WO2019065186A1

WO2019065186A1 - Cylinder head, internal combustion engine, and method for manufacturing cylinder head

Info

Publication number: WO2019065186A1
Application number: PCT/JP2018/033464
Authority: WO
Inventors: 貴晴鈴木
Original assignee: ヤマハ発動機株式会社
Priority date: 2017-09-28
Filing date: 2018-09-10
Publication date: 2019-04-04

Abstract

A cylinder head (1) according to an embodiment of the present invention is provided with: a cylinder head body (10) having an intake port (11) and an exhaust port (12), the cylinder head body being formed of an aluminum alloy; and a valve seat formed of an iron-based alloy and resistance-welded to a downstream end portion of the intake port (11). The valve seat (20) has at least one groove (21), which extends in the circumferential direction of the valve seat (20), on a portion contacting the cylinder head body (10).

Description

Cylinder head, internal combustion engine and method of manufacturing cylinder head

The present invention relates to a cylinder head. The present invention also relates to a method of manufacturing an internal combustion engine provided with a cylinder head and a cylinder head.

The cylinder head of an internal combustion engine is generally formed of an aluminum alloy. At the downstream end of the intake and exhaust ports of the cylinder head are provided valve seats for receiving the valves.

The valve seat is exposed to high temperatures and repetitively loaded from the valve during operation of the internal combustion engine. Therefore, the valve seat is often formed of an iron-based alloy excellent in high temperature strength and wear resistance.

As a structure for attaching a valve seat to a cylinder head, after carrying out the lower hole processing to a cylinder head, the structure which press-fits the valve seat processed precisely is adopted in many cases. Generally, since the thermal expansion coefficient of an aluminum alloy is larger than that of an iron-based alloy, the pressing force of a pressed-in valve seat becomes smaller as the temperature of the cylinder head becomes higher. Since there is a risk that the valve seat may fall off when the tension force is reduced, a fixed amount of press-fit allowance for the valve seat is secured.

However, in designing the port, the smaller the valve seat press-in allowance, the higher the freedom of port design. As the internal combustion engine in recent years has been increased in output and size, a technique for further improving the port design freedom is desired.

Patent Document 1 proposes a technique which has a high degree of freedom in port design and can firmly connect a valve seat to a cylinder head. In the technique of Patent Document 1, a valve seat base material formed of an iron-based sintered alloy and having a metal film (for example, a copper film) on the surface is joined to a cylinder head made of an aluminum alloy by resistance welding.

Unexamined-Japanese-Patent No. 8-296417

Although the design freedom of the port can be enhanced and the valve seat can be firmly joined to the cylinder head by the technique of Patent Document 1, it is desirable that the valve seat can be more reliably prevented from falling off.

The present invention has been made in view of the above problems, and an object thereof is to provide a cylinder head in which falling off of a valve seat is more reliably prevented.

A cylinder head according to an embodiment of the present invention is a cylinder head main body having an intake port and an exhaust port, and is a cylinder head main body formed of an aluminum alloy and a valve seat formed of an iron-based alloy And a valve seat resistance-welded to the downstream end of the port, the valve seat having at least one groove extending in the circumferential direction of the valve seat at a portion contacting the cylinder head body.

In one embodiment, the at least one groove is a single groove.

In one embodiment, the one groove is disposed in a port-side half portion vertically divided from a valve contact surface middle point of the valve seat.

In one embodiment, the at least one groove is two grooves.

In one embodiment, the two grooves are respectively disposed in a port side half and a combustion chamber side half vertically divided from a middle point of a valve contact surface of the valve seat.

In one embodiment, the depth of the at least one groove is 0.1 mm or more and 0.3 mm or less.

In one embodiment, the at least one groove includes an undercut surface, and the undercut surface is formed at an outer peripheral end formed at one end in the radial direction and at the other end in the radial direction. The inner peripheral end is formed at the same position as the outer peripheral end in the axial direction of the valve seat or at a position closer to the combustion chamber than the outer peripheral end in the axial direction of the valve seat It is formed.

In one embodiment, each of the at least one groove is defined by a first groove surface and a second groove surface, and a cross section along a radial direction of the valve seat is substantially triangular.

In one embodiment, an angle between the first groove surface and the second groove surface is 45 ° or more and 75 ° or less.

In one embodiment, the bottom of each of the at least one groove has a rounded shape.

In one embodiment, the radius of curvature of the rounded shape is 0.02 mm or more and 0.15 mm or less.

In one embodiment, the solidus temperature of the aluminum alloy is 520 ° C. or more and 580 ° C. or less.

In one embodiment, the iron-based alloy is an iron-based sintered alloy in which copper or a copper alloy is infiltrated.

In one embodiment, the volume resistivity of the iron-based sintered alloy is higher than the volume resistivity of the aluminum alloy.

In one embodiment, the volume resistivity of the iron-based sintered alloy at room temperature is 10 μΩcm or more and 38 μΩcm or less.

In one embodiment, the valve seat has a copper plating layer or a copper alloy plating layer formed on a portion not in contact with the cylinder head body.

In one embodiment, in the vicinity of the interface between the valve seat and the cylinder head main body, the aluminum alloy intrudes into pores of the iron-based sintered alloy.

In one embodiment, the valve seat is thicker at the intake port side than at the combustion chamber side.

In one embodiment, the cylinder head according to the present invention has an Fe—Al based intermetallic compound layer having a thickness of 10 nm or more and 700 nm or less in the vicinity of the interface between the valve seat and the cylinder head main body.

An internal combustion engine according to an embodiment of the present invention includes a cylinder head having any of the configurations described above.

A method of manufacturing a cylinder head according to an embodiment of the present invention is a method of manufacturing a cylinder head including a cylinder head main body having an intake port and an exhaust port, and a valve seat disposed at the downstream end of the intake port. A step (A) of preparing the cylinder head body formed of an aluminum alloy, a step (B) of preparing the valve seat formed of an iron-based alloy, and the valve at the downstream end of the intake port Bonding the sheets by resistance welding (C), wherein the valve seat prepared in the step (B) extends at least in the circumferential direction of the valve seat to a portion in contact with the cylinder head body. It has one groove.

