JP2012236257A - Method and device for performing pore electric discharge machining on tip concave part of spout of injection nozzle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for performing pore electric discharge machining, in each of which the length of a spout of an injection nozzle can be machined with high accuracy.SOLUTION: The method for performing pore electric discharge machining on a tip concave part of the spout of the injection nozzle comprises: a step 1 of detecting contact with a reference sphere 35 to set the starting point of a machining electrode D; a step 2 of mounting a reference object to be machined in a unit for clamping the object to be machined; a step 3 of detecting coordinates of a surface position of the reference object to be machined by using a contact detection means; a step 4 of storing data on the coordinates; a step 5 of mounting the injection nozzle being the object to be machined in the unit for clamping the object to be machined; a step 6 of detecting the coordinates of the surface position of a part to be machined of the injection nozzle; a step 7 of calculating a difference between the Z-axis coordinate of the surface position of the part to be machined which is detected at the step 6, and the Z-axis coordinate stored at the step 4 and correcting a feed rate on the basis of the calculated difference when the Z-axis of the tip concave part of the spout of the injection nozzle is machined, and executing the electric discharge machining; a step 8 of performing the steps 3-7 on a plurality of parts to be machined when the reference object to be machined has the plurality of parts to be machined.

Description

  TECHNICAL FIELD The present invention relates to a method and apparatus for fine hole electric discharge machining of a nozzle tip recess of an injection nozzle.

  For example, in a fuel injection nozzle of an internal combustion engine, the length and the diameter of the injection hole are factors that greatly affect the spray characteristics such as the fuel injection amount and the spray state. Therefore, higher accuracy is required for processing the length and diameter of the injection hole of the fuel injection nozzle.

  Drilling of the fuel injection nozzle can be drilled, but there are problems such as breakage of the drill and burring at the end of the injection hole when processing a small injection hole with a diameter of 1 mm or less. For machining such a small-diameter injection hole, machining by a pore electric discharge machine is more suitable than drilling.

  Further, a stepped hole or a recess larger than the inner diameter of the injection hole is provided at the tip of the fuel injection nozzle in order to promote atomization of the injected fuel and mixing with air (for example, Patent Document 1).

  When processing such a stepped hole or recess of a fuel injection nozzle with a conventional fine hole electric discharge machine, if the thickness of the tip of the injection nozzle changes, the depth of the stepped hole or recess from the surface of the injection nozzle However, there is a problem that the length of the injection hole below the stepped hole or the concave portion is changed.

  7 and 8 are schematic explanatory views of a stepped hole or a recess provided in the tip portion of the fuel injection nozzle described above.

For example, a wall thickness t ₀ of the distal end portion of the fuel injection nozzle 100 shown in FIG. 7, the fuel injection side Yes in stepped bore 101 of larger diameter depth l ₀ is provided in diameter D, with the stages It is assumed that an injection hole 103 having a diameter d (d <D) and a length L ₀ is communicated with the inside (not shown) of the fuel injection nozzle 100 below the hole 101.

  When the above-described stepped hole 101 of the fuel injection nozzle 100 is processed by a conventional fine hole electric discharge machine, the upper surface on the fuel injection side of the fuel injection nozzle 100 is processed as the processing reference surface 105 (for example, Patent Document 2). .

Japanese Utility Model Publication No. 57-158773 Japanese Patent Laid-Open No. 03-221323

