JP2007211351A - Method of forming valve seat coating film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming a valve seat coating film, which speeds up overall processing operation for forming a valve seat coating film on a valve seat part of a cylinder head using discharge energy and can be applied to mass production. <P>SOLUTION: A green compact electrode 25 for forming the valve seat coating film is rotated to intermittently induce dielectric breakdown between itself and the valve seat part 102, the discharge energy generated thereby is used to melt a green compact component of the green compact electrode 25 for forming the valve seat coating film, and the green compact component is reacted with carbon atoms in a machining fluid 24 in an electric discharging tank 23 to produce a hard carbide which is transferred and laminated onto the valve seat part 102. By rotating the green compact electrode 25 for forming the valve seat coating film, the carbide can be uniformly laminated on different sites of the valve seat part 102 so that a process for forming the coating film can be stabilized and that settings of working voltage or current, pulse width, duty ratio, etc. can be increased compared to those in conventional technology. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention improves the valve seat film forming method, specifically, speeds up the processing operation for forming a valve seat film instead of the valve seat ring on the valve seat portion of the cylinder head using discharge energy as a whole. , Relating to improvements for application as mass production technology.

  Conventionally, a valve seat ring made of a different member from the cylinder head has been press-fitted and attached to the valve seat portion of the cylinder head, and this valve seat ring has generally secured confidentiality around the valve. Some prior arts have the disadvantage that the valve seat ring interferes with heat conduction, causing an excessive temperature rise in the valve, and this temperature rise prevents normal ignition of the engine. .

  In view of this, Patent Document 1 has already proposed a technique that avoids the use of a valve seat ring composed of a member different from the cylinder head and that applies laser beam machining to the valve seat portion.

  However, in order to build up the valve seat portion by using laser processing, it is necessary to irradiate the laser with a large energy laser beam circulating around the annular valve seat portion. As a result, the laser beam irradiation start position (machining start point) overlaps with the laser beam irradiation end position (machining end point), and the energy irradiated to this overlapping portion is from other parts of the valve seat portion. As a result, the thickness of the entire overlay is not constant, and there is a possibility that problems such as pressure leakage may occur.

  Strictly speaking, immediately after the start of laser light irradiation, laser light is continuously irradiated in time series to each location adjacent to the circumferential direction of the valve seat portion. Is accumulated cumulatively in the vicinity of the valve, so that even if the intensity of the laser beam is kept constant, the amount of energy supplied to each part of the valve seat will gradually increase in time series There is. Such a change in the energy amount is continuous. Therefore, as described above, although the difference in temperature between the portions adjacent to each other in the circumferential direction of the valve seat portion is slight, the laser light is circulated in the annular valve seat portion. Therefore, the difference between the temperature at the start of processing and the temperature at the end of processing cannot be ignored.

  Therefore, in order to solve the above-mentioned problems, the present applicants have repeatedly studied the configuration of the valve seat portion instead of the overlay using the valve seat ring and laser processing, and using the discharge energy, the valve seat ring and the laser Patent Document 2 proposes a valve seat film forming technique in which a valve seat film is formed in place of the build-up using the above.

  Briefly speaking, this valve seat film formation technology is intermittent dielectric breakdown between the two while maintaining a predetermined discharge gap between the green electrode for forming the valve sheet film and the valve seat part of the cylinder head. The green powder component of the green compact electrode for forming the valve seat film is melted by the discharge energy generated at this time, and further reacted with carbon atoms in the working fluid in the electric discharge machining tank to produce hard carbides. Then, a valve seat film is formed on the surface of the valve seat portion by transferring and laminating to the valve seat portion.

  The green compact electrode for valve seat film formation used at this time is shown in FIG. The green compact electrode 100 for forming the valve seat film includes a green compact electrode portion 103 having an outer peripheral shape (tapered surface) following the shape of the valve seat portion 102 formed on the cylinder head 101 side, and an electric discharge machine. And a conductive support member 104 for energizing the green compact electrode portion 103 from the servo head.

  The conductive support member 104 is a cylindrical body formed of copper or the like, and the green compact electrode portion 103 is a hollow annular body, and the upper surface of the green compact electrode portion 103 is electrically connected to the distal end surface of the conductive support member 104. The two are substantially integrated by bonding with the adhesive 105.

  In the green compact electrode 100 for forming the valve seat film, the green compact electrode portion 103 is formed into a hollow annular body, so that the material of the green compact component can be saved. Since the adhesion surface with the powder electrode portion 103 becomes slight, there is a problem that the green compact electrode portion 103 falls off from the front end surface of the conductive support member 104 during processing. As a result, it is difficult to continuously perform the film forming operation. As a result, the processing operation as a whole is delayed, which is inconvenient for mass production of cylinder heads.

  Therefore, the present applicants further developed a green compact electrode 106 for forming a valve seat film as shown in FIG.

