JP4434058B2 - EDM method - Google Patents

Description

  The present invention relates to an electric discharge machining method, and more particularly to an electric discharge machining method for machining high-precision fine holes provided in a fuel injection nozzle or the like.

  A plurality of fuel injection holes of a fuel injection nozzle of a vehicle engine or the like are required to be fine and to have high precision in size and direction. There is electrical discharge machining as a method of machining pores in a workpiece with high accuracy. Electrical discharge machining is generally performed in a machining fluid such as water or oil, and the machining fluid is positively supplied to the machining position to remove machining dust and machining gas and perform machining while cooling the machining portion. For this reason, a pipe electrode is used as the discharge electrode for hole machining, and the machining liquid is supplied to the machining portion through the hollow hole to improve the machining efficiency.

However, if the diameter is 200 μm or more, a pipe electrode can be used, but if the diameter is 100 μm or less, particularly 50 μm or less, it becomes difficult to use the pipe electrode, and a solid electrode is used. However, if pore processing with a diameter of 100 μm or less is performed with a solid electrode, the machining fluid in the machining portion hardly flows, so that the machining efficiency is greatly reduced.
As a processing method for such a high-precision fine hole, a method is conceivable in which finishing is performed by electric discharge machining on a workpiece provided with a fine hole as laser drilling (for example, see Patent Document 1). In this case, if the hole drilled with a laser beam is a lower hole and finish machining is performed by electric discharge machining using a solid needle-like electrode, highly accurate hole machining is possible. Since the machining fluid can be supplied to the machining part through the pilot hole, the machining speed is improved.

  However, in such a conventional electric discharge machining, when a minute deep hole having a diameter of 0.1 mm or less and length (L) / diameter (D) ≧ 8 is machined, the electrode explosive force during machining is low because the electrode rigidity is low. Or, when the water vapor (bubbles) vaporized by the discharge explosion passes through the side surface of the electrode, the electrode touches. Further, the amount of deflection further increases due to the occurrence of concentrated discharge. For this reason, the hole diameter is increased by about 30 to 40 μm with respect to the electrode diameter, resulting in variations in the diameter and shape accuracy. Moreover, since the electric discharge machining itself does not have straightness, a hole bent in a different direction is formed each time depending on the touching method.

JP 2001-150248 A

  The present invention has been made in view of the above-described circumstances. In order to prevent the above-mentioned problems, the hole diameter is prevented from being enlarged by suppressing the deflection of the electrode during the electric discharge machining, and the hole machining with high accuracy and high straightness is performed. It is an object of the present invention to provide an electric discharge machining method for high-precision fine holes that can be performed.

According to the first aspect of the present invention, in order to achieve the above-described object, an electric discharge machining method for forming a pore in a workpiece includes a pilot hole step for forming a pilot hole, and an electric discharge between the electrode and the workpiece. And a processing step of drilling holes. The machining step includes an excitation procedure for vibrating either the electrode or the workpiece and a machining fluid supply procedure for supplying a machining fluid to the workpiece. In the excitation procedure, short-circuit electrode control is performed in which the electrode is guided by contacting the pilot hole every time the electrode vibrates due to discharge explosion , and the direction of vibration of either the electrode or the workpiece is , The axial direction of the electrode. The lower hole is a hole extending in the axial direction of the electrode. In the processing fluid supply procedure, the processing fluid is sucked from the direction of the pilot hole, and the suction direction of the processing fluid coincides with the axial direction of the electrode.

By constructing in this way, a pilot hole that is 10 to 50 μm smaller than the target hole diameter is made in advance, and the electrode is controlled in a short-circuited manner to give an opportunity to forcibly contact the electrode and the workpiece. Each time the electrode vibrates, the electrode is guided in the pilot hole, and expansion of the vibration of the electrode can be suppressed. Further, by vibrating the electrode in its axial direction, the sludge discharge performance is improved, and the concentrated discharge is reduced, so that an increase in electrode deflection can be suppressed. By performing the above-described action, it is possible to perform pore processing with higher straightness and high accuracy. In addition, since the machining fluid is sucked from the direction of the pilot hole and the machining fluid flows along the side surface of the electrode, an electrode guide effect is exhibited, and an increase in electrode deflection can be suppressed.