When the stepped hole 101 of the fuel injection nozzle 100 is processed by the conventional fine hole electric discharge machine, the thickness t ₀ of the tip of the fuel injection nozzle 100 is increased or decreased by α as shown in FIG. _When increasing from ₀ to t ₁ (= t ₀ + α) or decreasing to t ₂ (= t ₀ −α), the upper surface on the fuel ejection side is processed as the processing reference surface 105, so a stepped hole The depth of 101 is constant (l ₀ = l ₁ = l ₂ ), but the length of the small-diameter injection hole 103 is L ₁ (= L ₁ + α)> L ₀ or L ₂ (= L ₂ −α) <L ₀ , and the length L ₀ of the injection hole that greatly affects the fuel injection amount and the spray characteristics in the fuel injection nozzle cannot be processed with high accuracy. That is, it was not possible to process the length L ₀ of the machining direction opposite inner surface of the reference injection hole of the injection hole of the fuel injection nozzle with high accuracy.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to inject a fuel injection nozzle having a stepped hole or a recess larger than the inner diameter of the injection hole on the outlet side of the injection hole. It is an object of the present invention to provide a pore electric discharge machining method and apparatus capable of machining a hole length with high accuracy.

As a means for solving the above-mentioned problems, the electric discharge machining method for the injection nozzle tip recess according to claim 1 is characterized by comprising the following steps.
1. Contact between the Z-axis coordinate setting reference sphere provided in the workpiece clamping device on the X and Y tables and the electrode tip is detected by the contact detection means to set the origin of the electrode tip.
2. A reference workpiece serving as a reference for the injection nozzle is mounted on the workpiece clamping device.
3. The processing part of the reference workpiece is moved and positioned to the processing position, and the coordinates of the contact position of the surface position of the processing part of the reference workpiece are detected using the contact detection means.
4). The coordinate data detected in step 3 is stored.
5. The reference workpiece is removed from the workpiece clamping device, and an injection nozzle that is the workpiece is mounted.
6). The processing portion of the injection nozzle is moved and positioned to the processing position, and the coordinates of the surface position of the processing portion of the injection nozzle are detected using the contact detection means.
7). The difference between the Z-axis coordinate of the surface position of the machining part detected in step 6 and the Z-axis coordinate stored in step 4 is obtained, and based on this difference, the Z-axis machining feed amount of the injection nozzle tip recess is determined. Correct and perform electrical discharge machining.
8). If the reference workpiece has a plurality of machining portions, the steps 3 to 7 are performed on the machining portions at the plurality of locations.

  A fine hole electric discharge machining method according to a second aspect is the fine hole electric discharge machining method according to the first aspect, wherein the injection nozzle is a fuel injection nozzle.

  A fine hole electric discharge machining apparatus for an injection nozzle tip recess of an injection nozzle according to claim 3, wherein a machining electrode that can be moved up and down in the Z-axis direction and a workpiece mounted on the workpiece clamping device are arranged in the XY-axis direction. In the fine hole electric discharge machining apparatus provided so as to be relatively movable and positionable, contact with the tip of the machining electrode is detected by the contact detection means in the workpiece clamping device, and an origin which is a reference position of the machining electrode tip is set. A reference sphere is provided for detecting when the origin contacts the processing position surface of the workpiece mounted on the workpiece clamping device or the processing position surface of the reference workpiece and the processing electrode. Contact detection data storage means for storing position coordinate data, and a comparison operation means for obtaining a difference between the Z-axis coordinates of the processing position surface of the workpiece and the Z-axis coordinates of the surface position of the reference workpiece, The comparison Based on the difference obtained by the calculation means, is characterized in that the processing to correct the Z-axis machining feed amount of injection port tip recess of the injection nozzle.

  The fine hole electric discharge machining apparatus for the injection nozzle tip recess of the injection nozzle according to claim 4, wherein the injection nozzle is a fuel injection nozzle. It is characterized by this.

  According to the method and apparatus for forming a discharge hole at the tip of the injection nozzle of the injection nozzle according to the present invention, the length of the injection hole of the fuel injection nozzle provided with a stepped hole or a recess larger than the inner diameter of the injection hole on the outlet side of the injection hole Can be processed with high accuracy.

  In addition, if the Z-axis coordinate that is the reference position of the tip of the machining electrode and the Z-axis coordinate of the surface position of the machining part of the reference workpiece are stored in advance, it is not necessary to measure the machining position of the reference workpiece for each workpiece. Thus, the processing time can be shortened.

