JP2006218581A - Helical gear cutting method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a helical gear cutting method and device capable of manufacturing a desired synthetic resin made helical gear by directly cutting a gear blank for tooth space cutting of the helical gear with a general purpose machine tool such as an NC milling machine. <P>SOLUTION: In the helical gear cutting method, a desired helical gear is machined by a machine tool cutting while rotating a tool. The gear blank 32 to be prepared has the same diameter as the tip circle diameter of the desired helical gear and the same thickness as the tooth width of the helical gear. An NC rotary table 17 which can be set at an arbitrary angle is tilted by the same angle as the helical angle of the helical gear with respect to the center line of the main spindle 12 mounting the rotating tool 61. The gear blank 32 is fixed in parallel leaving a space to the rotary table 30 on the rotary table 30 which is rotatably provided on the upper surface of the NC rotary table 17 to form the tooth space on the gear blank with the rotating tool 61. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method and an apparatus for machining an involute groove of a helical gear with a machine tool such as a general NC (numerical control) milling machine, and more specifically, by directly cutting a resin material using a small-diameter rotary tool. The present invention relates to a helical gear processing method and a cutting apparatus for manufacturing a helical gear.

  Many helical gears (helical gears) are used as power transmission elements for paper feeding mechanisms of office machines such as copying machines and printers. The feature of the helical gear is that the gear teeth have a torsion angle with respect to the rotation axis, as the word says.

  The material of the helical gear used for the paper feeding mechanism is mainly made of polyacetal resin such as POM (polyoxymethylene) or synthetic resin such as MC (monomer cast) nylon. This helical gear is injection molded. It is manufactured by an injection molding machine using a mold.

  Here, the conventional general manufacturing method of a helical gear is demonstrated easily.

  As a first example, an electrode having the same shape as a desired helical gear is manufactured by a dedicated gear shape processing machine (for example, see Patent Documents 1 and 2) such as a hobbing machine or a gear grinding machine. Subsequently, by using this electrode, a desired helical gear shape is formed by electric discharge machining on a nested part (cavity) of an injection mold with an electric discharge machine. Next, the manufactured nested part is assembled into an injection mold, the completed mold is attached to an injection molding machine, and a desired synthetic resin helical gear is obtained by injection molding.

  As a second example, a wire-cut electric discharge machine (see, for example, Patent Documents 3 and 4) is used to form a desired helical gear shape on the nested part, and subsequently manufactured in the same manner as in the first example. A desired helical gear is injection-molded using the mold.

  That is, in order to obtain a desired helical gear, a dedicated gear shape processing machine and a wire-cut electric discharge machine are required, and after these, a mold is first manufactured, and then an injection molding machine with the mold attached is used. The resin material (for example, POM) must be injection-molded.

  A general helical gear machining method uses a dedicated tool as disclosed in Non-Patent Document 1.

Japanese Patent Laid-Open No. 7-219612 JP 11-347930 A JP-A-5-4121 JP-A-8-71852 Onishi Kiyoshi, "Handbook of mechanical design and drawing based on JIS", 10th edition, Science and Engineering, April 2001, 6-20, 6-21

  By the way, at the initial trial production stage of the product, the specification of the helical gear is changed for the purpose of changing the motor that is the driving source of the helical gear or increasing the paper feed speed. Therefore, it is necessary to manufacture a nested part of the gear portion of the prototype mold every time the helical gear specifications are changed.

  When making a trial production of a helical gear at a product development stage such as a copying machine or a printer, even if it is a trial production of a small number of about 10 helical gears, a mold is produced and molded by an injection molding machine to produce a desired helical gear. The prototype cost of such a helical gear includes the manufacturing cost of the electrode parts, the manufacturing cost of the nested parts of the injection mold, and the running cost of the injection molding machine, and this is repeated every time the specification is changed. The cost of trial production of helical gears is very high. In addition, a production period for producing electrode parts, nested parts, and the like is also required, for example, for about 1 to 2 weeks, and the production time also increases.

  The present invention has been made in view of such a problem. Therefore, the object of the present invention is to directly cut a gear blank by using a general-purpose machine tool such as an NC milling cutter for helical gears. A helical gear cutting method and a cutting apparatus capable of producing a synthetic resin helical gear are provided.

