Patent Application
20180345450
This application claims the benefit of priority to Japanese Patent Application No. 2017-108813, filed on May 31, 2017, the entire contents of which are hereby incorporated by reference.
The present invention relates to a burnishing tool for finishing grooves or other surfaces.
A groove for receiving a seal such as an O-ring is typically formed by cutting a cylindrical workpiece using a cutting tool tip designed for O-ring groove machining. Despite the recent demand for higher sealing performance, O-ring grooves finished by such metal cutting can have rough surfaces and have low sealing performance, and may not easily achieve intended surface roughness.
To finish cut groove surfaces as intended and provide higher sealing performance, a burnishing tool for flat surfaces including the bottoms of grooves formed by metal cutting is known (e.g., Japanese Patent No. 5005406, hereafter Patent Literature 1).
The burnishing tool for flat surfaces described in Patent Literature 1 has a flat and circular press portion at the tip of a cylindrical (shaft) mandrel, which is pressed against a machining target surface of a workpiece for burnishing the bottom of a rectangular groove for an O-ring. A machine tool such as a lathe, which uses a selected type of burnishing tool for flat surfaces, presses its press portion against fine irregularities on the surface of a workpiece while rotating. This causes plastic deformation at the surface, which is thus finished into a smooth surface like a mirror surface.
The burnishing tool for machining flat surfaces described in Patent Literature 1 has the flat end face of its press portion in contact with the bottom of an O-ring groove on a workpiece for burnishing. The burnishing tool for machining flat surfaces uses surface contact with the workpiece, and thus applies a large machining load in the large surface contact area.
The burnishing tool for machining flat surfaces operates, with its tip to endure a large load. Unfortunately, the burnishing tool tip for machining flat surfaces described in Patent Literature 1 is difficult to strengthen any further. The tip strength of the tool currently limits its use to workpieces formed from a soft material such as aluminum.
One or more aspects of the present invention are directed to a burnishing tool that uses a relatively small pressing load in burnishing.
A burnishing tool for machining a target surface of a workpiece, the tool comprising:
a base; and
a tip portion located on a distal end of the base, the tip portion including a linear slide-contact portion configured to linearly contact and slide on the target surface.
The burnishing tool according to the above aspects uses a relatively small pressing load in burnishing.
A burnishing tool according to one embodiment will now be described with reference to
A finishing machine (not shown) to which a burnishing tool 1 is attached and a workpiece W will be described first. For ease of explanation, an end where a body 2 is located in
The finishing machine (not shown) is a machine tool that rotates the workpiece W attached to its drive, and aligns and feeds the burnishing tool 1 and the workpiece W. Examples of the finishing machine include a lathe, a milling machine, and a machining center. Burnishing (machining involving plastic deformation) using a lathe as the finishing machine will be described below.
The workpiece W shown in
The target surface Wa may be a bottom We of a groove Wb on an outer circumferential surface Wd of a cylindrical member, or a flat bottom Wj of a groove Wi on an end face We of a cylindrical member shown in
The grooves Wb and Wi shown in
In the example below, burnishing of the workpiece W, or a round rod having the grooves Wb and Wi, which are O-ring grooves or oil seal grooves, will be described.
The burnishing tool 1 is used for burnishing target surfaces by flattening and smoothing them into mirror-finished surfaces. The burnishing tool 1 has the linear slide-contact portion 42a on its tip end 42 (tip portion) pressed against the target surface Wa or Wh (the bottom We of the groove Wb or the bottom Wj of the groove Wi) of the rotating workpiece W (refer to
As shown in
As shown in
The hollow part 2b is a stepped cylindrical space defined inside the shaft body 2a. The hollow part 2b includes the head joint compartment 2c and the urging member compartment 2d. The head joint compartment 2c accommodates the head joint 31 in a retractable manner. The urging member compartment 2d accommodates the urging member 32. The hollow part 2b may have no step, and may be a cylindrical space including the head joint compartment 2c and the urging member compartment 2d both with the same diameter.
The head joint compartment 2c is located on the distal end within the hollow part 2b. The head joint compartment 2c accommodates the head joint 31, which is urged by the urging member 32 toward the distal end with the support pin 33 abutting against an edge of an elliptic hole 31d on the basal end. The head joint 31 is located nearer the distal end by a distance corresponding to a difference between the outside diameter of the support pin 33 and the inside diameter of the elliptic hole 31d along its major axis. The head joint 31 is thus elastically supported on the body 2 in a manner movable toward the basal end.