  The green compact electrode 106 for forming the valve seat film includes a green compact electrode portion 103 having an outer peripheral shape (tapered surface) following the shape of the valve seat portion 102, and a green compact electrode from the servo head of the electric discharge machine. 6 is the same as that of FIG. 6A in that it comprises a conductive support member 107 for energizing the portion 103, but a reduced diameter portion 107a is formed at the tip of the conductive support member 107, and a green compact is formed. A conductive adhesive 105 is used to bond the upper surface of the electrode portion 103 and the distal end surface of the conductive support member 107, and the inner peripheral surface of the green compact electrode portion 103 and the outer peripheral surface of the reduced diameter portion 107a. Due to the improvement, the problem that the green compact electrode portion 103 dropped from the conductive support member 107 during processing was solved.

  As a result, it seemed that it was possible to continue the film forming operation continuously. However, when the film forming operation was actually performed, as shown in FIG. Dielectric breakdown may occur between the outer peripheral portion of the reduced diameter portion 107a of the conductive support member 107 and the valve seat portion 102 before the portion between the powder electrode portion 103 and the valve seat portion 102. It has been found that film formation by the green compact component may be inhibited.

  Further, when the green compact electrode portion 103 is consumed due to the continuation of a certain work or more, as shown in (b) of FIG. 6B, the outer periphery of the distal end of the reduced diameter portion 107a of the conductive support member 107 This causes a serious problem that frequent discharge occurs between the valve portion and the valve seat portion 102 or the port 108.

  For this reason, even if the omission of the green compact electrode part 103 is eliminated, the same green compact electrode 106 for forming a valve seat film cannot be used continuously. That is, the portion of the green compact electrode portion 103 must be frequently replaced, the adhesive 105 applied to the conductive support member 107, the green compact electrode portion 103 adhered to the conductive support member 107, and the adhesive 105. However, there is a drawback that the set-up work such as the heat curing process is complicated, a delay occurs in the entire processing operation, and it is not suitable for mass production of the cylinder head.

  In addition to the above, the present inventors have conceived the following two points as the cause of difficulty in mass production of a cylinder head to which this kind of film forming technology is applied.

  First of all, there is an attachment structure of a compact electrode for forming a valve seat film to a servo head of an electric discharge machine.

  This type of film formation technology is carried out using an ordinary die-sinking electric discharge machine, but the electrode attachment structure of the die-sinking electric discharge machine is composed of an electrode holder that is detachably attached to the servo head, such as copper. An electrode formed of a nonmagnetic material is attached to the servo head via an electrode holder. The attachment of the electrode to the electrode holder is generally realized by a substantially L-shaped electrode receiver and two fixing bolts provided on the electrode holder, but the operation of attaching the electrode to the electrode holder itself is complicated. This poor setup increases the delay in processing operations as a whole.

  Another cause of the difficulty in mass production of cylinder heads to which the film forming technology is applied is that the green compact component of the green compact electrode for forming the valve seat film is melted by the discharge energy, It is in the process of forming a film itself, which reacts with carbon atoms in the working fluid to form hard carbide, which is transferred to the valve seat and laminated.

  In other words, the pulse power supply for machining used to form the film can be used directly for the electrical discharge machine, and the machining voltage, machining current, pulse width, duty ratio, etc. can be set freely. However, for example, if the pulse width is set to be long in order to increase the film formation speed, there arises a problem that the surface roughness of the film becomes rough, and it is very difficult to achieve both the film formation speed and accuracy. That is, in order to improve the surface roughness, the processing speed is slow, and naturally the processing operation as a whole is delayed.

  In normal electric discharge machining, which is a type of removal machining, the power supply conditions for roughing and the power supply conditions for finishing are individually set by the NC device, and high power removal machining is performed at the initial stage of machining. It is possible to clean the remaining machining allowance under the power supply conditions for finishing, but when forming a film using discharge energy, the film surface becomes rough or uneven at the initial stage. If this is the case, these roughnesses and irregularities remain as undulations or shape errors until the end, so that it is not possible to perform rough machining in the initial stage to shorten the time required for machining. In other words, even if the electric discharge machining technique is applied as it is, it is impossible to achieve both film formation speed and accuracy.

Japanese Patent No. 2964819 JP 2002-242621 A

  Therefore, the problem of the present invention is to improve the problems of the above-described conventional technology, speed up the processing operation for forming the valve seat film on the valve seat portion of the cylinder head using discharge energy as a whole, and as mass production technology An object of the present invention is to provide a valve seat film forming method which can be applied.

The valve seat film forming method of the present invention is a valve seat film forming method for forming a valve seat film instead of a valve seat ring of a cylinder head on a valve seat part of a cylinder head using discharge energy. Therefore, the dielectric breakdown is intermittently excited between the outer peripheral shape and the valve seat portion while rotating the green electrode for forming the valve seat film having the outer peripheral shape following the shape of the valve seat portion. The green compact component of the green compact electrode for forming the valve seat film is melted by the discharge energy generated during the reaction, and reacts with the carbon atoms of the machining fluid in the electric discharge machining tank to form hard carbides that are transferred to the valve seat. It has a structure characterized by being laminated by wearing.

Since the dielectric breakdown is intermittently excited between the valve seat part while rotating (rotating) the green electrode for forming the valve seat film, carbide is laminated on each part of the valve seat part on average. Since the film formation process is stabilized, even if the conditions such as machining voltage, machining current, pulse width and duty ratio are set higher than before, the same surface roughness and shape error as before can be achieved. Can be guaranteed.
That is, the film formation process can be speeded up while maintaining the same accuracy as before, and the overall processing operation is speeded up. As a result, mass production of cylinder heads has become possible.
Further, if the time required for the processing operation as a whole can be the same as that of the prior art, it is possible to obtain surface roughness and shape accuracy higher than those of the prior art when forming the valve seat film.