  In order to achieve the above object, a helical gear cutting method according to the present invention is a helical gear cutting method for cutting a desired helical gear using a machine tool that rotates a tool and cuts a workpiece. A gear blank having the same diameter as the tip circle diameter of the desired helical gear and the same thickness as the helical gear tooth width is prepared, and a numerically controlled rotary table that can be set to an arbitrary angle is provided as a spindle on which the rotary tool is mounted. The gear blank is inclined parallel to the rotary table on a rotary table rotatably provided on the upper surface of the numerically controlled rotary table. And a tooth gap is formed in the gear blank by the rotary tool.

  Furthermore, the helical gear cutting method of the present invention provides a tool trajectory obtained by offsetting the tooth right-angle cross section of one tooth of the desired helical gear or the tooth profile contour section perpendicular to the central axis of the helical gear by the radius of the rotary tool. The rotary tool is moved from the reference point along the cutting path, the tooth gap for one tooth is cut, the rotary tool is returned to the reference point, and then the rotary table provided on the numerically controlled rotary table. Is rotated by one tooth, a tooth groove for one tooth is cut again along the tool trajectory, and this is repeated for a desired number of teeth.

  In addition, the helical gear cutting device according to the present invention for executing the above method includes an NC milling cutter, an inclined base having a mounting surface having the same inclination angle as the torsion angle of the desired helical gear, and an attachment surface of the inclined base. And a rotary table rotatably mounted on the numerically controlled rotary table to which gear blanks are attached in parallel and spaced apart.

  According to the helical gear cutting method and the cutting apparatus of the present invention, it is possible to manufacture a helical gear with a general-purpose NC milling cutter, and it is possible to significantly reduce the cost of trial manufacture of the helical gear prototype parts and the delivery time.

  In the following, an embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a front view of an NC milling machine provided with a cutting device as one embodiment according to the present invention, and FIG. 2 is a right side view of the NC milling machine shown in FIG. FIG. 3 is an enlarged front view of a main part for explaining attachment of the gear blank and the rotary table to the NC milling cutter, and FIG. 4 is an enlarged main part showing a state in which the gear blank and the rotary table are attached to the NC milling cutter. It is a right view. FIG. 5 is a main part enlarged schematic top view showing the relationship between the tool locus of the rotating tool center line and the gear blank, and FIG. 6 is a perspective view showing the tool locus of the rotating tool center line for one tooth, FIG. 7 is an enlarged perspective view of a main part showing a processing state of a gear blank by a rotary tool, and FIG. 8 is a perspective view showing a helical gear processed into a desired shape. FIG. 9 is a flowchart for explaining a processing method as one embodiment according to the present invention.

  In this embodiment, in order to produce a helical gear of modules 0.3 to 1.0 used for a paper feeding mechanism of office equipment such as a copying machine and a printer, for example (but not limited to) A method of directly cutting a synthetic resin gear blank such as POM or MC nylon using an NC milling cutter with a small-diameter rotating tool is shown.

  As shown in FIGS. 1 and 2, the NC milling machine as a processing machine includes an X-axis table 15 and a Y-axis table 20 on the support base 10 that move the table 16 in the X-axis direction and the Y-axis direction, respectively. Yes. Specifically, the Y-axis table 20 moves the X-axis table 15 in the Y-axis direction via the servo motor 2a, and the X-axis table 15 moves the NC milling table 16 via the servo motor 1a in the X-axis direction. Move to. As a result, the NC milling table 16 is provided so as to be movable in the X-axis and Y-axis directions.

On the NC milling table 16, a numerically controlled rotary table 17 is fixed at a desired angle via an inclined table 41. On the upper surface of the numerically controlled rotary table 17, a rotary table 30 to which a disc-like gear blank 32 as a workpiece (workpiece) is attached is provided to be rotatable around the central axis O ₁ -O ₁ ′ of the table 17. (See FIG. 4).

  As shown in FIG. 4, the numerically controlled rotary table 17 can be set (adjusted) by the tilt table 41 so that the tilt angle β is equal to the twist angle of the helical gear to be manufactured with respect to the NC milling table 16. It is. The method of setting the angle of the numerically controlled rotary table 17 includes, for example, preparing a plurality of tilt tables 41 having different tilt angles, and setting the tilt angle β of a desired angle with respect to the NC flange table 16, in other words, with respect to the horizontal plane. The tilt table 41 may be selected, and the numerically controlled rotary table 17 may be fixed on the tilt table 41 having the selected desired angle β, or automatically by using a stepping motor or the like. It may be possible to adjust to a desired angle β. The rotary table 30 is driven by the rotary shaft servomotor 14.

