JPH07112671B2 - Processing device with magnetic bearing on spindle - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a processing device in which a spindle on which a processing tool is mounted is supported by a magnetic bearing, and particularly, grinding resistance or cutting resistance due to oscillation operation is fast. Even if it fluctuates, it relates to a technique for accurately processing the work.

《Prior Art》 Conventionally, a processing device in which a spindle of this type is supported by a magnetic bearing, for example, an inner surface grinding machine is provided with a grindstone at a tip portion and is equipped with a spindle which is rotationally driven, and the spindle is an electromagnet. Therefore, it is magnetically levitated in the radial and axial directions, while the position of the spindle is detected by the radial and axial position sensors, and the exciting current of the electromagnet is adjusted based on the detected value to target the spindle. It is configured to float and hold in position.

Further, on the grindstone side of the spindle, a headstock having a cylindrical work that is held in rotation is disposed, and this headstock is for grinding the inside of the work when the grindstone of the spindle enters the work. , Is configured to move at a predetermined grinding speed via a ball screw mechanism, whereby the work is ground.

By the way, when grinding a workpiece as described above,
The grinding resistance generated in the grindstone varies due to variations in the work allowance, a change in the cutting edge of the grindstone, and the like, and the machining accuracy and the machining efficiency are reduced. Therefore, in this type of conventional device, in order to keep the grinding resistance constant, the grinding resistance generated in the grindstone is detected from the exciting current of the electromagnet, and the grinding resistance is equal to a predetermined value. It is configured to control the grinding speed of a headstock driven via a ball screw mechanism.

<< Problems to be Solved by the Invention >> However, in such a conventional device, in order to keep the grinding resistance constant, as described above, is configured to control the grinding speed of the headstock, Further, since the headstock is driven by the ball screw mechanism, it is inevitable that the grinding speed control is delayed.

Therefore, for example, when the grinding wheel of the spindle is moved to the left and right like an oscillation operation, and the grinding resistance fluctuates rapidly with this, the control of the grinding speed of the headstock should follow the fluctuation of the grinding resistance. However, there is a problem that it is difficult to machine the work with the above-mentioned predetermined grinding resistance, and the machining accuracy and the machining efficiency are not improved so much.

<< Means for Solving the Problems >> The present invention has been made in view of the above circumstances, and the purpose thereof is to instantaneously move a processing tool such as a grindstone attached to a spindle, For example, when processing a work using an oscillation operation, the present invention is to provide a processing device for processing the work with high accuracy and high processing efficiency, and the present invention is configured as follows.

That is, as shown in FIG. 1, according to the present invention, a spindle rotatably disposed, a processing tool provided at the tip of the spindle, a rotation driving means for rotating the spindle, and the spindle in the radial direction. And a radial electrode stone and an axial electromagnet for magnetically levitating in one of the axial direction or one of the electromagnets, and a radial position sensor and an axial position sensor for detecting a radial position and a floating position in the axial direction of the spindle, In a device comprising a control means for adjusting the exciting current of the electromagnet based on the detection value of each position sensor to levitate and hold the spindle at a target position, processing such as rough grinding and precision grinding by the processing tool The reference grinding resistance or reference cutting resistance, which has been individually preset for each level,
Level-specific reference value output means that outputs according to the machining level, and resistance detection means that detects the grinding resistance or cutting resistance in the radial direction and / or the axial direction that occurs in the processing tool based on the excitation current. , A target position correction amount of the spindle for making the current grinding resistance or cutting resistance equal to the reference grinding resistance or reference cutting resistance is calculated based on the detection result by the resistance detection means, and the target position correction amount is calculated. Is provided to the target position of the spindle.

<Operation> In the present invention, as shown in FIG. 2, in place of L2 which moves the headstock by the conventional ball screw mechanism, L1 which moves the spindle magnetically levitated by the electromagnet has a better step. According to the present invention, the target position of the spindle magnetically levitated to the target position is corrected by the radial electromagnet and the axial electromagnet or one of the electromagnets, and the correction is made. The spindle is floated and held at the set target position, and acts so as to equalize the grinding resistance or cutting resistance generated in the working tool in the radial direction and / or the axial direction with one of the predetermined values.

Example An example in which the device of the present application is applied to an inner surface grinding machine will be described in detail below with reference to FIGS. 3 and 5.

