EP0740055B1 - Method of bonding a valve seat - Google Patents

Method of bonding a valve seat Download PDF

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Publication number
EP0740055B1
EP0740055B1 EP19960106675 EP96106675A EP0740055B1 EP 0740055 B1 EP0740055 B1 EP 0740055B1 EP 19960106675 EP19960106675 EP 19960106675 EP 96106675 A EP96106675 A EP 96106675A EP 0740055 B1 EP0740055 B1 EP 0740055B1
Authority
EP
European Patent Office
Prior art keywords
valve seat
cylinder head
base material
seat base
valve
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP19960106675
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0740055A2 (en
EP0740055A3 (enrdf_load_stackoverflow
Inventor
Shuhei Adachi
Junichi Inami
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Yamaha Motor Co Ltd
Original Assignee
Yamaha Motor Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from JP7101998A external-priority patent/JPH08296416A/ja
Priority claimed from JP7102004A external-priority patent/JPH08296417A/ja
Application filed by Yamaha Motor Co Ltd filed Critical Yamaha Motor Co Ltd
Publication of EP0740055A2 publication Critical patent/EP0740055A2/en
Publication of EP0740055A3 publication Critical patent/EP0740055A3/xx
Application granted granted Critical
Publication of EP0740055B1 publication Critical patent/EP0740055B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L3/00—Lift-valve, i.e. cut-off apparatus with closure members having at least a component of their opening and closing motion perpendicular to the closing faces; Parts or accessories thereof
    • F01L3/22—Valve-seats not provided for in preceding subgroups of this group; Fixing of valve-seats
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
    • F02F1/00—Cylinders; Cylinder heads 
    • F02F1/24—Cylinder heads
    • F02F1/26—Cylinder heads having cooling means
    • F02F1/36—Cylinder heads having cooling means for liquid cooling
    • F02F1/38—Cylinder heads having cooling means for liquid cooling the cylinder heads being of overhead valve type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
    • F02F1/00—Cylinders; Cylinder heads 
    • F02F1/24—Cylinder heads
    • F02F2001/241—Cylinder heads specially adapted to pent roof shape of the combustion chamber
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
    • F02F1/00—Cylinders; Cylinder heads 
    • F02F1/24—Cylinder heads
    • F02F2001/244—Arrangement of valve stems in cylinder heads
    • F02F2001/245—Arrangement of valve stems in cylinder heads the valve stems being orientated at an angle with the cylinder axis