The urging member compartment 2d accommodates the urging member 32 in an axially movable manner. The urging member compartment 2d is a hole either with the same diameter as or with a smaller diameter than the head joint compartment 2c. The urging member compartment 2d and the head joint compartment 2c may thus be continuous with a step at a basal end of the head joint compartment 2c. The urging member 32 is, for example, a compression coil spring. The urging member compartment 2d can guide the urging member 32 to be axially centered. The inner bottom of the urging member compartment 2d on the basal end functions as a stopper for receiving and stopping the urging member 32.
As shown in
As shown in
The head joint 31 elastically supports a base 41 included in the tip 4 to allow the base 41 to move in the axial direction within a predetermined distance L1 (within a distance corresponding to a difference between the outside diameter of the support pin 33 and the inside diameter of the elliptic hole 31d along its major axis). As shown in
The joint body 31a is defined by the outer circumferential surface of the head joint 31, which is substantially cylindrical and is received in the hollow part 2b in a retractable manner. The joint body 31a has the elliptic hole 31d on its basal end.
The tip receptacle 31b is a blind hole for receiving a connection protrusion 41b of the base 41. The tip receptacle 31b is located at the center of a distal end of the joint body 31a.
The elliptic hole 31d is a through-hole for receiving the support pin 33 in a manner axially movable by the predetermined distance L1. The elliptic hole 31d is formed through the head joint 31 and extends from the upper surface to the lower surface of the head joint 31.
As shown in
The support pin 33 pivotally supports the head joint 31. The support pin 33 is a substantially rod-shaped member extending in the radial direction of the head joint 31 (vertical direction in
The urging member 32 is an elastic member for applying a machining pressure and urging the head joint 31 toward the tip 4. The urging member 32 is a spring for load control, which can adjust the machining pressure for pressing the tip 4 against the target surface Wa (toward the distal end) to an intended value using the head joint 31. The urging member 32 is compressed between the head joint 31 and the inner bottom of the urging member compartment 2d in a stretchable manner.
As shown in
The base 41 is attached to the head joint 31. As shown in
The base body 41a is a cylindrical body.
The connection protrusion 41b protrudes from a basal end of the base body 41a toward the basal end in the figure. The connection protrusion 41b is substantially cylindrical and has a smaller diameter than the base body 41a. The connection protrusion 41b may not have a smaller diameter than the base body 41a, and may have any shape instead of being substantially cylindrical.
The trapezoidal protrusion 41d is a tapered trapezoidal plate as viewed from above, which protrudes from a distal end of the base body 41a.
The tip end 42 is fixed to the tip installation part 41e. The tip installation part 41e is, for example, a V-shaped groove formed on a distal end of the trapezoidal protrusion 41d. The tip installation part 41e may not be a V-shaped groove, and may be in any shape that allows engagement with a basal end of the tip end 42. The tip installation part 41e may be in a shape in a cross-sectional view being rectangular, U-shaped, semicircular, arch-shaped, stepped, irregular, or flat. The shape can be determined in accordance with the shape of the basal end of the tip end 42.
As shown in
As shown in
The tip end 42 is formed from a hard material, such as industrial diamond, natural diamond, cubic boron nitride (CBN), ceramic, and hard metal.
The tip end 42 formed from hard metal or steel may also be coated with diamond-like carbon (DLC) to harden the surface of the tip end 42.
As shown in
The linear slide-contact portion 42a may have a cylindrical surface with a radius R of 0.2 to 20 mm, desirably 0.3 to 10 mm, or more desirably 0.5 to 5 mm.
As shown in
As shown in
The operation of the burnishing tool 1 according to the present embodiment will now be described in accordance with the machining procedure with reference to
To precisely finish the bottom Wc or Wj (target surface Wa or Wh) of the groove Wb or Wi of the workpiece W, the groove Wb or Wi is pre-machined by, for example, metal cutting before burnishing as shown in
The workpiece W is fastened firmly on the table of the finishing machine (not shown).
The burnishing tool 1 is attached to the finishing machine and then is moved close to the target surface Wa or Wh. The axis of the workpiece W (rotation axis of the workpiece W) and the axis of the burnishing tool 1 may be aligned parallel to or perpendicular with each other. In the burnishing operation, the tip end 42 of the burnishing tool 1 can be pressed against the workpiece W along the axis of rotation.
For burnishing the bottom Wc of the wide groove Wb as the target surface Wa using the burnishing tool 1 as shown in
The workpiece W is rotated under the appropriate machining condition to have the linear slide-contact portion 42a pressed against a machining starting point on the target surface Wa, and is fed in the feed directions (indicated by arrows a and b) to reciprocate on the target surface Wa in the groove Wb for burnishing.
