thermal actuator by taking into account thermal displacement based on the detected overall temperature distribution. In that case, accuracy is improved compared to the case where each thermal actuator and its attached sensor are individually controlled.

Furthermore, these inventions, in which a thermal actuator is installed on the wall of a hollow structure to generate thermal displacement to control the posture of the structure, can also be applied to the structures of various machine tools other than machining centers. It is possible to further improve the machining accuracy of various applied machine tools.

(Effects of the Invention) As described above, according to the first invention, even if displacement occurs on the wall surface of the column part of a machine tool due to temperature change, processing reaction force of a tool, etc., the column part The wall surface is heated or cooled by the column thermal actuator to control expansion and contraction of the column. As a result, the tool is held in place and machining accuracy is significantly improved compared to conventional machine tools.

Further, according to the second invention, even if displacement occurs in the head section and the column wall surface of the machine tool due to temperature change, tool machining reaction force, etc., the column section wall surface is adjusted according to the displacement. A thermal actuator heats or cools the column to control expansion and contraction, holding the tool in place.

As a result, machining accuracy is significantly improved compared to conventional machine tools.

Furthermore, according to the third invention, even if displacement occurs in the head and column wall surfaces of the machine tool due to temperature changes, tool machining reaction forces, etc., the head and column wall surfaces are adjusted according to the displacement. are heated or cooled by their respective thermal actuators to control the expansion and contraction of the head and column sections to hold the tool in place. As a result, machining accuracy is significantly improved compared to conventional machine tools.

Furthermore, in the first, second, and third inventions, processing can be performed by generating a minute displacement in advance at the tool position using a thermal actuator installed on the wall surface of the column part, etc.
This enables ultra-precise machining that could not be achieved with conventional machine tools.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of an embodiment in which the first and second inventions are applied to a machining center, Fig. 2 is a sectional view taken along the line ■-■ in Fig. 1, and Fig. 3 is an embodiment of the third invention. Fig. 4 is a cross-sectional view of Fig. 3, Fig. 5 is a sectional view taken along line V-■ in Fig. 4, and Fig. 6 is an explanatory diagram showing an example of the control mode of the column section. , FIG. 7 is an explanatory diagram showing an example of the control mode of the head section, and FIG. 8 is an explanatory diagram of the occurrence of thermal displacement in a conventional example. 12...Head part 13...Motor 14...Column part 17...Tool mounting part 19...Flow path 2
9... Channel 39... Channel 69 River channel 21-28
...Thermal actuators 31-38...Thermal actuators 41a-48a...Thermal actuator 41b for cooling
~48b...Heating thermal actuators 51a~58
a... Cooling thermal actuators 51b to 58b...
- Thermal actuators for heating 61b to 68b... Thermal actuators for heating 62a to 67a... Thermal actuators for cooling 71b to 78b... Thermal actuators for heating 72a to 77a... Thermal actuators for cooling 81~SIO...Displacement sensor with temperature compensation Fig. 1 Agent Patent attorney Mori 1) Male - Toni Fig. Fig. 1 (a)

Claims (3)

[Claims] (1) At least one pair of hollow columns are arranged facing each other in the circumferential direction of a hollow column section that supports the head section that grips and drives the tool by attaching it to a fixed base, and generates thermal displacement by heating or cooling the wall surface of the column section. A thermal actuator for the column, a displacement sensor that is installed on the wall of the column to which the thermal actuator is attached, and that detects displacement of the column wall caused by temperature changes, tool machining reaction forces, etc.; An attitude control device for a machine tool, comprising: a control section that outputs a thermal actuator control signal that expands and contracts a column section based on a detected value so as to maintain a preset tool position. (2) At least one pair of hollow columns are arranged facing each other in the circumferential direction of a hollow column section that supports the head section that grips and drives the tool by attaching it to a fixed pedestal, and generates thermal displacement by heating or cooling the wall surface of the column section. A thermal actuator for the column, a displacement sensor installed on the wall of the head that detects displacement of the wall of the head caused by temperature changes, tool processing reaction forces, etc., and a wall of the column to which the thermal actuator for the column is attached. A displacement sensor is installed in the column to detect displacement of the column wall surface caused by temperature changes, tool machining reaction force, etc., and a preset tool position is maintained based on the detected value of each displacement sensor. An attitude control device for a machine tool, comprising: a control section that outputs a thermal actuator control signal for expanding and contracting a column section; (3) At least one pair of thermal actuators for the head are arranged facing each other in the circumferential direction of the head that grips and drives the tool, and generate thermal displacement by heating or cooling the wall surface of the head, and the head is fixed. One or more pairs of column thermal actuators and head thermal actuators are disposed facing each other in the circumferential direction of a hollow column that is attached to and supported by a pedestal, and heat or cool the column wall surface to generate thermal displacement. A displacement sensor is installed on the wall of the attached head to detect displacement of the head wall caused by temperature changes, tool machining reaction forces, etc., and a displacement sensor is installed on the wall of the column to which the thermal actuator for the column is attached. A displacement sensor detects the displacement of the column wall surface caused by temperature changes, tool machining reaction forces, etc., and the column and head are arranged to maintain preset tool positions based on the detected values of each displacement sensor. An attitude control device for a machine tool, comprising: a control section that outputs a thermal actuator control signal for expanding and contracting each section;