JPH04372361A - Grinding machine equipped with magnetic bearing spindle - Google Patents

Abstract

PURPOSE:To enable the high-accuracy grinding of a workpiece by micro-depth of cut of sub-micron unit. CONSTITUTION:A wheel spindle stock table 12 is moved, and the rotor shaft 22 of a magnetic bearing spindle 10 is rotated to perform rapid grinding (A), rough grinding (B) and fine grinding (C) to a workpiece by a grinding wheel 25. In order to further perform micro-depth of cut of 0.1mum unit after the termination of the fine grinding (C), an exciting current corresponding to this micro- depth of cut is fed to the radial direction electromagnets 24a, 24b, 26a, 26b of the magnetic bearing spindle 10 by the control of the main controller 70 and magnetic bearing spindle 10 of a control part 16 so as to displace the rotor shaft 22 slightly into the direction of the workpiece W.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a grinding machine equipped with a magnetic bearing spindle used in a cylindrical grinding machine, and in particular, it controls minute displacement of the rotor shaft of the magnetic bearing spindle to make minute cuts in submicron units after precision grinding, etc. This invention relates to a grinding machine equipped with a magnetic bearing spindle that performs (micro-feed).

0002

2. Description of the Related Art Recently, with the demand for high-precision machining of workpieces, cylindrical grinders are used to perform grinding by constantly changing the cutting speed of the grindstone. Such a cylindrical grinding machine includes a headstock table on which a main spindle for attaching a workpiece is arranged, and a movement mechanism that moves one or both of the grindstone table. This moving mechanism uses, for example, a servo motor and a ball screw, and further includes a sizing detection section that detects the grinding dimension of the workpiece.

[0003] In the above-mentioned cylindrical grinding machine, the size of the workpiece during machining is detected by the sizing detection section as the remaining machining amount from the set finished size. FIG. 4 shows an example of a cutting state in a cylindrical grinder that performs cutting using a grindstone table. As shown in Figure 4, the grinding progresses rapidly (A)
, rough grinding (B) followed by fine grinding (C), spark out (D) when a desired predetermined dimension is reached, followed by rapid retraction (E).

0004

[Problems to be Solved by the Invention] However, in the above-mentioned conventional cylindrical grinding machines, etc., the grindstone table, etc. is relatively heavy, and therefore, even when attempting to make a minute cut, the responsiveness of the movement of the grindstone table, etc. It is not possible to make small incisions in the submicron level because of poor followability and poor followability. Additionally, ball screws have backlash and have limited feed resolution, making it difficult to make minute cuts. Furthermore, a moving mechanism using a V-groove/flat guide has the disadvantage that stick slip occurs and it is impossible to make minute cuts.

The present invention was made in view of the above-mentioned problems, and an object of the present invention is to provide an excellent grinding machine equipped with a magnetic bearing spindle that is capable of making minute cuts in submicron units after predetermined grinding such as precision grinding.

[0006]

[Means for Solving the Problems] In order to achieve the above object, a grinding machine equipped with a magnetic bearing spindle of the present invention includes a magnetic bearing spindle having a grinding wheel fixed to a rotor shaft and equipped with an electromagnet for magnetic levitation, and a magnetic bearing spindle equipped with a magnetic bearing spindle. The grindstone table on which the spindle is placed, the spindle that holds the workpiece, the headstock table on which the spindle is placed, the grindstone table, the headstock table, or both move, and the rotor axis of the magnetic bearing spindle is rotated. and a control means for displacing the rotor shaft in the cutting direction by controlling the excitation current of the magnetic levitation electromagnet of the magnetic bearing spindle in order to make a finer cut after finishing the prescribed grinding of the workpiece with the grindstone. It is. be a sign.