  Further, the green electrode for forming a valve seat film having an outer peripheral shape following the inclined surface of the valve seat portion is rotated (spinned), and a predetermined discharge gap is formed between the outer peripheral shape and the inclined surface of the valve seat portion. While maintaining the revolution of the green electrode for forming the valve seat film, the dielectric breakdown is intermittently excited between the outer peripheral shape and the valve seat portion, and the valve seat film is generated by the discharge energy generated at this time. The green compact component of the green compact electrode for forming is melted and reacted with carbon atoms in the machining fluid in the electric discharge machining tank to form hard carbides that are transferred to the valve seat and laminated. Good.

By revolving the compacted electrode for forming the valve seat film, even if the compacted electrode for forming the valve seat film with a small diameter is used, it is between the inclined surface of the valve seat part having a larger diameter. It is possible to form a bulb seat film while discharging while maintaining a constant discharge gap. At this time, since the green compact electrode for forming the valve seat film is rotating (spinning), there is no fear that the green compact component of the electrode is partially consumed. Carbide can be averaged to form a precise valve seat film.
In other words, as long as the slopes of the slopes of the valve seats are the same, the valve seats with respect to the valve seats of the cylinder heads having different specifications (different diameters) can be used without replacing the green electrode for forming the valve seat film A film can be formed, the time required for setup work related to electrode replacement is shortened, and the overall processing operation is speeded up.

  In the valve seat film forming method of the present invention, the dielectric breakdown is intermittently excited between the valve seat portion while rotating the green compact electrode for forming the valve seat film, and the valve seat film is formed by the discharge energy generated at this time. In addition to melting the green compact component of the green compact electrode, it reacts with the carbon atoms of the machining fluid in the electric discharge machining tank to produce hard carbides that are transferred to the valve seat and stacked. Therefore, by rotating the green compact electrode for forming the valve seat film, carbide can be averagely laminated at each location of the valve seat portion to stabilize the film forming process. As a result, even if conditions such as machining voltage, machining current, pulse width, and duty ratio are set on the higher power side than before, it is possible to guarantee the same surface roughness and shape error as before. It is possible to speed up the film forming process while maintaining the same accuracy, speed up the overall processing operation, and achieve mass production of cylinder heads. (If the time required for the processing operation as a whole is the same as that of the prior art, it is possible to obtain surface roughness and shape accuracy higher than those of the prior art.)

  Further, by rotating and revolving the green compact electrode for forming the valve seat film, it is also possible to form the valve seat film on the valve seat portion having a large diameter with the small compact diameter electrode for forming the valve seat film. As long as the slope of the slope of the valve seat part matches, the valve seat film can be formed on the valve seat part of the cylinder head having a different specification without replacing the green compact electrode for forming the valve seat film. It is possible to shorten the time required for the setup work related to the replacement of the electrodes, and to further speed up the overall work flow related to the formation of the valve seat film.

  Hereinafter, some embodiments of the present invention will be described in detail with reference to the drawings.

  First, the structure of the green compact electrode for valve seat film formation will be described.

  FIG. 1A is a cross-sectional view illustrating the structure of the green compact electrode 1 for forming a valve seat film.

  The green compact electrode 1 for forming the valve seat film includes a green compact electrode portion 2 having an outer peripheral shape (tapered surface) following the shape of the valve seat portion 102 formed on the cylinder head 101 side, and an electric discharge machine. Conductive support member 3 for energizing the green compact electrode portion 2 from the servo head, and non-conductive support that is substantially integrated with the conductive support member 3 and protrudes from the tip of the conductive support member 3 It is comprised by the member 4.

  The non-conductive support member 4 is made of ceramics having an electrical insulating function, and is fixed to the hole 3a formed at the center of the copper conductive support member 3 so as to be substantially the same as the conductive support member 3. It is integrated with.

  In addition, a hole 5 is formed at the center of the green compact electrode portion 2, and the green compact electrode portion 2 is electrically conductively bonded with the hole 5 fitted to the tip of the non-conductive support member 4. The agent 105 is fixed to the distal end surface 3 b of the conductive support member 3 and the outer peripheral surface 4 a of the nonconductive support member 4 by the agent 105.

  In this way, the green compact electrode portion 2 is fixedly supported by the distal end surface 3 b of the conductive support member 3 and the outer peripheral surface 4 a of the nonconductive support member 4 integrated with the conductive support member 3. Therefore, the mounting strength of the green compact electrode part 2 with respect to the conductive support member 4 is increased, and partial chipping of the green compact electrode part 2 is prevented in advance, and the green compact is formed during the formation of the valve seat film. The problem that the body electrode part 2 falls off from the conductive support member 4 does not occur.