The front view of the fine hole electric discharge machining apparatus which concerns on this invention. The right view which fractured | ruptured the thin hole electric discharge machining apparatus which concerns on this invention partially. Explanatory drawing of the workpiece clamp apparatus with which a turntable is mounted | worn. The figure which measures the coordinate of the process part of a reference | standard workpiece by inclining a turntable. FIG. 5A shows an example of the shape of a stepped hole or recess at the tip of the fuel injection nozzle. FIG. 5A shows a countersink hole having a constant inner diameter, and FIG. 5B shows a funnel-like recess opened on the surface side. Example with Explanatory drawing of a structure of the fine hole electric discharge machining apparatus CNC control apparatus which concerns on this invention. It is typical explanatory drawing of the stepped hole or recessed part provided in the fuel injection nozzle front-end | tip part. Explanatory drawing in the case of processing the stepped hole of a fuel injection nozzle with the conventional fine hole electric discharge machine.

    Embodiments of the present invention will be described below with reference to the drawings.

  1 and 2 show an embodiment of a 6-axis control (X, Y, Z, A, B, W) fine hole electric discharge machining apparatus according to the present invention.

  Referring to FIGS. 1 and 2, a Y-axis that can be moved and positioned in the Y-axis direction by a driving means (not shown) and a Y-axis driving motor MY is provided on a base 3 of a thin hole electric discharge machining apparatus 1 that is generally shown. A table 5 is provided.

  A tray 7 is integrally fixed to the Y-axis table 5, and a stone surface plate 9 that is an insulator is provided on the plate 7, and an L-shaped bracket member 11 is integrally formed on the stone surface plate 9. Is provided.

  On the bracket member 11, a processing tank 15 for containing a processing liquid 13 such as pure water having a low electrical conductivity is mounted, and a fuel injection nozzle 37 for a workpiece is fixed in the processing tank 15. A tiltable turntable device 17 is provided (see FIGS. 3 and 4).

  The turntable device 17 described above has an A axis centering on an axis parallel to the Z axis (vertical direction in FIG. 1) and a center axis B orthogonal to the A axis (parallel to the Y axis) B. And an axis (tilt axis).

  The B-axis rotation shaft 19 as the B-axis drive unit described above extends upward from the bottom of the L-shaped bracket member 11 along the rear wall (right side in FIG. 2) of the processing tank 15. (Not shown) is rotatably supported. The B-axis rotation shaft 19 is provided so as to extend through the rear side wall surface of the processing tank 15 to a substantially central portion inside the processing tank 15.

  The turntable device 17 is rotatably attached to the upper left end of the B-axis rotation shaft 19 via a speed reducer (not shown). The rotation drive of the B-axis rotation shaft 19 is performed by a B-axis drive motor MB provided outside the processing tank 15, and the rotation drive of the turntable device 17 is provided along the axis of the B-axis rotation shaft 19. It is provided so that it can be rotated by an A-axis drive motor MA through a blind hole 23 that opens to the outside.

  An annular energization ring (not shown) is provided on the back surface of the turntable device 17, and the turntable device 17 is connected to a discharge power source (not shown) via the energization ring.

  In the above configuration, if the A-axis drive motor MA is appropriately rotated under the control of the CNC controller 61, the turntable device 17 can be rotated at an appropriate angle about the A-axis.

  Similarly, if the B-axis drive motor MB is appropriately rotated forward or reversely, the turntable device 17 can be tilted (tilt) clockwise or counterclockwise about the B-axis. Furthermore, the turntable device 17 can be positioned at an arbitrary position in the Y-axis direction by appropriately rotating the Y-axis drive motor MY.

  On the base 3 at the rear of the processing tank 15 (right side in FIG. 2), a pair of support columns 21 (a, b) erected on the left and right as viewed from the front side, and the pair of support columns 21 A portal frame 23 composed of a beam member 25c suspended horizontally is provided above (a, b).

  The beam member 25c of the portal frame is provided with an X-axis guide rail (not shown) protected by a bellows 27, and an X-axis carriage 29 driven by an X-axis drive motor MX is provided on the X-axis guide rail. It can be moved and positioned in the X-axis direction orthogonal to the Y-axis.