In the form of Claim 2 of this invention, in the form of the said Claim 1, in the said short circuit electrode control, the short circuit rate which is a ratio which contacts the said electrode in electric discharge machining in the range of 20% to 40% It is characterized by that.
According to the present embodiment, the short-circuit electrode control in the vibration procedure is more concrete.

According to a third aspect of the present invention, in any one of the first and second aspects, the amplitude of vibration of either the electrode or the workpiece is in the range of 5 to 30 μm. .
According to this embodiment, the vibration procedure is made more specific.

In the form according to claim 4 of the present invention, in any one of Embodiment 3 to the claim 1, wherein said working fluid is a liquid.
According to this embodiment, the working fluid is made more specific.

In the form according to claim 5 of the present invention, in any one of Embodiment 3 to the claim 1, wherein said working fluid is a gas.
According to this embodiment, by performing gas deep hole electric discharge machining using gas as the machining fluid and further sucking in from the direction of the lower hole, the deflection of the electrode is reduced without deteriorating the sludge discharge performance. It is possible to process.

According to a sixth aspect of the present invention, the method according to any one of the first to fifth aspects further includes a step of attaching a cap to the workpiece in the processing step. If the shape of the workpiece is a male shape, it has a female shape that matches the male shape, so that it can be attached so as to contact the workpiece, and when the cap is attached to the workpiece, the cap is processed. Only the hole portion is opened and can be processed.
According to this embodiment, when processing a plurality of holes while sucking from the lower hole, the processed hole is sealed to cover the already processed hole that hinders suction from the lower hole. Since the suction of the machining liquid from the prepared prepared hole is prevented from weakening, the effect of suppressing the vibration of the electrode is prevented from diminishing.

According to a seventh aspect of the present invention, in any one of the first to sixth aspects, the pilot hole is formed by a laser in the pilot hole step.
According to this embodiment, since the electrode is guided to the pilot hole with high straightness by performing the pilot hole processing with laser processing with particularly high straightness, it is possible to perform pore processing with higher straightness.

According to an eighth aspect of the present invention, in any one of the first to seventh aspects, the electric discharge machining method further includes a positioning step for positioning the workpiece, and in the positioning step, A procedure for detecting a pilot hole of a workpiece by a visual device; a procedure for receiving detection data from the visual device and recognizing a workpiece position and a position of a pilot hole to be machined in the workpiece by a processing device; and the electrode or the workpiece Moving at least one of them in a plane perpendicular to the axis of the electrode, and positioning the workpiece with respect to the electrode.
According to the present embodiment, the pilot hole of the workpiece can be detected accurately, so that the positioning of the pilot hole of the workpiece can be performed automatically with high accuracy, and processing can be performed more quickly.

According to a ninth aspect of the present invention, in any one of the first to eighth aspects, the present invention is used for fine hole processing of a fuel injection nozzle.
According to this form, the application object of this invention is actualized more.

  Hereinafter, an apparatus according to a preferred embodiment of the present invention will be described in detail with reference to the drawings. 1 and 2 schematically show a first embodiment of an electric discharge machine capable of carrying out a high-precision micro-drilling method according to the present invention, and FIG. 1 shows an electric discharge according to the first embodiment. FIG. 2 is an explanatory view showing a schematic configuration of the entire processing machine 10, and FIG. 2 is a partial view of the vicinity of the discharge head of the electric discharge machine 10 of FIG. In the present embodiment, the electric discharge machine 10 performs a process of making an injection hole in a fuel injection nozzle for a vehicle engine as the work 3.