  The gear blank 32 attached to the rotary table 30 is made of a synthetic resin as described above, and has a disk shape having the same diameter and thickness as the tip diameter and tooth width of the desired helical gear to be manufactured, that is, the helical gear. Is made. As shown in FIG. 3, the gear blank 32 is mounted on the turntable 30 by a fixing nut 31 via a fixing jig 33 that is screwed onto the turntable 30 as illustrated in FIG. 3. It is fixed parallel to the surface of the table 30 and at a distance.

  On the other hand, in the NC milling machine, a Z-axis table 13 is provided on a column 11 extending upward from the support base 10 so as to be movable in the Z-axis direction. The Z-axis table 13 is driven in the Z-axis direction by a servo motor 1b. A cutting rotary tool 61 is further attached to the tip end of the main shaft 12 rotatably attached to the Z-axis table 13. The main shaft 12 is driven and rotated by a motor (not shown).

  In this embodiment for producing a helical gear for a copying machine or a printer, a small diameter end mill having a diameter of 0.5 mm or less, more preferably 0.3 mm is adopted as the cutting rotary tool 61, and cutting is performed at a high speed rotation of 20,000 rpm or more. Processing is not limited to this.

As can be understood from the above description, the tool center line OO ′ parallel to the Z axis passing through the center of the rotary tool 61 is the center axis of the numerically controlled rotary table 17 to which the gear blank 32 is attached. An angle equal to O ₁ −O ₁ ′ and a twist angle β is formed (see FIGS. 4 and 7).

  A method for processing the gear blank 32 to which the NC milling machine is attached will be described below.

  As described above, the cab blank 32 is positioned at a predetermined position by adjusting the X-axis table 15, the Y-axis table 20, the tilting table 41 and the like so as to form a twist angle β with the rotary tool 61, and is positioned on the rotary table 30. Fixed.

  The rotary tool 61 operates along a tool locus 51 for helical gear tooth gap machining as shown in FIGS. The tool path 51 shown in FIGS. 5 and 6 is a tool center obtained by offsetting a tooth perpendicular section of one tooth of a helical gear to be manufactured or a tooth profile outline of a section perpendicular to the central axis of the helical gear by the radius of the rotary tool 61. It is a locus of line OO ′. The shape of the tool locus 51 and the feed pitch p of the rotary tool 61 in the Z-axis direction are based on the helical gear diameter, number of teeth, torsion angle, module or gear blank material, rotary tool diameter, etc. Multiple trajectories are created and stored in advance, and can be selected by inputting data such as the diameter of the helical gear to be manufactured, the number of teeth, the torsion angle, the material of the module or gear blank to be cut and the diameter of the rotating tool to be used. You may be made to do. Alternatively, the tool trajectory 51 may be created when the diameter of the helical gear, the number of teeth, the torsion angle, the material of the module or gear blank, the diameter of the rotating tool, and the like are input.

  Specifically, the rotary tool 61 operates along a tool locus 51 shown in FIG. 5 from an initial position (point A on the line OO ′ in the embodiment of FIG. 6) that is a reference point, that is, a machining start point. Cut the first layer and return to the initial position. This operation of the rotary tool 61 does not move so that the rotary tool 61 itself draws the tool path 51, but the X-axis table 15 and the Y-axis table 20 move, and the gear blank 32 on the table 16 moves. Thus, it will be easily understood by those skilled in the art that the rotary tool 61 moves relative to the tool path 51 to perform the cutting process.

  When the first-layer cutting is completed, the rotary tool 61 is then moved down the Z-axis minus direction by a fixed cutting pitch p from the initial position by moving the Z-axis table 13. The rotary tool 61 operates again along the tool path 51 and performs the second layer cutting. By repeating such a machining operation of the rotary tool 61, the shape of one tooth of the helical gear is cut.

