JPH1061419A - Joint type valve seat and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a joint type valve seat having desired mechanical property and a manufacturing method thereof. SOLUTION: In a manufacturing method of a joint type valve seat in which a seat ring material 6' formed like a ring by Fe sintered material is heated and pressurized to form a solid phase diffusion layer on a joint boundary face of the seat ring material 6' and a cylinder head 3, a plastic deformation layer 25 is formed at least on a cylinder head 3 side of the joint boundary face to join the seat ring material 6' with the cylinder head 3 metallically, and the seat ring material 6' is machined into a desired shape after they are joined, the seat ring material 6' is heat-treated when the seat ring material 6' is joined. It is possible to give desired mechanical property including hardness to the joint type valve seat by heat-treating the seat ring material 6' when the seat ring material 6' is joined.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joint type valve seat which is metallurgically joined to a cylinder head by a resistance heat joining method and a method of manufacturing the same.

[0002]

2. Description of the Related Art In a four-stroke engine, intake and exhaust ports opened to a combustion chamber are opened and closed at appropriate timing by intake and exhaust valves to perform required gas exchange. A valve seat on which the intake / exhaust valve should be intermittently seated is generally press-fitted around the opening. For example, as shown in FIG. 20, around the openings of the intake port 104 and the exhaust port 105 of the cylinder head 103,
Valve seats 106 and 107 on which the intake valve 101 and the exhaust valve 102 are to be intermittently seated are mounted by press fitting.

Meanwhile, the press-fit type valve seat is set to have a relatively large thickness in order to secure necessary strength and rigidity, and the height dimension is set to be relatively large because a predetermined press-in allowance is required. Have been. For this reason, in a multi-valve engine having a plurality of valves, the distance between the valves is increased, and there is a limit in increasing the diameter of the valves or disposing the valves near the center of the combustion dome. Could not be planned.

On the other hand, in the field of internal combustion engines, in recent years, the number of valves has been increased as part of speeding up, and a plurality of intake / exhaust ports are arranged close to each cylinder of a cylinder head. When the interval between the ports is becoming narrower, and the valve seat is press-fitted into the peripheral edge of the intake / exhaust port in the conventional manner under such circumstances, a problem such as generation of a crack between ports of the cylinder head occurs.

Therefore, an attempt has been made to form the valve seat from, for example, an Fe-based sintered material and join the valve seat to the periphery of the intake / exhaust port of the cylinder head by a resistance heat joining method. This resistance thermal bonding method is a method of metallurgically bonding a valve seat to a cylinder head by forming a solid-phase diffusion layer at a bonding interface and forming a plastic deformation layer at least on the cylinder head side of the bonding interface. .

[0006]

The hardness required for the valve seat varies depending on the type of the internal combustion engine and the like. However, according to the conventional resistance heat joining method, the hardness of the valve seat after joining is set to a desired value. It was impossible to set.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a joint type valve seat having desired mechanical properties and a method of manufacturing the same.

[0008]

In order to achieve the above object, according to the first aspect of the present invention, a solid-phase diffusion layer is formed at a bonding interface and a plastic deformation layer is formed at least on the cylinder head side of the bonding interface. By doing so, the structure of the base after bonding of the bonded type valve seat that is metallurgically bonded to the cylinder head contains martensite or bainite.

A second aspect of the present invention is characterized in that, in the first aspect of the present invention, the martensite or bainite is contained at a ratio of 1 to 80% in the area ratio in the matrix.

According to a third aspect of the present invention, a sheet ring material formed into a ring shape from an Fe-based sintered material is heated and pressed to form a solid-phase diffusion layer at a joint interface between the sheet ring material and a cylinder head. Manufacture of a joint type valve seat in which a seat ring material is metallurgically joined to a cylinder head by forming a plastic deformation layer at least on a cylinder head side of a joining interface, and after joining, the seat ring material is machined into a desired shape. The method is characterized in that the seat ring material is heat-treated at the time of joining the seat ring material.

