JPH0512103B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <<Industrial Application Field>> The present invention relates to a dressing control device for a grindstone, and particularly to one suitable for dressing a so-called new wheel when replacing a grindstone.

<<Prior Art>> Traditionally, truing and dressing of a grindstone has been carried out using a dresser equipped with, for example, a diamond tool on the grindstone which is provided at the tip of a grindstone shaft of a spindle and is driven to rotate.

This dressing is also performed when replacing the grindstone. This is because the grinding wheel (new wheel) attached to the rotor shaft rotates eccentrically and there is so-called runout, so it is necessary to remove this runout and adjust the shape. The total dressing depth at this time is controlled so that the dresser, the spindle, or both are moved to make a predetermined dressing depth so as not to cause insufficient dressing.

In addition, in recent years, as grinding has become more precise, grinding wheels have been rotated at ultra-high speeds, and for this reason magnetic bearing type spindles, in which the rotor shaft of the spindle is supported by electromagnets, are being used. It is becoming easier to do so.

<<Problems to be Solved by the Invention>> However, in the above-mentioned conventional dressing control device, the new foil dressing control is performed in a uniform manner so as to achieve at least a predetermined dressing depth that does not cause insufficient dressing. Therefore, depending on the grinding wheel, excessive dressing may be performed. Moreover, in this case, there are disadvantages in that the excessive dressing causes the wear of the dresser to progress more than necessary and the dressing time becomes longer.

The present invention has been made in view of the above-mentioned problems, and consists of a spindle having a grindstone for dressing at the tip of a rotor shaft that is floated and held by the magnetic force of an electromagnet and driven to rotate; a dresser for dressing the spindle or the dresser, a movement mechanism for moving the spindle or the dresser, or both, and controlling the excitation current of the electromagnet to keep the rotor shaft floating at a target position;
A dressing control device comprising a control means for moving the moving mechanism to control a dressing depth of cut and a dressing feed speed, and dressing the grindstone by a predetermined amount by gradually bringing the grindstone and dresser closer together, the control means comprising: detects that the grinding wheel and the dresser have started contact due to the movement of the moving mechanism from a change in voltage proportional to the excitation current of the electromagnet, and a calculated value calculated from the detected value reaches a predetermined value. The present invention is characterized in that a dressing controller is provided which determines that the new wheel dressing of the grindstone is completed when the grinding wheel is completely dressed.

<<Operation>> In the present invention, the contact state between the grinding wheel and the dresser is detected from a calculated value calculated by a change in voltage proportional to the excitation current (control current) of the electromagnet, and when the calculated value reaches a predetermined value, It acts so that the new wheel dress completion of the grinding wheel is determined.

<<Example>> The present invention will be described below based on the illustrated example.

FIG. 1 is a block diagram showing a schematic configuration of a dressing control device according to the present invention, which is composed of a spindle a, a headstock table b, a grindstone table c, and a control means d.

In the spindle a, radial electromagnets 2a, 2b, 2c and 2 are installed on the left and right end sides of the rotor shaft 1.
d, by which the rotor shaft 1 is supported in the radial direction, and axial electromagnets are provided on both sides of the disk 3, which is provided integrally with the rotor shaft 1 at the center of the rotor shaft 1. 4a, 4b, 4c and 4d are provided, and the rotor shaft 1 is supported in the axial direction by these.

The floating position control of the rotor shaft 1 by each of the electromagnets described above is carried out by radial direction position sensors 5, 6, 7, 8 provided on the left and right ends of the rotor shaft 1, and
The position of the rotor shaft 1 is detected by the axial position sensor 9 provided at one end, and this detection signal is processed by the control means d, and each electromagnet is activated so that the rotor shaft 1 is floated and held at a reference target position. This is done by adjusting the excitation current.

In the figure, reference numeral 10 denotes a dressing grindstone (new wheel) detachably provided at the other end of the rotor shaft 1, and is configured to rotate as the rotor shaft 1 rotates. That is, when a drive current is supplied from the control means d to the motor 11 provided approximately at the center of the rotor shaft 1, the rotor shaft 1 acts as a rotor of the motor and rotates, thereby causing the grinding wheel 10 to move at an ultra-high speed. be rotated.

The spindle a is configured to be movable in the axial direction of the rotor shaft 1 (in the direction of arrow Z in the drawing) by a grindstone shaft table c. In other words, the grindstone shaft table c on which the spindle a is placed is connected to the servo motor 1.
3 and the ball screw 1 rotated thereby
It is configured so that it can be moved by 4.