  The X-axis carriage 29 is provided with a Z-axis carriage 31 that can be moved and positioned at an arbitrary position on the Z-axis (processing axis) by a Z-axis drive motor (not shown).

  The X-axis carriage 29 can be positioned at any position on the X-axis by an X-axis drive motor MX. The Z-axis carriage 31 is provided with a W-axis motor MW that moves the Z-axis carriage 31 up and down to an appropriate height with respect to the X-axis carriage 29.

  The Z-axis carriage 31 is rotatably supported by solid or hollow rod-like machining electrodes D, and a motor (not shown) for rotating these rod-like electrodes D is provided. Further, a processing liquid supply means (not shown) for supplying a processing liquid (pure water or the like) is provided for the hollow rod-shaped electrode, that is, the pipe electrode.

  A workpiece clamping device 33 as shown in FIG. 3 is mounted on the turntable device 17, and the workpiece clamping device includes an origin (a reference position of the tip of the machining electrode D). A reference sphere 35 for setting X, Y, Z) is provided.

  As shown in FIGS. 3 and 4, the workpiece clamping device 33 described above has a clamp for mounting a reference workpiece 37 ′ or a fuel injection nozzle 37 whose tip injection hole shape is as shown in FIGS. 5a and 5b. It has a mechanism. The shape of the stepped hole or recess at the tip of the fuel injection nozzle 37 includes various shapes such as a circular counterbore 101 shown in FIG. 5a and a funnel-like recess 102 as shown in FIG. 5b. The reference workpiece 37 ′ is a fuel injection nozzle that is precisely processed to a specified dimension so as to be a reference for the fuel injection nozzle 37 that is a workpiece.

  On the base 39 of the workpiece clamping device 33, a positioning pin 41 fitted to the inner diameter portion of the base portion 37a of the fuel injection nozzle 37 or the reference workpiece 37 ′ and an annular member 43 fitted to the outer diameter portion of the base portion 37a. Are provided.

  On the upper surface portion of the annular member 43, a cap mounting portion 45 having a male screw having a diameter smaller than the outer diameter of the annular member 43 is provided so as to protrude. An annular cap 47 that is screwed into the male thread portion of the cap mounting portion 45 is provided. Note that the lower end portion of the cap 47 is abuttingly engageable with the upper surface portion of the annular member 43.

  In the above configuration, when mounting and fixing the fuel injection nozzle 37 to the workpiece clamping device 33, first, the inner diameter portion of the fuel injection nozzle 37 is inserted into the positioning pin 41, and the cap 47 is inserted into the male screw of the cap mounting portion 45. It is mounted and fixed by screwing into the part. At this time, a spring 49 that presses and urges the fuel injection nozzle 37 toward the base 39 of the workpiece clamping device 33 is elastically mounted on the inner side of the cap 47. Can be fixed securely.

  The fuel injection nozzle 37 is formed with an engaging step portion that engages with the spring 49. Further, a ring-shaped spacer 51 having an appropriate plate thickness capable of adjusting the height in the Z-axis direction can be inserted between the base 39 of the workpiece clamping device 33 and the fuel injection nozzle 37.

  Referring to FIG. 1 again, the support 21b of the portal frame 23 is provided with a CNC control device 61 capable of controlling the above-described six control axes (X, Y, Z, A, B, W) and the like. It is provided. The CNC control device 61 controls the X-axis drive motor MX, the Y-axis drive motor MY, and the Z-axis drive motor (not shown) so that the machining electrode D is applied to the fuel injection nozzle 37 that is a workpiece. Three-dimensional (X, Y, Z) positioning can be performed.

  As shown in FIG. 6, a data input means 67 such as a keyboard, a display means 69 such as an LCD, a machining program memory 71 and the like are connected to the data bus 65 of the CPU 63 provided in the CNC control device 61 described above. Contact detection for detecting the coordinates (X, Y, Z, A, B, W) when the tip of the machining electrode D contacts the reference sphere 35 and the fuel injection nozzle 37 or the reference workpiece 37 ′. A means 73 is connected.

  The CNC control device 61 includes a contact detection data storage means 75 for storing Z-axis coordinates when the tip of the machining electrode D and the fuel injection nozzle 37 or the reference workpiece 37 ′ are in contact with each other. The CPU 63 is connected with a comparison calculation means 77 for obtaining a difference between the Z-axis coordinate of the surface position of the processing portion of the fuel injection nozzle 37 which is a workpiece and the Z-axis coordinate of the surface position of the processing portion of the reference workpiece. .

  A case will be described in which, for example, the counterbore hole 101 at the tip of the injection port of the fuel injection nozzle 37 of the internal combustion engine is machined by the fine hole electric discharge machining apparatus 1 at the nozzle tip recess of the injection nozzle having the above-described configuration.

  As shown in FIG. 3, a reference workpiece 37 ′ is inserted into a positioning pin 41 erected on a base 39 of a workpiece clamping device 33 mounted on a turntable device 17 in a processing tank 15, and the base The reference workpiece 37 ′ is securely fixed by screwing the cap 47 into the male thread portion of the annular member 43 provided in 39, and then, for example, processed in the next step.

(1) By operating the X-axis drive motor MX and the Y-axis drive motor MY under the control of the CNC control device 61, the axis of the reference sphere 35 provided in the workpiece clamping device 33 and the machining in the Z-axis direction The axis of the electrode D in the Z-axis direction is made coincident, and the Z-axis drive motor is controlled to lower the machining electrode D to a position where it comes into contact with the reference sphere 35, so that the machining electrode D contacts the reference sphere 35. Is detected by the contact detection means 73, and the origin (X, Y, Z) which is the reference position of the tip of the machining electrode D is set.

(2) A reference workpiece 37 'serving as a reference for the injection nozzle 37 is mounted on the workpiece clamping device.

(3) The processing portion of the reference workpiece 37 ′ is moved and positioned to the processing position, and the contact position coordinates (X, Y, Z, A, B, W) is detected.

(4) Contact position coordinate (X, Y, Z, A, B, W) data on the surface of the processed part of the reference workpiece 37 ′ is stored in the contact detection data storage means 75.

(5) The reference workpiece 37 'is removed from the workpiece clamping device 33, and the fuel injection nozzle 37, which is the workpiece, is mounted.

  (6) The processing portion of the fuel injection nozzle 37 is moved and positioned to the processing position, and the position coordinates (X, Y, Z, A, B, W) of the surface of the processing portion of the injection nozzle using the contact detection means. Is detected.

(7) A difference between the detected Z-axis coordinate of the surface position of the processing portion of the injection nozzle and the Z-axis coordinate of the surface position of the processing portion of the reference workpiece is obtained, and the tip of the injection nozzle of the injection nozzle is determined based on this difference. Electric discharge machining is performed by correcting the Z-axis machining feed amount of the recess.

(8) When the reference workpiece has a plurality of machining portions, the steps (3) to (7) are performed on the machining portions at the plurality of locations.

  Note that when the countersink hole 101 at the tip of the injection port of the fuel injection nozzle 37 of the internal combustion engine is processed, for example, in the fine hole electric discharge machining apparatus 1 at the recess at the tip of the injection nozzle of the above-described configuration, The processing hole D may be replaced later to process the injection hole 103, or the counterbore hole 101 may be processed after the injection hole 103 is processed first.

According to the method and apparatus for processing the fine hole electric discharge at the injection nozzle tip recess of the injection nozzle of the present invention, the fuel injection nozzle 37 having a counterbore 101 or a recess larger than the internal diameter of the injection hole 103 on the outlet side of the injection hole 103 it can be processed length L ₀ of the injection hole 103 with high accuracy.

