1. Field of Invention
The present invention relates to a roller-burnishing tool to process an inner surface of a work hole, and more particularly to a roller-burnishing tool to finish inner holes of small parts in the wide range of fields such as automobile, home electronic appliance, semiconductor and so forth by a rolling compaction of multiple rollers.
2. Prior Art
A roller-burnishing tool, for example, such as the like indicated in Japanese Utility Model Publication No. 64-275 is common. FIG. 1A and FIG. 1B illustrate this kind of roller-burnishing tool 111. The multiple rollers 113,113 to carry out a rolling compaction processing of an inner work hole W1 of a work W are engaged in a tip of an outer circumference of the cylindrical frame 112 with universal function for rising and setting and rotating, and the mandrel 114 formed as transmitting a rotary driving force is imbedded in said frame 112 with rotary supporting of these rollers 113 from the center axis of the frame 112. This structure imparts a rotary driving to this mandrel 114 through the shank 115 by a driving machine such as a machine tool, a rotary drill and so forth.
In said roller burnishing tool 111, when the diameter (hereinafter called tool diameter) of the enveloping circle of multiple rollers 113,113 for the internal diameter of the work hole W1 is adjusted, the mandrel 114 is moved by screwing forward or backward along screw hole 117 processed on the rear of the housing parts 116 connected with an outer diameter of said frame 112, and the degree of rising and setting of each of rollers 113 for the outer circumference of frame 112 is adjusted by changing the position of contact of the taper shaped mandrel 114 with each roller 113.
In this way, however, the structure for positioning the mechanism outside frame 112 to adjust a tool diameter is not applicable for effective downsizing and lightening since the compression and downsizing of tool length has an automatic limitation.
Accordingly, in this kind of roller-burnishing tool, the protruding length of a tip side of the frame 112 and the housing part 116 is automatically longer than the shank 115, so the usage for installing in a miniature type of machining center and NC lathe and so forth is not feasible.
In addition, the method of driving rollers 113, 113 by transmitting the rotary driving of the mandrel 114 can not obtain a floating function even though a clearance in the radial direction is set between the mandrel 114 and the frame 112.
Hence, this can not be sufficiently applicable for an eccentricity of a work hole. In addition, the improvement of an efficient rapid rotation is difficult since the tool rigidity is low due to the structure of imparting a rotary drive to a detailed mandrel 114 positioned along an axis of the frame 112.
Moreover, when tweaking a tool diameter, the position of the rollers 113,113 is also moved due to the structure of adjusting a tool diameter by moving the frame 112 in an axial direction. Whenever this is done, a readjustment of stroke in the driving machine is indispensable which has been a shortcoming. The purpose of the present invention is to solve these shortcomings.
The present invention provides a roller-burnishing tool, which includes a cylindrical frame for a rolling compaction processing. The frame is coaxially connected with a cylindrical shank portion, which mounts to a rotary driving machine. The multiple rollers for rolling compaction processing are formed in a radial direction along this frame with universal function for rising and setting, and the grooves to engage said rollers are formed in circular direction at regular intervals along this frame with universal function for rotation. The rollers engage said grooves. The multiple rollers contact the taper shaped mandrel which provides support for rotation. The mandrel is fitted into said shank portion and frame with universal function for rotation. An adjustable mechanism is provided to adjust tool diameter by moving mandrel position in an axial direction relative to said frame an elastic mechanism in said shank portion to stimulate said mandrel from the shank portion side toward the frame side.
Another embodiment of the roller-burnishing tool provides, when reversing the rotation of said frame from a processing direction, to allow a tip of said mandrel to move from said frame side to said shank side, a feed angle is provided in both said grooves of said frame and the rotation axis of said rollers engaged in said grooves.
Still another embodiment of the roller-burnishing tool provides clearance between an outer circumference of said mandrel and an inner surface of said frame to allow this mandrel to float.
In the first embodiment, when inserting said frame into the work holes with normal rotation drive, each roller contacts with a tip taper shaped mandrel and begins to revolve by relative friction force generated in between. Each roller dependently rotates in accordance with the rotation of the frame since the mandrel is free from a rotary direction by being supported in a freely rotatable condition. The rolling compaction force of a roller for an inner work hole depends upon the gap between tool diameter and diameter of the work hole. As a result of driving the frame, the rollers perform a rapid feeding processing by the principle of planetary motion compared with the structure of driving a conventional mandrel. As a result of coaxially positioning the mandrel along the center axis of the frame improves rotational accuracy which leads to a capability for a rapid rotation, and moreover, coaxially connecting the frame with the shank portion of the rotary drive improves rotational accuracy which allows the rollers to perform rapid rotation with high accuracy. Hence, efficiency is significantly improved compared with a conventional one.
With respect to the second embodiment, when reversing the rotation of said frame, a retreat force is generated in the mandrel by the agency of a feed angle., the tool diameter is shrunk when this retreat force exceeds the impetus force of said elastic mechanism. Accordingly, by reversing the rotation of the frame, it becomes possible to easily withdraw the frame from a work hole. The feed angle is provided in each groove for engaging rollers. Imparting normal rotary motion to the frame keeps the tool diameter to an initial set value. When retreating, reversing the rotation of the frame causes the taper shaped mandrel to move backward to the shank portion and each roller moves inwardly in a radial direction. Hence, tool diameter is shrunken, and quick withdrawing becomes practical. When the frame is withdrawn from inside a work, the tool diameter returns to an initial state by accumulated impetus of the elastic mechanism imbedded in the shank portion.
Moreover, with respect to the third embodiment, since the mandrel is floating in a radial direction due to the clearance between inner surface of the frame and the mandrel, processing accuracy is sustainable even under the condition of establishing a tool diameter on the position slightly slipped from the center of the work hole.