As described above, the burnishing tool 1 is fed while burnishing the workpiece W to increase the machinable area of a machining part Wf to be machined with the linear slide-contact portion 42a.
Once the target surface Wa is mirror-finished as appropriate with the linear slide-contact portion 42a, the tip end 42 is moved away from the workpiece W to stop rotating the workpiece W. This ends the machining.
As shown in
As shown in
During burnishing, the linear slide-contact portion 42a linearly contacts the workpiece W and thus has a smaller contact area with the workpiece W than when a burnishing tool having surface contact with a workpiece (refer to Patent Literature 1) is used. This reduces the pressing load (indicated by arrow c in
Further, as shown in
This increases the length of a contact area A between the linear slide-contact portion 42a and the workpiece W (refer to
As shown in
A semi-cylindrical portion herein refers to a raised portion shaped like a half-moon in a longitudinal cross-section. The semi-cylindrical portion may be in the shape of a reversed U, a protrusion, an arch, a semicircle, or a semi-ellipse.
As described above, a machining part with a narrow curvature, such as an O-ring groove, can be burnished by moving the chamfered end 42b of the tip end 42 to the corners of the bottom Wc or Wj of the groove Wb or Wi as shown in
The burnishing tool 1 has its linear slide-contact portion 42a pressed against the bottom Wc or Wj of the groove Wb or Wi on the workpiece W for burnishing by moving the linear slide-contact portion 42a while the workpiece W is rotating. More specifically, the linear slide-contact portion 42a is pressed against the bottom Wc or Wj of the groove Wb or Wi on the rotating workpiece W for burnishing.
This structure allows machining near the corners of the groove Wb or Wi. Thus, for example, the bottom Wc or Wj of an O-ring groove including its portions near the edges (side walls) can be burnished to reduce an unmachined area Wg or Wm.
The target surface Wa machined with the burnishing tool 1 can be finished like a mirror surface. The burnished bottom Wc or Wj of the groove Wb or Wi has a smoother surface roughness, and thus provides higher sealing performance. In addition, the bottom Wc or Wj of the groove Wb or Wi as the target surface Wa is pressed with the tip end 42 to cause plastic deformation, which increases the strength of the workpiece more than with metal cutting or grinding.
Referring now to
As shown in
Simply pressing the burnishing tool 1 without feeding can also reduce the unmachined area Ws in the bottom Wq of the groove Wp.
As described above, the burnishing tool 1 according to the present embodiment can be used for burnishing the bottom Wc, Wj, or Wq of the narrow groove Wb, Wi, or Wp for receiving O-rings or oil seals and can reduce the unmachined area Wg, Wm, or Ws (refer to
The invention is not limited to the embodiments described above, and may be changed and modified variously within the scope of its technical idea. It is intended that the appended claims be interpreted as covering all alterations, and modifications as falling within the spirit and scope of the invention. The components that are the same as described in the above embodiments will be given the same reference numerals, and will not be described.
The tip 4 according to the embodiment (refer to
The tip end 42A of the tip 4A is fixed to a tip installation part 41Ae, which is a C-shaped groove as viewed from above, using an adhesive. A distal end of the cylindrical tip end 42A protrudes in the shape of an arch (semi-cylinder) as viewed from above from a trapezoidal protrusion 41Ad. This achieves a smaller corner located in a feed direction in the same manner as for the tip 4 according to the embodiment, and thus can reduce or eliminate an unmachined area.
Although the bottom Wc or Wj of the groove Wb or Wi, which may be an O-ring groove on the outer circumferential surface Wd and on the end face We serves as the target surface Wa or Wh of the workpiece W in the embodiment as shown in
As shown in
For example, the target surface W1a to be machined with the burnishing tool 1 may be a bottom W1c of a groove W1b formed on an inner wall of the cylindrical workpiece W1. In other words, the workpiece W1 to have a cylindrical inner surface to allow the burnishing tool 1 to be fed onto the surface.
The base 41 may not have the shape shown in
A base 41C may be prepared separately, and a tip end 42C may be fastened to the base 41C using a screw 43C as in a tip 4C shown in
The burnishing tool 1 can be used for burnishing the target surface Wa, Wh, or Wo shown in
The groove Wb, Wi, or Wp shown in
Although the tip 4 according to the above embodiment includes the base 41 and the tip end 42 formed from a hard material, such as diamond or a hard metal, attached using an adhesive, the tip 4 may have any other structure. For example, the tip may have its tip end 42 welded to or embedded in the base 41.
Although the tip end 42 includes the linear slide-contact portion 42a with the shape defined by an arch-like curve cut from a cylinder with a perfect circle as viewed from above as shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-108813 | May 2017 | JP | national |
