JP2003247405A - Method of joining valve seat - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase freedom of design by enabling reduction of thickness of a valve seat by providing a method of joining the valve seat, wherein an excessive torque is not induced when the valve seat having a constricted part formed on its outer circumference is pressed and pressure-welded while being rotated. <P>SOLUTION: The method of joining the valve seat is used for joining an annular valve seat 6 made of a hard metal having a constricted part 23 provided on its circumference to an opening of a head 5 made of a soft metal. In the method, solid phase fluid of the soft metal produced during pressure welding is filled in the constricted part 23, and the pressurization pressure 102b from the time of starting deceleration of the rotation speed of the valve seat 6 until a stop in a final stage of pressure welding is controlled at a pressure lower than the pressurization pressure 102a during pressure welding at an approximately steady rotation speed. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for joining a valve seat in an engine valve of an engine or the like to an opening of a head, and more particularly to a valve which pressurizes while rotating a valve seat having a reduced diameter portion on its outer circumference. A method for joining sheets.

[0002]

2. Description of the Related Art In general, a valve seat of an engine valve of an engine is joined to a ring-shaped valve seat made of a ferrous sintered alloy or the like by surrounding an opening of an intake port and an exhaust port of an aluminum alloy cylinder head. This was done by heating and press-fitting into the recess.

In this heat press-fitting method, it is necessary to make the ring-shaped valve seat relatively thick in order to withstand internal stress such as shrink fit. Therefore, attempts have been made to reduce the thickness of the valve seat by joining the valve seats by welding or the like with less internal stress. Japanese Patent Laid-Open No. 11-50823
In the publication, a method using friction welding performed by applying ultrasonic vibration is proposed. In addition, Japanese Patent Laid-Open No. 8-296417
Japanese Patent Laid-Open No. 2000-263241 and Japanese Patent Laid-Open No. 2000-263241 propose a pressure welding method using electric resistance welding.

In any of the methods, since the aluminum alloy cylinder head and the ferrous sintered alloy valve seat are joined together by different materials, the brittle intermetallic compound or oxide film formed at the joint boundary causes Bonding strength cannot be secured. Therefore, it has been proposed to secure bonding strength by fixing or impregnating the valve seat itself with a diffusing material having diffusibility with respect to an aluminum alloy, or interposing a brazing material.

In the above-mentioned joining of valve seats by friction welding or electric resistance welding, the degree of freedom in design can be secured such that the thickness can be made relatively thin, but the joining strength for completely preventing slipping out cannot be secured, and it is still unsuccessful. It has not been put to practical use. Therefore, it is conceivable to adopt a joint shape in which the valve seat is physically held to the head to secure the joint strength and improve the degree of freedom in design. That is, it is a method of joining valve seats in which a valve seat having a reduced diameter portion on its outer circumference is pressed while being rotated to fill the solid phase fluid of the soft metal head generated during the pressure contact into the reduced diameter portion.

[0006]

However, even in such a valve seat joining method, the valve seat is required to have at least a strength enough to withstand the torque when pressurizing while rotating. Therefore, although it is improved as compared with the case of press-fitting, the material strength and size of the valve seat are restricted. Therefore, there is a demand for a joining method in which the valve seat is pressed and pressed while rotating without generating an excessive torque.

The present invention has been made in view of the above problems, and an object thereof is to apply an excessive torque when pressurizing and pressing a valve seat having a reduced diameter portion on its outer periphery while rotating. It is to provide a valve seat joining method that does not occur, thereby making it possible to reduce the thickness of the valve seat and improve the degree of freedom in design.

[0008]

According to a first aspect of the present invention, there is provided a method for joining valve seats, comprising: a ring-shaped hard member having an outer periphery having a reduced diameter portion with respect to an opening of a soft metal head. A method of joining valve seats, wherein metal valve seats are pressurized and pressed while rotating, wherein the reduced diameter portion is filled with the solid phase fluid of the soft metal generated during press contacting, and the valve seats are provided at the final stage of press contacting. The pressurizing pressure from the start of deceleration of the rotation speed to the stop is adjusted to be smaller than the pressurizing pressure at the time of pressure contact while rotating at a substantially constant speed. According to the structure of claim 1, when the valve seat is pressure-welded while rotating, the friction torque acting on the valve seat becomes excessive when the rotational speed of the valve seat is decelerated and stopped at the final stage of the pressure contact. Can be suppressed. As a result, the valve seat can be made thinner, and the degree of freedom in design can be improved.