In one embodiment, the step (C) is performed in a state in which a copper layer or a copper alloy layer is interposed between the valve seat and the cylinder head body.

In one embodiment, the step (C) is performed such that the temperature of the portion of the valve seat in contact with the cylinder head body does not exceed the melting point of the iron-based alloy.

In the cylinder head according to the embodiment of the present invention, the valve seat is resistance-welded to the downstream end of the intake port. Thereby, the design freedom of the port can be increased compared to the conventional configuration in which the valve seat is press-fit into the cylinder head body. Further, by using resistance welding, the valve seat can be firmly joined to the cylinder head body. Furthermore, in the cylinder head according to the embodiment of the present invention, the valve seat has at least one groove extending in the circumferential direction of the valve seat at a portion in contact with the cylinder head body. The groove is filled with an aluminum alloy which is a material of the cylinder head body. In other words, the groove is engaged with the projection of the cylinder head body. Therefore, by providing such a groove, even if the valve seat is not sufficiently joined to the cylinder head main body (when the valve seat is separated from the cylinder head main body), the valve seat falls off. Can be prevented.

According to an embodiment of the present invention, a cylinder head is provided in which the valve seat is more reliably prevented from falling off.

1 is a cross-sectional view schematically showing a cylinder head 1 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing the vicinity of a valve seat 20 of the cylinder head 1 in an enlarged manner. FIG. 2 is a cross-sectional view showing the vicinity of a valve seat 20 of the cylinder head 1 in an enlarged manner. FIG. 5 is an enlarged cross-sectional view showing the vicinity of a groove 21 of a valve seat 20. FIG. 5 is an enlarged cross-sectional view showing the vicinity of a groove 21 of a valve seat 20. FIG. 2 is a cross-sectional view schematically showing a valve seat 20. (A) And (b) is the front view and side view which each show resistance welding machine 200 typically. FIG. 6 is a cross-sectional view showing a state in which the upper electrode 209 of the resistance welder 200 is in contact with the valve seat 20. FIG. 5 is a cross-sectional view showing a state in which the valve seat 20 is superimposed on the cylinder head main body 10 (state before bonding). FIG. 6 is a cross-sectional view showing an initial state when joining the valve seat 20 to the cylinder head main body 10; FIG. 6 is a cross-sectional view showing a state at the time of joining when the valve seat 20 is joined to the cylinder head main body 10; (A), (b) and (c) is a figure which shows the state of the contact interface vicinity of the valve seat 20 and the cylinder head main body 10 in the case of resistance welding in a time series. (A) And (b) is a figure which shows the state of the contact interface vicinity of the valve seat 20 and the cylinder head main body 10 in the case of resistance welding in a time series. FIG. 2 is a cross-sectional view schematically showing a valve seat 20. It is a figure for demonstrating the method of a peeling test. It is a graph which shows the result of a exfoliation test about the case where valve seat 20 has slot 21 (when slot 21 is two), and the case where it does not have. 1 is a cross-sectional view schematically showing an internal combustion engine 100 provided with a cylinder head 1;

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments.

FIG. 1 shows a cylinder head 1 in the present embodiment. FIG. 1 is a cross-sectional view schematically showing a cylinder head 1 in the present embodiment. In FIG. 1, the intake valve 61 and the exhaust valve 62 are shown together.

As shown in FIG. 1, the cylinder head 1 of the present embodiment includes a cylinder head main body 10 and a valve seat 20.

The cylinder head body 10 is formed of an aluminum alloy. In the present embodiment, the cylinder head body 10 is formed by casting (that is, a cast product) from an aluminum alloy having a solidus temperature of 520 ° C. or more and 580 ° C. or less. As an aluminum alloy having a solidus temperature of 520 ° C. or more and 580 ° C. or less, for example, an Al-Si-Cu-based, Al-Si-Mg-based or Al-Si-Cu-Mg-based aluminum alloy can be used.

The cylinder head body 10 has an intake port 11 and an exhaust port 12. In the assembled state as an internal combustion engine, an intake valve 61 is disposed at the intake port 11 and an exhaust valve 62 is disposed at the exhaust port 12. The recess 10 a formed on the lower surface of the cylinder head body 10 constitutes a part of the combustion chamber.

The valve seat 20 is provided at the downstream end of the intake port 11. More specifically, the valve seat 20 is resistance welded to the downstream end of the intake port 11. The method of joining the valve seat 20 to the cylinder head body 10 by resistance welding will be described in detail later. The valve seat 20 is generally annular as a whole. The valve seat 20 is formed of an iron-based alloy. In the present embodiment, the valve seat 20 is formed of an iron-based sintered alloy in which copper or a copper alloy is infiltrated.

The cylinder head 1 of the present embodiment also includes a valve seat 30 provided at the downstream end of the exhaust port 12 in addition to the valve seat 20 provided at the downstream end of the intake port 11.

Hereinafter, the valve seat 20 and the structure in the vicinity thereof will be described with reference to FIG. FIG. 2 is an enlarged cross-sectional view showing a region in the vicinity of the valve seat 20 in FIG. 1 (a region R1 surrounded by a circle in FIG. 1).

As shown in FIG. 2, the valve seat 20 has at least one groove 21 extending in the circumferential direction of the valve seat 20 in a portion in contact with the cylinder head body 10. In the example shown in FIG. 2, the valve seat 20 is formed with two

grooves

21A and 21B. Each of the two

grooves

21A and 21B is typically formed over the entire circumference of the valve seat 20 (that is, in an annular shape).

One of the two grooves 21 is disposed in the port half 20 a of the valve seat 20, and the other 21 B is disposed in the combustion chamber half 20 b of the valve seat 20. In the specification of the present application, the combustion chamber side 20b located on the combustion chamber side of the valve seat 20 is referred to as “combustion chamber based on the vertical dividing line of the middle point of the valve contact surface 20c (position of half the length of the valve contact surface 20c) The half 20 a is called “side half”, and the half 20 a located on the side opposite to the combustion chamber side (sometimes called “port side”) is called “port half”.

Each of the

grooves

21A and 21B is filled with an aluminum alloy which is a material of the cylinder head body 10. In other words, the cylinder head body 10 has, at a portion in contact with the valve seat 20, a convex portion engaged with the

grooves

21A and 21B of the valve seat 20.