  Referring first to FIG. 1, an electric discharge machine 10 according to a first embodiment of the present invention is shown. The electric discharge machine 10 includes an electric discharge head 1 and an electrode 2 attached thereto. In addition, workpieces 3 to be machined are installed and arranged on the same straight line. The electric discharge machine 10 further includes a visual device 5 that detects a prepared hole, an image processing device 6, and an XY table 8 that corrects the position of the workpiece 3. Further, in the present embodiment, a vibration device 11 for applying vibration to the electrode 2 is preferably installed in the discharge head 1 on the electrode side. This state is shown in FIG. It may be installed in the part. The vibration device 11 may be a vibration method known to those skilled in the art, such as a piezo method, a voice coil method, and a cam type piston method. The electric discharge machine 10 further includes a discharge power source 7 for supplying a current to the electrode 2 and a machining liquid nozzle 4 for injecting a machining liquid 14. The positive terminal of the discharge power supply 7 is connected to the electrode 2, and the negative terminal is connected to the work 3. The workpiece 3 is held by a chuck of the base part 13, and the base part 13 is installed on the XY table 8. As shown in FIG. 3, a jig (cap 17) for sealing the drilled hole is installed on the work 3.

In the above configuration, processing of the pores by the electric discharge machine 10 will be described.
First, by a laser processing with particularly high straightness, a pilot hole processing that is preferably 10 to 50 μm smaller than the target hole diameter is performed. As a result, since the electrode 2 is guided in the lower hole, in order to obtain the straightness of the hole, the straightness of the prepared lower hole is important. Therefore, it is possible to finish the hole with higher straightness. . Next, the pre-drilled hole is detected by the visual device 5 at the position of the dotted line in FIG. 1 and the position is recognized by the image processing device 6. The XY table 8 is operated so that the discharge head 1 and the electrode 2 are at the positions, and the position of the work 3 mounted on the pedestal 13 is corrected to the position of the solid line. Thereafter, a discharge pulse is applied between the electrode 2 and the work 3 from the discharge power source 7, and the electrode 2 is brought close to the work 3 to discharge. At that time, if necessary, the machining fluid 14 is sprayed from the machining fluid nozzle 4 onto the workpiece 3 to pour machining waste. During discharge from the electrode 2, electric discharge machining is performed while the electrode 2 is vibrated by the vibration device 11. At this time, only vibration along the electrode axis direction is applied to the electrode 2. Since the discharge gap is usually about 5 μm, the condition for applying vibration is a condition that promotes a short circuit, and the amplitude needs to be greater than or equal to the discharge gap, preferably 5 to 30 μm. However, if only the vibration along the electrode axis direction is not given, the vibration will increase greatly, so care must be taken when applying the vibration.

  In the present embodiment, the short-circuit rate between the electrode 2 and the workpiece 3 is preferably 20 to 40 by performing an operation such as increasing the electrode feed speed or delaying the electrode pull-back timing as compared with the normal electrode control method. By performing the processing using a control method (control of short circuit) of about%, the ratio of the electrode 2 in contact with the prepared hole increases. Here, a short circuit rate means the ratio of the time when the electrode and the work are short-circuited (contacted) with respect to the time during which electric discharge machining is performed. Differences between the electrode control method of the present embodiment and the conventional electrode control method will be described with reference to FIGS. FIG. 6 shows a state of fine hole machining by a conventional electric discharge machining method when a pilot hole cannot be formed. The electrode 2 approaches the workpiece 3 while being vibrated in the lateral direction due to the previous discharge explosion or the like. When the electrode 2 approaches the work 3 sufficiently, if the side surface of the electrode 2 also approaches the work 3 due to lateral vibration and a discharge explosion occurs, the lateral vibration of the electrode 2 is further amplified by the discharge explosion. When such discharge explosion is repeated, the lateral vibration (vibration) of the electrode 2 increases. Therefore, the machining hole becomes large as indicated by a dotted line.