  For exchanging the machining electrode D, an electrode exchanging device as described in JP-A-8-290332, which is an application of the present applicant, can be used.

DESCRIPTION OF SYMBOLS 1 Fine hole electric discharge machining device 3 Base 5 Y-axis table 7 Sauce tray 9 Stone surface plate 11 Bracket member 13 Processing liquid 15 Processing tank 17 Turntable device 19 B axis | shaft rotating shaft 21a, 21b Post 23 Gate type frame 25 Beam member c
27 Bellows 29 X-axis Carriage 31 Z-axis Carriage 33 Workpiece Material Clamping Device 35 Reference Ball 37 Fuel Injection Nozzle 37 ′ Reference Workpiece 39 Base 41 Positioning Pin 43 Ring Member 45 Cap Mounting Portion 47 Cap 49 Spring 51 Spacer 61 CNC Control Device 63 CPU
65 Data bus 67 Data input means 69 Display means 71 Processing program memory 73 Contact detection means 75 Contact detection data storage means 77 Comparison calculation means 100 Fuel injection nozzle 101 Countersink hole 102 Funnel-shaped recess 103 Injection hole 105 Processing reference surface D Processing electrode
L ₀ , L ₁ , L ₂ injection hole length MA A-axis drive motor MB B-axis drive motor MX X-axis drive motor MW W-axis motor Thickness of tip of t ₀ , t ₁ , t ₂

Claims (4)

A method for forming an electric discharge hole in a recess at the tip of an injection nozzle of an injection nozzle, comprising the following steps.
1. Contact between the Z-axis coordinate setting reference sphere provided in the workpiece clamping device on the X and Y tables and the electrode tip is detected by the contact detection means to set the origin of the electrode tip.
2. A reference workpiece serving as a reference for the injection nozzle is mounted on the workpiece clamping device.
3. The processing part of the reference workpiece is moved and positioned to the processing position, and the coordinates of the contact position of the surface position of the processing part of the reference workpiece are detected using the contact detection means.
4). The coordinate data detected in step 3 is stored.
5. The reference workpiece is removed from the workpiece clamping device, and an injection nozzle that is the workpiece is mounted.
6). The processing portion of the injection nozzle is moved and positioned to the processing position, and the coordinates of the surface position of the processing portion of the injection nozzle are detected using the contact detection means.
7). The difference between the Z-axis coordinate of the surface position of the machining part detected in step 6 and the Z-axis coordinate stored in step 4 is obtained, and based on this difference, the Z-axis machining feed amount of the injection nozzle tip recess is determined. Correct and perform electrical discharge machining.
8). If the reference workpiece has a plurality of machining portions, the steps 3 to 7 are performed on the machining portions at the plurality of locations. 2. The method of fine pore electric discharge machining of an injection nozzle tip recess of an injection nozzle according to claim 1, wherein the injection nozzle is a fuel injection nozzle. In the fine-hole electric discharge machining apparatus in which a machining electrode which can be positioned up and down in the Z-axis direction and a workpiece mounted on the workpiece clamping apparatus are relatively movable and positioned in the XY-axis direction, the workpiece clamping apparatus Provided with a reference sphere for detecting a contact with the tip of the machining electrode by a contact detection means and setting an origin which is a reference position of the tip of the machining electrode. The reference sphere is attached to the workpiece and the workpiece clamping device. Contact detection data storage means for storing position coordinate data detected when the processing electrode of the processing position of the workpiece or the surface of the processing position of the reference workpiece and the processing electrode comes into contact with each other; Comparison operation means for obtaining a difference between the Z-axis coordinate of the processing position surface and the Z-axis coordinate of the surface position of the reference workpiece is provided, and based on the difference obtained by the comparison operation means, Z Pore discharge machining apparatus of the injection inlet apical recess of the injection nozzle, characterized in that machining by correcting the machining feed amount. 4. The apparatus for fine pore electric discharge machining of an injection nozzle tip recess of an injection nozzle according to claim 3, wherein the injection nozzle is a fuel injection nozzle.

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