  Further, since the non-conductive support member 4 fitted in the hole 5 in the central portion of the green compact electrode portion 2 is an insulator that does not conduct electricity, as shown in FIG. Unlike the case, no dielectric breakdown occurs between the outer peripheral portion of the tip of the non-conductive support member 4 and the valve seat portion 102 during film formation. Even when the servo feed is performed with a constant gap while the tip of the non-conductive support member 4 is exposed and the tip of the non-conductive support member 4 enters the port 108 even when the tip of the non-conductive support member 4 is exposed, FIG. Unlike the case shown in (b) of (b), there is no fear that abnormal discharge occurs between the nonconductive support member 4 and the valve seat portion 102 or the port 108.

  Therefore, even if the green compact electrode 1 for forming the valve seat film is not frequently replaced, abnormal discharge is prevented and the process of forming the film with the green compact component of the green compact electrode part 2 is stably continued. As a result, the processing operation as a whole can be speeded up, and mass production of cylinder heads becomes possible.

  FIG. 1B is a cross-sectional view showing the structure of another green compact electrode 6 for forming a valve seat film that can be used in place of the green compact electrode 1 for forming a valve seat film.

  The green compact electrode 6 for forming the valve seat film includes a green compact electrode portion 7 having an outer peripheral shape (tapered surface) following the shape of the valve seat portion 102 formed on the cylinder head 101 side, and an electric discharge machine. A conductive support member 8 made of copper or the like for energizing the green compact electrode portion 7 from the servo head, and a reduced diameter portion 9 formed by cutting the outer periphery of the end of the conductive support member 8 by lathe processing or the like. It consists of and.

  A non-conductive film 10 made of polymer coating or the like is formed on the outer peripheral portion and the front end surface of the reduced diameter portion 9, and the reduced diameter portion 9 is electrically insulated from the outside. A combination of the reduced diameter portion 9 and the nonconductive film 10 is a nonconductive support member 11.

  Similar to that shown in FIG. 1A, the powder electrode portion 7 is formed by the conductive adhesive 105 with the hole 12 fitted in the nonconductive support member 11 and the front end surface of the conductive support member 8. 8b and the outer peripheral surface 11a of the non-conductive support member 11 are fixed.

  The difference from the one shown in FIG. 1A is that the non-conductive support member 11 is formed by using a part of the conductive support member 8. Since the non-conductive support member 11 can be formed by a simple operation of turning and coating the non-conductive film 10, the material cost required for manufacturing the green compact electrode 6 for forming the valve seat film is required. There is an advantage that manufacturing costs can be reduced.

  The other points are the same as those of the green electrode 1 for forming a valve seat film shown in FIG.

  In the above, an example in which the cylinder head is mass-produced by speeding up the overall processing operation by extending the substantial service life of the compacted electrode for forming the valve seat film and reducing the number of electrode replacements has been described. It was.

  Next, an example will be described in which cylinder heads are mass-produced by speeding up the overall processing operation by reducing the time required for the setup work required to replace the compacted electrode for forming the valve seat film.

  FIG. 2 (a) is a side view showing the structure of another green compact electrode 13 for forming a valve seat film, and FIG. 2 (b) is a manufacturing process of the green compact electrode 13 for forming a valve seat film. It is the schematic diagram simplified and shown.

  The green compact electrode 13 for forming the valve seat film includes a green compact electrode portion 14 having an outer peripheral shape (tapered surface) following the shape of the valve seat portion 102 formed on the cylinder head 101 side, and an electric discharge machine. And a conductive support member 15 for energizing the electromagnetic chuck provided in the servo head with the green compact electrode portion 14 attached thereto.

  The manufacturing process of the green compact electrode 13 for forming the valve seat film is as shown in FIG. 2B. First, the green compact molding die 16 for molding the green compact electrode 13 for forming the valve seat film is shown. Is prepared in advance, and a green compact 14 ′ for forming the green compact electrode portion 14 is introduced into the green compact molding die 16, and further laminated on the green compact 14 ′. After introducing the magnetic powder 15 ′ for forming the conductive support member 15, a piston-like pressing member 17 is fitted into the green compact molding die 16 and pressed strongly.

  The green compact 14 ′ and the magnetic powder 15 ′ are integrated and solidified by this one molding process, and the green compact electrode for forming a valve seat film comprising the green compact electrode portion 14 and the conductive support member 15. 13 is formed. If the green compact electrode 13 for forming the valve seat film is taken out from the green compact molding die 16, the work of the molding process is completed.

  In this example, a mixture of metal powders shown in Table 1 was used as the green compact 14 ′ for forming the green compact electrode portion 14, and ordinary iron powder was used as the magnetic powder 15 ′.

  FIG. 3 is a schematic diagram showing a simplified structure of a main part of a die-sinking electric discharge machine used when forming a valve seat film using the green compact electrode 13 for forming a valve sheet film.

  The servo head 18 is fixed to the column portion of the electric discharge machine, and a pulse power supply 19 for machining based on machining conditions such as machining voltage, machining current, pulse width and duty ratio set by an NC device (not shown). Is supplied with electric power, and the green compact electrode 13 for forming the valve seat film is energized through the electrode holder 20 and the electromagnetic chuck 21.

  The electromagnetic chuck 21 itself is detachably fixed to the electrode holder 20 by a fixing bolt or the like like a conventional electrode for electric discharge machining, but the green compact electrode 13 for forming the valve seat film solidifies iron powder. Since the conductive support member 15 is formed, the valve seat film is formed on the electromagnetic chuck 21 by a simple operation of turning on / off the magnetized state of the electromagnetic chuck 21 while the electromagnetic chuck 21 is mounted on the electrode holder 20. The attaching / detaching operation of the green compact electrode 13 can be performed, and no operation is required for the electrode holder 20 itself.