According to a fourth aspect of the present invention, in the third aspect of the invention, the structure of the joined valve seat after joining is adjusted to include martensite or bainite by adjusting the joining conditions and the sectional shape of the seat ring material. It is characterized by having done.

According to a fifth aspect of the present invention, in the fourth aspect of the invention, the area ratio of the martensite or bainite in the base is set to 1 to 80%.

According to a sixth aspect of the present invention, in the invention of the fourth aspect, the joining condition is a heating / cooling condition of the seat ring material, and the seat ring material is heated to a temperature higher than a temperature at which a part of its structure reaches the austenite region. It is characterized by heating and rapid cooling.

According to a seventh aspect of the present invention, in the sixth aspect, the seat ring material is cooled at a speed of 2 deg / sec or more.

Therefore, according to the present invention, desired mechanical properties including hardness can be imparted to the joint-type valve seat by heat-treating the seat ring at the time of joining the seat ring. For example, if the structure of the joined valve seat after joining is made to contain martensite or bainite by adjusting the joining conditions and the cross-sectional shape of the seat ring material, the hardness of the joined valve seat is set to a desired value. be able to. The hardness of the joint type valve seat increases as the content of martensite or bainite increases.

[0016]

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

In this embodiment, a case where a valve seat is joined to a cylinder head of a four-cycle engine will be described.

First, the structure of a cylinder head of a four-stroke engine will be outlined with reference to FIGS.

FIG. 1 is a longitudinal sectional view of a cylinder head of a four-cycle five-valve engine, and FIG. 2 is an enlarged detailed view of a portion A (a valve seat portion on the intake side) in FIG. Three intake valves 1-1 and 1-2
(1-1 is an intake valve on both sides, 1-2 is a central intake valve (center valve)) and two exhaust valves 2. The three intake ports 4 and the two exhaust ports 5 formed in the cylinder head 3 made of a lightweight cast Al alloy are respectively connected to the intake valves 1-1, 1-2,
It is opened and closed at an appropriate timing by the exhaust valve 2, whereby a required gas exchange is performed. The cast Al alloy as the material of the cylinder head 3 is JIS: A
C2B, AC4B, AC4C, etc. are selected.

On the lower surface of the cylinder head 3, a concave combustion dome 3a forming a combustion chamber 16 is formed, and the combustion chamber of the intake port 4 and the exhaust port 5 formed in the cylinder head 3 is formed. Valve seats 6 and 7 on which the intake valves 1-1 and 1-2 and the exhaust valve 2 are to be intermittently seated are respectively mounted on the periphery of the opening to the opening 16.

The intake valves 1-1 and 1-2 and the exhaust valve 2 are slidably inserted into the valve guides 8 and 9, respectively, and are urged in the closing direction by valve springs 10 and 11. Have been. And the intake valve 1
-1,1-2 and the exhaust valve 2 are connected to the valve lifters 12,1.
3 are driven at appropriate timings by the cams 14 and 15 which rotate while sliding on them. In FIG. 1, reference numerals 17, 18, and 19 denote water jackets formed around the intake port 4 and the exhaust port 5 of the cylinder head 3.

Here, the valve seats 6, 7 will be described.

In the present embodiment, the valve seats 6 and 7 are joined valve seats, which are formed in a ring shape from an Fe-based sintered material having excellent impact resistance, wear resistance and high-temperature strength. And is metallurgically joined to the cylinder head 3 by a resistance heat joining method. In addition, in order to impart high thermal conductivity and impact resistance to the valve seats 6, 7, the Fe-based sintered material, which is a material of the valve seats 6, 7, is filled with a metal such as Cu by infiltration. I have.

FIG. 2 shows the details of the joint portion of the valve seat 6 on the intake side. A plastic deformation layer, which will be described later, is provided on the cylinder head 3 side from the joint interface between the valve seat 6 and the cylinder head 3. 25 are formed. On the surface of the valve seat 6, a region a in which the structure is transformed from austenite to martensite is formed as described later.