As described above, in the cylinder head 1 of the present embodiment, the valve seat 20 is resistance-welded to the downstream end of the intake port 11. Thereby, the design freedom of the port can be increased compared to the conventional configuration in which the valve seat is press-fit into the cylinder head body. Further, by using resistance welding, the valve seat 20 can be firmly joined to the cylinder head body 10 by a mechanism which will be described in detail later.

Furthermore, in the cylinder head 1 of the present embodiment, the valve seat 20 has at least one groove 21 extending in the circumferential direction of the valve seat 20 in a portion in contact with the cylinder head main body 10. As described above, the groove 21 is filled with the aluminum alloy that is the material of the cylinder head main body 10, in other words, the groove 21 is engaged with the convex portion of the cylinder head main body 10. Therefore, even if the joint force between the valve seat 20 and the cylinder head main body 10 is reduced by providing such a groove 21 (when the valve seat 20 is separated from the cylinder head main body 10), the valve It is possible to prevent the sheet 20 from falling off.

Although the case where the number of grooves 21 is two is illustrated in FIG. 2, the number of grooves 21 is not limited to two. The valve seat 20 may have one groove 21 or may have three or more grooves 21 in a portion in contact with the cylinder head body 10.

FIG. 3 shows an example of a configuration in which the valve seat 20 has one groove 21. In the example shown in FIG. 3, one groove 21 is disposed in the port side half 20 a of the valve seat 20.

From the viewpoint of more reliably preventing the valve seat 20 from falling off, it is preferable that the number of grooves 21 be large. That is, as in the example shown in FIG. 3, the configuration with two grooves 21 as in the example shown in FIG. 2 is preferable to the configuration with one groove 21. Although it can be said that the configuration of three or more grooves 21 is preferable to the configuration of two from the viewpoint of preventing the valve seat 20 from falling off, if the number of grooves 21 is too large, The groove 21 may be too close to the contact point of the cylinder head body 10, so that energization may not be performed preferably. Therefore, from the viewpoint of suitably performing resistance welding, it is preferable that the number of grooves 21 is two or less.

In the case where two grooves 21 are provided, as illustrated in FIG. 2, when two grooves 21 are respectively disposed in the port side half 20 a and the combustion chamber side half 20 b of the valve seat 20, Highly effective in preventing falling off. Further, it is more preferable that one 21A of the two grooves 21 is disposed in the upper half of the port half 20a and the other 21B is disposed in the lower half of the combustion chamber half 20b. .

In the case where one groove 21 is provided, as shown in FIG. 3, it is preferable that the groove 21 be disposed in the port side half 20 a of the valve seat 20. Since the port side half 20a of the valve seat 20 receives more vertical load from the intake valve 61 than the combustion chamber side half 20b, peeling of the valve seat 20 occurs on the combustion chamber side half at the port side half 20a. It is more likely to occur than at 20b. In the case where the number of the grooves 21 is one, by arranging the groove 21 in the port side half portion 20 a of the valve seat 20, the effect of preventing the falling off becomes high.

Subsequently, with reference to FIG. 4, a preferable configuration of the groove 21 of the valve seat 20 will be described.

In the example shown in FIG. 4, the groove 21 is defined by the first groove surface 21 a and the second groove surface 21 b. The cross section of the groove 21 along the radial direction of the valve seat 20 is substantially triangular.

The depth d of the groove 21 is not particularly limited. However, if the depth d of the groove 21 is too small, the effect of the drop prevention may be reduced. Therefore, the depth d of the groove 21 is preferably 0.1 mm or more. If the depth d of the groove 21 is too large, it may be difficult to fill the groove 21 with an aluminum alloy, or the thickness of the valve seat 20 may be locally reduced to cause a crack. Therefore, the depth d of the groove 21 is preferably 0.3 mm or less.

From the viewpoint of more reliably preventing the valve seat 20 from falling off, the groove 21 preferably has a shape that is easily caught by the protrusion of the cylinder head main body 10. Specifically, the groove 21 is undercut with respect to the axis (central axis) Bc of the valve seat 20 (that is, it is hooked when trying to lower the valve seat 20 along the axis Bc) Is preferred. Specifically, the groove 21 preferably includes an undercut surface. In the example shown in FIG. 4, the first groove surface 21 a is an undercut surface. The first groove surface 21a, which is an undercut surface, is formed at an outer peripheral end 21a1 formed at one end in the radial direction and at the other end in the radial direction and an inner periphery formed inward in the radial direction than the outer peripheral end 21a1. The inner peripheral end 21a2 is formed at the same position as the outer peripheral end 21a1 or at a position closer to the combustion chamber than the outer peripheral end 21a1 in the direction of the axis Bc.

There is no restriction in particular in angle alpha which the 1st slot side 21a and the 2nd slot side 21b make. However, if the angle α between the first groove surface 21 a and the second groove surface 21 b is too small, it may be difficult to fill the groove 21 with the aluminum alloy. Therefore, the angle α is preferably 45 ° or more. If the angle α between the first groove surface 21a and the second groove surface 21b is too large, the groove 21 may not be easily caught by the convex portion of the cylinder head main body 10 (the undercut is eliminated). Therefore, the angle α is preferably 75 ° or less.

Another example of the shape of the groove 21 is shown in FIG. The bottom of the groove 21 does not have to be a sharp corner as schematically shown in FIG. 4 and may have a rounded shape as shown in FIG. The rounded shape of the bottom of the groove 21 facilitates filling the groove 21 with the aluminum alloy that is the material of the cylinder head body 10.

There is no particular limitation on the radius of curvature of the radius of the bottom of the groove 21. However, if the radius of curvature of the rounded shape is too small, the effect of the rounded shape may not be obtained sufficiently, and if the radius of curvature of the rounded shape is too large, the groove 21 is less likely to be caught by the convex portion of the cylinder head body 10 There is a risk that it will not be undercut. Therefore, the radius of curvature of the rounded shape of the bottom of the groove 21 is preferably 0.02 mm or more and 0.15 mm or less.