  FIG. 7 shows a state of pore machining by a conventional electric discharge machining method when a pilot hole is drilled. The electrode 2 approaches the workpiece 3 while still vibrating in the lateral direction due to the previous discharge explosion or the like. When the electrode 2 is sufficiently close to the workpiece 3 to cause a discharge explosion, the lateral vibration of the electrode 2 is further amplified by the discharge explosion. When such a discharge explosion is repeated, the lateral vibration of the electrode 2 becomes large, so that the machining hole becomes large as shown by a dotted line.

  FIG. 5 shows a state of pore machining by the electric discharge machining method according to the present embodiment described above when a pilot hole is drilled. The electrode 2 approaches the workpiece 3 while still vibrating in the lateral direction due to the previous discharge explosion or the like. The electrode 2 is sufficiently close to the workpiece 3 and discharges and explodes. At this time, the short-circuit time in which the electrode 2 is in contact with the workpiece 3 is long, so that the lateral vibration (vibration) of the electrode 2 is suppressed by the workpiece 3. Therefore, in the state where the electrode 2 is separated from the workpiece 3, although there is a lateral vibration, it is suppressed to be smaller than the conventional example shown in FIGS. By performing such electrode control, every time the electrode 2 vibrates due to a discharge explosion, the electrode 2 comes into contact with the pilot hole and is guided, and expansion of lateral vibration (vibration) of the electrode 2 can be suppressed.

  As described above, the machining liquid 14 is sprayed onto the workpiece 3 as necessary during the electric discharge machining. At this time, the entire machining liquid 14 is sucked from the prepared hole by a suction device (not shown), so that bubbles are released from the prepared hole. The rate of exit increases. Thereby, bubbles passing through the side surface of the electrode are reduced, and the deflection of the electrode can be suppressed. The suction effect of the machining fluid will be described with reference to FIG. FIG. 8A shows a state of supplying the machining fluid of the conventional example. In the case of the conventional example, as shown in FIG. 8A, the flow of the machining liquid 14 flows into the main hole (finished hole) 21 and overflows from the main hole 21 rather than toward the narrower lower hole 22. A lateral flow is formed. Since the bubbles 15 also flow in the lateral direction together with the machining liquid 14, the electrode 2 receives a lateral force due to the fluid force of the machining liquid 14 and the bubbles 15, thereby amplifying the lateral vibration of the electrode 2.

  On the other hand, FIG. 8B shows the case of this embodiment. In FIG. 8B, the processing liquid 14 is sucked from the direction of the lower hole 22 by an absorption device (not shown), and thus flows into the main hole 21 and almost flows in the direction of the lower hole 22. At this time, the bubbles 15 also flow out through the prepared holes 22 together. Accordingly, the fluid force of the machining liquid 14 and the bubbles 15 acts as an axial force on the electrode 2, so that the machining liquid 14 having a flow through the electrode side surface also has an electrode guide effect. By the suction of the machining liquid of the present embodiment, no lateral vibration is applied to the electrode 2. The suction device may be a variety of suction devices known to those skilled in the art.

  In the present embodiment, the fuel injection nozzle that is the work 3 is usually provided with a plurality of holes. Since the hole finished by electric discharge (main hole) is larger than the lower hole, the machining liquid flows more easily in the hole finished normally. Therefore, as the machining progresses and the number of discharge finish holes increases, the attractive force decreases, and the effect of suppressing the deflection of the electrode diminishes. Therefore, as a countermeasure, a jig for sealing the already opened hole is required. In the present embodiment, a cap 17 shown in FIG. 3 is attached to the workpiece 3 as a jig for sealing the hole. As shown in FIG. 3, the cap 17 has a groove only in the processed portion, and the shape of the cap 17 is a female tip having a workpiece tip shape. Therefore, when the cap 17 is attached to the workpiece 3, holes other than the hole to be processed are blocked. The cap 17 preferably uses a rubber material for the contact portion in order to completely seal the holes other than the target, but may be a metal seal. Even if the hole is not completely sealed, the inflow of the machining fluid can be sufficiently prevented.