  Since the electrode holder 20 is constituted by an electrode holder, a fixing bolt or the like as already described, and has a structure capable of dealing with electrodes for electric discharge machining having various shapes and sizes, these electrodes are used. If a receiver, a fixing bolt, etc. are used well, it is not necessary to design and manufacture a special one as the electromagnetic chuck 21, and the electromagnetic chuck 21 diverted from a commercially available product can be mounted on the electrode holder 20 as it is. .

  Further, the cylinder head 101 to be processed is discharged as shown in FIG. 3 with the valve seat portion 102 facing upward and facing the green compact electrode portion 14 of the green compact electrode 13 for forming the valve seat film. A pulse power source 19 is connected to the table 22 with a polarity opposite to that of the servo head 18 side.

  The green sheet electrode 13 for forming the valve seat film and the cylinder head 101 are insulated from each other by the machining fluid (oil) 24 filled in the electric discharge machining tank 23 covering the table 22.

  The servo head 18 is configured so that the separation distance between the tip of the compact electrode 13 for forming the valve seat film and the valve seat portion 102 of the cylinder head 101 to be processed becomes constant by an NC device (not shown). A vertical feed is applied to maintain the discharge gap at a constant value. This is a control method called servo feed in the field of electric discharge machining. Actually, feedback control of the Z-axis servo motor is performed so as to maintain the discharge current value at a predetermined set value. The discharge gap is maintained at a constant value.

  Further, when replacing the green compact electrode 13 for forming the valve seat film, the column itself is retracted upward by a jog feed command or the like from the manual control device, and a sufficient working space is secured in the vertical direction to form the valve seat film. It is possible to replace the working green compact electrode 13.

  Here, the difference from the conventional electrode replacement work will be described with reference to FIG.

  When the conventional green compact electrode 106 for forming a valve seat film as shown in FIG. 6 (b) is used, it is usually necessary to replace the electrode because the cost of the conductive support member 107 made of copper is high. This is done by replacing only the green compact electrode portion 103.

  Therefore, as shown in FIG. 4, the steps required for this electrode replacement operation are a forming step of the green compact electrode portion 103 (required time t 1) and a step of applying the adhesive 105 to the conductive support member 107 ( The required time t2), the step of bonding the green compact electrode part 103 to the tip of the conductive support member 107 (the required time t3), and the heat curing for heating the adhesive 105 to exhibit practical strength Step (required time t4), and further, the green compact electrode 106 for forming the valve seat film composed of the green compact electrode portion 103 and the conductive support member 107 integrated by bonding is mounted on the electrode holder of the electric discharge machine. There are five steps of the mounting step (required time t5).

  On the other hand, as shown in FIG. 4, the steps required for the electrode replacement work when the green compact electrode 13 for forming the valve seat film is used are as follows. There are only two steps: a molding step for integrally molding the green compact electrode 13 for forming the sheet coating and a mounting step for mounting the green compact electrode 13 for forming the valve seat coating to the electromagnetic chuck 21 of the electric discharge machine.

  Among these, as described above, the compacting process of the compacting electrode 13 for forming the valve seat film is performed by pressing the compact 14 'and the magnetic powder 15' into a single compacting mold 16 and pressurizing. Therefore, the required time is substantially the same as the forming process (required time t1) when the green compact electrode portion 103 is formed by applying the conventional technique.

  In addition, in the mounting process of the compact electrode 13 for forming the valve seat film, it is not necessary to mount the compact electrode 13 for forming the valve seat film on the electrode holder 20 using a fixing bolt or the like. It is only necessary to switch the magnetized state on the electromagnetic chuck 21 side to ON / OFF while attaching the electromagnetic chuck 21 to the valve seat film forming powder electrode 13, so that the mounting process (required time t 5 ′) is required. ) Is much shorter than the mounting process (required time t5) in the prior art.

  As described above, according to the green compact electrode 13 for forming the valve seat film, even when the green compact electrode 13 for forming the valve seat film is replaced with the same frequency as before, an adhesive application process (required) The time t 2), the bonding step (required time t 3), and the heat curing step after bonding (required time t 4) can be omitted completely, and the green compact electrode 13 for forming the valve seat film is attached to the electromagnetic chuck 21. The mounting process (required time t5 ′) can be performed much more quickly than the conventional electrode mounting process (required time t5) that is performed on the electrode holder 20 using a fixing bolt or the like. Therefore, the overall time required for electrode replacement, in other words, the downtime of the electric discharge machine can be greatly reduced compared to the conventional one, and the overall processing operation is speeded up so that mass production of cylinder heads can be achieved. Can be realized.

  In the prior art as shown in FIG. 6B as well, an adhesive application step is performed by preparing a large number of green compact electrodes 106 for forming a valve seat film in advance and replacing the entire electrodes 106 one after another. (Required time t2), Adhesion process (Required time t3), Heat-curing process after adhesion (Required time t4) can be omitted to shorten the required time for electrode replacement work. Even when the green compact electrode 13 is used, if a large number of green compact electrodes 13 for forming the valve seat film are prepared in advance, the same can be realized.