Diamond dresser 1 is installed on the headstock table b.
A dresser head 16 with 5 is mounted. This headstock table b is configured to be movable by a moving mechanism similar to that of the spindle a. That is, it is configured to be movable in a direction perpendicular to the axial direction of the rotor shaft 1 (direction of arrow X in the drawing) by a servo motor 17 and a ball screw 18 rotated thereby.

Therefore, the headstock table b, the grindstone table c
The contact position between the grindstone 10 and the diamond dresser 15 is adjusted by the movement of the diamond dresser 15, and the dressing depth and dressing feed rate are determined.

The control means d collectively controls the magnetic bearing controller e for floating and holding the rotor shaft 1 at a predetermined target position, the dressing controller f for determining whether the new wheel dressing of the grindstone 10 is completed, and the controllers e and f. main controller g
Each controller is assembled.

Of these, the magnetic bearing controller e includes a position detection circuit 20 that detects the floating position of the rotor shaft 1 by processing detection signals from each position sensor 5 to 9 using a bridge circuit or other processing circuit; A processing circuit 21 that compares the detection signal from the reference target position with a reference target position and adjusts the excitation current of each electromagnet 2a to 2d, 4a to 4d so as to compensate for the difference in the target position; The electromagnet driver 22 supplies excitation current to each electromagnet 2a to 2d and 4a to 4d using an output signal.

The dressing controller f is a characteristic component of the present invention, and is an electromagnet of any one of the electromagnet drivers 22 (electromagnet 2a here).
an integrating circuit 30 that integrates a voltage value proportional to the excitation current (control current) value; a peak hold circuit 31 that holds the peak value of the voltage that is proportional to the excitation current value; The width l of the grinding wheel 10 (the grinding wheel width in the direction of the arrow Z in the drawing) is determined by the dressing feed rate V _D (the width of the grinding wheel in the direction of the arrow Z in the drawing).
A first multiplier circuit 32 that multiplies the dressing time Δt, which is a value divided by the feed speed in the direction), and a predetermined constant K (0.9 in the figure)
a second multiplication circuit 33 that multiplies the output value of the integration circuit 30; a comparator 34 that compares the output value of the integration circuit 30 with the output value of the second multiplication circuit 33;
A counter 35 counts the number of outputs from the comparator 34 when the output value is greater than or equal to the output value of the multiplication circuit 33.

The main controller g has a built-in programmable controller, and controls both controllers e and f, as well as an inverter 41 for supplying drive current to the motor 11, and for moving the grindstone table c and the headstock table b. The controller is configured to control servo motor drivers 42 and 43 that drive servo motors 13 and 17, respectively.

The operation of this embodiment having the above configuration will be explained with reference to the second control current proportional voltage state diagram and the flowchart of the control operation shown in FIG.

Now, a new wheel (grinding wheel 10) is set on the rotor shaft 1, and a magnetic bearing drive command is issued from the main controller g to the magnetic bearing controller e. As a result, excitation current is supplied to each electromagnet 2a to 2d, 4a to 4d, and the rotor is rotated. While the shaft 1 is held floating at a predetermined target position, a motor drive command is issued to the inverter 41, an excitation current is supplied to the coil of the motor 11, and the rotor shaft 1 is rotationally driven (step 100).

Furthermore, the main controller g also issues a drive command to the dressing controller f, which is given a dressing time _Δt and a constant K ( 0.9) is set (step 101).

Next, the counter value N of the counter 35 is reset and returned to 0 (step
102), the diamond dresser 15 starts moving toward the grindstone 10 (step 103). That is, from the main controller g to the servo motor driver 4
A drive command is given to servo motor 2, which causes the servo motor 17 to rotate and move the headstock table b in one direction (downward in the drawing) in the direction of arrow X. Furthermore, the servo motor 13 rotates in response to a drive command to the servo motor driver 43, and the grindstone shaft table c moves in the Z-axis direction, thereby moving the grindstone 10 and the diamond dresser 1.
5, but since the grindstone 10 is in a swinging state at the beginning of the movement, the contact occurs intermittently.
Since a load is applied to the rotor shaft 1 at the time of this contact, a change occurs in the excitation current, that is, the control current, of each electromagnet that keeps it floating. As shown in FIG. 2, this state of change appears as a tendency that the contact ratio is small at the beginning of movement, so the change is small, and gradually increases.

By the way, a voltage proportional to the control current of the electromagnet 2a is applied to the integrating circuit 30 and the peak hold circuit 31.
Since the integration circuit 30 outputs the integrated value E (corresponding to the area of E in Figure 2) obtained by integrating the voltage V proportional to the control current over ΔT, the integration circuit 30 also outputs the output value of the integral value E (corresponding to the area of E in Figure 2). The circuit 31 outputs the value of _MAX at the time of the change (step 104).

The first multiplication circuit 32 multiplies the V _MAX by ΔT to calculate a virtual integral value E _D (see FIG. 2).
However, as shown in FIG. 2, since the rotor shaft 1 is rotating, the upper end of the voltage V proportional to the control current does not appear flat but somewhat undulating. Therefore, a predetermined _constant K (here,
0.9) in the second multiplier circuit 33 and outputs the E _DI (step 106).

Then, the comparator 34 compares the reference output value E from the integrating circuit 30 and the output value _EDI output from the second multiplier circuit 33. In this comparison, when the output value E is greater than or equal to E _DI (step 108 affirmative), an output signal is sent from the comparator 34 to the counter 35, and the count of the counter 35 is incremented by 1 each time it is sent (step 108 is affirmative).
110).

When the output value E is less than E _DI (step 108 negative),
Returning to step 102, the counter value N is reset to zero.

When the count of the counter 35 becomes 3 or more (Yes at step 112), a signal is output from the counter 35 to the main controller g, and the main controller g stops driving the servo motor drivers 42 and 43, thereby driving the servo motors 17 and 1.
3 is stopped and the new foil dressing is completed.

The reason why the counter value was set to 3 in step 112 above is as follows.
This is a value obtained from an experimental result that when E exceeds 3 times or more from the output value E _DI , eccentricity (runout) of the new wheel can be removed 100%. Therefore, it is at least good if the value is larger than this value, but if it is larger, the amount of dressing increases, which is not preferable, and if it is 1, for example, eccentricity may remain, which is not preferable.

As described above, in this embodiment, the rotor shaft 1
From the change in voltage proportional to the control current of the magnetic bearing electromagnet, the diamond dresser 15 and the grinding wheel 10
Since the new foil dressing is determined to be completed by detecting the contact ratio with the new foil, it is possible to minimize the amount of dressing cutting to remove the runout of the new foil.

Therefore, unnecessary dressing of the grindstone can be prevented, wear of the dresser can also be prevented, and the dressing time can be shortened.

In the above-described embodiment, a voltage proportional to the control current of the electromagnet 2a is detected, but it goes without saying that a voltage of another electromagnet may be used.

<<Effects>> As described above, the present invention detects the contact ratio between the dresser and the grindstone from the change in the voltage proportional to the control current of the electromagnet for the magnetic bearing of the rotor shaft, and determines the total cutting depth for dressing. With this structure, the total amount of dressing cutting to eliminate runout of the new foil can be minimized.

Therefore, unnecessary dressing of the grindstone is prevented, wear of the dresser is also prevented, the life of the dresser is extended, and the dressing time is shortened.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the schematic configuration of the device of the present invention, FIG. 2 is a control current proportional voltage state diagram, and FIG.
The figure is a flowchart of control operation. 1... Rotor shaft, 2a to 2d, 4a to 4d...
Electromagnet, 5 to 9... Position sensor, 10... Grinding wheel (new wheel), 13, 17... Servo motor,
14, 18...ball screw, 15...diamond dresser, 16...dresser head, a...spindle, b...headstock table, c...grinding wheel table, d...control means, e...magnetic bearing controller , f...dressing controller, g
...Main controller.

Claims (1)

[Scope of Claims] 1. A spindle having a grindstone for dressing at the tip of a rotor shaft which is held floating and rotationally driven by the magnetic force of an electromagnet, a dresser for dressing the grindstone, and the spindle or the dresser, or these. a moving mechanism that moves both;
a control means for adjusting the excitation current of the electromagnet to control the floating and holding of the rotor shaft at a target position, and for controlling the dressing depth of cut and dressing feed rate by moving the moving mechanism, In the dressing control device for dressing a grinding wheel by a predetermined amount by gradually approaching the grinding wheel, the control means is provided with a voltage proportional to the excitation current of the electromagnet to indicate that contact between the grinding wheel and the dresser has started due to movement of the moving mechanism. A dressing control device comprising a dressing controller that detects a change in the grinding wheel and determines that the new wheel dressing of the grindstone is completed when a calculated value calculated from the detected value reaches a predetermined value. .