[0007]

[Operation] The grinding machine equipped with a magnetic bearing spindle of the present invention configured as described above uses a magnetic bearing spindle that has a quick response in controlling the displacement of the rotor shaft and has good followability.
After the predetermined grinding of the workpiece, the rotor axis of the magnetic bearing spindle is controlled to be slightly displaced after the fine grinding.
A minute incision is made in units of 0.1 μm. by this,
High precision grinding of workpieces is possible. In other words, the machined surface roughness,
It is possible to improve dimensional accuracy and roundness.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of an embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows the configuration of an embodiment. This example includes a magnetic bearing spindle 10, a grindstone table 12 to which the magnetic bearing spindle 10 is fixed, a headstock table 14 on which a workpiece W is placed, and a control unit (corresponding to control means) 16 such as a programmable controller. Consisting of

The magnetic bearing spindle 10 is provided with a rotor shaft 22 made of a magnetic material, and a grindstone 25 is fixed to one end of the rotor shaft 22 . Around the rotor shaft 22, there are a pair of radial direction electromagnets 24a and 24b for floating and holding the rotor shaft 22 in the radial direction, and a radial direction electromagnet 2.
6a and 26b are arranged. Furthermore, a pair of axial direction electromagnets 32a, 32b and axial direction electromagnets 34a, 34b are arranged to hold the rotor shaft 22 in the axial direction with a magnetic disk 30 integrated with the rotor shaft 22 sandwiched therebetween. ing.

Further, a motor 36 is provided around the rotor shaft 22, and the rotor shaft 22 is rotationally driven by the motor 36. Further, position sensors 40a and 40b are arranged around both ends of the rotor shaft 22 to detect the radial direction position of the rotor shaft 22, and a detection signal from these sensors is sent to the radial direction electromagnet 2 through the control section 16.
The excitation currents of 4a and 24b are controlled. Similarly, position sensors 42a and 42b are provided to control the excitation current of the radial direction electromagnets 26a and 26b. This allows the rotor shaft 22 to be held at a predetermined position in the radial direction.

Further, a position sensor 44 is provided apart from the other end of the rotor shaft 22.
4, the axial direction electromagnets 32a, 32b, 34a, 34
The excitation current b is controlled to hold the rotor shaft 22 at a predetermined position in the axial direction. The grindstone table 12 is provided with a servo motor 50 for moving the magnetic bearing spindle 10 described above, and a ball screw 52 that is rotationally driven by the servo motor 50. 12 moves in the arrow direction Xa or the arrow direction Xb.

The headstock table 14 is provided with a main shaft 60 to which a workpiece W is attached, and a tail stock portion 62 for the workpiece W. Further, a sizing detector 6 having a sizing contact for detecting whether the workpiece W has been processed to a desired dimension.
4 is provided, and the detection signal from here is sent to the control unit 1.
6. The control unit 16 includes a main controller 7
0 and a magnetic bearing controller 72.

[0013] The main controller 70 includes a CPU and a RAM.
, ROM, I/O, etc.
A size detection circuit 74 is connected to which a detection signal from a sizing detector 64 is supplied and which converts it into a digital signal. Further, a grindstone table servo motor driver 76 is connected between the main controller 70 and the servo motor 50. This grindstone table servo motor driver 76 sends a drive current to the servo motor 50 according to instructions from an operation panel 78 connected to the main controller 70 . by this,
Grinding wheel head table 12, i.e. magnetic bearing spindle 1
0 moves in the arrow direction Xa or the arrow direction Xb.

[0014] Furthermore, the main controller 70 and the motor 3
A motor driver 80 is connected between 6 and 6. This motor driver 80 supplies a drive current to the motor 3 to obtain the rotational speed instructed by the main controller 70.
6. The magnetic bearing controller 72 is a PID (correction circuit) to which detection signals from the position sensors 40a, 40b, 42a, 42b, and 44 are respectively supplied.
and an amplifier connected to the output terminal of each PID. Radial direction electromagnets 24a, 24b, 26a, 26b and axial direction electromagnets 32a, 32b, 34a, 34b are connected to each amplifier.