Definitions

  • This invention relates to a method for producing a valve seat within a cylinder head unit provided with valve openings associated with respective valve guide holes for receiving valve guides for associated intake or exhaust valves opening and closing said valve openings, respectively, and a device conducting said method.
  • a method for producing a valve seat as defined in the preamble of claim 1 is known from patent abstract of Japan, volume 95, no. 004, and JP-A-07 103070, filed in the name of the applicant of this patent application.
  • This prior art document also discloses a device in accordance with the preamble of independent claim 15.
  • EP-A-0 195 177 discloses a device for induction heating of a valve seat comprising an inductive rod to be inserted into a bore of a cylinder head unit.
  • the inductive head is coupled with a heat source.
  • the desired alignment of the inductive head and the bores is achieved.
  • a conventional cylinder head body for engines is mainly made of Al alloy, and a valve seat is provided where the valve face of an intake or exhaust valve engages the cylinder head body. Since the valve seat engages the intake or exhaust valve repeatedly and is subject to high temperature, the valve seat is made of sintered Fe alloy of excellent wear resistance and high temperature strength, press-fit in the recess formed in the intake or exhaust port opening of the cylinder head on the combustion chamber side as shown in FIG. 17, and finished by grinding so as to be held integrally in the cylinder head body.
  • FIG. 17 is an enlarged sectional view of a portion of a conventional cylinder head with a valve seat press-fit therein, numeral 1 designating a cylinder head body, numeral 2 a press-fit type valve seat, and numeral 3 a recess for the press-fit valve seat.
  • the cylinder head with a valve seat 2 of different material press-fit in the cylinder head body 1 must have an appropriate dimensional allowance for the valve seat 2 not to come off even when the cylinder head temperature went high during running.
  • the wall thickness between adjacent ports must be kept large to a certain degree and dimension reduction between ports cannot be effected. That is, the press-fit type valve seat 2 has a great difficulty in designing port-related dimensions of the cylinder head due to its large sectional area.
  • the heat conductivity of Fe-based sintered alloy, the material of valve seat 2, is lower than that of Al alloy, the material of the cylinder head body 1, and the valve seat 2 has an appropriate thickness for preventing deformation during press-fitting as well as has a minute clearance between the valve seat 2 and the cylinder head body 1, therefore heat resistance will be high when heat is transmitted from the intake or exhaust valve face and exhaust gas to the cylinder head 1. As a result, cooling capacity of the cylinder head will be insufficient, which might cause abnormal combustion and excessive temperature rise of the valve.
  • the thermal expansion coefficient of the material of the valve seat 2 is larger than that of Al alloy, the material of the cylinder head body 1, the minute clearance between the cylinder head body 1 and the valve seat 2 is widened at a temperature higher than a certain value and accordingly heat transmission to the cylinder head body 1 will be further hindered. As a result, the valve seat 2 may be heated excessively and wear resistance will be apt to be lowered.
  • valve seat material of high heat resistance, high wear resistance, and high anticorrosion is melted by heat using laser as a heat source, clad over the portion of the cylinder head body 1 to be used as a valve seat, and the clad layer is finished by machining to form a valve seat (for example, see Japanese Unexamined Patent Publication Sho 62-150014).
  • FIG. 18 shows a valve seat formed using this laser clad method.
  • FIG. 18 shows an enlarged sectional view of a valve seat portion of a cylinder head formed using the laser clad method, numeral 4 designating the valve seat portion, numeral 5 the bond interface between the cylinder head body and the valve seat portion 4, and numerals 6, 7 the melt reaction layer formed in the vicinity of said bond interface 5.
  • valve seat is formed using the laser clad method, a problem is left in bond strength associated with melting and cladding of the valve seat material. This is because a portion of the cylinder head body 1, close to the bond interface, also melts when the valve seat material is melted by heat.
  • this laser clad method has the disadvantage of being liable to be affected by cavities and impurities in the Al alloy.
  • the bond strength of the bonded portion formed by melting and solidifying of material is liable to decrease when the engine is kept running for a long time in a condition in which the temperature of the valve seat portion goes high.
  • One possibility to match the pushing direction with the axis of said intake or exhaust valve is given by advancing a guide rod coaxially aligned with said electrode such that said guide rod enters said valve guide hole and simultaneously guides said electrode.
  • the pressing force and/or said electricity are applied according to a predetermined pattern.
  • step (b) a sampling test is carried out by applying a tensile force to the bonded valve seat base material. This will save production time and costs and especially enhances the reliability of said cylinder head because scrap cylinder heads may be eliminated before the final finishing treatment and especially before using same for an internal combustion engine.
  • this means for ensuring the coaxial alignment between the electrode and said valve guide hole is a guide rod slidingly received in a through hole of said electrode and being capable to be inserted into said valve guide hole of said cylinder head unit.