  When the cutting of the shape for one tooth of the gear blank 32 is completed, the rotary tool 61 rises in the plus direction of the Z axis and returns to the initial position A. Thereafter, the rotary table 30 is rotated by an angle θ (= 360 ° / z) determined by the number of teeth (z) of the helical gear to be manufactured by the rotary shaft servomotor 14, and cutting of the next tooth is started. Is done. When such cutting is repeated for the number of teeth, a helical gear having a desired twist angle β as shown in FIG. 8 is completed.

  The flow of such helical gear cutting will be described with reference to the flowchart shown in FIG. The gear blank 32 is positioned at a predetermined position by the positioning command (G00), the rotary tool 61 is positioned at the machining start point, and the helical gear cutting cycle starts.

  Data such as the number of teeth (z) related to the helical gear to be manufactured, which is set in step S0, is input, and then the origin return operation of the numerically controlled rotary table 17 is executed in step S1. When the origin return of the table 17 is completed, the variable n of the tooth number counter is initialized in step S2. That is, the variable is reset to zero. Next, in step S3, the subprogram call M code (M98; equivalent to the Basic language GOSUB instruction) is read in the main program, jumping to the subprogram and executing the subprogram at the designated address. When M99 is read by the subprogram, the program returns to the main program.) Is read, and the processing subprogram for one tooth of the desired helical gear is called, and in step S4, the tooth gap is processed for one tooth. Next, in step S5, the value (n) of the tooth number counter is counted up, and in step S6, the value (n) of the tooth number counter is compared with the number of teeth (z). When the value (n) of the tooth number counter is smaller than the number of teeth (z), the process proceeds to step S7, the rotation table 30 is rotated by one tooth (θ), and steps S3 to S6 are executed again. When the value of the tooth number counter is equal to or larger than the number of teeth, the process proceeds to step S8, and the processing of the helical gear is completed.

  Thus, a desired helical gear 32 as shown in FIG. 8 can be manufactured.

It is a front view of NC milling machine provided with the cutting device as one example concerning the present invention. It is a right view of NC milling machine shown by FIG. It is a principal part enlarged front view for demonstrating the attachment to the NC milling of a gear blank and a rotary table. It is a principal part expansion right view which shows the state in which the gear blank and the turntable were attached to NC milling machine. It is a principal part expansion schematic top view which shows the relationship between the tool locus | trajectory of a rotary tool centerline, and a gear blank. It is a perspective view which shows the tool locus | trajectory of the rotary tool centerline for one tooth. It is a principal part expansion perspective view which shows the processing state of the gear blank by a rotary tool. It is a perspective view which shows the helical gear processed into the desired shape. It is a flowchart for demonstrating the processing method as one Example which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Support stand 11 Support | pillar 12 Main axis | shaft 13 Z-axis table 14 Servo motor 17 Numerical control type rotary table 30 Rotary table 41 Tilt base 51 Tool locus 61 Rotary tool

Claims (3)

In a helical gear cutting method of cutting a desired helical gear using a machine tool that rotates a tool to cut a workpiece,
Preparing a gear blank having the same diameter as the tip diameter of the tip of the helical gear and the same thickness as the helical gear;
Tilt the numerically controlled rotary table that can be set to an arbitrary angle by the same angle as the helix angle of the helical gear with respect to the center line of the spindle to which the rotary tool is mounted.
On the rotary table that is rotatably provided on the upper surface of the numerically controlled rotary table, the gear blank is fixed in parallel with an interval from the rotary table;
A tooth gap is formed in the gear blank by the rotating tool.
The helical gear cutting method characterized by the above-mentioned. The rotary tool is moved from the reference point along a tool trajectory obtained by offsetting the tooth perpendicular cross section of one tooth of the desired helical gear or the profile of the tooth profile cut perpendicular to the central axis of the helical gear by the radius of the rotary tool. Cutting the tooth gap for one tooth,
Return the rotary tool to the reference point,
Next, the rotary table provided on the numerically controlled rotary table is rotated by one tooth, and a tooth groove for one tooth is cut along the tool path again, and this is processed for a desired number of teeth. repeat,
The helical gear cutting method according to claim 1, wherein: NC milling machine,
A tilting base whose mounting surface has the same tilt angle as the torsion angle of the desired helical gear;
A numerically controlled rotary table attached to the mounting surface of the tilt table;
A turntable rotatably mounted on the numerically controlled turntable, wherein gear blanks are attached in parallel and spaced apart;
A helical gear cutting apparatus comprising:

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