Data processing: measuring – calibrating – or testing – Calibration or correction system – Position measurement
Reexamination Certificate
2001-01-16
2003-02-25
Hilten, John S. (Department: 2863)
Data processing: measuring, calibrating, or testing
Calibration or correction system
Position measurement
C702S151000, C702S167000
Reexamination Certificate
active
06526364
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to an apparatus for measuring roundness of a work. More particularly, it relates to an apparatus for measuring roundness and method of centering and leveling, which has improved precision and operability in compensation of an eccentricity (centering) and tilt (leveling) of the work.
2. Description of the Related Art
A roundness measuring apparatus is employed to measure a roundness of a cylindrical or tubular work. The work is mounted on a table to trace a circumferential surface (an inner or outer surface) of the work by a detector while the table or the detector itself is rotated around the work. The detector has a mechanical measurement range (stroke) of about 1 mm in common, and an electrical measurement range that decreases as a sensitivity (magnification) is increased. This depends mainly on a constraint from a performance of an AID converter (bit width). If the center of the work is deviated from the rotational center of the table or of the detector at the time of measurement, the detector is required to have a much larger stroke (at least double the eccentricity). This leads the detector to an immeasurable situation in over-stroke, otherwise the sensitivity can not be increased due to the above-mentioned reason. Accordingly, a precise centering is required essentially to perform a high sensitive measurement. Further, when the roundness is measured at a plurality of locations along the height of the work, a tilt of the axial center of the work also causes an eccentricity similar to the above and thus it requires leveling as well.
From the above reasons, the table for receiving the work mounted thereon is provided with mechanisms for centering and leveling (Japanese Patent Nos. 2,569,390 and 2,628,122, for example). The centering mechanism comprises mechanisms for moving the table in X- and Y-axes both perpendicular to the axial center of the work (the vertical axis=Z-axis). These centering axes are hereinafter referred to as CX- and CY-axes. The leveling mechanism comprises mechanisms for positioning the table on a spherical base and pushing the table in X- and Y-axes to slide it along the spherical base. These leveling axes are hereinafter referred to as LX- and LY-axes.
On centering and leveling, the work is first mounted on the table and the detector traces the circumference of the work to position the work at a location inside the stroke of the detector. A height of the detector at this situation is referred to as ZA. A measurement is performed in this situation to collect data, from which a set of central coordinates of the work at the height ZA is derived. Next, the detector is positioned at a height of ZB and another measurement is performed similarly to collect data, from which another set of central coordinates of the work at the height ZB is derived. From these sets of central coordinates of the work at the heights ZA and ZB, an amount of centering (an amount of eccentric compensation) and an amount of leveling (an amount of tilt compensation) of the work in the X- and Y-axes are computed and displayed. The centering and leveling mechanisms comprise micrometer heads. Therefore, these mechanisms can be manipulated manually, on the basis of the amounts of compensation thus displayed, to perform centering and leveling while reading displays on the micrometer heads.
SUMMARY OF THE INVENTION
The present invention has an object to provide an apparatus for measuring roundness, which can afford much simplified workability and improved precision to centering and leveling.
The present invention has another object to provide an apparatus for measuring roundness and method of centering and leveling, which can perform precise centering and leveling, thereby reducing a period of time required for setup activities.
The present invention is provided with an apparatus for measuring roundness, which comprises: a table for receiving a work mounted thereon, the work having a circumferential surface with a roundness to be measured; displacement detecting means for detecting displacements on the circumferential surface of the work; rotational driving means for rotationally driving either the table or the displacement detecting means such that the displacement detecting means detects the displacements along the circumferential surface of the work; eccentricity adjusting means for adjusting an eccentricity in the work, the eccentricity adjusting means including an eccentricity adjusting motor to move the table in a plane perpendicular to the rotational axis of the rotational driving means; tilt adjusting means for adjusting a tilt of the work to the rotational axis, the tilt adjusting means including a tilt adjusting motor to incline the table; computing means for calculating the eccentricity and tilt of the work from the displacements on the circumferential surface of the work detected by the displacement detecting means; and eccentricity/tilt compensating means for driving the eccentricity adjusting motor and tilt adjusting motor on the basis of the eccentricity and tilt obtained by the computing means to compensate the eccentricity and tilt.
According to the present invention, the eccentricity adjusting motor and tilt adjusting motor are respectively provided in the means for adjusting the eccentricity in the work and means for adjusting the tilt of the work. In addition, the eccentricity/tilt compensating means drives these motors on the basis of the eccentricity and tilt of the work obtained by the computing means to compensate the eccentricity and tilt of the work. This prevents any sophisticated manual operations and matching errors on manual operations from occurring and can improve the operability and matching precision effectively.
The motors may be controlled in open-loop though, preferably, the apparatus may further comprise detecting means for detecting amounts of movements of the table in a plane perpendicular to the rotational axis and in a tilt direction about the rotational axis. In this case, the eccentricity/tilt compensating means drives the eccentricity adjusting motor and tilt adjusting motor using the amounts of movements of the table detected by the detecting means as amounts of feedback. This enables precise operations of centering and leveling to be performed by feedback control.
When the eccentricity and tilt of the work are obtained by the computing means, the following may be effective, for example. Namely, the computing means calculates central coordinates of the work mounted on the table at a plurality of locations along the rotational axis from the displacements on the locations of the circumferential surface of the work, which are measured by the displacement detecting means. Then, it computes the eccentricity and tilt based on the central coordinates.
The eccentricity/tilt compensating means may drive the eccentricity adjusting motor and tilt adjusting motor simultaneously to further reduce a period of compensation time.
The present invention is also provide with an apparatus for measuring roundness, which comprises: a table for receiving a work mounted thereon, the work having a circumferential surface with a roundness to be measured; displacement detecting means for detecting displacements on the circumferential surface of the work; rotational driving means for rotationally driving either the table or the displacement detecting means such that the displacement detecting means detects the displacements along the circumferential surface of the work; eccentricity adjusting means for adjusting an eccentricity in the work, the eccentricity adjusting means including means for detecting an adjusted eccentricity by detecting an amount of movement of the table when it is moved in a plane perpendicular to the rotational axis of the rotational driving means; computing means for calculating an eccentricity in the work from the displacements on the circumferential surface of the work detected by the displacement detecting means; and display means for displaying
Omori Yoshiyuki
Shindo Hideki
Tsuruta Atsushi
Ueno Syuuzou
Watanabe Ryosuke
Hilten John S.
Le John
Mitutoyo Corporation
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