Further, three tapered surfaces 6a, 6b, 6c are formed on the inner peripheral portion of the valve seat 6, and the tapered surface 6b is a contact surface (seating surface) of the intake valves 1-1, 1-2. It has become. Also, the outer peripheral surface of the valve seat 6 has
Tapered surfaces 6d and 6e are formed, and both tapered surfaces 6d and 6e are formed.
The portion where 6e intersects constitutes an obtuse projection 6f.
The cross-sectional shape of the exhaust-side valve seat 7 is the same as that of the intake-side valve seat 6, and a description thereof will be omitted.

Next, the process of joining the intake side valve seat 6 to the cylinder head 3 will be described with reference to FIGS. 3 is a schematic configuration diagram of a resistance welding machine, FIGS. 4 to 9 are partial cross-sectional views for explaining a joining process of a valve seat, and FIG. 10 is an enlarged detailed view of a portion B in FIG.

The resistance welding machine 20 shown in FIG.
1, an electrode 22 pressurized by the pressurizing device 21,
A power supply device (not shown) for supplying power to the electrode 22 is included. The electrode 22 is made of Cu or an alloy thereof, and a circular hole 22a is formed through the center of the electrode 22. A round bar-shaped guide bar 23 is slidably fitted in the circular hole 22a.

Thus, the resistance welding machine 20 having the above configuration
, A cylinder head 3 and a seat ring material 6 'are set as shown. That is, the cylinder head 3 is positioned by fitting the guide bar 23 of the resistance welding machine 20 into the valve guide hole 3b formed therein, and the opening of the intake port 4 formed in the cylinder head 3 is formed. The periphery is accurately positioned with respect to the electrode 22.
The seat ring material 6 'is a material of the valve seat 6, and is formed into a ring shape by an Fe-based sintered material.
The details of the cross-sectional shape are shown in FIG.

As shown in FIG. 4, when the seat ring member 6 'is joined to the cylinder head 3, the projection 6a' on the outer periphery of the seat ring member 6 'has an opening in the intake port 4 of the cylinder head 3. The electrode 2 is set in a state in which the electrode 2 is in contact with the peripheral edge of the electrode 2 and is then pressed by the pressing device 21 shown in FIG.
2 is moved down along the guide bar 23 to be fitted on the inner peripheral tapered surface 6b 'of the seat ring member 6', and the seat ring member 6 'starts to be pressed by the electrode 22 with a predetermined pressure P.

As described above, the seat ring member 6 'is
When current is applied to the seat ring member 6 ′ by the electrode 22 while the pressure is applied by 2, current flows from the seat ring member 6 ′ to the cylinder head 3, and the contact portion between them and the periphery thereof are heated. Then, the casting A having a smaller deformation resistance than the Fe-based sintered material that is the material of the seat ring material 6 ′.
As shown in FIG. 5, the cylinder head 3 made of an alloy is plastically deformed, and the seat ring material 6 ′ sinks into the cylinder head 3.

In the present embodiment, the heating temperature in the joining process of the cylinder head 3 made of cast Al alloy, which is a low melting point material, is controlled so as not to exceed the solidus temperature of the cast Al alloy. Is set within a temperature range in which plastic flow can be performed in the vicinity of the joining interface in a solid phase. In addition, the energizing time to the electrode 22 of the resistance welding machine 20 is as follows.
The current supply time is set to be sufficient and sufficient to allow the cast Al alloy to plastically flow in a solid phase in the vicinity of the joining interface.

On the other hand, the heating temperature in the joining process of the seat ring material 6 'composed of the Fe-based sintered material, which is a high melting point material, is such that a part (particularly, the center) of the Fe-based sintered material has an A ₃ transformation point temperature ( (About 700 ° C.).