FIG. 3 shows a block diagram of the inner surface grinding machine, which comprises a spindle 3 housed in a spindle body 1 and provided with a grindstone 2 as a processing tool at the tip thereof. It is rotatably provided, and the spindle 3 is configured to be rotationally driven by a motor 4 arranged near the center thereof.

In addition, the radial electromagnets 5a, 5 are provided on the left end side of the spindle 3.
b, 5c, 5d (see FIG. 4), and 5e, 5f, 5g, 5h are provided on the right end side at an angle of 45 ° to the vertical direction,
The spindle 3 is magnetically levitated in the radial direction by these radial electrode stones. On the other hand, axial electromagnets 7a, 7b, 7c, 7d are provided so as to face both sides of a disk 6 integrally formed in the center of the spindle 3,
The spindle 3 is magnetically levitated in the axial direction by these axial electromagnets.

Further, radial position sensors 8a, 8b, 8c, 8d (see FIG. 4) are provided on the left end side of the spindle 3 and 8e, 8e, on the right end side.
Similar to the radial electromagnet, 8f, 8g, and 8h are provided at an angle of 45 ° with respect to the vertical direction, and an axial position sensor 9 is provided on one end side of the spindle 3. 3 is configured to detect the magnetic levitation position, and the detection value from each of these sensors is
Through the position detection circuit 16 and the processing circuit 17 and the electromagnet driver 18 which form the electric circuit portion described later, the exciting currents of the radial electromagnets 5a to 5h and the axial electromagnets 7a to 7d are adjusted to adjust the spindle 3 It is configured to float and hold at the target position.

Reference numeral 10 is a table on which the spindle body 1 is mounted, and the table 10 is moved in the Z-axis direction by a servomotor 11 via a ball screw mechanism 12. Reference numeral 13 is a headstock that holds the work W by a work mounting mechanism (not shown). The headstock 13 is configured to be moved in the X-axis direction by a servomotor 14 via a ball screw mechanism 15.

Next, the electric circuit portion of the grinder will be described. The position detection circuit 16 is composed of a bridge circuit or the like. Based on the detection values detected by the position sensors 8a to 8h and 9, the position detection circuit 16 is connected via the bridge circuit or the like. The flying position of the spindle 3 is obtained by the above, and the obtained flying position is output to the processing circuit 17.

Further, the processing circuit 17 stores the target position where the spindle 3 floats, compares the floating position of the spindle output from the position detection circuit 16 with the target position, and compensates for the difference from the target position. While outputting the adjustment amount for adjusting the exciting current of each of the radial electromagnets 5a to 5h and each of the axial electromagnets 7a to 7d to the electromagnet driver 18, as described above,
This processing circuit 17 is configured to add the correction amount to the target position when the correction amount for the target position is output from the correction amount calculating circuit 20 described later.

Further, the electromagnet driver 18 uses the adjustment amounts of the exciting current output from the processing circuit 17 to adjust the radial electromagnets.
An exciting current is supplied to 5a to 5h and the axial electromagnets 7a to 7d, and the electromagnet driver 18 is configured to output an exciting current to each of the electromagnets to a grinding resistance detection circuit 19.

Then, the grinding resistance detection circuit 19 uses the electromagnet driver 18
Utilizing the fact that the exciting current output from the grindstone 2 changes in magnitude depending on the magnitude of the grinding resistance generated in the grindstone 2.
The present grinding resistance 19a generated in the above is detected, and this is output to the correction amount calculation circuit 20.

The correction amount calculation circuit 20 performs a processing operation when a constant grinding resistance control command 21a and a predetermined grinding resistance 21b in rough and fine grinding are output from the grinder NC device 21 described later. The circuit 20 compares the current grinding resistance 19a output from the grinding resistance detection circuit 19 with a predetermined grinding resistance 21b output from the grinder NC device to correct the target position of the spindle. The correction amount is calculated and the correction amount 20a is output to the processing circuit 17. The correction is performed when the current grinding resistance (c) is larger than the predetermined grinding resistance (a) as shown in FIG. 3, for example. , The spindle 3 is moved in the X ₂ direction to reduce the current grinding resistance (c), and thereby the current grinding resistance is corrected to be equal to a predetermined grinding resistance.

On the other hand, when the current grinding resistance is smaller than the predetermined grinding resistance, the spindle 3 is moved in the X ₁ direction to increase the current grinding resistance so that the current grinding resistance becomes equal to the predetermined grinding resistance. Is to be corrected.

