JPH03107512A - Valve sheet for engine - Google Patents

Abstract

PURPOSE:To prevent any fall of a ring member due to a difference in thermal expansion by forming a valve sheet of a ceramic unit member and the ring member made of an aluminum alloy, and providing holding engagement portions engaged with each other between the two members. CONSTITUTION:A valve sheet 4 is disposed in a groove 3 formed in the suction port 2 of a cylinder head 1. A valve body 5a of a suction valve 5 is brought into contact with or separation from the valve seat 4. The valve seat 4 is constituted of an annular unit member 7 made of ceramics and an annular ring member 8 made of an aluminum alloy and surrounding around the member 7. A seat surface 7a is formed at the inner circumference of the unit member 7, and an engagement groove 7b is formed at the periphery thereof. Meanwhile, an engagement projection 8a engaged with the engagement groove 7b is formed at the inner circumference of the ring member 8, and an adiabatic space is defined between the projection 8a and the groove 7b.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a valve seat for an engine.

[Prior art]

Generally, a valve seat that contacts an intake valve or an exhaust valve is press-fitted into an aluminum alloy cylinder head.

Normally, the valve seat is exposed to high temperatures and pressures and is subjected to shocks caused by the opening and closing of intake valves or exhaust valves, so it is required to have sufficient wear resistance, shock resistance, and heat resistance.

Traditionally, iron-based forged products or sintered alloy products manufactured using powder metallurgy have been used as the above valve seats, but in recent years, ceramics have been used to improve their wear resistance, impact resistance, and heat resistance. Valve seats made of materials have been proposed.

By the way, the valve seat made of the ceramic material is relatively brittle and may be damaged during press-fitting, and also has high hardness, making it difficult to accurately machine the outer diameter dimension. Moreover, ceramic materials, such as silicon nitride (thermal expansion coefficient: approximately 3.3
Thermal expansion coefficient: approx. 22 Occurs.

Therefore, for example, Japanese Utility Model Application Publication No. 62-54206 discloses a main body member made of a ceramic material made by adding a binder to a ceramic material such as silicon nitride or silicon carbide, molded and sintered, and a main body member made by a powder metallurgy method etc. A valve that is composed of a ring member made of an iron-based alloy that is fitted onto a member, and has a conical tapered part or uneven part that engages with the outer circumference of the main body member and the inner circumference of the ring member. The sheet is listed.

In the above valve seat, the main body member is held within the ring member via the tapered portion or the uneven portion, so that the main body member is prevented from falling off from the ring member, and the coefficient of thermal expansion of the ring member is 10 to 13. X 10-6/”C
Since this value is intermediate between that of the aluminum alloy material that makes up the cylinder head and the ceramic material that makes up the main body member, the difference in thermal expansion coefficient at high temperatures becomes small.

[Problem to be solved by the invention]

In the valve seat 1 described in the above publication, the main body member and the ring member are manufactured separately and the ring member is externally fitted onto the main body member, so shrinkage and thermal distortion occur when the ceramic main body member is manufactured. It is necessary to precisely finish the outer circumferential surface of the main body member and the inner circumferential surface of the ring member. That is, this is to prevent the main body member from being damaged when the ring member is fitted onto the outside, or from being damaged by impact from the intake valve or the exhaust valve. However, since the main body member is made of a highly hard ceramic material and the ring member is made of a relatively hard iron-based alloy such as an iron-chromium alloy, there is a problem in that the finishing process requires a great deal of labor and cost.

On the other hand, since the coefficient of thermal expansion of iron-based alloys is relatively small, due to the difference in the coefficient of thermal expansion between the ring member and the cylinder head, it is not possible to secure sufficient restraining force between the ring member and the cylinder head during operation, and the cylinder head There is a problem with the valve seat falling off.

An object of the present invention is to provide an engine valve seat that can be easily manufactured and that can reliably prevent falling off from a cylinder head.

[Means to solve the problem]

In the engine valve seat according to the present invention, in the valve seat that comes into contact with the intake valve or the exhaust valve of the cylinder head, the valve seat is made of a main body member made of a ceramic material and an aluminum alloy powder containing aluminum and silicon. A ring member is formed by hot forging a cylindrical preform to fit onto the main body member, and a holding engagement member is provided that engages the outer circumferential portion of the main body member and the inner circumferential portion of the ring member. A joint is formed.

