JPH1080840A - Positioning device of machine tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably perform positioning in a microscopic unit at high speed in a short time by an easy method by driving/controlling a moving means so as to move a worktable or a work means by a moving error quantity between a preset moving distance and an actual moving distance at which the worktable or the work means actually moves. SOLUTION: An actual moving distance being a real moving distance is detected on the basis of a position of a table 1 detected by a position detector 9, and is stored as this actual moving distance feedback quantity. It is compared with a feedback quantity, and when a difference between a moving distance and the feedback quantity becomes less than 1, operation is switched to a control system of a 0.017μ system. A piezoelectric element incorporated into a driving ring 5 is operated against energizing force of a ring-shaped spring by driving the driving ring 5, and a space between the driving ring 5 and the table 1 is expanded, and the table 1 is fed in slight movement. An excess and deficiency caused by rough positioning by a servomotor 2 is eliminated by this slight movement feed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positioning device for a machine tool, and more particularly to a technology capable of performing positioning in minute units.

[0002]

2. Description of the Related Art In a machine tool, a workpiece is mounted on a table, and a processing means such as a table or a drill is moved so that a predetermined processing position of the workpiece is processed. . Conventionally, a servomotor has been used as a drive source of a table, a linear scale is provided on the table, the position of the table is read from the linear scale by a position detector, and the table is moved based on the position data. ing.

[0003] In recent years, fine processing has been required, and accordingly, it has been necessary to perform positioning in units of nanometers. For example, in order to obtain accuracy in units of 10 nanometers, a position detector of 0.01 μm is required. The positioning speed of the table is set to a high speed of about 10 to 30 m / min in order to use a precision one and improve productivity.

[0004]

By the way, in order to perform such fine positioning, it is required to ensure the ability to follow the control in fine units and to maintain high rigidity. In a mechanical positioning device, moving the table at a high speed like the above-mentioned positioning speed, positioning it in a short time, and holding it with high rigidity is difficult due to the problems of resolution of motor control, processing speed, and rigidity of servo. Have difficulty.

[0005] The present invention has been made in view of such conventional problems, and positioning in minute units can be performed at high speed, in a short time, more stably, and with high rigidity. It is an object of the present invention to provide a machine tool positioning device capable of securing a stop position of the machine tool.

[0006]

Therefore, the apparatus according to the first aspect of the present invention comprises, as shown in FIG. 1, a work table on which a work is placed, and a processing means for working the work. Prepared,
In a machine tool for processing a workpiece by moving the worktable or processing means, a position detection means for detecting a position of the worktable or processing means, and a worktable based on the detected position of the worktable or processing means. Alternatively, a movement amount setting means for setting the movement amount of the processing means, a first movement means for moving the worktable or the processing means, and a first movement based on the set movement amount set by the movement amount setting means First drive control means for driving and controlling the means, and the work table or the processing means being connected with the first movement means and the worktable or the processing means in a smaller movement unit than the first movement means. The second moving means to be moved, the worktable or the processing means is moved by a movement error between the set movement amount by the first moving means and the actual movement amount actually moved by the worktable or the processing means, Drive the second mode of transportation A second driving control means for controlling, with a.

According to this configuration, the position of the worktable or the processing means is detected by the position detection means, and the set movement amount is set by the movement amount setting means based on the detected position of the worktable or the processing means. . The first drive control means drives and controls the first movement means based on the set movement amount. Further, when an error occurs in the actual movement amount by the first moving means with respect to the set movement amount, the second drive control means drives and controls the second movement means to set the movement amount and the actual movement amount. The work table or the processing means is moved by the amount of the movement error. Since the second moving means moves the worktable or the processing means in smaller units than the first moving means, the positioning accuracy is improved.

[0008] In the apparatus according to the second aspect of the present invention, the second moving means expands and contracts in the moving direction of the worktable or the processing means when a voltage is applied to move the worktable or the processing means. It is provided with. According to such a configuration, a voltage is applied, and the piezoelectric element expands and contracts. This expansion and contraction operation is minute, and the worktable or the processing means moves in minute movement units.

[0009]

FIG. 2 is a block diagram showing an embodiment of the present invention.
This will be described with reference to FIG. In FIG. 2 showing the present embodiment, a table 1 is a work table provided on a machine tool on which a work is placed. Although not shown, the machine tool is provided with processing means such as a drill and a cutting tool for processing the workpiece on the table 1.

The servo motor 2 is a first moving means for moving the table 1. A ball screw 3 is directly connected to the servo motor 2, and when the servo motor 2 rotates, the ball screw 3 rotates together. The servo motor 2 and the ball screw 3 have a resolution of, for example, about 0.01 μm. A drive ring 5 is assembled to the nut 4 of the ball screw 3 via a support member 5a.
Are connected to the table 1.

FIGS. 3 and 4 are enlarged views of this part of FIG. 2 and plan views of the drive ring 5, respectively. As shown in these figures, the drive ring 5 includes a ring-shaped spring 6, Four piezoelectric elements 7a to 7d are incorporated. As shown in FIG. 3, the ring-shaped spring 6
It is urged in a direction to narrow the space between the drive ring 5 and the table 1.

The piezoelectric elements 7a to 7d expand and contract when a voltage is applied, and are arranged on the drive ring 5 so as to be balanced as shown in FIG. Then, when a voltage is applied, the piezoelectric elements 7 a to 7 d operate in a direction to expand the space between the drive ring 5 and the table 1 against the biasing force of the ring-shaped spring 6. This drive ring 5 includes
For example, those with a stroke of 10 μm, a generated force of 3400 N, a single unit rigidity of about 350 N / μm, and a resolution of 10 nm are used.
It is driven by a two-clock pulse or an analog input of DC0 to 5V.