  • said first means is a lower platen fixed to a lower portion of said base frame and said second means is an upper platen disposed upwardly of the lower platen for vertical movement so as to be able to come into contact with the lower platen, whereby the upper platen is fixed to the lower end of a rod being an end portion of the cylinder device mounted on the upper portion of the base frame vertically.
  • said device comprises a shield made of a ferromagnetic material for controlling the direction and magnitude of magnetic flux in the magnetic field caused by energization.
  • energization causes resistance heat at the contact portion between the valve seat base material and the cylinder head body, temperature rises at the interface of the contact portion where said valve seat base material and the cylinder head body are pressed against each other, so that atoms on both sides of the interface will diffuse to each other.
  • a eutectic alloy layer made of material metal of the film of the valve seat base material and material metal of the cylinder head body is produced in the vicinity of said interface.
  • This eutectic alloy layer is changed by said resistance heat to a liquid phase because of its low transformation temperature, and removed to the outside from the bonded portion together with the material metal of the cylinder head body developing plastic flow by heating, as the valve seat base material is pushed against the cylinder head body.
  • pushing force is exerted in the axial direction of the port opening at this time, so that not only said atom diffusion phenomena are brought about uniformly over the entire circumference of the valve seat base material, but also pores associated with the atom diffusion, or defective structure associated with deformation can be avoided.
  • pushing the electrode according to a certain pattern of pushing force and energizing according to a certain pattern of electric current make it possible to control the rate of plastic flow in the cylinder head body.
  • a valve guide hole is formed on the valve axis so that the pushing direction of the electrode exactly coincides with said valve axis.
  • FIG. 1 is a sectional view of a valve seat portion of a cylinder head, with a valve seat bonded using a bonding method according to the invention
  • FIG. 2 is a sectional view showing a valve seat base material being placed on a port opening, depicting only a part of a cylinder head body and a valve seat base material on an enlarged scale.
  • FIG. 3 is a front view of a pressure devise for use in performing the bonding method according to the invention
  • FIG. 4 is a side view corresponding to FIG. 3
  • FIG. 5 is a sectional view of an electrode being engaged with the valve seat base material
  • FIG. 6 is a diagram showing the patterns of pushing force and electric current, and the amount of sinking
  • FIG. 7 is a sectional view of an alloy layer being produced, said alloy layer consisting of material metal of the film of the valve seat base material and material metal of the cylinder head body
  • FIG. 8 is a sectional view of material metal of the cylinder head body developing plastic flow
  • FIG. 9 is a sectional view of the valve seat base material being embedded into the cylinder head body
  • FIG. 10 is a sectional view of the valve seat portion being finished by machining.
  • numeral 11 designates a cylinder head body of a four-stroke engine, which is molded with Al alloy, formed with a combustion chamber recess 12 of a dome-like shape facing downward, and with an intake port 13 and an exhaust port 14 each having an opening at the recess 12.
  • valve guide 15, 16 are press-fit in valve guide holes lla' formed in the cylinder head body 11.
  • the valve guide hole lla' are formed with their axes C coinciding with the axes of the openings 13a, 14a of the intake and exhaust ports 13, 14.
  • valve seat 19 shown in FIG. 1 is a seat in which a valve seat base material of a ring shape is bonded to the cylinder head 11 using a bonding method of this invention and finished by machining.
  • Said valve seat base material is designated symbol 20 in FIG. 2.
  • the valve seat base material 20 consists of a ring body 21 made of Fe-based sintered alloy covered with a Cu film 22. However, it is not compulsary that said ring body 21 is provided with such a film or coating. It is sufficient that the materials of said cylinder head body 11 and said ring body 21 may form an eutectic alloy, as described later.
  • the Fe-based sintered alloy is infiltrated with Cu for the purpose of avoiding development of internal resistance heat during energization as described later.
  • Said Cu film 22 is formed by electroplating the ring body 21 so as to be 0.1-30 ⁇ m in thickness.
  • material of AC4C specified in JIS is used in this embodiment.
  • the valve seat base material 20 is formed, as shown in FIG. 2, into a shape such that a part of its outer circumferential surface faces the opening 13a or 14a when it is placed on the opening 13a or 14a of the intake or exhaust port 13 or 14.
  • the cylinder head body 11 is shown with the bottom (the face at which the combustion chamber recess 12 is open) upward.
  • the outer circumferential surface 20a of the valve seat base material 20 is inclined in such a manner that its outside diameter becomes smaller toward the cylinder head body 11, the bottom surface 20b is inclined in the direction nearer to the cylinder head body 11 toward the axial center of the valve seat base material 20, and the outer circumferential surface 20a and the bottom surface 20b are joined together to form a convex surface.
  • the convex surface is designated by symbol 20c.
  • the inner circumferential surface of the valve seat base material 20 consists of a slant surface 20d inclining in such a manner that the inside diameter of the valve seat base material 20 becomes smaller toward the cylinder head body 11, and a axial surface 20e extending axially from the inner edge of the slant surface 20d.
  • a pressure device 24 shown in FIG. 3 and FIG. 4 is used to bond the valve seat base materials 20s to the cylinder head body 11 on said openings 13a and 14a.
  • the pressure device 24 has a lower platen 26 fixed to the lower portion of a base frame 25, and an upper platen 27 is disposed upwardly of the lower platen 26 for vertical movement so as to be able to come into contact with the lower platen 26.
  • the upper platen 27 is fixed to the lower end of a rod 28a which is the end portion of a cylinder device 28 mounted to the upper portion of the base frame vertically.
  • Said upper and lower platens 26, 27 are supplied with electricity from a power supply (not shown) through conductors 26a, 27a.
  • the conductor 27a connected to the upper platen 27 is adapted to be bent or moved vertically in response to the vertical movement of the upper platen 27.
  • the upper platen acts as an anode and the lower platen as a cathode.
  • a laser displacement meter 30 for measuring displacement of the upper platen 27, said displacement meter measuring, using a laser beam, the distance from a reflection member 29 fixed to the front portion of the upper platen 27.
  • valve seat base material 20 To bond the valve seat base material 20, first is fixed on said lower platen 26 an underside electrode 31, on which is mounted fixedly the cylinder head body 11. At this time, the cylinder head body 11 is positioned with the combustion chamber recess 12 side upward and with the axis of the port opening, on which the valve seat base material 20 is bonded, coinciding with the axis of a rod 28a of said cylinder device 28.
  • a guide rod 32 is inserted, from the combustion chamber recess 12 side, into the valve guide hole 11a of the port on which the valve seat base material 20 is bonded.
  • the guide rod 32 is made of a metallic rod 32a covered with insulating material such as alumina, and has a length such that it protrudes from the end face of the cylinder head body 11 on the combustion chamber side when inserted into the valve guide hole 11a and held in place by a stopper 32c.
  • Said insulating member 32ba is formed, in this embodiment, using a method in which ceramic material such as alumina is flame sprayed and then finished by polishing.
  • the valve seat base material 20 On the port opening is placed the valve seat base material 20, on which is laid the upper electrode 33.
  • the upper electrode 33 is formed with a through hole 33a for fitting said guide rod 32 at the axial center of its cylindrical metallic body, and at the lower end portion, with a tapered surface 33b adapted to be in close contact with said slant surface 20d (FIG. 2) of the valve seat base material 20 and a positioning circumferential surface 33c adapted to be in close contact with the axial extending surface 20e over its entire circumference.
  • a magnetic body 33d On the lower end portion of this upper electrode 33 is fixed a magnetic body 33d for magnetically attracting the valve seat base material 20.
  • the upper electrode 33 is positioned coaxially with the axis of the port opening of the cylinder head body 11, and when said tapered surface 33b and the circumferential surface 33c are brought into close contact with the valve seat base material 20, the valve seat base material 20 is also positioned coaxially with the port opening.
  • the upper electrode 33 is turned so as to check whether the valve seat base material 20 is fitted reliably.
  • the cylinder device 28 is driven to move the upper platen 27 downward and bring it into close contact with said upper electrode 33.
  • the bottom surface of the upper platen 27 and the top surface of the upper electrode 33 are adapted to be parallel to each other.
  • said cylinder device 28 is driven to move the upper platen 27 downward and press said valve seat base material 20 against the cylinder head body 11 with a certain pushing force. Since the movement of the upper electrode 33 is restricted by the guide rod 32, the direction of the pushing force exerted on the valve seat base material 20 coincides with the axis of the port opening 13a or 14a. Therefore, the valve seat base material 20 is pressed coaxially with the port opening 13a or 14a.
  • the pushing force is changed according to the pattern of pushing force shown in solid line in FIG. 6. That is, a first pushing force P1 of a certain lower value is applied at early stage of the bonding process and then a second pushing force P2 of a certain higher value is applied till the downward movement is completed.
  • the distance between said laser displacement meter 30 and the reflection member 29 is measured by the displacement meter and recorded as a sinking movement starting point of the upper platen 27.
  • a voltage is applied between said upper and lower platens 27, 26, so that an electric current flows through the upper electrode 33, valve seat base material 20, cylinder head body 11, and lower electrode 31.
  • the current flows from the upper electrode 33 toward the cylinder head body 11, and the current value is changed according to the pattern of the current value shown in dash line in FIG. 6. That is, the current valve is increased first, then decreased near to 0, and then increased further again before reduced to 0 during the time said pushing force is still applied at the final stage of the bonding process.
  • the convex surface 20c of the valve seat base material 20 is in contact with the convex portion 23 of the cylinder head 11 and the contact area between these two components is very small, so that when electric current is applied as described above, electric resistance becomes large enough to develop resistance heat at the contact portion. The heat will be transmitted over the entire interface between the valve seat base material 20 and the cylinder head body 11.
  • the crystalline structure near the interface turns to eutectic alloy between Cu in the Cu film 22 and Al alloy in the cylinder head body 11, that is, into the state capable of changing from solid phase to liquid phase at lower temperature than pure Cu does.
  • the state near the interface at the time is shown schematically in FIG. 7, and the portion where said eutectic alloy layer is produced as a result of the mutual atom diffusion, is designated by symbol A.
  • FIG. 8 shows the removed portion of the eutectic alloy in symbol B.
  • a part of the Cu film 22 of the ring body 21 is turned into Al eutectic alloy and removed from the contact portion, therefore a part of the ring body 21 comes into contact with the Al alloy, which brings about the atom diffusion phenomena between these materials.
  • the portion developing atom diffusion is shown in symbol C in FIG. 8.
  • the increased pushing force causes the increase in the rate of plastic flow in the Al alloy, thereby increasing the volume of the eutectic ally removed.
  • new eutectic alloy consisting of Cu-Al alloy is produced in a contact portion where no reaction has occured so far, the phenomena described above is repeated and these eutectic alloy layers are liquidized to be removed.
  • the area where mutual atom diffusion occurs will expand in the interface between Fe-base sintered alloy, the material of the ring body 21, and Al alloy.
  • the current value is lowered temporarily near to 0 and raised again to the original value.
  • Lowered current value will prevent heat development temporarily to hold plastic flow in check, so that increase in the sinking rate of the valve seat base material 20 is lowered temporarily.
  • the aim of temporarily lowering the current value is to prevent the Al alloy from melting by heat.
  • the current value is raised to the original one as described above, and then lowered gradually to 0 during the time from point T5 to T6. Not only during the time the current is flowing, but after the current is shut off, said reaction proceeds till the temperature falls to the point where the reaction is impossible to occur; the phenomena of generation of the eutectic alloy layer ⁇ liqudization ⁇ removal associated with plastic flow, and the phenomena of mutual atom diffusion between Fe-based sintered alloy and Al alloy, occur simultaneously, while the valve seat base material 20 continues to sink; almost all the circumferential surface is embedded into the cylinder head 11 as shown in FIG. 9.
  • the allowable value D is set to be about 0.5mm-2mm. Usually, the allowable value of about 1mm-1.5mm is preferable, depending on the material of the cylinder head body 11.
  • the cylinder head which has passed the sinking amount determination described above also receives a judgment whether said mean current value and total energization time are within the range of allowable values, and only if this judgment is favorable and also the cylinder head passes a sampling test described below, the lot of the cylinder head is machined to be finished.
  • the sampling test is performed, for example, on every production lot of the valve seat base materials 20; tensile force is applied to the valve seat base material 20 after bonding in the state shown in FIG. 9, in the direction of the valve seat 20 separating from the cylinder head 11. More specifically. a pulling Jig is hooked to the valve seat base material 20 at the inner circumferential edge of the bottom surface 20b (FIG. 2), a tensile testing machine (not shown) exerts a tensile force on the Jig in said direction, and if the load is higher than a predetermined separation limit at the time the valve seat base material 20 is separated from the cylinder head body 11, the test sample is judged to be acceptable.
  • the heat endurance test is performed after the cylinder head 11 in the state of FIG. 9 is kept in a furnace of 300 °C and atmospheric condition for 24-200 hours and cooled at room temperature.
  • the cylinder head body 11 in the state of FIG. 9 is heated to 300°C in the furnace of 300°C and atmospheric condition, taken out from the oven, and then immersed immediately in ice water of 0 °C. This procedure is repeated 10 times, and separation, cracks, etc. are checked before the separation test is performed.
  • an unnecessary portion is removed from the cylinder head body 11 bonded with the valve seat base material 20, for example, by grinding as shown in FIG. 10.
  • the finishing process removes the unnecessary portion of the ring body 21 together with the Cu film 22, and the valve seat 19 bonded to the cylinder head body 11 through the atom diffusion area shown in symbol C in FIG. 10, is obtained.
  • the metallographical bonding between Al alloy of the cylinder head body 11 and Fe-based sintered alloy of the valve seat 19 in a cylinder head as described above, is essentially different from the mechanical bonding in the metallographecally separated state without atom diffusion. Further, it is different from the metallographical bonding such as resistance heat bonding in which materials to be bonded are locally melted to form liquid alloy using electrical resistance heat generated in the interface, and cooled to be solidified by deenergization.
  • the metallurgical bonding of a cylinder in this embodiment is performed without leaving melt reaction layer between different materials and provides a continuous structure through mutual atom diffusion in the interface between two materials.
  • FIG. 11 is a plan view showing an embodiment using the shield device, with an upper electrode 33 mounted on a cylinder head body 11 together with a valve seat base material 20.
  • the same or equivalent components in this figure as described in FIG. 1 through FIG. 10 are designated by the same symbol and detailed explanations are omitted.
  • the shield 34 is made of Fe-based ferromagnetic material,formed into a semi-cylindrical shape, and disposed with the top of the circumferential surface facing the base frame 25 of the pressure device 24.
  • the direction of the base frame 25 is shown in an arrow head in the figure.
  • the shield 34 makes it possible to control the direction and the magnitude of magnetic flux in the magnetic field caused by energization, and accordingly the direction of the eutectic alloy removed from the bonded portion.
  • the inventor used various aluminum alloys for the material of the cylinder head body (11) to which the valve seat member (20) is joined, conducted the separation test for each of the alloys, and found aluminum alloys which provide a separation force to stand the use for the valve seat for engines. The test results are shown in FIgs. 12 to 15.
  • the symbols ⁇ and ⁇ represent the material AC4C used in this embodiment.
  • the symbols ⁇ and ⁇ represent the material AC4B
  • the symbols ⁇ and ⁇ represent the material AC2B.
  • Both materials AC4B and AC2B are specified in JIS and typically used in cylinder head bodies for engines.
  • the material AC4B is an Al-Si-Cu-based aluminum alloy
  • the material AC2B is an Al-Cu-Si-based aluminum alloy.
  • the symbols ⁇ , ⁇ , and ⁇ represent the results when the separation tests were conducted in the state the valve seat member (20) was joined to the cylinder head body (11) as it was.
  • the symbols ⁇ , ⁇ , and ⁇ represent the results of the separation tests after the cylinder head body (11) joined with the valve seat member (20) was let stand in the atmospheric 300°C heating oven for 24 hours and air-cooled.
  • test samples were determined acceptable when the separation force in the separation test was equal to or exceeded 20 KN.
  • the solidus temperature is the temperature at which the aluminum alloy transforms from solid phase to liquid phase. The reason for the material AC4C having a relatively high solidus temperature having proved acceptable seems that a molten layer is less likely to be formed than in other materials.
  • the 0.2% yield strength at 400 °C is the stress at residual plastic deformation of 0.2% when an aluminum alloy is subjected to a tensile strength test at 400 °C.
  • the reason for the material AC4C having a relatively small yield strength having proved acceptable seems to be that plastic flow is more likely to occur in AC4C than in AC4B.
  • valve seat base material 20 and the port openings 13a, 14a of of the cylinder head body 11 are formed with convex portions (the convex surface 20c, the convex portion 23) and these convex portions are bonded to each other, both of said components are not necessarily formed with the convex portions, but only one of them may. These embodiments are shown in FIG. 16(a)-(c).
  • FIG. 16 shows sectional views of other embodiments with bonded portions of different shapes
  • FIG. 16(a) and (b) are examples in which only valve seat base materials are formed with convex portions
  • FIG. 16(c) an example in which only the cylinder head body is formed with a convex portion.
  • the same or equivalent components in this figure as described in FIG. 1 through FIG. 10 are designated by the same symbol and detailed explanations are omitted.
  • valve seat base material 20 is formed into a shape equivalent to the foregoing embodiment, and the portion of the port opening 13a or 14a to be engaged with the valve seat base material 20 is in the shape of a flat slanting surface.
  • valve seat base material 20 is formed in such a manner that the outer circumference is adapted to be fitted in the port opening 13a or 14a.
  • the shape of the inner circumferential surface of the valve seat base material 20 is different from the foregoing embodiment, and formed into an axially extending surface 20e over its entire depth.
  • the portion of the valve seat base material 20 to be engaged with the convex portion 23 of the cylinder head body 11 is in the shape of a flat slanting surface.
  • valve seat base material 20 and the cylinder head body 11 Forming either one of the valve seat base material 20 and the cylinder head body 11 with a convex portion as shown in FIG. 16(a)-(c), will provide results equivalent to the foregoing embodiment. If both of said components are formed with convex portions as shown in this embodiment, material metal of the cylinder head 11 tends to develop plastic flow easily and to relatively a large extent in volume, so that the area of the bonded portion (contact interface) of the valve seat base material 20 can be expanded, which provides high bond strength.
  • AC4C is used as a material for cylinder head body 11, Cu-infiltrated Fe-based sintered alloy for the ring body 21 of the valve seat base material 20, and Cu coated by electroplating for the film of the ring body 21, but the materials and the methods of forming films are not restricted to those described in this embodiment. That is, for the cylinder head body 11, materials generally used in the cylinder head for engines, such as AC4B, AC2B, etc. may be adopted. For the ring body 21, any kind of Fe-based sintered alloy may be used, and sintered metals with similar electrical conductivity to that of Cu, may be employed.
  • any kind of metal that will produce eutectic alloy with material metal of the cylinder head body 11 may be used.
  • the most economical options are adopted in this embodiment in view of the cylinder head being manufactured as an industrial product.
  • the magnitude of sinking may be measured continuously from the beginning of the pushing process and determined whether it is within the tolerable range from time to time. In so doing, any defective can be detected in the middle of the bonding process, so that time loss due to defective products spending the same working time as good ones, may be avoided.
  • one method of bonding a valve seat comprises placing a valve seat base material on a port opening of a cylinder head body, the valve seat base material being a ring body made of sintered Fe alloy covered with a film of metallic material, and subsequently pushing an electrode against this valve seat base material with the pushing direction matched with the axis of the valve, the electrode being adapted to apply electricity to the cylinder head through the valve seat base material. Therefore, energization causes resistance heat at the contact portion between the valve seat base material and the cylinder head body, temperature rises at the interface of the contact portion where said valve seat base material and the cylinder head body are pressed against each other, so that atoms on both sides of the interface will diffuse to each other.
  • a eutectic alloy layer made of material metal of the film of the valve seat base material and material metal of the cylinder head body is produced in the vicinity of said interface.
  • This eutectic alloy layer is changed by said resistance heat to a liquid phase because of its low transformation temperature, and removed to the outside from the bonded portion together with the material metal of the cylinder head body developing plastic flow by heating, as the valve seat base material is pushed against the cylinder head body.
  • valve seat can be bonded to the cylinder head body through mutual atom diffusion instead of press-fitting, and said mutual atom diffusion will develop almost uniformly over the entire circumference of the valve seat due to the direction of the pushing force during bonding, so that high bond strength can be obtained.
  • dimensional allowance for press-fitting is not necessary compared to the case in which the valve seat is press-fit in the cylinder head body, so that the sectional area of the valve seat portion can be reduced, which provides larger freedom in designing the structure around the port area in the cylinder head.
  • resistance against heat transmission through the valve seat is small, so that abnormal combustion in the engine, or wear of damage of the valve seat due to its thermal degradation, can be prevented.
  • a valve seat matching the pushing direction of the electrode with the axis of the valve is performed by inserting the electrode into a guide rod fitted to be held in a valve guide hole in the cylinder head. Therefore, a valve guide hole is formed on the valve axis, so that the pushing direction of the electrode exactly coincides with said valve axis.
  • the direction of the pushing force coincides with the axis of the port opening with simple structure.
  • a still further method of bonding a valve seat comprises placing a valve seat base material on a port opening of a cylinder head body, the valve seat base material being a ring body made of sintered Fe alloy covered with a film of metallic material, subsequently pushing an electrode against this valve seat base material according to a predetermined pattern of pushing force, and applying electricity to the cylinder head body through the valve seat base material according to a predetermined pattern of current value a predetermined time after the pushing operation. Therefore, energization causes resistance heat at the contact portion between the valve seat base material and the cylinder head body, temperature rises at the interface of the contact portion where said valve seat base material and the cylinder head body are pressed against each other, so that atoms on both sides of the interface will diffuse to each other.
  • a eutectic alloy layer made of material metal of the film of the valve seat base material and material metal of the cylinder head body is produced in the vicinity of said interface.
  • This eutectic alloy layer is changed by said resistance heat to a liquid phase because of its low transformation temperature, and removed to the outside from the bonded portion together with the material metal of the cylinder head body developing plastic flow by heating, as the valve seat base material is pushed against the cylinder head body.
  • the valve seat can be bonded to the cylinder head body through mutual atom diffusion instead of press-fitting.
  • the electrode is pushed to the valve seat base material according to a certain pattern of pushing force and an electric current is applied according to a certain pattern, so that the rate of plastic flow in the cylinder head body will be controlled, Fe-based sintered alloy will be brought into contact with the cylinder head body securely, and the area in which said mutual atom diffusion occurs will be expanded, whereby high bond strength can be obtained.
  • dimensional allowance for press-fitting is not necessary compared to the case in which the valve seat is press-fit in the cylinder head body, so that the sectional area of the valve seat portion can be reduced, which provides larger freedom in designing the structure around the port area in the cylinder head.
  • resistance against heat transmission through the valve seat is small, so that abnormal combustion in the engine, or wear of damage of the valve seat due to its thermal degradation, can be prevented.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Cylinder Crankcases Of Internal Combustion Engines (AREA)
EP19960106675 1995-04-26 1996-04-26 Method of bonding a valve seat Expired - Lifetime EP0740055B1 (en)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
JP7101998A JPH08296416A (ja) 1995-04-26 1995-04-26 バルブシートの接合方法
JP10199895 1995-04-26
JP10200495 1995-04-26
JP102004/95 1995-04-26
JP7102004A JPH08296417A (ja) 1995-04-26 1995-04-26 エンジン用シリンダヘッド
JP101998/95 1995-04-26

Publications (3)

Publication Number Publication Date
EP0740055A2 EP0740055A2 (en) 1996-10-30
EP0740055A3 EP0740055A3 (enrdf_load_stackoverflow) 1996-11-27
EP0740055B1 true EP0740055B1 (en) 2002-01-30

Family

ID=26442753

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19960106675 Expired - Lifetime EP0740055B1 (en) 1995-04-26 1996-04-26 Method of bonding a valve seat

Country Status (2)

Country Link
EP (1) EP0740055B1 (enrdf_load_stackoverflow)
DE (1) DE69618841T2 (enrdf_load_stackoverflow)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2016041915A (ja) 2014-08-18 2016-03-31 トヨタ自動車株式会社 内燃機関
CN111456864B (zh) * 2019-01-22 2022-09-09 长城汽车股份有限公司 用于车辆的气缸盖组件及车辆
CN114717511B (zh) * 2022-03-30 2023-08-04 北矿磁材（阜阳）有限公司 一种烧结钕铁硼磁体表面Al薄膜的制备方法

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4535212A (en) * 1984-07-06 1985-08-13 Tocco, Inc. Apparatus and method of hardening valve seats
EP0195177A2 (de) * 1985-03-18 1986-09-24 Tocco, Inc. Einrichtung zum induktiven Erhitzen von Ventilsitzen sowie Verfahren zur Anwendung der Einrichtung
US5060374A (en) * 1989-06-05 1991-10-29 Electric Power Research Institute, Inc. Method for fabricating a valve
JPH07103070A (ja) * 1993-10-06 1995-04-18 Yamaha Motor Co Ltd バルブシート

Also Published As

Publication number Publication date
EP0740055A2 (en) 1996-10-30
EP0740055A3 (enrdf_load_stackoverflow) 1996-11-27
DE69618841D1 (de) 2002-03-14
DE69618841T2 (de) 2002-06-20

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