The grinder NC device 21 executes the flowchart shown in FIG.
A constant grinding resistance control command 21a and a predetermined grinding resistance 21b for rough and fine grinding are output to 20.

In this way, the grinder NC device 21 has a function of outputting a predetermined grinding resistance 21b individually predetermined for each processing level such as rough grinding and fine grinding, that is, a reference grinding resistance or a reference cutting resistance for each processing level. (Reference value output means for each level).

The servo motor driver 22 drives the servo motors 11 and 14 for moving the headstock 13 and the table 10, and the motor driver 23 supplies an exciting current to the motor 4 for rotationally driving the spindle 2. To do.

Next, the operation of the inner surface grinding machine configured as described above will be described with reference to the flowchart shown in FIG. In addition,
This flow chart is executed by the NC machine for the grinding machine.

First, the position detection circuit 16 and the processing circuit 17 in FIG.
The spindle 3 is levitated and held at the target position stored in the processing circuit 17 via the electromagnet driver 18, and then the spindle 3 is rotationally driven via the motor driver 23. (Step 100).

Then, a drive command is issued from the grinder NC device 21 to the servo motor driver 22, which causes the servo motor 11 to rotate rapidly to move the table 10 forward until the grindstone 2 enters the work W (step 101), and further the above grinding is performed. The panel NC unit 21 issues an oscillation command to the servo motor driver 22,
As a result, the servomotor 11 is rotated in the forward and reverse directions, and the table 10 is reciprocated in the axial direction of the spindle 3 by a predetermined amount to perform the oscillation operation of the grindstone 2 (step 10).
2).

Next, the servomotor driver 22 from the grinder NC device 21
Drive command is issued to the servo motor 14, which causes the headstock 13 to move forward in the X ₁ direction (step 103).
From the increase in grinding resistance, it is judged whether or not the grindstone 2 and the workpiece W are in contact with each other (step 104). If they are not in contact with each other (NO)
The above steps 103 and 104 are repeated. On the other hand, when the grindstone 2 and the work W come into contact with each other and a grinding resistance is generated in the grindstone 2 (YES), a constant grinding resistance control command 21a from the grinder NC device 21 and a predetermined grinding resistance 21b in the rough grinding are used as a correction amount calculation circuit. It is output to 20 and constant grinding resistance control is performed (step 105).

That is, the above-mentioned constant grinding resistance control includes rough grinding and fine grinding.First, in order to perform rough grinding, the grinder NC device 21 moves the headstock 13
Drive command is issued to move the workpiece in the X ₁ direction at the rough grinding speed, which causes the servo motor 11 to move forward at the rough grinding speed to move the workpiece W.
To carry out rough research. At the same time, based on the exciting current output from the electromagnet driver 18, the present grinding resistance generated in the grindstone 2 is obtained by the grinding resistance detection circuit 19, and the grinding resistance 19a becomes equal to the predetermined grinding resistance 21b in the rough grinding. As described above, the correction amount calculating circuit 20 calculates the correction amount 20a for correcting the target position of the spindle, and the spindle 3 is quickly floated and held based on the new target position obtained by adding the target position and the correction amount, It is ground with a predetermined rough grinding resistance (step 106).

Then, it is judged whether or not the rough polishing of the work W is completed based on the inner diameter dimension measured by the inner diameter measuring machine of the work W (not shown) (step 107), and when the rough polishing is not completed (N
In step O), step 106 and step 107 are repeated. On the other hand, when the rough grinding is completed (YES), the grinding machine NC device 21 outputs a predetermined grinding resistance 21b in the fine grinding to the correction amount calculation circuit 20 (step 108),
The grinding machine NC device 21 issues a drive command to move the headstock 13 forward in the X ₁ direction at the polishing speed in order to perform the polishing. This causes the servomotor 11 to move forward at the polishing speed to perform the polishing of the workpiece W. To do.

At the same time, in this refinement as well as in the above-mentioned rough polishing, the correction amount of the target position of the spindle is calculated so that the present grinding resistance 19a and the predetermined grinding resistance 21b in the above-mentioned refinement become equal, and the spindle Is quickly levitated and held based on the new target position obtained by adding the target position and the correction amount 20a above,
Always grind with constant grinding resistance (Step 10
9).