These radial direction electromagnets 24a, 24b
, 26a, 26b include position sensors 40a, 40b,
A controlled excitation current is supplied through an amplifier based on the value of the detection signal from 42a, 42b. This allows the rotor shaft 22 to be held at a predetermined position in the radial direction. Additionally, a PID (correction circuit) to which a detection signal from the position sensor 44 is supplied, and a PID
It has an amplifier connected to the output terminal of the This amplifier includes axial direction electromagnets 32a, 32b, 34a,
34b is connected. These axial direction electromagnets 32a, 32b, 34a, 34b have position sensors 44
Based on the value of the detection signal, a controlled excitation current is supplied through the amplifier, thereby holding the rotor shaft 22 at a predetermined position in the axial direction.

At this time, the magnetic bearing controller 72 works in conjunction with the main controller 70 according to instructions from the operation panel 78, and performs minute displacement control after precision grinding of the workpiece W in units of 0.1 μm, as will be explained in detail later. Make small incisions. Next, the operation of cutting the workpiece in the above configuration will be explained. Figure 2 shows the cutting state of the workpiece,
FIG. 3 shows a flowchart of the control operation.

The workpiece W is set on the main spindle 60 and the grinding operation is started. The main controller 70 instructs the magnetic bearing controller 72 to operate the magnetic bearing spindle 10 in a predetermined manner. From the magnetic bearing controller 72, radial direction electromagnets 24a, 2
4b, 26a, 26b and axial direction electromagnet 32a
, 32b, 34a, and 34b, and the rotor shaft 22 is magnetically levitated. At the same time, the motor 36 is energized from the motor driver 80, and the rotor shaft 22 rotates (
Step (S) 100).

Next, it is determined whether or not the start of grinding has been instructed from the operation panel 78. If the instruction is Yes, proceed to the next step. If there is no instruction (No), an instruction to start grinding is awaited, and this decision is repeated. Next, an instruction to drive the servo motor 50 is given to the whetstone table servo motor driver 76, and the whetstone table 12 rapidly moves forward in the arrow direction driver 76
Control is performed to stop the operation of the servo motor 50 (S102).

Subsequently, rough grinding (B) shown in FIG. 2 is performed. An instruction to drive the servo motor 50 is given to the grindstone table servo motor driver 76, and the grindstone table 12 further advances in the arrow direction Xb to perform rough grinding (B) shown in FIG. 2. A predetermined dimensional change amount of this rough grinding (B) is detected by a sizing detector 64. The main controller 70 receives this detection signal through the dimension detection circuit 74, and controls the operation of the servo motor 50 to be stopped through the grindstone table servo motor driver 76 (S103).

Furthermore, it is determined whether the rough grinding (B) has been completed. If Yes, the process is completed, proceed to the next step. If there is no instruction (No), the process waits for the rough grinding (B) to be completed, and this decision is repeated (S104). Next, fine grinding (
C) is performed (S105). In this fine grinding (C), the main controller 70 instructs the servo motor 50 to rotate at low speed through the grindstone table servo motor driver 76, and the grinding wheel is rotated so that the predetermined dimensional change amount of the fine grinding (C) shown in FIG. The base table 12 moves. Note that the amount of dimensional change is determined in the same manner as in the rough grinding (B).

Furthermore, it is determined whether fine grinding (C) has been completed. If Yes, it is assumed that the process has ended, then proceed to the next step. If there is no instruction (No), the process waits for the fine grinding (C) to be completed, and this decision is repeated (S106). After this fine grinding (C), the main controller 70 drives the servo motor 50 through the grindstone table servo motor driver 76.
is instructed to stop moving, which causes the grindstone table 1 to stop moving.
2 stops moving (S107).

[0022] Thereafter, the rotor shaft 22 of the magnetic bearing spindle 10 is controlled to be slightly displaced to make a minute cut in units of 0.1 μm. First, the rotor shaft 22 is moved from the main controller 70 to the magnetic bearing controller 72 in the direction of the arrow Xb, that is, in the direction of the workpiece W, by a predetermined dimensional change amount of the minute cut (M) shown in FIG. 2, that is, 0.1μ.
An instruction is given to move in m units. As a result, the magnetic bearing controller 72 sends a displacement command (ramp wave) of a value corresponding to a predetermined dimensional change amount of the minute cut (M) to the radial direction electromagnets 24a, 24b, 26a, 26b.
The rotor shaft 22 is minutely displaced in the direction of the arrow Xb in units of 0.1 μm (S108). In this case, the grindstone table 12 is stopped (T) as shown in FIG.
It's inside.