  Referring to FIG. 4, a second embodiment of the present invention is shown. In the second embodiment of the present invention, in the first embodiment, the vibration device 12 is attached to the base portion 13 to vibrate the workpiece 3 in the axial direction of the electrode 2. Since the second embodiment is different from the first embodiment only in this configuration, the description of other configurations in the second embodiment is omitted.

  In the third embodiment of the present invention, in any of the first and second embodiments, the liquid machining fluid 14 is not supplied to the workpiece 3 in the electric discharge machining. In the present embodiment, electric discharge machining is performed in the air. Gas may be supplied from the nozzle 4 to the workpiece 3. In normal air, the discharge explosive power is lower than in liquid, and naturally no bubbles are generated. However, it is a problem that it is difficult to discharge the processing waste in the deep hole. In the present embodiment, as in the first embodiment, suction is performed by a suction device (not shown) from the prepared hole. By discharging the machining waste by this suction, deep-hole electrical discharge machining is performed. Thereby, it is possible to process the electrode with less deflection.

Next, effects and operations of the above embodiment will be described.
The following effects can be expected from the electric discharge machining method according to the first embodiment of the present invention.
・ Each time the electrode vibrates due to an electric discharge explosion, in addition to drilling the prepared hole by laser processing, which has a particularly high degree of straightness, the electrode is controlled by a short circuit to force the electrode to contact the workpiece. The electrode is guided by the pilot hole to suppress the expansion of the lateral vibration (vibration) of the electrode.
Further, by vibrating the electrode in the axial direction, the sludge discharge performance is improved, and the concentrated discharge is reduced, thereby suppressing the increase in electrode deflection.
-By sucking the machining liquid from the direction of the pilot hole, the machining liquid flows along the side surface of the electrode, thereby exhibiting an electrode guide effect.
・ When machining multiple holes of the fuel injection nozzle while sucking from the lower hole, cover the fuel injection nozzle to be processed with a cap in order to avoid strong suction through the already finished holes. Then, the already processed hole that hinders suction is sealed to prevent weakening of the processing liquid from the processed lower hole, thereby preventing the effect of suppressing the vibration of the electrode from diminishing.
-Due to the above effects, it is possible to perform highly accurate pore processing with higher straightness and, for example, 5 to 10 [mu] m smaller than conventional ones.

With the electric discharge machining method according to the second embodiment of the present invention, the following effects can be expected.
-By vibrating the workpiece in the axial direction of the electrode, the sludge discharge performance is also improved, and the increase in electrode deflection can be suppressed by reducing the concentrated discharge.

The following effects can be expected from the electric discharge machining method according to the third embodiment of the present invention.
-By performing deep-hole electric discharge machining in the air and further sucking in from the direction of the lower hole, it is possible to machine with less electrode deflection without deteriorating sludge discharge.

In the above description, the electric discharge machining method for machining high-precision pores of the present invention was used for drilling a fuel injection nozzle of an engine. However, the present invention is not limited to this, and machining of a device different from this is performed. May be used.
Further, in the embodiment described above or shown in the accompanying drawings, the positioning of the electrode with respect to the workpiece is performed by positioning the base portion holding the workpiece with the XY table. A positioning mechanism may be provided.

  In the above description, the pilot hole is described as being drilled by laser processing. However, the present invention is not limited to this, and the pilot hole may be drilled by another processing method such as electroforming. good.

  The above-described embodiment is an example of the present invention, and the present invention is not limited by the embodiment, but is defined only by matters described in the claims, and other embodiments than the above are also possible. It can be implemented.