[Effect]

In the engine valve seat according to the present invention, the valve seat is composed of a main body member made of a ceramic material and a ring member made of an aluminum alloy containing aluminum and silicon, and the ring member is a cylindrical member made of aluminum alloy powder. Since the preformed body is formed by hot forging while being held in an externally fitted manner on the main body member, the ring member can be shrink-fitted to the main body member with almost no gaps, without having to precisely process the outer peripheral surface of the main body member. The main body member can be strongly restrained by the ring member, and the impact force acting on the main body member from the exhaust valve or intake valve can be uniformly received and stopped on the inner peripheral surface of the ring member. . Moreover, since the main body member is held within the ring member via the holding retaining portion provided on the outer circumferential portion and the inner circumferential portion of the ring member, it is reliably prevented from falling off from the ring member.

The coefficient of thermal expansion of the aluminum alloy that constitutes the ring member is 12 to 15 x 10-'/'C, which is relatively close to the coefficient of thermal expansion of the cylinder head. Sufficient binding force is ensured in between. In addition, aluminum-based alloys are easier to process than iron-based alloys, making it easier to finish the ring member.

〔Effect of the invention〕

According to the engine valve seat according to the present invention, the above [
As detailed in the section 2.1, "Function", the manufacturing process of the valve seat can be simplified by omitting finishing machining of the outer peripheral surface of the main body member, and the manufacturing cost can be reduced. It is possible to prevent the main body member from being damaged due to impact from the intake valve or exhaust valve by preventing poor fitting between the main body member and the ring member, and to ensure that the main body member does not fall off from the ring member. Effects such as being able to prevent this, and increasing the coefficient of thermal expansion of the ring member to increase the restraining force of the valve seat to the cylinder head can be obtained.

〔Example〕

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

This example is a case where the present invention is applied to a valve seat of a gas heat pump engine.

As shown in FIG. 1, a substantially U-shaped intake boat 2 and an exhaust port (shown in the figure) are formed in a thin lidar head 1 of the engine, and an intake valve 5 and an exhaust port are formed to open and close the intake boat 2 and the exhaust port, respectively. A valve (path shown) is mounted so as to be movable up and down, an annular mounting groove 3 is formed at the downstream end of the intake boat 2 and at the upstream end of the exhaust port, and the valve seat 4 is held in the mounting groove 3 at its normal size. ing. The intake valve 5 is driven downward by a valve mechanism (not shown) and its spring 6, and the valve body 5a at the lower end of the intake valve 5 is driven downwardly by the valve seat 4.
It is driven to open and close against. This also applies to exhaust valves.

The cylinder head 1 is made of aluminum alloy and has a coefficient of thermal expansion of about 21 x 10-6/''C.

The valve seat 4 is, as shown in FIGS. 2 to 4,
It is composed of an annular main body member 7 made of a ceramic material and an annular ring member 8 made of an aluminum alloy that is fitted onto the main body member 7 with almost no gaps. A seat surface 7a that gradually expands downward is formed on the upper surface of the outer peripheral edge of the main body member 7 and can be brought into contact with the upper surface in a substantially airtight manner.
b is formed, and a retaining groove 7b is formed on the inner circumference of the ring member 8.
An annular engagement protrusion 8a that engages with the engagement groove 8a is formed in a protruding shape, and a hottest space 9 is formed between the inner end of the engagement groove 7b and the engagement protrusion 8a. 7b and the engagement protrusion 8a, the valve seat 4 is fixedly held within the ring member 8, and the valve seat 4 is held in the mounting groove 3 of the cylinder head 1 in its normal size via the ring member 8.

Next, a method for manufacturing the valve seat 4 will be briefly described.

First, a mixed powder of Si3N4 (silicon nitride) powder and a sintering aid is pressed to form a substantially annular preform, and this preform is heated at approximately 1200°C in a nitrogen atmosphere for 30 minutes. After pre-sintering, an engagement groove 7b with a depth of 1 mm is formed on the outer peripheral surface, and then heated at approximately 1800°C in a nitrogen atmosphere.
The coefficient of thermal expansion after sintering for 2 hours at
/'C main body member 7 was manufactured.

Next, mix powder of 30% by weight of aluminum and silicon,
Approximately 7 tons/crn2 by cold isostatic pressing method
The thermal expansion coefficient is approximately 13 x 10-6/”C.
A substantially cylindrical preformed body 8A was manufactured.

Next, as shown in FIG.
The preformed body 8 is set in the protrusion 11a of the lower mold 11 of 0.
A is set on the main body member 7 in an externally fitted manner, and the lower mold 11 and the upper mold 1
2 are clamped in the fixed mold 14, then the die 10
The preform 8A is heated to about 580'C and hot forged by pressurizing the preform 8A with a punch 13 fitted onto the upper die 12.
The preformed body 8A was externally fitted onto the main body member 7 in a shrink-fitting manner with substantially no gaps. Through this hot forging, a part of the preform 8A also fills the engagement groove 7b to form the engagement protrusion 8a, which is engaged with the inner end of the engagement groove 7b due to contraction after hot forging. A heat insulating space 9 is formed between the protrusions 8a.

Next, the hot forged compact was heated to 120 to 200°C.
After applying T6 treatment to age-harden for a predetermined period of time to increase its mechanical strength, the inner peripheral surface of the lower half of the main body member 7 is polished to form the seat surface 7a, and the outer peripheral surface and A valve seat 4 was obtained by finishing both the upper and lower end surfaces.

Next, the function of the valve seat 4 will be explained.

Since the ring member 8 was formed by hot forging with the preform 8A set in an externally fitted manner on the main body member 7, the outer circumferential surface of the main body member 7 made of a highly hard ceramic material did not need to be finished. The ring member 80 is fitted onto the main body member 7 in a shrink-fitting manner with almost no gap, and the main body member 7 can be strongly restrained by the ring member 8.

Furthermore, since the main body member 7 is held within the ring member 8 by the engagement between the engagement groove 7b and the engagement protrusion 8a, falling off from the ring member 8 is reliably prevented.

Further, since the impact force acting on the main body member 7 from the intake valve 5 is uniformly received by the inner peripheral surface of the ring member 8, the main body member 7
damage is prevented.

Since the coefficient of thermal expansion of the aluminum alloy constituting the ring member 8 is relatively high, even when the valve seat 4 and the parts of the cylinder head 1 in the vicinity become high temperature, the valve seat 1-4 has a strong restraining force. is securely held in the cylinder head 1. Moreover, since aluminum-based alloys are easier to process than iron-based alloys, the ring member 8
It becomes relatively easy to finish the upper and lower end surfaces and the outer circumferential surface.

On the other hand, in an industrial engine operated at a relatively low speed, such as the gas heat pump engine mentioned above, the temperature of the valve seat 4 becomes low, and the sulfuric acid component in the combustion gas condenses on the seat surface 7a of the valve seat 4. Although there is a problem that the outer peripheral edge of the valve body 5a that comes into contact with the seat surface 7a becomes severely worn, the temperature near the seat surface 7a is maintained at a relatively high temperature by the heat insulating space 9, so that dew condensation of the sulfuric acid component is prevented. This can prevent abnormal wear of the valve body 5a.

As described above, the manufacturing process of the valve seat 4 can be simplified by omitting the finishing process of the outer peripheral surface of the main body member 7, and the manufacturing cost can be reduced, and the finishing process of the ring member 8 is relatively easy. It is possible to prevent damage to the main body member 7 by preventing poor fitting between the main body member 7 and the ring member 8, it is possible to reliably prevent the main body member 7 from falling off, and it is possible to reduce the coefficient of thermal expansion of the ring member 8. Enlarge and Bulb Sea 1-
4 can be prevented from falling off, and dew condensation of the sulfuric acid component onto the seat surface 7a can be prevented, thereby preventing abnormal wear of the valve body 5a.

Next, a modification of the valve seat 4 will be described.

Incidentally, the same members as in the above embodiment are given the same reference numerals, and detailed explanation thereof will be omitted.

