Abrading – Precision device or process - or with condition responsive... – With indicating
Reexamination Certificate
2002-04-04
2003-01-28
Morgan, Eileen P. (Department: 3725)
Abrading
Precision device or process - or with condition responsive...
With indicating
C451S011000, C451S049000, C451S251000
Reexamination Certificate
active
06511364
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and an apparatus for grinding eccentric cylindrical portions of a workpiece such as crankpins on a crankshaft, and more particularly to a method and apparatus for grinding an eccentric cylindrical portion while rotating the workpiece around its central axis to effect a planetary motion of the eccentric cylindrical portion.
2. Description of the Prior Art
In a conventional process of grinding eccentric cylindrical portions such as crankpins of a crankshaft used in an internal combustion engine or a compressor, a crankshaft workpiece is rotated around the workpiece spindle axis of a grinding machine to effect a planetary motion of the crankpin portion, and at the same time, a grinding wheel is infed against the crankpin portion while it is reciprocated toward and away from the spindle axis in synchronism with the planetary motion. The feature of grinding operation of this type resides in that there is no need of providing various kinds of dedicated chucks for the respective individual shapes of the crankshafts, as the crankshaft workpiece is rotated around its central (principal) axis. This provides versatile machining process using a general-purpose machine tool. More specifically, in the grinding machine, parameters for controlling the grinding machine in accordance with various different types of crankshafts are registered (or stored) beforehand, so that the machine is flexibly adaptable to the manufacturing of various different types of crankshafts.
An example of such a type of conventional method and apparatus in the art is disclosed in unexamined Japanese patent publication No. 2000-218531. In this technology, a crankpin of a trial workpiece is first ground based on the theoretical grinding parameters (data), and the diameter of the crankpin thus ground is measured by means of a measuring device equipped on the machine. Then, the measured diameter is employed to prepare modified parameters for the rough grinding step, the finish grinding step and so forth by compensating for the errors or differences in diameter involved in the theoretical parameters for the rough grinding step, the finish grinding step and so forth, and thereafter crankpins of workpieces to be produced are ground based on the thus modified parameters. The measuring device used in such a conventional machine is of the type that measures the radius of the crankpin for the diameter thereof. More specifically, a V-block provided at the tip of the measuring device contacts the crankpin with a probe provided projectably at the bottom of the V-cut touching the crankpin surface continually, and then the amount of the probe advance is detected electrically to compute the diameter. Such a measuring device is capable of measuring the diameter during the grinding process, but requires a link mechanism for making the V-block of the measuring head move horizontally and vertically in synchronism with the planetary motion of the crankpin. From the measured crankpin diameter, the measuring device of this type judges the respective timings of switching the grinding operations between two continuous steps among a plurality of grinding steps including a rough grinding step, a fine grinding step, a finish grinding step and so forth and feeds back the judgments to the control unit of the machine in order to properly change the speed of infeeding the grinding wheel against the workpiece.
However, the measuring device as described above uses a V-block for the measuring head which is designed to measure the radius of the workpiece, and therefore, cannot measure the diameter directly with a high accuracy. In addition, the device has such another drawback that it becomes expensive due to the use of a dedicated unit including a link mechanism which permits the reciprocal movement of the measuring head in synchronism with the planetary motion of the crankpin.
SUMMARY OF THE INVENTION
It is therefore a primary object of the present invention to provide a novel method and apparatus capable of grinding an eccentric cylindrical portion of a workpiece with a high accuracy in the dimension of diameter by the use of a general-purpose measuring device which is not only inexpensive to make, but also capable of directly measuring the diameter of the eccentric cylindrical portion on the workpiece with a high accuracy.
According to the present invention, the object is accomplished by providing a method of grinding an eccentric cylindrical portion of a workpiece on a grinding machine with a measuring device, which method comprises the steps of rotating the workpiece around a work spindle axis of the grinding machine, the eccentric cylindrical portion being eccentric away from the work spindle axis to effect a planetary motion when the workpiece is rotated around the work spindle axis; infeeding a grinding wheel toward the work spindle axis while reciprocating the grinding wheel toward and away from the work spindle axis in synchronism with the planetary motion for grinding the eccentric cylindrical portion into a cylindrical profile; indexing the eccentric cylindrical portion to a predetermined angular position upon completion of a part of the grinding operation; moving a diameter measuring device from a rest position to a measuring position to engage the eccentric cylindrical portion held at the predetermined angular position; measuring the diameter of the eccentric cylindrical portion; retracting the diameter measuring device to the rest position; and resuming the feeding of said grinding wheel toward said work spindle axis while reciprocating said grinding wheel toward and away from said work spindle axis in synchronism with said planetary motion, for performing the remaining part of said grinding operation. With this feature of the method according to the present invention, the diameter measurement of the eccentric cylindrical portion is carried out with the eccentric cylindrical portion being held at the predetermined angular position wherein the measuring device is advanced to the standstill object so as to measure the diameter. Therefore, the measurement with a high accuracy can be realized using a simple and thus inexpensive general-purpose measurement device.
According to the present invention, the object is further accomplished by providing a method of the character set forth above wherein the diameter measured upon completion of a part of the grinding operation is compared with a target diameter to obtain the difference in diameter and wherein the eccentric cylindrical portion is further ground by the difference in diameter. With this feature of the method according to the present invention, the further or finish grinding is conducted based on the diameter difference between the measured value and the target value, whereby the workpiece can be finished with a high accuracy.
According to the present invention, the object is also accomplished by providing an apparatus for grinding an eccentric cylindrical portion of a workpiece, comprising: a workpiece rotating device including a workpiece spindle having a work spindle axis for rotating the workpiece around the work spindle axis, the eccentric cylindrical portion being eccentric away from the work spindle axis for effecting a planetary motion when the workpiece is rotated around the work spindle axis; a grinding wheel movable toward the work spindle axis while being reciprocated toward and away from the work spindle axis in synchronism with the planetary motion, for grinding the eccentric cylindrical portion into a cylindrical profile; an indexing device associated with the workpiece rotating device for indexing the eccentric cylindrical portion to a predetermined angular position upon completion of a part of the grinding; and a diameter measuring device movable from a rest position to a measuring position and having a pair of feelers which are engageable with the eccentric cylindrical portion at diametrically opposite surfaces thereof for measuring the diameter of the eccentric cylindrical p
Ido Masahiro
Okada Kikutoshi
Morgan Eileen P.
Toyoda Koki Kabushiki Kaisha
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