Next, it is determined whether or not the minute incision (M) has been completed. If Yes, it is assumed that the process has ended, then proceed to the next step. If there is no instruction (No), the process waits for the minute cut (M) to end, and this decision is repeated (S109). Then, after the minute cut (M) is completed, the main controller 70 instructs the magnetic bearing controller 72 to
Radial direction electromagnets 24a, 24b, 26a, 26b
Stop supplying displacement commands (ramp waves) to (S110
).

Subsequently, the main controller 70 issues an instruction to the magnetic bearing controller 72 to cancel the minute displacement of the rotor shaft 22 . This allows the magnetic bearing controller 72 to control the radial direction electromagnets 24a, 24b, 26a.
, 26b are supplied with a normal value of excitation current, and the rotor shaft 2
2 is displaced in the arrow direction Xa and returns to the normal position (S111). After this, it becomes a retreat (R).

[0025] As described above, the rotor shaft 22 of the magnetic bearing spindle 10 has a fast response to displacement control and good followability, so by utilizing these characteristics, the rotor shaft 22 can be minutely displaced after fine grinding (C). can be controlled. This makes it possible to make minute cuts (M) in units of 0.1 μm, which enables high-precision grinding of the workpiece W, that is,
It is possible to improve machined surface roughness, dimensional accuracy, and roundness.

In the above embodiment, after fine grinding (C), minute cuts (M) were made by controlling the rotor shaft 22, but the present invention is not limited to this. For example, after either rapid grinding (A) or rough grinding (B), or after rapid grinding (A)
, the fine cutting (M) may be performed after each of the rough grinding (B) and the fine grinding (C). moreover,
In the above embodiment, the grindstone table 12 is moved in the direction of the workpiece W, but the grindstone table 12 may be fixed and the headstock table 14 may be moved, or both may be moved. Also good.

Furthermore, it is also possible to switch between rough grinding, fine grinding, etc. using the grindstone table coordinates without using a sizing device. Moreover, not only plunge grinding but also traverse grinding may be used.

[0028]

[Effects of the Invention] As is clear from the above description, the present invention has the following features:
After a predetermined grinding of the workpiece, for example, after precision grinding, the rotor shaft of the magnetic bearing spindle is controlled to perform minute displacement to perform a minute cut in submicron units, so that the workpiece can be ground with high precision. That is, it has the effect of improving machined surface roughness, dimensional accuracy, and roundness.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a grinding machine equipped with a magnetic bearing spindle according to the present invention.

FIG. 2 is a diagram showing a cutting state of a workpiece for explaining the operation of the embodiment.

FIG. 3 is a flowchart of control operations in the embodiment.

FIG. 4 is a diagram showing the cutting state in conventional workpiece grinding.

[Explanation of symbols]

10 Magnetic bearing spindle 12 Grinding head table 14 Headstock table 16 Control unit 22 Rotor shafts 24a, 24b, 26a, 26b Radial direction electromagnet 25 Grinding wheels 32a, 32b, 34a, 34b Axial direction electromagnet 40a, 40b, 42a, 42b, 44 Position sensor 70 Main controller 72 Magnetic bearing controller W Work

Claims (1)

[Claims] Claim 1: A magnetic bearing spindle having a grinding wheel fixed to a rotor shaft and equipped with an electromagnet for magnetic levitation, a grindstone table on which the magnetic bearing spindle is arranged, a spindle for holding a workpiece, and a headstock table on which the spindle is arranged. and,
Either the above grindstone table or the above headstock table,
Alternatively, after both have moved and the rotor shaft of the magnetic bearing spindle has been rotated to complete the specified grinding of the workpiece with the grindstone, the excitation current of the magnetic levitation electromagnet of the magnetic bearing spindle is controlled in order to make even finer cuts. A grinding machine equipped with a magnetic bearing spindle, comprising: control means for displacing the rotor shaft in the cutting direction.