The valve seat 30 provided at the downstream end of the exhaust port 12 may have the same configuration as the valve seat 20 provided at the downstream end of the intake port 11, or may have a different configuration. Good. The valve seat 30 does not have to be resistance welded to the downstream end of the exhaust port 12 and may be press-fit.

Subsequently, a method of manufacturing the cylinder head 1 of the present embodiment will be described.

First, a cylinder head body 10 formed of an aluminum alloy is prepared. In the present embodiment, a cast product formed by casting from an aluminum alloy having a solidus temperature of 520 ° C. or more and 580 ° C. or less is prepared as the cylinder head body 10. As an aluminum alloy having a solidus temperature of 520 ° C. or more and 580 ° C. or less, for example, an Al-Si-Cu-based, Al-Si-Mg-based or Al-Si-Cu-Mg-based aluminum alloy can be used.

Further, separately from preparing the cylinder head body 10, a valve seat 20 formed of an iron-based alloy is prepared. In the present embodiment, the valve seat 20 is formed of an iron-based sintered alloy in which copper or a copper alloy is infiltrated.

FIG. 6 shows an example of the valve seat 20 prepared. In FIG. 6, in the completed cylinder head 1, the portion on the combustion chamber side is shown as the upper side, and the portion on the port side is the lower side. In the example shown in FIG. 6, the valve seat 20 has two grooves 21 extending in the circumferential direction of the valve seat 20 in a portion (specifically, the outer peripheral surface 20 o) in contact with the cylinder head body 10. The outer peripheral surface 20o of the valve seat 20 is inclined such that the outer diameter of the valve seat 20 decreases toward the port side. Further, the outer peripheral surface 20 o of the valve seat 20 is formed to be a convex curved surface. On the other hand, the inner peripheral surface 20i of the valve seat 20 is substantially parallel to the axis Bc from the inner peripheral end of the inclined surface 20i1 and the inner peripheral side of the inclined surface 20i1 inclined such that the inner diameter of the valve seat 20 decreases toward the port side. And an axially extending surface 20i2.

Further, in the example shown in FIG. 6, the valve seat 20 has a copper alloy plated layer (or copper plated layer) 22 on the surface thereof. The thickness of the copper alloy plating layer 22 is, for example, 0.1 μm or more and 30 μm or less. In addition, the valve seat 20 prepared in this process may differ in the shape from the valve seat 20 in the completed cylinder head 1. This is because finish processing and the like are performed as described later.

Subsequently, the valve seat 20 is joined to the downstream end of the intake port 11 by resistance welding. In the present embodiment, since the valve seat 20 has the copper alloy plated layer (or copper plated layer) 22 on its surface, this bonding step is performed by using a copper alloy between the valve seat 20 and the cylinder head body 10. It will be carried out with the layer (or copper layer) interposed. Hereinafter, this bonding step will be described more specifically.

First, a resistance welding machine (press device) 200 used in the bonding step will be described with reference to FIG. 7. FIGS. 7A and 7B are a front view and a side view schematically showing the resistance welder 200, respectively.

As shown in FIGS. 7A and 7B, the resistance welder 200 includes a base 201, a lower platen 202 fixed to a lower portion of the base 201, and an upper platen disposed above the lower platen 202. And 203. The upper platen 203 is vertically movable, and can approach and separate from the lower platen 202. The cylinder device 204 is attached to the upper portion of the base 201 so that the axis line is in the vertical direction, and the upper platen 203 is fixed to the lower end of the rod 204 a of the cylinder device 204.

The lower platen 202 and the upper platen 203 are supplied with power from a power feeding device (not shown) via the

conductive members

202a and 203a, respectively. The conductive member 203 a connected to the upper platen 203 is configured to be deformed or raised and lowered according to the raising and lowering operation of the upper platen 203. Here, the upper platen 203 functions as an anode, and the lower platen 202 functions as a cathode.

A reflective member 205 is fixed to the front of the upper platen 203. A laser displacement gauge 206 is attached to the top of the base 201. The laser displacement meter 206 reflects the laser light on the reflecting member 205 and measures the displacement amount of the upper platen 203 from the distance to the reflecting member 205.

When the resistance welding is performed, first, the lower electrode 207 is fixed on the lower platen 202, and the cylinder head body 10 is mounted on the lower electrode 207. At this time, in the cylinder head body 10, the lower surface (the surface on which the recess 10a is formed) is directed upward, and the axis at the downstream end of the intake port 11 coincides with the axis of the rod 204a of the cylinder device 204. Place on

Next, as shown in FIG. 8, the guide rod 208 is inserted into the valve guide hole 11 a of the intake port 11. The guide rod 208 has a metal round rod 208a and an insulating layer (for example, an alumina layer) 208b formed on the outer peripheral surface of the round rod 208a, and is positioned by the stopper 208c in a state fitted to the valve guide hole 11a. It is held.

Subsequently, the valve seat 20 is stacked on the downstream end of the intake port 11, and the upper electrode 209 is placed on the valve seat 20. The upper electrode 209 has a cylindrical shape, and a hole 209a in which the guide rod 208 is fitted is formed in the shaft portion thereof. At the lower end of the upper electrode 209, a tapered surface 209b in contact with the inclined surface 20i1 of the valve seat 20 and a positioning circumferential surface 209c in contact with the axially extending surface 20i2 over the entire circumference are formed. Further, at the lower end portion of the upper electrode 209, a magnetic body 209d for magnetically attracting the valve seat 20 is provided.

By fitting the guide rod 208 into the hole 209 a of the upper electrode 209, the upper electrode 209 is positioned coaxially with the downstream end of the intake port 11 of the cylinder head body 10. Further, by bringing the tapered surface 209 b and the circumferential surface 209 c of the upper electrode 209 into contact with the valve seat 20, the valve seat 20 is positioned so as to be coaxial with the downstream end of the intake port 11.

Thereafter, the cylinder device 204 is driven to lower the upper platen 203 so as to be in close contact with the upper electrode 209. At this time, the lower surface of the upper platen 203 and the upper surface of the upper electrode 209 are parallel to each other.