When the contact portion between the seat ring member 6 'and the cylinder head 3 and its surroundings are heated in the above-mentioned temperature range as described above, the atomic motion activated by the temperature rise results in As shown in FIG. 10, solid-state diffusion of Fe atoms and Al atoms occurs, and by this solid-phase diffusion, the seat ring member 6 ′ is strongly metallurgically bonded to the cylinder head 3, and as shown in FIG. A very thin solid-state diffusion layer 24 having an Al alloy composition is formed. FIG. 11 is a diagram showing the concentration distribution of the main component Al of the cast Al alloy near the joint interface between the seat ring member 6 ′ and the cylinder head 3.

At the same time, the cast Al alloy constituting the cylinder head 3 causes a plastic flow in the direction of the arrow in FIG. 10 at the joint interface with the seat ring material 6 ', and the oxide film covering the surfaces of both metal materials is It is destroyed by the plastic flow of the cast Al alloy and is pushed out of the joint interface, and further,
The dirt adhering to the joint surface of both metal materials is also discharged out of the joint interface by the plastic flow of the cast Al alloy, so that the oxide film and the dirt do not get caught in the joint interface.

When the seat ring member 6 'sinks into the cylinder head 3 by a predetermined amount as shown in FIG. 7, the power supply to the electrodes 22 is terminated, and the seat ring member 6' draws air from the cylinder head 3. It is firmly joined to the periphery of the opening of the port 4. Then, as shown in FIGS. 7 and 11, a plastically deformable layer 25 having a predetermined thickness is formed on the cylinder head 3 side (Al alloy side) with the joining interface as a boundary.

When the seat ring member 6 'is metallically joined to the periphery of the opening of the intake port 4 of the cylinder head 3 as described above, the electrode 22 is removed and the seat ring member 6' is removed as shown in FIG. When the pressure applied to the valve seat 6 is released, and finally, as shown in FIG. Is completed, and the valve seat 6 is firmly joined to the periphery of the opening of the intake port 4 of the cylinder head 3 to be integrated.

Although the joining process of the valve seat 6 on the intake side has been described above, the valve seat 7 on the exhaust side has been described.
Is firmly joined to the cylinder head 3 in the same manner.

By the way, in the present embodiment, FIG.
In the state where the seat ring member 6 ′ is heated and pressurized, a part of the heat of the seat ring member 6 ′ is transferred from the inner peripheral tapered surface 6 b ′ and the contact surface with the cylinder head 3 to the electrode 22, as shown in FIG. As shown in FIG.
The temperature at the central part indicated by a is partially higher than other parts, and the temperature rises above the A ₃ transformation point temperature (about 700 ° C.).

In the state shown in FIG. 7 where the heating of the seat ring member 6 'is completed, the seat ring member 6'
Is rapidly cooled at a rate of 2 deg / sec or more and heat-treated, and the region a heated to a temperature not lower than the A ₃ transformation point is transformed into a martensite in which the structure is transformed from austenite to a supersaturated carbon in a supersaturated state. Becomes very hard.

Here, the cooling rate of the seat ring 6 '(d
FIG. 12 shows the relationship between the hardness (eg / sec / eg / sec) and the hardness.
If the seat ring 6 'is rapidly cooled at a cooling rate of eg / sec or more, the desired hardness of the seat ring 6' is ensured. The cooling rate on the horizontal axis in FIG. 12 is displayed on a logarithmic scale.

FIG. 13 shows the relationship between the area ratio (%) of martensite in the matrix of the seat ring material 6 'and the hardness. As shown in FIG. The hardness of the material 6 'also increases linearly.
Here, the term “base” refers to a portion obtained by removing hard particles and infiltrated copper from the entire structure of the seat ring 6 ′.

By the way, in this embodiment, by adjusting the joining conditions (heating / pressurizing conditions and cooling rate) of the seat ring member 6 'and the cross-sectional shape of the seat ring member 6', the seat ring member after joining is adjusted. The area ratio of martensite in the base of the material 6 'is set to 1 to 80%.