According to a second aspect of the present invention, in the valve seat joining method according to the ninth aspect, when the rotational speed of the valve seat is decelerated and stopped at the final stage of the pressure contact, the valve seat is decelerated from the start to the deceleration. The position with respect to the head is adjusted so as to be substantially constant. According to the structure of the second aspect, it is possible to reliably prevent the friction torque acting on the valve seat from becoming excessive at the final stage of the pressure contact.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION First, an example of a valve seat joining structure constructed by applying the valve seat joining method according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a valve seat joining structure 1 to which the valve seat joining method according to the present embodiment is applied, in which the valve seat and the cylinder head have been joined together and have been shaped into an engine. The state where it is installed in the valve is shown.

In FIG. 1, a valve seat joining structure 1 is shown.
Is composed of a cylinder head 5 and a valve seat 6. A recess 12 formed by pressure contact is formed at the end of the opening 11 of the cylinder head 5, and the ring-shaped valve seat 6 is joined in the recess 12 in a fitted state. An inclined portion (reduced diameter portion) 23 is formed on the outer periphery of the valve seat 6 so as to reduce its diameter toward the opposite head side, and this inclined portion (reduced diameter portion) 23 is formed.
The solid-phase fluid 14 in the shape of a wedge is filled around and solidified. Hereinafter, in the present specification, the solid phase fluid means a material which is softened by a temperature rise and is in a fluid state in a solid state. The inner periphery of the valve seat 6 on the side opposite to the head (combustion chamber side) is machined to 45 ° to form the valve seat 15. In the valve seat joining structure 1 as described above, the engine body valve 2 of the engine is configured by disposing the valve body 7 so as to be movable up and down with respect to the valve seat 15 of the valve seat 6.

FIG. 2 shows a state before the cylinder head 5 and the valve seat 6 are joined. The cylinder head 5 is formed of a soft metal such as an aluminum alloy (for example, Al-Si system). The valve seat 6 is made of a hard metal such as an iron-based alloy or a sintered body of those alloys.

The recess 21 before joining the cylinder head 5 is
A bottomed first expanded diameter hole 211 having an inside diameter D2 larger than the inside diameter D1 of the opening 11, and a bottomed second expanded diameter hole 212 having an inside diameter D3 larger than the inside diameter D2 of the first expansion hole 211.
And a step 213 between the first expanded diameter hole 211 and the second expanded diameter hole 212.

The valve seat 6 has an inner diameter D5 and a maximum outer diameter D7, and is formed in a ring shape having a thickness of H5.
On the outer periphery of the valve seat 6, a first inclined portion (reduced diameter portion) having a conical surface shape formed from the top 22 having the maximum outer diameter to the opposite head side.
23, and a conical second inclined portion 24 formed on the head side from the top 22 having the maximum outer diameter. Since the solid-phase fluid is filled in a wedge shape around the first inclined portion 23,
The angle α of the first inclined portion 23 is preferably 10 to 15 °. The second slanted portion 24 stores the solid-state fluid in the first slanted portion 23.
The angle β of the second inclined portion 24 is 45 because it is pushed toward
It is preferably not more than °.

The maximum outer diameter D7 of the valve seat 6 improves the flow of the solid phase fluid toward the first inclined portion 23.
It is preferable to make it slightly smaller than the inner diameter D3 of the second expanded hole 212. The inner diameter D6 of the bottom surface of the second inclined surface 24 of the valve seat 6 is preferably slightly smaller than the inner diameter D2 of the first enlarged diameter hole 211 so that the second inclined surface 24 contacts the tip of the step portion 213. It is preferable that the inner diameter D5 of the valve seat 6 be slightly smaller than the inner diameter D1 of the opening 11 in order to control how the burr flows out of the solid phase fluid.
The thickness H5 of the valve seat 6 is set to be the depth H1 of the recess 21 in order to secure a pressing margin (upsetting margin) during pressure contact.
It is preferably slightly larger.

The valve seat joining method according to the present embodiment is applied to the valve seat joining structure 1 described above. First, FIG. 3 shows a procedure of pressing the valve seat 6 against the cylinder head 5. The pressure contact is performed by pressing rotary friction bonding. In FIG. 3A, the valve seat 6 is fitted into the recess 21 of the cylinder head 5. The tip of the step 213 contacts the second inclined surface 24. In this state, the valve seat 6 is pressed toward the cylinder head 5 with a predetermined pressure P. In FIG. 3B, when the valve seat 6 is rotated while being pressed, the tip of the step portion 213 becomes a solid phase fluid and flows along the second inclined surface 24.