Next, the cylinder device 204 is driven to lower the upper platen 203 further, and the valve seat 20 is pressed against the cylinder head body 10 with a constant pressing force via the upper electrode 209. The pressing force is set to be relatively weak at the beginning of the bonding process and then relatively strong.

After a predetermined time has elapsed from the start of pressing, a voltage is applied to upper platen 203 and lower platen 202, and current is applied between these two platens, ie, upper electrode 209, valve seat 20, cylinder head body 10 and lower electrode 207. Flow. At this time, current flows from the upper electrode 209 toward the cylinder head body 10.

The state at this time (that is, before bonding) is shown in FIG. As shown in FIG. 9, the outer peripheral surface (which is a convex curved surface) 20o of the valve seat 20 is in contact with the cylinder head body 10, and the area of the portion where these contact is extremely small. Therefore, when electricity is supplied, local heat is generated because the electrical resistance is large at this portion.

When the temperature of the contact interface between the valve seat 20 and the cylinder head main body 10 rises due to this heat generation, the composition in the vicinity of the interface is the copper contained in the copper alloy plated layer 22 and the aluminum alloy which is the material of the cylinder head main body 10 As a eutectic alloy, a liquid phase of a copper-rich aluminum alloy is generated. The state at this time (initial stage of bonding) is shown in FIG. As shown in FIG. 10, the aluminum oxide film and foreign matter are swept away to the outside of the contact portion by the eutectic alloy La which has been liquid phased.

Thereafter, when the temperature of the contact interface is further increased, the aluminum alloy of the cylinder head body 10 in the vicinity of the eutectic alloy layer is plastically flowed by the pressure of the valve seat 20 and the temperature rise due to heat generation. Causes (plastic deformation). Therefore, the valve seat 20 starts to sink into the cylinder head body 10, and when joining is completed, substantially the entire outer peripheral surface 20o of the valve seat 20 is buried in the cylinder head body 10 as shown in FIG. At this time, the groove 21 of the valve seat 20 is filled with the aluminum alloy which is the material of the cylinder head body 10.

Thus, the valve seat 20 can be joined to the downstream end of the intake port 11 of the cylinder head body 10 by resistance welding.

Thereafter, the cylinder head 1 can be obtained by finishing and removing unnecessary portions. When joining by the mechanism described above is performed, as described in Patent Document 1, the valve seat 20 can be firmly joined to the cylinder head main body 10.

From the viewpoint of suitably performing joining by resistance welding, it is preferable to use an aluminum alloy having a solidus temperature of 520 ° C. or more and 580 ° C. or less as the aluminum alloy.

Further, the volume resistivity of the iron-based sintered alloy which is the material of the valve seat 20 is made higher than the volume resistivity of the aluminum alloy which is the material of the cylinder head body 10, and the bonding process is performed in the cylinder head body of the valve seat 20. It is preferable to carry out so that the temperature of the part which contacts 10 does not become more than the melting point of the material of the valve seat 20. Thereby, the valve seat 20 can be prevented from being melted and damaged at the time of joining by resistance welding. The volume resistivity of the iron-based sintered alloy which is the material of the valve seat 20 is preferably 10 μΩcm or more and 38 μΩcm or less. The volume resistivity referred to here is that at room temperature (for example, 25 ° C.).

When the cylinder head 1 is manufactured using the valve seat 20 having the copper alloy plated layer (or copper plated layer) 22 on the surface, the valve seat 20 does not contact the cylinder head main body 10 in the completed cylinder head 1 It will have a copper alloy plating layer (or copper plating layer) 22 in the part. The remaining copper alloy plated layer (or copper plated layer) 22 provides an antirust effect.

In addition, when bonding is performed by the above-described mechanism, a phenomenon occurs in which an aluminum alloy intrudes into the pores of the iron-based sintered alloy in the vicinity of the interface between the valve seat 20 and the cylinder head main body 10. Hereinafter, this phenomenon will be described with reference to FIGS. 12 and 13. 12 (a), (b), (c) and FIGS. 13 (a) and (b) show the state near the contact interface between the valve seat 20 and the cylinder head body 10 at the time of resistance welding in time series. FIG. 12 (a), (c) and 13 (b) correspond to the states shown in FIGS. 9, 10 and 11, respectively.

As can be seen from FIGS. 12 (a), (b) and (c) and FIGS. 13 (a) and (b), the temperature of the valve seat 20 and the cylinder head body 10 rises during resistance welding, and copper rich aluminum A liquid phase of the alloy is formed. At this time, not only copper in the copper alloy plating layer 22 but also copper infiltrated into the pores 20v of the iron-based sintered alloy which is the material of the valve seat 20 also flows. Therefore, the plastically flowed aluminum alloy intrudes into the holes 20v. When the structure 20va in which the aluminum alloy intrudes into the holes 20v is formed, the anchor effect improves the bonding strength. This effect is due to the fact that the metal material infiltrated into the iron-based sintered alloy and the metal material of the plating layer (film) formed on the surface of the valve seat 20 are the same (both copper or copper alloy). It can be said that it is a unique effect to be obtained.

In addition, the shape of the valve seat 20 prepared when manufacturing the cylinder head 1 is not limited to what was illustrated in FIG. For example, a valve seat 20 as shown in FIG. 14 may be prepared. The valve seat 20 shown in FIG. 14 differs from the example shown in FIG. 6 in that it is thicker on the port side than on the combustion chamber side. By making the valve seat 20 thick on the port side, it is possible to increase the calorific value on the port side. By setting the thickness distribution of the valve seat 20 according to the specification of the intake port 11, etc., bonding by resistance welding can be suitably performed.

Further, when bonding is performed by the above-described mechanism, an Fe—Al based intermetallic compound layer (for example, FeAl ₃ layer) is formed in the vicinity of the interface between the valve seat 20 and the cylinder head body 10. The thickness of the intermetallic compound layer is, for example, 10 nm or more and 700 nm or less. Therefore, the junction structure according to the present embodiment (which can be said to be a metallurgical junction structure) can be distinguished from a mechanical junction structure (such as a caulking method) by the presence of such an intermetallic compound layer.

Then, the result of having conducted the exfoliation test about the case where valve seat 20 has slot 21 like this embodiment, and the case where it does not have it is explained.