FIG. 1 is an explanatory diagram showing an overall schematic configuration of a first embodiment of an electric discharge machine capable of performing high-precision fine hole machining by an electric discharge machining method according to the present invention. FIG. 2 is a partial explanatory view of the vicinity of the discharge head of the electric discharge machine shown in FIG. 1, and shows the vibration device according to the first embodiment. FIG. 3 is an explanatory diagram of the cap mounted on the workpiece in the first embodiment. FIG. 4 is a partial explanatory view of the vicinity of the base portion on which the vibration device according to the second embodiment is mounted. FIG. 5 is an explanatory diagram illustrating a state of pore machining by short-circuiting electrode control in the electric discharge machining method according to the first embodiment. FIG. 6 is an explanatory diagram showing a state of pore machining by the electric discharge machining method of the conventional example when the pilot hole is not drilled. FIG. 7 is an explanatory view showing a state of pore machining by the conventional electric discharge machining method when a pilot hole is drilled. FIG. 8 is an explanatory view of the effect when the machining liquid is sucked from the pilot hole. The conventional case (A) without suction and the case (B) of the first embodiment of the present invention with suction are compared. ing. FIG. 8 is an explanatory view of the effect when sucked from the pilot hole in the air-discharge machining, and shows the conventional case (A) without suction and the case (B) of the third embodiment of the present invention with suction. Comparing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Discharge head 2 Electrode 3 Workpiece 4 Work fluid nozzle 5 Visual device 6 Image processing device 7 Discharge power supply 8 XY table 10 Electric discharge machine 11 Vibrating device 13 Base part 14 Work fluid

Claims (9)

In the electric discharge machining method for opening pores in the workpiece, this electric discharge machining method is:
A pilot hole process for drilling a pilot hole;
A machining step for generating a hole between the electrode and the workpiece to form a hole;
It has
In the processing step,
An excitation procedure for vibrating either the electrode or the workpiece;
A machining fluid supply procedure for supplying the machining fluid to the workpiece;
It has
The pilot hole is a hole extending in the axial direction of the electrode,
In the excitation procedure,
Each time the electrode vibrates due to a discharge explosion, short-circuit electrode control is performed in which the electrode contacts and guides the pilot hole, and the vibration direction of either the electrode or the workpiece is the electrode In the machining fluid supply procedure, the machining fluid is sucked from the direction of the pilot hole,
An electric discharge machining method, wherein a suction direction of the machining fluid coincides with an axial direction of the electrode.   2. The electric discharge machining method according to claim 1, wherein in the short-circuit electrode control, a short-circuit rate, which is a ratio of bringing the electrode into contact with the workpiece during electric discharge machining, is in a range of 20% to 40%.   3. The electric discharge machining method according to claim 1, wherein an amplitude of the vibration of either the electrode or the workpiece is in a range of 5 to 30 μm.   The electric discharge machining method according to claim 1, wherein the machining fluid is a liquid.   The electric discharge machining method according to claim 1, wherein the machining fluid is a gas.   In the processing step, a procedure for attaching a cap to the workpiece is further provided, and the cap has a female shape that matches the male shape when the shape of the workpiece is a male shape. 2. The apparatus according to claim 1, wherein the cap can be mounted so as to be in contact with a workpiece, and when the cap is mounted on the workpiece, only the portion of the processing hole is opened to be processed. The electric discharge machining method according to claim 5.   The electric discharge machining method according to any one of claims 1 to 6, wherein the pilot hole is formed by a laser in the pilot hole step. The electric discharge machining method further includes a positioning step of positioning the workpiece,
In the positioning step,
A procedure for detecting a pilot hole in the workpiece with a visual device;
A procedure of receiving detection data from the visual device and recognizing a workpiece position and a position of a pilot hole to be machined in the workpiece by a processing device;
A step of positioning at least one of the electrode and the workpiece in a plane perpendicular to the axis of the electrode to position the workpiece with respect to the electrode;
The electric discharge machining method according to any one of claims 1 to 7, further comprising:   The electric discharge machining method according to claim 1, wherein the electric discharge machining method is used for machining a fine hole of a fuel injection nozzle.

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