  In any case, the electrode mounting process is necessary, and the electrode mounting process (required) when using the green electrode 13 for forming the valve seat film as compared with the electrode mounting process (required time t5) in the prior art. Since the time t5 ′) is shorter, even when a large number of electrodes are prepared in advance, in order to speed up the processing operation as a whole, the green compact electrode 13 for forming the valve seat film is used. It is much more advantageous to use

  Further, when the green compact electrode 13 for forming the valve seat film is used, it is necessary to prepare a large number of conductive support members 107 made of expensive copper, unlike the conventional example as shown in FIG. Since the conductive support member 15 manufactured at a low cost by compacting using a magnetic powder 15 ′ such as iron powder can be used, the manufacturing cost of the compact electrode 13 for forming a valve seat film is not required. There is a merit that itself is reduced.

  In order to obtain the maximum working efficiency, several green sheet electrodes 13 for forming a valve seat film manufactured as described above are prepared in advance, and for forming a valve sheet film one after another according to the consumption of the electrodes. It is only necessary to replace the green compact electrode 13, and the time required for setup, that is, the processing stoppage time, is changed at most by switching the magnetization state of the electromagnetic chuck 21 and compacting powder for film formation. Only the required time t5 ′ required to replace the body electrode 13 is obtained.

  Next, the valve seat film forming method of the present invention is applied to rotate (spin) the green electrode for forming the valve seat film to relatively speed up the formation process of the valve seat film as a whole. An embodiment will be described in which the processing operation is speeded up to achieve mass production of cylinder heads.

  FIG. 5A is a conceptual diagram showing a valve seat film forming method according to an embodiment. As the green electrode 25 for forming the valve seat film, the green electrode for forming the valve seat film as shown in FIG. 1 (a) and FIG. 1 (b), or as shown in FIG. 2 (a). A green electrode for forming a valve seat film, and a conventional green electrode for forming a valve seat film as shown in FIGS. 6 (a) and 6 (b) can be used.

  The green compact electrode 25 for forming the valve seat film includes a green compact electrode portion 26 having an outer peripheral shape (tapered surface) following the shape of the valve seat portion 102 formed on the cylinder head 101 side, and an electric discharge machine. A conductive support member 27 for energizing the green compact electrode portion 26 from the servo head is substantially integrated with the electrode rotating mechanism (not shown) fixed to the servo head of the electric discharge machine. It is attached via a holder.

  This electrode rotation mechanism rotates (rotates) the electrode while keeping the center of rotation of the electrode at a predetermined position in order to equalize the wear of the electrode tip when performing electric discharge machining using a cylindrical electrode for electric discharge machining. Furthermore, using a small-diameter cylindrical electric discharge machining electrode, a hole having a diameter larger than the electrode diameter is drilled in the workpiece, or using an inexpensive tubular electric discharge machining electrode. In order to perform drilling or pocket machining on a workpiece without leaving a gap, it was devised for the purpose of revolving while rotating (spinning) the electrode, and is already known in the field of die-sinking electric discharge machines.

  In the present embodiment, the electrode rotation mechanism (rotation) function of the electrode rotation mechanism stabilizes the film formation process by stacking carbides on each part of the valve seat portion 102 on average, thereby enabling processing voltage and processing The conditions such as current, pulse width, duty ratio, etc. are set on the high power side and used to obtain the same surface roughness and shape error as in the prior art.

  The setup for workpiece setting and the like is the same as described above, and the cylinder head 101 to be machined is directed to the green compact electrode portion 26 of the green compact electrode 25 for forming the valve seat film with the valve seat portion 102 facing upward. In the state of being opposed to each other, as shown in FIG. 5 (a), the green compact electrode 25 for forming the valve seat film and the cylinder are installed in the electric discharge machining tank 23 by the machining liquid (oil) 24 filled in the electric discharge machining tank 23. The head 101 is insulated.

  The cylinder head 101 of this embodiment is made of an aluminum alloy, and the green compact electrode portion 26 of the green compact electrode 25 for forming the valve seat film is carbonized with Al, Zn, Sn, Cu to produce a hard carbide. A green compact mixed with metal powders of Ti, Nb, V, Cr, Mn, Zr, Mo, W, Hf, Ta, Co, and Ni is used, and discharge in oil is performed according to the configuration of FIG. Thus, a hard valve seat film mainly composed of titanium carbide having excellent wear resistance was formed on the valve seat portion 102. Table 2 shows the power supply conditions set for the pulse power supply for machining and the drive conditions for the electrode rotation mechanism.

  However, the value of 0.5 to 15 mm / sec indicating the relative speed between the compact electrode 25 for forming the valve seat film and the valve seat portion 102 is the peripheral speed of the tapered surface of the outer peripheral portion of the compact electrode portion 26. .