FIG. 15 shows the method of peeling test. As shown in FIG. 15, the peeling test was performed by applying a tensile load in a direction away from the cylinder head body 10 to the valve seat 20 after bonding. Specifically, after a portion of the intake port 10 directly above the valve seat 20 has been subjected to spot facing processing, a jig 70 is hooked on the port side end (inner peripheral side edge) of the valve seat 20 and this jig is used. 70 was pulled by a tensile tester, and the load at peeling was measured.

FIG. 16 shows the results of the peeling test. The results of “with grooves” shown in FIG. 16 are for the case where there are two grooves 21 (the structure shown in FIG. 6). It can be seen from FIG. 16 that when the groove 21 is present, the load at which the peeling starts is larger (that is, it is difficult to be peeled) as compared with the case where the groove 21 is not present. Further, it can also be understood that even if the grooves 21 are present, even after the peeling starts, it is difficult to achieve complete peeling. As described above, it was confirmed that the valve seat 20 has the groove 21 so that the peeling and the detachment of the valve seat 20 are suitably suppressed.

The cylinder head 1 of the present embodiment is suitably used for various internal combustion engines (engines) because the valve seat 20 is more reliably prevented from falling off as described above. An example of an internal combustion engine provided with the cylinder head 1 of the present embodiment is shown in FIG.

An internal combustion engine 100 shown in FIG. 17 includes a cylinder head 1, a cylinder (cylinder block) 30, and a crankcase 35. Further, the internal combustion engine 100 further includes a piston 40, a crankshaft 45, and a connecting rod (connecting rod) 50.

The cylinder 30 has a cylinder wall 32 that defines a cylinder bore 31. The cylinder 30 is formed of an aluminum alloy.

The cylinder head 1 is provided on a cylinder 30. The cylinder head 1 together with the cylinder wall 32 and the piston 40 defines a combustion chamber 60.

The crankcase 35 is provided on the side opposite to the cylinder head 1 with respect to the cylinder 30. The crankcase 35 may be separate from the cylinder 30, or may be integrally formed with the cylinder 30.

The piston 40 is accommodated in the cylinder bore 31. The piston 40 is provided to reciprocate in the cylinder bore 31. The piston 40 is formed of an aluminum alloy.

The crankshaft 45 is accommodated in the crankcase 35. The crankshaft 45 has a crank pin 46 and a crank arm 47.

The connecting rod 50 has a rod-like rod body 51, a small end 52 provided at one end of the rod body 51, and a large end 53 provided at the other end of the rod body 51. The connecting rod 50 connects the piston 40 and the crankshaft 45. Specifically, the piston pin 48 of the piston 40 is inserted into the through hole (piston pin hole) of the small end 52, and the crank pin of the crankshaft 45 is inserted into the through hole (crank pin hole) of the large end 53. 46 is inserted, whereby the piston 40 and the crankshaft 45 are connected. A bearing 56 is provided between the inner peripheral surface of the large end portion 53 and the crankpin 46.

The internal combustion engine 100 may be provided in a vehicle, a ship, or an aircraft, or may be provided in other means of transportation. The vehicle may be an on-snow vehicle traveling on snow, a land vehicle traveling on land, or any other vehicle. Land vehicles include two-wheeled vehicles, three-wheeled vehicles, and four-wheeled vehicles. A straddle-type vehicle belongs to both snow vehicles and land vehicles.

As described above, the cylinder head 1 according to the embodiment of the present invention is the cylinder head body 10 having the intake port 11 and the exhaust port 12 and formed of the cylinder head body 10 formed of aluminum alloy and iron-based alloy And the valve seat 20 resistance-welded to the downstream end of the intake port 11. The valve seat 20 has at least one groove 21 extending in the circumferential direction of the valve seat 20 at a portion in contact with the cylinder head body 10.

In the cylinder head 1 according to the embodiment of the present invention, the valve seat 20 is resistance-welded to the downstream end of the intake port 11. As a result, compared with the conventional configuration in which the valve seat 20 is press-fit into the cylinder head body 10, the design freedom of the port can be increased. Moreover, the valve seat 20 can be firmly joined to the cylinder head body 10 by using resistance welding. Furthermore, in the cylinder head 1 according to the embodiment of the present invention, the valve seat 20 has at least one groove 21 extending in the circumferential direction of the valve seat 20 in a portion in contact with the cylinder head body 10. The groove 21 is filled with an aluminum alloy which is a material of the cylinder head body 10. In other words, the groove 21 is engaged with the projection of the cylinder head body 10. Therefore, even if the valve seat 20 is not sufficiently joined to the cylinder head body 10 by providing such a groove 21 (when the valve seat 20 is peeled off from the cylinder head body 10) And the valve seat 20 can be prevented from coming off.

In one embodiment, at least one groove 21 is a single groove 21.

In one embodiment, one groove 21 is disposed in the port side half 20 a vertically divided from the middle point of the valve contact surface 20 c of the valve seat 20.

When the groove 21 is one, it is preferable that the groove 21 be disposed in the port side half 20 a of the valve seat 20. Since the port side half 20a of the valve seat 20 receives more vertical load from the intake valve 61 than the combustion chamber side half 20b, peeling of the valve seat 20 occurs on the combustion chamber side half at the port side half 20a. It is more likely to occur than at 20b. In the case where the number of the grooves 21 is one, by arranging the groove 21 in the port side half portion 20 a of the valve seat 20, the effect of preventing the falling off becomes high.

In one embodiment, at least one groove 21 is two grooves 21.

In one embodiment, the two grooves 21 are respectively disposed in the port side half 20 a and the combustion chamber side half 20 b vertically divided from the middle point of the valve contact surface 20 c of the valve seat 20.

When the two grooves 21 are arranged in the port side half 20a and the combustion chamber side half 20b of the valve seat 20, respectively, the effect of preventing the valve seat 20 from falling off is high.

In one embodiment, the depth d of at least one groove 21 is 0.1 mm or more and 0.3 mm or less.

If the depth d of the groove 21 is too small, the effect of the drop prevention may be reduced. Therefore, the depth d of the groove 21 is preferably 0.1 mm or more. If the depth d of the groove 21 is too large, it may be difficult to fill the groove 21 with an aluminum alloy, or the thickness of the valve seat 20 may be locally reduced to cause a crack. Therefore, the depth d of the groove 21 is preferably 0.3 mm or less.