Then, it is determined whether or not the precision polishing of the work W has been completed, and from the inner diameter dimension similarly to the precision polishing (step 110), if the precision polishing is not completed (NO), the steps 109 and 110 are performed. It is repeated. On the other hand, when the polishing is finished (YES), the constant grinding resistance control as described above is finished (step 111), the headstock 13 is retracted in the X ₂ direction, and the oscillation operation of the table 10 is stopped (step 112) and thereafter, the table 10 is retracted from the work W (step 113).

As described above, according to the apparatus of this embodiment,
When the cutting resistance changes, the magnetically levitated spindle moves in the direction that absorbs this change in force, that is, the magnetically levitated spindle itself moves to make the grinding / cutting resistance of the work tool constant. Therefore, for example, even if the grinding / cutting resistance fluctuates rapidly by performing an oscillation operation, the spindle moves in accordance with the fluctuation, so that the grinding / cutting resistance of the processing tool can be kept constant at all times. It is possible to improve the machining accuracy and machining efficiency of the work.

Further, in the apparatus of this embodiment, a predetermined grinding resistance (reference grinding resistance or reference cutting resistance) is output from the grinder NC device for each processing level such as rough grinding and fine grinding, and based on this, the spindle itself of the spindle itself is output. The grinding resistance and the like are made constant by movement, that is, the grinding resistance and the like are made constant for each machining level. Therefore, it is possible to improve the machining accuracy and the machining efficiency of the work in that the constant machining such as the grinding resistance can be performed according to the machining level.

In this embodiment, the target position correction in the radial direction was described for the inner surface grinding machine provided with a grindstone at the spindle tip, but a cutting tool is attached instead of the grindstone, for example, in the case of milling or the like. The target position correction in the axial direction or the target position correction in the radial direction may be added thereto.

<< Effects of the Invention >> The present invention is configured such that when the grinding / cutting resistance of the processing tool changes, the magnetically levitated spindle moves in a direction that absorbs this change in force, that is, the magnetically levitated spindle itself. This is configured so that the grinding / cutting resistance of the processing tool can be made constant by moving. For this reason, even if the grinding / cutting resistance fluctuates rapidly, the spindle moves in accordance with the fluctuation, so that the grinding / cutting resistance of the processing tool can be kept constant at all times, and the machining accuracy and processing efficiency of the workpiece can be improved. Can be improved.

Moreover, according to the present invention, the grinding resistance and the like are made constant by the movement of the spindle itself for each machining level such as rough grinding and precision grinding, so that the grinding resistance and the like can be made consistent according to the machining level. Also in terms of processing, it is possible to improve the processing accuracy and processing efficiency of the work.

[Brief description of drawings]

FIG. 1 is a diagram for responding to complaints, FIG. 2 is an explanatory diagram for explaining step responsiveness of spindle movement and headstock movement, FIG. 3 is a block diagram of an inner surface grinding machine to which the device of the present invention is applied, and FIG. FIG. 5 is a sectional view taken along the line III-III in FIG. 5, and FIG. 5 is a flowchart showing the operation of the inner surface grinding machine to which the device of the present invention is applied. 2 …… Whetstone 3 …… Spindle 5a ～ 5h …… Radial electromagnet 7a ～ 7d …… Axial electromagnet 8a ～ 8h …… Position sensor in radial direction 9 …… Position sensor in axial direction 17 …… Processing circuit 18 …… Electromagnetic driver 19 …… Grinding resistance detection circuit 20 …… Correction amount calculation circuit 21 …… Grinding machine NC device

Claims (1)

[Claims] 1. A rotatably arranged spindle, a processing tool provided at the tip of the spindle, a rotation driving means for rotating the spindle, and the spindle in a radial direction and / or an axial direction. Radial and / or axial electromagnets for magnetic levitation, radial position sensors and axial position sensors that detect the radial and axial levitation positions of the spindle, and the detected values of the position sensors And a control means for controlling the exciting current of the electromagnet to levitate and hold the spindle at a target position. Grinding resistance or reference cutting resistance is output according to the machining level Force means, resistance detecting means for detecting the grinding resistance or cutting resistance in the radial direction and / or the axial direction occurring in the working tool based on the exciting current, and based on the detection result by the resistance detecting means. , A target position correction amount for calculating the target position correction amount of the spindle for making the current grinding resistance or cutting resistance equal to the reference grinding resistance or reference cutting resistance, and adding this target position correction amount to the target position of the spindle A machining device having a magnetic bearing as a spindle, characterized in that: