JPH0315051B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic bearing device with variable stiffness. This application includes, for example, grinding spindles for machine tools that use magnetic bearings. By making the rigidity value variable, there is an advantage that a grinding spindle for both rough grinding and fine grinding can be provided.

In recent years, in machine spindles for machine tools,
By additionally equipping with AE sensors, eddy current sensors, etc., grinding or cutting conditions can be monitored, dramatically improving machining efficiency and machining quality. In order to improve machining efficiency and machining quality, it seems common to add a function to constantly monitor and measure the machining process status, and to set machining conditions based on the obtained signals. Since conventional mechanical spindle units do not have the above functions, various sensors, actuators, control logic devices, etc. are newly added. Additional equipment has the drawback of increasing the size of the entire processing machine, making it complex and expensive. In addition, if you are trying to improve machining efficiency or machining quality by monitoring or measuring some kind of substitute characteristic rather than by directly monitoring or measuring the machining process, it is necessary to thoroughly check the correlation between the substitute characteristic and the machining result in advance. There was the inconvenience that it could not be put to practical use unless it was investigated.

The present invention was made to eliminate the above-mentioned drawbacks, and the machining process is directly measured by a displacement sensor built into a magnetic bearing, and the signal can be used to determine whether the grinding state is in the rough grinding or fine grinding range. In the coarse grinding area, the rigidity of the spindle is increased to create a cut into the material to be ground to shorten the grinding time, and in the fine grinding area, the rigidity is lowered to achieve a good finished surface. . FIG. 1 shows an embodiment of the invention. In the figure, 1 is a radial position detection device, 2 is a radial magnetic bearing, 3 is a motor, 4 is an axial magnetic bearing, 5 is an axial position detection device, and 6 is an armature disk attached to a rotating body 6. , 8 is a grindstone attached to the tip of the rotating body 7. The output of the radial position detection device 1 is connected to a position detection circuit 9 to become an electric signal, and the output is connected to a compensation circuit 10.
The signal is subjected to signal processing and drives the electromagnet drive circuit 11 to magnetically support the rotating body 7. Grinding process information can be obtained directly from the output of the position detection circuit 9. That is, the output of the position detection circuit 9 is large at the start of cutting in the grinding process, and the output converges as the grinding process approaches the end. Such an output change is detected by the determination circuit 12, and the gain control circuit 13 is operated to lower the gain of the electromagnet drive circuit 11 at the time when the fine-sharpening state should be entered. That is, the shift is made from a high-rigidity spindle to a low-rigidity spindle by controlling the gain of the controlled magnetic bearing device depending on the grinding process conditions. In the low-rigidity spindle state, grinding is performed along the machined shape of the material to be ground, so only the finished surface precision can be further improved without deteriorating the shape and dimension precision. In order to change the stiffness, the gain of the control system is controlled. For example, in the electromagnet drive circuit 11 shown in FIG. 2, the feedback resistor 14 is a variable resistance element such as an FET, and the gain is controlled. The resistance value may be increased or decreased using the output of the circuit 13.

According to the variable-rigidity magnetic bearing device of the present invention, in addition to the device necessary for magnetic support, a judgment circuit 12 and a gain control circuit 13 are added, thereby improving machining efficiency and machining quality at the same time. It becomes possible to provide a spindle for both fine polishing and polishing. It is easy to imagine that controlling the stiffness value of a mechanical spindle is either impossible or requires an extremely complex mechanical mechanism.

The present invention not only adds the function of a spindle for rough grinding and fine grinding to a grinding spindle for machine tools using magnetic bearings, but also improves the rigidity of general rotating bodies supported by magnetic bearings. By changing the value, it provides an effective means for easily passing the resonance point.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing a variable rigidity magnetic bearing device according to the present invention. FIG. 2 is a circuit diagram showing an embodiment for controlling the gain of the electromagnet drive circuit. DESCRIPTION OF SYMBOLS 1... Radial position detection device, 2... Radial magnetic bearing, 3... Motor, 4... Axial magnetic bearing, 5... Axial position detection device, 6... Armature disk, 7... Rotation Body, 8... Grindstone, 9...
Position detection circuit, 10... Compensation circuit, 11... Electromagnet drive circuit, 12... Judgment circuit, 13... Gain control circuit, 14... Feedback resistor.

Claims (1)

[Claims] 1 At least two radial magnetic bearings that rotatably support a rotating body, at least one axial magnetic bearing that axially supports the rotating body, and a rotating shaft near the radial magnetic bearing. a radial position detection device that detects radial displacement in two perpendicular directions in orthogonal planes; an axial position detection device that detects axial displacement; and an axial position detection device that detects axial displacement; In a controlled magnetic bearing device comprising a control circuit that performs control according to an output signal, the control circuit determines the magnitude of the load applied to the rotating body by monitoring the output signal of each of the position detection devices. A variable-rigidity magnetic bearing device comprising: a determination circuit; and a gain control circuit that changes the rigidity of a magnetic bearing by controlling the gain of an electromagnet drive circuit according to the output of the determination circuit.