  In general, if the pulse width, duty ratio, discharge current, etc. are set large to increase the speed of forming the valve seat film, problems such as rough surface roughness of the valve seat film occur, and sufficient surface roughness Since it is necessary to set the pulse width, duty ratio, discharge current, etc. to a small value in order to obtain the same, it is difficult to achieve both the formation speed and accuracy of the valve seat film. Breaking down intermittently between the outer peripheral shape (tapered surface) of the green compact electrode portion 26 and the valve seat portion 102 under the conditions shown in Table 2 while rotating (rotating) the green compact electrode 25 for forming. The green compact component of the green compact electrode portion 26 is melted by the discharge energy generated at this time, and reacted with carbon atoms of the working fluid (oil) 24 in the electric discharge machining tank 23 to produce hard carbides. Then, a valve seat film of titanium carbide having a highly accurate surface roughness and a uniform composition is formed on the valve seat portion 102 in a relatively short time by transferring and laminating to the valve seat portion 102. Will be able to.

  In other words, even if the discharge itself generated between the green compact electrode part 26 and the valve seat part 102 is dispersive, by rotating (spinning) the green compact electrode part 26 itself, Since electric discharge frequently occurs at various locations on the valve seat portion 102 on average, a carbide film is uniformly formed over the entire area on the valve seat portion 102 as a whole. This also eliminates the adverse effect that the surface of the valve seat film becomes porous.

  However, the rotational speed of the green compact electrode 25 for forming the valve seat film needs to be adjusted according to the size (diameter) of the valve seat part 102 to be coated, and if the rotational speed is too high, the valve seat part Since it is difficult to determine the discharge point (where insulation is broken) on 102, it is difficult to form a valve seat film, and when the number of revolutions is low, the surface roughness becomes rough. It is desirable to set the rotation speed of the electrode rotation mechanism so that the relative speed between the forming green compact electrode 25 and the valve seat portion 102 is 0.5 to 15 mm / sec.

  As described above, the surface roughness and smoothness of the valve seat film are ensured by forming the valve seat film by discharging while rotating (spinning) the green electrode 25 for forming the valve seat film. Therefore, even if conditions such as the machining voltage, machining current, pulse width, and duty ratio are set on the higher power side than before, it is possible to maintain the same surface roughness and shape error as in the past.

  In other words, conditions such as machining voltage, machining current, pulse width, duty ratio, etc. can be set on the high power side to speed up the formation of the valve seat film, thereby speeding up the overall processing operation. As a result, mass production of the cylinder head is facilitated.

  Further, if the time required for the processing operation as a whole can be the same as that of the prior art, it is possible to obtain surface roughness and shape accuracy higher than those of the prior art, which is suitable for forming a more precise valve seat film.

  Next, an embodiment of a valve seat film forming method in which the valve seat film is formed while rotating (rotating) and revolving the green electrode for forming the valve seat film will be described with reference to FIG. To do.

  Also in this case, as the green compact electrode 28 for forming the valve seat film, the green compact electrode for forming the valve seat film as shown in FIGS. 1 (a) and 1 (b), or FIG. 2 (a). And a green electrode for forming a valve seat film as shown in FIG. 6 and a conventional green electrode for forming a valve seat film as shown in FIGS. Is possible.

  The green compact electrode 28 for forming the valve seat film has an outer peripheral shape (tapered surface) following the slope of the valve seat portion 102 formed on the cylinder head 101 side, and has a diameter smaller than the diameter of the valve seat portion 102. And a conductive support member 30 for energizing the green compact electrode portion 29 from the servo head of the electric discharge machine, and the servo head of the electric discharge machine. It is attached to a fixed electrode rotation mechanism via an electrode holder.

  The valve seat film forming method of this embodiment is used when a valve seat film is formed on the slope of the valve seat portion 102 having a large diameter by using the compacted electrode 28 for forming a valve seat film having a small diameter. The purpose is to rotate (rotate) the green compact electrode 28 for forming the valve seat film using the above-mentioned electrode rotating mechanism, and to form the outer peripheral shape (tapered surface) of the green compact electrode portion 29. This is achieved by revolving the green compact electrode 28 for forming the valve seat film such that a predetermined discharge gap is maintained between the valve seat 102 and the slope of the valve seat portion 102.

  As shown in the example of FIG. 5B, the diameter of the valve seat portion 102 is D, the slope of the inclined surface of the valve seat portion 102 is θ, and the outer peripheral shape (tapered surface) of the green compact electrode portion 29. If the desired discharge gap is S and the desired discharge gap is S, the valve seat film is formed along a circle having a radius r = (D−d) / 2− (S / sin θ) from the center of the bulb seat portion 102. The rotation center of the green compact electrode 28 may be revolved.

  Thus, by rotating and revolving the compacted electrode 28 for forming the valve seat film, a larger diameter can be obtained even when the compacted electrode 28 for forming the valve seat film having a small diameter is used. The valve seat film can be formed while maintaining a constant discharge gap with the slope of the bulb seat portion 102 having the same. At this time, since the green compact electrode 28 for forming the valve seat film is rotating (autorotating), there is no concern that the green compact component of the green compact electrode portion 29 is partially consumed. In the same manner as in the embodiment of 5 (a), carbide is averagely laminated at each location of the valve seat portion 102, so that a valve seat film excellent in surface roughness and smoothness is formed in a relatively short time. can do.

  That is, the valve seat of the cylinder head 101 of another specification in which the diameter of the valve seat portion 102 is different without replacing the green compact electrode 28 for forming the valve seat film as long as the slopes of the slopes of the valve seat portion 102 match. It is possible to continue the formation work of the valve seat film on the part 102, the time required for the setup work related to the electrode replacement is shortened, and the overall processing operation is speeded up. .

