JPH07150913A - Valve guide for internal combustion engine and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a valve guide excellent in processability without deteriorating abrasion resistance to be required. CONSTITUTION:Both ends 11 requiring abrasion resistance in a valve guide 10 are made of high abrasion resistant materials, and a center part 12 is made of materials having good machinability, thereby a valve guide having good machinability can be obtained without deteriorating abrasion resistance on both ends to which high load is applied during operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve guide for guiding an engine valve of an internal combustion engine, and more particularly to a valve guide having machinability and wear resistance during machining and a method for manufacturing the same.

[0002]

2. Description of the Related Art FIG. 3 is a sectional view showing an example of a valve mechanism of an internal combustion engine.

A valve seat (03) is attached to the lower end of the opening of the port (02) provided in the cylinder head (01).

The valve body of the engine valve is composed of a stem portion (05) and an umbrella portion (04) that abuts on the valve seat (03) to open and close the port (02). The stem (05) is a cylinder head ( The spring retainer (06) is attached to the upper end of the spring retainer (06).

Spring retainer (06) and cylinder head
A valve spring (07) is contracted between the valve retainer (06) and the valve (01), and biases the spring retainer (06) and the valve body upward.

The rocker arm (08) arranged above the cylinder head (01) contacts the upper end of the stem (05) and presses it downward to open / close the port (02).

The stem (05) is slidably held by an elongated cylindrical valve guide (09) press-fitted into the cylinder head (01).

The valve guide (09) not only guides the movement of the stem (05), but also transfers the heat of the valve body to the cylinder head (01) to prevent the valve body from overheating.

[0009]

The valve guide (09) used in the valve operating mechanism as described above is
Since the stem (05) is constantly guided and repeatedly slid back and forth, it is manufactured by using a material having high wear resistance such as gray cast iron or alloy cast iron.

However, since a material having high wear resistance generally has poor machinability, a guide hole into which the stem (05) is inserted and a tool for machining the outer diameter are worn out in a relatively short period of time and have a long service life. The problem is that it is short.

The present invention solves the above problems by focusing on the fact that the wear resistance is required at both the upper and lower ends of the valve guide, and solves the above-mentioned problems. An object of the present invention is to provide a valve guide having excellent properties and a manufacturing method thereof.

[0012]

A valve guide of the present invention for achieving the above object is a valve guide for slidably holding a stem of an engine valve, and has high resistance at both ends in a longitudinal direction. It is characterized in that it is made of an abradable material and the central portion is made of a material having good machinability.

Preferably, the high wear resistant material is one of low alloy steel and heat resistant high alloy steel, or one in which hard particles and / or machinability improving particles are added. Preferably, the material having good machinability is copper-containing steel or a material having machinability improving particles added thereto.

The method of manufacturing the valve guide of the present invention comprises:
In the middle of the annular gap formed in the press lower mold, a powder of a material with good machinability, and the gap between the upper and lower sides of the gap are filled with powder of a high wear resistant material to form three layers, A feature is that a punch having a shape corresponding to the annular gap is press-fitted into the gap to form a cylindrical green compact, and then the green compact is sintered.

Further, in the method of the present invention, the powder of the high wear-resistant material forming the both end portions and the powder of the material having good machinability forming the central portion are compression molded into separate cylindrical shapes. After that, it may be sintered, and the cylinders at both ends may be joined to both ends of the cylinder at the center.

[0016]

[Function] Since both ends of the valve guide, which are required to have wear resistance, are made of a material having high wear resistance and the central portion is made of a material having good machinability, the resistance of both ends subjected to high load is A valve guide with excellent workability can be obtained without impairing wear resistance.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view showing the structure of a valve guide according to the present invention. The valve guide (10) has an inner diameter corresponding to the diameter of the stem of the engine valve and an outer diameter corresponding to the diameter of the mounting hole of the cylinder head. And is formed in a cylindrical shape having.

In this valve guide (10), the central portion (12) and both end portions (11) in the length direction are integrally formed by using different materials.

Both end portions (11) are made of a material having high wear resistance and preferably relatively good machinability.

The central portion (12) is made of a material having good machinability and good thermal conductivity.

As described above, the both ends (11) are made of a material having high wear resistance and the central portion is made of a material having good machinability, so that the life is long and the material to be machined during machining is long. A valve guide (10) with improved machinability can be realized.

That is, during operation of the engine, the force acting on the valve guide (10) is a pressing force mainly based on the bending load acting on the stem of the engine valve, and this force is at both ends of the valve guide (10). It is known to have a great effect on the part (11).

Therefore, a material having high wear resistance is used for both ends (11) on which a large pressing load acts, and a material having excellent machinability is used for the central part (12) where the load is small. Valve guide with long life and good machinability
It can be (10).

A valve guide (10) having such characteristics
Can be manufactured using materials having the following compositions.

The material forming both ends (11) is a mixture of low alloy steel with hard particles and machinability improving particles, or
A mixture of heat resistant high alloy steel and hard particles and machinability improving particles is applied.

The composition of the above low alloy steel is Fe and Ni (1
~ 5%), Cu (0.5-2.5%), Mo (0.2-0.8)
%), C (0.2-0.5%) and inevitable impurities.

Similarly, the composition of the heat resistant high alloy steel is Fe and C.
r (16-18%), Ni (12-14%), Mo (2-3)
%), Cu (1 to 3%), Sn (0.5 to 1%) and inevitable impurities.

The hard particles are preferably low carbon ferro-molybdenum powder (Fe and Mo (60 to 70%) and others) and Co-Mo-Si based intermetallic compound powder having a particle diameter of 74 μm or less, and the weight ratio of each is 5%. It is recommended to add ~ 15%.

The machinability-improving particles are MnS powder having a particle size of 74 μm or less, CaF ₂ or Ba having a particle size of 105 μm or less.
F ₂ powder is preferable, and it is preferable to add 0.5 to 5% by weight of each powder.

On the other hand, for the central portion (12), a mixture of copper-containing steel and machinability improving particles is suitable.

The composition of the copper-containing steel is Fe and Cu (4 to 7%).
And C (0.2 to 0.4%), the machinability improving particles are
This is the same as the case of the both ends (11).

FIG. 2 is a schematic view showing an example of a compression molding process for manufacturing the valve guide (10) of the present invention.

A circular hole having a diameter corresponding to the outer diameter of the valve guide (10) to be machined is formed in the lower mold (21) of the molding machine,
A core (22) having a circular cross section with a diameter corresponding to the inner diameter of the valve guide (10) is erected concentrically therein.

In the gap (23) formed between the lower mold (21) and the core (22), the material powder (24) (25) that constitutes the valve guide (10)
(26) is packed in three layers.

Lower layer material powder (24) and upper layer material powder (26)
Is a mixture forming the both ends (11) described above, and similarly, the material powder (25) in the middle layer is a mixture forming the central part (12).

After filling the three layers of material powder (24) (25) (26),
The punch (27) formed in the annular cross section is attached to the lower die (21) and the core (2
The material powder is press-fitted into the gap (23) with the (2) to integrally compression-mold each material powder into a cylindrical green compact.

Then, the molded cylindrical green compact is removed from the lower mold (21) and the core (22) and sintered at a predetermined temperature, and then the inner and outer peripheral surfaces and the entire length are sized as required. Cut or grind into the desired valve guide (10)
To finish.

In the cylindrical green compact made of the above-mentioned material, the material (25) of the central portion (12) tends to bulge slightly outward due to the sintering. There is an advantage that it is necessary to apply it only to both ends (11) where the valve makes strong contact.

In the above embodiment, the material powders (24) and (26) forming both end portions (11) and the material powder (2) forming the central portion (12) are
Although 5) and 5 are simultaneously and integrally compressed to form a cylindrical body, the three layers do not necessarily have to be simultaneously compression-molded.

That is, two end portions (11) and one central portion (12) are separately compression-molded and then sintered,
You may make it join integrally by brazing etc.

The present invention can be applied not only to the valve guide but also to bushes, bearings and the like.

[0042]

【The invention's effect】

(a) High wear resistance material is used for both ends that receive a large load while the engine is operating, and material with good machinability is used for the center part where the load is small, resulting in excellent durability and workability. A valve guide is obtained.

(B) Powder of a material having good machinability forming the central portion of the valve guide and powder of a high wear resistant material forming both end portions are laminated in three layers and simultaneously compression-molded and fired. The valve guides having excellent durability and workability can be easily manufactured by tying or by separately compression-molding and then sintering and joining them together.

(C) When copper-containing steel is used in the central portion, the thermal conductivity becomes good and the cooling performance of the engine valve is improved.

[Brief description of drawings]

FIG. 1 is a vertical sectional front view showing an embodiment of a valve guide of the present invention.

FIG. 2 is a schematic view showing a compression molding step in the method for manufacturing a valve guide of the present invention.

FIG. 3 is a cross-sectional view of a main part schematically showing a valve mechanism having a valve guide.

[Explanation of symbols]

 (10) Valve guide (11) Both ends (12) Center part (21) Lower die (22) Core (23) Gap (24) High wear resistance material (25) Material with good machinability (26) High resistance Abrasive Material (27) Punch

Claims (5)

[Claims] 1. A valve guide for slidably holding a stem of an engine valve, wherein both lengthwise end portions are made of a highly wear-resistant material and a central portion is made of a material having good machinability. A valve guide for an internal combustion engine. 2. The internal combustion engine according to claim 1, wherein the high wear resistance material is one of a low alloy steel and a heat resistant high alloy steel, or a material to which hard particles and / or machinability improving particles are added. Valve guide. 3. The valve guide for an internal combustion engine according to claim 1, wherein the material having good machinability is copper-containing steel or a material to which machinability improving particles are added. 4. A powder of a material having good machinability is filled in an intermediate portion of an annular gap formed in the lower press die, and a powder of a high wear resistance material is filled in upper and lower gaps sandwiching the powder. Valve guide for an internal combustion engine, characterized in that a punch having a shape corresponding to an annular gap is press-fitted into the gap to form a cylindrical compact, and the compact is sintered. Manufacturing method. 5. A powder of a highly wear-resistant material forming both ends and a powder of a material having good machinability forming a central part are respectively compression-molded into separate cylindrical shapes and then sintered to form a central part. A method for manufacturing a valve guide for an internal combustion engine, characterized in that the cylindrical bodies at both ends are joined to both ends of the cylindrical body.