In one embodiment, at least one groove 21 includes an undercut surface 21a, and the undercut surface 21a is formed at an outer peripheral end 21a1 formed at one end in the radial direction and at the other end in the radial direction And an inner peripheral end 21a2 formed radially inward of the end 21a1, the inner peripheral end 21a2 being at the same position as the outer peripheral end 21a1 in the axial line Bc direction of the valve seat 20 or the combustion chamber than the outer peripheral end 21a1 It is formed in the position near.

From the viewpoint of more reliably preventing the valve seat 20 from falling off, the groove 21 preferably has a shape that is easily caught by the protrusion of the cylinder head main body 10. Specifically, the groove 21 is undercut with respect to the axis (central axis) Bc of the valve seat 20 (that is, it is hooked when trying to lower the valve seat 20 along the axis Bc) Is preferred. That is, it is preferable that the groove 21 includes the undercut surface 21a. Undercut surface 21a includes an outer peripheral end 21a1 formed at one end in the radial direction, and an inner peripheral end 21a2 formed at the other end in the radial direction and further inward in the radial direction than the outer peripheral end 21a1. The inner peripheral end 21a2 is formed at the same position as the outer peripheral end 21a1 or at a position closer to the combustion chamber than the outer peripheral end 21a1 in the direction of the axis Bc.

In one embodiment, each of the at least one groove 21 is defined by the first groove surface 21a and the second groove surface 21b, and the cross section along the radial direction of the valve seat 20 is substantially triangular.

In an embodiment, an angle α between the first groove surface 21 a and the second groove surface 21 b is 45 ° or more and 75 ° or less.

If the angle α between the first groove surface 21 a and the second groove surface 21 b is too small, it may be difficult to fill the groove 21 with the aluminum alloy. Therefore, the angle α is preferably 45 ° or more. If the angle α between the first groove surface 21a and the second groove surface 21b is too large, the groove 21 may not be easily caught by the convex portion of the cylinder head main body 10 (the undercut is eliminated). Therefore, the angle α is preferably 75 ° or less.

In one embodiment, the bottom of each of the at least one groove 21 has a rounded shape.

The rounded shape of the bottom of the groove 21 facilitates filling the groove 21 with the aluminum alloy that is the material of the cylinder head body 10.

If the radius of curvature of the R-shaped bottom of the groove 21 is too small, the effect of the R-shaped may not be obtained sufficiently. If the radius of curvature of the R-shaped is too large, the groove 21 may be formed on the convex portion of the cylinder head body 10 There is a risk that it will be difficult to get caught (it will not be undercut). Therefore, the radius of curvature of the rounded shape of the bottom of the groove 21 is preferably 0.02 mm or more and 0.15 mm or less.

When the volume resistivity of the iron-based sintered alloy which is the material of the valve seat 20 is made higher than the volume resistivity of the aluminum alloy which is the material of the cylinder head body 10, the joining by resistance welding is performed by the cylinder head body of the valve seat 20 It can be carried out so that the temperature of the portion in contact with 10 does not exceed the melting point of the material of the valve seat 20. Thereby, the valve seat 20 can be prevented from being melted and damaged at the time of joining by resistance welding.

The volume resistivity of the iron-based sintered alloy which is the material of the valve seat 20 is preferably 10 μΩcm or more and 38 μΩcm or less.

In one embodiment, the valve seat 20 has a copper plating layer or a copper alloy plating layer 22 formed on a portion not in contact with the cylinder head body 10.

When the valve seat 20 has a copper alloy plated layer (or copper plated layer) 22 on the surface, the joint by resistance welding is a copper alloy layer (or copper layer) between the valve seat 20 and the cylinder head body 10 It will be carried out in the state where it intervened. Thus, the valve seat 20 can be firmly joined to the cylinder head body 10.

In one embodiment, in the vicinity of the interface between the valve seat 20 and the cylinder head body 10, the aluminum alloy intrudes into the pores 20v of the iron-based sintered alloy.

When the structure 20va in which the aluminum alloy intrudes into the pores 20v of the iron-based sintered alloy is formed, the anchor effect improves the bonding strength.

In one embodiment, the valve seat 20 is thicker at the intake port 11 side than at the combustion chamber side.

By making the valve seat 20 thick on the intake port 11 side, it is possible to increase the amount of heat generation on the intake port 11 side. By setting the thickness distribution of the valve seat 20 according to the specification of the intake port 11, etc., bonding by resistance welding can be suitably performed.

In one embodiment, the cylinder head 1 according to the present invention has an Fe—Al intermetallic compound layer having a thickness of 10 nm or more and 700 nm or less in the vicinity of the interface between the valve seat 20 and the cylinder head body 10.

The joint structure by resistance welding (a metallurgical joint structure) is a mechanical joint structure due to the presence of an intermetallic compound layer (for example, an Fe-Al intermetallic compound layer having a thickness of 10 nm to 700 nm). It can be distinguished from (such as caulking).

An internal combustion engine 100 according to an embodiment of the present invention includes a cylinder head 1 having any of the configurations described above.

A method of manufacturing a cylinder head 1 according to an embodiment of the present invention includes a cylinder head main body 10 having an intake port 11 and an exhaust port 12 and a valve seat 20 disposed at the downstream end of the intake port 11. A manufacturing method of the cylinder head main body 10 formed of an aluminum alloy, a step (B) of preparing a valve seat 20 formed of an iron-based alloy, and a downstream side of the intake port 11 And (C) joining the valve seat 20 by resistance welding at the end. The valve seat 20 prepared in the step (B) has at least one groove 21 extending in the circumferential direction of the valve seat 20 at a portion in contact with the cylinder head body 10.