In FIG. 3 (c), the solid-phase fluid extruded toward the top 22 passes over the top 22 and reaches the first position.
It flows to the side opposite to the head along the inclined surface 23. In FIG. 3D, the bottom surface of the valve seat 6 on the head side contacts the bottom of the first enlarged diameter hole 211 of the cylinder head 5, and the first enlarged diameter hole 21
Continue pressing and rotating until a solid-state fluid is formed at the bottom of 1. In FIG. 3E, upset pressurization for stopping the rotation of the valve seat 6 and pressing it is performed. Since the portion of the cylinder head 5 that hits the valve seat 6 is a solid phase fluid, the valve seat 6 is further pushed. The overflowing solid phase fluid is extruded around the first inclined surface 23 and toward the opening 11.

When cooled in the state of FIG. 3 (e), the solid phase fluid 14 around the first inclined surface 23 of the valve seat 6 becomes wedge-shaped and solidifies. The outer periphery of the valve seat 6 is filled with the solidified solid-phase fluid 14 so that the valve seat 6 does not physically escape. In FIG. 3F, excess burr of the solid phase fluid is removed by processing the inner periphery of the valve seat 6 and the surface on the side opposite to the head. At the same time, the valve seat 15 is processed at the corner on the side opposite to the head of the inner circumference of the valve seat 6. Valve seat 6 finished to a specified size by these shape processing
The junction structure 1 of 1 is obtained.

In FIG. 3 (f), if the solid phase fluid 14 around the first inclined surface 23 of the valve seat 6 is insufficiently filled, cavities or the like are left in the solid phase fluid 14 after deburring. Therefore, it becomes possible to select only those that have been reliably pressure-contacted by the visual inspection.

As described above, the solid phase fluid from the cylinder head is filled in the slanted portion 23 as a reduced diameter portion provided on the outer periphery of the valve seat 6 without any gap, and this solid phase fluid is the base material of the cylinder head. Since the valve seat 6 is solidified continuously, the valve seat 6 is joined to the cylinder head 5 so as not to physically come off.

The valve seat joining structure 1 is constructed by the joining method described above. The thrust control of the pressure rotary friction joining at that time will be described in more detail below.

When friction joining that does not physically come off is possible, as described above, solid phase flow is generated, so the initial pressing force during friction joining is reduced, and the thin wall thickness is reduced compared to the case of heat press fitting. It becomes possible to make a valve seat of a shape. Therefore, the degree of freedom in designing the dimensions and material of the valve seat can be significantly improved. However, in the case of pressure contact by pressure rotary friction bonding (hereinafter referred to as “friction pressure contact”), the valve seat is required to have at least a strength enough to withstand torque during rotary friction. Therefore, although it is improved as compared with the case of press-fitting, there is some restriction on the material strength and size of the valve seat. Further, a holder for holding the holder, a main shaft of equipment and the like are required to have high rigidity, and in some cases, the shape of the cylinder head may be restricted.

First, the case of joining the valve seat to the cylinder head by utilizing a general friction welding cycle will be described. FIG. 4 is a diagram for explaining a general friction welding cycle, and conceptually shows how the friction welding conditions and the like change from the start to the end of the friction welding process over time. FIG. 4 (a) shows how the friction welding rotational speed (that is, the rotational speed of the valve seat or its holder) changes, and FIG.
FIG. 4C shows a change in pressurizing pressure (thrust) when the valve seat is pressed against the cylinder head, and FIG. 4C shows a change in position of the valve seat with respect to the cylinder head. ) Are the changes in the magnitude of the torque transmitted to the valve seat during friction welding.

When the valve seat is pressed against the cylinder head using the general friction welding cycle shown in FIG. 4 (hereinafter referred to as "friction welding cycle 101"), first, the rotational speed of the valve seat (holding The rotation speed of the holder) is increased to a rotation speed at which a desired heat generating effect is obtained by friction (see FIG. 4A). Then, the valve seat is pressed against the cylinder head while being rotated at a substantially steady speed (dotted line s1 in the figure). In addition,
At this time, the deviation (position of the valve seat with respect to the cylinder head) is set to zero (see FIG. 4C).

As the valve seat is pressed against the cylinder head to pressurize, the thrust increases rapidly (see FIG. 4).
(See (b)), the torque transmitted to the valve seat also instantaneously rises to reach the peak value p1 (see FIG. 4 (d)). After that, while the friction pressure 101a is generated while pressing the valve seat against the cylinder head with a substantially constant thrust (see FIG. 4 (b)), the valve seat is pushed in gradually while gradually increasing the deviation (FIG. 4B). 4 (c)). During this friction time, softening of the valve seat begins as frictional heat is generated between the valve seat and the cylinder head, and the torque value generated in the valve seat gradually decreases to the right (FIG. 4 (d )reference).