FIG. 14 shows the hardness of the seat ring member 6 'when the current supply pattern and the pressing force pattern are variously changed. In the examples shown in FIGS. (3 steps) and the pressure P is also increased and applied stepwise (2 steps).

In the example shown in FIG. 14A, since the relatively high current I is supplied in a short time, the range of the region a in which the seat ring member 6 'is rapidly heated to the austenite region is heated. And the content of martensite after quenching increased, indicating a high hardness value. Also, FIG.
In the examples shown in FIGS. 4B and 4C, a lower current I is supplied for a longer time than in the example shown in FIG. As a result, in the example shown in FIG. 14B, the hardness is lower than that shown in FIG.
As shown in the graph, when the pressure P is increased, the hardness is further reduced.

Here, FIGS. 15 to 17 show the state of the region a (the region where the structure is transformed into martensite) of the seat ring material 6 'and the hardness distribution along the line CD shown in the figure, respectively.

In the example shown in FIG. 15, the range of the region a is relatively wide, and in the hardness distribution, the region having high hardness is widened corresponding to the wide region a. In the example shown in FIG. Is relatively narrow, and the hardness shows a generally flat distribution showing a high value at the approximate center in the width direction as shown by the solid line in the same figure, or the hardness is narrow at the approximate center in the width direction as shown by the broken line The distribution showing a sharp peak value in the region is shown.

In the example shown in FIG. 17, FIGS.
Is not formed inside the seat ring material 6 ', and accordingly, the hardness shows a substantially constant low value over the entire width.

Next, FIG. 18 shows the results of actual measurement of the hardness of the seat ring member 6 'with various cross-sectional shapes.

In the cross-sectional shape of the seat ring member 6 ′, the longer the length L of the surface in contact with the electrode 22 (that is,
The larger the contact area) and the smaller the maximum thickness t (that is, the smaller the heat capacity), the higher the heat dissipation of the seat ring member 6 ′, so that the temperature rise inside the seat ring member 6 ′ is suppressed. As a result, the range of the region a is narrowed, and accordingly, the hardness of the seat ring material 6 ′ is reduced (FIG. 18A,
(C) and (d)). Conversely, the shorter the length L (that is,
The smaller the contact area) and the larger the maximum thickness t (that is, the larger the heat capacity), the lower the heat dissipation of the seat ring member 6 ′, so that the temperature rise inside the seat ring member 6 ′ is accelerated. As a result, the range of the region a is widened, and accordingly, the hardness of the seat ring material 6 ′ is increased (FIG. 18B,
(E)).

As described above, according to the present invention, the valve seats 6, 7 are metallurgically joined to the cylinder head 3 by the resistance thermal joining method. Since the martensite is contained in the base of the seat ring material 6 'after joining by adjustment at an area ratio of 1 to 80%, the joint type valve seat 6 is adjusted by adjusting the content of martensite. 7
Can be set to a desired value corresponding to each engine type and the like.

By the way, the structure of the region a heated up to the austenite region is transformed into martensite by rapidly cooling the seat ring material 6 ′, but at a predetermined temperature (below the “nose” of the transformation start curve). The same effect as described above can be obtained even when the structure in the region a is subjected to constant temperature transformation from austenite to bainite by cooling at a predetermined rate from a low temperature. In the present invention, the area ratio of bainite is also set to 1 to 80%.

FIG. 19 shows the isothermal transformation diagram (T
In the figure, Ms and Mf respectively indicate the start temperature and the end temperature of the martensitic transformation, and the protruding portion (point N in the drawing) of the transformation start curve is referred to as "nose".

In the above, the manufacturing method for controlling the hardness of the joint type valve seat by the heat treatment at the time of joining has been particularly described. However, according to the present invention, the mechanical properties other than the hardness (elongation, etc.) by the heat treatment at the time of joining are performed. ) Can be controlled.

[0054]

As is apparent from the above description, according to the present invention, by heat-treating the seat ring material at the time of joining the seat ring material, the desired mechanical properties including the hardness of the joined type valve seat are obtained. Can be obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a cylinder head of a four-stroke engine provided with a joint type valve seat according to the present invention.

FIG. 2 is an enlarged detailed view of a portion A (a valve seat portion on an intake side) in FIG. 1;

FIG. 3 is a half sectional view for explaining a joining process of a joined type valve seat.

FIG. 4 is a schematic configuration diagram of a resistance welding machine.

FIG. 5 is a partial cross-sectional view for explaining a joining process of the joined type valve seat.

FIG. 6 is a partial cross-sectional view for explaining a joining process of the joined type valve seat.

FIG. 7 is a partial cross-sectional view for explaining a joining process of the joined type valve seat.

FIG. 8 is a partial cross-sectional view for explaining a joining process of the joined type valve seat.

FIG. 9 is a partial cross-sectional view for explaining a joining process of the joined type valve seat.

FIG. 10 is an enlarged detail view of a portion B in FIG. 6;

FIG. 11 is a view showing a structure near a joint interface between a joint type valve seat and a cylinder head.

FIG. 12 is a diagram showing a relationship between a cooling rate and hardness of a seat ring material.

FIG. 13 is a diagram showing a relationship between the area ratio (%) of martensite in a base of a seat ring material and hardness.

FIG. 14 is a diagram showing the hardness of the seat ring material when the current supply pattern and the pressing force pattern are variously changed.

FIG. 15 is a diagram showing a state of an internal structure and a hardness distribution of the seat ring material.

FIG. 16 is a diagram showing the state of the internal structure and the hardness distribution of the seat ring material.

FIG. 17 is a view showing the state of the internal structure of the seat ring material and the hardness distribution.

FIG. 18 is a view showing the results of actually measuring the hardness of the seat ring material while changing the cross-sectional shape of the seat ring material in various ways.

FIG. 19 is a isothermal transformation diagram (TTT diagram) of the eutectoid steel.

FIG. 20 is a longitudinal sectional view of a cylinder head of a conventional four-stroke engine including a press-fit valve seat.

[Explanation of symbols]

 Reference Signs List 3 Cylinder head 6, 7 Joint type valve seat 6 'Seat ring material 20 Resistance welder 21 Pressurizing device 22 Electrode 25 Plastic deformation layer

Claims (7)

[Claims] 1. A joint type valve seat which is metallurgically joined to a cylinder head by forming a solid phase diffusion layer at a joint interface and forming a plastic deformation layer at least on the cylinder head side of the joint interface. A joint type valve seat characterized in that the structure of the joined base contains martensite or bainite. 2. The joint type valve seat according to claim 1, wherein the martensite or bainite is contained in a matrix at a ratio of 1 to 80% in area. 3. A solid-state diffusion layer is formed at a joint interface between a sheet ring material formed into a ring shape from an Fe-based sintered material and a cylinder head by heating and pressurizing the sheet ring material. Forming a plastically deformable layer on the side, metallurgically joining the seat ring material to the cylinder head, and after joining, machining the seat ring material into a desired shape. A method for manufacturing a joined type valve seat, comprising heat-treating the seat ring material at the time of joining the members. 4. The joint type valve according to claim 3, wherein the structure of the joint type valve seat after joining includes martensite or bainite by adjusting the joining conditions and the sectional shape of the seat ring material. Sheet manufacturing method. 5. The method according to claim 4, wherein an area ratio of the martensite or bainite in the matrix is set to 1 to 80%. 6. The bonding condition includes heating of a seat ring material.
The method for manufacturing a joined type valve seat according to claim 4, wherein cooling conditions are such that the seat ring material is heated to a temperature higher than a temperature at which a part of its structure reaches an austenitic region and rapidly cooled. 7. The seat ring material is 2 deg / sec.
The method according to claim 6, wherein the cooling is performed at the above-described speed.