  The relative speed between the compact electrode 28 for forming the valve seat film and the valve seat portion 102 is preferably 0.5 to 15 mm / sec as described above. In this case, the relative speed is the pressure for forming the valve seat film. The value obtained by adding the peripheral speed of the outer peripheral portion due to the revolution of the powder electrode 28 for forming the valve seat film to the peripheral speed of the outer peripheral portion due to the rotation (rotation) of the powder electrode 28 itself [the revolution direction and the rotation (rotation) direction are the same. Or the peripheral speed of the outer peripheral portion by the revolution of the valve seat film forming powder electrode 28 from the peripheral speed of the outer periphery of the powder electrode 28 for forming the valve seat film by rotation (spinning). The absolute value of the subtracted value [when the revolution direction and the rotation (spinning) direction are reversed].

It is sectional drawing illustrated about the structure of the compacting electrode for valve seat film formation, FIG.1 (a) is an example at the time of forming a nonelectroconductive support member with ceramics, and FIG.1 (b) is nonelectroconductive. This is an example in which the support member is formed of a reduced diameter portion of the conductive support member and a non-conductive film. FIG. 2 (a) is a diagram showing the structure of a green compact electrode for forming a valve seat film, and FIG. It is the figure shown about the manufacturing process of the green compact electrode for sheet membrane formation. It is the schematic diagram which simplified and showed the structure of the periphery of an electric discharge machining tank about the die-sinking electric discharge machine used when forming a valve seat membrane | film | coat. It is the conceptual diagram shown about the process of the electrode replacement | exchange operation | work. The embodiment in which the valve seat film forming method of the present invention is applied to relatively speed up the film forming process to speed up the overall processing operation and achieve mass production of cylinder heads. FIG. 5 (a) shows the overall processing operation by rotating the green electrode for forming the valve seat film to ensure the surface roughness and smoothness of the film and setting the discharge condition to the high power side. FIG. 5 (b) shows an example of dealing with film formation on a large-diameter valve seat portion by revolving the green electrode for forming the valve seat film simultaneously with rotation. FIG. 6A is a cross-sectional view showing a conventional example of a green electrode for forming a valve seat film. FIG. 6A is a first developed green electrode for forming a valve seat film, and FIG. 6B is an improvement. It is a green electrode for forming a valve seat film.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Compact electrode for valve seat film formation 2 Compact electrode part 3 Conductive support member 3a Hole 3b Tip surface 4 Non-conductive support member 4a Outer peripheral surface 5 Hole 6 Compact sheet electrode 7 for forming valve seat film Body electrode part 8 Conductive support member 8b Tip face 9 Reduced diameter part 10 Non-conductive coating 11 Non-conductive support member 11a Outer peripheral face 12 Hole 13 Compact electrode 14 for forming valve seat film Compact electrode 14 'Pressure Powder 15 Conductive support member 15 ′ Magnetic powder 16 Compact molding die 17 Press member 18 Servo head 19 Pulse power source 20 Electrode holder 21 Electromagnetic chuck 22 Table 23 Electric discharge machining tank 24 Processing fluid 25 Compact for forming valve seat film Body electrode 26 Compact electrode part 27 Conductive support member 28 Compact sheet electrode for forming valve seat film 29 Compact electrode part 30 Conductive support member 100 Compact for forming valve sheet film Electrode (conventional example)
101 Cylinder Head 102 Valve Seat Part 103 Compact Electrode Part (Conventional Example)
104 Conductive support member (conventional example)
105 conductive adhesive 106 green sheet electrode for valve seat film formation (conventional example)
107 conductive support member (conventional example)
107a Reduced diameter part (conventional example)
108 ports

Claims (2)

A valve seat film forming method for forming a valve seat film instead of a valve seat ring of a cylinder head on a valve seat part of a cylinder head using discharge energy,
While rotating the green compact electrode for forming the valve seat film having the outer peripheral shape following the shape of the valve seat portion, the dielectric breakdown is intermittently excited between the outer peripheral shape and the valve seat portion. The green compact component of the green compact electrode for forming the valve seat film is melted by the generated discharge energy and reacted with the carbon atoms of the working fluid in the electric discharge machining tank to form hard carbides and transferred to the valve seat portion. A valve seat film forming method characterized in that it is laminated by laminating. A valve seat film forming method for forming a valve seat film instead of a valve seat ring of a cylinder head on a valve seat part of a cylinder head using discharge energy,
A green electrode for forming a valve seat film having an outer peripheral shape following the inclined surface of the valve seat portion is rotated, and a predetermined discharge gap is maintained between the outer peripheral shape and the inclined surface of the valve seat portion. Thus, while revolving the green compact electrode for forming the valve seat film, the dielectric breakdown is intermittently excited between the outer peripheral shape and the valve seat portion, and the valve seat film is formed by the discharge energy generated at this time. The green compact component of the green compact electrode for use is melted and reacted with carbon atoms in the machining fluid in the electric discharge machining tank to form hard carbides that are transferred to the valve seat portion and laminated. Valve seat film forming method.

Images