Then, when the valve seat is pushed into the cylinder head by a predetermined amount (at the end of the friction time shown by the dotted line S2 in the figure), the rotational speed of the valve seat is decelerated and stopped (FIG. 4 (a)). reference). At this time, in the general friction welding cycle 101, for the purpose of ensuring the joint strength, during a predetermined upset time (dotted lines s2 to s in the figure).
(Up to 3)), the upset step of further pushing the valve seat with the upset pressure 101b in which the thrust is larger than the friction pressure 101a is performed (see FIGS. 4B and 4C). At this time, it is considered that the frictional resistance increases, but when the valve seat rotation speed starts decelerating, the torque transmitted to the valve seat increases and shows an instantaneous peak value p2.

As described above, when the torque peak value p2 is generated, the valve seat will be broken or the like unless strength enough to withstand the torque peak value p2 is secured. Therefore, although it is possible to make the valve seat thinner than in the case of press-fitting, it is necessary to make the thickness sufficient to withstand the torque peak value p2. Also,
Not only the friction deviation margin 101c, which is the deviation margin during the friction time, but also the upset deviation margin 101d is generated.
Therefore, it becomes difficult to accurately perform the final positioning of the valve seat with respect to the cylinder head.

Therefore, in the valve seat joining method according to the present invention, when the rotational speed of the valve seat is decelerated and stopped at the final stage of friction welding without applying upset pressure as shown in FIG. 4 (b). The joining is performed so that the pressurizing pressure becomes smaller than the pressurizing pressure at the time of press-contacting while rotating at a substantially constant speed.

A concrete example is shown in FIG. FIG. 5 is a view for explaining the friction welding cycle 102 according to the present embodiment, and similarly to FIG. 4, changes in the rotational speed of the valve seat from the start to the end of friction welding (FIG. 5A), the valve seat. Of the pressurizing pressure (thrust) for pressurizing the cylinder head to the cylinder head (Fig. 5 (b)), the position of the valve seat relative to the cylinder head (shift margin) (Fig. 5 (c)), and the change being transmitted to the valve seat. Change in torque magnitude (Fig. 5 (d))
Are shown respectively.

The friction welding cycle 102 is different from the friction welding cycle 101 shown in FIG. 4 in the final stage of welding. That is, the pressurization pressure is not raised above the friction pressure 102a when the valve seat rotation speed starts decelerating, but is decreased to the pressurization pressure 102b.

The joining structure 1 of the valve seat to which the joining method according to the present embodiment is applied enables a joining structure that does not physically come off. Therefore, unlike the case of welding by general friction welding, there is a request to generate an upset pressure larger than the friction pressure for the purpose of securing the welding strength at the final stage of welding, and to enhance the intermetallic bond.
It will fade significantly.

Therefore, as in the friction welding cycle 102 of FIG. 5, the pressurizing pressure 102b is adjusted to be smaller than the friction pressure 102a (see FIG. 5 (b)), as shown in FIG. 5 (d). As described above, it becomes possible to reduce the magnitude of the torque peak value p2 when the valve seat rotation speed is decelerated and stopped. As a result, it is possible to prevent the friction torque transmitted to the valve seat from becoming excessive at the final stage of the pressure contact without deteriorating the joint quality. Therefore, compared to the case of joining by a general friction welding cycle, the constraint for securing the strength of the valve seat is relaxed, a thinner shape can be realized, and the valve seat size and material design freedom The degree can be greatly improved.

By appropriately setting the value of the pressurizing pressure 102b, as shown in FIG. 5D, the torque peak value p2 becomes smaller than the torque peak value p1 generated when the valve seat comes into contact. Can be Also,
If the pressurizing pressure 102b is set to zero, a gap may occur at the boundary between the valve seat and the cylinder head. However, if the pressurizing pressure 102b is not zero, there is a gap at the boundary surface. 6 without causing
As shown in, the torque peak value p2 can be further reduced.

Further, in the friction welding cycle 102, since the pressurizing pressure 102b is adjusted to be smaller than the friction pressure 102a, there is an upset side margin as in the case of the friction welding cycle 101 shown in FIG. Can be almost eliminated. Therefore, as shown in FIG. 5 (c), the movement of the valve seat is stopped while the friction seat margin 102c has been moved, and the final positioning of the valve seat with respect to the cylinder head can be accurately performed. become.