As shown in FIGS. 6 and 7, the valve seat 4A is composed of an annular main body member 17 and an annular ring member 18 that is externally fitted onto the main body member 17 with almost no gap. An annular receiving part 18a extending upwardly of the main body member 17 is formed at the upper end of the main body member 17, a pair of inner and outer annular grooves 17a are formed at the upper end of the main body member 17, and heat insulation is provided between the receiving part 18a and the groove 17a. A space 19 is formed, and the main body member 17
The ring portion +
The valve seat 4A is fixedly held in the mounting groove 3 of the cylinder head 1 via the ring member 18. Incidentally, the main body member 17 and the ring member 18 are made of the same materials as in the previous embodiment.

Next, a method for manufacturing the valve seat 4A will be briefly described.

First, a mixed powder of Si3N4 (silicon nitride) powder and a sintering aid is pressed to form a substantially annular preform, and this preform is heated at approximately 1200°C in a nitrogen atmosphere for 30 minutes. After pre-sintering, an engaging groove 7b and a groove 317a each having a depth of 1 hole are formed on the outer circumferential surface and the upper end surface, respectively.
The main body member 17 was manufactured by sintering at C for 2 hours.

Next, a substantially cylindrical preform 18A was produced by cold isostatic pressing in the same manner as in the above embodiment.

Next, as shown in FIG. 8, the main body member 17 is placed on the protrusion 11a of the lower mold 11 of the die 10, and the preform 18A is set in an external fit on the main body member 17, and the lower mold II
After clamping the die 10 and the upper mold 12 in the fixed mold 14, the preform 18A is pressurized with the punch 13 fitted onto the upper mold 12 while the die 10 is heated to about 580"C, and hot forged. Then, the preformed body 18A is inserted into the main body member 17 with almost no gaps.
It was fitted externally. Through this hot forging, the preformed body 18A
The upper part of the groove 17a flows into the gap between the main body member 17 and the upper mold 12 to form the receiving part 18a, but since the fluidity of the preform 18A is not very good, the groove 17a is hardly filled and the groove 17a A heat insulating space 19 is formed inside.

Next, the hot forged compact is subjected to a T6 treatment of age hardening at 120 to 2400°C for a predetermined period of time,
After increasing its mechanical strength, the inner peripheral surface of the lower half of the main body member 17 is polished to form the seat surface 7a, and
Half Sea-1-4A was manufactured by finishing the outer peripheral surfaces and both upper and lower end surfaces of the main body member 17 and ring member 18.

In the above-mentioned valve seat) 4A, the same effects as in the above embodiment can be obtained. In addition, the pair of inner and outer heat insulating spaces 19 further suppresses heat conduction from the main body member 17 to the cylinder head 1, thereby preventing a drop in temperature of the receiving surface 7a.

Note that ceramic materials other than the above-mentioned Si and N may be used as the ceramic material for manufacturing the main body members 7 and 17.
Further, the shape of the retaining groove portion 7b may be a rectangular groove shape, and one or more pairs of the engaging groove portion 7b and the engaging protrusion 8a may be formed vertically.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a vertical cross-sectional view of the main part of the cylinder head, the second is a vertical cross-sectional view of the valve seat, and FIG. 3 is a plan view of the valve seat. 5 is a longitudinal sectional view of the vicinity of the engagement groove and the engagement protrusion, FIG. 5 is a longitudinal sectional view of the die during hot forging, and FIGS.
Figure 8 relates to a modified example, and Figure 6 is a diagram equivalent to Figure 2;
FIG. 7 is an enlarged longitudinal cross-sectional view of the vicinity of the upper end of the valve seat, and FIG. 8 is a view corresponding to FIG. 5. 1...Cylinder head, 4.4A...Valve seat,
5. Intake valve, 7.17.. Main body member, 7b.. Engagement groove portion, 8.18.. Ring member, 8a.. Engagement protrusion, 8A. 1.8A.. Preformed body. Patent applicant Mazda Motor Corporation 6 (1

Claims (1)

[Claims] (1) In a valve seat that comes into contact with the intake valve or exhaust valve of the cylinder head, the valve seat is connected to a main body member made of a ceramic material,
It is composed of a ring member formed by hot forging a cylindrical preformed body made of aluminum alloy powder containing aluminum and silicon into a body member, and the outer circumference of the body member and the inner part of the ring member are 1. A valve seat for an engine, characterized in that a retaining engagement portion is formed in a peripheral portion to engage with the circumferential portion.