In the method of manufacturing the cylinder head 1 according to the embodiment of the present invention, the valve seat 20 is joined to the downstream end of the intake port 11 by resistance welding. Thereby, compared with the case where the valve seat 20 is press-fit into the cylinder head body 10, the design freedom of the port can be increased. Moreover, the valve seat 20 can be firmly joined to the cylinder head body 10 by using resistance welding. Furthermore, in the method of manufacturing the cylinder head 1 according to the embodiment of the present invention, the provided valve seat 20 has at least one groove 21 extending in the circumferential direction of the valve seat 20 in a portion contacting the cylinder head main body 10 . The groove 21 is filled with an aluminum alloy which is a material of the cylinder head body 10. In other words, the groove 21 engages with the protrusion of the cylinder head body 10. Therefore, even if the valve seat 20 is not sufficiently joined to the cylinder head body 10 by providing such a groove 21 (when the valve seat 20 is peeled off from the cylinder head body 10) And the valve seat 20 can be prevented from coming off.

In one embodiment, step (C) is performed with a copper layer or a copper alloy layer interposed between the valve seat 20 and the cylinder head body 10.

The valve seat 20 is firmly joined to the cylinder head body 10 by performing the joining step by resistance welding in a state in which the copper alloy layer (or copper layer) is interposed between the valve seat 20 and the cylinder head body 10. It can.

In one embodiment, step (C) is performed such that the temperature of the portion of the valve seat 20 in contact with the cylinder head body 10 does not exceed the melting point of the iron-based alloy.

By performing the joining step by resistance welding so that the temperature of the portion of the valve seat 20 in contact with the cylinder head body 10 does not exceed the melting point of the material of the valve seat 20, the valve seat 20 can be prevented from melting.

1: Cylinder head, 10: Cylinder head body, 11: Intake port, 12: Exhaust port, 20: Valve seat, 20a: Port side half of valve seat, 20b: Combustion side of valve seat half, 20i: Valve Inner surface of seat, 20o: Outer peripheral surface of valve seat, 20v: Hole, 21: groove, 21a: first groove surface, 21b: second groove surface, Bc: valve seat axis, 22: copper alloy plated layer , 100: internal combustion engine

Claims

A cylinder head body having an intake port and an exhaust port, the cylinder head body formed of an aluminum alloy,
A valve seat formed of an iron-based alloy, the valve seat being resistance-welded to the downstream end of the intake port;
Equipped with
The cylinder head has at least one groove extending in the circumferential direction of the valve seat at a portion in contact with the cylinder head body.
The cylinder head according to claim 1, wherein the at least one groove is a single groove.
The cylinder head according to claim 2, wherein the one groove is disposed in a port side half vertically divided from a valve contact surface middle point of the valve seat.
The cylinder head according to claim 1, wherein the at least one groove is two grooves.
The cylinder head according to claim 4, wherein the two grooves are respectively disposed in a port side half and a combustion chamber side half vertically divided from a valve contact surface middle point of the valve seat.
The cylinder head according to any one of claims 1 to 5, wherein a depth of the at least one groove is 0.1 mm or more and 0.3 mm or less.
The at least one groove includes an undercut surface,
The undercut surface includes an outer peripheral end formed at one end in the radial direction, and an inner peripheral end formed at the other end in the radial direction and further inward in the radial direction than the outer peripheral end.
The cylinder head according to any one of claims 1 to 6, wherein the inner peripheral end is formed at the same position as the outer peripheral end or a position closer to the combustion chamber than the outer peripheral end in the axial direction of the valve seat. .
Each of the at least one groove is defined by a first groove surface and a second groove surface, and a cross section along a radial direction of the valve seat is substantially triangular. Cylinder head.
The cylinder head according to claim 8, wherein an angle between the first groove surface and the second groove surface is 45 ° or more and 75 ° or less.
The cylinder head according to claim 8 or 9, wherein the bottom of each of the at least one groove has a rounded shape.
The cylinder head according to claim 10, wherein the radius of curvature of the rounded shape is 0.02 mm or more and 0.15 mm or less.
The cylinder head according to any one of claims 1 to 11, wherein a solidus temperature of the aluminum alloy is 520 ° C or more and 580 ° C or less.
The cylinder head according to any one of claims 1 to 12, wherein the iron-based alloy is an iron-based sintered alloy in which copper or a copper alloy is infiltrated.
The cylinder head according to any one of claims 1 to 13, wherein a volume resistivity of the iron-based sintered alloy is higher than a volume resistivity of the aluminum alloy.
The cylinder head according to claim 14, wherein the volume resistivity of the iron-based sintered alloy at room temperature is 10 μΩcm or more and 38 μΩcm or less.
The cylinder head according to any one of claims 13 to 15, wherein the valve seat has a copper plating layer or a copper alloy plating layer formed on a portion not in contact with the cylinder head body.
The cylinder head according to any one of claims 13 to 16, wherein the aluminum alloy intrudes into the pores of the iron-based sintered alloy in the vicinity of the interface between the valve seat and the cylinder head body.
The cylinder head according to any one of claims 1 to 17, wherein the valve seat is thicker at the intake port side than at the combustion chamber side.
The cylinder head according to any one of claims 1 to 18, further comprising an Fe-Al based intermetallic compound layer having a thickness of 10 nm to 700 nm in the vicinity of the interface between the valve seat and the cylinder head body.
An internal combustion engine comprising the cylinder head according to any one of claims 1 to 19.
A method of manufacturing a cylinder head comprising: a cylinder head body having an intake port and an exhaust port; and a valve seat disposed at a downstream end of the intake port,
Providing the cylinder head body formed of an aluminum alloy (A);
Providing the valve seat formed of an iron-based alloy (B);
Bonding the valve seat to the downstream end of the intake port by resistance welding (C);
To include
The method for manufacturing a cylinder head, wherein the valve seat prepared in the step (B) has at least one groove extending in the circumferential direction of the valve seat in a portion in contact with the cylinder head body.
The method for manufacturing a cylinder head according to claim 21, wherein the iron-based alloy is an iron-based sintered alloy in which copper or a copper alloy is infiltrated.
The method for manufacturing a cylinder head according to claim 22, wherein the step (C) is performed in a state where a copper layer or a copper alloy layer is interposed between the valve seat and the cylinder head body.
The cylinder head according to any one of claims 21 to 23, wherein the step (C) is performed such that the temperature of the portion of the valve seat in contact with the cylinder head body does not exceed the melting point of the iron-based alloy. Production method.