Further, it is desirable to adjust the pressurizing pressure (thrust) while measuring the actual thrust with a strain gauge or the like attached to the cylinder head side, but it is not always necessary to measure the actual thrust. For example, the thrust force may be adjusted by controlling the position (approaching margin) from the valve seat with respect to the cylinder head. in this case,
It is also possible to adjust the position (closeness) from the valve seat to the cylinder head from the start of deceleration of the valve seat rotation speed to the stop thereof so as to be substantially constant. Even by adjusting in this way, it is possible to reliably prevent the torque peak value p2 from becoming excessively large without generating a thrust force larger than the friction pressure 102a. It should be noted that when the rotation is stopped, a command may be given to slightly retract the position of the holder that holds the valve seat, so that the bending or the like on the machine side that supports the holder may be absorbed and adjusted. .

Further, in the friction pressure welding cycle 102, the torque peak value p is adjusted by adjusting the pressurizing pressure 102b at the final stage of pressure welding so as to be smaller than the friction pressure 102a.
2 is to prevent it from becoming excessive,
By using a lubricant such as lubricating oil when the valve seat is brought into contact with the cylinder head, the torque peak value p1 can also be reduced.

FIG. 7 shows a friction welding cycle 102 when a lubricant is used to bring the valve seat into contact with the cylinder head. In this case, at the start of contact, the frictional resistance does not increase due to the interposition of the lubricant, so that FIG.
As shown in (d), the torque transmitted to the valve seat gradually increases. Then, the steep torque peak value p
Friction welding is performed without producing 1.
At this time, as shown in FIG. 7C, the value of the side margin at the time of starting contact also gently increases. As described above, by interposing the lubricant between the valve seat and the cylinder head at the time of starting the friction welding, the torque increase at the start of the pressure welding can be suppressed.
In addition to the effect of reducing the torque peak p2, it is possible to make the valve seat thinner.

In the above-described valve seat joining method, the timing at which the rotation speed starts to be lowered and the timing at which the thrust is lowered are described as substantially the same, but the timing is not limited to this. For example, as shown by the chain double-dashed line n in FIG. 7B, the thrust may be reduced before the rotation speed is reduced. Even in this case, the same effect as the present invention can be obtained.

The valve seat joining method according to this embodiment has been described as being applied when the valve seat joining structure 1 is constructed, but the valve seat joining structure 1 is applied by the present joining method. It is merely an example of the valve seat joining structure. That is, the present joining method can be widely applied to the opening of the soft metal head when the ring-shaped hard metal valve seat provided with a reduced diameter portion is pressed against the opening while being rotated. Is.

[0040]

As described above, according to the invention of claim 1 or 2, when the valve seat is pressure-welded while rotating, the rotational speed of the valve seat is decelerated and stopped at the final stage of the pressure contact. It is possible to prevent the friction torque acting on the valve seat from becoming excessive. As a result, the degree of freedom in design such as reducing the thickness of the valve seat can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a valve seat joining structure to which a valve seat joining method according to an embodiment is applied.

FIG. 2 is a cross-sectional view showing a state before joining the cylinder head and the valve seat.

FIG. 3 is a sectional view showing a procedure for joining a cylinder head and a valve seat.

FIG. 4 is a diagram illustrating a general friction welding cycle.

FIG. 5 is a diagram illustrating a friction welding cycle in the valve seat joining method according to the present embodiment.

FIG. 6 is a diagram illustrating a friction welding cycle in the valve seat joining method according to the present embodiment.

FIG. 7 is a diagram illustrating a modified example of the friction welding cycle in the valve seat joining method according to the present embodiment.

[Explanation of symbols]

1 Valve seat joint structure 5 Cylinder head (head) 6 valve seats 11 openings 14 Wedge-shaped solid phase fluid 23 First inclined portion (reduced diameter portion) 102 Friction welding cycle 102a friction pressure 102b Pressurized pressure

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazunobu Kamiya             2-1, Toyota-cho, Kariya City, Aichi Stock Association             Inside Toyota Toyota Industries F term (reference) 3G024 AA15 FA14 GA32 HA01 HA07                 4E067 BG00 DA13 DA17 DC03 EA07                       EB00

Claims (2)

[Claims] 1. A method for joining valve seats, wherein a ring-shaped hard metal valve seat having a reduced diameter portion provided on the outer periphery is pressed against the opening of the soft metal head while rotating, and the press contacting is performed. The solid phase fluid of the soft metal that occurs at times is filled in the reduced diameter portion, and the pressurizing pressure from the start of deceleration of the rotational speed of the valve seat to the stop is pressed at the final stage of pressure welding while rotating at a substantially constant speed. A method for joining valve seats, characterized in that the pressure is adjusted so as to be smaller than the pressure applied during the operation. 2. When the rotational speed of the valve seat is decelerated and stopped at the final stage of pressure contact, the position of the valve seat with respect to the head from the start of deceleration to the stop is adjusted to be substantially constant. The valve seat joining method according to claim 1.