The drive ring 5 corresponds to a second moving means for performing fine movement in a unit of nanometer. Table 1
Is provided with a linear scale 8. The position detector 9 detects the position of the table 1 by reading the linear scale 8, and corresponds to a position detecting means. The position detector 9 has a resolution of 0.01 μm or less. The position data of the table 1 detected by the position detector 9 is input to a control unit (hereinafter referred to as “C / U”) 10.

The C / U 10 includes a ROM, a RAM, a microcomputer and the like, and controls the drive of the servomotor 2 and the drive ring 5 based on the input position data of the table 1. Next, the operation will be described based on the flowchart of FIG. Steps (marked "S" in the figure,
In (1), a movement amount A is commanded. This step corresponds to the movement amount setting means.

In step 2, when the difference (A−B) between the movement amount and the feedback amount B is not 0, the process proceeds to step 3. Further, in step 3, the difference (A−B) is compared with 1, and when it is 1 or more, it is determined that the coarse feed is to be performed, and the process proceeds to step 4. In step 4, the control system is set to the 0.1 μ system.
At this time, the drive ring 5 is not driven, and is urged by the ring-shaped spring 6 in a direction to narrow the space between the drive ring 5 and the table 1.

In step 5, the table 1 is moved by driving the servo motor 2. The positioning speed of the table 1 is set to, for example, about 10 to 30 m / min. When the servo motor 2 is driven, the ball screw 3 directly connected to the servo motor 2 rotates, and the nut 4 moves at a high speed, and the table 1 is coarsely fed with the movement, whereby coarse positioning is quickly performed. Since the resolution of the servo motor 2 and the position detector 9 is 0.01 μ as described above, the coarse movement feed provides a resolution of about 10 times, that is, a resolution of about 0.1 μm.

This step corresponds to the first drive control means. In step 6, the table 1 is detected by the position detector 9.
Detect the position of. In step 7, the actual movement amount, which is the actual movement amount, is detected based on the position of the table 1 detected by the position detector 9, the actual movement amount is stored as the feedback amount B, and the process returns to step 2.

If the difference (AB) is less than 1 in step 3, the process proceeds to step 8. Step 8
Then, switch to the 0.01 μ control system. In step 9, the driving ring 5 is driven by applying a two-clock pulse or an analog voltage of 0 to 5 V DC to the driving ring 5. As a result, the piezoelectric elements 7a to 7d incorporated in the drive ring 5 operate against the urging force of the ring spring 6, the space between the drive ring 5 and the table 1 is widened, and the table 1 is finely fed. . Since the resolution of the drive ring 5 and the position detector 9 is 10 nm or less, a resolution of about 10 nm can be obtained by this fine movement. Servo motor 2
The excess or deficiency caused by the coarse positioning by the above is eliminated by this fine movement feed.

This step corresponds to the second drive control means. When the difference between the set movement amount A and the feedback amount B becomes 0, the positioning is completed, and this routine ends. According to such a configuration, coarse positioning is performed by controlling the servomotor 2 and fine unit positioning is performed by the drive ring 5 including the piezoelectric elements 7a to 7d. Can be performed, and the workpiece can be precisely machined.

Further, since a conventional control system such as the servomotor 2 can be used, an inexpensive system can be realized, and it can be effectively used especially for a production type machine tool. Further, one position detector 9 can perform coarse and minute unit positioning. Although the table 1 is moved in the present embodiment, the present invention is not limited to this.
The table 1 may be fixed and the processing means such as a drill and a cutting tool may be moved.

[0021]

As described above, according to the apparatus of the first aspect of the present invention, the drive control can be performed at a high speed, and the worktable or the processing means can be positioned in minute units. According to the apparatus according to the second aspect of the present invention, the worktable or the processing means can be moved in minute units by the piezoelectric element to which the voltage is applied and which expands and contracts.

[Brief description of the drawings]

FIG. 1 is a claim correspondence diagram showing a configuration of the present invention.

FIG. 2 is a system diagram showing an embodiment of the present invention.

FIG. 3 is a partially enlarged view of FIG. 2;

FIG. 4 is a plan view of the drive ring of FIG. 2;

FIG. 5 is a flowchart showing the operation of FIG. 2;

[Explanation of symbols]

 Reference Signs List 1 table 2 servo motor 5 drive ring 7a to 7d piezoelectric element 9 position detector 10 control unit (C / U)

Claims (2)

[Claims] 1. A machine tool, comprising: a worktable on which a work is placed; and processing means for processing the work, wherein the worktable or the processing means is moved to process the work. Or a position detection means for detecting the position of the processing means, a movement amount setting means for setting the movement amount of the worktable or the processing means based on the detected position of the worktable or the processing means, and the worktable or the processing means First moving means for moving, first driving control means for driving and controlling the first moving means based on the set moving amount set by the moving amount setting means, the first moving means and the work table Or a second moving means coupled to the processing means for moving the worktable or the processing means in a smaller moving unit than the first moving means; and a set movement amount by the first moving means and the worktable. Or the processing means has actually moved As the movement amount and movement error of only worktable or processing means is moved, the positioning device for a machine tool, characterized by comprising a second driving control means for driving and controlling the second moving means. 2. The apparatus according to claim 1, wherein said second moving means comprises a piezoelectric element which is moved by applying a voltage to extend or contract in a moving direction of the worktable or the processing means to move the worktable or the processing means. The positioning device for a machine tool according to claim 1, wherein: