A detailed description will be given below of a preferred embodiment according to the present invention in reference to the attached drawings.
In the description below, a left side in reference to
A spindle device is provided with a hollow spindle 11 having an axis in a horizontal direction, a horizontally cylindrical sleeve 12 fitted around the spindle 11, a first bearing 21 and a second bearing 22 which support the spindle 11 on the left side thereof with an axial interval, a third bearing 23 which supports the spindle 11 on the right side thereof, a left housing 24 which surrounds the first bearing 21 and the second bearing 22 and is fixed to an inner surface of the sleeve 12, and a right housing 25 which surrounds the third bearing 23 and is fixed to the inner surface of the sleeve 12.
At an outer surface of the spindle 11 are formed a large-diameter portion 31, a middle-diameter portion 32 and a small-diameter portion 33 in sequence via steps from left to right.
A stator 35 for a motor 34 is secured to the inner surface of the sleeve 12 between the second bearing 22 and the third bearing 23. Furthermore, a rotor 36 for the motor 34 is secured to the outer surface of the spindle 11 in such a manner as to correspond to the stator 35.
At a left end of an inner surface of the left housing 24 is disposed a left inward annular projection 37. In the meantime, at a right end of an inner surface of the right housing 25 is disposed a right inward annular projection 38.
The first to third bearings 21 to 23 have the same structure.
Referring to
A left opening of the sleeve 12 is capped with a left presser cap 51. The left presser cap 51 presses the outer races 41 of the first bearing 21 and the second bearing 22 toward the left inward annular projection 37 together with the outer race inter-seat 45. A left pressing nut 52 is screwed on a right side of the second bearing 22. The left pressing nut 52 presses the inner races 42 of the first bearing 21 and the second bearing 22 against the step of the large-diameter portion 31 and the middle-diameter portion 32 together with the inner race inter-seat 46. A right opening of the sleeve 12 is capped with a right presser cap 53. The right presser cap 53 presses the outer race 41 of the third bearing 23 toward the right inward annular projection 38. A right pressing nut 54 is screwed on a right side of the third bearing 23. The right pressing nut 54 presses the inner race 42 of the third bearing 23 against the step of the middle-diameter portion 32 and the small-diameter portion 33.
Referring to
Returning to
A rotational speed detecting sensor 74 is attached to a side surface of the right presser cap 53 in such a manner as to expose a right side end of the spindle 11. In addition, an acceleration detecting sensor 75 is attached to an intermediate portion in a longitudinal direction of the outer surface of the sleeve 12.
Next, description will be made on an air supplying operation.
First of all, the rotational speed detecting sensor 74 detects the rotational speed of the spindle 11. Incidentally, the rotational speed may be detected by using a spindle control command value. Upon the detection of the rotational speed, an air flow rate is determined in reference to a previously created table, as illustrated in
In order to create the table, the following is taken into consideration. The attitude of the retainer 44 for guiding the outer race 41 is varied due to its own weight since the clearance is defined between the inner circumferential surface of the outer race 41 and the rolling element 43. When the inclination angle of the spindle 11 is, for example, 90°, that is, θ2 or θ4, the center of the rotation of the retainer 44 is moved downward. If the rotation is continued as it is, imbalance occurs, thereby possibly generating an abnormal noise or an abnormal vibration. In order to prevent any occurrence of such abnormality, the air flow rate at each of the positions I to IV is set. The table may be created in consideration of the rotational speed. Alternatively, the table illustrated in
Subsequently, in the case where the vibration generated in the spindle is detected and the air flow rate is set so as to suppress the vibration, a description will be given by way of one example in which the air flow rate at each of the positions I to IV is set by the use of the rotational speed detecting sensor 74 and the acceleration detecting sensor 75.
The acceleration detecting sensor 75 detects the axis of the sleeve 12 and a vertical acceleration. A frequency of a signal obtained from the acceleration detecting sensor 75 is analyzed at real time or a signal is stored in a memory, and then, its frequency is analyzed, so that only a multiple component of a rotational frequency is extracted. Multiple component to be extracted may be arbitrarily determined. The rotational speed detecting sensor 74 gives the rotational frequency component of the spindle 11. In the case where the size of the signal indicating the extracted multiple component is greater than a predetermined threshold as a result of comparison, a phase having a larger vibration in the spindle rotational direction is specified by the rotational speed detecting sensor 74, and then, the flow rate and direction of the air are determined in such a manner as to reduce the vibration of the phase. In the case of the consideration of both of the axis and the horizontal vibration, each of values may be set to become smaller by the use of the biaxial acceleration detecting sensor 75. Furthermore, several kinds of air supplying patterns are prepared in order to reduce the vibration, and then, the flow rate and direction of the air may be determined by testing the patterns in sequence. Alternatively, the air flow rate may be manually regulated in such a manner as to reduce the value of the vibration sensor while monitoring the value of the vibration.
Although the acceleration detecting sensor 75 is used as one example for obtaining the vibration in the present preferred embodiment, a sound pressure sensor and a displacement sensor may be used singly or in combination as unit for detecting information relating to the vibration.
Number | Date | Country | Kind |
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2006-286054 | Oct 2006 | JP | national |